U.S. patent application number 10/103263 was filed with the patent office on 2002-10-31 for turntable for a disc-shaped information carrier and player provided with such a turntable.
Invention is credited to Bierhoff, Waltherus Cornelis Jozef.
Application Number | 20020157579 10/103263 |
Document ID | / |
Family ID | 8180076 |
Filed Date | 2002-10-31 |
United States Patent
Application |
20020157579 |
Kind Code |
A1 |
Bierhoff, Waltherus Cornelis
Jozef |
October 31, 2002 |
Turntable for a disc-shaped information carrier and player provided
with such a turntable
Abstract
The invention relates to a turntable (1) for a disc-shaped
information carrier (2), such as a DVD, having a central round
opening (21). The turntable comprises a centering element (3, 4),
which is rotatable about an axis of rotation (7) by means of a
driving element. The centering element (3, 4) comprises a fixed
centering member (3) having a supporting surface (8) for the
information carrier, and a further centering member (4) for final
centering of the information carrier, said further centering member
being movable in axial direction along the axis of rotation between
an upper position, in which the centering member is unloaded, and a
lower position, in which the centering member is loaded. An
end-centering portion (32) of the movable centering member has the
shape of a first truncated cone, which is directed upwards and
which has a first apex angle. The turntable is further provided
with a pressure member (5) for pressing the information carrier
onto the support surface, as a result of which the movable
centering member is moved from the upper position to the lower
position. The turntable is used in a player for reading and/or
writing disc-shaped information carriers having a central round
opening, such as a CD or DVD player.
Inventors: |
Bierhoff, Waltherus Cornelis
Jozef; (Eindhoven, NL) |
Correspondence
Address: |
Michael E. Marion
c/o U.S. PHILIPS CORPORATION
Intellectual Property Department
580 White Plains Road
Tarrytown
NY
10591
US
|
Family ID: |
8180076 |
Appl. No.: |
10/103263 |
Filed: |
March 21, 2002 |
Current U.S.
Class: |
108/20 ;
G9B/17.006 |
Current CPC
Class: |
G11B 17/0284
20130101 |
Class at
Publication: |
108/20 |
International
Class: |
A47B 085/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 28, 2001 |
EP |
01201149.0 |
Claims
1. A turntable for a disc-shaped information carrier having a
central round opening, comprising a centering element which is
rotatable about an axis of rotation by means of a driving element,
characterized in that the centering element comprises a fixed
centering member having a supporting surface for the information
carrier, and a movable centering member for final centering of the
information carrier which is axially movable along said axis of
rotation between an upper, unloaded position and a lower, loaded
position, with an end centering portion of said movable centering
member being in the form of an upwardly extending, first truncated
cone having a first apex angle, and in that the turntable is
furthermore provided with a pressure member for pressing the
information carrier onto the supporting surface, as a result of
which the movable centering member moves from the unloaded position
into the loaded position.
2. A turntable as claimed in claim 1, characterized in that the
turntable is provided with a supporting element by means of which
the movable centering member is supported substantially without
play in radial direction with respect to the fixed centering
member.
3. A turntable as claimed in claim 2, characterized in that the
supporting element, seen in axial direction, is arranged in a
position which substantially corresponds to a position which the
information carrier occupies on the supporting surface in use, seen
in axial direction.
4. A turntable as claimed in claim 2, characterized in that the
supporting element is provided with a circular cylindrical guiding
surface which is present on one of the two centering members and
which is concentrically positioned relative to the axis of
rotation, and with a number of guide members arranged in a circle
which are present on the other centering member and which abut
against the aforesaid guiding surface substantially without play,
seen in radial direction.
5. A turntable as claimed in claim 1, characterized in that a
pre-centering portion of the fixed centering member has the shape
of an upwardly extending second truncated cone having a second apex
angle which is greater than the first apex angle.
6. A turntable as claimed in claim 1, characterized in that the
turntable is provided with spring means acting between the fixed
centering member and the movable centering member.
7. A turntable as claimed in claim 6, characterized in that said
spring means are formed by a membrane spring.
8. A turntable as claimed in claim 7, characterized in that the
membrane spring is fixedly connected only either to the fixed
centering member or to the movable centering member.
9. A turntable as claimed in claim 1, characterized in that the
movable centering member is provided with a lead portion adjacent
to the upper side of the end centering portion, which lead portion
is in the shape of an upwardly extending third truncated cone
having a third apex angle which is greater than the second apex
angle.
10. A turntable as claimed in claim 1, characterized in that
magnetic means are accommodated within the fixed centering member
for attracting the pressure member.
