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Патент USA US2131369

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Sept. 27, 1938.
_|_. C.' BRlssQN
`2,131,369 '
BRAKING' DEVICE
Filed oct. 27, 193e
'7 Sheets-Sheet 1
Sept. _27, 193s.
L. C. BRISSON
BRAKING DEVICE
2,131,369
`
Filed Oct. 27. 1936
7 Sheets-Sheet 2
LduìS ChQvles BYÍSSon
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Sept. 27, 1938.
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BRAKING DEVICE
Filed Oct. 27, 1936
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BRAKING DEVICE
Filed oct. 27. 1956
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I’nl’l‘enïov:
Louis Charles ßrlpq
Àtt'avweys.
sept-2n 19a-s.
»
I
L. C. BRISSON
_
BRAKING
DEVICE
Filed oct. À27; 193e
»
`
2,131,369
I
7 Vsheets-shew; v
2.131.369.
Patented se'pi. 27, 193s
' UNITED _STATES
__
_
_
BEARING
*A
_
Louis Charles Brlsson, Neuilly-sii‘r4-Seine,France,~
' assigner to Societe Anonyme: Societe desL
Freins' Hydranlìques S. de Lavaud, Paris, France _- » Application
-
In
ociosa-_27. _1936, seriailNo. 101,181
France September 30,1936
-
_
accompanying drawings; but _it is tobe under
This invention relates. to _braking devices ap
stood that
description and drawings are
presented merely by/_way of illustration, and that
they should not be construedin any fashion
plicable to all varieties of machinery involving
rotating elements, namely to> such devices com
_ monly used on vehicles oi all kinds,'fór example
5 on automotive vehicles; and it relates more par-`
as limiting »the appended claims short of the
true‘and most comprehensive'scope 'of thein
ticularly, although not exclusively, to drum-type
brakes comprising friction shoes, _in which the
ventionin the art.
'
In the drawings:
forces and reactions acting on said friction shoes
A _~
_
_
Fig. 1 is a' view in elevation of> one of the pre
have deñnite and fixed directions and converge
10
at one -point for each of 'said shoes, which point fferred embodiments of my invention; ‘
Fig. 2 is alarga-scale view in cross-sectional
is called the “pole” of the shoe.` `
In this type of brake, di?culty has been found elevation through line ZCI-l1 oi?> Fig. 3, -of-l cer
heretofore in returning the brake shoes, at the
end ofthe braking period,- to deñnite and fixed
Fig. 3`is'a view in cross-sectional Yside eleva'- â
tion through line 'III-_III of Fig. 2', of the 'def 15
15 “off” positions, or positions of` rest.
The main purpose o_f my invention is to pro-'_
vide a simple, practical, reliable -and not costlyv
solution of this problem.v
~
tails shownïin Fig. 2;
.'
_
_
'
l
' Fig'. 4 is a view,`in cross-_sectionaL'side eleva-_
tion, of thesame details, but through line'IV-IV
_
The principal object ofniy invention-Lis .to
` Fig. 5 is a view in plane cross-section 'through
ties of machinery involving rotating elements, - 'line V-V ofvFig. 2, of one of the details illus
provide a braking device applicablev to allvarie
in which the brakeY shoes, during the y»idlejor
tratedin that iigure;
’
>-
_'
-
_
Fig.'6 isa ~view in cross-section through
“oiï” periods, are automatically returned to deñ
nite and ñxed positions _of rest.`
'
VI--VIofFlgsn
Fig. 7 is a view in crossfsection
__
through line
25
In certain brakes of the type hereinbeforede- '
ÍVII-VII
of
Fig.
1;”.
‘
:i
« scribed, use is made of` hydraulic `meansfor ex
_ Fig. 8 is aview in‘ cross-section through ‘line
' pending the brake shoes and appLving’them
against the brake drum.
It has further _been
VIII-VIH 0I F18. _ 1;
'
'
AFig.»9 is~ a view in cross-section through
"proposed, in my co-_pending application Ser.
IX-IX' of Fig. 1;
30 No. 63,458, filed on Feb. 11, 1936, to attach lsaid
10 is a view in >cross-»section through line; _ _
hydraulic expanding means to one of. theïbrake
shoes; furthermore, U. S. `Patent N_o. 1,998,533
discloses the combination in such brakes of_ hy- -_
f draulic expanding> means
_
35
panding
means.
-
with mechanical exf 'method to' be followed -in laying out uio brake
_
`
'
-'
"
_ Fig. 12 is _a view in elevation- ,similar to that
Another objectof my
YaV braking device of LtheÑinvention
type-describedwh'ich'
toY provide of Fig. 1, but. referring to a variant _o_f my in
is equipped with combined hydraulic and.me-‘_
_
'_vention;`
rig; 1a is a'view »ii'i'eievation similar to that
vchanical operating means, the body of Said com-v
40 bined mechanism being mounted onone of the ___of F1g._1, but referring to a.second__preferrei'lV
brake shoes.
-
\
'
A further objectv is -to provide a braking delV
_
_embodiment of my_inventiom'
_
.
~
Fig. _14 is a _similar view, but referring-eo a _ l
Vvice oi' the type described, embodying the auto
matic self-applying feature.
>
-
"
A-still further object is to provide a braking->
device oi the type described, incorporating,
" - forms
' Fig. offthe
isis a.brake-_operating
detail view of one
mechanism.
ofthe preferred
'
‘
l thefriction
`I_n'tl'ie preferredfembodiment
infFig.j1,«
membera'or
'I' is'the
brakebrake
of
Shoea’intendedl
my_inventio ¿
combination with the various features herein- ï_ 'illustrated
before deñned, means for automatically adjust-A
ing the slack, in order to compensate for the
50 wear in the brake‘packing. said slack adjusting'
means >being operativeY both inicase of hydraulic
and of mechanical operation of the brake.
Further objects and advantages of my inven
tion will-appear to one skilled in the artfrom`
toÍbe applied against the inner faceof said’drum,
are shownat _2, 3> and 4. The drumfljis
ilxed to the rotating machine part to__be braked,
__ `as_for- example to the «wheeljfo? amautomotive- - "
vehicle; _but‘it is; to 'be lunderstoodthat my in
vention is _in no wayjlimite'd in its
Aizo-this
55 the following description, with referencetotvhe~;v 'particular application'. ,' The normalldirection'
2
r2,191,369
of rotation of the drum I’is indicated, in Fig. 1,
i
`
.
the brake shoes. Said body 43 is rigidly secured
by the arrow f; hence, in the case of an auto
to said brake shoe 4 by means of a bolt 44’ and
motive vehicle, said arrow f indicates the direc
nut 45. Said body 43 is provided internally with
tion of rotation of thedrum corresponding to . a cylindrical bore 46, the end of which forms a
forward motion of the vehicle.
