Note: Descriptions are shown in the official language in which they were submitted.
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Ihis invention relates to backflow prevention apparatus to be
installed between a supply p;pe and a discharge pipe. Such devices are
commonly used in water supply systems in order to insure that polluted
water in a discharge pipe cannot flow in a reverse direction into a supply
pipe. Such apparatus commonly employs an upstream check valve and a
downstream check valve with a zone between them~ along with a relief
val~e operated by differential pressure for venting the zone to atmosphere
whenever the discharge pressure approaches the supply pressure within pre-
determined limits.
According to one aspect of the invention, there is provided in
backflow prevention apparatus for installation between a supply pipe and a
discharge pipe, the apparatus including upstream and downstream check valve
assemblies with a zone between them, and a relief valve device for venting
the zone to atmosphere under predetermined pressure conditions in the pipes,
the improvement comprising, in combination: an inlet passage ~rom the
supply pipe terminating in a stationary valve seat forming a part of the
upstream check valve assembly, a stationary barrel positioned coaxially
of said valve seat, a valve poppet guided for movement in said barrel toward
and away from said valve seat, a spring acting to move said valve poppet
2~ into sealing contact with said valve seat, said spring acting to create a
pressure drop through the upstream check valve assembly when sald valve
poppet is lnitially moved away from said seat by fluid pressure 11l sald
inlet passage, means cooperating with said barrel and said valve poppet to
define a chamber remote from said valve seat, an ejector nozzle on said valve
poppet receivlng fluid from said barrel when said valve poppet has separated
from said valve seat, said ejector nozzle having a discharge end communicat-
ing with said chamber so that relatively rapid -fluid flow from said ejector
nozzle causes a reduction in fluid pressure in said chamber to oppose
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the action of said spring and thereby reduce the pressure drop across the
upstream check valve assembly, the downs-tream check valve assembly having ~ :~
a valve poppet communicati.ng with the zone and positioned to receive t.he
velocity head discharge from the upstream check valve assembly.
According to a second aspect of the invention there is provided
in backflow prevention apparatus for installation bet~een a supply pipe .:
and a discharge pipe, the apparatus including upstream and downstream check ~:
valve assemblies with a zone between them, and a relief valve device for
venting the zone to atmosphere under predetermined pressure conditions in
the pipes~ the improvement comprising, in combination: an inlet passage ;-:
from the supply pipe terminating in a stationary valve sest forming a part
of the upstream check valve assembly, a stationary barrel positioned
coaxially of said valve seat, a valve poppet guided Eor movement in said
barrel toward and away from said valve seat, a spring acting to move said
valve poppet into seallng contact with said valve seat, said spring acting
to create a pressure drop throug]l the upstream check valve assembly when
said valve poppet is initially moved away from said seat by fluid pressure
in said inlet passage, means cooperating with said barrel and said valve
poppet to define a spring chamber remote from said valve seat and enclosing
said spring, an ejector nozzle on said valve poppet receiving fluid :Erom
said barrel when said valve poppet has separated from said valve seat, said
ejector nozzle having a discharge end communicating with said spring
chamber so that relatively rapid fluid flow from said ejector nozzle
ca~lses a reduction in fluid pressure in said spring chamber to oppose the
action of said spring and thereby reduce the pressure drop across the
upstream check valve assembly.
According to a third aspect of the invention there is provided
in backflow prevention apparatus for installation between a supply pipe
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and a discharge pi.l)e, the apparatus including upstream and downstream
check valve assemb:lies with a zone ~etween t~em, and a relie:E valve device
for venting the zone to atmosphere under predetermined pressure conditions
in the pipes, the improvement comprising, in combination: an inlet passage
from the supply pipe terminating in a stationary annular valve seat forming
a part of the upstream check valve assembly, a stationary barrel positioned
coaxially of said valve seat, a valve poppet guided for movement in said
barrel toward and away from said valve seat, a spring acting to move said
valve poppet into sealing contact with saïd valve seat, said spring acting
to create a pressure drop through the upstream check valve assembly when
said valve poppet is initially moved away ~rom said seat by fluid pressure
in said inlet passage, means cooperating with said barrel and said valve
poppet to define a chamber remote from said valve seat, aspirator means
receiving fluid :Erom said barrel when said valve poppet has separated
from said valve seac, sa~-l aspirator means acting to reduce the pressure
in said chamber to oppose the action of said spring and thereby reduce
the pressure drop across thé upstream check valve assembly, said relief
valve device having a va~ve subjected to differential pressure between
the pressure in the inlet passage and the pressure in said chamber of
the upstream check valve assembly.
