Electricity: magnetically operated switches – magnets – and electr – Electromagnetically actuated switches – With housing or support means
Reexamination Certificate
2000-04-06
2001-03-27
Donovan, Lincoln (Department: 2832)
Electricity: magnetically operated switches, magnets, and electr
Electromagnetically actuated switches
With housing or support means
C200S293000
Reexamination Certificate
active
06208229
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to power switches for interrupting current in electric power circuits. More particularly, it relates to a molded housing for such switches having a removable secondary cover which encloses recesses for auxiliary devices in a primary cover, and an attachment arrangement for repeatedly removing and replacing the secondary cover over the primary cover.
BACKGROUND INFORMATION
Power switches, such as circuit breakers, transfer switches and the like, used in low voltage (600 volts and below) electric power distribution systems commonly have a housing molded of an electrically insulative resin and are, therefore, referred to as molded case circuit breakers, transfer switches and the like. The molded housing includes a base and a cover which together form an enclosure in which are mounted one or more switch poles, a switch operating mechanism and, where appropriate, a trip device. Typically, the molded case circuit breaker has a trip device that responds to short circuits, and/or to persistent overcurrent conditions, by opening the main switch contacts to interrupt the current.
Often, it is desirable to provide additional features on the switch, sometimes as options. Such additional features can include a remote trip, an auxiliary switch which provides an indication of the open or closed state of the main switch contacts and/or a bell alarm which provides an indication that the trip device has been activated. In some installations, it is desirable to have the switch open on undervoltage or off frequency conditions to prevent damage to a protected load.
These additional features can be incorporated within the switch housing formed by the base and cover. However, in some instances, the devices providing the desired features are received in cavities formed in the cover of the housing. In this latter case, a secondary cover encloses the cavities in what has become the primary cover. The secondary cover should be easily removable for inserting, removing or servicing the devices providing the additional features. Typically, the secondary cover is removably secured to the molded housing by self-tapping screws. However, with repeated insertion and removal of these screws, the threads in the molded resin can be stripped out. One solution to this problem is to have fasteners that are retained in the secondary cover; however, these add to the cost and manufacturing effort required.
There is a need, therefore, for an improved molded case power switch housing and particularly for an improved arrangement for removably attaching a secondary cover to the molded housing. There is a more particular need for such an improved molded case power switch that does not require repeated insertion and removal of self-tapping screws into the molded housing.
There is an additional need for such an improved molded case power switch housing which is economical to manufacture and easy to use.
SUMMARY OF THE INVENTION
These needs and others are satisfied by the invention which is directed to a molded case power switch housing in which a secondary cover is removably secured over the primary cover to enclose cavities in the primary cover containing auxiliary devices by an attachment assembly which includes at least one, and preferably a plurality, of attachment members secured to the top face of the primary cover and having a mounting aperture which registers with a mounting hole in the secondary cover. First fasteners extend through the mounting holes in the secondary cover and engage the mounting aperture in the attachment member to removably secure the secondary cover to the primary cover. Preferably the mounting apertures and the attachment members are tapped apertures and the first fasteners have threaded shafts which are threaded into the tapped apertures. The attachment members are preferably metal so that the first fasteners can be repeatedly inserted and removed for mounting and removing the secondary cover repeatedly without becoming worn.
The attachment members can have second mounting apertures which are aligned with mounting holes in the primary cover and through which second fasteners extend to secure the attachment members to the primary cover. The mounting holes in the insulative resin of the primary cover can be tapped and the second fasteners have threaded shafts which engage the tapped resin holes. Even though the second fasteners are threaded into the insulative resin, the attachment is secure as these second fasteners do not have to be removed and reinserted each time the secondary cover is removed or installed.
Some of the attachment members are extended in length and have a third mounting aperture which is aligned with aligned apertures extending all the way through the primary cover and the base for receiving third fasteners which mount the molded case power switch housing such as to a panel board.
REFERENCES:
patent: 5910760 (1999-06-01), Malingowski et al.
patent: 6-124639 (1994-06-01), None
patent: 6-111707 (1994-06-01), None
patent: 6-111659 (1994-06-01), None
patent: 6-139899 (1994-06-01), None
Humbert Joseph Bell
Zindler Mark Owen
Donovan Lincoln
Eaton Corporation
Moran Martin J.
Nguyen Tuyen T.
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