Note: Descriptions are shown in the official language in which they were submitted.
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aACKGROUND OF THE INVENTION
1 The present invention relates to so-called "ring"
brakes that have an axially extending cyllndrical drum ox riny
presenting braking surfaces on either side of the rin0.
Sometimes, -these brakes are re~erred to as internal/external
shoe drum brakes, althouyh -the drum is preferably a cylinder.
The prior art shows various forms of ring brakes, such
as that disclosed in United States Patent 4238007, United
States Patent 4,236,610, United States Patent 3,933,237 and
United States Patent 3,974,~95 as but some examples.
A number of problems occur in ring brakes with respect
to mounting of the ring on a wheel member, the compensation for
unequal heat exposure throughout the braking system, the
capability of the brake to eliminate the entry of or improve
the exit of dirt that comes in contact with the braking
surfaces and the operation of the brake pads to achieve a
positive separation to avoid drag. These problems are not
restricted to ring brakes, however, they do present substantial
problems for brakes of this type.
There is a need in some applications for a highly
efficient brake which essentially can be determined from the
total swept braking surface, the effective braking surface over
the swept area and the distance of the braking surface from -the
wheel axial. Ring brakes present some advantages in that the
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1 braking sur~ace is at a ~ixed rad;ial spacing ~rom -the wheel
axlal, whereas a disc brake this radial spacing is varyiny.
Drum bral<es have a fixed radial spaciny a:Lthough the braking
surface is quite limited.
One particular application for e~ficient brakes, is in
skock cars, where the cars are continually accelerating and
decelerating and are exposed to very demanding requirernents.
The brakes presently used in these stock cars are often
completely ineffective at the end o~ a race and heat build-up
within the brakes can even cause cracking of the components due
- to thermal stresses.
There remains a need to provide a brake which has
improved control characteristics, to avoid situations such as
wheel lockup, improved effectiveness with respect to the amount
braking available and improvements in the life expectancy of
the brakes.
SUMMARY OF THE INVENTION
According to the present invention, in a brake for -the
wheel of a vehicle a ring braking mernber is mounted to rotate
with the wheel of the vehicle about the wheel axis. The
braking member extends generally parallel to the wheel axis and
presents a surface either side of the braking member for
inneraction with a braking pad. The ring brake member includes
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a plurality of cleaning holes from one braking surface to the
other with the holes being spaced about the circumference and
across the width of the braking member to at least
substantially overlap in a manner that an effective gap is
provided across the braking surfaces when the ring brake is
rotated about the axis 1 revolution resùlting from the combined
effect of the holes. These holes assure dirt or grit which
come in contact with the inner surface of the ring brake, will
find their way out of the ring to the environment through one
ln of the holes. This removal of dirt or the fact that dirt
cannot collect within the ring member significantly improves
the life of the ring member.
According to an aspect of the invention, the ring
brake is mounted to a wheel mount member in a manner to
accommodate different thermal expansion of different components
; in the braking system. The ring braking member is secured at a
number of positions at a point spaced from the wheel axis to
strut members which are joined to radially extending arms of a
wheel mount member. These struts deflect under the forces
caused by thermal expansion of the ring braking member, thus
allowing movement of the ring braking member relative to the
wheel mount.
