WO2019111117A1

WO2019111117A1 - Temperature control device or circuit for moulds or moulding systems

Info

Publication number: WO2019111117A1
Application number: PCT/IB2018/059514
Authority: WO
Inventors: Paolo Bonvicini
Original assignee: Green Box Srl
Priority date: 2017-12-07
Filing date: 2018-11-30
Publication date: 2019-06-13

Abstract

Temperature regulation circuit (10) for moulds (S) or moulding systems, comprising a loading line (11) suited to load a process fluid, a hot circuit (20) provided with a heating element (22) and an accumulation tank or hot tank (24), a cold circuit (30) provided with a heat exchanger (32) and an accumulation tank or cold tank (34). The circuit (10) comprises also a connection pipe (41) with a valve (42), mounted between said hot tank (24) and said cold tank (34), in order to selectively place said hot tank (24) and said cold tank (34) in hydraulic communication with each other.

Description

TEMPERATURE CONTROL DEVICE OR CIRCUIT FOR MOULDS OR MOULDING SYSTEMS

The present patent is related to mould temperature control systems and in particular concerns a new device or temperature control circuit for moulds or moulding systems with alternating multiple temperatures and a procedure for the startup and operation of the circuit.

The prior art comprises temperature control devices for moulding systems intended for plastic items based on the circulation of the thermoregulation fluid inside the mould itself. The temperature control devices of the prior art comprise a heating and cooling system for a fluid, usually water, which regulate the temperature of the fluid entering the mould depending on the moulding phase.

One example of a mould temperature control device in the prior art comprises at least one line to load the fluid into a circuit, at least one pump for the circulation of the fluid in the circuit itself, and means to regulate the temperature of the fluid in the circuit. Normally, the aforementioned means comprise a fluid heating tank, in which there is an electrical element and a temperature sensor which brings the fluid temperature to a preset value before the fluid is pumped into the mould to be heated. These means also comprise at least one heat exchanger with a cooling fluid, where the temperature of fluid to be pumped into the mould is lowered for the cooling phase where the hardening of the plastic occurs.

Patent document EP 1563975 A2 describes a device to control the moulding temperature in a moulding machine comprising a mould equipped with a temperature probe. The device described comprises a cooling tank and a heating tank which are hydraulically connected to each other by a pipe or the like equipped with an opening/closing valve. The cooling tank is not airtight and therefore the device requires two pumps to ensure sufficient pressure for the processes: the first pump to pump cold water into the circuit and the second pump to increase the pressure of the circuit itself.

Patent document WO2013/186287 Al describes a device to change the temperature of an object and comprises a circuit with a cold water tank and a hot water tank which communicate with each other via a compensation line with a valve, and where the water coming from these tanks is mixed in various ways and brought into contact with the object to control the temperature.

Patent document DE 2217545 Al concerns a heating/cooling apparatus for rotational moulds, also comprising a cold tank and a hot tank hydraulically connected to each other.

The object of the present patent is a new device or temperature control circuit for moulds or moulding systems with alternating multiple temperatures.

The main object of the present invention is to alternately inject hot and cold fluid into moulds and/or systems to rapidly and cyclically raise/lower their surface temperature and enable specific production sequences.

Another important object of the present invention is to have two sub-circuits, one of which is for the circulation of hot fluid, for example and advantageously having a temperature of l80°C, and one for the circulation of cold fluid, for example and advantageously having a temperature of 8°C. Through a system of valves, the cold fluid and the hot fluid are injected quickly and alternately inside the mould.

Still another important object of the present invention is to speed up the alternation between hot fluid and cold fluid inside the mould, which can also be performed in a few seconds, even in a time interval of 2-3 seconds.

A further important object of the present invention is that this alternation between hot fluid and cold fluid may be implemented in different times and sequences on different parts of the mould at the same time.

One important advantage achieved by the present invention is that it effectively separates the hot and cold fluids which are partially mixed in the mould, directing them to the respective separate sub-circuits of the device. Another advantage resulting from the effective separation of fluids at different temperatures is that the production cycle can be carried out with very low energy consumption.

