Note: Descriptions are shown in the official language in which they were submitted.
`~
113785S
C ~OL V~LVE ASS~MBLY
Background of the Invention
The pres`ent invention relates to an assembiy for
mixing or blending cold water with overheated hot water to
form a stream of hot water at a desired temperature. In
particular the present invention relates to a control
valve assembly which is capable of maintaining a stream of
blended hot water at a nearly constant temperature over a
wide range of flow rates of blended hot water.
In hot water heating systems, particularly in
institutional systems, it may be practical to heat water
with a supply of steam. In such a system co],d water is
passed through one set of passages in a heat exchanger an~
~'
1~37~3SS
is heated by the steam which passes through an adjoining
set of passages. The output from the heat exchanger is
overheated, that is, it is much too hot to be safe for use
as a hot water tap. This overheated water is blended with
cold water in the water heater until the resultant mixture
is at a suitable temperature for the hot water tap.
There have been previous attempts to provide a
controller which is capable of maintaining the temperature
of the blended water constant over a wide range of flow
rates. Some of these have used sleeve valves. Problems
have been encountered when using sleeve valves to regulate
water flow because the machined surfaces of those valves
tend to corrode and to accumulate deposits making them
difficult to operate. In addition, the constant contact
between the sliding and fixed members of a sleeve valve
creates friction which must be overcome to change the
valve position. Some patents disclosing the use of sleeve
valves in blending hot water heaters are U.S. Patent Nos.
3,670,807, 3,388,861, and 3,232,336.
Further problems have been encountered when a flow of
heated water is regulated by passing the hot water through
a variable orifice. This can be explained by the
principle that heated water passing through an orifice of
the proper size will regulate its own flow. The size of
1~378SS
the orifice establishes a reference temperature. If the
temperature of the heated water exceeds the reference
temperature, the flow through the orifice is choked off by
cavitation or flashing downstream of the orifice. Choking
continues until the temperature drops down to the
reference temperature.
This choking phenomenon can be dangerous, since the
result of choking off the flow is a rise in the pressure
upstream of the valve or orifice. If the heat exchanger
is upstream of the flow regulating valve, the pressure
rise may cause the heat exchanger to explode. Blending
hot water heaters having valves to regulate the flow of
hot water downstream of the heat exchanger are disclosed
in each of the above mentioned patents and in U.S. Patent
2,610,837.
Difficulties have been encountered in producing a
blending hot water heater which can maintain the
temperature of blended water constant over a wide range of
demand. To maintain the water leaving the blending
chamber at a constant temperature the ratio between the
superheated water arriving in the blending chamber and the
cold water arriving in the blending chamber must be varied
to compensate for two factors. First the pressure drop
1137~5
--4--
associated with the heat exchanger changes with the rate
of flow throuc3h the heat exchanger. Second, the
superheated water temperature tends to fall with increasing
flow through the heat exchanger. Consequently, any
controller which is to keep the blended water temperature
constant must be able to compensate for the changes in these
two factors with changing flow rates.
Further, many known control valve assemblies for
blending hot water heaters have cumbersome external lines
for conducting pressure to diaphragm controllers. These
lines are not only difficult to install, they are prone to
damage in service because they are generally made of a
thin wall tubing and are in vulnerable locations.
. -:
113~5S
Summary of the Invention
The present invention provides a new and improved
control valve assembly for use in a blending hot water
heater. The flow of cold water into the valve assembly is
split, a portion of it flowing through an inlet valve into
a heat exchanger, and a portion of it flowing through a
bypass valve into a blending or mixing chamber. Overheated
water from the heat exchanger flows into the blending or
mixing chamber. The relative flow rates of cold water and
overheated water into the blending or mixing chamber are
regulated by diaphragm actuated inlet and bypass valves.
Both the inlet and bypass valves are poppet-type
valves which inherently require little maintenance.
Because no tight fitting machined surfaces slide on one
another, there is little tendency for corrosion to be a
problem. Further, the overheated water from the exchanger
never flows through a flow regulating orifice, and
consequently the dangerous tendency for the flow of hot
water to choke itself ofE and raise the heat exchanger
pressure is not present.
The ratio of the flow of water bypassed around the
heat exchanger to the flow through the heat exchanger is
controlled by a controller including a diaphragm which
~13~5
actuates a valve stem. A pressure drop caused by an
increase in demand is sensed hy the diaphragm. The valve
stem moves an amount which corresponds to the size of the
demand increase and opens one of the poppet valves a like
amount. The other poppet valve also opens when the valve
stem moves, but the extent of opening is adjusted to
compensate for changes in the pressure drop across the
heat exchanger and for changes in the superheated water
temperature, both caused by the changing flow rate.
Two adjustments are provided to assure that the
blended water temperature is very nearly constant over a
wide range of demand. A first or low-flow temperature
adjustment is made when the demand for blended hot water
is small. The amount of cold water admitted through the
bypass valve into the blending or mixing chamber is
adjusted by moving a bypass valve seat toward or away from
the bypass valve member until the desired blended hot
water temperature is achieved.
The second adjustment is made when the flow is about
50% of capacity. In one preferred embodiment a pair of
opposing springs supports the bypass valve member for
sliding movement on the valve stem. The compressive force
in the springs is changed to cause the valve member to
1~37B~5
--7--
move toward or away from the bypass valve seat and thus to
regulate the amount of cold water admitted to the blending
chamber at 50% flow.
In a second preferred embodiment, an inlet valve seat
floats between two opposed springs. The second adjustment in
this embodiment regulates the amount of cold water admitted
to the heat exchanger at about 50% of maximum flow. The low-
flow adjustment is the same in both preferred embodiments.
In addition, either embodiment of the present invention
may include a steam control valve operatively connected with
the controller to regulate the flow of steam through the heat
exchanger. The steam control valve includes a variable
orifice which is manually adjustable to select the maximum
flow rate of steam through the heat exchanger. The steam
control valve also includes poppet valves which vary the flow
of steam in response to variations in demand between no flow
at no demand conditions and the maximum flow established by
the manually adjustable orifice at maximum demand conditions.
