Vented piston, dispensing assembly and method of filling a vented piston

Abstract

The present invention relates to a vented piston for use with a 2K material comprising granular material and a fluid material, the vented piston comprising a piston body and a piston plunger, the piston body having a front end and a rear end, with one or more air passages being provided between the front end and the rear end, the piston plunger being arranged moveable within the piston body between an open position and a sealed position, with the air passages being open for an exchange of air between the front end and the rear end when the piston plunger is in the open position and with the air passages being sealed when the piston plunger is in the sealed position. The present invention further relates to a dispensing assembly comprising such a piston and to a method of filling the dispensing assembly.

Description

[0001] Vented Piston, dispensing assembly and method of filling a vented piston

[0002] The present invention relates to a vented piston and to a method of filling a vented piston.

[0003] A wide variety of ways of dispensing masses from cartridges is known in the prior art. The masses can be a so-called one-component mass, this means single component materials that e.g. harden via a chemical reaction which is brought about either by an external energy source, such as UV light or heat, or e.g. due to moisture etc. present in the surroundings of the position of application. Typical applications of one component materials can be found e.g. in the dental field or in the building industry, for example to bond products such as windows and concrete elements, or to provide seals between different components.

[0004] Another known type of mass is a multi-component mass. The materials to be dispensed may be a matrix material and a hardener. The filled cartridges come in different ratios referred to as 1 :1 , 2:1 , 4:1 and 10:1 etc., the numbers specifying the ratios of the amounts of each of the two materials that are to be dispensed. The reason for these different ratios is to allow a wide variety of different compositions to be mixed and dispensed. For example some compositions require more hardener and some require less hardener. Also some compositions require more mixing. Mixing tips are known from the prior art which are adapted to mix the compositions as they exit the cartridge.

[0005] Yet other types of 2K material can be a solid granular type of material that is mixed with a fluid, e.g. liquid, material. These types of materials once mixed frequently have a very short shelf life and react which is why the material is stored separate from one another and only brought into contact shortly before use. Such materials are frequently used in the medical and dental field.

[0006] Two-component materials are typically used as impression materials, e.g. on the formation of dental impressions, as a cement material for prosthetic restorations and during surgery, as a temporary cement for trial cementing restorations or for cementing temporary crowns. Further applications of two-component materials are in the building industry where they are e.g. used as a replacement for mechanical joints that corrode over time. Adhesive bonding can be used to bond products such as windows and concrete elements. The use of multi-component protective coatings, for example moisture barriers, corrosion protection and anti-slip coatings, is also becoming increasingly common.

[0007] Specifically on preparing a mixture from a 2K material formed from granular material and a fluid it is desirable to remove the air from a cartridge once the fluid is added to the granular material in order to avoid a faulty mixing of the two-compo- nent material and to thereby enhance the quality of the mixing result.

[0008] On filling the cartridges with the fluid, the cartridges are typically filled via their outlet with the piston already being positioned in the cartridge. The air previously present between the grains of granular material can be trapped between the piston and the material to be stored therein and it is this trapped air that should be removed from the cartridge prior to a dispensing process.

[0009] Thus it is an object of the invention to provide a cartridge which facilitates an improved mixing with reduced air once the fluid material is added to the granular material. It is a further object of the present invention to provide a piston which facilitates the venting of air present from a cartridge. It is yet a further object to provide a piston that is simple and cost effective to manufacture. This object is satisfied by a piston according to claim 1 , a dispensing assembly according to claim 17 and by a method according to claim 21 .

[0010] Such a piston may be a vented piston for use with a 2K material comprising granular material and a fluid material, the vented piston comprising a piston body and a piston plunger, the piston body having a front end and a rear end, with one or more air passages being provided between the front end and the rear end, the piston plunger being arranged moveable within the piston body between an open position and a sealed position, with the air passages being open for an exchange of air between the front end and the rear end when the piston plunger is in the open position and with the air passages being sealed when the piston plunger is in the sealed position.

[0011] Thereby a piston is made available via which air present in a cartridge can be removed which facilitates an improved mixing with reduced air once the fluid material is added to the granular material.

[0012] Such piston comprises only two parts and is thus simple and cost effective to manufacture.

[0013] In this connection it should be noted that a piston body is regarded as a main part of the piston that acts as a frame and / or support of the piston.

[0014] It should further be noted that a piston plunger is a part of the piston that is moveable relative to the piston body.

[0015] It should further be noted that an air passage is a channel like structure that is used to guide the air from one end of the piston to the other. The one or more air passages may open at the front end via venting apertures or venting slots. In this way the air passages have a direct connection to the cartridge chamber and can extract as much air as possible from the cartridge. Such air passages are simple and cost effective to manufacture, e.g. in an injection molding process.

