Abstract:
An operating table including at least three elements which are moveable in relation to each other; at least two actuators, each controlling displacement of two elements in relation to the other; a controller which drives each actuator; a sensor to detect a risk of collision of one of the elements with an obstacle when executing a displacement request of a first actuator; a controller which determines a corrective command order of a second actuator different from the first actuator upon detecting a risk of collision, wherein execution of the corrective command order by the second actuator causes cessation of the detected risk of collision upon subsequent execution of the displacement request of the first actuator; and a display to view the corrective command order.

Description:
RELATED APPLICATION 
     This is a continuation of International Application No. PCT/FR02/00051, with an international filing date of Jan. 8, 2002, which is based on French Patent Application No. 01/00218, filed Jan. 9, 2001. 
    
    
     FIELD OF THE INVENTION 
     The present invention pertains to an operating table of the type comprising at least three elements which are mobile in relation to each other, and at least two actuators each controlling the displacement of two elements in relation to the other, the table moreover comprising means for driving each actuator and means for detecting a risk of collision of one of the operating table&#39;s mobile elements with an obstacle when executing a displacement request of a first actuator. 
     BACKGROUND 
     In modern surgical operating tables each mobile element is controlled by a motorized actuator, especially electrically powered, enabling the surgeon or an operator to effortlessly displace the controlled element. 
     Because of the multiplication of the mobile elements in relation to each other and thus the multiplication of the possible configurations of the table, numerous risks of collision of the elements with each other can occur. Similarly, the end elements can strike obstacles present in the operating room, especially the floor. 
     When such a collision occurs or immediately before such an occurrence, the movement of the operating table controlled by the user is interrupted. The stopping of the maneuver is often perceived by the user as a malfunction of the operating table. Moreover, such a stopping is difficult for the user to interpret because he helplessly encounters a request for displacement that he wants to execute but that he can not implement for mechanical reasons that he does not always perceive. 
     After an involuntary stopping of a maneuver, the user often acts blindly on the other controls available to him but nevertheless is unable to subsequently perform with certainty the maneuver that he initially wanted to implement. 
     It would therefore be advantageous to provide an operating table that prevents this user predicament when a collision occurs or risks to occur between an element of the table and a neighboring obstacle especially on the floor, or when there is the risk that two of the table&#39;s mobile elements might collide with each other. 
     SUMMARY OF THE INVENTION 
     This invention is an operating table of the previously mentioned type, characterized in that it comprises means for determining a corrective command of a second actuator different from the first actuator upon detecting a risk of collision, the execution of the corrective command order by the second actuator causing the cessation of the detected risk of collision upon subsequent execution of the displacement request of the first actuator, and means to make available to the user this corrective command order. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Better comprehension of the invention will be obtained from the description below presented solely as an example and with reference to the attached drawings in which: 
         FIG. 1  is a perspective view of an operating table according to the invention; 
         FIG. 2  is a schematic view of the actuation means of the table; 
         FIG. 3  is an elevation view of a control unit of the table; 
         FIG. 4  is a partial perspective view at an enlarged scale of the translational movement guiding device of the table&#39;s platform; 
         FIG. 5  is a flow chart explaining an operating routine of the table; and 
         FIGS. 6A ,  6 B,  6 C,  6 D,  6 E,  6 F and  6 G are schematic elevation views of the table illustrating cases of collision of the table&#39;s mobile elements with each other or of one of the table&#39;s mobile elements with the floor. 
     
