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Патент USA US3043413

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July 10, 1962
0. K. KELLEY
3,043,403
BRAKE MECHANISM
Filed Oct. 10. 1958
2 Sheets-Sheet l
IN VENTOR.
#770,057
July 10, 1962
3,043,403
0. K. KELLEY
BRAKE MECHANISM
Filed Oct. 10. 1958
'
BY
INVENTOR.
69.47%’! Z/fé/éy
477004;)’
'
f it
3,043,403
VPatented July 10, 1362
2
1
tooth 2d which interengages with teeth 21 on the locking
3,043,403
BRAKE MECHANISM
Oliver K. Kelley, Bloom?eld Hills, Mich, assignor to
General Motors Corporation, Detroit, Micln, a corpo
ration of Delaware
Filed Oct. 10, 1958, Ser. No. 766,543
12 Claims. (Cl. 138-69)
gear 12.
Pivotal movement of the pawl 14 is generated by an
actuator, shown generally at 22, which has , journaled
thereon, a pair of cam rollers 24 and 26 in rolling contact
with each other. Cam roller 26 travels along a support
ing abutment 28 provided along the transmission casing
16 while the roller 24 is engageable with a cam follower
surface 30 on the pawl 14. Hence, when the actuator 22
This invention relates generally to brake mechanisms
and particularly to improvements in parking brake mech 10 is moved to the right and to the restraining position de
picted, the pawl 14 will be moved to the engaged position
anisms for motor vehicles.
Whenever a positive brake is employed, such as the kind
with interengaging teeth, there is always the problem of
disengagement under load, especially when the inferen
in which the upper roller 24 bears against a substantially
?at portion 32 of the cam follower surface 30. This flat
portion 32 is substantially perpendicular to the radial line
gaged teeth 'are designed so as to tend not to separate 15 from the rotational axis of shaft 10 through the rotation
al axes of the rollers 24 and 2.6 so that there is no com
under load. A speci?c example of the problem occurs
with the positive type parking brake mechanism com
monly employed in automatic transmissions for motor
vehicles. When the vehicle is stationed ‘on a hill, the
transmission parking ‘brake is loaded so that the forces re
ponent of force from the pawl tending to move the rollers
out of the restraining position and the pawl 14 is posi
tively prevented from disengaging movement. Addition
ally, with this arrangement there is no force on the roller
axes. When the actuator 22 is shifted to the left from
sisting disengagement are so great that they interfere with
the restraining position, a spring 33 becomes effective to
easy disengagement. Consequently, to design for this
pull the pawl 14 downwardly until the tooth 20 disen
extreme condition, leverages must {be increased through
gages from the mating teeth 21 on the locking gear 12.
the agency of links and levers and dimensional tolerances
The actuator 22 at the left end, as viewed in FIGURE
must be carefully maintained to insure that the parking 25
1, carries therewith a pin 34 which at the upper part
brake can always be easily disengaged. With critical tol
slidably receives a shiftable rod 35. Shiftable rod 35,
erances and the need for maximum leverages, of course,
somewhat intermediate the ends thereof, is provided with
the cost per unit is increased. '
a shoulder 36 against which abuts an end of a spring 38
Accordingly, the invention contemplates a brake mecha
nism wherein any load thereon may be removed to facili 30 surrounding the rod 35. The opposite end of the spring
38 is in engagement with the pin 34. Preferably, spring
tate easy disengagement.
33 is preloaded and will urge the rod 35 to the position
Speci?cally, the invention affords the foregoing brake
demonstrated which is the limit of its leftward movement
mechanism with an auxiliary arrangement for relieving
the load on an actuator for the brake mechanism so that
permitted by a retainer 40 secured to the end of the rod
the actuator may be easily operated in producing a dis 35 35. The end of the rod 35 opposite the end with the
retainer 40 is pinned at 42 to the end of a cable 44 which
engagement of the brake mechanism.
is then joined to an appropriate driver operated control,
More speci?cally, the invention seeks to provide a ve
i101’, shown, e.g., the conventional transmission‘ selector
hicle transmission parking brake mechanism which in
cludes an expansible chamber motor and a control valve
mechanism therefor, the latter being in communication
with the fluid pressure. system for the vehicle wheel
ever.
