US2733352A

US2733352A - billin

Info

Publication number: US2733352A
Authority: US
Publication date: 1956-01-31
Anticipated expiration: 1973-01-31

Description

Jan. 31, 1956 A. e. BILLIN RECIPROCATING BUCKY ACTUATOR Filed Feb. 20, 1952 (5 Sheets-Sheet 1 ,-& /2

{1 12 4 s4 25 12 1 70 105 12. A 11 so 6 w-nfii wi uua INVENTOR.

ATTOQNEYS.

Jan. 31, 1956 A. G. BILLIN RECIPROCATING BUCKY ACTUATOR 3 Sheets-Sheet 2 Filed Feb. 20. 1952 A m p m m 3 l 8 m u l um Qm do (am; up 2 2 8 INVENTOR. M 9. Whi

ATTORNEYS- Jan. 31, 1956 A. s. BILLIN 2,733,352

RECIPROCATING BUCKY ACTUATOR Filed Feb. 20, 1952 5 Sheets-Sheet 3 W WZOTPUwZZOU wad m.

United States Patent This invention relates to photograph-st Itis-directe 1 mechanismfor phragms is helpful:

A conventional diaphragm, termed 7 in respect to the name of its-inventonconsists: of-a p1urays generated at the tube. a subject, some by producingso-calledsecondary radiations whichwould strips of a Bucky diaphragm would cast eopaque' their shadows upon the film if tionary during ment of the-film, the- However,.in passing through' X-rays are scattered or deflected, there 2583,352- Patente'd Jan; 31, 1956 However, such inconvenient and'uncertain.

A-diflicultproblem is encountere'd'in-all X-ray pho'tdg raphyutilizing-aBucky diaphragm because of 1 the puls'af- Since suchtubes ternatingvcurrent; usually 60 cycl if an X-ray pulsation happens to does,- just when the Jay'opaqueare operated upon' al c; it is apparentthat posures; e.- g. nature;

lngtnatureof the X-ray: emanations' generatedlay the tube medium. A photocell, focused upon this screen, generates a current in proportion to the light emitted from the screen, and such current is employed in the charging of a condenser in a control circuit. When the charge upon the condenser reaches a critical value, which is adjusted in respect to the known sensitivity of the photographic medium, the control circuit is energized to terminate the exposure. The arrangement, therefore, constitutes an automatic exposure meter which eliminates the need for the operator to exercise his independent skill or judgment.

It will be apparent that a conventional single-pass Bucky diaphragm is very difiicult, if not impossible, to use successfully in photographing a variety of subjects with phototirned X-ray equipment, since the operator has no means of determining the rate or duration of movement of the diaphragm necessary to accommodate an unknown, but automatically terminated, exposure governed by the phototimer.

To accommodate the longer exposure periods, several mechanisms have been proposed for reciprocating the diaphragm back and forth over the film while the X-ray tube is energized. However, the results obtained with such apparatus have generally been quite unsatisfactory because of the incidence of synchronism and because of the inherent tendency for imperfect pictures to be produced when exposure happens to be started at a moment of reversal of the direction of movement of the diaphragm. A diaphragm is quite heavy, embodying as it does a substantial number of lead strips plus a frame in which the diaphragm is supported. By virtue of such weight, momentum and inertial forces are involved which must be overcome in first bringing the diaphragm to rest at the end of a stroke in one direction and in then causing the diaphragm to reach intended speed in the opposite direction. The rates of deceleration and acceleration of the devices proposed in the past have been so slow that undesirable conditions of synchronism occur during the reversal periods when the diaphragm is moving at less than intended speed, or so fast that undesirable vibration is established.

The present invention embodies a Bucky actuating mechanism which is of utmost simplicity and which is relatively inexpensive to construct, yet which provides singularly desirable results in the elimination of synchronous conditions. The apparatus of the present invention is actuable either for short or long exposure periods and operates the Bucky diaphragm reciprocably during an exposure period at substantially uniform rates of speed in opposite directions, but provides rates of deceleration and acceleration of the diaphragm, such that undesirable shadow efiects are substantially prevented from occurring during reversal periods.

