Abstract: An arrangement of two elements of a sewing machine which are in frictional, or sliding, contact during operation. At least one of elements is formed of a ceramic material and a minute amount of a lubrication oil is applied to the frictional, or siding, portion defining the surfaces in contact. Such a combination of elements is found in the upper looper mechanism, the shuttle body assembly, the needle bar mechanism and the fabric piece feeding mechanism in a sewing machine that are subject to high speed, high load friction or sliding conditions.

Abstract: Disclosed is a hydraulic servomechanism including a control loop consisting of an input device, an adder-amplifier, a servovalve, a cylinder or actuator and a load operatively connected in the order named for controlling the position of the load, a position feedback loop and an acceleration feedback loop. In one embodiment of the invention, the hydraulic servomechanism further includes a feedback loop wherein an output from an accelerometer or pressure sensor for detecting a differential pressure across a piston in the cylinder and an error signal from the adder-amplifier are arithmetically processed and fed back to the adder-amplifier.