[1]United States Patent Office @@560,969 3,500,969 PLURAL ACTUATED DISC BRAKE MECHANISM AND ADJUSTING MEANS THEREFOR George C. Asher, Northridge, Ohio, assignor of one-balf to Forrest Ray Johnson, New Lebanon, Obio Filed Jan. 17, 1968, Ser. No. 698,525 Int. Cl. F16d 65114, 65138, 55100 U.S. 'Cl. 138-106 7 Claims ABSTRACT OF THE DISCLOSURE A mechanically operated "emergency" brake system for piimarily hydraulically operated disc brakes includes a mechanically applied push rod passing through the hydraulic cylinder and piston. Usin- a caliper, presstire is applied to both sides of a brake disc during both hydraulic and mechanical operation. A self-adjustment is provided by a dra- rin- encircling the hydraulically operated piston. In one embodiment the mechanism for mechanically operating the brakes includes a rot,,ttable lever and a ratchet mechanism for intermittently adjusting the position of the rotatable lever. This invention relates to a brake mechanism and more particularly to a combined hydraulic and mechanical device for applying pressure to both sides of a brake disc. Disc brakes are considered to have niimerous advantages lor use in automobiles and trucks not found in more conventional drum brake mechanisms. However, disc bi-akes have not become widely accepted for varioiis reasons. One of these reasons is that a satisfactory, safe and reasonably inexpensive mechanical or "emergency" brake mechanism has not been developed. Therefore, many United States automobile manufacturers provide disc @ front brakes as optional accessories but only for the wheels of vehicles. Various solutions bave been suggested for emergency or mechanical braking. Some of these solutions involve entirely separate brake mechanisms either acting upon the rear wheel brake discs or upon the vehicle drive shaft. Other solutions have involved the use of relatively complex mechanisms for mechanically applying pressure to the brake discs in the same area as the hydraulically operated mechanisms. The latter solutions typically involve several moving parts and are expensive to manufacture. An object of thif invention is to provide a combined hydraulically and mechanically operated brake mechanism. This is accomplished in accordance with this invention by passing part of a mechanical brake actuating mechanism throiigh the hydraiilic mechanism. Thus, both the hydraulic and the mechanicalmechanisms engage and actuate the same braking members. However, the mechanical mechanism, because it passes through the hydraulic mechanism, does not interfere substantially therewith. The mechanical mechanism may be operated by a conventional emergecny brake cable system of the type having a hand or foot controlled operating member conveniently near the vehicle driver. A further object (>f this invention is to provide a new and improved self-adjustment for disc brakes. This involves the use of a drag ring encircling the hydraulically operated piston, which drag ring is ti.-htly held in the hydraulic cylinder. The drag ring serves as a stop for limiting the maximum separation between the brake disc and the piston. As the brake linings become worn the drag ring is automatically advanced toward the brake disc. Still another object of this invention is to provide an improved self-adjustment means for a rotatina brake acttiating arm or lever. To this end, a ratchet mechanism is Patented Mar. 17, 1970 2 provided for intermittently chan-ina the released position of the brake actuating arm or lever relative to the brake linings as the brake linings become worn. Other objects will become apparent from the following description and the drawings in which: 5 FIGURE 1 is an elevational view with parts in cross section and parts broken away of a vehicle wheel provided with a brake mechanism in accordance with this invention; 10 FIGURE 2 is a transverse cross sectional view of the wheel and part of the brake mechanism as viewed in the direction of arrows 2-2 of FIGURE 1, other parts of the brake mechanism being illustrated in plan view; FIGURE 3 is a perspective view of a brake shoe of a 15 type which may be used with the brake mechanism of this mvention; FIGURE 4 is a perspective view of a caliper forming part of the mechanism of