Note: Descriptions are shown in the official language in which they were submitted.
CA 02540341 2006-03-20
APPARATUS FOR APPLYING METALLIC CLADDING
TO INTERIOR SURFACES OF PIPE ELBOWS
FIELD OF THE INVENTION
The present invention relates in general to methods and apparatus for applying
metallic cladding materials to the interior surfaces of pipe. In particular,
the invention
relates to methods and apparatus for helical deposition of metallic cladding
materials to
interior surfaces of pipe, especially curved sections of pipe such as elbows.
BACKGROUND OF THE INVENTION
It is desirable in numerous industrial applications to armor the interior
surfaces of
metallic pipe with metallic cladding materials to protect against corrosion,
abrasion,
and/or surface contamination, and to provide improved impact resistance. For
example,
the processing of bitumen-laden sands (or "tar sands") to produce synthetic
crude oil
typically involves mixing the tar sands with liquid to form a slurry, which is
then piped to
a processing plant. Because of its high content of sand and/or rock particles,
the flowing
slurry is extremely abrasive and will readily wear away the kinds of steels
most
commonly used for industrial piping. Metals such as stainless steel and
chromium alloys
have much greater resistance to abrasion (and corrosion) than common steels,
but in most
cases it would be prohibitively expensive to use piping made of such metals,
particularly
for larger diameter pipe.
A common and less expensive alternative in highly abrasive or corrosive
industrial applications is to use ordinary steel pipe internally clad or
armored with a more
abrasion-resistant and/or corrosion-resistant material such as stainless
steel, tungsten
carbide, or a chromium alloy. The pipe is typically clad by depositing the
cladding metal
on the internal surfaces of the pipe using methods well known in the field of
automatic
and semi-automatic electric arc welding. Metal cladding wire is continuously
fed from a
wire spool to an applicator head (or "weld head") disposed an optimal distance
from the
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internal surface of a grounded pipe such that the introduction of an
electrical current to
the wire it will cause arcing between the wire and the pipe, in turn
generating
temperatures sufficient to melt the wire so that it will be deposited on and
fused to the
pipe. As with analogous welding procedures, the best results are typically
achieved when
this procedure is conducted in the "flat" position; i.e., with the surface to
receive the
molten metal being disposed beneath the weld head, as opposed to the
"horizontal" and
"overhead" positions (as those terms are commonly understood in the welding
field).
The weld head is moved continuously relative to the pipe so that a continuous
bead of metal cladding material is deposited on the pipe. This may be
accomplished by
moving the weld relative to the pipe, or vice versa. The mode of movement may
be
parallel to the pipe axis so to result in deposition of longitudinally-
oriented cladding
beads. It has been observed, however, that cladding beads oriented
substantially parallel
to the direction of flow appear to be more prone to abrasion than cladding
beads oriented
transversely to the flow direction. In addition, it has been observed that the
application of
cladding beads parallel to the flow direction tends to distort the cross-
sectional shape of
the pipe, due to residual stresses caused by differential cooling of the
cladding beads.
For the foregoing reasons, it is preferable to use cladding beads that are of
substantially circumferential orientation (i.e., transverse to flow
direction), particularly in
applications where the pipe is intended to carry highly abrasive materials
such as tar sand
slurries. It is possible to apply circumferentially-oriented cladding as a
series of adjacent
circular beads; however, this would involve repeated stopping and starting of
the bead,
which is inefficient and thus undesirable. As a practical matter, therefore,
it is preferable
to apply the cladding as a continuous helical bead.
Circumferential application of metallic cladding is relatively simple for
straight
sections of pipe. For example, the applicator head may be maintained in the
"flat"
position while the straight pipe is rotated around it. The pipe may be moved
longitudinally relative to the applicator head after completion of each
circumferential
cladding bead, to allow the next bead to be deposited adjacent thereto.
Preferably,
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however, the longitudinal movement of the pipe is continuous so that a
continuous helical
cladding bead will be deposited.
Helical application is considerably more difficult in the case of curved pipe
sections such as pipe elbows. The procedure described above for cladding
straight pipe is
not workable with curved pipe. It is theoretically possible to apply helical
cladding beads
manually to a pipe elbow where the dimensions of the elbow permit manual
access.
However, this would entail an excessive amount of undesirable starting and
stopping of
the cladding bead due to the nearly constant need to reposition the elbow as
the work
progresses, particularly if it is being attempted to apply the cladding in the
desirable
"flat" position.
Because of the practical difficulties associated with helical cladding of
elbows,
longitudinal application methods are commonly used in spite of previously
noted
drawbacks. Moreover, this method is time-consuming, and therefore expensive.
For
these reasons, more efficient and economical means for helical cladding of
elbows would
be highly desirable.
Apparatus for helical application of cladding to curved pipe can be found in
the
prior art. Canadian Patent No. 2,282,134 and corresponding U.S. Patent No.
6,234,383,
issued to Harmat et al., disclose a rotatable framework having a curved cavity
contoured
to suit the shape of a curved pipe section which to receive internal metallic
cladding.
Guide tracks are provided along the sides of the cavity. Collars are fitted to
each end of
the pipe section, and the collars have wheels that engage the guide tracks so
as to control
the orientation of the pipe section as it moves into and through the cavity.
One of the
collars has a pair of guide pins that engage a guidance mechanism that is
longitudinally
movable so as to draw the pipe section progressively into the cavity as the
framework is
rotated about a longitudinal axis. The guidance mechanism has guide rails and
other
features adapted to compensate for the curvature of the pipe.
An elongate weld arm extends from one end of the framework into the cavity. At
its outer end, the weld arm is fitted with a conventional weld head to which
continuous
welding wire is fed, for deposition on the interior surfaces of the pipe. The
weld arm is
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geometrically configured such that it will not interfere with a pipe section
passing
through the cavity, and such that it moves in an eccentric path similar to a
skipping rope
as the framework is rotated about the longitudinal axis. During this rotation,
the weld
head remains in a fixed longitudinal position while at the same time
describing an orbital
path around the longitudinal axis. The weld head is connected to the weld arm
in a
fashion such that it remains in a fixed orientation (e.g., with the welding
wire always
feeding downward, in the "flat" position) regardless of the orbital rotation
of the weld
head.
To operate the apparatus, the guidance mechanism draws the pipe section into
the
cavity until the pipe reaches the weld head, with the weld head in position to
engage the
pipe's interior surface. The framework and weld arm are then cooperatively
rotated, in
coordination with the guidance mechanism which gradually draws the pipe
further into
the cavity. The circular rotation of the weld head, combined with coordinated
longitudinal movement of the pipe through the cavity, results in a continuous
helical bead
of metal being deposited on the interior surface of the pipe.
Although the Harmat apparatus may be effective for helical deposition of
internal
cladding of curved pipe sections, it has certain drawbacks and disadvantages.
Different
guide tracks and other components of the apparatus must be used for different
pipe sizes
and curvatures. The Harmat apparatus is not readily suited for use with pipe
sections
having comparatively small diameters (e.g., 12-inch diameter or smaller)
and/or
comparatively small curvature radii, nor does it appear to be possible to use
the apparatus
to clad 90-degree elbows (or even 45-degree elbows). In addition, the Harmat
apparatus
cannot be used, without difficulty or at all, with a curved pipe section
having a straight
transition section.
For the foregoing reasons, there is a need for apparatus for helical
deposition of
metallic cladding to interior surfaces of curved pipe sections, where the
apparatus is
readily configurable for use with pipe sections of different diameters,
without needing to
change or replace any components of the apparatus. There is a further need for
such
apparatus which is readily adaptable for internally cladding curved pipe
sections having
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smaller diameters and curvature radii than can be clad using known apparatus.
In
addition, there is a need for such apparatus which can internally clad not
only the internal
surfaces of curved pipe sections but also the internal surfaces of straight
transition
sections connected thereto. The present invention is directed to these needs.
BRIEF DESCRIPTION OF THE INVENTION
In general terms, the present invention is an apparatus for applying a
circumferentially-oriented metallic cladding bead around the interior surface
of a pipe
elbow. In the preferred embodiment, the apparatus applies the cladding bead in
a helical
pattern, but other bead application patterns are possible using alternative
embodiments of
the apparatus.
The apparatus is particularly adapted to cladding a pipe elbow having a
uniform
circular curvature; i.e., where the elbow centerline is uniformly curved about
a center of
curvature. The apparatus includes a stationary frame with a pipe opening
adapted such
that a pipe elbow can pass through it. In the preferred embodiment, the
stationary frame
is vertically oriented, although this is not essential to the invention. The
apparatus further
includes an elbow carriage with a rotor that is rotatable about a primary axis
passing
through the opening in the stationary frame. In the preferred embodiment, in
which the
stationary frame is vertically oriented, the primary axis will be horizontal.
The frame has
centering means for positioning the elbow within the pipe opening such that
its curved
centerline will remain substantially tangential to the primary axis as the
elbow moves
through the pipe opening (in a manner to be described in further detail
herein), in a
selected direction.
For optimal understanding of the present invention and its operation, the
frame
may be considered as having associated with it a reference plane perpendicular
to the
primary axis and passing through or close to the pipe opening. In the
preferred
embodiment, in which the stationary frame and the pipe opening are vertically
oriented,
the reference plane will be a vertical plane.
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The elbow carriage is positioned such that the rotor faces the stationary
frame.
The rotor has an elbow cradle to which a first end of a pipe elbow can be
swivelably
mounted, with the swivel axis coinciding with a diameter of the elbow and
lying in a
plane substantially transversely perpendicular to the primary axis. The elbow
cradle is
mounted to the rotor such that its position is radially adjustable relative to
the primary
axis. By means of this arrangement, a pipe elbow can be mounted at a first end
to the
elbow cradle, with the second end of the elbow projecting through the pipe
opening in the
stationary frame.
In the preferred embodiment of the invention, counterweight means will be
provided in association with the rotor, for counterbalancing forces imposed by
an elbow
mounted to the cradle. The counterweight means may be mounted to the rotor in
a fixed
position, in which case it will preferably be adapted such that its mass can
be varied; e.g.,
by adding or removing weighted sections. In the preferred embodiment, the
position of
the counterweight means is radially adjustable, such that its operational
effect can be
varied without varying its mass. In an alternative embodiment, the
counterweight is
radially adjustable and its mass can be varied as well, to suit the mass of
the elbow being
clad.
The apparatus further includes elbow carriage drive means that can
simultaneously and continuously rotate the rotor, move the elbow carriage in a
selected
direction parallel to the primary axis (either toward or away from the
stationary frame),
and adjust the radial position of the elbow collar on the rotor, either toward
or away from
the primary axis. These three modes of movement are coordinated, using
suitable
mechanical linkages and control systems (non-limiting examples of which are
described
hereinafter), such that when an elbow is mounted in the apparatus as described
above,
actuation of the elbow carriage drive means will cause the elbow to move a pre-
set
distance through the pipe opening during each rotation of the rotor, as
measured at the
intersection of the elbow centerline and the reference plane. This pre-set
distance (which
may be referred to as the pitch) will depend on the particular requirements of
the cladding
job being carried out, but will typically be equal to the desired average
width of weld
bead to be applied to the elbow, as measured along the elbow centerline.
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As the rotor rotates, thus rotating the elbow cradle and the first end of the
elbow
around the primary axis, the elbow's center of curvature will also rotate
about the
primary axis, while at all times being substantially coincident with the
reference plane.
In order for the movement of the elbow through the pipe opening to meet the
foregoing operational criteria, the distance that the elbow carriage moves
parallel to the
primary axis during each rotor revolution (which distance may be referred to
as AX), and
the distance that the elbow cradle moves radially relative to the primary axis
during each
rotor revolution (AY), will vary with each revolution. AX and AY will
correspond to the
sides of a right triangle having a hypotenuse equal to the pitch (as
previously defined),
and these values will vary according to the position of the elbow relative to
the stationary
frame. This basic geometric relationship will apply regardless of the
rotational position
of the rotor.
