GB2159896A - Improvements relating to clutches - Google Patents

Abstract

A clutch for use on spinning machines comprises first and second clutch members (3 and 4) rotatable on a common axis (51) and disposed axially of one another. An electromagnetic actuator (5, 6 and 12) effects a driving connection between the clutch members (3 and 4). The actuator includes a stationary magnet body (5) disposed on the side of the second clutch member (4) remote from the first clutch member (3), and an electro- magnetic coil (6) supported on the magnet body (5). A shroud (22) is fixedly secured at one end to the magnet body (5) and extends axially so that it surrounds the first and second clutch members (3 and 4). Preferably, the shroud (22) extends to a position in which its rim is axially beyond the first clutch member (3). <IMAGE>

Description

SPECIFICATION Improvements relating to clutches The present invention relates to clutches of the kind comprising first and second clutch members rotatable on a common axis and disposed axially of one another, and an electromagnetic actuator for effecting a driving connection between the clutch members, the electromagnetic actuator including a stationary magnet body supporting an electromagnetic coil and being disposed on the side of the second clutch member remote from the first clutch member.In known mannerthe electromagnetic actuator may also include an armature connected to the first clutch member through a spring which biases the armature away from the second clutch member, energisation of the electromagnetic coil of the actuator causing deflection of the armature against the spring bias so that the armature engages the second clutch member to effect the driving connection between the first and second clutch members.

Clutches of the above described kind are often used in dusty environments such as in textile spinning mills where the clutches are included in the drive mechanisms of the spinning machines. In such environments the atmosphere is laden with cotton fibres and/or lint particles which can worktheirway into the clutches and cause their malfunctioning and eventual failure unless precautions are taken to prevent the ingress of the fibres and particles into the clutches.

In the past it has been attempted to prevent the ingress of fibres and particles into the clutches by the use of rotating shrouds and seals which close off various gaps between working parts of the clutches, particularly the gap between the first and second clutch members.

It is the main object of the present invention to provide a simpler way than hitherto of preventing the ingress of fibres and particles into clutches of the kind described above.

According to the invention, in a clutch of the kind described above, a cup-shaped shroud is fixedly secured at one end to the magnet body and extends axially so that it surrounds the first and second clutch members and preferably extends to a position in which its rim is axially beyond the first clutch member.

Thus the shroud remains stationary during rotation of the clutch and if its rim is at a position beyond the first clutch member it can be designed so that in use it is in close contact with a stationary surface of for example a spinning machine so that this stationary surface effectively closes off the mouth of the cup. If the stationary surface is profiled then the rim of the cup can be correspondingly profiled to provide the close contact.

Two clutch constructions in accordance with the invention and incorporating other advantageous constructional features will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 shows a part longitudinal sectional view and a part elevational view of the first clutch construction, Figure 2 shows an end view of the first clutch construction looking in the direction of arrow A in Figure 1 with the driving clutch member removed.

Figures 3 and 4 show corresponding views of the second clutch construction.

Figures 5 to 7 show respectively a sectional view, an end view and a plan view of a modified shroud construction.

Referring to Figures 1 and 2, the clutch has a central bore 1 for receiving a driven shaft on centre line 51. The shaft is referenced 52 and passes through side wall 2 of a spinning machine. The clutch has a driving clutch member 3 which is rotatably supported on the driven shaft 52, a driven clutch member 4 which is keyed to the driven shaft 52 and an electromagnetic actuator comprising a stationary magnet body 5 supporting an annular energising coil 6 and an annular armature 12. The magnet body 5 is secured to a stationary part of the spinning machine through a bracket 7.

The driving clutch member 3 comprises a plastics gear member8 moulded on to a hub 9 in the form of an aluminium extrusion. Needle bearings 10 are press fitted into the bore of the hub 9 whereby the driving clutch member 3 is rotatably mounted on the driven shaft 52.

