A coupling for transferring torque and axial force from a first member to a second member. The coupling includes a first cylindrical member having an outer peripheral surface and an end portion and a second cylindrical member having a receiving end portion. The receiving end portion has an end face with a longitudinal bore in the receiving end portion for receiving the end portion of the first cylindrical member. The end portion of the first cylindrical member has a plurality of transverse keyways in the outer peripheral surface. The receiving end portion of the second cylindrical member has a plurality of transverse slots in the receiving end portion corresponding to the plurality of transverse keyways. A key is received in each transverse keyway and protrudes from each transverse keyway into the corresponding transverse slot. A retainer ring has a bore such that the retainer ring extends over the plurality of transverse slots of the receiving end portion of the second cylindrical member. The keys axially and non-rotatably connect the first member to the second member.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a high strength coupling which transfers 
axial force and torque from one member to another via a key and keyway 
arrangement. 
2. Description of the Prior Art 
Many types of couplings have been used to connect one cylindrical member to 
another. In many instances, it is necessary to transfer axial force and 
torque from one shaft or pipe member to a second shaft or pipe member. 
Oftentimes, it is desirable that the coupling be easy to connect and 
disconnect which eliminates connecting the members by a permanent means 
such as welding. 
Threaded couplings have been used to provide a quick connect/disconnect 
coupling. Threaded couplings transfer axial compressive and tensile forces 
and torque in one direction about the longitudinal axis. Threaded 
couplings have the disadvantage in that the threaded coupling will not 
take high torque loads in both the clockwise and counter-clockwise 
directions due to the threaded make-up of the coupling. Furthermore, the 
threaded coupling is extremely difficult to disconnect after prolonged 
periods of torque transfer due to the frictional engagement of the 
threads. Threaded couplings are also subject to damaged threads and 
cross-threading during the coupling make-up which can result in the 
replacement of the coupling member. 
Various arrangements of keys and keyways have been used to form axial load 
and torque transferring couplings as, for example, shown in U.S. Pat. Nos. 
4,893,962, 3,433,512, 3,315,993, 2,756,022, and 2,032,491. Typically, in 
key/keyway couplings, the key is subjected to shear stress both by the 
torque and the axial load. Shear stress is directly proportional to the 
cross-sectional area of the key in shear. The maximum design rating for 
the coupling is often limited by the shear stress of the key. 
U.S. Pat. No. 573,695 discloses a coupling for joining an inner cylindrical 
tube to an outer cylindrical tube wherein the inner cylindrical tube 
includes a transverse keyway and the outer cylindrical tube includes a 
transverse slot. A key having an arcuate surface extends through the slot 
and into the keyway. A retaining band is driven over the arcuate surface 
of the key thereby forcing the key inward to complete the joint. The 
downward pressure applied to the key by the retaining band causes the 
inner tube to expand somewhat or spring into more intimate binding contact 
with the outer tube. 
U.S. Pat. No. 2,756,022 discloses a shock absorber coupling wherein an 
inner cylindrical tube is joined to an outer cylindrical tube. The inner 
cylindrical tube includes a longitudinal keyway and the outer cylindrical 
tube includes an elongated longitudinal slot. A rectangular key extends 
through the longitudinal slot and into the longitudinal keyway. A 
retaining sleeve is positioned over the longitudinal keyway and the 
rectangular key to maintain the connection of the inner and outer 
cylindrical members. 
It is desirable to have a high strength coupling which can transfer both 
axial tensile and compressive forces and torque in both directions around 
the longitudinal axis of the connected members. The high strength coupling 
should be of simple construction, low cost and quick and easy to connect 
and disconnect. 
SUMMARY OF THE PRESENT INVENTION 
The present invention is a high strength coupling which can transfer both 
axial tensile and compressive forces and torque in both directions around 
the longitudinal axis of the connected members. The coupling is simple in 
construction, economical, compact and easy to assemble and disassemble. 
The coupling can be quickly and easily connected and disconnected. 
