US2418379A - Apparatus for establishing a vacuum in manometer-type instruments - Google Patents

Description

April- 1, 1947. c. F. WALLACE APPARATUS FOR ES'JZABLISHING A VACUUM INMANOMETER-TYPE INSTRUMENTS Filed Sept. 14, 1944 lZy INVENTOR. JM/PLES fi 41 441405 Patented Apr. 1,1947

UNITED STATES PATENT OFFICE n APPARATUS roas mett msc A mount:

in MANOMETER-TYPE INSTRUMENTS up Charles F. Wallace, Westfield, 7N. 5., assigfior'to Wallace & Tiernan Products, Inc. Belleville, N. L, a corporation of New Jersey Application September 14, 1944, Serial No. 554,098

3 Claims.

rometers and more particularly to the apparatus for introducing the liquid into the column and establishing thereabove a desired and substantially perfect vacuum. y

In apparatus such as mercury barometer s, for example, it has been necessary in order to obtain the desired vacuum above the mercury, to fill the glass tube completely with mercury and then by holding the same closed, possibly by thumb of the operator over the end thereof or by the use of some other closure, to invert it and introduce the open end into a bath of mercury in a container arranged to be associated with the'lower end thereof. This is inconvenient, to say the least, particularly with sensitive scientific instruments of the type to which the present invention is applicable Furthermore, there is" always the danger of a bubble of air'g'ettinjg into the mercury above the closure when the tube is first filled, so that when it is inverted, this bubble will rise to the upper closed end of the tube and prevent the establishment of the desired vacuum. The same difliculty may also arise if the vacuum is destroyed or diminished for any reason and it is desired to reestablish a desired vacuum. The structure of the present invention and the methods hereinafter set forth for using that structure provides a simple and efficient solution for these problems. The provision of suchapparatus is, therefore, a principal object of the present invention. A further and more detailed object of the present invention is to provide a device whereby dirt or' other foreign matter of a relatively lower specific gravity than that of the liquid (usually mercury) may be kept out of the mercury in the column, the height of which is to be determined, thus enabling more accurate readings to be made than could be done if this foreign matter was allowed to remain and float upon the surface of the liquid.

Other objects and advantages of the present invention will become apparent from the following specification and appended claims when taken in connection with the accompanying drawings, in'which:

Figure 1 is a view principally in elevation, but with parts broken away and in central vertical section showing a mercury barometer constructed in accordance with the present invention, the view being foreshortened for space requirements onthedrawing; and

plied to a mercury baremeter.

- 2 n L V Fi 2 is a detai view substantially in horizontal section o'n line 2-2 of Fig. 1.=-

While-the present inventidri is appucable t0 manometers of various types and further may be employed with liquids other than mercury, I have chosen to illustrate the invention as ap Turning now particularly to the drawings, there is shown a barometer including a base i, which may be formed as a mercury containing chamber and which is provided with a'cover 2 adapted to be secured the'reto in" any suitable manner as by screws 3, the joint between the base I and the cover 2 preferably being" made air-tight in any usual manner. Secured to the cover 3 are a plurality of posts 4, which Support arid are tied together attheir upper ends by a plate 5. This plate is adapted to supportthe-upper enact a tube 6, preferably of glass, which is allliquid I such as mercury, the level of is shown at 8 and isindicative of a gaseous pressure being measured. Thispressure is communicated to the upper pbrtion 0f the chamber Within the base I through a fi'eiiible tube 9' and an angle fitting 19-, it being understate that the 6' extends down below the surface of the bath 6f mercury within the chambered screen in the base I in the usuaf I'Iianrieia A;- suitable scale ll having desired graduations thereon as shown may be s'e-' Cured to the (Edi/er 2" afid the plate 5' in any suitable manner not particularly illustrated in the drawings; but which will be obvious" to those skilled in the art.

