Patent Publication Number: US-11046503-B2

Title: Liquid dispenser for dispensing a liquid, having an additional reservoir for an additional medium

Description:
APPLICATION FIELD AND PRIOR ART 
     The invention relates to a liquid dispenser which has a liquid reservoir with a main liquid and has an additional medium which is mixed with the main liquid in the course of dispensing the liquid. 
     A corresponding demand exists if the main liquid and the additional medium as two components may be mixed only directly before being dispensed, because the action of the mixed liquid would be reduced if the additional medium were provided already mixed with the main liquid. Above all, however, there arises a corresponding demand if the additional medium should allow the possibility of dispensing an individual mixture on the basis of the same main liquid, that is to say, with the same liquid dispenser, the possibility of producing and dispensing optionally different mixtures with the addition of different additional media. 
     U.S. Pat. No. 3,593,894 A discloses a dispenser which has a mixing chamber which can be screwed on for the purpose of introducing an additional medium. 
     JP H02-160068 A discloses a dispensing head into which an additional medium of tablet form type is inserted in order to deliver an additional medium to a liquid as the latter flows through. 
     EP 1166885 A1 discloses a dispensing head which has a receiving space into which an additional medium of tablet form type can be inserted. 
     OBJECT AND ACHIEVEMENT 
     The object of the invention is to develop a liquid dispenser of the type in question to the effect that an additional medium can be admixed with the main liquid in a convenient and hygienically satisfactory manner and the possibility is provided of also using optionally different additional media. 
     What is proposed according to the invention for this purpose is a liquid dispenser which has a liquid reservoir filled with a main liquid, wherein the liquid reservoir is designed either as a pressure reservoir and has a switching valve by means of which the main liquid can be conveyed from the liquid reservoir to a reservoir outlet, or is designed as a pressureless liquid reservoir and has a conveying device by means of which the main liquid can be conveyed from the liquid reservoir to a reservoir outlet. 
     In order to dispense liquid, the liquid dispenser has a dispensing head which has a dispensing opening. A dispensing duct connects the dispenser outlet of the liquid reservoir, that is to say a duct portion of the liquid reservoir beyond the switching valve or the conveying device, to the dispensing opening. 
     The dispensing head can be pressed down to actuate the switching valve or the conveying device. As a result, main liquid is discharged at the reservoir outlet of the liquid reservoir and flows into the dispensing duct of the outlet head up to its dispensing opening, from where the discharge takes place. 
     According to the invention, the liquid dispenser has an interchangeable exchange unit which, in a functional state, forms the dispensing duct at least in certain portions. This exchange unit comprises a mixing chamber in which an additional medium is arranged. The mixing chamber is as intended traversed by the flow of the main liquid during a dispensing operation, which liquid here flows via an inlet into the mixing chamber, is mixed in the mixing chamber with the pulverulent, solid or liquid additional medium and flows out of the mixing chamber again through the outlet separated from the inlet. The mixing chamber is thus arranged in the dispensing duct in such a way that the inlet is communicatively connected with the reservoir outlet, and the outlet is communicatively connected with the dispensing opening. 
     In a storage state prior to use by the end user, the exchange unit has closures at the inlet and at the outlet by means of which the mixing chamber is closed in a fluid-tight manner in a storage state. These closures are opened as intended in the course of the preparation or use of the liquid dispenser. Until then, however, they isolate, the additional medium in the mixing chamber on the inlet and outlet sides of the mixing chamber with respect to the surroundings, with the result that neither a leakage or the like nor a short-term impairment of the medium by contact with surrounding air has to be feared. 
     With the exception of said inlet and outlet, the mixing chamber of the exchange unit is not accessible without destruction. Filling or refilling by the end customer is not intended. In particular, apart from the inlet and the outlet, the mixing chamber is delimited by walls which are formed in one piece with one another. 
     The liquid reservoir with the switching valve or the conveying device and also the reservoir outlet of the liquid reservoir are intended for multiple use with a plurality of exchange units, with the result that the liquid volume of the main liquid is at least double the volume of the additional medium or in particular the additional liquid in the mixing chamber. The volume is preferably between 100 ml and 500 ml. 
