Abstract:
In a dispenser for liquid media, applicator of the dispenser is fixed to a medium reservoir. A finger rest for actuating the dispenser is configured such that it is axially displaceable relative to this subassembly. As advantageous refinements, a dispenser is proposed whose pump is realized as a user-independent pump, a variety of mechanical realizations being considered advantageous.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention relates to a dispenser for media having a medium reservoir, an applicator having at least one discharge opening, a finger rest, which can be manually subjected to force, and a pump having at least two pump parts which are axially movable relative to each other.  
       BACKGROUND OF THE INVENTION  
       [0002]     Such dispensers are used, above all, for liquids, suspensions, pastes and foams and serve for the dosed discharge of these media. In the medical field, such dispensers are also used, inter alia, for nasal applications, in which the applicator is realized such that it can be inserted in the nose so as to deliver liquids or suspensions therein.  
         [0003]     In the prior art, for example in DE 19940234 A1, primarily such dispensers of the generic type are known in which the applicator and the finger rest are realized in one piece, so that a relative movement of the finger rest relative to the medium reservoir also constitutes, at the same time, a relative movement of the applicator relative to the medium reservoir. These dispensers are usually operated with one hand, the medium reservoir of the dispenser being clasped with the hand and held stationary relative to the particular body part, for example the nose, while the finger rest is operated with one or two fingers. A perceived drawback with this is that, during the discharge operation, the applicator with the discharge opening departs from its original position relative to the particular body part, or the discharge operation is triggered following the departure of the applicator from its original position. In the case of a nasal application, this results, for example, in the nose applicator being withdrawn from the nose, which adversely affects the delivery of the medium. Although this can be offset by readjustment of the medium reservoir, this is difficult from the motory aspect and reduces the convenience of use of the dispenser.  
       SUMMARY OF THE INVENTION  
       [0004]     The object of the invention is therefore to provide a media dispenser of the type stated in the introduction, which allows greater convenience of use compared with the prior art.  
         [0005]     This object is achieved by the applicator being fixedly connected to the medium reservoir and the finger rest being axially movable relative to the medium reservoir and the applicator between a first, unpressed operating end position and a second, pressed operating end position.  
         [0006]     In such a dispenser according to the invention, the applicator and the media reservoir form a, during use, one-piece unit, which dictates that the discharge opening shall be at a fixed and non-variable position relative to the medium reservoir. The medium reservoir serves to accommodate at least one medium. A position of the medium reservoir which is fixed relative to the particular body part during use also therefore results in a fixed position of the discharge opening. In the case of a nose applicator for nasal applications, the discharge opening of the applicator remains, for example, at is position defined prior to the start of the discharge operation by the insertion of the applicator into the nose. The finger rest can be moved in translatory motion relative to this one-piece unit comprising medium reservoir and applicator. The principal axis of this translatory mobility is preferably identical with a longitudinal axis of the applicator. The applicator and the medium reservoir can be provided as a one-piece component, but are preferably separate components which are detachably joined together, for example by a screw joint. In a particularly preferred embodiment, a connecting element for connecting the applicator to the medium reservoir, in particular a screw fastening, is provided. The pump is preferably disposed within the applicator and has a dosing chamber, which is limited, at least partially, by the applicator. The volume of the dosing chamber is determined by a pump piston operatively connected to the finger rest, both a direct connection between piston and finger rest and an operative connection via intermediate elements being possibly expedient. Depending on the embodiment, the filling of the dosing chamber with medium originating from the medium reservoir can be realized in the course of the pressing of the finger rest or with the return of the finger rest into its original setting. The same applies to the discharging of the medium present in the dosing chamber.  
         [0007]     In a preferred refinement of the invention, the pump is realized in such a way that a constant discharge stroke can be obtained independently of a manual operating force.  
         [0008]     In a user-independent pump of this kind, the discharge operation for the medium present in the dosing chamber is not influenced by the characteristics of the operating process. This is preferably achieved by the finger rest and a pump piston of the pump not being joined together in one piece and being able to be mutually separated by kinematic means. Hence, an actuation of the finger rest does not directly result in a diminution of the volume of the dosing chamber of the pump. Instead, the applied energy is stored and is utilized only at a later point to compress the medium present in the dosing chamber, for example once a defined actuating position has been reached. It is precisely in those applications in which the quantity of medium to be discharged and the nature of the discharge operation, for example by spraying, must be strictly adhered to that this independence from the manner of operation by the user is expedient.  
         [0009]     In a refinement of the invention which is based on the above, a carrier is provided, which is connected in a non-detachable manner to a pump piston, the applicator, the carrier and/or the finger rest having coupling means which are configured to create an axial coupling state between the carrier and the finger rest in the region of a first pump stroke end position assigned to the first operating end position, and to create a decoupled state of carrier and finger rest in the region of a second stroke end position assigned to the second operating end position, and the carrier being subjected to a spring force in the direction of the first stroke end position.  
         [0010]     The carrier, which is connected in a non-detachable manner to the pump piston, directly determines the volume of the dosing chamber. It can be moved both relative to the applicator and relative to the finger rest in the direction of the principal axis. In the first stroke end position of its movement relative to the applicator, the dosing chamber of the pump has a minimum volume. In its second stroke end position, the dosing chamber has a maximum volume. As a result of the force subjected upon the carrier, it is forced in the direction of its first stroke end position, i.e. the end position having minimum dosing chamber volume. The opposite direction of the carrier in the direction of the second stroke end position is obtained by coupling the carrier motion to the operating motion of the finger rest. The coupling means provided for this purpose are configured such that, in the region of the first stroke end position or of the first operating end position, they provoke a coupling between the finger rest and the carrier, so that, during the maintenance of this coupling state during operation, the carrier is tensioned against the action of the spring force, and such that, when the stroke end position is reached, they release this coupling, so that the carrier which has thus been pretensioned is transferred back by the spring force into the first stroke end position. As a result of the movement of the carrier from the second stroke end position back into the first stroke end position, the volume of the dosing chamber is reduced and a discharge operation necessitated. For this discharge operation, it is not important for the finger rest to be meanwhile returned into its first operating end position. This can also be done after the conclusion of the discharge operation. As soon as the finger rest has regained the first operating end position, the coupling between carrier and finger rest is restored—preferably automatically.  
         [0011]     In a preferred refinement of the invention, the coupling means have a time-delay means, by which, following decoupling of the carrier from the finger rest in the region of the second stroke end position, a retarded return stroke motion is obtained.  
