Abstract:
A lighting appliance ( 1 ), in particular for illuminating an operating field ( 4 ), comprises a light module ( 8 ) having a handle ( 11 ) mounted to turn, and a monitoring and control unit ( 10 ) that responds to said handle ( 11 ) turning by acting on an adjustment setting of said lighting appliance ( 1 ), and the monitoring and control unit ( 10 ) is arranged to read, at successive regular time intervals, an indication of the relative angular position of the handle ( 11 ), and to act on the adjustment setting on the basis of the indications of the current relative angular position and of the preceding relative angular position that are read respectively for a current time interval and for a time interval immediately preceding the current time interval.

Description:
TECHNICAL FIELD 
       [0001]    The invention relates generally to a lighting appliance, and more particularly to a lighting appliance used in an operating theater for illuminating an operating field. 
       PRIOR ART 
       [0002]    In known manner, a lighting appliance comprises a light module having one or more light sources connected to an electrical power supply controlled by a monitoring and control unit. 
         [0003]    The light module can be provided with a handle for moving it. The handle can be further mounted to turn about its longitudinal axis so as to deliver an angular position signal that is used by the illumination monitoring and control unit for adjusting the illumination, e.g. for adjusting the brightness of the illumination. 
         [0004]    Patent Document US 2006/0109650 describes such a lighting appliance in which the handle is coupled to a differential transducer outputting an electrical signal that depends on the angular position of the handle and that makes it possible to modulate the power of the illumination as a function of that position. The turning of the handle is unlimited and is said to be “endless”. 
         [0005]    Such lighting is generally carried by an articulated arm enabling the illumination to be steered in three dimensions. Thus, the handle is also used by the medical staff to steer the illumination relative to the operating field. It is therefore important to make sure that acting on the handle to move the illumination does not unintentionally cause the illumination power to be modulated. 
         [0006]    To this end, Patent Document EP 2 159 485 describes a lighting appliance in which turning the handle causes the size of the field of illumination to vary, that lighting appliance having two angular abutments limiting the extent to which the handle can be turned. Each abutment is associated with a mechanical sensor making it possible to detect contact between the handle and one or the other of the abutments. The variation in the size of the field of illumination is thus dependent on such contact being detected. As a result, the handle can be used to steer the illumination with little risk of that leading to an unintentional change in the field of illumination. However, that arrangement has functional possibilities that remain limited. 
         [0007]    Documents US 2012/043915 and EP 2 065 634 also disclose medical lighting devices provided with handles for adjusting the illumination with precision. However, those adjustments do not depend on predetermined parameters. 
       SUMMARY OF THE INVENTION 
       [0008]    An object of the invention is to remedy those drawbacks by proposing a lighting appliance provided with a handle that, when turned, makes it possible to adjust the illumination with precision, without physical abutments and while allowing the illumination to be moved by pulling on the handle without any risk of adjusting the illumination in untimely manner. 
         [0009]    To this end, the invention provides a lighting appliance, in particular for illuminating an operating field, the lighting appliance comprising a light module having a handle mounted to turn, and a monitoring and control unit that responds to the handle turning by acting on an adjustment setting of the lighting appliance, said lighting appliance being characterized in that the monitoring and control unit is arranged to read, at successive regular time intervals, an indication of the relative angular position of the handle, and to act on the adjustment setting on the basis of the indications of the current relative angular position and of the preceding relative angular position that are read respectively for a current time interval and for a time interval immediately preceding the current time interval, and in that the monitoring and control unit is arranged to compute a current angular difference on the basis of the indications of the current angular position and of the preceding angular position, and to compare the current angular difference with a predetermined threshold. 
         [0010]    The general idea lying behind the invention is thus to adjust the illumination on the basis of detection of the relative angular positions of the handle respectively on two consecutive time intervals. 
