US2464876A - Attachment plug base - Google Patents

Description

March 22, 19.49. L LUDWIG 2,464,876

ATTACHMENT PLUG BASE Filed June 11, 1946 INVENTOR au/5 u ovv/G BY f TORNEY Patented Mar. 22, 1949 UNITED STATES PATENT OFFICE ATTACHMENT PLUG BASE Louis Ludwig, Brooklyn, N. Y.

Application June 11, 1946, Serial No. 675,872

3 Claims. l

This invention relates to attachment plug bases and, more particularly, to attachment plug bases whose bodies include two similar molded halves.

Heretofore these molded halves had threads integrally formed on their external surfaces, and therefore required separate mold cavities to provide matching thread ridges. Furthermore, because of the threads, a tubular terminal shell which held the two halves together had to be threaded onto the body.

It is the main object of my invention to provide an attachment plug base of the character described whose two body halves are identical, rather than merely similar, whereby to reduce mold expense, and which halves are so constructed that the terminal shell can be pushed on, rather than threaded into place, whereby to reduce assembly expense.

It is another object of my invention to provide an attachment plug base of the character described in which the contact ngers are xedly held in position simply by permanently mounting the terminal shell and Without the use of any other means.

It is a further object of my invention to provide an attachment plug base of the character described in which the side contact finger is always in good electrical Contact with the terminal shell and in which the contact pressure between said finger and shell will be increased when a jack blade is inserted in the plug base.

Other objects of my invention will in part be obvious and in part be hereinafter pointed out.

The invention accordingly consists in the features of construction, combinations of elements and arrangement of parts which will be exemplied in the construction hereinafter described and of which the scope of application will be indicated in the claims.

In the accompanying drawings, in whichl is shown one of the various possible embodiments of my invention,

Fig. 1 is a front view of an attachment plug base constructed in accordance with my invention;

Fig. 2 is a top View thereof;

Figs. 3 and 4 are sectional views taken substan tially along the lines 3-,3 and d-ll respectively of Fig. 2;

Figs. 5 and4 G are sectional views taken substantially alongthe lines 5-5 and 6-6 of Fig. 3; and

Fig. 'I is a bottom view of the plug base.

In, general, I accomplish the objects of my invention by providing a hollow casing of electrical insulating material which is split into two halves along a plane including the axis of symmetry of the casing and passing through plug-blade-admitting slots inthe top wall of the casing. The two halves are provided with mating recesses and indentations of different sizes and shapes which cooperate to firmly and captively mount within the casing at least one pairof spaced contact lingers when the two halves of the casing are secured together. The contact fingers have suitable extensions running to the outside of the casing, one beneath the casing at the center thereof and the other at the side of the casing. The central extension serves as one of the contact terminals of the plug base. The side extension engages an'electrically conductive terminal shell which surrounds the side walls of the casing. This shell, which forms the other contact of the plug base, is threaded to enable it to be screwed into an electrical socket. Although the shell is threaded, the casing is not, so that the shell can easily slip into position. To hold the shell against axial displacement once it is in position, the casing is provided with an annuuar channel into which the top edge of the shell is spun. In addition, the casing may have one or more non-annular depressions to receive tines or projections struck from the shell whereby to prevent relative angular movement of the shell and casing.

Referring now to the drawings, it denotes an attachment plug base constructed in accordance with my invention and adapted to be used in conjunction with a conventional male jack, the blades of which are detachably receivable in the plug base. Said plug base comprises a casing I2 of electrical insulating material, such, for example, as hard rubber or a phenolic condensation resin in which are contained two electrically conductive I contact fingers I4, i6. A shell I8, of electrically conductive material, holds the various parts of the plug base together.

The casing l2 includes two identical halves 2t, 2t (see Fig. 2) which when assembled are disposed in registry and abutment along a plane 23, including the axis of symmetry of the casing. Due to the identity in construction of the two halves only the half 2l) will be described, and, for convenience, the same elements of the other half 22 will be identified by the same reference numerals primed.

The half 20 is approximately semi-cylindrical, the saine comprising an arcuate side wall 24 which is semi-circular in cross-section (see Figs. 5 and 6). The upper end 2d of said half is .fiared out like aA gonventional plug base to facilitate turning. Said upper end carries aintegral top wall 28 forming one half of the top surface of the plug base. This wall has a pair of indentations 30 which cooperate with mating indentations 30 in the other half 22 to provide spaced slots 3| for the reception of plug blades. Said top wall may be plain or, if desired, the same may be ornamented as indicated in the drawings.

