Arrangement of subtrays in a main tray of an optical disc drive apparatus

An optical disc drive apparatus including a main tray having a stack of subtrays mounted thereon and movable between withdrawn and inserted positions. When the main tray is moved to the inserted position, the subtrays stacked thereon are held at a stand-by position and a selected one of the subtrays is ready to be drawn towards a loaded position so that an optical disc resting on the selected one of the subtrays can be clamped in position and optically read out. When an optical disc resting on one of the subtrays other than the uppermost subtray then held at the loaded position is desired to be removed or replaced, not only can such one of the subtray be returned from the loaded position to the stand-by position, the main tray is allowed to withdraw from the inserted position back to the withdrawn position carrying such one of the subtrays and the subtray or subtrays positioned immediately thereabove while leaving the subtray or the subtrays positioned above such one of the subtrays at the stand-by position, so that such one of the subtrays can readily be exposed to the outside for removal or replacement of the optical disc resting thereon.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention generally relates to an optical disc drive apparatus 
and, more particularly, an optical disc drive apparatus of a type having a 
disc changer capability for recording and/or reproducing information on 
and from a selected one of a plurality of optical discs resting on 
drawable subtrays stacked on a main tray. 
In particular, the optical disc drive apparatus of the present invention is 
suited for use in a personal computer and is so sized and so configured as 
to permit an existing single disc drive in the personal computer to be 
replaced with it 
2. Description of the Prior Art 
With the advent of the age of personal computers, CD-ROM drives have come 
into widespread use as a computer peripheral device and are now standard 
with a majority of the computers. In addition, it is not rare for a single 
computer user to have a number of optical discs in possession. In this 
context, user demands are now increasing for CD-ROM drives having an 
automatic disc changing capability by which a plurality of optical discs 
can be loaded automatically one at a time to a position where access is 
made by an optical information read-out device. 
On the other hand, in most of the desk-top personal computers, a CD-ROM 
drive or any other disc drive is installed in a housing space generally 
known as a "5-inch bay". The opening leading to this housing space is of a 
standard size generally known as a "5-inch half-height" size, and any 
peripheral device that is desired to be accommodated in the 5-inch bay 
must have a maximum size of 146 mm in width and 41.3 mm in height. 
Accordingly, a CD-ROM drive having a built-in automatic disc changer must 
also satisfy the size requirement if it is desired to install it in the 
5-inch bay. If indiscriminate design is made to allow the drive apparatus 
to accommodate an increased number of optical discs, the resultant drive 
would no longer satisfy the size requirement. 
In any event, the CD-ROM drive having an automatic disc changing capability 
and satisfying the size requirement, i.e., capable of being installed in 
the 5-inch bay, is well known in the art. By way of example, Japanese 
Laid-open Patent Publication No. 3-216857, published Sep. 24, 1991, 
discloses an optical disc drive apparatus comprising a main tray supported 
for movement between withdrawn and inserted positions relative to the 
drive housing and having a plurality of subtrays stacked thereon, each for 
supporting thereon an optical disc. This optical disc drive apparatus is 
so designed that when the main tray is moved to the inserted position with 
the stacked subtrays held consequently at a stand-by position, a selected 
one of the subtrays then held at the stand-by position can be drawn 
towards a loaded position where the optical information read-out device 
accesses the optical disc resting on such selected subtray. 
According to this publication, the main tray is formed with grooves for 
holding the subtrays in equidistantly spaced relation to each other. When 
the optical disc resting on an arbitrarily chosen one of the subtrays then 
held at the stand-by position with the main tray held at the inserted 
position is desired to be removed or replaced with a different optical 
disc, the main tray carrying the entire number of the subtrays must be 
withdrawn to the withdrawn position so that the optical disc on the 
arbitrarily chosen subtray can be removed. After this removal has been 
made, the main tray must again be moved to the inserted position. 
A similar optical disc drive apparatus is also disclosed in Japanese 
Laid-open Patent Publication No. 6-259865, published Sep. 16, 1994. This 
known apparatus makes use of an elevating stocker positioned on one side 
of a disc playback position remote from the withdrawn position for the 
main tray and is so designed and so configured that, after a tray with a 
carriage or subtray thereon has been moved to the inserted position, the 
optical disc resting on the carriage or subtray is drawn to a playback 
position where it is played back. The optical disc having been played back 
is then transported together with the subtray towards the elevating 
stocker where it is accommodated. The stocker disclosed therein has a 
capacity to accommodate a plurality of, for example, 7, subtrays and, 
accordingly, by stacking the subtrays, each having an optical disc resting 
thereon, within the stocker, an arbitrarily chosen one of the subtrays can 
be drawn to the playback position that is defined intermediate between the 
inserted position for the tray and the stocker. 
According to this second-mentioned publication, separate drive motors are 
required for driving the tray and for selectively lowering and lifting the 
stocker. In addition, the stocker is supported by a movable member and, 
therefore, when an impact acts on the apparatus during, for example, 
transport of the apparatus, not only may lifting pins be disengaged from 
the stocker, but also the movable member may be damaged. 
Japanese Patent Publication No. 6-14423, first published Nov. 25, 1982, 
under Laid-open Publication No. 59- 96559, discloses a magnetic disc drive 
apparatus including a magnetic disc drive device for transporting a 
disc-shaped recording medium to a loading position at which the recording 
medium is mounted on a rotary drive within a housing and a forced ejector 
with which the recording medium then held at the loading position can be 
manually forcibly removed. 
The teachings of this publication No. 6-14423 may be employed in the 
optical disc drive apparatus disclosed in the previously mentioned 
publication No. 3-216857 so that, in the event of, for example, an 
electric power failure occurring when the main tray having the subtrays 
stacked thereon is moved at least to the inserted position, the subtrays 
can be manually forcibly removed out of the drive housing together with 
the main tray. In this resultant apparatus, it may be contemplated to 
manually rotate an output shaft of the drive motor used to drive an 
arbitrarily chosen one of the subtrays then held at the stand-by position 
towards the loaded position or to manually forcibly drive the output shaft 
of the motor used to drive the main tray between the withdrawn position 
and the inserted position. However, where the drive of the motor is 
transmitted by the use of a pinion and a worm gear meshed with such 
pinion, such as disclosed in the publication No. 6-14423, a relatively 
large manipulating force would be required, resulting in reduction of the 
operability. 
Japanese Laid-open Utility Model Publication No. 5-96936, published Dec. 
27, 1993, discloses a design in which the space between neighboring 
subtrays stacked on the main tray exhibited when the main tray is moved to 
the stand-by position is minimized to render the apparatus as a whole to 
have a reduced height, but in which the space between the neighboring 
subtrays when the subtrays positioned between those neighboring subtray 
has been moved to the loaded position with a part thereof situated between 
such neighboring subtrays, is expanded to allow the optical disc to be 
rotated within such space. 
SUMMARY OF THE INVENTION 
In view of the foregoing, the present invention is intended to provide an 
improved optical disc drive apparatus of a type having an automatic disc 
changing capability, and which can accommodate a maximized number of 
optical discs in a limited space without the reliability of operation 
thereof being sacrificed. 
Another important object of the present invention is to provide an improved 
optical disc drive apparatus of the type referred to above, wherein the 
subtrays stacked on a main tray and each having an optical disc resting 
thereon can be automatically and selectively drawn to the loaded potion to 
accomplish an efficient and effective disc change. 
A further object of the present invention is to provide an improved optical 
disc drive apparatus of the type referred to above, wherein removal or 
replacement of an optical disc on any one of the subtrays stacked on the 
main tray can efficiently be accomplished with no complicated handling 
procedure required. 
A still further object of the present invention is to provide an improved 
optical disc drive apparatus of the type referred to above, which has a 
safety ejecting device built therein for enabling the main tray with the 
subtrays stacked thereon to be manually withdrawn from the inserted 
position in the event of, for example, an electric power failure occurring 
during the use thereof. 
A yet further object of the present invention is to provide an improved 
optical disc drive apparatus of the type referred to above, wherein a 
single drive motor is employed to drive the main tray between the 
withdrawn and inserted position and to drive an elevating table to being 
the optical information read/write device in position to handle any one of 
the optical discs resting on the associated subtrays stacked on the main 
tray. In this respect, where the single drive motor is used, a drive 
transmission is generally comprised of a train of gears and, in such case, 
a phase displacement may occur as a result of the presence of a backlash 
or deformation of the gears. 
Therefore, a yet further object of the present invention is to provide an 
improved optical disc drive apparatus of the type referred to above that 
is substantially free from any phase displacement even though an excessive 
load acts. 
A yet further object of the present invention is to provide an improved 
optical disc drive apparatus of the type referred to above which is 
substantially robust against any possible impact or shock. 
A yet further object of the present invention is to provide an improved 
optical disc drive apparatus of the type referred to above wherein means 
is provided to eliminate any possible lateral displacement of each of the 
stacked subtrays to thereby ensure a stabilized movement between the 
stand-by position and the loaded position. 
It is a related object of the present invention to provide a method of 
replacing an optical disc resting on any one of the stacked subtrays with 
another optical disc, which method is uniquely carried out with the 
optical disc drive apparatus of the type referred to above. 
In order to accomplish these and other objects and features of the present 
invention, there is provided, in accordance with one aspect of the present 
invention, an optical disc drive apparatus including a main tray having a 
stack of subtrays mounted thereon and movable between withdrawn and 
inserted positions, means for moving the main tray from the withdrawn 
position towards the inserted position, means for drawing an arbitrarily 
chosen one of the subtrays from a stand-by position towards a loaded 
position while the main tray is held at the inserted position, and a clamp 
device for clamping an optical disc resting on the subtray then drawn to 
the loaded position. Each of the subtrays has opposite side edges formed 
with a support step extending from a front end towards a rear end thereof. 
A support guide is formed on and positioned inwardly of each of opposite 
side walls of a chassis for engagement with the corresponding support 
step, such that when the main tray is withdrawn to the withdrawn position 
while the arbitrarily chosen subtray is held at the stand-by position, at 
least a portion of a front end of the arbitrarily chosen subtray overlaps 
at least a portion of a rear end of the subtray remaining in the main 
tray. 
With this design, when an optical disc resting on one of the subtrays other 
than the uppermost subtray then held at the loaded position is desired to 
be removed or replaced, not only can such one of the subtray be returned 
smoothly from the loaded position to the stand-by position, but the main 
tray is allowed to withdraw from the inserted position back to the 
withdrawn position carrying such one of the subtrays and the subtray or 
subtrays positioned immediately thereabove while leaving the subtray or 
the subtrays positioned above such one of the subtrays at the stand-by 
position in a substantially horizontal posture, so that such one of the 
subtrays can readily be exposed to the outside for removal or replacement 
of the optical disc resting thereon. 
According to another aspect of the present invention, there is provided a 
method of replacing an optical disc resting on any one of the stacked 
subtrays with another optical disc, which is method is uniquely carried 
out with the optical disc drive apparatus of the type referred to above. 
According to this method, at least one subtray positioned above the n-th 
subtray is held at the stand-by position and the main tray is subsequently 
withdrawn towards the withdrawn position together with the n-th subtray 
and at least one subtray positioned below the n-th subtray. Accordingly, 
the subtray immediately below the n-th subtray can readily be exposed to 
the outside for removal or replacement of the optical disc resting 
thereon. 
Preferably, where one of the subtrays has been drawn to the loaded 
position, such subtray at the loaded position is returned to the stand-by 
position prior to the main tray being returned to the withdrawn position. 
This is particularly advantageous in that the optical disc resting on the 
subtray or subtrays above the subtray returned to the stand-by position 
prior to the main tray being returned to the withdrawn position can 
readily be removed or replaced. 
The present invention also provides, in accordance with a further aspect 
thereof, an optical disc drive apparatus which comprises a main tray 
adapted to have a stack of subtrays mounted thereon and movable between 
withdrawn and inserted positions; a main tray drawing means for moving the 
main tray from a withdrawn position, at which the main tray is positioned 
outside a drive housing, and an inserted position at which the main tray 
is housed within the drive housing with the stack of the subtrays held at 
a stand-by position; a loading drive means for drawing an arbitrarily 
chosen one of the subtrays from the stand-by position towards a loaded 
position while the main tray is held at the inserted position; a clamp 
device for clamping an optical disc resting on the subtray then drawn to 
the loaded position; an elevating means for selectively lifting and 
lowering the loading drive means in a direction in which the subtrays are 
stacked on the main tray so that the arbitrarily chosen subtray may be 
drawn from the stand-by position towards the loaded position; a drive 
means comprised of a single drive motor for both of the main tray drawing 
means and the loading drive means; a first drive switching means for 
selectively transmitting an output of the drive motor to one of the main 
tray drawing means and the loading drive means; and a second drive 
switching means interposed between the drive means and the first drive 
switching means for transmitting the output of the drive means selectively 
to one of the first drive switching means and the elevating means. 
The use of the first and second drive switching means is particularly 
advantageous in that the single drive motor can be employed for the drive 
means. Specifically, when the second drive switching means is set in 
position to cause the first drive switching means to transmit the output 
of the drive means to the main tray drawing means, the single drive motor 
is effective to move the main tray towards the inserted position, but when 
the second drive switching means is set in position to drive only the 
elevating means, the loading drive means can be lifted or lowered to a 
height level aligned with the optical disc resting on the selected one of 
the stacked subtrays on the main tray then held at the inserted position. 
Also, when the first drive switching means is set in position to transmit 
the output of the drive means to the loading drive means, the optical disc 
resting on the selected subtray can be drawn towards the loaded position 
and then to cause the optical disc to be clamped in readiness for 
information recording or reproduction. All of those functions involving 
the drive force are accomplished by the single drive motor. 
According to a still further aspect of the present invention, the optical 
disc drive apparatus comprises a main tray adapted to have a stack of 
subtrays mounted thereon and movable between withdrawn and inserted 
positions; a main tray drawing means for moving the main tray from a 
withdrawn position, at which the main tray is positioned outside a drive 
housing, and an inserted position at which the main tray is housed within 
the drive housing with the stack of the subtrays held at a stand-by 
position; a loading drive means for drawing an arbitrarily chosen one of 
the subtrays from the stand-by position towards a loaded position while 
the main tray is held at the inserted position; a clamp device for 
clamping an optical disc resting on the subtray then drawn to the loaded 
position; a drive means comprised of a single drive motor for both of the 
main tray drawing means and the loading drive means; a first drive 
switching means for selectively transmitting an output of the drive motor 
to one of the main tray drawing means and the loading drive means. 
