WO2006100619A2

WO2006100619A2 - Optical disc drive and follower for use in an optical disc drive

Info

Publication number: WO2006100619A2
Application number: PCT/IB2006/050777
Authority: WO
Inventors: Robertus J. M. Verhoeven; Johannes A. Van Rooij
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2005-03-24
Filing date: 2006-03-13
Publication date: 2006-09-28
Also published as: WO2006100619A3; TW200639838A

Abstract

Optical disc drive comprising an optical pickup head slidably supported by guide bars (4, 4'), a driving shaft (7) and a follower (3) for transmitting rotation of said driving shaft into a displacement of said optical pickup head. The follower comprises a tooth holder (10) engaging a groove (11) of the driving shaft during normal use. The follower further comprises a stopper (13) which at least abuts the side of the driving shaft that is faced away from the tooth holder. The stopper is configured to restrict said driving shaft to move away from the tooth holder utilizing spring force.

Description

Optical disc drive and follower for use in an optical disc drive

The invention relates to an optical disc drive comprising an optical pickup head slidably supported by guide bars, a driving shaft and a follower for transmitting the rotation of said driving shaft into a displacement of said optical pickup head, wherein the follower comprises a tooth holder engaging a groove of said driving shaft during normal use, wherein the follower comprises a stopper which at least abuts the side of the driving shaft that is faced away from the tooth holder.

An optical disc drive of this kind is known from JP-2003249042. This known optical disc drive is provided with a follower comprising a preloaded rack section and a fixed part. The rack section comprises a teeth part and a stopper positioned at a predetermined distance opposite the teeth part.

The stopper can prevent the teeth part to move away from a lead screw, and therefore avoids the optical pickup head from colliding with other components of the optical disc drive. In case of an external shock, the toothed part can overcome the lead screw groove, such that the stopper contacts the driving shaft. This contact will decrease the movement speed of the optical pickup head due to factional force and therefore prevents it from colliding with other components of the optical disc drive. A disadvantage of this known optical disc drive is that in case of an external shock, there is still a possibility that damage occurs to the teeth of the toothed part. As a result, failure in performance of the optical disc drive will be likely. A solution to prevent the optical pickup head from colliding with other components of the optical disc drive might be, to use a higher preload force between the tooth holder and the driving shaft. However, a disadvantage of such a solution is that a higher preload force results in higher friction and higher wear, causing more power dissipation of the disc drive. Another disadvantage of such a solution is, that it can result in a variable the step size during tracking. Accurate step size is very critical, especially for DVD and Blu-ray disc applications that are used for writing and reading high-density information. Furthermore, due to technical developments, increasing speed of the operational pickup head are desired, for quick data search on the surface of the optical disc, which also asks for higher positioning accuracy. It is therefore an object of the invention to provide an optical disc drive of the above-described type, wherein the disadvantage of the known optical disc drive is overcome, while maintaining the advantages thereof. More particular, it is an object of the invention to provide an accurate, energy efficient, durable and fast optical disc drive, wherein it is prevented that components of the drive are damaged due to relatively high non-operational shocks.

To that end, an optical disc drive according to the invention is characterized by the features of claim 1.

In order to achieve this object, an optical disc drive in accordance with the invention is particularly characterized in that the stopper is configured to restrict said driving shaft to move away from the tooth holder utilizing spring force.

The combination of the stopper and the tooth holder is capable of regulating unwanted movements of the optical pickup head efficiently. Due to said spring force, the follower is able to react smoothly to external shock forces. This results in avoiding collisions of the optical pickup head with other components of the optical disc drive, as well as in avoiding the possibility of damage of the tooth holder, thus providing a durable disc drive. Another advantage is that the present construction of the follower enables the follower to continue to guide the tooth holder along the groove of the driving shaft during operational shocks. Besides, the transmission of driving shaft rotation into displacement of the optical pickup head will be smooth, resulting in an accurate step size. In the disc drive according to the invention, a constant high engaging accuracy can be kept between the tooth holder and the driving shaft, so as to displace the optical pickup head to an adequate position corresponding to a rotational angle of the driving shaft.

