U.S. patent application number 10/921640 was filed with the patent office on 2005-03-17 for disc brake caliper.
This patent application is currently assigned to PBR Australia Pty Ltd. Invention is credited to Reeves, Keith Clarkson.
Application Number | 20050056496 10/921640 |
Document ID | / |
Family ID | 3834267 |
Filed Date | 2005-03-17 |
United States Patent
Application |
20050056496 |
Kind Code |
A1 |
Reeves, Keith Clarkson |
March 17, 2005 |
Disc brake caliper
Abstract
An opposed piston disc brake caliper (10), including a caliper
housing (11) arranged for mounting brake shoes on each of opposite
sides of a rotor which in use is disposed between the brake shoes
(17), each brake shoe (17) having radially inner (26) and outer
(27) edges when mounted in the housing (11) and side edges (28, 29)
extending therebetween. A piston is associated with each brake shoe
(17) and is operable in use to shift the respective brake shoe (17)
toward the rotor for engagement therewith to effect braking. First
mounting means (20) for mounting the brake shoes (17) within the
housing (11), and second mounting means (41) for mounting the
caliper (10) to a wheel assembly. The second mounting means (41)
extending from the housing (11) on one side of the rotor. The
housing (11) including side walls (12,13) which extend generally in
planes parallel to the plane of the rotor and on opposite sides of
the rotor plane and which accommodate the pistons, and end walls
(14, 15) which extend transverse to the side walls (12, 13) and are
connected therebetween. An axial extension (36) that extends
axially from a first of the side walls (12) towards the rotor from
a position adjacent the radially inner brake shoe edge (26) and
fully along the first side wall (12) to connect with each of the
end walls (14, 15) and the first side wall (12) being disposed on
the side of the rotor opposite to that of the second mounting means
(41).
Inventors: |
Reeves, Keith Clarkson;
(Mount Eliza, AU) |
Correspondence
Address: |
CHARLES N.J. RUGGIERO, ESQ.
OHLANDT, GREELEY, RUGGIERO & PERLE, L.L.P.
10th FLOOR
ONE LANDMARK SQUARE
STAMFORD
CT
06901-2682
US
|
Assignee: |
PBR Australia Pty Ltd
|
Family ID: |
3834267 |
Appl. No.: |
10/921640 |
Filed: |
August 19, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10921640 |
Aug 19, 2004 |
|
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PCT/AU03/00223 |
Feb 21, 2003 |
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Current U.S.
Class: |
188/71.1 |
Current CPC
Class: |
F16D 55/228 20130101;
F16D 2055/002 20130101; F16D 65/092 20130101; F16D 65/095 20130101;
F16D 2055/007 20130101; F16D 2055/0091 20130101 |
Class at
Publication: |
188/071.1 |
International
Class: |
F16D 055/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 21, 2002 |
AU |
PS 0668 |
Claims
1. An opposed piston disc brake caliper comprising: a caliper
housing being arranged for mounting brake shoes on opposite sides
of a rotor, said rotor being disposed between said brake shoes with
each brake shoe having an radially inner edge and a radially outer
edge relative to the rotor when mounted in the caliper housing,
said brake shoes having side edges extending therebetween; a piston
associated with each brake shoe, said piston being operable to
shift said brake shoe toward said rotor for engagement therewith to
effect braking; first mounting means for mounting each brake shoe
within said caliper housing; second mounting means for mounting the
opposed piston disc brake caliper to a wheel assembly, said second
mounting means extending from said caliper housing on one side of
said rotor, said caliper housing including side walls which extend
generally in planes parallel to a plane of said rotor and on
opposite sides of said plane, said side walls accommodating each
piston, and end walls which extend transverse to said side walls
and are connected therebetween; and an axial extension that extends
axially from a first of said side walls toward said rotor from a
position adjacent said radially inner edge and fully along said
first of said side walls to connect with each of said end walls,
and wherein said first of said side walls is disposed on a side of
said rotor opposite said second mounting means.
