US 3639752 A
An explosionproof fixture hanger is disclosed which is adapted to support a depending explosionproof fixture in a manner providing resilient cushioning and lateral flexibility. An annular housing, formed for mounting on a junction box, is fitted with a laterally resilient stem. The stem protrudes through a housing hub and is telescopically carried on a resilient member within the housing for limited axial movement. The inner surface of the housing hub and the outer surface of the stem define a pressure-dissipating explosionproof joint. A lighting fixture is mounted at an opposite end of the resilient stem.
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Description (OCR text may contain errors)
United States Patent Appleton Feb. 1,1972
 EXPLOSIONPROOF FLEXIBLE FIXTURE HANGER [2i] Appl. No.: 875,112
3,l68,252 2/1965 Cabemoch ..240/78 Primary Examiner-Richard C. Queisser Assistant Examiner-Herbert Goldstein Anorney-Wolfe, Hubbard, Voit & Osann [5 7] ABSTRACT An explosionproof fixture hanger is disclosed which is adapted to support a depending explosionproof fixture in a manner  0.8. CI. ..240/78 R, 174/61, 240/] 1.2 E, providing resilient cushioning and lateral flexibility An anmh l l 248/32 lar housing, formed for mounting on a junction box. is fitted 2; m]: with a laterally resilient stem. The stem protrudes through a 1 o are 4 j 248/2342 housing hub and is telescopically carried on a resilient member within the housing for limited axial movement. The  R i cud inner surface of the housing hub and the outer surface of the e I stem define a pressure-dissipating explosionproof joint. A UNITED STATES PATENTS litghting fixture is mounted at an opposite end of the resilient s em. 2,652,482 9/1953 Bissell ..240/l 1.3 2,753,39l 7/l956 Northup 1 74/62 10 Claims, 3 Drawing Figures /J x4 m m I za 1/ 2; Z!
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EXILOSIONPROOF FLEXIBLE FIXTURE HANGER DESCRIPTION OF THE INVENTION The present invention relates to the field of explosionproof electrical fittings and, more particularly, to a novel explosionproof flexible cushion fixture hanger for use with an explosionproof lighting unit such, for example, as the unit disclosed and claimed in my prior U.S. Pat. No. 2,786,936, granted Mar. 26, I957.
Explosionproof electrical fittings are designed for use in socalled hazardous areas. These may be places such, for example, as refineries, chemical plants or other installations where inflammable or explosive mixtures of gases, vapors or dust are present in the atmosphere. These mixtures tend to penetrate into the interior of the electrical conduit system and the fittings and units connected thereto. The potential arcing portions of the system must therefore be isolated from the surrounding atmosphere in such a manner that an internal explosion can either be prevented altogether or permitted to occur with no propagation of flame into the surrounding atmosphere. This can be done by filling the system with inert gas under pressure, by venting in such a manner that explosive pressure is rapidly dissipated without propagation of flame into the surrounding atmosphere, or by resorting to explosionproof wall and joint construction so as to contain the full pressure of the explosion. It is with the vented type of explosionproof fitting that the present invention is concerned.
One object of the invention is to provide a pressure dissipating explosionproof hanger for supporting a depending explosionproof lighting unitand providing vibrational cushioning on a vertical axis and flexibility laterally of such axis.
'Another object is to provide an explosionproof fixture hanger of the character set forth above and wherein the vibrational cushioning means, the explosionproof structure, and the laterally flexible support means are compactly nested together.
A further object of the invention is to provide an explosionproof fixture hanger of the foregoing type wherein fixtures of widely varying weights can be readily accommodated by changing a simple resilient element.
Still another object of the invention is to provide an explosionproof fixture hanger of the type set forth above, and which will maintain good ground continuity under all conditions of operation to which the fixture may be subjected.
Other objects and advantages of the invention will become apparent as the following description proceeds, taken in light of the accompanying drawing in which:
FIG. I is a perspective view of an illustrative explosionproof fixture hanger embodying the present invention and operatively supporting a depending explosionproof lighting fixture.
FIG. 2 is an enlarged fragmentary vertical sectional view through the illustrative fixture hanger shown in FIG. 1.
FIG. 3 is an enlarged fragmentary transverse sectional view taken in the plane of the line 3-3 through the fixture hanger as shown in FIG. 2.
While the invention is susceptible of various modifications and alternative constructions, a certain illustrative embodiment has been shown in the drawing and will be described in detail below. It should be understood, however, that there is no intention to limit the invention to the specific form disclosed, but rather to cover all modifications and alternative constructions falling within the spirit and scope of the invention.
