Floor Plug

Abstract

An electrical plug for three-phase, high-power electrical applications is provided. The plug is adapted for use in connection with a floor receptacle and has a generally flat, thin casing to provide a low profile on the floor. Safety means are provided within the casing to prevent electrical flashover between the terminals and to prevent the ingress of moisture into the casing. The casing encloses electrical terminals which include relatively thin flat terminal bars received in grooves in the casing, which is made in separable halves, from which extend terminal elements which project exteriorly of the casing for connection to an electrical receptacle. A socket is provided on the casing to act as additional support for the terminal elements and to provide an enclosure therefor.

Description

BACKGROUND OF THE INVENTION

The floor plug is adapted to utilize three-phase AC electrical power. It is for use in connection with electrical devices having high-power requirements and wherein the electrical devices are not permanently installed which would justify making a permanent electrical connection to power. For example, in convention halls wherein industrial shows are held, a show may be set up and dismantled within a period of a few days or a week. Shows which feature electrically operated machinery such as machine tools, computers and the like have high-power requirements. It is not economical to make permanent connections for the purposes of such shows. Other instances where temporary electrical connections are desired are heavy duty portable equipment such as electric welders and electric vehicles wherein the battery must be recharged at certain intervals.

Permanent floor receptacles have been provided for use in connection with plugs attached to power cables extending from the electrical devices for the purpose of making temporary electrical connections. The receptacle does not form part of the present invention but, in general, as will be appreciated, the receptacle must be sufficiently electrically isolated from the surrounding area for safety purposes. Such receptacles have been recessed into the floor in order to prevent direct contact therewith by a person or object making contact with the floor surface in the area of the receptacle. Additionally, remote switches have been provided to connect the receptacles to a source of power only at such times as a proper connection with a floor plug has been made and inspected.

Floor plugs for use in connection with such receptacles must meet certain safety standards. Firstly, the plug casing must be waterproof to prevent ingress of water which may cause dangerous short circuiting of the terminals. Further, the terminals, being high-power terminals, should be electrically isolated from each other to prevent dangerous flashover therebetween. An additional desired feature of the plug is that it not be bulky so as to provide an obstacle which may easily be tripped over. The present invention provides a plug which meets these requirements and which is inexpensive to manufacture and sturdy in construction and easily opened and closed for maintenance purposes.

SUMMARY OF THE INVENTION

An electrical plug for use in connecting high-power multiphase electrical cables to a floor receptacle is provided. The plug comprises a generally flat, thin casing including detachably fastened casing portions secured together by means of detachable means. The casing portions are separable along a plane through the thickness of the casing. The casing portions have abutting faces fabricated of electrically insulating material. A plurality of grooves are provided in at least one of the faces of a casing portion. The grooves extend from one end of the casing portion and terminate within the periphery of the face of the portion. The sections of the grooves at said one end define cable opening means for reception of electrical cables. Terminal openings are provided in one of the casing portions in alignment with the inner end section of each groove for outward projection of electrically conductive terminal elements from the casing interior. An electrical terminal is provided in the casing for each groove. The electrical terminals each comprise an electrically conductive bar received in a groove and an electrically conductive terminal element extending therefrom and through the terminal opening means. The bars extend to a point adjacent the cable opening means for attachment to an electric cable.

In the drawings:

FIG. 1 is a view in perspective of the lower face of a floor plug in accordance with one embodiment of the present invention;

FIG. 2 is a view in perspective of the upper face of the floor plug of FIG. 1;

FIG. 3 is a plan view of the interior face of the lower casing half of the floor plug;

FIG. 4 is a view similar to FIG. 3 illustrating the mounting of the terminals in the casing;

FIG. 5 is a view in perspective of one of the terminals utilized in the floor plug; and

FIG. 6 is a sectional view taken substantially along the line 6--6 of FIG. 1 looking in the direction of the arrows.

The floor plug 10 includes a casing comprising upper and lower casing halves. The casing is generally flat and thin with the casing halves being separable along a plane through the thickness of the casing. The lower casing half 12 is a one-piece structure. The upper casing half includes two elements 14, 16 which are individually attachable and removable. The casing halves are fabricated from a material having high mechanical strength and satisfactory electrical characteristics of arc tracking, dielectric strength, arc resistance, insulation resistance, moisture absorption and burning or flame resistance. One satisfactory material is a melamine resin. This resin does not track easily, is hard to burn, and has good mechanical and high dielectric strength. Phenolic resins are another example of a satisfactory material. Instead of fabricating the entire casing of an electrically insulating plastic material, a casing may be made with an outer shell of metal for high strength and an inner shell of plastic for the desirable electrical properties.

