EP0225898A1

EP0225898A1 - Method and device for dosing viscous materials

Info

Publication number: EP0225898A1
Application number: EP19860903366
Authority: EP
Inventors: Ferdinand Geyer
Original assignee: DETEC KUNSTSTOFFTECHNIK GmbH
Current assignee: DETEC KUNSTSTOFFTECHNIK GmbH
Priority date: 1985-06-07
Filing date: 1986-06-05
Publication date: 1987-06-24
Also published as: DE3520454A1; WO1986007304A1

Abstract

Le dispositif ci-décrit comporte dans une soupape d'arrêt (33) un coulisseau de soupape (17), lequel relie, dans une position de la soupape, un cylindre doseur et injecteur (9) avec un ajutage (7'). Le coulisseau (17) possède à son extrémité avant un piston plongeur (23) qui, au début de sa course de retour, produit dans l'espace (24) situé avant l'ajutage (7') une dépression, de sorte que la matière se détache au niveau de l'embouchure de l'ajutage (7'), empêchant ainsi la formation d'un filet de matière ou un égouttage ultérier. Le dispositif est destiné par exemple au remplissage de cartouches.The device described below comprises in a stop valve (33) a valve slide (17), which connects, in a position of the valve, a metering and injector cylinder (9) with a nozzle (7 '). The slide (17) has at its front end a plunger (23) which, at the start of its return stroke, produces in the space (24) located before the nozzle (7 ') a vacuum, so that the material comes off at the mouth of the nozzle (7 '), thus preventing the formation of a thread of material or subsequent drainage. The device is intended for example for filling cartridges.

Description

Method and device for dosing viscous materials

The invention relates to a method for dosing viscous materials which are injected through a nozzle into a space to be filled in a metered amount, a valve closing a chamber located between the nozzle and the valve at the end of the metering process. The invention further relates to advantageous devices for performing this method.

When dispensing viscous materials, in particular highly viscous materials such as silicone rubber, liquid plastics and the like, there is the difficulty that at the end of the filling process, when the mold to be filled is separated from the nozzle used for this purpose, contamination by material threads or dripping material occurs.

Typical filling processes in which the material to be filled is also metered are, for example, the injection molding of rubber or silicone rubber or the filling of viscous or highly viscous materials in cartridges, from which the material is pressed out for later processing using metering guns. This also includes multi-chamber cartridges.

The object of the invention is therefore to provide a method of the type mentioned in the introduction, in which thread formation or dripping of the material is reliably avoided at the end of the metering or filling process. This object is achieved in that a vacuum is generated in the chamber between the valve and the nozzle after the valve is closed. This negative pressure causes the material to tear off at the nozzle mouth at the latest when the nozzle is separated from the mold or cartridge to be filled, so that thread formation or dripping is prevented.

When filling an injection mold, it is achieved in this way that no or at most a very small sprue remains on the molded part, so that it is no longer necessary to remove such a sprue. When filling cartridges, there is a clean material separation at the nozzle mouth. Therefore, it becomes possible to fill the cartridge from its discharge opening, because after the

Filling process no material residues remain that contaminate the discharge opening or the discharge channel of the cartridge and would interfere with the use of the cartridge. In contrast, cartridges of this type have previously been filled from the rear, and so too

Difficulties existed in carrying out the filling exactly up to the discharge opening or a cartridge valve arranged there, without either excess material escaping at the cartridge opening or an air residue remaining between the filling and the cartridge valve.

A device for carrying out the method with a metering device, which can optionally be connected via a deflection valve to a material supply line and to a line leading to the nozzle, is characterized in accordance with the invention in that a shut-off valve is arranged in the line leading to the nozzle, which is used as a slide valve with a Valve slide is designed, which is displaceable in a housing bore, that the valve slide has an axially extending connecting recess which connects the metering device in a valve position with a chamber located in front of the housing bore, that in the Chamber of the injector channel protruding end of the valve spool is a plunger sealed against the housing bore, and that the smallest cross section of the injector channel lies in _{5 of} the injector nozzle.