    
    
     DETAILED DESCRIPTION 
     The operating table  10  shown in  FIG. 1  comprises a base  12 , a pillar or column  14  and a patient-support platform  16 . The platform is constituted by an assembly of elements articulated with respect to each other and enabling deformation of the surface on which the patient rests. 
     Each of the table&#39;s mobile elements is associated with at least one actuator and a sensor, such as a potentiometer, enabling determination of the position of the actuator, and thereby deduction of the current position of the controlled element in relation to the element in relation to which it is mobile. 
     For each mobile element, the associated actuator is designated by the same reference number as the element followed by the letter A; the sensor is designated by the same reference number as the element followed by the letter B. 
     The actuators and sensors are not shown in  FIG. 1 . They are only shown schematically in  FIG. 2 . The installation of the sensors and actuators in the operating table is known by the expert in the field. 
     Each actuator can be controlled by two specific buttons provided on a table control unit  18  shown by itself on an enlarged scale in  FIG. 3 . 
     On this control unit, two control buttons are provided for controlling each actuator in two opposite directions. For each actuator, the two buttons associated with the opposite directions are designated by the same reference number as the controlled element of the table, followed by the letters C and D. 
     The column  14  can be displaced in relation to the base  12  so as to regulate the height of the patient-support platform  16 . For this purpose, it has an actuator  14 A installed between the base  12  and the platform  16 . This actuator is associated with a position sensor  14 B. The actuator is controlled by the buttons  14 C and  14 D of the control unit  18 . 
     The platform assembly  16  is mounted so that it can be displaced in a sliding manner in relation to the column  14  along a direction transverse to the axis of the column. For this purpose, guiding and motorization means for the platform in relation to the top of the column are provided. These means are shown in an enlarged scale in  FIG. 4 . 
     They comprise on each side of the platform  16  a first essentially horizontal bottom rail  20  attached to a top end of the column  14  by two cross-pieces  22 . They also comprise a second essentially horizontal top rail  24  positioned above the bottom rail  12  and parallel to it. The top rail  24  is integral with a side rail  26  of the platform and can be displaced in translational movement with this side rail in relation to the first fixed bottom rail  20 . 
     For each of the two pairs of rails  20 ,  24 , a carriage  28  is mounted such that it can freely slide horizontally on the fixed bottom rail  20  from one end to the other of this rail. The top rail  24  is mounted on the carriage  28  and can slide horizontally in relation to it. 
     The operating table  10  is equipped with an actuator identified as  16 A for the translational movement of the platform assembly  16  in relation to the column  14 . This actuator provides for the translational displacement of each top rail  24  in relation to the associated fixed bottom rail  20 . 
     In the envisaged mode of implementation, the actuator  16 A is rotatory. Its body is integral at one end of the fixed bottom rail  20 . Its output pinion is connected by a chain to a pinion of a rotatory shaft positioned in the medial part of the rail  20 . This shaft extends perpendicularly to the rails  20  and  24 . At its other end, the rotatory shaft comprises a pinion meshing a rack extending along the entire length of the rail  24 , the rack being carried by the interior surface of the rail  24 . 
     With an arrangement such as described below, the top rail  24  can be displaced from one end to the other of the bottom rail  20  and can, in its extreme positions, extend overhanging the bottom rail  20 , thereby enabling a very large amplitude of displacement of the platform  16 . 
     The actuator  16 A is equipped with a position sensor  16 B and is controlled from two buttons  16 C and  16 D of the control unit enabling respectively the displacement of the platform toward the patient&#39;s head (forward movement) and toward the patient&#39;s feet (backward movement) when a patient is lying on the table. 
     The platform  16  comprises in its center part a baseplate  30  carried by the side rails  26 . An actuator  30 A is positioned between the baseplate and the top of the column  14  to enable control of the tilting of the platform  16  in relation to the axis of column  14  and around an axis extending generally transversely to the longitudinal axis of the platform  16 . 
     The actuator  30 A is associated with a position sensor  30 B and is controlled by two buttons  30 C and  30 D of the control unit  18 , these buttons corresponding respectively to a downward tilting of the patients&#39; head (backward sloping) or the opposite, an upward raising of the patient&#39;s head (forward sloping). 
