Abstract:
A screen made of radiation shielding material for protecting an operator from ionizing radiation, includes: (i) a lower part equipped with a front wall made of radiation shielding material, having an upper border; (ii) an upper part equipped with a front wall made of a radiation shielding material, at least one part of which is transparent, which front wall includes a lower border; and (iii) at least one passage for the arms of the operator. The front walls of the upper part and of the lower part are separable from each other, the upper part being borne by supporting elements allowing the screen to be reversibly maneuvered either into an active radiation shielding position in which the upper and lower borders are juxtaposed, or into a retracted position in which the upper and lower borders are separated from each other, in order to free a space above the lower part.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to the radioprotective screens, and more particularly the screens that are used in medical environment or other, to protect an operator from emissions of ionising radiations, for example X-rays. It also relates to an equipment in the form of a sterile cover for covering such screens, with a view to using them in a sterile protected environment. 
     Description of the Related Art 
     Within the framework of some examinations or interventions, the patients are subjected to ionising radiations, in particular of the X-ray type, used for the purpose of control, diagnosis or treatment. 
     This is the case in particular for interventions such as catheterism, installation of pacemaker, vascular, neurological or urological examinations, CRM (Cardiac Rhythm Management), CRT (Cardiac Resynchronization Therapy) . . . . 
     It is then important to correctly protect the operator (technician, doctor, surgeon or other) from such radiations, on pain of exposing him/her to significant doses, cumulated over time, liable to generate various pathologies (necroses of the upper limbs, cerebral tumors, etc.). 
     Protection structures exist, which consist in clothes such as overalls, chasubles or aprons made of a radioprotective material, but that do not always cover the totality of the body and whose significant weight harms the comfort of the operator, limits his/her capacities of movement and generates a rapid fatigue. 
     Shields or screens also exist, which are consisted of panels or assemblies of panels made of a suitable radioprotective material, put directly on the ground or through a support base, for example a rolling frame. 
     For example, the document US20120049093 describes a screen structure, a vertical part of which is intended to come in position under a support table adapted for receiving a patient, and another vertical part of which, carried by the first one, is intended to come in position above said support table and the patient. 
     This second part is mounted vertically mobile relative to the first one, in particular to facilitate the positioning of the screen the nearest possible of the body of the patient lying on the table. 
     But such a structure is not adapted to allow an operator located on the protected side of the screen to accede, by his/her arms and hands, to the other side of this screen, for example to intervene on a part of the patient&#39;s body exposed to the radiations. 
     Other known radioprotective shields or screens, as described for example in the documents FR2915868, WO-2009/156660 or U.S. Pat. No. 3,308,297, consist in structures well adapted to protect an operator intervening on a patient exposed to radiations, through orifice(s) or opening(s) for the passage of his/her arms and hands. 
     But the current structures of this type do not always allow the operator to work in optimum conditions. 
     In particular, some interventions include intermediate phases or steps during which the operator does not need radioprotection, but needs a great freedom of movement, for example for the installation of implantable cardiac devices, pacemakers, defibrillators, etc. 
     The presence of the screen is then relatively embarrassing. The operator has to bypass it or the screen has to be temporarily moved apart, which is not easy to implement and poses problems of space, organisation and even of security within the intervention room. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to propose a new structure of radioprotective screen through which an intervener can pass his/her hands, and possibly his/her arms, to intervene on a patient, while having the remaining of his/her body efficiently protected from the radiations, this screen structure being adapted to be very easily conformed according to an optimum radioprotection configuration, but also according to a configuration in which the operator has a more significant freedom of movement, in particular as regards his/her upper limbs, for the access to the patient or to the close environment of the latter. 
     The radioprotective material screen according to the invention is hence of the type comprising: 
     a lower part that has a base and at least one front wall made of a radioprotective material, which front wall extends in a vertical or substantially vertical plane and has an upper edge, a front face and a rear face, 
     an upper part having at least one front wall made of a radioprotective material, at least one part of which is transparent to permit a visual access through it, which front wall has a front face, a rear face and a lower edge, and 
     at least one passage for the operator&#39;s arms, so that the latter can intervene on the non-radioprotected side, with the remaining of his/her body efficiently protected, 
     said front wall of the lower part and said front wall of the upper part being arranged in the continuation of each other, by juxtaposition of their respective upper and lower edges, hence occupying an active position ensuring the desired protection. 