The plunger formed at the end of the valve slide causes a metering or filling process at the beginning of its return stroke that in the nozzle and in the

10 contained chamber in front of the material is exposed to negative pressure and is withdrawn. As a result, the viscous, mostly highly viscous material tears off in the area of the nozzle mouth, at the latest as soon as the filled mold or cartridge is moved away at this point.

15

At the beginning of the next valve stroke with which a new one

Filling process is initiated, the material contained in the chamber is advanced to the same extent before the

Filling process begins. This ensures that the

_ _{n The} cavity created by the previous retraction of the plunger in the area of the nozzle mouth is first filled with material before the filling process begins. This also ensures that the amount of material injected during each filling process is exactly that

₂₅ set dosage corresponds.

According to one embodiment, which has proven itself particularly for use as an injection device for injection molding, it is provided that the slide valve is also the

_{3Q diverter valve} forms that the material feed line and the metering device open into the housing _bore at an axial distance, and that the axially extending connecting recess of the valve slide the metering device in a first valve position with the

₃₅ material supply line and in a second valve position in front of the housing bore chamber. The valve slide of the shut-off valve not only forms the plunger, but also the valve slide for the Diverter valve, so that a particularly compact design is achieved. Instead, however, it can also be advantageous to design the diverter valve as a 3-way valve which is arranged separately from the shut-off valve and is connected to the shut-off valve via a line. This type of construction is preferably used in filling stations for kart searches.

The plunger is preferably sealed in front of the outlet of the housing _bore by a lip seal directed toward the _housing bore. This lip seal seals more, the greater the negative pressure generated by the plunger in the chamber. This ensures that this negative pressure causes material to flow into the chamber only from the nozzle.

15

In a further development of the inventive concept, it is provided that the metering device has an injection and metering cylinder with a freely movable floating piston which can be driven by a piston rod of a drive cylinder,

__ which has an adjustable stroke stop. The stroke stop can be adjusted by hand or by a control so that a quick and easy changeover to different dosing quantities is possible even in an automatic workflow.

25

Further advantageous embodiments of the inventive concept are the subject of further dependent claims.

The invention is described below using exemplary embodiments

30 explained in more detail, which are shown in the drawing. It shows:

1 shows an injection device for injection molding in longitudinal section in a first valve position,

35

2 shows a partial section corresponding to FIG. 1 in a second valve position, 3 shows a simplified representation of a device for filling cartridges,

Fig. 4 in an enlarged section a filling head of a device according to Fig. 3 with two nozzles and

Fig. 5 is a circuit diagram of a system for simultaneously filling two two-chamber cartridges.

The injection device 1 shown in FIGS. 1 and 2 has a housing 2, in which a cylindrical valve insert 3 is arranged, which has a cylindrical housing bore 4. An injector channel 5 adjoins the housing bore 4, which can be at least partially surrounded by a cooling jacket 6 through which water flows and leads to an injector nozzle 7. For a spraying process, the injector nozzle 7 is connected to an injection mold 8, only indicated by dash-dotted lines in FIG. 1, in which a molded part is to be formed from highly viscous material, for example from synthetic or natural rubber or silicone rubber.

An injection and metering cylinder 9, in which a freely movable floating piston 10 is arranged, opens into the housing 2 from above. One presses on the floating piston 10

Piston rod 11, which is connected to a piston 12 of a pneumatic drive cylinder 13. An upwardly extending extension 14 of the piston rod 11 comes into contact with an adjustable threaded spindle 15 at the upper stroke end, which forms an adjustable stroke stop. In the illustrated embodiment, the stroke stop can be adjusted by hand. Instead, it is also possible to electronically control the adjustable stroke stop for the drive cylinder 13 and to adjust it via a servo motor or stepper motor (not shown). In the housing bore 4, a valve slide 17 is arranged to be longitudinally movable and sealed by a plurality of sealing rings 16, which is connected at its end remote from the injector channel 5 to a piston 18 of a pneumatic control cylinder 19, which is formed by part of the housing 2.

