Note: Descriptions are shown in the official language in which they were submitted.
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BRAKE WEAR COMPENSATOR
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to disc brakes and more particularly to
improvements for wear compensation in large area contact disc brakes for
vehicles.
2. Description of the Prior Art
The disc brake of the present invention is a disc brake of the type described
in United States patent No. 5,330,034 issued July 19, 1994 and United States
patent RE 35055 issued October 10, 1995 referring to full annular disc brakes
for large
vehicles such as trucks. The concept of the full annular disc brake is also
proposed for
automobiles and light trucks and the applicant describes a structure of a full
annular disc
brake for such vehicles in the applicant's PCT patent application
PCT/CA97/01014,
entitled IMPROVED DISC BRAKE ASSEMBLY and published as W098/29671 in the
inventor's name, Rancourt on July 9, 1998.
The disc brake assembly for a vehicle as described in the applicant's PCT
application W098/29671 generally includes a housing mounted to the vehicle, an
annular rotor disc within the housing, and means for mounting the disc to the
wheel.
The disc has at least a first radial planar annular friction surface and the
housing
includes a first annular brake shoe provided adjacent to the first friction
surface of the
2 0 disc. The brake shoe is axially moveable towards and away from the first
friction
surface and is restrained from rotating with the disc. An annular fluid
expandable
bladder extends between the first annular brake shoe and a radial wall of the
housing, so
that upon expansion of the bladder the first brake shoe moves axially to
frictionally
engage the first friction surface of the disc. There is a means provided for
disengaging
2 5 the first brake shoe from frictional contact with the first friction
surface of the rotor disc.
However, the travel distance of the brake shoe increases as a result of the
wearing of the
friction surface of the disc and the brake shoe. The longer distance the brake
shoe
travels, the more time is needed to react to a brake action and fully stop the
vehicle.
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Therefore, the travel distance of the brake shoe must be adjusted to an
acceptable range
when the wearing exceeds the range.
Methods of compensation for wear of disc brakes are well known and, for
example, are described in United States patent 5,660,250 issued to Treude on
August 26, 1997 and United States patent 5,433,299 issued to Sundstrom et al
on
July 18, 1995: The applicant in his Canadian patent application 2,289,812
filed
November 1 S, 1999, describes a friction plate return mechanism which is
adapted to be
automatically adjusted to compensate for the increase in the travel distance
of the brake
shoe in brake actions.
l0 Nevertheless, the industry is continuously making efforts to improve wear
compensation mechanisms, to better serve different types of disc brakes,
multiple disc
brakes in particular, with more efficient, simpler and less expensive
solutions.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a simple structure of a
wear compensation mechanism for use in disc brakes, particularly in a full
annular disc
brake for vehicles.
It is another object of the present invention to provide a disc brake housing,
especially for a full annular disc brake for automobiles, that has an improved
configuration to aid in adjustment of axial space for wear composition of the
disc brake.
It is a further object of the present invention to provide a disc brake
assembly that is provided with a simple structure for adjustment to compensate
for
wear.
It is a still further object of the present invention to provide a wear
compensation multiple disc brake assembly which has more than one rotor disc
and
2 5 provides a simple structure for adjustment to compensate for wear.
A disc brake assembly for a vehicle wheel generally includes a housing, at
least first and second annular brake shoes, and at least a rotor disc co-
axially mounted to
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the wheel and axially moveable with respect to the wheel. During a braking
action the
second brake shoe is adapted to move axially towards the rotor disc and
further press the
rotor disc against the first brake shoe, resulting in respective frictional
engagement
between the rotor disc and the first brake shoe, and between the rotor disc ~
and the
second brake shoe.
In accordance with one aspect of the invention, the disc brake housing of the
assembly comprises an annular radial wall for supporting the first annular
brake shoe
thereto, and a plurality of link members extending axially from an external
periphery of
the annular radial wall for detachably connecting an annular radial support
structure
mounted to the vehicle and housing the rotor disc and the brake shoes. There
is a means
provided for securing a distal end of the respective link members to the
annular radial
support structure in a selective axially position so that an axial space
between the
annular radial wall of the annular radial support structure is selectively
determined.
