Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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SPEclFIcATIoN
The present invention relates to improvements in
valve assemblies having a valve element which is slidably move-
able relative to a valve seat so as to open and close the valvei,
and where either the valve seat or the valve element has a xe-
silient and deformable valve ~acing for sealing the closed
valve a~ainst leakage. Speci~ically, ~he invention relates to
such valve assemblies in the form o a gate valve an~ more spe-
cifically to the form of gate valves used as a fire hydrant
~rain valve.
BACKGROUND OF THE INVEMTIO~
For many years valve assemblies have been manufactur-
ed wherein the valve seat and its cooperating valve element are
movable relative to one another by sliding contact to open and
close the valve. One of the members of such a valve has been
provided wi~h a resilient and deformable valve facing for pro-
viding the necessary seal between the members. The facing is
conventionally leather, but rubber has also been used. The
valve facing must be deformable since it is necessary for effec- ;;
tive sealing that the valve facing be very tightly wedged be-
tween the valve seat and valve element and to this end the valve
facing in the uncompressed coniguration is slightly larger than
the available space between the valve seat and the valve element. ~;~
However, the valve facing must also be resilient since it must
again expand to the larger uncompressed configuration when the
valve i5 in the opened position 50 that it may again be tightly
wedged into the space between the valve seat and valve element
when the valve is in the closed position. Also, since this
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wedging action places a severe abrasion or shear force on ~he ~;
valve facing, the material of the valve acing must be abrasion
resistant in order to provide a minimum acceptable number of
cycles of valve opening and closing. Both leather and rubber
have acceptable properties in these regards, but on the other
hand, the number of cycles o~ the valve with these materials is
much less than would be desired.
A typical type of valve having a valve facing of the
present nature is that of the drain valve of a ~dry" barrel type
of fire hydrant. These drain valves usually consisted of a
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drain passage from the exterior of the hydrant ~rough the bar~
rel or shoe and through a portion of the main valve seat assem-
bly, the passage opening into the interiox o~ the barrel at a
point above the main hydrant valve when the same is closed. A
valve facing strip is carried by the movable main valve element
of the hydrant. This strip is arranged to have sliding contact
with the valve seat assembly so as to close the opening of the
drain passage to the interior of the barrel when the main hydrant ;~
valve element is moved to the open position.
Conventional leather drain valve facing strips can
function effectively in such ser~ice, but they do have the ser-
ious disadvantage of deteriorating in time and allowing substan-
tial leaki~g after a relatively low number of cycles of opera~
tion of the valve. Thus, they fail due to lack of continued re-
siliency and lack of abrasion and aging resistance,
More recently, efforts have been made to utilize drain ;
valve facing strips made of rubber. These strips may be of a
solid configuration, i.e., haviny a uniform cross section some~
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what simi.lar to that of conventional leather facing strips~ or
they may be of a special configuration so that water pressure on
one side thereof provides a seal Both configurations, however,
have not proven to be totally satisfactory when used over long
periods of time as they have a tendency to "cold-flow" and the
required overall resiliency is lost and leakage occurs. Further,
the rubber tends to deteriorate with age and further los~ re-
siliency and abrasion resistance.
More recently, efforts have been made to utilize
10 valve facing strips made of polyethylene, since this material
is substantially more resistant to aging than ru~ber. These
strips may be of a solid configuration similar to the leather
strips but the very low order of resiliency of the material re-
sults in significant leakage with increased numbers of cycles
of operation. In an effort to mitigate this problem, the poly~
ethylene strips have been provided with a recessed configuration
on one side thereof in order to increase resiliency. While both ~.
of the polyethylene strips provide greater numbers of cycles in ~.
drain valves than strips made with leather or rubber, they still
have undesired increasing leakage with the number of cycles of
operation.
