EP3366612A1 - Piston for cartridges - Google Patents

Abstract

The present invention relates to a one-piece piston for cartridges for expressing mass from a cartridge, having a front piston breast, a circumferential side wall and at least one arranged on the side wall, projecting forward flexible sealing lip, wherein the side wall has a rear wall portion, starting from extends from the piston breast behind the forward projecting flexible sealing lip, wherein on the rear wall portion of the side wall, a circumferential first rear sealing projection is arranged, which has a maximum wall thickness D _max1 , which is greater than a minimum wall thickness d _{min of} the side wall in the between forwardly projecting flexible sealing lip and the rear sealing projection arranged portion of the rear wall portion and / or the side wall (5) in the starting from the piston breast behind the rear sealing projection (11) arranged portion of the rear wall portion.

Description

The present invention relates to a one-piece piston for cartridges for pressing masses and a cartridge with such piston.

Cartridges for auspressbare masses, such as sealants or fillers, consist of a tubular cartridge body, in which the mass is filled. The cartridge body is closed at the front end and the filling of the mass takes place from the open rear end. Subsequently, the piston is also inserted from the rear end into the cartridge body to seal it.

Out EP 1 845 033 A1 (Fischbach ) a piston with two sealing lips is known, which run along the wall of the cartridge body and which seal the space containing the auspressende mass against the environment. A front sealing lip is provided with apertures through which when setting the piston, that is, when inserting the piston into the cartridge, air, which is located in front of the piston in the cartridge, can escape. At the rear lip there are passages, so that the rear lip can not lie all over the inner surface of the cartridge and thus the air can escape via the rear sealing lip.

EP 2 108 599 B1 (Fischbach ) provides, in addition to the sealing lips, a protective edge which is rigid with respect to the sealing lips and partially covers the lips in axial projection. Due to the protective edge, the flexible lips located there are protected from the mass located in the cartridge, and thus folding over or damaging of the sealing lips during piston setting due to mass that is pressed against the sealing lips is avoided.

The prior art pistons have been found to be particularly advantageous, since when setting the piston, the excess air can escape in an advantageous manner and still seal the piston sealing. The sealing lips are directed at such piston forward and when pressing with a mechanical caulking gun very good results are achieved. In the piston described above, both when setting in the space in front of the piston breast, an increased pressure, which expels the air. In later use of the cartridge, the mass presses against the sealing lips, wherein the sealing lips are pressed due to the pressure to the outside against the cartridge wall, whereby an advantageous sealing takes place.

When using compressed air guns, compressed air can act directly on the cartridge piston. In order for the cartridge piston to be moved by the compressed air, there must be a pressure difference between the extrusion mass in the cartridge and the area arranged in or behind the piston, with a higher pressure prevailing in or behind the piston. As a result, the compressed air applied from the rear on the piston can enter the gap between the side wall of the extrusion piston and the cartridge and overcome the forwardly projecting flexible sealing lips and thus reach the area of the extrudable mass. As a result, the auspressbare mass harden or spoil on the one hand and it can cause air bubbles in the auspressbaren mass, which lead during the Auspressvorgangs the cartridge to unwanted interruptions of the pressed Füllmassenstranges.

Out DE 3005855 A1 (Fischbach ) is known a cartridge piston for driving with compressed air, in which in addition to a forwardly directed wiping lip at least one rearwardly directed further sealing lip is provided, which forms a pressure pocket. The compressed air entering from behind into the gap between the side wall of the cartridge piston and the cartridge presses from down against the pressure pocket and thus the sealing lip sealing to the cartridge wall.

However, such a piston is advantageous only for use with compressed air as a propulsion drive. When using a conventional pneumatic gun with stamp the rearward sealing lips can be easily pushed by filler from the rear slightly to the side due to the lack of pressure, if the front arranged in front wiping lip fails. Furthermore, the vent in this prior art cartridge piston is inadequate in some situations.

It is therefore an object of the present invention to provide a piston for cartridges for extruding masses from a cartridge, which has a low susceptibility to interference during piston handling even when using different extrusion tools.

The invention is defined by the features of claim 1.

In the one-piece piston for cartridges according to the invention for extruding mass from a cartridge having a front piston breast, a circumferential side wall and at least one arranged on the side wall, projecting forward flexible sealing lip, wherein the side wall has a rear wall portion extending from the piston breast extends beyond the forward projecting flexible sealing lip, it is provided that on the rear wall portion of the side wall, a circumferential first rear sealing projection is arranged, which has a maximum wall thickness D _max1 , which is greater than a minimum wall thickness d _{min of} the side wall in the between forward projecting flexible sealing lip and the rear sealing projection arranged portion of the rear wall portion and / or arranged in the starting of the piston breast behind the rear sealing projection portion of the rear wall portion.

