Patent Application
20180264698
The present invention refers to apparatus for injection moulding of plastic materials including a mould comprising a distributor of plastic material to be injected, at least one injector including a nozzle with respect to which a valve pin is moveable, and actuator means for controlling the displacement of the valve pin between a closing position and an opening position to enable the flowing of the pressurised fluid plastic material from the distributor to the mould cavity.
Conventionally, actuator means for controlling the valve pin of the or of each injector consist in fluid actuators which entail sensitive complications due to the need of providing dedicated systems and pipings for supplying oil or air, as well as almost zero control options except for an ON/OFF actuation. In addition, there are problems related to cleaning, and overall dimensions due to the presence of the pipings.
Actuation systems employing electric motors, in particular of the rotary type, and provided with devices for detecting the position of the valve pin, for example an encoder or resolver associated to the shaft of the rotary motor and connected to a stand-alone electronic unit through which a prompt and precise control of the position, speed and acceleration of the valve pin is carried out, alongside the monitoring and recording data in real time, were proposed with the aim of overcoming these drawbacks. The electronic unit is usually provided separately with respect to the mould and it is designed to be indistinctly combined with any mould provided with electric actuators, regardless of the number thereof. However, the undeniable advantages in terms of flexibility and precision in controlling the moulding process have a negative impact on the supply and operating costs of the equipment and the overall dimensions of the work area, considering that the unit should necessarily always remain connected to the system during operation. Examples regarding this are described and illustrated for example in the published
European patent applications EP-2679374A1, EP-2918389A1 and EP-3009251A1, all on behalf of the Applicant of the present patent. In the concrete application of the solutions described in these documents, whose costs are high and considerably higher than those of fluid actuators, rotary electric motors are of the brushless type provided with an encoder or resolver and combined with a stand-alone electronic unit.
The object of the present invention is to provide a simpler, more cost-effective and less cumbersome alternative to the prior art systems with the aforementioned electric motors, while maintaining the undeniable advantages with respect to systems with fluid actuators in terms of construction simplicity of the apparatus, cleaning and possibility of adjusting the main opening and closing parameters of the single injector (e.g. position, speed, acceleration).
According to the invention, this object is attained thanks to an injection moulding apparatus of the type defined above, whose distinctive characteristic lies in the fact that the supply and control unit is fixed to the mould and univocally associated thereto.
The supply and control unit is preferably secured to the fixing plate of the mould. The electric supply is provided by means of connectors located on the unit, while the control of the main parameters for opening and closing of the injectors occurs by suitably configuring the driver of the circuit board associated to each electric motor and positioned in the unit.
This solution idea enables at least partly obtaining the advantages of the electric motors provided for in the aforementioned prior art solutions, but eliminating the use of the stand-alone electronic control unit, thus cutting costs considerably and reducing the the overall dimension of the working area.
Preferably, the electric motor is of the rotary brushless type and provided with an encoder or resolver.
Alternatively, the electric motor is of the direct current and rotary type, or, according to a less advantageous variant, it can be of the asynchronous or universal type.
The configuration of the main parameters for opening and closing the single injectors is simplified and occurs by manually setting the driver of each electronic control board arranged inside the unit. The configuration control is carried out by the operator preferably for example through a universal external control panel (e.g. a PLC), i.e. usable for configuring the drivers of any unit according to the invention. Alternatively, the control can be carried out through potentiometers associated to the circuit board, for example accessible through a special opening obtained in the supply and control unit, or even by means of dedicated push buttons or a control unit directly arranged on the supply unit. According to a further variant, the configuration controls may be carried out from remote, for example directly on the control panel of the injection machine.
According to a preferred embodiment of the invention, upon configuring the drivers of the circuit boards regarding each electric motor, the opening and closing control of each injector can be directly sent by the control panel of the injection machine or, alternatively, by a general sequential control unit already owned by the customer.
The moulding apparatus which uses the electric motors may be variously configured, in that they can be alternatively carried by the fixing plate of the mould or by the machine platen or by the distributor.
The invention will now be described in detail, purely by way of non-limiting example, with reference to the attached drawings, wherein:
The described embodiment refers—for the sake of simplicity—to an injection moulding apparatus provided with electric motors with configuration control of the driver of the circuit board that each motor is provided with, for example by means of potentiometers or other equivalent systems to be addressed hereinafter.
The apparatus is provided with three injection points generally indicated with 1, 2 and 3 in
The central injection point 1 is shown in detail in
In the case of the illustrated example the distributor 6 is housed in a cavity 11 of a fixing plate or clamping plate 12 configured, possibly combined with further plates, for fixing the mould 4 to a machine platen 13 of the moulding apparatus.
The cavity 11 of the fixing plate 12 within which the distributor 6 is housed, is faced towards the moulding cavity 5.
The valve pin 10 of the injector 8 is actuated by a pre-assembled actuator unit illustrated in detail in
According to a preferred embodiment, the rotary motor 15 is a brushless electric motor provided with an encoder or resolver. Alternatively, the rotary motor could be of the direct current, asynchronous or universal type.
Now back to
According to the distinctive characteristic of the invention each rotary electric motor 15 is housed, through respective supply and control conductors 21 extending on the same face of the fixing plate 12, to a supply and control unit 22 preferably applied to such fixing plate 12 or to one of the plates that form the mould 4. Alternatively, the unit 22 may be fixed to the distributor 6 indirectly, i.e. on the support structure of the cables of the distributor 6, as previously known as concerns solenoid valves for controlling fluid actuators (see for example FIG. 1 of the Chinese patent application CN-104943065A on behalf of Guandong Yudo).
