FIELD OF TECHNOLOGY 
     The invention relates to the field of disk positioning during recording and/or playing an optical disk. 
     BACKGROUND OF THE INVENTION 
     The invention relates to a clamping device for a disc-shaped information carrier having a central clamping opening, which clamping device is provided with a supporting member for the information carrier, a clamping member which can be displaced from a first position, in which the clamping member clamps the information carrier against the supporting member close to the clamping opening, to a second position in which the clamping member releases the information carrier, and a lifting member which co-operates with the clamping member and can be displaced from a first position, in which the lifting member is recessed relative to the supporting member, to a second position in which the lifting member is in a raised position relative to the supporting member. 
     The invention also relates to a scanning device for scanning information on a disc-shaped information carrier, which scanning device is provided with a table for the information carrier which can be rotated about an axis of rotation, a clamping device for clamping the information carrier on the table, and a scanning unit which can be displaced with respect to the table. 
     The invention also relates to the field of disk positioning during recording and/or playing an optical disk. 
     BACKGROUND AND SUMMARY 
     A clamping device of the type mentioned in the opening paragraphs is known from WO 93/01598. Said known clamping device can suitably be used in a box-shaped holder, for example, for a CD. The clamping member of the known clamping device comprises a number of clamping elements which can be displaced, while undergoing elastic deformation, from their first positions to their second positions. In order to clamp a CD in the holder, the central clamping opening of the CD must be pushed past the clamping elements, thereby causing the clamping elements to be displaced, by the central clamping opening, from their first positions to their second positions. After the central clamping opening has gone past the clamping elements, the clamping elements are displaced from their second positions to their first positions under the influence of the elastic deformation forces in the clamping elements, so that the CD is clamped by the clamping device. The lifting member of the known clamping device comprises a number of lifting arms which can be displaced, thereby also undergoing elastic deformation, from their first positions to their second positions. The known clamping device is further provided with a centrally arranged operating member by means of which the CD can be removed from the clamping device. To achieve this, the user must press the operating member, thereby causing the operating member to simultaneously move the clamping elements from their first positions to their second positions and the lifting arms from their first positions to their second positions. As a result, the CD is released by the clamping elements and lifted from the clamping device by the lifting arms. In this manner, a user-friendly operation of the clamping device is obtained. 
     The above citations are hereby incorporated in whole by reference. 
     A drawback of the known clamping device resides in that the clamping elements are pressed against the inner edge of the central clamping opening of the information carrier under the influence of said elastic deformation forces, when the central clamping opening is pressed past the clamping elements during providing the information carrier in the clamping device. As a result, the information carrier may be damaged near the central clamping opening. Said drawback of the known clamping device is particularly unfavorable if the known clamping device is used to clamp a DVD comprising two discs which are attached to one another. Under the influence of said pressure forces on the central clamping opening, the two discs may become detached, causing the DVD to become useless. 
     It is an object of the invention to provide a clamping device of the type mentioned in the opening paragraphs, in which the above-mentioned drawback of the known clamping device is precluded. 
     To achieve this, the clamping device in accordance with the invention is characterized in that the clamping device is provided with a first locking member, which locks the clamping member in its second position if the lifting member is not substantially in its first position, and a second locking member which locks the lifting member in its first position if the clamping member is not substantially in its second position. During placing an information carrier in the clamping device in accordance with the invention, the lifting member is displaced to its first position by the information carrier. Since the first locking member locks the clamping member in its second position if the lifting member is not substantially in its first position, the clamping member can only be displaced from its second position to its first position if the lifting member is substantially in its first position and the information carrier rests on the supporting member. In this manner, it is precluded that, during placing the information carrier in the clamping device, the clamping member contacts the information carrier before said information carrier rests on the supporting member. Since the second locking member locks the lifting member in its first position if the clamping member is not substantially in its second position, the lifting member can only be moved from its first position to its second position if the clamping member is substantially in its second position. In this manner, it is precluded that, during lifting and removing the information carrier from the clamping device, the clamping member contacts the information carrier. Since it is precluded, in this manner, that both during placing the information carrier in the clamping device and during removing the information carrier from the clamping device, the clamping member contacts the information carrier, it is precluded that, during placing the information carrier in and/or removing it from the clamping device, said information carrier is damaged near the central clamping opening by the clamping member. 
     A particular embodiment of a clamping device in accordance with the invention is characterized in that the clamping device is provided with means for exerting a pre-stressing force on the lifting member, said pre-stressing force being directed from the first position of the lifting member to the second position of the lifting member. If the lifting member is released by the second locking member, then the lifting member is displaced from its first position to its second position under the influence of said pre-stressing force, so that the information carrier is automatically lifted from the clamping device. By virtue thereof, the ease of use of the clamping device is improved. 
