Note: Descriptions are shown in the official language in which they were submitted.
CA 02352899 2001-07-20
FIELD OF THE INVENTION
Steam generating apparatus for providing live steam to a
shower or other enclosed area to create a steam room.
This application is a division of copending Canadian
Application Serial No.: 2,155,478, filed August 4, 1995.
BACKGROUND OF THE INVENTION
Heretofore steam generating apparatus had taken the form of
relatively large floor-supported units that were housed at a
location remote from the shower or other steam room, such as in a
closet, an attic or a basement. The unit provided, through an
elongated steam line or hose, a supply of live steam into the
room. The line could be quite long, such as 50 feet, which would
result in substantial heat loss. The user might have to control
the unit from the unit itself at the remote location. Further,
the unit would take up space and could not be put too close to
certain.structure or objects because of the high temperature of
1.5 the boiler of the unit.
The control of such unit was generally very basic, i.n tOat
the user-set temperature was generally maintained, but it was
based on monitoring and then turning the steam generator on and
off in reaction to changes in the room temperature, which
2U resulted in noticeable cyclical fluctuations in temperature above
and below that set temperature. Also the sound of the teat
generation going on and off were noticeable and made the
temperature variations more noticeable. This lack of a constant
temperature and sound level detracted from the tranquility and
25 enjoyment of the steam room.
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CA 02352899 2001-07-20
Another problem encountered by use of such units was fogging
over of mirrors in the shower or steam room. Various defogging
mirrors have been used, but they were costly, complex or both.
One prior art attempt to solve the problem is illustrated in U.S.
Patent No. 4,150,869 which discloses a special apparatus that
caused heated water or steam to flow continuously over the rear
of a shower mirror to warm it. A similar approach is disclosed
in U.S. Patent Nos. 4,993,821, 4,836,668, 4,557,003, 4,904,072
and 5,032,015. U.S. Patent No. 4,076,374 discloses a device
which uses a continuous flow of'heated water over the front face
of the mirror. Such an arrangements are also subject to clogging
and other maintenance problems associated with flow devices.
U.S. Patents No. 3,708,218 and 4,556,298 disclose devices that
run heated water through special coils located behind the
mirrors.
SUMMARY OF THE INVENTION
In accordance with one embodiment of the present invention
there is provided a wall-mounted steam fixture comprising: a
frame for being mounted on a first side supporting wall of a
closed area which has a floor, a ceiling and a plurality of side
walls and into which steam may be introduced to provide a steam
room area, the frame having an upright wall section that provides
a front face which is generally aligned with the first side wall
when the frame is mounted and which has a front face that is
directed into and accessible from within the steam room area, a
mirror mounted on the upright wall section of the frame, the
mirror having a front surface directed into and exposed to the
steam room area and a rear surface facing the opposite direction,
a steam generating unit supported on the frame, and a steam line
connected to the steam generating unit for directing steam from
the mounted steam generating unit into the steam room area, the
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steam generating unit including a closed boiler that is
disposed adjacent to the rear surface of the mirror so as to
radiate heat to the rear surface and thereby limit fogging of
the front surface of the mirror by the steam in the steam room
area when the fixture is mounted.
In accordance with another embodiment of the present
invention there is provided a thin compact wall-mountable
essentially self-contained steam generating fixture comprising:
a frame mountable in a first side support wall of an enclosed
steam room having a floor, a ceiling and a plurality of side
walls, the frame having an upright porcelain face section for
being generally aligned with the first side wall when the
fixture is mounted, the frame having a front-to-rear depth of
no more than about four inches, so as to fit generally within
a standard wall, and a width of no more than about fourteen
inches to fit in the space between a pair of standard spaced
vertical wall studs, and a closed boiler tank unit supported
generally within by the frame, the unit including electrical
heating coils, a steam delivery line connected to the boiler
tank unit for transporting steam from the boiler tank to the
interior of the steam room, an electrical regulating system
connected to the heating coils for regulating the operation of
the heating coils and thereby the temperature in the steam room
area, manually operable controls connected to the regulating
system for selecting the desired temperature for the steam room
area.
