Modular strain relief device for electrical connectors

A modular strain relief device is plugged directly into an electrical connector location in the interior of a housing assembly, according to one embodiment of this invention. The body of the strain relief connector provides a surface around which a portion of the wire conductor is wrapped for additional strain relief. Arm-like projections keep the wire conductors in close proximity to the body of the strain relief connector. An integrally molded locking structure attached to one end of the body of the strain relief connector allows it to be locked into an unused plug-in connector location inside the housing assembly. A bundle of wire conductors is secured to the flexible body of the strain relief connector with a cable tie placed through an aperture in a molded projection located at one end of the body of the strain relief device.

BACKGROUND OF THE INVENTION 
The device relates generally to the field of strain relief devices for use 
with electrical connectors and more particularly to a removable plug-in 
strain relief device for use in a housing assembly having multiple plug-in 
connector locations. 
It has been realized in the art of electrical connectors that it is useful 
to provide strain relief protection to preserve the electrical connection 
between a wire conductor and an electrical connector. Strain relief 
devices are designed to reduce excessive force, such as a pulling force, 
applied to a cable made up of a number of wire conductors in order to 
preserve the electrical contact. 
Prior devices are typically of two main types. The first type of device 
provides for a strain relief component integrally molded to the connector 
housing, as in U.S. Pat. No. 4,822,286 to Bianca. The second type of 
strain relief device is external to the connector housing. The latter 
appears in two categories: a protective yoke formed around the cable 
entering the connector assembly, see U.S. Pat. No. 4,840,581 to Leufert; 
or a strain relief device and a connector assembly both specially designed 
to couple together using a pair of molded projections on the sides of the 
housing assembly to mate with recesses on the strain relief, see U.S. Pat. 
No. 4,538,873 to Worth. 
There is a need for a strain relief device that is modular for use without 
the need for a specially designed or molded housing assembly. There is a 
further need for a strain relief device that locks into a housing assembly 
designed for the use of multiple plug-in connectors without undergoing any 
additional molding or design. 
SUMMARY OF THE INVENTION 
Briefly describing one aspect of the present invention, a modular plug-in 
device is provided which is useful for preserving the electrical contact 
between a wire conductor and an electrical plug-in connector in a housing 
assembly having multiple plug-in connector locations. In one embodiment a 
strain relief device, as described herein, emulates the physical 
characteristics of a plug-in connector, enabling its insertion into 
pre-existing housing assemblies without the need for special tools or 
fasteners and having no multiple pieces. 
The device comprises a flexible, strain absorbing body used to support a 
portion of a wire conductor wrapped transversely across the body, arms for 
maintaining the wire conductor in close proximity to the body, and locking 
means for locking the device into the interior of a housing assembly. 
Wrapping the wires transversely across the body allows the body of the 
device to absorb any external forces exerted on the wire conductors rather 
than allowing the force to strain the conductor to connector interface. 
Another aspect of the present invention is that the modular strain relief 
device locks into an unused cavity, preferably a plug-in connector 
location, inside the housing assembly. One advantage of this feature is 
that it is no longer necessary to mold special housing assemblies in order 
to provide strain relief for the electrical connectors. Nor is it 
necessary to mold or assemble multiple parts or to use special tools to 
construct the strain relief device in order to obtain the desired strain 
relief. 
A further aspect of the present invention is to provide a modular plug-in 
strain relief connector having a molded projection containing an aperture 
useful for securing a cable of wire conductors to the body of the strain 
relief connector for the purpose of providing additional strain relief. 
The flexibility of the body provides ample protection from forces exerted 
by pulling up or down on the cable of wire conductors. 
Further objects and advantages of the present invention may be discerned by 
persons of ordinary skill in the art after reviewing the following written 
description and accompanying figures.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
For the purposes of promoting an understanding of the principles of the 
invention, reference will now be made to the embodiment illustrated in the 
drawings and specific language will be used to describe the same. It will 
nevertheless be understood that no limitation of the scope of the 
invention is thereby intended, such alterations and further modifications 
in the illustrated device, and such further applications of the principles 
of the invention as illustrated therein being contemplated as would 
normally occur to one skilled in the art to which the invention relates. 