‘
convex surface 41 which may optionally be
spherical, said convex surface being covered by a
thick cup-shaped membrane' of rubber, 48. Said
projecting convex portion 41 is provided with
. 'I'he brake shoe 2 is interconnected with brake
shoe 3 by link members 5 and 6, which are ar
ticuiated b‘y means of a pin 1 onto the brakeshoe 2, and by means of a pin 8 onto the brake
10 shoe 3. 'I'he articulated joint on pin 1 is free,
meaning thereby that no special precaution is
taken to provide substantial frictional resistance
an annular groove 49 in which groove 49 ter
minate two ducts 50 -and'5I. Said duct 58 con 10
nects with another duct 52 supplied with añuid
under pressure by means of a feed- pipe 53,'said
between said-pin and said articulated members;
feed pipe being connected by suitable tight joint
the pin- 1 is simply held in place by means of
ing means with the cylinder 43. For this pur
pose, the feed pipe 53 is provided ,with a conical
_outlet 54 within which fits a conical washer 55,
15 washers 9 and I0 and cotter pins II and I2.
On the‘contrary, the articulated joint on the
pin 8 is designed to provide a relatively large
frictional resistance tending to oppose the rela
tive rotation ofthe `link members 5 and 6 with
the joint being made tight by the pressure of a
screw collar 56. On _the other hand, the duct
5I communicates with another duct 51, the lat
20 respect to the brake -shoe 3. For this purpose,
the pin 8 is provided on one end Awith a head
I3, and on the other end with a
tion I4, _upon'which is screwed
acting with a spring washer I6.
25A ner, the members articulated on
subjected to an elastic pressure
ter being "closed by means of a blind screw 20
plug 58.
.
The edges of the cup-shaped rubber diaphragm
or membrane 48 is firmly clamped by means
threaded por
a 'nut I5 co
In this man
the pin 8 are
that may be
of a cylindrical sleeve 59, which is pressed down
upon the edges of said .membrane by means' 25
which will be described later.
adjusted at will by tightening orloosening the
On the other end
of said sleeve 59 is applied a ñat disk 60 provided '
Y nut I5, said elastic pressure producing between
»at its center with an orifice 6I through which
passes the rod 62 of a piston-like member 63, said
the link members 5 and 6 and the brake shoe
30 3 the frictional resistance required. _'I‘he nut
piston member 63 being applied against the 30
I5 may be notched and held in position by means
membrane 48. The disk 60 is provided on its
outer face -with a crown of ratchet teeth 64,
which teeth' co-act with a pawl 65 pivoted at 66
on a secondary piston member 61. Said pawl 65
is subjected to the action of a spring 65’ which 35
Atends to maintain it in continual engagement
` of a cotter pin I1, or by any other suitable means.
At its other end, the brake shoe 3 is provided
with another pin I8, upon which are articulated
35 two other link members I9 and 20. The articu
lation at _I8 is also a friction joint, and to this
, end the pin I8 is provided -at one end with a
head 2|, and at the other end kwith a threaded
portion 22 upon which is screwed a nut 23 co
40 acting with a spring washer 24 tò exert a suit
able elastic pressure on the articulated members,
said -nut 23, when screwed to the position pro-
'ducing _the ‘correct frictional resistance, being
Amaintained-in said position by means of a cot
ter-pin 25. The link members I9 and 28 are
‘ freely articulated on a fixed pivot pin 26 (Figs.
1 and 9). Said pivot pin 26 is provided with a
base or collar 21 formed integrally thereon and
with a threaded portion 28 which engages in a
with said ratchet teeth 64. Said secondary pis
ton member 61 slides axially within a'. cylinder
68 which is pressed against the disk 66; To this
end, the cylinder 68 is provided on its outer edge 40
with a threaded portion 69, while the cylinder 43
` comprises on its outer edge, facing that of cylin
der 68, a similar threaded portion 10, but of op
" posite pitch to that of 69. A threaded‘collar 1I
provided with opposite screwthreads correspond-` 45
ing with those on cylinders 43 and 68, engages
vsimultaneously said screwthreads 69 and 10, thus
clamping the cylinder 68 against the disk 60, said
pressure being transmitted byv the sleeve 59 to
the periphery of the rubber membrane 48.
hole 29 drilled in the fixed cheek `member of'
with a deep lateral groove 12 and an axially
bored hole 13, which hole is tapped so as to form
a nut on a screw member 14 terminated by a
£2 tcâäae rigidly secured to said fixed cheek mem
55
~head 15. ` Said head 15 comprises a slot 16 with
Two other link >members 32 and 33 are further
articulated onto the -pin 26, preferably on oppo
site sides of link members I9 and 26, the latter
- brake
shoe 2.
`
The complete articulated
'
'I'he link members 32 and 33 are articulated
with friction onto the brake shoe 4 by means of
' resistance between the articulated members, it‘is
locked in position byA means _of a cotter _pin 42.
The brake shoe 4' carries, at its other end, the
75 body or cylinder 43 of the device for expanding
`
being axially slidable within~a ñexible guiding
a pin»31 provided with a head 38 and threaded
portion 39, upon which is screwed a nut 40 which
presses upon said articulated members» through
70 theV medium of an elastic washer 4I. When the
nut 46 is tightened to give the correct frictional
`
A finger 80 formed integrally on. a lever'8l
pivoted by means of a pin 82 onto the cylinder
68 engages the lateral groove 12. 0`n its other
end, the lever 8l is articulated by means of a
pin 83 to a knuckle joint 84 to which is attached
a> flexible control .cable 85, said ñexible cable 65
is maintained in position by means of a cotter
pin 36. Said articulated- members are therefore
free to rotate without substantial frictional re
sistance.
In‘this manner, the screw 14 is
prevented from rotating.
60 joint on the pin 26 rests upon the base 21, and
65
55
in winch fits tightly an abutment member 11
`secured by means of rivets 18 and 19 to the
being preferably separated `from each other by
means of a washer 34.
_
The secondary piston member._61 is'v provided
the brake 30. A nut 3| screwed onto said thread
ed portion, with a washer 324, enable said pin
sheath 86 (Figs. 2 and 8), the end of which sheath
is anchored to a supporting bracket 88 riveted at
.
