Note: Descriptions are shown in the official language in which they were submitted.
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: Roller retainer for brake assembly
Backaround of the Invention
Field of the Invention
; ~ The present invention is directed to an improvement
~: in a vehicle brake mechanism and more specif;cally to
a roller retainer for a cam actuated brake assembly.
:~ The invention is particularly useful in a brake
assembly of the type disclosed in U.S. Patent No.
:~ 4,206,834 issued on June 10, 1980. That brake assembly
includes a paîr o~ brake shoe~ having adjacent ends
~: 10 pivotally mounted to a support and a rotatable actuating
cam disposed between the other ends of the brake shoes.
: A roller-type cam follower is provided between each of
: those other ends of the brake shoes and the actuating
cam. The roller-typ~ cam followers are seated in open-
ended recesses provided to the brake shoes. Rotary
:~ movement of the actuating cam is applied to the roller-
~: type cam followers which cause their respective brake
; shoes to pivot outwardIy about their pivot or anchor
pins to contact the inwardly facing friction surface
of a brake drum.
The roller-type cam followers are comprised of a
~ stepped cylindrical steel pin having a center portion
j which bears against the actuating cam and smaller dia-
meter end portions which serve as trunnions seated in the
open ended recess provided to the spaced webs of a dual
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,~ web brake shoe. Under normal conditions, the roller-type
~. cam follower is trapped between the open ended recesses
s provided to the dual web brake shoe and the bearing sur-
face of the actuating cam and held in that arrangement by
the brake
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return spring. However, the brake assembly is comprised of
a number of different parts and it is also advantageous to
maintain the cam followers in the recesses provided to the
brake shoes during assembly and disassembly of the brake
5 mechanism for repair purposes. This limits the number of
parts the mechanic has to be concerned with at any given
time and the attendant possibility of dropping and losing
the relatively small c~m-follower rollers.
It has also become known that means for retaining
10 a roller between the actuating cam and the open recesses
provided to the ends of the brake shoe is also beneficial
under conditions where the brake assembly is not maintained
'~ in adjustment particularly during extremely cold weather.
Under such conditions, rollers have become displaced from
15 their position in the open-ended recesses of the brake shoe
webs which of course adversely affects operation o~ the
brake assembly.
It is also desirable for assembly and maintenance pur-
~ poses if the roller retaining means allow the cam-follower
'~ 20 roilers to be appLied and removed withouttheuse of anytools.
Descri~tion o~ the Prior Art
U.S. Patent No, 3,114,437 discloses one method of
` retaining a roller-type cam follower in open-ended recesses
provided to brake shoes, In t~at patent the mouth of the
25 open-ended recesses is formed to retain the ends of the
~, rollers and a tool such as a screw driver may be required
} to remove the rollers from the brake shoes.
s A spring has also been employed to retain a roller in
i its brake shoe during transfer andassembly. The prior art
;~ 30 spring retainedthe roller satisfactorily but the roller could
not be withdrawn from the brake assembly without risk o~ in-
jury to the mechanic's hand. The dis-tance required for the
retainer spring to clear other componentsof thebrake assembly
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is such that a screwdriver or other tool was often used as
a pry bar to expand the return spring.
_ mmarY of the Invention
According to the invention there is provided in a
rotary cam actuated vehicle brake assembly including a
pair of brake shoes with each brake shoe having a pair
of spaced parallel webs, a rotary cam between adjacent
ends of said brake shoes, and a roller type cam follower
between said cam and said adjacent end of at least one
of said brake shoes, said cam follower having a pair of
trunnions seated in open recesses provided at the ends
of said one brake shoe web, the improvement comprising:
~; a roller retainer member secured to said one brake shoe
and having two substantially parallel legs, a manual
grip intermediate said legs and located on one side of
a reference plane defined by said legs and a portion of
said member intermediate at least one of said legs and
said manual grip on the other side oE said reference plane
formed to extend only partly around the circumference of a
roller trunnion surface.
In its pre~erred forms, the present invention is a
roller retainer for a vehicle brake assembly comprising a
member Pormed to provide two substantially parallel legs
; with a tang formed at the end of each leg, a manual grip
formed in the member intermediate the legs and at least
one portion of the member intermediate the tangs and the
grip formed to extend in one direction circumferentially
around part of a roller with the legs of the member ex-
tending tangentially away from the roller in the other
circumferential direction. The roller retainer is pre-
- ferably formed from a length of spring wire and is used in
combination with a brake shoe having a dual web structure
in which the webs are formed with similar and laterally
aligned open end recesses and an aperture adjacent each
recess. The tangs formed at the ends of each leg of the
retainer are seated in one of the apertures and a portion
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of each leg intermediate the manual grip and the tang
extends partially around one of the roller trunnions and
returns around that same portion of the roller trunnion
;` so the manual grip and the tangs are disposed on the same
~; 5 side of a reference plane parallel to the legs and passing
through the axis of the roller. This arrangement enables
the retainer to be rotated about the apertures thereby
allowing the roller to be safely removed from the brake
shoe while the shoe remains in the assembly without the
use of any tools.