In one embodiment of the present invention, a strain relief device 10 is 
provided to aid in preserving electrical contact between wire conductors 
40 and an electrical plug-in connector array 50 (FIG. 3). The connector 
array 50 can be of well known construction and is adapted to be located in 
a housing assembly 30 having multiple plug-in connector locations. FIGS. 3 
and 4 show the removable strain relief device 10 providing strain relief 
for a bundle of conductors 60 which are attached to multiple plug-in 
connectors 51 forming the connector array 50, all of which are then locked 
into a housing assembly 30. 
The details of the strain relief device 10 are shown in FIGS. 1 and 2. 
Strain relief is provided by the flexible body 11 of the strain relief 
connector 10. The flexible body 11 has an outer surface 11a for supporting 
a portion of the wire conductors 40 wrapped around the body 11. The 
wrapped conductors 40 are enclosed by arm means or arm-like projections 13 
when the wire conductors 40 are supported by the outer surface 11a. 
Optimum strain relief is provided by wrapping the wire conductors 40 
transversely across surface 11a and around body 11 as is shown in FIGS. 3 
and 4. 
The arm means 13 initially extend perpendicular from the body 11 and curve 
about 90 degrees to terminate in an orientation parallel to the body 11. 
This provides edge surfaces 13a for the purpose of enclosing a portion of 
the wire conductors 40 and causing them to remain in close proximity to 
the body 11. The end of a first arm means 13 points in a direction 180 
degrees opposite to that of the second arm means on the opposite side of 
the body 11. The purpose of the arm means 13 extending opposite with 
respect to each other is to prevent the wire conductors from sliding along 
the body of the strain relief device 10. The bends 13b of the arm means 
define an area along the body 11a of the strain relief device within which 
the wire conductors 40 are forced to remain. 
The removable strain relief device 10 has locking means 12 designed to lock 
directly into an unused connector location in the interior of the housing 
assembly 30 as shown in FIG. 3. The locking means 12 includes a body 12a 
shaped substantially like an individual plug-in electrical connector 51. 
The body 12a carries a locking tab 15 to engage the housing in a 
conventional manner, and a number of slots 17 for slidably receiving pins 
from a mating electrical connector to which the connector 50 is engaged. 
This enables the strain relief device 10 to emulate a plug-in electrical 
connector 51 for the purpose of locking into the housing assembly 30. The 
locking tab 15 also acts as a polarization feature to prevent upside-down 
assembly of the strain relief device 10 into the housing assembly 30. 
In the assembled embodiment shown in FIGS. 3 and 4, at least one plug-in 
connector 51 is necessary to help lock device 10 into place in the 
interior of the housing assembly 30. 
The strain relief device 10 enters the housing assembly 30 simultaneously 
with the plug-in electrical connectors as shown in FIGS. 3 and 4. As such, 
the device 10 occupies a plug-in connector location in the housing. The 
results in a reduced number of usable connector locations. In an alternate 
embodiment, the strain relief device can also be configured to engage an 
empty cavity in the housing, for example unused space between the 
connector array 50 and the inside wall of the housing 30, thereby 
permitting the full use of all of the plug-in connector locations defined 
for the housing assembly. 
In an alternate embodiment of the invention, a strain relief device 
includes locking means 112 comprising includes a body 112a configured to 
resemble two plug-in connectors, one laid on top of the other, as depicted 
in FIG. 5. Thus, the strain relief device 110 can be seated in the housing 
30, independent of the presence of adjacent plug-in connectors 51. 
Referring again to FIGS. 1-4, the number of slots 17 located in the locking 
means 12 ppreferably corresponds to the number of plug-in electrical 
connector locations that the strain relief device 10 occupies in the 
housing assembly 30. Alternatively, electrical connectors can be placed in 
the slots 17. These connectors can be attached to wire conductors 40. In 
this manner, the strain relief device 10 can also act as an electrical 
connector when it is necessary to use all available connector spaces. 
