US3627904A

US3627904A - Bushing for incorporation in electrical connector assembly

Info

Publication number: US3627904A
Application number: US26928A
Authority: US
Inventors: John D Milne
Original assignee: MM PLASTICS Mfg CO
Current assignee: MM PLASTICS Mfg CO
Priority date: 1970-04-09
Filing date: 1970-04-09
Publication date: 1971-12-14
Anticipated expiration: 1988-12-14
Also published as: CA944828A

Abstract

An electrically insulating bushing presenting one or more prongs which so project that, with the bushing incorporated in an electrical connector assembly in which an end portion of an electric cable is connected to, for example, a junction box, the bushing being disposed within the connector with a cylindrical portion of the bushing disposed between the electrical conductors and the outer casing of the electric cable, the ends of the prongs project from the connector to be visible externally of the connector assembly, either with or without the removal of an element of the connector. Thus, although removal of an element of the connector may be required in order to permit inspection of the connector assembly to ensure that a bushing has been installed therein, such inspection can be performed without requiring dismantling of the connector assembly. The projecting ends of the prongs present informational indicia concerning, for example, the size of the bushing, each prong being of segmental form in cross section with the arcuate face thereof facing towards, and the flat face thereof facing away from, the longitudinal axis of the bushing.

Description

United States Patent John D. Milne c/o MM Plastics (Mfg) Company, 62 Shaft Road, Rexdale, Ontario, Canada Apr. 9, 1970 Dec. 14, 1971 [72] Inventor [21 Appl. No. [22] Filed [45] Patented [54] BUSHING FOR INCORPORATION IN ELECTRICAL CONNECTOR ASSEMBLY 7 Claims, 3 Drawing Figs.

[52] US. Cl 174/83, 174/65 R [51] Int. Cl H02g 15/00 [50] Field of Search 174/64, 65

R, 65 SS, 656, 74A, 82, 83, 135, 151, 1526, 167; 16/2, 108

[56] References Cited UNITED STATES PATENTS 1,799,765 4/1931 Schneider et al. 174/83 1,842,216 l/l932 Thomas, Jr. 174/83 X 1,857,197 5/1932 Knoderer 174/83 X 1,912,115 5/1933 Allen 174/74AX 1,966,451 7/1934 Le Manquais 174/65 R X 2,082,279 6/1937 Fore 174/74 A 2,603,682 7/1952 Uline et al. 174/83 X 3,219,367 11/1965 Franck 174/83 UX FOREIGN PATENTS 116,745 2/1970 Denmark 1,494,898 8/1967 France Primary Examiner-Laramie E. Askin Attorney-Maybee & Legris ABSTRACT: An electrically insulating bushing presenting one or more prongs which so project that, with the bushing incorporated in an electrical connector assembly in which an end portion of an electric cable is connected to, for example, a junction box, the bushing being disposed within the connector with a cylindrical portion of the bushing disposed between the electrical conductors and the outer casing of the electric cable, the ends of the prongs project from the connector to be visible externally of the connector assembly, either with or without the removal of an element of the connector. Thus, although removal of an element of the connector may be required in order to permit inspection of the connector assembly to ensure that a bushing has been installed therein, such inspection can be performed without requiring dismantling of the connector assembly. The projecting ends of the prongs present informational indicia concerning, for example, the size of the bushing, each prong being of segmental form in cross section with the arcuate face thereof facing towards, and the flat face thereof facing away from, the longitudinal axis of the bushing.

