Piston, dispensing device and method of filling and venting a dispensing device

Abstract

The invention refers to a piston for a dispensing device, the piston comprising a first end and a second end opposite to the first end along a longitudinal axis of the piston, and a membrane arranged between the first end and the second end along the longitudinal axis, the membrane comprising a sealingly closed slit or forming a sealingly closed slit upon piercing of the membrane. Furthermore, the invention is also directed at a dispensing device and a method of filling and venting a dispensing device.

Description

[0001] Piston, dispensing device and method of filling and venting a dispensing device

[0002] The present invention refers to a piston for a dispensing device, the piston comprising a first end and a second end opposite to the first end along a longitudinal axis of the piston. The invention also refers to a dispensing device comprising such kind of piston and a method of filling and venting a dispensing device.

[0003] Dispensing devices are well known in the art and are generally used for storage and subsequent dispensing of a material. In particular, a typical dispensing device comprises at least one cartridge which is used to store the material therein and which also accommodates said piston movable by a plunger for discharge action.

[0004] The material stored in the dispensing device may be used in a plethora of fields of application ranging from industrial applications, such as the use of adhesives to bond structural components one to another, or as coatings for buildings or vehicles, to medical and dental applications, in particular as filling material, mold material or bleaching material. Furthermore, the dispensing device can also be used to store and discharge a multi-component material, such as for example a two-component adhesive comprising a filler material and a hardener.

[0005] The dispensing device can be filled for example from a rear side of the dispensing device. This is done by filling the material into a reception space formed inside a cartridge of the dispensing device. However, when the piston is inserted into the cartridge, the piston closes the cartridge and gasses, such as air, might get trapped inside the cartridge. Such trapped gasses may lead to a premature degradation of the material stored inside the cartridge. Furthermore, gasses trapped inside the cartridge might cause unwanted spouting of the material during discharge operation.

[0006] It is therefore one object of the invention to improve the filling and venting of a dispensing device. The object is satisfied by a piston comprising the features of claim 1.

[0007] The invention is based on the idea that a venting path can be formed by means of a tubular hollow needle extending through a piston closing a rear end of a cartridge of dispensing device filled with a material. The venting path formed by the tubular hollow needle thus connects the inside of the cartridge storing the material with the outside, such that gasses trapped inside the cartridge can be transferred to the outside by means of the venting path. In order to enable the tubular hollow needle to be pushed through the piston, the piston comprises either a sealingly closed slit penetrateable by the tubular hollow needle or forms a sealingly closed slit upon piercing of the membrane with the tubular hollow needle. However, after retraction of the tubular hollow needle from the piston, the slit formed in the membrane remains sealingly closed to prevent any leakage therefrom.

[0008] Preferably, venting is already possible as the piston is inserted into the cartridge. This may be achieved for example by a setting tool holding the piston during insertion, the setting tool further comprising a tubular hollow needle configured such that the tubular hollow needle extends through the membrane of the piston as the piston is inserted into the cartridge by means of the setting tool.

[0009] A sealingly closed slit allows for the penetration of a tubular hollow needle, but at the same time prevents leakage of the material stored in the cartridge as the needle penetrates the membrane. Furthermore, the sealingly closed slit remains closed, i.e. free of leakage, even after removal of the needle and even if pressure is applied onto the piston during dispensing operation, for example by using a plunger acting on the piston. By means of example, the pressure applied to the piston may be caused by a typical discharge force of a user of the dispensing device during manual operation. However, the sealingly closed slit may also sustain pressures commonly applied to the piston in motor driven dispensing devices and remains then free of leakage. In this regard, it is to be expected that a sealingly closed slit formed in a thicker membrane can sustain higher pressures to remain free of leakage. It has been shown that a sealingly closed slit is best formed upon piercing of a not yet slit- ted membrane if the tubular hollow needle is preferably an irrigation or non-coring needle type. Such kind of needles tear the membrane without forming any gaps being the source of leakage. It is further noted that a slitted membrane, i.e. a membrane already comprising a sealingly closed slit, can be sealingly penetrated using a blunt tube or cannula type needle.

[0010] A tubular hollow needle in the context of this disclosure may refer to a tubular hollow needle comprising either an acute, a rounded or a flat tip. In particular, the tubular hollow needle may also refer to a thin hollow tube having a cross-sectional size of typical tubular hollow needles. Furthermore, a tubular hollow needle may also comprise a cannula.

[0011] In the following the tubular hollow needle will be shortly also referred to as needle.

[0012] It is to be noted that the above described venting is not only possible for dispensing devices filled from the rear side, but also for cartridges filled from the front side. In this context, such kind of front filling is possible by filling the material into the cartridge from a front opening, which may be the same opening as the one used for discharging the material from the cartridge.

[0013] The longitudinal axis of the piston may extend between the first end and the second end of the piston, such that the first end may be referred to as an axial first end of the piston and the second end may be referred to as an axial second end of the piston.

[0014] Furthermore, the longitudinal axis of the piston may be arranged at least substantially parallel to a discharge direction, when the piston is assembled to the dispensing device. In this regard, the longitudinal axis of the piston and a longitudinal axis of the cartridge are also arranged parallel to each other, when the piston is received in the cartridge. Furthermore, the first end of the assembled piston may face towards a discharge outlet of the dispensing device or the cartridge formed at the front of the dispensing device and may be therefore referred to as front end of the piston. The second end of the assembled piston may face a rear opening of the cartridge and may therefore be referred to as rear end of the piston. The rear end of the piston is preferably engageable with a plunger of the dispensing device inserted into the cartridge. It is further noted that the first end of the piston may face the inside of the cartridge, whereas the second end of the piston may face towards the outside.

[0015] Further advantages and embodiments become apparent from the dependent claims, the description and the drawings.

[0016] Preferably, the piston comprises a passage extending along the longitudinal axis of the piston between the first end and the second end of the piston. A first portion of the passage may extend between the first end of the piston and the membrane and a second portion of the passage may extend between the second end of the piston and the membrane.

[0017] Arranging the membrane in the passage allows for the membrane to be thinner than a thickness of the piston in direction of the longitudinal axis of the piston and therefore reduces a force to penetrate the membrane. Preferably, the thickness of the membrane in the passage is adapted such that after the retraction of the needle a sealingly closed slit remains in the membrane.

