MECHANISM FOR ACTUATING A VEHICLE PARKING BRAKE

Abstract: The mechanism comprises a pivotable hand-operated actuating lever (101) which engages a drive plate (102) biased upright by a spring (122). The drive plate (102) moves an output rod (103) connected to a brake cable. The output rod (103) is held by a lock plate (104) which is released by a push rod (110) passing through the lever (101). THe linkage (115, 117) between the lever (101) and the drive plate (102) prevents the lever from returning to its lowered position when the brake has been applied. A spring (162) returns the lever (101) to its lowered position when the brake is released. The mechanism automatically adjusts for variation in the brake cable tension by the action of the spring (122) on an abutment plate (130) fixed to the end of the output rod (103). Additional self adjustment mechanisms are described (figures 4 to 7). Further hand or foot operated brake actuating mechanisms are also described (figures 1 to 3 and figure 10), together with additional hydraulic or manually operated mechanisms for release of the lock plate (104). A mechanism is described which signals that the brake has been applied (figure 11). A "soft-release" mechanism (figure 12) and a release damper (figure 14) are also described.

Description: MECHANISM FOR ACTUATING A VEHICLE PARKING BRAKE This invention relate s to actuatin mechanisms for parking brakes of vehicles . A known type of hand-operated vehicle parkin brake uses a lever to tighten a brake cable, which i held taut by a locking pawl engaged with a ratchet . typical lever ratio is 7 to 1 so a long lever i neces sary . During the l if etime of the vehicl adjustment of the hand brake is necessary, in order t take up sag in the cable . Hand brakes are noisy as th ratchet and pawl mechanism clicks as the brake i applied . Similar problems arise with foot-operate parking brakes . The present applicants ' patent applicatio O92/08628 (PCT/GB91/02022 , claiming priority from G 9025041.6 ) describes a handbrake which replaces th ratchet and pawl mechanism with a tiltable frictiona drive plate . The handbrake used a collapsing leve which returned a drive plate to a rest position whe the handbrake was applied , which has the advantag that, as the lever is not integral with the mechanism one can construct this lever from a f lammable o meltable material such as certain plastics , without th risk that the brake could be released during a vehicl fire . However the feature of a collapsible leve may prove unacceptable to the car industry an therefore it is an object of this invention to overco the above mentioned disadvantage whilst retaining th other advantages of a handbrake which do not use a paw and ratchet mechanism. The invention provides an actuating mechanis for a vehicle parking brake , comprising an actuatin member which i s movabl e rel ative to a mechani s mounting means between a first and a second position an output member which moves in a brake-applying direction when the actuating member moves from its first to its second position, and moves in a brake- releasing direction when the actuating member moves in the opposite direction, a tiltable apertured drive element, which is connected through a coupling means to the actuating member and couples the actuating member to the output member, the drive element having an aperture through which the output member extends and through which the output member is free to move in a released position of the drive element which is tiltable to engage the output member frictionally in its aperture, a releasable means for holding the output member at least when in a position corresponding to the second position of the actuating member , a release means for the holding means , and a blocking means which prevents movement of the actuating member from its second to its first position prior to release of , the holding means . The actuating member is preferably pivotably mounted on the mounting means . Advantageously, the actuating member is resiliently biased into its first position. The bl ocking means can c ompri s e the cooperation between the drive element, the actuating member and the coupling means , in resisting the movement of the actuating member from its second position prior to release of the holding means. Preferably the coupling means comprises a pivotable connection between the actuating member and the drive element, the fulcrum of which may be movable. More preferably the coupling means comprises a pin mounted on one of the actuating member and the drive element, slidably located in a slot in the other of these, the slot advantageously extending substantially perpendicular to the direction of movement of the output member in the released position of the drive element. When s uch a mechani sm i s mounted in a vehicle, the actuating member will be positioned for hand or foot operation by the driver. Preferably the actuating member is operated manually . The actuating member can comprise a lever, or a pi stol grip which when pul led operate s the actuating member . Alternatively the actuating member comprises a foot-operated