Patent Number: 041587790
Section: description

Referring specifically to the drawings, there is shown a plate assembly 1 which comprises a plurality of plates of thin metal or plastic material which are assembled in layers and between which a lead plate 2 of the same shape and about 2-3 mm thickness is interposed. A plurality of spacer strips arranged in pairs are inserted for forming guide slots. The arrangement of the spacer strips between the preferably square plates is effected alternately in different planes and in transverse directions extending at right angles to each other. The resultant guide slots extend over the total width of the plate assembly and in each case receive slides 3, 4, 5 and 6 and which, as shown in FIG. 4, are provided with a rack-like extension 3a, 4a, 5a, and 6a respectively. Engaging with the teeth formed on each extension is a pinion 7. The pinion 7 is non-rotatably mounted on an adjusting spindle 9 passing through a bore of the plate assembly 1. The spindle 9 is provided with a knob 8. Each slide 3-6 is provided with a downwardly extending portion at its end extending out of the plate assembly 1. The lower end of the downwardly extending portion is also bent inwardly at a right angle. The resultant strips 3b, 4b, 5b, and 6b serve for securing or supporting lead sheets 10, 11, 12 and 13, respectively. Varying the length of the particular downwardly extending portion enables the linearly displaceable lead layers to be disposed in parallel but different planes relative to the plane in which the center lead plate 2 is disposed. In addition to the linearly displaceable first lead sheets 10 to 13, segment-like lead sheets 14, 15, 16 and 17 are provided which serve to screen the corners. These second sheets are associated with each other in pairs and are arranged so as to rotate by means of respective support levers 19 and fixing screws 20 or the like on the particular securing strip 4b or 6b of the slide 4 or 6. For safety purposes, to avoid apertures such as bores or the like on the first lead sheets 10 to 13, the connection of said sheets with the support slides 3 to 6 and the connection of the lead sheets 14 to 17 with the particular support lever 19, are effected by means of a contact adhesive suitable for metal adherence. The segment-like lead sheets 14 and 15 or 16 and 17 are associated with each other in pairs and are under the influence preferably of respective double-shank spiral springs 22 and 23. These springs are disposed on the respective securing strips 4b and 6b. The shanks 22a and 22b or 23a and 23b of springs 22 and 23 engage on lugs 19a formed on the respective support levers 19 and consequently exert an oppositely directed torque on the pairs of lead sheets 14 and 15 or 16 and 17 relative to their centers of rotation. The spring load acting on the lead sheets is received by guide lugs 3c and 5c which, as shown in FIGS. 5 and 6, are formed on the slides 3 and 5. The lugs are provided for slidably guiding the sheets 14 and 15 or 16 and 17 which are supported by their free ends. Relative movement in opposite directions is accomplished by the associated pairs of lead sheets when the holders or slides 10 to 13 which are guided displaceably in the guide slots of the plate assembly 1, are driven by the pinion 7. According to the direction of rotation of the pinion 7, the sheets 10 and 12 or 11 and 13, supported by the slides 3 and 5 or 4 and 6 move either continuously towards or away from each other. This also applied to the lead sheets 14 and 15 or 16 and 17 which cover the corner cut-outs and rest under spring load on the guide lugs 3c and 5c of the slides 3 and 5. The latter lead sheets slide along when the slides 3 to 6 are executing relative movement, in which they simultaneously execute rotations about their pivotal axis. In turn, such movements result in either an expansion or reduction on all sides of the area to be covered by the protecting screen completely formed of lead sheets, while the function of covering the "opening" in the area of the plate assembly 1 is effected by the center lead plate 2. In order to achieve a reduction in the area to be covered by the protecting screen formed of the displaceable lead sheets 10 to 17, so that the operating conditions are also available in these instances where only a small surface area has to be screened, e.g. for a child, an arrangement of the linearly displaceable lead sheets 10 to 13 is provided, as is clearly seen in FIG. 1. Conditions could therefore be provided in which the lead sheets 10 to 17 may be moved towards each other and overlapping to form an extremely small protecting screen, as shown in FIG. 6. The protecting screen, whose construction is described above, is formed by the center lead plate 2 and the displaceable lead sheets 10 to 17. The screen is held by a support arm 26 which may be telescopic and secured to a supporting fork 27 by means of bent-over portion 26a. The fork 27 is vertically adjustable relative to a vertical support column 28. This column 28 may be secured in upright fashion on a preferably metal triangular base plate 29. The arrangement of the support column 28 on the base plate 29, is, as shown in FIG. 2, effected so that the protecting device may be set rigidly