GB2108605A

GB2108605A - Tire pressure-independent brake device for wheel chairs

Info

Publication number: GB2108605A
Application number: GB8228964A
Authority: GB
Inventors: Dr Uwe Brudermann; Gunter Krehl; Karl-Heinz Kunze
Original assignee: Ortopedia GmbH
Current assignee: Ortopedia GmbH
Priority date: 1981-10-26
Filing date: 1982-10-11
Publication date: 1983-05-18
Also published as: NL8203864A; FR2515123A1; SE8205597L; DE3142362A1; SE8205597D0

Abstract

The device has a brake shoe (9) actuable through an operating lever (1) and adapted to be brought into operative contact with the tread of a tire (2) in such a manner that the brake device may be operated both as a wheel (travel) brake and a locking (parking) brake independently of the tire inflation pressure. The operating lever is connected to the brake shoe (9) through spring means (15) having characteristics, whereby if the tire pressure is reduced the spring means expands to maintain contact between the shoe (9) and tire (2)-the contact pressure is limited by virtue of the spring means. As shown, lever (1) has cam discs (28) acting via rollers (12) to move a cylinder (6) and hence a cylinder (7) -the spring means (15) comprising a stack of dish or cup springs (or coiled or helical springs) are provided between the ends of cylinders (6, 7). When the device acts as a locking brake, rollers (12) are seated in cutout (25) in cam discs (28). <IMAGE>

Description

SPECIFICATION A tire pressure-independent brake device for wheel-chairs The present invention relates to a brake device, especially for wheel-chairs, wherein a brake shoe which may be actuated through an operating lever is adapted to be brought into operative contact with the tread of a tire, and in which the operating lever is to this effect particularly adapted to be brought (moved) from an initial position corresponding to a non-braking state to a locking position in which the brake shoe acts as a locking brake, with a gradually increasing braking action, and in which the brake shoe is adapted to be returned to the non-braking state by a return spring.

Conventional brake devices for wheel-chairs include an operating mechanism by means of which a brake shoe or a brake rubber block is pressed against the tread of a tire in radial direction. This operating mechanism has a dead center position in its terminal position in which the brake shoe is pressed onto the tire tread with maximum pressure, and when this dead center is overcome the brake device, normally acting as a wheel brake (for travel), operates as a locking brake. The brake device is operated as a wheel brake for retarding and steering the wheel-chair, while the locking brake is used to stop the wheelchair, in its stationary state, to prevent it from rolling on sloping ground, for example.

Now, when in this conventional brake device air escapes from the tire against which the brake shoe has been pressed, then the pressing forces of the brake shoe are simultaneously reduced to zero or to a value close to zero; this means that the braking action is lost. Under certain circumstances, this represents a substantial impairment of safety, such that wheel-chairs equipped with brake devices of this type do not necessarily guarantee safe operation. For this reason, brake devices operating independently of the tire inflation pressure should be adopted for wheel-chairs.

As to tire pressure-independent brake devices, there may be reflected upon, for example, drumtype brakes, rim-type brakes, cone (taper-sleeve) brakes, etc., all of which may be used as wheel (travel) and locking brakes. If necessary, other types of brake devices may be also adopted, which can be used only as locking brakes, however.

Disadvantageous with drum-type brakes, rimtype brakes, cone brakes, etc., is in the first line the weight and the complex structure of these brake devices; further, brake devices of this kind are not suitable, or with difficulties only, for later installation in a wheel-chair; finally, such complex brake devices also significantly increase the dimensions of the wheel-chair. On the other hand, if brake devices are used which act as locking brakes only, then a separate wheel (travel) brake must be provided for the wheel-chair, which measure again involves high expenses or impairs the operation of the brake.

Accordingly, it is the object of the present invention to improve a tire pressure-independent brake device of the type as outlined at the beginning, in such a way that this brake device may be used both as wheel (travel) brake and locking (parking) brake without any particular expenditure.

In a tire pressure-independent brake device according to the preamble of claim 1, this object is solved in that said operating lever is connected to said brake shoe through an operating mechanism and through spring means having degressive characteristics, so as to effect a braking operation independent of the tire inflation pressure.

If in a wheel-chair equipped with the brake device according to the invention the tire pressure is reduced, the spring means expands to such extent that contact between the brake shoe and the tire tread is maintained and the tire contact pressure of the brake shoe applied to the tire tread is not or only slightly reduced in correspondence with the degressive characteristics of the spring means. Also and as a consequence of the degressive characteristics of the spring means, the increase of the pressure applied to the tire tread upon reaching the bias (pretension) force of the spring means is only low, such that the tire in its inflated state is not compressed down to its rim when the operating lever is turned completely to its locking position, and, moreover, the operating force need not, or only slightly, be increased.

Thus, it is achieved with the brake device according to the invention that the tire in its inflated state is not compressed down to its rim, i.e. the pressure applied to the tire by the operating lever through the brake shoe is not increased unnecessarily. However, the braking force remains at a satisfactory level even with tires of lower or lost inflation air pressure, such that a sufficient braking action is ensured in the locking position of the operating lever, and the brake device may thus be used both as wheel (travel) brake and locking brake.

