Patent GB-791872-A (GB)
Title: X-ray apparatus
Inventor: STAVA ROBERT JOSEPH
IPC: G03B42/02
Filed: 1956-03-16
Abstract: 791,872. X-ray apparatus. PICKER X-RAY CORPORATION WAITE MANUFACTURING DIVISION. Inc. March 16, 1956, No. 8269/56. Class 98(1) X-ray apparatus for serial radiography includes a frame carrying a fluorescent screen and having a work station under the screen and a storage station beside the screen, a carriage movable from one station to the other along the frame, and a cassette tray movable along the carriage transversely of the frame independently of the longitudinal movement of the carriage; an electric motor being provided on the frame to move the carriage along the frame and the tray along the carriage, and a settable member and indexing means being provided to stop the carriage and tray in pre-selected positions with respect to the work station. As shown in Fig. 2, a frame 12, which is adjustably supported on the tube stand of an X-ray table in known manner, carries a fluorescent screen 15 at one end. A carriage 30 is movable along the frame between the working position under the screen and the storage position at the side thereof, and a cassette tray 21 is movable along the carriage. The carriage and tray may be stopped in various positions to allow the film in the cassette to be exposed sequentially in parts which are in turn centred on the axis of the X-ray beam. The carriage is moved along the frame by means of an arm 52, Fig. 18, which is driven through a slipping clutch, from an electric motor. A shift lever 53 is connected to the arm 52 by means of a link 61 having a curved arm and which carries a pin 62. which extends through a slot 60 in arm 52 and carries a roller engaging a channel-like guideway 64 on the carriage 30. As a result, when the motor is energized, the carriage 30 is moved towards the fluorescent screen until it is arrested by means to be described later. For effecting the transverse travel of the cassette carrier, an arm 70, Fig. 17, is also driven from the same electric motor by a slipping clutch, and incorporates a lost motion connection between a plate 73 of the clutch and a projection 72 on the arm 70. The outer end of the arm 70 is connected by a link 76 to an inverted channel shaped guideway 78 pivoted at one end 79 to the frame (see also Fig. 2). A roller mounted on the tray engages the guideway 78. The extent of the movement of the arm 70, and hence the guideway 78, is determined by means also to be described below. Mechanism for controlling the longitudinal travel. The member for selecting the position to which the cassette tray is to be moved is set by means of an indexing member 35, Fig. 12, which may be set to various positions in which different parts of the film in the cassette are to be exposed, as shown. The spindle 91 of the knob 35 carries a cam 90 (see Figs. 18 and 20) having a series of holes 92 therein to co-operate with a spring pressed ball, not shown. A spring loaded lever 94 has a pin 93 acting as follower to the cam 90, whereby a pin 102 at the end of the lever 94 takes up various positions according to the position selected by the knob 35. The pin 102 may occupy three positions, in one of which it engages the shoulder 105 on the lever 53, and in the third position it engages none of the shoulders so that the lever 52 can rotate unchecked through 180 degrees. Cam 90 thus controls the selection of three of the longitudinal positions to which the carriage 30 can be moved A second cam 108 (see Figs. 18 and 19) cooperates with a pin 109 on a spring loaded lever 110, in order that the pin 113 carried at the end thereof may be brought into three different positions. This pin may be brought into the path of either of the shoulders 114, 115 on the lever 53, or out of the path of either, in order to select a further two longitudinal positions of the carriage 30. Mechanism for controlling the cross travel. As shown in Fig. 17, the movement of the arm 70 controlling the cross travel of the cassette tray is controlled by a cam 116, which is also mounted on the spindle 91. A lever 117, pivoted at 96, has a pin- and-slot connection with the arm 70, so that when the arm 70 is rotated, it is free to turn until a pin 120 on the lever 117 meets the edge of the cam 116. Cam 116 is provided with indentations of various depths, which determines the position in which the cassette tray is to be stopped, and also prevent movement of the spindle 91 once the pin 120 has been moved into an indentation. This prevents alteration of the index 35 until the cassette carriage and tray have been retracted. Automatic indexing mechanism. When the film in the cassette is to be exposed in four quarters, the spindle 91 is first set for exposure of the first quarter, and thereafter movement of the carriage causes the selector mechanism to move automatically into the positions required for exposure of the subsequent three quarters. Similarly, where the film is to be exposed in two halves, after exposure of the first half the movement of the carriage resets the mechanism for the exposure of the second half. As shown in Fig. 8, a plate 131 is mounted to move slidably under action of a spring 135. When the carriage 30 is retracted, a projection thereon engages a finger 130 on the plate 131, and moves the plate back against action of spring 135 to the position shown in full lines in Fig. 8. When the carriage begins its first movement, the plate is allowed to move into its chain-dotted line position. In this position, a bell crank lever 140 is pulled by a spring 143 into a position such that a pin 142 at its end is brought into position where it will engage a shoulder on a wheel 145 mounted on the shaft 91. On retraction of the carriage 30, plate 131 is returned to its full line position, upon which pin 142 engages the shoulder 146 of the wheel 145. rotating the shaft 91 with its cams and the knob 35 to the next position. A fixed stop 147 rocks lever 140 so that pin 142 is clear of the wheel 145. If the knob 135 has originally been set for the exposure of the first quarter of the film, in the three subsequent movements the cassette tray is positioned for the exposure of the remaining three quarters. In the next position, no exposure is to be made and there is no notch provided on the indexing wheel 145. Two further shoulders are provided on other positions of the wheel 145 in order to provide automatic -indexing when the film is to be exposed in two halves. Electrical circuit. Fig. 4 shows the arrangements for driving the motor 40, which provides the power for moving the carriage and the cassette tray. One side of the motor 40 is connected by a line 152 to a supply of electrical current S. The other side of the electrical supply is connected to the motor through a thumb-operated switch 150, through a switch 155, if closed. This circuit causes the motor to rotate in .such a direction as to retract the carriage, at the end of which movement switch 155 is open. When switch 150 is operated, a circuit is completed through a switch 158, if that switch is closed; and switch 158 is always closed unless the knob 35 is in its fifth position, in which no exposure is to be made. The circuit completed through the switch 158 causes the motor to rotate in a direction to move the carriage and cassette tray to the chosen work position, where it is held when the selected stops have been engaged. Release of the switch 150 immediately causes retraction of the carriage 30, which causes automatic resetting of the indexing means when the film is to be exposed in quarters. Grid actuating device. A Bucky grid may be reciprocated during radiography by means of a heart-shaped cam 173, Fig. 7, co-operating with rollers 174, 175 on an arm 176 attached to the grid. The cam is driven by an electric motor 171, which, as will be seen from Fig. 4, is energized whenever the switch 150 has been actuated to make an exposure.