Patent GB-753062-A (GB)
Title: A method and apparatus for forming a true cylindrical surface on an elongated member, such as a crankshaft or a calender roll
IPC: B24B5/42
Filed: 1954-05-03
Abstract: 753,062. Chucks; lathe details. BERRY, E. V. May 3, 1954 [May 11, 1953], No. 12809/54. Class 83 (3). [Also in Group XXIII]- Apparatus for machining a cylindrical surface on an elongated member such as a crankshaft or calender roll, of such length and weight that it tends to sag when supported at its ends, comprises a support 47, Fig. 1, contacting the underside of the member and urged upwards by the piston of a fluid-pressure cylinder 43 so as to support substantially the entire weight of the member, and means for rotating the member when it is engaged by the support. The crank-shaft S, of which the pins P are to be machined, is mounted between chucks 10, 10a on a headstock Hand tailstock T which are axially slidable on a bed B; machining is effected by a power-driven grinding-wheel W mounted on a carriage C which is also slidable on the bed. Each chuck is fixed by a tongue- and-groove connection to a heavy plate 11 arranged for adjustment radially of the crankshaft on a heavy plate 12 rotatable in the headstock or tailstock; the axes of the chucks can therefore be adjusted to and from the rotational axis of the plates 12 so that the pins P, when being ground, can be positioned to rotate about their own axes. To prevent sagging of the crankshaft the supports 47 are arranged as cradles engaging under the main journals 53 of the shaft and have rollers 50, Fig. 5, to contact the journal. Each cradle 47 is carried by rods 46 from the piston-rods 44 of two pneumatic jacks 43 (or, if desired, the piston-rod of a single jack), which depend from a rod 40 supported by hangers 38 adjustable along a superposed rail R. During machining, air from a supply-header 58, Fig. 12, is supplied to the lower ends of each pair of jacks through a reducing-valve 57a and reservoir 55a, the capacity of the latter being large enough to compensate for the variations of pressure in the jacks 43 as the main journals rotate about the axes of the chucks and so prevent a variation of the upward force sufficient to permit deformation of the crank-shaft beyond the tolerance to which it is to be machined. At the same time, in order that the upward pressure on the crankshaft may always be vertical, the rail R is reciprocated transversely of the crank-shaft on its end tracks 32 in time with the rotation of the crank-shaft by hydraulic cylinders 85, 851, Figs. 1 and 12, mounted on the rail and having their piston-rods 87, 871 connected to the tracks 32. The opposite ends of each of these cylinders are connected by pipes 89, 90 in a closed hydraulic circuit with a cylinder 79 (or 791). The two cylinders 79, 791, which are connected together so as to swing about a horizontal axis, have their rods 78, 781 operated by an arm 74 rotated in time with the crank-shaft by the motor M driving the head-stock chuck 10, the piston-rods being connected to a crossbar 77 pinned at any one of a series of radiallyspaced positions on the arm 74. To ensure that the fluid systems are fully charged, and therefore avoid the possibility of the rail R and crankshaft getting out of phase, the air supply header 58, Fig. 12, is connected through pipes 96, 961 to one end of each of two cylinders 93, 931 so that pistons therein are urged towards the opposite ends of the cylinders which at those ends are connected by pipes 98, 981 into the hydraulic circuits between the cylinders 79, 79<SP>1</SP> and cylinders 85, 85<SP>1</SP>. For machining the main journals of a crankshaft, the latter is supported by cradles 47 at all the main journals except the one being ground; the chucks 10, 10a are then positioned to rotate about their own axes and the rail R is not reciprocated. The machine may be used similarly for machining a cylindrical surface on a calender roll.