US 3894234 A
A radial scanning device which provides a moving adjustable slit or window that transverses along an aligned path with respect to a radiation detection device. The repetitive slit motion of the scanning device allows sampling of the liner propellant interface area of a missile motor when the missile is circumferentially rotated.
Claims available in
Description (OCR text may contain errors)
[4 1 July 8,1975
RADIAL SCANNER Inventors: John W. Mauch, Danville; Emil M.
Bergh, Walnut Creek, both of Calif.
Assignee: The United States of America as represented by the Secretary of the Navy, Washington, DC.
Filed: Jan. 28, 1974 Appl. No.: 437,441
US. Cl. 250/358; 250/308; 250/321;
250/452; 250/490 Int. Cl. G01t 1/16 Field of Search 250/358, 360, 308, 321,
References Cited UNITED STATES PATENTS 2/1934 DeAmicis l78/7.6 6/1950 Kaiser ..250/338 Primary ExaminerHarold A. Dixon Attorney, Agent, or FirmR. S. Sciascia; Charles D. B. Curry  ABSTRACT A radial scanning device which provides a moving adjustable slit or window that transverses along an aligned path with respect to a radiation detection device. The repetitive slit motion of the scanning device allows sampling of the liner propellant interface area of a missile motor when the missile is circumferentially rotated.
5/1932 Jenkins l78/7.6 5 Claims, 11 Drawing Figures RADIATIoN ABSORBER) RAD '3] I33 IAL SCANNER RADIATION ASSEMBLY I BEAM 1 2 newt l STEPPING I29 65 |29O 5 RADIATION SOURCE MoToR TIA |9 49 I2I I n-f-il 2/ SHELIX SUB-ASSEMBLY 66 DIzTEcToR ASSEMBLY PMET'HEUJUL 8 1975 3.894.234
5g RADIATION H/SCANNER ASSEMBLY 4| DETECTOR ASSEMBLY SUB-ASSEMBLY 66 6| STEPPING 7| MOTOR l9-HEL|cAL SLIT 87 lzucom-zrz FIG 3 SHEET M G-m w wE PATEHTEMUL 8 1975 3.894.234
sum 4 4|\DETECTOR ASSEMBLY 39 l l T 8| l l l I l l 195225 45/SCINTILLATION CRYSTAL NETWORK PHOTOMULTIPLIER COLL IMATI N6 95 WIN DOW 1 RADIAL SCANNER This application is a co-pending application of the following applications: Ser. No. 270,780 filed July 11, 1972 US. Pat. No. 3,766,387; Ser. No. 270,781 filed July 11, 1972 US. Pat. No. 3,803,498; and Ser. No. 328,206 filed Jan. 31, 1973 US. Pat. No. 3,832,564.
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial scanner and more particularly a radial scanner which provides a moving slit or window that travels transversly across the detecting surface of a radiation detector to sample the liner propellant interface area of a missile motor.
2. Description of the Prior Art Prior systems have used fixed devices such as X-ray systems that record defects on film. This method is very expensive because of the high cost of the film. Moreover the X-ray technique requires tedious repetitive filming sessions to make the necessary tests to determine the defects in the missile rocket motor.
SUMMARY OF THE INVENTION The present invention relates to a radial scanning device which provides a moving adjustable slit or window that transverses along an aligned path with respect to a radiation detection device. The repetitive slit motion of the scanning device allows sampling of the liner propellant interface area of a missile motor when the missile is circumferentially rotated.
The propellant bond integrity can be determined for each level of circumferential scan revolution by the missile motor.
STATEMENT OF THE OBJECTS OF THE INVENTION A primary object of the present invention is to provide a radial scanner that will function with a radiation source.
Another object of the present invention is to provide a radial scanner that is accurate and relatively inexpensive to operate.
Still another object of the present invention is to provide a radial scanner for sampling the liner propellant interface area of a missile motor or the like.
Other objects advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings wherein:
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a pictorial illustration of the radial scanner with its helix system, and the accompanying radiation absorber.
FIG. 2 is an isometric view of the radial scanner illustrated in FIG. 1.
FIG. 3 is a detailed top cross sectional view of the radial scanner illustrated in FIG. 1, parts being broken away for illustrative purposes.
FIG. 4 is a cross sectional view of the helix subassembly of the radial scanner including the radiation detector assembly illustrated in FIG. 1.
FIG. 5 is a side sectional view of the left hand section of the helix assembly illustrated in FIG. 4.
