Optical pickup sending device

[0002] The present invention relates to an optical pickup sending device for freely moving back and forth an optical pickup within an information recording/reproducing apparatus such as a disc player so as to read information from an information recording medium such as an optical disc.

[0003] There have been known several types of conventional pickup sending devices such as those disclosed in Japanese Utility Model Unexamined Publication No. 5-61861 and Japanese Patent Unexamined Publication No. 6-68619.

[0004] FIG. 6 is used to schematically indicate the structure of a conventional pickup sending device disclosed in Japanese Utility Model Unexamined Publication No. 5-61861. As shown in FIG. 6, the sending device comprises a pair of guide shafts 2 and 3 for slidably supporting an optical pickup body 1, a screwed shaft 4, a rack member 6 supported by two arm members 5 extending from the pickup body 1. The teeth 6aof the rack member 6 are engaged with the screwed shaft 4. When the screwed shaft 4 is rotated, a relative positional relationship between the teeth 6aand the screw shaft 4 will he changed, so as to cause the pickup body 1 to freely move back and fourth along the guide shafts 2 and 3, i.e., in a radial direction of an optical disc such as a CD (Compact Disc) mounted on a turntable (not shown).

[0005] With the pickup sending device shown in FIG. 6, although the rack member 6 is elastically urged by the screw shaft 4 through a least spring 6bprovided in parallel with the arm members 5, since the teeth 6aof the rack member 6 are simply engaged with a part of the circumferential surface of the screwed shaft 4, an engagement between the teeth 6aof the rack member 6 and the screw shaft 4 is apt to collapse even due to a small vibration. As a result, it is difficult for the optical pickup 1 to read information from the optical disc in a correct manner and hence there will be some defects in the obtained information read by the optical pickup 1.

[0006] FIG. 7 is used to schematically indicate the structure of another conventional pickup sending device disclosed in Japanese Patent Unexamined Publication No. 6-68619. As shown in FIG. 7, the sending device comprises two guide shafts 8 and 9 for slidably supporting an optical pickup body 7 in a manner such that the pickup body 7 can be freely moved back and forth in the radio direction of an optical disc. A support member 10 is provided on the pickup body 7. The support member 10 has an engaging pin 12 provided at a front end thereof which is capable of engaging with a screw portion 11 formed integrally with the guide shaft 8. When the guide shaft 8 is rotated, a relative positional relationship between the engaging pin 12 and screw portion 11 will be changed, so as to cause the optical pickup body 7 to freely move back and fourth along the guide shafts 8 and 9.

[0007] With the pickup sending device shown in FIG. 7, since only the front end of the engaging pin 12 is engaged with the screw portion 11 of the shaft 8, an engagement between such two members 8 is apt to collapse even due to a small vibration. As a result, it is difficult for the optical pickup 7 to read information from the optical disc in a correct manner and hence there will be some defects in the obtained information read by the pickup 7.

[0008] In order to solve the problems existing in the above conventional devices shown in FIGS. 6 and 7, there has been suggested an improved structure shown in FIG. 8. Referring to FIG. 8, a half-nut 14 engaged with a screwed shaft 13, is integrally formed with a holding member 16 extending outwardly from the pickup main body 15. The inner diameter of the half-nut 14 is made almost the same as that of the screwed shaft 13, so that it is sure to prevent the half-nut 14 from getting off the screwed shaft 13.

[0009] However, if there is a relative deviation between a pair of guide shafts 17, 18 on one hand and the screwed shaft 13 on the other, an undesired gouging force will happen since it is difficult to absorb a dislocation caused by the above deviation between the screwed shaft 13 and the half-nut 14. As a result, there will he an unduly increased load on a driving motor (not shown) for driving the screwed shaft 13, hence undesirably causing an increase in the starting voltage of the driving motor.

[0010] It is an object of the present invention to provide an improved optical pickup sending device capable of solving the above-mentioned problems peculiar to the above-discussed prior arts.

