GB2114687A - Industrial friction clutches - Google Patents

Abstract

A friction clutch for industrial use has a drive plate (13) sandwiched between a clutch body (14) and an axially movable pressure plate (16). Clamping pressure is provided by a Belleville spring (21) whose outer peripheral margin is held between two fulcra (22) on a carrier (23) axially fast with a release bearing (28). When the clutch is released the Belleville spring goes "over-centre" to the reverse direction of coning and no external load is then required from the release bearing. <IMAGE>

Description

SPECIFICATION Industrial friction clutches This invention relates to friction clutches and particularly to industrial friction clutches of the type used to engage and disengage drives on machinery.

In industrial friction clutches it is common for a driven plate to be rotationally fast with a flywheel member and for it to be sandwiched between a pair of plates which are rotationally fast with a driven member. In order to transfer the torque drive from the flywheel member to the driven member the driven plate is typically clamped between the two plates by a hand lever operated over-centre mechanism, usually toggle clamps, so that the clutch is locked in its driven position by the over-centre toggle action. The hand lever is operated to disengage the clutch and again the over-centre toggle mechanism ensures that clutch remains fully disengaged until its condition is changed by an operator.

Usually in each clutch there are three equiangularly spaced toggle clamps, which are expensive to produce and difficult to adjust to the correct clamping load.

The present invention seeks to provide a simplified industrial clutch assembly having a drive plate rotationally fast with one of a driving member and driven member and frictionally engageable with the other of said members under a clamp load applied by an over-centre mechanism, wherein said over-centre mechanism includes a belleville spring which when coned in one direction applies a clamp load to the drive plate and engages the clutch and when coned in the other direction the clutch is released.

Preferably the driving member is a flywheel and the drive plate is rotationally fast therewith, the driven member is a shaft having a pair of pressure plates rotationally fast therewith, one of which is axially movable along the shaft, and the drive plate is sandwiched between the pressure plates, and the belleville spring acts against said one pressure plate to clamp the drive plate between the pressure plates.

The invention will be described by way of example and with reference to the accompanying drawings in which: Fig. 1 is a longitudinal section through a clutch assembly according to this invention showing the assembly above its centre line C, in the engaged condition; and Fig. 2 is a section through the clutch assembly showing the release assembly in the disengaged condition.

With reference to Fig. 1 and Fig. 2 which illustrate a clutch suitable for use on saw mills, compressors, power shovels, mixing plants and other typical industrial applications.

A flywheel 11 of an engine, or motor, has an internally toothed drive ring 12 bolted to its outer peripheral margin. The drive ring 12 meshes with teeth on the external periphery of a friction material drive plate 13. The drive plate 13 is located between a clutch body 14 which is secured onto the tapered end portion of a driven shaft 1 5, and a pressure plate 1 6.

The clutch body 14 carries the reaction of the pressure plate 1 6 which is rotationally fast with and axially slidable on an axially extending central neck portion 18 of the clutch body 14. Three equiangularly spaced compression springs 1 7 act between the body 14 and plate 1 6 to space the two apart when the clutch is released. The pressure plate 1 6 is moved towards the body to clamp the drive plate 1 3 therebetween when the clutch is engaged.

The clamp load to engage the clutch is applied by an over-centre mechanism 20 which comprises a belleville spring 21 whose outer peripheral margin is held between two opposed circular fulcrums 22 formed on an annular carrier 23 which is axially slidable along the shaft 1 5. The inner peripheral margin of the belleville spring 21 is pivoted, on its face away from the pressure plate 1 6, against a circular fulcrum 25 formed on the free end portion of the neck 18 of the body 14, and the spring 21 reacts against the pressure plate through the intermediary of an annular ring 24. The ring 24 is axially slidable on the neck 1 8 and has a circular fulcrum 26 thereon that bears against the belleville spring 21 on its side adjacent the pressure plate 1 6.