     A further embodiment of a clamping device in accordance with the invention is characterized in that the lifting member includes a number of lifting arms each extending substantially in a radial direction with respect to the information carrier, which lifting arms are provided, near a first end portion, with a supporting element for the information carrier, and which lifting arms are tiltable, near a second end portion, about a tilting axle extending substantially in a tangential direction with respect to the information carrier. By virtue thereof, a simple and practical construction of the lifting member is obtained. 
     Yet another embodiment of a clamping device in accordance with the invention is characterized in that the tilting axle of each of the lifting arms is formed by an elastically deformable hinge, the hinges jointly supplying the pre-stressing force exerted on the lifting member. As a result, said pre-stressing force is obtained in a simple and practical manner, and the number of parts of the clamping device is reduced. 
     A particular embodiment of a clamping device in accordance with the invention is characterized in that the clamping member includes a number of clamping elements each extending in a direction transverse to the information carrier, which clamping elements are provided with a clamping surface near a first end portion, and are tiltable, near a second end portion, about a tilting axle extending substantially in a tangential direction with respect to the information carrier. In this manner, a simple and practical construction of the clamping member is obtained. 
     A further embodiment of a clamping device in accordance with the invention is characterized in that the clamping member comprises a number of clamping elements which each extend in a direction substantially parallel to the information carrier, which are provided, near an end portion, with a clamping surface and can be swiveled about a swivel axle extending substantially perpendicularly to the information carrier. This too results in a simple and practical construction of the clamping member. 
     Yet another embodiment of a clamping device in accordance with the invention is characterized in that the clamping elements are coupled to a common operating member which can be displaced in a direction perpendicular to the information carrier, said clamping elements being jointly displaceable from their first positions to their second positions by a displacement of the operating member. Since the clamping elements can be jointly displaced from their first positions to their second positions by displacing the operating member, the ease of use of the clamping device is further improved. 
     A particular embodiment of a clamping device in accordance with the invention is characterized in that the clamping device is provided with further means for exerting a pre-stressing force on the operating member in a displacement direction of the operating member which corresponds to a displacement of the clamping elements from their second positions to their first positions. By virtue thereof, the ease of use of the clamping device in accordance with the invention is considerably increased. To clamp the information carrier into the clamping device, the user only has to place the information carrier on the supporting member. As a result, the lifting member is displaced into its first position, so that the clamping member is released from its second position by the first locking member, the clamping elements are displaced, under the influence of said pre-stressing force, from their second positions to their first positions, and the information carrier is clamped against the supporting member. 
     A further embodiment of a clamping device in accordance with the invention is characterized in that the clamping device is provided with an electromagnetic actuator for displacing the operating member. This further embodiment of the clamping device in accordance with the invention can very suitably be used in a scanning device for scanning information present on the information carrier. The electromagnetic actuator is controllable, for example, by means of an electrical control unit of the scanning device. 
     Yet another embodiment of a clamping device in accordance with the invention, in which the clamping device includes a number of clamping elements which can each be tilted about a tilting axle extending substantially in a tangential direction with respect to the information carrier, is characterized in that the first locking member is provided with a stop surface which is provided on the operating member and extends substantially parallel to the information carrier, while each of the lifting arms is provided, near its second end portion, with a locking element pertaining to the first locking member, which locking element serves to co-operate with the stop surface. This results in a simple and practical construction of the first locking member. 
     A particular embodiment of a clamping device in accordance with the invention, in which the clamping member includes a number of clamping elements which can each be tilted about a tilting axle extending substantially in a tangential direction with respect to the information carrier, is characterized in that the second locking member is provided with a further stop surface, which is provided on the operating member and extends substantially perpendicularly to the information carrier, while each one of the lifting arms is provided, near its second end portion, with a further locking element pertaining to the second locking member, which locking element serves to co-operate with the further stop surface. In this manner, a simple and practical construction of the second locking member is obtained. 
     A further embodiment of a clamping device in accordance with the invention, in which the clamping member includes a number of clamping elements which can each be swiveled about a swivel axle extending substantially perpendicularly to the information carrier, is characterized in that, near a further end portion, the clamping elements bear against a stop surface of the operating member while being subjected to a pre-stress, which stop surface comprises a conical portion extending transversely to the information carrier and serving to co-operate with the further end portions of the clamping elements. This results in the clamping elements being coupled in a simple and practical manner to the common operating member. 