[0018] According to one embodiment, a size of a first opening of the passage formed at the first end and a size of a second opening of the passage formed at the second end is substantially the same. Alternatively, the size of the first opening of the passage and the size of the second opening of the passage may be different. Preferably, the opening of the second passage is larger than the opening of the first passage. This allows for an easy access of the needle from the second end. The size of the respective openings preferably refers to a size perpendicular to the longitudinal axis of the piston.

[0019] Furthermore, a length of the first portion of the passage and a length of the second portion of the passage may be substantially the same. Alternatively, the length of the first portion of the passage and a length of the second portion of the passage may be different. Preferably, the length of the second portion of the passage may be larger than the length of the first portion of the passage. The larger length of the second portion of the passage allows for a guidance of the needle towards the membrane, whereas the shorter length of the first portion of the passage reduces a dead volume of the first portion. In this context, a length of the respective portions of the passage refers to a length in direction of the longitudinal axis of the piston.

[0020] Preferably, at least one of the first portion of the passage and the second portion of the passage tapers towards the membrane. This means that the radial size of the membrane with respect to the longitudinal axis of the piston is smaller than the size of the first portion's opening and / or the size of the second portion's opening. In particular, at least one of the first portion of the passage and the second portion of the passage may form a hollow truncated cone. However, other tapering shapes of the first portion and / or the second portion may be envisaged, for example a hollow truncated pyramidal shape.

[0021] The tapering shape of the first portion allows for compensation of a possibly misaligned needle, i.e. a needle that is tilted with regard to the longitudinal axis of the piston, pushed through the membrane and pointing towards the reception space. The tapering shape of the second portion allows for a guidance of the needle towards the membrane.

[0022] According to a preferred design of the piston, both the first portion and the second portion of the passage respectively taper towards the membrane, wherein a shape of the tapering first portion and a shape of the tapering second portion is substantially the same or different. In this regard, an opening angle of the tapering first portion and an opening angle of the tapering second portion may be substantially the same. Alternatively, the opening angle of the tapering first portion and the opening angle of the tapering second portion may be different.

[0023] Preferably, the opening angle of the tapering second portion is larger than the opening angle of the tapering first portion. A larger opening angle of the tapering second portion allows for a guidance of the needle as the needle approaches the membrane, thereby centering the needle towards the membrane. A smaller opening angle of the tapering first portion reduces the dead volume of the first portion of the passage.

[0024] In order to provide a sufficient sealing of the reception space at the rear side of the cartridge, the piston preferably comprises at least one sealing lip formed on an outer side surface of the piston. In particular the sealing lip is configured to sealingly engage with an inner wall of the cartridge.

[0025] The sealing lip may have an outer circumference that is slightly larger than an inner circumference of an inner wall of the cartridge, such that the sealing lip is pressed against the inner wall of the cartridge, when the piston is received in the cartridge.

[0026] The sealing lip may be preferably formed on an outer side surface of at at least one of the first end and the second end. However, the sealing lip may be also formed on an outer side surface of the piston between the first end and the second end along the longitudinal axis of the piston.

[0027] The piston may comprise at least two sealing lips axially separated along the longitudinal axis of the piston to prevent unwanted tilting of the piston during its movement inside the cartridge.

[0028] The piston may comprise a guidance lip formed on a guidance lip formed on an outer side surface of the piston. In particular, the guidance lip is configured to guide the piston during its movement along the longitudinal axis of the cartridge. The guidance lip may have an outer circumference that is at least substantially the same as the inner circumference of the inner wall of the cartridge, such that the guidance lip bears against the inner wall of the cartridge. In this context, it is noted that the outer circumference of the guidance lip is smaller than the outer circumference of the sealing lip.

[0029] The sealing lip and the guidance lip may radially extend from the outer side surface of the piston.

[0030] The piston may comprise at least one sealing lip and at least one guidance lip axially separated along the longitudinal axis of the piston. Such kind of configuration prevents unwanted tilting of the piston inside the cartridge.

[0031] For stabilization of the piston, the membrane may be formed at an axial height, in particular at the same axial height, of the sealing lip or the guidance lip. Furthermore, if the membrane is formed at the sealing lip or the guidance lip, a radially inwardly directed counterforce caused by the sealing lip or the guidance lip due to the lips bearing against the inner wall of the cartridge causes that the slit is firmly engaged with the needle extending through the slit or that the slit remains firmly closed after retraction of the needle.

[0032] The piston may comprise an engagement means configured to engage the piston with the plunger. Preferably, the engagement means is present at the second end of the piston, i.e. the end facing the plunger. In particular, the engagement means may be formed on an outer surface of the piston, preferably on an outer side surface of the piston. If the engagement means is formed on an outer side surface of the piston, the portion of the passage extending towards the membrane remains free, even during engagement with the plunger. In this regard it is noted that the side surface of the piston is that surface that extends between the first end and the second end of the piston.

[0033] Preferably, the engagement between the piston and the plunger is releasable. The engagement means may be formed by a snap-fit engagement means. However, other types of engagement means may be envisaged, such as for example bayonet-type engagement means or frictional engagement means.

[0034] Furthermore, the engagement means may be also formed in the passage extending through the piston or by the passage itself. That is the piston may engage with the plunger at the passage of the piston.

[0035] It is to be understood that the piston may also be moved by the plunger, in particular towards the front end, by mere contact of the piston and the plunger. That is, the rear end of the piston may form an engagement means, in particular configured to engage with a front end of the plunger.

[0036] According to an advantageous embodiment, the piston may have a D-shaped cross-section such that the piston has a flat outer side surface and a bowed out outer side surface. Such kind of cross-section is advantageous if the cartridge also has a D-shaped cross section which allows for a more compact design of the entire dispensing device. In such a configuration, the engagement means may be formed at the second end or adjacent to the second end of the piston on at least one of the flat outer surface and the bowed out outer surface.

[0037] According to a preferred embodiment, the piston may be formed by injection molding.

[0038] The piston may be formed at least in parts of an elastomeric material, such as a silicone or a rubber material. In particular, the entire piston may be formed of an elastomeric material. However only parts of the piston may be formed of an elastomeric material, whereas other parts of the piston may be formed of another material, in particular of a less elastomeric material.