         [0011]    The lighting appliance of the invention may, in particular present the following features: 
         [0012]    the monitoring and control unit is arranged to modify the value of an adjustment parameter of the lighting appliance when the current angular difference is greater than the threshold; 
         [0013]    the monitoring and control unit is arranged to determine, at each current time interval, a direction for the current angular difference and to increase or to decrease the value of the adjustment parameter as a function of the direction of the current angular difference; 
         [0014]    the monitoring and control unit is arranged to compare the current angular difference with a predetermined first threshold for a first turning direction of the handle, and to compare the current angular difference with a predetermined second threshold for a second turning direction of the handle that is opposite from the first turning direction, the first threshold being different from the second threshold; 
         [0015]    the monitoring and control unit is arranged to detect a change of turning direction of the handle during the current time interval and the preceding time interval, and to respond to the detection by changing over the adjustment of the lighting appliance from a current adjustment parameter to a predetermined adjustment parameter; 
         [0016]    the value of the adjustment parameter is an illumination power, a color temperature, or a light spot size; 
         [0017]    the monitoring and control unit changes over from a current adjustment parameter to another adjustment parameter following a predetermined circular list of adjustment parameters; 
         [0018]    the lighting appliance has a toothed wheel that is on the same axis as the handle and that is constrained to turn with the handle, a pinion arranged to mesh with the toothed wheel, and a relative angular position sensor suitable for detecting the relative angular position of the handle via the relative angular position of the pinion; 
         [0019]    the angular position sensor is of the potentiometer type; and 
         [0020]    the handle is hollow and is suitable for receiving a video connector support. 
         [0021]    This arrangement of the monitoring and control unit makes it possible to avoid untimely modulations in the adjustment parameter(s) that can be triggered by the handle turning a little when said handle is used for moving the illumination. 
         [0022]    In addition, with this arrangement, it is not necessary to know precisely the absolute angular position of the handle because a relative angle of turning is used. The lighting appliance of the invention thus operates in relative manner and not in absolute manner. 
         [0023]    In addition, by adjusting the value(s) of the threshold(s), it is possible to act on the sensitivity of the adjustment control, e.g. so as to adapt it to suit each user. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    The present invention can be better understood and other advantages appear on reading the following detailed description of an embodiment given by way of non-limiting example and with reference to the accompanying drawings, in which: 
           [0025]      FIG. 1  is a diagrammatic perspective view of a lighting appliance of the invention that is used in an operating theater; 
           [0026]      FIG. 2  is a perspective view of a portion of the handle of the lighting appliance of the invention; 
           [0027]      FIG. 3  is an exploded perspective view of the handle of the lighting appliance of the invention shown in a first configuration of use; 
           [0028]      FIG. 4  is an exploded perspective view of a portion of the handle shown in a second configuration of use; 
           [0029]      FIGS. 5 and 6  are plan views of the handle of  FIG. 3  shown in two distinct angular positions; 
           [0030]      FIG. 7  is a view similar to  FIGS. 5 and 6 , showing the handle of  FIG. 4 ; 
           [0031]      FIG. 8  is a diagrammatic view of the steps of the stage of switching ON the lighting appliance of the invention; and 
           [0032]      FIG. 9  is a diagrammatic view of the steps of the n th  loop for modulating the illumination by means of the lighting appliance of the invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0033]    With reference to  FIG. 1 , the lighting appliance  1  of the invention is, in particular, designed to be used in the medical field, e.g. in an operating theater  2 , for forming an illumination spot  3  (shown diagrammatically by shading) on an operating field  4 . 
         [0034]    In known manner, the lighting appliance  1  has a base that is fastened to the ceiling of the operating theater  2  and from which an articulated arm  6  extends that carries a lighting dome  7  that houses light sources  8  (shown diagrammatically in dashed lines in  FIG. 1 ), that are part of one or more light modules, such as light-emitting diodes (LEDs) disposed in a ring configuration. 
         [0035]    The LEDs  8  are connected electrically to an electrical power supply  9  coupled to a monitoring and control unit  10  suitable for controlling the electrical power supply  9  so as to modulate one or more adjustment parameters, e.g. the size of the illumination spot  3 , or indeed the intensity of the light produced by the LEDs  8 . 
         [0036]    The lighting appliance  1  is also provided with a handle  11  that is on the same axis as the ring of LEDs  8  and that extends axially in the lighting dome  7  so as to be grasped easily by the medical staff  12 . Said handle  11  is carried by the lighting dome  7  via a support  13  that can be seen in  FIGS. 2 to 4  and that, for that purpose, is provided with orifices  14  and with fastening rods  15  suitable for receiving screws (not shown) or for receiving any other suitable fastening element. 