The high strength coupling of the present invention transfers torque and 
axial force from a first member to a second member. The coupling includes 
a first cylindrical member having an outer peripheral surface and an end 
portion and a second cylindrical member having a receiving end portion. 
The receiving end portion has an end face with a longitudinal bore therein 
for receiving the end portion of the first cylindrical member. The end 
portion of the first cylindrical member has a plurality of transverse 
keyways in the outer peripheral surface. The receiving end portion of the 
second cylindrical member has a plurality of transverse slots therein 
corresponding to the plurality of transverse keyways. A key is received in 
each transverse keyway and protrudes therefrom into the corresponding 
transverse slot. A retainer ring has a bore therethrough such that the 
retainer ring extends over the plurality of transverse slots of the 
receiving end portion of the second cylindrical member. The keys axially 
and non-rotatably connect the first member to the second member and 
provide a high strength coupling. Torsional forces radially force the keys 
against the retainer ring. The retainer ring counteracts the torsional 
forces and results in an extremely high strength coupling.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to the drawings in greater detail, the high strength coupling 
of the present invention, generally designated by the letter C, comprises 
a first cylindrical member 10 having an outer peripheral surface 12 and an 
end portion 14 with an end face 15. The coupling C includes a second 
cylindrical member 16 having a receiving end portion 18. Referring to 
FIGS. 1, 3, 4 and 7, the receiving end portion 18 has an end face 20 with 
a longitudinal bore 22 therein for receiving the end portion 14 of the 
first cylindrical member 10. The receiving end portion 18 includes an 
internal shoulder 19 at the inner end of the longitudinal bore 22. The 
first cylindrical member 10 has a longitudinal axis 11 and the second 
cylindrical member 16 has a longitudinal axis 17 as shown in FIGS. 1, 3, 4 
and 7. 
For purposes of illustration, the first and second members 10 and 16, 
respectively, have been shown as having a longitudinal bore 24 and 26, 
respectively, therethrough which are in axial alignment and form a 
continuous throughbore in the coupled configuration as shown in FIGS. 1, 
3, 4 and 7. A circumferential groove 28 in the peripheral surface 12 of 
the end portion 14 of the first member 10 receives a seal means 30, as for 
example an O-ring, to provide a fluid-tight seal between the first and 
second members 10 and 16, respectively. Alternatively, the circumferential 
groove 28 and the seal means 30 could be included in either the end face 
15 of the first cylindrical member 10 or the shoulder 19 of the second 
cylindrical member 16. It is to be understood that the first and second 
members 10 and 16, respectively, could also be solid members with no 
throughbores 24 and 26, respectively, such as shafts. In such a case, the 
circumferential groove 28 and seal means 30 would not be necessary. 
Referring to FIGS. 1-5, 7 and 8, the end portion 14 of the first 
cylindrical member 10 has one or more transverse keyways 32 in the outer 
peripheral surface 12. Each keyway 32 includes a pair of parallel side 
surfaces 38 and 40 and a bottom surface 42 therebetween. Preferably, the 
bottom surface 42 is parallel to a plane tangential to the outer 
peripheral surface 12 of the first cylindrical member 10. Due to the 
curvature of the outer peripheral surface 12 of the first cylindrical 
member 10, each keyway 32 gradually decreases in depth from its middle to 
its ends where it merges into the outer peripheral surface 12 of the first 
member 10. 
In the first embodiment shown in FIGS. 1 and 2, the first cylindrical 
member 10 is shown as having three transverse keyways 32 which are 
equidistantly spaced from one another in a common plane transverse to the 
longitudinal axis 11. It is to be understood that the coupling C can have 
one or more transverse keyways 32 although three is preferable in a common 
plane. If the coupling C has two transverse keyways 32, the transverse 
keyways 32 should be displaced 180.degree. from each other. In the 
embodiment shown in FIGS. 4 and 5, the transverse keyways 32 are 
equidistantly spaced about the longitudinal axis 11 in separate parallel 
planes. This "staggered" configuration serves to further improve the 
stress characteristics of the first cylindrical member 10 and may be 
preferred in those applications where the increased length of the coupling 
C is of no concern. Alternatively, two or more sets of a plurality of 
transverse keyways 32 could be placed in two parallel planes. The exact 
configuration to use will depend on various design, manufacturing and 
economic parameters. 