         [0012]     By a retarded return stroke motion is meant a return stroke motion which is retarded relative to a return stroke motion which, in terms of its temporal progression, is dependent merely upon the spring force and the pressure in the dosing chamber. Such a retardation can be expedient, in particular, where a certain discharge characteristic is to be obtained or where a filling operation of the dosing chamber is not to be prematurely interrupted by the return stroke of the piston in the direction of the first stroke end position. The time-delay means can be configured such that they display a time-delay effect only in a part-region of the stroke, in particular in a part-region adjoining the second stroke end position. A possible realization of the time-delay means provides guide elements, which, in the course of the return stroke motion of the carrier, cause the stroke motion to be overlaid with a rotary motion about a pump longitudinal axis.  
         [0013]     In a refinement of the invention, the coupling means on the carrier have at least one latching element, preferably at least one latch boss, which can be coupled to the finger rest in such a way that a movement of the finger rest from the first operating end position to the second operating end position produces a movement of the carrier from the first pump stroke end position to the second pump stroke end position, and further have a decoupling section, which, in the region of the stroke end position, decouples the latching means from the finger rest, preferably by radial deflection of the latch boss.  
         [0014]     Embodiments of the dispenser according to this refinement are very simply constructed in terms of their design. The latching element provided on the carrier preferably extends radially outward into the region of the finger rest, so that, in the course of the pressing of the finger rest, it latch locks with the latter in a manner which allows a joint movement of the finger rest and the carrier in the direction of the second operating end position. Special preference is given to the use of an elastically configured latch boss as the latching element. This is radially deflected, once the second operating end position is reached, to the point where it is no longer engaged with the finger rest and, consequently, the carrier, which in this state is pretensioned by the spring force, is forced in the direction of its first stroke end position. Depending on the embodiment, the deflected latch boss hereupon slides down on an inward-pointing contact surface of the finger rest. In this case, the finger rest and the latch boss can be designed such that the friction force opposite to the spring force, generated by the contact of the latch boss with this surface, is low. Following the discharge operation or during the discharge operation, the finger rest, preferably spring-aided, can be returned into the first operating end position, in which the latch boss of the carrier gets back into the non-deflected engagement setting with the finger rest. Alternatively thereto, the elastic latching element can also be provided on the finger rest side and, in the region of a stroke end position, can be deflected radially outward by a decoupling apparatus on the applicator side.  
         [0015]     In another refinement of the invention, the applicator and the finger rest are configured such that they are rotationally secure one to the other with respect to a principal axis, and the carrier, in a first guide section adjacent to the first stroke end position, is secured against twisting relative to the applicator, at least in a rotational direction about the principal axis, and, in a second triggering section adjacent to the second stroke end position, are configured such that they can be twisted in this rotational direction, guide means being provided, which, following attainment of the state decoupled from the finger rest, guide the carrier in an overlaid rotary and translatory motion back into the first stroke end position.  
         [0016]     In this refinement it is also envisaged that, in the course of the actuating motion of the finger rest, the finger rest and the carrier are guided in a fixed rotational alignment to each other and to the applicator until the stroke end position is reached. While the finger rest remains connected to the applicator in a rotationally secure manner, even following the attainment of the stroke end position, the carrier, from the moment the stroke end position is reached, is rotationally movable relative to the applicator about the principal axis. The guide means have the effect that the return stroke motion of the carrier, provoked by the, in this state, high spring force, is overlaid with a rotary motion. As a result of this rotary motion, the carrier, during the return stroke, is rotated relative to the applicator and the finger rest about the principal axis. Following the return of the finger rest into the first operating end position, the carrier then re-enters, in the first stroke end position, a state in which it is rotationally secured and coupled to the finger rest. A particularly preferred embodiment envisages that the guide means are formed by sawtooth-shaped projections, which extend on the inner wall of the applicator in circular arrangement about the longitudinal axis of the applicator. The teeth are here separated from one another by longitudinally aligned grooves on the inner wall of the applicator. The grooves are used in the guide section of the stroke for the rotational securement of the carrier by means of carrier-side coupling sections. Where appropriate, they can additionally be used, also in the same manner, for the rotational securement of coupling sections on the finger rest side. The coupling sections of the carrier and of the finger rest have mutually facing beveled coupling surfaces, the gradient of which preferably conforms to that of the sawteeth. When the dispenser is actuated by depression of the finger rest, the coupling surfaces bear flush one against the other. As a result of the oblique shaping of the coupling surfaces, a torque hereupon acts upon the carrier, which, due to the guidance of the coupling sections in the grooves between the sawteeth or owing to the longitudinally aligned, vertical flanks of the sawteeth, does not lead to a rotation of the carrier. Once the tip of the sawteeth is reached, the carrier-side coupling section then slides down, however, on the coupling surface on the finger rest side and the oblique flank of the sawteeth, thereby producing a combined translatory and rotary motion of the carrier. Once the finger rest has regained its first operating end position, the carrier-side coupling section reengages with the coupling section on the finger rest side. The advantage of this refinement according to the invention lies, on the one hand, in the fact that it constitutes a time-delay means of the above-described type, i.e. retards the return stroke of both the carrier and the piston, which is expedient, in particular, in respect of a time-critical upstream filling of the dosing chamber and that, on the other hand, compared with a variant of the coupling means with latching elements, no elastic components are needed and are deformed in the course of their operation. A failure of the dispenser due to damage to elastically deflected components is thereby avoided.  
         [0017]     In a refinement of the invention, the pump piston fixedly connected to the carrier limits, jointly with a cylindrical pump wall and a front-side end wall of the applicator, a dosing chamber of the pump.  
         [0018]     This constitutes a very simple construction of the pump. For the supply of medium into the dosing chamber, a connecting line to the medium reservoir is provided, this supply line being able to be opened and closed in dependence on the stroke position of the piston and/or the pressure in the dosing chamber. The pump is additionally connected to the discharge opening by a connecting line and, where appropriate, further elements which influence the discharge operation.  
         [0019]     In a refinement of the invention, the carrier is connected by an inlet valve to the medium reservoir, which, if the dosing chamber pressure is lower than the pressure in the medium reservoir, opens. Such a valve prevents medium from flowing off into the medium reservoir in the course of actuation of the dispenser.  