When the transmission selector lever is moved to a
specific setting, e.g., the Park position, the movement
thereof is transferred through cable 44 to the shiftable
rod '35, and then by spring 38 to the pin 34 ‘and to the
brakes. After an actuator ‘for the brake mechanism is
moved to a restraining position, holding the brake en
actuator 22. If the tooth 20 on the pawl 14 and the
gaged, the control valve mechanism will cause, when the
wheel brakes are operated, fluid pressure from the wheel 45 teeth 21 on the locking gear 12 are misaligned so that
they cannot mesh the spring 38 will be compressed as the
brake system to be delivered to the expansible chamber
selector lever is moved to the Park position, although the
motor and relieve the actuator of the load thereon so as
actuator 22 is prevented from further movement. Then,
to enable easy removal of the actuator from the re
straining position.
as soon as the output shaft ltl is revolved to facilitate
The foregoing ‘md other objects and advantages of 50 engagement of the pawl tooth 20 and the locking gear
teeth 21, the spring 38 will force the actuator 22 to the
the invention will be apparent from the following descrip
FIGURE ‘1 restraining position. To disengage the pawl
tion and the accompanying drawings, in which:
14, the selector lever is removed from the Park iposition
FIGURE 1 is a sectional view through a portion of a
whereupon, through cable 44, rod 35, and retainer 40, a
transmission showing a parking brake mechanism incor
positive pull is exerted through the pin 34 on the actuator
porating the principles of the invention; and
FIGURE 2 is a schematic illustration of a ?uid con
trol system for operating a servo motor which aids in dis
engaging the parking brake mechanism.
Referring ?rst to FIGURE 1, the numeral 10 denotes
a'transmission output shaft which may be drive con
nected to the vehicle wheels in a well known manner.
22 which will shift it to the left and permit the spring 33
to urge the pawl 14 from the engaged position.
Because of certain extreme conditions, for instance,
when the vehicle is parked on an incline, a very substan
tial load may be exerted on the cam rollers 24 and 26
such that it is difficult to move the actuator 22 to the left
Attached to the output shaft lit is a locking gear 12, the
and from the restraining position. Since a cable is pref
rotation of which is prevented by a locking element, such
as the pawl viewed generally ‘at 14. Pawl 14 is pivoted
erably utilized for cost and simplicity purposes, there can
be very little leverage afforded which may be inadequate.
to the transmission casing 16 at 18 and is formed with a . 65 Consequently, the effort needed to .be exerted by the
3,043,403
3.
4
driver on the selector lever ‘to effect a disengagement may
To engage the pawl 14, the transfer lever 126 is re
be considerable or possibly the required effort may be
more than the driver is capable of render-ing. For this
reason auxiliary provision is made in the form of an ex
pansible chamber motor, .e.g., the servo motor denoted 5
generally at 46.
Servo motor 46 is attached to the trans
mission casing 16 in the vicinity of the pawl 14, as seen
in FIGURE 1, and is utilized to relieve this load and per
mit easy movement of the actuator 22 to the left from
the restraining position.
As best shown-by FIGURE _2,..the servo motor ~26 in
.
volved counterclockwise, as depicted in FIGURE 2, by
maneuvering the cable 44 and the follower device 114
will be shifted to the solid line setting in which the supply
and exhaust valve rods 78 and 96 assume the viewed
positions due to the engagement of the device holder 124
with lever 126. Then, when the brake pedal 60 is de
pressed, ?uid pressure will be transferred by branch con
duit 64 through side opening 74 and center ‘opening 72
in the cup-shaped sleeve 70 t0 the chamber 102.