PATENTEU DEC 1 4 l9?! INVIZNI'OR. JOHN D. MILNE ATTORNEYS BUSHING FOR INCORPORATION IN ELECTRICAL CONNECTOR ASSEMBLY This invention is concerned with improved bushings which are adapted operatively to be incorporated in electrical connector assemblies of the type comprising a connector having a through passage within which an end portion of an electrical cable is disposed, the connector being secured to the tubular outer casing of the electric cable and being mounted on a support structure such as a wall of a junction box or electric switch within which are disposed electrical terminals to which it is desired to connect the electrical conductors of the electric cable. It is conventional practice in such an assembly to incorporate an electrically insulating bushing having a tubular portion which is disposed between the insulated electrical conductors and the outer casing of the electric cable, a flange portion of the bushing which is presented at one end of the tubular portion being positioned in abutting contact with the end face of the outer casing of thecable. As will be appreciated, this end face of the outer casing is disposed at a spaced distance from the associated ends of the electrical conductors which pass, within the through passage in the connector, through an opening or hole formed in a wall of the junction box or switch for connection to the terminals disposed therein, the bushing serving the purpose of substantially preventing chafing on the insulated electrical conductors of the end of the outer casing of the cable, particularly where this outer casing is of metallic form such as of a type comprising interlocking spiral metal tape of hard drawn aluminum or galvanized steel.

Electric cable the outer casing of which is of this type is known as AC cable. The presence of the bushing thus prevents or minimizes the risk of the electrical conductors being short-circuited.

Such an electrical connector assembly is usually installed and assembled by an electrical contractor but requires to be inspected, prior to use, by independent inspection personnel, the inspector's functionbeing to ensure that the assembly has been properly installed and assembled according to the applicable regulations and other requirements. It has hitherto been a disadvantage of such an assembly that, in many cases, it has not been possible once the assembly has been completed to determine by inspection whether an electrically insulating bushing has been incorporated in the hereinbefore described manner without dismantling the assembly, and it is accordingly a primary object of the present invention to provide an improved bushing which, when incorporated in an electrical connector assembly, substantially overcomes the above disadvantage of the hitherto known forms of bushing by enabling an inspector to determine with certainty whether a bushing has, in fact, been incorporated in the assembly without dismantling of the connector assembly being required, although it may be necessary for the inspector temporarily to disconnect an element of the connector.

A bushing according to the present invention comprises a tubular portion having a longitudinal axis, and a flange portion which is presented at one end of the tubular portion and which projects outwardly from and around the tubular portion. The flange portion presents at least one prong which projects from the flange portion in a direction opposite from the direction in which the tubular portion projects from the flange portion said at least one prong being of approximately segmental form in cross section with the arcuate face of the prong directed substantially towards the longitudinal axis of the tubular portion.

In order that the invention may be more clearly understood and more readily carried into effect the same will now be more fully described, by way of example, with reference to the accompanying drawing in which:

FIG. I is an exploded and partially broken away isometric view of an electrical connector assembly incorporating a bushing according to a preferred embodiment of the invention;

FIG. 2 is a generally axially sectioned view of the assembly shown in FIG. I when in the fully assembled condition; and

FIG. 3 is an isometric view of a bushing according to an alternative embodiment of the invention.

With reference tothe drawing, in the different views of which like reference numerals are used to denote like parts, I0 denotes generally a bushing which is preferably integrally formed of an electrically insulating plastics material, such as linear polyethylene or nylon. The bushing 10 comprises a tubular portion 11 which is of cylindrical form and which has a longitudinal axis 12 (shown, for clarity, only in FIG. 3). At one end of the cylindrical portion 11 there is presented a flange portion 13 which projects outwardly from and around the cylindrical portion 11. The flange portion 13 presents at least one prong 14 which projects from the flange portion 13 in a direction opposite from the direction in which the cylindrical portion 11 projects from the flange portion I3, and preferably in a direction substantially parallel to the longitudinal axis 12 of the cylindrical portion 11, the bushing I0 illustrated in FIGS. 1 and 2 incorporating two such prongs 14 which are diametrically opposed to one-another relative to the axis 12, and the bushing 10 illustrated in FIG. 3 incorporating three such prongs 14 which are equi-angularly spaced about the axis 12. Although not specifically illustrated in the accompanying drawing, it is clearly to be understood that, in bushings 10 according to alternative embodiments of the invention, there may be more than three prongs 14 or only a single prong 14, as is indicated above.