PRIOR ART
prior art relating to fire hydrants and/or gate valves
of the present nature and to articles with a foamed core and
~. :
Z5 solid outer surface (an~ to processes therefor) are:
3,980,096 Ellis et al September 14, 1976 :
3,751,534 Oxley ~ ~ugust 7, 1973
3,662,778 Leopold Jr., et al May 16, 1972
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3,630,098 Oxl~y December 2B, 1971 li~
3,531,553 Bodkins September 29, 1970
3,506,027 Dunton April 14, 1970
3,436,446 Angell April~l, 1969
3,268,636 Anyell Augus~ 23, 1966
2,996,764 Ross et al August 22, 1961 - ,~
978,385 Lofton December 13~ 1310
BRIEF SUMMAR~ OF THE INVENTION
Broadly stated, the present invention relates to valve
lQ assemblies having the valve members o~ a valve seat and valve
element which is slidably movable relative to the valve seat to
open and close the valve and a resilient and deformable valve
~acing on one of the valve members whereby the valve facing
contacts the other valve member when the valve is closed to seal
the closed valve against leakage. The present improvement
relates to the valve facing which is comprised of a foamed poly-
meric core and an impervious and solid polymeric outer surface ';
which overlays the foamed core at every point where the valve
facing contacts the other valve member. The foamed core provides
20 resiliency and deformability and the impervious and solid poly-
meric outer surface provides abrasion resistance. The polymeric
material provides aging resistance. These characteristics are -
maintained for very long periods of time by virtue of the `
impervious outer surface.
In accordance with one broad aspect, the invention
relates to a valve assembly subject to liquid under high pressure,
said valve assembly having va1ve members including a valve seat `~
a~d a valve element which is slidably movable relative to the ;
valve seat to open and close the valve assembly and a resilient
and deformable valve facing on one of the said valve members
whereby the valve facing contacts the other valve member when the
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valve assembly is closed to tightly wedge and seal
the closed valve assembly against liquid leakage,
the improvement wherein the valve facing comprises a
resilient and deformable foamed polymeric core and an
impervious abrasion resistant solid polymeric outer
surface which overlays the foamed core at every point
where the valve facing contacts the other valve member
and the rakio of the thickness of the outer surface is
about 0.5:1 up to about 5
In accordance with a further aspect, the
invention relates to a valve assembly subject to liquid : .
under high pressures, said valve assembly having valve ~:~
members including a valve seat and a valve element which
is slidably movable relative to the valve seat to open
and close the valve assembly and a resilient and deformabte
valve facing on one of the said valve mem~)ers whereby the
valve facing contacts the other valve member when the ~. :
valve assembly is closed to tightly wedge and seal the :~
closed valve assembly against liquid leakage,
the improvement wherein the valve facing com- ~
prises a resilient and deformable foamed polymeric core ~ ` :
and an impervious, abrasion resistant solid polymeric :
outer surface which overlays the foamed core at every
point where the valve facing contacts the other valve :~
member, the ratio of the thlckness of the foamed core
to the thickness of the outer surface is about 0.5~
up to about 5:1 and thus providing sufficient com- ~.
pressiveness and sufficient outer space material to
allow for loss thereof by abrasion.
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Although the present invention may be : .
utilized on conventional gate valves, it is of
part.icular util.ity for use on special gate valves
such as that described in U.S. Patent 3,662,778.
However, the present invention provides most unex-
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pecte~ results in terms of length of useful service when used
as a drain valve facin~ strip for a drain valve of a fire hy- -~
drant. An example of a suitable fire hydrant is that described
in U.S. Patent 3,98~,096, although the invention is not limited
to that particular type of fire hydrant. Nevertheless, for sake
of simplicity, the present invention will be described in con- .
nection with a drain valve of a fixe hydrant, and in particular
in connection with the drain valve of the fire hydrant of ~he
foregoing U.S. Patent, but it should be understood that the in-
vention extends to the breadth described above and is limited
only by ~he spixit and scope of the annexed claims.
BRIEF DESCRIPq~ION OF T~IE DRAWINGS
Figure 1 is a side elevational view of a fire hydrant
embodying the present invention;
Figure 2 is a fragmentary vertical sectional view on
an enlarged scale of the lower portion of the hydrant of Figure
1, the view illustrating the main hydrant valve in the closed ~.