     A backrest  32  is articulated at one end of the baseplate  30 . An actuator  32 A is positioned between the backrest and the baseplate to enable the angular displacement of the baseplate under the control of two buttons  32 C and  32 D of the control unit, these buttons being associated respectively with a raising and a lowering of the baseplate. 
     A position sensor  32 B is also associated with the actuator  32 A to determine the position of the backrest in relation to the baseplate. 
     The free end of the backrest is extended by a removable headrest  33 . 
     The baseplate  30  has at its end, in the region of connection to the backrest  32 , a mobile support or block  34  that can be displaced between a retracted position in the general plane of the baseplate  30  and a deployed position in which it protrudes from the general plane of the baseplate  30 . 
     The block  34  is intended to act on the patient&#39;s lower back to push it out of the way of the backrest  32 . 
     The block  34  is controlled by an actuator  34 A positioned between this support and the baseplate  30 . This actuator  34 A is controlled from two buttons  34 C and  34 D of the control unit enabling respectively the deployment or retraction of the block  34 . The actuator is associated with a position sensor  34 B. 
     A legrest  36  is articulated at the other end of the baseplate  30 . It is controlled by an actuator  36 A positioned between the legrest  36  and the baseplate  30 . This actuator is associated with a position sensor  36 B. It can be displaced under the control of the buttons  36 C and  36 D of the control unit, these buttons being associated respectively with the raising and lowering of the legrest. 
     Finally, a final actuator is interposed between the platform  16  and the top end of the column  14  to enable lateral tilting to the right and left of the baseplate  16  along its longitudinal axis. Thus, the actuator  38 A enables the tilting of the platform assembly. This actuator is indicated as  38 A and does not respect the notation convention because it constitutes a second actuator acting on the platform  16 . 
     Whereas the actuator  30 A enables a tilting of the baseplate and the platform assembly  16  along a transverse axis of the platform, the actuator  38 A enables a lateral tilting of the baseplate and the platform assembly along a longitudinal axis of the platform. The actuator  38 A is associated with a position sensor  38 B and is controlled by two buttons  38 C and  38 D of the control unit  18  enabling a lateral tilting respectively to the left and to the right. 
     The table&#39;s control circuit is illustrated schematically in  FIG. 2 . It comprises a central data processing unit  50  to which is connected the control unit  18  by a bidirectional data transfer connector. 
     The central data processing unit  50  is also connected to a command interface  52  to which each of the actuators  14 A,  16 A,  30 A,  32 A,  34 A,  36 A and  38 A is connected. The command interface  52  is designed to provide electric current to the actuators as a function of the control data received from the central data processing unit. In particular, the command interface is designed to control in one direction or the other each of the actuators as a function of the data received from the central unit  50  for a duration corresponding to the displacement course desired for the element controlled by the corresponding actuator. 
     Similarly, the central data processing unit  50  is linked to a read interface  54  to which is connected each of the sensors  14 B,  16 B,  30 B,  32 B,  34 B,  36 B and  38 B associated with the actuators. This read interface is designed to continuously receive the current position values of each of the elements of the operating table and to send them to the central data processing unit  50 . 
     The central data processing unit  50  is also connecting to means  56  for storing a set of programs and routines implemented for the functioning of the table as well as means  58  for storing a set of data relative to the structure of the table and its particular control concepts. 
     The central data processing unit  50  also comprises means  59  for storing operating default messages produced during the functioning of the operating table. 
     In addition to the previously described control buttons, the control unit  18 , represented in an enlarged scale in  FIG. 3 , comprises a set of control buttons to lock the operation of the table or to shut off the power to the table. 
     All of the control buttons are advantageously backlit to facilitate their identification and the handling of the control unit. 