2. The opposed piston disc brake caliper according to claim 1,
wherein said caliper housing further includes a second axial
extension which extends axially toward said rotor adjacent said
radially inner edge and fully along said side wall to connect with
each of said end walls, said second axial extension being disposed
on the same side of said rotor as said second mounting means.
3. The opposed piston disc brake caliper according to claim 1,
wherein said axial extension has a generally square or rectangular
axial cross-section.
4. The opposed piston disc brake caliper according to claim 1,
wherein said first mounting means comprises mounting members
extending from said side walls of said caliper housing toward said
rotor for engagement with each side edge of each said brake shoe,
wherein said engagement substantially limits movement of each brake
shoe other than in a direction toward or away from said rotor with
at least one of said mounting members being removable from said
caliper housing to facilitate removal of a said brake shoe from
said caliper housing.
5. The opposed piston disc brake caliper according to claim 4,
wherein at least two of said brake shoes are mounted adjacent each
other in said caliper housing on each side of said rotor.
6. The opposed piston disc brake caliper according to claim 4,
wherein said brake shoes are mounted in said caliper housing on
each side of said rotor, and three said mounting members are
provided on each side of said rotor for mounting said brake shoes
with two of said three mounting members being positioned to engage
an outer edge of said side edges of each brake shoe, and a third of
said three mounting members being positioned to engage each of said
radially inner side edge of said pair of said brake shoes adjacent
to one another.
7. The opposed piston disc brake caliper according to claim 6,
wherein said third mounting member is removable.
8. The opposed piston disc brake caliper according to claim 5,
wherein three of said brake shoes are mounted in said caliper
housing on each side of said rotor, and further comprising a pair
of outer brake shoes and a central brake shoe, and four of said
mounting members being provided on each side of said rotor for
mounting said brake shoes, wherein two of said four mounting
members are positioned to engage an outer side edge of each of said
outer brake shoes, wherein two of said four mounting members are
positioned to engage a side edge of said central brake shoe and an
adjacent inner side edge of said pair of outer brake shoes.
9. The opposed piston disc brake caliper according to claim 8,
wherein said mounting members are positioned to engage said side
edge of said central brake shoe, and wherein each of said mounting
members is removable.
10. The opposed piston disc brake caliper according to claim 4,
wherein each of said mounting members is removable.
11. The opposed piston disc brake caliper according to claim 4,
wherein said mounting members are disposed between adjacent side
edges of adjacent brake shoes, and wherein said mounting members
are removable.
12. The opposed piston disc brake caliper according to claim 4,
wherein said mounting members are formed as pins.
13. The opposed piston disc brake caliper according to claim 4,
wherein one or more of said mounting members arc is threadably
received in an opening formed in said caliper housing.
14. The opposed piston disc brake caliper according to claim 13,
wherein said opening extends through said caliper housing, and
wherein said mounting member can be threaded into position and
removed from outside said caliper housing.
15. The opposed piston disc brake caliper according to claim 14,
wherein said threaded member includes a head arranged for
engagement with a driving tool from outside said caliper
housing.
16. The opposed piston disc brake caliper according to claim 4,
wherein said brake shoes have a slot formed in each side edge and
said mounting members have an outer surface to snugly engage said
slot.
17. The opposed piston disc brake caliper according to claim 16,
wherein said slots are concave.
18. The opposed piston disc brake caliper according to claim 17,
wherein said mounting members are formed as pins and have a
generally circular cross-section and said slots define a generally
curved concave internal surface complementary to said outer surface
e received within said slots.
19. The opposed piston disc brake caliper according to claim 4,
wherein said brake shoes comprise a projection extending from each
side edge, and wherein said mounting members have a slot for
accommodating said projection.
20. The opposed piston disc brake caliper according to claim 1,
wherein said caliper has two or more brake shoes, wherein said two
or more brake shoes are mounted on each side of said rotor, and
wherein said end walls and said side walls of said caliper housing
define an opening, wherein said opposed piston disc brake caliper
has a bar that extends across said opening transverse to said side
walls for increasing a stiffness of said caliper housing against an
outward bending of said side walls during braking, said brake shoes
being removable from said caliper housing through said opening when
said caliper is installed about said rotor.
