GB2242715A

GB2242715A - Clutch assembly

Info

Publication number: GB2242715A
Application number: GB9107025A
Authority: GB
Inventors: Ernst Elsner
Original assignee: JM Voith GmbH
Current assignee: JM Voith GmbH
Priority date: 1990-04-04
Filing date: 1991-04-04
Publication date: 1991-10-09
Also published as: DE9201511U1; GB9107025D0

Abstract

A clutch assembly employs components (4, 6) coupled together with a friction safety clutch (1), for load-dependent isolation of the power or torque in a drive line. To operate a driven machine briefly, even after the safety clutch has responded, an auxiliary clutch (12) is connected in parallel with the safety clutch. By means of this auxiliary clutch, a reduced torque can be transmitted for a short time so that it is possible to eliminate the cause of the safety clutch having responded and, in the case of a rolling mill, to prevent the mill being shut down. The auxiliary clutch (12) may be either a positive or friction clutch and may be switchable or constantly ready for operation. In a switchable embodiment the actuator is externally and non-rotatably disposed alongside the clutch assembly or integrated into the auxiliary clutch. The switchable auxiliary clutch may be constructed so that it can be actuated by a pressurised medium or electromagnetically. <IMAGE>

Description

IMPROVEMENTS IN CLUTCH ASSEMBLIES The invention relates to a clutch assembly with a frictional safety clutch for the load-dependent isolation of the power or torque in a drive line. Clutches of this type are used particularly in heavy engineering in a drive line which is subject to intensely alternating loadings and in which the torque may abruptly assume a level which exceeds the transmission capacity of the driving motor and/or interposed gear mechanism or other components. As a safeguard against destruction and operational breakdowns, safety clutches are incorporated into the drive line and are intended to react as quickly as possible to unacceptably high torque levels.

A safety clutch of this type is known from DE-OS 36 38 596. This clutch constitutes the intermediate member between a universal shaft and a shaft journal, e. g. a shaft journal of a rolling mill. The arrangement in such a case is that the two components of the clutch are disposed coaxially in each other and are rotatably mounted. For the transmission of torque, a clamping element is used which engages around the outer clutch component and which has on the inside a pressure chamber to which high pressure can be applied. When. pressure is applied from outside, the two inner clutch components are tensioned so that they are capable of transmitting torque via a frictional connection. If, on overload, there is a

slip between the two clutch components, then a releasing arrangement disperses the high pressure in the tensioning element so that the transmission of torque between the two clutch components is interrupted. It is true that this means that the flow of power is broken but at the same time the driven machine remains in the condition which resulted in the formation of peak torque and releasing of the safety clutch. Only the renewed establishment of the full transfer capacity of the safety clutch makes it possible to start the machine again.

There is then the danger that the safety clutch will respond again at once. Even elimination of the cause of the fault may represent a serious hindrance to operation, particularly if the workpiece being machined at the time or the machine itself is caused to break down in sympathy, for example by reason of a red-hot cog.

An object of the invention is to provide a clutch assembly with a safety clutch of the type described that despite the interruption in power flow permits emergency operation.

According to the invention there is provided a clutch assembly with a frictional safety clutch for loaddependent isolation of torque in a drive line, the safety clutch comprising two coaxially interdisposed and reciprocally rotatable clutch components which can be connected to each other frictionally by the action of an hydraulic tensioning element, and an auxiliary clutch

connected in parallel with the safety clutch between the first and second clutch components, the auxiliary clutch serving to connect the two clutch components operatively to each other when the frictional connection of the first safety clutch is interrupted.

For the drive line of which the maximum acceptable transmission torque has once been exceeded, the assembly according to the invention allows emergency operation without limiting the maximum torque at least until the reason for the breakdown and which was responsible for triggering the safety device has been remedied. This brings a substantial easing of operation and in many cases it does in addition permit of a more rapid reaction of the actual safety clutch.

Further features of the invention can be understood from the specific embodiments disclosed herein but it can be mentioned that the auxiliary clutch which is connected in parallel with the safety clutch is preferably constructed with a slip capacity. The auxiliary clutch can constantly be in rotationally rigid connection and, as a friction clutch, it can be provided with springloaded, ie conical friction rings which are subject to axial spring force and connect the two clutch components together in frictional and rotationally rigid fashion.

Alternatively the auxiliary clutch may be switchable, e. g. constructed as a remotely controlled

electromagnetically or pressurised medium-actuated friction clutch. In this case, the auxiliary clutch comes into action immediately when the safety clutch is tripped. A switchable auxiliary clutch has the advantage that it can be so controlled that there is no emergency operation of optional duration.

J A switchable and positive auxiliary clutch construction can be adopted which may indeed be engaged by remote control but which can itself be disengaged when the torque exceeds a fixed value. In this case there is provided between the two clutch components a radial toothed system with oblique flanks so that in the event of an overload the actuating force for engaging the clutch is overridden. To engage the auxiliary clutch, a hydraulic actuating cylinder may be provided.

