Abstract:
A dispenser assembly is provided that has a rigid plunger with a ring-shaped protrusion. The protrusion contacts the inner wall of a flexible barrel to form a liquid-tight seal. Advantageously, the dispenser assembly does not require additional components, such as o-rings, and can be fabricated by injection molding techniques.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a non-provisional of U.S. Patent Application Ser. No. 61/905,501 (filed Nov. 18, 2013) the entirety of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The subject matter disclosed herein relates to dispenser assemblies for liquids such as liquid medications. Traditional dispenser assemblies have a hollow barrel with a fitting, such as a luer fitting, at a discharge end. A plunger rod fits within the barrel and engages a sidewall of the barrel with a rubber o-ring. The rubber o-ring has ribs that extend in a radial direction outward to form a liquid seal with the barrel. These traditional dispensers are expensive to manufacture. The separate steps of forming the barrel, the plunger and the o-ring add manufacturing complexity to the overall production. The o-rings must be properly fitted to the plungers and, after assembly with the barrel, a liquid seal must be provided. This requires precision manufacturing techniques that adds to the expense of the dispenser assembly. An improved dispenser assembly that addresses at least some of these shortcomings is therefore desired. The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0003]    A dispenser assembly is provided that has a rigid plunger with a ring-shaped protrusion. The protrusion contacts the inner wall of a flexible barrel to form a liquid-tight seal. Advantageously, the dispenser assembly does not require additional components, such as o-rings, and can be fabricated by injection molding techniques. 
         [0004]    In a first embodiment, a dispenser assembly is provided. The dispenser assembly comprises a plunger with a first diameter, the plunger formed from a first polymeric material and comprising a ring-shaped protrusion that extends in a radial direction from an outer surface of the plunger to define a second diameter, the ring-shaped protrusion being disposed proximate a distal end of the plunger, wherein the plunger has a first flexibility; and a barrel that, in an un-tensioned state, defines a third diameter, the barrel formed from a second polymeric material, different than the first polymeric material, wherein the second diameter of the ring-shaped protrusion is greater than the third diameter of the barrel, wherein the barrel has a second flexibility that is more flexible than the first flexibility such that the ring-shaped protrusion applies a force to the barrel in the radial direction to provide a liquid-tight seal between the plunger and the barrel. 
         [0005]    In a second embodiment, a dispenser assembly s provided. The dispenser assembly consists of a plunger with a first diameter, the plunger formed from a first polymeric material and comprising a protrusion that extends in a radial direction from an outer surface of the plunger to define a second diameter, the protrusion being disposed proximate a bottom end of the plunger, wherein the plunger has a first flexibility; and a barrel that, in an un-tensioned state, defines a third diameter, the barrel formed from a second polymeric material, different than the first polymeric material, wherein the second diameter of the plunger is greater than the third diameter of the barrel, wherein the barrel has a second flexibility that is more flexible than the first flexibility such that the protrusion tensions the barrel in the radial direction to provide a liquid-tight seal between the plunger and the barrel. 
         [0006]    In a third embodiment, a dispenser assembly is provided. The dispenser assembly consists of a plunger with a first diameter, the plunger formed from a first polymeric material and comprising a protrusion that extends in a radial direction from an outer surface of the plunger to define a second diameter, the protrusion being disposed proximate a bottom end of the plunger, wherein the plunger has a first flexural modulus, wherein the plunger, including the ring-shaped protrusion, is monolithic; and a barrel that, in an un-tensioned state, defines a third diameter, the barrel formed from a second polymeric material, different than the first polymeric material, wherein the second diameter of the plunger is greater than the third diameter of the barrel, wherein the barrel has a second flexural modulus and is more flexible than the first flexural modulus such that the protrusion tensions the barrel in the radial direction to provide a liquid-tight seal between the plunger and the barrel. The second flexural modulus of the barrel is between 500 MPa and 1200 MPa and the first flexural modulus of the plunger is at least 200 MPa more rigid than the second flexural modulus. 
