Patent Publication Number: US-9901947-B2

Title: Apparatus and related methods for dispensation of a liquid

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of currently pending U.S. patent application Ser. No. 13/924,135 filed 21 Jun. 2013 and titled APPARATUS AND RELATED METHODS FOR DISPENSATION OF A LIQUID, which is hereby incorporated by reference in its entirety herein. 
    
    
     BACKGROUND 
     Field 
     The present disclosure relates to apparatus and related methods for spray dispensation of a liquid, and, more particularly, to apparatus and related methods for dispensation by spray of a unit dose of liquid from a hermetically sealed container. 
     Background 
     It may be desirable to dispense a unit dose of liquid by spray from a hermetically sealed container in various medical applications. Liquid, as used herein, includes, for example, various materials in the liquid phase, solutions, suspensions, and emulsions that may be required to be hermetically sealed from the environment until just prior to dispensing with precision in a controllable and reproducible manner. The liquid may be, for example, an adhesive for the closure of surgical incisions, attachment of tissues, the closure of cuts or wounds, such as a polymerizing or cross-linking medical adhesive. In various aspects, the liquid may be, for example, a disinfectant, an analgesic, an antibiotic, or other such medically useful liquid, as would be readily recognized by those of ordinary skill in the art upon study of the present disclosure. In various aspects, the liquid may be a liquid having use in medical, automotive, aerospace, marine, or any other applications in which a unit dose of liquid may be applied and wherein the liquid is hermetically sealed until dispensed. A unit dose refers an amount of the liquid desired to be available for dispensing. This amount may be the total amount required for one application, in some aspects. In other aspects, the unit dose may be an amount of liquid sufficient for multiple applications usable in one or more dispensing sessions. 
     The liquid may be hermetically sealed within a container to prevent exposure to the environment until dispensed. Hermetic seal and hermetically sealed, as used herein, means a seal that is impervious to air, gas, atomic clusters, molecular clusters, or particulates. The hermetic seal may conform to specific technical standards, in various aspects, and these standards may reflect various degrees of imperviousness to air, gas, atomic clusters, molecular clusters, or particulates. The hermetic sealing of the liquid within the container may, for example, prevent contamination of the liquid by various contaminants such as dust or microbes within the environment, may prevent degradation of the liquid by exposure to oxygen or other gasses in the atmosphere, or may prevent the loss of liquid from the container, the degradation of an evacuated container by leakage of air, gas, atomic clusters, molecular clusters, or particulates. into the container. As a further example, the hermetic sealing of the liquid within the container may prevent the escape of gas from the container, the gas, such as an inert gas, being included with the liquid within the container. The hermetic seal may prevent intrusion of bacteria, dirt or any other contaminants, or premature chemical or other reactions prior to dispensing, in various aspects. 
     Various devices have been developed for the spray dispensation of liquid from a hermetically sealed container. For example, one such device includes a breakable glass ampoule that contains the hermetically sealed liquid within. The ampoule is placed within a cavity formed within a flexible casing, so that breaking the ampoule causes the liquid to fill the cavity. Subsequent squeezing of the casing dispenses the liquid through a nozzle in fluid communication with the casing. However, the ampoule breaks in a random non-repeatable fashion that may contribute a measure of randomness to the dispensation of a unit dose of liquid by spray from the device. The breaking of the ampoule causes glass fragments to be suspended in the liquid. These glass fragments may block small passages formed in or about the nozzle, which may cause unpredictable variations in the spray delivered by the nozzle. Furthermore, the spray may contain glass fragments, which may be undesirable or even dangerous in a medical application. 
     Other devices either pressurize the liquid directly or indirectly through deforming container that contains the liquid. Deformation of the container causes a seal to rupture, with the liquid being dispensed following rupture of the seal. Such devices may be characterized by the randomness of the seal-rupturing process. The controllability of such devices may be compromised by the non-reproducible liquid pressure spike and flow spike directly following the rupture of the seal, which may make it difficult to deliver a unit dose of liquid by spray from such devices. 
     Yet another device requires a manual opening of the nozzle exit to unseal the initially hermetically sealed container and requires an inherently random squeezing of the container to dispense the liquid from through the nozzle from the container. This opening process presents impediments to designing appropriate nozzle systems. The randomness with which the container is squeezed may inhibit precise or predictable dispensation of a unit dose from the device. 
     Accordingly, there is a need for improved apparatus as well as related methods for dispensation by spray of a unit dose of liquid from a hermetically sealed container. 
     BRIEF SUMMARY OF THE INVENTION 
     These and other needs and disadvantages may be overcome by the apparatus and related manufactures and methods disclosed herein. Additional improvements and advantages may be recognized by those of ordinary skill in the art upon study of the present disclosure. 
     A dispenser is disclosed herein. In various aspects, the dispenser includes a piston slidably sealingly engagable with a container containing a unit dose of liquid therein. The dispenser includes a cutting edge disposed about a piston face of the piston, the cutting edge configured to open a covering of rigid construction sealingly engaged with the container, in various aspects. A passage is formed between a piston face of the piston and a nozzle outlet of a nozzle to communicate fluid from the container through the nozzle outlet by sliding of the piston within the container, in various aspects. Methods of use of the dispenser are disclosed herein. 
     This summary is presented to provide a basic understanding of some aspects of the apparatus and methods disclosed herein as a prelude to the detailed description that follows below. Accordingly, this summary is not intended to identify key elements of the apparatus and methods disclosed herein or to delineate the scope thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates by perspective view and exemplary implementation of a dispenser; 
         FIG. 2  illustrates by side cross-sectional view the exemplary implementation of the dispenser of  FIG. 1 ; 
         FIG. 3  illustrates by perspective view portions of the exemplary implementation of the dispenser of  FIG. 1 ; 
         FIG. 4  illustrates by frontal view portions of the exemplary implementation of the dispenser of  FIG. 1 ; 
         FIG. 5A  illustrates by side view portions of the exemplary implementation of the dispenser of  FIG. 1  at a first operational stage; 
         FIG. 5B  illustrates by side view portions of the exemplary implementation of the dispenser of  FIG. 1  at a second operational stage; 
         FIG. 5C  illustrates by side view portions of the exemplary implementation of the dispenser of  FIG. 1  at a third operational stage; 
         FIG. 5D  illustrates by side view portions of the exemplary implementation of the dispenser of  FIG. 1  at a fourth operational stage; 
         FIG. 5E  illustrates by side view portions of the exemplary implementation of the dispenser of  FIG. 1  at a fifth operational stage; 
         FIG. 5F  illustrates schematically volumetric relationships within the exemplary implementation of the dispenser of  FIG. 1  at the fourth operational stage as illustrated in  FIG. 5D ; 
         FIG. 6  illustrates by side cross-sectional view another exemplary implementation of a dispenser; 
         FIG. 7A  illustrates by side cross-sectional view portions of the exemplary implementation of the dispenser of  FIG. 6 ; 
         FIG. 7B  illustrates by top view portions of the exemplary implementation of the dispenser of  FIG. 6 ; 
         FIG. 7C  illustrates by side cross-sectional view portions of the exemplary implementation of the dispenser of  FIG. 6 ; 
         FIG. 7D  illustrates by frontal cross-sectional view portions of the exemplary implementation of the dispenser of  FIG. 6 ; 
         FIG. 8A  illustrates by side view portions of the exemplary implementation of the dispenser of  FIG. 6  at a first operational stage; 
         FIG. 8B  illustrates by side view portions of the exemplary implementation of the dispenser of  FIG. 6  at a second operational stage; 
         FIG. 8C  illustrates by side view portions of the exemplary implementation of the dispenser of  FIG. 6  at a third operational stage; 
         FIG. 8D  illustrates by side view portions of the exemplary implementation of the dispenser of  FIG. 6  at a fourth operational stage; 
         FIG. 8E  illustrates schematically volumetric relationships within the exemplary implementation of the dispenser of  FIG. 6  at the third operational stage as illustrated in  FIG. 8C ; 
         FIG. 9  illustrates by exploded perspective view portions of another exemplary implementation of a dispenser; 
         FIG. 10  illustrates by side view portions of yet another exemplary implementation of a dispenser; 
         FIG. 11  illustrates by perspective view portions of another exemplary implementation of a dispenser; 
         FIG. 12  illustrates by exploded perspective view portions of another exemplary implementation of a dispenser; 
         FIG. 13  illustrates by perspective view portions of another exemplary implementation of a dispenser; 
         FIG. 14  illustrates by perspective view portions of another exemplary implementation of a dispenser; 
         FIG. 15  illustrates by perspective view portions of another exemplary implementation of a dispenser; 
         FIG. 16  illustrates by process flow chart an exemplary method of use of a dispenser; and, 
         FIG. 17  illustrates by perspective view portions of yet another exemplary implementation of a dispenser. 
