Abstract:
The dispenser outlet ( 13 ) is microbiologically sealingly closeable by a valve stopple ( 25 ) which closes counter flow direction ( 11 ). Outlet  13  is manually reversely opened prior to the pump stroke against a spring ( 34 ). The medium reaches outlet ( 13 ) via throttles ( 22, 21, 49 ). Thus the medium creeps practically non-pressurized to an adhering face ( 51 ) of a droplet former ( 50 ). There the medium accumulates to a droplet suspending in the upside-down position. The medium contained in the dispenser ( 1 ) is effectively protected from germ contamination and the droplet may be simply administered to an eye or the like.

Description:
TECHNICAL FIELD AND BACKGROUND OF THE INVENTION 
     The invention relates to a dispenser for releasing flowable media by pressurizing. Particularly liquid media, but also pasty, powdery and/or gaseous media are suitable. The dispenser is held and simultaneously actuated for discharge single-handedly. Most or all parts are injection molded from plastics. The medium may be discharged atomized or delivered in discrete clusters or droplets of a colume of at least 5 or 15 μl and at the most 40 or 25 μl while containing medical active substances for eye treatment, or the like. 
     Such dispensers need microbiological sealing to prevent the stored medium from germ contamination gaining access from without. The medium is to be protected from such detrimental effects during a long shelf life not only prior to the dispensers first-time use (priming) but also after the initial discharge. The dispenser may be made for a single dose discharge or for moving the actuator only unidirectional without return or suction stroke up to being totally emptied. The total input of medium may be in a single conveying chamber right from the start without provision of any additional medium reservoir. The chamber volume is then variable for pressurized medium delivery. However, the dispenser or its actuator may also operate reversible, namely repeatedly via a working stroke for pressurized delivery directly followed by a return stroke for sucking a further medium dose into the chamber. After discharge of the medium dose the microbiological seal is always to be reproduced until the next discharge. This is not necessary in the case of a disposable dispenser. 
     For this seal either a single valve or several valves may be suitable. The valves closing gaps sequentially follow within the outlet duct in the flow direction. The last downstream valve is as near as possible to the medium outlet or its bound which is formed by the transition between an inner circumference and a transversely adjoining end face. At this transition the medium detaches from all inner circumferences or inner dispenser surfaces for release to the environment. Downstream thereof the medium may be still guided on external dispenser faces. 
     OBJECTS OF THE INVENTION 
     An object of the invention is to provide a dispenser which avoids the drawbacks of known configurations and achieves advantgeous effects of the aforementioned kind. Another object is to ensure a repeated microbiological seal against germ ingress through the bounds of the outlet or of inflow openings. Other objects are simple handling or uncomplicated construction. A further object is to provide a dispenser for modular composition permitting adaptation to media differing in flowability. 
     SUMMARY OF THE INVENTION 
     According to the invention the dispenser comprises a valve closing with high surface pressure. Its closing gap may also form the named opening bound. Thus the closing gap extends up to the outermost possible location of the outlet duct at which the medium detaches. With the valve closed this location is a microbiological seal. Thus, at the most, germs are able to collect on the permanently freely accessible dispenser outside but have no upstream access to internal dispenser faces past the tight closing gap. 
     The closing force is not reduced until the medium pressure in the outlet duct has attained at least 0.7 or 1 or 1.4 bar. The valve could be opened by fluid control once the medium pressure has attained this value. Otherwise it is opened pressure independently by pure mechanical actuation. The cited sealing effect and the germ ingress prevention with the valve open may also be improved by keeping the valves operating travel smallest. The maximum relative opening or closing travel of the two valve bodies is less than 2 mm, 1 mm, 0.7 mm or 0.4 mm, e.g. 0.3 mm. On droplet discharge the medium then emerges practically with zero pressure or by capillary creeping through the valve gap. Still further upstream means such as a pump for generating a medium pressure higher than the aforementioned pressures, i.e. two to five times higher, may be provided. This medium pressure amounts to e.g. at least 4, 6 or 7 bar. 
     To nevertheless attain a medium discharge at the outlet under reduced or without pressure, a throttle gap adjoines the valve upstream. This gaps passage cross-section is significantly smaller than that of the opened valve and may be varied as a function of the medium pressure. For example, the open valve cross-section may be at least 2, 40 or 50 times more than the throttle cross-section. 
     Upstream of the end valve or throttle gap a further valve or throttle is provided in the outlet duct. E.g. the medium flow is prethrottled in constant cross-sections already upstream of the throttle gap or end valve. The flow of the medium is also throttled at the transition from the converging chamber to the outlet duct or shut off microbiologically sealed at this transition. The further valve is a spring-loaded outlet or pressure relief valve. For forming the closing gap the closing faces of each of the valves may have only linear contact or maximum closing pressure along a sole e.g. annular micro line for maximum specific areal pressures. Therefore one of the closing faces of each valve is a sharp edge bounded by two angularly adjoining flanks or a spherical surface. 