The securing means preferably comprises an elongated aperture defined in
the distal end of each link member and extending radially therethrough. A
plurality of
elongated mounting keys each having a mounting bore extending therethrough for
receiving a mounting screw. The mounting bore is offset from a center of the
key and
the elongated mounting keys are adapted for insertion into the respective
elongated
apertures in either one of opposite orientations so that the mounting bores
are adapted to
2 0 . be selectively located in two different axial positions with respect to
the housing.
The disc brake housing is originally assembled with the mounting bores
more distal from the annular radial wall of the housing. After the rotor disc
and the
brake shoes or the brake pads attached thereto become thinner as a result of
wear,
leaving a longer axial distance for moving parts to travel, the elongated
mounting keys,
2 5 therefore, are reinserted into the respective elongated apertures in the
opposite
orientation to have the mounting bores located less far away from the annular
radial
wall so that the axial space between the annular radial wall and the annular
radial
support structure is smaller. The smaller axial space between the annular
radial wall
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and the radial support structure makes the travel distance of the moving parts
shorter
and therefore the adjustment is achieved.
In accordance with another aspect of the present invention, a disc brake
assembly for a vehicle wheel includes a housing; at least first and second
annular brake
shoes; at least a rotor disc having first and second annular radial planar
friction surfaces
substantially parallel to each other, the rotor disc being co-axially mounted
to the wheel
and axially moveable with respect to the wheel; means for restraining the
first brake
shoe from rotating with the rotor disc; means for restraining the second brake
shoe from
rotating with the rotor disc; and an annular fluid expandable bladder, whereby
upon
expansion of the bladder the second brake shoe moves axially towards the rotor
disc and
further presses the rotor disc against the first brake shoe, resulting in
respective
frictional engagement between the first friction surface of the rotor disc and
the first
brake shoe, and between the second friction surface of the rotor disc and the
second
brake shoe. The housing comprises an annular radial wall operatively
supporting the
first annular brake shoe adjacent to the first friction surface of the rotor
disc; an annular
radial support wall adapted to be mounted to a frame of the vehicle and
operatively
supporting the bladder and the second annular brake shoe adjacent to the
second friction
surface of the rotor disc; and means for connecting the annular radial wall to
the annular
radial support wall in an axially and selectively spaced relationship.
2 0 The connecting means preferably comprises a plurality of link members
extending axially from an external periphery of the annular radial wall. The
link
members are preferably equally and circumferentially spaced apart from one
another.
Each link member preferably includes a distal end having a mounting bore
radially
extending therethrough for receiving a mounting screw. An axial position of
the
2 5 mounting bore is selectively determined when the link members are
connected to the
annular radial support wall.
More especially according to one embodiment of the present invention, a
disc brake assembly for a vehicle wheel comprises a first annular brake shoe;
a first
rotor disc co-axially mounted to the wheel, axially spaced apart from the
first brake shoe
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and axially moveable with respect to the wheel; a second annular brake shoe
axially
spaced apart from the first rotor disc; a second rotor disc co-axially mounted
to the
wheel, axially spaced apart from the second brake shoe and axially moveable
with
respect to the wheel; and a third annular brake shoe axially spaced apart form
the second
rotor. An annular expandable bladder is provided and adapted to move the third
brake
shoe, second rotor, second brake shoe and second rotor axially towards the
first brake
shoe upon expansion of the bladder during a brake action, resulting in
frictional
engagement between the first brake shoe and the first rotor, the first rotor
and the
second brake shoe, the second brake shoe and the second rotor and the second
rotor and
the third brake shoe respectively. A housing is provided to house the brake
shoes and
rotor discs. The housing has an annular radial wall for operatively supporting
the first
brake shoe and an annular radial support wall adapted to be mounted to a frame
of the
vehicle for operatively supporting the third brake shoe. Also included in the
housing is
a means for connecting the annular radial wall to the annular radial support
wall in an
axially and selectively spaced relationship to adjust an axial space between
the annular
radial wall and the annular radial support wall so that the travel distance of
the axially
moveable brake shoes and rotor discs of the disc assembly is adapted to be
reduced in
order to compensate for wear of friction surfaces of the brake shoes.