Since
the exhaust valve rod 96 is in the closed position, the ?uid 7
cludes a cylinder 48 slidably housing a plunger 56 which
is biased by spring 52 intorcontinuous engagement with
pressure in the chamber 192 will be delivered by the con-1
duit 112 to the servo motor 46. This ?uid pressure will
an extension 54 on the pawl 14. The spring 52 exerts
force the plunger 50 upwardly, and accordingly, pivot the
less bias than the spring 33, and therefore, does not inter 15 pawl 14 su?iciently to relieve the load on therollers 24
fere with the disengaging function of the spring 33.
and 26 and permit the actuator 22 to be easily removed
Fluid pressure for operating the servo motor 46 is de
from the FIGURE 1 restraining position.
rived from the vehicle wheel brake system which is desig
As the cable 44 is pulled to remove the actuator 22 .
nated generally at 56 in FIGURE 2. The brake system
from the FIGURE 1 position, the transfer lever 126 will
56 is of the customary type employing a master cylinder 20 now be rotated clockwise whereupon a spring 132 be
58 which, when a brake pedal 60' is depressed, transfers
comes eifective to shift the follower device 114 to the left
?uid'pressure via a delivery conduit 6-2 to the mecha
nisms for engaging the wheel brakes.
and move the supply and exhaust valve rods 78 and 96 to
their respective dotted line positions.‘ The supply valve
In communication with theconduit 62’is a branch con
rod. 78, therefore, will be in the center opening 72 and
duit 64 extending to a control valve mechanism 66, which 25 cutting off communication between the chamber 102 and
constitutes a part of the auxiliary part and which com
the branch conduit 64. Exhaust valve rod 96 will be
prises a valve body 68 formed with a multi-stepped con
removed fromthe center opening 92, and consequently,
tinuous bore extending therethrough, the right end of
the chamber 102 and supply line 112'to the servo motor
which receives a cup-shaped sleeve 71D. Sleeve 70 has a
46 willbe drained through side opening 90 and return the
center opening 72 and a side opening 74 aligned with a
port connected with the branch conduit 64. Housed in
side the cup-shaped sleeve 70 is a tubular guide 76 ar
ranged to slidably receive a supply valve rod 78. Situated
so as to be axially aligned with the center opening 72 in
conduit 91 to the reservoir for the master cylinder 58;
To summarize the sequence of operation, consider ?rst
the events when the pawl 14 is engaged by moving the
the sleeve '70 are a pair of wiper seals 80 and 82 held -
apart by spring 84 and so positioned as to allow the sup
ply valve rod ‘78 to pass therethrough. The spring 84 ad-.
ditionally urges the tubular guide 76 against a snap ring
selector lever to the Park setting as has been described.
In so doing, the servomotor 46 is prepared for operation,
this being due to the actuation of the control valve mech
anism 66 through the agency of the follower device 114,
which has an operative connection with and is moved
by the transfer lever 126 in opposition to the bias from
spring 132 when the cable 44 is maneuvered by the selec
tor lever. This actuation of the control valve mechanism
66 causes the exhaust valve rod 96 to be in the closed
86 supported in the sleeve 70.
Mounted in the left side of the bore in thevalve body
68 and similar tothe cup-shaped sleeve 'itlis another cup
shaped sleeve 88.also provided with a side opening at 91}
position and the supply valve rod 78 the open position
in communicationwith a return conduit 91 extending to
so that communication ‘between the vehicle brake system
thereservoir for the master cylinder 58 and a center open
56 and the servomotor 46 is permitted.
ing 92. A tubular guide 94 slidably receives an ex 45
Now when the operator wishes to removethe selector
lever from the Park setting and disengage the pawl 14, his
haust valve rod 96 and axially aligns the valve rod% with
the center opening 92 in the sleeve88. A wiper seal 98 is
?rst act is to depress the brake pedal 60. Because of the
held in place on the exhaust valve rod 96 and against the
prior preparation of the servomotor 46-, pressure ?uid
inside end of the tubular guide 94 by a spring 100. Spring
from the system 56 will cause pressure ?uid actuation of
106 also holds the guide 94 against a snap ring 101 re 50 the pawl 14 upwardly as viewed in FIGURE 1 and
tained by the sleeve 88.
i
thereby permit easy effortless movement of the actuator
A chamber 162 is provided between the two sleeves’ 7t!