The constantly changing nature of AX and AY during the operation of the elbow
carriage drive means can be readily understood by considering an example case
where a
90 elbow is being clad using the apparatus of the invention. In accordance
with the
preferred mode of operation of the apparatus, the elbow would be positioned in
a medial
orientation in the pipe opening such that substantially equal portions of the
elbow
protrude from either side of the opening. In this configuration, a radial line
from the
elbow's center of curvature to the elbow centerline at the elbow's first end
(mounted to
the elbow collar) would be oriented at a 45 angle relative to the primary
axis (which is
horizontal in the preferred embodiment). Next, the elbow carriage drive means
would be
actuated so as to draw the elbow through the pipe opening until the second end
of the
elbow reaches the pipe opening. During the first revolution of the rotor, the
first end of
the elbow would need to move horizontally away from the stationary frame by AX
approximately equal to the cosine of 45 times the pitch, and the elbow cradle
would
need to move radially away from the primary axis by AY equal to the sine of 45
times
the pitch. In this specific position, AX would be equal to AY, since sine 45
is equal to
cosine 45 . With each further rotation of the rotor, however, AX would
decrease and AY
would increase (in accordance with the well-known Pythagorean theorem). As the
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second end of the elbow approaches the frame, having been rotated through a 45
angle,
AX would approach zero, and AY would approach the pitch.
In the preferred embodiment of the invention, this geometrically-coordinated
movement of the elbow carriage and the elbow collar is facilitated by
providing, as a
component of the elbow carriage drive means, a bull gear that serves as a
template for the
required movements of the elbow carriage and the elbow collar as the rotor
rotates the
first end of the elbow around the primary axis. This may be accomplished by
means of
suitable mechanical linkages, non-limiting examples of which will be described
in further
detail herein.
The apparatus also includes a rigid, sinuously-configured weld arm mounted to
a
weld arm carriage. This assembly is positioned on the side of the stationary
frame
opposite from the elbow carriage. The weld arm has a drive end and a free end.
The
drive end is mounted to the weld arm carriage such that it can be rotated
around the
primary axis, with the weld arm's free end extending in cantilever fashion
toward the
stationary frame, and with the weld arm's sinuous centerline coinciding, at
the free end,
with the primary axis. The free end of the weld arm extends to, or is capable
of being
extended to, a point close to or coincident with the aforementioned reference
plane.
The sinuous configuration of the weld arm is selected or designed to suit the
geometry of the particular pipe elbow (or elbows) to be clad using the
apparatus of the
invention. More specifically, the weld arm is shaped such that it can fit
inside a pipe
elbow extending through the stationary frame toward the weld arm carriage,
without
interference with the elbow. It will be appreciated that the specific shape of
the weld arm
will depend on the dimensional characteristics of the elbow or elbows to be
clad, and the
extent to which the elbow or elbows will be required to project through the
stationary
frame. Notably, however, the weld arm can be configured such that it can be
used to clad
elbows of different diameters.
The weld arm is hollow so as to define an internal passage extending from the
drive end to the free end. A weld head linkage is disposed within the internal
passage,
and a weld head is connected to the weld head linkage at the free end of the
weld arm.
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The weld head may be of any suitable type well known in the welding field, and
will
have associated means for feeding welding wire to the weld head.
In accordance with proper welding practice, the welding wire will preferably
stick
out approximately 1.0 to 1.5 inches from the end of the weld head. To
facilitate the use
of one weld arm for cladding elbows of different diameters, the weld head is
preferably
adapted to be fitted with extension elements so that the preferred "stick-out"
can be
maintained regardless of elbow size. For example, for a weld arm / weld head
combination configured to clad elbows with a minimum diameter of 12 inches
using a
stick-out of 1.25 inches, the welding head would be fitted with a 6-inch
extension in
order to clad a 24-inch-diameter elbow using the same stick-out; i.e., the
length of the
required extension element would correspond to the difference in elbow radius.
The weld head linkage is designed and adapted such that the weld head does not
rotate, so that the welding head can maintain a constant welding position
(preferably the
"flat" position, to use common welding terminology) in spite of the rotation
of the weld
arm. In the preferred embodiment, this is accomplished by fashioning the weld
head
linkage using a train of elongate shafts mounted inside the weld arm using
suitable
bearing means. The axes of adjacent shafts will intersect at an angle
generally
determined by the sinuous shape of the weld arm. Where two shafts meet, they
engage
each other by means of bevel gears mounted to the ends of the shafts. These
bevel gears
allow the angularly-offset shafts to "walk around" each other as the weld arm
rotates.
However, the shaft section nearest the weld head (and to which the weld held
is mounted)
is concentric with the primary axis, and therefore will not rotate.
In preferred embodiments, each shaft of the weld head linkage has a
longitudinal
central passage (most conveniently provided by making the shafts from round
pipe), and
each bevel gear has a central opening in communication with the central
passages of
adjacent shafts, so as to form the previously-mentioned continuous internal
passage for
feeding weld wire to the weld head. The central passage may also house
auxiliary
services which may be desired in various applications, such as conduits for
shielding gas
(if required), compressed air lines (for cooling and/or cleaning the weld
head), electrical
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power (e.g., for powering a wire feed mechanism associated with the weld
head), fiber
optic cable (for a video camera mounted in association with the weld head, for
monitoring cladding bead deposition), and vacuum lines (e.g., for removing
flux from
weld deposition areas, in applications using granular flux).
To clad the interior of a pipe elbow using the apparatus of the invention in
the
preferred mode of operation, a first end of the elbow is swivelably connected
to the elbow
collar and the other end of the elbow is disposed within the pipe opening of
the stationary
frame, in what may be referred to as a medial position or orientation; i.e.,
such that
approximately equal portions of the elbow project on each side of the frame.
The weld
head is preferably oriented in the "flat" welding position, and with the tip
of the welding
wire disposed an appropriate distance from the interior surface of the elbow,
such that a
bead of molten metal from the wire will be deposited on the interior surface
of the elbow
upon introduction of a suitable electrical current into the wire (in
accordance with well-
known arc welding methods and technology (using either alternating current or
direct
current as desired or appropriate). To close the electrical circuit to enable
arcing between
the wire and the elbow, the elbow is grounded by connection to suitable
grounding means
associated with the rotor. The grounding means is adapted in accordance with
known
methods so as to rotate with the rotor while maintaining electrical
conductivity with a
grounding source.The elbow carriage drive means is then activated so as to
draw the elbow through
the pipe opening in the fashion previously described (i.e., simultaneously
rotating the first
end of the elbow in orbital fashion around the primary axis, moving the elbow
carriage
horizontally away from the stationary frame, and moving the elbow cradle
radially
outward relative to the primary axis, in a manner corresponding to the
changing
geometric orientation of the elbow). At the same time, the weld arm is rotated
around the
primary axis in coordination with the rotation of the rotor, such that the
weld arm at all
time remains clear of the interior surfaces of the elbow, while the position
of weld head
remains fixed and non-rotating. Upon energizing the system, molten metal will
thus be
deposited on the interior surface of the elbow in a helical pattern.
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When the elbow has moved to a terminal position in the stationary frame (i.e.,
when the helical cladding has reached a desired end point near the second end
of the
elbow), the elbow may be disengaged from the apparatus, rotated 180 degrees
and
remounted in a medial orientation with the welding wire positioned to begin
depositing
metal at or near where the completed bead began. The apparatus is then
actuated as
before so as to deposit cladding in a helical pattern on the remaining unclad
portion of the
interior surface of the elbow. When this second phase of the operation is
complete, the
elbow will be continuously helically clad. The entire process may be repeated
one or
more times if it is desired to apply two or more layers of cladding to the
elbow.
Accordingly, in a first aspect the present invention is an apparatus for
applying a
helical cladding bead to interior surfaces of a circularly curved pipe elbow
having a first
end, a second end, a curved centerline, a center of curvature, and a plane of
curvature,
said apparatus comprising:
(a) an elbow carriage;
(b) a rotor mounted to the elbow carriage and rotatable about a primary axis;
(c) an elbow collar, to which the elbow may be removably mounted so as to be
swivelable about a swivel axis, said swivel axis passing through the curved
centerline and being substantially perpendicular to the elbow's plane of
curvature;
(d) collar-mounting means, for mounting the elbow collar to the rotor such
that:
d.1 the elbow collar is movable along a radial path perpendicular to and
passing through the primary axis; and
d.2 the swivel axis is perpendicular to said radial path, and lies in a plane
transversely perpendicular to the primary axis;
(e) a stationary frame defining a pipe opening, said frame being positioned
such that:
e.1 the rotor is oriented toward the stationary frame; and
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e.2 the primary axis passes through the pipe opening;
said frame having associated with it a reference plane transversely
perpendicular
to the primary axis;
(0 centering means, for centering the pipe elbow within the pipe opening
such that as
the elbow passes through the pipe opening:
f.1 the primary axis will coincide with the elbow's plane of curvature; and
f.2 the primary axis will be substantially tangential to the elbow's curved
centerline;
(g) elbow carriage drive means for simultaneously:
g.1 rotating the rotor in a selected direction about the primary axis;
g.2 moving the elbow carriage in a selected direction parallel to the primary
axis; and
g.3 moving the elbow collar in a selected radial direction relative to the
primary axis;
in coordinated fashion such that the pipe elbow, when swivelably connected at
its
first end to the elbow collar, with its second end disposed within the pipe
opening,
will pass through the pipe opening with its center of curvature rotating
orbitally
around the primary axis while remaining substantially coincident with the
reference plane;
(h) a weld arm carriage positioned on the side of the stationary frame
opposite the
elbow carriage;
(i) a rigid, sinuously configured weld arm having a drive end, a free end, a
sinuous
centerline, and an internal passage extending continuously between said drive
end
and said free end, said weld arm being mounted to the weld arm carriage such
that:
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1.1 the free end of the weld arm extends from the weld arm carriage toward
the stationary frame; and
i.2 the drive end of the weld arm is mounted to the weld arm carriage such
that the weld arm is rotatable about the primary axis, with the weld arm
centerline at the free end of the weld arm remaining substantially
coincident with the primary axis;
said weld arm being configured such that the weld arm may be positioned inside
the pipe elbow when the elbow is positioned within the pipe opening of the
stationary frame, without physically interfering with the elbow;
(j) weld arm rotation means, for rotating the weld arm about the primary axis
in
coordination with the rotation of the rotor, such that the weld arm will not
interfere with the pipe elbow as it passes through the pipe opening of the
stationary frame in response to actuation of the elbow carriage drive means;
(k) weld head linkage extending between the drive end and the free end of the
weld
arm within the internal passage thereof, said weld head linkage having a free
end
associated with the free end of the weld arm; and
(1) a weld head mounted to the free end of the weld head linkage such that its
spatial
orientation remains substantially fixed irrespective of rotation of the weld
arm
about the primary axis.
In the preferred embodiment, the apparatus comprises means for varying the
rotational speed of the rotor during each rotation, to facilitate deposition
of weld beads of
substantially uniform thickness around the inner perimeter of the elbow.
Because of the
curvature of the elbow, the width covered by each pass of the weld head will
be greater
than the pitch (as previously defined) at points on the elbow where the
distance to the
elbow's center of curvature is greater than the elbow's radius of curvature
(i.e., outboard
of the elbow centerline), and less than the pitch at points on the elbow where
the distance
to the center of curvature is less than the radius of curvature (i.e., inboard
of the elbow
centerline). The variable-rate rotation means progressively slows the rotation
of the rotor
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as the weld head moves from the most inboard zones of the elbow to the most
outboard
zones, and correspondingly increases the rotational speed of the rotor as the
weld head
moves from the most outboard zones toward the most inboard zones. Accordingly,
the
weld head dwells longer at outboard zones than at inboard zones, thereby
facilitating the
deposition of a weld bead of substantially uniform thickness around the
circumference of
the elbow if the wire feed rate to the weld head is kept constant.
The variable-rate rotation mechanism will of necessity be synchronized with
the
movements of the elbow carriage and the rotation of the weld arm carriage.
In alternative embodiments, uniform weld bead thickness may be achieved
without varying the rotor's rate of rotation, by instead varying the wire feed
speed.