[0039] For example, it is preferred that at least the membrane is formed of an elastomeric material. This allows for the slit to snugly engage with the needle as the needle penetrates the membrane of the piston. Furthermore, after the needle has been retracted from the piston, the elastomeric material sealingly closes the slit, thereby preventing leakage therefrom. By means of another example, the sealing lip may be formed of an elastomeric material. This enables the sealing lip to sealingly engage with the inner surface of the cartridge, when the piston is received in the cartridge. By means of yet another example, the guidance lip may be formed of an elastomeric material.

[0040] The elastomeric material is preferably selected such that during penetration as well as after retraction of the needle, the slit remains sealingly closed. In this regard, the elastomeric spring force of the elastomeric material ensures that the slit is closed. Yet the elastomeric material facilitates the slit being penetrated by the needle.

[0041] According to a preferred embodiment, the membrane may form a bulge. Preferably, the bulge is convex, with the curved surface of the bulge comprising a common center of curvature.

[0042] Furthermore, the bulge may face towards the first end of the piston. In this regard, the bulge may be convex towards the first end of the piston.

[0043] The bulge may comprise a sealingly closed slit or may form a sealingly closed slit upon piercing of the bulge.

[0044] The particular shape of the bulge allows for forming a sealingly closed slit.

[0045] In particular, the convex shape of the bulge centers a force exerted on the curved surface of the bulge to the center of curvature of the bulge. As the force acts from all directions on the surface of the so to say dome shaped bulge, a slit formed in the bulge will be pressed together, thereby enabling a sealingly closed slit. The force may be for example exerted by a material stored in the reception space of the cartridge, in particular as the piston is moved in a forward direction towards the front side of the cartridge.

[0046] It is noted that the bulge and the membrane may be a single piece. However, it is also possible to form the bulge and the membrane of separate pieces and / or separate materials.

[0047] Additionally or supplementary, the membrane may form a stub. The stub may axially extend towards the second end of the piston.

[0048] The stub may comprise a sealingly closed slit or may form a sealingly closed slit upon piercing of the stub.

[0049] In particular, the slit in the stub is closed by exerting a radial force onto the side surfaces of the stub. Such kind of force may be for example applied onto the stub by means of a plunger comprising a plug shaped at least substantially complementary to the stub. In this regard, the stub may be configured to receive the plug of the plunger. That is, the stub may form an engagement means of the piston configured to engage with a complementary engagement means of the plunger, the engagement means of the plunger being formed by the plug.

[0050] The plug of the plunger, when connected to the piston, squeezes the stub radially together, in particular towards the longitudinal axis of the piston, thereby sealingly closing the slit extending through the stub.

[0051] Closure of the slit may be for example achieved by forming a space provided radially inwardly of the plug slightly smaller than the circumferential dimension of the stub. By means of example, the space may be 1 to 10 %, preferably 2 to 8 % and in particular 5 % smaller than the circumferential dimension of the stub. It is noted that the stub and the membrane may be a single piece. However, it is also possible to form the stub and the membrane of separate pieces and / or separate materials.

[0052] The invention is also directed at a dispensing device, comprising a piston as described above, a cartridge and a plunger, the piston being accommodated in the cartridge and movable within the cartridge in direction of a longitudinal axis of the cartridge by means of the plunger.

[0053] Preferably, the cartridge of the dispensing device is filled with a material or configured to be filled with a material, in particular with the material being selected from one of a filling material, a mold material, a bleaching material or a multi-component material, such as a two-component adhesive comprising a filler material and a hardener.

[0054] The invention also covers a method of filling and venting a dispensing device. The method comprises the steps of: filling a material into a reception space formed inside a cartridge of the dispensing device, penetrating a membrane arranged in a piston with a tubular hollow needle, the piston being received in the cartridge, venting the reception space by means of the tubular hollow needle extending through the membrane, and retracting the needle from the piston after venting of the reception space is finished, such that a slit formed in the membrane remains sealingly closed.

[0055] In the following, exemplary embodiments and functions of the present disclosure are described herein in conjunction with the drawings, showing schematically:

[0056] Fig. 1 a perspective longitudinal-sectional view of a cartridge comprising a plunger and a piston according to a first embodiment; Fig. 2 the cartridge of Fig. 1 with the piston being penetrated by a needle ready for venting action;

[0057] Fig. 3 a longitudinal-sectional detail of Fig. 1;

[0058] Fig. 4 a longitudinal-sectional detail of Fig. 2;

[0059] Fig. 5 a perspective view of the piston according to the first embodiment;

[0060] Fig. 6. a longitudinal-sectional detail similar to Fig. 3 with a piston according to a second embodiment;

[0061] Fig. 7 a longitudinal-sectional detail similar to Fig. 4 with the piston according to the second embodiment;

[0062] Fig. 8 a perspective view of the piston according to the second embodiment;

[0063] Fig. 9 a longitudinal-sectional detail similar to Fig. 3 with a piston according to third embodiment;

[0064] Fig. 10 a perspective view of pistons according to the third embodiment respectively connected to plungers;

[0065] Fig. 11 a longitudinal-sectional detail similar to Fig. 3 with a piston according to a fourth embodiment;

[0066] Fig. 12 a perspective view of pistons according to the fourth embodiment respectively connected to plungers;

[0067] Fig. 13 a perspective front view of a piston according to a fifth embodiment;

[0068] Fig. 14 a perspective rear view of the piston of Fig. 13;

[0069] Fig. 15 a longitudinal sectional view along a first plane of section of the piston of Fig.

[0070] 13; and

[0071] Fig. 16 a longitudinal sectional view along a second plane of section perpendicular to the first plane of section of the piston of Fig. 15, the piston connected to a plunger.

[0072] In the following, a dispensing device 10 as well as its components are described with reference to the accompanying drawings. In this regard, a longitudinal section refers to a section along a longitudinal axis L, L', whereas a cross section refers to a direction perpendicular to the longitudinal axis L, L'. The longitudinal axis L may be defined in terms of a longitudinal axis of the dispensing device 10. However, the longitudinal axis L' may be also defined in terms of a longitudinal axis L' of components of the dispensing device 10.

[0073] The dispensing device 10 may be filled with a material or may be configured to be filled with a material. Preferably, the material is one selected of a filling material, a mold material, a bleaching material or a multi-component material, such as a two-component adhesive comprising a filler material and a hardener.

[0074] A typical dispensing device 10 is shown in Fig. 1.

[0075] The dispensing device 10 as shown in Fig. 1 comprises two cartridges 12 arranged parallel adjacent to each other and extending in a longitudinal direction defining a longitudinal axis L.

