GB2125123A - Disc brake - Google Patents

Abstract

The brake comprises a pair of brake members (25, 54), a disc (D) which is received between one ends (31, 61) of the brake members (24, 54), the disc (D) being rotatable with a shaft to be braked, the brake members (24, 54) being pivotable about respective pivots (44, 74) and carrying at or adjacent said one ends (31, 61) respective brake pads (32, 62) movable into and out of engagement with the disc (D) in response to pivotal movement of said member (24 or 54), brake applying means (14) for effecting said pivotal movement, an adjustment element (46) having at opposite ends thereof oppositely screw-threaded parts and extending between the pivots (44, 74) and being operatively connected thereto, so that when said element (46) is rotated it adjusts the separation of the pivots (44, 74) and hence the separation of the pads (32, 62), so that as pad wear occurs, the wear can be accommodated by moving the pivots (44, 74) apart and hence the one ends of the brake members (24, 54) together, by rotation of the element (46) unidirectionally. The adjustment element may be a rod (46) received in threaded bores (45) in pillars providing the pivots (44, 74), which rod is rotatable manually or automatically by a mechanism (100) including toggle levers (101, 102), a link 106 and a clutch mechanism (107). The applying means may utilise a spring (18) released by an electromagnet (14) or by a hydraulic or pneumatic ram. <IMAGE>

Description

SPECIFICATION Disc brake This invention relates to a disc brake, that is a brake wherein movable brake members are applied to both sides of a rotating disc to frictionally engage the disc to effect braking, and are movable away from the disc to release the brake.

The brake members usually carry brake pads which are made of a material able to withstand the great heat produced as a result of relative movement between the pads and the disc, as the brake members are applied.

In an industrial disc brake, such as that used in overhead cranes, hoists, etc., it is usual for the brake to be urged on, that is with the brake pads in frictional engagement with the disc, by spring means and for an actuating mechanism to be provided to move the brake members apart against the force of the spring means to release the brake.

As the brake pads become worn, it will be appreciated that the force imposed by the spring means on the brake pads, at least when the braking members are applied, decreases because the springs have to act along a longer path.

It is desirable therefore to provide some adjustment means so that pad wear is accommodated.

Adjusters which adjust automatically are known, for example from U.K. specification 1,208,317 (Ferodo).

This specification discloses a disc brake having an adjuster wherein the brake members comprise levers each pivoted about spaced points, and a trapezoidal shaped block which may drop gravitationaily between the pivot points, to increase the distance between the pivot points when the brake is released, to accommodate any pad wear.

Such mechanisms have certain limitations.

More particularly, in 1,208,317, movement of the trapezoidal block relies on gravity which reduces the versatility of the brake because the adjuster mechanism cannot operate with the brake in any orientation. Furthermore, downward movement of the block can be prevented, if for example there is an accumulation of dirt in the brake, such as dust produced as the pads wear.

Accordingly, it is an object of the present invention to provide a new or improved disc brake which overcomes or reduces these problems.

According to one aspect of the invention we provide a disc brake comprising a pair of brake supporting or backing members which extend generally alongside one another, a disc, an outer portion of which is received between the one ends of the brake members, the disc being rotatable with a shaft to be braked, the brake members being pivotable about respective pivots and carrying at or adjacent said one ends respective brake pads movable into and out of engagement with the disc in response to pivotal movement of said member, brake applying means for effecting said pivotal movement, an adjustment element having at opposite ends thereof oppositely screwthreaded parts and extending between the pivots and being operatively connected thereto, so that when said element is rotated it adjusts the separation of the pivots and hence the separation of the pads.

Thus as pad wear occurs, the wear can be accommodated by moving the pivots apart and hence the one ends of the braking members together, by rotation of the element unidirectionally.

Furthermore, such an arrangement enables the brake to be used in any orientation as required, because no reliance is laid upon gravity to effect any adjustment of the brake.

