Patent ID: 7690864

Claim:
A motorized, hydraulic riding trowel for finishing concrete, said riding trowel comprising: rotor means pivotally suspended from said riding trowel, said rotor means comprising a plurality of radially spaced apart blades for frictionally contacting the concrete; steering means for tilting the rotor means to effectuate trowel steering, maneuvering, and propelling; joystick means accessible to a trowel operator for selectively activating said steering means, whereby the operator of the trowel can steer and control the riding trowel hydraulically; one or more hydraulic drive motors for rotating said rotors; primary hydraulic pump means for supplying hydraulic flow under pressure to said drive motors; pump control head means for controlling said hydraulic pump means for supplying flow and pressure to said drive motors; a control head (PCH) control line for controlling said pump control head means; user operated foot-pedal valve means for controlling said primary hydraulic pump means by pressuring said PCH line; and, unloader valve means for dynamically responding to varying friction and load fluctuations encountered in trowel use and generating an unloader pressure signal (UPS), the unloader valve means comprising: unloader pressure signal means for sensing output pressure from said primary hydraulic pump means and deriving said UPS feedback signal when an optimum set point pressure condition occurs; and, pressure control head means for normally conducting fluid from said foot-pedal valve means to said PCH control line and for interrupting normal fluid flow from said foot-pedal valve means to said PCH line in response to said UPS feedback signal.