Patent GB-876171-A (GB)
Title: Improvements relating to bearing arrangements for machine tool and other slides
Inventor: GREGSON JOHN
IPC: B23Q1/38
Filed: 1956-12-07
Abstract: 876,171. Fluid bearings. FAIREY CO. Ltd. Dec. 4, 1957 [Dec. 7, 1956], No. 37547/56. Class 12 (1). A vertical-column milling machine comprises a bed 10 having two spaced parallel horizontal slide rails 11, 12 for a carriage 13 with a vertical column 14 which carries a vertically slidable carriage 16 provided with a milling head 15 with its associated motors, gearing and other equipment, and a vertical work-table 19 mounted alongside the bed 10. A pressurized oil circulating system for forcing films of oil between the bearing surfaces of the carriage 13 and the slide rails 11, 12 comprises an oil reservoir 32 for a high pressure pump 33 which forces oil into a pressure vessel 34 having an outlet pipe 35 which delivers it to a system of branch pipes 36-42 connected to the inlets of various passages 43-48 formed in the body of the carriage 13 and leading to delivery ports 50 formed in certain of the bearing surfaces of the carriage 13. Vertical movement of the latter from the slide rails 11, 12 is prevented by two keeper plates 53, 54 secured to the lower longitudinal outer edges of the carriage. Two parallel longitudinal rows of five ports 50 are formed in each horizontal carriage bearing face 26, the corresponding upper surfaces of the rails 11, 12 being provided, between the rows of ports 50, with troughs 30 which act as low pressure outlet conduits for the oil and may be inclined downwardly in one longitudinal direction. Other low pressure oil outlet passages are formed by bevelling the upper edges of the two slide rails as at 29, elongated receptacles 31 being provided on the bed 10 for catching the discharged oil. In each vertical bearing surface 27 and 28 of the carriage wing 24, which co-operates with the wider datum slide rail 11, and also in the upper bearing surface 52 of each keep plate 53, 54, is formed a single row of five delivery ports 50. Each end port, in each row of five, is in the form of a generally rectangular recess 65, the intermediate three ports each comprising a row of three spaced annular grooves 66 which are interconnected by longitudinal grooves 67, the central annular groove having a diametral groove 68. Adjustable oil flow restrictor valves 56, provided at the entrance of each passage 43-48, each comprise a needle valve 56 having a body 60 with a threaded nose 61 which screws into a correspondingly threaded recess at the mouth of the associated passage and an adjustable screw-threaded plunger 57 having a needle which co-operates with a valve seating 59 formed in the body 60. The setting of the restrictor valves 56, the delivery port, and outlet pressures, the clearance between opposed bearing surfaces and the areas of those surfaces are chosen, in practice to suit the particular application, the effect produced by the restrictor valves being that the fluid pressure available between the opposed bearing surfaces to support the applied load is automatically varied to correspond to any variation, e.g. in cutting loads set up during the operation of the machine tool. The delivery ports may each be formed as a frusto-conical flaring mouth, or as a generally rectangular recess defined by a protruding narrow rib. The pressure fluid may be other than oil and even gas, such as air may be employed.