US2186107A - Diaphragm of the bucky type - Google Patents

Description

Jan. 9, 1940. v w. H. HAUPT DIAPHRAGM OF THE BUCKY TYPE 7 Filed May 25, 1958 2 Sheets-Sheet 1 INVENTOR. H

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PatentedJan. ,9, 1940 v UNITED STATES PATENT OFFICE DIAPHRAGM OF'THE. BUCKY Walter. H. Haunt, Ludlow, KyQ, assignor to The Kelley-Koett Manufacturing Company, Incorporated, Covingtoli, Ky., a. corporation of ohio Ap plication May 2a, iess'g-lser l No. 209,515

s' Claims. (01.150563) In all radiographic work the secondary radiation from objects in the path ofthe rays have been a detriment to obtaining clear pictures. Inorder to overcome this difficulty diaphragms and 5 grids of the bucky diaphragm type have been employed to cut radiation coming to the film in direction other than those of the primary rays. In'ordinary practice the grid is arranged'to move across the film at a certain speed scans to eliminate shadows ofthe grid line or the grating which is made of lead and is fairly impenetrable to the X-radiation. Speed of travel is varied as a rule in order to complete one movement in a space of time slightly longer than that required for the actual exposures. In medical work the,

exposure time will 'varyas a rule from /10 or possibly of a'second up to about 30se'conds.

Oil pumps or other mechanismsare usedto control the speed of travelof the grid.

In industrial work', howeventhe exposure times are much greater, sometimes being as high as .30 minutes in order to penetrate heavy layers of steel or the like; It is not practical to slow up the bucky diaphragm movement to a point where it would take minutes to complete a single stroke. Hence, a reciprocating movement is generally used in order to move the grid across the screen or across the film. 1

Inherent in the nature of a reciprocating move- 30 ment there is a stop, however short, at'eachend of each reciprocating stroke. This stop will cast I a shadow of the grid upon the film and cannot be entirely eliminated regardless of how many reciprocations take place. I have designed a special type of mechanism operatedfrom the reciprocating movement and linked with it so as to.

change the point of reciprocation or the turning pointat the end of each stroke, until a cycleis completed. In other words if a certain point A is designated as the turning point at oneend of the stroke the next timethe bucky diaphragm comes to the position A it does not exactly turn at A but at a point A, plus .005" or .010", thereby making slight dilference in that turning point. Each successive turning point changes in like manner until a given cycle is completed wherein the variation of turning point is suflicient to prevent superposition of shadows of grid line.

In the drawings, Fig. 1 is a perspective view of my device from the front, the cassette being absent.

' Fig. 2 is a plan view of the diaphragm showing a cassette emerging from therebeneath. Fig. 3 is a detail from Fig. 1 showing on a larger A' lead grid M of the bucky type is adapted to 10,

reciprocate within the,,frame IO- and, on angle irons H on gibs [5. Power forreciprocation is supplied from an, electric motor 16 through a geared drive.

The direct pushing andpulling of the grid 14 is done bya pair of links l1,-each of which is pivoted to abell-crank l8 whichin driving, assumes the positionshown in dotted line in Fig. 3. Each bell-crank is pivotedto one'end of a shaft l9 each of'which in turn is tightly attached by its other end to a reciprocating bar 20 of theshape shown in Fig. 1'. A spring 2| is arranged so as to be stretched by each positive reciprocation of of the bar20, i.-e., to the left'as shown in'the drawings. The spring tension then returns the 25 bar to its originalposition. So much of the structure as has been described in detail is conventional; what follows is novel:

Attached to the inner side of one of the longer rails of the frame, there is an angled dog 22; 3O Upon the bar 20, there is mounted a ratchetwheel 23, thenumber of teeth of which is considerably greater than is shown. The ratchet wheel is supported upon a stud 24 which extends through its center and also through an eccentric 25 which'is' arranged to' rotate in unison with the ratchet wheel. Stud 24 also extends through a slot 26 in bar 20 and also through a hole 21 in a driving bar 28 which extends below. oscillating bar 20. A second stud 29- extends through both bars and is {$0 tight to driving bar 28, but permits bar 20 to slide under its head to allow the. length'of the stroke of' the latter to vary.

The bar 28 is driven from the end opposite the ratchet by means of a roller 3| and a cam 32, 45 which is eccentric and is mounted upon vertical motor shaft 33. The motor is of the special kind whichhas an inbuilt bevel worm gear drive.