         [0020]     In a refinement of the invention, the carrier and/or the applicator is/are configured such that the dosing chamber, in a first isolating stroke section adjacent to the first stroke end position, is separated from the medium reservoir and, in a thereto adjoining connecting stroke section, is connected to the medium reservoir.  
         [0021]     In the region of the isolating stroke section, upon an actuating motion from the first to the second operating end position, the volume of the dosing chamber is effectively enlarged without the medium meanwhile making its way into the dosing chamber. Instead, an underpressure or a vacuum is developed in the dosing chamber and the dosing chamber is only filled with medium once the connecting stroke section is reached. This procedure is advantageous compared with a continuous filling of the dosing chamber, since varying liquid quantities in the course of different operating motions are avoided. Instead, an always identical underpressure ratio is produced in the dosing chamber, which results in an only very slightly fluctuating quantity of medium in the dosing chamber after the connecting stroke section is reached. Upon the movement of the piston from the second stroke end position into the first stroke end position, i.e. during the diminution of the volume of the dosing chamber, the piston gets back into the isolating stroke section, in which it is separated from the medium reservoir. From the time of separation, no medium can make its way back into the medium reservoir. The medium quantity present in the dosing chamber at the time of the passage from the connecting stroke section into the isolating stroke section is consequently used for the following discharge operation.  
         [0022]     In a refinement of the invention, the dosing chamber, in a second isolating stroke section preceding the stroke end position, is separated from the medium reservoir.  
         [0023]     The effect of this separation in the second isolating stroke section is that the maximum volume of the medium which has flowed into the dosing chamber is defined not by the stroke end position, but by the second isolating stroke section. A higher accuracy is thereby obtained, since, depending on the mechanical construction of the coupling means, the stroke end position can fluctuate to an undesirably high extent, which likewise results in a fluctuation of the medium stored in the dosing chamber.  
         [0024]     In a refinement of the invention, the dispenser has a discharge valve, which is operatively connected to the finger rest by mechanical means and is configured such that it opens in a stroke intermediate position, before or as the second stroke end position is reached.  
         [0025]     Such a discharge valve allows a purposeful discharge of the medium once a pressure optimal for the discharge is reached. In contrast to a discharge valve which is opened in dependence on a discharge pressure, a discharge valve which is operatively connected to the finger rest by mechanical means is opened when a certain position of the finger rest is reached. A discharge valve can also be opened when there has been failure to reach a desired target pressure. Moreover, a discharge valve of this type is suitable for use in dispensers of different construction or different purpose, which have a mutually differing discharge pressure.  
         [0026]     In a refinement of the invention, between the dosing chamber and the discharge opening a pressure chamber is provided, which is separated from the dosing chamber by a pressure-actuated intermediate valve.  
         [0027]     In a dispenser having such a construction, the path of the medium runs from the medium reservoir through the dosing chamber into the pressure chamber. From the pressure chamber, the medium is then discharged. In such a construction, the dosing chamber is preferably configured such that its minimum volume is very small relative to the maximum volume. This allows very high pressures to be generated in the dosing chamber, which cause the medium to be transported into the pressure chamber. From this, the medium can only escape on the discharge opening side. Without medium discharge, the pressure in the pressure chamber therefore rises further with each pump stroke until a target discharge pressure is reached. Such an apparatus eliminates the risk that air within a dosing chamber will be compressed with each pump stroke and will be decompressed again with the return stroke, without any medium being consequently discharged. In such a case, it is virtually impossible to start using the dispenser without a rising pressure developing—as, in this refinement, in the pressure chamber—since the pressure ratios in the dosing chamber in respect of each pump stroke are identical.  
         [0028]     In a refinement of the invention, the discharge valve is configured in such a way that in the open state, from a discharge limit pressure of the medium, it maintains the open state, this limit pressure, in the case of a discharge valve actuated by the pressure of the medium, preferably being less than the opening limit pressure necessary to open the valve.  
         [0029]     The consequence is that the valve remains open even at a discharge pressure which is insufficient to open the valve. In a valve, in particular, which can be opened mechanically and not by pressure, it is expedient to provide such a design. The effect of this design is that the mechanical force by which the valve is opened does not have to be maintained for the period of the discharge. If this mechanical force is exerted directly by means of the finger rest of the dispenser, the use of such a discharge valve means that a premature release of the finger rest does not result in interruption of the discharge.  
         [0030]     In a refinement of the invention, the valve has an actuating surface, the pressurized portion of which in the open state of the valve is greater than in the closed state of the valve.  
         [0031]     Depending on the embodiment, the pressurized portion in the closed state of the valve can also be sufficiently small that, at operating pressures which are standard in the dispenser, an opening of the valve is not achieved on the basis of the pressure, but instead can only be realized mechanically. If the valve is open, however, this pressurized portion is greater, so that the open state is able to be maintained until the discharge pressure has fallen to the point where, despite the enlarged actuating portion, a closure of the valve—for example by a spring force—is performed. This spring force, once again, is accompanied by a diminution of the actuating surface. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0032]     Further features and advantages of the invention emerge from the claims and the description in association with the drawings, in which:  
         [0033]     FIGS.  1  to  3  show a first embodiment of a dispenser according to the invention in three stages of an actuating operation,  
         [0034]      FIG. 4  shows a second embodiment of a dispenser according to the invention, which operates on the basis of a dosing chamber filling principle which is changed from the first two embodiments,  
         [0035]      FIG. 5  shows a third embodiment of the invention having a pressure chamber separated by the dosing chamber, and  
         [0036]      FIGS. 6   a  to  7   b  show a fourth embodiment of a dispenser according to the invention in two different stages of the actuating operation and respectively in a perspective view and a sectional view. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0037]     In the context of this description, “at the top” or “upward” is used to denote a direction toward the discharge openings represented at the top in the figures, and “at the bottom” or “downward” is used to denote a direction toward the medium reservoirs (not represented in the drawings) adjoining, at the bottom, the respectively represented discharge apparatuses.  
         [0038]     FIGS.  1  to  3  show a first embodiment of a discharge apparatus of a dispenser according to the invention, in which the medium reservoir belonging to the dispenser is not represented. The figures show various stages during an actuating operation for the conveyance of a medium present in the medium reservoir.  
         [0039]     The discharge apparatus essentially has four subassemblies  12 ,  14 ,  16 ,  18 , which are configured such that they are axially mutually displaceable along a principal axis  10 . The subassemblies in question are an applicator subassembly  12 , a finger rest subassembly  14 , a discharge valve subassembly  16  and a piston subassembly  18 .  