pedal which may be biased to extend upwardly and forwardly, and which when depressed operates the actuating mechanism. The release means may be operated at a position separated from the actuating member . The release means may be , for example , mechanical , hydraulic or vacuum means . Preferably the release means comprise a hand operable portion of a lever actuating means adjacent a portion of the lever which is shaped for gripping by hand. The release means can be connected to the holding means by a link rod extending longitudinally within the lever. Advantageously , the mechani sm includes resilient biasing means acting between the lever and its hand-operable portion, the resilient bias requiring to be overcome by movement of the hand-operable portion before the holding means can be released. The resilient biasing means may take the for of a compres s ion spring which is compres sed upo movement of the hand-operable portion, for example release button , of the actuating member . It is thus very dif ficult to release the brake mechanism b movement of the hand-operable portion alone , it bein necessary also to relieve the load imposed by the brake mechanism by grasping the actuating member, the biasin force of the resilient biasing means being sufficient to release the holding means only when the imposed load is taken up through the actuating member. This provides an important safety feature against inadvertent release of the brake mechanism. When mounted in a vehicle the output member is connected to a rod, cable or other element linking it to the parking brake of the vehicle. Alternatively the output member may be the brake cable itself, which would be sheathed in a suitable protective material. The output member which is preferably slidably mounted on the mounting means, can be elongate. The output member can be constructed with any suitable transverse cross section, which need not be uniform along its length. The holding means advantageously comprises an element which has an aperture through which the output member extends and through which the output member is free to move in the released position of the holding means, the holding element being tiltable to engage the output member frictionally in its aperture. The holding element is preferably resiliently biased into a position which prevents the output member from passing through its aperture. For certain vehicle applications however the holding element may be constrained in its released position when the actuating member is in its first position. Advantageously, the mechanism includes resilient biasing means acting to assist the engagement of the drive element with the output member. Preferably the mechanism includes means to compensate for wear in the brake mechanism of the vehicle. Such compensation means can comprise means to vary the rest position of the output member. When the output member is elongate , the compensation means ca comprise an abutment element which abuts the mountin means to define the rest position of the mechanism an which is slidable on the output member so as to b brought into contact with a stop on the mounting mean when adjustment is necessary, such contact moving th abutment element on the output member to re-define th rest position. Alternatively , the compensation means ca comprise resilient biasing means acting between th output member and the mounting means to apply compensating force to the output member to define it rest position. Retaining means can be provided to hold th compensation means within the actuating mechanism whe a restraining force is not being applied to the outpu member . Conveniently there is provided a means tha senses when the parking brake has been applied an activates a remote signalling means that indicates whe the parking brake has been applied. The sensing mean can comprise a switch sensitive to applied forc mounted on the output side of the output member, or ma be a switch sensitive to the position of the slidabl abutment element of the compensation means . Advantageously , the mechanism include damping means for damping movement of the outpu member , at least in its brake-releasing direction Such damping means may comprise a piston which i movable in a cylinder containing a damping fluid, th piston for example having a bleed passage allowing th damping fluid to pass from one side of the piston t the other during its movement in the cylinder. By way of example , embodiments of th invention will be described with reference to th drawings in which: Figure 1 is a side view of a hand-operated brake actuating mechanism with the brake off. Figure 2 is a side view of the brake actuating mechanism shown in Figure 1 as the lever of the mechanism is raised in order to apply the brake. Figure 3 is a side view of the brake actuating mechanism shown in Figures 1 and 2 after an attempt at lowering the lever whilst the brake is still applied. Figure 4 is a side view of a first modification of part of the mechanism. Figure 5 is a side view of a second modification of part of the mechanism, Figure 6 is a section on the line A-A of Figure 5, Figure 7 is a