DESCRIPTION This invention relates to a thermo-protector designed in particular for electric water boilers.

The electro-mechanical devices commonly known as thermostats must perform two important tasks ; that is to say, the regulation of the heating temperature of water, for instance, and the protection necessary to ensure that given temperature threshold values are not exceeded.

The regulation function is provided for through a series of opening/closing operations performed by contacts inside the thermostats depending on the temperature reached and depending on the maximum temperature set by the user, said internal contacts being connected in turn to the heating elements.

The protection function is provided for through the irreversible opening of the contacts arranged in series with those specified above when the temperature exceeds the set critical value owing to various reasons among which, for instance, a failure of the aforementioned regulation function. In particular, in the case of a water boiler, it is common knowledge that a safety device capable of cutting off the heat supply to water in the tank is necessary to prevent damage to the equipment as well as the occurrence of operating situations liable of giving rise to hazards for the user. The devices performing said protection function to prevent that the critical temperature be exceeded are called thermo-protectors.

A thermo-protector can be either composed of a dedicated set of equipment or incorporated in a single device together with a regulation thermostat ; in case of the actuating of the thermo- protector owing, for instance, to a failure in the operating of the regulation thermostat, the

whole device needs to be replaced.

The use of a temperature-sensing element capable of extending itself inside the environment to be monitored and in particular in the tank of a water boiler is quite widespread. Said temperature-sensing element is composed of a thermally-dilatable tube usually made of brass inside of which there is a rod, generally made of INVAR, positioned coaxially and marked by an extremely low degree of thermal expansion. Said tube and said rod are connected to one another at the extremity immersed in the body of liquid to be heated. The brass tube elongates as the temperature rises and hence drags along in its movement the INVAR rod owing to the aforesaid connection. Said rod hence acts as a mechanical-type actuator suitable to interact with the contacts inside the thermostat responsible for the making/breaking of the power supply to the aforesaid heating elements.

As regards the temperature-sensing element used by the thermo-protector, it is usually formed by a bulged, bistable bimetallic disk capable of abruptly inverting its bulge once the set critical temperature is reached hence causing the opening of the relevant contacts through a series of mechanical rebounds.

The limits of said devices are well-known to all; in short, these limits lie in the difficulty to calibrate the bimetallic disk, in their coarse sensitivity owing to their position which is necessarily very far from the area whose temperature is to be monitored and finally in the risk of undesired retriggering-nut in the case of extremely low temperatures.

Document EP 0 651 412 proposes the use of the same brass tube/INVAR rod pair used by the regulation thermostat as the temperature-sensing element to be employed by the thermo- protector. Of course, this is a great improvement, but even this invention is not free from an inconvenience which, although unlikely, may occur in the case of the break in the connection between said brass tube and INVAR rod: in this case said rod can no longer follow the elongation of said brass tube as the temperature of the water rises and hence the breaking of the thermo-protector's contacts is no longer possible.

Said device does not provide for"active safety"."Active safety"devices are those devices which, in case of a failure, lead spontaneously to a state that ensures the protection of the controlled device.

Said problem is solved in the Italian document AN 2001A 000023 describing a non-

retriggerable thermo-protector using the aforesaid brass tube/INVAR rod pair as the temperature-sensing element. In this invention the contact opening mechanism composed of a thermally inert bulged disk capable of inverting abruptly the concavity of its bulge if mechanically actuated works even if the connection between said brass tube and the INVAR rod should break. Said device, however, requires an extremely fine setting of the pressure to be exerted on said bulged disk to make it trip at the set temperature.

The purpose of this invention is that of providing for an extremely sensitive and easily settable active safety thermo-protector.

These and other purposes are obtained by means of a temperature regulation device as described and illustrated below in the claims that form an integral part of the description and in the attached figures.

The following description illustrates two preferred versions of embodiments illustrated by way of example and in no exhaustive way in the attached drawings in which: - Figure 1 illustrates a cross-section view of a first version of a temperature regulation device equipped with a thermo-protector in idle position ; - Figure 2 illustrates the contents of the figure above but in a normal operating situation for the thermo-protector ; - Figure 3 illustrates the contents of the previous figures but in a thermo-protector operating situation in which the connection between the brass tube and the INVAR rod is broken; - Figure 4 illustrates a cross-section view of a possible alternative embodiment of the thermo-protector in idle position ; - Figure 5 illustrates the contents of figure 4 above in a thermo-protector operating situation regardless of whether the connection between the brass tube and the INVAR rod is intact or broken.

