CA2129331A1

CA2129331A1 - Switching device for instantaneous water heaters

Info

Publication number: CA2129331A1
Application number: CA002129331A
Authority: CA
Inventors: Walter Hochleitner
Original assignee: Individual
Current assignee: Gulf Energy Inc
Priority date: 1992-02-06
Filing date: 1992-02-06
Publication date: 1993-08-07
Also published as: EP0624237A1; SK92394A3; KR950700520A; NO942904L; JPH07505947A; BG99014A; FI943595A0; NO942904D0; FI943595A; AU1228092A; WO1993016336A1

Abstract

Abstract Switching Device for Instantaneous Water Heaters There is described a switch device (1) for flow heaters which, as a function of the flow rate, connects and disconnects a heating device (2) provided for the heating of water and for this purpose has a cylindrical switch body (11, 11'; 111, 111') consisting, for instance, of metal, which is arranged movably in a vertical flow-conduit section (10, 10'; 141, 141') which is traversed by water, which switch body can be moved by the flowing water, at a pre-established flow rate, out of a lower position of rest into an upper switch position, and a position sensor (16, 16') which detects this change of position of the movable switch body (11, 11'; 111, 111'), preferably in the form of a light-barrier switch including a source of light (17; 145, 145') and a photoelement (18; 146, 146') and connected to a switch unit (19) for the heating device (2).

Description

2 1 2 9 3 ") 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, - ~

2~ 3~,1 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.

2~',?.9~31 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 `~ 2~2~t 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 933~

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 ~Ye~ .. "~

~12~

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 212~3~l 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 :

` ~ 212933t 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 -~
:.
.

212~31 ~. g 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 -: 21~9~31 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 . , .
:

;.

:~

2129~3~

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, ` - ". :- .'-?

~29~31 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 ' " ' ': ., " ' : ' ~.

~ - 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 .

' ~

2~ 331 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 . ,.. ,- ~ - . , ~ ,. . :: . .

,. .: ''' ' ' ' ' '. ' ', ` ` :' ' : ' ` : `' ' ~ , ' ' . '` ~ . . .

2~29 ,3l 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 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.

;'' ~
J~

Claims

Amended Claims:

1. A switch device (1) for flow heaters having a sensor device for the flowing water associated with a water flow conduit and to which a switch unit (19) for a heating device (2) provided for heating the water is connected, wherein the sensor device comprises a respective switch body (11, 11'; 111, 111') arranged movably in a flow-conduit section (10, 10'; 141, 141') both upstream and downstream of the heating device (2), which switch body is movable by the flowing water at a pre-established flow rate from a position of rest into a switch position, as well as a respective position sensor (16, 16') detecting such a change in position of the movable switch body (11, 11'; 111, 111') and connected with the switch unit (19) for the heating device (2), characterized in that each flow-conduit section (10, 10'; 141, 141') with switch body (11, 11'; 111, 111') is a bypass conduit arranged in shunt to a main conduit (9; 140, 140') for the flow of water and consisting of a conduit section connected via connecting conduits (142, 143, 152, 154) with the main conduit (140, 140') and in both end regions of which the two positions of the switch body (111, 111'), i.e., the position of rest and the switch position, are established, and in that both position sensors (16, 16') as well as both movable switch bodies (11, 11'; 111, 111') are arranged in an integral housing block (8, 108) of synthetic material which contains the flow conduit sections (10, 10'; 141, 141') as well as the main and connecting conduits (9; 140, 140', 142, 143, 152, 154).

2. A switch device according to claim 1, characterized in that each bypass conduit (10, 10'; 141, 141') as well as the main and connecting conduits (9; 140, 140', 142, 143, 152, 154) are formed by bores provided on the block surface with connection fittings (127, 128, 129, 130) or optionally screw plugs (131 to 138).

3. A switch device according to claim 1 or 2, characterized in that each bypass conduit (10) has a smaller flow cross section than the main conduit (9).

4. A switch device according to any of claims 1 to 3, characterized in that the the housing block (8; 108) is made of transparent synthetic material and each each position sensor is comprised of a light-barrier switch formed of a source of light (17: 147, 147') and a photoelement (18; 146, 146') arranged opposite said source of light.

5. A switch device according to claim 4, characterized in that the housing block is made of acrylic glass.

6. A switch device according to claim 3 or 4, characterized in that the photoelement (18) is a phototransistor.

7. A switch device according to claim 4 or 5, characterized in that the photoelement (146, 146') is a photodiode.

8. A switch device according to any of claims 1 to 7, characterized in that each switch body (11, 11'; 111, 111') is of circular cylindrical shape and the corresponding bypass conduit (10, 10'; 141, 141') is linear.