ITMI20070936A1 - SYSTEM AND MIXING GROUP FOR SANITARY SYSTEMS WITH ANI-LEGIONELLA DISINFECTION FUNCTION - Google Patents

Description

DESCRIPTION of the invention having as TITLE:

"MIXING SYSTEM AND GROUP FOR SANITARY SYSTEMS, WITH ANTI-LEGIONELLA DISINFECTION FUNCTION"

SUMMARY

The system and the mixing unit for sanitary systems, with anti-legionella disinfection function, comprise a first and a second inlet duct respectively for hot and cold water, which open into a mixing chamber of a thermostatic mixer, from which a third mixed water delivery duct; the system and the unit also comprise a by-pass channel for a derivative flow of hot water between the first inlet duct and the third delivery duct for mixed water. In the by-pass channel there are first valve means, normally closed, for interception of the derived flow of hot water, while in the second conduit there are second valve means, normally open, for interception of the flow of cold water; control means are also provided that are operatively connected to the first and second valve means to simultaneously control, in a controlled manner, the opening and closing of the first and second valve means themselves, during an anti-legionella infection phase.

BACKGROUND DESCRIPTION OF THE INVENTION

The present invention relates to a system and a unit for mixing cold water and hot water for sanitary systems, with an anti-legionella disinfection function, in which in particular an anti-scald thermostatic mixer is provided for the distribution of domestic hot water. a predetermined temperature.

STATE OF THE ART

In the field of sanitary systems, in particular in systems for hotels, communities, hospitals and the like, the use of anti-scald thermostatic mixers is known, which, in compliance with current safety regulations, are designed to allow the distribution of domestic hot water at a predetermined temperature, lower than a safety value, in order to avoid burns to users.

These anti-scald thermostatic mixers are generally installed in junction boxes, in which the mixer is connected to a first inlet duct for a flow of hot water from the boiler, as well as to a branch of a second inlet duct for a flow of water. cold which extends at the outlet for powering the users; moreover, a third delivery duct is provided at the outlet of the mixer for the distribution of mixed water at the predetermined temperature.

The recent regulations on the disinfection of sanitary systems against the Legionella bacterium, which provide, among other things, that the water supply taps connected to the mixed water delivery duct can be subjected to thermal disinfection with hot water. high temperature, have led to the need to adopt a by-pass channel between the first inlet duct for hot water and the third delivery duct for mixed water, so as to allow, if necessary, the direct passage of high temperature water towards the taps themselves, without passing through the thermostatic mixer.

The by-pass channel has a valve, normally closed, for interception of the derivative flow of hot water, which can be electrically controlled, by means of a special actuator, or manually to be periodically brought to an open position in order to carry out anti-legionella disinfection. .

However, such a mixing system has the drawback that when anti-legionella disinfection is carried out, both the derivative flow of hot water coming from the by-pass channel and the flow of water converge in the mixed water delivery duct at the same time. from the mixer, with the consequence that the disinfection itself is less effective due to the decrease in the temperature of the water in the duct induced by the presence of mixed water.

This mixing system also has further drawbacks linked to the presence of different components to be connected together, which entail on the one hand a considerable installation complexity, and on the other a considerable bulk of the system itself.

AIMS OF THE INVENTION

The main purpose of the present invention is to provide a system and a mixing unit for sanitary systems, which allows to perform an effective anti-legionary disinfection of the system, thanks to the high temperature of the hot water that flows in the delivery duct of the system. water itself to the taps.

Another object of the present invention is to provide a system and a mixing unit for sanitary installations, in which the anti-legionella disinfection function can be controlled in a simple way and without the possibility of error by an operator.

A further object of the present invention is to provide a mixing unit for sanitary systems, which has a compact construction of limited dimensions, and which can be installed quickly and simply, while at the same time allowing a reduction in system costs.

