Abstract:
A disc changer apparatus includes a stacking unit for stacking at least two holder compartments, adapted to hold one disc each, in at least two stacking positions. The holder compartments are coupled to at least one spindle having a screwthread and are movable in a vertical direction by rotation of the spindles. The holder compartments are stacked in upper and lower stacking zones of the stacking. The changer apparatus has a play position for reading information stored on the information discs and/or writing information on the informaton discs. A central zone of the stacking unit between the upper and the lower stacking zone has a loading position, into which one of the holder compartments is movable by rotation of the spindles. A transporter unit is adapted to move the disc from the holder compartment, which is in the loading position, into the play and eject positions.

Description:
This is a continuation of application Ser. No. 09/090,039 filed Jun. 10, 1998, now U.S. Pat. No. 6,396,796. 

   FIELD OF THE INVENTION 
   Herein, a screwthread is to be understood to mean a helical path which can have different pitches. 
   DESCRIPTION OF THE RELATED ART 
   Such a changer apparatus for information discs is known from JP 6-131793 of Clarion Co. Ltd. This known changer apparatus comprises four threaded spindles with external screwthread. A plurality of holder compartments has been provided for holding one information disc each, which holder compartments each have four bores with internal screwthreads in which the external screwthreads of the threaded spindles engage. The external screwthreads of the threaded spindles have a small pitch in the axial direction in the upper and the lower stacking zone and a large pitch in the intermediate zone between the upper and the lower stacking zone. When the threaded spindles are rotated the holder compartments are moved in the vertical direction, the intermediate zone being free from holder compartments to allow the individual information discs to be read. A read unit is arranged on a pivotal arm and for reading it is pivoted into the intermediate zone of the stacking unit. 
   Such a read unit arranged on a pivotal arm has the disadvantage that it is susceptible to external vibrations and shocks. 
   This is of particular importance when the changer apparatus is used in motor vehicles. 
   SUMMARY OF THE INVENTION 
   It is an object of the invention to provide improved changer apparatus of the type defined in the opening paragraph. 
   According to the invention this object is achieved in that a loading position is provided in a central zone of the stacking unit between the upper and the lower stacking zone, into which loading position one of the holder compartments is each time movable by rotation of the spindles, and transport means are provided, which are adapted to move the information disc from the holder compartment, which is in the loading position, into the play position and into the eject position in which the information disc can be removed from the apparatus, the play position being arranged between the eject position and the loading position. 
   To load an information disc the information disc is first brought into the eject position by hand by a user. This information disc is then moved into a holder compartment of the stacking unit, which holder compartment is in the loading position, with the aid of the transport means. By rotation of the spindles this holder compartment together with the information disc is then moved into one of the stacking positions in the lower or the upper stacking zone. 
   For the transport of an information disc from the stacking position into the play position this information disc together with the holder compartment is moved into the loading position by rotation of the spindles. From this loading position the information disc is then removed from the holder compartment with the aid of the transport means and is brought into the play position. The transport means are also adapted to move the information disc into the eject position. The play position is situated between the eject position and the loading position. 
   Such a changer apparatus has the advantage that a read/write unit adapted to read information stored on the information discs and/or to write information on the information discs can be isolated more simply from external disturbances and vibrations. 
   This is particularly advantageous in the case of changer apparatuses intended for use in motor vehicles. 
   A further advantageous embodiment of the invention is characterized in that in the axial direction of the spindles the central zone has spacing zones at both sides of the loading position, which spacing zones define an axial spacing between the holder compartment in its loading position and the axially adjacent holder compartments in their stacking positions. 
   The spacing zones arranged at both sides of the loading position, i.e. above and below the loading position, provide room for the transport means and allow said means to move an information disc into a holder compartment in the loading position and an information disc out of a holder compartment in the loading position without the other holder compartments being touched. 
