Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TITLE: BRAKE ASSEMBLY AND BRAKE PAD
FIELD OF THE INVENTION
The present application relates to ring brakes for
vehicle use and in particular, relates to a ring brake
for an automotive application.
BACKGROUND OF THE INVENTION
Ring brakes for vehicle application have been
described in patents but have not been readily accepted
in the marketplace. The ring brake due to its inner and
outer braking surfaces is subject to more road
contamination, and for demanding braking applications,
heat must be removed from the large braking surfaces.
Various arrangements for forcing a large airflow through
or over the ring braking member have been proposed.
A ring braking member requires a much larger
rotating member and most of the mass of this larger
rotating member is spaced a substantial distance from the
rotary axis. From a design point of view, it is
desirable to keep the rotating mass as small as possible
and to provide a mass which allows effective heat
transfer through the mass and to the air.
Ring brakes have been proposed and made of cast
iron, however, in this case, the weight of the brake is
high. It has also been proposed as set out in my earlier
patents, to use an aluminum alloy as the ring braking
member with a series of parts provided therethrough which
assist in reducing problems associated with contamination
and also assist in the transfer of heat to the airflow.
Specialized aluminum alloys are of high wear, however,
their maximum temperature is in the order of 800 degrees
Fahrenheit before the structural properties thereof
diminish rapidly.
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Brake pads far use in association with aluminum
alloy ring braking members use braking pads having
organic fibers as metal fibers tend to scare and rapidly
wear the braking surfaces. The organic fibers used in
braking pads for ring brakes have not proven entirely
satisfactory as these fibers tend to be bundles of thin
filaments and these fibers tend to lie in a plane
parallel to the braking surface. As these fibers become
exposed to the braking surfaces, the fibers tend to strip
out of the braking surface and often leave a rut or gouge
in the braking pad. The fibers tear out readily as they
are a bundle of individual filaments and thus once one
filament separates, the other filaments tend to follow.
A further problem associated with ring braking
members is the caliper for holding of the braking pads.
Floating calipers are prone to contamination of the
slideway and in addition, a floating caliper inherently
uses some contact of the brake pad with the braking
surface to retract the pads. With this arrangement there
is often some drag during rotation of the ring brake even
when the brake is not. actuated. Furthermore, the pistons
used to apply pressure to the pads for braking, are also
affected by the mass of the caliper which also moves.
Attempts have been made to modify disc brakes to
provide more effective braking. The diameter of the disc
can be increased in accordance with the wheel design of
the vehicle and many disc brakes have a series of
ventilation channels therein for pumping the air through
the disc. Although this assists in removing heat from
the disc member, the wheel size limits the size of the
disc and for many applications, the life of the brake is
relatively short or the performance of the brake
deteriorates quickly. This is particularly true for many
racing applications. Some racing vehicles such as
shifter carts have relatively small diameter wheels and
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this limitation further decreases the performance of disc
brakes.
The present invention seeks to overcome a number
of the problems associated with the prior art.
SUMMARY OF THE INVENTION
A ring brake comprises a ring braking member
having an interior braking surface and an exterior
braking surface, a caliper arrangement with opposed brake
pads, and means for supporting said caliper relative to
said ring brake member to position said brake pads to the
inside and the outside of said ring braking member for
engaging said braking surfaces. The caliper includes
piston means for selectively moving said brake pads into
braking engagement with said surfaces. The ring braking
member is of an aluminum composite material and the brake
pad are of a composite material having at least 30%
organic fibers with a disproportionate of said fibers
being orientated such that said fibers extend in the
depth of the respective brake pad.
According to an aspect of the invention, a
disproportion of the fibers form an angle with a braking
surface of the respective pad of at least 20°.
According to a further aspect of the invention, the
brake pads are of a composite material consisting
primarily of organic fibers and barium sulphate.
In a different aspect of the invention, the ring
brake is attached to a front wheel of a racing vehicle.
In a further aspect of the invention, the racing
vehicle is a vehicle having front wheels of a diameter
less than 16 inches.
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According to a preferred aspect of the invention,
the ring braking member is of a diameter of less than 12
inches.