89 and 90 to the brake shoe 4._ A helical spring
9| is inserted between said bracket 8_8 and said 70
knuckle 84, in such manner as to push said
knuckle in the direction of the arrow 92.
On a pivot pin V`93.(1ï‘igs. lfand 8), rigidly
mounted on the fixed cheek member 38 of the
brake, islrotatably mounted a -`sleeve member` 75
3
l' 2,131,369
“àl threaded et its outer end as. on> seideleeve revolving brake drum `l upon the shoes applied
against its surface. I have shown that all the
i >member `94 are mounted in successionthree op
forces acting on each brake shoe converge at one
erating levers 96, 91 and 98, a Árigid washer“,
point, which point is the pole of that brake shoe.
washer |0| , the- assembly of the three levers andv Therefore- the condition of equilibrium of the
three washers being 'pressed together by means brake shoe during the braking period necessarily
of a nut |02 screwed onto. the screwthread 95 requires that the reaction of the brake ldrum upon
Y an elastic washer |00 and iinally another rigid
said brake shoe should also pass through thepole. .
of the sleeve 94, in such manner as to create a
f material frictional resistance> between- said op- L. The problem of the determination of the direc-'10
10 erating levers 96, 9] and 98 and said sleeve 94. tion of said reaction of the'brake drum has been~
The latter is maintained in its position on the pin completely treated in '-the German Patent No.
93 by a cotter pin |03.
' 603,850. It has been demonstrated in said Ger
-
A link member |04 is articulated by means of man patent that the reaction is tangent to a cir
>a pin |05 onto the other end of lever 96, and by . cle having the same center O as the brake 'drum
a pin |06 onto the brake shoe 2.. Furthermore, I, and whose radius p is given by the formula:
a helicalspring |01 attached to a support ||5,
rigidly secured to the cheek member 30 of the >
brake, engages at |08 a second arm 96a of the -
InFormula (1)
lever »96. A link member |09 is articulated by
means of a. pin ||0 ontothe lever 91, and by
means of a pin ||| tothe brake shoe 3. Finally,
p=s sin «p
(i)
«p is the angle of friction
s is the radius of’ the
“pressure circle,” the
value
mula.:
pin ‘||3 onto the lever 98,> and by means of a.'A
pin ||4 onto the brake shoe 4.
_
s_`_> 4 sin 'y1
' Pins ||6, ||1 and H8, which are rigidly se
cured to the iixed cheek member 300i the brake,
pass freely, with ample clearance, respectively
vthrough slotted oriñces H9, |20 and |2I formed
«in the brake shoes 2, 3 and 4; and said pins bear
.onc‘their outer ends guiding washers |22, |23 and ‘
. |24, held in position by cotter pins ~suchas |25
(Fig. 10).
_
~
_
»
.‘
r-'sin 2714-271
l'nFormula (2)--
_ ,TheV result is, of course, that the contact pressure
betweenv the head 15'and the abutment member
11 terminating the brakesboe 2 is directed along
a geometric straight line AB, which coincides
with the center line of the screw 14. The forces
' transmitted by the link members 5 and 6 between
the brake shoes 2~ and 3. are evidently directed
' along the center lines, of said link members, that
is along the straight line CD passing through
the centers of the pins 1.a1`1d 8. « -The straight
lines AB and CD intersect at a point E, and the
pins |05 and |06 are so .located that the straight
.line passing through the geometric centers of said
pins also passes through point E, which is known
as the “pole” of the brake shoe 2.
-
The forces transmitted by thelink members 5
_
25
(2)
r is the radius of the
.
`
brake -drum i;
271 represents the angular
opening of the brake
» , packing --2a
on
the
brakeshoe 2.
y
- 'I'he bottom of the slot 16 ¿cut in the head 15
of the screw member 141s a plane surface per
pendicular to the center line 'of said screw 14.
,35
of ' which .is
computed by the for
a link member ||2 is articulated by means of a ‘
‘It is therefore possible to lay out the 'reaction
EL, which intersects the pressure circle at a 'point
I called “center of pressure." In accordance with
the teachings of German Patent No. 603,850, .the
brake packing 2a, for example, is arranged syin
metrically with respect to ,the axis _of pressure _OL
Said axis of pressure is that'which corresponds
to forward motion of the vehicle, that is to rota 40
tion of the drum in the direction of the arrowvf.
Of course, on all the other brake' shoes, the pack
ings arelalso set symmetrically with respect to the ’ `
axis of pressure of each brake shoe for forward
motion. This insures the advantages mentioned 45
in the German Patent No. 603,850, to wit: Uni
formity ofwear of the brake packing, great im
provement> in the constancy of the braking effect
in spite of variations in the coefñcient of friction. ~
between the brake packing- and the drum, a much-
and 6 to the brake shoe 3 -are directed along the
more gradual progression in the braking effect, ’
and the elimination of the tendency to‘sudden l
straight line CD, and the reaction transmitted by
blocking of the wheels.
'
,
It will _be explained further that the ,relative
the link members I9 and 20 to the same brakev
55 shoe 3 are directed along the line GF, which passes positions of the links |04,. |09- and |I2 with re
through the geometric’ centers of the pins 36 and
spect tothe corresponding levers 96, 91 and-98,
I8. The straight lines, CD and GF intersect at a
point not shown on the iigures, which point is
and the -relative positions> ofpins |06, ||| and ||4\
55
on one hand, and'of the pin 93 on the other hand,
' the pole of the brake shoe 3. The pins H0 and
60 ||| are so located that the straight line passing
are by no means indifferent, and sh’ould be accu
65 along the straight line GH which passes through
tion of its operation; for that reason, they will be
rately determined; and finally that the lengths of
through their geometric centers also passes levers 96, 91 and 98 must be correctly laid out. Al
though these explanations properly form a part
through said pole,
'
Finally, the reactions transmitted to the brake . of the description of the brake mechanism, they
shoe `4 by the link members 32 and 33 are directed can only be easily'understood after the descrip
the geometrie centers of thepins 26 and 31. The
' line GH intersects the line AB ata point K, which
is the pole of the brake shoe 4. Thepins ||3 and
|14 are so located that the straight line which
70 passes through their geometriccenters also passes
through the pole K.
l v
.
-
In the foregoing discussion, I have considered
deferred until later.