In this optical disc drive apparatus, in order for the drive of the single 
drive motor to be transmitted to one of the main tray drawing means and 
the loading drive means, only the drive switching means is employed. This 
drive switching means is so designed as to transmit the output of the 
drive motor to the main tray drawing means by rotating a gear from a 
stand-by position towards a loaded position and to transmit the output of 
the drive motor to the loading drive means after the main tray has been 
drawn to the inserted position. The gear forming a part of the drive 
switching means is accessible from front of the drive housing and is 
manipulatable and, accordingly, where the optical disc is desired to be 
forcibly ejected such as occurring, for example, in the event of the 
electric power failure, manipulation of the gear of the drive switching 
means results in a reversed rotation of the loading drive means to return 
the optical disc and the subtray at the loaded position back to the 
stand-by position and further manipulation of the gear results in a 
reversal of the main tray drawing means to return the main tray carrying 
the stacked subtray from the inserted position back to the withdrawn 
position. 
However, according to a yet further aspect of the present invention, the 
optical disc drive apparatus comprises a main tray adapted to have a stack 
of subtrays mounted thereon and movable between withdrawn and inserted 
positions; a main tray drawing means for moving the main tray from a 
withdrawn position, at which the main tray is positioned outside a drive 
housing, and an inserted position at which the main tray is housed within 
the drive housing with the stack of the subtrays held at a stand-by 
position; a loading drive means for drawing an arbitrarily chosen one of 
the subtrays from the stand-by position towards a loaded position while 
the main tray is held at the inserted position; a clamp device for 
clamping an optical disc resting on the subtray then drawn to the loaded 
position; an elevating means for selectively lifting and lowering the 
loading drive means in a direction in which the subtrays are stacked on 
the main tray so that the arbitrarily chosen subtray may be drawn from the 
stand-by position towards the loaded position; a drive means comprised of 
a single drive motor for both of the main tray drawing means and the 
loading drive means; a first drive switching means for selectively 
transmitting an output of the drive motor to one of the main tray drawing 
means and the loading drive means; a second drive switching means 
interposed between the drive means and the first drive switching means for 
transmitting the output of the drive means selectively to one of the first 
drive switching means and the elevating means; and a safety ejecting 
device permitting a gear of the first drive switching means to be 
manipulatable from front of the drive housing. 
The first drive switching means in this optical disc drive apparatus is 
operable to transmit the output of the drive motor to the main tray 
drawing means by rotating the gear from a stand-by position towards a 
loaded position and to transmit the output of the drive motor to the 
loading drive means after the main tray has been drawn to the inserted 
position. Accordingly, where the optical disc is desired to be forcibly 
ejected such as occurring, for example, in the event of the electric power 
failure, manipulation of the gear of the drive switching means results in 
a reversed rotation of the loading drive means to return the optical disc 
and the subtray at the loaded position back to the stand-by position and 
further manipulation of the gear results in a reversal of the main tray 
drawing means to return the main tray carrying the stacked subtray from 
the inserted position back to the withdrawn position. 
Preferably, regardless of whether only the drive switching means is 
employed or whether the first and second drive switching means is 
employed, the optical disc drive apparatus may be provided with a 
manipulatable safety ejecting lever slidable between a disengaged 
position, in which the safety ejecting lever is disengaged from a gear 
forming a part of the first drive switching means, and an ejecting 
position in which it is coupled with the gear. 
Similarly, the optical disc drive apparatus may preferably be provided with 
a friction gear assembly interposed between the drive motor and the first 
drive switching means so that, when the main tray carrying the stacked 
subtrays is desired to be forcibly ejected, slip can take place in the 
friction gear assembly to disconnect the drive of the drive means to 
thereby allow the main tray to be ejected with a minimized amount of the 
manual force. 
Furthermore, a different aspect of the present invention provides an 
optical disc drive apparatus which comprises a main tray adapted to have a 
stack of subtrays mounted thereon and movable between withdrawn and 
inserted positions; a main tray drawing means for moving the main tray 
from a withdrawn position, at which the main tray is positioned outside a 
drive housing, and an inserted position at which the main tray is housed 
within the drive housing with the stack of the subtrays held at a stand-by 
position; a subtray drawing means for drawing an arbitrarily chosen one of 
the subtrays from the stand-by position towards a loaded position while 
the main tray is held at the inserted position; a clamp device for 
clamping an optical disc resting on the subtray then drawn to the loaded 
position; a drive means comprised of a single drive motor for both of the 
main tray drawing means and the loading drive means; a drive switching 
means for selectively transmitting an output of the drive motor to one of 
the main tray drawing means and the subtray drawing drive means; and a 
drawing inhibiting means adapted to be driven to cause the drive switching 
means to halt the drive gear while the drive gear is disengaged from the 
drive switching means. The subtray drawing means employed therein includes 
a gear train for transmitting a drive from the drive switching means to 
the subtray drawing means, the gear train including a drive gear 
selectively engageable and disengageable with and from the drive switching 
means 
Preferably, the drive gear is formed with at least one recess and the 
drawing inhibiting means is provided with a pawl member engageable in the 
recess in the drive gear and wherein when the drawing inhibiting means is 
driven with the drive switching means disengaged from the drive gear the 
driven gear is driven to minimize a backlash in the subtray drawing means 
by means of engagement of the pawl in the recess in the drive gear. The 
recess in the drive gear preferably has an inner wall surface delimited by 
a first straight surface portion lying radially of the drive gear, a 
second straight surface portion lying radially of the drive gear, and a 
tapered surface portion connecting the first and second straight surface 
portions together, and wherein the pawl has a shape substantially 
complemental to that of the first straight surface portion when the 
drawing inhibiting means is engaged with the drive gear. 
By this design, during the main tray being drawn, the drawing inhibiting 
means halts the drive gear to thereby lock the subtray drawing means and, 
therefore, no phase displacement occur in the subtray drawing means during 
the operation. When the subtray is returned from the loaded position back 
to the stand-by position at which it is stacked on the main tray together 
with the remaining subtrays, and even though the drive switching means is 
disconnected from the drive gear shortly before completion of the drive 
being switched, the drive switching means drives the drawing inhibiting 
means to cause the pawl of the drive inhibiting means to drive the tapered 
segment of the drive gear to thereby rotate the drive gear. Accordingly, 
the drive gear can be halted with the backlash in the subtray drawing 
means consequently minimized and the subtray can assuredly be returned to 
the main tray with no phase displacement occurring even when an excessive 
load acts. 
According to a further different aspect of the present invention, the 
optical disc drive apparatus which comprises a main tray adapted to have a 
stack of subtrays mounted thereon and movable between withdrawn and 
inserted positions; a main tray drawing means for moving the main tray 
from a withdrawn position, at which the main tray is positioned outside a 
drive housing, and an inserted position at which the main tray is housed 
within the drive housing with the stack of the subtrays held at a stand-by 
position; a subtray drawing means for drawing an arbitrarily chosen one of 
the subtrays from the stand-by position towards a loaded position while 
the main tray is held at the inserted position; a clamp device for 
clamping an optical disc resting on the subtray then drawn to the loaded 
position; a drive means comprised of a single drive motor for both of the 
main tray drawing means and the loading drive means; a drive switching 
means formed with a plurality of engagements and operable to selectively 
transmit an output of the drive motor to one of the main tray drawing 
means and the subtray drawing means; and an auxiliary drive member 
sequentially engageable with the engagements in the drive switching means 
one at a time from outside the drive housing for driving the drive 
switching means. 
The auxiliary drive member is utilized to forcibly eject the main tray 
together with the subtrays mounted thereon in the event of occurrence of, 
for example, the electric power failure. This auxiliary drive means is 
insertable into the drive housing through a front wall thereof to 
intermittently drive the drive switching means so that the main tray 
drawing means can be reversed to allow the main tray to be returned to the 
withdrawn position. 
The optical disc drive apparatus according to a yet further different 
aspect of the present invention comprises a main tray adapted to have a 
stack of subtrays mounted thereon and movable between withdrawn and 
inserted positions; a main tray drawing means for moving the main tray 
from a withdrawn position, at which the main tray is positioned outside a 
drive housing, and an inserted position at which the main tray is housed 
within the drive housing with the stack of the subtrays held at a stand-by 
position; a loading drive means for drawing an arbitrarily chosen one of 
the subtrays from the stand-by position towards a loaded position while 
the main tray is held at the inserted position; a clamp device for 
clamping an optical disc resting on the subtray then drawn to the loaded 
position; an elevating table movable in a direction parallel to the 
direction in which the subtrays are stacked on the main tray; an elevating 
means for selectively lifting and lowering the elevating table to one of a 
plurality of stop positions aligned respectively with the stacked 
subtrays; and a main substrate for movably holding the elevating means and 
for holding the elevating table at a position corresponding to the 
lowermost one of the stacked subtrays on the main tray. 
This optical disc drive apparatus is particularly advantageous in that, 
when the apparatus is to be transported, the elevating table is retained 
by the main substrate at a position corresponding to the lowermost one of 
the stacked subtrays, to thereby avoid any possible damage to a 
information recording and/or reproducing means. 
According to one feature of the present invention, a fixed guide is 
provided in the drive housing for engagement with the subtrays, then held 
at the stand-by position, to keep them spaced apart from each other so 
that when the main tray is held at the withdrawn position, the respective 
front ends of the subtrays on the main tray are engaged with the 
corresponding engagements in the main tray to secure a space between the 
neighboring subtrays and the respective rear ends of the subtrays on the 
main tray rest on the neighboring subtrays through the spacer projections, 
and that when the main tray is held in the inserted position, the 
respective front ends of the subtrays on the main tray being engaged with 
the corresponding engagements in the main tray to secure the space between 
the neighboring subtrays, but the respective rear ends of the subtrays on 
the main tray are engaged with the fixed guide to secure a space between 
the neighboring subtrays. Accordingly, as compared with the case in which 
holding members are used and provided in the main tray to keep the 
respective rear portions of the stacked subtrays apart from each other, 
the position of any one of the subtrays 6.sub.1, to 6.sub.5 stacked on the 
main tray 1 relative to the loading mechanism can be accurately 
controlled. 
Moreover, according to another feature of the present invention, a fixed 
guide is provided in the drive housing for engagement with the subtrays, 
then held at the stand-by position, to keep them spaced apart from each 
other. This fixed guide is provided with a guide projection engageable in 
a guide groove formed in the lower surface of each subtray and a control 
projection for avoiding any possible lateral displacement of each subtray, 
the control projection being formed in the fixed guide at a location above 
the guide projection and operable to engage with the respective subtray 
when the guide projection is disengaged from the guide groove as a result 
of the subtray having been pushed upwardly by the subtray immediately 
below the subtray. According to this feature, each of the subtrays has 
first and second projections formed on upper and lower surfaces thereof 
such that, when the n-th subtray counted from the lowermost subtray is to 
be drawn from the stand-by position towards the loaded position, the first 
projection on the n-th subtray is brought into abutment with the second 
projection on the subtray immediately above the n-th subtray to push such 
subtray immediately above the n-th subtray upwardly to expand a space 
between the n-th subtray and the subtray immediately above the n-th 
subtray. 
According to another one of the features of the present invention, the 
optical disc drive apparatus comprises a main tray adapted to have a stack 
of subtrays mounted thereon and movable between withdrawn and inserted 
positions and having an engagement formed therein for engagement with a 
front end of each of the subtrays, each of the subtrays having a rear end 
formed with a spacer projection engageable with the next adjacent subtray; 
a main tray drawing means for moving the main tray from a withdrawn 
position, at which the main tray is positioned outside a drive housing, 
and an inserted position at which the main tray is housed within the drive 
housing with the stack of the subtrays held at a stand-by position; a 
loading drive means for drawing an arbitrarily chosen one of the subtrays 
from the stand-by position towards a loaded position while the main tray 
is held at the inserted position; a clamp device for clamping an optical 
disc resting on the subtray then drawn to the loaded position; an 
elevating means for selectively lifting and lowering the loading drive 
means in a direction in which the subtrays are stacked on the main tray so 
that the arbitrarily chosen subtray may be drawn from the stand-by 
position towards the loaded position; and a subtray holding means operable 
when the n-th subtray counted from the lowermost subtray is to be drawn 
from the stand-by position towards the loaded position, to hold one or 
some of the subtrays positioned above the n-th subtray at the stand-by 
position. 
The provision of the subtray holding means is effective to lock the subtray 
or subtrays above the n-th subtray when the subtray or subtrays above the 
n-th subtray are to be pushed upwardly to permit the n-th subtray to be 
drawn towards the loaded position. Accordingly, the subtray or subtrays 
above the n-th subtray can be assuredly held at the stand-by position. 
According to a further one of the features of the present invention, a main 
tray adapted to have a stack of subtrays mounted thereon and movable 
between withdrawn and inserted positions is formed with an engagement for 
engagement with a front end of each of the subtrays, each of the subtrays 
having a rear end formed with a spacer projection engageable with the next 
adjacent subtray. A fixed guide is also provided in the drive housing and 
has guide faces each operable to guide the respective subtray therealong 
during movement of the respective subtray from the stand-by position 
towards the loaded position, each of the guide faces having a protuberance 
formed at a terminating portion thereof. Each of the subtrays has a lower 
surface formed with a recess for accommodating therein the protuberance on 
each guide face. A pressing means is employed for depressing a rear end of 
the arbitrarily chosen subtray downwardly in contact with a rear end of 
the arbitrarily chosen subtray shortly before completion of loading so 
that the amount of movement of the clamp device for clamping the optical 
disc on the n-th subtray can advantageously be minimized and, also, the 
space between the n-th subtray and the subtray immediately above the n-th 
subtray can be expanded upon lowering of the n-th subtray. 
When the arbitrarily chosen subtray is drawn from the stand-by position 
towards the loaded position accompanied by upward push of the subtray 
immediately above such arbitrarily chosen subtray, the subtray immediately 
above the arbitrarily chosen subtray is preferably pivoted about a point 
of engagement between the main tray and the subtray immediately above the 
arbitrarily chosen subtray with the rear end of the subtray immediately 
above the arbitrarily chosen subtray consequently shifted upwardly. This 
ia particularly advantageous in that as compared with the case in which 
the subtrays as a whole are lifted upwardly, the space between the 
neighboring front end portions of the respective subtrays can be minimized 
to thereby avoid the possibility that two subtrays may be loaded 
simultaneously. 
