Explosion-proof Electrical Connector And Cable Assembly

Abstract

A greatly simplified explosion-proof fitting for use particularly in the petroleum industry comprises a minimal number of parts including a conductor passing through a housing, a sealer and a strain relief member. The housing is crimped about the strain relief member to retain the conductor in position.

Description

BACKGROUND OF THE INVENTION

This invention pertains to electrical fittings for use particularly in holding a cable in position on the frames of motors. More particularly this invention concerns an explosion-proof fitting, that is, a fitting for use on explosion-proof motors such as the type used for installations in volatile gaseous environmental conditions.

Fittings of this type have been known for many years and normally consist of a great number of parts which are accurately machined and require careful assembling all of which makes them rather expensive.

The following prior art patents are representative of the state of the art: ---------------------------------------------------------------------------

U.S. Pat. No. Inventor Issued __________________________________________________________________________ 2,604,315 Hargett July 29, 1952 2,684,398 Strunk July 20, 1954 2,759,989 Anderson Aug. 21, 1956 2,881,241 Stecher Apr. 7, 1959 2,939,906 Harwood June 7, 1960 3,055,972 Peterson Sept. 25, 1962 3,072,415 Lombard et al. Jan. 8, 1963 3,163,703 McLoad Dec. 29, 1964 3,314,030 Mallett et al. Apr. 11, 1967 3,371,150 Bachman Feb. 27, 1968.

As can be seen from these patents the structure is generally rather complicated and it is therefore most desirable particularly from an economic standpoint that a simplified device be provided which will perform satisfactorily in the intended environment.

SUMMARY OF THE INVENTION

I have provided a simple and relatively inexpensive fitting for use in explosive environments comprising a connector through which an electrical cable is passed, said connector being retained on the cable. At one end of the connector the cable is sealed by a sealing compound and at the other end of the connector a strain relief member is disposed around the cable between the cable and the connector body and the body is crimped over to retain the connector in place. It is preferable to provide a washer between the end of the cable insulation and an inner annular shoulder in the connector body.

Accordingly, it is an object of this invention to provide a new and improved explosion-proof fitting of the type described which includes a minimal number of parts and yet performs satisfactorily in its intended environment.

This and other objects of my invention will become apparent from the following description with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of the parts of the fitting and the cable which goes through the fitting shown prior to being assembled;

FIG. 2 is a section of the parts shown in FIG. 1 shown after they have been assembled; and

FIG. 3 is a section taken along the lines and arrows 3--3 in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Although specific forms of the invention have been selected for illustration in the drawings, and the following description is drawn in specific terms for the purpose of describing these forms of the invention, this description is not intended to limit the scope of the invention which is defined in the appended claims.

FIG. 1 shows the unassembled parts of the connector together with a portion of a cable upon which the connector is to be mounted. The cable 10 is a standard three-wire cable having three separate wires 11, 12 and 13 therein, each of which has its own insulation as shown. The wires pass through an outer insulation 15.

The explosion-proof fitting comprises a connector designated generally 16 having a threaded portion 17 at one end for insertion into a mating threaded hole in a motor housing, a centrally disposed enlarged hexagonal portion 18 which provides a means for permitting the fitting to be gripped by a wrench or similar device so that the threaded portion can be tightened into the housing as aforesaid, and an elongated thin-walled tubular portion 19 at the other end which is preferably cylindrical in its condition prior to being assembled and fixed to the cable 10.

The threaded portion 17 has a standard external tapered thread 20 thereon and a cylindrical hole 22 passing therethrough. The hole 20 terminates within the central hexagonal portion 18 of the connector 16 in an outwardly extending annular shoulder 24. This shoulder is located at one end of the cylindrical hole 26 in FIG. 1 which passes through the thin-walled tubular portion 19. After complete assembly this hole 26 is no longer cylindrical and therefore has been designated 126 in FIGS. 2 and 3.

Prior to assembling the cable with the connector, the cable is first stripped of a portion of its outer covering 15 so then enough of the insulated conductors 11, 12 and 13 extend from the cable to pass through the connector and extend beyond it for the ultimate purpose of being connected to the electric fittings in the machinery. In stripping the outer insulation covering 15 from the cable there is provided a shoulder 30.