FIG. 6 is an end view of the helix assembly of FIG.
FIG. 7 is another side sectional view of the right hand section of the helix assembly of FIG. 4.
FIG. 8 is a radius section of the longitudinally adjustable assembly of helices illustrating the point of contact to form the slit of the helices illustrated in FIG. 4.
FIG. 9 is the radiation detector to be used with the device illustrated in FIGS. 1 and 2.
FIG. 10 is a side view of the secondary collimating unit illustrated in FIGS. 1 and 3.
FIG. 10A is a side sectional view showing the hollow shaft coupled to the secondary collimating unit illustrated in FIG. 10.
DESCRIPTION OF THE PREFERRED EMBODIMENT Before describing the radial scanner in detail, it should be noted that the radial scanner may be used with an integrated system such as the radiation detector scanner arrangement described in co-pending patent applications, Ser. No. 270,780 and Ser. No. 270,781 both filed on July 11, 1972.
Referring to FIGS. 1 3, the radial scanner assembly 11 comprises generally of a helix sub-assembly 13 which consists of a first cylinder 15 and a second cylinder 17 which together forms helical slit 19. The radial scanner sub-assembly 13 consists of two precisely machined cylinders, with a minimum density of about 16.76 grams/cc. First cylinder 15 is about 6 inches in length while second cylinder is about 2% inches in length. Cylinders 15 and 17 may be made of tungsten or its equivalent. Moreover, the scanner system may be constructed in any size desired since size is not generally a controlling factor in the scanner construction or function.
Referring to FIGS. 3 8, a 211' helical surface 16 and 18 is machined into one end of cylinders 15 and 17 respectively. Precise machining of the helical surface may be accomplished by any number of well known machine methods.
Referring to FIG. 3, after machining, cylinders 15 and 17 are mounted and supported by a precision ground drive sleeve 21, which is used to couple the torque from timing pulley 73 to each of the cylinders 15 and 17. Drive sleeve 21 may be made of honed stainless steel or its equivalent. With cylinders 15 and 17 mounted on drive sleeve 21, the deflection at the center of the sleeve 21 is less than 0.001 inch when properly adjusted. Cylinders 15 and 17 are adjustable in the longitudinal direction and may be locked in position by standard latching devices. Drive sleeve 21 is formed by a hollow tube, one inner sleeve 23 and one outer sleeve 25, machined preferably from stainless steel, is bonded to the drive sleeve 21. The bonding material may be of the adhesive type or any equivalent bonding material. Referring to FIG. 3, outer sleeve 25 also fits into a ball bearing 26 mounted in bearing 30 support plate 31 which acts as a guide bearing. Inner sleeve '23 is keyed to helix end support 29, which is bolted to cylinder 17 and rotates inside of large ball bearing which is clamped and mounted in heavy support plate 32. The outsidediameter of this bearing assembly is slightly larger than all the other helix diameters allowing the complete helix sub-assembly 13 to be removed as a unit upon removal of end plate 69. Cylinder 15 is bolted to helix end support 27. A splined surface 25a is machined into outer sleeve 25. Moreover, a splined surface is machined into the inside of helix end support 27. These splined surfaces allow for adjustment of the helix slit 19 width from about 0.000 inches to about 0.250 inches. Adjustment of the helix slit 19 is made by rotating adjustment nut 33 which is threaded to helix end support 27 which is held in place on outer sleeve 25 by retaining ring 35. After the required slit width is obtained, lock nut 37 is snubbed against rotating adjustment nut 33 to lock cylinder 15 to outer sleeve 25. The whole sub-assembly 13 is mounted in the bored section of support plates 31 and 32.
Referring to FIGS. 3, 4 and 9 detector holder tube 39 is held stationary and is used to hold detector assembly 41 which consists of a photomultiplier tube 43, sodium iodide scintillation crystal 45 and voltage divider network assembly 47. Detector holder tube 39 and support shaft 81 are suspended inside of inner sleeve 23 of drive sleeve 21. Detector holder tube 39 is mounted within drive sleeve 21 and positioned so that no contact can occur between drive sleeve 21 and detector holder tube 39 even when cylinders 15 and 17 and drive sleeve 21 are rotating. Support for detector holder tube 39 is provided at one end by support shaft 81 and end plate 69 which is the essentially closed end 81a and at the other end by end plate 67 and end plate holder 83. The detector 41 is slipped into cylinder 15 from the open end of detector holder tube 39. Detector 41 can be easily removed or replaced as illustrated in FIG. 3.