     The control unit  18  has in its top part a display screen  60  on which appears a schematic representation of the table, with each of the table&#39;s mobile elements being associated with its own display on which is permanently displayed a value representative of the position of the element in question. The display screen  60  is advantageously backlit for better legibility. 
     The control unit furthermore comprises, according to the invention, means  62  making available to the user a corrective command order to stop a situation in which there exists a risk of collision of an element during a particular command applied to the operating table. 
     The means  62  making available the corrective command order comprise, for example, a screen allowing the display of a line of text indicating, especially, the element to be displaced and the direction of displacement of the element so as to stop the potential collision situation. 
     The control unit  18  furthermore has an alarm  64  such as a warning light and/or sound emission transducer to alert the user when a collision issue occurs and that the displacement request being executed is stopped. 
     The data displayed on the display device  60  and in particular on the screen  62  stem from the central data processing unit  50 . The values presented on the individual displays associated with each of the table&#39;s mobile element are sent by the central data processing unit  50  collecting these data from the read interface  54  to which each of the sensors is linked. 
     The message displayed on the screen  62  is sent by the central data processing unit  50  upon implementation of the routine the algorithm of which is illustrated in  FIG. 5 . 
     At rest, the central data processing unit  50  awaits in step  70  the receipt of a displacement request. For this purpose, it monitors the set of buttons of the control unit  18 . Step  70  remains continuously in effect until a button is pressed. 
     When a button is pressed, the routine ascertains in step  70  whether the requested displacement is possible without there being a risk of collision for one of the table&#39;s mobile elements. For this purpose, the position of the element whose displacement is requested is compared to a limit value. 
     According to a first mode of implementation of the invention, the limit values for each actuator are stored in memory in the storage means  58 . 
     According to a second mode of implementation of the invention, the limit values for each actuator are calculated as a function of the positions of the table&#39;s other mobile elements. The limit values are calculated from laws stored in memory in the storage means  58 . Examples of such laws are presented in the description below. These laws are designed to enable determination of whether the displacement requested by the user is possible without it resulting in a collision either between two of the table&#39;s elements or between one of the table&#39;s elements and an environmental obstacle such as the floor. 
     Such a law can take the form of an inequation that must be ascertained by the current position value of the mobile element in question, this inequation being dependant on parameters formed by current position values of the other mobile elements. 
     If the displacement is not possible in step  72  because the measured position value does not satisfy the criteria allowing the displacement, the warning light  64  is lit in step  73  to warn the user that the requested displacement cannot be executed. Thus, no actuator commands are implemented. 
     Step  74  is then implemented during which the central data processing unit  50  determines a corrective command order for another element of the table so as to make it possible—after displacement of this other element of the table—for the displacement initially requested by the user to be implemented without risk of collision. 
     This corrective command order is collected in the storage means  58  as a function of the initial displacement request formulated by the user. 
     Examples of such corrective command orders are presented in the description below. The function of these corrective command orders is to stop the risk of collision upon the implementation of the displacement initially requested by the user. Thus, these corrective command orders have the purpose of modifying the table&#39;s configuration to stop the impossible situation resulting from the nonsatisfaction of the criteria during the test performed in step  72 . 
     The corrective displacement order determined in step  74  is made available to the user in step  76  by being displayed on the screen  62 . 
     The corrective order made available to the user comprises an identification of the actuator to be activated or the element of the table to be displaced as well as identification of its direction of displacement. 
     In other words, the message displaced on the screen  62  allows the user to determine which button of the control unit  18  he should press to stop the risk of collision detected in the case of movement of the table according to his initial displacement request. 
