US2741706A

US2741706A - Ionization-measuring instrument

Info

Publication number: US2741706A
Application number: US445796A
Authority: US
Inventors: Futterknecht Rudolf
Original assignee: NASSAU DISTRIBUTING CO Inc
Current assignee: NASSAU DISTRIBUTING CO Inc
Priority date: 1954-07-26
Filing date: 1954-07-26
Publication date: 1956-04-10
Anticipated expiration: 1973-04-10

Description

April 10, 1956 FUTTERKNECHT 2,741,706

IONIZATION-MEASURING INSTRUMENT 2 Sheets-Sheet 1 Filed. July 26, 1954 INVENTOR: RUDOLF FUTTERKNECHT AGENT April 1956 R. FUTTERKNECHT 2,741,705

IONIZATION-MEASURING INSTRUMENT 2 Sheets-Sheet 2 Filed July 26, 1954 INVEN TOR: RUDOLF FUTTERKNECHT AGENT States Patent r 2,741,705 Egg Patented Apr. 10, 1956 HEN iZATION -MEASURIN G INSTRUIVIENT Rudolf Futterlrnecht, Stuttgart, Germany, assignor to Nassau Distributing Co., Inc., New York, N. Y., a corporation of New York Application July 26, 1954, Serial No. 445,796

15 Ciaims. (Cl. 250-8316) My present invention relates to an ionization-measuring instrument of the general type disclosed in my U. S. Patent No. 2,646,516, issued July 21, 1953.

Instruments of the type referred to include a sealed charge generator comprising a set of dielectric pellets movable within a housing and adapted to produce, by their movement, a charge across a pair of condenser plates which can be read by a suitable indicating device, such as as electrometer. The two condenser plates define an ionization chamber Whose atmosphere, when ionized by impinging radiation, will cause a gradual dissipation of the charge at a rate determinable by means of the indicator.

In my co-pending application Ser. No. 356,278, filed May 20, 1953, I have disclosed an improved version of such instrument wherein the charge generator is adapted to be locked, preferably by magnetic means, in a reading position in which a first condenser, representing a charging capacitance associated with the generator, is efitectively disconnected from a second condenser, representing a storage capacitance associated with the indicating device. The presence of this charging capacitance, however small, introduces an element of uncertainty in that it afiects the magnitude of the charge stored after a finite number of charging operations (shakings or inversions).

An important object of my present invention is to provide an improved instrument of the general character referred to in which the aforementioned charging capacitance is substantially eliminated by short-circuiting after each charging step and in which stray capacitances of a similar character are practically eliminated.

Another important object of this invention is to introduce substantial simplifications in the construction of such instrument.

In accordance with the instant invention 1' provide a charge generator in the form of a preferably cylindrical housing, of dielectric material, within which the aforementioned pellets are movable by gravity or inertia between two extreme positions and which is provided with means for establishing a conductive path between the generator and one or the other condenser plate in one or the other extreme position, respectively. As in the system of my above-identified co-pending application, the generator is preferably provided with magnetic locking means for immobilizing it in a reading position in which the circuit to at least one of the condenser electrodes is permanently broken.

The invention will be more fully described with reference to the accompanying drawing in which:

Fig. 1 is a view, in axial section, of an ionizationmeasuring instrument according to the invention, shown in partially discharged condition;

Fig. 2 is a view similar to Fig. 1 but showing the instrument in the process of charging by shaking or inversion, the same being illustrated, however, in upright position for easier comparison with Fig. 1;

Fig. 3 is a sectional View taken on the line 3-3 of Fig. 1;

Fig. 4 is a cross-sectional view taken on the line 4-4 of Fig. 1;

Fig. 5 is a cross-sectional view taken on the line 55 of Fig. 2; and

Fig. 6 is a cross-sectional view taken on the line 6-6 of Fig. 1.

Throughout the several views of the drawing I have used, so far as applicable, the same reference numerals as in my co-pending application Ser. No. 356,278 to designate similar parts.

The instrument shown in the drawing comprises a housing composed of a tubular central body 10 of insu lating material, a cap 11 of similar but highly transparent material, and a base 12 of insulating material. The body 10 is internally lined, over substantially its entire length, with a metallic coating 18 constituting one of the plates of a charge-storing condenser, the other condenser plate being represented by a similar coating 15 on a dielectric insert 16 which is press-fitted inside body 19. A plastic piston 21, comprising an upper disk 21a, a lower disk 21b and a connecting tube 21c, is slidably mounted within insert 16 by means of an axially extending metal rod 121 traversing the tube 210. Dielectric pellets 42, preferably of quartz glass, occupy part of the space between

disks

21a and 21b.

The rod 121 terminates at its bottom in a cylindrical boss 43 having a pin 143 projecting laterally therefrom. This boss is rigid with a metal plate 22 having a radially extending lug 122 which plays in a slot 123 of insert 16, whereby the

unit

121, 43, 22 is held against rotation within this insert but is axially slidable over a short distance limited by the length of slot 123. The upper end of rod 121 is fixed to a short metallic thimble 114 within which a metal ball 31 is held for limited axial movement. Thimble 114 is slidably received in an aperture 29 of a flanged spacer member 13 inserted between the housing body 10 and the upper end of insert 16; member 13, which consists of dielectric material, is provided at its underside with a metal plate 13a making contact with the outer conductive coating 15 of insert 16 and with the sliding thimble 114.

