GB622574A - Improvements in and relating to glass tube bending apparatus - Google Patents

Abstract

622,574. Bending glass tubes. BRITISH THOMSON-HOUSTON CO., Ltd. March 28, 1947, No. 8493. Convention date, March 30, 1946. [Class 56] A glass tube is bent sharply into U-form, e.g. to form an envelope of an electric discharge device, by bending the middle heatsoftened part of the tube over an abutment pin. The tube is rotated during the heating of the middle zone, and means are provided for upsetting or thickening the middle zone, preparatory to bending, so that an adequate thickness of glass is obtained on the outside of the final bend. As shown, the tube 12 is gripped at each of its ends by holders 13 which each comprise an L-shaped bracket 14, 15 fixed to shafts 11 which are slidable and rotatable in bearing brackets 9, 10 carried by pivoted arms 1 which initially lie in horizontal alignment, but are swung upwardly towards one another to bend the tube. The shafts 11 are hollow so that slight gas pressure may be supplied through the tube 35 and a connector 34 to the exhaust end 25 of the glass envelope, to prevent the collapse of the heated part. The exhaust end 25' is shown as having been tipped off. A spring 23 acts on a clamp 22 to retain the tube 12 in a V-notch 17 in the holder, the clamp being manually releasable. Pinions 31 on the ends of the shafts 11, of a width to allow for the axial movements of the shafts, mesh with gears 29 on a shaft 30, so that, by oscillation of a handle 33, the tube 12 is rotated during the heating of the middle part by a burner 27. The arms 1 have a common pivot axis through which projects the abutment pin 49, Fig. 5, which is cranked upwardly at 58 to clear the tube 12, a weight 59 ensuring that the part 58 is always uppermost. The pin 49 is urged by a spring 60 into operative position, but is kept retracted during the heating of the tube, by a latch 62 which engages a collar 63 on the pin 49. The latch is under the control of a pedal which is coupled also with a lever 87 which flattens the rubber supply pipes 84, 85 to the burner 27. A hand lever 38, the movement of which is limited by an adjustable stop 48, is coupled by links 40 to upstanding brackets 41 having guide means 45 and bifurcated upper ends which engage collars 43 on the shafts 11, so that by moving the lever 38 the holders 13 are made to approach one another and thus the softened glass is thickened. The shafts 11 are then locked in the bearings 10 by raising pivoted camended levers 53 which bear on the shafts through slots in the bearings, and serve also as handles to swing the arms 1 upwardly. In operation, the pin 49 is latched back, the tube 12 is inserted in the aligned holders 13, the pedal is depressed to release the lever 87 whereby the burner is ignited by a pilot jet, supplied by a pipe 86, and the handle 33 is oscillated to rotate the tube 12 which has been connected to the gas supply pipe 35 to prevent it from collapsing. When the glass is softened, the handle 38 is moved to thicken the glass at the proposed bend, the pedal is released to release the latch and the pin 49, and the lever 87 cuts off the burner supply. The handles 53 are then lifted to clamp the shafts 11 and to swing the levers 1 the mutual approach of which is limited by a stop pin 50 and by spring-pressed balls 51 which engage recesses in the levers and retain them in the raised position. In a modification, the shafts 11 are rotated by a motor through reduction gearing, the motor switch also controlling a magnetic brake. Cam means are provided in connection with the switch to ensure that the stopping position of the holders is correct and that the arms 1 may accordingly be actuated. Specification 622,563 is referred to.