The connecting means preferably comprises a plurality of link members
2 0 extending axially from an external periphery of the annular radial wall
and equally and
circumferentially space apart from one another. Each link member has an
elongated
aperture defined at a distal end thereof and extending radially therethrough.
A plurality
of elongated mounting keys each having a mounting bore extending through the
key for
receiving a mounting screw are adapted for insertion into the respective
elongated
2 5 apertures. The mounting bore is offset from a center of the key so that
the mounting
bores are adapted to be selectively located in two different axial positions
with respect
to the housing when each key is inserted in the bore in opposite orientations.
The disc brake assembly further, preferably comprises means for inhibiting
relative rotation between the third brake shoe and the annular radial support
wall, and
3 0 between the third and second brake shoes while permitting relative and
axial movement
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therebetween respectively. A means is also preferably provided for inhibiting
the first
brake shoe from rotation with respect to the housing.
The present invention advantageously provides a very simple structure of
the housing to enable the housing to have selective axial spaces for adjusting
the travel
distance of the axially moving parts of the disc brake assembly to compensate
for wear.
The adjustment structure is very reliable because there are no moving parts
needed for
the adjustment. The adjusted length is dependent on the distance between the
center of
the bore and the center of the elongated key which can be predetermined within
a wide
range with no restrictions. This is particularly good for a multiple disc
brake assembly
which has more than one rotor disc because the more friction surfaces the disc
brake
assembly has, the longer distance might be necessarily adjusted. As a result
of the
simple structure, the cost to incorporate the adjustable feature for wear
compensation is
inexpensive. Other features and advantages of the present invention will be
better
understood with reference to the preferred embodiment described below.
BRIEF DESCRIPTION OF THE DRAWINGS
Having thus generally described the nature of the invention, the invention
will now be described in detail with reference to the accompanying drawings in
which:
Fig. 1 is a partial, longitudinally cross-sectional view of a disc brake
assembly incorporating a preferred embodiment of the invention;
2 0 Fig. 2 is a perspective view of a disc brake housing in accordance with
the
preferred embodiment in Fig l;
Fig. 3 is a partial front view of Fig. l, showing the supportive relationship
between the first brake shoe and an annular radial wall of the housing;
Fig.4 is a partial rear view of Fig. 1, showing the connection of link
2 5 members of the housing to an annular radial support wall and the
supportive
relationship between the annular radial support wall and the second and third
brake
shoes;
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Fig. 5 is a partial view taken from a direction indicated by arrow P in Fig.
3,
showing an original axial location of the mounting bores;
Fig. 6 is the same view illustrated in Fig. 5, showing the adjusted axial
location of the mounting bores to compensate for wear;
Fig. 7 is a partial cross-sectional view of a key inserted into the aperture
of
the link member according to another embodiment of the invention;
Fig. 8 is a partial, longitudinally cross-sectional view of a disc brake
assembly incorporating another preferred embodiment of the invention;
Fig. 9 is a partial top view of Fig. 8, showing the engagement of a fork
member of the second brake shoe with an axial member of the third brake shoe;
Fig. 10 is a partial cross-sectional view taken along lines B-B in Fig. 9,
appearing on the sheet of Fig. 8;
Fig. 11 is a partial, longitudinally cross-sectional view of a disc brake
assembly incorporating a further preferred embodiment of the invention; and
Fig. 12 is a partial top view of Fig. 11, appearing on the sheet of Fig. 9 and
showing the engagement between the axial members of the second and third brake
shoes.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to drawings, more particularly Figs. 1 and 2, the disc brake
2 0 assembly 10 for an automobile wheel (not shown) is illustrated having a
housing 12.