BRIEF DESCRIPTION OF THE INVENTION

The above can be achieved by means of a system for mixing cold water and hot water for sanitary systems, with anti-legionella disinfection function, comprising:

- a first inlet conduit for a flow of hot water;

- a second inlet conduit for a flow of cold water;

- a thermostatic mixer having a mixing chamber in which said first and said second water inlet conduits open;

- a third delivery duct of mixed water leaving said mixing chamber; and

- a by-pass channel between said first inlet conduit for hot water and said third delivery conduit for mixed water, said by-pass channel comprising first valve means, normally closed, for interception of a derivative flow of hot water between said first and third ducts,

characterized in that it comprises second valve means, normally open, for intercepting the flow of cold water in said second inlet duct, and

by the fact of comprising control means operatively connected to said first and said second valve means, said control means being shaped and arranged to simultaneously control, in a controlled manner, in opening, respectively in closing said first and second valve means, during a step anti-legionella disinfection.

The above can also be achieved by means of a mixing unit for sanitary installations, with an anti-legionella disinfection function, characterized in that it comprises a hollow body having: - a first inlet duct for a flow of hot water;

- a second inlet conduit for a flow of cold water;

- a mixing chamber in which said first and said second water inlet conduits open;

- a third delivery duct of mixed water leaving said mixing chamber; and

- a by-pass channel for a derivative flow of hot water between said first inlet duct for hot water and said third delivery duct for mixed water,

the mixer unit also comprising:

a thermostatic device for mixing hot and cold water, having a thermostatic wax actuator which extends into said mixing chamber,

- first valve means, normally closed, in said by-pass channel, said first valve means comprising a first sealing seat for a first mobile shutter for interception of the derived flow of hot water, and

- second valve means, normally open, in said second inlet duct, said second valve means comprising a second sealing seat for a second mobile shutter for intercepting the flow of cold water, and

from the fact of comprising an operative connection rod between said first and said second shut-off shutter, the rod being also connected to a command actuator shaped and arranged to simultaneously command, in a controlled manner, opening and closing respectively of said first and second interception shutter, during an anti-legionella disinfection phase.

BRIEF DESCRIPTION OF THE DRAWINGS

These and further characteristics according to the present invention will become clearer from the following description with reference to the attached drawings, in which:

- Fig. 1 is a longitudinal section view of a mixing unit according to a first embodiment of the invention, with the valve means in the mixing position;

- Fig. 2 is a sectional view of the assembly of Fig. 1, with the valve means in the anti-legionella disinfection position;

- Fig. 3 is a perspective view of the group of Fig. 1;

- Fig. 4 is a sectional view of the group of Fig, 1, along the line 4-4;

- Figs. 5 and 6 are a schematic representation of a mixing system according to a second embodiment of the invention, with the valve means in the mixing position, respectively in the anti-legionella disinfection position; And

- Figs. 7 and 8 are a schematic representation of a mixing system according to a third embodiment of the invention, with the valve means in the mixing position, respectively in the anti-legionella disinfection position.

DETAILED DESCRIPTION OF THE INVENTION

The general characteristics of the present invention will be illustrated hereinafter through some embodiment examples.

A first preferential embodiment of the present invention is illustrated in Figures 1 to 4, which show a mixing unit for mixing cold and hot water in sanitary systems, with an anti-legionella disinfection function.

The unit, indicated as a whole with the numerical reference 10, comprises a hollow body 11, preferably made in a single piece by casting, which in turn comprises a first inlet duct 12 for a flow of hot water, and a second inlet duct 13 for a flow of cold water which opens into a mixing chamber 14 from which a third delivery duct 15 for mixed water emerges.

The hollow body 11 also comprises a by-pass channel 16 for a derivative flow of hot water between the first inlet duct 12 for hot water and the third delivery duct 15 for mixed water.

The unit 10 also comprises a thermostatic device 17 for mixing hot and cold water, having a thermostatic wax actuator 18 which extends into the mixing chamber 14

In the by-pass channel 16 there are first valve means 19, normally closed, which comprise a first sealing seat 20 for a first mobile shutter 21 for interception of the derived flow of hot water.

