US2257050A - Timing apparatus for x-ray exposures - Google Patents

Description

p 2 1941. E. R. GOLDFIELD TIMING APPARATUS FOR X'RAY EXPOSURE-S Filed Aug. 19, 1940 2 Sheets-Sheet 1 nmm INYENTOR I EDWIN R. GOLDFIELD BY w oE / ATTORNEYS Sept- 23, 'E. R. GOLDFIELD 2,257,050

TIMING APPARATUS FOR X RAY EXPOSURES Filed Aug. 19, 1940 2 Sheets-Sheet 2 FIG-3 INVENTOR EPWIN R. GOLDFIELD 4 B A ATTORN EYS Patented Sept. 23, 1941 TIIWING APPARATUS FOR X-RAY EXPOSURES iEdwin R. Goldfield, University Heights, Ohio, assignor to Picker X-Ray Corporation, Waite Manufacturing Division, Inc., Cleveland, Ohio, a corporation of Ohio Application August 19, 1940, Serial No. 353,179

8 Claims.

This invention relates to improvements in timing apparatus for X-ray exposures.

An object of the present invention is to provide cheap but effective means for timing X-ray exposures arranged in a novel manner.

Another object of the present invention is to provide a relatively simple exposure timing means which utilizes to the utmost the rays generated by the tube during the time it is operating but which prevents the taking of roentgenographs during the first few moments after the tube starts to operate so that pictures are not taken while current is surging in the tube and thus grid lines on the plate are avoided.

The invention also includes the structure hereinafter disclosed for carrying out the above described purposes and the essential features thereof are set forth in the claims.

In the drawings, Fig. 1 is a top plan view of an X-ray tube equipped with my improved timing apparatus; Fig. 2 is an elevational view of the same device; Fig. 3 is an end view thereof; while Figs. 4 and 5 are diagrammatic views of the operating and control circuits.

While my invention may utilize various means for controlling the X-rays during an exposure including shutters of various types such as the scissors type and others, I have illustrated as a preferred embodiment thereof the use of a shutter involving an open slit in a screen which is caused to move transversely of the tube opening. In the various views an X-ray tube of the usual type is illustrated at in a housing Illa which is provided with an opening at II which is normally closed by a lead plate screen l2 provided with an open slit l3 which is in the position of Fig. 2 before an exposure is made. This lead plate is supported for reciprocating movement from the full line position of Fig. 2 to the dot-dash position thereof in frictionless supports which for the purpose of simplification are shown at M in a conventional manner. It will be understood that this detail has nothing to do with the present invention. Means is provided for urging the lead plate screen i2 from the position of Fig. 2 towar the right upon release of the controlling mecha nism. The means here shown comprises a helical spring l supported at one end on a stud Hit of the lead screen and supported at the other end on a shoulder I6a of a bracket 16 which carries a pointer Iiib which passes over readings on a scale l'i calibrated in seconds of exposure. The bracket IE is controlled by a screw 18 threaded into a fixed bracket I!) mounted on the tube.

Obviously by moving the screw I8 toward the 55.

right as viewed in Figs. 1 and 2 the spring I5 is compressed so as to give a greater speed of movement to the lead screen l2 as it moves from left to right. The lead screen is moved against the action of spring l5 to the cooked position shown in full lines in Figs. 1 and 2. It is held in this position by a dog 20 which engages a finger I2b on the screen. The dog has a pivotal mounting at 2| and is controlled by the armature of a relay 22. The movement of screen [2 toward the right is cushioned by a dashpot 23 in which is housed a piston 24 which is connected by rod 25 with the finger I2b or some other suitable portion of the lead screen.

A suitable control circuit for the device of Figs. 1 to Sis indicated in Fig. 4. The tube at H) is supplied with current from the secondary 26a of the high tension transformer 26 whose primary 2% is connected by lines 21 and 28 and switches 29 and 30 with a source of power L1, L2. Another switch 3| connected for movement simultaneously with switches 29 and 30 serves to control the supply of current to relay 22 and also to maintain the switches 29, 30 and 3! closed after such closure has been manually initiated. The power circuit for relay 22 is from the source La through line 32, switch 3|, line 33, relay 22, line 34, switch 35, line 36, manually controlled switch 31 and line 38 to the source L4. Another circuit passes from the source L3 through line 39, solenoid 40 and line 41 to the line 34 and thence back to the source L4.

The switch 35 as best seen in Fig. 1 comprises a pair of normally closed contacts 35a and 35b, the latter being provided with an arm 350 which extends into the path of travel of some part of the lead screen l2 such as the finger l2b which engages the arm 35c and opens switch 35 when the lead screen reaches the dot-dash position of Fig. 2.