     
    
    
     The Figures are exemplary only, and the implementations illustrated therein are selected to facilitate explanation. The number, position, relationship and dimensions of the elements shown in the Figures to form the various implementations described herein, as well as dimensions and dimensional proportions to conform to specific force, weight, strength, flow and similar requirements are explained herein or are understandable to a person of ordinary skill in the art upon study of this disclosure. Where used in the various Figures, the same numerals designate the same or similar elements. Furthermore, when the terms “top,” “bottom,” “right,” “left,” “forward,” “rear,” “first,” “second,” “inside,” “outside,” and similar terms are used, the terms should be understood in reference to the orientation of the implementations shown in the drawings and are utilized to facilitate description thereof. Use herein of relative terms such as generally, about, approximately, essentially, may be indicative of engineering, manufacturing, or scientific tolerances such as ±0.1%, ±1%, ±2.5%, ±5%, or other such tolerances, as would be recognized by those of ordinary skill in the art upon study of this disclosure. 
     DETAILED DESCRIPTION OF THE INVENTION 
     A dispenser apparatus and related methods for dispensing a unit dose of liquid by spray from a hermetically sealed container are disclosed herein. The spray emitted from the dispenser may have precise and repeatable spray characteristics. 
     In various aspects, the dispenser includes a piston that is slidably receivable within the container. The container contains the liquid to be sprayed in a unit dose, and a covering of rigid construction sealingly engages the container to hermetically seal the liquid within the container. A cutting edge may be disposed about a piston face of the piston to open the covering as the piston is aligned with the container, in various aspects. The dispenser includes a nozzle fluidly communicating with the piston such that the nozzle sprays liquid communicated to the nozzle by advancement of the piston within the container, in various aspects. In various aspects, the dispenser may include a container assembly that includes the container, and the dispenser may include a sleeve surrounding the piston configured to engage the container assembly. Various arms, grippable surfaces, and the like may be formed about the dispenser including the sleeve and the container assembly, and the user may manipulate the dispenser using these arms, grippable surfaces, and the like. 
     In operation, the user may manipulate the dispenser thereby opening the covering and then aligning the piston with the container. Opening includes, without limitation, cutting, piercing, cleaving, bursting, parting, or otherwise causing the covering to fail thereby opening the cover. The covering may be engineered to include weak points at which the covering will open upon being engaged with the piston. The covering may include concentrated stress points at which the stress induced by the piston is concentrated thereby causing the covering to open through failure of the covering material at the concentrated stress points upon engagement of the covering with the piston. The user may advance the piston so that the cutting edge first contacts the covering and then opens the covering. The cutting edge, which is disposed about the piston face of the piston, extends forth from the piston face to contact the covering and then opens the covering prior to engagement of the piston with the container, in various aspects. Following the opening of the covering by the cutting edge, the piston may be further advanced into alignment with the container. The piston may be aligned with the container as the piston is advanced in engagement with the container by shoulders formed about the circumference of the piston face of the piston, in various aspects. The piston may be advanced through the opened covering as the piston is aligned with the container. Following alignment with the container, the piston may be advanced within the container thereby expelling liquid from the container as spray from the nozzle, which is in fluid communication with the piston, and, thence, the liquid within the container, in various aspects. 
     Opening the covering with only the cutting edge in contact with the covering may reduce or eliminate pressure spikes in the liquid pressure as the covering is opened because only the cutting edge and not the piston contacts the covering to open the covering. The covering may be rigid to minimize deformation of the covering as the covering is being opened, which may reduce or eliminate pressure spikes in the liquid. 
     In various aspects, the piston is aligned with the container following opening of the covering. Following alignment with the container, the piston is advanced within the container in engagement with the liquid thus spraying a unit dose of liquid from the container. A passage formed between a piston face of the piston and the nozzle conveys the liquid from the container through the nozzle, which emits the liquid as a spray, in various aspects. By manipulation of the dispenser, the user may control the advancement rate of the piston within the container, thereby controlling the liquid pressure developed within the liquid by the piston and the flow rate at which the liquid is sprayed from the nozzle. Note that the flow rate equals the rate at which the piston displaces the volume of the container, and the liquid pressure is related to the force applied to the liquid by the piston, both of which may be controlled by the user. The spray characteristics of the spray from the nozzle may be related to the liquid pressure and the flow rate, so that the user may control the spray characteristics by controlling the advancement rate of the piston and the force applied to the liquid by the piston. 
     In various aspects, the dispenser is formed so that the displaced volume of liquid that is displaced when the piston is aligned with the container to be slidingly engaged with the container and engaged with the liquid to be positioned to initiate controlled dispensing of the liquid is less than the priming volume. The priming volume is the volume of the passage(s) between the piston face of the piston and the nozzle exit of the nozzle. Making the displaced volume less than or equal to the priming volume may eliminate wastage of liquid from the nozzle caused by spikes in the liquid pressure during opening of the covering and alignment of the piston with the container. 
     Spray characteristics of the spray from the nozzle may include the flow rate, spray angle, spray pattern, spray quality, droplet spectrum, distribution on target, and droplet drift. Spray quality may be expressed in terms of its average droplet size, and spray quality may be an indicator of droplet drift, which may be undesirable. Droplet drift characterizes the portions of the spray that does not reach an intended target due to factors such as air velocity (wind), spray height, operating speed, air temperature, and humidity. 
     The spray characteristics of the spray may be important in various applications, and the desired spay characteristics may vary depending upon the particular application. The spray may be formed of droplets having a find droplet size some applications, while the spray may be formed of droplets having a coarse droplet size in other applications. For example, droplet sizes less than about 150 microns may be used for applications where the coverage of the spray is to be maximized. Coarse droplet sizes of around 300 microns may be used in applications that seek to minimize spray drift, which may cause the spray to miss a target, in order to direct the maximum amount of spray onto the target. Note that droplets generally less than about 100 microns may be prone to drift, so that it may be desirable to avoid droplets less than about 100 microns. 
     The absence of a pressure spike in the liquid pressure coupled with control of the liquid pressure and the liquid velocity by control of the advancement of the piston within the container, in various aspects, may enhance the ability of the user to produce spray having consistent spray characteristics from the dispenser. Because the nozzle may produce different droplet sizes at different pressures, controlling the liquid pressure of the liquid within the container as the piston is inserted into the container and controlling the liquid pressure as the piston is advanced within the container may enhance control of the spray characteristics including the droplet size. The user may visually monitor the spray characteristics of the spray and adjust the advancement rate of the piston within the container to control the spray characteristics of the spray during dispensation of the unit dose. Such visual monitoring by the user may constitute a feedback mechanism, which may be inherent in the dispenser. Consistent opening of the covering from container to container may allow the user to develop facility with the dispenser thereby allowing the user to produce consistent spray characteristics. 
     In various aspects, the nozzle is formed as a pressure-atomizing nozzle. In various aspects, the nozzle includes a swirl chamber. Nozzles including a swirl chamber may produce sprays having better spray characteristics in comparison with the spray characteristics of spray produced by a pressure-atomizing nozzle. The dispenser may include two or more interchangeable nozzles, in various aspects selectable to produce spray having selected spray characteristics. 
     The nozzle, in various implementations, may be formed, for example, as a flocked tip nozzle, brushed tip nozzle, porous tip nozzle, wetted tip nozzle, or other such nozzle capable of depositing liquid upon an application surface. Spray, as used herein, includes the liquid discharges from, for example, a flocked tip nozzle, brushed tip nozzle, porous tip nozzle, or wetted tip nozzle. Spay characteristics includes characteristics of the liquid discharges from, for example, a flocked tip nozzle, brushed tip nozzle, porous tip nozzle, or wetted tip nozzle. The characteristics of such liquid discharges may include the thickness of the liquid deposited upon the application surface, the width of the liquid deposited upon the application surface, or other such characteristics, as would be readily recognized by those of ordinary skill in the art upon study of this disclosure. The tip nozzle may be wetted in a controllable and precise manner as liquid is transferred from the wetted tip to the application surface by sliding the wetted contact area over the application surface. For a uniform application of the liquid, the rate at which the liquid is dispensed should be proportional to the rate at which the contact surface slides over the application surface. The rate at which a porous or flocked contact tip nozzle is wetted is controlled by the user through the advancement of the piston and the force applied to the liquid. If a non-uniform application is desired, the flow rate of the liquid to the contact area is adjusted accordingly. 
