US2501756A - Device for diaphragming x-rays - Google Patents

Description

March 28, 1950 Filed May 9, 1946 D. E. BERGGREN 2,501,756

DEVICE FOR DIAPHRAGMING X-RAYS 2 Sheets-Sheet 1 INVENTOR ATTORNEY March 28, 1950 E. BERGGREN 2,501,756

DEVICE FOR DIAPHRAGMING X-RAYS Filed May 9, 1946 2 Sheets-Sheet 2 INVENTOR 574 0F 5 MAM/f L BERGGRf/V Patented Mar. 28, 1950 UNITED STATES PATENT OFFICE DEVICE FOR DIAPHRAGMING X-RAYS Application May 9, 1946, Serial No. 668,377 In the Netherlands March 21, 1942 Section 1, Public Law 690, August 8, 1946 Patent expires March 21, 1962 Claims. (Cl. 250-105) In screening by means of X-rays it is usual to stop the beam of X-rays to such a degree as is admissible in view of the range to be viewed. This is essentially effected for reducing the detrimental secondary radiation.

In order to explore a body to be examined by means of the diaphragmed beam the X-ray tube and the fluorescent screen are usually coupled and jointly movable in a vertical and horizontal direction, the X-ray tube being so placed that the centre of the beam of rays transmitted by the stop coincides with the centre of the screen.

The device for stopping the rays usually consists of a housing which is shaped as a flat box having a window and is secured to the X-ray tube. This housing contains the stop proper which is made from a material by which the X- rays are strongly absorbed. As a rule use is made of a beam having arectangular section, and the size and ratio of the lengths of the sides of this section are variable. In this case the housing has a square window and the stop is constituted by two pairs of coupled slides, one pair being movable in a vertical direction and the other pair in a horizontal direction symmetrically with respect to the center lines of the square'window.

The movable system consisting of.the X-ray tube and the fluorescent screen represents a considerable mass; although it is balanced out by counterweights or by springs the continuous displacement of this mass in screening requires much bodily exertion in the long run. Hence, a progress is achieved if the device for stopping the rays is so arranged as to be movable with respect to the X-ray tube, so that the centre of the aperture of the stop can be shifted in every direction of its plane. In this case an optional part of the beam of rays emitted by the X-ray tube can be admitted to the fluorescent screen and in screening the whole object can be explored by moving solely the housing and the stop contained therein in front of the X-ray tube. The X-ray tube itself and the fluorescent screen need no longer be shifted.

The invention envisages another simplification. According to the invention, in a device for stopping X-rays, in which a stop is lodged in a housing having a window for the passage of the rays, the stop is movable with respect to the housing in such manner that the centre of the aperture is movable relatively to the centre of the window. By means of the device according to the invention the stopped beam of X-rays can be moved over the fluorescent screen without the need of shifting the X-ray tube or the housing of the stop.

The invention may be used both with a stop, having an invariable aperture and with a stop having a variable aperture, for instance a stop consisting of two dovetailed plates of an iris s op.

The stop is preferably movable to such a degree that with the smallest aperture to be adjusted the edge of the aperture can still be brought to the edge of the window which permits a maximum field to be covered, irrespective of the fact how far the stop is opened. The larger the aperture the smaller the required deflection.

According to the invention, a device for obtaining a rectangular section of the beam of rays, which comprises a stop operating with the usual four closing plates each of which bounds one side of the section of the beam, comprises a mechanism for moving the closing plates with respect to the housing, by means of which each pair of opposite sides of the rectangle can be moved at will in opposite directions symmetrically or in the same direction with a constant distance. The control of such a device can be simpler than that of a device in which the housing follows the movement of the stop. In the last-mentioned device sepa rate knobs are required for choosing the size and the place of the aperture with respect to the X- ray tube, since in one case solely the closing plates are to be shifted, and in the other case motive power has to be exerted on the housing. In the device according to the invention the same parts must be shifted in both cases and a similar movement is wanted. This permits the control knobs for the two adjustments to be easily combined.

This may be effected by connecting the closing plates mechanically to a movable element which can be shifted by means of a control knob. This element should be movable along a line and, moreover, be rotatable about an axis cutting this line. One movement of the closing plates can then be performed by the linear displacement and the other movement by rotation of the movable element.

This will be more fully explained by reference to Figures 1, 2 and 3 of the drawing.

Figures 1 and 2 represent very schematically two examples of the actuating mechanism on only one pair of closing plates and in Fig. 3, which is another example thereof, both pairs are also represented very schematically.