The brake device according to the present invention provides for sufficient braking action throughout the full normal and permissible range of inflation air pressures of the tire, namely between a value of zero and a maximum permissible tire pressure as multiplied by a safety factor; this being due to the use of the spring means having degressive characteristics. The extra power to be spent for actuating the operating lever is extremely small in the inflated state of the tire, while the braking effect remains sufficiently constant in the case of a pressure loss in the tire(s), thereby fully complying with the safety requirements.

A further embodiment of the invention is characterized in that said operating lever has its end remote from a handle provided with a cam disc along which rollers are adapted to be guided and moved substantially normal to the tire tread, that said rollers are operatively connected to a first cylinder, that a second cylinder is guided within said first cylinder, and that said spring means is mounted between the one end of said second cylinder connected to said brake shoe, and the end of said first cylinder remote from said one end, in which said spring means comprises preferably a pretensioned spring column formed of a dish or cup spring stack. Instead of the dish or cup springs, any other types of springs, such as, for instance, coiled springs or helical springs, may be used.Still further, the operating lever is advantageously operatively associated with the rollers through a cam disc. Finally, a cutout, especially of a circular sector shape, may be provided at the end of the link guide for receiving the rollers in the locking position.

On its end remote from the handle, the operating lever includes cam discs which are arranged symmetrically on opposite sides of the peripheral surface of the two cylinders and formed such that actuation of the operating lever results in forces extending essentially only in axial direction to the cylinders, whereby the operating force or power may be reduced as far as possible.

The sector-shaped cutout at the end of the cam disc defines the locking position such that the brake device may be used both as wheel (travel) brake for assisting the steering operation and as a locking (parking) brake.

If pressure loss in the tire occurs in a braking operation in the course of which the spring means is compressed by actuation of the operating lever, automatic "readjustment" of the braking effect takes place in either of the two possible operating states, without any variation of the position of the operating lever, namely to an extent to which the spring stack had been compressed. In the position defining the locking brake, this extent is sufficient to ensure a satisfactory function even when the tire inflation pressure is completely lost.

If, additionally, the pressing force of the brake shoe applied to the tread of the tire is just equal to the bias (initial tension) of the spring means, this force is sufficient to safely stop the wheel-chair on slopes.

Optionally, the bell crank or toggle principle may be applied for the operating mechanism.

Below, the present invention is explained in detail by referring to the drawings, wherein Figure 1 is a side elevational view of the brake device according to the present invention, partially shown in section; and Figure 2 is a view of the brake device of Figure 1, as seen in the direction of an arrow A.

A bracket 4 for the brake device is clamped to a wheel-chair frame 3, preferably by means of a quick-acting clamping device 16, 26, 21. Thus, the quick-acting clamping device acts to connect the brake device to the wheel-chair frame 3 against rotation, since this frame is provided with a U-shaped recess 27.

Preferably, the connection between the bracket 4 and the brake device is effected through a positive-engagement notched (ratchet) plate coupling 19 in order to permit the action of the brake shoe 9 to be radially directed towards the tire even under the most varied states of operation.

The brake device as such comprises an operating lever 1 which has its upper end (as shown in the Figures) provided with a handle 22, and its lower end provided with a symmetrical fork the ends of which are formed as cam discs or plates 28. The cam discs each include a circular sector-shaped cutout 25. The operating lever 1 is mounted for rotation on a shaft 5 in the vicinity of the fork and locked by locking washers 10 so as to be adapted to be rotated by 860 to a position illustrated in broken lines in Figure 1. The shaft 5 in turn is mounted (for rotation) in a beam 29 connected to a tube 8 which latter, in turn, is clamped to the bracket 4 through a connecting element 30 and a (further) connecting element 19 by means of a threaded bolt 1 7 and a washer 1 8.

The cam disc 28 engages rollers 12 which are movable within a slot 31 of tube 8 when the operating lever 1 is rotated (to the right as seen in Figure 1). These rollers 12 through the pins 20 are connected to a cylinder 6 being slidably guided within the tube 8, which cylinder in turn is secured against slidingly coming out of a cylinder 7 by means of a bolt and a nut 1 The cylinder 7 is slidably guided in the axial cylinder 6, and a spring column 1 5 comprising a plurality of dish or cup springs is provided between the right hand end of cylinder 6, as seen in Figure 1, and the left hand end of cylinder 7, as seen in Figure 1.The cylinder 7 is connected to a brake shoe 9 adapted to be brought into abutment against the tread of a tire 2 mounted on a rim 32, with the rim being connected, through a mounting angle 33, to a handwheel 34 by means of which the wheel-chair may be moved manually. A return spring 1 3 is tensioned between a portion 29 and a base 14 of the brake shoe 9.

When the operating lever 1 is rotatea te the position shown in broken lines in Figure 1, the rollers 12 are in their left hand position, as shown in Figure 1, to be seated in the cutout 25 of the cam disc 28. This results in longitudinal movement of the cylinders 6 and 7 to the left in Figure 1, whereby the brake shoe 9 is pressed onto the tread of the tire 2; in this state, the return spring 13 is stretched. Upon further actuation of the operating lever 1, the tire 2 becomes deformed; besides, upon reaching the bias force of the spring stack 15, the latter is fully compressed.

