GB2043805A - Power Take-off Clutches - Google Patents

Abstract

A power take-off clutch for disengageably driving a power take- off shaft of a vehicle such as an agricultural tractor is basically urged into engaged condition by internal resilient means, is urged into and latched in engaged condition by driver-operated means against the action of a spring the force of which in the clutch-disengaging direction is greater than the engaging force of the internal resilient means. <IMAGE>

Description

SPECIFICATION Power Take-off Clutches The invention relates to power take-off clutches for disengageably driving power take-off shafts on vehicles such as agricultural tractors.

Hitherto, such clutches have been engaged by resilient means and urged into and latched in disengaged condition by driver-operated means.

This arrangement has the disadvantage that if the driver-operated means are released abruptly, the resilient means impose shock loading on the power take-off clutch and on said machinery.

The object of the present invention is to eliminate the aforesaid disadvantage.

According to the invention, a power take-off clutch, for a vehicle, is urged into and latched in engaged condition by driver-operated means against the disengaging action of resilient means.

A preferred embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings of which: Fig. 1 is a sectional side elevation of a dual (that is to say drive and power take-off) clutch assembly; Fig. 2 is a sectional view of a detail of said assembly; and Fig. 3 is a side elevation of an external operating mechanism for the power take-off clutch.

Referring now to Fig. 1 of the drawings, an agricultural tractor includes an engine having a flywheel 10 associated with a dual clutch assembly comprising a driven plate 11 mounted on splines 12 on a sleeve 13 constituting the input shaft of the tractor's transmission gearing (not shown), and a driven plate 14 mounted on splines 1 5 on a shaft 1 6 extending through the sleeve 1 3 and driving a power take-off shaft by way of two-speed gearing (not shown).The driven plates 11 and 14 are engaged in well known manner by the action of common resilient means interposed between two pressure plates 1 7 and 1 8 so as to clamp the driven plate 14 between the pressure plate 1 7 and a driving surface on the flywheel 10, and to clamp the driven plate 11 between the pressure plate 1 8 and a driving surface in a clutch casing 1 9 rigidly secured to the flywheel 10. The resilient means comprise a plurality of circumferentially-disposed helical compression springs 41 (see Fig. 2) in conjunction with a diaphragm spring 20.The pressure plate 1 8 is moveable axially in its disengaging direction against the action of the resilient means 20 and 41 by a linkage operated by a transmission clutch foot pedal, and the pressure plate 1 7 is independently moveable axially in its disengaging direction against the action of said means by a linkage operated by a power take-off clutch hand lever.The foot-pedaloperated linkage comprises three circumferentially-spaced studs 21 each of which is rigidly secured at one end to the pressure plate 1 8 and is adapted at the other end to abut against the periphery of a pin 22 rigidly secured between the ends of one of three radial second-class levers 23 pivoted at points 24 at their respective outer ends on the clutch casing 1 9. The inner ends of the levers 23 are together moveable in a direction towards the flywheel 10 via a yoke plate 25 by a bearing 26 mounted on a collar 27 slideable coaxially upon a fixed tubular member 28 surrounding the sleeve 13. The collar 27 is actuated by a disengaging fork 29 secured on a cross-shaft 30 journalled in a housing 31 for the dual clutch assembly.The hand-lever-operated linkage comprises three circumferentiallyspaced links 32 each of which is disposed between two of the studs 21 and is pivotally connected at one end to the pressure plate 1 7 and at the other end to the outer end of one of three radial first-class levers 33 pivoted at respective points 34 between their ends on the clutch casing 1 9. The inner ends of the levers 33 carry adjustable studs 35 and are together moveable in a direction towards the flywheel 10 by a flanged annulus 36 journalled on a bearing 37 mounted on a collar 38 slideable co-axially upon the collar 27. The collar 38 is actuated by a disengaging fork 39 secured on a cross-shaft 40 journalled in the housing 31.