side view of a third modification of part of the mechanism. Figure 8 is a perspective view of a frame part of the mechanism, Figure 9 is a side view of a second embodiment. Figure 10 is a side view of a third embodiment which is foot operated, Figure 11 is a side view of a mechanism for signalling that the brake has been applied. Figure 12 shows, in section, a part of a first modification of the second embodiment. Figure 13 shows a part of a second modification of the second embodiment, and Figure 14 shows, in section, a part of a further modification of the first embodiment. It should be noted that in both figures 2 and 3 the inclination of the tilt of the drive plate has been exaggerated to increase the clarity of the dr awing s . Referring to Figure 1, the mechanis comprises a pivotable hand-operated actuating lever 1 engaging a drive plate 2, which moves an output rod 3, which can be frictionally held by a lock plate 4. Th rod 3 is connected to a brake cable through an eye 5. The lever 1 can rotate about a pivot pin 6 which is mounted in a frame 8 (see Figure 8) rigidl fixed to the vehicle. A coil spring 62 of the rat trap type is mounted around the pivot pin 6 of th lever 1 and acts between the frame 8 and the lever 1. Thus the spring 62 biases the lever towards its lowered, rest, position. For the sake of clarity th spring 62 is omitted from Figures 2 and 3. A releas button 12 pivots on a pin 14 fixed to the lever 1. Th lever 1 has a lobe 16 which is connected to the driv plate 2 through a pin 15 mounted on the lobe 16, th pin 15 passing through a longitudinal slot 17 in the top of the drive plate 2. A pull rod 10 is pivotally attached at its outer end to the release button 12 and extends withi the lever 1. A slot 13 in the pull rod 10 receives th pivot pin 6 and allows longitudinal movement of th pull rod 10 relative to the lever 1. The output rod 3 is mounted to slide throug apertures in inwardly-turned tabs 18, 20 of the frame and through holes in the drive plate 2 and the loc plate 4. To facilitate the rod 3 sliding through th frame 8 a bush 19 is positioned on the tab 18. Th drive plate 2 is constructed so it will frictionall hold the rod 3 unless substantially perpendicular wit it. The lock plate 4 is arranged to frictionally hol the output rod 3 against movement in a direction whic would release the brake, that is from right to left i Figures 1 to 3. If the plate 4 is substantiall perpendicular with the output rod 3 then the rod 3 can move through the lock plate 4 in either direction. The end of the rod 3 is prevented from sliding through its aperture in the tab 20 by a nut 21 threaded on the end of rod 3. A light helical compression spring 22 is concentric with the output rod 3 and acts between the drive plate 2 and the tab 20 of the frame 8. The lock plate 4 has one end located in a recess 24 in the frame 8; the other end has a slot 26 through which a neck 28 formed near the inner end of the pull rod 10 extends. The inner end of the pull rod 10 terminates at a stop plate 27. A spring 25 is positioned concentrically about the rod 3 between the lock plate 4 and the bush 19 such that the lock plate 4 is biased into a tilted position in which it engages the output rod 3. The arrangement may be as shown in Figure 1, in which the lock plate 4 is substantially perpendicular to the output rod 3 in the lowered position of the lever 1. Such an arrangement may be advantageous in certain vehicle applications. Preferably however the arrangement is such that the spring 25 biases the lock plate 4 into a tilted position (as shown in Figures 2 and 3) in the lowered position of the lever 1. A switch (not shown) which is sensitive to applied force is mounted on the output side of the output rod 3. When a force is applied to the brake cable which exceeds the force required to balance the spring 22, the switch operates a remote signalling means, for example a light on the facia, which indicates that the parking brake has been applied. When the brake is released the mechanism adopts the position shown in Figure 1. To apply the brake the lever 1 is raised manually, by rotating it anti-clockwise as viewed in Figure 1, about the pivot 6. During this movement, the pin 15 tilts the drive plate 2 by acting through the slot 17 until this plate becomes frictionally engaged with the output rod 3. This engagement is assisted by the action of the spring 22 on the drive plate 2. Further rotation of the lever 1 about the pivot 6 causes the output rod 3 to slide so as to tighten a brake cable pivotably attached to the eye 5 and so apply the brake. During initial raising movement of the lever 1, the inner end of the pull rod 10 follows the profile of the lock plate 4, the slot 26 in the lock plate 4 allowing movement of the pull rod 10 relative to the plate 4 and the upper portion of the plate 4 being arcuate to accommodate movement of the pull rod 10 as the lever 1 is raised. The pull rod 10 is thus prevented from sliding longitudinally relative to the pin 6 until a position of the lever 1 is attained in which the drive plate 2 has moved the output rod 3 forward. If the lock plate 