The lower casing half 12 is generally rectangular in shape with the sides being longer than the ends. Four shallow grooves 18, 20, 22, 24 extend generally parallel from one end 26 towards the other end. Matching grooves are provided on the upper casing elements 14, 16. The grooves terminate short of the opposite end 28 with each groove terminating at a different distance, and so arranged that the termination points of the grooves lie at 90.degree. intervals around a common center. The groove 18 has a right angular portion 30 which extends towards the center of the casing half to terminate at a point which lies in alignment with the groove 22. An opening 32, 34, 36, 38 is provided adjacent the termination point of each groove for passage of an electrical terminal element therethrough. Each of the grooves has an enlarged recess 40, 42, 44, 46 adjacent the end 26 to receive an electrical connector. As will be noted in FIG. 6, a similar recess 48 in groove 50 is provided in the upper casing element 16.

A semicircular recess 52, 54, 56, 58 is provided at the end 26. As will be noted in FIG. 6, a similar recess 60 is provided in the casing element 16 so that when the casing halves are assembled, these recesses form a circular opening for the reception of the insulated outer coverings of electrical cables 62, 64, 66, 68.

A transversely extending trough 70 is provided in the lower casing half 12. The trough 70 extends across the grooves 18, 20, 22, 24 and serves as a trap for any moisture which may enter the casing via the openings in the end 26. An aligned groove 72 is provided in the casing element 16. An electrically insulating rod 74 is received in groove 72 to press against the cables and form a dam to the ingress of water so that any water entering the casing is forced into the trough 70 thus preventing movement thereof further into the casing interior where a short circuit might be caused.

Three longitudinally extending slots 76, 78, 80 are provided in the space between the grooves 18, 20, 22, 24. The slots extend from the trough 70 to a point beyond the portion 30 of groove 18. A transversely extending slot 82 extends from the slot 76 to a point beyond the groove 24. The slot 82 is positioned between the groove portion 30 and the termination point of the adjacent grooves 20, 24. Matching slots 84 are provided in the upper casing elements 14, 16. A strip of electrically insulating material 86, 88, 90, 92 is received in each of the slots as will be noted in FIGS. 4 and 6. These strips serve as a flash dam to prevent arcover between the electrical terminals which might occur along the abutting faces of the casing halves. Extension of the strips across the abutting faces and well into the material of each of the casing halves obviates any possibility of such flashover.

A terminal socket 93 is provided on the outer face of the casing half 12. The socket comprises a relatively thick cylindrical member 94 having a projection 96 on one face thereof which extends through an opening in the casing half 12. The projection makes a tight fit in the opening and is permanently secured in place as by means of welding. Openings 100, 102, 104, 106 are provided in the member 94 for passage of electrical terminal elements 108, 110, 112, 114. The member 94 provides support for the terminal elements. A cylindrical sleeve 116 fabricated of electrically insulating material is received on the outer end of the member 94. The sleeve 116 has a peripheral flange 118 which is received in a peripheral groove provided in the member 94. The elements are secured together as by welding. An exterior notch 120 is provided for engagement with a locating element on the electrical receptacle so that the plug will be properly oriented with respect thereto upon insertion. As will be noted, the terminal elements extend well into the space defined by the sleeve 116 for electrical engagement with a receptacle. The sleeve 116 and outwardly extending portions of the terminal elements are entirely received in the electrical receptacle for firm secure attachment thereto.

Each of the terminal elements extends at substantially right angles from an electrically conductive bar 122, 124, 126, 128. The bars, which are flat and relatively thin, match the configuration of the shallow grooves on the interior faces of the casing halves and are snugly received therein. An opening is provided at the end of each bar for reception of a nut and bolt structure for detachable connection to the electrical connectors 130, 132, 134, 136 which are received in the recesses previously described. Each of the connectors is clamped to an exposed wire portion of the cables 62, 64, 66, 68. A plurality of threaded openings 138 are provided in the casing half 12. Aligned openings 140 are provided in the elements 14, 16 for reception of socket head screws 142 to secure the assembly together.

As will be appreciated from the structure thus described, the floor plug 10 possesses a number of advantages. For example, the entire casing is relatively thin as a consequence of the unique terminal structure and mounting means therefor. This provides a desirable "low-profile" configuration. The water-dam structure and the flash-dam structure provided interiorly of the casing result in high safety characteristics. The two-part casing elements 14, 16 permit easy maintenance of the cable end of the plug without the necessity for complete disassembly of the plug. Most problems in connection with the plug will occur at the point of connection with the cables and not at the terminal element structure.