     Many different designs are possible to the effect that some constituent parts, apart from the liquid reservoir, are part of the reusable unit intended for multiple use and some are part of the exchange unit. A distinction that should be drawn in principle between designs in which the dispensing head as a whole forms the exchange unit and those in which the dispensing head is configured as a reusable constituent part of the dispenser and designed for coupling to interchangeable exchange units. 
     In a first preferred embodiment, the reservoir outlet is designed as an outlet connector. The exchange unit is intended for coupling thereto, for which purpose it is designed as a complete dispensing head and has a coupling connection which is designed for coupling to the outlet connector. A communicative connection with the inlet of the mixing chamber is created as a result. 
     Accordingly, in such a configuration, the exchange unit is designed in such a way that it comprises the entire dispensing duct from the coupling connection to the dispensing opening, with the mixing chamber being provided between the coupling connection and dispensing opening. In such a configuration, the two closures assigned to the outlet and the inlet of the mixing chamber can be provided directly on the dispensing opening and on the coupling connection, with the result that the dispensing duct as a whole forms the isolated mixing chamber. 
     In the configuration described, the entire dispensing head is exchanged as an exchange unit. In the storage state, before the mounting on the reservoir outlet, the closures are closed. Before or during the mounting on the reservoir outlet, the inlet-side closure is preferably opened. In the course thereof, or upon first actuation, the outlet-side closure is then likewise opened. 
     A very high degree of hygiene is ensured as a result of the complete exchange of the dispensing head, since all fluid-conducting parts which conduct the mixture of main liquid and additional medium are exchanged. In addition, the mounting of a dispensing head forming the exchange unit is very simple and intuitive, since all that is required is a mere placement of the dispensing head. 
     In alternative configurations, the dispensing head is provided in principle for reuse and is, if required, connected to an exchange unit. In some such variants, such a dispensing head has a receiving space which is designed for receiving the exchange unit. A feed duct portion of the dispensing duct, which forms a part of the dispensing head, opens into this receiving space. The exchange unit is designed in such a way that, upon insertion into the receiving space, it assumes a desired position in which the mouth of the feed duct portion comes into communicative connection with the inlet of the mixing chamber of the exchange unit. 
     Accordingly, the main liquid flows from the reservoir outlet into a feed duct portion of the dispensing duct which opens into the receiving space of the dispensing head. The exchange unit is positioned therein and secured in a force-fitting or form-fitting manner. The feed duct portion bears flush at the inlet or an inlet duct such that the liquid does not pass into an intermediate region between walls of the receiving space and outer walls of the exchange unit and the latter thus remains clean for reusability. 
     The receiving space preferably has an opening element which is arranged and designed so as to be adapted to the exchange unit in such a way that, by introducing the exchange unit into the receiving space or by closing a closing element which closes the receiving space, the closure at the inlet of the mixing chamber or the closure at the outlet of the mixing chamber is destructively opened. 
     Such an opening element comes, in the course of insertion, into mechanical contact with one of the closures and opens said closure as a result. The opening element is preferably designed to be pointed or with a sharp edge such that it can as it were puncture or cut the closure. The opening element is preferably produced from plastic, but can also be of metallic design. 
     As will be described in more detail below, the closure can be in particular a thin-walled surface portion which is injection-molded directly on the housing of the exchange unit or can be a separate thin-walled and/or film-like surface portion. 
     The receiving space can be configured as a receiving space which completely isolates the exchange unit from view. In such a configuration, there can be provision in particular that the dispensing head has a closing element which delimits the receiving space and which is movable between a closed position and an open position with respect to a basic component of the dispensing head. 