         [0037]    In accordance with the invention, and with reference to  FIGS. 2 and 3 , the support  13  is in the shape of a dished collar through which a passage  16  extends, allowing the handle  11  to pass through it. The handle  11  is mounted on the support  13  via any known suitable means allowing the handle  11  to turn relative to the support  13 . The dished collar is closed by a plate  17  fastened to the support  13 , e.g. by means of screws  18  and of tapped orifices  19 . The lighting appliance  1  of the invention is provided with a toothed wheel  20  that is on the same axis as the handle  11 . The toothed wheel  20  is in the shape of a ring and it is received in the dished collar of the support  13 . The toothed wheel  20  is separated from the support  13  and from the plate  17  by washers  21  that are on the same axis and that limit the friction. The toothed wheel  20  has an internal bore  22  in which a video connector support  23  can be received that is suitable for carrying a camera (not shown), and that is provided with electrical connectors  24  for connecting the camera to the electrical power supply  9 . 
         [0038]    In accordance with the invention, the handle  11  is axially hollow, thereby allowing the camera to pass through so that it can film the operating field  4 , or allowing any equivalent electrical instrument to pass through. The plate  17  is also provided with a passage  25  allowing the electrical power supply wires (not shown) of the camera to pass through. 
         [0039]    With reference to  FIGS. 3 to 7 , the lighting appliance  1  of the invention further includes a pinion  26  housed in the dished collar of the support  13  and having its axle carried by the support  13 . The pinion  26  is disposed in such a manner as to be in the same plane as the toothed wheel  20  with which it meshes. The ratio between the number of teeth of the toothed wheel  20  relative to the number of teeth of the pinion  26  may, for example, be five. The axle of the pinion  26  passes through the plate  17  via an orifice provided for this purpose. Thus, as shown in  FIGS. 5 and 6 , when the handle  11  and the toothed wheel  20  turn through an angle of −β 1 , the pinion  26  turns through an angle of −α 1 . 
         [0040]    With reference to  FIGS. 3 ,  5 , and  6 , the handle  11  is, in this example, provided with a first lug  27  and the toothed wheel  20  is provided with a first notch  28  suitable for receiving the first lug  27  and for co-operating therewith so that, by turning, the handle  11  drives the toothed wheel  20  in turning. Naturally, this configuration may be inverted, the toothed wheel being provided with the first lug and the handle being provided with the first notch. This configuration makes it possible to modulate an adjustment parameter. In this configuration, the video connector support  23  does not turn with the handle  11 . Thus, the handle  11  can be turned without any risk of the electrical power supply wires of the camera becoming twisted. 
         [0041]    With reference to  FIGS. 7 and 4 , in this example, the handle  11  is provided with a second lug  29  that is radially offset relative to the above-mentioned first lug towards the axis of the handle  11 , and the video connector support  23  is provided with a second notch  30  suitable for receiving the second lug  29  and for co-operating therewith so that the handle  11  turning causes the video connector support  23  to turn without causing the toothed wheel  20  to turn. Naturally, this configuration may be inverted, the video connector support being provided with the second lug and the handle being provided with the second notch. This construction makes it possible to use a lighting module of the invention in a configuration in which modulating the adjustment parameter is obtained by turning the handle  11 , and in a second configuration in which the handle  11  turning has no effect on the adjustment parameter. 
         [0042]    The lighting appliance  1  of the invention also includes a relative angular position sensor  31  (shown in  FIGS. 2 and 3 ) that is in the form of a potentiometer card through which the axle of the pinion  26  passes. The angular position sensor  31  is suitable for emitting a signal indicating the relative angular position of the pinion  26  and thus of the handle  11 . The angular position sensor  31  passes a current having its voltage varying as a function of the angular position of the pinion  26 , e.g. over the range 0 to 5 volts. 
         [0043]    In accordance with the invention, the monitoring and control unit  10  or “MCU” is coupled to the angular position sensor  31  and is programmed so that, at successive regular time intervals, it reads indications giving the relative angular positions of the pinion  26  and thus of the handle  11 , and, on the basis of these successive readings, it modulates a particular adjustment parameter and/or changes adjustment parameter. 
         [0044]    As appears below, the MCU  10  repeats a processing loop at each time interval for modulating the current adjustment parameter. The length of each time interval may, for example, be 5 milliseconds (ms), but it may be longer or shorter depending on the desired adjustment sensitivity. 
