Spring devices – Resilient shock or vibration absorber
Reexamination Certificate
1998-12-15
2001-03-13
Schwartz, Christopher P. (Department: 3613)
Spring devices
Resilient shock or vibration absorber
C361S689000
Reexamination Certificate
active
06199839
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to computer peripheral devices and more particularly to vibration dampening mechanisms for removable drives and storage systems.
BACKGROUND OF THE INVENTION
Removable hard disk drives are sometimes grouped together into a larger unit or array, such as in Redundant Arrays of Inexpensive Disks (commonly referred to as “RAID systems”). A cast rack with guide rails generally houses the array of hard disk drives. Typical racks may house six rows of disk drives, and each row may contain eight drives arranged horizontally. Each disk drive in the rack is housed in a plastic drive carrier that slides into the rack along a guide rail. Each drive carrier is typically constructed of two substantially symmetrical halves or pieces, each of which has a number of air channel openings. The pieces are fastened together around grooved symmetrical guides.
Unfortunately, these systems face a serious problem with vibration which is a significant cause of disk drive failure. Each hard drive contains a rotating spindle which generates vibrations. The vibrations are not fully absorbed by the carrier. In addition, the construction of the carrier precludes fixing the drive in a manner that eliminates vibration. Furthermore, it is not economically feasible to construct the disk carriers in such a way that they fit together in the cast racks with tolerances tight enough to eliminate the vibration of the carrier within the rack.
Five and a quarter inch disk drives which were previously in use tolerated the vibration well, in part because the higher form factors had lower track and bit densities. However, with the movement towards miniaturization, such as in three and a half inch disk drives, the smaller form factors have higher bit and track densities and are extremely susceptible to vibration. With smaller drives presently in use even slight vibrations cause read and write errors, and substantial vibration(s) may cause disk drive failure.
One implementation aimed at addressing the vibration problem involved compressing a strip of Velcro® between the drive carrier and rack structure. Velcro® is a compressible material that slides with relative ease along the guide rail. This method of dampening vibrations poses several problems. Because it is difficult to fix the Velcro® to the drive carrier, the Velcro® has a tendency to slip out of place as the drive is slid relative to the rack structure. The Velcro® also makes it more difficult for the drive to be inserted because engagement channels on the drive carrier cannot fully engage the guide rail with the Velcro® in place. Furthermore, the Velcro® compresses after a period of time thereby reducing the vibration dampening properties resulting from disposing the compressible material between the drive carriers and the rack structure.
SUMMARY OF THE INVENTION
The present invention provides a vibration dampening mechanism which considerably reduces the probability of disk drive failure and which ensures vibration damped engagement between a drive carrier and a rack structure.
According to the invention, the vibration dampening mechanism comprises a torsion spring connected to two movable ramps located on either side of the carrier. The dampener is designed so that the ramps are moved along the sides of the drive as a function of the tolerance between the drive carrier and the rack structure. If the tolerance between the drive carrier and the rack is slight (i.e., the carrier fits tightly in the rack), the ramp is actuated in a first direction to a great extent as it is displaced by the rack's structure. On the other hand, if the tolerance between the drive carrier and the rack is higher (i.e., the carrier fits loosely in the rack), the ramp is actuated in the first direction to a lesser extent so that the ramp effectively decreases the tolerance between the carrier and the rack. This mechanism allows the carriers in the rack to fit along side each other with minimal vibration as the tolerance between carriers and the rack is taken up by the ramps of respective vibration dampening mechanisms.
In further accord with the invention, the vibration dampening mechanism is implemented in clam shell drive carriers configured with four slide ridges, two mated on each side of the assembled carrier. The dimensions of the ridges are such that each receives a ramp which engages with a respective guide rail on the cast rack. Each of the two substantially identical plastic ramps slides on the slide ridges as a function of the tolerance between the carrier and the respective guide rail on the cast rack. A tapered section of each ramp is dimensioned to fill the maximum possible gap between the drive carrier and the rack. Both ramps on a drive carrier are connected to a single biasing, torsion spring in a manner that substantially prevents the ramps from twisting or moving in an undesirable direction. The torsion spring rests against an abutting surface on the drive carrier.
Features of the invention include mimimized vibration of the disk drives in an array. The dual ramp system effectively eliminates the tolerance in dimensions of the drive carriers and the rack. The ramps are designed to fit on to existing drive carriers with minimal modifications to the drive carrier. They are compact and slide along the slide ridges easily. This makes the insertion of the drive carrier into the chassis easier on the installer. The ramps are connected to an inexpensive torsion spring which is compact enough to fit inside the clam-shell drive carrier. The torsion spring is connected to the ramps in a manner that substantially prevents them from twisting or moving in an undesirable direction, to maintain them in alignment with the guide rail. This also ensures that the whole assembly fits together securely and reduces the possibility of mechanical problems arising with the movable parts. The vibration dampening mechanism is a cost-effective, compact and efficient method of combating the vibration problem in arrays of hard disk drives. By minimizing vibration, the present invention reduces read and write errors and lowers the likelihood of bad sector formation. This enhances the performance of the drives.
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Brown Rudnick Freed & Gesmer, PC
EMC Corporation
Michaelis, Esq. Brian L.
Schwartz Christopher P.
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