GB2317209A

GB2317209A - Brake mechanism

Info

Publication number: GB2317209A
Application number: GB9718490A
Authority: GB
Inventors: David Michael Abbott
Original assignee: Twil Handling & Display Ltd
Current assignee: Twil Handling & Display Ltd
Priority date: 1996-09-06
Filing date: 1997-09-02
Publication date: 1998-03-18
Anticipated expiration: 2017-09-02
Also published as: GB9618632D0; GB2317209B; GB9718490D0

Abstract

A brake mechanism for a wheeled unit comprises a brake shoe 15 pivotably mounted on a brake rod 16 or lever 31 and movable towards and away from tyre 11. The brake shoe 15 has projections 17, 18 which effect twin contacts with the tyre and which have a width greater than the width of the tyre. Stabilising means 28 or 33, 34 is provided to ensure that in the "brake-off" position the brake shoe 15 cannot pivot and cause either projection 17 or 18 to contact the tyre 11.

Description

BRAKE MECHANISM This invention relates to brake mechanisms for wheeled units, such as trollies, rollpallets and the like, and particularly but not exclusively to parking brakes for such units.

Parking brakes are required to restrain units during loading or unloading or whilst the unit is parked, i.e., within a vehicle. Previously braking has been achieved by fitting foot operated brakes to swivel castors or by incorporating a mechanism into the structure of the wheeled unit to provide brake operation by means of a hand brake.

Frequent adjustment of these systems is necessary to allow for tyre wear or brake pad wear which is often difficult and/or costly to effect. In many instances the responsibility is on the operator of the wheeled unit to identify that the brakes are ineffective and notify maintenance engineers, but in practice, wheeled units continue to be used with ineffective brakes increasing the risk of serious accidents.

Existing braking mechanisms operate on the principle of applying a brake shoe, which may have a brake pad, against a wheel. The wheels, in order to be durable, have been made of relatively hard materials, such as nylon or polyurethane, and the forces on the brake shoe need to be high to ensure effective braking. Thus, mechanisms to apply these forces are therefore complex and resultant wear either in the mechanism or in the tyre or brake pad can render the brake ineffective. In fact quite a low degree of wear will result in considerable loss of brake power.

Taking advantage of higher performance resilient rubber tyres which are softer but tougher and very durable, EP-A-O 509 786 discloses a brake mechanism in which one end of a brake rod directly engages the periphery of a wheel under spring-loading applied through a brake handle against a counter-spring for withdrawing the brake rod when the handle is moved to release position.

However, while this mechanism works well as a parking brake, when used repeatedly as a dynamic brake, i.e. the brake handle being moved to braking position whilst the wheeled unit is in motion, the brake rod end eventually wears a groove in the tyre.

The object of the present invention is to provide a brake mechanism of improved effectiveness in either direction of motion, being effective as a dynamic brake without causing undue wear on the tyre.

According to the present invention, a brake mechanism for a wheeled unit comprises a brake shoe pivotable on a brake rod or lever for movement towards and away from the tyre of the wheel, the brake shoe being provided with fore and aft projections towards the wheel so as to effect twin contacts with the tyre of the wheel in either direction of rotation of the wheel when the brake shoe is moved into contact with the wheel.

Stabilising means is preferably provided to ensure that in the "brake-off' position of the brake shoe it cannot pivot and cause either projection to contact the tyre of the wheel.

Preferably both the fore and aft projections on the brake shoe are adapted to make contact with the wheel at positions substantially along lines from the brake rod end that are tangential with the wheel. Thus, when the brake is applied and the wheel turning in either direction there will be two contacts on the wheel with neither of them providing a lifting force directly against the force on the brake rod.

The projections on the brake shoe preferably have a width commensurate with the width of the tyre surface into engagement with which it is moved, so that each projection makes line contact with the tyre (as compared with substantially point contact by the brake rod end in the mechanism of EP-A-O 509 786) so that wear is distributed across the whole or a major part of the width of the tyre surface, but the projections may be provided with blunt serrations for engagement with the tyre.

The brake shoe may have a ball-and-socket connection with a longitudinally movable brake rod projecting through a hole in a mounting for the wheel, so that upon contacting the tyre the brake shoe can assume a balanced position with regard to distribution of contact between the projections and across the width of the tyre surface. Thus a socket on the brake shoe can be engaged with a ball on the end of the brake rod. The upper end of a longitudinally movable brake rod may be connected, through a coil compression spring providing wear-compensated loading, to any suitable operating handle having braking and release positions e.g., such as is described in EP-A-0509786.

