Fluid actuated brake locking mechanism

Abstract

A brake locking mechanism for heavy vehicles, adapted to be installed in existing braking systems without altering the normal operation thereof, functions to prevent involuntary movement of the vehicle, due to system failure such as air or hydraulic fluid leakage, while standing. The mechanism includes a spring biased pawl engageable with rack teeth formed on the diaphragm actuated brake rod, the pawl being operated by an air or hydraulically actuated piston associated therewith and connected into the vehicle air or hydraulic system.

Description

REFERENCE TO RELATED APPLICATION

This application is and affect effect this coupling, the pawl rod is provided with an axial slot 52 at its upper end which is traversed by a pin 53. The pawl rod slot is dimensioned to receive the distal end of the crank horizontal arm, and this arm is provided with a horizontal slot 54 to receive the pin 53. With this arrangement, any vertical oscillation of the distal end of the horizontal crank arm will result in corresponding vertical movement of the pawl rod 46.

The pawl rod is normally urged downwardly to engage the actuator rod teeth 19 by means of a compression spring 56, which is seated in a suitable casing recess opening from the chamber 43 and which bears against the vertical arm of the crank arm 50 to urge the crank arm in a clockwise direction.

To rotate the crank arm in a counterclockwise direction, the casing 41 is provided with a transverse cylindrical bore 60 which defines the cylinder chamber for a spool-like piston element 61. The cylinder bore 60 opens to a side wall of the casing and is closed by a cylinder plate 62 secured to the casing by means of suitable screws for example, with the cylinder pressure chamber being defined by the bore 60 and the plate 62. The piston element 61 includes an axial extension 63 which bears against the crank vertical arm opposite from the spring 56. For communicating fluid to the cylinder chamber, the casing includes a threaded inlet chamber 65 for receiving the coupling of a flexible conduit 66; and a restricted passage 67 communicates the inlet chamber 65 with the cylinder bore 60 adjacent to the outer wall; this passage 67 providing for restricted flow of fluid into the cylinder chamber.

The cylinder plate 62 is provided with a central threaded hole for accommodating an adjustment screw such as a cap screw 68 carrying a lock nut 69. This adjustment screw is provided to manually move the piston 61 to the left to effect disengagement of the pawl rod from the actuator rod in the event of failure of the fluid system.

OPERATION

The operation of the above described brake locking unit will now be described with reference to FIG. 6, assuming that a pneumatic braking system is used. Reference will also be made to a typical system for a semi-trailer, wherein the trailer braking system includes an emergency air tank or reservoir 100 which is supplied with compressed air from the tractor air system 103 through an RE (relay-emergency) valve 101 and an emergency line 102 which is coupled to the tractor air system 103 through a disconnect coupling. The several wheel unit brake actuator chambers 11 are connected by way of conduit 14 to a service line 104 through the RE valve; with the service line 104 again being connected to the tractor system 103 through a disconnect coupling, to be pressurized by actuation of the tractor service brake valve 105 (foot valve). In normal operation of the trailer brakes, the RE valve serves as a relay valve to direct the pressurized air to the brake actuator chambers 11. When the emergency line 102 is opened for any reason, the RE valve 101 is actuated to supply compressed air from the trailer emergency reservoir to the trailer actuator chambers 11 to set the brakes.

Referring now to a wheel brake assembly which includes a locking unit 10 of FIG. 3, the locking pawl is normally disengaged from the actuator rod 15 by the spring 27; and the locking pawl is set by supplying pressurized air to the cylinder chamber. For operation of these units then, the conduits 35 for the several locking units 10 may be conveniently connected to the air line which communicates the RE valve with the brake actuator chambers 11; and this connection should be made through a three-way shutoff valve which serves in the open condition to direct compressed air from the RE valve to the locking unit chambers, and which serves in the closed condition to shut off the supply of air and to vent the cylinder chambers of the locking units 10.

This arrangement will prevent operation of the locking units during normal operation of the service brakes when the trailer is coupled to a tractor. When the trailer is disconnected from the tractor, the service brakes are set from the emergency reservoir; and the shutoff valve is then opened to pressurize the chambers of the units 10. When the trailer is again hooked up to a tractor for normal operation, the shutoff valve must be first closed to vent the locking unit chambers and condition the locking units for release of the pawls by the respective springs.

With this system the pawls are maintained engaged by the pressure from the trailer emergency reservoir; and should this pressure reduce to an extent to allow the pawl rods to retract this pressure reduction will also permit some movement of the brake actuator rod to the left creating back pressure on the pawl to maintain the pawl in engagement with the rack teeth by friction. To assist in this action, the faces of the rack teeth may be reversely inclined with the face of the pawl having a complementary inclined face to effectively lock the pawl rod and actuator against disengagement.