A racing vehicle according to the present
invention has a frame supporting two steerable front
wheels and a pair of rear wheels at a rear portion of
said frame. The vehicle includes an engine and a drive
arrangement for powering the rear wheels. Each front
wheel has a ring brake with a rotating braking surface
made of an aluminum alloy with a pair of opposed brake
pads movable into and out of contact with said rotating
braking surface for braking thereof. Each pad is of a
material having organic fibers embedded in a suitable
mixture of binders and fillers with a significant portion
of said fibers during the manufacture of said pad having
the orientation of the fibers shifted to have the ends
thereof exposed to the rotating braking member for
progressive wear of the fibers by shortening their length
during normal wear of the respective brake pad.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention are shown
in the drawings, wherein:
Figure 1 is a top view of a shifter cart with the
improved ring brake system;
Figure 2 is a partial exploded view of the shifter
card of Figure 1;
Figure 3 is an exploded perspective view of a
front corner of the shifter cart showing the caliper, the
mounting bracket and the ring braking member;
Figure 4 is an exploded perspective view of the
brake caliper;
i5 Figure 5 is a sectional view through the braking
system;
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Figures 6, 7 and 8 show a conventional brake pad
having a series of fibers which due to their orientation
tend to strip out of the pad;
Figures 9, 10 and 11 show a brake pad when made in
the manner of the present invention to orientate the
reinforcing fibers generally perpendicular to the braking
surf ace ;
Figure 12 shows an assembled brake pad when made
according to this approach;
Figure 13 shows the multi step process for
orientating most of the fibers in a generally
perpendicular manner;
Figure 14 is a partial perspective view of an
apparatus for feeding of the brake pad material to
orientate it as desired and the subsequent manufacture of
the brake pad;
Figure 15 is a side view through the device of
Figure 14 showing the movement of the brake pad material;
and
Figure 16 is a front view of the device of Figure
14.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The shifter cart 2 shown in Figures 1 and 2 has
front wheel corners 4 which share a number of common
components. The shifter cart includes a live rear axle 8
which is driven by the engine 10 in combination with the
drive sprocket 12. A rear ring brake assembly 18 is
provided to one side of one of the rear wheels 14 and is
rotated with the rear axle. The shifter cart includes
the steering wheel 22 and a driver seat 24.
The front corner includes a mounting bracket 40
having a steering arm 42, a vertically disposed bearing
44, a generally horizontal wheel spindle 46, a removable
caliper 48 and opposed brake pads 50. The ring braking
member 60 is of an aluminum alloy and includes outer
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braking surface 62 and inner braking surface 64. The gap
70 between the brake pads 50 receives the edge of the
ring braking member such that the pads are immediately
adjacent the inner and outer braking surfaces. The fan
74 is connected to the ring braking member and causes a
flow of air through the ring braking member to remove
heat therefrom. The fan 74 also acts as a heat sink for
the ring braking member. A wheel mounting spindle 76
includes bearings at either end thereof for engaging the
wheel spindle 46 and allowing rotation of the ring
braking member and the associated wheel.
The mounting bracket 40 has the wheel spindle 46
integral therewith and this wheel spindle includes a
slight angle. For this reason, the mounting bracket 40
will be a right hand bracket or a left hand bracket for
accommodating the different wheel at the front of the
vehicle. The caliper and the ring braking member and fan
and wheel mounting tube 76 can be used for a left front
wheel or a right front wheel.
The caliper 48 is mechanically connected to the
mounting bracket 40 by means of upper and lower screw
bolts 43. There are two further bolts 45 (one shown)
above and below the piston which pass through plate 47
and engage the aluminum block 100. The caliper is made
from an aluminum block 100 having a center recess 101 for
receiving the brake pads and receiving an edge of the
ring braking member 60. The caliper includes two opposed
pistons 106 each having an associated cup seal 108 which
moves within the respective cylinders 102 or 104 of the
caliper. The aluminum block 100 includes upper internal
conduit 114 and a similar lower internal conduit 116.
These conduits serve to connect the two cylinders 102 and
104 and thus the pistons 106 effectively share the same
hydraulic fluid pressure supply. An end plate 120 is
provided on the end of the caliper closing cylinder 102.
As can be appreciated, cylinder 102 and 104 are aligned
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and can be drilled through the end of the caliper that
would be closed by the end plate 120. Cylinder 104 is a
blind cylinder although it does connect with the internal
conduits 114 and 116.
