Roller bearing unit for guiding a linear movement and method of mounting the same

A roller bearing unit for guiding a linear movement essentially comprising;

• a bearing unit body having a flat portion at the upper part and two inwardly inclined projected portions located opposite to one another in a symmetrical relation at the lower part thereof with a longitudinally extending considerably large groove provided therebetween, said flat portion having an upper non-loading roller groove and a lower loading roller groove both of which longitudinally extend in parallel to one another for guiding the movement of rollers, while having curved end parts at both the front and rear ends of said roller grooves for ensuring the circulation of the rollers therethrough, and said inwardly inclined projected portions having stepped parts provided at both the outer non-loading and inner loading sides thereof both of which longitudinally extend in parallel to one another for guiding the movement of the rollers, while having curved end parts at both the front and rear ends of said stepped parts for ensuring the circulation of the rollers therealong,
• a track shaft having a substantially X-shaped cross-sectional configuration to be slidably fitted into said considerably large groove of the bearing unit body, said track shaft containing three sliding surfaces comprising an upper sliding surface on which the loading rollers received in the lower roller groove of the flat portion of the bearing unit body are adapted to roll and both upper inclined sliding surfaces against which the loading rollers carried along the inner stepped parts of the projected portions of the same are adapted to roll,
• an upper retainer fixedly mounted on the flat portion of the bearing unit body for covering the non-loading rollers received in the upper roller groove thereof,
• side retainers fixedly mounted on the projected portions of the same for displaceably carrying the non-loading rollers along the outer stepped parts, and
• a number of rollers adapted to circulate through the roller grooves of the flat portion of the bearing unit body as well as along the inner and outer stepped parts of the projected portions of the same at both the sides thereof.