Abstract: A positive displacement pump system has first and second delivery passages for pumped fluid and a main delivery passage receiving flow from the first delivery passage and, via a non return valve, from the second delivery passage. A control valve is provided to apportion flow from the first and second delivery passage to an overspill port. A pressure sensitive control orifice is provided in the main discharge passage to receive the combined flows and the control orifice is of variable size.

Abstract: A pump having an inlet port, an outlet port and a pumping mechanism for pumping fluid from the inlet port to the outlet port. The pumping mechanism includes a carrier (2) that is provide with a plurality of pumping of pumping elements. The pumping mechanism also includes a flexible cam ring (6) surrounding the carrier and having an internal cam surface that is followed by the pumping elements. The cam ring is flexible so that the discharge flow rate of the pump can be varied by varying the shape of the cam ring. Also, a control device is provided for controlling the shape of the cam ring. The control device and one or more cam orifices for controlling fluid pressure.

Abstract: A harmonic drive in which the teeth on either or both of the flexspline and internal spline have a modified involute profile with a small contact angle when fully meshed, and considerable tip relief. The former preferably comprises three discs in line on an input shaft which is cranked to a small eccentricity, the center disc eccentricity being diametrically opposite that of the outside pair. Pressure lubricated plain bearings are advantageously used.