A ball retainer is provided. The ball retainer includes a chain belt, a hook portion, and a recess portion. The chain belt has a first end and a second end. The hook portion is disposed at the first end. The recess portion is disposed at the second end. An outer circumferential side and an inner circumferential side are formed after the hook portion of the ball retainer is snapped into the recess portion. During operation of the ball retainer after the hook portion is snapped into the recess portion, an acting force is applied to the chain belt so that the hook portion is disengaged from the recess portion. During operation of the ball retainer after the acting force disappears, the first end and the second end of the chain belt approach each other so that the hook portion is accordingly snapped into the recess portion.

A gear device includes an internal gear, an external gear having flexibility configured to partially mesh with the internal gear and relatively rotate around a rotation axis with respect to the internal gear, a bearing disposed at an inner side of the external gear, and a cam section having an elliptical shape disposed at an inner side of the bearing and configured to move a meshing position of the internal gear and the external gear in a circumferential direction around the rotation axis. The bearing is deformed in an elliptical shape by the cam section and includes a plurality of balls disposed side by side in the circumferential direction and a holder including a plurality of partition walls disposed alternately with the balls in the circumferential direction and holding the balls. A gap is provided between the ball located on a major axis of the bearing and the partition wall adjacent to the ball in the circumferential direction. The ball located on a minor axis of the bearing is in contact with each of the partition walls adjacent to the ball at both sides in the circumferential direction.

A flexible bearing cage includes a base ring comprising a plurality of mount sections arranged along a circular path and a plurality of compressible fold sections. One of the compressible fold sections is located between each adjacent pair of the mount sections, and a finger projects axially from each of the plurality of mount sections. Each of the fingers has a partially spherical concave surface configured such that the finger projecting from a first mount section on one side of a first one of the compressible fold sections and the finger projecting from a second mount section on a second side of the first one of the compressible fold sections define a partially spherical cavity configured to receive and retain a respective rolling body.

A ball housing band is provided which can encourage increases in precision and rigidity of a motion guide apparatus and make the motion guide apparatus compact. A ball housing band includes: a housing band including a band formed with ends, the band having at least two rows of opening portions, and a plurality of spacers placed between the opening portions of the rows; and at least two rows of balls housed in the at least two rows of the opening portions. One of adjacent rows of and the other row of the balls are placed in a staggered arrangement in a state where the spacers are disposed between the balls and between the balls. The one row of the balls overlap the other row of the balls as viewed in the length direction of the ball housing band.

A tape-shaped product and a belt for a ball chain are provided. A tape-shaped product of synthetic resin includes a tape of a thermoplastic resin, and a preliminarily stretched fibrous member of a thermoplastic resin contained therein along longitudinally parallel edges or in proximity thereto of the tape. A belt for a ball chain, includes a tape-shaped product of synthetic resin formed by injection molding, together with a fibrous member as an insert of a resin of the same kind as that of the fibrous member so that the fibrous member is disposed along the longitudinal edges or in proximity thereto, ball-insetting holes are disposed at equal intervals, and ball-retaining projections are disposed around the holes.

A flexible bearing cage includes a base ring comprising a plurality of mount sections arranged along a circular path and a plurality of compressible fold sections. One of the compressible fold sections is located between each adjacent pair of the mount sections, and a finger projects axially from each of the plurality of mount sections. Each of the fingers has a partially spherical concave surface configured such that the finger projecting from a first mount section on one side of a first one of the compressible fold sections and the finger projecting from a second mount section on a second side of the first one of the compressible fold sections define a partially spherical cavity configured to receive and retain a respective rolling body.

A flexible cage of a rolling bearing belonging to a wheel hub assembly for motor vehicles, having a substantially circular rib and a plurality of fingers which extend from a side of the rib and have a base portion, the rib and the fingers having partially spherical concave surfaces defining together a plurality of partially spherical cavities for retaining respective rolling bodies. The rib has substantially straight portions, each of them integrally connected to a base portion of a finger, substantially oblique portions and protrusion portions.

A ball housing band is provided which can encourage increases in precision and rigidity of a motion guide apparatus and make the motion guide apparatus compact. A ball housing band includes: a housing band including a band formed with ends, the band having at least two rows of opening portions, and a plurality of spacers placed between the opening portions of the rows; and at least two rows of balls housed in the at least two rows of the opening portions. One of adjacent rows of and the other row of the balls are placed in a staggered arrangement in a state where the spacers are disposed between the balls and between the balls. The one row of the balls overlap the other row of the balls as viewed in the length direction of the ball housing band.

Provided is a motion guide device, which includes: a track rail; rolling elements; a moving block, which has an endless circulation path; and a holding belt having pockets, wherein the holding belt has a pair of end portions opposed to each other through intermediation of a free rolling element in the endless circulation path, and wherein a condition of (XY)Z>(B+C)A>0 is satisfied, where: A represents a path length of the endless circulation path; B represents a total length of the holding belt; C represents a diameter of the free rolling element; X represents a diameter of each of the pockets; Y represents a diameter of each of the rolling elements; and Z represents the number of the rolling elements arrayed in the holding belt.

A flexible cage of a rolling bearing belonging to a wheel hub assembly for motor vehicles, having a substantially circular rib and a plurality of fingers which extend from a side of the rib and have a base portion, the rib and the fingers having partially spherical concave surfaces defining together a plurality of partially spherical cavities for retaining respective rolling bodies. The rib has substantially straight portions, each of them integrally connected to a base portion of a finger, substantially oblique portions and protrusion portions.