     The medium is manually conveyed by a thrust piston pump or a flexible squeeze receptacle, such as a tube. In the latter the dispensers complete valve control is arranged in the constricted tube tip which is in one part with the tube shell. In the case of a piston pump the cylinder or piston runs commonly with the medium outlet counter the opening direction of the movable valve bodies during the pump stroke. 
     Irrespective of the described constructions a droplet former, particularly in the upside-down position of the dispenser with the medium outlet held downwards, accumulates a freely exposed medium droplet of a metered volume. The droplet then hangs adheringly suspended on the dispenser with a transition diameter smaller than its largest diameter. Thus the droplet does not detach until its lower end face comes into contact with a counter face, e.g. the eyeball. With this the droplet commences to flow onto the counter face. For the droplet the accumulator has a convex and/or concave adhering face which may be spherical, smooth or polygonal to increase the areal size at a same plan view area. This face directly adjoins the end valves closing faces and is formed by the end of a needle traversing the medium outlet. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     Example embodiments of the invention are explained in more detail in the following and illustrated in the drawings in which: 
     FIG. 1 is the dispenser in partly sectinoal side view and in initial or rest position, 
     FIG. 2 is a sector of a further dispenser, 
     FIG. 3 is a still further dispenser shown as in FIG. 1, and 
     FIG. 4 is another dispenser with the valve open, on commencement of the pump stroke and in the upside-down position. 
    
    
     DETAILED DESCRIPTION 
     The dispenser  1  has two units  2 ,  3  with one-part base bodies  4 ,  5 . Mutual displacement results in shortening or lengthening the dispenser  1 . Support body  5  is sealingly secured by a flange  7  to the bottleneck of a reservoir  6 , e.g. a bottle of glass or the like. Units  2 ,  4  and  3 ,  5  form a pump  9  with a manual actuator  8 . All parts are located in axis  10 . On discharge, the medium flows parallel to axis  10  in direction  11  from unit  3  through unit  2  out of medium outlet  13 . Unit  2  and outlet  13  are thereby commonly displaced in the opposite direction  12  and relative to unit  3 . 
     The axis of outlet  13  may be perpendicular to axis  10 . Outlet  13  is the end of outlet duct  14  traversing only unit  2 . The upstream end of duct  14  directly connects to conveying chamber  15  which is volumetrically variably bounded by bodies  4 ,  5 . Upstream chamber  15  adjoins valveless a pre- or presuction chamber  16  supplied valveless with medium via a riser duct  17  from the bottom of reservoir  6 . Corresponding to its emptying reservoir  6  receives an atmospheric air flow from without on each working stroke via a vent  18  which is bounded by bodies  4 ,  5 . The return or down-stroke of units  2 ,  3  to the dispensers longer rest position is powered by a spring  19  directly supported on bodies  4 ,  5  as a permanently pretensioned helical compression spring. 
     In flowing from chamber  15  up to and out of outlet  13  the medium is sequentially and separately controlled by passages  20  to  23 , such as chambers, throttles and valves located in this numerical and actual sequence from the vicinity of outlet  13  upstream up to the end of chamber  15 . Each control passage  20  to  23  formes a separate length section of duct  14 . Vent  18  is controlled via valve  24 . Control valve  20  has two separate nested valve bodies  25 ,  26  each in one part. The valves closing faces  27 ,  28  bound outlet  13 . At outlet  13  the medium detaches from the dispenser  1  into the atmosphere or it remains attached to only one integral, freely accessible outer surface of the dispenser  1 . The outer, annular closing face  28  is conically widened in direction  11  and is the end of an integrally bounded nozzle bore  29  of unit  2 . The inner complementary annular or conical closing face  27  is formed by pinshaped body  25 . For opening face  28  is moved by a control  30  in direction  12  before the medium pressure is increased in chamber  15  and in duct  14  and before valve  23  is opened. 
     Control  30  includes a one-part piston  31  with a cylindrical lip  43  freely protruding from a piston crown in direction  11 . 
     Fixedly anchored in the crown is the upstream end of body  25 . Duct  14  and the rotationally symmetrical stem  33  of body  25  traverse the crown where they commonly bound duct  14 . At the downstream end of body  25  the stem  33  has a widened head  32  forming face  27  which adjoines the outer circumference of stem  33 . Body  25  is loaded toward the closed position by a permanently pretensioned spring  34  which directly adjoines the crown downstream and within duct  14  surroundes only stem  33  as a helical compression spring. In each position body  25  is made fast on bodies  4 ,  31  by a collar sleeve  35 . Support  35  belongs to piston  31  and juts from its crown in direction  12 . Within support  35  the upstream end of stem  33  is made fast, e.g. by a resilient snap connector. 
     Cap-shaped valve body  26  is fixedly seated in a shell or shield  36  which is up to twice as long as its outer diameter. Shell  36  transits in one part into an end wall  37 . Wall  37  is traversed by duct  29 , outlet  13  and a passage for body  26 . A sleeve or lug  38  of body  4  engages displaceably the upstream, cylindrical and widened end of shell  36  in direction  11 . Shell  35  fixedly engages inside lug  38 . The piston crown rests on the end face of sleeve  38 . Shell  36  extends up to a handle  39  of actuator  8 . Shell  36  and handle  39  are in one part. 
