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Glass Spirals for use in Sensitive Pressure Gauges

Glass Spirals for use in Sensitive Pressure Gauges Laboratory and Workhop Notes The Editor invites the submission of contributions to this section. The devices described need not necessarily be original; 10s. is paid for each note published, OY alternatively a limited number of reprints can be supplied. Glass Spirals for use in Sensitive Pressure Gauges. By S. G. YORKE, University of Bristol [MS. recerved I August I 94 j] The mechanism here described has been designed with a view to a Q in. diameter steel rod is welded to the four bearing strips, to the increasing the efficiency and sensitivity of glass spirals and, at the strip holding the metronome, and to the supporting rod on the same time, overcoming many of the difficulties in their making and shield Thus, with very slight adjustment, the complete spindle reproduction. The spiral mounted as a pressure gauge is useful in will revolve freely in the bearings. chemical kinetics research with corrosive gases. It is very superior The guide, G, consists of three turns of A in iron wire wound to the 'spoon' and diaphragm gauges, since it will withstand into the thread of the rod C and fixed to a bearing strip, causing the pressures of the order of 3 atm., and sudden change of about I atm. carbon to travel to the right as it revolves A similar quartz spiral has been described by M. Bodenstein and The spirals are made from tubing prepared from 6 mm. diameter W. Dux.' Hysil tubing which is softened and drawn, whilst blowing, to approximately 1.25 mm. diameter parallel up to 30 mm. from the parent tubing. The wall must be thin enough to crumble easily when gently squeezed between finger and thumb. A length of zj cm. of this tubing, joined to approximately 8 cm. of 6 mm. tube to act as a weight whilst winding, and also for mounting, is required for a spiral of 7 or 8 turns. I cm of the thin end is bent through 90' to put through the hole in the carbon. A coal gas air-oxygen blowpipe flame is directed on the back portion of the iron shield, opposite the hole in the carbon, heating an area of approximately I sq. in. to a cherry red. The bent end of V,II cni the tubing: is anchored through the hole h the carbon, and trhe I1 wire, H, is adjusted to guide and D E B H AJj ?. steady the glass. The carbon and glass are protected from the direct flame by the shield, which also serves as an oven to distribute the heat for even softening of the ii glass. The machine is set in motion Whenthe spiralis wound, Fig. I. Machine for winding glass spirals the mechanism is stopped and, after cooling, the end through the A slightly tapered &in. diameter carbon rod A (Fig. I), on carbon is broken off with forceps. which the glass is wound, has a &in. hole drilled through the By reverse turning of the spindle smaller end. The other end is held in a steel socket B attached to and a gentle side movement of 3 in. of &in. diameter steel rod. The latter IS fixed into a steel the spiral, the glass will slide from rod C, 3 x Q in., on which is cut a right-handed thread, ten threads the carbon. per inch for half of its length, to provide an automatic feed. The Two methods of mounting the other half is drilled $3 in. and slotted to form a cylinder with a spirals are shown in Fig. 2. In in. key-way to allow 14 in. travel along a &in. driving rod the one on the left, the spiral has carrying a +g in. key-pin. A z& in. pulley wheel, E, having a length a pointer sealed to the end at goo of carpet thread wound round it, and weighted, drives the spindle. to the axis of the coil. The de- The speed is controlled at 15-20 rev./hr. by connecting to the flexion of this pointer can be winding spindle of a metronome, D, the spring of which is removed measured directly or against a and the ratchet reversed for resetting the machine. An iron shield, fixed zero pointer as shown. Fig. 2. Methods of mounting F, +in. thick, 3 in. wide, covers the carbon, extending for I in. A more accurate instrument, spirals for use as pressure gauges down the front and 2 in. down the back, leaving $ in. space between the carbon and shield. A vertical supporting rod, +in. in diameter, shown on the right of Fig. 2, has the spiral mounted vertically with a spindle sealed to the end along is welded to the top of the shield, and an adjustable guide wire, H, the axis of the coil supported at the top in a bearing of capillary slides in a block welded on to the bottom of the rear portion. Four pieces of bright mild steel, z& x + x & in., each having a tubing (a). The rotation of the spindle is measured by a beam of & in. hole near one end, are used for bearings as indicated in the light reflected from a galvanometer mirror (b) waxed to the spindle. diagram. Another short piece of bright steel is bolted to the frame To avoid distortion of the light beam, a plain optical window is of the metronome. When the complete assembly is in alinement, fused on to the outer jacket. The recorded deflexion of the light beam of an instrument of this design is at one metre, of the order * M. Bodenstein and W. Dux. Z.phys. Chem. 85, p. 300 (1913). of 4-5 cm. for I cm. of mercury pressure. Making Very Thin Vacuum-tight Glass Windows. By S. ROSENBLUM and R. WALEN, The H. H. Wills Physics Laboratory, University of Bristol and The Curie Laboratory, Paris [MS. received 23 Bly 19451 Recently a method has been described for fusing thin mica windows equivalent to only a few mm. of air, and yet to be vacuum-tight on to glass or metal.' In certain cases it would be an advantage if against a pressure difference of I atm. or more. a slmilar result could be obtained with windows of glass instead The method 1s as follows : A bubble, thin enough to show inter- of mica, and we have recently succeeded in devising a simple ference cok", is first blown on the end of a glass tube, A second method for this purpose. For our experiments it was necessary to glass tube 1s then drawn down to I or 2 mm. internal diameter with obtain windows thin enough to have a stopping power for a-particles thickened walls. Whilst the thickened end is still hot it is brought close to an area of the bubble which, judged by the interference * T. S. Donald, Rev. Sci. Instrum. 13, p. 267 (1942). colours, is of uniform thickness, and light suction is applied at the http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Scientific Instruments IOP Publishing