Another object of the present invention is that it is able to regulate, manually and/or automatically, the opening/closing of the hot and cold fluid delivery/retum valves during the moulding processes, so as to optimize energy consumption while simultaneously achieving the desired performance.

These and other objects, direct and complementary, are achieved by the new temperature control device or circuit for moulds or moulding systems with alternating multiple temperatures.

The new device or circuit includes, in its main parts:

• at least one process fluid loading line for the circuit, where the process fluid is normally water;

• at least one first sub-circuit, hereinafter called a hot circuit, in turn comprising at least one recirculation pump, at least one heating element, from which the process fluid receives heat; at least one hot fluid delivery line to the mould, at least one air vent valve, at least one airtight fluid tank, hereinafter called the hot tank, at least one return line of fluid from the mould to the hot tank, at least one first by-pass line calibrated between the delivery line and the return line; the heating element is for example a tank with one or more electric elements; this hot circuit also advantageously comprises at least one safety valve;

• at least one second sub-circuit, hereinafter called a cold circuit, in turn comprising at least one recirculation pump, at least one heat exchanger, wherein the process fluid transfers heat to a cooling fluid, at least one cold fluid delivery line to the mould, at least one airtight fluid tank, hereinafter called the cold tank, at least one fluid return line from the mould to the cold tank, at least one first adjustable by-pass line between the delivery line and the cold tank, at least one second adjustable by-pass line between the hot circuit delivery line and return line; the cold circuit also advantageously comprises at least one expansion tank and preferably at least one drain valve hydraulically connected to the cold tank;

• a valve system for the selective injection of the hot and cold fluids into the mould, the valves being mounted on the hot and cold circuit delivery pipes, in correspondence with each of the possible branches of the delivery pipes themselves;

• a valve system for the extraction of fluid from the mould and for the separation of the hot and cold fluids, these valves being mounted on the hot and cold circuit return pipes at each of the possible branches of the return pipes themselves, to selectively convey the fluid leaving the mould to the hot circuit or to the cold circuit according to the temperature of the fluid itself; and where the circuit also comprises at least one device, hereinafter called flow conveying device, in turn comprising at least one connection pipe between the hot and cold tanks and at least one cut-off valve mounted on the connecting pipe.

The new circuit is advantageously equipped with at least one electronic control unit, with interface, to manage functions, and store and exchange data with external equipment.

The new circuit also comprises at least one exchanger cooling circuit, comprising at least one cooling liquid delivery and return line, usually water. This cooling circuit in turn also comprises at least one regulation valve.

The valves for the injection and separation of the hot and cold fluids in the mould are preferably remote controlled and are equipped with temperature probes with which it is possible to detect the temperature of the hot and cold fluids entering and leaving the mould.

In brief, the start up and operation procedure comprises the following operations:

• loading phase: the process fluid is loaded into the circuit by means of the loading line, after opening at least one loading valve. It is recommended that the correct pressure of the circuit be verified by means of a possible pressurization pump, able to load additional process fluid in the circuit, if necessary, so as to guarantee the required pressure; in this loading phase, the flow conveying device is configured with the cut-off valve open, so that the hot and cold tanks are hydraulically connected to each other.

• regulation phase: once the minimum working pressure of the process fluid in the circuit has been reached, the hot circuit recirculation pump is activated and the electric resistance inside the heat tank turns on to bring the temperature of the fluid in the hot circuit to the preset temperature; at the same time, the cold circuit recirculation pump is activated as is the cooling circuit regulation valve to bring the fluid into the cold circuit at the set temperature; during this adjustment step, the injection and separation valves for the hot and cold fluids in the mould are opened so that the process fluid flows smoothly in the mould and in the entire circuit. This, among other things, facilitates the elimination of air from within the circuit. In this phase, as in the others, if the pressure in the cold circuit or the hot circuit exceeds a preset limit value, the respective safety and discharge valves are opened.