     Yet another embodiment of a clamping device in accordance with the invention, in which the clamping member includes a number of clamping elements which can each be swiveled about a swivel axle extending substantially perpendicularly to the information carrier, is characterized in that the first locking member comprises a cylindrical portion of the stop surface of the operating member, which cylindrical portion extends perpendicularly to the information carrier and serves to co-operate with the further end portions of the clamping elements, said cylindrical portion connecting to the conical portion of the stop surface near an end portion of the conical portion where the diameter of the conical portion is largest, while each one of the lifting arms is provided, near its second end portion, with a locking element pertaining to the first locking member, which locking element serves to co-operate with a recessed portion provided in the operating member. In this manner, a practical and simple construction of the first locking member is obtained. 
     A particular embodiment of a clamping device in accordance with the invention, in which the clamping member includes a number of clamping elements which can each be swiveled about a swivel axle extending substantially perpendicularly to the information carrier, is characterized in that the second locking member comprises a further cylindrical portion of the stop surface of the operating member, which further cylindrical portion extends perpendicularly to the information carrier and connects to the conical portion of the stop surface near a further end portion of the conical portion where the diameter of the conical portion is smallest, while each one of the lifting arms is provided, near its second end portion, with a further locking element pertaining to the second locking member, which locking element serves to co-operate with the further cylindrical portion and a further recessed portion provided in the further cylindrical portion. This results in a practical and simple construction of the second locking member. 
     A scanning device of the type mentioned in the opening paragraphs is characterized in that the clamping device used therein is a clamping device in accordance with the invention. The above-described advantages of the clamping device in accordance with the invention manifest themselves in a particular manner in the scanning device in accordance with the invention. 
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 diagrammatically shows a scanning device in accordance with the invention, 
     FIG. 2 shows a plan view of a first embodiment of a clamping device in accordance with the invention, which can be used in the scanning device shown in FIG. 1, 
     FIG. 3 a  is a diagrammatic, sectional view taken on the line IIIa—IIIa in FIG. 2, in which a lifting member and a clamping member of the clamping device are both in a first position, 
     FIG. 3 b  is a diagrammatic, sectional view in accordance with FIG. 3 a , in which the lifting member and the clamping member are both in a second position, 
     FIG. 4 is a sectional view of a second embodiment of a clamping device in accordance with the invention, which can be used in the scanning device shown in FIG. 1, 
     FIG. 5 a  is a diagrammatic plan view of a third embodiment of a clamping device in accordance with the invention, which can be used in the scanning device in accordance with FIG. 1, a lifting member and a clamping member of the clamping device both being in a first position, 
     FIG. 5 b  is a diagrammatic sectional view taken on the line Vb—Vb in FIG. 5 a,    
     FIG. 5 c  is a diagrammatic sectional view taken on the line Vc—Vc in FIG. 5 a,    
     FIG. 6 a  is a diagrammatic plan view of the clamping device in accordance with FIG. 5 a , in which the lifting member and the clamping member are both in a second position, 
     FIG. 6 b  is a diagrammatic sectional view taken on the line VIb—VIb in FIG. 6 a , and 
     FIG. 6 c  is a diagrammatic sectional view taken on the line VIc—VIc in FIG. 6 a.   
    
    
     DETAILED DESCRIPTION 
     The scanning device in accordance with the invention, as diagrammatically shown in FIG. 1, is an optical player which can suitably be used to scan information on a discshaped optical information carrier  9 , such as a CD or DVD. The term “scanning” includes reading of information from the information carrier  9  and/or writing of information on the information carrier  9 . The scanning device comprises a table I which is rotatable about an axis of rotation  3  and drivable by an electric motor  5  which is mounted on a frame  7 . On the table  1 , an optically scannable information carrier  9  can be arranged which is provided, for example, with a disc-shaped carrier  11  and a transparent protective layer  13 . A side of the carrier  11  bordering on the protective layer  13  forms an information layer  15  of the information carrier  9  on which a spiral-shaped information track is present. The scanning device further includes an optical scanning unit  17  for optically scanning the information track of the information carrier  9 . The scanning unit  17  can be displaced with respect to the axis of rotation  3  predominantly in two opposite radial directions X and X′ by means of a displacement device  19  of the scanning device. For this purpose, the scanning device  17  is secured to a slide  21  of the displacement device  19  which is further provided with a straight guiding means  23  over which the slide  21  is displaceably guided, which guiding means extends parallel to the X-direction and is provided on the frame  7 , and with an electric motor  25  by means of which the slide  21  can be displaced over the guiding means  23 . In operation, an electrical control unit of the scanning device, not shown in the Figures, controls the motors  5  and  25 , thereby causing the information carrier  9  to be rotated about the axis of rotation  3  and, simultaneously, the scanning unit  17  to be displaced parallel to the X-direction, in such a manner that the spiralshaped information track present on the information carrier  9  is scanned by the scanning unit  17 . 
