US3567934A - Film badge with improved radiation filtering structures - Google Patents

Abstract

A radiation monitoring film pack and a holder therefor are disclosed. The film pack has a wrapper with a flap extending from it carrying identifying data. The holder defines a slot for receiving the film pack, novel U-shaped radiation filters for shielding the film from edgewise, as well as head-on radiation, and a frame which overlies the film-holding structure and holds the flap such that a surface on which the identifying data appears is visible.

Description

United States Patent lnventor Eric T. Clarke Lexington, Mass.

Appl. No. 756,582

Filed Aug. 30, 1968 Patented Mar. 2, 1971 Assignee Technical Operations, Incorporated Burlington, Mass.

FILM BADGE WITH IMPROVED RADIATION FILTERING STRUCTURES 2 Claims, 10 Drawing Figs.

Int. Cl G01t 1/08 Field of Search 250/ 8 3 [56] References Cited UNITED STATES PATENTS 2,496,218 l/l950 Kieffer 250/83ph 2,624,846 l/1953 Tochilin et a1 250/83ph Primary ExaminerWalter Stolwein Assistant ExaminerMorton J. Frome Attorneys-Alfred H. Rosen and John H. Coult ABSTRACT: A radiation monitoring film pack and a holder therefor are disclosed. The film pack has a wrapper with a flap extending from it carrying identifying data. The holder defines a slot for receiving the film pack, novel U-shaped radiation filters for shielding the film from edgewise, as well as head-on radiation, and a frame which overlies the film-holding structure and holds the flap such that a surface on which the identifying data appears is visible.

PATENTED MAR 2 Ian SHEET 2 OF 2 ERIC [CLARKE INVENTOR AL FRED H ROSEN 0nd JOH/VH c0011 ATTORNEYS FELM BADGE WITH IMPROVED RADIATION FILTERING STRUCTURES CROSS-REFERENCE TO RELATED APPLICATIONS This application relates to, but is in no way dependent upon, copending applications of Robert J. Prest, Ser. No. 534,255 filed Jan. 4, 1966 now abandoned; and Ser. No. 671,390, filed Sept. 28, 1967 now Pat. No. 3,567,933.

BACKGROUND OF THE INVENTION This invention, in general, relates to radiation-monitoring film badges worn by people who spend time in the vicinity of radioactivity such as ionizing radiation or lower energy radiation that is capable of producing secondary ionizing effects. More particularly, it relates to film badges that are improved with respect to size, cost and adaptation to mass processing techniques. The specific contribution of this invention concerns improved radiation shielding structures.

FIG. I is a full scale illustration of a typical prior art film badge. These badges are restricted in size and shape by the conventional use of dental X-ray film packs. These film packs have been used due to their ready commercial availability. While the desirability of a different type of film pack for badge use has been obvious for some time, there has been no system devised that would provide the desired advantages particularly without incurring intolerable costs in producing a new type of pack.

The size of the conventional badge is a problem for people whose greatest radiation exposure is at their hands, for example. A smaller badge could be worn more readily as a finger ring or on a wrist strap. A very small amount of the film is actually used for determining radiation exposure and the excess film is needed to enable identification marking on the film. This is done for example, using X-ray exposures through a stencil or the like so as to penetrate the pack. The dental films also require individual handling since they are not adapted for operation in continuous webs with accurate position information. I

The above-referenced copending applications describe and claim film badges of reduced size using strips of film adapted for splicing into reels for mass production processing. Sprocket apertures like those used in moving picture film are provided on the strips for accurate position information. Identification data is provided directly on the film strips with a marking material that does not interfere with the utilization of the film. An extended free flap of the pack wrapper provides a surface for external identification data and coacts with a unique holder or badge to provide readily visible identification without increasing the face area or reducing the effectiveness of the film.

These improved film badges, like all prior art badges, suffer from the inability to shield the film from radiation entering edgewise of the film.

OBJECTS OF THE INVENTION It is an object of this invention to provide improved radiation filtering structures for film badges designed to monitor high energy radiation. More specifically, it is an object to provide structures for filtering radiation approaching the film edgewise as well as head-on.

