US 2198504 A
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Description (OCR text may contain errors)
A. R. POOL April 23, 1940.
SPRING LOCK FOR ELECTRICAL CONTACT PLUGS Filed March 2'?, 1959 nventor 0L @Lam Patented Apr. 23, 1940 PATENT oFFicE SPRING LOCK FCR. ELECTRICAL CONTACT PLUGS Austin R. Pool, Wetmore, Kans.
Application March 27, 1939, Serial No. 264,341
This invention relates to electrical fittings of that type involving 'two pairs of conducting strips or straps adapted to be brought into latwise slideable engagement for the completion of an electric circuit, in which positive means is provided to insure a good electri-cal connection between the members, as well as one in which the members are reliably locked against accidental breaking of the circuit. With devices of this kind, of ordinary construction, the connection is easily severed by a slight pull on the electric cord of one or both of the parts.
A further object of the invention is to produce a construction of the general character outlined which will maintain its life over a much longer' period than the usual plug, since positive locking means is provided which takes up wear or looseness of the parts.
Another object of the invention is to produce a construction of the general character mentioned which is strong, durable, ei'licient and inexpensive; and in order that it maybe fully understood, reference is to be had to the accompanying drawing, in which:
Figure l. is a central longitudinal section of an electric fitting embodying the invention.
Figure 2 is a section on the line II-II of Figure 1.
Figure 3 is a central cross-section through Figure 4, a boX-typetting embodying the invention.
Figure 4 is a longitudinal section on the line IV-IV of Figure 3.
Figure 5 is a detail perspective of one of the contact elements of the box-type tting.
The usual fitting which is adapted for threaded engagement with an electric socket is shown in Figures I and 2, while Figures 3 and 4, illustrate the permanent type which is mounted in a wall 40 box or the like, not shown. Referring rst to Figures 1 and 2, the fitting comprises a cylindrical shell member I of non-conducting material, having a closed end 2 and a center stem 3 projecting from said closed end. The closed end of the shell is formed with a pair of parallel openings 4 on opposite sides of the center stern 3; and the end of the stem carries a projecting rivet 5. Closing the open end of the shell is an externally threaded metal cap 6, and extending downwardly from the cap in substantially parallel spaced relation are a pair of conducting metal strips 1 and 8 having their opposite ends in close proximity to the openings 4. The two strips are in non-conductive relation, one of them being electrically 56 connected tol the threaded cap Ii from which it is supported, and the other being electrically connected to a center contact 9 forming a washer between an insulation disk Iii and the upset end of the rivet 5, or the parts can be otherwise assembled. The other member' of the iitting comprises 5 a cylindrical non-conducting cap II from which conducting wires I2 extend, the ends of said Wires being electrically connected to a pair of parallel strips it and i4 projecting from said fitting and spaced slightly closer together than the strips 1 10 and 8 of the tting iirst described. The parts are electrically connected by thrusting the strips I3 and I4 of the second member, through the openings @I of the first member, wher'e they make electrical contact with the strips I and 8 as 15 common inthe art. The above construction is by way of example, and forms no part per se, of the present invention other than to indicate a general type of fitting of the character under consideration. n
Heretofore, various means have been adopted in the endeavor to hold the two pairs of strips in good electrical Contact, lbut because of the thinness and softness of the metal forming the parts, it has been found that they soon become 25 loose to such a point that electrical contact is not only lost, but the second fitting will fr'equently fail to maintain its position and becomes quickly separated, even by its own weight.
In order to maintain positive contact and lock the second tting against movement except under a strong pull, I mount a casing I6 in the stem 3 of the first tting between the strips 'l and 8 and at right angles thereto, Within the casing I6 I provide positive frictional pressure locking means for coacting with the strips I3 and I4 of the second or separable member, to force them apart into positive contact with the strips 'I and 8 of the first member'. In the present embodiment of the invention, the casing IB is cylindrical and may be molded in the non-conducting stem 3 of the member I. Mounted in said casing is a spring I1 which presses in opposite directions against a pair of non-conducting balls I8. The balls come into frictional contact with their respective proximate strips I3 and I4 and press them outwardly against their companion strips l and 8, and thus maintain the parts tightly together and take up wear and hold a good electrical contact. In the preferred construction, the `ends of the strips I3 o and I4 have stops to receive the balls to more reliably lock the two fittings in connected relation.
In the present embodiment of the invention, the
stops are in the form of a pair of openings I9 into which the balls are seated as will be readily u understood. To stiifen the cap 6, and make its connection with the member I, the former may have an insulation lining 6a to abut the member i, and be provided with openings 6b and 6c for the accommodation of the strips 1 and 8, and the stem 3 of the member I. The insulating lining, however, is not essential.
In the permanent or Wall box form of construction, 20 is a non-conducting casing provided with a pair of spaced internal chambers 2|, each receiving one of a pair of contact strip members 22. The strip members 22 each having an external bolt 23 for connection to electric wires (not shown) as common in the art, and the assembly is adapted to be secured in an outlet box by means of its cross strap support 24. The casing 20 is provided with a pair of openings 25 to receive the projecting strips 26 extending from a second electrical tting or separable cap member 21 corresponding in all respects to the member 9 above described. A pair of frictional ball members 28 are mounted in a casing 29 carried by the central body portion of the casing 20. The balls 28 are pressed in opposite directions by a spring 3G. This construction corresponds in operation to that above described, the balls 28 pressing the strips 26 into contact with the strips 22.
From the above description, it will be apparent that I have produced a construction embodying all of the features of advantage set forth as desirable; and while I have described the preferredembodiment, it is to be understood that I reserve the right to all changes Within the spirit of the invention and without the ambit of the prior art.
l. An electric contact plug comprising an insulating shell provided with an inner portion of less diameter than the interior wall of the shell and forming spaced chambers of reduced width at one end and terminating in ilaring mouths, a pair of insulating balls in said inner portion, a spring tending to project said balls into said chambers, a pair of fiat spring contacts occupying said chambers and bowed toward the balls of the shell, corresponding ends of the contacts being free for approaching or receding movement, a second hollow fitting communicating with the said flaring mouths, and relatively fixed contact strips projecting from the second fitting into said spaced chambers through the reduced portion thereof and said flaring mouths and respectively disposed between and in contact with said bowed portions of the contact strips and said balls, the said fixed strips having openings to partially receive the spring urged balls to lock the strips against accidental disengagement through relative endwise movement.
2. An electric contact plug comprising an insulating shell provided with an inner portion of less diameter than the interior wall of the shell and forming spaced chambers of reduced width at one end and terminating in flaring mouths, a pair of insulating balls in said inner portion, a spring tending to project said balls into said chambers, a pair of ilat spring contacts occupying said chambers and bowed toward the balls of the shell, corresponding ends of the contacts being free for approaching or receding movement, a second hollow tting communicating with the said flaring mouths, relatively xed contact strips projecting from the second fitting into said spaced chambers through the reduced portion thereof and said flaring mouths and respectively disposed between and in contact with said bowed portions of the contact strips and said balls, the said xecl strips having openings to partially receive the spring urged balls to lock the strips against accidental disengagement through relative endwise movement, electric conductors leading from the iixed contact strips exteriorly of the second fitting, a threaded metal socket receiving the first-named tting and electrically connected to one of the bowed contact strips, a center contact carried by said rst-named iitting in electric connection with the other bowed contact and insulated from the threaded socket.
AUSTIN R. POOL.