         [0040]     The finger rest subassembly  14  is configured such that it is axially displaceable relative to the applicator subassembly  12  between a first, upper actuating end position and a second, lower actuating end position. The discharge valve subassembly  16  is configured such that it is axially displaceable relative to the applicator subassembly  12  between an upper closing position and a lower opening position. The piston subassembly  18  is configured such that it is axially displaceable relative to the applicator subassembly  12  between a first, upper stroke end position and a second, lower stroke end position. The applicator subassembly  12  itself is fixedly connected to the medium reservoir (not represented in the figures).  
         [0041]     The applicator subassembly  12  consists of a substantially cylindrical nose applicator  22  having a discharge opening  22   a  disposed at the upper end, a screw fastening  24 , by which the nose applicator  22  is connected to a medium reservoir (not represented), a medium supply apparatus  26 , disposed within the screw fastening  24  and the nose applicator  22  and comprising an axially aligned medium duct  26   b,  as well as a blocking insert  28  disposed in the medium duct  26   b  and an inlet valve piece  30   a  likewise disposed in the medium duct  26  over the blocking insert  28 . Above the inlet valve piece  30   a  there is provided in the medium supply apparatus a radial through bore  26   e,  through which medium fed through the medium duct  26  can make its way into a dosing chamber  54 . Above and below the blocking insert  28 , radial through bores  26   c,    26   d  are provided in the medium supply, which allow the blocking insert  28  to be by-passed in the course of the conveyance of the medium. Disposed in the through bore  26   e  is a ball valve  30   b,  which, together with the inlet valve piece  30   a,  forms a ball seat valve  30 , which opens when an underpressure obtains in the dosing chamber  54 .  
         [0042]     The components  22 ,  24 ,  26 ,  28 ,  30  of the applicator subassembly  12  are fixedly connected to one another and are configured such that their relative position does not alter if the dispenser is used according to specification.  
         [0043]     The second subassembly, the finger rest subassembly  14 , consists merely of the finger rest  32 . The finger rest  32  has a cylindrical section, having a cylindrical wall  32   a,  and an actuating section  32   b,  extending radially therefrom, for the resting of the fingers. The cylindrical section is of double-walled construction in an upper region and has an inner wall  32   d.  The lower end of the cylindrical wall  32   a  constitutes a functional section  32   c,  the working of which will be further described later. The finger rest  32  is slipped onto the applicator subassembly  12  from outside and is axially movable relative to the latter between a first actuating end position, represented in  FIG. 1 , and a second actuating end position, represented in  FIG. 3 .  
         [0044]     The third subassembly, the discharge valve subassembly  16 , has a one-piece valve element  34  having a cylindrical main section  34   e.  At the lower end of the main section  34   e  there is provided an actuating ring  34   a.  At the upper end of the main section  34   e,  an upwardly closed inner cylinder  34   c  is integrated, via radial webs  34   b,  integrally into the valve element  34 . At the upper end of this inner cylinder  34   c,  a closing pin  34   d,  extending axially upward, is molded onto the inner cylinder  34   c.  The valve element  34  is axially displaceable relative to the applicator subassembly  12 . The upper end position of the valve element  34 , represented in  FIGS. 1 and 2 , constitutes a closing state, in which the closing pin  34   d,  in the region of the discharge opening  22   a  of the nose applicator  22 , bears flush against an annular surface  22   b  of the nose applicator  22  and thereby prevents a medium discharge through the discharge opening  22   a.  The lower end position of the valve element  34  relative to the applicator subassembly  12 , represented in  FIG. 3 , constitutes the opening state in which the annular surface  22   b  of the nose applicator  22  and the closing pin  34   d  are spaced apart in the direction of the principal axis  10 , enabling pressurized medium to escape through the discharge opening  22   a.    
         [0045]     The last subassembly, the piston subassembly  18 , consists of a total of three components. These components are a carrier  36 , a sealing ring  38  and a piston packing  40 . These components  36 ,  38 ,  40  are fixedly connected to one another and do not alter their relative position if the dispenser is used according to specification. The carrier  36  has a cylindrical section  36   a,  adjoined at the lower end by an outward-pointing radial section  36   b.  Molded onto this radial section  36   b  are latch bosses  36   c,  which extend outward away from the principal axis  10 . The latch bosses  36   c  are of elastic configuration and are formed such that they can be deflected radially inward. In the region of the transition between the cylindrical section  36   a  and the radial section  36   b  of the carrier  36 , the latter is fixedly connected to the inner sealing ring  38 . The upper end of the carrier  36  is adjoined by the piston packing  40 , which consists of an elastic material. The piston packing  40  has a substantially cylindrical basic form, exhibiting the greatest external diameter at its upper end  40   a  and the smallest internal diameter at its lower end  40   b.  It is connected to the carrier  36  in such a way that its lower end  40   b  is disposed inside the cylindrical section  36   a  and its upper end projects upward over the carrier  36 . The piston subassembly  18  is disposed within the nose applicator  22  and the discharge valve subassembly  16  is disposed in the discharge apparatus and encloses the medium supply apparatus  26 . The sealing ring  38  and the lower end  40   b  of the piston packing  40  are configured such that they form a tight inward seal against the medium supply apparatus. The upper end  40   a  of the piston packing  40  is configured such that it forms a tight outward seal against the inner side of the main section  34   e  of the valve element  34 . The piston subassembly  18  is configured such that it is displaceable between a first, upper stroke end position and a second, lower stroke end position, the first, upper stroke end position being determined by a stop position of the piston packing  40  at the end of the cylindrical section  34   e  of the valve element  34  and the lower stroke end position being defined by a decoupling web  24   b  of the screw fastening  24  of the applicator subassembly  12 , against which the latch bosses  36   c  are forced radially inward out of the operative connection with the functional section  32   c  of the finger rest  32 , thereby preventing any further movement of the piston subassembly  18  in the downward direction. This is explained in greater detail further below.  
         [0046]     The discharge apparatus represented in FIGS.  1  to  3  has a total of three springs, by which the finger rest  32 , the valve element  34  and the piston subassembly  18 , relative to the applicator subassembly  12 , are subjected to force in the direction of their respectively upper end position. The finger rest  32  is forced upward by the finger rest spring  46 , which is supported on an annular shoulder  22   c  of the nose applicator  22 . The valve element  34  is forced into its closing position by a valve spring  48 , the valve spring  48  being held in a downwardly closed-off cylindrical supporting section  26   a  at the upper end of the medium supply apparatus  26 , and in the inner cylinder  34   c  of the valve element  34 . The piston subassembly  18  is acted upon by an energy store spring  50  in the direction of its first, upper stroke end position.  
