GB2142101A

GB2142101A - Synchromesh clutch

Info

Publication number: GB2142101A
Application number: GB08415603A
Authority: GB
Inventors: Eric Charles Hodgson; Roger Michael Weyman
Original assignee: Case Poclain Corp Ltd
Current assignee: Case Poclain Corp Ltd
Priority date: 1983-06-22
Filing date: 1984-06-19
Publication date: 1985-01-09
Also published as: GB2142101B; GB8415603D0

Abstract

In a synchromesh clutch (9), an inner sleeve (50) having external dog clutch teeth (53) is slideable on splines (15) on a driving member (12),a co-axial driven member (11) has internal dog clutch teeth (54) engageable by the external teeth (53), and an outer sleeve (55) having a friction surface (57) engageable with a friction surface (58) on the driven member (11) is slideable on the external teeth (53). The external teeth (53) have a zone (64) of increased backlash onto which the outer sleeve (55) is urged by a spring (60) when the clutch (9) is disengaged. The zone (64) terminates in shoulders (65) on the tooth flanks which act as baulking means during engagement. The clutch can be employed for example in a rear power take-off assembly of an agricultural tractor. <IMAGE>

Description

SPECIFICATION Synchromesh clutch The invention relates to a synchromesh clutch, particularly but no means exclusively for use as a power take-off clutch in an agricultural tractor or the like.

The object of the invention is to provide a simple and compact synchromesh clutch.

According to the invention, a synchromesh clutch comprises an inner sleeve slideable axially on splines or a key on a driving member by a selector fork or the like and having external dog clutch teeth, a driven member co-axial with the driving member and having internal dog clutch teeth engageable with said external teeth, and an outer sleeve slideable axially on said external teeth and having a friction surface engageable with a friction surface on the driven member, the outer sleeve being urged by resilient means towards the driven member so as to contact a stop on the inner sleeve when both sleeves are not required to engage the driven member, and said external teeth having a zone of increased backlash terminating in shoulders on the tooth flanks which temporarily prevent the inner sleeve from sliding through the outer sleeve against the action of the resilient means when the friction surfaces are brought into engagement with one another until synchronisation of the driving and driven members is substantially achieved whereupon said shoulders can slide through the outer sleeve to allow said external teeth to engage with the internal teeth on the driven member.

A preferred embodiment of the invention will now be described by way of example, with reference to the accompanying drawing which is a sectional side elevation of a synchromesh clutch for a tractor power take-off mechanism, the clutch being shown in disengaged condition above its axis and in engaged condition below its axis.

Referring now to the drawing, the power take-off shaft assembly forming the subject of our United Kingdom Patent No. 1 442362 is provided with a synchromesh clutch indicated generally at 9 in place of its simple dog clutch. A long power input shaft 12 of said assembly is driveably connectible at its front end to the engine of an agricultural tractor by a friction clutch (not shown) operable from the driver's seat and forming part of a dual clutch the other part of which constitutes the tractor's main transmission clutch, and at its rear end to a short co-axial countershaft 11 by the synchromesh clutch 9 which is operable by a hand lever (not shown) rigidly secured on a short cross-shaft 20 disposed at the rear of the tractor.The countershaft 11 is journalled in a csing 10 and has formed integrally on it a gear 24 forming part of two-speed power take-off gearing housed within the casing 10. The synchromesh clutch 9 comprises an inner sleeve 50 slideable axially on splines 15 on the power input shaft 12 by a selector fork shown in part at 16 which engages in an annular groove 51 formed in an external boss 52 at the front end of the inner sleeve 50. The fork 16 is slideable on a dead shaft 18 between the disengaged position shown in full lines and the engaged position shown in broken lines by a forked lever 19 welded to the cross-shaft 20.The inner sleeve 50 has external dog clutch teeth 53 engageable with internal dog clutch teeth 54 formed in the front end of the countershaft 11, and is held selectively in engaged or disengaged position in known manner by detent means (not shown) comprising a spring-loaded ball housed in the selector fork 16 and two annular grooves formed in the dead shaft 18 in either one of which said ball is engageable. An outer sleeve 55 has internal teeth 56 enabling it to slide axially on the external teeth 53, and a friction surface 57 engageable with a friction surface 58 at the extreme front end of the countershaft 11, the friction surfaces 57 and 58 being perpendicular to the axis 59 of the synchromesh clutch 9.The outer sleeve 55 is urged towards the countershaft 11 by a helical compression spring 60 confined between the boss 52 on the inner sleeve 50 and an external flange 61 at the rear of the outer sleeve 55, so that a circlip 62 carried in the bore of the outer sleeve 55 abuts against a stop constituted by a circumferential face 63 on the inner sleeve 50 when both sleeves are not required to engage the countershaft 11 as shown above the axis 59 of the synchromesh clutch 9 in the drawing. The external teeth 53 on the inner sleeve 50 have a rear zone 64 of increased backlash terminating in shoulders 65 on the tooth flanks, the whole of the internal teeth 56 in the outer sleeve 55 being disposed to the rear of the shoulders 65 when both sleeves are not required to engage the countershaft 11.The shoulders 65 act as baulking means to temporarily prevent the inner sleeve 50 from sliding through the outer sleeve 55 against the action of the spring 60 when the friction surfaces 57 and 58 are brought into engagement with one another by movement of the selector fork 16 in the appropriate direction.Such engagement immediately causes circumferential movement of the outer sleeve 55 on the inner sleeve 50 which takes up the increased backlash and thus effects baulking at the shoulders 65 until synchronisation of the two shafts 11 and 12 is substantially achieved, whereupon the shoulders 65 can slide through the internal teeth 56 in the outer sleeve 55 to allow the external teeth 53 on the inner sleeve 50 to engage with the internal teeth 54 in the countershaft 11 to establish a positive driving connection between the two shafts 11 and 12 as shown below the axis 59 of the synchromesh clutch 9 in the drawing.

