Patent Number: 044505787
Section: description

DETAILED DESCRIPTION OF THE INVENTION Reference is made to FIGS. 1 and 5 showing a variable aperture beam collimator 10 of the invention utilizing four block assemblies defining a constant size beam channel extending through the collimator. An energy beam source 11, for example a neutron beam source, emits an energy beam B for projection through the aligned apertures 12 of the block assemblies of the collimator of the invention. The beam B projects through the channel in a straight line and emerges from the last in-line aperture 12 as a collimated beam (represented by the arrow B). The collimator 10, as best seen by viewing FIG. 1 in connection with FIG. 5, includes separate block assemblies 14, 15, 16 and 17. Assemblies 14 and 16 are in congruent relationship, that is physically oriented in the same way, as are assemblies 15 and 17. In particular, assemblies 15 and 17 are inverted front-to-back about axis A with respect to assemblies 14 and 16. This difference in orientation can also be seen by comparing FIGS. 2A and 3A showing the first two in-line assemblies 14, 15, respectively. Referring to FIGS. 2A and 2B, a plurality of opaque blocks 18, 19, 20 and 21 are illustrated forming assembly 14. The blocks have adjacent edges 22 in interfacial contact. When in the closed position, as shown in FIGS. 2A, the blocks form a completely beam opaque structure. To form the aperture 12, as shown in FIG. 2B, the blocks 18-21 slide relative to one another along the edge interfaces 22. A mechanism is provided for advantageously adjusting the blocks to slid the blocks to create aperture 12. To best explain the adjustment means for sliding the blocks 18-21 to provide the aperture 12, reference is made to the block assembly 14 shown in FIGS. 2A, 2B; it being understood that the adjustment means in the block assemblies 15-17 are substantially the same. In particular, an endless cable 25 is trained around corner pulleys 26, 27, 28 and a drive gear 29. The drive gear meshes with a perforated belt section 30 to insure non-slip driving in response to operation of the hand wheel assembly, generally designated by the reference numeral 31 (see FIG. 2A). The cable is attached in the preferred embodiment to slide brackets 32, 33 attached to the opposite blocks 18, 20. Thus as the drive gear 29 is rotated in the direction of the arrow shown in FIG. 2A, the cable 25 moves and in turn the blocks 18-20 move in the direction of the arrows shown also. The mechanical pressure at the edge interfaces 22 in turn move the blocks 19, 21, also as shown by the arrows. The movement of the blocks 18-21 results in opening of the aperture 12, as shown in FIG. 2B. The configuration of the aperture 12 is assured by the guiding influence of guide rods 35, 36 engaging corresponding apertures in the upstanding legs of slide brackets 32, 33 (compare FIGS. 2A and 2B). Similarly, follower blocks 19, 21 are provided with slide brackets 37, 38, respectively and guided by additional guide rods 39, 40, respectively. The edge interfaces 22 in combination with the guide rods 35, 36 and 39, 40 advantageously insure easy and efficient sliding of the blocks for opening and closing. As will be seen in detail later, the rods are bodily movable toward and away from the center of the array of blocks 18-21 in a unique manner to control the shape of the aperture. It is clear that the drive gear 29 can be actuated in a number of well known ways. Preferably, the assembly 31 includes a worm gear 35 engaging the outer peripheral teeth of the drive gear 29 and a hand wheel 46 for turning shaft 47 of the worm gear. The shaft is suitably rotatably mounted by bearing assembly 48 (see FIG. 2A). The pulleys 26-28 and the drive gear 29 are rotatably mounted on four shafts 50-53, respectively. (See FIG. 1 also). In other words, the pulleys and the gear 29 rotate independently of the corresponding shafts upon which they are rotatably mounted. The ends of the shafts 50-53 are suitably journaled in frame plates F.sub.1, F.sub.2. The operation of a single array of blocks, such as block assembly 14 in order to form the aperture 12 can now be clearly seen. The blocks 18-21 are initially set or closed in FIG. 2A and upon rotation of the hand wheel 46 the cable 25 is moved providing movement to the blocks 18, 20, that is shifting in the direction of the arrows and guided by the rods 35, 36 respectively. Because of the sliding pressure against the two adjacent blocks 19, 21, these blocks are also moved in accordance with the arrows of FIG. 2A and guided along the corresponding rods 39, 40. As a result, the aperture 12 is