[0016] The one or more air passages may open at the front end at an outer region of the piston body. In this way air can be reliably collected at an outer side of the piston body. The outer region may be an annular outer region arranged radially outside of a central region of the piston body.

[0017] The one or more air passages may open at the front end between a central region of the piston body and an outer region of the piston body. In this way air can be reliably collected at a middle region of the front side of a piston body.

[0018] In this connection it should be noted that the central region is arranged about a longitudinal axis of the piston.

[0019] The one or more air passages may open at the front end at central region of the piston body. In this way air can be reliably collected centrally at a front side of the piston body.

[0020] The one or more air passages may have an opening dimension at the front end of less than 1 mm. In this connection it should be noted that the one or more air passages respectively their openings, i.e. the apertures or slots, at the front end can have one or more dimensions selected in the range of 0.2 to 1 mm, preferably in the range of 0.25 to 0.9 mm. In this way the granular material having diameters of around 1 mm cannot fall into and thereby block a respective one of the one or more air passages and venting apertures or slots The piston may further comprise one or more seals arranged at a peripheral sidewall of the piston body. Such seals ensure that the material stored in the cartridge has as little contact as possible to the environment via the piston and the cartridge.

[0021] At least one of the one or more seals may be provided in the form of an O-ring. An O-ring provides a reliable seal between the piston and a cartridge once the piston is inserted into a cartridge.

[0022] The one or more air passages may open at the front end upstream of a peripheral sidewall of said piston body. In this way the seal is not affected by the air passages.

[0023] The one or more air passages may open at the front end upstream of at least one of the one or more seals of the peripheral sidewall of said piston body. This ensures an improved venting from a cartridge chamber once the piston is installed in the cartridge.

[0024] In this connection it should be noted that between 3 and 12 venting slots may be provided and more specifically between 3 and 8 venting slots may be provided. The venting slots may extend radially around a crown of the piston and / or may extend radially outwardly from the crown of the piston. In this way a sufficient venting can be ensured.

[0025] Said one or more air passages may open at the front end upstream of a first one of said at least one of O-rings arranged at the peripheral sidewall of said piston body, with the first O-ring being arranged closer to the front end to any further O- ring that can be provided. This ensures an improved venting from a cartridge chamber once the piston is installed in the cartridge and at the same time a reliable seal between the piston and the cartridge. The piston may further comprise a filter material arranged at said piston body. Such a filter material can prevent material stored in the cartridge from seeping through the piston and thus reduce a potential source of contamination.

[0026] Said filter material may be arranged at the front end of the piston body. In this way the filter acts as a barrier at the front end of the piston to ensure the material does not inhibit the movement of the piston through the cartridge.

[0027] Said filter material may be arranged within the piston body between said front end and said piston plunger. Such a filter material can prevent material stored in the cartridge from seeping through the piston and thus reduce a potential source of contamination.

[0028] The filter material may be air permeable and liquid tight. In this way the air can be vented from the cartridge and at the same time the filter can stop the fluid material and the granular material from entering the piston. Such filters offer both surface and depth filtration functionality, and may comprise a porous structure that is comprised of an omnidirectional, interconnecting matrix, which can be optimized for filtration efficiencies to match the application’s requirements. Additionally, such filters can be surface-modified or include additives to enhance functionality for improved performance, durability, and design flexibility.

[0029] Said filter material may be a filter made of porous plastic such as porous PTFE (Polytetrafluoroethylene). A trade name for such a filter material is POREX as defined in the Porex datasheet MD-003-081418-003 as published in 2018.

[0030] The piston plunger may be locked to the piston body when in the sealed position. By locking the piston plunger to the piston body the piston is locked in the sealed position preventing air from entering the cartridge chamber once this has been vented via the piston. The piston plunger may be locked to the piston body by at least one of a tongue and groove connection, and a snap fit connection. By way of example, one of the piston plunger and the piston body comprises snap hooks that can engage into cut-outs present in the other one of the piston body and the piston plunger. Such snap-fit connections are simple to manufacture and cost effective.

[0031] The piston plunger may comprise a front end having a peripheral seal arranged around the front end, with the piston body having a sealing surface arranged at an inner surface thereof, with the peripheral seal sealing against the sealing surface in the sealed position.

[0032] A dispensing assembly may comprise a vented piston as described herein and a cartridge, the cartridge comprising a chamber having a front end and a rear end, the rear end optionally comprising a flared end and the front end comprising an outlet, with the piston being arranged in the chamber, with the dispensing system being filled with a 2K material.

[0033] Such a dispensing assembly has the same advantages associated therewith as the piston according to the invention.

[0034] In this connection it should be noted that the flared end is provided as an insertion aid for the piston into the cartridge ensuring a simple and cost effective manufacture of the dispensing assembly.