Referring more specifically to FIG. 1, the invention is there exemplified in an illustrative explosionproof fixture hanger mounted on a suitable overhead support which may be a junction box 11 in a power supply conduit system. The box 11 and conduit 12 are of heavy wall construction commonly used in explosionproof electrical systems, and the hanger 10 in this instance comprises the cover of the box. The hanger 10 supports an explosionproof lighting fixture 14 in depending relation therefrom via a fixture stem 15 of heavy wall electrical conduit. Although the present invention is not concerned with the lighting fixture per se, the fixture 14 may, for example, be of the type described in U.S. Pat. No. 2,786,936, supra, to which reference may be made for further details. The fixture hanger 10 is adapted to support the lighting fixture 14 so as to protect its lamp, and the explosionproof integrity of the fixture and system, against vibrational or impact forces in its environment. The structure of the fixture hanger 10 thus supports the fixture with vibrational cushioning on a vertical axis, and flexibility laterally of the vertical axis through an angle which may be approximately 15 in any direction, giving a total swing of approximately 30 from one extreme to the other.
In keeping with the invention, the fixture hanger 10 is constructed as a sturdy, compact explosionproof enclosure of minimum vertical length. This is accomplished by nesting or telescoping together the vibrational cushioning means, the laterally flexible suspension means, and the explosionproof venting means of the device 10. As shown particularly in FIG. 2, the fixture hanger 10 is formedin the present instance as a box cover assembly and comprises a support or housing 16 secured to the junction box 11 in sealed, explosionproof relation as by means of a ground joint and cap screws 18. The housing 16, which may be made of malleable iron, has an inturned hub 19 defining a relatively large central bore 20. A cushion stem 21, which may be of brass, is telescopically housed within the bore 20 and disposed for limited axial movement relative to the housing 16. The cushion stem 21 is formed with a downwardly and outwardly flaring main bore 22 which terminates at its upper end in a shoulder 24 and counterbore 25. The latter terminates at its upper end in a stop shoulder 26 having suitably flaired inner edges to avoid chafing against the wiring for the fixture 14. A length of flexible explosionproof conduit 28 which may, for example, be of conventional woven metallic construction with an impervious liner 29 is anchored in the counterbore 25 adjacent to the upper end of the cushion stem as by means of a soldered or brazed joint. The opposite or depending end of the flexible conduit 28 is similarly anchored in counterbore 30 of a fixture connector 31. The fixture stem 15 may readily be threaded into the fixture connector 31 either directly or through an adapter 32, depending upon its size, and is retained in place by means of a setscrew 34. The main bore 22 of the cushion stem 21 is of substantially greater diameter than the flexible conduit 28 and the length of the latter is such as to locate the fixture connector 31 a short distance below the lower end of the housing 16.
Nested within the housing 16, in surrounding relation with the cushion stem 21 and the hub 19, is a resilient cushion member which in the present instance is formed as a coil spring 35. The latteris disposed to bear against the lower inside surface of the housing wall surrounding the hub 19, and against a lateral abutment in the form of a large annular flange 36 integral with or fixed to the cushion stem 21. The cushion stem 21 is retained in the bore 20 against the biasing force of the spring 35 by means of one or more abutments such as drivescrews 37. The flange 36, and thus the fixture 14, is restrained against rotational movement about the vertical axis by means of an integral rib 38 on the inside wall of the housing 16 which engages a peripheral notch 39 in the flange. The flange 36 is so proportioned that it defines, together with the upper central end portion of the cushion stem 21, a closure for the void space within the housing 16 and thus prevents the inadvertent entry of wiring from the junction box.
Upon more specific reference to FIG. 2, it will be noted that the mounting surface of the housing 16 abutting the box 11 is substantially coplanar with the annular flange 36 of the cushion stem and the upper end portion of the flexible conduit 28 anchored in the cushion stem. This arrangement minimizes bending forces on the fixture hanger and its holding means, enhancing both its rigidity and compactness.
The coil spring 35 may be made of a variety of materials and in this case happens to be of spring steel. To avoid corrosion and facilitate good ground continuity, the spring 35 may be coated with a rustproof metallic plating such as cadmium. The
fixture hanger 10 may readily be adapted to a variety of fixtures having different weights by simply matching the springs 35 to the respective weights of the fixtures to be supported. If it becomes. necessary to change a particular lighting fixture after installation to one of appreciably different weight, the fixture hanger 10 may be converted for use with the new fixture by changing the spring 35 to one adapted for the weight of the new fixture. By matching the cushioning action to the fixture weight, the life of the incandescent lamp in the fixture is enhanced.
