A compressor and a method of manufacturing the same are disclosed. The compressor includes a piston having formed therein a suction space, in which refrigerant gas is sucked; and a cylinder in which a piston is accommodated, the cylinder defining a compression space that is configured, based on the piston reciprocating in an axial direction, to compress the refrigerant gas therein. A plurality of grooves having a partial spherical shape and having a diameter of 10 micrometers is formed in an outer circumferential surface of the piston or an inner circumferential surface of the cylinder.

A system and process for predicting the failure of a machine begins with the step of loading a slope signature library into the control system, in which the slope signature library correlates time-to-failure based on rates of change of one or more measured conditions. The process includes the steps of activating the machine, determining baseline measurements, and detecting an out-of-spec measurement. Once an out-of-spec measurement is made, the process includes the determination of the rate of change for the out-of-spec measurement. A slope signature is calculated based on the rate of change for the measured condition, which is compared against the slope signature library to determine a predicted time-to-failure based on the calculated slope signature, and outputting the predicted time-to-failure. The process can be used to modify the operation of the machine to extend the predicted time-to-failure.

A linear compressor includes a cylinder, a piston, and a discharge valve, wherein the piston includes a first part extending in the axial direction, a second part having a diameter greater than that of the first part and formed at one end of the first part facing the discharge valve, and a third part having a diameter greater than that of the first part and formed at the other end of the first part. The second part includes a first outer circumferential surface extending backward from a front surface of the piston, and a second outer circumferential surface spaced apart from the first outer circumferential surface in a direction away from the discharge valve, and a distance between the first outer circumferential surface and an inner circumferential surface of the cylinder is less than a distance between the second outer circumferential surface and the inner circumferential surface of the cylinder.

The invention relates to a method and to an apparatus for vibration compensation in a piston compressor, the piston compressor of which is driven by means of a crankshaft by a three-phase motor controlled by a frequency converter, wherein the current position the crankshaft of the piston compressor is determined, and based on this the frequency converter, a torque (M.sub.M) for the three-phase motor is predetermined, which torque follows the load torque (M.sub.L) of the piston compressor in order to reduce the vibration stimulation of the entire piston compressor.

A compressor and a method of manufacturing the same are disclosed. The compressor includes a piston having formed therein a suction space, in which refrigerant gas is sucked; and a cylinder in which a piston is accommodated, the cylinder defining a compression space that is configured, based on the piston reciprocating in an axial direction, to compress the refrigerant gas therein. A plurality of grooves having a partial spherical shape and having a diameter of 10 micrometers is formed in an outer circumferential surface of the piston or an inner circumferential surface of the cylinder.

A fluid-working machine has a plurality of working chambers, e.g., cylinders, of cyclically changing volume, a high-pressure fluid manifold and a low-pressure fluid manifold, at least one valve linking each working chamber to each manifold, and electronic sequencing means for operating said valves in timed relationship with the changing volume of each chamber, wherein the electronic sequencing means is arranged to operate the valves of each chamber in one of an idling mode, a partial mode in which only part of the usable volume of the chamber is used, and a full mode in which all of the usable volume of the chamber is used, and the electronic sequencing means is arranged to select the mode of each chamber on successive cycles so as to infinitely vary the time averaged effective flow rate of fluid through the machine.

The invention relates to a method and to an apparatus for vibration compensation in a piston compressor, the piston compressor of which is driven by means of a crankshaft by a three-phase motor controlled by a frequency converter, wherein the current position the crankshaft of the piston compressor is determined, and based on this the frequency converter, a torque (M.sub.M) for the three-phase motor is predetermined, which torque follows the load torque (M.sub.L) of the piston compressor in order to reduce the vibration stimulation of the entire piston compressor.

A fluid-working machine has a plurality of working chambers, e.g., cylinders, of cyclically changing volume, a high-pressure fluid manifold and a low-pressure fluid manifold, at least one valve linking each working chamber to each manifold, and electronic sequencing means for operating said valves in timed relationship with the changing volume of each chamber, wherein the electronic sequencing means is arranged to operate the valves of each chamber in one of an idling mode, a partial mode in which only part of the usable volume of the chamber is used, and a full mode in which all of the usable volume of the chamber is used, and the electronic sequencing means is arranged to select the mode of each chamber on successive cycles so as to infinitely vary the time averaged effective flow rate of fluid through the machine.

An apparatus and method for controlling a linear compressor and a linear compressor and a refrigerator having the same are provided. The apparatus may include a drive configured to drive the linear compressor based on a control signal, a detector configured to detect a motor current of the linear compressor, an asymmetric current generator configured to generate an asymmetric motor current by applying a current offset to the detected motor current, and a controller configured to generate the control signal based on the asymmetric motor current. The current offset may be changed based on a change in a position of a piston of the linear compressor.

A pumping unit for a machine to distribute concrete includes a pair of cylinders provided with a relative pumping piston movable linearly for a determinate travel to feed the concrete to a determinate circuit to distribute the concrete; and a hydraulic command circuit operatively connected to both the cylinders, to determine an alternate pumping movement of the relative pumping pistons. The pumping unit includes at least a sensor member operatively associated to at least one of the cylinders in order to detect point-by-point one or more data relating to the operating condition of the pumping piston during its movement for the whole travel. The data includes at least one of position, speed, stress and direction of movement of the relative piston.