4 adopts a perpendicular position when the lever 1 is lowered, the next lower portion of the lock plate is shaped such that, towards the end of the raising movement of the lever 1, the lock plate is tilted relative to the output rod 3 to retain the rod against return movement, as shown in Figure 2. Once the brake has been applied the lever 1 cannot be lowered to the brake releasing position, without first operating the release button 12. If an attempt is made to lower the lever when the output rod 3 is locked by the lock plate 4, because the drive plate 2 is unable to slide the rod 3, it is possible to lower the lever only a small distance, which moves the pin 15 within the slot 17 and tilts the drive plate 2 in the opposite direction as shown in Figure 3. As the drive plate remains tilted with respect to the output rod 3 it continues to be in frictional engagement with the rod 3. Thus when the brake has been applied the drive plate 2 can wobble between the limits of the two positions shown (greatly exaggerated) in Figures 2 and 3 and the free travel of the lever 1 is similarly restricted. To release the handbrake the release button 12 is depressed which rotates it about the pin 14 and slides the pull rod 10 longitudinally relative to the pin 6. Thus the lock plate 4 is released from engagement with the output rod 3. As the output rod 3 is free to slide within the lock plate 4, when the lever is lowered, the drive plate 2 pivots anticlockwise about the output rod 3 as the pin 15 moves upward within slot 7. The output rod 3 is moved to the left (as shown in the Figures 1 to 3) under the control of the driver lowering the lever 1 and the brake cable is released gradually. Thus the handbrake returns to the rest position shown in figure 1. In order to improve the engagement between the lock plate 4 and the output rod 3 in the embodiment described the contact surfaces of these components can, if desired, be suitably treated or shaped, for example roughened or serrated. In the embodiment just described the rest position of the output rod 3 is determined by the nut 21 which must be adjusted from time to time. This tends to be a difficult operation. Modifications of the embodiment provide means to adjust the rest position of output rod 3 in order to compensate for a reduction in the brake cable tension over a vehicle's lifetime. A means which compensates for cable sagging is shown in Figure 4 and comprises a bush housing 34 forming an extension of the frame 8, a bush 36 which is an interference fit on the output rod 3 and a bush stop 38 on the housing 34. When the output rod 3 moves, the bush 36 and the rod 3 move together until the bush 36 abuts the stop 38. If the output rod 3 moves further it slides through the bush 36 which shortens the operative length of rod and thus compensates for any reduction in the cable tension. An alternative adjusting means, shown in Figures 5 and 6, comprises a bush 40 with a rib 42, which is slidable within a slot 44 in the frame 8. The bush 40 is in interface fit with the output rod 3. As the mechanism is operated the bush 40 and the output rod 3 slide together until the bush 40 is arrested by the end of the slot 44, when the rod 3 slides through the bush 40 to take up any slack in the cable. If either of the self-adjusting mechanisms described above is fitted to the actuating mechanism, part of these self-adjusting mechanisms can be used to signal that the parking brake has been applied. When the parking brake is applied the bush 36 or 40 moves, and a switch, sensitive to the position of the bush 36 or 40 operates a signalling device. Such a signalling means is shown in Figure 11. A peg 50, which protrudes from the siding bush 36 or 40, extends through a slot 51 in a tubular housing 52 with a closed end. The end of the peg 50 is located in a groove in a piston 53. The piston 53, which is an electrical conductor, is slidable within the housing 52 and is in electrical contact with an electrical terminal 54. A rivet 55, which is also an electrical conductor, is positioned between the closed end of housing 52 and the piston 53. The rivet 55 extends through a hole in the closed end of the housing. An electrical conductor 56 and a bush 57 are positioned between the head of the rivet 55 (which extends from the housing 52) and the outside of the housing 52. The electrical conductor 56 is in electrical contact with an electrical terminal 58. A spring 59 is mounted concentrically around that part of the rivet 55 which is inside the housing 52. The spring 59 abuts a plate 64 which forms the end of the rivet 55 furthest from the head of the rivet. The force of the spring 59 acting between the plate 64 and the inside of the housing 52 keeps the rivet head closely in contact with the conductor 56. A battery and a bulb are connected in series between the electrical terminals 54 and 58. When the actuating mechanism moves the output rod 3, the bush 36 or 40 also moves (to the right, as shown in Figure 11). Thus the piston 53 also moves within the housing 52 such that, the piston 53 initially makes contact with the plate 64 at the end of rivet 55 