EP2522438B1 - Closure and expression plunger for cartridges for plastic masses and method for inserting such a plunger into a cartridge - Google Patents

Description

The invention relates to a sealing and ejecting piston made of elastic plastic for cartridges for plastic masses, which has a venting function, which allows the escape of between the piston and the filling material of the cartridge when inserting the piston in the open rear cartridge end after filling the cartridge.

Pistons with bleeding function have long been known. In previously conventional such piston with rearwardly facing, cooperating with the cartridge inner wall sealing lips, the venting function by itself, because the necessary to achieve a good seal necessarily relatively soft sealing lips at the onset of the piston in the rear end of the cartridge under the pressure of the compressed trapped air between Piston and filling mass moved back the sealing lips and let the trapped air escape.

In the course of further development of such pistons but it was recognized that, especially at higher extrusion pressures, the conventional, reverse-facing sealing lips of the piston for a clean seal is not sufficient because when expressing the back pressure of the material acts on the sealing lips, so that they no longer lie perfectly close to the cartridge wall and Füllmaterialfilme form between the sealing lips and the cartridge wall. It has therefore gone over to provide a forward-facing sealing lip at the front of the piston, which increases with increasing Pressing pressure is pressed by the back pressure of the filling material stronger to the cartridge inner wall and results in better sealing results.

However, when using a forward-facing sealing lip no automatic venting of the piston is possible when it is inserted into the filled cartridge. It has therefore been developed valves in such pistons, which have a valve element which open the valve element by a piston setting tool when inserting the piston into the rear end of the cartridge, which then closes elastically again.

However, such valve arrangements are not without problems. In particular, provision must be made that no filling material can penetrate into the venting passages through the valve mechanism, which could prevent a clean closing of the valve, otherwise the permanent leakage of the valve and the gradual intrusion of ambient air constituents would lead to spoilage of the cartridge contents.

It has therefore been proposed to avoid the need for a valve mechanism already such a piston with forward-facing sealing lip and an associated setting tool so that when inserting the piston in the rear end of the cartridge thin fingers of the setting tool the forward-facing sealing lip in places something of the Lift off the inner wall of the cartridge so that trapped air can escape. However, this is not entirely unproblematic, since there is a certain risk of damaging the sealing lip by the fingers of the setting tool, and moreover, the setting tool is complicated.

In addition, it has been shown that the setting of piston with forward-facing sealing lip is not unproblematic and there is a risk of damage to the forward facing sealing lip.

A modification of a setting tool of the type just described is from the WO 99/47 433 A1 known, where the setting tool has a conically tapered front ring, which engages in a corresponding, formed on the piston rear V-groove and slightly reduced when advancing the piston diameter, so that air can escape at the periphery.

From the DE 20 2006 015 313 U1 an example of a piston with bleed valve is known as addressed in the introduction.

From the DE 20 2008 007 834 U1 a piston is known which has no forward-facing sealing lip, these are rather reverse-pointing. About the venting there is nothing said.

From the DE 203 19 464 U1 Although a piston is known which has a forwardly facing sealing lip, however, is formed on its inner side facing the cartridge inner wall so that there has a voltage applied to the cartridge inner wall projecting profile with a rearwardly facing inclined surface, which allows compressed air between the piston and the filling of the cartridge when inserting the sealing lip lifts slightly from the cartridge inner wall to form an annular gap can escape through the residual air to the outside. The disadvantage of such an arrangement, however, as well as in reverse-facing sealing lips, is that the filling material can also produce a leak here.

The invention is therefore an object of the invention to provide a piston with forward-facing sealing lip with vent function, which does not require vent valve and allows for insertion into a cartridge reliable ventilation. Preferably should Even the risk of damage to the forward facing sealing lip can be largely reduced.

Alternatively, the invention has for its object to provide a method by which a piston with forward-facing sealing lip, which is not itself formed with a special, causing a vent function design, can be used in a cartridge with simultaneous generation of a vent.

This object is achieved according to the invention by the alternative embodiments of a piston indicated in the independent claims 1 and 2 or by the method of insertion specified in the independent claim 3.

