EP0344491B1 - Dispensing cartridge with a supply cylinder and an expulsion piston - Google Patents

Description

The invention relates to a discharge cartridge with a storage cylinder and sealingly displaceable delivery piston whose bottom surface facing the cartridge contents has radially extending, slot-shaped depressions which open into a closable vent hole leading from the center of the bottom surface to the outside.

Discharge cartridges with delivery pistons are used in a known manner to hold, store and process pasty to thin-bodied masses, which are usually conveyed by the plunger of a e.g. "Gun-shaped" discharge device - driven out through the cartridge mouth. When filling such cartridges, any air pockets inside the cylinders must be carefully avoided because they form an elastic "cushion" and thereby impair a precisely metered squeezing of the contents; Such air cushions are particularly disruptive when dispensing two-component masses from double cartridges, because the volume ratio between the components, which should exactly be observed, is then changed. In addition, certain masses processed by means of discharge cartridges can tend to react with the moisture of the enclosed air during storage, as a result of which they harden prematurely and become unusable.

In a known discharge cartridge of the type mentioned, the bottom surface of the cartridge facing the cartridge Delivery piston convexly curved (DE-OS 23 02 364). Here, the radial, slot-shaped depressions in the base surface cannot prevent air from being trapped at the piston rim, at least in the case of a low-viscosity filling compound, ie cannot escape through the vent hole. This bore is closed by means of an axially displaceable stopper which has ventilation grooves over part of its length and which must be driven completely into the bore at the end of the filling process. In order to achieve a permanent, tight seal (press fit), however, considerable forces must be exerted on the stopper. Nevertheless, the plug is not axially secured, which would be absolutely necessary because the bore is "lubricated" through the cartridge contents.

The object of the present invention is to design a discharge cartridge with a delivery piston in such a way that complete cylinder ventilation is ensured both with a low-viscosity as well as with a highly viscous filling compound, with a secure and permanent closure being achieved with little effort and also in automatic filling systems. According to the invention, this object is achieved in that the aforementioned bottom surface of the dimensionally stable delivery plunger facing the cartridge contents is continuously deepened from the plunger edge to the vent hole and in that a screw plug is seated in the vent hole, along the shaft of which at least one longitudinal groove runs in the bore, the longitudinal grooves engaging the outside of the piston are surrounded by an annular sealing surface on the piston, which is intended as an axial seat for the screw head. As a result, the filling process can be carried out reliably and unhindered in various common ways and with any filling materials. After filling and complete venting, all you need to do is tighten the screw against the sealing surface to create a secure, permanent seal.

A piston with a bottom surface recessed towards a central vent hole - but without radial depressions - is known in another context, namely in a so-called Dispenser for pasty masses (DE-OS 36 35 849). That piston, however, is not a delivery piston moved by external force, but only a displaceable closure member which follows the filling compound. The vent hole is also closed in this device by an axially press-fit plug.

Fig. 1

zeigt die gefüllte Kartusche mit dem Förderkolben im Längsschnitt,

Fig. 2

zeigt in einem grösseren Massstab einen Schnitt entlang der Linie II-II in Fig. 1,

Fig. 3

zeigt, ebenfalls in grösserem Massstab, eine Partie der Fig. 1 in geschlossenem Zustand, d.h. mit festgezogener Verschlussschraube,

Fig. 4

ist die (hälftige) Ansicht der Kolben-Bodenfläche, und

Fig. 5

zeigt stark vergrössert einen Ausschnitt des Kolbens entlang der Linie V-V in Fig. 4 im Kontakt mit der Füllmasse.

An exemplary embodiment of a discharge cartridge according to the invention is explained in more detail in connection with the drawing.

Fig. 1

shows the filled cartridge with the delivery piston in longitudinal section,

Fig. 2

1 shows a section on a larger scale along the line II-II in FIG. 1,

Fig. 3

shows, also on a larger scale, a lot of FIG. 1 in the closed state, ie with tightened locking screw,

Fig. 4

is the (half) view of the piston bottom surface, and

Fig. 5

shows a greatly enlarged section of the piston along the line VV in Fig. 4 in contact with the filling compound.

The discharge cartridge 1 shown in FIG. 1 has a storage cylinder 3 with a mouth 4 and a dimensionally stable delivery piston 10 which can be moved in a sealing manner in the cylinder 3. An elastic ring seal 12 (so-called O-ring), which is inserted into an annular groove 11 of the delivery piston 10, expediently serves as the piston seal; however, an elastic sealing lip formed on the piston edge can also be provided, which rests against the inner wall of the cylinder 3 (not shown). The cartridge content 2 is stored in the storage cylinder 3 and later pressed out through the mouth 4 when used. As can be seen from FIG. 1, the filling compound forms after filling, but before venting, in the case of a thin liquid a level surface 5 (dash-dotted lines), or in the case of a pasty mass it is delimited at the top by an irregular surface 6. It is important that regardless of the viscosity of the filling compound 2 or the shape of its surface, all air can escape under the bottom surface 13 of the piston 10. This bottom surface 13 facing the cartridge content 2 is continuously deepened towards the center from the piston rim. A vent hole 15 extends from the deepest point 14 of the bottom surface 13 (lying at the top in the illustrated position of the discharge cartridge), which leads through the piston to the outside. In this bore 15 there is a screw plug with shaft 16 and screw head 17. As shown, it can be a screw with a self-tapping thread and a Phillips head, and it can be tightened from the outside by means of a screwdriver 8.

