Electric Lamp Socket Assembly Having Stripless Wiring Terminals

U.S. Pat. No. 4,283,107 for "Lampholder Having Terminals of the Insulation-Displaying Type" issued to Walter Anthony is hereby incorporated by reference.

This invention pertains to electric lamp sockets and, more particularly, is concerned with lamp sockets having stripless wiring terminals.

Portable lighting units, which include desk lamps, floor lamps, and the like, use a lamp socket assembly usually enclosed in either a paper sleeve or a metal shell. The socket assembly is also called a "lampholder" or an "interior".

During manufacture of the lighting unit an electric cord set must be electrically connected to the socket assembly. In the past this has usually been accomplished by use of screw terminals.

Underwriter's Laboratories (UL) Standards applicable for portable lamp screw terminals call for the end of stripped wires to be either tin dipped or otherwise restrained to prevent unraveling of the wire strands. Alternately, the wires may be soldered to the terminals. Either method requires semi-skilled labor and takes longer than desired, thereby increasing the cost of the assembled lamp. This problem has long been recognized as evidenced by a number of patents directed to electric lamp sockets having stripless terminals. Stripless terminals may be broadly grouped as being of the insulation piercing type of the insulation displacing type.

Examples of patents dealing with the insulation piercing type are U.S. Pat. Nos. 2,728,059; 3,397,379; and 3,151,926. U.S. Pat. No. 2,728,059 issued to Lagin discloses an electric lamp socket with two insulation piecing terminals extending from a socket body. A separate snap-on cover covers the terminals. One of the terminals is connected to the screwshell while the other is connected to a switch contact within the body. The terminals are spaced so that the electric wires must be separated from each other. There is no provision to assure that the neutral wire is connected to the screwshell.

U.S. Pat. No. 3,397,379 issued to Puig calls for wires to be fed through separate passages in a threaded body to be proximate insulation piercing terminals. A separate sleeve with a mating thread is screwed onto the body and presses the wires against the terminals.

U.S. Pat. No. 3,151,926 issued to Schick et al. describes a lamp socket of the type intended to be placed in parallel along the length of an electric cord (e.g., Christmas lights). The socket body has a channel into which an electric cord is placed. Terminals within the channel pierce the cord's insulation. A separate wedge piece is clipped to the body to hold the cord in the channel and to provide strain relief.

The sockets described above are not one piece assemblies and, furthermore, do not appear adaptable for use in standard paper or metal shells.

The aforeincorporated U.S. Pat. No. 4,283,107 issued to the present applicant divulges a one-piece socket assembly having terminals of the insulation displacing type eliminating the need to strip insulation from the cord set.

In one aspect of the invention, there is provided an electrical lamp socket assembly which includes insulation piercing terminals protruding from the end of a body. A cover is pivotably mounted on the body and can close over the terminal. The cover includes means to hold an electric cord and align it with the terminals. When the cover is closed, it clamps the cord against the socket body. In another aspect of the invention, the body may include ridges to increase the grip on the cord.

In the drawings:

FIG. 1 is a pictorial view of an electric lamp socket according to the invention;

FIG. 2 is a side view of the assembly with part of the screwshell or body cutaway;

FIG. 3 is a view of the terminal end of the socket assembly;

FIG. 4 is a rear view of the assembly with parts of the screwshell or body cutaway;

FIG. 5 illustrates terminals adapted to on-off switching;

FIG. 6 illustrates terminals adapted for two filament lamp switching;

FIG. 7 illustrates terminals for three terminal switching; and

FIG. 8 illustrates terminals for keyless socket assemblies.

For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims in connection with the above-described drawings.

FIG. 1 illustrates an embodiment of the present invention in the form of a socket assembly 10. The socket assembly is illustrated as including a rotary knob type switch although the invention is not so limited. The socket assembly may include a switch or be without a switch, known in the trade as "keyless". The type of switch, if any, is not important to the invention. Suitable switches include the rotary knob type, the push-through type, and the pull-chain type.

The socket assembly 10 includes the usual screwshell 11 for receiving and holding a threaded lamp bulb base. According to industry standards, the screwshell is to be connected to electrical neutral. In FIG. 2 the screwshell 11 is shown cutaway. At the bottom of the socket defined by the screwshell 11 is an insulating disc 12 supporting a central inner socket contact 13 for making electrical connection to a corresponding contact in the lamp base. The inner socket contact is energized when it is connected to the "hot" wire of an electric cord 14.

Beneath the screwshell is an insulated body 15 preferably made of a thermoset or a thermoplastic material.

As seen in FIG. 1 and FIG. 3, at least one pair of insulation piercing terminals 16, 17 (or 17, 45) is provided at the terminal end 18 of the body 15. Each terminal includes one or more sharp metal projections extending from the end of the body. In the embodiment illustrated, two slightly offset projections are used for each terminal. The two terminals in a pair are separated by a distance about equal to the distance between the centerlines of wires in a cord set.

One terminal 45 extends into the body and is switchably connected to one or more of the aforesaid inner socket contacts if a switch is provided. This terminal 45 is to be connected to the "hot" wire of an electric cord set and accordingly referred to as the "hot" terminal. Terminal 16 is also referred to as a "hot" terminal.