In further elaboration of the invention, the stopper is made of a resilient material, for example a resilient plastic. For example, the follower and/or stopper can have such materials properties, that the stopper is bendable when a transversal force is applied to said stopper. The stiffness of the material is preferably such, that the stopper will not substantially bend during normal disc drive operation.

According to a further elaboration of the invention, said tooth holder comprises at least one tooth that reaches into a groove of said driving shaft, said groove being helical, wherein said at least one tooth holder can move back and forth along said driving shaft for driving said optical pickup head back and forth along said guide bars when said driving shaft is rotated. Due to the rotational movement, the at least one tooth is guided through the helical groove of the driving shaft. The tooth holder can comprise one tooth, or more than one tooth. The pressure that the at least one tooth applies to the driving shaft is preferably be distributed such that the driving shaft is not subject to high friction and can smoothly rotate, contributing to an accurate step size and low energy consumption.

According to a further elaboration of the invention, a distance between said stopper and said tooth holder is larger than an outer diameter of the driving shaft. For example, the stopper does not touch the driving shaft during normal use, and preferably not under influence of operational shocks, thus reducing friction there-between, and providing low power dissipation.

In further elaboration of the invention, when a high external shock is applied to the optical disc drive, the at least one tooth moves away from the driving shaft, wherein the driving shaft engages the stopper. The tooth can even be released from the driving shaft and overcome the groove. In this way nor the tooth neither the groove will be damaged. Preferable, the stopper decelerates the tooth holder/driving shaft movement, and then returns the tooth holder and the driving shaft back to their engaging position, utilizing said spring force. Thus after the external shock, the optical disc drive can continue to operate in a proper way.

The invention also relates to a follower, having the afore-mentioned features, to be used in an optical disc drive.

EXPLANATION OF THE DRAWINGS

To explain the invention, it will hereinafter be described with reference to the accompanying drawings, wherein: Fig. 1 shows a perspective view of the optical disc drive according to an embodiment of the invention;

Fig.2 shows a schematic view of a preferred embodiment of the follower;

Fig. 3 shows a perspective view of the follower and the driving shaft, during normal disc drive operation; Fig. 4 shows a schematic view of the follower during non-operational shock;

Fig. 5 shows a schematic view of a second embodiment of the invention;

Fig. 6 shows a schematic view of a third embodiment of the invention; and

Fig. 7 shows a schematic view of a fourth embodiment of the invention. In this description, identical or corresponding parts have identical or corresponding reference numerals.

DETAILED DESCRIPTION OF THE DRAWINGS Figure 1 shows a perspective view of an embodiment of the optical disc drive

1 comprising a follower 2. The optical disc drive 1 further comprises a mounting plate 3 and two guide bars 4, 4' that are mounted on the mounting plate 3. Furthermore, an optical pickup head 5 is provided, that is displaceable back and forth along the two guide bars 4, 4'. The optical pickup head is driven by a driving shaft 7, which is rotatable by a sledge motor 6. The follower 2 is coupled to the optical pickup head 5 by a coupling part 8. The follower 2 further comprises a tooth holder 10 that is situated nearby the driving shaft 7. The teeth 12 of the tooth holder 10 are engaged with a helical groove 11 of the driving shaft 7 during normal use. In the present application, the term "normal use" can understood as meaning "normal disc drive operation". In this configuration, the follower 2 and the driving shaft 7 are the interface between the optical pickup head 5 and the sledge motor 6, providing a movement of the optical pick up head 5 in X-directions, parallel to the guide bars 4, 4'.

Figure 2 shows a schematic view of a preferred embodiment of the follower 2. The follower 2 comprises a stopper 13 which at least abuts the side of the driving shaft 7 that is faced away from the tooth holder 10. The stopper 13 is configured to restrict the driving shaft 7 to move away from the tooth holder 10 utilizing spring force. Furthermore, the stopper 13 is spaced-apart from the driving shaft 7 during normal use. The stopper 13 is connected to the tooth holder 10 by a bridging part 9, which extends transversely with respect to the stopper 13 towards the tooth holder 10. The bridging part 9 might be considered as being part of the stopper 13, but this is not necessary. The stopper 13 and tooth holder 10 are designed to at least partially enclose the driving shaft 7.

