Seal ring and method of manufacture

A sealing ring having a U-shaped shell member and an actuator member formed in situ from liquid elastomer. The shell member has a base portion with two legs extending from the base to form a cavity therebetween which is filled with the liquid elastomer and cured in situ. This integrally formed U-shaped composite ring seal yields a highly reliable seal with minimal dimensional variation problems and is easy and economical to manufacture.

BACKGROUND OF THE INVENTION 
This invention relates generally to the field of machinery joint packing or 
fluid sealing members and more specifically to an improved U-shaped 
composite packing ring seal and a method for making same. 
"U" type ring seals are for use in sealing dynamic and static hydraulic or 
gas applications for prevention of internal and external leakage. "U" type 
seals are pressure energized with pressure against the open end of the "U" 
acting equally on the inner surface in all directions, statically 
balancing the seal. U-seals are normally assembled with an interference 
fit with the width dimension between sealing lips being most critical 
especially in dynamic machinery joint packing applications. This 
interference fit of the sealing lips must provide for good sealing which 
will withstand frictional wear problems. 
In the past multiple part "U" type seals have found great usage due to 
their ability to provide the desired ultimate sealing properties. Seals of 
this type are, for example, illustrated and described in U.S. Pat. No. 
3,342,500 to C. B. Knudson and U.S. Pat. No. 3,653,672 to Maurice D. Felt. 
These prior art seals due to their multipart, nonintegral construction, 
however, can lead to sealing reliability problems. The separately formed 
parts of this ultimate seal construction all have manufacturing tolerances 
which in the aggregate can easily produce wide variations in the critical 
sealing dimensions from seal to seal which in turn gives rise to sealing 
problems in machinery joint packing use. That is, the outer U-shaped 
packing ring and the internal insert member both have manufacturing 
tolerances which when combined with finish operation variations can lead 
to standard size seals with wide variations of critical dimensions. 
Additionally, many seals of various sizes are needed for the numerous 
machinery joint packing applications which necessitates the need for 
manufacture and accurate inventory of many components many of which can be 
nearly the same size. Efforts have to be made to insure individual 
component parts of the seal and especially the internal member are not 
mixed together or mistaken one for another. Lastly, the use of the 
multipart construction which is not integrally formed together 
necessitates final assembly operations and the costs associated with them. 
Accordingly, it is an object of the present invention to provide a novel 
sealing ring member which is rugged, effective and reliable in use and 
simple in design and economical to manufacture. 
It is another object of this invention to provide an integrally formed 
composite sealing ring. 
It is another object of this invention to provide an integrally formed 
U-shaped composite sealing ring. 
It is yet another object of this invention to provide a method for 
producing an integrally formed composite sealing ring with high 
reproducibility sealing ring to sealing ring. 
It is still another object of the invention to provide a method for 
producing an integrally formed U-shaped composite sealing ring which is 
reliable in use and economical to manufacture. 
These and other objects of the invention will become apparent to those 
skilled in the art from a reading of the following specification and 
claims. 
Briefly the foregoing objects are accomplished by providing U-shaped 
composite packing ring seal including a U-shaped shell member and an 
actuator member formed in situ in which the shell member has in transverse 
cross section a base portion with two legs extending from the base to form 
a cavity therebetween. This cavity is filled with liquid elastomer which 
is cured in situ to form the actuator portion of seal. This integrally 
formed U-shaped composite ring seal yields a highly reliable seal with 
minimal dimensional variation problems. Also this seal is easy and 
economical to manufacture. 
The invention also includes the provision of a method for making a U-shaped 
composite ring seal including: forming a U-shaped shell having a base, two 
legs extending from the base and a cavity between the legs; filling the 
cavity with a liquid material which forms a substantially incompressible 
elastomer material when cured; curing said material and moving a cutting 
tool along a predetermined path to remove a portion of said legs and said 
material thereby providing for the sealing lips of the seal. This method 
of integral seal construction does away with final seal assembly 
operations and the costs associated with them. Also by varying the cutting 
angle calibration adjustments can be made in critical lip seal dimension 
in the as assembled state.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION 
Referring now to the drawings by reference characters, there is shown in 
FIG. 1 a composite packing or sealing ring generally designated 10 having 
an outer U-shaped shell member 12. Shell member 12 as best shown in FIG. 2 
has a base portion 14 with two leg members 16 extending from base portion 
14 to define a cavity 18. Shell member 12 can be made from any suitable 
resilient, incompressable, deformable elastomer or plastic composition 
such as polyurethane, rubber, neoprene, teflon or the like. Preferably, 
this material has a high abrasion resistence with a shore A durometer 
reading of over 90. 
