EP1799357A1

EP1799357A1 - Metering device

Info

Publication number: EP1799357A1
Application number: EP05804435A
Authority: EP
Inventors: Stefan Ritsche
Original assignee: Erich Pfeiffer GmbH; Ing Erich Pfeiffer GmbH
Current assignee: Aptar Radolfzell GmbH
Priority date: 2004-10-13
Filing date: 2005-10-13
Publication date: 2007-06-27
Anticipated expiration: 2025-10-13
Also published as: US20070262090A1; ATE475484T1; JP2008515630A; DE502005010015D1; DE102004050679A1; EP1799357B1; JP5069563B2; WO2006040146A1

Abstract

The invention relates to a known metering device ( 1 ) for at least one medium. Said device comprises a pump unit ( 2 ), which co-operates with a medium reservoir for the delivery of said medium and an aeration device that is allocated to the medium reservoir and/or the pump unit. The aeration device comprises an aeration channel ( 16, 18, 26, 27 ), to which a filter membrane ( 20 ) is allocated. According to the invention, the filter membrane is configured for a reduced diffusion rate. The device can be used for metering pharmaceutical products.

Description

Description dosing device

The invention relates to a metering device for at least one medium, with a pumping device, which is in operative connection for a medium discharge with a Mediumspei¬ cher, as well as with a medium storage and / or the pumping means associated ventilation device having a Belüf¬ tungskanal, which a filter membrane assigned.

From EP 1 295 644 A1 a metering device with a ventilation device is known. The metering device is used for discharging a medium from a medium reservoir by means of a pumping device in a plurality of, spaced apart from each other or directly successive discharge strokes. For this purpose, the pump device communicates with the medium reservoir in a communicating operative connection, which allows medium to be discharged from the medium reservoir into an environment of the metering device. The ventilation device according to EP 1 295 644 A1 has a ventilation duct to which a filter device is assigned as a barrier for contaminating constituents of the outside air with respect to the medium enclosed in the medium reservoir. Such a filter device is intended to make it possible to dispense with the preservation of the medium, since the air entering the medium reservoir when the pressure is equalized between the environment and the medium reservoir is to be kept free of contaminating constituents by the filter device. This is of particular importance for medical substances. Through the filter device a continuous exchange of gas molecules between the medium enclosed in the medium container and the environment is possible, so that the desired pressure compensation can take place while leakage of the medium into the aeration device and penetration of contaminating substances into the medium reservoir the filter device is prevented verhin¬. The object underlying the invention is to provide a Dosiervorrich¬ device, which ensures an improved long-term stability of the enclosed medium and a high dosing accuracy in terms of Wirkstoffkonzentra¬ tion of the medium to be discharged.

This object is achieved by a metering device of the type mentioned, in which the filter membrane is designed for a reduced diffusion rate. This results in a reduced exchange of gas molecules between the volume enclosed in the medium reservoir and the environment compared with known metering devices. The diffusion rate is determined on the basis of the volume flow of gas molecules, which passes through the filter membrane within a time interval at a given pressure ratio between the internal pressure in the medium reservoir and the external pressure in the environment. A low diffusion rate expresses that with a high pressure difference between the internal pressure in the medium reservoir and the external pressure prevailing in the environment, only a small volume flow of gas molecules passes through the filter membrane. In the case of a filter membrane which has a reduced diffusion rate, evaporated medium components are less likely to escape from the medium container, and at a negative pressure in the medium reservoir, air molecules from the environment are less likely to enter the medium reservoir. An improvement in the long-term stability of the medium enclosed in the medium container is achieved, on the one hand, by a lower loss of easily detachable medium constituents, which otherwise could escape from the medium reservoir as readily volatile constituents. Because of the reduced diffusion rate of the filter membrane, the vaporized, easily dissolvable medium components are retained in the medium reservoir over a relatively long period of time and also at a higher pressure difference between internal pressure and external pressure. As a result, a change in the concentration of the medium can be substantially prevented or at least reduced. Ande¬ hand, is caused by the reduced diffusion rate, a time-delayed influx of air from the environment at a negative pressure in the medium storage. This ensures that, for example, after a discharge process by a negative pressure in the medium storage occurs, first pass in the medium dissolved gas components in the gas phase and thus cause degradation of the Un terdrucks before air flows from the environment. Therefore, a filter membrane with a reduced diffusion rate over a long period of time can prevent or at least substantially prevent a change in the concentration of the medium. This influence of the filter membrane on the enclosed medium is an essential criterion in an assessment of the suitability of a metering device for the storage and discharge of medi¬ zinischer substances. By changing the concentration, there is a risk that the medium to be discharged from the metering device contains an increasing amount of active substance while the delivery volume remains constant, as a result of which requirements for metering accuracy for the active substance can no longer be met, even if the discharged medium volume remains exactly the same. In order to determine such a behavior of the metering device and of the medium accommodated therein, stability tests are carried out in connection with the respectively provided metering device, in particular in the case of media which are used as medical active substances and in which precise metering is necessary. The change in the concentration of the medium (can of content uniformity) over a longer period of time and under changing climatic external conditions is considered and assessed on the basis of given limit values. In a simple stability test, it is examined to what extent a weight decrease of the metering device takes place over a longer period of time. Thus, starting from the original active substance concentration, it is possible to conclude an altered active substance concentration in the medium. The reduced diffusion rate ensures that, on the one hand, the pressure compensation required for correct medium discharge can take place and, on the other hand, the long-term stability of the enclosed medium is ensured. The proper solution is particularly suitable for the dosing of pharmaceutical products. Suitable media are liquid and solid substances and mixtures thereof, which can be administered in particular as medicaments. Depending on the medium to be discharged, low to high requirements are imposed on the dosage of - A -

