As is known, said thermostats, or heat con- trolled electric switches, can be used for adjust- ing and limiting the desired temperature of elec- trically heated metal plates, for instance of metal plates of irons.

US Patent No. 4,899, 124 describes a heat con- trolled electric switching apparatus equipped with: a temperature regulator comprising a bimetallic strip and a snap switch actuated by said bimetallic strip containing a movable contact and a contact spring, whose dead center (or snap center) position can be adjusted by means of a manual adjusting de- vice; a temperature limiter substantially consist- ing of a fuse element, a pressure element engaged with the latter and a switching contact having a stationary contact and a movable contact held in its closing position by the pressure element; in said apparatus said stationary contact of the limi- ter is respectively provided with a first and a second opposed contact surfaces, so that said mov- able contact of the limiter cooperates with said first contact surface of said stationary contact, whereas the movable contact of the temperature regulator, affected by the contact spring, cooper- ates with said second contact surface of the sta- tionary surface.

In short, in said apparatus the temperature limiter and the temperature regulator are equipped each with its own movable contact cooperating with only one stationary contact. Therefore, in the ap- paratus structure said regulator and said limiter obviously lie one above the other, which results in a great overall height of said apparatus. It should be kept in mind that said apparatuses used as ther- mostats for instance in an iron often have to meet - when positioned on the plate-room requirements within the iron. Furthermore, said systems can show a low efficiency just because both the limiter and the regulator share the same electric contact.

The present invention, therefore, aims at ob- viating the drawbacks of known heat control elec- tric switching apparatuses or thermostats as men- tioned above.

Said aim is achieved by the present invention by means of a thermostat comprising: a temperature regulator equipped with a bimetallic strip and a snap switch actuated by said bimetallic strip and equipped with a movable electric contact cooperat- ing with a stationary electric contact placed on a support element of the thermostat; and a tempera- ture limiter provided with a body housing a fuse element and a pressure pin cooperating with said fuse element; said temperature limiter comprises a first movable electric contact connected to said housing body and a second movable electric contact connected to the support element of the thermostat; moreover, said body is attached to support means electrically connected to said support element of the thermostat.

Advantageously, therefore, by means of the thermostat according to the present invention, the transfer of current within said thermostat changes in a more efficient way, thanks to the use of two pairs of separate electric contacts, one for the temperature regulator and one for the temperature limiter: this enables a structural though not elec- trical separation of said limiter from said regula- tor, thus obtaining a thermostat with a shape that can be more easily adapted to room needs within common irons.

Further aims and advantages of the present in- vention will be more evident from the following de- scription, regarded as a mere non-limiting example with reference to the enclosed drawings, in which: - Fig. 1 shows a partially sectioned view in side elevation of a thermostat equipped with means for adjusting and limiting temperature according to the present invention during normal operation; - Fig. 2 shows a partially sectioned view in side elevation of the thermostat of Fig. 1 with the tem- perature limiter working due to a overheating con- dition; - Fig. 3 shows a view from above of the thermostat in Fig. 1; and - Fig. 4 shows a view from behind, or from the left in Fig. 1, of the present thermostat.

With reference to the enclosed drawings and in particular to Fig. 1, the numeral 1 refers to a bimetallic strip on which front end, or right end looking at the figure, the lower end of a pin 2 moving vertically upwards and downwards, as indi- cated by the double arrow V, is attached. The upper end of said pin 2 is attached to the front portion 4 of a suitably shaped plate 16 actuating the snap- action switch 5. Said switch 5 has a dead center, or snap center, which is set by means of a tempera- ture regulator 6 placed above said switch 5 and comprising a support arm 7 attached to a metallic hollow rivet 8. Said support arm 7 has in its front portion a threaded cylindrical guide 9 into which a corresponding threaded screw 10 is engaged, whose head is inwardly attached to the lower end of a hollow handle 11. On the lower end of said screw 10 a substantially conical pin 12 is obtained, which pin cooperates with one of the strips 3 and 13 of a known spring system provided within the snap-action switch 5 for adjusting its dead center, or snap center. The rear portion of the actuating plate 4 of said switch 5 contains a first movable contact 14 cooperating with a second stationary contact 15 substantially parallel to the bimetallic strip 1.

Both the plate 16 actuating the switch 5 and the stationary contact 15 are attached to the hollow rivet 8, to this purpose said stationary contact 18 is supported by a plate 17 put onto said rivet 8.

The rear front portion of the present thermostat shows a temperature limiter 18 comprising a suita- bly shaped base 19 structurally and electrically connecting said limiter 18 to the hollow rivet 8.

