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The present invention relate~ to an apparatu~ for success-ively positiQning radiographic f~l~ cassettes under a patient-esu~lning plane and retracting the cassettes after e~posure of the fll~s, eapo-¢iaIly when the latter are of lsrge dimensions.
~no~n apparatuses for succe~ively positioning cas~ettes of large d~mens$on~ camprlse a dru~ af ho~agonal cross-sootion~ and `si~ radiogrsphic fil~ cassettes are posltioned on the respective face3 of the drum. The transfer of the cassettes is effected by 8UC-cessi~e rotation Or the dru~ through 60 de&rees but the presence Or the dru~ apices i plios that the ~ru~ ~ust ~e ~aintained at a relat~vely lar~o distance from the patient-o~amiLl4g plane when the drum ax~s i8 fi~ed. Since the quslity of the r~diographlc pictures decreases with the distance betwe~n the exa~ining plane and the cassette, lt i~, in pract~ce~ necessary ~or e~posing each film~ to ~ove the dru~ closeP
to the e~amlning plaD~; then ~ove the drua aws~ to en~ble the inde~ing or po~itioning o~` the follo~ln~ c&~sette. This entalls a certain nechanical comple~ity which increaJes the ~aLufscturlng cost of tho apparatw and re~ults in a lack o~ precision in the positioning o~ tho ca~sottes with consequont lowering of the quality of the radiographs.
An ob~-ct of th~ invention i8 to provide an apparatus of the character deocribed~ wbich will overco~e the above-not~d dis-advantages Or convention~l apparatu~e~.
With this in ~ind, the apparatus in accordance with the i~vention compri~es a chsin, the links of which consist of boxe~ hin~ed one to the other and each adapted to receive a radiographic film css-~ette, this chsl~ being tr~ined on t~o dru~s having Plat ~a¢es, the d dth of Yhich 1~ equal to th- loDgth ~f a chain link a~d ~hich aro ~ounted for rotation on t~o parall~l shafts, the dl~tance of the ~xca of vhlch i3 equal to the len~t`h Or a chain link~ or to a ~ultiple of oaid l~n~th, theso shafts boing ~ouuted parallel to the patient-
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examining plane and at a distance from this plane as small as possible without preventing rotation of the drums.
Such an apparatus, which is of very simple construction, enables, by a simple angular indexing of the drums, of effecting the positioning of each cassette at a distance very close to the patient-examining plane and precisely parallel to the latter for exposing the radiographic film and then moving the cassette away from the examining plane and approaching the next cassette under the same conditions.
In accordance with one embodiment of the invention, the apparatus comprises two drums in the form of regular prism with a triangular base, the inter-axial distance of the two drums being equal to the length of one link of the chain, as well as a third drum located such that its axis determines an equilateral triangle with the axes of the first two drums.
The invention will become more apparent during the follow-ing disclosure and by referring to the drawings, which show non-limitative embodiments of the apparatus in accordance with the invention.
In the drawings:
Figure 1 is an elevation of a first embodiment of the invention in a position for exposing a radiographic film;
Figure 2 is a cross-section along line 2-2 of Figure l;
Figure 3 is a cross-section similar to that of Figure 2 but in an intermediate position during a change of cassette;
Figure 4 is a perspective view of an embodiment of the cassette boxes different from those shown in Figures 1 and 2;
Figure 5 is a cross-section of still another embodiment of the boxes;
Figure 6 is an end elevation of another embodiment of the apparatus comprising four drums of square cross-section and in a position for film exposure;
Figure 7 is a view similar to that of Figure 6 but showing the the apparatus in an interuediate posit~on during c~aset~e tranafer;
Figure 8 i8 an elevation of one embodiment of a drum; and Figure 9 i~ A longitudinal ~ection of another embodiment of a druo.
In the drawlngs, liko reference charaoter~ indicate like elemonts throughout.
~ The apparatus ~or-~ucc~ssivel~ positioning a ~eries of radio-gra~hic film csssettes st a ~ilm-expoelng station, and which is ~hown in Figures 1 and 2, ¢omprises an e~dless ohain 1, tho chain links o~ which ¢on~ist of thin boxes 2 hinged one to snother by means of hinges 3 and each adapted to receive a radiographic film cassette 4. The chain 1 i~
trained on thrse drums 7, 8, and 9, each in the form of a regular prlsm with a trlangular base d~tining flat faces, the width of ~hich ls equal to the length of a chain link, that i8 to the width of a box 2. The two druDs 7 and 8 are ~ach carried by t~o parall d ~hafts 12 and 13, respectl~elg, located in a horizontal plan- parallel to-the patient-ex~ining plsne 14.
The third drum 9 i~ carried by a shaft 16 paraIlel to Jhafts 12 and 13.
Tho axes of tho three ~ha~ts 12, 13, and 16 are located at the apice~ Or an equilateral trisngle. The distance between esch pair of shaft a~es 18 equal to the length Or a chaln link. The ~hafts 12, 13, and 16 are Journalled in lateral wall8 17 and 18 of a frame 19 provlded with a base 20.