this invention; FIGURE 5 is a transverse cross sectional view of a 20 portion of a modified brake mechanism made in accordance with this invention; FIGURE 6 is an elevational view, with parts in cross section and parts broken away, of a vehicle wheel provided with a brake mechanism of still another embodi25 ment in accordance with this invention; FIGURE 7 is a transverse cross sectional view of part Of the brake mechanism of FIGURE 6 as viewed in the direction of arrows 7-7 tbereof; and FIGURE 8 is a perspective view of a ratcbet member 30 used in the embodiment of FIGURES 6 and 7. Referring to FIGURES 1 and 2, a brake mechanism 10 in accordance with this fnvention is shown in association with a vehicle wheel 12 which may be driven in a conventional manner by a vehicle rear axle (not shown) 35 in a rear axle housing 14. The brake mechanism 10 includes a brake disc 16 which rotates with the wheel 12 and is attached tbereto in any suitable fashion. The brake mechanism 10 further includes a bifurcated brake support member 18 mounted by bolts 20 to an annular flange 22 40 which may be inte@ral with or fixedly connected to the axle housin- 14. As apparent, the axle hotising 14 and accordingly the support member 18 and the elements to be described below mounted thereon do not rotate with the wheel 12 or the brake disc 16. 4'3 As best shown in FIGURE 2, a pair of mountin- bolts 24 pass through apertures in the legs of the support member 18 and mount a cylinder housing 26 thereon which has a cylindrical chamber 28 therein slidably receiving a 50 brake actuating piston 30. It will be observed that the piston 30 is axially slidable along an axis parallel to the axis of rotation of the brake d;sc 16. Also slidably received in the cylindrical chamber 28 is a cylindrical brake engagin- member 32 having a wear pad 34 on its outer end. The brake engaging member 32 and the wear 55 pad 34 project a considerable distance beyond the base of the cylinder housing 26 opening to the cylindrical chamber 28. A ring-shaped dust cover or boot 36 having an internal margin received within an annular groove in the brake engaging member 32 and an outer margin clamped 60 to the base of the cylinder housing 26 by an annular clamp 38 may be used to protect the cylindrical chamber 28 from dust and other foreign matter. With reference to FIGURES 2 and 3, a brake shoe 40 having a friction brake lining 42 is engageable with one 65 side surface of the brake disc 16. The brake shoe 40 has aperatures 44 through upstanding ear portions 46 thereof which slidably receive the mounting bolts 24 for mounting of the brake shoe 40 between the wear pad 34 and 70 the brake disc 16 in such a position that the longitudinal axis of the piston 30 passes centrally through the brake shoe 40 and its lining 42.
[2]3,500,969 3 A pressure fluid such -as a hydraulic brake fluid is introduced to the inner end of the cylindrical chamber 28 through a fluid pressure port 52 and a passageway 54 in the cylinder housing 26 for applying pressure to the brake actuating piston 30. An 0-ring pressure seal 50 located in an annular groove in the piston 30 and engaging the wall of the cylindrical chamber 28 provides a seal cojifining the pressure fluid to the inner end of the cylindrical chamber 28. As apparent, the introduction of fluid under pressure into the cylindrical chamber 28 causes the piston 30 to advance toward the brake shoe 40 whereupon the brake lining 42 is forcibly brought into frictional engagement with one face of the brake disc 16. Release of the fluid under pressure will result in a slight movement of the piston 30 away from the brake shoe 40 and, accordingly, there will be little or no frictional engagement between the brake lining 42 and the surface of the brake disc 16. Fluid under pressure can be supplied to the port 52 by means of a conventional brake fluid distribution system and for this purpose it will be understood that a fluid brake line will be attached to the outer end of the fluid pressure valve 48. For checking the brake system or relieving the brake system of air, a conventional bleeder valve 48 (FIGURE 1) is mounted externally of the housing 26 and connected to the inner end of the cylindrical chamber 28 by a