In the embodiments shown in FIGS. 1-5, the receiving end portion 18 of the 
second cylindrical member 16 has a cylindrical outer surface 36 and one or 
more transverse slots 34 therein. Each transverse slot 34 includes a pair 
of parallel side walls 44 and 46 and a pair of end walls 48 and 50 
therebetween as shown in FIGS. 2 and 5. In the embodiments shown in FIGS. 
1-5, the pair of end walls 48 and 50 are in generally planer alignment 
with the bottom surface 42 of the corresponding transverse keyway 32. The 
number of transverse slots 34 corresponds to the number of transverse 
keyways 32. 
Still referring to the embodiments shown in FIGS. 1-5, a key 52 is received 
in each transverse keyway 32 and protrudes therefrom into the 
corresponding transverse slot 34. Each key 52 has an arcuate surface 54 
corresponding to the cylindrical outer surface 36 of the receiving end 
portion 18 of the second cylindrical member 16 and a substantially planer 
surface 56 having a length of approximately the distance between the 
corresponding pair of end walls 48 and 50 at the cylindrical outer surface 
36. Each key 52 has a thickness approximating the distance between the 
pair of parallel side walls 44 and 46 of the corresponding transverse slot 
34. Typically, the distance between the corresponding pair of parallel 
side surfaces 38 and 40 of the transverse keyway 32 approximates the 
thickness of the key 52. 
Typically, it may be desirable to have the end face 15 of the first 
cylindrical member 10 in substantially abutting contact with the shoulder 
19 of the second cylindrical member 16 to lessen or eliminate the shear 
stress in the keys 52 when the coupling C is subjected to compressive 
axial loading. 
In some instances, it may be desirable to have a coupling C which, in 
addition to transferring axial loads and torque, will also allow a 
generally small amount of axial movement of the first and second members 
10 and 16, respectively, relative to one another. One such example is a 
shock absorber coupling for a rotary drill stem as described in U.S. Pat. 
No. 2,756,022. In the present invention, relative axial movement between 
the first and second members 10 and 16, respectively, can be accomplished 
by increasing the distance between the pair of parallel side surfaces 38 
and 40 of the transverse keyway 32 as shown in FIG. 3. The keys 52 will 
remain in place by the surface contact with the bottom surface 42 of the 
transverse keyway 32, the transverse slot side walls 44 and 46, and a 
retainer ring 58 as described below. 
With specific reference to the embodiment shown in FIGS. 6-8, the receiving 
end portion 18 of the second cylindrical member 16 has a cylindrical outer 
surface 36 and one or more transverse slots 34' therein. Each transverse 
slot 34' includes a pair of parallel side walls 44' and 46' and a pair of 
end walls 48' and 50' therebetween as shown in FIGS. 6 and 8. In the 
embodiment shown in FIGS. 6-8, the pair of end walls 48' and 50' are 
generally transverse to the bottom surface 42 of the corresponding 
transverse keyway 32. As shown in FIG. 6, the transverse slots 34' 
preferably include rounded corners 51' where the side walls 44', 46' meet 
the end walls 48', 50'. The rounded corners 51' distribute the stress over 
a large area and eliminate high concentrated stress points located at 
sharp corners. The number of transverse slots 34' corresponds to the 
number of transverse keyways 32. 