     Alternatively, the receiving space can be designed as a receiving shaft which is open at least on one side from an outer side of the dispensing head and into which the exchange unit can be inserted in an insertion direction. For this purpose, the reusable part of the dispensing head requires no relatively movable part such as the aforementioned closing element. For insertion purposes, the shaft can be oriented counter to the dispensing direction of the dispensing opening, in particular in a configuration in which the dispensing opening is provided on the exchange unit. Alternatively, for insertion of the exchange unit, the shaft can be formed in the dispensing direction, with it being the case, in a particular configuration, that the shaft can be formed as a continuous shaft in which the insertion of the exchange unit is provided in the dispensing direction. The exchange unit can then project through the shaft and directly have the dispensing opening. 
     The insertion direction is preferably oriented nonparallel to the actuating direction such that an inadvertent actuation during insertion is improbable. An angle of approximately 90°, in particular between 75° and 105°, is preferred. 
     In another possible configuration, there is provision that the liquid dispenser has a dispensing head which has an outer connection piece for coupling the exchange unit. 
     In such a configuration, the exchange unit is accordingly mounted on the outer side of the dispensing head provided for reuse, thereby making mounting very straightforward. The exchange unit and the connection piece are preferably configured to interact in a force-fitting or latching manner, with the result that the exchange unit can be snapped onto the housing of the dispensing head against a slight resistance and can be removed after use. 
     It is particularly advantageous if the connection piece itself is designed for use as a dispensing opening and it is additionally provided that the exchange unit has a dispensing opening which is communicatively connected with the outlet of the mixing chamber in the exchange unit. This configuration allows the dispensing head to be used with and without an exchange unit. If an exchange unit is fastened to the connection piece, its dispensing opening forms the dispensing opening of the liquid dispenser. The liquid flows through the connection piece into the exchange unit, is mixed there with the additional medium and is then dispensed in mixed form through the dispensing opening. If no exchange unit is fastened to the connection piece, the unmixed main liquid is dispensed directly through the connection piece then acting as a dispensing opening. 
     Embodiments in which the dispensing opening is part of the exchange unit are also possible and expedient in other types of exchange units. What is common to such configurations is that the exchange of the exchange unit also leads to the exchange of all parts which have come into contact with the additional medium. Such a configuration is therefore particularly expedient for applications in which different types of additional medium are used as intended or customarily with the same liquid dispenser. 
     A further advantageous possibility for realizing the invention provides that the liquid dispenser has a dispensing head which has a coupling connector, facing the liquid reservoir, on the dispensing duct pointing in the direction of the liquid reservoir. The exchange unit likewise has a coupling connector which is designed for coupling to said coupling connector of the dispensing head, wherein the exchange unit-side coupling connector is communicatively connected with the outlet of the mixing chamber. Furthermore, the exchange unit has an inlet connector which is designed for communicative connection with the reservoir outlet of the liquid reservoir. 
     In such a configuration, there is provision that the exchange unit is inserted between the dispensing head, which is intended for reuse, and the liquid reservoir, wherein the outlet is connected to the coupling connector of the dispensing head and the inlet is connected to the reservoir outlet. For the purposes of replacement, the dispensing head is removed and then the used exchange unit is removed from the dispensing head or the reservoir outlet. A new exchange unit is then plugged onto the dispensing head or the liquid reservoir, and the dispensing head and the liquid reservoir are reassembled with the exchange unit arranged therebetween. 
     In a configuration of the liquid dispenser with a receiving space for receiving the exchange unit, a configuration is considered to be particularly advantageous in which the mixing chamber of the exchange unit is delimited at least partially and preferably, with respect to the area, for the most part by film walls. Such an exchange unit can be produced in a particularly favorable manner. The film wall can comprise a single plastic wall. Of advantage, however, is a combination of film layers which together ensure that the additional medium is stored in an aging-resistant manner. Depending on the type of the additional medium, different layers, possibly also metallic foil layers, can be expedient. 
     It is particularly advantageous if the exchange unit has a rigid portion. The exchange unit is then constructed as a type of composite unit from a flexible bag-like portion and a rigid portion which is adjoined by the flexible portion. The exchange unit and in particular its rigid portion are preferably adapted to the receiving space in such a way that the rigid portion can be fixed in a defined position at the receiving space in a form-fitting manner. This facilitates the insertion of the exchange unit and ensures a precise orientation as is required for the opening of the closure assigned to the inlet and/or outlet. 