Said base 19 houses a body 20 supporting the limi- ter 18 having a first cylindrical rear seat 21, in which a metallic rivet 22 projecting upwards is at- tached, and a second cylindrical seat 23 housing a pressure pin 24. In the lower portion of said cy- lindrical seat 23 a compartment 25 is obtained, housing a pellet 26 made of a material melting at a given temperature. Said pellet 26 rests with its lower surface on a suitably shaped portion 27 of the base 19, whereas the lower end of the pressure pad 24 rests on its lower surface. The upper end of said pin 24 cooperates with the lower surface of a first flexible strip 28 having a first electric contact 29 cooperating with a second electric con- tact 30 attached onto the lower surface of a second flexible strip 31. Said first flexible strip 28 is attached to the rivet 22 of the body 20 supporting the temperature limiter 18 together with a first power supply connection 32, whereas said second flexible strip 31 is attached to the rivet 8. Going back to the temperature regulator 6, as can be ob- served, a wheel 33 is attached onto the turning handle 11, which wheel comprises a notch 34 indi- cating the temperature to be reached for the ther- mostat before the automatic snap of the switch 5.

The stroke end positions of said notch 34 are de- termined by its contact with an upright 35 provided on the front end of the arm 7. As an alternative to what is shown in the present figure and in the sub- sequent ones, the second flexible strip 31 support- ing the second electric contact 30 can be obtained as one piece with the plate 16 actuating the snap switch 5.

Such wheel 33 for adjusting temperature in the thermostat with its notch 34 can be better seen in Fig. 3, which also shows a second power supply con- nection 36. As can be observed, advantageously, the temperature limiter 18 is connected laterally to the rivet 8 by means of the support base 19 and the flexible strip 31: this allows to reduce the height. of the whole thermostat, with obvious advantages concerning its arrangement within an iron, and en- ables its higher efficiency due to the separation of the electric contacts 14,15 of the temperature regulator 6 from the electric contacts 29,30 placed on the flexible strips 28,31 of the tem- perature limiter 18. By the way, it should be pointed out that, depending on where the thermostat needs to be placed within an iron, it is evident that said limiter 18 could be arranged around the rivet 8 in any position, not only the one shown in the present description by way of example: for in- stance, it could be placed wholly on the rear por- tion, or left portion looking at the figures, of the rivet 8, thus obtaining a thermostat character- ized by a reduced lateral size and height.

Said separation of the body 20 supporting the temperature limiter 18 from the regulator 6 is even more evident looking at Fig. 4 of the enclosed drawings. Said body 20, as previously mentioned, is connected to the rivet 8 by means of the lower base 19 of the limiter 18, which base is further in di- rect contact with the lower bimetallic strip 1 of the thermostat. Starting from below said rivet 8 is provided above the base 19 with a first spacer 37, the second power supply connection 36 cooperating with the plate 17 supporting the stationary contact 15 of the switch 5, a second spacer 38 made of in- sulating material, the plate 16 actuating the snap- action switch 5, the second flexible strip 31 sup- porting the contact 30 of the temperature limiter 18, a third spacer 39 made of insulating material 39 and, eventually, the arm 7 supporting the tem- perature regulator 6.

The method of operation of the present thermo- stat is as follows: by acting upon the handle 11 of the temperature regulator 6 and thanks to the notch 34, it is possible to determine the temperature at which both contacts 14 and 15 are separated by the snap-action switch 5, which are normally closed as shown in Fig. 1. By supplying the thermostat with power by means of both connections 32 and 36, the lower bimetallic strip 1 starts to heat up and to warp causing a movement upwards, in the direction shown by the arrow V, of the pin 2 cooperating with the actuating plate 4, which is then also lifted upwards causing the separation of the movable con- tact 14 from the stationary contact 15. The more the pin 12 is moved upwards through the rotation of the handle 11, the greater the lifting of said pin 2 will be, i. e. the higher the desired temperature will be on the bimetallic strip 1. When said bimetallic strip 1 cools down, the spring system comprising the two strips 3 and 13 allows the switch 5 to close again the contact 14 upon the contact 15, after the lowering of the pin 2. The temperature limiter 18 starts working if, due to any operating failure of the thermostat, the mov- able contact 14 of the regulator 6 is not separated from the stationary contact 15 after reaching the desired temperature. As can be observed from Fig.

1, the electric contacts 29 and 30 supported by the two flexible strips 28 and 31 are normally closed so as to enable the working of the thermostat, i. e. the flow of electric current between the two con- nections 32 and 36: if the bimetallic strip 1 gets overheated and the temperature exceeds a given threshold value, the pellet 26 made of fusible ma- terial housed in the compartment 25 of the body 20 melts causing the pressure pin 24 to lower, see Fig. 2, which usually keeps the two flexible strips 28 and 31 of the limiter 18 lifted in a position substantially parallel to the bimetallic strip 1.

Said lowering of the pressure pin 24 results in a subsequent bending of the lower strip 28 and to a lower extent also of the upper strip 31, thus ena- bling the opening of the electric contacts 29 and 30 supported by said strips and the subsequent in- terruption of power supply to the whole thermostat, thus stopping the heating of the bimetallic strip 1.

As can be inferred from the previous descrip- tion, the advantages deriving from the use of a thermostat equipped with means for adjusting and limiting the temperature according to the embodi- ment disclosed by way of example are manifold, and manifold are the embodiments that can be used in order to achieve said advantages without leaving the framework of the enclosed claims.