WO2002037485A1

WO2002037485A1 - Device for fixing a component in the basic body of a unit

Info

Publication number: WO2002037485A1
Application number: PCT/EP2001/012497
Authority: WO
Inventors: Alexander Elsässer
Original assignee: Thomson Licensing S.A.
Priority date: 2000-10-30
Filing date: 2001-10-29
Publication date: 2002-05-10
Also published as: DE10053797A1; AU2002221782A1

Abstract

The invention proposes a device for fixing a component in the basic body (1) of a unit, a cavity (2) with a stop surface (3) for the component (4, 5) being formed in the basic body (1), and the component (4, 5) being pressed against the stop surface (3) with the aid of a spring (6), by means of which the spring (6) is isolated from other components (9) which are to be positioned in said cavity (2). For this purpose, a fixing element (8) is provided according to the invention as an abutment for the spring (6), which is dimensioned such that it at least partially deforms as it is introduced into the cavity (2), with the result that it wedges with the inner wall of the cavity (2) in the installed state on account of the spring force acting on it.

Description

Device for fixing a component in the basic body of a unit

The invention relates to a device for fixing a component in the basic body of a unit, a cavity with a stop surface for the component being formed in the basic body, and the component being pressed against the stop surface with the aid of a spring.

It is often necessary in practice for certain components of a unit to be positioned very precisely in the unit body, with the result that they assume a defined position relative to other components of the unit. An example which may be mentioned here is the arrangement of the optical components in the beam path of an optical pickup, as is used in CD and DVD players.

Such an optical pickup is provided with a laser diode as a light source. The laser beam emitted by the laser diode passes through an optical grating and a half-mirror, in order then to be collimated with the aid of a collimator lens arranged in the beam path. Following total reflection on a prism, the laser light is focused on the surface of an optical disc, CD or DVD, with the aid of a lens system such that three beams impinge as microspots on three locations of the optical disc. These three beams are selected on the surface of the optical disc and run through the abovedescribed beam path in the rearward direction as far as the half-mirror, on which they are reflected. The reflected beams then pass through a cylindrical lens, in order finally to be detected individually, corresponding to the respective microspot, with the aid of a photodiode. Clean detection and evaluation of the reflected beams is only possible with precise positioning and alignment of the individual optical components in the beam path and relative to one another . "JP U. M. Appln. Disclosure No. 2-76320" discloses the practice of fixing the optical grating of an optical pickup in a cavity in the optics body, the basic body of the optical pickup. For this purpose, a stop surface is formed in said cavity, the holder of the optical grating being pressed against said stop surface with the aid of a helical spring. Serving as the abutment for the helical spring here is the base plate of the laser-diode unit, which closes off the opening of the cavity in the optics body.

This variant for fixing an optical component proves to be problematic in a number of respects in practice since it requires mechanical, albeit non-rigid, coupling to a further optical component, which likewise has to be adjusted in the beam path.

It is thus the case with the optical pickup described in the prior art that the positioning and fixing of the laser diode in the optics body is complicated to a considerable extent by the helical spring, which actually serves for fixing the optical grating. The connection of the laser-diode unit to the optics body counter to the spring force of the helical spring is usually produced here by crimping. As a result of the relatively high wear of the crimping tool - partially broken-away crimping lugs - correct, play-free fastening of the laser diode in the optics body is nevertheless not always ensured by crimping alone. It is thus also frequently the case that the laser diode is adhesively bonded to the optics body by means of adhesive. Moreover, each movement of the optical component following the adjustment of the optical pickup is associated with the optical and electrical parameters being adversely affected. It is possible, however, for these movements to be caused not just by shock, vibration tests and thermal tests. It is also the case that a compression spring which serves for fixing the optical grating and is supported on the laser-diode unit may cause the laser diode to change its position, to be precise not just during installation.

The object of the present invention, then, is to specify a device of the type mentioned in the introduction which is intended for fixing a component and by means of which the spring which presses the component against a stop surface in the cavity of the basic body of a unit is isolated from other components which are to be positioned in said cavity.

This object is achieved by features specified in independent claims. Advantageous configurations are specified in dependent claims.

A fixing element is provided as an abutment for the spring, which is dimensioned such that it at least partially deforms as it is introduced into the cavity, with the result that it wedges with the inner wall of the cavity in the installed state on account of the spring force acting on it. The fixing element has an opening which renders it advantageously suitable as an abutment for optical subassemblies .