Referring to FIGS. 1, 3, 10 and 10A, secondary colli mating window 49 is formed by collimating bars 51, 53, 55 and 57. The collimating bars may be made of tungsten or an equivalent material. Collimating bars 51, 53, 55 and 57 are mounted inside side plate 63 and centered within a hollow shaft assembly. In operation the collimating bars 51, 53, 55 and 57 thus form a secondary collimator window along the axial direction of helical slit 19. Gamma-ray photons or other radiation which pass through hollow shaft 60 and collimating window 49 are detected by the Sodium Iodide Crystal 45 or the equivalent as the helical slit 19 scans across the selected window area. Bars 51 and 53 are adjustable as indicated by the directional arrows in FIG. 10 to vary the window area.
Referring to FIGS. 1, 2 and 4 angular rotation of helical slit 19 to follow the contour of the material to be tested is provided by .gimbaling the entire radial scanner assembly 11 between pillow block gimbal bearing assemblies 59 and 61. Pillow block gimbal bearing assemblies 59 and 61 are respectively bored to accept hollow shaft 60 and solid shaft 87. Gear assembly 85 may be of any type which will provide the proper drive ratios desired and solid shaft 87 is fixedly attached to assembly 85. Hollow shaft 60 and solid shaft 87 which are attached to side plates 64 and 66 respectively, provide the pivot surfaces for pillow block 59 and 61 respectively. Pillow blocks 59 and 61 can be mounted to a fixed or movable base B of FIG. 2 as desired; however, the heights of the base centers should be located equidistant above the base surface for proper alignment.
Referring to FIGS. 1, 2, 3 and 10A pivot point of cylinders 15 and 17 is located so that a line L passing through the centers C of pillow blocks 59 and 61 bore diameters is perpendicular to the axis of cylinders 15 and 17, bisects the cylinder diameter d illustrated in FIG. 6, and also bisects the helix pitch when the slit 19 is completely closed as illustrated in FIG. 8.
The radial scanner assembly 11 is gimbaled and is capable of rotating through any angle between 0, horizontal, and 90 vertical and can be driven if desired so as to follow the contour of any material to be tested.
Referring to FIGS. 1 and 2 angular rotation of the gimbaled radial scanner assembly 11 is provided by a stepping motor 71. A Superior Electric 1184008 or the like may be used. A positional readout of the angle is determined by encoder 73. A DECITRAK Model TR- 1 lB2-CCW may be used if desired. Timing pulley 72 is mounted on cylinder 17 end support 29 and driven by stepping motor 71A as depicted in FIG. 1. A Superior Electric S8400 stepping motor using a 2:l pulley ratio is preferred although other equivalent devices may be used. If a 2:1 pulley ratio is selected and stepping motor 71A is rotating at 200 steps/second, the helical slit 19 rotates at 30 revolutions/minute. Positional readout information for helical slit 19 is provided for by slip gear 75A which is mounted to pulley 72. Using a 1:1 pulley ratio belt 76 is used to drive a second precision tooth no slip pulley 75 and a shaft to drive, standard 360 helipot 77 and a conventional dual cam switch 79. The continuous rotatable helipot 77 is used to determine the angular position of the helix and also to provide the horizontal sweep voltage for controlling or monitoring oscilloscopes. Dual cam switch 79 preferably is adjustable to provide a 24 volt mark pulse when the helical slit 19 angular position is at 0. In addition, other adjustments on switch 79 provide a 24 volt output when the angular position of the helix slit is between 60 and 300. This 24 volt output can be used to switch on during the 60 and 300 and off between 300 and 60 of the helix sub-assembly l3 rotation; see patent applications Ser. No. 270,780 and Ser. No. 270,781 described above.
The operation of the radial scanner device 11 will be described in light of the drawings as follows.
In FIGS. 1, 2 and 3 is illustrated the radiation scanner 11 in combination with a radiation absorber 131 which functions to absorb radiation emitted from source 133 to vary the intensity of radiation beam 127. The source 133 is mounted in inclosure 135. The radiation source 133 is further located juxtapositioned with the inside face of radiation absorber 131. Radiation absorber 131 may be of different types; however, it is preferably of the wedge type which is described in a co-pending patent application. The amount of radiation absorbed by radiation absorber 131 is determined by the degree of rotation of the radiation stepping motor, not shown, but described in co-pending patent application Ser. No. 328,206 filed on Jan. 31, 1972. Different types and intensity of radiation sources may be employed; however, it has been found that an about 2,000 curie cobalt 60 source is adequate for most purposes. The angular position of the detector, helix and sensitivity indicator is or may be determined by an angulation stepping device or the like.