The venting when setting the piston takes place according to the invention in each case in such a way that the piston is offset by the setting force acting on it by generating a slight bending deformation about a diametrical transverse axis in a slightly out-of-round condition, whereby the forward-facing sealing lip is no longer perfect on the whole Scope of the inner wall of the cartridge abuts, but at diametrically opposite areas leaks are generated, through which the Kobenentlüftung takes place. The piston or the setting tool used for this purpose is designed so that upon application of the setting force by the pressure of the setting tool on the piston, this deformation is generated.

die Fig. 1a und 1b

einen dem Stand der Technik entsprechenden Kolben in perspektivischer Ansicht und im Axialschnitt,

die Fig. 2a und 2b

einen Kolben mit modifizierter Dichtlippe in perspektivischer Ansicht und im Axialschnitt,

die Fig. 3a, 3b, 3c, 3d, 3e und 3f

einen modifizierten Kolben in perspektivischer Ansicht, gerader Draufsicht, perspektivischer Untersicht, gerader Untersicht, Seitenansicht und im Axialschnitt,

die Fig. 4a, 4b und 4c

ein Setzwerkzeug in zwei um 90° zueinander gedrehten Ansichten sowie in Draufsicht, und

Fig. 5

ein abgewandeltes Setzwerkzeug in perspektivischer Ansicht.

The further details of the invention will become apparent from the following description of embodiments with reference to the accompanying drawings. In the drawings show:

Figs. 1a and 1b

a piston according to the prior art in a perspective view and in axial section,

FIGS. 2a and 2b

a piston with modified sealing lip in a perspective view and in axial section,

Figures 3a, 3b, 3c, 3d, 3e and 3f

a modified piston in perspective view, straight plan view, perspective bottom view, straight bottom view, side view and in axial section,

Figs. 4a, 4b and 4c

a setting tool in two rotated by 90 ° to each other views and in plan view, and

Fig. 5

a modified setting tool in perspective view.

The pistons shown in the drawings each consist of a slightly forwardly curved piston plate 1 and a backward cylindrical skirt 2.

The transition region between the piston plate 1 and the contactor 2 is formed with a V-shaped cross-sectional profile which opens to the front, so that a forward-facing obliquely forward and outwardly extending sealing lip 3 is formed on the circumference of the piston plate 1, which cooperates with the inner wall of the cartridge. On the outside of the skirt further, axially spaced, but facing rearward sealing lips 4 are formed, which also cooperate with the cartridge inner wall.

At the back of the piston plate 1 is a radially inner, formed approximately cylindrical and formed over a short distance to the rear projecting ring 5, which is called setting ring and cooperates on insertion of the piston in the open rear cartridge end on the one hand centering with the setting tool, on the other hand from the setting tool exerts axial thrust and transmits to the piston plate. Further, a radially outer, rearwardly projecting ring 6 is formed on the rear side of the piston plate, which is conical and has an obliquely backwards and inwards to the piston axis extending cross-section and projecting axially beyond the setting ring 5 to the rear. This radially outer ring 6 serves to transmit the thrust force of a Auspressstempels when expressing the cartridge on the piston, causing its conical shape, that the forward-facing sealing lip 3 seeks to spread outwards and thereby their sealing contact with the cartridge inner wall is reinforced.

All of these features described so far are known per se. The in the Fig. 1a and 1b shown piston has only these features.

The in the Fig. 2a and 2b illustrated piston differs from the further feature that the forwardly facing sealing lip 3 has on its inside a coronary arrangement distributed with equal circumferential intervals arranged small radial ribs 7, which are arranged on the inner, so the piston axis side facing the sealing lip. They are not connected to any other part of the piston. They project axially forward slightly beyond the sealing lip 3 and each have an outwardly facing inclined ramp surface 8, which extends obliquely backwards and outwards and merges into the sealing edge surface of the sealing lip 3.

These small ribs 7 form with their ramp surface 8 insertion aids when inserting the piston in the rear cartridge end in which they act centering and ensure that the forward facing sealing lip 3 can not get caught with the rear edge surface of the cartridge wall and in particular the cartridge wall, about due to an existing slight runout, the piston plate 1 can get into it.