   A further advantageous embodiment of the invention is characterized in that the average screwthread pitch of the spindles in the loading position is smaller than the average screwthread pitch in the upper and the lower stacking zone. 
   The screwthread pitch of the spindles in the upper and the lower stacking zone is basically determined by the height of the holder compartments. For a trouble-free and reliable cooperation of the transport means with the information disc which is in the loading position it is advantageous that the axial orientation of the information disc in the loading position is defined as accurately as possible. Therefore, it is favorable to choose the average screwthread pitch of the spindles in the loading position smaller than the average screwthread pitch in the upper and the lower stacking zone. The effect of tolerances of the angle of rotation of the threaded spindles on the axial position of the holder compartments and of the information disc in the loading position decreases as the average screwthread pitch of the spindles in the loading position becomes smaller. Therefore, it is particularly advantageous that the screwthread pitch of the spindles in the loading position is substantially zero. As a result of this, the individual holder compartments can be moved into the loading position very accurately as regards the axial height and in a reproducible manner. Tolerances as regards the angle of rotation of the threaded spindles, for example owing to overshoot of the drive system of the threaded spindles or step tolerances of a stepper motor which drives the threaded spindles have no or only a minimal influence on the axial height of the loading position. 
   A further advantageous embodiment of the invention is characterized in that the average screwthread pitch in the spacing zones is greater than the average screwthread pitch in the upper and the lower stacking zone. 
   When the average screwthread pitch in the spacing zones is increased the axial distance between the holder compartment in the loading position and the adjacent holder compartments in the lower and the upper stacking zone increases and the transport means have more room for access to the information disc. 
   A further advantageous embodiment of the invention is characterized in that there is provided a lower and an upper guide pin for guiding the information discs into the holder compartments of the stacking unit, which guide pins are engageable into the center holes of the information discs from above and from below, respectively. 
   Such an arrangement prevents the information discs from radially slipping out of the holder compartments during the axial movement of the holder compartments. The radial positions of the information discs inside the stacking unit are defined exactly by the guide pins. For the transport of an information disc out of or into a holder compartment which is in the loading position the upper and the lower guide pin are moved up and down, respectively. 
   A further advantageous embodiment of the invention is characterized in that a read/write unit for reading information stored on the information discs and/or writing information on the information discs is movably supported on a chassis plate of the apparatus. 
   As a result of this, the available mounting space can be utilized in an optimum manner. This is particularly important in the case of automotive uses because the available mounting space is then very limited. 
   A further advantageous embodiment of the invention is characterized in that the read/write unit comprises a base plate and a laser mounting plate, the base plate and the laser mounting plate are coupled by means of dampers, the base plate is slidably mounted on the chassis plate, and the laser mounting plate carries a clamping device for clamping the information disc in the play position and an optical unit for reading information stored on the information disc. 
   Such an arrangement provides a very effective isolation of the read/write unit from external vibrations and shocks. 