     Higher aspect ratio cylindrical containers (height/diameter for the particular case of a cylindrical container) may give more accurate control of sprays with larger droplet sizes and less droplet drift. Lower aspect ratio cylindrical containers may give more accurate control of sprays with smaller droplet sizes. 
     In various aspects, the container is separable from other portions of the dispenser including the piston, sleeve, and nozzle. Use of a separable container may, for example, facilitate the filling of the container without interference from the other portions of the dispenser. Use of a separable container may, for example, facilitate thermal treatment of the liquid hermetically sealed within the container, or radiation treatment of the liquid hermetically sealed within the container without interference from the other portions of the dispenser. 
     The dispenser may dispense by spray multiple unit doses from multiple containers in succession, in various aspects. The dispenser may dispense multiple unit doses from a single container, in various aspects. In various aspects, the dispenser apparatus may be formed of materials such as, for example, polyethylene, polyethylene terephthalate, polypropylene, polyamides, glass, metal such as aluminum or stainless steel, synthetic or natural rubber, and combinations thereof. The material(s) may be selected based upon compatibility with the liquid to be dispensed. In various aspects, the dispenser apparatus and methods disclosed herein may be used in medical, automotive, aerospace, marine, or any other applications for application of a unit dose of liquid wherein the liquid is hermetically sealed until dispensing. 
     Turning now to the exemplary implementations illustrated in the various Figures,  FIG. 1  illustrates exemplary dispenser  10 . As illustrated in  FIG. 1 , dispenser  10  includes body  20 . Stalk  40  extends forth from distal end  23  of body  20  with proximal end  41  of stalk  40  being secured about distal end  23  of body  20 , as illustrated, and proximal end  51  of nozzle  50  secured to distal end  43  of stalk  40 . The length of stalk  40 , in various implementations, may be determined by the application. For example, to deliver a fluoride varnish, anti-inflammatory, or other medical agents in oral-hygiene applications, a long and slender stalk  40  may be desirable to enable comfortably reaching any desired location. To deliver medical agents in the aural or nasal passages, stalk  40  may be short in order to prevent too deep insertions of the dispensing device that may be harmful. 
     Nozzle outlet  52  is formed in distal end  53  of nozzle  50 , in this implementation, and spray  14  may be sprayed forth from nozzle outlet  52  of nozzle  50 . In various other implementations, the stalk  40  may have various lengths, bends, and other such configurations. One or more nozzle outlets, such as nozzle outlet  52 , may be located about various portions of nozzle  50 , to spray the spray  14  in various orientation(s) with respect to nozzle  50 . Some implementations may omit stalk  40  entirely. In such implementations, the nozzle, such as nozzle  50 , may be located within body  20  or, for example, about distal end  23  of body  20 . Nozzle  50  may be configured as a flocked tip nozzle, brushed tip nozzle, or pressure atomizing nozzle, in various implementations. Nozzle  50  may be removably secured to stalk  40  so that nozzle  50  may be interchangeably selectable from a plurality of differing nozzles, such as, for example, a brushed tip nozzle or a flocked tip nozzle. 
     Body  20  includes arms  27 ,  29  that extend forth from outer surface  32  of body  20 , as illustrated in  FIG. 1 . Arms  27 ,  29  include grippable surfaces  28  that may be formed, for example, as checkering, corrugations, indentations, roughening, patterning, or combinations thereof on portions of the surface of arms  27 ,  29 . Grippable surface  28  in conjunction with arms  27 ,  29  may enhance the gripping of arms  27 ,  29  by the user to facilitate the user&#39;s manipulation of dispenser  10 . Other implementations may include a single arm, such as arm  27  or arm  29 , that extends circumferentially around body  20 . Still other implementations, may include additional arms, such as arms  27 ,  29 , and the arms may assume various shapes, for example, with holes or curves that accommodate the finger(s) or hand(s) of the user. Grippable surfaces, such as grippable surface  28 , may be variously formed about the arm(s) or body  20 , in various implementations. A grippable surface, such as grippable surface  28 , may be formed about proximal end  71  of container assembly  70  to allow the user to apprehend proximal end  71  with the thumb, in various implementations. 
     Dispenser  10  includes container assembly  70  that is insertably received within body  20  through proximal end  21  of body  20 , as illustrated in  FIG. 1 . Key  74 , which is formed as a protuberance on outer surface  72  of container assembly  70 , engages male-female with keyway  24 , which is formed as a slot in body  20 , in this implementation. The slidable interlocking engagement between key  74  and keyway  24  illustrated in  FIG. 1  may orient the container assembly  70  with respect to body  20  and may prevent rotation of container assembly  70  as container assembly  70  is advanced into body  20  through proximal end  21  in implementations wherein container assembly has a cylindrical shape with a cylindrical cross-section. Key  74  and keyway  24  may be formed with various combinations of male elements—e.g. flanges, rails, protuberances—and corresponding female elements—e.g. slots, grooves, channels—to allow key  74  of container assembly  70  to slidably engage keyway  24  of body  20 , in various other implementations. The male element(s), such as key  74 , and the corresponding female element(s), such as keyway  24 , may be variously distributed between body  20  and container assembly  70 , in various other implementations. Some implementations may omit key  74  and keyway  74 . 
     In various implementations, key  74  and keyway  24  may be formed as a safety lock. For example, container assembly  70  may be inserted within body  20  as distributed from a supplier but may be unable to engage piston until key  74  and keyway  24  are engaged with one another, thereby preventing inadvertent premature opening of container  80  of container assembly  70 . Key  74  and keyway  24  may be engaged with one another by rotation of container assembly  70  within sleeve  30 , in various implementations. 
     As illustrated in  FIG. 2 , body  20  forms both sleeve  30  and piston  60 , and sleeve  30  and piston  60  are of generally a unitary piece. Inner surface  34  of sleeve  30  defines chamber  36 . Piston  60  extends forth from body  20  into chamber  36  proximate distal end  23  of body  20 , and piston face  61  of piston  60  is oriented toward proximal end  21  of body  20 , as illustrated. Inlet  62  is formed in piston face  61  of piston  60 , and inlet  62  communicates with passage  65 , which is formed within piston  60 . Passage  65 , in turn, communicates with passage  45  within stalk  40 , passage  45  communicates with passage  55  within nozzle  50 , passage  55  communicates with passage  57  within nozzle  50 , and passage  57  communicates with nozzle outlet  52 . Accordingly, liquid  12  may pass into inlet  62  into passage  65 , through passages  65 ,  45 ,  55 ,  57 , respectively, and from passage  57  through nozzle outlet  52 , in this implementation. Passage  57  has a smaller cross-section than passage  55 , in this implementation, so that the liquid  12  is accelerated as the liquid  12  passes from passage  55  through passage  57  to exit nozzle  50  through nozzle outlet  52  as spray  14 . In certain implementations, for example, implementations wherein nozzle  50  is formed as a porous tip or flocked tip, passage  57  may have a larger cross section than passage  55  to allow the liquid to wet nozzle  50  uniformly through capillary and convective fluid motion. 
     Container assembly  70  is insertably received within chamber  36  of sleeve  30  through proximal end  21  of body  20 , as illustrated in  FIG. 2 ., with distal end  73  of container  70  oriented toward piston face  61  of piston  60 . Key  74  is slidably engaged with keyway  24 , as illustrated, and key  74  may be so engaged with keyway  24  as container assembly  70  is inserted into chamber  36 . In other implementations, container assembly  70  may be rotated within sleeve  30  to engage keyway  24  with key  74 . 
     Container  80  is formed within portions of container assembly  70 , in the implementation of  FIG. 2 , and reservoir  86  of container  80  is defined by surface  75  of container assembly  70 , inner surface  82  of container assembly  70 , and inner surface  91  of covering  90 . Accordingly, in this implementation, apart from covering  90 , container  80  and container assembly  70  are formed a unitary structure. The container assembly, such as container assembly  70 , and the container, such as container  80 , may be separable elements that may be, for example, slidably engaged with one another to allow replacement of the container within the container assembly, in other implementations (see  FIG. 12 ). 
