USRE20021E - Fluid pressure operated brake - Google Patents

Description

June 30, 1936. BQWEN Re. 20,021

FLUID PRESSURE OPERATED BRAKE MECHANISM Original Filed Aug. 18, 1.928 2 Sheets-Sheet l i if i Y i v i H z I E firfierf'jazaezz 2 Sheets-Sheet 2 w w M I:

H. C. BOWEN FLU ID PRESSURE OPERATED BRAKE MECHANISM Jun 30, 1936.

Reissued June 30, 1936 PATENT OFFICE FLUID PRESSURE orEnATEn BRAKE MECHANISM Herbert G. Bowen, Detroit, Mich., assignor to Hydraulic Brake Company, Detroit, Mich., a corporation of California Original No. 1,886,936, dated November 8, 1932,

Serial No. 300,407, August 18, 1928. Application for reissue May 11, 1933, Serial No. 670,596

20 Claims. (01. 188-152) This invention relates to a fluid pressure operated brake mechanism, and more particularly to a device for applying an initial pressure to a fluid operated brake system prior to the application of. the brake operating pressure.

In fluid pressure operated brake systems there is frequently a lost motion between the pressure applying device and the brakes due in part to a loose fit or play between the mechanically interconnected parts and to the clearance between the brake shoes and drums when the brake shoes are retracted from the drums, which often results in a considerabie movement of the pressure applying device before the. brakes become effective.

An object of the invention is to provide an apparatus for applying an initial pressure to the fluid pressure operated system prior to the application of the brake operating pressure to remove the slack therefrom.

A further object of the invention is to provide a slack remover operable by energy received from the manifold of the motor for propelling a motor vehicle.

Other objects and advantages of the invention will appear as the description proceeds.

A complete understanding of the invention may be had by reference to the following description taken in conjunction with the accompanyin drawings, in which Fig. 1 represents schematically an apparatus embodying the invention for applying the brakes in a fluid pressure operated brake system;

Fig. 2 is a cross sectional view of the cylinder for applying the initial slack removing pressure to the system;

Fig. 3 is a cross sectional view of a fluid pressure actuated cylinder for operating the initial pressure cylinder shown in Fig. 2;

' Fig. 4 is a cross sectional view taken on lines 8-4 of Fig. 2, and

Fig. 5 is a cross sectional view taken on the lines 5-5 of Fig. 2.

Referring to the drawings, and more particularly to Fig. 1, a pluralityof brake mechanisms 8 are actuated by the pressure produced in a master cylinder I. Each brake mechanism may comprise brake shoes 6a pivoted at El; on a supporting pan 6c and actuated by pistons Ed in a cylinder 6e 7 .to engage the drum 6f from which the brake shoes are retracted by spring By. The specific structure of the brake mechanisms forms no part of my invention and it' is to be understood that other brake mechanisms than that. illustrated may be utilized in a. braking system. embodying my invention. The master cylinder I is operated by a pinion 22.

lever 8 which is connected through a link 8 to a manually operable pedal II and serves to reciprocate a piston l2 within the master cylinder I to communicate a pressure through a tube I to the brakes 6.

A secondary cylinder I3 is also connected through the tube III to the pressure system and has a. piston I4 reciprocally mounted therein. Attached to the piston I4 is a threaded piston rod I which is slidably mounted in a bearing cap l6 having an upper bearing I1 and a lower bearing I8. The piston rod I5 is provided with a longitudinal groove I9 into which a projection 2| of the upper bearing II extends for the purpose of allowing longitudinal movement of the piston rod and preventing rotative movement thereof.

A pinion 22 is supported between the bearings l1 and I8 and is provided with an internal thread which engages the threads of the piston rod I5. The threads of the piston rod I5 and the pinion 22 are of such a pitch that the connection is irreversible; that is, a rotation of the pinion 22- will cause a longitudinal movement of the piston rod I5, but a longitudinal force exerted upon the piston rod I5 will not cause a rotation of the In order to rotate the pinion 22 ,a rack 23 is held in engagement therewith by a support 24 integral with the bearing cap l6.