Under maximum wall thickness is understood in the invention, the largest wall thickness of a component, wherein the component can basically have a varying wall thickness. Under minimal wall thickness is understood to mean the wall thickness of a component that is the lowest, wherein the component can basically have a varying wall thickness. In other words, the maximum wall thickness indicates the wall thickness of the "thickest point" of the component, whereas the minimum wall thickness denotes the wall thickness of the "thinnest portion" of the component.

When determining the wall thickness, an extension orthogonal to the neutral fiber of the corresponding component is understood within the scope of the invention. At the maximum wall thickness D _{max1 of} the rear sealing projection, the wall thickness D _{max1 is measured} either orthogonally to the neutral fiber or parallel to the side wall.

Due to the inventive design of the rear wall portion with a minimum wall thickness d _min , which is less than maximum wall thickness D _{max1 of} the rear sealing projection is achieved that the rear sealing projection is at least partially stiffer than the side wall in the wall portion of the minimum wall thickness d _min . When the piston is acted upon by compressed air, the side wall is thus relatively flexible in the region of the minimum wall thickness d _min , so that a spreading of the side wall in the rear wall section can occur. Preferably, the side wall is elastically deformable in the region of the minimum wall thickness d _min . If the region of the rear wall section with the minimum wall thickness d _{min is arranged} between the forwardly projecting flexible sealing lip and the rear sealing projection, it is ensured that the spreading of the side wall of the rear sealing projection in an advantageous manner against the inner wall of the cartridge in which Piston is inserted, is pressed. The forwardly projecting flexible sealing lip effects an advantageous sealing of the piston with the cartridge when the mass is pressed out of the cartridge. The fact that the flexible sealing lip protrudes forward, between the flexible sealing lip and the side wall a Formed pocket into which the auspressbare mass can pass, which thus presses the forwardly projecting flexible sealing lip in an advantageous manner sealingly against the inner wall of the cartridge. On the other hand, the design of the rear wall section of the side wall with the first rear sealing projection ensures that, when compressed air is applied, there is a good seal against the compressed air entering the gap between the cartridge inner wall and the side wall of the piston.

Preferably, the piston is made of a plastic having a modulus of elasticity E ≦ 500 N / mm ² , preferably E ≦ 300 N / mm ² , measured according to ISO 178. The plastic may be, for example, an LDPE.

It is preferably provided that the circumferential first rear sealing projection is a sealing lip which protrudes to the rear. Characterized a pressure bag open to the rear between the side wall and the sealing lip is formed, so that the compressed air entering into the gap between the side wall of the piston and the cartridge presses into the pressure pocket and thus sealingly presses the sealing lip against the inner wall of the cartridge in an advantageous manner. Furthermore, when venting the piston, air from the piston can advantageously be pressed from above against the sealing lip so that it is pushed away from the inner wall of the cartridge when the piston is set and thus a venting path is created. In this case, on the one hand, a part of the sealing lip and on the other hand also deform the side wall. The pressing of the rear sealing lip on the inner wall of the cartridge is effected by an elastic deformation of the side wall at least in the region of the minimum wall thickness and can be supported by an elastic deformation at least a portion of the sealing lip.

Preferably, it is provided that the side wall in front of the forwardly projecting flexible sealing lip has a circumferential or interrupted front protective edge, which covers in axial projection a portion of the at least one forward projecting flexible sealing lip. The front protective edge has a greater rigidity than the front protruding flexible sealing lip. It is relatively rigid and serves as a protective shield, so that when a set of the piston in the cartridge, the forward projecting flexible sealing lip is protected.

It is preferably provided that the side wall has at least a first straight section with a first middle wall thickness d1 and in the rear wall section a second straight section with a second middle wall thickness d2, the second straight section extending from the piston chest behind the first straight section and where: d ₁ > d ₂ . In other words, the first straight section basically has a greater wall thickness than the second straight section. A straight section is understood to mean a section of the piston which, in the state inserted into the cartridge, runs with its outer wall parallel to the cartridge wall. By medium wall thickness is meant the wall thickness of a section averaged over the length of the section.

The first straight section is substantially parallel to the forward projecting flexible sealing lip. Thus, the piston in this area has a high rigidity and deformation of the side wall is prevented. The thinner straight portion with the second wall thickness d2 in the rear wall portion, however, can be elastically deformed. It can be provided that the average wall thickness d2 is greater than the minimum wall thickness d _min or equal to the minimum wall thickness d _min . The side wall is in the entire second straight portion advantageously elastically deformable and can be pressed by applied compressed air to the outside, so as to press the sealing projection to the inner wall of the cartridge in an advantageous manner.

Directly below the front piston breast ribs may be provided for stiffening the piston, which are connected within the first straight portion with the side wall. At least part of the rear ends of the Ribs can lie in one plane, so that a plate of a Auspresswerkzeugs can rest against them.