Accordingly, it is an object of the present invention
to provide a new and improved control valve assembly for
use in a blending hot water heater in which an incoming
stream of cold water is split, one portion following a path
through a heat exchanger and into a mixing chamber, the
other portion flowing directly into the mixing chamber.
113~8S5
It is a further object of the present invention to
provide a new and improved control valve assembly for use in
a blending hot water heater which is capable of controlling
the proportion of hot and cold water entering a mixing
chamber by using poppet valves.
It is a further object of the present invention to
provide a new and improved control valve assembly for use in
a blending hot water heater wherein there is no variable
orifice valve interposed in the flow of hot water to the
blending chamber to regulate the flow thereof.
It is a further object of the present invention to
provide a new and improved control valve assembly for use in
a blending hot water heater having a controller which is
capable of maintaining the temperature of the blended water
leaving the control valve assembly at a nearly constant
temperature over a wide range of demand.
It is a further object of the present invention to
provide a new and improved control valve assembly for use in
a blending hot water heater which is free of external pressure
sensing lines and in which all pressure conducting passages
are internal to the control valve assembly.
It is a further object of the present invention to
provide a new and improved control valve assembly for use in
a blending hot water heater in which the ratio of cold
water entering a mixing chamber to the hot water entering
1~3~5S
the mixing chamber is maintained properly despite
variations in the demand for mixed hot and cold water in
order to keep the mixed water temperature nearly constant
over a wide range of demand.
It is a further object of the present invention to
provide a new and improved control valve assembly for use
in a blending hot water heater in which the control valve
assembly is adjustable to select the mixed hot and cold
water output temperature at a low rate of flow and to
select the mixed water output temperature at a high rate
of flow.
It is a further object of the present invention to
provide a new and improved control valve assembly for use
in a blending hot water heater in which the control valve
assembly includes a steam regulating valve to regulate the
flow of steam through a heat exchanger in response to
variations in demand for blended hot water between a
minimum flow at no demand conditions and a manually
adjustable maximum at maximum demand conditions.
8~5
-10~
Brief Description of the Drawings
.
These and other objects and features of the present
invention will become apparent from the following
specification aescribing preferred embodiments shown in the
accompanying drawings.
Fig. 1 is a schematic view of a hot water system showing
a shower and a blending hot water heater having a heat
exchanger and a control valve assembly constructed according
to the present invention;
Fig. 2 is a side sectional view of the heat exchanger
and control valve assembly of Fig. 1 showing an inlet valve
and a bypass valve;
Fig. 3 is an enlarged front section view of the control
valve assembly shown in Fig. l;
Fig. 4 is a side sectional view of the control valve
assembly of Fig. 3 showing both valves opened a small amount
in response to a small demand for blended hot water;
Fig. 5 is a sectional view similar to Fig. 4 but showing
both valves opened a large amount in response to an increased
demand for blended hot water;
Fig. 6 is a side sectional view through a second
preferred embodiment of the present invention showing a
1137~355
~ypass valve member and valve seat and an inlet valve
member and a floating inlet valve seat;
Fig. 7 is a side sectional view of a third embodiment
of the control valve assembly illustrated in Fig. 3
differing primarily in the arrangement of springs;
Fig. 8 is a partly sectional view of a fourth
preferred embodiment of the present invention showing a
steam control valve; and
Fig. 9 is an enlarged sectional view generally similar
to Fig. 3 but showing a control valve assembly having a
gain ad~ustment.
11378~5
-12-
~escription of a Preferred Embodiment
A control valve assembly 10 constructed in accordance
with the present invention is adapted to supply blended
hot water at a constant temperature over a wide variation
in the amount of blended hot water demanded (Fig. 1). It
is particularly adapted for heating water for use in
locker rooms or change houses associated with athletic
facilities or anywhere the demand for hot water may vary
widely from time to time. A continuously flowing low
pressure steam supply 12 heats cold water passing through
a conventional heat exchanger 14. The temperature of the
water supplied to a hot water tap 15 is regulated by the
control valve assembly 10 which mixes a controlled amount
of cold water with overheated hot water leaving the heater
exchanger 14. The user may regulate the final temperature
to preference by opening or closing cold water valve 15a.
To create a demand for blended hot water a tap 15 is
opened. In response to this demand cold water is supplied
by the control valve assembly 10 to the heat exchanger
14. Cold water entering the heat exchanger 14 is heated
to a temperature greater than the temperature desired at
the hot water tap 15. Upon leaving the heat exchanger 14,
the overheated hot water enters a mixing chamber 16 (Fig. 2)
~3~85S
-13-
where cold wa-ter is mixed wlth the overheated water to form
a mixture at -the temperature desired at the hot water tap 15.
As the demand for hot water increases, the pressure
drop between the inlet 23 and the outlet 24 of the heat
exchanger 14 also increases. The water leaving the heat
exchanger ].4 under high demand conditions is at a lower
pressure than it is when the demand for hot water is low.
Under high demand and high flow rate conditions, viscous
friction forces oppose the flow of water through the heat
exchanger 14. These friction foxces increase with
increasing water flow rate. To maintain the hot water
temperature at tap 15 constant the bypass valve 22
regulates the cold water flow into the blending chamber
16. The bypass valve 22 does not open as rapidly in
response to an increase in demand as the inlet valve 18
which regulates the flow of water to the heat exchanger 14.
This compensates for the decrease in pressure of the over-
heated water leaving the heat exchanger 14 under high demand
conditions.
Minerals, whi.ch are found in all water supplies and
which may make the water hard, may break down and precipitate
out of the water when the water temperature exceeds about
120F. This phenomenon can cause problems for valves which
.
113~i5
-14-
regulate the flow oE hot water. The inlet valve 18
regulates the flow of cold water into the heat exchanger `
14 but does not come in contact with the flow of overheated
hot water out of the heat exchanger. The inlet valve 18 is
located upstream of the inlet 23 to the heat exchanger 14,
and it encounters only cold water. Thus, the inlet valve
18 has little tendency to accumulate mineral deposits, and it
requires less frequent maintenance than blending valves which
come in contact with heated water.
Another problem with valves which regulate the flow of
hot water is that hot water passing through an orifice tends
to regulate its own flow. If hot water from a heat exchanger
encounters a restriction of the proper size, the flow may be
choked off causing the pressure in the heat exchanger to rise.
