Dynamic information storage or retrieval – Dynamic mechanism subsystem – Having power driven transducer assembly
Reexamination Certificate
1998-08-28
2001-04-17
Ometz, David L. (Department: 2652)
Dynamic information storage or retrieval
Dynamic mechanism subsystem
Having power driven transducer assembly
Reexamination Certificate
active
06219326
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a feed device, particularly to an optical pickup feed device for use in a disc-type recording medium reproducing apparatus.
In a conventional reproducing apparatus for reproducing a disc-type recording medium such as a compact disc or a CD-ROM, an optical disc is rotated while an optical pickup is sent properly in a radial direction of the disc by virtue of a pickup feed device, so that the optical pickup may trace along an information track on the disc and irradiate a laser beam toward the track, thereby reading out the information recorded on the disc in terms of a reflection light reflected from the disc.
FIG. 4
illustrates a conventional optical pickup feed device for use in the above described recording medium reproducing apparatus. As shown in
FIG. 4
, the feed device comprises a driving motor
104
, a feed screw
101
, a nut
103
fixed in a rack
106
which is integrally connected with an optical pickup
102
. The nut
103
is engaged on the feed screw
101
. The feed screw
101
may be rotated by a driving force from the driving motor
104
, so that the nut
103
is caused to move along the feed screw
101
, thereby rendering the rack
106
and the optical pickup
102
to move integrally and linearly along guide rods
105
.
In use of the above optical pickup feed device, to quickly search for a desired information recorded on an optical disc, it is necessary for a driving motor to rotate slightly in a clockwise direction and a counterclockwise direction, so as to cause the optical pickup
102
to move reciprocatingly in a radial direction of the disc. For this reason, it is required that a tooth pitch of the feed screw
101
be made large so as to render the nut
103
to move back and forth in a large pitch. Further, it is required that the number of teeth of the nut
103
be made fewer and that an inclining angle of each tooth of the feed screw
101
be made different from that of each tooth of the nut
103
, so as to reduce a contact area between the teeth of the two members. In this way, it is sure for the optical pickup
102
to move easily and smoothly with only a reduced load.
However, a reduced contact area between the teeth of the feed screw
101
and those of the nut
103
will cause a reduction in a stability which is necessary for the nut
103
to move along the feed screw
101
, resulting in an inclination of the nut
103
on the feed screw
101
when the optical pickup
102
is being moved. If the nut
103
is often inclined on the feed screw
101
due to a vibration from the outside of the device, it will be difficult for the optical pickup
102
to move in a stabilized manner.
FIGS. 5A and 5B
are sectional views in side elevation illustrating engagements between the feed screw
101
and the nut
103
. In more detail,
FIG. 5A
indicates an engagement between the feed screw
101
and the nut
103
when both of them are in a stationary condition, whilst
FIG. 5B
indicates an engagement between the feed screw
101
and the nut
103
when both of them are in motion (i.e., when the feed screw
101
is rotated about a central axis X in a clockwise or counterclockwise direction, driven by the motor
104
at a high speed).
As shown in
FIG. 5A
, when the feed screw
101
is stopped, the nut
103
will get engaged properly on the feed screw
101
. On the other hand, as shown in
FIG. 5B
, when the feed screw
101
is rotated at a high speed by a driving force from the driving motor
104
, since the teeth of the feed screw
101
will proceed at a high speed in a direction shown by an arrow in the drawing, at each time point there will be at least one tooth of the feed screw
101
whose top portion P gets strong bump into a base wall portion of a tooth of the nut
103
. As a result, the nut
103
tends to rotate about the top portion P in a plane parallel with the paper surface of FIG.
5
A.
Moreover, the nut
103
will get inclined gradually and an edge portion thereof will bump into an inclined portion Q of a tooth of the feed screw
101
. As a result, the nut
103
is changed greatly from a position of
FIG. 5A
to a position of
FIG. 5B
, causing an inclination of the rack
106
and hence making it impossible to move the optical pickup
102
in a correct manner.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved optical pickup feed device capable of moving an optical pickup at a high speed but in a stabilized correct manner, so as to solve the above-mentioned problems peculiar to the above-mentioned prior arts.
According to the present invention, there is provided an optical pickup feed device for feeding an optical pickup in a radial direction of an optical disc, said device including: guiding means enabling the optical pickup to move in a predetermined radial direction of an optical disc; a driving system for producing a driving force to the optical pickup.
The driving system comprises: a feed screw arranged in parallel with a direction in which the optical pickup moves, and is rotatable by a driving force from a driving motor; a nut engaging on the feed screw for moving the optical pickup, said nut including an engaging portion engageable with the feed screw and a bank portion provided on either side of the engaging portion, said bank portion being protruding toward the feed screw.
According to one aspect of the present invention, each bank portion is formed so as to be closer to the feed screw than any valley portion formed between two teeth of the nut.
According to another aspect of the present invention, each bank portion is closer to the feed screw than any valley portion formed between two teeth of the nut, and has a height not in contact with any tooth of the feed screw.
According to a further aspect of the present invention, each bank portion has a width which is larger than a tooth pitch of the feed screw.
According to a still further aspect of the present invention, each bank portion is formed integrally with the nut.
The above objects and features of the present invention will become better understood from the following description with reference to the accompanying drawings.
REFERENCES:
patent: 6046974 (2000-04-01), Uehara
patent: 6052358 (2000-04-01), Morikawa et al.
patent: 6058098 (2000-05-01), Kato
patent: 6081500 (2000-06-01), Seino
Furusawa Shigeharu
Morinaga Jiro
Sato Taichi
Shimizu Akira
Shinkai Yasuhiro
Altman Franklin D.
Arent Fox Kintner & Plotkin & Kahn, PLLC
Ometz David L.
Pioneer Electronic Corporation
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