[0035] The cartridge may have a cartridge wall that is transparent.

[0036] The outlet may comprises an outer thread for connecting to different accessories, with the accessories being selected from the group of members comprising a cap, and a dispensing outlet. Such accessories enable a reliable use of the dispensing assembly.

[0037] The rear end may comprise a handle at an outer surface of the cartridge. Such a handle ensures an improved handling of the dispensing assembly

[0038] The rear end may comprise a handle with the handle being formed by two wings. Such wings ensure a simple and cost effective manufacture of a handle at a dispensing assembly.

[0039] By way of example a method of filling a dispensing assembly as described herein may comprise the steps of: providing the cartridge filled with granular material and the piston being arranged in the cartridge chamber, with the piston plunger being in the open position; filling the cartridge chamber with the fluid material; and subsequently sealing off said piston by moving the piston plunger from the open position into the sealed position and locking the piston plunger to the piston body when the fluid material has a pre-defined filling level.

[0040] In this connection it should be noted that a pre-defined filling level can be considered to correspond to a state when the fluid material reaches the front end of the piston.

[0041] The advantages discussed in the foregoing can be exploited through use of the present method.

[0042] The method may further comprise the step of monitoring a filling level of the fluid material and sealing off the piston once a pre-determined threshold is reached. Such monitoring ensures a reliable and repeated filling of the cartridge with fluid at a desired quality criterion.

[0043] The step of monitoring the filling level may comprise the step of optically measuring the filling level via the transparent cartridge wall. Such an optical measurement ensures the reliable and repeated filling of the cartridge with fluid to a pre-determined level.

[0044] Exemplary embodiments of the present disclosure are described herein in conjunction with the following drawings, showing schematically:

[0045] Figs. 1 A to E various views of a first type of dispensing assembly with a first type of piston;

[0046] Figs. 2A to Cvarious views of a second type of dispensing assembly with a second type of piston;

[0047] Fig. 3A to C various views of a third type of dispensing assembly with a third type of piston;

[0048] Fig. 4A to C various views of a fourth type of dispensing assembly with a fourth type of piston;

[0049] Fig. 5 schematic view of a fifth type of piston;

[0050] Fig. 6 schematic view of a sixth type of piston;

[0051] Fig. 7 schematic view of a seventh type of piston; and

[0052] Fig. 8 schematic view of an eighth type of piston.

[0053] Figs. 1 A and 1 B show respective schematic part sectional views of a dispensing assembly 10 comprising a cartridge 12 and a piston 14. The piston comprises a piston body 16 and a piston plunger 18 (see Fig. 1 B).

[0054] The cartridge 12 further has a cartridge chamber 20 having a front end 22 and a rear end 24, with a longitudinal axis A extending between the front end 22 and the rear end 24. The piston body 16 shown in Figs. 1 and 1 B is arranged at the rear end 24 of the cartridge chamber 16.

[0055] The front end 22 comprises an outer thread 26 on an outer wall 28 of the cartridge 12. The outer thread 26 is configured such that different accessories can be connected to the cartridge 12.

[0056] By way of example a cap (not shown) can be connected to the cartridge 12 via the outer thread 26 as an accessory 30. Additionally a dispensing outlet 30’ as shown in Fig. 1 B can be connected to the cartridge 12 via the outer thread 26.

[0057] In this connection it should be noted that the accessory 30 has an inner thread 32 on an inner surface 34 thereof, with the inner thread 32 being shaped complementary to the outer thread 26 of the cartridge 12.

[0058] The cartridge further comprises two wings 36 at the rear end 24 that act as a handle 38 of the cartridge 12. The wings extend radially away from the cartridge 12.

[0059] In this connection it should be noted that the handle 38 can also have a different shape and acts as a grip plate for the user of the dispensing assembly 10 for dispensing a two-component material M, M’ from the dispensing assembly via the outlet 30’.

[0060] In this connection it should be noted that the piston 14 is arranged moveable within the cartridge chamber 20 along the longitudinal axis A from the rear end 24 to the front end 22 on dispensing the material M, M’ from the cartridge chamber 20 via the outlet 30’. Fig. 1 C shows a perspective view of the piston 14. The piston is a vented piston 14 having a front end 40 and a rear end 42. The front end comprises a sealing lip 44 surrounding a piston cover 46 arranged at the front end 40.

[0061] The front end 40 further comprises an annular groove 48 surrounding the piston cover 46, with the annular groove 48 being set back from the piston cover 46 and the sealing lip 44.

[0062] In the example of Fig. 1 C a plurality of venting slots 50 are arranged at a base 52 of the annular groove 48. The venting slots 50 extend radially around the annular groove 48. The venting slots 50 have an elongate extent.

