Adjustable strain relief for wiring devices

An electrical connector is provided with an adjustable strain relief including a pair of movable barriers captively mounted by the connector housing for selective rotational positioning such as to cooperate with fixed barriers formed on the two parts of the connector housing in providing strain relieving labyrinth grips on the terminal portions of at least two sizes of electric cord.

The present invention relates to wiring devices and particularly to 
electrical connectors, such as plugs and receptacles, utilized as 
terminations for electrical cords. 
BACKGROUND OF THE INVENTION 
Electrical connectors for terminating the ends of extension cords, lamp 
cords, small appliance cords, etc., are commonplace items in the home. 
Original equipment connector-terminated electric cords are typically 
manufactured with the cord insulation and the connector body or housing 
intimately bonded together or molded in integral relation. As such, 
adequate strain relief for the cord is provided to prevent separating the 
connections between the cord wires and their terminating electrical 
connector elements should the cord and connector body be repeatedly 
subjected to tension. 
Unfortunately, after prolonged abuse, the electrical connection between a 
cord wire and plug or receptacle connector element tends to break, and a 
replacement plug or receptacle must be then installed to reterminate the 
electric cord. The replacement connector should be equipped with 
appropriate strain relief provisions such that the cord is gripped by the 
connector body during installation to prevent premature failure of a cord 
wire/connector element connection or joint. It will be appreciated that 
reliable strain relief is especially important in the case of those 
connectors that rely on insulation piercing prongs or barbs to make 
electrical connections between the cord wires and the connector elements 
(plug blades or receptacle jaws). 
Typically the strain reliefs provided in replacement electrical connectors 
are designed for a particular cord size. Unfortunately, electrical cords 
in residential applications can be and typically are of different sizes. 
Thus, the do-it-yourselfer must be sure to obtain a replacement connector 
that is specifically designed for the size of the cord to be reterminated, 
which can be a hit or miss proposition for the inexperienced. Previous 
attempts to provide replacement connectors adaptable to different cord 
sizes have resorted to the selective use of cord gripping inserts, which 
are susceptible to being misplaced. Other designs utilize wedge elements 
which are selectively, adjustably crammed into gripping engagement with 
the cord by the installer. Both of these approaches require the installer 
to use a certain degree of judgment to achieve adequate strain relief. 
SUMMARY OF THE INVENTION 
It is accordingly an objective of the present invention to provide a wiring 
device, such as an electrical plug or receptacle connector, equipped with 
a strain relief that is readily and simply adjustable to accommodate 
electrical cords of different sizes. To this end, the connector includes a 
two-part housing, wherein at least one of the housing parts is provided 
with a longitudinal guideway for receiving the terminal portion of an 
electric cord. A plurality of longitudinally distributed, fixed barriers 
are formed in the two housing parts in transverse relation to the 
guideway, such as to produce a first strain relieving labyrinth grip on 
the cord terminal portion of a large size cord when the housing parts are 
secured in mated relation. 
One of the housing parts captively mounts at least one movable barrier 
which is selectively manipulated by the installer either into a 
longitudinal orientation disassociated from the first labyrinth grip or 
into a transverse orientation to produce, in combination with at least one 
of the fixed barriers, a second strain relieving labyrinth grip on the 
terminal portion of a small size cord disposed in the guideway as the 
housing parts are secured in mated relation. 
In the preferred embodiment of the invention, two movable barriers are 
commonly mounted by a carrier which is, in turn, mounted by the one 
housing part for limited 90.degree. rotation. Indicia borne by the housing 
indicate to the installer the appropriate angular carrier position 
providing the requisite movable barrier orientation for the cord size 
involved. Detents maintain the movable carrier orientation selected by the 
installer during installation and also provide tactile feedback that the 
movable barriers are properly in their selected orientation.