Furthermore, fig. 2 shows that stopper 13 and tooth holder 10 extend substantially adjacent to a coupling part 8, which couples the follower 2 to the optical pick up head 5. The tooth holder 10 and the coupling part 8 are hingedly connected to each other. In the present embodiment, the tooth holder 10 comprises two teeth 12 that fit in the groove 11 of the driving shaft 7. The teeth 12 are engaged with the groove 11 of the driving shaft 7, providing a smooth transmission of the rotary movement of the driving shaft 7 into a displacement of the optical pickup head 5. The tooth holder 10 is preloaded towards the driving shaft 7 by preloading means, in this case a spring 14. The preloading means 14 are configured to force the tooth holder 10 and the driving shaft 7 together, utilizing a relatively low spring force, during normal disc drive use. For example, the preload forces provided by the preload spring 14 have a value that is such to keep the teeth 12 in engagement with the driving shaft 7 during normal disc drive operation, to secure an accurate tracking of an optical disc. Besides, the preload forces are such to allow a release of the teeth 12 from the groove 11 during certain high non-operational shocks.

In the present embodiment, the stopper 13 is an elastic finger which is made of a resilient material, for example a resilient plastic. The elastic finger 13 is provided oppositely and parallel to the tooth holder 10. During normal operation, the elastic finger 13 is positioned at a predetermined distance A of the tooth holder 10. In the present embodiment, this distance A is a bit larger than the outer diameter D of the driving shaft 7.

In figure 3, a perspective view of the follower 2 and the driving shaft 7 is shown. It is clearly seen in this figure that the teeth 12, 12' of the tooth holder 10 are positioned in the groove 11 of the driving shaft 7 during normal operation. When the sledge motor 6 is driving the driving shaft 7, the driving shaft 7 will rotate. This rotary movement causes the displacement of the teeth 12, 12' in the X-direction. This displacement for its part causes the optical pickup head 1 also to displace in the X-direction. During normal operation, the elastic finger 13 does not touch the shaft 7. Thus, during normal operation, the stopper 13 does not apply friction to the driving shaft, resulting in low energy consumption and accurate tracking. Preferably, between stopper 13 and the driving shaft 7 there is a gap G that is smaller than the tooth height p. However, such a gap G can also have a different size.

Because of the non-operational shocks, for instance caused by dropping optical disc drives or external vibrations, impact forces might result in collisions of the separate components of optical disc drives. Figure 4 shows a schematic view of the follower 2 of the present embodiment during a relatively large non-operational shock. As shown in fig. 4, in the present embodiment, after the shock is exerted, the tooth holder 10 turns around the hinge 15 in direction M. Therefore, the end 10a of the tooth holder 10 displaces in the direction of the preloading spring 14 and the spring 14 compresses. As a result, the teeth 12 jump out of the driving shaft groove 11. At the same time, or at least after a certain transversal displacement between the driving shaft 7 and the tooth holder 10, the elastic finger 13 contacts the driving shaft 7. Due to the impact force, the elastic finger 13 bends, and the end 13a of the elastic finger moves away from the tooth holder 10, providing additional space for the driving shaft 7. After the shock, the elastic finger 13 can move the driving shaft 7 and tooth holder 10 back towards each other by inherent spring force, so that they are again in the normal position as shown in fig. 3. Then, the drive 1 is again ready for normal operation. Because of the application of the elastic finger 13 as a stopper, damage to the teeth of the tooth holder 10 can be prevented well. In figure 5, a schematic view of a second embodiment of the invention is shown. As in the embodiment shown in figure 2, also in this embodiment the elastic finger 13 and the tooth holder 10 extend substantially adjacent to the coupling part 8. In fig. 5, the bridge part 9 is provided in an opposite position in comparison to the figure 2 embodiment. In case of an external shock, the lower corner 10b of tooth holder 10 of the second embodiment moves in the direction of the coupling part 8, due to the rotation M. Also in this case, the preloader spring 14 compresses, and the elastic finger 13 elastically bends away from tooth holder 10 to gradually counteract the shock, to avoid damage to the tooth holder and driving shaft 7 components.

