USRE205E - Improvement in steam and vacuum gages - Google Patents

Description

UNITED 'STATES' PATENT OFFICE.

Specification forming part of Letters Patent No. 5,552 dated May 9, 'i848 ;I Reissue No. 205, dated July 29, 185.1.

To all whom it may concern Beit known that I, PAUL STILLMAN, of the city, county, and State of New York, have invented a new and useful improvement in the manometer or gage for determiningthc pressnre of steam and the extent of vacuum in ing drawings, making 'part of this specifica,

tion, in which- Figure lis afi-ont elevation of my improved instrument, with one-half of it represented in section to show the internal arrangement; Fig. 2, a side eleva tion, and Fig. 3 a horizontal section of one ofthe tubes with the surrounding case and scales.

The same letters indicate like parts lin all the figures.

"he iirst part of my invention consists in combining with the reservoirl of -mercury at the lower end ot' the tube ofthe ga gea second reservoir of mercury, elevated above the first and communicating with it. This causes the top of the mercurial column to be visible above4 the open-ing in the case of the instrument when the mercury stands at the lowest possiblel point-viz., in vacuum-gages the point wherea perfect vacuum is indicated; in steamgages the point where an entire absence of pressure is indicated.. y

The second part of my invention consists in placingaround the lower end of the glassk tube a hollow metallic cylinder which screws into the tubeholder above and extends below beyond -the end of the glass tubefar enough to allow a metallic cap to be screwed into its lower end, and\thus close it,l but not so tight as to prevent the mercury from pressingbe tween the threads of the screw. This serves threel purposes: First, as 'a gland to tighten the packing placed 'above its upper end around the glass in. a stuffing-box provided" for the-purpose in the tube-holder; second,A

to protect from injury the end of the glass tube filling of the tube, and to prevent, bythe narrowness of the passage between the threads of the screws, all excessive oscillations of the mercurial column in the tube. To facilitate the passage of tlfe mercury, I tin the threads indicated in the next section.

the methods I adopt to prevent' the water, (arising from condensed-steam,) which almost always rests upon the surface of the-mercury in the reservoir, from insinuating itself into themercurial column. This Ido in two Ways, either, first, by tinning the'exterior of this hollow cylinder spoken of inthe last section, if made of iron, or washing `it with mercury, it of copper, and thus establishing so close an ratlinity between the surface of this cylinder andthe mercury in the reservoir that no water can insiuuate itself between them 5 or, second, by plunging the tube so deeply into the mercury in the reservoir that no water will pass between the mercury and the cylinder.

The last part of my invention consists in my mode of preventing theoxydation ofthe mer-4 cury in the tube, and, consequently, soiling of the glass, which Ido,either, iirst, by intro- Aoxygen-or, second, by filling the tube, not i with atmosphericair, but with some gas which is free from oxygen.

ln the accompanying drawings, A l represents a sole-piece, to which all the main parts the instrument can be secured in place. -From the under surface of this sole-piece project downward two hollow reservoirs, A A', one

diameter inside as to contain the requisite quantity of mercury forthe working of the in'- strumcnt.' To the. upper surface is properly secured a spherical or other formed bulb or chamber, K, which communicates by a hole sole-piece (see dotted lines) with the reservoir A'. A pipe, X, passes through the sole-piece, and extends up into and near the top of the bulb, and' a pipe, J, provided with astop cock,

below the'tubeh01derthira, to emanate um of the screws, which also serves the purposes The third part of my invention consists in the glass tube,and thus tndin g its way aboveducing in to the tube above 'the mercury some fluid-such as naphtha, which contains no of the instrument are attached, and provided`r at the backside with ailange piece, h., by which near each end, and'made of such .length and through the bottom thereof and through the` tight.

is secured to the bottom of the sole-piece, so

as to form a continuation of the pipe X, and

to extend to the boiler or other steam-vessel,

in order that the steam may pass into the bulb or chamber K and `communicate its pressure to the sulface of the mercury conta-ined therein.' The other reservoir, A, communicates by a hole, Z, in the sole-piece with a vertical pipe, 1', also provided with a stop-cock, which -pipe is to communicate with the condenser, or any other vessel in which the degree of exhaustion or vac-unmis to be measured.