With reference to the embodiment shown in FIGS. 6-8, a key 52' is received 
in each transverse keyway 32 and protrudes therefrom into the 
corresponding transverse slot 34. Each key 52' has an arcuate surface 54' 
corresponding to the cylindrical outer surface 36 of the receiving end 
portion 18 of the second cylindrical member 16 and a substantially planer 
surface 56' having a length of approximately the length of the bottom 
surface 42 of the transverse keyway 32. Each key 52' includes a pair of 
end faces 53' which are substantially transverse to the planer surface 56' 
as shown in FIG. 8. Preferably, the end faces 53' are also rounded where 
the end face 53' meets the upper and lower faces 55' and 57', 
respectively, of the key 52' to cooperatively fit with the rounded corners 
51 of the transverse slot 34. Each key 52' has a thickness approximating 
the distance between the pair of parallel side walls 44 and 46 of the 
corresponding transverse slot 34. Typically, the distance between the 
corresponding pair of parallel side surfaces 38 and 40 of the transverse 
keyway 32 approximates the thickness of the key 52'. 
As indicated above, it is typically desirable to have the end face 15 of 
the first cylindrical member 10 in substantially abutting contact with the 
shoulder 19 of the second cylindrical member 16 to lessen or eliminate the 
shear stress in the keys 52' when the coupling C is subjected to 
compressive axial loading. It is to be further understood that the 
embodiment shown in FIGS. 6-8 and as described above may also be modified 
and utilized in the same manner as the previous embodiments described 
above and/or shown in FIGS. 1-5. 
Referring to FIGS. 1-8, the retainer ring 58 has a bore 60 therethrough 
such that the retainer ring 58 extends over the plurality of transverse 
slots 34, 34' of the receiving end portion 18 of the second cylindrical 
member 16. The diameter of the bore 60 generally corresponds to the outer 
diameter of the receiving end portion 18 proximate to the transverse slots 
34, 34'. The retainer ring 58 can be maintained in position over the 
transverse slots 34, 34' in various ways. FIGS. 1, 3 and 4 show the 
cylindrical outer surface 36 of the receiving end portion 18 having a 
shoulder 62 abutting the retainer ring 58 and a ring 64, such as a snap 
ring, inserted in an outer groove 66 to limit the movement of the retainer 
ring 58 in the longitudinal direction. FIGS. 7 and 8 show a pair of rings 
64 inserted in a pair of outer grooves 66 to limit the longitudinal 
movement of the retainer ring 58. Alternatively, the retainer ring 58 
could be maintained in position by one or more set screws (not shown) 
extending through the side of the retainer ring 58 and engaging the 
receiving end portion 18 of the second member 16. Other means for 
maintaining the retainer ring 58 in place include clamps, split ring 
clamps, swedge locks, drilled and tapped bolts, or weld metal placed 
adjacent to the desired position of the retainer ring 58 to name a few. 
Alternatively, with reference to FIGS. 7 and 8, the retainer ring 58 could 
be extended in length and include an upper inner flange which would 
contact end face 20 and be further provided with a set screw for 
maintaining the retainer ring 58 in this position. As can be easily seen 
by the foregoing examples, the retainer ring 58 may include any one of a 
wide variety of means for maintaining the retainer ring 58 in the 
The retainer ring 58 maintains the keys 52, 52' in the transverse slots 34, 
34' and the transverse keyways 32 and between the bottom surface 42 of the 
transverse keyway 32 and the retainer ring 58. 
The assembly of the various embodiments of the high strength coupling C is 
essentially the same for all of the embodiments. The assembly of the 
embodiments shown in FIGS. 1-5 will first be described followed by a 
description of the embodiment shown in FIGS. 6-8. 
Referring to FIGS. 1-5, the high strength coupling C is assembled by 
placing the snap ring 64 and the retainer ring 58 over the end portion 14 
of the first cylindrical member 10 and then inserting the end portion 14 
of the first cylindrical member 10 into the receiving end portion 18 of 
the second cylindrical member 16. The transverse keyways 32 are aligned 
with the transverse slots 34. The keys 52 are inserted through the 
transverse slots 34 until the planer surface 56 of the keys 52 contacts 
the bottom surface 42 of the transverse keyways 32 and the pair of end 
walls 48 and 50 of the transverse slots 34. When the keys 52 are 
installed, the arcuate surface 54 of the key 52 is substantially flush 
with the adjacent cylindrical outer surface 36 of the receiving end 
portion 18 of the second cylindrical member 16 as shown in FIGS. 2 and 5. 