21. The opposed piston disc brake caliper according to claim 20,
wherein the caliper includes a pair of transverse bars, which are
spaced apart in said plane of said rotor to each extend across said
opening.
22. The opposed piston disc brake caliper according to claim 20,
wherein said bars are formed integrally with said caliper
housing.
23. The opposed piston disc brake caliper according to claim 1,
wherein said side walls include piston bores, and wherein said
piston bores are for accommodating each piston, each piston bore
having substantially a same diameter and an axial extent relative
to one another, and wherein each piston has substantially a same
diameter and substantially a same length, and wherein during
braking, equal pressure is applied to each brake shoe.
Description
[0001] The present invention relates to disc brake calipers and to
improvements thereof. The present invention has particular
relevance to disc brake calipers of the kind which include opposed
pistons and it will therefore be convenient to describe the
invention in relation to that type of caliper. It is to be
appreciated however, that the invention could apply to calipers not
of the opposed piston kind.
[0002] Opposed piston calipers have traditionally been applied to
high performance vehicles, such as racing cars and top end sports
cars. Such calipers have been perceived as providing higher
performance than non-opposed piston calipers.
[0003] When used in high performance cars, the brake shoes of the
caliper are supported on torque abutments positioned on the
radially inward edge of the shoe (relative to the rotor), and a
spring bias operates on the opposite or radially outer edge of the
shoe to resists movement of the shoe away from one or each of the
abutments during braking. The calipers are arranged in this manner,
so that the brake shoes can be removed quickly after the spring or
springs are removed, through an opening in the radially outer part
of the caliper housing. However, the springs are required to be
highly loaded to resist the signification loads applied by the
brake shoes during braking. This does mean that the disassembly and
reassembly of the caliper requires some expertise if it is to be
done in a quick manner. This is one reason why the calipers have
generally been used on high performance vehicles only.
[0004] Given the need for an opening in the housing for brake shoe
removal, known opposed piston calipers such as those described
above, have not been as stiff as desirable. Caliper stiffness is
always a characteristic that is desirable to be maximised.
[0005] In known disc brake calipers friction lining wear tends to
occur in a tapered manner, with the wear being maximum at the
leading end of each shoe and tapering to minimum wear at the
trailing ends. To eliminate or reduce the amount of tapering wear,
ie to cause the friction lining to wear evenly or more evenly, some
calipers have employed multiple pistons to drive the brake shoe,
with a piston of greater diameter at the trailing end of the brake
shoe compared to the leading end. Accordingly, greater pressure is
applied to the brake shoe at the trailing end than the leading end,
so having an evening effect on the friction lining wear. A drawback
associated with this approach is that each caliper requires at
least two different piston sizes and related seals and other parts,
so complicating the manufacture and assembly process and therefore
increasing costs.
[0006] It is an object of the invention to overcome or at least
alleviate one or more of the drawbacks associated with the prior
art.
[0007] According to the present invention there is provided an
opposed piston disc brake caliper, including a caliper housing
arranged for mounting brake shoes on each of opposite sides of a
rotor which in use is disposed between said brake shoes, each said
brake shoe having radially inner and outer edges when mounted in
said housing and side edges extending therebetween, a piston
associated with each said brake shoe and being operable in use to
shift the respective brake shoe toward the rotor for engagement
therewith to effect braking, first mounting means for mounting said
brake shoes within said housing, and second mounting means for
mounting said caliper to a wheel assembly, said second mounting
means extending from said housing on one side of the rotor, said
housing including side walls which extend generally in planes
parallel to the plane of the rotor and on opposite sides of the
rotor plane and which accommodate said pistons, and end walls which
extend transverse to said side walls and are connected
therebetween, an axial extension that extends axially from a first
of said side walls toward the rotor from a position adjacent said
radially inner brake shoe edge and fully along said first side wall
to connect with each of said end walls and said first side wall
being disposed on the side of the rotor opposite to that of the
second mounting means.
