U.S. patent application number 09/794117 was filed with the patent office on 2001-07-05 for disc brake assembly.
Invention is credited to Wang, Nui.
Application Number | 20010006134 09/794117 |
Document ID | / |
Family ID | 3777710 |
Filed Date | 2001-07-05 |
United States Patent
Application |
20010006134 |
Kind Code |
A1 |
Wang, Nui |
July 5, 2001 |
Disc brake assembly
Abstract
A disc brake assembly is disclosed which incorporates a disc 50
which includes radially inner and outer portions (54 55) which are
separated by a gap 56. Two pad assemblies (11, 12) are located on
respective sides of the disc and are interconnected by a draw bar
29 which extends through the gap and is connected to a piston
cylinder assembly. Actuation of the piston cylinder assembly
imparts a force to the pad assemblies through the draw bar which
causes them to move either towards or away from the disc to thereby
effect actuation and release of the brake assembly. The draw bar is
rotatable about its axis 71 and is releaseably coupled to the
outboard pad assembly 12 so as to be operative to move between an
engaged configuration with the pad assembly to a released
configuration on rotation about the draw bar axis.
Inventors: |
Wang, Nui; (Croydon,
AU) |
Correspondence
Address: |
Anthony P. Venturino
STEVENS, DAVIS, MILLER & MOSHER, L.L.P.
SUITE 850
1615 L STREET, N.W.
WASHINGTON
DC
20036
US
|
Family ID: |
3777710 |
Appl. No.: |
09/794117 |
Filed: |
February 28, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09794117 |
Feb 28, 2001 |
|
|
|
09058306 |
Apr 10, 1998 |
|
|
|
09058306 |
Apr 10, 1998 |
|
|
|
08666394 |
Jun 21, 1996 |
|
|
|
Current U.S.
Class: |
188/72.4 ;
188/250B; 188/370 |
Current CPC
Class: |
F16D 2121/02 20130101;
F16D 55/226 20130101; F16D 2065/1376 20130101; F16D 65/092
20130101; F16D 2069/0491 20130101; F16D 55/2262 20130101; F16D
65/128 20130101; F16D 2065/138 20130101; F16D 2069/004 20130101;
F16D 65/12 20130101; F16D 2055/0091 20130101; F16D 2065/1372
20130101; F16D 2250/0076 20130101; F16D 2055/0054 20130101; F16D
65/18 20130101; B24B 7/17 20130101; F16D 65/127 20130101; B62L 1/00
20130101; F16D 2250/003 20130101; Y10T 82/21 20150115; F16D
2065/1328 20130101 |
Class at
Publication: |
188/72.4 ;
188/370; 188/250.00B |
International
Class: |
F16D 055/18; B60T
011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 22, 1993 |
AU |
PM 3086 |
Claims
1. A disc brake assembly including, a disc having an axis of
rotation and including a radially outer portion and a radially
inner portion, a gap forming a radial separation between said outer
and inner portions and extending in a continuous circle coaxial
with said axis of rotation, two pad assemblies located on
respective opposite sides of said disc and each being mounted for
movement towards and away from said disc, an actuating means
operable for cause each said pad assembly to move towards and
engage a respective adjacent said side of the disc and including
force transmitting means which extends through said gap and
provides at least part of an interconnection between said pad
assemblies such that one responds to movement of the other towards
or away from said disc, wherein said actuating means includes a
piston cylinder assembly in which the piston is moveable relative
to the cylinder, either the cylinder or the piston being connected
to said other pad assembly for movement therewith and said force
transmitting means includes a draw bar which extends along an axis
and connects either said piston or said cylinder respectively to
said one pad assembly, said draw bar being rotatable about its axis
and being releasably coupled to said one pad assembly so as to be
operative to move between an engaged configuration with said one
pad assembly to a released configuration on rotation about said
draw bar axis.
2. A disc brake assembly according to claim 1, further including a
retaining device operative to inhibit rotation of said draw bar
when in engagement with said one pad assembly.
3. A disc brake assembly according to claim 2, further including
biasing means to bias the draw bar towards the one pad assembly
when in engagement with said one pad assembly.
4. A disc brake assembly according to claim 1, wherein said draw
bar is fixed relative to either the cylinder or the piston to which
it is connected.
5. A disc brake assembly according to claim 1, wherein the
connection between the draw bar and either the cylinder or piston
to which it is connected allows for relative rotation about the
axis of the draw bar but restrains the members from relative axial
movement along said draw bar axis.
6. A disc brake assembly according to claim 1, wherein said one pad
assembly includes a passage adapted to receive a first end of said
draw bar, said draw bar includes at or adjacent said first end at
least one abutment surface disposed radially outwardly from said
draw bar axis and which faces towards said piston cylinder
assembly, the assembly being configured such that in said engaged
configuration, said abutment surface engages with a complimentary
abutment surface of said one pad assembly so as to prevent removal
of said draw bar from within said passage, and wherein when in said
released configuration, said abutment surface is locatable within
said passage so as to enable said draw bar to be released from said
one pad assembly.
7. A disc brake assembly according to claim 6, wherein said one pad
assembly includes a support member having opposite first and second
major surfaces, a friction lining connected to, or integrally
formed with the support member along said first major surface to
form an operative surface of the pad assembly and wherein said
passage extends through said operative surface and at least into
said support member,
8. A disc brake assembly according to claim 7, wherein said passage
extends through to said second major surface of said support member
to thereby enable the first end of said draw bar to be accessed
from said second major surface, said first end further including a
drive coupling operative to transmit loading to rotate said draw
bar about its axis.
9. A disc brake assembly according to claim 7, wherein a region of
the operative surface corresponds to the passage, the region being
approximately a size proportional to an expected actuation load
induced on the operative surface by the draw bar received within
the passage and wherein the passage is located substantially at the
centre of that region.
10. A disc brake assembly according to claims 6, wherein said draw
bar includes a plurality of abutment surfaces angularly spaced
about said draw bar axis.
11. A disc brake assembly according to claim 10, wherein said draw
bar includes a T-shaped head having a pair of abutment surfaces
spaced apart about said draw bar axis by approximately
180.degree..
12. A disc brake assembly according to claim 3, wherein said
retaining device is in the form of a clip connected to or
integrally formed with said one pad assembly, said clip including a
resiliently deformable body which includes at least one cavity
adapted to receive a part of the draw bar, the cavity incorporating
an inner surface which is engagable with said draw bar to inhibit
rotation of said draw bar about its axis.
13. A disc brake assembly according to claim 12, wherein said
biasing means is formed as part of said clip and includes an
abutment member which abuts the draw bar so as to bias the draw bar
into engagement with said one pad assembly.
14. A disc brake assembly according to claim 13, wherein said clip
is caused to deform when said draw bar is captured within said
cavity to thereby bias said abutment member into engagement with
said draw bar.
15. A disc brake assembly according to claim 1, wherein said piston
is movable relative to the cylinder along a movement axis and
wherein said draw bar extends co-axial with said movement axis.
16. A disc brake assembly according to claim 1, wherein each said
pad assembly overlies part of each of said outer and inner disc
portions and is engagable with the respective said adjacent side of
the disc at both said outer and inner portions.
17. A disc brake assembly according to claim 1, wherein said force
transmitting means includes a plurality of said draw bars.
18. A disc brake assembly according to claim 17, wherein the
actuation means includes a plurality of said piston cylinder
assemblies each having a respective one of said draw bars connected
thereto.
19. A disc brake assembly according to claim 1, further including
an anchor bracket securable to a support structure, the anchor
bracket including a pair of support elements arranged to extend
through said gap to support said pad assemblies and accommodate
torque loading induced in operation of the assembly.