According to one of the features of the present invention, there is 
provided an optical disc drive apparatus which comprises a main tray 
adapted to have a stack of subtrays mounted thereon and movable between 
withdrawn and inserted positions and having an engagement formed therein 
for engagement with a front end of each of the subtrays, each of the 
subtrays having a rear end formed with a spacer projection engageable with 
the next adjacent subtray; a main tray drawing means for moving the main 
tray from a withdrawn position, at which the main tray is positioned 
outside a drive housing, and an inserted position at which the main tray 
is housed within the drive housing with the stack of the subtrays held at 
a stand-by position; a loading drive means for drawing an arbitrarily 
chosen one of the subtrays from the stand-by position towards a loaded 
position while the main tray is held at the inserted position; a clamp 
device for clamping an optical disc resting on the subtray then drawn to 
the loaded position; an elevating means for selectively lifting and 
lowering the loading drive means in a direction in which the subtrays are 
stacked on the main tray so that the arbitrarily chosen subtray may be 
drawn from the stand-by position towards the loaded position; a fixed 
guide provided in the drive housing for guiding each of the subtrays 
during movement of the respective subtray from the stand-by position 
towards the loaded position; and a pressing means engageable with a rear 
end of the arbitrarily chosen subtray shortly before completion of loading 
to depress the rear end of the arbitrarily chosen subtray downwardly. In 
this apparatus, each of the subtrays has a first projection defined in an 
upper surface thereof and a second projection and a recess both defined in 
a lower surface thereof, the recess being positioned at a terminating 
portion of a slide face and operable to receive therein the fixed guide. 
Thus, when the n-th subtray counted from the lowermost subtray is to be 
drawn from the stand-by position towards the loaded position, and prior to 
a space between the n-th subtray and the subtray immediately above the 
n-th subtray being expanded as a result of engagement of the first 
projection on the n-th subtray with the second projection on the subtray 
immediately above the n-th subtray to push such subtray immediately above 
the n-th subtray upwardly, the fixed guide is positioned in alignment with 
the recess in the n-th subtray and the rear end of the n-th subtray 
contacts the pressing means. This is particularly advantageous in that the 
amount of lift of the subtray immediately above the n-th subtray can be 
minimized to permit the apparatus as a whole to be assembled compact.

DETAILED DESCRIPTION OF THE EMBODIMENTS 
While various components of the optical disc drive apparatus according to 
the present invention will be described later item by item under separate 
headings, the principle thereof will first be described with reference to 
FIGS. 1 to 34. 
As best shown in FIG. 2, the optical disc drive apparatus comprises a drive 
housing 2 of a generally rectangular box-like configuration having a disc 
chamber defined therein and also having a generally rectangular front 
opening 3 through which the disc chamber opens to the outside of the drive 
housing 2. The drive housing 2 includes a complementary shaped front door 
4 for selectively opening and closing the front opening 3 which is 
normally biased by a suitable biasing element such as, for example, a 
spring so as to close the front opening 3, and a main tray 1 adapted to be 
driven by a drive means between a withdrawn position, in which the main 
tray 1 is positioned outside the drive housing 2 as shown in FIG. 1A, and 
an inserted position in which the main tray 1 is positioned inside the 
drive housing 2 as shown in FIGS. 1B to 1D. 
When the main tray 1 is in the withdrawn position, a plurality of, for 
example, five, subtrays 6.sub.1 to 6.sub.5 each carrying an information 
bearing optical disc 5, as best shown in FIG. 2, can be stacked on the 
main tray 1. When information on any one of the optical discs 5 is desired 
to be read out or reproduced, the stack of the subtrays 6.sub.1 to 6.sub.5 
on the main tray 1 must be held at a stand-by position as shown in FIGS. 
1B to 1D with the main tray 1 moved to the inserted position. The number 
of the subtrays that can be stacked on the main tray 1 may be of any 
desired value unless it exceeds the maximum available capacity of the main 
tray 1 which is, in the illustrated embodiment, chosen to be five for 
illustrative purpose, each subtray having the respective optical disc 5 
placed thereon. 
Where information on any one of the optical discs 5 is desired to be 
reproduced, this is possible only when the main tray 1 carrying the 
subtrays 6.sub.1 to 6.sub.5 is moved to the inserted position with the 
stack of the subtrays 6.sub.1 to 6.sub.5 brought to the inserted position 
and one of the subtrays carrying such one of the optical discs 5, for 
example, the subtray 6.sub.5, must be subsequently drawn to a loaded 
position as shown in FIG. 1C. When the subtray 6.sub.5 is so drawn to the 
loaded position, the optical disc 5 on such subtray 6.sub.5 is clamped to 
a disc drive unit (not shown) so that such optical disc can be driven in 
one direction about a spindle in any known manner. 
As best shown in FIG. 3, each of the subtrays 6.sub.1 to 6.sub.5 has its 
opposite side edges formed with a substantially L-sectioned support step 7 
and extending from a portion adjacent the front edge thereof towards 
another portion adjacent the rear edge thereof so that, when the plural 
subtrays 6.sub.1 to 6.sub.5 are stacked on the main tray 1, the support 
steps 7 on each side of the stack of the subtrays 6.sub.1 to 6.sub.5 can 
define a generally U-shaped guide groove 8 between the neighboring members 
of the stacked subtrays 6.sub.1 to 6.sub.5 as best shown in FIG. 19, the 
guide groove 8 opening laterally outwardly of the stack of the subtrays 
6.sub.1 to 6.sub.5. It is to be noted that although the guide grooves 8 
referred to above are formed on both sides of the stacked subtray 
assembly, no guide groove is needed between only a right-hand side edge of 
the lowermost one of the stacked subtrays, that is, the subtray 6.sub.1, 
and a subtray receiving surface or bottom surface 9 of the main tray 1. 
Referring to FIGS. 4, 15 and 19, the drive housing 2 includes a chassis 13 
installed inside the drive housing 2 and including right and left side 
walls 13L and 13R having respective fixed guide blocks 11a and 11b secured 
thereto so as to confront the disc chamber. Each fixed guide block 11a or 
11b has a plurality of parallel ribs 10 formed therein which can be 
engaged slidingly in the respective guide grooves 8 in the stacked subtray 
assembly when the main tray 1 carrying the stacked subtrays 6.sub.1 to 
6.sub.5 is moved to the inserted position with the stacked subtrays 
6.sub.1 to 6.sub.5 consequently held at the stand-by position. 
Replacement of the optical disc 5 on any one of the subtrays 6.sub.1 to 
6.sub.5 with a different optical disc, while as shown in FIG. 1B the main 
tray 1 carrying the stacked subtrays 6.sub.1 to 6.sub.5 is held at the 
inserted position, or while one of the subtrays 6.sub.1 to 6.sub.5 on the 
main tray 1 then held at the inserted position is drawn from the stand-by 
position towards the loaded position as shown in FIG. 1C, can be carried 
out in the following manner. 
Assuming that one of the stacked subtrays 6.sub.1 to 6.sub.5 is held at the 
loaded position, the one of the stacked subtrays 6.sub.1 to 6.sub.5 has to 
be returned to the stand-by position before replacement of the optical 
disc on such one of the subtrays is carried out. By way of example, 
assuming that the uppermost one of the subtrays, that is, the subtray 
6.sub.5, is held at the loaded position as shown in FIG. 1C, replacement 
of the optical disc 5 on the uppermost subtray 6.sub.5 is carried out 
after the uppermost subtray 6.sub.5 is returned to the stand-by position 
and the main tray 1 carrying the stacked subtrays 6.sub.1 to 6.sub.5 is 
subsequently moved back to the withdrawn position as shown in FIG. 1E. 
Once the main tray 1 is moved back to the withdrawn position as shown in 
FIG. 1E, the optical disc 5 resting on the uppermost subtray 6.sub.5 is 
readily exposed to the outside and, therefore, the optical disc 5 on the 
uppermost subtray 6.sub.5 can readily be replaced with a different optical 
disc. 
On the other hand, where the optical disc 5 on one of the subtrays 
intervening between the uppermost and lowermost subtrays 6.sub.5 and 
6.sub.1 is desired to be replaced, for example, where the optical disc 5 
on the fourth subtray 6.sub.4 immediately below the uppermost subtray 
6.sub.5 is desired to be replaced, the main tray 1 carrying the subtrays 
6.sub.4, 6.sub.3, 6.sub.2 and 6.sub.1 is moved back to the withdrawn 
position leaving only the uppermost subtray 6. at the stand-by position as 
shown in FIG. 1F, so that when the main tray 1 is brought to the withdrawn 
position the optical disc 5 resting on the fourth subtray 6.sub.4 can be 
exposed to the outside and can, therefore, be readily replaced. 
The uppermost subtray 6.sub.5, left at the stand-by position as shown in 
FIG. 1F during the replacement of the optical disc on the fourth subtray 
6.sub.4 as discussed above, is held there and retained substantially 
horizontally with its rear ends supported by the associated ribs 10 of the 
fixed guide blocks 11a and 11b and with its front edge resting on 
respective rear ends of the subtrays 6.sub.1 to 6.sub.4 remaining on the 
main tray 1 then moved to the withdrawn position. 
Replacement of the optical disc 5 on any one of the subtrays 6.sub.3, 
6.sub.2 and 6.sub.1 can be carried out in a manner similar to that 
described above. Briefly speaking, replacement of the optical disc 5 on 
the subtray 6.sub.3, 6.sub.2 or 6.sub.1 is carried out by leaving the 
uppermost and fourth subtrays 6.sub.5 and 6.sub.4, the uppermost, fourth 
and third subtrays 6.sub.5, 6.sub.4 and 6.sub.3, or the uppermost, fourth, 
third and second subtrays 6.sub.5, 6.sub.4, 6.sub.3 and 6.sub.2, at the 
stand-by positions and then moving the main tray 1 carrying the subtrays 
6.sub.3, 6.sub.2 and 6.sub.1, the subtrays 6.sub.2 and 6.sub.1, or only 
the lowermost subtray 6.sub.1, back to the withdrawn position, 
respectively, as shown in FIGS. 1G, 1H or 1I. 
As described above, while the optical disc drive apparatus of the present 
invention is so designed as to allow the plural subtrays to be mounted on 
the main tray in a stacked fashion and as to allow the plural subtrays to 
be accommodated within the disc chamber together with the main tray then 
moved to the inserted position, one of the subtrays which carries the 
optical disc to be replaced can be exposed to the outside when the main 
tray is moved back to the withdrawn position. Thus, the optical disc drive 
apparatus of the present invention has an excellent operation. In 
addition, the optical disc drive apparatus of the present invention can 
accommodate an increased number of the subtrays since the plural subtrays 
can be stacked on the main tray 1 in a reasonable fashion, making it 
possible to accomplish maximized utilization of the limited space. 
Hereinafter, the various components of the optical disc drive apparatus of 
the present invention effective to accomplish the foregoing principle of 
disc replacement will be described in detail. 
[Drive System for Main Tray 1] 
As best shown in FIG. 2, a rack 12 is formed on an undersurface of the main 
tray 1 so as to extend along at least one side edge, for example, a left 
side edge, thereof in a direction lengthwise of the main tray 1, i.e., in 
a direction conforming to the direction of movement thereof between the 
withdrawn and inserted positions. In the condition in which the main tray 
1 is set in the drive housing 2, the rack 12 is, as best shown in FIGS. 5 
and 6, drivingly engaged with a pinion gear 15 that is rotatably mounted 
on a pin 14 secured to the chassis 13 of the drive housing 2 and that is 
drivingly coupled with a main gear assembly 17. 
The main gear assembly 17 is rotatable about a pin 16 secured to the 
chassis 13 and is comprised of an upper and a lower gear wheel formed 
coaxially therewith. The upper gear wheel has a toothless portion and a 
toothed portion 17D, whereas the lower gear wheel is in the form of a spur 
gear 17U. The pinion gear 15 meshed with the rack 12 is engageable with 
the toothed portion 17D of the upper gear wheel of the main gear assembly 
17 so that when the pinion gear 15 is drivingly engaged with the toothed 
portion 17D a driving force of a drive motor 19 (FIG. 12) can be 
transmitted to the pinion gear 15 and in turn to the rack 12 through a 
gear 32 that is, as shown in FIG. 4, meshed with the lower gear wheel of 
the main gear assembly 17, that is, the spur gear 17U. 
The chassis 13 has a pin 20 secured thereto, on which a friction gear 
assembly 21 is rotatably mounted. This friction gear assembly 21 may be of 
a design utilizing any known friction mechanism and includes input and 
output gears 21a and 21b rotatably mounted on the pin 20 in coaxial 
relation with each other, a friction element such as, for example, a piece 
of felt (not shown) interposed between the input and output gears 21a and 
21b, and a biasing element (also not shown) such as, for example, a coil 
spring, for urging one of the input and output gears 21a and 21b towards 
the other of the input and output gears 21a and 21b. 
As shown in FIG. 12, a worm 22 mounted on a drive shaft of the drive motor 
19 is meshed with the input gear 21a of the friction gear assembly 21 
through an intermediate gear 23. Lower and upper gears 25 and 26 (FIG. 4) 
are coaxially rotatably mounted on a pin 24 secured to the chassis 13 and 
are respectively meshed with the input and output gears 21a and 21b of the 
friction gear assembly 21. Unless slip takes place between the input and 
output gears 21a and 21b of the friction gear assembly 21, the lower and 
upper gears 25 and 26 rotate together with each other about the pin 24. 
Accordingly, when the drive motor 19 is driven in a first direction, the 
friction gear assembly 21 is rotated in a direction shown by the arrow A 
and the gear 32 is thus driven in a direction shown by the arrow B through 
gears 26, 27, 28 and 29, then through an idler gear 30 and finally through 
a gear 31. Since the gear 32 is meshed with the spur gear 17U of the main 
gear assembly 17 as hereinbefore described, the main gear assembly 17 is 
rotated in a direction shown by the arrow C and subsequently causes the 
toothed portion 17D of the upper gear wheel thereof to engage with the 
pinion gear 15, the pinion gear 15 being consequently rotated in a 
direction shown by the arrow D. Upon rotation of the pinion gear 15 in the 
direction of the arrow D, the main tray 1 is driven towards the inserted 
position in a direction shown by the arrow E shown in FIGS. 5 and 6. 
