U.S. patent number RE36,313 [Application Number 08/886,734] was granted by the patent office on 1999-09-28 for disc brake shoe assembly.
This patent grant is currently assigned to Westinghouse Air Brake Company. Invention is credited to Joseph C. Kahr.
United States Patent |
RE36,313 |
Kahr |
September 28, 1999 |
Disc brake shoe assembly
Abstract
A disc brake shoe in which a relatively thin gage, low-cost
metal backing plate has bonded to one face a friction brake lining
and is formed on the opposite face with a plurality of straps that
are adapted to engage corresponding recesses formed in a
complementary thick gage metal backing plate to interlock the
respective backing plates into a unitary brake shoe assembly which
can be easily disassembled to permit change-out of a worn brake
shoe by simply substituting a newly lined, low cost backing plate
for the existing backing plate having worn lining without the need
to re-claim the backing plate for re-use.
Inventors: |
Kahr; Joseph C. (South Pines,
NC) |
Assignee: |
Westinghouse Air Brake Company
(Wilmerding, PA)
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Family
ID: |
22252680 |
Appl.
No.: |
08/886,734 |
Filed: |
July 1, 1997 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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095585 |
Jul 23, 1993 |
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Reissue of: |
242690 |
May 13, 1994 |
05429216 |
Jul 4, 1995 |
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Current U.S.
Class: |
188/250R;
188/250E; 188/73.31 |
Current CPC
Class: |
F16D
65/092 (20130101); F16D 69/0408 (20130101); F16D
2125/58 (20130101); F16D 2055/007 (20130101); F16D
2069/045 (20130101); F16D 2069/0441 (20130101) |
Current International
Class: |
F16D
65/092 (20060101); F16D 69/00 (20060101); F16D
69/04 (20060101); F16D 55/00 (20060101); F16D
069/00 () |
Field of
Search: |
;188/25R,25E,73.31,25B,25C,25D,25F,25G,264G,261,253,234,235 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2713377 |
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Sep 1977 |
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DE |
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2625348 |
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Dec 1977 |
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DE |
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3109992 |
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Sep 1982 |
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DE |
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0080532 |
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Jul 1981 |
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JP |
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0211032 |
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Dec 1983 |
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JP |
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0093527 |
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Apr 1987 |
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JP |
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1092251 |
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Nov 1967 |
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GB |
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Primary Examiner: Poon; Peter M.
Attorney, Agent or Firm: James Ray & Associates
Parent Case Text
This is a continuation of copending application Ser. No. 08/095,585
filed on Jul. 23, 1993, now abandoned.
Claims
I claim:
1. A disc brake shoe assembly comprising:
(a) separate primary and secondary metal backing plates;
(b) a block of brake lining material bonded to one face of said
secondary backing plate, said primary backing plate having one face
with which the face opposite said one face of said secondary
backing plate is engaged in an assembled condition of said primary
and secondary backing plates, wherein said secondary backing plate
is interposed between said primary backing plate and said block of
brake lining material, the thickness of said secondary backing
plate being less than the thickness of said primary backing
plate;
and
(c) interconnecting means for releasably locking said primary and
secondary backing plates against relative movement in response to a
tangential force acting on one of said backing plates in said
assembled condition thereof comprising:
(i) a plurality of elongated radial slots all being formed in said
one face of said primary backing plate, each said slot having a
planar base recessed from said one face of said primary backing
plate and elongated parallel sides perpendicular to said one face
of said primary backing plate; and
(ii) a plurality of elongated radial straps all projecting from
said opposite face of said secondary backing plate, each said strap
having a planar head upraised from said opposite face and elongated
parallel sides perpendicular to said opposite face, said plurality
of straps having a configuration complementary to said plurality of
slots and being engageable therewith such that the respective
elongated sides therebetween are contiguous in said assembled
condition, said primary and secondary backing plates in said
assembled condition having free relative movement in a direction
parallel to said perpendicular sides of said slots and said
recesses in the absence of a tangential force on said primary and
secondary backing plates to accommodate disassembly thereof.