the pumping device to be discharged amount of medium and the concentration of optionally medically active ingredients contained therein. The pump device can be designed, for example, for an atomized medium discharge or for individual jets of the medium. The ventilation device provided on the metering device serves to equalize the pressure between an internal pressure of a volume enclosed in the medium reservoir and an external pressure prevailing in the vicinity of the medium reservoir. A pressure difference can result from the discharge of medium from the medium reservoir or else from thermally induced expansion or shrinkage processes of the medium (s) enclosed in the medium reservoir. However, pressure differences are generally undesirable in such metering devices, since they can have a negative influence on the metering accuracy of the medium to be discharged. Therefore, a pressure compensation between the Innendmck and the external pressure is possible by means of the Be¬ ventilation device, wherein gas from the environment can flow into the medium storage or gaseous or possibly liquid or solid-like components of the medium can escape from the medium storage. As a result, the pressure compensation and thus the desired high metering accuracy of the metering device are ensured with regard to the medium volume to be discharged.

In an embodiment of the invention, the filter membrane has a compared to be¬ known filter membranes reduced effective cross-section. The effective cross section is the product of the number of pores provided in the filter membrane and the mean free cross section of these pores. Filter membranes are in particular designed as stretched or perforated plastic films or as sintered materials, but also as metal foils and, depending on the selected production method, can be produced in a wide range with regard to the number of pores and the free cross sections of the pores. The pores or channels formed in the plastic film or in the sintered material each have a free cross-section which can be determined on the basis of the maximum molecular size which can pass through the channel. Of the Effective cross-section is directly related to the diffusion rate of the filter membrane. A large number of channels or pores and a large free cross section of the individual channels or pores results in a large effective cross section and allows a high diffusion rate, ie even at a low pressure difference, a large number of molecules can pass through the filter membrane. According to the invention, the effective cross section is reduced compared to known filter membranes, ie the product of the number of pores and the average free cross section of the pores is less than in conventional membranes.

In a further embodiment of the invention, the reduced active cross-section of the filter membrane is realized by a comparison with known filter membranes reduced effective area. In this way, a reduction of the effective cross section is achieved in a particularly advantageous manner. The effective area of the filter membrane is the surface area of the membrane penetrated by pores, which is available for passage of gas molecules. On the effective surface, the pores are arranged, which determine the effective cross-section of the filter membrane.