[0063] In this connection it should be noted that each venting slot 50 can have a width selected in the range of 0.05 to 0.3 mm and a length selected in the range of 0.1 to 2 mm. In the specific example shown eight venting slots are provided and each venting slot has a width of 0.1 mm and a length of 0.4 mm.

[0064] The piston cover 46 has a crown portion 54 forming a central region 56 of the piston 14 and the annular groove 48 forming an annular outer region 58 of the piston 14.

[0065] In this connection it should be noted that the crown portion 54 can extend over 10 to 30% of the diameter of the front end 40 of the piston, i.e. over 10 to 30% of the diameter of the piston 14 as defined by the outermost diameter of the sealing lip 44. In this present example the crown portion 54 extends over 22% of the diameter of the front end 40.

[0066] In this connection it should be noted that the outer region 58 can extend over 5 to 20% of the diameter of the front end 40 of the piston, i.e. over 5 to 20% of the diameter of the piston 14 as defined by the outermost diameter of the sealing lip 44. In the present example the outer region 58 extends over 12% of the diameter of the piston 14.

[0067] The region between the outer region 58 and the central region 54 is known as the middle region 76. The front end 40 of the piston 14 has a most proximal portion formed by the crown portion 54 which then tapers distally towards the outer region 58 via the middle region 76 and then comprises the outer region 58 formed by the annular groove 48 and the sealing lip 44.

[0068] In this connection it should be noted that the middle region 76 can extend over 50 to 85% of the diameter of the front end 40 of the piston, i.e. over 50 to 85% of the diameter of the piston 14 as defined by the outermost diameter of the sealing lip 44. In the present example the middle region 76 extends over 66% of the diameter of the piston 14.

[0069] An outer peripheral surface 64 of the piston 14 further comprises an O-ring 60 arranged in a peripheral groove 62.

[0070] As indicated in Figs. 1 D and 1 E, a peripheral wall 78 of the piston body 16 having the peripheral surface 64 from the rear end 42 of the piston 14 to the front end 40 comprises a further seal 66 that is arranged directly at the rear end 42 of the piston 14. The further seal 66 is directly adjacent to an annular recess 68 that is directly adjacent to a projecting wall 70 bounding the peripheral groove 62 housing the O- ring. The peripheral groove 62 extends along the piston 14 up to the sealing lip 44.

[0071] The venting slot 50 at the base 52 of the annular groove 48 is an opening of an air passage 72 that in the present example extends axially through the piston cover 46 and then radially through the piston body 16 into an inner space 74 of the piston body 16. The piston 14 comprises the piston body 16 and the piston plunger 18, the piston plunger 18 is arranged moveable within the piston body 16 between an open position and a sealed position, with the air passages 72 being open for an exchange of air between the front end 40 and the rear end 42 when the piston plunger 18 is in the open position as indicated in Figs. 1 B and 1 E and with the air passages 72 being sealed when the piston plunger 18 is in the sealed position as indicated by Figs. 1 A and 1 D.

[0072] In the sealed position the piston plunger 18 is locked to the piston body 16, this can be achieved by several modes of connection such as a tongue and groove connection, and / or a snap fit connection.

[0073] In the example shown in Figs. 1 A and 1 D the piston plunger comprises several snap arms 80. The snap arms 80 project axially towards a front end 82 of the piston plunger 18 from a shoulder 92 of the piston plunger 18 in parallel to the longitudinal axis A. An end 94 of the respective snap arm 80 comprises a snap hook 86.

[0074] The snap hooks 96 of the snap arms 80 engage into cut-outs 98 present in the piston body 16 in the inner space 74 thereof and thereby lock the piston plunger 18 to the piston body 16 via a snap-fit connection.

[0075] In this connection the snap fit connection can also be formed by a collar that snaps into a groove or recess of the piston body or vice versa.

[0076] The cut-outs 98 are arranged in the inner space 74 of the piston body 16 at the axial height of the piston body 16 along the longitudinal axis corresponding to an axial height of the annular recess 68 is arranged. The piston plunger 18 further a peripheral seal 86 extending around the piston plunger 18 at the front end 82. The piston body 16 has a sealing surface 88 arranged at an inner surface 90 of the inner space 74. The peripheral seal 86 seals against the sealing surface 88 in the sealed position and in this way blocks the air passages 72.

[0077] It should be noted in this connection that when the peripheral seal 82 is not contacting, i.e. sealing against the sealing surface 88 in the sealed position, but in the open position, it does not seal with respect to the remaining parts of the inner surface 90 not comprising the sealing surface 88.

[0078] The air passages 72 open into the inner space 74 of the piston body 16 at the sealing surface 88.

