A VEHICLE BRAKE SELF ADJUSTMENT SYSTEM

Abstract: A vehicle brake adjustment device (11) consists of a vehicle brake having a stator (1), an actuation system (3), a rotor (8) and linings (7); the adjustment of linings (7) relative to rotor (8) being by means of a washer or C clip (14) or spring (104) unidirectionally binding on a shaft (13), in association with a disengagement limitation device (22, 23). A handbrake (27) may be incorporated in the vehicle brake which acts through the binder (14) and shaft (13). A further version for pedal and motor cycles which uses cable actuation is also described.

Description: A Vehicle Brake Self Adjustment System This invention relates to vehicle brakes that have a stator connected to a chassis, an actuator that energises and de-energises the brake, a sacrificial friction member (hereinafter called a lining) , a rotor that is connected to a wheel, and arranged such that energising the actuator has the action of bringing the lining into contact with the rotor, the fi*ictional torque produced and the actuator, reacting against the stator. There are a large number of brakes of the type described, on the more sophisticated brakes, various types of adjustment devices (either manually operated at servicing intervals or automatically operated throughout the life of the linings ) are provided to obviate the necessity of the actuator moving through a stroke equivalent to the worn part of the lining on each energisation of the brake. The actuator normally consists of a hydraulically operated piston or a wedge or a lever or a cam or a cable which has a potential stroke of the possible lining wear. Devices are included to ensure that on de-energising the actuator, the lining is positively disengaged from the rotor , the disengagement device being an energy store such as a spring or a gravity operated device. The disengagement energy may be obtained by the rotor running out of a true relationship when the brake components are strained by the motion of the vehicle. This invention is simpler and more reliable than self adjustment devices presently known. According to the present invention, an energy storing device, such as a first spring, either impells the lining away from the rotor, or creates a space such that mechanical strains can knock the lining away from the rotor, and where the lining is connected to a shaft such that there is a limited range of movement between lining and shaft (this limited movement is usually between .01mm and 1mm and relates to the disengagement between lining and rotor) and where the shaft is associated with a device that unidirectionally binds on the shaft, such as a washer or a C clip (hereinafter referred to as a binder) at a slight angle to the normal plane of the shaft and where the shaft and binder arrangement (hereinafter referred to as a ratchet) can advance the lining towards the rotor, but can only retreat the lining beyond the disengagement distance when the ratchet is manually manipulated at servicing intervals, and where a second spring ensures that the ratchet does not advance towards the rotor unless impelled by the actuator, and where energising the actuator brings the lining into frictional contact with the rotor, and, if the lining is worn, advances the ratchet such that when the actuator is subsequently de-energised, the lining is not permitted to retreat from the rotor for more than the limited movement. In a preferred embodiment, the ratchet comprises a small diameter hardened shaft surrounded by a thin hardened close fitting washer, where one edge of the washer acts on a projection and is kept in contact with the projection by a third spring. When a handbrake is fitted, the ratchet must take high loads, and a large shaft and thick washer are necessary. The invention will now be described in greater detail with reference to the following figures which are used for the purpose of example only in which; Figure 1 shows a side view of a drum brake with the rotor partially removed. Figure 2 shows an enlarged view of the ratchet system of figure 1. Figure 3 shows an enlargement of cross section AA of figure 1. Figure 4 shows the head of a servicing tool and part of figure 2. Figure 5 shows a side view of a drum brake incorporating a handbrake. Figure 6 * shows an enlargement of cross section BB of figure 5. Figure 7 shows an enlargement of cross section CC of figure 5. Figure 8 shows a side view of a disc brake. Figure 9 shows an enlargement of cross section DD of figure 8. Figure 10 shows an enlargement of the ratchet system of figure 9. Figure 11 shows a cross section of a disc brake incorporating a hand brake. Figure 12 shows an enlargement of the ratchet system of figure 11. Figure 13 shows a pedal cycle brake. Figure 