Brake adjusters

Abstract

An automatic adjuster comprises a mechanism of adjustable length operative between a hydraulic brake piston and either a cylinder or an opposed piston. A cam journalled in the cylinder or the opposed piston serves to apply the brake mechanically (hand brake) and act as a stop for the mechanism. The adjustable length mechanism comprises two members, one of which may be the first mentioned piston in interengagement with one another through a non-reversible screw-thread connection. A reversible screw-thread connection or a reversible face cam is provided for turning one member of the mechanism relatively to the other responsively to excessive piston travel to effect adjustment.

I claim: 
     
       1. In a vehicle braking system having an automatic adjuster operative between two relatively movable elements actuable to apply a brake: a mechanism of adjustable length for limiting relative travel between said elements upon brake release and comprising first and second members and a .[.nonreversible.]. .Iadd.non-reversible .Iaddend.screw-thread connection between said members; and means for effecting adjustment and comprising opposed relatively rotatable and axially displaceable means, helically inclined surface means thereon, said opposed means being coaxial with one another and with said non-reversible screw-thread connection and being in interengagement with one another through said helically inclined surface means whereby relative to and fro axial displacement between said opposed means responsive to an excess relative travel between said elements causes relative back and forth rotation between said opposed means, and means for effecting transmission of said relative rotation in one direction only to said first and second members .Iadd., said last mentioned means comprising axial abutment means to frictionally resist relative rotation between said one of said opposed means and one of said members during relative rotation in one direction between said opposed means and axial thrust bearing means acting in the opposite axial direction to said abutment means and freely permitting relative rotation between said one of said opposed means and said one member during relative rotation in the opposite direction between said opposed means.Iaddend.. 
     
     
       2. In a vehicle braking system having a hydraulic actuator, a cam and an automatic adjuster, said hydraulic actuator including a piston and reaction means opposed to said piston, said cam being rotatably journalled in said reaction means, said automatic adjuster being operative between said piston and said cam: a mechanism of adjustable length for limiting relative travel between said piston and said cam upon brake release and comprising first and second members and a nonreversible screw-thread connection between said members; means providing a fixed resting position for said cam which is rotatable therefrom to apply a brake-applying thrust through said mechanism of adjustable length to said piston; and means for effecting adjustment and comprising opposed relatively rotatable and axially displaceable means, helically inclined surface means thereon, said opposed means being in interengagement with one another through said helically inclined surface means whereby relative axial displacement between said opposed means responsive to an excess relative travel betweeen said piston and said cam causes relative rotation between said opposed means and means for transmitting said relative rotation in one direction only to said first and second members. 
     
     
       3. An adjuster according to claim 2 in which said reaction means comprises a cylinder body having a bore in which said piston is slidable. 
     
     
       4. An adjuster according to claim 2 in which said reaction means includes another piston opposed to the first-mentioned piston, said actuator also including a cylinder body having a through-bore, both said pistons being slidable in said through-bore. 
     
     
       5. In a vehicle braking system having a hydraulic actuator and an automatic adjuster operative between two relatively movable elements actuable to apply a brake: a mechanism of adjustable length for limiting relative travel between sad elements upon brake release and comprising a piston of said hydraulic actuator and a spindle having a non-reversible screw-thread connection with said piston; and means for effecting adjustment and comprising opposed relatively rotatable and axially displaceable means, helically inclined surface means thereon, said opposed means being in interengagement with one another through said helically inclined surface means, one of said opposed means comprising an annular member and the other of said opposed means comprising means .[.of.]. .Iadd.on .Iaddend.said spindle, and an abutment and a thrust bearing on one of said elements, said annular member being axially movable between said abutment and said thrust bearing whereby excess relative travel between said elements causes relative rotation between said opposed means, said relative rotation being transmitted in one direction only to said piston and said spindle. 
     
     
       6. An adjuster according to claim 5 in which said abutment includes a yieldable spring means and in which said hydraulic actuator includes means opposed to said piston and having a bore therethrough, said spindle being sealingly slidable in said bore whereby said screw-thread connection is loaded by an axial force arising from the hydraulic pressure applied to the hydraulic actuator. 
     
     
       7. In a vehicle braking system having a hydraulic actuator and an automatic adjuster operative between two relatively movable elements actuable to apply a brake, one of said elements comprising a piston of said hydraulic actuator: a mechanism of adjustable length for limiting relative travel between said elements upon brake release and comprising a spindle and a cap having a non-reversible screw-thread connection with said spindle, said spindle having a head normally in abutment with said piston, said adjuster including means preventing rotation of said cap relative to said piston; and means for effecting adjustment and comprising opposed relatively rotatable and axially displaceable means, helically inclined surface means thereon, said opposed means being in interengagement with one another through said helically inclined surface means whereby relative axial displacement between said opposed means responsive to an excess relative travel between said elements causes relative rotation between said opposed means and means for transmitting said relative rotation in one direction only to said spindle and said cap. 
     
     
       8. An adjuster according to claim 7 in which one of said opposed means comprises an annular member having in abutment thereon, said head of said spindle being movable against said abutment, and the other of said opposed means is on said piston. 
     