[0079] The piston plunger 18 further comprises a rear end 84 via which a force can be imparted onto the piston 14 for moving the piston in the cartridge 12. The force can be imparted e.g. manually or through the use of a dispenser (not shown).

[0080] As can further be seen in Figs. 1 D and 1 E, the rear end 24 of the cartridge 12 comprises a flared end such that an opening of the cartridge at the rear end 24 has a larger diameter than the remaining cartridge chamber 20. The flared end has the shape of a truncated cone.

[0081] Figs. 2A to C show various views of a second type of piston 14. The piston 14 shown in Fig. 2A has elongate venting slots 50 that extend radially outwardly from the middle region 76 into the annular groove 48. The venting slots 50 are arranged in the shape of a cross at the piston cover 46. The piston 14 is shaped generally in the same way as the piston described in the foregoing in connection with Fig. 1 apart from the specific features relating to the venting slots 50. In this connection it should be noted that each venting slot 50 can have a width selected in the range of 0.05 to 0.3 mm and a length selected in the range of 0.1 to 2 mm. In the specific example shown four venting slots are provided and each venting slot 5 has a width of 0.2 mm and a length of 1 mm.

[0082] Fig. 2A shows a perspective view of the piston 14. The piston is also a vented piston 14 having a front end 40 and a rear end 42. The front end 40 comprises a sealing lip 44 surrounding the piston cover 46 arranged at the front end 40.

[0083] The front end 40 further comprises an annular groove 48 surrounding the piston cover 46, with the annular groove 48 being set back from the piston cover 46 and the sealing lip 44.

[0084] In the example of Fig. 2A the plurality of venting slots 50 are arranged at the piston cover 46 and extend up to the base 52 of the annular groove 48.

[0085] The venting slots 50 start in a middle of the middle region 74 of the piston 14 and extend into a middle of the outer region 58 of the piston 14.

[0086] The piston cover 46 has a crown portion 54 forming a central region 56 of the piston 14 and the annular groove 48 forming an outer region 58 of the piston 14.

[0087] In this connection it should be noted that the crown portion 54 can extend over 10 to 30% of the diameter of the front end 40 of the piston, i.e. over 10 to 30% of the diameter of the piston 14 as defined by the outermost diameter of the sealing lip 44. In this present example the crown portion 54 extends over 22% of the diameter of the front end 40.

[0088] In this connection it should be noted that the outer region 58 can extend over 5 to 20% of the diameter of the front end 40 of the piston, i.e. over 5 to 20% of the diameter of the piston 14 as defined by the outermost diameter of the sealing lip 44. In the present example the outer region 58 extends over 12% of the diameter of the piston 14.

[0089] The region between the outer region 58 and the central region 54 is known as the middle region 76. The front end 40 of the piston 14 has a most proximal portion formed by the crown portion 54 which then tapers distally towards the outer region 58 via the middle region 76 and then comprises the outer region 58 formed by the annular groove 48 and the sealing lip 44.

[0090] In this connection it should be noted that the middle region 76 can extend over 50 to 85% of the diameter of the front end 40 of the piston, i.e. over 50 to 85% of the diameter of the piston 14 as defined by the outermost diameter of the sealing lip 44. In the present example the middle region 76 extends over 66% of the diameter of the piston 14.

[0091] An outer peripheral surface 64 of the piston 14 further comprises an O-ring 60 arranged in a peripheral groove 62.

[0092] As indicated in Figs. 2B and 2C, a peripheral wall 78 of the piston body 16 having the peripheral surface 64 from the rear end 42 of the piston 14 to the front end 40 comprises a further seal 66 that is arranged directly at the rear end 42 of the piston 14. The further seal 66 is directly adjacent to an annular recess 68 that is directly adjacent to a projecting wall 70 bounding the peripheral groove 62 housing the O- ring. The peripheral groove 62 extends along the piston 14 up to the sealing lip 44.

[0093] The venting slot 50 at the base 52 of the annular groove 48 is an opening of an air passage 72 that in the present example extends axially through the piston cover 46 and then radially through the piston body 16 into an inner space 74 of the piston body 16. The piston 14 comprises the piston body 16 and the piston plunger 18, the piston plunger 18 is arranged moveable within the piston body 16 between an open position and a sealed position, with the air passages 72 being open for an exchange of air between the front end 40 and the rear end 42 when the piston plunger 18 is in the open position as indicated in Fig. 2B and with the air passages 72 being sealed when the piston plunger 18 is in the sealed position as indicated by Figs. 2C.

[0094] In the sealed position the piston plunger 18 is locked to the piston body 16, this can be achieved by several modes of connection such as a tongue and groove connection, and / or a snap fit connection.