     Shell  36  of unit  2  forms in axis  10  or parallel thereto a stud-shaped discharge head  40  continually tapered in direction  11  up to its end and also suitable for being introduced into a bodily aperture such as a nostril. The cylindrical inner circumference of shell  36  may form a sealing running face or a radial support for lip  43  of piston  31 . The inner circumference of piston  31  bounds duct  14 . Downstream thereof the same inner circumference forms a conical face  42  surrounding an annular throttle body or piston  44 . Lip or guide member  45  of piston  44  protrudes in direction  12  into piston  31 , slides sealingly on the inner circumference  41  of lip  43  and bounds duct  14  by its inner circumference. Throttle  22  connects upstream directly to those duct sections which are bounded by lips  43 ,  45 . Throttle  22  is located in sleeve  35  and bounded by stem  33 . The outer circumferences of piston lips  43 ,  45  and of lug  38  bound an annular dry space of shell  36  which is permanently without medium contact. Lips  43 ,  45  bound the widened, but volumetrically variable chamber  21  provided for mollifying the flow directly following throttle  22 . 
     A piston or throttle body  46  downstream directly juxtaposes chamber  21  inside shell  36  and surrounds stem  33 . Shell  46  freely protrudes in direction  11  from the crown of piston  44 . Sleeve  46  has the bore  29  and bounds the annular throttle gap  49  commonly with the outer circumference of stem  33 . In direction  11  the crown of piston  44  is put against a stop  47 , e.g. ribs of shell  37 , which adjoin sleeve  46 . A corresponding stop  48  may also be provided for the end of lip  43 . Spring  34  directly supports on the two crowns of pistons  31 ,  44  and is surrounded by sleeves  43 ,  45 . The annular gap  49  of duct  14  is multiply longer than its diameter and sealingly closed only at face  28 . Spring  34  urges face  28  and shell  37  in direction  11  permanently against face  27  with no self-locking effect. With valve  20  closed the nozzle duct  49  is also bounded by part of face  27  due to it being longer than seat  28 . Sleeve  46  is slimmer than lips  43 ,  45  and sealingly supports against the inner circumference of the wall  37 . 
     A protuberance or droplet former  50  is permanently freely accessible on the dispensers outside and communicates with orifice  13 . Former  50  is provided by head  32  and, possibly, by adjoining sections of planar end face  53  of sleeve  46 . The freely exposed end face  51  of head  32  is spherically curved or hemispherical. Face  51  directly adjoines by an annular edge  52  the widest zone of end face  27 . With valve  20  closed the edge  52  is located apart from face  53  of wall  37  or from the ring edge of seat  28  flanked by face  53 . Edge  52  is acutely and ring edge is obtusely flanked in axial cross-section. 
     In the vicinity of the crown of piston  31  throttle ducts  54  of throttle  22  are permanently permeable. Ducks  54  are longitudinal grooves in the plunger crown and in sleeve  35 . The common passage cross-section of ducts  54  is significantly smaller than that of chamber  15  or valve  23  up to sleeve  35  and that of chamber  21 , but greater than that of duct  49  and that which exists between faces  27 ,  28  when valve  20  is open. These longitudinal grooves are bounded by ribs which form the snap members for holding body  25 . 
     Outlet valve  23  of the pump chamber  15  has an acutely concial valve seat  55  on body  4  and a ball  56  with a spherical counter face of plastics, metal or the like. Valve body  56  is loaded in direction  12  against annular or linear contact with valve body  55  by a permanently pretensioned spring  57 . Helical compression spring  57  directly contacts bodies  35 ,  56 . Spring  37  is centered on a mandrel which freely protrudes in direction  12  and belongs to seal  35 . This mandrel limits the opening path of element  56  by abutment. From valve  23  up to body  35  the duct  14  is bounded constantly wide by lug  38  or the inner circumference  58  thereof. Face  58  is provided with longitudinal or control grooves (FIG. 2) spaced from the valve seat in direction  11 . On a first opening path of element  56  only a very small passage cross-section is free. Over the subsequent opening path up to the stop on body  35  a correspondingly greater cross-section is freed. A valve inlet  59  connects upstream to the closing seat of valve  23 . Inlet  59  is more constricted than this seat and chamber  15 . Inlet  59  is formed by a lug of body  4 . This lug freely protrudes in direction  12  into chamber  15 . 
