Disk player system having a disk sucking function

A disk player system having a disk sucking function includes a disk sucking member of a configuration defining a suction space between it and a disk and a suction channel provided for communicating the suction space with an atmosphere about a center spindle or about a peripheral portion of the disk sucking member. A suction pump provided for sucking the disk is made detachable from a turntable so that a disk sucking operation is performed before the disk is played and the suction pump is detached when the disk is played. According to the system, deterioration of quality of the reproduced signal is prevented and a sucking efficiency is improved.

FIELD AND BACKGROUND OF THE INVENTION 
This invention relates to a disk player system incorporating a disk sucking 
device which causes an information record medium in the form of a disk 
such as a phonograph record disk and a video disk (hereinafter referred to 
as "disk") to be sucked to the upper surface of a turntable of the player 
system by producing a state of a reduced pressure below an atmospheric 
pressure (hereinafter sometimes referred to as "vacuum") and utilizing 
this state of the reduced pressure for the sucking of the disk. 
Disk sucking devices utilizing vacuum for sucking a disk to a turntable 
have been proposed for realizing reproduction of the disk in a desirable 
state in which warping of the disk is corrected by keeping the disk sucked 
to the turntable. FIG. 1(a) shows one of such prior art devices disclosed 
in the specification of U.S. Pat. No. 4,065,135. In this prior art device, 
a channel communicating a suction space a with a suction pump b (indicated 
by arrows) is provided. This channel is formed partly through a rotatable 
member d along an axis of rotation L of the rotatable member d and partly 
through a stationary member e fixed to a chassis of the player. A 
switching valve V is provided on the channel. When a disk f is to be 
reproduced, the suction space a is caused to communicate with the suction 
pump b by changing over of the valve V and the suction pump b is actuated 
to produce vacuum in the suction space a and thereby to suck the disk f to 
a turntable c. When the disk f is to be removed from the disk, the suction 
space a is caused to communicate with the atmosphere by changing over the 
valve V so that air is let in the suction space a. In FIG. 1, reference 
characters g and h designate packings, i a center spindle and M a driving 
motor. 
The prior art disk sucking device in which the suction channel is provided 
in the turntable c is disadvantageous in that the device requires a 
complicated manufacturing process resulting in a high cost and that the 
device is not applicable to a turntable of an ordinary type of record 
reproduction system. Further, since the suction channel of this prior art 
device is formed through members which rotate relative to each other, 
sealing means must be provided between these relatively rotating members 
and this causes wow-flutter and adversely affects signal-to-noise ratio of 
reproduced signals. Furthermore, the suction channel in the prior art 
device is so long that sucking efficiency is rather low. 
A major problem in such disk sucking divice is that air leakage makes it 
difficult to maintain a state in which a disk is sucked to a turntable for 
a long period of time. For compensating for such air leakage, the above 
described prior art disk sucking device employs a method according to 
which the suction pump b is driven each time the vacuum in the suction 
space a decreases beyond a predetermined degree. This method, however, 
requires a control system for detecting the degree of vacuum in the 
suction space a and driving the suction pump b in response to a detected 
signal. Besides, driving of the suction pump b during reproduction of the 
disk causes vibration which deteriorates the signal-to-noise ratio. 
Another problem in such disk sucking device is to maintain an optimum 
degree of vacuum in the suction space. If the vacuum is too high, the disk 
sucked to the turntable will be injured whereas if the vacuum is too low, 
the disk will be disengaged from the turntable. 
There has also been proposed a disk sucking device as shown in FIG. 1(b). 
In this device, annular lip-like seal members j and k made of rubber are 
provided on a turntable c in such positions as will support a disk f in 
portions immediately inside of a groove guard fa and immediately outside 
of a label fb of the disk f. By evacuating air from a space a defined by 
these annular seal members j and k and the disk f, the disk f is sucked 
toward the turntable c with the seal members j and k serving as sort of 
suckers and warping of the disk f thereby is corrected. 
In this device, however, the periphery of the seal member j by which the 
disk f is sucked is liable to be bent downward to come apart from the disk 
f as shown in FIG. 1(c) so that the seal member j is in close contact with 
the disk f only in the limited portion indicated by reference character h 
and hence a seal thus provided is not entirely free from the air leakage. 
In order to enhance the sealing ability of the seal j, it could be made 
thinner but this would only result in a wavelike deformation of its 
periphery as shown in FIG. 1(d) thereby expediting the air leakage instead 
of reducing it. Same condition is also noted as to the seal member k. 
Further, the above described prior art devices have a relatively small area 
for supporting the disk and this is disadvantageous in that it allows 
warping of the disk due to the sucking force. 
SUMMARY OF THE INVENTION 
It is, therefore, a primary object of the present invention to provide a 
disk sucking system in which a suction pump provided for sucking a disk is 
made detachable from a turntable structure so that a disk sucking 
operation is performed before the disk is reproduced and the suction pump 
is detached while the disk is being reproduced. 
According to the invention, there is provided a disk player system having a 
disk sucking function comprising a turntable, means for driving said 
turntable, a disk sucking member of a configuration defining a suction 
space between said disk sucking member and a disk, means provided in said 
disk sucking member for defining a suction channel which communicates with 
said suction space at one end and with the atmosphere about a center 
spindle or about a peripheral portion of said disk sucking member at the 
other end, a check valve provided in said suction channel, and a suction 
device capable of being detachably connected to said turntable at about 
said center spindle for reducing pressure in said suction space and 
thereby causing said disk to be sucked to said disk sucking member, said 
suction device being disconnected from said turntable when said disk is 
reproduced. 
It is another object of the invention to provide a disk sucking system 
eliminating an adverse effect to the turntable and preventing 
deterioration of quality of the reproduced signal such as signal-to-noise 
ratio. 
It is another object of the invention to provide a disk sucking system 
having an improved sucking efficiency and being capable of maintaining a 
state in which the disk is sucked to the turntable for a sufficiently long 
time without occurrence of air leakage. 
It is another object of the invention to provide a disk sucking system 
capable of maintaining an optimum pressure for sucking a disk so as to 
prevent injury and warping of the disk and thereby eliminate deterioration 
of quality of a reproduced signal. 
It is another object of the invention to provide a disk sucking system in 
which a disk is stably supported by enlarging a disk support area. 
It is another object of the invention to provide a disk sucking system in 
which release of a disk from suction is facilitated. 
It is another object of the invention to provide a disk sucking system in 
which a disk sucking operation is simplified. 
It is still another object of the invention to provide disk sucking system 
which is applicable to a conventioned type of disk playing system. 
These and other objects and features of the invention will become apparent 
from the description made hereinbelow in conjunction with the accompanying 
drawings.

DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring first to FIG. 2, this embodiment of the invention is one in which 
the air is withdrawn upwardly through a gap between the periphery of a 
central opening of a disk and a spindle. The diameter of the central 
opening of the disk generally is slightly larger than the diameter of the 
spindle so that there is a gap, though it is a very narrow one, between 
the periphery of the central opening of the disk and the spindle. In the 
embodiment shown in FIG. 2, this gap is utilized to permit the air to be 
withdrawn from the space defined between the underside of the disk and the 
upper surface of a disk sucking member. 
A spindle or a disk locating pin 2 is fixedly provided in the center of a 
turntable 1. A disk sucking member 3 generally is of a disk shape and can 
be disposed on the turntable 1 by fitting the spindle 2 into a central 
opening 4 of the member 3. 
The disk sucking member 3 is composed of a metal sheet 5 and rubber sheets 
6 and 7 rigidly attached to the metal sheet 5. The metal sheet 5 is made, 
e.g., of aluminium or zinc. 
