Note: Descriptions are shown in the official language in which they were submitted.
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IMPROVED CUSHION CONNECTOR
INTRODUC'.1'ION
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This invention relates to a cushion connector
and, more particularly, to a cushion connector used for
blast hole above ground drilling.
BACKGROUND OF THE INVENTION
Cushion connectors are used to cushion the shock
created by the drill bit during drilling and passed
through the drill string or drill steel to the drill head
of the rig. Such cushion connectors are known and, in
general, act to absorb the drilling shocks by moving so as
to allow a certain amount of movement between the 'top of
the drill string which is connected to the box end of the
cushion connector and the drill drive head which is
connected to the pin end of the cushion connector.
From that point of similarity, however, the
tools act considerably differently and absorb the shock in
a variety of different ways. In one connector, a
resilient elastomeric material is inserted into the
connector between the housing and the piston which moves
relative to the housing and acts principally to absorb
compression shocks which are passed from the drill bit to
the drill drive head.
A problem with the use of elastameric material
as a compression absorber, however, is that the material
inherently has a limited axial elasticity with the result
that the stroke available in the connector is limited. It
is desirable to have as long a stroke as possible in order
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to absorb the shocks from the drill bit with maximum
efficiency.
A further disadvantage with known cushion
connectors is that the drive splines do not act within the
axial length of the springs. Rather, the springs are
located above or below the drive splines. Such a
configuration results in an increased axial length for
the cushion connector which is 'undesirable when it is
preferred to keep the axial length to a minimum for more
convenient operating characteristics.
SU1~IMARY OF THE INVENTION
According to one aspect of the invention, there
is provided a cushion connector comprising a pin component
at one end of said connector, a box component at the
opposite end of said connector, a housing extending
between and connected to one of said pin and box
components, a piston movable within said housing and
connected to the other of said pin and box components, a
drive spline extending outwardly from the axis o.f said
piston, at least one drive lug extending inwardly from
said housing, a drive block between said housing and said
piston, and being engageable with said drive spline and a
spring acting between said pin and box components, said
drive spline being coaxial with said spring and operable
to move axially within said drive blocks.
Further objects and advantages of the invention
will become apparent from the description of a preferred
embodiment of the invention below.
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BRIEF DESCRIPTION OF T1HE SEVERAL VIEWS OF THE DRAWINGS
A specific embodiment of the invewtion will now
be described, by way of example only, with the use of
drawings in whiche
Figure 1A is a sectional side view of the
cushion connector according to the invention;
Figure 1B is an enlarged partial view of Area 1B
in Figure 1A;
Figure 2 is a sectional view taken along the
plane II-II of Figure 1:
Figure 3 is an isometric view of a single one of
the cushion blocks: and
Figure 4 is a sectional view of a further
embodiment of the invention.
DESCRIPTION OF SPECIFIC EMBODIMENT
Reference is now made to the drawings and, in
particular, to Figure d where a cushion connector
according to the invention is generally illustrated at 10.
It comprises a pin component 11 at one end and a box
component 12 located at the opposite end of the cushion
connector 10.
A housing 13 extends axially from the box
component 12 and a cap 14 is connected to the housing 13
on the pin end with cap screws 20 located about the
periphery of t:he cap 14. A piston 21 extends from the pin
component 11 and is movable with the pin component 11
relative to trbe housing 13 and box component 12. The
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piston 21 includes a plurality of drive splines 22 (Figure
2) extending outwardly from the axis 23 of the piston 21,
the drive splines 22 engaging with complementary drive
blocks 24 and being movable relative thereto, the drive
blocks 24 extending inwardly from the housing 13 as best
seen in Figure 2 and which have an arc shaped outer
periphery as illustrated in Figvure 1. Two sets of
Belleville or disc springs 30, 60, having different
outside diameters, are mounted in a recess provided
between the piston 21 and a skirt 31 in respective
cylindrical recesses 35, 36. The two sets of disc springs
30, 60 extend between the pin component 11 and the box
component 12 as is seen in Figure 1. A first grooved ring
75 is mounted between the disc springs 30 and the inside
surface 76 of the box compartment 12. Grooved ring 75 has
a radially extending groove which allows grease to pass
from the grease fitting 15 to the annular space 79 between
the outside diameter of the extension 61 and the insider
diameter of the disc springs 30. A second and similar
2o grooved ring 77 is positioned between the disc springs 60
and the inside surface 7~ of the pin end 11 to allow the
grease to flow outwardly from annular space 79 into recess
36 and, thence, out hole 72 in skirt 31 and into the area
of the drive block keyways 69, the drive spline 22 and the
cushion blocks 70.
Piston 21 has an integral extension 61 which
extends axially into the box component 12. Extension 61
maintains annular alignment between the pin and box
components 11, 12, respectively, and is permitted a degree
of radial movement by cushion 16 which is mounted within
the box component 12 as illustrated.
