GB2088527A

GB2088527A - Fricton overload coupling

Info

Publication number: GB2088527A
Application number: GB8131570A
Authority: GB
Original assignee: GKN Walterscheid GmbH
Current assignee: Walterscheid GmbH
Priority date: 1980-11-27
Filing date: 1981-10-20
Publication date: 1982-06-09
Also published as: NL8103963A; GB2088527B; IT1194995B; IT8105222A0; JPS6246015Y2; FR2494793A1; IT8107069V0; ATA357881A; JPS5797924A; DE3044679A1; JPS6215627U; DE3044679C2

Abstract

A fricton over-load coupling has housing parts 3,12 held together by a plurality of circumferentially spaced axially extending bolts 7 each having a nut at both ends. The setting of the nut on the bolts determines the force exerted by a Belleville spring 5 in the coupling, and hence the torque at which the coupling will slip. The nuts 10 at the one ends of the bolts are captive thereon and moveable to a limited extent only, and the nuts 4 at the other end of the bolt are welded in position after initial adjustment. A user can then only alter the setting of the clutch to the extent permitted by the range of movement of the movable nuts 10. <IMAGE>

Description

SPECIFIICATION Friction overload clutch This invention relates to a friction overload (torque limiting) clutch, comprising driving and driven members between which torque is transmitted by friction elements biased into engagement with one another by spring means, the clutch including parts connected together by screw threaded fastening means, the setting of which determines the force exerted by the spring means. Such a clutch may be utilised in a drive line by which agricultural machinery is driven from the power take-off shaft of a tractor. If, for example, the machinery should become jammed the torque which the clutch attempts to transmit will exceed a pre-determined value set by the adjustment of the spring means, and the clutch will slip to protect the drive line and machinery.

One form of adjustable over-load clutch is described in German Published Patent Application 1,194,654. In that clutch, the force exerted by the spring means is determined by a single central nut, with fine adjustment possible by way of a plurality of circumferentially spaced adjusting bolts surrounding the central nut. The purpose of this is to enable the clutch to be set at the factory with a basic torque setting, which can subsequently be modified by the user within certain limits by the adjusting bolts.

A disadvantage of adjustable clutches is that, if an over-load frequently occurs, the user may increase the slipping torque to such an extent that the clutch will not slip in use. As a result, the clutch can no longer fulfil its protective function. Cases have been known, for example, where a clutch has been adjusted so that it cannot slip at all. Afurther disadvantage is that, if the spring load of the clutch is completely removed, eg. to clean the clutch or remove abraded material from the friction linings, it is very difficult to re-establish the original basic setting.

It is an object of the present invention to provide a friction over-load clutch whose basic setting can be factory adjusted and yet whose spring biasing force can be relieved if necessary without changing the basic setting.

According to the invention, we provide a friction over-load clutch, comprising driving and driven members between which torque is transmitted by friction elements biased into engagement with one another by spring means, and parts connected together by screw threaded fastening means the setting of which determines the force exerted by the spring means, wherein the screw threaded fastening means comprises a plurality of circumferentially spaced bolt elements, each having a first screw threaded portion carrying a nut captive and moveable on a limited length of the bolt element, and a second screw threaded portion carrying a nut which has been permanently fixed in position after having been initially adjusted thereon.

An advantage of this construction is that the nuts on the second screw threaded portions of the bolt elements can be used for the basicfactorytorque setting of the clutch, whereafter the nuts can be permanently fixed in position, eg. by welding, to retain such basic setting. It is then possible for the user to alter the setting of the clutch only by the amount by which the nuts on the first screw threaded portions of the bolt elements are capable of being moved. It is relatively easy to re-establish the basic setting of the clutch if it is disturbed.

The bolt elements may be headed at the ends of their first screw threaded portions, to hold the nuts captive thereon. If the user wishes completely to dismantle the clutch he must, for example, grind off the headed ends of the bolt elements to enable the nuts thereon to be removed. If there should be any complaint by the user, it is easy for the manufacturer to determine whether the clutch has been tampered with in this way.