position and the hydrant drain valve in the open position;
Figure 3 is an enlarged side elevational view, partly
in vertical section, and illustrating the upper valve plate for
the main hydrant valve;
Figure 4 is an~elevational view looking from the left
to the right of Figure 3;
Figure 5 is an enlarged view of the drain valve facing
strip of the present invention looking at ~he side of the same
which seals against the drain passage in ~he hydrant valve seat
assembly;
Figure ~ is a view of the dr~in valve facing strip of
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Figure 5 but looking at the opposite side thereof; and
Figure 7 is a side elevational view of the drain:~
valve facing strip of the present invention, the view being
partly in section taken on the line 7-7 of Figure 5 and
diagrammatically showing the polymeric foam construction of
the same. . :
DETAILED DESCRIP-TION OF TH~:IN9ENTION
Referring now to the drawings wherein like characters
and reference numerals represent like or similar paxts, there
is disclosed in Figure 1 a fire hydrant generally designated at ; ~ :
10 and having a barrel 12 which is of the sectional type ~
including an upper barrel section 14 and a lower barrel section ~:
16. The upper barrel section 14 is provided with the usual .
nozzles 18 and with a bonnet or cap 2b through which extends an ~.
operating nut 22 operatively connected by means (not shown) to a
non-rotating but reciprocating valve stem 24. The upper barrel
section 14 is connected to the lower barrel section 16 by the : :
usual frangible connecting ring 26 which is located immediately
above the "bury" line 28. A hydrant shoe 30 is detachably
; 20 connected to the lower barrel section 16 by bolt means 32. (See
U.S. Patent 3,980,096 for a detailed description of a typical
arrangement of this nature.)
. As also dlsclosed in the aforementioned patent
3,980,096, the fire hydrant 10 is provided with a hydrant valve
seat assembly generally designated at 34 and supported between
the lower barrel section 16 and shoe 30, the hydrant valve seat
assembly 34 including a brass valve seat ring 36 having a down-
w ædly facing frusto conical seat 38 for cooperating with an - ~:
upwardly facing frusto conical surface 40 on a main hydrant valve
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generally designated at 42. :~
In more detail, the valve seat assembly 34 includes -.
.
a housing member 44 ana a.drai.n ring 46, the drain ring being
provided with a drain passage 48. The drain 46 threadably sup~
ports the valve seat ring 36 and as fully disclosed in the
aforementioned patent 3,980,096, the drain ring is provided with
at least one lug 50 through which the drain passage 48 extends, ~.
the lug 50 being suitably received in a cut-out provided in the
housing ring 44. The valve seat ring 36 is provided with drain
10 passages52 which communicate with an annular drain manifold
groove 54 and, thus, it will be appreciated a passageway is pro- ~
vided from the exterior of the hydrant t.hrough the passage 48 ~:
to the interior of the hydrant thxough the passages 52 when the
main hydrant valve 42 is in the closed position.
Returning now to the description of the main hydrant
valve, it includes a lower valve plate 56, an upper valve plate
5~ and a valve element 60 sandwiched therebetween, the valve
element 60 being made according to the present invention of a
foam polyethylene material. The ~alve element 60 is provided
20 with the frusto conical surface 40 previously mentioned. As `
will be appreciated, the main hydrant valve 42 is supported on ~.
the lower end of ths reciprocatiny valve stem 24 by means of the ;. ~:
valve nut assembly 62 and thus when the valve stem 24 recipro- ` :
cates downwardly, it will cause the main hydrant valve to open
to allow water to flow upwardly into the barrel to the hydrant
nozzles 18.
As shown in Figure 2, tbe annular brass valve seat
ring.36 is provided with a pair of oppositely disposed and facing
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longitudinally extending grooves 64 ~or receiving ribs 66 (Fig
ures 3 and 4) o~ the upper valve plate 58 and, thus, when the
main hydrant valve 42 i5 reciprocated by the valve stem 24, it
cannot rotate relative to the seat ring. The ribs 66 are each
provided with a longitu~inally extending groove 68 which is
dovetail in section and which is arranged to receive elongated
drain valve facing strips 70 (Figures 5-7), the elongated drain
valve facing strips having generally a cross-sectional config
uration complementary to the groove. The drain valve facing
strips 70 are secured to the ribs by bronze, stainless steel,
or other sultable corrosion resistant screws 72 (Fi~ure 2). As
will now be apparent, when the main hydrant valve 42 is in the
closed position, as shown ln Flgure 2, the drain passages 52 in
the valve seat ring 36 are open to the interior of the barrel 12
above the main hydrant valve 42 since the elongated drain valve
facing strips terminate with their lower end just short of~the
passages 52. Any water ln the hydrant can drain through the pas- ~ ~
sages 52 to the manifold 54 and through the passages 48 to the
exterior of the hydrant. However, when the main hydrant valve
42 is moved downwardly to an open position, the drain valve fac-
ing strips 70 move downwardly with the upper valve plate 58 and
cover the drain passages 52 so that water passing through the
.
shoe 30 into the hydrant barrel 12 cannot escape through the
drain passages to the exterior of the hydrant.