[0095] In the example shown in Fig. 2C the piston plunger comprises several snap arms 80. The snap arms 80 project axially towards a front end 82 of the piston plunger 18 from a shoulder 92 of the piston plunger 18 in parallel to the longitudinal axis A. An end 94 of the respective snap arm 80 comprises a snap hook 86.

[0096] The snap hooks 96 of the snap arms 80 engage into cut-outs 98 present in the piston body 16 in the inner space 74 thereof and thereby lock the piston plunger 18 to the piston body 16 via a snap-fit connection.

[0097] In this connection the snap fit connection can also be formed by a collar that snaps into a groove or recess of the piston body or vice versa.

[0098] The cut-outs 98 are arranged in the inner space 74 of the piston body 16 at the axial height of the piston body 16 along the longitudinal axis corresponding to an axial height of the annular recess 68 is arranged. The piston plunger 18 further a peripheral seal 86 extending around the piston plunger 18 at the front end 82. The piston body 16 has a sealing surface 88 arranged at an inner surface 90 of the inner space 74. The peripheral seal 86 seals against the sealing surface 88 in the sealed position and in this way blocks the air passages 72.

[0099] It should be noted in this connection that when the peripheral seal 82 is not contacting, i.e. sealing against the sealing surface 88 in the sealed position, but in the open position, it does not seal with respect to the remaining parts of the inner surface 90 not comprising the sealing surface 88.

[0100] The air passages 72 open into the inner space 74 of the piston body 16 at the sealing surface 88.

[0101] The piston plunger 18 further comprises a rear end 84 via which a force can be imparted onto the piston 14 for moving the piston in the cartridge 12. The force can be imparted e.g. manually or through the use of a dispenser (not shown).

[0102] Figs. 3A to C show various views of a third type of piston 14. The difference between the pistons 14 shown in connection with Figs. 1 and 2 is that the outer seals of the piston 14 are present on an outer surface of the piston plunger 18, the position of the venting slots 50 and the shape of the front end 40.

[0103] In this connection it should be noted that the piston plunger comprises a sealing lip at the front end 40 of the piston 14 and two peripheral seals 66 extending about the front end 40of the piston 14.

[0104] The venting slots 50 extend radially around the crown 54 around the central region 56. In this connection it should be noted that each venting slot 50 can have a width selected in the range of 0.05 to 0.3 mm and a length selected in the range of 0.1 to 2 mm. In the specific example shown three venting slots are provided and each venting slot 5 has a width of 0.2 mm and a length of 1 mm.

[0105] Fig. 4A to C show various views of a fourth type of piston 14. The piston 14 has a centrally arranged venting slot 50 and air passage 72 that are coaxially arranged with the longitudinal axis A and have a cylindrical shape.

[0106] The front end 40 is formed by a filter 106 as the piston cover 46. The filter 106 is press-fit into the piston body 16.

[0107] To this end the front end 40 of the piston comprises a reception space 112 formed by an annular wall 108 forming a collar into which the filter 106 is pressed. The reception space 112 further comprises three pillars 1 10 that support the filter material.

[0108] The filter 106 sits on the venting slot 50 and permits the flow of air through the piston body 16, but avoids a fluid flowing through the piston body 16, as the filter 106 is selected such that is gas permeable but liquid impermeable. The filter 106 is set back axially from the sealing lip 44.

[0109] Fig. 5 shows a schematic view of a fifth type of piston 14. The piston body 16 and the piston plunger 18 is identical to the piston body 16 and the piston plunger taught in connection with Fig. 2.

[0110] The filter 106 is press fit into the inner space 74 in a space between the piston body 16 and the piston plunger.

[0111] In this connection it should be noted that the filter can have a thickness selected in the range of 1 to 5 mm and in the example of Fig. 4 has a thickness of 1 .5 mm and in the example of Fig. 5 has a thickness of 2.5 mm. Fig. 6 shows a schematic view of a sixth type of piston 14. The difference to the example shown in Figs. 1 , 2 and 5 is that only one venting slot 50 is provided that is coaxially arranged with the longitudinal axis A. The venting slot 50 has a cylindrical shape and may have a diameter selected in the range of 0.2 to 1 mm. In the specific example the air passage 72 and the venting slot 50 have a diameter of 0.3 mm.

[0112] A filter 106 not shown may also be present in the inner space 74 of the piston body 16 like as is shown in Fig. 5. This filter may also be press-fit into the inner space 74.

[0113] The remaining features of the shape of the piston body 16 and the piston plunger other than the position of the venting slot 50 are identical to those discussed in connection with Figs. 1 and 2.