     As shown in FIG. 1, the scanning device in accordance with the invention further comprises a clamping device  27  in accordance with the invention for clamping the information carrier  9  on the table  1 . Said clamping device  27  is shown in detail in FIGS. 2,  3   a  and  3   b , and co-operates with a central clamping opening  29  provided in the information carrier  9 . It is noted that the information carrier  9  is not shown in FIG.  2 . The clamping device  27  is provided with a ring-shaped supporting member  31  for the information carrier  9 , which is concentrically arranged with respect to the axis of rotation and provided with a supporting surface  33  which extends at right angles to the axis of rotation  3 . The clamping device  27  is further provided with a clamping member  35  and a lifting member  37  which co-operates with said clamping member  35 . As shown in FIG. 2, the clamping member  35  includes three identical clamping elements  39  which are triangularly arranged around the axis of rotation  3 . The FIGS. 3 a  and  3   b , in which only one of the clamping elements  39  is shown in section, show that the clamping elements  39  each extend in a direction transverse to the supporting surface  33 , that they are provided, near a first end  41 , with a clamping surface  43  for cooperation with the central clamping opening  29  of the information carrier  9 , and that, near a second end  45 , they are tiltable about a tilting axle  47  which extends substantially in a tangential direction with respect to the axis of rotation  3 . As is further shown in FIG. 2, the lifting member  37  includes three identical lifting arms  49  which are also triangularly arranged around the axis of rotation  3  between the clamping elements  39 . The FIGS. 3 a  and  3   b , in which only one of the lifting arms  49  is shown in section, show that the lifting arms  49  each extend substantially in a radial direction with respect to the axis of rotation  3 , that they are provided, near a first end  51 , with a supporting element  53  for the information carrier  9 , and that they are tiltable, near a second end  55 , about a tilting axle  57  which extends also substantially in a tangential direction with respect to the axis of rotation  3 . 
     As the FIGS. 2,  3   a  and  3   b  further show, the clamping device  27  includes a bush-shaped operating member  59  which is centrally arranged between the clamping elements  39  and the lifting arms  49 , and which is concentrically arranged with respect to the axis of rotation  3  and displaceably guided, parallel to the axis of rotation  3 , with respect to a bush-shaped guide  61  which is secured to the table  1 . The clamping elements  39  are each coupled to the operating member  59  via a separate bridge  63  which is connected to the relevant clamping element  39  via a first elastic hinge  65  and to the operating member  59  via a second elastic hinge  67 . The clamping elements  39 , the bridges  63  and the operating member  59  are, for example, jointly integrated so as to form a product of injection-molded synthetic resin. By displacing the operating member  59 , the clamping elements  39  can be jointly displaced from a first position shown in FIG. 3 a , in which the information carrier  9  can be clamped against the supporting member  31  by means of the clamping elements  39 , to a second position shown in FIG. 3 b , in which the information carrier  9  is released by the clamping elements  39 . The operating member  59  thus forms a common operating member for the three clamping elements  39  of the clamping member  35 . The tilting axle  47  of each of the clamping elements  39  is formed by an elastic hinge  69 , each of the clamping elements  39  being connected via the hinge  69  to a securing element  71  by means of which the clamping element  39  is secured to the table  1 . The elastic hinges  69  exert an elastic pre-stressing force on the clamping elements  39  and the operating member  59  in a displacement direction of the operating member  59  which corresponds to a displacement of the clamping elements  39  from their second positions to their first positions. 
     As shown in the FIGS. 3 a  and  3   b , the tilting axle  57  of each of the lifting arms  49  is also formed by an elastic hinge  73 , each one of the lifting arms  49  being connected via the hinge  73  to a securing element  75  by means of which the relevant lifting arm  49  is secured to the table  1 . The lifting arms  49  can be displaced, by a rotation about the hinges  73 , from a first position shown in FIG. 3 a , in which the supporting elements  53  of the lifting arms  49  are recessed with respect to the supporting surface  33  of the supporting member  31 , to a second position shown in FIG. 3 b , in which the supporting elements  53  are raised with respect to the supporting surface  33 . The elastic hinges  73  exert an elastic pre-stressing force on the lifting arms  49  of the lifting member  37 , which elastic pre-stressing force extends in a direction which corresponds to a displacement of the lifting arms  49  from their first positions to their second positions. 