In a further embodiment of the invention, the active surface of the filter membrane is limited by a Strömungsleitgeometrie, which is at least partially ko¬ formed nisch. As a result, in a particularly simple manner, in the case of a given filter membrane which, for example, has over its entire surface an essentially constant number of pores per surface section, influence is exerted on the effective area and thus on the effective cross section. The Strömungsleitgeometrie on the one hand closes the excess pores, which should not be available for passage of gas molecules available and on the other hand serves to bundle the hin¬ through the filter membrane hin¬ passing gas flow to the predeterminable region of the filter membrane. In addition, the flow-guiding geometry can be used to grasp and stabilize the filter membrane mechanically, in particular in a form-fitting manner. The flow-guiding geometry can form a particularly advantageous inflow and / or outflow of the at least partially conical design Gas molecules cause the filter membrane, since a substantially Verwelungsfreiefreie guidance of the gas flow through the conical contour can wer¬ achieved.

In a further embodiment of the invention, the effective area of the filter membrane is less than 1, 4 mm ² , preferably less than 0.6 mm ² , more preferably less than 0.2 mm ² . This achieves a reduction of the effective area and the associated diffusion rate with respect to a known filter membrane by at least about 15%, preferably by about 60%, particularly preferably by about 85%.

In a further embodiment of the invention, a mean free cross section of pores in the filter membrane is smaller than in known filter membranes for the reduced effective cross section. This ensures that the size of the gas molecules that can pass through the filter membrane is reduced. An escape of vaporized medium components from the medium reservoir is thereby made more difficult, as is the diffusion rate reduced because not all gas molecules contained in the ambient air can pass through the filter membrane.

In a further embodiment of the invention, a reduced number of pores over a known filter membrane is provided for a reduced effective cross section. As a result, the product of free pore cross section and the number of pores is reduced in a simple manner and thus the desired reduction in the diffusion rate is achieved. Depending on the production method of the filter membrane, a reduction in the pore number is achieved in particular by introducing a small number of pores by means of a material-removing process for a plastic film or by selecting a larger particle size in conjunction with a sintering process at higher pressure and / or or higher temperature for a sintered material. In a further embodiment of the invention, the filter membrane has a mean pore number less than 1 million pores per mm ² , preferably less than 600,000 pores per mm ² , more preferably less than 300,000 pores per mm ² . A simple influence on the number of pores can be taken, for example, in a material-removing method in which the pores are introduced into a plastic film by means of high-energy electromagnetic radiation.

In a further refinement of the invention, the filter membrane is provided on a sealing device arranged in the ventilation duct, in particular between the fluid reservoir and the pumping device. Thus, the filter membrane can be easily integrated into the aeration device and does not require a separate support for stabilization and / or positioning. For a tight connection between the medium reservoir and the pump device, a sealing device is provided in known metering devices, which can be designed for example as an annular flat gasket. In particular, the filter membrane can be applied, in particular partially or completely, to at least one end face facing the medium reservoir or the pump device, in particular coated, on this flat gasket. For an advantageous separate production of Dichteinrich¬ device with applied filter membrane is possible. The installation of the sealing device can take place in the same way as in the case of known metering devices and at the same time easily involves the positioning of the filter membrane.

In a further embodiment of the invention, the filter membrane is designed for a closure of a passage opening provided in the sealing device and assigned to the ventilation channel. Through a passage opening in the sealing device, which is assigned to the ventilation channel, a Durchtritts¬ cross-section is defined exactly, can flow through the gas molecules from the medium storage in the environment or in the reverse direction in the media storage. This passage cross section is closed by the filter membrane. so that a diffusion rate can be exactly specified, which results from the passage cross section and the associated effective area of the filter membrane and from the resulting effective cross section of the filter membrane.

In a further embodiment of the invention, the filter membrane ange¬ in the region of a ventilation opening of the medium reservoir and / or the pumping device, in particular laminated. As a result, the filter membrane can already be applied during the production of the medium reservoir and is supported by a wall section of the medium reservoir, as a result of which a particularly compact design of the filter device can be realized. The filter membrane is preferably applied to the end of a ventilation path on a front or outer surface of a section of the medium reservoir or of a part of the pump device, in particular welded or laminated thereto.

In a further embodiment of the invention, the filter device is designed as a discrete filter cartridge. As a result, the filter direction can be produced independently of the pump device or the medium dispenser and, if necessary, checked. In addition, the filter device can be provided as a mass product for a large number of different metering devices.