According to the invention, it has first of all been found that the spring which presses the component against the stop surface formed in the cavity can only be isolated from other components which are to be positioned in the cavity when an additional abutment is provided for the spring. According to the invention, it has also been found that realizing such an abutment does not necessarily require the basic body to be modified; rather, such an abutment may also be realized by the introduction of an additional fixing element into the cavity during installation. On account of its specific dimensioning and configuration according to the invention, the fixing element wedges in the cavity as the spring force acts on it and thus forms a sufficiently reliable abutment for the spring.

The invention thus proposes arranging in the cavity of the basic body a fixing element which serves exclusively as an abutment for the spring and of which the positioning is otherwise not critical for the functioning of the unit. This also proves to be advantageous in particular in respect of the positioning and adjustment of further components in the cavity, which is explained hereinbelow using the example of the positioning and fixing of the optical grating and of the laser diode of an optical pickup in a cavity of the optics body thereof.

By virtue of an additional fixing element being used according to the invention as an abutment for the spring which presses the optical grating against a stop surface provided for this purpose in the cavity of the optics body, the spring force of said spring is kept away from the laser diode, which is to be arranged at a defined distance from the optical grating, i.e. the spring is isolated from the laser diode. It is not thus necessary for the laser diode - as in the prior art - to be fixed in the cavity of the optics body counter to the spring force of said spring, with the result that the crimping operation may be dispensed with. The laser diode may then advantageously be fixed exclusively by adhesive bonding since the laser diode is not subjected to any spring force during the setting time of the adhesive. This proves to be advantageous not just in respect of installation being as straightforward, and thus also cost-effective, as possible, but also in respect of straightforward repair of the optical pickup, since a defective laser diode which is fixed in the optics body exclusively by adhesive bonding can be exchanged more straightforwardly than a laser diode which has been connected to the optics body by crimping. A further advantage of using the fixing element according to the invention as an abutment for the spring resides in the fact that the conventional variant of the basic body can be used, since the geometry of the cavity need not be changed and the fixing element according to the invention only requires a very small amount of installation space. For producing the basic body, use may thus be made of the already existing moulds.

In principle, there are various possible ways of realizing the fixing element according to the invention, by the very fact that its shape and dimensioning are at least partially determined by the geometry of the respective cavity.

It proves to be particularly advantageous if the fixing element is realized in the form of a toothed disc with tooth-like protrusions formed on the circumference, and the toothed disc is dimensioned such that at least some of the tooth-like protrusions are deformed during introduction into the cavity, with the result that these protrusions wedge with the inner wall of the cavity in the installed state on account of the spring force acting on the toothed disc. On the one hand, a disc-like fixing element requires only a comparatively small amount of installation space. On the other hand, only a comparatively small amount of deformation work is required during introduction of a toothed disc into the cavity, since only the tooth-like protrusions, or only some of these protrusions, have to be deformed. On account of the interspaces between the tooth-like protrusions, in addition, this deformation takes place in a controlled manner, with the result that the toothed disk also wedges with the inner wall of the cavity in a controlled manner as the spring force acts on it, which is a prerequisite for a reliable abutment. In order to ensure that the tooth-like protrusions provided for this purpose actually deform during introduction into the cavity, the diameter of the toothed disc, in an advantageous configuration of the invention, is greater in the region of the deforming protrusions than the corresponding diameter of the cavity.

As has already been mentioned, not all the tooth-like protrusions of the toothed disc according to the invention are to be deformed during introduction into the cavity. The toothed disc may also be dimensioned such that some of its tooth-like protrusions are not deformed during introduction into the cavity. These non-deformed tooth-like protrusions may advantageously serve as a stop surface for the spring. It is also advantageous if the non-deforming protrusions of the toothed disc are dimensioned such that they extend as far as the inner wall of the cavity following introduction of the toothed disc into the cavity. In this case, the non-deforming protrusions act as positioning aids and centring means as the toothed disc is introduced into the cavity. In this context, it proves to be advantageous, in addition, if the deforming and the non-deforming protrusions are formed alternately on the circumference of the toothed disc and/or the tooth-like protrusions are arranged on the circumference of the toothed disc such that in each case a deforming protrusion and a non-deforming protrusion are located opposite one another.