Referring now to the unit 40 of FIGS. 4 and 5, in the normal condition of the locking unit the spring 56 effects engagement of the pawl with the actuator rod 15. For the operation of these units 40 then, the respective supply conduits 66 may be conveniently connected to the above described trailer emergency line 102 (FIG. 6). With such arrangement whenever the emergency line is pressurized, the cylinder chambers of the locking units will also be pressurized to disengage the pawl rods 46. This of course would be the normal condition when the trailer is coupled to a tractor. Whenever the emergency line 102 is vented, either through a suitable tractor control valve 106, through breaking the tractor-trailer coupling, or due to a break in the emergency line 102, the locking unit chambers are vented to permit the setting of the pawls and simultaneously the trailer brakes are set through the emergency reservoir and the RE valve. To prevent engagement of the pawls with the actuator rod until such time as the brakes are fully set, the restricted passage 67 retards the flow of pressurized air from the cylinder chamber to atmosphere through the conduit 66. With the brake locking units 40, the lock is maintained by the force of the spring 56; and the trailer brakes will remain locked indefinitely regardless of any loss of pressure from the system.

What has been described are two forms of brake locking units or mechanisms for use with conventional braking systems which are simple and rugged in construction, and which are simple and reliable in operation, and which may be readily adapted for use with the braking systems on existing vehicles. Because of the simplicity of construction, the units can be made available to operators of trucking lines or other heavy duty vehicles at a reasonable cost. A particular advantage of the system of FIGS. 4 and 5 is that the unit can be readily controlled by the existing air brake system, and the locking device once set is independent of the air system and will hold the brakes for an indefinite period.

A particular advantage of the above described locking system is its simplicity and lack of heavy parts. This means that the brake locking units which must be added to each wheel unit are much lighter in weight than so-called spring brakes which serve this function, and thereby reducing dead weight which otherwise would have to be hauled every mile of operation. Another important feature, resulting from simplicity of design and operation, is the reduction of installation and maintenance costs for brake locking systems.

While preferred embodiments of the invention have been illustrated and described, it will be understood by those skilled in the art that changes and modifications may be resorted to without departing from the spirit and scope of the invention.

Claims

1. In a fluid operated brake setting system for heavy vehicles including, for each wheel unit, a brake, a brake actuator chamber and a brake actuator rod reciprocated by said actuator chamber and operatively connected to the wheel unit brake; a brake locking mechanism comprising:

a casing adapted to be mounted in association with said actuator chamber; said casing having a first passage therethrough, for accommodating the brake actuator rod for reciprocating movement, and a second passage transverse to and communicating with said first passage;

said brake actuating rod being provided with longitudinally spaced transverse rack teeth; a pawl rod supported and guided for reciprocating movement in said second passage, having pawl means at one end for engagement with said rack teeth;

means in said casing defining a cylinder chamber; piston means disposed in said cylinder chamber for reciprocating movement; means coupling said piston means to said pawl rod;

spring means coupled to said pawl rod, normally urging said pawl rod in a first direction relative to said first passage to engage said pawl means with said rack teeth; conduit means communicating said cylinder chamber with a source of pressurized fluid acting on said piston and urging said pawl rod in a second direction relative to said first passage to disengage

said pawl means from said rack teeth. 2. A brake locking mechanism as set forth in claim 1 11

said coupling means comprising a crank arm pivoted within said casing; one end of said crank arm being coupled to said pawl rod to provide for reciprocation of said pawl rod in response to oscillation of said crank

arm; said piston means acting on the other end of said crank arm. 3. A brake locking mechanism as set forth in claim 2

said piston means being moved, upon the introduction of fluid into said cylinder chamber, from a first position to a second position to disengage said pawl means from said actuator rod; a threaded hole in the casing wall confronting the head of said piston; and an adjusting screw disposed in said hole for maintaining said piston in said second position to disengage

said pawl means from said actuator rod. 4. A brake locking mechanism as set forth in claim 2

said spring means acting on said other end of said crank arm, in opposition to said piston means, to normally engage said pawl means with said

actuator rod. 5. A brake locking mechanism as set forth in claim 1 11

restricted passage means in said casing communicating said cylinder chamber with a fluid inlet chamber to restrict the rate of fluid flow into and out of said chamber.

6. In a pneumatically operated brake system for applying and releasing a wheel brake of a wheeled vehicle, said brake system being of the type including a primary air source; a brake actuator chamber; a brake actuator rod operatively connected with said brake actuator chamber and said wheel brake and mounted for reciprocating movement to apply said wheel brake in response to the pressurization of said actuator chamber from said primary air source; and foot-operated valve means for supplying air from said periphery source to said actuator chamber; the improvement consisting of an auxiliary brake setting and locking mechanism for applying as well as maintaining said brake against release, independent of the operation of said foot-operated valve means, said auxiliary brake setting and locking mechanism comprising:

(a) a casing mounted in association with said brake actuator chamber; said casing having a first passage therethrough for accommodating the reciprocating movement of said brake actuator rod and a second passage transverse to, and communicating with, said first passage;

(b) said brake actuator rod being provided with longitudinally spaced transverse rack teeth; a pawl rod supported and guided for reciprocating movement in said second passage and having pawl means at one end for engagement with said rack teeth;