The object on which the invention is based is also achieved by a metering device of the type mentioned at the beginning, in which the ventilation channel is at least partially designed as a capillary channel which at least in sections has a ratio between an effective channel diameter and a capillary channel length which is less than 1/25. With such a design, the ventilation channel has a high flow resistance for liquids and gases and thus reduces undesirable Abströ¬ men of liquid components or gases, in particular of evaporated medium components, from the medium storage. In this way, without or with the filter device, an advantageous long-term stability of the medium reservoir can be achieved. be taken ensured medium. In a preferred embodiment of the invention, the ratio between the effective channel diameter and the capillary channel length is less than 1/50, in a particularly preferred embodiment less than 1/100. With a ratio of the effective channel diameter relative to the capillary channel length of 1/140, an evaporation rate which is determined at normal pressure of 1013 hPa, a temperature of 40 degrees Celsius and a relative humidity of 25 percent can be approximately a factor of 10 from about 0.05 g / week to 0.005 g / week.

In a further embodiment of the invention it is provided that the capillary channel is formed helically. Thus, a particularly compact design of the capillary channel can be realized. The capillary channel can be provided on an inner surface of a bore in a component and / or on an outer surface of a component. The compact design allows an integration of a capillary channel with a ratio of effective channel diameter and capillary channel length according to the invention, without thereby necessitating a structural enlargement of the dosing device equipped therewith.

In a further embodiment of the invention it is provided that the capillary channel is designed as a circumferential, helical groove between a conical outer surface and egg ner cover having a conical, adapted to the Konusaußenflä¬ surface recess. This allows an advantageous production of the capillary channel in the plastic injection molding method, since the cone-shaped geometry allows introduction of the helical groove of the capillary channel against a demoulding direction of the component provided therewith from a plastic injection mold, so that a simple design of the plastic injection mold can be ensured. The capillary channel can be introduced into the conical outer surface and / or into the conical recess of the cover; the advantageous method of production applies both to the outer surface of the cone and to the recess in the cover. In a further embodiment of the invention, it is provided that the capillary channel is formed between an outer surface of a cylinder arrangement and an inner surface of a slip-on sleeve, wherein a plurality of webs are provided on the outer surface of the cylinder arrangement and / or on the slip-on sleeve, which are substantially in the direction of a central longitudinal axis By the webs, which in particular each offset by 120 degrees on the cylinder assembly and / or can be provided on the slip-on, an oversize or interference fit between the cylinder assembly can be ausge¬ aligned and the sleeve are realized. As a result, a secure pressing of the slip-on sleeve onto the cylinder arrangement is made possible, without leading to an undesired constriction or deformation of the cylinder bore provided in the cylinder arrangement.

In a further embodiment of the invention, it is provided that the capillary channel is introduced in sections in at least one of the webs as a groove. Thus, the bridge has a double function as a spacer and as a capillary channel. The introduced in the web groove is closed by the opposing ange¬ arranged component, ie in a cylinder arrangement associated web through the slip-on sleeve or provided in the slip sleeve web through the cylinder assembly and thus forms the ge desired capillary channel. With an alignment of the web in the direction of the central longitudinal axis of the metering device, a simple production of the cylinder assembly and the plug-on sleeve in the plastic injection molding process can be realized.

In a further embodiment of the invention, it is provided that the capillary channel is formed from at least one annular section and at least one channel section, which is aligned at least substantially along the central longitudinal axis of the metering device. By the annular portion, which may be arranged circumferentially around the central longitudinal axis, which is arranged parallel to the central longitudinal axis channel portion is connected to the medium reservoir. The ring Section is part of the capillary channel and can be formed as the channel portion between the cylinder assembly and the sleeve. The ring section can be realized, in particular, by means of two projections spaced apart from one another between the cylinder arrangement and the slip-on sleeve, whereby a simple production of these components in the plastic injection molding process is made possible.

Further advantages and features of the invention will become apparent from the claims and from the following description of preferred Ausführungsbei¬ games, which are illustrated with reference to the drawings. Showing:

1 shows in a planar sectional view a metering device with a filter cartridge provided in the ventilation device,

2 shows in a planar sectional view a detail enlargement of the filter cartridge according to FIG. 1, FIG.