A plurality of insulating rods 113, rising from the spacer member 13, support a central electrode 14 consisting of a conductively coated, molded plate 14:: and a pair of similarly coated, spaced

segments

14b, 14c integral with and carried by plate 14a. The

segments

14b, 14c define a gap 32 for the movement of an indicating member 33 which comprises a segmental body 33a, a pointer 33b and a reinforced hub portion 330. Member 33 is supported by a pin 34 which spans the gap 32 and is journaled in

bearings

35, 36 extending inwardly from the top of housing portion 19, whereby a metallic connection is formed between this indicator member and the inner conductive coating 13 of the housing. A metal rod depends from central electrode 14 and terminates just short of ball 31 in the normal position of the instrument (Figs. 1 and 3).

The transparent cap 11 of the instrument housing is formed integral with a pair of parallel,

upstanding walls

11a, 11b substantially aligned with

electrode segments

14b, 14c respectively; wall 11b carries a scale 38 cooperating with the pointer 33b.

Press-fitted inside housing portion 10 immediately below insert 16 is a metal ring 17 having a horizontal flange portion 117 which makes contact with lug 122 when the latter is in its bottom position, as shown in Fig. l. reely rotatable within ring 17 is a metallic retaining member 45, of inverted cup shape, formed with a roughly segmental cutout 34 as best seen in Fig. 4. A plastic insert 48 within member .is partly molded with respect to this member.

The base 12 has a depend platelSa to coating'lS.

ing flange 12a provided externally with an annular groove 50; acon-trol knob 51 is molded arounda bar magnet 52 and has a peripheral portion surrounding the fiange 12a, this portion having imbedded therein at least one pin '3 projecting into groove "56 'to hold the knob '51 in place.

The operation of the instrument shown in the drawing is as follows: I

Knob 51 at the bottom of housing base 12 is manually rotatable between a reading position (Fig. l) and a Jdiametrically opposite charging position (Fig. 2) which may be'marked on the instrument by suitable legends and/or indexing means (not shown). In the reading position the "magnet 52 holds the magnet '49 and, thereby, the retaining member 4% in a position in which a solid portion of this retaining member overlies the pin 143 and the assembly 43, 22 123., 114 is substantially immobilized nearithelower end of its short axial travel. in this position, and with the instrument held upright, the

charging capacitance

15, 18 is 'sh'ort-circuited 'over a conductive path extending from metallic layer 18 to ring 17 and lug 122 of plate 2.2, rod 121, thimble 114 and thence via The position of the pointer 35!: on scale 33 is determined by the charge on a storage condenser represented by coating 18 and member 33 on the one hand and central electrode 14 on the other.

When the knob '51 is rotated by 180 and the instrument inverted or shaken horizontally into a position as illustrated in Fig. 2, pin 143 passes through the cut-out 44 and rod 121 is unlocked. Lug 3122 now disengages the ring 117 and breaks the connection between plates '15 and 18 of the charging condenser; also, ball 30 conductively connects thimble 114 to rod 2%, thereby establish ing a path from coating to central electrode 1d. At the same time the presence of frictionally charged pellets 42 "near plate'13a attracts electrons toward the coating 15 and positively charges the central electrode 14. When the instrument is new again righted, or shaken in the opposite direction, electrode 14 is again insulated from coating 15 and the aforementioned'short circuitacross the capacitance 15S, '15 is reestablished, the negative charge on coating 15 being thereby communicated to coating 18.

'When, by repetition of the above operations, the instrument has been fully charged, the pointer 33b will register with the 0-point or" the scale 38 and the lmob 51 may now be returned to reading position. If radiation is present, ionization will occur in the space between the plates of the

aforementioned storage condenser

14, 13, 33 and this condenser will gradually discharge; the rate of the pointers return to no-charge position, or the position reached by the pointer at the end of a predetermined time interval (as read on the suitably calibrated scale 33), will give an accurate indication of the radiation intensity.

It will be noted that the capacitance of

charging condenser

15, 18 is considerably greater than that of the storage condenser at the top of the instrument, and that the two condensers are ,eliectively in parallel When'the instrument is inverted and'unlocked, whereby discharges due to ionization will occur at a much more rapid rate than in normal reading position. It is, accordingly, possible to correct overcharges or to produce limited discharges in this manner even where no appreciable radiation is 'present. More rapid discharges are possible by unlocking the instrument (as in Fig. 2) and shaking it several times in inverted position, whereby pellets 42 and ball 30 will move out of step (owing to differences in weight and mobility) and electrons will be returned to the central electrode 14.

.My invention is, of course, not limited to the specific embodiment described and illustrated but may be realized in numerous modifications and adaptations without departing from the spirit andscope of the appended claims.