The outer rubber sheet 6 is provided for sucking the disk (not shown). For 
this purpose, the outer and inner edges of the rubber sheet 6 project 
upwardly to form seal portions 8 and 9. These seal portions 8 and 9 
respectively are of an annular shape so that, when the disk is placed on 
these seal portions 8 and 9, a space defined by the seal portions 8 and 9 
and the underside of the disk (hereinafter referred to as a suction space 
14) becomes airtight and the seal portions 8 and 9 serve as a sucker by 
withdrawing the air from the suction space 14 to draw the disk toward the 
upper surface of the rubber sheet 6. The rubber sheet 6 is formed with 
radially extending grooves 10 as shown in FIG. 3. These grooves are 
provided to prevent occurrence of difficulty in the evacuation of the air 
which could result by abutting of the disk against the upper surface of 
the rubber sheet 6. 
A suction hole 11 is formed in the botton of each groove 10. These holes 11 
are communicated with a space underside of the seal portion 9 through 
passageways 12. The air in the suction space 14 is withdrawn through the 
suction holes 11 and the passageways 12. 
A check valve 13 is provided between each suction hole 11 and its 
corresponding passageway 12. The check valve 13 is made, as shown in FIG. 
4 in an enlarged scale, of a resilient material one end of which is fixed 
to the underside of the rubber sheet 6 in the portion defining the 
passageway 12. The check valve 13 functions to open only in the direction 
of withdrawing the air from the suction space 14. 
The check valve 13 may alternatively be composed of a projecting member 15 
which, as shown in FIG. 5, is simply placed on the bottom of the 
passageway 12 and has a projection 15a which projects upwardly in the 
suction hole 11. 
The suction channel may alternatively be defined, as shown in FIG. 6, by a 
suction hole 16 formed in the seal portion 9 and a check valve 17 attached 
to the seal portion 9 in a position where the valve can open or close the 
suction hole 16. 
Reverting to FIGS. 2 and 3, the rubber sheet 7 is formed with radially 
extending grooves 18. These grooves 18 are provided also to prevent 
occurrence of difficulty in the evacuation of the air from the suction 
space 14 resulting from abutment of the disk against the upper surface of 
the rubber sheet 7. The grooves 18 thus serve to guide the air withdrawn 
from the passageways 12 to the outer periphery of the spindle 2. 
As shown in FIG. 3, the rubber sheet 6 is formed with annular grooves 19 
and 20 in addition to the radial grooves 10 and the rubber sheet 7 with 
annular grooves 21 annd 22 in addition to the radial grooves 18. With all 
these grooves 18, 19, 20, 21 and 22, the disk can be uniformly drawn to 
the upper surfaces of the rubber sheets 6 and 7 in all of the underside of 
the disk. As shown in FIG. 2, an elastic member 23, e.g. an adhesion tape 
or a felt sheet, is attached to the sucking member 3 along the outer 
peripheral portion thereof for enabling the sucking member 3 to be seated 
stably on the turntable. A tab 24 projecting outwardly from the seal 
portion 8 is provided for releasing the air from the suction space 14 by 
pulling the tab 24 downardly thereby to enable the disk to be disengaged 
from the sucking member 3. 
Another example of the disk sucking member 3 composed of a rubber sheet 
only without using a metal sheet is shown in FIG. 7. In this example, an 
inner annular seal 29 is buried in the upper portion of a rubber sheet 25 
and a recess 26 is formed in the lower portion of the rubber sheet 25. 
Suction holes 30 and 31 are formed in the rubber sheet 25 to communicate 
inner and outer grooves 27 and 28 formed in the rubber sheet 25 with the 
recess 26. A check valve 32 is provided on the underside of the rubber 
sheet 25 so as to cover the suction hole 31. A seal 33 is provided to 
cover the recess 26. 
FIG. 8 shows an example of a suction device for evacuating the air from the 
gap between the central opening of the disk and the spindle 2. The suction 
device includes an attachment 34 which covers the gap between the central 
opening of the disk and the spindle 2, a manually operated pump 35, lines 
36 and 37 connecting the attachment with the pump 35 and a pressure sensor 
38 provided between the lines 36 and 37. 
The attachment 34 is of a bell shape and made of an elastic material such 
as rubber. The attachment 34 is formed with an opening 39 which can be 
fitted with the spindle 2. The opening 39 is communicated with the line 36 
through a connection tube 40. The attachment 34 is also formed with 
vertical grooves 41 adjacent to and continuous with the opening 39 for 
introducing the air withdrawn from the gap between the central opening of 
the disk and the spindle 2 to the connection tube 40. A cross section cut 
along lines A--A in FIG. 8 is shown in FIG. 9. The attachment 34 has a 
skirt portion 42 which closely engages the surface of a label portion of 
the disk to define a seal. 
The manually operated pump 35 is provided for sucking the air from the 
suction space 14. The pump 35 is of a piston type and a stationary portion 
thereof includes a frame 43 and a bottom plate 45 fixed to the underside 
of the frame 43 by means of screws 44. A movable portion of the pump 35 
includes a piston 46 disposed inside the frame 43, an annular rubber sheet 
47 which is provided between the outer peripheral portion of the piston 46 
and the lower inside portion of the frame 43 for providing a seal for a 
space defined by the piston 46 and the frame 43, a rod 48 fixed rigidly to 
the piston 46 and projecting upwardly from the central portion of the 
frame 43 so that the piston 46 can be moved in a vertical direction and a 
handle 49 attached to the upper end of the rod 48. 
Seals 50 and 51 and an O-ring 52 are provided about the rod 48 to provide a 
seal between the rod 48 and the frame 43. An upright portion 53 is 
provided in the upper surface of the frame 43 to provide communication 
between the space defined by the upper surface of the piston 46 and the 
frame 43 and the line 37. A check valve 54 is provided in the upper 
portion of the frame which check valve 54 is opened only when the piston 
46 is lifted so as to release the air from the space defined by the piston 
46 and the frame 43 outside. A hole 55 is formed in the bottom plate 45 
for releasing the air below the piston 46. A groove 56 is formed in the 
lower end portion of the frame 43 to receive the lower end portion of the 
rubber sheet 47. 
The pistion 46 is made of a suitable material, e.g. an ABS resin. The 
piston 46 is attached to the rubber sheet 47 by means of screws 57. Iron 
plates 58 are provided between the screws 58 and the rubber sheet 47 to 
provide sealing between the piston 46 and the rubber sheet 47. 
A helical spring 59 is provided between the lower surface of the piston 46 
and the bottom plate 45. This helical spring 59 urges the piston 46 
upwardly. 
For operating the pump 45, the handle 49 is pushed down by hand. The state 
of the movable portion of the pump 35 upon pushing down of the handle 49 
is shown by a two-dot-chain line. In this state, the piston 46 is in its 
lowermost position, compressing the helical spring 59 and causing the 
rubber sheet 47 to bulge upwardly thereby defining the space between the 
pistion 46 and the frame 43. Since the check valve 54 is closed when the 
piston 46 is lowered, the air is introduced from the line 36 into this 
space. When the handle is released, the piston 46 is pushed up by the 
helical spring 59 and the withdrawn air is released outside of the pump 35 
through the check valve 54. Thus, the evacuation operation is performed. 
In the embodiment shown in FIG. 8, no check valve is provided in the line 
37. It should be appreciated that no reverse flow of the air takes place 
when the pistion 46 is raised, for the check valve 13 (FIG. 2) provided in 
the turntable device is closed at this time. 
