Described embodiments relate generally to the field of connectors, and more particularly to the connection of a conduit to an enclosure.
Connections between electrical conduits and enclosures, such as an electrical box, are typically secured using a locknut. As shown in
It is desirable to form a seal of the aperture 13 where the conduit 10 extends through the enclosure wall 12. For example, in a combustible dust area, a fire or explosion may occur if dust permeates the enclosure of a piece of electrical equipment. The Occupational Safety and Health Administration (OSHA) has specified Occupational Safety and Health Standard No. 1910.269. Subpart V, section XII of this standard has been adopted by all electrical utilities. This standard requires all coal handling portions of a power plant to comply with NFPA 70 (National Electric Code), Article 502, which in turn requires all equipment in combustible dust areas to be dust-tight (i.e., to be sealed from entry of dust into the equipment). In addition, other elements, such as water, gases, or liquids, can be harmful if they penetrate the enclosure of a piece of equipment. It is desirable to makes the conduit connection dust-tight against the hazards of a Class II Div. 2 environment. It is desirable to provide an IP-66 certified seal, meaning that the conduit connection will be dust-tight and water spray resistant.
Standard locknuts, such as those often used to provide conduit connections in equipment in combustible dust areas, are not sealed in a dust-tight manner. In order to comply with the Articles discussed above, these standard locknuts need to be retrofitted with a dust-tight seal. However, conventional practices of retrofitting standard locknuts with a dust-tight seal are expensive and time consuming. For example, one conventional method for providing a dust-tight conduit connection is by using a myers hub. A myers hub, however, is typically used for a new installation, and if it is used in a retrofit application, all wires in an enclosure must be disconnected and pulled back to the closest pull box, the conduit must be disassembled and cut, the conduit threading must be retapped, the myers hub must be attached, and all wires must then be reconnected. This process must be repeated for every piece of conduit entering the enclosure. Depending on the number of conduits in an enclosure it could take a two-man crew several days to retrofit a single enclosure.
Accordingly, there is a desire for devices and methods that provide a quick and certifiable way of retrofitting connections to form the desired seal for an enclosure.
Described embodiments include structures and methods for fastening conduit connections that include a two-piece clamp designed to encompass a standard locknut on the exterior surface of the enclosure wall, and to provide a seal at the conduit connection. The described embodiments permit attachment without requiring disconnecting of wires or modification of the conduits, wireways, or enclosure. Using the clamps described herein provides a fast and cost-effective way of sealing standard locknuts. In one aspect the described embodiments provide a two piece fitting with flanged gasket at the enclosure and compression gasket between the fittings.
As shown in
Clamp 200 includes a shaft 222, which is the area of the clamp 200 that runs perpendicular with the conduit 10 (
Clamp 200 includes an inwardly projecting and circumferentially extending cap 224 located at the top of clamp 200. The inner circumference of the cap 224 is about the same dimension as the maximum outer diameter of the conduit 10, and overhangs the area for the shaft gasket 244. The cap 224 provides a barrier to aid in positioning the gasket 244 and to protect the shaft gasket 244 (
Each piece 210 of clamp 200 includes a flange 226 on each side. The flanges 226 define the primary area of the clamp 200 where the two pieces 210a, 210b (
Each flange 226 contains two holes 228 for receiving respective screws. In some embodiments, one piece (e.g., piece 210a) of the clamp 200 includes flanges 226 with threaded holes 228, while the other piece (e.g., piece 210b) includes flanges with untapped holes 228. Holes 228 can be configured to receive four screws to attach the two pieces 210a, 210b of the clamp 200 around the conduit 10. Tightening the screws creates a compression gasket between the fittings by compressing the two fittings 210a and 210b together at flanges 226, and/or by compressing shaft gaskets 244.
