GB2097491A

GB2097491A - A friction clutch

Info

Publication number: GB2097491A
Application number: GB8211636A
Authority: GB
Original assignee: Machinefabriek en Technische Handelsonderneming MH Van der Graaf BV
Current assignee: Machinefabriek en Technische Handelsonderneming MH Van der Graaf BV
Priority date: 1981-04-24
Filing date: 1982-04-22
Publication date: 1982-11-03
Also published as: NL8102043A; IT8220912A0; DE3213073A1; SE454531B; DE3213073C2; IN156484B; SE8202543L; BR8202271A; NL187538C; IT1151146B; FR2504624A1; GB2097491B

Abstract

A friction clutch is provided with a plurality of swivelling levers (8) positioned in longitudinal slots (7) of a hub (3), an axially displaceable link ring (26) for pressing the operating ends (12) of the levers (8) and at least one friction element (22) opposite a friction face of a portion to be coupled (4). An axially stationary (18) and an axially slidable thrust ring (17) press the friction element (22) radially outwards, said ring (17) being acted on by the working ends (15) of the levers (8). The hub (3) is coupled in axial direction slidably with one of the shafts (2) and the friction face of a portion to be coupled (4), usually a drum, is fitted with a stop shoulder (28). This prevents axial forces from the clutch being transmitted to the bearings of the members to be coupled. <IMAGE>

Description

SPECIFICATION A friction clutch The invention relates to a friction clutch provided with a plurality of swivelling levers positioned in longitudinal slots of a hub, an axially displaceable ring for pressing the operating ends of the levers, at least one friction element opposite a friction face of a part to be coupled, an axially stationary and an axially slidable pressure ring for pressing the friction element, which slidable thrust ring abuts against the working ends of the levers.

Such a friction coupling is disclosed in the present applicants' Dutch patent 106.1 18. In this prior art clutch, the hub is fixedly attached to the shaft, with the result that, after the two shafts have been coupled, i.e. the driving and the driven shaft, as result of the cross-sectionally cynical shape of the friction element and the co-acting pressure plates, one of which is fixedly connected to the hub and the other being adapted to be operated by the said swivelling levers, the two shafts will be drawn towards each other.These axial bearing loads may be highly detrimental if, for instance, the one clutch portion is connected to the crankshaft of a piston engine: as a result, in the case of a shaft or crankshaft having a bearing which is provided with lateral bearing surfaces whereby a slight play in axial direction is possible, the bearing surfaces are constantly loaded and the axial freedom of movement of the shafts is entirely prevented.

It is an object of the invention to substantially eliminate the axial loads on the bearings of the shafts to be coupled, after the coupling has been effected.

Accordingly, the present invention provides a friction clutch which is provided with a plurality of swivelling levers positioned in longitudinal slots of a hub, an axially displaceable link ring for pressing the operating ends of the levers, at least one friction element opposite a friction face of a portion to be coupled, an axially stationary and an axially slidable thrust ring for pressing the friction element, the slidable thrust ring abutting against the working ends of the levers, and wherein the hub is coupled in the axial direction slidably with one shaft, and the friction face of the portion to be coupled is fitted with a stop shoulder.

Since the hub is connected in the axial direction freely movably with the one shaft, no axial forces will be exerted on the shafts or the supporting bearings. By providing the friction face of the part to be coupled, i.e. the drum, with a stop shoulder, against which a part of the friction elements finds support, it is likewise ensured that during the coupling by means of the axially movable link ring, the axially freely movable hub is not entirely or partly removed from the shaft.

As friction element, a plurality of radially arranged friction segments may be used, in a peripheral recess of which there is mounted a circular tension spring. It has been found that in such a construction, in the freewheel position, where the link ring is retracted, as a result of the speed of the driving shaft, the peripheral tension spring is not capable of returning the friction segments on the conical pressure plate, so that the friction element, i.e. the segments, remains in slipping contact with at least one of the conical pressure plates.

It is an object of an embodiment of the invention to substantially eliminate this drawback.

Accordingly, the friction clutch of the invention preferably comprises means for axially displacing the hub in the uncoupled final position of the friction clutch. These means may consist of a resilient element, e.g. a Belleville washer, disposed between a retaining ring fixedly attached to the shaft and the hub.

One embodiment of the friction clutch according to the invention will now be described, by way of example, with reference to the accompanying drawings wherein: Fig. 1 is a cross-section of a friction clutch in a mounted condition, wherein the clutch is represented in the upper half in the coupled condition and in the lower half in the uncoupled position; Fig. 2 shows the apparatus according to Fig. 1 in the upper half in the uncoupled position of the friction clutch, but with the friction element abutting against the drum and against one of the pressure rings, and in the lower half with the friction element running clear off the two pressure rings and exclusively abutting against the drum; and Fig. 3 is a cross-section on the line Ill-Ill in Fig. 1.