As illustrated in detail in
The number of the electronic control boards 26 does not necessarily coincide with the number of electric motors 15 present in the mould 4, i.e. the driver of a single electronic control board 26 may be combined with more than one electric motor 15, for example given that two or more injectors 8 require the same opening and closing parameters. In other cases, a single driver may be capable of memorising more than one configuration of the opening and closing parameters designated for more than one injector 8.
The operator may manually configure the driver of the single circuit boards 26 by means of potentiometers 24, for example attainable through a special opening 25 obtained in the supply and control unit 22, so that it does not have to be opened completely thus avoiding the risk of damaging or dirtying the components contained therein. Alternatively, the configuration of the single circuit boards 26 may be carried out by means of special push buttons or a control panel arranged on the unit 22, or it may be carried out remotely for example directly on the control panel of the injection machine.
However, according to a preferred embodiment, the configuration is carried out by the operator through a universal external control panel (for example PLC), i.e. usable for the configuration of the drivers of any supply and control unit 22 according to the invention, even fixed to different moulds.
Upon configuring the drivers of the circuit boards 26 regarding each electric motor 15, the control panel (contrary to what occurs in the prior art solutions with a stand-alone electronic unit) can be disconnected and a control for opening and closing each injector 8 can be directly sent by the control panel of the injection machine or, alternatively, by a general sequential control unit already owned by the user.
The above clearly shows the extreme simplicity of the actuation system of the injectors 8 which enables obtaining moulding apparatus which, excluding the absence of hydraulic/pneumatic connections, are substantially similar to the fluid actuation moulding apparatus, even more so given that the connections between the injection machine and mould remain intact.
The supply and control unit 22 is also externally similar to the boxes designated for supplying the solenoid valves in fluid systems and, as concerns what has been illustrated above, the input for opening and closing the valves of the injectors may be directly carried out out by the control panel of the injection moulding machine, just like in conventional pneumatic or hydraulic systems. However, with respect to the latter, there are obtained considerable advantages in terms of construction simplicity, cleaning and the possibility of intervening on the main parameters for opening and closing the injectors, and with considerable reduction of costs and overall dimensions with respect to those of the prior art electric systems. Basically, the customer gets a mould complete with a unit for supplying and controlling electric motors univocally associated thereto, without having to purchase, position and connect a stand-alone electronic control unit, often over-dimensioned with respect to the actual need.
According to an alternative embodiment, the rotary motor 15 is a direct current electric motor without an encoder or resolver. This solution enables reducing costs further when a control on the speed and/or acceleration for opening and closing the injectors 8 (not on the position) is sufficient.
For example, with reference to the configuration of the speed for opening and closing the injector, upon setting the configuration the driver directly acts on the actual operating voltage, or alternatively on voltage splitting through a PWM (pulse width modulation) system.
Costs saving is further accentuated by the elimination of the limit switch adjustment devices, necessarily present in the prior art solutions, in that the control board of the direct current motor is per se capable of recognising when the motor, or the valve pin 10 driven by it, is under stress, so as to be able to stop automatically. Such evaluation is carried out based on the absorption of the electric motor currents.
Lastly, given the absence of the encoder or resolver, the motor output only features the conductors intended for supplying power, thus adding further advantages in terms of reducing overall dimensions and facilitating installation.
Electric motors can also be used equally advantageously in cases where the latter with the relative transmissions are carried—in place of the fixing plate 12—by the machine platen 13, or by a support thereof arranged laterally with respect to the fixing plate, according to the description and illustration subject of the aforementioned patent no EP-3009251A1. In this case, the variable length transmission rods 17 will extend through the fixing plate 12.
Same applies in cases where the electric motors and the relative transmissions are directly carried by the distributor 6, as described in the aforementioned patent application no EP-2679374A1.
Lastly, the invention remains valid even in cases where electric motors 15 move respective valve pins 10 in transversal direction, or however not coaxial, with respect to the corresponding injector 8 between a closing position and an opening position, for example as described by the Italian patent application no IT-102016000044688 on behalf of the Applicant of this patent (not published as of date of filing of the present application).
According to a further characteristic of the invention, the supply and control unit 22 is removably fixed to the mould 4, in particular to enable the user to pass to an advanced system provided with a stand-alone electronic unit according to the prior art, or vice versa, at any time.
For example, every mould provided with electric motors may be manufactured provided with supply and control connectors designated for motors 15 and the stand-alone electronic unit according to the prior art. However, the user has the freedom of removably fixing the supply and control unit 22 according to the invention above and laterally with respect to the connectors.
The supply and control unit 22 may also be removed from one mould and fixed to another mould provided with electric motors 15, and then subsequently configuring, adding or removing control boards 26 depending on the number of motors 15 and required parameters.
Obviously, the construction details and embodiments may widely vary with respect to what has been described and illustrated, in particular as regards the type of motor used or the instrument used by the user to configure the driver of the circuit board or for sending the control for opening and closing each injector, without departing from the scope of protection of the present invention as defined in the claims that follow.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102015000081904 | Dec 2015 | IT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2016/056168 | 10/14/2016 | WO | 00 |