and then compresses the spring 59. Thus the electrical circuit between terminals 54 and 58 is completed and the bulb illuminates indicating that the actuating mechanism has tightened the brake cable and thus applied the brake. When the actuating mechanism is released the output rod 3 moves to the left as shown in Figure 11 which moves the bush 36 or 40 and hence the peg 50 and the piston 53 also to the left as shown in Figure 11, and the contact between the piston 53 and the plate 64 is broken which extinguishes the bulb, indicating that the parking brake has been released. A further self-adjusting means is shown in Figure 7 and comprises a bush 29 which is positioned on the tab 20 and through which the output rod extends, an abutment plate 30 fixed to the end of the output rod 3, and a helical compression spring 32 mounted concentrically on the rod 3 between the plate 30 and the bush 29. The force exerted on the plate 30 by the spring 32 decreases the operating length of the outpu rod 3 when the tension in the brake cable decreases. A shear pin or a wedge can be used to retai any of the self-adjusting mechanisms within th actuating mechanism during assembly of the actuatin mechanism. Once the actuating mechanism has been fixe to a vehicle a brake cable is either attached to th output member or threaded through the mechanism t serve as the output member. The wedge or the shear pi lock the mechanism in the rest position. The firs time the actuating mechanism is to be operated, eithe the wedge is removed, or the shear pin breaks as the actuating member is applied. The self-adjustin mechanism then automatically alters the rest positio of the output member to optimise operation of th actuating mechanism. The second embodiment, shown in Figure 9, is broadly constructed as the first embodiment with th following modifications. Elements corresponding t those of the first embodiment are numbered identicall in Figure 9 with the addition of one hundred. A spring 122 acts between the drive plate 10 and an abutment plate 130 fixed to the end of th output rod 103. Thus the spring 122 automaticall adjusts the cable tension. The lever 101 is biased int its lowered, rest, position by the coil spring 162. The pull rod 10 of the first embodiment i replaced by a push rod 110 which is slidable within th lever 101. To release the lock plate a button 152 i depressed. The button 152 is biased by a spring 150 t protrude from the end of the lever and is connected t the end of rod 110. The push rod 110 is retained i its rest position by a restraining head 109 which i fixed to the push rod 110 and abuts against the leve 101 at a point adjacent to the pivot 106. The rod 11 moves down the lever, and pushes the upper end of the lock plate 104, slanted in the opposite direction from the first embodiment which releases the output rod 103. This arrangement has the advantage that because the push rod 110 pushes the lock plate to release the output rod 103, the lock plate 104 does not have to be connected to the rod 110 through a slot in the rod 10 as in the first embodiment. The upper end of the lock plate 104 and the push rod 110 are both shrouded by the lever 101. It will be noted that, in the lowered position of the lever 101, the push rod 110 does not contact the lock plate 104. This allows the spring 125 to bias the lock plate 104 into a tilted, locking position, the lock plate pivoting against one edge of the slot 124 in the frame. In the modification of Figure 13, the lock plate is held in its perpendicular position in the lowered position of the lever. In the third embodiment, shown in Figure 10, elements corresponding to those in the first embodiment are numbered identically with the addition of two hundred. In general the parts of the actuating mechanism that are not described below are arranged similarly to the previous embodiments. The mechanism comprises a foot pedal 260 biased by a helical torsion spring 262 into a rest position as shown in Figure 10. The pedal 260 is connected through a lever 201, a pivot 206, a lobe 216 and a pin 215 to the slot 217 in the drive plate 202. one end of the lock plate 204 is attached to a release cable 263. At the other end of the release cable 263 is a release handle 267. The other end of the lock plate 204 is attached to a release rod 265 which forms part of a pressure release mechanism shown generally as 264. The lock plate 204 can be attached to both the manual and the pressure operated release mechanisms as is show in Figure 10, or these two releasing mechanisms can b considered as alternatives, a single one of them bein attached to either end of the lock plate 204. The pressure release mechanism 264, comprise a release rod 265 attached to a piston 266 house within a cylinder 268 which is connected via a flui conduit 270 (e.g. an air line) to a means for reducin pressure (e.g. a pump) . To operate the parking brake (as viewed i Figure 10) the foot pedal 260 is depressed against th spring.262, in the direction of arrow 261. This cause the left side of drive plate 202 to move upwards of th pin 215 rotates counter-clockwise about pivot 20 within