Note: Descriptions are shown in the official language in which they were submitted.
2 1 2 9 3 ") 1
1 -
Switching Device for Instantaneous Water Heaters
The present invention relates to a switch device for flow
h~aters having a sensor device for the flowing water associated
with a water flow conduit and to which a switch unit for a
heating device provided for heating the water ls connected.
In practice, at the present time flow heaters are generally
used in which the switch device detects a drop in the pressure
in the conduit traversed by the water which takes place upon the
opening of an outlet valve (water faucet) and is used to
activate a switch or, in general, a switch unit for the water
heating device. Specifically, there is provided for this a
diaphragm, for instance, of rubber or of sheet metal, on which
there is arranged a stem, for instance, switches a microswitch,
a control circuit, or pairs of contacts in the load circuit. In
its position of rest (with the outlet valve closed) the
diaphragm is acted on by static pressure on both its sides via a
return conduit. In this position of rest, the switch unit for
the heating device is in the inactive position so that the
heating device is disconnected. When opening the outlet valve,
the static pressure on one side of the diaphragm drops and a
pressure difference is produced on the diaphragm so that the ~ ~
diaphragm is deflected and the stem arranged on it is thus ~`
displaced. In this way, the desired switching process is
effected.
Such diaphragm control is admittedly advantageous insofar as
it provides a relatively high mechanical force for the switching
process so that even several pairs of contacts can be switched,
but it has the disadvantage that the arrangement with the
diaphragm is cumbersome since it requires a considerable space
and the pressures acting on it also must be taken up in the
housing. Moreover, the necessary sealing and clamping of the
diaphragm are problematical, there also being the disadvantage -
that the diaphragm is in continuous contact with water, this
direct contact of the liquid to be controlled with the
mechanical parts leading to corrosion, premature aging, and the
like. The constant elastic deflection movement, furthermore,
produces fatigue of the material, so that the diaphragm is of
limited life only. Such switch devices are, thus,
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disadvanta~eous in construction as well as in manufacture and
installation as a result of the many individual parts which
require precise manufacture.
The known switch devices also have serious disadvantages
with respect to their operation since switching is effected as a
function of a pressure difference, the pressure difference
utilized for the switching occurring only above a certain
minimum pressure. However, the line pressure of the water
differs at different places, so that there is already the danger
that the switching process does not always take place properly.
In particular, there is the risk that a pressure difference
which is sufficient for the switching procedure occurs already
at merely relatively slight flow rates, for instance in the case
of a high power pressure, so that overheating - as far as to the
formation of vapor bubbles - takes place, as no large amount of
water is flowing. Furthermore, included air bubbles cannot be -
recognized by the switch device which responds to the pressure
difference, and upon disconnection, i.e. upon the closing of the
outlet valve, hysteresis phenomena occur since the flow rate is
throttled while nevertheless there is still a sufficient
pressure difference on the diaphragm to continue to keep the
switch activated. Overheating can occur also as a result of
this.
One object of the present invention is to provide a switch ;
device of the aforementioned type which is substantially
independent of pressure in its switching behavior, avoids
phenomena of overheating such as occur with the known switch
devices, and assures a high reliability of switching.
Another object of the invention is to permit a simple
construction and to facilitate the manufacture as well as the
installation of the switch device.
The switch device of the aforementioned type in accordance
with the invention is characterized by the fact that the sensor
device has a switch body which is arranged movably in a section
of the flow conduit and is movable by the flowing water at a
given predetermined flow rate, out of a position of rest into a
switch position, and a position sensor which detects this change
in position of the movable switch body, said sensor being
connected to the switch unit for the heating device.