Valve facing strips 70 are comprised of a foamed poly-
meric core 81 and an impervious and solid polymeric outer sur-
face 82. The strips may have at least one attaching device re- -~
ceiving aperture 83 for receiving an appropriate attaching means,
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such as screws 72. The attaching device will secure the valve
facing strips to ribs 66. ~hus, one side 8S of the valve ac-
ing strip 70 contacts and is secured to ribs 66 while the other
side 84 of the valve facing strip contacts the valve seat ring
36. of course, other means of attaching the valve acing strip
to the ribs may be used, or additional means o securing or
stabilizing of the strips to the ring may be used. In this lat-
ter regard, the valve facing strips may have indentations 89 or
receiving a guide or stub projecting from ribs 66 (not shown in
the drawings). Alternatively, a projection 86 (see Figure 3)
may be provided on the valve strips to mate with a corresponding
recess in ribs 66 for providing attachment and/or stabilization
of the valve facing strips For convenience, the valve strips `
may be beveled as shown at 87 to allow a more gradual contact
15 with the valve seat ring. `
As will be appreciated, an important feature of the
invention is the critica~ combination of the foamed polymeric ~;
core and the impervious and solid polymeric outer surface which
overlays the foamed core at every point where the valve facing
contacts the other valve member. In the embodiment o Figure 7,
therefore, outer surface 84 must entirely overlay foamed core 81
so that the outer surface overlays the foamed core at every
point where the valve faciny contacts the valve seat ring. While
not absolutely necessary, it is preferred that the outer surface
overlay the foamed core, also, at every point where the valve
facing contacts the valve member carrying the valve facing. Thus,
in the embodiment of Figure 7, outer surface 85 would also be an ;-
impervious and solid polymeric outer surace, since that entire
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outer surface will contact the val~e member carrying the valve
facing, i.e., rib 66
As noted above, the valve facing may have at least
one attaching device receiving aperture which extends rom the
side of the valve facing contacting one valve me.mber to the
side of the valve facing contacting the other valve. member. It ;~
is not necessary for the outer surface io overlay the foamed
core at that aperture, since ~he foamed core is pro~ected in the
aperture by the attaching devices passing therethrough. ~ever-
lG theless, it is preferred that the outer surface also overlay
that aperture as shown in Figure 7 at 88. Further, w~en a plu-
rality of the apertures are proviaed in the valve facing strip,
it is preferred that each of the apertures have the outer sur-
face overlaying the apertures.
It should be understood that the outer surface is com-
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prised o~ substantially unfoamed polymeric material, but it is
not necessary that the outer surface be totally devoid of any
foaming whatsoevér. For sxample, the strips may be produced by
injecting a foamable polymeric material ~containing a blowing
agent) into a mold cavit~ in such a manner that foaming commences
during the injection step. Thus, the outer surface will foam,
but the mold walls may be maintained at a sufficiently high tem-
perature that the foamed composition will collapse to a non-
~oamed state when contacting t~e heated mold walls. While this
method produces substantially unfoamed polymeric material in the ;~
outer surace, some minor amounts of uncollapsed foam may remain.
This will not, however, seriously degradate the desired proper-
ties of the outer surface.
~070Z~
~ Iowever, to avoid even the amount of uncollapsed foam
associated with the foregoing process, the foamable composition
may be injected at such a rate that foaming is not allowed to
substantially take place and the foamable composition will con-
tact cooled mold walls which will prevent the foamable composi-
tion from substantially foaming. The interior, remaining hot,
however, will foam to provide the foamed core. This process,
however, does result in even smaller amounts of foam being con-
tained in the outer sur~ace.
