Coupling device

A coupling device for connecting a male member and a female member comprises a lock pin resiliently urged toward the male member by means of a spring to permit an insertion of the female member but extend into a lock groove of said male member to connect these members, an outer race rotatively resiliently urged in one direction relative to the female member and formed with a recess for receiving a part of the lock pin to permit it to remove from the lock groove of the male member, a slide pin for locking the outer race relative to the female member when the male member is not in the female member and releasing the outer race relative to the female member when the male member is inserted in the female member, and an outer race lock pin urged by an outer race lock pin spring to lock the outer race relative to the female member when the outer race is rotated. The coupling device is capable of connecting two members by a mere insertion of one member into the other member and disconnecting the two members by a slight rotation of the outer race on the other member.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a coupling device particularly suitable 
for connecting shafts for rotative power transmission and, more 
particularly, to a coupling device for all kinds of mechanical connections 
not exclusively for power transmission, capable of connecting a male 
member and a female member without any particular operation and 
disconnecting these members by a simple operation with ease if desired. 
2. Description of the Prior Art 
Connections for shafts have been used for various kinds of machines. Such 
connections are often located in limited spaces in the machines and are 
generally difficult and dangerous in operation. Particularly covers for 
protecting the connections from dusty atmosphere make more difficult the 
operation of the connections. It is clearly evident that a coupling device 
is advantageous in all kinds of machines, which is rapid and easy in 
connecting and disconnecting operations to improve the maneuverability of 
the machines. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a coupling device 
capable of connecting two members by a mere insertion of one member into 
the other member and disconnecting the two members by a slight rotation of 
a member provided on the other member. 
It is another object of the present invention to provide a coupling device 
in simple in construction, easy and positive in operation and economical 
of manufacture. 
In order to achieve these objects, the coupling device according to the 
invention including a male member having a tip tapered portion and a lock 
groove and a female member for receiving said male member comprises a lock 
pin resiliently urged toward said male member by means of spring means 
such that when said male member is inserted into said female member said 
lock pin is once forced away from said male member by a camming action of 
the tip tapered portion of the male member and extends into said lock 
groove when said lock pin becomes in opposition to said lock groove by a 
further insertion of the male member into said female member; an outer 
race rotatively resiliently urged in one direction relative to said female 
member by outer race spring means and formed with a recess for receiving a 
part of said lock pin to permit it to remove from said lock groove of said 
male member, said outer race being rotated by said outer race spring means 
when said lock pin extends into said lock groove of said male member to 
locate said recess of the outer race in a position remote from said lock 
pin to lock it relative to said male member; a slide pin for locking said 
outer race relative to said female member when said male member is not in 
said female member and releasing said outer race relative to said female 
member by an movement of said slide pin when said male member is inserted 
in said female member; and an outer race lock pin urged by outer race lock 
pin spring means to lock said outer race relative to said female member 
when the outer race is rotated to bring said recess in aligned with said 
lock pin for removing said male member from said female member. 
In order that the invention may be more clearly understood, preferred 
embodiments will now be described, by way of example, with reference to 
the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIGS. 1 and 2 of the drawings, illustrating the first 
embodiment of the coupling device according to the present invention, the 
device is applicable to a coupling for connecting a spline shaft 2 to a 
yoke 4 to be driven in the direction of an arrow 1. It should of course be 
understood that the present invention may also be applicable to 
connections of shafts other than splined shafts such as those including 
keys and key ways and other torque transmission means. 
The spline shaft 2 is formed at its end with a tip tapered portion 6 and at 
a location away therefrom with a circular lock groove 8 for a lock pin. As 
shown in FIG. 1, an outer race 10 is closely fitted on the yoke 4 and held 
in position by means of a retaining or snap ring 12 for preventing the 
outer race 10 from coming off from the yoke 4. The outer race is 
preferably made of a plastic material. 
