Dynamic information storage or retrieval – Dynamic mechanism subsystem – Specified detail of transducer assembly support structure
Reexamination Certificate
1998-10-02
2001-06-12
Ometz, David L. (Department: 2754)
Dynamic information storage or retrieval
Dynamic mechanism subsystem
Specified detail of transducer assembly support structure
Reexamination Certificate
active
06246662
ABSTRACT:
The present invention relates to a vibration damping system and to a servowriter.
Many types of apparatus need to be isolated from vibrations which would otherwise be transmitted to the apparatus from a substrate such as a stand, shelf or other fixture on which the apparatus is mounted.
In particular, information for systems such as data processing systems is typically stored on storage media. Particular use is made of storage disks such as magnetic disks, opto-magnetic disks, and the like. In manufacturing storage media such as hard disk drives, a head disk assembly consisting of the disk or disks, the read/write head(s), the motor and arm electronics, is mounted in a mastering station known as a servowriter. The servowriter writes a pattern of magnetic information (the “servo track pattern” ) onto the disk. The servo track pattern becomes the master reference which is used by the disk drive during normal operation in order to locate the tracks and sectors on the disk for data storage and retrieval.
The time taken to write the servo tracks is increasing each year, for several reasons. In particular, the number of tracks per inch on the disk is increasing annually, owing to improved manufacturing techniques and improved control of the read/write head or heads. Furthermore, head disk assemblies are being manufactured and assembled more quickly each year so that the rate at which the assembled head disk assemblies come off the production line ready for servo track writing is increasing each year. Because the servowriting process is normally carried out in a clean room, and clean room space is expensive, there is generally a desire to reduce the size of the servowriters so that more servowriters can be fitted in a particular clean room space.
Traditionally, servowriters have used a linear positioning system to position the product head (i.e. the read/write head of the head disk assembly) in the head disk assembly during the servowriting process. This meant that a large stable base was required to support the servowriter. The servowriter base in such cases was typically granite. However, it was still necessary to isolate the servowriter from external vibrations. Thus, a low frequency active damping system was applied to the base, which was inevitably expensive. Preferably, therefore, a low cost passive damping system should be used.
Modern servowriters use rotary positioning systems to position the product arm, the rotary positioning system typically being mounted within the footprint of the head disk assembly when mounted on the servowriter. Because a rotary positioning system is used to position the product arm, and a balanced product head arm is used, the sensitivity of the servowriter to translational movement such as base distortion and creep is much reduced compared to a linear positioning system. However, because of the increase in the track density, the need for good isolation against vibration is even greater than previously. It would be possible to provide an active vibration damping system, but the cost of an active system is significant. Accordingly, it is desirable to provide a low cost passive vibration damping system which can provide damping of vibrations in a rotary direction generally or substantially in the plane of the servowriter.
According to a first aspect of the present invention, there is provided a vibration damping system for damping vibrations in an apparatus, the damping system comprising: resilient means for supporting at least the majority of the weight of the apparatus, the resilient means having a first spring rate; and, damping means for damping vibrations of the apparatus, the damping means having an effective second spring rate; the ratio of the first spring rate to the effective second spring rate being r:1 where r<1.
The resilient means carries at least the majority, and preferably substantially the whole, of the weight of the apparatus. This means that in the preferred embodiment the apparatus is “floating” on the resilient means. This in turn allows inexpensive damping means (such as rubber mounts) to be used to damp vibrations arising in the apparatus as the damping means is not subjected to any substantial load. The use of resilient means having a relatively low spring rate compared to the effective spring rate of the damping means ensures that the damping effect of the damping means is not diluted by the resilient means, the resilient means therefore contributing relatively little to the overall damping effect provided by the damping system as a whole.
The damping means is preferably arranged to passively damp rotary vibrations of the apparatus.
The resilient means is preferably mounted to support the apparatus at the centre of mass of the apparatus.
The damping means is preferably mounted to be radially outwards of the centre of mass of the apparatus. In other words, the damping means is preferably mounted so as not to be at the centre of mass of the apparatus.
It is most preferred that the damping means be mounted at or towards the periphery of the apparatus.
Preferably, r is in the range 0.5 to 0.1.
The damping means preferably comprises plural damping mounts.
The resilient means may be a compression spring. The compression spring may be a coil spring.
The damping means may be rubber. Any other suitable material may be used.
In one specific application of the system, the apparatus is a servowriter base.
The servowriter base may be integral with a servowriter.
Alternatively, a servowriter may be mounted on the base.
The servowriter may have a rotary positioning system for rotary positioning of a product arm of a head disk assembly mounted on the servowriter.
According to a second aspect of the present invention, there is provided a servowriter, the servowriter comprising: a rotary positioning system for rotary positioning of a product arm of a head disk assembly mounted on the servowriter; a compression spring mounted at or substantially at the centre of mass of the servowriter for supporting at least the majority of the weight of the servowriter base, the compression spring having a first spring rate; and, plural vibration damping mounts at or towards the periphery of the servowriter for passively damping rotary vibrations of the servowriter, the vibration damping mounts having an effective second spring rate; the ratio of the first spring rate to the effective second spring rate being in the range r:1 where r<1.
REFERENCES:
patent: 4722505 (1988-02-01), Kaiser
patent: 4932019 (1990-06-01), Bessho
patent: 5379990 (1995-01-01), Ando et al.
patent: 5659436 (1997-08-01), Yarmchuk et al.
patent: 5668679 (1997-09-01), Swearingen et al.
patent: 5875064 (1999-02-01), Chainer et al.
patent: 5988513 (1999-11-01), Dean et al.
patent: 1 332 669 (1973-10-01), None
patent: 1 354 105 (1974-05-01), None
Collins Graham
Hearn Anthony R.
Presly Colin
Altman, III Franklin D.
Havant International Limited
Ometz David L.
Pillsbury & Winthrop LLP
LandOfFree
Vibration damping system and servowriter does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Vibration damping system and servowriter, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Vibration damping system and servowriter will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2521072