• working phase: once the hot fluid and cold fluid inside the respective hot and cold tanks have reached the preset temperatures, the flow conveying device valve closes, hydraulically insulating the hot and cold tanks from each other. The valves for the injection and separation of the hot and cold fluids in the mould begin to function in a programmed manner according to the moulding cycles: the hot and cold fluids are then injected separately and alternately in the mould, according to the moulding cycles. At the mould outlet the valves separate the fluid in the hot and cold circuits according to the detected temperatures of the outbound fluid. The temperature values of the fluids, as well as the valve opening and closing times, are preset in the control unit and can be modified manually or automatically according to the operating requirements.

During the working phase, the hot fluid flow rate and the cold fluid flow rate are balanced due to the differentiated pressures in the respective hot and cold tanks. In fact, the storage tanks are airtight and have a fixed volume, therefore the volume of the air contained therein works as a buffer to balance the pressure of the respective fluids and thus the flow rates of the respective pumps.

Thanks to the complete separation of the hot fluid and the cold fluid during the working phase, the new circuit ensures relevant energy savings.

In the case in which an imbalance occurs and must be corrected, it is still possible to open the flow conveying valve, in order to connect the two tanks, thus restoring the balance with minimal mixing of hot and cold fluids.

The new circuit has many advantages. In particular, the hot and cold tanks have a preferably vertical layout, which therefore allow the stratification of the fluid, partially separating the fluid at a higher temperature from that at a lower temperature.

In fact, the design may enable the flow conveying device to draw the water from the upper zone of the cold tank, so as to transfer the warmest water to the hot tank by compensation, thus further limiting energy consumption to bring/maintain the hot fluid to/at the desired temperature.

The aforementioned flow conveying device also selectively enables the communication between the two circuits, that is, the cold and hot circuits, or to separate them completely.

The cooling circuit heat exchanger enables the substantially immediate availability of cold fluid.

The availability of hot fluid is also substantially immediate since the hot circuit recirculating pump is installed in series with respect to the hot tank.

On the return pipes upstream of the separation valves, temperature probes are also installed to monitor the temperature of the fluid exiting the moulds in order to enable the management of the separation valves and direct the fluid into the hot circuit or the cold circuit.

These injection valves and separation valves can all operate synchronously or asynchronously. The control unit makes it possible to set operating parameters to optimize the separation of fluids and energy consumption.

The operation and the injection and separation valve opening/closing time, as well as the regulation of the operating parameters (pressure, temperature, fluid flow rates) are a function of the process temperature to be obtained in the mould at least in the initial start up of the work phase. Subsequently, these parameters and the valve opening/closing times are adjusted manually or automatically so as to optimize energy consumption.

It is therefore envisaged that the control unit of the new device or circuit works according to a management program that manages these parameters after an initial "self-learning" phase, in which those parameters can be manually entered by an operator. After this initial learning phase, the management program regulates the parameters in a substantially continuous manner so as to obtain the greatest possible energy savings while maintaining the desired performance.

At the operational level it is possible to proceed as follows:

1. at the start-up phase of a moulding process, the fluid temperature variation times of the fluid exiting the mould are measured and evaluated;

2. according to the temperature probes used, which may have different sensitivities and detection speeds, and of the fluid circuits, the hot/cold heat exchange times are determined on the return lines, that is, the opening/closing times of the separation valves located at the mould outlet;

3. these exchange times are set so as to work in "timed" mode, that is, according to the calculated times;

4. energy consumption is monitored; 5. the valve opening/closing times are gradually adjusted to reduce energy consumption;

6. the management program starts and automatically regulates the parameters, including the valve opening/closing times, so as to optimize the energy consumption.

Furthermore the first "self-learning" phase may take place automatically by the control unit in question which, by means of the management program and once the process requirements are established, automatically regulates the operating parameters (valve opening/closing times, flow rates, hot/cold fluid pressure and temperature) thus enabling even this first phase of use as described above to be automated.

In particular, after the first "self-learning" phase, the control unit calculates the relevant operating parameters, controls them and, if necessary, regulates them continuously, with the aim of minimizing the energy consumption of the entire system.