     In accordance with the invention, the clamping device  27  is provided with a first locking member  77 , which locks the clamping member  35  in its second position if the lifting member  37  is not substantially situated in its first position, and a second locking member  79  which locks the lifting member  37  in its first position if the clamping member  35  is not substantially situated in its second position. As shown in FIGS. 3 a  and  3   b , the first locking member  77  is provided with a stop surface  81  for each of the lifting arms  49 , which stop surface is provided on the operating member  59  and extends substantially perpendicularly to the axis of rotation  3 , and with a locking element  83  which, for co-operation with the stop surface  81 , is provided on the relevant lifting arm  49 , near the second end  55  of the lifting arm  49 . The second locking member  79  is provided, for each one of the lifting arms  49 , with a further stop surface  85  which is also provided on the operating member  59  and extends substantially parallel to the axis of rotation  3 , and with a further locking element  87  which, for co-operation with the further stop surface  85 , is provided on the relevant lifting arm  49 , near the second end  55  of the lifting arm  49 . In the embodiment of the clamping device  27  shown in FIGS. 3 a  and  3   b , the stop surface  81  connects substantially at right angles to the further stop surface  85 , while the locking element  83  also forms the further locking element  87 . 
     The operation of the above-described clamping device  27  in accordance with the invention is as follows. In the state shown in FIG. 3 b , the clamping member  35  and the lifting member  37  are both in their second positions. In this state, the lifting member  37  is held in its second position under the influence of the elastic pre-stressing force exerted by the elastic hinges  73 . By means of the first locking member  77 , the clamping member  35  is held in its second position, against the elastic pre-stressing force exerted by the elastic hinges  69 , by the co-operation of the locking element  83  with the stop surface  81 . To place and clamp an information carrier  9  on the table  1 , a user should place the information carrier  9  on the supporting elements  53  of the lifting arms  49  and subsequently push said information carrier, against the elastic pre-stressing force exerted by the elastic hinges  73 , towards the table  1 . Due to this, the central clamping opening  29  of the information carrier  9  goes past the clamping surfaces  43  of the clamping elements  39 . The stop surfaces  81  and the locking elements  83  of the first locking member  77  are formed such that the stop surfaces  81  are only released by the locking elements  83  if the lifting arms  49  of the lifting member  37  are substantially situated in their first positions and the information carrier  9  substantially rests on the supporting surface  33 . If the first locking member  77  thus releases the operating member  59 , the clamping elements  39  of the clamping member  35  are displaced, under the influence of the elastic prestressing force of the elastic hinges  69 , from their second positions shown in FIG. 3 b  to their first positions shown in FIG. 3 a , so that the information carrier  9  is clamped against the supporting surface  33 , near its central clamping opening  29 , by the clamping surfaces  43  of the clamping elements  39 . Since the first locking member  77  only releases the clamping member  35  from its second position if the information carrier  9  already substantially rests on the supporting surface  33 , it is precluded that an inner edge  89  of the central clamping opening  29  of the information carrier  9  is damaged by the clamping elements  39  when the information carrier  9  goes past the clamping elements  39  in the placing operation. This advantage is very useful if the information carrier  9  is a DVD. The reason for this being that such a DVD comprises two discs which are attached to one another, which discs may be pushed apart under the influence of a force exerted on the inner edge  89  of the central clamping opening  29 . This would render the DVD useless. 
     In the state shown in FIG. 3 a , the lifting arms  49  of the lifting member  37  are held in their first positions, against the elastic pre-stressing force of the elastic hinges  73 , by means of the second locking member  79  by co-operation of the further locking element  87  with the further stop surface  85 . To unclamp and remove the information carrier  9  from the clamping device  27 , the user should displace the operating member  59 , against the elastic prestressing force of the elastic hinges  69 , towards the table  1 , so that the-clamping elements  39  are displaced, from their first positions shown in FIG. 3 a , to their second positions shown in FIG. 3 b . The further stop surfaces  85  and the further locking elements  87  of the second locking member  79  are formed such that the further stop surface  85  only release the further locking elements  87  if the clamping elements  39  are substantially situated in their second positions and the information carrier  9  is entirely released by the clamping member  35 . If the second locking member  79  thus releases the lifting member  37 , the lifting arms  49  of the lifting member  37  are displaced, under the influence of the elastic pre-stressing force of the elastic hinges  73 , from their first positions shown in FIG. 3 a  to their second positions shown in FIG. 3 b , so that the information carrier  9  is lifted from the clamping device  27  and can be removed by the user without hindrance. As soon as the lifting arms  49  are no longer substantially in their first positions, the clamping member  35  is locked in its second position by the first locking member  77 . Since the second locking member  79  only releases the lifting member  37  from its first position if the clamping member  35  is substantially situated in its second position, the information carrier  9  is only lifted from the supporting surface  33  by the lifting member  37  if the information carrier has already been substantially released by the clamping member  35 . In this manner, it is precluded, also during removing the information carrier  9  from the clamping device  27 , that the inner edge  89  of the central clamping opening  29  of the information carrier  9  is damaged by the clamping elements  39  when the information carrier  9  goes past the clamping elements  39 . 