[0008] The above arrangement provides for increased stiffness of
the caliper housing by the provision of the axial extension. The
axial extent of the extension determines the increase in stiffness
achieved over a caliper in which the axial extension is absent, but
the maximum extent is determined by a need to avoid engagement with
the rotor.
[0009] A major increase in the stiffness of the housing is realised
by a single axial extension, which extends along the side wall
described, although additional stiffness can be realised by a
second axial extension extending from the opposite side wall and in
connection with each of the end walls and adjacent the radially
inner brake shoe edge of the brake shoe or shoes on that side of
the rotor. The increased stiffness provided by the second axial
extension is less than that provided by the first axial extension,
because the second mounting means already contributes some
stiffness to that side wall of the housing.
[0010] The or each axial extension can have any suitable
configuration but preferably each has a generally square or
rectangular configuration.
[0011] In a preferred arrangement, the first mounting means are
mounting members which extend from the housing for engagement with
each side edge of each brake shoe and the engagement being such as
to substantially limit movement of each brake shoe other than in a
direction toward or away from the rotor. At least one of the
mounting members engaged with each brake shoe is removable from the
housing to facilitate removal of a brake shoe from the housing.
[0012] In a further preferred arrangement, two or more brake shoes
are mounted in the housing on each side of the rotor. In this
arrangement, a piston is associated with each brake shoe and
sufficient mounting members are provided for engagement of the side
edges of each brake shoe. In one such preferred arrangement, a pair
of brake shoes are provided adjacent one another on each side of
the rotor and in this arrangement, three mounting members are
provided, one to engage each of the outer side edges of each brake
shoe and the third to engage the side edges of the brake shoes
which are adjacent. In this arrangement, the central or third
mounting member can be removable, whereby removal of that member
alone can facilitate removal of the pair of brake shoes from the
housing. That is, the arrangement can be such that by removal of
the central or third mounting member, the restraint against
movement of the brake shoes by the mounting members is lifted, so
that the brake shoes can then be removed.
[0013] In a further arrangement, three brake shoes are provided
adjacent one another on each side of the rotor. Accordingly, four
mounting members can be provided, one at each end of the adjacent
brake shoes and one disposed between each of the two pairs of
adjacent side edges. In this arrangement, the mounting members
disposed between the two pairs of adjacent side edges can be
removed for removal of each of the three brake shoes.
[0014] It will be appreciated that any number of brake shoes and
associated mounting members may be provided and that for brake shoe
removal, mounting members disposed between adjacent side edges of
adjacent brake shoes normally will be required to be removed for
brake shoe removal. Alternatively however, each of the mounting
members may be removable, and this may be desirable not only to
provide flexibility in which members may be removed, but also to
maximise the number of like parts in the caliper.
[0015] In an alternative arrangement, some of the mounting members
may be fixed against removal and for example, one or more of the
mounting members may be cast as part of the housing. Alternatively,
those members may be disposed as a friction fit in openings formed
in the housing. The number of fixed mounting members is however
limited by the requirement for brake shoe removal.
[0016] In a preferred arrangement, one or more of the mounting
members is threadably received in an opening in the housing.
Preferably the opening extends fully through the housing so that
the member is threaded into the opening from the outside of the
housing, thereby facilitating removal of the member from the
outside. The or each member may therefore be formed as threaded
stud or the like, with an outwardly exposed head which includes a
suitable configuration for engagement with a driving tool, such as
a spanner.
[0017] The mounting members may engage the side edges of the brake
shoes in any suitable manner to limit brake shoe movement as
required. In one preferred arrangement, the backing plate of the
brake shoes include a slot or groove formed in a side edge and the
mounting member has an outer surface to snugly engage that slotted
or grooved surface. The slot or groove may have any suitable shape,
such as concave, while the mounting member, at least in the region
of the backing plate may be circular in cross-section. In this
arrangement, the slot or groove may be of a radius slightly greater
than that of the mounting member for a snug fit about the mounting
member. The slot or groove may however be otherwise shaped.