DETAILED DESCRIPTION 
FIGS. 1 and 2 illustrate in longitudinal cross section an electrical plug 
connector, generally indicated at 10, which incorporates an adjustable 
strain relief in accordance with the present invention as generally 
indicated at 12. The connector includes a two-part housing consisting of a 
base 14 and a cover 16 which are hinged together at 18, such that the 
housing parts can be swung open, as illustrated in phantom, to accommodate 
electrical installation of the connector to the end of an electric cord 
20. The housing parts are secured in the closed, mated relation seen in 
FIGS. 1 and 2 by a resilient clip 22 secured at its illustrated lower end 
to cover 16 and configured to releaseably engage a latching nose 24 formed 
on base 14. The free end of the clip is accessible in an opening 26 in the 
base to disengage the clip from the latching nose and thus permit 
separation of the housing parts preparatory to connector installation. It 
will be appreciated that, in lieu of the hinge/latch connections of the 
housing parts, they may be united by plural, removable fasteners, such as 
screws. 
Cover 16 is formed, as best seen in figure 3, with a longitudinal guideway 
28 essentially defined by raised, transversely spaced, longitudinally 
extending ribs 30. The terminal portion of an electric cord 20 that is to 
be electrically terminated with connector 10 is inserted longitudinally 
along the guideway until the cord end abuts a transverse guideway endstop 
32. The cord terminal portion extends through an opening in clip 22 and 
under a leaf spring 34 serving to press the cord terminal portion against 
the guideway floor. 
Base 14, as seen in FIGS. 1 and 2, fixedly mounts a pair of connector 
elements, each integrally formed having an external blade 36 and an 
internal prong or barb 38. Thus, when the housing parts are mated, the 
barbs pierce the cord insulation 20a and make electrical connection with 
the cord stranded wire conductors 20b pursuant to installation of the 
connector to cord 20. 
To provide strain relief for the cord, cover 16 is formed with a pair of 
fixed, longitudinally spaced barriers 40 and 42 oriented transversely of 
guideway, as seen in FIGS. 1-3. Base 14, as also seen in FIGS. 4 and 5, is 
formed with a fixed barrier 44 which assumes a position transverse of the 
guideway and intermediate the cover barriers 40 and 42 when the housing 
parts are mated. Thus, as seen in FIG. 2, when the terminal portion of a 
large size cord 20 is disposed in guideway 28, and the cover and base 
latched in closure relation, barriers 40, 42 and 44 effect a labyrinth 
grip on the cord terminal portion to provide effective strain relief 
preventing the cord from being separated from connector 10. 
In the illustrated embodiment of the invention, adjustable strain relief 12 
is only involved in a strain relieving labyrinth grip of a cord of a 
smaller size than that illustrated in FIG. 2. Thus, as seen in FIGS. 1, 2 
and 6, the adjustable strain relief comprises a carrier, generally 
indicated at 45, including a disk 46 serving to mount a pair of spaced, 
parallel barriers 48 and 50 upstanding from its inner side. A central post 
52 projects from the outer side of the disk and is provided with a pair of 
laterally extending, diametrically opposed ears 54 in closely spaced, 
parallel relation to the disk. To captively mount the carrier to the 
connector, base 14 is provided with a keyhole slot which, as seen in FIG. 
6, is configured to have a central, circular opening 56 of a diameter 
slightly larger than the post diameter and diametrically opposed, 
laterally extending slots 58 dimensioned to permit the insertion of ears 
54 there-through. To assemble the carrier to the base, the post and ears 
are inserted through the keyhole slot from the inner side of the base. 
When disk 46 abuts the inner side of semi-circular shelves 60 intermediate 
slots 58, the carrier is rotated to swing ears 54 out of registry with the 
slots. Thus, the carrier becomes captively mounted to the base with the 
shelves received in the close-fitting space between the disk and ears. 
To permit carrier assembly while discouraging disassembly, diametrically 
opposed, a ramped stop 62 is positioned adjacent one edge of each slot 58. 
Once the carrier is inserted in the keyhole slot and rotated in the 
counter-clockwise direction illustrated in FIG. 6, the ears are ramped up 
and over the revelled front sides of stops 62. Once clear of these stops, 
their straight, back sides limit reverse rotation of the carrier to an 
angular position short of registering the ears with slots 58. Thus 
inadvertent disassembly is precluded. Additional stops 64 are stationed 
adjacent the slot edges in opposed relation to stops 62 to limit 
counter-clockwise rotation short of also registering the ears with the 
slots. It is thus seen that stops 62 and 64 preserve the captive, 
rotational mounting of the carrier to the base and also serve to limit the 
extent of permissible carrier rotation to 90.degree.. 
When carrier 45 is angularly positioned as illustrated in FIGS. 2 and 4, 
its barriers 48 and 50 are longitudinally oriented to in effect straddle 
guideway 28. It is thus seen that, as noted above, these movable barriers 
do not participate in the strain relieving labyrinth grip of the large 
size cord. However, when the carrier is rotated 90.degree., its barriers 
48 and 50 are oriented transversely of the guideway, as illustrated in 
FIGS. 1 and 5, and, when the housing parts are closed, act with 
intervening cover barrier 40 to produce a strain relieving labyrinth grip 
on the terminal portion of a smaller size cord. 
To ensure proper installation, indicia depicting the most common large cord 
size, SPT-2 (16 and 18 AWG), and small cord size, SPT-1 (18 AWG), is 
provided on the exterior surface of base 14. The outer faces of ears 54 
bear arrow heads 66 which indicate , when pointing to the terminations of 
respective lead lines 68 running to depictions 70 (SPT-1) and 72 (SPT-2) 
of the two cord sizes, the appropriate carrier position for the cord size 
involved. The arrow heads can also serve to indicate the orientation of 
barriers 48 and 50. 
As a further convenience to the installer in achieving proper carrier 
angular positioning and to preserve the selected carrier position during 
installation, detents in the form of bumps 76 formed in the surface of 
shelves 60 and dimples 78 formed in the undersides of ears 54 are 
provided. The bumps are located such that, when the carrier is in either 
of its two different cord size positions, they snap into respective 
dimples to also provide tactile feedback to the user that the movable 
barriers are properly positioned in each case. The head of post 52 is 
provided with a slot 80 for accepting a tool, such as a coin, screwdriver, 
etc., to facilitate rotational positioning of the carrier. 
While the strain relief of the present invention is illustrated as having 
two movable barriers cooperating with one fixed barrier to effect a 
labyrinth grip on a cord, it will be appreciated that one movable barrier 
could cooperate with a single or a pair of fixed barriers to provide a 
strain relieving cord grip. Furthermore, rather than having the adjustable 
strain relief barrier participate only in a labyrinth grip of a small 
electric cord, additional shorter barriers may be provided in orthogonal 
relation to barriers 48 and 50 for participation in a labyrinth grip of a 
large (SPT-2) cord. 
It will be further appreciated that the adjustable strain relief of the 
present invention is equally adaptable to an electrical cord terminating 
receptacle connector in the same manner as illustrated herein for a cord 
terminating plug. In addition, the present invention is not limited in 
application to connectors using insulation-piercing barbs to effect 
electrical connection with the cord conductors. Rather, such connections 
may be made via binding head screws. 
From the foregoing Detailed Description, it is seen that the objectives of 
the present invention are efficiently and effectively achieved, and, since 
certain changes may be made in the constructions set forth, it is intended 
that matters of detail be taken as illustrative and not in a limiting 
sense.