In preferred embodiments, the apparatus is adapted to clad interior surfaces
of
straight transition sections attached to pipe elbows.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention will now be described with reference to the
accompanying figures, in which numerical references denote like parts, and in
which:
FIGURE 1 is a side view of a circularly-curved pipe elbow, with
associated geometric parameters indicated.
FIGURE 2 is an end view of the pipe elbow shown in Figure 1.
FIGURE 3 is a schematic elevation of the apparatus of the invention in
accordance with the preferred embodiment, shown with a pipe elbow in a
medial position, and with the rotor in the six-o'clock position.
FIGURE 4 is a schematic elevation of the apparatus with a pipe elbow in
a medial position, and with the rotor in the twelve-o'clock position.
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FIGURE 5 is a schematic elevation of the apparatus with a pipe elbow in
a terminal position, and with the rotor in the six-o'clock position.
FIGURE 6 is a schematic elevation of the apparatus with a pipe elbow in
a primary terminal position, and with the rotor in the twelve-o'clock
position.
FIGURE 7 is a schematic elevation of the apparatus being used to clad a
pipe elbow having a straight transition section, and with the rotor in the
six-o'clock position.
FIGURE 8 is an elevation of the stationary frame of the apparatus in
accordance with one embodiment of the invention (viewed looking from).
FIGURE 9 is an elevation of the rotor and elbow collar of the apparatus in
accordance with one embodiment (viewed looking from the stationary
frame toward the rotor).
FIGURE 10 is a cutaway elevation of a weld arm in accordance with the
preferred embodiment.
FIGURE 11 is an elevational view of the weld arm carriage (viewed
looking from the stationary frame toward the weld arm carriage), with the
weld arm carriage turntable in the six-o'clock position.
FIGURES 12A and 12B are schematic free-body diagrams of a pipe
elbow illustrating the geometrical relationship between longitudinal
movements of the elbow carriage and radial movements of the elbow
collar for different positions of the elbow relative to the stationary frame.
FIGURE 13 is a schematic diagram illustrating the variability of the
width of each pass of the weld head at different positions around the
perimeter of a pipe elbow clad using the present invention.
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FIGURE 14 is a cross-sectional elevation through a preferred
embodiment of the apparatus, illustrating a preferred primary drive
mechanism and variable-rate rotation mechanism.
FIGURE 14A is an enlarged elevation of the elbow carriage drive means
shown in Fig. 14.
FIGURE 15 is a plan view of the apparatus shown in Fig 14.
FIGURE 15A is an enlarged plan view of the elbow carriage drive means
shown in Fig. 15.
FIGURE 16 is an illustration of selected components of the variable-rate
rotation mechanism of the preferred embodiment of the invention.
FIGURE 17 is a frontal elevation of the variable-rate rotation mechanism
in an offset configuration.
FIGURE 18 is a side view of the variable-rate rotation mechanism
configured as in Fig. 17.
FIGURE 19 is a top view of the variable-rate rotation mechanism as in
Fig. 17, with the mechanism's ring gear and sliding drive plate omitted for
clarity to illustrate the inter-engagement of the mechanism's rack plates.
FIGURE 20 is a frontal elevation illustrating the range of orbital rotation
of the variable-rate rotation mechanism when in an offset configuration.
FIGURE 21 is cross-sectional plan view of the apparatus illustrating the
bull gear assembly of the elbow carriage drive means of the preferred
embodiment.
FIGURE 21A is an enlarged plan view of the bull gear assembly shown
in Fig. 21.
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CA 02540341 2011-06-06
FIGURE 22 is a cross-sectional elevation of the elbow carriage drive
means (looking toward the stationary frame, as indicated by section
markings in Fig. 14).
FIGURE 23 is a further cross-sectional elevation (as indicated by section
markings in Fig. 14), illustrating the bull gear drive mechanism in
accordance with a preferred embodiment.
FIGURE 24 is cross-sectional plan view of the apparatus, further
illustrating components of the bull gear drive mechanism as well as the
weld arm's rotary drive mechanism.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The apparatus of the present invention will be best understood by first
reviewing
Figs. 1 and 2, which illustrate the basic geometric properties of a pipe elbow
to be clad
using the apparatus. As indicated in Fig. 1, pipe elbow 80 has outside
diameter D1, outer
radius R1, wall thickness T, inner diameter D2, inner radius R2, outer surface
82, and
inner surface 84. Elbow 80 is circularly curved about a center of curvature
90, with a
curved centreline 94 having a curvature radius 92. Elbow 80 may have a
straight
transition section 86 (or "tangent" section) at one or both ends; as will be
seen, the
present invention may be readily adapted to apply helical cladding to the
inner surface of
transition 86 as well as to inner surface 84 of the curved portion of elbow
80. As best
seen in Fig. 2, elbow 80 is longitudinally bisected by a plane of curvature
96, with both
center of curvature 90 and curved centreline 94 coinciding with or lying in
plane of
curvature 96.
Referring now to Fig. 3, the apparatus of the present invention (generally
indicated by reference numeral 10) comprises a stationary frame 20 having a
pipe
opening 21, with an elbow carriage 30 having an inner end 30A and an outer end
30B, a
rotor 40 mounted to inner end 30A of elbow carriage 30 so as to be rotatable
about a
primary axis X-1, and a weld arm carriage 50 having an inner end 50A and an
outer end
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CA 02540341 2006-03-20
50B. A weld arm 60, sinuously configured and having an internally-disposed
weld head
linkage, is mounted to weld arm carriage 50, with weld arm 60 having a drive
end 60D
associated with weld head carriage 50 and a free end 60F extending toward
frame 20.
Elbow carriage 30 is longitudinally movable parallel to primary axis X-1. The
means by which this longitudinal movability is provided is not critical to the
invention,
and persons skilled in the art will readily appreciate that this can be
accomplished in
various ways using known technology and methods. In the preferred embodiment,
as
illustrated in the Figures, elbow carriage 30 longitudinally movable by means
of rollers
33 which roll on tracks 34 mounted to a fixed base B (such as a foundation or
floor
structure).
Elbow carriage 30 may house components of an elbow carriage drive means an
exemplary embodiment of which will be described in detail later in this
specification. In
the preferred embodiment, elbow carriage drive means is operably connected to
a tubular
primary drive shaft 46 and to a secondary drive shaft 48 which is coaxially
disposed
inside primary drive shaft 46. The functions and operational features of these
drive shafts
will be explained in detail later in this specification.
In Figs. 3-7, elbow carriage 30 is shown in the form of a box-like enclosure,
but
the invention does not require the elbow carriage 30 to be of any particular
shape or
configuration.
As best seen in Fig. 8, stationary frame 20 has a pipe opening 21 for
receiving a
pipe elbow in a manner as described in detail elsewhere herein. As may be seen
in Figs.
3-7, frame 20 is located a suitable distance from elbow carriage 30, with
primary axis
X-1 passing through opening 21. To facilitate proper understanding of the
invention,
frame 20 may be considered as having associated therewith a reference plane RP
perpendicularly transverse to primary axis X-1. In Figs. 3-7, reference plane
RP is
shown as being centered on frame 20, but this is not strictly essential.
Reference plane
RP may be shifted slightly toward one side or the other of frame 20 without
departing
from the invention, but reference plane RP will typically be disposed within
the lateral
width of frame 20.
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CA 02540341 2006-03-20
In the embodiment shown in Fig. 8, frame 20 is fashioned from a pair of side
plates 22 structurally supported on a main mast 23A and a secondary mast 23B.
Optionally, secondary mast 23B may extend upward to an overhead support
element
(such as a structural component of a building) to provide enhanced lateral
stability and
stiffness to frame 20. Additional structural elements, such as gusset 24 shown
in Fig. 8,
may be used for additional stiffening. However, it is not essential to the
invention for
frame 20 to take any particular structural form, provided that it has a pipe
opening 21
generally as described. In the embodiment shown in Fig. 8, pipe opening 21 is
circular
and has a continuous perimeter, but this is by way of example only. In
alternative
embodiments, pipe opening 21 could be non-circular in shape, and/or it could
have a
discontinuous perimeter, or it could take some other shape, without departing
from the
present invention.
Stationary frame 20 has centering means associated with pipe opening 21, for
centering a pipe elbow 80 passing through the pipe opening such that curved
centerline
94 of elbow 80 will be substantially tangential to primary axis X-1 at
reference plane RP,
irrespective of the longitudinal or rotational position of elbow 80 relative
to frame 20. To
state this a different way, the centering means provides a "steady rest" which
positions
elbow 80 such that curved centerline 94 will always substantially coincide
with primary
axis X-1 at the point where centerline 94 intersects reference plane RP.
Persons skilled in the art will appreciate that the centering means could take
various forms using known technologies. In the preferred embodiment shown in
Fig. 8,
however, the centering means is in the form of three elbow guides 25
(individually
designated, for descriptive purposes, as elbow guides 25A, 25B, and 25C)
mounted to
frame 20 in spaced relation around opening 21. Each elbow guide 25 can be
radially
extended or retracted (relative to primary axis X-1) so as to engage outer
surface 82 of an
elbow 80 passing through opening 21 of frame 20. Elbow guides 25 may take any
of
several forms that are known or readily devisable using known technology, such
as
hydraulic rams, pneumatically-actuated cylinders, and rack-and-pinion gear
mechanisms.
Preferably, each elbow guide 25 has, at its radially inward end, a freely
rotatable ball or
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CA 02540341 2011-06-06
roller 26 or other suitable friction-reducing means which will engage outer
surface 82 of
elbow 80 as it passes through opening 21.
In the exemplary arrangement shown in Fig. 8, elbow guides 25 are housed in
the
space between side plates 22, one or both of which are provided with an access
opening
28 for providing access to the radially outward portion of elbow guide 25C. It
will be
readily appreciated that the centering means could incorporate more than three
elbow
guides 25 without departing from the present invention. It will be further
appreciated that
it is not essential for elbow guides 25 to be housed between side plates 22 or
otherwise
disposed within the basic width of frame 20; for example, elbow guides 25 (or
other form
of centering means) could be mounted on the side of frame 20.
In the preferred embodiment, both opening 21 and elbow guides 25 are
configured and adapted to accommodate pipe elbows 80 having different outside
diameters Dl. This can be best seen from Fig. 8, in which the perimeters of a
larger-
diameter elbow 80L and a smaller-diameter elbow 80S are shown in stippled
outline. For
conceptual illustrative purposes, elbow guides 25A and 25B are shown engaged
with the
outer surface 82 of larger-diameter elbow 80L, and elbow guide 25C is shown
engaged
with the outer surface 82 of smaller-diameter elbow 80S. In actual use of the
apparatus,
of course, all of the elbow guides 25 would be radially extended to the same
extent, so as
to engage the outer surface 82 of whatever size of elbow 80 is to be clad.
Rotor 40, which may take any form suitable to provide the functionality
described
herein, has an elbow collar 42 which is movable in a radial path toward or
away from
primary axis X-1. In the preferred embodiment, as shown in Fig. 9, rotor 40
includes a
rotor arm 402 mounted to one face of a grounding wheel 404. One function
served by
grounding wheel 404 is to facilitate grounding of an elbow 80 being clad using
the
apparatus 10. A flexible grounding cable 406 of suitable length may be
connected
between grounding wheel 404 and elbow collar 42. As will be explained, elbow
80 is
mounted to elbow collar 42 in a manner that establishes an electrically
conductive
connection therebetween. As grounding wheel 404 rotates, it is in constant
sweeping
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CA 02540341 2006-03-20
contact with a grounding source 408 as conceptually illustrated in Fig. 9,
thereby
continuously grounding elbow 80 as rotor 40 rotates about primary axis X-1.
In the illustrated embodiments, rotor arm 402 has two parallel edges 410. For
explanatory purposes, rotor arm 402 may be considered as having first and
second
sections 402A and 402B, one on either side of primary axis X-1. An elbow
collar 42 is
mounted to first section 402A so as to be movable along rotor arm 402 in a
radial sense
relative to primary axis X-1. In the preferred embodiment, this radial
movability is
facilitated by providing elbow collar 42 with V-grooved rollers 42A which run
along
tracks 420 associated with edges 410 of rotor arm 402.
