US1780851A - Plug cap - Google Patents

Description

Nov. 4 1930. H. L. STRONGSON 1,780,851

PLUG CAP Filed March 27, 1929 INVENTOR ATTORNEYS Herman ,jlran san Patented Nov. 4, 1930 HERMAN L. STRONGSON, OF NEW YORK, N. Y.

PLUG CA? Application filed March 27, 1929. Serial No. 350,146.

This invention relates to electrical connecting means such as plug caps and connecters for separable attachment plugs on flexible conductors used to make electrical connections, and may be considered broadly as terminal members for electrical conductors. The subject matter of Figures 1 thru 7 of this application is the same as that of my earlier application for patent,

10 Serial No. 163,877, filed Jan. 27, 1927, al-

lowed Sept. 16, 1927, forfeited Mar. 17, 1928, renewed Sept. 12, 1928, allowed Sept. 27 1928, and forfeited Mar. 29, 1929 through failure to pay the final fee.

An object is to produce a plug cap of increased durability, of low production cost, having improved yielding contacts, and including means to maintain the contact prongs in parallel relation, and for these purposes I make the body of elastic material and embed the contacts in a novel way to maintain parallelism.

. Electrical connecting plug caps have usually heretofore been formed ofhard insu lating material. In the more commonly used types this material has been frangible. Where the insulating material has been unbreakable, the cost of manufacture has been high and has rendered these better grade caps incapable of competing in the commercial field with the cheaper varieties as far as price was concerned. Low cost frangible caps frequently chip and crack or break at the point where a contact prong is anchored,

thus loosening the prong from the base so they are not durable. a

When composed of either frangible or infrangible material, the edges of the base are unyielding so that the constant rubbing of the wires thereover wears the wire insulation and eventually exposes and cuts the wire. Attempts have been made to over come this wear at the point where the wires enter the passage in the cap base by the provision of a coil spring which has resisted to some extent the tendency of the wires to bend over the edge, but that is objectionable m that it involves the use of an additional part which increases the cost of manufacture, is lnconvenient in many instances and Y 1s less sightly, and comes apart. a

It is also well known that within the interior of the base at the'point where the wires diverge for connection with the respective cap terminals, it has been difiicult to prevent the wear of the insulation by the hard unyielding edges over which the wires are bent in general service.

On the other hand, elastic plug cap connecters have been suggested but lacked in structural arrangement by which to restore or maintain parallel relation between the contact prongs, but my invention overcomes that difficulty.

The present invention has for one of its objects the provision of a cap for separable attachment plugs which shall meet the requirements of standard practice and still avoid the deficiencies of known constructions mentioned above. According to the invention, this plug cap connecter is composed of an unbreakable insulating material having a relatively high degree 0 elasticity, such as rubber, whereby no injury will result to the cap upon implngement with another substance or upon rough usage of the contacts. The contact prongs are anchored within or on the elastic material, which has the capacity of yieldin under shock, so that if a prong is struc its anchorage will not be loosened, but instead will yield slightly and absorb the shock. If the body is struck it also yields and does notfracture.

- Also the contacts are anchored to the elastic cap in an improved way which insures an effective yielding contact of the cap prongs within the receptacle contacts of a plug into which this cap is inserted, and the improved anchorage in function insures parallelism between the cap plug-in contact prongs, Tn

these respects and others my plug cap is novel and makes for the success of this new construction.

With each contact prong, there is carried, substantially perpendicular thereto, a foot support to receive the wire clamp screw, which foot may, if desired, be moulded within the elastic base so that only a relatively small portion thereof adjacent the clamp screw is exposed to permit an electrical connection to be made. The feet carrying the parallel contacts are so molded within the base or anchored to the surface thereof that they act to hold the integral contact prongs in parallel relation. Thus, should the contact prongs be displaced, the return of the elastic material between these adjacent parts, from distorted to normal position or condition, restore the prongs to operative position, i. e., to parallel position. Furthermore, each foot is preferably provided, near the upstanding contact prong with an anchorage member extending into the elastic material, in a direction opposite to that of the contact prong so that the prong is fulcrumed, so to speak, at its base within the elastic material and pivotal movement thereof is damped or resisted by the engagement and compression and tension of the elastic material in WhlCll the anchorage memher is embedded. Short stretch insulation portions of rubber are formed between the two adjacent contact-carrying feet to restore the contact prongs to parallel relation if distorted therefrom.