bleeder passageway similar to the passageway 54 illustrated in FIGURE 2. A second brake shoe 56, which may be identical to the brake shoe 40, is slidable on the mounting bolts 24 and has a brake lining 58 edgageable with the opposite face of the bral-,e disc 16. The second brake shoe 56 is forcibly brought into engagement with the brake disc 16 upon movement of the cylinder housing 26 away from the brake disc 16 when fluid under pressure is introduced through the fluid pressure port 52. Referring to FIGURES 2 and 4, confronting faces 60 and 62 in a pair of inverted U-shaped ends 64 of a brake caliper 66 have pairs of aligned apertures 68 and 70 therein also slidably receivin- the mounting bolts 24. The inverted U-shaped ends 64'straddle the two brake shoes 40 and 56 and part Df the housing 26, the arrangement being such that the confronting surfaces 60, 62 engage the rear of the housing 26 and the rear of the brake shoe 56, respectively. A head 72 on one end of each mounting bolt 24 and a nut 74 threaded on the other end of each bolt 24 engage the outer surfaces of the caliper ends 64 and thereby maintain the desired alignment of the housing 26, the brake shoes 40, 56 and the caliper 66. Movement of the cylinder housing 26 away from the brake disc 16 when pressure fluid is introduced therein directly results in a force transmitted by the caliper 66 causing the brake lining 58 to be forcibly brought into frictional engagement with one side of the brake disc 16 at the same time as the brake lim'ng 42 is forcibly brought into frictional engagement with the other side of the brake disc 116, whereupon the rotation of the brake disc 16 is decelerated or braked. To better dissipate heat resulting from the frictional en.-agement of the brake lining 58 with the brake disc 16, the facd of the caliper 66 engaging the brakd shoe 5.6 is provided with several air cooling grooves or passageways 76. In accordance with this invention the brake mechanism 10 also includes mechanically or manually operated means for forcibly applying the brake linings 42 and 58 to the brake disc 16 for use as a,parking brake or for use in, the event the hydraulic system fails. Referring to FIGURE 2, a'push rod 78 is slidably m6unted in both the cylinder h I ousing 26 and the piston 30 with its longitudinal axis coaxial with the chamber 28 and the piston 30. The end of the push rod 78 nearest the brake disc 16 is connected to the cente@ of the c@lindrical brake engaging -member 32. The piish rod 78 could be made integral with th,- brake engaging member 32 or could be press fit therein as illustrated 6r connected thereto in any other suitable fashion. A lever 80 havin,@, a socket at one end 4 thereof recei@ing the ball-shaped exterior end of ihe push rod 78 may be used for mechanically the push rod 78. A mid-portion of the mounted on the housing 26 by a pivot pin 82 passing through the lever 80 and aligned apertures in a clev s 84 threadedly received in a bracket 86 rnounted on the cylinder housing 76. A force applied to the end of the lever 80 remote from the push rod 78 in a counterclockwise direction as indicated by the arrow in FIG. 2, wiH cause 10 the lever 80 to pivot about the pivot pin 82 whereupon the push rod 78 is advanced toward the brake disc 16. The mechanical force so applied to the push rod 78 results in the brake engaging member 32 with its wear pad 34 urging the lining 42 of the brake shoe 40 into forcible 15 frictional engagement with the brake disc 16. Simultaneously, because the lever 80 is mounted on the cylinder housing 26, the cylinder housing 26 will be pulled away from the brake disc 16 whereupon, as in the case of the hydraulic operation described above, the force applied to 20 the cylinder housing 26 will be transmitted by the caliper 66 to the brake shoe 56 so that the brake disc 16 is gripped from both sides by the brake linings 42 and 58. Mechanical force can be applied as indicated by the arrow in FIGURE 2 by means of a conventional manually 25 operated remote brake lever (not shown) convenient to the vehicle driver, and actidg through a conventional brake cable system including a cable 88 connected to the free end of the lever 80. An 0-rin.