GB959665A - Thermometer manufacture - Google Patents

Abstract

<PICT:0959665/C1/1> <PICT:0959665/C1/2> <PICT:0959665/C1/3> <PICT:0959665/C1/4> Apparatus for forming a chamber on a thermometer stem comprises means for clamping the stem in a vertical position, means for heating around the lower end of the stem, means for forcing gas down the bore of the stem to form a chamber and gripping means mounted for vertical reciprocation below and in line with the stem for engaging the bottom end of the heated stem after formation of the chamber to draw out the chamber as the gripping means are lowered. The stem 59 is clamped on a hollow shaft 6 pivoting by means of a handle 13 through about 90 degrees so that the stem 59 lies either over a multi-jet gas burner 17 or gripping means 56. Rigidly fixed to shaft 6 is a stay 10 joined thereto by a yoke 11 and yoke 12 with a projection 14 from which a stud 16 projects to engage either one of two adjustable stops 15 secured on the main frame 1. The stem 59 is held in a clamp, Fig. 3, having a ceramic-lined fixed V-shaped jaw 35 and a movable jaw 36 mounted on an arm pivoted at 37 and actuated by a toggle link 38, lever 39 and spring 40. The clamp is mounted on a slide 5, vertically adjustable on shaft 6 and locked by a screw 8, the slide having a fork 9 to engage the stay 10 to prevent rotation about the shaft 6. An upper slide 5 carries a mounting for an air connection including a hard rubber ring against which the stem 59 is pressed, air being supplied through pipes 46 and 51a under the control of a valve 53 actuated by a button 54 from a compressed air supply. The multijet burner 17, Fig. 2a, has tubular arms 18 passing into a mixing chamber 20 to which gas and air is supplied from a pipe 30 through a tube 19 and an eccentric pipe 23 which is rotatably held in a gas-tight joint 24 on the tube 19, the chamber 20 being rotated by handle 26 to centre the stem 59 and burners 17. The tube 19 is slidably mounted in bushes 25 in plates 1 and 25a and is held in its lower-most position by a spring 29, the movement being limited by adjustable stops 27. The tube 19 is moved upwardly so that the burners 17 surround the lower end of the stem 59 by a lever 32 having a double fork end to engage ball races 34 on the tube 19. After heating of the stem 59, air is passed into the bore of the stem to expand the glass to the shape shown in Fig. 7, the burners 17 being lowered and the shaft 6 provided so that the stem 59 is in line with the tongs 56 which engage the thick end of the stem by sliding rod 57 upwardly against the pressure of spring 58 which then pulls the stem downwardly to draw out the chamber. Later, the chamber is cut off to leave an open, wider bore which is joined to the bulb of the thermometer.