GB2421991A

GB2421991A - Motor vehicle handbrake mechanism

Info

Publication number: GB2421991A
Application number: GB0500210A
Authority: GB
Inventors: Michael Niel Basnett
Original assignee: Nanjing Automobile Group Corp; MG Rover Group Ltd
Current assignee: Nanjing Automobile Group Corp
Priority date: 2005-01-07
Filing date: 2005-01-07
Publication date: 2006-07-12
Anticipated expiration: 2025-01-07
Also published as: GB2421991B; GB0500210D0

Abstract

A handbrake mechanism for a motor vehicle comprising a metal mounting bracket 10 defining a rack formation 26, and a metal plate 28,30 pivotally mounted on the bracket 10 and connected to a hand lever 50, a pawl 66 pivotally mounted on the metal plate 28,30 and biased into engagement with the rack formation 26, a release mechanism 80,82 to release the pawl 66 from the rack 26, the metal plate 28,30 being pivoted to the bracket 10 by means of a pivot pin 32, said metal plate having additional holes 34/36 so that the pivot point may be changed to vary the lever ratio. An independent claim discloses a handbrake wherein a leaf spring formed integrally with the lever biases the pawl. Another independent claim discloses a handbrake lever made of plastics, and the handbrake mechanism comprising a switch connected to the handbrake warning light circuit.

Description

MOTOR VEHICLE HAND BRAKE MECHANISMS

The present invention relates to motor vehicle hand brake mechanisms.

The invention is particularly suited to a motor vehicle hand brake lever mechanisms comprising a lever portion made of plastics material, the mechanism having a mounting bracket made of metal, the mounting bracket defining a rack formation, and a metal plate pivotally mounted on the bracket, the metal plate having a pawl formation for engagement of the rack formation on the bracket, the plastic lever portion being secured to the metal plate, and means to connect the metal plate to a brake actuation means, the lever portion including a release mechanism by which the pawl mechanism may be disengaged from the rack formation of the bracket, to permit release of the hand brake.

Hand brake levers of this type have the advantage that a hand grip may be moulded integrally of the lever and also reduce the complexity and number of parts, as compared to a conventional metal hand brake lever. This design also overcomes the problems of plastic creep and the melting of the lever in a vehicle fire, engagement of the hand brake being maintained by the metal plate which is held in the applied position, by the rack and pawl mechanism.

The invention is however also applicable to hand brake mechanisms of similar construction but having a metal lever portion, for example of pressed steel construction.

According to one aspect of the present invention, a hand brake mechanism for a motor vehicle comprises a mounting bracket made of metal, the mounting bracket defining a rack formation, and a metal plate pivotally mounted on the bracket, the metal plate being connected to a hand lever, a pawl formation for engagement of the rack formation on the bracket and means to connect the metal plate to a brake actuation means, the lever portion including a release mechanism by which the pawl mechanism may be disengaged from the rack formation of the bracket, to permit release of the hand brake, the metal plate being pivoted to the bracket by means of a pivot pin located through holes in the bracket and metal plate, alternative holes being provided in the metal plate, so that the pivot point may be changed to vary the lever ratio.

This arrangement will permit a standard design of hand brake lever to be used for different models of vehicle. According to a further embodiment, further adjustment of the lever ratio may also be achieved by providing alternative locations for attachment of the hand brake actuation means to the metal plate.

According to conventional designs, the pawl mechanism is released by means of a push rod mechanism, which extends from a free end of the hand brake lever. This push rod normally has spring means, which will urge the rod outwardly, thereby biasing the pawl mechanism into engagement with the rack formation. In accordance with a further embodiment of the present invention, the lever portion is formed from plastics material, the pawl mechanism being biased into engagement with the rack formation by means of a resilient leaf formation, which is formed integrally of the plastic lever portion.

According to a further embodiment of the present invention, a formation on the rack formation of the bracket is engaged by the pawl, to limit movement of the lever in the release direction. The pawl may however be released from the formation to permit over-travel of the lever when, for example, additional slack is required when connecting the hand brake mechanism to the brake actuation means.

