THERMOSTATIC MIXER

DE SC RIPTION

The object of the present invention is a thermostatic mixer for electrical storage water heaters.

As is known, the application of thermostatic mixers to the devices for producing hot sanitary water implies a series of considerable advantages. In fact, thermostatic mixers keep the temperature of the mixed water sent to the users constant, at the value set, as the temperature and the feeding pressure of the incoming hot and cold water changes.

Moreover, thermostatic mixers allow storing water in the water heater even at temperatures above 60°C, thus preventing the proliferation of bacteria and above all, allowing a considerable energy saving avoiding the dispensing of water at temperatures above what required in the distribution network, and thus reducing passive dispersions through said network.

The construction and the operation of a thermostatic mixer are well known, thus a brief description in some versions thereof are sufficient herein. For example, a type of thermostatic mixer is described in patent EP 0 767 332. The thermostatic mixer comprises a mixer body having a first and a second inlet respectively for a flow of cold water and one of hot water, a longitudinal mixing chamber, and means for adjusting said flows axially sliding into said mixing chamber, and an outlet section of mixed water at the desired temperature "set" by the user through manual calibration means. The adjustment means is actively connected

to a thermostatic actuator so as to allow the adjustment of the incoming hot and/or cold water flows according to the temperature of the mixed water which invades the thermo-sensitive element, for example a wax bulb, of the actuator itself.

In particular, said adjustment means operates by directly varying the inlet section to the mixer of the mains cold water which is mixed with the hot one coming from the water heater.

A version of thermostatic mixer, also well known, is instead provided with a shape memory alloy means as thermo-sensitive element of the actuator.

This mixer is therefore characterised by a thermo-sensitive element, the material whereof during the make is plastically deformed during suitable thermal treatments; the result is a shape memory thermo-sensitive element, that is, capable of taking up two different lengths according to whether it is kept below or above predetermined temperatures, retaining such feature over time.

Said thermostatic mixers, according to the two versions briefly described, are mounted outside and right downstream of the water heater, in particular on the hot water outlet duct.

These thermostatic mixers therefore have as a main drawback that of requiring additional and/or by-pass fittings so that the cold water, withdrawn from the inlet duct of the water heater, may be mixed with the hot one. The thermostatic mixers mounted outside the water heater imply further drawbacks, such as the risk of accidental tampering by the user.

Moreover, while such solution is the most used one, it does not appear to be aesthetically satisfactory.

A first object of the present invention is to provide a thermostatic mixer for water heater with a simplified and improved construction.

A second object of the present invention is to provide a thermostatic mixer suitable for engaging on a single pipe of the water heater.

A further object of the present invention is to provide a thermostatic mixer for water heater capable of ensuring a considerable energy saving. Said objects and further advantages are achieved with a thermostatic mixer as

described below, in some preferred versions thereof, with the aid of the accompanying figures and in the annexed claims, which are an integral part of the description itself.

In particular, the present invention will be described in a non-limiting manner, according to several preferred embodiments relative to an electrical storage water heater.

Figure 1 shows a section of an electrical storage water heater provided with the thermostatic mixer object of the invention.

Figure 2 shows a section of the thermostatic mixer object of the invention. Figure 3 shows a section of the thermostatic mixer identical to that of figure 2 but showing the path of the water through said thermostatic mixer.

Figure 4 shows the thermostatic mixer object of the invention mounted on the water heater outlet pipe.

With reference to figures 1 and 4, an electrical storage water heater 2 is shown, comprising a tank 201 and a flange 202 which in turn comprises one or more electrical resistances 203 for water heating and a sheath 204 of the thermostat, containing one or more temperature sensors, not shown in the figure.

The cold water is introduced, through an inlet pipe 205, in the proximity of the bottom cap 207 of tank 201, whereas the hot water, at the maximum temperature, is withdrawn through an outlet pipe 206, in the proximity of the dome 208 of tank 201.

The thermostatic mixer 1 object of the invention is arranged on the hot water outlet pipe 206, as described hereinafter in greater detail.

For simplicity of description, reference numeral 2O6.a indicates the portion of the hot water outlet pipe 206 substantially comprised between the thermostatic mixer 1 and the bottom cap 207; reference numeral 2O6.b, on the other hand, indicates the portion of said hot water outlet pipe 206 comprised between the thermostatic mixer 1 and said dome 208.

As is clear from figure 1, said thermostatic mixer 1 is mounted inside tank 201 of water heater 2, substantially in the proximity of the bottom cap 207, so as to be externally lapped by the cold water fed by said inlet pipe 205.

With reference to figure 2, 3 and 4, said thermostatic mixer 1 is shown according to a preferred embodiment.

Said thermostatic mixer 1 substantially comprises a mixer body 3, with longitudinal axis A-A, a first inlet 4 for feeding hot water, coaxial to said mixer body 3, a second inlet 5 for feeding cold water, a thermostatic actuator 6 and a box 7 for adjusting the flow rates of cold and hot water to be mixed.