Although not essential to the invention, it is highly preferable for the
apparatus to
have counterweight means 44 mounted in association with second section 402B of
rotor
arm 402 to enhance smoothness of operation of the apparatus. Counterweight
means 44
will preferably be adapted so that its mass can be varied to suit particular
applications
(i.e., particular pipe elbow characteristics). As well, counterweight means 44
is
preferably mounted to second section 402B so as to be radially movable along
rotor arm
402 relative to primary axis X-1, with the radial movement of counterweight
means 44
coordinated with the radial movement of elbow collar 42 such that they will
both be
moving either radially outward or radially inward. As shown in Fig. 10, the
radial
movability of counterweight means 44 is preferably facilitated by providing
counterweight means 44 with V-grooved rollers 44A which run along tracks 420.
Elbow collar 42 is radially movable between an outboard position away from
primary axis X-1 (as shown in Figs. 5, 6, 7, and 9) and an inboard position
nearer primary
axis X-1 (as shown in Figs. 3 and 4). Similarly, counterweight means 44 is
radially
movable between an outboard position away from primary axis X-1 (as in Figs.
5, 6, 7,
and 9) and an inboard position nearer primary axis X-1 (as in Figs. 3 and 4).
In the
preferred embodiment, the coordinated radial movement of elbow collar 42 and
counterweight means 44 along rotor arm 402 is enabled by a pair of spaced,
parallel rack
gears 45A and 45B as shown in Fig. 9. Rack gear 45A is connected to elbow
collar 42,
and is of sufficient length to extend at least slightly beyond primary axis X-
1 and to a
21
CA 02540341 2006-03-20
first side thereof when elbow collar 42 is in its outboard position, with the
teeth of rack
gear 45A oriented toward primary axis X-1. Similarly, rack gear 45B is
connected to
counterweight means 44 and extends at least slightly beyond primary axis X-1
and to a
second side thereof when counterweight means 44 is in its outboard position,
with the
teeth 45C of rack gear 45B oriented toward primary axis X-1 (and thus toward
the teeth
of rack gear 45A). Guide rollers 450 may be mounted to rotor arm 402 so as to
engage
the non-toothed outer edges 45D of rack gears 45A and 45B. As indicated in
Fig. 9 (and
as explained in greater detail elsewhere in this specification), when rotor 40
is mounted to
elbow carriage 30, inner end 48A of secondary drive shaft 48 extends through
rotor 40
and has a pinion gear 480 which engages rack gears 45A and 45B (in a manner
described
later in this specification). Accordingly, rotation of secondary drive shaft
48 relative to
rotor 40 will cause rotation of pinion gear 480, which in turn will cause rack
gears 45A
and 45B to move elbow collar 42 and counterweight means 44 radially inward
(toward
their inboard positions) or outward (toward their outboard positions),
depending on the
direction of rotation of secondary drive shaft 48.
As may be seen from Figs. 3-7, 9, 14, and 15, elbow collar 42 has a pair of
spaced
side arms 42B extending toward stationary frame 20. A swivel axis X-2 passes
through
side arms 42B in an orientation such that swivel axis X-2 always lies in a
plane
perpendicularly transverse to primary axis X-1 irrespective of the radial
position of elbow
collar 42 and irrespective of the rotational position of rotor 40. In the
illustrated
embodiment, each side arm 42B has a pivot pin 42C aligned with swivel axis X-
2, for
pivoting engagement with a mounting ring 81 which may be temporarily connected
to
elbow 80 (by use of clamps, spot welding, and/or other suitable means).
Mounting ring
81, which is conceptually illustrated in Fig. 15, may be of any suitable
construction.
When elbow 80 has been properly mounted in elbow collar 42, swivel axis X-2
will pass
through a point on the curved centreline 94 of elbow 80.
Weld arm 60 is sinuously configured such that it can fit, without
interference,
inside a pipe elbow 80 passing through pipe opening 21 of frame 20. As
indicated in Fig.
14, weld arm 60 may be configured to fit inside several different sizes of
elbows of
different diameters (as indicated for illustrative purposes by elbow outlines
801, 802, and
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CA 02540341 2006-03-20
803). Weld arm 60 is rotatable about primary axis X-1 in coordination with the
rotation
of rotor 40 (and the corresponding rotation of pipe elbow 80) about primary
axis X-1,
such that weld arm 60 will remain non-interferingly disposed within elbow 80
as it
rotates.
Fig. 10 illustrates a weld arm 60 in accordance with the preferred embodiment.
Weld arm 60 has a rigid outer case 62 enclosing an internal passage 64
extending from
drive end 60D to free end 60F of weld arm 60. To provide the general shape
required for
weld arm 60, outer case 62 has a series of segments, with adjacent segments
being
connected at nodes 66 where direction changes occur. A weld head linkage 63 is
disposed within passage 64, and a weld head 70 is connected to linkage 63 at
free end
60F of weld arm 60. Weld head linkage 63 is adapted such that weld head 70
will not
rotate as weld arm 60 rotates about primary axis X-1, so that the welding head
can
maintain a constant welding position. In the illustrated embodiment, weld head
linkage
63 includes a train of elongate shafts 65 mounted inside the weld arm using
suitable
bearings. Where two shafts 65 meet at a node 66, they engage each other by
means of
bevel gears mounted to the ends of shafts 65 (and generally indicated by
reference
numeral 68 in Fig. 10). Bevel gears 68 allow angularly-offset shafts 65 to
"walk around"
each other as weld arm 60 rotates. However, shaft section 65A nearest the weld
head
(and to which weld head 70 is mounted) is concentric with primary axis X-1,
and
therefore will remain non-rotatingly fixed in space as outer case 62 of weld
arm 60
rotates about primary axis X-1.
Each shaft 65 has a longitudinal central passage 67, and each bevel gear 68
has a
central opening in communication with the central passages 67 of adjacent
shafts 65, so
as to provide a continuous internal passage 69 for feeding weld wire 74 to
weld head 70.
As previously noted, continuous internal passage 69 may also be used to run
additional
utilities such as gas, air, and vacuum lines, as well as power lines and fiber
optic cable to
weld head 70.
In the illustrated embodiments, weld arm 60 passes through a turntable 58
mounted to inner end 50A of weld arm carriage 50 so as to be rotatable about
primary
23
CA 02540341 2006-03-20
axis X-1, with drive end 60D of weld arm 60 being rotatably mounted in
association with
outer end 50B of weld arm carriage 50 so as to be concentric with primary axis
X-1. The
point at which weld arm 60 passes through turntable 58, at a fixed distance
radially
outward from primary axis X-1, is indicated by reference character 60A.
Turntable 58
may be of any suitable construction that achieves these operational
requirements. In the
preferred embodiment, as shown in Fig. 11, turntable 58 is in the form of a
disk rotatably
mounted to weld arm carriage 50 and guided by a plurality of guide rollers 59
mounted to
weld arm carriage 50 around the periphery of turntable 58.
A suitable weld arm rotary drive means is provided to rotate weld arm 60 about
primary axis X-1. By virtue of its sinuous configuration, weld arm 60 will
rotate in an
orbital fashion (much like a skipping rope). The particular nature of the weld
arm rotary
drive means is not critical to the invention; what is important is that it
will rotate weld
arm 60 about primary axis X-1 in synchronous coordination with the rotation of
rotor 40
and elbow 80 about primary axis X-1. In alternative embodiments, the weld arm
rotary
drive means could rotate turntable 58 directly. In the preferred embodiment,
however,
and as will be described in detail further on in this specification, the weld
arm rotary
drive means is directly engaged with drive end 60D of weld arm 60, and even
more
preferably will be integrated with the elbow carriage drive means..
In the preferred embodiment of the invention, weld arm 60 is movable in either
direction parallel to primary axis X-1, to facilitate cladding of a straight
transition section
86 on either end of elbow 80. In the illustrated embodiments, this mode of
movement is
enabled by having weld arm carriage 50 movable in either direction parallel to
primary
axis X-1. For this purpose, weld arm carriage 50 in the preferred embodiment
is mounted
with rollers 53 that run on tracks 54, with any suitable weld arm carriage
drive means
(conceptually indicated by reference character 51 in Fig. 14) being provided
for moving
weld arm carriage 50 parallel to primary axis X-1 as may be required. Persons
skilled in
the art will readily appreciate that various types and combinations of
rollers, tracks, and
drive mechanisms could be used for this purpose, and that other means of
facilitating
guided movability of weld arm carriage 50 are possible without departing from
the
present invention.
24
CA 02540341 2011-06-06
In Figs. 3-7, weld arm carriage 50 is shown positioned atop an elevated
stationary
base 56, but this arrangement is exemplary only, and not essential to the
invention.
Weld head 70 may be of any suitable type capable of being fed with continuous
welding wire 74, from a spool (not shown) associated with weld arm carriage
50, through
internal passage 620 of weld arm 60. By using a suitable weld head extension
72, weld
head 70 can be easily adapted to clad pipe elbows 80 of different diameters
while
maintaining a desired welding wire "stick-out". This can be appreciated
particularly well
with reference to Fig. 5, in which welding wire 74 may be seen extending
downward
from weld head extension 72.
The preferred mode of operation of the apparatus 10 may now be understood with
reference to Figs. 3-7. A pipe elbow 80 is positioned within pipe opening 21
of
stationary frame 20, preferably in a medial orientation in which approximately
equal
portions of elbow 80 extend from either side of frame 20, with a first end 80A
of elbow
80 mounted to elbow cradle 42 so as to be swivelable about swivel axis X-2,
with swivel
axis X-2 passing through curved centreline 94 perpendicular to curvature plane
96, and
with center of rotation 90 of elbow 80 substantially coinciding with reference
plane RP.
The initial set-up of elbow 80 in the apparatus 10 may be carried out in more
than
one way, but it will preferably commence with the positioning of elbow 80
generally as
shown in Fig. 5. Suitable hoist means (not forming part of the invention) may
be
provided to facilitate positioning of elbow 80. Weld arm carriage 50 is then
moved
toward frame 20 so as to position weld arm 60 inside elbow 80 with weld head
70 in
close proximity to reference plane RP. At this stage, the longitudinal
position of weld
arm carriage 50 is temporarily fixed. Elbow carriage 30 is then moved
longitudinally
toward frame 20, while elbow cradle 42 is moved radially toward primary axis X-
1 (in
coordinated fashion with the movement of elbow carriage 30 so as to keep
center of
rotation 90 of elbow 80 substantially coincident with reference plane RP),
until the
apparatus 10 and elbow 80 are oriented generally as shown in Fig. 3. As shown
in Fig. 3,
elbow 80 may be considered as being in a "medial" position (meaning that it is
25
CA 02540341 2006-03-20
approximately centered relative to frame 20), with elbow cradle 42 (and
counterweight
means 44) in an inboard position (relative to primary axis X-1).
To begin applying metallic cladding to the interior surfaces of elbow 80, from
a
starting point at which elbow 80 is in a medial position as described, the
elbow carriage
drive means and the weld arm rotary drive means are actuated such that:
= rotor 40 continuously rotates clockwise about primary axis X-1 (note that
unless
otherwise indicated expressly or by context, all references herein to
clockwise or
counterclockwise rotation are as viewed looking from elbow carriage 30 toward
weld arm carriage 50);
= elbow cradle 42 continuously moves along rotor 40 in a radial direction away
from primary axis X-1;
= elbow carriage 30 continuously moves longitudinally away from frame 20
parallel
to primary axis X-1;
= weld arm 60 continuously rotates clockwise about primary axis X-1, in
synchronization with the rotation of rotor 40; and
= welding wire 74 is continuously fed to weld head 70, with the welding
circuit
being energized and with elbow 80 being suitably grounded;
with the longitudinal movement of elbow carriage 30 and the radial movement of
elbow
cradle 42 being coordinated such that center of rotation 90 of elbow 80 at all
times
remains substantially coincident with reference plane RP.
