Patent GB-168636-A (GB)
Title: Improvements in the manufacture of blading for turbines
IPC: B23P15/02
Filed: 1920-05-25
Abstract: 168,636. Parsons, Sir C. A., Carnegie, A. Q., and Bone, M. May 25, 1920. Turbines.-Turbine blades are formed integral with their base pieces by first forming a blank by a series of punching, forging, or like operations and then rolling or drawing a portion of the blank to form the blade. Various methods for obtaining blanks adapted to be rolled or drawn are described. Figs. 1 and 2 show a blank cut from the bar and comprising a base portion a and a portion b from which the blade is rolled. The blank is placed in a two-part insert-piece q, Fig. 3<c>, having a pocket space g corresponding to the base of the blade and fitting in a transverse slot in a forming-bar h, Fig. 4, provided with a longitudinal parallel groove s the bottom of which is of concave section corresponding with the bladeform to be produced and reciprocated beneath an adjustable roll l carried in a frame k, the hardened bottom face n bearing against anti-friction supports o. The portion v of the insert piece may be radiused at wand the surface y serves as an abutment when withdrawing the blade. Backward flow of the metal during the operation is prevented by a slotted stop plate 5 which is held friction tight against the forming- bar by a bolt 6. In a modification three rolls l, Fig. 10, having convex working faces and of such diameter as will give the required reduction may be mounted in a reciprocating frame k. A fixed forming-bar h having a longitudinal groove s has a slidable portion m carrying the blank-holding insert piece q. During the return stroke of the roll-carrier a trigger 1 engages a projection 2 on the movable portion of the forming-bars to withdraw the finished blank. Fig. 30 shows an alternative construction embodying means for preventing tilting of the blank during the operation. The side walls of the guiding-channel are provided on a member s' pivoted to the forming bar c' and operated automatically by a wedge piece w'. The member s<1> is pressed down by tracks l' on the roll l, and after the working stroke of the forming-bar is completed the wedge is driven inwards by a stop x<1>, thus allowing springs t<1> to raise the member s<1> and lifting the insert piece q to eject the blank. During the return stroke mechanism (not shown) raises the roll and returns the wedge to the position shown in Fig. 30. In a further modification, Fig. 29, two rolls l are carried in a reciprocating bar k having hardened strips k' in contact with the forming bar. Pressure is applied by means of pinching-screws M and the finished blade may be ejected by automatically operated pins l<1>. In other process the blank shown in Fig. 13 may be punched from the sheet and pressed by dies 4 into a form suitable for rolling, such a blank requiring less working than that shown in Fig. 1. Or a blank may be cut from a bar of substantially rectangular section and bent to a cranked form. The blade is then rolled and finally the base-piece is pressed to the required shape in a die. In a continuous acting machine, Fig. 35, the former bar is replaced by a disc 3 having a number of blank-holding pockets g in insert segments 9. The roll l has a concave working surface and side flanges which closely embrace the forming-segments and its frame is retained by - cover plates 13 and adjusted by screws 11. The blanks are inserted at the top of the disc and are retained while passing to the roll by a spring- mounted trough. An adjustable stripper piece 12 prevents tilting during the operation and the finished blades are subsequently straightened. The invention is stated to be applicable to the manufacture of blades for either impulse or reaction turbines and, if preferred, the rolling operations above described may be replaced by drawing operations.