According to a further aspect of the invention, with a plastic lever portion a spring blade electrical contact may be provided on the lever portion, the spring blade contact coming into contact with the metal bracket, when the hand brake is applied, in order to control the brake warning light circuit of the vehicle.

The invention is now described, by way of example only, with reference to the accompanying drawings in which: - Figure 1 is an exploded perspective view of a hand brake lever in accordance with the present invention; Figure 2 is a part sectional side elevation of a hand brake lever shown in Fig. 1; Figure 3 is a part side elevation from the opposite side; and Figure 4 shows a section along the lines IV-IV of Fig. 3.

As illustrated in figures 1 to 3, a hand brake for a motor vehicle comprises a metal mounting bracket 10. The mounting bracket 10 has forward and rearward leg formations 1 2, 14 with flange formations 1 6, 1 8, having apertures through which bolts may locate to secure the bracket 10 to the floor of a vehicle. The leg formationsl2, 14 extend from the forward and rearward ends of a planer body portion 22, which will extend longitudinally of the vehicle when the bracket 1 0 is secured to the floor of the vehicle. The rearward leg formation 14 extends transverse to the body portion 22, the lower portion of the rearward leg formation being cut away to provide longitudinal clearance from the rearward end of the bracket 10.

A circular aperture 24 is provided towards the rearward end of the body portion 22, adjacent the leg formation 14. The forward edge of the body portion 22 defines a rack formation 26.

s A pair of metal plates 28, 30 are mounted one on either side of the body portion 22 of bracket 10, the plates 28, 30 being pivotally attached to the bracket 10 by means of a pin 32 which passes through aperture 24 in the bracket 10 and one of a pair of corresponding apertures 34, 36 in each of the plates 28, 30. The forward ends of the plates 28, 30 are secured together by means of pins 38, 42 which engage through apertures 40, 44 in the plates 28, 30.

A further aperture 46 is provided in each of the plates 28, 30 at the rearward lower corners thereof. The aperture 46 and apertures 34, 36 in plates 28, 38 are Positioned such that the distance between apertures 46 and 34 is greater than the distance between apertures 46 and 36.

The pins 32, 38 and 42 are secured on one side of the plate 28 to a moulded plastic hand brake lever 50, the ends of the pins 32,38 and 42 being an interference fit in splined sockets 52, 54 and 56 respectively, in the hand brake lever 50. The splined bore of the sockets 52, 54 and 56 will allow a tight interference fit, without excessive hoop loads. Alternative formations, for example ribs or flats may be used for this purpose. Alternatively the end of the pins 32,38,42 may be splined. According to a further alternative, threads on the pins 32, 38 and 42 may engage corresponding threads in the sockets 52, 54 and 56.

The pins 32, 38 and 42 are provided with a circumferential rib formation 60 adjacent the socket formations 52, 54, 56, which will bear against the outer surface of plate 28 and will prevent the pins 32, 38 and 42 from being pulled out of the sockets 52, 54, 56 when axial loads are applied thereto. These circumferential ribs will also ensure that the plates 28, 30 will remain attached to the bracket 10 and that the hand brake will hold, even if the plastic hand brake lever 50 were to fail or melt in a fire. Other suitable means of providing an abutment against the outside of plate 28, for example circlips or star washers may be used. The assembly of the plates 28, 30 and bracket 10 are held together on the other side by washers and nuts 62 with engage against the outside of plate 30.

A spacer element 64 is located on pin 38, between plates 28 and 30, to maintain the distance between the plates 28 and 32, so that there is a small clearance with the body portion 22 of the bracket 10 and the plates 28, 30 and hand brake lever attached thereto are free to pivot with respect to the bracket 10.

A pawl 66 is pivotally mounted on pin 42 between plates 28 and 30, for engagement of the rack formation 26 on the body portion 22 of bracket 10. A resilient leaf spring formation 70, formed integrally of the hand brake lever 50, engages an abutment 72 on the pawl 66, to urge it into engagement with the teeth of the rack formation 26. A lever formation 74 on the pawl 66 has a part circular formation 76 which engages in a cup formation 78 on the push rod 80.

