Spiral groove bearing

Spiral groove bearings (also known as Rifle bearings) are self-acting (journal and thrust), or hydrodynamic bearings used to reduce friction and wear without the use of pressurized lubricants. They have this ability due to special patterns of grooves. Spiral groove bearings are self-acting because their own rotation builds up the pressure needed to separate the bearing surfaces. For this reason, they are also contacless bearings. Spiral groove bearings (also known as Rifle bearings) are self-acting (journal and thrust), or hydrodynamic bearings used to reduce friction and wear without the use of pressurized lubricants. They have this ability due to special patterns of grooves. Spiral groove bearings are self-acting because their own rotation builds up the pressure needed to separate the bearing surfaces. For this reason, they are also contacless bearings. Spiral groove thrust bearings produce the required pressure to keep the bearing surfaces lubricated and separated purely by the pumping effect of the grooves, whereas journal, conical and spherical forms also get extra pressure generation by the hydrodynamic bearing wedge action. When the parts of the bearings are rotated with respect to each other the grooves push the lubricant through the bearing between the surfaces causing an overall rise in the pressure. The motion of the surfaces will then cause the fluid to flow over the grooves and a pressure ripple, perpendicular to the direction of the motion, is formed. Between the surface of the bearings and the fluid, a net pressure rise occurs because this flow is limited by a plain bearing section or another set of grooves producing a pressure rise that acts to counter the pressure rise created by the first set of grooves (herringbone pattern). At a sufficient speed, the internal pressures create enough force to support the applied load and the bearing surfaces are completely separated. It is the pressure acting perpendicular to the direction of motion that supports the bearing load. Most gases or liquids can be used as the lubricant, including refrigerants, liquid metals, oil, grease, water or air. This explanation neglects the effects of inertia, compressibility of the lubricant and other factors. The dimensions of the grooves are tailored to the intended operating conditions of the bearing. If the indentations on the grooved surface are too deep, then there will be significant leakage of the lubricant. If the depth is reduced, the pump effect will stop. The speed of the rotation of the bearing surfaces and the accuracy of the dimensions must also be taken into account. Designers and manufactures calculate the optimal dimensions for greatest efficiency.The grooves are made by the following methods: