# US 4,398,771 A · Braking system for towed vehicles > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,398,771 A - Document ID: US4398771A - Status: Granted - Kind: A - Application number: 06/208,483 - Filed: 1980-11-19 - Granted: 1983-08-16 - Earliest claimed: 1980-11-19 - Inventors: Walter W. McCurry; Walter G. Pettit - Web page: https://patentgrep.com/patent/US4398771A ## CPC - B60T 7/20: specially for trailers, e.g. in case of uncoupling of {or overrunning by} trailer (inertia-actuated overrun brakes B60T13/08) - B60T: VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL (electrodynamic brake systems for vehicle, in general B60L; brakes per se, i.e. devices where braking effect occurs, including ultimate brake actuators, F16D); ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES ## Abstract A braking system for automatically braking a towed vehicle coupled to a towing vehicle having an electrical brake control circuit and a vacuum line wherein the towed vehicle is provided with a normally closed solenoid valve for connecting both a vacuum reservoir in the towed vehicle and the vacuum line in the towing vehicle with a vacuum responsive bellows operatively connected to the brake pedal in the towed vehicle with the solenoid operated valve electrically connected through a normally open breakaway switch to the battery whereby the operation of the braking system on the towing vehicle is accompanied by an actuation of the solenoid operated valve and the application of a vacuum to the bellows for concomitant operation of the brake pedal on the towed vehicle and upon a decoupling of the towed and towing vehicles, a similar actuation of the solenoid operated valve when the breakaway switch closes to apply vacuum to the bellows for actuation of the brake pedal to brake the decoupled towed vehicle. ## Claims ### Claim 1 A braking system for automatically braking a towed vehicle having an engine, a battery and a braking arrangement including a brake pedal, the towed vehicle being detachably coupled to a towing vehicle also having an engine, battery and braking system and having a vacuum line using compressible fluid and a braking unit including an electrical control circuit comprising, in combination, vacuum responsive actuator means on said towed vehicle, means for operatively connecting said actuator means to said towed vehicle brake pedal, a source of vacuum on said towed vehicle, conduit means including a normally closed, solenoid operated valve for communicating said source of vacuum with said actuator means, circuit means on said towed vehicle including a normally open breakaway switch for connecting said towed vehicle battery to said solenoid operated valve, means for detachably connecting said circuit means and said conduit means to said control circuit and said vacuum line and said towing vehicle respectively in the coupled condition of said towed and towing vehicles for energizing said solenoid operated valve and supplying a vacuum to said actuator means to brake said towed vehicle during the braking of said towing vehicle, said breakaway switch being responsive to the uncoupling of said towed and towing vehicles for energizing said solenoid operated valve to apply a vacuum to said actuator means from said vacuum source for braking said towed vehicle should the towed vehicle be dissociated from the towing vehicle while being towed. ### Claim 2 (depends on 1) A braking system in accordance with claim 1 wherein said actuator means comprises a vacuum responsive device and means for operatively connecting said vacuum responsive device to said solenoid operated valve. ### Claim 3 (depends on 2) A braking system in accordance with claim 2 wherein said vacuum source comprises a reservoir on said towed vehicle and means for evacuating said reservoir to provide a vacuum therein. ### Claim 4 (depends on 3) A braking system in accordance with claims 3 wherein said means for evacuating said reservoir includes said towing vehicle vacuum line. ### Claim 5 (depends on 4) A braking system in accordance with claim 4 wherein fluid means for evacuating said reservoir further comprises a conduit having a on-off valve for connecting said conduit means to the vacuum in the engine of said towed vehicle. ### Claim 6 (depends on 3) A braking system in accordance with claim 3 wherein said vacuum responsive device comprises a bellows having an interior said bellows being movable into an expanded inoperative position in the absence of a vacuum in said interior and into a contracted operative position upon the presence of a vacuum in said interior and wherein said means for connecting said vacuum responsive device with said valve includes a conduit for communicating said bellows interior with said solenoid operated valve. ### Claim 7 (depends on 6) A braking system in accordance with claim 6 wherein said means for operatively connecting said actuator means to said towed vehicle brake pedal comprises a linkage connected between said vacuum responsive device and said brake pedal, said linkage including overriding means to permit manual movement of said brake pedal for braking said towed vehicle. ### Claim 8 (depends on 7) A braking system in accordance with claim 7 wherein said linkage comprises a rod connected at one end to said vacuum responsive device, said rod having a threaded portion adjacent the other end of said rod, a tubular member having a central bore connected at one end to said brake pedal, the other end of said tubular member having an opening defining a stop for insertion of said rod threaded end portion within said tubular member central bore and a nut adjustably positioned in threaded engagement with said threaded end portion within said central bore, said nut being engageable with said stop during the movement of said vacuum responsive device into said operative position for actuating said brake pedal and said tubular member being movable relative to said rod in overriding relationship therewith to permit manual actuation of said brake for braking said towed vehicle. ### Claim 9 (depends on 5) A braking system in accordance with claim 5 wherein said means for detachably connecting said circuit means and said conduit means to said control circuit and said vacuum line comprises a coupling and wherein said reservoir is provided with an outlet, a T-fitting including a one-way valve connected to said reservoir outlet, a conduit for connecting said T-fitting to said solenoid operated valve, a conduit having one end connected to said T-fitting and having the other end mounted on said coupling for connection to said towing vehicle vacuum line in the coupled condition of said towing and towed vehicles. ### Claim 10 (depends on 9) A braking system in accordance with claim 9 wherein said conduit for connecting said conduit means to said engine vacuum is connected at one end to said conduit between said solenoid valve and said T-fitting. ### Claim 11 (depends on 7) A braking system in accordance with claim 7 wherein said linkage comprises a cable connected at one end to said bellows and at the other end to said brake pedal and a pulley around which said cable extends in a U-shaped configuration between said bellows and said brake pedal and a spring fixed at one end and connected at the other end to said cable between said pulley and said bellows.