According to yet a further aspect of the invention, a
unique brake pad retract mechanism is provided, where the
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1 distance of separation of the pads is essentially
predetermined, and will not vary with brake pad wear. The
structure includes a particular combination where one washer
slideable on a pin with -the movement of the washer on the pin
being determined by the extent of brake wear. This washer is
only slideable in one direction and cooperates with a spacer
member. The washer upon release of the brake mechanism can
move into contact with the spacer through a predetermined
distance, and at that point the brake pads are fully
retracted. Thus with brake wear, the washer slides on the pin
to a point that will result in the same brake pad separation
upon release of the brake pads.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention are shown in
the drawings wherein;
Figure 1 is a perspective view of the brake for the
wheel of a vehicle;
Figure 2 is a partial elevation showing securement of
the ring braking member to the wheel mount member;
Figure 3 is a partial exploded perspective view of the
ring brake and caliper associated therewith;
Figure 4 is a perspective exploded view of the ring
brake without the caliper;
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1 Flgure 5 is a partial perspective view showing one
form of securlng of the ring brake to a strut;
Figures 6 and -/ show ~urther details of the securernent
shown in Figure 5;
Figure 8 shows a partial perspective view of the ring
braking member including central cooling conduits;
Figure 9 is a section taken along line A-A shown in
Figure 8;
Figure 10 is a perspective view of the braking caliper
showing the cooperation of the various components;
Figure 11 is a vertical section through the braking
system;
Figure 12 and 13 are sectional views through the brake
caliper showing a clear position in Figure 12 and a braking
position in Figure 13;
Figure 14 is a side view of the brake caliper showing
the return mechanism; and
Figures 15 and 16 show the return mechanism in further
detail.
DETAILED DESCRIPTION
The brake, generally shown as 2 uses a ring brake
member 4 having opposed braking surfaces 4a and 4b. This
braking member is concentrically mounted about the wheel axis 6
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1 and lncludes a number of cleaning holes indicated as 8 which
preferably at least partially overlap w.ith an adjacent c1earliny
hole, such that the entixe braking surfaces 4a and 4b include
an effective gap there across when they are rotated thruugh one
revolution about the wheel axis 6. These holes allow dirt and
grit to clear out of the ring and thus substantially increases
the life of the brake pads. It is preferred to leave the brake
open to air circulation to achieve additional cooling. The
holes render the open brake form more practicle.
1 The ring braking member 4 is secured to the circular
flange 10 preferably by welding with the flange 10 including
securing tabs 12 generally perpendicular to the flange. A
securing hole 13 is provided in the securing tabs 12 and
cooperates with securing hole 20 provided in the individual
struts 18. These struts 18 are positioned to join the ends of
radially extending arms 16 of the wheel mounting member 14.
The wheel mounting member 14 is adapted to releasably secure
the rim of a tire to the opposite side of the brake member 4.
The wheel mounting member 14 includes a splined wheel axial
sleeve 22 which provides a support surface for the bearing
surface 72 of the caliper mount 70.
The ring brake mernber 4 is secured by the cooperation
of the tabs 12 and the struts 14 to the bolts 27 passing
through the holes 20 and 13. Details of the securing of the
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l tabs to the struts can be appreciated from a review of Figures
5, 6 and 7. To assist in positioning of the circular flange lO
during assembly or repair, aligning guides 24 have been
provided on the arms 16 of the wheel mount 14 which
approximately position the braking surface 14 with respect to
the wheel axis 6.
A brake caliper 30 includes a support member 32, a
fixed brake pad 34 and a moveable brake pad 36. This caliper
is releasably held within the caliper mount 70 by the
cooperation o-f the sleeve bracket 74, the bar 76 the spring 78
and pins 80. These components coopera-te to releasably receive
the brake caliper 30 by compression of the spring 78 to provide
sufficient space for insertion of the caliper. This provides a
somewhat self adjusting mounting of the caliper 30 and also
simplifies replacement of the caliper should it be required.
The brake caliper 30 includes a support member 32
having a central bore therethrough for receiving the piston 38,
the sealing cup 40, the coil spring 42 and the hydraulic
pressure inlet 59, as generally shown in Figures lO and 12.