22 to pawl disengaged position by cable 44. As the cable
and 88 in which is situated a spring 104, which both holds
44 is so moved, the transfer lever 126 is revolved clock
a wiper seal 106 in position in the inside end of sleeve
wise thereby from- the FIGURE 2 position and this en
88 and urges the sleeves 70 ‘and 88, respectively, against 55 ables the spring 132, due to the removal of the compres
snap rings ‘108 and 110. Chamber 102 communicates
sive force’ exerted by lever 126, to return the follower
with a supply conduit 112 extending to the servo motor
device 114 to the'dotted line FIGURE 2 position inwhich
the supply valve rod 78 interrupts communication be
Opening and closing movements of the supply and ex
tween the servomotor 46 and the vehicle brake system 56,
haust valve rods 78 and 96 is coordinated through a fol 60 and the exhaust valve rod 96 permits the servomotor 46
lower device indicated generally at 114, which is provided
to be relieved of pressure ?uid. The relief of servomotor
with an elongated rod 116 in parallel alignment with the
46 allows the vspring 33 to withdraw the pawl 14 from
axis of. the bore in the valve body 68. An arm 118 at
engagement with the locking gear 12. '
one end is attached to the right side of the rod 116 while
From the foregoing, it can be seen that with the park
the other end of the arm 118 is af?xed to a holder 120 >
ing brake engaged the driver may depress the brake pedal
which, inturn, is joined to and supports the supply valve
60 which will relieve the actuator 22 of any excessive
rod 78. Secured to the left side of the rod 116 is an
arm 122, similar to arm 118, and like the arm 118 is
joined to a holder 124 which ?xedly supports the ex
haust valve rod 96. The follower device 114 is shifted
back and forth by a transfer vlever 126 or the equivalent,
loads which the driver would otherwise be required to
overcome. Therefore, a simple cable can be used to re
move theactuator 22 from the restraining position with
a minimum of effort. Consequently,.there is considera
ble savings from the omission of the multiple links and
pivoted {at 128 which preferably moves with‘ the trans
mission selector lever. This may be accomplished by
attaching to the medial portion of lever 126 a stud 130
and securing the cable 44 to this stud 130. ,
levers normally needed, and furthermore, manufacturing
tolerances have little in?uence on‘ the operation of the
75
parking brake.
'
A
3,043,403
The ‘invention is to be limited only by the‘followin'g
claims.
' “What is claimed is:
1. 1In a brake mechanism, the combination of a rotat
able locking member, a locking element movable to and
from an engaged position relative to the locking member,
the locking element being adapted in the engaged position
to prevent rotation of the locking member, actuator
means for moving the locking element to the engaged po
sition and operative in a restraining position thereof to
maintain the locking element in the engaged position and
thereby resist a disengaging force urging the locking ele
6
the‘ locking element so ‘as to relieve the manually con
trolled means of the load from the disengaging forces
acting on the locking element thereby freeing the manu
ally controlled means vfor removal from the restraining
position and control valve mechanism interposed be
tween the ?uid pressure system and the motor, the con
trol valve mechanism being operatively connected to
the manually controlled means and so arranged as‘ to
connect the expansible chamber motor to the wheel brake
?uid pressure system when the manually controlled means
is in the restraining position thereby rendering the ex
pansible chamber motor effective when the wheel brakes
are operated.
5. In a parking brake mechanism, for a vehicle hav
and from the restraining position, and auxiliary means co 15 ing wheel brakes of a character that are operated by a
?uid pressure system, the combination of a rotatable
acting with the locking element to cause the locking ele
member drive connected to the vehicle wheels, a toothed
ment to be maneuvered so as to tend to urge the locking
locking member connected to the rotatable member, a
element towards the engaged position to relieve the ac
toothed locking element movable to and from an engaged
tuator means from the disengaging force acting on the
position relative to the locking member so as to prevent
locking element and thereby permit removal thereof from
ment from the engaged position, means connected to the
actuator means for maneuvering the actuator means to
the restraining position by the maneuvering means.