     At the end of step  76 , the test performed in step  70  is implemented again to enable the user to implement another table displacement request from the control unit  18 . 
     In particular, the user is encouraged to take into account the corrective command order displayed on the screen  62  and to implement this command order by pushing on the corresponding button to displace the designated element in the direction indicated in the corrective order. 
     After implementation of the corrective order, the displacement initially requested by the user can be executed. 
     If, in step  72 , the requested displacement is judged to be possible by the data processing unit  50 , the corresponding actuator is driven in step  78  from the interface  52 . Upon displacement of the actuator, the test executed in step  80  is implemented in a loop to ascertain whether the displacement is still possible without risk of collision for the various table elements. 
     As soon as a risk of collision is detected, the actuator is commanded to stop in step  82  and steps  73  to  76  are implemented again. In particular, a corrective command order is displayed on the screen  62  to provide the user with an indication of a new table displacement request which—after implementation—should enable implementation of the initially requested displacements. 
     When the displacement is possible, the test executed in step  84  ascertains whether the displacement request is still valid, i.e., whether the user still pushes the button corresponding to the control of an actuator. As long as the request is still valid, steps  80  to  84  are implemented in the loop. 
     When the displacement request is no longer valid, i.e., when the user releases the control button that he was pushing down on, the stopping of the actuator is commanded in step  86 , after which the test executed in step  70  is again implemented in the loop until a new table displacement request. 
     It can be understood that with the implementation of such a routine, the user is not confused when, upon a request for displacement by pushing on a button, no movement of the table takes place, or when this movement is only executed temporarily and is interrupted even though the user has not released the corresponding control button. 
     When such a stopping of the actuator or a refusal to trigger the actuator occurs because of the detection of a risk of collision of one of the table&#39;s elements, the user is immediately so informed by an alarm and a corrective command order is made available by being displayed on the screen  62 , this corrective order being such that when it has been implemented, the initially demanded displacement request can be implemented. 
     In the table below are presented examples of corrective command orders with the indication of displacement requests made impossible and the indication of the message provided to the user. 
     In the table below the first column indicates the command for which a risk of collision can be produced. The button number on the control unit  18  providing for this displacement is indicated in parentheses. 
     The second column indicates the figure on which is illustrated the operating table in a position in which a collision can be produced during the implementation of the command indicated in the first column. 
     The third column lists the elements that could be involved in a collision with each other. 
     The fourth, fifth and sixth columns each indicate an elementary condition that could cause a collision, these conditions pertaining to the current position values of each of the actuators provided by the sensors placed on the operating tables. 
     Depending on the case, when the two or three conditions are ascertained, then the stopping of the actuator in movement is triggered and a message appears on the screen to indicate to the user a corrective command order to be implemented. 
     Thus, the movement space of the operating table is cut into distinct situations by the conditions. 
     The seventh column contains the corrective command order made available to the user by being displayed on the screen  62 . The button number on the control unit that must be pressed to apply this corrective command order is shown in parentheses. 
     The eighth column indicates the default operating message recorded in the storage means  59  upon detection of a risk of collision or a collision. 
     The following variables are used in the table below: 
     h=vertical displacement of the column, 
     t=translational movement of the platform, 
     d°=angle of the legrest, 
     b°=angle of the backrest, 
     l°=angle of lateral tilt, 
     k=height of the block. 
     F1 to F6 are geometric and arithmetic functions dependent on the kinematic of the operating table. 
     C1 to C6 are constants characteristic of the geometry of the operating table and act as a base for the comparisons. 
     