[0076] Furthermore, the dispensing device 10 further comprises two pistons 14 respectively accommodated inside the respective cartridges 12. The pistons 14 will be described later in greater detail with regard to Figs. 3 to 16.

[0077] Each piston 14 is moveable along the longitudinal axis L by means of a respective plunger 16. The plungers 16 may be separate parts to allow the plungers 16 to be separately moved or the plungers 16 may be connected to be commonly movable.

[0078] The cartridges 12 are respectively surrounded by tubular walls 18. Furthermore, the cartridges 12 are connected to each other and share a mutual wall section 20 arranged between the cartridges 12. However, the cartridges 12 may be also separate parts. It is noted that the dispensing device 10 may comprise only one cartridge 12 or more than two cartridges 12, such as for example three, four or more cartridges 12. In this regard it is further noted that the number of pistons 14 and plungers 18 may correspond to the number of cartridges 12.

[0079] Each of the cartridges 12 defines a reception space 22 configured to receive a material. The reception spaces 22 are respectively surrounded by the tubular walls 18. Furthermore, on a front side 24 of the dispensing device 10, the reception spaces 22 are respectively limited by a front wall 26, whereas the respective reception spaces 22 are closed by the pistons 14 inserted into the cartridges 12 from a rear side 28 of the dispensing device 10.

[0080] The front side 24 further comprises connection means 30 configured to connect the cartridges 12 with a dispensing outlet tip (not shown). The dispensing outlet tip may comprise a mixing element, in particular a static mixer, to mix the materials discharged from the cartridges 12.

[0081] The connection means 30 as shown in Fig. 1 is configured as a channel 32 which extends perpendicular to the longitudinal axis L of the dispensing device 10 and which is open to a lateral side of the dispensing device 10 such that the dispensing outlet tip can be easily connected by laterally sliding the dispensing outlet tip into the channel 32. However, the dispensing outlet tip can be also connected to the cartridges 12 by other connection means 30, such as for example bayonet-type connection means.

[0082] In order to discharge material out of the cartridges 12 through the front wall 26, the front wall 26 comprises respective outlet orifices 34 of which only one is shown in the longitudinal-sectional drawings of Figs. 1 and 2 due to an asymmetric structure of the dispensing device 10. The outlet orifices 34 are in fluid communication with the cartridges 12 and may be in fluid communication with inlet orifices of the dispensing outlet tip when the dispensing outlet tip is connected to the cartridges 12.

[0083] Now turning to Figs. 3 to 5 a piston 14 according to a first embodiment will be now described. The piston 14 comprises a first end 36 and a second end 38. Furthermore, the piston 14 axially extends between the first end 36 and the second end 38 in a longitudinal direction defining a longitudinal axis L' of the piston 14.

[0084] In an assembled state of the dispensing device 10, i.e. when the piston 14 is received in the cartridge 12, the longitudinal axis L of the cartridge 12 and the longitudinal axis L' of the piston 14 are aligned parallel to each other.

[0085] When the piston 14 is received in the cartridge 12, the first end 36 of the piston 14 faces towards the front side 24 of the dispensing device 10, in particular the front wall 26 of the cartridge 12, and may be therefore also referred to as a front end 36 of the piston 14.

[0086] The second end 38 of the piston 14 is arranged opposite to the first end 36 and faces towards the rear side 28 of the dispensing device 10 and may therefore be referred to as rear end 38 of the piston 14.

[0087] Furthermore, as can be best seen from Fig. 5, the piston 14 is D-shaped, in particular such that the cross-section of the piston 14 is D-shaped, and comprises a flat outer side surface 40 and a bowed out outer side surface 42. However, the piston 14 may also have other cross-sectional shapes, like a circular cross-sectional shape.

[0088] In order to engage the piston 14 with the plunger 16, the piston 14 comprises engagement means 44 that are configured to interact with corresponding engagement means 46 formed at the plunger 16.

[0089] As can be seen from Fig. 3, the engagement means 44, 46 are formed as snap-fit engagement means, but may be also formed as frictional engagement means, for example.

[0090] In particular, the engagement means 44 of the piston 14 is formed as a radially outwardly protruding hook 48 and a pocket 50 present on an outer side surface 52 of the piston 14. In this embodiment, the engagement means 44 are formed at the bowed out outer side surface 42 of the piston 14. The engagement means 44 may also be formed on the flat outer side surface 40 of the piston 14 and / or on a section of the outer side surface 52 formed between the bowed out outer side surface 42 and the flat outer side surface 40.

[0091] The engagement means 46 of the plunger 16 is formed as radially inwardly projecting hook 54 and a pocket 56 correspondingly shaped to the pocket 50 and the hook 48 formed at the piston 14.

[0092] In the engaged state the hook 48 of the piston 14 is received in the pocket 56 of the plunger 16, whereas the hook 54 of the plunger 16 is received in the pocket 50 of the piston.

[0093] The engagement between the piston 14 and the plunger 16 allows for a rearward retraction of the piston 14, in particular out of the cartridge 12 to allow for a re-filling of the cartridge 12.

[0094] The piston 14 further comprises a sealing lip 58 that circumferentially surrounds the outer side surface 52 of the piston 14.

[0095] The sealing lip 58 is formed at the first end 36 of the piston 14 and sea lingly bears against an inner side wall 60 of the cartridge 12 to allow for an optimum sealing between the piston 14 and the inner side wall 60 of the cartridge 12. In this context, it is noted that the outer circumference of the sealing lip 58 is larger than an inner circumference of inner wall 60 of the cartridge 12. In the drawings, this is schematically shown as a partial overlap between the sealing lip 58 and the inner side wall 60 of the cartridge 12, i.e. it is shown as if the sealing lip 58 extends into the side wall 60. However, when the piston 14 is assembled to the cartridge 12, the sealing lip 58 does not overlap the inner side wall 60, but rather bears against a surface of the inner side wall 60. Furthermore, in order to prevent unwanted tilting of the piston 14 during its movement along the longitudinal axis L of the cartridge 12, the piston 14 further comprises a guidance lip 62 at the outer side surface 52 of the piston 14.

[0096] The guidance lip 62 is axially separated from the sealing lip 58 along the longitudinal axis L' of the piston 14.