In a modification, the aforesaid friction surfaces are conical.

The simple dog clutch disclosed by our United Kingdom Patent No. 1 442 362 can be difficult and noisy to engage because the power input shaft 12 tends to rotate due to drag when disconnected from the tractor engine by disengagement of the friction clutch at its front end. The substitution of the synchromesh clutch 9 hereinbefore described avoids any difficulty in engagement.

1. A synchromesh clutch comprising an inner sleeve slideable axially on splines or a key on a

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Synchromesh clutch The invention relates to a synchromesh clutch, particularly but no means exclusively for use as a power take-off clutch in an agricultural tractor or the like. The object of the invention is to provide a simple and compact synchromesh clutch. According to the invention, a synchromesh clutch comprises an inner sleeve slideable axially on splines or a key on a driving member by a selector fork or the like and having external dog clutch teeth, a driven member co-axial with the driving member and having internal dog clutch teeth engageable with said external teeth, and an outer sleeve slideable axially on said external teeth and having a friction surface engageable with a friction surface on the driven member, the outer sleeve being urged by resilient means towards the driven member so as to contact a stop on the inner sleeve when both sleeves are not required to engage the driven member, and said external teeth having a zone of increased backlash terminating in shoulders on the tooth flanks which temporarily prevent the inner sleeve from sliding through the outer sleeve against the action of the resilient means when the friction surfaces are brought into engagement with one another until synchronisation of the driving and driven members is substantially achieved whereupon said shoulders can slide through the outer sleeve to allow said external teeth to engage with the internal teeth on the driven member. A preferred embodiment of the invention will now be described by way of example, with reference to the accompanying drawing which is a sectional side elevation of a synchromesh clutch for a tractor power take-off mechanism, the clutch being shown in disengaged condition above its axis and in engaged condition below its axis. Referring now to the drawing, the power take-off shaft assembly forming the subject of our United Kingdom Patent No. 1 442362 is provided with a synchromesh clutch indicated generally at 9 in place of its simple dog clutch. A long power input shaft 12 of said assembly is driveably connectible at its front end to the engine of an agricultural tractor by a friction clutch (not shown) operable from the driver's seat and forming part of a dual clutch the other part of which constitutes the tractor's main transmission clutch, and at its rear end to a short co-axial countershaft 11 by the synchromesh clutch 9 which is operable by a hand lever (not shown) rigidly secured on a short cross-shaft 20 disposed at the rear of the tractor.The countershaft 11 is journalled in a csing 10 and has formed integrally on it a gear 24 forming part of two-speed power take-off gearing housed within the casing 10. The synchromesh clutch 9 comprises an inner sleeve 50 slideable axially on splines 15 on the power input shaft 12 by a selector fork shown in part at 16 which engages in an annular groove 51 formed in an external boss 52 at the front end of the inner sleeve 50. The fork 16 is slideable on a dead shaft 18 between the disengaged position shown in full lines and the engaged position shown in broken lines by a forked lever 19 welded to the cross-shaft 20.The inner sleeve 50 has external dog clutch teeth 53 engageable with internal dog clutch teeth 54 formed in the front end of the countershaft 11, and is held selectively in engaged or disengaged position in known manner by detent means (not shown) comprising a spring-loaded ball housed in the selector fork 16 and two annular grooves formed in the dead shaft 18 in either one of which said ball is engageable. An outer sleeve 55 has internal teeth 56 enabling it to slide axially on the external teeth 53, and a