GB825783A - Method and apparatus for treating hollow or tubular workpieces - Google Patents

Abstract

825,783. Making gun barrels, altering physical properties. BASSET, J. F. E. April 12, 1957 [April 27, 1956], No. 12078/57. Classes 83 (2) and 83 (4). A method of pressure treating tubular bodies, e.g. gun barrels, comprises passing an hydraulic pressure medium continuously through said body so as to maintain pressure therein which decreases along the length of the body from a very high value to a lower value, the value being sufficiently high at all points to produce a substantial change in viscosity of the medium. In an embodiment pre-stressing fluid is delivered to the tube T continuously from an hydraulic pump 16 the maximum delivery pressure being limited by an adjustable plug 18. The feed of the pump is adjusted by a speed change device 19 interposed between the motor 20 and the pump. The tube is filled with metal blocks 21 to 25 leaving peripheral gaps of predetermined size. The outlet cap 26 is provided with a flow control valve 27 ensuring an adjustable flow of pressure fluid regulated by a servomotor 28. Pressure gauges 29 and 30 show the pressure on the tube at the inlet and outlet. The pressure fluid comprises a mixture e.g. of two parts gas oil and one part petroleum such mixture becoming viscous at pressures above 3000 k.g. per sq. cm. so that when this mixture is passed at high pressure through a long tube of small diameter at a constant rate of flow considerable pressure differences, namely P1, P2 and P3, are produced and become stabilized along the tube. This pressure distribution is maintained by control means 31 comprising a piston 32 which receives the inlet pressure P1 and a piston 33 which receives the outlet pressure P3 (Fig. 3). These pistons are mechanically opposed by a pivoted beam 34 which is in equilibrium when the pressure ratio is equal to the ratio of the cross-sections of the pistons. If the pressure ratio changes the beam rocks and controls the servomotor by means of the electric contacts 36, 37 to open or close the relief valve 27. The pressure ratio is regulated by adjustable springs 38 and 39 acting on the pistons 32 and 33 respectively. Alternatively, instead - of the springs, the beam axis may be moved mechanically to vary the length of each arm. The beam may be replaced by a frame supporting two windings carrying currents regulated by electric pressure gauges. A wide range of variation of the pressure ratio may thus be obtained merely by adjusting the shunt resistors.