       
         
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                   
                   
                   
                 (lf) 
                   
                   
                   
                   
               
               
                   
                   
                 Fig- 
                   
                 Condi- 
                 (&amp;lf) 
                 (&amp;lF) 
                 (Then) 
               
               
                   
                 Commands 
                 ure 
                 Possible collision 
                 tion 1 
                 Condition 2 
                 Condition 3 
                 ALS &amp; Display 
                 Error code 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 lower 
                 6E 
                 leg plate/base 
                 p° &lt; 0° 
                 F1(d°, t, p°) &gt; C1 
                 F2(h, d°, t, p°, l°) &lt; C2 
                 raise legrest (36C) 
                 legrest/base 
               
               
                 2 
                 column (14D) 
                 6D 
                 leg plate/floor 
                 p° &lt; 0° 
                 F1(d°, t, p°) &lt; C1 
                 F3(h, d°, t, p°, l°) &lt; C3 
                 raise legrest (36C) 
                 legrest/floor 
               
               
                 3 
                   
                 6C 
                 headrest/floor 
                 b° &lt; 0° 
                 d° &lt; 0° 
                 F4(t, d°, b°, l°, h) &lt; C4 
                 forward slope (30D) 
                 headrest/floor 
               
               
                 4 
                 head 
                 6B 
                 leg plate/translation 
                 p° &lt; 0° 
                 t &lt; 0 
                 F6(t, p°) &lt; C6 
                 raise legrest (36C) 
                 legrest/slide 
               
               
                 5 
                 translational 
                 6E 
                 leg plate/base 
                 p° &lt; 0° 
                 F1(d°, t, p°) &gt; C1 
                 F2(h, d°, t, p°, l°) &lt; C2 
                 raise legrest (36C) 
                 legrest/base 
               
               
                 6 
                 movement (16C) 
                 6F 
                 leg plate/column 
                 p° &lt; 0° 
                 d° &gt; 0° 
                 F5(d°, t, p°) &gt; C5 
                 raise legrest (36C) 
                 legrest/column 
               
               
                 7 
                 feet 
                 6A 
                 backrest/translation 
                 b° &lt; 0° 
                 t &gt; 0 
                   
                 raise backrest (32C) 
                 backrest/slide 
               
               
                 8 
                 translational 
                 6E 
                 leg plate/base 
                 p° &lt; 0° 
                 F1(d°, t, p°) &gt; C1 
                 F2(h, d°, t, p°, l°) &lt; C2 
                 backward slope (30C) 
                 legrest/base 
               
               
                 9 
                 movement (16D) 
                 6D 
                 leg plate/floor 
                 p° &lt; 0° 
                 F1(d°, t, p°) &lt; C1 
                 F3(h, d°, t, p°, l°) &lt; C3 
                 backward slope (30C) 
                 legrest/floor 
               
               
                 10 
                 lower 
                 6E 
                 leg plate/base 
                 p° &lt; 0° 
                 F1(d°, t, p°) &gt; C2 
                 F2(h, d°, t, p°, l°) &lt; C2 
                 raise column (14C) 
                 legrest/base 
               
               
                 11 
                 legrest (36D) 
                 6D 
                 leg plate/floor 
                 p° &lt; 0° 
                 F1(d°, t, p°) &lt; C1 
                 F3(h, d°, t, p°, l°) &lt; C3 
                 raise column (14C) 
                 legrest/floor 
               
               
                 12 
                   
                 6B 
                 leg plate/translation 
                 p° &lt; 0° 
                 t &lt; 0 
                 F6(t, p°) &lt; C6 
                 plate toward feet (16D) 
                 legrest/slide 
               
               
                 13 
                   
                 6F 
                 leg plate/column 
                 p° &lt; 0° 
                 d° &gt; 0° 
                 F5(d°, t, p°, l°) &gt; C5 
                 plate toward feet (16D) 
                 legrest/column 
               
               
                 14 
                 raise backrest 
                 6G 
                 block/backrest 
                 b° &lt; 0° 
                 k &gt; 0 
                   
                 retract block (34D) 
                 block/backrest 
               
               
                   
                 (32C) 
               
               
                 15 
                 lower  
                 6C 
                 headrest/floor 
                 b° &lt; 0° 
                 d° &lt; 0° 
                 F4(t, d°, b°, l°, h) &gt; C4 
                 raise column (14C) 
                 headrest/floor 
               
               
                 16 
                 backrest (32D) 
                 6A 
                 backrest/translation 
                 b° &lt; 0° 
                 t &gt; 0 
                   
                 plate toward feet (16D) 
                 backrest/slide 
               
               
                 17 
                 raise block (34C) 
                 6G 
                 block/backrest 
                 b° &lt; 0° 
                 k &gt; 0 
                   
                 lower backrest (32D) 
                 block/backrest 
               
               
                 18 
                 backward 
                 6C 
                 headrest/floor 
                 b° &lt; 0° 
                 d° &lt; 0° 
                 F4(t, d°, b°, l°, h) &gt; C4 
                 raise column (14C) 
                 headrest/floor 
               
               
                   
                 slope (30C) 
               
               
                 19 
                 forward 
                 6D 
                 leg plate/floor 
                 p° &lt; 0° 
                 F1(d°, t, p°) &lt; C1 
                 F3(h, d°, t, p°, l°) &lt; C3 
                 raise column (14C) 
                 legrest/floor 
               