The use of the disc springs 30 having a larger
diameter than the diameter of disc springs 60 is permitted
by the use of the skirt 31 which has a larger internal
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diameter at its end furthest removed from the pin
component 11. The increased diameter of the second set of
disc springs 30 allows a longer stroke over a given length
which allows the cushion connector 10 to be shorter than
otherwise would be required.
The axial movement of the pin component 11
relative to the box component 12 is limited by the drive
splines 22. Skirt 31 has an additional function in
preventing the migration of the cushion blocks 70 inwardly
and away from their position between the drive lugs 71 arid
the drive blocks 24 as set out hereafter. A wear and
corrosion resistant sleeve 63 is mounted about the distant
periphery of the extension 61.
Guide rings 50 and wiper seals 51 are mounted
on a ring 54 between the box component 12 and the
extension 61 of piston 21. Likewise, a guide ring 52 and a
wiper seal 53 are mounted between the cap 14 and the
piston 21.
An elastomer back up cushion 67 (Figure 2) is
connected to each of the drive blocks 24 with screws 64.
Elastomer cushion blocks 70 (also illustrated in Figure 3)
are mounted between each drive block 24 and the inwardly
extending lugs 71 which are integral with housing 13. The
cushion blocks 70 contact the faces of the drive blocks 24
and lugs 71 in a surface, contacting area distributed over
a significant quantity of the surface area of the face
portion of both the drive blocks 24 and the lugs 71 and
extend axially a distance between the upper and lower
surfaces 34, 41, of the cap 14 and box component 12,
respectively. The cushion blocks 70 are compressed when
the cushion connector 10 is assembled as will be described
in greater detail.
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High radial loads are imposed on the cover plate
or cap 14 by the piston 21. This is so because it is
contemplated that the interaction between the drill drive
head (not shown) and the rotating drill steel (not shown)
connected to the cushion connecaor 10 attempts to use the
cushion connector 10 as a ball joint in an attempt to
accommodate bent or flexing drill steel. Such radial
loads will, therefore, act between cap 14 and housing 13
and tend to loosen the cap screws 20 with resulting damage
to the mating surfaces.
To avoid or significantly reduce this condition,
a conical type interference fit is provided between the
cap 14 and the housing 13 in the area 74 (Figure 1). The
use of the cap screws 20 to pull the cap 14 axially into
the housing 13 utilizing the interference fit between the
two components results in a preload or residual force or
stress which must be overcome. Thus, any relative
movement between the cap 14 and the housing 13 will be
significantly reduced or eliminated entirely with the
result that the cap screws 20 will remain tightly
fastened.
As the cap screws 20 are tightened, the cushion
blocks 70 are compressed axially between the upper and
lower surfaces 34, 41, respectively. This causes the
cushion blocks 70 to expand at their girth to not only
occupy the initial clearance space but to also be
compressed between the lugs 71 and drive blocks 24.
OPERATION
The cushion connector 10 will be initially
assembled by having the box component 12 in the lowermost
position with the axis 23 of the cushion connector 10
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being vertical. The housing 13 will be open with the cap
14 not yet being attached.
The cushion blocks 70 are of a dimension such
that when they are positioned between the drive lugs 71
and the drive blocks 24, sufficient clearance is available
to permit the drive blocks 24 to slide around the inside
of housing 13 a limited angular amaunt such that the drive
blocks 24 are free to align with and permit insertion of
the drive splines 22 into the respective keyways 69 in the
drive blocks 24.
~.Che disc springs 30, 60 will then be positioned
in recesses 35, 36.
The cap 14 which has guide ring 52 and the
wiper seal 53 previously inserted is then fastened
securely to the housing 13 using the cap screws 20.
The compression of the cushion blocks 70 will
increase as the torque between the pin and box components
11, 12 is increased. Thus, the cushion blocks 70 achieve
a preloaded coupling effect which transmits torque and
reduces the torsional shock transmission from the drill
string to the drill head as described further hereafter.
As referred to before, the fitting 3.5 is
provided to allow for grease insertion for lubricating the
cushion connector 10. The grease is routed through the
3o fitting 15 and the radial groove in grooved ring 75 to
recess 79 between the inside of the disc springs 30, 60
and the outside of the extension or wash pipe 61, 'through
the groove in the grooved ring 77 into recess 35 and out
through hole 72 into the drive block keyways 69 and spline
sliding fit areas. The excess of the grease exits through
relief fitting 73.
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The shape of the cushion blocks 70 is
illustrated in Figure 3. The width of the block 70 is
greatest at its center point. This ensures that the
initial contact area between the cushion blocks 70
separating the drive blocks 24 and the lugs 71 occurs
over a small area when the cover plate 14 expands the
girth of the cushion blocks 70 during assembly.