The size of the restriction in a flow of hot water
determines a reference temperature. If the water is above the
reference temperature r the flow through the restriction will
choke itself off until the temperature drops. The choking
of a flow of hot water througharestriction is caused by
flashing or cavitation just downstream of the restriction.
The flashing and resulting expansion of the flowing fluid
tends to block off flow through the restriction. This later
effect can be dangerous since it may result in increased
~1378~i
-15
pressure in an upstream heat exchanger, and may cause the heat
exchanger to burst.
According to the present invention, overheated water
leaving the heat exchanger 14 enters the mixing chamber 16 by
flowing along a path that is free of restrictions which could
choke the flow. The overheated water is met by a flow of cold
water which has bypassed the heat exchanger 14. The overheated
water and the cold water blend and form a mixture of water at
the desired temperature before leaving the control valve
assembly 10.
The bypass valve 22 regulates the flow rate of cold water
which is mixed with the overheated water in the mixing chamber
16 and thus the final temperature of the water leaving the
control valve assembly 10. Utilizing the bypass valve 22 to
regulate the final temperature of the water at the tap 15 has
two important beneficial effects. First it assures that hot
water does not encounter a valve. This construction prevents
the dangerous build up of pressure upstream of a valve or
restriction when the hot water passing through the valve
regulates its own flow. Second, the bypass valve 22 regulates
only cold water, and thus does not accumulate mineral deposits
as rapidly as a hot water valve would.
The inlet valve 18 controls the flow of cold water to the
heat exchanger 14. There is a pressure drop across the heat
exchanger 14 caused by the frictional forces opposing motion
1137~35~;
-16-
of the water through the tubes 35 in the exchanger ~Fig. 2).
This causes the pressure of the overheated water entering the
mixing chamber 16 to be less than the pressure of the cold
water entering the mixing chamber 14 through bypass valve 22.
Since the water will not flow from low pressure to high
pressure, pressure losses in the heat exchanger assure that
no hot water will flow through the bypass valve 22.
The pressure drop across the heat exchanger 14 is a
function of the flow rate through it. Increasing the opening
of valve 18 a small amount when the flow rate is large
produces a smaller change in the flow through the heat
exchanger than making the same size increase in the opening of
valve 18 when the flow rate is small. A controller 36
compensates for the changing pressure drop across the heat
exchanger 14 to maintain the proper ratio between the over-
heated water and the cold water entering the mixing chamber
16. This assures that the blended water temperature will be
constant over a wide range of demand.
It is within the scope of the present invention to
construct a control valve assembly using sleeve valves. How-
ever, one preferred embodiment utilizes poppet valves 18 and
22. Poppet valves as a class require smaller forces to
operate them since they have less internal friction than do
113~ 5
-17-
sleeve valves. Further, poppet valves tend to be self-
cleaning and to resist the accumulation of mineral deposits.
~ oth the inlet 18 and bypass 22 valves include frustro-
conical poppets or valve members 26 and 28 and cooperating
circular valve seats 30 and 32 (Fig. 3). In a preferred
embodiment the two valve seats 30 and 32 are approximately
the same diameter. When the flow rate through valves 18 and
22 is the same, the pressure drop across each is also the
same.
The valve controller 36 actuates the valves 18 and 22 in
response to variations in the demand for blended hot water.
The controller 36 includes a diaphragm 38 which forms a
movable barrier between an upper chamber 40 formed in the
upper controller body member 41 and a lower chamber 42 formed
in the lower controller body member 43. The upper 41 and lower
43 controller body members are generally cylindrical and have
opposed coaxial cylindrical recesses which form the upper
pressure chamber 40 and the ]ower pressure chamber 42.
Pressure from the blended water outlet 20 reaches the
lower chamber 42 through cylindrical passages 47 and a central
passage 44 in the stem 46. The stem 46 extends through and is
fixedly connected with the diaphragm 38 by suitable means such
as diaphragm retainer 48.
The pressure acting on the top side of the diaphragm 38
is supplied through a passage 50. The passage 50 connects the
~13~3SS
18-
co].d water inlet 52 with the upper pressure chamber. Upon
initiation of demand for blended hot water, the pressure at
the blended water outlet 20 drops. This pressure drop is com-
municated through the central cylindrical passage 44 in the
stem 46 to the lower diaphragm chamber 42. The pressure
differential across the diaphragm 38 causes the diaphragm to
move downward, which moves the stem 46 downward and actuates
the valves 18 and 22.
The inlet valve member 26 is fixedly connected with the
stem 46. The smaller diameter upper end 54 of the inlet
valve member 26 abuts an annular surface 55 projecting
radially outward from the stem 46. A portion of the lower
larger diameter end surface 57 of the inlet valve member 26
abuts a spacer cylinder 58 which is coaxial with the stem 46.
The lower end of spacer cylinder 58 abuts the diaphragm re-
tainer 48. Thus the inlet valve member 26 is held in a fixed
axial position on the stem 46, and when the stem 46 moves
downward, the inlet valve 18 is opened an equal amount.
A range spring 62 biases the stem 46 and the inlet valve
member 26 upward toward the closed position shown in Fig. 3.
The range spring 62 presses between a lower annular end
surface 63 of the inlet valve member 26 and the bottom of an
annular recess 64 in the lower stem guide 65. The annular
recess 64 in the lower stem guide 65 is provided to keep the
11378SS
--19--
range spring 62 centered around the axis of the stem 46 and
to prevent binding.
The motion of the bypass valve member 28 is also con-
trolled by the motion of the stem 46. When the stem 46 is in
its uppermost position corresponding to a zero demand for
blended hot water as shown in Fig. 3 and during the initial
portion of the downward stroke of the stem, the radially
projecting annular shoulder 60 contacts the bottom 73 of the
bypass valve member 28 and urges it upward against the net
force of the compression spring 66 and the yield spring 68.
When the bypass valve 18 is open, cold water from the cold
water inlet 52 enters the mixing chamber 16 after passing
through the bypass valve seat 32 and passages 76 in the
tubular member 80.