The fixture hanger 10 includes an explosionproof joint between the cushion stem 21 and the housing 16. This joint is defined by the telescoping inner surface 20 of the hub 19 and the adjacent opposed outer surface 23 of the cushion stem 21. The surfaces 20, 23 areformed with a smooth or satin finish and so proportioned as to have a radial clearance space therebetween of approximately 0.003to 0.0035 inches. In the event of leakage of an explosive gaseous'mixture into the interior of the fixture hanger and a breakdown of electrical insulation at the junction box, pressure due to the resulting internal explosion will be dissipated through the long thin annular clearance path between the surfaces 20, 23 of the hub and the" cushion stem. This cools the hot gases sufficiently to preclude leakage of flame from the interior of the device 10 into the surrounding atmosphere.
1. An explosionproof fixture hanger comprising, in combination:
a. a support provided with an inner surface, I
b. a cushion stem extending through said support, mounted within said support for limited axial movement relative thereto and provided with an outer surface,
. a resilient cushioning member interposed between said cushion stern and said support,
d. an explosionproof joint defined by the clearance between support surface and said outer cushion stem surface for dissipating internal pressure to the surrounding atmosphere,
e. a fixture connector,
f. and a laterally flexible explosionproof conduit interposed between and connecting'said cushion stem and fixture connector.
2. An explosionproof fixture hanger as defined in claim 1 wherein said cushion stem, said cushioning member, said explosionproof joint, and said flexible conduit are disposed in telescoping relation with each other.
3. An explosionproof fixture hanger comprising, in combination: v
a. a support in the form of a substantially annular housing having an in-turned hub, the hub formed with an annular inner surface,
b. a cushion stern mounted within said hub for limited axial movement relative to said support, extending through said support and formed with an annular outer surface,
c. a laterally extending abutment on said cushion stem,
d. a resilient cushioning member interposed between said cushion stem abutment and said support and disposed in surrounding relation with said hub,
. an explosionproof joint defined by the clearance between said annular inner hub surface and said annular applied outer cushion stem surface for dissipating internal pressure to the surrounding atmosphere,
f. a laterally flexible explosionproof conduit mounted at one end on said cushion stem,
g. and means on the other end of said conduit for connection to an explosionproof lighting fixture.
4. An explosionproof fixture hanger as defined in claim 3 wherein said cushion stem is formed with a main bore of substantially greater diameter than said flexible conduit and said flexible conduit is secured to said cushion stem adjacent the upper end of said main bore.
5. An explosionproof fixture hanger as defined in claim 4,
wherein said main bore of said cushion stem is downwardly and outwardly flared to provide clearance for lateral swinging movement of said flexible conduit.
6. An explosionproof fixture hanger as defined in claim 3, wherein said support has an internal abutment disposed for engagement with said laterally extending abutment to preclude turning of said cushion stem about a vertical axis.
7. An explosionproof fixture'hanger comprising, in combination:
a. a support in the form of a hollow housing adapted for mounting on an overhead junction box and provided with an annular inner surface,
a cushion stem mounted withinsaid support for limited axial movement relative to said support, and provided within an annular outer surface extending through said support, 3
c. an annular flange adjacent the upper end of said cushion stem, I
d. a resilient cushioning member interposed between said annular flange of said cushion stern and the depending end of said support,
e. explosionproof joint defined by the clearance between said annular inner support surface and said outer cushion stem surface for dissipating internal pressure to the surrounding atmosphere,
f. a laterally flexible explosionproof conduit secured at its upper end to said cushion stem,
g. and means secured to the lowerend of said conduit for connection to an explosionproof lighting fixture.
8. An explosionproof fixture hanger as set forth in claim 7, wherein said support has a mounting surface substantially coplanar with said annular flange of said cushion stem and said upper end portion of said flexible conduit.
9. An explosionproof fixture hanger for use with a depend ing explosionproof lighting fixture and comprising, in combination: i
a. a hollow housing of generally annular form adapted for mounting in explosionproof relation on an overhead junction box, 7 I v I b. an in-turned hub adjacent the lower end of said housing and provided with an elongated annular inner surface,
c. a cushion stem mounted within said hub for limited relative movement with respect thereto along a vertical axis extending through said hub and provided with an elongated annular outer surface,
. an annular flange integrally secured to the upper end portion of said cushion stem,
e. a coil spring interposed between the lower end of said housing and said annular flange of said cushion stem, said coil spring being disposed in surrounding relation with said hub and said cushion stern,
. an explosionproof joint defined by the clearance between said elongated annular inner surface and said hub and said elongated annular outer surface of said cushion stem for dissipating internal pressure to the surrounding atmosphere,
g. a laterally flexible explosionproof conduit sealingly anchored at its upper end to said cushion stem,
h. and a connector fitting sealingly anchored to the lower end of said flexible conduit for attachment of an explosionproof lighting fixture.
10. An explosionproof fixture hanger as defined in claim 9, wherein said housing is formed with a vertically extending rib which engages said annular flange to restrain said cushion stem against turning about the vertical axis.