Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02434316 2003-07-31
APPARATUS FOR SPREADING A BOLT LOAD
This application is divided from Canadian Patent Application 2,266,040,
filed August 15, 1997. The expression "the invention", and the like, as used
herein may encompass the subject matter claimed in both the parent
application and this divided application.
This invention relates generally to spreading the clamping load of a bolt
which holds an inner liner to an outer shell used in ore milling operations,
sealing the shell so that the wet ore slurry in the inner lining does not leak
out of
to the shell through the mounting holes, and repairing enlarged mounting holes
which go through the liner and shell to re-establish the ability of the bolt
to
maintain its designed and desired preload.
Because of individual geometry, the head shape of a conventional
tapered or spherical head, counter-sunk mill-liner bolt, presents a poor load
bearing contact with the liner and ifs mating surface. This condition is due
primarily to clearance and manufacturing tolerances between the liner, which
is
cast, and the radiused, tapered, load-bearing area of the bolt, which is
forged.
This poor load-area contact always causes early embedment with subsequent
loss of bolt clamp load soon after assembly. It requires repeated, expensive
mill
2o shut downs, for bolt tightening, before an adequate surface contact can be
formed to support the required bolt clamp load. In a majority of instances,
bolts
never establish enough surface area contact to stay tight and have to be
periodically tightened through the life of the liners. Often, loose bolts
fatigue
and break with expensive consequences if the liners fall out.
While it is known to provide round headed bolts with a plurality of hard
metal protrusions of various types, i.e., wings, keys, or fins, formed along
the
neck and shank of the bolt which embed themselves in the softer work piece to
prevent the bolt from turning when a load is applied to the bolt, such
structures
are unnecessary when a non-round bolt head is supported in a non-round
3o recess and, moreover, will not work in the environment of the present
invention
where the work piece, i.e., the mill liner, is made of harder steel than the
bolt of
the fastener.
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Accordingly, it is an object of one aspect of the invention to provide
improved bolt-tightening features which provide improved mating surfaces and
preload holding ability which minimize these problems of the prior art.
Moreover, running with loose bolts is also the cause of bolt holes in the
mill shell becoming enlarged, which encourages further loosening and leaking
problems eventually leading to expensive repair. Typically, the bolt holes in
the
liners are cast approximately 1/8" larger, all around the bolt head, for a
standard
1 '~2' liner bolt. Fig. 3 shows how inadequately the bolt load surtace mates
with
the liner in a horizontal (radial) plane. Figs. 1,2 show loss of vertical
(axial)
to contact face with small neck angle differences.
Thus, it is an object of another aspect of the invention to provide
improved bolt tightening mechanisms which prevent loosening and enlargement
of the holes through which the bolt passes thereby minimizing these problems
of the prior art.
Prior sealing systems used with liner bolts are designed to give good
sealing characteristics, but in doing so, sacrifice jointing efficiency.
Typically
rubber is introduced between the joint surfaces so that a hard joint, i.e.,
metal-
to-metal, is never attained. This condition then becomes a gasketed joint and
will never hold bolt preloads adequately.
2o Accordingly, in another aspect the invention provides an improved
sealing system without sacrificing joint efficiency, by providing metal-to-
metal
contact with simultaneous adequate sealing thereby reducing these problems of
the prior art.
Set forth below is a brief summary of the invention which can achieve the
forgoing and other benefits and advantages, in accordance with the purposes of
the present invention as embodied and broadly described herein.
A first aspect of the invention is a bolt including a head of predetermined
shape, a shank, a neck integral with the head and shank, and a plurality of
raised contact surface portions uniformly positioned adjacent the neck, and
3o constructed and configured for spreading an applied bolt load.
A feature of this aspect of the invention is the raised contact surface
portions may include a base portion contiguous the neck, and a ridge portion
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raised above the base portion and constructed and configured to contact a
congruent wall portion of a bolt bore in a support structure.