The rack 23 is formed integral with a piston rod 25 which is attached to the piston 26 reciprocally mounted in a cylinder 21. Supported on the upper portion of the cylinder 21 is a valve mechanism 28 having a double valve 29 which may be engaged with either the valve seat 3| or the valveseat 32.

A valve stem 33 for operating the valve extends from the valve mechanism and contacts with the lever 8 which holds the valve 29 in engagement with the seat 3| when the lever B is in its inoper ative position, in which position of the valve the cylinder 21 is connected through a duct 35 to a plurality of ports 38 leading to the atmosphere. Upon a. slight movement of the lever 8 a spring 34 will shift the valve 29 into engagement with the valve seat 32, in which'position of the valve the cylinder 21 will be connected through the duct 35 to a tube 36 leading to themanifold 36' of the vehicle motor.

The operation of-the apparatus is as follows: v

rotation of the pinion 22 through the rack 23 and g to the manifold of the motor vehicle in which the operation of the motor constantly maintains a vacuum.

The vacuum thus applied to the cylinder 21 tends to withdraw the air therefrom and allows the atmospheric pressure to force the piston 26 into the cylinder 21 against the action of a spring The movement of the piston 26 causes the engage the brake shoes with the drums but with cylinder.

insufllcient force to produce a braking effect. At this time the lever 8 will have moved only far enough to operate the valve 29. As the pressure in the system increases, due to the continued movement ,of the lever B in applying the brakes, the piston M will not be forced upwardly on account of the irreversible connection between the piston rod l5 and the pinion 22.

The initial pressure produced in the cylinder l3 therefore remains effective during the entire braking process, and the piston I4 is not withdrawn until the lever B resumes its normal position and moves the valve 29 to its right hand position.

When the valve 29 is returned to its right-hand.

position, the cylinder 21 is connected through duct 35 and ports '38 to the atmosphere, allowing the spring 31 to move the piston 26 outwardly until it engages the bearing 39, which limits its outward movement, restoring the piston I4 in the cylinder I 3 to its normal position.

It will be seen, therefore, that the apparatus serves to apply an initial pressure to the fluid pressure system and retain that pressure'during the entire braking process.

The embodiment of the invention herein described and illustrated is merely a convenient and useful form of the invention which is capable .of many other modifications without departing from the spirit and scope of the invention, which is to be limited only by the scope of the appended claims.

Iclaim:

1. The combination in a fluid pressure oper ated brake system, of means for producing a pres- 2. In a fluid pressure operated brake system, a master cylinder and piston, means for actuating the pistonof the master cylinder to produce a pressure in the system, and fluid pressure actuated means responsive to the initial movement of said actuating means for removing the slack from the brake system. a

3. In a fluid pressure operated'brake system, means for producing a fluid pressure in the system, means movable to actuate the pressure producing means, and fluid pressure actuated means responsive to the initial movement of the movable means to remove the slack from the system.

4. In a fluid pressure operated brake system, a slack remover comprising a cylinder, a piston in said cylinder, and an irreversible driving connection for movingthe piston in the cylinder to remove the slack from the system.

5. In a fluid pressure operated brake system, a. slack remover comprising a cylinder, a piston in said cylinder, a threaded piston rod for moving the cylinder, a rotatable threaded member enthe secondary cylinder piston,

pressure means for rotating said rotatable mem- 6. The combination in a fluid operated system, a main pressure means, a secondary pressure means, fluid pressure actuated means for completely operating the secondary pressure means upon a partial operation of the main pressure means, and means for causing the secondary pressure means to remain in its operated position until the main pressure means has returned to normal position.

'7. The combination in'a fluid pressure operated system, a master cylinder having a piston, means for operating the piston of the master cylinder, a secondary cylinder having a piston, and means for operating the piston of the secondary cylinder comprising a fluid operated cylinder, and means for connecting said fluid operated cylinder to a source of energy upon a slight movement of the means for operating the piston of the master tion until the means for operating the piston of the master cylinder has returned'to normal position.