A con'ventional filling opening may be provided in the cover 2 and closed by a screw plug I2; It will be understood that mer'cury (or other liquid)- may be introduced into the body thereof within the base l and the d 'eningi thereafter Closed by the plug t2. 7 Means are provided for supporting the tubes,- suchme'aris the present instance in'cluding' the provision of a reduced diameter exte sion 1'3 at the upperend thereof which passes throughand in frictional supporting relation with a resilient member M such as a cork, the outside of which is tapered and is received in a similarly tapered hole in a uppert'ing plate (-5-, which is in turn supported fromthe-plate E'thrdug'h legs l 6-, which may, if desired; be i iteg'ral therewith-.-

Indevicesor this itis necessary that a substantially perfect vacuum be "maintained in a space I! at-the upper end of the tube 6'- above the level 8 or the liquid F therein. The present invention providesapparatus and nietliodsior establishing this vacuum. For this purposeth'er'e extends upwardly I through the closure 1 9 andhas secured to the upper end thereof an operating. knob 22. A-suitable gland packing means indicated generally at '23 is provided for preventing leakage around the valve stem 2| and for maintaining thelvalve stem against undesired movement by providinga fric tional engagement therewith of the packing,

which may be suitably compressed in the usual manner as shown. The underside of the'closur'e.

I9 may be provided with a suitable counter-bore .24, communicating through a lateral bore and a fitting with a flexible tube 26, which is adapted to be connected to a suitable source of vacuum (not shown).

When it is desired to initiate the operation of the apparatus just described, the valve 2| is opened by pulling the knob 22vertically upwardly. The apparatus as a whole may then be tipped sufficiently to reduce. the vertical distance between the surface of the liquid within the body thereof in the base I and a point part way up the 7 upper chamber l8 to permit the liquid level to be raised as hereinafter set forth. A differential pressure is then applied to the opposite ends of the liquid, that is, to the surface of the liquid within the base I outside the tube 6 onthe one' hand and that within the tube 6 on the other, so as to cause theliquid 1 to rise in the tube 6 through the'passage 20 and in the chamber is up to a point within the upper chamber such asthe level 21. Thus there will be a body of the liquid 23 in the upper chamber above the passage 20. The knob 22 is then moved downwardly to move the valve stem through the passage 20, thus eifecting a mercury-tight seal at this-point. Then the differential pressure may be relieved and the apparatus as a whole righted to its normal vertical position, At this time the liquid 1 within the tube 6' will attain its equilibrium level, which may beat the level 8 as shown, so that there will be produced a vacuum in the space I! between the level 8 and the upper end of the tube 6, that is, up to the constricted passage 20. At the same 7 time, a part of the liquid 28 will be retained V the liquid up into the upper chamber by the application of a differential pressure, it willbe understood that this differential pressure may be obtained either by applying a super-atmospheric pressure through the tube 9 into the interior of the chamber formed in the base I or by applying a suitable vacuum through the tube 2Bto the chamber [8 or by some combination of the two. Inthe event that a super-atmospheric pressure is appliedthroughthe tube 9 suificient to cause though .it may involve additional mechanical manipulation. The reason for this may be exemplified in the following way. Let us suppose for example, that it is desired to maintain in the *space- I! a vacuum equivalent to one-onethousandth of an atmosphere pressure. If now 1 a tiny bubble of air were by some inadvertence .trapped within the tube 6 when the level of the liquid was raised as aforesaid so that this bubble did not pass upwardthrough the passage 20 and exhaust'above the level of the liquid, then if the liquid were being raised by pressure applied through the tube 9 and the bubble were formed at atmospheric pressure, the air inthis bubble would; expand about a thousand times upon the liquid attaining its equilibrium level. This would make a substantial difierence in the degree of vacuum resulting from the operation. If, on the other hand, the liquid were caused to'rise through the tube 6 and the passage 20 by the application of vacuum to the tube 26 and a vacuum equiv alent to one-one-thousandth of an atmosphere pressure were applied, which can be done by a good vacuum pump, then any bubble of air trapped above the liquid. would be at the pressure at this point, which would be one-one-thousandth of an atmosphere pressure. If then the opera,- tion were completed as hereinabove taught. this bubble would not substantially interfere with the establishment of the desired vacuum as the air of the bubble would be at such an extremelylow pressure that it would make practically nodifference in the degree of vacuum attained,

