As is generally known, a thermoregulation system for moulds used in injection moulding of thermoplastic or thermosetting resins should be able to carry out a precise control on the temperature of every mould de- pending on specific manufacturing needs. To said pur- pose a thermoregulation system comprises a hydraulic thermoregulation circuit that can be connected to at least a heat exchange coil associated with a mould.

The thermoregulation circuit normally comprises a pri- mary hydraulic cooling circuit equipped with an intake tube for a liquid, generally water, used for thermo- regulation, and with a return tube for the liquid heated after going through the heat exchange coil.

Said primary circuit can be connected to other similar thermoregulation circuits for controlling the tempera- ture of the corresponding moulds.

The primary circuit also comprises a cooling device placed between the return tube and the intake tube, which can cool the liquid before conveying it into the thermoregulation circuit.

In some technical solutions the primary circuit can be excluded by taking water directly from the water net- work at normal supply temperature.

The aforesaid thermoregulation circuit, beyond having a cooling function, can also be used to heat the mould always through the heat exchange coil by switching on, by actuating suitable valves, a hydraulic heating cir- cuit.

At the state of the art the flow of liquid coming from the intake tube of the primary cooling. circuit is nor- mally adjusted by means of flow meters equipped with a tap that can be actuated manually by an operator so as to adjust the flow rate of the cooling liquid in the circuit as needed. Recently, automatic thermoregula- tion devices have been launched on the market, in which the flow of cooling liquid is adjusted by means of an on-off intake valve in the thermoregulation cir- cuit, i. e. fully open or fully closed. The intake valve is interlocked to an electronic control unit which receives in its turn signals from at least a temperature sensor detecting mould temperature di- rectly or indirectly. Also the heating circuit is in- terlocked to said control unit so as to adjust the amount of heat thus generated.

In practice, the thermoregulation circuit for cooling the mould works by opening and closing successively the intake valve for time lapses defined automatically by the control unit, corresponding to the amounts of cold liquid to be conveyed into said thermoregulation circuit depending on the temperature reduction to be obtained.

The heating circuit, which can be selectively con- nected to the thermoregulation circuit, comprises at the state of the art a pump with quite a high dis- charge head in a tank equipped with suitable electri- cal resistors that can bring to high temperature the liquid stored therein and introduced into the thermo- regulation circuit.

At the state of the art the operating mode in a heat- ing circuit envisages that the liquid stored in the tank is brought to a given temperature together with the actuation of the pump which circulates it in the thermoregulation circuit.

The state of the art as briefly described above has several limitations and drawbacks.

As a matter of fact, first of all the on-off intake valve does not enable a gradual variation of the tem- perature of the liquid in the thermoregulation circuit since its full opening, also for a short time, results in a sudden introduction into the latter of quite a large mass of cold liquid causing fast temperature changes, sometimes too sudden and anyhow difficult to be controlled.

Moreover, the heating circuit requires, especially at first start of the system, long times and a high con- sumption of electric energy so as to bring to the re- quired temperature the large mass of water stored in the tank it is equipped with.

Eventually, the large size of said tank makes known thermoregulation systems globally bulky.

Under these circumstances the technical task underly- ing the present invention is to conceive a mould ther- moregulation system that can basically obviate the aforesaid drawbacks.

In the framework of said technical task an important aim of the invention is to conceive a thermoregulation system for moulds enabling an extremely precise con- trol of the temperature thereof.

Another important aim of the invention is to conceive a thermoregulation system that can increase the tem- perature of the liquid used for thermoregulation, and therefore also mould temperature, in far shorter times than that or those required at the state of the art, thus sparing energy especially at first start of the tex. system.

A further aim is to conceive a thermoregulation system that has globally a small overall size.

The technical task and the aims referred to above are basically achieved by a mould thermoregulation system characterized in that it comprises one or more of the technical solutions as claimed below.

The following contains as a mere indicative and non- limiting example the description of a preferred though not exclusive embodiment of a mould thermoregulation system according to the invention, shown in the accom- panying figures, in which: - Figure 1 shows a drawing of the system according to the invention; and - Figure 2 shows a longitudinally sectioned view of a heating assembly used in the heating circuit of the system in Figure 1.

With reference to the aforesaid figures, the system according to the invention is globally referred to with the numeral 1.

