Internal shoe drum brakes

Claim 2

For an internal shoe drum brake comprising a stationary back plate, first and second arcuate shoes carrying friction linings for engagement with a rotatable drum mounted on said back plate and having at least one pair of adjacent shoe ends, and a mechanical actuator linkage for separating said adjacent shoe ends in the application of the brake, said mechanical actuator linkage comprising an angularly movable lever having first and second opposite ends, a pivotal connection between said first end of said lever and said first shoe, a connection between said second end of said lever and brake applying means, a strut acting at an intermediate point in the length of said lever and said second shoe, and means for adjusting automatically braking clearances between said shoes and said drum, the invention comprising a backstop for holding said angularly movable lever in a first retracted position spaced from a second fully retracted position in which said braking clearances are increased, said back stop comprising an insert assembly adapted to be received in an opEning in said back plate and being movable between first and second positions, said assembly having an inner end which in the first position of said assembly is adapted to be engaged normally by said lever to hold the same in its first retracted position, the inner end of said insert assembly being constructed and arranged that in a second position of said assembly the lever is enabled to move to its second fully retracted position, and means externally of said back plate and operatively connected to said insert assembly for effecting movement thereof from its first to its second position.

Claim 3

For an internal shoe drum brake comprising a stationary back plate, first and second arcuate shoes carrying friction linings for engagement with a rotatable drum mounted on said back plate and having at least one pair of adjacent shoe ends, and a mechanical actuator linkage for separating said adjacent shoe ends in the application of the brake, said mechanical actuator linkage comprising an angularly movable lever having first and second opposite ends, a pivotal connection between said first end of said lever and said first shoe, a connection between said second end of said lever and brake applying means, a strut acting at an intermediate point in the length of said lever and said second shoe, and means for adjusting automatically braking clearances between said shoes and said drum, the invention comprising a backstop for holding said angularly movable lever in a first retracted position spaced from a second fully retracted position in which said braking clearances are increased, said back stop comprising an insert assembly adapted to be received in an opening in said back plate and having an inner end adapted to be engaged normally by said lever to hold said lever in said first retracted position, the engagement between said lever and said inner end being so constructed and arranged that said lever is movable into said second fully retracted position upon manipulation of said insert assembly externally of said back plate, wherein said insert assembly comprises a cylindrical sleeve of fixed axial length, an end closure at one end of said sleeve normal to the main axis of said sleeve, said sleeve having in the external wall thereof an annular groove adapted to receive a portion of said back plate which surrounds the said opening when said sleeve is in its position of use, said end closure being normally adapted to be engaged by said lever to hold said lever in said first retracted position, and said sleeve being removable from said back plate to permit said lever to move into said second fully retracted position.

Claim 4

For an internal shoe drum brake comprising a stationary back plate, first and second arcuate shoes carrying friction linings for engagement with a rotatable drum mounted on said back plate and having at least one pair of adjacent shoe ends, and a mechanical actuator linkage for separating said adjacent shoe ends in the application of the brake, said mechanical actuator linkage comprising an angularly movable lever having first and second opposite ends, a pivotal connection between said first end of said lever and said first shoe, a connection between said second end of said lever and brake applying means, a strut acting at an intermediate point in the length of said lever and said second shoe, and means for adjusting automatically braking clearances between said shoes and said drum, the invention comprising a backstop for holding said angularly movable lever in a first retracted position spaced from a second fully retracted position in which said braking clearances are increased, said back stop comprising an insert assembly adapted to be received in an opening in said back plate and having an inner end adapted to be engaged normally by said lever to hold said lever in said first retracted position, the engagement between said lever and said inner end being so constructed and arranged that said lever is movable into said second fully retracted position upon manipulation of said insert assembly externally of said back plate, wherein said insert assembly comprises a cylindrical sleeve of fixed axial length, an end closure at one end of said sleeve normal to the main axis of said sleeve, said sleeve having in the external wall thereof an annular groove adapted to receive a portion of said back plate which surrounds the said opening when said sleeve is in its position of use, said end closure being normally adapted to be engaged by said lever to hold said lever in said first retracted position, and said sleeve being removable from said back plate to permit said lever to move into said second fully retracted position.

