As is generally known, in mould thermoregulation cir- cuits used for instance for injection moulding of thermoplastic or thermosetting resins, it is provided for at least a heat exchange coil associated with each mould, which depending on specific manufacturing needs enables to heat or cool said mould.

At the end of its use the thermoregulation liquid left in the coil should be completely removed from every mould, also in order to avoid stagnations which might lead to corrosion or scales. In order to empty the mould as referred to before, at the state of the art the mould should first be disconnected from the ther- moregulation circuit into which it is fitted, and then compressed air should be let into the mould so as to push the {thermoregulation liquid outside and thus fully dry said mould.

Beyond the problem of removing the residual liquid from moulds, in thermoregulation circuits air bubbles that might be present in tubes are also to be blown off. To said purpose de-aerating devices are used, fitted into thermoregulation circuits and comprising at the state of the art small casks containing nets or metal meshes trapping air bubbles mixed with the liq- uid. Trapped air bubbles get above the nets. and reach an element floating on the liquid surface. Said float gets down and opens an air bleeder from which air can get out.

Known techniques for emptying moulds and for de- aerating thermoregulation circuits, as briefly de- scribed above, have several limitations and drawbacks.

As a matter of fact, first of all, it is little con- venient and basically extremely complicated to discon- nect a mould that is still full of liquid from the thermoregulation circuit into which it is inserted, since said liquid should be gathered into buckets which are then to be emptied and, unavoidably, part of it is spilled out to the ground. Also the use of com- pressed air for blowing off liquid residues results in the latter being spurted all around the mould and in annoying drying operations.

Under these circumstances the technical task underly- ing the present invention is to conceive a device for blowing off air from hydraulic circuits that can basi- cally obviate the aforesaid drawbacks. To this purpose the Applicant has resolved to empty the mould without disconnecting it from the thermoregulation circuit, letting compressed air into the latter.

At the current state of the art this operation is oth- erwise unconceivable. As a matter of fact, air should anyhow be let off, so as to avoid its presence in tubes, by one of more known de-aerating devices, but' the latter cannot work properly in case air at high pressure and/or flow rate values required for removing liquid from the moulds is introduced therein.

In. the framework of said technical task an important aim of the invention is therefore to conceive a device for blowing off air that enables to introduce com- pressed air into a thermoregulation circuit so as to empty a mould after its use without disconnecting said mould from the circuit, avoiding at the same time that air that has been let it, after emptying the mould, remains in the tubes of the thermoregulation circuit.

Another important aim of the invention is to conceive a device for blowing off compressed air that can work also as de-aerating device for removing air bubbles that might be present in the tubes during the normal operation of a thermoregulation circuit.

The technical task and the aims referred to above are basically achieved by a device for blowing off air from hydraulic circuits characterized in that it com- prises one or more of the technical solutions claimed below.

The following contains as a mere indicative and non- limiting. example the description of a preferred though not exclusive embodiment of a device for blowing off air according to the invention, shown in the accompa- nying figures, in which: - Figure 1 shows a sectioned view of a device for blowing off air according to the invention; and - Figure 2 shows a drawing of a mould thermoregulation system comprising the device of Figure 1.

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

It can advantageously be used in a thermoregulation system 2 as shown in Figure 2, comprising a hydraulic thermoregulation circuit 3 to be connected to at least a heat exchange coil 4 associated with a mould 5 to be used for instance for injection moulding of thermo- plastic or thermosetting resins.

The thermoregulation circuit 3 is connected to a pri- mary hydraulic cooling circuit 6 equipped with an in- take tube 7 for a thermoregulation liquid, generally water, and with a return tube. The primary hydraulic cooling circuit 6 further comprises a relief tank (not shown) and a cooling device 9 placed between the re- turn tube 8 and the intake tube 7 and designed to bring back to low temperature the heated thermoregula- tion liquid coming from the return tube 8.

Moreover, the thermoregulation circuit 3 comprises an intake branch 10 placed upwards from the mould 5, a return branch 11 placed downwards from the mould 5, a heating circuit 12 placed between the intake branch 10 and the return branch 11, an intake valve 13 for let- ting the liquid coming from the intake tube 7 into the intake branch 10, a first shut-off valve 14 placed on the heating circuit 12 and a second shut-off valve 15 placed on the return branch 11 upwards from the con- nection to the return tube 8.

Preferably, the device 1 is fitted onto the return branch 11 downwards from the second shut-off valve 15.

Furthermore, it is provided for an intake valve for compressed air 16 placed on the intake branch 10 and designed to be connected to a tube for supplying com- pressed air.

