US 2892947 A
Description (OCR text may contain errors)
June 30, 1959 R. M. 'EMANUELSON 2,392,947
X-RAY GENERATOR MOUNT Filed Aug. 31, 1955 2 Sheets-Sheet 1 V 1/ A .4 :G
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Juhe 30, 1959 R. M. EMANUELSON 2,392,947
X-RAY GENERATOR MOUNT Filed Aug. 31, 1955 2 Sheets-Sheet 2 il w //////I/III Unitcd States Patet 2,892,947 Patented June 30, 1959 X-RAY GENERATOR MOUNT Roy M. Emanuelson, Woburn, Mass, assignor to High Voltage Engineering Corporation, Cambridge, Mass, a corporation of Massachusetts Application August 31, 1955, Serial No. 531,785
3 Claims. (Cl. 25091) This invention relates to apparatus for supporting highvoltage X-ray generators, and in particular to a mount for heavy X-ray generators, such as those used in supervoltage therapy and industrial radiography, adapted to provide vertical movement of such heavy X-ray generators with minimum power, maximum safety, and a minimum amount of heavy machinery.
In accordance with the invention, power requirements are minimized by providing the equivalent of a counterweight, wherein the downward force exerted by the heavy X-ray generator is opposed by the upward force of a hydraulic or pneumatic ram, one end of which is connected to the X-ray generator and the other end of which is mounted in some fixed position. The hydraulic or pneumatic ram derives its upward force from gas under pressure provided by a gas reservoir.
The source of motive power which imparts the desired vertical movement to the X-ray generator is a leadscrew system comprising a lead-screw and a gear motor mounted in a fixed position and a lead-screw nut attached to the X-ray generator. When the lead-screw is rotated by the gear motor, the X-ray generator is lifted or lowered; but the. actual force that the lead-screw system has to work. against is very small, since it is the difference between the force of the Xray generator exerted downward and the force of the hydraulic or pneumatic ram system exerted upward.
Safety is provided by-virtue of the fact that the leadscrew system by'itself is capable of supporting the X-ray generator, in the event of gas pressure failure, in any position.
The use of a hydraulic or pneumatic ram system avoids the heavy machinery required with ordinary counterweights or with such mechanical devices as would be required to lift the X-ray generator with no counterweight or its equivalent. By thus making possible the use of small cylinders, pistons, motors, and other such components, the invention avoids the use of bulky apparatus.
The invention may best be understood from the following detailed description thereof, having reference to the accompanying drawings, in which:
Fig. 1 is a diagram illustrating the principles of the invention, and showing the use of a pneumatic ram;
Fig. 2 is a diagram similar to that of Fig. 1, but showing the use of a hydraulic ram in conjunction with a hydraulic accumulator; and
Fig. 3 is an isometric projection showing an X-ray generator supported on an overhead mount constructed in accordance with the invention.
Referring to the drawings, and first to Fig. 1 thereof, a pneumatic ram 1 comprising a piston 2 and a cylinder 3 is connected to a heavy X-ray generator 4 in such a way that the downward force of the generator 4 tends to push the piston 2 into the cylinder 3. Gas under pressure is fed into the cylinder 3 from a gas reservoir 5 via a suitable length of tubing 6, so that the gas under pressure exerts an upward force on the piston 2 which opposes the downward force exerted by the weight of the generator 4. The total volume of the gas enclosure, which includes the gas reservoir 5, the tubing 6 and part of the cylinder 3, should be large relative to the total displacement of the piston 2, so that changes in both volume and pressure are small as the piston 2 moves from its collapsed to its extended position. The gas in the reservoir 5 is contained under substantially constant pressure and consequently is not to be considered as the source of motive power which imparts vertical movement to the X-ray generator 4.
The source of motive power is a lead-screw system comprising a lead-screw 7 and a gear motor 8, which are mounted in a fixed position, and a lead-screw nut 9, which is attached to the X-ray generator 4. Operation of the gear motor 8 causes the lead-screw 7 to rotate, which in turn imparts translational movement to the lead-screw nut 9, so as to move the X-ray generator 4 vertically. However, owing to the action of the pneumatic ram 1, the actual work which must be done by the lead-screw system is very small, so that the size and power output of the gear motor 8 may be correspondingly small.
For practical reasons, it will generally be preferable to employ, instead of the pneumatic ram 1, a hydraulic ram whose cylinder communicates with a suitable hydraulic accumulator upon which pressure is exerted by the gas from the reservoir 5. Such a modification is shown in Fig. 2, wherein a hydraulic ram 10, comprising a piston 11 and a cylinder 12, is connected to the X-ray generator 4 in the same manner as the pneumatic ram 1 of Fig. l. The piston 11 rests on a liquid, such as oil, which is fed into the cylinder 12 from a hydraulic accumulator 13 via a length of tubing 14. The hydraulic accumulator 13 comprises an elastic membrane 15 compression of which moves the piston 11 upward and expansion of which permits the piston 11 to move downward. The elastic membrane 15 is enclosed in a chamber 16 into which gas is admitted from the gas reservoir 5 via a length of tubing 17. Since a liquid is virtually incompressible, the pressure of the gas, which is exerted on the outer surface of the elastic membrane 15, is transmitted into the cylinder 12 so as to provide the required upward force against the piston 11.
