US3727017A

US3727017A - Radioactive timing mechanism

Info

Publication number: US3727017A
Application number: US00321063A
Authority: US
Inventors: C Schlesman
Original assignee: US Department of Navy
Current assignee: US Department of Navy
Priority date: 1952-11-17
Filing date: 1952-11-17
Publication date: 1973-04-10
Anticipated expiration: 1990-04-10

Abstract

2. A radioactive timing apparatus for closing an electrical circuit comprising, in combination, a tubular member, a quantity of electrical conducting fluid mounted in said tubular member, a first volume of gas on one side of said fluid, a second volume of gas on the other side of said fluid, a quantity of radioactive material in said first volume of gas and adapted to increase the first volume as the material disintegrates, and a pair of spaced contacts mounted in said tubular member on the side thereof of the second volume of gas whereby the fluid is caused to move to engage the contacts in a predetermined period of time as the first volume of gas is increased.

Description

United States Patent Schlesman Apr. 10, 1973 [54] RADIOACTIVE TIMING MECHANISM 2,621,268 12/1952 Lindstrom at al. ..200/8l.6

75 I t: C letonH.Schl man,W h' nven or at es as mgton Primary Examiner-Ben am1n A. Borchelt D.C. Assistant Examiner-Robert Kinberg Asslgnefli The ts: b l S; 85 Attorney-R. S. Sciascia and J. A. Corke represen y e retary o the y EXEMPLARY CLAIM [22] Filed: 17, 1952 2. A radioactive timing apparatus for closing an elec- [21] APPL N05 321,063 trical circuit comprising, in combination, a tubular member, a quantity of eiectncai conductmg flu1d mounted in said tubular member, a first volume of gas [52] US. Cl. ..200/8l.6, [02/16, 102/82, on one Side f i fluid, a Second Volume f gas 0n 200/191 the other side of said fluid, a quantity of radioactive [51] III. Cl. .1101]! 29/28 material in Said first volume of gas and adapted to [58] Field 0 Search ..200/81.6, 191, 1522, Crease the first volume as the material disintegrates, 102/16 82 and a pair of spaced contacts mounted in said tubular 1 member on the side thereof of the second volume of [56] Reerences cued gas whereby the fluid is caused to move to engage the UNITED STATES PATENTS COI'IIHC'LS ifn a predetermiged period Of time'as the first vo ume 0 gas 1s mcrease 2,047,427 7/1936 Nyquist... ..200/81.6 2,566,369 9/1951 Putman ..200/81.6 6 Claims, 6 Drawing Figures 1 Y e we I PATENTEBAPR 1 01975 SHEET 2 [IF 2 FIG.6.

STERILIZER FICA.

E H C s H N O T E .L R A C RADIOACTIVE TIMING MECHANISM The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to radioactive timing mechanisms. More particularly the present invention relates to a radioactive timing mechanism capable of resisting high shock forces and for sterilizing a mine after a predetermined period of time has elapsed after the planting thereof.

Prior art devices such, for example, as spring-driven clocks and other such devices have been found to be incapable of resisting the shock forces developed in mines during the laying thereof in shallow water from high-speed aircraft, nor are such devices capable of great accuracy over a long period of time.

The device of the present invention comprises a pair of volumes of gas such, for example, as helium gas enclosed in the very small axial bore of a spiral glass tube. The two volumes of gas are separated in the bore by a small quantity of mercury. One end of the tube (preferably the outer end) is provided with a sealed chamber communicating with the bore, the chamber having contained therein a coiled sheet of thin platinum plated with a quantity of polonium or other radioactive material. It is well-known that as polonium slowly disintegrates, alpha particles are given off in the form of helium gas. It will thus be seen that when the gas generated by the polonium is combined with the gas volume on one side of the mercury the pressure on that side will'rise, and as the pressures equalize on both sides of the mercury, the mercury will move in the direction of the lesser volume or in this case in the direction of a pair of contacts communicating with the interior of the tube. In this manner the contacts are bridged by the mercury when a predetermined amount of gas has been generated by the polonium. Thus a circuit is closed to sterilize the mine. It is, of course, clear that the contacts may be employed to close circuits to perform a variety of functions other than sterilizing a mine.

An object of the present invention is to provide a novel radioactive timing mechanism for sterilizing a mine which has high accuracy over a long period of time.