     And within the framework of the present invention, said front walls of the upper part and of the lower part are separable from each other, said upper part being carried by support means allowing the reversible operation thereof to a retracted position in which the lower edge of the front wall of the upper part is spaced apart from the upper edge of the front wall of the lower part, to clear a space above said lower part. 
     According to another characteristic, said passage for the operator&#39;s arms is arranged at the level of the zone of juxtaposition between said lower and upper parts, when these latter are in an active juxtaposed position. 
     In this case, said passage for the operator&#39;s arms is advantageously arranged at the level of the lower edge of the front wall of the upper part, and consists in a flexible curtain in the form of a plurality of vertical strips or bands juxtaposed to each other, made of a radioprotective material, and the upper end of which is fixed on an upper panel made of a radioprotective material. 
     According to another feature, the upper part of the screen is carried by the lower part, through linking means allowing said reversible operations between said above-mentioned active and retracted positions. 
     In this case, said linking means advantageously include means for the pivoting operation of said upper part with respect to said lower part, about at least one horizontal axis. 
     Preferably, the upper part is mounted at the end of two lateral uprights fastened to the lower part, which uprights are offset rearwardly with respect to the plane of the front wall of the lower part. 
     Still according to another characteristic, the front wall of the lower part has lateral edges that are continued, on the side of its rear face, by lateral returns made of a radioprotective material. 
     Preferably, these lateral returns each include an upper flap mobile about a vertical articulation formed along the lateral edge of the front wall of the lower part; and these upper flaps are mobile between a closed position in which they are located in or substantially in the plane of said lateral returns, and an open position in which they are adapted to be located in or substantially in the plane of the front wall of the lower part. 
     The lateral uprights of the screen are then advantageously arranged along the rear edge of the lateral returns of the lower part. 
     According to still another feature, the front wall of the upper part includes an upper panel made of a transparent radioprotective material that, once in active position, is inclined forwardly with respect to the front wall of the lower part, forming an overhanging, to allow the operator to move closer to the zone of intervention. 
     Preferably, the upper panel of the upper part is continued rearwardly by a covering panel made of a radioprotective material (preferably transparent). 
     On the other hand, the lateral edges of this upper panel, and possibly those of the covering panel, are continued rearwardly by lateral returns made of a radioprotective material. 
     Then, the lower end of the lateral returns of the upper part comprise a flexible curtain made of a radioprotective material, so as to create lateral passages for the operator&#39;s arms, in the continuation of the above-mentioned passage arranged between the front walls of the lower and upper parts of the screen. 
     Moreover, the lateral returns of the upper part of the screen each advantageously include a lower flap mobile about an articulation, which flaps carry said flexible curtains and are mobile between a closed position in which they are located in or substantially in the plane of said lateral returns, and an open position in which they are extended outwardly. 
     According to still another arrangement, the upper part of the screen is fastened to the lower part through lateral arms articulated about a first horizontal axis of articulation, forming a pivot, located at the upper end of the lateral uprights, which lateral arms are fastened to the lateral returns of said upper part, through a second horizontal axis of articulation, forming a pivot, located above said first axis of articulation, which articulations are associated with means for controlling the pivoting movements, such as cylinder(s) for example. 
     Preferably, the front wall of the lower part consists in a rigid panel made of a radioprotective material, in which is formed an opening closed by a flexible curtain in the form of a plurality of vertical strips of bands juxtaposed to each other, made of a radioprotective material, allowing the passage of devices or parts of devices though said opening. 
     On the other hand, the lower part of the screen is advantageously consisted of two complementary parts sliding vertically relative to each other, and which partially overlap each other to allow a variation of its height, which two parts are assembled to each other by means in the form of guides or slides associated with one or several actuators allowing to adapt the respective position of said two constitutive parts. 