In accordance with one configuration, the contour of the tooth-like protrusions of the toothed disc is rounded, in order to avoid damage to the cavity wall as the toothed disc is introduced. It should also be possible, however, for the contour of the tooth-like protrusions to be adapted to the geometry of the inner wall of the cavity, in order to ensure good introduction of the spring force into the toothed disc and the cavity wall. For the installation of the toothed disc according to the invention, it proves to be advantageous if the toothed disc has a preferably centrally arranged through-passage opening. Such a through-passage opening could serve as a means of engagement for a tool, by means of which the toothed disc could then be introduced into the cavity to a defined depth.

For production reasons, the cavity is formed in a basic unit body, and in which components are to be arranged and adjusted in relation to one another, are frequently of conical or essentially cylindrical form. Such basic bodies may then be produced by (injection) moulding. The device according to the invention or the fixing element according to the invention is particularly well-suited for fixing a component in such a basic body with an essentially conical or cylindrical cavity, an end surface of the cavity serving as a stop surface for the component, and the component being pressed against the stop surface with the aid of a helical spring which is arranged parallel to the longitudinal axis of the cavity. In particular, the fixing element according to the invention is suitable for fixing an optical component, such as an optical grating, in the basic body or optics body of an optical pickup.

In principle, there are different possible ways of advantageously configuring and developing the present invention. For this purpose, you are referred, on the one hand, to the claims and, on the other hand, to the following explanation of an exemplary embodiment of the invention with reference to the drawings, in which

Figure 1 shows a sectional illustration through the optics body of an optical pickup in the region of the optical grating and of the laser diode, the optical grating being fixed with the aid of a fixing element according to the invention, Figure 2 shows a plan view of the fixing element according to the invention illustrated in Figure 1, and

Figures 3a/b show two possible contours for the toothlike protrusions of the toothed disc which serves as a fixing element according to the invention.

In Figure 1, 1 designates the basic body of an optical pickup, which will always be referred to as optics body 1 hereinbelow. An essentially cylindrical cavity 2 is formed in the optics body 1, the end surface 3 of said cavity serving as a stop surface for an optical grating 4 and/or the holder 5 thereof. The optical grating 4 is pressed against the stop surface 3, and thus fixed in the cavity 2, with the aid of a helical spring 6, which acts on the holder 5 via an intermediate disc 7.

According to the invention, a fixing element 8 arranged in the cavity 2 forms an abutment for the spring 6. Said fixing element 8, which in the exemplary embodiment illustrated here is realized in the form of a toothed disc 8, is dimensioned such that it at least partially deforms as it is introduced into the cavity 2, with the result that it wedges with the inner wall of the cavity 2 in the installed state on account of the spring force acting on it.

The spring force of the spring 6 is absorbed in full by the stop surface 3, on the one hand, and the fixing element 8 or the cavity wall, on the other hand, with the result that it is not possible for a spring force to act on a laser-diode unit 9, which is arranged in the cavity 2 behind the fixing element 8, although the spring 6 is arranged spatially between the optical grating 4 and laser-diode unit 9. The laser-diode unit 9 may thus simply be adhesively bonded into the cavity 2 of the optics body 1.

A stop 10 for the precise positioning of the laser-diode unit 9 is formed in the wall of the cavity 2. Said stop 10 may advantageously also be used for the precise positioning of the fixing element 8, which has to be introduced into the cavity 2 before the laser-diode unit 9 is secured. For this purpose, it would be possible to use a special tool which interacts with the stop 10 such that the fixing element 8 can only be introduced into the cavity 2 as far as its desired position.

As has already been mentioned, the fixing element illustrated in Figure 1 is a toothed disc 8, which is illustrated again in Figure 2 on its own and in plan view. Tooth-like protrusions 11 and 12 of different lengths and widths are formed on the circumference of the toothed disc 8. The toothed disc 8 with these tooth-like protrusions 11 and 12 is dimensioned such that at least the longer, narrower tooth-like protrusions 11 are deformed, i.e. bent to a slight extent counter to the direction of introduction, during introduction into the cavity 2 of the optics body 1, with the result that these protrusions 11 wedge with the inner wall of the cavity 2 in the installed state on account of the spring force acting on the toothed disc 8 counter to the direction of introduction .