2. A disc brake shoe assembly as recited in said claim 1, wherein
the minimum depth of said plurality of slots is at least as great
as the maximum height said plurality of straps are upraised from
said opposite face of said secondary backing plate to assure said
face-to-face contact between said one face of said primary backing
plate and said opposite face of said secondary backing plate.
3. A disc brake shoe assembly as recited in claim 2, wherein said
plurality of straps are formed integral with said secondary backing
plate.
4. A disc brake shoe assembly as recited in claim 2, wherein each
one of said plurality of straps comprises a displaced section of
said secondary backing plate.
5. A disc brake shoe assembly as recited in claim 1, wherein said
primary backing plate is an arcuate segment having at least one lug
projecting from the outer periphery thereof, said at least one lug
lying in the plane of said primary backing plate and having an
opening therethrough.
6. A disc brake shoe assembly as recited in claim 5, wherein said
at least one lug is the same thickness as said primary backing
plate.
7. A disc brake shoe assembly as recited in claim 6, wherein said
secondary backing plate is an arcuate segment having at least one
lug projecting from an outer periphery thereof, said at least one
lug lying in a plane of said secondary backing plate and having an
opening therethrough.
8. A disc brake shoe assembly as recited in claim 7, wherein said
at least one lug of said secondary backing plate is the same
thickness as said secondary backing plate between said one and said
opposite faces thereof.
9. A disc brake shoe assembly as recited in claim 8, wherein said
opening in said at least one lug of said primary backing plate is
coaxial with said opening in said at least one lug of said
secondary backing plate. .Iadd.
10. A disposable secondary backing plate for use in a disc brake
shoe assembly having separate primary and secondary backing plates,
and having an interconnecting means for releasably locking the
primary and secondary backing plates against relative movement in
response to a tangential force acting on one of said backing plates
in such assembly, said disposable secondary backing plate
comprising;
(a) a thickness less than the thickness of such primary backing
plate,
(b) a block of brake lining material bonded to a first face of said
secondary backing plate, and
(c) a plurality of elongated radial straps projecting from a second
face of said secondary backing plate, said elongated radial straps
having a configuration adapted to mate with and engage a plurality
of complementary radial slots formed in an abutting face of such
primary backing plate..Iaddend..Iadd.11. A disposable secondary
backing plate for use in a disc brake shoe assembly having separate
primary and secondary backing plates, according to claim 10, in
which said plurality of elongated radial straps each have a planar
head upraised from said second face of said
secondary backing plate..Iaddend..Iadd.12. A disposable secondary
backing plate for use in a disc brake shoe assembly having separate
primary and secondary backing plates, according to claim 10, in
which said plurality of elongated radial straps each have elongated
parallel sides perpendicular to said second face of said secondary
backing plate..Iaddend..Iadd.13. A disposable secondary backing
plate for use in a disc brake shoe assembly having separate primary
and secondary backing plates, according to claim 10, in which said
plurality of elongated straps are formed integral with said
secondary backing plate..Iaddend..Iadd.14. A disposable secondary
backing plate for use in a disc brake shoe assembly having separate
primary and secondary backing plates, according to claim 10, in
which said plurality of elongated straps comprise displaced
sections of said secondary backing plate..Iaddend..Iadd.15. A
disposable secondary backing plate for use in a disc brake shoe
assembly having separate primary and secondary backing plates,
according to claim 10, in which said secondary backing plate is
generally an arcuate segment in
shape..Iaddend..Iadd.16. A disposable secondary backing plate for
use in a disc brake shoe assembly having separate primary and
secondary backing plates, according to claim 15, in which said
secondary backing plate has at least one lug projecting from an
outer periphery thereof, said at least one lug adapted to mate with
a lug on such primary backing plate..Iaddend..Iadd.17. A disposable
secondary backing plate for use in a disc brake shoe assembly
having separate primary and secondary backing plates, according to
claim 16, in which said at least one lug is provided with an
aperture therethrough adapted to coaxially mate with an aperture
through such lug on such primary backing plate..Iaddend..Iadd.18. A
disposable secondary backing plate for use in a disc brake shoe
assembly having separate primary and secondary backing plates,
according to claim 10, in which said secondary backing plate is
made of sheet steel having a thickness of about 0.0897
inch..Iaddend..Iadd.19. A disposable secondary backing plate for
use in a disc brake shoe assembly having separate primary and
secondary backing plates, according to claim 18, in which said
plurality of elongated straps are formed by
stamping..Iaddend..Iadd.20. A disposable secondary backing plate
for use in a disc brake shoe assembly having separate primary and
secondary backing plates, according to claim 19, in which said
plurality of elongated straps each have a planar head upraised from
said second face of said secondary backing plate by a distance of
approximately 0.1103 inch..Iaddend.