It is another object to provide radiation filters for film badges which are easier to fabricate and incorporate into a film badge and which render the associated film badges less expensive to produce.

Further objects and advantages of the invention will in part be obvious and will in part become apparent as the following description proceeds.

The features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of the invention, reference may be had to the following detailed description taken in connection with the accompanying drawings, wherein:

FIG. 1 is a front elevation of a prior art film badge;

FIGS. 27 illustrate an improved film badge described and claimed in the first of the above-referenced copending applications;

FIG. 2 is a front elevation view of the said improved film badge;

FIG. 3 is an isometric projection view showing a film holder or badge according to the referenced invention;

FIG. 4 is a view of a low sensitivity film strip;

FIG. 5 is a view of a high sensitivity film strip;

FIG. 6 is a fragmentary perspective view of a film pack according to the referenced invention with one corner folded over to reveal otherwise hidden structure;

FIG. 7 is an enlarged cross section taken along line 7-7 of FIG. 2;

FIG. 8 illustrates another improved film badge described and claimed in part in the second of the above-referenced applications;

FIG. 9 is a section view of the FIG. 8 badge illustrating novel radiation filtering structures implementing the teachings of this invention; and

FIG. 10 is a fragmentary exploded perspective view of the FIG. 8 badge illustrating my novel radiation filters.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a showing of prior art already mentioned. It shows in full scale a typical prior art badge. For comparison purposes FIG. 2 shows an improved badge in accordance with the above-referenced invention in a one-to-one'scale. The front elevation of FIG. 2 shows a frame member 10 containing a window 11 for viewing identification data 12 on the face 13 of a portion of a film pack supported in the frame. Measurements of F IGS. l and 2 will show that the surface area of the badge in accordance with the invention is about l/ s quare inches as compared to about 3%square inches of the prior art badge of FIG. 1.

An improved film holder in accordance with the abovereferenced invention is illustrated in an opened-up condition in FIG. 3 and comprises a first member 15 rectangular in shape and having side edges 16 and 17 therein relatively long as compared to the ends 18. Member 15 is suitably made of a rigid or semirigid material such as metal or certain plastics and contains one or more metallic filters that permit an energy independent system. In one preferred embodiment, member 15 is made of aluminum and has a first filter 20 of cadmium about one-fourth inch square and 1 mm. thick and a second filter 21 of copper about one-fourth inch square and one-fourth mm. thick. These dimensions are not critical to the invention and are set forth only to provide a complete disclosure of a specific embodiment. The aluminum of member 15, which may be about one-sixteenth of an inch thick, shields against the softest X-rays and lower radiation energy levels. The copper filter 21 shields against radiation below about 25 kilo-electron-volts energy. The cadmium filter 20 shields against substantially all radiation below about 50 kilo-electron-volts energy. The ends 18 of member 15 extend upward a small amount above the plane of member 15 providing support for a hinge connecting member 15 to a second member 22.

Second member 22 is rectangular in shape and similar to member 15 but somewhat smaller in rectangular dimensions. One specific embodiment as illustrated in FIG. 3 uses a hinge made with pins extending through holes 23 in ends 18 and extending into an enlarged edge 25 of member 22. This hinge secures one edge of member 22 along edge 17 of member 15. Member 22 contains a cadmium filter 26 and a copper filter 27 substantially identical to filters 20 and 21, respectively, in member 15 and arranged to register precisely with filters 20 and 21, respectively, when member 22 is folded across member 15. A window 28 is also suitably provided in member 22 for passing radiation having an energy below the penetration level for the aluminum.

A third member is hinged to edge 16 of member and incorporates the frame shown in FIG. 2 around an open window 11. Member 10 suitably carries spring metal clamping devices 3i so that when second member 22 is folded down across first member 15 and third member 10 is then folded across second member 22 clamping devices 31 are clamped onto edge 17 of first member 15 securing the assembly together (see FIG. 7). Third member 10 can be made of materials such as stainless steel, brass, copper, or other metals plated or otherwise. It may also be made of various other materials, such as plastics materials, suited as a decorative frame with means to secure the assembly together. While the first and second members 15 and 22 have been described as being made of aluminum, they can also be made of other materials providing the shielding effect of aluminum is supplied by other means, such as appropriate inserts, or a wrapping in the film pack.

