US1794268A - U-tube for vacuum gauges and the like - Google Patents

Description

Feb. 24, 1931. WQQLLEY 1,794,268

U-TUBE FOR VACUUM GAUGES AND THE LIKE Filed Sept. 15 192 Liouid Levei.

Inventor: Raw E, \A/ooHe His flttovnay.

Patented F eh. 24, 1931 UNITED STATES PATENT oFFicE REW E. WOOLLEY, 0F SGHENECTADY, NEW YORK, ASSIGNOR, BY MESNE ASSIGN- MENTS, TO BAILEY METER COMPANY, A CORPORATION OF DELAWARE U-TUBE FOR VACUUM GAUGES AND THE LIKE Application filed September 15, 1924. Serial No. 737,956.

10 stood, however, that this is only by way of example and that my invention may be utilized wherever found applicable.

For a consideration of what I believe to be novel and my invention, attention is di- 15 rected to the accompanying description and the claims appendedthereto.

In the drawing, the figure is a diagrammatic view of a vacuum gauge embodying my invention. 7

Referring to the drawing, 1 indicates a base or pedestal comprising a vertical tube 2 upon the top of which is mounted a casing 3. Casing 3 is closed by a cover plate 4. Mounted inside of easing 3 is a transformer core 5, comprising three legs, the two outer legs being mounted in vertical grooves 6 in casing 8. On the middle leg is arranged a primary winding 7, which is embedded in a cylinder 7 a of suitable insulating material and which at one end is grounded on casing 3, as is indicated at 8. The other end of primary winding 7 projects out through an insulating bushing 9 in cover plate 4, and is connected to one terminal of the transformer winding 10 the other terminal of which is grounded on casing 3, as is indicated at 11. Transformer winding 10 forms the secondary winding of a stepdown transformer which has its primary winding 12 connected by conductors 18, 14 to a source of alternating current of constant potential indicated by the lead wires 15. Primary winding 7' is thus connected to a source of alternating current 15 through the intermediary of the stepdown transformer comprising windings 10 and 12. It is desirable that a voltage of comparatively small value be impressed on winding 7 while the voltage ordinarily met with is of the order of 110 volts or more, and the purpose of the stepdown transformeris to provide a voltage for winding 7 of suitable value. I

Connected to the bottom of easing 3 is a pipe 16, which is located in tube 2 and pro jects down a suitable distance, and at its lower end is connected to the lower end of a vertical pipe or well 17 of relatively large diameter, which is supported by a bracket 17*. Connected to the top of pipe or well 17 is a pipe 18 of relatively small diameter which extends up to a point somewhat above the bplttom of casing 2, and is open to the atmosp ere.

Casing 3 and pipe16'form one leg of a U-tube, the other leg of which is formed by pipes 17 and 18, which may be considered as a single pipe having sections of difierent diameters. This U-tube is filled with a liquid, such as mercury, which is a conductor of electricity, up to a level such that the mercury forms a ring around the lower end of the middle leg of the trzinsformer-core, as is indicated at 19. This is the liquid level indicated in the drawing and represents zero vacuum.

The mercury ring 19 around the middle leg of the transformer core forms a closed secondary winding of a single turn for the transformer comprising core 5 and winding 7, the resistance of which varies in accordance with the depth of the mercury ring. The current flowing in primary winding 7 will be proportional to the resistance of the secondary winding formed by the mercury ring so that as the mercury rises and falls in casing 3 the current flowing in primary winding 7 and hence in the circuit comprising lead wires 13and 14: will vary in accord ance with the depth of the mercury ring. In the circuit comprising lead wires 13 and 1e are suitable electrical measuring instruments, an indicating ammeter 20 and a curve drawing ammeter 21 being illustrated. Gonnected to the upper end of casing 3 is a pipe 22. In use, pipe 22 is connected to the chamher in which the vacuum is to be measured, pipe section 18 being open-to atmosphere. Now, as the vacuum increases, atmospheric pressure acting on the surface of the liquid in the open end of pipe section 18 will force the mercury down pipe sections 18 and 17 and up in casing 3, thereby increasing the roe depth of the mercury ring surrounding the middle leg of the transformer core. This causes an increase in the current flowing in the primary winding which increase in current will be proportional to the increase in the depth of the mercury ring, and since the depth of the mercury ring is proportional to the degree of vacuum, it follows, therefore,

that the current flowing in the circuit comprising lead wires 13 and 1% and transformer winding 7 will be proportional to the vacuum. nstruments 2-0 and 21 may be calibrated in terms of inches of mercury vacuum, in terms of absolute pressure or other suitable terms, and as the vacuum varies, causing the mercury ring in casing '3 to rise and fall, these instruments will measure continuo-usly the value of the vacuum.