As can be appreciated from the foregoing, both o~ the - -
described methods of producing the foamed core of the valve fac-
ing strip resuQts in the outer surface containing a blowing
agent. In one case the blowing atent has foamed and the foam has
been collapsed and in the other case, the blowing agent has not
been allowed to foam. While the presence of the blowing agent
will not normally be of any di~ficulty, especiàlly in non-corro-
sive service such as fire hydrants and the like, for special or
severe services as may be encountered by other embodiments o~ ;
gate valves, it might be desirable that the outer surface con-
tain no blowing agent. This can be accomplished by injecking
into the mold cavity a first polymeric material containing no
blowing agent and then injecting into the first polymeric mater- -
ial a second polymeric material which does contain a blowing
agent. Foaming can be accomplished as the two materials expand
in the mold cavity or the mold cavity can be filled before any
~oaming takes place and the mold cavity can then be enlarged to
provide foaming. These methods do result in ~he outer surface
having no blowing agent tllerein.
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For the sake of conciseness, these well known methods
of injection molding an unfoamed outer sur~ace and a oamed core
will not be further discussed, since the details of these proc-
esses are well known to the art. ~Iowever, as examples of such
processes, see U.S. patents 3,268,636; 3,436,446; 3,531,553 and
3,751,534.
As can be appreciated, the invention departs signifi-
cantly from prior art efforts in that the valve facing strip is
an inte~ral combination of an unfoamed, impervious and solid
polymeric outer surface and a foamed polymer~c coreO The outer
surface provides abrasion resistance so that many cycles of the
valve operation may be accomplishad without wearing away the
outer surface and destroying the sealing effect. However, as
noted above, sealing in valves of the present nature require the
tight wedging of the valve facing strip between the valve ele
ment and the valve seat. m e rubber strips of ~he prior art
were deformable so as to allow this wedging, but those rubber
s~rips were not compressible. In other words, the deformable
rubber was moved into space available so that overall compres-
sion o the rubber could take place. As opposed to that func-
tion o the rubber, the present valve facing strips are compress-
ible so that the space actually occupied by the strips under
c~mpxessive forces is less than the space occupied by the strips
under no compressive forces. This is, of course, a well known
function of a foamed polymeric material. In a sense, ~he foamed
core acts as resilient springs which allow compression of the
outer surace into the available space be~ween the valve element
and the valve seat and which function continually urges the outer
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5ur~ace in-to tlght contact with the other valve member to e~fect
exc01]ent sealing of the closed valve.
As can also be appreciated, the foamed polymeric core,
while being compressible, has a high degree of resiliency in
that it is not necessarily subjected to flow forces as is a
solid rubber strip and the ~oame~ core is, ~herefore, capable
o~ continually restoring the valve facing strip to essentially
the same shape of the strip prior to compression. This allows
the valve facing strip to be considerably larger than the space
available between the valve seat and the valve element, since
the foam can be compressed and the strip can still fit into that
space Hence, considerable abrasion of the outer surface can
take place ana yet the valve facing strip will have sufficient
material associated therewith to still cause a tight wedging of
the valve facing strip between the valve members and, hence,
avoid leakage of the closed valve.
However, to ensure these functions, especially of suf~
ficient compressiveness in the valve facing strip and of suffi-
cient outer surface material to allow reasonable loss thereof
by abrasion, it is preferred that the thickness of the foamed
core to the thickness of the outer surface which contacts the
other valve member (for example surface 84 of Figure 7) be at
least 0.5:1 and preferably at least 1:1. Even better results
are provided when that ratio is at least 1.5:1 to 5.0:1.
The outer surface can provide yet a further function
The imperviousness can protect the foamed core rom corrosive ~-
fluias which may be controlled by the valve. This is opposed
to, for example, the situation of a leather valve facing where
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the fluids being controlled by the valve would ultimately soak
into and through the leather valve facings. While this is not
a substantial problem in ~ater service, such as in a fire hy-
drant, even in that environment the impervious surface provides
the function of avoidin~ leakage by virtue of the water passing
through the foamed core. If the foamed core is a closed cell
core, that leakage will be substantially mitigated, but never-
theless the impervious surface is important in that regard.
While the valve facing may be made of a variety of
polymeric matarials, it is pre~erred that the polymeric materi-
al be a substantially inert thermoplastic material. Preerably,
the core material is selected from the group consisting of poly-
olefins, nylon, polyvinyl chloride, natural and synthet.ic rub-
bers and polyesters. Again, the outer surface material can be
selected from any inert thermoplastic material, but it is pre-
ferred that the outer surface be made af an abrasion resistant
polymeric material and to this end it is preferred that the
outer surface material be selected from the group consisting o~
: polyolefins, nylon, polyvinyl chloride, polytetra~luroethylene
and polyesters.