As previously noted, as the demand for blended hot water
increases, the controller 36 moves the stem 46 downward. Once
the stem 46 has moved beyond the position corresponding to
between 10% and 25% bf maximum flow, the shoulder 60 on the
stem is no longer in contact with the bypass valve member 28.
The position of the bypass valve member 28 is then controlled
only by the compression spring 66 and the yield spring 68.
The exact flow rate at which the bypass valve member 28
lifts from the shoulder 60 depends on the blended hot water
temperature selected. If the selected temperature is high,
~13~3SS
20-
i.e. 200F, the bypass valve 22 will open a relatively small
fraction compared to the inlet valve 18, and the bypass
valve member 28 will lift off the shoulder 60 at about 10%
of maximum flow. On the other hand, if the selected
temperature is relatively low, i.e. 100F, the bypass valve
22 will open a relatively large fraction compared to the
inlet valve 18. In this case the bypass valve member 28 will
lift off the shoulder 60 at about 25~ of maximum flow.
At some flow rate greater than between 10% and 25% of
maximum flow the bypass valve member 28 floats axially on the
valve stem 46 between two helical springs, an upper compression
spring 66 and a lower yield spring 68. The compression force
in the springs 66 and 68 is controlled by the position of the
stem. The valve member 28 has a central cylindrical passage
70 in sliding abutting engagement with the outside surface of
the stem 46. This assures that the compressive force in each
spring will be the same. Any imbalance of force will cause
the valve member 28 to slide on the stem 46 until the forces
applied by the springs 66 and 68 to opposite sides of the
valve member are balanced again.
The compression spring 66 extends between the top side 71
of the bypass valve member 28 and an annular stem guide 72
connected with ~he stem 46. The yield spring 68 extends
between the bottom 73 of the bypass valve member 28 and an
1~3'78~S
-21-
annular recess 74 in the inlet valve seat member 75. As the
stem guide 72 moves up or down, the compressive force in the
springs 66 and 68 changes. The spring rate or stiffness of
the compression and yield springs 66 and 68 may be selected
so that the ratio of the flow of cold water through the bypass
valve 22 into the mixing chamber 16 to the flow of overheated
hot water from the heat exchanger 14 into the mixing chamber
remains constant despite variations in the flow rate of
blended water. Maintaining the ratio of these flow rates
constant serves to keep the blended water temperature uniform
over the entire range of flow rates.
The flow rate of cold water into the mixing chamber 16
depends only on the position of valve 22. The flow rate of
overheated water from the heat exchanger 14 into the mixing
chamber 16 depends on the position of valve 18 and on a heat
exchanger friction factor which varies with the flow rate. In
addition the temperature of the overheated water entering the
blending chamber 16 tends to fall with increasing flow rates
through the heat exchanger 14. Consequently the controller
36 must open the valves 18 and 22 to an extent which compen-
sates for the changing friction factor and the changing
temperature of the overheated water if the temperature of the
blended water is to remain constant over a range of flow rates.
The friction factor increases with increasing flow rates
~137BS5
-22-
to reflect an increase in the viscous resistence to flow
with increasing flow rates through the heat exchanger 14. In
addition as the flow rate through the heat exchanger 14
increases, the temperature of the water leaving the heat
exchanger decreases. Together these two factors tend to
cause a decrease in the blended hot water temperature with
increasing flow. In order to compensate for the increase in
resistence to flow through the heat exchanger 14 and the falling
overheated water temperature as the flow rate increases, at flow
rates above about 25~ of the maximum flow rate the bypass valve
22 is opened less than the inlet valve 18.
When the stem 46 moves from a closed position to an open
position in response to a demand for blended hot water which
is less than 25~ of the maximum demand, the downward force
exerted by the compression spring 66 exceeds the upward force
of the yield spring 68 with the result that the bypass valve
member 28 remains seated against the shoulder 60 of the stem
46 during the first quarter of its downward stroke. When the
stem 46 reaches a position corresponding to about 25% of
maximum flow, the upward force of the yield spring 68 balances
the force of the compression spring 66. Further downward
motion of the stem 46 will cause a downward motion of the by-
pass valve member 28 which is less than the downward motion of
the stem 46.
1~3~ 5
-23-
When the bypass valve member 28 is floating on the stem
46, that is during approximately the last three quarters of
the stroke of the stem, the position of the bypass valve
member is governed by the opposing forces of the compression
and yield springs 66 and 68. The lower end of the yield spring
68 abuts shoulder 74 while the upper end of the compression
spring 66 abuts the stem guide 72 which moves up and down with
the stem. Thus it will be observed that the downward motion
of the bypass valve member 28 is proportional to and less than
the downward motion of the stem 46 and the inlet valve member
26.
The proportional movement of bypass valve member 28
closely follows the changing friction factor and thus assures
that the ratio of cold water to overheated water entering the
mixing chamber 16 is constant over a wide range of flows. In
the preferred embodiment the stiffnesses of the compression
and yield springs 66 and 68 are selected to provide a slight
increase in the blended hot water temperature with increasing
flow rates. However it is to be understood that by changing
the stiffnesses of the springs the control valve assembly lO
will provide a constant blended water temperature or one that
decreases with increasing flow.
Two adjustments of the control valve assembly 10 may be
to assure that the proportions of overheated hot water
~1378S5
-24-
entering the blending chamber 16 from the heat exchanger 14
and bypassed cold water entering the blending chamber are
nearly constant over a wide range of demand. The first
adjustment is made at low flow conditions when demand for
blended hot water is small and the flow rate of water through
the heat exchanger 14 is small (Fig. 4). The second adjust-
ment is made when demand for blended hot water is large and
water is flowing through the hot water tap 15 at at least 50%
of the maximum flow (Fig. 5). The ability to adjust the
valve openings at two different demand levels to achieve the
same blended water temperature assures a nearly constant
temperature over the entire range of flow rates.
The first, or low flow, adjustment is made when a small
demand for blended hot water has opened the inlet valve 18
and the bypass valve 22 a small amount through the action of
the controller 36 (Fig. 4). This adjustment is accomplished
by moving the bypass valve seat 32 toward or away from the
bypass valve member 28.
