Abstract:
The invention relates to a discharge device for a liquid pharmaceutical medium having a reservoir for storing the medium, a pressurizing device ( 10 ) for feeding the medium and at least one discharge opening ( 80 ) for delivering the medium to an environment, the pressurizing device ( 10 ) having a pressure chamber ( 16 ), whose content can be pressurized by a translationally movable piston ( 14 ). 
     According to the invention there is a piezoactuator device with a piezoactuator operatively coupled to the piston, or a coil actuator device ( 30 ) with an actuator coil ( 30 ) and an actuator core ( 32 ) to which force can be applied relative to actuator coil ( 30 ) by energizing the latter and either actuator coil ( 30 ) or actuator core ( 32 ) is fixed relative to the piston. 
     Use for producing precisely defined fluid pressures in a discharge device.

Description:
FIELD OF APPLICATION AND PRIOR ART 
       [0001]    The invention relates to a discharge device for a liquid pharmaceutical medium having a reservoir for storing the medium, a pressurizing device for feeding the medium and at least one discharge opening for delivering the medium to an environment, the pressurizing device having a pressure chamber, whose content can be pressurized by means of a translationally movable piston. 
         [0002]    Numerous different such discharge devices are known from the prior art and are used for the delivery of pharmaceutical media which, in the sense of the invention, is understood to mean substances which are applied to or into the body of a patient for medical purposes. As a function of the discharge device discharge can take place in the form of droplets, a jet, a mist or the like. 
         [0003]    In such discharge devices the reservoir is used for storing the medium prior to the discharge thereof. For discharging the medium part of the medium previously delivered to the pressure chamber from the reservoir is pressurized in order to feed it to the discharge opening. 
         [0004]    The actuation of the pressurizing device preferably constructed as a pumping device in most discharge devices known from the prior art takes place manually, i.e. by a pressurization during which the necessary energy is introduced by the user into the system. This leads to numerous disadvantages, including for elderly people difficult operation and also the possibility of incorrect manipulation. 
       Problem and Solution 
       [0005]    Thus, the problem of the invention is to so further develop such a discharge device that the prior art disadvantages are reduced or avoided. 
         [0006]    According to the invention this is achieved by such a discharge device which has a piezoactuator device or coil actuator device, the piezoactuator device having a piezoactuator which is operatively coupled to the piston, or where the coil actuator device has an actuator coil and a actuator core, to which force can be applied via the actuator coil by energizing the latter and either the actuator coil or actuator core is constructed in fixed manner with respect to the piston. 
         [0007]    In the sense of the invention piston is understood to mean a section movable in translational manner with respect to the casing of the discharge device and whose position determines the pressure chamber volume. A piston in the sense of the invention can also be the movable front side of a pump bellows of a bellows pump. 
         [0008]    In the embodiment with a piezoactuator device, the piezoactuator changes its extension in at least one dimension by energization and is supported with one side on a surface fixed with respect to a casing of the discharge device, whereas the opposite side is movable due to the length extension of the piezoactuator and is so directly or indirectly connected to the piston that the movable of said opposite side brings about a movement of the piston. The piezoactuator is preferably constructed as a piezo-stack in order to bring about a comparatively significant displacement of the movable side. As a result of the high forces attainable and the accurate dosability of the forces, piezoactuators are particularly suitable for force application to the piston and make it possible to produce a clearly defined pressure in the pressure chamber. 
         [0009]    It is particularly advantageous if the piezoactuator device is operatively coupled to the piston by means of a converter, the latter being constructed in order to displace the piston as a result of the deformation of the piezoactuator by a path length L 1  by a path length L 2  which is greater than the path length L 1 . Thus, the converter is constructed for lengthening the comparatively limited deformation path of the piezoactuator, accompanied by a corresponding reduction of the forces. This makes it possible to obtain a significant piston stroke. The converter can be constructed as a mechanically acting gear, which e.g. brings about a conversion by means of a fixed mounted lever. It is also possible to use a hydraulic converter such that as a result of the piezoactuator an auxiliary piston with a large piston surface is directly moved and which displaces an auxiliary fluid, which in turn is used for moving a second auxiliary piston with a comparatively small piston surface. The main piston, which defines the pressure chamber, can be directly linked with said second auxiliary piston. 
