Combined electrical shield and environmental seal for electrical connector

A combined EMI/RFI shield and environmental sealing element for an electrical connector in which a helical coil spring is partially embedded in an elastomeric ring having an enlarged sealing portion on at least one side of the spring. The exposed surfaces of the coil spring engage facing peripheral surfaces on the shells of the mating connector halves of the electrical connector.

BACKGROUND OF THE INVENTION 
The present invention relates generally to an electrical connector and, 
more particularly, to an arrangement for providing electrical shielding 
and environmental sealing for the mating halves of an electrical 
connector. 
The use of shielding in electrical connectors to eliminate unwanted radio 
frequency and electro-magnetic signals (RFI/EMI) from interfering with 
signals being carried by the contacts in connectors is well known. U.S. 
Pat. Nos. 3,521,222; 3,678,445; 4,106,839 and 4,239,318 disclose annular 
shields formed of sheet metal with resilient fingers which electrically 
engage the outer surface of the plug barrel and the inner surface of the 
receptacle shell of the electrical connector. 
U.S. Pat. No. 3,835,443 discloses an electrical connector shield comprising 
a helically coiled conductive spring which is interposed between facing 
annualar surfaces on the mating halves of an electrical connector. The 
spring is coiled in such a manner that the convolutions thereof are 
slanted at an oblique angle of the center axis of the connector members. 
When the connector members are mated, the spring is axially flattened to 
minimize the gap between the convolutions thereof and to provide a wiping 
electrical engagement with the annular surfaces on the mating halves of 
the connector. 
U.S. Pat. No. 4,033,654 discloses another form of slant coil spring shield 
for an electrical connector in which the spring is mounted in an internal 
groove formed in the receptacle shell. The convolutions of the spring are 
arranged in such a fashion that they will collapse radially when the plug 
barrel is slid into the receptacle shell. 
Of course, it is well known in the art to utilize various forms of annular 
rings, such as O-rings, for providing environmental sealing between the 
mating halves of electrical connectors. However, such seals have been 
separate from any electrical shield which might be provided in the 
connector. As a consequence, separate annular grooves have been formed in 
the connector members in order to receive the electrical shield and the 
environmental sealing ring, which adds to manufacturing and assembly 
costs, and increasing the size of the connector assembly. Also, it is 
possible that the slant coil spring may be damaged during handling upon 
assembly of the connector or during use of the connector in the field. 
It is the object of the present invention to overcome the aforementioned 
disadvantages of the conventional electrical shielding and sealing 
arrangement used for electrical connectors. 
Of interest in the art of electrical shielding and environmental sealing is 
a composite EMI shield and environmental sealing gasket comprising a 
plurality of individual fine wires embedded and bonded in a solid silicone 
elastomer, with the wires oriented perpendicular to the mating surfaces of 
the product in which the gasket is installed. The manufacturer states that 
the wires are convoluted to allow compressing and rebounding like 
individual springs. Another composite shielding gasket for EMI shielding 
and environmental sealing utilizes a resilient knitted wire mesh strip 
which is mated to a silicone rubber strip wherein some of the elastomer is 
permitted to penetrate the porous boundary face of the wire mesh strip. In 
each case, the composite shielding and sealing elements are in strip or 
sheet form, and to our knowledge have not been shaped into closed loops 
for use in electrical connectors. Furthermore, the prior art gaskets do 
not embody any means for preventing dirt and other contaminants from 
reaching the conductors of the gaskets. 
SUMMARY OF THE INVENTION 
According to a principal aspect of the present invention, there is provided 
an electrical connector comprising first and second mating connector 
members having spaced peripheral surfaces thereon facing each other when 
the connector members are mated defining a space therebetween. A 
substantially closed loop combined electrical shielding and environmental 
sealing element is disposed in this space. The element comprises an 
elastomeric ring having a helical coil spring partially embedded therein. 
The convolutions of the coil spring are exposed at the edges of the ring 
on opposite sides thereof adjacent to the peripheral surfaces of the 
connector members. The elastomeric ring embodies an enlarged sealing 
portion on at least one side of the coil spring providing oppositely 
facing sealing ribs each adjacent to a respective peripheral surface. The 
outside dimensions of the convolutions and of the enlarged sealing portion 
of the ring in the direction between the peripheral surfaces are greater 
than the distance between said surfaces whereby the convolutions will 
deform and the sealing ribs of the ring will be compressed when the 
connector members are mated. 