It is preferably provided that the first rear sealing projection is arranged on the second straight portion or on the side facing away from the piston breast end of the side wall.

The front guard edge may be disposed in a first transitional portion of the sidewall extending obliquely outwardly from the piston breast and merging into the first straight portion, the guard edge projecting laterally from the sidewall. Preferably, the protective edge projects laterally forward from the side wall. Such a configuration has proven to be particularly advantageous.

The sidewall may include a second transition section disposed between the first and second straight sections, the second transition section having a wall thickness decreasing in the direction of the second straight section. This creates an advantageous transition between the first and second straight sections. The second transition section may extend obliquely outward so that the second straight section is located slightly farther outboard than the first straight section. In the embodiment in which the sealing projection is arranged on the second straight section, this is achieved in that the second sealing projection in the radial direction only has to have a relatively small extent in order to reach the inner diameter of the cartridge. This ensures that the first rear sealing projection has sufficient rigidity to advantageously achieve a sealing effect by pressing the sealing projection on the inner wall of the cartridge, in particular by deforming the rear wall portion of the wall.

Preferably, the forwardly projecting flexible sealing lip is arranged on the second transition section. Since this second transition section a has relatively high rigidity, it is ensured that a sealing effect is carried out by a flexible deformation of the flexible sealing lip and the side wall is almost not deformed in this section. This ensures that, for example, when setting the piston of the intended outer diameter of the forward projecting flexible sealing lip is not exceeded, so that the forward projecting flexible sealing lip can be inserted into the cartridge without bumping against the rear edge of the Kartuschenwandung.

In a particularly preferred embodiment of the invention it is provided that the side wall has a peripheral edge projecting outwardly from the side wall, on which the forwardly projecting flexible sealing lip is arranged, wherein on the peripheral edge, a second rear sealing lip is further arranged according to protrudes behind. The outwardly projecting peripheral edge on the side wall increases the rigidity of the side wall in the area. The fact that the forwardly projecting flexible sealing lip is arranged on the area of the side wall reinforced by the edge ensures that deformation of the side wall in this area can not occur, so that the problem described above is avoided in a particularly advantageous manner , The arranged on the peripheral edge also second rear sealing lip seals the gap formed between the side wall and the inner wall of the cartridge against compressed air from behind. This serves as an additional seal to the rear. Furthermore, it is achieved by the second rear sealing lip that compressed air, which passes when moving the piston, the first rear sealing projection, stops it from pressing against the projecting forward flexible sealing lip. Thus, a pocket is formed between the second rear sealing lip and the first rear sealing projection, in which the compressed air passing through the first rear sealing projection will be retained. The retained compressed air, has a higher pressure than the pressure acting from above against the protruding flexible sealing lip pressure. The fact that the second rear sealing lip prevents the compressed air, thus preventing the after front protruding sealing lip can be pressed and air can enter the auspressbare mass.

The embodiment of the piston according to the invention with an outwardly projecting from the side wall peripheral edge on which the forwardly projecting flexible sealing lip and a second rear sealing lip, which protrudes to the rear, also has independent inventive importance and is therefore without first rear Sealing projection feasible. Such a configuration of the piston can furthermore be combined individually or jointly with all the features described above.

In the embodiment of the inventive piston without the first rear sealing projection, the second rear sealing lip causes a sole seal against the compressed air acting from behind. In this case, a pressure pocket is again formed by the protrusion to the rear of the second rear lip, against which can press the compressed air acting from behind, whereby the sealing lip is pressed in an advantageous manner against the inner wall of the cartridge. By contrast, when setting the piston, the second rear sealing lip can advantageously be pushed away from the inner wall in order to form a venting path.

It is preferably provided that the second rear sealing lip has a maximum wall thickness D _max2 which is greater than the maximum wall thickness D _{max3 of} the forwardly projecting flexible sealing lip. In other words, the second rear sealing lip has a higher rigidity than the forward projecting flexible sealing lip, wherein the higher stiffness is further supported by the fact that the second rear sealing lip is formed shorter than the projecting forward sealing lip. Preferably, the second rear sealing lip has a length which has a maximum of half the length of the forwardly projecting flexible sealing lip. The length of the sealing lips is determined in the context of the invention along the neutral fiber.

Preferably, it is provided that the side wall in the region of the peripheral edge has a maximum wall thickness D _max4 encompassing the side wall and the peripheral edge which is greater than the wall thicknesses of the rear wall section and the region of the side wall arranged between the piston breast and the front projecting flexible sealing lip , In other words, the side wall has in the area of the peripheral edge of a very large wall thickness, which is measured including the peripheral edge, and thus an area with high rigidity, so as to ensure that the side wall in this area, at which the second rear Sealing lip and the projecting forward flexible sealing lip is arranged, is not or only slightly deformed.