In order for the movement of elbow 80 through pipe opening 21 to meet the
foregoing operational criteria, the incremental distance AX that elbow
carriage 30 moves
toward or away from stationary frame 20 during each revolution of rotor 40,
and the
incremental distance AY that elbow carriage 30 moves radially toward or away
from
primary axis X-1 during each revolution of rotor 40, will vary with each
revolution. AX
and AY will correspond to the sides of a right triangle having a hypotenuse
equal to pitch
26
CA 02540341 2006-03-20
P (as previously defined), and these values will vary according to the
position of elbow
80 relative to stationary frame 20. This basic geometric relationship will
apply regardless
of the rotational position of rotor 40.
The constantly changing nature of AX and AY during the operation of the elbow
carriage drive means can be readily understood by considering an example case
where a
90-degree elbow is being clad using the apparatus of the invention. This case
is
schematically illustrated in the free-body diagrams shown in Figs. 12A and
12B. Fig.
12A shows a 90-degree elbow 80 in an initial medial position within pipe
opening 21
(i.e., centered about reference plane RP). In this initial position, the angle
0 between
reference plane RP and a line drawn between swivel axis X-2 and center of
curvature 90
is 45 (01). When elbow 80 is rotated counterclockwise about center of
curvature 90
from this initial medial position by a distance P (as measured at curved
centreline 94), the
incremental distance AX1 through which swivel axis X-2 moves horizontally will
be
approximately equal to P cosine 0, and the incremental distance AY1 through
which
swivel axis X-2 moves radially relative to primary axis X-1 will be
approximately equal
to P sine 01. Since 01 is 45 in Fig. 12A, and since sine 45 equals cosine 45
(i.e.,
0.707), AX1 and AY1 will both be approximately equal to 0.707 P as elbow 80
begins to
move from its initial medial set-up.
Fig. 12B illustrates the situation after elbow 80 has been rotated about 15
from
its initial medial position, such that angle 0 now equals 60 (02). When elbow
80 is
rotated further from this position by a distance P. the incremental horizontal
movement
AX2 of swivel axis X-2 will be approximately P cos 02, or 0.5P, while the
incremental
radial movement AY2 of swivel axis X-2 will be approximately P sin 02, or
0.866 P.
Accordingly, it can be readily appreciated that the required horizontal
movement of
elbow carriage 30 away from stationary frame 20 decreases with each revolution
of rotor
40, while the required radial movement of elbow collar 42 radially away from
primary
axis X-1 increases with each revolution of rotor 40. As elbow 80 continues
moving
through pipe opening 21 and approaches the orientation at which angle 0 equals
90 , AX
will approach zero (cos 90 being equal to zero) and AY will approach P (sin
90 being
equal to 1.0).
27
CA 02540341 2011-06-06
The rate of rotation of rotor 40 and weld arm 60 is selected such that inner
surface
84 of elbow 80 rotates past weld head 70 at an average rate (i.e., an average
circumferential speed) corresponding to the desired average rate of deposition
of the
cladding bead (typically measured in inches per minute). This average
circumferential
speed will vary to suit particular applications, depending on the physical
characteristics
of elbow 80, the size and metallurgical properties of the weld wire being
used, and the
capabilities of the welding equipment used to energize the system.
By virtue of the coordinated movements of elbow carriage 30 and elbow cradle
42, curved centreline 94 of elbow 80 will pass through reference plane RP at a
constant
average rate K. In the typical preferred usage of the apparatus, in which it
is desired to
apply a dense pattern of helical cladding beads to inner surface 84 of elbow
80, rate K
will be equal to one average bead width per revolution about primary axis X-1.
The bead
width thus may also be considered as equivalent to the average pitch P of the
helical
cladding bead (which commonly will be approximately 3/16 of an inch, but other
average
pitches may be used to suit specific applications). Accordingly, average rate
K may also
be stated by the expression, K = P per revolution.
Because of the curvature of elbow 80, the width W1 covered by each pass of
weld
head 70 at inner surfaces 84 farthest from center of curvature 90 will be
greater than
average pitch P, and the covered pass width W2 at inner surfaces 84 closest to
center of
curvature 90 will be less than average pitch P. This inherent geometric
relationship is
illustrated in Fig. 13. Although the apparatus 10 of the invention can be
operated such
that rotor 40 and weld arm 60 rotate about primary axis X-1 at a constant
rate, this will
result in a cladding bead 77 that has varying dimensional properties from one
position to
another around the perimeter of elbow 80 (assuming that welding wire 74 feeds
to weld
head 70 at a constant rate). This result might be acceptable in some
applications. It is
highly preferable, however, for cladding bead 77 to be of substantially
uniform average
thickness T, (as measured radially with reference to curved centreline 94).
For this reason, the preferred embodiment of apparatus 10 incorporates
variable-
rate rotation means, for varying the rate at which rotor 40 and weld arm 60
rotate about
28
CA 02540341 2011-06-06
primary axis X-1 during each revolution. The rate of rotation will increase as
rotor 40
approaches the six-o'clock position (as in Figs. 3 and 5), and it will
decrease as rotor 40
approaches the twelve-o'clock position (as in Figs. 4 and 6). As a result of
this variable-
rate rotation, the average thickness T, of cladding bead 77 can be kept
substantially
uniform. The rotational speed variations required to achieve this result can
be easily
determined using well-known methods of trigonometric analysis.
Fig. 4 illustrates the configuration of elbow 80, rotor 40, and weld arm 60 in
the
twelve-o'clock position, after a 1800 rotation from the position shown in Fig.
3. It can be
readily appreciated from this view how weld arm 60 remains disposed within
elbow 80
without interference therewith, while weld head 70 remains spatially fixed.
Fig. 4 also
illustrates how center of rotation 90 of elbow 80 remains substantially
coincident with
reference plane RP, while orbitally rotating about primary axis X-1.
The apparatus 10 is operated in the manner described above until elbow 80 is
in a
primary terminal position generally as shown in Fig. 5 (or Fig. 6). In this
context,
"primary terminal position" means that the weld head has reached a point where
cladding
of inner surface 84 of the curved portion of elbow 80 is intended to be
stopped. At this
stage (with a first half of elbow 80 having received a continuous internal
helical cladding
bead), elbow 80 is disengaged from apparatus 10, turned 180 , and remounted to
apparatus 10 in a medial position, with weld head 70 positioned to begin
depositing a
cladding bead near the point where the first cladding bead began. Apparatus 10
is then
reactuated as previously described, to deposit a continuous helical cladding
bead on the
second half of elbow 80.
In the Figures, elbow 80 is shown with a straight transition 86 which also can
be
clad using the apparatus 10. When elbow 80 has reached a primary terminal
position
(i.e., the point at which the straight centreline of transition 86 coincides
with primary axis
X-1), the longitudinal movement of elbow carriage 30 and the radial movement
of elbow
cradle 42 are stopped, but rotor 40 continues to rotate about primary axis X-
1. As well,
the variable-rate rotation means is disengaged, such that rotor 40 now rotates
at a
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CA 02540341 2006-03-20
constant rate. The weld arm rotary drive means is preferably (but not of
necessity)
disengaged at this stage as well.
The effect of this change in the mode of operation of apparatus 10 is that
straight
transition 86 will be rotated axially about primary axis X-1 at a constant
rate. Weld arm
carriage 50 is then actuated so as to move longitudinally away from frame 20,
at a
constant rate of travel corresponding to the previously-referenced rate K
(i.e., a
longitudinal distance P per revolution of rotor 40). As a result, weld arm 60
is drawn
toward the outer end 86A of transition 86, with weld head 70 depositing a
continuous
helical cladding bead to the inner surface thereof. Because transition 86 is
straight, and
because rotor 40 rotates at a constant rate during this phase of the
operation, the helical
bead deposited on the inner surface of transition 86 will be of substantially
uniform width
and thickness (provided that the wire feed speed remains constant).
When the bead reaches a secondary terminal position at or near the end of
transition 86 as illustrated in Fig. 7 (with a first half of elbow 80 and the
associated
transition 86 having received a continuous internal helical cladding bead),
elbow 80 is
disengaged from apparatus 10, turned 180 , and remounted to apparatus 10 as
previously
described, to begin cladding the second half of elbow 80 (and any associated
transition
86).
In accordance with an alternative embodiment of the apparatus and an
alternative
procedure, a transition 86 may be clad without requiring longitudinal movement
of weld
arm carriage 50. Instead, when elbow 80 has reached a primary terminal
position (as
shown in Fig. 5), elbow carriage 30 may be moved longitudinally at constant
rate K away
from frame 20, with elbow cradle 42 remaining in a set outboard position (as
shown in
Figs. 5 and 6). Transition 86 will thus be drawn through pipe opening 21 while
it
continues to rotate at a constant rate, while weld head 70 remains
substantially coincident
with reference plane RP.
As previously noted, various means may be devised for achieving the required
coordinated longitudinal travel of elbow carriage 30, radial travel of elbow
cradle 42 (and
counterweight means 44), and rotational travel of rotor 40 and weld arm 60, in
order for
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CA 02540341 2006-03-20
apparatus 10 to clad an elbow 80 in accordance with the procedure described
above. In
the preferred embodiment, these operational features are provided by means of
a
coordinated primary drive mechanism 100 as illustrated in Figs. 16-20.
Referring first to
Fig. 15, a primary drive motor 110 is operably connected to a primary rotation
mechanism 120 by means of a swivelling drive linkage 115 as explained in
greater detail
below.
As shown in Fig. 16, the components primary rotation mechanism 120 include a
sliding drive plate 130, first and second rack plates 140A and 140B, and a
circular ring
gear 150. Sliding drive plate 130 has a centerpoint 131 and a circular
perimeter 132, with
perimeter 132 being interrupted by a gap 134 opening into a radial slot 136
having a
radial axis 137 and extending inward from perimeter 132 to a point beyond
centerpoint
131. Radial slot 136 is bounded by two straight edges 138 which are parallel
to and
equidistant from radial axis 137.
As shown in Fig. 16, and except as indicated below, rack plates 140A and 140B
may be substantially similar to each other. Each has a centerpoint 141A or
141B (for
rack plates 140A and 140B respectively) and a circular perimeter 142A or 142B,
with
perimeter 142A (or 142B) being interrupted by a gap 144A (or 144B) opening
into a
radial slot 146A (or 146B) which extends inward from perimeter 142A (or 142B)
to a
point beyond centerpoint 141A (or 141B). Radial slot 146A (or 146B) has a
radial axis
147A (or 147B), and is bounded on one side by a rack gear 148A (or 148B)
offset from
and parallel to radial axis 147A (or 147B). As viewed in Fig. 16, each rack
gear 148A or
148B is offset an equal distance, and in a clockwise sense, from its
corresponding radial
axis 147A or 147B. The width of each rack gear 148A or 148B, as measured
perpendicular to the plane of its corresponding rack plate, is greater than
the thickness of
its corresponding rack plate, and preferably at least twice that thickness.
Each rack gear
148A or 148B is mounted to its corresponding rack plate 140A or 140B so as to
be flush
with one face of thereof, with the excess rack width projecting beyond the
other face of
the rack plate. More specifically, and with reference to the views shown in
Figs. 16 and
19, rack gear 148A is flush with the far face of rack plate 140A, and rack
gear 148B is
flush with the near face of rack plate 140B.
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CA 02540341 2006-03-20
Ring gear 150 has a centerpoint 151, a continuous circular outer perimeter 152
with continuous gear teeth 153, and a smooth concentrically circular inner
perimeter 154.
Rack plate 140A is concentrically connected to sliding drive plate 130, with
radial
axis 147A of rack plate 140A aligned with radial axis 137 of sliding drive
plate 130, and
with gap 144A of rack plate 140A aligned with gap 134 of sliding drive plate
130. The
resultant assembly of rack plate 140A and sliding drive plate 130 may be
referred to as
slide assembly 160.
Ring gear 150 is concentrically connected to rack plate 140B by means of
suitable
spacers and fastening means, so as to provide a space 156 between ring gear
150 and rack
plate 140B. The resultant assembly of ring gear 150 and rack plate 140B may be
referred
to as slide assembly 170.