In accordance with a further embodiment of the present
invention there is provided an improved steam head comprising:
a support portion for being mounted to a support wall, an
elongated intermediate portion having opposed rear and forward
ends, the rear end being fixed to the support portion, the
intermediate portion extending forwardly from the support
portion, and an outer steam dispensing portion fixed to the
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forward end of the intermediate portion and extending at least
in part radially outwardly beyond the intermediate portion, the
steam dispensing portion having a rearwardly facing dispensing
surface disposed radially outwardly of the intermediate
portion, the intermediate portion having an internal passageway
therealong, the steam dispensing portion having an internal
cavity in fluid communication with the passageway, the support
portion having an opening for communicating both with a supply
of steam and with the intermediate portion passageway for
introduction of steam into the steam head, the rearwardly
facing dispensing holes dispensing surface having a plurality
of spaced-apart steam.
30
3a
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A steam generating apparatus or unit for providing steam
into a shower or other enclosed steam room 22. The illustrated
unit is in the form of a thin compact self-contained fixture 20.
The fixture 20 has a mirror 24 and is adapted to be a wall-
mounted to position the mirror at face height of a standing user.
The fixture 20 is narrow enough to fit between a standard-spaced
pair of vertical wall studs 26. The illustrated fixture 20 is
also very thin, having a front-to-back dimension of less than
about four inches, which allows it to be contained within a
normal wall of a steam room.
The illustrated fixture 20 has a porcelain front face
section 28 that may be sealed to a steam room support wall 23.
The unit 20 has an electrical control system 30 which is user-
operated from a control panel 31 on the front face section 28.
The illustrated unit 20 includes a frame or housing 32 fixed
to the rear of the face section 28 for being generally disposed
within the wall 23. The frame 32 supports a steam generating
boiler 34 that has a steam line 36 leading to a steam head 38 in
a wall of the steam room. Preferably the steam head 38 is
located close to the fixture, as in the same support wall 23, to
minimize the length of the steam line 36 and reduce heat loss.
The boiler 34 is located adjacent to the exposed rear of the
mirror 24 so that heat radiated from the boiler warms the mirror
and inhibits steaming over of the mirror. A small gap separates
the mirror from the boiler to prevent overheating of the mirror.
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The illustrated steam head 38 has a novel and improved
design. It may be made of porcelain or the like to limit its
heat absorption and thus its heated temperature. The steam flow
is reversed in the steam head 38 so that it is directed
rearwardly away from the interior of the room and back against a
steam guard surface 40 aligned with the wall that supports the
steam head. Thus, there is no direct flow of the live steam
outwardly into the room. This arrangement also reduces the noise
level of the entering steam. Further, directing the steam
against steam guard protects the adjacent areas of the supporting
wall.
The illustrated electrical control system 30 greatly
improves the temperature maintenance ability of the fixture 20 by
determining and then maintaining an effectively generally steady
level of power input to the boiler 34. As a result, instead of
the temperature cyclically varying as much as 1 1/2-2°
Fahrenheit, which is readily noticeable by the users (especially
when accompanied by intermittent steam generation), the variation
is reduced to a non-noticeable span of about 1/2° Fahrenheit.
Further, during a steam session, the effective power level
provided to the heating coils of the steam boiler maintains the
heat level of the coils so as to maintain generally continuous
steam generation. This also avoids disturbing sounds caused by
the coils cooling substantially and then reheating.
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IN THE DRAWINGS
Figure 1 is a schematic perspective view of a prior art
steam bath generator.
Figure 2 is a schematic perspective view of a steam room
with a steam generating fixture installed therein, the fixture
embodying a presently preferred form of the invention.
Figure 3 is a schematic front elevational view showing the
fixture of Fig. 2 mounted on a wall between vertical studs.
Figure 4 is a schematic side elevational view of the wall
studs and fixture of Fig. 3.
Figure 5 is a schematic front elevational view of the
fixture, with portions broken away to show details of
construction.
Figure 5A is a schematic side elevational view of the
fixture.
Figure 5B and 5C are schematic side elevational views of the
flow control means of the fixture.