     In a particularly advantageous variant, the rigid portion is penetrated on the inlet side or outlet side by the dispensing duct. The outlet duct on the inlet or outlet side is accordingly likewise precisely positioned by the positioning of the rigid portion in the receiving space, thus serving for the connection to dispensing head-side portions of the dispensing duct or the precise positioning of the dispensing opening as part of the rigid portion. 
     There are various possibilities for configuring the closures of the mixing chamber on the outlet and inlet side. Possible and preferred configurations here are in particular configurations in which a thin and preferably film- or membrane-like closure surface is provided which is either destroyed in the course of insertion of the exchange unit and the first actuation or removed. 
     Also possible, however, are closures in the manner of switching valves which are brought into a stable opening state upon being put into operation. Particularly preferred here is a configuration in which the exchange unit has two sub-units which can be displaced relative to one another once for the purpose of activation, wherein the closure at the inlet and/or at the outlet of the mixing chamber is designed as a sliding valve which is opened by the relative movement in the course of the activation. In order to transfer the valve, in particular said sliding valve, into an opening state, a pressure surface, by means of which the sub-units can be displaced relative to one another, is preferably provided on an outer side of the exchange unit, particularly preferably on an outer side of the exchange unit designed as a dispensing head. It is thus directly evident from the exchange unit whether it has already been used or is still unopened. The pressure surface can also correspond with an actuating surface of the dispensing head such that a uniform movement opens the exchange unit and initiates the dispensing operation. 
     A number of configurations are possible for said thin and preferably film- or membrane-like closure surfaces, with it being possible also to provide different types of closure surfaces and/or types of said switching valves for the inlet and the outlet. 
     Thus, the closure at the inlet and/or at the outlet of the mixing chamber can be configured with a peel-off film. Such a peel-off film usually has an adhesive side by means of which it is adhered to a surface breached by the dispensing duct on the inlet side or outlet side. The peel-off film preferably further has a free portion which does not stick to the surface and can therefore be easily gripped for the purpose of detaching the peel-off film. 
     Another form of such a closure is provided by a closure surface which, in the course of placing the exchange unit on the reservoir outlet or the connection piece, is destroyed by an opening element. In such a configuration, there is provision that the opening element, which is preferably configured to be at least partially sharp-edged, is arranged in the installed or attached state of the exchange unit at a point where previously the closure surface of the exchange unit was arranged. During the movement of the exchange unit into the intended position, the opening element therefore comes into contact with the closure surface and punctures, tears or breaks it. 
     A closure surface provided for destruction can preferably be formed with local weakenings in order to ensure defined bursting. 
     In a particular embodiment with an opening element in the receiving space, the receiving space and the exchange unit are designed in terms of their outer shape in such a way that, upon insertion of the exchange unit into the receiving space, an elastic stress is generated in walls of the receiving space and/or of the exchange unit and, upon continued insertion, is unloaded in such a way that the opening element is pressed against and destroys the closure surface as a result. 
     In such a configuration, there is accordingly provision that, as a result of the shaping of the exchange unit and receiving space, the insertion of the exchange unit leads to a provisional storage by elastic deformation which, toward the end of the insertion movement, supports the latter and thus ensures that the opening element strikes the closure surface with an increased force impact. Such a configuration is particularly also expedient when both a closure surface at the inlet and at the outlet is intended to be destroyed during the same insertion movement. 
     A further way for a closure surface, which delimits the mixing chamber of the exchange unit on the inlet or outlet side, provides that the closure surface is configured in such a way that it can be destructively opened by means of an opening pressure which is less than the pressure which can be generated by the pressure reservoir or by the conveying device. The pressure from the pressure reservoir or the conveying device is accordingly sufficient to destroy the closure surface as intended. Such a closure surface can therefore remain intact until first actuation of the liquid dispenser with a previously unused exchange unit. However, as soon as pressurized liquid from the liquid reservoir side presses against the closure surface, the latter is destroyed such that the liquid can pass through. 
