WO2008102004A1

WO2008102004A1 - Device comprising a scanning apparatus and shock protection

Info

Publication number: WO2008102004A1
Application number: PCT/EP2008/052175
Authority: WO
Inventors: Stephan Knappmann; Michael Bammert; Stefan Kimmelmann
Original assignee: Thomson Licensing
Priority date: 2007-02-22
Filing date: 2008-02-22
Publication date: 2008-08-28
Also published as: DE102007009324A1

Abstract

The invention relates to a scanning device with shock protection comprising a swing arm, wherein the swing arm comprising a pickup for recording/reproducing data is operably connected to a storage medium and is supported on a pivot axis extending perpendicularly to the swing arm by means of a support, and wherein a magnetic drive initiating a swivel motion in parallel to the storage medium and a magnetic drive initiating a motion perpendicularly thereto are allocated to the swing arm, comprising an acceleration sensor for detecting a shock event. The invention solves the object of designing the shock protection apparatus such that the swing arm is located in a simple manner if a shock event is indicated. To achieve the, a permanent magnet (15) is arranged on the swing arm (1), with an electromagnet (16) that is permanently attached to the scanning device and arranged spaced apart from the swing arm (1) being allocated to the permanent magnet (15), the electromagnet (16) being connected to a power source (19) if the acceleration sensor (22) indicates a shock event and attracting and locating the permanent magnet (15) including the swing arm.

Description

DEVICE COMPRISING A SCANNING APPARATUS AND SHOCK PROTECTION

TECHNICAL FIELD OF THE INVENTION

The invention relates to a device with shock protection comprising an acceleration sensor for detecting a shock event and a scanning apparatus, in particular a swing arm. The scanning apparatus comprises a pickup for recording and/or reading data on a data storage medium, for example an optical disc.

BACKGROUND OF THE INVENTION

A swing arm is allocated to a storage medium which is designed as a data carrier and is held on a supporting device, the swing arm comprising at its free end a read/write pickup for recording/reading data. Together with the pickup, the swing arm is moved in the form of an arc in a plane extending in parallel to the recording surface of a storage medium which is driven to make a rotational motion, and in a plane extending perpendicularly to this plane, either motion being achieved by a magnetic drive, e.g. a voice coil motor.

If the drive unit of the supporting device is switched off, the storage medium is brought to a standstill and the swing arm is moved to a parking position and located in the position while being protected against shock. This is in particular a requirement, when the drive unit is arranged in a mobile device. In the parking position, the swing arm may be situated on a parking ramp outside of the periphery of the storage medium, such as described in EP 1 672 620 A2, or above a recording-free inner region of the storage medium, as described in US 6,005,736. In particular where drive units in mobile devices, such as portable computers and laptops, are concerned, it is important to protect the components allocated to each other against a shock event or impact even in operating mode, for example if the device is falling down. Such an impact may cause damage to the components or lead to a tracking error. To prevent these consequences of a shock, there are known apparatuses with acceleration sensors detecting a forthcoming shock in time and causing the moving parts inside the device, in particular the swing arm, to be put out of operating mode and into a safe parking position where they are located in order to be better protected mechanically against the expected shock. The swing arm can be held in the parking position by means of grippers . These grippers, however, require installation space and must be extremely accurate.

US 5,982,573 discloses a shock protection apparatus that is mechanically less complex and laborious. If the device falls down from a first height to a second height, this shock protection apparatus uses fall detecting means, e.g. acceleration sensors, to determine the occurring acceleration of the device and to indicate the acceleration to a control system if the acceleration exceeds a predefined threshold value within a selected reference time of at least 90 ms . The control means are operably connected to the drive of the swing arm and cause the latter to prepare the swing arm for the forthcoming impact by moving the swing arm away, in order to prevent damage to the storage medium.

Furthermore, US 6,005,736 describes another shock protection apparatus. This shock protection apparatus provides that a predefined electrostatically attracting voltage is applied across the swing arm and the storage medium in case of a shock event, indicated by a shock sensor. Therein, the latter is operably connected to an electronic switch through which the swing arm is connected to a voltage source, the storage medium also being directly connected to the voltage source. In normal operation without a shock event, the switch is open and voltage is not applied. If a shock is indicated, the switch is closed with the result that the swing arm is connected to the voltage source and the predefined voltage is applied across the swing arm and the storage medium. The electrostatic attractive force thus generated causes the swing arm to be held in its particular position in relation to the storage medium, wherein the voltage is selected such that the resulting attractive force prevents the two components from contacting each other. In this manner, an unpredictable movement of the swing arm relative to the storage medium and any potentially resulting damage are supposed to be prevented without locating the swing arm mechanically.