Other features of this aspect of the invention can include the bolt being a
forged bolt. The head shape may be round, elliptical, square, oblong,
spherical,
or rectangular, and may have an axially-extending portion of predetermined
thickness having a constant circumference, and the bolt may have a tapered
neck portion between the head and shank. The bolt can include the neck
having a circumference either intermediate the circumferences of the head and
shank or greater than both said circumferences. The raised contact surface
~o portions may be elongated V-shaped ridges raised above the base portion and
forged integrally with the neck.
Still other features of this aspect of the invention include the raised
portions may be symmetrically placed relative to the neck, extend
substantially
an entire length of the neck, may also extend substantially along an entire
length of the head, extend axially and radially relative to the longitudinal
axis of
the bolt, and may be deformable and fay to an adjacent bore wall portion,
whereby when a load is applied to the bolt the load is spread more uniformly
over a surface of the neck.
A second aspect of the invention is an insert including a base portion
2o having a width, a length and a thickness, and a plurality of surface
contact
portions raised above and extending along a length of the base portion.
In this aspect of the invention the plurality of surface-contact portions can
be short relative to a width of the insert, coterminous with a length of the
base
portion, and formed as parallel, symmetrically placed, V-shaped ridges, the
height and width of which vary relative to each other according to the amount
of
a clearance of an adjacent wall portion of a bore hole in a support structure.
A feature of this aspect of the invention is the insert having a flat shape in
one stage of its production, and an arcuate shape in its final form which is
self-
aligning relative to the neck of the bolt when a load is applied to the bolt
3o whereby the load is spread onto the raised contact surfaces.
A third aspect of the present invention is a repair washer for enlarged
holes including a shaped body having a top major surface and a bottom major
surface and a central bore therethrough, an annular groove in the top major
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surface constructed and configured to receive an o-ring seal, an annular
groove
in the bottom major surface constructed and configured to receive an o-ring
seal, and a plurality of teeth integral with the bottom major surface
constructed
and configured for gripping a surface which is to be sealed.
In this aspect of the invention the annular groove in the top major surface
usually is located near the central bore and constructed and configured to
cooperate with a bolt through the central bore and through an overlying
fastener
to seat the central bore at the top surface, while the annular groove in the
bottom major surface may be located near the periphery of the bottom major
surface and constructed and configured to cooperate with the bolt through the
central bore and through the fastener overlying the top major surface to
simultaneously seal the central bore at the bottom surface.
Other preferred features of this aspect of the invention include the teeth
being serrated and constructed and configured to prevent movement and
subsequent loosening of the washer while the top and bottom seals are effected
when the washer is tightly secured to the sealed surface by an overlying
fastener. The bottom major surface portion may be either flat or curved to
cooperate with the curved surface which is to be sealed, and the bottom major
surface is a load surface and the annular groove therein is constructed and
2o configured to effect a bottom seal on the periphery of the load surface.
The invention now will be described in greater detail, with reference to
the accompanying drawings, in which:
Fig. 1 is a front vertical elevation view in partial section of a prior art
mill
liner bolt through a liner and shell to hold the assembly together. This
drawing
shows radial contact with existing geometry.
Fig. 2 is a view similar to Fig. 1 showing different angles between the
countersunk hole in the liner and the chamfered edge of the bolt head of the
prior art. This drawing shows axial contact with mismatch of neck angles.
Fig. 3 is a top view in partial section taken along the lines 3-3 of
3o Figs. 1,2 showing the point of contact between the oval shaped countersunk
liner hole and chamfered oval shaped bolt head.
Fig. 4 is a view similar to Fig. 1 showing the forged spreader with ridges
of the present invention which make good and complete contact with the
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countersunk hole of the liner when the bolt is preloaded to its desired
amount.
This drawing shows spreader correcting action both radial and axial.
Fig. 5 is a view similar to Fig. 2 again showing the forged ridged spreader
of the present invention.
Fig. 6 is a top view in partial section taken along the lines 6-fi of
Figs. 4,5.
Fig. 7 is a elevational schematic view of the assembly of Fig. 4 and is
identified as Liner 1.5 ShapelA:
Fig. 8 is a plan schematic view of Fig. 7.
to Fig. 9 is an oblique perspective of the mill bolt with forged ridged
spreader of the present invention seen in Figs. 4-8. This drawing shows a load
spreader liner 20 having spreader areas 31 and a liner bolt hole 12.