The yoke 4 is formed with a stepped hole 14 to form a shoulder therein, 
upon which a push pin 16 rests such that a reduced diameter portion 18 of 
the push pin 16 in the from of a mushroom extends into a splined bore of 
the yoke and adapted to engage the spline shaft 2. The outer race 10 is 
formed with an aperture 20 in alignment with the stepped hole 14 for 
slidingly receiving a slide pin 22. A cover 24 is arranged at the outer 
end of the aperture 20, and a spiral spring 26 in the form of a frust-cone 
is located between the cover 24 and the slide pin 22 in the aperture 20 to 
cause the slide pin 20 to urge the push pin 16 inwardly with the aid of 
the compressive force of the spiral spring 26. 
The slide pin 22 is formed with a blind hole 28' perpendicular to an axis 
of the slide pin 22 for a lock pin 28 slidable in the hole 28' and adapted 
to be urged outwardly by a compression spring 30 located at the bottom of 
the blind hole 28'. The term "blind hole" used herein means a hole having 
a bottom, which is not a through hole. The hole 28' in the slide pin 22 
may be a through hole. As can be seen in FIGS. 1 and 2, a shallow recess 
32 is formed in the yoke 4 at a location slightly shifted from a contact 
position of the lock pin 28 of the slide pin 22 with the yoke 4. (The 
shallow recess 32 is shifted slightly to the upper right as viewed in FIG. 
2.) The shallow recess 32 includes a taper surface 34 on the side near the 
center of the yoke 4 (FIG. 1). Functions of the recess 32 and the taper 
surface 34 will be explained latter. 
As shown in FIGS. 1 and 3, the yoke 4 is formed with a lock pin hole 36 for 
slidably receiving a lock pin 38. The inner end of the lock pin 38 is 
semicircular as viewed in FIG. 1, but is flat as viewed in a plane normal 
to that of FIG. 1, which engages in the circular groove 8 in the spline 
shaft 2 to lock it in the yoke 4 when they are connected. The lock pin 38 
is formed at its outer end with a small aperture 40 through which an 
annular spring 42 passes to restrain resiliently the outward movement of 
the lock pin 38. Such an annular spring 42 additionally serves to prevent 
the lock pin 38 from rotating and falling off into the splined bore of the 
yoke 4. The annular spring is particularly advantageous in case of two 
diametrically opposite lock pins or three or more lock pins 
circumferentially equally spaced apart in the yoke. The outer race 10 is 
formed on its outer periphery with saw-toothed surface 44 to facilitate 
rotating the outer race 10 manually or by means of a lever. A knurled 
surface may be substituted for the saw-toothed surface when the outer race 
10 is operated only by hand. If mechanical driving means is used for 
rotating the outer race 10, any suitable means on the outer race 10 mating 
with the driving means may be used. The outer race 10 is formed in its 
inner surface with a recess 60 (FIG. 3), which will be explained latter. 
It is preferable to provide one push pin 16, one slide pin 22 and two lock 
pins 38 diametrically opposite to each other. 
As can be seen from FIG. 2, the outer race 10 is formed in its surface in 
contact with the yoke 4 with an arcuate groove 46, within which slides a 
protrusion 48 formed in the yoke to limit the rotation of the outer race 
10 relative to the yoke 4 by an abutment of the protrusion 48 with one end 
or left end of the arcuate groove 46 as viewed in FIG. 2. Furthermore, a 
compression spring 50 is arranged along the arcuate groove 46 between the 
protrusion 48 and the other end of the arcuate groove 46 to urge the outer 
race in a counterclockwise direction as viewed in FIG. 2 (the direction of 
an arrow 52). 
In the urged condition of the outer race 10 in the direction of the arrow 
52, the slide pin 22 is urged against the enlarged diameter portion 14' of 
the stepped hole 14 in the yoke 4 at the lower end of the slide pin 22 in 
contact with the push pin 16. In this embodiment, the diameter of the 
enlarged portion 14' of the stepped hole 14 was 2 mm larger than that of 
the slide pin 22. The shallow recess 32 was shifted 1 mm. toward the right 
and the center of the lock pin 38 was shifted 1 mm. toward the left as 
viewed in FIG. 2. 
