GB2110780A

GB2110780A - Wheeled vehicle fitted with a brake

Info

Publication number: GB2110780A
Application number: GB8136848A
Authority: GB
Inventors: Nigel Terry Walter Platt; Michael William Turrell
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-12-07
Filing date: 1981-12-07
Publication date: 1983-06-22

Abstract

A wheeled vehicle, particularly a wheelchair, is fitted with a brake comprising a disc 1 eccentrically mounted on a spindle 2 forming a cam to turn in the plane of rotation of the wheel, so that when the cam is pushed into contact with the circumference 10 of an adjacent wheel of the vehicle (position A or position B) it permits the wheel to rotate in one direction by dragging thereon but prevents rotation in the other direction by creating a jam between the cam and the circumference of the wheel. When the cam 1 is held in a neutral position (C), it is out of contact with the wheel which is thus free to rotate in both directions. The cam 1 is releasably held in the neutral position by the engagement of a ball (3) with a dimple in the floor of a groove in spindle 2 (see Figs. 2, 3). <IMAGE>

Description

SPECIFICATION Wheeled vehicle fitted with brake This invention relates to a wheeled vehicle fitted with a brake to act on the circumference of one or more of the wheels. According to the invention, the brake comprises a cam pivotally mounted to turn in the plane of rotation of the wheel, which cam can be pushed into either of two positions where its surface touches the circumference of the wheel and drags thereon when the wheel is rotated in one direction but causes the cam and the circumference of the wheel to jam and prevent rotation when the wheel is urged in the opposite direction. The brake preferably also includes means for releasably holding the cam in a neutral position out of contact with the circumference of the wheel.

In the accompanying drawings: Figure 1 illustrates diagrammatically the principle of operation of the invention by showing the cam in three positions: A-with the cam in contact with the circumference of the wheel to permit only forward movement, B-with the cam in contact with the circumference of the wheel to permit only backward movement, C-with the cam in a neutral position out of contact with the circumference of the wheel.

Figure 2 is an elevation showing the detailed construction of an example of a cam for use in the invention.

Figure 3 is a section along line X-X of Fig.

2.

Referring to Fig. 1, the cam is provided by a disc 1 eccentrically mounted on a spindle 2 to turn in the plane of rotation of the wheel.

When the cam is pushed into contact with the circumference 10 of an adjacent wheel of a wheeled vehicle, it permits the wheel to rotate in one direction by dragging thereon but prevents rotation in the other direction by creating a jam between the cam and the circumference of the wheel. When the cam is pushed into position A, forward rotation of the wheel is permitted but backward rotation is prevented. When the cam is pushed into opposite position B, backward rotation of the wheel is permitted but forward rotation is prevented. When the cam is held in a neutral position C, it is out of contact with the wheel which is thus free to rotate in both directions.

The invention is particularly useful for wheelchairs, which generally have a pair of large wheels controllable manually by the occupant. There is a need for an improved safety device to prevent a wheelchair from rolling backwards while its occupant is trying to propel it up a slope, and the invention is directed to this end.

The cams for each wheel may be mechanically linked together so that they contact the wheels at the same time and in the same position (i.e. for forward or for reverse motion).

A specific embodiment of the invention is described below with reference to Figs. 2 and 3.

A cam 1 is fitted by means of a suitable bracket and spindle 2 just beyond the circumference of each of the two large wheels (not shown but see Fig. 1) of a manually propelled wheelchair. The cam consists of an eccentrically mounted nylon disc 78 mm in diameter and 20 mm in thickness. It is rotatably mounted on the terminal portion (diameter 20 mm) of a steel spindle 2 carried on the fixing bracket. The disc is mounted so that the axis of the spindle lies 1 2 mm from the centre of the disc. The terminal portion of the spindle has a thread of pitch 1 mm per revolution, with a corresponding thread in the aperture of the disc, thereby rotatably securing the disc to the spindle with no more than 0.5 mm lateral displacement per half revolution.

The spindle is fixed to the wheelchair so that its axis lies parallel to the axis of rotation of the adjacent wheel and the distance from the axis of the spindle to the circumference of the wheel is about 34 mm; i.e., about 1 2 mm less than the maximum distance from the edge of the cam to the axis of the spindle.

The spindle has a circumferential groove 4 mm in width in the centre of the threaded portion carrying the disc, and running in the groove is a 4 mm stainless steel ball 3 mounted under action of a spring 4 under a retaining screw 5 contained within the widest part of the cam. A dimple in the floor of the groove, at the point farthest from the circumference of the adjacent wheel, lightly engages the ball and thus releasably holds the cam in a neutral position.