Another advantageous result of the operation of the device just described,.and in accordance with the method set forth, is that vin the event thatany foreign material, which is usually ofa lower specific gravity than that of the liquid being employed (usually mercury) such foreign material may be removed from that portionof theapparatus within the tube 6, where it-= is desired to obtain an accurate reading, by the normal operation of renewing the Vacuum as just set forth. This is due, to the fact that such foreign materialwill floatupon the liquid due to the relative specific gravities of the foreign material and the liquid, Thus when the valve, is open and the liquid raised to a level as shown at 21, the foreign materialwill pass upwardly through the'passage 20 and will floatupon the body 28 of the liquid in the upper chamber [8 where it will do no harm If then, the, operation is completed as explained h'ereinabove that portion of the liquid within the tube 6 Will be clean and have a clean surface, thelevel of which may be easily read in any desired manner. V

The type of valve particularly shown in the ace companying drawings, including a substantially cylindrical stem which may be of considerable diameter as shown, is particularly advantageous in order to obtain clearance for the passage of foreign material as just explained, for if the pas sage '20 were very fine, such material might not pass through it when the liquid-ismovedup Wardly into the upper chamber. I contemplate, however, that any suitable type of valve which will be fluid-tight, may be used to close off the passage between the upper chamber and the interior of the tube 6. Many modifications of suitable valves will occur to those skilled in the art.

While there is shown and described herein but one apparatus embodiment of the invention and but a few possible methods of operation thereof, further modifications may be resorted to Within the spirit and scope of the appended claims, which are to be construed validly as broadly as the state of the prior art permits.

What I claim is:

1. In an instrument of the manometer type for the determination of gaseous pressures by the height of a liquid column in a tube at the upper part of which a substantial vacuum is maintained, in combination, means forming an upper chamber adjacent to the upper end of said tube, a passage communicating between said upper chamber and the upper end of said tube, valve means operable from outside the apparatus for controlling communication through said passage, and means for applying a differential pressure to the opposite ends of said liquid column.

2. In an instrument of the manometer type for the determination of gaseous pressures by the height of a mercury column in a tube at the upper part of which a substantial vacuum is to be maintained, and wherein a mercury chamber is provided at the lower end of said tube arranged to be exposed to a gaseous pressure to be determined, in combination, means forming an upper chamber communicating with the upper portion of said tube, means adapted to communicate between said upper chamber and a source of vacuum, means forming a passage between said upper chamber and the upper portion of said tube, and valve means operable from out side said apparatus to open and close communication through said passage between said upper chamber and the upper part of said tube, the aforementioned parts being so constructed and arranged that when it is desired to establish a vacuum in the upper portion of said tube, the entire instrument may be tilted to reduce the vertical distance between the pool of mercury and the upper end of the apparatus, a vacuum may then be applied to said upper chamber with said valve open and the mercury drawn up until a portion thereof is in said upper chamber and said tube, said passage and at least a part of the upper chamber are filled with mercury, said valve may then be closed and the apparatus brought back to its normal vertical position, so that the mercury in said tube will attain its equilibrium level with a vacuum thereabove and a small portion of mercury is maintained in said upper chamber.

3. Apparatus in accordance with claim 1 wherein said tube, said upper chamber and the passage forming means therebetween are all constructed integrally of glass, and wherein said upper chamber is above and in substantially vertical alignment with said tube, and further wherein said valve is formed as a cylindrical stem movable axially of said upper chamber and said tube and forms a mercury-tight seal with the wall. of said passage.

CHARLES F. WALLACE.

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