~ ccording to a fourth aspect of the inventi.on there is provided
in backElow prevention apparatus :Eor :installa~ion betweon a s~lpply p:ipe
and a discharge pipe, the apparatus inclucling upstream and downstream
check valve assemblies with a zone between them, and a relief valve device
for venting the zone to atmosphere under predetermined pressure conditions
in the pipes, the improvement comprising, in combination: an inlet passage
from the supply pipe terminating in a stationary annular valve seat forming
a part of the upsteam check valve asse~ly~ a stationary barrel positioned
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co~lxially of said valve seat, a va.:lv~ poppet guided :Eor movement in said
barrel toward and al~ay from sa;d va:lve seat, a spring acting to move said
valve poppet into sealing contact with said valve seat, said spring acting
to create a pressure drop through the upstream chec~ valve assembly when
said valve poppet is initially moved away from said seat by fluid pressure
in said inlet passage, means cooperating with said barrel and said valve
poppet to define a chamber remote from said valve seatl an ejector no~le
on said valve poppet receiving fluid from said barrel when said valve
poppe~ has separated from said valve seat, said ejector nozzle having a
discharge end communicating with said chamber so that relatively rapid
fluid flow from said ejector causes a reduction in fluid pressure in
said chamber to oppose the action of said spring and thereby reduce the
pressure drop across the upstream check valve assembly, said relief valve
device having a valve subjected to differential pressure between the
pressure in the inlet passage and the pressure in said chamber of the
upstream check valve assembly.
~ccording to a ifth aspect of the invention there is provided
in backflo~ prevention apparatus for installation between a supply pipe
and a discharge pipe, the apparatus including upstream and downstream
check valve assemblies with a zone between them, and a relief valve device
for venting the zone to atmosphere under predetermlned pressure conditions
in the pipes, the ilnp~ovement comprisi.ng, in combination: an inlet passage
from the supply pipe terminating in a stationary valve seat forming a part
of the upstream check valve assembly, a stationary barrel positioned
coaxially of said valve seat, a valve poppet guided for movement in said
barrel toward and away from said valve seat, a spring acting to move said
valve poppet into sealing contact with said valve seat, said spring
acting to create a pressure drop through the upstream check valve assembly
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wilen said valve poppet is initi.ally moved away from said seat by fluid
pressure in said inlet passage, means cooperating with said barrel and
said valve poppet to define a spring chamber remote from said valve seat
and enclosing said spring, an ejector nozzle on said valve poppet receiving
fluid from said barrel when said valve poppet has separated from said
valve seat, said ejector nozzle having a discharge end communicating with
said spring chamber so that relatively rapid fluid flow from said ejector
nozzle causes a reduction in fluid pressure in said spring chamber to
oppose the action of said spring and thereby reduce the pressure drop
across the upstream check valve assembly, the downstream check valve
assembly having a valve poppet communicating with the zone and positioned
to receive the velocity head d;scharge from the upstream check valve
assembly, said relief valve device having a valve subjected to differential
pressure between the pressure in the inlet passage and the pressure in
said chamber of the upstream check valve assembly.
According to a sixth aspect of the invention there is provided
in backflow prevention apparatus for installation between a supply pipe
and a discharge pipe, the apparatus including upstream and downstr0am
check valve assemblies with a zone between them, and a relief valve device
for venting the zone to atmosphere under predetermined pres!sure conditions
in the pipes, the improvement comprising, in combination: an inlet pass-
age from the supply pipe terminating in a stationary valve seat forming
a part of the upstream check valve assembly, a stationary barrel positioned
coaxially of said valve seat, a valve poppet guided for movement in said
barrel toward and away from said valve seat, a spring acting to move said
valve poppet into sealing contact with said valve seat, said spring acting
to create a pressure drop through the upstream check valve assembly when
said valve poppet is initially moved a.way from said seat by fluid pressure
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ln said in:Let passage, means cooperating with said barrel and said valve
poppet to defiTIe a chamber remote from said valve seat, an ejector noz~le
on said valve poppet receivîng fluid from said barrel when said valve
poppet has separated from said valve seat, the outer surface of the valve
poppet cooperating with said barrel to form two series of pockets and ribs
symmetrical with respect to said ejector nozzle and acting to minimize flow
from said seat into said chamber, said ejector nozzle having a discharge
end communicating wlth said cllamber so that relatively rapid fluid flow
from said ejector nozzle causes a reduction in fluid pressure in said :
1~ chamber to oppose the action of said spring and thereby reduce the
pressure drop across the upstream check valve assembly.