It is preferably provided that the front protective edge has at least one opening. Through the opening on the one hand advantageously the venting of the piston is ensured by the air can pass through the openings. Further, a portion of the extrudable mass may also pass through the aperture and flow into the pocket formed between the sidewall and the forwardly projecting flexible lip. About the auspressbare mass the forward projecting flexible sealing lip is then pressed outwards against the cartridge wall.

Preferably, the front protective edge has a plurality of openings, preferably at least ten openings, wherein the openings are preferably evenly spaced. It has been found that the provision of a plurality of openings and thus a relatively large flow cross section, through which the squeezable mass can pass, has the advantageous effect that the squeezable mass relatively quickly in between the side wall and the front projecting flexible sealing lip is pressed.

In the piston according to the invention, it is thus intended that the pocket formed between the side wall and the forward projecting flexible sealing lip completely or almost completely with the auspressbaren mass is filled, so that the auspressbare mass presses in a particularly advantageous manner, the forward projecting flexible sealing lip to the outside. The uniform spacing ensures that relatively evenly compressible mass passes into the pocket between the side wall and the forward projecting flexible sealing lip.

In a preferred embodiment of the piston is provided that the forwardly projecting flexible sealing lip has a plurality of passages. Through the passages, when the piston is set, the air flowing backwards can pass the flexible sealing lip protruding forwards. As a result, an advantageous venting is possible. It can also be provided that when setting the piston after venting mass that enters the bag formed between the projecting forward flexible sealing lip and the side wall, is also pushed to the passages and seals them. In the subsequent use of the cartridge in which the auspressbare mass is expressed by the piston, due to the continuous pressure on the mass, they can even be pushed through the passages and in between the forward projecting flexible sealing lip, the second rear sealing lip and enter the gap wall formed by the cartridge wall. The mass in the gap pocket causes a sealing effect against compressed air, which has possibly passed the outwardly bent sealing portion, the first rear sealing projection and the second rear sealing lip. As a result, it is advantageously achieved that compressed air, which could optionally flow past the first rear sealing projection and / or the second rear sealing lip, can not pass through the passages or the sealing lip projecting forward and can enter the cartridge. The mass in the gap pocket is stripped off the cartridge wall via the second rear sealing lip.

The passages preferably have a width and height adapted to the viscosity of the extrudable mass of the cartridge, so that at a predetermined pressure and a predetermined period of time, the mass passes through the Passages is pushed through. It can also be provided that the passages have different dimensions. For example, a portion of the passages may have a greater width than a second portion of the passages.

The second part of the passages can be adapted, for example, to the viscosity of the extrudable mass, so that they are slowly penetrated by the extrudable mass when it is pressed out, and the extrudable mass passes into the gap pocket. The first part of the passages, however, can be pressed at least partially against the cartridge wall by the continuous pressure during extrusion of the extrudable mass, whereby a penetration of the mass through these passages is at least largely prevented.

It is preferably provided that a first number of the passages are offset relative to the openings in the circumferential direction and a second number of the passages is arranged in the axial projection in the overlapping region of the openings. In other words, some of the passages have been arranged in the same circumferential region as the apertures in the protective edge, whereas other passages are offset from the apertures. It has been found that such an arrangement is advantageous in order to avoid air pockets in the portion between the protective edge and the forward projecting flexible sealing lip and in particular in the formed between the forwardly projecting flexible sealing lip and the side wall pocket, as the air when setting the piston can very quickly pass the second sealing lip.

It can be provided in particular that a large number of passages are provided on the protruding therefrom flexible sealing lip compared to the number of openings. For example, the number of passages greater than three times may preferably be five times the number of passages.

It is preferably provided that in the inserted into the cartridge state of the piston, the openings together with the Kartuschenwandung in their entirety have a lower flow resistance than that of the entirety of the passages together with the Kartuschenwandung. In other words, all the apertures taken together have a flow resistance which is smaller than the flow resistance formed together by all the passages. Characterized in that the flow resistance of the passages is greater than that of the openings, the passages of the escaping air are relatively easily passed, but not when setting the piston from the mass. This is initially completely or almost completely retained by the passages.

It is preferably provided that the passages are provided in a beaded edge at the end of the forwardly projecting flexible sealing lip as beadless areas. The fact that the passages are arranged at the free end of the forward projecting flexible sealing lip, it is ensured that first the mass passes into the pocket formed between the forward projecting flexible sealing lip and the side wall of the piston and after this is almost completely filled to the Passages and retained by the passages. By forming the passages in a bead as beadless areas a particularly simple production of the passages is possible.