The bolt elements may extend between axially spaced housing parts of the clutch, with the nuts accessible on the exterior of the housing parts. The spring means may comprise a Belleville spring operative between one of the housing parts and a friction element of the clutch.

These and other features of the invention will now be described in more detail by way of example with reference to the accompanying drawing, which is a part sectional view through a clutch incorporating the invention.

The illustrated friction over-load clutch is intended to form part of a driveline by which an item of agricultural machinery can be driven from the power take-off shaft of a tractor. The clutch comprises driving and driven elements in the form, respectively, of a hub 17 with a splined bore for fitting on a power take-off shaft and provided with a quick release locking device 14, and a universal joint yoke 1 which will be connected to a shaft via the conventional cross member and other yoke of a Hookes joint, not shown.

The joint yoke 1 is connected to a housing part 3, a radially inner part of which provides an abutment for a Belleville spring washer 5. The Belleville spring washer 5 bears against a pressure plate 6, which is supported relative to the hub 17 by a bearing 2. The hub 17 is welded to a clutch driving plate 13 with friction linings 8 on both sides thereof, the driving plate 13 lying between the pressure plate 6 and a further housing part 12.

The housing parts 3, 12 are held together by a plurality of circumferentially spaced axially extending bolt elements 7, which extend through apertures in the housing parts. Each bolt element 7 carries at its one end a nut 4, and at its other end a nut 10. The nuts 10 clamp the housing part 11 against abutment surfaces provided by collars 9 on the bolts 7. It will be apparent that the setting of the nuts 4, 10 determines the force with which the driving plate 13 is engaged between the pressure plate 6 and housing part 12.

In manufacture of the clutch, the nuts 10 will be screwed onto the bolts 7 as far as possible tightly to clamp the housing part 12 against the collars 9 on the bolts. The torque setting of the clutch is then determined by the distance to which the nuts 4 are screwed onto the bolt 7. At the desired setting, the nuts 4 are welded at 15, 16 to the bolts and to the housing part 3. The bolts are headed at 11 to hold the nuts 10 captive thereon.

Thereafter, the setting of the clutch can be relieved only to the extent that the nuts 10 can be unscrewed until they reach the headed ends 11 of the bolts. This will be sufficient for a user, for example, to clear abraded friction material from the interior of the clutch. The original setting of the clutch is easily recovered, by tightening nuts 10 to their limit determined by abutment with collars 9.

Claims

1. Afriction over-load clutch, comprising driving and driven members between which torque is transmitted by friction elements biased into engagemenu with one another by spring means, and parts connected together by screw threaded fastening means the setting of which determines the force exerted by the spring means, wherein the screw threaded fastening means comprises a plurality of circumferentially spaced bolt elements each having afirstscrewthreaded portion carrying a nut captive and moveable on a limited length of the bolt element, and a second screw threaded portion carrying a nut which has been permanently fixed in position after having been initially adjusted thereon.

2. A clutch according to Claim 1 wherein said parts comprise axially spaced housing parts, and said bolt elements extend between said housing parts with said nuts on the exterior thereof.

3. A clutch according to Claim 2, wherein said spring means comprises a Belleville spring operative between one of said housing parts and a friction element.

4. A clutch according to any one of the preceding claims wherein said nuts on said second screw threaded parts of said bolt elements are welded thereto.

5. A clutch according to any one of the preceding Claims, wherein said bolt elements are headed at the free ends of their first screw threaded portions to hold said nuts captive thereon.

6. A clutch according to any one of the preceding Claims wherein said bolt elements include abutment surfaces to determine the extent to which the nuts on said first screw threaded portions can be tightened thereon.

7. Afriction over-load clutch substantially as hereinbefore described with reference to and as shown in the accompanying drawings.