Patent Number: 047556862
Section: description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The embodiments according to the present invention are shown in FIGS. 1-4. An electron beam irradiation apparatus shown in FIG. 1 is adapted to introduce one of the objects A, B having different sizes into an irradiation zone 4 to be treated. Because the side view of the apparatus is similar to that of the prior art shown in FIG. 6, it is omitted. The apparatus comprises a frame 9, and pulley units 7,7' having a pair of pulleys 5,5 and a pair of pulleys 6,6, respectively. The pulleys are disposed end to end in the axial direction of the pulleys. The pulleys 5,5 and the pulleys 6,6 have different diameters. Wires may be wound around the pulleys across the paired pulleys either so as not to be parallel to each other as shown in FIGS. 6 and 8 or so as to cross each other. These pulley units 7,7' are separately driven by means of drives 10,10' and one of them is disposed at a position corresponding to the irradiation zone 4. In the embodiment of FIG. 1, the electron beam emitted from an electron beam accelerator irradiates only the object B stretched between two pulleys 6,6' of the lower pulley unit 7' and passing through the zone 4 as the pulleys 6 rotate. It irradiates only the object A when the position of two pulley units is changed so that the object A fed by the other pulley unit 7 enters the irradiation zone 4. Their positions can be changed by shifting the pulley units 7,7', separately or together with the frame, in the directions of the arrow in FIG. 1. FIGS. 2 and 3 show two examples of means for changing the position of the pulley units to perform the above-mentioned shifting mechanically. In FIG. 2, a position changing means 11 comprises rundles 12 mounted on the the bottom of the frame 9, rails 13 for guiding the rundles 12 in the axial direction of the pulleys 5 and 6, and a cylinder 15 which extends in the same direction as the rails 13 and has one end secured to a fixed object 14 and has the other end secured to the frame 9. The reciprocating motion of a ram of the cylinder moves the frame 9 so that one of the two pulley units 7 will enter the irradiation zone 4. With regard to the position changing means shown in FIG. 3, two cylinders 16, 17 are secured to the frame 9 at opposite ends of the frame so that each pulley unit 7 is separately movable into the irradiation zone by the reciprocating motion of cylinder rams. Means for driving the pulley units separately or the pulley unit with the frame are not limited to cylinders. Other known means may be used such as motors, linear rails and the combination of a ball screw and a motor. With the apparatus for irradiating electron beam shown in FIG. 1, the treatment ratio between the object A and the object B can be changed between 1:0 and 0:1 by changing the positions of the pulley units 7,7'. FIG. 4 shows another embodiment in which the irradiation zone 4 is divided into two parts. Its side view is substantially the same as that of the prior art apparatus shown in FIG. 8. The apparatus for electron beam irradiation according to the second embodiment comprises four pulley units 7,7' juxtaposed in the axial direction of the pulleys, and among them, two inner units are placed at the position corresponding to the irradiation zone 4. Each pulley unit 7,7' has its own drive 10,10' so as to be driven separately. The pulleys 5,5' of the upper two pulley units 7 have the same diameter and the pulleys 6,6' of the lower two pulley units 7' have the same diameter. The object A is wound around the pulleys 5,5' and the object B having a size that is different from that of object A is wound around the pulleys 6,6'. Furthermore, the irradiation zone 4 is divided in two parts and a device 8 for interrupting the electron beam is provided for each part. The numeral 15 designates a cylinder as the position changing means which is the same as that in FIG. 2. If the devices 8 for interrupting the electron beam operate in neither of the two parts, the treatment ratio of the object A to the object B will be 1:1, when the pulley units 7,7' are positioned as shown in FIG. 4. But, it will be 2:0 when the frame 9 is moved in the direction (a) which moves the pulleys 5' into the irradiation zone 4 and which moves the pulleys 6 out ot it. Also, it will be 0:2 when the frame 9 is moved in the direction (b) in which direction the pulleys 6,6' will enter the irradiation zone. In addition, the devices 8 for interrupting the electron beam eliminate the need for stopping the accelerator to discontinue operation even though there is no object in one of the irradiation parts. Either of the two embodiments can average the variations in load, i.e. differences in throughput between the objects having different sizes, by changing the treatment ratio and thus preventing the work efficiency of the accelerator from diminishing. Although in the second embodiment the pulleys having the same diameter are combined, the pulleys having different diameters may be combined. Although in the present invention one pair of pulleys is taken into the irradiation zone while another pair of pulleys is taken out of it, two or more pairs may be introduced into it. Introduction and withdrawal may be performed in any desired pattern. For example, one pair of pulleys 1 meter wide may be introduced into it while two pairs of pulleys 0.5 meter wide are taken out ot it. Also, introduction may be performed separately from withdrawal, i.e. not at the same time. As described above, the apparatus according to the present invention can withdraw, manually or by means of the position changing means, at least one of the pulley units from the irradiation zone, while moving thereinto another pulley unit loaded with an object having a different size. Therefore, this can render it unnecessary for an operator to enter the irradiation room to replace one pulley unit with another one. This can also shorten considerably the setup time for a change in the size of the object to be treated. For example, about one hour required with the conventional apparatus can be reduced to about 5 minutes. In addition, the present apparatus can compensate for the variations in load among the pulley units due to differences in throughput between the objects having different sizes by changing the treatment ratio. The work efficiency of the installation and of the accelerator can be increased, lowering the production cost. Moreover, the apparatus having a device for interrupting the electron beam for each divided irradiation zone allows the operation to continue even when there is no object passing through one divided zone.