     Covering  90  is sealingly engaged about distal end  73  of container assembly  70  by hermetic seal  94  to enclose sealingly reservoir  86  of container  80  and liquid  12  therein, in this illustrated implementation. Covering  90  may be formed of, for example, metal foil, various plastics, glass, or other such materials, as would be readily recognized by those of ordinary skill in the art upon study of this disclosure. The foil, for example, may be aluminum covered in part with a liquid-compatible coating, so that surface  91  of covering  90  is compatible with liquid  12 . 
     Piston  60  is formed to be insertable through covering  90  into reservoir  86  of container  80  to be aligned with container  80  in the implementation of  FIG. 2 . When so aligned, piston face  61  is faced toward surface  75  and piston side  64  is faced toward surface  82 . Piston side  64  may be sealingly slidably biased against surface  82  to prevent leakage of liquid  12  between piston side  64  and surface  82  as piston  60  is advanced within reservoir  86  toward surface  75 . Annular slot  37 , which is generally defined by inner surface  34  of sleeve  30  and piston side  64  of piston  60 , is sized to accommodate wall  77  of container assembly  70  as piston  60  is advanced within reservoir  86 , and annular slot  37  extends sufficiently toward distal end  23  to allow piston  60  to advance within reservoir  86  until piston face  61  contacts surface  75 , which is the limit of advance of piston  60 , in this implementation. 
       FIG. 3  further illustrates piston  60  of dispenser  10 . As illustrated in  FIG. 3 , inlet  62  is located at the center of circularly shaped piston face  61 . Shoulder  67  is formed about the periphery of piston face  61  of piston  60 , and portions of shoulder  67  extend forth from piston face  61  and are tapered into a point to form cutting edge  68 , as illustrated. 
       FIG. 4  further illustrates container assembly  70  and container  80 . As illustrated in  FIG. 4 , key  74 , which is rectangular in shape, extends forth from outer surface  72  of container assembly  70  to engage keyway  24  in body  20 . Keyway  24  is formed as a rectangular slot configured to receive rectangular key  74  therein, in this implementation. Covering  90  covers reservoir  86  extending to overlap portions of wall  77 , as illustrated. Covering  90  is bonded to portions of wall  77  at distal end  73  that faces piston surface  61  of piston  60  to form hermetic seal  94 , in this implementation. Hermetic seal  94  extends around the entire circumference of wall  77 , which is circular in shape, to hermetically seal liquid  12  within reservoir  86 , in this implementation. In other implementations such as that in  FIG. 6 , covering  290  may be bonded to inner surface  282  of container  280  to form hermetic seal  294 . In the implementation of  FIG. 4 , inner surface  82  of container  80  is circular in shape in conformance to the circular shape of piston side  64  of piston  60  (see  FIG. 3 ), so that piston side  64  may be sealingly slidably biased against surface  82  as piston  60  is advanced within reservoir  86  toward surface  75 . 
     In operation, the user may insert container assembly  70  into chamber  36  of sleeve  30 . Container assembly  70  includes container  80  with liquid  12  hermetically sealed within reservoir  86  by covering  90 , in this implementation. As the user inserts container assembly  70  into sleeve  30 , in this implementation, key  74  of container assembly  70  is engaged with keyway  24  of sleeve  30 , which orients container assembly  70  with respect to sleeve  30  and piston  60 , and prevents rotation of container assembly  70  within sleeve, particularly as piston  60  engages container assembly  70  including container  80 . 
     With the container assembly  70  inserted into sleeve  30 , the user may, for example, grasp body  20  by arms  27 ,  29  using the index finger and the middle finger, and the user may press upon proximal end  71  of container assembly  70  with the thumb to force piston  60  through covering  90  into reservoir  86  to be aligned with container  80 . With piston  60  aligned with container  80 , the user may press upon arms  27 ,  29  and proximal end  71  to advance piston  60  within reservoir  86  until piston face  61  contacts surface  75  thereby administering a unit dose of liquid  12  as spray  14  from dispenser  10 . 
       FIGS. 5A-5E  illustrate operational stages  103 ,  107 ,  109 ,  115 ,  119  respectively, of dispenser  10  as piston  60  is forced through covering  90 , piston  60  is aligned with reservoir  86  of container  80 , and then piston  60  is advanced within reservoir  86  to dispense a unit dose of liquid  12  from container  80  as spray  14 . With container assembly  70  received within sleeve  30 , the user may press upon arms  27 ,  29  and proximal end  71  to slidably advance piston  60  and container assembly  70  toward one another thereby progressing consecutively through exemplary operational stages  103 ,  107 ,  109 ,  115 ,  119 . 
       FIG. 5A  illustrates piston  60  and container assembly  70  at operational stage  103  wherein piston  60 , including cutting edge  68  on piston face  61  of piston  60 , is set apart from container assembly  70  including container  80  and covering  90 . Piston  60  may be proximate container assembly  70  and piston  60  and container assembly  70  may be advancing toward one another as manipulated by the user, at operational stage  103 . 
     As illustrated in  FIG. 5A , piston face  61  has a concave shape between shoulder  67  and inlet  62  curving inward from shoulder  67  toward inlet  62 . In other implementations, piston face  61  may be flat thereby forming a right angle with respect to piston side  64 . As illustrated in  FIG. 5A , piston  60  includes shoulder  67  that extends around piston face  61  at the periphery of piston face  61 . In this implementation, portions of shoulder  67  are formed as an angled surface. Portions of shoulder  67  extend forth to form cutting edge  68 , as illustrated. As indicated by the dash-dot line in  FIG. 5A , piston  60  and container assembly  70  are misaligned with one another at operational stage  103 , so that distal end  73  of container assembly  70  will strike shoulder  67  of piston  60  as piston  60  and container assembly  70  are advanced toward one another. Shoulder  67  functions to correct such misalignment, when necessary, by aligning piston  60  with container  80  thereby allowing piston  60  to be inserted into reservoir  86  of container  80 . Some implementations may omit the shoulder, such as shoulder  67 . 
       FIG. 5B  illustrates operational stage  107  of dispenser  10 . At operation stage  107 , cutting edge  68  contacts outer surface  93  of covering  90 , as illustrated. The portions of shoulder  67 , other than those portions of shoulder  67  that form cutting edge  68 , are set apart from container assembly  70  including wall  77 , which forms a portion of container  80 , in this implementation. Covering  90  is sufficiently rigid so that covering  90  does not bend appreciably into reservoir  86 , which would create liquid pressure in liquid  12 , as cutting edge  68  opens covering  90 . The protrusion of cutting edge  68  from piston face  61  is exaggerated for illustrative purposes in the Figures. Cutting edge  68  may protrude in the range of 10% of the hydraulic diameter (see equation 1) of piston  60 , in various implementations. 
     While the process of opening covering  90  may be cutting-tip dependent, covering dependent, and dependent on how much gas is present next to the liquid in the container, dispenser  10  opens the covering before any appreciable liquid pressurization takes place. This is likely the case with most applications where a gas is present in the container with the liquid and where the uncompressed volume of gas is substantially less than the volumetric displacement caused by the deformation of the covering by the cutting surface prior to the actual opening of the covering, which would relieve the pressure. 
       FIG. 5C  illustrates operational stage  109  of dispenser  10 . At operation stage  109 , cutting edge  68  penetrates covering  90  from outer surface  93  through inner surface  91  to open covering  90 , as illustrated. Only cutting edge  68  contacts covering  90  as covering  90  is opened during the progression from operational stage  107  to operational stage  109 . The opened covering  90  is included in  FIG. 5C , but is omitted from  FIGS. 5D, 5E  for clarity. 
     At operational stage  109 , distal end  73  of container assembly  70  contacts shoulder  67  of piston  60  following opening of covering  90  by cutting edge  68 , as illustrated, due to misalignment between piston  60  and container assembly  70 . The misalignment shown in the Figures may be exaggerated for illustrative purposes. Misalignment may be less than 1% of the hydraulic diameter (see equation 1) of piston  60 , in various implementations. The contact between distal end  73  and shoulder  67  may seal reservoir  86 , at least in part, thereby preventing escape of liquid  12  from reservoir  86  following opening of covering  90  as piston  60  is inserted into reservoir  86 . The progression from operational stage  109  to operational stage  115  (see  FIG. 5D ) exemplifies the alignment of piston  60  into reservoir  86 . Recognizing that distal end  73  is circumferential, other portions of distal end  73  not included in the illustration may be otherwise misaligned with piston  60 . Alternatively, piston  60  may be aligned with container assembly  70 , in which case piston side  64  sealingly engages portions of inner surface  82  proximate distal end  73  thereby retaining liquid  12  within reservoir  86  upon opening covering  90 . 