The pressure sensor 38 has couplings 60 and 61 on both sides thereof to 
which the lines 37 and 36 are respectively connected. The couplings 60 and 
61 are communicated with each other through a chamber 62 which has an open 
end. A metal diaphragm 63 of a partial spherical surface shape is provided 
in the open end of the chamber 62. When the pressure of the air in the 
suction channel has dropped below a certain predetermined level by 
operation of the pump 35, the diaphragm 63 is inverted, making a snapping 
sound. This makes a signal informing the person operating the device of 
completion of the sucking operation, i.e., a state in which the disc is 
sufficiently sucked to the sucking member 3. FIG. 10 is a top plan view of 
the pressure sensor 38. 
The sucking of the disk to the disk sucking member shown in FIG. 2 by the 
operation of the suction device shown in FIG. 8 is conducted in the 
following manner. 
First, a disk 64 is placed on the turntable device as shown in FIG. 11 (a). 
The attachment 34 is placed on the disk 64 in such a manner that the 
spindle 2 is fitted with the opening 39 of the attachment 34. In this 
state, the disk 64 is in abutting engagement with the seal portion 8 and 9 
and the skirt portion 42 of the attachment 34 is in close engagement with 
a label portion 64a of the disk 64. Upon operating the pump 35, the air in 
the suction space 14 is introduced into the space under the seal 9 through 
the hole 11, check valve 13 and hole 12. The air is further introduced to 
the space about the surface of the spindle 2 through a space defined 
between the inner rubber sheet 7 and the lable portion 64a of the disk 64 
and then enters the attachment 34 through a gap d formed between the wall 
of a central opening 64b of the disk 64 and the spindle 2. The air is 
ultimately sucked into the pump 35 through the groove 41, line 36, 
pressure sensor 38 and line 37. Since the suction space 14 is interrupted 
from the atmosphere in this state, the pressure of the air in the suction 
space 14 gradually drops. The disk 64 therefore is lowered until the the 
label portion 64a abuts against the upper surface of the rubber sheet 7 as 
shown in FIG. 11 (b). Upon reaching this state, the diaphragm 63 of the 
pressure sensor 38 is inverted and makes a snapping sound, thereby 
informing completion of the sucking operation. Upon disengaging the 
attachment 34 from the spindle 2, the check valve 13 is closed and the 
disk 64 is held in a state in which it is sucked to the turntable device 
with the seal portions 8 and 9 serving as suckers. Reproduction of the 
disk 64 is then started by rotating the disk 64 in this state. For 
releasing the disk 64, the tab 24 is pulled down to let the outside air 
into the suction space 14. 
In the embodiment shown in FIG. 2, a hand-operated device is employed as 
the suction device. Alternatively, the suction device may be composed of 
an automatic type structure such as one operated by the electric motor. 
Further, the evacuation of the air may be achieved simply by depressing 
the disk by hand without using the suction device shown in FIG. 8. 
It should be noted that the informing of completion of the sucking 
operation is achieved alternatively by a display device such as a meter 
device, instead of above-mentioned sound information. 
The above-mentioned embodiments utilizes the gap defined between the 
central opening of the disk and the spindle for evacuating the air. It 
should be appreciated, however, that the following alternatives may also 
be utilized. 
(A) FIG. 12(a) shows a disk sucking system wherein a spindle 2 is formed 
with vertical grooves 2a at its periphery for the purpose of facilitating 
the evacuating of the air. Same reference numerals as in the above 
embodiments are used to designate similar parts and explanation thereof is 
omitted. The suction device as shown in FIG. 8 is utilized. 
(B) FIG. 12(b) illustrates another disk sucking system wherein passages to 
guide the sucked air are provided through a spindle 2 rather than on its 
periphery. More specifically, a passage 2b is made through the spindle 2 
along its axis and communicates in the vicinity of its lower end with 
passages 2c formed radially through the spindle 2. The passage 2c are 
provided such that they can communicate with grooves 18 of a rubber sheet, 
i.e. on a level of an annular groove 22 adjacent the periphery of the 
spindle 2. The suction device as shown in FIG. 8 is also utilized. Similar 
parts to those of the above embodiments are also designated by same 
reference numerals and explanation thereof is omitted. It should be noted 
that the vertical grooves 41 formed on the inner wall of the attachment 34 
may be omitted. 
(C) Suction channels may be alternatively provided by forming notches at a 
central opening of a disk as shown in FIG. 12(c) instead of on or through 
the spindle itself. A disk 70 shown in FIG. 13 is formed at the periphery 
of its central opening 71 with a plurality of notches 75 which allow space 
between the spindle and the central opening 71 of the disk 70 for the 
sucked air to pass through. Alternatively, the central opening may be 
formed as polygons 76a to 76d to circumscribe the spindle 2, respectively 
as shown in FIGS. 14(a) to 14(d). FIG. 12(c) illustrates the disk 70 shown 
in FIG. 13 being sucked by the disk sucking system shown in FIG. 2 using 
the suction device illustrated in FIG. 8. The air confined beneath the 
disk 70 is withdrawn into the attachment 34 of said suction device through 
the notches 75 of the disk 70. 
(D) FIG. 15 shows a disk 80 through which one or more perforations 83 are 
formed in its label portion 82 instead of notches provided at its central 
opening 81. FIG. 12(d) shows the disk 80 being sucked by the disk sucking 
system illustrated in FIG. 2. In this example, the annular groove 22 needs 
to be large enough so that the perforations 83 may not be abutted by the 
rubber sheet 7. The opening 39' of the attachment 34' needs to be so 
formed as to cover the perforations 83 overall. 
The openings 39 and 39' of the attachments 34 and 34', respectively, are 
both so made as to fit the spindle 2 in order that the sucking operation 
may be performed without requiring the operator's hand pressing thereon. 
When, therefore, held in contact with the disk by the operator's hand, the 
opening of the attachment, as exemplified by an opening 91 of an 
attachment 90 shown in FIG. 16, does not have to be so formed as to fit 
the spindle 2. 
Another example of the attachment of the suction device according to the 
invention comprises a stabilizer therein. The attachment so made is 
advantageous in that the weight of the stabilizer aids in sucking air from 
the suction space thereby facilitating the sucking operation and also 
serves to keep a disk sucked for a long period of time and stabilized 
during reproducing. Shown in FIG. 17 for example, is an attachment 100 
which comprises a stabilizer 101 and a connection member 110 detachably 
connected to the stabilizer 101. The stabilizer 101, which is set on the 
disk placed on the disk sucking member aids in the sucking operation as 
well as serves to keep the disk stably disposed on the disk sucking member 
while reproduction. The stabilizer 101 is of a columnar shape and made of 
relatively heavy material such as brass. The stabilizer 101 is provided 
along its axis throughout with a passageway 103 for the spindle 2 to 
enter. The lower end of the passageway 103 is formed straight so as to fit 
the spindle 2 and is provided with vertical grooves 103a for permitting 
the sucked air into the passageway 103. The upper end of the passageway 
103 is funnel-shaped or coned about 15 deg. to the axis so as to 
facilitate locating of the connection member 110 therein. The stabilizer 
101 has on its bottom an O-ring 104 to secure sealed connection between 
the disk and the stabilizer 101. FIG. 18 is a bottom view of the 
stabilizer 101. The connection member 110, which is fixed at the end of 
the line 36, serves to connect or disconnect the line 36 to or from the 
stabilizer 101. More specifically, the connection member 110 is connected 
to the passageway 103 of the stabilizer 101 to perform the sucking 
operation and disconnected therefrom when the operation is completed, 
leaving the stabilizer 101 on the disk for stable rotation thereof during 
reproduction. The connection member 110 has a duct 111 formed therethrough 
and comprises an O-ring 112 attached thereto to ensure airtight insertion 
of the connection member 110 into the passageway 103 of the stabilizer 
101. Further, the connection member 110 is formed with a flange 113 to 
rest on the coned portion provided at the upper end of the passageway 103 
of the stabilizer 101. 