     The invention also relates to an equipment in the form of a sterile cover intended to cover at least one part of the surface of a screen as defined herein above, such equipment comprising: 
     a flexible envelope adapted to come and cover the lower end of the front wall of the upper part and provided with means for the fixation thereof to said front wall, 
     two flexible envelopes adapted to come and cover the mobile lower flaps of the lateral returns of the upper part, provided with means for the fixation thereof to said associated mobile flap, 
     a flexible envelope adapted to come and cover the upper end of the front wall of the lower part and the upper flaps of the associated lateral returns, provided with means for the fixation thereof to said front wall and said flaps, and 
     two structures for covering the lateral uprights, provided with means for the fixation thereof to said lateral uprights. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       Other characteristics and advantages will appear from the reading of the following description of a particular embodiment, given only by way of example and shown in the appended drawings in which: 
         FIG. 1  shows a radioprotective screen according to the invention, in a ¾ front perspective view, and in the active radioprotection position; 
         FIG. 2  is a vertical sectional view of the screen of  FIG. 1 ; 
         FIG. 3  shows the screen of  FIGS. 1 and 2 , in a ¾ front perspective view, but here with its upper part in a partially retracted position; 
         FIG. 4  is a vertical sectional view of the screen of  FIG. 3 ; 
         FIG. 5  is still a view of the same radioprotective screen, with its upper part in the fully retracted position; 
         FIG. 6  is a vertical sectional view of the screen of  FIG. 5 ; 
         FIG. 7  is a view of the screen with its upper part in a partially retracted position, and with its lateral flaps in the open position, illustrating the installation of an equipment in the form of a sterile cover; 
         FIG. 8  is a face view of the screen according to  FIGS. 1 to 7 , herein in the active radioprotection position and with its lower part extended, to increase its height. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The radioprotective screen  1  shown in  FIGS. 1 to 6  comprises a lower part  2  and an upper part  3 , which are mobile relative to each other, herein by rotation/pivoting of the upper part  3  with respect to the lower part  2 , so as to allow the conformation thereof according to different configurations that will be detailed hereinafter. 
     The lower part  2  includes a base or stand  4 , provided with wheels  5   a ,  5   b  for resting on the ground, from which extends upwardly a front wall  6  made of a radioprotective material (for example, for a part, a 2 mm lead equivalent massive steel, and for another part, a flexible plastic material charged with radio-attenuating metal particles), continued rearwardly by two lateral returns  7  also made of a radioprotective material (for example, a 1 mm lead equivalent massive steel). 
     The front wall  6  and the lateral returns  7  extend in a vertical or substantially vertical plane; they form together a structure with a U-shaped horizontal cross-section. 
     The front wall  6  is delimited by an upper edge  8 , two lateral edges  9 , a front face  10  and a rear face  11 . 
     The upper edge  8  is horizontal and the lateral edges  9  are vertical. 
     In an alternative embodiment, the plane of this front wall  6  may be slightly inclined forwardly or rearwardly with respect to the vertical. 
     The two lateral returns  7  extend from lateral edges  9  of the front wall  6 , rearwardly, i.e. on the side of the rear face  11  of this front wall  6 , and straightly or, herein, in a slightly outwardly flared manner. 
     They each have—an upper edge  12  that continues rearwardly the horizontal upper edge  8  of the front wall  6 , —a front edge  13  connected to one of the lateral edges  9  of the front wall  6 , —a rear edge  14 , —a front face  15  (directed the outside of the screen), and—a rear face  16  (directed to the inside of the screen). 
     These returns  7  each have an upper flap  7   a  that is mobile about a vertical articulation  7   b  formed on the lateral edge  9  opposite the front wall  6 ; each mobile flap  7   a  extends over a part of the height of the returns  7  (for example about half this height) and over all or part of their width. Their upper edge defines the upper edge  12  of the returns  7 . 
     Hence, these mobile flaps  7   a  can occupy a closed position, as illustrated in  FIGS. 1 to 6 , in which they are located in the plane of the remaining of the returns  7 ; they are then locked in position by any suitable means, for example a removable latch, a magnet, and/or using ratchet hinges at their articulation to the ends of the front wall  6 . 