Thus, by the present invention there is provided a composite electrical 
shielding and environmental sealing element which is in the form of a ring 
that may be inexpensively manufactured and easily installed in a single 
annular or closed loop groove thus eliminating one machining operation and 
reducing assembly costs. The element may be conveniently manufactured by 
molding the elastomeric ring around the coil spring whereby the elastomer 
will provide protection for the spring against damage during assembly and 
during use of the connector in which it is installed. An important 
advantage of the invention is that the enlarged sealing portion of the 
elastomeric ring will prevent contaminants from reaching the exposed 
convolutions of the coil spring so that an effective electrical contact 
may be maintained between the coil spring and the connector body even over 
a long period of time and exposure to adverse environments. Preferably the 
elastomeric ring is molded as a continuous loop so as to provide a 
continuous sealing surface around the ring which is not interrupted by a 
bond line that might create a leakage path across the opposite sides of 
the ring.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings in detail, there is shown in FIG. 1 one 
embodiment of the connector of the present invention, generally designated 
10, comprising a plug connector member 12 and a receptacle connector 
member 14. The plug connector member comprises a cylindrical barrel 16 
which is telescopically positioned in the front end of the cylindrical 
shell 18 of the receptacle connector member. A plurality of socket 
contacts 20 are axially positioned in insulators 22 and 24 mounted in the 
barrel 16. Each such contact 20 receives a pin contact 26 which is mounted 
in an insulator 28 in the receptacle connector member 14. A coupling nut 
32 is retained on the barrel 16 of the plug connector member by a 
retaining ring 34. The forward end of the coupling nut is threadedly 
engaged with the shell 18 of the receptacle connector member 14. 
The combined electrical shielding and environmental sealing element of the 
present invention, generally designated 36, is mounted in an annular 
groove 38 formed in the outer cylindrical surface 40 of the barrel 16. 
Alternatively, the groove could be formed in the inner surface of the 
receptacle shell 18. The bottom 42 of the groove provides a cylindrical 
surface which faces the inner cylindrical surface 44 of the receptacle 
shell 18. 
The combined electrical and environmental sealing element 36 is a closed 
loop composite preferably comprising a continous elastomeric ring 46 in 
which a slant helical coil spring 48 is partially embedded. In this 
embodiment of the invention, the coil spring is similar to that disclosed 
in the aforementioned U.S. Pat. No. 4,033,654. Each convolution of the 
helical coil spring lies in a slanted plane which is generally parallel to 
the center axis x--x of the connector and inclined with respect to the 
axis of the helix as seen in FIGS. 5 and 6. Expressed in other words, the 
plane of each convolution of the spring is disposed at an angle from a 
tangent to the outer circumference of the circular spring. 
The elastomeric ring 46 preferably comprises a generally cylindrical ring 
having enlarged toroidal sealing portions 50 along its edges integral with 
a relatively narrow intermediate cylindrical web portion 52. The major 
portion of the spring 48 is embedded within the web portion of the 
elastomeric ring. The outer portion 54 of each convolution protrudes 
outside the outer surface 56 of the web portion of the elastomeric ring 
while the inner portion 58 of each convolution protrudes outwardly through 
the cylindrical inner surface 60 of the web portion of the ring so that 
the convolutions are exposed at both the inner and outer surfaces of the 
ring. The radial thickness of the enlarged annular sealing portions 50 of 
the elastomeric ring and the dimensions of the convolutions of the coil 
spring in the radial direction are greater than the depth of the groove 38 
and greater than the distance between the cylindrical surfaces 42 and 44 
in which the element 36 is mounted so that both the sealing portions of 
the ring and the coil spring will be compressed in the radial direction as 
the plug barrel 16 is pushed into the interior of the mating receptacle 
shell 18 when the plug and receptacle connector members are being 
interengaged. Before mating of the connector halves, the coil spring 48 
takes the form illustrated in FIG. 6. When mating occurs, the convolutions 
of the coil spring increase their slant to provide an almost continuous 
metal shield between the mating halves. In addition, because of the slant 
design of the spring convolutions, a wiping action between the spring and 
the facing surfaces on the connector halves takes place which assures 
positive electrical continuity and thus an effective electrical joining 
(grounding) of the respective connector halves. 