In order to perform a sucking operation using the attachment 100 with the 
disk sucking system shown in FIG. 2, the disk 64 is first placed on the 
disk sucking member, and the stabilizer 101 is located on the disk 64 by 
the spindle 2, as shown in FIG. 19(a), causing the disk 64 to be depressed 
by the weight of the stabilizer 101. As a result, the air in the suction 
space 14 is forced out toward the space under the seal portion 9 through 
the hole 11, check valve 13 and passage 12. The air is then introduced to 
the space about the surface of the spindle 2 through the space defined 
between the inner rubber sheet 7 and the label portion 64a of the disk 64 
and then reaches the bottom of the stabilizer 101 through the gap d 
allowed between the wall of the central opening 64b of the disk 64 and the 
spindle 2. The air then passes through the grooves 103a and the passageway 
103 to be finally let out into the atmosphere. The connection member 110 
is now inserted into the passageway 103 of the stabilizer 101 and a manual 
pump such as shown in FIG. 8 (not shown) is operated. By operating the 
pump, air is further withdrawn from the suction space 14 and introduced, 
after running through said suction channel, into the pump through the duct 
111 of the connection member 110 and line 36. This causes the disk 64 to 
be lowered until the label portion 64a abuts the upper surface of the 
rubber sheet 7 as shown in FIG. 19(b). Upon detaching the conection member 
110 from the stabilizer 101, the check valve 13 is closed to allow the 
disk 64 to remain sucked to the turntable device with the seal portions 8 
and 9 serving as suckers. Reproduction of the disk 64 is then started by 
rotating it with the stabilizer 101 serving to ensure stable rotation of 
the disk 64. For releasing the disk 64, the stabilizer 101 is removed and 
the tab 24 is pulled down to let the outside air into the suction space 
14. The grooves 103a made at the passageway 103 of the stabilizer 101 may 
be dispensed with by alternatively providing a suction channel on or 
through the spindle 2 as shown in FIG. 12(a) or 12(b). 
While the passageway 103 of the stabilizer 101 establishes direct 
communication between its lower end to receive the spindle 2 and its upper 
end to engage the connection member 110, a suction channel through the 
stabilizer may be otherwise provided as illustrated in FIG. 20, wherein a 
stabilizer 121 is formed with a hole 122 to receive the spindle 2, a 
separately provided opening 123 to locate the connection member 110 and 
passages 124 and 125 joining the opening 123 from below inside the O-ring 
104. 
In all of the embodiments described above, the air evacuated from the 
suction space is sucked from above the turntable but it may be sucked from 
the periphery of the turntable, as exemplified in FIG. 21, with a suction 
channel as simple as in the preceding embodiments. 
The disk sucking system shown in FIG. 21 comprises a turntable 131 and a 
sub-turntable 133 mounted thereon. The sub-turntable 133 has, on its upper 
surface, annular soft rubber seal portions 134 and 135 which support a 
portion immediately inside of the groove guard of a disk (not shown) and 
immediately outside of the label portion, respectively. A sheet 142 is 
formed with radially extending grooves 136 so as to prevent occurrence of 
difficulty in the evacuation of the air which could result by abutting of 
the disk against the upper surface of the sheet 142. A suction space 14 
communicates with the atmosphere by an opening 137 made in each of the 
grooves 136 and by a passage 138 opening at the periphery of the 
subturntable 133. A check valve 141 is provided between each suction 
opening 137 and its corresponding passage 138. While a disk is sucked, the 
check valve 141 is closed to prevent air from flowing back into the 
suction space 14. An inner sheet 139 of the sub-turntable 133, against 
which the label portion of the disk abuts, is formed with radially 
extending grooves 140. FIG. 22 is a top plan view of the turntable device 
shown in FIG. 21. FIG. 23 illustrates an attachment 144 to be used with 
the disk sucking system shown in FIG. 21. The attachment 144 is of a pipe 
structure and has a narrow end 144a to be inserted into the passage 138 of 
the sub-turntable 133. FIG. 24(a) illustrates the attachment 144 with the 
end 144a inserted in the passageway 138 of the sub-turntable 133 on which 
a disk 64 is placed. Upon operating a suction pump such as shown in FIG. 8 
(not shown), the air in the suction space 14 is introduced into the pump 
through the opening 137, check valve 141, passageway 138 and thence 
through attachment 144 and line 36. Since the suction space 14 is 
interrupted from the atmosphere, the pressure of the air in the suction 
space 14 gradually drops. The disk 145 therefore is lowered and remains 
sucked as shown in FIG. 24(b) while the air in the space below the label 
portion is let out through the gap d between the spindle 2 and the central 
opening of the disk 64. Upon pulling out the attachment 144 from the disk, 
the check valve 141 is closed to allow the disk 64 to stay sucked to the 
disk sucking system with the seal portions 134 and 135 serving as suckers. 
Reproduction of the disk 64 is then started by rotating the disk 64 in 
this state. 
FIG. 25 illustrates another embodiment of the disk sucking system according 
to the invention, which is provided with a passage opening at the 
periphery of the turntable. In FIG. 25, where the same reference numerals 
as used in FIG. 24 indicates the corresponding parts, a turntable 131' is 
provided with an opening 153 which establishes communication between a 
passageway 138' formed in a sub-turntable 133' and a passage 154 formed in 
the turntable 131'. The passage 154 opens at the periphery of the 
turntable 131' to communicate with the atmosphere. FIG. 26 shows an 
attachment 160 or a pressure sensor to be used with the embodiment 
illustrated in FIG. 25. The attachment 160 has couplings 162 and 163 on 
both sides thereof. The coupling 163 communicates with a suction pump (not 
shown) by a line 36 while the coupling 162 has an O-ring 165 about it for 
sealing. A chamber 161 has an open end wherein is provided a metal 
diaphragm 164 of a partial spherical surface shape. In order to conduct 
the sucking of a disk 64, the coupling 162 of the attachment 160 is 
inserted in the passage 154 of the turntable 131' and the suction pump is 
operated. When the suction has been fully conducted the diaphragm 164 of 
the attachment 160 is inverted as shown in FIG. 27 and makes a snapping 
sound, thereby informing completion of the sucking operation. 
While in all of the preceding embodiments, the sucking operation is 
performed with a suction seat mounted on a turntable, it may be 
alternatively conducted by first having a disk sucked to a suction seat 
separately provided from a turntable, thereafter removably placing the 
disk-loaded suction seat or sub-turntable on the turntable for 
reproduction of the disk, said sub-turntable being of a disk shape made of 
a sturdy material and formed with a suction channel therein which provides 
communication between the suction spaced defined above the upper surface 
of the sub-turntable and the underside or periphery thereof with a check 
valve provided halfway. 
