DE102010051528A1 - Device for determining gas consumption and volume of gas generated by inner cavity of molded portion, has sensors that are connected to programmable logic controller, such that control valve is closed for implementation of work cycle - Google Patents

Abstract

The temperature sensor (T1) and pressure sensor (S1) are pneumatically connected with an inlet associated with an injector (I1) of proportional valve (V2) for pressure control. The sensors are connected to programmable logic controller (PLC), such that control valve (V1) is closed for the implementation of a work cycle, in accordance with start signal from PLC. The gas compression coefficient, cycle time, gas volume, initial pressure, final pressure, initial temperature and final temperature detected by respective sensors are related by predetermined equation.

Description

Generally speaking, the invention is concerned with the internal gas pressure method (abbreviated to "GIT"), which is commonly used nowadays to produce moldings having an internal cavity. To generate the inner cavity, pressurized gas is introduced into the still mouldable plastic mass.

For the quality control and the documentation of the manufactured parts, the collection and the documentation with regard to the gas used in the manufacturing process gains in importance, in particular with regard to the volume. The amount of the introduced gas can be accurately detected by a mass flow device disposed in the gas injection passage. However, this requires an additional external control system and, in particular, such mass flow rate measuring devices are very expensive in terms of production costs.

The invention therefore aims to provide a device for determining a volume of an inner cavity of a molding produced by internal gas pressure and a gas consumption, which allows a cost-effective manner and without expensive mass flow meters reliable detection of the volume and gas consumption in the gas internal pressure process.

ΔV:

verbrauchtes Volumen

Δt:

Zykluszeit

P:

Druck (Pi, Pf)

T:

Temperatur (Ti, Tf)

z:

Gaskompressionskoeffizient abhängig von Druck (Pi, Pf) und Temperatur (Ti, Tf)

V_c1:

Volumen des Vorratszylinders C1 mit Volumina der Anschlüsse.

For this purpose, an apparatus for determining a volume of an inner cavity of a molded part generated by internal gas pressure and gas consumption is provided according to the invention, in which a normally open control valve (V1), a reservoir (C1) with a predetermined volume, a temperature sensor (T1) and a pressure sensor (S1) are pneumatically connected to an inlet of a proportional valve (V2) connected to an injector (I1) for pressure control in the gas internal pressure process (GIT) and are electrically connected via a programmable controller (PLC) such that in response to a start signal from the (PLC) the control valve (V1) is closed to perform a duty cycle, the initial pressure (Pi) and the initial temperature (Ti) are stored and the final pressure (Pf) and the end temperature (Tf) after the duty cycle by means of the pressure sensor (S1) and the temperature sensor (T1) are detected and therefrom by means of programmable Steuerun g (PLC) the mass flow rate is determined in accordance with the following equation: Q = ΔV / Δt = (Δ (P / z) × V _C1 ) / Δt → Q = [(Pi / Z _{(Pi, Ti)} ) - (Pf / Z _{(Pf, Tf)} )] × V _C1 / ( t _i -t _f ) where:

.DELTA.V:

used volume

.delta.t:

cycle time

P:

Pressure (Pi, Pf)

T:

Temperature (Ti, Tf)

z:

Gas compression coefficient dependent on pressure (Pi, Pf) and temperature (Ti, Tf)

V _c1 :

Volume of stock cylinder C1 with volumes of connections.

The device according to the invention permits, via a controlled integrated determination of the gas volume and the gas consumption, an exact determination of the gas volume per injection channel of an injection mold in the internal gas pressure method. In particular, in the solution according to the invention, the detection and the programmable controller are preferably integrated on a software basis, which is also used for controlling the gas introduction into the injection mold. Thus, according to the invention, an additional function is assigned to this programmable controller, and appropriate sensors and a storage container having a predetermined volume are provided for detecting the parameters which are essential for the determination, such as pressure, volume and temperature. Thus, cost-effective components, such as reservoir, pressure sensor and temperature sensor are sufficient for realizing the device according to the invention. As a result, the device according to the invention represents a cost-effective solution, which also takes up little space, since complex mass flow devices can be omitted without replacement.

For simplified documentation, the determined values are stored in the programmable controller according to a preferred embodiment. Thus, the respectively determined volume, temperature and gas consumption data can be secured in a simple manner.

In order to enable universal compatibility and further transmission of the determined values, the determined values can be exported via an interface from the programmable controller. Preferably, the export is via USB or other suitable interface such as Ethernet or the like. As a result, the device according to the invention can be seamlessly integrated in the entire process flow and in the process documentation.

Preferably, the device is further designed such that the determined values can be displayed on a visual display. As a result, the controlled processes can be clarified and illustrated. In order to control the internal gas pressure process, alarm messages may be issued according to tolerance values for the volume or gas consumption.

The invention will be explained below with reference to a preferred embodiment with reference to the accompanying drawings.

ΔV:

verbrauchtes Volumen

Δt:

Zykluszeit

P:

Druck (Pi, Pf)

T:

Temperatur (Ti, Tf)

z:

Gaskompressionskoeffizient abhängig von Druck (Pi, Pf) und Temperatur (Ti, Tf)

V_c1:

Volumen des Vorratszylinders C1 mit Volumina der Anschlüsse.

