Article for protecting a substrate

An article for protecting a multiconductor connector comprising a container containing a layer of gel. In one embodiment the container can be moved relative to the container to compress the gel to seal the connector. In another embodiment the gel layer contains a plurality of holes which tend to close when the gel is compressed.

This invention relates to an article for protecting a substrate, in 
particular to an article which can be used to seal wires and/or contact 
pins entering a connector. 
Known prior art methods of sealing wires and/or contact pins include the 
use of grommets or other similar compression seals, and the use of heat 
shrinkable sealing sleeves. Other prior art methods use articles 
containing greases. However, greases lack any type of three-dimensional 
structural network, and this results in the greases generally being 
viscious and flowing when subjected to temperature and humidity cycling, 
thereby providing a relatively unstable means for protecting the pins 
and/or wires. In addition, greases, once applied are difficult to remove 
making inspection and/or repair difficult. Epoxies and other adhesives 
have also been used, but they are also disadvantageous in that reentry is 
difficult. 
U.S. Pat. No. 4,662,692 describes a method of using a layer of gel to seal 
contact pins. The gel is surrounded on its sides, but not on either face 
by a container for ease of handling and subsequent to being cured is 
disposed adjacent a terminal block usable for connecting the electrical 
contact pins with the block, and such that an opposite exposed face of the 
gel is not covered by the container which allows the electrical contact 
pins to be inserted there through so as to pierce through the gel and 
therefore be capable of making contact on the block side of the gel. 
The present invention provides an improved article for sealing to a 
multiconductor connector in which the gel container is provided with 
special securement means to improve the compression on the gel and hence 
improve the seal. 
In another embodiment the present invention provides a new form of article 
suitable for sealing to contact pins and/or wires, which uses a layer of 
gel through which holes for the pins and/or wires are preformed, so that 
the gel is not deleteriously damaged during insertion of the pins and/or 
wires, the holes sealing up against the wires trailing from the contact 
pins when the gel is subjected to compression. 
An excellent seal is particularly important in applications where the seal 
is to be subjected to pressure, e.g. where a terminal block (which once 
connected is a sealed system) is used in applications subject to 
temperature fluctuations. 
A first aspect of the invention provides an article for protecting a 
multiconductor connector having a plurality of contact holes therein for 
receiving a plurality of contact pins, the article comprising: 
(a) an open container having a base and sides and; 
(b) within the container a layer of gel, wherein at least one of the 
following is satisfied: 
(i) the sides of the open container can be secured in use in first and 
second positions relative to the multiconductor connector, and the base of 
the open container, is adjacent to the gel layer and allows passage of 
said contact pins and trailing wires therethrough but substantially 
prevents egress of the gel from the container, wherein at least when the 
container is secured in the said second position relative to the connector 
the gel is compressed; and 
(ii) the layer of gel contains a plurality of holes which can be aligned in 
used with the holes in the multi-conductor connector, the holes tending to 
close when the gel is compressed. 
A second aspect of the invention provides an assembly comprising an article 
according to the first aspect of the invention in combination with the 
multiconductor connector, the connector and article being movable towards 
each other to compress the gel. 
In the assembly, the connector and the article according to the first 
aspect of the invention may or may not be detachable. Where they are not 
detachable by the installer, the connector and the article according to 
the first aspect of invention may be integrally formed so that they are 
initially in the said first position relative to each other. 
A third aspect of the invention provides a method of protecting a 
multiconductor connector having a plurality of contact holes therein for 
receiving a plurality of contact pins, the method comprising: 
(a) positioning an article according to the first aspect of the invention 
adjacent to the connector so that the first securing means on the 
container engages the connector in the first position; 
(b) inserting the contact pins, and wires trailing from the contact pins 
through the base and through the gel into the contact holes in the 
multiconuuctor connector, and 
(c) moving the container relative to the connector so that it is in the 
said second position relative thereto and the gel is thereby compressed 
against the said inserted trailing wires. 
Movement of the container relative to the connector from the first to so 
second positions increases the compression on the gel so that in the 
second position the gel is more compressed than in the first position. 
Preferably in the second position the gel is compressed at least 40%, more 
preferably at least 50%, more preferably at least 70%, especially 
preferably at least 80%. 