The operation of the coupling device shown in FIGS. 1-3 will be explained 
with reference to FIGS. 4-8. FIGS. 4a-4c illustrate the coupling device in 
the condition the same as that of FIGS. 1-3 capable of connecting the 
spline shaft by a mere insertion thereof into the yoke without requiring 
any particular operation. The push pin 16 is urged inwardly by the slide 
pin 22 with the aid of the compressive force of the spiral spring 26 so 
that the reduced diameter portion of the push pin 16 extends into the 
spline groove of the yoke. The lock pin 38 is also urged inwardly by the 
action of the annular spring 42 so that the inner end of the lock pin 38 
extends into the spline groove of the yoke. 
The outer race 10 is urged by an action of the spring 50 in the 
counterclockwise direction as viewed in FIG. 4a but does not rotate 
relative to the yoke 4 because of the lower end of the slide pin 22 within 
the stepped hole 14 in the yoke 4. 
Starting from the condition in FIG. 4, the spline shaft 2 is inserted into 
the yoke 4 (FIG. 5). First the lock pin 38 is forced outwardly away from 
the spline shaft against the compressive force of the annular spring 42 by 
a camming action of the tapered portion 6 of the spline shaft 2, so that 
the spline shaft 2 can be inserted into the yoke 4 beyond the position of 
the lock pin 38. The push pin 16 is then forced outwardly against the 
compressive force of the spiral spring 26 by the camming action of the 
tapered portion 6 of the spline shaft 2 so that the spline shaft 2 can be 
further inserted into the yoke 4 (FIG. 5). 
In the condition shown in FIG. 5, the outer end of the lock pin 38 extends 
in the recess 60 formed in the inside of the outer race 10. The lock pin 
28 has been raised outwardly together with the slide pin 22 and in the 
proximity of the recess 32 of the yoke. In this condition, however, the 
lock pin 28 could not extend into the recess 32 in spite of the 
compressive force of the spring 30, because the lock pin 28 is not in 
alignment with the recess 32 as shown in FIG. 5a. 
The spline shaft 2 is further inserted from the position shown in FIG. 5 
into the splined bore of the yoke until the lock pin 38 becomes in 
registry with the lock groove 8 of the spline shaft 2 just when the inner 
end of the lock pin 38 extends into the lock groove 8 of the spline shaft 
2 by the action of the annular spring 42 (FIG. 6). When the inner end of 
the lock pin 38 has extended in the lock groove 8 of the spline shaft 2, 
the outer end of the lock pin 38 has moved inwardly out of the recess 60 
of the outer race 10. The slide pin 22 has been moved outwardly by the 
push pin 16 and out of the stepped hole 14 of the yoke, so that there is 
now no obstruction of the rotative movement of the outer race 10 caused by 
the spring 50 relative to the yoke. The outer race rotates, therefore, in 
the counterclockwise direction as viewed in FIG. 6a to the position shown 
in FIG. 6a. In this position, the recess 60 formed in the inside of the 
outer race assumes a position away from the lock pin 38, so that the lock 
pin 38 will never come off from the lock groove 8 of the spline shaft 2 
with the result that the spline shaft is firmly connected and locked to 
the yoke. 
When it is required to disconnect the spline shaft from the yoke, the outer 
race 10 is manually rotated by a hand or a lever 62 in a clockwise 
direction as viewed in FIG. 7a to the position as shown in FIG. 7a wherein 
the outer race 10 assumes a position slightly beyond in the clockwise 
direction the position shown in FIG. 5a. In this position, the lock pin 28 
extends into the recess 32 by the compressive force of the spring 30 so as 
to lock the outer race 10 relative to the yoke, and the recess 60 in the 
inside of the outer race 10 is in alignment with the lock pin 38 to permit 
the outward movement of the lock pin into the recess 60, so that the 
spline shaft 2 is ready to be removed from the yoke 4 (FIG. 7). In this 
condition, right side of the slide pin 22 is aligned with the right side 
of the enlarged diameter portion of the stepped hole 14 as viewed in FIG. 