With reference to figures 1,2 and 3,1 indicates a rod usually made of INVAR positioned internally and co-axially to a tube 2 generally made of brass ; said two elements are usually connected together in a way not illustrated in the figures. Said tube and rod are composed of a single temperature-sensing element protruding from the body 13 of a thermostatic device equipped with a thermo-protector to be immersed in the water of the tank of a water boiler not

illustrated herein.

Inside the body 13 there is a first contact 3 for normal thermostat setting and a pair of second contacts 4 belonging to the thermo-protector. Only one of these is visible in the figures. Said contacts are connected to heating elements not visible in the drawings.

Inside the body 13, a ring-nut 6 is fastened to the rod 1 so that it can be freely positioned along the axis of the rod to adjust the temperature threshold value at which the thermo-protector must be actuated; for example, said connection can be threaded. The position of the ring-nut 6 along the axis of the rod 1 must be adjustable to provide for the setting of the temperature at which said ring-nut must trigger the actuating of the thermo-protector.

Below the ring-nut 6 there is a rocking component 7 equipped with an oscillation fulcrum 10; said fulcrum is fastened to the interior walls of the body 13. One end 7.2 of the rocking component 7 is fastened to said body of the thermo-protector by means of an arc-shaped elastic element 13, which, in turn, is laid against the body 13 near end 9.1, while end 7.1 on the opposite side is the point of support for a stem 5 positioned vertically and capable of sliding in longitudinal direction along the relevant guides in the body 13. The kinematical mechanism formed by the rocking component 7, elastic element 9 and fulcrum 10 is well known per se and it is already used in thermo-protectors with a bulb-shaped sensor.

Above the rocking component 7 there is a plate 8 made of an elastic material which runs basically in parallel to the rocking component and is connected to the latter at one end near end 7.2.

Both the rocking component 7 and the plate 8 above have bulges, 14. a and 14. b respectively, both overlapping near the ring-nut 6 whose lower surface touches the upper surface of said plate 8. Near bulges 14. a and 14. b, to provide for the centering-nut of the ring-nut 6, rocking component 7 and plate 8, the latter items have a slot through rod 1 is inserted.

Plate 8 lays against the stem 5 by means of a second support element 5.3, which can be, for instance, cross-shaped, fastened to stem. A first support element 5.1, it too, for instance, cross- shaped, is fastened to the stem 5 in a position located above support element 5.3 ; said first support element 5.1 is close to the arms 4.1 of the contacts 4 of the thermo-protection device and capable, according to a known technique, to open these arms if the stem 5 is raised.

The operating of the device forming the subject matter of this invention is now described and

reference is made to figures 1,2 and 3. The operating is described in particular in the state in which the first contact 3 inside the body 13 of the thermo-protector does not work, for instance, owing to its"jamming"even though in the figures said contact is shown to be open.

When operating with the connection between the tube 2 and the rod 1 in intact conditions, the latter tends to lower gradually as the temperature of the water in the boiler's tank rises because it must follow the elongation of the tube 2 following the thermal expansion of the latter; said gradual lowering-nut leads also to the downward movement of the ring-nut 6 which gradually presses on the convex surface of the bulge 14. b of the plate 8 which, owing to the pressure of said ring-nut 6, comes directly into contact with the corresponding bulge 14. a of the rocking component 7; said pressure of the ring-nut 6 on the plate 8 and on the rocking component 7 makes the latter turn around its fulcrum 10 and lower its end 7.2 ; the elastic element 9 starts to deform thus contrasting the aforesaid lowering-nut of the end 7.2. As the rod 1 and ring-nut 6 lower, the plate 8 and the rocking component 7 remain at an equal distance from one another because they are both in contact with one another near their respective bulges 14. a and 14. b, both subject to the pressure exerted by the ring-nut 6. This way the end 7.1 of said rocking component and the end of the plate 8 supporting the stem 5 by means of the second support element 5.3 both remain at an equal distant from one another as well so that said stem 5 rests basically both on the end 7.1 and on the plate 8. It must be pointed out that the first support element 5.1 and the arm 4.1 have at the outset only a limited degree of clearance which diminishes as the ring-nut 6 descends and hence as the upward tipping of the end 7.1 increases.