According to a seventh aspect of the invention there is provided
in a backflow prevention apparatus for installation between a supply
pipe and a discharge pipe, the apparatus including upstream and downstream
check valve assembl:ies with a zone between them, and a relief valve device
for venting the zone to atmosphere under predetermined pressure conditions
in the pipes, the improvement comprising, i.n combination: an inlet passage .
rom-the supply pipe terminating in a stationary valve seat forming a part
of the upstream check valve assembly~ a stationary barrel positioned
coaxially of said valve seat, a valve poppet guided for movement in said
barrel toward and away from said valve seat~ a spring acting to move said
valve poppet into sealing contact wlth said valve seat~ said sprlng actlng
to create a pressure drop through the upstream check valve assembbly when
said valve poppet is initially moved away from said seat by fluid pressure
in said inlet passage, means cooperating with said barrel and said valve
poppet to define a chamber remote from said valve seat, an ejector no~zle
on said valve poppet receiving fluid from said barrel when said valve
poppet has separated from said valve seat, the outer surface of the valve
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poppct cooperating with saicl ~arrel to form pockets and ribs to produce
circumferential flow o-E fluid on -tlle outer surEace of said valve poppet
away from said ejector ~ozzle and thereby acting to minimize axial flow
from said seat along said valve poppet into said chamber, said ejector
nozzle having a discllarge end communicating with said chamber so that
relatively rapid fluid flow from said ejector nozzle causes a reduction
in fluid pressure in said chamber to oppose the action of said spring and
thereby reduce the pressure drop across the upstream check valve assembly.
According toan eighth aspect of the invention there is provided
in backflow prevention apparatus for installation between a supply pipe
and a discharge pipe, the apparatus including upstream and downst~eam
check valve assemblies wïth a zone between them, and a relie:E valve device
for venting the zone to atmosphere under precletermined pressure conditions
in the pipes, the ïmprovement comprising, in combination: an inlet
passage from the supply pipe terminating in a stationary valve seat
forming a part of the upstream check valve assembly, a stationary barrel
positioned within the body coaxially of said valve seat, a body having a
removable cover, a valve poppet guided for movement in said barrel toward
and away from said valve seat, a spring acting to move said valve poppet
into sealing contact with said valve seat, means cooperating with said
barrel and said cover and said valve poppet to define a spring chamber
remote from said valve seat and enclosing said spring, said valve poppet
having a central axial stem fixed thereto, a spring retainer positioned
within a portion of said spring and having a central opening for sliding
contact with said stem, saicl valve poppet, stem, spring and retainer
being axially insertable into said barrel as a unitary assembly in the
absence of said cover, an ejector nozzle on said valve poppet receiving
fluid from said barrel when said valve poppet has separated from said
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va.lve seat, said ejector nozzle having a discharge end communicating with
said spring chamber so tilat relatively rapid fluid flow from said ejector
nozz:lc causc~s cl re~d~ction in f.luid press~lre in said spring chamber to
oppose the action oE said sprïng and thereby reduce the pressure drop
across the upstream check valve assem~ly.
According to a ninth aspect of the invention there is provided
in backflow prevention apparatus for installation between a supply pipe
and a discharge pipe, the apparatus including upstream and downstream
check valve assemblies w;~h a zone between ~hem~ and a relief valve device
for venting the zone to atmosphere under prede~ermined pressure conditions
in the pipes, the improvement comprising, in combination: an inlet passage
from the supply pipe terminating in a stationary valve seat forming a
part of the wpstream check valve assembly, a valve poppet guicled for
movement toward and away from said valve seat, a first spring acting to
move said valve poppet into sealing contact with saicl valve seat, said
first spring acting to create a pressure drop through the upstream check
valve assembly when said valve poppet is initially moved away from said
seat by fluid pressure in said inlet passage~ means cooperating with said
valve poppet to define a chamber remote from said valve seat, aspirator
means on said valve poppet receiving fluid when said valve poppet has
separated from said valve seat, ancl acting to cause a reduction in Eluid
pressure in said chamber to oppose the action of said first spring and
thereby reduce the pressure dxop across ~he upstream clleck valve assembly,
sai.d relief valve device having relatively movable valve parts for controlling
flow from said zone to atmosphere, a second spring acting to cause
relative movement of said valve parts toward open position, and di:Eferen- :
tial pressure mecms sensitive to pressure in said inlet passage and in
said aspira~ed chamber for changing the effective force of said second
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spring.