As can be seen above all from FIGS. 2 and 3, the vent hole 15 has e.g. four longitudinal grooves 18, which run along the screw shaft 16, but outside the same. The longitudinal grooves 18 are surrounded by an annular sealing surface 19 (e.g. an annular bead) on the outside of the piston 10, which is intended as an axial seat for the screw head 17. Then the bottom surface 13 of the piston 10 has a system of radially extending, slot-shaped depressions 20 which open at the vent hole 15 and thereby communicate with the longitudinal grooves 18 in this hole. The piston 10 can expediently have a number of radial ribs 21 formed on the piston head 23. These form a recess 22 surrounding the sealing surface 19, which receives the screw head 17 when it is tightened.

It is assumed that when the cartridge 1 is upright, the filling compound is introduced from below through the open mouth 4 and rises in the cylinder 3, while the delivery piston 10 is expediently still outside the cylinder. The filling process comes to a standstill when a certain amount of the filling mass, measured by a metering device in the filling station (not shown), is in the cylinder 3, whereupon the mouth 4 is closed. The delivery plunger 10 is then inserted into the cylinder 3 from above - preferably with a preassembled but not yet tightened screw 16, 17 (FIG. 1) - and pressed down against the filling compound 2 until all the air under the plunger passes through the Longitudinal grooves 18 has emerged. The complete ventilation with full surface contact of the bottom surface 13 by the filling compound is clearly noticeable in the strongly increasing resistance to the pushing in of the piston at the moment when the filling compound is pressed through the narrow grooves 18, and finally can also be easily visually determined when the Mass begins to emerge from the grooves 18 above. The screw is then tightened, the head 17 abutting the sealing surface 19 and closing all the longitudinal grooves 18. The screw is tightened with only a small amount of force on the piston and without any significant volume displacement inside the cartridge. The tightened screw forms a tight, reliably secured closure during distribution and storage of the filled cartridge. If, for the purpose of processing the cartridge content, the piston 10 is pushed through the plunger of a discharge device (not shown) and the contents are pressed out through the mouth 4, the countersunk screw head 17 (FIG. 3) remains unaffected by the mentioned plunger.

For the venting process described above, a filled liquid with a level surface 5 will hardly pose any difficulties in the present shape of the bottom surface 13: it will first touch the piston 10 at the edge and then continuously along the bottom surface 13 to the point 14 and then into the bore 15 penetrate while displacing the air. A viscous filling compound 2 with a "heap-shaped", irregular surface 6, on the other hand, will generally first touch the bottom surface 13 at other points (and often, as in the heap formation shown, in a central area), air still being radially outside. In this case, the complete ventilation is still ensured thanks to the slot-shaped recesses 20. This can be seen particularly from the greatly enlarged FIG. 5: thanks to the narrow, but relative deep cross section of the slots 20, "trapped" air located radially outside the contact points can nevertheless escape, since, according to FIG until the entire bottom surface 13 is touched by the filling compound.

Moreover, when filling the cartridge, the procedure can also be such that, when the delivery piston 10 is not yet inserted into the cylinder 3, the contents of the cartridge are filled in from above in a measured amount (not shown). The piston is then inserted into the cylinder 3 with the screw not yet or not fully screwed in and pressed against the filling compound 2. The complete ventilation by pressing the piston 10 and the closing by tightening the screw is then carried out as described above.

As can easily be seen, the design of the delivery piston described allows particularly reliable and efficient venting of the cartridge cylinder after filling. The processes of filling, venting and closing can also be automated without any particular difficulties.

Claims (3)

1. Dispensing cartridge comprising a storage cylinder (1) and a self-sealing delivery piston (10) sliding within, the piston face (13) nearest the contents (2) of the cartridge having radial, groove-shaped depressions (20) which open out at a closable vent hole (15) leading from the centre of the piston face (13) to the outside, characterised in that said face (13) of the rigid-shape delivery piston (10) is formed as a continuous concavity from the edge of the piston to the vent hole (15) and that seated in the vent hole (15) is a closing screw (16, 17), along the shaft (16) of which the hole (15) has at least one longitudinal groove (18), the longitudinal grooves (18) being surrounded on the outside of the piston (10) by an annular sealing surface (19) which provides an axial seating for the screw head (17).
2. Dispensing cartridge according to claim 1, characterized in that on the outside the delivery piston (10) has a depression (22) which surrounds the annular sealing surface (19) to countersink the screw head (17).
3. Dispensing cartridge according to claim 1, characterized in that the delivery piston (10) is sealed towards the storage cylinder (1) by a ring gasket (12) fitted into an annular groove (11).

Images