GB2373035A - Parking brake assembly for an automotive vehicle - Google Patents

Abstract

A parking brake assembly 10 for an automotive vehicle comprises a hand lever 12 or pedal arranged to actuate an adjusting rod 16 through an apertured tiltable drive plate 18 which is tilted and grips the rod and thus applies the brake. A ratchet mechanism 20 maintains the brake lever in the brake-on position and thus maintains tension in the cable 14, via the tilted drive plate, throughout the brake applying, brake- on and brake-releasing stages. A compression spring 32 applies tension to the rod 16 and thus tensions the brake- applying cable 14 so that the drive plate 18 always picks up on the adjustment rod at the precise location such that the cable is fully tensioned whereby no adjustment of the cable is needed.

Description

AUTOMOTIVE PARKING BRAKE ASSEMBLY

This invention relates to automotive parking brake assemblies and in particular, but not exclusively, to a hand brake assembly for use in actuating (typically) the rear wheel brakes of an automotive vehicle through the medium of a control cable. The embodiments of the invention are equally applicable to foot-actuated parking brake assemblies.

Various requirements apply to the design of parking brake mechanisms. The usual requirements for simplicity and cost-effectiveness go without saying. Likewise mechanical effectiveness. Additionally, there is a need to accommodate the ever-present tendency for control cables to stretch, clearances to develop, and general slackness in the system to become apparent. A strong driver preference exists for a parking brake assembly that operates throughout its working life between services intervals on the basis of a constant hand lever or foot pedal stroke.

Another requirement made by users of such mechanisms is with respect to what may be termed user confidence. There is a need for the driver to receive mechanical feedback through the medium of the operating mechanism itself (quite apart from any control panel signals) that the system has been correctly actuated and remains actuated when the user so desires. Such is a feature of conventional hand brake mechanisms which are arranged to operate in the manner that the controlling hand lever or foot pedal generates tension in the cable and remains tensioned during the entire time period that the brake remains applied. Thus, when the user comes to release the hand lever or foot pedal, it can be sensed that the mechanism remains effective in carrying out its function because the hand lever or foot pedal is itself also detectably tensioned accordingly.

This latter requirement has some significant relevance in relation to technical evaluation of the parking brake assemblies disclosed in: EP 0 557 340 B1 (Simplistik Design) EP 0 633 848 B1 (Simplistik Design) which disclose assemblies having significant technical advantages in relation to the mechanism for effectively actuating the brake-applying cable, but which do not meet this latter requirement with regard to user feedback and confidence with respect to actuation status.

However, this latter fact is not particularly surprising in view of the nature of the actual mechanism used for transferring brake-applying loads to the operating cable, and the consequential arrangement adopted for maintaining the tensioned state of the cable during brake application. In short, the mechanisms use pivotally mounted drive plates and lock plates through which a control rod connected to the actuating cable is able to slide. Apertures in the drive plate and the lock plate through which the rod passes have only slight clearance whereby rocking motion of the drive plate and the lock plate causes gripping and locking for drive and non-return purposes respectively.

Such mechanisms are relatively well known, being widely used in such mechanisms as hand devices for progressively extruding mastic or the like from a tube thereof by means of a stepwise-advanced piston. Another application of such mechanisms is to hand devices for the extraction of tubes from heat exchangers by means of a hydraulic pulling device which utilises drive and lock plates to apply in sequence an outwardly-directed pulling force to a tube followed by the application of a locking action to prevent tube return, whereby a tube is progressively pulled from its mounting in a heat exchanger or boiler/furnace.

In the above EP 340 B1 and 848 B1 specifications and

the above-described other applications of drive and lock plate mechanisms, the pivoted lock plate performs the function of acting (very effectively) to lock the progressively-moved (by force) member against return or retraction movement when the drive mechanism reaches the end of its stroke. Indeed, the usual arrangement is that the lock plate is spring biased into its locking position and the angular disposition of the lock is such that it freely permits onward (advance) movement of the associated rod or other member, but immediately locks (by means of its welldefined or sharp edges) upon the rod tending to move in the opposite direction. Such is a classic feature of drive and lock plate mechanisms.