9. The combination in a fluid pressure operated brake system, a master cylinder, a pistontherefor, means for actuating said piston to produce a brake operating fluid pressure in the brake system, a secondary cylinder, a piston in said secondary cylinder, a threaded piston rod attached to an internally threaded pinion engaging said threaded piston rod, a pressure actuated cylinder having a piston therein, a piston rod therefor adapted to rotate said pinion, and means for producing an operating pressure in the pressure cylinder upon a movement of the means for actuating the piston of the master cylinder whereby the secondary cylinder is caused to produce a slack removing pressure in the brake system prior to the brake operating pressure.

10. The combination in a fluid pressure operated brakesystem, a master cylinder, a piston therefor, means for actuating said piston to produce a brake operating pressure-in the system, a

secondary cylinder, a piston therefor, a threaded piston rod attached to said piston, an internally threaded pinion engaging the threaded piston rod, a fluid pressure operated cylinder, a piston therefor, a piston rod attached to said last mentioned piston adapted upon its movement to rotate said pinion, means including a valve for connecting the pressure operated cylinder to a source of low pressure, and means for operating said valve upon the initial movement of the means for actuating the piston of the master cylinder whereby the pressure operated cylinder causes the secondary cylinder to produce a slack removing pressure in the system prior to the brake operating pressure.

operably connected with the piston in said secondary cylinder whereby it is moved its full amount coordinately with the partial movement of the piston in said master cylinder, and means means, disengageable from said secondary pressure means upon a partial operation of the main pressure means whereby the said secondary pressure means is completely operated.

13. In brake apparatus, an operator, a brake,

fa connection between said operator and said brake, means responsive to the initial movement of said operator for varying the effective length of the connection between said operator and said brake to take up the slack in said connection and in said brake without corresponding movement of said operator, said means comprising a source of suction, a vacuum motor, a conduit extending from said source of suction to said motor, a valve in said conduit, and a connection from said operator to said valve.

14. In brake apparatus, an operator, a brake, a connection between said operator and said brake, means responsive to the initial movement of said operator. for varying the eifective length of the connection between said operator and said brake to take up the slack in said connection and in said brake without corresponding movement of said operator.

15. A hydraulic brake system comprising a brake pedal, brake shoes, means comprising a power device for taking up the clearance of the.

master cylinder, lines connecting said master cylinder and said wheel cylinder, a power slack' take-up device operated by initial movement of the brake pedal to produce pressure in the lines sufllcient to take up. the 'shoe clearance, and a piston in the master cylinder operated by further movement of the pedal which after the slack take-up -will produce braking pressures in the lines without assistance from the power device.

. 17. In brake apparatus using fluid and having a rotatable friction element and a cooperating friction elementadapted to be anchored against movement and adapted to be brought into contact with said rotatable friction element for retarding movement of said rotatable friction element, means responsive to fluid pressure for moving said cooperating element into contact with said rotatable element, power operated means for applying pressure to said fluid solely for the purpose of removing all slack from said brake apparatus regardless of the condition of wear thereof, and additional means for applying higher pressures to said fluid for urging said cooperating element into closer contact with said rotatable element.

18. In hydraulic brake apparatus using a hydraulic fluid and having a rotatable friction element and a cooperating friction element adapted to anchor against movement and adapted to be brought into contact with said rotatable friction element for retarding movement of said rotatable friction element, means responsive to fluid pressure for moving said cooperating element into contact with said rotatable element, a vacuumoperated power motor for applying non-braking pressures to said fluid, and additional means for applying braking pressures to said fluid.

l9. Thercombination with brake mechanism including a rotatable friction element, an anchored friction element, and an operating cylinder for said last-named element, of a master cylinder, a piston in said cylinder, connections between said master cylinder and said operating 1 cylinder, means comprising a vacuum cylinder for creating non-braking pressures in the operating cylinder and for applying the anchored friction element to the rotatable friction e'lement, and manually-operated means including the piston for creating braking pressures in the operating cylinder and for forcing the anchored friction element more tightly against the rotatable friction. element. I

20. In brake apparatus of'the class described, the combination of an operator, a brake drum, .a brake element adapted to be moved into engage pment with said drum, a fixed anchor for said brake element, a connection between said operator and said brake element, means responsive to the initial movement-of said operator' for varying the effective length of the connection between said operator and said element to move said element into engagement with said drum without corresponding movement oif said operator.

HERBERT C. BOWEN.

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