The invention and the advantages offered thereby will
~; become apparent from the following detailed description of
~;~ the embodiment shown by the accompanying drawings.
Brief Description of the Drawings
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~ 15 In the drawings wherein like reference numerals refer
;i, to like parts:
,; ~ Figure 1 is a side elevation, partly in section, of a
brake assembly according to the present invention;
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Figure 2 is an enlarged view o~ a portion of Figure 1
showing the roller retainer of the present invention;
Figure 3 is a section on line 3-3 of Figure 2;
Figure 4 is a view similar to Figure 2 but showing a
5 prior art roller retainer;
Figure 5 is a plan view of tlle roller re~ainer of
the present invention;
Figure 6 i~ a side elevatlon of the roller retainer
of the present inven~ion; and
Figure 7 is a end elevation o~ the roller retainer
of the present invention.
: Description o~f the Invention
~'
With reference to the drawings there is shown a cam
actuated brake assembly generally designated by the numeral
15 10. The brake assembly 10 is supported b~ a spider 11 ri~id
with a vehicle axle housing 12. The brake assembly 10
includes a pair of brake shoes 14 each of which is pivotally
mounted by a recess 16 at one end to an anchor pin 15
carried by the spider 11. A cam 19 is ~ounted or rotary
20 movement between the adjacent ends of the brake shoes 14
opposite from the anchor pins 15. The brake shoes 14 are
each provided with a ro}ler type cam follower 20. The cam
is nonrotatably secured to a cam shaft mounted to the
- spider for rotary movement by conventional means to rock
25 the cam 19 in a clockwise direction through an arc ln the
range of about 10 to 30 degrees, The cam 19 provides
an outwardly direc~ed force to:the rollers 20 and the brake
:: shoes 14 which cause the brake shoes to pivot about the
-: anchor pins 15. This movement orces friction lining pads
: 30 24 carried by the brake shoes 14 into contact with the
inwardly facing friction surface 26 of a brake drum 25
secured by conventional means to a wheel rotatably mounted
to a spindle at the outer end of axle housing 12. I~hen the
brakes are released the brake shoes 14 and the friction
35 lining pads 24 are withdrawn fro~ contact with the brake drum
surface 26 by a return spring 28 secured at its opposite ends
to the brake shoe webs.
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The brake shoes 14 are dual web fabricated brakeshoes.
That is, each brake shoe includes a pair of axially spaced
webs 31 secured to a table 32. The webs 31 are flat in a
radial direction and curved in a longitudinal or circum-
ferential direction. The brake shoe table 32 is~curvedin the circumferential direction and the webs 31 are
welded in parallel relation along the interior curved
portion of the table. This provides a generally rigid
assembly of component parts to which the friction lining
pads 24 may be secured by rivets or by chemical bonding.
Each of th~ brake ~ho~ webs 31 is provided with an
open recess 34 opposite the cam follower 20 and an aperture
36 adjacent thereto. The recess 34 is in the form of a
slot which includes an inner arcuate bearing surface or
lS journal 35 and a mouth formed by integral brake shoe por-
tions. The recesses are identical and laterally aligned.
! The bearing surfaces 35 are semi-circular bearing suraces
and are adapted to engage a complementary arcuate surface
of the generall~ cylindrical end portion 22 of the ca~
~` 20 follower roller. As best shown b~ Figures 2 and 3 each cam
roller ollower 22 is comprised of a cylindrical roller
surface 21 located intermediate the brake shoe webs 31 and
~ supported by coaxial reduced diameter cylindrical shaft
i sections or trunnions 22 seated in the arcuate journal
sur~ace 35.
Each roller type cam follower 20 is retained in
its respective recess 34 by a roller retainer 40. As best
shown in Figures 5-7 the roller retainer 40 is preferably
formed from a continuous length of steel spring wire. The
stock wire is cut to a length of about twelve inches and
formed to provide a "U" shaped manual grip 41 and two sub-
stantially parallel legs 42 and 44 and a tang 46, 48 at the
end of each respective leg 42, 44. The roller retainer legs
' 42,44 are each respectively bent in a "U" shape or hairpin
type bend and arcuately formed at 50 and 52 to e~tend
` circumferentially around a portion of a cam follower roller
~; trunnion 22 and to return partly around that same circum-
feren~ial portion with each tang 46, 4~ seated in an aperture
;. 36.
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' With reference to Figures 5-7, the intermediate por-
, tions 50, 52 of the legs 42, 44 are tangentially curved at
,~ x to project in one direction away from a reference plane
`; m defined by the manual grip 41, rather sharply bent in
,~ 5 the form of a hairpin bend to return in the direction of
~'; the reference plane m and tangentially curved at y to
again project away from the same side of the reference
plane m. The intermediate portions 50, 52 of the legs
~ 42, 44 are preferably accurately formed between x and y
'`~ 10 to fit snugly and partly around and to resiliently embrace
~ the trunnions 22 of a roller cam follower 20.