The drawings show a friction clutch which is arranged between a crankshaft 1 and a driven shaft 2. The one clutch portion is designed with a hub 3, slidably connected to the driven shaft 2 through a key not further shown, while the other clutch portion is formed by a drum 4 fixedly connected to the crankshaft 1. The hub 3 is provided at the outer circumference side with circular slots 5 and 6 and with a plurality of axially extending slots 7. In each of the axial slots 7 there is provided a lever 8, consisting of a package of, in the present case, some identical, punched out hard spring steel plates 9, which are loosely and adjacently disposed relative to each other.In the slot 5 there are provided two semi-circular wire rods 10 bent from hard spring steel wire and which serve for the hinge bearings of the levers 8, which levers are provided for the purpose with a recess 1 The oblique ends 1 2 of the levers 8 are adapted to be pressed towards the shaft centre by an axially displaceable link ring formed by the inner shaft ring 13 of a ball bearing 14, so that the levers 8, pivoting about the wire ends, press a thrust ring 17, via an adjustment disc 16, with a nose 15.

Opposite the thrust ring 1 7 lies an inverted corresponding thrust ring 1 8. Upon axial pressure, at which the thrust ring 18 abuts against an adjusting nut 21 screwed on the hub 3, the thrust rings 1 7 and 1 8 press, with their conical faces 20 facing towards each other, the friction element radially outwardly against the inner wall of the drum 4. The friction element consists of friction segments 22 kept together by a helical spring 29.

The thrust rings 17 and 18 are provided with keyslots 25. wherein the levers 8 positioned in the hub grooves 7 extend, so that the hub 3 and thrust rings 17, 18 are coupled clockwise by the levers 8. Between the thrust rings 1 7 and 18 there are provided three pressure springs 24, which ensure that in the uncoupled condition the thrust rings 1 7, 1 8 are returned to their starting position.

The ball bearing 14 is mounted in an operating or link ring 26. For uncoupling purposes, the link ring is retracted to a position against a stop or spring ring 27, arranged in the groove 6.

In order to ensure that, during the movement from the uncoupled to the coupled position of the link ring 26, the link ring 26 does not wholly or partly slide the axially freel; movable hub from the driven shaft 2, drum 4 is provided with a stop shoulder 28. Upon coupling, during displacement of the link ring, the friction element, i.e. the friction segments 22, will first be moved against the stop shoulder 28 and subsequently against the inner face of the drum.

As shown in Fig. 2, wherein numerals of corresponding elements shown in Fig. 1 are not repeated upper half, upon uncoupling of the clutch, whereby the link ring 26 impinges on the stop ring 27, the movable thrust ring 17 will move the friction element 22 away from the stop shoulder. However, it has been found in practice that as a result of the high speed of the driving shaft, the peripheral helical spring 29 is not capable of returning the friction ring segments 22 to the conical thrust rings 17 and- 18, and therefore heat development occurs at the cone face 20 (see Fig. 2, at the left hand top side).

In order to eliminate this problem, there is provided between the hub and a retaining ring 30 fixedly attached on the driven shaft (see Fig. 1) a Belleville washer 31. As a result, when the link or operating ring 26 is retracted and the hub has moved in the same sense through the stop ring (see Fig. 2 upper half), the Belleville washer will ensure an axial movement of the hub, so that the two thrust rings 17, 18 come to lie free from the friction elements consisting of friction segments 22.

Claims

1. A friction clutch which is provided with a plurality of swivelling levers positioned in longitudinal slots of a hub, an axially displaceable link ring for pressing the operating ends of the levers, at least one friction element opposite a friction face of a portion to be coupled, an axially stationary and an axially slidable thrust ring for pressing the friction element, the slidable thrust ring abutting against the working ends of the levers, and wherein the hub is coupled in the axial direction slidably with one shaft, and the friction face of the portion to be coupled is fitted with a stop shoulder.

2. A friction clutch according to claim 1, wherein the portion to be coupled is a drum.

3. A friction clutch according to claim 1 or 2, wherein the friction element comprises a plurality of radially adjacently disposed friction segments which are kept together by a resilient element, and wherein the clutch further comprises means for displacing the hub in the uncoupled end position of the clutch in the axial direction.

4. A friction clutch according to claim 3, wherein the said means comprise a resilient element mounted between a retaining ring fixedly attachable on the shaft and the hub.

5. A friction clutch according to claim 4, wherein the resilient element is a Belleville washer.

6. A friction clutch substantially as herein described with reference to the accompanying drawings.