[0018] The engagement between the mounting member and the brake
shoe may alternatively be the opposite to that discussed above, so
that the mounting member includes a slot or groove and the backing
plate incudes a protrusion which is a snug fit in the slot or
groove.
[0019] The mounting members must extend from the housing to
maintain engagement of the brake shoes during movement thereof into
engagement with the rotor. That movement will be a minimum when the
friction lining of the brake shoe is new and at a maximum when the
friction lining has worn. The amount of movement will vary but
typically the maximum movement when the friction lining has worn
will be in the order of 2 to 3 mm.
[0020] The brake shoes preferably are of identical shape to
minimise different parts. The brake shoes typically are of
generally rectangular or square construction, and if multiple brake
shoes are employed on each side of the rotor, they preferably have
a combined length approximately equal to that of a single brake
shoe. The number of brake shoes can vary as discussed above, and
one arrangement that has been envisaged includes a six brake shoe
caliper (three brake shoes on each side of the rotor) for the front
wheels of a vehicle and a four brake shoe caliper for rear wheels
thereof. It is possible to have different numbers of shoes on each
side of the rotor if desirable, such as a traditional single shoe
on one side and a pair of shoes on the other. The invention
therefore is not restricted to even numbers of brake shoes.
[0021] The caliper arrangement of the invention preferably includes
biasing means for biasing the brake shoes against rattling movement
and for this, a light spring may be employed to bias the brake
shoes into engagement with the mounting members against rattling.
The biasing force required for this can be substantially less than
the spring employed in the prior art discussed above, because it
has a very different purpose and is not required to resist the
substantial loading of the prior art caliper during braking.
[0022] In an alternative embodiment, an opposed piston disc brake
caliper is provided in which the caliper housing is arranged for
mounting a plurality of brake shoes on each of opposite sides of a
rotor and a piston is associated with each brake shoe. The end and
side walls of the housing define an opening, and the caliper
includes a bar extending across the opening transverse to the side
walls for increasing the stiffness of the housing against outward
bending of the side walls during braking, the brake shoes being
removable from the housing through the opening past the bar when
the caliper is installed about a rotor.
[0023] The above embodiment is advantageous by the provision of
both the plurality of brake shoes on each side of the rotor and the
transverse bar which traverses the housing opening. In the prior
art, a transverse bar could not be employed with single brake shoes
disposed on either side of the rotor, because the bar prevented
brake shoes being removed from the caliper through the opening.
However, brake shoes of lesser length parallel to the plane of the
rotor can be removed through the housing on either side of the
bar.
[0024] There can be more than a single transverse bar if the
relative dimensions of the opening and the brake shoes permit. In a
six brake shoe caliper, the length of the housing in the plane of
the rotor can be greater than in a four brake shoe caliper and a
pair of transverse bars may be employed in a six brake shoe
caliper, whereas a single bar may be employed in a four brake shoe
caliper.
[0025] In a further preferred embodiment, the housing side walls
include piston bores for accommodating each piston, and each of the
piston bores have the same diameter and axial extent and each
piston has the same diameter and length, so that during braking,
equal pressure is applied to each brake shoe.
[0026] In the above embodiment, caliper costs can be reduced by the
piston arrangements being identical, rather than different. Such an
arrangement previously would have not been desirable, because the
friction lining would wear in a tapered profile as discussed
earlier. However, by employing a plurality of brake shoes on each
side of the rotor, the shortened length of each brake shoe in the
direction of rotor rotation, means that while the friction lining
of each shoe will still wear in a tapered profile, the extent of
tapered wear will be lessened. Accordingly, the friction lining
will wear more evenly and will therefore have an extended life.