     In the case of a pressure reservoir, the maximum liquid pressure depends solely on the structural design of the pressure reservoir and the pressure built up therein at the factory. In the case of a manually actuated conveying device in the manner of a pump, the maximum pressure is, where appropriate, dependent on the actuating force. In such a case, said closure surface is preferably designed such that it can be destroyed by pressing down the dispensing head with a constant 20 newtons, preferably with a constant 10 newtons. 
     The invention relates primarily in the described manner to a liquid dispenser of said type which comprises the reusable unit, comprising the liquid reservoir and, where appropriate, a reusable dispensing head, and an exchange unit having said closures, wherein the closures are still intact in the delivery state and are opened first by the end consumer. 
     Such a dispenser is preferably intended to be used successively with a plurality of structurally identical exchange units having the same or different additional media. The invention therefore also relates to a corresponding set, which comprises the liquid dispenser of the type described and at least one additional exchange unit, with the result that at least two structurally identical exchange units are part of the set. 
     To supplement a liquid dispenser already acquired previously, the exchange units can preferably also be acquired separately individually or multiply, with the result that the separate exchange units of the type described, individually or in sets of at least two exchange units, are also understood as part of the invention. 
     Preferred intended applications of a liquid dispenser according to the invention are in particular skin and hair care. For the field of skin care, it is considered to be advantageous if the main liquid in the liquid reservoir is a skin cream or lotion, in particular for face care. The exchange units can then be used to individualize the skin cream to suit the personal needs of the skin, for example with active ingredients which, in a targeted manner, treat different effects of skin aging, such as wrinkles, an uneven skin or enlarged skin pores. A similar purpose is served by the use of exchange units which are filled with a tanning medium in different quantities or with different effects in order, during a treatment with tanning cream, to achieve only a gentle change instead of a very short-term change. In the field of hair care products, the main liquid can be a shampoo, a conditioner or an intensive hair treatment which is individualized via the exchange units, for example with additional media for improving hair shine, for avoiding dandruff formation or for treating/calming the scalp. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further advantages and aspects of the invention will emerge from the claims and from the following description of preferred exemplary embodiments of the invention which are explained below with reference to the figures. 
         FIGS. 1 and 1A and 1B  show a first liquid dispenser according to the invention and the steps for putting it into operation. 
         FIG. 2  shows a dispensing head for a second liquid dispenser according to the invention. 
         FIGS. 3 and 3A and 3B  show a third liquid dispenser according to the invention and the steps for putting it into operation. 
         FIGS. 4 and 4A to 4C  show a fourth liquid dispenser according to the invention and the steps for putting it into operation. 
         FIGS. 5A to 5C and 6A to 6D  show a dispensing head for a fifth liquid dispenser according to the invention and the steps of putting it into operation. 
         FIGS. 7A to 7D  show a dispensing head for a sixth liquid dispenser according to the invention and the steps for putting it into operation. 
         FIGS. 8A to 8C  show a dispensing head for a seventh liquid dispenser according to the invention and the steps of putting it into operation. 
         FIGS. 8AA, 8BB and 8CC  are cross-sectional views of the dispensing head for the seventh liquid dispenser which respectively correspond to  FIGS. 8A, 8B and 8C . 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
       FIGS. 1 and 1A and 1B  show a first exemplary embodiment of the invention. The liquid dispenser  100  according to the invention comprises a liquid reservoir  110  having a reservoir outlet  120 . Pressing down the reservoir outlet  120  in the form of an outlet connector  122  in the direction of the arrow  2  makes it possible for a switching valve  112 , which is merely indicated in  FIG. 1 , to be switched, with the result that the liquid, which was previously already under pressure, can be delivered through the reservoir outlet  120 , which is designed as a hollow connector, out of the liquid reservoir  110  in the direction of a dispensing head  10 . 