rotation of the rotatable member, a manually controlled
2. In a brake mechanism, the combination of a ro
actuator movable to and from a restraining position in
acting on the locking element so as to maintain the lock
30 connected to the actuator and so arranged that when the
which the disengaging forces acting on the locking ele
tatable locking member, a locking element movable to
ment are opposed so as to maintain the locking element
and from an engaged position relative to the locking
member, the locking element being adapted in the en 25 in the engaged position, and auxiliary means including
a servo motor for urging the locking element towards‘
gaged position to prevent rotation of the locking member,
the engaged position and a control valve mechanism in
actuator means for moving the locking element to the
terposed between the ?uid pressure system and the servo
engaged position, the actuator means being operative in
motor, the control valve mechanism being operatively
a restraining position thereof to oppose disengaging forces)
ing element in the engaged position, means connected
actuator is in the restraining position and the wheel
to the actuator means for maneuvering the actuator
means coacting with the locking element to cause the
brakes are operated ?uid pressure is supplied to the servo
motor causing the servo motor to relieve the actuator of
the load from the disengaging forces acting on the lock
the locking element towards the engaged position to re
from the restraining position.
lieve the actuator means of the load imposed thereon
6. In a parking brake mechanism for a vehicle having
Wheel brakes of a character that are operated by a ?uid
pressure system, the combination of a rotatable mem
means to and from the restraining position, and auxiliary
locking element to be maneuvered so as to tend to urge 35 ing element thereby freeing the actuator for removal
from the disengaging forces acting on the locking ele
ment thereby freeing the actuator means for removal
from the restraining position by the maneuvering means.
3. In a parking brake mechanism for a vehicle having
wheel brakes, the combination of a rotatable member
drive connected to the vehicle wheels, a locking member
ber drive connected to the vehicle wheels, a toothed lock
ing member connected to the rotatable member, a toothed
locking element movable to and from an engaged posi
tion relative to the locking member so as to prevent ro—
tation of the rotatable member, an abutment, a manually
‘ movable to and from an engaged position relative to the 45 controlled actuator movable to and from a restraining
connected to the rotatable member, a locking element
positon between the abutment and locking element so
as to oppose disengaging forces acting on the locking
element and maintain the locking element in the engaged
position, a servo motor rendered effective when ?uid pres
tive in a restraining position thereof to oppose disengag 50 sure is ‘delivered thereto to urge the locking element
towards the engaged position and relieve the actuator of
ing forces ‘acting on the locking element so as to main
the load from disengaging forces acting on the locking
tain the locking element in the engaged position, means
element thereby freeing the actuator for easy removal
connected to the actuator means for maneuvering the
from the restraining position, and a control valve mecha
actuator means to and from the restraining position, and
auxiliary means coacting with the locking element and 55 nism interposed between the wheel brake ?uid pressure
system and the servo motor and having ?rst and second
the wheel brakes so as to be rendered effective when the
‘settings, the control valve mechanism having an opera
wheel brakes are operated to tend to urge the locking
tive connection with the actuator so as to be placed in
element towards the engaged position ‘to relieve the ac
the ?rst and second settings when the actuator is moved
tuator means of the load from the disengaging forces
respectively to ‘and from the restraining position, the
acting on the locking element thereby freeing the actua
control valve mechanism also including supply and ex
tor means for removal from the restraining position by
haust valves and being so arranged that in the ?rst setting
the maneuvering means.
,
g
thereof the supply valve is opened and the exhaust valve
4. In a parking brake mechanism for a vehicle having
closed and in the second setting thereof the supply valve
wheel brakes of a character that are operated by a ?uid
pressure system, the combination of a rotatable member 65 is closed and the exhaust valve is opened, the servo motor
being supplied ?uid pressure when the control valve
drive connected to the‘ vehicle wheels, a locking mem
mechanism is in the ?rst setting and the wheel brakes are
ber connected to the rotatable member, a locking ele
operated and relieved of ?uid pressure when the valve
ment movable to and from an engaged position relative
mechanism is in the second setting.
‘to the locking member, the locking element being adapted
in the engaged position to prevent rotation of the rotat 70 7. In a transmission parking brake mechanism for a
vehicle having wheel brakes of a character that are op
able member, manually controlled means operative in a
erated by a fluid pressure system, the combination of a
a restraining position thereof to oppose disengaging forces
transmission output shaft drive connected to the vehicle
acting on the locking element so as to maintain the lock
wheels, a locking gear connected to the output shaft, a
ing element in the engaged position, and auxiliary means
including an expansible chamber motor engageabletwith 75 toothed pawl provided with a cam surface thereon, the
locking member, the locking element being adapted in
‘the engaged position to prevent rotation ‘of the rotatable
member, actuator means for moving the locking element
to the engaged position, the actuator means being opera
3,043,403
7
pawl being movable to and from an engaged position
lieved of ?uid pressure when the valve mechanism is in
relative to the locking gear so ‘as to prevent rotation of
the second setting.