The cup formation 78 is moveable axially by means of a push rod 80, which is connected to a control plunger 82, mounted coaxially of a hollow grip formation 84 of the hand brake lever 50, whereby the pawl 66 may be disengaged from the rack formation 26 to permit release of the hand brake.

A hand brake control cable 90 is connected to the plates 28, 30 by means of a clevis coupling 92 and screw adjuster 94, the clevis coupling engaging a pin 96 secured through apertures 46 in the plates 28, 30.

The rack formation 26 has a lower stop formation 86, which extends radially further than the teeth of the rack formation 26, this lower abutment 86 in normal use being abutted by the pawl 66 when the hand brake lever 50 is fully released. The pawl 66 may however be over-rotated by further depression of the plunger 82, SO that the pawl 66 is moved clear of the lower abutment 86, allowing over-travel of the lever mechanism, to facilitate connection of the hand brake cable 90, without the requirement for excessive slack in the cable 90, which would otherwise have to be taken up by adjuster mechanisms.

As illustrated in figures 3 and 4, a brake warning light switch 100 may be formed integrally with the plastic hand brake lever 50. A plastic housing 102 is formed integrally of the moulded plastic hand brake lever, the housing 102 extending from the lower edge of the hand brake lever 50 to a point which is below the level of the body portion 22 of bracket 10, when the hand brake is released, but will overlap the body portion 22 of bracket 10 when the hand brake is applied. A metal spring blade 104 is retained by the housing 102, the spring blade 104 having a terminal formation 106 by which it may be connected to the brake warning light circuit of the vehicle, using a blade connector. The lower part of the spring blade 104, which is below the level of the body portion 22 of bracket 1 0 when the hand brake is released, is bent to form a contact portion 1 08 which extends transversely and overlaps the vertical plane of the body portion 22 of bracket 10, so that when the hand brake is applied, the contact portion 108 will be moved into engagement with the body portion 22 of bracket 10, closing the brake warning light circuit, through the earth system of the vehicle.

With the hand brake mechanism described above, when the hand brake lever and plates 28, 30 are pivotally attached to the bracket 10 through apertures 34, as illustrated, the lever ratio will depend on the ratio of the length of the hand brake lever 50 to the distance between apertures 46 and 34. Pin 32 may however be located in and alternative socket 52' in the hand brake lever 50 and through apertures 36 in plates 28, 30, in order to reduce the lever ratio. In this manner the hand brake mechanism may be used for different models of motor vehicle, without having to produce different components.

Various modifications may be made, without departing from the present invention. For example, while in the above embodiment a dual ratio hand brake lever mechanism is provided, multi-ratio levers may be provided by providing three or more holes in the plates 28, 30 and alternate sockets in the hand brake lever 50, for the pivot 32. Different ratios may also be provided by providing alternate holes in the plates 28, 30 for connection of the hand brake cable 90.

Moreover, the hand brake lever 50 need not be made of moulded plastic but may be formed from other materials, for example pressed steel. Also while in the above embodiment the grip formation 84 is formed integrally of the hand brake lever 50, these may be formed as separate parts. When the hand brake lever is made of conductive material, it will not of course be possible to form the brake warning light switch 100 integrally thereof, however a similar switch may be formed with an insulating housing which may be mounted on the lever in suitable manner, Instead of the integral pawl spring 70 of the above embodiment, separate resilient elements, for example coiled torsion springs may be used to urge the pawl 66 into engagement with the rack formation 26.

Claims

1. A hand brake mechanism for a motor vehicle comprising a mounting bracket made of metal, the mounting bracket defining a rack formation, and a metal plate pivotally mounted on the bracket, the metal plate being connected to a hand lever, a pawl formation pivotally mounted on the metal plate and biased into engagement of the rack formation on the bracket and means to connect the metal plate to a brake actuation means, the hand lever including a release mechanism by which the pawl mechanism may be disengaged from the rack formation of the bracket, to permit release of the hand brake, the metal plate being pivoted to the bracket by means of a pivot pin located through holes in the bracket and metal plate, alternative holes being provided in the metal plate, so that the pivot point may be changed to vary the lever ratio.