The two closing plates bounding the horizontal sides of the rectangular section of the beam are constructed to constitute flat slides designated by l and 2 in Fig. 1. One may imagine the upper slide I to be suspended, by means of a rod 3, from.

one end of a lever 4 whose other end can be moved up and down by means of a rod 5. This rod is shifted in its turn by means of a yoke 6 which is to be considered as the above-mentioned movable element. At the opposite end of the yoke the bottom slide 2 is suspended by means of the rod 1. The middle of the yoke 6 is movable in a vertical slot 8. This middle portion has also secured to it the handle 9. By means of this handle the yoke can be lifted along the line III untilit occupies the position indicated by the line i I, the rod 4 pivoting about the point I2 and the side I descending, the slide 2 being at the same time lifted by the rod I. Consequently, the plates -I and 2 approach each other, the slit indicated by a becomes steadily narrower, but the centre of the slit remains at the same point. Finally the slit is completely closed.

The handle 9 may also be turned about an axis normal to the line I!) through the point I3. In this case the yoke 6 occupies the position indicated by the line l4. During this displacement the left-hand end of the lever 4 descends and the slide I rises, the slide 2 rising too. Consequently the distance between the opposite sides of the rectangular section of the beam bounded by the plates I and 2 remains constant, but the slit moves from a to b.

In this way the handle 9 permits the vertical width of the slit to .be varied, but also the slit to be moved .over the fluorescent screen in a vertical direction.

The device may also be such that by moving the yoke along the line II) the slit is shifted and by rotation of the yoke about the point l3 the 7 width of the slit is varied. This is illustrated in Fig. 2. Both of the plates are suspended from the yoke by a rod the plate I by the rod is .at the right hand end and the plate .2 by .therod I5 .at the left-handend.

A similar mechanism may be used for the plates bounding the vertical sides of the rectangle. In this way the four movements can be accomplished by means of two control knobs. Instead of the closing plates being actuated by means of levers and rods this may be effected by a system of Bowden wires. Such a system is schematically represented in Fig. 3, where the reference number 2| designates the housing of the stop whose front plate has a square window 22. The closing plates 23 and 24 bound the 'vertical sides of the rectangular section of the beam of 'X rays passing through the window 22, whereas two other closing plates 25, 26 bound the horinarrower as the wires 21 and 28 are slackened.

In the same way the plates 25 and 26 are movable in a vertical direction. by means of Bowden wires 3! and 32.

The end of the wires 21 and 28 is connected to a slidable and rotatable yoke 33, whereas the end of the wires 3| and 32 is connected to a-slidable and rotatable yoke 34. When lifting the yoke 34 both of the wires 3| and 32 are slackened and the slit between the plates 25 and 26 becomes narrower. When lifting the yoke '33 the slit between the plates 23 and 24 becomes narrower.

The yoke 34 has been represented in a horizontal position and the yoke 33 in an oblique position, because the slit has been shifted to the left-hand side of the window 22. When turning the yoke i and is laterally supported therein.

4 33 about the axis 35 in a clock-wise direction the wire 28 is pulled and at the same time the wire 21 is slackened. Consequently the slides 23 and 24 move simultaneously with a constant relative distance over the window 22 to the right and upon further rotation of the yoke the aperture 36 of the stop moves to the extreme position at the opposite side of the window 22. Similarly a displacement of this aperture in a vertical direc- .tion can be obtained by rotation of the yoke 34 about theaxis 31.

.An accurate adjustment of the vertical and horizontal width of the slit can be obtained by a helicoidal movement. To this end the control knob,'in another form of construction of the device according to the invention, is secured to a screw spindle which is movable about its axis by means of this knob. Moreover, the screw spindle is'movable about an axis cutting the axis of the spindle. It carries a nut which upon rotation of the spindle about its axis does not follow this movement and may be connected to the closing plates by means of Bowden wires transmitting its movement-to these plates. In this construction the nut constitutes the movable element which by turning the screw is moved along-the axis of the screw spindle and, moreover, can be turned about an axis cutting the spindle. 1

The actuating mechanism of the stop according to the invention can be further simplified by uniting the control knob of one pair of clos-' ing plates and that of the other pair to form an assembly. By-moving the movable element associated with one pair of plates along a line and by moving the movable element associated with the other pair of plates along the same line one obtains one movement of the closing plates, for instance, the opening and closing of the slit; By rotation of the combined control knobs about two axes cutting each other at right angles at a point of the'said line the other movement of the closing plates is obtainable -i. e. shifting'of the slit in the present example. In this case two co-axial screw spindlesmay be used, one of which projects from the other and each comprising a control knob and a nut supported on a yoke which is rotatable about the point of intersection of a stationary shaft and the common axis of the screwspindles bymeans of a cardan joint or a ball and 'socket'joint. To both of the nuts are secured Bowden wires by which the movement '01 the nuts is transmitted to the closing plates of the stop. The shafts of these Bowden wires are secured with their ends crosswise around the stationary shaft and end parallel with this shaft.