         [0010]    In the case of the design with a coil actuator device use is made of the fact that an energized coil forms a magnetic field in which a force is applied to the actuator core as a result of magnetic forces. To increase this effect the actuator core is preferably constructed as a permanent magnet. The force acting on the actuator core is dependent on the intensity of the current flowing in the actuator coil. 
         [0011]    The described force can be directly used for displacing the piston or supplying a force thereto. For this purpose it is possible to provide the actuator coil in fixed manner with respect to the pump casing and for the actuator core to be fixed relative to the piston. Any movement and force application to the actuator core leads to a corresponding movement or force application to the piston. This construction is particularly simple, because a power supply only has to be provided for fixed components. 
         [0012]    However, it is alternatively possible for the actuator core to be fixed relative to the pump casing and to provide the actuator coil on the piston. This second design, which with respect to its construction roughly corresponds to a loudspeaker, offers the advantage that the comparatively lightweight actuator coil is moved relative to the actuator core, so that the energy requirements are lower. 
         [0013]    In a further development of the invention a measuring device is provided making it possible to detect the deflection of the piston relative to a pump casing. 
         [0014]    In the simplest case the measuring device can be so constructed that it merely detects whether there has been a piston movement. However, it can also be constructed so as to precisely detect the piston position. The measuring device inter alia makes it possible to check prior to putting into operation or operation, whether the piston has moved as a reaction to the energization of the piezoactuator or actuator coil. With more complex designs the measuring device is also able to detect which further forces, such as e.g. frictional forces or spring forces act on the piston. Such an analysis of the characteristics of the specific discharge device makes it possible in operation to produce a precisely defined pressure in the pressure chamber, which offers numerous advantages as a function of the intended use. 
         [0015]    A discharge device in which the measuring device has a measuring coil constructed for determining the position of a measuring core relative to the measuring coil is particularly advantageous. Use is made of the fact that a movement of the permanent magnetic measuring coil leads to the induction of a voltage in the coil. The higher the speed of the measuring core relative to the measuring coil the higher said voltage. It is consequently possible to detect as a result of this whether the measuring core is moving and also how fast it is moving. The mere detection of the fact that the core is moving makes it possible to determine the frictional forces acting between piston and pump cylinder, in that the piston is moved between a first and a second end position and the movement time is detected and this increases with the magnitude of the frictional forces. 
         [0016]    The pressure produced in the pressure chamber can be directly used for discharging the medium through the discharge opening. For this a direct connection is provided between the pressure chamber and the discharge opening, a discharge valve being preferably provided and only opens when a specific minimum pressure is reached. However it is alternatively also possible for the medium delivered by the pumping device to be initially fed into another chamber from which it is discharged by means of a specific discharge mechanism. 
         [0017]    Thus, preferably a discharge chamber connected to the pressure chamber is provided, said discharge chamber being connected to the environment by a plurality of discharge openings and where the discharge chamber is bounded by a wall section, which can be brought into a vibration state by a vibration actuator. 
         [0018]    With such a design the actual discharge process is brought about by the vibrating wall section, which leads to a high frequency pulsating volume of the discharge chamber. As a result of this volume change the medium present in the pressure chamber passes out of the discharge opening in the form of a mist with minute droplets. The pressure produced by the pumping device is merely used for supplying the discharge chamber with medium. Particularly with such a design the use of an inventive piezoactuator device or an inventive coil actuator device is advantageous, because said device makes it possible to provide a precisely dosed, limited pressure dimensioned in such a way that the discharge chamber medium supply is ensured without a discharge through the discharge opening taking place merely as a result of the pressure produced by the pumping device. 
         [0019]    According to a further development for controlling the pumping device a control unit is provided, which controls a force application to the piston by means of the piezoactuator device or the coil actuator device. In the case of a piezoactuator device control takes place in that the control unit makes available a clearly defined voltage. With a coil actuator device the control unit provides a clearly defined current intensity. The voltage or current intensity directly influence the force applied to the piston. Whilst including the piston surface this makes it possible to produce a clearly defined pressure in the pressure chamber. So that this clearly defined pressure can be obtained independently of other influencing factors such as frictional forces between piston and pump cylinder wall, values determined beforehand by the measuring device can be incorporated, e.g. the time required when the pressure chamber is still empty to transfer the piston from one end position into the other. For this purpose the control unit is preferably additionally constructed in order to detect frictional and/or spring forces acting on the piston through an evaluation of the values determined by the measuring device during a piston displacement. 