@ seal 90 located in a groove in the push rod go 78 and acting a,@ainst the surroi-inding wall of the piston 30 and a pressure seal 92 press fit in the housing 26 and acting against the push rod 78 prevent escape of the brake operating fluid from the chamber 30 around the push rod 78. It will be noted that the mechanical aetuation 35 of the brake is essentially independent of the hydraulic operation since the push rod 78 is slidably Mounted in the piston 30. To avoid drawing the piston 30 toward the brake disc 16 upon mechanical actuation, the confronting contacting surfaces of the piston 30 and the brake en40 gaging member 32 shotild not be too smooth or polished. It may even be desirable to reduce the contact area therebetween by cutting grooves in either the end of the piston 30 or the confronting end of the brake engaging member 32. 15 To accommodate wear of the brake linings 42 and 58, a drak ring 102 is located within an annular groove 104 in the periphery of the piston 30, and is pressed by force within the cylindrical chamber 28, The axial thickness of the drag ring 102 is less than the axial width of the 50 groove 104. Becatise of the force fit of the drag ring 102 in the cylindrical chamber 28, a considerable force is required to move the drag ring 102 axially along the chamber 28. The pressure seal 50 is located between the drag ring 102 and the inner end of the cylindrical cham55 ber 28. Durin.@ ordinary operation of the brakes, tberefore, the drag ring 102 is not moved. The drag ring 102 may be a split ring constructicyn and should bave an air gap or aperture therein permitting air to flow freely into and out of the cavity between the split ring 102 and the 60 Pressure seal 50. If the brake linings 42 and 58 become worn to the extent that the face of the groove 104 farthest from the brake disc 16 engages the confronting face of the drag ring 102 as hydraulic pressure is applied, the drag ring 102 will be forcibly advanced toward the brake disc r,5 16. In FIGURE 2 it will be noted that the face of the groove. 104 closest to the brake disc 16 is engaged with the confrontliig face of the drag ring 102. Accordingly, the drag ring 102 acts as a stop which limits'the dist@nce by which the pislon 30 can withdraw from the brake disc 76 16 when no braking pressure is appiied thereto. In the eveht the drag ring 102 is advanced toward the brake disc 16 due to wea'r of the brake lining 42 and 58, the piston 30 will subsequently withdraw by a less distance frc>m the brake disc 16 when braking pressur s released. 7,5 In practice, the brake linings 42 and 58 will be lightly a e to s pivotally
[3]5 engaged with the bi-ake disc 16 even when no braking pressure is applied. Typically, movement of the piston 30 to apply a braking force is approximately 40 thousandths of an inch. For this reason the axial width of the groove 104 (which is exaggerated in FIGURE 2) should be sli-htly more than 40 thotisandths of an inch greater than the axial thickness of the drag ring 102. Because of the self-adjustment feature accommodatin-. brake linin.a wear described above, it will be observed that the brake engaging member 32 will be repositioned . upon niovement of the dra.- ring 102 and, because of its connection to the -member 32, the ptish rod 78 will also be repositioned or advanced toward the brake disc 16 as the brake linin.-s 42 and 58 become worn. This advancement of the push rod 78 is of course away from the lever 80. The pivot ass@mbly shown in FIGURE 2 for pivotally mounting the lever 80 on the cylinder housing 26 is so designated that it can easily be taken apart and the threaded shank of the clevis 84 threadedly advanced deeper into the bracket 86. Upon reassembly, then, the lever 80 will be drawn closer to the brake disc 16 whereupon the socket end of the push rod 78 will again be properly seated. The brake mechanism described above can conveni.cntly be used on the rear wheels of vehicles where both a hydraulic and a mechanical brake operation are desired. The brake mech,-inisms for the front wheels of the vehicle could be quite similar except that the provision for mechanical operation supplementing hydraulic operation nor.,mally would not be made. FIGURE 5 shows a modification of the mechanism for mechanically