Hydraulic fluid is introduced through inlet 140 of
the end plate 120. Thus the cylinder 102 is exposed to
hydraulic pressure and this hydraulic cylinder is also
connected to the ports 126 and 128 via the channels 122
and 124 in the end plate. An 0-ring seal 124 is provided
about these components and serves to provide an outer
seal. Hydraulic fluid through the inlet 140 finds its
way through channels 122 and 124 to the enlarged ports
127 and 129 in the caliper. These enlarged ports are
connected to the internal conduits 114 and 116
respectively. Thus hydraulic fluid is introduced through
inlet 140 and this hydraulic fluid will serve to provide
power for the piston in cylinder 102 and via the internal
conduits 114 and 116 will provide power to the piston
located in cylinder 104.
The end plate 120 is fastened to the caliper by
means of a pair of bolts 131 which are outside of the O-
ring 124 and a pair of bolts 130 which are to the
interior of the 0-ring. The bolts 130 also include their
own 0-ring seal 132. As can be appreciated, there will
be an upper bolt 130 and a lower bolt 130 depending upon
whether the caliper is being used for the front right or
the front left wheel. The more elevated bolt is used as
a bleed screw for allowing bleeding of the brake fluid
lines. Basically, brake fluid is provided to the caliper
through the inlet 140. The upper bolt 130 is loosened
such that the hydraulic fluid can find its way through
the lower conduit to the opposite piston and returned
through the upper conduit to the bolt which has been
loosened and now allows bleeding through the end plate.
Once the air has been purged from the system, the bolt
130 can be tightened and the O-ring 132 provides a proper
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seal. The brake is actuated by feeding hydraulic fluid
under pressure through inlet 140 causing piston 106 in
the first cylinder 102 to move the associated brake pad
and also cause the piston 106 in the cylinder 104 to move
and causing the opposite brake pad to contact the inner
and outer braking surfaces respectively. The caliper is
fixed and therefore the pistons only move the brake pads.
The aluminum block 100 includes either side of the
recess 101 and at both the top and bottom surfaces, guide
plates 150 fixed to the body 100. The brake pads include
their own metal or reinforcing backing plate which have
been recessed to receive the guides 150 to allow sliding
movement of the brake pads to engage the brake surfaces.
These members serve to lock the brake pads against
movement sideways within the recess 101,
With the arrangement as shown in Figure 4, a
common shape caliper. 48 is used for the front left wheel
and the front right wheel. This is possible as the
caliper is basically symmetrical about a horizontal axis.
The mounting of the caliper 48 to the mounting
bracket 40 such that it is fixed, allows each of the
pistons 106 to basically only act on the brake pads.
When the hydraulic pressure is removed, the ring brake
will encourage the brake pads to move to a clear position
and the pistons are forced back. With this arrangement,
the brake runs essentially without drag as the brake pads
have been moved away from the braking surface. A
floating caliper arrangement does not operate as
effectively as a fixed caliper as the pistons are also
affected by the mass of the floating caliper. A fixed
caliper has proven to work very effectively on small
racing vehicles such as shifter carts, go-carts and small
diameter wheel formula cars. The ring caliper assembly
allows a large braking surface to be provided on a
relatively small diameter wheel. This is a great benefit
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for small diameter wheels used in many different types of
racing applications.
As shown in the sectional view of Figure 5, the
fixed caliper 48 can have the internal conduits 114 and
116 easily machined into the aluminum block 100 by a
series of drill holes which are appropriately plugged.
Thus the internal porting of the aluminum block 100 is
easily accomplished.. Figure 5 also illustrates how the
conduits are connected to the cylinders at one end of the
caliper through the enlarged ports 127 and 129.
Figures 6, 7 and 8 show a standard type of brake
pad used in association with a rotating braking surface.
The brake pad has a series of higher strength fibers 150
which are trapped within binder and filler material 152.
This braking material is mechanically fastened or molded
onto the backing plate 154. The fibers 150 are at
various angles within the material but generally extend
across the material and are not perpendicular to the
braking surface 156. As the braking surface 156 starts
to wear, additional fibers 150 are exposed, however, they
are generally exposed along their lengths as opposed to
across their lengths. For many materials such as metal
fibers and depending upon the particular binders and
fillers, this is acceptable.