slot 217 which forces the output rod 203 upward tightening the brake cable. Once the brake pedal i depressed it cannot be raised until the lock plate i released. To release the parking brake the driv applies the foot pedal 260 of the parking brake and th lock plate 204 can then be pivoted in the correct sens to release the output rod 203. When the lock plate i released the foot pedal will rise slowly due to th action of the spring 262 against the force applied b the lever. Thus the brake will be released graduall i n a controlled manner due to the tilt of the driv plate 202. The lock plate 204 can be pivoted eithe manually by pulling handle 267 to tighten the releas cable 263, or by reducing the pressure to the pressur system 264 which moves rod 265 upward (as viewed i Figure 10) . The pressure system can be actuate remotely from an electrical switch on the facia, o automatically such as in response to a means fo detecting that the accelerator pedal is depressed Such detection means could operate as follows. Th source of reduced pressure in the pressure means 264 of this embodiment is the pressure differential across the engine manifold. When the car is parked the engine is idle, and there is not a large enough pressure differential across the pressure release mechanism 264 to release the lock plate 204. However, when the accelerator is depressed the pressure differential across the engine manifold increases to its maximum and hence the pressure release mechanism 264 can pivot lock plate 204 to release the parking brake. Figure 12 of the drawings shows a modification of the release button of the embodiment shown in Figure 9. As in the Figure 9 embodiment, the release button 152 is biased by a spring 150 which acts between the button 152 and the lever 101. The release button 152 is not however attached directly to the push rod 110. Instead, the button 152 has a cylindrical " recess 154, in which a further helical compression spring 155 is located. The spring 155 acts between the closed end of the recess 154 and an enlarged head 156 attached to the end of the push rod 110. A circlip 157, seated in a groove in the wall of the recess 154, retains the release button 152 on the rod 110. The arrangement just described provides a "soft-release" feature, whereby the possibility of inadvertent release of the brake through accidental contact with the release button 152 is reduced. This is because, to release the brake mechanism, it is necessary for an operator not only to depress the release button 152 but also to take up the load imposed by the brake mechanism by grasping the lever 101. It is only when the imposed load is taken up in this way that depression of the release button 152 will produce the movement of the push rod 110 necessary for release of the brake mechanism, the force of the spring 155 be sufficient to release the lock plate 4 only when the braking load is relieved by the operator holding the lever 101. It is thus made very difficult for the brake to be released by unintentional contact with the release button alone. Figure 13 of the drawings shows a further modification of the embodiment shown in Figure 9. In this modification, the lock plate 104 is shaped such that, in the rest position of the lever 101, the upper end of the lock plate 104 is in contact with the end of the push rod 110. The lock plate 104 is thus maintained in a position in which it is substantially perpendicular to the axis of the output rod 103. This has the result that, in the rest position of the lever, the lock plate 104 is maintained in a position in which the output rod 103 is free to move through the lock plate aperture and the drive plate aperture. As a result, any movement of the output rod resulting from movement in the linkage to the vehicle's brakes, arising, for example, during transportation or normal use of the vehicle, will simply result in movement of the output rod 103 relative to the remainder of the actuating mechanism. The movement of the brake linkage will have no effect on, for example, the state of adjustment of the actuating mechanism which operates as described above with the lock plate 104 engaging the output rod 103 during raising of the lever 101. Figure 14 of the drawings shows a release damper fitted to the actuating mechanism of Figures 1 to 3. The damper consists of a cylindrical sleeve 60 which is fitted to a boss 62 on the frame 8, the adjacent, inner end of the sleeve 60 being tapere inwards to engage the boss 62. The other, outer end of the sleeve 60 is similarly tapered and engages a plu 64 which seals the outer end of the sleeve, the plug 64 being expanded by a bolt 66 for.this purpose. The output rod 3 is slightly longer than in Figures 1 to 3 and carries a piston 68 which is held in place by the nut 21. The piston 68 has an axial passage 70 which is small in cross-section compared with that of the sleeve 60. The interior of the sleeve 60 forms a sealed space which contains a viscous liquid 72, in which the piston 68 moves upon movement of the output rod 3. During such movement, the liquid 72 flows from one side of the piston to the other through