Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to electric brake mechanisms
for wheeled vehicles and to control systems therefore~
An object of the present invention is to provide an
electric brake structure capable of applying significantly
S increased braking forces at a vehicle braked wheel as -
compared with typical prior art brakes of similar type without
substantial increase in the overall brake size.
Another object of the invention is to provide a brake mech-
anism in which undesirable bending forces on the brake -
actuator, the brake shoes and/or the brake shoe anchor pin
are reduced, and in which the operating life-time of the
brake mechanism is thereby increased.
A further object of the present invention is to provide a
brake control system which controls braking forces by a
pair of brake actuators separately from but in controlled
relation to each other.
A more specific object of thc invention is to provide
a brake control circuit for applying brakes at a second
of a pair of electrically operated brake actuators in a
composite or double-actuator wheel brake in controlled
relation to operator-controlled braking at the first
electrically-operated brake actuator.
The invention, together with additional objects, features
and advantages thereof, will be best understood from the
following description, the appended claims and the accom-
panying drawings in which:
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FIG. 1 is an elevational view of a presently preferred
: embodiment of the electric brake provided by the present
invention;
FIGS. 2-4 are sectional views respectively taken along
the lines 2-2, 3-3 and 4-4 in FIG. l; and
FIG. 5 is a schematic diagram of a presently preferred
embodiment of the brake control system in accordance with
the invention.
Referring to FIGS. 1-4, a presently preferred embodiment
10 of the electric brake provided by the present invention
includes a backing plate 12 having a central opening 14 for
locating plate 12 on a vehicle axial or spindle (not shown)
` for fixed attachment thereto as by we.lding, brake 10 being
thereby mounted in fixed relation to the associated vehicle.
An anchor pin 16 is carried by backing plate 12 and includes
a rolled or peened head portion 18 (FIG. 3) and an anchor
portion 20 connected by a shank portion 22 of lesser diameter
and embracing therebetween backing plate 12 and a bracket
24 welded to the backing plate for angularly locating the
brake mechanism with respect to the vehicle axle. A
primary brake shoe assembly 26 and a secondary brake shoe
assembly 28 (FIG. 1) are carried by plate 12 substantially
coaxially with the axis of rotation of an associated wheel,
and are connected to each other by the usual adjustment
link 30 and a coil spring 32 parallel thereto. A second
coil spring 34 is connected between the upper portion of
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shoe assemblies 26,28 and biases the opposing yoke portions
36,38 of the respective shoes against the anchor por~ion 20
of anchor pin 16, thereby cooperating with spring 32 to retain
the shoes in the normally disengaged position with respect to an
associated surrounding brake drum, the drum being of conven~
tional and well known construction and therefore the same
not being shown.
Primary shoe assembly 26 comprises a shoe member 40
(FIGS. 1 and 4) which includes the usual arcuate platform 42
having a brake lining 44 bonded thereto and a pair of stiffening
webs 46,48 (FIG. 4) extending radially inwardly therefrom on
either side of backing plate 12 to help maintain platform
44 perpendicular to the backing plate during brake operation.
A stiffening element 50 (FIGS. 1 and 3) is welded to the
upper portion of web 46 and cooperates with the web to form
yoke 36 for embracing anchor pin 16. A cam element 52 is
welded to stiffening element 50 and includes a flat
tangentially-directed surface 53 disposed at an angle of
about 30 with respect to the vertical axis passing through
the center of anchor pin 16 and backing plate opening 14 as
best seen in FIG. 1. With the exception of cam element 52
which i~ not included on secondary brake shoe assembly 28 the
latter is a substantial mirror image of shoe assembly 26 and
has the elements thereof indicated in FIG. 1 by similar
reference numerals followed by the suffix "a".
An arcuate actuator arm 54 is mounted at one end 56 to
pivot about a second shank portion 58 on anchor pin 16
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extending axially outwardly from anchor portion 20 (FIG. 3)
and is captured thereon by a retaining ring 60 received in
a corresponding groove 62 on pin shank portion 58. End 56
of actuator arm 54 includes a tangentially extending nose
5 64 which terminates in a parabolic camming surface 66.