The annular carrier 23 is slidable on the shaft 1 5 and is attached to the rotary race of a release bearing 28. The stationary race of the release bearing 28 is attached to a carrier 29 which has diametrically opposed radially outwardly projecting lugs 31 for engagement with the arms of a release fork 32 which in turn is operated by a hand lever 34 pivoted on the exterior of the clutch housing (not shown).

The clutch operates as follows: In Fig. 2 the clutch is shown in the fully released condition. The springs 1 7 bias the pressure plate 1 6 away from the body 14 and the belleville spring 21 is in a totaliy relaxed state and has biased the carrier 23 and release bearing 28 as far to the right as is possible.

To engage the clutch the hand lever 34 is moved in the direction of arrow B and the load to distort the belleville spring 21 is applied to the outer periphery of the spring via the circular fulcrum 22 on the carrier 23. The spring pivots about the fixed fulcrum 25 on the neck 1 8, and the mid portion of the spring moves the annular ring towards the pressure plate. This will continue with increasing effort being applied through the lever 34 until the spring goes flat.

Further movements of the lever in the direction of arrow B will cause the spring to invert and the operator will feel a change in the direction of load applied to the lever, i.e. up to that point he will push against the spring load and after that point he will pull against the spring load to engage the clutch smoothly. When the spring has inverted, the spring load will be reacting back on the fulcrum 25, and will be applying a clamp load through the fulcrum 26 on the ring 24. Until such time as the drive plate 13 is fully clamped between the body 14 and the pressure plate 16 the operator will be allowing the belleville spring to cone slowly by controliing the movement of the carrier 23 through the hand lever.

To disengage the clutch the operator will move the hand in the direction of arrow A; and pulls the outer periphery of the bellevilie spring 21 away from the pressure plate. The spring pivots on fulcrum 25 and the release load applied by the operator has a mechanical advantage over the clamping load applied by the spring of the radial distance between 22 and 25 the radial distance between 26 and 25 This is ideally between 5:1 and 7:1. The spring goes flat and then inverts as previously described, with the operator feeling a change in load at the hand lever.

Claims (7)

1. A friction clutch assembly having a drive plate rotationally fast with one of a driving member and driven member and frictionally engageable with the other of said members under a clamp load applied by an over-centre mechanism, wherein said over-centre mechanism includes a belleville spring which when coned in one direction applies a clamp load to the drive plate and engages the clutch and when coned in the other direction the clutch is released.

2. A clutch assembly as claimed in Claim 1, wherein the driving member is a flywheel and the drive plate is rotationally fast therewith, the driven member is a shaft having a pair of pressure plates rotationally fast therewith one of which is axially movable along the shaft, and the drive plate is sandwiched between the pressure plates, and the belleville spring acts against said one pressure plate to clamp the drive plate between the pressure plates.

3. A driven plate as claimed in Claim 2, wherein the belleville springs act against the one pressure plate through an axially movable annular ring which has a circular fulcrum thereon for contact with the belleville spring.

4. A clutch assembly as claimed in any one of Claims 1 to 3, wherein the outer peripheral margin of the belleville spring is trapped between two opposed circular fulcrums on an axially slidable release bearing assembly, and the inner margin of the belleville spring reacts against a fixed circular fulcrum.

5. A clutch assembly as claimed in Claim 4 when dependent upon Claim 3, wherein the outer peripheral margin of the belleville spring on its side away from the cone pressure plate reacts against an axially fixed circular fulcrum associated with the other pressure plate, and its side adjacent the one pressure plate reacts against the circular fulcrum on the annular ring at a point intermediate the inner and outer peripheral fulcrums.

6. A clutch assembly as claimed in Claim 5, wherein the ratio of the distance between the outer peripheral circular fulcrums and the inner peripheral fulcrum on the carrier, and the distance between said intermediate fulcrum and the inner peripheral fulcrum is between 5:1 and 7:1.

7. An industrial friction clutch assembly substantially as described herein and as illustrated in the accompanying drawings.