the restricted passage 70. The sleeve and piston thus act as a damper which restrains the movement of the rod during release of the vehicle brake, so that the effect of any strong restoring force in the parking brake mechanism is reduced and progressive release of the brake is achieved. It will be appreciated that the modifications shown in Figures 12 to 14 can be applied to any of the embodiments described in this specification, either separately or in combination. The brake actuating mechanisms described in this specification have several advantages over the prior art. When the lever is raised, the point at which the force is applied to the drive plate (through the slot by the pin) moves, increasing the mechanical ratio of the lever to the drive plate. Thus the work required to produce a given force on the cable reduces as the brake actuator is applied. In any event less work is required to tighten the brake cable compared with a traditional hand brake. This is a particular advantage for drivers who are disabled, elderly or infirm. The reduced mechanical ratios required allow the mechanism to be made smaller, which further reduces its weight and cost. Because the actuating mechanism does not use a ratchet and pawl mechanism, the actuation mechanism is very quiet to operate, operates continuously on the brake cable rather than in steps, and reduces or eliminates the free travel of the actuator before the brake cable tightens. This is to be compared with known handbrakes, which typically apply no work to the brake cable during the first three clicks of the ratchet. The mechani sm c an s el f -adj ust f or variations in brake cable tension and prevent sagging. This reduces maintenance costs and improves the safety and reliability of the actuating mechanism. A wedge or shear pin holds the self adjusting part of the actuating mechanism until the initial operation of the actuating member. Thus assembly of the whole mechanism is made easier. Once the actuating member is applied the self adjusting mechanism optimises the position of the output member whic h remove s the need f or adjustments to be made on the vehicle assembly line . This saves time and reduces the assembly cost of the vehicle . The mechanism can be removed or replaced from the vehicle easily, and can be attached to a variety of different vehicles without modification because the self adjusting mechanism optimises the actuating mechanism for operation in each vehicle . The hand operat ed embodiment s of the invention have the further advantage of being operated in the traditional way , i . e . the lever cannot be lowered without first unlocking the brake . Thus the brake can be operated without additional instruction of the driver . All embodiments of this brake are particularly safe , as when applied the brake cable is held in place by frictional contact with two plates (both the lock plate and the drive plate) . The modi ications described with reference to Figures 12 to 14 provide advantageous features , as already mentioned.

Claims: CLAIMS ; 1. An actuating mechanism for a vehicle parking brake, comprising an actuating member which is movable relative to a mechanism mounting means between a first and a second position, an output member which moves in a brake-applying direction when the actuating member moves from its first to its second position, and moves in a brake-releasing direction when the actuating member moves in the opposite direction, a tiltable apertured drive element, which is connected through a coupling means to the actuating member and couples the actuating member to the output member, the drive element having an aperture through which the output member extends and through which the output member is free to move in a released position of the drive element which is tiltable to engage the output member frictionally in its aperture, a releasable means for holding the output member at least when in a position corresponding to the second position of the actuating member, a release means for the holding means, and a blocking means which prevents movement of the actuating member from its second to its first position prior to release of the holding means. 2. A mechanism according to claim 1, in which resilient biasing means act to assist the engagement of the drive element with the output member. 3. A mechanism according to claim 1 or 2, in which the actuating member is pivotably mounted on the mounting means. 4. A mechanism according to any preceding claim, in which the actuating member is resiliently biased into its first position. 5. A mechanism according to any preceding claim, in which the actuating member is operable by manual means. 6. A mechanism according to any preceding claim, in which the actuating member is a lever. 7. A mechanism according to claim 6, in which the release means is connected to the holding means by a link rod extending longitudinally within the lever. 