Patent GB-632409-A (GB)
Title: Machine for twisting workpieces such as airscrew blades
IPC: B21D53/88
Filed: 1947-08-05
Abstract: 632,409. Twisting. OILGEAR CO. Aug. 5, 1947, No. 21.259. Convention date April 29, 1940. [Classes 83 (ii), 83 (iii) and 83 (iv)] Making screw propellers.- In a machine for twisting workpieces such as airscrew blades, the work is held by axiallyspaced fixed and rotatable clamps, the latter being yieldingly held in neutral position, but being rotatable under manual control to impart the required twist to the work. The machine comprises a bed 1 carrying guides 8, Fig. 2, in which lugs of the frame 5 of the non-rotary clamp 3 are adjustable by a screw 10 to vary the length of the work W which is to be twisted. The frame 5a of the rotary clamp 4 has arms 40, Fig. 1, connected by links 54 to double-acting hydraulic cylinders 50, 50a which are cross-connected to the fluid supply so that they act simultaneously to rotate the clamp in one direction or the other. Clamp 4 is normally maintained in neutral position by springs 69 acting between the ends of fixed cylinders 68 and rods 72 pivoted at 65 to cylinders 62 on the arms 40, springs 63 in cylinders 62 acting to press rollers 57 against vertical guides 58 to maintain the clamp in a central position during its rocking movements. In order to maintain the torque on the clamp 4 concentric with the axis of the work, the weight of the frame &c. is balanced by a hydraulic cylinder 79 pressing a roller 76 upwardly against an arcuate surface 75 on the frame 5a. Work-holders.-The frame 5a, Fig. 4, of the rotatable clamp 4 has an arcuate surface 44 to receive a cylindrical pad 11a provided with a cylindrical sloping recess 12a in which rests a cylindrical work-engaging jaw 13a. The cylindrical axes of the surfaces are perpendicular so that the jaw may pivot in all directions to align itself with the surface of the work W. The jaw is movable axially along the recess 12a to adjust its upper surface into contact with the work, a dog 14a engaging serrations 15a on the jaw to lock it in the adjusted position. The upper movable jaw 19a carries spherical gripping pads 21a and has a cylindrical upper surface which seats against a similar surface 20a on the vertically movable ram 16a. A dog 46 engages serrations 45 on the jaw after it has engaged the work in order to prevent further rotation under the twisting torque, and the jaw is prevented from falling when out of contact with the work by a pin 23a engaging arcuate slots 24a in the ram. The ram is actuated by a wedge 31a, fitting dovetails on the ram and frame and operated by two singleacting hydraulic plungers 33a, 34a. The non- rotary work clamp 3 is similar to the clamp 4, but the pad 11, Fig. 2, for the lower jaw 13 rests on a flat surface of the frame 5 and the locking dog 46 is omitted. Operation. To impart the required twist to a partly formed propeller blank, the clamp 3 is spaced from clamp 4 according to the length of the work which is to be twisted, the work W is placed in the clamp, the jaws 13, 13a are adjusted to position the work axis coaxial with the clamp 4, and solenoid-controlled valves are actuated to admit fluid from a gear-pump to plungers 33, 33a to close the clamps on the work. A hand lever 84 is then operated to cause a variable delivery pump 80 to supply cylinders 50, 50a and rotate the clamp 4, the direction of movement of the lever determining the direction of rotation, and the movement being stopped when the required twist is reached. If the pressure from pump 80 exceeds that of the gear pump supplying the plungers 33, 33a, a check valve opens to admit the higher pressure to the plungers and increase the clamping pressure on the work. Lever 84 returns to neutral position on release, and on release of pressure to clamp 4 the springs 69 rotate the clamp to normal position. The work may then be moved axially in the clamp to correct the twist of another portion thereof.