According to ~q tenth aspect o~ the invention there is provided
backflow prevention apparatus for installation between a supply pipe
and a discharge pipe, having in combination: a check valve assembly
having an inlet passage from the supply pipe terminating in a stationary
valve seat, a stationa.ry barrel positioned coaxially of said valve seat,
a valve poppet guided for movement in said barrel ~oward and away from
said valve seat, a spring acting to move said valve poppet into sealing
contact with said valve seat, said spring acting to create a pressure
drop through the check valve assembly when said valve poppet is initially
moved away from sai.d seat by fluid pressure in said inlet passage, means
cooperating with said barrel and said valve poppet to define three chambers,
the first chamber being formed be~ween said valve seat and one side of
said valve poppet, the second chamber being formed on the other side of
said valve poppet and in cooperation with said stàtionary barrelJ the
third chamber being formed downstream of said valve poppet and said
barrel~ an ejector nozzle having an intake receiving flow from the first
chamber when said valve poppet has separated from said valve seat, a
discharge passage from said ejector nozzle communicating with said third
chamber, and a space between its intake and its discharge passage connected
to said second chamber so that relatively rapid flow from said ejector
nozzle causes a reduction :in :Fluid pressure in sn:i.d seconcl chnmbcr to
oppose the action of said spring and thereby reduce the pressure drop
across the check valve assembly.
Accord:ing to an eleventh aspect of the invention there is provided
a pressure differential valve assembly for installation between a supply
pipe and a discharge pipe, comprising in combination: an inlet passage
from the supply pipe terminati.ng in a stationary valve seat forming a
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part of the valve assembly, a stationary barrel positioned coaxially of
said valve seat, a valve poppet guided :for movelllent in said barrel toward
and away from said valve seat, a spring acting to move said valve poppet
into sealing contact with said valve seatj said spring acting to create
a pressure drop through the valve assembly when said valve poppet
is initially moved away from said seat by fluid pressure in said inlet
passage, means cooperating with said barrel and said valve poppet to
define three chambers, the first chamber ~eing formed between said valve
seat and one side of said valve poppet, the second chamber being formed : .:
on the other side of said valve poppet and in cooperation wlth sa.id
stationary barrel, the third chamber being formed downstream of said
valve poppet and said barrel, aspirator means receiving fluid from said
first chamber when said valve poppet has separated from said valve
seat, said aspirator means havIng a discharge passàge communicating with
said third chamber, said aspirator means being connected to said second
chamber so that relatively rapid flow from said aspirator means causes a
reduction in fluid pressure in said second chamber to oppose the action :; :
of said spring and thereby reduce the pressure drop across the valve
assembly.
According to a twelfth aspect of the inventlon there is
provided in backflow prevention apparatus or installat.ion between n supply
pipe and a discharge pipe, the apparatus including upstream and downstream
check valve assemblies with a zone between them, and a relief valve device
for venting the zone to atmosphere under predetermined pressure condit:ions
in the pipes, the :Lmprovement comprising, in combination: an inlet
passage from the supply pi.pe terminating in a stationary valve seat
forming a part of the upstream check valve assembly, a stationary barrel
positioned coaxially of said valve seat, a valve poppet guided for
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movement in said barrel -toward and away Erom said valve seat, a spring
acting to move said valve ~poppet into seali:ng contact with said valve
seat, said spring acting to create a pressure drop through the upstream
check valve assembly when said valve poppet is initially moved away from
said seat by fluid pressure ïn said ïnlet passage, means cooperating with
said barrel and said valve poppet to define three chambers, the first :
chamber being formed between said valve seat and one side of said valve
poppet, the second chamber being formed on the other side of said valve
poppet and in cooperation with said stationary barrel, the third chamber
being formed downstream of said valve poppet and said barrel, aspirator
means receiving fluid from said :Eirst chamber when said valve poppet has
separated from said valve seat, said aspirator means acting to reduce
the pressure in said second chamber to oppose the action of said spring
and thereby reduce the pressure drop across the upstream check valve
assembly, said relief valve device having a valve subjected to differential
pressure between the pressure in the inlet passage and the pressure in
said second chamber.