Another object is to provide a novel timing mechanism for sterilizing a mine which is highly resistant to shock.

Still another object of the invention is to provide a novel timing mechanism for a mine which is positive in operation and simple in construction.

A further object is to provide a novel timing mechanism which is self energized and thus does not cause a drain on the batteries of the device to which it is attached.

. A still further object is to provide a novel timing mechanism in which the timing thereof is readily set during the manufacture thereof.

A still further object is to provide a novel timing mechanism which may be readily adjusted in the field.

Other objects and many of the attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a schematic side elevation of a mine, a portion thereof being broken away and showing the mechanism of the present invention mounted therein;

FIG. 2 is an enlarged sectional view of the device of the present invention;

FIG. 3 is a sectional view taken along the line 33 of FIG. 2;

FIG. 4 is a cross sectional view of the polonium plated scroll;

FIG. 5 is a sectional view of one end of the tube showing a slight modification for adjusting the relative amounts of gas on each side of the mercury; and

FIG. 6 is a diagram of a further modification of the invention.

Referring more particularly to the drawings wherein like numerals indicate like parts throughout the several views, a spirally arranged glass tube is indicated generally at 10 and has an enlarged portion 11 at the outer end thereof and an enlarged portion 12 at the inner end thereof. Spaced from the inner end of tube 10 are a pair of contact members 13 extending through and sealed in the walls of the tube at opposite sides thereof and communicating with small diameter axial bore 14 in tube 10, bore 14 being on the order of 0.3 mm to 0.1 mm or less in diameter. Enlarged portion 11 contains chamber 15 in which is positioned a scroll of sheet platinum l6 plated with a small quantity of polonium 17. Enlarged portion 12 contains a chamber 18 equaling the volume of chamber 15 containing the platinum 16. A small quantity of mercury 19 is positioned in the bore 14 approximately midway of the ends thereof. Equal quantities of helium gas are forced into the bore 14 under a predetermined pressure on both sides of mercury 19. The gas 21 is on the chamber 15 side of the mercury, while gas 22 is on the chamber 18 side thereof.

Certain radioactive materials, as is well known, emit alpha particles in the form of helium at a known rate as the radioactive material disintegrates. Polonium, having a half life of days, is one such material, though it is obvious that other radioactive compounds having a suitable half life may also be employed in this invention.

Gas gradually generated by the polonium plating l7 of scroll 16 within the chamber 15, mixes with gas 21, increasing the pressure thereof. As the pressure of

gases

21 and 22 equalize within bore 14, mercury 19 moves toward contacts 13 compressing gas 22. As the pressure within the tube increases by reason of the gases generated by the polonium 17, mercury 19 moves closer to the contacts 13 and further compresses gas 22 into chamber 18. In the final stage the generated gas reaches a pressure sufficient to move mercury 19 into engagement with contacts 13. At this point a circuit is closed to sterilize mine M in any desired manner such, for example, as shorting the batteries of the mine or flooding the explosive charge thereof, thus to render the mine ineffective.

It is, of course, understood that the device of the present invention may be employed to close an electrical circuit after a predetermined time delay to perform a large variety of functions other than sterilizing a mine.

In order to vary the time constant of the foregoing apparatus the initial quantities of

gases

21 and 22 may be varied with respect to each other. Thus a larger quantity of gas 21 and a smaller quantity of gas 22 will cause mercury 19 to be initially closer to contacts 13 at the start of disintegration of polonium 17 and causing mercury 19 to reach the contacts 13 in a shorter period of time, while if a smaller quantity of gas 21 and a larger quantity of gas 22 are employed mercury 19 will reach contacts 13 in a longer period of time. It is also conceivable that pressure of

gases

21 and 22 may be initially higher or lower thus changing the proportions of the initial gas pressure with respect to the generated gas and causing the contacts to be closed by the mercury after a greater or lesser time delay.

In order to prevent breakage of tube under conditions of great impact force such as when the mine M strikes the surface of a body of water during launching of the mine and when the mine thereafter strikes the bed of the body of water and to provide for visual inspection of the position of the mercury with respect to the contacts, tube 10 is case solidly in a block of clear plastic material 23. It is further contemplated to support the plastic block 23 containing the timing mechanism of the present invention in a quantity of sponge rubber 24 or other suitable shock absorbing material thus to further prevent injury to the mechanism.