               
                 20 
                 slope (30D) 
                 6E 
                 leg plate/base 
                 p° &lt; 0° 
                 F1(d°, t, p°) &gt; C1 
                 F2(h, d°, t, p°, l°) &lt; C2 
                 raise column (14C) 
                 legrest/base 
               
               
                 21 
                   
                 6F 
                 leg plate/column 
                 p° &lt; 0° 
                 d° &gt; 0° 
                 F5(d°, t, p°, l°) &gt; C5 
                 plate toward feet (16D) 
                 legrest/column 
               
               
                 22 
                 lateral tilt 
                 6D 
                 leg plate/floor 
                 p° &lt; 0° 
                 F1(d°, t, p°) &lt; C1 
                 F3(h, d°, t, p°, l°) &lt; C3 
                 raise column (14C) 
                 legrest/floor 
               
               
                 23 
                 (38C or 38D) 
                 6E 
                 leg plate/base 
                 p° &lt; 0° 
                 F1(d°, t, p°) &gt; C1 
                 F2(h, d°, t, p°, l°) &lt; C2 
                 raise column (14C) 
                 legrest/base 
               
               
                 24 
                   
                 6F 
                 leg plate/column 
                 p° &lt; 0° 
                 d° &gt; 0° 
                 F5(d°, t, p°, l°) &gt; C5 
                 raise legrest (36C) 
                 legrest/column 
               
               
                 25 
                   
                 6C 
                 headrest/floor 
                 p° &lt; 0° 
                 d° &lt; 0° 
                 F4(t, d°, b°, l°, h) &gt; C4 
                 raise column (14C) 
                 headrest/floor 
               
               
                   
               
             
          
         
       
     