In each of the reservoirs A A' is to beinserted the open end vof a glass tube, (l C', the one, C,to measure the degree of exhaustionor vacuum in the condenser, and the other, C',

the pressure of steam in the boiler; and as these tubes are both inserted. in their appropriate reservoirs-in the sameway, the descriptionof oneof them will be sunicient. The glass tube is .inserted fintol a metallic tubeholdcr, B, that is tapped into the upper surface of the sole-piece, and for the purpose of seeuri-ng the glass tube therein suliiiciently tight the lower endv of the holder is enlargedl and tapped so as to form a stuing-box, and to receive the upper end of a hollow: metal cylinder,d, made of iron or copper, and by screwing this up into the lube-holder the packing 'is compressed around-the glass tube. The

lowervend of this metallic cylinder d extends down a little below the end of the glass tube to receive a screw-cap, e, which is either provided with a small hole, f, or-screwed into'the gland with a loose threadso as. to allow suftieient passage for the mercury through it, and thus to establish a communication between the reservoir and thel inside of the tube, yet so small as to prevent-any sudden variation of pressure from producing a. prejudicial degree otl oscillation'. This cylinder d also protects the glass-and facilitates the filling ofthe tube, when used as a vacuum-gage, with mercury,

- `which. is done in the following manner: After the tube'bas been secured lnthe holder' it is inverted and filled with mercury. The screwcap e is then screwed in, and any air that may be in the cy linderd lor cape iindsitsV way out throu ghthe hole f, which should, however, be very small, j ust large enough to permit the y escape of the air, or, what is "more safe, large lenough to admita screw to close itquite sage through the interstices of the screw,

or the hole just gnentioned being. too small to admit the air o 'that-the. operation ot' inverting andl insertdisplace :the mercury, so

p tube into the reservoir v until the proper level has been established, leaving a vacuum; in the upper end, which has been hermetically sealed. Of course,` so long as the pressure in the tube The tube is then turned up again and inserted into the reservoir, 'the' escape of the mercury being prevented by the pasj' is equal to the atmosphere, the mercury will b x sustained in the tube G at the height due .to that pressure; but-as the condenser 1s exhausted the mercury, being unsupported, will t descend .a corresponding amount, and thus show the extent ofy such exhaustion on a scale properly marked and screwed to the metallic -case g, which' partly surrpunds the glass tube, the lower end of which is secured into the upper en( of the tube-holder. As there is no aliinity between the mercury and the surface of the cylinder d, air and moisture .gradually iind their way between the mercury a'nd the surface of the cylinder and through the threads or hole of the screw-cap e, and thence rise into the upper part of the tube, and thus derange 'the instrument. To prevent this, -as I; before stated, 1 tin the outside surface of the cylinder d, if made of iron, or wash it with mercury, it' of copper, in order to establish a sufficient affinity between its surface and the mercury in the reservoir, and thus e'ectually cut oft' the passage of air and moisture.` The other tube, C', is, as stated above, secured in the tubeholder -B in the same manner. It is, however, differently prepared'for use-' that is to say, it is to be filled in part with. air, or anyelastic gas, and in part with mercury. As the instrument is constructed-to act upon the principle of condensing the gas contained within the tube, and as from several causes-such as variation of temperature, or absorption, or decomposition--this quantity is liable to be changed -in volume, it is evident that it should be so constructed that its initial quantity or i 'zero-point should be always determinable.

To eii'ect this end, two methods are pursued, either of which is alike eiiicacious z first, by compressing the 'air within the tube by an elevated column of mercury secondly, by partially exhausting the air or gas from the tube. This I--do by filling the tube with mercury to a-xed point, so that when inverted it shall bg subjected to less than the atmospheric pressure ;V or I` can do it by the use ot au air-pump, from which the desired quantity of air may be exhausted. the bulb be used o r not is .immaterial to this part of my invention, so long as the reservoir 1s of suiiicient depth or capacity to prevent theexpansion of the air in the tube, when the steam 1s ccmdeused in the boiler, from forcing allot` the mercury out of the tube, and so disturbing the zero-point or theinitial quantity Vof gas. The pipeX, which communicates irom the steam-boiler to tlie bulb K, should extend some distance above the level of the mercury vin the bulb, so that when a partial vacuum is effected in the boiler the tension of the air above the mercury in the tube C shall notforce the mercury high enough in the bulb to pass over into the tube X. By the use of this bulb Kit will be seen that a suii'icient column of `mercury may always be kept above the lower end of the tube G to prevent the tension of the air therein from forcing the mercury entirely Vout of it. The steam being admitted to Therefore, whether the bulb orchamber the mercury is forced` of which is indicated by a scale, i, attached to the case. rlhe scales iifor the tubes C C w-ill,