A control unit (not shown) is so designed that upon arrival of the main 
tray 1 at the inserted position as shown in FIG. 6, a microswitch 33a 
fitted to the chassis 13 as shown in FIG. 6 can be activated by a feeler 
17a formed integrally with an undersurface of the main gear assembly 17 to 
deenergize the drive motor 19 with the main tray 1 consequently held at 
the inserted position. During this movement of the main tray 1 from the 
withdrawn position towards the inserted position, an elevating unit of a 
loading drive system as will be described later is held at an uppermost 
one of plural operative positions, at which the uppermost subtray 6.sub.5 
can be loaded, as will be described later. 
[Drive System for Loading Subtrays] 
Where the optical disc 5 placed on the uppermost subtray 6.sub.5 with the 
main tray 1 held at the inserted position is to be loaded, with the 
uppermost subtray 6.sub.5 drawn from the stand-by position to a loaded 
position, the pinion gear 15 is disengaged from the toothed portion 17D of 
the upper gear wheel of the main gear assembly 17 and is instead aligned 
with the toothless portion of the upper gear wheel as shown in FIG. 6 upon 
arrival of the main tray 1 at the inserted position as shown in FIG. 7. 
When during this condition a command is given to the control unit to load 
the uppermost subtray 6.sub.5 to the loaded position, the drive motor 19 
is driven in the first direction to rotate the gear 32 in the direction of 
the arrow B through the gear train. Consequently, the main gear assembly 
17 is rotated in the direction of the arrow C with the spur gear 17D of 
the main gear assembly 17 consequently meshed with a gear 38 as shown in 
FIGS. 8 and 9 to drive the latter in a direction shown by the arrow F. 
Rotation of the gear 38 is then transmitted to a gear 39c through first 
and second intermediate gears 39a and 39b, rotatably secured to the 
undersurface of the chassis 13, and then to a gear 39i through a gear 
train including gears 39d, 39e, 39f, 39g and 39h all rotatably mounted on 
an upper surface of the chassis 13, to drive the gear 39i in a direction 
shown by the arrow G. 
The gear 39i is meshed with a sector gear 42 pivotally mounted through a 
pin 41 on an elevating table 40 of a loading drive system and, therefore, 
when the gear 39i is driven in the direction of the arrow G in the manner 
described above, the sector gear 42 pivots from a first position towards a 
second position in a direction shown by the arrow H. The sector gear 42 
carries a pin 43 fixedly mounted on one end of the sector gear 42, which 
pin 43 is relatively movably engaged in a cut groove 46 defined in a 
motion translating lever 45 journalled at one end thereof to the elevating 
table 40 through a pin 44 as shown in FIG. 8. Accordingly, as the sector 
gear 42 is pivoted in a direction shown by the arrow H about the pin 41, 
the motion translating lever 45 is pivoted about the pin 44 from a 
position shown in FIG. 8 towards a position shown in FIG. 9 in a direction 
shown by the arrow I. 
Another cut groove 47 defined in one end of the motion translating lever 45 
remote from the pin 44 and adjacent the cut groove 46 receives therein a 
pin 50 fixed on a loading hook member 49 that is slidably engaged in a 
longitudinal guide slot 48 defined in the elevating table 40 so as to 
extend in a direction parallel to the direction of insertion of the main 
tray 1. Accordingly, as the motion translating lever 45 is pivoted about 
the pin 44 in the direction of the arrow I, the loading hook member 49 is 
guided along a bent region of the longitudinal guide slot 48 that is 
defined at a front end thereof, and is, upon escape of the loading hook 
member 49 from the bent region of the guide slot 48, pivoted about the pin 
50 in a direction shown by the arrow J so as to enter a straight region of 
the guide slot 48 before the loading hook member 40 attains the position 
shown in FIG. 9. 
As the loading hook member 49 is moved from a position shown in FIGS. 7 and 
8 towards the position shown in FIG. 9, the loading hook member 49 is 
engaged with an engagement 51 formed integrally with and defined at a left 
rear end of the subtray 6.sub.5 and then draws only the subtray 6.sub.5 
from the stand-by position towards the loaded position. When the sector 
gear 42 is pivoted to the second position as shown in FIG. 9 with the 
subtray drawn from the stand-by position within the main tray 1 to the 
loaded position, the opposite end of the sector gear 42 remote from the 
end thereof where the pin 43 is fixedly mounted is brought into abutment 
with a leaf switch 52 secured to the elevating table 40 of the loading 
drive system. The control unit detects abutment of that end of the sector 
gear 42 against the leaf switch 52 to halt the drive motor 19, having then 
driven in the first direction. 
It is to be noted that the gear 39i that drives the sector gear 42 in the 
manner described above is engaged with a clamp drive rack 76 as shown in 
FIG. 25 and that a pin 77 secured to one end of the clamp drive rack 76 
remote from the gear 39i is slidingly engaged in a cam groove 80 defined 
in one end of a clamp support plate 79 having the opposite end rockingly 
supported by the elevating table 40 by means of pins 78a and 78b as shown 
in FIG. 4. 
Thus, when the clamp drive rack 76 is slid in a direction shown by the 
arrow S along the elevating table 40 as a result of rotation of the gear 
39i, the clamp support plate 79 is pivoted from a position, shown by the 
phantom line in FIG. 26, about a common axis connecting between the pins 
78a and 78b with the pin 77 guided along the cam groove 80 so as to 
approach the elevating table 40 as shown by the solid line in FIG. 26, 
resulting in that the optical disc 5 on the subtray 6.sub.5 then drawn to 
the loaded position is clamped by any known clamp device (not shown) so 
that such optical disc 5 can eventually be driven in one direction. 
In any event, where any one of the other subtrays 6.sub.4, 6.sub.3, 6.sub.2 
and 6.sub.1, having the respective optical discs resting thereon is 
desired to be drawn to the loaded position, the elevating table 40 should 
be lowered to a level aligned with the optical disc accommodated in such 
one of the other subtrays and, thereafter, the optical disc accommodated 
in such one of the other subtrays has to be loaded as shown in FIG. 10 in 
a manner similar to that discussed in connection with the uppermost 
subtray 6.sub.5. 
[Elevating System of Loading Drive System] 
A drive system for selectively elevating and lowering the elevating table 
40 while the main tray 1 is held at the inserted position is so structured 
and so designed as follows. 
As shown in FIGS. 4 and 8, the idler gear 30 is mounted on a generally 
T-shaped pivot lever 54 pivotable about a pin 53 secured to the chassis 13 
and is generally biased by a spring 55 so as to engage with the gear 31. 
This pin 53 also has the gear 29 rotatably mounted thereon and positioned 
below the T-shaped pivot lever 54. The position of the T-shaped pivot 
lever 54 is controlled by the shape of a cam member 56A integrally formed 
on an upper surface of an intermittent gear 56 as will be described later, 
since a pin 54a secured to the T-shaped pivot lever 54 is slidingly 
engaged with the cam member 56a. The intermittent gear 56 is of a 
structure wherein first and second toothless recesses 56a and 56b are 
formed spaced an angle of 180.degree. from each other about the axis of 
rotation of the intermittent gear 56 as clearly shown in FIG. 11. It is to 
be noted that unless the loading drive system is in a mode of elevating or 
lowering the elevating table, the intermittent gear 56 is held in a 
position with the first toothless recess 56a aligned with a gear 57 and, 
therefore, the intermittent gear 56 will not be rotated. 
The intermittent gear 56 has an undersurface formed with a trigger cam 
member 56c of a shape as best shown in FIG. 11. Cooperable with this 
trigger cam member 56c is a trigger lever 60 pivotally supported at a 
generally intermediate portion thereof by a pin 58 secured to the chassis 
13. The trigger lever 60 has one end formed with a projection 60a and the 
opposite end engaged with a movable piece 61a of a solenoid unit 61 and is 
normally biased by a tension spring 59 in one direction about the pin 58 
with the projection 60a tending to separate away from the trigger cam 
member 60c. 
In order to lower the elevating table 40 of the loading drive system, the 
solenoid unit 61 has to be temporarily energized to draw the movable piece 
61a inwardly to cause the trigger lever 60 to pivot in a direction, shown 
by the arrow K in FIG. 11, about the pin 58 against the tension spring 59. 
As the trigger lever 50 is so pivoted against the tension spring 59, the 
projection 60a integral with the trigger lever 60 pushes the cam member 
56c to rotate the intermittent gear 56 a slight angle in a direction shown 
by the arrow L until the intermittent gear 56 is brought into engagement 
with the gear 57. At the same time, the drive motor 19 has to be driven in 
the first direction. 
When the drive motor 19 is thus driven in the first direction subsequent to 
engagement between the intermittent gear 56 and the gear 57, the 
intermittent gear 56 is driven in the direction shown by the arrow L and 
the trigger cam member 56A does therefore drive the T-shaped lever 54 in a 
direction shown by the arrow M about the pin 53 with the idler gear 30 
consequently brought into engagement with a large-diameter gear wheel 63 
to drive the latter as shown in FIG. 12. This large-diameter gear wheel 63 
is rotatably supported by a pin 62 secured to the chassis 13. Once the 
large-diameter gear wheel 63 is so driven about the pin 62, rotation of 
the large-diameter gear wheel 63 continues until the intermittent gear 56 
is rotated to a position where the second toothless recess 56b is aligned 
with the gear 57 to thereby disengage the intermittent gear 56 from the 
gear 57. In other words, the large-diameter gear wheel 63 is halted at the 
moment the second toothless recess 56b in the intermittent gear 56 then 
being rotated is brought into alignment with the gear 57. 
When the drive motor 19 is subsequently driven in a second direction 
counter to the first direction to drive the friction gear assembly 21 in a 
direction counter to the direction of the arrow A, the large-diameter gear 
wheel 63 is rotated in a direction shown by the arrow N through the gear 
trains including the gears 26 to 29 and the idler gear 30. 
Referring particularly to FIG. 12, the large-diameter gear wheel 63 has an 
undersurface formed with a generally helical cam groove 62a defined 
therein and slidably accommodating therein a guide pin 65a rigidly secured 
to a generally intermediate portion of a drive lever 65. This drive lever 
65 has one end rotatably mounted on a pin 64 secured to the chassis 13 and 
the other end pivotally coupled with a lower end of a right guide plate 
66R slidably supported by and positioned exteriorly of the right side wall 
13R of the chassis 13 for sliding movement therealong. Accordingly, as the 
large-diameter gear wheel 63 is rotated in the direction of the arrow N, 
the drive lever 65 is pivoted about the pin 64 in a direction shown by the 
arrow O with the guide pin 65a slidingly guided along the helical cam 
groove 62a and that end of the drive lever 65 remote from the pin 64 
consequently causes the right guide plate 66R to move along the right side 
wall 13R in a direction shown by the arrow P, that is, in a direction 
towards the front opening 3 of the drive housing 2. 
As best shown in FIG. 4, the right guide plate 66R and a similar left guide 
plate 66L slidably supported by and positioned exteriorly of the left side 
wall 13L of the chassis 13 for sliding movement along the left side wall 
13L have respective upper portions to which pins 66a and 66b are secured. 
Those pins 66a and 66b are loosely engaged in associated cutouts 67a and 
67b defined in opposite ends of a connecting lever 67 that has an 
intermediate portion pivotally mounted on a pin 13a depending from a 
ceiling plate of the chassis 13. Accordingly, movement of the right guide 
plate 66R towards the front opening 3, that is, in the direction of the 
arrow P, is accompanied by movement of the left guide plate 66L in a 
direction counter to the direction of the arrow P. That is, the left and 
right guide plates 66L and 66R are supported for movement along the left 
and right side walls 13L and 13R in respective directions counter to each 
other depending on the direction of pivot of the connecting lever 67. 
As best shown in FIG. 13A, the right guide plate 66R is formed with a pair 
of inclined guide grooves 68Ra and 68Rb, both extending generally parallel 
to each other at an angle relative to the longitudinal axis of the right 
guide plate 66R, and a straight guide groove 68Rc extending parallel to 
the longitudinal axis of the right guide plate 66R. Similarly, the left 
guide plate 66L is formed with a pair of inclined guide grooves 68La and 
68Lb, both extending generally parallel to each other at an angle relative 
to the longitudinal axis of the left guide plate 66L, and a straight guide 
groove 68Lc extending parallel to the longitudinal axis of the right guide 
plate 66L. All of the inclined guide grooves 68Ra, 68Rb, 68La and 68Lb are 
of an identical configuration, but the inclined guide grooves 68Ra and 
68Rb in the right guide plate 66R are inclined in an opposite sense 
relative to the inclined guide grooves 68La and 68Lb in the left guide 
plate 66R. This is necessitated because, as discussed previously, the 
right and left guide plates 66R and 66L are driven in the respective 
directions opposite to each other in response to the pivotal movement of 
the connecting lever 67 to thereby selectively lift or lower the elevating 
table 40 without allowing the latter to tilt relative to a plane in which 
the optical disc may lies. 
The elevating table 4 of the loading drive system has opposite side 
portions to which guide pins 40Ra and 40Rb and similar guide pins 40La and 
40Lb are secured, respectively, so as to extend laterally outwardly. The 
guide pins 40Ra and 40Rb secured to the right side portion of the 
elevating table 4 extend through respective vertical slots 69Ra and 69Rb, 
defined in the right guide plate 13L of the chassis 13, and then through 
the corresponding inclined guide grooves 68Ra and 68Rb also defined in the 
right guide plate 66R. Similarly, the guide pins 40La and 40Lb secured to 
the left side portion of the elevating table 40 extend through respective 
vertical slots 69La and 69Lb, defined in the left guide plate 13L of the 
chassis 13, and then through the corresponding inclined guide grooves 68La 
and 68Lb also defined in the left guide plate 66L. 
Pins 40Rc and 40Lc secured to the right and left guide plates 66R and 66L, 
respectively, are engaged in the associated straight guide grooves 68Rc 
and 68Lc. 