However, this feature of the mechanism disclosed in the 340 Bl and 848 B1 specifications has, we have discovered, had the effect of deterring implementation of these otherwise useful mechanisms. Just to explain the details of this aspect of the matter a little further, reference is directed to Figs 1,2 and 3 of the EP 340 B1 specification which show, respectively, the mechanism with the brake off, the mechanism with the lever raised in order to apply the brake, and the mechanism with the lever lowered whilst the brake is still applied. From these descriptions of the figures it is clear that, as explained above, when the brake is applied, the hand lever itself is not loaded and has no function as such in order to release the brake. The hand lever is raised in order to transfer the load from the lock plate to the drive plate for manual angular release. An alternative would be to provide some means for unlocking the lock plate on its own, but this would cause an instantaneous relaxation of the springs in the system, probably accompanied by significant noise, which would not be to the user's benefit.

Therefore, an object of the present invention is to

provide a method and apparatus offering improvements in relation to one or more of the matters discussed above or generally.

According to the invention there is provided a method an apparatus as defined in the accompanying claims.

Therefore, some means is needed whereby the abovediscussed mode of operation of drive and lock plate mechanisms could be modified for use specifically in relation to parking brakes, in order to meet the user confidence requirement discussed above. Indeed, we have realised that if the locking plate of the EP 340 Bl and EP 848 Bl specifications could somehow be caused to act through the drive plate and/or through the hand brake lever itself, this would meet the requirement. However, this more conventional approach to the question appears to be difficult to achieve and we have therefore determined that what is needed in the circumstances, in combination with the drive plate and rod mechanism of the EP 340 Bl and EP 848 Bl specifications is simply the provision of means to lock the parking brake lever or pedal itself in its actuated (tensioned) position with the drive plate itself serving to maintain tension in the system, rather than the separate lock plate. In this way, contrary to established practice in relation to drive and locking plate devices, the drive plate acts to establish and maintain (and indeed subsequently to allow to decrease again) the tension in the system throughout a given brake application cycle, instead of being used only for the tension increasing and tension decreasing phases.

As to the means to lock parking brake lever or pedal in its actuated or tensioned position with the drive plate performing this function, a variety of such devices could be designed, but perhaps the simplest is a ratchet device somewhat analogous to that used in other parking brake

mechanisms. Ratchets of course have a stepwise operating characteristic and in the case where a non-stepwise operating characteristic is required, it would be easy to devise a stepless or continuous adjustment mechanism utilising (for example) a roller type locking device in which the rollers are releasable by means of a manually operable release nob or device.

In this way, the embodiments of the invention provide a parking brake mechanism having significant advantages in relation to previously known devices, including those advantages disclosed in the above EP 340 Bl and EP848 Bl specifications one notable advantage of which is that which is exhibited by the embodiment of Fig 7 in those specifications in which a cable-tensioning compression spring 32 acts on one end of the cable-actuating and tensioning rod on which the drive plate acts) so as to maintain a substantially constant tension in the cable at all times. This feature relates importantly to the fact of using a drive plate for actuating the rod and thus the brake cable. Because the drive plate has sharpened edges and is able to grip at any location on the rod in a stepless manner, the use of a spring 32 as disclosed in the abovementioned EP specifications ensures that (between successive brake applications) the cable is always tensioned and the system always picks up from that status of the cable so that (to the user) the cable never need adjustment and the mechanism always operates in the same way.

By providing an arrangement in which a drive plate (of a drive and lock plate mechanism, but without the lock plate) is used to provide both the driving and locking functions (the latter by means of an associated locking mechanism) this important characteristic of the previously disclosed mechanisms in the EP 340 Bl and EP 848 B1 specifications is provided in association with the even more

important feature of driver feedback control and confidence as discussed above.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawing which shows a side elevation view of an operating lever for an automotive parking brake assembly.