As actuating device for the auxiliary clutch can be either an electromagnet or a hydraulic cylinder, which is disposed preferably not on the clutch assembly itself but is non-rotatable and rigidly disposed alongside the clutch assembly. This arrangement simplifies the inner construction and control of the clutch combination and at the same time increases the reliability which is required particularly in heavy engineering. In order to provide compact and ready-to-fit units, the auxiliary clutch actuating means, in other words the hydraulic cylinder (s) or electromagnet (s), are integrated directly into the auxiliary clutch.

The invention will be explained in greater detail hereinafter with reference to examples of embodiment shown in the accompanying sectional drawings in which: Fig. 1 shows a clutch assembly with a switchable positive auxiliary clutch; Fig. 2 shows a construction according to Fig. 1 with integrated hydraulic actuation; Fig. 3 shows a clutch assembly with an electromagnetically switchable auxiliary friction clutch; Fig. 4 shows a construction according to Fig. 3 with an integrated electromagnet and Fig. 5 shows a clutch assembly with a non-switchable auxiliary clutch.

Fig. 1 shows a clutch assembly with a safety clutch 1 and an auxiliary clutch 12. A first clutch component 4 is constructed as a universal shaft flange 2 which is intended to transmit torque to a shaft 3. A second clutch component 5 is constructed as a tubular friction sleeve 6 disposed coaxially within the first clutch component 4 and is, by means of a bearing 7, mounted to rotate within the first clutch component 4 when in the relieved state. The first clutch component 4 is closely enclosed by an annular clamping element 8. This clamping element 8 has an internal elongated pressure chamber 9 which has only a minimal radial extension and which can be via a screwed connection 10 filled with fluid at high

pressure. When the clamping element 8 is pressurised, the pressure spreads radially inwardly to the first clutch component 4 and thence to the friction sleeve 6 and on to the shaft 3 so that a frictional connection is established between the component 4 and the shaft 3. As is known per se, the radially outermost end of the screwed connector 10 is disposed inside an aperture in a releasing ring 11 which is mounted on a coupling ring 14.

The coupling ring 14 is itself axially movable but it is rotationally rigidly mounted on the friction sleeve 6 via a splined shaft toothed arrangement 17. Thus, the release ring 11 is associated with whatever is the rotated condition of the friction sleeve 6 or the shaft 3. If, due to excessive torque, there is a slip between the component 4 and the friction sleeve 6, then the outermost end of the screwed connection 10 is sheared off so that the pressure chamber 9 is relieved. This results in a free mobility between the component 4 and the friction sleeve 6. By means of the tensioning element 8, the clutch assembly thus fulfils the task of providing a safety clutch.

In order to bring about a temporary emergency operation of a machine in the drive line of which the present clutch assembly is installed, the two clutch components 4,5 are bridged by the auxiliary clutch which is suitable. For this purpose, both at the end of the tubular part of the component 4 and also on the coupling

ring 14 there are radial teeth 13. In normal operation, an expanding spring 18 keeps the coupling ring 14 disengaged by displacement on the splined shaft teeth 17. Engagement of the auxiliary clutch 12 takes place via a thrust ring 16 mounted axially onto the release ring 11.

For this purpose, an axial displacement force which is applied either by a hydraulic cylinder 16 or instead of this by a functionally equivalent electromagnet 26 is applied to the thrust ring 16. The actuating means for the thrust ring 16, in other words the hydraulic cylinder 15 or electromagnet 26, is stationary and not rotatable and is disposed alongside the clutch assembly.

Preferably, there are disposed on the thrust ring 16 two or a plurality of hydraulic cylinders 15 or electromagnets 26 to guarantee a uniform engagement of the clutch 13 of the clutch ring 14 and the component 4. In consideration of the external dimensions, the dimensioning of the auxiliary clutch 12 is so chosen that it is possible to transmit between the first and second clutch components 4,5 a torque which is just sufficient to permit of brief operation of the machine and to remedy the cause of the safety clutch having responded.

The teeth 13 preferably have sloping flanks.

Therefore, there is, caused by the torque, an axially directed force against the action of the expanding spring

18. At a specific torque, then, the equilibrium is overcome and the teeth 13 are automatically disengaged. The auxiliary clutch 12 thus also has the action of a safety clutch.

Fig. 2 shows a clutch assembly similar to the embodiment shown in Fig. 1, in which an auxiliary clutch 22 is provided which has a directly integrated actuation. For this purpose, a coupling ring 24 is constructed as an axially displaceable cylinder. Pressurised fluid is supplied via a hose connection 23 to a rotary bush 25 which is mounted in sealed relationship in the coupling ring 24. The pressure fluid which is fed in is propagated radially inwardly. An angular end piece on the friction sleeve 6 forms a solid piston for the cylinder-like construction of the coupling ring 24. The hose connection 23 is preferably mounted on the rotary bush 25 directly the safety clutch has responded and emergency operation by means of the auxiliary clutch 22 is necessary. The tube connection 25 is thus established for emergency operation only after the safety clutch 1 has responded so that it is not constantly ready to function.