Description
BACKGROUND OF THE INVENTION
The present invention is related to disc type brake shoes for
railway vehicles and particularly to a segmented disc brake shoe
assembly.
Presently, disc brake shoe linings are molded and machined into a
block of composition friction material having a configuration, as
shown in FIG. 1, corresponding generally to a metal backing plate
such as shown in FIG. 2. The molded block of friction material and
the backing plate are provided with a multitude of conforming holes
through which rivets are inserted to secure the brake shoe lining
to the backing plate. In order to support the brake shoe lining
under heavy brake loads without any appreciable bending, which
could cause the lining to crack, the backing plate is formed from
relatively thick gage, high strength steel and thus represents a
costly item of a brake shoe. Consequently, it is desirable to
reclaim these backing plates for re-use, which requires removal of
the multitude of securing rivets in order to dis-assemble the worn
brake shoe lining from its backing plate. This, in itself, is an
expensive operation.
Moreover, the multitude of rivet holes in the brake lining reduce
the strength and wearability factor of the composition friction
material of the brake shoe lining, while the cost of machining the
friction material as required by the specific backing plate design,
and the expense of securing the replacement brake shoe lining to
the backing plate by means of rivets still exists.
State-of-the-art technology makes it possible to chemically bond
the composition friction brake lining to the metal backing plate to
eliminate the above-discussed disadvantages of rivets, but
reclaiming the backing plate from worn brake shoes for re-use still
entails a difficult, time-consuming operation to remove the
friction material and to clean the backing plate sufficiently, as
required for bonding the new brake shoe material thereto during the
re-lining process. In addition, the thick gage backing plate with
worn linings must be transported from the customer to the brake
lining manufacturing facility for relining and subsequent delivery
back to the customer. These expenses are even further exacerbated
where different thickness backing plates must be stocked to
accommodate various wear states of the brake disc, where brake
units without automatic slack adjusting means are employed.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a
disc brake assembly having a secondary or throwaway metal backing
plate to which the friction brake lining is molded for assembly
with a primary or permanent backing plate without requiring the use
of rivets.
It is an extension of the foregoing object to form the secondary
backing plate out of thin gage metal to permit high volume,
low-cost stamping, in order to justify discarding the secondary
backing plate with the worn brake lining.
It is still another object of the invention to provide a single,
standard designed, secondary backing plate segment for use with
different gage primary backing plate segments.