According to a thirteenth aspect of the invention there is
provided in backflow prevention apparatus for ins~allation between a supply
pipe and a discharge pipe, the apparatus including upstream and downstream
check valve assembli.es with a zone between them, and a relie:E valve
device ~or venting the zone to atmosphere ~mder predeterm:ined pressure
conditions in the pipes, the improvement comprising, in combination: an
inlet passage from the supply pipe terminating in a stationary valve seat
forming a part o~ the upstream check valve assembly, a stationary barrel ~`
positioned coaxially of said valve seat, a valve poppet guided for movement
in said barrel toward and away from said valve seat, a spring acting to
move saïd valve poppet into sealing contact with said valve seat, said
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spring acting to create a pressure drop through the upstream check valve
assembly ~ en sai(Z valve poppet is ;nit;ally moved away Erom said seat
by fluid pressure in said inlet passage, means cooperating with said
barrel and said valve poppet to define three chambers, the first chamber
being formcd between said valve seat and one side of said valve poppet, :
the second chamber being formed on the other side of said -valve poppet
and in cooperation with said stationary barrel, the third chamber being
formed downstream of said valve poppet and said barrel, an ejector nozzle
having an intake receiving flow from the first chamber when said valve
poppet is separated from said valve seat, a discharge passage rom said
ejector nozzle communicating with said third chamber, and a space between
its intake and its dîscharge passage connected to said second chamber so
that relatively rapid flow from said ejector nozzle causes the reduction
in pressure in said second chamber to oppose the action of said spring
and thereby reduce the pressure drop across the check valve assembly.
According to a fourteenth aspect of the invention there is provided
in backflow prevention apparatus for installation between a supply pipe
and a discharge pipe, the apparatus including a differential check valve ~-
assembly for connection to the supply pipe, the improvement comprising, .
in combination: a stationary valve seat, a stationary barrel positioned
coaxially of said valve seat, a valve poppet guided for movement in said
barrel toward and away from said valve seat, a spring acting to move said
valve poppet into sealing contact with said valve seat, means cooperating
with said barrel and said valve poppet to define a chamber remote from
said valve seat, an ejector nozzle on said valve poppet receiving fluid
from said barrel when said valve poppet has separated from said valve seat,
the outer surface of the valve poppet having pockets and ribs cooperating
with said barrel to produce circumferential Elow of fluid on the outer
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s~lrface of saicl vaLve poppe-t away from said ejector noz~le and thereby
acting to minimize axial flo~ from sai.d valve seat along said valve
poppet into said chamber, said ejector nozzle llaving a portion communicat-
ing ~ith said cha~,ber so that relatively rapid fluid flow from said
ejector nozzle causes a reduction in fluid pressure in said chamber to
oppose the action of said spring.
According to a fifteenth aspect of the invention there is
provided in a check valve assembly, the improvement comprising, in
combination: a stationary valve seat, a stationary barrel positioned
coaxially of said valve seat, a removable cover secured relative to said
barrel, a valve poppet guided for movement in said barrel toward and away
from said valve seat, a spring acting to move said valve poppet into seal-
ing contact with said valve seat, means cooperating with said barrel and
said cover and said valve poppet to define a spring chamber remote from
said valve seat and enclosing said spring, said valve poppet having a
central axial stem fixed thereto, a spring retainer positioned within a
portion of said spring and having a central opening for sliding contact
with said stem, said valve poppet, stem, spring and retainer being axially `~
insertable into said ~arrel as a unitary assembly in the absence of said
removable cover, aspirator means receiving fluid from said barrel when
said valve poppet has separated from said valve seat, said aspirator
means communicat.ing with said spring chamber so that relatively rapid
fluid flow through said aspirator means causes a reduction in fluid
pressure in said spring chamber to oppose the action of said spring and
thereby reduce the pressure drop across the check valve assembly.
According to a sixteenth aspect of the invention there is
provided in a check valve assembly, the improvement comprlsing, in
combination: a stationary body, a stationary barrel positioned within
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the ~ody and having a coaxial valve seat thereonJ a removable cover
secured relative to said barrel and body, a valve poppet guided for
movement in said barrel toward and away from said valve seat, a spring
acting to move said valve poppet into sealing contact with said va]ve
seat, means cooperating with sa;d barrel and said cover and said valve
poppet to define a spring chamber remote from said valve seat and enclos-
ing said s,pring, said valve poppet having a central axial stem fixed
thereto, a spring retainer positioned within a portion of said spring
and having a central opening for sliding contact with said stem, said
valve poppet, stem, spring, retainer, barrel and seat being axially
insertable into said body as a unitary assembly in the absence of said
removable cover~ aspirator means receiving fluid from said barrel when
said valve poppet has separated from said valve seat, said aspirator
means communicating with said spring chamber so that relatively rapid
flow through said aspirator means causes a reduction in fluid pressure
in said spring chamber to oppose the action of said spring and thereby
reduce the pressure drop across the check valve assembly.