At the point where the wires enter the body or cap passage, the base may be formed with a. flexible neck which has a degree of resiliency and elasticity and positions the wires so that they extend straight out from the cap, the edges of the neck yielding upon contact with the wires and aflording a relatively soft edge over which the wire may bend in a gradual curve without wear on the wire insulation.

Being of elastic material, the central passage through the cap base accommodates itself to different size of wire conductors and affords resilient gripping engagement which resists withdrawal of the wires and may take the place of the set screw sometimes employed for that purpose and thus takes some of the strain off the connections.

The foregoing features are also considered as objects of the invention, and to those ends the base is made of rubber, as such material may have the desired degree of resiliency and elasticity, is readily moulded, and has the requisite degree of strength. The contacts may be easily moulded and partly concealed in a rubber base for anchorage therein and function as above related to' produce a less expensive and more durable plug cap.

While the device forming the subject matter of the present invention is referred to in general as a cap it is to be understood that the invention in its broadest aspect is applicable to any type of contact means which form end terminals on flexible conductors used to make electrical connections,

These and other objects of the invention 7 and the means for their attainment will be more apparent from the following description taken in connection with the accompanying drawings illustrating an embodimentof the invention, in which:

Figure 1 shows the improved electrical plug prong feet being dotted in to disclose their U relation transversely to the facing surfaces of the contact prongs.

Figure 3 isa sectional view, taken on the line 3-3 of Figure 2, showing the contact prongs embedded in the elastic insulating base, and showing anchorage members about which the material of the base is molded to secure the contact-carrying feet to the cap.

Figure 4 is a sectional view, on the line 4-4 of Figure 2 showing the clamp screw terminals and gradually enlarging central passage for the wires.

Figure 5 is a view of the blank in the flat from which the contact prong and foot support is formed.

Figure 6 is an isometric view' of the completed contact prong including flat curved foot to be embedded in or anchored on surfaceof the plug cap and showing the upstanding contact prong.

Figure 7 is a side elevation showing the yielding cap in distorted position from which distortion it will return to normal shape by the inherent resiliency of the material and by reason of the novel way and position in which the contact feet are mounted on the plug base.

Figures 8 thru 12 show improvements added in respect to a modified notched contact prong to receive the wire and a yieldable rib to press the wire into the notch; and also shows the foot on the surface of the cap.

, Figure 8 is a face view of an improved prong Contact bent up from a base or foot and shows a half-round wire receiving notch in the base of the prong, in one edge thereof, just above the upper surface of the foot, and into which the wire is received when bending it around the edge of the upstanding prong to bring the wire to the clamp screw under. which it is clamped. That notch makes room for the wire and an adjacent soft rubber rib presses the wire into the notch and the rib positively insulates the wire from the other contact of opposite elec-' trical sign.

Figure 9 is a plan view of the composite prong and foot shown in Figure 8 and also of Figure 6, since the formation of E/igureifi 8 part is effected by simply notching the prong of Figure 6.

Figure 10 1s a new of the section line Figure 12 is the same as Figure 11 exceptthe wires are removed to show the ribs as flexed back against the notched upstanding contact.

As will be obvious from the drawing, the general shape of the cap according to the present invention may be substantially similar to that commonly found on the market at the present time although changed and improved in many respects.

ach contact element is preferably formed from a single stamping, as illustrated in Figure 5, and includes a stamping of standard configuration or preferably of general segmental shape, the part 11 of which is adapted to be bent upwardly at right angles to a foot portion indicated as a Whole at 12 so that the foot portion lies in a plane normal to the plane-of the prong 11 Which stands up from one end of the foot and said foot having a toe 31 at its other end. One edge 13 of the'foot portion is circular or segmental to conform to the periphery of a cap base 20 so that the major portion of the foot is substantially in the form of a segment 14 which is tapped centrally thereof as at 15 for the reception of a terminal screw 25 and is extended by a neck 16 to form the prong carrying heel portion 17 which is in the same plane as the foot- 12. This portion or heel 17 is also perforated as at 18 to receive an anchorage pin member 19 about which the material of the cap base is molded. Other forms of contact elements or prongs may be molded in the yielding base.

