US 2277293 A
Description (OCR text may contain errors)
March 24, 1942. B. B. BRADFORD SE PARABLE ELECTRICAL ATTACHMEN'I PLUG Filed July 13, 1940 a INVfZNTORl Patented Mar. 24-, 1942 UNITED STATES PATENT OFFICE Bruce B. Bradford, Danville, Iowa Application July 13, 1940, Serial No. 345,388
This invention relates to separable attachment plugs for connecting electric circuits and more particularly to that type of plug having two sections, one called the cap or male section provided with forwardly projecting contact prongs adapted to engage cooperating contact parts in the plug base or female receptacle. In plugs of this type, as ordinarily used, the cap section frequently becomes loosened or disengaged from the plug base causing poor electrical contacts. Also in many other cases they are of such close contact as to be very diflicult to disengage or extract, thereby causing many b-roken cords, bent prongs and other annoying and troublesome results to the user.
A few so-called self-locking and releasing plugs, using pins or push buttons for release, and cap-body of flexible rubber to produce resilient contact action, have been devised, but in the main are rather complicated in use and manufacture, also the rubber tends to lose its resiliency by use and age. And in some designs it requires skill and experimentation to determine the correct pressure to be exerted on such pins or releasing means so as to assure the proper alignment of blades in order to efiect their ready insertion in plug base.
It is the general object of this invention, to provide a novel and improved plug of cheap and simple construction which embodies efficient locking means adapted to prevent such inadvertent disengagement and also provide reliable resilient means of holding the connections in firm contact.
A further object of this invention is to provide automatic releasing means whereby the natural instinctive act of gripping the cap with the fingers will produce easy disengagement and withdrawal whenever electrical disconnection is desired.
Another object of this invention is to provide a plug cap of this type, in such form, whereby said act of finger gripping will produce automatic and accurate location of contact means so as to permit their ready insertion in its cooperative plug base or any standard type of plug base receptacle, when necessary.
It is also a noteworthy feature of this invention that the plug section bodies may be made of any suitable insulating material, such as porcelain, Bakelite, hard rubber, or yieldable rubher, as the resilient action within the plug-cap, in no wise is dependent on the flexibility oi the body material.
Other objects and advantages of the invention may appear in the following description, made in connection with the accompanying drawing, wherein like reference characters indicate like parts, in which- Fig. l is a plan view of the plug cap section illustrating the contact prongs in locking position, with their releasing position shown by the dotted lines. I
Fig. 2 is a plan view of one of the improved plugs showing the form and relative position of the finger grip sections.
Fig. 3 is a combined central section and elevation of the complete assembled plug, taken on the line 3-3 of Fig. 2.
Fig. 4 is a plan view of the face of one of the improved plug caps with the contact prongs thereof illustrated in section.
Fig. 5 is a face view of the plug base section.
Fig. 6 is an enlarged section of a portion of the following Fig. 7.
Fig. 7 is a central horizontal section through the plug cap but taken at right angles to that of Fig. 3.
In the drawing, the body portion of the plug cap is indicated by I, and may be formed of any suitable insulating material, the face of which is recessed or hollowed out so as to form an annular rim 2, and also provide suitable space for the moving finger-grip sections 3, also of proper insulating material, on opposite sides thereof, with an axial bore 4 therebetween for housing the electric cord 5. Contact blades or prongs 6 are hingedly secured to body portion I, intermediate of their ends, by means of proper hinge rivets I, embedded in body portion I, one end of each blade being embedded in each of said finger-grip sections 3, as shown by 8 in Figs. 3 and '7, and their other ends extending outwardly from the face of said body portion I, for contactive insertion in the plug base. Holes 9, shown in Fig. '7, are provided in outer ends of blades 6 for locking contact purposes. Laterally attached to the prongs 6, at their intermediate hinged points, are two arcuately shaped extensions I0, in Fig. 4, upon the free end of which is a suitable screw II which serve as connecting binding posts for the separate wire conductors of the electric cord 5. Also attached to extensions II], by rivets I2 or other approved means, are two fiat shaped springs I3 which are adapted to engage in suitable slot shaped recesses I4 in body portion I. These springs tend to retain the finger grips 3 and prongs 6 in locked contactive position, but at the same time their resiliency allowing free release and Withdrawal of prongs 6, by proper pressure on finger grips 3. The inner edges l5 of the finger grips 3 are so designed that when they are fully pressed together, as shown by dotted lines in Fig. 3, they definitely align the contact blades 6 so as to be in correct position for insertion in its cooperative plug base or any standard plug base now in use.