Figure 5D is a schematic front elevational view of the
fixture showing the heating coils.
Figure 6 is a schematic diagram of the electrical control
system of the fixture.
Figure 7 is a graph showing heat vs. power levels for prior
art systems.
Figure 8A is a graph showing reported temperature vs. power
level during start-up of the fixture of Figs. 2-6.
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Figure 8B is a graph like Fig. 7, but showing operation of
the improved fixture of Figs. 2-6.
Figure 9 is an enlarged schematic side section view of the
steam head and the steam pipe of the fixture, and a portion of
the supporting wall.
Figure 10 is a schematic front view of the steam head of
Fig. 9.
Figure 11 is a schematic sectional view taken generally
along line 11-11 of Fig. 9, showing of the rearward facing steam
outlet of the steam head.
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DETAILED DESCRIPTION OF THE DRAWINGS
PRIOR ART
Figure 1 illustrates a common prior art form of steam bath
generator "G." Such units were characteristically basic black
box units designed to be floor mounted at some location remote to
the shower or other steam room facility, such as in a closet, an
attic, a basement or a vanity under a sink. The steam outlet
line might be very long, e.g., 50 feet, to accommodate the remote
location. A typical unit is 8 inches wide by 20 inches long by
15 inches high. Typically, the unit would include a simple timer
that also acted as the on/off switch and possibly a temperature
and/or time control.
PRESENTLY PREFERRED FORM OF THE INVENTION
Figure 2 illustrates schematically an enclosed steam room 22
and portions of the steam generating fixture 20 mounted in a
support wall 23 of the room, the fixture 20 comprising a
presently preferred form of the present invention.
As noted above, and shown best in Fig. 4, the illustrated
fixture 20 is quite thin, somewhat less than about four inches
front-to-back. This allows it to fit within the usual supporting
wall. The frame 32 of the illustrated fixture 20 has a width of
about 14 inches, which allows it to be mounted (by suitable
support means such as nails or screws not shown) in the
approximately 14.5 inch space between a pair of standard-spaced
upright vertical studs 26 in the supporting wall 23 of the steam
room 22. Figure 3 shows the tile covered wall 23 cut away to
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CA 02352899 2001-07-20
reveal the location of the studs 26. The illustrated fixture
20 includes the generally rectangular front face section 28 which
supports the mirror 24 and the user-operable control panel 31.
The fixture 20 is mounted at a height placing the mirror 24 at
the height of the head of a user standing in the steam room.
As shown best in Figure 5A, the front face section 28
supports the frame or housing 32 that is generally a rectangular
box made of metal or the like. Within that housing 32 the thin
steam tank or boiler 34 is mounted. As shown in Fig. 5D, the
tank 34 contains electrical resistance heating elements or coils
41 that are energized to heat water in the tank to produce steam.
The steam tank 34 is connected intermediate its height to an
incoming water line 42 that is connected to the facility water
supply. Flow control means 43 automatically maintain the desired
water level in the tank 34. The tank 34 is also connected
adjacent its top to the outgoing steam outlet line 36 that leads
to the steam head 38. The steam head 38 may be mounted at a
desired location in a wall of the steam room. Preferably the
steam head 38 is located as close as feasible to the fixture 20.
The fixture 20 is connected by a high power line 46 to the
electrical power supply of the facility that provides the
electrical energy for the heating coils 41 and the control. system
30.
More particularly, the front face section 28 is a generally
flat rectangular plate that is rounded off at its corners. It
may be made from porcelain or like material that is suitable for
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CA 02352899 2001-07-20
a shower or steam room. Other materials such as natural marble
or granite or man-made synthetic materials such as high
temperature resistant plastic may also be used. Such materials
do not readily absorb heat and therefore do not attain high
temperatures as would metals. Such materials are therefore
preferred for safety reasons. When face section 28 is mounted on
the steam room wall 23, it is generally aligned with the wall.
The face section 28 may be sealed around its edges to the
adjacent surface of the wall 23 as with a silicone seal that can
withstand high temperatures. This prevents moisture from leaving
the steam room and adversely affecting the structural integrity
of the wall or areas beyond the wall.