The adjustment element may be rotated manually but preferably, it is rotated automatically by an operating device which operates as the brake members are pivoted. The operating device may comprise a friction clutch which engages to rotate the element only when the brake members pivot about an angle exceeding the maximum angle previously pivoted.

The clutch may comprise a first clutch member fixed to the adjustment element, and rotatable therewith, and a second clutch member fixed to an adjustment link, said first and second clutch members being engageable to rotate the adjustment element as the link is moved in one direction only.

The adjustment link may be connected to the brake members via a pair of toggle levers which are each pivotally secured to a respective brake member at positions between the pivots and the said one ends.

Thus as the brake members pivot, and the distance between the said pivot positions of the toggle levers changes, the link will be moved.

Thus automatic adjustment of the brake can be achieved.

The brake apply means may comprise an actuating mechanism which comprises a spring means which normally urges the members to bring the brake pads into frictional engagement with the disc, and a release means to move the brake members against the force of said spring means to release engagement between the brake pads and the disc.

In a preferred embodiment, the brake members are mounted for pivotal movement about further pivotal axes, which further axes are movable towards and away from one another by the actuating mechanism. One of the brake members may be pivotally mounted with respect to a base framework, whilst the other brake member is pivotally mounted with respect to an actuating member of the actuating mechanism, which mechanism may comprise an electro-magnetic device, although any other electrical, mechanical or electro-mechanical actuating mechanism could alternatively be employed.

These pivotal axes may coincide with the pivotal axes of the toggle levers of the adjustment mechanism. The electro-magnet may comprise a housing which is fixed to the base framework, and an armature comprising said actuating member, the spring means acting between the armature and the housing to normally urge the actuating member in a direction to move the brake pads towards one another, and the electro-magnet when energised, moving the armature against the force of said spring means to release the brake.

The brake members may be constrained at said one ends against any movement other than said pivotal movement, and the brake pads may each be mounted on a backing plate which is pivotally mounted to the brake members.

Thus, as the brake pads are moved towards one another, a front surface of each may be maintained parallel with the disc, and any force imposed on the brake pads which would tend to cause relative movement between the brake members and the base framework, is prevented.

According to a second aspect of the invention we provide a disc brake comprising a disc, pads disposed at opposite sides of the disc, brake applying means for moving the pads relatively to each other into braking positions in frictional engagement with the disc, or released positions permitting the disc to rotate relatively freely between the pads, and an adjusting mechanism for adjusting the separation between the pads in their released positions and including supporting or backing members mounted for relative pivotal movement with respect to each other in response to operation of the brake applying means to move the pads between the released and braking positions and further including screw and nut means determining the separation of the brake applying members and hence of the pads in the released positions, and operable to vary reduce the separation of the pads whenever the travel of the pads in moving between then released and braking positions exceeds a predetermined value.

The invention will now be described with the aid of the accompanying drawings in which: Figure 1 is a plan view of a disc brake in accordance with the invention; and Figure 2 is a side view of the disc brake of Figure 1.

Referring to the drawings, there is shown an industrial disc brake 10 of the type wherein the brake is normally urged on, and is released by an actuating mechanism although the invention is applicable to disc brakes which are normally off, and urged on.

The brake 10 comprises a framework 11 provided with holes 12 to enable the framework 11 to be fixed to a rigid base with bolts or other fasteners (not shown).

Secured to the framework 11 is an actuating mechanism comprising an electro-magnet 14 having a housing 13 secured to the framework 11 via packing 1 5.

The electro magnet 14 further comprises the usual coils which may be energised to release the brake 10 as hereinafter described, by moving an armature thereof comprising an armature rod 17, against a considerable force of a stack of disc springs 1 8 which springs 1 8 act between an adjustment collar 1 6 of the rod 17, and the inside surface of a front plate 1 9 of the housing 13.

A shim seal 20 is located between the housing 1 3 and the front plate 1 9 so that the electromagnet 14 is sealed against the ingress of dirt, etc.