The elastomer of the ring 46 is preferably relatively soft, having a 
durometer of about 40, so that the slant helical coil spring 48 
constitutes the principal spring member of the composite element 36, while 
the sealing portions 50 of the elastomer perform basically only a sealing 
function, rather than a spring function. By providing the toroidal 
portions 50 on both axial sides of the coil spring, it will be appreciated 
that such portions not only provide two sets of sealing ribs between the 
mating halves of the connector, but also provide seals on both sides of 
the coil spring to prevent dirt or other particles from reaching the 
interface between the exposed convolutions of the coil springs and the 
cylindrical surfaces 42 and 44 engaged thereby. 
Reference is now made in FIGS. 7-11 of the drawings which illustrate the 
second embodiment of the invention, wherein parts similar to those 
employed in the embodiment illustrated in FIGS. 1-6 bear the same 
reference numerals primed. In this embodiment of the invention, the 
composite electrical shielding and environmental sealing elment 36' is 
mounted in an annular groove 38' formed in forwardly facing surface 60 of 
the receptacle shell 18. The bottom 42' of the groove provides an annular 
surface which faces the front annular surface 44' on the plug barrel 16' 
of the electrical connector 10'. Thus, in this embodiment of the invention 
the element 36' provides a compression seal, rather than a sliding seal as 
in the first embodiment of the invention. 
The composite element 36' comprises an annular elastomeric ring 46' having 
an outer enlarged toroidal sealing portion 50' which surrounds an inner 
enlarged toroidal sealing portion 50a. The sealing portions are integral 
with a radially extending intermediate annular web portion 52'. A slant 
coil spring 48' is partially embedded in the web portion 52' of the 
elastomeric ring. The spring may be similar to that disclosed in the 
aforementioned U.S. Pat. No. 3,835,443. Each convolution of the spring 
lies in a slanted plane that intersects the center axis x--x of the 
connector members at an oblique angle, as seen in FIGS. 10 and 11. The 
forward portions 54' of the convolutions of the coil spring protrude 
forwardly beyond the front surface 56' of the web portion of the 
elastomeric ring, while the rear portions 58' protrude rearwardly beyond 
the rear surface 60' of the web portion of the ring. The thickness of the 
coil spring and the elastomeric ring in the axial direction of the 
connector is greater than the depth of the groove 38' so that when the 
mating halves are interengaged, the enlarged sealing portions 50' and 50'a 
of the ring will be axially compressed and the convolutions of the coil 
spring will be axially flattened as illustrated in FIG. 10. FIG. 11 shows 
the configuration of the coil spring before it is flattened. Therefore, it 
will be appreciated that the composite element 36' functions in a manner 
similar to the element 36 in the first embodiment of the invention except 
that the element is axially compressed upon mating of the connector 
halves, rather than radially squeezed in a sliding seal arrangement as in 
the first embodiment. 
The composite RFI/EMI shielding and elastomeric sealing element of the 
present invention described so far may be manufactured by providing a coil 
spring of the desired length to fit into a groove in the connector shell, 
butt welding the ends of the spring so that it will be a continuous, 
integral element, molding the elastomeric ring around and through the 
spring in a suitable mold so that the opposite sides fo the spring, either 
radial or axial, will be exposed whereupon there is provided a one-piece 
element which may be easily mounted in a single groove in a connector 
shell. By this arrangement sealing continuity is provided around the 
periphery of the element since no butt joints are required to be made in 
the elastomer. 
While it is preferred that the elastomeric ring and coil spring embedded 
therein of the composite electrical shielding and environmental sealing 
element of the present invention are both in the form of continuous loops, 
it will be appreciated that the ends of the coil spring need not 
necessarily be joined so long as they are very close to each other. 