     In addition to a housing  15  and a dispensing opening  12 , which penetrates through the housing  15 , the dispensing head  10  comprises a sleeve-shaped component  21  which delimits a mixing chamber  22  and at which, with reference to  FIG. 1A , in a delivery and storage state, there is provided, on both sides of the mixing chamber  22 , in the region of an inlet  23  and an outlet  24 , a respective closure  90 ,  92  having a closure surface  91 ,  93 . At the lower end of the sleeve-shaped component  21 , the latter has a coupling connection  26  which is designed for coupling to the outlet connector  122 . The housing  15  and the sleeve-shaped component  21  are fixedly connected to one another and could also be formed in one piece. 
     There is provision as intended that, in a dispenser as shown in  FIGS. 1 to 1B  a main liquid or carrier liquid can be repeatedly discharged from the liquid reservoir  110  by pressing down the dispensing head  10 . This liquid is as intended discharged together with an additional medium which, in the delivery and storage state of  FIG. 1A , is situated in the mixing chamber  22 . The dispensing head  10  as a whole constitutes an exchange unit  20 , with different exchange units  20  having different additional media in the mixing chamber  22  customarily being held available. As intended, an actuation occurs after coupling the dispensing head  10 , which forms an exchange unit  20 , to the outlet connector  122 , by means of which actuation the main liquid is conveyed from the liquid reservoir  110  in the direction of the dispensing duct  14  and toward the dispensing opening  12 . Here, the liquid flows through the mixing chamber  22  and is mixed here with the additional medium previously stored therein. 
     Since the exchange units  20  in the form of the dispensing heads  10  are intended to maintain an isolation of the mixing chamber  22  and of the additional medium situated therein over a relatively long storage period, said closures  90 ,  92  are provided. The closure  90  provided on the inlet  23  side comprises a closure surface  91  which can be formed in one piece with the sleeve  21  or is incorporated as a separate component. As is evident by way of the transition from the state of  FIG. 1A  to the state of  FIG. 1B , the placement of the dispensing head  10  on the outlet connector  122  leads as intended to the closure surface  91  being breached. This is illustrated in  FIG. 1B . 
     The closure  92  having the closure surface  93  on the outlet  24  side of the mixing chamber  22  is, however, still intact at this time. However, as soon as the dispensing head  10  is pressed down in the direction of the arrow in the manner illustrated in  FIG. 1 , there occurs an over pressure in the mixing chamber  22  by which the closure surface  93  is destroyed, with the result that now the dispensing duct  14  with the mixing chamber  22  integrated therein provides for free dispensing. The fact that only the overpressure opens the mixing chamber on the outlet side promotes the mixing between the additional medium previously stored in the mixing chamber  22  and the main liquid, which flows via the inlet  23  into the mixing chamber  22 . 
     The exemplary embodiment of  FIG. 2  differs from the exemplary embodiment of  FIG. 1  in that the housing  15 , as main constituent part of the dispensing head  10 , is provided for reuse. In this exemplary embodiment, the exchange unit  20  is formed solely by the sleeve  21  and the mixing chamber  22  with inlet  23  and outlet  24 , the mixing chamber surrounding said sleeve and being filled with additional medium. 
     Unlike in the exemplary embodiment of  FIGS. 1 to 1B , for putting into operation, the exchange unit  20  is accordingly coupled in the region of a coupling connector  30  to a coupling connector  18  of the dispensing head  10  by plugging, and the combination of the dispensing head  10  or its housing  15  and the exchange unit  20  is coupled jointly to the outlet connector  122  with the use of an inlet connector  32 . However, the manner of opening the closures  90 ,  92  at the inlet  23  and outlet  24  remains identical. 
     In the embodiment as shown in  FIG. 3 , there is provision, first of all by way of example as a difference, that the liquid reservoir  110  is not designed as a pressure reservoir, but instead as a pump reservoir having a schematically illustrated conveying device  114  in the manner of a pump which can be actuated by pressing down the dispensing head  10  in the actuating direction  2  and then conveys liquid from the liquid reservoir  110  to the reservoir outlet  120 . 