   Other alternatives and advantages of the inventions herein will be disclosed or become obvious to those skilled in the art by studying the detailed description below with reference to the following drawings which illustrate the elements of the appended claims of the inventions. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A diagrammatically represented embodiment of the invention will be described hereinafter, by way of example, with reference to  FIGS. 1 to 13  of the drawings. In the drawings: 
       FIG. 1  is a perspective view of a changer apparatus for information discs with an information disc shown in an eject position, in which it can be removed from the apparatus by hand by a user, with a read unit for reading information stored on the information disc, with a stacking unit for stacking at least two information discs, and with a first, a second, a third and a fourth guide for the transport of the information disc from the eject position into a play position and into a loading position, 
       FIG. 2  is a front view of the changer apparatus in the eject position as shown in  FIG. 1 , 
       FIG. 3  is a perspective view of the read unit, 
       FIG. 4  is a perspective view of parts of the changer apparatus with a sliding plate for translating the read unit, not shown, and for controlling the pivotal movement of the first, the second, the third and the fourth guide as well as for controlling guide pins of the stacking unit and a clamping arm of the read unit, 
       FIG. 5  is a side view of the changer apparatus in the eject position as shown in  FIG. 1 , 
       FIG. 6  is a plan view of the changer apparatus in the eject position as shown in  FIG. 1 , 
       FIG. 7  is a side view of the changer apparatus in a first intermediate position, in which the information disc is freely interposed between a clamping disc and a driving disc, from which first intermediate position the information disc is movable into the play position and into the loading position, 
       FIG. 8  is a side view of the changer apparatus in a second intermediate position, in which the information disc is clamped between the clamping disc and the driving disc of the read unit, 
       FIG. 9  is a plan view of the changer apparatus in the first intermediate position, the information disc being held by the first, the second, the third and the fourth guide, 
       FIG. 10  is a plan view of the changer apparatus in a play position, the first, the second, the third and the fourth guide being in positions pivoted away from the disc edge of the information disc, the information disc being clamped between the driving disc and the clamping disc of the read unit, and the information stored on the information disc being readable by means of the read unit, 
       FIG. 11  is a side view of the changer apparatus in the play position, 
       FIG. 12  is a plan view of the changer apparatus with an information disc in the loading position, and 
       FIG. 13  shows the changer apparatus of  FIG. 12  in a perspective view with an information disc in the loading position. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  is a perspective view and  FIG. 6  is a plan view of a changer apparatus for information discs with an information disc  1  in an eject position, in which it can be removed from the apparatus by hand by a user and in which it can be inserted into the apparatus by hand by the user for the purpose of loading. The information disc  1  has a circular disc edge  1   a  and a center hole  1   b . The changer apparatus is accommodated in a housing  2 , which is shown only partly and which has a base formed by a chassis plate  3 . The chassis plate  3  has a front edge  3   a , a rear edge  3   b , a left-hand side edge  3   c  and a right-hand side edge  3   d . The chassis plate  3  extends in an x-y plane, the x direction being defined as the direction from left to right in the same direction as the front edge  3   a  and the y direction being defined as a direction which extends in the same direction as the left-hand side edge  3   c . A direction perpendicular to the x-y plane is defined as the z direction. As is shown in the perspective view of  FIG. 1 , a stacking unit  4  is arranged in the rear right area of the housing  2 , which unit comprises a first threaded spindle  5 , a second threaded spindle  6  and a third threaded spindle  7 , which extend vertically with respect to the chassis plate  3  in the z direction. The first threaded spindle  5  has an external screwthread  5   a , the second threaded spindle  6  has an external screwthread  6   a  and the third threaded spindle  7  has an external screwthread  7   a . There is a first holder compartment  8 , a second holder compartment  9 , a third holder compartment  10 , a fourth holder compartment  11  and a fifth holder compartment  12 , which are arranged one above the other in the z direction and which serve for holding one information disc each. The first holder compartment  8  has a first opening  8   a , in which the external screwthread  5   a  of the first threaded spindle  5  engages, a second opening  8   b , in which the external screwthread  6   a  of the second threaded spindle  6  engages, and a third opening  8   c , in which the external screwthread  7   a  of the third threaded spindle  7  engages. Likewise, the second holder compartment  9 , the third holder compartment  10 , the fourth holder compartment  11  and the fifth holder compartment  12  each have three openings, not shown, in which the external screwthreads of the first threaded spindle  5 , the second threaded spindle  6  and the third threaded spindle  7  engage. By means of a gear train  60  comprising the gear wheels  60   a ,  60   b ,  60   c ,  60   d  and  60   e  the first threaded spindle  5 , the second threaded spindle  6  and the third threaded spindle  7  can be driven by a drive mechanism, not shown. Alternatively, driving by means of a toothed belt is possible. The holder compartments  8 ,  9 ,  10 ,  11  and  12  are movable in the vertical z direction by rotation of the threaded spindles  5 ,  6  and  7 . 