The foregoing assembly may be supported in the mine case M in any desired manner such, for example, as by a bracket 50 secured as at 60 to the cover plate of mine M.

The tube 10 is arranged in spiral form for the reason that when subjected to inertia forces the mercury 19 contained therein will not move out of the immediate convolution of the spiral in which it rests, thus preventing a pile-up of the mercury in either of the end chambers or 18 which would permit the gas volumes to by-pass the mercury and thus disturb the desired timedelay. The spiral form has also the advantage of compactness.

In the modification of FIG. 5 one end of the tube 30, which is in the form of a spiral as is tube 10 of the preferred form, is formed with a bulbous portion 31 into which a portion of the long thread of mercury 32 may be deposited when it is desired to shorten the time delay period. In this form of the invention the enlarged portion 33, similar to portion 1 1 of the preferred form, is of appendicular form with respect to tube 30. The neck portion 34 of portion 33 is formed with a bore 35 communicating with bore 36 of tube 30 in spaced adjacency to outer end thereof.

Chamber 37 of enlarged portion 33 communicates with bore 36 through bore 35 and containes the scroll of polonium plated platinum 16 as in the preferred form. Contacts 13 are sealed in tube 30 in spaced adjacency to the inner end thereof. The elongated thread of mercury 32 extends from a point adjacent bulbous portion 31 to a measured distance from contacts 13. A volume of helium gas 38 is positioned between mercury 32 and the inner end of tube 30, while a volume of heliuin gas 39 is positioned between the other end of mercury 32 and the outer end of tube 30. Gas 39 is contained principally in bulbous portion 31 and in enlarged portion 33, the volumes 38 and 39.being sufficient to cause mercury 32 to assume the desired initial position. If desired the position of mercury 32 may be changed with respect to contacts 13 by ejecting a portion thereof into bulbous portion 31. This may be accomplished by any well-known means such, for example, as expanding the gas volume 38 by heat directed at the inner end of tube 30 until the desired amount of mercury has been ejected therefrom.

It is, also, conceivable that a plurality of spaced contacts may be employed as shown in the diagram of FIG. I

6 to vary the time delay incorporated in the device of the present invention. A single contact 41 is sealed in one side of tube 42 which may be of the configuration of tube 10 of the preferred form of the invention, while on the other side of tube 42 is a plurality of

contacts

43, 44, 4S and 46 the first 44 of which is diametrically opposite contact 41, the rest of the

contacts

44, 45, and 46 being spaced successively from the first contact 44 in a direction away from the mercury shown at 47. A selector switch 48 is provided having a switch arm 54 which may selectively engage contacts 1, 2, 3, and 4. These contacts are connected by leads 49, 51, 52 and 53 to

contacts

43, 44, 45 and 46, respectively. Thus the time delay may be increased from the shorter delay selected by setting switch 48 at contact 1 position thereof through contacts 2 and 3 to the longer delay selected by setting switch 48 at the contact 4 position. After mercury 47 engages contact 41 the sterilizer 54 will be energized when the mercury bridges the distance between contact 41 and the selected

contact

43,44,45 or 46.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

l. A radioactive timing apparatus for closing an electrical circuit comprising, in combination, a conduit having closed ends, an electrical conducting element in said conduit in gas tight engagement therewith, a quantity of gas on each side of said element, a quantity of radioactive material on one side of said element and adapted to generate a gas as the material disintegrates and a pair of spaced contacts fixed in said conduit and spaced at predetermined distance from the other side of said element, said element being moved in said conduit to engage said contacts to close the circuit as the gas generated by the radioactive material increases the quantity of gas on one side of said element.

3. A radioactive timing apparatus for sterilizing a mine comprising, in combination, a spiral tubing having closed bulbous inner and outer ends thereon, said tubing having a small axial bore therethrough and communicating with said ends, a quantity of mercury in said bore and having an initial position and an operative position, a first volume of helium gas between said mercury and the outer end thereof, a second volume of helium gas between the mercury and the inner end thereof, a quantity of polonium mounted in said outer end of the tube, a pair of contacts mounted in the tube between the initial position of said mercury and the inner end of said tube, said polonium generating a measured quantity of helium gas which is added to said first volume as the polonium disintegrates, said mercury moving toward the contacts in accordance with the generation of the gas whereby the contacts are bridged thereby at a predetermined time after the initiation of the generation of the gas, and circuit means energized as said contacts are bridged.