'
’
_
When the driver wishes to apply said brake, he
may either produce a hydraulic pressure inside
the feed pipe 53 by any suitable means, or else
exert a pull on the flexible cable 85.
»
f
' - Fig. l5 shows one of the preferred forms o
all the forces and reactions to which are sepa- ’ said brake applying means.
16
'
The operation of the brake is as follows:
In that ligure, |25 '
rately subjected each of the brake shoes 2, 3 and 4, ' represents a ñxed 'frame upon which is~ mounted'l
with the exception of the reaction exerted by the a _body 26, said body being provided, for mounting
,4j
.
.
.
2,181,369
purposes, with a. screw-threaded portion |21 pass
ing through said frame, and a. nut -|28 engaging
said threaded portion. 'I'he body |26 is hollow and
isclosedbyascrew cap |29 which co-operates with
a tapped portion |30 of saidbody |26. `When
screwed down into place, the screw cap |29 firmly
clamps the edges of a heavy cup-shaped rubber~
membrane or diaphragm |3|, which may, for ex
ample, be of spherical shape. Said rubber dia
10 phragm is made perfectly tight by means of a
peripheral metallic sealing ring- |32, which also
serves as a guide for a piston member |33, the pis
ton'rod of which |34, terminating in a‘ pedal |35,'
of the brake shoes,_ at least'at the start of said
motion, causes the three levers 96, 91 and 98 to
rotate as one ‘integral unit.
It should of course
be noted that the friction between said levers is
suiiicient to overcome the resistance of the 5
spring
|01.
_
"
'
`
l
-
The brake shoe 3 is articulated with friction,
through the pin-I8, to the link members |9 and
20, which are .themselves freely rotatable with
respect to the pin 26. Hence the brake shoe 3 10
and the link members |9 and 20 tend to rotate
as "an integral unit around the pin 26, under the
action of the thrust transmitted by the link |09
passes through. the screw cap |29. The space |34 to the pin |||.
'
15 inside said body |26 communicates with the feed
The motion of the brake shoe 2 is somewhat
pipe 53; a filling hole closed by a screw plug is more complex, for said shoe is freely articula-ted,
shown at | 35. It will be readily seen that, once 'through the pin 1, to the link members 5 and 6,
the feed pipe 53 and the entire space |34 have which are themselves articulated with friction
been filled with liquid, a hydraulicpressure will be onto the pin 8 and the brake shoe 3. »The pin 1
20 created therein by pressing upon the pedal |35, therefore moves with the link members 5 and 6,
which _hydraulic pressure will be transmitted to the brake shoe 3 and the link members |9 and
the expanding mechanism contained in the body 20, around the pin 26 as a center, while the brake
43.
shoe 2 may rotate around the pin 1. The move-l
On the other hand, the mechanical operating ment of the brake shoe 2 is therefore the result
25 mechanism is as follows: The cable 85, one end of ant of two rotations, one around the pin 1 and
which is attached to the lever 8|, is attached at the other around thel pin 26.
.the other end to a guiding rod |36, to which is se
After a certain time, the brake shoes come into
cured a handle |31. Said rod |36 slides within a contact with the brake drum |, and from that
bore |38 drilled in a support |39 secured to the time on, the effect of the reaction of the drum
30 frame |25 by means of> a threaded portion |40, a is felt.
,
nut |4| engaging said threaded portion and_a
The brake drum is here supposed to revolve in
lock nut |42. Furthermore, the support |39 is the direction of the arrow f. It will be under
tapped at |43 to accommodate the threaded ring stood. that the reaction of the drum tends to
terminating the sheath 86 guiding the flexibley ' force the brake'shoe 2 to revolve with said drum;
35 cable 85. It will readily be seen that a pull ex
this movement is opposed by the reaction of the
erted on the handle |31 will be transmittedby the link members `5 and. 6, which is ’transmitted
15
20
25-
30
35
cable 85 to the brake operating lever 8|, thus through the pin 8 to the brake shoe 3, which in
operating the brake expanding mechanism.
‘ turn transmits said reaction through the pin I8
'I'he operation of the hydraulic brake-expand
andthe link members I9 and 20, to the fixed pin
ing mechanism will now be described. ,
,
26. It is thus seen that the system comprising 40
The hydraulic pressure produced by pressure * the brake shoes 2 and 3, the link members 5 and
on the pedal |35 swells out the cup-shaped rubber' 6 on one end and |9fand 20l on the other end,l
membrane or diaphragm 48, which in turn dis
forni a self-applying brake which functions in
places towards the right the piston member ,Y 63
45 and its rod 62. Said rod 62, which contacts with
the secondary piston ‘61, transmits its motion to\
said secondary piston, which in turn transmits
a manner already well known in the art.
For“
this direction ofrotation of the brake drum, the'“45
brake shoe 4> has no self-applying effect.
`
`Therefore if it is supposed that one of the
its motion to the brake shoe 2, through the med- A brake shoes has come in contact with the drum
ium- of the screw ~'|4, whose threads have a very .before the others, it is seen that the displace
50 low pitch.> Thev force` exerted by the hydraulic
pressure therefore tends to move the brake shoe 2
towards the right, and the brake shoe 4 towards
the left, since the body 43 of the expanding mech
anism is secured to said brake shoe 4.
The force applied to the brake shoe 4 tends
55
to make the latter rotate around the pin 26 as
a- center; for, as explained above, the brake
shoe 4 is articulated with friction to the link.
' members 82 and 33, while said link members are
60 freely articulated onto~the pin 26. It is clear,
therefore, that the assembly of the brake shoe 4
and the link members 32 and 33 rotates as a
whole around the pin 26. In the course of this
movement, the pin ||4 moves with the brake
65 shoe 4 and entrains, by means of the link mem
ber ||2, the lever 98. It will be recalled that
‘the lever 98 is coupled by frictional resistance
to the levers 96 and 91, and also to the sleeve
94. Therefore the levers 96, 91 and 98 tend to
70y revolve together, the more readily that the ef
i \ fort exerted on the brake shoe 2 causes said
Mbrake shoe to move to the right, which motion
is transmitted to the lever 96 by the pin |06, the
link ,member |04 and the pin |05. . It~^will be
understood therefore that the expanding -motion
ment of the first, shoe- stopsv while that of the 5
Ñother shoes continues, until they in turn are in
contact with the drum. Under these conditions,
it is clear that the levers 96, 91 and 98 change
their relative positionsslightly. Said change in
relative position will, at'the end of the braking 55
period, when the spring |01 begins to draw the",A
brake shoes back into their “olf” positions, allow '5
the automatic centering of the brake shoes with
in the _drum to be eñected; in other words,
through the medium of said slight change in the 60
relative positions of said levers 96, 91 and 98
during the preceding braking period, when the
brake is next applied, the brake shoes will all
come simultaneously in contact with the drum.'