The bypass valve seat 32 comprises one annular end of the
cylindrical tubular member 80 which surrounds the stem 46. The
tubular member 80 is held coaxial with the housing 82 by sliding
abutting engagement with a cylindrical surface 83 which projects
radially inward from the center member 84 of the housing 82.
The tubular member 80 may slide axially and rotate within the
center member 84 of the housing 82.
1~37~
-25-
Suitable threads 85 are located on the end portion of
the tubular member 80 which is opposite the valve seat 32.
sy rotating the tubular member 80, the bypass valve seat 32
can be moved toward or away from the bypass valve member 28
to regulate the amount of cold water flowing through the
bypass valve 22.
The second adjustment is made when the flow rate is at
about 50% of full capacity (Fig. 5). The adjustment is
effective to move the bypass valve member 28 relative to the
bypass valve seat 32 by changing the load on the yield spring
68 and the compression spring 66. The upper end of the
compression spring 66 abuts a teflon upper stem guide 72
which in turn abuts an adjusting nut 88. By turning the
adjusting nut 88, the compression and yield springs 66 and
68 may be compressed or allowed to expand to move the bypass
valve member 28 on the stem 46.
The stem guide 72 serves to keep the stem 46 coaxial
with the tubular member 80. The guide 72 is annular, having
a cylindrical outside surface disposed in sliding abutting
engagement with the inside of the tubular member 80. An in-
side cylindrical surface of the stem guide 72 is disposed in
sliding abutting engagement with the outside of the stem 46.
The bottom surface of the stem guide 72 receives the upper end
of the compression spring 66 in a shallow cylindrical recess 93.
. ~.
~37~55
-26-
Axial adjustment of the adjusting nut 88 causes a
proportional movement of the bypass valve member 28 along the
stem 46. The adjusting nut 88 is threadably connected to the
stem 46. The adjusting nut 88 abuts the top surface of the
stem guide 72 and may be moved up or down the stem to adjust
the load on the compression spring 66 and yield spring 68.
This regulates the flow of cold water through the bypass
valve 22.
A tool 90 for rotation of the adjusting nut 88 extends
through and sealingly engages the central cylindrical passage
94 in the tubular member 80. The tool includes a pawl 96 at
one end to engage a slot 98 in the head of the adjusting nut
88. The tool 90 is rotatable and axially slidable in a
cylindrical passage 94 through the tubular member 80. The
tool 90 may be disengaged from the nut 88 after adjustment
and moved upward to a position where it wi.ll not interfere
with the up and down motion of the stem 46.
It may be desirable to provide the control valve assembly
10 with an additional adjustment 100 (Fig. 9) to control the
blended hot water temperature at the maximum flow rate. When
the valve assembly 10 is e~uipped with such a gain adjustment
100, the compression and yield springs 66 and 68 are selected
so that the flow ratio of overheated water to cold water into
~3~ S
-27-
the mixing chamber 16 decreases slightly with increasing flow.
With these springs the water leaving the mixing chamber 16 at
maximum flow is at slightly lower temperature than at low flow
rates. The gain adjustment 100 is adjustable to provide an
increased flow of cold water to the heat exchanger to thereby
raise the blending chamber temperature a desired amount.
When the gain adjustment 100 is open, cold water from
the cold water inlet 52 flows through passage 50l needle
valve 101 and passage 102 into the inlet valve chamber 104.
The needle valve 101 includes an axially adjustable
needle 108. A shoulder 120 provides a surface against which
the tapering end portion 122 of the needle 108 may seat.
Rotation of the needle 108 toward or away from the shoulder
120 regulates the flow of water from the cold water inlet 52
to the inlet valve chamber 104 via passage 50 and passage 102.
The housing 82 for the control valve assembly 10 is
composed of four members connected with the controller 36 in
stacked coaxial arrangement. The cap 124 is the uppermost
member. The cap 124 is adapted to engage the threads 85 on
the tubular member 80 to enable axial movement of the tubular
member. A concentric smooth walled cylindrical passage 125
sealingly engages an O-ring 83 in the outside surface of the
7~
-28-
tubular member 80 to prevent water leakage as the tubular
member moves.
The outlet section 126 of the housing 82 includes a
central cylindrical passage which forms the mixing chamber 16.
The upper end of the outlet section 126 sealingly engages the
cap 124. The opposite end of the outlet section 126
sealingly engages the center section 84 of the housing 82.
The cylindrical blended water outlet 20 intersects the mixing
chamber 16 and suitable means are provided to connect the out-
let with conduits leading to the tap 15 for blended hot water
shown in Fig. 1.
The center member 84 (Figs. 3 and 4) of the housing 82
includes suitable means for connecting the cold water supply
to the cold water inlet 52. The outlet 23 from the inlet
valve chamber 104 to the heat exchanger 14 and the inlet 24
for overheated water from the heat exchanger to the blending
chamber 16 are sealingly connected with the corresponding
openings in the heat exchanger.
A shoulder 129 (Fig. 31 on the inside of the center
member 84 separates the inlet chamber 130 from the blending
chamber 16. A second shoulder 131 on the inside of the center
member 84 provides a stop for the inlet valve seat member 75.
The inlet valve seat member 75 is a generally hollow
cylinder. The upper end portion of the inlet valve seat
1~37~5
-29-
member 75 projects radially inward to form the inlet valve
seat 30. During assembly the valve seat member 75 is
inserted into the center member 84. The inlet valve seat
member 75 is held against axial motion by abutting engagement
with the shoulder 131 at one end and the lower stem guide 65
at the opposite end.
The cap 124, the outlet member 126, the center member 84
with the inlet valve seat member 75, and the lower stem guide
65 are all connected with the controller 36 in stacked,
coaxial relationship to form the housing 82 of the control
valve assembly 10.
Another preferred embodiment of the present invention is
illustrated in Fig. 6 in which similar numerals have been
used to indicate similar parts.
The controller 36a operates in much the same manner as
in the previous embodiment. Water pressure from the blended
water outlet 20a is conducted through holes 47a in the tubular
member 80a and down the central passage 44a in the hollow stem
46a to the lower pressure chamber 42a. Water pressure from
the cold water inlet 52a passes to the upper diaphragm
chamber 4Oa through a passage (not shown) substantially the
same as the passage 50 shown in Fig. 3.