     These mobile flaps  7   a  may also occupy an open position, in or substantially in the plane of the front wall  6 , as illustrated in  FIG. 7 ; then, their upper edge  12  is located in the alignment of the upper edge  8  of the front wall  6 . 
     The base  4  of the screen  1  includes—two front wheels  5   a  that extend from the front face  10  of the front wall  6 , on the sides and within the spatial requirement of the latter, and—two rear wheels  5   b  that extend in the continuation of the lateral returns  7 . 
     Two lateral uprights  17  extend vertically along the rear edges  14  of the lateral returns  7 . 
     These uprights  17  may be an integral part of the lateral returns  7 , or may consist in independent added elements. They are offset rearwardly with respect to the plane of the front wall  6  and their upper end  19  extends above the level of the upper edges  12  of the lateral returns  7  and of the upper edge  8  of the front wall  6 . 
     The upper part  3  of the screen  1  consists in a cap or caisson pivotally mounted on the lower part  2 , and more particularly at the upper end  19  of the lateral uprights  17 . 
     This upper part  3  has a front wall  20  made of a radioprotective material, delimited by an upper edge  21 , a lower edge  22  and two lateral edges  23 . It also has a front face  24  and a rear face  25 . 
     This front wall  20  of the upper part  3  includes an upper panel  26  made of a transparent radioprotective material (for example, 2 mm lead equivalent laminated lead glass), of generally rectangular shape, continued downwardly by a flexible curtain  27 , formed of a plurality of vertical strips or bands juxtaposed to each other, made of a radioprotective material (for example, a flexible plastic material including a radio-attenuating metallic filler). 
     This flexible curtain  27  extends over all the width of the upper panel  26 ; its upper end is fixed on the lower edge  26   a  of this panel  26 , by any suitable means; its lower end is free. 
     As will be seen hereinafter, this flexible curtain  27  is intended to constitute a passage for the operator&#39;s arms (when the screen is in an active radioprotection configuration), and its height can be comprised between 20 and 30 cm, for example. 
     The lower edge  27   a  of the flexible curtain  27  constitutes the lower edge  22  of the front wall  20  of the upper part  3  of the screen  1 ; this lower edge  27   a - 22  is free. 
     The upper edge  26   b  of the upper panel  26  constitutes the upper edge  21  of the front wall  20 ; herein, this upper edge  26   b  is continued upwardly and rearwardly by a covering panel  28  also made of a preferably transparent radioprotective material (for example, a 0.5 mm lead equivalent lead-filled composite). 
     This covering panel  28  includes a rear free edge  29  and two lateral edges  30 . 
     These lateral edges  30  extend in the continuation of the lateral edges  23  of the upper panel  26 . 
     The upper panel  26  and the covering panel  28  are arranged in planes that form between each other an angle of the order of 120°. 
     The lateral edges  23  and  30  of the upper panel  26  and of the covering panel  28  are continued on the sides by lateral returns  31  made of a radioprotective material. 
     These returns  31  can extend perpendicular or substantially perpendicular to the plane of the panels  26  and  28 , and hence parallel or substantially parallel to each other; in this case, they herein extend rearwardly in a slightly flared manner relative to each other. 
     The distance that separate them corresponds approximately to the distance that separates the lateral returns  7  of the lower part  2 . 
     Each return  31  is in fact consisted by an upper panel  32  made of a preferably transparent radioprotective material (for example, a 0.5 mm lead equivalent lead-filled composite)—the front edge  32   a  of which is connected to the lateral edges of the upper  26  and covering 28 panels, —the lower edge  32   b  of which, which extends parallel or substantially parallel to the lower edge  26   a  of the panel  26  and which is arranged slightly above the latter, is continued downwardly by a flap  33  made of a radioprotective material, and—the rear edge  32   c  of which is continued by a platen  34 , also made of a radioprotective material (for example, 1 mm lead equivalent massive steel). 