3 is a plan sectional view of a detail enlargement of a second embodiment of a filter cartridge,

Fig. 4 in a planar sectional view of a detail enlargement of a third embodiment of a filter cartridge, and

Fig. 5 in a planar sectional view of a metering device with a Flachdich¬ device with integrated filter device

6 is a planar sectional view of a metering device with a ventilation duct, to which a filter device and a capillary channel coupled thereto are assigned,

7 is a plan view of the metering device according to FIG. 6 with the piston arrangement removed, FIG. 8 is a sectional view of the metering device according to FIG. 6,

9 shows, in a planar sectional representation, a metering device with a ventilation duct, to which a filter device and a helically designed capillary channel coupled thereto are assigned.

The metering device 1 according to FIG. 1 essentially shows a pump device 2, which is provided for mounting on a medium reservoir (not shown). The pump device 2 has a schematically illustrated piston arrangement 3, which is accommodated in a cylinder arrangement 4, likewise shown schematically, and is provided for conveying a medium accommodated in the medium reservoir into an environment of the metering device 1. The cylinder arrangement 4 is accommodated in a substantially conically shaped applicator 5, at the tapered end of which an outlet opening 6 is provided, through which the medium pressurized by the pumping device 2 can be discharged into the environment in finely atomized form. To initiate a necessary for the discharge Rela¬ tivbewegung between the piston assembly 3 and the cylinder assembly 4, a handle 7 is provided, which is provided with finger pads 8. Thus, a user can operate the metering device 1 by pressing between the thumb and index or middle finger, the thumb is placed on a bottom of the medium storage, not shown. To reset the piston arrangement 3 into the starting position shown in FIG. 1, a return spring 9 is provided, which applies a restoring force when the dosing device 1 is actuated. The applicator 5 is provided with a Schutzabde¬ cover 10, which is removed for the discharge process.

At one of the discharge opening 6 remote from the end of the pumping device 2, an interface 11 is provided for the attachment of the medium reservoir. The interface 11 has a substantially cylindrically shaped outer shell 12, which receives the piston assembly 3 and in relatively movable, form-fitting conclusive operative connection with the applicator 5 stands. The outer shell 12 is provided with an internal thread 13, which is provided for the positive reception ei¬ nes provided on the media storage external thread. On a circumferential end face 14 of the piston assembly 3 is a wesentli chen annularly shaped gasket 15 which is made of an elastic material and is provided for sealing a vor¬ on the medium storage vor¬ considered bottleneck with respect to the pumping device 2. The flat gasket 15 has a vent opening 16, which is provided for a communicating connection of the volume enclosed by the medium reservoir with the environment. On a side facing the interface 11, the flat gasket 15 has a sealing surface 17, which is provided for a sealing effect with respect to the medium reservoir. Above the vent opening 16, a recess for a positive reception of a filter cartridge 18 is provided in the piston assembly 3, which is equipped with a filter membrane 20 shown in detail in FIG. The filter cartridge 18 communicates with a cavity 19 in communicating connection, which in turn communicates with the environment via gaps not shown in the dosing device 1. This allows an inflow or outflow of gas molecules from or into the medium reservoir. Thus, the ventilation opening 16, the filter cartridge 18 and the cavity 19 form the ventilation device of the metering device 1. A gas stream emerging from the medium reservoir, for example from evaporated medium components, must inevitably flow through the ventilation device in order to escape into the environment. The same applies to the reverse case that gas from the environment is sucked into the medium storage, also here is voll¬ constantly flow through the ventilation device.

In the detail enlargements shown in FIGS. 2 to 4, the same reference numerals as in FIG. 1 are used for functionally identical components. The filter cartridge 18 shown in more detail in Fig. 2 has a filter membrane 20 which is formed as a germ barrier and which is received in a passage bore 21 of the filter cartridge 18. In this case, a longitudinal axis 22 of the passage bore 21 is aligned parallel to a longitudinal axis of the metering device 1. The filter membrane 20 is intended to prevent the entry of contaminants from the environment in the medium storage, not shown. The passage bore 21 has an inner diameter 23 which is at least approximately constant over the entire length of the filter cartridge 18. The filter membrane 20 is injected in a form-fitting manner into the filter cartridge 18 designed as a plastic injection-molded part and is delimited by the through-bore 21. The effective area of the filter membrane 20 is determined by the effective diameter 24, which is smaller than the inner diameter 23. Only in the active surface of the filter membrane 20 are pores or channels 26 provided, which allow a passage of gas molecules, while outside the effective area no pores or channels are provided. The channels 26 provided in the filter membrane 20 are shown only schematically, they can also take a curved course depending on the manufacturing process for the filter membrane 20 and have different cross-sections over their course. The generation of the channels 26 can be carried out before or after the injection into the filter cartridge 18 and in particular be realized by a bombardment of the filter membrane 20 with a high-energy electromagnetic radiation. Critical to the passage of gas molecules is the minimum free cross section of the channels 26, as this limits the size of the gas molecules that can pass through the channels. The diffusion constant of the filter membrane 20 is additionally determined by the thickness 25 of the filter membrane 20, wherein a greater thickness 25 leads to a reduction in the diffusion constant, since the passage of gas molecules is limited by the increased length of the channels 26 and by the larger di ¬ Cke the basic material is difficult. In the illustrated filter cartridge 18, the inner diameter 23 of the through-bore 21 is approximately 1.4 mm, whereas the effective diameter 24 is approximately 0.9 mm, so that the effective area is approximately 0.65 mm ² . - -