When the hydraulic pressure is released; the 65
spherical rubber membrane or diaphragm.“ is
free to resume its initial position under theÍac
tion of the spring |01; for said spring, in con
tracting, causes the assembly of parts compris
ing levers 96, 91 and 98, and the sleeve 94, t`o`70
rotate anti-clockwise on the pin 93. _The result>-§l
is that the link members |04, |09 and ||2 trans-
A
mit respectively to the brake shoes 2, 3 and 4
motion which draws them away from the brake
drum. The motion of brake shoes 2 and 4 to- 75
5
2,131,369
of the pin |05# and through point b a parallel is
14, theV
n member ’61, the piston rod 62 and 'drawn to the line |04. On a »perpendicular to
the line |_I2 is laid out a length c-d proportional,
the piston 63, back into the body 43 of the hy
draulic expanding mechanism, so that all these with the same ratio of proportionality as in the
previous case, to the displacement of the pin'
parts resume the positions shown in the draw
ings. In their “oli” position, the brake shoes ||3; and through the point d is drawn aparallel
must be equally spaced away from 'the brake to the line H2, which parallel intersects at e
drinn, and it will be understood that, in order to that drawn through b to the- line |04. Through
wards each other evidently thrusts the screw
the point e, a perpendicular is now dropped onto
line |09, and on said perpendicular is laid out a
length e-g proportional to the displacement of
-secure this result, it is necessary that the'move
10 ment transmitted to the brake >`-shoes 2, 3 and 4
by the contraction of the _spring |01 should not
be substantially modiñed by the relative displace
the pin _||0; and, finally, through the point g
ments to which the levers 96, 91 and 98 may have
is drawn a parallel to the line |09.
"
' In this manner, a triangle Ic-l-m is obtained,
been subjected during the previous braking pe
which is similar to the triangle k-m-p, the]-15,
15 riod. In order to satisfy this condition, it is evi
dently suñlcient-that the link members 96 and
|04, 91 and |09, and 98 and ||2, respectively
ratio of proportionality'being that of _
form betweenthem angles differing only slightly
,
from 90°; forexample, that said angles be in
,»'_
k-p
Evidently,r the point within the" triangle 20
cluded between the limits of 80° and- 100°. Under
these conditions the displacements of theipins k-n_-p which should mark the geometric >cen
|06, III, and ||4, for a given angular displace-_ ter of the pin 93 should beV homologous to point
-ment of levers 96, 91 and 90 under the' action of Ye in triangle 7o--Z-m. The center of the. pin
the spring |01, are not substantially altered, 93 may therefore easily be located, and will give
even when the pins v|05, |I0 and ||3 have been , simultaneously the lengthsrof the levers lili,- 91
slightly displaced from their original positions. and -98, which will be the lengths of perpendicu
Since the brake shoes 2, 3 and 4, whenin thev lars dropped respectivelyofrom the point 93 onto
“oli” position; must be equally spaced away from the straight lines |04, |0'9 and | |2. .
the surface of the drum I, and since the clear
30 ance. between them is a function of the angular
v In a brake designed as above indicated, it is
Aclear that, inthe “oli” position, or position of
displacement of the levers 96, 91 and 98 as. an
integral unit, it is clear that the- lengths of said
levers must have- deñnite values, and likewise,l
that the position of the pivot pin 93 musthe~
correctly determined, even if the positions of
the'pins |06, ||| andV ||4 have been arbitrarily
chosen. The following proceduremay be used
to determine the correct values ofY these quan
tities.
_
_
~
_
_ On a drawing representing the outline of the
rest, the brake shoesrwill be equally spaced away
from the drum |, and that-> during the brakingperiods, they will all come simultaneously in con
tact Awith Ythe'- vdrum surface.v The adjustment of
the relative vpositions _of thellevers 96, >91 and 90
will be'eiïected automatically at the first appli
cation of.the brake, and will continue in thesame
automatic manner thereafter, »whenever a new
adjustment becomes _necessary through unequal
brake, as in Fig. 1'1, the brake shoes 2, 3 and 4
wear of the packing on the different brake shoes.`
s >The disk 60 provided with’a crown of 'ratchet
are iirst laid out in their working positions, that "
teeth 64 co-actingV withîfl’the pawiA 65, the sec-l
is in contact with .the drum |, and then in the ondary piston .61 and the' screw 14, constitute an
'positions of rest which it is desired to ascribe> ' automatic slack-adjusting mechanism which
45 to them between the braking periods, in which functions in the -sa'me manner as that disclosed
positions said brake shoes should be equally
in U. S. Patent 1,971,643, of August 28, 1934, to
spaced away- from the brake drum surface. It
is known that the center lines of all the link
D. Sensaud de Laveau.. Hence the description of -
said slack-adjusting mechanism` would be super
members interconnecting said brake shoes must ñuous, since it is already known> inthe art.' The
all pass through- the poles of the corresponding ' use olf` -such -a-device in combination with the
-_brake shoes. _»Therefore, as shown in Fig. 11, novel means hereinbefore described makes it- pos- '
the lines |04, |09 and H2, which indicate vthe sible to design` a brake having automatic self
geometric equivalents of the corresponding link , centering brake shoes and a constant slack, re
members, may be laid out; hence the- projection gardless of the ’wear ofthe brake packing.`
of the displacement of the pin |06 on line I 04 - ` When it is desired to apply the brake’by me-.
may also be determined; and since the lever 96 chanical
'ad ofY hydraulicmeans, the driver
is approximately perpendicular to the line |04, exerts, by ' ans of the handle |31, a tractive ei'
the _length of said projection represents very fort on the’ñexible cable 85. . VItshould be'noted
closely the actualdisplacement‘of the pin |05.` that, in ‘the best known methods of vtransmitting
Likewise, the projection of_ the-displacement of ' mechanicalv forces' lthrough the medium of -iiexthe pin ||| on the line |09 may also be laid out; ible cables, the- reaction'of the forcés applied ¿to
and, since the lever 91 is substantially ~perpen .- the cable proper is- taken >u‘p by -the lsheath-86 .v
dicularto the line |09, the length of said pro
of said cable. Now‘said sheathY is anchored'ato. . v
jection may be taken as representing closely the the ¿supporting bracket 08, whiîzh‘is itself; rigidly
displacement of. the pin |10. Finally, the pro
jection of the ‘pin H4 on the line ||2 may be
laid out; and since the lever 98 is substantially
perpendicular to the`iine ||2, the length of said
secured to the brake shoe 4_. Hence", `in the case
of mechanical operation of thebrake, asin that*
of-` lhydraulic,1operation`,'j the
o1' forces,
brought into'play to; expand theî brakg/f'shoes is
projection gives the measure of the displacement
'entirely internal to >thefbralr'e and „presents no.