         [0020]    The control unit can also be constructed for determining by means of a measurement of the piston displacement on putting the discharge device into operation whether air is still enclosed in a flow path between pumping device and discharge opening. The control unit can also be used for numerous other purposes, e.g. for counting the number of discharge processes or preventing a discharge process if a certain time period has not elapsed since a preceding discharge process. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    Further aspects and features of the invention can be gathered from the claims and the subsequent description of three preferred embodiments of the invention shown in the drawings and described hereinafter. In the drawings show: 
           [0022]      FIG. 1  A first embodiment of an inventive discharge device with a coil actuator device and a discharge valve opening in pressure-dependent manner. 
           [0023]      FIG. 2  A second embodiment of an inventive discharge device with a coil actuator device and an atomizer. 
           [0024]      FIG. 3  A third embodiment of an inventive discharge device with a piezoactuator device and a discharge valve opening in pressure-dependent manner. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0025]      FIG. 1  shows a first embodiment of a inventive discharge device having a pumping device  10  connected by means of a channel  40  to a discharge valve  70 .  FIG. 1  does not show further discharge device components which largely coincide with the known prior art components. Thus, a casing with a medium reservoir surrounding the discharge device is not shown. The discharge device also has a not shown control unit, which is e.g. operable by means of key switches and which is provided for controlling a discharge process. 
         [0026]    Pumping device  10  has a pump cylinder  12 , which defines a pressure chamber  16  together with a piston  14 . The piston has a circumferential piston lip  14   a  engaging in liquid-tight manner on the pump cylinder. As a result of the mobility of piston  14  it is possible to vary the volume of pressure chamber  16  and to pressurize liquid in said chamber  16 . Into the pressure chamber  16  issue an intake channel  18  and a discharge channel  20  connected by means of connecting channel  40  to discharge valve  70 . Intake channel  18  and discharge channel  20  are displaced relative to a movement direction  2  of piston  14 , so that during a movement of the piston in direction  2   a  firstly the intake channel  18  leading to the not shown medium reservoir is separated from the pressure chamber. 
         [0027]    On the left-hand side to the piston  14  is connected a coil actuator device, which comprises an actuator coil  30  and an actuator core  32  surrounded by the actuator coil  30 . Actuator core  32  is firmly connected by a plug connection to piston  14 , so that the actuator core always moves together with piston  14 . The actuator core  32  is also surrounded by measuring coil  34 , which runs parallel to actuator coil  30 . 
         [0028]    Pressure generation in pressure chamber  16  takes place in the following way: 
         [0029]    The not shown control unit introduces current into actuator coil  30  which generates a magnetic field in the vicinity of actuator core  32 . The strength of said magnetic field is dependent on the current intensity in actuator coil  30 . As a result of the magnetic field the actuator core  32 , which is at least zonally constructed in permanent magnetic manner, is supplied with a force in direction  2   a  or  2   b.  Force application in direction  2   a  also forces piston  14  in direction  2   a  towards pressure chamber  16 . As soon as piston lip  14   a  of piston  14  has passed over intake channel  18 , said force produces a pressure in the volume-reduced pressure chamber  16 . Said pressure also acts on the valve body  72  of discharge valve  70 , which is consequently moved in direction  4   b  and consequently frees the discharge opening  80  previously closed by valve body  72 . The discharge process is brought about by said opening of discharge opening  80 . 
         [0030]    The discharge process ends as soon as the force application to piston  14  is terminated. This can be brought about by stopping the energization of actuator coil  30 . It is alternatively possible through an additional coil device  7  on discharge valve  70  to again press the valve body  72  back into the closed position of  FIG. 1  counter to the fluid pressure and thereby terminate the discharge process. 