2~ose 64 cooperates with follower surface 5,3 on cam elemen~ 52
to move primary brake shoe assembly 26 radially outwardly
into engagement with a corresponding braking surface on a
brake drum (not shown) upon pivotal movement of actuator
arm 54 about the axis of anchor pin 16 in the counter-
clockwise direction as viewed in FIG. 1. The cooperative
combination of a parabolic surface 66 on the actuator arm
and a straight or flat follower surface 53 on the brake shoe
operate to move.the brake shoe outwardly in a linear direction
rather than in an arcuate direction as in the usual prior
art arrangements; thereby resulting in a more efficient
transfer of braking forces to the brake drums.
A pair of electromagnets or brake "pucks" 70,72 are
carried at an end of actuator arm 54 remote from pin 16 and
are mounted at substantially equal radii with respect to ::
the axis of pin 16 but at differing radii with respect to
the axis 74 (FIG. 1) of backing plate 12, puck 72 being
disposed radially outwardly of puck 70 with respect to axis
74. Referring to FIG. 2, puck 70 is mounted adjacent ~he
free end 75 of arm 54 and includes a frustoconical body ;
portion 76 which is loosely mounted for axial movement on
the shank 78 of a rivet 80 affixed to actuator arm 54 and
is biased outwardly with respect to the actuator arm by a
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coil spring 82. An integral ear 84 extends radially from
puck body 76 to loosely embrace the shank 86 of a rivet
88 affixed to actuator arm 54 and is captured thereon by a
retaining ring 90, thereby retaining puck body 76 on rivet
shank 78 against the outward force of spring 82 and preventing
rotation of the puck on pin 7~. Puck 72 is mounted to
actuator arm 46 inwardly of end 75 in similar fashion, the
elements thereof being indicated in FIG. 2 by identical
; reference numeral followed by the suffix "a". Single-puck
electric brakes of the general type illustrated in FIGS. 1-4
as well as details of puck construction are discussed in
~; _.ail in the U.S. patent of Brede et al 3,244,259. Pucks
70,72 have conductors 92,94 éxtending separately therefrom
along actuator arm 54 and are fed through a grommet or the
like 96 carried by backing plate 12 for connection to suit-
able control means later to be described. Conductors 92,94
are fastened to arm 54 by suitable retaining clips 98 (FIG. 1).
` As is conventional and well known, an electrical
braking signal to either or both of the electromagnetic pucks
70,72 will attract such puck or pucks to an armature plate
100 (FIG. 2) rotatably coupled to the vehicle wheel. When
the wheel and armature plate are rotating counter-clockwise
with respect to the braking mechanism as viewed in FIG; l,
attraction of pucks 70,72 into frictional sliding engagemcnt
with the armature plate causesactuator arm 54 to pivot about
the axis of pin 16 in the counter-clockwise direction,
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thereby camming primary brake shoe assembly 26 into en-
gagement with the corresponding braking surface on the
surrounding brake drum. Reactive braking forces on shoe
assembly 26 are transferred by line 30 to shoe assembly
2~ such that the latter also engages the drum braking
surface. The total brake reaction force is transferred
to the vehicle frame through yoke 38, anchor pin 16 and
backing plate 12 in the usual fashion.
The brake mechanism 10 lllustrated in the drawings
is specifically adapted for use in applying braking forces
at a wheel carried on the left side of a recreational
trailer, mobile home or the like. During forward motion
of the trailer, wheels on the left side thereof are rotating
counter-clockwise as viewed away from the trailer such that
braking forces may be applied at the wheels in the manner
above-described. A brake mechanism for a right hand trailer
wheel will, of course, be a mirror image of that illustrated
in the drawings.
An embodiment of the brake control system provided by the in-
vention is illustrated in FIG. 5 and comprises a vehicle
operator-responsive brake controller 102 connected in series
with the coil 70a of first or primary brake puck 70 between ~,
a vehicle battery 104 and electrical ground. I~hen the,present
invention is utilized to control braking forces on a trailer
having at least one and preferably a plurality of braked
wheel, i.e., wheels which includes means such as brake mechan;sm
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10 capable of applying braking forces, controller 10 may be
of the type shown in the U.S. patents of Hubbard 3,371,235
or VandenBroek 3,503,652, the latter of which is responsive
both to direct actuation by a tractor vehicle operator through
a control arm or the lilce and to indirect operator actuation
through the tractor brake system. A relay 106 is connected
to control the braking signal to the coil 72a of secondary
brake puck 72 and comprises a relay coil 108 connected in
parallel with brake coil 70a and a normally-open relay
switch 110 connected in series with coil 72a between battery
104 and ground.