This regulation is continuously updated, adapting to any change in operating conditions determined by the process in which the system is used, so as to always obtain the lowest energy consumption.

The characteristics of the new circuit will be better clarified by the following description with reference to the drawing, attached by way of a non-limiting example.

Figure 1 shows a diagram of the new circuit (100) where for simplicity a single mould (S) is shown with two delivery lines (23, 33) and two return lines (25, 35) for the hot and cold fluids.

The new temperature control device (10) for moulds or moulding systems (S) comprises at least one process fluid loading line (11) for the circuit, where that process fluid is normally water.

Advantageously, the loading line (11) comprises the necessary input fluid control devices, such as a valve (112), a pump (111), a non-return valve (113), a pressure sensor (114), etc.

The circuit (10) comprises one first sub-circuit, hereinafter called hot circuit (20), shown in Figure 1 with a thick line, and one second sub-circuit, hereinafter called cold circuit (30), shown in Figure 1 with a fine line.

The hot circuit (20) comprises a recirculation pump (21), at least one heating element (22), in which the fluid is heated, at least one vent valve (223), at least one temperature probe (28) suitably installed downstream of the heating element (22), at least one delivery line (23) for the hot fluid towards the mould (S), at least one fluid storage tank, hereinafter called hot tank (24), at least one return line (25) of the fluid from the mould (S) to the hot tank (24).

The heating element (22) is suitably a tank (221) containing at least one electric element (222) in which the fluid to be heated circulates.

The hot circuit (20) also comprises at least one first adjustable by-pass line (26) between the delivery line (23) and the return line (25).

The hot circuit (20) also advantageously comprises one or more safety valves (27). The cold circuit (30) comprises at least one recirculation pump (31), at least one heat exchanger (32), wherein the process fluid transfers heat to a cooling fluid, at least one temperature probe (38), suitably installed downstream of the at least one heat exchanger (32), at least one cold fluid delivery line (33) towards the mould (S), at least one fluid storage tank, hereinafter called cold tank (34), and at least one return line (35) of the fluid from the mould (S) to the cold tank (34).

The circuit (10) also comprises at least one heat exchanger (32) cooling circuit (50), comprising at least one delivery line (51) and at least one outlet line (52) of the cooling fluid which is normally water. The cooling circuit (50) in turn also comprises at least one regulation valve (53).

The cold circuit (30) also comprises at least one first adjustable by-pass line (36) between the delivery line (33) and the cold tank (34), at least one second adjustable by-pass line (37) between the delivery line (33) and the return line (25) of the hot circuit (20).

The cold circuit (30) also advantageously comprises at least one expansion tank (341) hydraulically connected to the cold tank (34) and preferably at least one drain valve (342) and a drain/vent/overpressure valve (343) hydraulically connected to the cold tank (34).

Each of the delivery lines (23, 33) of the hot circuit (20) and cold circuit (30) preferably comprise delivery branches (231, 331) for the distribution of the fluid on the mould (S).

At least one injection valve (232, 332) is installed on each of the delivery branches (231, 331) for the selective injection of hot and cold fluids into the mould (S).

Each of the return lines (25, 35) of the hot circuit (20) and cold circuit (30) preferably comprise the return branches (251, 351) conveying the fluid from the mould (S).

At least one separation valve (252, 352) is installed on each of the return branches (251, 351) to selectively convey the fluid exiting the mould to the hot circuit (20) or to the cold circuit (30) depending on the measured temperature of the fluid itself.

The hot and cold fluid injection (232, 332) and separation (252, 352) valves in the mould (S) are preferably remotely controlled and equipped with temperature probes with which it is possible to detect the temperature values of the hot and cold fluids entering and exiting the mould (S).

In particular, temperature probes (12) are also installed upstream of the separation valves (252, 352) and, according to the temperature of the fluid exiting the mould (S), the valves (252, 352) convey the fluid towards the hot circuit (20) or towards the cold circuit (30).

