Patent GB-1160845-A (GB)
Title: A new or improved Stretch Bending Apparatus
IPC: B21D11/02
Filed: 1968-06-30
Abstract: 1,160,845. Stretch bending. CYRIL BATH CO. 30 Jan., 1968 [31 Jan., 1967], No. 4655/68. Heading B3E. A stretch bending apparatus comprises a pair of gripping heads operable to grip opposite ends of an elongated structural member and movable firstly relatively apart to apply endwise tension to said member and secondly in a direction transversely of the tensioning direction, and a segmental die including a plurality of die segments arranged in a row extending generally parallel to the tensioning direction, means being provided for moving each of the die segments respectively in a direction transverse to the tensioning direction into selected positions and for holding said segments relatively in such selected positions. The machine consists of a bed 1 on which are mounted two similar gripping and stretching units 2, each of which comprises a carrier 3 which is supported by rollers 4 and guided by rollers 4a for movement transversely of the bed, being driven by a lead screw 41 which is rotated by a motor, 44. A support 6 is connected to the carrier 3 by a vertical pivot pin 7, for rotation in a horizontal plane along curved guides 8. Mounted on the support 6 is an inverted U-shaped frame 9, the front and rear ends of which are closed by plates 12 and 12a respectively. Mounted on the front plate 12 by a vertical pivot pin 15 is a gripper head 16 and mounted on the rear plate 12a is an hydraulic cylinder 23, the piston-rod 25 of which is connected by a bracket to the support 6. By pressuring the cylinder the frame 9 can be moved relative to the support, longitudinally of the bed, the frame having guide tracks 18 which run on rollers 19. Each of the units 2 is mounted on a sub-frame 30, which moves longitudinally of the bed on skids 31. The movement is produced by a motor (32), Fig. 3 (not shown), which drives a shaft 35, connected through gearing 36 to two vertical spindles. At the lower end of each spindle is a pinion which meshes with a rack secured to the bed. Die construction. Fig. 8.-Mounted on the bed 1 between the units 2 are a plurality of carriers 50, each slidable in guideways 51, transversely of the bed, and actuated by a lead screw 52, driven by a reversible motor 53. To lock the carriers in a selected position, either the screws are self-locking or brakes are provided. On each carrier is a die segment 54 which is curvilinear about an upright axis. The carriers can be moved by hand or the motors controlling them can each be provided with a servomotor which varies the speed and position of the shaft of the motor 53, the motor shaft in turn driving a feed-back unit which supplies signals to a numerical control unit using a punched programme tape. In forming a member M it is tensioned to above its elastic limit by movement of the piston and cylinder assembly 22 and then the stretching units 2 are moved transversely of the bed to apply the member M against the surfaces of the die segments 54, the gripper heads 16 rotating freely about their pivots. Clamps may be provided which are successively applied to hold the already bent portion of the member as it engages the die segments. Each clamp comprises a shoe 62 pivotally mounted at one end of a ball crank 63 which is actuated by an hydraulic cylinder 67.