A mechanism of motion comprises a moving part and a guiding part. The moving part and the guiding part comprise at least a raceway coupled and there exists a row of load-carrying balls rolling along the raceway coupled. For each raceway coupled the moving part further provide a return channel as well as a turn-around channel to form a recirculation passage, so that the ball chain can circulate in the recirculation passage and the moving part can therefore continue its slide motion on the guiding part without limit. To avoid collision between and the wear of the balls during the slide motion, a plurality of separators are provided among the balls so as to isolate adjacent balls from each other for reducing noises and frictional resistance, wherein the adjacent separators is formed to have un-uniform thickness so as to isolate the adjacent balls in an unequally spaced manner as disclosed in U.S. Pat. No. 5,927,858. However, because of the clearance between the balls and their neighboring separators, the separators are easy to get tilted, causing an interference with the passing channel and unsmooth running of the slide motion.
Another connecting chain of balls comprises a pair of strip-like connecting member and a multiple spacers, connected to said connecting member and interposed among respective rolling balls; wherein said spacers form a rosary-like shape for receiving the balls. Further, the connecting chain of balls is fabricated by molding flexible resin and able to deflect in the direction perpendicular to a plane defined by the connecting member. However, because of the rigidity of the band-like connecting chain in the transverse direction, the connecting chain cannot be bent effectively in that direction, which forbids effective three-dimensional bending.
To overcome the problem of unsmooth recirculation occurring when the ball chain bending is not on a plane perpendicular to the elongated surface of the connecting chain, linear motion mechanisms such as ball screws or linear guides, as disclosed by U.S. Pat. No. 5,593,064. In that patent, a ball connector comprises a number of balls arranged in one row at predetermined interval; and a flexible connector belt includes four belt members formed in a strip-like shape along peripheral faces of the balls and brought into contact with the plurality of balls; wherein the belt members are connected mutually with other ones of the belt members at intermediaries of the balls contiguous to each other and the connector belt is formed in a shape constrict in comparison with an outer diameter of the ball at positions of the intermediaries connecting the balls. The ball connector is accordingly easy to flex compliantly in any direction at the position and easy to absorb twist operated on the ball connector. This design allows more freedom for the ball connector being bent and twisted, and a smooth slide motion of the ball chain when it is bent deviated from the plane perpendicular to the elongated surface of the connecting chain. However, this invention, since the connector belt is formed in a shape constrict in comparison with an outer diameter of the ball at positions of the intermediaries connecting the balls, that only the top side of four belts falls in the guide grove of the recirculation channel and that the recirculation channel is at least composed of two parts, there must be an engagement section between the two parts, where misalignment could happen. Therefore, every time the top fringe of the four belts pass through the engagement section, they have to be realigned, or the ball connector is easy to get jammed. Moreover, to provide enough flexibility the connecting portion of the belt member should have certain longitudinal length and constriction, such will affect the number of the balls receiving the load and the spacer size negatively. Similarly, the rolling-element hold spacer disclosed by the U.S. Pat. No. 6,247,846 B1 comprises a thick hold section having spherical indents formed on both sides thereof, the thick hold sections being adapted to be interposed between rolling elements and thin bent sections for interconnecting only one thick hold section pair in which the rolling element is to be interposed. The thin bent section can be deflected or twisted in a curved portion of a rolling-element circulation path and the hold spacers which are adjacent to each other with a single rolling element interposed therebetween mutually perform pivotal movement around the rolling element, thereby enabling smooth circulation in three-dimensional change of direction of the rolling elements. However, since the hold spacers are moving independently in the recirculation channel, each of the balls will have to realign itself with the channel when passing through the engagement section between the parts of the recirculation channel, where misalignment could happen and may cause a unsmooth slide motion.