friction surface 57 engageable with a friction surface 58 at the extreme front end of the countershaft 11, the friction surfaces 57 and 58 being perpendicular to the axis 59 of the synchromesh clutch 9.The outer sleeve 55 is urged towards the countershaft 11 by a helical compression spring 60 confined between the boss 52 on the inner sleeve 50 and an external flange 61 at the rear of the outer sleeve 55, so that a circlip 62 carried in the bore of the outer sleeve 55 abuts against a stop constituted by a circumferential face 63 on the inner sleeve 50 when both sleeves are not required to engage the countershaft 11 as shown above the axis 59 of the synchromesh clutch 9 in the drawing. The external teeth 53 on the inner sleeve 50 have a rear zone 64 of increased backlash terminating in shoulders 65 on the tooth flanks, the whole of the internal teeth 56 in the outer sleeve 55 being disposed to the rear of the shoulders 65 when both sleeves are not required to engage the countershaft 11.The shoulders 65 act as baulking means to temporarily prevent the inner sleeve 50 from sliding through the outer sleeve 55 against the action of the spring 60 when the friction surfaces 57 and 58 are brought into engagement with one another by movement of the selector fork 16 in the appropriate direction.Such engagement immediately causes circumferential movement of the outer sleeve 55 on the inner sleeve 50 which takes up the increased backlash and thus effects baulking at the shoulders 65 until synchronisation of the two shafts 11 and 12 is substantially achieved, whereupon the shoulders 65 can slide through the internal teeth 56 in the outer sleeve 55 to allow the external teeth 53 on the inner sleeve 50 to engage with the internal teeth 54 in the countershaft 11 to establish a positive driving connection between the two shafts 11 and 12 as shown below the axis 59 of the synchromesh clutch 9 in the drawing. In a modification, the aforesaid friction surfaces are conical. The simple dog clutch disclosed by our United Kingdom Patent No. 1 442 362 can be difficult and noisy to engage because the power input shaft 12 tends to rotate due to drag when disconnected from the tractor engine by disengagement of the friction clutch at its front end. The substitution of the synchromesh clutch 9 hereinbefore described avoids any difficulty in engagement. CLAIMS

1. A synchromesh clutch comprising an inner sleeve slideable axially on splines or a key on a driving member by a selector fork or the like and having external dog clutch teeth, a driven member co-axial with the driving member and having internal dog clutch teeth engageable with said external teeth, and an outer sleeve slideable axially on said external teeth and having a friction surface engageable with a friction surface on the driven member, the outer sleeve being urged by resilient means towards the driven member so as to contact a stop on the inner sleeve when both sleeves are not required to engage the driven member, and said external teeth having a zone of increased backlash terminating in shoulders on the tooth flanks which temporarily prevent the inner sleeve from sliding through the outer sleeve against the action of the resilient means when the friction surfaces are brought into engagement with one another until synchronisation of the driving and driven members is substantially achieved whereupon said shoulders can slide through the outer sleeve to allow said external teeth to engage with the internal teeth on the driven member.

2. Asynchromesh clutch according to claim 1, wherein the friction surfaces are perpendicular to the axis of the clutch.

3. A synchromesh clutch according to either of the preceding claims, wherein the stop is a circumferential face on the inner sleeve against which a circlip carried in the bore of the outer sleeve is arranged to abut.

4. A synchromesh clutch according to any one of the preceding claims, wherein the driving member is a power input shaft and the driven member is a countershaft of a power take-off mechanism.

5. A synchromesh clutch constructed, arranged and adapted to operate substantially as hereinbefore described with reference to, and as illustrated by, the accompanying drawling.