2. A hand brake mechanism according to claim 1 in which a pair of metal plates are positioned, one on either side of a body portion of the bracket, the metal plates being connected together and to the lever, for movement relative to the body portion of the bracket, about the pivot pin, alternative holes being provided in both metal plates, for the pivot pin.

3. A hand brake mechanism according to claim 2 in which the pawl is pivotally mounted between the two metal plates.

4. A hand brake mechanism according to any one the preceding claims in which an aperture is provided in the or each metal plate, for engagement of a pin by which the brake actuation means may be connected to the metal plate by means of a clevis or similar connection.

5. A hand brake mechanism according to claim 4 in which, in which alternative means are provided at alternative locations on the metal plate, for connection to the brake actuation means, whereby the lever ratio of the hand brake mechanism my be adjusted.

S

6. A hand brake mechanism according to any one the preceding claims in which the rack formation has a stop formation to limit movement of the hand brake lever in the release direction, the pawl release mechanism being moveable beyond its normal release position to disengage the pawl from the stop io formation and permit over travel of the hand brake lever to facilitate connection of the brake release mechanism.

7. A hand brake mechanism according to any one the preceding claims in which the hand brake lever is formed from plastics material.

8. A hand brake mechanism according to claim 7 in which the pivot pin between the metal plate and the bracket, and additional pins connecting the hand brake lever to the metal plate, engage in socket formations in the hand brake lever.

9. A hand brake mechanism according to claim 8 in which the pins are an interference fit in the sockets.

10. A hand brake mechanism according to claim 8 in which interengaging screw threads are provided on the pins and socket formations.

11. A hand brake mechanism according to any one of claims 8 to 10, in which additional sockets corresponding to the alternative holes in the or each metal plate, are provided on the hand brake lever.

1 2. A hand brake mechanism according to any one of claims 1 to 11, in which a resilient leaf spring formation is formed integrally of the hand brake lever, for engagement of the pawl, to bias the pawl into engagement with the rack on the bracket.

13. A hand brake mechanism according to any one of claims 7 to 12, in which a brake warning light switch housing is formed integrally of the hand brake lever, the housing extending from a lower edge of the lever and serving to retain a resilient conductive blade member, the blade member defining a contact formation which, when the hand brake is released will be clear of the metal bracket, but when the hand brake is applied will engage the metal bracket, to close a hand brake warning light circuit.

14. A hand brake mechanism for a motor vehicle comprising a mounting bracket made of metal, the mounting bracket defining a rack formation, and a metal plate pivotally mounted on the bracket, the metal plate being connected to a hand lever, a pawl formation pivotally mounted on the metal plate and biased into engagement of the rack formation on the bracket and means to connect the metal plate to a brake actuation means, the lever portion including a release mechanism by which the pawl mechanism may be disengaged from the rack formation of the bracket, to permit release of the hand brake, the metal plate being pivoted to the bracket by means of a pivot pin located through holes in the bracket and metal plate, a resilient leaf spring formation being formed integrally of the hand brake lever, for engagement of the pawl, to bias the pawl into engagement with the rack on the bracket.

15. A hand brake mechanism for a motor vehicle comprising a mounting bracket made of metal, the mounting bracket defining a rack formation, and a metal plate pivotally mounted on the bracket, the metal plate being connected to a hand lever, a pawl formation pivotally mounted on the metal plate and biased into engagement of the rack formation on the bracket and means to connect the metal plate to a brake actuation means, the lever portion including a release mechanism by which the pawl mechanism may be disengaged from the rack formation of the bracket, to permit release of the hand brake, the metal plate being pivoted to the bracket by means of a pivot pin located through holes in the bracket and metal plate, the hand brake lever being made of plastics material, a brake warning light switch housing being formed integrally of the hand brake lever, the housing extending from a lower edge of the lever and serving to retain a resilient conductive blade member, the blade member defining a contact formation which, when the hand brake is released will be clear of the metal bracket, but when the hand brake is applied will engage the metal bracket, to make a hand brake warning light circuit.

1 6. A hand brake mechanism substantially as described herein, with reference to and as shown in figures 1 to 4 of the accompanying drawings.