Horizontally supported planar surfaces – Vertically adjustable – With force-multiplying means
Reexamination Certificate
2001-06-08
2003-07-01
Wilkens, Janet M. (Department: 3637)
Horizontally supported planar surfaces
Vertically adjustable
With force-multiplying means
C188S07700R
Reexamination Certificate
active
06584917
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
REFERENCE TO A “MICROFICHE APPENDIX”
Not Applicable
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a device for mounting on a shaft which can prevent the rotation of the shaft. In particular, the present invention relates to a device which mounts on a rotatable shaft which is part of the movement mechanism for a work surface of a workstation. The device prevents rotation of the shaft when the device is in the lock position. The device also prevents rotation of the shaft when the load on the work surface is out-of-balance.
(2) Description of the Related Art
The related art has shown various devices for controlling the rotation of a shaft in either direction using the frictional force of a wrap spring. Illustrative are U.S. Pat. Nos. 5,010,983; 5,197,704 and 5,354,028 all to Kitamura.
Kitamura '983 describes a device for locking the rotation of a shaft in both directions using a device having a single spring mounted around a fixed shaft and a movable shaft. Further, the device does not prevent unlocking or rotation of the shaft when an out-of-balance load is applied to the shaft.
Kitamura '704 describes an angle adjusting device for adjusting an angle of indication of a display device. The device includes a rotatable axis having small diameter end portions with a large diameter center portion spaced therebetween and a pair of fixed axis rotatably supporting the small diameter portions. A pair of coil springs having the same winding direction are mounted on the center large diameter portion and the pair of fixed axis.
Kitamura '028 describes a device for adjusting the angle of indication of a display device. The device includes a rotatable axis rotatably supported by a fixed axis with at least one (1) coil spring closely mounted over the rotatable axis and having an end fastened on the fixed axis.
Also of interest are U.S. Pat. Nos. 4,457,406; 5,219,045; 5,441,129 and 5,568,843 all to Porter et al and 5,794,470 to Stringer which show a mechanism lock having a rod axially movable through a lock housing, with one (1) or more coil springs tightly wound about the rod and axially fixed to the housing so as to normally grip the rod against axial or longitudinal movement through the housing. A release is provided for partially unwinding the coil springs to release the rod for axial movement relative to the lock housing.
U.S. Pat. No. 4,600,240 to Suman et al describes a unidirectional friction clutch for a headrest. The headrest is rigidly secured to an axle. The axle is pivotally mounted within a U-shaped fixed bracket. The spring clutch includes a coil spring which extends over the axle. One (1) end of the spring is anchored to the fixed bracket and the opposite end is anchored to the headrest. The spring is wound around the axle to prevent clockwise rotation of the headrest since clockwise rotation tends to tighten the grip of the spring around the axle. Movement of the headrest in a counterclockwise position expends the spring which loosens the grip of the spring on the axle allowing the axle and headrest to move. Thus, this device only prevents rotation of the axle in one (1) direction. Further, the device does not prevent movement of the shaft when an out-of-balance load is applied to the headrest.
Only of minimal interest is U.S. Pat. No. 5,186,285 to van der Werff describes a device for controlling the rotation of a shaft in one (1) direction in response to a continuous torque being applied to the shaft. A control member is used to wrap and unwrap the spring. The device is not intended to control rotation of a shaft in both directions.
None of the above devices prevent unlocking of the device or rotation of the shaft when an out-of-balance load is applied to the shaft.
There remains the need for a device which prevents the rotation of a shaft in either direction when in the lock position and which can not be moved into the unlock position if an out-of-balance force is applied to the shaft.
SUMMARY OF THE INVENTION
In one (1) embodiment, the device is mounted on a shaft or axle extending between the legs of a counterbalance table or workstation. When in the active or lock position, the device prevents the shaft from rotating which prevents the movement mechanisms in the legs from raising or lowering the work surface. The device also includes an anti-release mechanism which prevents release of the device by the main release lever when an out-of-balance force is applied to the work surface such that the work surface is out-of-balance. The additional force can be applied in either direction. The force can be in the form of an additional load or less load on the work surface.
In one (1) embodiment the device includes a housing plate and a U-shaped mounting bracket with the shaft extending through the legs of the mounting bracket. A pair of fixed hubs are fixably mounted on the shaft between the legs of the mounting bracket. One of the fixed hubs is mounted adjacent the inner side of each of the legs of the mounting bracket. The fixed hubs have a first portion and a second portion. Each portion preferably has a cylindrical shape. The fixed hubs are mounted on the shaft such that the first portion of the hub is adjacent the leg of the mounting bracket and the second portion extends inward along the shaft. A rotatable hub is rotatably mounted on the shaft spaced between the fixed hubs. The rotatable hub has a first end portion, a second portion and a center portion. The rotatable hub is mounted on the shaft such that the first and second end portions extend outward toward the fixed hubs. The center portion of the rotatable hub includes an extension which extends downward toward and through an opening in the center portion of the mounting bracket. A spring wire is connected at one end to the extension. The other end of the spring wire is fixably mounted. A first and second wrap spring extend between each of the fixed hubs and the rotatable hub and are mounted over the second portions of the fixed hubs and end portions of the rotatable hub. The diameters of the second portion of the fixed hubs and the end portions of the rotatable hub are preferably only slightly greater than the inner diameter of the wrap springs such that the wrap springs are force fit over the second portions of the fixed and rotatable hub. The first end of each wrap spring adjacent the fixed hubs extend through the first and second slots in the housing plate. An anti-release mechanism is mounted on the front side of the center portion of the housing plate adjacent the slots. The anti-release mechanism preferably includes a first and second release lever and a sliding release block. The levers are pivotally mounted to the housing plate between the slots. The levers have opposed first and second ends with the pivot point located between the ends. The first release lever is mounted such that the first end of the release lever extends across the first slot and a top edge of the first end of the first release lever is in contact with the first end of the first wrap spring. The second end of the first release lever is connected to a spring which is connected at the other end to the housing plate. The spring acts to bias the first release lever into the release position. The first end of the second release lever extends adjacent the first end of the first release lever. The second end of the second release lever extends across the second slot in the housing plate and the bottom edge of the second end is in contact with the first end of the second wrap spring. The second lever is connected to one end of a spring. The other end of the spring is connected to the housing plate. The spring acts to bias the second release lever into the release position.
The sliding, release block is mounted adjacent the first ends of the release levers and is connected by a cable to the main release lever. The main release lever is preferably adjacent the front of the work surface where it is easily accessible by
McLeod Ian C.
Moyne Mary M.
Wilkens Janet M.
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