Reduced to its simplest terms, the diaphragm actuator of the present invention consists of a reversible drive motor, control devices which govern the direction of power movement of the drive motor, and which, in turn, are governed by the diaphragm when it reaches the respective ends of its strokes in opposite directions, and a simple string connection through which the power of the drive motor is imparted to the diaphragm for reciprocating it. The power motor drives the diaphragm through the string connection at a rate which may be the same, or substantially the same, in one direction as in the other, but the limited resiliency of the string, plus prompt reversibility of the motor, enables sufficiently high acceleration and deceleration to be obtained in the reversal periods to eliminate undesirable mechanical and photographic results which would otherwise be obtained by an inelastic or positive connection type of drive.

The actual rate of movement imparted to the diaphragm is non-synchronous with respect to the X-ray frequency; that is, the rate of movement of the Bucky does not hear an integer or simple sub-multiple relation to the frequency of pulsations of the X-ray tube, or otherwise coincidence in the positions of the grid strips might lead to incidence of shadows during passage of the diaphragm in either direction. Also, it is desirable that the rate at which the diaphragm is movable be great enough to cause a sufficient number of opaque strips of the diaphragm to pass a given point on the subject or film and thereby provide proper screening of secondary radiations from the film.

A further feature of the present invention resides in apparatus capable of returning the diaphragm to a predetermined starting position at the end of an exposure period, no matter where the diaphragm happens to be at the moment exposure is terminated. By means of this feature of the invention, the position from which the diaphragm will start to move in the next successive utilization of the apparatus is established and variations or undesirable results which might otherwise occur through variations in the starting position are eliminated. This feature is particularly important when a short exposure is to be made.

The invention also contemplates a mechanism in which the Bucky will assume movement at a desired speed before X-ray exposure can commence, thereby eliminating the incidence of shadows on the film through inadequate Bucky movement at the very start of an exposure.

From the foregoing principles upon which the present invention is predicated, and the following detailed description of the drawings in which a preferred embodiment of the invention is disclosed, those skilled in the art will readily understand the modifications to which the invention is susceptible.

In the drawings:

Figure 1 is a plan view of a diaphragm actuating mech anism of the present invention.

Figure 2 is a sectional elevation taken on the line 22 of Figure 1.

Figure 3 is a sectional elevation taken on the line 3--3 of Figure l. a

Figure 4 is a sectional elevation taken on the line 4-4 of Figure 1.

Figure 5 is a sectional elevation taken on the line 5-5 of Figure 1.

Figures 6 and 7 are simplified, somewhat diagrammatic views, showing actuation of reversal switches by the diaphragm in respective phases of its movement, and

Figure 8 is a circuit diagram illustrating a control circuit through which reversal of movement is accomplished in conjunction with return of the diaphragm to starting position at the end of an exposure.

The diaphragm with which the actuator mechanism of the present invention is attached to be used may be of any suitable type, and is indicated generally in the drawings at 1. The diaphragm is equipped with a peripheral frame 2, and a longitudinal edge 4 of the frame is provided with spaced guide blocks 6 and '7 through which the diaphragm movably is-mounted. The diaphragm 1 is contained within an overall frame or housing 8, which is made up, for example, of plates or channel irons of suitable configuration, all joined together by bolts or welding.

The overall frame 8, as will be noted from Figure l, is both longer and wider than the screen diaphragm l, the additional length providing a the diaphragm, and the additional width providing space, indicated generally at 9, within which components of the actuating and control mechanism are housed. The area 9 is delineated from the remainder of the overall frame 8 by a dividing wall It the top of which is spaced from the bottom of the diaphragm 1.

Guide blocks 6 and 7 are bored longitudinally to receive guide rods 11 which are supported rigidly upon pairs of

brackets

12, 12 extending upwardly from the face of the dividing wall 10. The rods 11, therefore, 'slidably support the diaphragm along one longitudinal edge thereof, Similar guide rods may be provided to sustain the field of movement of c'arry plate members 161 to y means of screws 18. In the trated; each of

plates

16 and 17 has an attachment post 19,-;l9--extending from it, and 'a string 'drivemember 20 or otherwise suit- 21 or anchoredhto it, drive sheave is'actuated by meanso'f 1n nuts,,-a s at 24 (Figure 3).

The string of drive member 20 is p'referably in-the form of -a fibrous cord having sutficient-pliability to pass around the drivesheave 21, and suiiicient strength to withstand the forces to whichit is subjected in causing the diaphragm to reciprocate. Braided cord fabricatedof posts and 31 extending speed -'reduction; geartrain e i gear' train,

to note-th'at the reversible electric motor drives the gear trai'n and the gear train, in turn, drives the sheave "21 around-which the string 20 is wound for frictional engagementtherewith.