A large generally rectangular centered opening 48 is
provided in the face section 28 for receiving the forwardly
facing mirror 24. The illustrated mirror 24 is generally
rectangular, being rounded at its corners. The opening 48 is
generally the same shape, and the mirror 24 is sealed to the face
section 28 as by means of a double-sided adhesive gasket that is
resistant to high temperatures. Alternatively, the mirror and
opening might be oblong or some other suitable shape.
The generally rectangular housing or frame 32 is fixed to
the rear of the face section 28 by any suitable means such as
screws (not shown). The frame 32 may be of any suitable rigid
material such as steel or metal alloy.
The generally rectangular steam tank or boiler 34 is mounted
in the housing 32 immediately behind the mirror 24. As noted
CA 02352899 2001-07-20
above, the tank 34 and the housing 32 are both quite thin so they
normally fit within the confines of a standard wall. The heating
coils 41 are located at the bottom of the tank 34 and are
connected through the electrical control system 30, to the source
of electrical power. As shown by the cut-away section of Fig.
5A, the rear of the mirror 24 is exposed to the adjacent wall 34a
of the steam tank 34 so that the heat from the tank will radiate
outwardly against the rear of the mirror and thereby heat the
mirror to inhibit fogging of the front of the mirror. In the
illustrated fixture 20, the rear of the mirror 24 is spaced about
1/8 inch to about 1/16 inch from the adjacent face 34a of the
tank. This creates an in space that prevents the mirror from
becoming too hot and dangerous to touch.
In the illustrated fixture 20, the water level "L" in the
tank 34 is maintained about half way to the top as shown in Fig.
5. The illustrated tank 34 uses about three quarts of water.
As shown generally in Fig. 5, the mechanical water flow
control means or mechanism 43 that controls the flow of fresh
water into the tank 34 from the water inlet line 42, is located
at the inlet 50 from the inlet line 42 at about midway up the
height of the tank. The flow control means 43 includes a
mechanical valve mechanism 53 that is located in the inlet 50 and
is operable to open and close that inlet. The flow control means
43 also includes a cylindrical floater 52 that rides at the
surface of the water in the tank 34 and is connected through an
offset crank arm 54 to the valve mechanism 53. Vertical movement
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of the floater 52, caused by changes in the tank water level "L,"
operates the valve mechanism 53 at the inlet 50 to regulate the
inflow of fresh water into the tank 34. Each time the level of
water in the tank 34 goes slightly below a predetermined level,
the floater 52 thereby drops sufficiently to actuate the valve
mechanism 53 to allow additional incoming water to flow into the
tank to maintain the desired level. This control is quite
sensitive, reacting to a change in the water level of about one-
sixteenth of an inch. Thus, there is a generally steady,
constant, limited tear drop or trickle flow of water into the
tank. The sound of this flow is not noticeable to the users.
More particularly, as shown in Figs. 5B and 5C, the valve
mechanism 53 has a tubular housing 55 which is connected to the
inlet 50 of the inlet water line 42. An O-ring 56 is supported
within the housing 55. A generally disc-shaped valve 57 is
located in the housing 55 upstream of the O-ring 56. As shown in
Fig. 5B, when the water level L is at the desired level, the
valve 57 is upright and urged against the O-ring 56 to close the
valve mechanism 53 and block the flow of water past the O-ring
56. In this connection, the disc valve 57 is fixed on the end of
the arm 54 and urged into sealing engagement with the O-ring 56
by a compression spring 58 and line water pressure. The end of
the arm 54 opposite the floater 52 is connected at 61 to the
spring 58 to allow pivoting of the arm about this connection 61.
Figure 5C illustrates what happens when the water level L in
the tank 34 drops. When the weight of the floater 52 overcomes
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the forces of the water line pressure and of the spring 58, the
floater 52 moves downwardly and the arm 54 tilts, pivoting at the
connection 61 with the spring 58. This tilts the valve 57 to
separate the lower portion of the valve from the O-ring 56 to
allow flow of water past the O-ring and through the exit 6o into
the tank 34. When the level L reaches the desired level in Fig.