14 shows an enlargement of the ratchet system of figure 13. Figure 15 shows a cross section of a motor cycle disc brake. Figure 16 shows an alternative to the adjuster of figure 14. It will be noted that like reference numbers refer to like components throughout the specification. Referring to figure 1 in which a stator 1 mounted on a vehicle chassis by mounting holes 2 and having a hydraulic actuator 3 fixed to stator 1 has piston 4 which operates on web 5 transmitting force via•platform 6 t lining 7 and frictionally contacting rotor 8 (part shown) . Spring 9 pull webs 5 and therefore lining 7 away from rotor 8. Web 5 reacts on abutment 10 which is fixed to stator 1. Adjuster 11 ensures that linings 5 7 are maintained within a predetermined distance of rotor 8 throughout their useful life. Hold down device 12 ensures that platform 6 is slideably in contact with stator 1. Referring to figure 2 showing an enlarged view of adjuster 11. Shaft 13 is slotted over web 5 and surrounded by binder 14 (having a close fittin 10 centre hole) and which is loaded against projection 15 of web 5 by sprin 16 and reacts against abutment 17 of shaft 13. Fixed pin 18 through web 5 maintains adjuster 11 in position gravitationally, and allows shaft 13 to slide when adjusting. Spring 19 is stronger than spring 16 and is located between washer 20 (which abuts on web 5) and abutment 21 so that when the 15 forces due to springs 9 are removed, spring 19 does not allow shaft 13 to move relative to binder 14. Referring to figure 3 pin 22 is a good fit in shaft 13 and passes throug slot 23 in web 5, and ^ is retained by split pin 24. When the actuator 3 is unpressurised, pin 22 contacts edge 23a of slot 23, and prevents further 20 disengagement of linings 7 from rotor 8. On pressurisation of actuator 3, forces in spring 9 are overcome, web 5 moves towards rotor 8, and, (if linings are worn) , pin 22 contacts edge 23b of slot 23 and moves shaft 13 relative to binder 14. Depressurisation of actuator 3 permits springs 9 t return web 5 to a new position determined by pin 22 contacting edge 23a 25 of slot 23. It is theoretically possible to have springs 16 and 19 of equal value, or to remove abutments 17 and 21 and have a single spring (not shown), but vibrations could disturb shaft 13, and the arrangement shown is preferred. Referring to figure 4, it is convenient to stop binder 14 binding on shaf 30 13 and allow web 5 to revert to minimal adjustment position before attempting to remove rotor 8. Slot 25 is provided in stator 1 which covers possible positions of shaft 13, projection 15, and binder 14 throughout the life of lining 7. Insertion of tool 26 between web 5 and binder 14 will release the binding action of binder 14, and spring 9 will 35 return lining 7 to minimal position. Hole 25 can be stopped with a grommet (not shown) when not in use. It will be noted that the vehicle brake illustrated is a leading- trailing brake. The adjustment principle descrxbed is suitable for twin leading shoe brakes and twin trailing shoe brakes (where an adjuster for each shoe is advisable) or for duo servo or uni servo brakes (where a single adjuster is sufficient). The method of actuation is irrelevant and the hydraulic cylinder illustrated is for example only. Referring to figure 5 which shows the vehicle brake of figure 1 with a handbrake fitted. The adjuster 11 is between web 5 and handbrake lever 27. The handbrake is actuated by cable 28, which is sheathed by cable outer 29 (reacting on stator 1), and which passes through stator 1 and is connected to lever 27 by passing nipple 30 through a suitable hole (not shown). Spring 31 is located between stator 1 and lever 27 and ensures that lever 27 abuts against stop 32 of stator 1 when the handbrake is not in use. Lever 27 is pivoted on web 5 by pin 33. Referring to figure 6 which shows an enlarged view of section BB of figure 5. Tube 34 is slotted over web 5 and held in pivoting position by pin 35, and retained by washer 36 and split pin 37. Shaft 38 is surrounded by binder 39 which is loaded against projection 40 of tube 34 by spring 41 and unidirectionally binds on shaft 38, spring 41 reacts against abutment 42 of shaft 38... Referring to figure 7 which shows an enlarged view of section CC of figure 5. Spring 43 is stronger than spring 41 (figure 6) and is located around shaft 38 between washer 45 (which abuts on lever 27) and abutment 46, so that when the forces due to springs 9 are relieved, spring 43 does not allow shaft 38 to move relative to binder 39. Pin 47 is a good fit in shaft 38 and passes through slot 48 in lever 27, and is retained by washer 49 and split pin 50. When cable 28 is not actuated, pin 47 contacts edge 48a of slot 48, and prevents further disengagement of