The flexible sealing lip projecting forward must have a high degree of flexibility in order to be able to conform to the cartridge wall in a deforming manner, even at low pressures. For this purpose, the sealing lip is designed so flexible by having at least in some areas a small Wanddike, but at the same time has the greatest possible length. Preferably, the forwardly projecting flexible sealing lip is at least three times, better five times, more preferably at least eight times longer than the wall thickness at the thinnest point of the sealing lip. In such an embodiment is a protected by a protective edge sealing lip given. The protective edge is in any case made more rigid than the forward projecting flexible sealing lip and protects it. It is preferably provided that in the non-inserted state of the piston in the cartridge, the protective edge more than 20% of the radial height of the forward projecting flexible sealing lip, better more than 35%, more preferably more than 50% of the radial height of the forward projecting flexible Sealing lip covered.

In the inserted state of the piston into the cartridge, the protective edge covers at least 50%, better more than 70%, particularly preferably more than 90% of the radial height of the forwardly projecting flexible sealing lip.

The front protective edge preferably has no contact with the inner wall of the cartridge, that is to say its diameter is smaller than that of the inner wall of the cartridge.

In a preferred embodiment of the invention, it is provided that the side wall has an outwardly bent sealing section at the end facing away from the piston breast. This sealing portion forms another seal against the pressurized air from below on the piston when the piston is operated by means of a compressed air gun. At the same time, the outwardly bent sealing portion can also develop a protective effect for the first sealing projection.

It is preferably provided that the sealing portion has an average wall thickness d3, which corresponds to the wall thickness d2 of the second straight portion or is larger.

In principle, the first rear sealing projection or the first rear sealing projection and the sealing portion may also have a Abstreiffunktion. In particular, when using compressed air, wherein the first rear sealing projection or the first rear sealing projection and the sealing portion due to the pressure on the side wall are pressed tightly against the cartridge wall, they can perform stripping in a particularly advantageous manner.

The first rear sealing projection and / or the second rear sealing lip may have an outer sealing surface, which is formed as a polished surface. The first rear sealing projection and / or the second rear sealing lip thus have a surface which bears sealingly against the cartridge inner wall. Due to the design as a polished surface, a particularly advantageous sealing effect is possible because the polished surface can be applied particularly tightly against the cartridge inner wall. The design of the first rear sealing projection and / or the second rear sealing lip with the exposed sealing surface has the additional advantage that they are subject to less wear and unlike sealing tips of sealing lips are less prone to damage. Preferably, the outer sealing surface is curved outward, that is convex.

It is preferably provided that the first rear sealing projection and the second rear sealing lip have an unloaded state same or approximately the same diameter.

It can also be provided that the first rear sealing projection or the second rear sealing lip and the outwardly bent sealing section have an unloaded state same or approximately the same diameter.

It is preferably provided that the forwardly projecting flexible sealing lip, the second rear sealing lip, the first rear sealing projection and the outwardly bent sealing portion have the same or approximately the same diameter. The fact that these components or a part of these components have the same diameter, the piston can roll on the outer periphery of these components in an advantageous manner. In the Supplying the piston to the cartridge to insert the piston into the cartridge, this can thus be transported advantageously rolling. To insert the piston into the cartridge, the forwardly projecting sealing lip, the first rear sealing projection and / or the outwardly bent sealing section are moistened with oil in order to ensure reliable sliding on the inner wall of the cartridge. By providing the same or approximately the same diameter of these components, the wetting with oil can be done by rolling them over an oil-soaked cloth, such as a felt. Further, the same or approximately equal diameter ensures that the pistons do not tilt during rolling and thus can be reliably machine-mounted to be inserted into the cartridge.

In the context of the invention, "approximately the same diameter" is understood to mean that two components have a diameter difference of a maximum of ± 0.25 mm, preferably a maximum of ± 0.1 mm.

The invention further relates to a combination of a cartridge with a piston according to the invention.

The invention is particularly applicable to pistons with rigid piston breast. However, it is also suitable for cartridge pistons, which have a so-called "membrane bottom". When the product is pressed out of the cartridge, the membrane bottom swings outward so that a piston breast bulges out to the front. Upon release of the extrusion pressure on the cartridge piston, the membrane bottom forms elastically back to its original shape, thereby the mass is sucked back into the cartridge, so that dripping is prevented.

• Es zeigen

  Fig. 1

  eine perspektivische Ansicht eines erfindungsgemäßen Kolbens für Kartuschen,

  Fig. 2

  eine schematische Schnittdarstellung des in Fig. 1 gezeigten Kolbens im in eine Kartusche eingesetzten Zustand,

  Fig. 3

  eine schematische vergrößerte Schnittdarstellung der Seitenwand des erfindungsgemäßen Kolbens und

  Fig. 4

  eine schematische Seitenansicht des erfindungsgemäßen Kolbens.

The invention will be described in more detail below with reference to the following figures:

• Show it

  Fig. 1

  a perspective view of a piston according to the invention for cartridges,

  Fig. 2

  a schematic sectional view of the in Fig. 1 shown piston in the inserted into a cartridge state,

  Fig. 3

  a schematic enlarged sectional view of the side wall of the piston according to the invention and

  Fig. 4

  a schematic side view of the piston according to the invention.