70 of the pin ||3. It is evident- that the .radii of point of .application 'outside of Asaid brake.,
70
the levers 96, 91 and 98 must be proportional' A The tractive `effort, exerted/on the cable `85
to the displacements so determined.' 'Therefore 'causesîthe lever 8| to revolve clockwisefar'ound
the geometric lay out may be effected as follows: ' `
On a perpendicular to the line |04 is laid out
a length _a--o proportional to the displacement
the pin 82 as a center. '-.Throughlthe' medium _of
the iinger 80, said Ylever 8| -exerts a' thrustfon the
secondary piston'61 which causesthe.A latter to 76
6
2,181,369
slide axially outwards with respect to the body
the pin 93, are mounted on two separate pins
43, which is secured to the brake shoe 4._ The symmetrically disposed. Thus-it is seen that the
operation of the >brake-expandingl mechanism is ' levers 96 and 91 are mounted on the sleeve 94
therefore identical, from that point on, to that previously described, which sleeve is itself
produced by the hydraulic means previously de
mounted on the pin 93. But the levers 98 and
~scribed; and itis interesting to note that the |48 are mounted on another sleeve |52, similar
slack-adjusting mechanism is operative in both ‘to sleeve 94, whichsleeve |52 is mounted on a
cases.
.
second pin |53, similar to the pin 93. The return
The fixed pins ||6, ||1 and H8,- with their re ` spring |54 of the brake shoes is not connected
taining washers |22, |23 and |24, serve only to between the-lever 96' and a fixed support ||5, but
limit the freedom of motion of the brake shoes directly between said lever 96 and the lever |48.
substantially to the plane of the brake drum, and This arrangement functions in exactly the same
said pins play no active part in the operation of manner as that shown in Fig. 13, and therefore
the brake. The orientation of the slots H9, |20 ' constitutes a simple variant thereof, which, under
and | 2| is determined graphically; moreover, as certain circumstances, may facilitate the con-_ 15
specified hereinbefore, said slots H9, -|20 and |2| struction or the assembly of the brake parts,
leave considerable clearance aroundj the corre
owing to the fact that the levers 96,- 91, 98 and
sponding pins, and are intended to leave the
|48 are no longer mounted all on the same pin.
brake shoes -free to take up their correct posi
However, the above design, as described, might,
20 tions.
under certain conditions, prove unsatisfactory,
' The operation of the brake during reverse mo
in that the assembly of brake parts might tend
. tion of the vehicle, that is when the brake drum
to‘rotate as a whole around the pin 26 as a.
I revolves in the opposite direction from that in
dicated by the arrow f, is similar tothe operation
during forward motion, with the exception that,
center, unless special precautions were taken to
prevent said motion; in which case, the accurate
centering' of the brake shoes would no longer be
in the second case, the brake shoe 4 is subjected>
insured.
to the automatic self-applying effect, whereas
the brake shoes 2 and 3 are no longer subject to
this effect.
I
30 l As shown in the variant illustrated in Fig. 12,
the spring |01 could be _attached directly to the
brake~ shoe 2, instead of acting on the lever 96.
In this case, the pull of the spring |01 must be
directed towards the pole E of the brake shoe `2,
in order to satisfy the basic condition that all
the forces acting on said brake shoe converge at
the pole thereof.
-
`
.
~
~
f I_n_ order to correct this defect, the lever |48
may be extended, as shown in Fig. 14, to> form
an extension arm |55 beyond the pin |53, which
extension armf |55 is connected by means of a 80
link member r|56 to the lever 96, said connection
-being effected by means of the articulations |51
and |58. Inthisumannenthe displacementsof
levers |48- and 96 are co-ordinated.
I.
The various embodiments o'fmy invention here.
inbefore'described and illustrated in> the accom
panying drawings constitute certain preferred,
. It should be understood, of course, that the
forms of said invention; but I wish it to be under
scope of this invention extends to the case where l stood that I do not desire to be limited to the
40 said forces acting on each brake shoe, instead of
converging exactly at the respective poles there
of, intersect in pairswithin a reasonable distance
from said poles.
.
'
'
'
The embodiment of the invention indicated in
45 Fig. 13 differs from that shown in Fig. 1 in that itl
actual structural details and assemblies shown
and described, for obvious modifications thereto
will occur _to one skilled in the art.
.What I claim is:
‘
’
,
_
'
1. In a' braking device, a brake drum, a plu
rality of brake shoes adapted to contact with 45
comprises four brake shoes instead of three. The said brake drum, pressure applying means for '
brake shoe 4, instead of supporting the body 43 -applying said brake shoes against said brake
of the hydraulic expanding device, is connected drum, elastic means adapted to oppose _said pres
by means of the link members |44 to the fourth sure applying means and to return said brake
504 brake shoe |45, which now supports said body shoes to their position of rest when said pres-l 50
4'3, together with the supporting bracket 88 to sure applying means cease to function, affixed
which is anchored the sheath of the cable of the pivot pin, a plurality of levers freely and rotat
mechanical operating> device. ' The. link mem
ably mounted on said pivot pin, means for creat- '
bers |44 are articulated with friction at |46 -to
ing frictional contact between said levers, and)
to the brake shoe |45. Asupplementary lever
|48 is added to the levers„96, 91 and 98 on the
sleeve 94, and said ulever` | 48> is connected by a
link member |49 to the brake shoe |45. Said '
link member |49 is articulated at |58 onto the
lever |48, and`at|5| onto the brake shoe |45..
For said brake shoe as for the others, the direc p
said brake shoes.