The housing 12 has an annular radial wall 14 and a plurality of link members
16
extending axially from an external periphery of the annular radial wall 14.
The link
members 16 are equally and circumferentially spaced apart from one another.
Supportive portions 18 are provided between adjacent link members 16,
connecting the
2 5 external periphery of the annular radial wall 14 to increase the strength
and solidity of
the connection between the link members 16 and the annular radial wall 14. The
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housing 12 including the annular radial wall 14, the link members 16 and the
supportive
portions 18 is integrally made from casting metal.
The annular radial wall 14 has a substantially flat inner surface 20 and a
smoothly curved outer surface 22. A plurality of openings 24 axially extending
through
the annular radial wall 14 and equally, circumferentially spaced apart from
one another.
Each link member 16 includes a distal end 26 having an elongated aperture 28
(shown
in Fig. 2) radially extending therethrough. The elongated apertures 28 are
axially
oriented, each having an axially extending longitudinal axis. A first annular
brake
shoe 30 includes an annular axial section 32 and an annular radial section,34
extending
outwardly from the axial section 32. A plurality of axially protruding members
34 that
are equally and circumferentially spaced apart from one another and received
in the
respective openings 24 (see Fig. 3) when the first annular brake shoe 30 is
supported to
the annular radial wall 14 with the axial section 32 resting on an inner edge
36 of the
annular radial wall 14. As shown in Fig. 3, a plurality of radially extending
grooves 38
and 40 are provided on the outer surfaces of the respective axial section 32
and the
axially protruding members 34 to increase the air contacting surfaces of the
first brake
shoe 30 for a better cooling solution. The radial section 34 of the first
annular brake
shoe 30 has an annular inner planar surface 42 on which an annular brake pad
44 is
securely attached by any well known mechanism.
2 0 Adjacent to the first brake shoe 30 is a rotor disc 46 which is co-axially
mounted to the wheel of the vehicle and axially moveable with respect to the
wheel,
which is well known. The rotor disc 46 includes first and second annular
planar friction
surfaces 48 and 50 that are parallel to each other and perpendicular to the
rotation axis
of the wheel. The brake pad 44 is also perpendicular to the rotation axis of
the wheel so
2 5 that the first annular radial planar friction surface 48 is parallel to
the first annular brake
pad 44 while slightly and axially spaced apart therefrom. A circumferentially
extending
groove 52 is provided around the rotor disc 46 to improve the cooling
condition of the
rotor disc.
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A second or intermediate annular brake shoe 54 includes a radial section 56
having first and second annular radial planar surfaces 58 and 60, parallel to
each other.
A pair of annular brake pads 62 and 64 are securely attached to the surfaces
58 and 60
respectively, by any well-known means. The second or intermediate annular
brake
shoe 54 is positioned adjacent to the first rotor disc 46 at the side opposite
to the first
brake shoe 30 so that the annular brake pad 62 is parallel to and slightly
spaced apart
from the annular radial planar friction surface 50 of the first rotor disc. A
plurality of
axial legs 66 extend axially from the external periphery of the radial section
56 and are
equally and circumferentially spaced apart from one another as shown in Figs.
1 and 4.
Adjacent to the second or intermediate annular brake shoe 54 and at the side
opposite to the first rotor disc 46 is a second rotor disc 68. Similarly to
the first rotor
disc 46, the second rotor disc 68, is co-axially mounted to the wheel of the
vehicle and
axially moveable with respect to the wheel. Parallel annular radial planar
friction
surfaces 70 and 72 are perpendicular to the rotation axis of the wheel and a
circumferentially extending groove 74 is provided around the rotor disc to
improve the
cooling condition of the second rotor disc 68. The annular radial planar
friction
surface 70 is parallel to the brake pad 64 and slightly spaced apart
therefrom.