The cap base or body 20 is formed of a yielding insulating material having a high degree of elasticity and resiliency, such as rubber, and may be molded to the desired shape to conform generally to standard practice. Being of soft rubber the several edges are yielding upon contact with the wire to avoid abrasion of the insulation and wire tending to sever the wire, and furthermore the base 20 will not fracture and that means the cap is good for long service.

The body or base 20 is formed with a central passage 21 for the entry of wires. If desired, the central passage 21 may be of less diameter than the normal diameter of the Wires and expand to receive the wires and contract again and grip the Wires yieldingly to contribute'to the anchorage of the wires in the base 20. Upon diametrically opposite sides, as at 22, the central passage 21may be of increased diameter, that is, at these por tions the central passage flares or tapers outwardly or gradually wins on the opposite sides 22 to permit the wires to separate and be led to the terminal screws 25. This wirepassage portion 22 of increased diameter also permits the formation of a knot in the wiring, such as is frequently tied in the wires to form a wire portion of increased size, which will not pass through the passage 21.

The yielding and tapering walls 22 of the cylindrical passage 21 thus conveniently form a restricting shoulder against which the wire knot rests and pulls. Thus the rubber cap 20 may be carried on the end of a flexible Wire with the strain on the knot rather than the screws 25 and contact parts.

The segments or contact-carrying feet 12 may be molded in the rubber base 20 as shown in dotted lines in Figure 2 so that the screws 25 are opposite one another adjacent the bevelled or tapering opening 22 of the wire passage 21 While the contact prongs 11 are disposed opposite one another on the narrower diameter of the passage and on the wider portion of the rubber base. The feet 12 are embedded within the molded material comprising the base, the face26 thereof being provided with grooves 27 which lays bare those portions of the feet 14 which are proximate the terminal screws 25 so that a good electrical contact is afforded for the wires under the screw head. The groove 27 also serves asa passage or path for the respective wires leading to the clamp screws 25 and permits the wires to lie substantially entirely below the surface 26. In other words the two contact bearing grooves or recesses 27 are simply continuations of the tapering passage 22. 7.

If desired, a fibre disc, not shown, of the usual kind, may be disposed over the prongs 11 and within the rim 30 of the cap to mask and insulate the screws as will be understood, but that is an old expedient in the art-to conv ceal the exposed foot segments of the contract prong, and is eliminated by my invention because I conceal the parts by molding them inside the plug body beneath the surface 26. Y

In concealing the prong feet 12, it is note- Worthy that a small portion is left exposed under each screw head by the grooves 27 to make contact with wires not shown which connect with the cap. a

It will be observed that the foot segments 12 lie opposite one another with their edges 13 preferably inwardly of the plug rim 30 but conforming to the periphery of the cap base 20. In other words, the edge 13 is defined by an arc of slightly less radius than that of the cap base 20, and the foot segment 12is positioned in the base. 20 so that the arc 13 and the base 20 are substantially concentric.

The rectilinear or chord edges 29 of the feet 12 are shown as disposed in substantially parallel relation separated by the longerldiameter or tapered side 22 of the wire passage. The necks 16 position the prongs 11 substantially midway between the respective segmental feet 12 so that the prong carrying heels 17 are adjacent the reduced toe ends 31 of the feet but spaced and insulated therefrom by the short elastic stretch of rubber portions 32 of the base 20. Thus the feet 12 extend substantially in a direction normal to the plane defined by the line 44 of Figure 2 and passing thru the terminal screws 25, and the feet 12 extend substantially parallel but on opposite sides of a plane defined by the line 33 in Figure 2 including the contact prongs 11.