Preferably the layer of gel in the container is of uniform thickness and 
after compression decreases its thickness by at least 40%, preferably at 
least 50% more preferably at least 70%, especially preferably at least 
80%. 
The term "base" of the container is used to mean the face of the container 
away from the face of the gel which is urged towards the connector to be 
sealed. 
The base may be integrally formed with sides of the container, or separate 
therefrom. Where it is separate from the sides it may be considered simply 
as a backing layer for the gel. The base and sides may comprise the same 
or different materials. The base is arranged to allow passage of contact 
pins and their trailing wires therethrough, but substantially prevent 
egress of the gel from the container. In one embodiment the base comprises 
a grid having square or rectangular apertures therein. Where the base is 
an apertured grid the lines defining the grid preferably correspond with 
lines defining the apertures of the face of the multiconductor connector. 
This means when the container is pressed against the connector in the 
second position, the backing plate grid and connector face press together 
defining individually rectangular or square cells in which the contact 
pins end wires pass. The compression on the pins and trailing wires is 
thereby concentrated. 
Where the base is separately formed from the sides of the container its 
movement out of the container in the direction away from the layer of gel 
is preferably limited. This maintains the base and the gel in the same 
position in relation to the container. The limiting may conveniently be 
affected by an inwardly directed lip on the sides of the container, 
against which the base abuts. 
Any suitable securement means may be provided to allow the container to be 
secured in said first and second positions relative to the connector. In 
one embodiment the container comprises first and second securement means, 
which engage a member on the connector. For example the first and second 
securement means may comprises first and second lips on the side of the 
container which engage a corresponding lip on the connector. 
Preferably when the container is secured to the connector the container 
sides overlap the edges of the connector, and movement of the container 
relative to the connector from said first to second position increases the 
area of overlap of the two parts. This may be achieved for example with a 
container the cross-sectional inner periphery of which corresponds 
substantially to the cross-sectional outer periphery of the connector, and 
in which first and second securement lips extend along the sides of the 
container in a plane parallel to backing plate. The first securement lips 
are preferably further from the backing layer than the second securement 
lips. 
In an alternative embodiment, the connector itself comprises first and 
second securement lips, and the container a single securement lip. 
The securement lips on the container and/or connector may extend along all 
or only some sides of the container. In one preferred embodiment, for a 
rectangular container, the securement lips thereon extend along the long 
sides only of the container. This container is preferably used in 
combination with a connector in which the securement lip thereon extends 
around all sides of the connector. In another preferred embodiment the 
securement lips extend around all sides of the container. 
Any suitable material may be used to form the container, depending on the 
manner in which the container is secured on the connector. When securement 
lips extend along all sides of the container, the container preferably 
comprises a deformable, extendable material, to allow the container to be 
deformed to engage the lips. An example of a suitable deformable material 
is high tear strength silicone rubber. Where securement lips extend along 
only some, e.g. only two sides of the container a more rigid material can 
be used, since the position of the lips allows the container to be flexed 
for installation. Examples of suitable materials in this case are 
glass-filled nylon or polypropylene. 
The contact pins may simply be pushed through the base of the container, or 
the base may also contains a plurality of holes, in alignment with those 
in the gel layer. 
Where there are holes in the gel and/or base these may be the same shape 
and size as each other or different. Also they may be the same shape of 
size as the contact pin cross-section, and/or of the wire trailing from 
the contact pin. The hole sizes in the container base and in the gel may 
be the same size or slightly smaller, (preferably less than 0.5 mm 
smaller) than the size of the contact pins inserted therein. 
As used herein, the term gel means a liquid-extended polymer composition 
having a cone penetration value (measured by a modifed version of ASTM 
D217, as described below) within the range from 30 to 400 (10.sup.-1 mm); 
an ultimate elongation (measured by ASTM D412 as described below) greater 
than 100%, with substantially elastic deformation to an elongation of at 
least 100%. The term gel is used to cover compositions that are sometimes 
known as gelloids. The gel may either contain three-dimensional 
cross-linked molecular formations (gels) or may merely behave as if it 
contained such molecular formations (gelloids). 