20. A brake pad assembly for use in a disc brake assembly having an
axis of rotation, the pad assembly including a support member and a
friction lining connected to or integrally formed with the support
member, a surface of the friction lining forming an operative
surface of the pad assembly having relative to the axis of
rotation, a radially outer and a radially inner edge interconnected
by two side edges, the pad assembly incorporating at least one
passage extending through said friction lining and at least into
the support member, the or each passage being arranged to receive
an end of a draw bar operable to impart an actuating force to said
pad assembly, wherein the passage is of non circular cross section
and the pad assembly includes at least one abutment surface
disposed adjacent the or each passage which is operative to engage
with a complimentary abutment surface of the draw bar to couple the
pad assembly to said draw bar.
21. A brake pad assembly according to claim 20, further including a
retaining device operative to inhibit rotation of the draw bar
relative to the pad assembly when in engagement with said abutment
surface.
22. A brake pad assembly according to claim 20, wherein the support
member includes a first major surface on which the friction lining
is located and a second major surface opposite said first surface,
and wherein said passage extends through said support member to
said second major surface.
23. A brake pad assembly according to claim 20, wherein the passage
includes a central axis and is configured to include a slot which
extends radially to said central axis and which allows an end of
the draw bar to be received in the passage, and wherein the
abutment surface is angularly spaced from said radial slot so that
the draw bar can engage with said abutment surface on rotation
about said central axis.
24. A brake pad assembly according to claim 23, wherein the passage
is elongate having relative to its axis, a first radial dimension
which is larger than an orthogonal second radial dimension, and
wherein the radial slot extends in the direction of the first
radial dimension and a pair of said abutment surfaces are spaced
apart in the direction of the second radial dimension and disposed
on respective opposite sides of the slot.
25. A brake pad assembly according to claim 21, wherein said
retaining device is in the form of a clip including a resiliently
deformable body which includes at least one cavity adapted to
receive a part of the draw bar, the cavity including an inner
surface which is engagable with said draw bar to inhibit rotation
of said draw bar about the passage axis.
26. A brake pad assembly according to claim 25, wherein the clip
further includes an abutment member which abuts the draw bar so as
to bias the draw bar into engagement with said one pad
assembly.
27. A brake pad assembly according to claim 20, wherein a region of
the operative surface corresponds to the or each passage, each
region being approximately a size proportional to an expected
actuation load induced on the operative surface by the draw bar
received within the respective passage and wherein each passage is
located substantially at the centre of that region.
28. A brake pad assembly according to claim 20, wherein each side
edge of the support member includes an abutment surface, the
abutment surfaces being engagable with respective support elements
of the disc brake assembly to transfer torque loading from said
brake pad assembly to said support elements on operation of said
disc brake assembly.
29. A brake pad assembly according to claim 28, wherein the
abutment surfaces are located in recesses formed in the said side
edges of said support member, the recesses being adapted to receive
the support elements of the disc brake assembly therein.
30. A brake pad assembly according to claim 28, wherein the side
edges include laterally extending protrusion which incorporates
said abutment surfaces, said protrusions being configured to be
received in corresponding recesses located in the support elements
of the disc brake assembly.
31. A brake pad assembly according to claim 20, wherein the
friction lining is separated into two parts by a space which
extends circumferentially to the rotation axis of the disc with
each part of the friction lining being engagable with a respective
one of two radially separated portions of the disc.
32. A brake pad assembly according to claim 31, wherein the or each
passage communicates with the channel, or at least one of said
channels, formed in said friction lining.
33. A brake sub assembly adapted for use in a disc brake assembly
according to claim 1, and including said two pad assemblies and
said actuating means.
34. A disc brake assembly including a disc having an axis of
rotation and including a radially outer portion and a radially
inner portion, each of the outer and inner portions having a
braking surface on each of two opposite sides of the disc, and a
gap forming a radially separation between said outer and inner
portions and extending in a continuous circle co-axial with said
axis of rotation, connecting means spaced from the braking surface
and interconnecting the inner and outer portions, the connecting
means being in the form of a bracket located on one side of the
disc and adapted to fixedly secure said inner and outer portions in
spaced relation to one another which prevents relative axial
movement of the portions, two pad assemblies located on respective
said opposite sides of the disc and each being mounted for movement
towards and away from said disc, and actuating means operable to
cause each said pad assembly to move towards and engage the
respective adjacent said side of the disc and including force
transmitting means which extend through said gap and provides at
least part of an interconnection between said pad assemblies such
that one responds to movement of the other towards or away from
said disc, wherein said actuating means includes a piston cylinder
assembly in which the piston is moveable relative to the cylinder
along a movement axis, either the cylinder or the piston being
connected to said other pad assembly for movement therewith, and
said force transmitting means including a draw bar extending
co-axial with said movement axis and connecting either said piston
or said cylinder respectively to said one pad assembly.
35. A brake pad assembly for use in a disc brake assembly including
a disc having an axis of rotation, the pad assembly including a
support member and a friction lining connected to, or integrally
formed with, the support member, a surface of the friction lining
forming an operative surface of the pad assembly having relative to
the axis of rotation, a radially outer and a radially inner edge
interconnected by two side edges, the pad assembly incorporating at
least one passage extending through said friction lining and at
least into the support member, the or each passage being arranged
for receiving a force transmitting element operable to interconnect
the pad assembly with another pad assembly, and abutment surfaces
located on opposite sides of said support member, the abutment
surfaces being engagable with respective support elements of the
disc brake assembly and being adapted to transfer torque loading
from said brake pad assembly to said support member on operation of
said disc brake assembly.
36. A brake pad assembly according to claim 35, wherein a region of
the operative surface corresponds to the or each passage, each
region being approximately a size proportional to an expected
actuation load induced on the operative surface by the force
transmitting element received within the respective passage and
wherein each passage is located substantially at the centre of that
region.
37. A brake pad assembly according to claim 35, wherein the
abutment surfaces are located in recesses formed in the said
opposite sides of said support member, the recesses being adapted
to receive the support elements of the disc brake assembly
therein.
38. A brake pad assembly according to claim 35, wherein the or each
passage extends to the radially inner edge of the support
member.
39. A disc for a disc brake assembly, the disc being rotatable
about an axis of rotation and including a radially outer portion
and a radially inner portion, each of the outer and inner portions
having a braking surface on each of two opposite sides thereof and
a gap forming a radial separation between said outer and inner
portions and extending in a continuous circle co-axial with said
axis of rotation, and connecting means spaced from the braking
surfaces and interconnecting the inner and outer portions of the
disc, the connecting means being in the form of a bracket located
on one side of the disc, the bracket being spaced from the braking
surface on that side of the disc to form a cavity in which a brake
pad assembly is able to be located, the bracket further
incorporating at least one passage providing access to the
cavity.
40. A disc according to claim 39, wherein the bracket includes a
plurality of passages.
41. A disc according to claim 39, wherein the bracket is adapted to
be connected to a hub of a wheel assembly so as to connect the disc
to said wheel assembly.
42. A disc according to claim 39, wherein at least one of the outer
or inner portion is movable relative to the other of the outer or
inner portion in a direction substantially parallel to the axis of
rotation of the disc.
43. A disc according to claim 39, wherein at least one of the inner
or outer portions is formed from a plurality of segments.
44. A disc according to claim 39, wherein the inner and outer
portions and the bracket is formed as a single piece.
45. A disc according to claim 39, wherein the inner and outer
portions are connected to the bracket.