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Such a configuration results in the switching process taking
place as a function of the flow rate instead of a pressure
difference, as a result of which independence from the
respective value of the power pressure is achieved. There is
furthermore the advantage that, instead of an elastically
deflectable mechanical structural part (diaphragm), a freely
movable body is provided for triggering the switching procedure,
which switch body can easily be protected or designed on its
surface such that, despite its arrangement within the flow
conduit, i.e. in the water to be controlled, practically
unlimited life without impairment in operation is obtained. For
this, it is also of importance that the position sensor which is
associated with this movable switch body can be arranged outside
of the flow conduit, so that it also does not come into contact
with water. The position sensor is in a blocking position or
position of rest as long as no water, or only a small amount of
water, is flowing and the switch body practically does not leave
its position of rest and the switch unit is thus inactive, i.e.
the heating device is disconnected. When a stipulated flow rate
is reached, the switch body is carried along sufficiently far by ~-
the water into its switch position, the position sensor then
responding to this change in position of the switch body so that
the switch unit for the heating device becomes active and ~ ~`
connects the heating device. If the flow rate of the water then
is reduced, for instance by throttles provided at an outlet
valve, the switch body moves back again from its switch
position, thereby influencing the position sensor, also in an
intermediate position still in front of its outermost position
of rest, such that the sensor again opens the control circuit
(the switch unit) so that the heating device is again
disconnected.
The dimensions of the switch body and of the section of the
flow conduit receiving said switch body are adapted to each
other in accordance with the existing circumstances, such as
heating output, desired switch flow rate, and possibly also
average water temperature and other water characteristics
affecting viscosity, in such a manner that the desired switch
behavior is assured upon the occurrence of the predetermined
flow rate. In general, it can be said that the cross section of
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flow of the section of the flow conduit will only be slightly
greater than the cross section of the switch body.
By the development in accordance with the invention, in
addition to the functional advantages as mentioned, an
improvement is also obtained in structural respects as well as
with respect to manufacture and installation in that only a
simple movable switch body is present in the flow conduit, as a
result of which sealing problems as well as complicated
installation and manufacturing processes can be advantageously
avoided.
As a whole, therefore, the switch device of the invention
has a simple strong construction of long life and, furthermore,
also has an lmproved switching function as compared with the
known switch devices.
In this connection, a very substantial additional
improvement and substantially increased reliability can be
obtained with a particularly advantageous embodiment of the
sw$tch device of the invention which is characterized by the
fact that a movable switch body is arranged both upstream of and
downstream of the heating device, seen in the flow direction of
the water, in a section of the flow conduit each, separate
position sensors being associated with said switch bodies. In
this way, particularly high reliability is obtained in
connecting and disconnecting the heating device as the flow rate
reaches or drops below the predetermined value, wherein failure
in operation practically cannot occur even if, depending on the
season of the year, the cold water is warmer or colder on the
feed side upstream of the heating device, the viscosity of the
incoming water changing with its temperature, and these changes
in viscosity could possibly lead to a movement of the switch
body in the event of slightly differing flow rates.
In the said preferred embodiment, a logical circuit
establishing an average flow rate at which the switching process
is triggered could be connected to both position sensors in
order, in this way, to effect a compensation between possible
variations on the "hot" and "cold" sides in the sections of the
flow conduit with switch body. However, it has been found that
a simple design is made possible while at the same time
obtaining a particularly high safety, if the heating device is
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actuatable by the switch unit only if both position sensors have
detected a chan~e in position of the movable switch bodies from
the position of rest into the switch position. In this further
development, the output signals of the two position sensors are
thus connected with each other in the switch unit in the manner
of a logical "AND" circuit, and the switch unit activates the
heating device only if both position-sensor switch signals are
present. The same applies to the disconnection process when the -~
flow rate is gradually throttled, for instance by closing a
water faucet. In particular, upon disconnection, the increased
reliability of the present embodiment is especially advantageous
since possible excessively long heating of water as a result of
hysteresis phenomena is avoided.
As an additional safety means against excessively strong
heating of the water, it may, furthermore, be provided that a -~
temperature sensor is associated with that flow-conduit section
which is arranged downstream of the heating device in order to
detect the temperature of the heated water, said temperature
sensor being connected with the switch unit as a safety switch
element to avoid overheating. In this connection, a simple -
design may be obtained by forming the temperature sensor as a
temperature-dependent electric resistor, in particular, an NTC
resistor.
In order to permit the flow of water to be as unimpaired as
possible, it has also proven advantageous if the or each flow- ;
conduit section with switch body is a bypass conduit which is
arranged in shunt to a main conduit for the flow of water. In ~ -~
this way, the flow of water is split up and only a part of the
flow of water, in the shunt, is used for the switching process,
whereby a particularly accurate switching behavior can be
obtained. It is, furthermore, of particular advantage if the
bypass conduit has a smaller flow cross section than the main
conduit. In this way, independence practically is obtained
between the conditions in the main conduit and those in the -
bypass conduit, in the "switch conduit".