     Bodies  4 ,  5  form a housing  60  extending from an end wall  61  of body  5  in direction  12  up to the upstream end of body  5 . Only lug  38 , body  26  and head  40  freely protrude beyond wall  61  in direction  11 . The outer surfaces of head  40  are freely accessible. An end face of wall  61  forms a stop for delayed driving by handle  39 . Beyond the outer end face commonly one-part shells  62  to  64  of body  4  protrude only in direction  12 . Lug  38  protrudes only in direction  11 . Body  5  likewise has an endwall  65  spaced from its ends. Annular wall  65  is permanently located within body  4 . Body  5  has shells  66  to  68  freely protruding in direction  11  and commonly in one-part. Outermost and longest shell  62  permanently surrounds all remaining walls  63  to  68  and radially commonly boarders with the outer circumference of wall  61 . The next or middle shell  63  is radially spacedly located within shell  62  and its outer circumference directly opposes the inner circumference of shell  67 . This outer circumference has an end lip sealingly engaging the inner circumference in the rest position. 
     Shells  66 ,  67  are located permanently between shells  62 ,  63 . Innermost shell  64  is radially spaced from and located within shell  63  as well as within inner shell  68 . Shell  67  has the same radial spacings from shells  66 ,  68 . Each of the upstream free ends of shells  63 ,  64  forms an annular piston lip which is acutely widened in direction  12 . The inner circumference of pressurizing cylinder  64  bounds chamber  15  with a cylindrical running face or boundary  69 . The upstream end of boundary  69  is acutely conically widened in direction  12  to form a closing face of flow control means a closure or an inlet valve  70 . Within shell  68  a piston  71  of body  5  permanently freely protrudes from wall  65  into shell  64 . Piston  71  has at its downstream end an annular lip  72  or valve element of valve  70 . In rest position face  69  and lip  72  bound an annular inlet gap. This gap sealingly closes after an initial smaller stroke path by the lip  72  running onto the slanting end of face  69 . Chamber  16  connects upstream to this gap. Chamber  16  is bounded by lugs  68 ,  71  and by end lip  73  of shell  64 . Lip  73  slides permanently sealed on the inner circumference of shell  68 . 
     With radially spacing within lip  72  the plunger  71  has a projecture or mandrel  76 . At the end of the pump or up-stroke lug  76  sealingly or permeably engages inlet  59  and mechanically lifts valve body  56  from seat  55  only so far that the valve passage is not freed over its maximum cross-section. The lug of inlet  59  then engages the annular groove between projections  72 ,  74  and lip  72  abuts on the bottom of the annular groove which surrounds this projection. Connectors or ribs  75  of body  5  adjoin the upstream end of piston  71 . This end is conically tapered. Ribs  75  extend from the conical intermediate section of piston  71  and from within chamber  16  upstream only over part of the thickness of wall  65  as well as of the length of slimmer mandrel  76  of piston  71 . Thus wall  65  is centrally penetrated by an annular duct which is circumferentially subdivided by ribs  75 . At the end of the up-stroke lip  73  can abut on the bottom of chamber  16  or on wall  65  while receiving those sections of parts  75 ,  76  which protrude over wall  65 . 
     Conically widened end lip  77  of shell  63  is set back in direction  11  relative to lip  73 . After a first short partial stroke of the working or up-stroke lip  77  slides over a control face or step  78  of the inner circumference of shell  67 . Thus valve  24  is opened on closing valve  70 . Commonly shells  67 ,  68  and  63 ,  64  bound an annular chamber  79 . Air flows or is sucked into chamber  79 , while inflowing between shells  62 ,  66 ,  63 ,  67 . Bottom  65  of chamber  79  is traversed by a vent duct  81 . Duct  81  is totally covered by a germicidial filter  80  which is annular about axis  10  and located in chamber  79 . Disk-shaped filter  80  contacts shells  67 ,  68  with radial pressure and also contacts bottom  65 . At the stroke end filter  80  may be reached or crushed out by valve body  73 . Spring  19  surrounds parts  63 ,  64 ,  67 ,  68 ,  80 . Spring  19  is located in the annular chamber which is directly bounded between and by shells  62 ,  63 ,  66 ,  67 . Spring  19  is directly supported on walls  61 ,  65 . 
     One-part flange  7  forms an annular disk-shaped seal  82  which engages without radial motion play or at its outer and inner circumferences with radial pressure into an annular groove of wall  65 . This groove is remote from member  80 . Member  82  has an annular groove on its downstream end face. Commonly with wall  65  this groove communicates with duct  81  and bounds an annular duct which continuously extends around axis  10 . A cap  84  of flange  7  connects to the inner circumference of seal  82  and protrudes in direction  12 . A sleeve-shaped lug  83  of body  5  engages inside cap  84  and protrudes from wall  65 . A passage connects to the bottom of the annular groove and is in line with passage  81 . The connecting passage traverses seal  82  and is continued as an inclined groove in the outer circumference of the shell of cap  84 . The free end of mandrel  76  which protrudes beyond ribs  75  in direction  12  is conical or pointed tapered. This end engages with radial spacing a conical bore which is provided in the bottom of cap  84 . Thus an annular inlet opening is bounded and widened as a hollow cone in direction  11 . The passage cross-sections of this opening are significantly smaller than those in the region of ribs  75  or of chambers  15 ,  16 . A connecting member or sleeve  85  of flange  7  protrudes from the end wall of cap  84  solely in direction  12  to provide a mount or shaft into which the riser tube  17  is inserted. 