In the drawings:
Figure 1 is a side elevation showing a preferred embodiment of
this invention.
Figure 2 is a sectional elevation showing a portion of Figure 1.
Figure 3 is a perspective view showing the valve poppet employed
in the upstream check valve assembly.
Figure 4 is a transverse sectional view of the valve poppet
shown in Pigure 3, taken substantially on the lines 4-4 as shown in
Figure 2.
Figure 5 is a sectional elevation of the relief valve assembly.
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Figure 6 is an encl view of the relief valve asse:mbly taken
substantially on the lines 6-6 as shown in F;gure 5.
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~ eferring to the drawings, the backflow prevention
device generally designated 10 is posi.tioned between
two Gonventional gate valves ll and 12. The ~ate valve
ll forms a part of a water supply pipe, and the gate
valve 12 forms a part of a water discharge pipe. The
device 10 prevents flow of water from the discharge pipe
bac~ into the supply pipe.
As shown in Figure 2, the device 10 includes an
upstream check valve assembly generallv designated 13,
a downstream check valve assembly generally designated
14 having a zone 15 between them. ~ relief ~alve assembly -
generally designated 16 vents ~he zone 15 to atmosphere
whenever the pressure in zone 15 and chamber 53 approaches
the pressure in the inlet passage 17, within predetermined
limits. The passages 17 and 18 and the zone 15 are all
formed within the integral body 19. The upstream check
valve assembly 13 and the downstream check valve assembly
14 are mounted on the body l9 at right angles to each other,
and each is positioned at an angle of 45 degrees to the
aligned axes of the inlet and outlet passages 17 and 18.
The upstream check valve assembly 13 includes a sta
tionary barrel 21 mounted within the body 19 and having
a flange 33 clamped between the body 19 and the station-
- ary cover 23. An alignment pin 20 assures the proper
orientation of the barrel 2I within the body l9, One end
of the barrel 21 has a circular opening 24 defined within
a stationary annular seat 25. The barreI 21 has a side
window 26 communicating with the zone 15.
A valve poppet 28 is slidably mounted in the barrel
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21 for movement toward and away from the stationary seat
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25. The valve poppet 28 is provided with an annular
resilient disk 29 which cooperates with the sea~ 25
to form a bubble tight seal. A re~ainer plate 31 holds
the resilient disk in position and is itself fixed to
the valve poppet 28 by means of the screw 32. A coil
compression spring 33 has one end seated against the
internal shoulder 34 of the valve poppet 28 and the
other end engaging an end flange 35 on the spring re-
tainer 36. The spring 33 encircles the tapering portion
36a of the retainer. A key 37 presents turning of the
retainer within the cover 23, which cover is secured to
the body 13 by means of threaded fastenings 38, as shown
in Figure l. A central non-circular tubular stem 39 is
secured to the valve poppet 28 by means of the threaded
element 41 and washer 42, and slides through a notching
non-circular opening 43 in the radial portion 36b of
the spring retainer 36. The stem 39 is received into a
matching recess 40 in the valve poppet 28. The valve
poppet 28, stem 39, element 41, washar 42, retainer 36
and spring 33 constitute a unitary assembly for installa- -tion into position, in the absence of the cover 23. For
safety reasons a special tool is required to engage the
threaded element 41. The assembly of cover 23 causes
the spring to be further compressed beyond its relaxed
positiont
An ejector nozzle 44 is mounted OIl the valve poppet
28 and has a relatively large entrance opening 45 commun-
icating with the space 46 defined between the valve poppet
28 and the barrel 21 and between the ribs 47 and 48. The
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discharge opening 49 is smaller and is directed toward
a transverse passage 51 in the valve poppet 28 but ~.
which is separated therefrom by the space 52. ~ The space
52 communicates with a reduced pressure chamber 53 con- :
taining the spring 33. This chamber 53 extends into the
upper portion of the barrel 21 and into the cover 23
both inside and outside of the spring retainer 36.
A circumferential~ groove 54 is formed in the outer
cylindrical surface of the valve poppet 28, and this
groove 54 is interrupted at two locations to communicate
with the arcuate spaces 55 and 56 formed in the outer
surface of the valve poppet 28 and bounded by the inter-
: ior surface 57 of the stationary barrel ~l. The arcuate
space 55 extends from the rib 48 to the rib 5~, and the
arcuate space 56 extends from the rib 47 to the rib 59.