7a. 
The spline shaft 4 can be removed from the yoke in this manner. Upon 
removal of the spline shaft, the push pin 16 extends into the spline 
groove of the yoke 4 and the lower end of the slide pin 22 extends into 
the enlarged diameter portion of the stepped hole 14. This is achieved by 
the fact that when the lock pin 28 of the slide pin 22 moves inwardly of 
the yoke together with the slide pin 22, the lock pin 28 moves 
simultaneously inwardly of the slide pin 22 with the aid of the taper 
surface 34 of the recess 32 of the yoke to release the lock of the outer 
race. At this moment the outer race 10 is slightly rotated together with 
the slide pin 20 by the action of the compression spring 50 from the 
position shown in FIG. 8a and returned to the position shown in FIG. 4a. 
FIGS. 9-12 illustrate the second embodiment of the present invention which 
is similar to the first embodiment shown in FIGS. 1-3 is provided with 
members the same as the push pin 16 and slide pin 22 in the previous 
embodiment, with the exception that the lock pin of the slide pin is not 
provided in the slide pin but in the yoke and hence the recess for locking 
the lock pin is provided in the slide pin and the slide pin is 
quadrilateral in crosssection. The feature of providing the lock pin out 
of the slide pin makes it easy to manufacture the coupling device and 
ensures a more aesthetical apperance and a positive operation of the 
coupling device. The quadrilateral crosssection of the slide pin prevents 
the rotation thereof about its axis. 
Only the difference of the second embodiment of the invention from the 
first embodiment will be explained hereinafter since the construction and 
operation of the second embodiment may be clearly evident in comparison of 
FIGS. 9-12 with FIGS. 1-3 or 4-8. In the drawings, reference numerals 
added with 100 have been utilized to identify like parts in FIGS. 1-8. 
As can be seen in FIG. 12, a slide pin 122 square in crosssection does not 
include a lock pin. In stead, there is provided with a blind hole 122' in 
the axial direction of the slide pin for a compression spring 126 for 
urging slide pin 122 and push pin 116 inwardly of the yoke 104. A 
compression spring may of course be provided out of the slide pin without 
forming the blind hole 122' as in FIGS. 1-8. 
Referring to FIG. 9, a yoke 104 is formed with a blind hole 128' for 
slidably accommodating therein a lock pin 128 adapted to be urged against 
the slide pin 122 by a compression spring 130 received at the bottom of 
the blind hole 128'. The slide pin 122 is formed in its side surface 
facing to the lock pin 128 with a recess 132 having a taper surface 134 at 
its outer end. It can be understood that the taper surface 134 serves to 
push back into the blind hole 128' the lock pin 128 which extends in the 
recess 132 formed in the slide pin 122 when it is lowered down, which 
function is the same as that of the taper surface 34 in the embodiment 
shown in FIGS. 1-3. As can be seen in FIGS. 10 and 12, in an assembled 
condition prior to the insertion of the spline shaft center lines 158, 154 
and 156 of the recess 132 of the slide pin 122, push pin 116 and lock pin 
128 are slightly shifted as in the center lines 58, 54 and 56 in FIG. 2. 