In the second inlet duct 13 for cold water, on the other hand, second valve means 22, normally open, are provided, which comprise a second sealing seat 23 for a second mobile shutter 24 for intercepting the flow of cold water.

The unit 10 also comprises an operative connection rod 25 between the first and the second shut-off shutter 21, 24, which is also connected to a control actuator 26 shaped and arranged to simultaneously control, in a controlled manner, opening, the first and second interception obturators 21, 24 are closed respectively, during an anti-legionella disinfection phase.

The mixing chamber 14 extends along a longitudinal axis, between a first axial end, in which an insertion opening 14 'is provided for the thermostatic mixing device 17, and a second end opposite the first, from which it extends coaxially the delivery duct 15.

The mixing chamber 14 has a first passage opening 27 connected to the first inlet duct 12, and a second passage opening 28 connected to the second inlet duct 13, which ports are arranged axially spaced apart along the mixing chamber 14 .

The thermostatic mixing device 17 comprises a tubular obturator 29 which is operatively connected to the thermostatic wax actuator 18, so as to be axially movable in the mixing chamber 14 between a first retracted position and a second advanced closing position of the first, respectively of the second light 27, 28 of passage of the water.

Preferably, the first inlet duct 12 for hot water comprises a first fitting 30 for connection to a hot water supply pipe coming from a heat source (not shown), which extends transversely to the axis of the chamber. mixing 14 on a first side of the hollow body 11; a first portion of duct 12 'extends from said first fitting 30 and extends parallel to the axis of the mixing chamber 14 on the first side of the hollow body.

The first duct 12 also comprises a second portion of duct 12 '', visible in Figures 3 and 4, which extends from the first portion 12 'transversely to the axis of the mixing chamber 14, on one side of the mixing chamber 14 itself; starting from this second section 12 '' extends a third section of duct 12 '' 'which opens into the mixing chamber 14 through the first passage opening 27.

The third portion of duct 12 '' in particular extends substantially parallel to the axis of the mixing chamber 14 on a second side of the hollow body 11 opposite to the first side, presenting a shaped intermediate part connecting the second portion 12 '' of the duct, which is offset with respect to the mixing chamber 14, and the first passage opening 27.

Preferably, the second inlet duct 13 for cold water comprises a second fitting 31 for connection to a cold water supply pipe (not shown), which extends transversely to the axis of the mixing chamber 14 on the first side of the hollow body 11; starting from this second fitting 31 a longitudinal portion of duct 13 'extends which extends parallel to the axis of the mixing chamber 14 on the first side of the hollow body 11 to open into the mixing chamber 14 through the second passage opening 28.

Between the longitudinal portion 13 'of the second duct 13 and the second fitting 31 there is a narrow communication hole or passage 32 arranged on the first side of the hollow body 11; furthermore, again on the first side of the hollow body 11, the longitudinal portion 13 'itself is axially spaced from the first portion 12' of the first conduit 12.

As said, the third delivery duct 15 extends coaxially starting from the second axial end of the mixing chamber 14, and ends with a third connection fitting 33 to a mixed water distribution pipe, not shown.

In particular, the third delivery duct 15, at the second axial end of the mixing chamber 14, comprises an initial section 15 'which is interposed between the third section 12' '' of the first inlet duct 12 and the longitudinal section 13 'of the second inlet duct 13.

The by-pass channel 16 extends between a lateral hole 34 of the third section 12 '' of the first inlet duct 12, and an intermediate point of the third delivery duct 15; preferably, in the section plane of Fig. 1, the third delivery duct 15 and the by-pass duct 16 have a Y-shaped section, in which the base leg of the Y is represented by the third connection fitting 33.

In particular, the lateral hole 34 of the third section 12 '' 'is arranged on the second side of the hollow body 11 in a condition axially aligned with the communication hole 32 of the second inlet duct 13, according to an axis orthogonal to the longitudinal axis of the mixing chamber 14.

