US2843754A

US2843754A - Gamma-ray projectors

Info

Publication number: US2843754A
Application number: US450693A
Authority: US
Inventors: Robert B Costello
Original assignee: MW Kellogg Co
Current assignee: MW Kellogg Co
Priority date: 1954-08-18
Filing date: 1954-08-18
Publication date: 1958-07-15
Anticipated expiration: 1975-07-15

Description

July 15, 1958 R. B. COSTELLO 2,343,754

GAMMA-RAY PROJECTORS Filed Ru 18. 1954 2 Sheets-Sheet 1 INVEN TOR ROBERT B. COSTELLO BY v{4.14. #1 FM ATTORNEYS United States Patent 2,843,754 Patented July 15, 1958 ice GAMMA-RAY PROJECTORS Robert B. Costello, Rahway, N. J., assignor to The M. W.

Kellogg Company, Jersey City, N. J., a corporation of Delaware This invention relates to projectors for subsurface photographic examination of metal bodies and more particularly to a projector of this character adapted to use radioactive isotopes as the energy source.

The subsurface photographic examination of metal bodies by the use of X-ray machines as well as by the use of gamma-ray projectors has reached a high state of development and is in widespread use in the arts. The X-ray machines include a great deal of auxiliary electrical equipment so that when they are of a capacity capable of penetrating several inches of steel, as is required in the examination of pressure vessels for instance, they involve such large equipment installations as to make transportation from work site to work site a major problem which often is impossible of solution. Such large X-ray machines are very expensive in initial cost and in day-today cost as well by reason of the high maintenance requirements. Gamma-ray projectors are simple and comparatively inexpensive but have not in the past displaced X-ray equipment even in cases where X-ray offered no substantial advantages over gamma-ray primarily because of the high cost ofthe energy source. The radioactive isotope, radium, universally employed before the event of atomic fission even now costs over twenty-two thousand dollars ($22,000.00) per gram, or as can be otherwise stated, per curie. With the availability of the comparatively inexpensive radioactive isotopes produced by irradiation by neutrons in an atomic pile, there is a good possibility that gamma-ray projectors will displace X-ray machines in all examination applications except those that require the peculiar properties of the X-ray, i. e., continuous spectrum, etc. The presently available comparatively cheap radioactive isotopes produced in atomic piles make it possible to provide energy sources of extremely high value which would require X-ray installations of prohibitive size and cost. Energy sources in the order of curies are ordinary and comprise a metal pellet of about /2" long and Ms" in diameter. Much larger sources can be made and used without raising any serious problem.

The present gamma-ray projectors include a mass of shielding material, usually lead, in which is formed a passageway through which a rod may be moved from the back of the camera to carry the energy source from the safe position intermediate the ends of the passageway to the exposure position at the exterior of the camera. The movable rod closes the rear end of the passageway while the front end is closed by a removable cap. These projectors are hazardous and, hence, not completely satisfactory. Some radiation always escapes around the cap and around the positioning rod when the cap is in the passageway closing position and the rod has located the energy source in the safe position. Furthermore, there is always the possibilityof accidental or inadvertent removal of the cap from the passageway closing position. The positioning rod usually extends a considerable disstance from the projector and consequently limits the range of movement of the camera with the result that the energy source cannot'be aligned as desirable in some directions.

It is a principal object of this invention to provide a comparatively inexpensive projector adapted to use gamma-ray radiation for the subsurface photographic examination of metal bodies, the projector being of such weight as to be readily portable and of simple and rugged construction and so arranged that the escape of radiation when the energy source is in position of non-use is effectively eliminated.

It is also a principal object of this invention to provide a projector adapted to use gamma-ray radiation for the subsurface photographic examination of metal bodies which is of simple, rugged construction, may be readily transported from place to place and can be readily manipulated to align the source during exposure in all directions.

It is a further principal object of. this invention to provide a projector adapted to use gamma-ray radiation for the subsurface photographic examination of metal bodies in which the energy source is carried by a rotatable support whose polar axis is disposed normal to the plane of movement of the energy source, said support being housed in a chamber defined by shielding material, said chamber including a window opening exteriorly located in the path of the energy source whereby the energy source is effectively shielded against radiation leakage at all times except when it is deliberately positioned in registry with the window for exposure.