on the X-ray table 30, as shown in FIG. 1. In order to adapt the vertical adjustment of the protecting screen to the prevailing conditions, the support column 28 is provided on one edge with a locking device 28a which may have a saw-tooth profile, as shown in FIG. 1, or a semi-circular or any other suitable profile. In turn, the support fork 27 is provided with a pin which provides a hooking engagement with the saw-tooth profile 28a of the column 28 by means of another pin 32 supported on the smooth edge of the support column 28. A tilting movement is sufficient for adjusting the vertical position of the protecting screen and this is effected by slightly raising the support arm 26 in order to bring the pin 31 of the support fork 27 out of engagement with the locking arrangement 28a. Thus the protecting screen can be brought to a different vertical position by raising or lowering the support arm 26 and then re-secured by engaging the cross pin 31 in the locking arrangement 28a in the new vertical position. As a consequence, when the support arm 26 is released, the pin 32 as shown in FIG. 1, under the influence of gravity, becomes disposed again on the smooth edge of the support column 28, and, as a result, the pin 31 is firmly drawn into the teeth 28a and maintained in engagement. Easier manipulation of the supporting frame 26 to 28 may be obtained for vertical adjustment if the support arm 26 is provided with a handle 33 having a T-shaped cross-section. As may be seen more particularly from the illustrations in FIGS. 1 to 3, two different basic positions are provided for the protecting screen which are indicated by "M" (male) and "F" (female). The characteristic difference in these two basic positions resides only in the fact that, in position "M," the longer axis of the protecting screen, of elliptical shape, is aligned with the support arm 26, whilst in the other adjustment "F" the longitudinal axis of the ellipse extends transversely to the support arm 26. For this purpose the protecting screen as a whole is mounted to rotate about a vertical axis, on the shaft 9 on the end of the support arm 26. By means of an adjusting ring 35, preferably having a segment-like cut-out, as shown in FIGS. 2 and 3, the screen is adjustable between positions "M" and "F." The basic positions differ from each other by an angle of 90.degree.. The adjusting ring 35 is preferably connected securely to the plate assembly 1 by a screw connection or the like, and is associated with the support arm 26 so that the latter can assume the function of a stop limiting the rotation of the adjusting ring 35 both in one direction and the other. A circular disc preferably of plexiglass is indicated by the numeral 36, the purpose of which is primarily to protect the displaceable and rotatable parts of the protecting screen, such as slides, support levers and lead sheets carried thereby. According to the arrangement of FIG. 7, a supporting frame for a protective screen may also be provided by means of a guiding member 42 arranged to be rotatable on a support 41 and preferably by the form of a parallelogram guide. In addition, the outer end of this guide could have a rotatably secured support arm 43 for the suspension of the protective screen, thus ensuring that the screen always retains a horizontal position in any adjusted vertical position. In order to ensure that the above described setting and screening mechanism is protected against harmful effects, such as from soiling after a comparatively long period of use, or even when the operators do not provide appropriate care and attention to the apparatus, it is possible to hermetically seal the entire mechanism, in a casing. This casing may, as shown in FIGS. 8, 9 and 10, be formed of upper and lower portions 46 and 47. The portions are joined together at the edges, preferably by means of a contact adhesive or the like. The shape of the casing itself may be accomplished in accordance with the embodiment shown in FIG. 10. As shown, a part 46 is constructed as a flat disc and another part 47 has a surface 47a extending at an incline in the direction of radiation X of the X-ray machine. It is important that the angle of incline of the conical surface 47a of the part 47 should be shallow so that the degree of penetration of the X-rays does not experience any appreciable increase. An angle of incline of less than 30.degree. is necessary for this purpose. According to the other embodiment shown in FIGS. 8 and 9, the casing may also consist of two identical parts 46 and 47 each having a plate-like shape. Both parts, similar to the parts of the casing shown in FIG. 10 are preferably made of transparent material, for example, plexiglass so that they can be moulded in a simple manner, by heating the material in a die or the like. If both parts 46 and 47 or at least one of them (FIG. 10) is provided on the edge with an annular contact surface, this facilitates joining or connecting the parts together by the application of contact adhesives. It is to be understood that while the invention has been described in some detail, this is only for the purpose of facilitating an understanding thereof and is not at all intended to limit the scope of the invention as defined in the appended claims.