The thickness of each cushion block 70
corresponds over its length to the annular space between
the outside diameter of piston 21 and the interior
diameter of housing 13 and they are therefore prevented
from expanding radially. ~~Ihen the elastomeric material
from which the blocks 70 are made is compressed, the
material will charge in shape but not in volume. Since
changes to the height and thickness of the cushion blocks
70 are limited by the surrounding metal parts of the
connector 10, any change in shape to accammoda~te the
reduced width, while maintaining a constant volume, must
take place in the areas not confined by the metal and
inflexible parts of the connector 10.
As compression of the blocks increases with
increasing torque transmission by the connector 10 the
area not confined by contact with the metal parts
decreases and more compressive force is required to change
the shape of the blocks. That is, the resistance of the
blocks 70 to compression of their width increases at an
escalating rate when compared to a unit amount of
compression. The actual relationship is determined by the
hardness of the elastomeric material from which the
cushion blocks are made and the shape of the curved edges
of the cushion blocks. Thus the rate of torsional
stiffness increase of the connector can be determined by
the material properties and shape of the cushion blocks
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The cushion connector 10 is then connected with
the pin component 11 to the drill drive head (not
illustrated] and the drill steel (not illustrated) is
connected to the box component 12 of the cushion connector
10. Drilling now commences.
As the compression shocks created by the action
of the drill bit on the ground formation are transferred
through the drill steel, the cushion connector 10 will
alternatively compress the springs and extend the springs
30, 60. The torsion created by the drill head on the pin
component 11 of the cushion connector 10 will be
transferred through the drive splines 22 to 'the drive
blocks 24.
The torque will be transmitted by the drive
blocks 24 to the cushion blocks 70 which will absorb the
torsional excesses and distribute the torque more
uniformly. The torque will then be transmitted to the
lugs 71 of the housing 13 and thence to the drill steel
through box component 22.
As compared to the Figure 4 embodiment described
hereafter, the Figure 1 embodiment allows a larger
diameter for some of the Belleville or disc springs. The
springs 30, 6o have a common inside diameter and spring
rate but the springs 30 have a larger outside diameter,
being at a location which makes the increased volume
available.
The larger diameter disc springs 30 provide a
longer stroke per spring which allows the overall length
of the cushion connector 10 to be shorter. The larger
volume of spring material results in lower spring stresses
and, hence, a longer fatigue life for the springs 30.
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The extension or skirt 31 of piston 21 in Figure
1 prevents the elastomer cushion blocks 70 from being
deformed into the space beneath the end of the drive area
and thereby interfering with the axial movement of the
connector 10.
An additional embodiment of the cushion
connector 10 according to the invention is illustrated in
Figure 4 wherein like numerals represent similar elements
l0 as those illustrated in the embodiment of Figures 1 and 2.
In this embodiment, the extension 61 of the
Figure 1 embodiment is replaced with a wear and corrosion
resistant washpipe 80 which is not integral with either
the pin or box components 11, 12 but which is, rather, a
separate piece and which is mounted between two collars
81, 82, collar 81 being removably mounted within box
component 12 and collar 82 being removably mounted within
pin component 11. The washpipe 80 allows for limited
angular movement between the pin and box components 11, 12
and is maintained in an axial position within the
connector 10 by the reduced bore 85 of the pin component
11 and the retaining ring 86. The washpipe 80 can be
removed without disassembly of the connector 10 by
removing the retaining ring 86.
The outside diameter of the disc springs 30 in
this embodiment are identical which is different from the
springs 30, 60 of the Figure 1 embodiment as earlier set
out. This is so because the piston 21 must take some
force resulting from angular misalignment between the box
and pin components 12, 11, respectively, and, therefore,
it being of a size having increased load bearing capacity
with the result that there is a smaller inside diameter of
the piston 21 available to house the disc springs 30.
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Wiper rings 83, 84 are provided which act as
seals between the collars 81, 82, the washpipe 80 and the
pin and box components 11, 12.
It is contemplated that the cushion connector
may readily be used for raise boring in addition to above-
ground drilling. In this event:, the teachings of the
invention would apply.
Although the rings 83, 84 are illustrated in the
Figure 4 embodiment as being inserted in recesses in the
collars 81, 82, it is cantemplated that the rings 83, 84
could be mounted in the washpipe 80. In this event, the
rings 83, 84 could be replaced by removing the washpipe
80 which can be conveniently accomplished by simply
removing the retaining ring 86 and retrieving the washpipe
80 together with the rings 83, 84 from the box component
12 without otherwise disassembling the cushion connector
10.
Many further modifications to the apparatus
described and illustrated will readily occur to those
skilled in the art to which the invention relates and the
specific embodiments set forth herein should be considered
as illustrative of the invention only and not as limiting
its scope as defined in accordance with the accompanying
claims.
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