Any suitable gel can be used. The gel may contain three dimensional 
cross-linked molecular formations, or may merely behave as if it contained 
such molecular formations. One example of a gel that can be used is is a 
silicone gel. Another suitable gel comprises a block copolymer having 
relatively hard blocks and relatively elastomeric blocks (e.g. 
hydrogenated rubber blocks) examples of such copolymers including 
styrene-diene block copolymers (linear or radial) for example 
styrene-butadiene or styrene-isoprene diblock or triblock copolymers, or 
styrene-ethylene-butylene-styrenes triblock copolymers, as described in 
copending U.S. patent application Ser. No. 304,431 filed July 17, 1987. 
Other examples of suitable gels include a urethane, a silicone, or a 
nonsilicone liquid rubber with low or no unsaturation which has been 
cross-linked. 
The gel may be formed in any suitable way. As examples: the gel may be 
formed from a single liquid material which becomes a gel when subjected to 
radiation or chemicals; the gel may be formed from two-components which 
become a gel when mixed; or the gel may be a composition which is a gel at 
room temperature and can be remelted by heating, so that it is formable, 
and again cooled, without any significant change in its physical 
properties. 
In a particularly preferred embodiment the gel is provided on a foam 
support member. Specifically the foam network is characterized by a 
flexible matrix having a plurality of open interstices having an average 
volume of less than 0.01 ins.sup.3, the gel including a plurality of 
interconnected segments which lie within the interstices of the matrix, 
the matrix and the gel being such that when they are stretched, the matrix 
reaches its ultimate elongation before the gel reaches its ultimate 
elongation. 
The ratio by volume of the encapsulant to the matrix is preferably at least 
7.0, particularly at least 9.0, especially at least 9.5. 
The matrix is preferably in the form of a sheet (this term being used to 
include tape), the sheet preferably having a thickness of 10 to 300 mils 
(0.025 to 0.76 cm), particularly 15 to 80 mils (0.04 to 0.20 cm), and the 
sheet preferably being extensible with an ultimate elongation which is 
preferably at least 50%, particularly at least 100%. 
A particularly preferred support member for this embodiment of the 
invention is an open cell foam sheet of an organic coplymer, e.g. a 
polyurethane in particular an open cell foam having an average cell size 
of 5 to 30 mils (0.013 to 0.076 cm), preferably 10 to 20 mils (0.025 to 
0.05 cm). Another useful support member is a woven or non-woven fabric 
comprising fibers which are natural or synthetic and composed of organic 
or inorganic material, e.g. glass fibers or organic polymer fibers. The 
foam sheet or fabric may be for example 5 to 60 mils (0.013 to 0.15 cm), 
particularly 10 to 50 mils (0.025 to 0.125 cm), thick. 
The supported gel is particularly advantageous in the present invention 
since it has improved mechanical strength compared to a corresponding 
non-supported gel. The improved mechanical strength is advantageous since 
it minimizes damage to the gel during insertion of the contact pins. Also, 
where the backing layer is apertured it minimizes egress of the gel 
through the apertures in the base. 
The preferred thickness of the gel depends inter alia on the type of gel 
used. For a gel on/in a support matrix a preferred thickness of gel is at 
least 2 mm, preferably at least 3 mm, more preferably about 4 mm. 
The gels used in the present invention preferably have cone penetration 
values of 100 to 300. For some applications a cone penetration 220-280 is 
preferred. 
The elongation of the gel is preferably at least 200%. Cone penetration and 
ultimate elongation values used in this specification are measured 
according to the following methods: 
Cone Penetration 
Test method ASTM D217, for testing cone penetration in greases, is applied 
to the gel or gelloid compositions of the present invention, using a 
standard full-scale cone, to determine the penetration at 23.degree. C. by 
releasing the cone assembly from a penetrometer and allowing the cone to 
drop freely into the gel for 5 seconds. 
The gel sample is contained in a straight-sided circular cylindrical 
container which is filled to the brim with the gel. The height of the 
beaker is 72 mm and its internal diameter is 74 mm. The surface of the 
sample should be level and free from defects where possible. Air bubbles, 
especially close to the surface of the sample, should be avoided, and the 
surface should be protected from dust prior to testing. 
Each measurement should be made close to the center of the sample but not 
directly in the same place each time. Surface damage caused by the cone is 
generally clearly visible and must be avoided when making a subsequent 
measurement. 