[0097] Furthermore, for guiding purposes, it is sufficient that the guidance lip 62 has an outer circumference that has about the same size as the inner circumference of the inner side wall 60 of the cartridge 12. Therefore, the outer circumference of the guidance lip 62 is smaller than the outer circumference of the sealing lip 58.

[0098] As can be seen best from Fig. 3, the piston 14 comprises a membrane 64 arranged in a passage 66 extending along the longitudinal axis L' of the piston 14 between the first end 36 and the second end 38 of the piston 14. In particular, a first portion 68 of the passage 66 extends between the first end 36 and the membrane 64, whereas a second portion 70 of the passage 66 extends between the second end 38 and the membrane 64.

[0099] For the purpose of venting the reception space 22, the membrane 64 is pierceable by means of a tubular hollow needle 72 of an irrigation or non-coring needle type, as can be seen for example from Fig. 4. The reception space 22 can then be vented by means of a venting path formed by the tubular hollow needle 72 extending through the piston 14, as will be described later.

[0100] After retraction of the needle 72 from the pierced membrane 64, a sealingly closed slit 74 remains in the membrane 64, as will be also described in detail later.

[0101] In the piston 14 of the first embodiment, the membrane 64 is formed at the same axial height as the guidance lip 62 in direction of the longitudinal axis L' of the piston 14. That is, the first portion 68 of the passage 66 and the second portion 70 of the passage 66 have about the same length in direction of the longitudinal axis L' of the piston 14. However, the membrane 64 may be also formed at another position, for example at the substantially same axial height as the sealing lip 58, as shown for example in Figs. 6 and 8 with regard to the second embodiment of the piston 14. The first portion 68 of the passage 66 is therefore shorter than the second portion 70 of the passage 66.

[0102] The first portion 68 of the passage 66 and the second portion 70 of the passage 66 each taper towards the membrane 64 in form of a hollow truncated cone. In particular, the first portion 68 forms a first tapering portion 76 that has the shape of a first hollow truncated cone 76 and the second portion 70 forms a second tapering portion 78 that has the shape of a second hollow truncated cone 78 (Figs. 3 and 4). However, the first portion 68 of the passage 66 and the second portion 70 of the passage 66 may have other tapering shapes, such as for example a hollow pyramidical shape.

[0103] As can be best seen from Figs. 3 and 4, the opening angle of the second hollow truncated cone 78 is larger than the opening angle of the first hollow truncated cone 76. This allows for a sufficient guidance of the needle 72 at the second hollow truncated cone 78, whereas the dead volume is reduced at the first hollow truncated cone 76. However, the first and second hollow truncated cones 76, 78 may have at least substantially the same opening angle. Furthermore, the opening angle of the first hollow truncated cone 78 may be larger than the opening angle of the second hollow truncated cone 76, which facilitates filling of the reception space 22.

[0104] Due to the different opening angles of the hollow truncated cones 76, 78, respective openings of the passage 66 at the first end 36 and second end 38 of the piston 14 also have a different size. In detail, a size of a first opening 80 of the first portion 68 of the passage 66 at the first end 36 of the piston 14 is smaller than a size of a second opening 82 of the second portion 70 of the passage 66 at the second end 38 of the piston 14. To put it in different words, the second opening 82 of the second portion 70 of the passage 66 is larger than the first opening 80 of the first portion 68 of the passage 66. A larger size of the second opening 82 facilitates the guidance of the needle 72 into the passage 66. It is noted that the different sizes of the openings 80, 82 may also be achieved if the first and second portions 68, 70 of the passage 66 are formed for instance as cylindrically shaped passage portions with different diameters instead of hollow truncated cones.

[0105] The openings 80, 82 have an at least substantially circular cross-sectional shape. However, the openings 80, 82 may have other cross-sectional shapes, as becomes apparent from the pistons 14 according to the other embodiments.

[0106] Like the openings 80, 82, the first and second portions 68, 70 of the passage 66 may have a circular cross-sectional shape, with the cross-sectional size reducing towards the membrane 64 due to the tapering of the first and second portions 68, 70. In this context, it is noted that the first and second portions 68, 70 of the passage 66 generally may have the same cross-sectional shapes as their respective openings 80, 82.

[0107] Now turning to Figs. 6 to 8, a second embodiment is described. The piston 14 of the second embodiment basically corresponds to the piston 14 of the first embodiment, so that emphasize is put on the differences.

[0108] The main difference between the piston 14 of the second embodiment and the piston 14 of the first embodiment is that the piston 14 of the second embodiment has a membrane 64 which already comprises a sealingly closed slit 74 (Fig. 6 and 8). Such kind of slit 74 can be easily penetrated by any blunt tube or cannula type needle 72 (Fig. 7).

[0109] In this regard, it is noted the piston 14 according to the first embodiment may have a slit- ted membrane 64 as described herein with regard to the second embodiment. Furthermore, the piston 14 of the second embodiment may comprises an unslitted membrane 64 as described with regard to the first embodiment. As can be seen from a comparison of Figs. 3 and 6, a radial size of the membrane 64 of the piston 14 according to the second embodiment is larger than a radial size of the membrane 64 of the piston 14 according to the first embodiment. The radial size in this context refers to the size of the membrane 64 in a direction perpendicular to the longitudinal axis L' of the piston 14.

[0110] Furthermore, the membrane 64 of the piston 14 of the second embodiment is not arranged at the same axial height as the guidance lip 62, but rather at the sealing lip 58 close to the first opening 82 of the passage 66. In this context, the axial length of the first portion 68 of the passage 66 is smaller than the axial length of the second portion 70 of the passage 66, which reduces the dead volume at the first portion 68 of the passage 66.

[0111] Even further, only the second portion 70 of the passage 66 forms a hollow truncated cone 76, whereas the first portion 68 of the passage 66 has the shape of a hollow cylinder.

[0112] Again, the hollow truncated cone 76 serves as a guidance for the needle 72.

[0113] Yet another difference is that the engagement means 44 of the piston 14 and the engagement means 46 of the plunger 16 are formed as frictional engagement means. That is the piston 14 and the plunger 16 keep engaged by frictional forces acting between the piston 14 and the plunger 16. The frictional forces are sufficient to retract the piston towards the rear side 28 of the cartridge 12. However, the piston 14 may also engage with the plunger 16 in a manner as described with regard to the piston 14 of the first embodiment.