         [0007]    This brief description of the invention is intended only to provide a brief overview of subject matter disclosed herein according to one or more illustrative embodiments, and does not serve as a guide to interpreting the claims or to define or limit the scope of the invention, which is defined only by the appended claims. This brief description is provided to introduce an illustrative selection of concepts in a simplified form that are further described below in the detailed description. This brief description is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    So that the manner in which the features of the invention can be understood, a detailed description of the invention may be had by reference to certain embodiments, some of which are illustrated in the accompanying drawings. It is to be noted, however, that the drawings illustrate only certain embodiments of this invention and are therefore not to be considered limiting of its scope, for the scope of the invention encompasses other equally effective embodiments. The drawings are not necessarily to scale, emphasis generally being placed upon illustrating the features of certain embodiments of the invention. In the drawings, like numerals are used to indicate like parts throughout the various views. Thus, for further understanding of the invention, reference can be made to the following detailed description, read in connection with the drawings in which: 
           [0009]      FIG. 1A  provides cross section views of a plunger and a barrel; 
           [0010]      FIG. 1B  provides a cross section view of a dispenser assembly formed from the plunger and the barrel; 
           [0011]      FIG. 2  is a magnified view of a portion of the dispenser assembly of  FIG. 1B  showing a ring-shaped protrusion; 
           [0012]      FIG. 3A  is a cross section view of the dispenser assembly engaging a container; 
           [0013]      FIG. 3B  is a perspective view of the dispenser assembly engaging the container; 
           [0014]      FIG. 4A  is a magnified view of a portion of the dispenser assembly of  FIG. 3A  engaging the container, wherein the dispenser assembly is shown in a compressed state; 
           [0015]      FIG. 4B  is a magnified view of a portion of the dispenser assembly of  FIG. 3A  engaging the container, wherein the dispenser assembly is shown in a partially withdrawn state; 
           [0016]      FIG. 5A  is a cross section view of the dispenser assembly that is similar to  FIG. 3A , except in that the dispenser assembly is shown in a partially withdrawn state; 
           [0017]      FIG. 5B  is a perspective view of the dispenser assembly engaging the container in an inverted state; 
           [0018]      FIG. 6A  is a cross section view of the dispenser assembly is shown in a partially withdrawn state; 
           [0019]      FIG. 6B  is a magnified view of a portion of the dispenser assembly of  FIG. 6A ; 
           [0020]      FIG. 6C  is a magnified view of a portion of the dispenser assembly of  FIG. 6B ; 
           [0021]      FIG. 7A  is a side view of an exemplary plunger; 
           [0022]      FIG. 7B  is a top perspective view of an exemplary plunger; 
           [0023]      FIG. 7C  is a bottom perspective view of an exemplary plunger; 
           [0024]      FIG. 7D  is another bottom perspective view of an exemplary plunger; 
           [0025]      FIG. 7E  is a side view of a distal end of an exemplary plunger; and 
           [0026]      FIG. 7F  is a cross section view of the distal end of  FIG. 7E . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]      FIG. 1A  depicts a barrel  102  and a plunger  202 . The barrel  102  comprises a dispenser end  104  that provides a bottom opening  106  for withdrawing a liquid from a container. In use, the plunger  202  is inserted through a top opening  108  of the barrel  102  such that the plunger  202  is disposed inside a cavity  110 . The resulting dispenser assembly  100  is depicted in  FIG. 1B . 
         [0028]    The plunger  202  is substantially rigid over its length and resists flexing in a radial direction. Flexibility may be quantified by measuring the flexural modulus according to ASTM-D790. The barrel  102  is thin-walled such that the barrel  102  will flex in the radial direction when a force is applied. Exemplary wall thickness values for the barrel  102  are between about 0.014 inches and about 0.022 inches. In one embodiment, the thickness value for the barrel  102  is between 0.017 inches and 0.019 inches. In contrast, traditional barrels are about 0.035 inches thick and are relatively rigid. 
         [0029]    In one embodiment, a ring-shaped protrusion  200  is disposed at a distal end  214  of the plunger  202 . In one such embodiment, the ring-shaped protrusion  200  is disposed within 5 mm of a terminus of the distal end  214 . As shown in  FIG. 2 , the ring-shaped protrusion extends from an outer surface  212  of the plunger  202  in the radial direction to define a diameter that is slightly greater than a diameter of the plunger  202 . The ring-shaped protrusion  200  provides a raised bump that circumscribes the circumference of the distal end  214  of the plunger  202 . The diameter defined by the ring-shaped protrusion  200  is greater than a diameter of the barrel  102  when the barrel  102  is in an un-tensioned state. As a result of the difference in diameters the ring-shaped protrusion  200  applies a force against the barrel  102  as the ring-shaped protrusion  200  passes over the length of the barrel  102 . The force causes the barrel  102  to flex in the radial direction to maintain a liquid-tight seal. In one embodiment, the diameter of the plunger  202  is undercut (relative to the diameter of the barrel  102 ) by a predetermined amount to provide a gap  216 . In one embodiment, the gap is between 0.0025 inches and about 0.010 inches. In another embodiment, the gap is between 0.004 inches and 0.008 inches. For example, the diameter of the plunger  202  may be undercut by 0.006 inches. This gap facilitates a sliding motion between the barrel  102  and the plunger  202 . In one embodiment, the plunger  202  is elongated and hollow. In some embodiments, the plunger  202  comprises a top opening  208  (see  FIG. 1A ) that is opposite a solid end  204  such that the plunger  202  forms an elongated tube that is open at only the top opening  208 . Such a hollow configuration reduces the mass of material used in fabrication of the plunger  202  and thereby reduces costs. 
