Dynamic information storage or retrieval – Dynamic mechanism subsystem – Specified detail of transducer assembly support structure
Reexamination Certificate
1999-02-11
2002-08-20
Miller, Brian E. (Department: 2652)
Dynamic information storage or retrieval
Dynamic mechanism subsystem
Specified detail of transducer assembly support structure
C369S269000
Reexamination Certificate
active
06438094
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a device for reading from and/or writing to recording media in disc form which has an unbalance compensation means.
BACKGROUND OF THE INVENTION
A device of this type is disclosed in WO 84/01863. This device has a brushless DC motor as drive motor which causes the recording medium in disc form to effect a rotary movement. The recording medium is secured to the drive motor by means of a securing means, in this case the motor hub. In order to obtain a rotary movement of the recording medium which is as free as possible from unbalance, the DC motor, as the unbalance compensation means, is designed in such a way that milling has to be effected only once at one location in order to obtain unbalance compensation. The device is constructed in such a way that no unbalance can arise in the course of assembly, repair or the like.
The known device may be regarded as having the disadvantage that freedom from unbalance exists only when the recording medium in disc form also has no unbalance at all. Although this can be ensured in the case of hard disc devices, this is not so in the case of devices having exchangeable recording media.
SUMMARY OF THE INVENTION
The object of the invention is to propose a device of the abovementioned type which has the smallest possible unbalance even when exchangeable recording media are used.
This object is achieved by means of the measures specified in the independent claims.
The invention provides for the unbalance compensation means to be a centrifugal force generation means which generates a centrifugal force which is variable during operation. The advantage of such a dynamic unbalance compensation means consists in the fact that tolerances of the recording medium, tolerances in the securing thereof and also tolerances of the drive motor are permitted to be relatively high without the unbalance caused thereby having a disruptive influence on the operation of the device, since this unbalance is compensated for by the dynamic unbalance compensation means and is adapted to possibly changing conditions even during operation. Recording media afflicted by unbalance, such as so-called shape CDs, for example, which under certain circumstances do not have uniform mass distribution, can be played back without difficulty in a device according to the invention.
Another aspect of the present invention provides for the unbalance compensation means to be a positioning means for positioning the recording medium. This has the advantage that the unbalance is compensated for directly at its source. That proportion of the unbalance which is caused by the recording medium or the positioning thereof in the device and, by its nature, cannot be compensated for during the production or service of the device is thus compensated for. The positioning means serves to position the recording medium in such a way that the centre of mass of the said recording medium is oriented such that it is centred with respect to the axis of the drive motor or the axis of rotation of the recording medium.
According to the invention, the positioning means has spring elements and damper elements, which are arranged such that they are distributed uniformly over the circumference of the unbalance compensation means. This has the advantage that automatic centring of the recording medium relative to its axis of rotation is enabled as a result of this. Spring and damper forces cancel one another out by virtue of the uniformly distributed arrangement, and forces occurring in the event of an unbalance act on the spring and damper elements in such a way that the centre of mass of the recording medium is displaced towards the axis of rotation. This is carried out at a relatively low speed of rotation which is matched to the spring and damper forces or properties. The self-centred position of the recording medium is subsequently fixed and maintained.
According to the invention, the centrifugal force generation means has a mass element, which can be moved during operation. This has the advantage that the centrifugal force can be altered in a simple manner by alteration of the position of the mass element. In this case, the mass element is advantageously arranged on a rotating part and in a manner such that it can move with respect to this part, with the result that a displacement of the mass element is accompanied by an alteration of the unbalance. The invention provides for the use of one or more mass elements of this type. A single mass element is advantageously designed such that it can be displaced both radially and in the angular direction with respect to the rotation of the rotating part. The use of two mass elements has the advantage that they need be arranged such that they can be displaced in each case only in one dimension, that is to say radially or in the angular direction, in order to be able to compensate for the unbalance. The use of a larger number of mass elements, for example three, four or more, leads to more uniform mass distribution also in the direction of the axis of rotation. The higher symmetry that is obtained for these and even higher numbers such as, for example, six, eight, etc., contributes to reducing the wear and to simplifying production of the device.
The invention provides for two mass elements to be arranged such that they can move about the axis of rotation of the recording medium. This has the advantage that a change in the angular position of the mass elements is easily possible by virtue of the arrangement allowing movement about the axis of rotation. Since two mass elements are involved, the radial component of the mass distribution can also be set in a simple manner by a symmetrical change in the angular position of these mass elements. The mass elements advantageously have essentially the shape of a segment of a circle or segment of an annulus, in particular the shape of a semicircle or of half an annulus. If there are more than two mass elements, provision is made for correspondingly smaller segments of a circle which together produce a full circular disc, the consequence of this being the most uniform mass distribution possible. The movable securing of the mass elements should be designed to be as compact as possible in order to disrupt the mass distribution as little as possible. Segments of an annulus have the advantage that a greater mass accumulation is present radially on the outside, which, given an identical additional mass, enables greater effectiveness than in the case of radially uniform mass distribution. The axis of rotation is generally identical to that of the drive motor. The mass elements are advantageously arranged in proximity to the recording medium in order to compensate for the unbalance as close as possible to its source, and consequently to minimize mechanical stresses on the spindle and the bearings thereof, and also to prevent the propagation of vibration on device or drive motor to the greatest possible extent.
A further refinement of the invention provides for a plurality of small mass elements to be used which can be placed along a circumference or a radius of the centrifugal force generation means. This has the advantage that a larger number of mass elements can easily be metered and a high outlay in terms of mechanical holding is unnecessary, as a result of which the centrifugal force generation means can be designed in a space-saving manner. The mass elements can advantageously be placed on a circumference which, in the radial direction, is relatively far removed from the centre, since, at that location, their influence is relatively large even when the total mass is relatively small. In this case, the mass elements are advantageously held by the centripetal force, which is not present without rotation of the recording medium, in which case, however, unbalance compensation is not necessary either.
Instead of a circumference or a radius of the centrifugal force generation means, it is likewise possible to use the circumference or the radius generally of a rotating part, without leavi
Mahr Peter
Oldermann Klaus
Chen Tianjie
Laks Joseph J.
Miller Brian E.
Thomson Licensing S.A.
Tripoli Joseph S.
LandOfFree
Device for reading from or writing to recording media in... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Device for reading from or writing to recording media in..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device for reading from or writing to recording media in... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2890074