The front plate 1 9 is secured to the remainder of the housing 13 by a nut 22 which is received on the end of the armature rod 1 7 which extends from the front plate 1 9.

Secured to the front plate 1 9 by welding for example, are a pair of mountings 23 comprising trunnions between which a first brake member 24 is received.

The brake member 24 comprises a caliper made up of two plates 25 secured together by a number of nut and bolt connections 27, with spacers 28 maintaining the plates 25 a fixed distance apart although other arrangements are no doubt possible. A pivot pin 29 connects the caliper 24 to the mountings 23 for pivotal movement about a substantially vertical pivotal axis indicated at X (Figure 2).

The pivot pin 29 is retained in position by split pins 30.

At one end 31 of caliper 24 a brake pad 32 and backing plate 33 assembly is connected.

The backing plate 33 comprises a mounting 34 for the pad 32 from which extend two pairs of bosses, one pair of bosses 36 defining a slot in which the upper plate 25 of caliper 24 is received, and the other pair of bosses 36 a slot in which the lower plate 25 of caliper 24 is received. A pivot pin 40 passes through the bosses 36 and the plates 25 to connect the pad 32 and backing plate 33 assembly to the caliper 24 for relative pivotal movement about a further vertical axis indicated at Y.

Thus as the caliper 24 pivots about pivot 29, the front surface 41 of pad 32 can be maintained parallel to a centre plane P.

At the opposite end 43 of the caliper 24, the plates 25 are connected for pivotal movement about a pivot comprising a pillar 44. Between the plates 25, the pillar 44 is provided with a threaded bore 45 in which an end of adjustment element comprising a rod 46, is threadedly received.

A second caliper 54 is mounted alongside the caliper 24. The caliper 54 also comprises two plates 55 secured together in spaced relation by a number of nut and bolt connections 57, and spacers 58. Between the plates 55 a mounting 53 is received, which provides a trunnion for a pivot pin 59 so that the caliper 54 can rotate about a further vertical axis indicated at X', the pin 59 being retained by split pins 60, shown in Figure 1 only.

The caliper 54 carries at one end 61, adjacent end 31 of caliper 34, a brake pad 62 and backing plate 63 assembly similar but opposite to that of caliper 24, so that the assembly can rotate about a vertical axis Y' so that as the caliper 54 pivots about pin 59, the front surface 71 of pad 62 can be maintained parallel to plane P.

The mounting plate 53 of caliper 54 is secured by two long bolts 80, 81 which pass through guides 82, 83 respectively, secured to the front plate 1 9 of electro-magnet housing 13, to the armature rod 1 7. The caliper 54 has at one end 73 adjacent end 43 of caliper 24, a pillar 74 similar to pillar 44, the other end of the rod 46 being threaded and engaged in a threaded bore 75 between the plates 55.

The screw thread which engages aperture 75 is an opposite screw thread to that which is received in aperture 45 so that rotation of the rod 46 unidirectionally, causes the ends 43, 73 of calipers 24, 54 to be drawn together or moved apart depending on the direction of rotation. In the example shown, the threads are such that anticlockwise rotation of the rod 46 causes the ends 43, 73 to be moved apart.

In use, a disc D which is fast with a shaft which it is desired to brake, which disc D is indicated in dotted lines in Figure 1, is located between the pads 32, 62.

When the coils of the electro-magnet 14 are not energised, because the caliper 24 is pivotable about pivot pin 29 which is fast with the housing 13, and caliper 54 is pivotable about pivot pin 59 which is connected to the armature 1 6 via the bolts 80, 81, and the disc springs 18 act between the housing 13 and armature 17, the pivot pins 29, 59 are urged towards one another. This movement is permitted because the ends 43, 73 of the brake members 24, 54 are not constrained either with the housing or with the armature, in any way, but merely held together by rod 46.