     In the first case, illustrated in  FIG. 6A , the table&#39;s platform  16  is moved toward the patient&#39;s feet to a considerable degree. In this case, the lowering of the backrest  32 , by action on the button  32 D, is limited or blocked because of the risk that the rear surface of the backrest  32  could hit the end of the rail  20  as shown by the arrow F 6 A. 
     Upon stopping the lowering of the backrest, as soon as the conditions indicated in the sixteenth line of the table are satisfied, the corrective command order “displacement of platform toward the head” is displayed on the screen  62 . This order causes the user of the table to displace the platform by pushing on the button  16 C to move the backrest away from the rail  20  and thereby subsequently enable a greater lowering of the backrest. 
     In the following case also illustrated in  FIG. 6A , it is assumed that the platform is not completely displaced toward the feet and the backrest is already folded downward to a considerable degree. The command to displace the platform toward the feet causes a risk of the backrest  32  hitting the end of the rail  20 . The displacement of the platform toward the feet is interrupted when the conditions indicated in the seventh line of the table are satisfied. Upon the refusal to satisfy the displacement request from the user attempting to further displace the platform toward the feet, the message “raise backrest” appears on the screen  62 . 
     In the case in which the platform  16  is displaced toward the patient&#39;s head to a considerable degree, as shown in  FIG. 6B , the displacement request attempting to lower the legrest  36  is not satisfied until the conditions indicated in the twelfth line of the table are ascertained. As indicated by the arrow F 6 B, there is a risk of collision between the legrest  36  and the bottom rail  20 . When this condition is ascertained, the downward movement of the legrest  36  is blocked and the message “displacement of platform toward the feet” appears on the screen  62 . 
     Similarly, as illustrated in  FIG. 6B , when the legrest  36  is lowered to a considerable degree, the request for displacement of the platform  16  intended to move it toward the head is blocked or interrupted when the conditions indicated in the fourth line of the table are satisfied because there is a risk of collision between the legrest  36  and the bottom rail  20 . Upon stopping the displacement of the platform  16 , the message “raise legrest” is displayed. 
     When the platform  16  is tilted toward the side of the patient&#39;s head to a considerable degree as shown in  FIG. 6C , the request for descending the backrest  32  is blocked or interrupted to prevent its end fitted with the headrest  33  from hitting the floor as indicated by the arrow F 6 C. When the conditions indicated in the fifteenth line of the table are satisfied, the downward displacement of the backrest  32  is blocked and the message “tilt platform toward feet” is displayed. 
     Other conditions of possible collisions between the headrest and the floor, as illustrated in  FIG. 6C , are presented in table 1 on lines 3, 18 and 25. 
     As illustrated in  FIG. 6D , when the platform  16  is tilted toward the feet to a considerable degree, the downward tilting of the legrest  36  is blocked when the conditions indicated on the eleventh line of the table are ascertained and the message “raise column” is displayed because there is a risk of the end of the legrest  36  hitting the floor as indicated by the arrow F 6 D. 
     In the same situation illustrated in  FIG. 6D , when the legrest  36  is folded downward to a considerable degree, the further frontward tilting of the platform toward the feet (forward sloping) is blocked so as to prevent the legrest from hitting the floor as indicated by the arrow F 6 D. This blocking is implemented when the conditions indicated in the nineteenth line of the table are ascertained and the message “raise column” is displayed. 
     The cases of possible collisions such as are illustrated in  FIG. 6D  are specified in the second, ninth and twenty-second lines of the table. The displayed message is shown in the seventh column for each case. 
     When the legrest  36  is folded downward as illustrated in  FIG. 6E , the request intending to reduce the height of the column  14  is interrupted when the conditions indicated in the first column of the table are satisfied and the message “raise legrest” is displayed because, as illustrated by the arrow F 6 E, there is a risk that the end of the legrest could hit the floor. 
     Similarly, in the same situation illustrated in  FIG. 6E , when the table&#39;s platform  16  is already at a relatively low level, the downward displacement of the legrest  36  is limited when the conditions indicated in the tenth line of the table are ascertained to prevent the end of the legrest from hitting the floor. When the request for displacement of the legrest cannot be satisfied, the message “raise the column” is displayed. 
     Other cases of potential collisions and the messages then displayed on the screen in a case corresponding to that  FIG. 6E  are specified in the table on the fifth, eighth, twentieth and twenty-third lines. 
     As illustrated in  FIG. 6F , when the legrest  36  is folded to a considerable degree there is a risk that it could hit the column  14  as shown by the arrow F 6 F. 
     Thus, as shown in the sixth line of the table, upon a request for the translational movement of the platform toward the head, the command is interrupted when the conditions indicated in the sixth line are ascertained. The message “raise legrest” is then displayed. 
     Other conditions of potential collisions between the end of the legrest and the column are specified in the third, twenty-first and twenty-fourth lines of the table. 
     Finally, as illustrated in  FIG. 6G , when the block  34  protrudes in relation to the baseplate  30 , the command “raise backrest” must be limited so as to prevent a collision between the backrest and the block as indicated by the arrow F 6 G. 
     Thus, as indicated in the fourteenth line of the table, when the conditions indicated in this line are ascertained, the raising of the backrest is interrupted and the message “lower block” is displayed. 
     The cases of potential collision and the solutions provided appearing in the table above are only examples and other cases of collision are also handled by implementation of the routine presented in  FIG. 5 . 
     Moreover, the central data processing unit  50  is designed to determine the collision of each of the table&#39;s mobile elements during its movement with an object positioned on the trajectory of the mobile element. 
     For this purpose, upon displacement of one of the table&#39;s mobile elements, the central data processing unit monitors the evolution of the value provided by the sensor associated with the actuator acting on the mobile element. If an object positioned on the trajectory of the mobile element causes the stopping of the actuator—even momentarily—the central data processing unit detects this stopping due to the fact of the lack of temporal evolution of the value provided by the sensor associated with the actuator. The actuator command is immediately interrupted and a message “abnormal stop” is sent to the user by display on the screen  62 . 
     The user informed in this manner can then ascertain whether in fact an object hinders the displacement of the mobile element.