Electricity: conductors and insulators – Boxes and housings – Hermetic sealed envelope type
Reexamination Certificate
2001-01-26
2002-08-13
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Boxes and housings
Hermetic sealed envelope type
C174S050000, C220S004020, C248S906000
Reexamination Certificate
active
06433275
ABSTRACT:
BACKGROUND OF INVENTION
This invention relates to boxes and housings with electric device or mounting means therefor; coupling or mounting means, with stud or nipple and box supporting means. The invention also relates to sealed with box supporting means; or conduit or cable opening, coupling means or hole closures, and/or covers or face plates with closure for face plate opening.
There are instances when electrical equipment must be protected from moisture and dust. NEMA4 and NEMA4X are standards by NEMA* for electrical enclosures that do not allow the ingress of moisture and or dust. Enclosures that satisfy both NEMA4 and NEMA4X are referred to as satisfying NEMA4/4X. Prior art NEMA4 and NEMA4X housings are available with a lid, base, and gasket, attached by means of several screws. An example of such prior art, with an electrical device inside, can be seen in U.S. Pat. No. 5,239,129, entitled HOUSING FOR SWITCHED ELECTRICAL RECEPTACLE OR THE LIKE, by Alfred L. Ehrenfels, Aug. 24, 1993,
FIGS. 3
,
5
and
6
(discussed on p. 5, lines 16-18). For a NEMA4 seal, all screws must be outside of the lid-to-base sealing gasket. [Screw-holes are often placed within the perimeter of the rectangular shape to reduce overall housing size. When inside the rectangular box, the four screw holes take up limited housing space.] The narrow gasket (narrow in order to not enlarge the housing wall thickness) is difficult and expensive to produce. Setting this specialized gasket is labor-intensive: It is hard to place the rubbery gasket (
87
) into the narrow rectangular channel (
80
) of the baas, especially at it's sharp inverted corners near the screw holes. The gasket can shift or fold, especially when compressing the gasket/ screwing down the lid.
The wire feed-out arrangement using prior art housings is labor-intensive: An attached externally-threaded conduit and two internally threaded nuts (
65
-
67
) secure through the housings hole (conduit opening
39
). The junction box side, to which the device is to be attached, then requires an equal number of operations, plus another two additional internally threaded nuts. So housing-to-junction-box attachment requires an extensive number of hand-screwing operations. For a watertight seal, a washer would also be attached between the housing and external nut
66
.
Another (simpler) mounting arrangement is shown in Prior Art
FIG. 1
, Housing base
82
knock-out
85
is punched out (like with a screwdriver/hammer), nut
88
is screwed inside onto close-nipple
81
, and electronics
89
are inserted. [A close-nipple is the given name of the short, male metal nipple piece, with beveled ends, as pictured.] As the electronics are so packed in the small housing, wires
90
can get scraped when angularly fed (from strain-relief fold-over: drawn as a loop) through occasionally-internally-sharp metal nipple
81
. Often there is barely room for the electronics, strain-relief, fold-over, and the nut; making nut retainment very difficult. The nut must be turned or held in place in very cramped quarters of the housing. Without an exterior nut, close-nipple
81
is still loose against the housing when shipped to the installer. Lastly, lid
92
, with gasket
94
, is 4-screwed (screw posts
83
and
84
shown) to the housing base.
Though the housing may meet NEMA4 standards when it leaves the manufacturer, its water-seal is easily compromised at installation: An installer must slide rubber washer
87
over the close-nipple, all the way to outer surface of housing base
82
, extend the close-nipple through the opened junction-box knock-out, hold the housing tight against wall of junction box
86
, and apply/tighten nut
91
. If the washer isn't fully seated, or the nipple is not held tight to the junction box, the washer can end up a distance away from the housing, therein not water-sealing the junction. The problem is the close-nipple can be loose, with the nut loose, against the inner surface of the housing when the installer gets it (close-nipple
81
only secured by internal nut
88
). If the close-nipple is not pulled out fight from the housing, and isn't held exactly perpendicular to the housing while pushing on the washer, the washer won't be seated properly.
The nipple tends to be sizeably smaller in diameter than a junction-box knock-out. The rubbery washer may float with respect to the junction box and housing. As the junction box nut is tightened, the washer can squish into the clearance space between the outside surface of the close-nipple and the inside surface of the junction box knock-out. This will trap and deform the washer, further compromising the water-seal. [The gasket can start out a distance from the housing and it could be caught between the inside diameter of the knockout and the outside diameter of the close-nipple.]
If a nut restraint were molded into a prior-art housing at a knock-out, that would prevent prior-art seating problems, but such a restraint would take up valuable housing space (which is why no such housing is known to exist)
Again, as the wires are pulled through, the close-nipple's potentially-sharp internal corners can scrape off insulation. [This can cause the electrical grounding of the affected wires, and/or cause a malfunction of the overall system.]
In all, the installer is mainly concerned with feeding through and screwing down the wires leading out of the housing into the junction box. Because of this, the difficulty of securing the housing properly may often lead to a compromised watertight seal.
Prior-art NEMA4/4X enclosures are available with an opaque base and with an opaque, transparent or translucent lid, with the gasket retained by lid or base.
Another prior-art method of forming a NEMA4/4X seal is applying a rubber-like material that cures to form a gasket, often with a hypodermic needle. This can be labor intensive and leave globs of material on the outside of the housing. Even with a cured gasket, the lid is still secured with screws.
There are various methods of welding plastic parts, one to another. Some of these methods utilize friction-induced heating to momentarily melt the plastic while the parts are held together. When the friction-induced heating is discontinued, the plastic rapidly hardens to provide a watertight seal between the two parts. These methods include but are not limited to Ultrasonic Welding, Linear Vibration Welding, Orbital Vibration Welding, and Spin Welding. The advantages and disadvantages of each of these methods of welding are taught in the referenced sales literature of Branson—Applied Technologies Group * * * * * . The term friction-induced welding' is used for all of these welding methods in text and claims.
There are a multitude of prior art energy director configurations for ultrasonic plastic welds. An example of a prior art energy director configuration can be seen in U.S. Pat. No. 5148347; entitled Polymer-Encased Electrical Capacitor with Pressure Sensitive Circuit Interrupter, by Michael E. Cox, Sept. 15, 1992. Also the prior art energy director configurations are taught in the referenced Branson Ultrasonics Corporations Technical Information PW-3 * * * * .
Functional Devices, the Assignee of this patent, has prior-art produced a variety of opaque plastic housings with attached nipples * * * , including their Model RIBU1C (a pre-assembled relay in a housing). [An indicating LED (light emitting diode) also protrudes from a hole in this housing.] Such devices/housings were not NEMA4 rated, have no gasket between the base and the lid, and their lids were secured with as little as one screw. [Such a screw was positioned inside of the housing cavity area, thereby making the NEMA4 rating impossible.] In the past, other manufacturers have made plastic housings with nipples. Currently Functional Devices, and a competitor, [who began exactly reproducing Functional Devices RIBU1C product-plus-housing four years ago], manufacture nippled housings for relays, responders and the lik
Rittmann Albert D.
Rittmann Kenneth W.
Patel Dhiru R
Reichard Dean A.
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