In FIG. 1 the helix sub-assembly 13 is rotatably mounted on pillow block gimbal bearings 59 and 61. The helix sub-assembly 13 is driven by helix stepping motor 71A and the sensitivity indicator 129 is positioned by a sensitivity indicator stepping motor, not shown. The sensitivity indicator 129 is used for purposes of calibration. The sensitivity indicator may have multiple discrete positions or slots 129a. The function of the sensitivity indicator is described in patent application Ser. No. 270,780 filed on July ll, I972. Helix stepping motor 71 is mounted adjacent to gimbal 59 and rotates helix sub-assembly 13. Helix sub-assembly 13 is cylindrically shaped with a hollow interior and contains a helical slit 19 and a detector assembly 41. The helical slit 19 may be machined into a hollow thick-walled cylinder of high density material such as tungsten or its equivalent. The detector assembly 41 is stationary and is mounted on gimbals 59 and 61. The output signal is transmitted by conductor lead 121. The detector assembly 41 is preferably a photomultiplier tube having a sodium iodide crystal optically connected to the photomultiplier tube. A voltage detection circuit which may be used in conjunction with the photomultiplier tube is described in patent application Ser. No. 270,781 filed July 11, 1972. Bearings, not shown in FIG. 1, are provided between detector assembly 41 and helix subassembly 13 to provide rotatable support for the helix. The gimbal bearings 59 and 61 are driven by a conventional angulation stepping motor.
The angulation stepping motor 71 will be driven only when it is necessary to scan the hemispherical dome region of the missile motor or the like. The operation of the angulation stepping motor 71 may be by use of a numerical controlled punch tape electric drive which provides output pulses to the various motors as dictated by the particular tape that is being used which is considered conventional and well known to those skilled in the art and is not considered part of the present invention.
Sensitivity indicator 129 may be of any type; however, the most suitable would be a circular plate made of a radiation absorbing material that is provided with a plurality of slots 129a of progressively increasing size. The sensitivity indicator is driven by a stepping motor, not shown in FIG. 1, such that one of the slots 129a is positioned in alignment with opening 49. After calibrating the sensitivity, indicator 129 is taken out of the system operation by aligning the largest slot 129a with adjacent collimating window 49 of FIG. 3. The radiation beam 127 passes through radiation absorber 131, one of slots 1290, opening 49, helical slit l9 and impinges upon the surface of detector assembly 41. The window size of the detector, determined by the width and length of slit 19, is about 0.050 X 1 inch. The 0.050 is selected because it is large enough to receive sufficient photon flux to provide an acceptable signal to noise ratio and it is small enough to recognize separation defects of about 0.005 inch. That is, if the window were much wider than 0.050 inch, then a small defect would have little effect on the detector output signal. The length of 1.00 inch was selected because it is about the diameter of a defect necessary to be detected and is sufficiently long to provide an adequate inspection time.
What is claimed is:
l. A radial scanning devicefor sampling the interface area integrity of a member and including a radiation source and comprising:
a. a means for scanning said member;
b. said scanning means comprises a detector;
0. said radiation source emitting radiation for passing through said member;
d. said means positioned for scanning radiation passing through said member;
e. said detector of said scanning means comprises a cylinder having a helical slit formed therein;
f. said radiation detector positioned within said cylinder;
g. first means for rotating said cylinder about its longitudinal axis; and
h. second means for rotating said detector and said cylinder about an axis perpendicular to said longitudinal axis.
2. The device recited in claim 1 wherein:
a. said helical slit is comprised of a first cylinder and a second cylinder; and
b. each of said cylinders having a cam shaped helical surface.
3. The device recited in claim 2 wherein:
a. said scanner comprises an adjustable moving slitted window aligned with respect to said helix surface.
4. The device recited in claim 3 wherein:
a. said moving slit comprises afirst movable wall and a second movable wall.
5. The device recited in claim 2 wherein:
a. said cylinders are rotatably mounted on a rotating shaft; and
b. a detector located in alignment with said helical slit, said helical slit positioned opposite an adjustable window slot for scanning radiation passing through a member.