[0027] The attached drawings show an example embodiment of the
invention of the foregoing kind. The particularity of those
drawings and the associated description does not supersede the
generality of the preceding broad description of the invention.
[0028] FIG. 1 is a perspective view of a disc brake caliper
according to the invention.
[0029] FIG. 2 is a plan view of the disc brake caliper of FIG.
1.
[0030] FIG. 3 is a shows an internal arrangement of the disc brake
caliper.
[0031] FIG. 4 is a perspective view of the disc brake caliper of
FIG. 1 showing brake pads and mounting pins removed.
[0032] FIG. 5 is a cross-sectional view through the pad arrangement
of a two brake shoe disc brake caliper.
[0033] FIG. 6 is a cross-sectional view taken through VI-VI of FIG.
2.
[0034] FIG. 7 is a view of the FIG. 5 illustration shown pistons
and piston bores.
[0035] FIG. 1 shows a disc brake caliper according to the invention
as described above. The disc brake caliper 10 includes a housing 11
defining a pair of parallel side walls 12 and 13 and a pair of end
walls 14 and 15 which extend transversely to the side walls 12 and
13 and are connected thereto. The housing 11 has a generally
rectangular configuration in plan view and typically would be cast
in a suitable metal such as iron or aluminium. The housing would
then be machined as necessary.
[0036] The side walls 12 and 13 and the end walls 14 and 15 define
an opening 16 in the housing 11. The opening 16 is of generally
rectangular configuration and the internal surfaces of the opening
defined by the side walls 12 and 13 are machined for mounting of a
plurality of brake shoes 17 there against. In FIG. 1, three brake
shoes 17 are mounted to each side wall 12 and 13 and each brake
shoe consists of a metal backing plate 18 and a fiction lining 19.
While these parts of the brake shoes can be seen from FIG. 1, they
are better illustrated in FIG. 2.
[0037] The brake shoes 17 are mounted within the housing 11 in a
unique manner, by mounting members which are illustrated clearly in
FIGS. 3 and 4. Referring to FIG. 3, the brake shoes of FIGS. 1 and
2 are shown and it can be seen that these are aligned side by side
and one set of three brake shoes is spaced apart from the other set
of three shoes. That spacing is to accommodate a disc brake rotor
which is not shown in any of the drawings, but which would be
disposed between the sets of brake shoes, so that the brake shoes
can be shifted into engagement with the rotor to apply a braking
effect.
[0038] The mounting members shown in FIG. 3 consist of a plurality
of threaded pins 20 which include a head 21 incorporating a
hexagonal recess 22 for receipt of a complimentary shaped driving
tool, a threaded shaft portion 23 and a non-threaded shaft portion
24. The threaded portion 23 has a greater diameter than the shaft
portion 24 and therefore a step 25 is defined at the junction
between the respective portions 23 and 24.
[0039] Referring to FIG. 4, each brake shoe 17 is of generally
rectangular configuration, having a radially inner edge 26, a
radially outer edge 27 and side edges 28 and 29. The brake shoes 17
are not strictly rectangular as can be seen from FIG. 4, as the
inner edge 26 is formed of three flat surfaces, the outer edge 27
is curved and the side edges 28 an 29 are angled slightly inward.
The brake shoe configuration can be configured in any suitable
manner such as that shown or as otherwise required.
