Remote control circuit for electric trailer brakes

In a tractor/trailer combination having a source of electrical energy wherein said tractor is equipped with a hydraulic brake system and said trailer is equipped with an electric brake system of the type in which brake torque is a function of electric current through an electromagnetic brake coil, a circuit for controlling said coil current comprising a hydraulic transducer operatively connected to said hydraulic brake system to provide a first signal which varies as a function of hydraulic brake fluid pressure, amplifier means having an input and an output to apply said current from said energy source to said brake coils in proportion to said first signal, said input being operatively connected to said hydraulic transducer and said output being connected to said brake coils, means comparing said first signal to a first minimum threshold to provide a second signal when said first signal exceeds said first threshold, and means responsive to said second signal to provide a direct connection between said energy source and said brake coils independently of said amplifier means;

• said hydraulic transducer including a Bourdon tube connected to said hydraulic brake system, linkage means connected to said tube to provide pivotal motion about a first axis as a function of flexure of said tube, and means to provide said first signal as a function of said pivotal motion, said last-named means comprising light emitting means fixedly disposed at a first radial distance from said first axis, light responsive means in alignment with said emitting means along a second axis parallel to said first axis to provide said electrical signal as a function of the intensity of light incident thereon, and shutter means connected to said linkage means to pivot in a plane about said first axis which intersects said second axis between said emitting means and said responsive means, the periphery of said shutter means in said plane having at least a first portion at a radial distance from said axis which is greater than said first distance and a second portion at a radial distance from said axis which is less than said first distance.

In a tractor/trailer combination having a source of electrical energy wherein said tractor is equipped with a hydraulic brake system and said trailer is equipped with an electric brake system of the type in which brake torque is a function of electric current through an electromagnetic brake coil, a circuit for controlling said coil current comprising a hydraulic transducer operatively connected to said hydraulic brake system to provide a first signal which varies as a function of hydraulic brake fluid pressure, amplifier means having an input and an output to apply said current from said energy source to said brake coils in proportion to said first signal, said input being operatively connected to said hydraulic transducer and said output being connected to said brake coils, means comparing said first signal to a first minimum threshold to provide a second signal when said first signal exceeds said first threshold, and means responsive to said second signal to provide a direct connection between said energy source and said brake coils independently of said amplifier means;

• said circuit further comprising an operator-responsive control arm disposed to pivot between first and second limit positions about a fixed axis, light emitting means fixedly disposed on said control arm, light dependent means fixedly disposed with respect to said fixed axis, the intensity of light incident upon said dependent means from said emitting means being a function of pivotal displacement of said control arm between said first and second limit positions, and means operatively connecting said light dependent means to said amplifier input whereby the input current to said amplifier means is a function of pivotal displacement of said control arm between said first and second limit positions.