Brake assembly

Abstract

A brake assembly including a pair of brake shoes having adjacent ends pivotally mounted to a support and an actuator disposed between the ends of the brake shoes. The brake shoe webs are recessed at one end to engage a fixed anchor pin. The recess provides an arcuate bearing surface adapted to bear against a portion of the pin and permit pivoting movement of the brake shoe about the pin as the brake is actuated and released. The recess is also so oriented relative to the pin that the recess abuts the pin and prevents the brake shoe from moving away from the anchor pin. The brake assembly also includes an anchor pin having axially spaced cylindrical bearing areas adapted to radially, slidably receive the open ended recesses of a dual web brake shoe and a pair of oppositely facing surfaces extending radially outward at axially spaced locations on the pin to abut the brake shoe webs and prevent the anchor pin from being axially displaced from the support.

I claim: 
     
       1. A brake shoe .Iadd.for a brake assembly of the type including a brake drum and a pair of brake shoes having adjacent ends pivotally mounted to a support and actuating means disposed between the other ends of the brake shoes to pivot said brake shoes into frictional contact with said brake drum thereby developing a circumferential force which complements the force actuating one shoe and a circumferential force opposite to the force actuating the other shoe, said shoe .Iaddend.including at least one continuous rigid web having an open ended recess at one end, said recess being of a width to radially, slidably engage a cylindrical bearing surface of an anchor pin mounted to a support on a vehicle axle .[.housing.]. and being .[.oriented.]. .Iadd.adapted .Iaddend.to pivot about said cylindrical bearing surface of said pin in response to an outwardly directed .Iadd.brake actuating .Iaddend.force applied at the other end of said brake shoe .[.and.]..Iadd., said recess having an inner arcuate surface in bearing abutment with said bearing surface of said pin and being oriented to extend on both sides of a plane passing through the axis of curvature of said bearing surface and parallel to a major axis of said brake assembly which passes through the center of said actuating means, said arcuate surface intersecting said plane on the side of the axis of curvature of said bearing surface remote from said actuating means and said portion of said arcuate surface which lies on the side of said plane opposite to the major part of the web extending between 5° and 30° therebeyond .Iaddend.to .[.abut.]. .Iadd.maintain said arcuate surface in abutment with .Iaddend.said .[.cylindrical.]. bearing surface and prevent .Iadd.substantial .Iaddend.movement .Iadd.other than pivotal movement .Iaddend.of said brake shoe .Iadd.relative to said anchor pin .Iaddend.in response to a .Iadd.drum derived .Iaddend.force tending to move said brake shoe away from said anchor pin.  .[.2. The brake shoe defined by claim 1 wherein said recess is comprised of an inner arcuate bearing surface and a portion of said web extending tangentially from said 
     
     
        arcuate bearing surface at one end thereof..]. 3. The brake shoe defined by claim .[.2.]. .Iadd.1, .Iaddend.wherein said arcuate bearing surface extends through an arc no greater than 180° from end to end.  .[.4. The brake shoe defined by claim 2 wherein said one end of said arcuate bearing surface is disposed to abut said cylindrical surface of said anchor pin in response to a force tending to move said brake shoe away from said anchor pin..]. .[.5. The brake shoe defined by claim 2 wherein said portion of said web extending tangentially from said arcuate bearing surface is disposed to abut said cylindrical bearing surface of said anchor pin in response to a force tending to move said brake shoe away from said anchor pin..]. .[.6. The brake shoe defined by claim 2 wherein said one end of said arcuate bearing surface and said tangentially extending portion of said brake shoe web comprise a portion of said brake shoe web formed to be hooked around and abut said anchor pin in response to a force tending to move said brake shoe away from said anchor pin..]. .[.7. The brake shoe defined by claim 1 wherein said recess is in the form of a slot comprised of an inner arcuate bearing surface having oppositely disposed ends and a mouth portion formed by integral web portions at the opposite ends of said arcuate bearing surface and said slot is so oriented that the web portion at one end of said arcuate bearing surface will abut said anchor pin in response to a force tending to move said brake shoe 
     