FIGS. 4 and 5 illustrate film strips 32 and 33, respectively, to be utilized in the present invention. In one embodiment these have been made identical to pieces of 16 mm. film sliced in half giving a width of about 8 mm. with sprocket apertures 35 along one edge for accurate positioning in processing equipment. Each of the film strips is imprinted with identification data such as a serial number 36. This serial number is suitably typed, stamped, or printed on the film using a marking material. Marking materials commonly used in typewriter ribbons have been found suitable. Pigments in waxy binder materials are generally operative. Printing of data on these strips in the suggested way leaves a clear marking that is not necessarily indelible. However, as will be seen, the film strips are securely wrapped in a pack during use, and they can be handled automatically in processing equipment both before and after use. Thus no problem is encountered with deterioration or smearing of the markings. Film strips of FIG. 4 and 5 are illustrated as identical in size and shape; however, they are shown separately as having different respective sensitizations. Together their sensitivities are intended to cover ionizing radiation and beta particles. Ionizing radiation as used herein is to be taken as including radiation that is capable of producing secondary ionizing effects. For example, the film strip in FIG. 4 may be highly sensitive so as to be capable of recording exposures as small as one millirem. Rem will be recognized as roentgen equivalent man. The film strip of FIG. 5 has a much lower sensitivity, for example, it is appropriately sensitive so as to show density variations with doses up to as much as 300,000 millirems. In use in a badge the two film strips are placed in register one on top of the other.

FIG. 6 shows a wrapper made up of layers that are respectively reflective and absorptive of visible light. An interior layer 410 is suitably black cellulosic material while the exterior layer 41 may be a white cellulosic material. In a preferred embodiment a thin metal foil such as .aluminum foil 42 is laminated between layers 40 and 41.

In making up the film pack at least one strip of film and preferably two strips, as in FIGS. 4 and 5, are positioned against the interior layer 40 of the wrapper and a portion of the wrapper 43 is folded over to envelop the film strips as shown at the left side of FIG. 6. The surface of interior layer 40 is desirably coated with a fusible plastic coating so that the edges of portion 43 may be heat sealed around film strips 32 and 33 providing a tightly sealed enclosure for the film strips completely opaque to visible light. A second portion 45 of the wrapper extends out from the enveloping portion 43 to form an identification-data member, as shown at the right side of FIG. 6 and can be imprinted on the exterior layer 41 with identification data such as illustrated in FIG. 2. The wrapper enveloping the film strips is then positioned in the badge or holder of FIG. 3 as illustrated in the cross-sectional view of FIG. 7.

Cross section of FIG. 7 is enlarged for better illustration and is taken through line 7-7 of FIG. 2 Portion 43 of the film wrapper carrying film strips 32 and 33 is positioned on top of member 15 and member 22 is folded up and over, completely covering portion 43. Extending flap portion 45 is then brought over on top of member 22 and is secured firmly in place by crossing frame member 10 across it clamping the assembly together.

The badge assembly has been made with various means for attaching to a person. These means (not shown) include a finger ring, a tie clip, snaps for attaching to a laboratory smock or the like, and a wrist band.

In film badges as described above, substantially the entire viewable area of the badge is available at window 11 for identifying information. The film strips which, as illustrated, can be as little as 8 millimeters wide, provide space along their entire lengths near a first edge for identification data and space along their entire lengths near the opposite edge for position indexing means. Adequate space is still available along the length of each strip between identification data and indexing means for radiation exposure measurements. However, it is to be understood that neither the markings for data nor the indexing means need be of a form that interferes with exposure or exposure measurements.