The first sealing seat 20 of the first valve means 19 is of the annular type and is arranged on a peripheral edge of the side hole 34 of the first inlet duct 12, preferably on the side facing the by-pass channel 16; the second sealing seat 23 of the second valve means 22, also of the annular type, is instead arranged inside the second connection fitting 31 on a peripheral edge of the communication hole 32 between the fitting 31 itself and the longitudinal section 13 'of the second inlet duct 13.

In particular, the first and second sealing seats 20, 23 are arranged at a first mutual distance in the direction of the orthogonal alignment axis between the side hole 34 and the communication hole 32.

The connecting rod 25 extends through the side hole 34 of the first inlet duct 12 and the communication hole 32 of the second inlet duct 13; in this case, the first and second obturator 21, 24 are connected to the rod 25 in axially spaced positions, in the direction of the orthogonal axis, preferably at a mutual distance greater than the first distance between the sealing seats 20, 23, with the first shutter 21 arranged in the by-pass channel 16, and the second shutter 24 arranged in the second connection fitting 31.

However, a different arrangement of the shutters and the relative sealing seats is not excluded, providing for example that the first shutter 21 and the relative sealing seat are in the third section 12 '' 'of the first inlet duct 12, and that the second shutter and the relative sealing seat are in the longitudinal section 13 'of the second inlet duct 13.

The connecting rod 25 has a first end 25 'which extends through a lateral opening 35 of the by-pass channel 16 arranged on the second side of the hollow body 11 for the attachment of the control actuator 26; the end 25 'of the rod 25 is thus operatively connected to the control actuator 26, as well as to elastic thrust means 36 shaped and arranged to act in combination with the control actuator 26 itself, which are for example in the form of a spring 36 arranged coaxially to the rod 25 to act on a plate connected to the rod itself.

The control actuator 26 can for example be of the electric type and preferably of the electro-thermal type; in the latter case, as illustrated with broken lines in Figures 1 and 2, the actuator 26 comprises an axially extendable thermostatic actuator 37, of the wax type, operated by an electric heating resistor 38, as well as a contrast spring 39 acting as opposed to the actuator 37 to exert an axial thrust on the rod 25 tending to close the first valve means 19 and to open the second valve means 22,

In this way, when the actuator 37 is operated by the resistance 38 during the anti-legionella disinfection phase, the rod 25 is freed from the axial thrust of the spring 39, thus allowing the spring 36 to exert an opposite axial thrust tending to open the first ones. valve means 19 and to close the second valve means 22.

The unit 10 preferably comprises a transversal sleeve 40 for the passage for the connecting rod 25 in the initial section 15 'of the delivery duct 15, which sleeve is inserted hermetically in through holes 41, 42 provided in the lateral separation walls of the section initial 15 'from the third portion 12' '' of the first inlet duct 12, respectively from the longitudinal portion 13 'of the second inlet duct 13.

In particular, the through holes 41, 42 are aligned according to the orthogonal axis of alignment between the side hole 34 of the first inlet duct 12 and the communication hole 32 of the second inlet duct 13, and the connecting rod 25 is slidably sealed into the passage sleeve 40; such a solution allows to realize in a simple way the operative connection between the shutters 21, 24, while allowing to maintain compact dimensions of the hollow body 11, and to prevent unwanted leakage of water between the initial section 15 'of the delivery duct 15, the third portion 12 '' 'of the first inlet duct 12, and the longitudinal portion 13' of the second inlet duct 13.

The unit 10 comprises control means 43 for the control actuator 26, connected to an electrical power source, not shown; for example, these control means 43 can be in the form of an electric switch 44 and / or a timer 45 arranged to activate the control actuator 26 in a timed manner, or else an electronic control unit arranged to activate in a timed manner. controlled mode the control actuator 26.

Alternatively, the anti-legionella disinfection function can be controlled manually, and therefore in this case the control actuator 26 will be in the form of a manual control knob.

From the above, it is evident that the mixing unit according to the present invention integrates a first anti-scald function, which represents the normal operating condition of the unit, and a second function of periodic anti-legionella disinfection of the system.