Claim 5

For an internal shoe drum brake comprising a stationary back plate, first and second arcuate shoes carrying friction linings for engagement with a rotatable drum mounted on said back plate and having at least one pair of adjacent shoe ends, and a mechanical actuator linkage for separating said adjacent shoe ends in the application of the brake, said mechanical actuator linkage comprising an angularly movable lever having first and second opposite ends, a pivotal connection between said first end of said lever and said first shoe, a connection between said second end of said lever and brake applying means, a strut acting in an intermediate point in the length of said lever and said second shoe, and means for adjusting automatically braking clearances between said shoes and said drum, the invention comprising a back stop for holding said angularly movable lever in a first retracted position spaced from a second fully retracted position in which said braking clearances are increased, said back stop comprising an insert assembly adapted to be received in an opening in said back plate and having an inner end adapted to be engaged normally by said lever to hold said lever in said first retracted position, the engagement between said lever and said inner end being so constructed and arranged that said lever is movable into said second fully retracted position upon manipulation of said insert assembly externally of said back plate, wherein said insert assembly comprises a cylindrical sleeve of fixed axial length, an end closure at one end of said sleeve comprising a first portion normal to the main axis of said sleeve and a second portion inclined inwardly with respect to the first, and said sleeve is provided in the external wall thereof with an annular groove adapted to receive a portion of said back plate surrounding said opening when said sleeve is in its position of use, said first portion of said end closure being normally engaged by said lever to hold said lever in said first retracted position, and said sleeve being rotatable in said back plate to bring said second portion into engagement with said lever whereby the effective length of said sleeve within the brake is decreased and said lever is movable into said second fully retracted position.

Claim 6

For an internal shoe drum brake comprising a stationary back plate, first and second arcuate shoes carrying friction linings for engagement with a rotatable drum mounted on said back plate and having at least one pair of adjacent shoe ends, and a mechanical actuator linkage for separating said adjacent shoe ends in the application of the brake, said mechanical actuator linkage comprising an angularly movable lever having first and second opposite ends, a pivotal connection between said first end of said lever and said first shoe, a connection between said second end of said lever and brake applying means, a strut acting in an intermediate point in the length of said lever and said second shoe, and means for adjusting automatically braking clearances between said shoes and said drum, the invention comprising a back stop for holding said angularly movable lever in a first retracted position spaced from a second fully retracted position in which said braking clearances are increased, said back stop comprising an insert assembly adapted to be received in an opening in said back plate and having an inner end adapted to be engaged normally by said lever to hold said lever in said first retracted position, the engagement between said lever and said inner end being so constructed and arranged that said lever is movable into said second fully retracted position upon manipulation of said insert assembly externally of said back plate, wherein said insert assembly comprises a cylindrical sleeve of fixed axial length, an end closure at one end of said sleeve comprising a first portion normal to the main axis of said sleeve and a second portion inclined inwardly with respect to the first, and said sleeve is provided in the external wall thereof with an annular groove adapted to receive a portion of said back plate surrounding said opening when said sleeve is in its position of use, said first portion of said end closure being normally engaged by said lever to hold said lever in said first retracted position, and said sleeve being rotatable in said back plate to bring said second portion into engagement with said lever whereby the effective length of said sleeve within the brake is decreased and said lever is movable into said second fully retracted position.

Claim 7

A back stop as claimed in claim 2, wherein said sleeve is constructed from a resilient synthetic plastics material.

Claim 8

A back stop as claimed in claim 3, wherein said sleeve is constructed from a resilient synthetic plastic material.