     
        away from said anchor pin..]. 8. A rigid brake shoe .Iadd.for a brake assembly of the type including a brake drum and a pair of brake shoes having adjacent ends pivotally mounted to a support and actuating means disposed between the other ends of the brake shoes, said brake shoes .Iaddend.having a dual continuous web structure including an open recess formed at one end of each web, each said recess being laterally aligned with the other recess and comprised of an inner arcuate bearing surface having opposite ends and a mouth portion formed by integral shoe portions at the opposite ends of said arcuate bearing surface, said mouth portions being of a width to .Iadd.radially, .Iaddend.slidably engage said arcuate bearing surfaces with a fixed .Iadd.anchor .Iaddend.pin.Iadd., .Iaddend..[.and.]. said arcuate bearing surfaces being so oriented as to .Iadd.extend on both sides of a plane passing through the axis of curvature of said bearing surfaces and parallel to a major axis of said brake assembly which passes through the center of said actuating means, said bearing surfaces intersecting said plane on the side of said anchor pin remote from said actuating means and said portion of said bearing surface which lies on the side of said plane opposite to the major part of said webs extending between about 5° and 30° therebeyond to .Iaddend.bear against a complementary arcuate surface of said pin .Iadd.and enable the brake shoe to pivot therearound .Iaddend.in response to an outwardly directed .Iadd.actuating .Iaddend.force applied at the other end of said brake shoe with .[.said pin abutting against.]. a portion of said .[.recesses disposed relative to .]. .Iadd.arcuate bearing surfaces being maintained against .Iaddend.said pin to prevent substantial movement of said brake shoe in response to a .Iadd.drum derived .Iaddend.force .Iadd.existing when the shoe engages the drum 
     
     
        .Iaddend.tending to move said brake shoe away from said pin. 9. In a brake assembly for a vehicle wheel, a support, a pair of rigid brake shoes .Iadd.pivoted on said support.Iaddend., a rotary cam actuator disposed between adjacent ends of said brake shoes, an open ended recess formed in the web at the end of each of said brake shoes opposite from said adjacent ends, each said recess being adapted to be radially, slidably mounted to a pin carried by said support, each said recess having an inner arcuate bearing surface disposed to engage a surface portion of said pin on both sides of a plane passing through the center of said pin and parallel to a major axis of said brake assembly which axis passes through the center of said rotary cam with the lower portion of the arcuate bearing surface extending at least 5° .Iadd.and not more than 30° .Iaddend.on the remote side of said pin .[.and .]..Iadd., with the remainder of said arcuate bearing surface extending on the other side of the pin, whereby each said recess is .Iaddend.adapted to abut said pin and prevent .[.further.]. movement .Iadd.other than pivotal movement .Iaddend.of said brake shoe .Iadd.relative to said pin .Iaddend.in response to a .Iadd.drum derived .Iaddend.force tending to move said brake shoe away from said pin .Iadd.when the shoe engages the drum.Iaddend.. .[.10. The brake assembly defined by claim 9 wherein each of said recesses is a slot comprised of an inner arcuate bearing surface and a mouth portion formed by integral brake shoe portions at the opposite ends of said arcuate bearing surfaces and said slot is so oriented that said arcuate bearing surfaces are disposed to engage said pin on both sides of said plane..]. .[.11. In a brake assembly for a vehicle wheel, a support, a pair of rigid brake shoes, a rotatable cam disposed between adjacent ends of said brake shoes, an open ended recess formed in the end of the web of each brake shoe opposite from said adjacent ends, each said recess being adapted to be radially, slidably mounted to a pin carried by said support, each of said recess having an inner arcuate bearing surface disposed to engage a surface portion of said pin and a brake shoe portion extending tangentially outward from at least one end of said arcuate bearing surface, said brake shoe portion extending substantially beyond a radial plane passing through the center of said pin and the axis of rotation of said wheel on the side of said plane remote from a major 
     
     
        portion of said arcuate bearing surface..]. 12. An anchor pin for a vehicle brake assembly comprising an elongate pin having axially spaced cylindrical bearing areas adapted to radially, slidably receive .[.an.]. .Iadd.respective aligned .Iaddend.open ended .[.recess.]. .Iadd.recesses formed in the webs .Iaddend.of a dual web brake shoe.Iadd., said bearing areas being spaced by a cylindrical mounting surface of greater diameter than said bearing areas, .Iaddend.and a pair of oppositely facing .Iadd.radially extending .Iaddend.surfaces integrally formed with said anchor pin .[.and extending radially outward at axially spaced locations on said pin.]. .Iadd.at each end of said mounting surface, said radially extending surfaces being adapted to engage said webs adjacent said recesses .Iaddend.to prevent substantial axial movement of said anchor pin in either direction relative to said dual web brake shoe.  .[.13. The anchor pin defined by claim 12 wherein said axially spaced cylindrical bearing areas are provided by a cylindrical bearing surface at each end of said anchor pin and each of said cylindrical bearing surfaces is bounded at its axially inner end by a radially extending surface of said anchor pin..]. .[.14. The anchor pin defined by claim 12 wherein said axially spaced cylindrical bearing areas are provided by a cylindrical bearing surface intermediate the ends of said anchor pin and said cylindrical bearing surface is bounded at each of its axially outer ends by a radially extending surface of said anchor pin..]. .[.15. An anchor pin for a rotary cam actuated brake assembly comprising an elongate pin having a stepped cylindrical surface including a cylindrical brake shoe bearing surface of one diameter at each end thereof and a cylindrical mounting surface of greater diameter extending a substantial axial distance between said 
     