The further features, objects, and advantages of this invention will become apparent from the following detailed description and explanation thereof:

Fig. 1 is an isometric view of a projector, embodying the novel features of my invention and adapted to use gamma-ray radiation for the subsurface photographic examination of metal bodies;

Fig. 2 is a sectional view taken on lines 2-2 of Fig. l; and

Fig. 3 is a sectional view taken on lines 33 of Fig. 2.

The novel projector of this invention may be of any convenient size and shape in accordance with the service it is to perform and the energy rating of the energy source employed. Thus, the novel projector may be a comparatively small projector adapted to employ an energy source of about a half curie or it may be a projector of intermediate size and adapted to employ an energy source of about 5 or 6 curies, or it may be a large projector adapted to use an energy source of about 10 curies or more. Also, the novel projector may be arranged to remain in a substantially fixed position and the work to be examined brought to it, or it may be arranged to be easily movable from work site to work site and arranged for a maximum range of positional adjustment relative to the Work. For the purposes of this application and not by way oflim-itation, I have chosen to disclose the invention in connection with a movable projector of intermediate size adapted to employ an energy source of about 6 curies.

The projector 10 includes a support, or bed, 11 and a projector body 12. The bed 11 is formed in any convenient manner, as for instance it is formed out of cut plate welded together, as shown. The bed 11 while it may be of any preferred size and shape should be large enough to stably support the projector body 12 in its positions of alignment. The bed 11 includes a bottom 13 to which are united the sides 14 and the front and rear end pieces 15. At the upper ends of each of the sides 14 are the vertical slots 16 which are adapted to accommodate the trunnions 17 of the projector body 12. The trunnions 17 are held in position in the slots 16, but free to rotate therein by the bearing pieces 18 each of which includes a hole of proper size to accommodate the respective one of the trunnions 17. Each bearing piece 18 is also provided with a plurality of holes which accommodates thescrews which screw into appropriately tapped holes in the upper portions of the sides 14 to removably maintain the cover pieces 18 fixed in position. Thebearing pieces 18 and the bottom end of the slots 16 provide the necessary bearing surface for the trunnions 17.

. The projector body 12 comprises a main cylindrical portion 23 to which the trunnions 17 are united, whose rear end is closed by a dished head 24. The cylindrical portion 23 and the head 24 are preferably made of steel and formed into a unit by conventional welding. The space encompassed by the cylindrical portion 23 and the head 24 is filled with material 25, lead being used in this case, which absorbs radiation and acts as an effective radiation shield. The front end of the cylindrical portion 23 is open and is positioned against a short cylindrical portion 26 whose front end is closed by the stepped diaphragm 27. The portion 26 and the stepped diaphragm arelikewise preferably made of steel and united by conventional welding. The space encompassed by the cylindrical portion 26 and the stepped diaphragm 27 is filled with radiation absorbing material 28, lead is the material employed as the shield material 28. The complementary halves of a stepped cylindrical chamber 29 are formed in the continguous abutting portions of the shields and 28. As shown the chamber 29 includes a central section 31 of maximum diameter flanked on each side by the sections 32 of a lesser diameter. The chamber 29 is tapered between the section 31 and the sections 32 and between the sections 32 and the shaft accommodating bore 33. The axis of the chamber 29 is disposed substantially parallel to the axis of the trunnions 17. The complementary half of the stepped cylindrical chamber 29 in the shield material 28 is not complete but is shortened by the diaphragm'27 to form a window through which the energy source may project.

To removably unite the cylindrical portions 23 and 26 a pair of thin semi-circular straps 35 are provided which encircle the cylindrical portions 23 and 26. The straps 35. are removably united to each of the cylindrical portions 23 and 26 by circular series of screws 36 which pass through the straps 35 and screw into properly tapped holes in the cylindrical portions 23 and 26.

A rotor 40 is housed in the chamber 29 and is complementarily shaped relative thereto. The rotor 40 includes a large central section 41 and two smaller side sections 42. The shaft 43 is housed in the bore 33 and carries pinned or otherwise attached thereto for rotation therewith, the

sections

41 and 42. The shaft 43 extends .through appropriate reinforced holes formed at the juncture of the cylindrical portions 23 and 26. The shaft 43 is held in position by means of nuts 44 which are screwed on the threaded ends thereof, a suitable bearing washer being interposed between the nuts 44 and the juncture of the cylindrical portions 23 and 26. A portion of the central section 41 is cut away in stepped fashion as shown, to be substantially flush with the window 30 and to accommodate the energy capsule mounting piece 45. .The'mounting piece 45 is bent to shape and formed of comparatively light gauge steel. The piece 45 is fastened to the section 41 by means of the screws 46. A screw .29 and an appropriate groove 49 is cut in the shielding material 25 and 28, and likewise, the stepped diaphragm 27 is notched, to permit the passage of the capsule from the. safe position tothe exposing position. The capsule .48 is in the safe position when the rotor 40 is so positioned that the capsule 48 is on the longitudinal axis of the camera body 12 and points toward the head 24.

