DE3431322C1 - Device for the metered feeding of additives to plastics granules on a plastics processing machine - Google Patents

Abstract

A device for the metered feeding of lumpy or granular additives to plastics granules on a plastics processing machine, the metering apparatus of which, which is fed in a sequentially controlled manner by a plastication screw, dispenses the additive in portions via a conveying line is proposed, which device reacts both to the absence of a reserve of additive and to operational faults of the metering device and is also of simple construction and, with a few manual operations, can be combined - if necessary even subsequently - with a metering apparatus. A light barrier which responds to the additive flow is provided, the housing of which has tubular connectors for plug connection to the discharge connector of the metering apparatus on the one hand and to the conveying line on the other hand, said light barrier being connected to a pulse evaluation circuit via which, when a presettable or preset number of cycles of the plastication screw is reached but there has been no pulse from the light barrier, an optical and/or acoustic display instrument can be switched on and/or the drive of the plastication screw switched off.

Description

assume that after three cycle bars, i.e. after three shots the plasticizing screw a portion of the

If the additive is to be added, the monitoring is on four Set cycle rates. This ensures that after four cycle clocks at If the substance is not added, the alarm is evaluated. Until the alarm starts (or the machine shutdown) then only four missed shots are produced. If the monitoring works in the sense of switching off the machine, this remains the case low number of missed shots.

With a pulse memory with a reset circuit after the last cycle clock when the light barrier is pulsed during the preset number of machine cycle cycles the automatic pulse counting of the electronics always goes off when the device is operating properly itself back to the zero position and the pulse counting begins on the one hand for the cycle clocks and on the other hand the light barrier and the comparison of the same again.

The invention thus provides an overall very simple monitoring device available, which always reacts safely to malfunctions in the dosing process and at any time with just a few simple steps you can easily use existing dosing devices The invention is explained below with reference to one in the drawings illustrated embodiment explained in more detail. In the drawings shows F i g. 1 a schematic representation of the arrangement of the monitoring device, F i g. 2 shows a schematic representation of the pluggable arrangement of a light barrier and F i g. 3 is a block diagram of the monitoring electronics.

In a relatively large storage container 10 is colorless plastic granulate stored, which a plasticizing screw 11 one in F i g. 1 not complete plastic injection molding machine 12 shown over an outlet area 13 of the Storage container 10 can be supplied, but it is also possible to load the machine 12 with granules via a pipe opening at 13.

The granules intended for processing in the machine 12 are used in certain dosed amounts cyclically an additive - z. B. Color granulate - added.

This is stored in an addition container 14, which is on a metering device 15 is in place. The additive fills a channel in the metering device 15 16 and is made from this with the aid of a metering disk which is only indicated schematically 17 ("rotary valve") fed in portions to an outlet connection 18 on the device side. From there it arrives via a hose-like or tubular shape, which is designed here as a downpipe - Delivery line 19 into the outlet area 13 of the storage container 10. The metering device 15 is in the Ausführungsbei game above the lower mouth of the delivery line 19 so that the additive is delivered by free fall. She stands further elevated on a stand 20, which can also be part of the injection molding machine 12.

To monitor the promotion of the metering device 15 is at their Outlet nozzle 18 a light barrier 21 is attached, with which then the delivery line 19 is plugged in. An electrical line 22 connects the light barrier 21 with an electronic evaluation device 23, which if the light barrier pulses fail, that is, if there is no additive delivery, for example a warning flashing lamp 24 lights up or a signal lamp 33 turns on on the front panel of the device.

The simple plug connection of the light barrier 21 as an adapter part between the outlet nozzle 18 of the Do- siergeräts 15 and the upper end of the delivery line 19 is once again in FIG. 2 shown. Preferably made of metal (because of the Shielding) existing housing 25 of the light barrier 21 has two tubular Connection pieces 26 and 27, of which the connection piece 26 via the outlet connection 18 of the Dosing device 15 and the nozzle 27 are inserted tightly into the delivery line 19 can be. Thanks to this simple plug-in means, it can be carried out at any time, even afterwards It is possible to equip a metering device 15 with a light barrier 21.

For this you only need the delivery line 19 from the nozzle 18 of the Pull off the device 15 and insert the light barrier 21 in between as a connecting adapter.

With the help of this light barrier, which can easily be adapted subsequently 21 is thus registered whether additive from the metering device 15 of the machine 12 is funded. If this is the case, the light barrier pulse is sent to the evaluation device 23 reported and the pulse stored there. To visualize the process of saving an LED 29 or other indicator light on the front panel of the device 23 provided.

Since the dosing device 15 through the work cycle of the plasticizing screw 11 is switched on and off clock-controlled, the function shown in the block diagram of F i g. 3 before a cycle evaluation. The cycle signal becomes fed to the evaluation device 23 from the dosing device 15, galvanically through optocoupler 30 separated and processed (pulse converter 31) and then fed to a counting stage 32. After four cycle steps, if there is no additive delivery, the alarm evaluation takes place, d. h., it is z. B. by a lamp 33 on the front panel of the device 23 optically a malfunction reported. In addition, the already mentioned flash lamp 24 and / or a siren can be switched on.

It is also possible to switch off or switch off the machine 12. shut down the plasticizing screw 11.

For this purpose, the evaluation device 23 has a socket opening into a socket potential-free output 41. In the event that in the circuit of the evaluation device 23 should there be a defect itself, it is sufficient to switch the device off, since it will potential-free output 41 is switched via a relay with closed-circuit contacts.

The alarm can also be cleared by switching off the device possible.