     The flaps  33  are pivotally mounted about the edge  32   b  that connects them to the upper panel  32 , by means of hinges. They are consisted of a plate/base  35  made of a radioprotective material (for example, 0.75 mm lead equivalent massive steel), continued downwardly by a flexible curtain  36  also made of a radioprotective material (for example, flexible plastic material including a radio-attenuating metallic filler). The lower edge of the plate/base  35  extends at the lower edge  26   a  of the upper panel  26 . The two flexible curtains  36  continue, on the sides, the flexible curtain  27  of the front wall  20 . 
     When the flaps  33  are placed in the plane of their upper support panel  32 , the flexible curtains  36  are positioned in the continuity of the front flexible curtain  27  and they extend rearwardly, straightly or in a slightly outwardly flared manner. 
     The height of the flexible curtains  36  correspond to that of the front flexible curtain  27 . 
     The two lateral flaps  33  are pivotally mobile about the hinge formed on the above-mentioned edge  32   b , between a closed position, in which they are located in the plane of the upper panels  32  ( FIGS. 1 to 4 ) and an open position wherein they are outwardly spaced apart ( FIGS. 5 to 7 ). 
     Their operation can be performed manually and/or automatically by a system of cable(s) associated with the pivoting of the upper part  3  of the screen, as detailed hereinafter. The corresponding articulation is associated with means for controlling the movement, consisted of a cylinder  33   a , for example of the gas cylinder type, interposed between the plate/base  35  and the juxtaposed platen  34 . The cylinder  33   a  has for function to maintain the flap  33  in the desired position, in particular for the installation of sterile covers. 
     The two platens  34  are connected by a carrier bow  37  formed of an upper crossbar  37   a  whose ends are continued rearwardly by two lateral arms  37   b.    
     The crossbar  37   a  extends horizontally, approximately in the plane of the upper end of the lateral returns  31  and offset rearwardly with respect to the rear edge  29  of the covering panel  28 . 
     The lower end of the arms  37   b  is assembled to the upper end  19  of the lateral uprights  17  of the lower part  2  of the screen through a first horizontal axis of articulation  38 , forming a pivot, whose pivoting movement is controlled by two lateral cylinders  39 , for example of the gas cylinder type. 
     Each of the cylinders  39  is interposed between a first fork joint fixed to one of the lateral arms  37   b  and a second fork joint fixed to the corresponding lateral upright  17  (herein, this second fork joint is carried by the upper end of one bow  40  adapted for operating the screen and each upright  17  is equipped with). 
     The ends of stroke of the two cylinders  39  define the rotational degree of freedom of the upper part  3  with respect to the lower part  2 , about the axis  38 ; and these two cylinders  39  allow to damp the corresponding movement, in the two directions. 
     On the other hand, the lateral arms  37   b  are fastened to the lateral returns  31  (and in particular the platens  34  thereof) through a second horizontal axis of articulation  42 , forming a pivot, whose movement is controlled by two lateral cylinders  43 , for example also of the gas cylinder type. 
     Each of these cylinders  43  is interposed between a first fork joint fixed on one of the lateral arms  37   b  and a second fork joint fixed on the corresponding platen  34 . 
     The ends of stroke of the two cylinders  43  define the rotational degree of freedom of the upper part  3  with respect to the bow  37  (and hence also with respect to the lower part  2 ), about the axis  42 . These two cylinders  43  allow to damp the corresponding movement, in the two directions. 
     Preferably, the pivoting operation about the axis  42  is made possible only when the bow  37  is in maximum rearward tilting with respect to the lateral uprights  17 , this by a system of locking stops  44   a ,  44   b ; in the other direction, the return to the closed position is firstly performed by the tilting about the axis  42 , then about the axis  38 , still thanks to the system of locking stops  44   a ,  44   b.    
     The tilting movement about the axes  38  and  42  is obtained by a manual operation by the operator on the upper part  3 , by means of operating handles  45  provided at the lower edge of the upper panel  26 , on the rear face side of the latter, to be accessible from the inside of the screen  1 . 
     Such a structure allows a mobility of the upper part  3  with respect to the lower part  2  of the screen, by pivoting about the above-mentioned pivot joints  38  and  42 . 