Thespeed reduction provided by the gearing 2': is jap in driving connection with the sheave 21 propriate, in relation to the'diameter of the drive sheave 21' to cause linear movement of the string, and attendant linear movement of the diaphragm 1, at a rate which is non-synchronous with respect to the pulsations of the timing of the actuation of these moved to the right. eration of

switches

36 and 37 which are obtained in this I larly on a post (not shown) at the opposite end of switch 44 and at the opposite side thereof from post 58. Lever 57 extends along the switch and terminates in an offset portion 68 which is actuated when the diaphragm reaches the right hand end of its stroke.

The

levers

56 and 57 are served by an actuator assembly 62 which is supported on plate 17, the latter being fastened to the face of guide block 7 as previously described. Actuator 64 extending over and above switch 44, and

finger members

66 and 67 are mounted on the shelf, the finger members respectively providing fingers 63 and 69 which are positioned for engagement with the ofiset portions 59 and 6% of the

respective levers

56 and 57. The

finger members

66 and 67 are fastened to the shelf 64 by means ofscrews 7t) which pass through appropriate slots 71, thereby permitting the relative positions of thc finger members to be adjusted for timing purposes. When diaphragm 1, in moving to the right, reaches the end of its intended stroke, the depending finger 69 engages the offset portion 60 of actuating lever 57, the switch 44 is thrown, and this promptiy causes reversal of motor 27, as described at a subsequent point in the specification. Similarly, when the diaphragm, after moving to the left, reaches the end of its stroke in that direction, the finger 63 engages the offset portion 59 of lever 56, throwing the switch 44, and thereby again reversing the direction of motor rotation. Since the switch 44 is of the snap action type, it remains in any position in which it may be set until it is next actuated to the opposite position.

A relay 72, which is employed in the preferred electrical circuit of the apparatus, may be positioned in the housing area 9 and, to facilitate power connections to the entire apparatus, a plug receptacle 73 may also be mounted in the front wall of the overall frame 3. To avoid confusion in the illustration of the mechanical parts, the wiring connections are not illustrated in Figures 1-7, though it will be noted that the housing area 9 provides ample space for wiring without interference thereof with the movable parts of the apparatus.

Electric circuit An X-ray machine is provided with a primary control switch which, for present purposes, is indicated generally at 75. This control switch may be operated either manually or by a mechanical timer or by photoelectric timing means. In addition, an X-ray tube is usually powered through a magnetic switch or other suitable contactor, which is indicated generally at 76. For the purpose of illustrating the operation of the present apparatus, these elements are shown in the circuit diagram of Figure 8. Operating voltage is supplied through

leads

77 and 72*, while the leads from the control switch 75 are designated 79 and 86. All of these connections may be made through a plug (indicated diagrammatically), which is engageable with the plug receptacle '75 of the apparatus.

Input voltage leads 77 and 78 are connected directly to the field winding 81 of the motor 27, while lead 79 from the control switch 75 is taken to one terminal of relay 72, which is a single pole, double throw relay. The opposite terminal of the relay 72 is in connection with input lead 73, as at 33, arid is also in connection, through lead 84, with one of the contacts 35 of the exposure switch 37. One terminal of the magnetic switch 76 of the X-ray apparatus is in connection through lead 86 with the other of the contacts of the exposure switch 37,

and the opposite terminal of the magnetic switch is in connection with input lead 79 of the control switch 75 through lead 87.

Thus, the field winding 81 of motor 27 is connected directly across

input terminals

77 and 78, while

switches

75 and 37 are in a series circuit extending from input terminal 78 through junction 83 to switch 37 through lead 84, and from lead 86 of switch 37 through magnetic assembly 62 includes a shelf portion switch 76 to lead 87 which passes to lead 79 for control switch 75, the latter being connected to input terminal 77 through lead 80. Relay 72 is connected across junction 33 and lead 79, and therefore, is in parallel with switch 37 and coil 76 in series.