Claim 9

For an internal shoe drum brake comprising a stationary back plate, first and second arcuate shoes carrying friction linings for engagement with a rotatable drum mounted on said back plate and having at least one pair of adjacent shoe ends, and a mechanical actuator linkage for separating said adjacent ends in the application of the brake, said mechanical actuator linkage comprising an angularly movable lever having first and second opposite ends, a pivotal connection between said first end of said lever and said first shoe, a connection between said second end of said lever and brake applying means, a strut acting at an intermediate point in the length of said lever and said second shoe, and means for adjusting automatically braking clearances between said shoes and said drum, the invention comprising a back stop for holding said angularly movable lever in a first retracted position spaced from a second fully retracted position in which said braking clearances are increased, said back stop comprising an insert assembly adapted to be received in an opening in said back plate and having an inner end adapted to be engaged normally by said lever to hold said lever in said first retracted position, the engagement between said lever and said inner end being so constructed and arranged that said lever is movable into said second fully retracted position upon manipulation of said insert assembly externally of said back plate, wherein said insert assembly is telescopic and comprises an outer sleeve adapted to be detachable mounted in said opening in said back plate, and a piston working in said outer sleeve and provided at one end with a head of a diameter greater than the internal diameter of said sleeve, said piston being axially movable in said sleeve between a first position in which said head is spaced from an adjacent end of said sleeve and a second position in which said head is in abutment with said adjacent end of said sleeve, said head being normally adapted to be engaged by said lever to hold said lever in said first retracted position, and said assembly is adapted to be removed from said back plate to permit said lever to move into said second fully retracted position.

Claim 10

For an internal shoe drum brake comprising a stationary back plate, first and second arcuate shoes carrying friction linings for engagement with a rotatable drum mounted on said back plate and having at least one pair of adjacent shoe ends, and a mechanical actuator linkage for separating said adjacent ends in the application of the brake, said mechanical actuator linkage comprising an angularly movable lever having first and second opposite ends, a pivotal connection between said first end of said lever and said first shoe, a connection between said second end of said lever and brake applying means, a strut acting at an intermediate point in the length of said lever and said second shoe, and means for adjusting automatically braking clearances between said shoes and said drum, the invention comprising a back stop for holding said angularly movable lever in a first retracted position spaced from a second fully retracted position in which said braking clearances are increased, said back stop comprising an insert assembly adapted to be received in an opening in said back plate and having an inner end adapted to be engaged normally by said lever to hold said lever in said first retracted position, the engagement between said lever and said inner end being so constructed and arranged that said lever is movable into said second fully retracted position upon manipulation of said insert assembly externally of said back plate, wherein said insert assembly is telescopic and comprises an outer sleeve adapted to be detachable mounted in said opening in said back plate, and a piston working in said outer sleeve and provided at one end with a head of a diameter greater than the internal diameter of said sleeve, said piston being axially movable in said sleeve between a first position in which said head is spaced from an adjacent end of said sleeve and a second position in which said head is in abutment with said adjacent end of said sleeve, said head being normally adapted to be engaged by said lever to hold said lever in said first retracted position, and said assembly is adapted to be removed from said back plate to permit said lever to move into said second fully retracted position.

Claim 11

A back stop as claimed in claim 6, wherein said sleeve and said piston are both constructed from resilient synthetic plastic material.

Claim 12

In an internal shoe drum brake comprising a stationary back plate, first and second arcuate shoes carrying friction linings for engagement with a rotatable drum mounted on said back plate and having at least one pair of adjacent shoe ends, at least one pull-off spring acting between said shoes to urge said shoes away from said drum, and a mechanical actuator linkage for separating said adjacent shoe ends in the application of said brake, said mechanical actuator linkage comprising an angularly movable lever having first and second opposite ends, a pIvotal connection between said first end of said lever and said first shoe, a connection between said second end of said lever and brake applying means, a strut acting between an intermediate point in the length of said lever and said second shoe, and means for adjusting automatically braking clearances between said shoes and said drum, said lever being capable of moving to a fully retracted position so as to afford maximum braking clearance between said shoes and said drum, the invention comprising a back stop for determining said braking clearances in an off position of the brake, said back stop being mounted in said back plate in a first position for engagement with said lever to hold said lever normally in a first partially retracted position spaced from the fully retracted position so as to provide braking clearance less than said maximum clearance, said back stop being constructed and arranged to be movable to a second position enabling said lever to move from its partially retracted position to its fully retracted position under the influence of said pull-off spring, and means external to said back plate for moving said back stop from its first to its second position.