Glass Spirals for use in Sensitive Pressure Gauges

Yorke, S G
Journal of Scientific Instruments , Volume 22 (10) – Oct 1, 1945
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Copyright
Copyright © IOP Publishing Ltd
ISSN
0950-7671
DOI
10.1088/0950-7671/22/10/404
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Abstract

Laboratory and Workhop Notes The Editor invites the submission of contributions to this section. The devices described need not necessarily be original; 10s. is paid for each note published, OY alternatively a limited number of reprints can be supplied. Glass Spirals for use in Sensitive Pressure Gauges. By S. G. YORKE, University of Bristol [MS. recerved I August I 94 j] The mechanism here described has been designed with a view to a Q in. diameter steel rod is welded to the four bearing strips, to the increasing the efficiency and sensitivity of glass spirals and, at the strip holding the metronome, and to the supporting rod on the same time, overcoming many of the difficulties in their making and shield Thus, with very slight adjustment, the complete spindle reproduction. The spiral mounted as a pressure gauge is useful in will revolve freely in the bearings. chemical kinetics research with corrosive gases. It is very superior The guide, G, consists of three turns of A in iron wire wound to the 'spoon' and diaphragm gauges, since it will withstand into the thread of the rod C and fixed to a bearing strip, causing the pressures of the order of 3 atm., and sudden change of about I atm. carbon to travel to the right as it revolves A similar quartz spiral has been described by M. Bodenstein and The spirals are made from tubing prepared from 6 mm. diameter W. Dux.' Hysil tubing which is softened and drawn, whilst blowing, to approximately 1.25 mm. diameter parallel up to 30 mm. from the parent tubing. The wall must be thin enough to crumble easily when gently squeezed between finger and thumb. A length of zj cm. of this tubing, joined to approximately 8 cm. of 6 mm. tube to act as a weight whilst winding, and also for mounting, is required for a spiral of 7 or 8 turns. I cm of the thin end is bent through 90' to put through the hole in the carbon. A coal gas air-oxygen blowpipe flame is directed on the back portion of the iron shield, opposite the hole in the carbon, heating an area of approximately I sq. in. to a cherry red. The bent end of V,II cni the tubing: is anchored through the hole h the carbon, and trhe I1 wire, H, is adjusted to guide and D E B H AJj ?. steady the glass. The carbon and glass are protected from the direct flame by the shield, which also serves as an oven to distribute the heat for even softening of the ii glass. The machine is set in motion Whenthe spiralis wound, Fig. I. Machine for winding glass spirals the mechanism is stopped and, after cooling, the end through the A slightly tapered &in. diameter carbon rod A (Fig. I), on carbon is broken off with forceps. which the glass is wound, has a &in. hole drilled through the By reverse turning of the spindle smaller end. The other end is held in a steel socket B attached to and a gentle side movement of 3 in. of &in. diameter steel rod. The latter IS fixed into a steel the spiral, the glass will slide from rod C, 3 x Q in., on which is cut a right-handed thread, ten threads the carbon. per inch for half of its length, to