     As shown in FIGS. 3 a  and  3   b , the clamping device  27  is also provided with an electromagnetic actuator  91  having a ring-shaped permanent magnet  93 , which is attached to the operating member  59 , and an electric coil  95 , which is attached to the table  1 . The actuator  91  can be controlled by means of the above-mentioned control unit of the scanning device. If the coil  95  is energized in the state shown in FIG. 3 a , then the operating member  59  is displaced by the actuator  91  to the position shown in FIG. 3 b , as a result of which the information carrier  9  is automatically unclamped and lifted from the clamping device  27 . Since the actuator  91  can be controlled by the control unit, the information carrier  9  can be unclamped and lifted, for example automatically, from the clamping device  27  if the user stops or turns off the scanning device by means of an appropriate key. 
     In FIG. 4, parts of the second embodiment of a clamping device  27 ′ in accordance with the invention which correspond to parts of the above-discussed first embodiment of the clamping device  27 , are indicated by corresponding reference numerals. Hereinbelow, only a few differences between the clamping device  27 ′ and the clamping device  27  are discussed. The main difference between the clamping device  27 ′ and the clamping device  27  resides in that the clamping device  27 ′ is not provided with an electromagnetic actuator for displacing the operating member  59 , such as the actuator  91  of the clamping device  27 . Instead, the clamping device  27 ′ is provided with a mechanical coil spring  97 , as shown in FIG. 4, which exerts a pre-stressing force on the operating member  59  in the displacement direction of the operating member  59  which corresponds to a displacement of the clamping elements  39  from their second positions to their first positions. The pre-stressing force of the coil spring  97  thus complements the pre-stressing force exerted by the elastic hinges  69  on the operating member  59 . Consequently, an information carrier can only be removed from the clamping device  27 ′ in that a user pushes the operating member  59  towards the table  1 . The clamping device  27 ′ further differs from the clamping device  27  in that the clamping device  27 ′ is provided with leaf springs  99  which exert an additional prestressing force on the lifting arms  49  so as to complement the pre-stressing force of the elastic hinges  73 . It is noted that, in FIG. 4, the clamping element  39  is shown in its first position, whereas the lifting arm  49  is shown in its second position, and the locking element  83  and the operating member  59  are shown so as to demonstrate an overlap. It will be obvious to those skilled in the art, however, that such a position of the lifting arm  49  and the operating member  59  relative to each other cannot actually occur. 
     The FIGS. 5 a ,  5   b ,  5   c ,  6   a ,  6   b  and  6   c  diagrammatically show a third embodiment of a clamping device  27 ″ in accordance with the invention. In these Figures, parts of the clamping device  27 ″ which correspond to parts of the above-described clamping devices  27  and  27 ′ are indicated by corresponding reference numerals. In the following description, only the most important differences between the clamping device  27 ″ and the clamping devices  27 ,  27 ′ will be discussed. 
     The clamping device  27 ″ includes a lifting member  37 , which substantially corresponds to the lifting member  37  of the clamping devices  27 ,  27 ′and which is provided with three identical lifting arms  49 . As shown in FIGS. 5 b  and  6   b , the lifting arms  49  are each supported in bearings so as to be tiltable about a tilting axle  101 , which is only diagrammatically shown, and pre-stressed, by means of a leaf spring  103 , in a direction corresponding to a displacement of the lifting arm  49  from its first position, shown in FIG. 5 b , to its second position shown in FIG. 6 b . The clamping device  27 ″ further includes a clamping member  105  which co-operates with the lifting member  37 , which clamping member differs from the clamping member  35  of the clamping devices  27 ,  27 ′ and is provided with three identical swiveling arm-shaped clamping elements  107 , which each extend in a direction substantially parallel to the information carrier  9 , which are provided, near an end  109 , with a clamping surface  111  for co-operation with the central clamping opening  29  of the information carrier  9 , and which are bearing-supported, near a central part  113 , so as to be pivotable about a swiveling axle  115  which extends substantially parallel to the axis of rotation  3 . The lifting arms  49  and the clamping elements  107  of the clamping device  27 ″ are arranged in the same manner about the axis of rotation  3  as the lifting arms  49  and the clamping elements  39  of the clamping device  27 . For the sake of simplicity, however, FIGS. 5 a  and  6   a  only show one of the lifting arms  49  and one of the clamping elements  107 . 