Fig. 18 is a side view illustrating how slide assemblies 160 and 170 are
mounted
in association with primary drive shaft 46. Primary drive shaft 46 has a rotor
end 46A
which extends from elbow carriage 30 toward stationary frame 20, and
terminates at an
outer end 46B disposed within elbow carriage 30. A sleeve 200 is positioned
over rotor
end 46A of primary drive shaft 46 so as to be freely and concentrically
rotatable about
primary drive shaft 46. Sleeve 200 has a first end 202 and a second end 204,
plus a first
gear wheel 210 concentrically mounted around sleeve 200 toward first end 202
as shown.
A second gear wheel 220 is concentrically mounted to second end 204 of sleeve
200;
second gear wheel 220 has a central opening through which primary drive shaft
46
passes, such that second gear wheel 220 is free to rotate with sleeve 200
about primary
axis X-1, independently of primary drive shaft 46. For initial assembly
purposes, slide
assembly 170 may be concentrically positioned over rotor end 46A of primary
drive shaft
46, with ring gear 150 disposed toward elbow carriage 30, such that rack gear
148B
engages the teeth of second gear wheel 220 (as best seen in Fig. 19). Slide
assembly 160
is then concentrically positioned over rotor end 46A of primary drive shaft
46, with
sliding drive plate 130 disposed toward rotor end 46A, and such that rack gear
148A also
engages the teeth of second gear wheel 220. When slide assemblies 160 and 170
have
been thus installed, rack gear 148A and rack gear 148B are aligned with each
other, on
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CA 02540341 2006-03-20
opposite sides of second gear wheel 220 (as may be best seen in Fig. 19), and
slide
assemblies 160 and 170 are, for the moment, concentric with primary drive
shaft 46.
As shown in Fig. 18, a hub flange 230 is then connected to rotor end 46A of
primary drive shaft 46. Hub flange 230 has a central opening to allow
secondary drive
shaft 48 to pass through hub flange 230 as shown. Hub flange 230 has a first
face 232
disposed toward elbow carriage 30 and toward sliding drive plate 130, and a
second face
234 to which rotor 40 is mounted (preferably by means of a plurality of
mounting bolts
41). A set of four drive rollers 240 are positioned in association with outer
face 232,
radially equidistant from the center of hub flange 230 (i.e., equidistant from
primary axis
X-1) and forming a rectilinear pattern such that the drive rollers 240 are
disposed within
radial slot 136 of sliding drive plate 130, with one pair of drive rollers 240
engaging each
of the straight edges 138 of sliding drive plate 130.
In the preferred embodiment, primary drive motor 110 is mounted to elbow
carriage 30 and therefore moves longitudinally therewith. As previously
mentioned,
primary drive motor 110 is operably connected to primary rotation linkage 120
by means
of swivelling drive linkage 115. As may be seen in Figs. 15 and 20, primary
drive motor
110 has an output shaft 112 oriented parallel to primary axis X-1. A sprocket
114A is
mounted to output shaft 112 so as to be rotated thereby.
In the preferred embodiment, swivelling drive linkage 115 includes a rigid
link
117, the outboard end 117A of which is mounted over output shaft 112 adjacent
to
sprocket 114A, but so as to be freely rotatable about output shaft 112
independently of
the rotation thereof. As shown in Figs.14A and 18, rigid link 117 preferably
comprises a
pair of steel bars 117C, although it will be appreciated that alternative
constructions using
on a single bar 117C are possible. Rotatably and concentrically mounted to
inboard end
117B of rigid link 117 (using suitable bearings) are a sprocket 114B and a
ring gear drive
pinion 122, as may be seen in Fig. 20. A drive chain 119 is disposed around
sprockets
114A and 114B, such that actuation of primary drive motor 110 will cause
sprockets
114A and 114B to rotate at the same speed, while swivelling drive linkage 115
(comprising sprockets 114A and 114B, rigid link 117, and drive chain 119) is
free to
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CA 02540341 2006-03-20
swivel independently about output shaft 112. The sizes of sprockets 114A and
114B and
ring gear drive pinion 122 will be selected to suit desired mechanical ratios,
in
accordance with well-known mechanical engineering principles.
Also forming part of swivelling drive linkage 115 (as may be seen in Figs. 16
and
20) is a roller bracket 250 mounted to the inboard end 117B of rigid link 117
so as to be
swivelable about the common axis of sprocket 114B and ring gear drive pinion
122.
Roller bracket 250 is fitted with a pair of retainer rollers 252 arranged such
that the axes
of retainer rollers 252 are the vertices at the base of an isosceles triangle,
with the axis of
sprocket 114B and ring gear drive pinion 122 being the third vertex. Roller
bracket 250
is mounted to ring gear 150 such that ring gear drive pinion 122 engages gear
teeth 153
of ring gear 150 while retainer rollers 252 engage the smooth inner perimeter
154 of ring
gear 150. As shown in Fig. 18, each roller 252 preferably has a
circumferential flange
254 on one side, to help keep retainer rollers 252 laterally in position on
ring gear 130. In
the illustrated embodiment, roller bracket 250 is disposed adjacent to the
inner side of
ring gear 150 (i.e., nearer elbow carriage 30). By virtue of the space 156
provided
between ring gear 150 and rack plate 140B, flanges 254 will not interfere with
rack plate
140B as retainer rollers 252 travel along inner perimeter 154 of ring gear
150.
Having reference to Fig. 20, it may now be appreciated that when primary drive
motor 110 is actuated, with slide assemblies 160 and 170 clustered together so
as to
remain concentric with primary axis X-1, the rotation of ring gear drive
pinion 122 will
cause rotation of ring gear 150 (and, therefore, slide assemblies 160 and 170)
concentrically about primary axis X-1. This rotation will be transferred from
sliding
drive plate 130 to hub flange 230 by means of drive rollers 240, in turn
causing rotation
of primary drive shaft 46 and rotor 40. When the apparatus is in the
configuration
described (i.e., with slide assemblies 160 and 170 concentric), all rotational
movement
will be at a constant rate, which will be desirable when cladding a straight
transition 86 of
a pipe elbow 80 as previously discussed.
However, for purposes of cladding the curved portion of a pipe elbow 80, slide
assemblies 160 and 170 are spread apart along their coincident radial axes
(147A/137 and
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CA 02540341 2006-03-20
147B, respectively), such that their respective centerpoints 141A and 141B
will be offset
by an equal distance Q from primary axis X-1 (as shown in Fig. 17). Now, the
rotation
of gear wheel 122 will still cause slide assembly 170 to rotate about primary
axis X-1, but
the rotation will be eccentric due to the fact that centerpoint 141B of slide
assembly 170
is offset from primary axis X-1. The result of this eccentric rotation is that
the rate of
rotation of the combined rotational linkage assembly (i.e., slide assemblies
160 and 170)
about primary axis X-1 will vary during each revolution, as will the rate of
rotation
imparted to primary drive shaft 46 by drive rollers 240 (which remain
effective to rotate
hub flange 230 despite being offset from centerpoint 131 of sliding drive
plate 130, since
they remain at all times in contact with straight edges 138 of radial slot 136
of sliding
drive plate 130 irrespective of the offset of slide assemblies 160 and 170).
Whereas rigid
link 117 of swivelling drive linkage 115 will remain in a fixed spatial
position when slide
assemblies 160 and 170 are concentric with primary axis X-1, when slide
assemblies 160
and 170 are offset, rigid link 117 will swivel about output shaft 112 and
oscillate between
a lower position 117L and an upper position 117U as the rotational linkage
assembly
rotates (i.e., one oscillation cycle for each rotation of the rotational
linkage assembly).
The eccentric rotation of offset slide assemblies 160 and 170 may be
particularly
well understood with reference to Fig. 20. In Fig. 20, slide assembly 170
(incorporating
gear 150) is shown in an uppermost position, with rigid link 117 being in
upper position
117U. At this stage, slide assembly 160 would be in a position corresponding
to circle
C-2 in Fig. 20. When slide assemblies 160 and 170 have rotated 180 so as to
be in a
position corresponding to circle C-2, their positions will be correspondingly
reversed.
When slide assemblies 160 and 170 have rotated 90 , their positions will
correspond to
circles C-1 and C-3 (or vice versa). Accordingly, it will be appreciated that
slide
assemblies 160 and 170, with each revolution about primary axis X-1, will
describe an
outer circular path corresponding to circle C-4 in Fig. 20, said circle C-4
being concentric
with primary axis X-1 and having a radius that will vary depending on offset
distance Q.
The variability of the rotation speed will vary directly with the offset
distance Q.
The appropriate offset distance Q for a given application may be easily
determined using
known mathematical calculations (or, alternatively, by trial and error). More
particularly,
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CA 02540341 2006-03-20
the appropriate offset will depend on the relative curvature ratio of the
elbow 80 being
clad (i.e., the relative curvature ratio, for purposes of this specification,
being defined as
the ratio of curvature radius 92 to inner elbow radius R2). In other words, an
elbow
having a lower relative curvature ratio will require a greater offset than an
elbow having a
larger relative curvature ratio.
It will be appreciated that slide assemblies 160 and 170 need to be maintained
in a
desired relationship (i.e., concentric or offset) as they rotate about primary
axis X-1. In
the illustrated embodiment, the actuation of primary drive motor 110 rotates
primary
drive shaft 46 clockwise when actuation begins with elbow 80 in a medial
position. As
shown in Fig. 15A, outer end 46B of primary drive shaft 46 has a
concentrically-mounted
gear wheel 310 which engages (and rotates counterclockwise) an idler gear 320
which in
turn engages (and rotates clockwise) a gear wheel 330 mounted to a first
auxiliary shaft
340 oriented parallel to primary axis X-1. First auxiliary shaft 340 has a
centroidal axis
X-3, a first end 340A extending toward inner end 30A of elbow carriage 30,
plus a
second end 340B. First end 340A of first auxiliary shaft 340 extends into a
first cluster
gear 350, which comprises:
= an outer case 352 having a front end 352F and a back end 352B;
= a bevel gear 354 rotatable about an axis perpendicular to and passing
through axis
X-3 of first auxiliary shaft 340;
= a bevel gear 342 mounted in association with back end 352B of outer case 352
and rotatable about axis X-3 independently of outer case 352, so as to be
operably
engaged with bevel gear 354;
= a bevel gear 362 mounted in association with front end 352F of outer case
352
and rotatable about axis X-3 independently of outer case 352, so as to be
operably
engaged with bevel gear 354; and
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CA 02540341 2006-03-20
= an exterior gear wheel 356 concentric with axis X-3 and fixedly mounted to
outer
case 352 in association with front end 352F, such that rotation of gear wheel
356
will cause corresponding rotation of first cluster gear 350 as a whole.
First end 340A of first auxiliary shaft 340 engages bevel gear 342 of first
cluster
gear 350. A second auxiliary shaft 360, coaxial with first auxiliary shaft
340, has a first
end 360A and a second end 360B. Second end 360B extends through an opening in
exterior gear wheel 356 so as to operably engage bevel gear 362 of first
cluster gear 350.
First end 360A is fitted with a gear wheel 370 which engages first gear wheel
210 of
sleeve 200, which is rotatably disposed around primary drive shaft 46.
As shown in Fig. 15A, the apparatus includes a slide adjustment mechanism 500
for setting or adjusting the relative positions of slide assemblies 160 and
170 (i.e.,
concentric or offset). Slide adjustment mechanism 500 includes a reversible
auxiliary
motor 510 having a drive shaft 520 fitted with a gear wheel 530 which engages
exterior
gear wheel 356 of first cluster gear 350. Gear wheel 356 thus serves to
restrain rotation
of first cluster gear 350 when auxiliary motor 510 is idle, and to rotate
first cluster gear
350 upon actuation of auxiliary motor 510. It can be appreciated, therefore,
that auxiliary
motor 510 can be actuated to rotate first cluster gear 350 in a first
direction (clockwise or
counterclockwise as the case may be), thereby rotating second auxiliary shaft
360 and
gear wheel 370 in the same first direction, thereby causing rotation (in the
opposite
direction) of first gear wheel 210, sleeve 200, and second gear wheel 220. The
ultimate
effect of these mechanical interactions is that second gear wheel 220 rotates
relative to
primary shaft 46, with the consequence that second gear wheel 220
correspondingly
rotates relative to slide assemblies 160 and 170, and, due to the engagement
of second
gear wheel 220 with rack gears 148A and 148B, shifting the positions of slide
assemblies
160 and 170 relative to each other (i.e., adjusting offset distance Q).