As soon as the end 7.2 of the rocking component 7 descends below the dead center located along the imaginary line joining the fulcrum 10 and the end 9.1, the elastic element 9 is no longer balanced and hence trips by pushing the end 7.2 downward thus causing as a consequence the immediate opening of the second set of contacts 4 by means of the kinematical mechanism form by rocking component 7, plate 8, the second support element 5. 3, the stem 5, first support element 5.1 and the arms 4.1.

The foregoing is a description of how the thermo-protector works if its parts and in particular the temperature-sensing element composed of tube 2 and rod 1 prove to be intact. Please note that hitherto the plate 8 has not performed any independent or necessary function since it has

simply followed passively the movements of the rocking component 7 pressed between the latter and ring-nut 6.

If, instead, the connection between the tube 2 and the rod 1 should fail for any reason whatsoever, the ring-nut 6 will no longer be able to press on the plate 8 and on the rocking component 7. In this invention this case does not prevent however the opening of the second contact 4 ; in fact, the lack of the pressure exerted by the ring-nut 6 makes the plate 8, which exploits its elasticity and is no longer pressed against the rocking component 7 near bulges 14. a and 14. b, move away from the rocking component. Simultaneously, said rocking component, no longer subject to the pressure of ring-nut 6, remains in the equilibrium position determined by the elastic element. Said increase in the distance between the plate 8 and the rocking component 7 pushes the free end of the plate against the second support element 5.3 with the subsequent rising of the stem 5. This rise makes the first support element 5.1 press against the arm 4.1 thus breaking the contact 4 of the thermo-protector.

This way, as per the invention, the power supply to the heating elements is cut off also and as soon as the bond between tube 2 and rod 1 is broken.

A second possible embodiment of this invention is illustrated in figures 4 and 5 and it envisages that the ring-nut 6 be positioned between a compression elastic element 12 located above the ring-nut 6 and a bistable spring-nut 11 of a known type and widely employed in thermostats although in different ways. The spring-nut 11 has one end 11.1 firmly fastened to the body 13 and the opposite end 11.2 that supports an end 5.2 below the stem 5 and acts as the point for the application of the resistance exerted by said stem as well as a relief 15 acting as the point for the application for the force exerted by the ring-nut 6 in case of the pulling of the rod 1. The stem 5 is simply laid against the bistable spring-nut 11 and is equipped only with the first support element 5. 1 ; said support element supports the arm 4.1 of contact 4.

The operating of this second embodiment envisages that in normal operating conditions, i. e. if the connection between tube 2 and rod 1 is intact, the pressure exerted downward by the ring- nut 6 following the pulling of said rod lead the end 11.2 to rise suddenly when the movement of the rod 1 matches that determined by the critical temperature of the water in the tank ; said rise leads also to the rise of the first support element 5.1, to the rising of the arm 4.1 and to the breaking of the contact 4.

In the case in which the connection between the tube 2 and rod 1 is broken, the ring-nut 6 is affected by the downward pressure exerted on it by the compression elastic element 12 which makes up for the lack of pulling on the part of the rod 1 and keeps the ring-nut 6 pressed down.

This ensures always the breaking of thermo-protection contact 4 and hence the cut-off of the power supply to heating elements not illustrated herein regardless of whether the connection between the tube 2 and rod 1 is intact.

As it can be seen from the kinematical mechanisms described above, the opening of the contacts 4 is irreversible because no part of the thermo-protector can make the rocking component 7 or the plate 8 or the bistable spring-nut 11 return to the initial positions in idle state as per figures 1 and 4.

It must be pointed put that the terms"down","up","downward","upward"used in the description above to indicate the positions of the kinematical elements and their movement's refer to the position that the devices have in the figures.

The main advantage of this invention is its capacity to provide for the safe cut-off of the electrical power supply to the heating elements even in case of the breaking of the connection between the tube 2 and rod 1 and if coarsely settable kinematical elements are employed.