GB2128253A - Diaphragm actuator - Google Patents

Abstract

In a friction-engaging device, for example a friction clutch or brake, the actuator has an elastomeric diaphragm 65 of rubber or plastics which, together with a rigid insert 60, forms a pressure chamber. The diaphragm is sealed at its periphery to the insert or is beaded 66 over the insert outer edge. A packing piece 67 is located between the diaphragm 65 and an insulating disc 51 to provide movement freedom for the diaphragm. <IMAGE>

Description

SPECIFICATION Friction-engaging device This invention relates to a friction-engaging device, for example, a brake or clutch of the type in which two relatively movable members are frictionally engageable or disengageable.

According to the invention, a friction-engaging device includes a fluid pressure operable actuator, connected to move two relatively movable members into or out of frictional engagement when the pressurised fluid is supplied to the actuator, including an enclosed space into which the fluid is fed, said space being bounded partially by a rigid member and partially by an elastomeric diaphragm.

Conveniently, the rigid member and the diaphragm are sealed directly together at or adjacent their edges. The rigid member may be metal and the diaphragm may be a rubber or plastics material and may incorporate cloth or fibrous reinforcement.

The rigid member and diaphragm may be circular or annular to suit the shape of the relatively rotatable members.

Preferably the diaphragm is formed with a bead at the edge thereof, to seal on the opposite side of the edge of the rigid member from the rest of the diaphragm.

The friction-engaging device may be a brake or a clutch and the relative movement between the two members may be relative rotation.

The invention is described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is an end elevation of a frictionengaging device according to the invention, and Figure 2 is a section along the line Il-I I in Figure 1.

In the drawings, a shaft 10, which is to be braked protrudes from a face 11 of part of a machine 12. A brake disc 13, formed of substantially identical castings 1 4, 1 5 mounted in back-to-back relationship is mounted on the shaft 1 0. The castings 14, 1 5 are fastened together by circumferentially spaced screws 1 6. The disc 1 3 is driven from the shaft 10 by a key 17 and is located by a grub screw 1 8.

The brake disc 13 is formed with 2 annular outwardly-facing working faces 1 9.

Extending radially opposite each face 1 9 are two substantially identical stator discs 20. Each stator disc 20 has a central circular aperture 21 leaving a gap 22 around with shaft 10. The stator discs 20 are fastened to the machine 12 by circumferentially spaced studs 23 and are spaced from the face 11 by sleeves 24 and from each other by sleeves 25 on the studs 23.

Braking of the disc 13 is effected by opposing pairs of pads 26. Each pad 26 has a cylindrical outer surface, mounted for axial sliding in one of a plurality of bores 28 through each stator disc 20.

There will typically be 4, 6 or more bores 28 in each stator disc 20.

Each pad 26 is screwed to a flanged metal dish 49. The flange 50 of the dish 49 is abutted by a helical spring 30 and has an unshown notch into which one end of the spring 30 is engaged, to inhibit rotation of the pad 26. The dish 49 is filled with a disc of fibreboard heat insulating material 51.

The pad 26 is pressed against the face 19, in operation, by an actuator fed with pressurised air.

A metal disc 60 is located by a spigot 61 through a central bore 62 in a cap 34, the spigot 61 containing a threaded air inlet connection 63. An integral flange 64 of the disc 60 is spaced slightly away from the bore and the inner rear face of the cap 34. An elastomeric diaphragm 65 of suitable rubber or plastics materials, reinforced if appropriate, extends across the left-hand face of the disc 60 and extends through the gap between the bore of the cap 34 and the edge of the disc 60.

A bead 66 formed integral with the diaphragm 65 is positioned on the opposite side of the flange 64 to the pad 26 to hold the diaphragm 65 to the disc 60 and to seal onto the disc 60 when pressurised air is supplied through the air inlet 63.

Each actuator is located and retained in a separate cap 34 which is fastened to the outer face of the stator disc 20 by two screws 35. As can be seen from the drawings, each cap 34 is provided with slotted ears 36, whereby the assembly comprising the cap 34, actuator, spring 30, dish 49, disc 51 and pad 26 may be simply withdrawn for inspection or replacement of components by slackening the screws 35, partially rotating the cap 34 until the ears 36 disengage from the screws 35 and withdrawing the cap 34 axially until the pad disengages from the stator disc 20.

The pressurised air causes the diaphragm 65 to extend towards the pad 26 and press it against the working faces 1 9. A packing piece 67 between the diaphragm 65 and insulating disc 51 provides freedom of movement for the periphery of the diaphragm 65. The disc 60 may be of rigid plastics material instead of metal.

Although the invention has been described as applied to a brake, it could be applied to any other appropriate friction-engaging device, such as a friction clutch. Furthermore, instead of a brake or clutch of the spot type, the invention is applicable to actuators for other types of friction-engaging devices. For example, some friction-engaging devices have annular friction faces around the axis of rotation, in place of pads 26. Such annular friction faces may be actuated by an annular actuator of similar size to the friction face and the actuator construction may then be in the form of a metal annulus in place of the disc 60 sealed to a corresponding annular elastomeric diaphragm having beads 66 adjacent to the inner and outer diameters of the metal annulus.

Similarly, some friction-engaging devices are of a construction in which the member against which the pad 26 is to be pressed, is rotatable relative to the pad 26 about the same axis as the central axis of the pad 26.

For some installations pressurised liquid may be used in place of pressurised air. In place of the bead 66 the adjacent edges of the disc 60 and the diaphragm 65 may be bonded together.

Claims (11)

1. A friction-engaging device including a fluid pressure operable actuator, connected to move two relatively movable members into or out of frictional engagement when the pressurised fluid is supplied to the actuator, including an enclosed space into which the fluid is fed, said space being bounded partially by a rigid member and partially by an elastomeric diaphragm.

2. A friction-engaging device, according to claim 1, in which the rigid member and the diaphragm are sealed directly together at or adjacent their edges.

3. A friction-engaging device, according to claim 1 or 2 in whicht he rigid member is metal.

4. A friction-engaging device, according to any preceding claim in which the diaphragm is a rubber material.

5. A friction-engaging device, according to any of claims 1 to 3 in which the diaphragm is of flexible plastics material.

6. A friction-engaging device according to claim 4 or 5 in which the diaphragm incorporates cloth or fibrous reinforcement.

7. A friction-engaging device, according to any preceding claim in which the diaphragm is formed with a bead at the edge thereof, to seal on the opposite side of the edge of the rigid member from the rest of the diaphragm.

8. A friction-engaging device, according to any preceding claim, which is a brake.

9. A friction-engaging device, according to any of claims 1 to 7, which is a clutch.

10. A friction-engaging device, constructed and arranged to operate substantially as described herein and as shown in the accompanying drawings.

11. A fluid operable actuator for use in a friction-engaging device according to any preceding claim.