   In the center of the stacking unit  4  an upper cover plate  61  carries an upper guide pin  62  and the chassis plate  3  carries a lower guide pin  63 . The upper guide pin  62  and the lower guide pin  63  can be moved in the z direction by means of a drive mechanism, not shown. 
   The operation of the stacking unit  4  will be explained hereinafter with reference to  FIG. 2 , which is a front view of the changer apparatus in the eject position as shown in  FIG. 1 . The third threaded spindle  7  and, likewise, the first threaded spindle  5  as well as the second threaded spindle  6 , which is not visible in  FIG. 2 , have an upper stacking zone  13 , a lower stacking zone  14  and a central stacking zone  15  between the upper stacking zone  13  and the lower stacking zone  14 . The central zone  15  has a vertical loading position  16 , which is spaced from the upper stacking zone  13  by an upper spacing zone  17  and which is spaced from the lower stacking zone  14  by a lower spacing zone  18 . The external screwthread  7   a  of the third threaded spindle  7  and, likewise, the external screwthreads  6   a  and  5   a  of the second threaded spindle  6  and the first threaded spindle  5 , respectively, have a pitch which is zero over an angle of rotation of 45°. In the upper spacing zone  17  and the lower spacing zone  18  the threaded spindles  5 ,  6  and  7  each have a pitch which is basically defined by the vertical height in the z direction of the holder compartments  8 ,  9 ,  10 ,  11  and  12 . The pitch of the threaded spindles  5 ,  6  and  7  in the upper spacing zone  17  and in the lower spacing zone  18  is substantially greater than the pitch in the loading position  16  and the pitch in the upper stacking zone  13  and the lower stacking zone  14 . In the representation shown in  FIG. 2  the first holder compartment  8  is in the loading position and the other holder compartments  9 ,  10 ,  11  and  12  are in the lower stacking zone  14 . The lower stacking zone  14  has a first stacking position  14   a , a second stacking position  14   b , a third stacking position  14   c  and a fourth stacking position  14   d . The upper stacking zone  13  has a first stacking position  13   a , a second stacking position  13   b , a third stacking position  13   c  and a fourth stacking position  13   d . In the representation shown in  FIG. 2  the second holder compartment  9  is in the first stacking position  14   a  of the lower stacking zone  14 , the third holder compartment  10  is in the second stacking position  14   b , the fourth holder compartment  11  is in the third stacking position  14   c , and the fifth holder compartment  12  is in the fourth stacking position  14   d . If starting from the situation represented in  FIG. 2  the threaded spindles  5 ,  6  and  7  are rotated, the first holder compartment  8 , which is in the loading position  16 , moves into the fourth stacking position  13   d  of the upper stacking zone  13 , the second holder compartment  9  moves into the loading position  16 , the third holder compartment  10  moves into the first stacking position  14   a , the fourth holder compartment  11  moves into the second stacking position  14   b  and the fifth holder compartment  12  moves into the third stacking position  14   c  of the lower stacking zone  14 . Likewise, the third holder compartment  10 , the fourth holder compartment  11  and the fifth holder compartment  12  can be moved into the stacking position  16  one after the other. Thus, by rotation of the threaded spindles  5 ,  6  and  7  each of the holder compartments  9 ,  10 ,  11  and  12  situated in the lower stacking zone  14  can be moved into loading position  16  one after the other and by further rotation the holder compartments  9 ,  10  and  11  can be moved into the upper stacking zone  13 . 
   During the vertical travel of the holder compartments  8 ,  9 ,  10 ,  11  and  12  the information discs in these holder compartments are moved in the z direction by means of the upper guide pin  62  and the lower guide pin  63  in that the upper guide pin  62  and the lower guide pin  63  engage the center holes  1   b  of the information discs  1 . 