'the output shaft, anabutment, an actuator for the pawl
.
,
9. In a parking brake mechanism fora vehiclehaving
including a ?rst roller 'journalled on the actuator and
wheel brakes of a character‘that are operatedtby a-?uid
adapted to engage the cam surface on the pawl and a Ul pressure system, the combination of a rotatable locking
‘second roller journalled on the-actuator-and adapted to
member drive connected to the vehicle wheels, a locking
element movable to and from anengagedposition rela
support the actuator on the abutment, means both for
yieldably moving the ,actuator along the abutment to
tiveto the locking member so as to prevent rotation
wards a’ restraining position was to oppose disengaging
thereof, actuating means maneuverable to and fromxa
forces acting on the pawl and maintain the pawl in the 10 restrainingposition in which the disengaging forcesact
‘engaged position and for positively removing the actua
ing on the locking element are opposed so as to main
tor from the restraining position so as to permit the pawl
tain the locking element in the engagedposition, and
to be removed from the engaged position, biasing means
‘for urging the pawl from the engaged position, a servo
motor rendered effective when fluid pressure is delivered
auxiliary means including a servomotor'for urgingthe
locking element toward the engagedposition and acou
trol valve mechanism controlling the supply of ?uid pres
thereto to urge the pawl towards the engaged position
‘and relieve the actuator of the» disengaging forces acting
the control valve mechanism being operatively connected
sure to the servomotor from the ?uid pressure system,
on the pawl and permit the actuator to be removed from
the restraining position, and a control valve mechanism
interposed between the wheel brake ?uid pressure system
to the actuating means so that when the actuating means
and the servo motor and having ?rst and second settings,
the control valve mechanism having an operative con
nection ‘with the actuator so as to be placed in the ?rst
in the ?rst setting thereof in which communication be
tween the ?uid pressure system and the lservomotor is
‘and second settings when the actuator is moved respec—
tively to and from the restraining position, the control
valve mechanism also including supply and exhaust valves
and being so arranged that in the ?rst setting thereof the
supply valve is opened and the exhaust valve closed and
in the second setting thereof the supply valve is closed
is maneuvered, respectively, to and from the restrain
ing position the control valve mechanism is positioned
permitted and in the second setting thereof in which com
munication between the ?uid pressure system and the
servomotor is interrupted, the servomotor being supplied
?uid pressure when the control valve mechanism isin
the?rst setting and the wheel brakes are operated and
relieved of ?uid pressure when the valve mechanism isin
the second setting.
and the exhaust valve opened, the servo motor being sup 30
10. In a brake mechanism, the combination of a'ro~
plied ?uid pressure when the control valve mechanism
tatable vlocking member, a locking element movable to
is in the ?rst setting'and the wheel brakes are operated
and from an engaged position relative to the locking
“and relieved of ?uid pressure when the valve mecha~
member, the locking element being adapted in them
nism is in the second setting.
gaged position to prevent rotation of the locking mem
8. ‘In a transmission parking brake mechanism for a '
ber, actuator means for moving the locking element to
the engaged position and operative in a restraining posi
vehicle having wheel brakes of a character that are op~
erated by a ?uid pressure system, the combination of a
tion thereof to m-aintain'the locking element in the en
transmission output shaft drive connected to the vehicle
wheels, a locking gear connected to the output shaft,
gaged position and thereby resist a disengaging force urg
ing the locking element from the engaged position, means
a toothed pawl provided with a cam surface thereon, 40 connected to the actuator means for maneuvering the
actuator means to and from the restraining position, and
tion relative to the locking gear so ‘as to prevent rotation
auxiliary means operatively connected to the actuator
means, the auxiliary means coacting with thewlocking ele
of the output shaft, an abutment, an actuator. for the
pawl including a ?rst roller journa'lled on the actuator
ment to tend to urge thelocking element towards the. en
and adapted to engage the cam surface on the pawl and a. gaged position when the actuator means is in the restrain
ing position to relieve the actuator means from the disen
a second roller journalled on the actuator and adapted
gaging force imposed thereon by the locking element
to ‘Support the actuator on the abutment, means both for
and thereby facilitate removal of the actuator means from
yieldably moving the actuator along the abutment to
the restraining position by the maneuvering means.