With the operating lever 1 fully rotated to the right, rollers 12 come to be seated in the cutout 25, such that the brake device acts as a locking (parking) brake and the return spring 13 is rendered ineffective.

Namely, the dead center lies on a lug 36 of the cam disc 28 when the center of the roller 12,,the lug 36 and the center of the shaft 5 are disposed on a straight line. When the operating lever 1 is thereafter rotated slightly in forward direction, then the roller 12 engages into the cutout 25 which may have, for example, the shape of a sector of a circle.

Claims

CLAIMS 1. A brake device, especially for wheel-chairs, wherein a brake shoe (9) which may be actuated through an operating lever (1) is adapted to be brought into operative contact with the tread of a tire (2), characterized in that said operating lever (1) is connected to said brake shoe (9) through an operating mechanism and through spring means (1 5) having degressive characteristics, so as to effect a braking operation independent of the tire inflation pressure. 2. The brake device according to claim 1, characterized in that said operating lever (1) is adapted to be moved from an initial position corresponding to a non-braking state to a locking position in which said brake shoe (9) acts as a locking (parking) brake, and that said brake shoe (9) is adapted to be returned to the non-braking state. 3. The brake device according to claims 1 or 2, characterized in that said operating lever (1) has its end remote from a handle (22) provided with a cam disc (28) along which rollers (12) are adapted to be guided and moved substantially normal to the tire tread, that said rollers (12) are operatively connected to a first cylinder (6), that a second cylinder (7) is guided within said first cylinder (6), and that said spring means (15) is mounted between the one end of said second cylinder (7) connected to said brake shoe (9), and the end of said first cylinder (6) remote from said one end. 4. The brake device according to any one of claims 1 to 3, characterized in that said spring means comprises a biased or pretensioned spring column (15). 5. The brake device according to claim 4, characterized in that said spring column (15) comprises a stack of dish or cup springs. 6. The brake device according to claim 4, characterized in that said spring column (15) comprises coiled springs or helical springs. 7. The brake device according to any one of claims 1 to 6, characterized in that said operating lever (1) is operatively associated with said rollers (12) through a link guide including said cam disc (23). 8. The brake device according to claim 7, characterized by a cutout (25), preferably of a circular sector shape, formed in the end of said cam disc and adapted to receive said rollers (12) in the locking position. 9. The brake device according to any one of the preceding claims, characterized in that said operating mechanism is constructed in accordance with the bell crank or toggle principle. New claims or amendments to claims filed on 10 February 1983. Superseded claims 1-9. New or amended claims:

1. A brake device as a wheel (travel) and locking (parking) brake, especially for wheel chairs, wherein a brake shoe (9) which may be actuated through an operating lever (1) is adapted to be brought into operative contact with the tread of a tire (2), characterised in that said operating lever (1) is connected to said brake shoe (9) through an operating mechanism and through spring means (15) having degressive characteristics, so as to effect a braking operation independent of the tire inflation pressure.

2. The brake device according to Claim 1, characterised in that said operating lever (1) is adapted to be moved from an initial position corresponding to a non-braking state with increasing braking action and operating force to a locking position in which said brake shoe (9) acts as a locking (parking) brake, and that said brake shoe (9) is adapted to be returned to the nonbraking state.

3. The brake device according to Claims 1 or 2, characterised in that said operating lever (1) has its end remote from a handle (22) provided with a cam disc (28) along which rollers (12) are adapted to be guided and moved substantially normal to the tire tread, that said rollers (12) are operatively connected to a first cylinder (6), that a second cy nder (7) is guided within said first cylinder (6), and that said spring means (15) is mounted between the one end of said second cylinder (7) connected to said brake shoe (9), and the end of said first cylinder (6) remote from said one end.

4. The brake device according to Claim 3, characterised in that said operating lever (1) is provided with one or more rollers, and said cam disc (28) is operatively connected to said first cylinder (6).

5. The brake device according to any one of the preceding claims, characterised in that said spring means comprises a biased or pretensioned spring column (15).

6. The brake device according to Claim 5, characterised in that said spring column (15) comprises a stack of dish or cup springs.

7. The brake device according to Claim 5, characterised in that said spring column (15) comprises coiled springs or helical springs.

8. The brake device according to Claim 5, characterised in that said spring column (1 5) comprises a gas spring.

9. The brake device according to any one of Claims 1 to 8, characterised in that said operating lever (1) is operatively associated with said rollers (12) through a link guide including said cam disc (23).

10. The brake device according to Claim 9, characterised in that sliding blocks are provided in the place of said rollers.

11. The brake device according to any one of the preceding claims, characterised in that said cam disc (28) has at the end of the stroke of operation thereof a recess or a configuration of such type that the resetting forces of said spring column define a locking position at said end, which enables the brake device to be used also a locking (parking) brake.

1 2. The brake device according to any one of the preceding claims, characterised in that said operating mechanism is constructed in accordance with the bell crank or toggle principle.