It will be appreciated that various types of apparatus embodying the principles of the invention may be constructed without departing from the spirit and scope of the invention. However, for illustrative purposes only, there is shown in Fig. 3 one embodiment of the invention in which a heavy X-ray generator 4 is supported from the ceiling of the room in which it is installed by means of an overhead mount constructed in accordance with the invention.
Referring to said Fig. 3, a frame 18 is attached securely to the ceiling in any suitable manner, so as to constitute a fixed support for the rest of the apparatus. A carriage 119 is mounted in the frame 18 in such a manner that it is guided by and capable of horizontal movement with respect to the frame 18. One pair of idler sprockets 2b is mounted on the frame 18, and another pair of idler sprockets 21 is mounted on the carriage 19. The X-ray generator 4 is suspended from the frame 18 by a pair of roller chains 22, one end of each of which is attached to a trunnion 23 on the X-ray generator 4 and the other end of each of which is attached to the frame 18. The pair of roller chains 22 pass over both pairs of sprockets 2t 21 as shown, so that horizontal translational movement of the carriage 19 is always accompanied by a corresponding vertical translational movement of the X-ray generator 4. In the embodiment of the invention shown in Fig. 3, the X-ray generator 4 always moves through a distance twice that through which the carriage 19 moves. By using more or fewer sprockets, the ratio of vertical movement of the generator 4 to horizontal movement of the carriage 19 may be increased or decreased. A set of telescoping tubular members 24 surrounding each roller chain 22 between the frame 18 and the trunnion 23 serve to prevent the X-ray generator 4 from swinging.
The cylinder 12 of the hydraulic ram 10 is mounted on the frame 18, and the piston 11 of the hydraulic ram 10 is mounted on a cross-bar 2S affixed to the carriage 19. The gear motor 8 is mounted on the frame 18, and is connected to the lead-screw 7 so as to be adapted to rotate the same. The lead-screw nut 9 is mounted inside the cross-bar 25, so that rotation of the lead-screw 7 by the gear motor 8 couses horizontal translational movement of the carriage 19 with corresponding vertical translational movement of the X-ray generator 4.
The cylinder 12 is connected to the liquid-containing part of the hydraulic accumulator 13 via a length of tubing 14, and the gas chamber of the hydraulic accumulator 13 is connected to the gas reservoir by another length of tubing 17. The hydraulic accumulator 13 and the gas reservoir 5 may be installed at any readily accessible place, since the tubing 14 may be of extended length. The gear motor 8 may be controlled by a suitable switch mechanism 26, which is connected to the gear motor 8 by suitable leads 27 of appropriate length.
By means of the invention, an X-ray generator weighing over 5,000 pounds may be raised and lowered by a fractional horsepower motor, without the use of heavy machinery or complex devices otherwise necessary to move a load of such magnitude. Moreover, the ability of the lead-screw system to support the X-ray generator by itself ensures safe operation even in the event of gas or liquid pressure failure. The weight of the X-ray generator is supported entirely by the gas and liquid pressure, so that the only work which need be expended in raising or lowering the X-ray generator is that necessary to overcome frictional forces and small pressure changes.
Having thus described several embodiments of the invention, it is to be understood that although specific terms are employed, they are used in a generic and descriptive sense and not for purposes of limitation, the scope of the invention being set forth by the following claims.
1. A mount for heavy X-ray generators, such as those used in supervoltage therapy and industrial radiography,
adapted to provide vertical movement of such heavy X- ray generators with minimum power, maximum safety, and a minimum amount of heavy machinery, comprising in combination: a hydraulic ram having a cylinder and a piston adapted to slide snugly in said cylinder, a hydraulic accumulator having two compartments, the first of which contains a liquid and is connected to said cylinder so as to form a liquid-tight enclosure of substantially constant volume, a gas reservoir connected to the second compartment so as to form a chamber of variable volume containing a substantially constant quantity of gas under pressure; a heavy X-ray generator connected to said hydraulic ram in such a way that the weight of the X-ray generator exerts a force which tends to decrease the volume of said chamber; and a source of motive power other than said gas under pressure for imparting vertical movement to said X-ray generator and capable of supporting the entire weight of said X-ray generator, the volume of said chamber being sufficiently large so that changes in both volume and pressure are small during vertical movements of said X-ray generator.
2. A mount according to claim 1, wherein said source of motive power comprises a lead-screw and a lead-screw nut coacting therewith, said lead-screw being rotatably mounted in a fixed position and said lead-screw nut being connected to said X-ray generator in such a way that translational movement of said lead-screw nut resulting from rotation of said lead-screw results in vertical translational movement of said X-ray generator, and means for rotating said lead-screw.
3. A mount according to claim 1, wherein said gas reservoir contains gas at high pressure, whereby the size of said hydraulic ram may be reduced and wherein the first compartment of said hydraulic accumulator is connected to said hydraulic ram via an extended length of tubing, whereby said hydraulic accumulator and said gas reservoir may be installed at any readily accessible place.
References Cited in the file of this patent UNITED STATES PATENTS 2,623,361 Dungler Dec. 30, 1952 FOREIGN PATENTS 101,617 Sweden May 20, 1951 535,984 Germany Oct. 17, 1931