One'form of construction of this device is rep resented in Fig. 4. A screw spindle M is rotatable in a-tube42 and restsin a step bearing 43, the tube 42 being also provided with screw thread at the .outside. The step bearing 43 is secured to a'yoke'44. In order to support the coaxial screw spindles M and 42 a plate 45 and a cup 46 are secured to the yoke 44. The spindle 42 passes to the outside through an aperture in thiscu'p Below the yoke is a cardan joint 41 constituting a coupling between a shaft 49, which is stationary with respect to a bed plate 48 and extends normally to this plate, and-the movable axis 52 of the screw spindles. The screw spindle 4i carries a nut 50. To the end of the spindle 4| which stands above the spindle-His secured a control knob 5|. On' turning this knobthe .spindle 4 I rotates about its axis-and the nut moves along the axis 62.

The spindle -42 also carries a nut, which is designated by 53, and a control knob 54. On turning the knob 54 the nut 53 waves along the shaft 52. The nuts and 53 are prevented from following this movement by rods 55 and 56 which slide between two partitions 57 secured to thecup 45. Upon displacement of the movable elements 50 and 53 along the line 52 the yoke does not follow this movement in this case, but the Bowden wires 58 and 59, whose ends are secured to the nut 50, and the Bowden wires 56 and GI (indicated in dotted lines) which extend in a plane normal to the plane of the drawing and whose ends are secured to the nut 53, are pulled on turning the knobs 5| and 54 if the nuts are moved away from the yoke 44 and slackened if they are moved towards the yoke. They pass over a spherical part of the yoke 44 and through radial slits 62 in the plate 45.

The shafts 63 of the Bowden wires end parallel with the stationary shaft 49 and are secured crosswise about this shaft in apertures oi the bed plate 48. They are jointly surrounded by a funnel 64 which is secured to the bed plate and emerges into a tube 55 which may be flexible so that it can be easily placed along the constructional parts of the screening stand.

The other end of the wires 55 and 59 may be imagined to be secured to the closing plates bounding the vertical sides of the section of the beam of X-rays, whereas the other end ofthe wires and 6| is secured to the two other closing plates.

If on turning the knob 5| the nut 55 is moved away from the yoke 44 the wires 58 and 59 are pulled over the same distance. Consequently the jaws of the closing plates, to which these wires are secured, for instance the plates 23 and 24, move away from each other, one of them passing as far to the left as the other moves to the right. Consequently the slit between the plates becomes broader but the centre of the slit remains at the same point. The same holds for the two other plates if by turning the knob 54 the nut 53 is moved away from the yoke 44'. When moving the nut in an opposite direction along the shaft 52 the springs 29 and 30 (Fig. 3) keep the wires taut and cause the jaws of the closing plates to approach each other so that the slit becomes narrower without the centre of the slit being shifted. Hence, the size and the ratio of the sides of the image field can be controlled by means of both control knobs 5| and 54 jointly constituting one handle.

The spindles ll and 42 are also rotatable about an axis 55 (normal to the plane of drawing), by which the axis 52 is normally cut, and about an axis Bl normally cutting the axis 65 at the same point as the axis 52. The cup 45 is shaped as a hemisphere whose centre is located in the point of intersection of the three axes 52, 66 and 61. It is partly surrounded by a dust helmet 68 having a spherical portion which adjoins a cylindrical portion secured to the bed plate 43.

When turning the spindle 41 about the axis 56 so that the axis is shift-ed from 52 to 59, the wire 58 is slackened, whereas the wire 59 is pulled.

In this case both of the jaws of the closing plates 23 and 24 move in the same direction and their relative distance remains the same. The centre of the slit is now shifted over the image field but the width of the slit remains unchanged. The two other plates do not move, since the wires 6|] and 5| bend themselves about the edge of the slits 62 in the plate 45 but do not move in their own direction.

When it is desired to raise or lower the slit this may be efiected by turning the spindle 42 about the axis 51. In this case the wires 58 and 59 are not shifted, but bend themselves only about the edge of the slots 62, which are visible in the drawing, whereas the wires 50 and 6| provide for a displacement of the plates 25 and 25 in the same direction. The four movements referredto may be combined, thus bringing the centre of the aperture of the stop at any point of the image.

field, and the aperture can be made as high and as bright as is allowed by the slide construction in the housing 2|.