A driving connection between the clutch members 3 and 4 is effected by the annular armature 12 which is carried at the outer periphery of an annular spring 13. At its inner periphery the spring 13 is riveted to the plastics gear member 8 by a series of, for example three, rivets 14. The spring 13 biases the armature 12 out of engagement with the driven clutch member 4 and energisation of the coil 6 of the electromagnetic actuator deflects the armature 12 into engagement with the driven clutch member 4 against the bias of the spring 13, to effect the driving connection.

The driven clutch member 4 is in the form of a one-piece rotor of ferromagnetic material and which has magnetic isolation slots 15 pierced into it to ensure that the flux passes through the correct path between the magnet body 5 and the armature 12.

This form of rotor construction is relatively cheap as compared with the previously known three piece rotors.

The magnet body 5 is in the form of an annulus having radially inner and outer walls 20 and 21 forming inner and outer magnet poles respectively and defining a channel shaped cross-section with the mouth of the channel facing axially towards the clutch members 3 and 4. The annular coil 6 locates within the annular channel of the magnet body 5.

The magnet body 5 is supported on the driven clutch member 4 by a sealed bearing 16. A keyhole slot 17 is punched into the outer wall 21 of the magnet body 5, the narrow part of the slot 17 extending from the edge of the outer wall 21 up to the circular part of the slot 17. The lead wires from the coil 6 extend through an insulator 27 fixed in the circular part of the keyhole slot 17. The provision of a keyhole slot 17 enables the lead wires to be slipped down the slot, rather than having to thread them through a drilled hole as in previous clutches.

The use of a keyhole slot as well as assisting in assembly has advantages in construction and cost.

In the past the assembly procedure has been to: (i) feed the wires through the drilled hole in the magnet body which is a dexteriously difficult operation, (ii) slide the wires through a hole in an insulator, (iii) press the insulator firmly into the hole in the magnet body, (iv) put heat shrinking sleeving over the wires and shrink into place.

By providing the keyhole slot 17 the lead wires can be made from twin-core insulated and sheathed cable 28 with the insulator 27 pre-positioned by the coil manufacturer. It is then only necessary to drop the coil into the magnet body and at the same time pass the cable 27 down the slot 17. The insulator 26 can then be pressed into the circular part of the slot.

The coil 6 is wound on a bobbin 18 which has protrusions 19 on the surface of its central bore so that when the bobbin is pressed home on to the outside of the inner pole 20 of the magnet body 5 it will grip it to hold the bobbin in place.

To inhibit the ingress of fibres or particles into the moving parts of the clutch a stationary cup shaped shroud 22 is secured at one end to the magnet body 5. To effect this securement the cup-shaped shroud 22 has a sleeve portion 25 which fits on to the outer wall 21 of the magnet body 5. Thus the end of the shroud 22 opposite its rim 26 is closed off by the magnet body 5, the bearing 16 and the shaft 52. The shroud 22 extends axially from its securement to the magnet body 5 so that it surrounds the driving and driven clutch members 3 and 4 and the armature 12 to prevent cotton fibres falling into the gear member 8. Since the shroud 22 is stationary it will not pick up cotton fly at its rim 26 as is the case with a rotating shroud.The shroud extends beyond the driving clutch member 3 so that advantageously its rim 26 as shown in Figure 1 is in close contact with the facing surface of the wall 2 of the spinning machine to close off the mouth of the cup. It is also to be noted that the shroud 22 advantageously covers the narrow part of the keyhole slot 17.

A slot 24 is provided in the shroud 22 to allow engagement of the gear member 8 with a mating gear. The angular orientation of the shroud 22 on the magnet body 5 can be set by reference to the insulator 26 fitting in slot 17. This is important for indexing the position of the slot 24.

Referring to Figures 3 and 4, this shows a clutch construction generally similar to that shown in Figures 1 and 2 and as far as possible the same reference numerals have been used to designate corresponding parts of the two clutch constructions.