The structure of the locking means 12 permits easy deliberate removal of 
the strain relief device 10 from the assembly housing 30 while providing 
for difficult accidental removal. The strain relief device 10 is inserted 
into the housing assembly by sliding the body of the locking means 12 into 
the housing 30. The locking tab 15 engages with a groove 31 standard to 
the housing assembly 30 to ensure proper orientation and to prevent 
movement of the device 10. Typically connector 51 also includes at least 
one tab for sliding into the standard grooves 31. The strain relief device 
10 slides into the housing assembly 30 back-to-back with a plug-in 
electrical connector 51 until the locking means body 12a snaps into place 
between the flanges 32 at opposite edges of the housing 31 (see FIG. 4). 
The plug-in connector 51 locks into place in the same manner as the strain 
relief device 10. The presence of the plug-in electrical connector 51 
back-to-back with the body of the locking means 12 creates a tight fit 
inside the housing assembly 30 keeping both the plug-in connector 51 and 
the strain relief device 10 from slipping out of the housing assembly 30. 
The strain relief device 10 can then be pulled from the housing assembly 
30 while simultaneously forcing the flanges 32 of the housing assembly 
apart. Since the locking means 12 permits plug-in engagement with the 
housing assembly 30, the device can be used in a number of housing 
assemblies designed for the use of plug-in electrical connectors. 
Additional strain relief is provided by securing a bundle of wire 
conductors 60 incident to the strain relief device 10 directly to the body 
11. This is accomplished in one embodiment by securing the conductor 
bundle 60 to the device 10 using a cable tie 70 (FIG. 4). An example of a 
cable tie useful to this application is shown in U.S. Pat. No. 3,965,538 
to Caveney, et. al. The cable tie 70 is threaded through aperture 16 of an 
integrally molded projection 14 located on the body 11 of the strain 
relief device 10 (FIG. 2) and is used to secure the bundle of conductors 
60 to the strain relief connector 10 as shown in FIG. 4. As depicted in 
FIGS. 4 and 5, an identification tag 75 can be affixed to the strain 
relief device 10 using the projection 14 and insertion tie 70. The 
projection 14 can extend through a close-fitting opening 76 in the tag 75. 
Engagement of the tie 70 through the aperture 16 in the projection 14 
holds the tag on the projection 14. 
The body 11 is made of a flexible material, black nylon in the preferred 
embodiment, using conventional molding techniques, and can absorb strain 
applied to the bundle of conductors by bending vertically in the direction 
depicted by the arrows A in FIG. 1. In one specific embodiment, the body 
11 is flexible enough to bend 90 degrees in each direction. The 
flexibility of the device 10, the method of securing the wire conductors 
40 to the strain relief device 10 by wrapping them around the body 11 and 
the method of providing additional strain relief by securing the wire 
conductors to the body of the device 10 with a cable tie 70 secured 
through aperture 16 provide optimum protection for the electrical 
connection between the wire conductors 40 and the plug-in electrical 
connector 50. 
In an alternative embodiment of the invention shown in FIG. 6, a strain 
relief device 120 is similar to the device 10 except that the projection 
14 has been replaced by a self-closing integral eye 122. The ends 123 of 
the self-closing eye 122 are adapted to spread apart to permit insertion 
of a wire bundle into aperture 125. In this embodiment, the wire bundle is 
held against the device 120 without the need for a separate insertion tie. 
Referring to FIG. 7, a further embodiment comprises a device 130 which is 
again similar to the prior devices. In this embodiment, the cable tie 
feature is integral with the body 131. Thus, a strap member 133 is 
integrally formed at one end of the body 131. A locking member 135 is 
formed at one end of the strap member 133 and is adapted to receive the 
free end 136 of the strap in a manner substantially as described in the 
Caveney et al. U.S. Pat. No. 3,965,538. 
While the invention has been illustrated and described in detail in the 
drawings and foregoing description, the same is to be considered as 
illustrative and not restrictive in character, it being understood that 
only the preferred embodiment has been shown and described and that all 
changes and modifications that come within the spirit of the invention are 
desired to be protected.