In a filter cartridge 18 according to FIG. 2, a filter membrane 20 made of the material polyethylene terephthalate (PET, PEPT) can be provided. This filter membrane 20 has a pore size of 0.2 / 1000mm (0.2μm) at a membrane thickness of 36 / 1000mm (36μm) and an active filter area of less than 0.8mm ² . This results in a determination of a Ver¬ evaporation rate, which is carried out at atmospheric pressure of 1013 hPa, a temperature of 40 degrees Celsius and a humidity of 25 percent, for the filter cartridge 18 when used in the Dosiervorrich¬ tion 1 shown in Fig. 1 an evaporation rate of about 0.033 g / week. That is, about 0.033 grams of liquid escape from the medium reservoir per week. This represents a reduction of the evaporation rate compared to known metering devices equipped with conventional filters of about 30 percent. By varying the pore size, the density of the pores on the surface of the filter membrane, the thickness of the filter membrane and the active filter surface can the evaporation rate can be reduced by at least 15%, preferably by 30%, particularly preferably by 50%.

Compared with the filter cartridge shown in FIG. 2, the filter cartridge 18 shown in FIG. 3 is equipped with a filter membrane 20 which has a substantially constant number of channels 26 per unit area over its entire surface. A reduction of the diffusion rate is achieved by providing on one side a conical flow-guiding geometry 27 reaching down to the filter membrane, which leads to a reduction of the effective area. The active surface is accordingly determined by the minimum diameter 28 of the flow-guiding geometry 27 and is by way of example approximately 0.65 mm ² , while the inner diameter 23 of the through-bore 21 is approximately 1.4 mm. The filter membrane 20 can be cut out of a homogeneous raw material uniformly interspersed with channels 26 and introduced into the filter cartridge 18 in the plastic injection molding process. In the filter cartridge 18 shown in FIG. 4, in a modification of the filter cartridge known from FIG. 3, a flow guide geometry 27 is provided on each side of the filter membrane 20. The active surface is determined by the mini¬ maldurchmesser 28 of Strömungsleitgeometrie 27, the Filtermemb¬ ran ran 20 as in the embodiment of FIG. 3 as a homogeneous, uniformly interspersed with channels 26 membrane. By the Strömungsleitgeometrien 27 arranged on both sides a particularly advantageous stabilization of the filter membrane 20 is achieved, in addition, by the conical design of the flow guide geometries 27, an advantageous flow behavior of the gas stream passing through the filter membrane can be effected. With regard to the inner diameter 23 of the through-bore 21 and the minimum diameter 28, the same dimensions apply as for the filter cartridge of FIG. 3.

In a filter cartridge 18 according to FIG. 3 or 4, a filter membrane 20 made of polytetrafluoroethylene (PTFE) may be provided. Such a filter membrane 20 has a pore size of 0.2 / 1000 mm (0.2 .mu.m) and is applied to a Trägerrnembran made of PET, so that there is a total Mem¬ brand thickness of about 0.2 mm. The effective surface area is limited to approximately 0.5 mm ² by the flow guide geometries 27, so that a vaporization rate, which is determined at atmospheric pressure of 1013 hPa, a temperature of 40 degrees Celsius and an air humidity of 25 percent, of unge¬ 0.033 g / week for the filter cartridge 18 when used in the dosing device 1 shown in FIG. 1. This represents a reduction in the rate of evaporation compared with known dispensing devices equipped with conventional filters of approximately 30 percent.