     Together with wall  65  and upstream thereof body  5  forms a connector or cap  86  for engaging the reservoir neck. The necks annular end face and/or the necks annular opening edge which is set back from this end face rests fixedly against seal  82  and the outer circumference of cap  84  with axial respective radial pressure. The inner circumference of cap  86  is provided with a fastener or tensioning member, such as a thread. This fastener engages a corresponding counter member on the necks outer circumference. The end of shell  86 ,  87  abuts against an annular shoulder of reservoir  6 . This shoulder is formed by the transition between bulge and neck of reservoir  6 . At the end of the up-stroke body  4  or shell  62  do not reach the annular shoulder of shell  87 . 
     Securing means  90  prevent units  2 ,  3  and bodies  4 ,  5  from being mutually rotated or withdrawn. Shell  62  has a slot  88  adjoining wall  61 . The end of slot  88  is offset in direction  11  relative to the free end of shell  62 . Cam  89  engages slot  88  and projects from the outer circumference of shell  66 . In rest position the radially freely protruding cam  89  abuts against the slot end in the plane of the downstream end face of wall  65 . Body  4  is mounted on body  5  in direction  12 . Thereby cam  89  resiliently widens shell  62  by an inclined face until cam  89  snaps into slot  88 , namely after walls  62  to  69  have mutually over- and interengaged. Bodies  25 ,  31 ,  56 ,  57  are inserted in body  4  in direction  12 . Body  40  is slipped on body  4  in direction  12 . Bodies  31 ,  34 ,  44  and, in case,  31  are previously inserted in body  40  in direction  11 . Before or thereafter body  25  is inserted into bodies  4 ,  40  in direction  12  and the fixed connection with piston  31  is made. The free end of shell  63  is set back relative to the free ends of shells  62 ,  64 . The free end  73  of shell  64  is set back relative to that of shell  62 . The free ends of shells  66 ,  67  are set back relative to that of shell  68 . Shell  66  is set back relative to shell  67 . Relative to the free ends of shells  66  to  68  the piston  71  is set back. Body  56  is located in the plane of wall  61 . Bodies  43 ,  44  are located totally outside of body  4  and permanently spaced from body  4  in direction  11 . 
     Housing  60  is covered by an overcap  91  permanently totally accomodating body  4 . The annular disk or end wall  92  of cap  91  adjoins in one part the upstream end of shell  36 . With radial spacing therefrom the outer circumference of wall  92  translates into cap shell  93  which protrudes only in direction  12 . At its upstream end shell  93  has an annular collar  94  which protrudes beyond the outer circumference of shell  93 . The outer end face of wall  92  forms on both sides of head  40  pressure faces of handle  39  for simultaneously supporting fingers of the single users hand. In the rest position the inside of wall  92  is spaced from the outside of wall  61 . This spacing corresponds to that of lip  43  from stop  48 . Thus by pressing handle  39  the cap  91  or shell  36  can be displaced in direction  12  synchroniously with valve body  26  and relative to bodies  4 ,  5  by this spacing over an idle travel against the force of spring  34  and without loading spring  19 . Thus seat  28  is lifted from closing face  27  and valve  20  or outlet  13  is opened. After abutment body  4  is synchroneously driven commonly with and by body  91  relative to body  5 , whereby valve  20  invariably remains open. A lock  95  positively locks cap  91  relative to housing  60  or body  4  and prevents withdrawal in direction  11 . Cap  91  and valve body  26  may be commonly rotatable about axis  10  relative to body  4  or prevented from such rotation by lock  95 . Lock  95  has a protruding cam  95  on the outer circumference of shell  62 . Counter cam  97  on the inner circumference of shell  93  abuts on cam  96  by the force of spring  34 . Cam  97  is located in the plane of collar  94  at the open end of shell  93 . By displacing cap  91  cam  97  is lifted from cams  96 . Then shell  93  protrudes beyond shell  62  in direction  12 . Through the gap between walls  62 ,  93  or  61 ,  92  or  36 ,  38 ,  43  the said dry space is permanently aerated and de-aerated about lips  43 ,  45  up to wall  37 . 
     For the up-stroke handle  39  is pressed on both sides of head  40  by two handfingers and cap  91  inclusive wall  37  and control body  26  is displaced in direction  12  by the cited idle or stop travel against spring  34  and relative to unit  3  or body  4 . After less than a one millimeter stroke valve  20  is fully open by stop limiting and inlet valve  70  is closed. At this valve opening stroke lip  45  slides sealingly on face  41 , thus constricting chamber  21  like a pump chamber, pressurizing the medium contained therein and slowly pressing it into gap  49 . Simultaneously the sealing pressure of lip  45  increases by this medium pressure. Thereby chambers  15 ,  16  are totally filled with the medium. Directly thereafter valve  24  opens and any vacuum in reservoir  6  is compensated. At further stroke the pressure increases in chamber  15  until before the work stroke end the opening pressure of valve  23  is reached or until cam  74  reaches body  56 . Thus body  56  opens in direction  11  at seat  55  against the force of spring  57  either to the cited smaller passage cross-section or subsequently to the passage cross-section of the rib ducts. The medium thus gains access to duct  14  under the pressure in chamber  15 , flows through body  31  and throttle  22  into chamber  21  where after the flow acceleration in throttle  22  flow calming and deceleration occurs. The opening stroke of parts  26 ,  44 ,  91  amounts to but 0.3 mm for a maximum diameter of the opening  13  or  28  of 5 mm, 4 mm or 2 mm. 