In particular, with reference to the mixing position illustrated in Fig. 1, in which the flow interception shutter in the by-pass channel is closed and the incoming cold water flow interception shutter is open, the unit performs the anti-scald function, supplying mixed water at a predetermined temperature at the outlet.

On the other hand, with reference to the disinfection position illustrated in Fig. 2, in which the flow interception shutter in the by-pass channel has been brought to the open position by the control actuator and the incoming cold water has been brought into the closed position by the actuator itself, the unit allows to perform the anti-legionella disinfection function of the system, achieving particular effectiveness in the disinfection itself, as during this operation the cold water is kept closed and therefore the hot water flowing in the water delivery duct towards the taps has a high temperature.

Furthermore, the unit has a compact construction of limited cost and simple installation, compared to the systems in use.

More generally, the present invention can be configured as a system for mixing cold water and hot water for sanitary systems, with an anti-legionella disinfection function.

In particular, with reference both to the embodiment illustrated in Figures 5 and 6, and to the further embodiment illustrated in Figures 7 and 8, in which the same reference numbers have been used to indicate similar or equivalent parts with respect to the embodiment. embodiment of Figures 1 to 4, the system comprises a first inlet duct 12 for a flow of hot water (illustrated with a thick solid line), and a second inlet duct 13 for a flow of cold water (illustrated with a solid line of intermediate thickness between the thick line of the hot water and the thin line used to indicate the ducts), which open into the mixing chamber of a thermostatic mixer 17,

The system also comprises a third delivery duct 15 for mixed water (illustrated with thick lines) at the outlet from the mixing chamber, and a by-pass duct 16 between the first inlet duct 12 for hot water and the third delivery duct 15 for mixed water; the by-pass channel 16 in turn comprises first valve means 19, normally closed, for interception of a derivative flow of hot water between the first and third ducts 12, 15,

The second conduit 13 for cold water, on the other hand, comprises second valve means 22, normally open, for intercepting the flow of water.

Finally, the system according to the present invention comprises control means operatively connected to the first and second valve means 19, 22, to simultaneously control, in a controlled manner, opening and closing respectively of the first and second valve means 19, 22 themselves, during an anti-legionella disinfection phase.

In particular, as illustrated in Figures 5 and 6, the control means can comprise a single electric control actuator 47, preferably of the electrothermal type, operatively connected to the first and second valve means 19, 22, for example by means of a rod or mechanical connection member 48, in such a way as to simultaneously control, in a controlled manner, the valve means themselves, through suitable control means 44 of the actuator connected to an electrical power source (not shown).

Alternatively, as illustrated in Figures 7 and 8, the control means can comprise a first and a second electric control actuator 49, 50, respectively connected to the first and second valve means 19, 22, which actuators are operatively connected to control means, in turn connected to an electric power source and arranged for a controlled and simultaneous actuation of the actuators themselves.

The control means 44 may in particular comprise an electric switch 45 and / or a timer 46 arranged to activate the control actuators 47, 49, 50 in a timed manner, or an electronic control unit arranged to activate the actuators in a controlled manner. command themselves.

Similarly to what has been said for the mixing unit, to which reference is made, also the mixing system according to the present invention integrates a first anti-scald function, illustrated in Figures 5 and 7 for the two embodiments of the system described above, and a second function of periodic anti-legionella disinfection of the system, illustrated instead in Figures 6 and 8 for the two embodiments of the system.

What has been said and shown with reference to the attached drawings has been given purely by way of example and illustrative of the general characteristics of the invention, as well as some of its preferential embodiments; therefore other modifications and variations to the system and to the mixing unit for sanitary installations are possible, without thereby departing from the scope of the claims.