     The front walls  20  and  6  of the upper  3  and lower  2  parts, as well as the lateral returns  31  and  7  that are associated therewith are hence reversibly separable from each other, and it is possible to conform the screen according to different configurations, in particular: 
     a so-called “active” configuration, illustrated in  FIGS. 1 and 2 , in which the upper part  3  is lowered forwardly toward the lower part  2 , in such a manner that their front walls  6  and  20  come into the continuation of each other (like their associated returns  7  and  31 ) to ensure an efficient protection from the ionising radiations, 
     a so-called partially “retracted” configuration, illustrated in  FIGS. 3 and 4 , in which the upper part  3  is tilted upwardly and slightly rearwardly by a pivoting movement about the axis  38 , so as to separate said lower  6  and upper  20  front walls, with their associated returns, and hence clear a small space above the lower part  3 , and 
     a so-called “fully retracted” configuration, illustrated in  FIGS. 5 and 6 , in which the upper part  3  is possibly slightly upwardly tilted but also widely rearwardly tilted by a complementary pivoting movement about the axis  42 , offering to the operator a significant freedom of movement above the lower part  3 , for example toward a patient lying in front of the screen; 
     the corresponding cleared space is frontal and also lateral, due to the rearward offset of the lateral uprights  17  that carry the upper part  3  of the screen. 
     Advantageously, a cable control system ensures the outward spacing of the two flaps  33  during the pivoting of the upper part  3  rearwardly about the upper horizontal axis  42 . This feature allows to clear even more the space for the operator, in particular on the sides, as illustrated in  FIGS. 5 and 6 . 
     The corresponding cables, not visible in the figures, suitably connect the arms  37   b  of the bow  37  and the plates/bases  35 , by passing through suitable deflecting structures. 
     The rotation axis  42  extends above the axis  38 ; it is positioned approximately at half the height of the arms  37   b.    
     The presence of these two rotation axes  38  and  42 , offset in height, provides the upper part  3  with an optimum kinematics, during its rearward or forward tilting, by limiting its maximum level of elevation. This allows to limit the required space in height for the operation of the upper part  3  of the screen, for example to avoid the contact with devices or parts of devices located in height. 
     As an alternative, the upper part  3  of the screen may be articulated on the lateral uprights  17  about a single horizontal axis, in association with a suitable pivoting capacity. 
     According to still another alternative embodiment, it may also be contemplated to fasten the upper part  3  of the screen with the lateral uprights  17  through vertical slides, in association with one or several suitable actuators, to allow its vertical movement in height, to obtain the desired active and retracted positions. 
     In the active radioprotection position ( FIGS. 1 and 2 ), the front wall  6  of the lower part  2  and the front wall  20  of the upper part  3  are arranged in the continuation of each other, like their lateral returns  7  and  31 . The arms  37   b  are in the continuation of the lateral uprights  17 . 
     The lower end  27   a  of the flexible curtain  27  arrives at the upper edge  8  of the front wall  6  of the lower part  2 , or comes into slight overlap with the latter. 
     Likewise, the lower ends of the lateral flexible curtains  33  arrive at the upper edge  12  of the lateral returns  7  of the lower part  2 , or come into slight overlap with these latter. 
     The flexible curtains  27  and  33  made of a radioprotective material, present at the zone of juxtaposition between lower  2  and upper  3  parts hence ensure a passage for the operator&#39;s arms, who will be able to accede to the patient and/or to devices present just in front of the screen, while remaining efficiently protected from the radiations. 
     This arm passage has a U-shaped horizontal cross-section, without discontinuity between the front face and the sides, which ensures an optimum comfort of intervention for the operator. 
     Its height, for example of the order of 20 to 30 cm, is adapted to optimize this comfort, while being minimized in such a manner to maintain an efficient radioprotection. 
     The corresponding arm passage is herein arranged at the lower edge of the upper front wall  20  and of its lateral returns  31 ; the flexible curtains  27  and  36  extend vertically by simple effect of gravity. 
     In an alternative embodiment, these flexible curtains can be provided at the upper edge of the front wall and the lateral returns of the lower part of the screen; these flexible curtains will then be maintained in vertical position by any suitable means. 