If the additive is correctly dispensed by the dosing device 15, the storage of all pulses is deleted after the fourth cycle clock, and the evaluation takes place again. In the exemplary embodiment, the evaluation is up to to the fourth measure z. B. useful when the metering device 15 with a metering disc is equipped, which only conveys color granules every third cycle. One earlier alarm evaluation could result in false alarms in this case. aside from that there is a certain safety reserve against possible false alarms, if about the metering recesses of the metering disk 17 possibly once in one cycle dispense additive, but not in the correct amount. This shortage will the next time the metering disk 17 is switched on again later without further ado balanced.

The signal which has already been pre-amplified there arrives from the light barrier 21 to the evaluation device 23, is processed there - pulse amplifier 34 - and a Memory 35, which is designed as a master-slave flip-flop, is supplied. Its exit controls both the conveyor display (LED) 29) and the subsequent alarm evaluation logic 38 at.

The logic 38 ensures that either after cycle four by the alarm evaluation the alarm display or, in case of correct operation, at step five, the deletion of the memory 35 and the counter 32 (reset) takes place. The alarm evaluation logic 38 controls a relay stage 39 and the signal lamp 33 on the front panel of the device 23. Furthermore is nor a clock indicator lamp 28 attached to the front panel of the device 23, the signaled every second cycle. This display 28 is controlled by the counting stage 32.

Finally, there is also a power indicator light on the front panel of the device 23 40 available.

Claims (1)

Claims: 1. Device for metered addition of in particular Lumpy or granular additives to plastic granules on a plastic processing machine, with at least an indirect plasticizing screw for the portion-wise delivery of the additive clock-controlled metering device, whose Outlet connection via a hose or pipe-shaped conveying line with the machine-side Granulate entry is connected, characterized by an on the additive passage responsive light barrier (21), the housing (25) of which is tubular connecting piece (26, 27) for plug connection with the outlet nozzle (18) of the metering device (I5) on the one hand and the delivery line (19) on the other hand and connected to a pulse evaluation circuit connected via the after reaching a presettable or preset Number of cycle times of the plasticizing screw (11), however missing until then Impulse of the light barrier (21) an optical and / or acoustic display instrument (33, 24) can be switched on and / or the drive of the plasticizing screw (11) can be switched off is 2. Device according to claim 1, characterized by a pulse memory (35) with reset circuit after the last cycle when the light barrier is pulsed (21) during. the preset number of machine cycle clocks. The invention relates to a device for metered addition of in particular lumpy or granular additives to plastic granules a plastic processing machine, with at least one indirectly from one Plasticizing screw for batch-controlled delivery of the additive Dosing device, the outlet of which via a hose or tubular delivery line is connected to the machine-side granulate entry. The coloring of granules can be done by means of liquid colors, powder colors Dyes or color granules with a high proportion of color are made. Coloring colorless Plastic granulate directly on a plastic processing machine the particular advantage that the storage of colored granules is kept low and worked more economically due to the higher consumption of colorless granules can be. It is also known additives such as granular zinc stearate by means of suitable Add metering devices. Such color granules and additives are described below called "additives" for short. For the purpose of adding color granulate ("masterbatch") to colorless Plastic granules are z. B. from DE-PS 25 10 963 dosing devices of the introduction named type with a storage container for the color granulate known, from the The plasticizing screw of the plastic processing machine is cycle-controlled, the color granulate Dispense in portions and transfer it to the mouth area via a conveying line (granulate entry) of the container holding the colorless granulate. The portion formation and delivery of additive takes place in such devices mostly with the help of an, am Scope of dosing recesses, rotatable arranged dosing wheel disk (also Called "rotary valve"). The clock control is usually carried out in such a way that after several cycles of the plasticizing screw, for example after four Shots of a plastic injection molding machine, the dosing wheel for color granulate conveyance is controlled. The dosed portion of colored granulate then leaves the dosing device via an outlet nozzle. Such dosing devices have proven to be inexpensive in practice, Devices that are easy to transport and retrofit also thanks to their reliability very proven. In particular human inadequacy, however, mostly in that Failure to connect the storage container for the additive to the metering device to be refilled in good time. But also isolated malfunctions of the dosing device themselves can lead to the plasticizing screw operating for a longer period of time no more additives are added to the plastics processing machine, so that a more or less large amount of unusable waste is produced will. Accordingly, it is the object of the invention to monitor the additive emissions to propose the dosing device, both due to lack of supply of additive as well as reacting to malfunctions of the dosing device, is particularly simple It can be set up in just a few simple steps - possibly also with a dosing device at a later date can be combined. The solution to this problem is characterized by an additive run-through appealing light barrier, the housing of which is tubular connecting piece for plug connection with the outlet connection of the metering device on the one hand and the delivery line on the other and which is connected to a pulse evaluation circuit via which after Reaching a presettable or preset number of cycle rates of the Plasticizing screw, but until then there was no impulse from the light barrier, an optical one and / or an acoustic display instrument can be switched on and / or the drive of the plasticizing screw can be switched off. Should a device of the type mentioned with such a Monitoring, the light barrier is a simple adapter piece inserted between the outlet connection of the dosing device and the delivery line. These The clip-on coupling also enables one to be retrofitted at any time while it is in operation located, not yet monitored dosing device with a monitoring device. The light barrier as a particularly simple pulse pick-up reacts to the through additive particles interrupting their light beam. If there is no such thing, however Pulse, can be made appropriate with the help of a relatively simple electronic circuit Control switching functions such as optical and / or acoustic display instruments or the drive of the plastics processing machine shut down, reducing the amount of any rejects produced are limited to a negligible minimum remain. To avoid incorrect monitoring, the invention provides a pulse evaluation circuit before, after reaching a presettable or preset number of cycle clocks the plasticizing screw, but the light barrier does not have an optical impulse and / or the acoustic indicator switches on and / or the plasticizing screw stops. If you go z. B.