Abstract: A compressor may include a shell assembly, a first scroll, a second scroll, a piston, and a piston-retention member. The piston engages the first scroll and may be partially received within a recess defined by the shell assembly. The piston and the shell assembly may cooperate to define a pressure chamber. The pressure chamber may be in selective fluid communication with a source of working fluid to control movement of the piston relative to the shell assembly. The piston-retention member may be mounted to the piston and selectively engage a rotationally fixed structure. The piston-retention member allows rotation of the piston relative to the first scroll in a first rotational direction and restricts rotation of the piston relative to the first scroll in a second rotational direction.

Abstract: A compressor may include a shell assembly, first and second scrolls, a piston, and a piston-retention member. The piston engages the first scroll and may be partially received within a recess defined by the shell assembly. The piston and the shell assembly may cooperate to define a pressure chamber. The pressure chamber may be in selective fluid communication with a source of working fluid to control movement of the piston relative to the shell assembly. The piston-retention member may engage the piston and a rotationally fixed structure. The piston-retention member allows rotation of the piston relative to the first scroll in a first rotational direction and restricts rotation of the piston relative to the first scroll in a second rotational direction.

Abstract: A compressor may include a shell assembly, first and second scrolls, a piston, and a piston-retention member. The piston engages the first scroll and may be partially received within a recess defined by the shell assembly. The piston and the shell assembly may cooperate to define a pressure chamber. The pressure chamber may be in selective fluid communication with a source of working fluid to control movement of the piston relative to the shell assembly. The piston-retention member may engage the piston and a rotationally fixed structure. The piston-retention member allows rotation of the piston relative to the first scroll in a first rotational direction and restricts rotation of the piston relative to the first scroll in a second rotational direction.

Abstract: An improvement on phase difference instrumentation wherein an accurate phase difference may be determined between two noisy signals, each of which may have a DC offset, where the measured signals have identical periods.

Abstract: A digital system for measuring a phase relationship between two noisy signals of a given period wherein the phase difference measurement may lie in the range of from 0 to 360 degrees. The noisy signals are amplified and limited so that the processed signal only contains noise in the time vicinity around the zero crossing points. Time interval counters are utilized to measure the time delay between signals and the time period of the reference signal. Phase relationship may be determined by multiplying the ratio of the two digital numbers produced by 360.degree.. Errors in digital outputs are minimized by digitally integrating the counter input during the noisy zero crossover periods. The measurements are completed within two period times of the signals being measured and may be repeated in each of the succeeding two period times.