Patent ID: 6527348
Filing Date: 2003-03-04
Classification: B60T

Abstract:
A braking system for a construction machine having an opertor's cab mounted on a chassis supported in part by an axle having a pair of laterally spaced wheels driven by a power unit through a transmission having an output shaft, said braking system comprising:a fluid pressure applied and spring released service brake operatively associated with each of said wheels; an electrically controlled service valve connected in pressure fluid delivery relation to each of said service brakes; an electrically controlled safety valve connected in pressure fluid delivery relation to said service valves; each of said service and safety valves having flow control elements adjustable between fluid delivery and closed positions; a source of pressure fluid connected to said safety valve; an electric control connected in controlling relation to said service and safety valves including a manually moveable service brake control in said cab, all of said valves being adjusted to a fluid delivery position upon a predetermined movement of said service brake control; a primary electronic control module and a back-up electronic control module; normally inactive electric lines connecting said back-up electronic control module in controlling relation to at least one safety valve and to at least one service valves connected in fluid receiving relation to said safety valve; said service brake control being connected in controlling relation to said back-up electronic control module; a communication link between said control modules causing automatic activation of said normally inactive electric lines connected to said back-up electronic control module upon failure of said primary electronic control module, operation of said service brake control, when said back-up electronic control module is active, causing corresponding adjustment of said safety valve and the associated service valves to their fluid delivery positions; a spring applied and pressure fluid released parking brake operatively associated with said output shaft; a shuttle valve having a pair of inlets and an outlet, said outlet being connected in fluid communication with said parking brake, said source of pressure fluid including a fluid reservoir, first and second accumulators, a pump connected in fluid receiving relation to said reservoir and in fluid delivery relation to said accumulators; a first electrically controlled parking valve connected in fluid receiving relation to said first accumulator and in fluid delivery relation to one of said inlets of said shuttle valve; a second electrically controlled parking valve connected in fluid receiving relation to said second accumulator and in fluid delivery relation to the other of said inlets of said shuttle valve; an electric line connecting said first parking valve to said primary electronic control module; an electric line connecting said second parking valve to said back-up electronic control module; a parking brake switch in said cab; and a pair of signal lines connecting said parking brake switch to said primary and back-up electronic control modules, respectively.