Electrical wiring device with cord grip fingers having longitudinal flex joints

An electrical wiring device with a cord grip whose grip fingers are longitudinally hinged for circumferential spreading about a contained cord, in addition to being hinged for radially inward movement against a cord, under the force of an apertured cover through which the cord extends.

BACKGROUND AND SUMMARY OF THE INVENTION 
This invention relates to electrical wiring devices such as plugs and 
connectors. 
Wiring devices frequently have cord grips to restrain cords whose 
conductors are connected to contact terminals in the device. The cord 
grips are generally characterized by a plurality of flexible fingers 
hinged proximate the outer periphery of the base of the device. The 
fingers bear against the cord and are held tightly in place upon assembly 
of a cover element with the base. Examples of the foregoing are contained 
in Smith U.S. Pat. No. 3,437,980, Apr. 8, 1969 and McLaughlin et al. U.S. 
Pat. No. 4,304,455, Dec. 8, 1981. 
Despite the number and variety of previous cord grips and their general 
success, there is a need for further alternative and improved arrangements 
of cord grips in wiring devices for reliable retention of a cord and 
prevention of the entry of dirt and the like. Devices with those 
characteristics should desirably be economical both to manufacture and use 
with a single device accommodating cords of varying sizes. 
The invention achieves these purposes in a wiring device of a molded 
plastic plug or connector body and a molded plastic cover or housing. The 
cover has an opening through which a conductor is inserted to be wired to 
terminals in the body. The body has a plurality, such as two, integrally 
molded extensions or grip fingers designed to restrain the conductor, or 
the grip fingers may be on a separate molded part, such as a ring, 
adjacent the body. Assembly screws for joining the body and cover draw 
them together and apply an inward force on the grip fingers via a cam 
surface or ramp. The grip fingers restrict the conductor from movement 
when the assembly screws attain a specific torque level. A key feature of 
the combination of the invention is that the grip fingers are hinged 
longitudinally through the center of their individual contact surfaces and 
can flex to conform to diameters of varied conductor sizes. The grip 
fingers engage a greater surface area and close off more of the cover 
opening as compared to previous devices. The ramp surface within the cover 
serves a two-fold purpose. It applies a force to the grip fingers that 
restricts the conductor from pulling out and a force that conforms the 
grip fingers to the diameter of the conductor. Additional aspects of the 
invention will be discussed in connection with the preferred embodiments 
hereinafter.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIGS. 1 and 2 of the drawing, an electrical wiring device in 
accordance with the invention is shown. As shown in FIG. 2 the device is a 
plug with extending male contacts 10 for mating with a connector. However, 
the device of the invention could also be a connector having internal 
female contacts with which a plug having contact blades mates. The view of 
FIG. 1 would be common to both a plug or connector. 
The device comprises an insulating body 12, such as of a molded plastic 
material. The body has a plurality of electrical contact elements 13 
supported therein. The contact elements have terminal means 14, such as 
screws, for attaching conductors respectively thereto. The contacts 13 are 
not shown in detail; they may be suitably configured in accordance with 
prior practice. 
An insulating cover 16 is disposed over the body 12 and has an aperture 17. 
The aperture 17 accommodates an electrical line cord 18 which enters 
within the cover 16 to the space adjacent the body 12 so that the 
conductors 19 thereof may be attached to the contacts 13 by terminal means 
14 on the body. 
In this embodiment, a plurality of grip fingers 20 are each joined together 
at a flexible joint 21 integral with the body 12 at the outer periphery 
thereof. The fingers 20 are allowed by the flexible joint 21 to move 
radially toward the line cord 18. 
Fastener means such as two diametrically located screw fasteners 22 engage 
the cover 16 and base 12 together and, as shown in FIG. 2, an inner 
surface 23 of the cover 16 bears against the fingers 20. When fully 
assembled by the securing of the fasteners 22, the fingers 20 are forced 
by the cover 16 into tight engagement with the connected line cord 18. As 
best shown in FIG. 1, the grip fingers 20 each have a longitudinally 
running hinge 24 with a portion 20a and 20b on each side thereof. The 
hinge 24 permits circumferential spreading of the finger portions 20a and 
20b around the cord 18 under the force of the cover 16 bearing against 
them. 
The circumferential spreading of the finger portions 20a and 20b helps to 
provide greater retention force on a cord 18 and also helps to close the 
upper portion of the device against entry of foreign material. Preferably, 
also, a dust seal 26 of flexible material is disposed about the aperture 
through which the cord 18 extends and prevents entry of dirt and the like. 
Among variations of the device which may be readily practiced are that the 
grip fingers 20 need not be integrally molded with the base 12. Instead, 
they may be molded as a separate element such as a ring which is disposed 
proximate the periphery of the base with the fingers 20 upstanding 
therefrom in substantially the same arrangement as shown in FIG. 2. 
The device is preferably configured substantially as shown in FIG. 2 in the 
respect that the fingers 20 have shoulders 28 on each portion 20a and 20b 
against which the tapered surface 23 of the cover 16 bears. This provides 
a concentrated force against the fingers 20 for reliable gripping action. 
While variations can be suitably practiced, the device is shown with two 
grip fingers 20, each of which has two portions 20a and 20b spaced by a 
longitudinally extending joint or hinge 24. This has been found successful 
so that there is generally no need for additional grip fingers or 
additional numbers of hinged portions of the fingers although such may be 
used if desired. 
A further aspect of the invention that contributes to its success and 
utility as a commercially practical device is that the terminals 14 for 
the internal elements 13 of the body 12 to which the conductors 19 of the 
cord 18 attach are substantially adjacent each other on one side of the 
body as illustrated in FIG. 2. More particularly, the body 12 includes a 
face portion 12a with apertures for individual ones of the conductors 19 
to come into engagement with respective internal contacts and also has 
screw terminal means 14 on a side surface of the body for fastening those 
conductors to the contacts. Each of the internal contacts 13 as well as 
the screw terminals 14 are insulated from each other by parts of the 
molded base 12. 
The foregoing embodiments are presented by way of example only and do not 
limit the application of the invention in other specific forms.