     
       9. An adjuster according to claim 8 which further comprises one way clutch means operative between said spindle and said annular member. 
     
     
       10. An adjuster according to claim 9 which further comprises one way clutch means operative between said spindle and said piston. 
     
     
       11. In a vehicle braking system having a hydraulic actuator and an automatic adjuster operative between two relatively movable elements actuable to apply a brake, one of said elements comprising a piston of said hydraulic actuator which includes means opposed to said piston and having a bore therethrough: a mechanism of adjustable length for limiting relative travel between said elements upon brake release and comprising a spindle and a nut having a non-reversible screw-thread connection with said spindle, said nut being disposed for frictional engagement with said piston and said spindle being sealingly slidable in said bore of said hydraulic actuator whereby the spindle is subjected to the hydraulic pressure applied to the piston but in the opposite direction thereto; and means for effecting adjustment and comprising opposed relatively rotatable and axially displaceable means, helically inclined surface means thereon, said opposed means being in interengagement with one another through said helically inclined surface means whereby relative axial displacement between said opposed means responsive to an excess relative travel between said elements causes relative rotation between said opposed means and means for transmitting said relative rotation in one direction only to said spindle and said nut. 
     
     
       12. An adjuster according to claim 11 in which one of said opposed means comprises an annular member having a thrust bearing thereon, said nut being disposed to engage said annular member through said thrust bearing and the other of said opposed means comprises means on said piston, said adjuster including means preventing rotation of said spindle relative to said piston. 
     
     
       13. An adjuster according to claim 11 in which said opposed means respectively comprise means on said nut and means on said piston, and said adjuster includes means permitting rotation of said spindle in one direction only relative to said piston and preventing relative rotation therebetween in an opposite direction. 
     
     
       14. An adjuster as claimed in claim 1 in which .[.said opposed means and.]. said helically inclined surface means .[.thereon comprises.]. .Iadd.on said opposed means comprise .Iaddend.a reversible screw-thread connection. 
     
     
       15. In a vehicle braking system having an automatic adjuster operative between two relatively movable elements actuable to apply a brake: a mechanism of adjustable length for limiting relative travel between said elements upon brake release and comprising first and second members and a non-reversible screw-thread connection between said members; and means for effecting adjustment and comprising a reversible face cam which comprises opposed relatively rotatable and axially displaceable means with mutually co-operating, helically inclined surface means thereon, whereby relative to and fro axial displacement between said opposed means responsive to an excess relative travel between said elements causes relative back and forth rotation between said opposed means, said adjustment effecting means further comprising means for transmitting said relative rotation in one direction only to said first and second members. 
     
     
       16. An adjuster as claimed in claim 15 in which said helically inclined surface means comprise opposed helical surfaces on said opposed means and said reversible face cam includes balls fitted between said opposed helical surfaces. 
     
     
       17. An adjuster according to claim 15 which further comprises a torsion spring operative between said opposed means of said reversible face cam. 
     
     
       18. A disc brake comprising, in combination with an automatic adjuster according to claim 1; a body member and a pair of opposed brake pads adapted to engage opposite faces of a brake disc, said relatively movable elements between which said adjuster is operative being located in said body member and positioned to cooperate with respective ones of said pads. 
     
     
       19. A disc brake comprising, in combination with an adjuster according to claim 4; a yoke slidably mounted on said cylinder body or sliding movement longitudinally thereof and engaged by one of said pistons and a pair of opposed brake pads, one pad being engaged by the other of said pistons and the other pad being engaged by said yoke. 
     