         [0045]    As indicated above, the handle  11  turning may serve to cause a change of control or of adjustment parameter in the MCU  10 , independently of any modulation of the adjustment parameter, e.g. going over from the control of the adjustment parameter P 1  for the diameter of the illumination spot  3  to the control of the adjustment parameter P 2  for the level of visual illumination. 
         [0046]    It should be noted that, in the MCU  10 , it is possible to have more than two controls or adjustment parameters that are actionable selectively, going over from one control or adjustment parameter to another taking place in a predetermined order P 1 , P 2 , P 3 , . . . Pn of a predetermined circular list of controls or of adjustment parameters. 
         [0047]      FIG. 8  shows the stage of switching ON the MCU  10  of the invention, and in particular the first modulation loop. In this example, it is considered that the MCU  10  starts with a predetermined current adjustment parameter P 1 , e.g. size of the illumination spot  3 . 
         [0048]    In step  100 , the MCU  10  reads an initial indication giving the initial angular position A 0  for the handle  11 , this angular position being, for example, as shown in  FIG. 5 . This initial angular position A 0  may also be the angular position stored in a memory when the MCU  10  was switched OFF the last time the lighting appliance  1  was used, or indeed it may correspond to a reference position in which the handle  11  is repositioned before any switching ON of the MCU  10 . 
         [0049]    At successive predetermined time intervals n, e.g. every 5 ms after switching ON at the step  100 , the MCU  10  reads an indication of the current angular position of the handle  11 , which position is, in this example, the first current angular position A 1  such as, for example, shown in  FIG. 6 . This current angular position A 1  is recorded in a memory in the MCU  10 . 
         [0050]    In step  120 , the MCU  10  compares the current angular position A 1  with the preceding angular position, i.e. the initial angular position A 0 , which is also stored in the memory of the MCU  10 . 
         [0051]    If, in step  120 , the current angular position A 1  is not different from the initial angular position A 0 , the MCU  10  keeps the value of the adjustment parameter P 1  constant and the data processing process loops back for another time interval, which is 5 ms in length in this example. Otherwise, i.e. if, in step  120 , the current angular position A 1  is different from the initial angular position A 0 , the MCU  10  computes the angular difference al between the current angular position A 1  and the initial angular position A 0 . In step  130 , the MCU  10  also determines the turning direction (±α 1 ) of the handle  11  between the initial angular position A 0  and the current angular position A 1 , in particular the turning direction (+α 1 ) if the turning direction of the handle  11  is clockwise and the turning direction (−α 1 ) if the turning direction of the handle  11  is counterclockwise. 
         [0052]    If, in step  130 , the MCU  10  determines an angular difference +α 1  that is not zero in the clockwise direction, then in step  140  the MCU  10  compares this angular difference +α 1  with a first predetermined threshold S+ (clockwise threshold), it being possible for this clockwise threshold S+ to be recorded in a memory of the MCU  10  in order to be associated with the adjustment parameter P 1 . It should be understood that it is possible to have a plurality of different thresholds S+ associated with respective ones of different adjustment parameters that can be modulated in the MCU  10 . 
         [0053]    If, in step  140 , the MCU  10  determines that the angular offset +α 1  has a value less than the clockwise threshold S+, i.e. the handle  11  has not turned far enough clockwise, then the MCU  10  keeps the value of the adjustment parameter P 1  constant, and the data processing process loops back for another time interval. Conversely, if, in step  140 , the MCU  10  determines that the value of the angular difference +α 1  is greater than (or equal to) the clockwise threshold S+, then, in step  150 , the MCU  10  modulates (varies) the value of the adjustment parameter P 1  in predetermined manner, and continues the processing for a new time interval. The variation of the adjustment parameter P 1  is indicated at  150  by P 1 +. This variation may consist in gradually increasing the value, e.g. increasing the diameter for the illumination spot  3  by a centimeter. 
         [0054]    If, in step  130 , the MCU  10  determines an angular difference −α 1  that is not zero in the counterclockwise direction, then in step  160  the MCU  10  compares this angular difference −α 1  with a second predetermined threshold S− (counterclockwise threshold), it being possible for this counterclockwise threshold S− to be recorded in a memory of the MCU  10  in order also to be associated with the adjustment parameter P 1 . 