!~ " The roller retainer 40 is formed as described above
so the manual grip 41 and the tangs 46, 48 formed at the
ends of the legs 42 and 46 are both disposed in the brake
~- lS assembly on the same side of a reference plane n, see
Figure 2, parallel to the legs 42, 44 and passing through
~ ~ the axis of the roller type cam follower 20.
!','~ '; Figures 2 and 6 also show the manual grip 41 located
on one side of a plane passing through the legs 42, 44 and
~, 20 the arcuately formed intermediate portions,50, S,2 of the
}};;~ roller retainer 40 on the other side of that plane. This
is accomplished by forming the intermediate portions 50,
c'' 52 of each leg 42, 44 to extend circumferentially in
s one direction, i.e. clockwise as shown in Figs. 2 and 6,
25 partly around the trunnion 22 of a cam follower and to
return with the legs 42, 44 extending tangentially away
~! from the trunnion in the other circum~erential direction~
,;;, The roller retainer 40 with the tangs 46, 48 secured
in the apertures 36 secures the trunnions 22 against the
30 journal surfaces 35. The manual grip 41 is formed long
~ and wide enough so as not to interfere with rotary move-
,~ ment of the cam 19 and is used to withdraw the roller
~' retainer 40 when the brake assembly 10 is dismantled for
,, servicing.
~' 35 When the brake assembly 10 is to be dismantled the
drum 25 is withdrawn and one of the brake shoes (preferably
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the lower shoe) 1~ is manually rotated about its anchor
pin lS to expand the return spring 28. The manual grip
41 of the retainer 40 is then rotated radially outwardly
about the apertures 36 to free the roller type cam fol-
lower without traversing the reference plane n. Thecam follower is then withdrawn from that brake shoe.
The other brake shoe 14 is then manually rotated about
its anchor pin. The manual grip of the roller retainer
associated with that brake shoe is rotated to free the
cam follower which is then removed. The brake shoe re-
turn spring 23 is free of tension with the roller type
cam followers removed and the spring 28 may be manually
withdrawn. One brake shoe, preferably the lower shoe,
is then rotated approximately 180 to relieve the tension
on and thereby permit removal of the anchor end retaininy
springs 17. The brake shoes can then be manually with-
drawn from the anchor pins and new or relined brake shoes
-~ substituted therefor. Except for removal of the brake
drum the brake assembly can be dismantled manually with-
out the use of any tools and without substantial risk of
injury to the mechanic.
Figure 4 illustrates a prior art roller retainer 60
used to secure a cam follower 20 in a recess formed at
the end of a brake shoe web 31. The prior art retainer
60 is comprised of a "U" shaped manual grip 61 and a pair
of legs with a tang formed at each end of each leg. One
leg 62 and its tang 66 are depicted in Figure 4. The other
leg and tang are similar but disposed on the opposite side
of the cam follower 20. The legs are formed to curve
partly around the trunnions 22 of the cam follower with
the manual grip 61 disposed radially interiorly of the cam
follower 20 and the tangs disposed radially outwardly of
the cam follower 20. This poses a serious problem while
attempting to dismantle the brake assembly since the
manual grip 61 has to be rotated about the apertures 36
to free the cam follower 20. This requires the brake
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shoe 14 to be moved a substantial distance away from the
x cam 19 to permit the manual grip 61 to clear the cam 19
and such movement creates a large tensile force on the
.~ return spring 28. The force is of such a magnitude as to
~ 5 present a substantial risk of injury to the fingers of a
x~ mechanic attempting to rotate the manual grip 61 between
~,~ the cam follower 20 and the cam 19.
The roller retainer 40 as previously described and
claimed hereafter does not present such a risk since the
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manual grip 41 and the tangs 46, 48 are disposed on the
same side of the reference plane n and the arcuately
.:~ curved lntermediate portions 50, 52 can be easily with-
drawn with far less tensile stress on the return spring
28 and without
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having to manually move the retainer between the cam follow-
er and the cam. The roller retainer of the present inven-
tion thus provides for ease of assembly and dlsassembly
while avoiding the risk of personal injury attendant the
S use of the Figure 4 type of prior art roller retainer.
The invention may also be embodied in other specific
forms without departing from the spirit or essential char-
acteristics thereof. The roller retainer may be formed
from a synthetic material, stamped from a thin steel pla~e
or fabricated as a combination of separate elements. The
foregoing description is therefore to be considered as
illustrative and not restrictive, the scope of the invention
being defined by the appended claims, and all changes which
come within the meaning and range of equivalency of the
claims are ~herefore intended to be embraced thereby.
- ~hat is claimed and desired to be secured by letters
`~ patent is:
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