46. A disc according to claim 39, wherein the inner and outer
portions are formed from different materials.
47. A disc according to claim 39, wherein the braking surfaces are
machined on the inner and outer portions using a chip producing
process.
48. A method of forming a disc for a disc brake assembly, the disc
being rotatable about an axis of rotation and including a radially
outer portion and a radially inner portion, each of the outer
portion and the inner portion having two opposite sides thereof and
a gap forming a radial separation between said outer and inner
portion and extending in a continuous circle coaxial with the axis
of rotation, the method including the steps of: (i) providing a
tool including a central shaft and including at least one cutting
head having a cutting edge radially spaced from, and rotatable
about, the shaft; (ii) locating the cutting tool such that the
cutting head is on one side of the disc with the shaft being
substantially aligned with said gap; (iii) rotating the shaft to
cause the cutting head to move in a circular path such that the
cutting edge engages the one side of both the inner and outer
portions of the disc on rotation of the shaft to thereby machine
braking surfaces on the one side of both the inner and outer
portions of the disc.
49. A method according to claim 48, wherein the shaft of the
cutting tool is parallel to said axis of rotation.
50. A method according to claim 48, further including the step of:
(i) locating the cutting tool relative to the disc such that the
shaft extends through said gap.
51. A method according to claim 48, further including the steps of:
(i) providing the tool with a second cutting head having a cutting
edge radially spaced from the shaft, the second cutting head being
spaced from the first cutting head along the shaft; (ii)
positioning the cutting tool such that the shaft extends through
said gap and that the cutting heads are located on respective
opposite sides of said disc; and (iii) rotating the shaft to cause
both the cutting heads to move in a circular path such that the
cutting edges engage respective ones of the sides of both the inner
and outer portions of the disc on rotation of the shaft to thereby
simultaneously machine braking surfaces on both sides of both the
inner and outer portions of the disc.
52. A method according to claim 48, further including the steps of:
(i) moving at least one of the cutting edges in a direction
substantially parallel to the axis of rotation of the shaft to
thereby vary the depth of cutting of that cutting edge on machining
of the braking surfaces.
53. A method according to claim 48, further including the step of:
(i) providing the tool with the or each cutting head including a
plurality of cutting edges angularly spaced around the shaft.
54. A method according to claim 48, further including the step of:
rotating the disc about the axis of rotation to provide feed for
the cutting tool.
55. A method according to claim 48, further including the step of:
(i) varying the speed of rotation of the disc relative to the speed
of rotation of the shaft to vary the surface finish on the braking
surface.
Description
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 08/666,394 incorporated herein by reference in
its entirety.
[0002] The invention relates to disc brakes, and is particularly
but not exclusively concerned with such brakes as used with motor
vehicles. It will be convenient to hereinafter describe the
invention by reference to motor vehicle wheel brakes, but it is to
be understood that the invention has wider application.
[0003] In a typical disc brake assembly for a motor vehicle, a
caliper bridge is arranged to straddle a rotatable disc. The bridge
incorporates inboard and outboard portions each of which
incorporates an associated friction pad. The portions are able to
move relative to one another to enable the friction pads to engage
opposite faces of the disc under the influence of a hydraulic
piston cylinder assembly acting on the inboard portion.
[0004] In operation, stresses are induced in the brake assembly
which cause deflection of the caliper. In one form of deflection,
the caliper may stretch in an axial direction, i.e. in a direction
parallel to the axis of rotation of the disc. In another form, the
caliper may yawn or splay under load causing uneven loading to be
applied to the disc by the pad assemblies. Furthermore, the caliper
may tilt relative to the axis of the rotation of the disc causing
the pads to tend to taper after continued use. These deflections
are undesirable as they increase the fluid required to actuate the
brakes, cause variations in the specific torque output of the brake
assembly under different loadings, and result in uneven wearing of
the pads.
[0005] To compensate for the effects of this loading, different
caliper designs have been proposed to minimise the deflection of
the caliper. However, these designs have not been completely
effective in stopping deflection of the caliper. Furthermore, these
designs often add to the weight of the assembly, the complexity of
its manufacture and the manufacturing costs. In addition these
assemblies are often unable to dissipate heat as effectively due to
the additional structure provided to make the brake assembly
stiffer.
[0006] An aim of the present invention is to provide a disc brake
assembly which is better able to accommodate the stresses induced
in use of the brake assembly. It is a further aim of the invention
to provide a disc brake assembly which has enhanced characteristics
over prior art brake assemblies in relation to the cost of
manufacture, its weight, serviceability and efficiency in
dissipating heat.
[0007] In a first aspect, the present invention provides a disc
brake assembly including, a disc having an axis of rotation and
including a radially outer portion and a radially inner portion, a
gap forming a radial separation between the outer and inner
portions and extending in a continuous circle co-axial with the
axis of rotation, two pad assemblies located on respective opposite
sides of the disc and each being mounted for movement towards and
away from the disc, and actuating means operable to cause each pad
assembly to move towards and engage the respective adjacent side of
the disc and including force transmitting means which extends
through the gap and provides at least part of an interconnection
between the pad assemblies such that one responds to movement of
the other towards or away from the disc, wherein the actuating
means includes a piston cylinder assembly in which the piston is
movable relative to the cylinder along a movement axis, either the
cylinder or the piston being connected to the other pad assembly
for movement therewith, and the force transmitting means including
a draw bar extending co-axial with the movement axis and connecting
either the piston or the cylinder respectively to the pad
assembly.
[0008] Preferably each pad assembly overlies part of each of the
outer and inner disc portions and is engagable with the outer and
inner portions on respective sides of the disc.
[0009] By locating the force transmitting means to extend through
the gap in the disc, a caliper bridge is no longer required.
Furthermore when each pad assembly is engagable with both the outer
and inner disc portions, the brake assembly is better able to
accommodate the loads induced in operation of the assembly as the
bending moment on the force transmitting means generated by the
contact surface which is at a radially outer side of the force
transmitting means is offset by the bending moment generated by the
contact surface at the radially inner side. Furthermore, with the
draw bar extending along the axis of movement of the piston
relative to the cylinder, bending stresses acting on the force
transmitting means are minimised and the clamping load in the brake
assembly is able to be transferred substantially along the force
transmitting means. Consequently, the bending moment in the force
transmitting means is reduced or even eliminated as compared to a
conventional caliper bridge.
[0010] The individual pad assemblies include a section of friction
material, with a surface of the friction material forming an
operative surface of the respective pad assembly. Each pad assembly
may incorporate separate sections of friction material, each of
which has a discrete operative surface. However, for the purposes
of this specification, the discrete operative surfaces of a
respective pad assembly shall be collectively referred to as "an
operative surface" for that pad assembly and may be considered as a
single entity which has an outer perimeter defined by outer edges
of the discrete operative surfaces.
[0011] The force transmitting means is operable to apply a force to
a region of the operative surface of one of the pad assemblies at a
location substantially coincident with the centre of that region.
An advantage of invention is that as the draw bar extends through
the pad assemblies, the draw bar can be connected to the other pad
assembly at a position which provides a preferred load distribution
on the support member of that pad assembly. In this way, deflection
of the pad assembly in operation of the assembly may be
minimised.