The circuit (10) also comprises at least one flow conveying device (40) in turn comprising at least one connection pipe (41) between the hot tank (24) and the cold tank (34) and at least one cut-off valve (42) installed on the connection pipe (41). The valve (42) of the pipe (41) selectively connects the cold tank (34) and the hot tank (24) depending on the operating phase of the circuit (10) and depending on the temperature and pressure of the fluids in the cold circuit (30) and hot circuit (20). These injection valves and separation valves can all operate synchronously or asynchronously. The control unit makes it possible to set operating parameters to optimize the separation of fluids and energy consumption.

The system also advantageously comprises pressure sensors, specially installed in the delivery lines (23, 33) of the hot (20) and cold (30) circuits.

These specifications are sufficient for the expert person to make the invention, as a result, in the practical application there may be variations without prejudice to the substance of the innovative concept.

Therefore, with reference to the preceding description and the attached drawing the following claims are made.

Claims

1. Temperature regulation circuit (10) for a mould (S) or a moulding system, comprising:

• at least one loading line (11) suited to load a process fluid and equipped with the necessary devices for controlling the fluid flowing into the circuit;

• at least one second sub-circuit or hot circuit (20), in turn comprising at least one recirculation pump (21), at least one heating element (22), in which the process fluid receives heat, at least one delivery line (23) suited to deliver the hot fluid into said mould (S), at least one accumulation tank or hot tank (24), at least one return line (25) suited to allow said fluid flowing out of said mould (S) to return into said hot tank (24);

• at least one first sub-circuit or cold circuit (30), in turn comprising at least one recirculation pump (31), at least one heat exchanger (32), in which said process fluid transfers heat to a cooling fluid, at least one delivery line (33) suited to deliver the cold fluid into said mould (S), at least one accumulation tank or cold tank (34), at least one return line (35) suited to allow said fluid flowing out of said mould to return into said cold tank (34),

characterized in that said circuit (10) comprises also at least one flow conveying device (40), in turn comprising at least one connection pipe (41) suited to connect said hot tank (24) and said cold tank (34) together and at least one on-off valve (42) mounted on said connection pipe (41) and suited to selectively place said hot tank (24) and said cold tank (34) in hydraulic communication with each other.

2. Temperature regulation circuit (10) according to claim 1, characterized in that said hot circuit (20) comprises also at least one adjustable bypass line (26) between said delivery line (23) and said return line (25).

3. Temperature regulation circuit (10) according to claim 1, characterized in that said cold circuit (30) comprises also at least one first adjustable bypass line (36) between said delivery line (33) and said cold tank (34) as well as at least one second adjustable bypass line (37) between said delivery line (33) and said return line (25) of said hot circuit (20).

4. Temperature regulation circuit (10) according to any of the preceding claims, characterized in that it comprises also pressure sensors installed in said delivery lines (23, 33) of said hot circuit (20) and said cold circuit (30).

5. Temperature regulation circuit (10) according to any of the preceding claims, characterized in that it comprises also at least one temperature probe (38) in said cold circuit (30), conveniently located downstream of said at least one heat exchanger (32), and at least one temperature probe (28) in said hot circuit (20), conveniently located downstream of said heating element (22).

6. Temperature regulation circuit (10) according to any of the preceding claims, characterized in that:

• said cold circuit (30) comprises also at least one expansion tank (341), at least one outlet valve (342) and at least one breather valve (343) hydraulically connected to said cold tank (34);

• said hot circuit (20) comprises at least one breather valve (223).

7. Temperature regulation circuit (10) according to any of the preceding claims, characterized in that it also comprises at least one cooling circuit (50) for said heat exchanger (32), comprising at least one feeding line (51) for feeding the cooling liquid into said heat exchanger (32) and at least one outlet line (52) for said cooling liquid.

8. Temperature regulation circuit (10) according to any of the preceding claims, characterized in that each one of said delivery lines (23, 33) of said hot circuit (20) and said cold circuit (30) comprises delivery branches (231, 331) for the distribution of the fluid in the mould (S), and wherein said delivery branches (231, 331) are provided with valves (232, 332) for the selective injection of said hot fluid and said cold fluid into said mould (S).