The retainer ring 58 is slid onto the receiving end portion 18 of the 
second cylindrical member 16 and over the transverse slots 34 and keys 52. 
The retainer ring 58 abuts the shoulder 62 and the snap ring 64 is 
installed in the outer groove 66. The keys axially and nonrotatably 
connect the first member to the second member and provide a high strength 
coupling. 
Preferably, the keys 52 freely slide through the transverse slots 34 and 
into the transverse keyways 32 so that upon assembly and disassembly of 
the coupling C the keys 52 are easily installed and removed, respectively. 
It is desirable that the clearance between the keys 52 and the transverse 
slots 34 and the transverse keyways 32 be extremely small, for example on 
the order of approximately "0.002" or less to minimize the "play" in the 
coupling C while permitting easy installation and removal of the keys 52. 
In use, upon rotational force being applied to the first cylindrical member 
10, the bottom surface 42 of the transverse keyways 32 attempts to rotate 
the keys 52. For exemplary purposes, the rotational force shall be assumed 
to be applied in a clockwise direction. Assuming that the second 
cylindrical member 16 does not freely rotate, the keys 52 are resisted by 
the end walls 50 of the transverse slots 34. The rotational force radially 
forces the keys 52 against the retainer ring 58. The retainer ring 58 
counteracts the outward radial force of the keys 52 and distributes the 
torque load among the coupling components which results in an extremely 
high strength coupling. The retainer ring 58 is subjected to radial 
tensile force by the keys 52. The thickness of the retainer ring 58 can be 
designed to counteract the radial tensile forces expected to be 
experienced by the coupling C to prevent shear failure of the retainer 
ring 58. The keys 52 are subjected to shear stress by the applied axial 
load. The dashed lines in FIGS. 2 and 5 coincide with a shear line in the 
keys 52 under axial loading of the coupling C. 
Referring to FIGS. 6-8, this embodiment of the high strength coupling C is 
assembled by placing the upper snap ring 64 and the retainer ring 58 over 
the end portion 14 of the first cylindrical member 10. The lower snap ring 
64 is also either placed over the end portion 14 or installed in the lower 
outer groove 66 of the second cylindrical member 16. The end portion 14 of 
the first cylindrical member 10 is inserted into the receiving end portion 
18 of the second cylindrical member 16. The transverse keyways 32 are 
aligned with the transverse slots 34'. The keys 52' are inserted through 
the transverse slots 34' until the planer surface 56' of the keys 52' 
contacts the bottom surface 42 of the transverse keyways 32 and the pair 
of end walls 48' and 50' of the transverse slots 34'. When the keys 52' 
are installed, the arcuate surface 54' of the key 52' is substantially 
flush with the adjacent cylindrical outer surface 36 of the receiving end 
portion 18 of the second cylindrical member 16 as shown in FIGS. 7 and 8. 
The retainer ring 58 is slid onto the receiving end portion 18 of the 
second cylindrical member 16 and over the transverse slots 34' and keys 
52'. The retainer ring 58 abuts the lower snap ring 64 and the upper snap 
ring 64 is installed in the upper outer groove 66. The keys 52' axially 
and non-rotatably connect the first member 10 to the second member 16 and 
provide a high strength coupling C. 
Preferably, the keys 52' freely slide through the transverse slots 34' and 
into the transverse keyways 32 so that upon assembly and disassembly of 
the coupling C the keys 52' are easily installed and removed, 
respectively. It is desirable that the clearance between the keys 52' and 
the transverse slots 34' and the transverse keyways 32 be extremely small, 
for example on the order of approximately 0.002.increment. or less to 
minimize the "play" in the coupling C while permitting easy installation 
and removal of the keys 52'. 