[0012] In a further aspect, the present invention provides a disc
brake assembly including, a disc having an axis of rotation and
including a radially outer portion and a radially inner portion, a
gap forming a radial separation between the outer and inner
portions and extending in a continuous circle coaxial with the axis
of rotation, two pad assemblies located on respective opposite
sides of the disc and each being mounted for movement towards and
away from the disc, an actuating means operable to cause each pad
assembly to move towards and engage a respective adjacent side of
the disc and including force transmitting means which extends
through the gap and provides at least part of an interconnection
between the pad assemblies such that one responds to movement of
the other towards or away from the disc, wherein the actuating
means includes a piston cylinder assembly in which the piston is
moveable relative to the cylinder, either the cylinder or the
piston being connected to the other pad assembly for movement
therewith and the force transmitting means includes a draw bar
which extends along an axis and connects either the piston or the
cylinder respectively to the one pad assembly, the draw bar being
rotatable about its axis and being releaseably coupled to the one
pad assembly so as to be operative to move between an engaged
configuration with the one pad assembly to a released configuration
on rotation about the draw bar axis.
[0013] This arrangement has significant practical benefit as it
allows for a secure connection between the draw bar and the one pad
assembly which can be easily released or engaged by rotation of the
drawbar about its axis, thereby contributing both to the safety of
the assembly as well as its serviceability.
[0014] In a preferred form, the one pad assembly includes a passage
adapted to receive a first end of the draw bar, the draw bar
includes at or adjacent this first end at least one abutment
surface disposed radially outwardly from the draw bar axis and
which faces towards the piston cylinder assembly. The disc brake
assembly is configured such that in the engaged configuration, the
abutment surface engages with a complementary abutment surface of
the one pad assembly so as to prevent removal of the draw bar from
the passage and wherein when in the released configuration, the
abutment surface is locatable within the passage so as to enable
the draw bar to be released from the one pad assembly via the
passage.
[0015] In a preferred form, the assembly further includes a
retaining device operable to inhibit rotation of the draw bar when
in engagement with the one pad assembly. Further, the assembly
preferably includes biasing means to bias the draw bar towards the
one pad assembly when in this engaged configuration.
[0016] The retaining device prevents unwanted draw bar rotation
whereas the biasing means has a dual function of preventing rattle
in the assembly as well as maximising the retraction of the one pad
assembly on release of the brakes. The retaining device and the
biasing means may be combined in a single component or separate
components can be used for each device. Furthermore either of these
devices can form an integral part of the one pad assembly or may be
provided separately such as by a bolt on or a clip on feature.
[0017] In one form, the retaining device comprises a clip connected
to or integrally formed with the one pad assembly, the clip
includes a resiliently deformable body which includes at least one
cavity adapted to receive a part of the draw bar. The cavity
incorporates an inner surface which is engagable with the draw bar
to inhibit rotation of the draw bar about its axis. In one form the
biasing means is formed as part of the clip and includes an
abutment member which abuts the draw bar so as to bias the draw bar
into engagement with the one pad assembly. In one arrangement, the
clip is caused to deform when the draw bar is captured within the
cavity to apply the loading to bias the abutment member into
engagement with the draw bar.
[0018] In a preferred form, the draw bar includes a plurality of
abutment surfaces angularly spaced about the draw bar axis. In one
form, the draw bar includes a T-shaped head having a pair of
abutment surfaces spaced apart about the draw bar axis by
approximately 180.degree..
[0019] Preferably, the one pad assembly includes a support member
having opposite first and second major surfaces. A friction lining
is connected to or integrally formed with the support member along
the first major surface to form an operative surface of the pad
assembly and wherein the passage extends through the operative
surface and at least into the support member. Preferably the
passage extends through to the second major surface of the support
member to thereby enable the first end of the draw bar to be
accessed from the second major surface. Preferably in this
arrangement, the first end further includes a drive coupling
operative to transmit loading to rotate the draw bar about its
axis.
[0020] In a preferred form of this aspect of the invention, the
piston is movable relative to the cylinder along a movement axis
and the draw bar extends co-axial with this movement axis.
[0021] Preferably, the brake assembly according to either aspect of
the invention detailed above further incorporates an anchor bracket
which is securable to a support structure and includes a body on
which one of the pad assemblies is mounted to accommodate torque
forces generated in use of the assembly. Preferably the bracket
includes a pair of support elements which extend through the gap
and are connected to the other pad assembly to at least assist in
guiding movement of that pad assembly.
[0022] In a further aspect of the invention a brake sub assembly is
provided for use in any of the forms of the disc brake assembly
described above. The brake sub assembly includes the brake pad
assemblies, actuating means and force transmitting means which is
operable to pass through the brake pad assemblies to provide at
least part of the interconnection between the pad assemblies.
[0023] In yet a further aspect the present invention provides a
brake pad assembly for use in a disc brake assembly having an axis
of rotation, the pad assembly including a support member and a
friction lining connected to or integrally formed with the support
member, a surface of the friction lining forming an operative
surface of the pad assembly having relative to the axis of
rotation, a radially outer and a radially inner edge interconnected
by two side edges, the pad assembly incorporating at least one
passage extending through said friction lining and at least into
the support member, the or each passage being arranged to receive
an end of a draw bar operable to impart an actuating force to said
pad assembly, wherein the passage is of non circular cross section
and the pad assembly includes at least one abutment surface
disposed adjacent the or each passage which is operative to engage
with a complimentary abutment surface of the draw bar to couple the
pad assembly to the draw bar.
[0024] Preferably the brake pad assembly includes a retaining
device operative to inhibit rotation of the draw bar relative to
the pad assembly when in engagement with the abutment surface.
[0025] Preferably the support member includes a first major surface
on which the friction lining is located and a second major surface
opposite the first surface, and the passage extends through the
support member to the second major surface. Preferably the passage
includes a central axis and is configured to include a slot which
extends radially to said central passage and which allows an end of
the draw bar to be received in the passage. Preferably the abutment
surface is angularly spaced from the radial slot so that the draw
bar can engage with the abutment surface on rotation about the
central axis of the passage.
[0026] In a preferred form, the passage is elongate having relative
to its axis, a first radial dimension which is larger than an
orthogonal second radial dimension. In this arrangement the radial
slot extends in the direction of the first radial dimension and a
pair of abutment surfaces are preferably spaced apart in the
direction of the second radial dimension and disposed on respective
opposite sides of the slot.
[0027] In a preferred form, the retaining device is in the form of
a clip including a resiliently deformable body which includes at
least one cavity adapted to receive a part of the draw bar, the
cavity includes an inner surface which is engagable with the draw
bar to inhibit rotation of the draw about the passage axis.
Preferably the clip further includes an abutment member which is
adapted to be biased into engagement with an end of the draw bar so
as to bias the draw bar into engagement with the one pad
assembly.
[0028] Preferably a region of the operative surface corresponds to
the or each passage, each region being approximately a size
proportional to an expected actuation load induced on the operative
surface by the force transmitting element received within the
respective passage and wherein, the or each passage is located
substantially at the centre of that region. Further, the passage
may extend to an edge of the pad to thereby facilitate lateral
release of the pad from the force transmitting element.
[0029] The friction lining may also be separated into two parts by
a space which extends circumferentially to the rotational axis of
the disc with each part of the friction lining being engagable with
a respective one of two radially separated portions of the
disc.
[0030] Preferably each side edge of the support member also
includes an abutment surface, these abutment surfaces being
engagable with respective support elements of the disc brake
assembly to transfer torque loading from the disc brake assembly to
the support elements. In one form the abutment surfaces are located
in recesses formed on the side edges of the support member. In
another form, the abutment surfaces are formed on protrusions which
extend from the side edges.
[0031] Preferably the friction lining also includes at least one
radially extending channel extending across the operative surface
to promote heat dissipation at the operative surface. Preferably
the or each passage communicates with the channel or at least one
of the channels formed in the friction lining.