[0040] As is evident in FIGS. 3 and 4, the side edges 28 and 29
each include a part-circular slot or groove 30, while the friction
lining also includes a slot or groove 31 coaxially aligned with the
groove 30. The radius of each of the grooves 30 and 31, is slightly
greater than the radius of the shaft portion 24 of the pins 20 so
that the grooves 30 and 31 are a snug fit about the shaft portions
24. As is shown in FIG. 3, the shaft portion 24 of each mounting
pin 20 is disposed in each of the grooves 30 and 31 of each brake
shoe 17. It should be clear that the arrangement shown in FIG. 3
will permit each of the brake shoes to move axially with respect to
the shaft portion 24 of each of the mounting pins 20, but to be
substantially restrained against movement transverse to the axial
extent of the shaft portion 24. Thus, by the arrangement shown,
movement of each of the brake shoes 17 can be achieved to
facilitate engagement of the friction lining 19 of each brake shoe
17 with the disc brake rotor (not shown) disposed between the sets
of brake shoes, but to restrain the brake shoes against movement in
other directions. This arrangement is further shown in FIG. 5,
although the FIG. 5 arrangement relates to an assembly which
includes only a pair of brake shoes disposed on either side of the
rotor. In this respect, a disc brake caliper according to the
invention can have any number of brake shoes disposed on either
side of the rotor and therefore FIG. 5 is illustrative of an
alternative arrangement, which is otherwise operable in a very
similar manner to the FIGS. 1 to 4 arrangements.
[0041] In the FIG. 5 arrangement, the brake shoes 32 are of the
same construction and dimensions as the brake shoes 17 of the
earlier figures. Accordingly, it is not necessary to further
describe these. Likewise, the mounting members 33 each have the
same construction as the mounting pins 20 of the earlier figures.
Again, it is therefore unnecessary to further describe those
members. FIG. 5 shows the snug mating engagement between the outer
surface of the mounting members 33 and the slot or grooves formed
in each of the brake shoes 32. It will be readily seen from this
view that the shoes are constrained against rotating movement, or
against lifting movement, but as explained earlier, the brake shoes
can move axially with respect to the mounting members 33.
[0042] Referring to FIG. 4, the brake shoes 17 may be mounted
within the housing 11 by positioning each brake shoe against the
machined side wall surface and inserting each mounting pin 20 into
threaded engagement in the housing 11. For this, FIG. 4 shows
openings 34 machined into the housing 11 and to which a thread is
applied for threaded engagement with the threaded shaft portion 23
of each mounting pin 20. By this arrangement, the mounting pins 20
can be easily removed when one or more of the brake shoes 17 is to
be removed, although it will be appreciated that it is not
necessary to remove each of the mounting pins 20 and with reference
to FIG. 5, the center mounting pin 33 can be removed to facilitate
removal of each of the brake shoes 32, without also requiring
removal of the other two mounting pins 33. In the FIG. 4
arrangement, to remove each of the three brake shoes 17 on one side
wall of the housing 20, the two mounting pins 20 shown removed from
the openings 34 can be removed, without needing also to remove the
other pair of mounting pins 20 disposed outside the pair of central
pins. It is therefore acceptable, for the outside pair of mounting
pins 20 to be permanently fixed within the housing 11 or to be
formed integrally therewith, rather than being a separate pin which
is fixed in the housing. In one alternative, the pins may be a
friction fit within an opening formed in the housing 11, with the
intention that they remain as a permanent part of that housing, or
the shaft portions 24 of the mounting pins 20 maybe formed by a
cast protrusion which extends from the machined surface of the side
walls 12 and 13, instead of being a separate installable pin.
[0043] The extent of the mounting pins 20 into the opening 16 of
the housing 11 is required to be sufficient for each brake pad to
be shifted axially into engagement with the rotor and to still
maintain engagement with the shaft portion 24. FIG. 6 represents a
cross-sectional view taken through VI-VI of FIG. 2 and clearly
shows the mounting pins 20 received and fastened within the
openings 34, while the unthreaded shaft portion 24 extends into the
opening 16 in engagement with the side edges of the brake shoes 17.
It is also clear from FIG. 6, that the shaft portion 24 extends for
about twice the axial thickness of the backing plates 18 so that
brake shoe movement toward a rotor disposed between the brake shoes
17 is facilitated without disconnection between the brake shoes 17
and the shaft potions 24. It will be appreciated, that as the
friction linings 19 wear, that the brake shoes 17 will travel a
greater distance to engage the rotor and this is the reason for
providing a significant axial extent of the shaft portions 24.