The body portion of the plug base, represented by IS in Figs. 3 and 5, may be made of any suitable insulating material and formed with two properly spaced slots I1, each containing a fiat non-resilient contact m'ember l8 equipped with projecting tit 19 to engage with the locking holes 9 in the contact blades 6.
It is to be understood that the blade members 6 are of substantially the same width, length and thickness as those heretofore used in connection plugs, so that the plug cap may be used with socket members or plug bases now in general use. However it is recommended that cooperative plug bases be used in order to obtain the preferred benefits of this construction.
From the foregoing it is evident that I have produced a practical form of plug whereby the instinctive gripping of the plug cap by the fingers will produce correct and easy insertion of same in the plug base, the release of the fingers permitting the spring like action within the plug cap, positively independent of any inherent resiliency of the body material, to cause the prongs of my improved cap to exert a definite and sustained pressure towards each other on the contact members within the plug base. In like manner the instinctive gripping of the plug cap by the fingers, in the act of plug withdrawal, auto- It is to be understood that, while I have herein described and illustrated one preferred embodiment, the invention is not limited to this precise construction, but that various changes may be made in the form, arrangement and proportions of the various constructive parts, without departing from the scope of the following appended claims.
Having thus described my invention, I claim:
1. A separable electrical attachment plug assembly, comprising a plug cap with body of insulating material, having hollowed out body por-- tion and two separate finger-grip sections loosely recessed therein, on opposite sides thereof, forming a wire passage therebetween; contact blades or prongs hingedly secured to said body portion, intermediate of their ends, one end of each being embedded in each of said finger-grip sections, and their other ends extending outwardly from said body portion for contactive insertion in a cooperative plug base; and means upon said extending prongs cooperable with contact elements within the plug base, in combination with spring means wholly within the said plug cap body, and positively independent of any inherent resiliency of the cap body, for assuring positive and sustained electrical contact against any normal stress, when cap and base are in assembled relation, said first mentioned means, however, being readily releasable by instinctive gripping pressure on said finger-grip sections, whenever electrical disconnection is desired.
2. A separable electrical attachment plug assembly, comprising a plug cap of insulating material, with hollowed out body portion and two finger-grip sections loosely recessed therein, on opposing sides thereof; contact blades or prongs hingedly secured to said body portion, interme diate of their ends, one end of each being embedded in each of said finger-grip sections, and their other ends extending outwardly from said body portion so as to engage contacting elements within a cooperative plug base, and means upon said extending prongs cooperable with said contacting elements within said plug base, in combination with spring means wholly within the said plug cap body, for assuring positive and locked electrical contact against any normal stress, said first mentioned means, however, being readily releasable by instinctive gripping pressure on said finger-grip sections, forcing the said finger-grip sections and the embedded ends of the contact blades together, and the extended ends of said contact blades correspondingly apart, against the resistance of the said spring means within the plug cap, whenever electrical disconnection is desired.
3. A separable electrical attachment plug assembly, comprising a plug cap of insulating material with hollowed out body portion and two finger-grip sections loosely recessed therein; contact blades or prongs, bearing rigid wire holding binding posts, yet hingedly secured to said body portion, intermediate of their ends, one end of each being embedded in each of said finger-grip sections, and their other ends extending outwardly from said body portion for contactive insertion in a cooperating plug base, said finger-grip sections so designed that when they are fully pressed together the extended ends of said contact prongs will be definitely and accurately aligned so as to be in correct position for insertion in its cooperative plug base or any standard plug base.
BRUCE B. BRADFORD.