[0032] In yet a further aspect the invention provides a disc for a
disc brake assembly, the disc being rotatable about an axis of
rotation and including a radially outer portion and a radially
inner portion, each of the outer and inner portions having a
braking surface on each of two opposite sides thereof and a gap
forming a radial separation between said outer and inner portions
and extending in a continuous circle co-axial with said axis of
rotation, and connecting means spaced from the braking surfaces and
interconnecting the inner and outer portions of the disc, the
connecting means being in the form of a bracket located on one side
of the disc, the bracket being spaced from the braking surface on
that side of the disc to form a cavity in which a brake pad
assembly is able to be located, the bracket further incorporating
at least one passage providing access to the cavity.
[0033] Preferably the braking surfaces are provided on both the
inner and outer portion and when used with a brake pad assembly as
described above, the respective braking surfaces provide suitable
engagement surfaces for the operative surfaces of the respective
brake pad assemblies. Furthermore, the force transmitting means and
the anchoring bracket are able to pass through the aperture in the
disc, without inhibiting rotation of the disc.
[0034] Preferably there are a plurality of passages formed in the
bracket. This arrangement also assists in ventilation of the
assembly.
[0035] In a further aspect, the invention relates to a method of
forming a disc of the above type. The disc may be formed in one
piece or may be formed in separate pieces with the aperture and the
contact surfaces machined by any or ail of grinding, turning and
milling of the disc.
[0036] It will be convenient to hereafter describe various
embodiments of the invention in greater detail with reference to
the accompanying drawings. The particularity of these drawings in
the related description is not to be understood as superseding the
generality of the preceding broad description of the invention.
[0037] In the drawings:
[0038] FIG. 1 is an exploded perspective view of a sub assembly for
a disc brake assembly according to a first embodiment of the
invention;
[0039] FIG. 2 illustrates an exploded perspective view of a sub
assembly for a disc brake assembly according to a second embodiment
of the invention.
[0040] FIG. 3 is a sectional view of the first embodiment of a disc
for use in a disc brake assembly according to the invention;
[0041] FIG. 4 is a sectional view of a second embodiment of a disc
for use in the disc brake assembly according to the invention;
[0042] FIG. 5 is a variation of the disc of FIG. 4;
[0043] FIG. 6 is a perspective view of a disc brake assembly
including the sub assembly of FIG. 1;
[0044] FIG. 7 is a sectional view along section line VII-VII of
FIG. 6 and illustrating a full cast disc;
[0045] FIG. 8 is a perspective view of a variation of the brake pad
assembly for use in the sub assembly of FIG. 1;
[0046] FIG. 9 illustrates a machining tool for preparation of the
braking surfaces of the disc of the disc brake assembly;
[0047] FIG. 10 is a variation of the machining tool of FIG. 9
incorporating two cutting heads,
[0048] FIG. 11 is a schematic view of the braking surfaces on a
disc using the machining tools of either FIG. 9 or 10.
[0049] FIG. 12 is a rear perspective view of the outboard brake pad
assembly for use in the sub assembly of FIG. 2;
[0050] FIG. 13 is a detailed view to an enlarged scale of the
interconnection between the draw bar head and the pad assembly clip
of the sub assembly of FIG. 2 with the draw bar in a released
configuration with the pad assembly;
[0051] FIG. 14 illustrates the view of FIG. 13 with the draw bar in
an engaged configuration with the pad assembly;
[0052] FIG. 15 is a partial exploded perspective view of a
variation of the pad assembly anchor bracket of a disc brake sub
assembly;
[0053] FIG. 16 is a sectional elevation of the disc brake assembly
including the sub assembly of FIG. 2 with the draw bar fixedly
secured to the piston;
[0054] FIG. 17 is a variation of FIG. 16 with the draw bar
connected to the piston to enable relative movement; and
[0055] FIG. 18 is a further variation of the brake pad assembly of
FIG. 16 with the draw bar coupled to the cylinder.
[0056] FIG. 1 illustrates a sub assembly 10 of a disc brake
assembly 100 according to an embodiment of the invention. This
figure is an exploded view to more clearly disclose the various
component parts.
[0057] The sub assembly incorporates inboard and outboard friction
pad assemblies (11 and 12 respectively), each of which incorporates
a support plate (13, 14) and a friction pad (15, 16). Typically,
each friction pad is bonded or riveted to its respective support
plate to transmit shear load.
[0058] An anchor bracket 17 is adapted to be mounted to a motor
vehicle through mounting holes 18. Guide rails 19 extend along
opposing sides of the bracket to support the inboard and outboard
assemblies. Cooperable slots 20 are located on the respective
inboard and outboard assemblies 11, 12 and receive the guide rails
enabling the assemblies to be slidably mounted on the anchor 17 in
a direction away or towards each other. It should be appreciated
that the pad assemblies may be secured to the anchor bracket 17 in
other ways, such as with slideways located on the anchor bracket
arranged to receive respective ends of the assemblies, or by a pin
guided arrangement. Once such arrangement is disclosed in FIG. 15
where the pad assemblies 11 and 12 include laterally extending
protrusions 86. The anchor bracket 17 includes sideways 87 which
are configured to receive the protrusions 86. With either of these
arrangements, the pad assemblies are slidably mounted on the anchor
17. Furthermore torque loading induced on the pad assemblies can be
translated to the anchor bracket 17 via theses connections.
[0059] Two cylinder piston assemblies (22, 23) form the actuating
means 21 of the sub assembly 10. In the embodiments of FIGS. 1 and
2, each cylinder piston assembly includes a cylinder 24 mounted to
the inboard pad assembly through bracket 25, and piston 26. The
piston 26 is slideable within the cylinder 24 along a movement axis
71 (FIG. 7) and movable in a direction away or towards the support
plate 13 of the inboard assembly 11 under hydraulic pressure. A
seal 27 (FIG. 7) is located between the piston 26 and cylinder 24
and a boot (not shown) is located on the cylinder on the inboard
side of the seal 27. It should be realised that a single cylinder
could be used and that the number of cylinders in the assembly 10
may vary depending on the size of the assembly as well as the
specific torque output required. Furthermore, the cylinders may be
secured to the support plate 13 in any suitable form including
integrally forming the cylinders with the support plate.
Furthermore, it may be desirable to have only a reduced contact
area between the cylinder and the plate and this arrangement is
illustrated in FIG. 7.
[0060] Force transmitting means 28 is associated with the actuating
means 21 to provide at least part of an interconnection between the
pad assemblies such that the inboard assembly responds to movement
of the outboard assembly towards or away from the disc. In the
first embodiment, the force transmitting means 28 is in the form of
draw bars or rods 29 associated with each cylinder piston assembly
and, each of which has an axis which extend coaxial with the
movement axis 71. In FIG. 1, the rods 29 are integrally formed with
respective pistons 26. The rods pass through apertures (30, 31, 32)
in the respective cylinders 24 and pad assemblies 11 and 12 and are
secured to the outboard support plate 14. The rods 29 are slideable
within the apertures 30 and 31 enabling the rods to be movable
relative to the cylinders 24 and the inboard pad assembly 11. A
seal 33 (FIG. 7) is provided in the respective apertures 30 to seal
between the respective rods 29 and the cylinders 24.
[0061] Various different coupling arrangements between the rods 29
and the respective piston cylinder assemblies are illustrated in
FIGS. 16 to 17. Each of these arrangements relate to a second
embodiment of the disc brake assembly which is illustrated in FIG.
2 and which is described in more detail below. However it is
appreciated that the coupling arrangements between rods and the
piston cylinder assemblies could equally be used in conjunction
with the disc brake assembly of FIG. 1.