SUMN[ARY OF THE INVENTION

It is an object of the invention to design a device with a scanning apparatus having shock protection such that the scanning apparatus is secured in a simple manner in case of an indicated shock event.

This object is solved by means of a device as described in claim 1 and a method as described by claim 6. Advantageous embodiments are presented in the dependent claims.

A device with a scanning apparatus having shock protection according to the invention comprises a support with a pivot axis, a pickup for recording and/or reproducing data on a storage medium, the scanning apparatus being supported on the pivot axis. The device comprises further a first magnetic drive initiating a swivel motion in parallel to the storage medium and a second magnetic drive initiating a motion perpendicularly, and an acceleration sensor for detecting a shock event. A permanent magnet is arranged on the swing arm and an electromagnet is attached to the support and arranged spaced apart from the swing arm, the electromagnet being allocated to the permanent magnet and being connected to a power source, for attracting and locating the permanent magnet including the scanning apparatus in a parking position, if the acceleration sensor indicates a shock event.

The invention provides a shock protection by utilising an acceleration sensor for detecting a shock event of a device comprising a permanent magnet arranged on a scanning apparatus and an electromagnet permanently attached to a support of the device, the electromagnet being arranged spaced apart from the scanning apparatus and being allocated to the permanent magnet. In case of a shock event which is detected by the acceleration sensor and is indicated to a power source preferrably through a control unit and a switch, the electromagnet is connected to the power source. Due to the magnetic adhesive force generated by the electromagnet, the permanent magnet is attracted including the scanning apparatus and is located to the electromagnet. Thus, the scanning apparatus located in this manner is protected against damage and is also prevented from damaging other moving components if a shock is occurring .

The permanent magnet is to advantage in that it is arranged on that side of the scanning apparatus that is facing away from the storage medium, in order to ensure that the scanning apparatus is pulled away from the storage medium by the magnetic adhesive force. Therein, the permanent magnet should be spaced apart from the pivot axis of the swing arm by as great a distance as possible, in order to ensure that the distance between the magnets can be kept small and the deflection of the scanning apparatus is minimized while the latter is located to the electromagnet.

In addition, the electromagnet is to advantage in that it is arranged in the middle between the reversal points of the tracking swivel motion of the scanning apparatus, in order to minimize the maximum distance which the scanning apparatus, including the permanent magnet, travels to the electromagnet in case of a shock event. Therein, the electromagnet may be of an extremely flat design, thus rendering the shock protection apparatus suitable for extremely flat, in particular mobile, devices. Furthermore, the design of the magnet can be selected as desired and can be easily adjusted to the particular moving part.

A method for accelerating securing of the scanning apparatus to the electromagnet may be to supply the winding of the electromagnet with current such that the magnetic field is rectified in relation to that of the permanent magnet. If the acceleration sensor indicates the end of the shock event or the passing away of the danger of a shock, in conjunction with a decrease in the acceleration of the device, the control device can then supply the winding with current in opposite direction with the result that an opposite magnetic field is generated. This, in turn, causes the adhesive force of the permanent magnet to be overcome at an accelerated rate. Simultaneously with supplying the winding of the electromagnet with current in opposite direction, the tracking coil of the scanning apparatus can also be supplied with current in order to ensure that the permanent magnet moves in a lateral direction immediately after having detached from the core of the electromagnet. SHORT DESCRIPTION OF THE DRAWINGS

The invention will be illustrated below by means of an exemplary embodiment. In the related drawings,

Fig. 1 is a perspective top view of a swing arm comprising coil and magnet arrangements;

Fig. 2 is a perspective bottom view of the swing arm; and

Fig. 3 is a longitudinal cross-sectional view of the swing arm in its arrangement on a support with a shock protection apparatus.

DESCRIPTION OF PREFERRED EMBODIMENTS

Figs. 1 and 2 show a scanning apparatus 1, in particular a swing arm, of a device (not illustrated) , the swing arm being designed in the form of a two-arm lever and, in its center of gravity CG between the lever arms I and II, is mounted to a carrier 2, Fig. 3 such that it can be swiveled in a pivot bearing about a pivot axis PA extending perpendicularly to the swing arm. At its end side, the lever arm I supports an optical pickup 3 having a focus lens. Two printed coil arrangements 4 and 5 which are operably connected to magnets 6 and 7 are arranged on the other lever arm II, the magnets 6 and 7 being permanently attached to the support and being allocated to the coil arrangements 4 and 5 and the coil arrangements 4 and 5 forming magnetic drives for the swing arm with these magnets 6 and 7. OD indicates an optical disk to which the optical pickup 3 is allocated. The lever arm II comprises an edge region 8 extending coaxially in relation to the pivot axis and comprising a coaxially designed recess 9 spaced apart from the edge region 8, the recess 9 being surrounded by a printed coil 5 on each of its top and bottom sides. A leg of a U-shaped yoke 10 which is connected to the magnet 7 engages in the recess 9, wherein the magnet 7 itself coaxially encloses the edge region 8 at the latter' s outside with play PL. The magnetic drive thus formed causes the swing arm 1 to move perpendicularly to the pivot plane in focusing direction f .

