Abstract: A 4-axis positioner comprising two 2-axis assemblies sharing a common frame, with a platform connected between them. Each 2-axis assembly comprises a fixed assembly secured or integral to the common frame, two input assemblies secured to the fixed assembly by independently actuated linear motion connections, and a translation assembly secured to the input assemblies by additional linear motion connections. The connections between the input assemblies and the fixed assembly are parallel with one another, and the connections between the input assemblies and the translation assembly are both non-parallel from the connections to the fixed assembly, and non-parallel from one another. The translation assemblies move in two linear axes by common or opposing motion of the input assemblies. The platform is connected to each translation assembly by joints, and moves in two linear axes by common motion, and two rotational axes by opposing motion, of the translation assemblies.

Abstract: A 4-axis positioner comprising two 2-axis assemblies sharing a common frame, with a platform connected between them. Each 2-axis assembly comprises a fixed assembly secured or integral to the common frame, two input assemblies secured to the fixed assembly by independently actuated linear motion connections, and a translation assembly secured to the input assemblies by additional linear motion connections. The connections between the input assemblies and the fixed assembly are parallel with one another, and the connections between the input assemblies and the translation assembly are both non-parallel from the connections to the fixed assembly, and non-parallel from one another. The translation assemblies move in two linear axes by common or opposing motion of the input assemblies. The platform is connected to each translation assembly by joints, and moves in two linear axes by common motion, and two rotational axes by opposing motion, of the translation assemblies.

Abstract: A hysteresis brake including a casing having internal alternating first slots and first teeth, a pole having external alternating second slots and second teeth, a rotor including an annular portion located in spaced relationship between the casing and pole, and structure for permitting the pole and casing to be rotationally adjusted relative to each other and to lock the first slots and teeth of the casing in a rotationally adjusted position relative to the second slots and teeth of the pole to cause the brake to provide a torque output of a substantially predetermined value at a predetermined current. A method of calibrating a hysteresis brake to provide a torque of a substantially predetermined value at a predetermined current including the steps of rotating the casing and pole relative to each other to a position which provides substantially the desired torque at the predetermined current, and locking the casing and pole to each other in that position.

Abstract: A hysteresis brake including a casing having internal alternating first slots and first teeth, a pole having external alternating second slots and second teeth, a rotor including an annular portion located in spaced relationship between the casing and pole, and structure for permitting the pole and casing to be rotationally adjusted relative to each other and to lock the first slots and teeth of the casing in a rotationally adjusted position relative to the second slots and teeth of the pole to cause the brake to provide a torque output of a substantially predetermined value at a predetermined current. A method of calibrating a hysteresis brake to provide a torque of a substantially predetermined value at a predetermined current including the steps of rotating the casing and pole relative to each other to a position which provides substantially the desired torque at the predetermined current, and locking the casing and pole to each other in that position.

Abstract: A computer direct disc drive wherein a hub is mounted on a shaft supported in spaced bearings within a housing with one of the bearings being fixed and the other bearing having an outer race which is free to float both radially and axially and wherein a biasing spring arrangement and a preload sleeve is positioned around the shaft to bias the outer race of the floating bearing away from the fixed bearing, the improvement which consists mounting magnets within the preload sleeve in axially spaced relationship to each other and in radially spaced relationship to the shaft to set up a magnetic circuit through the shaft, preload sleeve and housing to bias the shaft toward the magnets and force the outer race of the floating bearing into engagement with the housing to thereby stabilize it against radial movement while still permitting it to move axially to compensate for thermal variations to which the direct disc drive is subjected.