Alternatively, the pivotal connection of the brake shoe may be provided at one end of a simple lever the other end of which is pivotally connected to the lower end of a longitudinally movable brake rod, with an intermediate fulcrum pivot of the lever fixed in the wheel mounting.

The brake rod may be tubular and/or provided with a tubular guide or guides.

Again, the brake shoe may be mounted on a lever adapted to be moved by a brake cable from an operating handle or lever remotely mounted on part of the unit, or it may be adapted for electric or radio control, e.g. by a solenoid controlled by a switch mounted on the unit.

Two embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a side elevation of a wheel and mounting incorporating an embodiment of the invention; Figure 2 is an elevation from the left hand side of Figure 1; Figure 3 is an elevation from the right hand side of Figure 1; Figure 4 is an enlarged fragmentary section taken from the line IV-IV of Figure 2, showing the "brake-off' position of the brake shoe; Figure 5 corresponds to Figure 4 but shows the "brake-on" position of the brake shoe; and Figures 6 and 7 correspond to Figures 4 and 5 on a slightly smaller scale and showing another embodiment of the invention.

In Figures 1 to 5, a wheel 10 having a high performance resilient rubber tyre 11 is carried by an axle 12 in a pressed steel mounting 1 3 having slots 14 to enable it to be bolted to a unit, such as a trolley, rollpallet or the like (not shown).

A brake shoe 15 is pivotable on a longitudinally movable brake rod 16 for movement towards and away from the tyre 11 of the wheel 10, and the brake shoe is provided with fore and aft projections 17, 18 respectively towards the wheel so as to effect twin contacts with the tyre of the wheel (as shown in Figure 5) in either direction of rotation of the wheel when the brake shoe is moved into contact with the wheel by means of downward movement of the brake rod, which is connected to suitable operating mechanism, not shown but which may be, for example, as described in EP-A-0 509 786. The brake rod 16 projects through a hole 19 in the mounting 13 and may be tubular and/or provided with a tubular guide or guides (not shown) in the unit to which the wheel mounting is attached.

The brake shoe 1 5 has a ball-and-socket connection 20, 21 with the brake rod 16, the ball 20 being integrally formed on (or attached) to the lower end of the brake rod and the socket 21 being in a component 22 formed of an engineering plastics material (such as ST801 SUPERTUF) having a projection 23 snap-fitting in a hole 24 in the pressed steel brake shoe, which has another smaller hole 25 for a locating peg 26 on the component 22. The brake shoe 15 is loosely guided between the cheeks 27 of the mounting 13, and in the "brake-off' position ofthe brake shoe (see Figure 4) the upper surface 28 of the component 22 abuts the bridging part 29 of the mounting 13 to act as stabilising means ensuring that the brake shoe cannot pivot and cause either projection 17, 18 to contact the tyre 11 of the wheel 10.

Both the fore and aft projections 17, 18 are adapted to make contact with the wheel 10 at positions along lines from the brake rod end 20 tangential with the wheel, so that when the brake is applied and the wheel turning in either direction there will be two contacts with the wheel with neither of them providing a lifting force directly against the force on the brake rod 16.

As can be seen from Figures 2 and 3, the projections 17, 18 have a width slightly greater than the width ofthe tyre surface, so that each projection makes live contact with the tyre (even allowing for the slight curvature of its profile), so that wear is distributed across the whole of the width of the tyre surface.

In Figures 6 and 7 like parts to those in Figures 1 to 5 have like reference numerals, but it is assumed that it is not possible for the brake rod 16 to project through a hole in the bridging portion 29 of the mounting 13, so the brake shoe 15 is pivoted on one end 30 of a simple lever 31 the other end 32 of which is pivotally connected to the lower end of a brake rod 1 6X guided by means not shown externally of the mounting, with an intermediate fulcrum pivot 33 of the lever being formed by a pin through and between the cheeks 27 of the mounting 13.

A pair of stabilising plates 34, 35 are welded to the brake shoe 15 to abut the bridging part 29 ofthe mounting 13 when the brake shoe is in the "brake-off' position (see Figure 6) to ensure that the brake shoe cannot pivot and cause either projection 17, 1 8 to contact the tyre 11 of the wheel, the plate 34 being provided with a notch 36 to clear the lever 31.

The brake rod 16X may be connected to suitable operating mechanism, again not shown but which may be, for example, similar to that described in EP-A-0 509 786.

