Abstract: The present specification relates to a piston and cylinder arrangement for use in a vehicle disc brake. Such arrangements are either hydraulically or pneumatically operable. In disc brakes the piston and cylinder of the brake actuator are usually sealed against the ingress of dirt, by a flexible boot arranged between the piston and cylinder at the cylinder open end. Additionally a separate pressure seal is advantageously provided between the piston and cylinder. The present invention provides for a flexible boot which engages in retaining grooves provided on the outside of the piston and on the inside wall of the cylinder adjacent to the open end of the cylinder, the part of the flexible boot engaging in the retaining groove in the inside wall of the cylinder, being compressed radially of the cylinder to thus act as a pressure seal between the piston and cylinder. By virtue of this dual function, the piston can be shortened and the weight of the arrangement induced. Also assembly is simplified.

Abstract: A heating system using two liquid heaters of the immersed rotor type is provided for supplying heated liquid to a heat exchanger, and the liquid heaters are alternately connected to and disconnected from the heat exchanger so that the disconnected heater will produce superheated liquid.

Abstract: A friction lining wear indicator for shoe-drum brakes comprising a sensor mounted on a brake shoe, which actuates an indicator when the thickness of a friction lining carried by a platform of the shoe for engagement with a drum is less than a predetermined value. In order to locate the sensor at the most effective position without machining the lining or fastening the sensor permanently to the shoe, the sensor is located by a mounting device located in a depression in an edge of the platform, and co-operates with the shoe to retain the sensor adjacent the lining. The mounting device comprises a plastics plug, or a resilient clip, and the retaining device is releasable. The sensor comprises a wire loop or a pressed insulation-coated metal strip, and may be integral with the mounting device. The sensor and the drum are connected in a circuit with the indicator which is actuated when the sensor touches the drum.

Abstract: In an hydraulic system an unloader valve is disposed in a supply line between a pump and an hydraulic accumulator. The unloader valve is operative to prevent the accumulator from being overcharged and to allow the pump to re-charge the accumulator should the pressure stored therein fall below a desired minimum value. The unloader valve incorporates a control valve comprising a spool and a pressure responsive slave which is operated by fluid pressure under the control of the control valve. The spool is movable between a first position in which the accumulator is isolated from the slave so that pump pressure is supplied to the accumulator and acts through a membrane on a trapped volume of gas under pressure, and a second position in which fluid pressure from the accumulator acts on the slave to unload the pump. The membrane of the accumulator acts directly on the spool to control movement of the spool between the two positions.

Abstract: A hand gun is provided with a trigger operable against the action of a trigger return spring which takes the form of a compression spring received in the stock of the hand gun to thereby provide a resistance which is relatively constant and the compression is adjustable.

Abstract: A variable inductance transducer for use in engineering metrology comprises a plunger with a tip and carried in a housing in linear bearings with a core mounted on the plunger within the overall axial length of the bearings, so as to produce an axially compact structure. The bearings can be two separate ball bushings with the core disposed between them.