     From calming chamber  21  the medium flows directly into duct  49 . Boundaries  33 ,  46  of duct  49  thereby remain dimensionally rigid. The width of gap  49  of maximally three or two tenths of a millimeter is at least 10- or 20-fold smaller than the axial stroke of the closing face  28 , e.g. between 0.005 and 0.01 mm. Thereby the pressure in chamber  15  may be at 7 bar to 8 bar. The medium flows very slowly in duct  49  along stem  33  and between the separated faces  27 ,  28 . The medium creeps over edge  52  onto face  51  where it accumulates to an adhered droplet of 20 μl. In the upside-down position of the dispenser  1  and in all valve positions this droplet is then freely suspended only from face  51 . Piston  44  is permanently stationary relative to housing  36 ,  37 . 
     When pressure drops in chamber  15  at the end of the stroke of pump  9 , spring  57  closes valve  23  which may first close the passages of the cited rib ducts and limit the valve passage to the more constricted passage cross-section before then sealingly resting at seat  55 . Thus reflowing of the medium from chamber  15  into duct  14  is temporarily possible. As soon as handle  39  is released spring  34  closes valve  20 . Thereby spring  34  pulls valve body  25  over the cited stroke into seat  28 . Thus the space between faces  28  and  55  remains either totally filled with medium or is at least partly emptied. Thus after first operation (priming) duct  14  always remains totally filled with medium. While valve  20  is closed, firstly piston  31  lifts off from stop  48  which limits the cited stroke resiliently yieldable or rigid. At the end of the down-stroke spring  19  opens valve  70 . Thus the medium which had been sucked into chamber  16  during the down-stroke by piston  73  flows abruptly into evacuated chamber  15 . Simultaneously medium is resucked through conduit  17  into chamber  16 . Thereby the medium flows around parts  76 ,  75 ,  71 . In rest position chambers  15 ,  16  permanently communicate due to valve  70  being open. Shortly before the down-stroke end, valve  24  of chamber  79  also closes. Air had flown from chamber  79  through flange  7  into reservoir  6  while mortifying any germs by filter  80 . 
     Duct  17  and lug  85  may also be eliminated. Then only in upside-down position pump  9  will suck medium from reservoir  6  through flange  7 , since then the medium flows by gravity up to and into chambers  15 ,  16 . 
     In FIGS. 2 to  4  like parts have like reference numerals as in FIG. 1 but indexed differently. All passages of the description apply accordingly to all embodiments. All features of each embodiment may be provided on the other embodiments in addition and/or in combination. 
     FIG. 2 illustrates instead of throttle  22  a valve  22   a  which opens against the force of spring  34   a  upon overpressure in duct  58   a.  When the overpressure drops, spring  34   a  closes valve  22   a.  The valve bodies  25   a,    31   a  are mutually movable. The crown inside of piston  31   a  forms the valve seat. A collar protrudes beyond the outer circumference of stem  33   a,  forms the movable valve body and directly supports the upstream end of spring  34   a.  This collar is an annular disk having a planar end face. Upstream beyond this valve body or its closing face stem  33   a  protrudes by a mandrel into sleeve  35   a.  This mandrel and the inner circumference of sleeve  35   a  commonly bound the annular throttle duct  54   a.  Sleeve  35   a  is radially spaced from the inner circumference of duct  58   a.  Thus sleeve  35   a  extends into and centers spring  57   a.  On the opening stroke for valve  20   a  spring  34   a  is further pretensioned. Then begins the pump stroke of pump  9   a  until firstly valve  23   a  and thereafter pressure relief valve  22   a  opens to let the medium flow directly into chamber  21   a.  In rest position the piston shell  45   a  is located almost totally in piston lip  43   a.    
     In rest position the end face  53   a  is not coplanar with the outer end face of wall  37   a,  as is the case in FIG.  1 . Face  53   a  protrudes over wall  37   a  by a fraction of a millimeter. End face  51   a  is entirely and up to edge  52   a  arcuated or recessed to form a flat tray. Thus liquid conveniently creeps from face  59   a  to face  51   a  where it attaches as a suspended droplet. Shell  36   a  only adjoins end wall  92   a  which is entirely parallel to wall  61  and provides a freely exposed annular edge at the outer circumference. The outer diameter of this edge corresponds to the outer diameter of shell  62   a  which is permanently freely exposed over its full length. Mandrel  76   a  has no pointed tip. Instead mandrel  76   a  has an entirely planar end face which is coplanar with the inner face of the bottom of cap  84   a.  This inner face has a recess which is wider than mandrel  76   a.  From the recess bottom the constricted passage emanates. Thus the medium perpendicularly impacts the end face of mandrel  76   a  in direction  11   a,  flows transversely against the circumference of the recess and then again perpendicularly in direction  11   a  into chamber  16   a,    15   a.    