5B, the valve 57 again seats against the O-ring 56 to block
further flow. An adjusting screw 62 may be provided to adjust
the force exerted by the spring 58 to afford the desired valve
opening in response to the water level dropping.
The electrical control system 30 regulates the power to the
heating coils 41. The coils 41 heat the water in the tank 34
above the boiling point and cause steam to be generated in the
upper portion of the tank. This steam then flows through the
steam outlet line 36 to the steam head 38 and into the steam room
22.
The steam head 38 is desirably located as near as feasible
to the fixture 20 as this reduces the length of the steam outlet
line and resultant heat loss. It is preferred that the length of
the outlet line 36 be less than about 10 feet, but in any event
on over about 15 feet.
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Figures 6 illustrates schematically the electrical
control means 30 of the illustrated steam generating fixture 20.
In general, after initial start up and an equilibrium situation
has been achieved, for the duration of the steam bath session the
power delivered to the heating element 41 is maintained at an
effectively generally constant level which the control means has
determined will produce the correct amount of heat to keep the
steam bath at the user selected temperature. A generally
continuous flow of steam into the steam room is also maintained.
In this respect, the illustrated fixture 20 provides a
significant improvement over prior art systems. In such prior
art systems, the unit would operate intermittently, being on full
blast, then off for maybe 10 to 15 seconds, and the on again full
blast. The cycle would repeat until the end of the steam bath
session. For example, if the user set the desired temperature at
100°, Fahrenheit, the old system would provide steam at maximum
output or full "on." When a temperature of approximately 100°
was reached, the power would be cut off but the steam unit would
continue to produce steam potentially raising the temperature to
possibly 102°.
The temperature of the steam bath would then begin
decreasing due to various heat losses, which would be noticeable
to the users, particularly because they could see and hear that
the unit was no longer generating steam. Assuming that the set
point to resume heating was 99°, as the temperature reached that
level, full power would again be applied to the steam unit.
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After a brief delay, during which the temperature continued to
fall, the steam production would begin and the temperature would
rise again. This temperature fluctuation, accompanied by the
intermittent operation of the unit would be very noticeable to
the user and would detract from the desired, calmed, relaxed
atmosphere of a steam bath. This fluctuation is illustrated in
Fig. 7.
In the illustrated fixture 20, the control means 30 provides
effectively continuous, at least partial power to the heating
coils throughout the steam session, and thus, generates a flow of
steam that is generally uninterrupted and non-disturbing to the
users. As noted above, after start up, the control means 30
maintains an effective averaged level of power delivered to the
heating element 41 to keep it at a generally constant temperature
as is necessary to maintain the user indicated temperature level
in the steam room. Although small variations in the power level
may be necessary to maintain that desired temperature, the user
would not be aware of such variations, and is spared the large
and noticeable temperature swings, and accompanying changes in
sound level, of the prior art systems. Another advantage of
always maintaining at least partial power to the heating coils
throughout the steam session is the avoidance of popping sounds
produced as the heating element or coil expands and contracts as
it cools and reheats.
Tn general, at the control panel 31, the user first selects
the temperature desired for the steam bath session. Then the
CA 02352899 2001-07-20
control means 30 automatically determines, as described in detail
below, the correct effective power level for the heating coils to
maintain the user preset steam room temperature. This may
involve some trial and error, initially trying an effective power
level and then adjusting that level as necessary. Several
adjustments may be required. Finally the control means
essentially maintain that determined effective power level to the
heating coils 41 throughout the steam bath session. If the steam
room temperature does change, as if a door is left open, the
control means 30 will automatically make an adjustment in the
power level. The fixture 20 never stops producing steam and no
changes in temperature or sound are experienced or noticed by the
users.
The control means 30 thus takes into account a variety of
factors which influence the temperature in the steam room such as
the steam room materials, the level of insulation, the external
environment, the amount of leaking in or out between the steam
room and the environment, the number of users of the steam room,
the siza of the steam room, etc., etc. The control means
accommodates all of these factors for a particular steam room and
the device can be calibrated so that settings can represent
temperature. Figure 6 illustrates in detail the apparatus and
circuitry for achieving this control of the heating coils 41 and
the temperature in the steam room.