With reference to Figure 1, the device 1 comprises a closed vessel 17 equipped on a bottom 17a with a first opening 18 coupled with an intake tube 19 and with a second opening 20 coupled with a discharge tube 21. In practice, the intake tube 19 and the discharge tube 21 globally define the return branch 11 of the thermo- regulation circuit 3 placed downwards from the mould 5.

The intake tube 19 comprises an end portion 19a devel- oping vertically and inside the vessel 17 between the bottom 17a and the upper portion of said vessel 17 so as to convey liquid and air into said upper portion thus defining an air lung 22.

Into the vessel 17 is fitted a level sensor 23 com- prising a vertical tube 24, a float 25 slidingly cou- pled with the tube 24 and designed to stay on the sur- face of the liquid 26 stored in the lower portion of the vessel 17. The level sensor 23 further has a first electric switch 27a engaged into the tube 24 at a first height hl, measured with respect to the bottom of the vessel 17, and a second electric switch 27b en- gaged into the tube 24 at a second height h2, greater than the first one hl. Preferably, the float 25 com- prises a magnet which, being near the first 27a or the second 27b switch, depending on the level of the liq- uid 26, closes it.

An electric blow-off valve 28a is arranged on top of the vessel 17 and is operatively interlocked to the level sensor 23. In further detail, the electric blow- off valve 28a, normally closed, is open when the float 25 gets down to the level of the first electric switch 27a.

An intake valve 28b is arranged on top of the vessel 17 and is operatively interlocked to the second switch 27b. The intake valve 28b is connected to a compressed air generator A, only schematically shown, and is opened when the float 25 gets up to the level of the second electric switch 27b.

Eventually, on the discharge tube it is provided for a non-return valve 29 arranged near the second opening 20.

The. device for blowing off air, described above from a mainly structural point of view, works as follows.

During the normal operating condition of the thermo- regulation system 2, in the blow-off device 1 the 1i q- uid is present in the lower portion of the vessel 17 in such an amount to keep the float 25 of the level sensor 23 spaced away from the first electric switch 27a. The electric blow-off valve 28a is closed and in the upper portion of the vessel 17 an air lung 22 is present. The liquid gets into the vessel 17 through the intake tube 19 and gets out of said vessel flowing in the discharge tube 21.

If the level of the liquid 26 gets up so as to bring the float 25 to the second height h2, the intake valve 28b opens and compressed air is introduced into the vessel 17, so as to prevent a further raising of the level and to keep the upper air bag 22.

When the thermoregulation liquid has to be removed from the mould 5 wherein it is contained, first'of all the intake valve 13 for the liquid coming from the in- take tube 7 and the first shut-off valve. 14 are closed so as to insulate the heating circuit 12 from the re- maining portion of the thermoregulation circuit 3.

Then compressed air is introduced upstream from the mould through the intake valve 16, after closing, if necessary, the liquid intake valve 13. Compressed air progressively removes the thermoregulation liquid from the mould 5 and from the return branch 11 arranged downwards from the latter, which flows into the upper portion of the vessel 17, causing first a raising of the level inside it up to the maximum height h2 con- trolled by the second switch 27b.

After this initial step, also air reaches the vessel 17. Consequently, air pressure in the bag 22 gradually rises and lowers the level of the underlying liquid flowing out of the discharge tube 21. When the level of the liquid gets down to the first height h1 and the float 25 reaches the first electric switch 27a, the electric blow-off valve 28a opens and air-contained in the bag 22 is immediately blown off outside, thus not getting into the discharge tube 21.

The liquid remains at the minimum level reached since the non-return valve 29 prevents the liquid under pressure contained in the discharge tube 21 from get- ting back into the vessel 17. Only during a following operating cycle the liquid getting in through the in- take tube 19 brings the float 25 back to such an upper level to space it away from the first electric switch 27a. Also during the normal operation of the thermo- regulation system 2 the device 1 is useful because it works as a de-aerating device: air bubbles that might build in the tubes flow into the bag 22 within the vessel 17 and are periodically let off through the electric blow-off valve 28a when they cause such a pressure of said bag 22 to lower the underlying liquid at the level of the first electric switch 27a.

The invention has important advantages.

As a matter of fact, first of all, the device accord- ing to the invention makes operations of complete re- moval of thermoregulation liquid from moulds, where it would remain after their use, simpler and faster.

In particular, it should be pointed out that said moulds can be removed from the thermoregulation cir- cuit into which they are fitted without problems re- lated to liquid dripping or spurts, as it usually oc- curs in the processes carried out according to known techniques.

Eventually, it should be pointed out that the blow-off device according to the invention enables to avoid the installation of further de-aerating devices in hydrau- lic mould thermoregulation circuits and is therefore advantageous from an economic point of view.