         [0047]     The described discharge apparatus represented in FIGS.  1  to  3  functions as a user-independent discharge apparatus. This means that the dosing quantities and the discharge pressure are independent of the manner of the actuation by the operator.  
         [0048]     The working method of the described dispenser is set to be illustrated with reference to the sequence of FIGS.  1  to  3 :  
         [0049]      FIG. 1  shows the dispenser in a starting position. The finger rest  32 , the valve element  34  and the piston subassembly  18  are found respectively—acted upon by the respective springs  46 ,  48 ,  50 —in their upper end position. In this upper end position, the functional section  32   c  of the finger rest  32  is disposed above the latch bosses  36   c  of the carrier  36  of the piston subassembly  18 . The latch bosses  36   c  are in a non-deflected state and extend through axially aligned cutouts  22   d  in the nose applicator  22  to below the functional sections  32   c  of the finger rest  32 . The dosing chamber  54  located between the piston packing  40  and the dosing element  34  has, in this stage, a minimum volume.  
         [0050]     Starting off from this state, the finger rest  32  is pressed downward by an operator relative to the applicator subassembly  12  and counter to the spring force of the finger rest spring  46 . Since the latch bosses  36   c  are disposed beneath the functional sections  32   c,  the piston subassembly  18 , too, is likewise forced downward jointly with the finger rest  32 . This produces a volume enlargement of the dosing chamber  54 . The underpressure which is thereby formed opens the ball seat valve  30  and draws medium into the dosing chamber  54 . This medium, starting from the medium reservoir (not represented in the figures), hereupon takes a path through the medium duct  26   b  of the medium supply apparatus  26 , through the lower through bores  26   c  beneath the blocking insert  28  out of the medium supply apparatus  26 , and through the upper through bores  26   d  above the blocking insert  28  back into the medium supply apparatus  26 . With progressive displacement of the finger rest  32  in the downward direction and the parallel displacement of the piston subassembly  18  in the downward direction, the dosing chamber  54 , accordingly, is increasingly filled. Meanwhile, the energy store spring  50 , which subjects the piston subassembly  18  to an upwardly directed force, is increasingly compressed and, hence, tensioned. An unwanted escape of the medium outward in the section between the first through bores  26   c  and the second through bores  26   d  is prevented by the sealing ring  38  and the lower end  40   b  of the piston packing  40 , which tightly seal, at the bottom and top respectively, an annular through chamber, which is closed off on the inside by the medium supply apparatus and on the outside by the valve element. An escape of the medium through the discharge opening is not possible during this phase of the actuation, since the closing pin  34   d  bears flush against the annular surface  22   b  of the nose applicator  22  and thus seals the discharge opening  22   a.    
         [0051]      FIG. 2  shows a state of the dispenser in the first embodiment shortly before the start of the discharge operation. The finger rest  32  is here pressed so far downward that the lower end  40   b  of the piston packing  40  covers the upper through bores  26   d  and thus prevents a further influx of medium into the dosing chamber  54 . The piston subassembly  18  is displaced, together with the finger rest  32 , sufficiently far down that the latch bosses  36   c  have made their way into that region of the cylindrical decoupling web  24   b  which is molded onto the screw fastening  24  and, as the finger rest  32  and the piston subassembly  18  are progressively pressed down, are deflected radially inward by the said decoupling web. The contact surface between the functional section  32   c  of the finger rest  32  and the latch bosses  36   c  of the carrier  36 , commencing with the time of initial contact between the latch bosses  36   c  and the decoupling web  24   b,  therefore becomes increasingly small.  
         [0052]     The result is that, as the finger rest  32  is progressively pressed down, the functional section.  32   c  loses contact with the latch bosses  36   c  and these spring onto the inner surface of the cylindrical wall  32   a  of the finger rest  32 . From this moment, the piston subassembly  18  can be forced upward without hindrance from the energy store spring  50 . The latch bosses  36   c  hereupon slide upward along with it, on the inner side of the cylindrical wall  32   a  of the finger rest  32 . As a result of the action by the spring force of the energy store spring  50 , the medium in the dosing chamber  54  is pressurized, an escape of the medium back into the medium reservoir being prevented by the ball seat valve  30 .  
         [0053]     The movement of the finger rest  32  up to an actuating end position, in which the functional section  32   c  of the finger rest  32  rests upon the decoupling web  24   b  of the screw fastening  24 , has the effect, apart from the decoupling of the latch bosses  36   c  from the functional sections  32   c,  that the downward-pointing front face of the cylindrical inner wall  32   d  of the finger rest  32  forces the actuating ring  34   a  of the valve element  34 , and hence the entire valve element  34 , downward. Consequently, the closing pin  34   d  is lifted off downward from the annular surface  22   b  of the nose applicator  22  and the discharge opening  22   a  for the medium present in the dosing chamber  54  is thereby made accessible.  
         [0054]      FIG. 3  shows a state toward the end of the medium discharge. The medium present in the dosing chamber  54  is forced out of the discharge opening  22   a  by the pressure generated by the energy store spring  50  and thus escapes in a precisely defined quantity. The discharge operation ends when the piston packing  40  butts against the end of the cylindrical section  34   e  of the valve element  34  and the dosing chamber  54  can consequently be diminished no further. Once the discharge operation is concluded, the finger rest  32  is guided back upward and released by the operator and is consequently forced upward by the tensioned spring rest spring  46 . Once the finger rest  32  has reached the upper actuating end position, the functional section  32   c  is located, once again, above the latch bosses  36   c  of the carrier  36  of the piston subassembly  18 . The latch bosses  36   c  are therefore forced outward back into a non-deflected position and thus reengage with the finger rest  32 . The starting state for a further actuation is thus achieved.  