Figure 6 shows a schematic view of a third embodiment of the invention. In this embodiment, the elastic finger 13 and the tooth holder 10 extend substantially perpendicular from the coupling part 8, whereas the bridging part 9 abuts, and is hingedly connected to, the coupling part 8. This also applies to the fourth embodiment of the invention that is schematically shown in figure 7, wherein the locations of the tooth holder 10 and elastic finger 13 have been swapped with respect to the fig. 6 embodiment. The invention is not in any way limited to the exemplary embodiments presented in the description and drawings. All combinations (of parts) of the embodiments shown and described in this description are explicitly understood to be incorporated within this description and are explicitly understood to fall within the scope of the invention. For example, the spring used for preloading the tooth holder can also be another preloading means. Also, the shape of the helical groove and the shape of the tooth can be of various kinds. Furthermore, the shape of the follower is changeable, as well as the number of teeth provided at the tooth holder.

Moreover, many variations are possible within the scope of the invention, as outlined by the claims.

Claims

CLAIMS:

1. Optical disc drive (1) comprising an optical pickup head (5) slidably supported by guide bars (4, 4'), a driving shaft (7) and a follower (2) for transmitting rotation of said driving shaft (7) into a displacement of said optical pickup head (5), wherein the follower (2) comprises a tooth holder (10) engaging a groove (11) of said driving shaft (7) during normal use, wherein the follower (2) comprises a stopper (13) which at least abuts the side of the driving shaft (7) that is faced away from the tooth holder (10), wherein the stopper (13) is configured to restrict said driving shaft (7) to move away from the tooth holder (10) utilizing spring force.

2. Optical disc drive (1) according to claim 1, wherein the stopper (13) is configured to restrict said driving shaft (7) to move away from the tooth holder (10) utilizing such a spring force, that the tooth holder (10) only releases the driving shaft (7) under influence of certain non-operational shocks, and not under influence of operational shocks.

3. Optical disc drive (1) according to claim 1 or 2, wherein the stopper (13) is configured to bend away from said tooth holder (10) under influence of certain non- operational shocks.

4. Optical disc drive (1) according to any one of the preceding claims, wherein the stopper (13) is made of a resilient material, for example a resilient plastic.

5. Optical disc drive (1) according to any one of the preceding claims, wherein the stopper (13) is spaced-apart from the driving shaft (7) during normal use.

6. Optical disc drive (1) according to any one of the preceding claims, wherein the stopper (13) is connected to the tooth holder (10) by a bridging part (9).

7. Optical disc drive (1) according to any one of the preceding claims, wherein said tooth holder (10) comprises at least one tooth (12) that reaches into a groove (11) of said driving shaft (7), said groove (11) being helical, wherein said at least one tooth holder can move back and forth along said driving shaft (7) for driving said optical pickup head (5) back and forth along said guide bars (4, 4') when said driving shaft (7) is rotated during use.

8. Optical disc drive (1) according to any one of the preceding claims, wherein a distance (A) between said stopper (13) and said tooth holder (10) is larger than an outer diameter (D) of the driving shaft.

9. Optical disc drive (1) according to any one of the preceding claims, wherein a gap (G) between said stopper (13) and said driving shaft (7) is smaller than the tooth height

(P)-

10. Optical disc drive (1) according to any one of the preceding claims, wherein said tooth holder (10) is preloaded towards the driving shaft by preloading means.

11. Optical disc drive (1) according to claim 10, wherein said preloading means are a spring (14).

12. Optical disc drive (1) according to any one of the preceding claims, wherein said stopper (13) and tooth holder (10) are designed to at least partially enclose said driving shaft (7).

13. Optical disc drive (1) according to any one of the preceding claims, wherein said stopper (13) and said tooth holder (10) extend substantially adjacent to a coupling part (8), which couples the follower (2) to the optical pick up head (5).

14. Optical disc drive according to claim 12, wherein the tooth holder (10) and the coupling part (8) are hingedly connected to each other.

15. Optical disc drive (1) according to claim 13 or 14, wherein said stopper (13) and said tooth holder (10) extend substantially perpendicular from said coupling part (8).

16. Follower (2) of an optical disc drive (1) according to any one of the preceding claims.

17. Use of an optical disc drive (1 ) according to any of claims 1 - 15 to read information from an information carrier and/or to write information to an information carrier.