[0062] In the version illustrated with reference to FIG. 16, the
rod 29 is connected to the piston 26 via a screw threaded
arrangement 88. In this arrangement the rod includes a threaded
shaft 89 which is receivable in a complementary threaded hole 90
formed in the piston 26. The piston 26 it is arranged to be
tightened into engagement with a shoulder 91 of the rod to thereby
fixedly secure the piston 26 to the rod 29 so as to prevent
relative movement between the rod 29 and the piston 26.
[0063] In contrast, in the arrangement illustrated in FIG. 17, the
coupling between the piston 26 and the rod 29 is designed to allow
relative movement between the rod and the piston so that the rod 29
is capable of rotation about its axis 71 relative to the piston 26
whilst being restrained from relative axial movement in the
direction of the rod axis. In the coupling illustrated in FIG. 17,
the rod 29 includes an end region 92 which is stepped to include
first and second parts (93 and 94) of increasingly reduced
diameter. The second part 94 is threaded and adapted to receive a
nut 95. The end region 92 passes through an aperture 96 in the
piston. The aperture is dimensioned so as to be less than the
diameter of the main part of the rod 29 so that the piston 26 abuts
against a shoulder 97 formed between the main part of the rod 29
and the first part 93.
[0064] The length of the first part 93 is arranged to be slightly
longer than the aperture 96 so that the first part extends into a
cavity 98 formed in the piston 26. With this arrangement the nut 95
is arranged to be screwed against a shoulder 99 formed between the
first part 93 and the second part 94 of the rod 29. This causes the
piston to be captured between the nut 95 and the abutment surface
97 thereby preventing relative axial movement between the piston 26
and the rod 29 beyond that provide by the clearance obtained by
making the length of the first part 93 longer than the apature 96.
However this arrangement allows for rotation of the rod 29 relative
to the piston 26 about the rod axis 71. A seal 101 is provided to
cause a fluid tight seal between the piston and the first part 93
of the rod 29.
[0065] If it is required in the embodiment of FIG. 17, that the rod
29 be fixed to the piston 26, the second part 94 could be shortened
to be less than the aperture 96 so that the nut 95 bears against
the cavity 98 thereby preventing relative rotation between the rod
and the piston.
[0066] In the arrangement of FIG. 18, the rod 29 is secured to the
cylinder 24 rather than to the piston 26 In this arrangement the
piston is releasably coupled to support plate 13 of the inboard pad
assembly 11 by a bracket 102 which operates in a similar fashion to
the bracket 25. The bracket 102 is secured to the back plate 13 and
includes a radially inwardly directed bead 103 which is adapted to
locate within a corresponding annular groove 104 formed in the
piston 26.
[0067] The rod 29 passes both through the piston 26 and through
aperture 105 formed on an end surface 106 of the cylinder 24. Seals
107 provide a fluid tight seal between the rod 29 and the cylinder
26 and cylinder 24 respectively. Similar to the arrangement of FIG.
17, the rod 29 is stepped to include first and second parts (108
and 109 respectively) of increasingly reduced diameter with the
second part being threaded to receive a nut 110. With this
arrangement, the nut is adapted to be tightened against a shoulder
111 formed between the first and second parts. The first part
extends through the aperture 105 and the rod is dimensioned so that
the first part is captured in the aperture by the nut bearing
against the shoulder 111 and the main part of the rod 29 bearing
against the inner surface of the cylinder 24. The first part 108 is
slightly longer than the aperture 105 so as to restrain the rod
from axial movement relative to the cylinder. Limited axial
movement is provided by the dimensions of the first part and the
aperture. This ensures that the rod is able to rotate relative to
the cylinder without binding and also assists in allowing a
positive running clearance to be established on release of the
brakes by the restoring forces of the seals 107 acting on the rod
29.
[0068] In the arrangement of FIG. 1, to secure the rod 29 to the
outboard pad assembly 12, each rod incorporates a threaded stud 34
on its outer end which is arranged to receive a cooperable nut 35.
Furthermore, the rod 29 is keyed to the support plate 14 to prevent
relative rotation thereof during tightening of the nut 35 by a
portion 36 located adjacent the stud 34 and having a rectangular or
any other non-circular shape cross-section which is received in the
suitably shaped aperture 32 in the outboard support plate.
Furthermore, the rods 29 are positioned across the support plate 14
at a position to optimise the load distribution induced on the
plate 14 by the rods 29. In this arrangement, as there are two
rods, the friction pad 16 may be divided notionally into two
regions with each rod connected at a centre of a respective one of
the regions. To evenly distribute the load across the plate the
size of each region would be proportional to the expected actuation
load induced by each rod. In the illustrated case as each rod is
expected to transmit half the actuation load, the size of these
regions is approximately the same.
[0069] FIG. 2 illustrates a different arrangement, where each rod
29 incorporates an enlarged T-shaped head portion 37 and each
aperture (31, 32) in the pad assemblies is elongated to accommodate
entry of the respective head portions. Each slot has relative to
the central axis of the passage a radial dimension which is larger
in the direction across the pad than in an orthogonal direction
extending between the inner and outer edges. The rods 29 are
arranged to be secured to the outboard support plate 14, once the
respective heads have passed through apertures 32, by rotating the
rods through 90.degree.. The heads are biased towards support plate
14 to minimise rattle by spring clip 112. At the same time this
clip also acts as an antirotational device for the head.
[0070] FIGS. 12 to 14 and 16 illustrate the constructions of the
clip 112 and the coupling arrangement between the outboard pad
assembly and the T-shaped head 27 of the rods 29.
[0071] In the illustrated form, a clip assembly 113 which
incorporates a pair of clips 112 and base a plate 114 is secured to
the support plate 14 of the outboard pad assembly with each clip
112 being aligned over the elongate aperture 32 of that pad
assembly. Each clip 112 includes a body 115 which is formed from
resiliently deformable sheet material. The clip 112 is formed out
of plane so as to have a generally arcuate cross section in
elevation as best illustrated in FIG. 16. The body 115 includes a
central aperture 116 aligned over a respective one of the apertures
32 and has two laterally adjacent slots 117 separated by marginal
regions 118. Each of the slots 117 include an inner surface
119.
[0072] FIG. 13 illustrates the head in a released configuration
with the outboard pad assembly. In this position the head is
aligned with the aperture 32 so that it can pass through the
aperture 32 in the outboard pad assembly 12. A space 120 is
provided between the clip 112 and the support plate 14 which is
configured to accommodate the head portion 37 when it has passed
through the support plate 14 in this released configuration.
[0073] To couple the outboard pad assembly 12 to the rod 29, the
head is rotated through 90.degree. from the position of FIG. 13 to
the position illustrated in FIG. 14. In this engaged configuration,
the head is arranged to locate within the laterally adjacent slots
118. Furthermore rotation between the released position of FIG. 13
and the engaged position of FIG. 14 causes the clip 112 to deform
outwardly such that the marginal regions 118 are biased into
engagement with the end surface of the head 37. In this position,
the inner surface 119 of the lateral slot 117 inhibit rotation of
the rod 29 about its axis 71. Furthermore the head 37 is biased
into engagement with the support plate 14 by the applied force of
the marginal regions 118 of the clip.
[0074] As best illustrated in FIG. 16, when in the engaged position
of FIG. 14, an inner surface 121 of the head portion 37 is arranged
to abut a region 122 of the support plate 14 adjacent the aperture
32, thereby preventing release of rod 29 from the outboard pad
assembly 12.