11. A turntable as claimed in claim 1, characterized in that the
first apex angle ranges between 25 degrees and 45 degrees.
12. A turntable as claimed in claim 11, characterized in that the
first apex angle ranges between 30 degrees and 40 degrees.
13. A player for reading and writing a disc-shaped information
carrier having a central round opening, which player comprises a
turntable for the information carrier, characterized in that said
turntable is a turntable as claimed in any one of the preceding
claims.
Description
[0001] The invention relates to a turntable for a disc-shaped
information carrier having a central round opening, comprising a
centering element which is rotatable about an axis of rotation by
means of a motor.
[0002] The invention further relates to a player for reading and/or
writing a disc-shaped information carrier having a central round
opening, which player is provided with a turntable for the
information carrier.
[0003] A turntable and a player of the kinds referred to in the
opening paragraphs are generally known and common. The invention is
in particular intended for use with information carriers which are
rotated at relatively high speeds in a player. An important
exponent thereof is a DVD disc, which is rotated at 200 revolutions
per second. Such high speeds reveal new problems which do not play
a role at lower speeds, for example speeds of ten revolutions per
second (in the case of audio CDs). An important cause of these
problems is the imbalance effects that occur during rotation of the
information carrier. These imbalance effects are caused by various
factors. Distributed over its volume, the information carrier
material exhibits an inhomogeneous density. The opening in the
information carrier has certain dimensional tolerances as regards
the diameter and the concentricity. Another factor is that the
layers of the information carriers being built up of several
disc-shaped layers, which layers are glued together, for example,
are not concentrically positioned with respect to each other
either. All these factors contribute to the occurrence of imbalance
problems, particularly at higher rotational speeds. This leads to
an unstable behavior of the information carrier, as a result of
which the laser is no longer capable of following the information
track on the information carrier, or even worse, causes damage to
the information carrier inside the player.
[0004] It is an object of the invention to provide a turntable and
a player of the kinds referred to in the opening paragraphs which
exhibit a high degree of insensitivity to the imbalance effects as
described above and largely caused by the inherent characteristics
of the information carrier.
[0005] In order to achieve this object, a turntable according to
the invention is characterized in that the centering element
comprises a fixed centering member having a supporting surface for
the information carrier, and a movable centering member for final
centering of the information carrier which is axially movable along
said axis of rotation between an upper, unloaded position and a
lower, loaded position, with an end centering portion of said
movable centering member being in the form of an upwardly
extending, first truncated cone having a first apex angle, and in
that the turntable is furthermore provided with a pressure member
for pressing the information carrier onto the supporting surface,
as a result of which the movable centering member moves from the
unloaded position into the loaded position.
[0006] In order to achieve said object, a player according to the
invention is characterized in that the turntable used therein is a
turntable according to the invention.
[0007] Within the framework of the present invention, the term
"unloaded position" is understood to mean that position in which no
forces act on the movable centering member as a direct consequence
of the presence of the disc-shaped information carrier. It is
emphasized that it is not excluded that there is indeed a certain
bias which acts on the movable centering member. Within the
framework of the present invention, the relative concept "upper" is
to be understood to refer to that side of the turntable where the
pressure member is located. The concept "lower" obviously refers to
the opposite side of the player. It is quite possible, however, to
use a turntable according to the invention in which the turntable
is positioned upside-down, or in which the axis of rotation extends
horizontally. The axial movability of the axially movable centering
member renders it possible to accommodate the information carrier
in a correctly clamped-down position between the supporting surface
and the pressure member, so that there will be no imbalance effects
resulting from the centering.
[0008] The advantage mentioned above is achieved in particular in a
special embodiment of a turntable according to the invention, which
is provided with a supporting element by means of which the movable
centering member is supported substantially without play, seen in
radial direction, with respect to the fixed centering member. As a
result, imbalance forces from a rotating information carrier cannot
to give rise to an uncontrolled radial movement of the movable
centering member towards the fixed centering member or in a
direction away therefrom.
[0009] A very effective radial support as described above is
obtained in another embodiment of a turntable according to the
invention, in which the supporting element, seen in axial
direction, is arranged in a position which substantially
corresponds to a position which the information carrier occupies on
the supporting surface in use, seen in axial direction. In this
embodiment, the imbalance forces from the movable centering member
are transmitted directly, i.e. not by a circuitous route, in radial
direction to the fixed centering member. As a result, a very stiff
and stable support of the information carrier on the turntable is
provided, seen in radial direction.