     The clamping device  27 ″ further includes an operating member  117  which is centrally arranged between the lifting arms  49  and the clamping elements  107 , which operating member is concentrically arranged relative to the axis of rotation  3  and displaceably guided, parallel to the axis of rotation  3 , relative to a bush-shaped guide  61  which is secured to the table  1 . The clamping elements  107  each comprise a further end  119  which is situated, with respect to the swiveling axle  115  of the relevant clamping element  107 , approximately diametrically opposite the end  109 . With their further ends  119 , the pre-stressed clamping elements  107  lie against a stop surface  121  of the operating member  117 , as shown in detail in FIGS. 5 c  and  6   c .Said pre-stress is supplied, for example, by a torsion spring  123 , which is known per se and customarily used, which is only diagrammatically shown in FIGS. 5 a  and  6   a  and arranged around each of the swiveling axles  115 . As shown in FIGS. 5 c  and  6   c ,the stop surface  121  has a conical portion  125 , which is concentrically arranged relative to the axis of rotation  3 , a cylindrical portion  127 , which connects to the conical portion  125  near an end of the conical portion  125  where the diameter of the conical portion  125  is largest, and a further cylindrical portion  129 , which connects to the conical portion  125  near a further end of the conical portion  125  where the diameter of the conical portion  125  is smallest. Co-operation between the further ends  119  of the clamping elements  107  and the stop surface  121  of the operating member  117  enables the clamping elements  107  to be jointly swiveled by a displacement of the operating member  117 , from a first position shown in the FIGS. 5 a  and  5   c , in which the ends  119  lie against the further cylindrical portion  129  of the stop surface  121  and in which the information carrier  9  can be clamped against the supporting member  31  by means of the clamping elements  107 , to a second position shown in FIGS. 6 a  and  6   c ,in which the ends  119  lie against the cylindrical portion  127  of the stop surface  121  and in which the information carrier  9  is released by the clamping elements  107 . The clamping device  27 ″ is further provided with a mechanical coil spring  131 , shown in FIGS. 5 b ,  5   c ,  6   b  and  6   c ,which exerts a pre-stressing force on the operating member  117  in a direction which corresponds to a displacement of the clamping elements  107  from their second positions to their first positions. 
     The clamping device  27 ″ is provided, just like the clamping devices  27  and  27 ′, with a first locking member  133 , which locks the clamping member  105  in its second position if the lifting member  37  is not substantially in its first position, and with a second locking member  135 , which locks the lifting member  37  in its first position if the clamping member  105  is not substantially in its second position. The first locking member  133  comprises the cylindrical portion  127  of the stop surface  121  of the operating member  117 , a recess  137  which is formed in the further cylindrical portion  129  of the stop surface  121 , and a locking element  139  which is provided on each of the lifting arms  49  for co-operation with the recess  137 . The recess  137  and the locking element  139  are shown in the FIGS. 5 b  and  6   b . The second locking member  135  comprises the further cylindrical portion  129  of the stop surface  121  of the operating member  117 , and a further locking element  141  which is provided on each of the lifting arms  149  for co-operation with the further cylindrical portion  129  of the stop surface  121  and for co-operation with a further recess  143  formed in the further cylindrical portion  129 . In the embodiment of the clamping device  27 ″ shown in the FIGS. 5 b  and  6   b , the locking element  139  also forms the further locking element  141 , while the recess  137  also forms the further recess  143 . 
     As will be explained hereinbelow, the operation of the clamping device  27 ″ corresponds to the above-described operation of the clamping devices  27  and  27 ′, which can be attributed to the use of the first locking member  133  and the second locking member  135 . In the state shown in FIGS. 6 a ,  6   b  and  6   c ,the clamping member  105  and the lifting member  37  are both in their second positions. In this state, the lifting member  37  is held in its second position under the influence of the pre-stressing force of the leaf springs  103 . By means of the first locking member  133 , the operating member  117  is held in a position shown in FIGS. 6 b  and  6   c , against the pre-stressing force of the coil spring  131 , by co-operation of the locking element  139  with the recess  137 . In this position of the operating member  117 , the ends  119  of the clamping elements  107  rest against the cylindrical portion  127  of the stop surface  121 , so that the clamping elements  107  are locked in their second positions. To place and clamp an information carrier  9  on the table  1 , a user should place the information carrier  9  on the supporting elements  53  of the lifting arms  49  and, subsequently, move said information carrier, against the pre-stressing force of the leaf springs  103 , towards the table  1 . The recess  137  and the locking element  139  of the first locking member  133  are shaped so that the operating member  117  is only released from its position shown in FIGS. 6 b  and  6   c  if the lifting arms  49  are substantially situated in their first positions, and the information carrier  9  substantially rests on the supporting surface  33 . If the first locking member  133  releases the operating member  117 , the operating member  117  is displaced, under the influence of the prestressing force exerted by the coil spring  131 , to a position shown in FIGS. 5 b  and  5   c . As a result, the clamping elements  107  are displaced, by co-operation of the ends  119  with the conical portion  125  of the stop surface  121 , from their second positions shown in FIG. 6 a  to their first positions shown in FIG. 5 a , so that the information carrier  9  is clamped, near its central clamping opening  29 , against the supporting surface  33  by the clamping surfaces  111  of the clamping elements  107 . 