         [0055]    It should be understood that it is possible to have a plurality of different clockwise and counterclockwise thresholds S+, S− associated with respective ones of different adjustment parameters that can be modulated in the MCU  10 . 
         [0056]    If, in step  160 , the MCU  10  determines that the angular difference −α 1  has a value less than the counterclockwise threshold S−, then the MCU  10  keeps the value of the adjustment parameter P 1  constant, and the data processing process continues for a further time interval that starts running on expiry of the current time interval n. Conversely, if, in step  160 , the MCU  10  determines that the value of the angular difference −α 1  is greater than (or equal to) the counterclockwise threshold S−, then, in step  170 , the MCU  10  modulates (varies) the value of the adjustment parameter P 1  in predetermined manner, and continues the processing for a new time interval. The variation of the adjustment parameter P 1  is indicated at  170  by P 1 −. This variation may consist in gradually decreasing the value, e.g. by decreasing the diameter for the illumination spot  3  by a centimeter. 
         [0057]    It can be understood that the modulations in the steps  150  and  170  of the adjustment parameter P 1  normally go in opposite directions (increase/decrease). 
         [0058]      FIG. 9  shows a modulation loop subsequent to the first modulation loop shown in  FIG. 8 , i.e. subsequent to data processing in the MCU  10  that corresponds to the n th  time interval. 
         [0059]    In step  180 , the MCU  10  reads the current angular position An of the handle  11  and records it in the memory. In step  190 , the MCU  10  compares the current angular position An with the preceding annular position An−1 of the handle  11  that has been kept in the memory in the MCU  10 , i.e. the angular position occupied by the handle  11  at the end of the preceding time interval n−1, immediately before the current time interval n. If the current angular position An is identical to the preceding angular position An−1 of the handle  11 , the MCU  10  keeps constant the current adjustment parameter that is activated in the MCU  10  and that is indicated by Pi, and the process continues over a new modulation loop for another time interval. 
         [0060]    Otherwise, i.e. if, in step  90 , the current angular position An is different from the preceding angular position An−1 of the handle  11 , then, in step  200 , the MCU  10  computes the angular difference an between the current angular position An and the preceding angular position An−1. In step  200 , the MCU  10  also determines the turning direction of the handle  11  on going from the preceding angular position An−1 to the current angular position An, in particular the turning direction (+αn) if the turning direction of the handle  11  is clockwise, and the turning direction (−αn) if the turning direction of the handle  11  is counterclockwise. This current angular difference ±αn and the current turning direction are also recorded in step  200  in the memory by the MCU  10  at each current time interval n. 
         [0061]    If, in step  200 , the MCU  10  determines that the turning direction during the current time interval n is the clockwise turning direction (+αn), then, in step  210 , the MCU  10  checks whether the preceding turning direction αn−1 during the preceding time interval n−1 was also a clockwise turning direction (+αn). If it is, then in step  220 , the MCU  10  compares the current angular difference +αn with the predetermined clockwise threshold S+ associated with the current adjustment parameter Pi. If the value of the current angular difference +αn is less than the clockwise threshold S+, then the MCU  10  keeps the value of the adjustment parameter Pi constant (no adjustment action on the lighting appliance  1 ) and the process loops back for another time interval n+1. Conversely, if the value of the current angular difference +αn is greater than (or equal to) the clockwise threshold S+, then the MCU  10  varies (increments) the value of the adjustment parameter Pi as indicated above, and loops back for another time interval n+1. 
         [0062]    If, in step  200 , the MCU  10  detects a change of turning direction of the handle  11  both for the current time interval n and for the preceding time interval n−1, i.e. if the turning direction of the handle  11  for the preceding time interval n−1 was the counterclockwise direction (−αn−1), then, in step  240 , the MCU  10  compares the current angular difference +αn with the clockwise threshold S+ associated with the current adjustment parameter Pi. 
         [0063]    In step  240 , if the value of the current angular difference +αn is less than the clockwise threshold S+, then the MCU  10  keeps the value of the adjustment parameter Pi constant (no variation of the parameter) and loops back for another time interval n+1, and, conversely, if the value of the current angular difference +αn is greater than (or equal to) the clockwise threshold S+, then the MCU  10  changes the adjustment parameter. In the example, the MCU  10  goes over to the adjustment parameter Pi+1 that, for example, corresponds to adjustment of the brightness of the illumination. The process then loops back for another time interval n+1. 