In the region between the first magnetic drive and the pivot axis PA, the magnet 6 having the shape of a ring section and being permanently attached to the support is arranged coaxially in relation to the pivot axis PA and spaced apart from the swing arm 1. Two coils 4 corresponding to the magnet 6 and adjusted to the coaxially curved design thereof are also allocated to the magnet 6, one of these coils being arranged on the bottom side of the swing arm 1 and the other one being arranged on the top side of the swing arm 1. The second magnetic drive formed with these coils 4 and the magnet 6 serves to initiate a swivel motion of the swing arm 1 about the pivot axis PA, in tracking direction, radially in relation to the optical disk OP.

The lever arm I supporting the optical pickup 3 is connected non-rotatably to a bearing bushing 11 and comprises an elastically bendable region 12 to initiate a motion of the pickup 3 in focusing direction f perpendicularly to the pivot plane. In the region between the optical pickup 3 and the bendable region 12, the lever arm II is securely connected to the lever arm I, the lever arm II being exclusively held in the region and, thus, up to its edge region 8 being freely suspended on that side of the bendable region 12 that is facing away from the optical pickup 3, as shown also in Fig. 3.

Due to a groove 13 incorporated in the bottom side and the top side of the lever arm I, the bendable region 12 is considerably reduced as compared with the thickness of the lever arm I while being designed in its thickness such that the pickup-sided part of the otherwise rigid lever arm I is moved in focusing direction f once the lever arm II is loaded by the first magnetic drive which is formed with the magnet 7. The secure connection of the two lever arms I and II is also used to initiate the swivel motion of the lever arm I about the pivot axis PA and, thus, to initiate a swivel motion of the entire swing arm 1, wherein the swivel motion of the lever arm I about the pivot axis PA results from a swivel motion of the lever arm II caused by the second magnetic drive formed with the magnet 6.

Fig. 3 shows the arrangement and mounting of the swing arm 1 to the support 2. A pivot pin 14 is permanently arranged at the support 2, with the swing arm 1 being mounted to the pivot pin 14 such that it can be pivoted with the bearing bushing 11. The optical disk OD which is allocated to the optical pickup 3 is arranged in parallel therewith. A swivel motion of the swing arm 1 about the pivot axis PA causes the optical pickup 3 to be moved in radial direction relative to the disk OD, tracking direction t. Focusing of a specific point on the disk OD is achieved through a motion of the lever arm II and, thus, of the optical pickup 3 in focusing direction f and perpendicularly to the tracking direction t.

The swing arm is provided with a shock protection apparatus which is shown schematically in Fig. 3. The shock protection apparatus is formed of a permanent magnet 15 arranged on the bottom side of the lever arm II in the vicinity of the lever arm I and, for example, made of NdFeB, see also Fig. 2; an electromagnet 16 arranged on the support 2 spaced apart from the lever arm I and comprising a soft-iron core 17 which is 5 mm in diameter and 2 mm in height as well as a winding 18 surrounding the soft-iron core 17; a power source 19 supplying the winding 18 with current; an electronic switch 20 arranged in the electric circuit; a control device 21 allocated to the electronic switch 20; and an acceleration sensor 22 coupled to the control device 21. Therein, the electromagnet 16 is arranged at the support 2 in the middle between the reversal points of the tracking swivel motion, not visible, and is spaced apart from the pivot axis PA by the same distance as the permanent magnet 15.

If the acceleration sensor 22 indicates a forthcoming shock event to the control device 21, the normally open switch 20 is closed, the winding 18 is supplied with current, and the electromagnet 16 generates a magnetic attractive force which attracts the permanent magnet 15 and the swing arm 1 connected thereto and, according to calculations performed, holds the swing arm 1 with an adhesive force of 6 N. In order to accelerate securing of the swing arm to the electromagnet, the swing arm 1 can, in addition, be moved towards the electromagnet 16 by means of the second magnetic drive.

If the swing arm 1 comprises a weight of approx. 300 mg and the permanent magnet also comprises a weight of 300 mg, the swing arm can be held up to a shock of 1000 G. The shock- proof position of the swing arm 1 is indicated by the dash- dotted line. The position can, in particular, also be used for the safe parking position of the swing arm while the scanning device is switched off since, owing to the use of the soft-iron core, the electromagnet reliably locates the swing arm even in the currentless state due to the close contact .