advancing the brake linings 42 and 58 toward the brake disc 16. In FIGURE 5, parts identical or nearly identical -to those in FIG. 2 have been given the same reference characters. Helical grooves 106 in the Push rod 78 in FIGURE 5 and grooves internally of a sleeve 108 press fit within the housing 26 coaxially with the piston 30 cooperate with ball elements (not shown) to form a "ball screw" connection. A portion 110 of the push rod 78 projecting out of the bousing 26 is of a reduced diameter and of a bexagon-,tl shape for receiving a rotatable brake actuating lever 112 held thereon as by a iiut and washer assembly 114 received on a threaded end portion of ihe push rod 78. As obvious, rotation of the lever 112 about th-. longitudinal axis of the push rod 78 will cause the push rod 78 @to advance the brake engaging member 32 toward the brake disc 16 (not shown in FIGURE 5). A conventional brake cable system can be used to rotate the lever 112. In this case the end of the push rod 78 engagin- the brake en-agin- member 32 is not connected t' there o so -that hydraulic actuation of the brake in FIGURE 5 will not be impeded by the mechanical mechanism. Referring now to FIGURES 6, 7 and 8, a more elaborate and preferred brake actuating mechanism having a lever @which rotates about the longitudinal axis of the push rod 78 and piston 30 is disclosed. Again, in FIGURES 1 throuah 4 parts identical or nearly identical to the parts shown in FIGURES 1 and 2 are referred to by the same number. As shown in FIGURE 7, the outer end of the push rod 78 in this embodiment terminates within a sleeve extension 118 of the housing 26.. As in the embodiment of FIGURES I thro-tigh 4, @the inner end of the push rod 78 is connected to or integral with the brake en.-aging membei- 32. Except for the mee anism for actuating rod 78 it will be appreciated that the operation brake mechai)ism of FIGURES 6 and 7 is ident that of FIGURES 1 through 4. Me@chanical or manual operation of the brake mechanism in th.- embodiment of FIGURES 6 and 7 is accomplished by a brake actuating arm or lever 120 which, as shown in FIGURE 6, may be rotated in a clockwise direction by a brake cable 122 connected thereto by a clevis 124. The brake actuatin.@ arm or lever 120 is normally biased to its "home" or released position by a rettirn spi-ing 126 which, as shown in FIGURE 6, is connected 3)500,969 6 between the ]ever or arm 120 and a bracket 128 mounted in fixed reiation to the housing 26 by the adjacent mounting bolt 24. As shown in FIGURE 7, the brake actuating lever 120 has a cup-shaped end portion 130 axially and rotatably slidable on the sleeve extension 118. It will be obseryed, therefore, that the axis of rotation of the lever 120 is co-incident with the longitudinal axis of the pusti rod 78. Centrally located within the cup-shaped end portion 130 is a drive rod 132 which projects axially into the bore 10 in the end of the sleeve extension 118 for en@@aging and axial.ly driving the push rod 78. The drive rod 132 has a squared end portion 134 received within a square, bore in the lever 120 and therefore rotates therewith. The oppo15 site end of the drive rod 132 may have a wear pad 136 thereon for preventing metal-to-metal contact with the push rod 78. The sleeve extension 118 may be apertured or the brake actuator parts may be sufficiently loosely positioned thereon that air can flow to the cavity formed 20 be@tween the wear pad 136 and push rod 78 when these parts are separated. Rotary to axial motion conversion means in the form of a ball screw arrangement 138 between the drive rod 132 and the inner surface of the sleeve extension 118 25 causes the drive rod 132 to be advanced toward the brake disc 16 as the lever 120 is rotated in a clockwise direction as viewed in FIGURE 6. Accordingly, upon such rotation of the lever 120, the push rod 78 will be advanced toward the brake disc 16. Because of the ball screw connection 30 138, the housing 26 will simultaneously be drawn away from the brake disc 16 and both brake shoes will be forcibly br6ught into engagement with,the brake disc 16 in the manner described in connection with FIGURES 1 throu,-h 4. Advantageously, the force drawing the housing 26 away 35 from the brake disc 16 in the embodiment of FIGURES 6 throu.