       FIG. 5D  illustrates operational stage  115  of piston  60  with respect to container assembly  70  including container  80  with covering  90 . Between operational stage  109  and operational stage  115 , distal end  73  of container assembly  70  slides over shoulder  67  thereby aligning piston  60  with reservoir  86  of container  80 , if necessary, thus enabling the advancement of piston  60  into reservoir  86  of container  80  between operational stages  115  and  119 . 
     At operational stage  115 , piston  60  is aligned with reservoir  86  of container  80 , as illustrated in  FIG. 5D . Edge  69  formed between piston face  61  and piston side  64  is positioned slightly past distal end  73  within reservoir  86  of container  80  so that portions of piston side  64  of piston  60  are slidingly sealingly biased circumferentially against inner surface  82  of container  82  at exemplary operational stage  115 . The sealing biasing of piston side  64  of piston  60  against inner surface  82  of container  80  prevents leakage of liquid  12  between piston side  64  and inner surface  82  at exemplary operational stage  115 . The sliding sealing biasing of piston side  64  against inner surface  82  prevents leakage of liquid  12  between piston side  64  and inner surface  82  as piston  60  is advanced within reservoir  86  during the progression from operational stage  115  to operational stage  119  (see  FIG. 5E ). 
     The process of aligning piston  60  with reservoir  86  of container  80  encompasses the progression from operational stage  109 , illustrated in  FIG. 5C , to operational stage  115 , illustrated in  FIG. 5D , in this implementation. Piston  60  including the curvature, if any, of piston face  61  and the cutting edge  68  that extends forth from piston face  61  may be sized so that the displaced volume  88  with piston  60  aligned with reservoir  86  at operational stage  115  (illustrated by the cross-hatched region in  FIG. 5D ) is less than priming volume  59 , which is the volume of passages  65 ,  45 ,  55 ,  57  between inlet  62  in piston face  61  of piston  60  and nozzle outlet  52  in order to avoid wastage of liquid from nozzle  50  caused by displacement of liquid  12  during inserting piston  60  into reservoir  86  of container  80 . Piston  60 , passages  65 ,  45 ,  55 ,  57 , or both may be sized or otherwise formed accordingly. Displaced volume  88  is the volume of liquid  12  displaced by piston  60  as piston  60  is inserted into container  80  and equals the volume of those portions of piston  60  that lie within container  80  at operational stage  115 , in this implementation. 
       FIG. 5F  presents this schematically with the displaced volume  88  illustrated as the crosshatched region. Priming volume  59 , as illustrated schematically in  FIG. 5F , equals the volume of passages  65 ,  45 ,  55 ,  57  between inlet  62  in piston face  61  of piston  60  and nozzle outlet  52  in this implementation. Following alignment of piston  60  with reservoir  86  at operational stage  115 , the displaced volume  88  occupies a portion of priming volume  59  as indicated by the striped region in  FIG. 5F . Displaced volume  88  may occupy all of priming volume  59  or essentially all of priming volume  59 , in various implementations. 
     Operational stage  119  is illustrated in  FIG. 5E . At operational stage  119 , as illustrated, piston  60  has been advanced within reservoir  86  of container  80  such that at least portions of piston face  61  of piston  60  are biased against surface  75  of container  80 . 
     As piston  60  is advanced within container  80  during the progression from operational stage  115  to operational stage  119  to deliver a unit dose of liquid  12  from container  80 , liquid  12  is forced from reservoir  86  through inlet  62  into passage  65 , through passages  65 ,  45 ,  55 ,  57 , in progression, and from passage  57  through nozzle outlet  52 . Liquid  12  is sprayed forth as spray  14  from nozzle outlet  52  of nozzle  50  during delivery of the unit dose of liquid  12 . 
     The user may direct the spray  14  toward a target by orienting nozzle outlet  52  toward the target. The user may regulate the spray characteristics of the spray  14  emitted from dispenser  10 , for example, by controlling the force applied by the forefinger, the middle finger, and the thumb to arms  27 ,  29  of body  20  and proximal end  71  of container assembly  70 . The user may observe the spray characteristics of the spray  14  emitted from dispenser  10 , and the user may adjust the force applied to arms  27 ,  29  and proximal end  71  of container assembly  70  to adjust the spray characteristics in order to obtain the desired spray characteristics. 
     As the unit dose of liquid  12  is delivered from container  80 , the piston  60  moves with piston stroke S 1 , illustrated in  FIG. 5D , as piston  60  is advanced within container  80  from alignment with container  80  at operational stage  115  to biasing of at least portions of piston face  61  against surface  75  of container  80  at operational stage  119 . Container  80  is cylindrical with circular cross-section of diameter D and hydraulic diameter D H  given by 
                     D   H     =       4   ⁢           ⁢   area     perimeter             (   1   )               
where area in equation (1) is the cross-sectional area of the cross-section and the perimeter is the perimeter of the cross-section. For a circular cross-section of diameter D, then D H =D. The hydraulic diameter D H  may be defined for non-circular cross sections using equation (1). For example, for a square cross section of side B, then D H =B.
 
     In implementations wherein the piston stroke S 1  is larger than the hydraulic diameter D H  of the container may produce an even and controlled low flow of spray  14  from dispenser  10 . In implementations wherein the piston stroke S 1  is less than or equal to the hydraulic diameter D H  of the container may produce an even and controlled high flow of spray  14  from dispenser  10 . An aspect ratio A R  may be defined as
 
 A   R1   =S   1   /D   H   (2)
 
     In implementations with A R1 ≧2 (a slender container), the flow rate and liquid pressure is smaller during advancement of the piston from operational stage  115  to operational stage  119 , that may produce larger, less drift-prone droplets in spray  14 . 
     In implementations with A R1 ≦1, the flow rate and liquid pressure is larger during advancement of the piston from operational stage  115  to operational stage  119 , causing smaller droplets in spray  14  that may result in wider spray coverage and a more delicate control of the thickness of liquid layers delivered to a surface. This decrease in average droplet size in spray  14  increases the specific surface area thereby enhancing the vaporization of the liquid, which might be desirable in certain applications. 
     The aspect ratio A R1  of the container may be dictated by the desired liquid-delivery characteristics. Whereas in applications, for example, where medical inhalants are required to be vaporized, a short piston stroke with a low aspect ratio container  80  may be appropriate. When applying a numbing agent or a medical adhesive to the skin in the open air, a longer piston stroke with a higher-aspect ratio container  80  may be more appropriate to prevent droplet drift. 
     Another exemplary implementation of a dispenser  200  is illustrated in  FIG. 6 . As illustrated in  FIG. 6 , piston  260  and sleeve  230  of dispenser  200  are generally formed as a unitary piece as portions of body  220 . Chamber  236  is defined by inner surface  234  of sleeve  230 , and piston  260  extends forth from body  220  into chamber  236  such that piston face  261  of piston  260  is oriented toward proximal end  221  of body  220 , as illustrated. 
     Container assembly  270  is insertably received within chamber  236  of sleeve  230  through proximal end  221 , as illustrated in  FIG. 6 , with distal end  273  of container  270  oriented toward piston face  261  of piston  260 . Key  274  is slidably engaged with keyway  224  to allow container assembly  270  to slide within chamber  236 , as illustrated. 
     As illustrated in  FIG. 6 , container  280  is formed within portions of container assembly  270 , and reservoir  286  of container  280  is defined by surface  275  of container assembly  270 , inner surface  282  of container assembly  270 , and inner surface  291  of covering  290 . Accordingly, in this implementation, container  280 , apart from covering  290 , is formed as a unitary structure with container assembly  270 . Covering  290  is sealingly engaged about inner surface  282  proximate distal end  273  of container assembly  270  by hermetic seal  294  to enclose sealingly reservoir  286  of container  280  and liquid  212  therein, in this illustrated implementation. 