When this shoulder is fully inserted into the fitting it rests against the fiber washer 32 in FIG. 2. This washer is designed to fit within the confines of the overall diameter of the hole 26 and rest against the shoulder 24 of the fitting and at the same time provide a clearance hole for the insulated conductors 11, 12 and 13. The washer 32 provides a dam for the sealer 60, as will be more fully described hereinafter.

The parts can be assembled by first placing the fiber washer 32 against the shoulder 24 of the fitting. Next the cable strain relief member 34, which is made of resilient material such as buna-N or neoprene hose of the type commonly known in the trade being resistant to gasoline and oil, is placed about the insulation covering 15 of the cable. The conductors are then inserted through the hole in the center of the fiber washer 32 and the cable is fed through the fitting until the shoulder 30 of the insulated covering of the cable engages the washer 32. The cable strain relief member is also pushed up against the washer 32. The diameter of this member is less than the diameter of the hole 26 in FIG. 1.

With the parts thus assembled the cylindrical portion 19 of the fitting is crimped, preferably in three places, so that its external appearance in section is that shown in FIG. 3. That is, the cylindrical walls are deformed inwardly along three major arcs, and portions of the metal are forced outwardly as at 40, 42 and 44. This has the effect of deforming the strain relief member 34; such deformation being shown at 50 in FIG. 2. The crimping must be sufficient to firmly grip the strain relief member and compress it against the insulation 15 of the cable thereby restraining the cable from longitudinal movement with respect to the fitting.

As a final step, a sealing compound 60 is forced into the open end of the fitting around the conductors completely filling the hole 22 and packing against the washer 32 and the cable. The sealing compound may be of any type as is known in the art and must be free of voids and provide a tight fit in the connector all around the insulated conductors to provide a vaportight seal.

To provide those skilled in the art with a typical set of dimensions in order that they may appreciate the extent of the crimping operation, I will now deliniate very specifically the dimensions in inches used on one cable and connector assembly made in accordance with my invention. The cylindrical portion 19 of the fitting was 1-inch long and had an outside diameter of 0.906 .+-. 0.005 and an inside diameter of

The cable strain relief member had an outside diameter of 0.765 .+-. 0.005 and an inside diameter of

The washer 32 had an outside diameter of

and an inside diameter of 0.375.+-. 0.005. The cable used was a neoprene covered three conductor 14 AWG stranded wire 600-volt rating. After assembly the portion 19 was crimped securely in three places to secure a vaportight seal as shown and described above. After crimping, the outside diameter of the arcuate portions was approximately in the range of 0.815 to 0.830 inch.

It will be understood that various changes in the details, materials and arrangement of parts which have been described and illustrated in order to explain the nature of this invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the following claims.

It will further be understood that the "Abstract of the Disclosure" set forth above is intended to provide a nonlegal technical statement of the contents of the disclosure in compliance with the Rules of Practice of the U.S. Pat. Office, and is not intended to limit the scope of the invention described and claimed herein.

Claims

What is claimed is:

1. A connector and cable assembly comprising: an electrical cable; a connector having an elongated body with a threaded portion at one end, having a substantially cylindrical hole passing therethrough, a centrally located portion providing a means for engagement with a tool whereby said body can be secured in threaded engagement in a hole in its intended environment, and an elongated thin-walled substantially cylindrical portion at the other end having a substantially cylindrical hole passing therethrough, said hole being of a greater diameter than said last-mentioned hole, said holes terminating in a common plane providing an annular shoulder in said body, said holes being in axial communication with one another; said cable passing through said holes in said connector; a fiber washer disposed against said shoulder; at least a portion of said cable engaging said washer; a resilient strain relief member disposed about said cable within said hole passing through said thin-walled portion of said body; said thin-walled portion being crimped to engage said strain relief member and force it against said cable to hold said connector in longitudinal position on said cable; and a sealing material disposed in the hole on the threaded portion of said body to provide a vaportight seal between said connector and said cable.