   Hereinafter, the changer apparatus is described further with reference to  FIG. 1 . For the transport of the information disc  1  from the eject position shown in  FIG. 1  into the first holder compartment  8 , which is in its loading position  16  as shown in  FIG. 2 , a first guide  20 , a second guide  21 , a third guide  22  and a fourth guide  23  have been provided. The first guide  20  is constructed as a passive supporting guide and by means of a pivotal arm  20   a  it is mounted so as to be pivotable about a pivot  20   b  on the left-hand side of the chassis plate  3 . The first guide  20  has a V-shaped groove  20   c  for guiding the disc edge  1   a  of the information disc  1 . The second guide  21  is arranged at the opposite side on the right-hand side of the housing  2  and comprises a first transport wheel  25 , which is supported on a pivotal arm  21   a  so as to be rotatable about a spindle  25   a . The pivotal arm  21   a  is mounted on the chassis plate  3  so as to be pivotable about a pivot  24 . For the transport of the information disc  1  the first transport wheel  25  has a V-shaped groove  25   b  adapted to engage with the disc edge  1   a  of the information disc  1 . The third guide  22  comprises a second transport wheel  26  which is supported on a pivotal arm  22   a  so as to be rotatable about a spindle  26   a . The pivotal arm  22   a  is supported on the chassis plate  1  on the same pivot  24  which carries the pivotal arm  21   a  of the second guide  21 . The second transport wheel  26  also has a V-shaped groove  26   b . The first transport wheel  25  and the second transport wheel  26  are rotationally drivable by means of a intermediate drive  27  comprising three intermediate wheels  27   a ,  27   b  and  27   c . The intermediate wheel  27   a  is rotatable about the spindle  24  and is driven by a motor, not shown, via a drive chain, not shown. The intermediate wheels  27   b  and  27   c  are rotatably supported on the pivotal arm  22   a.    
   The first guide  20 , the second guide  21 , the third guide  22  and the fourth guide  23  are each pre-loaded towards a curve-shaped loading path  28  by means of a spring, not shown. 
   In the eject position of the information disc  1 , which position is shown in  FIG. 1 , the first guide  20  and the first transport wheel  25  are urged against the disc edge  1   a  of the information disc  1  with the groove  20   c  and with the groove  25   b , respectively, under the influence of the spring-loads of the pivotal arms  20   a  and  21   a . The second transport wheel  26  of the third guide  22  is pressed away from the stacking unit  4  against the spring load, so that by rotation of the threaded spindles  5 ,  6  and  7  any one of the holder compartments  8 ,  9 ,  10 ,  11  and  12  can be moved into the loading position  16 . The transport wheel  26  is then pivoted away so far that any information discs present in the holder compartments  8 ,  9 ,  10 ,  11  and  12  are not touched by the second transport wheel  26 . 
   A read unit  30  is arranged so as to be movable on the chassis plate  3  in the front-left area of the changer apparatus. 
   The read unit  30  carries the fourth guide  23  which is constructed as a passive supporting guide and is mounted on the read unit  30  so as to be pivotable about a pivot  23   a . The fourth guide  23  has a V-shaped groove  23   b  for guiding the disc edge  1   a  of the information disc  1 . 
   The construction of the read unit  30  will be described in more detail hereinafter with reference to  FIG. 3 .  FIG. 3  is a perspective view of the read unit  30 . The read unit  30  has a base plate  31  comprising a first guide pin  31   a,  a second guide pin  31   b  and a third guide pin  31   c . The base plate  31  is coupled to a laser mounting plate  35  by means of a first damper  32 , a second damper  33  and a third damper  34 . A clamping arm  36  with a clamping disc  37  is mounted on the laser mounting plate  35  so as to be rotatable about a clamping spindle  36   a . The laser mounting plate  35  supports a driving disc  38  which is rotationally drivable by means of a motor, not shown. Furthermore, an optical unit formed by a laser unit  39  is supported on the laser mounting plate  35  so as to be movable. The base plate  31  of the read unit  30  is mounted on the chassis plate  3  so as to be slidable. 