8. A mechanism according to claim 6 or 7, in which the release means comprises a hand-operable portion of the lever which is adjacent a portion of the lever which is shaped for gripping by hand. 9. A mechanism according to claim 8, in which the release means includes a resilient biasing means which must be overcome by movement of the hand- operable portion relative to the lever, simultaneously with operation of the lever, in order to release the holding means. 10. A mechanism according to any of claims 1 to 5, in which the actuating member comprises a hand operated pistol grip which when pulled operates the actuating member. 11. A mechanism according to any of claims 1 to 5, in which the actuating member comprises a foot operated pedal, biased to extend upwardly and forwardly, which when depressed operates the actuating member. 12. A mechanism according to any preceding claim, in which the release means is operated at a position separated from the actuating member. 13. A mechanism according to any preceding c laim , in which the releas e means c ompris e s a mechanical means . 14. A mechanism according to any preceding c laim, in which the release means comprises an hydraulic means . 15. A mechanism according to any preceding claim, in which the blocking means comprises the cooperation between the drive element, the actuating member and the coupling means, in resisting the movement of the actuating member from its second position prior to release of the holding means. 16. A mechanism according to any preceding claim, in which the coupling means comprises a pivotable connection between the actuating member and the drive element. 17. A mechanism according to claim 16, in which the fulcrum of the pivotable connection is movable. 18. A mechanism according to claim 16 or 17, in which the coupling means comprises a pin mounted on one of the actuating member and the drive element, slidably located in a slot in the other of these. 19. A mechanism according to claim 18, in which the slot extends substantially perpendicular to the direction of movement of the output member in the released position of the drive element. 20. A mechanism according to any preceding claim, in which the output member is slidably mounted on the mounting means. 21. A mechanism according to claim 20, in which the output member is elongate. 22. A mechanism according to any preceding claim, in which the holding means comprises an element which has an aperture through which the output member extends and through which the output member is free to move in the released position of the holding means, the holding element being tiltable to engage the output member frictionally in its aperture. 23. A mechanism according to claim 21, in which the holding element is resiliently biased into a position which prevents the output member from passing through its aperture. 24. A mechanism according to claim 22 or 23, in which the holding element is constrained in its released position when the actuating member is in its first position. . 25. A mechanism according to any preceding claim, including means to sense when the parking brake has been applied, and to activate a remote signalling means to indicate such application. 26. A mechanism according to claim 25, in which the sensing means comprises a switch sensitive to applied force mounted on the output side of the output member. 27. A mechanism according to any preceding claim, in which means are included to compensate for the wear in the brake mechanism of the vehicle, the compensation means comprising means to vary the rest position of the output member. 28. A mechanism according to claim 27, in which the compensation means comprises an abutment element which abuts the mounting means to define the rest position of the mechanism and which is slidable on the output member so as to be brought into contact with a stop on the mounting means when adjustment is necessary, such contact moving the abutment element on the output member to re-define the rest position. 29. A mechanism according to claim 28, in which the sensing means comprises a switch sensitive to the position of the slidable abutment element. 30. A mechanism according to claim 27, in which the compensation means comprises resilient biasing means acting between the output member and the mounting means to apply a compensating force to the output member to define its rest position. 31. A mechanism according to any of claims 27 to 30, in which retaining means are provided to hold the compensation means within the actuating means, when a restraining force is not being applied to the output member. 32. A .mechanism according to any preceding claim, including damping means for damping movement of the output member, at least in its brake-releasing direction. 33. A mechanism according to claim 32, in which the damping means comprises a piston which is movable in a cylinder containing a damping fluid. 34. A mechanism according to claim 33, in which the piston has a bleed passage allowing the damping fluid to pass from one side of the piston to the other during its movement in the cylinder.

Inventors: BUNKER GAVIN, BUNKER TIMOTHY, BUNKER, GAVIN, BUNKER, TIMOTHY
Applicants: BUNKER GAVIN, BUNKER TIMOTHY, SIMPLISTIK DESIGN LTD, SIMPLISTIK DESIGN LIMITED
Application year: 1993
Main classification: B60T7
IPC codes: B60T7