     The dispensing head  10  in this embodiment has the particular feature that use can be made of a dispensing opening  12  provided on the housing  15  of the dispensing head without fastening an exchange unit  20  on the dispensing head  10 . 
     However, an exchange unit  20  can also be used. The latter is pushed from outside onto a connection portion  11  in the manner illustrated by  FIGS. 3A and 3B  where it is held by a latching connection. As can be seen from  FIG. 3B , when pushing the exchange unit  20  onto the connection portion  11  the latter is inserted into the exchange unit  20  to such an extent that it opens the closure  90  at the inlet side  23  by destroying the closure surface  91 . On the outlet  24  side, however, the closure  92  with the closure surface  93  remains first of all intact. In a corresponding manner to the preceding exemplary embodiment, there is provision here too, that the closure surface  93  at the closure  92  is destroyed only upon first actuation, since the conveying device  114  is designed to make available a sufficiently high pressure to allow opening when the dispensing head  10  is pressed down in the direction of the arrow  2  with at least 10 newtons of actuating force. 
     In the exemplary embodiment of  FIG. 4 , there is provision as a particular feature that the housing of the dispensing head has a base  17 A and a closing element  17 B which can be folded with respect to the latter about a film hinge, said base and closing element together delimiting a receiving space  16 . 
     The exchange unit  20  in this exemplary embodiment can be readily seen from  FIG. 4A . The exchange unit  20  has a mixing chamber  22  which is surrounded by a flexible film wall  36 , wherein the membrane is fastened to a rigid portion  38  which is penetrated by part of the dispensing duct  14  and at whose end the dispensing opening  12  is provided. To put the liquid dispenser  100  as shown in  FIG. 4  into operation, the receiving space  16  is made accessible by tilting up the closing element  17 B, and the exchange unit  20  is inserted in such a way that an annular web  38 A on the rigid portion  38  engages in a corresponding groove  13  on the two housing parts  17 A,  17 B. In this state, and corresponding to the illustration of  FIG. 4B , the receiving space  16  is closed, with the result that the bag, surrounded by the film wall  36 , having the mixing chamber  22  is pressed, in the region of an inlet-side closure  90  with closure surface  91 , against an opening element  80  and is thereby opened, as illustrated in  FIG. 4C . If the first actuation now occurs by pressing down the dispensing head  10 , liquid flows out of the liquid reservoir  110  into the mixing chamber  22 , here fills up a sufficiently high pressure and, through this pressure, destroys the closure surface  93  of the outlet-side closure  92 , with the result that the dispensing duct  14  is then free of barriers and the liquid of the reservoir outlet  120 , with the addition of the additional medium from the mixing chamber  22 , is conveyed to the dispensing opening  12 . 
       FIGS. 5A to 5C and 6A to 6D  show a further variant of a dispensing head  10  of the type according to the invention. As illustrated in  FIGS. 5A to 5C , there is provision here that the dispensing head  10 , which, apart from the insertable exchange unit, is provided for reuse, has a receiving space  16  in the form of a receiving shaft  16 A. Here, the exchange unit  20  is inserted transversely to the actuating direction  2  in the direction of the arrow  4  such that a dispensing opening  12  provided on the exchange unit  20  reaches as far as the opposite side during the insertion. The inserted state can be seen in  FIG. 5B . At this time, an inlet-side closure in the mixing chamber  22  has already been opened, as will be explained below. All that therefore remains is to open the closure  94  by removing the closure surface formed as a peel-off film  95 . 