4. A radioactive switch closing apparatus comprising, in combination, a glass tubing, a first bulb member formed on one end of said tubing, a second bulb member formed on the other end of said tubing, said tubing having a small diameter axial bore therein communicating with the bulb members, a quantity of radioactive material in the first bulb member, a quantity of mercury in the bore of said tube, a first volume of gas interposed between the first bulb member and the mercury, and a second volume of gas interposed between the second bulb member and the mercury, said mercury assuming a position in said bore where the pressures of the first and second volumes of gas are equalized, said radioactive material mounted in the first bulb member being adapted to generate a gas as the material disintegrates, and a pair of spaced contacts in said bore a predetermined distance from the initial position of said mercury and between the mercury and the second bulb member, said mercury being moved in a direction toward the contacts as the first volume of gas is increased by the disintegration of the radioactive material.

5. A timing apparatus for energizing an electrical circuit comprising, in combination, a tubular member, a first bulb closing said tubular member at one end thereof, a second bulb closing said tubular member at the other end thereof, said tubular member having an axial bore communicating with the bulbs, a bulbous appendage on said tubular member adjacent said first bulb and communicating with the bore, a quantity of radioactive material in said bulbous appendage and adapted to generate a gas as the material disintegrates, a quantity of mercury in said tubular member, a volume of gas in said tubular member on the first bulb 'side' thereof, a second volume of gas in said tubular member on the second bulb side thereof whereby heat may be applied to the second bulb a sufficient length of time to expand the second volume of gas thus to move a measured quantity of the mercury intosaid first bulb to reduce the efiective quantity of mercury in the tubular member; anda pair of contacts in the tubular member and adapted to be bridged by said mercury when the volume of the first volume of gas has increased suffieiently therefor.

6. Sterilizing apparatus for a mine comprising, in combination, a spiral glass tubing having closed bulbous inner and outer ends thereon, a clear plastic block cast about said tubing, the tubing having an axial bore of small diameter therethrough and communicating with the bulbous ends therof, a thread of mercury positioned in the bore, a first volume of gas under predetermined pressure between said outer end and said mercury, a second volume of gas under predetermined pressure between said inner end and said mercury, a measured quantity of radioactive material contained in the outer bulbous end of the tube, a plurality of contacts mounted in the tube and communciating with said second volume of gas a predetermined distance from the initial position of the mercury, said radioactive material generating a measured quantity of gas as the material disintegrates, said generated gas adding to the volume of said first volume of gas whereby the mercury is moved toward the inner end of the tube, a plurality of contacts mounted in said tube adjacent the inner end thereof and communicating with the bore thereof at measured positions with respect to the initial position of the mercury, and means energized as the contacts are bridged by the mercury during the movement thereof toward the inner end of the tube.

Claims

1. A radioactive timing apparatus for closing an electrical circuit comprising, in combination, a conduit having closed ends, an electrical conducting element in said conduit in gas tight engagement therewith, a quantity of gas on each side of said element, a quantity of radioactive material on one side of said element and adapted to generate a gas as the material disintegrates and a pair of spaced contacts fixed in said conduit and spaced a predetermined distance from the other side of said element, said element being moved in said conduit to engage said contacts to close the circuit as the gas generated by the radioactive material increases the quantity of gas on one side of said element.

5. A timing apparatus for energizing an electrical circuit comprising, in combination, a tubular member, a first bulb closing said tubular member at one end thereof, a second bulb closing said tubular member at the other end thereof, said tubular member having an axial bore communicating with the bulbs, a bulbous appendage on said tubular member adjacent said first bulb and communicating with the bore, a quantity of radioactive material in said bulbous appendage and adapted to generate a gas as the material disintegrates, a quantity of mercury in said tubular member, a volume of gas in said tubular member on the first bulb side thereof, a second volume of gas in said tubular member on the second bulb side thereof whereby heat may be applied to the second bulb a sufficient length of time to expand the second volume of gas thus to move a measured quantity of the mercury into said first bulb to reduce the effective quantity of mercury in the tubular member; and a pair of contacts in the tubular member and adapted to be bridged by said mercury when the volume of the first volume of gas has increased suffieiently therefor.