Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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RAILWAY VEHICLE BRAKE SHOE
Field of the Invention
The present invention relates to composition brake
shoes and more particularly to an improved backing plate
structure for fastening the composition brake material
thereto.
Background of the Invention
Composition brake shoes of the type to which the present
invention relates generally comprise a molded body of friction
material including a heat curable binder such as a therm
setting resin or a vulcanizable rubber. The molded friction
body is adhered to a rigid backing plate such as steel or
the like. A backing strip is usually interposed Boone the
friction composition and the backing plate to compensate for
the different rates of coefficient of expansion between the
backing plate and the friction material so that the composition
material does not delaminate during normal braking causing-
the backing plate and composition to become heated.
Heretofore it has been common practice to provide the
rigid backing plate with a plurality of generally circularly
openings through which the binder in the backing strip and
or of the composition brake material is extruded or forced
during the brake shoe molding and assembly process in the
well known manner. The binder thus extruded, cures in the
or of buttons disposed in the openings. The buttons serve
to help resist shearing forces at the interface ox the
molded friction composition and the backing plates. However,
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the button-like projections provide little if any resistance
against separation of the interface so that it is necessary
to provide an adhesive at the interface to bond the backing
strip and the friction composition thereto.
By the present disclosure it is proposed to provide a
mechanical attachment arrangement for fastening the friction
member to the backing plate of the composition shoe.
This is accomplished generally by providing the
backing plate with a plurality of depressions about which an
array or cluster of openings are disposed. The openings
communicate with the depressions such that the heat responsive
binder in a backing strip during the molding and assembly
process flows through the openings and fills the depressions.
Upon curing the binder forms a positive tie extending through
and between the openings to prevent separation of the molded
friction composition and the backing plate.
Brief Description of the Drawings
- FIG. 1 is a front elevation view of a composition
brake shoe embodying the structure of the present invention.
FIG. 2 is a top plan view of the brake shoe with some
of the parts being broken away to show underlying details of
structure.
FIG. 3 is a cross sectional view taken generally along
the lines 3-3 of FIG. 2 with parts broken away to show
underlying details of structure.
-- 2 --
l Z 15 I 5 3
issue a cross sectional view taken gen'er~l'ly,'along. ;'. '" '..
. the lines 4-4 of FIG. 2 with parts broken away show .,:
. underlying details of.s~ructure. ': . : '. .
, . , . ................................... : .
Description of the Preferred Embodiment
Referring now to the drawings there is shown a composition
brake shoe 10 of the general type used in railway vehicles
such as locomotives, freight and transit vehicles. The
composition brake shoe comprises generally a back plate 12
to the underside of which there it adhered a backing strip
14 and a friction member 16.
The backing plate 12 is made from a rigid material such
as steel stamping or the like and is generally arcuately
shaped about a center common with a center of a railway
wheel with which the brake shoe is adapted to be used. The
plate 12 includes an upper convex surface 18 and an inner
lo concave surface 20 on which the backing strip 14 is superposed
in face-to-face relationship. An inverted U-shaped key
attachment bracket 21 is located at the lengthwise center ox
the plate and positioning lugs 23 are provided adjacent the
ends of the plate. Spanning the space between the legs ox
the lug 21 and secured to the back plate is a tie plate 27.
The backing strip 14 serves to provide a layer of
material which permits different rates of expansion and
contraction between the back plate 12 and the friction
member 16 as caused by the heating and cooling of the brake
shoe in normal operation.
The backing sheet or pad I conventionally includes a
heat responsive binder such as a thermosetting resin or
- :12~ 3 : -
vulcanizable tubber; dispersed within the binder is no-
.- ,:: . , . .;-, .-, .:;
inorcing media such as armed or glass fibers, or the like.
. . . .. . - . . . . . , , . .: . .. .
The binder may be any one of the commonly available compost
itchiness including as mentioned above a thermosetting resin or
vulcanizable rubber either clone or in combination. The
composition may include the usual rubber curing agents such
as sulfur, be~zothiazyl disulfide, tetramethyl thrum
disulfide, tetraethyl thrum disallowed or the like.
The jacking sheet or pad 14 may be adhered in face-to-
face engagement with the underside by an adhesive which misapplied thereon and provides a bond as more fully to be
explained hereinafter. Suitable adhesives may be finlike,
nitrite finlike, bromated dichlorobutadiene or other types
of rubber to metal adhesives.