A third annular brake shoe 76 is placed adjacent to the second rotor disc 68,
at the side opposite to the second or intermediate annular brake shoe 54. The
third
2 0 annular brake shoe 76 includes a radial section 78 having at opposite
sides, two parallel
annular radial planar surfaces 80 and 82. An annular brake pad 84 is securely
attached
to the surface 80 by any well-known means so that the brake pad 84 is parallel
to the
annular radial planar friction surface 72 of the second rotor disc 68 and
slightly spaced
apart therefrom. A plurality of axial members 84 radially protrude, axially
extend from
2 5 an external periphery of the radial section 78 and are equally and
circumferentially
spaced apart, as shown in Figs. l and 4. A recess 86 is provided on an
external surface
of each axial member 84 and axially extends through the entire axial member.
The
number of the axial members 84 and the size of the recesses 86 correspond to
those of
the axial legs 66 of the second or intermediate annular brake shoe 54 so that
the axial
3 0 legs 66 are slidably engaged in the respective recesses of the third
annular brake
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shoe 76. Therefore, the second brake shoe 54 is radially supported to the
third brake
shoe 76 and a relative axial movement therebetween is permitted but relative
rotation is
restrained. A plurality of axial grooves 88 and 90 are provided on the
external surface
of each axial leg 66 and each axial member 84 (see Fig. 4) to increase air
contacting
surfaces of the second and third annular brake shoe, resulting in a better
cooling
solution.
An annular radial support wall 92 is provided in order to hold the disc brake
assembly 10 together. The annular radial support wall 92 is adapted to be
mounted on a
frame of the vehicle and have a first group of grooves 94 extending axially on
the
external periphery thereof and equally circumferentially spaced apart from one
another,
as shown in Fig. 4, to receive the respective axial legs 16 of the housing 12.
Each axial
leg 16 of the housing 12 has an elongated aperture 96 having its longitudinal
axis
extending axially, as shown in Fig. 5. An elongated key 98, sized and shaped
correspondingly to the elongated aperture 96 is inserted into the aperture 98.
A
mounting bore 100 is defined in the elongated key 98, radially extending
through the
key for receiving a mounting screw 102 (shown in Figs. 1 and 4) that is
threadably
secured to the annular radial support wall 92. The position of the center of
the mounting
bore 100 is on the longitudinal central line of the key 98, and offset a
distance marked A
in Fig. S from the center of the elongated key 98. The key 98 is oriented so
that the
2 0 mounting bore 100 is offset from the center of the key 98 towards the
distal edge of the
axial leg 16.
The annular radial support wall 92 includes a second group of grooves 104
extending axially on the external periphery of the annular radial support wall
92 and
equally circumferentially spaced apart to slidably receive the respective
axial
2 5 members 84 of the third annular brake shoe 76 with the respective axial
legs 66 of the
second or intermediate annular brake shoe 54 slidably engaged thereto (see
Fig. 4).
Therefore, the second and third brake shoes 54 and 76 are radially supported
to the
annular radial support wall 92. An annular expandable bladder 106 is placed
between
the annular radial support wall 92 and the radial section 78 of the third
annular brake
3 0 shoe 76. Upon expansion of the bladder 106 when pressurized fluid is
forced into it
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during a brake action, the bladder 106 moves the third annular brake shoe
towards the
second rotor disc 68. The second rotor disc 68 begins to move towards the
second or
intermediate annular brake shoe 54 when the second rotor disc is pressed by
the third
annular brake shoe 76. In a similar procedure the second or intermediate
annular brake
shoe 54 and the first rotor disc 46 are pressed to move towards the first
annular brake
shoe 30 until a complete frictional engagement occurs between the brake pad 44
and the
annular radial planar friction surface 48, the annular radial planar friction
surface 50 and
the brake pad 62, the brake pad 64 and the annular radial planar friction
surface 70, the
annular radial planar friction surface 72 and the brake pad 84 while the first
brake shoe
is firmly pressed against the inner surface 20 of the annular radial wall 14
of the
housing 12. The first brake shoe 30 is inhibited from rotation by the annular
radial
wall 14 through the axially protruding members 34, and the second and third
brake
shoes are restrained from rotation by the annular radial support wall 92
through the
respective axial legs 16 and axial members 84 so that the frictional
engagement between
the brake shoes and rotor discs will eventually stop the rotation of the rotor
discs and
bring the vehicle to a full stop. However, before the complete frictional
engagement is
achieved, relative frictional movement exists between each brake pad and the
corresponding friction surface of the rotor discs which produces heat energy
and causes
wearing of the break pads. Therefore, each brake pad will become thinner and
leave
2 0 more axial distance for the moving parts of the brake to travel after a
certain extent of
the brake wearing is done. That means, more time is needed to bring the
vehicle to a
full stop when the driver applies the brakes.
