Antifriction assemblies

Abstract

There is disclosed an antifriction assembly of relative moving machine elements such as shaft and thrust bearing or screw and nut assemblies having engagement surfaces formed of materials characterized by a coefficient of friction which is inversely dependent upon compressive loading. Typical of such materials are plastics such as fluorocarbons, polyamides and/or acetal resins. The antifriction assembly utilizes the aforementioned characteristics of these materials to achieve minimal force and wear and maximum life. The shaft and thrust bearing assembly comprises a shaft having a grooved land to receive a bearing plate which has a slotted aperture to capture the shaft. The shaft and bearing are formed of the aforementioned plastics. The screw and nut assembly comprises members that are also formed of the aforementioned plastics. The screw member has external helical threads and the annular nut member has internal helical threads of the same or substantially the same pitch as the external threads and is threadably engaged on the screw member. The external and internal helical threads have distinctly different flank angles to provide a minimal length of thread engagement and a maximum of surface loading. In the preferred embodiment the thread engagement comprises a line spiral contact between the members and is obtained by providing substantially square threads on one of the members and threads with an acute flank angle on the other member.