Patent Number: 
Section: claims

1. A multi-leaf collimator comprising leaf plate driving bodies, each including a plurality of movable leaf plates and provided respectively on one side and the other side, the plurality of leaf plates of said leaf plate driving body on one side and the plurality of leaf plates of said leaf plate driving body on the other side being disposed in an opposing relation to form an irradiation field of a radiation beam between the opposing leaf plates, wherein each of said leaf plate driving bodies comprises one rotating device for moving said plurality of leaf plates along one direction by engaging with said plurality of leaf plates; and  driving force transmitting/cut-off device for transmitting driving force of said rotating device to said plurality of leaf plates by moving said plurality of leaf plates along the other direction across said one direction and engaging them with said rotating device and cutting off said driving force selectively for each leaf plate by disengaging a selected one of said plurality of leaf plates with said rotating device. 2. A multi-leaf collimator according to  claim 1 , wherein each of said leaf plate drive bodies further comprises holding device for abutting against the leaf plates to hold the leaf plates in stationary positions. claim 1 3. A multi-leaf collimator comprising leaf plate driving bodies, each including a plurality of movable leaf plates and provided respectively on one side and the other side, the plurality of leaf plates of said leaf plate driving body on one side and the plurality of leaf plates of said leaf plate driving body on the other side being disposed in an opposing relation to form an irradiation field of a radiation beam between the opposing leaf plates, wherein each of said leaf plate driving bodies comprises one rotating device for moving said plurality of leaf plates together along one direction by engaging with said plurality of leaf plates; and  a plurality of engaging/disengaging devices provided in a one-to-one relation to the plurality of leaf plates for selectively engaging and disengaging a corresponding leaf plate with and from said rotating device by moving said corresponding leaf plate along the other direction across said one direction. 4. A multi-leaf collimator according to  claim 3 , wherein each of said leaf plate driving bodies further comprises holding device for abutting against the leaf plates to hold the leaf plates in stationary positions. claim 3 5. A medical system including an accelerator, the medical system comprising: an accelerator; and  an irradiator having a collimator through which a radiation beam emitted from said accelerator passes, and irradiating the beam having passed said collimator,  said collimator comprising leaf plate driving bodies, each including a plurality of movable leaf plates and provided respectively on one side and the other side, the plurality of leaf plates of said leaf plate driving bodies being disposed in an opposing relation to form an irradiation field of the radiation beam between the opposing leaf plates, each of said leaf plate driving bodies comprising one rotating device for moving said plurality of leaf plates along one direction by engaging with said plurality of leaf plates, and driving force transmitting/cut-off device for transmitting driving force of said rotating device to said plurality of leaf plates by moving said plurality of leaf plates along the other direction across said one direction and engaging them with said rotating device and cutting off said driving force selectively for each leaf plate by disengaging a selected one of said plurality of leaf plates with said rotating device. 6. A medical system including an accelerator according to  claim 3 , further comprising control device for controlling said rotating device and said transmitting/cut-off device. claim 3 7. A medical system including an accelerator, the medical system comprising: an accelerator; and  an irradiator having a collimator through which a radiation beam emitted from said accelerator passes, and irradiating the beam having passed said collimator,  said collimator comprising leaf plate driving bodies, each including a plurality of movable leaf plates and provided respectively on one side and the other side, the plurality of leaf plates of said leaf plate driving bodies being disposed in an opposing relation to form an irradiation field of the radiation beam between the opposing leaf plates,  each of said leaf plate driving bodies comprising one rotating device for moving said plurality of leaf plates together along one direction by engaging with said plurality of leaf plates, and a plurality of engaging/disengaging devices provided in a one-to-one relation to the plurality of leaf plates for selectively engaging and disengaging a corresponding leaf plate with and from said rotating device by moving said corresponding leaf plate along the other direction across said one direction. 8. A medical system including an accelerator according to  claim 7 , further comprising control device for controlling said rotating device and said engaging/disengaging device. claim 7