1137~S5
-30-
In this second preferred embodiment both valve members
26a and 28a (Fig. 6) are held in fixed axial positions on the
stem 46a. A conical inlet valve member 28a and a conical
bypass valve member 26a are coaxial with the stem 46a and
held against axial movement in a stacked arrangement by
suitable spacer cylinders 202 and 204. The lower spacer
cylinder 202 is effective to maintain a fixed distance be-
tween the inlet valve member 28a and the bypass valve member
26a. The upper spacer cylinder 204 abuts the top of the
bypass valve member 26a and a teflon stem guide 72a. A nut
88a threadably engages the stem 46a and the s-tem guide 72a
and prevents motion of the entire stack relative to the stem.
The range spring 62a urges both the inlet 18a and the
bypass 22a valves to a closed position by urging the stem 46a
upward as viewed in Fig. 6. A lower pressure on the lower
side 42a of the diaphragm 38a than on the upper side 40a
causes the diaphragm and the stem 46a to move downward to
open the inlet 18a and bypass valves 22a. This downward
motion is opposed by the helical range spring 62a which abuts
the lower side of the diaphragm retainer 48a and the housing
end cap 239.
The inlet valve seat 220 forms a movable barrier
between the cold water supply chamber 130a and the inlet
valve chamber 104a. The valve seat 220 is annular in shape
~137~S
-31-
and its cylindrical outside surface 222 is slidably and
sealingly engaged by the central cylindrical passage 222 in
the center member 84a of the housing 82a. One end of a
cylindrical passage 226 through the inlet valve seat 220
provides a circular surface 228 which sealingly engages a
tapering side surface 230 of the inlet valve member 28a when
the inlet valve 18a is closed.
The inlet valve seat 220 floats axially in housing 82a
between a yield spring 68a and a compression spring 66a. The
center member 84a of the housing 82a is provided with an
annular surface 232 which projects radially inward from the
cylindrical passage 2240 The yield spring 68a extends be-
tween the annular surface 232 and an upper surface 234 of the
inlet valve seat 220. The compression spring 66a e~tends
between an opposi-te lower, surface 236 of the inlet valve
seat 220 and an adjusting nut 238 threadably connected to the
stem 46a.
In operation the controller 36a senses the demand for
blended hot water and moves the stem 46a accordingly. Down-
ward motion of the stem 46a moves the bypass valve 22a a like
amount away from the bypass valve seat 32a. This enables cold
water to enter the mixing chamber 16a.
1~378~S
-32-
The inlet valve 18a also opens when the stem 46a moves
downward. Downward motion of the inlet valve member 28a is
accompanied by a proportional downward motion of the inlet
valve seat 220. The position of the movable inlet valve seat
220 is controlled by the yield and compression springs 68a
and 66a in the same manner as the bypass valve member 28
(Fig. 3) of the first preferred embodiment. When the stem
46a (Fig. 6) moves, the inlet valve seat 220 moves downward
a distance that is less than and proportional to the extent
of motion of the stem 46a. This enables water to flow
through the inlet valve 18a, through the heat exchanger 14
and into the mixing chamber 16a.
The amoun-t of water flowing through the inlet valve 18a
is larger than the amount flowing through the bypass valve
22a. This is true despite the fact that in all open positions
the distance between the inlet valve member 28a and the inlet
valve seat 228 is smaller than the distance between the bypass
valve member 26a and the bypass valve seat 32a. The inlet
valve seat 228 has a larger diameter than the bypass valve
seat 32a. Therefore a given space between the inlet valve
member 28a and the inlet valve seat 228 produces a larger flow
rate through the inlet valve 18a than is possible through the
bypass valve 22a with a larger space between the bypass valve
member 26a and the seat 32a.
113~8~5
As the demand for blended hot water varies, the stem 46a
and the inlet valve seat move to regulate the flow of water
admitted to the heat exchanger 14 and bypassed around the
heat exchanger so that a constant temperature of water leaving
the blending chamber 16a may be maintained.
The control valve assembly lOa of the second preferred
embodiment is adjustable at two different flow rates to assure
a uniform temperature of blended hot water at all levels of
demand. The first temperature adjustment is made at low flow
and the second at about 50% of maximum flow. The low flow
adjustment is substantially the same as the low flow adjust-
ment in the first preferred embodiment. The low flow adjust-
ment is made by rotating the tubular member 80a to move it
relative to the bypass valve member 28a. This regulates the
temperature of the blended water by controlling the amount of
cold water in the mixture.
I'he second adjustment is made when the valve stem 46a has
moved approximately one half of its total stroke in response
to demand for blended hot water. To make the adjustment,
adjusting nut 238 is moved axially on the stem 46a to change
the compressive force exerted on springs 66a and 68a. This
moves the valve seat 220 and varies the flow through the
inlet valve 18a.
1137~3~S
-3~-
The adjusting nut 238 which supports the lower end of
the compression spring 66a threadably engages the stem 46a.
A pin 242 extends radially from the nut 238 into a vertically
extending slot 240 in the housing 82a. The pin 242 holds the
nut 238 against rotation relative to the housing 84a. The
valve stem 46a may be rotated using a tool 90a. When the
pawl 96a on the tool 90a engages a slot 98a in the upper end
portion of the stem 46a, it is possible to rotate the stem.
Axial motion of the adjusting nut 238 on the stem 46a
increases or decreases the compressive force exerted on the
yield spring 68a and the compression 66a spring which in turn
causes the inlet valve seat 220 to move relative to the inlet
valve member 26a. This changes the amount of water admitted
to the heat exchanger 14. When the pawl 96a of the tool 90a
engages the stem 46a and the tool and stem are rotated, the
adjusting nut 238 moves up and down on the stem. Regulating
the amount of water entering the heat exchanger 14 regulates
the final temperature of the blended hot water.
The rotation of the stem 46a during the second adjustment
necessitates some means for enabling the stem to rotate while
the diaphragm 38a and diaphragm retainer 48a do not, yet the
means must also be able to transmit upward and downward motion
of the diaphragm to the stem. Such a swivel-joint is shown
generally at 244 and includes a central passage 246 which is
~13'~S
-35-
in communication with the passage 44a through the stem 46a
and with the lower pressure chamber 42a. The swivel-joint
244 is of ordinary design and does not form part of the present
invention.