         [0055]     It should particularly be emphasized with this first embodiment that the medium quantity in the dosing chamber  54  is not determined by the lower stroke end position, in which the latch bosses  36   c  disengage from the functional sections  32   c  of the finger rest  32 , but is instead defined by the setting from which the lower ends  40   b  of the piston packing  40   b  seal off the upper through bores  26   d  of the medium feed  26 . A particularly high dosing accuracy is thereby achieved, since the dosing accuracy is not dependent on the position in which the latch bosses  36   c  disengage from the functional sections  32   c,  which position varies to a certain extent. The second peculiarity of this embodiment lies in the fact that the discharge valve formed by the closing pin  34   d  and the annular surface  22   b  of the nose applicator  22  is not opened on a pressure-dependent basis. Instead, an opening of the discharge valve is compelled by the fact that the actuating ring  34   a  of the valve element  34  is forced downward directly by the finger rest  32 . The advantage with this solution is that the discharge valve does not need to be specially adapted for dispensers of different type and of different maximum pressure in the dosing chamber.  
         [0056]      FIG. 4  shows a second embodiment of a discharge apparatus of a dispenser according to the invention.  
         [0057]     Just like the first embodiment represented in FIGS.  1  to  3 , this second embodiment has four mutually displaceable subassemblies, an applicator subassembly  112  having a nose applicator  122 , a finger rest subassembly  114 , a discharge valve subassembly  116  and a piston subassembly  118  having a valve element  134 . With respect to the interaction of the finger rest subassembly  114  and the piston subassembly  118  in the coupling and decoupling of the subassemblies, the working method of this second embodiment is consistent with the working method of the embodiment of FIGS.  1  to  3 : When a finger rest  132  is pressed down, a cylindrical guide section  133 , fixedly connected to the finger rest  132  and having a functional section  133   c,  is forced jointly downward. This functional section  133   c  forces downward the piston subassembly  118 , which is operatively connected by a latch boss  136   c  to the finger rest subassembly  114 . Upon this—similarly to the first embodiment—an energy store spring  150  is compressed. Once a cylindrical decoupling web  122   b  is reached by the latch boss  136   c  in the course of the finger rest subassembly  114  being pressed down, the latch boss  136   c  is forced radially inward and thus enters a state decoupled from the functional section  133   c.  The piston subassembly  118  can then be forced upward by the energy store spring  150 , whereupon the volume of a dosing chamber  154  is reduced and the medium present therein is pressurized.  
         [0058]     This represented second embodiment differs from the first embodiment of FIGS.  1  to  3  particularly in respect of two aspects:  
         [0059]     On the one hand, the displacement of the valve element  134  with the closing pin  134   d  is pressure-dependent and the discharge valve is therefore pressure-activated, so that the discharge automatically takes place once a necessary limit pressure is reached in the dosing chamber. On the other hand, the actuating operation differs in terms of the process of filling the dosing chamber  154  with the medium.  
         [0060]     While the first embodiment of FIGS.  1  to  3  envisages that the dosing chamber  54 , as a result of the generated underpressure, is immediately filled in the course of the actuation, in this second embodiment it is envisaged that, as a result of the actuation, a pronounced underpressure or a vacuum is generated in the dosing chamber  154 , which is subsequently used, in the course of the actuation, to suck in the medium. For this purpose, a medium supply device  126 , in this second embodiment, is designed such that, in the starting position represented in  FIG. 4 , no connection exists between the dosing chamber  154  and a medium duct  126   b.  This is achieved by a configuration of a piston packing  140  belonging to the piston subassembly, which piston packing, in this starting position, bears with an inward-pointing sealing web  140   d,  which limits the dosing chamber  154  in the downward direction, flush against a sealing cylinder  126   f  adjoining the medium supply device at the top. In the course of the finger rest  132  being pressed down and of the piston packing  140  being displaced to the same extent, the dosing chamber  154  is enlarged with respect to its volume, the sealing web  140   d  terminating, over a first part-section of the movement, with the sealing cylinder  126   f.  Only once the piston packing  140  or the sealing web  140   d  of the piston packing  140  makes its way into the region of a through bore  126   e  of the medium supply apparatus  126  is a direct and uninterrupted connection established between the medium reservoir and the dosing chamber  154 . Due to the underpressure developed in the dosing chamber  154 , the medium flows at this moment out of the medium reservoir through the medium duct  126   b  into the dosing chamber  154 . After the latch boss  136   c  is forced inward against the decoupling web  122   b  and is freed from engagement with the functional section  132   c,  as the finger rest  132  continues to be pressed down, the piston subassembly  118 , and hence the piston packing  140 , darts upward under the action of the energy store spring  150 . At the moment in which the sealing section  140   d  comes back into the region of the sealing cylinder  126   f,  the dosing chamber  154  is separated from the medium reservoir. From this moment, the pressure in the dosing chamber  154  is increased as a result of the reduction in volume and the force subjected upon the cylinder subassembly. As soon as the pressure in the dosing chamber has exceeded a discharge limit value, the valve element  134 , and the closing pin  134   d  molded thereto, is forced downward counter to the spring force of a valve spring  148 , and the discharge operation commences through a discharge opening  122   a.  The discharge operation is continued until such time as the dosing chamber  154  is completely reduced in size and the pressure in the dosing chamber  154  has fallen below this limit value and the closing pin  134   d  of the valve element  134  seals off the discharge opening again.  
         [0061]     The peculiarity of this second embodiment lies in the manner in which the medium is conveyed into the dosing chamber. Differently than in the first embodiment, in which the conveyance commences simultaneously with the displacement of the piston packing  40 , in this second embodiment a vacuum or a pronounced underpressure is firstly developed in the dosing chamber  154 , which, in the further course of the actuation, leads to the conveyance of a defined quantity of the medium.  
         [0062]      FIG. 5  shows a third embodiment of a discharge apparatus of a dispenser according to the invention. This—just like the first two embodiments—has four mutually separate subassemblies. An applicator subassembly  212  having a nose applicator  222  is in this case fixedly connected, in a non-represented manner, to a medium reservoir. A finger rest subassembly  214  is arranged such that it is axially displaceable in the direction of a principal axis  210  relative to the applicator subassembly  212 . Within the applicator subassembly  212 , a discharge valve subassembly  216  and a piston subassembly  218  are arranged such that they are axially displaceable relative to the applicator subassembly  212 .  