In other words the two prong feet 12 are disposed transversely of'the plane 4-4, i. e., a plane parallel to the flat faces of the contact prongs. This relation imposes resistance of- 20 fered by the rubber base to the displacement of the prongs 11 from their normal arallel position. In fact the short stretch 0 rubber portions 32 stretch or compress if the prongs 11 are displaced and serve to restore them to parallel position. It is each elastic or restricted stretch portion 32, primarily, which is distorted, yields, or moves when the prongs 11 are displaced for instance as shown in Figure 7 and the inherent tendency of these 80 portions 32 to return to normal non-stressed condition due to the elasticity of the material effects a return of the prongs 11 to parallelisms to register with the receptacle contact elements of a screw plug, base receptacle or 35 other type of receptacle. r 7

As has been pointed out hereinbefore, there is carried with each prong base foot support 17 proximate the prong 11, an anchoring pin member 19 which extends into the base 20 in a direction op osite to that of the prong 11 and slightly 0 set with respect thereto. The contact prong 11 and anchorage pin 19 thus forms a lever of the first order fulcrumed in the elastic material substantiall at or just beneath the surface 26 and the plvotal movement of the prong 11 is damped or resisted by the engagement of the .elastic yielding nonmetallic material of the base 20 with the anchoragepin 19 and should the prong be displaced for any reason the elasticity of the material of the base 20 will tend to return the part 11-19 to normal upright position in the rubber base and above it.

In the manufacture of the cap, the prong feet or supports 14 and contact prongs 11 are either molded in the rubber base 20 or anchored to the surface 26 and have the screws 25 run down in the holes 15. Then, upon completion of the molding process, the screws 25 maybe unscrewed anddepressions 33 will be formed by the screws 25 for their reception when again screwed home into the feet 14. Thus a 'cap for a separable attachment plug has been provided which is itself'unbreakable and its contacts cannot be broken out because it is formed of yielding or elastic material, such as rubber, and even though the cap strike harder substances there is no danger of its fracturing.

Since the upstanding prongs 11 are carried by the yielding material, even though the prongs themselves are knocked about, the base will not be broken because the material will yield sufficiently to cushion the blow and permit the prong to be temporarily displaced as shown in Figure 7 without danger of breaking or bending it or fracturing the anchorage. This yielding and elastic mounting for the prongs 11 is also advantageous in that it permits the prongs to move in functionand more effectively register with the receptacle openings in current outlet supply devices, such as attachment'plugs, and contributes to the yielding engagement of the prongs 11 with the contacts in attachment plug. Thus, what may be called a tolerance is afforded in manufacture which is a feature not possible to attain with a rigidly mounted prong, and thus exact alignment of the contact prongs 11 with the contact blades in a plug receptacle is not so essential.

The walls of passage 21 may be found to yield sufficiently to accommodate a knot such as is frequently tied in the wires to form a portion of increased size which will not slip through the cap. The 'yielding walls may conveniently form a shoulder against which the knot rests. Thus the rubber cap 20 may be carried on the end of a flexible wire with the strain on the knot rather than the screws.

It is noteworthy that in any electric connecting device I so arrange and construct the parts that elastic means resists the displacement of the contacts from parallel position. To enable this principle to be carried out, one end of the contacts project from or stand up above the surface of the base or bod of the device, and the other end extends into the body. Elastic means is included in the structure embedding the last mentioned end, the

latter end itself including a portion preferably extending-parallel to theplan'e of greater motion or movement of the projecting or upstanding part.

Explaining further my principle, -it is noted that the line 3-3 of Figure 2 defines the plane of movement of the two upstanding contacts 11 for it is along this line that the parallel contacts move in function toward or away from each other. \I therefore take advantage of that fact and dispose the supports or feet 14 parallel to this line 33 rep resenting the line of relative movement between the contacts. This design and construction creates the elastic zone or stretch and insulating portion 32 which reacts between the adj acent support feet to hold them in normal position within the base which results in maintaining and restoring parallelism between the outside upstandingcontacts.

The stretching of the short rubber portion 32 quickly restores and maintains parallelism.

Again it may simply be restated that each prong foot 14 lies transversely of a plane 4-4 which is parallel to the confronting fiat surfaces of the upstanding parallel contacts 11 and this relative position of parts is new and attains a novel mode of action and enables me to use rubber as the base part. Since the mean center of the proximate parallel upstanding contacts 11 must be diametrically opposite each other and include a line passing through the center ofthe wire passage 21, I have off-set the foot support 14 from the contact 11 so that this relationship is brought about. The support 14 extends around the passage 21 while the contact 11 is adjacent the passage. In this way, the contacts 11 are placed toward the-centerof the base adjacent the wire passage 21 while the feet 14 are disposed outwardly away-from the passage toward the periphery of the base.