- The pipe 16 and the pipe comprising pipe sections 17 and 18 should have a length such that when the mercury is in Zero position, a column of mercury about 30 inches high will be established in pipe sections 17 and 18. The instrument then will be capable of measuring the highest vacuum met with in ordinary commercial practice.

In a great many applications, such as, for example, in measuring the vacuum in turbine condensers, there is little interest in indica ing or measuring accurately vacuums of low value, the thing oat primary importance being to measure the vacuum when of higher value, the vacuum being of higher value all the time except when starting up. The scale deflection of an indicating ammeter, such as that indicated at 20, is necessarily limited, and for this reason it is desirable to use the maj or portion or" the available scale space for indicating the higher-vacuum values so that the unit scale markings may be wide apartand easily read. It is for this reason that pipe section 17 made ofrelatively large diameter and pipe section 18 of relatively small diameter. \Vith .the arrangement shown it will be clear that the initial deflection of the mercury, i. e. the deflection which takes place in pipe section 18, will efiect but a relatively small rise in the mercury in casing 3 and hence but a small increase in the current flowing through the indicating instruments. Hence this part of the deflection will cover but a. small partof the scale oi the indicating instrument. Now, when the deflection begins to take place in pipe section 17 .a much larger volume of mercury will be displaced so that the rise oi the mercury in casing 3 will be much more rapid, thus more rapidly increasing the rate of flow of current through the indicating instruments. For example, the deflection in pipe section 18 may represent vacuum from zero inches of mercury to twenty inches of mercury, and that in pipe section 17 from twenty inches of mercuryto thirty inches of mercury. It will be understood that any suitable relative which indicates the vacuum on ordinary elecdiameters for pipes 17 and 18 may be used to take care of the conditions met with in any particular instance, and also that the one leg may comprise sections of more than two diameters. In any event, the indicating instruments wil hare scale markings to conform to the a'rangement in any particular case.

By my invention, Iprovide a vacuum gauge trical indicating instruments and'these instruments may be placed at any suitable point or points desired. Also it will be clear by using what may be termed the leading leg of the U-tube, pipe sections of different relative diameters, I-am enabled to utilize the major portion of the scale of an indicating instrument for a relatively small portionot the range of the quantity tobe indicated, thereby enabling large easily read markings to be provided on the instrument.

In accordance with the provisions of the patent statutes, 1 have described the principle of operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof, but I desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure :by Letters Patent of the United States is i 1. In an instrument of the character-described, a U-tuloe having'two legs and indicating liquid in said legs, one of said legs comprising a lower section of relatively large diameter and an'u'pper section of small diameter, and theother of said legs having a portion of large diameter in line with the upper end of the upper section-of the first referred to leg, said upper section of the first referred to leg being so small in diameter compared to the diameter of the upper portion of the other leg that when the liquid in such upper section of the first referred to leg is forced downward it affects to but a limited extent the level of the liquid in such other leg, and indicating means actuated by the level of the liquid in the upper portion of such other leg.

' 2. In an instrument of thecharacter described, the combination of a casing, a pipe of small diameter connected to the bottom of said casing, said casing and pipe forming one leg of a U-tube', a second casing adjacent the lower portion of said pipe and connected thereto, apipe of small diameter connected to the top of said second casing, said second casing and pipe forming the otherleg of the U-tube, said second-named pipe being of a diameter so small compared to the diameter of the first-named casing that when indicating 1 liquid is forced out of it, it afiects to but a limited extent the'level of the liquidin said first-named casing. I

3. A U-tube comprising two adjacent parallel logs, the upper portion of one of said legs being of relatively large diameter, indicating liquid in said U-tube, and means associated with said portion or" relatively large diameter for indicating the liquid level therein, the upper portion of said other leg being small com pared to its remaining portion and to said portion of relatively large diameter whereby the initial deflection of the liquid in said other leg afiects to but a limited extent the liquid level in the one leg.

In witness whereof, I have hereunto set my hand this 12th day of September, 1924.

REW E. WOOLLEY.

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