Alternatively, the end 30 of the lever 31 may be connected by a brake cable (e.g. a Bowden cable) to an operating handle or lever remotely mounted on part of the unit to which the wheel mounting 13 is secured, or it may be adapted for electric or radio control, e.g. by a solenoid attached to the mounting 1 3 and controlled by a switch remotely mounted on part of the wheeled unlit.

Claims

1. A brake mechanism for a wheeled unit comprising a brake shoe pivotable on a brake rod or lever for movement towards and away from the tyre of the wheel, the brake shoe being provided with fore and aft projections towards the wheel so as to effect twin contacts with the tyre of the wheel in either direction of rotation of the wheel when the brake shoe is moved into contact with the wheel.

2. A brake mechanism as in Claim 1, wherein stabilising means is provided to ensure that in the "brake-off' position of the brake shoe it cannot pivot and cause either projection to contact the tyre of the wheel.

3. A brake mechanism as in Claim 1 or Claim 2, wherein both the fore and aft projections on the brake shoe are adapted to make contact with the wheel at positions substantially along lines from the brake rod end that are tangential with the wheel.

4. A brake mechanism as in any one of Claims 1 to 3 wherein the projections on the brake shoe have a width commensurate with the width of the tyre surface into engagement with which it is moved.

r. A brake mechanism as in any one of Claims 1 to 4, wherein the brake shoe has a ball-and-socket connection with a longitudinally movable brake rod projecting through a hole in a mounting for the wheel.

6. A brake mechanism as in Claim 5, wherein a socket on the brake shoe is engaged with a ball on the end ofthe brake rod.

7. A brake mechanism as in Claim 5 or Claim 6, wherein the upper end of a longitudinally movable brake rod is connected, through a coil compression spring providing wear-compensated loading, to any suitable operating handle having braking and release positions.

8. A brake mechanism as in any one of Claims 1 to 4, wherein the pivotal connection of the brake shoe is provided at one end of a simple lever the other end of which is pivotally connected to the lower end of a longitudinally movable brake rod, with an intermediate fulcrum pivot of the lever fixed in the wheel mounting.

9. A brake mechanism as in Claim 8 with the alternative in which the brake shoe is mounted on a lever adapted to be moved by a brake cable from an operating handle or lever remotely mounted on part of the unit.

10. A brake mechanism for a wheeled unit substantially as hereinbefore described with reference to Figures 6 and 7 othe accompanying drawings.

10. A brake mechanism for a wheeled unit substantially as hereinbefore described with reference to Figures 1 to 5 of the accompanying drawings.

11. A brake mechanism for a wheeled unit substantially as hereinbefore described with reference to Figures 6 and 7 of the accompanying drawings.

Amendments to the claims have been filed as follows

1. A brake mechanism for a wheeled unit comprising a brake shoe pivotable on a brake rod or lever for movement towards and away from the tyre of the wheel, the brake shoe being provided with fore and aft projections towards the wheel so as to effect twin contacts with the tyre of the wheel in either direction of rotation of the wheel when the brake shoe is moved into contact with the wheel, and wherein both the fore and aft projections on the brake shoe are adapted to make contact with the wheel at positions substantially along lines from the brake rod end that are tangential with the wheel.

2. A brake mechanism as in Claim 1, wherein stabilising means is provided to ensure that in the 'brake-off' position of the brake shoe it cannot pivot and cause either projection to contact the tyre of the wheel.

3. A brake mechanism as in Claims 1 or Claim 2, wherein the projections on the brake shoe have a width commensurate with the width of the tyre surface into engagement with which it is moved.

4. A brake mechanism as in any one of Claims 1 to 3, wherein the brake shoe has a ball-and-socket connection with a longitudinally movable brake rod projecting through a hole in a mounting for the wheel.

5. A brake mechanism as in Claim 4, wherein a socket on the brake shoe is engaged with a ball on the end of the brake rod.

6. A brake mechanism as in Claim 4 or Claim 5, wherein the upper end of a longitudinally movable brake rod is connected. through a coil compression spring providing wear-compensated loading, to any suitable operating handle having braking and release positions.

7. A brake mechanisni as in any one of Claims i to 3, wherein the pivotal connection of the brake shoe is provided at one end of a simple lever the other end of which is pivotally connected to the lower end of a longitudinally movable brake rod, with an intermediate fulcrum pivot of the lever fixed in the wheel mounting.

8. A brake mechanism as in Claim 7 with the alternative in which the brake shoe is mounted on a lever adapted to be moved by a brake cable from an operating handle or lever remotely mounted on part of the unit.

9. A brake mechanism for a wheeled unit substantially as hereinbefore described with reference to Figures 1 to 5 of the accompanying drawings.