GB1246303A - Apparatus and method for photographic recording of instrument readings - Google Patents

Abstract

1,246,303. Optical apparatus. N. A. DE BRUYNE. Oct. 15, 1969 [Oct.24, 1968], No. 50539/68. Heading G2J. [Also in Division G1] Apparatus for determining the melting point of a substance comprises (i) a mercury-in-glass thermometer 5 in a bath 4 controlled by a thermostat, itself controlled to change the temperature of the bath at a predetermined rate, the mercury column reflecting a beam of light on to a mirror 11A which is moved angularly at a predetermined rate to reflect the beam continuously and progressively across a photographic plate 11C, the graduation markings of the thermometer scale creating lines of contrast, (ii) a transparent tube 6 (containing a sample of a substance which, in melting, shows a phase change between opacity and transparency) supported in the bath 4 so that light from a small lamp 7 is beamed thereon and gated by the specimen (through a flexible light-pipe 8) so as to be incident upon the mercury column of the thermometer 5 and to be reflected thereby to the mirror 11A and thence to the plate 11C. In the course of a test, before the temperature reaches the anticipated melting point, a cable button 40, Fig. 6, is pressed and a cable 40A (a) closes a micro-switch 44 ((i) to start a motor (25) and operate a clutch (23) for driving the mirror 11A, and (ii) to light lamp 7, producing the beams for reflection) and then (b) opens the camera shutter by means of a cable 41 which is retained by a detent until released by an electromagnet 43. The graduation marks of the thermometer scale cause corresponding parallel temperature graduation lines to be recorded and movement of the mercury meniscus causes a sloping line of demarcation between the parts of the plate exposed and unexposed to the first beam as a record of the changing temperature. When the specimen becomes transparent light from a lamp 7 reaches the pipe 8 and emerges as a second beam impinging on the mercury column for reflection via the mirror 11A on to the plate whereon the beginning of a continuous line marks the phase change and comparison with the sloping line enables the temperature to be read. Towards the end of the drive of mirror 11A by motor (25) a micro-switch (26) is closed to switch on a lamp (16) and start a motor 27 which turns the thermometer 5 to "roll" on to the plate 11C a record of the scale numbers, finally closing a micro-switch 33 to cause electromagnet 43 to remove the detent from cable 41 so that the camera shutter closes and the micro-switch 44 opens. Several specimen tubes each with a lamp 7 and light-pipe 8 may be immersed in the same bath 4 and the apparatus may be used to calibrate a thermostatic control.