created. Similarly, in the alternate block assembly 15, wherein like parts are indicated by the same reference numeral but with the suffix a for further identification, the aperture 12a can be generated by moving blocks 18a-21a. Of significance, it will be noted that the entire assembly 15 is inverted front-to-back about axis A with respect to the assembly 14 previously described. Furthermore, the adjustment wheel assembly 31a is positioned not only at 90.degree. from the wheel assembly 31 but also so as to provide movement to the blocks 18a-21a in the opposite direction, as shown by the arrows in FIG. 3A. In other words, the blocks 18a-21a move in a clockwise direction, as viewed in FIG. 3A whereas the blocks 18-21 move in the counter clockwise direction as viewed in FIG. 2A. This is of importance since it assures the relative movement of sliding interfaces 22a in the opposite direction to the sliding interfaces 22. Thus as the aperture 12a is opened (see FIG. 3B) none of the sliding interfaces are congruent. In other words, the sliding interfaces 22, 22a do not overlie each other and accordingly maximum efficiency of sealing against stray neutron beams is assured. This non-congruency is repeated in block assemblies 16, 17, as best shown in FIG. 5 of the drawings. In each position where a sliding interface 22, 22a is provided, on the adjacent block assembly there is a solid block to block any possible leakage of radiation. As mentioned above, the adjustment means of the adjacent block assemblies, such as assemblies 14, 15 are inverted with respect to each other and this is accomplished by simply providing four additional shafts supported by the frame members F.sub.1, F.sub.2. The shafts have been designated 50a-53a (see FIG. 3A) supporting in turn pulleys 26a-28a and drive gear 29a. The relationship of this orientation can be best comprehended viewing the perspective in FIG. 1. The components for the adjustment means in the block assembly 16 are numbered, and are the same as those shown in assembly 14; and likewise the components in assembly 17 are like those shown in assembly 15. While four assemblies 14-17 are shown in the preferred embodiment, it is readily apparent that one assembly 14 could be used as a collimator in accordance with the principles of the present invention. Adding a second block assembly, such as block assembly 15 in back of the block assembly 14, as shown in FIG. 5, provides an additional aperture 12a to regulate the neutron beam B or the like. Furthermore, a third assembly, such as block assembly 16 can be put behind the assembly 15 to provide additional collimation; and the additional assembly 17 can be added if desired. Of course, any additional number of block assemblies may be added as required in order to provide the necessary beam opaque structure desired when utilizing the device as a beam collimator, such as for the neutron source 11. Also, the particular thickness shown for the blocks is for purposes of illustration and it should be understood that the blocks can be wider (indeed up to face-to-face contact) or narrower as desired. As mentioned above, the guide rods 35, 36 and 39, 40 may be simultaneously moved toward and away from the center of the block assemblies. This movement of the rods is generated by moving means including T shaped intermediate actuators 60-63 (see FIG. 2A). As shown, the adjacent ends of the rods are pivotally mounted on the actuators and the actuators are fixedly attached to the shafts supporting the pulleys. For example, the actuators 60-63 for the assembly 14 are mounted on shafts 50a-53a. In FIGS. 1 and 2A, it can be seen that actuator 60 is clamped on to shaft 50a. Similarly, the actuator 60a (see FIG. 3A also) is clamped on shaft 50. In turn, shafts 50, 50a include large drive pinions 70, 70a fixed to the shafts on the outside of frame F.sub.1. A worm gear 71 meshes with the two pinions 70, 70a and is a part of the moving wheel assembly, generally designated by the reference numeral 72 (FIG. 1). Since the pinions 70, 70a engage opposite sides of the worm 71 it will be realized that the shafts 50, 50a may be rotated in opposite directions giving the desired opposite movement described with respect to the blocks in FIGS. 2A and 3A. The advantageous result of movement of all of the guide rods 35, 36, 39, 40 and 35a, 36a, 39a, 40a is that the shape of the apertures 12, 12a can be varied in shape and the variation can be accomplished in unison. For example, in the preferred embodiment the apexes of the blocks 18-21 are offset or skewed, as shown in FIG. 2A. This is accomplished by moving the guide rods as shown by the rotational arrows