GB2241766A - Toothed couplings - Google Patents

Abstract

A toothed coupling for the final drive of an endless-track vehicle must be disengageable so that the vehicle can be towed, and disengagement is effected by an axially operated manual system. A toothed coupling includes an axially moveable coupling sleeve 15 with toothed end zones, a collar 29 movable rotationally but not axially on the sleeve, and a peripherally operated manual disengagement system comprising a radially projecting hand lever 32 detachably securable to the collar for moving the collar 29 rotationally between respective positions in which it acts to lock and unlock the sleeve axially and also for moving the unlocked sleeve 15 axially between engaged and disengaged positions. An axially fixed hub 19 disposed within the sleeve 15 forms part of the locking mechanism which comprises three pairs of balls 39, 42 urged apart by springs. <IMAGE>

Description

TOOTHED COUPLING This invention relates to toothed couplings, particularly but not exclusively for use between the transmission output shafts and the final drive means of endless-track vehicles.

In such a vehicle, the couplings must be disengaged to enable the vehicle to be towed, and due to access problems, disengagement has hitherto been effected by axially operated manual means. However, axially operated disengagement can be difficult depending upon the type of final drive means required.

The object of the present invention is to circumvent this problem despite difficulty of access.

According to the invention, a toothed coupling moveable axially between, and lockable in both, engaged and disengaged positions comprises a sleeve moveable axially between stops; an internally toothed zone of broad face-width at one end of the sleeve slidably engageable with a first externallytoothed member; an internally toothed zone at the other end of the sleeve slidable into and out of engagement with a second externally toothed member; an axially fixed hub connected to the first member; a flange extending inwardly from the sleeve into close proximity to the periphery of the hub; means for releasably locking the sleeve to the hub in either of two axiallyspaced engaged and disengaged positions; and peripherally operated manual means for unlocking the sleeve from the hub, sliding the sleeve between said positions, and relocking the sleeve to the hub.

A preferred embodiment of the invention will now be described. by way of example, with reference to the accompanying drawings, of which : Figure 1 is a sectional side elevation of a toothed coupling, shown in its engaged position above the centre-line and in its disengaged position below the centre-line; Figure 2 is a section on the line 2-2 in Figure 1, with the coupling in its engaged position; and Figure 3 is an end view in the direction of the arrow 3 in Figure 1, with the final drive means omitted for clarity.

Referring now to the drawings, a vehicle with two endless tracks has a transmission with two output shafts and including differential means whereby the vehicle is both driven and steered through the transmission in well-known manner. Each of the output shafts 10 is normally connected to final drive means for the associated track by a disengageable double toothed coupling. The output shaft 10 has an externally-toothed crowned gear 11 fixed on it, and the associated final drive means has an input shaft 12 with a similar externally-toothed crowned gear 13 and a part 14 fixed on it.The coupling basically comprises a sleeve 15 having at one end an internally toothed zone 16 of broad face-width which is slidably-engageable with the gear 11 fixed on the output shaft 10 of the transmission, and at the other end an internally toothed zone 17 which is slidable into and out of engagement with the gear 13 fixed on the input shaft 12 of the final drive means. A flange 18 extends inwardly from the sleeve 15 into close proximity to the periphery of an axially fixed hub 19, which is connected to the output shaft 10 of the transmission by a rod 20 and a ball joint 21 in order to accommodate limited misalignment of the output shaft 10 of the transmission with the input shaft 12 of the final drive means.Axial stops for the sleeve 15 comprise a face 22 on a part 23 fixed on the output shaft 10 of the transmission adjacent to the gear 11 thereon, and a shoulder 24 at that end of the hub 19 remote from the output shaft 10. The part 23 has an integral sleeve 25 and the aforesaid part 14 has an integral sleeve 26, with the respective bores of which seals 27 and 28 on the adjacent ends of the sleeve 13 make contact when the coupling is engaged. A collar 29 is mounted on the periphery of the sleeve 15 for rotational but not axial movement relative to the sleeve 15, and stops for the collar 29 comprise three short circumferentiallyextending grooves 30 formed 120 apart within it, each groove 30 being engaged by a pin 31 projecting radially from the periphery of the sleeve 15.

A radially projecting hand lever 32 is insertable and operable peripherally through a gap between the transmission's casing 33 and the vehicle's hull 34, which gap extends over more than 30O of the circumference of the coupling and also extends a short distance axially of the coupling. The hand lever 32 can be detachably screwed to the collar 29 at any one of twelve locations 35 disposed 30O apart. Means for releaseably locking the sleeve 15 to the hub 19 comprise three radial bores 36 formed 120 apart in the flange 18 and each housing two balls urged apart by a spring 37 and a plunger 38.The inner balls 39 engage in either of two axially-spaced zones 40, 41 of the same reduced diameter in the periphery of the hub 19, and each of the outer balls 42 engages in either of two axial grooves 43, 44 of different depths within the collar 29. The axial spacing of the two zones 40, 41 is the same as the distance through which the sleeve 15 can move axially between its stops 22, 24, and the angular spacing the two axial grooves 43, 44 associated with each outer ball 42 is the same as the angle through which the collar 29 is permitted to rotate relative to the sleeve 15 by the pin-and-groove arrangement 30. 31 therebetween.The three shallower axial grooves 43, and likewise the three deeper axial grooves 44, are 120O apart, and the two axial grooves 43, 44 associated with each outer ball 42 are circumferentially positioned some distance from the adjacent pin-and-groove arrangements 30. 31. A friction disc 45 is interposed between an end face on the collar 29 and an end face on a lock nut 46 mounted on a screw thread 47 on the periphery of the sleeve 15 and held in position by a lock nut tab 48, whereby the collar 29 is located axially on the sleeve 15 whilst the friction disc 45 reduces any possibility of the collar 29 moving rotationally into the unlocked position due to sudden shock loading.A plate 49 fixed to the transmission's casing 33, and visible through the gap between said casing and the vehicle's hull 34, indicates the respective angular directions in which the hand lever 32 must be moved in order to lock and unlock the coupling.