For this purpose, the diameter of the toothed disc 8 illustrated here is greater in the region of the deforming protrusions 11 than the corresponding diameter of the cavity 2. Moreover, the toothed disc 8 is dimensioned such that the shorter, wider tooth-like protrusions 12 are not deformed during introduction into the cavity. These non-deforming protrusions 12 of the toothed disc 8 are dimensioned such that they extend as far as the inner wall of the cavity 2 following introduction of the toothed disc 8 into the cavity 2. These protrusions 12 are intended to centre the toothed disc 8 during introduction into the cavity 2 and, at the same time, form a defined abutment surface for the helical spring 6.

The deforming, longer and narrower protrusions 11 and the non-deforming, shorter and wider protrusions 12 are formed alternately on the circumference of the toothed disc 8. Moreover, the tooth-like protrusions 11 and 12 are arranged on the circumference of the toothed disc 8 such that in each case a deforming protrusion 11 and a non-deforming protrusion 12 are located opposite one another.

Finally, the toothed disc 8 also has a centrally arranged, round through-passage opening 13 for an installation tool.

Figures 3a and 3b illustrate that the tooth-like protrusions 11 and 12 may have different contours. It is thus possible for the contour at least of some of the tooth-like protrusions to be adapted to the geometry of the inner wall of the cavity, as is illustrated in Figure 3a, or else to be rounded, as is illustrated in Figure 3b.

The embodiments described here are only specified as examples, and a person skilled in the art may realize other embodiments of the invention which remain within the scope of the invention.

Claims

Patent Claims

1. Device for fixing a component in the basic body (1) of a unit, a cavity (2) with a stop surface (3) for the component (4, 5) being formed in the basic body

(1), and the component (4, 5) being pressed against the stop surface (3) with the aid of a spring (6), characterized in that a fixing element (8) is provided as an abutment for the spring (6), which is dimensioned such that it at least partially deforms as it is introduced into the cavity (2), with the result that it wedges with the inner wall of the cavity (2) in the installed state on account of the spring force acting on it.

2. Device according to Claim 1, characterized in that the fixing element (8) is realized in the form of a toothed disc (8) with tooth-like protrusions (11, 12) formed on the circumference, and in that the toothed disc (8) is dimensioned such that at least some of the tooth-like protrusions (11) are deformed during introduction into the cavity (2), with the result that these protrusions (11) wedge with the inner wall of the cavity (2) in the installed state on account of the spring force acting on the toothed disc (8) .

3. Device according to Claim 2, characterized in that the diameter of the toothed disc (8) is greater in the region of the deforming protrusio,ns (11) than the corresponding diameter of the cavity (2) , and the toothed disc (8) is dimensioned such that some of its tooth-like protrusions (12), in order to form a centring means with the inner wall of the cavity (2) , are not deformed during introduction into the cavity (2) .

4. Device according to Claim 2, characterized in that the deforming and the non-deforming protrusions (11, 12) are arranged alternately on the circumference of the toothed disc (8) .

5. Device according to Claim 2, characterized in that the tooth-like protrusions (11, 12) are arranged on the circumference of the toothed disc (8) such that in each case a deforming protrusion (11) and a non- deforming protrusion (12) are located opposite one another.

6. Device according to one of Claims 1 to 5, characterized in that the tooth-like protrusions (11, 12) are rounded or adapted to the geometry of the inner wall of the cavity (2) .

7. Device according to one of Claims 1 to 6, characterized in that the toothed disc (8) has a preferably centrally arranged through-passage opening (13) .

8. Use of a device according to one of Claims 1 to 7 for fixing a component (4, 5) in a basic body (1) with an essentially conical or cylindrical cavity (2), an end surface (3) of the cavity (2) serving as a stop surface (3) for the component (4, 5), and the component (4, 5) being pressed against the stop surface (3) with the aid of a helical spring (6) which is arranged parallel to the longitudinal axis of the cavity (2) and is supported on a fixing element (8) as abutment.

9. Use of a device according to one of Claims 1 to 7 for fixing an optical component (4, 5), in particular an optical grating (4), in the basic body (1) of an optical pickup.

0. Unit for recording or reproducing information on optical recording media, having a pickup (3), characterized in that a device for fixing an optical component (4, 5) in the optics body (1) according to one of Claims 1 to 7 is provided in the pickup (3) .