The embodiments shown in Figures 1 to 3 and described above only reflect preferred exemplary embodiments of the invention without limiting the invention defined in the claims, and the invention also comprises, in particular, further modifications which can be made by those skilled in the art. For example, the shock-proof position of the swing arm 1 can also be arranged in an edge region of the operating range of the swing arm, in particular laterally and outside of the area of the optical disk OD.

L I S T O F R E F E R E N C E S Y M B O L S

1 Swing arm

2 Support

3 Optical pickup

4 Coil

5 Coil

6 Magnet

7 Magnet

8 Edge region

9 Recess

10 Yoke

11 Bearing bushing

12 Bendable region

13 Groove

14 Pivot pin

15 Permanent magnet

16 Electromagnet

17 Soft-iron core

18 Winding

19 Power source

20 Switch

21 Control device

22 Acceleration sensor

I Lever arm

II Lever arm f Focusing direction t Tracking direction

OD Optical disk

CG Center of gravity

PA Pivot axis

PL Play

Claims

1. A device with a shock protection comprising a support (2) with a a pivot axis (PA), a scanning apparatus (1) with a pickup (3) for recording and/or reproducing data on a storage medium (OD), the scanning apparatus (1) being supported by the pivot axis (PA) , a first magnetic drive (4, 6) initiating a swivel motion in parallel to the storage medium and a second magnetic drive (5, 7) initiating a motion perpendicularly, and an acceleration sensor (22) for detecting a shock event, characterized in that a permanent magnet (15) is arranged on the scanning apparatus (1), and an electromagnet (16) is attached to the support (2) and arranged spaced apart from the scanning apparatus (1), the electromagnet (16) being allocated to the permanent magnet (15) and being connected to a power source (19), for attracting and locating the permanent magnet (15) including the scanning apparatus in a parking position, if the acceleration sensor (22) indicates a shock event.

2. The device according to Claim 1, characterized in that the permanent magnet (15) is arranged on that side of the scanning apparatus that is facing away from the storage medium (OD) .

3. The device according to Claim 1 or 2, characterized in that the scanning apparatus is a swing arm, the swing arm (1) comprising a first lever arm (I) with the pickup (3) and a bendable region (12) for providing a focus motion and being connected to a bearing bushing (11) for the pivot axis (PA), a second lever arm (II), on which a first coil (4) of the first magnetic drive (4, 6) and a second coil (5) of the the second magnetic drive (5, 7) are arranged and the second lever arm (II) being connected to the first lever arm (I) for providing the swivel motion in parallel to the storage medium, wherein the permanent magnet (15) is arranged on the second lever arm (II) between the pivot axis (PA) and the pickup (3) , in particular on that end of the second lever arm (II) being connected to the first lever arm ( I ) .

4. The device according to Claim 1, 2 or 3, characterized in that the electromagnet (16) is connected to the power source (19) through a switch (20) and that the switch (20) is coupled to a control device (21) which is connected to the acceleration sensor (22).

5. The device according to one of the Claims 1 - 4, characterized in that the electromagnet (16) comprises a soft-iron core (17) and is arranged in the middle between the reversal points of the tracking swivel motion (t) of the scanning apparatus (1), therein being arranged spaced apart from the pivot axis (PA) by the same distance as the permanent magnet (15), or is arranged in a parking position of the scanning apparatus (1) away from the storage medium (OD) .

6. A method for protecting a scanning apparatus in case of a shock event by means of a shock protection apparatus, wherein the scanning apparatus comprises a pickup for recording and/or reproducing data, the scanning apparatus being operably connected to a storage medium, and wherein the shock protection apparatus locks the swing arm in a parking position by means of an electric current coming from a power source and generating an attractive force and by means of an acceleration sensor indicating a forthcoming shock and triggering the electric current, with the step of generating an attractive force between a permanent magnet (15) arranged at the scanning apparatus (1) and an electromagnet (16) attached to a support (2) for the scanning apparatus and allocated to and spaced apart from the permanent magnet (15) on the side facing away from the storage medium (OD) , when the acceleration sensor indicates a forthcoming shock, wherein a winding (18) of the electromagnet (16) is connected to a power source (19) and the electromagnet (16) attracts and locates the permanent magnet (15) including the scanning apparatus (1).

7. The method according to Claim 6, characterized in that the winding (18) of the electromagnet (16) is supplied with current such that the magnetic field of the winding (18) is in parallel with that of the permanent magnet (15) .

8. The method according to Claim 6 or 7, characterized in that a control device (21) supplies the winding (18) of the electromagnet (16) with current in the opposite direction once the end of the shock event or the passing away of the danger of a shock is indicated by the acceleration sensor (22).

9. The method according to Claim 8, characterized in that a tracking coil (4) of the scanning apparatus is supplied with current at the same time when the winding (18) of the electromagnet (16) is supplied with current in the opposite direction.