Figs. 10, 12, 14, 17, 20, and 22 are perspective views similar to Fig. 9
showing the alternative round, elliptical, square, oblong, spherical, and
rectangular neck and head shapes of the present invention. Figs. 11, 13, 15,
18, 21, and 23 are sectional views along the lines 11-11, 13-13, 15-15, 18-18,
21-21, and 23-23 of Figs. 10, 12, 14, 17 and 19, 20 and 22, respectively.
Fig. 16 is a top plan view of Fig. 14. Fig. 19 is an alternate embodiment of
the
present invention showing convex teeth similar to the concave teeth of Fig.
17.
2o Fig. 24 is an oblique perspective view of an alternate embodiment of the
present invention in the form of forged spreader inserts having deformable
ridges according to the present invention. This drawing shows a standard liner
bolt 20 in a liner bolt hole 2 with load spreader inserts 40 having spreader
areas
41.
Fig. 25 is a form of the forged spreader of Fig. 10 during an early step in
the manufacturing process of the present invention prior to being forged in
its
curved final form and is identified as Liner 1.5 ShapelA.
Fig. 26 is a top plan view of the forged insert of Fig. 25.
Fig. 27 is a top plan view of Fig. 26 following the forming step which
3o forms the forged spreader into its final curved form.
Fig. 28 is an oblique perspective view of the underside of the special
repair washer of the present invention. This drawing shows a special repair
washer for enlarged mill liner holes. Fig. 28 shows a serrated load area 53 to
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prevent movement and subsequent loosening and a special o-ring sealing
groove 51 to seal on outside of load area.
Fig. 29 is an oblique perspective top view of the special repair washer of
the present invention. This drawing shows a liner bolt, nut 23, washer 50, and
additional "o"-ring 54 (in phantom).
Fig. 30 is a perspective view of a special repair plate of the present
invention also showing an additional embodiment of the improved repair washer
of the present invention. This drawing shows a special repair washer
(rectangular) having a concave bottom face to match shell 1 curvature, holes
for
io socket screws to clamp plate to shell, and, in a top view, a Valley
ForgeT"" two
piece sealing system around liner bolt 20 and under nut 23.
Fig. 31 is an oblique partial perspective view of the underside of the
repair plate of Fig. 30. This drawing shows a back view of the "o"-ring
special
sealing groove to seal plate to shell.
Fig. 32 is a plan view of the repair plate and repair washer assembly of
the present invention, and is identified as a repair washer new S/A. This
drawing also shows 2 dowell pin holes (unnumbered).
Fig. 33 is a front elevation view in partial section of the repair plate of
Fig.
32. The bottom face of this plate will be concave.
2o Fig. 34 is a front elevation view of a drill stopper bushing used in making
the present invention.
Fig. 35 is a top plan view of Fig. 34.
Fig. 36 is a top plan view of a center drill bushing used in making the
present invention.
Fig. 37 is a front elevation view in partial section of the center drill
bushing of Fig. 36.
Fig. 38 is a top plan view of a tap drill bushing used in making the
present invention.
Fig. 39 is a front elevation view in partial section of the tap drill bushing
of
3o Fig.38.
Fig. 40 is a top view in partial section of a drilling process step which is
used in making the present invention. This drawing shows a tap bushing in one
hole of plate 61.
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Fig. 41 is a front elevational view of a drilling process step used in
making the present invention. This drawing shows the repair assembly having a
certain drill 71 in a drill stopper 74 on a tap bushing 73. The bottom face of
the
repair assembly will be concave with radius to order.