     Piston  260  may be forced through covering  290  and then aligned with reservoir  286  of container  280 , in the implementation of  FIG. 6 . When so aligned, piston face  261  is faced toward surface  275  and piston side  264  is faced toward inner surface  282 . Portions of piston side  264  proximate piston face  261  engage inner surface  282  proximate end  273  when piston  260  is aligned with reservoir  286  of container  280 . Piston side  264  may be sealingly slidably biased against inner surface  282  to prevent leakage of fluid  212  between piston side  264  and inner surface  282  when piston  260  is aligned with reservoir  286  and as piston  260  is advanced within reservoir  286  toward surface  275 . Annular slot  237 , which is generally defined by inner surface  234  of sleeve  230  and piston side  264  of piston  260 , is sized to accommodate wall  277  of container assembly  270  as piston  260  is advanced within reservoir  286  toward surface  275 , and annular slot  237  is sized to allow piston  260  to advance within reservoir  286  until piston face  261  contacts surface  275 , in this implementation. 
     As illustrated in  FIG. 6 , inset  240  is disposed within body  220 . Inset  240  is generally frustoconical in shape, in this implementation. Inset  240  may be formed separately from body  220  and then joined to inner surfaces of body  220  to form the illustrated structure. End  241  of inset  240 , which forms the frustum, protrudes forth from piston face  261  of piston  260 , with end  241  formed into cutting edge  268  for the opening of covering  290 , in this implementation. Recess  279  in surface  275  is configured to receive therein the portion of inset  240  that protrudes forth from piston face  261  so that piston face  261  may be biased against surface  275 . 
     Slots  333 ,  343  are formed in surface  242  and in end  243  of inset  240  to define passages  335 ,  345 , respectively, when surface  242  of inset  240  is joined to inner surface  226  of body  220 , as illustrated in  FIG. 6  (see also  FIGS. 7B, 7D ). Passages  335 ,  345  fluidly communicate with swirl chamber  256  of nozzle  250 , as illustrated. Nozzle  250  is configured as a pressure atomizing nozzle, in this implementation. As illustrated in  FIG. 6 , liquid  212  may pass through inlets  321 ,  329  into passages  335 ,  345 , respectively, then from passages  335 ,  345  into swirl chamber  256 , and exit swirl chamber  256  through convergent passage  257  (see  FIG. 7C ) and thence through nozzle outlet  252  as spray, such as spray  14 . 
       FIG. 7A  illustrates end  241  of inset  240  that protrudes forth from piston face  261  of piston  260 . As illustrated in  FIG. 7A , end  241  includes recess  247  with cutting edge  268  formed radially about the centerline of inset  240 . Cutting edge  268  may be set at various radial distances from the centerline, in various implementations, and inset  240  may be sized accordingly. Cutting edge  268  extends forth from piston face  261  of piston  260 , as illustrated, or may be slanted to minimize further the initial contact are with membrane  290 , increasing the piercing pressure and thus decreasing any deformation of membrane  290  prior to opening of membrane  290 . 
       FIG. 7B  illustrates inset  240  received by body  220  at piston face  261  of piston  260 . As illustrated in  FIG. 7B , cutting edge  268  is disposed circularly about recess  247 . Surface  242  of inset  240  is joined to inner surface  226  of body  220  to secure inset  240  to body  220 . Inlets  321 ,  323 ,  327 ,  329  are disposed about end  241  of inset  240 , and liquid may pass through inlets  321 ,  323 ,  327 ,  329  into passages  335 ,  347 ,  345 ,  349 , respectively (see also  FIG. 7D ). Passages  347 ,  349  may defined by slots, such as slots  333 ,  343  (see  FIG. 6 ) formed in surface  242  and in end  243  of inset  240  when surface  242  of inset  240  is joined to inner surface  226  of body  220 . The inner surface  226  of body  220  in conjunction with the slots in surface  242  of inset  240  defines passages  335 ,  347 ,  345 ,  349 , in this implementation. Portions of surface  242  between the slots are joined to inner surface  226 , in this implementation, and these portions of surface  242  may be bonded to inner surface  226 . Various other implementations may include various numbers of inlets, such as inlets  321 ,  323 ,  327 ,  329 , and the inlets may be variously disposed about end  241  of inset  240 . Because of the frustoconical shape of inset  240 , passages  335 ,  347 ,  345 ,  349  have a conical arrangement with respect to one another, in this implementation. 
       FIG. 7C  illustrates portions of dispenser  200  proximate distal end  223  of body  220 , including swirl chamber  256  and nozzle outlet  252 . As illustrated in  FIG. 7C , passages  335 ,  345 , pass along side  242  of inset  240  and end  243  of inset  240  to communicate fluidly into swirl chamber  256 . Swirl chamber  256  is a generally cylindrical shaped region that transitions into convergent passage  257  and thence into outlet  252 , as illustrated. The cross-sectional area of convergent passage  257  converges from swirl chamber  256  to outlet  252 . 
       FIG. 7D  illustrates passages  335 ,  347 ,  345 ,  349  in communication with swirl chamber  256 . Passages  335 ,  347 ,  345 ,  349  connect tangentially to swirl chamber  256  to induce swirl into liquid  212  as liquid  212  flows from passages  335 ,  347 ,  345 ,  349  into swirl chamber  256 . This swirl in liquid  212  is increased by conservation of angular momentum as liquid  212  is accelerated by passage through convergent passage  257  from swirl chamber  256  to outlet  252 . A spray will be formed as the swirling liquid  212  is released through outlet  252 . In various implementations, the cylindrically shaped swirling chamber  256  has a bit more volume (re. height) in proportion to the volume of the convergent channel  257 . 
     In operation of dispenser  200 , the user may insert container assembly  270  into chamber  236  of sleeve  230 . Container assembly  270  includes container  280  with liquid  212  hermetically sealed within reservoir  286  by covering  290 . As the user inserts container assembly  270  into sleeve  230 , key  274  of container assembly  270  is engaged with keyway  224  of sleeve  230 , which orients container assembly  270  with respect to sleeve  230  and prevents rotation of container assembly  270  within sleeve, particularly as piston  260  engages container assembly  270 . 
     With the container assembly  270  inserted into sleeve  230 , the user may apply force to proximal end  271  of container assembly  270 , for example, by pressing upon proximal end  271  with the thumb to slide container assembly  270  and sleeve  230  with respect to one another thereby inserting piston  260  through covering  290  into reservoir  286  of container  280  and then advancing piston  260  within reservoir  286  of container  280  to dispense the unit dose of liquid  212  from container  280  as spray, such as spray  14 , through nozzle  250 . 
       FIGS. 8A, 8B, 8C and 8D  illustrate operational stages  207 ,  213 ,  215 ,  217 , respectively, of dispenser  200 . As illustrated in  FIG. 8A , piston face  261  is flat between shoulder  267  and inset  240  forming a right angle with respect to piston side  264 . Piston  260  includes shoulder  267  that extends circumferentially around piston face  261  at the periphery of piston face  261  proximate piston side  264 , in this implementations. Shoulder  267  is curved, as illustrated, and shoulder  267  functions to correct misalignment between piston  260  and container  280  thereby aligning piston  260  with reservoir  286  of container  280 . In this implementation, hermetic seal  294  is formed between covering  290  and inner surface  282  of container  280  to enclose reservoir  286  that contains liquid  212  therein. 
     At operation stage  207 , as depicted in  FIG. 8A , cutting edge  268  contacts outer surface  293  of covering  290 . In this implementation, other than cutting edge  268  contacting outer surface  293 , piston  260  and container assembly  270  are set apart from one another at operational stage  207 . Covering  290  is sufficiently rigid so that covering  290  generally does not deform significantly into reservoir  286 , which would create liquid pressure in liquid  212 , as cutting edge  268  opens covering  290 . This effect of deformation of the covering on liquid pressure is further minimized for containers that are not completely filled and have some gas sealed inside. 
     Operational stage  213  is illustrated in  FIG. 8B . Piston  260  is advanced toward surface  275  of container  280  during the progression from operational stage  207  to operational stage  213 , in this implementation, to open covering  290  with cutting edge  268  at end  241  of inset  240 . At operation stage  213 , cutting edge  268  has penetrated covering  290  from outer surface  293  through inner surface  291  to open covering  290 , as illustrated. Only cutting edge  268  contacts covering  290  as covering  290  is opened during the progression from operational stage  207  to operational stage  213 . Because cutting edge  268  has a circular configuration (see  FIG. 7B ), covering  290  is opened circumferentially in correspondence to cutting edge  268 , in this implementation. Cutting edge  268  can also be slanted to increase the opening pressure upon initial contact of cutting edge  268  on covering  290 , further minimizing the impact of the deformation of covering  290  into reservoir  286 . Distal end  273  of wall  277  of container assembly  270  is biased against shoulder  267  of piston  260  to seal reservoir  286  thereby preventing escape of liquid  212  from reservoir  286  at operational stage  213  following the opening of covering  290 . 