Fig. 3 shows a clutch assembly with a safety clutch which corresponds to that in the embodiments shown in Figs. 1 and 2. In this assembly, a switchable auxiliary clutch 32 is provided in the form of a friction clutch. To this end, there are on the tubular part of the

component 4 inner plates 33 and, inside the release ring 11, outer plates 34. The plates 34,33 can be frictionally engaged by co-operation between an armature plate 35 and an electromagnet 36 which is disposed outside the clutch assembly. The release ring 11 is mounted on the friction sleeve 6 but has no axial mobility.

Fig. 4 shows a clutch assembly according to the embodiment shown in Fig. 3 but in this case an auxiliary clutch 42 has a co-rotating electromagnet 46 mounted on the release ring 11. The transmission of current to the electro magnet 46 occurs in this case via slip rings 43 and brushes 44.

All constructions of the described switchable clutch assembly according to Figs. 1 to 4 can be optionally constructed with an hydraulically actuated or electromagnetically actuated auxiliary clutch. In each case it is possible to adopt an arrangement with a separate non-rotating fixing alongside the auxiliary clutch, e. g. with an electromagnet having no slip ring, or an integrated arrangement with a rotary bush for the pressurised medium or supply of current via slip rings with brushes.

Fig. 5 shows a clutch assembly with a non-switchable auxiliary clutch 52. The release ring 11 here extends towards the friction sleeve 6 by way of a friction plate

53. Within the release ring 11 are friction rings 54 which are preferably conical on their outer periphery and which bear by means of a spreader spring 53 on corresponding mating surfaces on the release ring 11 and the friction plate 53. Radially inwardly, the friction rings 54 are rotationally rigidly supported on the tubular part of the component 4 by means of splines 56.

In this way, there is a constant connection between the two clutch components 4 and 5, namely via the end of the component 4, the friction rings 54 and the release ring 11 on the friction plate 53 to the friction sleeve 6.

When the safety clutch is transmitting the torque by

frictional connection between the two clutch components 4 \ and 5, the auxiliary clutch 52 is inoperative. If excessive torque results in the safety clutch being released, then the auxiliary clutch 52 immediately takes over the torque between the two clutch components 4,5 and possibly there may initially be slip within the auxiliary clutch 52. The advantage of this embodiment however lies in the fact that no switching manoeuvre or corresponding assembly operations are involved. The premise which is adopted in this construction is that the auxiliary clutch 52 only has to transmit the torque required for brief emergency operation. Consequently, an additional safety function devolves upon the auxiliary clutch 52.

Claims

CLAIMS 1. A clutch assembly with a frictional safety clutch for load-dependent isolation of torque in a drive line, the safety clutch comprising two coaxially interdisposed and reciprocally rotatable clutch components which can be connected to each other frictionally by the action of an hydraulic tensioning element, and an auxiliary clutch connected in parallel with the safety clutch between the first and second clutch components, the auxiliary clutch serving to connect the two clutch components operatively to each other when the frictional connection of the first safety clutch is interrupted.
2. A clutch assembly according to Claim 1, wherein that the auxiliary clutch is capable of slip.
3. A clutch assembly according to Claim 1 or 2, wherein the two clutch components are in constant rotationally locked connection via the auxiliary clutch.
4. A clutch assembly according to Claim 3, wherein the auxiliary clutch is constructed as a cone clutch with spring-loaded friction rings acting axially between the clutch components.
5. A clutch assembly according to Claim 1 or 2, wherein the auxiliary clutch is constructed as a switchable clutch.
6. A clutch assembly according to Claim 5, wherein the auxiliary clutch is constructed as a remotely controlled electromagnetic friction clutch.

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7. A clutch assembly according to Claim 6, wherein an electromagnetic device serves for operating the auxiliary clutch and the device is mounted on the assembly and is actuated via a supply of current through slip rings and brushes.
8. A clutch assembly according to Claim 5, wherein the auxiliary clutch is constructed as a friction clutch which is actuated hydraulically by a pressurised medium.
9. A clutch assembly according to Claim 5,6, 7 or 8 wherein the auxiliary clutch is engagable by remote control and disengaged under load.
10. A clutch assembly according to Claim 1, wherein the auxiliary clutch has components with radial teeth which can be engaged by axial displacement, the radial teeth having oblique flanks which on overload, can be disengaged against the action of the axial displacement force.
11. A clutch assembly according to Claim 10, wherein the auxiliary clutch is electromagnetically actuated.
12. A clutch assembly according to any one of Claims 6 to 11, wherein an actuating device for operating the auxiliary clutch is non-rotatable and disposed alongside the clutch assembly.
13. A clutch assembly accordion to 9 or 10, wherein an actuating cylinder for operating the auxiliary clutch is fixed on the clutch and has means for accepting an

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externally fed supply of pressurised medium.
14. A clutch assembly according to Claim 1, wherein the auxiliary clutch is constructed as a positively switchable clutch.
15. A clutch assembly substantially as described, with reference to, and as illustrated in, any one or more of the Figures of the accompanying drawings.