Figure 6 also shows a second preferred embodiment of a
gain controller lOOa which regulates the temperature of
blended hot water at the maximum flow rate. When the control
valve assembly is used with gain controller lOOa, the springs
66a and 68a and the slopes of the tapering surface of the
inlet valve member 28a are selected so that the temperature
of the blended hot water increases with increasing flow rates.
The gain controller lOOa is adapted to supply cold water to
the blending cham~er 16a to lower the blended water temperature.
The gain controller lOOa includes a needle valve lOla
which regulates the flow of cold water through a passage 252
between the upper 40a and lower 42a pressure chambers. By
opening the valve lOla, cold water flows from the upper
pressure chamber 40a to the lower pressure chamber 42a and
through the central passage 44a in the stem 46a to the blending
chamber 16a. By admitting more or less cold water to the
blending chamber 16a, the needle valve lOla controls the
temperature of blended hot water.
'';
~137~3~5
Either embodiment of the invenkion may also include an
adjustment to regulate the preload on the range spring 62b.
(See Fig. 7 in which similar numerals have been used to
indicate similar parts). If it is desired to provide such
an adjustment, the range spring 62b is located in the lower
diaphragm pressure chamber 42b. The range spring 62b
presses between a lower flat washer 248b which is part of
the diaphragm retainer 48b and an axially adjustable spring
support 254. The spring support 254 has an annular upper
surface 256 which abuts the lower end of the range spring
62b. The lower surface 258 of the spring support 254 abuts
a bolt 260 which extends through an end cap 239b. Rotation
of the bolt 260 causes the spring support 254 to move up or
down to change the preload on the spring 62b.
It may be desirable to provide the control valve assembly
10 with the capability of being connected with a high pressure
steam supply 300 (Fig. 8). This may be accomplished by
utilizing the steam control valve 310 in connection with
control valve assembly 10.
The steam control valve 310 is operatively linked to the
controller 36. Steam is admitted to the heat exchanger 14
through the steam control valve 310 when the controller 36
moves the stem 46 downward in response to initiation of
demand for blended hot water.
11378~i5
-37-
The steam control valve 310 includes three concentric
sleeves 312, 314, 316. The outermost sleeve 312 forms the
body of the steam control valve 310 and is connected with
the lower body member 43 of the control valve assembly 10.
A steam supply 300 is connected at an inlet 318 in the outer
sleeve 312. When the steam control valve 310 is open, steam
passes through the valve and out the steam out]ets 330 and
332 in the outer sleeve 312.
The rotatable middle sleeve 314 cooperates with the
outer sleeve 3l2 to form a manually operable valve. The
rotatable sleeve 314 has a cylindrical outside surface in
sliding abutting engagement with an inside cylindrical
surface of the outer sleeve 312. The rotatable sleeve 314
includes an inlet passage 334 and a pair of outlet passages
336 and 338. The rotatable sleeve 314 may be rotated to a
position where the inlet passage 334 in the rotatable sleeve
314 is in alignment with the inlet 318 in the outer sleeve
312. When the rotatable sleeve 314 is in this position, the
outlet passages 336 and 338 are aligned with the outlets 330
and 332 respectively.
The rotatable sleeve 314 is held against axial motion in
one direction with respect to the outer sleeve 312 by a
surface 350 which pro~ects radially inward on the inside of
the outer sleeve. Axial motion in the opposite direction is
1~3~78S;5
-38-
prevented by abutting engagement of the end 352 with the
rotatable sleeve 314 and the end cap 354.
The rotatable sleeve 314 may be rotated to select the
maximum steam flow through the steam control valve 310. An
axially extending member 356 is adapted to transmit rotary
motion from a tool (not shown) to the sleeve 314. Rotation
of the rotatable sleeve 314 increases or decreases the extent
of overlap or alignment of the inlet 318 and outlets 330 and
332 in the outer sleeve 312 with the inlet passage 334 and
the outlet passages 336 and 338 in the rotatable sleeve.
The member 356 has two concentric end portions. The
upper end portion 358 is permanently connected with the
rotatable sleeve 314 by a transverse pin 360. The lower end
portion 362 has a cylindrical outside surface which is
sealingly contacted by a seal 364. A socket 366 in the lower
end portion 362 is adapted to receive a tool (not shown) to
rotate the member 356 and the sleeve 314.
During set up and installation of the control valve
assembly 10 and the steam control valve 310, hot water
taps are opened to create a large demand for blended hot
water. The rotatable sleeve 314 is then rotated from a
closed position to a partially open position to admit steam
to the heat exchanger 14. The temperature of the blended hot
water is then measured,and if it is below the desired
1~3~8~5
39~
temperature, the rotatable sleeve 314 is rotated to a more
open position. In this way the rotatable sleeve may be
adjusted to regulate the maximum blended water temperature.
The rotatable sleeve 314 acts as a pressure control
valve for the steam flowing through the heat exchanger 14.
For any given flow rate of water through the control valve
assembly 10 and the heat exchanger 14, the rate of steam
condensation within the heat exchanger is constant. This
means that the condensation process is isothermal and also
isobaric. Thus by adjusting the rotatable sleeve 314 to
select the maximum desired water temperature, the maximum
pressure in the heat exchanger 14 may also be selected.
The steam control valve 314 includes lower and upper
frustro-conical valve members 390 and 392 which cooperate
with a pair of circular valve seats 394 and 396. The valve
members are fixedly connected with a valve stem 398. The
valve members 390 and 392 are coaxial and spaced apart so
that when the valve stem 398 moves to its uppermost position
both valves are seated against their respective valve seats
394 and 396.
However, the valve members 390 and 392 may be spaced on
the valve stem 398 so that when one valve is closed a small
amount of steam is permitted to flow through the other valve
to the exchanger 14. This prevents steam pressure from block-
ing downward motion of the controller 36.
