Automatic trailer sway sensing and brake applying system

Abstract

An apparatus for automatically sensing trailer sway and applying trailer brakes, thereby minimizing or eliminating the sway is provided. A hydraulic device, similar to a shock absorber with the addition of a pressure operated switch at each end of the cylinder, is mounted between the trailer A frame and the hitch head assembly. A sudden sway in either direction causes one of the switches to close and apply power to the electric trailer brakes thus minimizing or eliminating the sway and causing the car and trailer to "line up". The hydraulic device has an orifice in the piston or at each end of the cylinder so that normal turns made by the car and trailer do not cause sufficient pressure build up to cause either switch to operate. Similar automatic performance can be realized by the use of a gas filled bellows device.

I claim: 
     
       1. A sway control system for controlling brakes of a towed vehicle in response to the detection of a sway condition comprising: a hydraulic unit having first and second ends mounted to coupling means between the towed vehicle and a towing vehicle, which hydraulic unit includes first and second fluid passages associated with said first and second ends of the unit.Iadd., .Iaddend.each passage including a check valve shunted by a bypass restricted orifice and a pressure switch, and   an electric brake circuit for applying and releasing the brakes of the towed vehicle in response to said pressure switches being opened or closed, said hydraulic unit constituting a sway detection device for sensing the onset of a sway condition of a towed vehicle relative to a towing vehicle. .Iadd.   
     
     
       2.  A sway control apparatus for controlling the brakes of a towed vehicle joined to a towing vehicle by a towing connection permitting turning movement of said towed and towing vehicles relative to each other about a yaw axis, said apparatus comprising: signal generating means connected between said towed and towing vehicles for providing a signal having a characteristic responsive to the rate of change of the angle between said vehicles about said yaw axis; and,   actuator means for actuating said brakes in response to said signal, said actuator means being effective to actuate said brakes in response to a single turning movement between said vehicles in either direction about said yaw axis when said rate of angle change exceeds a predetermined magnitude. .Iaddend. .Iadd.3. The apparatus of claim 2 in which said signal generating means includes a first member, a second member movable relative to said first member, coupling means mounted on said towed and towing vehicles for causing said first and second members to move relative to each other as said towed and towing vehicles turn relative to each other about said yaw axis, and sensing means for providing a signal in response to a predetermined rate of said relative movement between said first and second members. .Iaddend. .Iadd.4. The apparatus of claim 3 in which said first member is a cylinder, said second member is a piston slidable in said cylinder, and said coupling means causes said piston to slide in said cylinder as said towed and towing vehicles turn relative to   
     
     
        each other about said yaw axis. .Iaddend. .Iadd.5.  The apparatus of claim 4 in which said piston and said cylinder define a chamber for pressurizing a fluid, and said actuator means includes pressure responsive means for actuating said towed vehicle brakes in response to a predetermined fluid pressure in said chamber. .Iaddend. .Iadd.6. The apparatus of claim 5 in which said sensing means includes conduit means for conveying said fluid between said chamber and said pressure responsive means. .Iaddend. .Iadd.7. The apparatus of claim 6 in which said conduit means includes valves means for controlling the flow of fluid through said conduit means. .Iaddend. .Iadd.8. The apparatus of claim 7 in which said valve means includes a check valve .Iaddend. .Iadd.9. The apparatus of claim 7 in which said valve means includes an orifice. .Iaddend. .Iadd.10. The apparatus of claim 7 in which said valve means is adjustable. .Iaddend. .Iadd.11. The apparatus of claim 6 in which said conduit means includes a first fluid passage containing a check valve for permitting free flow from said chamber to said pressure responsive means while preventing flow from said pressure responsive means to said chamber, and a second fluid passage bypassing said check valve and containing an orifice for restricting flow between said chamber and said pressure responsive means. .Iaddend. .Iadd.12. The apparatus of claim 2 in which said signal generating means includes cylinder means having a first chamber and a second chamber, piston means cooperating with said cylinder means for pressurizing a fluid in said first chamber and said second chamber, and coupling means for causing fluid in said first chamber to be pressurized in response to relative turning movement between said vehicles in one direction about said yaw axis and fluid in said second chamber to be pressurized in response to relative turning movement between said vehicles in the other direction about said yaw axis, and in which said actuator means includes pressure responsive means for actuating said towed vehicle brakes in response to a predetermined fluid pressure in said first and second chambers. .Iaddend.