In use, upon rotational force being applied to the first cylindrical member 
10, the bottom surface 42 of the transverse keyways 32 attempts to rotate 
the keys 52'. For exemplary purposes, the rotational force shall be 
assumed to be applied in a clockwise direction. Assuming that the second 
cylindrical member 16 does not freely rotate, the keys 52' are resisted by 
the end walls 50' of the transverse slots 34'. The rotational force 
radially forces the keys 52' against the retainer ring 58. The retainer 
ring 58 counteracts the outward radial force of the keys 52' and 
distributes the torque load among the coupling components which results in 
an extremely high strength coupling. The retainer ring 58 is subjected to 
radial tensile force by the keys 52'. The thickness of the retainer ring 
58 can be designed to counteract the radial tensile forces expected to be 
experienced by the coupling C to prevent shear failure of the retainer 
ring 58. The keys 52' can be subjected to shear stress by applying an 
axial load. 
Preferably, the members used in the high strength coupling C of the present 
invention are made of high strength steels to provide a very strong 
coupling. The cylindrical members of the high strength coupling C are 
interengaged by the key or keys independent of deformation of the 
cylindrical members. 
The high strength coupling C of the present invention uniquely distributes 
the torque load. The high strength coupling C is highly efficient and 
allows greater torque transmission than typical key/keyway couplings. The 
high strength coupling C provides perfect alignment of the members 10 and 
16, requires no threaded connection, and is quick and easy to assemble and 
disassemble. 
The high strength coupling C has many and varied uses in numerous 
industries and applications. The high strength coupling C can be used in 
applications in which torque and/or axial loads are to be transferred from 
one member to another. For example, the high strength coupling C can be 
used for drive shaft couplings, automatic break-outs, shock subs, saver 
subs, pull swivels and tool joints, just to name a few. 
Some of the various configurations of the high strength coupling C have 
been shown in the drawings and are intended to be representative of the 
various adaptations which might be used. The preferable configuration for 
a certain application will be determined from various parameters, for 
example design loads, strengths of the various materials being joined and 
used to form the coupling, physical coupling dimension limitations, size 
of members being joined, tooling availability, and manufacturing costs. 
For example, it has been found that for joining cylindrical members having 
a diameter of approximately 2" or smaller that the preferred design is to 
use two keys of the type shown in FIGS. 1-5 as opposed to the rounded keys 
shown in FIGS. 6-8. When joining cylindrical members having a diameter 
greater than approximately 2" the preferred design is to use three keys of 
the type shown in FIGS. 6-8. 
The rounded key design as shown in FIGS. 6-8 is also the preferred design 
in applications where the coupling is going to be subjected to shock loads 
resulting from axial impacts. As stated above, the rounded keys improve 
the stress distribution resulting from shock loads. 
As yet another example as to which configuration is the preferred coupling 
design, the general configuration of the high strength coupling C shown in 
FIGS. 6-8 has demonstrated a higher ultimate strength and loading 
capability than the embodiment shown in FIGS. 1 and 2, although the 
embodiment shown in FIGS. 6-8 requires different tooling equipment to 
manufacture the rounded openings and keys and may also have a slightly 
higher cost to manufacture. Both of these embodiments provide couplings of 
high strength which are easy to assemble and disassemble. However, if 
ultimate strength of the coupling is of primary importance, the embodiment 
shown in FIGS. 6-8 with the rounded corners provides higher ultimate 
strength and loading capability and would be the preferred coupling 
design. Although, for a particular application, the embodiment of FIGS. 1 
and 2 may provide ample load capability, be easier to manufacture and at a 
slightly less cost than the embodiment of FIGS. 6-8 in which case the 
embodiment of FIGS. 1 and 2 may be preferred. Similarly, there will be 
certain applications where other of the embodiments shown in the drawings 
will be the most desirable coupling due to the circumstances. 
The foregoing disclosure and description of the invention is illustrative 
and explanatory thereof, and various changes in the size, shape, and 
materials, as well as in the details of illustrative construction and 
assembly, may be made without departing from the spirit of the invention.