Tensile Testing 
The method for the tensile testing of gels is a modified version of ASTM 
D412 in which tensile strength and ultimate elongation are measured at 
23.degree. C. on dumbell shaped gel specimens that have not been 
prestressed. Ultimate elongation is measured by `jaw separation` and 
tensile strength is based on the original cross sectional area of a 
uniform section of the specimen. 
Tensile tests are performed on a power driven machine equipped to produce a 
uniform rate of grip separation of 50 mm/min for a distance of at least 
1000 mm. The equipment should be capable of measuring the applied force to 
within 2% and of recording the resultant stress strain curve on a chart 
recorder. In the current work tensile stress strain measurements of the 
gel samples were made using an Instron floor model, TT-BM, fitted with a 
load cell capable of measuring to a lower limit full-scale deflection of 
0.4 Newton. The load was indicated on a variable speed chart recorder to 
an accuracy of 0.5%. 
Samples for tensile testing are cut from sheets of gel of uniform thickness 
between 1 and 6 mm using a Type 1 BS 2782/IS0 37 or a Type 3ASTM D412 
dumbell cutter. 
The gel specimens once cut may be difficult to handle. This may be improved 
by wrapping the ends of each specimen in lint-free tissue up to the 
distance where the sample will protrude from the machine jaws, (see 
below). This has also been observed to have the additional beneficial 
effect of restricting the flow of gel from within the grips themselves 
when the sample is tested, thereby improving the accuracy of the 
elongation measurement. 
The tensile machine should first be calibrated in the normal way. 
Conventional air-grips may be used at an operating air pressure of 
approximately 20 psi. The dumbell sample is placed in the jaws of the 
air-grips such that the jaws will hold predominately onto the tissue 
covering the ends of the specimen rather than the gel itself. Some 
exudation of the gel from the far ends of the grips may be observed on 
closing the jaws. This will not prove to be a problem provided that 
exudation into the restricted section of the sample, between the two grips 
is minimal. The tissue wrap will help to minimize this in the case of very 
soft gels. 
The sample is then tested to failure, which should ideally occur in the 
restricted section, at a cross-head speed of 50 mm/min and the 
stress-strain curve recorded on a chart recorder. A chart speed of 20 
mm/min was found to be adequate was found to be adequate for most samples. 
The Ultimate Elongation of the sample may be obtained by calculating the 
cross-head movement from the chart recorder, (knowing the speeds of both). 
The elongation as a percentage of the original gauge length may then be 
determined. 
The sample will preferably undergo elastic deformation and recovery as 
aforesaid, by which is meant that the stretched sample will "snap back" 
substantially to its original unstressed state if released from the 
elongation tension. 
The invention is applicable for sealing any multicontact connectors, for 
example terminal blocks with at least 3, 6,12, or even 18 contact pin 
holes. The invention is particularly advantageous since it allows the 
sealing part (the article) to be placed against the connector before the 
contact pins are inserted. This is an important advantage for automated 
pin-insertion. In contrast, with other prior art methods, for example 
where sealing shrinkable sleeves, are used, these sleeves have to be fed 
over the contact pin wires before the contact pins are inserted in the 
connector. 
The article is also advantageous where good sealing is required, both 
against external chemical environment and internal and external pressure. 
A range of wire diameters can be sealed according to the invention. For 
example wires with outer diameters in the range of 2-2.6 mm or even 1-3.5 
mm.

Referring to the drawings, FIGS. 1 and 2 show an article 2 according to the 
invention comprising a rectangular container 4, base 6 and gel layer 8. 
The container 4 is made from polypropylene and has sides 10, and open 
faces 12 and 14, thereby defining an open ended rectangular structure. On 
the two long sides 10 of the rectangular container 4 are two rows of 
securement lips 16 and 18 are for securement to a connector, as will be 
explained later. The sides 10 of the container 4 also comprise a third lip 
20 at end face 12. This lip extends around the entire periphery of the 
container. Against this lips 20 abuts base 6, thereby limiting movement of 
the base out of the container in a direction away from the gel (i.e. to 
the right in the Figure). 
Base 6 comprises glass-filled nylon material. It is in the form of a grid 
with apertures 22 therein in a 6.times.3 array. The grid 6 fits inside 
container 4, but is stopped from passing therethrough by lip 20. 