Each of the prongs 14 is of approximately segmental forming cross section with arcuate face of the prong 14 facing substantially towards the longitudinal axis 12, and with the flat face of each prong 14 facing substantially directly away from the axis 12. In the preferred embodiments of the invention illustrated in FIGS. 1 to 3 the portion 16 of each prong 14 immediately adjacent to the associated flange portion 13 is of substantially circular form in cross section, with this portion 16 merging with the remaining portion of approximately segmental cross section of the prong I4 through a concave fillet 17, the provision of the portion 16 and the fillet 17 in each prong 14 substantially reducing the risk of the prong 14 being inadvertently broken off from the flange portion I3 where the bushing 10 is integrally formed of linear polyethylene or nylon.-

Remote from the flange portion 13 the end portion of each prong 14 is preferably of tapered form as indicated by the reference numeral 18, with the end of each prong l4 remote from the flange portion 13 disposed on the side of the prong 14 which is directed substantially towards the longitudinal axis 12 of the tubular portion 11. The inclined face constituting the tapering 18 presents informational indicia l9 relating to the bushing 10. This indicia 19 may constitute, for example, a size marking identifying say, the diameter of the bushing 10. It is to be characteristic however, that the'indicator 19 may relate to any characteristics or characteristics of the bushing 10. Furthermore, although in the bushing 10 according to the preferred embodiments of, the invention illustrated in the accompanying drawing, the end of each prong l4 remote from the flange portion 13 is of sharp configuration because of the presence of the tapering 18, it is clearly to be understood that this is not an essential feature of the invention and that the term prong" as herein used is not to be construed as necessarily referring to an elongated projection the end of which is pointed.

With particular reference to FIGS. 1 and 2, there is therein illustrated an electrical connector assembly which incorporates a bushing 10 as hereinbefore described. The connector assembly comprises an electric cable which is denoted generally by the reference numeral 20, and a connector which is denoted generally by the reference numeral 21.

The electric cable 20 comprises insulated electrical conductor means constituted by the insulated conductors 22, together with an outer substantially tubular casing 23 constituted by an interlocking spiral metal tape of hard drawn aluminum or galvanized steel, the cable 20 thus being of the type known as AC cable.

The connector 21 comprises a body portion 24 which is formed with a through passage 25 and which is constituted by a first part 26 and a second part 27, an end portion of the first part 26 being externally screw threaded and an end portion of the second part 27 being internally screw threaded whereby these

parts

26, 27 may be detachably interconnected by engagement between said screw threaded end portions thereof, as shown at 28 FIG. 2. The adjacent end faces 29 of the first and

second parts

26 and 27, respectively, are of frustoconical form, a resiliently deformable sealing ring 30 of substantially triangular form in cross section being disposed between these end faces 29.

The end portion of the second part 27 of the connector 21 remote from the first part 26 thereof is externally screw threaded and is disposed through an opening or hole 31 formed in a wall 32 which is only partially shown in FIGS. 1 and 2 and which may, for example, constitute a wall ofajunction box or electric switch. Disposed between the wall 32 and the adjacent face of the second part 27 is a washer 33, a lock nut 34 being screw-threadedly engaged with said screwthreaded portion of the second part 27 on the opposite side of the wall 32 thereby securely to mount the connector 21 on the wall 32 which thus constitutes a support structure for the connector 21. A cap 35, having a central opening 36 which constitutes a continuation of the through passage 25 and through which the insulated conductors 22 are disposed in the manner shown in FIG. 2 for connection of the conductors 22 to electrical conducting means such as terminals (not shown) disposed within the junction box or electric switch, in screwthreadedly mounted on the end portion of the second part 27 remote from the first part 26.

The end portion of the first part 26 of the connector 21 remote from the second part 27 thereofis in the form ofa support cradle 37 on which a complementary bridge portion 38 is adapted to be securely mounted by means of screws 39 with the cable disposed between the cradle 37 and the bridge portion 38 thereby securely to connect the connector 21 to the outer casing 23 of the cable 20.