Claim 13

In an internal shoe drum brake comprising a stationary back plate, first and second arcuate shoes carrying friction linings for engagement with a rotatable drum mounted on said back plate and having at least one pair of adjacent shoe ends, at least one pull-off spring acting between said shoes to urge said shoes away from said drum, and a mechanical actuator linkage for separating said adjacent shoe ends in the application of said brake, said mechanical actuator linkage comprising an angularly movable lever having first and second opposite ends, a pIvotal connection between said first end of said lever and said first shoe, a connection between said second end of said lever and brake applying means, a strut acting between an intermediate point in the length of said lever and said second shoe, and means for adjusting automatically braking clearances between said shoes and said drum, said lever being capable of moving to a fully retracted position so as to afford maximum braking clearance between said shoes and said drum, the invention comprising a back stop for determining said braking clearances in an off position of the brake, said back stop being mounted in said back plate in a first position for engagement with said lever to hold said lever normally in a first partially retracted position spaced from the fully retracted position so as to provide braking clearance less than said maximum clearance, said back stop being constructed and arranged to be movable to a second position enabling said lever to move from its partially retracted position to its fully retracted position under the influence of said pull-off spring, and means external to said back plate for moving said back stop from its first to its second position.

Claim 14

In an internal shoe drum brake comprising a stationary back plate, first and second arcuate shoes carrying friction linings for engagement with a rotatable drum mounted on said back plate, and having at least one pair of adjacent shoe ends, at least one pull-off spring acting between said shoes to urge said shoes away from said drum, and a mechanical actuator linkage for separating said adjacent shoe ends in the application of said brake, said mechanical actuator linkage comprising an angularly movable lever having first and second opposite ends, a pivotal connection between said first end of said lever and said first shoe, a connection between said second end of said lever and brake applying means, a strut acting between an intermediate point in the length of said lever and said second shoe, and means for adjusting automatically braking clearances between said shoes and said drum, the invention comprising a back stop for determining said braking clearances in an off position of brake, said back stop being mounted in said back plate for engagement with said lever to hold said lever normally in a first retracted position spaced from a second fully retracted position in which said braking clearances are increased, and said back stop is adapted to be manipulated externally of said back stop whereby said lever is adapted to be moved from said first retracted position into said fully retracted position under the influence of said pull-off spring, wherein said back stop comprises an insert assembly of fixed axial length projecting into the brake through an opening in said back plate in which said insert assembly is removably mounted, and said insert assembly normally engages at its inner end with said angularly movable lever to hold said lever in said first retracted position, and said insert assembly is removable from its mounting in said back plate to permit said lever to move into said second fully retracted position under the influence of said pull-off spring whereby said clearances between said friction linings and said rotatable drum are increased.

Claim 15

In an internal shoe drum brake comprising a stationary back plate, first and second arcuate shoes carrying friction linings for engagement with a rotatable drum mounted on said back plate, and having at least one pair of adjacent shoe ends, at least one pull-off spring acting between said shoes to urge said shoes away from said drum, and a mechanical actuator linkage for separating said adjacent shoe ends in the application of said brake, said mechanical actuator linkage comprising an angularly movable lever having first and second opposite ends, a pivotal connection between said first end of said lever and said first shoe, a connection between said second end of said lever and brake applying means, a strut acting between an intermediate point in the length of said lever and said second shoe, and means for adjusting automatically braking clearances between said shoes and said drum, the invention comprising a back stop for determining said braking clearances in an off position of brake, said back stop being mounted in said back plate for engagement with said lever to hold said lever normally in a first retracted position spaced from a second fully retracted position in which said braking clearances are increased, and said back stop is adapted to be manipulated externally of said back stop whereby said lever is adapted to be moved from said first retracted position into said fully retracted position under the influence of said pull-off spring, wherein said back stop comprises an insert assembly of fixed axial length projecting into the brake through an opening in said back plate in which said insert assembly is removably mounted, and said insert assembly normally engages at its inner end with said angularly movable lever to hold said lever in said first retracted position, and said insert assembly is removable from its mounting in said back plate to permit said lever to move into said second fully retracted position under the influence of said pull-off spring whereby said clearances between said friction linings and said rotatable drum are increased.