The capsule 48 is in the exposed position when the rotor 40 is so oriented that the capsule 48 is on the longitudinal ,axis of the projector 'body 12 and extends from the window 30. It is to be noted that in the same position of the capsule 48 all radiation leakage is completely prevented. However, this is not to imply that the safe position is the only position in which there is no radiation leakage. Radiation in directions lengthwise of the rotor 40 are completely cut off and absorbed as soon and as long as the capsule 48 is withdrawn within the groove 49. Radiation in directions transverse to the polar axis of the rotor 40 reduce as soon as the capsule 48 enters the groove 49 and are completely cut off and absorbed as soon as the capsule 48 is sufficiently within the groove 49 so that a straight line cannot be drawn in the groove 49 connecting the capsule 48 and the exit hole of the groove 49 at the window 30.

To facilitate the rotation of the rotor 41, one end of the shaft 43 is reduced to accommodate the sprocket 50 thereon. The sprocket 50 is keyed on the reduced end of the shaft 43 and held in position through the nut and lock washer arrangement 51. For easy manipulation of the rotor 41 a chain 52 terminating at each end in a ring 53, is positioned to engage the sprocket 50 with at least one link fastened to the sprocket 50. To facilitate the determination of the position of the energy source 48 an index pointer 54 is attached to the sprocket 50 and arranged to point in the direction that the capsule 48 is pointing. In place of the sprocket 50 and the chain 52 a pulley and belt, not shown, may be used. If operation from a more remote point is required, it is only necessary to attach pull cords to the rings 53.

The projector body 12 is rotated about the trunnions 17 so that the energy source 41 in exposed position may be aligned with the work. For this purpose, and to provide for a comparatively wide range of such alignment, a gear wheel section 55 is is attached to the head 24 in a plane which includes the orbit of the energy capsule 48. The gear wheel section 55 may be conveniently cut out of plate and attached to the head 24 in any convenient manner as by conventional welding. If preferred the upper end of the gear wheel section 55 may be provided with a hole 56 therethrough through which a hook may be inserted for lifting or otherwise moving the projector 10 into and out of position. If desired, one or more holes similar to hole 56, may be provided along the length of the gear wheel section 55. In lieu of the holes 56, separate pieces of plate, not shown, which include the holes 56 may be welded to the projector body 12. A shaft 57 is journaled in the sides 14 and fixed against longitudinal movement relative thereto by the collars 58 positioned thereon. The shaft 57 carries a gear 59 which meshes with the gear section 55 so that by the rotation of shaft 57 the projector body 12 may be rotated about the trunnions 17. A crank 60 is carried by the shaft 57 for rotation of said shaft. In order to lock the shaft 57 against rotation in predetermined alignment positions of the projector 12, the shaft 57 also carried a disc 61 which has a plurality of angularly spaced holes 62 therein. The holes 62 are equi-spaced around the circumference and are adapted to be brought into registry with a tapped hole 63 in the side 14. Thus by inserting a threaded peg 64 in the hole 62 in registry with the tapped hole 63, the disc 61 and consequently the projector body 12 is locked against movement in the then position of adjustment.

When the energysource is exposed with the projector structure as so far described, the stepped diaphragm 27 provides for an angle of exposure of approximately 220". Such a wide angle of exposure may at times be unnecessary, if not in fact, undesirable as when panoramic shots are not required. To provide for the applications when a narrow angle of exposure is required, a disc-like mask is provided. The mask 70 is formed of a ring member 71 which is adapted to rest upon the outer end of the cylindrical portion 26. The ring 71 is filled with a body of lead 72 shaped to provide a convex outer face into which opens the nozzle 73 of the exposure angle required. The apex angle of the cone of the nozzle 73 determines tis intended for an energy source of 6 curies. jector complete and including the mask 70 weighs only .a little more than 800 lbs., its bed 11 is some 20 inches long and 17 inches wide, while its body 12 is some 16 finches in diameter and some 16 inches long. Such a the angle of exposure and may range from about 20" or less to 90 or more. The inner face of the body of lead 72 is stepped approximately obversely to the diaphragm 27 so that it may rest easily thereon. The stepped meshed arrangement of the diaphragm 27 and the inner face of the body of lead 72 insures against radiation leakage through the interface between the mask 70 and the cylindrical portion 26. A pair of semi-circular straps 74 carry lugs 76 which accommodate screws 77 which removably fasten the mask 70 to the projector body 12. To facilitate the removal of the mask 70 the eyes 79 are provided. Similar eyes 80 are provided from removing the cylindrical section 26. i