In Fig. 1 is a one-piece piston 1 for cartridges 100 for expressing masses of a cartridge shown schematically in a perspective view.

The piston 1 has a front piston breast 3 and a circumferential side wall 5. How best Fig. 2 can be seen, in which the piston 1 according to the invention is shown in a schematic sectional view in the inserted state in a cartridge 100, on the side wall 5 of the piston 1, starting from the piston breast 3, first a protective edge 9, a forward projecting flexible sealing lip 7, a second rear sealing lip 23, a first rear sealing projection 11 and an outwardly bent sealing portion 25 integrally formed.

The forward projecting flexible sealing lip 7, the first rear sealing projection 11, the second rear sealing lip 23 and the outwardly bent sealing portion 25 are sealingly against the cartridge 102. The protective edge 9 has a slightly smaller diameter than the cartridge wall 102. From the piston breast 3, ribs 14 extend in the rearward direction. The rear ends of at least a portion of the ribs 14 are approximately in a plane against which the plate of a Auspresswerkzeugs not shown, which press the piston 1 in the Cartridge 100 advances. Alternatively it can be provided that a Druckluftauspresswerkzeug is used. For this purpose, a higher pressure is generated in the space 110 located in the piston and behind the piston by means of compressed air than in the space 105 located in front of the piston 1 in the cartridge 100. By this pressure difference, a propulsion of the piston 1 is effected.

How out Fig. 3 can be seen, in which the side wall 5 of the piston 1 according to the invention is shown schematically in an enlarged sectional view, the side wall 5 consists of several sections. Starting from the piston breast 3, the side wall 5 initially extends in a first transition section 17. From the first transition section 17 of the protective edge 9 is laterally and slightly directed forward. The transition section 17 merges into a first straight wall section 13, the outside of which runs approximately parallel to the cartridge wall 102. The first straight wall section 13 further extends almost parallel to the forwardly projecting flexible sealing lip 7, so that between the first straight section 13 and the forwardly projecting flexible sealing lip 7 a pocket 8 is formed. The first straight wall section 13 merges into a second transition section 19, which connects the first straight wall section 13 to a second straight wall section 15, the outside of which runs approximately parallel to the cartridge wall 102. At the end remote from the piston breast 3 end of the side wall 5, this has the outwardly bent sealing portion 25.

In the region of the transition between the first straight section 13 and the second transition section 21, the side wall 5 has a peripheral edge 21. The peripheral edge 21 forms the basis for the forwardly projecting flexible sealing lip 7 and the second rear sealing lip 23. In other words, the forward projecting flexible sealing lip and the second rear sealing lip are arranged on the outwardly projecting peripheral edge 21. This ensures that the portion of the side wall by the forward projecting flexible sealing lip. 7 is arranged, has a particularly high rigidity, so that no or only a small deformation of the side wall 5 takes place. The first straight section 13 has a first average wall thickness d1. The second straight section 15 has an average wall thickness d2. The first rear sealing projection 11, which is formed in the embodiment illustrated in the figures as an obliquely outwardly and rearwardly projecting sealing lip, is arranged on the second straight section 15. The side wall has in the region of the second straight portion 15 a minimum wall thickness d _min, where the portion with the minimum thickness d _min at least in the region of the second straight portion 15 is formed on the piston chest 3 facing side of the first rear sealing projection 11 is arranged. As a result of this configuration of the second straight section 15 with the minimum wall thickness d _{min of} the side wall 5, the side wall in this rear wall section is relatively flexible. Upon pressurization of the piston 1 with compressed air, the compressed air hits the inside of the side wall 5 and presses the rear wall portion of the side wall 5 to the outside, whereby the first rear sealing projection 11 is pressed against the cartridge 102. At the same time, the outwardly bent sealing portion 25 is pressed against the cartridge wall 102.

How out Fig. 4 shows, the protective edge 9 openings 27. Further, a bead 7a is disposed at the free end projecting to the front of the flexible sealing lip 7, which has a plurality of passages 29. When setting the piston, the air located in the space 105 in front of the piston 1 penetrates through the openings 27 of the protective edge 9 and over the outer edge of the protective edge 9 and enters the region of the pocket 8. Through the passages 29, the air can forward pass the protruding flexible sealing lip 7. Further, when the piston is set, the air pushes the second rear seal lip 23, the first rear seal protrusion 11, and the outward bent seal portion 25 to the side, and the desired ventilation can be performed. Since the setting of the piston takes place with a punch, there is no counter-pressure due to compressed air, so that the second rear sealing lip 23, the first rear sealing projection 11 and the outward curved sealing portion 25 can be easily detached from the cartridge 102. To simplify the venting when setting the piston, it can also be provided that this obliquely, that is not axially parallel, is inserted into the cartridge. As a result, an enlarged flow path for the air is formed on one side of the piston.