As previously explained, clockwise rotation of primary drive shaft 46 will
result
in clockwise rotation of first auxiliary shaft 340, which in turn engages
first cluster gear
350 and results in counterclockwise rotation of second auxiliary shaft 360 due
to the
operative interaction of bevel gears 342, 354, and 362. Second auxiliary shaft
360 in turn
37
CA 02540341 2006-03-20
rotates second gear wheel 220 on sleeve 200, so as to rotate sleeve 200
clockwise. The
various components of the mechanism described immediately above are sized and
configured in accordance with well-known engineering principles such that
sleeve 200
will be rotated at the same rate (i.e., constant or variable, depending on the
offset Q of
slide assemblies 160 and 170) as the rotation of primary drive shaft 46 and
rotor 40. This
rotation of sleeve 200, coordinated with that of rotor 40, results in second
gear wheel 220
remaining in its preset position relative to rack gears 148A and 148B, thus
maintaining
slide assemblies 160 and 170 in their preset relative positions despite their
rotation
around primary axis X-1.
The relative positions of slide assemblies 160 and 170 (i.e., concentric or
offset)
may be set by means of a slide adjustment mechanism 500. In the embodiment
illustrated
in Fig. 15A, slide adjustment mechanism 500 includes a reversible auxiliary
motor 510
having a drive shaft 520 fitted with a gear wheel 530 which engages exterior
gear wheel
356 of first cluster gear 350. When auxiliary motor 510 is not in operation,
the
engagement of gear wheel 530 and exterior gear wheel 356 is effective to
prevent rotation
of outer case 352 of first cluster gear 350 (as will typically be the desired
case during
elbow-cladding operations). However, actuation of auxiliary motor 510 in one
direction
or the other (as required in a given situation) will cause corresponding
rotation of outer
case 352 about axis X-3. This results in rotation of second auxiliary shaft
360 and its
attached gear wheel 370, in turn resulting in opposite rotation of first and
second gear
wheels 210 and 220 attached to sleeve 200. Since these rotations are
independent of the
apparatus's primary drive mechanism 100, and thus independent of the rotation
of
primary drive shaft 46, the rotation of second gear wheel 220 results in
operative
engagement between second gear wheel 220 and rack gears 148A and 148B, thereby
adjusting the relative positions of slide assemblies 160 and 170 (as may be
readily
appreciated with reference to Fig. 17).
Accordingly, slide adjustment mechanism 500 may be actuated to spread slide
assemblies 160 and 170 radially apart or to draw them inward toward a
concentric
configuration (i.e., with offset distance Q equal to zero), as desired
operational
parameters may require. Subject to any fine adjustment that might be desirable
or
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CA 02540341 2006-03-20
necessary during operation of the apparatus, the relative positions of slide
assemblies 160
and 170 will typically be set only once (i.e., in a desired offset position)
for purposes of
cladding the curved portion of a pipe elbow 80, and then returned to adjusted
the
concentric configuration for purposes of cladding a straight transition
section 86 of elbow
80.
In the preferred embodiment of the invention, adjustment mechanism 500 is
adapted such that slide assemblies 160 and 170 may be set in a desired
configuration
selected from a variety of relative curvature ratios (as previously defined),
using control
switches or selector means of any suitable type. Accordingly, the appropriate
configuration of slide assemblies 160 and 170 will depend on the relative
curvature ratio
of elbow 80 to be clad, irrespective of its diameter. For example, the same
slide
assembly setting would be used for an elbow 80 having a 12-inch diameter as
for an
elbow 80 having a 24-inch diameter, if the radius of curvature 92 of the 24-
inch elbow is
twice that of the 12-inch diameter elbow.
In the preferred embodiment, the apparatus 10 is adapted such that slide
assemblies 160 and 170 will be automatically moved to the concentric
configuration
when elbow 80 reaches a primary terminal position (as illustrated in Fig. 6)
at which
point weld head 70 has reached one end of the curved portion of elbow 80 and
it is
desired to begin cladding a straight transition section 86. This may be
achieved, for
example, by the use of limit switches in accordance with well-known
technology.
As previously discussed, the preferred mode of operation for the apparatus 10
of
the invention requires elbow 80 to be drawn through pipe opening 21 of
stationary frame
20 by means of incremental longitudinal movements of elbow carriage 30
coordinated
with incremental radial movements of elbow cradle 42, such that the center of
rotation 90
of elbow 80 at all times remains substantially coincident with reference plane
RP. To
achieve these operational criteria, the elbow carriage drive means 36 of the
preferred
embodiment includes a bull gear 600 located in association with outer end 30B
of elbow
carriage 30 and being pivotable about a spatially fixed vertical pivot axis Y-
1, as
illustrated in Figs. 21 and 21A. As shown, bull gear 600 preferably
corresponds
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CA 02540341 2006-03-20
approximately to a 45-degree circular segment having a curved perimeter 602
with gear
teeth 602A, and bounded by side edges 604A and 604B. A first threaded shaft
610 is
disposed in a radial slot 601 in bull gear 600 adjacent to side edge 604A so
as to be
rotatable about a horizontal axis X-4 which passes through pivot axis Y-1, and
which will
sweep through an arc corresponding to any rotation of bull gear 600 about
vertical pivot
axis Y-1. First threaded shaft 610 has an inner end 610A adjacent pivot axis Y-
1 and an
outer end 610B adjacent toothed perimeter 602 of bull gear 600.
As best seen in Figs. 14A and 21A, inner end 610A of first threaded shaft 610
is
disposed within a first gear housing 620 mounted to bull gear 600. First gear
housing
620 encloses an upper bevel gear 622 and a lower bevel gear 624 connected by a
vertical
shaft 626 such that upper bevel gear 622 and lower bevel gear 624 will be
concurrently
rotatable about pivot axis Y-1. Inner end 610A of first threaded shaft 610 is
fitted with a
bevel gear 612 which engages lower bevel gear 624 within first gear housing
620, such
that rotation of lower bevel gear 624 about pivot axis Y-1 will cause rotation
of first
threaded shaft 610 about horizontal axis X-4. Outer end 610B of first threaded
shaft 610
passes through a threaded hub 630, which is disposed beneath and swivelably
connected
to a second gear housing 640 which houses a bevel gear 642 rotatable about a
vertical
axis Y-2 which passes through horizontal axis X-4 of first threaded shaft 610
and which
is movable along horizontal axis X-4 as the position of hub 630 and second
gear housing
640 is adjusted, as will be described below.
A smooth round shaft 650 having an inner end 650A and an outer end 650B
extends between first gear housing 620 and second gear housing 640, as shown
in Fig.
14A. At its inner end 650A, smooth shaft 650 is fitted with a bevel gear 652
which
engages upper bevel gear 622 inside first gear housing 620. The outer end 650B
of
smooth shaft 650 extends through second gear housing 640 such that second gear
housing
640 can slide along smooth shaft 650. However, smooth shaft 650 is also fitted
with a
bevel gear 654 which is keyed to smooth shaft 650 in such a way that bevel
gear 654 will
rotate with smooth shaft 650 while at the same time being free to slide along
smooth shaft
650. Bevel gear 654 is rotatably retained by second gear housing 640 such that
bevel
gear 654 engages bevel gear 642.
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CA 02540341 2006-03-20
As shown in Figs. 21 and 21A, the apparatus also includes a second threaded
shaft
660 having a horizontal centroidal axis X-5, an inner end 660A fitted with a
bevel gear
662, and an outer end 660B. Inner end 660A of second threaded shaft 660
projects into
second gear housing 640 such that bevel gear 662 engages bevel gear 642, with
horizontal axis X-5 oriented perpendicular to primary axis X-1 and passing
through
vertical axis Y-2. Outer end 660B of second threaded shaft 660 is retained by
a bearing
664 mounted to a frame 670 which forms part of elbow carriage 30 and which is
movable
within elbow carriage 30 in a horizontal direction perpendicular to primary
axis X-1.
Accordingly, second threaded shaft 660 is able to move parallel to primary
axis X-1 with
longitudinal movements of elbow carriage 30, and is also able to move
horizontally
within elbow carriage 30 perpendicular to primary axis X-1, with horizontal
axis X-5 of
second threaded shaft 660 always remaining perpendicular to primary axis X-1.
As best
seen in Fig. 22, the horizontal movement of second threaded shaft 660
perpendicular to
primary axis X-1 is enabled by mounting second threaded shaft 660 within a
frame 38
which is movable relative within and relative to elbow carriage 30 by any
suitable means
(such as by use of rollers or slide members moving within corresponding tracks
mounted
to the main structure of elbow carriage 30)
Second threaded shaft 660 passes through a threaded hub 680, such that
rotation
of second threaded shaft 660 will cause hub 680 to travel along second
threaded shaft
660. As best seen in Fig. 22, hub 680 is connected to the underside of a rack
gear 685
which is oriented perpendicular to primary axis X-1 and which is movable
parallel to
primary axis X-1 with longitudinal movements of elbow carriage 30, while also
being
able to move horizontally within elbow carriage 30 perpendicular to primary
axis X-1.
A reversible elbow size adjustment motor 690 is provided in association with
first
gear housing 620. Actuation of reversible motor 690 in a desired direction
will cause the
simultaneous rotation of first threaded shaft 610 and smooth shaft 650 as
previously
discussed. The rotation of first threaded shaft 610 will result in the
movement of hub 630
and second gear housing 640 along first threaded shaft 610. The concurrent
rotation of
smooth shaft 650 will cause keyed bevel gear 654 to rotate bevel gear 642,
which in turn
will cause rotation of bevel gear 662 and second threaded shaft 660, thereby
causing hub
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CA 02540341 2006-03-20
680 to move along second threaded shaft 660 by the same amount as hub 630 and
second
gear housing 640 move along first threaded shaft 610 (both threaded shafts
having the
same diameter and thread pitch). This results in a corresponding movement of
vertical
axis Y-2 along first threaded shaft 610, to suit different sizes and
configurations of elbow
80. This is further illustrated in Fig. 21A in which reference character Y-2A
indicates an
alternative location of vertical axis Y-2 (corresponding to a smaller diameter
elbow).
By means of the described mechanism, therefore, the apparatus can be readily
adjusted to accommodate elbows 80 of different curvature radii 92. More
specifically,
when the apparatus is properly set up for a given elbow 80, the distance
between vertical
axes Y-1 and Y-2 will equal the curvature radius 92 of elbow 80.
The functionality of bull gear 600 and related components described above may
be appreciated from Figs. 15, 15A, and 22, which illustrate further components
of the
coordinated drive mechanism of the apparatus. A first sprocket 351 is fitted
to the outer
end of first auxiliary shaft 340, which as previously described will rotate at
the same rate
(constant or variable, as the case may be) as primary drive shaft 46. A non-
cylindrical
drive shaft 365 (i.e., a solid or tubular shaft having a polygonal cross-
sectional profile)
having a first end 365A and a second end 365B, is mounted in a convenient
fixed
position so as to be rotatable about a horizontal axis X-6 parallel to primary
axis X-1. In
the illustrated embodiment, non-cylindrical drive shaft 365 is square in cross-
section, but
it could be of hexagonal, octagonal, or other polygonal or non-cylindrical
cross-section.
A second sprocket 370 is mounted on non-cylindrical drive shaft 365 such that
it
can slide longitudinally along non-cylindrical drive shaft 365, and such that
rotation of
second sprocket 370 will cause corresponding rotation of non-cylindrical drive
shaft 365.