The valve spool 17 has a communication hole 20, for example an axially extending constriction, the first as shown in Fig. 1 valve position connects an opening into, ₀ the housing bore 4 material supply line 22 to the injection and metering. 9 In this

Position is the injection and metering cylinder 9 with the

Material filled under pressure by the

Material supply line is brought up. The piston 12 of the -J5 drive cylinder 13 is moved upwards until the

Extension 14 comes to rest on the threaded spindle 15.

This sets and limits the amount of material to be dosed.

20 The valve spool 17 has at its front end facing the injector channel 5 a plunger 23 which, when the valve spool 17 moves forward, is moved into a chamber 24 which forms the beginning of the injector channel 5 and whose diameter is larger than that

25 housing bore 4 is. In the area of the transition between the housing bore 4 and the chamber 24, a lip seal 25 with sealing lips directed towards the housing bore 4 is arranged in contact with the plunger 23. As soon as the rear edge of the plunger 23 has passed the lip seal 25

3Q the piston 12 is pressurized with compressed air; it pushes the material contained in the injection and dosing cylinder 9 into the injector channel and through the injector nozzle 7 into the mold 8 via the floating piston 10. In this valve position, shown in FIG. 2, the mouth is the

35 material supply line 22 is closed in the housing bore 4 by the valve slide 17. After the injection and metering process has ended, the valve slide 17 is moved back again. As soon as the rear edge of the plunger 23 has passed the lip seal 25, the chamber 24 is closed off from the housing bore. The further return stroke movement of the plunger 23 creates a negative pressure in the chamber 24 and in the injector channel 5, which leads to the material in the tip 7a of the injector nozzle 7 tearing off. Since the form 8 is heated and the

«Q The vulcanization or setting process of the material begins immediately, leaving no or only a very slight sprue on the molded part formed in mold 8, which does not require any reworking. The volume of material that was withdrawn during the return stroke movement of the plunger 23

15 is determined by the displacement volume of the plunger 23 in the chamber 24 and is advanced again at the beginning of the next valve stroke so that it completely fills the injector channel and the injector nozzle 7 before the metering process begins.

20th

As you can see from the drawing, is the

Injection and metering cylinder 9 in the axial direction between the chamber 24 and the mouth of the material supply line 22, the axial distances being chosen so that the 25 connecting recess 20 of the valve slide 17

Injection and metering cylinder 9 connects either to the chamber 24 or to the material supply line 22.

Around the injection device 1 for each injection process

30 to be able to move the mold 8 up and then move it away again, the housing 2 of the injection device 1 can be accommodated on a feed unit 26, which is only indicated in FIG. 1 and which is formed, for example, by a pressure-operated piston-cylinder unit becomes.

The system shown in FIG. 3 for filling cartridges with viscous or highly viscous material differs from of the injection device according to FIGS. 1 and 2 partly with regard to the structure, but not with regard to the basic functioning.

The material to be filled is filled in a material conveying station 27

Material in a large container 28 is pressurized by an air motor 29 and passes through a line 30 to a deflection valve 31, which is designed as a ball valve. In the schematically indicated valve position indicated by 31a in FIG. 3, the material reaches the valve position

Dosing cylinder 9.

3, which essentially correspond to parts from FIGS. 1 and 2, are the same

Designated reference numbers. Under the pressure of the material in the cylinder 9, the metering piston 10 deflects upwards. Its piston rod 11 takes the piston 12 of the drive cylinder 13 with it until the extension 14 comes into contact with the threaded spindle 15. This can be adjusted manually or by an electronic control to change the dosing quantity.

After the diverter valve 31 has been switched over, the metering piston 10 driven by the drive piston 12 presses the material through the material supply line 22 into a slide valve 32, which forms a shut-off valve. The slide valve 32 is basically constructed in the same way as the injection device 2, but no further line opens into the housing bore 4 except for the material supply line 32. The mode of operation has already been described with reference to FIG. 1.