provide an automatic feed. The Two methods of mounting the other half is drilled $3 in. and slotted to form a cylinder with a spirals are shown in Fig. 2. In in. key-way to allow 14 in. travel along a &in. driving rod the one on the left, the spiral has carrying a +g in. key-pin. A z& in. pulley wheel, E, having a length a pointer sealed to the end at goo of carpet thread wound round it, and weighted, drives the spindle. to the axis of the coil. The de- The speed is controlled at 15-20 rev./hr. by connecting to the flexion of this pointer can be winding spindle of a metronome, D, the spring of which is removed measured directly or against a and the ratchet reversed for resetting the machine. An iron shield, fixed zero pointer as shown. Fig. 2. Methods of mounting F, +in. thick, 3 in. wide, covers the carbon, extending for I in. A more accurate instrument, spirals for use as pressure gauges down the front and 2 in. down the back, leaving $ in. space between the carbon and shield. A vertical supporting rod, +in. in diameter, shown on the right of Fig. 2, has the spiral mounted vertically with a spindle sealed to the end along is welded to the top of the shield, and an adjustable guide wire, H, the axis of the coil supported at the top in a bearing of capillary slides in a block welded on to the bottom of the rear portion. Four pieces of bright mild steel, z& x + x & in., each having a tubing (a). The rotation of the spindle is measured by a beam of & in. hole near one end, are used for bearings as indicated in the light reflected from a galvanometer mirror (b) waxed to the spindle. diagram. Another short piece of bright steel is bolted to the frame To avoid distortion of the light beam, a plain optical window is of the metronome. When the complete assembly is in alinement, fused on to the outer jacket. The recorded deflexion of the light beam of an instrument of this design is at one metre, of the order * M. Bodenstein and W. Dux. Z.phys. Chem. 85, p. 300 (1913). of 4-5 cm. for I cm. of mercury pressure. Making Very Thin Vacuum-tight Glass Windows. By S. ROSENBLUM and R. WALEN, The H. H. Wills Physics Laboratory, University of Bristol and The Curie Laboratory, Paris [MS. received 23 Bly 19451 Recently a method has been described for fusing thin mica windows equivalent to only a few mm. of air, and yet to be vacuum-tight on to glass or metal.' In certain cases it would be an advantage if against a pressure difference of I atm. or more. a slmilar result could be obtained with windows of glass instead The method 1s as follows : A bubble, thin enough to show inter- of mica, and we have recently succeeded in devising a simple ference cok", is first blown on the end of a glass tube, A second method for this purpose. For our experiments it was necessary to glass tube 1s then drawn down to I or 2 mm. internal diameter with obtain windows thin enough to have a stopping power for a-particles thickened walls. Whilst the thickened end is still hot it is brought close to an area of the bubble which, judged by the interference * T. S. Donald, Rev. Sci. Instrum. 13, p. 267 (1942). colours, is of uniform thickness, and light suction is applied at the

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Journal of Scientific Instruments – IOP Publishing

Published: Oct 1, 1945

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