The disc brake assembly 10 according to this embodiment is adapted to
adjust the travel distance of the moving parts of the brake. After the travel
distance
2 5 reaches a predetermined extent, the mounting screws 102 are removed.
Therefore, the
elongated keys 98 can be removed from the elongated apertures 96 and
reinserted into
the apertures 96 with an opposite orientation so that the mounting bores 100
are located
on the other end of the elongated apertures 96, located a longer distance away
from the
distal edge of the axial leg 16 as shown in Fig. 6. As indicated in Figs. 5
and 6, the
3 0 distance between the center of the mounting bore 100 and the center of the
key 98 is A,
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and therefore, the axial position of the mounting bore 100 is moved a distance
2A
inwardly from its original position. As a result, the annular radial support
wall 92 must
be moved a distance 2A inwardly in order to align the mounting bores 100 with
the
corresponding mounting bores (not shown) in the annular radial support walls
92 to
reattach the mounting screws 102 so that the axial distance between the
annular radial
wall 14 and the annular radial support wall 92 is reduced by 2A. The distance
A is
predetermined when the disc brake assembly 10 is designed and manufactured.
Fig. 7 illustrates an alternative embodiment of the key 98 that is indicated
as 98a and includes a top portion greater than the elongated aperture 96 to
form a
shoulder 106 around the key 98a. When the key 98a is inserted into the
aperture 96, the
top portion of the key 98a is left above the aperture 96 that is easily
gripped for
removal.
Figs. 8, 9 and 10 illustrate a disc brake assembly 110 according to another
preferred embodiment. The disc brake assembly has structures similar to the
disc brake
assembly 10 shown in Fig. 1. The similar parts identified by the same numerals
indicated in Fig. 1 are not redundantly described. In contrast to the
embodiment shown
in Fig. 1, the disc brake assembly 110 has a different structural arrangement
for
inhibiting the rotation of second and third brake shoes and an improved
bladder system.
A third annular brake shoe 112 includes an annular radial section 114 having
at opposite
2 0 sides, two parallel annular radial planar surfaces 116 and 118. The
annular brake pad 84
is securely attached to the surface 116 so that the brake pad 84 is parallel
to the annular
radial planar friction surface 72 of the second rotor disc 68 and slightly
spaced apart
therefrom. The third brake shoe 112 further includes an annular axial section
120 to
form an external periphery of the third brake shoe 112, which is more clearly
shown in
2 5 Fig. 10. A plurality of axial members 122 protrude radially and axially
from the annular
axial section 120, being equally and circumferentially spaced apart, as shown
in Figs. 9
and 10. The axial members 122 at their rearward end slidably fit into the
respective
axial grooves 104 which are located on the periphery of the annular radial
support
wall 92, more clearly shown in Fig. 4, whereby the third brake shoe 112 is
restrained
3 0 from rotation relative to the housing 12 while permitted axial movement
thereto. With
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such a structure, the third brake shoe 112 is radially supported on the
annular radial
support wall 92. A plurality of axial grooves 124 are provided on the external
surface
of each axial member 122 for a better cooling solution.