   To illustrate this slidable mounting of the base plate  31  on the chassis plate  3 ,  FIG. 4  shows parts of the changer apparatus in a perspective view, the read unit  30 , the base plate  31  as well as the information disc  1  not being shown for the sake of clarity. 
   To guide the read unit  30 , as shown in  FIG. 4 , the chassis plate  3  carries a first guideway  40  and a second guideway  41 . The first guideway  40  serves for guiding the first guide pin  31   a  of the base plate  31  and the second guideway  41  serves for guiding the second guide pin  31   b.  A sliding plate  43  is movable in the y direction by a drive mechanism, not shown. This sliding plate  43  comprises a first slider  44  having a V-shaped sliding slot  44   a , a second slider  45  having a V-shaped sliding slot  45   a , and a third slider  46  having a V-shaped sliding slot  46   a . The V-shaped sliding slot  44   a  serves for guiding the first guide pin  31   a  of the base plate  31 , the V-shaped sliding slot  45   a  serves for guiding the second guide pin  31   b  of the base plate  31 , and the V-shaped sliding slot  46   a  serves for guiding the third guide pin  31   c  of the base plate  31 . 
     FIG. 5  is a side view in the x direction showing the changer apparatus in the eject position of  FIG. 1 . As is apparent from  FIG. 5 , the first guideway  40  and the second guideway  41  are L-shaped and thus comprise horizontal guideway sections  40   a  and  41   a  and vertical guideway sections  40   b  and  41   b.    
     FIG. 5  shows the clamping arm  36  with the clamping disc  37  in the open position, i.e. the clamping disc  37  does not bear on the driving disc  38 . 
   For the transport of the information disc  1  into the stacking unit  4  or into a play position, starting from the eject position shown in  FIG. 1 , the first transport wheel  25  is rotated by a drive unit, not shown, by means of the intermediate wheel  27   a , as a result of which the information disc  1 , supported by the first guide  20 , is rolled onto the curve-shaped loading path  28  into the apparatus. 
   At the same time, the sliding plate  43  shown in  FIG. 4  and, consequently, the read unit  30  ( FIG. 3 ) is moved into the apparatus in the y direction. The first guide pin  31   a  of the read unit  30  is then guided in the first guideway  40  and the second guide pin  31   b  is guided in the second guideway  41 . The first slider  44 , the second slider  45  and the third slider  46  then exert the driving force in the y direction on the first guide pin  31   a , the second guide pin  31   b  and the third guide pin  31   c  of the base plate  31 . 
     FIG. 7  is a side view of the changer apparatus in a first intermediate position. In this first intermediate position the first guide pin  31   a  and the second guide pin  31   b  of the base plate  31  are disposed at the rearward end of the horizontal guideway section  40   a  of the first guideway  40  and the horizontal guideway section  41   a  of the second guideway  41 , respectively, which extend in the y direction. Upon a further movement of the sliding plate  43  in the y direction the first guide pin  31   a , the second guide pin  31   b  and the third guide pin  31   c  are urged upward in the z direction in the V-shaped slots  44   a ,  45   a  and  46   a  of the first slider  44 , the second slider  45  and the third slider  46 , respectively, as a result of which a second intermediate position is reached. The first guide pin  31   a  and the second guide pin  31   b  then move upward in the vertical guideway sections  40   b  and  41   b.    
   The second intermediate position is shown in side view in  FIG. 8 .  FIG. 8  shows that the first guide pin  31   a  and the second guide pin  31   b  are situated at the respective upper ends of the vertical guideway sections  40   b  and  41   b . This results in the read unit  30  being lifted, thereby causing the clamping disc  37  to be pressed onto the driving disc  38 , in a manner not shown, and the information disc  1  being clamped between the clamping disc  37  and the driving disc  38 . 