To insure against inadvertent, or unauthorized, rotation of the rotor 40 from the safe to the exposing position, a lug 81 is united to the sprocket t) and a similar lug 82 is united to the cylindrical portion 23 of the projector body 12. The lugs 81 and 82 are so positioned that they abut when the source 48 is in the fully retracted, or safe, position so they can be locked together as by inserting the padlock 83 through appropriate holes provided therein.

As stated heretofore the projector disclosed in detail This proprojector is small and easily transportable.

While the invention has been described with particular :reference to a specific embodiment, it is to be understood that it is not to be limited thereto, but is to be construed broadly and restricted solely by the scope of the appended claims.

I claim:

1. A projector adapted to employ a radioactive energy source in the subsurface photographic examination of metal bodies which comprises a mass of dense radiation absorbing material, a chamber with cross section in the form of a circular segment formed in said mass of absorbing material with external surface of said mass defining the chord of said circular segment toprovide a window in the periphery of said chamber opening externally of said mass of radiation absorbing material, a rotor of cross section in the form of a circular segment substantially complementarily shaped with said chamber and mounted for rotating therein, means on the chordal periphery of said rotor mounting a radioactive source, and means for rotating said rotor to carry said source into registry with said window for exposure and to remove said source out of registry with said window to a position substantially diametrically opposite thereto.

2. A projector adapted to employ a radioactive energy source in the subsurface photographic examination of metal bodies which comprises a mass of dense radiation absorbing material, a chamber with cross section in the form of a circular segment formed in said mass of absorbing material with external surface of said mass defining the chord of said circular segment to provide a window in the periphery of said chamber opening externally of said mass of radiation absorbing material, a rotor of cross section in the form of a circular segment substantially complementarily shaped with said chamber and mounted for rotation therein, said rotor formed of dense radiation absorbing material, means on the chordal periphery of said rotor mounting a radioactive energy source to extend outwardly therefrom beyond the projection of the maximum radius of said rotor, said chamber including a peripheral groove extending beyond the maximum diameter of said chamber permitting movement of said source from a position in registry with said window to a position in which said source is surrounded by said mass of radiation material, and means for rotating said rotor to carry said source into registry with said window for exposure and to remove said source out of registry position and in which said source is surrounded by said radiation absorbing material.

3. A projector adapted to employ a radioactive energy source in the subsurface photographic examination of metal bodies which comprises a mass of dense radiation absorbing material having one end adapted to be pointed at the body to be examined, a chamber with cross section in the form of a circular segment formed in said mass of absorbing material with external surface at said end defining the chord of said circular segment to provide a window in the periphery thereof opening at said end, a rotor of cross section in the form of a circular segment substantially complementarily shaped with said chamber and mounted for rotation therein, said rotor formed of dense radiation absorbing material, means on the chordal periphery of said rotor mounting a radioactive energy source, and means for rotating said rotor to carry said source into registry with said window for exposure and to remove said source out of registry with. said window to a position spaced from the registry position and in which said source is surrounded by said radiation absorbing material, said chord defining surface at said end approaching a planar surface whereby the angle of exposure of said source when in registry with said window is in the order of 4. A projector adapted to employ a radioactive energy source in the subsurface photographic examination of metal bodies which comprises a mass of dense radiation absorbing material having one end adapted to be pointed at the body to be examined, a chamber with. cross section in the form of a circular segment formed in said mass of absorbing material with external surface at said end defining the chord of said circular segment to provide a window in the periphery of said chamber opening externally at said end, a rotor of cross section in the form of a circular segment substantially complementarily shaped with said chamber and mounted for rotation therein, said rotor formed of dense radiation absorbing material, means on the chordal periphery of said rotor mounting a radioactive energy source, means for rotating said rotor to carry said source into registry with said window for exposure and to remove said source out of registry with said window to a position spaced from the registry position and in which said source is surrounded by said radiation absorbing material, said chord defining surface at said end approaching a planar surface whereby the angle of exposure of said source when in registry with said window is in the order of 180, and mask means positionable on said end adapted to reduce said angle of exposure to an acute angle, said mask including a body of dense radiation absorbing material with an elongated outwardly tapering aperture therein adapted to be aligned with said source in said registry position.