The piston 38 acts against the rear face of the moveable brake
pad 36 and provides a continuous bias urging the pad towards
the fixed pad 34. Member 54 acts as a stop for piston 38. A
return mechanism 44 is provided which includes return spring
46, and pin 48 which is received within the moveab~e brake pad
36. This return mechanism 44 can be further
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1 appreciated from a review of Figures 14, 15 and 16 where it
can be seen that pin 4~ also carries a lock washer 52 slideable
in one direction on the pin and lockable in the other
direction. In this case, the washer is slidable on pin 48 once
it bottoms out on face 53, to allow movement of the brake pad
36 towards the fixed pad 34 and locks in the direction opposite
to arrow 51. A spacer member 50 is provided which cooperates
with the lock washer 52 to provide a predetermined distance of
retraction of the moveable pad 36 generally indicated as "X" in
the drawings. This "X" is essentially predetermined and
remains the same even with brake pad wear. The washer 52 is
moveable within the spacer 50 and will bottom out against the
spacer 50 as shown in Figure 15 when the hydraulic pressure is
released from the inlet 54.
Full actuation of the brake forces the moveable pad 36
outwardly from the support member 32 and the washer 52 will
bottom out against face 53 of the support member 32 at a
distance "X" spaced from the interior portion of the spacer 50
as shown in Figure 16. Upon release of the hydraulic pressure,
the washer 52 is locked on the pin 40 which is urged by spring
42 to pull the pacl in the direction indicated by arrow 51,
until such time as the washer 52 bottoms out against the spacer
50. The spacer 50 is maintained in engagement with the face 53
due to the spring 42 acting upon the rear surface thereof.
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1 Therefore, the predetermlned movement oF the washer 52 within
the spacer 50 accurately determines the spaciny between the
moveable pad and the fixed pad regardless of wear of the pads.
Returning to Figure 3, it can be seen that the caliper
mount 7û includes arms 82 which are part of the vehicle
suspension or steering system.
Turning to Figures 5, 6 and 7 a speciFic cooperation
oF the strut 18, the tab 12 is shown, where the collapsible
filler 26 is sized to initially pass through holes 13 and 20
and upon tightening oF the bolt 27 and nut 28, the Filler 26
deforms to Fill the hole and to provide a tight fit. This
allows a very simple arrangement for mounting of the circular
flange 10 to the strut arms 18, and does not require the
precision machining and placement oF the various holes ~0 and
13. It can be appreciated that some tolerance variation can
exist and the filler 26 will merely accommodate these
variations.
In a braking system, thermal expansion oF the
components can be a problem and complicating mounting
arrangements. Thermal expansion is accommodated in the present
system as generally shown in Figure 2, where the struts 18 can
deFlect outwardly as generally shown by the arrow 19 to
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1 accommodate the thermal expansion of the braking surf'ace.
Therefore, the circular flange 10 is in effect moveable over
arms 16 which will have dif~erent thermal exposure and/or
characteristics. The difference in -these thermal exposure and
characteristics is accommodated by the struts 18 and the
securement ot` the flange intermediate the arms 16.
The suppor-t member 32 of the brake caliper 30 is shown
as a single casting, however, it can also be made as two pieces
whereby the bore 43 in the outer part of the caliper could be
avoided. In this case, the piston 38, the seal 40 and spring
42 would be received in bore 45 prior to assembly of the two
pieces. Furthermore, brakepad 34 could be made part of the
second piece.
The positive retract mechanism to achieve a ~airly
wide brake pad separation, preferrable in the order of about
.015 inches, the open brake with cleaning holes, allows the use
of so~ter brake pads and improved sensitivity. The hydraulic
system including the cup washer and piston provide better
"feel" and allows additional control to effect braking and
; 20 reduce wheel lock. This device although suitable for many land
vehicles is particularly suitable ~or stock cars where brake
wear, wheel lock up and heat dissipation and compensation are
most troublesome.
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1 ~he riny braking member 4 and the flanye 10 have been
shown as separate members welded together which is particularly
applicable if the ring braking member is of stainless skeel.
In some circumstances it may be desirable to cast the ring
braking member 4 and the flange 10 as an integral casting which
is subsequently machined. In this case, a ductile iron is
preferred. The tabs 12 can also be part of the casting.
Al-though 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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