of course, differ, one indicating the vacuum and the other the pressure. The bulb or chamber K is provided with a screw-plug, m,

through which the mercury can be introduced, and with 'another one, l, at the side to regulatethe height to which it is to be llefd. `It a perfect vacuum were nowformed within this bulb or chamber K, the mercurywould fall to the sanie level in the tube as in the bulb or chamber K, which is' out of view. Thus the level Vot' the mercury in the tube, with'a'perfeet vacuum, would always be visible above its insertion in its case. When used for press ure, it is usual to ill them withair, but atmospheric air oxidizes the mercury, and the oxide is attached by the pressure to the surface of the tube, and the consequence is that in a short time the glass becomes so darkened that the level of the mercury cannot be seen. prevent-this, I introduce into the upper part of the glass tube C a few drops of naphtha, or any other liquid which" contains no oxygen or is otherwise inoperatiye upon the mercury, and.

which will iioat on its suri'ace or I charge the tube with any gas that does notcontai-n oxygen, and thus prevent the oxidizing effects of the mercury in the glass tube C of the steam-ga ge, and thus preserve the transparency of the glass. This is not necessary in thevacuum gage as there is a perfect vacuum and, 'of course, no oxygen in the upper part of that tube. i y

As `that part of the instrument which measures exhaustion in the condenser isJnot generall y required to indicate more than twentyeight inches, and therefore only. an approxi mation to a perfect vacuum, I usually make that part 'ot' the instrument without the elevated reservoir, as described above, and represented in the accompanying drawings, because when the mercury is drawn down to the lowest lpoint within the capacity ot' the working of the air-pump the level of the mercury in the tube will be visible in the tube above the place of its insertion in the tube-holder and vreservoir', but when the instrument is to be usedto measure the pressure in a vessel in which a perfect vacuum is to be, then I provide the instrument' with the elevated bulb or c amber K, as described.

That part of the instrument which measures the pressure of the' steam may also be used without the elevatedbulb or chamberK by connecting the reservoir with the boiler or Iother steam-vessel by means of a pipe, jf, in manner similar tothe vacuum-gage described above, in which case the air is partially exhausted, as before described, so as to elevate the mercury at .the zero-point to a place within the tube susceptible of observation.

n maybe wen to aduuianifaesirea, when the bulb or bulbs K are not used the tubes J and J It will beobvious from thel foregoing that4 this instrument may be divided, and that for.

high-pressure steam-eh gines, o r any other pur-A pose which requires only the indication of the pressure of steam, the vacuum gage may be dispensed with, and so of the other part ot' thel instrument; but for condensingengines the entire instru-ment isrequired, as the actual pressure of the steam can only be ascertained by comparing it with the vacuum in the condenser, the ei'ective pressure on the piston belng dependent on this vacuum.

What I claim as my invention, and desire to secure by Letters Patent, lis

1. The combining with the reservoir of mercury at the lower end ofthe tube an elevated chamber forming part of the reservoir, substantially as herein described, so thatthe zeropoint may-be high enough to be visible above the reservoir, as herein described, and also that the air contained in the tube, being condensed bythe pressure of the mercury in the elevated chamber, may furnish more desirable divisions ou the scale when very high pressures are to he indicated. y t

2. '.lhel producing a partial vacuum in the tube of the steam-gage at the time offllling it with mercury, for the purpose of bringing the zero-point high enough to be visible above the reservoir, and also in order to prevent any partial vacuum produced in the boiler from drawing all themercury out of the tube.

3. Surrounding gthe lower end of the glass tube with a metallic cylinder provided with a cap or plug at its lower end for protecting the glass tube, and allowing the mercury only to pass slowly either through a very small hole or` between the threads of the screw, and thus establishing a connection between the reservoir and the boiler, substantially in the manner and for the purpose above specified.

4. The method of preventing the air or moisture from passing between the'mercury and the cylinder cl into the tube, either by tinn'ingthe cylinderV or washing it with mercury, or by plunging -it deeply into 'the mercury, as aboveA described.

5. Preventing the inside of the tube from being soiled with oxidized mercury, by either placing on the surface of the mercury in the tube some tlnid (such as naphtha) which does lnot act perceptibly upon mercury, or by tillin g the tube with gas, as herein made known.

PAUL STILL-MAN. l

Vituesses: I

DANIEL BOWLY, J. L. Bosswon'rn.

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