     
        cylindrical bearing surfaces..]. 16. An anchor pin for a rotary cam actuated brake assembly comprising an elongate pin having a stepped cylindrical surface including a cylindrical mounting surface of one diameter integrally formed at each end thereof and a cylindrical brake shoe bearing surface of smaller diameter extending a substantial axial 
     
     
        distance between said cylindrical mounting surfaces. 17. In a rotary cam actuated brake assembly for a vehicle wheel comprising a support having .[.an.]. .Iadd.a cylindrical .Iaddend.opening therethrough and a pair of brake shoes with each brake shoe having a pair of axially spaced webs, the combination of an elongate member having a first .Iadd.cylindrical .Iaddend.portion adapted to be axially inserted in said support opening .Iadd.for free rotation therein .Iaddend.and a second portion providing axially spaced cylindrical bearing areas, and an open ended recess in each web at one end of each of said brake shoes, the recesses at each of said brake shoe ends being laterally aligned with each other and the width of said recesses being large enough to radially, slidably engage said cylindrical bearing areas but less than the corresponding width of said first portion of said member to prevent said first portion of said member from moving a substantial axial distance between said webs when both of 
     
     
        said recesses are engaged with said cylindrical bearing areas. 18. The rotary cam actuated brake assembly defined by claim 17 wherein said opening is a bore through said support and said first portion of said elongate member is a cylindrical mounting surface intermediate said cylindrical bearing areas and of greater diameter than said cylindrical 
     
     
        bearing areas. 19. The rotary cam actuated brake assembly defined by claim 17 wherein said opening is a bore provided through axially spaced bosses on said support, said first portion of said elongate member is comprised of a pair of axially spaced cylindrical mounting surfaces seated in said bosses and said second portion of said elongate member is a cylindrical brake shoe bearing surface of a diameter less than the diameter of said axially spaced cylindrical mounting surfaces and extends between said 
     
     
        axially spaced cylindrical mounting surfaces. 20. In a brake assembly for a vehicle wheel comprising a support, a pair of brake shoes with each brake shoe having a pair of axially spaced webs, a rotary cam actuator disposed between adjacent ends of said brake shoes, the opposite ends of said brake shoes being mounted for pivotal movement about an anchor pin carried in a cylindrical bore provided through said support and means biasing the adjacent ends of said brake shoes toward said rotary cam, the improvement comprising: an anchor pin having a cylindrical center portion seated in said bore and a cylindrical brake shoe bearing surface at each end of said center portion, each of said cylindrical brake shoe bearing surfaces being of smaller diameter than the diameter of said center portion of said anchor pin, and   an open ended recess in each web at said opposite ends of said brake shoes, the width of said recesses being adapted to radially, slidably engage said cylindrical brake shoe bearing surfaces of said anchor pin but less than the diameter of said center portion of said anchor pin, said webs being spaced to seat said recesses adjacent the axially spaced ends of said cylindrical center portion of said anchor pin to prevent .[.the center portion of.]. said anchor pin from being axially displaced from said bore.   
     
     
        1. The brake assembly defined in claim 20 wherein each of said open ended recesses is comprised of an inner arcuate bearing surface and a portion of said web extending tangentially at one end of said arcuate bearing surface and said recesses are so oriented as to pivot about said cylindrical brake shoe bearing surfaces of said anchor pin in response to an outwardly directed force applied at the other end of said brake shoe and to abut said cylindrical brake shoe bearing surfaces and prevent further movement of said brake shoe in response to a force tending to move said brake shoe 
     
     
        away from said anchor pin. 22. In a brake assembly for a vehicle wheel comprising a support, a pair of brake shoes with each brake shoe having a pair of axially spaced webs, a rotary cam actuator disposed between adjacent ends of said brake shoes, the opposite ends of said brake shoes being mounted for pivotal movement about an anchor pin carried in a pair of axially aligned bores provided through axially spaced portions of said support and means biasing the adjacent ends of said brake shoes toward said rotary cam, the improvement comprising: an anchor pin having a cylindrical mounting surface at each end thereof and a cylindrical brake shoe bearing surface intermediate said mounting surfaces, each of said cylindrical mounting surfaces being of a diameter larger than the diameter of said cylindrical brake shoe bearing surface and carried in one of said axially aligned bores, and   an open ended recess in each web at said opposite ends of said brake shoes, the width of said recesses being adapted to radially, slidably engage said cylindrical brake shoe bearing surface of said anchor pin but less than the diameter of said cylindrical mounting surfaces of said anchor pin, said webs being spaced to seat said recesses adjacent said mounting surfaces to prevent said mounting surfaces from being displaced from said   
     