The operation of the coupling is as follows : When the coupling is locked in the engaged position driveably connecting the output shaft 10 of the transmission to the input shaft 12 of the final drive means as shown in the upper half of Figure 1, the clearance between the plungers 38 and whichever balls they do not contact, although sufficient to permit the outer balls 42 to be moved out of the shallower axial grooves 43 in the collar 29, is not sufficient to permit the inner balls 39 to be moved out of either of the zones 40, 41 in the hub 19. The coupling is disengaged by inserting the hand lever 32 through the aforesaid gap, screwing it to the collar 29, and operating it to rotate the collar 29 relative to the sleeve 15 so that the outer balls 42 are moved out of the shallower axial grooves 43 in the collar 29 into the deeper axial grooves 44 therein.This unlocks the coupling, as the clearance between the plungers 39 and whichever balls they do not contact is sufficient to permit the outer balls 42 to be moved out of the deeper axial grooves 44 in the collar 29 and also sufficient to permit the inner balls 39 to be moved out of either of the zones 40, 41 in the hub 19. The hand lever 32 is then operated to move the sleeve 15 axially into the disengaged position shown in the lower half of Figure 1 in which it does not engage the gear 13 fixed on the input shaft 12 of the final drive means, the inner balls 39 being moved out of the zone 41 in the hub 19 remote from the output shaft 10 of the transmission into the zone 40 in the hub 19 adjacent said shaft. The coupling can then be locked in the disengaged position by operating the hand lever 32 to rotate the collar 29 relative to the sleeve 15 so that the outer balls 42 are moved out of the deeper axial grooves 44 in the collar 29 into the shallower axial grooves 43 therein, after which the hand lever 32 is unscrewed and removed and, when the couplings on both output shafts 10 of the transmission have thus been disengaged, the vehicle can be towed. The couplings can be engaged by a reversal of the procedure outlined above.

In a modification of the invention, the axial grooves of unequal depth can be formed in the hub and the zones of equal depth can be formed in the collar.

Claims (9)

1. A toothed coupling moveable axially between, and lockable in both, engaged and disengaged positions comprising a sleeve moveable axially between stops; an internally toothed zone of broad face-width at one end of the sleeve slideably engageable with a first externally-toothed member; an internally toothed zone at the other end of the sleeve slid able into and out of engagement with a second externally toothed member; an axially fixed hub connected to the first member; a flange extending inwardly from the sleeve into close proximity to the periphery of the hub; means for releaseably locking the sleeve to the hub in either of two axially-spaced engaged and disengaged positions; and peripherally operated manual means for unlocking the sleeve from the hub, sliding the sleeve between said positions, and relocking the sleeve to the hub.

2. A toothed coupling according to Claim 1, wherein the means for releaseably locking the sleeve to the hub comprise at least one radial bore formed in the flange and housing two balls urged apart by a spring and a plunger; two axially-spaced zones of the same reduced diameter in the periphery of the hub in either of which the inner ball engages; a collar mounted on the periphery of the sleeve for rotational movement between stops, but not axial movement, relative to the sleeve; and two circumferentially-spaced axial grooves of different depths within the collar in either of which the outer ball engages; the arrangement being such that when in the locked position the clearance between the plunger and the ball which it does not contact is sufficient to permit the outer ball to be moved out of the shallower axial groove in the collar but not sufficient to permit the inner ball to be moved out of either of the zones in the hub, and when in the unlocked position said clearance is sufficient to permit the outer ball to be moved out of the deeper axial groove in the collar and also sufficient to permit the inner ball to be moved out of either of the zones in the hub.

3. A toothed coupling according to Claim 2, wherein the peripherally operated manual means comprise a radially projecting hand lever detachably securable to the collar for rotating the collar relative to the sleeve and for sliding the collar and sleeve axially relative to the hub.

4. A toothed coupling according to Claim 3, wherein the hand lever is securable to the collar at any one of a plurality of circumferentially-spaced locations.

5. A toothed coupling according to any one of Claims 2 to 4, wherein the stops for the collar comprise at least one short circumferentially-extending groove formed within it, the groove being engaged by a pin projecting radially from the periphery of the sleeve.

6. A toothed coupling according to any one of Claims 2 to 5, wherein a friction disc is interposed between an end face on the collar and an end face on a nut locked in position on a screw thread on the periphery of the sleeve.

7. A toothed coupling according to any one of the preceding Claims, wherein the stops for the sleeve comprise a face on a part connected to the first externally-toothed member and a shoulder at that end of the hub remote from the first member.

8. A toothed coupling according to any one of the preceding Claims.

wherein the hub is connected to the first member by a ball joint in order to accommodate limited misalignment of the first and second members, the teeth on said members being crowned.

9. A toothed coupling constructed, arranged and adapted to operate substantially as hereinbefore described with reference to, and as illustrated by, the accompanying drawings.