[0044] Returning to FIGS. 1 and 2, bars 35 extend transversely
across the opening 16 generally parallel to the end walls 14 and 15
and transverse to both the plane of the rotor and the side walls 12
and 13. The bars 35 are formed as an integral casting of the
housing 11, although they could be alternatively connected as
separate components. As shown, the bars are spaced apart in equal
increments from themselves and from the end walls 14 and 15. There
is no strict requirement for this spacing although it also means
that the bars 35 are aligned with the centre pair of mounting pins
20.
[0045] The bars 35 increase the stiffness of housing 11 under
braking conditions and resist bending of the side walls 12 and 13
in such conditions. However, the provision of the bars 35 as shown
also facilitates insertion or removal of individual brake shoes 17
upon removal of the required number of mounting pins 20. Thus the
caliper 10 does not need to be fully removed from a wheel assembly
of a vehicle to which it is fitted for removal of one or more of
the brake shoes 17. Instead, it is a relatively simply matter of
removing the required number of mounting pins 20 and then removing
through the opening 16, the required number of brake shoes 17. FIG.
4 is illustrative of this method, in which two of the mounting pins
20 are shown removed from the housing 11, to facilitate complete
removal of three of the brake shoes 17.
[0046] Referring to FIG. 6, a further stiffen mechanism is applied
to the caliper 10 to increase overall caliper stiffness. In FIG. 6,
the bar 35 is shown but additional to this, the side wall 12
includes an axial extension 36 which extends from the machined
surface 37 of the side wall 12 axially toward the rotor or opposite
side wall 13. To obtain the stiffness benefit, the axial extension
36 extends in connection with end wall 14 fully to and in
connection with the end wall 15. Thus, the axial extension is
effectively a ledge which is formed along the full internal length
of the side wall 12.
[0047] For further enhancing the housing stiffness, a second axial
extension 38 extends from the machined surface 39 of the side wall
13. That axial extension extends axially inwardly and fully between
the respective end walls 14 and 15. The provisions of the axial
extension 38 is not as important as the opposite extension 36,
because the side wall is already stiffened to a certain extent by
the provision of a mounting knuckle 40 which serves to mount the
housing 11 to the wheel assembly. The knuckle 40 may take any
suitable shape or form to achieve its mounting requirement. For
example and referring to FIG. 5, the knuckle is a radius extension
of the side wall 13 and includes an opening 41 to receive a fixing
bolt (not shown). However, any suitable mounting means or
arrangement may be employed for mounting the housing to the wheel
assembly.
[0048] The brake shoes 17 or 32 are displaced towards a disc brake
rotor generally by hydraulic pistons and as discussed previously,
the use of multiple brake shoes as shown in each of the earlier
figures, permits the pistons and their associated piston bores to
be of the same dimensions throughout the caliper. FIG. 7 represents
this arrangement, in which the pistons 42 and their associated
bores 33 are of identical dimensions. This arrangement will still
entail tapered wear of each brake shoe friction lining, but because
the brake shoes have a reduced length in the direction of rotor
rotation, the degree of tapering wear of each brake shoe will be
less than the tapered wear of a single brake shoe.
[0049] It will appreciated that the figures show a single piece
housing, or monoblock housing construction, although alternatively,
the housing could be cast and machined in two parts and then bolted
or otherwise connected together. It should also be appreciated,
that the caliper 10 does not show a biasing spring engaging the
brake shoes 17 or 32, however it is envisaged that such a spring
would be included as an anti-rattling device, to urge the brake
shoes into firm connection with each mounting pin 20. The spring
could act on either of the brake shoe edges 26 or 27 and a single
spring may be provided to engage all of the brake shoes of the
caliper 10, or all of the brake shoes mounted on one side of the
caliper 10, or a single brake shoe each. The spring could take a
variety of different forms, although a leaf spring is
envisaged.
[0050] The invention described herein is susceptible to variations,
modifications and/or additions other than those specifically
described and it is to be understood that the invention includes
all such variations, modifications and/or additions which fall
within the spirit and scope of the above description.
* * * * *