The right-side inclined guide grooves 68Ra and 68Rb and the left-side 
inclined guide grooves 68La and 68Lb are of an identical configuration and 
are so designed and so shaped that as the left and right guide plates 66L 
and 66R are moved in unison in response to the pivotal movement of the 
connecting lever 67, the elevating table 40 can, with the pins 40Lc and 
40Rc guided within the associated straight guide grooves 68Lc and 68Rc, be 
moved in a direction perpendicular to the direction of movement of each 
guide plate 66L or 66R to assume one of five stop positions associated 
with the subtrays stacked on the main tray 1: a first stop position at 
which the loading drive system can be accessible to the uppermost or fifth 
subtray 6.sub.5 as shown in FIGS. 13A and 14A, a second stop position at 
which the loading drive system can be accessible to the fourth subtray 
6.sub.4 as shown in FIGS. 13B and 14B, a third stop position at which the 
loading drive system can be accessible to the third subtray 6.sub.3 as 
shown in FIGS. 13C and 14C, a fourth stop position at which the loading 
drive system can be accessible to the second subtray 6.sub.2 as shown in 
FIGS. 13D and 14D, and a fifth stop position at which the loading drive 
system can be accessible to the lowermost or first subtray 6.sub.1 as 
shown in FIGS. 13E and 14E. 
As shown in FIG. 15, a generally rectangular slitted plate 70 having 
defined therein a row of sensing slits 70.sub.1 to 70.sub.5 equal in 
number to the number of the subtrays that can be accommodated in the main 
tray 1 is secured to a lower side edge of the left guide plate 66L. 
Cooperable with any one of those sensing slits 70.sub.1 to 70.sub.5 is a 
photo-interrupter 71 fixedly mounted on a portion of the chassis 13 where 
the slitted plate 70 moves together with the left guide plate 66L so that 
passage of any one of the sensing slits 70.sub.1 to 70.sub.5 can be 
detected by the photo-interrupter 71. 
When electric power is supplied to the control unit, the drive motor 19 is 
electrically energized for a predetermined length of time to drive in the 
first direction with the photo-interrupter 71 consequently set to an 
initial condition ready to detect the sensing slit 70.sub.5. When a 
command descriptive of the number allocated to one of the subtrays, for 
example, the third subtray 6.sub.3, desired to be accessed is inputted to 
the control unit, the drive motor 19 is driven in the second direction 
counter to the first direction until the photo-interrupter 71 detects the 
associated sensing slit 70.sub.3, causing the elevating table 40 to be 
lowered from the first stop position to the third stop position shown in 
FIGS. 13C and 14C past the second stop position shown in FIGS. 13B and 
14B. A similar operation takes place even where any one of the other 
subtrays is desired to be accessed. 
[Subtray Holding Mechanism] 
As hereinbefore described, assuming that the main tray 1 having a stack of 
the subtrays 6.sub.1 to 6.sub.5 mounted thereon is held in the inserted 
position, and where an optical disc 5 placed on one of the stacked 
subtrays 6.sub.1 to 6.sub.4 except for the uppermost subtray 6.sub.5 is 
desired to be replaced, or where an optical disc 5 is desired to be placed 
on one of the stacked subtrays 6.sub.1 to 6.sub.4 except for the uppermost 
subtray 6.sub.5 (applicable where such one of the stacked subtrays is 
empty), the uppermost subtray 6.sub.5 or all of the subtrays positioned 
above such one of the stacked subtrays can be retained at the stand-by 
position so that, when the main tray 1 is subsequently moved to the 
withdrawn position, the user can quickly access to such one of the stacked 
subtrays for replacement or placement of the optical disc 5. A subtray 
holding mechanism for this purpose will now be described. 
As shown in FIG. 14, a portion of the left guide plate 13L of the chassis 
13 is formed with a window 72. A holder 73 made of synthetic resin is 
supported by the left guide plate 13L so as to confront the window 72 as 
shown in FIGS. 4 and 15. This holder 73 is integrally formed with the 
fixed guide block 11b and includes first to fourth holder levers 74.sub.1 
to 74.sub.4 mounted at a generally intermediate portion thereof on the 
holder 73 by means of a pivot pin 73a secured thereto. Each of the holder 
levers 74.sub.1 to 74.sub.4 has one end branched into a feeler 75a and an 
elastically yieldable leg 75b of a length greater than that of the 
respective feeler 75a and the opposite end formed integrally with a hook 
75c and positioned remote from the fixed guide block 11b. Cooperable with 
the holder levers 74.sub.1 to 74.sub.4 are first to fourth cam projections 
66.sub.1 to 66.sub.4 secured to a portion of the left guide plate 66L 
generally in alignment with the holder 73, the first to fourth cam 
projections 66.sub.1 to 66.sub.4 being spaced at the same pitch as the 
holder levers 74 to 74.sub.4. 
(Removal or Placement of Disc from or on Subtray 6.sub.5) 
Where the elevating table 40 of the loading drive system is held at the 
first stop position at which the loading drive system is accessible to the 
uppermost or fifth subtray 6.sub.5 as shown in FIGS. 13A and 14A, the 
feelers 75a of the first to fourth holder levers 74.sub.1 to 74.sub.4 ride 
over the associated cam projections 66.sub.1 to 66.sub.4 with the feelers 
75a consequently pressed inwardly in a direction shown by the arrow Q. In 
this condition, the hooks 75c of the first to fourth holder levers 
74.sub.1 to 74.sub.4 are pivoted clockwise, as viewed in FIG. 15, about 
the pivot pin 73a against the resiliency of the legs 75b, to thereby 
disengage from respective recesses 6a defined in the left side edges of 
the subtrays 6.sub.5 to 6.sub.2 as shown respectively in FIGS. 16A to 16D. 
In this condition, the main tray 1 can be moved to the withdrawn position 
together with the entire number of the subtrays 6.sub.1 to 6.sub.5 resting 
thereon and, thus, the user can make access to the uppermost subtray 
6.sub.5 then exposed to the outside for removal or placement of the 
optical disc 5. 
Assuming that the hooks 75c of the holder levers 74.sub.1 to 74.sub.4 are 
held in position to disengage from the associated recesses 6a in the 
subtrays as discussed above, the entire number of the subtrays 6.sub.1 to 
6.sub.5 mounted on the main tray 1 can be withdrawn together with the main 
tray 1 then moving towards the withdrawn position. For this purpose, the 
main tray 1 is provided with a releasable catch mechanism for releasably 
trapping the subtrays 6.sub.1 to 6.sub.5, which will now be described. 
The releasable catch mechanism includes, as best shown in FIGS. 2 and 17, a 
leaf spring member 1a integrally formed at one end with an auxiliary 
spring element 1d and at the opposite end with generally V-shaped 
resilient tongues equal in number to the number of the subtrays 6.sub.1 to 
6.sub.5 that can be accommodated in the main tray 1. The generally 
V-shaped resilient tongues of the leaf spring member 1a are, when and so 
long as the subtrays 6.sub.1 to 6.sub.5 are stacked on the main tray 1, 
resiliently engaged in respective recesses 6b defined in the side edges of 
the subtrays 6.sub.1 to 6.sub.5 to thereby retain the latter temporarily 
on the main tray 1. 
The releasable catch mechanism also includes a stopper 1b mounted on the 
main tray 1 for pivotal movement about a pin 1c and normally biased by the 
auxiliary spring element 1d in one direction with one end thereof remote 
from the V-shaped resilient tongues consequently protruding inwardly of 
the main tray 1. So long as the stopper 1b is biased by the auxiliary 
spring element 1d with that end thereof consequently protruding inwardly 
of the main tray 1 as described above, that end of the stopper 1b is 
engaged in respective recesses 6c defined in the left side edges of the 
subtrays 6.sub.1 to 6.sub.5 to avoid any possible separation of those 
subtrays 6.sub.1 to 6.sub.5 relative to the main tray 1. 
However, since a lever 1e, formed integrally with the opposite end of the 
stopper 1b so as to protrude laterally outwardly from the left side wall 
of the main tray 1 as best shown in FIG. 17, is brought into sliding 
engagement with the left side wall 13L of the chassis as the main tray 1 
is moved towards the inserted position, the stopper 1b is pivoted in the 
opposite direction about the pin 1c against the biasing force of the 
auxiliary spring element 1d, with that end of the stopper 1b consequently 
retracted inwardly to disengage from the recesses 6c in the subtrays 
6.sub.1 to 6.sub.5. 
Even though that end of the stopper 1b remote from the V-shaped resilient 
tongues of the leaf spring member 1a is disengaged from the recesses 6c in 
the subtrays 6.sub.1 to 6.sub.5, the subtrays 6.sub.1 to 6.sub.5 resting 
on the main tray 1 can be retained in position on the main tray 1 by the 
action of the V-shaped resilient tongues then engaged in the recesses 6b 
in the subtrays 6.sub.1 to 6.sub.5. This condition is maintained so long 
as the main tray 1 is moved to and maintained at the inserted position. 
Thus, so long as the elevating table 40 of the loading drive system assumes 
the first stop position at which the loading drive system is accessible to 
the uppermost or fifth subtray 6.sub.5 as shown in FIGS. 13A and 14A, the 
hooks 75c of the first to fourth holder levers 74.sub.1 to 74.sub.4 are 
disengaged from the recesses 6a in the subtrays 6.sub.2 to 6.sub.5 on the 
main tray 1 as shown in FIGS. 16A to 16D. When during this condition a 
command indicative of replacement of the optical disc 5 resting on the 
uppermost subtray 6.sub.5 is inputted to the control unit, the control 
unit immediately instructs the drive motor 19 to rotate in the first 
direction to thereby drive the main gear assembly 17 in a direction 
counter to the direction of the arrow C so that the main tray 1 carrying 
the subtrays 6.sub.1 to 6.sub.5 can be driven towards the withdrawn 
position as shown in FIG. 1E. The supply of the electric power to the 
drive motor 19 then driven in the first direction is interrupted when 
another microswitch 33b detects a projection 17c formed on the 
undersurface of the main gear assembly 17. 
(Removal or Placement of Disc from or on Subtray 6.sub.4) 
Assuming that the elevating table 40 is held at the first stop position at 
which the loading drive system is accessible to the uppermost subtray 
6.sub.5, and when a command indicative of replacement of the optical disc 
on the fourth subtray 6.sub.4 is subsequently inputted to the control unit 
while the entire subtrays 6.sub.1 to 6.sub.5 are held at the stand-by 
position with the main tray 1 held at the inserted position, the control 
unit causes the right and left guide plates 66R and 66L to move in the 
respective directions in response to the pivotal movement of the 
connecting lever 67 to thereby cause the elevating table 40 to move down 
to the second stop position at which the loading drive system is 
accessible to the fourth subtray 6.sub.4 immediately below the uppermost 
subtray 6.sub.5 as shown in FIGS. 13B and 14B. 
In this condition, shown in FIGS. 13B and 14B, the feeler 75a of only the 
first holder lever 74.sub.1 is disengaged from the corresponding first cam 
projection .sup.66 i as best shown in FIG. 18A, causing the first holder 
lever 74.sub.1 to be pivoted about the pin by the resilient force of the 
leg 75b with the hook 75c of the first holder lever 74.sub.1 consequently 
engaged in the recess 6a in the uppermost subtray 6.sub.5. On the other 
hand, the hooks 75c of the remaining second to fourth holder levers 
74.sub.2 to 74.sub.4 associated with the subtrays 6.sub.4, 6.sub.3 and 
6.sub.2 remain disengaged respectively from the recesses 6a of those 
subtrays 6.sub.4, 6.sub.3 and 6.sub.2 since the feelers 75a of the second 
to fourth holder levers 74.sub.2 to 74.sub.4 are engaged with the 
corresponding cam projections 66.sub.2 to 66.sub.4 and are consequently 
pressed inwardly in the direction of the arrow Q as shown in FIGS. 18B to 
18D against the resiliency of the legs 75b of the second to fourth holder 
levers 74.sub.2 to 74.sub.4. 
Upon completion of the lowering of the elevating table 40 to the second 
stop position as described above, the control unit causes the drive motor 
19 to rotate in the first direction to thereby move the main tray 1 from 
the inserted position towards the withdrawn position, but the supply of 
the electric power to the drive motor 19 then rotating in the first 
direction is interrupted when the microswitch 33b detects the projection 
17c on the undersurface of the main gear assembly 17. 
As during this condition the main tray 1 with the subtrays thereon is moved 
towards the withdrawn position, only the uppermost and nest succeeding 
subtrays 6.sub.5, having their recess 6a in which the hook 75c of the 
first holder levers 74.sub.1 is engaged is retained at the stand-by 
position, allowing the remaining subtrays 6.sub.4, 6.sub.3, 6.sub.2 and 
6.sub.1 to move together with the main tray 1 then moving towards the 
withdrawn position. Upon arrival of the main tray 1 at the withdrawn 
position, the user can access the subtray 6.sub.4 then exposed to the 
outside with the other subtrays 6.sub.3, 6.sub.2 and 6.sub.1 positioned 
between it and the bottom of the main tray 1. 
(Removal or Placement of Disc from or on Subtray 6.sub.3) 
Assuming that the elevating table 40 is held at the first stop position at 
which the loading drive system is accessible to the uppermost subtray 
6.sub.5, when a command indicative of replacement of the optical disc on 
the third subtray 6.sub.3 is subsequently inputted to the control unit 
while the entire subtrays 6.sub.1 to 6.sub.5 are held at the stand-by 
position with the main tray 1 held at the inserted position, the control 
unit causes the right and left guide plates 66R and 66L to move in the 
respective directions in response to the pivotal movement of the 
connecting lever 67 to thereby cause the elevating table 40 to move down 
to the third stop position at which the loading drive system is accessible 
to the third subtray 6.sub.3 as shown in FIGS. 13C and 14C. 
In this condition shown in FIGS. 13C and 14C, the feelers 75a of only the 
first and second holder levers 74.sub.1 and 74.sub.2 are disengaged from 
the corresponding first and second cam projections 66.sub.1 and 66.sub.2 
as best shown in FIGS. 21A and 21B, causing the first and second holder 
levers 74.sub.1 and 74.sub.2 to be pivoted about the pin by the resilient 
force of the legs 75b with the hooks 75c of the first and second holder 
levers 74.sub.1 and 74.sub.2 consequently engaged in the recesses 6a in 
the fifth and fourth subtrays 6.sub.5 and 6.sub.4. On the other hand, the 
hooks 75c of the remaining third and fourth holder levers 74.sub.3 and 
74.sub.4 associated with the subtrays 6.sub.3 and 6.sub.2 remain 
disengaged respectively from the recesses 6a of those subtrays 6.sub.3 and 
6.sub.2 since the feelers 75a of the third and fourth holder levers 
74.sub.3 and 74.sub.4 are engaged with the corresponding cam projections 
66.sub.3 and 66.sub.4 and are consequently pressed inwardly in the 
direction of the arrow Q as shown in FIGS. 21C to 21D against the 
resiliency of the legs 75b of the third and fourth holder levers 74.sub.3 
and 74.sub.4. 