55 the brake shoe 4', and are freely articulated at |41 'linkage -means interconnecting said- levers with
55
’ 2. In a braking device, a. brake drum, a plu
rality of brake shoes adapted to contact with said
brake drum, linkage means interconnecting adja
cent brake'shoes for forming a chain terminating
in two end brake shoes, aflrst fixed pivot pin, link
age means connecting one end brake shoe to said
tion of the forces transmitted by the link mem
ñrst pivot pin, pressure applying means for thrust
ber |49 passes substantially through the pole of ing the> other end brake shoe- towards said- brake
65 said brake shoe. The operation is evidently iden
drum, elastic means adapted to oppose said pres 65
tical .to that described in connection with the em „ sure applying means, asecond fixed pivot pin, laI
bodiment illustrated in Fig. 1, with the exception plurality of levers freely and rotatably mounted on
that, in Fig.,13, the brake is symmetrical, and
operates in the same manner on forward andre
70
verse motion.
_
,
`
In the embodiment illustrated in Fig. 14, the
same elements are found as in that- of Fig. 13;
-that is, the brake comprises \four symmetrical
brake shoes; but the levers 96, 91, 98 and |48,
75 instead of having a common axis of rotation on
said second ñxed pivot pin, means for4 creating
frictional contact between ~said levers, and linkage
means connecting said levers to said brake shoes. 70
3. In a >braking device, a brake drum, a, plural
ity of brake shoes adapted to contact with said .
brakegdrum, linkage means interconnecting ad
jacent brake shoes for forming a chain terminat
ing in two end brake slices. a first ñxedpivot
7 ,
2,131,369 _
pin, linkage means connecting one end brake
shoe to said fixed pivot pin, pressure applying
means for thrusting the other end brake shoeto
wards said brake drum. in a given iixed direction,
‘in ' means adapted to oppose said pressure applying
means and to exertïa pull on said second end
brake shoe, a second ñxed pivot pin, a plurality
of levers freely and rotatably mounted .on said
second fixed pivot pin, means for creating frlc- ‘
'i0 tional contact between said levers and linkage
means interconnecting said levers with said brake
towards said brake
another brake shoe ar- Y
ranged between said iirst ñxed pivo't pin and said ì
pressure applying means and adapted to receive ’
a thrust from said- pressure applying means, >a. 'Y
second ñxed pivot pin, a. plurality of levers freely
and‘ rotatably mounted on said second ñxed pivot
pin, ’means for maintaining frictional resistance
between said levers, linkage means interconnect- l
-ing said levers with said brake shoes and elastic
meansadapted to oppose said pressure applying
means.
-
8. In a brakin'g device, a brake drum, two brake
shoes adapted to contact with said brake drum,
shoes adapted to contact with said brake drum, linkage means interconnecting the- ñrst of- said
l5 linkage means interconnecting said brake shoes, ' brake shoes with thevsecond, a ñrst ñxed pivot
a freely rotatable articulation connecting said pin, linkage means interconnecting said second
linkage means to one of >said brake shoes, an brake shoe with said ñrst ñxed pivot pin, a third
shoes.
4. In a braking device, a brake drum, two brake
articulation producing frictional resistance con
necting said linkage means and the second brake
l shoe, a ñxed support, a second linkage means, an
articulation producing frictional resistance con
necting said second linkage means to said second
brake shoe,-a free articulation ~connecting said
second linkage. means and said ñxed support, a
fixed pivot pin, a plurality of levers freely -and
rotatably- mounted on said iixed pivot pin, means
for maintaining frictional contact between said
levers, two linkage means interconnecting said
levers with said brake shoes, means for thrusting
one of said brake shoes towards said brake drum,
and elastic means adapted to oppose said thrust
ingmeans.
_
.
5. In a braking device, a brake drum, a plu-„
rality of brake shoes adapted to contact with said
.35 brake drum, a plurality of linkage means inter
'
`>connecting adjacent brake shoes, a first iixed f
pivot pin, linkage means interconnecting one end
_brake shoe with said first ñxed pivot pin, .pres
sure applying means for thrusting the _other- end
40 brake shoe towards vsaid brake drum, a second
ñxed pivot pin, a plurality of levers freely and
rotatably mounted on said second fixed pivot
l pin, means for maintaining frictional resistance
between said levers, linkage means interconnect
45 ing said- levers with -said brake shoes,- a spring
member adapted -to oppose said pressure applying
means, said spring member being attached tothe ~
lever linked with .said end brake shoe subjected
to the thrust of said pressure applying means.
50
6. In a braking device, a brake drum, two brake
shoes adapted to contact with said brake drum,"
linkage means interconnecting said brake shoes, a
free articulation connecting said linkage means
with one of said hi‘ake'shoes, an articulation _with
friction connecting said linkage means with said
second brake shoe, a _ñxed support, a second link
` age means, an varticulation with friction connect
brake shoe, means for connecting said third' brake
shoe with said iirst fixed pivot pin, pressure ap
plying means mounted on said third brake shòe
and adapted to exert a thrust on said lirst brake
shoe, a second fixed pivot pin, a plurality of le
vers freely and rotatably mounted on> said Vsecondl ñxed pivot pin, means for maintaining frictional
resistance between said levers, linkage means in-l
terconnecting said levers with said brake shoes,
and elastic means adapted to oppose said pres
sure applying means.
_
v
9. .Ina braking device, a brake drum', two brake.'
-shoes adapted to contact with saidv brake, drum,
linkage means interconnecting the ñrstlof said
brake shoes with the second, a first ñxedpivot
pin, linkage means interconnecting said second
brake shoewith said iirst ñxed pivot pin, a third
brake shoe, means for interconnecting >said third
4brake shoe withl said first ñxed pivot‘pin, pres
sure applying means supported by said third
brake shoe and adapted to exert a. thrust on said
flrst brake shoe, >a second ñxed pivot. pin, a plu
rality of levers freely and rotatably mounted on 40
said second pivot pin, means for maintaining fric
tional resistance vbetween said levers, linkage
‘means interconnecting said levers with said brake
' shoes, and a` spring attached to the lever linked
with said ,ñrst brake shoe.