Reference numeral 8 indicates the outlet of the mixed water to the users.

More in particular, reference numeral 401 indicates the passage section of hot water from said inlet 4 to a chamber 301 of the mixer body 3, and hereinafter therefore referred to as hot chamber.

Reference numeral 501, on the other hand, indicates the passage section of cold water from said inlet 5 to a mixing chamber 302 of the mixer body 3.

The hot water is thus mixed with cold one in said mixing chamber 302.

The passage section 501 of inlet 5 of the cold water is obtained through circumferential slots 501.

Said circumferential slots 501 are obtained on the side surface of the mixer body 3, at the mixing chamber 302.

The cold water thus enters into said mixing chamber 302 according to directions substantially orthogonal to axis A-A of the mixer body 3. With reference to the thermostatic actuator 6, reference numeral 601 indicates a thermo-sensitive element, preferably a wax expansion bulb, of the well known type normally used in thermostatic mixers.

However as an alternative, nothing prevents said thermo-sensitive element 601 from being any other heat expansible fluid or said thermostatic actuator 6 from being of a type based on shape memory elements.

The thermo-sensitive element 601 is arranged at the mixing chamber 302 so as to be lapped by the mixed water.

Said thermo-sensitive element 601 is then stiffly connected to a stop 602.

Said stop 602 is further constrained to a dilatation element like a bellows 603 which, in known manner and as will be explained hereinafter, undergoes axial movements

according to the temperature the thermo-sensitive element 601 is subject to, that is, the temperature of the mixed water sent to outlet 8.

Said thermo-sensitive element 601 is centred between ends 804 of ribs 803 at the edges whereof there are defined channels 801 that allow the passage of the mixed water.

Stop 602 on the other hand rests on the top edge 805 of said ribs 803. End 604 of the bellows 603, opposite the thermo-sensitive element 601, as per prior art, pushes on a box 7 for the adjustment of hot and cold water flow rates opposed by an abutment spring 9. Said box 7 therefore is capable of shifting relative to the hot chamber 301 under the action of said thermo-sensitive element 601.

In particular, said box 7 comprises a first shutter 701, hereinafter referred to as hot shutter, and a second shutter 702, hereinafter referred to as cold shutter, constrained to one another by a central core 704 and ribs 705 that extend radially, and lapping them the hot water can move from the hot chamber 301 to the mixing one 302.

As will be described in more detail hereinafter, said hot 701 and cold 702 shutters are such as to vary, according to the axial thrust of said bellows 603, respectively the passage section 401 of the hot water towards the hot chamber 301 and the passage section 501 of the cold water towards the mixing chamber 302. Reference numeral 9 further indicates the contrast spring for the same adjustment box 7.

A filter 10 may be inserted on said circumferential slots 501.

Said filter 10 prevents scale deposits from obstructing said slots 501 preventing the crossing thereof by cold water. It is now possible to proceed with a more detailed description of the thermostatic mixer 1 according to the invention.

As already partly mentioned, the hot water coming from portion 206. b of the outlet pipe 206 of the water heater 2 axially enters through the passage section 401 into the mixing chamber 301 and hence it goes into the mixing chamber 302, where it is mixed with the incoming cold water through the circumferential slots 501.

The mixed water then moves through channels 801, from the mixing chamber 302 to outlet 8 of the thermostatic mixer 1 to be delivered to the user at the desired temperature (in particular, see the arrows in figure 3).

The temperature of the mixed water thus obtained affects the expansion of the thermo-sensitive element 601 so as to change the passage sections 401 and 501, respectively for the inlet of hot and cold water into the thermostatic mixer 1. By way of an example only, in fact, if the temperature of the mixed water that externally laps said thermo-sensitive element 601 of the thermostatic actuator 6, is higher than the value required by the user, the wax of said thermo-sensitive element 601 will expand, with consequent expansion and movement of bellows 603 such as to cause an axial shifting of box 7.

Said shifting of box 7 takes place in opposite direction to the outlet direction of the mixed water in opposition to the pressure exerted by the abutment spring 9. In this way, the passage section 401 of the hot water is decreased through the shifting of the hot shutter 701, whereas the passage section 501 of the cold water is increased by the shifting of said cold shutter 702.

On the contrary, a temperature of the mixed water below the desired value will correspond to a shrinkage of the wax of the thermo-sensitive element 601 with consequent shifting of box 7 suitable for decreasing the passage section 501 of the cold water and increasing that 401 of the hot water.

In any case, a balance condition is automatically restored, wherein the temperature of the mixed water directed to the users actually is that desired.

It is therefore clear that the constancy, at the desired value, of the temperature of the mixed water, is expressly a function of the chemical-physical properties of the thermo-sensitive element 601, in particular of the expansion coefficient of the wax contained therein, besides the geometry of box 7 (and relative hot and cold shutters 701 and 702).