In order to obtain the whirl-free laminar flow desired for
an unambiguous switching behavior, it is also favorable for the
bypass conduit to consist of a linear section of conduit
connected via connecting conduits with the main conduit, in the
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I two end regions of which linear section the two positions of the
I switch body, namely the position of rest and the switch
position, are fixed. With such a design, there is also obtained
a linear path of movement for the switch body, so that an exact
switch movement, unaffected by scraping or striking against the
inner wall of the conduit is obtained for the switch body.
In order to obtain a robust, compact, small structural unit,
it is furthermore particularly advantageous if the position
sensor or both position sensors as well as the or both movable
switch bodies are arranged in a common housing block which
contains the flow conduit section or sections as well as
possibly the main and connecting conduits. Thus, all essential
parts of the switch device are arranged within this housing
block. For reasons of manufacture, this housing block is
advantageously a single-piece plastic block, preferably of
acrylic glass. Such a material is, on the one hand,
sufficiently impact-proof and temperature resistant, while, on
the other hand, it also makes possible the use of optical
position sensors, as will be explained in further detail below.
For reasons of manufacture, it is furthermore also preferred
for the or each flow-conduit section as well as, if desired, the
main and connecting conduits to be formed of a bore or bores
which is or are provided on the surface of the block with
connection fittings or possibly screw plugs.
The heating device is preferably an electric resistance
heater, although with the present switch device in principle
also a gas heater, for instance, could be connected and
disconnected. It is particularly advantageous if the resistance
heater is arranged directly in a conduit which is traversed by
the water to be heated. Such a resistance heater permits
highly efficient heating of the water, possible overheating
otherwise to be feared being avoided with sufficient safety by
the aforementioned perfect switching of the switch device of the
invention.
As already mentioned above, an optically operating position
sensor is preferably used and it is accordingly particularly
favorable for the position sensor or each position sensor to be
formed by a light barrier switch consisting of a source of light
and a photoelement located opposite said source of light. The
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path of movement of the switch body is contained in the path of
the beam of light from the source of light to the photoelement,
it being particularly provided that the light beam or "light
barrier" is interrupted by the movable switch body in its
position of rest and that the light beam can impinge on the `
photoelement as the movable switch element leaves its position
of rest and changes into its switch position. By the beam of
light impinging on the photoelement, an electric signal is
produced which is used in the switch device to trigger the `
switching process, i.e. for connecting the heater. A
phototransistor or a pho-todiode preferably is employed as said
photoelement. These components are inexpensive and they are of -~
high reliability in operation as well as small in size, so that
they can easily be installed.
Instead of an optical position sensor, however, there can -
also be used any desired conventional position sensor of
different construction. In particular, it is suitable for the
position sensor or each position sensor to be formed of an
inductive approximation switch or for the or each position
sensor to be formed of a capacitative position sensor. Such
inductive or capacitative position sensors are known per se and
available on the market, and they are advantageous if, for any
reason whatsoever, transparent material cannot be used for the
conduit walls, in which case, nevertheless, the position sensor
is to be arranged outside the flow conduit section in order
to install the electronic components outside the water.
Particularly in the last-mentioned cases, when the position
sensor is designed as an inductive or a capacitative position
sensor, it is advantageous for the movable switch body or each
movable switch body to be a metallic body. Such an embodiment
also has the advantage that, in general, a switch body is
available that can be designed with exact dimensions, which
permits the determination of the switching flow rate
particularly precisely. For this, it is also important that
there i8 a relatively large difference in the specific gravity
as compared to that of water, which facilitates the dimensioning
calculations.
In order to obtain a precise, steady, uniform switching
movement, it is also advantageous for the switch body or each
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switch body to be designed in the shape of a bar and, for the
corresponding section of flow conduit, to be linear. In order
to facilitate the adaptation of the cross section of the switch
body to the common cross sections of flow conduits, it is
furthermore advantageous for the switch body to be of circular
cylindrical shape.