A microprocessor 102 controls the heat output of heating
element 41 by controlling a solid state relay or triac 106. This
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relay 106 controls the voltage waveform across heating element 41
by blocking that portion of the a.c. waveform which is above a
predetermined "maximum voltage" dictated by the microprocessor
102 in response to a setting at the control panel. The heat
produced by the heating element 41 is inversely related to the
proportion of the voltage waveform blocked.
A preselected desired "set point" temperature is manually
chosen by the user at the control panel 31 and the setting is
processed and stored by the microprocessor 102. The
microprocessor 102 also receives a continuous flow of actual
temperature readings from a thermistor 110 that represents
current temperature in the steam room. As will be explained in
detail below, the microprocessor 102 uses this flow of actual
temperature readings relative to the set point temperature, to
regulate the average power to the heating element 41 so as to
stabilize and maintain the steam room temperature at the set
point temperature.
The microprocessor 102 can calculate the rate of temperature
change as a function of applied power. For example, if the
maximum power to the heating element results in a temperature
change of 1/4°/minute, and the system generates steam for
approximately 1 minute after power is cut off, then the
microprocessor could reduce power when the difference between the
actual and desired temperature is 1/2°.
The solid state relay or triac limits the portion of the a-c
cycle during which power is applied to the heating element 41.
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Since that power can range from 0-100% of available power, an
appropriate setting can maintain the difference between the
desired temperature and the measured temperature at 0° or close
to it. If the applied power is insufficient to maintain the
temperature at the desired level, the average power can be
incrementally increased or decreased until the temperature level
is held constant.
The thermistor 110 used in the present embodiment has a
resistance of 10 K~s at 72° F which drops by approximately 100 ~s
for every degree increase in temperature. The circuitry which
includes first, second and third resistors R1, R2, R3, R4 and R5;
potentiometer 114; first and second operational amplifier OA1 and
OA2: and analog to digital converter (A/D) 112 is all designed to
translate this changing resistivity into an eight bit word which
is periodically applied from the A/D converter 112 into the
microprocessor 102.
To obtain a voltage representative of resistance, the
thermistor 110 is placed in series with the first resistor R1 to
form a voltage divider, one end of which is connected to a power
supply, in this case a voltage regulator with 5.OV d.c. output.
The voltage at the ungrounded end of the thermistor 110 is a
function of the resistance of the thermistor 110 and the
resistance of the first resistor R1. Therefore, this voltage
varies with temperature, just as the resistive value of the
thermistor 110 varies with temperature. This voltage is isolated
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by the first Operational Amplifier OA1 and sent to the A/D
converter 112.
The range of temperatures represented by the 8 bit serial
word output of the A/D converter 112 is determined by the inputs
to the "lower limit" and "higher limit" inputs of the converter.
The "upper limit" voltage is maintained at approximately 3.3
volts, representing a temperature of 66° from the voltage
divider, composed of fourth and fifth resistors, R4 and R5, along
with a potentiometer, 114. The potentiometer 114 is set at the
factory so that a temperature of 66° sensed by the thermistor 110
registers as the highest value word from the A/D converter 112.
Higher temperatures would not be encountered because of safety
systems that would cause a system shutdown. The voltage produced
by this circuitry is isolated by a second operational amplifier
OA2.
The "lower limit" is maintained at 1.2 volts by the voltage
divider of second resistor R2 and third resistor R3. These
values are set so that a temperature of 130°F will register as
the lowest value word from the A/D converter 112.
Therefore, the serial word output by the A/D converter 112
is inversely related to the temperature sensed by thermistor 110
with its minimum value (all zeroes) representing a temperature of
130°F and its maximum value representing a temperature of 6G°F.
In the present embodiment, the smallest change in temperature
which can be reported is .25°, the value represented by the least
significant bit of this word.