The operation of the coupling device shown in FIGS. 9-12 is substantially 
the same as that of the device shown in FIGS. 1-3, which will be simply 
explained. Starting from the condition shown in FIGS. 9-12, the spline 
shaft 2 is inserted into the splined bore of the yoke 104. Then the lock 
pin 138 is pushed outwardly against an annular spring 142 by the camming 
action of the tip tapered portion 6 of the spline shaft. As a recess 160 
in the inside of the outer race 10 has been positioned in alignment with 
the lock pin 138, such an outward movement of the lock pin 138 is 
possible. A further insertion of the spline shaft into the spline bore of 
the yoke 104 causes the push pin 116 and slide pin 122 to move outwardly 
against the compression force of the spring 126 by means of the camming 
action of the tapered portion 6 of the spline shaft. As shown in FIG. 10, 
therefore, a reduced diameter portion 122" of the slide pin 122 has been 
moved out of a stepped hole 114 of the yoke 104. However, the outer end of 
the lock pin 138 has extended in the recess 160 in the inside of the outer 
race 110 thereby to prevent the rotation of the outer race 110 relative to 
the yoke 104. The spline shaft is inserted further inwardly into the 
spline bore of the yoke until the lock groove 8 of the spline shaft 2 is 
brought in alignment with the lock pin 138 which is immediately moved 
inwardly by the action of the annular spring 142, with the result that the 
outer end of the lock pin 138 is disengaged from the recess 160 of the 
outer race 110 to permit it to rotate in a direction of an arrow 152 by an 
action of a spring 150 (FIG. 10) into a position shown in phantom lines in 
FIGS. 10 and 11. In this position the spline shaft 2 is locked to the yoke 
104 because of the lock pin 138 limited to move outwardly. 
Then the outer race is rotated in a clockwise direction as viewed in FIG. 
10 until the lock pin 128 moves to the position where it extends into the 
recess 132 of the slide pin 122. In this position, the spline shaft can be 
freely removed from the yoke 104, because the outer end of the lock pin 
138 extends into the recess 160 of the outer race with the aid of the 
force for removing the spline shaft from the yoke. When the spline shaft 
has been removed from the yoke, the slide pin 122, push pin 116 and lock 
pins 128 and 138 return to the positions shown in FIG. 9. 
This embodiment shown in FIGS. 9-12 is intended to improve the positive 
operation of the device by means of the square sectional slide pin for 
preventing it from rotating and has advantages in that the lock pin 128 
for the slide pin is provided in the yoke to eliminate the difficulty in 
manufacture caused by the provision of a lock pin in a slide pin and to 
obtain a much more aesthetical appearance. 
FIGS. 13-17 illustrate the further embodiment of the invention which is 
different from the above described embodiments in push pin and slide pin 
being integrally formed in a unitary element. A lock pin for a slide pin 
is not provided in the slide pin but in a yoke as that in the embodiment 
in FIGS. 9-12. In FIGS. 13-17, reference numerals added with 200 have been 
utilized to identify like parts in FIGS. 1-8. 
A slide pin 222 in this embodiment is integrally formed with a push pin and 
has a circular cross-sectional inner end and a square crosssectional outer 
end. The outer end of the slide pin is formed with an axial blind hole 
272. A compression spring 226 is arranged between a holding ring 270 and 
the bottom of the blind hole to urge the slide pin 222 inwardly. A 
compression spring may be arranged out of the slide pin without the blind 
hole. An outer race 210 is formed with a blind hole 274 for slidably 
accommodating a lock pin 228 adapted to be urged toward the slide pin by 
means of a compression spring 230 as shown in FIG. 13b. The lock pin 228 
is formed at its end adjacent to the slide pin with a reduced diameter end 
228'. 
FIG. 13a is a sectional view taken along a line 13a--13a in FIG. 13b. The 
slide pin 222 is formed in its flat surface on the side of the lock pin 
228 with a U-shaped groove 232, the position of the reduced diameter end 
228' of the lock pin 228 being indicated at 228" which changes in various 
position in the operative stages shown in FIGS. 13-17. The length of the 
reduced diameter end 228' is preferably slightly shorter than the depth of 
the U-shaped groove 232 so that a shoulder of the lock pin 228 abuts 
against the slide pin around the U-shaped groove. Such a contact of the 
lock pin 228 with the slide pin 222 is advantageous in manufacture and 
operation. 
The spline shaft 2 is then inserted into the yoke 204 to urge a lock pin 
238 outwardly and then to move the slide pin 222 outwardly with its taper 
surface 234 facing to the reduced diameter end 228' of the lock pin 228 as 
the result of the outward movement of the slide pin 222. The lock pin 228 
has been slightly moved to the right as viewed in FIG. 14b by a camming 
action of the taper surface 234. At the moment, the reduced diameter end 
228' of the lock pin 228 is out of the U-shaped groove, so that the outer 
race 210 tends to rotate by an action of a compression spring 250. 