'
10. In a braking device, a brake drum, two'.
brake shoes adapted to contact with said brake '
drum, linkage means interconnectingv said brake
shoes, a free articulation connecting said linkage
means to the first of said- brake shoes, an articu
lation with frictionconnecting said linkage means
to the second of said brake shoes, a fixed support,
a second linkage means, an articulation with> fric
tion connecting said second linkage means to said
second brake shoe, a_ free articulation connecting
said second linkage means to said iixed support, a
third brake shoe, a third linkage means, a free ar
ticulation connecting said third linkage means to
ing said second linkage means with said second said, fixed support, an articulation with friction
brake shoe,v a free articulation .connecting said, connecting said> third linkage means to said third
60 second linkage means to said fixedA support, a brake shoe, pressure applying means Supported by
ñxed pivot pin, a plurality of levers freely and ro
tatably mounted on said ñxed -pivot pin, means
for maintaining frictional resistance between said
levers, two linkage means interconnecting said
65 levers with said brake shoes, means for thrusting
oneof said brake shoes towards said brake drum,
and a spring> attached to the lever linked >with
said ñrst brake shoe.
y
i -7. In a braking device, a brake drum, a ñrst
fixed pivot pin',- a plurality of brake shoes ar
ranged in sequence and adapted to contact with
said brake drum, linkage means interconnecting
' adjacent brake shoes and connecting said brake
\shoes with'said iirstñxed pivot pin, pressure ap
75 Lplying means for thrusting the end brake shoe
. said third brake shoe and adapted to exert a
thrust on said _ñrst brake shoe, a ñxed pivot pin, ,
a plurality of levers freely and rotatably mounted
on said fixed pivot pin, means for maintaining
frictlonal resistance between said levers, linkage
mea-ns interconnecting said levers with said. brake
shoes, and elastic means adapted tcl oppose _said~
pressure applying means.
~ -
11. In a braking device, a brake drum, two 70
brake shoes adapted to contact with said brake
drum, linkage vmeans interconnecting said brake '_
shoes, a free articulation connecting said link-
age means to the iirst of said vbrake shoes, anar
- ’
ticulation with friction connecting said linkage 75
2,1s1,se9
,
.
means to the second of said brake shoes, a fixed
support, a second linkage means, an articulation
for maintaining frictional resistance between
with friction connecting> said second linkage
said levers with said brake shoes.
means to said second brake shoe, a free articula
tion connecting said second linkage means to said
fixed support, a third brake: shoe, a third linkage
- means, a free articulation >connecting said third '
linkage means to said fixed support, an articula
said levers, and linkage means interconnecting
14. In a braking device, a brake drum, tw .
brake shoes adapted to contact with said brake
drum, linkage means interconnecting said ñrst
and second brake shoes, va vfirst fixed pivot pin,
linkage means interconnecting said second brake
tion with friction connecting said third linkage
shoe with said ñxed pivot pin, a third brake »
means to said third brake shoe, pressure applying
shoe, means for connecting said third brake shoe
to said iixed pivot pin, expanding means sup
ported by one of said brakeshoes and co-acting
with an adjacent brake shoe, said expanding
means supported by said third brake shoe and
adapted to exert a thrust upon said first brake
shoe, a fixed pivot pin, a plurality of levers freely
and rotatably mounted on said fixed-pivot pin,
15 means for maintainingfrictional resistance be
tween said levers, linkage means interconnecting
means comprising a lever pivoted on said sup
porting brake shoe, a spring inserted between 15
said supporting brake shoe and said lever, a
flexible traction cable attached to said lever, a
tached to the lever linked with the flrst brake- ñexible guiding sheath for said cable, said sheath
shoev
~
being anchored to said‘supporting brake shoe, a
n
12. >In a braking device, a brake drum, a plu-` second ñxed pivot pin, a plurality of levers freely l20
l rality of brake shoes adapted to' contact with> and rotatably mounted on said second fixed pivot
said brakey drum, expanding means supported pin,- means for .maintaining frictional _resistance
by one of said brake shoes and co-acting with an between said levers, linkage means interconnect
adjacent'brak'e shoe, said expanding means com
ing said levers with said brake shoes, and elastic
2.5 prising a lever pivoted on said supporting brake means adapted to oppose said expanding means. '25
shoe, a spring inserted between said brake shoe
15. In'a brakingdevice, a brake drum, two
and said lever, a ñexible traction cable attached brake shoes adapted to ‘contact with said brake
to“ said lever, and a flexible guiding sheath for - drum, linkage means interconnecting said brake
said cable, said guiding sheath being anchored shoes, a free articulation connecting. said linkage
30 to said supporting brake shoe, elastic means means to the ñrst of said brake shoes, an articu 30
adapted to oppose said expanding means and to lation with friction r‘connecting 'said linkage
draw vsaid brake shoes back to their positions of means to said second brake shoe, a fixed support,
rest, a fixed pivot pin, a plurality of levers freely va second linkage means,. an articulation with
and rotatably mounted on said fixed pivot pin, ‘ friction connecting said second» linkage means to
said second brake shoe, a free articulation con
35 means for maintaining frictional resistance be
tween said levers, and linkage means intercon
necting saidv second linkage means to said fixed as
\ ’
. necting said levers and said brake shoes.
support, a third brakel shoe, “' a third linkage
13. In a braking device, a brake drum, a plu
means, a free articulation connecting said third
rality of brake shoes a'dapted to _contact with linkage means to said fixed support, and articu
said brake drum, expanding means supported by lation with friction connecting said third linkage 40
one of said brake shoes and co-acting with an means to said third brake shoe, expanding means
adjacent brake shoe, vsaid expanding means com
supported by one brake shoe and >co-acting with
prising a’lever pivoted on¢said supporting brake an adjacent brake shoe, said expanding means
shoe,- a spring inserted between said ¿supporting comprising a lever pivoted on the supporting
brake shoe and said lever, a flexible traction brake shoe, a spring inserted between said sup
cable attached to said lever, a flexible guiding porting brake shoe and said lever, a flexible trac 45
" sheath for said cable, said sheath being anchored tion cable attached to said lever, a flexible guid
to said supporting brake shoe, elastic means ing sheath for said cable, said sheath being an?
adapted to oppose said expanding means„and to ` chored to said supporting brake shoe, a ñxed
5o draw said brake shoes back into a position of pivot pin, a plurality of levers freely and rotat
rest, linkage means interconnecting acüacent ably mounted‘on said fixed pivot pin, means for`
brake shoes, a first fixed pivot pin, linkage means ` maintaining frictional resistance between said
interconnecting one of the end brake shoes with levers, linkage means interconnecting said levers
said first ñxed pivot, pin, a second fixed pivot with said brake shoes, and elastic means adapted y
55 pin, a plurality of levers freely and rotatably ` to ~oppose said expanding' means.
A55
_mounted on said secônd ñxed pivot pin, means
LoUIs CHARLES BRISSON. \
said levers with said brake shoes, and a spring at
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