19
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Method of Control
FIG. 8A is a graph of the steam bath temperature as reported
by the analog-to-digital convertor (A/D) and power level to the
heating element versus time during start up operation of the
steam bath. At the beginning of a steam bath session full power
is commanded so that the room will warm up as quickly as
possible. Normally, steam is produced in from three to five
minutes, after which the temperature increases. The rapid rise
in temperature during the beginning time in FIG. 8A reflects
this. In the preferred embodiment, the temperature measurements
are quantized to 1/4 degree by the A/D.
4Jhen a first predetermined temperature, near the desired
temperature, ("near point temp") is registered by the A/D 112,
the microprocessor 102 reduces the power delivered to the heating
element 41. Each time an incremental increase in temperature is
registered, the power is decreased by the following amount:
~Pow = Full Power - Set Point Power * D Temp
Set Point Temp - Near Point Temp
The "Set Point Power" is a predetermined power level chosen
to stabilize the temperature at the set point temperature
commanded by the user. This value may be experimentally
determined at the factory. The incremental power decreases
yielded by the above equation are designed to result in "Set
Point Power" just as the temperature set point is reached, as
shown in FIG. 8A. Once the "Set Point Power" is set accurately,
CA 02352899 2001-07-20
the heat input from the steam should balance the heat loss from
all sources. The temperature should then remain at the set point
temperature indefinitely.
Until the system has been calibrated, there is a good chance
that "Set Point Power" will not be set accurately. If for
example there is no usage history available, for instance, "Set
Point Power" may be just a "guess" which is set at the factory at
"one half" power. The microprocessor can store a value of set
point power, which may be changed if that value is insufficient
to maintain temperature under different conditions. Once the
system has been calibrated, the control panel settings will
accurately reflect desired temperatures.
A preferred embodiment, the control panel 31, allows one or
more users to record a certain set of steam bath settings into
memory. As an example, a first user may prefer a steam bath that
lasts for 25 minutes at a temperature of 105°F. These values may
be stored in the microprocessor for later recall by the pressing
of a button.
The "Set Point Power" can be changed by the control means
during the steam bath so that accurate control of the power and
temperature may be achieved. When the temperature is below the
set point, for instance, the microprocessor 102 can compute the
rate of change of temperature over a predetermined period of
time. When the temperature difference between the desired
temperature and actual temperature reaches a predetermined value,
the power level is reduced, which reduces the rate of change of
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temperature. As the differential approaches zero, the power can
be further reduced to a level at which equilibrium is reached.
This value would be considered the "Set Point Power."
Without a history of temperature readings over time, the
flexibility of a variably controllable heater element is largely
wasted. This is because a single instantaneous reading of the
temperature yields little information to guide the adjustment to
the heating element that should be performed. For instance, if
the temperature were slightly below the user defined "set
temperature" and declining rapidly, it would be advisable to
increase the power to the heating element. But if the
temperature were at the exact same mark, but increasing rapidly,
it would be advisable to decrease the power to the heating
element so that the "set point" temperature would not be severely
overshot. Without a history of temperature readings over time it
is generally impossible to say in what way the power to the
heating element should be adjusted.
Furthermore, because of the great variety of different
environments in which the steam bath could be installed, it would
be impossible to design ahead of time a scheme that would work
for all of these environments if only a single temperature
measurement were available at any particular time. For a very
large, poorly insulated enclosure, the power to the heating
element could be modified greatly with only a slow effect on the
temperature in the steambath. Whereas, with a small, well
insulated enclosure, any change in power might cause a very rapid
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CA 02352899 2001-07-20
response in the steam bath temperature. A history of temperature
measurements over time would reflect the various environments.
Without this information it would be impossible for the designer
to anticipate any particular environment.
If, however, the temperature is rising so rapidly that it is
likely to rise above the set point even after. power has been
reduced, then the "Set Point Power" variable is reduced.
The microprocessor 102 also controls the system when a user
merely wishes to take a shower. In this mode, the boiler tank 34
behind the mirror is heated to~maintain a temperature above the
dew point, thereby keeping mirror fog free. To do this, the
microprocessor 102 turns on the heating element 41 at full power
for a predetermined time, one minute in a particular embodiment.
The heating element 41 is then turned off for 10 seconds and,
thereafter approximately one third full power is applied to the
heating element 41, which should maintain the temperature of the
mirror above the dew point.