In accordance with the foregoing objectives, there is provided a
disc brake shoe assembly comprising primary and secondary backing
plates, the secondary backing plate being of relatively thin gage
metal compared to the primary backing plate and having composition
brake lining material bonded thereto. The primary and secondary
backing plates include interlocking means for joining the
respective backing plates together to provide the aforementioned
brake shoe assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects and advantages of the invention will become
apparent from the following more detailed explanation when taken in
conjunction with the accompanying drawing in which:
FIGS. 1 and 2 are oblique pictorial views showing a molded
composition block of brake shoe lining and a metal backing plate,
respectively, to which the brake lining may be affixed by rivets,
as known in the prior art;
FIG. 3 is an oblique pictorial view showing a new backing plate to
which is bonded a composition brake shoe lining;
FIG. 4 is an oblique pictorial view showing a complimentary backing
plate with which the backing plate of FIG. 3 is adapted to be
mated;
FIG. 5 is an oblique pictorial view showing a novel brake shoe
assembly formed by interlocking engagement of the backing plates of
FIGS. 3 and 4;
FIG. 6 is a section view taken along the lines 6--6 of FIG. 5
showing the interlocking engagement of the backing plates of FIGS.
3 and 4;
FIG. 7 is a partial, enlarged, section view corresponding to the
view of FIG. 6; and
FIG. 8 is a section view taken along the lines 8--8 of FIG. 6
showing the interlocking engagement of the backing plates of FIGS.
3 and 4 looking in a direction perpendicular to the direction shown
in FIG. 6.
As shown in FIG. 4 of the drawings, a primary, metal backing plate
10, is formed of high strength steel and comprises a plurality of
equally-spaced, recessed slots 12 that are formed in an arcuate
pattern in face 14 of backing plate 10. These slots 12 are
elongated generally in a radial direction, having a depth of
preferably 0.1156 in., which is less than the thickness of primary
backing plate 10.
A secondary metal backing plate 20, as shown in FIG. 3, comprises a
plurality of radial straps 22 that are upraised from a face 24 of
backing plate 20 opposite the surface to which a composition brake
lining 26 is bonded. Straps 22 may be formed by stamping, for
example, so that sections of the backing plate are displaced from
face 24 and correspond in number and shape with the plurality of
slots 12 in primary backing plate 10. Secondary backing plate 20 is
formed from relatively thin gage steel to accommodate the
aforementioned stamping operation, the thickness of this secondary
backing plate 20 being preferably 0.0897 in. The height of the
upraised straps 22 above face 24 is less than the depth of slots
12, preferably 0.1103 in., for a purpose hereinafter explained.
Primary backing plate 10 and secondary backing plate 20 are
interconnected via the intermediary of slots 12 and upraised straps
22, the latter being engaged in slots 12 to form an integral disc
brake shoe assembly 30, as shown in FIG. 5, by mating the
confronting faces 14 and 24 of the respective backing plates 10 and
20. Each upraised strap 22 of backing plate 20 has parallel,
longitudinal sides 32, 34 that are contiguous with corresponding
sides 36, 38 of the respective slots 12 in backing plate 10, when
the backing plates are interconnected. Accordingly, a series of
force transmitting surfaces are provided between the plurality of
radial straps 22 and slots 12 for supporting bi-directional,
tangential, reactive forces of a brake disc (not shown) when a
braking force is applied to the disc brake shoe assembly 30, by
means of a disc brake unit (not shown) with which the brake shoe
assembly is associated.
Backing plate 10 is further provided with a pair of lugs 40 that
project beyond the outer radius of the brake disc; and backing
plate 20 is provided with a similar pair of projecting lugs 42,
these lugs having coaxially aligned holes 41 and 43, respectively,
in which bushings (not shown) may be installed by either the
manufacturer or customer to receive a pair of mounting pins (not
shown) of the disc brake unit on which the disc brake shoe assembly
30 is slidably hung.
As shown in FIG. 6, and particularly in the enlarged view of FIG.
7, the depth of slots 12 in backing plate 10 is slightly greater
than the height that straps 22 are upraised from face 24, so that
during mating of the primary and secondary backing plates,
confronting faces 14 and 24 are assured of having full surface
contact. Also, straps 22 are upraised sufficiently to provide full
side engagement thereof with the contiguous sides of slots 12, as
can be seen in the view of FIG. 8.