It is thought the operation of the device will now be apparent. When the pointer I'ob has been adjusted by screw [8 for the desired exposure as read upon scale I! and with the lead screen held by the dog 20 as shown in Figs. 1 and 2, the manually controlled switch 31 is closed thus energizing solenoid 40 and closing switches 29, 30 and 31; Current is immediately supplied to the X-ray tube but the shutter does not start to move immediately because of the combined electrical and mechanical delay in the tripping of the dog 20. This combined delay is of the order of a few half cycles of the high tension current so that the surging of the current in the Y- ray tube has ceased before an exposureoccurs. The device here disclosed is so constructed that the time necessary to build up sufficient pull in the relay 22 to release the dog 20 is at least three half wave lengths of the high tension current or say am of asecond. The relay 22 when sufficiently energized trips the dog 20 releasing the shutter or screen E2 to the action of spring [5 which moves the same toward the right as viewed in Figs. 1 and 2 causing the slit l3 to pass across the tube'opening and produce an exposure of the duration desired. At the end of its travel screen- I2 opens switch 35 which breaks the energizing circuit for solenoid 40 thus releasing the main switch whichisopened by its spring and causes operation of the tube to cease. Obviously the manually controlled switch or button 3'! could be opened at any time desired 'so as to cause deenergization of the solenoid 40 and the opening of the switches 29 and 30. An alternative control circuit is illustrated Fig. 5 where parts having similar functions to that already described are given similar reference characters; The only difference between the two' control systems is that the relay 22 is placed in circuit with the high tension transformer secondary. To this end the relay is connected by lines 42 and 43 in the ground circuit of the transformer secondary 26a. This control circuit operates in the same manner as the one already described.

'Power' means may be provided if desiredfor returning the screen 12' from the dot-dash position of Fig. 2- to the full line or cooked position thereof; Means here shown for this purpose includes a motor 44 which drives a pinion 45 meshing with a rack '46- carried by anextension of the dashpot rod 25. An arm 4'! carried by this rod is adapted to engage the flexible support 48a of contact 481: move it out of engagement with contact 49 to open the control circuit when the screen reaches the cocked position where dog 20 engages the projection l2b. The control circuit for motor 44 is shown in Fig. 4 wherelines- M ami connected respectively with the sources L3; L4, are'connected with lines 52' and 53 by switches 54 and 55 upon opening of the-switches 2-9, 38 and 3i. Line 53 is connected with motor 44 and line 52 is connected through switch 56 and line 51 with motor 44. Switch 56 comprises the contacts 43 and 49 previously described. It is believed the operation of motor 44 will now be apparent. With the screen in the dot-dash position of Fig. 2, switch 56 will be closed and at the completion of an exposure when switches 2-5 and 30 open, the switches 54 and 55 will close thus energizing motor 44. This will drive the screen back to the full line position of Fig. 2, finally causing the opening of switch 55 and stopping the operation of motor 44. 7 When the next exposure occurs the switches 54, 55 will be opened immediately and as the exposure takes place switch 55 will be closed later thus putting the parts in condition to re turn the screen to cocked position after the exposure has been completed.

It will be understood that the opening at the right-hand end of dashpot 23 as viewed in- Figs. 1 and: 2' is just sufficient to permit the passage of the rod which carries the rack-teeth 46. This rodis then cut awayfor the major portion of its length as shown at 450, but again increases to the full size of the opening in the end of the dashpot as shown at 461) for a short distance ahead of the piston 24.. It results from this construction. that on. exposure movement of the shutter it will travel for full speed. across the 75* X-ray tube opening trapping air ahead of the piston 24 just at the end of the shutter stroke so as to cushion the movement at that point.

While the screen or shutter I2 is shown for. simplicity mounted on the outside of the tube; housing Ina, it will be understood by those skilled time comprising an X-ray tube, a high tension operating circuit therefor, switch means for causing operation of said circuit, normally closed shutter means. opaque to X-rays for controlling the rays. from said tube, and means for causing opening of said shutter means at an interval after the closing. of said switch means of the order of a few half cycles of said operating circui-t.

3. Means for controlling X-ray tube exposure time. comprising an X-ray tube, a high tension operating circuit therefor, switch means for causing operation ofsaid circuit, normally closed shutter means opaque to. X-rays for controlling the rays from said tube, means for tripping said shutter to produce an exposure including an electrically operated relay, an electric circuit controlling said relay, and means'for closing said relay control circuit and said switch means substantially simultaneously, said relay having a combined electrical and mechanical delay causingoperation thereof at an interval after electrical energization of said relay of the order of a few half cycles of said operating circuit.

4. The combination of claim 3 including means for breaking. said tube operating circuit upon completion of exposure operation of said shutter.

5. Means for controlling X-ray tube exposure time comprising an X-ray tube, a high tension operating circuitv therefor, switch means for causing operation of said circuit, shutter means for controlling the rays from said tube, said shutter means comprising a reciprocating screen having a slit therethrough adapted to travel across. the tube opening'upon screen reciprocation, spring means urging said screen in exposure-producing direction, a dog for holding said screen against the action of said spring, an-

electrically operated relay for releasing said dog, an electric: circuit controllingsaid relay, means for closing said relay control circuit and said switch means substantially simultaneously, and means operable by said shutter upon completion of its exposure-producing travel for breaking said tube. operating circuit. 7

6. Means for controlling X-ray tube exposure time comprising an X-ray tube, an operating circuit. therefor, switch means for closing said circuit, shutter means for controlling the rays fromv said tube, said shutter means comprising a reciprocating screen having a slit therethrough adapted to travel across the tube opening upon screen reciprocation, spring means urging said screen. in exposure-producing direction, power means for moving said screen in the opposite direction. to cocked. position, means for holdingsaid screen in cocked position, and means for releasing said last named means responsive to closing of said switch means.

7. The combination of claim 6 wherein said power means is electrically operated and comprises an electrical circuit energized by completion of a shutter-controlled exposure.

8. The combination of claim 6 wherein said power means includes an electric motor and an energizing circuit therefor, said circuit including a. switch closable by opening of said first named switch means, and including a switch openable by movement of said screen to cocked position. v

EDWIN R. GOLDFIELD.

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