Claims (27)

Claims 1. System for mixing cold and hot water for sanitary systems, with anti-legionella disinfection function, comprising: - a first inlet conduit for a flow of hot water; - a second inlet conduit for a flow of cold water; - a thermostatic mixer having a mixing chamber in which said first and said second water inlet conduits open; - a third delivery duct of mixed water leaving said mixing chamber; and - a by-pass channel between said first inlet conduit for hot water and said third delivery conduit for mixed water, said by-pass channel comprising first valve means, normally closed, for interception of a derivative flow of hot water between said first and third ducts, characterized in that it comprises second valve means, normally open, for intercepting the flow of cold water in said second inlet duct, and from the fact that it comprises control means operatively connected to said first and second valve means, said control means being shaped and arranged to simultaneously control, in a controlled manner, in opening, respectively in closing, said first and second valve means, during a anti-legionella disinfection phase. 2. Mixing system according to claim 1, characterized in that said control means comprise a single electric control actuator operatively connected to said first and said second valve means for simultaneously controlling, in a controlled manner, the valve means themselves. 3. Mixing system according to claim 2, characterized in that it comprises a mechanical connection member operating between said control actuator and said first and second valve means. 4. Mixing system according to claim 2, characterized in that it comprises control means for said control actuator, connected to an electrical power source. 5. Mixing system according to claim 1, characterized in that said control means comprise a first and a second electric control actuator respectively connected to said first and said second valve means, said first and said second electric actuator being operatively connected to control means arranged for a controlled and simultaneous actuation of the actuators themselves, said control means being connected to an electrical power source. 6. Mixing system according to claim 4 or 5, characterized in that said control means comprise an electric switch. 7. Mixing system according to claim 4 or 5, characterized in that said control means comprise a timer arranged to activate said control actuators in a timed manner. 8. Mixing system according to claim 4 or 5, characterized in that said control means comprise an electronic control unit arranged to activate said control actuators in a controlled manner. 9. Mixing system according to claim 2 or 5, characterized in that the control actuator is of the electro-thermal type. 10. Mixing unit for sanitary systems, with anti-legionella disinfection function, characterized in that it comprises a hollow body having: - a first inlet conduit for a flow of hot water; - a second inlet conduit for a flow of cold water; - a mixing chamber in which said first and said second water inlet conduits open; - a third delivery duct of mixed water leaving said mixing chamber; and - a by-pass channel for a derivative flow of hot water between said first inlet duct for hot water and said third delivery duct for mixed water, the mixer unit also comprising: a thermostatic device for mixing hot and cold water, having a thermostatic wax actuator which extends into said mixing chamber, - first valve means, normally closed, in said by-pass channel, said first valve means comprising a first sealing seat for a first mobile shutter for interception of the derived flow of hot water, and - second valve means, normally open, in said second inlet duct, said second valve means comprising a second sealing seat for a second mobile obturator for intercepting the flow of cold water, and from the fact that it comprises an operative connection rod between said first and said second shut-off shutter, the rod is also connected to a command actuator shaped and arranged to simultaneously command, in a controlled manner, opening and closing respectively of said first and second interception shutter, during an anti-legionella disinfection phase. 11. Mixing unit according to claim 10, wherein said mixing chamber extends along a longitudinal axis, characterized in that said mixing chamber has a first passage opening connected to the first hot water inlet duct, and a second passage port connected to the second cold water inlet duct, said first and said second passage ports being axially spaced apart along said mixing chamber. 12, Mixing unit according to claim 11, characterized in that said thermostatic mixing device comprises a tubular shutter operatively connected to said thermostatic wax actuator, said tubular shutter being axially movable in said mixing chamber between a first retracted position and a second advanced closing position of said first, respectively of said second water passage opening. 13. Mixing unit according to claim 12, characterized in that said first inlet duct for hot water comprises: - a first connection fitting to a hot water supply pipe coming from a heat source, said first connection fitting extending transversely to the axis of the mixing chamber on a first side of the hollow body; - a first portion of duct which extends parallel to the axis of the mixing chamber on said first side of the hollow body; a second portion of duct which extends transversely to the axis of the mixing chamber, on one side of the mixing chamber itself; and - a third portion of duct extending substantially parallel to the axis of the mixing chamber on a second side of the hollow body opposite said first side, said third portion opening into said mixing chamber through said first passage opening. 