[0114] Furthermore, the openings 80, 82 have an oval cross-sectional shape instead of an at least substantially circular cross-sectional shape of the openings 80, 82 of the piston 14 according to the first embodiment.

[0115] Referring to Figs. 9 and 10 a third embodiment is described. The piston 14 of the third embodiment has a symmetrical longitudinal cross-sectional shape in form of an H, with the center dash of the H being formed by the membrane 64 (see Fig. 9).

[0116] The membrane 64 of this embodiment is unslitted. However, the membrane 64 may also comprise such kind of slit 74 as described with regard to the second embodiment.

[0117] Furthermore, the membrane 64 is arranged at the same axial height as the guidance lip 62.

[0118] The guidance lip 62 is axially arranged between two sealing lips 58, each present at the respective ends 36, 38 of the piston 14.

[0119] Furthermore, as can be also seen from Fig. 9 each of the first and second portions 68, 70 of the passage 66 symmetrically taper towards the membrane 64, i.e. the shape of the tapering first portion 68 and a shape of the tapering second portion 70 is substantially the same.

[0120] Furthermore, as can be seen from Fig. 10, the opening 80 of the first portion 68 of the passage 66 at the first end 36 of the piston 14 has a C-shaped cross-sectional shape. The same applies to the opening 82 of the second opening 82 of the second portion 70 of the passage 66 at the second end 38 of the piston 14. Furthermore, the C-shaped cross-section of the openings 80, 82 may continue in the first and second potions 68, 70 of the passage 66.

[0121] The piston 14 of the third embodiment is engaged with the plunger 16 by means of a protrusion 83 having substantially the same outer shape as the second portion 70 of the passage 66 (Fig. 9). In other words, the passage 66 forms the engagement means 44 configured to engage with the plunger 16, in particular with the protrusion 83 forming the engagement means 46 of the plunger 16. The protrusion 83 and the passage 66 may engage by press-fitting. A fourth embodiment is described with regard to Figs. 11 and 12.

[0122] The piston 14 of the fourth embodiment basically corresponds to piston 14 of the third embodiment but does not comprise a guidance lip 62. However, the sealing lips 58 allow for a safe guidance of the piston 14.

[0123] Furthermore, Fig. 11 shows another way of an engagement between the plunger 16 and the piston 14. The plunger 16 engages with the piston 14 by contacting the rear end 38 of the piston 14 with a front end 90 of the plunger 16 (Fig. 11).

[0124] The plunger 16 has at least substantially the same cross-sectional size as the inner side of the cartridge 12.

[0125] The following description applies to each piston 14 of the respective first to fourth embodiments.

[0126] The pistons 14 of the first to fourth embodiments are respectively formed by injection molding of an elastomeric material, such as a silicone or a rubber material.

[0127] The elastomeric material provides multiple benefits.

[0128] At first, the elastic material allows for the sealing lip 58 to be sealingly pressed against the inner side wall 60 of the cartridge 12.

[0129] Furthermore, as the needle 72 is retracted from the membrane 64, the spring-elastic force of elastomeric material closes the slit 74, thereby forming a sealingly closed slit 74.

[0130] Even further, as the needle 72 penetrates the membrane 64, the force of the elastomeric material allows for a sealingly engagement of the membrane 64 with the needle 72. In the following, a method for filling material into the reception space 22 of the cartridges

[0131] 12 will be described.

[0132] At first, a material is filled into the reception space 22 which is then closed by inserting the piston 14 into the cartridge 12 from the rear side 28.

[0133] Next, the tubular hollow needle 72 is inserted into the cartridge 12 from the rear side 28. As can be seen from Figs. 2, 4 and 7, the needle 72 formed at a setting tool 85 (Figs. 2, 4 and 7). The needle 72 is supported by a support sleeve 84 of the setting tool 85, the support sleeve 84 having an outer circumference which is about the same size as the inner circumference of the cartridge 12. This allows for the sleeve 84 of the setting tool 85 to be inserted into the cartridge 12 to set the piston 14 into position inside the cartridge 12. Furthermore, the sleeve 84 allows for a safe guidance of the needle 72 to the membrane 64.

[0134] At the membrane 64, further advancing of the needle 72 towards the front side 24 of the cartridge 12 either pierces the yet unslitted membrane 64 to form the slit 74 by means of an irrigation needle type (Figs. 2 to 4), or a blunt tube or cannula type needle 72 penetrates the slit 74 already formed in the membrane 64 (Figs. 6 and 7). It is noted that instead of an irrigation needle a non-coring needle could be used to pierce the membrane 64 for the formation of the slit 74.

[0135] Further advance of the needle 72 towards the front side 24 of the cartridge 12 enables the tip 86 of the needle 72 to pass beyond the membrane 64.

[0136] After a tip 86 of the needle 72 has passed the membrane 64, a venting path is formed by the needle 72 thus connecting the reception space 22 to the outside at the rear side 28 of the dispensing device 10. Gasses trapped inside the reception space 22 of cartridge 12 can be then transferred out of the reception space 22 to the outside by means of the venting path formed by the needle 72. It is noted, that the membrane 64 may be penetrated by the needle 72, when the piston 14 is already inserted into the cartridge 12. In this regard, the material filled into the cartridge 12 prevents the piston 14 from being moved by the setting tool 85 towards the front side 24 of the dispensing device 10, in particular due to the incompressibility of the material. However, the piston 14 may be attached to the setting tool 85 prior to insertion into the cartridge 12. The membrane 64 is then penetrated by the needle 72 as the piston 14 is attached to the setting tool 85.

[0137] Now turning to Figs. 13 to 16, a fifth embodiment of a piston 14 is described in the following.

[0138] The piston 14 of the fifth embodiment is similar to the piston 14 of the fourth embodiment.

[0139] In particular, like the piston 14 of the fourth embodiment, the piston 14 of the fifth embodiment comprises two sealing lips 58. Each sealing lip 58 is formed at respective ends 36, 38 of the piston 14. That is, one sealing lip 58 is formed at the front end 36 and the other sealing lip 58 is formed at the rear end 38 of the piston 14.

[0140] It is noted, that the piston 14 may comprise less or more than two sealing lips 58, like only one or three, four or more sealing lips 58. Furthermore, the piston 14 of the fifth embodiment may also comprise at least one guidance lip 62 as is described for example with regard to the first to third embodiments. In particular, the piston 14 of the fifth embodiment may comprise at least one sealing lip 58 as well as at least one guidance lip 62, preferably in a manner as described above.