     
        axially aligned bores. 23. The brake assembly defined in claim 22 wherein each of said open ended recesses is comprised of an inner arcuate bearing surface and a portion of said web extending tangentially at one end of said arcuate bearing surface and said recesses are so oriented as to pivot about said cylindrical brake shoe bearing surface of said anchor pin in response to an outwardly directed force applied to the other end of said brake shoe and to abut said cylindrical brake shoe bearing surface and prevent further movement of said brake shoe in response to a force tending to move said brake shoe away from said anchor pin. .Iadd. 24. In a vehicle brake assembly wherein a wheel mounted drum surrounds a pair of brake shoes having longitudinally continuous rigid webs pivoted at one end on an anchor means having at least one cylindrical anchor pin surface and their other ends in operative association with a rotary cam actuator adapted to displace said shoes from a retracted position where return springs hold them away from frictional contact with the drum and a braking position in contact with the drum thereby developing a circumferential force which complements the force actuating one shoe and a circumferential force opposite to the force actuating the other shoe; the improvement which comprises means providing an open ended recess at said one end of each brake shoe of such width as to radially slidably fit upon said cylindrical anchor pin surface, said recess having an inner arcuate bearing surface portion abutting in full surface engagement with said cylindrical anchor pin surface in said brake retracted position and said recess being so oriented that a portion of said arcuate bearing surface of the recess extends to engage said anchor pin surface not more than 30° at one side of the intersection of that surface with a plane passing through the center of said anchor pin surface and parallel to a major axis of said brake assembly which passes through the axis of said rotary cam and the remainder of said arcuate surface of the recess engages said anchor pin surface at the other side of said plane whereby when said brake shoes are pivotally displaced from retracted position into braking engagement with the rotating drum said arcuate recess surface will maintain such effective abutment with said cylindrical anchor pin surface as to prevent movement of said brake shoes away from said anchor pin in response to a force derived from engagement of said brake shoes with the drum and tending to move said brake shoes relative to said anchor pin. .Iaddend. .Iadd. 25. A brake shoe adapted for coaction with a surrounding rotatable wheel mounted drum in a brake assembly, said shoe having a continuous rigid web, one end of which is adapted to be operatively connected to an actuator and the other end of which is formed with an open ended recess providing an arcuate surface adapted for bearing engagement with a cylindrical anchor pin surface and a straight edge extending from the end of said arcuate surface that is furthest from the end of the web connected to said actuator, said recess being of such width as to be slidably engaged with said anchor pin surface and said recess being so inclined that, in assembly, said edge extends at an angle between 60° and 85° relative to a plane parallel to a diameter of said wheel passing through the center of said actuator. .Iaddend. .Iadd. 26. A brake shoe adapted for coaction with a surrounding rotatable wheel mounted drum, said shoe having a continuous rigid web, one end of which is adapted to be operatively connected to an actuator and the other end of which is formed with an open ended recess providing an arcuate surface adapted for bearing engagement with a cylindrical anchor pin surface and parallel straight edges extending from the ends of said arcuate surface, said recess being of such width as to be slidably engaged with said anchor pin and said recess being so inclined that, in assembly, said edges extend at an angle between 60° and 85° relative to a plane parallel to a diameter of said wheel passing through the center of said actuator, whereby, upon actuation of said brake, said arcuate surface is maintained in engagement with said anchor pin surface. .Iaddend. .Iadd. 27. A brake shoe adapted for coaction with a surrounding rotatable wheel mounted drum, said shoe having a continuous rigid web, one end of which is adapted to be operatively connected to a rotary cam actuator and the other end of which is formed with an open ended recess providing an arcuate surface adapted for bearing engagement with a cylindrical anchor pin surface and parallel straight edges extending from the ends of said arcuate surface, said recess being of such width as to be slidably engaged with said anchor pin surface and said recess being so inclined that, in assembly, said edges extend at an angle between 60° and 85° relative to a plane parallel to a diameter of said wheel passing through the axis of said rotary cam actuator, whereby, upon actuation of said brake, said arcuate surface is maintained in engagement with said anchor pin surface. .Iaddend..Iadd. 28. An anchor pin for a vehicle brake assembly comprising an elongate pin having axially spaced cylindrical bearing areas adapted to radially slidably receive respective open-ended recesses formed in the webs of a dual web brake shoe, said bearing areas being provided by a cylindrical bearing surface intermediate the ends of said anchor pin and a pair of oppositely facing radial surfaces integrally formed with said anchor pin at the opposite ends of said cylindrical bearing surface, said surfaces being adapted to engage said webs adjacent said recesses to prevent substantial axial movement of said anchor pin in either direction relative to said dual brake shoe. .Iaddend.