     
       20. A vehicle brake comprising, in combination with an automatic adjuster according to claim 1; a pair of opposed brake pads and a hydraulic actuator comprising a body member having a cylinder bore therein and at least one piston slidable in said bore and constituting one of said relatively movable elements, the other of said elements also being located in said body member, said first and second members and said opposed means all being located within said cylinder bore of said body member, said relatively movable elements being positioned to co-operate with respective one of said pads..[.21. An adjuster according to claim 1 wherein said means for effecting transmission of relative rotation includes means resisting relative rotation between one of said opposed means and one of said elements during relative rotation in one direction between said opposed means and freely permitting relative rotation between said one of said opposed means and said one of said elements during relative rotation in the opposite direction between said opposed means..]. .[.22. An adjuster according to claim 21 wherein the last-mentioned means comprises axial abutment means to frictionally resist relative rotation between said one of said opposed means and said one element and axial thrust bearing means acting in the opposite axial direction to said abutment means and freely permitting relative rotation between said one of said opposed means and said one element..]. .[.23. An adjuster according to claim 21 wherein the last-mentioned means comprises a one way clutch..]. .Iadd. 24. An adjuster according to claim 14 in which said reversible screw-thread connection comprises a multi-start screw-thread connection. .Iaddend..Iadd. 25. An adjuster according to claim 1 in which said opposed means comprise face cam means and said helically inclined surface means comprise mutually cooperating helically inclined surfaces thereon. .Iaddend..Iadd. 26. In a vehicle braking system having an automatic adjuster operative between two relatively movable elements actuable to apply a brake: a mechanism of adjustable length for limiting relative travel between said elements upon brake release and comprising first and second members and a non-reversible screw-thread connection between said members; and means for effecting adjustment and comprising opposed relatively rotatable and axially displaceable means, helically inclined surface means thereon, said opposed means being coaxial with one another and with said non-reversible screw-thread connection and being in interengagement with one another through said helically inclined surface means whereby relative to and fro axial displacement between said opposed means responsive to an excess relative travel between said elements causes relative back and forth rotation between said opposed means, and means for effecting transmission of said relative rotation in one direction only to said first and second members, said last-mentioned means comprising a stepless one way clutch for resisting relative rotation between one of said opposed means and one of said members during relative rotation in one direction between said opposed means and permitting relative rotation between said one of said opposed means and said one of said members during relative rotation in the opposite direction between said opposed means. .Iaddend. .Iadd. 27. An adjuster according to claim 1 in which said axial abutment means includes a conical friction surface. .Iaddend..Iadd. 28. An adjuster according to claim 1 further comprising frictional abutment surfaces between said second member and a second of said elements and spring means operative to urge said first and second members respectively to follow movement of the first and second elements to cause said to and fro axial displacement and operative to hold said frictional abutment surfaces in engagement with one another when the braking system is released, said second element being non-rotatable and said second member being normally rotatable. .Iaddend. .Iadd. 29. In a vehicle braking system having an automatic adjuster operative between two relatively movable elements actuable to apply a brake: a mechanism of adjustable length for limiting relative travel between said elements upon brake release and comprising first and second members and a non-reversible screw-thread connection between said members; and means for effecting adjustment and comprising opposed relatively rotatable and axially displaceable means, helically inclined surface means on said opposed means, said opposed means being in interengagement with one another through said helically inclined surface means and said helically inclined surface means comprising a reversible screw-thread connection between said opposed means, said opposed means being coaxial with one another and with said reversible and non-reversible screw-thread connections, and means for applying to one of said opposed means a first frictional torque which is high relative to that at said reversible screw-thread connection in one direction of rotation and a second frictional torque which is low compared with the frictional torque at said reversible screw-thread connection in the opposite direction of rotation, whereby relative to and fro axial displacement between said opposed means responsive to an excess relative travel between said elements causes relative back and forth rotation between said opposed means but relative rotation in one direction only between said first and second members. .Iaddend..Iadd. 30. In a vehicle braking system having an automatic adjuster operative between two relatively movable elements actuable to apply a brake: a mechanism of adjustable length for limiting relative travel between said elements upon brake release and comprising first and second members and a non-reversible screw-thread connection between said members; and means for effecting adjustment and comprising opposed relatively rotatable and axially displaceable means, helically inclined surface means on said opposed means, said opposed means being in interengagement with one another through said helically inclined surface means and said helically inclined surface means comprising a reversible screw-thread connection between said opposed means, said opposed means being coaxial with one another and with said reversible and non-reversible screw-thread connections, axial clearance determining the desired brake travel being provided at at least one of said screw-thread connections, whereby relative to and fro axial displacement between said opposed means responsive to an excess relative travel between said elements causes relative back and forth rotation between said opposed means, and means for effecting transmission of said relative rotation in one direction only to said first and second members. .Iaddend..Iadd. 31. In a vehicle braking system having an automatic adjuster operative between first and second relatively movable elements actuable to apply a brake: a mechanism of adjustable length for limiting relative travel between said elements upon brake release and comprising spindle and nut members having a non-reversible screw-thread connection therebetween, said spindle and nut members cooperating respectively with said first and second elements; and means for effecting adjustment and comprising opposed relatively rotatable and axially displaceable means operative between said second element and said nut member, helically inclined surface means on said opposed means, said opposed means being annular and coaxial with one another and with said non-reversible screw-thread connection and being in interengagement with one another through said helically inclined surface means, whereby relative to and fro axial displacement between said opposed means responsive to an excess relative travel between said elements causes relative back and forth rotation between said opposed means, and means for effecting transmission of said relative rotation in one direction only to said spindle and nut members. .Iaddend..Iadd. 32. An adjuster according to claim 29 in which said spindle member and said second element are both non-rotatable. .Iaddend..Iadd. 33. In a vehicle braking system having a fluid operated actuator, an automatic adjuster operative between two relatively movable elements of the fluid operated actuator actuable to apply a brake and a mechanical actuator also actuable to apply said brake: a mechanism of adjustable length for limiting relative travel between said elements upon brake release and comprising first and second members and a non-reversible screw-thread connection between said members, said mechanical actuator being arranged in one of said elements and said first and second members being disposed to be engaged by said mechanical actuator and by the other of said elements, respectively; and means for effecting adjustment and comprising opposed relatively rotatable and axially displaceable means associated respectively with said second member and said other element, helically inclined surface means on said opposed means, said opposed means being coaxial with one another and with said non-reversible screw-thread connection and being in interengagement with one another through said helically inclined surface means, whereby relative to and fro axial displacement between said opposed means responsive to an excess relative travel between said elements upon operation of said fluid operated actuator causes relative back and forth rotation between said opposed means, and means for effecting transmission of said relative rotation in one direction only to said first and second members. .Iaddend.