[0141] Furthermore, as can be seen from Figs. 13 and 14, the outer circumference of the piston 14 of the fifth embodiment is also D-shaped. However, depending on the application, the piston 14 may also have other outer shapes, such as a circular round or a polygonal outer shape. In this regard, it is noted that the passage 66 extending through the piston 14 of the fifth embodiment basically reflects the same shape as the outer circumferential shape of the piston 14. That is, the passage 66 is also D-shaped in cross-section. However, the passage 66 may also have another cross-sectional shape, like for example a circular or a polygonal cross-sectional shape.

[0142] Furthermore, like in the pistons 14 of the other embodiments, a membrane 64 is arranged inside the passage 66, thereby separating the passage 66 into a first portion 68 and a second portion 70 of the passage 66.

[0143] As can be seen from the cross-sectional views in Figs. 15 and 16, the first portion 68 tapers from the front opening 80 of the passage 66 towards the membrane 64. Likewise, the second portion 70 tapers from the rear opening 82 of the passage 66 towards the membrane 64.

[0144] However, at least one of the first portion 68 and the second portion 70 may not be tapering. For example, the first portion 68 and / or the second portion 70 may be straight with the inner side walls surrounding the respective portion 68, 70 of the passage 66 extending at least substantially parallel to the longitudinal axis L' of the piston 14.

[0145] As can be seen from the perspective front view depicted in Fig. 13 as well as the longitudinal sectional views in Figs. 15 and 16, the membrane 64 of the piston 14 according to the fifth embodiment forms a bulge 92.

[0146] The bulge 92 is curved outwardly, i.e. convex, and extends into the first portion 68 of the passage 66. In particular, the bulge 92 faces towards the front end 36 of the piston 14.

[0147] As can be best seen from Figs. 15 and 16, the bulge 92 slightly protrudes in axial direction beyond the end of the piston's side wall, i.e. the part of the side wall comprising the front sealing lip 58. However, the bulge 92 may also be retracted into the passage 66, i.e. the bulge 92 does not axially protrude beyond the piston's side wall. Furthermore, the bulge 92 and the end of the piston's side wall may have at least substantially the same axial height, in particular such that the tip of the bulge 92 and the side wall together form the axial front end 36 of the piston 14.

[0148] The bulge 92 may comprise a sealingly closed slit 74 or may form a sealingly closed slit 74 upon piercing of the membrane 64 and its bulge 92. In the embodiment shown in Figs. 13 to 16 the piston 14 has no pre-formed slit 74. That is the slit 74 needs to be formed upon piercing of the membrane 64 and the bulge 92.

[0149] The particular shape of the bulge 92 allows for sealingly closing of the slit 74. In detail, the convex shape of the bulge 92 centers a force exerted by a material stored in the reception space 22 towards the center of the bulge's curvature as the piston 14 is pushed forwards towards the front side 24 of the cartridge 12. That is, the force acting on the rounded surface of the bulge 92 is centered towards the center of curvature of the bulge 92 and the slit 74 in the bulge 92 is squeezed together, thereby sealingy closing the slit 74. In Figs. 15 and 16 the center of curvature of the bulge 92 is schematically depicted as center point C.

[0150] The membrane 64 of the piston 14 of the fifth embodiment further forms a stub 94.

[0151] The stub 94 axially extends into the second portion 70 of the passage 66 towards the rear end 38 of the piston 14.

[0152] As can be seen from Figs. 15 and 16, the bulge 92 and the stub 94 face towards opposite directions.

[0153] As can be further seen from Fig. 15, the stub 94 is retracted with regard to the rear end 38 of the piston 14. However, the stub 94 may also project out of the second portion 70 of the passage 66, thereby forming the rear end 38 of the piston 14. Even further, the axial end of the stub 94 and the rear end of the piston's side wall may lie at least substantially flush. The stub 94 tapers towards the rear end 38 of the piston 14. However, the stub 94 may be also straight with side walls of the stub 94 at least substantially extending parallel to the longitudinal axis L' of the piston 14.

[0154] The stub 94 may comprise a sealingly closed slit 74 or may form a sealingly closed slit 74 upon piercing of the membrane 64 and its stub 94. In the embodiment shown in Figs. 13 to 16 the piston 14 has no pre-formed slit 74. That is the slit 74 needs to be formed upon piercing of the membrane 64 and its stub 94.

[0155] In this connection it is noted that a pre-formed slit 74 may entirely extend through the membrane 64 and the stub 94 as well as the bulge 92 formed on the membrane 64. However, the pre-formed slit 74 may only extend partially through at least one of the membrane 64, the bulge 92 and the stub 94, such that the partially extending slit 74 needs to be further pierced to form a slit 74 entirely extending through the membrane 64, the bulge 92 and the stub 94. However, none of the membrane 64, the bulge 92 and the stub 94 may comprise a pre-formed slit 74. That is, the slit 74 needs to be formed by piercing the membrane 64, the bulge 92 and the stub 94.

[0156] The stub 94 may comprise a recess (not shown) to facilitate the piercing of the membrane 64 and / or the alignment of the needle towards the membrane 64. The recess may be formed at a surface of the stub 94 facing towards the rear end 38 of the piston 14. Furthermore, the recess may be aligned with the longitudinal axis L' of the piston 14, such that the needle for piercing is centered.

[0157] The stub 94 is radially off-set to the inner side wall surrounding the passage 66. In this connection, a groove 96 is formed between the stub 94 and the inner side wall.

[0158] In the present embodiment, the groove 96 is formed as a closed loop. However, the groove 96 may only extend partially around the stub 94. The groove 96 and the stub 94 allow for the reception of a plunger 16 comprising an at least substantially complementary shaped plug 98 at the front end of the plunger 16. In other words, the stub 94 forms an engagement means 44 of the piston 14 and the plug 98 forms an engagement means 46 of the plunger 16. In this regard, it is noted that the piston 14 of the fifth embodiment may additionally or alternatively comprise an engagement means 46 as described in the context of the first to fourth embodiments. It is understood that the plunger 16 is then configured in a complementary manner. In particular, the piston 14 of the fifth embodiment may comprise the hook 48 / pocket 52 engagement means 44 of the first embodiment.

[0159] The plug 98 of the plunger 16, when connected to the piston 14, radially squeezes the stub 94 together, in particular towards the longitudinal axis L' of the piston 14. This enables to sea lingly close the slit 74 extending through the stub 94.