Referring, for example, to FIG. 28, a sub-turntable 171 of a suction device 
170 is of a disk shape made of a sturdy material such as aluminum. A disk 
is sucked onto the sub-turntable 171 which in turn is mounted on a 
turntable (not shown). The sub-turntable 171 has a central opening 172 for 
a center spindle to enter. On the upper surface of the sub-turntable 171 
are fixedly attached liplike rubber seals 173 and 174 which respectively 
abut the portions immediately inside of the groove guard of a disk and 
immediately outside of the label portion. These seals 173 and 174 act as 
suckers to draw a disk. On the upper surface of the sub-turntable 171 are 
provided rubber abutments 175 arranged between the seals 173 and 174 at 
regular intervals annularly and radially. These abutments 175 serve to 
support the underside of the disk as it is sucked so that the disk may not 
be warped by low pressure in the suction space 14 caused by evacuation of 
air. The sub-turntable 171 is formed with a passage 176 to provide 
communication between the upper surface surrounded by the seals 173, 174 
and the underside of the sub-turntable 171. The passage 176 is provided to 
discharge the air withdrawn from the suction space 14 defined between the 
disk and the upper surface of the sub-turntable 171 and sealed by seals 
173 and 174. A check valve 177 is provided in the passage 176 to prevent 
air from flowing into the suction space 14 from an aperture 176a of the 
passage 176. FIG. 29 is a top plan view of the suction device 170 shown in 
FIG. 28. In order to perform the sucking operation with this embodiment, a 
disk 64 is placed on the suction device 170, whereon a bowl-shaped 
attachment 182, which communicates with a suction pump such as shown in 
FIG. 8 (not shown) by tube 181, is attached to the underside of the 
sub-turntable 171 so as to cover the aperture 176a as shown in FIG. 30(a), 
and the pump is operated to suck out air from the suction space 14. Upon 
completion of the sucking operation, the attachment 182 is disengaged from 
the sub-turntable 171 to close the check valve 177 as shown in FIG. 30(b), 
allowing the disk 64 to say sucked. The sub-turntable 171 is now ready to 
be mounted on a turntable 183 for reproduction of the disk 64 as shown in 
FIG. 30(c). 
The aperture 176a may be formed at the periphery of the sub-turntable 
instead of at the underside thereof as in the above embodiment. 
The disk sucking operation may be facilitated with the aid of an auxiliary 
suction device 185 as shown in FIG. 31. The auxiliary suction device 185 
is of a disk shape made of a sturdy material and formed with a protrusion 
186 at its center corresponding to the center spindle. The auxiliary 
suction device 185 is also formed with a passage 187 therein which joins 
the passage 176 provided in the suction device 170. The passage 187 
provides communication between the upper surface and the periphery of the 
auxiliary suction device 185. The passage 187 has a protruded end 191 to 
engage with an attachment 189 which communicates by a tube 188 with a 
suction pump such as shown in FIG. 8 (not shown). Further, an O-ring 192 
is provided on the upper surface of the auxiliary suction device 185 
around the opening of the passage 187 to provide a seal. FIG. 32 
illustrates the auxiliary suction device 185 shown in FIG. 31 aiding in 
the suction operation. 
FIG. 33 illustrates a suction sub-turntable which can be removably mounted 
on a main turntable and is provided with a valve which is closed by the 
weight of the sub-turntable when the sub-turntable is placed on the main 
turntable and which is opened when the sub-turntable is lifted from the 
main turntable, disengagement of a disk from the turntable device thus 
being facilitated as it accompanies the lifting of the sub-turntable from 
the main turntable. More specifically, a base plate 201 of a sub-turntable 
200 shown in FIG. 33 is of a disk shape made of a sturdy material. To the 
upper surface of the base plate 201 is fixedly attached an annular rubber 
sheet 204 formed with seal portions 202 and 203 which respectively abut 
the portions immediately inside the groove guard of the disk and 
immediately outside the label portion. A valve device 205 is provided so 
as to allow air into the space sealed by the seal portions 202 and 203 to 
release the disk from suction. The valve device 205 is shown on an 
enlarged scale in FIG. 34. The base plate 201 is provided with a chamber 
201a while the rubber sheet 204 is formed therethrough with apertures 204a 
communicating with the chamber 201a. A support 206 is fixed to the bottom 
of the base plate 201 and formed with a hollow 206a to accommodate an 
actuator 207. The hollow 206a is formed with apertures 206b. The actuator 
207 opens or closes the apertures 206b by a valve 207a formed at the lower 
end of the actuator 207. The valve 207a is made of a resilient material 
such as rubber and supported via a rod 207b by the support 206 so as to be 
vertically movable. The upper end of the rod 207b is formed with an 
umbrella-like portion 207c to overlap the hollow 206a of the support 206. 
The umbrella-like portion 207c has apertures 207e and is formed with a 
flange 27b at its lower end. Between the flange 207d and the rubber sheet 
204, a helical spring 208 is provided so as to bias the flange 207d 
against the support 206. In this state, the valve 207a is apart from the 
follow 206a of the support 206 and the suction space above the rubber 
sheet 204 is in communication with the atmosphere below the base plate 201 
by the apertures 204a, 207e and 206b. This is the state which the valve 
device 205 reaches to release a disk from suction. Upon placing the 
sub-turntable 200 on the main turntable, the actuator 207 is lifted 
against the biasing of the helical spring 208 by the weight of the 
sub-turntable 200 as shown by a dotted line in FIG. 34. More specifically, 
the valve 207a is accommodated in the hollow 206a to close the apertures 
206b, thereby interrupting communicating between the suction space above 
the rubber sheet 204 and the atmosphere below the base plate 201. The 
valve device 205 in this state is ready for the disk sucking operation. 
Reverting to FIG. 33, a passage 210 is provided through the rubber sheet 
204 and base plate 201 to guide toward the center of the sub-turntable 200 
the air withdrawn from the space sealed by the seal portions 202 and 203 
when the disk is rested thereon. The base plate 201 is fixedly provided at 
the central portion of its upper surface with a rubber sheet 211 to 
support the label portion of the disk. The rubber sheet 211 is formed with 
grooves 211a to guide the sucked air to the center of the sub-turntable 
200. The rubber sheet 211 is provided with a check valve 212 for 
preventing a reverse-flowing of the air at the aperture of the passage 
210. The sub-turntable 200 has a central opening 200a vertically formed 
through the rubber sheet 211 and the base plate 201 for the spindle to 
enter. FIGS. 35(a) and 35(b) illustrate how to operate the disk sucking 
operation using the suction device shown in FIG. 33. Referring to FIG. 
35(a), the sub-turntable 200 is mounted on a main turntable 220 with a 
center spindle 2 inserted in the central opening 200a of the sub-turntable 
200, whereon the valve 207a of the actuator 207 is accommodated in the 
hollow 206a of the support 206 by the weight of the sub-turntable 200 to 
close the apertures 206b of the hollow 206. A disk 64 is then placed on 
the sub-turntable 200 and an attachment 226 communicating with a suction 
pump such as shown in FIG. 8 (not shown) is attached to the disk 64 so as 
to cover the central portion of the disk 64. Upon operating the suction 
pump, the air in the space defined by the rubber sheet 204 and the disk 
225 is withdrawn and introduced into the pump finding its way, as 
indicated by the arrows, through the passage 210, groove 211a in the 
rubber sheet 211, and through a gap d between the central opening of the 
disk 64 and the spindle 2 and thence through an attachment 226 and a 
suction tube 227, while the disk 64 is lowered by the atmospheric pressure 
to depress the seal portions 202 and 203. When a label portion 64a of the 
disk 64 abuts the rubber sheet 211, the operation is discontinued and the 
attachment 226 is removed as shown in FIG. 35(b), leaving the check valve 
212 closed to prevent the sucked air from flowing backwards so that the 
disk 64 remains sucked for a long period of time. Upon termination of 
reproduction as shown in FIG. 36, the disk 64 can be released by lifting 
the sub-turntable 200 to cause the actuator 207 to be depressed by the 
spring 208 with the result that the unblocked apertures 206b of the hollow 
206 allow air to flow from below the sub-turntable 200 into the space 
defined by the disk 64 and the rubber sheet 204 via the apertures 206b, 
207e and 204a, thereby gradually lifting the disk 64 until it is finally 
released from suction. The disk 64 can then be easily removed from the 
sub-turntable 200 after placing the sub-turntable 200 back on the main 
turntable 220. It should be noted that, in case a main turntable and a 
sub-turntable can tightly fit to each other, a valve device described 
above can be dispensed with. 