     It can be seen from  FIGS. 6A to 6D  how the closure  90  is opened on the inlet  23  side. If in the manner illustrated in  FIG. 6B , the exchange unit  20  is inserted into the receiving shaft  16 A, it hereby deforms part of the housing  15  of the dispensing head  10 . As soon as the exchange unit  20  has been inserted far enough, namely approximately up to the position of  FIG. 6C , this deformation ceases again since now an opening element  80  on the housing  15  of the dispensing head  10  that has been temporarily deflected can spring back into its original position and thereby destroy the closure surface  91  of the closure  90  on the inlet  23  side of the mixing chamber  22 . Finally, starting from the state of  FIG. 6C , which corresponds to the state of  FIG. 5B , the peel-off film  95  at an end  96  is manually removed such that the dispensing duct  14  is free and dispensing of the main liquid and the addition of the additional medium from the mixing chamber  22  can occur. 
       FIGS. 7A to 7D  show a further embodiment, which can be regarded as a variant to the embodiment of  FIG. 5A to 6D . In this embodiment, the dispensing opening  12  is not, as in the preceding variant, part of the exchange unit  20  but provided on the housing  15  of the dispensing head  10 . Just as for opening the closure  90  on the inlet  23  side, on this housing of the dispensing head  10  the dispensing opening  12  is also assigned an opening element  80  which is intended to destroy a corresponding closure surface  91  on the outlet  24  side of the mixing chamber  22 . 
     If the exchange unit  20  is inserted in the manner illustrated in  FIG. 7B  in the direction of the arrow  4 , there is here again reached an intermediate state of  FIG. 7C , starting from which the elastic deformation that has taken place until then can be relieved again. Here, however, the exchange unit  20  is pressed further to the left, with the result that the closure surfaces  91  on the inlet  23  side and the outlet  24  side of the mixing chamber  22  are destroyed approximately simultaneously by the respective opening elements  80 . As a result, the state of  FIG. 7D  is achieved, in which the dispensing duct is free and it is possible for mixed liquid to be dispensed. 
     In the exemplary embodiment of  FIGS. 8A to 8C  there is merely shown a dispensing head  10  which simultaneously as a whole forms the exchange unit  20  and is thus provided for placing on a liquid reservoir corresponding for example to  FIGS. 1 and 3 . There is in this respect a certain degree of correspondence with the exemplary embodiment of  FIGS. 1 to 1B , in which the entire dispensing head likewise constitutes the exchange unit. 
     The particular feature of the dispensing head  10  of  FIGS. 8A to 8C  and  FIGS. 8AA, 8BB and 8CC  is that it is composed of two components  39 ,  40  as a two-part exchange unit  20 , with component  39  being the main component which is fastened on the outlet connector  122  of the liquid reservoir. The other component  40  of the exchange unit  20  has approximately the shape of an inverted bowl and is blocked off at its underside by a closure  90  having a closure surface  91 . However, an outlet-side closure surface in this sense is not provided. 
     The state of  FIGS. 8A and 8AA  is an intermediate state during assembly, in which the component  40  has not yet been inserted into the main component  39 . It is possible at this time for the mixing chamber  22  to be filled with the additional medium through the outlet  24 . The state of  FIGS. 8B and 8BB  is then established, in which the outlet  24  is blocked off by inserting the component  40 . 
     In this delivery and storage state of  FIGS. 8B and 8BB , in which the mixing chamber  22  is filled with additional medium, the outlet  24  is closed by a sliding valve  42 . This sliding valve  42  is formed by walls of the component  39  and a duct at the outlet  24 . In the delivery and storage state of  FIGS. 8B and 8BB , the mixing chamber  22  is thus isolated from the surroundings. 
     As soon as the exchange unit  20  is intended to be used, the dispensing head  10  forming the exchange unit  20  is placed on the outlet connector  122  of the liquid reservoir  110 , and the component  40  is pressed deeper into the component  39 . In this way, an opening element  80  on the component  39  comes into contact with the closure  90  with closure surface  91  on the inlet side of the mixing chamber  22  and destroys said surface, as can be seen from  FIGS. 8C and 8CC . At the same time, a communicative connection between the outlet  24  and the dispensing opening  12  is established in the region of the sliding valve  42 . After pressing down the component  40 , the dispensing duct  14  is thus completely free and main liquid from the liquid reservoir  110  can be discharged from the mixing chamber  22  while the additional fluid is being admixed.