Chain 1 of ca~sette boxes 2 surrounds the a~sembly of the three drums 7, 8, and 9 and form a prism which takes varlous config-urstions durin~ rotation of the drums and, more particularly, an hexagonal conflguration~shown in Figure 2 and a triangular configuration, sho~n in Figure 3. Each dru~, for e~smple, drum 7, can be ~olid, hollow or made of lattice-work. ~s a ~odification, each of tho drums can be provlded with end nange~ 21 ~nd 22 for lateral guiding Or the chsin 1, as shown in Flgure ô. The drum could be made in a dlf~erent mannffr, for example by bein~ formed by two end 1063Z6~
flanges 25, 26 (Figure 9) secured to the ends of shaft 12 and having shoulders 28, 29 for the lateral guiding of the chain 1.
The drums are driven in rotation by means of an electric motor 32 through a transmission comprising a pulley 33 secured to the motor shaft 34, a belt 35 trained on pulley 33 and on another pulley 36, which is fixed to one end of shaft 16. Chain 1 drives the the two other drums 7 and 8 in synchronism with the rotation movement of drum 9. The electric supply circuit of eléctric motor 32 is controlled by a device, not shown, which ensures stepwise rotation movement of the three drums through 120, for the taking of a radio-graphic picture.
In Figures 1 and 2, a very simple structure of each box 2 is shown as an example. Each box has a flat bottom 41 provided with an upstanding peripheral flange 42. The film cassette 4 is maintained in position within the box by means of four pivotable latches 43 mounted on the edges of the box and which can take either the cassette latching position shown in Figure 1~ or a cassette-releasing position by pivoting the latches towards the exterior of the box.
The apparatus operates as follows:
The apparatus being, for example, in the picture-taking position shown in Figures 1 and 2, the cassette in position within the topmost box 2 is located just underneath the station-examining plane 14, parallel to said plane and very close to the same. To bring the following cassette to the film-exposing station, the lectric motor 32 is started to rotate the drums through 120. The drums can rotate in either direction. When the drums have turned about their respective axis through an angle of 60 degrees, they occupy the position shown in Figure 3, wherein it is seen that the box 2, which was at the film-exposing station, has moved parallel to itself towards the right of drawing while progressively moving away from the patient-examining plane 14. Starting from this position, further rotation movement of the drums in the direction of arrows f, causes the following box 2, which had started from an oblique position and had come to a position parallel to the patient-examining plane 14, to move upwardly, while remaining parallel to itself, until it finally occupies a position at the film-exposing station which was previously occupied by the preceding box.
It is, therefore, apparent that the apparatus, while of very simple construction, enables the positioning of the successive cassettes very close to the patient-examining plane due to the suc-cessive approaching and withdrawing movements of the boxes with respect to the examining plane 14, these movements being automatic by the simple angular indexing movement of the drums without the necessity of providing complex specific mechanisms. The cassettes are always not only very close to the examining plane but precisely parallel to the latter; even if the indexing movement of the drums is not stopped precisely at the same pOSitiOn~ the cassettes will nevertheless occupy a position precisely parallel to the examining plane, because they form one side of an articulated parallelogram beginning with the moment corresponding to the middle of the transfer phase of the cassettes.
Although the apparatus just described comprises three drums, the number of drums is not limitative. For example, the lower drum 9 can be absent, in which case at least one of the other drums 7 and 8 would be driven in rotation. The drums could also have a cross-sectional shape other than an equilateral triangle, for example a square cross-sectional shape, as shown in the embodiment of Figures 6 and 7. In this embodiment, the two upper drums 51 and 52 and the two lower drums 53 and 54 have their rotation axes distant from each other a distance equal to a multiple of the length of a chain link;
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in this particular case, a distance equal to the length of two main links.
In Figure 6, the chain is in a position for picture taking, whereas in Figure 7 the chain has a configuration taken at the middle of a cassette transfer phase.
The box structure and the means for holding the cassette within the boxes can be different from those shown in Figures 1 and 2. Figure 4 shows a first modification in which each box 2 is composed of a bottom 61 with an ed8e portion comprising a part 62 upstanding perpendicular to the bottom and followed by a part 63 folded parallel to said bottom to thus form a peripheral channel on three sides of the box to receive the marginal portions of a cassette.
A latch, of any appropriate type, such as for example, the L-shaped pivoted finger 65, enables, when in raised position shown in dotted lines, the insertion of a cassette within the box 2 by sliding the same in the guideways parallel to the bottom 61. The movement of the latch 65 to the full line position latches the cassette in position within the box.
Figure 5 shows still another modification of the box 2 wherein it consists of a bottom 71 with an upstanding edge 72 on the four sides of the bottom, whereas on two opposite sides, flanges 73 and 74, respectively, extend parallel to the bottom to form channels, in one of which is located a compression spring 75. mus, a cassette can be inserted by slightly compressing the spring 75 until the cas-sette can be hooked underneath flange 73, the inserting movement of the cassette beinB shown in dot-and-dash lines and in full lines in Figure 5. By inverse movement, it is obviously easy to remove the cassette after picture taking.
It is obvious that the present invention is not limited to the embodiments shown and described and modifications can be made without departing from the scope of the annexed claims.