A first drive chain 375 is disposed around first sprocket 351 and second
sprocket 370 as
shown, preferably in conjunction with an idler sprocket 372 the position of
which can be
adjusted (e.g., manually or automatically, such as with a spring-loaded
mechanism) in
order to maintain a desired tension in first drive chain 375. Second sprocket
370 is
mounted to a suitably stiff bracket 378 or other means connected to elbow
carriage 30
such that second sprocket 370 will move along non-cylindrical drive shaft 365
in
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CA 02540341 2006-03-20
coordination with longitudinal movements of elbow carriage 30 parallel to
primary axis
X-1. A third sprocket 380 is non-slidingly fixed to drive shaft 365 at a
selected point not
within the range of sliding travel of second sprocket 370.
As shown in Figs. 15, 21, and 24, a longitudinal drive shaft 700 having a
centroidal axis X-7 parallel to primary axis X-1, extends from a first end 710
near elbow
carriage 30 to a second end 720 near weld head carriage 50. A fourth sprocket
390 is
mounted to longitudinal drive shaft 700 near the first end 710 thereof, and a
second drive
chain 395 is disposed around third sprocket 380 and fourth sprocket 390. By
means of
the mechanical linkages thus described, rotation of primary drive shaft 46
will cause
corresponding rotation of both non-cylindrical drive shaft 365 and
longitudinal drive
shaft 700. Persons skilled in the art of the invention will appreciate that it
is then a
straightforward matter to provide weld arm rotation means (schematically
indicated by
reference character 1000 in Fig. 21) to transfer the rotation from
longitudinal drive shaft
700 to weld arm carriage 50, such that weld arm 60 will rotate about primary
axis X-1 in
coordination with the rotation of primary drive shaft 46 and, in turn, the
rotation of rotor
40 and elbow 80.
Weld arm rotation means 1000 may take the form of any suitable mechanical
linkage, using appropriately sized gears, sprockets, shafts, and/or other
components in
accordance with well-known mechanical design principles. In the preferred
embodiment,
weld arm rotation means 1000 is integrated with weld arm carriage drive means
51,
which enables selective longitudinal movement of weld arm carriage 50 for
purposes of
cladding a straight extension section 86 of a pipe elbow 80, as previously
described. As
generally illustrated in Fig. 21, a first linkage 1010 transfers rotation from
longitudinal
drive shaft 700 to a parallel non-cylindrical drive shaft 1020 (in
substantially the same
fashion as rotation is transferred from non-cylindrical drive shaft 365 to
longitudinal
drive shaft 700, as previously described). Non-cylindrical drive shaft 1020
Rotation from
non-cylindrical drive shaft 1020 is then transferred to drive end 60D of weld
arm 60 by
means of a second linkage 1030 which is fixed to weld arm carriage 50 but
which can
slide longitudinally along non-cylindrical drive shaft 1020 while still being
actuated
thereby (in substantially the same fashion as second sprocket 370 slides along
non-
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CA 02540341 2011-06-06
cylindrical drive shaft 365). The range of travel of second linkage 1030 along
non-
cylindrical drive shaft 1020 (which of course corresponds to the range of
travel of weld
arm carriage 50) is conceptually indicated by reference character 1035 in Fig.
21.
Referring now to Fig. 24, first end 365A of non-cylindrical drive shaft 365
engages a gearbox 800 which has a horizontal output shaft 810 which in turn
rotates a
vertical drive shaft 820 having a fixed vertical axis Y-3 (by means of a
suitable
mechanical linkage 815). As best seen in Figs. 21A and 23, the upper end of
vertical
drive shaft 820 is fitted with a drive pinion 830 which engages teeth 600A of
bull gear
600. Gearbox 800 is adapted and adjusted, for a given elbow 80, such that for
each
rotation of primary drive shaft 46, vertical axis Y-2 of hub 630 and second
gear housing
640 will move about vertical axis Y-1 through an arc equal to pitch P; i.e.,
the desired
average width of weld bead to be applied to interior surface 84 of elbow 80 on
each pass
of weld head 70.
Referring now to Figs. 21 and 21A, it may be readily appreciated how the
rotation
of bull gear 600 about vertical axis Y-1 will result in incremental
longitudinal movements
AX of elbow carriage 30, along with incremental radial movements AY of rotor
40, as
required to move elbow 80 through stationary frame 20 while maintaining center
of
rotation 90 of elbow 80 at all times substantially coincident with reference
plane RP. In
Figs. 21 and 21A, bull gear 600 is shown in a position corresponding to the
position of
elbow 80 as shown in Fig. 5 (i.e., a terminal position), with axis X-4 of
first threaded
shaft 610 substantially parallel to primary axis X-1, and with second threaded
shaft 660 at
an terminal position farthest from vertical axis Y-1 as measured in a
direction parallel to
primary axis X-1. Also schematically illustrated, however, are the positions
of axis X-4,
second threaded shaft 660, hub 680, and axis X-5 when elbow 80 is mounted in a
medial
configuration ¨ as indicated by reference characters X-4m, 660m, and X-5m
respectively.
Although not explicitly shown, the spatial position of bull gear 600 when
elbow 80 is
mounted in a medial configuration, can be readily visualized from these
schematic
representations. The rotational displacement of bull gear 600, first threaded
shaft 610,
and axis X-4 is indicated by angle O. The longitudinal displacement of second
threaded
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CA 02540341 2006-03-20
shaft 660, hub 680, and axis X-5 is indicated as distance Dx, and the lateral
displacement
thereof is indicated as distance D.
From a starting point with elbow 80 in a medial position (and with bull gear
600
in a corresponding configuration), actuation of primary drive motor 110 will
cause
coordinated rotation of rotor 40 and weld arm 60 about primary axis X-1, while
also
causing bull gear 600 to rotate counterclockwise about vertical axis Y-1, all
as previously
described, so as to move bull gear 600 toward the position shown in Figs. 21
and 21A
(i.e., corresponding to the primary terminal position of elbow 80 as shown in
Fig. 5).
Because the distance between vertical axes Y-1 and Y-2 is preset to equal
curvature
radius 92 of elbow 80, the incremental movements of vertical axis Y-1 parallel
to primary
axis X-1 as bull gear 600 rotates will be equal to the desired incremental
longitudinal
movements AX of elbow carriage 30. Similarly, the incremental movements of
vertical
axis Y-1 perpendicular to primary axis X-1 as bull gear 600 rotates will be
equal to the
desired incremental radial movements AY of rotor 40.
As bull gear 600 rotates, it draws elbow carriage 30 longitudinally away from
stationary frame 20, due to the fact that hub 680 is connected to the
underside of a rack
gear 685, which necessarily moves longitudinally with elbow carriage 30. As
can be
appreciated from Figs. 12A and 12B and related discussion, the initial
longitudinal
movement of hub 680 during the first rotation of rotor 40 (and therefore the
initial
longitudinal movement of elbow carriage 30), as elbow 80 begins moving from a
medial
position, will be approximately P cos 45 ), which as will be recalled
corresponds to the
incremental longitudinal distance AX through which swivel axis X-2 needs to
move in
order to keep center of rotation 90 of elbow 80 coincident with reference
plane RP. It
will be appreciated that this relationship will be maintained as bull gear 600
rotates
toward the position shown in Figs. 21 and 21A.
As bull gear 600 rotates, it also causes the horizontal movement of second
threaded shaft 660 perpendicular to primary axis X-1. It can be readily
appreciated from
Figs. 12A and 12B that the incremental perpendicular movements of second
threaded
shaft 660 will correspond to the required incremental radial movements AY of
rotor 40.
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CA 02540341 2006-03-20
Because of its connection to hub 680 on second threaded shaft 660, rack gear
685 will
have identical movements perpendicular to primary axis X-1. These movements
are
transferred to secondary drive shaft 48 which coaxially disposed inside
primary drive
shaft 46. As shown in Figs. 15, 15A, 18, and 19, secondary drive shaft 48 has
an inner
end 48A and an outer end 48B. Inner end 48A of secondary drive shaft 48
extends
beyond hub flange 230 and connects to pinion gear 480 which is operably
engageable
with rack gears 45 of rotor 40 as will now be described.
Outer end 48B of secondary drive shaft 48 extends into a second cluster gear
900,
which comprises:
= an outer case 910 having a front end 910F and a back end 910B;
= a bevel gear 920 rotatable about an axis perpendicular to and passing
through
primary axis X-1;
= a bevel gear 930 mounted in association with front end 910F of outer case
910
and rotatable about primary axis X-1 independently of outer case 910, so as to
be
operably engaged with bevel gear 920;
= a bevel gear 940 mounted in association with back end 910B of outer case 910
and rotatable about primary axis X-1 independently of outer case 910, so as to
be
operably engaged with bevel gear 920; and
= an exterior gear wheel 950 concentric with primary axis X-1 and fixedly
mounted
to outer case 910 in association with front end 910A, such that rotation of
gear
wheel 950 will cause corresponding rotation of second cluster gear 900 as a
whole.
Outer end 48B of secondary drive shaft 48 operatively engages bevel gear 930.
A
third auxiliary shaft 960, which is coaxial with secondary drive shaft 48, has
a first end
960A which operatively engages bevel gear 940, and a second end 960B connected
to a
pinion gear 970, which in turn is operably engaged with rack 685. As shown in
Fig. 15A,
exterior gear wheel 950 engages an idler gear 980 which engages gear wheel 990
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CA 02540341 2006-03-20
mounted on first auxiliary shaft 340, which it will be recalled rotates in
coordination with
primary drive shaft 46 upon actuation of primary drive motor 110. As a result
of the
engagement of pinion gear 970 with rack 685, when rack 685 is stationary it
serves to
prevent rotation of third auxiliary shaft 960. Therefore, the clockwise
rotation of
secondary shaft 340 will cause clockwise rotation of second cluster gear 900
and
consequent clockwise rotation of secondary drive shaft 48. The relative sizes
of the
various gears incorporated in the mechanism just described are selected so
that primary
drive shaft 46 and secondary drive shaft 48 rotate at the same rate. However,
lateral
movement of rack 685 in response to the rotation of bull gear 600 rotates
pinion gear 970
and third auxiliary shaft 960. By virtue of the engagement of third auxiliary
shaft 960
with second cluster gear 900, an incremental movement of rack 685 therefore
causes an
incremental rotation of secondary drive shaft 48 relative to primary drive
shaft 46. As
may be appreciated with reference to Fig. 9 in particular, this will cause
pinion gear 480
to rotate relative to rotor 40 such that elbow collar 42 and counterweight
means 44 move
radially toward or away from primary axis X-1 (depending on the direction of
relative
rotation of secondary drive shaft 48), due the operative engagement of pinion
gear 480
with rack gears 45A and 45B.
In accordance with the exemplary mechanisms described above, by using gears of
suitable relative sizes, the rotation of bull gear 600 will result in radial
movements of
elbow collar 42 (and counterweight 44) in coordination with longitudinal
movements of
elbow carriage 30 so as to keep center of rotation 90 of elbow 80 coincident
with
reference plane RP as elbow 80 moves through stationary frame 20, thus
facilitating the
application of a uniform cladding bead on the inner surfaces of elbow 80.
It will be readily appreciated by those skilled in the art that various
modifications
of the present invention may be devised without departing from the essential
concept of
the invention, and all such modifications are intended to be included in the
scope of the
claims appended hereto. To provide only one non-limiting example, it would be
possible
to provide the various required coordinated movements of the elbow carriage
30, rotor
40, elbow cradle 42, counterweight means 44, and weld arm 60 using multiple
independent drive mechanisms and control systems. Such alternative embodiments
could
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CA 02540341 2006-03-20
incorporate computerized control systems, which could be readily adapted,
using known
programming methods, to control the incremental longitudinal movements of
elbow
carriage 30, and to control the incremental radial movements of elbow cradle
42 (and
counterweight means 44), control functions which in the illustrated embodiment
are
served by bull gear 600 and associated mechanisms. Computerized control
systems
could also be used to provide for variable-rate rotation as an alternative to
the variable-
rate rotation means described herein.
In this patent document, the word "comprising" is used in its non-limiting
sense to
mean that items following that word are included, but items not specifically
mentioned
are not excluded. A reference to an element by the indefinite article "a" does
not exclude
the possibility that more than one of the element is present, unless the
context clearly
requires that there be one and only one such element.
48
