US1768415A - Vacuum gauge - Google Patents

Description

June 24, 1930. N A 1,768,415

VACUUM GAUGE Filed April '7, 1927 F'Lgl. FL Z.

U Inventor:

Yostnobu Matu n aga.

HLs Attorney.

. Patented June 24, 1930 UNITED STATES PATENT: OFFICE YOSIWOBU KATUNAGA, OI" AZABUKU, TOKYO, JAPAN, ASSIGNOB TO Gm ELEGIRIO COMPANY, A CORPORATION OF NEW YORK vacuum canon Application fled April 7, 1927, skim In.

My invention relates to electric vapor ressure measuring apparatus and its ob-e Ject is to eliminate a troublesome source of error and deterioration previously existing in such devices.

Many vacuum measuring schemes employ an electric conductor which is exposed directly to the vacuum; for example, resistance wires are employed which are heated by a given electric current or at a constant voltgie and the degree of vacuum determin by the variation in resistance of the wire due to the variation in the heat conducting capacity of the surrounding gas 16 residue as the vacuum changes. Where the conductor is exposed directly to the vacuum, I have discovered that the properties of the conductor undergo a change with variations in the vacuum; for exam le, at very low 20 absolute pressures occlu ed gas escapes from the conductor and changes its resistance. As soon as the conductor is again exposedto a higher premure, it absorbs gases. Not only does the resistance of the conductor vary under these chan 'ng conditions, but it also deteriorates. he heat intensity of such a conductor must be reduced to a safe value when exposed to a rfect vacuum which makes its action slug- 80 gish for higher pressures.

I have overcome these difiiculties by mounting the electric conductor or conductors in a chamber sealed from the vacuum. This sealed conductor chamber is then mounted in the vacuum chamber. I prefer to fill the sealed conductor chamber with an inert gas at a suitable ressure so that the conductor may be sa e1 heated to a much higher temperature t an was, heretofore possible. The ressure in the heater chamber remains su stantially constant and deterioration and resistance errors due to variations in pressure are thus avoided. I

The features of my invention which are believed to be novel and patentable will be ointed out in the claims ap ended hereto. Eor a better understandin o my'invention reference is made in the ollowing description to the accompanying drawing which 181,889, 1'111 in- Japan September 7', 1m.

illustrates in Fig. 1a vacuum gauge of the chamber, 11 the heater wire or conductor,

and 12 the inner sealed conductor chamber of my invention.

In Fig. 1 representative of the prior art, the heater wire which has a.high temperature coefiicient of resistance is exposed directly to the vacuum in chamber 10 without any protective covering. A constant electric current is conve ed through conductor 11 through the "lea ng-in wires 13 or a constant voltage is impressed across the conductor an variations of its resistance are measured in any suitable manner. The

heat of the wire is conveyed awayat a rate which varies directly with the absolute pressure, thus varying the temperature and resistance of the conductor. It is at once apparent to those skilled in the art that the amount of gas occluded in the conductor wire will vary depending upon theabsolute pressure. The escape and absorption of the occluded gas of the conductor is a fairly slow process so that this condition changes for a considerable period of time and at a varying rate even after the surrounding pressure becomes constant. This changes the resistances of the conductor and causes its deterioration so that accurate calibration and measurements of vacuum, are practically impossible. directly to a partial vacuum contaming oxygen and other elements tends to oxidize if operated at high temperatures, thus. limitin the efiiciency of the device.

hese disadvantages are overcome by mounting the conductorll in the separate sealed chamber 12'represented 1n the rema1n ing figures of the drawing. This chamber preferably contains an inert gas such as argon nitro en, helium, or the like, in order that e con uctor may be operatedat a high temperature without oxidizing or deterio- The conductor being exposed rating. Variations in resistance due to variations in the occluded gas condition of the conductor are eliminated or reduced to a negligible factor. The heat of the conductor 11 is conveyed rapidly to the outer wall of the chamber 12 which thus exposes a much larger heating area to the vacuum chamber than is possible in Fig. 1. The efiiciency, life, and accuracy of the device is thus very much improved.

In Fig. 2 the inner chamber 12 is supported by integral legs 14; extending to the outer chamber. Both chambers are spherical.

In Fig. 3 the chamber is supported by a I tube 15 which encloses the leading-in wlres In Fig. 4 the outer and inner chambers are tubular in shape.

In Fig. 5 I have shown how the heating chamber and wire may be arranged to have a large surface area with the heater wire 11 in close proximity to the wall of chamber 12. The inner chamber of this modification is preferably made of refractory material such as pyrex glass. This makes a very sensitive device.

Fi 6 shows a further modification and also lllustrates how the vacuum chamber 10 is connected to the vacuum pump or other vacuum chamber 16 of which the vacuum is to be measured. The improvement permits a larger heating current to be used.

The external measuring instruments, relays,

or the like, operated or controlled in response to the vacuum measuring device may, therefore", be more rugged and less expensive than those heretofore used with this class of apparatus.

In accordance with the provisions of the patent statutes, I 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 and described is onl illustrative and that the invention may be carried out by other means. 1

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a vapor pressure measuring s stem an electric pressure measurin unit a apted to be exposed'to a vapor t e pressure of having an appreciable temperature coefiicient of resistance, said gas-filled contalner serving to protect the heater from direct contact with the vapor, the pressure of which which is to be measured, comprlsing an electric heating element having an appreciable temperature coefficient of resistance and a vapor tight container within which said heatmg element is sealed for protecting such element from direct contact with the vapor.

2. In a vapor pressure measuring s stem, an electric pressure measuring unit a apted to be exposed to a vapor the pressure of which is to be measured, comprising a vapor tight sealed chamber containing an inert gas and an electric heater in said chamber

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