Since a rotation in a clockwise direction usually corresponds to a closing movement that is good practice to provide the spindles 4i and 42 with a left-handed screw thread. When turning the knobs 5| and 54 in a clockwise direction the nuts 50 and 53 move towards the yoke 44 and the wires are slackened, so that the slits are closed.

Of course, the same can also be achieved with a right-handed screw-thread if the movement at the stop is reversed by a lever system or toothed gearing. In this case the springs have to separate the'closing plates. Such a reversing system may also be used for increasing or decreasing the displacement of the plates.

Easy control is also promoted by providing that the upward movement of the knobs 5| and 54 corresponds to the rise of the aperture 35, and the movement of these knobs to the left corresponds to a lateral displacement of this aperture to the left. This may be considered in securing the operating mechanism (shown in Fig. 4) to the stand. In this case, the exploration of the image field and adjustment of the aperture of the stop is extremely simple. What I claim is: 1. X-ray apparatus comprising an X-ray tube housing, a window in said housing, a diaphragm the beam, and a common control mechanism for simultaneously actuatingeach pair of shutters selectively to move in opposite and the same directions an equal distance for altering the dimensions of said aperture and to move the center of said aperture relative to the center of said Window.

2. X-ray apparatus comprising an X-ray tube housing, a window in said housing, a diaphragm for defining an effective aperture in said Window of said housing for the passage of a beam of X- rays comprising two pairs of adjustable shutters impervious to X-rays for defining a section of ters selectively to move in opposite and in the same directions an equal distance for altering the dimensions of said aperture and to move the center of said aperture relative to the center of said window, and flexible members coupling said control member to said shutter to transmit movement of said control member to produce movement of said shutters.

3. X-ray apparatus comprising an X-ray tube housing, a window in said housing, a diaphragm for defining an effective aperture in said window of said housing for the passage of a beam of X- rays comprising a plurality of adjustable shutters impervious to X-rays, a control member movable along an axis to efiect movement of said shutters in order that the center said aperture is moved relative to the center of said window and rotatable about'an axis perpendicular to said axis of movement to effect movement of said shutters in order that the dimensions of said apertures are altered, and flexible members coupling said control member to said shutters to transmit movements of said control element to produce the corresponding movements of said shutters.

4. X-ray apparatus comprising an X-ray tube housing, a window in said housing, a diaphragm for defining a rectangular aperture in said window of said housing for the passage of a beam of X-rays from said tube comprising four adjutable shutters impervious to X-rays, a first control member movable along an axis to efiect lateral movement of one; pair of said shutters and rotatable about an axis perpendicular to said axis of movement to effect movement of said pair of shutters toalter the, one dimension of said rectangular aperture, a second control member movable along a second axis to effect lateral movement of a second pair of shutters and rotatable about an axis perpendicular to said second axis of movement to effect movement of said second pair of shutters to alter the other dimensions of said rectangular aperture, and flexible members coupling said control members to said respective pairs of shutters to produce the corresponding movements of said shutters.

5. X-ray apparatus comprising an X-ray tube housing, a window in said housing, a diaphragm in said housing for defining a rectangular aperture in said window of saidhousing for the passage of a beam of X-rays from said tube com prising four adjustable shutters impervious to xrays, and a control mechanism for adjustably positioning said shutters with respect to said window to alter the dimensions of said rectangular aperture and to move the center of said aperture relative to the center of said window comprising a pair of coaxial screw spindles, a nut on each spindle movable laterally along said spindle when said spindle is rotated, a shaft member, means to rotate said coaxial spindles about said shaft member, and flexible members coupling each of said nuts to respective pairs of shutters to transmit lateral movement of said nut to actuate each pair of shutters to move in opposite directions an equal distance to alter the dimensions of said aperture and to transmit rotary movement 01' said spindles about said shaft member to actuate each pair of shutters to move in the same direction an equal distance to move the center of said aperture relative to the center of said window.

DETLOF EMANUEL BERGGREN.

REFERENCES CITED The iollowing references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,117,266 Snook et a1. Nov. 17, 1914 1,709,626 McGunnigle Apr. 16, 1929 1,738,945 Brenkert et a1. Dec. 10, 1929 1,909,118 Raab May 16, 1933 1,953,497 Nelson Apr. 3, 1934 2,082,965 Lundquist June 8, 1937

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