[0010] From a constructional point of view it is very advantageous
if the supporting element is provided with a circular-cylindrical
guiding surface which is present on one of the two centering
members and which is concentrically positioned relative to the axis
of rotation, and with a number of guide members arranged in a
circle which are present on the other centering member and which
abut against the aforesaid guiding surface substantially without
play, seen in radial direction. As a result, it is possible to
position the first cone and the second cone so as to extend one
through the other, as it were.
[0011] An accurate centering is preferably obtained if the
pre-centering portion of the fixed centering member has the shape
of an upwardly extending second truncated cone having an apex angle
which is greater than the first apex angle. The separate
pre-centering and the final centering prevent an incorrect
positioning of the information carrier by the turntable. In the
case of an initial eccentric position, the information carrier will
first slide down along the second cone of the pre-centering portion
and subsequently be taken over by the first cone of the final
centering portion.
[0012] In order to create a counterpressure for the pressure member
and to cause the movable centering member to return from the lower,
loaded position to the upper, unloaded position as soon as an
information carrier is removed, the turntable is preferably
provided with spring means acting between the fixed centering
member and the movable centering member.
[0013] The spring means may be very suitably made up of a membrane
spring, which exhibits a very rigid behavior in the plane of the
membrane and which exhibits the desired elastic behavior in the
direction perpendicular to the plane of the membrane.
[0014] Preferably, the membrane spring is fixedly connected only
either to the fixed centering member or to the movable centering
member. In the case of deflection of the membrane spring, positions
on the membrane spring will tend to move in the direction of
rotation. This might lead to undesirable tangential forces acting
on the two centering members. This risk is excluded owing to the
one-sided connection, which enables the membrane spring to move
freely along one of the two centering members and/or to cause one
of the two centering members to move along with the spring as a
result of the active frictional forces that occur.
[0015] According to a preferred embodiment, the movable centering
member is provided with a lead portion adjacent to the upper side
of the end centering portion, which lead portion is in the shape of
an upwardly extending third truncated cone having a third apex
angle which is greater than the second apex angle. Thus the
occurrence of a horizontal edge in the upper, unloaded position of
the movable centering member is prevented. An information carrier
to be received on the turntable might hook behind such an edge,
resulting in a slanting position of the information carrier on the
turntable.
[0016] In order to achieve a proper abutment of the information
carrier on the supporting surface, magnetic means are preferably
provided for attracting the pressure member, which magnetic means
are accommodated within the fixed centering member. This leads to a
very compact construction at the same time.
[0017] An advantageous situation is obtained if the first apex
angle ranges between 25 degrees and 45 degrees, or even more
preferably between 30 degrees and 40 degrees. The use of such
angles on the one hand prevents the information carrier exhibiting
a tendency to move upwards along the end centering portion owing to
imbalance effects, during operation of the turntable, whilst on the
other hand a compact construction is still possible owing to the
fact that the required height of the end centering portion is
limited.
[0018] The invention also relates to a player for reading and
writing a disc-shaped information carrier having a central round
opening, which player comprises a turntable according to any one of
the preceding claims. The specific advantages of such a player have
already been described above with reference to the turntable. Such
a player may be a DVD player, although the invention is not limited
thereto.
[0019] The invention will be explained in more detail hereinafter
by means of the description of a preferred embodiment, in which
reference is made to the following figures.
[0020] FIG. 1 shows an assembled turntable according to the
invention in longitudinal sectional view.
[0021] FIG. 2 shows the detail in the boxed part in FIG. 1.
[0022] FIG. 3A shows the fixed centering member of FIG. 1 in plan
view.
[0023] FIG. 3B is a sectional view taken on the line IIIB-IIIB in
FIG. 3A.
[0024] FIG. 4A shows a movable centering member in plan view.
[0025] FIG. 4B is a sectional view taken on the line IVB-IVB in
FIG. 4A.
[0026] FIG. 5A shows a membrane spring in plan view.
[0027] FIG. 5B shows the membrane spring in side elevation.
[0028] FIG. 1 shows a turntable 1 for a DVD disc 2. The turntable 1
mainly comprises a fixed centering member 3 (cf. FIG. 3A and FIG.
