Pneumatically controlled hydraulic trailer brake system

• US 4,054,325 A
• Filed: 09/27/1976
• Issued: 10/18/1977
• Est. Priority Date: 09/27/1976
• Status: Expired due to Term

• Current Assignee: Midbrake Corporation
• Original Assignee: Midland-Ross Corporation (Honeywell International Inc.)
• Inventors: Popp, Roger C.
• Primary Examiner(s): Blix, Trygve M.
• Assistant Examiner(s): Kazenske, Edward R.
• Application Number:
  US05/727,282
• Time in Patent Office: 386 Days
• Field of Search: 303/7, 303/114, 303/115, 303/118, 303/119, 91/376 R, 91/459, 137/627.5, 251/30, 251/322, 251/323
• US Class Current: 303/7
• CPC Class Codes: B60T 13/52 indirect, i.e. vacuum booster units
• CPC Class Codes: B60T 13/581 both hydraulic and pneumatic
• CPC Class Codes: B60T 13/68 by electrically-controlled valves B60T13/662 and B60T13/665 take precedence
• CPC Class Codes: Y10T 137/86919 Sequentially closing and opening alternately seating flow controllers

Abstract

Disclosed herein is a trailer brake control system comprising a trailer-mounted servo-motor type booster in direct operating connection, e.g., by hydraulic lines, with the trailer wheel brakes, an electrical transducer and signal amplification apparatus mounted on the towing vehicle, and a solenoid synchronizing valve for controlling the booster operably positioned between the signal amplification apparatus and the booster for translating electrical signals of varying magnitude into correspondingly varying brake action. The system enables the operator of a tow vehicle and trailer combination to operate the trailer brakes with power-applied effort which is proportional to manual pedal effort applied to the braking system of the tow vehicle, or optionally, to operate the trailer brakes independently of the tow vehicle brakes to any extent desired through manual control of the signal amplification apparatus.

Claims

1. A braking system carried in a towed vehicle and a towing vehicle for operating the brakes of the towed vehicle comprising:

control apparatus on the towing vehicle comprising signal means operable throughout an input signal range, and electrical means responsive to the signal means to generate a solenoid activating output current throughout a range of current corresponding to said signal range;

a power brake booster on the towed vehicle having a brake actuating rod, a sealed housing partitioned by a flexible diaphragm dividing the housing into first and second chambers, said rod extending through the first chamber into connection with a central portion of said diaphragm, and spring means urging said diaphragm and rod to a brake-off position deflating said second chamber and inflating said first chamber;

a solenoid valve on one of the vehicles comprising a solenoid having a coil, a central plunger, and a valve assembly attached thereto for supplying a fluid at a control pressure in a range between a higher supply pressure and a lower supply pressure in proportion to an electric current passed through the coil of the solenoid by said electrical means, said valve assembly comprising;

a housing enclosing in the order named proceeding in a direction away from said solenoid, a first chamber and an inlet port therefor for said lower pressure fluid, a second control chamber and an outlet port therefor, a third chamber and an inlet port therefor for said higher pressure fluid, and an annular valve seat located at the end of the third chamber nearer the solenoid and facing away therefrom, said second and third chambers being communicable through said seat;

a valve member supported in said third chamber for reciprocation toward and away from said seat and being normally engaged with the seat;

resilient means for urging said member toward said seat;

a spool in axial tandem-connected relation with said plunger and reciprocably supported within said first and second chambers of the valve assembly;

a flexible diaphragm in concentric relation with the spool and connected in sealed relation with the spool and the housing for separating the first and second chambers of the valve assembly;

said spool having an open end remote from said plunger and a central passageway extending from an opening of the spool in said first chamber to said open end;

separate spring means seated in said housing and seated on the spool to act toward each other on said spool to axially urge the spool toward a neutral position corresponding to equal pressures in the first and second chambers in the housing with said open end in spaced relation with said member when said solenoid is deenergized and said member is in seated position;

said spool being movable by said plunger to engage said member and then carry it to a position spaced from said seat with said member closing off said open end to enable passage of fluid from said third chamber to said second chamber;

a source for said lower supply pressure connected with said inlet port of said first housing chamber and said first booster chamber;

a source for said high supply pressure connected with the inlet port of said third chamber;

said plunger upon electrical excitation of the solenoid being movable from a retracted position corresponding to a neutral position of the spool permitting communication of the first housing chamber with the second housing chamber and equal pressures therewithin to a second position against said valve member terminating communcation between the first and second housing chambers and thence to a third position wherein communication of the first and second housing chamber remains terminated and said member is unseated to place the third chamber in communication with said second housing chamber to transmit a higher pressure to said second booster chamber.

2. The braking system of claim 1 wherein:

said tow vehicle has a hydraulic brake system;

said signal means comprises a pressure transducer connected in hydraulic pressure transmitting relation to said tow vehicle brake system;

said electrical means comprising logic and amplification circuitry connected for signal input with said transducer and for amplified electrical output with said solenoid.

3. The braking system of claim 1, comprising:

manual control potentiometer means and means for optionally connecting said potentiometer means and said transducer with said logic and amplification circuitry for selectively establishing control of towed vehicle brakes independently of the tow vehicle brakes through said potentiometer, or dependently of the tow vehicle brakes through said transducer.

4. The braking system of claim 1 wherein:

said source of the lower supply pressure is vacuum power generated on the tow vehicle; and

said source of said higher pressure is the atmosphere.