14. Mixing unit according to claim 13, characterized in that said second inlet conduit for cold water comprises: - a second connection fitting to a cold water supply pipe, said second connection fitting extending transversely to the axis of the mixing chamber on said first side of the hollow body; and - a longitudinal section of duct which extends parallel to the axis of the mixing chamber on said first side of the hollow body, said longitudinal section being provided with a hole for communication with the second connection on said first side, the longitudinal section opening in said mixing chamber through said second passage opening, said longitudinal portion of the second inlet duct being axially spaced from said first portion of the first inlet duct for hot water. 15. Mixing unit according to claim 14, wherein said mixing chamber has an insertion opening at a first axial end for said thermostatic device, characterized in that said third delivery duct extends coaxially starting from a second axial end of said mixing chamber opposite to said first axial end, the delivery duct ending with a third connection fitting to a mixed water distribution pipe, and by the fact that said third delivery duct, in correspondence with said second axial end of the mixing chamber, comprises an initial portion interposed between said third portion of the first inlet duct and said longitudinal portion of the second inlet duct. 16. Mixing unit according to claim 15, characterized in that said bypass channel extends between a lateral hole of said third section of the first inlet duct for hot water and said third delivery duct, said lateral hole being arranged on said second side of the hollow body in a condition axially aligned with said communication hole of the second inlet duct, according to an axis orthogonal to said longitudinal axis of the mixing chamber. 17. Mixing unit according to claim 16, characterized in that said first sealing seat of the first valve means is arranged on a peripheral edge of said lateral hole of the first inlet duct, on the side facing said by-pass channel, and in that said second sealing seat of the second valve means is arranged in said second connection fitting on a peripheral edge of said communication hole between said fitting and the longitudinal portion of the second inlet duct. 18- Mixing unit according to claim 17, in which said first and said second sealing seats are arranged at a first mutual distance in the direction of the orthogonal axis of alignment between said lateral hole of the first inlet duct and said communication hole of the second inlet duct, characterized in that said connecting rod extends through said lateral hole of the first inlet duct and said communication hole of the second inlet duct, said first and said second obturator being connected to the rod itself in axially spaced positions , in the direction of said orthogonal axis, by a mutual distance greater than said first distance between said sealing seats, the first shutter being arranged in said by-pass channel, the second shutter being arranged in said second connection fitting, 19. Mixing unit according to claim 18, wherein the by-pass channel has an attachment opening for said control actuator arranged on said second side of the hollow body, characterized in that said connecting rod has a first end which extends through said attachment opening, said first end of the connecting rod being operatively connected to said control actuator, as well as to elastic thrust means shaped and arranged to act in combination with said control actuator. 20. Mixing unit according to any one of claims from 16 to 19, characterized in that it comprises a transversal sleeve for the passage for said connecting rod in said initial section of the delivery duct, said passage sleeve being inserted tightly into the through holes provided in lateral walls separating the initial portion itself from said third portion of the first inlet duct and from said longitudinal portion of the second inlet duct, said through holes being aligned according to said orthogonal alignment axis between said lateral hole of the first inlet duct and said communication hole of the second inlet duct, the connecting rod being slidably sealed into said passage sleeve. 21. Mixing unit according to any one of claims 10 to 20, characterized in that said control actuator is of the electric type. 22. Mixing unit according to claim 21, characterized in that it comprises control means for said control actuator, connected to an electrical power source. 23. Mixing unit according to claim 22, characterized in that said control means comprise an electric switch, 24. Mixing unit according to claim 22, characterized in that said control means comprise a timer arranged to activate said control actuator in a timed manner. 25. Mixing unit according to claim 22, characterized in that said control means comprise an electronic control unit arranged to activate said control actuator in a controlled manner. 26. Mixing unit according to any one of claims 21 to 25, characterized in that the control actuator is of the electro-thermal type. 27. Mixing unit according to any one of claims 10 to 20, characterized in that said control actuator is a manual control knob