         [0031]    On ending the discharge process a reverse polarity current is supplied to actuator coil  30 , so that force is applied to actuator core  32  and piston  14  in direction  2   b.  As at this time discharge valve  70  is closed again, the resulting enlargement of the pressure chamber  16  leads to an underpressure, which sucks medium out of the medium reservoir when piston lip  14  has passed over intake channel  18 . 
         [0032]    As a result of the described control of actuator coil  30  it is possible to apply a largely defined force to piston  14 , so that there is a pressure generation with a largely defined pressure. If particularly high demands are made regarding the pressure to be produced in pressure chamber  16  in connection with the maintaining of a desired pressure value, account must also be taken of the fact that frictional forces occur between piston  14  and cylinder wall  12  and during pressurization said forces act counter to the movement direction of piston  14 . To determine the level of said frictional forces, prior to the initial filling of pressure chamber  16  a measurement with measuring coil  34  takes place. By a clearly defined current intensity in actuator coil  30 , piston  14  is moved from its first end position into its second end position and the measuring coil  34  simultaneously detects how long this process takes. The higher the frictional forces, the longer the movement time interval. 
         [0033]    This detected time interval can subsequently be used for compensating the frictional forces by varying the current intensity in actuator coil  30  during the pressurizing of the medium in pressure chamber  16  and for producing the desired pressure ratios in the pressure chamber  16 . 
         [0034]    The discharge device according to  FIG. 2  largely corresponds to that of  FIG. 1 . No differences arise with regards to the pumping device  110 , so that what has been stated concerning the embodiment of  FIG. 1  again applies. Unlike in the embodiment of  FIG. 1  there is no discharge valve and it is instead replaced by an atomizer  170  connected by a line  140  to pressure chamber  116 . Said atomizer comprises a casing  172  terminated on its top side by a perforated plate  174 , said perforated plate  174  and said casing  12  jointly enclosing a discharge chamber  176 . On the side of the casing  172  remote from perforated plate  174  a vibration piezo-device  178  is provided on a vibration wall section  172   a  and as a result of high frequency vibration can bring about a vibration of vibration wall section  172   a.  These vibrations in vibration wall section  172   a  lead to a high frequency volume change of discharge chamber  176  through which the medium enclosed in chamber  176  is pressed through the discharge openings  180  of perforated plate  174  and escapes in the form of a mist. 
         [0035]    The representation of  FIG. 2  is not true to scale. Atomizer  170  has been represented on a significantly larger scale than pumping device  110 . Thus, in reality, the volume of pressure chamber  116  is much larger than the volume of discharge chamber  176 , so that a long lasting discharge process enables the medium to be fed into the pressure chamber  116 . 
         [0036]    During operation the discharge device of  FIG. 2  is so controlled by the not shown control unit that only a very limited overpressure is produced in pressure chamber  116 . This limited overpressure ensures that the discharge chamber  176  permanently remains in a filled state without the pressure produced by pumping device  110  bringing about a discharge of medium through discharge openings  180  independent of the vibration of vibration wall  172   a.    
         [0037]    In the embodiment of  FIG. 3  the structure of the embodiment of  FIG. 1  has been retained, except that a force is not applied by the coil actuator device to piston  214  and instead this takes place through the piezoactuator device  230 . Said piezoactuator device  230  comprises a piezo-stack  232  which increases its extension in direction  206  when a voltage is applied. Said direction  206  forms a right angle with the movement direction  202  of piston  214 . For transmitting the force from piezo-stack  232  to piston  214  a converter  236  is provided and comprises two wedge elements  236   a,    236   b.  Wedge element  236   b  is provided on the movable end  232   a  of piezo-stack  232 . The other wedge element  236   a  is engaged onto the side of piston  214  remote from pressure chamber  216 . The wedge surfaces form an angle of approximately 15ø with movement direction  202 , so that a displacement of the movable end  232   a  of piezo-stack  232  leads to a much greater displacement of piston  214 . A comparatively small movement of piezo-stack  232  can consequently bring about a much larger piston stroke. 
         [0038]    The represented design consequently makes it possible to use the force produced by piezo-stack  232  for pressurization in pressure chamber  216 . As converter  236  is so designed that it is only possible to apply a force to piston  214  in direction  202   a,  a return spring  238  is also provided and when the force produced by the piezo-stack  232  is ended it presses piston  214  back into its starting position.