     In the state shown in FIGS. 5 a ,  5   b  and  5   c , the lifting arms  49  of the lifting member  37  are locked in their first positions, against the pre-stressing force exerted by the leaf springs  103 , by means of the second locking member  135  by co-operation of the further locking element  141  with the further cylindrical portion  129  of the stop surface  121 . To unclamp and remove the information carrier  9  from the clamping device  27 ″, the user must press the operating member  117 , against the pre-stressing force exerted by the coil spring  131 , towards the table  1 , thereby causing the clamping elements  107  to be displaced from their first positions shown in FIG. 5 a  to their second positions shown in FIG. 5 b , as a result of cooperation of the ends  119  with the conical portion  125  of the stop surface  121 . The further recess  143  is formed in the further cylindrical portion  129  of the stop surface  121  in such a manner that, under the influence of the pre-stressing force exerted by the leaf spring  103 , the further locking element  141  only drops into the further recess  143  if the clamping elements  107  are substantially situated in their second positions and the information carrier  9  is entirely released by the clamping member  105 . If the second locking member  135  thus releases the lifting member  37 , the lifting arms  49  of the lifting member  37  are displaced, under the influence of the pre-stressing force exerted by the leaf springs  103 , from their first positions shown in FIG. 5 b  to their second positions shown in FIG. 6 b , so that the information carrier  9  is lifted from the clamping device  27 ″ and can be removed by the user. As soon as the lifting arms  49  are no longer substantially in their first positions, the clamping member  35  is locked again in its second position by the first locking member  133  by co-operation of the locking element  139  and the recess  137 . It will be obvious to those skilled in the art that by means of the above-described operation of the clamping device  27 ″, advantages are obtained which correspond to the above-discussed advantages of the clamping devices  27  and  27 ′. 
     The above-described embodiments of the clamping device  27 ,  27 ′ and  27 ″ can suitably be used in the above-described scanning device in accordance with the invention. It is noted that a clamping device in accordance with the invention can also be used in a different manner, for example in a box-shaped holder for a disc-shaped information carrier. It is further noted that a clamping device in accordance with the invention cannot only be used in an optical player as described hereinabove, but also in other types of scanning devices, such as a magnetic or magneto-optical scanning device. 
     Finally, it is noted that a clamping device in accordance with the invention may be provided with a type of clamping member, lifting member, first locking member and second locking member, which differ from the above-described clamping members  35  and  105 , the above-described lifting member  37 , the above-described first locking members  77  and  133 , and the above-described second locking members  79  and  135 . One might think, for example, of a clamping member including a different type or a different number of clamping elements, and a lifting member including a different type or different number of lifting arms. The construction of the first locking member and the second locking member in such an alternative clamping device in accordance with the invention is determined to a substantial degree by the construction of the clamping member and the lifting member. 
     The invention has been disclosed with reference to specific preferred embodiments, to enable those skilled in the art to make and use the invention, and to describe the best mode contemplated for carrying out the invention. Those skilled in the art may modify or add to these embodiments or provide other embodiments without departing from the spirit of the invention. The scope of the invention is not limited to the embodiments, but lies in each and every novel feature or combination of features described above and in every novel combination of these features. Thus, the scope of the invention is only limited by the following claims:
A clamping device for a disc-shaped information carrier having a central clamping opening, includes a clamping member which is displaceable from a first position, in which the information carrier is clamped by the clamping member, to a second position in which the information carrier is released by the clamping member. The device further includes a lifting member which co-operates with the clamping member and which is displaceable from a first position, in which the lifting member is recessed with respect to a supporting member of the clamping device, to a second position in which the lifting member is raised relative to the supporting member. The device also includes a first locking member, which locks the clamping member in its second position when the lifting member is not substantially situated in its first position, and a second locking member, which locks the lifting member in its first position when the clamping member is not substantially in its second position. The device prevents the clamping member from exerting forces on the inner wall of the clamping opening of the information carrier when the information carrier is placed into or removed from the clamping device. Thus, preventing damage to the inner wall, and when the information carrier is a DVD, it prevents the two disc-shaped substrates of the DVD, which are adhered to each other, from being pressed apart by such forces. The clamping device can be used in a scanning device such as an optical disc player, for clamping an information carrier onto a turntable of the scanning device.