As in any device, there is some danger that, due to a
malfunction, the heating element 41 could be energized at a time
the water tank is empty. A temperature sensitive safety switch
116 is included in the circuitry as a safeguard against that
eventuality. The switch is positioned to detect excess heat
above the boiling temperature of water. The switch 116 responds
to excess heat by opening the circuit, removing all power from
the heating element 41.
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CA 02352899 2001-07-20
A transformer 118 combined with rectifier 120 and voltage
regulator 122 receive high voltage (220v) power through line 46
and provide isolated and low voltage power that is delivered
through low voltage line 47. This low voltage output of the
voltage regulator 122 is used to run all of the solid state
circuits of the steam bath. An LED display 124 is also provided
next to the control panel 31., to report to the user, the elected
steam bath temperature, and duration and to report measured
temperature and elapsed time to the user during the steam bath.
All of the electrical components used for the steam bath
control means are widely available in many different varieties.
The suitable microprocessor 102 is available from Microchip, Inc.
with the model designation 16C64. A suitable analog to Digital
converter is supplied by National Semiconductor as Model No.
ADC0831CCN.
Figures 7 and 8B show the improvement of the current system
over previous steam bath control systems. FIG. 7 shows a
temperature and power versus time graph for a previous system.
Note the fairly large swings in temperature and power. FIG. 8B
shows the same graph for the system as described herein. Note
the far smaller swings in temperature.
Figures 9 through 11 illustrate the improved steam head 38
utilized in the fixture 20. The illustrated steam head 38
includes a steam guard portion 56 which may be mounted against
the front surface of a steam room supporting wall "W". The steam
guard portion 56 provides the annular forwardly facing steam
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CA 02352899 2001-07-20
guard surface 40. The steam head 38 also includes a steam outlet
portion 58 that provides the rearwardly facing steam outlet 39.
(See Fig. 11.) Both the illustrated steam guard portion 56 and
the steam head portion 58 are generally circular or disk shaped.
Alternative shapes such as oblong or multisided could also be
utilized.
A central hollow tubular intermediate conduit or hub portion
60 with a passageway 61 extends forwardly from the steam guard
portion 56 to the steam head portion 58. As shown best in Fig.
9, the steam pipe or line 36 leading from the steam tank 34
extends through a central opening in the steam guard portion 56
and communicates with the passageway 61 through the conduit
portion 60.
Steam from the line 36 flows through the passageway way 61
into a hollow interior or manifold 62 of the steam outlet portion
58. The forward face 64 of the steam outlet portion 58 is solid,
however, the annular inward or rearwardly facing steam outlet 39
has a series of small circular steam outlets or openings 66 as
shown in Fig. 11. The steam outlet 39 faces the steam guard
surface 40. Thus, the steam is essentially reversed in the
direction of its flow so that it flows back against the annular
steam guard surface 40. This protects the supporting wall "w."
An acrylic or fiber glass wall would be directly damaged by the
steam flow, and the grout of a tile wall would be stained and/or
cracked. After it is deflected by the steam guard surface 40,
CA 02352899 2001-07-20
the steam flows outwardly and forwardly around the edges of the
steam outlet portion 58 into the steam room.
The illustrated steam head 38 is formed as a single integral
porcelain part for convenience of manufacture and assembly. As
noted above, use of such material, which does not become overly
hot when subjected to the high temperature of the live steam,
limits potential harm to the users should they accidentally touch
the steam head. The emerging steam is very hot, e.g., 211-212°
Fahrenheit. Such steam would heat metal, which is a heat sink,
to around 200° Fahrenheit. The porcelain will only be heated to
about 150° Fahrenheit.
The steam guard portion 56 may be suitably sealed to the
supporting wall "w" as by a high temperature silicone sealing
material to limit steam escaping from the steam room. The
illustrated steam head 38 may include a fragrance reservoir 68
formed adjacent the top edge of the steam guard portion 56 for
holding a quantity of fragrance which may be vaporized by the
heating of the live steam.
Various modifications and changes may be made to the
illustrated structure without departing from the spirit and scope
of the invention as set forth in the following claims.
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