(c) means on said casing defining a cylinder chamber; piston means disposed in said cylinder chamber for reciprocating movement; means coupling said piston means to said pawl rod whereby air pressure within said cylinder chamber acts upon said piston to urge said pawl rod in a first direction relative to said first passage to disengage said pawl means from said rack teeth when the said air pressure is at least equal to a predetermined amount, thereby preventing the locking of said wheel brake by engagement of said pawl rod with said brake actuator rod;

(d) spring means coupled to said pawl rod normally urging said pawl rod in a second direction opposite to said first direction to engage said pawl means with said rack teeth when the air pressure within said cylinder chamber is below said predetermined amount;

(e) means for maintaining said predetermined amount of air pressure within said cylinder chamber when said actuator chamber is pressurized from said primary air source, and

(f) means for pressurizing said actuator chamber as well as reducing the air pressure in said cylinder chamber below said predetermined amount in response to loss of air pressure from said primary air source, thereby to apply said wheel brake independent of the operation of said foot-operated valve means and lock said wheel brake in said applied position by engagement of said pawl rod with said brake actuator rod.

7. The improvement as defined in claim 6 further including means simultaneously supplying air of at least said predetermined amount of air pressure to said cylinder chamber from said primary air source during the pressurization of said actuator chamber from said primary air source; an emergency air source; and means responsive to the loss of air pressure from said primary air source below said predetermined amount to pressurize said actuator chamber from said emergency air source and enable locking engagement of said pawl rod with said brake actuator rod.

8. The improvement as defined in claim 7 further including controllable valve means for providing said loss of air pressure from said primary air source.

9. The improvement as defined by claim 8 further including means for manually disengaging said pawl rod from said brake actuator rod.

10. In a pneumatically operated brake system for applying and releasing a wheel brake of a wheeled vehicle, said brake system being of the type including a primary air source; a brake actuator chamber; a brake actuator rod operatively connected with said brake actuator chamber and said wheel brake and mounted for reciprocating movement to apply said wheel brake in response to the pressurization of said actuator chamber from said primary air source; and foot-operated valve means for supplying air from said primary source to said brake actuator chamber; the improvement consisting of an auxiliary brake setting and locking mechanism for applying as well as maintaining said brake against release, independent of the operation of said foot-operated valve means, said auxiliary brake setting and locking mechanism comprising:

(a) means for accommodating the reciprocating movement of said brake actuator rod;

(b) means supporting and guiding a pawl rod for reciprocating movement in a direction transverse to said brake actuator rod, said pawl rod having means at one end thereof for engagement with said brake actuator rod;

(c) means defining a cylinder chamber; piston means disposed in said cylinder chamber for reciprocating movement; means coupling said piston means with said pawl rod whereby air pressure within said cylinder chamber acts upon said piston to urge said pawl rod in a first direction away from said brake actuator rod when the said air pressure is at least equal to a predetermined amount, thereby preventing the locking of said wheel brake due to engagement of said pawl rod with said brake actuator rod;

(d) spring means coupled to said pawl rod normally urging said pawl rod in a second direction opposite to said first direction, thereby to engage said pawl rod with said brake actuator rod when the air pressure within said cylinder chamber is below said predetermined amount;

(e) means maintaining said predetermined amount of air pressure within said cylinder chamber when said actuator chamber is pressurized from said primary air source, and

(f) means for pressurizing said brake actuator chamber as well as reducing the air pressure in said cylinder chamber below said predetermined amount in response to a loss of air pressure from said primary air source, thereby to apply said wheel brake independent of the operation of said foot-operated valve means and lock said wheel brake in said applied position by engagement of said pawl rod with said brake actuator rod.

11. In a pneumatically operated brake system for applying and releasing a wheel brake of a wheeled vehicle; said brake system including a primary air source, a brake actuator chamber, a brake actuator rod operatively connected with said brake actuator chamber and said wheel brake and mounted for reciprocating movement to apply said wheel brake in response to the pressurization of said brake actuator chamber from said primary source, and foot-operated valve means for supplying air from said primary source to said actuator chamber; the improvement consisting of an auxiliary brake locking mechanism for applying as well as maintaining said brake against release, independent of the operation of said foot-operated valve means, said brake locking mechanism comprising:

(a) a casing mounted in association with said brake actuator chamber, said casing having a first passage therethrough for accommodating the reciprocating movement of said brake actuator rod and a second passage transverse to, and communicating with, said first passage;

(b) said brake actuator rod being provided with longitudinally spaced transverse rack teeth; a pawl rod supported and guided for reciprocating movement in said second passage and having pawl means at one end for engagement with said rack teeth;

(c) means in said casing defining a cylinder chamber; piston means disposed in said cylinder chamber for reciprocating movement; means coupling said piston means to said pawl rod whereby air pressure within said cylinder chamber acts upon said piston to urge said pawl rod in a first direction relative to said first passage to disengage said pawl means from said rack teeth when the said air pressure is at least equal to a predetermined amount, thereby preventing the locking of said wheel brake by engagement of said pawl rod with said brake actuator rod; and

(d) spring means coupled to said pawl rod normally urging said pawl rod in a second direction opposite to said first direction to engage said pawl means with said rack teeth when the air pressure within said cylinder chamber is below said predetermined amount.