In the embodiment of the invention shown in FIG. 5, which in its basic structure corresponds to the metering device of FIG. 1, the filter membrane 20 is provided in a depression of the flat gasket 15 and closes a ventilation opening 16 which is part of the ventilation device , With the filter membrane 20 is a ventilation channel 29 in communicating Active compound which allows inflow and outflow of gas molecules into the cavity 19. As in the embodiments of FIGS. 3 and 4, the effective area of the filter membrane 20 is determined by the minimum diameter of the ventilation aperture 16, while the filter membrane is interspersed with a homogenous number of channels per unit area.

In one embodiment of the invention, not shown, the filter membrane 20 is applied to a surface of the flat gasket 15, in particular laminated.

In a further embodiment, the filter membrane in the area of the ventilation opening 29 of the piston or cylinder arrangement 3, similar to FIG. 5, is applied tightly, particularly welded or laminated, to the top or bottom of a corresponding surface of the piston or cylinder arrangement 3.

In the embodiments provided with capillary channels of the metering device according to FIGS. 6 to 9, the same reference numerals as for the metering devices according to FIGS. 1 to 5 are used for functionally identical components.

The metering device 1 shown in FIGS. 6, 7 and 8 has a filter cartridge 18 which is provided on the cylinder arrangement 4 and which can be designed according to the embodiments of FIGS. 1 to 5. At an end of the filter cartridge 18 facing away from the medium reservoir, the passage bore 21 opens into a distributor bore 30, which communicates via an outlet opening 38 with a circumferential annular section designed as an annular channel 31, as shown in greater detail in FIG. 6a becomes. The annular channel 31, which is formed between the cylinder arrangement 4 and a slip-on sleeve 32 pressed thereon, opens into a channel section 33 of the capillary channel oriented in the direction of the longitudinal axis of the metering device 1, as shown in greater detail in FIG. 6b. The annular channel 31 is formed by a circumferential stepped shoulder 34 on the cylinder arrangement 4 and a correspondingly executed discharge. sentence 43 formed on the slip-on sleeve 32 and is due to its design as a long channel with a narrow cross section, a part of the capillary.

As shown in FIG. 7, the channel section 33 is formed by a groove 37 in a support web 35 and the plug-in sleeve 32 opposite the support web 35. Another function of the support webs 35 is to enable a non-positive reception of the slip-on sleeve 32 on the cylinder arrangement 4 without the cylinder bore in the cylinder arrangement 4 being deformed by the slip-on sleeve 32. In order to ensure a defined geometry of the capillary channel, a peripheral collar 36 is provided above the mouth of the distributor bore 30, which ensures a peripherally sealing reception of the adapter sleeve 32 in an end region facing the medium reservoir, as shown in FIG. 8 is shown in more detail. In the circulating collar 36, only the groove 37 shown in FIG. 8 a is provided, which forms the channel section 33. The capillary channel has a length of approximately 60 mm in the embodiment shown in FIGS. 6 to 8 and has an effective capillary channel diameter of approximately 0.42 mm, so that a ratio of effective capillary channel diameter and capillary channel length of 1/140 results. With such a ratio, an evaporation rate, which is determined at normal pressure of 1013 hPa, a temperature of 40 degrees Celsius and a humidity of 25 percent, of about 0.005 g / week can be realized.

In the embodiment according to FIG. 9, the capillary channel is designed as a wendeiför¬-shaped groove between a cone outer surface 39 and a cover 40 ausge¬. The cover 40 has a conical recess and is pressed with a collar 41 in a retaining groove 42, as shown in more detail in Figs. 9a and 9b. The penetration of the cover 40 with the cylinder arrangement 4 represents that an interference fit, also referred to as a press fit, is provided between these components in order to ensure a secure fit of the cover 40 and a good sealing effect of the capillary channel. The cone outer surface 39 is part of the cylinder assembly 4 and has a helical and helical peripheral shoulder made in the manner of a conical worm. Such a configuration of the conical outer surface 39 ensures that the cylinder arrangement 4 can be produced as a plastic injection-molded part, since demolding from the injection-molded plastic mold without a slide or other expensive mold components is possible due to the frontal orientation of the surfaces. As shown in more detail in FIG. 9 a, the distributor bore communicating with the filter cartridge 18 opens through an outlet opening 38 into the capillary channel, which is formed by the cone outer surface 39 and the cover 40. The cover 40 also serves as a support surface for the return spring. 9

In one embodiment, not shown, the filter membrane is housed in a recess of the gasket, as shown in Fig. 5 and is coupled to a capillary according to one of Figs. 6 to 9, resulting in a simple design and by a very low evaporation rate ge marked dosing can realize.