Thus, the brakecontrol signal fed to a secondary coil
72a is a function of the braking signal from controller 102
to primary coil 70a. More specifically, when the braking
signal to coil 72a reaches a first preselected threshold
such as nine volts, for example, relay coil 108 is energized
and switch 110 is closed to apply battery voltage directly
to secondary coil 72a. Thereafter, braking forces due
to secondary puck 72 are applied at a maximum level while
braking forces are due to primary puck 70 remain responsive
to operator control. Preferably, coil 108 exhibits a
hysteresis characteristic such that the relay coil will not
be de-energized and switch 110 will not reopen until the
control signal to primary brake coil 70a drops below a
second threshold level, for example three volts, which is
well below the first threshold level. This feature has been
found to yield enhanced brake control over a wide range of
braking conditions.
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It will be evident that the total braking force avail-
able at shoe assemblies 26,28 due to attractive forces between
pucks 70,72 and armature plate 100 is significantly greater
than the braking forces made available through either puclc
considered alone. It will also be appreciated from the fore-
going description that the effective frictionally developed
motive force generated at secondary puck 72 is greater than
that for primary puck 70. More specifically, the angular
velocity of the armature plate 100 at the radius of puck
72 from axis 74 (FIG. 1) is greater than that at the radius
of puck 70 while the pivotal radii of the pucks from the axis
of pin 16 are substantially identical. Hence, the brake
shoes will be moved into engagement with the brake drum
with greater force for a given current through secondary
puck coil 72a than for the same current to primary coil 70a.
This feature has been found empirically to yield enhanced
brake control throughout the intermediate bral<ing range
when both brake pucks are engaged.
Yet another advantage of the embodiment thus far des-
cribed lies in the pivotal mounting of actuator arm 54 on
the pin 16 which simultaneously serves as anchor for the brake
shoes rather than on a separate pivot pin disposed therebelow
as in the prior art. The mechanical advantage provided by
the embodiment shown to scale in the drawings, i.e., the
ratio of the puck pivotal radii to the distance between the
point of engagement of surfaces 53,66 (FIG. 1) and the pin
axis, is about 14:1 and may be compared with an 8:1 mechanical
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advantage of conventional prior art arrangement of which the
above-noted Brede et al patent is typical. I~ will also be
appreciated with the reference to FIG. 3 that the actuator
arm 54 is mounted to pivot about pin 16 axially adjacent
the anchor portion 20, such that bending stresses on the
anchor pin caused by opposite radial forces applied thereto
by the actuator arm and by the yoke 38 of secondary brake
shoe assembly 28 (FIG. 1) are minimized.
The brake mechanism 10 illustrated in the drawings is -
specifically adapted for use in applying braking forces at
a wheel carried on the left side of a recreational trailer,
mobile home or the like. During forward motion of the
trailer, wheels on the left side thereof are rotating counter-
clockwise as viewed away from the trailer such that braking
forces may be applied at the wheels in the manner above-
described. A brake mechanism for a right-hand trailer
wheels will, of course, be a mirror image of that illustrated
in the drawings.
Although the invention has been described in connection
with a specific embodiment thereof, many alternatives, modi-
fications and variations are contemplated. For example, when
a vehicle includes a number of braked wheels each having -
first and second brake actuators as in the preferred
application of the invention to~trailers having multiple
braked wheels as described above, the various first actuators
or pucks may be connected in parallel with coil 70a in FIG. 5
and the various second actuators may be connected in parallel
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with coil 72a. Moreover, the control features of the present
invention illustrated in FIG. 5 are potentially useful in
their broader aspects in successively applying braking
forces at separate first and second braked wheels each
having one or more associated brake actuators. It will also -
be appreciated that the control aspects of the invention are
equally applicable to other types of electrically-operated
brakes, such as electropneumatic or electrohydraulic brakes, ;
wl7erein coils 70a,72a (FIG. 5) would be disposed in suitable
metering valves. Similarly the eiectromagnetic relay 106
illustrated in FIG. 5 could readily be replaced by a
suitable equivalent solid-state relay. Indeed the invention
is intended to embrace the above-noted and all other
alternatives, modifications and variations as fall within
the spirit and broad scope of the appended claims.
This application is a divisional application from
our earlier applicatlon serial No. 291,720 filed on
Novembe~ 24, 1977.
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