In principle, with the present switch device, the
arrangement can be such that the switching movement of the
switch body is effected independent of the direction, a return
device being provided for the switch body, in particular, in the
form of a (tension) spring, for instance a coil spring or a
rubber spring. Since such return devices, however, are
additional structural parts which can shorten the life of the
switch device as a whole, return of the switch body from the
switch or operating position into the position of rest solely on
the basis of gravity is preferred. Accordingly, it is
particularly favorable if the flow-conduit section or each flow-
conduit section containing a movable switch body is of linear
structure and is arranged vertically. In such case, the switch
body has a lower position of rest and an upper switching
position, from which, if no water or only a small amount of
water is flowing, it drops down as a result of gravity; for this
purpose, also, the abovementioned preferred metallic development
of the switch body is advantageous.
For the exact determination of the different positions of
the switch body or of each switch body, it has finally proven
advantageous for the outermost position of rest and the
outermost switching position of the movable switch body or each
movable switch body to be defined by end stops.
The invention will be explained below in further detail with
reference to particularly preferred embodiments, shown solely by
way of example in the drawing. In detail, in the drawings:
Fig. 1 is a basic diagram of a fundamental embodiment of the
switch device;
Fig. 2 is a similar basic diagram of a switch device with
double switch function;
Fig. 3 is a perspective exploded view showing the housing
block with screw plugs and connection fittings for such an
embodiment of the switch device with double switch function in a -~
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switch block,
Fig. 4 is a top view on such a switch block;
Fig. 5 is a front view of such a switch block;
Fig. 6 is a ver~ical section through such a switch block
along the line VI-VI of Fig. 4 on an enlarged scale, showing the
two flow-conduit sections, each containing a switch body;
Fig. 7 is a horizontal section, again on an enlarged scale,
through such a switch block, along the line VIl-VIl of Fig. 5,
showing the arrangement of the optical position sensors;
Fig. 8 is a view of the switch block according to Figs. 3 to
5, seen from the left, in accordance with the arrow VIII in Fig.
4;
Fig. 9 is a view of this switch block, seen from the right, ~ ~;
in accordance with the arrow IX of Fig. 4; and -~-~
Fig. 10 is a block diagram of a switch unit with thyristor
control for a three-phase heater. -~
Fig. 1 shows a switch device generally denoted by 1, for a
flow heater, a heating device 2, for instance in the form of an
electric resistance heater, being shown only very
diagrammatically. This heating device 2 is contained, for
instance, within a container 3, from which an outlet conduit 4
leads to an outlet valve or water faucet of a fitting generally
indicated by 5, and from there to an outlet 6.
The switch device 1, in more detail, comprises a switch
block 7, which consists of a one-piece housing block 8 within
which the sensor elements necessary for triggering the
connection and disconnection of the heating device 2 are
arranged, as will be explained in further detail below. The
housing block 8 is preferably a single-piece block of plastics
material, in particular acrylic glass, but it may also consist
of some other material.
The housing block 8 is provided with bores in order to form
on the one hand a main conduit 9 for the flow of water as well
as a bypass conduit 10 arranged in a shunt to said main conduit
and parallel to it as that section of the flow conduit within ~ `
whlch a switch body 11 is freely movable. The two conduits 9,
10 are connected by a common connecting conduit or bore 12 to a
cold-water supply, i.e. to a water conduit 13, and an outlet
conduit 15 leading to the heating device 2 is connected to a
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common outlet bore 14 on the output side of the switch block 7.
The switch body 11 in the section 10 of the flow conduit,
i.e. in the bypass conduit is, in particular, a metallic body
which has a circular-cylindrical bar shape and which, for
1nstance, has a plastic covering in order to assure sufficient
resistance to corrosion. The switch body 11 is shown in its
lower position in solid line in Fig. 1 while it is shown in
dotted line in its upper switch position. The arrangement of
the bypass conduit 10 is vertical, the water flowing from bottom
to top in the direction of the arrow within the housing block 8.