The in the Fig. 3a to 3f illustrated piston is formed with other features, which, as will be described below, alternatively or cumulatively used to accomplish a venting function of the piston when inserted into the rear end of the cartridge without the need for a valve can.

As can be seen from the perspective view and the top view of the Fig. 3a and 3b and from the axial section Fig. 3f can recognize this piston is again formed with arranged on the forward facing sealing lip 3 radial ribs 7, but now, in contrast to the arrangement in the piston after the Fig. 2a and 2b , Not freestanding are arranged only on the sealing lip, but are attached to the piston plate 1. These turn ramp surfaces 8 forming ribs 7 are on both sides of a Fig. 3b drawn, a transverse line formed by two radial lines corresponding cross-axis symmetrical arranged, but each of the transverse axis of the nearest ribs have a distance from each other, which is substantially greater than the remaining rib spacing.

Next, in the embodiment of the piston according to the Fig. 3a to 3f that the soffits after the Fig. 3c and 3b show, the setting ring 4 at two diametrically opposite locations in each case a survey in the form of a over the rest of the set ring 5 to the rear projecting nubs 9. These two pimples are on the same (in Fig. 3b drawn) diameter line or transverse axis, with respect to which the ribs 7 are arranged on both sides.

The nubs 9 may alternatively be provided to or cumulatively connected to the piston plate 1 ribs 7.

The not rotationally symmetrical, but only in relation to the diameter line or transverse axis in Fig. 3b arranged axially symmetrically, connected to the piston plate 1 ribs 7 cause the flexural rigidity of the piston is no longer rotationally symmetrical, but that the flexural rigidity to the in Fig. 3b drawn diameter line or transverse axis is softer than any other diameter line. When exerting an axial pressure on the setting ring 5 by a setting tool, even if the nubs 9 are not present, the piston is, because the setting ring 5 is disposed on a radius between the piston axis and the skirt 2, subjected to a bending stress due to the Connection of the ribs 7 to the piston plate 1 transmits to the forward-facing sealing lip 3. But because the piston in terms of in Fig. 3b plotted diameter line is flexurally soft than transversely thereto, takes place when exercising the set pressure on the riser ring 5, a slight deflection of the piston about this transverse axis, which at transversely diametrically opposite areas, the sealing of the sealing lip 3 is reduced with the cartridge inner wall and a vent can take place.

Although the connection of the sealing lip 3 on the piston plate 1 via the ribs 7 limits the free mobility of the sealing lip 3 in the radial direction, but because of their divergent shape in conjunction with the curved piston plate 1 still enough radially resilient movement possibility for the sealing lip 3 is present to ensure a clean seal with the inner wall of the cartridge.

In the presence of the nubs 9 on the rear end surface of the setting ring 5, the mentioned bending of the piston around said transverse axis is already generated by the fact that the setting no longer distributed over the circumference of the setting ring 5 uniformly attacks with its axial pressure on this, but at two diametrically along these transverse axis opposite points of the setting ring.

Such nubs 9 can therefore also in piston embodiments, as shown in the Fig. 1a and 1b 2a and 2b, are provided, which then with a conventional unchanged setting tool the same effect of bringing about a slight deflection of the piston about the transverse axis or diameter line, on which the two nubs 9 are to bring about, and thereby produce a venting function.

So that is so in order to accomplish a piston vent when inserting into the rear cartridge end so that the trapped air between filler and piston can escape, no valve on the piston longer required that would be expensive to manufacture and could cause any problems in practice.

The same function of venting a piston without the need for a vent valve but can in a prior art piston according to the Fig. 1a and 1b or with a piston after the Fig. 2a and 2b where the setting ring 5 each has a straight rear end surface, so no nubs 9 are provided can be achieved by using a modified setting tool, as shown in the Fig. 4a to 4c or 5 is shown.

The setting tool has there each a projecting central cylindrical portion 10 which engages centering in the setting ring 5, and a graduated, larger diameter cylindrical portion 11 which engages with its front end surface on the rear end surface of the setting ring 5 and the axial thrust transfers to this.