adjacent the actuators 60-63. In particular, blocks 18, 20 are moved away from each other and blocks 19, 21 are moved toward each other providing the offset or skewing at the apexes. Thus, when the aperture 12 is generated or opened, as shown in FIG. 2B, the sliding movement caused by the cable 25 creates a non-equilateral or in this case a rectangular opening, as desired. When the aperture 12 is closed, the blocks return to the offset or skewed position with the interfaces 22 sealed, as shown in FIG. 2A. The alternate block assemblies, such as block assembly 15 act in the same manner and the offsetting or skewing action is generated concurrently, since as it will be remembered the pinions 70, 70a are simultaneously rotated by the moving wheel assembly 72. Thus in FIG. 3A, the blocks 19a, 21a are moved toward each other by bodily translation of the guide rods 39a, 40a whereas the blocks 18a, 20a are moved away from each other by an equal amount by movement of guide rods 35a, 36a (note movement arrows in FIG. 3A). It will also be noted that the aperture 12a is congruent with the aperture 12 and remains so in all adjusted positions of the blocks. As shown in FIGS. 4A and 4B, the movement of the actuators to shift the guide rods in the direction opposite to that described above allows alignment of the apexes of the blocks 18-21 (FIG. 4A) and then upon actuation of the blocks by the adjustment wheel assembly 31 the aperture 12 formed is square rather than rectangular. It will thus be realized that by a simple adjustment of the rods in unison a desired configuration of each of the apertures 12, 12a can be effected and thus the area for the channel accommodating the beam B is advantageously varied. Also, it will be recognized that where a different number of blocks are used, as indicated above, a different shape of the aperture 12, 12a does result. For example, if three blocks are used, a triangular aperture results; if five blocks are used in an array, then the aperture is a pentagon; and so forth for additional configurations. However, the apparatus of the present invention is such that regardless of the shape of the aperture the apertures of the assemblies remain congruent and thus form a beam channel when set up as shown in FIG. 5. In accordance with another aspect of the present invention, the assemblies 14-17 can be adjusted separately by simply moving the hand wheels of the adjustment wheel assemblies 31, 31a a different amount. Thus in the embodiment of FIG. 6, the adjustment wheel 46 is opened to provide an aperture 12' of a particular size. The aperture 12a' of the blocks in the adjacent assembly 15 is turned a lesser amount providing a smaller aperture 12a'. Similarly, the adjustment assembly of block assembly 16 is opened a lesser amount and the adjustment assembly in the block assembly 17 is opened still less to provide a diverging channel allowing the passage of the beam B'. The beam is thus a diverging beam that can be rectangular as shown, or could be diverging and square if the adjustment of FIGS. 4A, 4B is used. When the diverging channel is to be closed to cut off the beam B' each of the individual adjustment assemblies is simply moved in the reverse direction thus moving the blocks and closing each of the apertures in turn, as described above. In view of the foregoing, it will now be realized that substantial results and advantages over the prior art collimators is provided. The beam opaque blocks 18-21 are capable of efficient opening and closing through the individual adjustment assemblies 14-17. The blocks move along the sliding interface 22 so as to provide a barrier that is tight except for the aperture 12 and with no overlapping surfaces. When closed, the blocks converge at the apexes in the center of the block assembly. The adjustment for creating the variable apertures is provided by a novel cable drive engaging brackets attached to at least one of the sliding blocks. The mechanical pressure on the follower blocks provides the desired opening in a controlled fashion. Guide rods extending through the brackets ensure proper movement of the blocks and the guide rods may be translated toward and away from each other in order to adjust the shape of the apertures. When multiple block assemblies are utilized, a beam channel, including a diverging channel if desired, can be provided in an efficient manner. The foregoing description of a preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiment was chosen and described in order to best illustrate the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to best utilize in the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.