Because the distance between ends 43, 73 of calipers 24, 54 is constrained by the rod 46, the pads 32, 52 are urged towards one another into engagement with the disc D. Thus the brake is normally applied, that is in a braking condition.

When it is desired to release the brake, the coils of the electro-magnet 14 are energised so that the armature rod 1 7 moves in the direction of arrow R and hence the pivot pin 59 which moves with armature 17, moves away from pin 29.

Again, because the distance between the ends 43, 73 of calipers 24, 54 is constrained, this has the effect of moving the pads 32, 62 apart to release the brake.

It will be appreciated that when the coils are de-energised again, that the pads 32, 62 will move again into frictional engagement with the disc D under the influence of springs 1 8. As this re-engagement occurs, a considerable vertical force (vertical in Figure 2) will be imposed on the pads 32, 62 and hence on calipers 24, 54 and brake 10 as a whole.

To restrain any such vertical movement, the lower ends 83 of the backing plates 33, 63 are each secured to a mounting 84 fixed to the framework 11. The mountings 84 each have a horizontally extending pin 85 and the backing plates 33, 63 can slide longitudinally of these pins, but not move transversely.

Thus the mountings 84 do not hinder pivotal movement of the calipers 24, 54 and the backing plates 33, 63 can pivot about their respective axes Y, Y' and travel longitudinally of the pins 85.

It will be appreciated that the pads 32, 62 gradually wear and as this occurs, the force imposed by the stack of springs 1 8 will reduce as the distance over which the springs 1 8 will need to act, will increase.

To accommodate pad wear, an adjustment mechanism 100 is provided which includes the adjustment rod 46.

Along with calipers 24, 54, toggle levers 101, 102 are pivoted about pivot pins 29, 59 respectively, the levers 101, 102, being connected together by a further pivot 104.

As the calipers 24, 54 pivot, the pivot 104 will move along a path co-incidental with or parallel to plane P because the distance between pivots 29, 59 varies.

The pivot 104 is mounted on a bifurcated mounting element 105 between the forks of which, an adjustment link 106 is pivoted. The other end of link 106 is connected to a one-way friction clutch mechanism 107 mounted on rod 46.

The clutch mechanism 107 comprises a first clutch member 108 comprising a pair of plates mounted for rotation on rod 46, and having mounting lugs between which the link 106 is received for pivotal movement. Thus as the link 106 moves, the first clutch member 108 is rotated about the axis of rod 106.

The clutch mechanism 107 also comprises a second clutch member 109 fixed to the shaft 46, between the plates of the first clutch member 1 08 with a friction plate between, which friction plate is adapted to permit relative movement between the first 108 and second 109 clutch members as the link 107 moves to the right shown in the Figures, but couple the members 108,109 together as the link 107 moves to the left, although the friction plate includes a slip device so that the members 108, 109 are only coupled together once the link 106 moves further to the left than previously. This further movement occurs as a result of the calipers 24, 54 pivoting about the pillars 44, 74 a greater angle than previously, as a result of pad wear.

Thus each time the brake is released and hence the link 106 moves to the left, if the link moves further than previously as a result of pad wear, the rod 46 will be rotated anti-clockwise an amount depending on the amount of pad wear, to move the ends 43, 73 of the calipers 24, 74 further apart. In this manner wear of the pads 32, 52 is automatically accommodated.

Use of such a brake includes in an overhead crane, or a hoist when a pair of such brakes may be used to operate simultaneously to brake the disc either side of the shaft on which the disc D is mounted.

However, by a suitable modification, such a brake could be put to many other uses, for example in a vehicle.

For example if desired, the actuating mechanism need not comprise an electro-magnet 14 and spring 1 8 arrangement as described, but could comprise an urging means such as a spring and a release means such as a hydraulic or pneumatic ram.

The brake members 24, 74 need not be pivoted about pivots 29, 44 and 59, 74 as described, with the ends 43, 73 free from the framework 11, but they could each be pivoted about a single pivot for example between which pivots the rod 46 extends.

