US2956105A - Packing for counter tube - Google Patents

Description

Oct. 11, 1960 v SSE 2,956,105

PACKINGFOR COUNTER TUBE Filed Sept. 18, 1953 INVENTOQR Otto PR55L United States Patent PACKING FOR COUNTER TUBE Otto Pressel, Carshalton, England, assignor, by mesne assignments, to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Filed Sept. 18, 1953, Ser. No. 381,064

Claims priority, application Great Britain Sept. 24, 1952 "3 Claims. (Cl. 174-59) The invention relates to packing means containing a so-called Geiger Miiller counter tube with a thin window.

So-called counter tubes are widely used for indicating and counting charge particles and radiations. In accordance with the nature of the particles or radiations to be detected, counter tubes of different construction are employed. One of the most widely used counter tubes is known as a Geiger-Muller counter tube and for the sake of simplicity this term is here to be understood to mean any counter tube packed in means according to the invention.

For low-energy radiations, which term is to be understood to include a stream of corpuscular particles, Geiger- Miiller counter tubes are often furnished with a thin window for the passage of this radiation. The window is required to withstand pressure differences between the atmosphere outside the tube and the gas within the tube. Hence, the window is so constructed as to readily cope with said pressure differences, the direction of the overpressure also being considered.

It may, however, happen that the external pressure changes such that the direction of the overpressure is opposite to that occurring in normal conditions. Very often the window cannot withstand such pressures and is broken or becomes detached. The aforesaid conditions frequently occur if tubes, whose pressure is only slightly, for example to 20 cm. mercury, below atmospheric pressure, are forwarded in airplanes flying at considerable heights, with the result that a great many tubes arrive with broken windows and are consequently wasted. This inconvenience might be avoided by forwarding the counter tubes in hermetically closed packing means, but in this case it is very difficult to ascertain whether the counter tubes are intact on arrival without opening the packing. On opening the packing, however, it is often no longer possible to ascertain whether the counter tube was already broken at the instant of packing or whether it was damaged during transport or even on breaking the packing means.

The present invention has for its purpose to pack Geiger-Muller counter tubes with a thin Window in such a manner as to minimize the risk of breakage of the window during unfavorable conditions and to permit the counter tubes either to be tested without opening the packing or to be used inside the packing. The packing means may then act as a filter.

In accordance with the present invention, the packing contains a Geiger-Muller counter tube having a thin window and comprises a thin-walled, hermetically closed metal vessel with an electrically conducting lead-through secured in an insulating wall portion and connected to an electrode of the counter tube inside the packing.

Most counter tubes comprise only two electrodes, viz. an anode and a cathode. According to the invention the two electrodes may be connected to an electrically conducting lead-through insulated from the wall or, as an alternative, one electrode may be electrically 2,956,105 Patented Oct. 11, 1960 ice connected to the wall within the tube. If the counter tube comprises more than two electrodes, for example two insulated lead-through conductors may be employed and connected to two electrodes of the counter tube, the third electrode being connected to the metal wall of the packing.

Since most counter tubes are of elongated cylindrical shape, the packing means according to the invention are preferably shaped as a cylindrical box which is open at one end where it is hermetically closed by an insulating disc through which passes the electrically conducting lead-through.

In order that the invention may be readily carried into effect, it will now be described in detail with reference to the accompanying drawing, given by way of ex ample, and in which the Geiger-Muller counter tube comprises par- ts 1, 2 and 3, the reference numeral 2 designating a cylindrical cathode and the reference numeral 3 denoting the extension of the central anode. The reference numeral 1 denotes an insulating portion, for example made from glass. The cylindrical cathode 2 is provided at one end with a mica window which, as may be seen from the drawing, is protected by means of a rubber cap 4. This cap may be removed when the tube is to be used for measuring purposes, but inside the packing it serves to protect the window.

The counter tube is housed in a cylindrical aluminium box 5 having a bottom 20. The part of the box opposite the bottom 20 is provided with an embossment 9 on which rests an insulating disc 10, for example made from plastic. In order to ensure a hermetic seal, a packing ring 12 is provided between the disc 10 and the embossment 9. The Geiger-Miiller tube is supported by means of members 6, 7 and 8 consisting of sponge rubber. The rubber member 6 is slightly compressed, since the counter tube is slightly forced into the packing on closing the box. Besides by the cmbossment 9, the insulating disc 10 is secured in place by flanging the aluminium box 5 at 11.

The cathode 2 is electrically connected to the wall 5 by means of a wire 18. The anode 3 is electrically connected to the conductive lead-through 13 which is hermetically secured in the member 10. This hermetic seal is ensured by means of a packing ring 16 which is tightened by means of a nut 15 and washer 14. A second nut .17 screwed onto the lead-through 13 permits of establishing an electrical connection with the anode.

Near the bottom 20 of the box 5 its wall is provided with a shallow V-shaped groove 19 where the box is consequently slightly weakened and permits of being easily opened by means of some tool, for example a knife.

What is claimed is:

l. A sealed packing device for a Geiger-Muller tube having a thin window and a plurality of electrodes, comprising a container, means for mounting said tube in said container in spaced relation therefrom, means hermetically sealing said container, and means for electrically testing said tube while it is sealed in said container comprising electrical conductors and means for connecitng said electrical conductor-s from at least two of said electrodes to the outside of said container.

2. A hermetically sealed packing device for a Geiger- Miiller tube having a thin window and a plurality of electrodes, comprising an electrically conductive container having an opening at one end thereof, a plurality of yieldable inserts in said container engaging said tube to thereby space said tube from said container, an electrically insulated closure member for hermetically sealing said container opening, and means for electrically testing said tube while it is sealed in said container comprising a conductive lead-in passing through said closure member and electrically connected to one of said electrodes, and means for electrically connecting another of said electrodes to said container.

3. A hermetically sealed packing device for a Geiger- Miiller tube having a thin glass window and a plurality of electrodes, comprising a metal container having an opening at one end thereof, a plurality of yieldable inserts in said container engaging said tube to thereby space said tube from said container, an electrically insulated closure member for hermetically sealing said container opening, and means for electrically testing said tube while it is sealed in said container comprising a conductive lead-in passing through said closure member and electrically connected to one of said electrodes, and an electrically conductive wire connecting another of said electrodes to the wall of said container.

References Cited in the file of this patent UNITED STATES PATENTS

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