-h 8 is centered on the housin.- 26. Therefore, there will be an equal force applied to both end portions 64 of the caliper 66. As already mentioned, the axial travel of the push rod 40 78 during ordinary operation would only be about 40 thousandths of an inch and, for this reason, the rotary throw of the lever 120 would only be tbrough a few de@grees when the brakes are manually applied. After the brake linings become worn, however, the throw of the lever 120 necessarily will increase. Also, the end of the 45 push rod 78 will gradually advance toward the brake disc 16 and away from the drive rod 132 as a result of a movement of the drag ring 102 described above in connection with FIGURES 1 throu.@h 4. Therefore, it is desirable that @the home or released position of the lever 120 50 be occasionally adjusted or indexed in a clockwi e direcS tion to bring the drive rod 132 closer to engagement witb the push rod 78. This is accomplished by interposing a rin-,-shaped ratchet member 140 (FIGURES 7 and 8) between the outer end of the sleeve extension 118 and,the 55 confronting surface of the cup-shaped end 130 of the lever 120. The ratchet member 140 freely rotates upon the drive rod 132 but its total rotation is limited by an abutment or stop pin 142 mounted on the end face of the sleeve extension 118 and projecting into a pie-shaped 60 recess 144 in the confronting face of the ratchet m--mber 140. Desirably the ratchet member 140 is so mounted relative to the stop pin 142 that, in the home or released position, the stop pin 142 engages one stop surface 144a of -the recess 144. On the face opposite the recess 144, the 65 ratchet member 140 is provided with an annular array of closely spaced ratchet teeth 146 engaged by a pawl or detent 148 slidable in a bore 150 and biased by a detelit spring 152 in the bore 150 into engagement between a pair of teeth 146. The detent spring 152 and detent 148 70 are confined within ithe bore 150 by a cap washer 154 held against the back surface of the lever 120 by a bolt 156 extending into the end of the drive rod 132. The. bolt 156 also serves to affix the drive rod 132 to the lever 120. During normal operation when the brakes are to be 75 manually ipplied, rotation of the lever 120 is imparted
[4]7 to the ratchet member 140 by the detent 148, whereupon the stop surface 144a rotates away from en,,agement with the stop pin 142. The throw of the lever 120 in applying the brake normally will be insufficient for the stop pin 142 to be engaged by the stop surface 144b. Should howaver, the brake linings be worn to the point th@t th. stop surface 144b engages the stop pin 142, further rotation of the ratchet member 1140 will thereby be prevented and continued rotation of the lever 120 will result in the detent 148 being cammed by the sloping surface of the adjacent tooth 146 into a new position between a different pair of teeth 146. Thus, the relative positions of the ratchet member 140 and the lever 120 will be reset. When the remote brake actuating lever (not shown) is thereafter released and the return spring 126 rotates the brake actuating lever 120 in a counterclockwise direction, as viewed in FIGURE 6, the stop pin 142 will be engaged by the stop surface 144a at a position slightly clockwise of the former released position. The lever 120, accordingly, will then have a new home or released position with the drive rod 132 nearer to the brake disc 16 and such that the subsequent throw of the lever 120 in successive operations of the mechanical brake is lessened. It will be appreciated that the effective strength of the return spring 126 must be less than the effective strength of the detent spring 152 in order to cause the home or released position of the lever 120 to index gradually in a clockwise direction. It will also be understood and it is conventional to provide a brake cable system which can tolerate changes in the position of a lever such as the lever 120. Further, parts (not shown) of the brake cable system may occasionally be adjusted to reduce slack in the cable system as the lever 120 is pro.@ressively indexed by the ratchet mechanism just described. Having thus described my invention, I