Instead of the axial legs 66 shown in Fig. l, a plurality of fork members 126
protrude radially, extend axially from the external periphery of the second
brake shoe 54
and are circumferentially spaced apart from one another. Each of the fork
members 126
includes two axial legs 128 slidably engaging a front end of a corresponding
one of the
axial members 122, whereby the second brake shoe 54 is restrained from
rotation
relative to the third brake shoe 112 but permitted axial movement with respect
to both
the housing 12 and the third brake shoe 112. Each fork member 126 has a width
fitting
in the space between two adjacent link members 16 of the housing 12 and the
axial
legs 128 of the fork member 126 are supported on the annular axial section 122
of the
third brake shoe 112.
The disc brake assembly 110 incorporates an improved bladder system
which is described in the applicant's co-pending patent application entitled
FLEXIBLE
BRAKE SHOE which is incorporated herewith by reference. An annular expandable
bladder 130 is adapted to axially compress an annular piston member 139 which
has a
hollow structure defining an inner annular space 134 therein, and protruding
axially
from the radial section 114 of the third brake shoe 112. An annular thermal
2 0 insulator 136 is disposed between the radial section 114 of the third
brake shoe 112 and
the annular piston member 132. A plurality of bores (not shown) are preferably
provided, extending through the annular piston member 132 to communicate with
the
inner annular space 134 and the outside of the annular piston member 132. With
such a
structure, the heat produced as a result of the frictional movement between
the second
2 5 rotor disc 68 and the third brake shoe 112 during brake actions, are
inhibited from
transferring to the annular expandable bladder 130, which improves the working
condition of the bladder 130 and thereby prevents premature aging of the
material of
which the bladder 130 is made.
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Figs. 11 and 12 illustrate a further preferred embodiment of the invention, as
indicated at numeral 210. The disc brake assembly 210 is similar to the
embodiment 10
shown in Fig. 1 and the identical parts indicated by the same numerals are not
redundantly described. The improved bladder system of the disc brake assembly
210 is
identical to that of the disc 'brake assembly 110 shown in Fig. 8 which is
indicated by
the same numerals and not redundantly described. The third brake shoe 112 has
a
plurality of axial members 138 circumferentially spaced apart from one
another. Each
axial member 138 includes a first section 140 protruding radially and
extending axially
and rearwards from the annular axial section 120 of the third brake shoe 112,
and a
second section 142 extending axially and forwardly from the external periphery
of the
third brake shoe 112. A plurality of axial grooves 144 are provided on the
external
surface of the first section 140 of the axial member 138 to increase air
contact areas for
a better cooling solution. The second section 142 of the axial member 138 has
a
recessed end as shown in Fig. 12 to reduce the weight thereof. The second
brake shoe
54 has a plurality of axial members 146 extending rearwards and axially from
the
external periphery thereof, and circumferentially spaced apart from one
another to
slidably engage the second sections 142 of the axial members 138 of the third
brake
shoe 112, whereby the relative rotation between the second and third brake
shoes 54
and 112 is inhibited but axial movement therebetween is permitted. The
rearward end
2 0 of the first section 140 of the axial member 138 of the third brake shoe
112 is slidably
received in the grooves 104 of the annular radial support wall 92 to inhibit
the third
brake shoe 112 from rotation but permit axial movement thereof with respect to
the
housing 12. The axial members 146 of the second brake shoe are disposed in a
circumferential position having a diameter smaller than the diameter of the
2 5 circumferential position of the link members 16 of the housing 12 so that
the axial
members 146 of the second brake shoe 54 is contained within the cylindrical
space
defined by the interior surface of the link members 16 of the housing 12, and
radially
supported on the inner surface of the link members 16.
CA 02475452 2004-08-20
WO 02/066852 PCT/CA02/00217
- 15 -
Changes and modifications to the embodiment of the invention described
above may be made without departing from the spirit and the scope of the
invention
which are intended to be limited only by the scope of the appended claims.