As previously noted, the motor 27 of the power .unit 22 embodies shading coils which are magnetically coupled with the field winding 81 and which govern the direction ofmotor rotation. These shading coils are designated 89 and 90,- the common connection between them being designated 91. When the circuits to both coils are open, the motor 27 is idle, but when either coil is short circuited, the motor will run. The coils are so wound or arranged that short circuiting of one will cause the motor to run in a direction of rotation WhlCh is opposite the direction of rotation prevailing when the other coil is short circuited. The electric circuit is arranged to cause short circuiting of these coils through actuation of cycling switch 44. For this purpose, the common terminal 91 of the shading coils 89 and is in connection through a lead 92 to the movable armature 93 of relay 72. The movable armature is biased in one direction, for instance by means of spring 94, but when the relay winding 95 is energized, the armature 93 of the relay is attracted sufiiciently to overcome the bias of the spring 94. Thereby, the armature 93 alternately serves the two

contacts

96 and 97 of the relay.

Contact 96 of the relay is in connection with the movable contact of homing switch 36 through a lead 99. The other contact of the homing switch is connected as at 1613 to the end of the shading coil 89 opposite the common connection 91 thereof. The other contact 97 of the relay 72 is in connection through lead 101 to movable contact arm 102 of cycling switch 44. This cycling switch, as previously noted, is of the double throw type, having two

stationary contacts

103 and 104, with'which the contactor arm 102 alternately makes engagement; Contact 103 is connected through lead 105 to the end of shading coil 99 which is opposite the common terminal 91, while contact 104 of the cycling switch is connected through lead 106 to the junction at which lead from the homing switch 36 joins the shading coil 89.

Description of operation When the diaphragm is at rest, preceding usage of the apparatus, exposure switch 37, and homing switch 36 are open, and the contact 93 of the relay 72 is in engagement with contact 96 thereof under the influence of spring 94. For purposes of the description, it is assumed that the contactor arm 192 of cycling switch 44 is in down" position, in engagement with contact 103 thereof. The circuit of shading coil 89 is open at the cycling switch 44, and the circuit of shading coil 90 is open at relay 72. The field of motor 27 is energized through the

leads

77 and 78, and the apparatus is ready for operation.

As soon as control switch 75 is closed, either manually, mechanically, or electrically, relay 72 is energized caus-' ing contactor 93 thereof to make engagement with contact 97 against the bias of spring 94. This operation causes shading coil 90 to be short circuited, the circuit extending from the mid connection 91 through lead 92 to armature 93 of relay 72, and through lead 101 and contacts 192 and 103 of the cycling switch 44, thence back to the shading coil 90 through lead 105. Short circuiting of the shading coil 90 causes the motor to operate the diaphragm to the right, for example as shown by the arrow adjacent shading coil 99 in the drawing.

Shortly after the diaphragm starts to move, the arms 43, 48, respectively controlling homing switch 36 and exposure switch 37, are released, and these switches close. Closure of the exposure switch completes a circuit to the magnetic switch 76 of the i 84, and 87, ar1d control switch 75, thereby energizing the X-ray tube, only after the diaphragm is in motion.

Closure of homing switch 36 conditions the circuit so X-ray tube through leads 86,-

9 that it subsequently may be governed, by, the, homing switch.

Placed in motion,

Atthis time, finger, the lever 57,

otherpositiont, This; ineflect, causescontact arm102 otlcycling switch-M,as shown. in Figure 8,;to break enga ment, withcontact 103., andamake engagement with contact 104. Since, the relay,72.,is energized, contact 93 75.,is, closed; hence-there is no limit on the time duzingwh-ichithe.diaphragm, maybe oscillated back and fOl'tha,

right or left as; the case'may be; arrangedthatthe diaphragm, Whatever its position,

of; the, apparatus in the. next usage.

To illustrate. theoperation of-the homing featureof the circumstance, cycling switch44 Will he down?; position, 115e,, contact 102 'thereofiwill be allowing the diaphragm to come to rest.

When the diaphragm is moving to the left, the cycling now opened, relay 72 is de-energized and contactor 93 moves into engagement with contact 96, which re-estabtheright untilj'ittreaches the right hand .endof its However, the diaph tuates it so that it when the apparatus is next used.v

From this description,

move the Bucky from.

fr me,

tric motor and a diaphragm driven thereby in opposite directions, a reciprocation control circuit including switch means for energizing the motor to cause it alternately to operate in opposite directions, and a homing circuit including said electric motor and a homing switch which is responsive to movement of said diaphragm for completing a circuit to said motor following reciprocating operations thereof and efiective thereafter to cause continued motor operation suflicient to drive the said diaphragm to a predetermined position.