   The first intermediate position of  FIG. 7  is shown in plan view in  FIG. 9 . From  FIG. 9  it is apparent that in the first intermediate position the information disc  1  is held by the first guide  20 , the second guide  21  with the first transport wheel  25 , the third guide  22  with the transport wheel  26  as well as the fourth guide  23 . The first guide  20 , the second guide  21 , the third guide  22  and the fourth guide  23  are urged against the disc edge  1   a  of the information disc  1  under the spring loads of their pivotal arms and hold the information disc  1  in the first intermediate position. 
     FIG. 10  is a plan view which shows the changer apparatus with the information disc  1  in a play position. In this play position the first guide  20 , the second guide  21  with the first transport wheel  26 , the third guide  22  with the second transport wheel  26 , and the fourth guide  23  are pivoted away from the information disc  1 , as a result of which the V-shaped grooves of these guides no longer act upon the disc edge of the information disc  1 . The pivoting away of the first guide  20 , the second guide  21 , the third guide  22  and the fourth guide  23  is controlled by the movement of the sliding plate  43 , which performs a movement in the y direction between the second intermediate position and the play position. During this movement between the second intermediate position and the play position the sliding plate  43  urges the first guide  20 , the second guide  21 , the third guide  22  and the fourth guide  23  away from the information disc  1  against the pre-loading forces. 
   In the play position shown in  FIG. 10  the information disc  1  is held exclusively by the clamping disc  37  and the driving disc  38 . In the play position the information disc  1  is rotated as a result of the rotation of the driving disc  38 , and the information stored on the information disc  1  can be read by means of the read unit  30 . In the play position the laser mounting plate  35  is coupled to the base plate  31  and, consequently, to the chassis plate  3  via the dampers  32 ,  33  and  34  only. Thus, the laser mounting plate  35  is isolated from external vibrations and shocks of the housing  2  and the chassis plate  3  by means of the dampers  32 ,  33  and  34 , as a result of which the read unit  30  can read or play back the information stored on the information disc  1  without being affected by external vibrations. 
     FIG. 11  is a side view which shows the changer apparatus in the play position. In comparison with the second intermediate position shown in  FIG. 8  the sliding plate  43  has been moved in the y direction, so that the first guide pin  31   a , the second guide pin  31   b  and the third guide pin  31   c  have been urged downward in the V-shaped sliding slots  44   a ,  45   a  and  46   a . As a result of this, the read unit  30  has also been lowered with respect to the second intermediate position. 
   From the first intermediate position shown in  FIGS. 7 and 9  it is possible to move the information disc  1  into the play position shown in  FIGS. 10 and 11  and also to move the information disc  1  into the stacking unit  4 . 
   For the transport into the stacking unit  34  from the first intermediate position shown in  FIG. 9  the information disc  1  is rolled onto the curve-shaped loading path  28  into the stacking unit  4 . Essentially, driving is effected by the second transport wheel  26 , which takes over the driving function from the first transport wheel  25 . The supporting function is essentially provided by the fourth guide  23 . 
     FIGS. 12 and 13  show the changer apparatus with the information disc  1  in the loading position shown in  FIG. 2 ,  FIG. 12  being a plan view and  FIG. 13  being a perspective view. The second transport wheel  26  has been pivoted out of the stacking unit  4 , so that now the information disc  1  together with the first holder compartment  8 , in accordance with  FIG. 2 , can be moved from this loading position  16  shown in  FIGS. 12 and 13  into one of the four upper stacking positions  13   a ,  13   b ,  13   c  or  13   d  by rotation of the threaded spindles  5 ,  6  and  7 . Conversely, the information disc  1  can be moved from the loading position shown in  FIG. 13  into the first intermediate position in that the second transport wheel  26  is pivoted against the disc edge  1   a  and the second transport wheel  26  is rotated in the opposite direction and subsequently into the eject position in that the first transport wheel  25  is driven. 
   In the situation shown in  FIGS. 12 and 13  the read unit  30  has been moved completely out of the range of operation of the stacking unit  4 . 
   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.