Upon completion of the lowering of the elevating table 40 to the third stop 
position as described above, the control unit causes the drive motor 19 to 
rotate in the first direction to thereby move the main tray 1 from the 
inserted position towards the withdrawn position, but the supply of the 
electric power to the drive motor 19 then rotating in the first direction 
is interrupted when the microswitch 33b detects the projection 17c on the 
undersurface of the main gear assembly 17. 
As during this condition the main tray 1 with the subtrays thereon is moved 
towards the withdrawn position, only the uppermost and next succeeding 
subtrays 6.sub.5 and 6.sub.4, having their recesses 6a in which the hooks 
75c of the first and second holder levers 74.sub.1 and 74.sub.2 are 
engaged, are retained at the stand-by position, allowing the remaining 
subtrays 6.sub.3, 6.sub.2 and 6.sub.1 to move together with the main tray 
1 then moving towards the withdrawn position. Upon arrival of the main 
tray 1 at the withdrawn position, the user can access the subtray 6.sub.3 
then exposed to the outside with the other subtrays 6.sub.2 and 6.sub.1 
positioned between it and the bottom of the main tray 1. 
(Removal or Placement of Disc from or on Subtray 6.sub.2) 
Assuming that the elevating table 40 is held at the first stop position at 
which the loading drive system is accessible to the uppermost subtray 
6.sub.5, when a command indicative of replacement of the optical disc on 
the fourth subtray 6.sub.2 is subsequently inputted to the control unit 
while all of the subtrays 6.sub.1 to 6.sub.5 are held at the stand-by 
position with the main tray 1 held at the inserted position, the control 
unit causes the right and left guide plates 66R and 66L to move in the 
respective directions in response to the pivotal movement of the 
connecting lever 67 to thereby cause the elevating table 40 to move down 
to the fourth stop position at which the loading drive system is 
accessible to the third subtray 6.sub.2 as shown in FIGS. 13D and 14D. 
In this condition shown in FIGS. 13D and 14D, the feelers 75a of only the 
first to third holder levers 74.sub.1 to 74.sub.3 are disengaged from the 
corresponding first to third cam projections 66.sub.1 to 66.sub.3 as best 
shown in FIGS. 22A to 22B, causing the first to third holder levers 
74.sub.1 to 74.sub.3 to be pivoted about the pin by the resilient force of 
the legs 75b with the hooks 75c of the first to third holder levers 
74.sub.1 to 74.sub.3 consequently engaged in the recesses 6a in the fifth, 
fourth and third subtrays 6.sub.5, 6.sub.4 and 6.sub.3. On the other hand, 
the hooks 75c of the fourth holder lever 74.sub.4 associated with the 
subtray 6.sub.2 remains disengaged respectively from the recess 6a of 
those subtrays 6.sub.2 since the feeler 75a of the fourth holder lever 
74.sub.4 is engaged with the corresponding cam projection 66.sub.4 and is 
consequently pressed inwardly in the direction of the arrow Q as shown in 
FIG. 22D against the resiliency of the leg 75b of the fourth holder lever 
74.sub.4. 
Upon completion of the lowering of the elevating table 40 to the fourth 
stop position as described above, the control unit causes the drive motor 
19 to rotate in the first direction to thereby move the main tray 1 from 
the inserted position towards the withdrawn position, but the supply of 
the electric power to the drive motor 19 then rotating in the first 
direction is interrupted when the microswitch 33b detects the projection 
17c on the undersurface of the main gear assembly 17. 
As during this condition the main tray 1 with the subtrays thereon is moved 
towards the withdrawn position, only the subtrays 6.sub.5 to 6.sub.3 
having their recesses 6a in which the hooks 75c of the first to third 
holder levers 74.sub.1 to 74.sub.3 are engaged are retained at the 
stand-by position, allowing the remaining subtrays 6.sub.2 and 6.sub.1 to 
move together with the main tray 1 then moving towards the withdrawn 
position. Upon arrival of the main tray 1 at the withdrawn position, the 
user can make an access to the subtray 6.sub.2 then exposed to the outside 
with the lowermost subtray 6.sub.1 positioned between it and the bottom of 
the main tray 1. 
(Removal or Placement of Disc from or on Subtray 6.sub.1) 
Assuming that the elevating table 40 is held at the first stop position at 
which the loading drive system is accessible to the uppermost subtray 
6.sub.5, when a command indicative of replacement of the optical disc on 
the lowermost subtray 6.sub.1 is subsequently inputted to the control unit 
while the entire subtrays 6.sub.1 to 6.sub.5 are held at the stand-by 
position with the main tray 1 held at the inserted position, the control 
unit causes the right and left guide plates 66R and 66L to move in the 
respective directions in response to the pivotal movement of the 
connecting lever 67 to thereby cause the elevating table 40 to move down 
to the fifth stop position at which the loading drive system is accessible 
to the lowermost subtray 6.sub.1 as shown in FIGS. 13E and 14E. 
In this condition shown in FIGS. 13E and 14E, the feelers 75a of only the 
first to fourth holder levers 74.sub.1 to 74.sub.4 are disengaged from the 
corresponding first to fourth cam projections 66.sub.1 to 66.sub.4 as best 
shown in FIGS. 24A to 24D, causing the first to fourth holder levers 
74.sub.1 to 74.sub.4 to be pivoted about the pin by the resilient force of 
the legs 75b with the hooks 75c of the first to fourth holder levers 
74.sub.1 to 74.sub.4 consequently engaged in the recesses 6a in the fifth, 
fourth, third and second subtrays 6.sub.5, 6.sub.4, 6.sub.3 and 6.sub.2. 
Upon completion of the lowering of the elevating table 40 to the fifth stop 
position as described above, the control unit causes the drive motor 19 to 
rotate in the first direction to thereby move the main tray 1 from the 
inserted position towards the withdrawn position, but the supply of the 
electric power to the drive motor 19 then rotating in the first direction 
is interrupted when the microswitch 33b detects the projection 17c on the 
undersurface of the main gear assembly 17. 
As during this condition the main tray 1 with the subtrays thereon is moved 
towards the withdrawn position, the subtrays 6.sub.5 to 6.sub.2 having 
their recesses 6a in which the hooks 75c of the first to fourth holder 
levers 74.sub.1 to 74.sub.4 are engaged are retained at the stand-by 
position, allowing only the lowermost subtray 6.sub.1 to move together 
with the main tray 1 then moving towards the withdrawn position. Upon 
arrival of the main tray 1 at the withdrawn position, the user can access 
the subtray 6.sub.1 then exposed to the outside with the other subtrays 
6.sub.2 to 6.sub.5 retained at the stand-by position inside the disc 
chamber. 
[Lock Mechanism for Main Tray] 
As shown in FIG. 2, the main tray 1 has a projection 81 formed on the 
undersurface thereof so as to protrude downwardly therefrom. On the other 
hand, the main gear assembly 17 has an upper surface formed with a 
generally arcuate projections 82a concentric with the pin 16 as shown in 
FIG. 27. Two separate tapered segments 82b and 82c are formed adjacent one 
end of the arcuate projection 82a in concentric relation with the pin 16. 
FIG. 27 illustrates a condition in which the main tray 1 is being drawn 
towards the inserted position by the gear 15 then driven as a result of 
rotation of the main gear assembly 17, and the main gear assembly 17 may 
assume such transit conditions as shown respectively in FIGS. 27 to 31 
before the main tray 1 is completely drawn to the inserted position as 
shown in FIG. 32, the sequence of which will now be described. 
When as a result of rotation of the main gear assembly 17 the projection 81 
fast with the main tray 1 moves past laterally of the tapered segment 82c 
fast with the main gear assembly 17 and the tapered segment 82b 
subsequently comes to a position where the tapered segment 82b encompasses 
the projection 81 as shown in FIG. 30, the main gear assembly 17 is 
disengaged from the pinion gear 15, allowing the main tray 1 to be drawn 
towards the inserted position, as shown in FIG. 31, by the action of the 
tapered segment 82c fast with the main gear assembly 17. Also, even though 
the main gear assembly 17 rotates until a condition is established in 
which one of the subtrays on the main tray 1 is drawn from the stand-by 
position towards the loaded position and is then clamped by the clamping 
mechanism at the loaded position, the projection 81 fast with the main 
tray 1 is engaged with the arcuate projection 82a fast with the main gear 
assembly 17 to thereby inhibit the main tray 1 from being manually drawn 
towards the withdrawn position, thereby locking the main tray 17 at the 
inserted position. 
[Lock Mechanism for Subtray Drawing System] 
As shown in FIG. 41, the gear 38 is formed with five recesses 38a spaced an 
equal angle from each other with respect to the axis of rotation thereof. 
Each of the recesses 38a has one side wall delimited by straight wall 
segments 38b and 38c extending in a direction generally radially of the 
gear 38 and an inclined wall segment 38d connecting the straight wall 
segments 38b and 38c together. A mode lock lever (drawing inhibitor) 101 
is pivotally mounted on the chassis 13 and has one end formed with a pawl 
101a of a shape identical with the shape of each recess 38a in the gear 38 
and the other end carrying a pin 101b engageable in arcuate grooves 100a 
and 100b and a tapered groove 100c defined in the main gear assembly 17 as 
will be described later. This mode lock lever 101 is normally biased by a 
torsion spring 102 in a direction required for the pawl 101a to be engaged 
in one of the recesses 38a in the gear 38. 
The arcuate grooves 10a and 100b have a curvature different from each other 
and are formed on the undersurface of the main gear assembly 17 together 
with the tapered groove 100c communicating the arcuate grooves 10a and 
100b together. Thus, as the main gear assembly 17 is rotated, the mode 
lock lever 101 is pivoted to bring the gear 30 to a halt or to release the 
gear 38 depending on the direction of pivot of the mode lock lever 101. 
FIG. 39 illustrates a stand-by condition in which the elevating table 40 is 
ready to move, During this condition, the pin 101b rigid with the mode 
lock lever 101 is engaged in the arcuate groove 110a in the main gear 
assembly 17 to thereby lock the gear 38 non-rotatable at a predetermined 
phase. 
When starting from the condition shown in FIG. 39 the main gear assembly 17 
is rotated, the mode lock lever 101 is pivoted against the biasing force 
of the torsion spring 102 with the pin 101b guided along the tapered 
groove 100c in the main gear assembly 17 and the pawl 101a is subsequently 
disengaged from the straight wall segment 38c of the recess 38a in the 
gear 39, allowing the gear 38 to engage with the main gear assembly 17 to 
drive the latter as shown in FIGS. 8 and 40. Starting from this condition, 
the loading hook member 49 is driven to draw one of the stacked subtrays 
on the main tray 1 towards the loaded position in the manner hereinbefore 
described. Up until the optical disc on the subtray then drawn to the 
loaded position is clamped in position as shown in FIG. 10, the gear 38 is 
released from a locked condition by sliding engagement of the pin 101b 
rigid with the mode lock lever 101 in the arcuate groove 101b in the main 
gear assembly 17. 
When the optical disc drive apparatus is to be assembled, the loading hook 
member 49 as shown in FIG. 8 has to be moved in a direction counter to the 
direction of the arrow I and the gear 30a has to be rotated in a direction 
shown by the arrow T to eliminate any possible rattling motion which would 
otherwise result from backlash and/or flexure of the gear trains. While in 
this condition, the gear 38 should be mounted on the chassis 13 with the 
pawl 101a of the mode lock lever 101 matched in phase with any one of the 
recesses 38a in the gear 38. 
By so doing, even though the main gear assembly 17 is disengaged from the 
gear 38, rotation of the main gear assembly 17 causes the pawl 101a of the 
mode lock lever 101 to push the inclined wall segment 38d of the recess 
38a in the gear 38 to thereby rotate the gear 38 to a predetermined phase 
at which any possible backlash is compensated for. Also, since the pawl 
101a is engaged deep in the recess 38a even at the moment the main gear 
assembly 17 is disengaged from the gear 38, there is no possibility that 
the pawl 101a would push the straight wall segment 38b to reverse the gear 
38 when the gear 38 is excessively loaded, and therefore, any possible 
occurrence of a phase shift can be advantageously eliminated. 
[Forced Ejector--First Embodiment] 
As shown in FIG. 31, a lever support plate 84 is fixedly mounted on the 
chassis 13 by means of a plurality of set screws so as to overlay the gear 
mechanism. This lever support table 84 has engagement pieces 84a, 84b and 
84c integrally formed therewith, and a safety ejection lever 85 is 
slidably supported by those engagement pieces 84a to 84c. In FIGS. 30 and 
31, the safety ejection lever 85 is shown as held still at a disengaged 
position at which a rack 85a formed in the safety ejection lever 85 is not 
engaged with a toothed portion 86 of the arcuate projection 82a fast with 
the main gear assembly 17. FIG. 32 illustrates the condition in which the 
safety ejection lever 85 is still held at the disengaged position while 
the main tray 1 is moved to the inserted position. 
In the event of a power failure occurring while the clamp device clamps the 
optical disc 5, a manual pull of the safety ejection lever 85 effected 
after the lid 4 then closing the front opening 3 of the drive housing 2 
has been opened results in that a projection 85b integral with the safety 
ejection lever 85 is brought into engagement with the tapered segment 82b 
fast with the main gear assembly 17 to drive the main gear assembly in a 
direction counter to the direction of the arrow C. In this condition, the 
safety ejection lever 85 has been moved from the disengaged position to an 
eject position. The resultant rotation of the main gear assembly 17 is 
transmitted through a gear train to the gear 39i to initiate an unloading 
operation in which not only is the clamp device caused to release the 
optical disc, but the corresponding subtray then held at the loaded 
position is returned to the stand-by position. It is to be noted that 
where the gear train is manually forcibly driven by means of the safety 
ejection lever 85, relative slip takes place between the input and output 
gears 21a and 21b of the friction gear assembly 21 to thereby disconnect 
the output gear 21b from a gear train ranging from the input gear 21a to 
the drive motor 19 and, therefore, the manual force necessary to apply to 
the safety ejection lever 85 can be lessened to facilitate a ready and 
quick manual pull of the safety ejection lever 85. 