That general structural arrangement existing between the wire passage 2122 and the metal parts improves the utility of the plug cap and facilitates its installation. For example, each screw 25 is located within the foot baring or exposing groove 27 at the end of the longer axis of the tapered passage portion 22 of the wire passage 21, i. e., the screws '25 are at the endof the lengthwise passage 22. The wire passage 21 is round or nearly so and small in size at one end of the base 20, and is flared out and lengthwise at 22 and somewhat larger at the other end of the base so as to form the grooves 27.

All edges are yieldable to a wire conductor which provides against wear and tear and affords long life to an extension cord made up 'with my rubber plug cap. The rubber neck 37 provides a gradual bend over a long radius for a wire cord and preserves the insulation thereof where it enters the cap. The neck 37 defines the wire passage 21 which changes in form as it progresses through the base, first flaring out to form the lengthwise passage 22, and finally terminating in two 0 positely disposed wire receiving grooves 27 embracing and exposing the foot 12 under the screw head. In these particulars my construction is novel.

. In Figures 8 thru. 12, a wire notch or groove 40 is formed in a contact prong 41 upstanding from the end ,of a foot 42. The

notch 40 is cut in that edge of the prong which is opposite a wire clamp screw 43 which is screw threaded thru the foot 42. Thus the wire W wraps around the edge of the prong and rests in the notch 40. The notch 40 permits the adjacent heel and toe of the two feet 42 to be closely spaced and yet leave room for the wire W to fit therebetween.

Cooperating with the notch 40, is a resilient rib 45 which lies proximate the notch 40 and this rib serves as a spacing insulation between the foot inner edge 29 and the edge of the adj acent heel of the other foot. The rib 45 projects upwardly from the face of the cap and between the adjacent prong 41 and foot 42 and is flexible and easily pressed back away from the notch 40 thus making room for the wire to be pushed into the notch 40 in the operating of wrapping the wire about the prong and carrying it to the screw 43. The rib 45 is made sufficiently thick if desired to fill in the space between the two adjacent electrical contact parts of opposite sign, since the rib is yieldable to allow the Wire to mash it back for placement of the wire in final position.

Furthermore the views Figures 10, 11 and 12 illustrate how the contact-carrying foot 42 is anchored to the inside face of the plug cap if desired rather than mold it within'the plug as shown in the other views of the invention. Anchorage eyelets, rivets or other means 47 are molded in the body of the plug and project from the surface thereof and thru holes in the feet 42 and are then spun down or riveted over against the feet to attach the latter to the rubber body. I have shown the metal contact and wire connecting part mounted in two ways, first embedded in the rubber body and second anchored to the surface thereof.

In both forms, whether molded in the cap or anchored to its surface, there is employed the short stretch of rubber to insulate the arts and hold the contact prongs in parallel.

he reference numeral 32 clearly points out the rubber portion in the first instance. The ribs 45 are above or cover a similar short or narrow rubber stretch portion in the second instance. The principle and structure is the same in each instance.

The plug cap is durable and easy to attach to the wires and is easy to insert in any standard pll'ug receptacle.

W at is claimed is:

1. An electrical plug cap comprising a soft rubber-like body provided with a wire passage, a pair of feet of substantial length embedded within the body and separated at their ends by short stretches of rubber and separated at their centers by the passage, a contact upstanding from each foot, and wire connecting means. 7

2. A cap for an attachment plug comprising a soft rubber-like body provided with a wire passage, two feet of substantial length embedded within the body and separated at their ends by short stretches of rubber and separated at their centers by the passage, a plug in contact prong on each foot, said body eing recessed above each foot to expose a portion of the same, and wire connecting means carried with each exposed foot portion. v

3. A cap for an attachment plug comprising a soft rubber-like body provided with a wire passage, two segmentally-shaped feet molded in the body and separated at their centers by the passage and separated at their ends by short stretches of rubber which yieldingly resist relative movement of said separated ends, said feet including an outer curved edge and inner straight edge which centers by the passage, said feet including a heel and toe portion, the heel of one foot being placed adjacent the toe of the other foot, a contact prong upstanding from each heel portion, and the rubber-like body separating the adjacent toes and heels to insulate the feet and to yieldingly resist displacement of the contact prongs.

