Packing life extender ring

A packing life extender ring assembly which includes a first annular ring and a second annular ring concentrically encircling the first ring, both rings having tapered surfaces matingly engaging one another. The first and second rings are both made of a composition containing 60% to 85% by weight virgin polytetrafluoruethylene, the remainder being calcium metasilicate.

FIELD OF THE INVENTION 
This invention relates to a packing life extender ring assembly and, more 
particularly, to an assembly having a pair of annular rings, each with a 
tapered surface thereon matingly engaging the other, which rings are made 
of a composition consisting of virgin polytetrafluoruethylene and calcium 
metasilicate. 
BACKGROUND OF THE INVENTION 
Slurries, abrasives, dry product and many chemicals can be hard on shaft 
packing. Even with sufficient flush back pressure, dimensional wear and 
shaft runout can render packing all but useless in a matter of weeks, or 
even days. At this point, the only solution has heretofore been to shut 
down the associated system and repack the stuffing box. 
Accordingly, it is an object of this invention to provide, in a stuffing 
box environment, a packing life extender ring assembly which includes a 
pair of annular rings each having a tapered surface thereon matingly 
engaging the other, the rings being made of a composition containing 
virgin polytetrafluoruethylene and calcium metasilicate. 
It is a further object of the invention to provide a packing life extender 
ring assembly, as aforesaid, wherein the composition includes 60% to 85% 
by weight virgin polytetrafluoruethylene, the remainder being calcium 
metasilicate. The preferable composition is 75% by weight 
polytetrafluoruethylene, the remainder being 25% by weight calcium 
metasilicate. This composition includes materials that are suitable for 
use in the food processing industry and the pharmaceutical industry as 
well as other industries. 
SUMMARY OF THE INVENTION 
The objects and purposes of this invention have been met by providing a 
packing life extender ring assembly which includes a first annular ring 
and a second annular ring concentrically encircling the first ring, both 
rings having tapered surfaces matingly engaging one another. In a first 
embodiment, the first and second rings are both made of a composition 
containing 60% to 85% by weight virgin polytetrafluoruethylene, the 
remainder being calcium metasilicate.