It comprises a hydraulic thermoregulation circuit 2 that can be connected to at least a heat exchange coil 3 associated with a mould 4 to be cooled or heated de- pending on planned manufacturing processes.

The thermoregulation circuit 2 comprises a primary hy- draulic cooling circuit 5, conventional and known per se, comprising an intake tube 6 for a thermoregulation liquid, for instance water, a return tube 7 for the heated liquid coming from said thermoregulation cir- cuit, and a cooling device 8 placed between the return tube 7 and the intake tube 6 and designed to bring back to low temperature the heated liquid.

In further detail, the thermoregulation circuit 2 com- prises an intake branch 9'placed upwards from the mould 4 and connected to the intake tube 6, and a re- turn branch 10 placed downwards from the mould 4 and connected to the return tube 7.

A hydraulic heating circuit 11 has an-operating branch lla connected on its end to the intake branch 9 and to the return branch 10, which can be selectively con- nected to the thermoregulation circuit 2.

It is further provided for: an intake valve 12 placed on the intake branch 9 near the intake tube 6, a tem- perature sensor 13, advantageously placed on the re- turn branch 10 directly downwards from the mould 4, if necessary an auxiliary sensor 13a placed upwards from the mould 4, and an electronic control unit 14 sending control signals at least to the heating circuit 11 and to the intake valve 12 and receiving signals coming from the temperature sensors 13 and 13a.

Originally, the intake valve 12 consists of a propor- tional flow-adjusting valve, i. e. which can gradually vary the area of its passage gap for the liquid and therefore also its flow rate according to any value between a maximum value corresponding to full opening and a zero value corresponding to full closing.

The heating circuit 11 advantageously comprises a cirez culation pump 15 installed in the operating branch lla defined by said heating circuit, and a continuous flow heating assembly 16 preferably operating upwards from the mould 4 and from the auxiliary sensor 13a.

With reference to Figure 2, the heating assembly 16 comprises a metal mass 17 with a high thermal conduc- tivity equipped with a passage channel 18 for the thermoregulation liquid, and one or more electric re- sistors 19 drowned in said metal mass 17 and opera- tively interlocked to the control unit 14.

Eventually, it is provided for a first shut-off valve 20, i. e. an on-off valve, arranged on an operating . branch 11a of the heating circuit 11 upwards from the circulation pump 15, and a second shut-off valve 21 arranged on the return branch 10 upwards from the con- nection to the return tube 7 of the primary circuit 5.

Both shut-off valves 20 and 21 can be managed by the electronic control unit 14.

A thermoregulation system, described above mainly from a structural point of view, works as follows.

If the mould 4 has to be cooled, the first shut-off valve 20 is closed so as to exclude the heating cir- cuit 11, and the second shut-off valve 21 is opened.

The control unit 14 adjusts the opening degree of the intake valve 12 and therefore the amount of liquid flow coming from the intake tube 6 conveyed into the thermoregulation circuit 2.

If the mould 4 has to be heated, the first shut-off valve 20 is opened, the intake valve 12 is closed and then also the second shut-off valve 21 is closed.

The liquid is circulated by the circulation pump 15 in the closed circuit comprising the operating branch lla and the two portions of intake 9 and return tube 10 between the mould 4 and said operating branch lla. In a short time the heating assembly 16, interlocked to the control unit 14, increases the temperature of the liquid going with continuous flow through it.

If mould temperature is above the set value, the con- trol unit immediately switches off the electric resis- tors 19 of the heating assembly 16 and, if necessary, adjusts the opening of the intake valve 12 and opens the second shut-off valve 21 so as to enable a flow of cold liquid in the thermoregulation circuit, which mixes immediately with the warm liquid and lowers its temperature.

The invention has important advantages.

As a matter of fact, first of all, the proportional intake valve enables the control unit to vary continu- ously the flow rate of cold liquid to be introduced into the thermoregulation circuit, thus obtaining a similarly gradual and precise variation of mould tem- perature.

In particular, it should be pointed out that the ar- rangement of the temperature sensor on the return branch of the thermoregulation circuit allows to ob- tain temperatures that are closer to those required in the mould than other solutions envisaging to place the temperature sensor upwards from said mould.

Moreover, it should be noted that the continuous flow heating assembly, beyond enabling a small overall size for the system since it does not require the presence of a bulky tank, limits times required for heating the liquid, especially at first start, to values that are far lower than those at the state of the art.