According to the invention are in the modified setting tool on the forward facing end face of the axial thrusting part 11 of the setting tool at diametrically opposite positions elevations in the form of round nubs 12, which in the embodiment after the Fig. 4a to 4c represented, or ribs 13, as in the embodiment according to Fig. 5 shown, provided. As a result, the axial thrust is concentrated on two diametrically opposite, ie on a transverse axis or diameter line areas of the set ring of the piston, so that it is slightly bent due to the unequal load around this transverse axis when setting and the venting function takes place.

Deviating from the representations in the Fig. 3a to 3f . Fig. 4a to 4c and Fig. 5 , Where in each case a bending stress is generated about a transverse axis corresponding to a diameter line, a modification is conceivable such that at three points distributed at approximately equal angular intervals we create a bending stress, namely by using three nubs 9 on the setting ring or three large distances between ribs 7, or by three nubs 12 or ribs 13 on the setting tool.

Claims (8)

1. A closure and expression plunger made of elastic plastics, for cartridges for plastic masses, having a plunger plate (1) and a cylindrical skirt (2) following the plate on the back side, the transition area between the plunger plate (1) and the skirt (2) being configured with a V-like cross section, thereby forming on the periphery a sealing lip (3) facing to the front and to the outside at an angle, and with additional sealing lips (4) formed on the periphery of the skirt (2) and facing backwards, further having a stacking ring (5) formed onto the backside of the plunger plate and projecting from the plunger plate (1) axially backwards, characterised in that at least two axial projections (9) that are equally distributed around the periphery are provided on the end face of the stacking ring (5) facing backwards.
2. A closure and expression plunger made of elastic plastics, for cartridges for plastic masses, having a plunger plate (1) and a cylindrical skirt (2) following the plate on the back side, the transition area between the plunger plate (1) and the skirt (2) being configured with a V-like cross section, thereby forming on the periphery a sealing lip (3) facing to the front and to the outside at an angle, and with additional sealing lips (4) formed on the periphery of the skirt (2) and facing backwards, further having a stacking ring (5) formed onto the backside of the plunger plate and projecting from the plunger plate (1) axially backwards, characterised in that the plunger plate (1) is arched towards the front and that the sealing lip (3) facing to the front is connected by a plurality of ribs (7) connecting the sealing lip (3) facing to the front with the plunger plate (1) and overstretching the V-shaped groove formed between this sealing lip (3) and the plunger plate (1), the ribs being arranged rotationally symmetrically along the periphery of the sealing lip (3) between two radial lines that form a diameter line, wherein the ribs respectively adjacent to the radial lines have a distance to one another that is greater than the distance between the remaining ribs (7), so that the ribs (7) are arranged symmetrically to both sides of a transverse axis that corresponds to this diameter line, but wherein the ribs (7) respectively adjacent to the transverse axis have a distance to one another that is greater than the remaining rib distances.
3. A method for insertion of a plunger made of elastic plastics into the open back end of a cartridge, wherein the plunger has a plunger plate (1), a cylindrical skirt (2) following the plate axially on the back side, and a stacking ring (5) projecting axially backwards from the back side of the plunger plate (1) and having a straight back end face, the transition area between the plunger plate (1) and the skirt (2) being configured with a V-like cross section, thereby forming on the periphery of the plunger plate (1) a sealing lip (3) facing to the front, characterised in that a setting tool is used to insert the plunger into the cartridge, wherein the part (11) of the tool that transfers an axial thrust force onto the stacking ring (5) of the plunger has at least two axial projections (12; 13) distributed on the periphery.
4. The plunger according to claim 1, wherein the stacking ring (5) has two knobs (9) projecting axially backwards and lying on a common diameter line.
5. The plunger according to claim 2, wherein the ribs (7) each project axially towards the front above the sealing lip (3) and form a ramp surface (8) extending backwards and outwards at an angle, the ramp surface merging with the edge surface of the sealing lip (3).
6. The plunger according to claim 2 or 5, wherein the stacking ring (5) has at least two axially projecting knobs (9) arranged on its periphery and lying on said radial lines.
7. The method according to claim 3, wherein the setting tool has two diametrically opposed axial projections (12; 13).
8. The method according to claim 3 or 7, wherein the projections of the setting tool are configured as round knobs (12) or as ribs (13).

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