       FIG. 8C  illustrates operational stage  215  of dispenser  200 . At operational stage  215 , piston  260  is aligned with reservoir  286  of container  280 . Shoulder  267  lies generally within reservoir  286  of container  80  so that portions of piston side  264  proximate piston face  261  are slidingly sealingly biased circumferentially against inner surface  282  of container  280  proximate distal end  273 , as illustrated in  FIG. 8C . Liquid  212  is sealed within reservoir  286  by the sealing engagement between piston side  264  and inner surface  282 . 
     The process of aligning piston  260  with reservoir  286  of container  280  encompasses the progression from operational stage  213 , illustrated in  FIG. 8B , to operational stage  215 , illustrated in  FIG. 8C , in this implementation. Piston  260  including the curvature, if any, of piston face  261  and the portion of inset  240  that extends forth into reservoir  286  from piston face  261  may be sized so that the displaced volume  288  (illustrated by the cross-hatched region in  FIG. 8C ) is less than the priming volume  259 . Displaced volume  288  is the volume of liquid  212  displaced by piston  260  upon alignment of piston  260  with container  280  and equals the volume of those portions of piston  260  that lie within container  280  at operational stage  215 , in this implementation. The priming volume  259  may be defined as the volume of the various passages, swirl chambers, reservoirs, and so forth between piston face  261  and nozzle outlet  252  that may be filled with liquid  212  prior to the emission of liquid  212  from dispenser  200 . For example, in this implementation, priming volume  259  equals the volume of passages  335 ,  347 ,  345 ,  349  and swirl chamber  256  between inlet  262  in piston face  261  of piston  260  and nozzle outlet  252 . 
     Configuring the displaced volume  288  to be less than the priming volume  259  may avoid wastage of liquid from nozzle  250  caused by displacement of liquid  212  during the aligning of piston  260  with reservoir  286  of container  80 . Wastage may include splashing, spraying, or other inadvertent or undesired discharge prior to application of the unit dose. Piston  260 , passages  335 ,  347 ,  345 ,  349 , or swirl chamber  256  may be sized or otherwise formed accordingly so that the displaced volume  288  is less than priming volume  259 . It may be desirable to size passages  335 ,  347 ,  345 ,  349 , and swirl chamber  256  and piston  260  such that the displaced volume  288  almost fills passages  335 ,  347 ,  345 ,  349 , and swirl chamber  256  with liquid  212  to prime dispenser  212 . Once primed, further advancement of piston  260  within reservoir  286  causes liquid  212  to be emitted as spray, such as spray  14 , from nozzle  250 . 
       FIG. 8E  presents this schematically with the displaced volume  288  illustrated as the crosshatched region. Priming volume  259 , as illustrated schematically in  FIG. 8F , equals the volume of passages  335 ,  347 ,  345 ,  349  and swirl chamber  256  between inlet  262  in piston face  261  of piston  260  and nozzle outlet  252 , in this implementation. Following alignment of piston  260  with reservoir  286  at operational stage  215 , the displaced volume  288  occupies almost all of priming volume  259  as indicated by the striped region in  FIG. 8F . The displaced volume  288  will be decreased for a concave piston face that is convergent to the inlet of passages  335 ,  347 ,  345 ,  349  in comparison to the flat piston face  261  of this exemplary implementation. 
     Operational stage  217  of dispenser  200  is illustrated in  FIG. 8D . At operational stage  217 , as illustrated, piston  260  has been advanced within reservoir  286  from operational stage  215  to deliver the unit dose of liquid  212  as spray, such as spray  14 , from nozzle  250  such that piston face  261  of piston  260  is biased against surface  275 . The portion of inset  240  that extends forth from piston face  261  is received within recess  279 , which allows piston face  261  to be biased against surface  275 , in this exemplary implementation. 
     As piston  260  is advanced within container  280  in the progression from operational stage  215  to operational stage  217 , liquid  212  is forced from reservoir  286  through inlets  321 ,  323 ,  327 ,  329  into passages  335 ,  347 ,  349 ,  345 , respectively, through passages  335 ,  347 ,  349 ,  345  into swirl chamber  256 , and then liquid  212  is sprayed from swirl chamber  256  of nozzle  250  though nozzle outlet  252 . Dispenser  200  delivers the unit dose of liquid  212  during the progression from operational stage  215  to operational stage  217 . The user may manipulate dispenser  200  including the force applied to proximal end  271  to adjust the spray characteristics of the spray during the delivery of the unit dose from dispenser  200 , and the user may so adjust the spray characteristics of the spray based upon visual observation of the spray while delivering the unit dose from dispenser  200 . 
     As the unit dose of liquid  212  is delivered from container  280 , the piston  260  moves with piston stroke S 2 , illustrated in  FIG. 8C , as piston  260  is advanced within container  280  from alignment with container  280  at operational stage  215  to biasing of at least portions of piston face  261  against surface  275  of container  280  at operational stage  217 . Container  280  is cylindrical with circular cross-section having hydraulic diameter D 2 , which is the diameter of the circular cross section, as illustrated in  FIG. 8C . 
     Portions of exemplary dispenser  400  are illustrated in  FIG. 9 . As illustrated in  FIG. 9 , body  420  of dispenser  400  forms sleeve  430 . Inner surface  434  of sleeve  430  defines chamber  436 , which is configured to receive container assembly  470  therein. 
     Container assembly  470 , as illustrated in  FIG. 9 , includes container  480  with reservoir  486  therein. Keys  452 ,  454 ,  456  of varying lengths, as illustrated, are formed as slots (female) in outer surface  472  of container assembly  470 , and configured to engage keyway  424  (male) that extends forth from surface  434  of sleeve  430  within chamber  436 . Distal end  473  of container assembly  470  may be inserted through proximal end  421  of body  420  into chamber  436 , and container assembly  470  may be rotated as it is inserted into chamber  436  to selectively engage keyway  424  with one of keys  452 ,  454 ,  456 . The lengths of keys  452 ,  454 ,  456  limit the advancement of a piston (not shown) of dispenser  400 , such as piston  60 ,  260 ,  810 ,  835 ,  855 , within reservoir  486  so that the piston stroke, such as piston stroke S 1 , S 2 , of the piston is mechanically segmented to allow selection of the unit dose delivered by dispenser  400 . The lengths of keys  452 ,  454 ,  456  may be calibrated to unit doses to be delivered from container  480 , in this implementation. Accordingly, the user may select the unit dose to be delivered by selecting the corresponding key  452 ,  454 ,  456 . In some implementations, the user may engage keys  452 ,  454 ,  456  successively with keyway  424  to deliver multiple unit doses from container  480 . The user may push on proximal end  471  of container assembly  470 , in this implementation, to engage container  480  with the piston. Container assembly  470  includes grippable surface  428  to assist the user in rotating container assembly  470  in order to engage one of keys  452 ,  454 ,  456  with keyway  424 . 
       FIG. 10  illustrates portions of exemplary dispenser  500 . As illustrated in  FIG. 10 , steps  534  formed in sleeve  534  are selectively engagable with steps  544  formed in container assembly  570 . The advancement of a piston of dispenser  500  within a container of container assembly  570  may be selected by selecting the engagement between steps  534  and steps  544 , in this implementation. Accordingly, in this implementation, the unit dose delivered by dispenser  500  may be selected by selecting the engagement between steps  534  and steps  544 , which selectively mechanically segments the piston stroke, such as piston stroke S 1 , S 2 , of the piston, such as piston  60 ,  260 ,  810 ,  835 ,  855 , within dispenser  500 . 
       FIG. 11  illustrates portions of exemplary dispenser  600  including container assembly  670 . Covering  690  extends across distal end  673  of container assembly  670  to hermetically seal chamber  686  within. The user may push upon surface  671  to insert container assembly  670  and advance container assembly  670 . Container assembly  670  is elliptically shaped in cross section but is cylindrical in length, in this implementation, to be received within a corresponding elliptically shaped sleeve (not shown) and to engage with a piston, such as piston  60 ,  260 ,  810 ,  835 ,  855 . The piston may be elliptically shaped in correspondence to the container. The elliptical shape of container assembly  670  may orient the container assembly  670  with the corresponding sleeve and prevent rotation of the container assembly  670  within the sleeve in lieu of a key-keyway configuration. Note that container assembly  670  is devoid of a key, in this implementation. The container assembly  670  may assume various other cross-sectional shapes such as square, hexagonal, or rectangular, in other implementations. Chamber  686  may assume various cross-sectional shapes such as square, hexagonal, or rectangular, in other implementations. The cross-sectional shape of chamber  686  may either be the same as or differ from the cross-sectional shape of container assembly  670 , in various implementations. 