Although the rod 46 has been described as being rotatable by an operating mechanism, if required the rod 46 could be manually or otherwise rotatable.

Many other modifications are no doubt possible.

Claims (17)

1. A disc brake comprising a pair of brake supporting or backing members which extend generally alongside one another, a disc, an outer portion of which is received between the one ends of the brake members, the disc being rotatable with a shaft to be braked, the brake members being pivotable about respective pivots and carrying at or adjacent said one ends respective brake pads movable into and out of engagement with the disc in response to pivotal movement of said member, brake applying means for effecting said pivotal movement, an adjustment element having at opposite ends thereof oppositely screwthreaded parts and extending between the pivots and being operatively connected thereto, so that when said element is rotated it adjusts the separation of the pivots and hence the separation of the pads.

2. A brake according to Claim 1 wherein the adjustment element is rotated manually.

3. A brake according to Claim 1 wherein the adjustment element is rotated automatically by an operating device which operates as the brake members are pivoted.

4. A brake according to Claim 3 wherein the operating device comprises a friction clutch which engages to rotate the element only when the brake members pivot about an angle exceeding the maximum angle previously pivoted.

5. A brake according to Claim 4 wherein the clutch comprises a first clutch member fixed to the adjustment element, and rotatable therewith, and a second clutch member fixed to an adjustment link, said first and second clutch members being engageable to rotate the adjustment element as the link is moved in one direction only.

6. A brake according to Claim 5 wherein the adjustment link is connected to the brake members via a pair of toggle levers which are each pivotally secured to a respective brake member at positions between the pivots and the said one ends.

7. A brake according to any one of the preceding claims wherein the brake apply means comprise an actuating mechanism which comprises a spring means which normally urge the members to bring the brake pads into frictional engagement with the disc, and a release means to move the brake members against the force of said spring means to release engagement between the brake pads and the disc.

8. A brake according to Claim 7 wherein the brake members are mounted for pivotal movement about further pivotal axes, which further axes are movable towards and away from one another by the actuating mechanism.

9. A brake according to Claim 8 wherein one of the brake members is pivotally mounted with respect to a base framework, whilst the other brake member is pivotally mounted with respect to an actuating member of the actuating mechanism.

10. A brake according to Claim 8 or Claim 9 where appendant to Claim 6 wherein the further pivotal axes coincide with the pivotal axes of the toggle levers of the adjustment mechanism.

11. A brake according to any one of Claims 7 to 10 wherein the actuating mechanism comprises an electro-magnetic device.

12. A brake according to Claim 11 where appendant to claim 9 wherein the electro-magnet comprises a housing which is fixed to the base framework, and an armature comprising said actuating member, the spring means acting between the armature and the housing to normally urge the actuating member in a direction to move the brake pads towards one another, and the electro-magnet when energised, moving the armature against the force of said spring means to release the brake.

13. A brake according to any one of Claims 8 to 12 where appendant to Claim 8 wherein the brake members are constrained at said one ends against any movement other than said pivotal movement.

14. A brake according to any one of the preceding claims wherein the brake pads are each mounted on a backing plate which is pivotally mounted to the brake members.

1 5. A disc brake comprising a disc, pads disposed at opposite sides of the disc, brake applying means for moving the pads relatively to each other into braking positions in frictional engagement with the disc, or released positions permitting the disc to rotate relatively freely between the pads, and an adjusting mechanism for adjusting the separation between the pads in their released positions and including supporting or backing members mounted for relative pivotal movement with respect of each other in response to operation of the brake applying means to move the pads between the released and braking positions and further including screw and nut means determining the separation of the brake applying members and hence of the pads in the released positions, and operable to reduce the separation of the pads whenever the travel of the pads in moving between then released and braking positions exceeds a predetermined value.

16. A disc brake substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

17. Any novel feature or combination of features described herein and/or shown in the accompanying drawings.