Patent GB-272424-A (GB)
Title: Improvements in large measuring instruments for machine installations legible at great distances using luminous indicators
IPC: G01D7/04
Filed: 1927-03-08
Abstract: 272,424. Hardingham, G. G. M., (Hartmann & Braun Akt.-Ges.). March 8, 1927. Indicating, optical devices for.-In measuring instruments and meters for use at large power stations the moving elements or meter mechanisms are provided with mirrors and are mounted in large narrow instrument casings having screens upon which the indicating movements are projected by rays of light from suitable sources. The instruments may be fitted with several mirrors from which the light is reflected successfully by the mirrors being formed of differently coloured glass to give a corresponding 'optical indication and to act as a signal. An auxiliary instrument with a distinguishing coloured mirror may be mounted in the casing to give an indication serving as a pilot or limit reading, the auxiliary instrument being under the control of a separate source of power. In Figs. 1 and 2, a single instrument is shown comprising a casing k of angle iron covered with sheet iron, a measuring instrument m with a mirror s mounted in the rear side, and an optical system with a source of light l. A wire or other marker is placed in the path of light to serve as an indicating mark projected on to the opal glass or other screen as shown in Fig. 1. The scale on the glass is preferably mounted in a compartment separate from that of the indicator track and for a plurality of measuring instruments of the same order the tracks are arranged adjacent to one another between side scales as shown in Figs. 4, 8. The instruments may be provided with a plurality of mirrors s<1> - - s<3> Fig. 5 or mirrored surfaces g<1>, g<2> Fig. 6 each having a different coloured glass in the path of the light to distinguish indications above or below certain limiting values. In a modification an auxilary meter mh Fig. 7, may be provided for indicating the limit or correct value, the meter being operated by auxiliary current from a battery and variable resistance w. In Fig. 8 is represented a boiler installation with instruments for six boilers giving the consumption of coal in tons or steam in lbs. per hour, the images fw being the actual instrument readings and the images fr the pilot or limit readings. In order to adjust the meter mechanism in the casing k the securing bolts b, Fig. 9, pass through resilient packing layers i and by tightening or unscrewing of the bolts the mechanism can be positioned so that the track of the image agrees with the scale. The mechanism may be fitted with a rear indicating scale co-operating with a pointer z, a reduction gearing r<1>, r<2> being provided between the pointer and mirror spindle to reduce the angle of oscillation of the mirror. A ground glass cover plate t, placed at an angle so as to reflect the light to the side of the casing, is provided to exclude dust &c. from the meter mechanism. If the measuring instruments are of varied types and for different kinds of variables the instruments may be used as transmitting devices such as m<1> - - m<6>, Fig. 16, which are connected by resistances w<1> - - w<6 >and distance leads to a set of central receivers or quotient meters mz<1> - - mz<6> with optical systems as described above. An arrangement in which the rays of light cross over or cut through one another is shown in Figs. 18 and 19, wherein four images z<1> - - z<4> are projected on to a common track.