FIGS. 8-10 show an embodiment of the improved badge which incorporates the teachings of, my invention. This badge has members 102 and 104 (corresponding to members 15 and 22, respectively, in FIG. 3) permanently fastened together. These members provide a slotlike opening 106 between them for reception of the film-enveloping portion 43 of the film package (see FIG. 6). The identification-data member 45 can then be held between the one of film-holding members 102 and an apertured third member 108 (corresponding to the apertured frame member 10 in FIG. 3 which is hinged to the other of the film-holding members 104 in the manner illustrated in FIG. 7. The plastic material of which this badge is preferably made is an absorber of the radiation sought to be monitored, and therefore takes part in the radiation monitoring function. A suitable plastic material is polypropylene, but this is exemplary only, since many suitable plastic materials are available. The choice of filters vary widely, depending upon the application. One example is illustrated and described in detail in connection with FIG. 3. In the FIGS. 8-10 embodiment one of the film-holding members 102 has an aperture 110 and a portion 112 of reduced thickness in it for use in the radiation monitoring function. These have been used in combination with metallic filters, to be described in detail hereinafter, as follows:

a. a filter 1 14 of tin and lead combined;

b. a filter 116 of aluminum adjacent the portion 112 of reduced thickness;

c. a filter consisting of the full thickness plastic of both members 104 and 102; and

d. a filter adjacent the aperture 110 consisting of the full thickness of only member 102.

As suggested above, prior art film badges have all utilized radiation filters comprising one or a pair of individual filter elements disposed adjacent the radiation sensitive film. Such an arrangement allows radiation actinic to the film to enter beneath the edges of the filter elements without attenuation attenuation thereby, and to expose the film. Erroneous dosage readings are very apt to result from this leakage of radiation to the film. In accordance with this invention, improved radiation filtering structures are provided which effectively prevent exposure of the film beneath the filter except by filtered radiation. By this invention, erroneous radiation measurements caused by the described edgewise entrance of radiation beneath the filter elements is precluded.

To this end, filters 114 and 116 are formed from a single strip of shielding material folded upon itself in a Ll-shaped configuration. The filters 114, 116 are ensconced in pockets molded in the support members 102, 104 with the slot formed within the filters being registered with the slotlike opening I06 defined by the support members 102, 104. Thus, with a film packet disposed in the slot, the filters effectively wrap around the lowermost edge of the film and prevent the impingement of unattenuated radiation on the radiation-sensitive film within the packet.

in addition to the above, filters fabricated according to this invention are easier to fabricate and to incorporate into the film badges, due largely to their integral construction, and are effective to lower the cost of film badge manufacture.

The invention is not limited to the particular details of construction of the embodiments depicted, and it is contemplated that various and other modifications and applications will occur to those skilled in the art.

Therefore, because certain changes may be made in the above-described product without departing from the true spirit and scope of the invention herein involved, it is intended that the subject matter of the above depiction shall be interpreted as illustrative and not in a limiting sense.

lclaim:

1. A film badge useful for monitoring high energy radiation comprising:

a radiation-sensitive film element;

a film packet opaque to visible light comprising a portion completely enveloping said element and a flexible flap extending from said portion with a surface for identification data;

a holder defining a slot for receiving said portion of said packet enveloping said element;

a radiation filter for attenuating radiation before impingement upon said film elemenfisaid filter comprising a U- shaped radiation shielding member supported in said holder in registration with said slot for receiving said portion of a film packet inserted into'said slot; and

clamping means pivotally connected to said holder, said clamping means being movable between an open position for loading said film packet and a closed portion against said holder wherein said clamping means acts to bend said packet such that said flap is clamped against said holder, said clamping means defining an aperture through which said identification data on said flap is visible when said flap is in its clamped position.

2. The badge defined by claim 1 wherein said holder comprises two mating elements adapted to capture said radiation filter therebetween.

Claims (2)

1. A film badge useful for monitoring high energy radiation comprising: a radiation-sensitive film element; a film packet opaque to visible light comprising a portion completely enveloping said element and a flexible flap extending from said portion with a surface for identification data; a holder defining a slot for receiving said portion of said packet enveloping said element; a radiation filter for attenuating radiation before impingement upon said film element, said filter comprising a U-shaped radiation shielding member supported in said holder in registration with said slot for receiving said portion of a film packet inserted into said slot; and clamping means pivotally connected to said holder, said clamping means being movable between an open position for loading said film packet and a closed portion against said holder wherein said clamping means acts to bend said packet such that said flap is clamped against said holder, said clamping means defining an aperture through which said identification data on said flap is visible when said flap is in its clamped position.

2. The badge defined by claim 1 wherein said holder comprises two mating elements adapted to capture said radiation filter therebetween.

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