wards a restraining position'so as to oppose disengaging
11. In a brake mechanism, the combination of a rotat
forces acting on the ‘pawl and maintain the pawl in the
the pawl being movable to and from an engaged posi
engaged position and for positively removing the actua
-~ tor from the restraining ‘position so as to permit the pawl
able locking member, a locking ‘element movable to and
‘from an engaged position relative to the locking
member, the locking element preventing in the engaged
to be removed from the engaged position, biasing means
position the rotation of the locking member,‘ actua
for urging the pawl from the engaged position, a servo
tor means for moving the locking element to the en
motor rendered effective when ?uid pressure is delivered
gaged position ‘and operativein a restraining position
thereto to urge the pawl towards the engaged position
thereof'to oppose disengaging forces acting on the lock-.
and relieve the actuator of the disengaging forces acting
ing element so as to maintain the locking element in the
on the pawl and permit the actuator to be removed from
engaged position, means connected to the actuator means
the restraining position, a control valve mechanism inter
for maneuvering the actuator to and from the restraining
posed between the wheel brake ?uid pressure system and
\position'and auxiliary means operatively connected to
the servo motor, the ‘control valve mechanism having
the actuator means, the ‘auxiliary means coacting with
?rst and second settings and including supply and exhaust
the locking element to tend to urge the locking element
valves, and follower means having an operative connec
towards the engaged position when the actuator means
tion with the actuator so'as'to causethe controlvalve
mechanism to be placed in the ?rst and second settings 65 is in the restraining position so as to relieve the actuator
means from the load imposed thereon from the disen
when the actuator is moved respectively to and from the
gaging forces acting on the locking element thereby free~
restraining position thereby correlating the opening and
ing the actuator means for the removal of the restraining
closing of the supply and exhaust valves with movements
position by the maneuvering means.
of the actuator, the control valve mechanism being so
12. ‘In ‘a parking brake mechanism for a vehicle hav
arranged that in the ?rst setting thereof the ‘supply
ing wheel brakes, the combination ofi'a rotatable mem
valve is. opened and the exhaust valve closed and in the
ber drive connected to the vehicle wheels, a locking ele
second setting thereof the supply valve is closed and the
ment movable to and from an engaged position relative
exhaust valve opened, the servo motor being supplied
to the rotatable member, the locking element preventing
?uid pressure when the control valve mechanism is in
the ?rst setting and the wheel brakes operated and re~ 75 'in the engagedposition the rotation :of therrotatable
3,043,403
10
.
.
member, actuator means for moving the ‘locking element 7
tor means from the restraining position by the maneuver
to the engaged position and operative vin 1a restraining
ing means.
position ‘thereof to oppose disengaging forces acting on I
the locking element so as to maintain the locking ele
ment in the engaged position, means connected to the
actuator means for maneuvering the actuator to and from
the restraining position ‘and auxiliary means coacting with
the locking element and the vehicle brakes, the auxiliary
means being rendered effective when the wheel brakes
are operated ‘and the actuator means is in a restraining 10
position to tend to urge the locking element towards the
engaged position so as to relieve the actuator means from
the load from the disengaging force acting on the lock
ing element thereby facilitating the removal of the "actua
v
References Cited in the ?le of this patent
UNITED STATES ‘PATENTS
2,306,739
2,797,780
Maier _______________ .._ Dec. 29, 1942
Wemp ________________ __ Ian. 4, 1951
. 2,821,275
Martin _______________ .. Jan. 28, 1958
2,841,251
2,860,731
2,875,856
Shelton _______________ .. July 1, 1958
xI-Iause ______________ __ Nov. 18, 1958
Mrlik et a1. ___________ .._ Mar. 3, 1959
De Lorean ___________ -1 Nov. 10, 1959
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