3B), a movable centering member 4 (cf. FIG. 4A and FIG. 4B), and a
pressure member 5. The fixed centering member 3 has a central bore
6 for receiving an output shaft (not shown) of an electric motor
for rotating the turntable 1 about an axis of rotation 7. On its
outer side, the fixed centering member 3 is provided with an
annular supporting surface 8, on which a (likewise annular) rubber
friction mat 9 is arranged for transmitting a rotational movement
of the turntable 1 to the DVD disc 2. The upper side of the fixed
centering member 3 forms a pre-centering portion 10, within which
radial ribs 24 are arranged in evenly spaced radial positions over
the circumference thereof, which ribs 24 have flanks 11 on their
outer sides which collectively have the shape of an upwardly
extending truncated cone having an apex angle of 60 degrees. An
opening 12 is present between the ribs 24 after every fourth rib
24, six openings 12 being provided in all, which openings are
substantially square in shape and which define a guiding surface 19
by their inner sides. The guiding surfaces 19 are arranged on a
virtual circular cylinder which is concentric with the axis of
rotation 7. Three substantially tangentially extending slotted
openings 14 are present in the bottom 13 of the fixed centering
member 3, between the tubular wall 16 of the bore 6 and the ribs
24, which openings are evenly spaced apart in radial direction over
the circumference. A magnet 17 is accommodated in the space 15
above the bottom 13 and between the ribs 24 and the wall 16, which
magnet serves to attract the pressure member 5, which is for that
purpose provided with a part 18 extending into the space 15.
[0029] The movable centering member 4 is a substantially made up of
a ring 30 from which six arms 31 extend in upward direction, which
arms are evenly spaced apart in radial direction over the
circumference of the ring 30. Flanks 33 are arranged within an end
centering portion 32 on the outer side of the arms 31, which arms
jointly have the shape of an upwardly extending truncated cone
having an apex angle of 40 degrees. At the upper side, flanks 35
merge into the flanks 33 within a lead portion 34. The flanks 35
jointly form an upwardly extending truncated cone having an apex
angle of 70 degrees. Present on the inner side of the arms 31 is a
supporting member, which includes a number of guide members 36
which are arranged in a circle in the illustrated embodiment and
which each abut against the guiding surface 19 with a flat side 38
which faces towards the guiding surface 19 in the assembled
position, substantially without play in radial direction. The
movable centering member 4 is thus supported, substantially without
play in radial direction, with respect to the fixed centering
member 3 by means of the aforesaid supporting element. The guide
members 36 extend over such a distance, seen in axial direction,
and they are disposed at such a position opposite the flanks 33,
seen in axial direction, that the circular (interrupted) contact
edge 50 between the DVD disc 2 present on the supporting surface 8
and the flanks 33 will at all times occupy a position, seen in
axial direction, which substantially corresponds to the axial
position of the guide members 36 of the supporting element,
provided the opening 21 of the DVD disc 2 complies with the
applicable tolerance requirements.
[0030] In the assembled condition as shown in FIGS. 1 and 2, the
arms 31 extend through the openings 12, in which the flat sides 38
of the guide blocks 36 guidingly cooperate with guiding surfaces 19
present on the inner side of each opening 12. Seen in the direction
of rotation, a limited amount of play is present between the two
sides of the arms 31 and the side walls 52 of the openings 12.
Owing to said guiding cooperation, the movable centering member 4
is movable in axial direction along the axis of rotation 7 with
respect to the fixed centering member 3, without any play in radial
direction.
[0031] A membrane spring 40, which is slightly curved in an
unloaded state on account of a bias tension acting between the
fixed centering member 3 and the movable centering member 4, is
present at the lower side of the fixed centering member 3 and the
movable centering member 4. In said unloaded state, in which a bias
tension does obtain, the upper surface 39 abuts against a stop
surface 51 on the lower side of the fixed centering member 3. Said
bias is selected at least such that the maximum weight of the DVD
disc can be absorbed. The membrane spring 40 is shown in more
detail in FIGS. 5A and 5B. In order to obtain the desired
elasticity in axial direction, i.e. perpendicularly to the surface
of the leaf spring 40, three substantially circumferentially
extending slots 41 are provided in said surface. An opening 42 is
centrally provided in the membrane spring 40, through which opening
the driving shaft (not shown) of the driving element can extend.
Present at the edge of the opening 42 are three axially extending
snap elements 43 which extend through the openings 14 in the
assembled position, forming a snap connection therewith so as to
connect the membrane spring 40 to the fixed centering member 3. No
connection is present between the lower side 37 of the ring 30 of
the movable centering member 4 and the outer circumferential edge
of the spring 40, as a result of which the membrane spring 40 can
slide along the bottom surface 37 upon a rotational movement of the
outer circumferential edge of the membrane spring resulting from
the deformation thereof, as is shown in FIGS. 1 and 2, without
exerting undesirable tangential forces on the fixed centering
member 3 and/or the movable centering member 4.