The switch body 11 is in its lower position of rest when the
outlet valve 5 is closed and thus no water flows. When the
outlet valve 5 is opened, the water begins to flow via the
supply conduit 13 into and through the switch block 7 and from
there, via the outlet conduit 15, to the heater 2, and finally
to the outlet 6. Within the switch block 7 the water flows
mainly upward through the main conduit 9, but a proportional
part of the water also flows upward through the bypass conduit
10, and when a predetermined flow rate is reached the switch
body 11 is carried along and lifted. When the outlet valve 5 is
only slightly opened, a correspondingly small amount of water
flows through the main conduit 9 and the bypass conduit 10, and
the switch body 11 is lifted only slightly if at all,
however, not getting into its upper switch position; it remains
essentially in its position of rest, wherein an optical position
sensor 16 in the form of a light-barrier switch consisting of a
llght bulb as the source of light 17 and a phototransistor as
photosensitive element or, in short, photoelement 18, remains
inactive since the switch body 11 interrupts the beam of light
from the source of light 17 to the photoelement 18 as before.
Accordingly, in this situation, the photoelement 18 does not a
output control signal, so that the resistance heater 2 is not
connected to current and the watbr is thus not heated. However,
lf, as mentioned, a predetermined flow rate is reached, the
switch body 11 moves upwardly with the flowing water within the
flow-conduit section 10 (see the dotted position in Fig. 1), the
beam of light now passing from the source of light 17 to the -
photoelement 18 and producing an electric control signal in the
latter, which signal is used in a switch unit 19 shown merely
11 ~ 2 1 2 ~ 3 ~3 r~ 3
diagrammatically in Fig. 1 to connect the heating current for
the resistance heater 2 so that the water is heated. When
further opening the outlet valve 5, this switch position does
not change, i.e. the water is continued to be heated.
If, finally, the water outlet is again throttled, i.e., the
outlet valve 5 is partially closed and then entirely closed, the
metallic switch body 11 drops downward again in the bypass
conduit 10 as a result of gravity when the flow rate set is
dropped below and it again enters into the light-barrier switch,
i.e. into the path of radiation between the source of light 17
and the photoelement 18, so that the control signal output by
the photoelement 18 is again interrupted; as a result, the
switch unit 19 disconnects the heating current from the heater 2
and the heater 2 no longer heats the water.
The directions of flow of the water are in general indicated ~ ~-
by arrows in Fig. I as well as in the following Figs. 2 and 3 to
9.
It should be mentioned that Fig. 1 is intended to serve as a
general illustration o~ the principle of the invention, the
individual parts and, in particular, also the switch block 7 not
being shown to scale but only diagrammatically.
An embodiment of the switch device of the invention which is
particularly preferred at present will be explained below with
reference to Figs. 3 to 9, wherein, however, first of all, the
principle of this switch device with a double switching function
will be briefly described by way of the basic diagram of Fig. 2.
The representation of Fig. 2 also is merely diagrammatic and, in
particular, in order to facilitate understanding, two switch
blocks 7, 7' with corresponding switch bodies 11, 11' are shown,
which are freely movable in corresponding flow-conduit sections
10 and 10', respectively, - similar to Fig. 1 - whereas, in
actual practice, as w$11 become evident from the following
description given with reference to Figs. 3 to ~, a single
co~mon uniform switch block containing both switch bodies is
actually provided.
Furthermore, in Fig. 2, the same reference numbers as in
Fig. 1 are used for components which correspond to those of Fig.
1, possibly with the addition of prime sign. -
In accordance with Fig. 2, not only is a switch block 7
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having a movable switch body 11 arranged in the cold-water
supply upstream of the heating device 2 in a flow-conduit
section 10 but, in addition, a corresponding flow-conduit
section 10', also having a freely movable switch body 11',
arranged in the outlet conduit 4 downstream of the heating
device 2, the water faucet or outlet valve with the following
outlet 6 being connected to the outlet side of said switch body
11'. The position sensors represented only schematically in Fig.
2, which are associated with the two switch bodies 11, 11' and
which preferably are also optical position sensors similar to
those of Fig. 1, are connected via corresponding signal lines
20, 21 to the switch unit 19 associated with the heating device
2. Furthermore, within the region of the flow-conduit section
11' arranged to follow the heating device 2, there is arranged a
temperature sensor 22, preferably in the form of a temperature-
dependent resistor, in particular an NTC resistor, which is also
connected, via a corresponding signal line 23, to the switch
unit 19. The three signal lines 20, 21 and 23 are logically
connected to each other in the switch unit 19 in such a manner
that the activation of the heating device 2 (for the activation
of which a switch 24 is shown diagrammatically in the current
supply 25 of the heating device 2) takes place if, and only if,
corresponding control signals are present on all three signal
lines 20, 21 and 23, i.e. when both switch bodies 11, 11' have
moved from the position of rest into the switch position, which
means that a flow rate above the preestablished minimum flow
rate is present, and when the NTC resistor 22 detects a
temperature of the heated water which is below an upper limit
value. There is thus a logical connection between the three
control signals on the lines 20, 21 and 23 in the manner of a
logical "AND", which has been shown diagrammatically in Fig. 2
by the block 26. Of course, this AND function can also be
obtained, according to the circumstances, with any desired known -
switching technique, in particular also an analog switching ;~-
technique, as will be immediately realized by the person skilled
in the art.