Claims

claims

1. metering device (1) for at least one medium, with a Pumpeinrich¬ device (2), which is in Wirk¬ connection for a medium discharge with a medium storage, as well as with a medium storage and / or the pumping means associated ventilation device, the Belüf¬ tungskanal (16, 18, 26, 27), which is assigned to a filter membrane (20) zuge¬, characterized in that the filter membrane (20) is formed for a reduced diffusion rate.

2. Metering device according to claim 1, characterized in that the filter membrane has a relation to known filter membranes reduced effective cross-section.

3. Metering device according to claim 2, characterized in that the reduced effective cross section of the filter membrane is realized by a comparison with be¬ known filter membranes reduced effective area (24).

4. Metering device according to claim 3, characterized in that the active surface of the filter membrane by a Strömungsleitgeometrie (27) be¬ limits, which is at least partially conical.

5. Metering device according to claim 3 or 4, characterized in that the effective area of the filter membrane is less than 1, 4 mm ² , preferably less than 0.6 mm ² , more preferably less than 0.2 mm ² .

6. Metering device according to one of claims 2 to 5, characterized gekenn¬ characterized in that for the reduced effective cross-section, a mean free cross section of pores (26) in the filter membrane is smaller than in known filter membranes.

7. Metering device according to one of claims 2 to 6, characterized gekenn¬ characterized in that for a reduced effective cross-section a comparison with be¬ known filter membranes reduced number of pores is provided.

8. Metering device according to claim 7, characterized in that the filter membrane has an average number of pores less than 1 million pores per mm ² , preferably less than 600,000 pores per mm ² , more preferably less than 300,000 pores per mm ² .

9. Metering device according to one of the preceding claims, characterized in that the filter membrane is provided on a in the ventilation channel an¬ arranged, in particular between the medium tank and Pumpeinrich¬ device provided sealing means (15).

10. Metering device according to claim 9, characterized in that the filter membrane for a closure of a vorgese¬ in the sealing device Henen, the ventilation channel associated passage opening (16) ausge¬ is formed.

11. Dosing device according to one of claims 1 to 8, characterized gekenn¬ characterized in that the filter membrane mounted in the region of a ventilation opening of the medium reservoir and / or the pumping device, in particular reiaminiert re, is.

12. Metering device according to one of claims 1 to 8, characterized gekenn¬ characterized in that the filter device is designed as a discrete filter cartridge.

13. Dosing device according to the preamble of claim 1 or according to ei¬ nem of the preceding claims, characterized in that the ventilation channel is at least partially designed as a capillary channel, at least in sections, a ratio between an effective - -

Ven channel diameter (d) and a Kapillarkanallänge (I), which is less than 1/25, preferably less than 1/50, more preferably less than 1/100.

14. Metering device according to claim 14, characterized in that the capillary channel is formed helically.

15. Metering device according to claim 14, characterized in that the capillary channel is designed as a circumferential, helical groove between a Konus¬ outer surface and a cover having a conical, adapted to the cone outer surface recess.

16. Dosing device according to claim 13, characterized in that the capillary channel is formed between an outer surface of a cylinder arrangement and an inner surface of a slip-on sleeve, wherein on the outer surface of the cylinder arrangement and / or on the slip-on sleeve a plurality of webs are provided which are substantially in the direction a Mittellängs¬ axis of the metering device are aligned and ensure a defined spacing of the slip sleeve.

17. Metering device according to claim 16, characterized in that the capillary channel is partially introduced ein¬ in at least one of the webs as a groove.

18. Metering device according to claim 17, characterized in that the capillary channel is formed from at least one annular section and at least one channel section, which is aligned at least substantially along the central longitudinal axis of the metering device.