As shown in the drawing an automotive parking brake assembly 10 comprises an operating lever 12 adapted to actuate a tension member 14 which is itself adapted to actuate a wheel brake (not shown).

Operating lever 12 is adapted to actuate tension member 14 by being operably connected to an adjusting rod 16 which is mounted for lengthwise linear movement and is also connected to tension member 14.

Operating hand lever 12 is connected to adjusting rod 16 by means of an apertured pivoted drive plate 18 which is adapted to grip adjusting rod 16 on executing angular movement relative to the rod from a position in which the rod can slide through the aperture in the drive plate.

Releasable locking means 20 is provided to lock the brake assembly 10 in its brake-on position. The releasable locking means comprises means to lock hand lever 12 in its brake-applied position with drive plate 18 serving to maintain tension in tension member 14, as will be more fully explained below.

Having thus identified some of the principal structures of the parking brake assembly 10 we will now consider the structure in more detail.

Operating lever 12 is mounted for pivotal movement about an operating axis 22 at which it is pivotally connected to an upstanding flange 24 mounted on a slideway assembly 26 within which adjusting rod 16 is slidably mounted for lengthwise movement in the direction of arrow A.

Tension member 14 comprises a conventional tension

transmitting inner cable and an associated cable sheath (not shown) suitably connected to one end 28 of adjusting rod 16 by means of a suitable end fitting (not shown).

The parking brake operating lever assembly 10 is suitably fixed within the automotive vehicle's superstructure for convenient operation by the driver by means of a mounting (30 at one end of slideway assembly 26) and apertured to receive a mounting bolt. Further details of the fixing of the parking brake assembly to the vehicle are not considered necessary.

Adjusting rod 16 is biased by a cable-tensioning spring 32 in the cable-tensioning direction (to the right in the drawing) so as to maintain a generally constant tension within tension member 14 during use. Spring 32 acts between one end of slideway assembly 26 and a boss 34 mounted adjustably (by a screw thread) towards one end of rod 16.

Operating lever 12 is connected to rod 16 through drive plate 18 by means of a drive assembly 36, which will now be described.

Drive assembly 36 comprises drive plate 18 which is formed with a slightly oversized aperture through which adjusting rod 16 passes and is pivotally connected at 38 to a generally L-shaped mounting member 40 through which rod 16 also passes with larger clearance. At the upper side of drive plate 18, the latter is formed with a yoke 42 between the two upwardly-extending limbs 44,46 of which is located a drive pin 48 carried at the lower actuating end 50 of operating lever 12 in order to actuate drive plate 18.

It can now be seen that lifting hand lever 12 so as to execute anticlockwise angular movement about operating axis 22 causes drive pin 48 to pivot yoke 42 to the right or clockwise about pivot 38 so as to lock drive plate 18 onto rod 16.

It has been said that drive plate 18 is formed with a

clearance opening through which rod 16 extends. Such clearance opening is only slightly larger than the rod and formed with hardened and sharpened edges effective to cause gripping action with respect to the rod.

A release spring 52 of helical compression-spring format but of light duty construction acts between one face of drive plate 18 and mounting bracket 30 so as to have a return action in respect of drive plate 18 after completion of a braking action.

Turning now to locking means 20, this comprises, as already noted, means to lock the brake assembly in its brake-on position. For this purpose, there is provided a sector-shaped toothed ratchet member 54 positioned to cooperate with a pawl 56 which is pivoted at 58 for releasable cooperation with the teeth of ratchet member 54 under the control of a release button 60 having a return spring 62 for convenient driver control.

In use, the parking brake assembly 10 operates in the manner which will already be apparent form the description above. From the position shown in the drawing, lever 12 may be raised by anticlockwise motion about operating axis 22 thereby causing drive plate 18 to execute angular movement about its pivot axis 38 to grip rod 16 and from then onwards to move rod 16 in the direction of increased tension in tension member 14 (to the right in the drawing) thereby applying the parking brake.