     FIG. 3 illustrates lip  45   b  sealingly directly guided by the cylindrical inner circumference  41   b  of shell  36   b.  Body  31   b  is thus permanently spacedly out of contact with body  44   b  and has no lip but only a widened collar which provides an end wall corresponding to the plunger crown of FIG.  1 . In FIGS. 2 and 3 the rib ducts or longitudinal grooves on the inner circumference of duct  58   a  or  58   b  are apparent and also extend over a length part of sleeve  35   a  or  35   b.  Instead of the seal between lips  43 ,  45  in FIG. 1, the seal is provided directly between shells  36   b,    38   b.  The inner circumference of shell  36   b  has an annularly protruding seal bead  43   b  which sealingly slides on the outer circumference of lug  38   b.  End face  51   b  is entirely planar up to edge  52   b.  As in FIG. 2 spring  34   b  is supported on the end side of the movable valve disk of valve  22   b.  Valve  20   b  is opened to a first width by the stop limited idle stroke of handle  39   b  relative to body  4   b.  By opening valve  22   b,  valve  20   b  subsequently opens to an even greater width. This second opening stroke may be significantly smaller than the first or idle stroke. 
     Shell  93   b  of body  91   b  extends only over part of the height of shell  62   b,  e.g. by only twice, three times or four times the thickness of wall  61   b.  Slots  88   b  are engaged by cams  89   b  and cams  97   b.  In rest position the stop face of cam  97   b,  which is remote from the stop face of cam  89   b,  is in contact with that end of slot  88   b  which is juxtaposed with wall  61   b.  In the up-stroke end position cams  89   b,    97   b  are in contact or inter-spaced with their mutually opposed and inclined faces. 
     In FIG. 4 piston unit  71   c  is snugly fitted to unit  2   c  with a piston rod. A one-part and resiliently yieldable piston sleeve is fixed to the rod. The downstream end of the piston sleeve forms the axially joltable spring  57   c.  The other end forms lip  72   c  which is widened in direction  12   c.  Between its ends the piston sleeve forms annular valve body  56   c.  The valve seat  55   c  is formed by the piston rod. Outlet duct  14   c  and a core body traverse the piston sleeve. The core body has ducts  58   c  in the outer circumference. Sleeve  76   c  is fixed to the core body with a widened end  75   c  and protrudes in direction  11   c.  Sleeve  76   c  positionally secures the piston sleeve. A further sleeve  35   c  of seal  31   c  is fixed to sleeve  76   c.  Downstream end  43   c  of seal  31   c  sealingly slides on face  41   c.  Oppositely to seal  31   c  the end  45   c  of seal  44   c  fixedly and sealingly contacts the same face  41   c.  Piston  44   c  is fixedly and sealingly seated on the outer circumference of shell  46   c  by a sleeve which protrudes from its piston crown in direction  11   c.  This inner shell  46   c  is radially spaced from shell  36   c  and protrudes in one part from wall  37   c  in direction  12   c.  Piston  31   c  has at the upstream end of sleeve  35   c  a radially protruding cam  47   c  which engages axially shiftable in an opening of shell  36   c  while being prevented from relative rotation. This opening traverses the upstream end face of shell  36   c  and forms stop  48   c  by its closed end. 
     Shell  67   c  protrudes freely into reservoir  6   c  and bounds chamber  15   c.  Shell  67   c  has an inner shoulder  74   c  on which lip  72   c  abuts at the end of the up-stroke. Thus valve  23   c  is opened during the subsequent stroke travel. An annular cover is mounted in direction  12   c  on the end of shell  67   c.  This casing cover may also be in one part with shell  67   c  or body  5   c.  Shell  66   c  of this cover overengages in close contact the outside and shell  68   c  likewise overengages the inside of shell  67   c.  The open end of shell  67   c  is fixed between shells  65   c,    66   c  by a snap lock. Flange  7   c  is in one part with the cover. The end of shell  68 c forms valve body  78   c  and the conical outside of lip  72   c  forms the movable valve body of valve  24   c.  The cover is traversed by the piston rod. The piston sleeve is permanently located in the cover with the majority of its length. Sleeves  31   c,    76   c  may commonly be in one part. 