5. A cap for attachment plugs comprising a rubberlike body provided with a flared Wire passage, including a flexible neck through which a wire passes, the neck serving to protect the wire from damage at its point of entry into the body, a pair of feet carried by the body and being separated at their centers by the flared passage and whose ends are separated by short stretches of rubber, a contact upstanding from one end of each foot adjacent each short stretch of rubber, and wire connecting means.

6. In a plug cap for electrical connections, a rubber-like body provided with a wire passage therethru, a pair of feet of substantial length carried by the body and separated at their adjacent ends by short stretches of rubber therebetween and separated by the wire passage, a contact upstanding from each foot, said contacts being maintained in parallel relation by the rubber aforesaid. and wire connecting means.

7. In a cap to connect with electrical attachment plugs, a soft rubber-like body, two feet of substantial length carried by the body and separated at their ends by short stretches of "rubber, a plug-in contact prong on each foot, said body being recessed above each foot substantially in the center thereof to expose a portion of the same, and wire connecting means carried with each centrally exposed foot portion.

8. In a plug cap, a soft rubber-like body, two segmentally-shaped feet attached to the body and separated at their ends by short stretches of rubber which yieldingly resist relative movement of said separated ends,

each foot including an outer curved edge and an inner straight edge which disposes the in.-

ner edges in parallel spaced relation, a fiat contact upstanding at one end of each foot and said contacts being placed between the spaced parallel foot edges, the plane of each "flat contact being disposed transversely of the straight edge of the feet, and wire connecting means.

9. In a plug cap, a rubber-like body provided with a wire passage, a pair of substantially long parallel feet attached to the body and separated at their centers by the wire passage, each foot including a heel and toe portion, the heel of one footbeing placed adjacent to the toe of the other foot, a contact prong upstanding from each heel portion, and the rubber-like body separating the adjacent toes and heels to insulate the feet and to yieldingly resist displacement of the contact prongs.

10. A cap for attachment plugs comprising a rubber-like body provided with aflared wire passage, including a flexible neck through which a wire passes, the neck serving to protect the wire from damage at its point of entry into the body, a pair of feet carried by the body and being separated at their centers by the flared passage and whose ends are separated by short stretches of rubber, a contact upstanding from one end of each foot adjacent each short stretch of rubber, and wire connecting means.

11. In a plug cap, a resilient rubber-like body of round formation and provided with a wire passage centrally formed therein, a pair of contact carrying feet of substantial length carried by the body and extending over a large portion of the body to effect a good grip on a substantially large portion thereof, wire connecting means on each foot, said feet being disposed in a plane at'right angles to the axis of the wire passage, said body having a restricted stretch portion and a rib extending between the adjacent ends ofthe feet effecting insulation thereof, anchorage means joined to' the feet and projecting into the body to secure the feet to said body, and a pair of contacts carried by the feet and held in parallel relation by the long length of'the feet anchored to the body.

12. In a plug cap, a-round rubber-like bodyprovided with a central wire passage, a pair of contact-carrying feet attached to the rubber body with the passage disposed between the feet, a contact prong upstanding on each 7 foot, a wire clamp screw which is threaded thru each foot, and each of said contact prongs bemg provided with a wire receiving notch formed in that edge thereof which is opposite the screw carried in the foot, and said notch being formed at the base of the contact and close to the foot.

13. In a plug cap, a round rubber-like body provided with a central wire passage,

a pair of contact-carryin feet attached to the rubber body with the passage disposed between the feet, a contact prong upstanding on each foot, a wire clamp screw which is threaded thru each foot,-and each of said contact prongs being provided with a wire receiving notch formed in that edge thereof which is opposite the screw carried in the foot, said notch being formed atthe base of i the contact and close to the foot, and a yieldable rib pro ecting upwardly from the cap surface and being interposed between the notch in the edge of the contact prong and the adjacent foot which is spaced therefrom. In testimony whereof I afix my signature.

HERMAN L. STRONGSON.

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