Abstract: A filter press comprises a main frame having upper side bars for movably supporting a plurality of plates in horizontally stacked relation. The plates are moved to open the filter press by plate transporting trolleys which are supported on the upper side bars. Light emitters are mounted at one end of the press on each side bar and light detectors are mounted at the opposite end of the press on each side bar and are aligned to receive light from the light emitters. Shutters are coupled to the plate transporting trolleys such that the light from the light emitters is normally blocked by the shutters. The shutters are opened for a brief period of time when the plate transporting trolleys are moved into engagement with one of the filter plates such that plate engagement signals are generated by the light detectors.

Abstract: A control mechanism for a hydraulically driven vehicle in which a control member is mounted and linked to forward and reverse actuating pedals such that when one of the directional pedals is depressed the control member body is maintained stationary and an operating shaft is rotated to generate a first directional control signal, and when the other directional pedal is depressed the operating shaft is held stationary and the control member body is rotated to generate a second, opposite directional control signal.