However, the outer race 210 could not rotate relative to the yoke 204 
because an outer end of the lock pin 238 extends in a recess 260 in the 
inside of the outer race 210. 
When the spline shaft 2 reaches a position shown in FIG. 15b, the lock pin 
238 moves inwardly by an action of an annular spring so that the outer end 
of the lock pin 238 removes from the recess 260 permitting the rotation of 
the outer race 210. As the result, the lock pin 228 assumes a position 
228" in FIG. 15a. In this condition, the lock pin 238 could not be moved 
and the spline shaft 2 is locked to the yoke 204. 
In order to remove the spline shaft from the yoke, the outer race 210 is 
rotated in an direction of an arrow in FIG. 16c until the lock pin 228 
assumes a position 228" in FIG. 16a. As can be seen in FIG. 16c, the lock 
pin 238 is spaced apart the recess 260 of the outer race 210, so that the 
spline shaft 2 can freely be removed from the yoke. 
When the spline shaft 2 has been removed from the yoke, the slide pin 222 
is moved inwardly by the action of the spring 226 so that the lock pin 228 
assumes a position 228" in FIG. 17a. At this moment the outer race 210 is 
slightly rotated by the spring 250 to return the position shown in FIG. 
13. 
FIG. 18 illustrates partial crosssection of the U-shaped groove of the 
slide pin 222. 
A further preferred embodiment of the invention is shown in FIGS. 19-21, 
which employs a slide pin and its lock pin different from those 222 and 
228 of the embodiment shown in FIG. 13 and the lock pin is provided in the 
slide pin to shorten a length of an outer race. Moreover, an inner end of 
the slide pin is enlarged to prevent the slide pin from extending into the 
lock groove 8 of the spline shaft when it is inserted into a yoke 304 
unintentionally beyond the determined final position. 
The embodiment shown in FIGS. 19-21 is remarkably different from the above 
described embodiments in that the compression springs (26, 126 and 226) 
for the slide pins can be dispensed with. Referring to FIG. 13b, it will 
be seen that when the coupling device is suddenly stopped, inertia tends 
to cause the outer race 210 to continue to rotate relative to the yoke 204 
and this rotation is in the same direction as that obtained by the lever 
62 (FIG. 7a) for disconnecting the spline shaft from the yoke 204; so such 
inertial rotation is dangerous. To avoid this in the form of the invention 
shown in FIGS. 13a, 13b, and 13c, the compression spring 250 should be as 
stiff and strong as it can be, in order to overcome that inertial force. 
However, when the spring 250 is made stronger, the compression springs 230 
and 226 must also be made stronger than before, and this means that 
greater force is required for inserting the spline shaft into the yoke 
against the compression force of the spring 226, making that operation 
more difficult than before. To solve this problem, the spring 226 is 
dispensed with in the embodiment shown in FIG. 19. In addition, a longer 
slide pin can be employed to prevent a jam of the slide pin and obtain a 
much more aesthetical appearance. 
The slide pin 322 of the coupling device shown in FIGS. 19-21 is circular 
in section as shown in FIG. 21 with its reduced diameter inner end 
extending in a spline groove of the yoke 304. 
The slide pin 322 is formed with an aperture 328' passing therethrough for 
slidably accommodating a lock pin 328 adapted to be urged by a compression 
spring 330. The aperture 328' may be a blind hole as the case may be. The 
lock pin 328 is formed at its end with a reduced diameter portion 328" 
adapted to abut against an arcuate plate 380 fixed to the outer race 310. 
A length of the reduced diameter portion 328" of the lock pin 328 in an 
axial direction is preferably slightly shorter than the depth of a groove 
as in the embodiment in FIGS. 13-18. 