The main difference between the two constructions is that in Figures 3 and 4 construction the rear surface 31 of the driven clutch member 4 has been machined flat resulting in the length of the inner pole 20 of the magnet body 5 being reduced.

To compensate for the less efficient magnetic circuit thus provided, the thickness of the inner pole 20 has to be increased and to permit this a smaller sealed bearing 16 is used. The advantage in this construction over that of Figures 1 and 2 is the saving in expensive machining time.

By providing the thicker inner pole 20 it is possible to groove the inner pole to provide a circumferential groove 32 and to restrain the coil on the inner pole by a flange 33 on the bobbin 18 fitting in said groove.

In the clutch constructions shown in Figures 1 to 4, the magnet body 5 is restrained against rotation by the bracket 7 which is secured to a stationary part of the spinning machine. Traditionally the bracket 7 is a separately formed member which is spot welded on to the magnet body; the provision of the bracket 7 in this way is relatively expensive.

Referring to Figures 5 to 7 a modified form of shroud is shown which incorporates in simple and cheap manner the equivalent of the bracket 7. The shroud which has again been given the reference 22 has the slot 24 to allow engagement of the gear member 8 with a mating gear. The angular orientation of the shroud 22 as in the previous construction is located with reference to the insulator 26 and for this purpose has a slot 42. The slot 42 locates around the insulator 26 fitting in the keyhole slot 17. It will be readily appreciated that because of the direction of the slot 42, the shroud 22 must be fitted to the magnet body 5 before the magnet body 5 is assembled to the rest of the clutch.

The shroud 22 of Figures 5 to 7 can, in the same way as the previously described shrouds, be moulded, for example from plastics material.

However, it is additionally moulded with an integral block 43 having a slot 44 in order to provide the restraining bracket for the magnet body 5. The slot 42 provides the reference for the position of the block 43 so that the slot 44 is at the correct angle to the slot 42. Thus since the shroud 22 is fixedly secured to the magnet body 5, the block 43 provides a restraining bracket equivalent to the bracket 7.

Claims (9)

1. A clutch comprising first and second clutch members rotatable on a common axis and disposed axially of one another, an electromagnetic actuator for effecting a driving connection between the clutch members, said actuator including a stationary magnet body disposed on the side of the second clutch member remote from the first clutch member and an electromagnetic coil supported on said magnet body, and a cup-shaped shroud fixedly secured at one end to the magnet body and extending axially so that it surrounds the first and second clutch members.

2. A clutch according to claim 1, wherein the cupshaped shroud extends to a position in which its rim is axially beyond the first clutch member.

3. A clutch according to claim 1 or claim 2, wherein the cup-shaped shroud has a sleeve portion at one end which fits on the outside of the magnet body to effect the securement of the shroud.

4. A clutch according to any preceding claim, wherein the magnet body is in the form of an annulus having radially outer and inner walls defining a channel cross-section with the mouth of the channel facing axially towards the clutch members, the electromagnetic coil is disposed within the channel, a keyhole slot extends from the edge of said outer wall and electrical leads from said coil extend through a circular part of the keyhole slot at the end of the slot remote from said edge.

5. A clutch according to claim 4, wherein the coil is mounted on an annular bobbin which is a push fit over said inner wall.

6. A clutch according to claim 4 or 5, wherein the surface of the second clutch member facing the magnet body is machined flat.

7. A clutch according to claim 6, wherein the coil is mounted on an annular bobbin which fits over said inner wall and has an annularflangewhich locates in a circumferential groove in said inner wall.

8. A clutch according to any preceding claim, wherein said shroud has an integrally formed mounting bracket, whereby the shroud and the magnet body fixedly secured to it can be mounted on a stationary member and so restrained against rotation.

9. A clutch substantially as hereinbefore described with reference to Figures 1 and 2 or Figures 3 and 4 or Figures 5 to 7 of the accompanying drawings.