         [0030]    In one embodiment, the barrel  102  has a sufficiently high flexibility to be pulled onto the ring-shaped protrusion  200  when a vacuum is applied due to actuation of the plunger  202 . For example, the dispenser end  104  may be placed into a liquid and the plunger  202  withdrawn to produce a vacuum within the barrel  102 . The vacuum not only draws the liquid into the barrel  102  but also assists in the compression of the barrel  102  onto the ring-shaped protrusion  200 . When the liquid is dispensed by pushing the plunger  202  downward, a higher pressure is produced that is of a sufficiently low intensity to maintain a liquid-tight seal and prevent leaks while dispensing the liquid. Advantageously, no additional sealing components (e.g. rubber rings) are needed. 
         [0031]    The flexibility of the plunger and barrel may be quantified using any suitable technique such as ASTM International Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials D790. 
         [0032]      FIG. 3A  and  FIG. 3B  depict two views of the dispenser assembly  100  when connected to a container  300 . In the depicted embodiment, the container  300  is fitted with a press-in-bottle-adapter (PIBA)  302  that is disposed within a mouth of the container  300 .  FIG. 3B  is a perspective view of this configuration while  FIG. 3A  is a cross section view.  FIG. 4A  is a close-up view of a connection point of  FIG. 3A  wherein the dispenser assembly  100  is show in a compressed state.  FIG. 4B  is a close-up view of the connection point of  FIG. 4A  wherein the dispenser assembly  100  is shown in a partially withdrawn state. 
         [0033]      FIG. 5A  is a cross section view of the dispenser assembly  100  engaging the PIBA  302  to form a liquid-tight seal between the dispenser assembly  100  and the PIBA  302 .  FIG. 5B  shows the container  300  and the dispenser assembly  100  in an inverted state. The inverted state facilitates the remove of liquid from the container  300 . 
         [0034]      FIG. 6A ,  FIG. 6B  and  FIG. 6C  are cross section views of the dispenser assembly in a partially withdrawn state shown at different magnifications. In  FIG. 6C , the ring-shaped protrusion  200  is labeled for the sake of illustration. 
         [0035]      FIG. 7A  is a side view of the plunger  202  showing the ring-shaped protrusion  200 . In  FIG. 7A , a conical tip  700  is depicted that mates with a corresponding shape on the barrel  102 .  FIG. 7B  is a top perspective view of the plunger  202  illustrating both the top opening  208  and the ring-shaped protrusion  200 .  FIG. 7C  is a bottom perspective view of the plunger  202  showing the ring-shaped protrusion  200 .  FIG. 7D  is another bottom perspective view of the plunger  202  showing the ring-shaped protrusion  200 .  FIG. 7E  is a side view of the distal end  214  of the plunger  202  showing the ring-shaped protrusion  200 .  FIG. 7F  is a cross section view of the distal end of  FIG. 7E . 
         [0036]    In some embodiments, a proximal end  218  of the plunger  202 , which is opposite the distal end  214 , comprises a plunger flange  220 . The plunger flange  220  is proximate the top opening  208  of the plunger  202 . In such an embodiment, the plunger flange  220  provides a receptacle for a user&#39;s finger and/or thumb during operation of the dispenser assembly  100 . Likewise, in some embodiments, the barrel  102  comprises a barrel flange  112  proximate the top opening  108  of the barrel  102  that provides a receptacle for the user&#39;s finger and/or thumb during operation of the dispenser assembly  100 . 
         [0037]    In one embodiment, the dispenser assembly  100  is formed by injection molding. In one embodiment, the plunger  202  and/or the barrel  102  consists of only the polymeric material and lacks additional components (e.g. a rubber o-ring). Such a configuration is conducive to forming the plunger  202  and/or barrel  102  by injection molding which streamlines production of the dispenser assembly  100  and reduces costs. In one such embodiment, the plunger  202  and barrel  102  are respectively formed by injection molding from different polymeric materials. For example, the plunger may be formed from high density polyethylene (HDPE) while the barrel is formed of polypropylene (PP). A suitable polypropylene is a polypropylene random copolymer sold by EXXONMOBIL™ under the brand name PP9074MED. PP9074MED has a tensile strength at yield (510 mm/min) of about 32.8 MPA, a tensile strength at break (510 mm/min) of about 17.2 MPa, an elongation at yield (510 mm/min) of about 13%, an elongation at break (510 mm/min) of about 51% and a flexural modulus (1% secant, 1.3 mm/min) of about 1050 MPa (measured according to ASTM D790). In one embodiment, the barrel 102 has a flexural modulus of less than 1200 MPa while the plunger has a flexural modulus of more than 1200 MPa. In another embodiment, the flexural modulus of the barrel is between 500 MPa and 1200 MPa. In one such embodiment, the difference in flexural modulus of the barrel and the plunger is at least 100 MPa. In another embodiment, the difference is at least 300 MPa. In yet another embodiment, the difference is at least 500 MPa. The use of different polymeric materials in the plunger and barrel, respectively, provides natural lubricity and thereby promotes the operation of the dispenser assembly  100 . In one embodiment, the plunger  202 , including the ring-shaped protrusion, is monolithic. In another embodiment, the barrel  102  is monolithic. 
         [0038]    This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.