Details of the nozzle 7 ', which is used to fill a two-chamber coaxial cartridge 34, can be seen from FIG. 4. The filling head 35 has two adjacent nozzles 7 ¹ , which seal against the two outlet openings of the common cartridge valve 36 of the cartridge 34 be connected. Preferably, the nozzles 7 ¹ are designed so that their narrowest passage cross-section is at the nozzle mouth.

In the filling head 35, lines 37 each lead from the respectively assigned shut-off valve 33 to the nozzles 7 ¹ , the associated metering cylinders 9 and deflection valves 31 not being shown. If a vacuum is generated in the shut-off valves 33 in the manner already described by the plunger 23 at the end of the filling process, they tear

Strands of material at the latest when removing the cartridge 34 directly from the nozzle mouth, so that no disruptive material residues or material threads remain at the outlet openings of the cartridge 34, which were closed by the valve 36.

Fig. 5 shows that two filling heads 35 can be provided for the simultaneous filling of two cartridges 34 in one system. Each dosing head 35 is assigned two shut-off valves 33, each of which is connected to a dosing unit 39 via a line 38. The dosing units 39 are supplied with the two materials to be filled via lines 40 from the two material conveying stations 27.

Claims

Method and device for dosing viscous materials

1. A method for dosing viscous materials which are injected through a nozzle into a space to be filled in a metered amount, wherein a valve closes a chamber between the nozzle and the valve at the end of the metering process, characterized in that in the between the valve and a vacuum is generated in the chamber lying after the valve is closed.

2. Device for carrying out the method according to claim 1, in particular for filling cartridges with highly viscous materials or for injection molding, with a metering device which can be connected via a diverter valve either to a material supply line and to a line leading to the nozzle, characterized in that of the line leading to the nozzle (7, 7 ¹ ) a shut-off valve (3, 17; 33) is arranged, which is designed as a slide valve with a valve slide (17) which is in a

Housing bore (43) is displaceable such that the valve slide (17) has an axially extending connecting recess (20) which connects the metering device in a valve position with a chamber (24) located in front of the housing bore (4), so that the 24) projecting end of the valve spool (17) is a plunger (23) which is sealed with respect to the housing bore (4) and that the smallest cross section of the injector channel lies in the nozzle (7, 7 ').

3. Apparatus according to claim 2, characterized in that the slide valve (3, 17; 33) also forms the deflection valve that the material feed line (22) and the metering device (9) open into the housing bore (4) at an axial distance, and that the Axially extending connecting recess (20) of the valve slide (17) connects the metering device (9) in a first valve position to the material supply line (22) and in a second valve position to a chamber (24) located in front of the housing bore (4).

4. The device according to claim 2, characterized in that the plunger (23) is sealed in front of the outlet of the housing bore (4) 5 by a lip seal (25) directed towards the housing bore (4).

5. The device according to claim 2, characterized in that the metering device has an injection and metering cylinder o (9) with a freely movable oscillating piston (10) which can be driven by a piston rod (11) of a drive cylinder (13) which is adjustable Has stroke stop (14, 15).

5 6. Device according to claim 5, characterized in that the stroke stop (15) is adjustable by hand.

7. The device according to claim 5, characterized in that the stroke stop (15) is adjustable by a controller. 0

8. The device according to claim 5, characterized in that the injection and metering cylinder (9) with the floating piston (10) contained therein is exchangeable with the housing (2) of the injection device (1) and with the 5 drive cylinder (13).

/

9. The device according to claim 2, characterized in that the deflection valve (31) is a separate from the shut-off valve (33) arranged 3-way valve which is connected to the shut-off valve (33) via a line (32).

10. The device according to claim 2, characterized in that the metering device (9) with the deflection valve (31) and / or the shut-off valve (33) is connected via a pipeline.