In the embodiment in accordance with Figs. 3 to 9 there is
provided a single one-piece switch block 107 which is formed by
a one-piece housing block 108 of acrylic glass in which various
,~-`- ,`'.';i.~.~ : ," ,~ ~ ",~ ""~ ,.i.?,`~l, ` - ". :- .'-
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bores to be explained in further detail below are provided to
form the different conduits to be traversed by water as well as
the receiving spaces for the elements of the position sensors.
These bores are provided on the outside or surface of the
housing block 108 at the site where the different feed and
outlet conduits are to be connected, with threaded connection
fittings 127 (for the cold water supply conduit), 128 (for the
outlet conduit, 15 in Figs. 1 and 2, leading to the heating
device 2 in Figs. 1 and 2 and not shown in Figs. 3 to 9), 129
(for the outlet conduit coming from the heating device, which
conduit is designated 4 in Figs. 1 and 2), and 130 (for the
outlet conduit leading to the fitting 5 in Figs. 1 and 2); on
the other hand, for the bores to which no conduits are to be
connected on the outside of the housing block 108 screw plugs
131 to 138 are provided. The connection fittings 127 to 130 as
well as the screw plugs 131 to 138 are in each case screwed into
the corresponding holes with the interposition of 0-ring seals
139.
In the housing block 108 there are provided on the "cold"
side (corresponding to the block 7 in Fig. 2) two bores 140,
141, one of which, 140, forms the main conduit (9 in Fig. 1) for
the flow of water, while the other, 141, forms the flow-conduit
section (10 in Fig. 1) receiving the movable switch body 111
(see, in particular, Figs. 6 and 7) or the bypass conduit, as
mentioned above. The bore 141 which forms the bypass conduit is
in this case in communication via transversely extending
connecting conduits or bores 142 and 143, closed by the screw
plugs 131 and 132 respectively on the outside, with the main-
conduit bore 140 and the outlet bore 145 receiving the outlet
connection fitting 128, respectively.
On the "cold" side of the housing block 108 there are also
provided two mounting bores 144 and 145 which extend at a right
angle to each other and to the bores 14~, 141, the one bore 144
serving to receive a photodiode 146 (see also Figs. 6 and 7) and
the other, 145, to receive a source of light in the form of a
light bulb 147 (see also Figs. 6 and 7). The light bulb 147 and
the photodiode 146 are located opposite each other, the bypass-
conduit bore 141 in which the switch body 111 is movably
received being provided between them so that the photodiode 146
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~ - 14 - 21233~1
and the light bulb 147 together form an optical position sensor
or light-barrier switch for detecting the position of the switch
body 111. To these position-sensor elements 146, 147 there are
connected corresponding current supply and signal lines, as
shown merely very diagrammatically in Fig. 7 at 148 and 149,
respectively.
In a corresponding manner, on the "hot" side of the housing
block 108 (corresponding to the unit with the elements 7', 10'
and 11' shown in Fig. 2 downstream of the heating device 2),
conduit bores 140' and 141' are provided for forming the main
conduit and the bypass conduit or the flow conduit section
j receiving the movable switch body 111'. A difference from the
"cold" side is present here only insofar as the heating device
2, not shown in detail in Fig. 3 is to be connected via the
connection fittings 128, 129 to the top of the housing block 108
such that on the "hot" side the feed of water does not take
place from below as on the "cold" side but from above, coming
from the heating device 2. Accordingly, a third vertical bore
150 is provided on the "hot" side, forming a feed conduit for /
the bypass-conduit bore 141'. The main flow of the water takes ~ -
place, coming from the upper connection fitting 129, through
horizontal connecting bores 151, 152 extending at right angles
to each other, to the main-conduit bore 140' and from there to
the lower connection fitting 130. In order to lift the switch ~ -
body 111' not visible in Fig. 3 (see Figs. 6 and 7) in a
corresponding manner as well as the switch body 111 on the ~
"cold" side of the switch block 107 when reaching a -
predetermined flow rate against the force of gravity acting on
it, a part of the water is fed from above, from the connection
fitting 129, via the feed-conduit bore 150 downward and over a
lower horizontal connecting bore 153 of the bypass-conduit bore
141 from below in shunt.
