US 3161776 A
Description (OCR text may contain errors)
Dec. 15, 1964 c, P. MOORE 3,161,776
PORTABLE EADIOGEAPEIC EXPOSURE UNIT Filed March 20, 1961 A TTORNE Y United States Patent O 3,161,776 PORTABLE RADIGGRAPHIC EXPOSURE UNET Caleb P. Moore, Utica, Mich., assigner to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Mar. 2t?, 1961, Ser. No. 96,932 3 Claims. (El. Z50-105) This invention relates to a radiographic exposure unit, and more particularly to a portable radiographic exposure unit utilizing radioisotopes as the source of radiation.
Recent developments in low radiation energy radioisotope source materials have made it possible to use such sources in both medical and industrial radiography. It is well known to use high energy radioisotope sources such as cobalt-60 for industrial radiography. Such high energy sources have been limited to applications permitting use of bulky shielding, and hence, have been limited to more or less stationary installations. The advent of the low energy sources has led to forseeable uses of portable radiographic units whereby doctors in remote areas or eld hospitals and veterinarians on farms could readily take X-rays of their patients since neither complex electrical power supplies nor bulky X-ray equipment would be required. Similarly, in industry, radiography could be made available where either space or cost considerations make conventional X-ray or high energy radioisotope radiography impractical.
Accordingly, it is an object of this invention to provide a lightweight, compact, and relatively inexpensive radiographic exposure unit.
This invention is carried out by providing a body member containing shielding material and a movable radioisotope source surrounded in part by shielding material whereby the source may, by simple translational movement, be located so that it is completely shielded or partially Unshielded to provide a source of radiation.
The above and other advantages will be made more apparent from the following specification taken in conjunction with the accompanying drawings in which like numerals refer to like parts, and in which:
FIGURE l is an elevational cross section view of an exposure unit in open position according to the invention;
FIGURE 2 is an enlarged view of the radiation window of FIGURE 1;
FIGURE 3 is an elevational cross section view of an exposure unit of FIGURE l in closed position; and
FIGURE 4 is an elevational cross section end View along line 4-4 of the exposure unit of FIGURE l.
The requirements of a portable exposure unit containing radioisotopes is manifold. In order to be portable, it must be both lightweight and compact. To be practical, it must also serve as the storage container for a radioactive source and also must meet the rigid standards applying to containers for the transportation of radioactive materials. Hence, such an exposure unit needs to be of very durable construction and provide good radiation shielding even when accidentally exposed to high temperatures such as encountered in a burning building. It will be seen by reference to the following description that the present invention meets all of these requirements.
Suitable low energy gamma ray sources include the rare earth metals. For example, samarium-l53, thulium-170, lutetium-l77, ytterbium-l69, or gadolinium-l53 may be used in the form of the metal, the enriched metal, or the rare earth oxide powder mixed with aluminum and sintered to form a cermet. The cermet type of sources and the method of fabricating the same are more fully described in the patent application of Black et al., S.N. 19,009, led March 3l, 1960, and assigned to the assignee 3,i6l,776 Patented Dec. 15, 1964 ICC of the present invention. These sources are encased in an aluminum or stainless steel source container.
Referring now to FIGURES 1 through 4, the exposure unit includes a housing or body 10 having an elongated U-shaped lower portion 12 with an upwardly extending flange 14 along either side and a generally flat cap portion 16 having depending iianges 1S along either side mating with the iianges of the U-shaped lower portion 12. Both portions 12 and 16 of the body are preferably made of stainless steel and are fastened together by steel pins 20. The bottom of the body 10 has a cylindrical insert 22 of radiation shielding material. This material could be lead. However, it is preferably that a more durable substance, such as a tungsten composition, be used. Such a composition is known commercially as Mallory 1000 metal, which contains tungsten, 6% nickel, and 4% copper. This material has a minimum density of 16.7 grams per cubic centimeter, has a very high tensile strength, and will retain its integrity for temperatures up to 2300J F. The bottom of the body 10 also has longitudinally spaced from the insert 22 an aperture 24 of truncated conical form flaring outwardly toward the lower surface of the body 10. A support leg 26 is secured at each bottom corner of the body and a convenient carrying handle 28 is secured to the cap portion 16. The cap p0rtion 16 has a slot 30 located beneath the handle 28 and access holes 32 through the handle 28 communicate with the slot 30. An apertured lug 34 extends from the left end of the cap 16.