[0011] According to the present invention, there is provided an optical pickup sending device, comprising: an optical pickup for reading information from an information recording medium; a rack member provided in connection with the optical pickup; and a screwed shaft engaged with the rack member for sending the optical pickup along the screwed shaft. In particular, the rack member is formed with a plurality of curved teeth each having a radius of curvature larger than that of the screwed shaft.

[0012] In one aspect of the present invention, the rack member is integrally formed with a holder so as to be supported thereby, said holder is engaged in a frame structure which is integrally formed with an arm member extending from he optical pickup and facing towards the screwed shaft.

[0013] In another aspect of the present invention, a coil spring is attached onto the holder in a manner such that the rack member is elastically urged against the screwed shaft.

[0014] The above objects and features of the present invention will become better understood from the following description with reference to the accompanying drawings.

[0015] FIG. 1 is an explanatory plane view indicating the structure of an optical pickup sending device made according to the present invention.

[0016] FIG. 2 is an exploded plane view indicating in more detail how a rack member may be attached to an optical pickup main body.

[0017] FIG. 3 is a back view indicating the rack member.

[0018] FIG. 4 is a longitudinally sectional view taken along A—A line in FIG. 1.

[0019] FIG. 5 is an explanatory view indicating an engaging relationship between a screwed shaft and the rack member.

[0020] FIG. 6 is a perspective view indicating an optical pickup sending device made according to a prior art.

[0021] FIG. 7 is a plane view indicating another optical pickup sending device made according to a prior art.

[0022] FIG. 8 is a perspective view indicating a further optical pickup sending device made according to a prior art.

[0023] An embodiment of the present invention will be described in the following with reference to the accompanying drawings.

[0024] FIG. 1 is an explanatory plane view indicating the structure of an optical pickup sending device made according the present invention.

[0025] In FIG. 1, reference numeral 100 is used to represent an optical disc such as CD (Compact Disc), DVD (Digital Video Disc or Digital Versatile Disc). Reference numeral 101 is used to represent a turntable provided on a chassis 102 for mounting the optical disc 100 when the optical disc is being reproduced or new information is being recorded thereon. Further, reference numerals 103 and 104 are used to represent a Pair of guide shafts disposed on the chassis 102. In addition, a screwed shaft 105 serving as a pickup sending means and a driving motor 106 are also provided on the chassis 102.

[0026] In detail, the guide shafts 103, 104 and the screwed shaft 105 are arranged in parallel with one another, with the guide shafts 103 and 104 fixed on the chassis 102 by means of fixing members 107-110. The screwed shaft 105 is rotatably supported by bearing members 111 and 112 which are fixed on the chassis 120.

[0027] In more detail, one end face of the screwed shaft 105 is elastically urged by a thrust member 113 consisting of a leaf spring, in a manner such that it is sure to prevent a possible vibration of the screwed shaft 105 in the longitudinal direction thereof. Further, a driven gear 114 engaged with a driving gear 115 for transmitting a driving force from a driving motor 106 to the screwed shaft 105, is secured on the screwed shaft 105.

[0028] An optical pickup body 116 is slidably supported on the guide shafts 103 and 104, an objective lens 117 (for emitting a light beam on to the information recording surface of the optical disk 100 and for collecting its reflected light so as to read information from the disc) is provided on the upper surface of the pickup body 116.

[0029] Further, an arm member 118 (FIG. 1 and FIG. 2) is provided extending from the pickup body 116 towards the screwed shaft 105, a rack member 120 is provided in connection with the arm member 118 in a manner such that it receives an elastic force from a coil spring 119 provided therebetween and thus gets in contact with the screwed shaft 105.

[0030] FIG. 2 is an exploded plane view indicating in more detail how a rack member 120 may be attached to the pickup body 116. FIG. 3 is a back view indicating the rack member 120. FIG. 4 is a longitudinally sectional view taken along A—A line in FIG. 1.

[0031] In FIG. 2, the arm member 118 extending from the pickup body 116 is integrally formed with a frame structure 121 which includes two mutually facing side walls 121a, 121band one rear wall 121c. The side walls 121aand 121bare formed with through-holes 121dand 121e, and a support pin 122 is inserted there through.