The lower end of the half 20 includes an integral bottom wall 32 which cooperates with the mating bottom wall 32 of the half 22 to close the underside of the plug base. The wall 32 is of lesser diameter tha-n the side wall 24 in order to form an inset shoulder 34 between the bottom side walls of the plug base, the purpose of which will shortly be made clear.

The external surface of the arcuate side Wall is smooth and uninterrupted save for two depressions now to be described and a slot which will be described later. The iirst of these depressions is a semi-annular groove 35, which, in conjunction with the mating semi-annular groove 36' forms a continuous circumferential groove around the casing |2. The second depression constitutes a non-annular indentation 38 which may, as shown, be :contiguous with the groove 36. The groove 36 is located beneath the upper edge of the shell I8 and the depression 38 is disposed at any place within the region of the arcuate side wall covered by said shell.

The shell i6 is of tubular shape, having a thread 39 integrally formed therein. The lower edge of the shell terminates in an inturned flange 46 which is abutted against the shoulder 34 during assembly of the plug base. The upper edge 42 of said shell overlies the groove 36 and is spun into said groove as one of the nal steps in the assembly of the plug base, a tine 44 being struck from said shell to enter the depression 33 either at the same time that the edge 42 is spun in or immediately before or after the spinning operation.

To reinforce the weak spots in the casing the half 20 has a ridge 46 raised on the interior surface thereof in back of the groove 36 and a flat 48 built up in back of the depression 38.

The interior of the casing is hollow to accommodate the elongated contact fingers I4, I6, the same being fabricated from any resilient material well-known to the art. At least two :contact :lingers are employed, to wit, the center contact f linger |4, so-called because it is in electrical contact with the bottom central terminal, and the side contact finger, so-called because it is in electrical contact with the shell 8. vBoth contact lingers may be formed from a ribbon of sheet metal by any suitable bending and shaping operations.

The center contact finger 4 includes a shank 50 disposed beneath one of the slots 3| and adapted to be frictionally engaged by a plug blade. At its upper end said shank has an Outwardly inclined tip 52 which lies on a shelf 54 formed on the inner surface of the half 26 and located below and radially outwardly of the slot 3|. Said shelf is shallower than the width of the ribbon from which the contact finger I4 is formed, the depth of the shelf being such that when the tip 52 is placed on the shelf during assembly of the plug base, approximately one half of said tip will be received in the pocket formed by the shelf and the other half of the finger will extend above said pocket. In this fashion the mating shelves 54, 54' in the two halves of the casing cooperate to provide a recess which snugly receives the tip 52 and prevents the contact finger I4 from shifting transversely of itself. The bottom wall 56 of the shelf 54 is sloped, as indicated, to approximately match the slope of the tip 52, thus forming a substantial area of support for said tip.

The lower end of the finger I4 is formed into a proper shape to provide a bottom central terminal for the plug base. For this purpose the shank 50 has a dependent inwardly inclined integral leg 58 carrying a U-shaped extension 60, the base 62 of which rests against the bottom wall of the casing. Said base may, if desired, be provided with a raised boss 64 to expedite electric contact. The two sides of the U-shaped extension 54 are snugly received in slots 66 in the bottom wall 32 of the half 2|). These slots, like the shelf 54, have a depth of approximately equal to one-half the width of the linger I4, so that the opposed slots 66, 66 in the two halves of the casing cooperate to define openings in the bottom wall of the plug base through which the U-shaped extension first passes from the inside to the outside of the plug base and then from the outside to the inside of said base. This construction makes certain that the finger is securely locked in position. The linger is prevented from sliding axially, when the plug base is half assembled, by an outwardly inclined tip 68 projecting from the free end of the U-shaped extension. If desired, the bottom wall 32 may be provided with a depressed portion 'l0 intermediate the slots 66 to secure an opening beneath the boss 64 and thus lend some degree of resilience thereto.

The side contact nger IB includes a shank 12 located beneath the other slot 3| and having an upper outwardly inclined extension 14 received upon a shelf 'I6 on the inner surface of the half 20. Depending from the lower end of the shank 62 is a right-angled outwardly extending leg 18 which passes through a slot in one edge of said half. This leg terminates in an upwardly extending tip 82 which lies against the outside of the side wall of the half. Said slot 80 has a depth equal to approximately one half of the width of the linger I6 so that the mating slots 80, 86 on the two halves will cooperate to lock the finger in place at this point. The tip 82 preferably lies immediately below thegroove 36vso that the shell i8 can be forced against the ,same when its upper edge 42 is spun in.