Further, a portion of the mass penetrates through the openings 27 and fills the pockets 8, which is formed between the side wall 5 and the forwardly projecting flexible sealing lip 7. These are gradually filled with mass until the mass reaches the bead 7a of the forward projecting flexible sealing lip 7. The mass then at least partially fills the passages 29, whereby an additional sealing effect is achieved. The mass disposed in the pocket 8 also pushes the forwardly projecting flexible lip 7 outwardly, thereby forcing it closer to the wall 102 of the cartridge 100. In use of the cartridge in which the mass is squeezed out, due to the continuous pressure on the mass, it may even partially flow through the passages 29 and fill the between the forward projecting flexible sealing lip 7, the second rear sealing lip 23 and the cartridge wall This results in a further seal, so that possibly in use with compressed air, the outwardly bent sealing portion 25, the first rear sealing projection 11 and the second rear sealing lip 23 passing compressed air is held by the mass located in the gap pocket 24. The second rear sealing lip 23 may strip the mass in the gap pocket 24 from the cartridge wall 102. In principle, the first rear sealing projection 11 or the first rear sealing projection 11 and the outwardly bent sealing section 25 can also strip off mass that may not have been completely stripped off the second rear sealing lip 23 from the cartridge wall. Since the first rear sealing protrusion 11 and the sealing portion 25 are pressed against the cartridge wall 102 due to the compressed air applied to the side wall 5, the first rear sealing protrusion 11 and the sealing portion 25 can perform stripping in a particularly advantageous manner.

In use with compressed air to produce propulsion of the piston 1, the compressed air presses against the side wall 5 from the inside and pushes at least the second straight section 15 outwards. As a result, the first rear sealing projection 11 is pressed particularly firmly against the wall 102 of the cartridge 100. When setting the piston, air enters the gap between the outwardly bent sealing portion 25 and the first front sealing projection 11, between the first rear sealing portion 11 and the second rear sealing lip 23. By pressing the side wall 15 by the outside against the outside Piston acting on compressed air, the pressure of the air is increased in this gap. Further, small amounts of air of the compressed air may pass the outwardly bent sealing portion 25 or the first rear sealing protrusion 11, for example, by impurities in the cartridge or the like. As a result, there is a pressure in the previously described gap, which is higher than the pressure prevailing in the space 105 in front of the piston 1. Characterized in that the first rear sealing projection 11 is formed as an obliquely outwardly extending rearward sealing lip and the second rear sealing lip also protruding outward rearward, 23 pressure pockets 11b, 23b are formed on the rear side of the first rear sealing projection 11 and the second rear sealing lip in that the air in the previously described gaps pushes against the first rear sealing projection 11 and the second rearward sealing lip 23 and thus presses them more strongly against the cartridge walls 102, which gives an increased sealing effect. This largely prevents the air from passing through the first rear sealing projection 11 and the second rear sealing lip 23. Air, which is located in the gap between the second rear sealing lip 23 and the forward projecting flexible sealing lip 7 is retained by the forward flexible sealing lip 7 and the intermittently filled with mass passages 29 and located in the gap 24 mass.

The first straight section 13 has a first average wall thickness d1, which is greater than the average wall thickness d2 of the second straight wall section 15. Basically, the side wall 5 in the first transition section 17 and the first straight section 13 has a relatively large wall thickness, since these parts come into contact with the outside from the outside and the large wall thickness can prevent air from diffusing through the side wall. The circumferential first rear sealing projection has a maximum wall thickness D _max1 , which is greater than the minimum wall thickness d _{min of} the side wall in the rear wall section, in particular in the second straight section 15. The second rear sealing lip 23 has a maximum wall thickness D _max2 , which is greater than the maximum wall thickness D _{max3 of} the protruding forward flexible sealing lip 7. The bent outward sealing portion 25 has a wall thickness d3, which corresponds to the average wall thickness d2 of the second straight portion 15.

In the region of the peripheral edge 21, the side wall 5 including the peripheral edge 21 a maximum wall thickness D _max4 , which is greater than the wall thicknesses of the rear portion extending from the piston breast 3 behind the projecting forward flexible sealing lip 7 and the is also greater than the between the piston breast 3 and the forward projecting flexible sealing lip arranged portion of the side wall 5, which is formed essentially by the first transition portion 17 and the first straight portion 13. In other words, the side wall 5 has in the region of the peripheral edge 21, the largest wall thickness.

The wall thicknesses are measured orthogonal to the neutral fiber of the respective wall or lip. The neutral fiber is shown schematically in the figures by a broken line.