     As can be seen in  FIG. 1 , in this active radioprotection position, the upper panel  26 , made of a transparent radioprotective material is inclined forwardly with respect to the vertical front wall  6  of the lower part  2  of the screen. This transparent panel  26  hence forms an overhanging and allows the operator to move closer to the zone of intervention located in front of the screen. 
     The corresponding overhanging angle is advantageously comprised between 10 and 30° with respect to the vertical (it is preferably of the order of 15 to 20° with respect to the vertical). 
     In this active radioprotection position, the rod of the cylinders  39  is in abutment in one of its stable positions, herein the maximum extraction. 
     When the operator wants it, for example at the beginning of the intervention, before the implementation of the means for generating ionising radiations, or during the intervention, for example to accede directly to the patient, he/she can lift the upper part  3  of the screen as illustrated in  FIGS. 5 and 6 , so as to create a frontal access opening, above the upper edges  8  and  12  of the lower part  2 . 
     For that purpose, starting from the active position illustrated in  FIGS. 1 and 2 , the operator begins to tilt the upper part  3  upwardly, by gripping the operating handles  45 . 
     The upper part  3  then pivots about the horizontal articulation  38 , under the control of cylinders  39 , to obtain the intermediate retracted position illustrated in  FIGS. 3 and 4 . 
     The rod of the cylinders  39  reaches its other stable position (retracted position), the corresponding pivoting may be of the order of 18°. 
     As explained hereinabove, during this first pivoting about the axis  38 , the articulation about the axis  42  is locked by the system of locking stops  44   a ,  44   b.    
     Once this first intermediate position reached, the suitable set of locking stops  44   a ,  44   b  releases the axes  42 , and an additional thrust applied upwardly by the operator on the operating handles  45  leads to the pivoting of the upper part  3  about this axis  42 . 
     This pivoting is performed under the control of the cylinders  43 , until they reach their second stable position, herein with their rod fully retracted. 
     The fully retracted position illustrated in  FIGS. 5 and 6  is then obtained. 
     This second pivoting can be made over an angular sector of the order of 60°, to obtain in total (i.e. with the pivoting about the axis  38 ) a pivoting of the order of 78°. 
     As stated hereinabove, the upward and rearward pivoting movement about the axis  42  is advantageously accompanied by the outward spacing of the flaps  33  (as can be seen in  FIGS. 5 and 6 ), for example over an angular sector of the order of 40 to 60°, thanks to a suitable set of cables. 
     When the operator wants to come back to the active radioprotection position, he/she pulls on the operating handles  45  to begin lowering the upper part  3 , by pivoting about the articulation axis  42 , until the cylinders  43  reach their stable position with their rod fully extracted. Then, a continuation of the pulling operation leads to the second pivoting about the axis  38 , under the control of the cylinders  39 , until the rod of these latter arrive in its stable extracted position, to obtain the active configuration of the screen illustrated in  FIGS. 1 and 2 . 
     It is then understood that it is possible to obtain the active radioprotection and fully retracted positions in simple and rapid manner. 
     Within the framework of the use of the screen  1  in a sterile environment (for example for a surgical intervention), it is intended to cover at least one part of its different constitutive faces, and the screen is structured so as to allow a simple and rapid installation of this cover system. 
     In the present case, an equipment formed of a plurality of independent sterile elements is used to constitute this covering case. And the installation, as well as the removal of some of these elements, are performed in association with the pivoting of the above-mentioned flaps  7   a  and  33 , as illustrated in  FIG. 7 . 
     As can be seen in  FIG. 7 , the installation of this sterile equipment is performed whereas the screen is in the intermediate retracted position (i.e., with its upper part  3  pivoted rearwardly about the axis  38  only). 
     Moreover, for that purpose, the flaps  33  of the returns  31  are manually spaced apart toward the outside (positioned, for example, straight with respect to the upper panel  32 , and they are maintained in this position by the action of the associated cylinders  33   a ; moreover, the lower flaps  7   a  of the returns  7  are open and placed in or substantially in the plane of the front wall  6 . 