The core material may be of a different material than
the outer surface material, particularly when the method of form-
ing using a first and second injectable material, as describea
above, is used. However, the outer surface material and the core
material may be of the same~polymeric material and this will nor-
mally be the case when the other two above-described methods are
used for producing the valve facing strip.
The core should be foamed sufficiently to provide the
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functi~ns descrih~d above and the foam expansion is not criti-
cal so long as those functions are provided. Sufficient re-
siliency and compressibility are normally achieved with expan-
sion of as little as 1.5 (the expansion being the ratio of the
unfoamed volume of the polymeric composition forming the core
to the subsequent foamed volume thereof). However, it is pre-
ferred that the expansion be 2.0 or hi~her, e.g., 3.0 or 4.0 or
more. Usually the expansion will be between 5.0 and 12.0, e.g., ~-
5.0-8Ø
The foam may be either open cell foam or closed cell
foam, but closed cell foam is preferred, since this provides
less chance of liquid penetrating the valve facing.
Foaming may be accomplished with gaseous or chemical
~oaming agents, e.g., C02, chloro-fluoro-hydrocar~on (Freons),
sodium bicarbonate or the conventional diazo-carbonamiaes. The
particular foaming agent is not critical and may be chosen as
desired.
A full disclosure of suitable blowing agents, polymer- ;
ic material for the outer surface and polymeric material for t~e
foamed core is contained in U.S. Patent 3,751,534, the entire
disclosure of which is incorporated herein by reference and re-
lied upon for details of disclosure.
The following example is illustrative of the invention,
but the invention is not limited thereto.
EXAMPLE ~ -
Valve facing strips of the configuration of Figures 5-7
were produced with a foamed core and solid substantially unfoam- ~ -
ed outer surface by injecting polyethylene wi~h diazo-carbonamid
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blowin~ ag~nt therein in~o a mold cavity with mold wall temper-
atures such that any foam on the outer surface of the molding
was collapsed. The valve ~acing str.ips were atta.ched to a fire
hydrant as described in Figures 1-4 and the fire hydrant was
cycled under water main pressure and the leakage through the
test valve was determined at various numbers of cycles of oper-
ation of the valve. As c~mparisons, a valve facing strip of the
same configuration was molded of the same polyethylene, but in ~ :
such a manner that no foamed core was produced, in other words ~ ~.
the strip was solid polyethyl.ene. In yet a further comparison,
polyethylene valve facillg strips were molded with recesses, in
the nature as that proposed by the prior art. Finally, to
round out the comparisons, conventional rubber valve facing
strips and leather valve facing strips were used in the test.
Eacll of the strip materials were attached to the same
kind of fire hydrant, i.e., that described in Figures 1-4, and
cy~led in the same manner. The results are shown in the table
below
AVERAGE LEAKAGE I~ CC/5 MI~. ;
TYPE OF FACING O CYCLES 100 C~CLES 1000+ CYCLES
Leather 31.5 315.0 ~A-Material fails
Solid PE 15.6 177.5 212.5
Recessea PE .63 1.25 1.05
Rubber ,70 2.30 1.60
Foamed core solid .20 .20 .20 ~ -
outer surface
.
While not shown in the table, the rubber sample actual-
ly failed by tearing at 1618 cycles. Additionally, while not
shown in the table, the present foamed strip material continued .:
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to 17,856 cycles at which number of cycles the average leakage
in cc~5 minutes was only 1.0 and at which number of cycles the
fire hydrant valving mechanism failed and the valve facing strip
~as still intact and functioning well. Thus, the present valve
facing strip material has a longevity in number of cycles which
is greater than the longevity of the mechanical ~alve assemhly.
It should also be carefully noted that the present
valve facing strips, initially, had lower leakage than any of
the other strips and this lower leakage continued for all of ?
the tested cycles. Indeed, that low leakage rate was maintained
throughout the number of tested cycles shown in the table. ¦
This is clearly a most surprising and most unexpected result.
The terminology used throughout the application is
for the purpose o description and not limitation, the scope of
the invention being defined in the appended claims.
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