Furthermore, between the bores 140', 141' which are parallel
to each other but counter-traversed, a bottom horizontal
compensation bore 154 is provided for the connection, this
compensation bore 154 having a cross section smaller than the
other bore cross sections in order in this way, coming from the
connecting bore 153, to produce a damming of the water and
thereby move the switch body 111' in the bypass-conduit bore 141
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upwards when reaching the predetermined flow rate.
To establish the end positions of the switch bodies 111,
111' on the one hand, in the lower position of rest and, on the
other hand, in the lifted, upper outermost switch position, the
screw plugs 131, 136 and 132, 135, respectively, serve as stops,
these screw plugs 131, 136, 132, 135 extending, in screwed-in
condition, correspondingly far into the corresponding bores 141
and 141' respectively. This stop function is not, in itself,
shown in detail in the drawing but results indirectly from the
illustration, for instance, of Fig. 6 where the switch bodies
111, 111' are shown in their corresponding lowermost position of
rest, aligned with the corresponding transverse bores 142 and
154 respectively, the corresponding screw plugs, for instance
131, 136, being aligned axially with these transverse bores 142,
154 and corresponding to them with respect to their
circumference. The same applies also to the upper stops in
connection with the transverse bores 143 and 152, respectively.
Finally, on the "hot" side, in correspondence to the "cold"
side, there are provided receiving or mounting bores 144', 145'
for the application of a photodiode 146' or a light bulb 147',
respectively, for the formation of the optical position sensor
on the "hot" side of the switch block 107; see, in addition to
Fig. 3, in particular also the illustration in Figs. 6 and 7.
It should furthermore be mentioned that in Figs. 4, 5 as
well as 8 and 9 only the housing block 108 is shown, without
connection fittings and screw plugs, there being
diagrammatically indicated in the drawing at the mouths of the
bores, in each case by reference numbers enclosed in
parentheses, which connection fittings and screw plugs are to be
applied in each case.
From Figs. 3, 4 and 8, finally, it can also be noted that on
the rear of the housing block 108, mounting bores 156, 157 and
158 are provided for attaching the switch block 107 to a support
structure, not shown in detail.
The various connection fittings 127 to 130 and screw plugs
131 to 138 can consist, for instance, of brass.
In the screw plug 134 associated with the lower left-side
connection bore 153 there is then installed, for instance cast
in, e.g., an NTC resistor exposed with its front side as a
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2~29 ,3l
- 16 -
temperature sensor 122; see the illustration in Fig. 6; this
temperature sensor 122 being connected via a line 123 -
corresponding to the line 23 of Fig. 2 - with the electric
switch unit (see Fig. 10) not shown in detail in Figs. 3 to 9.
Fig. 10 is a block diagram for the diagrammatic illustration
of an embodiment of the switch unit l9 which is responsible for
the disconnecting and connecting of the heating device 2 and for
power control. For example, it is assumed that a three-phase
system having the three phases Ll, L2 and L3, a neutral conduit
N, and a ground 160 iS available and, accordingly, three
electric heating resistors 161, 162 and 163 are connected to the
three phases Ll, L2 and L3. These three heating resistors 161
to 163 form the aforementioned heating device 2. These heating
resistors 161, 162, 163 are connected to the corresponding
phases Ll, L2 and L3 via thyristors 164, 165 and 166 provided as
switches (see the switch 24 in Fig. 2) . The control electrodes
of the three thyristors 164, 165 and 166 are connected to the
output of a zero-crossing detector 167 which is connected with
three inputs to the three phases Ll, L2 and L3 and then, when
the heating device 2 iS to be connected or disconnected,
outputs, upon the corresponding zero crossing of the individual
phases, a switch signal to the control electrodes of the
thyristors 164, 165 and 166. In this way, no sudden voltage
changes occur during the operation and disturbing voltages are
avoided.