~37BSS
-40-
The upper valve seat 396 is formed at the edye of an
annular surface 410 which projects radially inward from the
inner surface of the rotatable sleeve 314. When the upper
valve member 392 is moved away from its seat 396, steam is
enabled to flow through the inlet 318 and the inlet passage
334, through the valve seat 396 and out the outlet passage
338 and the outlet 332.
The inside sleeve 316 has an outside diameter the same
as the inside diameter of the lower portion 412 of the
rotatable sleeve 314. A radially inwardly projecting shoulder
413 located just below the inlet passage 334 (as shown in
Fig. 9) abuts the inside sleeve 316. The inside sleeve 316
is pressed into the rotatable sleeve 314, and once in place
does not move independently of the rotatable sleeve.
The lower valve seat 394 is formed at the edge of an
annular surface 414 which projects radially inward from the
inside sleeve 316. When the lower valve member 390 has been
moved away from its seat 394, steam is enabled to flow
through the inlet 318 and inlet passage 334 through the lower
valve seat 394, through an opening 416 in the inside sleeve
316 and through the outlet passage 336 and the outlet 330.
A bias spring 418 urges the valve stem 398 upward and
the valve members 390 and 392 toward a closed position. The
bias spring 418 replaces the range spring 62 used in other
1~3~ 5i5
-41-
embodiments (Fig.3). One end of the bias spring 418 presses
against the lower end surface 430 of the lower valve member
390 (Fig. 9). The other end of the bias spring 418 abuts
the top 432 of member 356.
A cylindrical recess 436 in member 358 receives the
lower end portion 438 of the valve stem 398 and assures that
it is maintained concentric with the valve seats 394 and 396.
An adjustment is provided to coordinate the action of
the controller 36 with the steam control valve 310. The
upper end 450 of the valve stem 398 abuts a shaft 452 which
is threadably received in the central passage 44 of the stem
46 of the control valve assembly 10. The shaft 452 is
coaxial with the stem 46 and rotation of the shaft is effec-
tive to increase or decrease the distance between the lower
end of the stem 46 and the upper end of the valve stem 398.
In operation, the diaphragm controller 36 senses demand
for blended hot water and ~ctuates the stem 46 downward an
amount proportiorlal to the demand. Downward motion of the
stem 46 is transmitted through shaft 452 to the steam valve
stem 398 which moves downward and enables steam to flow
through the steam control valve 310 into the heat exchanger
14. The movement of the valve stem 398 thus follows the
demand for blended hot water, increasing the amount of steam
admitted to the heat exchanger in response to increases in
demand.
113~ 5
-42-
As previously noted, the rotatable sleeve 314 regulates
the maximum flow of steam -through the steam control valve
310. This means that the rotatable sleeve also regulates
the pressure drop between the inlet 318 and the outlets 330
and 332 to the steam control valve 310.
The action of the stem 398 and the valve members 390
and 392 further regulates the steam flow rate through, and
the pressure drop across, the steam control valve 310. The
pressure drop across the steam control valve 310 is maximum
when the valve stem 398 is in its uppermost position and
valv~s 390 and 392 are in sealing engagement with seats 394
and 396 respectively. As the valve stem 398 moves downward
in response to increasing demand, the pressure drop across
the steam control valve 310 decreases until it reaches the
lower limit established by the rotatable sleeve 314.
Thus it is clear that the present invention provides a
new and improved control valve assembly 10 for use in a
blending hot water heater (Fig. 2). The flow of cold water
into the valve assembly 10 is split, a portion of it flowing
through an inlet valve 18 into a heat exchanger 14, and a
portion of it flowing through a bypass valve 22 into a mixing
chamber 16. Overheated water from the heat exchanger flows
into the mixing chamber 16. The relative flow of rates cold
water and overheated water into the blending chamber 16 are
~137855
-43-
regulated by diaphragm actuated inlet and bypass valves 18
and 22.
Both the inlet and bypass valves 18 and 22 are poppet-
type valves which inherently require little maintenance. se-
cause no tight fitting machined surfaces slide on one another,
there is little tendency for corrosion to be a problem.
Furtherr the overheated water from the exchanger 14 never
flows through a flow regulating orifice, and consequently the
dangerous tendency for the flow of hot water to choke itself
off and raise the heat exchanger pressure is not present.
The ratio of the flow of water bypassed around the heat
exchanger 14 to the flow through the heat exchanger is con-
trolled by a controller 36 including a diaphragm 38 which
actuates a valve stem 46 (Figs. 2 and 3). A pressure drop
caused by an increase in demand is sensed by the diaphragm
38. The valve stem 46 moves an amount which corresponds to
the size of the clemand increase and opens one of the poppet
valves 18 and 22 a like amount. The other valve also opens
when the valve stem 46 moves, but the extent of opening is
adjusted to compensate for changes in the pressure drop
across the heat exchanger 14 and in the temperature of the
water leaving the heat exchanger, both caused by the changing
flow rate.
113~ i5
-~4-
Two adjustments are provided to assure that the blended
water temperature is very nearly constant over a wide range
of demand. A first temperature adjustment is made when the
demand for blended hot water is small (Fig. 5). The
amount of cold water admitted through the bypass valve 22
into the blending chamber is adjusted by moving a bypass
valve seat 32 toward or away from the bypass valve member
28 until the desired blended hot water temperature is
achieved.
The second adjustment is made when the flow is about
50% of capacity (Fig. 6). In one preferred embodiment a
pair of opposing springs 66 and 68 supports the bypass valve
member 28. The e~tent of compression of the springs 66 and
68 is changed to cause the valve member 28 to move toward or
away from the bypass valve seat 32 and thus to regulate the
amount of cold water admitted to the blending chamber 16 at
50~ flow.
In addition the present invention includes a steam
control valve 310 (Fig. 8) operatively connected with the
controller 36 to regulate the flow of steam through the heat
exchanger 14. The steam control valve 310 includes a
variable orifice which is manually adjustable to select the
maximum flow rate of steam through the heat exchanger 14.
The steam control valve also includes poppet valves 390 and
3~2 which vary the flow of steam in response to variations
1137~
-45-
in demand between no steam flow at no demand conditions
and the maximum steam flow established by the manually
adjustable orifice at maximum demand conditions.
