Abstract: A fluid compressor 10 comprising a stator 22, having a bore shaped first chamber 26 and an annular second chamber 30, and a piston 18 comprising a central piston rod 36 having a first piston head 44 and a concentrically arranged cylindrical piston sleeve 38 having a second piston head 48. The stator 22 and piston 18 together define a first compression chamber 12, a second compression chamber 14 provided concentrically around the first chamber 12, and a third compression chamber 16 provided concentrically around the first chamber 12 and linearly with the second chamber 14. The compression chambers 12, 14, 16 are interconnected via intercooling conduits 72, 74. A hydraulic actuator 20 is coupled to the piston 18 by a hydraulic ram 82. During left to right movement of the piston 18 fluid enters the third chamber 16 and fluid is compressed in the second chamber 14.

Abstract: A hydraulic compressor arrangement includes hydraulic rams A and B with associated non-return valves. A hydraulic pump, typically electrically operated, provides a pressurized fluid source to operate rams A or B to allow the associated chambers to receive and compress the low pressure gas provided by a valve. The rams A and B alternately compress and allow entry of the gas so as to produce a continuing source of compressed gas by a pipe to a gas storage tank by a quick release coupling. Two stage compression can also be utilized.

Abstract: A fuel burner control system is disclosed which uses a frequency sensitive diode pump circuit fed by a series of input pulses having a repetition rate within a predetermined range. The diode pump circuit produces an output having a direct current component which exceeds a predetermined threshold when the repetition rate of the input pulses is within a predetermined range. A comparator circuit delivers a pulse signal to a fuel control device when the direct current component exceeds a predetermined threshold.

Abstract: A testing circuit for a control system has a two-state input circuit connected across a plurality of switching devices. The input circuit assumes one state when any one of the contacts is closed and the other state when they are all open. An indicator device shows whether the contacts are functioning correctly.