The type of disk sucking systems which, as described above, are not adapted 
to resume a sucking operation when necessary while a disk is being played 
are not enough free, during reproduction of the disk, from air leakage 
which could make it impossible for the turntable to securely hold the disk 
against them for a long period of time. Such air leakage has 
conventionally been compensated by operating a vacuum pump whenever the 
vacuum in the suction space reduces. That method, however, suffers from 
disadvantages of necessitating such control system that operates the 
vacuum pump upon reduction of the vacuum in the suction space. Operation 
of the vacuum pump during reproduction of a disk, moreover, vibrates the 
disk, thus reducing the signal-to-noise ratio on the reproduced signal. 
Besides, where air is evacuated upwardly of or toward the periphery of, a 
disk sucking system, it is technically difficult to carry out the 
evacuating operation while the disk is being rotated for reproduction. It 
is therefore preferable that the initially obtained vacuum in the suction 
space be maintained for a long period of time without requiring the 
sucking operation to be resumed during reproduction of the disk. For 
example, an attempt may be made to keep the vacuum in the suction space at 
an initial level for as long as possible by setting a disk in better 
sealed contact with the turntable, namely, by improving the packing placed 
on the turntable. However, in order for an improved packing to provide 
good sealed contact between the disk and turntable, the disk needs to be 
free from scratches, dusts, etc. The attempt thus does not always prove 
successful. Another attempt to the same end would be to have initially 
created a vacuum in the suction space to such a high degree that it takes 
time before the vacuum in the suction space is reduced to a level normally 
required so that the disk may remain sucked onto the turntable for a 
longer period of time. This method, however, runs the risk of injuring or 
warping the disk. 
According to the present invention, a device is provided to solve the 
problem of such air leakage occurring during reproduction of a disk in a 
better, more satisfactory manner than those described above. More 
specifically, the device according to the invention is not aimed at 
prevention of said air leakage but is rather intended to allow the air 
pressure in the suction space to be raised by air leakage thereto, if any, 
at as slow a rate as possible so it may take relatively a long period of 
time for the disk to be freed from suction. FIG. 37, for example, shows an 
embodiment for carrying out such device as proposed above, wherein a 
turntable is so provided as to possess a cavity of a relatively large 
capacity between its upper surface and a disk placed thereon. The air 
leaking into the spacious cavity, if any, would be dispersed therein so 
that the pressure in the cavity would be raised by the leaking air only at 
a slow rate, thus enabling a disk to remain sucked for sufficiently a long 
period of time. In FIG. 37 a turntable device 233 is provided on a 
turntable 231 which is located by a center spindle 2. The device 233 
comprises a metal sheet 234 which is fixedly provided with annular rubber 
seals 235 and 236 which respectively abut the portions immediately inside 
of the groove guard of a disk (not shown) and immediately outside of the 
label portion. These seals 235 and 236 are provided to seal up a suction 
space 14, which is interrupted from the atmosphere, together with the disk 
and act as suckers. The seals 235 and 236 formed with rims 237 and 238 
respectively, which, together with the disk rested thereon, define a 
cavity 14a. The capacity of the cavity 14a as will be later described, is 
determined by factors including any amount of air that is expected to leak 
therein, and length of time during which a disk is required to remain 
sucked. The rim 238 is formed with a hole 239 and a passage 240 
communicating with it, through which air withdrawn from the suction space 
14 passes. Between the hole 239 and passage 240 is provided a check valve 
241 which is closed to prevent air from flowing back into the suction 
space 14 while the disk is drawn toward the turntable by suction. Grooves 
242 which communicate with the hole 239 are provided on the rim 238 so 
that air from the suction space 14 may be evacuated therethrough while the 
disk is rested on the rim 238. In the cavity 14a is annularly arranged a 
plurality of sustainers 250 spaced at regular intervals as shown in FIG. 
38. The sustainers 250 are provided to sustain the grooved portion of the 
disk from below so that the disk may not be warped while the disk is drawn 
toward the cavity 14a by sucking. The sustainers 250 are therefore of 
about the same height as the rims 237 and 238. The sustainers 250 are of 
such a form as to occupy the least space possible in the cavity 14a. For 
example, each of the sustainers 250 may be of a columnar shape having a 
hole 250a along its axis and an annular cut 250b on its periphery as shown 
in FIG. 37. Atop each of the sustainers 250 are formed channels 250c to 
provide communication between the holes 250a and the cavity 14a. On the 
upper surface of the metal sheet 234 is fixedly provided with a rubber 
sheet 251 surrounded by the seal 236 and is formed with grooves 252. The 
grooves 252 are provided to prevent occurrence of difficulty in the 
evacuation of air from the suction space 14 resulting from abutment of the 
disk against the upper surface of the rubber sheet 251. The grooves 252 
thus serve to guide the air evacuated from the suction space 14 to the 
periphery of the spindle 2. FIG. 38 is a top plan view of the turntable 
device shown in FIG. 37 which in turn is a sectional view taken along line 
C-C in FIG. 38. The sustainers 250 are spaced almost at regular intervals. 
In order to carry out the sucking operation with the turntable device 
illustrated in FIG. 37, a disk 64 is placed on the turntable device, 
whereon an attachment 255 is attached to the disk 64 so as to cover the 
spindle 2 as shown in FIG. 39(a). Upon operating a suction pump such as 
shown in FIG. 8 (not shown), air is evacuated from the suction space 14 
through the hole 239, passage 240 and thence through the gap d between the 
central opening of the disk 64 and the spindle 2 as indicated by arrows 
while the disk 64 is lowered due to depression of the air pressure in the 
suction space 14. The suction operation is completed when, as illustrated 
in FIG. 39(b), the seals 235, 236 are pressed down with the label portion 
64a of the disk 64 rested on the rubber sheet 251 while the grooved 
portion 64c of the disk 64 supported by the rims 237, 238 and sustainers 
250 thus defining the cavity 14a between the disk 64 and metal sheet 234. 
In this state, the check valve 241 is closed to keep vacuum in the cavity 
14a so that the disk 64 may stay sucked during its subsequent 
reproduction. During reproduction, the presence of scraches, dusts, and 
the like on the disk 64 may allow air to leak into the cavity 14a little 
by little through between the disk 64 and the seals 235, 236. However, 
because of the relatively large capacity of the cavity 14a, elevation of 
the air pressure in the suction space 14 due to the air leakage tekes 
place only at a slow rate and, therefore, the disk can remain sucked for a 
sufficiently long period of time. It will be noted that grooves are 
provided in the rubber sheet within the suction space in the previously 
described embodiments so as to afford space between the sucked disk and 
the rubber sheet at the bottom of the suction space, just like the grooves 
242 shown in FIG. 37 in order to prevent occurrence of difficulty in the 
evacuation of air which results from the abutment of the disk against the 
rubber sheet. Such grooves, however, have a small capacity and by no means 
perform the same function as the cavity 14a as shown in FIG. 37. 