linings 7 from rotor 8.On actuation of cable 28, lever 27 pivots about pin 33, forces in springs 9 are overcome, and pin 47 contacts edge 48a of slot 48 and web 5 moves towards rotor 8. Pin 47 will take the handbrake forces and should be substantial. Operating actuator 3 will adjust the position of binder 39 on shaft 38 as previously described in figures 1 to 4. It is necessary for the forces in springs 9 to be relieved and contact made by pin 47 on edge 48b before adjustment of binder 39 on shaft 38 can take place. The removal of worn linings is as previously described for figures 1 to 4. It will be noted that the vehicle brake illustrated is leading- trailing brake. The handbrake adjustment principle described is also suitable for duo servo or uniservo brakes. 5 Referring to figure 8 in which a stator 51 is mounted on a chassis by mounting holes 52 and having hydraulic actuator 53 fixed to stator 51. Rotor 54 is fixed to a wheel (not shown) by mounting, pins 55. Referring to figure 9, the actuator 53 has piston 56 and is sealed by dynamic seal 57. Seal 57 also serves as a spring to retreat piston 56 10 from rotor 54 when the actuator is de-energised. Adjuster 58 ensures that linings 59 and 60(integrally bonded with lining backing plates 61 and 62) are maintained within a predetermined distance of rotor 54 throughout their useful life. Referring to figure 10, shaft 63 is a free fit in holes through plates 61 15 and 62, the holes may have nylon inserts 64 and 65, to inhibit sticking of shaft 63. Compression spring 66 between plates 61 and circlip 67 normally ensures that plates 61 and 62 do not advance towards rotor 54 unless impelled by actuator 53. The free distance between circlips 67 and 68 is related to the disengagement of linings 59 and 60 from 20 rotor 54. Binder 69 surrounds shaft 63 and is loaded against projection 70 of insert 64 by spring 71 and reacts against washer 72 and split pin 73. On pressurisa ±gn of actuator 53, forces in seal 57 are overcome and plate 62 moves towards rotor 54, and, (if the linings are worn), plate 62 contacts circlip 67 and moves shaft 63 relative to binder 69. 25 Depressurisation of actuator 53 permits seal 57 to retreat piston 56 from rotor 54 and the strains in the brake components can knock the linings back until plate 62 contacts circlip 68. Referring to figure 11, adjuster 58 of figure 9 has been replaced with a combined adjuster and handbrake. The handbrake forces need to be 30 approximately along the centre line of linings 59 and 60, and a scissors arrangement operates about each side of actuator 53, making spring loaded contact with plates 61 and 62 at a total of four points by means of springs 74 and 75. Pivot 76 is located in stator 51 and legs 77 and 78 can be pulled together by the combined handbrake and adjuster 3579. Referring to figure 12 which shows an enlargement of adjuster 79 of of figure 11. Shaft 80 is attached to cable inner 81 by screwing into nipple 82. Spacer 83 is located between leg 78 and cable outer 84, gap 85 relates to the disengagement of linings 59 and 60 from rotor 54. 5 Modification is required to the fixed circlip S7 of figure 10 to allow the application of the handbrake forces to plates 61 and 62. A slot 86 is provided in shaft 80 to give limited movement to clip 87 such that when the handbrake forces are applied 'clip 87 moves along slot 86. Adjustment of shaft 80 through binder 69 takes place on energisation of actuator 53 10 as described for figure 10. Referring to figure 13 , a cycle tyre 88 is supported by a rotor or rim 89 and revolves about a hub (not shown). Stator pin 90 is rigidly attached to the chassis of the cycle and pivotally supports two arms 91 and 92. Linings 93 are normally kept out of contact with rotor 89 by compression 15 spring 94. Linings 93 can be brought into frictional contact with rotor 89 by energising cable 95 and adjustment for wear is by means of device 96. Referring to figure 14, cable 95 passes through a hole in binder 97, through a suitable slot (not shown) in arm 91,and recess 98 retains nipple 99. Cable outer 100 abuts on binder 97. Adjuster shaft 91 pivot on pin 102 20 (located through arm 92), passes through a close fitting hole in binder 97 and through a suitably shaped hole in arm 91 that permits the change in angular relationship between arms 91 and 92. Compression spring 103 keeps binder 97 in unidirectionally binding contact with shaft 101. Spring 104 has a number of coils 104a tightly wound around shaft 101, such that 25 spring 94 is not strong enough to move shaft 101 relative to spring 104, and arm 91 normally abuts coil 104b of spring 104. The operation is as follows; energisation of cable 95 pulls arm 91 and lining 93 into contact with rotor 89, similarly, outer