A shutter or slide member 36 preferably of stainless steel fits within the opening of the U-shaped body for translational movement therein. A cylindrical cavity 38 in the righthand portion of the slide member 36 contains a block 40 of radiation shielding material secured by pins 41 which block in turn has a central aperture 42 adapted to support a container 44 for radioactive material 46. The radioactive material 46 is situated in a nose portion of the container which extends downwardly in the aperture 42 and protrudes into a conical portion 48 of the aperture 42 which flares outwardly toward the bottom of the slide member 36. The lower part of the flared aperture 48 is closed off by a thin diaphragm S0 of stainless steel. The diaphragm Sil is held in place by a retaining ring 52 which is staked into place. The upper end of the aperture 48 in the shielding block 40 is threaded to receive a threaded cap 54 which is also made of radiation shielding material. A thin gasket 56 of soft metal between the shielding block 40 and cap 54 provides a tight seal and, in conjunction with the stainless steel diaphragm 50 in the flared aperture 4S, seals the source container 44 into the shielding block 40. This construction, hence, will be eifective t0 prevent any loss of radioactive material 46 in the event the source container 44 becomes damaged due to exposure to very high temperatures. However, since the stainless steel diaphragm 50 is very thin, preferably about .003 inch thick, it does not act as an effective radiation shield, but rather serves as a window.
A threaded pin 58 extending from the top of the slide member 36 rides in the slot 30 provided in the cap 16 thereby limiting the extent of movement of the slide 36 within the body 10. In order to disassemble the exposure unit for periodic replacement of the source material, it is necessary merely to move the threaded pin 58 into alignment with the openings 32 of the carrying handle 28 so that the pin 53 may be removed by a screwdriver. Then the slide 36 may be completely removed from the body 10. A handle 60 at the left end of the slide member 36 has an aperture 62 therethrough which, when the slide 36 is in its closed position as shown in FIGURE 3, is immediately below the aperture 64 of the lug 34 of the cap portion 16. Hence, a lockpr other fastening eans (not shown) may be inserted through the apertures i, 64 to prevent inadvertent or unauthorized opening of e unit. When the slide 36 is thus locked in this posim, the threaded pin S3 will be beneath the handle 28 1t of alignment with the openings 32 so that the pin 5S lnnot be removed by unauthorized personnel.
Obviously, the unit may be used in the horizontal posian shown in the drawings or may be tilted vertically or yherwise. ln order to holdthe slide member 36 in either aen or closed position, regardless of the orientation of the nit, two spring biased ball detents 66 are provided in ie lower part of the body and mate with either pair of indentations 68 on the left portion of the bottom i the slide or a pair of indentations 70 near the center the slide 36. A boss 72 is provided around the outer )ne opening Z4 so that a diaphragm (not shown) may iadily be mounted over the opening to modify the cone igle of emitted radiation, or so that larger cone extenons can be employed when desired.
in operation, the unit is placed the desired distance from le subject to be X-rayed with the axis of the conical perture 24 aligned with the subject. Then the shutter r slide 36 is manually moved to the open position (FlG. for the desired period of exposure time and is then Loved back to the closed position (EEG. 3). While the ide is in open position, the operator of the `unit as well s all other persons not in line with the aperture 24 are lielded from the radiation by the shielding block 40 and ap 54 carried by the slide member 36. When the slide 6 is in closed position, the cylindrical insert 40 of iielding material in the body of the unit blocks the adiation coming through the stainless steel window 50 f the shielding block 40, thereby providing effective aielding to minimize radiation fields to suitable intensity Jr safe storage or transportation. For example, where 1e shields comprise :the tungsten alloy and the insert hield is 2 dia. by 11/16, the shielding block is 21A ia. by 19/16, and the shielding cap is 2 dia. by 1%6, 00 euries of any radioactive material and larger amounts -f some-materials may be safely shielded.