Cavity 18 is filled with a liquid elastomeric material which is cured in 
situ yielding an actuator member 20 of the ring. The liquid elastomer 
forming actuator member 20 which essentially fills cavity 18 is chosen to 
be highly resilient low compression set liquid polymer material having 
flowability properties in the liquid state such as a silicone rubber. The 
resilient actuator has a shore A durometer reading of below 85 and 
preferably 65 or below in the cured form. 
Describing the ring in more detail, the leg members 16 extending from base 
portion 14 preferably flare outwardly as they reach their distal end and 
each has a shoulder 22. This shoulder area 22 extends outwardly on each 
leg until it intersects outside flared wall portion 24 of the legs to form 
"sealing lips" 26 of the ring. As shown by FIG. 2 the line defining the 
outer wall of the shoulder area forms an angle Z with the plane contacting 
the ends of the legs. This angle Z is preferably from zero to 45 degrees. 
The distance between the "sealing lips" 26 is designated A and is a very 
critical dimension in ring seal design as will be further explained below. 
The liquid polymer which forms actuator 20 is placed in cavity 18 filling 
the entire volume and is cured in situ preferably forming a single 
integral packing ring. This construction provides uniform sealing 
properties in use from sealing ring to sealing ring. That is, the critical 
dimension A varies only as provided by the manufacturing tolerance of the 
shell and the use of the liquid polymer cured in situ for the actuator 
does not effect this dimension. There is no additional solid actuator 
member inserted in the cavity. Additionally the actuator formed from the 
liquid polymer will uniformly fill the cavity providing consistent 
actuator forces in response to all types and directions of load. Finally 
if some change is needed in sealing lip dimension A it can be accomplished 
in final or "assembled" ring seal form as part of the cutting operation as 
will be described below. 
In the practice of the present invention, shell member 12 as shown in cross 
section in 3A of elastomeric material such as polyurethane or the like is 
molded by conventional means to the desired U-shape as described above. 
The shell material should have good wear and abrasion resistance and 
compression set. The shell material may contain fibers or fillers to 
modify shell properties as desired. 
The cavity of the shell member is then filled with a liquid elastomer 
component (as shown in FIG. 3B) having low compression set and 
compatibility with the intended sealing environment. A preferred elastomer 
includes various combinations of vinyl-functional dimethyl siloxane 
polymers together with the catalyst and crosslinkers required to achieve 
curing. An example is a 50/50 ratio of the vinyl-functional dimethyl 
siloxane polymers with the catalyst and crosslinkers. This elastomer is 
especially good due to the fact that it does not give off moisture or 
gases during curing. An example of a commerical elastomer of this type is 
a Dow Corning two component liquid silicon rubber referred to as Silastic 
Liquid Silicon Rubber, Q3-9591. Other liquid elastomeric polymer systems 
would also be functional so long as they were in a flowable condition. A 
typical viscosity representing a flowable elastomeric polymer would be 
1500 poise at room temperature in the liquid state ready for pouring. 
The liquid elastomer is then cured. The curing time varied with temperature 
but a preferred time is two hours and thirty minutes at 275.degree. F. in 
a conventional curing furnace. It is to be understood, however, that other 
curing processes of different times and temperatures could equally well be 
used. 
Finally the U-shaped sealing ring is then cut, as, for example, shown in 
FIG. 3C. The cut as by a lathe or similar device is typically a single 
uninterrupted cut forming an acute angle Z of between 0 and 45 degrees 
with the horizontal for each leg. This cut angle can be varied to 
accommodate seal ring size variations, so as to precisely set the critical 
dimension A as shown in FIG. 2 and discussed above. A final trim operation 
can also be used to square off the top of the sealing ring. This finish 
trim operation, if used, neatly finishes off the surface of the sealing 
ring yielding the final product as shown in cross section in FIG. 3D. 
FIG. 4 shows in cross section another embodiment of the present invention 
especially useful in applications where a seal is needed when there are 
fluid forces present alternatively from both the top and the bottom. This 
ring seal has similar components to that of the seal of FIG. 2 and is 
identified with like members and letters. The process for producing this 
U-shaped ring seal would be identical to that described above for the ring 
seal of FIG. 2. 
From the foregoing, it is obvious that the U-shaped ring seal and the 
method of manufacture of the present invention provide for and makes it 
possible to produce uniform highly reliable U-shaped ring seals in an 
efficient and economical manner. The ring seal of this invention provides 
for having uniformity in the critical "lip seal" dimension from seal to 
seal in addition to uniform sealing response characteristics in use. 
While there have been described herein what are at present considered to be 
the preferred embodiments of this invention, it will be apparent to those 
skilled in the art that various changes and modifications may be made 
therein without departing from the invention, and it is, therefore, 
intended in the appended claims to cover all such changes and 
modifications as all within the spirit and scope of the invention.