         [0063]     The finger rest subassembly comprises a finger rest  232  and a cylindrical guide section  233  having an inward-jutting functional section  233   c.  The piston subassembly  218  consists of a carrier  236  and a piston packing  240 . The carrier  236  has, at the lower end, latch bosses  236   c,  which, in a non-deflected state, as represented in  FIG. 5 , are extended radially outward into the region of the functional section  233   c.  Above the piston packing  240  there is disposed a dosing chamber  254 , which is closed off in the upward direction by a wall insert  260  belonging to the applicator subassembly  212 . Through a through duct  240   e  in the piston packing  240 , the dosing chamber  254  is connected by a medium duct  226   b  to the medium reservoir (not represented in  FIG. 5 ). Above the through duct  240   e,  a ball seat valve  240   f  is provided, which is configured such that it closes when a pressure higher than that in the medium reservoir obtains in the dosing chamber  254 . The wall insert  260  which closes off the dosing chamber  254  in the upward direction separates the dosing chamber  254  from a pressure chamber  262 . Medium can make its way out of the dosing chamber  254 , via a second ball seat valve  260   a,  into this pressure chamber  262 . The second ball seat valve  260   a  is here configured such that it opens when the pressure in the dosing chamber  254  is greater than the pressure in the pressure chamber  262 . When the pressure in the pressure chamber  262  has exceeded a discharge limit pressure, a valve element  234  of the discharge valve subassembly  216  is displaced in the axially downward direction axially counter to an upward-acting spring force of a valve spring  248 , thereby enabling the medium to be sprayed through the discharge opening  222   a.    
         [0064]     The working method of this embodiment, as far as the generation of the pressure in the dosing chamber  254  is concerned, is broadly comparable with the first embodiment represented in FIGS.  1  to  3 . The finger rest  232 , once again, is pressed manually downward, whereupon the piston subassembly  218 , because of the coupling of the latch bosses  236   c  to the functional sections  233   c,  is likewise forced downward. As in the illustrative embodiment of FIGS.  1  to  3 , medium hence flows into the dosing chamber  254 , since the ball seat valve  240   f  opens due to the underpressure obtaining in the dosing chamber  254  as a result of the volume enlargement. Unlike the second described embodiment, the discharge valve is not, however, opened in dependence on the pressure obtaining in the dosing chamber  254 , but instead in dependence on a pressure obtaining in the pressure chamber  262 . When, following the decoupling of the latch bosses  236   c  from the functional sections  233   c  by means of decoupling sections  224   b,  a volume diminution of the dosing chamber and an accompanying pressure increase within the dosing chamber  254  takes place, medium is conveyed from the dosing chamber  254  into the pressure chamber  262 . Insofar as the pressure which is thereby created in the pressure chamber  262  is not yet sufficient to open the discharge valve, the medium present in the pressure chamber  262  remains in the pressure chamber  262  until a subsequent next actuation of the dispenser, since the valve  260   a  prevents the medium from flowing back into the dosing chamber  254  or into the medium reservoir. As long as the discharge valve does not open, the pressure within the pressure chamber  262  can consequently only keep on rising upon subsequent actuations of the discharge apparatus. Once the pressure in the pressure chamber  262  is high enough, each further actuation of the dispenser and each further quantity of the medium supplied via the dosing chamber  254  leads always to a discharge process. When the dispenser comprising such a discharge apparatus is first used, it has therefore to be actuated a few times until the pressure in the pressure chamber  262  is sufficient to effect a discharge operation.  
         [0065]     The advantage with the represented embodiment is that, as a result of the separation of pressure chamber  262  and dosing chamber  254 , the volume of the dosing chamber  254  in the non-actuated state is relatively small. The result of this is that the pressure in the dosing chamber rises very strongly in the course of the actuation. The pressure in the pressure chamber  262  increases incrementally with each actuation of the discharge apparatus, until such time as the limit pressure necessary to open the discharge valve is reached. In this way, very high discharge pressures and corresponding discharge characteristics of the dispenser are able to be attained.  
         [0066]     Due to its construction with two valves  240   f,    260   a,  the discharge apparatus represented in  FIG. 5  can therefore be superior to a discharge apparatus in which the pressure chamber and the dosing chamber are configured as a unitary and not a valve-interrupted chamber. In such a discharge apparatus, it has to be feared, in case of poor design, that the, in the course of actuation, increased pressure in a unitary dosing and pressure chamber results merely in a compression of the residual air present in the unitary dosing and pressure chamber, the pressure not being sufficient, however, to open the discharge valve. Upon the next actuation, this compressed air would be further decompressed and then recompressed, without any change in pressure ratios in the unitary dosing and pressure chamber compared with the previous actuation. Since the air cannot escape, however, it would not be possible to actually start using the dispenser.  
         [0067]      FIGS. 6   a  and  6   b  and  FIGS. 7   a  and  7   b  show a further embodiment of a dispenser according to the invention. The fundamental construction of this fourth embodiment of a dispenser according to the invention is consistent with the construction of the dispensers represented in FIGS.  1  to  5 , inasmuch as four mutually separated and axially mutually displaceable subassemblies are likewise provided, constituted by an applicator subassembly  312  fixedly connected to a medium reservoir and comprising a nose applicator  322 , a finger rest subassembly  314 , a discharge valve subassembly  316  and a piston subassembly  318 . The interaction of the finger rest subassembly  314 , the applicator subassembly  312  and the piston subassembly  318 , and the manner of the conveyance of the medium from the medium reservoir into a dosing chamber  354 , here broadly corresponds to the second embodiment represented in  FIG. 4 . The basic difference to this and all other above-described embodiments lies in the nature of the coupling and decoupling of the finger rest subassembly  314  to/from the piston subassembly  318  in the course of the actuation of the dispenser, and in the motional sequence of the piston subassembly  318  following the decoupling from the finger rest subassembly  314  in the second, lower stroke end position.  
         [0068]      FIGS. 6   a  and  6   b,  on the one hand, and  FIGS. 7   a  and  7   b,  on the other hand, respectively show a state of the discharge apparatus, once in a sectioned side view and once in a likewise sectioned view from diagonally above.  
         [0069]     In the represented embodiment, the finger rest subassembly  314  comprising a finger rest  332 , the applicator subassembly  312  and the piston subassembly  318  are configured such that the movement of the piston subassembly  318  from a second, lower stroke end position into a first, upper stroke end position is realized in the form of a translatory motion in the direction of a principal axis  310 , with simultaneous rotary motion about the principal axis  310 . While the finger rest subassembly  314  is connected to the applicator subassembly  312  in a rotationally secure manner, so that the finger rest subassembly  312 , relative to the applicator subassembly, has only a translatory degree of freedom in the axial direction, the piston subassembly  318  is guided with restricted rotatability on a cylindrical outer surface of a medium supply apparatus  326 .  