By manually forcibly pulling the safety ejection lever 85 in a direction 
outwardly of the drive housing 2, the rack 85a of the safety ejection 
lever 85 and the toothed portion 86 of the arcuate projection 82a fast 
with the main gear assembly 17 are meshed with each other as shown in 
FIGS. 33 and 34 to drive the main gear assembly 17 in a direction counter 
to the direction of the arrow C to thereby complete the unloading 
operation, accompanied by movement of the main tray 1 from the inserted 
position towards the withdrawn position. In this way, a forced ejection is 
completed. 
As hereinabove described, even though power failure occurs, the unloading 
operation and the subsequent withdrawal of the main tray towards the 
withdrawn position are possible by the manipulation of the safety ejection 
lever 85. 
As discussed above, a main tray drawing system for drawing the main tray 
towards the inserted position is constituted by the rack 12, the pinion 
gear 15 and other component parts. The loading drive system for drawing 
one of the stacked subtrays from the stand-by position towards the loaded 
position and also for causing the clamp device to claim the optical disc 
placed on the subtray then drawn to the loaded position in response to 
completion of the drawing of such subtray is constituted by the gears 38, 
39a to 39i, the sector gear 42, the loading hook member 49, the clamp 
drive rack 76, the clamp support plate 79 and other component parts. Also, 
the elevating system for selectively lifting and lowering the loading 
drive system in a direction parallel to the direction, in which the 
subtrays are stacked one above the other on the main tray 1, so that one 
of the stacked subtrays on the main tray 1 then held at the inserted 
position can be drawn towards the loaded position is constituted by the 
large-diameter gear 63, the right and left guide plates 66R and 66L and 
other component parts, and a first drive switching means for transmitting 
rotation of the drive motor 19 selectively to one of the main tray drawing 
system and the loading drive system is constituted by the main gear 
assembly 17 and other component parts. 
A second drive switching means interposed between the drive motor 19 and 
the first drive switching means for transmitting rotation of the drive 
motor 19 selectively to one of the first drive switching means and the 
elevating system is constituted by the intermittent gear 56, the idler 
gear 30, the solenoid unit 61 and other component parts. Accordingly, even 
though the single drive motor 19 is employed in the practice of the 
present invention, drawing of the main tray, the loading of the optical 
disc and the selective lifting and lowering of the loading device can be 
accomplished by respective switching operations of the first and second 
drive switching means. 
Also, when the safety ejection lever 85 is manipulated when the loading of 
the optical disc has been completed, the loading drive system is reversed 
to return the subtray and the optical disc then held at the loaded 
position back to the stand-by position, and further manipulation of the 
safety ejection lever 85 results in reversed rotation of the main tray 
drawing system to return the main tray then held at the inserted position 
back to the withdrawn position. Accordingly, even though the drive motor 
19 is halted, all of the optical discs on the respective subtrays can be 
ejected out of the drive housing. 
Although in the foregoing embodiment the main gear assembly 17 has been 
described as manually rotated by means of the safety ejection lever 85, 
the use of the safety ejection lever 85 is not always essential in the 
practice of the present invention. Where no safety ejection lever 85 is 
employed, the unloading and the subsequent return of the main tray back to 
the withdrawn position can be accomplished by manually rotating the main 
gear assembly 17 directly while the lid 4 is opened as shown in FIG. 2. 
[Forced Ejector--Second Embodiment] 
A second embodiment of the forced ejector for forcibly ejecting the main 
tray carrying the subtrays back to the withdrawn position will now be 
described. As shown in FIG. 42, the main gear assembly 17 has its surface 
formed with a plurality of key-shaped projections (engagements) 99a to 99d 
for engagement with a free end of a safety ejection rod (an auxiliary 
drive member) 103 adapted to be inserted from outside of the drive housing 
2. 
While in the condition shown in FIG. 42 and the apparatus malfunctions by 
any reason, the lid 4 has to be opened manually and the safety ejection 
rod 103 should then be inserted to extend into a gap between the main tray 
1, then inserted into the disc chamber, and the main gear assembly 17 
until the free end of the safety ejection rod 103 is brought into 
engagement with the key-shaped projection 99a. Starting from this 
condition, the safety ejection rod 103 has to be pushed in a direction 
shown by the arrow W to rotate the main gear assembly 17 to a position 
shown by the double-dotted chain line to thereby release the optical disc 
from the clamp device. Since the key-shaped projections 99a to 99d are so 
shaped as to represent a generally channel-shape, the free end of the 
safety ejection rod 103 once engaged with any one of the key-shaped 
projections 99a to 99d will not be disengaged therefrom during rotation of 
the main gear assembly 17. 
As the safety ejection rod 103 is pushed in the direction of the arrow W, 
the safety ejection rod 103 will no longer be pushed because the next 
succeeding key-shaped projection 99b is brought into contact with the 
safety ejection rod 103 as shown in FIG. 43. Once this occurs, the safety 
ejection rod 103 should be withdrawn a certain distance in a direction 
counter to the direction of the arrow W and be again pushed t allow the 
free end thereof to be engaged with the next succeeding key-shaped 
projection 99b. This procedure is repeated four times as shown in FIGS. 42 
to 45 until the main gear assembly 17 is rotated an angular distance 
corresponding to the angular distance from the key-shaped projection 99a 
to the key-shaped projection 99d. By so doing, the main tray 1 can be 
withdrawn a certain distance out of the drive housing 2 as shown in FIG. 
46 and a complete return of the main tray 1 back to the withdrawn position 
is accomplished when the user subsequently manually pulls the main tray 1. 
At that time, one or some of the subtrays positioned above the subtray then 
drawn to the loaded position remain within the disc chamber of the drive 
housing 2. In order that the entire number of the subtrays including such 
one or some of the subtrays can be withdrawn out of the drive housing 
together with the main tray 1, the subtrays 6.sub.1 to 6.sub.5 employed in 
the practice of the present invention are preferably made of synthetic 
resin having a relatively small thickness. In other words, in order for 
the subtray or subtrays remaining within the disc chamber to be removed 
out of the disc chamber, it or they should be elastically deformed to 
allow it or them to escape from engagement with the corresponding holder 
lever or levers 74.sub.1 to 74.sub.4. By so doing, the subtray or subtrays 
remaining within the disc chamber can be forcibly removed out of the disc 
chamber. 
As discussed above, a main tray drawing system for drawing the main tray 
towards the inserted position is constituted by the rack 12, the pinion 
gear 15 and other component parts. The loading drive system for drawing 
one of the stacked subtrays from the stand-by position towards the loaded 
position and also for causing the clamp device to claim the optical disc 
placed on the subtray then drawn to the loaded position in response to 
completion of the drawing of such subtray is constituted by the gears 38, 
39a to 39i, the sector gear 42, the loading hook member 49, the clamp 
drive rack 76, the clamp support plate 79 and other component parts, and 
the drive switching means is constituted by the main gear assembly 17 
formed by the intermittent gear. The drawing inhibiting means is 
constituted by the mode lock lever 101 having the pawl 110a adapted to 
drive the gear 38 to minimize the backlash. Accordingly, even though the 
single drive motor 19 is employed in the practice of the present 
invention, the subtray loading operation and the main tray drawing 
operation can be accomplished with no phase shift occurring therebetween. 
Also, since the safety ejection rod 103 is adapted to repeatedly inserted 
to sequentially engage with the key-shaped projections 99a to 99d fast 
with the main gear assembly 17, the subtray then held at the loaded 
position can be removed out of the drive housing together with the main 
tray. 
Furthermore, where the disc drive apparatus of the present invention is 
transported from place to place, the elevating table 40 is lowered to the 
lowermost position with the pins 40Ra and 40Rb, 40La and 40Lb rigid with 
the elevating table 40 supported in the respective vertical slots 69Ra and 
69Rb, 69La and 69Lb defined in the chassis. Accordingly, the drive 
apparatus of the present invention is robust against an external impact. 
[Positional Control of (n+1)th Subtray] 
The structural details of each of the subtrays 6.sub.1 to 6.sub.5 are shown 
in FIGS. 49 to 52. As shown therein, each subtray is of a generally 
rectangular configuration having a front edge formed with a pair of nails 
88 engageable in corresponding slots 87 defined in a front wall of the 
main tray 1 as shown in FIG. 51. Each subtray also has a rear portions 
formed with upper and lower pairs of spacer ribs 89a and 89b, the spacer 
ribs 89a of the upper pair protruding outwardly from an upper surface 
thereof and the spacer ribs 89b of the lower pair protruding outwardly 
from the undersurface thereof. It is to be noted that the uppermost one of 
the subtrays 6.sub.1 to 6.sub.5 stacked on the main tray 1 is shown as 
having mounted thereon an optional adaptor 99 with which an optical disc 
D.sub.8 of a smaller diameter can be placed on the subtray. 
So long as the main tray 1 is held at the withdrawn position, the stacked 
subtrays 6.sub.1 to 6.sub.5 are uniformly spaced within the main tray with 
the nails 88 engaged in the respective slots 87 in the front wall of the 
main tray and with the lower pair of the spacer ribs 89b of one subtray 
resting on the upper pair of the spacer ribs 89a of the subtray 
immediately above such one subtray as shown in FIG. 52A. 
However, when the main tray 1 having the subtrays 6.sub.1 to 6.sub.5 
stacked thereon is moved to the inserted position, the respective rear 
portions of the subtrays 6.sub.1 to 6.sub.5 are supported by the fixed 
guide blocks 11a and 11b, as shown in FIG. 52B, with the ribs 10 engaged 
in the grooves 8 each defined between the neighboring subtrays stacked on 
the main tray 1 as hereinbefore described. Accordingly, as compared with 
the case in which holding members are used and provided in the main tray 
to keep the respective rear portions of the stacked subtrays apart from 
each other, the position of any one of the subtrays 6.sub.1 to 6.sub.5 
stacked on the main tray 1 relative to the loading mechanism can be 
accurately controlled. 
Since according to the present invention such holding members need not be 
employed, the drive apparatus as a whole can be assembled compact by 
disposing on both sides of the path of movement of the main tray 1 a lock 
mechanism for the subtrays such as comprised of the first to fourth holder 
levers 74.sub.1 to 74.sub.4 disposed in a space in front of the fixed 
guide block 11a. 
It is to be noted that although in FIG. 15 a portion of the lock mechanism 
for the subtrays and the fixed guide block 11a have been shown as formed 
integrally with the holder 73, in the example shown in FIG. 53 the subtray 
lock mechanism and the fixed guide block 11a are shown as members separate 
from each other. 
Referring now to FIG. 53, the fixed guide block 11a shown therein has 
defined therein holding passages 91.sub.1, to 91.sub.5 for supporting the 
respective subtrays 6.sub.1 to 6.sub.5, and is formed with guide 
projections 91a, each protruding a slight distance upwardly into the 
associated holding passages 91.sub.1 to 91.sub.5, and control projections 
91b each operable to suppress any possible lateral displacement of the 
subtrays and protruding a slight distance downwardly into the associated 
holding passages 91.sub.1 to 91.sub.5 and positioned forwardly of the 
corresponding guide projection 91b with respect to the direction of 
insertion of the main tray 1. Each guide projection 91a is engageable in a 
groove (See FIGS. 50 and 54) delimited by the L-sectioned support step 7, 
formed on the undersurface of each subtray 6.sub.1 to 6.sub.5, to suppress 
any possible lateral displacement of the subtray in a direction generally 
perpendicular to the direction of movement of the main tray 1 between the 
withdrawn and inserted positions. The function of the control projections 
91b will further be described in detail later. 
A front end of the groove delimited by the support step 7 on one side edge 
of each subtray 6.sub.1 to 6.sub.5 is formed with a recess 92 as shown in 
FIGS. 50 and 54. FIG. 55A illustrates the condition in which the subtray 
is being loaded and FIG. 55B illustrates the condition in which the 
subtray is loaded to a position a slight distance preceding the loaded 
position. The recess 92 in each of the subtrays 6.sub.1 to 6.sub.5 is so 
positioned that when the subtray is loaded to the position shown in FIG. 
55B, the associated guide projection 91a can be engaged in such recess 92. 
Accordingly, as shown in FIG. 55B, when one of the subtrays 6.sub.1 to 
6.sub.5 is loaded, the front end of such subtray is lowered a distance 
corresponding to the depth of the recess 92. 
Also, as shown in FIGS. 51 and 55, the elevating table 40 includes a 
depressing means such as a depressor member 93 fixed thereto, with which 
one of the subtrays drawn out from the stack engages during its movement 
from the position a slight distance preceding the loaded position to the 
loaded position. As shown in FIG. 55B, shortly before the loading is 
completed, the spacer ribs 89b in each subtray are engaged in respective 
recesses 93a defined in a lower surface portion of the depressor member 93 
defining a guide groove in cooperation with an upper surface portion 
thereof, while the rear portion of the subtray is depressed downwardly in 
contact with a projection 93a defined in the upper surface defining the 
guide groove in the depressor member 93. Accordingly, not only is the 
front end of the subtray lowered, but the rear portion thereof is also 
lowered, as the subtray then drawn towards the loaded position approaches 
the loaded position. 
One of the subtrays 6.sub.1 to 6.sub.5 so drawn to the loaded position in 
the manner described above is, after having passed through a gap in the 
clamping device for clamping and driving the optical disc, lowered a 
slight distance to thereby minimize the amount of movement of the clamp 
device that takes place when the latter clamps the optical disc. 
When the subtray drawn towards the loaded position is, after having been 
lowered in the manner described above, further drawn to a completely 
loaded position, a first projection 94a formed on the upper surface of the 
n-th subtray then drawn form the stack of the subtrays on the main tray 1 
is brought into engagement with a second projection 94b formed on the 
undersurface of the (n+1)th subtray (that is, another one of the subtrays 
positioned immediately above the n-th subtray). Where the n-th subtray is 
represented by the subtray 6.sub.4 and the (n+1)th subtray is hence 
represented by the subtray 6.sub.5, the subtray 6.sub.5 is, upon 
engagement of the first projection 94a integral with the subtray 6.sub.4 
with the second projection 94b integral with the subtray 6.sub.5, pivoted 
a slight angle upwardly about the point of engagement between each nail 88 
integral with the (n+1)th subtray 6.sub.5 and the associated slot 87 in 
the front wall of the main tray 1 to expand the space between it and the 
n-th subtray 6.sub.4 then drawn to the loaded position as shown in FIG. 