Finally gel layer 8 comprises a layer of GelTek strip as supplied by 
Raychem Limited. This strip is coterminous with base 6 and is positioned 
thereagainst. 
FIG. 3 shows the connector 24 to be sealed. It also contains eighteen holes 
26 in a 6.times.3 array. The connector comprises a lip 28 to cooperate 
with lips 16+18 on the article 2 of FIGS. 1 and 2. 
FIG. 4 shows the article 2 positioned adjacent connector 24. The 
positioning is such that the grid array of connector 24 is in alignment 
with the grid array of base 6. The connector and article are in a first 
positions in which lip 16 (nearest the connector 24) engages lip 28 on the 
connector 24. The gel is in this position not compressed. Contact pins 30 
and trailing wires 32 are inserted through the holes 22 in the base 6 and 
into the holes 26 in the connector 24, to contact mating contact pins 
inserted from the other side. 
FIG. 5 corresponds to FIG. 4 except that the article 2 and the connector 24 
have been pushed further towards each other into a second position in 
which the lip 18 on the container 4 engages the lip 28 on the connector 
24. In this second position the area of overlap of the container 4 and 
connector 24 is increased relative to the first position. The gel layer 8 
is compressed about 80%, and hence seals against the trailing wires 32. 
Typical dimensions for the article and connector described in FIGS. 1 to 5 
are as follows: 
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Connector 24 
Back face 35 mm .times. 27 mm 
Lateral extension of lip 
24 .times. 1.5 mm 
Base 6 
Face 27 mm .times. 36 mm 
Height 5 mm 
Gel Layer 8 
Face 27 mm .times. 36 mm 
Thickness 4 mm 
Contact Pins 
End pin shape: typically rectangular 
Male 3.0 mm flat 
Female 2.7 mm .times. 4.1 mm box-shape 
Conductors circular cross-section 
Typically 0.5 mm.sup.2 -2.5 mm.sup.2 
Typical example 2.3 mm OD 
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FIGS. 6 and 7 show another article 42 according to the invention. Article 
42 comprises a container 44, with base 46 and sides 48. It has one open 
side. The container is made from silicone rubber. Inside the container is 
a layer of precured gel 50 which partly fills the container 44 and 
comprises a silicone gel. 
The sides 48 of container 44 comprises a lip 52. This is for securement to 
the connector shown in FIG. 3. The gel layer 50, which is uniform in 
thickness, fills the container to the base of lip 52. 
Eighteen holes arranged in a 6.times.3 array are premade through the base 
46 of the container 44 and through the gel layer 50. The holes are 
numbered 54 and 56 respectively and are in alignment. The holes are 
circular in cross-section and are large in the base 46 of the container 44 
than in the gel 50. 
FIG. 8 shows the article 42 positioned adjacent connector 24 of FIG. 3. The 
positioning is such that the holes 54 and 56 in the container 44 are in 
alignment with the holes 60 in the connector, but the gel 50 is not 
compressed, and lips 52 and 62 are not engaged. Contact pins 66 and 
trailing wires 67 are inserted through the holes 54 in the base by the 
container 44, through the holes 56 in the gel layer 50 into the holes 62 
in the connector 58 to contact mating contact pins inserted from the other 
side. 
FIG. 9 corresponds to FIG. 8 except that the article 42 and the connector 
58 have been pushed towards each other so that lips 52 and 62 co-operate. 
This compresses gel 50 about 80%, and hence seals against the trailing 
wires 67 from contact pins 66. 
Typical dimensions for the article and connector described in FIGS. 6 to 9 
are as follows: 
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Connector 58 
Back face 35 mm .times. 27 mm 
Lateral extension of lip 
24 .times. 1.4 mm 
Article 42 
Base 46 40 mm .times. 31 mm 
Height 17 mm 
Thickness of base 2 mm 
Depth of gel 10 mm 
Height of lip 52 5 mm 
Lateral extension of lip 52 
1.5 mm 
Contact Pins 
End pin shape: typically rectangular 
Male 3.0 mm flat 
Female 2.7 m .times. 4.1 mm box shape 
Conductors circular cross-section 
Typically 0.5 mm.sup.2 -2.5 mm.sup.2 
Typical example 2.3 mm OD 
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