     Valve  70   c  is located in the upstream end  85   c  of a constricted end section  83   c  of shell  67   c.  Pressure relief valve  70   c  has a valve ball corresponding to valve  23 . This valve body is loaded by spring  19   c  toward the closed position. Spring  19   c  is located in chamber  15   c  and supported by the core body. Vent  18   c  is bounded between the casing cover and the piston sleeve. Downstream of valve  23   c  the vent traverses shell  67   c  outside of chamber  15   c.  Thus air flows therefrom through filter  80   c  into reservoir  6   c.  Filter  80   c  is also the reservoir seal which directly sealingly supports on flange  7   c  and shell  67   c.    
     An inlet  16   c  from reservoir  6   c  to chamber  15   c  may also traverse wall  67   c  directly adjacent to seal  80   c.  The bound of inlet  16   c  forms with the boundary or lip  72   c  an inlet or slide valve. This valve is closed after a first stroke path and reopened towards the end of the down-stroke. Thus the reservoir  6   c  can be totally emptied. This valve and valve  70   c  are configured without a riser conduit  17  so that intake suction of the medium is only possible in the upside-down position. Instead of having an inlet opening shell  67   c  could also be sealingly closed at the upstream end. 
     Wall  61   c  is perpendicularly conically widened in direction  12   c.  Wall  61   c  directly slidingly adjoins the outer circumference of shell  36   c.  Handle  39   c  has protuberances or coaxial annular cams to prevent the user&#39;s fingers from slipping off. Shells  61   c,    62   c  permanently envelope body  5   c  over the majority of its length so that only end  83   c  protrudes. A crimp ring  8   c  fastenes body  5   c.  Ring  8   c  is located within shell  62   c.  Ring  8   c  contacts flange  7   c  and a corresponding flange of the reservoir neck at remote end sides. Ring  8   c  internally receives seal  80   c.    
     Body  91   c  is located mainly within cap  61   c,    62   c.  Conical end wall  92  of body  91   c  is directly juxtaposed with the inside of wall  61   c.  Actuating members  93   c  protrude from wall  92   c  in direction  11   c.  Pins  93   c  traverse closely adapted openings in wall  61   c  and form handle  39  by their end edges at the outside of wall  61   c.  Projections  93   c  are distributed in several, e.g. three, coaxial annular zones and are, like the openings of wall  61   c,  circumferentially interrupted. The outermost pins  93   c  are directly juxtaposed with the inside of shell  62   c.  The innermost pins  93   c  are closely juxtaposed with shell  36   c  or with the inner circumference of wall  61   c.  The outer circumference of shell  36   c  is permanently slidingly mounted on this inner circumference or on the annular edge of wall  61   c.  When pressing handle  39   c  shell  36   c  follows commonly with piston  31   c,    44   c  until the users fingers have attained the outer end side of wall  36   c  and until valve  20   c  is opened. Thereby either piston  72   c  may execute a partial stroke for partly or completely closing opening  16   c  or the cited idle travel is provided between shell  36   c  or stop  48   c  and cam  47   c.  After the opening stroke wall  61   c  and cam  93   c  commonly form handle  39   c  for implementing the pump stroke. The snap connector for shell  33   c  is provided within lip  43   c.    
     The volume of the illustrated suspended 20 μl droplet is maximally three or two times larger or just as large as the volume of head  32   c  of stopple  25   c.  In FIG. 4 valve  20   c  is shown open and piston  72   c  is in rest position at the start of the pump stroke. Stops  47   c,    48   c  have attained each other. FIG. 4 also indicates dot-dashed a protection cap for head  40   c.  This cap is in close or sealing contact with the out-sides of walls  36   c,    37   c,    61   c  and is to be withdrawn from dispenser  1   c  in direction  11   c.  At its end wall the cap has a projection which presses linearly pointwise or annularly against face  51   c  of body  25   c  in its closed position. All other portions of face  51   c  are free of contact. Thus the closing pressure between the closing faces of valve  20   c  is increased during shelf life of the dispenser. Face  51   c  is hemispherical and obtusely adjoins face  27   c  at sharp edge  52   c  in axial cross-section. Except for spring  19   c  the dispenser  1   c  requires no other spring since no spring is provided between bodies  31   c,    44   c.  Spring  19   c  closes valve  20   c.    
     Valve  20  or control  30  may be composed of maximally four injection molded plastic parts and spring  34 . For instance, parts  31 ,  44 ,  57  or parts  31 ,  36 ,  38  may be commonly in one part. Without reservoir  6  the dispenser  1  may consist of seven or eight such injection molded parts to which three springs  19 ,  34 ,  57 , body  56 , filter  80  and, in case, riser tube  17  are added. Bodies  5 ,  7 ,  82  and bodies  4 ,  31  could be likewise commonly in one part. Each of the springs could also be made in one part with one or both of the components by which they are directly supported. All cited features and properties may be provided precisely as described, or merely substantially or approximately so and may also greatly deviate therefrom depending e.g. on the viscosity of the medium. The illustrated size relationships are particularly favorable, particularly when the length of the dispenser  1  as measured over bodies  4 ,  5 ,  40  is smaller than 10 cm or 7 cm and when its largest width is smaller, like smaller than 5 cm or 3 cm.