       FIG. 12  illustrates portions of exemplary dispenser  700 . As illustrated in  FIG. 12 , dispenser  700  include container  780  with proximal end  781  and distal end  783 . Covering  790  is disposed about distal end  783  to hermetically seal chamber  786  within container  780 . Proximal end  781  of container  780  may be inserted through distal end  763  of housing  760  into chamber  766  so that container  780  is received within housing  760 . In this implementation of container assembly  770 , container  780  is separable from housing  760  of container assembly  770 . Accordingly, various containers  780  may be placed in housing  760 , and multiple containers  780  that may contain multiple liquids may be used with housing  760 . Proximal end  761  provides a surface upon which the use may push to insert container assembly  770  including container  780  into a sleeve of dispenser  700 . 
       FIG. 13  illustrates portions of exemplary dispenser  800  including piston  810 . As illustrated in  FIG. 13 , piston  810  includes piston side  817  and piston face  815 . Inlet  825  is formed in piston face  815  for the inflow of liquid, such as liquid  12 ,  212 , therethrough. Axis  819  passes through piston  810 , as illustrated, and piston face  819  angled with respect to axis  819  such that cutting edge  828  forms angle  821  with respect to axis  819  with angle  821  being less than 90°. Cutting edge  828  thus extends forward of piston  810 , in this implementation, to open the covering, such as covering  90 ,  290 ,  690 ,  790 . 
       FIG. 14  illustrates portions of exemplary dispenser  830  including piston  835 . As illustrated in  FIG. 13 , piston  835  defines piston side  837  and piston face  841 . Cutting edges  838 ,  839 ,  843 ,  845  extend forth from piston face  841  of piston  835 , as illustrated, in a cross configuration. Inlet  847  is formed at the intersection of blades  838 ,  839 ,  843 ,  845 , in this configuration. 
       FIG. 15  illustrated portions of exemplary dispenser  850  including piston  855 . Piston  855  defines piston side  857  and piston face  861 . Inset  867  is secured within piston  855 , and an oblate spheroidal portion  868  of inset  867  extends forth from piston face  861 , as illustrated. Cutting edges, such as cutting edges  871 ,  873 ,  875  are formed circumferentially around oblate spheroidal portion  868  of inset  867  to open the covering, such as covering  90 ,  290 ,  690 ,  790 , in this implementation. Inlets, such as inlets  881 ,  883 ,  885 , are disposed circumferentially around piston face  861  proximate insert  867 , as illustrated. 
       FIG. 17  illustrates portions of exemplary dispenser  950 , in which container assembly  970  is threadedly engagable with body  955  to move container assembly within body  955  by rotation of container assembly  970 . As illustrated in  FIG. 17 , body  955  of dispenser  950  forms sleeve  960 . Inner surface  964  of sleeve  960  defines chamber  966 , which is configured to receive container assembly  970  therein. Container assembly  970 , as illustrated in  FIG. 17 , includes container  980  with reservoir  986  therein. Thread  988  (male), as illustrated, is formed helically around outer surface  972  of container assembly  970 , and configured to engage threadedly with thread  968  (female) formed helically within surface  964  of sleeve  960  within chamber  966 . 
     Distal end  973  of container assembly  970  may be inserted through proximal end  961  of body  950  into chamber  966 , and container assembly  970  may be rotated as container assembly  970  is inserted through proximal end  961  of body  950  into chamber  966  to engage thread  988  with thread  968 . With thread  988  engaged with thread  968 , rotation of container assembly  970  causes the container assembly  970  to advance within chamber  966  to engage a piston (not shown), such as piston  60 ,  260 ,  810 ,  835 ,  855 , within reservoir  986 , to first align the piston with container  980  of the container assembly  970  and then deliver a unit dose of liquid from reservoir  986  by the sliding of the piston within reservoir  986  of the container  980 . The user may rotate container assembly  970  using grippable surface  977  disposed circumferentially about proximal end  971  of container assembly  970  to advance threadedly container assembly  970  within sleeve  960  of dispenser  950 . Container assembly  970  may be withdrawn from sleeve  960  by reverse rotation of container assembly  970 . 
     The rate of advancement of the container assembly  970  within sleeve  960 , and, hence, the delivery of the unit dose may be controlled by the rate of rotation of the container assembly  970  and the lead of thread  988 . Thread  988  and thread  968  may have various pitches, leads, diameters, depths, left or right handedness, and other geometric properties, in various implementations. In some implementations, thread  968  may be male and thread  988  may be female. 
       FIG. 16  illustrates exemplary method  900  of dispensing a unit dose of liquid, such as liquid  12 ,  12 , from a dispenser, such as dispenser  10 ,  200 ,  400 ,  500 ,  600 ,  700 ,  800 ,  830 ,  850 ,  950  as spray, such as spray  14 . Method  900  is entered at step  901 . At step  905 , the user inserts a container assembly, such as container assembly  70 ,  270 ,  470 ,  570 ,  670 ,  770 ,  970  into a sleeve, such as sleeve  30 ,  230 ,  430 ,  530 ,  960 . In some implementations, a key, such as key  74 ,  274 ,  452 ,  454 ,  456 , disposed about the container assembly may be engaged with a keyway, such as keyway  24 ,  224 ,  424 , disposed about the sleeve as the container assembly is inserted into the sleeve. In some implementations, a thread, such as thread  968 , disposed about the sleeve may be threadedly engaged with a thread, such as thread  988 , disposed about the container assembly. 
     At step  910 , in implementations with slidable engagement between the sleeve and the container assembly, the user presses upon portions of the dispenser, such as arms  27 ,  29 , and presses upon portions of the container assembly, such as proximal end  71 ,  271 ,  471 ,  671 ,  761 , thereby causing the container assembly to slide within the sleeve. With the user so pressing, a cutting edge, such as cutting edge  68 ,  268 ,  828 ,  838 ,  839 ,  843 ,  868 , formed about a piston, such as piston  60 ,  260 ,  810 ,  835 ,  855 , opens covering, such as covering  90 ,  290 ,  690 ,  790 , that hermetically seals container, such as container  80 ,  280 ,  480 ,  680 ,  780 , per step  910 . 
     Alternatively, at step  910 , in implementations with threaded engagement between the container assembly and the sleeve, the user may rotate the container assembly, which is threadedly engaged with the sleeve, causing the container assembly to advance within the sleeve. As the container assembly advances within the sleeve, the cutting edge formed about the piston opens the covering that seals the container, at step  910 . 
     In implementations with slidable engagement between the sleeve and the container assembly, continued pressing upon the dispenser by the user causes the piston to align with the reservoir, such as reservoir  86 ,  286 ,  486 ,  686 ,  786 ,  986  of the container, at step  915 . Alternatively, in implementations with threaded engagement between the container assembly and the sleeve, continued rotation of the container assembly causes the piston to align with the reservoir, at step  915 . Upon alignment at step  915 , the displaced volume, such as displaced volume  88 ,  288 , is less than or equal to the priming volume, such as priming volume  59 ,  259 . 
     In implementations with slidable engagement between the sleeve and the container assembly, the user may then press upon the dispenser to dispense a unit dose of liquid from the container as spray at step  920 . The piston advances through the reservoir until the piston face, such as piston face  61 ,  261 ,  815 ,  841 ,  861  strikes a surface, such as surface  75 ,  275 , of the container, which thereby limits the advance of the piston within the reservoir. In implementations with threaded engagement between the container assembly and the sleeve, continued rotation of the container assembly causes the piston to advance within the reservoir thereby delivering the unit dose of liquid, at step  920 . 
     The foregoing discussion along with the Figures discloses and describes various exemplary implementations. These implementations are not meant to limit the scope of coverage, but, instead, to assist in understanding the context of the language used in this specification and in the claims. Upon study of this disclosure and the exemplary implementations herein, one of ordinary skill in the art may readily recognize that various changes, modifications and variations can be made thereto without departing from the spirit and scope of the inventions as defined in the following claims.