As seen in Figs. 4 to 9, the bolt 20 with forged head shape 30 is
designed to increase contact by spreading the load area in the taper neck both
radially and axially even with mismatched neck angles. This design introduces
additional bolt head forged surfaces 30 with ridges 31, which project into the
vacant clearance zones and touch the liner hole surfaces 12 uniformly around
to the faying surface of the bolt head. These projecting areas or ridges 31
are
dimensioned so that they deform under load when tightened against the harder
steel liner surface 12. As the bolt 20 is tightened, plastic deformation takes
place resulting in additional radial and axial surface contact, until full
clamp load
is reached, at which time this load will be spread over a larger and more
uniform
surface at the neck. Figs. 10-23 show the alternative round, elliptical,
square,
oblong, spherical, and rectangular neck and head shapes of the present
invention.
As best seen in Figs 24-27, using the same theory, spreader inserts 40
are used to fit between a regular standard head bolt 20,21 and the liner hole
20 10,12. Two inserts 40 with ridges 41 are temporarily attached, one at each
neck area on the bolt, and held in place with an elastic band. Once the bolt
head is assembled into the liner hole; the inserts will align themselves to
spread
load surface contact. Spreader inserts may be added to existing standard liner
bolts, to increase their load supporting capabilities. The choice of using a
forged spreader bolt (Figs 18-23) or spreader inserts (Figs 24-27) would
depend
on the application and customer preference.
As best seen in Figs 28-30, the system of the present invention will allow
the joint to be metal-to-metal and the seal to do its function independently.
It
will also apply the nut 23 load directly on the shell 1 through hardened
serrated
3o teeth 53 so that the assembly cannot move to loosen. The rubber or neoprene
O-ring seal in O-ring groove 51 on the underside of repair washer 50 stays on
the periphery of washer 50 away from the metal-to-metal contact area 53 where
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the actual load application is made. Another smaller O-ring (not shown) in
annular groove 54 (Fig. 29) seals the inner hole and the threads.
As best seen in Figs 30-41 a further aspect of the invention includes the
provision of a special repair plate and special repair washer 60 which allows
repair of enlarged holes in the liner and shell caused by dynamic movement
resulting from loosening of the bolt in place when prior art bolts were used.
The
improvement of the present invention includes a repair plate 61 having a
central
bore 62 (Fig. 30) and a plurality of socket holes 63. The top surface 64 of
the
repair plate 61 is flat. The bottom surface may be curved to match the shell.
~o Those skilled in the art would readily understand that the improved bolt of
the
present invention would be inserted through the hole in the liner 10 and the
hole
in the shell 1 through the plate 61 which is held in place by bolts (not
shown)
through socket holes 63, which bolts go through plate 61 and into shell 1 but
not
through shell 1 (to avoid causing a hole which only then would also have to be
sealed). A repair washer 50 (Fig. 29) or in alternate form as shown by repair
washer 60 (Fig. 30) is used to provide metal-to-metal contact and the improved
seating as described above.
The process for making repair plate 61 is demonstrated in Figs 34-41.
After socket holes 63 are drilled, the holding bolt is removed and replaced by
a
2o bolt 20 of the present invention having forged areas 30 or alternatively
using
load spreader inserts 40 to which is then secured repair washer 50,60 and nut
23 as described above. A center drill 71 held in place by center drill bushing
72
allows socket holes 63 to be precisely drilled white tap drill bushing 73
coupled
with drill stopper bushing 74 superimposed on top of tap drill bushing 73 as
shown in Fig. 41 controls the depth to which the holes are drilled into the
shell 1
but not through shell 1. When all of holes 63 are drilled, plate 61 is held in
place
by bolts through socket holes 63 into shell 1. First, repair plate 61 is
superimposed over the central bore 11 which goes into the shell 1 and liner 10
and is held in place by a large bolt through bore 11 to prevent repair plate
61
3o from moving while socket holes 63 are being drilled.
The forgoing description of a preferred embodiment and best mode of the
invention known to applicant at the time of filing the application has been
presented for the purposes of illustration and description. It is not intended
to
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be exhaustive or to limit the invention to the precise form disclosed, and
obviously many modifications and variations are possible in the light of the
above teaching. The embodiments were chosen and described in order to best
explain the principles of the invention and its practical application to
thereby
enable others skilled in the art to best utilize the invention in various
embodiments and with various modifications as are suited to the particular use
contemplated.
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