cable 100 reacts on binder 97, shaft 101 and arm 92 to bring opposing lining 93 into contact with rotor 89. Shaft 30 101 moves through arm 91 and, (if the linings are worn) overcomes frictional forces due to tightly wound coils 104a, and moves relative to spring 104. De-energisation of cable 95 allows spring 94 to push arms 91 and 92 away from rotor 109 until coil 104b contacts arm 91. Further retreat of arms 91 and 92 is prevented by friction of coils 104a on shaft 35101, and the tendency of coils 104a to become slightly smaller when coil 104b is pulled. Spring 103 moves binder 97 relative to shaft 101 if lining wear has taken place. The free distance between binder 97 and arm 91 allows for wear on linings 93 during a single stop, plus disengagement clearances, plus mechanical deflections, plus an appropriat safety factor. Spring 104 may be replaced with an elastomeric grommet 5 (not shown) which is a tight frictional fit on shaft 101 (such that the force of spring 94 does not overcome the frictional forces), and which is a loose fit in arm 91, allowing lateral displacement of the grommet relative to arm 91 for a distance that is related to lining disengagement. It should be noted that spring 104 performs the function of binders 14, 10 39, and 69 (figures 2,6,10 and 12) and binder 97 performs the function of actuators 3 and 53 (figures 1,5,9 and 11). The arrangement described is suitable for use in the caliper of figure 11. Referring to figure 15, rotor 105 revolves between linings 106 , integrall bonded to plates 107, which are pivoted to stator 108 by pins 109. 15 Springs 110 retract linings 106 when cable 111 is de-energised. The operation is as previously described for the adjuster of figure 14. Referring to figure 16 which shows a variant of figure 14. Springs 103 an 104 (figure 14) are replaced by assymetric grommet 113, having a suitable projection 114 to allow binder 115 to unidirectionally bind on shaft 101. 20 Spring 116 abuts on circlip 117 and keeps binder 115 in contact with projection 114. Spring 118 is stronger than spring 116 and ensures that shaft 101 does not move relative to binder 115 unless impelled by cable 95 The operation is as previously described for figure 14, except that the binding of binder 115 replaces the friction of coils 104a (figure 14), and 25 the edges of grommet 113 (113a and 113b) replace coils 104a and 104b of spring 104 (figure 14). Assymetric grommet 113 should be a very loose fit in arm 91 to ensure that changes in the angular relationship of arms 91 and 92 do not cause binding on arm 91. 30.

Claims: Claims: 1. A vehicle brake self adjustment system (11) where a vehicle brake consists of a rotor (8) connected to a wheel; a stator (1) connected to a chassis by mounting points (2) ; a lining (7) ; an actuator (3) 5 which brings said lining (7) into frictional contact with said rotor (8); an energy storing device (9) to disengage said lining (7) from said rotor (8); and characterised in that said system (11) is in the form of a shaft (13) and a binder (14) that unidirectionally binds on said shaft (13), and said system (11) has a means which permits limited 10 disengagement (22,23) of said lining (7) from said rotor (8). 2. A claim according to claim 1 where a spring (19) ensures that said shaft (13) does not move relative to said binder (14) unless impelled by said actuator (3). 15 3. A claim according to claims 1 and 2 where said limited disengagement (22,23) relates to the limits (23a,23b) of a hole or slot (23) or restrictions fixed in said shaft (13). 204. A claim according to claims 1,2 and 3 where a handbrake (27) has a separate actuation system (28,29) to impel said lining (7) onto said rotor (8) and where said handbrake (27) operates through said system (11). 255. A claim according to claims 1,2,3 and 4 where said binder (14) can be held in a non-binding position for servicing purposes by the use of a special tool (26). 6. A claim according to claim 1 where said actuator (95) acts through 30 a second binder (97) and said shaft (101) , — y — 7. A claim according to claims 1 and 6 where said limited disengagement relates to the edges of a gap (104a,104b) formed by a component (104) which can move relative to said shaft (101). 8. A vehicle brake adjustment system (11) substantially as described herein with reference to figures 1 to 3 and 5 to 7 and 8 to 10 and 11 to 12 and 13 to 16 of the accompanying drawings. 9. A vehicle brake adjustment system (11) servicing tool (26) substantially as described herein with reference to figure 4 of the accompanying drawings.

Inventors: POWELL GEORGE BERTRAM, POWELL, GEORGE, BERTRAM
Applicants: POWELL GEORGE BERTRAM, POWELL, GEORGE, BERTRAM
Application year: 1987
Main classification: F16D65
IPC codes: F16D65