Claim 16

In an internal shoe drum brake comprising a stationary back plate, first and second arcuate shoes carrying friction linings for engagement with a rotatable drum mounted on said back plate and having at least one pair of adjacent shoe ends, at least one pull-off spring acting between said shoes to urge said shoes away from said drum, and a mechanical actuator linkage for separating said adjacent shoe ends in the application of said brake, said mechanical actuator linkage comprising an angularly movable lever having first and second opposite ends, a pivotal connection between said first end of said lever and said first shoe, a connection between said second end of said lever and brake applying means, a strut acting between an intermediate point in tHe length of said lever and said second shoe, and means for adjusting automatically braking clearances between said shoes and said drum, the invention comprising a back stop for determining said braking clearances in an off position of brake, said back stop being mounted in said back plate for engagement with said lever to hold said lever normally in a first retracted position spaced from a second fully retracted position in which said braking clearances are increased, and said back stop is adapted to be manipulated externally of said back plate whereby said lever is adapted to be moved from said first retracted position into said fully retracted position under the influence of said pull-off spring, wherein back stop comprises an insert assembly of fixed axial length projecting into said brake through an opening in said back plate in which said insert assembly is mounted, and said insert assembly has an inner end inclined with respect to the axis of said assembly and with which said lever is adapted to engage in the off position of brake, whereby rotation of said insert assembly in the back plate is adapted to alter the effective length of a portion of said assembly within said brake to permit movement of said lever between said first retracted position and said second fully retracted position under the influence of said pull-off spring whereby said clearances between said friction linings and said rotatable drum are increased.

Claim 17

In an internal shoe drum brake comprising a stationary back plate, first and second arcuate shoes carrying friction linings for engagement with a rotatable drum mounted on said back plate and having at least one pair of adjacent shoe ends, at least one pull-off spring acting between said shoes to urge said shoes away from said drum, and a mechanical actuator linkage for separating said adjacent shoe ends in the application of said brake, said mechanical actuator linkage comprising an angularly movable lever having first and second opposite ends, a pivotal connection between said first end of said lever and said first shoe, a connection between said second end of said lever and brake applying means, a strut acting between an intermediate point in tHe length of said lever and said second shoe, and means for adjusting automatically braking clearances between said shoes and said drum, the invention comprising a back stop for determining said braking clearances in an off position of brake, said back stop being mounted in said back plate for engagement with said lever to hold said lever normally in a first retracted position spaced from a second fully retracted position in which said braking clearances are increased, and said back stop is adapted to be manipulated externally of said back plate whereby said lever is adapted to be moved from said first retracted position into said fully retracted position under the influence of said pull-off spring, wherein back stop comprises an insert assembly of fixed axial length projecting into said brake through an opening in said back plate in which said insert assembly is mounted, and said insert assembly has an inner end inclined with respect to the axis of said assembly and with which said lever is adapted to engage in the off position of brake, whereby rotation of said insert assembly in the back plate is adapted to alter the effective length of a portion of said assembly within said brake to permit movement of said lever between said first retracted position and said second fully retracted position under the influence of said pull-off spring whereby said clearances between said friction linings and said rotatable drum are increased.

Claim 18

In an internal shoe drum brake comprising a stationary back plate, first and second arcuate shoes carrying friction linings for engagement with a rotatable drum mounted on said back plate and having at least one pair of adjacent shoe ends, at least one pull-off spring acting between said shoes to urge said shoes away from said drum, and a mechanical actuator linkage for separating said adjacent shoe ends in the application of said brake, said mechanical actuator linkage comprising an angularly movable lever having first and second opposite ends, a pivotal connection between said first end of said lever and said first shoe, a connection between said second end of said lever and brake applying means, a strut acting between an intermediate point in the length of said lever and said second shoe, and means for adjusting automatically braking clearances between said shoes and said drum, the invention comprising a back stop for determining said braking clearances in an off position of brake, said back stop being mounted in said back plate for engagement with said lever to hold said lever normally in a first retracted position spaced from a second fully retracted position in which said braking clearances are increased, and said back stop is adapted to be manipulated externally of said back plate whereby said lever is adapted to be moved from said first retracted position into said fully retracted position under the influence of said pull-off spring, wherein said back stop comprises a telescopic insert assembly comprising an outer sleeve removably mounted in an opening in said back plate, and a piston working in said sleeve and provided at its inner end for engagement with said lever a head of a diameter greater than the internal diameter of said sleeve, and wherein said head is initially spaced from an adjacent inner end of said sleeve and is movable towards said sleeve during initial adjustment of said mechanical actuator linkage until said head engages with said end of said sleeve to define a desired initial adjustment of said mechanical actuator linkage in which said lever is held in said first retracted position, and said telescopic insert assembly is adapted to be removable from its mounting in said back plate to permit said lever to move into the said second fully retracted position under the influence of said pull-off spring acting between the shoes whereby clearances between said friction linings and said rotatable drum are increased.