[0114] Fig. 7 shows a schematic view of a seventh type of piston 14. This example includes features of some of the previously described examples, in particular the front end 40 is shaped as shown in the examples of Figs. 4A to C, but the filter 106 is press fit into the inner space 74 in a space between the piston body 16 and the piston plunger as shown in the example of Fig. 5. The difference to the example shown in Figs. 2C, 4A to C and 5 is that radial protrusions 87 are provided, which project from the piston plunger 18 orthogonally to the longitudinal axis A. The radial protrusions 87 engage into recesses 99 provided in the piston body 16 for locking the piston plunger 18 to the piston body 16.

[0115] Fig. 8 shows a schematic view of an eighth type of piston 14. The difference to the example shown in Fig. 7 is that the front end 82 of the piston plunger 18 comprises a peripheral groove 1 14 and the peripheral seal 86 comprises an O-ring 1 18 arranged in the peripheral groove 1 14. The O-ring 1 18 seals against the sealing surface 88 of the piston body 16 in the sealed position. It should be noted that the cartridge 12 described in the foregoing may have a cartridge wall 28 that is formed optically transparent. Int this way a filling level of a fluid filled into the cartridge can be monitored.

[0116] The cartridge is suitable for use with a 2K material and in a storage state stores granular material. On use of the material stored in the cartridge this is mixed with a fluid. The method of filling the dispensing assembly 10 thus comprises the steps of: providing the cartridge 12 filled with granular material while the piston 14 is arranged in the cartridge chamber 20, with the piston plunger 18 being in the open position; filling the cartridge chamber with the fluid material; and subsequently sealing off said piston 14 by moving the piston plunger 18 relative to the piston body 16 from the open position into the sealed position when the fluid material has reached a pre-defined filling level, e.g. when the fluid arrives at the front end 40 of the piston 14.

[0117] This can be detected optically e.g. via the optically transparent wall on filling the fluid into the cartridge 12.

[0118] Other forms of detection can also be used, for example, a pre-defined amount of fluid can be output via a valve system to the cartridge and once the fluid is dispensed a movement of the piston plunger 18 relative to the piston body 16 can be affected to seal off the piston 14.

[0119] Also a pressure sensor (not shown) can be arranged at the piston plunger 18 that detects a pressure on the piston body 16 and once a threshold value is exceeded a control and evaluation unit recognises this increase in pressure detected by the pressure sensor and signals the filling station to initiate the relative movement between the piston body 16 and the piston plunger 18.

[0120] List of reference numerals:

[0121] 10 Dispensing assembly

[0122] 12 cartridge

[0123] 14 piston

[0124] 16 piston body

[0125] 18 piston plunger

[0126] 20 cartridge chamber

[0127] 22 front end of 12

[0128] 24 rear end of 12

[0129] 26 outer thread

[0130] 28 outer wall of 12

[0131] 30, 30’ accessory, dispensing outlet

[0132] 32 inner thread

[0133] 34 inner surface of 30, 30’

[0134] 36 wings

[0135] 38 handle

[0136] 40 front end of 14

[0137] 42 rear end of 14

[0138] 44 sealing lip

[0139] 46 piston cover

[0140] 48 annular groove

[0141] 50 venting slot

[0142] 52 base

[0143] 54 crown

[0144] 56 central region

[0145] 58 outer region

[0146] 60 O-ring

[0147] 62 peripheral groove

[0148] 64 peripheral surface of 14

[0149] 66 seal

[0150] 68 annular recess

[0151] 70 projection

[0152] 72 air passage

[0153] 74 inner space of 16

[0154] 76 middle region

[0155] 78 peripheral wall

[0156] 80 snap arm

[0157] 82 front end of 18

[0158] 84 rear end of 18

[0159] 86 peripheral seal 87 radial protrusions

[0160] 88 sealing surface of 74

[0161] 90 inner surface of 16

[0162] 92 shoulder

[0163] 94 end of 80

[0164] 96 snap hook

[0165] 98 cut-out

[0166] 99 recess

[0167] 100 snap-fit connection

[0168] 102 flared end

[0169] 104 opening of 12

[0170] 106 filter

[0171] 108 annular wall

[0172] 110 pillar

[0173] 112 reception space

[0174] 114 peripheral groove

[0175] 118 O-Ring

[0176] A longitudinal axis

[0177] M, M’ material, material

Claims

Claims1 . A vented piston (14) for use with a 2K material (M, M’) comprising granular material and a fluid material, the vented piston (14) comprising a piston body (16) and a piston plunger (18), the piston body (16) having a front end (40) and a rear end (42), with one or more air passages (72) being provided between the front end (40) and the rear end (42), the piston plunger (18) being arranged moveable within the piston body (16) between an open position and a sealed position, with the air passages (72) being open for an exchange of air between the front end (40) and the rear end (42) when the piston plunger (18) is in the open position and with the air passages (72) being sealed when the piston plunger (18) is in the sealed position.