Working upon the ratchet wheel 23. is a pawl 34. which is pivotably mounted upon a trigger 35 50 and iscontrolled by the tension of a spring 36. The trigger bears a roller 31 upon its outer end, which roller makes contact at each stroke of bar 20 with the dog 22. A spring 38 by its ten- .sion, keeps the trigger in a position where it may loaded cassette is inserted in slides 39. The specimen to be examined is placed over the entire device, but no weight is placed upon the device. Motor IE3 is started and the X-ray beam is turned on Eccentric 32 then imparts an oscillatory mo-, I

tion to bar 28, carrying with it ratchet wheel 23 and eccentric 25. When the eccentric strikes a lug 42 on bar 291, the latter is set in motion toward the left but as soon as bar 28 ceases to drive it to the left, it is retracted by spring 2|. The setting or length of the stroke can be changed by changing the position of tight stud 29 and substitutinga difierently shaped eccentric 32. oscillatory motion of bar 20 rocks thebell-cranks l8 about pivot points 65, thereby oscillating links ll and the grid It at 90 directional difierence from the motion of bar 20.. At each rightward stroke of bar 28 pawl 36 engages and drives forward one notch of ratchet wheel 23. At each leftward stroke, the pawl slips back one notch because the trigger 35 which carries the pawl, is depressed by striking dog 22 until the pawl slips back. I

At each partial rotation of ratchet wheel 23 under'the driving force of pawl 34 the eccentric 25 is rotated an equal amount, thereby chang ing the distance that bar 28 will be pushed by bar 28. This change is reflected in the difference in stroke length imparted to grid l4 so that the amount of shadow thrown by a stoppage of the grid at any one place at all strokes will be reduced according to the number of different stopping places which are created by the ratchet teeth. If there are 30 teeth, there will be 30 different stopping places instead of one and the amount of shadow cast will be of what would ordinarily have been cast. The extent and clarity of the radiograph will thereby be much increased.

I claim as my invention: I

1. In a radiographic diaphragm of the bucky type a grid, a conventional reciprocating bell crank drive for said grid including a pair of bellcranks, a reciprocating bar driving said bellcranks, a driving bar driving said reciprocating bar, an electric motor,'an eccentric on said electric motor driving said driving bar, a case enclosing said grid and said drive, a dog mounted on the inner wall of said case, a ratchet, a lug on said reciprocating bar an eccentric adapted to be driven by said drivingbar to communicate motionof the latter to the reciprocating bar and ratchet rotating means carried upon said driving bar and making contact with said dog whereby to rotate partially at each stroke cycle of the driving bar, the eccentric, whereby to vary the length of throw imparted by reciprocating bar to said bell-cranks and so to said grid. p

2.. In an X-ray diaphragm of the bucky type a grid, a reciprocating bar attachedto said grid,

. said bar having a plurality of slots therein, a

spring attached to said bar, said. spring being adapted to return said bar from one extreme of its position to the other, a driving bar adjacent said reciprocating bar, an eccentric driving said reciprocatable bar, a lug on said reciprocatable bar adjacent a slot thereof, an eccentric having a displacement parallel to said reciprocatable bar and adapted to make contact with said lug and means for varying the stroke of said reciprocatable bar and of the grid attached thereto, said means comprising a ratchet wheel, a stud tightly connecting said eccentric and said ratchet wheel, said stud being attached to the said driving bar and passing through a slotin said reciprocatablebar, a trigger mounted on said stud, a pawl carried on said trigger and making contact with the periphery of said ratchet wheel, a doginounted upon a fixed point and adapted to make contact with the outer end of said trigger and a plurality of springs, one of which is adapted to hold said trigger in contact with said dog and another which is adapted to hold said pawl in contact with the periphery of said ratchet wheel.

3. In a radiographic diaphragm of the bucky type, a case, slides therein for the receptionv of a cassette, other slides for the guidance of a grid, a grid and-a drive for same, said drive comprising an electric motor of. the inbuilt gear type mounted on the floor 'of said case, an eccentric on saidmotor, a horizontal driving bar pivoted within said case, a roller on said driving bar in contact with said eccentric, a reciprocating bar likewise pivoted in said case and adiustably attached to said driving bar, slots in said reciprocating bar, studs extending through said slots and through both of said bars, .a ratchet wheel mounted below said driving bar on one of said studs, an eccentric mounted upon that stud which bears said ratchet -wheel, said eccentric being mounted above said reciprocating bar, a lug on said reciprocating bar in contact with said last named eccentricQtrigger-means actuable by the motion of said reciprocating bar whereby the position of said last named eccentric relative to said lug on said reciprocating bar may be changed through a partial revolution; at each stroke of the driving bar and reciprocating bar to vary in length of horizontal stroke imparted at each alternate stroke of said driving bar to said reciprocating bar, the throw imparted to said grid by said reciprocating bar.

. WALTER H. HAUPT.

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