Claims

What I claim as my invention is:

1. An electrical plug for use in connecting high-power, multiphase electrical cables to a floor receptacle, comprising a generally flat, thin casing including detachably fastened upper and lower casing portions, detachable fastening means securing the casing portions together, said casing portions being separable along a plane through the thickness of the casing, said portions having abutting faces fabricated of electrically insulating material, a plurality of grooves in the face of the lower casing portion extending from one end of the portion and terminating within the periphery of the face, the sections of the grooves at said one end defining cable opening means for reception of electrical cables, terminal opening means in the lower casing portion in alignment with the inner end section of each groove for outward projection of electrically conductive terminal elements from the casing interior, an electrical terminal in the casing for each groove, said electrical terminals each comprising an electrically conductive bar received in one of the grooves and an electrically conductive terminal element extending therefrom and through the respective terminal opening means, said bars extending to a point adjacent the cable opening means for attachment to electric cables, and a transversely extending trough in the lower casing portion adjacent the cable opening means end thereof, said trough extending across all of said grooves for collecting moisture entering said casing through said opening means.

2. An electrical plug as defined in claim 1, further characterized in the provision of a socket on the exterior face of the lower casing portion having the terminal opening means therein, said socket comprising a sleeve and a relatively thick cylindrical member, said cylindrical member being located adjacent to the lower casing portion and having opening means therein aligned with the terminal opening means and through which said terminal elements pass, said sleeve surrounding the exposed outer ends of the terminal elements and being secured to said cylindrical member.

3. An electrical plug as defined in claim 1, and further characterized in that the upper casing portion comprises a pair of separable sections, one of said sections overlying the main portion of the electrical terminals excepting for the end portions thereof adjacent the cable opening means, the other of said sections overlying the remaining terminal portions.

4. An electrical plug as defined in claim 1, further characterized in the provision of aligned slots in the opposed casing portion faces extending between each pair of grooves, and electrically insulating strips separate from said casing portions received in said slots to form electrical barriers between the terminals.

5. The electrical plug as defined in claim 1, further characterized in the provision of a transversely extending groove in the upper casing face which is aligned with said trough in said lower casing face, and a rod of electrically insulating material received in said last mentioned groove to bear against electrical cables extending into the casing and seal one side thereof thereby forcing any moisture entering the casing to flow into said trough.

6. The electrical plug as defined in claim 1, further characterized in that said grooves being four in number for three power lines and a ground line, said grooves and mating terminal bars terminating around a common center with an outer groove terminating in transverse alignment with the common center, the groove adjacent thereto terminating short of the common center, its adjacent groove terminating on the other transverse side of the common center, and the remaining outer groove being L-shaped with one long leg extending beyond the common center and a shorter leg extending back towards the common center and terminating in alignment therewith.

7. An electrical plug for use in connecting high-power, multiphase electrical cables to a floor receptacle, comprising a generally flat, thin casing including detachably fastened casing portions, detachable fastening means securing the casing portions together, said casing portions being separable along a plane through the thickness of the casing, said portions having abutting faces fabricated of electrically insulating material, a plurality of grooves in at least one of the faces of the casing portions extending from one end of the portion and terminating within the periphery of the face, the sections of the grooves at said one end defining cable opening means for reception of electrical cables terminal opening means in one of the casing portions in alignment with the inner end section of each groove for outward projection of electrically conductive terminal elements from the casing interior, an electrical terminal in the casing for each groove, said electrical terminals each comprising an electrically conductive bar received in one of the grooves and an electrically conductive terminal element extending therefrom and through the respective terminal opening means, said bars extending to a point adjacent the cable opening means for attachment to electric cables, said plug being adapted for use in connection with three-phase AC power, said grooves being four in number for three power lines and a ground line, said grooves and mating terminal bars terminating around a common center with an outer groove terminating in transverse alignment with the common center, the groove adjacent thereto terminating short of the common center.

8. An electrical plug for use in connecting high-power, multiphase electrical cables to a floor receptacle, comprising a generally flat, thin casing including detachably fastened casing portions, detachable fastening means securing the casing portions together, said casing portions being seperable along a plane through the thickness of the casing, said portions having abutting faces fabricated of electrically insulating material, a plurality of grooves in at least one of the faces of the casing portions extending from one end of the portion and terminating within the periphery of the face, the sections of the grooves at said one end defining cable opening means for reception of electrical cables, terminal opening means in one of the casing portions in alignment with the inner end section of each groove for outward projection of electrically conductive terminal elements from the casing interior, an electrical terminal in the casing for each groove, said electrical terminals each comprising an electrically conductive bar received in one of the grooves and an electrically conductive terminal element extending therefrom and through the respective terminal opening means, said bars extending to a point adjacent the cable opening means for attachment to electric cables, moisture trapping means in the casing adjacent the cable opening means end thereof, said moisture trapping means comprising a transversely extending trough in one of the casing faces extending across all of the grooves, an aligned groove in the other casing face, and a cylindrical rod of electrically insulating material received in said last-mentioned groove to bear against electrical cables extending into the casing and seal one side thereof thereby forcing any moisture entering the casing to flow into said trough.