Both of these arcuate spaces 55 and 56 communicate with
the window opening 26 in the barrel 21. As best shown
in Figure 4~ the transverse passage 51 in the valve poppet
~; 28 discharges through the center of the window opening
- 20 26 in:the stationary barrel 21.
The downstream check valve assembly 14 i5 similar to
the upstream check valve assembly 13 in many respects
except that it does not have an ejector nozzle 44 or a
transverse passage 51. The stationary barrel 61 carries
the stationary annular seat 62 which is engaged by the
resilient disk 63 carried on the valve poppet 64. The
coil compression spring 65 engages the cover 66 at one
end and engages the valve poppet 64 at the other end.
The cover 66 and the barrel 61 are secured to the body
and aligned in the manner described in connection with
~ the upstream chec~ valve assembly 13.
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The relief valve assembly 16 is best shown in
Figures 5 and 6 and it includes a stationary housing
67 and a ~alve member 68 in the housing movable toward
and away from a stationary annular seat 69. The
5 resilient disk 71 i.s carried on the valve member for
contact with the annular seat 69. The valve member 68
includes a valve stem 72 slidably mounted in the guide
73 and haviny the circular plate 74 ixed on one end by
means of the threaded stem element 75 and washer 75a.
The cover 76 is bolted to the housing 67 and clamps the
rim of a relatively large rolling diaphxagm 77 between
them. The relatively small rolling diaphragm 78 has its
outer periphery clamped between the guide 73 and a wall
of the housing 67. The inner portion of the rolling
diaphragm 78 is fixed to the valve member 68 by means
of the clamping plate 79 and threaded ~astenings 81.
The effect of the diaphragm 78 is to offset the unbalanced
forces resulting from the pressure differential between
zone 15 and atmospheric pressuxe in discharge 104. A
chamber 82 is formed within the housing 67 and between
the flexible diaphragms 77 and 78, and this chamber 82
communicates with a terminal fitting 83. A similar ter-
minal fitting 84 is carried on the cover 76 and commun-
icates with the chamber 85 between the cover 76 and the
flexible diaphragm 77.
The coil compression spring has one end seated on
the stationary guide member 73 and the other end contacts
the pressure plate 87 mounted for self-aligning movement
on the spherical surface of the central box 88 on the plate
74. The tubular flanged part 89 is bolted to the housing
67 and 91 and is bolted to the mating flanged part 92 on
the body 92 on the body 19, as shown in Figure 1.
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From this description it will be understood that
pressure in the cha~ber 85 acts to close the valve disk
71 against the stationary seat 69, in opposition to the
force of the spring 86. Pressure in the chamber 82 serves
to supplement the force of the spring 86. Movement of
the valve member 68 is guided by the sliding contact
between the stem 72 and the guide 73 and by the sliding
of the fingers 93 in the axial bore 94 of the member having
the stationary seat 69. The guide fingers 93 are formed
integrally with the circular plate 95 which holds the
resilient disk 7]. in place on the valve member 68.
Means are provlded for subjecting the relief valve
chamber 85 to pressure in the inlet passage 17 and, as
shown in the drawings, this means includes the velocity
;~ 15 sensitive pressure pickup tube 96 extending through the
body 19 and connected to the terminal itting 97. A pipe
98 connects the terminal fitting 97 to the terminal itting
84 of the relief valve assembly 16. Additional means are
: provided for connectiny the chamber 53 in the upstream
check valve assembly 13 to the space 82 in the relief valve
housing 67 between the flexible diaphragms 77 and 78. As
-; shown in the drawings, this means includes the terminal
:-~ fitting 99 which communicates with the chamber 53, and
` the terminal fitting 83 which communicates with the relief
valve space 82. A pipe 101 connects the terminal fitting
99 to the temminal fitting 83, as shown in Figure 1. Con-
ventional test fittings 102 and 103 are provided on the
:~ ~ body 19 in communication with the inlet passage 17 and
the outlet passage 18. These test fittings are normally
closed.