[0075] As will be appreciated, this coupling arrangement provides a
convenient yet secure means of coupling the outboard pad assembly
to the draw bar. This arrangement provides greater ease of
serviceability as compared to the nut and bolt arrangement of the
brake assembly of FIG. 1 and provides improved safety. In the
arrangement where a locking nut is used to secure the rod to the
outboard pad assembly, a minimum torque loading needs to be applied
to the nut to ensure that a secure connection is made. There is no
such requirement in the coupling of the FIG. 2 assembly.
[0076] The head portion 27 of the rod 29 further includes a drive
coupling 123 which enables a torque loading to be applied to the
draw bar to enable it to be rotated between its released and
engaged configuration from the outboard side of the disc brake
assembly. This drive coupling can be accessed through the central
aperture 116.
[0077] Whilst the illustrated arrangement discloses only a T-shaped
head portion 37 it is to be appreciated that the head portion could
be formed in a variety of non circular shapes. For example, the
head portion could be configured to have any number of abutment
surface 121 angular spaced about the rod axis 71. Of course, the
passage would need to be configured to accommodate each of these
abutment surfaces to allow the rod to pass through the pad
assembly.
[0078] Referring back to the different embodiments in FIGS. 16 to
18, in the embodiment of FIG. 16, rotation of the rod 29 between
the released configuration to the engaged configuration causes a
corresponding rotation of the piston 26 within the cylinder 24. In
contrast, in the versions of FIGS. 17 and 18, the rod can rotate
about its axis 71 without causing any corresponding rotation of the
piston in FIG. 17 or the cylinder in FIG. 18.
[0079] The friction pad (15, 16) of each pad assembly (11, 12)
provides operative surface (38, 39) which in use is arranged to
engage respective sides of a disc 50 (FIG. 7). While the friction
pad may be unitary, in the illustrated arrangement, the operative
surface of the respective pad assemblies incorporates channels 40
and 41 which divide each operative surface into four discrete
parts. One channel 40 extends with respect to the axis of rotation
of the disc, circumferentially across each pad assembly and
incorporates the respective apertures (31, 32) to receive
respective rods 29. The other channel 41 extends substantially
radially. Other arrangements of channels may be provided if
required.
[0080] As illustrated in FIG. 8, a quick release pad assembly 42 is
provided comprising a support plate 43 and friction pad 44.
Apertures 45 are formed through the plate and pad which are
arranged to receive respective rods 29. Each aperture is in the
form of a radial slot which extends preferably from the radially
lower edge 46 of the pad assembly 42 to enable quick release of the
pad assembly from the brake sub assembly.
[0081] FIG. 3 illustrates a first embodiment of the disc 50 which
may be used in association with the sub assembly 10 to form the
disc brake assembly 100.
[0082] The disc 50 is arranged to rotate about an axis of rotation
51 and rotate with the motor vehicle. The disc has an inboard side
52 and an outboard side 53 and incorporates a radially inner
portion 54 and a radially outer portion 55 which are separated by
gap 56 extending in a continuous circle coaxial with the axis 51 of
the disc.
[0083] Each portion (54, 55) has a respective inboard and outboard
braking surface (57, 58, 59, 60) located on opposite sides of the
disc 50. These braking surfaces provide the engagement surfaces for
the operative surfaces (38, 39) of the respective pad
assemblies.
[0084] A bracket 61 is located on the outboard side of the disc 50
and interconnects the inner and outer portions (54, 55). The
bracket 61 is secured to the inner and outer portions and is spaced
from the inner and outer portion outboard braking surfaces (58, 60)
to provide a cavity 62 in which the outboard assembly 12 is
located, enabling the operative surface 39 of the outboard assembly
to engage the outboard braking surface (58, 60) of the inner and
outer portions.
[0085] A second embodiment of the disc 50 is illustrated in FIG. 4.
This disc is similar to the disc of FIG. 3 and incorporates the
radially inner and outer portions (54, 55) separated by the gap 56.
However in this arrangement, the disc forms part of the wheel
assembly 63. The wheel assembly includes a hub 64, a rim 65, and a
plurality of spokes 66 interconnecting the hub and rim. In FIG. 4,
the inner and outer portions are bolted, or otherwise rigidly
connected, to the wheel assembly 63. This arrangement is feasible
for use where the wheel incurs little side loading (eg. in
cornering) and therefore, is not subjected to bending of the rim
relative to the hub. An example of such a situation would be with a
motor cycle.
[0086] A variation of this disc 50 is illustrated in FIG. 5 which
may be used in motor vehicles where cornering loads could deflect
the rim relative to the hub. In this case, the inner portion 54 is
fixed to the hub 64 and the outer portion is attached to the rim 65
or spoke 66 in a manner that allows limited movement in the axial
direction such as through a spline 67 as illustrated, or through
key/keyways or drives. In alternative arrangements (not shown), to
maintain correct alignment of the inner and outer portions, the
inner portion is movable relative to the hub in an axial direction,
while the outer portion is fixed, or both the inner and outer
portions are movable in the axial direction with the sub assembly
being fixed to form a datum surface. A further embodiment of the
disc is illustrated in FIG. 7 which comprises a fully cast disc 50.
This disc is arranged to be connected solely to the hub and
therefore deflection of the rim relative to the hub does not cause
misalignment of the inner portion relative to the outer
portion.
[0087] FIGS. 6, 7 and 16 to 18 illustrate the disc brake assembly
100 incorporating the sub assembly 10 and disc 50. The inboard and
outboard pad assemblies (11, 12) are supported on the anchor
bracket 17 and are located on opposing sides of the disc 50 with
the guide rails 19 of the bracket 17 extending through the gap 56.
The outboard pad assembly 12 is located in the cavity 62. The disc
50 includes a series of passages 68 which are formed in the bracket
61 to provide access to the cavity 62 and also improve ventilation
around the disc. The cylinders 24 are connected to the inboard
assembly 11 and the rods 29 are connected to the respective pistons
26 and extend through the gap 56 and are connected to the outboard
pad assembly 12. The movement axis 71 of each piston relative the
respective cylinder is substantially parallel to the axis of
rotation 51 of the disc 50 and each piston 26 is arranged to move
away from the inboard assembly in operation of the brake along the
movement axis 71 with the rods 29 acting as a draw bar which draws
the outboard assembly towards the inboard assembly causing the
operative surface 39 to be drawn into engagement with the outboard
braking surface (58, 60) of the disc 50. As the inboard assembly 11
is movable on the anchor bracket 17, on continued movement of the
pistons 26 away from the inboard assembly 11, the inboard pad
assembly is caused to move on the guide rails 19 on the bracket 17
to move the operative surface 38 of the inboard assembly 11 into
engagement with the inboard face (57, 59) of the disc 50.
[0088] An advantage of the disc brake assembly 100 is that each rod
29 is much better able to accommodate the loads induced in
operation of the assembly than prior art caliper bridge
arrangements by virtue of the location of each rod relative to the
operative surfaces and to the axis of movement of the respective
pistons. In this arrangement, the loads induced at these operative
surfaces are transferred substantially along each rod with little
bending moment being applied with any drag load or torque induced
at the respective pad assemblies being transferred to the anchor
bracket through their point of contact on the guide rails 19. As a
result, the brake assembly provides a much stiffer arrangement with
deflection of the brake assembly due to operational loading being
substantially reduced. As a result, the operative surface of the
pad assemblies on the disc will not change under increased loading
thus enabling the brake assembly to give a more consistent specific
torque output under different loadings. Furthermore, with the
stiffer construction, the pad assemblies may include larger
surfaces and the piston cylinder arrangement is more efficient
requiring a lower fluid displacement.