The arcuate plate 380 is formed with a groove which corresponds to the 
U-shaped groove 232 but is quite different in configuration from the 
U-shaped groove because of the absence of the spring for the slide pin. As 
shown in FIG. 20a, the groove formed in the arcuate plate 380 is a 
V-shaped groove and is angularly positioned relative to a radial 
direction. FIG. 20a is a sectional view of the device shown in FIG. 19 in 
a position where the spline shaft has not yet been inserted. In this 
position, the reduced diameter portion 328" of the lock pin 328 assumes a 
position shown in FIG. 20a to prevent a rotation of the outer race 310 
caused by a spring 350. When the spline shaft 2 is inserted into the yoke 
304, the reduced diameter 328" of the lock pin 328 is raised together with 
the slide pin so that the reduced diameter end 328" removes from the 
V-shaped groove 382 along a taper portion 384 at the upper right hand of 
the groove. The outer race is therefore released to move into a position 
shown in FIG. 20 b by the action of the spring 350. In this position, the 
spline shaft 2 is locked by the lock pin 338 as in the above described 
embodiments. 
In order to remove the spline shaft from the yoke, the outer race 310 is 
rotated against the compressive force of the spring 350 (FIG. 20c). As the 
result, the reduced diameter end 328" of the lock pin 328 moves to the 
left groove portion 386 of the V-shaped groove 382. In this position the 
spline shaft 2 is freely removed from the yoke. When the spline shaft 2 is 
removed, the spring 350 of the outer race 310 drives the arcuate plate 380 
together with the outer race in a counterclockwise direction as shown in 
FIG. 20c, so that the reduced diameter end 328" of the lock pin is pushed 
downwardly by a camming action of the left groove portion 386 of the 
V-shaped groove 382 to force the slide pin 322 inwardly into a position 
shown in FIG. 20a. Such an inward movement of the slide pin 322 is 
achieved by a radially inward component of the compression force of the 
spring 350 with the aid of the camming action of the oblique groove 386 of 
the V-shaped groove 382 without using a spring for pushing down the slide 
pin 322. 
A cover 324 may be dispensed with because of an absence of a spring for 
pushing down the slide pin 322 (FIG. 19). 
FIGS. 22-24 illustrate a further embodiment of the invention, which 
includes a push pin 416 similar to those in FIGS. 1-12 and slide pin 422 
quite different from those in the above described embodiments. 
The slide pin 422 is in the form of a relatively thin cylinder which is at 
its bottom in contact with the push pin 416 and slidably movable in an 
aperture 420 formed in an outer race 410. Within the cylindrical slide pin 
422 is provided an inner cylinder 426 comprising an inner end flange 428 
extending radially outwardly and an outer end flange 430 extending 
radially inwardly. A lock pin 432 is slidable in an aperture 434 leading 
up from the upper end of the aperature 420 of the outer race in FIG. 22 
and has an enlarged inner end 436 adapted to engage the inside of the 
outer end flange of the inner cylinder 426. A weak compression spring 438 
is arranged between the inner end 436 of the lock pin 432 and the inner 
bottom of the cylindrical slide pin 422 to urge the lock pin 432 
outwardly. Between the inner end flange 428 of the inner cylinder 426 and 
the bottom of the aperture 420 is provided a compression spring 440 
stronger than the spring 438 to urge the cylindrical slide pin 422 against 
the push pin 416. 
A yoke 404 is provided with an outer ring 442 fixed to the yoke by means of 
bolts. The outer ring 442 is formed with a recess 444 in opposition to the 
lock pin 432. As can be seen in FIG. 23, center lines 456 and 458 of the 
recess 444 and the lock pin 432 are slightly shifted relative to a center 
line 454 of the spline groove of the yoke in the same manner as in 56, 58 
and 54 in FIG. 2. 