9. Temperature regulation circuit (10) according to claim 1 or 8, characterized in that each one of said return lines (25, 35) of said hot circuit (20) and said cold circuit (30) preferably comprises return branches (251, 351) for the return of the fluid from the mould (S), and wherein said return branches (251, 351) are provided with partitioning valves (252, 352) suited to partition the fluid which flows out of said mould (S), in order to selectively convey the fluid flowing out of said mould (S) into said hot circuit (20) or into said cold circuit (30) according to the temperature values of the fluid itself.

10. Temperature regulation circuit (10) according to claims 8 and 9, characterized in that said valves for the injection (232, 332) and the separation (252, 352) of said hot and cold fluids are remotely controlled and are equipped with temperature probes by means of which it is possible to take the temperature values of the hot and cold fluids flowing into and out of the mould (S).

11. Temperature regulation circuit (10) according to the preceding claims, characterized in that it comprises a control unit suited to receive the data related to the delivery, pressure and temperature parameters of said hot and cold fluids and to the energy consumption, and suited to control the opening/closing times of said injection valves (232, 332) and separation valves (252, 352), and wherein, according to the moulding process, said control unit regulates said parameters and said opening/closing times of said injection valves (232, 332) and separation valves (252, 352) in order to optimize said energy consumption.

12. Process for commissioning and operating the circuit (1) according to one or more of the preceding claims, characterized in that it comprises at least one loading step, in which the process fluid is loaded into said circuit (10) through said loading line (11), after at least one loading valve has been opened, and wherein during said loading step said flow conveying device (40) is configured with open on- off valve (42), so that said hot tank (24) and said cold tank (34) are in hydraulic communication with each other.

13. Process according to claim 12, characterized in that it comprises the step of correction of pressure in said circuit (10) by means of a pressurisation pump (111) suited to load a further amount of process fluid into the circuit (10) in order to guarantee that the required pressure value is reached.

14. Process according to claim 12, characterized in that it comprises at least one setting step during which:

• once the minimum working pressure of the process fluid inside the circuit (10) has been reached, said recirculation pump (21) of said hot circuit (20) is tripped and said heating element (22) is switched on in order to bring the temperature of the fluid in the hot circuit (20) to the set value;

• said recirculation pump (31) of said cold circuit (30) is tripped together with said cooling circuit (50) in order to bring the cold fluid temperature to the set value;

• said valves (232, 332, 233, 353) for the injection and separation of said hot and cold fluids into said mould (S) are open, in such a way that the process fluid can flow smoothly inside the mould and in the whole circuit;

• said flow conveyance device (40) is configured with open on-off valve (42), so that said hot tank (24) and cold tank (34) are in hydraulic communication with each other.

15. Process according to claims 12, 13, 14, characterized in that it comprises at least one working step during which, once the hot fluid and the cold fluid inside the respective hot tank (24) and cold tank (34) have reached the set temperature values, said valve (42) of the flow conveyance device (40) closes, hydraulically isolating said hot tank (24) and said cold tank (34).

16. Process according to one or more of claims from 12 to 15, characterized in that it comprises a first "self-learning" phase during which all or part of the operating parameters of said circuit (10) are entered manually or automatically according to the utilization process, wherein said operating parameters comprise delivery, temperature and pressure of said hot and cold fluids, according to the following procedure: - taking and evaluation of the times of variation of the temperature of the fluid flowing out of a mould during the start-up phase of the moulding process; determination of the hot/cold exchange times on said return lines, meaning of the opening/closing times of said separation valves downstream of said mould;

setting of said exchange times on said control unit, in such a way that said circuit (10) operates according to said times;

monitoring of the energy consumption values;

gradual correction of said valve opening/closing times, intended to reduce said energy consumption;

start of said management program for the automatic regulation of said parameters and of said exchange times, in order to maintain an optimal energy consumption.

17. Process according to claim 16, characterized in that said“self-learning” phase is carried out manually.

18. Process according to claim 16, characterized in that said“self-learning” phase is carried out automatically by said control unit.