US2313734A - Temperature compensated bubble for panoramic sextants - Google Patents

Description

y March 16,1943.

.J.- :RANE Erm. 2,313,734

TEMPERATURE COMPENSATED BUBBLE `FOR PANORAMIC SEXTANT Ovriginal Filed March 14, 1940 Patented Mar. 16, 1943 UNITED STATES PATENT OFFICE TERIPERATURE COMPENSA'IED` BUBBLE FOR PANORAMIC1 SEXTANTS Carl J. Crane, Shreveport, La., and Samuel M. Burka, Dayton, Ohio 1941, Serial N0. 398,844

2 Claims.

The invention described herein may be manufactured and used by or for the Goverment for governmental purposes, without the payment to us of any royalty thereon.

This application is a division of application Serial No. 323,964, led March 14, 1940 now Patent No. 2,280,798 granted April 28, 1942.

This invention relates to uid levels and particularly to bubble levels used in connection with instruments such as sextants and the like.

It is an object of this invention to provide means for controlling the size of the bubble in a iluid level.

It is another object of this invention to provide means for varying the size of a fluid level bubble at will.

It is a further object of this invention to provide temperature control means for controlling the size of the bubble and for varying its size at will.

Other objects and advantages of the invention will become apparent from the following detailed descriptions of the invention, reference being had to the accompanying drawing wherein:

Fig. 1 is a cross sectional view of the lower portion of a sextant incorporating the present invention;

Fig. 2 is a cross sectional View taken along the lines 2-2 of Fig. 1; and

Fig. 3 is a diagrammatic view of the bubblecell heating circuit.

Referring to the drawing, the bubble-cell 23 received in chamber I8 is operatively positioned in the lower end of the sextant housing 2 in such a manner as to receive image-carrying light rays reflected by mirrors 2| and 22 in reilector chamber I'I. These rays pass through orice I9 and bubble 23 and are reflected by the inclined reflector 34 through lenses 39 so as to be observable in eye piece 31. The eye lens unites in the drum I 6 incorporating the low power lens 39 and the high power lens 4| for observing the images of the observed objects and the bubblecell is as described in the aforementioned application of which this is a division.

(Granted under the act of March 3, 1883, las amended April 30, 1928; 370 0. G. 757) Coming now to the subject matter of the instant invention, bubble-cell 23 is of a conventional and well known construction in which the bubble moves on the under side of the spherical surface of the top cover glass. The uid in the level is of any suitable substance. In view oi the fact that substances suitable for bubble levels are lsulzijected to expansion and contraction under varying temperature conditions, the bubble level is provided with a heating element 30, the temperature of which is controllable by a rheostat 3| adjustable by means of knob 32. Electrical energy for heating purposes may be supplied by a suitable source 33.

As described in the aforementioned application, the bubble-cell is provided with a cross mark 28 to be used for taking bearings; a light 29 for illumination of the bubble; a door 24 for the opening I8; a nut 25 for holding the door closed; a spring 26 carried by the door and adapted to engage a, projection |`I in the bubblecell 23 for positioning the same in the chamber I 8.

It is obvious that various modications can be made without departing from the spirit and scope of the present invention as pointed out in the appended claims.

We claim:

1. A bubble-cell having means by which the size of the bubble may be changed at will, said means comprising an electrical heating circuit including a heating element within the cell and a rheostat for controlling the temperature of the heating element.

2. A bubble-cell having in combination, top and bottom plates of glass between which the bubble is conned, a source of potential, a heating element between the said plates of glass and a rheostat for controlling the temperature of the heating element, said heating element and rheostat being connected in electrical circuit with said source of potential.

CARL J. CRANE. SAMUEL M. BURKA.

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