Beam-limiting device for radiographic apparatuses

A method of limiting a X-ray beam, in particular in connection with an extraoral radiographic apparatus, wherein at least two blades (3, 3′, 3″, 13;

• 4, 4′, 4″, 14) of a blade limiting device (1, 1′, 1″, 11) are moved by one common actuator (9, 9′, 9″, 19) only, so as to produce a X-ray beam having a desired shape, the at least two blades being movable one with respect to the other changing a mutual distance, thereby varying a width of an aperture through which a X-ray beam passes, the aperture being delimited on two opposite sides by respectively one of the at least two blades, the method comprising:
• displacing along a path of a predefined length the at least two blades (3, 3′, 3″, 13;
• 4, 4′, 4″, 14) together with the actuator (9, 9′, 9″, 19) in a same first and second direction, the second direction being opposite to the first direction;
• displacing a second one of the at least two blades relative to a first one of the at least two blades along a predefined path, thus enabling a distance between the at least two blades to be varied, either increased or decreased;
• linking the first blade (3, 3′, 3″, 13) to the actuator with a rigid link (35, 32), thereby maintaining the same relative position in relation to the actuator;
• linking the second blade (4, 4′, 4″, 14 to the actuator (9, 9′, 9″, 19) with a friction device interposed between the second blade (4, 4′, 4″, 14) and the rigid link (33, 35), the friction device allowing the second blade to be displaced relative to the rigid link (33, 35) to the actuator;
• and
• providing a stop device (5, 5′, 6, 6′) that cooperates respectively with a leading edge of the second blade (4, 4′, 4″, 14) relatively to the two opposed directions, thereby preventing a common displacement of the second blade in any of the two opposed directions with the first blade for a length of the path of the first blade.

A device (1, 1′, 1″, 11) limiting a X-ray beam emitted from a X-ray source, comprising:

• at least two blades (3, 3′, 3″, 13;
• 4, 4′, 4″, 14) collimating a X-ray beam;
• and
• a single common actuator (9, 9′, 9″,19) moving the at least two blades (3, 3′, 3″, 13;
• 4, 4′, 4″, 14) in a same direction, even under a condition of inversion of a movement direction, wherein a first one of the at least two blades (3, 3′, 3″, 13) is rigidly linked to the single common actuator (9, 9′, 9″,19) such that the first blade maintains its relative position in relation to the actuator (9, 9′, 9″,19), and
• wherein a second one of the at least two blades (4, 4′, 4″, 14) is linked to the common actuator (9, 9′, 9″,19) by interposing a friction device between the second blade and a rigid link to the common actuator (9, 9′, 9″,19), and a movement of the second blade in common with the first blade is limited on both sides of the second blade, which are oriented toward one of two opposed translation directions, respectively, by at least an end of stroke (5, 5′;
• 6, 6′;
• 94) cooperating with one of said sides.