The bushing 10 is disposed within the through passage with the cylindrical portion 11 of the bushing 10 between the insulated conductors 22 and the outer casing 23 of the cable 20, the flange portion 13 of the bushing 10 being in abutting contact with the end face 40 of the outer casing 23 of the cable 20, and the prongs 14 projecting through the through passage 25 with the end portions thereof remote from the flange portion 13 disposed beyond the connector 31 whereby these end portions are visible externally of the connector 21 by, for example, an inspector who requires merely to remove a cover plate or the like (not shown) associated with the junction box or electric switch and does not require to dismantle the connector assembly in order to confirm that a bushing 10 has been installed in the assembly. As will be appreciated, during this inspection the inspector can, furthermore, also confirm by checking the indicia 19 that it is the correct bushing 10, having regard to the particular characteristic or characteristics of the bushing 10 which are denoted by the indicia 19 which has been so installed.

While, as described above with reference to FIGS. 1 and 2, the end portion of each prong 14 remote from the flange portion 13 thereof projects beyond the cap 35, it is to be understood that said end portion of each prong 14 may alternatively project beyond the second part 27 of the connector 21 but not beyond the cap 35, in which case this end portion of each prong 14 is visible externally of the connector 21, by for example, an inspector, after the cap 35 has been temporarily disconnected from the remainder of the connector 21 by being unscrewed from the second part 27 of the connector 201 and slidably moved a short distance along the conductors 22. In such alternative embodiments there is still, however, no requirement for the connector assembly to be dismantled in order for the inspector to confirm that a bushing 10 has been installed in the assembly, since the connector 21 remains secured to the outer casing 23 of the cable 20, the connector 21 remains mounted on the wall 32 of the junction box or electric switch, and the conductors 22 remain connected to, for example, the terminals disposed within the unctlon box or electric switch.

What I claim as my invention is:

1. A bushing comprising a tubular portion having a longitudinal axis, and a flange portion which is presented at one end of the tubular portion and which projects outwardly from and around the tubular portion, wherein the flange portion presents at least one prong which projects from the flange portion in a direction opposite from the direction in which the tubular portion projects from the flange portion, said at least one prong being ofapproximately segmental form in cross section with the arcuate face of the prong directed substantially towards the longitudinal axis of the tubular portion.

2. A bushing according to claim 1, wherein the tubular portion is ofsubstantially cylindrical form.

3. A bushing according to claim 1, wherein said at least one prong comprises a plurality of prongs which are substantially equi-angularly spaced about the longitudinal axis of the tubular portion.

4. A bushing according to claim 1, wherein the end portion of said at least one prong remote from the flange portion presents informational indicia relating to the bushing.

5. A bushing according to claim 1, wherein the end portion of said at least one prong remote from the flange portion is of tapered form, with the end of said at least one prong remote from the flange portion disposed on the side of the prong which is directed substantially towards the longitudinal axis of the tubular portion.

6. A bushing according to claim I, wherein the bushing is integrally formed of linear polyethylene or nylon.

7. A bushing comprising a tubular portion having a longitudinal axis, and a flange portion which is presented at one end of the tubular portion and which projects outwardly from and around the tubular portion, wherein the flange portion presents at least one prong which projects from the flange portion in a direction opposite from the direction in which the tubular portion projects from the flange portion, said at least one prong being of approximately segmental form in cross section with the arcuate face of the prong directed substantially towards the longitudinal axis of the tubular portion, and the end portion of said at least one prong adjacent to the flange portion being of circular form in cross section and merging with the remaining portion of the prong of approximately segmental form in cross section through a concave fillet.

Claims

1. A bushing comprising a tubular portion having a longitudinal axis, and a flange portion which is presented at one end of the tubular portion and which projects outwardly from and around the tubular portion, wherein the flange portion presents at least one prong which projects from the flange portion in a direction opposite from the direction in which the tubular portion projects from the flange portion, said at least one prong being of approximately segmental form in cross section with the arcuate face of the prong directed substantially towards the longitudinal axis of the tubular portion.

2. A bushing according to claim 1, wherein the tubular portion is of substantially cylindrical form.

6. A bushing according to claim 1, wherein the bushing is integrally formed of linear polyethylene or nylon.