Referring now to Fig. 3, an external operating mechanism for the pressure plate 1 7 associated with the driven plate 14 on the shaft 16 comprises a lever arm 42 provided with a forked free end and secured on an end of the cross-shaft 40 which projects from the housing 31, a rod 43 having screw-threaded end zones and pivotally connected at one of its ends to the free end of the lever arm 42, and a lever assembly pivotally mounted at 44 on the chassis 45 of the tractor and having a long arm 46 forming a hand lever and a short arm 47 disposed on the same side of the fulcrum 44 as the long arm 45 and pivotally connected at its free end to the other end of the rod 43.The connection between the lever arm 42 and the rod 43 includes a pin 48 freely pivotable in the forked end of said arm and having a diametrical hole through which one of the screwthreaded end zones of the rod 43 passes with clearance. Said connection is adjustably established by means of a nut 49 and an associated lock-nut 50 disposed on said one end zone on each side of the pin 48. This adjustable connection enables wear in the clutch associated with the shaft 1 6 to be taken up. The arrangement thus far described in this and the preceding paragraph is known.However, we provide a helical compression spring 51 surrounding the rod 43 and interposed between an abutment 52 on the chassis 45 on the tractor and a collar 53 secured on the rod 43, the spring 51 being arranged to exert a force, in the direction to disengage the clutch associated with the shaft 1 6, greater than the engaging force of the resilient means 20 and 41 interposed between the two pressure plates 1 7 and 1 8. The collar 53 has a screw-threaded bore engaging, with an associated lock-nut 54, on the other end zone of the rod 43, the axial position of said collar thus being adjustable so that the force of the spring 51 can be adjusted to a value determinedly greater than the force exerted by the resilient means 20 and 41 when said means are fully compressed.A fork 55 has a screw-threaded bore engaging, with an associated lock-nut 56, on the extreme end of said other end zone of the rod 43, and is connected by a pivot pin 57 to the free end of the short arm 47. We also provide a latching pin 58 resiliently mounted in well known manner on the hand lever 46 and arranged to co-act with a slot 59 in a quadrant 60 secured to the chassis 45 of the tractor in such a way that the clutch associated with the shaft 1 6 can be latched in its engaged condition. The external operating mechanism and its latching pin 58 are shown in the "clutch engaged" position in Fig. 3, and the direction of clutch-disengaging movement of the lever arm 42 is indicated in said Fig. by the arrow 61.

In operation, the clutch associated with the shaft 16, which controls the tractor's power takeoff shaft, has to be urged into and latched in its engaged condition by operation of the hand lever 46 against the net disengaging force constituted by the difference between the force of the spring 51 and the force of the resilient means 20 and 41. If the latching pin 58 is released from the position shown in Fig. 3, either accidentally or deliberately, the clutch controlling the power take-off shaft is automatically disengaged by said net disengaging force, and cannot be re-engaged without deliberate effort by the driver. Thus no shock loading can unintentionally be imposed by the operating means for said clutch on said clutch or on any machinery coupled to said shaft.

It is within the scope of our inventive concept so to redesign the dual clutch assembly that its internal resilient means act to disengage the clutch associated with the shaft, thus permitting the external spring surrounding the rod to be dispensed with.

Claims (7)

Claims

1. A power take-off clutch, for a vehicle, which is urged into and latched in engaged condition by driver-operated means against the disengaging action of resilient means.

2. A power take-off clutch according to claim 1, which is basically urged into engaged condition by internal resilient means but which is provided with an external operating mechanism comprising a lever arm secured on a cross-shaft in conventional manner, a rod pivotally connected at one of its ends to the free end of the lever arm, a driver-operated lever pivotally mounted on the chassis of the vehicle and pivotally connected to the other end of the rod, a spring interposed between the chassis of the vehicle and a collar secured on the rod, the spring being arranged to exert a force in the clutch-disengaging direction greater than the engaging force of the internal resilient means, and latching means associated with the lever to enable the clutch to be latched in engage condition.

3. A power take-off clutch according to claim 2, wherein the axial position of the collar on the rod, and thus the force of the spring, is adjustable.

4. A power take-off clutch according to claim 2 or claim 3, wherein the latching means comprise a latching device on the lever arranged to co-act with a quadrant secured to the chassis of the vehicle.

5. A power take-off clutch according to any one of claims 2 to 4, wherein the driver-operated lever is a hand lever.

6. A power take-off clutch according to any one of claims 2 to 5, wherein the internal resilient means comprise a plurality of circumferentiallydisposed helical compression springs and/or a diaphragm spring.

7. A power take-off clutch, for a vehicle, constructed, arranged and adapted to operate substantially as hereinbefore described with reference to, and as illustrated by, the accompanying drawings.