The only 1 The drawing illustrates in a flow chart the details of a device for determining a volume of an inner cavity of a molded part generated by means of internal gas pressure and the gas consumption. The device itself is generally designated by the reference numeral 1 Mistake. In a schematic with 2 designated supply line to at least one injector I1, by means of which gas is introduced into the injection mold to produce an internal cavity, a control valve V1, a reservoir C1 with a predetermined (small) volume, a pressure sensor S1 and a temperature sensor T1 is shown. The control valve V1, the pressure sensor S1 and the temperature sensor T1 are pneumatically connected to an inlet of a proportional valve V2 connected to an injector I1 for pressure control in the internal gas pressure method. Electrically, they are operatively connected via a programmable controller PLC, as indicated by broken lines. This programmable controller PLC receives a start signal, by which the control valve V1 is closed to perform a work cycle. By means of the pressure sensor S1, the initial pressure Pi and by means of the temperature sensor T1, the initial temperature Ti is detected. The initial pressure Pi and the initial temperature Ti are stored, which are obtained in the working cycle, with the aid of the sensors S1 and T1. The programmable controller PLC then determines the mass flow rate in accordance with the following equation Q = ΔV / Δt = (Δ (P / z) × V _C1 ) / Δt → Q = [(Pi / Z _{(Pi, Ti)} ) - (Pf / Z _{(Pf, Tf)} )] × V _C1 / ( t _i -t _f ) where:

.DELTA.V:

used volume

.delta.t:

cycle time

P:

Pressure (Pi, Pf)

T:

Temperature (Ti, Tf)

z:

Gas compression coefficient dependent on pressure (Pi, Pf) and temperature (Ti, Tf)

V _c1 :

Volume of stock cylinder C1 with volumes of connections.

In the programmable controller PLC, this mass flow determination is realized by means of a software. The software permits the processing of the measured data in accordance with this above equation of determination.

In the device according to the invention, the determination of the volume of a cavity of a molded part produced by internal gas pressure and the gas consumption are thus integrated into the programmable controller, and only relatively inexpensive additional components such as a reservoir, a pressure sensor and a temperature sensor are required.

Thus, the invention is a low-component and cost-effective solution.

Although not shown, the values determined by the programmable controller PLC can be stored in the same via the volume and the gas consumption. Of course, the programmable controller PLC has sufficient storage capacity for this purpose. The values determined with the aid of the device can thus be secured in a simple and reliable manner.

The programmable controller PLC compares stored minimum and maximum values for the measurement data to control the internal gas pressure method and to trigger an alarm in case of overflow.

For documentation and the corresponding quality control, the determined values can be exported via an interface from the programmable controller PLC. The export is possible, for example, via USB or other suitable interfaces, such as Ethernet, in the PLC programmable controller.

If necessary, the values stored in the programmable controller PLC can be displayed in a visual display, so that the process flow can also be visualized visually. If the readings are out of tolerance, an alarm may sound, a message may be displayed, a buzzer may be activated, and / or the internal gas pressure procedure may be stopped.

Of course, the invention is not limited to the preceding embodiments or the details thereof, but numerous modifications and modifications are possible, which the person skilled in the art can make if necessary without departing from the spirit of the invention.

Claims (6)

Device for determining a volume of an internal cavity of a molded part produced by means of internal gas pressure and of gas consumption, characterized in that a control valve (V1) which is open in the ground state, a reservoir (C1) with a predetermined volume, a temperature sensor (T1) and a pressure sensor (S1) pneumatically connected to an inlet of a proportional valve (V2) connected to an injector (I1) for pressure regulation in the gas internal pressure process (GIT) and electrically via a programmable controller (PLC) are operatively connected in accordance with a start signal from the (PLC) the control valve (V1) is closed to perform a duty cycle, the initial pressure (Pi) and the initial temperature (Ti) are stored and the final pressure (Pf) and Final temperature (Tf) after the duty cycle by the pressure sensor (S1) and the temperature sensor (T1) are detected and using the programmable controller (PLC), the mass flow rate is determined in accordance with the following equation: Q = ΔV / Δt = (Δ (P / z) × V _C1 ) / Δt → Q = [(Pi / Z _{(Pi, Ti)} ) - (Pf / Z _{(Pf, Tf)} )] × V _C1 / ( t _i -t _f ) where: ΔV: consumed volume Δt: cycle time P: pressure (Pi, Pf) T: temperature (Ti, Tf) z: gas compression coefficient dependent on pressure (Pi, Pf) and temperature (Ti, Tf) V _c1 : volume of Stock cylinder C1 with volumes of connections. Apparatus according to claim 1, characterized in that the determined values of the programmable controller (PLC) can be stored. Apparatus according to claim 1 or 2, characterized in that the values determined by means of the programmable controller (PLC) are compared with minimum and maximum values in order to control the internal gas pressure method (GIT) and to trigger an alarm in the event of an overflow. Apparatus according to claim 2 or 3, characterized in that the determined values can be exported via an interface from the programmable controller (PLC). Apparatus according to claim 3, characterized in that the export takes place by means of USP or Ethernet. Device according to one of claims 2 to 5, characterized in that the determined values can be displayed on a visual display.

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