The heating power or three-phase current power is adjustable
in the present embodiment by the percentage connection time of
the thyristors 164, 165 and 166, for which a power setting
member 168, for example with a continuously variable
potentiometer, not shown in detail, is provided. The feeding of
the control or switch signals emitted by the two position
sensors (photodiodes 146, 146' ) and by the temperature sensor
122 iS shown diagrammatically in Fig. 10, a corresponding
control electronics 169, which can be designed in the most
different ways, being provided, to the output of which the zero-
crossing detector 167 iS connected.
In operation, a corresponding control signal is given off to
the zero-crossing detector 167 only if both position sensors,
i.e. both photodiodes 146, 146', note a change in the respective
- 17 _ 2 12~ 331
switch body 111, 111' from the position of rest into the upper
switch position, i.e., if they receive light and the NTC
resistor 122, at the same time, notes a water temperature that
is below a preestablished upper limit value. Via the control
electronics 169, corresponding control pulses are applied to the
zero-crossing passage detector 167 and effect the triggering of
the thyristors 164, 165 and 166 so that the load current is
passed temporarily by the thyristors 164, 165 and 166, depending
on the setting of the power setting member 168. For this
purpose, for instance, a pulse generator (not shown in detail)
can be provided within the control electronics 169. The zero-
crossing detector 167 has the effect that complete half waves
are always passed by the thyristors 164, 165 and 166.
As soon as just one of the switch bodies 111, 111' drops
down again into its position of rest or as soon as the NTC
resistor 122 detects a rise in temperature above the pre-
established limit value, the thyristors 164, 165, 166 are
blocked via the zero-crossing detector 167; i.e. the heating
device 2 is disconnected. This can be due, for instance, to a
throttling of the flow rate by means of the fitting (outlet
valve 5 in Figs. 1 and 2).
Otherwise, with regard to the manner of operation, reference
may be made to the explanation already given above. -~
In a practical embodiment constructed for test purposes and
having a heating power of 9 kW, the diameters of the different ~ ~
bores forming the main conduits, bypass conduits and connecting ~ ;
conduits amounted to 6.5 mm and the diameter of the bar-shaped
cylindrical switch bodies 111 and 111' was 6 mm. The length of
the main-conduit bores 140, 140' and of the bypass-conduit bores
141, 141' was about 34 mm, and the length of the switch bodies
111 and 111' was about 20 mm. The diameter of the compensation
bore 154 as well as the diameter of the receiving bores 145 and
145' for the light bulbs 147 and 147' was 3.3 mm, while the
diameter of the receiving bores 144 and 144' for the photodiodes
146 and 146', respectively, was 5.5 mm. The thickness of acrylic
resin remaining between the corresponding bypass-conduit bores
141 and 141' and the receiving bores 144, 144' and 145, 145' for
the photodiodes 146, 146' and light bulbs 147, 147',
respectively, was about 2 and 2.5 mm.
~:
212933l
- 18 -
Although the invention has been described in detail above
with reference to particularly preferred embodiments, further
developments and modifications are, of course, possible without
going beyond the scope of the invention. Thus, it is possible,
in particular, instead of the optical position sensors formed by
the photodiodes and sources of light to provide inductive
approximation switches or capacitative position sensors in
appropriately adapted bores. Furthermore, it would, in
principle, be conceivable to separate the "cold" and "hot" sides
of the switch block 107, i.e., to provide two separate housing
blocks ~herefor, as shown in the diagram of Fig. 2, and/or it
would also be conceivable to connect the "hot" side of the
switch block by its bottom to the heating device, i.e., to feed
the hot water coming from the heating device 2 at the bottom of
the switch block, in the same way as the cold water is fed on
the "cold" side at the bottom side, and to connect the conduit --~ -
leading to the outlet valve to the top of the switch block. In
this way, the separate feed-conduit bore 150 could also be.
obviated. However, for reasons of assembly, the embodiment
explained above with reference to Figs. 3 to 9 is preferred for
a compact manner of construction of the switch block together
with the heating device.
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