FIG. 40 shows another embodiment of the disk sucking system according to 
the invention, wherein air is withdrawn sidewardly. In FIG. 40, a 
turntable 270 located by a center spindle 2 is fixedly provided on its 
upper surface with annular rubber seals 272 and 273 which respectively 
abut the portion immediately inside of the groove guard of a disk (not 
shown) and immediately outside of the label portion. The seal portions 
272, 273 are formed with rims 274, 275 respectively. The turntable 270 is 
also provided fixedly with sustainers 276 spaced annularly at about 
regular intervals. The rims 274, 275 and sustainers 276 define the cavity 
14a together with the disk placed thereon. The sustainers 276 are 
cylindrical and each formed with a hole 276a therein which communicates 
with the cavity 14a by channels 276b provided atop each of the sustainers 
276. The cavity 14a communicates with a hole 278 and a passage 279, both 
made in a stepped portion 277 of the rim 274. A check valve 280 is 
provided between the hole 278 and passage 279. The passage 279 in the 
stepped portion 277 communicates with the atmosphere by another passage 
281 formed in the turntable 270. The air in the suction space 14 is 
withdrawn from this passage 281 to suck the disk. On the upper surface of 
the turntable 270 is fixedly provided also with a rubber sheet 282 at its 
central part to support the label portion of the disk. In this embodiment, 
the sucking operation is completed when, as shown in FIG. 41, the seals 
272, 273 are pressed down with the label portion 64a of a disk 64 rested 
on the rubber sheet 282 and the grooved portion 64c of the disk 64 
supported by the rims 274, 275 and sustainers 276, thus defining the 
cavity 14a between the disk 64 and the turntable 270. In this state, the 
check valve 280 is closed to keep vacuum in the cavity 14a so that the 
disk 64 may remain sucked during its subsequent reproduction. While 
reproduction, the presence of scratches, dusts and the like on the disk 64 
may allow air to leak into the cavity 14a little by little through between 
the disk 64 and the seals 272, 273. However, because of the relatively 
large capacity of the cavity 14a, elevation of the air pressure in the 
suction space 14 takes place only at a slow rate and, therefore, the disk 
can remain sucked for a sufficiently long period of time. 
The capacity of the cavity in the turntable device made according to the 
invention is determined in the following manner. With reference to FIG. 42 
which schematically illustrates an embodiment of the invention comprising 
a disk 64, turntable 291, suction pump 292, check valve 294, whereby air 
is evacuated from the cavity 14a by actuating a piston 293 in the suction 
pump 292, 
Vo indicates the capacity of the cavity 14a (cm.sup.3); 
k(t) indicates the amount of air leaking into the cavity per unit time 
(cm.sup.3 /sec); 
p(t) indicates the pressure in the cavity 14a(Kg/cm.sup.2); 
f(t) indicates a chucking force, i.e. force with which the disk is 
depressed by a pressure differential between the atmospheric pressure and 
the pressure in the cavity (Kg); 
A indicates a chuck area, i.e. area over which the chucking force f(t) is 
exerted (cm.sup.2); 
V indicates the displacement of the suction pump (cm.sup.3); 
and t indicates time (sec). 
With the piston 293 at the end of its compressing stroke, the disk 64 is 
placed on the turntable 291 and then the piston 293 is pulled once to 
obtain the relationship: 
EQU k(t)=.alpha.{l-p(t)} (1) 
wherein .alpha. is a leakage constant. It will be noted from the 
relationship (1) that the leakage k(t) reduces as the pressure p(t) in the 
cavity nears the atmospheric pressure as time goes by. The leakage k(t) 
for a given time may be expressed by Vo/.alpha. which is referred to as 
leakage time constant T and in which Vo indicates the capacity of the 
cavity, i.e., 
EQU Vo/.alpha..tbd.T (2) 
The pressure p(t) can be expressed by the formula: 
EQU p(t)=l+(.beta.-l)e.sup.-t/T (3) 
wherein .beta. indicates the initial value of the pressure p(t) while the 
chucking force f(t) is expressed by the formula: 
EQU f(t)=A(l-p(t)) (4) 
Substituting the right side of formula (3) for p(t) in the equation (4), 
the formula 
EQU f(t)=A(l-.beta.)e.sup.-t/T (5) 
is obtained. FIG. 43 shows how the chucking force f(t) varies with time t. 
The required leakage time constant T can be calculated from the formula 
(5) by measuring the chucking force f(t) against which the disk 64 is 
disengaged from the turntable 291; finding out the chuck area A and the 
initial value .beta. of the pressure p(t) in the cavity; and determining 
the time t during which the disk 64 is to remain sucked. 
Further, the leakage constant .alpha. may be found out from formula (1) if 
the initial leakage k(O) and the initial pressure P(O) (p(O)=.beta.) are 
known. 
With the leakage time constant T and the leakage constant .alpha. thus 
obtained, the capacity V.sub.o of the cavity necessary to keep the disk 64 
sucked for a period t can be calculated from the formula (2). 
By way of example, a capacity V.sub.o of the cavity 14a is now determined 
for the turntable 291 with its outer and inner annular seals having 
respective diameters of 28 cm and 10 cm to maintain suction of the disk 64 
for a period of 3000 seconds, with V=V.sub.o, the leakage k(O)=1/60 
cm.sup.3 /sec and the chucking force f=100 Kg against which the disk 64 is 
set free from suction. 
The chuck area A and the initial value .beta. of the pressure p(t) are 
calculated as follows: 
##EQU1## 
Substituting for A, .beta., f, and t in formula (5) the values 540, 0.5, 
100 and 3000 respectively, leakage time constant T is obtained as follows: 
##EQU2## 
while the leakage constant .alpha. is obtained from the formula (1) as 
follows: 
With T and .alpha. thus found, V.sub.o can now be calculated as follows: 
##EQU3## 
It follows therefore that, in order to maintain suction of a disk for a 
period of 3000 seconds, a cavity of 100 cm.sup.3 or more is necessary for 
the turntable 291 specified above. 
Since the chuck area A practically does not much vary from one turntable 
device to another and the time during which a disk needs to remain sucked 
does not show a wide range, nor the initial value .beta. of the pressure 
p(t), the leakage k(t) and chucking force f will appreciably vary from the 
respective values specified in the above example, a cavity with a capacity 
V.sub.o =100 cm.sup.3 or more will be sufficient in most cases. 
While a long suction of a disk is thus enabled, despite air leakage, by 
formation of a cavity as mentioned above, it may alternatively be ensured 
by the following sealing arrangement. 
Referring to FIG. 1(c) to 1(d), the undesirable bend of the periphery of 
the seal occurring in sucking of the disk can be prevented by providing a 
support member of a resilient material such as rubbers between the 
periphery of the annular seal and the turntable. FIG. 44, for example, 
illustrates resilient support members 311a and 311b fixedly provided on a 
turntable 310 and sub-turntable 312 respectively. The sub-turntable 312 is 
mounted on the turntable 310 and located by a center spindle 2. The 
sub-turntable 312 is formed with soft rubber liplike seal portions 315, 
316 so as to abut a disk 64 immediately inside the groove guard portion 
314a and immediately outside the label portion 64a. On the upper surface 
of the sub-turntable 312 are provided radially extending grooves 317 
surrounded by the annular seal portions 315 and 316 in order to prevent 
occurence of difficulty in evacuation of air from the suction space 14 
sealed by the seal portions 315 and 316 upon abutment of the disk 64 
against the upper surface of the sub-turntable 312. The air in the suction 
space 14 is discharged through passage 318. each of which has an upper end 
opening in the groove 317 and a lower end opening on the underside of the 
turntable 310. A resilient annular support member 311a made of an elastic 
material such as rubber or elastic foam substance is fixedly provided on 
the turntable 310 so as to adjacently surround the seal portion 315. A 
like resilient annular support member 311b is fixedly provided adjacently 
and surrounded by the seal portion 316 on the upper surface of the 
sub-turntable 312. These support members 311a and 311b serve to sustain 
the seal portions 315 and 316 respectively thereby to enable the seal 
portions 315 and 316 to closely contact the disk 64 as it is sucked. FIG. 
45 illustrates the support member 311a sustaining the seal portion 315 
against the disk 64 which is drawn downwardly. FIGS. 46 through 49 shows 
other examples of the support members according to the invention. FIG. 46 
shows a resilient support member 320 fixed onto the outer wall surface of 
a seal portion 315 while FIG. 47 shows a resilient support member 321 
fixed to both the outer wall surface of a seal portion 315 and the upper 
surface of a turntable 310. FIG. 48 shows a support member 322 of a 
tubular form made, for example, of vinyl, fixedly provided on the like 
portion of a turntable 310. FIG. 49, on the other hand, illustrates a 
support mebmber 323 integrally formed with a rubber sub-turntable 312 so 
as to sustain the inner seal portion 316 against a disk as it is sucked. 