     As illustrated in dashed line in  FIG. 7 , the sterile equipment used to ensure the protection of the screen  1  comprises several elements, including: 
     a flexible envelope  48 , adapted to come and cover the lower end of the front wall  20  of the upper part  3 . This flexible envelope  48  consists in two parallel panels, assembled on three of their edges and provided with an opening for its positioning about the flexible curtain  27  and the lower part of the transparent panel  26 . 
     This flexible envelope  48  can be made of any suitable material, preferably transparent; its positioning opening may be lined by elastic means to facilitate its installation; it is also advantageously provided with means for the fixation thereof to the screen, for example an adhesive and/or suction pad system. 
     two flexible envelopes  49 , adapted to come and cover the mobile lower flaps  33  of the lateral returns  31  of the upper part  3 . 
     Each of these envelopes  49  is formed of two rectangular flaps fastened on three of their edges, the fourth edge constituting a positioning opening, advantageously associated with elastic means. 
     Each of these envelopes  49  is made of any suitable material, for example non transparent. Their opening may be lined by elastic means to facilitate their positioning; and each of these flexible envelopes  49  is provided with means for the fixation thereof to the associated flap  33 , for example adhesive or suction pad means. 
     a flexible envelope  50  adapted to come and cover the upper end of the front wall  6  of the lower part  2  and the upper flaps  7   a  of the lateral returns  7 . 
     Here again, this flexible envelope  50  is consisted of two rectangular flaps assembled at three of their edges, and the fourth edge of which constitutes a positioning opening. It is made of any suitable material, for example transparent, and comprises means for the fixation thereof to the screen, for example of the adhesive or suction pad type. 
     Its opening may be lined by elastic means to facilitate its positioning. 
     two structures  51  for covering the lateral uprights  17  (with possibly a part of the returns  7 ). Each of these structures  51  can be constituted of a simple rectangular panel made of a suitable material (for example a nonwoven material), which is conformed so as to come and cover the periphery of the uprights  17  (with possibly a part of the returns  7 ) and which is maintained in place by any suitable fixation means, for example adhesive means. 
     Once the different elements  48  to  51  of the sterile equipment correctly positioned, the flaps  33  and  7   a  are manually replaced in the closed position. 
     The level of positioning in height of the upper edge  8  of the lower part  2  of the screen advantageously corresponds to the level where the operator&#39;s forearms rest, to optimize the comfort of use thereof. 
     The corresponding height with respect to the ground may be of the order of 110 to 130 cm. 
     The lower part  2  of the screen  1  is preferably made of two telescopic parts  2   a  and  2   b  to allow an adjustment of height of the screen, and also the positioning in height of the flexible curtains  27 ,  33  for the passage of the arms, in particular as a function of the operator&#39;s size. 
     The bottom part  2   a  is fastened to the base  4  and is assembled to the telescopic top part  2   b  by means of suitable guides or slides (not visible on the figures), associated with operating means in the form of actuator(s)  52 . 
     For example, an actuator  52  of the hydraulic cylinder type may be used, associated with a foot-operable control lever  53  (control pedal), adapted to manage a movement of lifting or lowering of the screen.  FIGS. 1 to 7  illustrate the screen  1  in the low position, with its lower part  2  in the fully retracted position.  FIG. 8  is a face view of the screen  1 , illustrated herein in the high position with its extended lower part  2 . 
     In  FIGS. 1 to 8 , it can be observed that the central zone of the front wall  6  of the lower part  2  includes an opening  54  closed by a flexible curtain  55  in the form of a plurality of vertical strips or bands juxtaposed to each other, made of a radioprotective material (for example, a plastic material filled with radio-attenuating metallic particles). 
     Such an opening  54  associated with a flexible curtain  55  allows the passage of devices or parts of devices through it (for example, the head of the X-ray emitting bow), while maintaining an efficient radioprotection. 
     For example, the opening  54  in question may be made in a rigid panel made of a radioprotective material constitutive of the bottom part  2   a  of the lower part  2 , on the upper edge of which are fixed the flexible strips or bands made of radioprotective material; and the telescopic top part  2   b  of the lower part  2  then includes an opposite opening, adapted not to hamper the passage through said flexible curtain.