Another terminal 17 is electrically connected to screwshell 11. This terminal 17 is to be connected to the neutral wire of the cord and is called the "neutral terminal." One feature of the invention is that the neutral terminal is formed from a metal neutral piece 19. The neutral piece 19 may have a tapped hole 20 for receiving a conductive fastener 21 (e.g., screw) from the screwshell 11. The screwshell 11 may, in addition, be fastened to the body by an eyelet 22 or other fastener.

As another feature of the invention, a cover 23 is arranged on the body to be closable over the terminals. In FIG. 1, the cover 23 is depicted separate from body 15 for clarity. In practice however the cover 23 is hinge mounted to the body 15 as seen in FIGS. 2, 3, and 4. The rear of the cover 23 has pivot pins 24, 25 which rotate in corresponding hollows 26, 27 provided in the body 15. A cam 28 is arranged on the pivot axis. A follower 29, which is preferably a spring formed of the same neutral piece 19 as are the neutral terminals, presses against the cam. The cam 28 is indented so that the follower 29 holds the cover 23 open during wiring procedures, such as shown in FIG. 3, and fully closed during shipping so that the cover will protect the terminals.

The cover front 30 has a slot or yoke 31 for receiving the end of the cord 14. The inner surface of the cover 23 has a groove 32 to guide the cord 14 from the cover front 30 to the cover rear 35 during cord insertion. The cover rear 35 is stepped, having a recess 36 sized to pass only one wire of the cord 14. Because of this recess 36, the end of the cord 14 must be step cut to be properly inserted. The step arrangement offers several benefits. The end of the cord must be step cut assuring electrical insulation between adjacent wires. It is anticipated that most lighting unit manufacturers will use a cord set which includes a length of cord terminated on one end by a molded plug. Industry standards call for one of the two flat prongs of the plug to be wider than the other. The wider prong is inserted into the neutral port of the AC receptacle. If the end of the cord is properly step cut, the wiring will be automatically correctly polarized with the neutral wire connected to the terminal 17 corresponding to the threaded screwshell 11. The recess on the rear cover 35 may be a through hole 36, in which case it would allow visual inspection of the wiring.

After the end of the cord 14 is inserted in cover 23, the cover is closed over the terminal end 18 of the body 15 causing the terminals 16, 17 to pierce the insulation of the corresponding wire of the cord set to make contact with the conductive strands within the wires. The cover 23 aligns the cord 14 with the terminals. Recesses 37, 38 on the inner side of the cover 23 opposite the terminals allow for clearance of pierce points. A captive screw 40 may be screwed in a threaded hole 41 securing the cover 23 closed over the end of the body 15.

The terminal end 18 of the body 15 has integral ridges 39 between the terminals and the entry of the cord. The closed cover clamps the cord against the ridges 39 which engage the insulation of the cord 14. The clamping action provides a strain relief.

As seen in FIG. 2 the electrical cord 14 is bent about the front 30 of the cover 23 allowing a paper sleeve or liner (not shown) to be slid over the assembly. A two-piece metal housing (not shown) may be snapped together over the insulating liner.

In the embodiment illustrated by FIG. 1, the body 15 contains a rotary-knob switch arranged to connect the "hot" terminal to one or more of the inner socket contacts. In this type of switch a knob 42 turns a shaft 43 supporting a four armed star rotor (not shown) within the body 15. The star rotor member itself is non-conducting but has a metal rim arranged on selected arms depending on the switching function. The star rotor ratchets with corresponding switch contacts. The hot terminal 16 may be an extension of a switch contact. This is shown in more detail in FIGS. 5, 6, and 7 which show various switch contact arrangements. The neutral terminal is electrically connected directly to the screwshell 11 in all cases.

For single lamp operation, only one pair of terminals is necessary. FIG. 5 shows a contact arrangement for one lamp, single filament applications wherein only one inner socket contact is necessary. The "hot" wire terminal 16 is switchably connected by the star wheel to the central socket contact 13 for simple on-off operation. Two opposite arms of the star rotor (not shown) have a common conductive rim.

FIG. 6 shows a contact arrangement for two filament "3-way" lamp operation. The "hot" wire terminal is switachably connected by the star rotor to one or both of two inner socket contacts, a center contact 13 and an intermediate contact 44. Three arms of the star rotor (not shown) have a common conductive rim.

Some applications call for a switchable socket assembly to control a keyless socket assembly. This is called a "three terminal socket", for which a contact arrangement is shown in FIG. 7. A second pair of terminals can be provided to interconnect socket assemblies. Both neutral terminals of the both pairs may be formed of the same neutral piece 19. The "hot" terminal 45 of the second pair is connected to another switch contact within the body. Three arms of the star rotor (not shown) have a common conductive rim.

U.S. Pat. No. 4,283,107 for "Lampholder Having Terminals of the Insulation-Displaying Type" issued to Walter Anthony describes the construction and operation of rotary knob switches having these functions.

Alternately, the socket assembly may be "keyless", which means no switch at all. In this case the "hot" terminal 45 is permanently connected directly to the central contact 13 as shown in FIG. 8.

Thus, there have been described several embodiments of a one piece lamp socket assembly which meets the objectives of ease of assembly, no wire stripping or tinning, strain relief and one screw assembly during wiring. Features aid correct polarization of the cord set and provide visual and mechanical aids during the wiring operation.

While there has been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.