[0160] By means of example, closure of the slit 74 in the stub 94 may be achieved by forming a space 100 formed radially inwardly of the plug 98 slightly smaller than the circumferential dimension of the stub 94. The space 100 may be 1 to 10 %, preferably 2 to 8 % and in particular 5 % smaller than the circumferential dimension of the stub 94.

[0161] It is noted that the piston 14 of the fifth embodiment may be also formed in a manner that the piston 14 comprises only either one of the bulge 92 and the stub 94. The respective, portions 68, 70 of the passage 66 are then free of the bulge 92 or stub 94.

[0162] Furthermore, the portion 68, 70 of the passage 66 not comprising the bulge 92 or the stub 94 may be formed in a manner as described with regard to the first to fourth embodiments. List of reference signs

[0163] 10 dispensing device

[0164] 12 cartridge

[0165] 14 piston

[0166] 16 plunger

[0167] 18 wall

[0168] 20 wall section

[0169] 22 reception space

[0170] 24 front side

[0171] 26 front wall

[0172] 28 rear side

[0173] 30 connection means

[0174] 32 channel

[0175] 34 outlet orifice

[0176] 36 first end, front end

[0177] 38 second end, rear end

[0178] 40 flat outer side surface

[0179] 42 bowed out outer side surface

[0180] 44 engagement means

[0181] 46 engagement means

[0182] 48 hook

[0183] 50 pocket

[0184] 52 outer side surface

[0185] 54 hook

[0186] 56 pocket

[0187] 58 sealing lip

[0188] 60 inner side wall

[0189] 62 guidance lip

[0190] 64 membrane

[0191] 66 passage 68 first portion of 66

[0192] 70 second portion of 66

[0193] 72 tubular hollow needle

[0194] 74 sealingly closed slit

[0195] 76 tapering portion, hollow truncated cone

[0196] 78 tapering portion, hollow truncated cone

[0197] 80 opening of 66

[0198] 82 opening of 66

[0199] 83 protrusion

[0200] 84 support sleeve

[0201] 85 setting tool

[0202] 86 tip

[0203] 88 opening

[0204] 90 front end

[0205] 92 bulge

[0206] 94 stub

[0207] 96 groove

[0208] 98 plug

[0209] 100 space

[0210] L longitudinal axis

[0211] L' longitudinal axis

[0212] C center point

Claims

Claims1. A piston (14) for a dispensing device (10), the piston (14) comprising a first end (36) and a second end (38) opposite to the first end along a longitudinal axis (L') of the piston (14), and a membrane (64) arranged between the first end (36) and the second end (38) along the longitudinal axis (L'), the membrane (64) comprising a sealingly closed slit (74) or forming a sealingly closed slit (74) upon piercing of the membrane (64).

2. The piston (14) according to claim 1, wherein the membrane (64) is arranged in a passage (66) extending along the longitudinal axis ( L') of the piston (14) between the first end (36) and the second end (38) of the piston (14), with a first portion (68) of the passage (66) extending between the first end (36) and the membrane (64) and a second portion (70) of the passage (66) extending between the second end (38) and the membrane (64).

3. The piston (14) according to claim 2, wherein a size of a first opening (80) of the passage (66) formed at the first end (36) and a size of a second opening (82) of the passage (66) formed at the second end (38) is substantially the same or different.

4. The piston (14) according to one of the claims 2 or 3, wherein a length of the first portion (68) in the direction of the longitudinal axis (!_') and a length of the second portion (70) in the direction of the longitudinal axis (L') is substantially the same or different.

5. The piston (14) according to one of the claims 2 to 4, wherein at least one of the first portion (68) and the second portion (70) tapers towards the membrane (64).

6. The piston (14) according to claim 5, wherein both the first portion (68) and the second portion (70) respectively taper towards the membrane (64), wherein a shape of the tapering first portion (68) and a shape of the tapering second portion (70) is substantially the same or different.

7. The piston (14) according to one of the previous claims, wherein at least one sealing lip (58) is formed on an outer side surface (52) of the piston (14), in particular on an outer side surface (52) of at least one of the first end (36) and the second end (38).

8. The piston (14) according to one of the previous claims, wherein a guidance lip (62) is formed on an outer side surface (52) of the piston (14).

9. The piston (14) according to one of the claims 7 or 8, wherein the membrane (64) is formed at an axial height of the sealing lip (58) or the guidance lip (62).

10. The piston (14) according to one of the previous claims, wherein the piston (14) comprises an engagement means (44) configured to engage the piston (14) with a plunger (16).

11. The piston (14) according to one of the claims 2 to 10, wherein the piston (14) is configured to engage with the plunger (16) on an outer side surface (52) of the piston (14) and / or at the passage (66).

12. The piston (14) according to one of the previous claims, wherein the piston (14) is formed at least in parts of an elastomeric material, such as a silicone or a rubber material.

13. The piston (14) according to one of the previous claims, wherein the membrane (64) forms a bulge (92), in particular a convex bulge (92).

14. The piston (14) according to claim 13, wherein the bulge (92) faces towards the first end (36) of the piston (14).

15. The piston (14) according to one of the previous claims, wherein the membrane (64) forms a stub (94).

16. The piston (14) according to claim 15, wherein the stub (94) axially extends towards the second end (38) of the piston (14).

17. A dispensing device (10), comprising a piston (14) according to one of the previous claims, a cartridge (12) and a plunger (16), the piston (14) being accommodated in the cartridge (12) and movable within the cartridge (12) in direction of a longitudinal axis (L) of the cartridge (12) by means of the plunger (16).

18. A dispensing device (10) according to claim 17, wherein the cartridge (12) is filled with a material or configured to be filled with a material.

19. A method of filling and venting the dispensing device (10) according to claim 17 or claim 18, the method comprising the steps of: filling a material into a reception space (22) formed inside a cartridge (12) of the dispensing device (10), penetrating a membrane (64) arranged in a piston (14), in particular according to at least one of the claims 1 to 13, with a tubular hollow needle (72), the piston being received in the cartridge (12), venting the reception space (22) by means of the tubular hollow needle (72) extending through the membrane (64), and retracting the needle (72) from the piston (14) after venting of the reception space (22) is finished, such that a slit (74) formed in the membrane (64) remains sealingly closed.

Images