4. Mechanism for reciprocating a Bucky grid continu ously during an X-ray exposure, comprising a base having means for slidably mounting a Bucky grid therein, a reversible electric power unit mounted in said base, a string drive member connecting the said power unit to said Bucky grid for imparting movements in opposite directions to said grid from said power unit, reversing switch means in electrical connection with said power unit, an actuator for said switch means secured to said grid, whereby reversal in the direction of movement of said electrical power means is effected at predetermined points in the movement of said grid, the said string being of limited elasticity for absorbing the momentum of the moving Bucky grid, means for initiating and terminating reciprocating movement of said power unit, and homing switch means for controlling movement of the said grid to a predetermined position after its reciprocating movements are terminated, whereby movement of the grid in a next successive usage of the mechanism commences from a predetermined point.

5. Mechanism for reciprocating a Bucky grid continuously during an X-ray exposure, comprising a base having means for slidably mounting a Bucky grid therein, a reversible electric power unit mounted in said base, a string drive member connecting the said power unit to said Bucky grid for imparting motor movements in opposite directions to said grid from said power unit, reversing switch means in electrical connection with said power unit, an actuator for said switch means secured to said grid, whereby reversal in the direction of movement of said electrical power means is efiected at predetermined points in the movement of said grid, the said string being of limited elasticity for absorbing the momentum of the moving Bucky grid, means for initiating and terminating reciprocating movement of said power unit, an homing switch means independent of said reversing switch means.

6. Mechanism for reciprocating a Bucky grid continuously during an X-ray exposure, comprising a base having means for slidably mounting a Bucky grid therein, a reversible electric power unit mounted in said base, a taut, slightly stretchable string connecting the said power unit to said Bucky grid for imparting movement to said grid in opposite directions from said power unit, re versing switch means in electrical connection with said power unit, an actuator for said switch means secured to said grid whereby reversal in the direction of movement of said electrical power means is effected at predetermined points in the movement of said grid, means for initiating and terminating reciprocating movements of said grid from. said power unit through said string, and a homing circuit including said motor and a homing switch which is independent of said reversing switch means for maintaining motor operation after termination of reciprocating movements of said grid until the said grid reaches a predetermined home position.

7. In an X-ray machine, the combination of a Bucky grid, means for reciprocating said grid including a reversible electric motor, a reciprocation control circuit including switch means for energizing the motor to cause it alternately to operate in opposite directions, a homing swith in parallel control connection with said reciprocation control circuit, a control switch for initiating and terminating motor operation, means actuable in response to the condition of said control switch for alternately placing said homing switch and said control circuit in operative control relationship with said reversible motor.

8. In an X-ray machine, the combination of a Bucky grid, means for reciprocating said grid including a reversible electric motor, said electric motor having two shading coils, a reciprocation control circuit including switch means for alternately short circuiting one or the other of said shading coils to cause the motor alternately to operate in opposite directions, a homing circuit for short circuiting one of said shading coils to cause said motor to drive said Bucky to a predetermined position after its reciprocating movements are terminated, said homing circuit including a homing switch operable upon Bucky movement to condition the homing circuit for control of the motor, a control switch for initiating and terminating motor operation, relay means actuable in response to the condition of said control switch for rendering said reciprocation control circuit ineffective for control of said mtor and placing said homing circuit in efiective circuit relationship with said shading coil upon opening of said control switch.

9. Mechanism for reciprocating a Bucky grid continuously during an X-ray exposure, comprising a base having means for slidably mounting a Bucky grid therein, a reversible electric power unit mounted in said base, means including a string drive connecting the said power unit to said Bucky grid for imparting movements in opposite directions to said grid from said power unit, reversing switch means in electrical connection with said power unit, an actuator for said switch means secured to said grid, whereby reversal in the direction of movement of said electrical power means is effected at predetermined points in the movement of said grid, said string drive means being of limited elasticity for absorbing the momentum of the moving Bucky grid, means for initiating and terminating reciprocating movement of said power unit, and means for effecting movement of the said grid to a predetermined position after its reciprocating movements are terminated, whereby movement of the grid in a next successive usage of the mechanism commences from a predetermined point.

References Cited in the file of this patent UNITED STATES PATENTS 2,123,182 Drake July 12, 1938 2,203,689 MacDonald June 11, 1940 2,205,209 Kunz et al June 18, 1940 2,334,447 Shaw Nov. 16, 1943 2,504,864 Morgan et al Apr. 18, 1950 2,583,213 Graves Jan. 22, 1952 FOREIGN PATENTS 305,322 Great Britain Feb. 7, 1929 495,215 Great Britain Nov. 19, 1938