[0032] The rack member 120 has an integrally formed holder 120aadapted to be engaged into the frame structure 121, an elongate through hole 120ballowing insertion of the support pin 122 is formed through the holder 120a. On the back surface of the rack member 120 there are formed curved teeth 120ccapable of engaging with the screwed shaft 105.

[0033] Then, the holder 120awith the coil spring 119 wound thereon is engaged into the frame structure 121, with one end 119athereof fixed on the rear wall 121cand the other end thereof on the rack member 120, so that the support pin 122 is inserted in the through holes 121d, 121eand elongated through hole 120b.In this way, as shown in FIG. 4, the rack member 120 may be attached in a proper position with respect to the pickup body 116, and will be elastically urged against the screwed shaft 105 by virtue of the coil spring 119.

[0034] In detail, as shown in FIG. 5, the semi-diameter R (radius of curvature) of the curved teeth 120cformed on the rack member 120 is set to be larger than the semi-diameter r (radius of curvature) of the screwed shaft 105, so that the screwed shaft 105 is allowed to be covered by the curved teeth 120c.

[0035] An operation of the optical pickup sending device having the above structure will be described in the following with reference to FIG. 1 and FIG. 4.

[0036] After an optical disc 100 is mounted on the turntable 101, the driving motor 106 is started so as to cause the rotation of the screwed shaft 105 through the gear 115 and the gear 114. For this reason, there will be a change in a relative positional relationship between the curved teeth 120cand the screwed shaft 105, thereby causing the pickup body 116 to move back and forth along the guide shafts 103 and 104 in the radial direction of the disc 100, thus enabling the optical pickup to read information from the information recording surface of the disc.

[0037] Here, since the curved teeth 120chas a larger semi-diameter than that of the screwed shaft 105, the screwed shaft 105 may be covered by the curved teeth 120cin the radial direction thereof, thereby making it possible to absorb a deviation or a dislocation possibly occurred in the engagement between the curved teeth 120cand the screwed shaft 105.

[0038] In this way, since it is sure to prevent a possible deviation or dislocation in the engagement between the curved teeth 120cand the screwed shaft 105, there will not be an unduly increased load on the driving motor 106, thus avoiding an undesired increase in the starting voltage of the driving motor.

[0039] Further, the pickup body 116 has a predetermined moving range depending upon the length of the guide shafts 103 and 104. However, when the pickup body 116 arrives at a terminal position closest to the turntable 101 or arrives at the opposite terminal position farthest from the turntable 101, since the curved teeth 120cwill go beyond the teeth portion of the screwed shaft 105 against the elastic force of the coil spring 119, it is allowed to exactly prevent an unduly increased load on the driving motor 106.

[0040] In this way, with the use of the above embodiment, since a good and stable engagement may be maintained between the screwed shaft 105 and the rack member 120, the pickup body 116 is allowed to move back and forth in the radial direction of the disc 100 with an improved precision.

[0041] As may be understood from the above description, with the use of the optical pickup sending device made according to the present invention, since the rack member 120 is formed with curved teeth 120cwhich has a larger semi-diameter than that of the screwed shaft 105, even if a deviation or a dislocation occurs between the curved teeth 120cand the screwed shaft 105, such kind of deviation or dislocation will be effectively absorbed. For this reason, it is sure to prevent an undesired gouging force possibly occurred due to the above deviation or dislocation. Further, even if there is a vibration occurred between the rack member 120 and the screwed shaft 105, such a vibration will not cause the rack member 120 to move away from the screwed shaft 105. In this way, since a good and stable engagement may be maintained between the rack member 120 and the screwed shaft 105, the pickup body 116 may be moved in accordance with a rotating amount of the screwed shaft 105 in a more stable manner and with a higher precision.

[0042] While the presently preferred embodiments of the invention have been shown and described above, it is to be understood that these disclosures are for the purpose of illustration and that various changes and modifications may be made without departing from the scope of the invention as set forth in the appended claims.