For brake pads for use in association with
aluminum alloy or lightweight, high strength composite
materials, this is 7_ess desirable. Metallic fibers cut
up in relatively short lengths can be mixed with the
binders and fillers for forming of a brake pad. These
small fibers are relatively strong and provide excellent
wear surfaces for the brake pad. Metal fibers
unfortunately are not suitable with an aluminum composite
alloy due to the lower strength thereof. Organic fibers
or filaments are used. In the case of glass fibers, each
fiber is essentially a small bundle of smaller glass
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filaments and exposure of the fiber along its length
basically peels out the individual. filaments and the
fiber rapidly fails. It can also leave a significant
trough or hole in the brake pad. Therefore although the
organic fiber was there to assist in providing improved
braking, it has not provided this useful result. This
problem becomes more acute as the operating temperature
of the brake goes up. Typically the maximum temperature
is somewhat below 800 degrees Fahrenheit.
Figures 9, 10 and 11 show a brake pad of the
present invention where the fibers have been orientated
generally perpendicular to the braking surface 156. As
can be seen, the length of the fiber is basically
embedded in the thickness of the brake pad and the ends
of the fibers are exposed in the braking surface. With
this arrangement, effective braking is provided and the
improved wear characteristics are achieved as the fibers
are exposed at their ends and there is a large portion of
the fiber embedded in the pad which is holding the fiber
in the pad. As can be appreciated, this requires
orientation of a significant portion of the fibers and
although it is desirable to have the fibers perpendicular
to the braking surface, this general orientation is
sufficient. It can be appreciated that some fibers will
not be orientated in this manner, however, fibers so
orientated improve the brake pad performance. Therefore
the desired braking pad with the fibers exposed with
their ends in and at an angle to the braking surface is
shown in Figure 12.
Figure 13 shows a general process for orientating
the fibers in a desired manner. Basically, the material
of the brake pad is a loose mixture of fibers, binders
and fillers. The normal brake pad manufacturing process
is to take this mixed material and deposit in a form for
the brake pad and then apply downward pressure on the
braking surface. With this arrangement, the fibers are
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mostly orientated as shown in Figures 6, 7 and 8. It is
desirable to take the random orientation of the fibers as
would be present in the mixture as shown in the first
step of Figure 13 and move the material through a chute
to generally orientate the fibers in a horizontal plane.
This intermediate material is then moved in a different
direction to provide more orientation of the fibers in a
manner to be perpendicular to the braking surface as
shown in the last step of Figure 13.
A system for_ accomplishing this desired
orientation of the material and the subsequent
manufacture of a brake pad with orientated organic fibers
is shown in Figures 14, 15 and 16.
Figures 14, 15 and 16 show an apparatus for making
of the brake pad shown in Figures 9 through 12 and for
accomplishing the orientation of the fibers and shown in
Figure 13.
As shown in Figures 14 and 15, a hopper 202
receives the loose brake pad material 200 which
preferably includes organic fibers such as glass fibers
in combination with binders and fillers. This brake pad
material is forced by the piston 204 downwardly into the
loading gap 214. T:he piston 204 continues to move
downwardly as shown in Figure 15 while the piston 206,
which is an intermediate load angled piston, is retracted
as shown in Figure 15. Once some of the brake
particulate matter has been loaded into the gap 214,
piston 204 is withdrawn upwardly to return to an initial
position whereafter the intermediate load angled piston
206 is driven downwardly as indicated. This forces the
particulate material into the brake pad forming chamber
210. Basically, the piston 204 forces some material down
into the chamber 214. This will cause the glass fibers
to be generally orientated across the chamber 214. The
intermediate load piston 206 will force this material
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into the chamber 210 and cause a movement of many of the
fibers through an angle of about 90 degrees to be
orientated in the depth of the resulting pad and at an
angle to the braking surface of the pad. The piston 204
and the piston 206 complete several cycles for loading of
sufficient material into chamber 210. Normally there is
anywhere from three to eight cycles for loading of the
chamber 210. Once the chamber 210 has been properly
loaded, the intermediate load angled piston 206 is forced
downwardly and into alignment with the wall 212. This
effectively closes the side of the chamber 210. The
final load piston 208 is basically applying force on the
end of the brake pad and applies a pressure of anywhere
from 4000 to 5000 psi. The material is also heated to
form the brake pad.