To put the brake into either of the operative positions, the cam is turned in the direction desired, forcing the spring-loaded ball from engagement with the dimple and is thence pushed into contact with the circumference of the wheel in the selected position. When free rotation of the wheel in both directions is required,the cam is lifted from the circumference of the wheel and turned until the ball engages the dimple.

1. A wheeled vehicle fitted with a brake to act on the circumference of a wheel, characterized in that the brake comprises a cam pivotally mounted to turn in the plane of rotation of the wheel, which cam can be pushed into either of two positions where its surface touches the circumference of the wheel and drags thereon when the wheel is rotated in one direction but causes the cam and the circumference of the wheel to jam and prevent rotation when the wheel is urged in the opposite direction.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Wheeled vehicle fitted with brake This invention relates to a wheeled vehicle fitted with a brake to act on the circumference of one or more of the wheels. According to the invention, the brake comprises a cam pivotally mounted to turn in the plane of rotation of the wheel, which cam can be pushed into either of two positions where its surface touches the circumference of the wheel and drags thereon when the wheel is rotated in one direction but causes the cam and the circumference of the wheel to jam and prevent rotation when the wheel is urged in the opposite direction. The brake preferably also includes means for releasably holding the cam in a neutral position out of contact with the circumference of the wheel. In the accompanying drawings: Figure 1 illustrates diagrammatically the principle of operation of the invention by showing the cam in three positions: A-with the cam in contact with the circumference of the wheel to permit only forward movement, B-with the cam in contact with the circumference of the wheel to permit only backward movement, C-with the cam in a neutral position out of contact with the circumference of the wheel. Figure 2 is an elevation showing the detailed construction of an example of a cam for use in the invention. Figure 3 is a section along line X-X of Fig. 2. Referring to Fig. 1, the cam is provided by a disc 1 eccentrically mounted on a spindle 2 to turn in the plane of rotation of the wheel. When the cam is pushed into contact with the circumference 10 of an adjacent wheel of a wheeled vehicle, it permits the wheel to rotate in one direction by dragging thereon but prevents rotation in the other direction by creating a jam between the cam and the circumference of the wheel. When the cam is pushed into position A, forward rotation of the wheel is permitted but backward rotation is prevented. When the cam is pushed into opposite position B, backward rotation of the wheel is permitted but forward rotation is prevented. When the cam is held in a neutral position C, it is out of contact with the wheel which is thus free to rotate in both directions. The invention is particularly useful for wheelchairs, which generally have a pair of large wheels controllable manually by the occupant. There is a need for an improved safety device to prevent a wheelchair from rolling backwards while its occupant is trying to propel it up a slope, and the invention is directed to this end. The cams for each wheel may be mechanically linked together so that they contact the wheels at the same time and in the same position (i.e. for forward or for reverse motion). A specific embodiment of the invention is described below with reference to Figs. 2 and 3. A cam 1 is fitted by means of a suitable bracket and spindle 2 just beyond the circumference of each of the two large wheels (not shown but see Fig. 1) of a manually propelled wheelchair. The cam consists of an eccentrically mounted nylon disc 78 mm in diameter and 20 mm in thickness. It is rotatably mounted on the terminal portion (diameter 20 mm) of a steel spindle 2 carried on the fixing bracket. The disc is mounted so that the axis of the spindle lies 1 2 mm from the centre of the disc. The terminal portion of the spindle has a thread of pitch 1 mm per revolution, with a corresponding thread in the aperture of the disc, thereby rotatably securing the disc to the spindle with no more than 0.5 mm lateral displacement per half revolution. The spindle is fixed to the wheelchair so that its axis lies parallel to the axis of rotation of the adjacent wheel and the distance from the axis of the spindle to the circumference of the wheel is about 34 mm; i.e., about 1 2 mm less than the maximum distance from the edge of the cam to the axis of the spindle. The spindle has a circumferential groove 4 mm in width in the centre of the threaded portion carrying the disc, and running in the groove is a 4 mm stainless steel ball 3 mounted under action of a spring 4 under a retaining screw 5 contained within the widest part of the cam. A dimple in the floor of the groove, at the point farthest from the circumference of the adjacent wheel, lightly engages the ball and thus releasably holds the cam in a neutral position. To put the brake into either of the operative positions, the cam is turned in the direction desired, forcing the spring-loaded ball from engagement with the dimple and is thence pushed into contact with the circumference of the wheel in the selected position. When free rotation of the wheel in both directions is required,the cam is lifted from the circumference of the wheel and turned until the ball engages the dimple. CLAIMS

2. A wheeled vehicle according to Claim 1, characterized in that the brake also includes means for releasably holding the cam in a neutral position out of contact with the circumference of the wheel.

3. A wheelchair in which a brake as claimed in Claim 1 or Claim 2 is fitted to act on the circumference of each of a pair of large manually controllable wheels.