Ventilation – Workstation ventilator – Movable
Reexamination Certificate
2003-07-11
2004-11-09
Boles, Derek S. (Department: 3749)
Ventilation
Workstation ventilator
Movable
C454S056000, C049S445000
Reexamination Certificate
active
06814658
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to counter-balance mechanisms for automatically controlling the opening or closing movement of sashes, doors or other closure members on housings or enclosures. More particularly, the invention relates to such counterbalance mechanisms that are especially well-suited for use in fume hoods, laboratory station enclosures, work chambers or other such housings or enclosures having systems for ventilating or exhausting their interiors.
Laboratory fume hoods and other such work station enclosures generally include a housing or other enclosed interior having an opening providing the user with access for performing various operations within an interior work chamber. Typically, a sash, door or other closure member is movably disposed within the access opening for opening or closing the enclosure. Because the operations conducted in such interiors often involve undesirable gases, fumes or vapors, these enclosures frequently include an exhaust conduit communicating the interior work space with a blower or other gas conveying device for removing such gases, fumes or vapors and for substantially preventing their escape into the surrounding environment.
In addition to the above components, these fume hoods or work enclosures typically include one or more counterweights that counterbalance the weight of the sash and any other forces tending to close the sash or door, thus allowing it to stay in a selected position when released by the operator. These counterbalance systems can include spring members that counterbalance the weight of the sash and can include sash weights hidden within the frame of the fume hood and cables that extend over pulleys and interconnect the sash or other closure member with the counterweights.
In many laboratories or other such facilities, fume hood enclosures are required to be large in order to allow relatively large equipment to be freely inserted into the interior work chamber. However, these configurations have resulted in unduly expensive exhaust equipment and high operating costs needed for exhausting the interior work chamber and maintaining it at a lower pressure than that of the surrounding environment due to the large access openings. These expenses have also been aggravated by the operating costs associated with replacing and reconditioning relatively large amounts of conditioned air from the surrounding environment that was lost by way of the large fume hood access opening and the exhaust system. In addition, although most users typically open fume hood sashes only enough to provide adequate access for performing the desired operations, these closure members are sometimes inadvertently left fully open or near fully open, in an at-rest position, after the user has completed the operations and vacated the area, thus further contributing to such increased expenses and costs.
In order to eliminate or substantially minimize these problems, a number of prior art devices have been proposed for automatically returning sashes or other closure members to either closed or minimally open positions. These solutions, however, have often involved tandem or multiple counterweight arrangements, and sensor-activated motorized closing equipment, for example, and thus have proved to be too complex, expensive or otherwise disadvantageous to be either effective or cost-justified in many fume hood or work chamber applications.
One such prior art device is disclosed in Schiles U.S. Pat. No. 5,688,168. In this patent the counterweight system includes a primary counterweight and a second adjusting weight. The second adjusting weight is arranged to add to the weight of this primary counterweight during certain movement of the sash to thereby allow the sash member to drop to a predetermined position after it is raised above that point. The second adjusting weight is dropped off of the primary counterweight during other movement of the sash.
One major disadvantage of this system is that the adjusting weight and the primary counterweight are both static, and the weight adjustment can be made at only one finish point during the vertical movement of the sash.
The present invention seeks to overcome these and other disadvantages and to further improve on prior art devices.
SUMMARY OF THE INVENTION
All embodiments of the present invention include an enclosure having an interior chamber, an access opening in the enclosure providing access to the interior chamber, a closure member movable between closed and fully open positions in the access opening for selectively allowing and restricting access to the interior chamber. The present invention relates to improvements in the counterweight system used with the closure member.
One series of embodiments of the present invention relate to an apparatus and method for uniquely using force moments to vary the effective weight of the counterweight and control the movement of a closure member, such as the sash of a fume hood. The first of these embodiments includes at least one primary counterweight, a primary connecting member interconnecting the primary counterweight and the closure member for movement therewith, and a primary roller member mounted for rotation about an axis of rotation, the primary roller member being engaged by the primary connecting member intermediate the primary counterweight and the closure member for rotation by the primary connecting member in response to movement of the closure member. Additionally, this embodiment includes at least one secondary counterweight, a secondary roller member arranged to rotate with the first roller member, and a secondary connecting member interconnecting the secondary roller member and the secondary counterweight, the secondary member movably winding and unwinding on the secondary roller member in response to movement of the closure member. When the closure member is moved between its fully closed position and a predetermined intermediate position between the closed and fully open positions, the secondary connecting member winds and unwinds from the secondary roller member in a first moment-producing direction on the secondary roller member. When the closure member is moved between the its fully opened position and the intermediate position, the secondary connecting member winds and unwinds on the secondary roller member in a second moment-producing direction on the secondary roller member, the second moment producing direction being opposite to the aforesaid first moment-producing direction.
Preferably, the closure member is a sash member movable generally vertically between the fully closed and fully open positions, and the primary and secondary counterweights maintain the closure member in a substantial stationary at-rest condition when the closure member is located at its predetermined intermediate position between its fully open and fully closed positions. The connecting members may be a chain or toothed belt engaging the outer periphery of teeth formed on pulleys, or a cable having one end fixedly interconnected to a pulley, or a cable having a traction-surface thereon for positively engaging a pulley. The primary and secondary pulleys may have diameters which are the same or different from one another.
The primary counterweight may be a single u-shaped weight, or a plurality of weights, each connected to the closure member by a separate connecting member, and some or all of the rollers may be pulleys that are connected together by a shaft for rotation about the axis of rotation of the shaft. The secondary counterweight may be attached to the shaft at a position intermediate the point at which two primary counterweights engage the shaft. Alternatively, the primary and secondary pulleys may be joined integrally as a double-grooved pulley mounted for rotation about an axis of rotation.
In another embodiment of the present invention generally similar the first embodiment described above, at least one primary counterweight is used as in the first embodiment described above. This embodiment also includes a pair of secondary
Poblete Rudolph
Rindoks Kurt P.
Boles Derek S.
Kennedy Covington Lobdel & Hickman, LLP
Kewaunee Scientific Corporation
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