The assembled coupling device of this embodiment is shown in FIG. 25a, 
which is ready for receiving the spline shaft 2. When the spline shaft 2 
is inserted into the yoke, the tip tapered portion 6 of the spline shaft 2 
causes the cylindrical slide pin 422 to push into the aperture 420 against 
the compression force of the spring 440 (FIG. 25b). The spline shaft 2 is 
further inserted into the yoke until the lock pin 38 extends into the lock 
groove 8 of the spline shaft, at which moment the outer race 410 is 
rotated by the spring 50 into a position shown in FIG. 25c to lock the 
spline shaft to the yoke in the same manner as in the above described 
embodiments. 
In order to remove the spline shaft from the yoke, the outer race 410 is 
rotated until the lock pin 432 extends into the recess 444 (FIG. 25d). In 
this position, the lock pin 38 can be moved into the recess 60 of the 
outer race so that the spline shaft can be removed from the yoke. Upon 
removal of the spline shaft, the push pin 416 is returned to its original 
position by the compression spring 440 to cause the cylindrical slide pin 
422 to return to its original position, so that the lock pin 432 is moved 
from the recess 444 to a position shown in FIG. 25e, immediately from 
which position the outer race 410 is returned into the position shown in 
FIG. 25a by the action of the spring 50. 
Referring back to FIGS. 1-3, assuming that the coupling device is stopped 
suddenly during a high speed rotation in the direction of the arrow 3 in 
FIG. 2 the outer race 10 tends to move in the direction for disconnection 
of the coupling owing to the inertia force of the outer race 10 itself. 
However, the strong compression spring 50 serves as a safety device which 
always urges the outer race 10 in the opposite direction and the outer 
race preferably made of a plastic material is generally light weight with 
small inertia force, so that there would not be any risk of disconnection 
of the coupling device. 
However, a safety device may be provided for more securely preventing the 
rotation of the outer race in a direction of the disconnection due to the 
inertia force upon a sudden stoppage of the coupling device. FIG. 26 
illustrates one example of a principle of the safety device. The yoke 4 is 
formed with a blind hole 502 for slidably accommodating a suitable length 
pin 506 adapted to be urged outwardly by means of a spring 508 at the 
bottom of the blind hole 502. When the coupling device according to the 
invention is in the position shown in FIGS. 4 and 5 where the spline shaft 
has not yet been locked in the yoke, the outer end of the pin 506 is 
completely depressed in the blind hole 502 and a surface of the outer race 
in contact with the yoke 4 prevents the pin 506 from extending out of the 
blind hole 502. 
The outer race 10 is formed with a stepped through aperture 510 for 
slidably receiving a stepped pin 512 having a suitable length adapted to 
be urged toward the pin 506 by means of a compression spring 514. The 
stepped through aperture 510 and stepped pin 512 are so located in the 
outer race that the stepped pin 512 of the outer race 10 is aligned with 
the pin 506 of the yoke 4 when the coupling device assumes the position in 
FIG. 6 where the outer race 10 has been in the locking position for 
locking the lock pin 38 in the lock groove 8 of the spline shaft as the 
result of the rotation of the outer race 10 by the action of the spring 
50. In the position shown in FIG. 26, the stepped pin 512 is urged to the 
right because of the spring 508 stronger than the spring 514, so that a 
reduced diameter end 516 of the stepped pin 512 extends out of the outer 
race. In this position, the pin 506 also extends from the yoke 4 in the 
outer race 10 to prevent the rotation of the outer race due to the inertia 
force. If it is desired to disconnect the coupling device, the reduced 
diameter end 516 of the stepped pin 512 is pushed down into the outer race 
by a finger of an operator to enable the outer race to be rotated. The 
reduced diameter end 516 of the stepped pin 512 may be painted red to 
facilitate its identification. The stepped pin 512 may be magnetically 
pushed down by a remote control. The protrusion of the reduced diameter 
end 516 of the stepped pin 512 may be indicated by turning on a red lamp 
with the aid of a proximity switch. 
As can be seen from the above description, the coupling device according to 
the invention is capable of connecting and disconnecting two mechanical 
parts in a very simple manner with a high reliability. 
While I have shown and described the preferred embodiments of the 
invention, it is to be understood that the invention is not limited 
thereto but may be otherwise variously embodied within the scope of the 
following claims.