56. It is to be noted that in order to avoid the possibility of the first 
projection 94a constituting an obstacle to reduction in thickness of the 
main tray 1, each of the subtrays 6.sub.1 to 6.sub.5 employed in the 
practice of the present invention has its undersurface formed with a 
recess 95 for accommodating therein the first projection 94a integral with 
the subtray immediately below the respective subtray when the subtrays are 
stacked on the main tray 1. 
Thus, it is clear that even though the space between the neighboring 
subtrays 6.sub.1 to 6.sub.5 stacked on the main tray is minimized to 
eventually reduce the size of the disc drive apparatus of the present 
invention, the space between the n-th subtray and the (n+1)th subtray is 
substantially expanded during playback of the optical disc and, therefore, 
the optical disc resting on the n-th subtray will not interfere with the 
(n+1)th subtray to accomplish a stabilized operation. 
In addition to the n-th subtray designed to push the (n+1)th subtray 
upwardly as described above, the n-th subtray does also push the (n+1)th 
subtray upwardly when the n-th subtray is lowered from the stand-by 
position and, therefore, the space between the n-th subtray held at the 
loading position and the (n+1)th subtray can be expanded to a size larger 
than that accomplished in the prior art optical disc drive apparatus. In 
other words, even though the space between each neighboring subtrays 
6.sub.1 to 6.sub.5 stacked on the main tray is further minimized, a 
stabilized operation can be attained in a manner similar to that 
accomplished with the prior art optical disc drive apparatus. Also, the 
lowering of the n-th subtray takes place at a timing earlier than the 
upward push of the (n+1)th subtray and, therefore, there is no possibility 
that the lowering of the n-th subtray and the upward push of the (n+1)th 
subtray take place simultaneously, not the possibility that where the 
upward push of the (n+1)th subtray takes place at a timing earlier than 
the lowering of the n-th subtray, the n-th subtray and the (n+1)th subtray 
may move up and down simultaneously. Thus, with the optical disc drive 
apparatus of the present invention, the stabilized operation can be 
obtained. 
The function of the control projections 91b formed in the fixed guide block 
11a for suppressing any possible lateral displacement of the subtrays will 
now be described. 
Each control projection 91b is so formed and so positioned in the fixed 
guide block 11a relative to the (n+1)th subtray 6.sub.5 then held at the 
stand-by position as to occupy a position above a hole 96 defined in each 
subtray as shown in FIG. 58A. In this condition, the guide projection 91a 
is engaged in the groove delimited by the corresponding L-sectioned 
support step 7. 
Even though the guide projection 91a is disengaged from the groove 
delimited by the support step 7 in the subtray 6.sub.5 as a result of the 
(n+1)th subtray 6.sub.5 having been pushed upwardly by the n-th subtray 
6.sub.4, the control projection 91b is engaged in the hole 96 in the 
subtray 6.sub.5 as shown in FIG. 58B to prevent the subtray 6.sub.5 from 
being laterally displaced in position so that when the n-th subtray 
6.sub.4 is returned to the stand-by position, the guide projection 91a can 
be assuredly engaged in the groove delimited by the support step 7 in the 
(n+1)th subtray 6.sub.5 to thereby restore to the initial condition. In 
other words, the (n+1) subtray 6.sub.5 can be pushed upwardly a 
considerable distance sufficient for the guide projection 91a to separate 
away from the groove delimited by the support step 7 in the (n+1)th 
subtray 6.sub.5 and, therefore, even though the space between the 
neighboring subtrays is further minimized, the stabilized operation can be 
obtained in a manner comparable to that accomplished in the prior art disc 
drive apparatus. 
While the foregoing description has been made in connection with the n-th 
subtray represented by the fourth subtray 6.sub.4, a similar description 
equally applies to any one of the other subtrays 6.sub.1 to 6.sub.3. 
As discussed above, since the first projection 94a is provided in each of 
the subtrays 6.sub.1 to 6.sub.5, there may be an undesirable possibility 
that when the n-th subtray is to be drawn towards the loaded position, the 
first projection 94a in the n-th subtray may contact the (n+1)th subtray 
to move the latter. In this respect, when the n-th subtray is to be 
loaded, the corresponding one of the first to fourth holder levers 
74.sub.1 to 74.sub.4 is engaged with the (n+1)th subtray to hold the 
latter at the stand-by position. 
In the holder 73 of the structure shown in FIG. 15, only the resilient 
force exerted by each leg 75b is utilized to urge the respective hook 75c 
to engage in the associated recess 6a in any one of the subtrays 6.sub.1 
to 6.sub.5 and, therefore, there may be a possibility that the (n+1)th 
subtray may move against the resiliency of the associated leg 75b. An 
alternative embodiment of the holder 73 designed to eliminate this 
possibility will now be described with particular reference to FIGS. 53 
and 59 to 61. 
[Alternative Embodiment of Holder 73] 
In the alternative embodiment shown in FIGS. 53 and 59 to 61, each of the 
holder levers and the corresponding cam projections 66.sub.1 to 66.sub.4 
have respective shapes different from that employed in the embodiment 
shown in FIG. 15. 
Specifically as shown in FIG. 53, a cam plate 97 is fixedly secured to the 
left guide plate 66L slidable relative to the left side wall 13L of the 
drive housing 2, and a holder support block 98 is secured to the left side 
wall 13L. The holder support block 98 has an upright pin 98a formed 
therein and on which first to fourth holder levers 74.sub.10 to 74.sub.40 
are pivotally mounted for detecting respective shapes of cam elements 
formed in the cam plate 97. 
The cam plate 97 is formed with first to eighth cam elements 97.sub.1 to 
97.sub.8, the odd-numbered and even-numbered cam elements being spaced an 
equal distance in a direction perpendicular to the longitudinal sense of 
the left side wall 13L. The first holder lever 74.sub.10 has one end 
formed with a first feeler 74a for detecting the first cam element 
97.sub.1 and also has the other end formed with a hook 74c engageable in 
the recess 6a in the associated subtray 6.sub.5 and a second feeler 74b 
for detecting the second cam element 97.sub.2. This first holder lever 
74.sub.10 has an engagement piece 74d formed on an upper surface region of 
the end thereof adjacent the first feeler 74a and an engagement recess 74e 
defined on an undersurface of that end thereof adjacent the first feeler 
74a for receiving therein the engagement piece 74d integral with the 
second holder lever 74.sub.20. 
Any one of the second to fourth holder levers 74.sub.20 to 74.sub.40 is of 
a structure identical with that of the first holder lever 74.sub.10 
discussed above, and all of the holder levers 74.sub.10 to 74.sub.40 are 
stacked one above the other and are in turn mounted on the upright pin 98a 
for pivotal movement about such upright pin 98a with the engagement piece 
74d in one holder lever loosely received in the engagement recess 74e in 
the holder lever immediately above such one holder lever. 
FIGS. 59A to 59D illustrate respective conditions of the first to fourth 
holder levers 74.sub.10 to 74.sub.40 assumed at the time the elevating 
table 40 is held at the first stop position at which the uppermost subtray 
6.sub.5 is to be drawn towards the loaded position. As shown therein, the 
first feelers 74a of the first to fourth holder levers 74.sub.10 to 
74.sub.40 are in position to detect the respective first, third, fifth and 
seventh cam elements 97.sub.1, 97.sub.3, 97.sub.5 and 97.sub.7 with the 
corresponding hooks 74c disengaged from the recesses 6a in the subtrays 
6.sub.1 to 6.sub.5. 
On the other hand, FIGS. 60A to 60D illustrate respective conditions of the 
first to fourth holder levers 74.sub.10 to 74.sub.40 assumed at the time 
the elevating table 40 is held at the second stop position at which the 
subtray 6.sub.4 immediately below the uppermost subtray 6.sub.5 is to be 
drawn towards the loaded position. In this condition, the first holder 
lever 74.sub.10 is in position to detect the second cam element 97.sub.2 
and the hook 74c of such first holder lever 74.sub.10 is consequently 
engaged in the recess 6a in the uppermost subtray 6.sub.5 while the second 
to fourth holder levers 74.sub.20 to 74.sub.40 remain in the same position 
as shown in FIGS. 59B to 59D. Thus, when the fourth subtray 6.sub.4 
immediately below the uppermost subtray 6.sub.5 is to be drawn towards the 
loaded position, the second feeler 74b of the first holder lever 74.sub.10 
is engaged with the second cam element 97.sub.2, thereby locking the first 
holder lever 74.sub.10 in position to not pivot in a direction required 
for the corresponding hook 74c to disengage from the recess 6a in the 
uppermost subtray 6.sub.5, and therefore, the uppermost subtray 6.sub.5 is 
held immovable even though the fourth subtray 6.sub.4 is drawn towards the 
loaded position. 
FIGS. 61A to 61D illustrate respective conditions of the first to fourth 
holder levers 74.sub.10 to 74.sub.40 assumed at the time the elevating 
table 40 is held at the third stop position at which the subtray 6.sub.3 
is to be drawn towards the loaded position. As shown therein, the second 
feeler 74b of the second holder lever 74.sub.20 is in position to detect 
the fourth cam element 97.sub.4 with the hook 74c of such second holder 
lever 74.sub.20 engaged in the recess 6a in the fourth subtray 6.sub.4. In 
this condition, the first holder lever 74.sub.10 is held in position with 
its feelers 74a and 74b disengaged from the associated first and second 
cam elements 97.sub.1 and 97.sub.2, but the engagement piece 74d of the 
second holder lever 74.sub.20 is engaged in the engagement recess 74e in 
the first holder lever 74.sub.10 to thereby urge the first holder lever 
74.sub.10 about the upright pin 98a in a direction required for the hook 
74c of the first holder lever 74.sub.10 to engage in the recess 9a in the 
uppermost subtray 6.sub.5. Thus, when the third subtray 6.sub.3 is to be 
drawn towards the loaded position, the second holder lever 74.sub.20 has 
its second feeler 74b brought into abutment with the fourth cam element 
97.sub.4 and the second holder lever 74.sub.20 is therefore locked in 
position not to pivot in a direction required for the corresponding hook 
74c to disengage from the recess 6a in the fourth subtray 6.sub.4. At the 
same time, because of the engagement of the engagement piece 74d in the 
second holder lever 74.sub.20 into the engagement recess 74e in the first 
holder lever 74.sub.10 as discussed above, the first holder lever 
74.sub.10 is also locked in position not to pivot in a direction required 
for the corresponding hook 74c to disengage from the recess 6a in the 
uppermost subtray 6.sub.5. Accordingly, the uppermost and next succeeding 
subtrays 6.sub.5 and 6.sub.4 are held immovable even though the third 
subtray 6.sub.3 is drawn towards the loaded position. 
Similarly, when the second subtray 6.sub.2 is to be drawn towards the 
loaded position, the hook 74c of the third holder lever 74.sub.30 is 
engaged in the recess in the third subtray 6.sub.3 and the second holder 
lever 74.sub.20 is urged by the third holder lever 74.sub.30 in a 
direction required for the hook 74c of the second holder lever 74.sub.20 
to engage in the recess of the fourth subtray 6.sub.4 and the first holder 
lever 74.sub.10 is urged by the second holder lever 74.sub.20 in a 
direction required for the hook 74c of the first holder lever 74.sub.10 to 
engage in the recess of the uppermost or fifth subtray 6.sub.5, resulting 
in that the third to fifth subtrays 6.sub.3 to 6.sub.5 are held immovable 
even though the second subtray 6.sub.2 is drawn towards the loaded 
position. 
Again similarly, when the first subtray 6.sub.1 is to be drawn towards the 
loaded position, the hook 74c of the fourth holder lever 74.sub.40 is 
engaged in the recess in the second subtray 6.sub.2 and the third holder 
lever 74.sub.30 is urged by the fourth holder lever 74.sub.40 in a 
direction required for the hook 74c of the third holder lever 74.sub.30 to 
engage in the recess of the third subtray 6.sub.3, the second holder lever 
74.sub.20 is urged by the third holder lever 74.sub.30 in a direction 
required for the hook 74c of the second holder leer 74.sub.20 to engage in 
the recess of the fourth subtray 6.sub.4, and the first holder lever 
74.sub.10 is urged by the second holder lever 74.sub.20 in a direction 
required for the hook 74c of the first holder lever 74.sub.10 to engage in 
the recess in the uppermost or fifth subtray 6.sub.5, resulting in that 
the second to fifth subtrays 6.sub.2 to 6.sub.5 are held immovable even 
though the first subtray 6.sub.1 is drawn towards the loaded position. 
As discussed above, the provision of the first to fourth holder levers 
74.sub.10 to 74.sub.40 in combination with the first to eighth cam 
elements 97.sub.1 to 98.sub.8 is effective to avoid the possibility that 
when the n-th subtray is to be drawn towards the loaded potion, the 
subtray or subtrays positioned above the n-th subtray may be erroneously 
moved rearwardly because of the presence of the first projection 94a on 
the upper surface of each of the subtrays 6.sub.1 to 6.sub.5. 
Also, the formation of the engagement piece 74d and the engagement recess 
74e in each of the first to fourth holder levers 74.sub.10 to 74.sub.40 is 
effective to permit one holder lever to be pivoted in response to the 
pivotal movement of the holder lever immediately below such one holder 
lever about the common upright pins 98a, allowing the use of the first to 
eighth cam elements 97.sub.1 to 97.sub.8 of a simplified configuration. 
More specifically, each of the second, fourth and sixth cam elements 
97.sub.2, 97.sub.4 and 97.sub.6 may have a reduced length and the width of 
the window 72 (See FIG. 14) as measured in a direction lengthwise of the 
left side wall 13L where it is defined can be reduced to compensate for 
any possible reduction in physical strength of the left side wall 13L 
which would otherwise result in because of the presence of the window 72. 
Although the present invention has been described in connection with the 
preferred embodiments thereof with reference to the accompanying drawings, 
it is to be noted that various changes and modifications are apparent to 
those skilled in the art. Such changes and modifications are to be 
understood as included within the scope of the present invention as 
defined by the appended claims, unless they depart therefrom.