Claim 19

In an internal shoe drum brake comprising a stationary back plate, first and second arcuate shoes carrying friction linings for engagement with a rotatable drum mounted on said back plate and having at least one pair of adjacent shoe ends, at least one pull-off spring acting between said shoes to urge said shoes away from said drum, and a mechanical actuator linkage for separating said adjacent shoe ends in the application of said brake, said mechanical actuator linkage comprising an angularly movable lever having first and second opposite ends, a pivotal connection between said first end of said lever and said first shoe, a connection between said second end of said lever and brake applying means, a strut acting between an intermediate point in the length of said lever and said second shoe, and means for adjusting automatically braking clearances between said shoes and said drum, the invention comprising a back stop for determining said braking clearances in an off position of brake, said back stop being mounted in said back plate for engagement with said lever to hold said lever normally in a first retracted position spaced from a second fully retracted position in which said braking clearances are increased, and said back stop is adapted to be manipulated externally of said back plate whereby said lever is adapted to be moved from said first retracted position into said fully retracted position under the influence of said pull-off spring, wherein said back stop comprises a telescopic insert assembly comprising an outer sleeve removably mounted in an opening in said back plate, and a piston working in said sleeve and provided at its inner end for engagement with said lever a head of a diameter greater than the internal diameter of said sleeve, and wherein said head is initially spaced from an adjacent inner end of said sleeve and is movable towards said sleeve during initial adjustment of said mechanical actuator linkage until said head engages with said end of said sleeve to define a desired initial adjustment of said mechanical actuator linkage in which said lever is held in said first retracted position, and said telescopic insert assembly is adapted to be removable from its mounting in said back plate to permit said lever to move into the said second fully retracted position under the influence of said pull-off spring acting between the shoes whereby clearances between said friction linings and said rotatable drum are increased.

Claim 20

An internal shoe drum brake as claimed in claim 11, wherein said sleeve is provided with a through bore Of constant diameter provided at an intermediate point in its axial length with an inwardly extending rib member, and said piston includes a land of reduced diameter which works in said rib member and which terminates at one end in a nose portion member located at the inner end of said piston, said nose portion member being of a diameter greater than that of said rib member and said nose portion member being forced through said rib member due to the resilience of at least one of said members to provide a coupling between said sleeve and said piston which limits relative axial movement of said head away from said sleeve.

Claim 21

An internal shoe drum brake as claimed in claim 12, wherein said land extends between said head and said nose portion member, and an annular rib at an intermediate point in the length of said land works in a portion of said through bore disposed between said inner end of the sleeve and said rib member.

Claim 22

An internal shoe drum brake as claimed in claim 12, wherein said land extends between said nose portion member and a shoulder at a step in diameter between said inner end of said land and a large diameter portion terminating at its inner end at said head and working in a portion of said through bore disposed between said inner end of said sleeve and said rib member.

Claim 23

An internal shoe drum brake as claimed in claim 14, wherein a radial rib located at an intermediate point in the length of said head is also forced through said rib member to act as a stop limiting axial movement of said head away from said sleeve.

Claim 24

An internal shoe drum brake as claimed in claim 15, wherein said nose portion member and said radial rib member each has a portion of maximum diameter, and said maximum diameter portions are of substantially equal diameters.

Claim 25

An internal shoe drum brake as claimed in claim 15, wherein a resilient annular member abuts against the free end of said sleeve remote from said head, and said resilient annular member engages at its inner peripheral edge against said land on the side of said radial rib remote from said nose portion member to form a seal between said piston and said bore in said sleeve.

Claim 26

An internal shoe drum brake as claimed in claim 11, wherein said head is of a diameter at least smaller than that of said opening through which at least said head and said inner end of said sleeve are inserted into the brake.

Claim 27

An internal shoe drum brake as claimed in claim 11 wherein said sleeve and said piston are both constructed from one-piece moldings of synthetic plastic materials.