Abstract: A boroscope has a first end and a second end, and the first end of the boroscope has an optical fiber and light source. A working head is attached to the first end of the boroscope. The working head has an electrical motor, and a tool is attached to and is arranged to be driven by the electrical motor. The boroscope carries a cable extending from the electrical motor to the second end of the boroscope.

Abstract: A boroscope (60) has a first end (62) and a second end (64) and the first end (62) of the boroscope (60) has an optical fibre (66) and light source (68). A working head (70) is attached to the first end (62) of the boroscope (60). The working head (70) has an electrical motor (72) and a tool (74) is attached to and is arranged to be driven by the electrical motor (72) and the boroscope (60) carries a cable (76) extending from the electrical motor (72) to the second end (64) of the boroscope (60).

Abstract: A sensorless method of detecting piston collisions in a reciprocating free piston linear compressor driven by an electronically commutated linear motor having at least one excitation winding is provided. A free piston gas compressor is also provided.

Abstract: A refrigeration system compressor including a hermetic housing and a linear compressor within said hermetic housing. The compressor includes at least two relatively reciprocating parts, with one part typically being much greater mass than the other part. The relative reciprocation of the centre of mass of each part occurs along an axis of reciprocation. The compressor hangs from a pair of suspension elements. Each suspension element includes a first attachment portion connected to the compressor and a second attachment portion connected to an upper support point above the compressor. A body spans between the first attachment portion and the second attachment portion. The body comprises a flexible planar or linear element, oriented perpendicular to the axis of reciprocation of the compressor.

Abstract: In a refrigeration compressor a pair of suspension elements support a linear compressor within a hermetic shell. Each suspension element includes a hub component is fixed to one of the compressor or shell. A substantially rigid ring is secured to the other of the compressor or shell, an elastic membrane extends across the area of the ring and is secured to the ring around its periphery. The hub component is secured to the membrane at the centre of the ring.

Abstract: A linear compressor comprising has a cylinder part including a cylinder bore. A piston disposed in, and is slidable within, the bore. A main spring connects the cylinder part directly or indirectly the piston. A connecting rod connects between the main spring and the piston. A stator has an air gap, and the connecting rod passes through the air gap. At least one armature pole is located along the connecting rod. Other inventions are also set forth.

Abstract: A sensorless method and apparatus for detecting piston collisions in a free piston linear compressor motor. The waveform of the back EMF induced in the motor stator windings is analysed for slope discontinuities and other aberrations in a time window centred on the back EMF zero-crossings. Waveform slope artefacts are indicative of piston collisions and cause the motor power to be decremented in response.

Abstract: A free piston gas compressor comprising a cylinder, a piston reciprocable within the cylinder and a reciprocating linear electric motor derivably coupled to the piston having at least one excitation winding. A measure of the reciprocation time of the piston is obtained, any change in the reciprocation time is detected and the power input to said excitation winding is adjusted in response to any detected change in reciprocation time.

Abstract: A sensorless method of detecting piston collisions in a reciprocating free piston linear compressor driven by an electronically commutated linear motor having at least one excitation winding is provided. A free piston gas compressor is also provided.

Abstract: A linear compressor includes a cylinder part and a piston part. A spring connects the cylinder part and the piston part and operates in the direction of reciprocation of the piston part relative to the cylinder part. The piston part includes a radially compliant but axially stiff linkage and piston. The cylinder part includes a cylinder and a cylinder liner therewithin. A bore runs through the cylinder liner and the piston reciprocates in the bore. Gas bearing passages are formed between the cylinder and the cylinder liner leading to opening through the wall of the cylinder liner to the bore. A gas bearing manifold receives compressed gases and supplies the compressed gases to the gas bearing passages. The gas bearing passages follow a tortuous path to the openings.

Abstract: A linear compressor has a hollow piston with crown and sidewall. The piston reciprocates in a cylinder. A piston rod connects the piston to a spring. A connection between the piston rod and the piston transmits axial forces directly to the piston crown. The connection transmits lateral forces to the piston at an axial location away from the piston crown. The connection allows rotational flexibility between the piston and the piston rod transverse to and uniformly around the piston reciprocation axis. Other improvements in or relating to linear compressors are disclosed and claimed.

Abstract: A free piston gas compressor comprising a cylinder, a piston reciprocable within the cylinder and a reciprocating linear electric motor derivably coupled to the piston having at least one excitation winding. A measure of the reciprocation time of the piston is obtained, any change in the reciprocation time is detected and the power input to said excitation winding is adjusted in response to any detected change in reciprocation time.

Abstract: A free piston gas compressor comprising a cylinder, a piston reciprocable within the cylinder and a reciprocating linear electric motor derivably coupled to the piston having at least one excitation winding. A measure of the reciprocation time of the piston is obtained, any change in the reciprocation time is detected and the power input to said excitation winding is adjusted in response to any detected change in reciprocation time.

Abstract: A free piston gas compressor comprising a cylinder, a piston reciprocable within the cylinder and a reciprocating linear electric motor derivably coupled to the piston having at least one excitation winding. A measure of the reciprocation time of the piston is obtained, any change in the reciprocation time is detected and the power input to said excitation winding is adjusted in response to any detected change in reciprocation time.