Furthermore, in the compression seal arrangement illustrated in FIGS. 7 to 
11, the composite element 36' need not be continuous. For example, the 
element could be formed of an elongated strip which is rolled into 
circular form with the ends of the strip beveled and overlapping. Such an 
overlapping joint would not be suitable for the sliding seal arrangement 
illustrated in FIGS. 1 to 6. 
In FIG. 12 there is shown a composite electrical shielding and 
environmental sealing arrangement to that illustrated in FIGS. 1 to 6 
except that the composite shielding and sealing element 60 has only a 
single enlarged toroidal sealing portion 62. The sealing portion 62 is on 
the side of the coil spring 64 which is open to the space between the plug 
barrel 66 and coupling nut 68 so that the seal will be effective for 
preventing dust and other particles from reaching the interface 70 between 
the mating halves of the connector. If only a single enlarged sealing 
portion were to be utilized in the embodiment of the invention illustrated 
in FIGS. 7 to 11, the outer sealing portion 50' would be retained and the 
inner sealing portion 50'a eliminated. 
In the embodiments illustrated in FIGS. 1 to 6 and in FIG. 12, it is 
preferred that the composite electrical shielding and environmental 
sealing element have a slight interference fit with the bottom of the 
groove in which it is mounted so that a seal is maintained between the 
element and the plug barrel even when the plug and receptacle members are 
disconnected from each other. If the shielding and sealing element were 
mounted in an internal groove in the receptacle shell, a like 
intereference fit would be desired. 
The embodiment of the invention illustrated in FIG. 13 is similar to that 
illustrated in FIGS. 1 to 6 except that the outer surface of the plug 
barrel 72 is provided with a non-conductive layer 74 while the inner 
surface of the receptacle shell 76 is provided with a similar 
non-conductive layer 78. The layers may be an anodized coating, a plastic 
coating or the like. The layers 74 and 78 are interrupted between the 
enlarged sealing portions 80 of the composite shielding and sealing 
element 82 so that the coil spring 84 of the element will contact the bare 
cylindrical surfaces of the barrel 72 and shell 76. The non-conductive 
layers may be desired for corrosion resistance. 
FIG. 14 shows an alternative form of the combined electrical shielding and 
environmental sealing element of the present invention, generally 
designated 86, which is similar to the element 36 illustrated in FIGS. 1 
to 6 except that there are provided a pair of enlarged sealing portions 88 
and 90 on opposite sides of the coil spring 92 thus providing a set of 
four sealing ribs on the inner and outer surface of the element 86, and a 
pair of oppositely facing sealing ribs on opposite sides of the spring. 
The composite element 36' illustrated in FIGS. 7 to 11 could likewise be 
provided with a multiple sealing arrangement similar to that illustrated 
in FIG. 14. 
The invention is not limited to the use of a slant coil spring as the 
electrical shielding spring in the composite shielding and environmental 
sealing element. As shown in FIGS. 15 and 16, the shielding and sealing 
element 94, mounted in a connector assembly similar to that illustrated in 
FIGS. 7 to 11, may be a standard helical coil spring 96 having elliptical 
convolutions which are compressed axially when the mating halves of the 
connector are interengaged, rather than flattened by increasing their 
slant as in the first two embodiments of the invention disclosed herein. 
While the composite shielding and sealing element of the present invention 
has been specifically described and illustrated herein as being in a 
circular form, it will be appreciated that the element could assume other 
shapes depending upon the configuration of the connector. For example, the 
element could be mounted in a "rectangular" connector in which case the 
element would assume the configuration of the D-shaped shell of the 
connector. Thus, the term "ring" as used in the claims appended hereto is 
intended to embrace loop structures of any configuration, including 
circular, rectangular, D-shaped, etc. 
While the spring in the environmental sealing element of the present 
invention has been characterized herein as providing EMI/RFI shielding, it 
will be appreciated that the extent of the shielding will be dependent 
upon the wave length of the interfering signals and the size of the gaps 
existing between the convolutions of the spring. In some applications of 
the invention the spring may function simply as a grounding connection, 
rather than as an effective shield. Accordingly, it is intended that the 
present invention embrace seals containing springs which may function as 
either effective shields and ground connections, or only as grounding 
connections. The term "electrical connecting" recited in the appended 
claims is intended to cover either or both functions.