Note: Descriptions are shown in the official language in which they were submitted.
CUSHION CONNECTOR ~ `
INTRODUCTION ;
This invention relates to a cushion connector
and, more particularly, to a cushion connector used for
blast hole above ground drilling.
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BACKGROUND OF THB INVENTION
Cushion connectors are u~ed to cushion the shock
c.eated by the drill bit during drilling and passed ~ - '
through the drill ~tring 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 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 pi~ton which moves
relative to the housinq and acts principally to absorb ~ ~
compression shocks which are passed from the drill bit to ~ -
the drill drivelh~ad.
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A problem with the use of elastomeric 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
confi~uration 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.
SUMMARY 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 of said
piston, at least one drive lug extending inwardly from
said housing, a drive block between said housing and said
25 piston, and being engageable with said drive spline and a ~ ~`
spring acting between said pin and box components, said
drive spline3 being coaxial with said spring and operable
to move axially within said drive blocks.
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BRIEF DESCRIPT~QN OF THE SEVERA~ VIEWS OF THE DRAWINGS -
A specific embodiment of the invention will now
be described, by way of example only, with the use of
drawings in which~
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Figure 1 is a sectional side view of the cushion
connector according to the invention;
Figure 2 i~ a sectional view taken along the
plane II-II of Figure 1;
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Figure 3 is an isometric view of a single one of ;~
the cushion blocks; and
~0 Figure 4 is a sectional view of a further
embodiment of the invention.
DESCRIPTION OF SPECIFIC EMBOD:EMEN~ ~;:
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Reference i8 now made to the drawings and, in .:~
: particular, to Figure 1 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.
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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 : :
: . 25 periphery of the cap 14. A piston 21 extends from the pin ~
: component 11 and is movable with the pin component 11 ;::
relative to the housing 13 and box end 12. The piston 21 : ~:
includes a plurality of,drive splines 22 (Figure 2) ..
extending outwardly from the axis 23 of the piston 21, the
30 drive splinefi 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 Figure 1. Two sets of Belleville or disc
~prings 30, 60, having different outside diameters, are
mounted in a recess provided between the piston 21 and a
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skirt 31 in respective cylindrical rece~ses 36, 35. The
two sets of disc springs 30, 60 extend between the pin
component 11 and the box component 12 as is seen in Figure
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 ~ounted within
the box end 12 as illu~trated.
The use of the disc springs 30 having a larger
diameter than the diameter of disc springs 60 is permitted
15 by the use of the skirt 31 which has a larger internal ,~
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 ,~
20 otherwise would be required. ,`~
The relative 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
2S preventing the migration of the cushion blocks 70 inwardly~'~,;,
and away ~rom their po~ltion between the drive lugs 71 and . `','',':'
the drive blocks 24 as ~et out hereafter. A wear and:,' ,'',~
corros,ion resistant sleeve 63 i8 mounted about the distant,
periphery of the extension 61. ~,,:~:"
Guide rings 50 and wiper seals 51 are mounted
between the box end 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. ~ , ':
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An elastomer back up cushion 63 (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. As illustrated in Figure 1, the cushion ~
blocXs 70 are compressed when the cushion connector 10 is ~ ;
assembled as will be described in greater detail.
High radial loads are imposed on the cover plate
or cap 14 by the piston 21. This is so because it is
contemplated the interaction between the drill drive head ;
(not shown) and the rotating drill steel (not shown)
20 connected to the cushion connector 10 attempts to use the ; ;~`~
cushion connector 10 as a ball ~oint 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.
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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 11 will be
significantly reduced or eliminated entirely with the
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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 lower and
upper 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.
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OPERATION
The cushion connector lo will be initially
asæembled by having the box component 12 in the lowermost
15 position with the axis 23 of the cushion connector 10 ;~
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 ~locks 24 to slide around the inside
of housing 13 a limited angular amount such that the drive
blocks 24 are free to align with and permit insertion of
the drive splines 22 into the respective keyway~ 64 in the
drive blocks 24.
The disc spri~gs 30, 60 will then be pasitioned
in recesses 35, 36.
The cap 14 which has guide ring 52 and the
wiper seal 53 previously inserted i8 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
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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.
A fitting 15 is provided to allow for grease
insertion for lubricating the cushion connector 10. The
grease is routed through the fitting 15 between the inside
of the disc springs 30, 60 and the outside of the
lo extension or wash pipe 61 through hole 63 and into the
drive block keyways 64 and spline æliding fit areas. The
excess of the grease exits through relief fitting 73. -
The shape of the cushion blocks 70 is
illustrate`d 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.
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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. When the elastomeric material
from which the blocks 70 are made is compressed, the
material will change in~shape but not in vqiume. 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 accommodate 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.
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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 ~ ~ -
5 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
70.
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The cushion connector lo is then connected with
the pin end 11 to the drill drive head (not illustrated)
and the drill steel (not illustrated) is connected to the
box end 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 compre~s the springs and extend the springs
30, 60. The tor~ion created by the drill head on the pin
end 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 12.
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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, 60 have a common in~ide diameter and spring
5 rate but the cprings 30 have a larger outside diameter,;; -;;
being at a location which makes the increased volume
available.
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The larger diameter disc springs 30 provide a
longer stroke per spring which allows the overall length
of the cushion connector $0 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 lo.
An additional embodiment of the cushion
connector 10 according to the invention i8 illustrated in
Figure 4 wherein like numerals represent similar elements
as those illustrated in the embodiment of Figures 1 and 2.
In thi~ embodiment, the extension 61 of the
Figure 1 embodiment is replaced with a wear and corrosion
resistant washpipe 80 w!hich i8 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 end -
12 and collar 82 being removably mounted within pin end -
ll. The washpipe 80 allows for limited angular movement
betwesn the pin and box components 11, 12 and is
35 mai~tained in an axial position within the connector 10 by `~
the reduced bore 85 of the pin end 11 and the retaining
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ring 84. The washpipe 80 can be removed without
disassembly of the connector 10 by removing the retaining
ring 84.
The outside diameter of the disc springs 30 in :~;` . .
this embodiment are identical which i 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 ~ :
lo and pin ends 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.
Wiper ring~ 83, 84 are provided which act as
seals between the collars 81, 82, the washpipe 80 and the
pin and box components 11, 12.
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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 seals 83, 84 are illustrated in the
25 Figure 4 embodiment as being in~erted in recesses ln the ~ ;
collars 81, 82, it is contemplated that the seals 83, 84
could be mounted in the washpipe 80. In this event, seals
83, 84 could be replaced by.removing the washpipe 80 which
can be conveniently accomplished by simply removing the
retaining ring 84 and retrieving the washpipe 80 together
with the seals 83, 84 from the box end 12 without
otherwise disassembling the cushion connector 10.
Many further modifications to the apparatus
35 described and illustrated will readily occur to those -~
skilled in the art to which the invention relates and the : ~ 3
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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