It will now be appreciated that in changing out worn brake shoe
linings, brake shoe assembly 30 of the present invention is removed
from the brake unit by removing the brake shoe mounting pins, after
which the secondary backing plate having the worn lining is
separated from the primary backing plate by disengagement of straps
20 from slots 12. This permits replacement of the worn brake shoe
lining by simply replacing the secondary backing plate having the
worn lining with another secondary backing plate having new lining.
The low cost of the thin, stamped, secondary backing plate 20 makes
it economically feasible to scrap the secondary backing plate with
worn lining. The replacement secondary backing plate having new
shoe lining is interlocked with primary backing plate 10 by placing
face 24 of secondary backing plate 20 against face 14 of primary
backing plate 10, so that the plurality of upraised straps 22 on
secondary backing plate 20 enter the corresponding slots 12 in
primary backing plate 10. The resulting brake shoe assembly 30 is
then located in the brake unit and secured in place by inserting
the brake unit mounting pins through the aligned holes 41, 43 in
lugs 40, 42 of the respective backing plates. In this manner, brake
shoe assembly 30 is restored to a new brake shoe condition without
having to remove any rivets or the like in order to reclaim the
primary backing plate 10 from its worn brake shoe lining for
subsequent re-use.
Application of the brakes following change-out of the worn brake
shoe lining positively interlocks straps 22 with slots 12, as the
primary and secondary backing plates are compressed between the
vehicle brake disc and brake unit. Depending upon the direction of
disc rotation, a tangential reaction force is imparted to the disc
lining, so that the longitudinal sides 32 or 34 of straps 22 engage
sides 36 or 38 of slots 12. As a result of this engagement,
reaction to the retarding force developed at the friction brake
lining is transmitted from the secondary backing plate 20 to the
primary backing plate 10 via the intermediary of the interlocking
straps and slots. In providing a plurality of interlocking straps
and slots, it will be appreciated that the tangential reaction
force effective at the respective backing plates is divided between
a multitude of side surfaces 32, 36 or 34, 38, so that the chance
of failure of the interlocking component parts due to high stresses
is eliminated. Being supported on mounting pins in the brake unit
via holes 41 in lugs 40, the primary backing plate in turn
transmits the reaction force to the brake unit body. It will be
noted, however, that the reaction force acting on the thin
secondary backing plate 20 is not supported by the mounting pins
that pass through holes 43 in lugs 42 thereof, due to the reaction
force being transmitted via the interlocking straps and slots. This
assures that the relatively thin section secondary backing plate
does not wear through the support lugs 42 at holes 43 therein.
Consequently the integrity of the secondary backing plate support
is assured.
In accordance with the foregoing, it will be appreciated that the
disc brake shoe assembly 30 takes advantage of the strength of the
thick gage, primary backing plate 10, without requiring the disc
brake lining to be directly bonded or mechanically affixed thereto.
The primary backing plate 10 may therefore be retained as part of
the vehicle disc brake unit without becoming involved in the brake
shoe relining process, thereby further saving considerable expense
in shipping and handling costs.
In accordance with the foregoing, it will be appreciated that the
unique brake shoe assembly of the present invention is advantageous
from the standpoint that:
1. The design accommodates direct bonding of the friction brake
lining material to a metal backing plate without requiring rivets
or other means of attachment.
2. The friction lined backing plate may be produced economically by
high-volume, low-cost metal stamping.
3. Assembly of the friction lined backing plate with the primary
backing plate may be accomplished without special tools.
4. Worn out brake shoes may be economically discarded and the thin
metal backing plate used as scrap metal.
5. Thick gage primary backing plates may be retained at customer
site to eliminate shipping between customer and
re-manufacturer.
6. A single molded product design is suited for application with
different thickness primary backing plates, to compensate for disc
wear, as required in the absence of automatic slack adjusting type
brake units.
* * * * *