It will be appreciated that with this construction when a plug blade engages the shank 'l2 of the side finger contact I6 it will force the tip B2 outwardly increasing the pressure with which it4 engages the shell I8.

It will thus be seen that I have provided an attachment plug base which achieves the several objects of my invention and which is well adapted to meet the conditions of practical use.

As various possible embodiments might be made of the above invention and as various changes might be made in the embodiment above set forth, it is to be understood that all matter herein described or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, I claim as new and desire to secure by Letters Patent:

1. An attachment plug base comprising a cylindrical casing of insulating material, said casing including two identical halves abutted along a plane including the axis of symmetry of said casing, the side walls of said casing being free of threads, a pair of contact fingers contained within said casing, each half of the casing having a top wall with a pair of spaced slots adapted to cooperate with mating slots in the other half to form openings for passing a pair of plug blades, means within said casing to captivelyand rmly secure said contact iingers beneath said openings whereby the same may be frictionally engaged by the plug blades, each said half having a bottom wall inset from the side walls to form a shoulder, a terminal shell having a screw thread integrally formed thereon, means integrally extending from the bottom edge of said shell and abutted against said shoulder, a depression in one of said halves, means extending 'inwardly from said shell and received within said depression to prevent rotation of said shell, one of said contact ngers having an integral extension projecting through the bottom wall of the casing to form a central contact for the plug base and the other of said ngers having an integral extension projecting through a side wall of the casing and in contact with said shell, said shell being imperforate in the region of said other finger, and an annular groove extending around said housing near the upper edge o-f said shell, said groove receiving an inwardly spun flange on said upper edge of the shell said other finger being near said inwardly spun flange, whereby said other finger is caught between the shell and the outer surface of the casing and thus is in intimate Contact with the shell.

2. An attachment plug base comprising a cy lindrical casing of insulating material, said casing including two identical halves abutted along a plane including the axis of symmetry of said l casing, the Side walls of said Casing being free of threads, a pair of contact fingers contained within said casing, each half of the casing having a top wall with a pair of spaced slots adapted to cooperate with mating slots in the other half to form openings for passing a pair of plug blades, means within said casing to captively and rmly secure said contact fingers beneath said openings whereby the same may be frictionally engaged by the plug blades, each said half having a bottom wall inset from the side walls to form a shoulder, a terminal shell having a screw thread integrally formed thereon, means integrally extending from the bottom edge of said shell and abutted against said shoulder, a depression in each of said halves, means extending inwardly from said shell and received within said depressions whereby to captively secure said shell to said casing, and an annular groove extending around said housing near the upper edge of said shell, said groove receiving an inwardly extending flange on said upper edge of the shell, the sides of said casing halves having mating slots which cooperate to form openings, one of said contact fingers having an outwardly extending portion passing through said openings and a finger on the end of said outwardly extending portion Which is disposed beneath the shell in the region of the inwardly spun upper flange whereby said finger is caught between the shell and the outer surface of the casing.

3. An attachment plug base comprising a cylindrical casing of insulating material, said cas- 'ing including two identical halves abutted along a plane including the axis of symmetry of said casing, the side walls of said casing being free of threads, a pair of contact fingers contained within said casing, each half of the casing having a top wall with a pair of spaced slots adapted to cooperate with mating slots in the other half to form openings for passing a pair of plug blades, means within said casing to captively and rmly secure said contact ngers beneath said openings whereby the same may be frictionally engaged by the plug blades, each said half having a bottom wall inset from the side walls to form a shoulder, a terminal shell having a screw thread integrally formed thereon, means integrally extending from the bottom edge of said shell and abutted against said shoulder, and an annular groove extending around said housing near the upper edge of said shell, said groove receiving an inwardly spun flange on said upper edge of the shell, the `sides of said casing halves having mating slots which cooperate to form openings, one of said iingers having an outwardly extending portion passing through said openings and a nger on the end of said outwardly extending portion which is disposed beneath the shell in the region of the inwardly spun upper ange, said shell being imperforate in the region of said iinger whereby said iinger is caught between the shell and the outer surface of the casing and is in intimate contact with the shell.

LOUIS LUDWIG.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,373,127 Freeman Mar. 29, 1921 1,875,270 Slade et al Aug. 30, 1932 2,210,603 Shaw Aug. 6, 1940

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