The friction member of body 16 may be ox any of the
well-known and available compositions suitable for use as
friction member for engagement with a railway wheel. Such
compositions are each characterized by the use of binder in
which there is dispersed particles of friction material such
as iron grit and alumina silicate and fillets such as clay,
burettes, graphite or other similar carbonaceous materials
and materials which serve as friction modifiers.
The binder composition as heretofore generally described
may be either a synthetic rubber or thermosetting resins.
The binder composition includes the usual curing agents
and/or solvents for the thermosetting resin such as Tulane,
alcohol and the like.
The friction member 16 is formed as by molding the
mixed friction shoe composition in a press and subjecting
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.... .. . ...... . . ...... .... . . . ....... ...... . ............... . . ..
... 'the c~mpressed,.composition to an elevated temperature foe' ' ,'
I' ''' " 'su~f~ëient peridot ure'or set the b~naer.~'"'.. ;' :. ' '; I' ',
`- In practice the friction member issue formed and'simul- - '''
.:
tonsil bonded to the steel back plate 12. To this end
-- 5 -the back plate 12 including the backing pad 14 and the .
friction shoe composition are inserted into a press whereupon
the composition is compressed and heat applied thereto. The
heat responsive constituents of the composition and the back
plate 12 are rendered plowable. When heated the thermosetting
lo and/or rubber composition cures and hardens in the usual
manner. The binders at the interface of the backing strip
I and the friction member 16 are then commingled. At the
same time the adhesive on the underside of the metal back
plate 12 which may also be heat curable serves to bond the
hardening friction member thereto.
With this structure it is to be noted-that the jacking
pad 14 remains interposed between the friction member and
the back plate 12 so as to perform its function. As mentioned
heretofore the pad 14 serves to permit relative and different
expansion rates of the back plate 12 and the friction member
16. Thus upon braking the different thermal expansions ox
the back plate 12 and friction member 16 are compensated for
by the pad 14 without shearing or separating at the adhesive
interface of the back plate 12.
do so
A 25 In accordance with the present~i~eo*~on it is proposed
to provide a mechanical tie or lock for retaining the friction
member 16 fastened to the back plate 12. To this as shown
the back plats 14 includes a plurality ox dimples or depressions
22 and 24. The depressions 22 and 24 are formed by displacing
- --5--
... I. . . the upper and inner faces toward the friction member and` the
ac~in'g~paa;.'`' Pyre ivy
Jo " but no greater than 3/8". As shown the dëpxesslons 22
are substantially circular and include a base 26 and an~~ 5 inclined side wall Z8 which extends between the upper and
inner surfaces 18 and 20. The depressions 24 are generally
rectangular and include a base 32, end walls 34 and side
walls 36. the end and side walls 34 and 36 respectively
also extend integrally between the upper and inner surfaces
of the plate The depressions 22 are located between the
key attachment bracket 21 and thy locating lugs and the
rectangular depressions 24 along side the locating lugs
adjacent the respective ends of the plate 12.
Associated with each of the depressions 22 are a array
or cluster of openings 38 which are disposed about the
circumference of the former. As shown each array 38 includes
three openings 40 which are uniformly angularly spaced about
the respective depression 22. Each opening 40 preferably
extends from the outer face 18 of the plate and into the
side wall 28 so that the base 26 of the depression lie on
common tangent.
Each of the rectangular depressions 22 include an array
or cluster 41 of two openings 42. The openings 22 are
located adjacent the end walls 34 and extend from the base
32 and into the inner undimpled outer race of the backing
plate.
During the assembly of the brake shoe 10 as heretofore
generally described the thermal responsive binder of the
back pad 14 is free to flow through the openings 40 and 42
., .. . . ' . , ! ' ' ' ': '
.-.... : and Jill the.respecti~e.de.p~ession~ 22 and..24...Up~n curing
'' he Sweeney
with the binder composition which extends through the openings
40 and 42 about the circular and rectangular depressions 22
~` 5 and 24 and form in the nature of attachment arms 44. The
arms 44 which are integral with the back pad 14 and the tie
portions 46 and 48 disposed in the respective depressions 22
and 24 lie in opposing relationship to the remainder of the
pad 14 to form a mechanical lock preventing separation of
the pad 14 and the friction material 16 from the metal plate
12.
It is to be noted that with the openings 40 and 42
extending along the side walls Z8 and 34 and into bases 30
and 32 of the depressions, the cross sectional area of the
binder material within openings is maximized and thereby
provide a tie having a maximum resistance in tension and
shear.