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In the operation of the backflow prevention device,
the pressume of water in the upstream gate valve 11 acts
through the inlet passage 17 and against the exposed
portion of the upstream check valve assembly 13 within
the annular stationary seat 25. This pressure tends to
open the valve in opposition to the force of the spring
33. When the upstream pressure has .reached a su~ficient
intensity to move the valve disk 29 away from the seat
25, the pressure acts over a larger cross-sectional area
of the valve poppet 28 and the additional force increases
the opening movement of the valve disk 29 away from the
stationary seat 25. Water flows into the arcuate space
46 between the shoulders 47 and 48 and passes through the
ejector nozzle 44 and into the flared entrance opening
50 of the transverse passage 51. The rapid ~low from
~: the small discharge end of the ejector nozzle 44 reduces
the pressure of liquid in the chamber 53 by an aspiration
efect. Water is discharged from the transverse;passage
~ 51 through the zone~l5 and its velocity head~acts directly
:~ 20 on the exposed surface of the valve poppet 64 in the:
downstream check valve assembly 14. Water is discharged
.~ through the window 60 in the wall of the barrel 61 and
: passes into the discharge passage 18 in the body 19.
The conEiguration of the ribs and spaces on the outer
surface o~ the valve poppet 28 i~ the upstream check valve
assembly 13 has the following beneficial effect: the flow .:
from the inlet passage 17 is shielded from any substantial .
communication directly with the zone 15, and instead the :.
:~ flow from the inlet passage 17 is directed toward the
arcuate space 46 which is defined between the inclined
ribs 47 and 48 and which space 46 feeds the ejector nozzle
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44. The spaces or pockets 55 and 56 on the other
side of these barrel-containing ribs 47 and 48 are in
direct open communication with the side window 26 in
the stationary barrel 21, and hence are in communication
with the zone 15. The circumferential cross flow on the
periphery of the valve poppet 28 through the groove 54,
pockets 55 and 56 and side window 26 serves as a barrier
to leakage from the inlet 17 axially along the cylindrical
surface of the valve poppet 28 into the aspirated chamber
53.
Check valve 13 is designed to maintain a specified
minimum pressure dlfferential and cooperates with the
relief valve assembly 16 to insure that no reverse flow
could ever occur. If for any reason the pressure differ-
ential reflected to the assembly falls below a prescribedlevel, the relief valve assembly will open and vent the
` zone 15 to atmosphere as a means of maintaining this
required differential. The second check valve 14 normally
will also maintain a lesser pressure diffexential; how-
ever, it is subject to system presssure conditions wherein
-~ the pressure in discharge chamber 18 can exceed the normal
~; supply pressure in chamber 17. Under these conditions the
; function of check valve 14 is to remain closed and isolate
zone 15 from the higher backflow pressures. If the second
check valve 14 should leak, this reverse flow would tend
to equalize the pressure differential maintained across
the first check valve 13 and consequently the relief valve
assembly 16 would be caused to open and vent the zone 15
to atmosphere and dissipate the reverse flow lea~age.
More particularly, if the differential pressure be-
tween the chamber 85 and the chamber 82 is not maintained,
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the spring 86 acts in a direction to open the valve by
moving the disk 71 away from the stationary seat 69.
Thls pressure differential could be reduced by reason of
leakage through the downstream check valve 14, or it
might be reduced by failure to maintain the pressure
drop through the upstream check valve 13. Any factor
or foreign ma~ter which could cause leakage through the
upstream check valve 13 would tend to diminish the
pressure differential between the chambers 82 and 85.
Check valve 13 functions to maintain a high initial
pressure differential as a backflow protection margin of
safety, and to resist initial flow through the check valve.
However, as normal flow is established and increases,
the initial pressure differential across its seat is re-
flected against the larger area of -the valve poppet 28
and is applied across the ejector 44 which in turn aspir- ~:
ates the chamber 53. This combined efect causes the
check valve 13 to provide a substantially reduced pressure
:~ differential under flowing conditions. This:substantially
20 reduced pressure differential is actually less than the :
initial pressure differential required under a no flow
condition. In order to prevent this lower than normal j:
pressure differential from causing the differential relief
valve to open, a higher pressure differential is reflected
to the relief valve assembly 16 as a result of adding the
velocity head pressure sensed through tube 96 to pressure :
chamber 85 and by also applying the reduced pressure in
the aspirated chamber 53 to pressure chamber 82. The
result is that the differential reflected to the control
is greater than the differential between pressure chamber
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17 and zone 15 but it is only greater under velocity
flowing conditions. Under static or reverse flow con-
ditions wherein the relief valve assembly may be reqwired
to open, unwanted pressure differentials related to
S normal flow conditions are not induced.
The device shown in the drawings and described
above has been found to have exceptional operating char-
acteristics. The pressure required for initial opening
of the upstream check valve 13 is relatively high, and
yet the pressure drop from the inlet passage 17 to the
outlet passage 18 is exceptionally low during normal flow
conditions.
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