GB811261A - Stretch press - Google Patents

Abstract

811,261. Stretch-bending. LALLI, R. A. June 24, 1957 [Sept. 13, 1956], No. 19827/57. Class 83 (4). A stretch press comprises a frame, a heating- box having a heating means disposed therein supported on said frame, a readily removable and replaceable die mounted on said heating- box the die having a contoured surface over which a sheet is adapted to be stretched, clamping means disposed on opposite sides of the die for gripping the margin of the sheet to be stretched and means providing relative movement between said die and clamping means for stretching and permanently shaping the sheet to conform substantially to the contours of the die surface. An open-topped insulated heating- box 18, having heating elements 20 therein, is mounted on a framework 11 and has a readily removable hollow die A fitted thereon. The die A has a contoured portion 23 of sheet steel, both longitudinally and transversely curved, and depending walls 24 open at the bottom and shaped to fit on to a shoulder 22 of the heating- box 18. If a sheet is to be stretch formed over one portion 62 of a die C, Fig. 5, the other flat portion 23c is backed by insulating material 63 to prevent it being heated. A sheet M of, for example, magnesium or titanium is held at opposed edges between clamping jaws 43a, 436 closed by bolts 46. The clamping jaws are connected by links 44 to a bracket 45 on a support 41 linked at 42 to a draw bar 36. The draw bar 36 is supported on springs 35 and guided by pins 34 secured to channel members 32 carried by arms 31 depending from a rod 29 mounted in bearings 30 in the frame 11. The clamping jaws are thus allowed movement about the axis of the rod 29 to adjust for slope of the die in a direction normal to said axis. The clamping jaws are moved downwards to stretch the sheet held thereby over the die by a pneumatically or hydraulically operated piston rod 48 connected to the draw bar 36 and moving in a cylinder 47 connected to the rod 29. Adjustable guide rollers 50 adjacent the edges of the die prevent creasing of the sheet thereover. A thermocouple 61 just under the surface 23 of the die controls the output of the heating means 20.