         [0070]     The concrete configuration and the advantages of the coupling and decoupling apparatus of the embodiment represented in  FIGS. 6   a  to  7   b  are described below.  
         [0071]     The applicator subassembly  312  has a cylindrically configured guide section  324   c,  which is molded onto a screw fastening  324  and the inner side of which is provided with a sawtooth profiling  366 . The sawtooth profiling  366  consists of individual sawteeth  368 , which, respectively, are mutually separated by grooves  370  extending in the direction of the principal axis  310 . The sawteeth  368  respectively have a vertical flank  368   a,  extending in the direction of the principal axis  310 , and a screw-section-shaped control cam flank  368   b,  configured as a control cam and lying opposite the vertical flank  368   a.  The sawteeth are respectively identically aligned, so that the control cam flanks  368   b,  if the control cylindrical section is viewed in the direction of the principal axis  310 , are either all in clockwise alignment or all in counterclockwise alignment.  
         [0072]     The piston subassembly  318  has a piston packing  340  and a carrier  336 . Molded onto the carrier  336  are a total of six vanes  372  extending radially outward, which are spaced 60° apart and have a radial length which makes them jut into the grooves  370 . The vanes  372  have a rectangular cross-sectional area, two parallel, mutually opposing support surfaces  372   a,  corresponding with the grooves  370  in the sawtooth profiling  366 , being realized perpendicularly and parallel to the principal axis  310 . A third, diagonally upward pointing contact surface  372   b  is inclined by an angle of about 60° relative to the principal axis  310 , the alignment of this contact surface  372   b  corresponding with the opposite control cam flanks  368   b  of the sawteeth  368 .  
         [0073]     The finger rest  332  has a total of twelve circularly arranged pusher arms  332   e,  respectively spaced 30° apart, which respectively extend identically from the principal axis  310 , at a distance apart in the direction of the principal axis  310 , from above into the guide cylinder section  324   c  of the applicator subassembly  312 . At their end, the pusher arms  332   e  respectively have a contact surface  332   f,  which is tilted relative to the principal axis  310  to the same degree as the contact surfaces  372   b  of the vanes  372  of the carrier  336 . Their direction of tilt herein corresponds to the direction of tilt of the control cam flanks  368   b  of the sawteeth  368 .  
         [0074]     As already explained above, the finger rest  332  and the applicator subassembly  312  are mutually connected in a rotationally secure manner. For this purpose, on the screw fastening  324  belonging to the applicator subassembly  312 , a groove  324   d  is provided, in which a securing section  332   g  of the finger rest  332  engages. The rotational position of the finger rest relative to the guide section  324   c  is defined such that each pusher arm  332   e  is assigned a groove  370  and lies opposite this groove.  
         [0075]     The carrier  336  is represented in  FIGS. 6   a  and  6   b  in its first, upper stroke end position. The six vanes  372  of the carrier  336  extend radially outward into the grooves  370  in the sawtooth profiling  366 . Since the vanes  372  are spaced respectively 60° apart and the grooves  370  are spaced respectively 30° apart, a vane  372  of the carrier  336  is present in only every second groove  370  in each case. The finger rest  332  is in its upper actuating end position. In this upper actuating end position, the pusher arms  332   e  extend downward into the guide cylinder section  324   c  and there bear with their contact surfaces  332   f  flush against the contact surfaces  372   b  of the vanes  372  of the carrier  336 .  
         [0076]     Starting from this starting position, a depression of the finger rest  332  results in the carrier  336 , too, being forced downward, since six of the contact surfaces  332   f  of the pusher arms  332   e  press upon the contact surfaces  372   b  of the vanes  372  of the carrier  336 . Apart from the force which hence acts upon the carrier  336 , downward in the direction of the principal axis  310 , the force applied via the finger rest  332  and the pusher arms  332   e  also causes a torque to be generated, since the carrier  336 , in accordance with the alignment of the contact surfaces  372   b,    332   f  and due to its subjection to an upwardly directed spring force by an energy store spring  350 , attempts to slide off from pusher arms  332   d.  This sliding-off is prevented, however, by the vertical tooth flanks  368   a  of the sawteeth  368  of the sawtooth profile  366 . Through the depression of the finger rest  332 , the piston subassembly  318  is therefore forced down to the same extent, without any possible change in the rotational position of the piston subassembly  318 .  
         [0077]     During the depression of the finger rest and of the piston subassembly  318 , an underpressure or vacuum comes to be generated in the dosing chamber  354 , in the same manner as described in relation to the second embodiment, represented in  FIG. 4 , whereafter medium, after having reached a through bore  326   b  through a sealing web  340   d  which closes off the dosing chamber  354  in the downward direction, proceeds to flow into the dosing chamber  354 .  
         [0078]     If the finger rest  332 , jointly with the piston subassembly  318 , is pressed downward to the point where the upward-pointing edges  372   c  of the vanes  372  of the carrier  336  level with the downward-pointing tips  368   c  of the sawteeth  368  are reached, the anti-twisting protection for the carrier  336  is no longer present. In a spiral motion, the vanes  372  of the carriers  336  then slide out of engagement with the pusher arms  332   e  and onto the control cams  372   b  of the sawteeth  368 . On the control cams  372   b,  the vanes  372  of the carrier  336 , upon simultaneous rotation of the carrier  336 , then slide on as far as the setting represented in  FIGS. 7   a  and  7   b.  This produces a diminution of the volume of the dosing chamber  354  and a pressure increase in the medium present therein, so that, in the same manner as in the other embodiments, a discharge operation is initiated. If the finger rest  332  is then returned to its upper actuating end position, the vanes  372  slip back into their starting position in the grooves  370 .  
         [0079]     Compared with the first to third embodiments, this fourth embodiment has two basic advantages: The represented motional sequence of the carrier  336 , and hence of the piston packing  340 , leads to a retarded intake stroke in the course of the return stroke motion, by which it is ensured that the filling of the dosing chamber  354  is concluded before the dosing chamber  354  is separated from the medium reservoir by the sealing web  340   d  of the piston packing  340 . This retarded motional sequence ensures that an underpressure is not maintained in the dosing chamber  354  if, at the same time, the target dosage is not reached. The second basic advantage lies in the fact that—unlike in embodiments 1 to 3—no elastic deformation of components is necessary for the coupling/decoupling of the piston subassembly  318  to and from the finger rest  332 . The risk of failure of the discharge apparatus, through wear, or breakage of a latch boss or some other elastic component, is thereby reduced.