2. The vented piston (14) according to claim 1 , wherein the one or more air passages (72) open at the front end (40) via venting apertures or venting slots (50).

3. The vented piston (14) according to claim 1 or claim 2, wherein the one or more air passages (72) open at the front end (40) at an annular outer region (58) of the piston body (16).

4. The vented piston (14) according to claim 1 or claim 2, wherein the one or more air passages (72) open at the front end (40) at a middle region (76)between a central region (56) of the piston body (16) and an outer region (58) of the piston body (16).

5. The vented piston (14) according to claim 1 or claim 2, wherein the one or more air passages (72) open at the front end (40) at central region (56) of the piston body (16).

6. The vented piston (14) according to one of claims 1 to 4, wherein the one or more air passages (72) respectively the venting slots (50) have an opening dimension at the front end (40) of less than 1 mm.

7. The vented piston (14) according to one claims 1 to 6, further comprising one or more seals (44, 60, 66) arranged at a peripheral wall (78) of the piston body (16).

8. The vented piston (14) according to claim 7, wherein at least one of the one or more seals is provided in the form of an O-ring (60).

9. The vented piston (14) according to one of claims 1 to 8, wherein the one or more air passages (72) open at the front end (40) upstream of a peripheral wall (78) of said piston body (16); and / or wherein the one or more air passages (72) open at the front end (40) upstream of at least one of the one or more seals (44; 60, 66) of the peripheral sidewall of said piston body (16).

10. The vented piston (14) according to claim 9, wherein said one or more air passages (72) open at the front end (40) upstream of a first one of said at least one of O-rings (60) arranged at the peripheral wall (78) of said piston body (16), with the first O-ring (60) being arranged closer to the front end (40) to any further O-ring that can be provided.1 1 . The vented piston (14) according to one of claims 1 to 10, further comprising a filter material arranged at said piston body (16).

12. The vented piston (14) according to claim 1 1 , wherein said filter material is arranged at the front end (40) of the piston body (16); or. wherein said filter material is arranged within the piston body (16) between said front end (40) and said piston plunger (18).

13. The vented piston (14) according to claim 1 1 or claim 12, wherein the filter material is air permeable and liquid tight; and / or wherein said filter material is porous plastic, such as porous PTFE.

14. The vented piston (14) according to one of claims 1 to 13, wherein the piston plunger (18) is locked to the piston body (16) when in the sealed position.

15. The vented piston (14) according to claim 14, wherein the piston plunger(18) is locked to the piston body (16) by at least one of a tongue and groove connection, a snap fit connection and a protrusion (87) and recess (99) connection.

16. The vented piston (14) according to one of claims 1 to 15, wherein the piston plunger (18) comprises a front end (82) having a peripheral seal (86) arranged around the front end (82), with the piston body (16) having a sealing surface (88) arranged at an inner surface (90) thereof, with the peripheral seal (82) sealing against the sealing surface (88) in the sealed position.

17. The vented piston (14) according to claim 16, wherein the peripheral seal (86) comprises an O-ring (118) arranged in a peripheral groove (114) of the piston plunger (18).

18. A dispensing assembly comprising a vented piston (14) according to one of claims 1 to 17 and a cartridge (12), the cartridge (12) comprising a chamber (20) having a front end (22) and a rear end (24), the rear end optionally comprising a flared end and the front end (22) comprising an outlet, with the vented piston (14) being arranged in the chamber (20), with the dispensing system (10) being filled with a 2K material.

19. The dispensing assembly according to claim 18, wherein the cartridge has a cartridge wall that is transparent.

20. The dispensing assembly according to claim 18 or claim 19, wherein the outlet comprises an outer thread for connecting to different accessories, with the accessories being selected from the group of members comprising a cap, and a dispensing outlet.21 . The dispensing assembly according to one of claims 18 to 20, wherein the rear end comprises a handle at an outer surface of the cartridge; and / or wherein the rear end comprises a handle with the handle being formed by two wings.

22. A method of filling a dispensing assembly in accordance with one or more of the preceding claims 18 to 21 , the method comprising the steps of: providing the cartridge filled with granular material and the piston (14) being arranged in the cartridge chamber, with the piston plunger (18) being in the open position; filling the cartridge chamber with the fluid material; andsubsequently sealing off said piston (14) by moving the piston plunger (18) from the open position into the sealed position when the fluid material has reached a pre-defined filling level, e.g. when the fluid arrives at the front end (40) of the piston (14).

23. A method according to claim 22, further comprising the step of monitoring a filling level of the fluid material and sealing off the piston once a pre-determined threshold is reached.

24. A method according to claim 23, wherein the step of monitoring the filling level comprises the step of optically measuring the filling level via the transparent cartridge wall.

Images