DETAILED DESCRIPTION 
A packing life extender ring assembly 10, also known as a wedge ring 
assembly, embodying the invention is illustrated in FIG. 1. The packing 
life extender ring 10 includes a first inner ring 11 having a cylindrical, 
radially inwardly, facing surface 12 concentrically oriented about a 
central axis A. The inner ring 11 also includes a conically tapered, 
radially outwardly, facing surface 13 also concentrically oriented about 
the central axis A. The inner annular ring 11 further includes a pair of 
axially spaced and axially facing surfaces 14 and 16, each oriented in 
planes that are perpendicular to the central axis A and bound the radially 
inwardly facing surface 12 and the radially outwardly facing surface 13. A 
cut 17 is provided through the material of the inner ring 17 so as to 
create a pair of mating mirror image surfaces R.sub.1 and R.sub.2 
extending between the pair of axially spaced and axially facing surfaces 
14 and 16, these surfaces each being oriented in a plane containing a 
diameter of the inner ring 11 and extending at an angle to the pair of 
axially spaced and axially facing surfaces 14 and 16 that is in the range 
of 25.degree. to 45.degree.. The preferable angle is 35.degree.. 
The packing life extender ring assembly 10 also includes a second annular 
outer ring 18 concentrically encircling the inner ring 11. The outer ring 
18 includes a cylindrical, radially outwardly, facing surface 19 
concentrically oriented about the central axis A. A conically tapered, 
radially inwardly, facing surface 21 is also concentrically oriented about 
the central axis A and is in a sliding, matingly engaging relation with 
the tapered, radially outwardly, facing surface 13 of the inner ring 11. 
The outer ring also includes a pair of axially spaced and axially facing 
surfaces 22 and 23 each oriented in planes that are perpendicular to the 
aforesaid central axis A and bound the radially inwardly and outwardly 
facing surfaces on the outer ring 18. In addition, the pair of axially 
spaced and axially facing surfaces 14 and 16 on the inner ring 11 are 
axially offset from the pair of axially spaced and axially facing surfaces 
22 and 23 on the outer ring 18 in a common direction. In this particular 
embodiment, the axial width W of both the inner ring 11 and the outer ring 
18 are identical. The outer ring 18 also includes a cut 24 which creates a 
pair of mating mirror image surfaces R.sub.3 and R.sub.4 each being 
oriented in a plane containing a diameter of the outer ring 18 and extend 
at an angle to the pair of axially spaced and axially facing surfaces 22 
and 23 that is in the range of 25.degree. to 45.degree.. The preferable 
angle is 35.degree. so that a mating and sealing engagement will occur 
between the tapered surfaces 13 and 21. 
The inner and outer rings 11 and 18 are both made of a composition 
containing in the range of 60% to 85% by weight virgin 
polytetrafluoruethylene and 15% to 30% by weight calcium metasilicate. The 
preferable composition is 75% by weight polytetrafluoruethylene, the 
remainder being 25% by weight calcium metasilicate. 
The aforesaid ring assembly 10 is adapted to be incorporated into a housing 
H, such as a pump housing having a hole 26 therein and out of which 
extends a shaft S rotatably supported about an axis of rotation A. The 
opening 26 is larger in diameter than the diameter of the shaft S so that 
a radial spacing 27 exist between an outer surface of the cylindrical 
shaft S and a radially inwardly facing cylindrical surface 28 on the 
housing H. The annular spacing terminates at one end in a wall 29 oriented 
in a plane that is generally perpendicular to the axis of rotation A. The 
packing life extender ring assembly 10 is inserted into the radial spacing 
27 so that the axially facing surface 16 abuts the wall 29 on the housing 
H. The radially inwardly facing surface 12 on the inner ring 11 slides 
onto the shaft S whereas the radially outwardly facing surface 19 on the 
outer ring 18 slidingly engages the surface 28 of the opening 26 as the 
assembly is moved into the annular spacing 27. Since the pair of rings 11 
and 18 are offset from one another by the dimension X, any force applied 
to the outer ring 18 would have a tendency to expand the diameter of the 
outer ring 18 and open the cut 24 to define a gap. However, expansion of 
the outer ring 18 is confined or restricted by the carefully selected 
dimension of the cylindrical surface 28 relative to the exterior surface 
of the shaft S. Any axial force applied to the outer ring 18 in a 
rightward direction (FIG. 3) would have a tendency to compress the inner 
ring 11 as well as compressing and sealing the mating surfaces formed by 
the cut 17. The cut 24 will remain closed and sealed by reason of the 
aforesaid carefully selected dimension of the cylindrical surface 28 
formed on the housing H relative to the exterior surface of the shaft S. 
Conventional packing P is placed into the annular space 27 and against the 
axially facing surface 22 of the outer ring 18. An adjustable gland G is 
provided for compressing the packing P between the outer ring 18 and the 
gland G and into sealing engagement with the surface 28 and the outer 
surface of the shaft S. Such an adjustable gland is illustrated in U.S. 
Pat. No. 863, 619 and reference thereto is to be incorporated herein. 
Compression brought about by the gland G will also cause a seal to be 
formed between the surface 19 of the ring 18 and the interior wall 28 of 
the housing H and between the surface 12 of the ring 11 and the exterior 
surface of the shafts and between the surface 16 of the ring 11 and the 
interior wall 29 of the housing H. A seal also will exist between the 
inclined and matingly engaged surfaces 13 and 21 on the rings. Even as 
shaft runout occurs due to wear, the aforementioned sealed locations will 
remain effective to prevent liquid from leaking past the packing life 
extender rings unto the packing P. 
The utilization of the composition described above has resulted in a very 
surprising result. As stated in the Background of the Invention above, 
frequent changes of the seal inside of a stuffing box was prevalent in 
instances where slurries, abrasives, dry product and other chemicals are 
utilized in association with a shaft packing. More specifically, the 
surprising result is 10 that a utilization of a packing life extender ring 
assembly made of the composition results in a very enhanced lifetime of 
the seal without necessitating a repacking of the stuffing box. One 
instance of experimental use in a water treatment plant resulted in a 
continued operation of the seal for in excess of one year without having 
to repack the stuffing box. 
Although a particular preferred embodiment of the invention has been 
disclosed in detail for illustrative purposes, it will be recognized that 
variations or modifications of the disclosed apparatus, including the 
rearrangement of parts, lie within the scope of the present invention.