Clamp 200 includes a locknut cavity 230, which is configured to enclose a standard locknut 14 on the exterior of enclosure wall 12 (
The locknut cavity 230 may include a notch 232. The contour of the notch 232 follows a circumference of a standard locknut 14, and is designed to extend at least part of the distance between the teeth of the standard locknut. The notch 232 is an inward protrusion located in the locknut cavity 230. The notch 232 may only be included on one piece of the clamp 200 (e.g., piece 210a or piece 210b), or may be included in both pieces 210a and 210b. The notch 232 is configured to mate against a standard locknut 14 (
The clamp 200 includes a lip 234 that forms the bottom portion of the clamp 200. Lip 234 may be the thinnest portion of the piece 210, in order to fit between the bottom surface of a standard locknut 14 and above the enclosure wall 12 (
The shaft gasket 244 is configured to be positioned at a shaft 222 in a clamp piece (e.g., piece 210a or piece 210b), to provide a seal along the circumference of the conduit 10 (
The lip gasket 246 is configured to be positioned at the bottom surface of the lip 234 of the clamp 200, in order to seal water and dust from infiltrating between the clamp 200 and the enclosure wall 12. As shown in
A method for attaching a clamp 200 to an enclosure 11 in accordance with one or more embodiments described herein is described with reference to elements in
Next, the standard locknut 14 on the exterior surface of the enclosure wall 12 is unscrewed at least two rotations. If the locknut 14 on the exterior surface cannot be unscrewed by at least two rotations, the locknut 16 on the interior surface of the enclosure wall 12 may need to be unscrewed a few rotations to achieve an adequate gap between the exterior surface of the enclosure wall 12 and the exterior standard locknut 14.
In an embodiment including shaft gaskets 244, the piece (e.g., piece 210a) including the shaft gasket 244 is then placed against the conduit 10 resting on the exterior of the enclosure wall 12. The opposite piece (e.g., piece 210b) including a shaft gasket 244 is then placed against the conduit 10, with the respective flanges 226 of the pieces 210a, 210b in contact with one another. The standard locknut 14 should be located within the locknut cavity 230, and the notch 232 should be aligned between the teeth of the standard locknut 14.
Next, screws (not shown) are inserted through each of the holes 228. Holes 228 should align in the corresponding flanges 226 of the opposing pieces 210a, 210b. The screws should be inserted into the piece including unthreaded holes 228 and towards the piece including threaded holes 228. The inserted screws are then partially tightened one screw at a time, alternating between screws to ensure all four screws are tightened equal amounts so binding does not occur. The screws of the clamp 200 are tightened in this manner until all of the screws are hand tight.
The conduit connection may then be tightened from the interior of the enclosure 11, if necessary, by tightening the standard locknut 16 on the interior side of the enclosure wall 12.
The clamp 200 may be twisted prior to tightening the screws in holes 228. Once the screws of clamp 200 are tightened, however, further twisting the clamp may reposition one or more of the gaskets 242, 244, 246 and break the seal.
The inner surface area of each piece 510a, 510b includes threads 520 that are configured to align when pieces 510a, 510b are attached, and sized to engage the conduit threads 15. Piece 510a of clamp 500 is a male piece, and piece 510b of clamp 500 is a female piece. Four Allen screws can be inserted into screw holes 522 on the exterior of the male piece 510a of the clamp 500. The screw holes 522 are configured to traverse through the flanges 526 of the male piece 510, and correspond to screw holes (shown in
As shown in
As shown in
When pieces 510a, 510b are attached and the respective gaskets 528a, 528b mated together, screws may be inserted into holes 522 to achieve proper compression to form a compression gasket between the fittings 510a and 510b. The threaded piece 520 will be twisted against the enclosure wall 12, creating a dust-tight connection replacing an existing standard locknut 14 (
Example embodiments of methods, systems, and components thereof have been described herein. As noted elsewhere, these example embodiments have been described for illustrative purposes only, and are not limiting. Furthermore, certain processes are described, including the description of several steps. It should be understood that the steps need not be performed in the described order unless explicitly identified as such, and some steps described herein may not be performed at all. The breadth and scope of the present invention should not be limited by any of the above described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.
This application is a continuation of U.S. patent application Ser. No. 13/869,596, filed Apr. 24, 2013, which claims priority under 35 U.S.C. §119(e) to U.S. provisional patent application 61/639,271 filed on Apr. 27, 2012, which are each hereby incorporated by reference in their entirety herein.
Number | Date | Country | |
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61639271 | Apr 2012 | US |
Number | Date | Country | |
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Parent | 13869596 | Apr 2013 | US |
Child | 15634431 | US |