I claim:

'1. [In an ionizationemeasuring instrument, in combination, a pair of conductive elements insulated from each other, a charge generator comprising charge-carrying means displaceable between two positions relatively close to and relatively remote from one of said elements, re spectively, electrostatic indicator means comprising a first and a second electrode relatively remote from said charge-carrying means in both of said positions, first bridge means for conductively connecting said one of said elements to said first electrode in said relatively close position of said charge-carrying means, thereby inducing a charge of predetermined polarity in said one of said elements and a charge of opposite polarity in said first electrode, second bridge means for conductively interconnecting .said elements in said relatively remote position of said charge-carrying means, and means conductively interconnecting the other of said elements and said second electrode at least in said relatively remote position of said charge-carrying means.

2. The combination according to claim 1, further inclu manually operable means for selectively blocking the operation of said ,firstbridge means.

3. In an ionization-measuring instrument, in combination, 'a pair of conductive elements insulated from each other, a charge generator comprising charge-carrying means displaceable between two positions relatively close to and relatively remote from one of said elements, respectively, electrostatic indicator means comprising a first and a second electrode relatively remote from said charge-carrying means in both of said positions, first bridge means on said charge generator for conductively connecting said one of said elements to said first electrode in said relatively close position of said charge carrying means, thereby inducing .a charge of predetermined polarity in said one of said elements and a charge of opposite polarity in said "first electrode, secondbridge means on said charge generator for conductively interconnecting said elements in said relatively remote position of said charge-carrying means, and means conductively interconnecting the other o'flsaid elements and said second electrode at least in said relativelyremote position of said charge-carrying means.

4. The combination according to claim'3, wherein said cbarge'generator comprises a tubular container of dielectric material, said charge-carrying means being held in said containerfor axial displacement relative thereto, and an elongated member traversing said container in axial direction and adapted .to move axially With respect thereto, said first and second bridge means being operative connected with said member.

.5. The combination according to claim 4, further including locking means .for substantially immobilizing said member in a position of inoperativeness of said first bridge means.

6..An apparatus for charging a'pair of electrodes, comprising a first and a second conductive element insulated from each other, a dielectric container of tubular configuration, charge-carrying means within said container movable between .a first and .a second axial position and adapted to become irictionally charged by such movement, said charge-carrying means being relatively close to said first elementin said first position and relatively remote therefrom in said second position, bridge means coupled with said container for :conductively connecting said first element to one of said electrodes-in said first axial position and for conductively interconnecting said elements'in said second axial position of 'said charge-carrying means, and means conductively interconnecting 'said second element and the other of said electrodes at least in said second position of said charge-carrying means.

7. An apparatus according to claim 6, wherein said elements are a pairof condenser plates.

8. An apparatus according to claim 6, wherein said container is provided with a member mounted thereon ior limitedrelative axial displacement, :said bridge means being operatively coupled with said member.

9. An apparatus according to claim 8, wherein said member is a rod axially traversing said container.

10. An ionization-measuring instrument comprising a charge indicator including a pair of electrodes together defining an ionization chamber, a pair of condenser plates remote from said electrodes, means conductively connecting one of said condenser plates to one of said electrodes, a tubular container of dielectric material, a conductive element adjacent one end of said container forming electrically a part of the other of said condenser plates, dielectric charge-carrying means movable inside said container between two extreme axial positions close to and remote from said conductive element, respectively, and adapted to become frictionally charged by such movement, first bridge means coupled with said container for conductively interconnecting said element and the other of said electrodes in said close axial position of said charge-carrying means, and second bridge means coupled with said container for conductively connecting said 1 element to said one of said condenser plates in said remote axial position of said charge-carrying means.

11. An instrument according to claim 10, further comprising a housing forming an air-tight enclosure around said indicator, said condenser plates and said container, magnetic control means outside of said housing and magnetic follower means inside said housing, said follower means being adapted to inactivate said first bridge means upon movement of said control means from a charging position to a reading position.

12. An instrument according to claim 10, further comprising an elongated member traversing said container in axial direction and mounted thereon for limited relafive axial displacement, said first and second bridge means being operatively coupled to said member.

13. An instrument according to claim 12, wherein said first bridge means comprises a metallic retainer mounted on an extremity of said member, adjacent said one end of said container, and a metallic connector telescoped within said retainer and adapted to engage part of said other of said electrodes only in an extreme position of said connector and of said member.

14. An instrument according to claim 13, wherein said member is a metallic rod, said second bridge means comprising a metallic part extending from the other extremity of said rod.

15. An instrument according to claim 13, further comprising locking means for substantially immobilizing said member in a position in which said connector is held out of engagement with said other of said electrodes, a housing forming an air-tight enclosure around said indicator, said condenser plates and said container, said locking means comprising a magnetic control member outside of said housing and a magnetic follower member inside said housing, said housing comprising a substantially cylindrical, dielectric wall, said one of said condenser plates being constituted by a conductive coating on the inside of said wall.

References Cited in the file of this patent UNITED STATES PATENTS 2,646,516 Futterknecht July 21, 1953 FOREIGN PATENTS 169,918 Great Britain Oct. 13, 1921