[0089] To inhibit binding of the piston within the cylinder without
compromising the efficiency of the assembly, a portion 70 of the
cylinder wall between seals 33 and 27 is relieved. In this way, the
possibility of binding of the piston 26 can be reduced without
compromising the effectiveness of the sealing arrangement between
the piston 26 of the cylinder 24 or rod 29. A neat fit is provided
between the cylinder and the piston or rod on either side of
respective seals 33, 27. This ensures that extrusion of the seals
does not occur which would otherwise increase fluid displacement.
While the rod 29 takes very little bending movement, any side
loading on the rod reacts against cylinder 27 at the location
adjacent the seals 27, 33 which provide a bearing surface for the
piston or rod.
[0090] Furthermore, as each rod is more efficient in accommodating
the stresses induced in the assembly, and as a caliper bridge is no
longer required, the brake assembly can be of lighter construction
and manufacturing costs can be reduced. Furthermore, as it is not
required to provide space for a caliper bridge on the radial
extremity of the disc, a larger diameter disc is possible which
provides a larger heat sink for the brake assembly, and a larger
effective radius.
[0091] In addition the brake assembly 10 is well equipped to
effectively dissipate heat in operation of the assembly. In
relation to the disc, with the radial separation there is more
surface area in the disc and vents 69 formed between the braking
surface are shorter. Furthermore, the longitudinal channel 40 in
each pad assembly is arranged to be located over the gap 56,
providing a gap which allows air flow around the contact surfaces.
The transverse channels 41 further assist in encouraging the air
flow. Furthermore, with this arrangement, there is no caliper
bridge or other structure to shield heat dissipation.
[0092] A further advantage is that the brake assembly may be more
easily removed from the disc. As a caliper bridge is not required,
once the rods are disconnected from the outboard pad assembly, the
brake assembly may be withdrawn from the disc by being moved in the
axial direction. Furthermore, the pad assemblies may be changed
without removal of the wheel. For example, in the brake assembly
shown in FIG. 2, the rods are released from the outboard pad
assembly by being rotated through 90.degree., and this can be
effected from the outboard side of the disc through passages 68.
The inboard pad assembly and piston cylinder arrangement is then
withdrawn from the disc in the axial direction and the outboard pad
assembly is removed through the spokes in the wheel provided an
adequate gap exists between adjacent spokes. A similar operation
can be undertaken to install the new pad assemblies.
[0093] Further benefits can be realised in the disc brake assembly
100 by the design and method of manufacture of the disc 50.
[0094] The disc 50 may be formed in one piece or may be cast in
separate pieces and assembled later. In one embodiment, the bracket
61 forms part of a centre support 76 which is secured to an axle
for rotation with the vehicle. Typically the centre support is made
from steel and is fabricated or pressed or formed from a
combination thereof. The inner and outer portions (54, 55) of the
disc are cast or otherwise formed on to the bracket. Each portion
may be formed as a single piece or may be formed from a plurality
of interfitting segments These portions may be cast from any
suitable material including aluminium, metal matrix composition or
cast iron. Alternatively, the bracket and inner and outer portions
may be cast from a single material and integrally formed together
as shown in FIG. 7.
[0095] To prepare the necessary inboard and outboard braking
surfaces (57, 58, 59, 60), the portions may be machined using a
chip producing process including grinding, turning and milling. The
surfaces usually need to be planar and have a suitable surface
texture to expedite burnishing of the friction pads.
[0096] FIG. 9 illustrates a suitable machining tool located in the
disc 50 to provide the outboard braking surfaces (58, 60). The
machining tool 77 incorporates a head 78 mounted on a rotatable
shaft 79. Cutters 80 (which may include single point or multiple
point cutting edges) are secured to the head and are spaced from
the axis of rotation 81 of the shaft and are separated by an angle
which is approximately 180.degree.. The spacing determines the
depth of the respective braking surface of the inner and outer
portions.
[0097] To prepare the outboard braking surface, the tool is
inserted in through the gap 56 within the disc 50. To facilitate
insertion of the head 78 in through the gap 56, the machining tool
77 is of suitable shape, such as substantially T-shape as
illustrated with the cross piece being arcuate to enable insertion
into the gap 56 or in an alternative embodiment (not shown), of a
substantially L-shaped configuration. To machine the face, the
cutters 80 are located against the disc surface and the tool 77
rotates about the shaft causing the cutters to move against the
disc surface. To vary the depth of the cut, relative axial movement
between the tool and the disc is provided. The disc 50 is also
caused to rotate to provide feed for the tool 77.
[0098] The relative speed of the rotation of the disc compared to
the tool 77 determines the finish on the surface. If the disc
rotates more slowly than the tool, a milling process occurs at the
surface. If the disc rotates at a faster speed than the tool, then
a process similar to a turning process occurs though the rake angle
of the cutter would not remain constant as in an ideal turning
process due to the rotation of the cutter shaft.
[0099] The milling process is preferred because the resultant
finished texture is of a cris-cross pattern 84 (which is
illustrated in FIG. 11) which is believed to be better for
burnishing the surface than the pattern produced by a turning
process, which is similar to a spiral.
[0100] To prepare the inboard braking surface, a similar tool (not
shown) is used except the cutters face outboard rather than inboard
as in the tool 77. The inboard surface may be prepared separately
or simultaneously with the preparation of the outboard surface. In
the latter arrangement, the two machining tools would typically be
spaced circumferentially about the disc.
[0101] An alternative tool 82 is illustrated in FIG. 10. This tool
is substantially the same as the tool illustrated in FIG. 9 except
that an additional head 83 is incorporated on a concentric shaft 85
in a position spaced from the head 73. In this arrangement, cutters
are located on opposing faces of the heads 78 and 83 and as in the
earlier embodiment, the cutters on each head are radially spaced
from the axis of rotation of the shaft and separated by an angle
which is approximately 180.degree., though other angles may be
used. For example the angle may be 90.degree. which may assist in
minimising vibration. The concentric shaft 85 is provided to enable
axial displacement between each head and the disc to enable the
depth of cut to be varied. With the tool 82 the inboard and
outboard braking surfaces can be processed simultaneously thereby
enabling the processing time to be further reduced. In other
respects the tool 82 processes the faces on the disc in the same
way as the earlier embodiment. In yet another alternative, two
heads are provided spaced along the axis of the shaft with each
head only having a single cutter which is arranged to cut a
respective one of the opposing inboard and outboard faces. In this
arrangement, each cutter is radially spaced from the axis of
rotation of the shaft with the angle between the cutters about the
axis of rotation being typically zero such that the cutters are
arranged to straddle a particular portion of the disc, or at
approximately 180.degree. such that one cutter is arranged to
engage the inner portion of the disc while the other cutter engages
the outer portion or at any other relative angular position.
[0102] In an alternative arrangement (not shown) the first portion
of the disc may be formed separately from the second portion and
may be processed individually, or assembled, and then processed
simultaneously. Each of these pieces may be formed in one uniform
material or may be composite or incorporate inserted portions.
[0103] In the manufacture of the disc either as a single piece or
in separate pieces, each portion may be solid or ventilated or the
disc may be formed with one portion ventilated and the other solid
depending on the performance characteristics required.
[0104] It will be appreciated from the foregoing description that
the disc brake assembly, sub assembly and disc in accordance with
the invention provides an arrangement which is better able to
accommodate the loads involved in operation of the brake assembly
while being of light weight construction, being relatively
inexpensive and effective in dissipating heat.
[0105] Finally it is to be understood that various alterations,
modifications and/or additions may be introduced into the
construction and arrangements previously described without
departing from the spirit or ambit of the invention described.
* * * * *