As the hand lever 12 is rotated anticlockwise, pawl 56 clicks over the teeth of ratchet member 54 until the lever reaches the brake-applied position in which the pawl is allowed to remain engaged between a pair of the ratchet teeth thereby locking the hand lever in the brake-applied position. In this position, the lever holds drive plate 18 in its tilted and gripping position in which the drive plate likewise maintains tension in rod 16 and thus in tension

member or cable 14. The brake is thus maintained in its brake-on position.

In order to release the brake, release button 60 is pressed by the driver and pawl 56 is disengaged from the teeth of ratchet member 54 thereby allowing the hand lever to be lowered where upon drive plate 18 is pivoted to the left as seen in the drawing thereby allowing adjusting rod 16 to move lengthwise in the tension-releasing direction so as to release the brake. When the rod reaches a position at which the tension in the cable 14 is largely released, the drive plate can then no longer grips the rod and can pivot leftwards under the action of return spring 62 to the position shown in the drawing.

Claims (10)

1) A method of operating an automotive parking brake assembly comprising; a) providing an operating lever or pedal adapted to actuate a tension member itself adapted to actuate a wheel brake; b) providing said operating lever or pedal adapted to actuate said tension member by being operatively connected to a rod which is mounted for lengthwise movement and is also connected to said tension member; and c) providing said lever or pedal connected to said rod by means of an apertured pivoted drive plate adapted to grip said rod on executing angular movement with respect to said rod from a position in which said rod can slide through the aperture in said drive plate; and d) providing releasable locking leans adapted to lock said brake assembly in its brake-on position; characterised by; e) providing said releasable locking means comprising means to lock said pedal or lever itself in its brake-applied position with said drive plate itself serving to maintain tension in said tension member, and causing same in use to effect such locking.

2) A method of operating an automotive parking brake assembly characterised by providing releasable locking means adapted to lock a brake pedal or lever in its brake-applied position in which a tiltable drive plate associated with a lengthwise-slideable rod member connectable to a brakeactuating tension member serves to maintain tension in said tension member, and the method comprising causing same in use to effect such locking.

3) A method according to claim 1 or claim 2 characterised by causing tension mans to apply tension to

said tension member at least during intervals between successive brake applications, said tension being arranged to cause lengthwise movement of said rod to take up clearance whereby said drive plate adopts a new drive takeup position on said rod.

4) A method according to any one of claims 1 to 3 characterised by providing said releasable locking means comprising a ratchet mechanism.

5) An automotive parking brake assembly comprising; a) an operating lever or pedal adapted to actuate a tension member itself adapted to actuate a wheel brake; b) operating lever or pedal being adapted to actuate said tension member by being operatively connected to a rod which is mounted for lengthwise movement and is also connected to said tension member; and c) said lever or pedal being connected to said rod by means of an apertured pivoted drive plate adapted to grip said rod on executing angular movement with respect to said rod from a position in which said rod can slide through the aperture in said drive plate; and d) releasable locking leans adapted to lock said brake assembly in its brake-on position; characterised by; e) said releasable locking means comprising means to lock said pedal or lever itself in its brake-applied position with said drive plate itself serving to maintain tension in said tension member.

6) An automotive parking brake assembly characterised by releasable locking means adapted to lock a brake pedal or lever in its brake-applied position in which a tiltable drive plate associated with a lengthwise-slideable rod member connectable to a brake-actuating tension member serves to maintain tension in said tension member.

7) An assembly according to claim 5 or claim 6

characterised by tension means to apply tension to said tension member at least during intervals between successive brake applications, said tension being arranged to cause lengthwise movement of said rod to take up clearance whereby said drive plate adopts a new drive take-up position on said rod.

8) An assembly according to anyone of claims 5 to 7 characterised by said releasable locking means comprising a ratchet mechanism.

9) A method of operating an automotive parking brake substantially as described herein with reference to the accompanying drawings.

10) An automotive parking brake assembly substantially as described herein with reference to the accompanying drawings.