[0032] The turntable as described above is used as follows. In a
starting situation, in which the membrane spring 40 is as yet
unloaded and only curved downward to a limited extent (on account
of the bias tension) at its outer side from the lower side 20 of
the bottom 13, the movable centering member 4 occupies an upper,
unloaded position. The turntable 1 forms part of a player which
also includes supplying means (not shown) for the DVD disc 2. Said
supplying means initially position the DVD disc 2 approximately
concentrically above the fixed centering member 3 and the movable
centering member 4, and subsequently lower it onto said centering
members, as a result of which the latter will extend through the
opening 21 of the DVD disc 2. Depending on the degree of
eccentricity of the DVD disc 2 with respect to the centering
members, the circumferential edge 22 of the DVD disc 2 will come
into contact with, successively, the flanks 11 and the flank 35 or
only with the flank 35, and slide down along said flank or flanks.
It is noted in this connection that the flank 35 extends outside
the flank 11 in the unloaded position, in which position the upper
outer edge 53 does not extend outside the flank 11, however. In the
case of a relatively small degree of eccentricity, the DVD disc 2
will pass the flanks 11 and 35 without coming into contact
therewith and directly engage round the flanks 30. The dimensions
of the pre-centering portion 10 have been selected such that the
greatest diameter at the lower side of the pre-centering portion 10
is smaller than the smallest diameter of the opening 21 that can be
expected on the basis of the required production tolerances of the
DVD disc 2. The same is true with regard to the greatest diameter
of the lead portion 34. Consequently, the DVD disc 2, starting from
a "maximum" degree of eccentricity, will slide further down the
flanks 11 and the flanks 35 into a position on the flanks 33. The
minimum diameter of the upper side of the end centering portion 32
and the maximum diameter of the lower side of the end centering
portion 32 have been selected so that they cover the full tolerance
range of the opening 21 of the DVD disc 2. Thus it is ensured that
the inner edge 22 of the DVD disc 2 will abut against the flanks 33
all around. From this position, the pressure member 5 is moved into
a position above and in the immediate proximity of the DVD disc 2
by mechanical means (not shown) of the player. The pressure member
5 is pulled downwards under the influence of the force of
attraction from the magnet 17, with the pressure member 5 pressing
the DVD disc 2 downwards with its annular circumferential edge 23
until the disc abuts on the friction mat 9 on the supporting
surface 8. On account of the abutment of the inner edge 22 against
the flanks 33, the downward movement of the DVD disc 2 is at the
same time transmitted, against the spring force of the membrane
spring 40, to the movable centering member 4, which will likewise
move downwards in axial direction, therefore, from the upper,
unloaded position to the lower, unloaded position. As was noted
above, the outer edge of the membrane spring 40 will tend to
perform a limited rotational movement under the influence of said
downward movement. Because of the limited amount of play between
the arms 31 and the openings 12 as described above, said limited
rotational movement of the outer ring of the membrane spring 40 may
be taken over by the movable centering member 4. From this
position, the DVD disc 2 is ready for being read or being written,
during which operations the DVD disc 2 is rotated about the axis of
rotation 7 as a result of the fixed centering member 4 being
rotated about the axis of rotation 7 by an electric motor (not
shown). After completion of the reading or writing operation, the
pressure member 5 is moved up, as a result of which the movable
centering member 4 will move from the lower, loaded position into
the upper, unloaded position under the influence of the membrane
spring 40 whilst carrying along the DVD disc 2. Following that, the
DVD disc 2 can be lifted by unloading means (not shown) and be
removed from the player.
[0033] As FIG. 2 clearly shows, the DVD disc comprises two layers
25, 26 which are glued together. Present at the outer
circumferential edge of the interface between the upper layer 25
and the lower layer 26 is a glue chamber 27. Owing to the
dimensional tolerances with regard to the holes 28, 29 of the
layers 25, 26, respectively, and owing to the tolerances as regards
the concentricity with which the layers 25 and 26 are glued
together, the outer edges of the holes 28 and 29 may well be
located in different radial positions. The dimensions of the fixed
centering member 3 and the movable centering member 4, and more
specifically of the flanks 11 on the one hand and the flanks 33 and
35 on the other hand, have been selected such that, given the
greatest possible difference in the radial positions of the inner
edges of the holes 28 and 29 owing to the tolerances, it is
nevertheless impossible for the DVD disc 2 to abut against one of
the aforesaid flanks 11, 33 and 35 with the inner edge of the upper
layer 25.
* * * * *