In the design and/or construction phase, the choice of the thermo-sensitive element 601 and of the geometry of said box 7 thus allows having models of thermostatic mixers 1 made for different temperature ranges (of the mixed water) according to the

requirements of the various markets, having multiple different models of sensitive elements 601 and/or suitably changing the geometry of shutters 701 and 702 (in order to change the passage sections 401 and 501 respectively of the hot and cold water). While the thermostatic mixer 1 as described so far has an operating principle according to the prior art, it exhibits the certain advantage of avoiding additional fittings and/or by-pass pipes for feeding the cold water to be mixed, since the thermostatic mixer 1 itself is immersed in the cold water (into tank 201 of water heater 2) it receives through said circumferential slots 501 of inlet 5. Normally in known thermostatic mixers, mounted outside the water heater, the adjustment of temperature of the mixed water takes place by operating a knob that substantially acts, through a screw-nut screw coupling, on the shutter allowing the modification of one or both passage sections of the hot and/or cold water. As a consequence, in general, no initial calibration procedure and/or device is required during the construction or inspection steps of the thermostatic mixer itself at the factory.

For the purposes of this patent, the thermostatic mixer 1 inside the water heater 2, as described, does not require an initial calibration either as the desired temperature of the mixed water is obtainable by construction, as said above (selection of the sensitive element 601 and/or of the geometry of shutters 701 and 702).

However, while it is not shown, an initial fine calibration may be provided in said thermostatic mixer 1.

A first solution may consist in making the inlet 4 for feeding hot water free to shift relative to the mixer body 3 through a screw-nut screw coupling, not shown. In this way, rotating inlet 4 relative to said mixer body 3, a corresponding variation of the hot water passage section 401 takes place, other conditions being equal. As an alternative it is possible to provide for bellows 603 of the thermostatic actuator 6, rather than acting on end 703 of the hot shutter 701, to press directly on an adjustment screw, not shown, in turn screwed to core 704 of said hot shutter 701 and coaxial thereto.

In this way, a shifting of box 7 is obtained by screwing said screw which moves it away from the tip of bellows 603, with the consequent reduction of the passage section 401 of the hot water and increase of the passage section 501 of the cold water

(and/or vice versa). As already said before and with particular reference to figures 1 and 4, the thermostatic mixer 1 is mounted inside the water heater 2 on the hot water outlet pipe

206.

Reference numerals 11 and 12 indicate the means for fixing the thermostatic mixer 1 to said hot water outlet pipe 206. More precisely, reference numeral 11 indicates the means for fixing portion 206. b of the outlet pipe 206 to orifice 402 of the hot water inlet 4.

Reference numeral 12, on the other hand, indicates the means for fixing portion

2O6.a of the outlet pipe 206 to orifice 802 of the mixed water outlet 8.

According to a preferred embodiment of the invention, since said portions of pipe 2O6.a and 2O6.b are not subject to any mechanical strain except for that due to their weight, said fixing means 11 and/or 12 may consist in a quick snap- wise coupling of any known shape.

However, nothing prevents the possibility of using known and equivalent means for coupling said orifices 402 and 802 to the hot water outlet pipe 206, such as for example threads, unions, bayonet couplings, fixed seaming, or internal caulking.

Once fixed as described at portions 206. a and 2O6.b of said hot water outlet pipe 206, the thermostatic mixer 1 is inserted into tank 201 of water heater 2 from the bottom through the threaded sleeve 209 welded to tank 201 itself.

In fact, it is clear that it may be constructed with an inside diameter at least so reduced as to be made to pass into a %" diameter pipe.

The hot water outlet pipe 206 is thus fixed and locked relative to tank 201 of the water heater by the insulating sleeve 210 of plastic material, which couples by interference with said threaded sleeve 209 (in particular, see fig. 3).

At the same time, said insulating sleeve 210 of plastic material also ensures seal and electrical insulation.

This type of coupling between the metal sleeve 209 welded to tank 201 and the insulating sleeve 210, in any case, is already commonly and widely used. However, nothing prevents from proceeding with the insertion of the thermostatic mixer 1 into tank 201 of water heater 2 according to alternative methods. For example it is possible to:

- insert a first portion 2O6.a of the hot water outlet pipe 206 from the outside into tank 201 of water heater 2 through the threaded sleeve 209 welded thereto, said first portion 2O6.a being then fixed by interference through the insulating sleeve 210 of plastic material, - fix a second portion 2O6.b of the outlet pipe 206 to orifice 402 of the hot water inlet 4 of the thermostatic mixer 1,

- manually insert the thermostatic mixer 1 into tank 201 through the hole of water heater 2, then closed by flange 202,

- proceed with fixing orifice 802 of outlet 8 of the mixed water of the thermostatic mixer 1 to said first portion 2O6.a of the outlet pipe 206.