It should be notd that those resilient support members may be provided at 
both or either of seal protions 315 and 316, considering the sealing 
ability of the seal portions 315 and 316. 
Where a disk is sucked to a turntable by negative pressure, the disk is 
liable to be warped as it is drawn to the turntable. A device for 
preventing such warping of a disk will now be described. FIG. 50 shows a 
suction sub-turntable adapted to first suck a disk thereonto and then be 
mounted on a main turntable while FIG. 51 is a fragmentary sectional top 
plan view of the sub-turntable shown in FIG. 50. The sub-turntable shown 
in FIG. 50 has an annular sheet surrounded by two concentric annular seals 
all provided on a base plate such that there is a space between said 
annular sheet and the base plate, the annular sheet being provided to 
support the grooved portion of the disk as it is sucked so that it may not 
be warped and procure as large the space as possible in order to ensure 
suction of the disk for a sufficiently long time. More particularly, a 
suction sub-turntable 331 shown in FIGS. 50 and 51 comprises a base plate 
332 which is of a disk form with a central opening 332a for a center 
spindle to enter and which is made of a sturdy material. On the base plate 
332, annular rubber seals 333, 334 are fixedly provided so as to abut, as 
it is sucked, the disk immediately inside of its groove guard and 
immediately outside of the label portion respectively. An annular sheet 
335 is made of a sturdy material such, for example, as metal, inorganic 
substances and the like. The annular sheet is located between the seals 
333 and 334 and spaced from the base plate 332 by spacers 336 so as to be 
of a height lower than the upper end of the seals 333, 334. The annular 
sheet 335 is provided to support the grooved portion of the disk as it is 
sucked so that it may not be warped. The spacers 336, which may be, for 
example, of a columnar shape, serve to procure a large space to be 
evacuated so that suction of the disk for a long time may be ensured 
despite a possible air leakage. A hole 332b is provided in the portion of 
the base plate 332 surrounded by the seals 333, 334 to discharge air from 
the space defined by the base plate 332, seals 333, 334 and the disk to be 
sucked. A check valve 337 is provided at the lower end of the hole 332b to 
prevent back-flow of the evacuated air. FIG. 52 (a) illustrates the disk 
being sucked by the suction device shown in FIGS. 50 and 51. In order to 
carry out the sucking operation, a disk 64 is first placed on the suction 
sub-turntable 331 such that the outer and inner annular seals 333 and 334 
respectively abut the portions of the disk 340 immediately inside of its 
groove guard and immediately outside of its label portion 64a. An 
attachment 341, which communicates with a suction pump such as shown in 
FIG. 8 (not shown), is then so connected to the underside of the base 
plate 332 as to cover the hole 332b. Upon operating the suction pump, air 
is evacuated from the space sealed by the annular seals 333, 334 and 
discharged through the channel indicated by arrows while the disk 64 is 
lowered by a pressure differential thereby to press down the annular seals 
333 and 334 until a grooved portion 64c of the disk 64 abuts the annular 
sheet, thus completing the suction operation. The attachment 341 is then 
disconnected in order for the sub-turntable 331 to be mounted on the main 
turntable 343 with a spindle 2 inserted through the central openings 332a 
and 64c of the base plate 332 and a disk 64, respectively. Back-flow of 
air is impossible due to the check valve 337 which is closed. FIG. 53 
illustrates another suction sub-turntable provided with a variation of the 
annular sheet shown in FIG. 50. This variation of an annular sheet 335 has 
a number of perforations 335a scattered all over it so that a disk can be 
placed in uniform contact with the annular sheet 335. The sub-turntable 
331 down in FIG. 53 further is fixedly provided with annular support 
members 344 and 345 on a base plate 332' along annular seals 333 and 334 
which are also fixedly provided on the base plate 332'. The annular 
support members 344 and 345 are made of a resilient material and provided 
to sustain the annular seals 333 and 334 against a disk as it is sucked, 
thus enhancing the sealing ability of the seals 333 and 334. FIG. 54 shows 
a turntable device of a type wherein the suction operation is performed 
with a suction sub-turntable 351 mounted on a main turntable 360 by 
evacuating air finally through the gap between the central opening of a 
disk (not shown) and a center spindle. The subturntable 351 shown in FIG. 
54 comprises a base plate 352, outer annular seal 353, inner annular seal 
354, annular sheet 355 provided with perforations 335a, spacers 356, and 
annular support members 358 and 359. The base plate 352 is provided with a 
passage 352a to guide toward a center spindle 2 the air evacuated from the 
space sealed by the annular seals 353 and 354. Surrounded by the inner 
seal 354, a rubber sheet 362 is provided on the base plate 352 to support 
the label portion of the disk. The rubber sheet 362 is formed with grooves 
362 a whereby air guided through said passage 352a is further led to the 
periphery of the spindle 2. The passage 352a is provided, where it opens 
in one of the grooves 362a with a check valve 357 to prevent back-flow of 
the evacuated air. In order to perform the suction operation with the 
device shown in FIG. 54 a disk 64 is placed on the sub-turntable 351 and 
an attachment 366 which communicates with a suction pump such as shown in 
FIG. 8 (not shown) is mounted on the disk 64 so as to cover the spindle 2 
as shown in FIG. 55. Upon operating the pump, air in the space sealed by 
the annular seals 353, 354 finds its way as indicated by arrows before it 
finally is sucked through the gap d between the spindle 55 and the central 
opening of the disk 64. FIG. 56 illustrates a suction device of a type, 
similar to the one shown in FIG. 50, wherein the suction operation is 
conducted by a sub-turntable 371 before it is mounted on a main turntable 
(not shown). The sub-turntable 371 comprises a base plate 372 and an 
annular sheet 375 both formed with dents. Each of the dents of the base 
plate 372 coincides with one of the dents of the annular sheet 375. The 
base plate 372 and annular sheet 375 are fastened to each other by means 
of bolts 376 passed through every coupled dents thereby define a cavity 
14a. The sub-turntable 371 further comprises an outer annular seal 373, an 
inner annular seal 374, a hole 372b for discharging air, perforations 375a 
through which air is introduced from above the annular sheet 375 into the 
cavity 14a before discharged through the hole 372b, a check valve 377 and 
a central opening 372a for a center spindle to enter. FIG. 57 illustrates 
a suction sub-turntable 380 wherein a valve drive 15 such as shown in FIG. 
34 is incorporated. More particularly, in the suction subturntable 380 
shown in FIG. 57, an annular sheet 381 has apertures 381a for allowing air 
into the space sealed by annular seals 392 and 393 to set a sucked disk 
free from suction, and a hole 381b for letting air out of the space sealed 
by the annular seals 392 and 393 to suck the disk. In order to perform the 
suction operation, the sub-turntable 380 is first mounted on a main 
turntable (not shown), whereon the valve in the valve device 15 is closed 
by the weight of the sub-turntable 380. Air is then withdrawn from the 
space sealed by the annular seals 392 and 393 through the hole 381b, 
passages 400, grooves 401a and a rubber sheet 401, and thence through the 
gap between the center spindle and the central opening of the disk, thus 
conducting the disk sucking operation. The disk can be set free from 
suction by bodily lifting the sub-turntable 380, thereby opening the valve 
of the valve device 15 to allow air into the space sealed by the annular 
seals 392 and 393. In FIG. 57, reference numeral 391 designates a base 
plate of the seals 392 and 393, the rubber sheet 401,and the valve device 
15.