It should be noted that although the preferred embodiient shown herein is limited to the use of one source of adioactive material 46 within the exposure unit, the deign can easily be extended Within the scope of the invenion to provide for the use of two or more sources so hat the operator can selectively operate the shutter 36 o expose the desired source.
Thus it will be readily seen that the invention provides compact and lightweight radiographic unit which is imple in operation and does not in any way sacrifice ,dequate shielding or rugged construction for portability.
It is understood that the preferred embodiment of the nvention described herein is not intended to limit the cope of the invention which is defined by the following ulaims.
1. A portable radiographic exposure unit comprising L body, a hollow channel portion defined by and extending hrough said body proximate one side thereof, the other ide of said body being provided with a rst mass of 'adiatiion shielding material on one end thereof and a irst conical aperture `on the other end thereof, a rectiinearly movable slide member within said channel, a 'adiation source mounted in a cavity in said slide memier, means for limiting escape of radiation from said aource to one direction comprising a second mass of ladiation shielding material on said slide member envelopng said source and defining a single conical aperture herethrough, said source and the second said aperture being arranged to register with said first mass of radiation shielding material when said slide member is positioned at one extreme position of its stroke and to register with said first conical aperature when said slide member is positioned at the other extreme position.
2. A portable radiographic exposure unit comprising a body provided with a carrying handle, a hollow channel portion defined by a U-shaped body portion having a cap portion thereon, said channel portion extending through said body proximate one side thereof, the other side of said body being provided with a first mass of radiation shielding material on one end thereof and a first conical aperture on the other end thereof, a rectilinearly movable slide member within said channel, a radiation source mounted in a cavity in said slide member, means for limiting escape of radiation from said source to one direction comprising a second mass of radiation shielding material on said slide member enveloping said source and defining a single conical aperture therethrough, said source and the second said aperture being arranged to register with said first mass of radiation shielding material when said slide member is positioned at one extreme position of its stroke and to register with said first conical aperture when said slide member is positioned .at the other extreme position, a handle connected to said slide member for rectilinearly moving said slide member relatively tot said body, and detent means for indexing said slide member at each of its extreme positions.
3. A portable radiographic exposure unit comprising a box-shaped body provided with a carrying handle, a hollow channel portion defined by a U-shaped body portion having a cap portion thereon, said channel portion extending through said body proximate one side thereof, the other side of said body being provided with a cylindrical mass `of radiation-shielding material on one end thereof and a first conical aperture on the other end thereof, a rectilinearly movable slide `member within said channel, a radiation source mounted in a cavity in said slide member, means for limiting escape of radiation from said source to one direction comprising a second mass of radiation shielding material on said slide member enveloping said source and defining a single conical aperture therethrough, a diaphragm of radiation permeable material closing the second said conical aperture, said source and the second said aperture being arranged to register with said cylindrical mass of radiation shielding material when "said slide member is positioned at one extreme position of its stroke and to register with said rst conical aperture when said slide member is positioned at the other extreme position, a handle connected to said slide member for rectilinearly moving said slide member relatively to said body, la ball detent means for indexing said slide member at each of its extreme positions, and abutment means on both said body and vsaid slide member for limiting the 'stroke of said slide member in relation to said body so as to prevent said slide member from becoming separated from said body.
References Cited in the file of this patent UNITED STATES PATENTS 2,649,549 Green Aug. 18, 1953 2,675,487 Schallert et al Apr. 13, 1954 2,821,636 Jefferson Jan. 2S, 1958 2,849,621 Clark Allg. 26, 1958 2,884,539 Swift Apr. 28, 1959 2,891,168 Goertz etal June 16, 1959 2,937,275 Thourson et al May 17, 1960 2,973,435 Reeder Feb. 28, 1961 3,048,701 Thomas Aug. 7, 1962