As shown in Figure 14, the chamber 210 is
effectively closed by the movable wall 220. This wall
220 closes the end of the cavity 210 but is movable to a
clear position to allow the brake pad to be removed from
the chamber. As can be appreciated, piston 204 through
its movement tends to take the randomly orientated fibers
in the brake material 200 and complete a first step as
shown in Figure 13. The subsequent movement of the
intermediate load angled piston 206 forces this partially
orientated material into the chamber 210 and causes a
further orientation of the fibers such that most of the
fibers are at an angle to the braking surface and
preferably with much of the fibers embedded in the depth
of the pad.
With this system, longer fibers can be used such
that more of the fiber is buried within the brake pad.
Typically brake pads have a thickness of three Bights of
an inch to one half inch and the fibers can be slightly
shorter than this thickness. The brake pads are
preferably about one and three quarter inches in width
and two and one quarter inches long. The brake pads can
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be drilled and secured by rivets or adhesives or other
techniques to secure the brake pad to the backing plate
230 as shown in Figure 12. This backing plate has two
notches 232 and 234 which are sized for close engagement
with the guide plates 150. Basically, these notches hold
the brake pads in the caliper due to their interaction
with the plates 150 while allowing the brake pads to move
towards and away from each other.
The brake pads as shown in Figures 8 through 12
show a flat surface suitable for a disc brake, however,
these pads would have an appropriate curved for engaging
the cylindrical surface of the braking member 60 for ring
brake applications.
The preferred material of the ring braking member
60 is an aluminum alloy material having nickel coated
graphite which is mixed with silicon carbide in the base
aluminum material. Such a composite material is sold by
Inco under the trade-name "GRA-NI". During the casting
of this material, the nickel coated graphite effectively
flakes off and mixes with the silicon carbide and the
aluminum. One particular composite material includes
approximately four percent of the nickel coated graphite
particulate with ten percent silicon carbide.
This composite material operates well at
temperatures below 800 degrees Fahrenheit and an organic
brake pad is used with the material. An organic brake
pad includes an organic fiber in combination with
suitable brake pad fillers. These fillers typically
include abrasives to assist in providing a braking force
and other materials which allow some slippage. A
phenolic binder can be used in small amounts as well as a
silicon based binder. It is preferable to use a silicon
binder as high concentrations of a phenolic have not
proven satisfactory. Preferably the binder is a silicon
binder present in an amount of six to ten percent. The
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preferred organic fiber are glass fibers which are in an
amount from 40 to 60 percent. The preferable filler is a
barium sulphate which can form the balance of the
material. It is typically present in the amounts between
40 and 60 percent. The barium sulphate produces a quiet
brake pad which is riot subject to squealing.
During operation of the brake, the rotating ring
member has a glaze formed on the braking surfaces and the
pad works on the glaze. The glaze appears to provide a
protective layer on the braking surface and is
continuously forming as the braking surface does wear.
This brake has functioned extremely well and has
found a particular application for small racing vehicles
such as shifter carts. The wheels on the shifter carts
are relatively small and a small diameter large width
ring brake can be used to provide effective braking. As
shown in Figure 1, the caliper is placed towards the
front of the vehicle and is exposed to the cooling
airflow. Also the positioning of the ring braking member
to the inside of the wheel in a generally clear area
further serves to remove heat from the ring braking
member. The fan hub further produces an airflow through
the system for removing heat.
The rear ring braking member can be made slightly
larger in size and only a single rear braking member need
be provided. As can be recognized, the more demanding
braking application is provided at the front of the
vehicle and thus separate wheel brakes are required.
The brake pad has been described and has
particular application for use in association with ring
brakes. It should be recognized that these brake pads
and the orientation of organic or metal fibers also have
application for other braking systems. The orientation
of the fibers provides more effective use thereof and the
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perpendicular orientation of the fibers also serves to
provide a conduit or heat path for removing heat from the
braking surface. For example, metal fibers which are
orientated generally perpendicular to the braking surface
will conduct heat at the surface of the pad back through
the pad distributing the heat to a larger area of the pad
and also moving it to the rear of the pad where the heat
can also be more easily dissipated. The orientation of
the fibers also improves pad life as the fibers are
effectively anchored in the thickness of the pad.
Although various preferred embodiments of the
present invention have been described herein in detail,
it will be appreciated by those skilled in the art, that
variations may be made thereto without departing from the
spirit of the invention or the scope of the appended
claims.
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