The predetermined wall thickness ratios ensure that on the one hand an advantageous sealing effect of the rear sealing projection 11 by the necessary stability of the first rear sealing projection 11th is reached and on the other hand, the necessary flexibility of the rear wall portion of the side wall 5 is given. Furthermore, it is achieved that the forwardly projecting flexible sealing lip 7 and the second rear sealing lip 23 are arranged at a particularly stable position of the side wall 5.

The second rear sealing lip 23 has an outer sealing surface 23a, which is formed as a polished surface. The first rear sealing projection 11 also has an outer sealing surface 11a, which is formed as a polished surface. In principle, the outwardly bent sealing section 25 may also have a sealing surface designed as a polished surface. In contrast to tips of sealing lips, which effect the seal, the present invention provides that polished surfaces are provided as sealing surfaces 11a, 23a, whereby an improved sealing effect is achieved. The sealing surfaces may be curved outwardly.

Claims (15)

One-piece piston (1) for cartridges (100) for expressing mass from a cartridge (100), with a front piston breast (3), a circumferential side wall (5) and at least one on the side wall (5) arranged, protruding flexible Sealing lip (7), wherein the side wall (5) has a rear wall portion extending from the piston breast (3) behind the projecting forward flexible sealing lip (7),
characterized,
in that a circumferential first rear sealing projection (11) having a maximum wall thickness D _max1 greater than a minimum wall thickness d _{min of} the side wall (5) in the _space between the forwardly projecting part is arranged on the rear wall section of the side wall (5) flexible sealing lip (7) and the rear sealing projection (11) arranged portion of the rear wall portion and / or the side wall (5) in the starting from the piston breast behind the rear sealing projection (11) arranged portion of the rear wall portion. Piston according to claim 1, characterized in that the circumferential first rear sealing projection (11) is a sealing lip which protrudes to the rear. Piston according to claim 1 or 2, characterized in that the side wall (5) in front of the forwardly projecting flexible sealing lip (7) has a circumferential or interrupted front protective edge (9), in axial projection a portion of the at least one front projecting flexible sealing lip (7) covered. Piston according to one of claims 1 to 3, characterized in that the side wall (5) at least a first straight portion (13) having a first average wall thickness d1 and in the rear wall portion a second straight portion (15) having a second average wall thickness d2 wherein the second straight portion (15) extends from the piston breast (3) behind the first straight portion (13) and where d1> d2. Piston according to claim 4, characterized in that the first rear sealing projection (11) on the second straight portion (15) is arranged. Piston according to claim 4 or 5, characterized in that the front protective edge (9) at a first transition portion (17) of said side wall (5) of the piston chest (3) obliquely outwards runs and (in the first straight section 13 ), wherein the protective edge (9) projects laterally from the side wall (5). Piston according to one of claims 4 to 6, characterized in that the side wall (5) has a second transition section (19) which is arranged between the first and the second straight section (13, 15), the second transition section (19). has a decreasing in the direction of the second straight portion (15) wall thickness. Piston according to the preamble of claim 1 or one of claims 1-7, characterized in that the side wall (5) has an outwardly of the side wall (5) projecting, circumferential edge (21) on which the forwardly projecting flexible sealing lip (7) is arranged, wherein on the peripheral edge (21) further comprises a second rear sealing lip (23) is arranged, which projects rearwardly. Piston according to claim 8, characterized in that the second rear sealing lip (23) has a maximum wall thickness D _max2 which is greater than the maximum wall thickness D _{max3 of} the forwardly projecting flexible sealing lip (7). Piston according to claim 8 or 9, characterized in that the side wall (5) in the region of the peripheral edge (21) has a side wall (5) and the peripheral edge (21) comprising maximum wall thickness D _max4 which is greater than the wall thicknesses the rear wall portion and the between the piston breast (3) and the front projecting flexible sealing lip (7) arranged portion of the side wall (5). Piston according to one of claims 3 - 10, characterized in that the front protective edge (9) has at least one opening (27) or that the front protective edge (9) has a plurality of openings (27), preferably at least 10 openings (27), wherein the Openings (27) are evenly spaced. Piston according to one of claims 1 to 11, characterized in that the forwardly projecting flexible sealing lip (7) has a plurality of passages (29). Piston according to claim 12, characterized in that a first number of the passages (29) offset from the openings (27) in the circumferential direction and a second number of the passages (29) in axial projection in the overlapping region of the openings (27) is arranged. Piston according to one of claims 1 to 13, characterized in that the side wall (5) at the end facing away from the piston breast (3) has an outwardly bent sealing portion (25), wherein preferably the outwardly bent sealing portion (25) a average wall thickness d3, which is equal to or greater than the average wall thickness d2 of the second straight section (15). Piston according to one of claims 1 to 14, characterized in that the first rear sealing projection (11) and / or the second rear sealing lip (23) has an outer sealing surface (11a, 23a) which is formed as a polished surface.

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