5. A projector adapted to employ a radioactive energy source in the subsurface photographic examination of metal objects which comprises an elongated body of dense radiation absorbing material having one end adapted to be pointed at the object to be examined, a chamber of circular section formed in said elongated body and having a window formed in the periphery thereof opening externally at said end, a rotor of circular section substantially complementarily shaped with said chamber and mounted for rotation therein, said rotor formed of dense radiation absorbing material and disposed with its polar axis transverse to the longitudinal axis of said elongated body, said rotor including a central cylindrical portion of maximum diameter flanked by cylindrical portions of lesser diameter, means mounting a radioactive energy source on the periphery of said central portion, and means for rotating said rotor to carry said source into registry with said window for exposure and to remove said source out of registry with said window to a position spaced from the registry position and in which said source is surrounded by said radiation absorbing material.

6. A projector adapted to employ a radioactive energy source in the subsurface photographic examination of metal objects which comprises an elongated body of dense radiation absorbing material having one end adapted to be pointed at the object to be examined, a chamber of circular section in said elongated body and having a window in the periphery thereof opening externally at said end, a rotor of circular section substantially complementarily shaped with said chamber and mounted for rotation therein, said rotor formed of dense radiation absorbing material and disposed with its polar axis trans verse to the longitudinal axis of said elongated body, said rotor including a central cylindrical portion of maximum diameter flanked by cylindrical portions of lesser diameter, said central cylindrical portion having a peripheral section removed to provide a surface approximately flush with said window when said surface is brought into registry with said window, means mounting a radioactive energy source on said surface at substantially the region of minimum radius of said central portion, and means for rotating said rotor to carry said source into registry with said window for exposure and to remove said source out of registry with said window to a position spaced from the registry position and in which said source is surrounded by said radiation absorbing material.

7. A projector adapted to employ a radioactive energy source in the subsurface photographic examination of metal objects which comprises an elongated body of dense radiation absorbing material having one end adapted to be pointed at the object to be examined, a chamber of circular section in said elongated body and having a window in the periphery thereof opening externally at said end, a rotor of circular section substantially complementarily shaped with said chamber and mounted for rotation therein, said rotor formed of dense radiation absorbing material and disposed with its polar axis transverse to the longitudinal axis of said elongated body, said rotor including a central cylindrical portion of maximum diameter flanked by cylindrical portions of lesser diameter, said central cylindrical portion having a peripherai section removed to provide a surface approximately flush with said window when said surface is brought into registry with said window, a recess intermediate the ends of said surface, radioactive energy source mounting means in said recess, a radioactive energy source mounted on said mounting means extending radially outward of said surface, and means for rotating said rotor to carry said source into registry with said window for exposure and to remove said source out of registry with said window to a position spaced from the registry position and in which said source is surrounded 'by said radiation absorbing material.

8. A projector adapted to employ a radioactive energy source in the subsurface photographic examination of metal objects which comprises an elongated body of dense radiation absorbing material having one end adapted to be pointed at the object to be examined, a chamber of circular section in said elongated body and having a window in the periphery thereof opening externally at said end, a rotor of circular section substantially complementarily shaped with said chamber and mounted for rotation therein, said rotor formed of dense radiation absorbing material and disposed with its polar axis transverse to the longitudinal axis of said elongated body, said rotor including a central cylindrical portion of maximum diameter flanked by cylindrical portions of lesser diameter, said central cylindrical portion having a peripheral section removed to provide a surface approximately flush with said window when said surface is brought into registry with' said window, a recess intermediate the ends of said surface, radioactive energy source mounting means in said recess, a radioactive energy source mounted on said mounting means, and adapted to extend outwardly beyond the projection of the circular periphery of said rotor, said chamber including a peripheral groove adapted to accommodate said source, and means for rotating said rotor to carry said source into registry with said window for exposure and to remove said source out of registry with said window to a position spaced from the registry position and in which said source is surrounded by said radiation absorbing material.

References Cited in the file of this patent UNITED STATES PATENTS 2,477,648 Piggot et a1. Aug. 2, 1949 2,670,443 Pennock et al. Feb. 23, 1954 2,684,447 Gilks July 20, 1954