         [0064]    If, in step  200 , the MCU  10  determines that the turning direction during the current time interval n is the counterclockwise turning direction (−αn), then, in step  260 , the MCU  10  checks whether the preceding turning direction αn−1 during the preceding time interval n−1 was also a counterclockwise turning direction (−αn−1). If it was, then in step  290 , the MCU  10  compares the current angular difference −αn with the predetermined counterclockwise threshold S− associated with the current adjustment parameter Pi. If the value of the current angular difference −αn is less than the counterclockwise threshold S−, then the MCU  10  keeps the value of the adjustment parameter Pi constant (no adjustment action on the lighting appliance  1 ) and continues its processing for another time interval n+1. Conversely, if the value of the current angular difference −αn is greater than (or equal to) the counterclockwise threshold S−, then the MCU varies (decreases) the value of the adjustment parameter Pi, and loops back for another time interval n+1. 
         [0065]    If, in step  260 , the MCU  10  detects a change of turning direction of the handle  11  both for the current time interval n and for the preceding time interval n−1, i.e. if the turning direction of the handle  11  for the preceding time interval n−1 was the clockwise direction (+αn−1), then, in step  290 , the MCU  10  compares the current angular difference −αn with the predetermined counterclockwise threshold S− associated with the current adjustment parameter Pi. 
         [0066]    In step  290 , if the value of the current angular difference −αn is less than the counterclockwise threshold S−, then the MCU  10  keeps the value of the adjustment parameter Pi constant (no variation of the parameter) and loops back for another time interval n+1, and, conversely, if the value of the current angular difference −αn is greater than (or equal to) the counterclockwise threshold S−, then the MCU  10  goes over to the adjustment parameter Pi+1, e.g. by following a circular list of adjustment parameters as indicated above, i.e. goes over to the adjustment parameter Pi+1. The process then loops back for another time interval n+1. 
         [0067]    It can thus be understood that turning in one direction and in the other over two consecutive time intervals can be detected by the MCU  10 , and can command parameter Pi to be changed being controlled by the handle  11  being turning. 
         [0068]    It can also be understood that an adjustment parameter Pi is varied by turning the handle  11  in the same direction over two consecutive time intervals n−1 and n, and that such a variation tends to be of the incremental or gradual type. It is also possible to make provision for progressive rather than incremental gradation without going beyond the ambit of the invention. 
         [0069]    Advantageously, particular counterclockwise thresholds S− and S+ may be assigned to each adjustment parameter Pi, it being possible for the counterclockwise threshold S− to be different from the clockwise threshold S+. It is thus possible to have as many pairs of counterclockwise and clockwise thresholds S− and S+ as there are adjustment parameters Pi under monitoring and control in the MCU  10 . 
         [0070]    By way of example, each of the counterclockwise and clockwise thresholds S− and S+ may be 45° but naturally if this threshold level is decreased, the sensitivity of the MCU  10  to monitoring and control of the adjustment parameter Pi is increased accordingly. 
         [0071]    In accordance with the invention, modulating the adjustment parameter Pi does not depend on an absolute angular position of the handle  11  in the dome  7 , but rather on a relative difference between angular positions of the handle  11 , between a current position and a preceding position that it occupied during the preceding reading. Thus, because a threshold S is to be reached between these two angular positions before triggering any modulation in the adjustment parameter Pi, the lighting appliance  1  of the invention makes it possible to limit the sensitivity of the modulation control. The handle  11  can thus continue to be used for moving the dome  7  without causing any unintentional adjustment. 
         [0072]    In addition, the absence of any physical abutment over the angular stroke of the handle  11  makes adjustment of the lighting appliance  1  operational at any time, as soon as the predetermined threshold S for turning of the handle  11  has been crossed. Finally, given the repeated modulation loops, modulation of the adjustment parameter Pi remains effective and precise. 
         [0073]    The particular construction of the lighting device  1  of the invention makes it possible, in addition, for the angular position sensor  31  to be off-center relative to the axis of the handle  11 . The handle  11  can thus be hollow and receive a vision device or any suitable device in it. 
         [0074]    Naturally, the present invention is in no way limited to the above description of one of its embodiments, which can undergo modifications without going beyond the ambit of the invention.