Abstract:
Pump systems are provided which allow for highly-accurate dose control. The pump systems may be provided with a valve stem or a piston, either having a constant-diameter stroke portion interposed between reduced-diameter portions. At least one stationary sealing member immovably affixed to a pump body is also provided formed to sealingly engage the stroke portion of the valve stem or the piston. The sealing member is also formed to not engage the reduced-diameter portions. As such, the volume of the administered dose is controlled by the stroke length, which, in turn, is a function of the dimensioning of the constant-diameter stroke portion and the dimensioning of the sealing member. Advantageously, with the subject invention, a minimal number of tolerances can be implicated in controlling dosing volume.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority of U.S. Provisional Application No. 60/383,076, filed May 23, 2002. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to pumps, and, more particularly, to pumps having highly-accurately controlled dosing. 
     Highly-accurate pumps are known in the prior art for repeatedly delivering doses within exacting tolerances, even at extremely low-dose volumes. For example, with reference to International Patent Application No. PCT/US00/23206, published as International Publication No. WO 01/14245 on Mar. 1, 2001, a pre-compression pump system is shown for repeatedly delivering microdoses of fluid. The pump of this design utilizes a stationary seal which bears against a moving valve stem. The stroke of the pump is defined by the length of a constant-diameter portion of the valve stem which terminates at a lower extreme defined by a plurality of circumferentially-spaced recesses. In this manner, the seal member remains in constant sealing engagement with the valve stem with fluid bypassing the sealing member via the recesses to re-charge the pump chamber. With this structural configuration, accurate control of dosing can be achieved through accurate dimensioning of the valve stem and recesses. In a different approach, U.S. Pat. No. 5,277,559, which issued on Jan. 11, 1994 to the inventor herein, a pump with a sliding seal is provided which moves, at least in part, with a valve stem that selectively controls flow through the pump. 
     SUMMARY OF THE INVENTION 
     With the subject invention, pump systems are provided which allow for highly-accurate dose control. In one embodiment, a pump system is provided which includes a pump body having a first chamber defined therein; a valve stem disposed to slide within at least a portion of the pump chamber, the valve stem having a constant-diameter stroke portion interposed between reduced-diameter portions; and at least one stationary sealing member immovably affixed to the pump body formed to sealingly engage the stroke portion of the valve stem. The sealing member is also formed to not engage the reduced-diameter portions of the valve stem. With the sealing member sealingly engaging the stroke portion of the valve stem, a portion of the first chamber of the pump body is isolated or substantially isolated from other portions of the chamber. Accordingly, fluid trapped within the first portion may be compressed and dispensed. 
     In a second embodiment, a pump system is provided which includes a pump body having a first chamber defined therein; a piston disposed to slide within at least a portion of the first chamber, the piston having a constant-diameter stroke portion interposed between reduced-diameter portions; and at least one stationary sealing member immovably affixed to the pump body formed to sealingly engage the stroke portion of the piston. The sealing member is also formed to not engage reduced-diameter portions of the piston. With the sealing member sealingly engaging the stroke portion, a portion of the first chamber is isolated or substantially isolated from other portions of the first chamber. Again, as with the first embodiment, fluid trapped within the first chamber can be pressurized in being dispensed. 
     With both embodiments, the volume of the administered dose is controlled by the stroke length, which, in turn, is a function of the dimensioning of the constant-diameter stroke portion and the dimensioning of the sealing member. Advantageously, with the subject invention, a minimal number of tolerances can be implicated in controlling dosing volume. 
     In third and fourth embodiments, “in-line” pump systems can be provided having an exit aperture extending along the longitudinal axis of the pump system (such as in the manner of a nasal spray). These embodiments each include a valve stem and operate in the same basic manner as the first embodiment. 
     These and other features will be better understood through a study of the following detailed description and accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIGS. 1-3 depict a first embodiment of a pump system formed in accordance with the subject invention herein; 
     FIGS. 4-6 show a second embodiment of a pump system formed in accordance with the subject invention herein; 
     FIG. 7 is a front elevational view of a possible external configuration of a pump system; 
     FIGS. 8-9 show a third embodiment of a pump system formed in accordance with the subject invention herein; and 
     FIG. 10 shows a fourth embodiment of a pump system formed in accordance with the subject invention herein; and 
     FIGS. 11A-11C are top, side and bottom views, respectively of a swirl plug which may be utilized in connection with the subject invention. 
    
    
     DETAILED DESCRIPTION 
     Pump systems are described herein having a relatively low number of dimensions critical for controlling dosing. The pump systems are particularly well-suited for use with ophthalmic medication, which can be repeatedly and accurately dosed in relatively small doses (less than or equal to 50 microliters). In manufacturing, a low number of critical dimensions translates to a small range of net inaccuracy (e.g., combined deviations within acceptable tolerances). 
     With reference to FIGS. 1-3, a first pump system  10  is shown in cross-section having an outer generally cylindrical wall  12 . A bulkhead  14  extends inwardly from the wall  12  to define an upper limit of a reservoir  16 . In a preferred embodiment, the reservoir  16  is not vented to atmosphere, and, thus, pressure piston  18  is provided to avoid the formation of a vacuum in the reservoir  16 . The pressure piston  18  is urged towards the bulkhead  14  by spring  20  and is responsive to reductions of fluid volume in the reservoir  16  (such as with fluid being drawn therefrom). The spring  20  is mounted onto, and acts against an end plate  22 , that is connected to the wall  12  using any technique known by those skilled in the art, such as with a snap fit. If required, and as will be recognized by those skilled in the art, venting may be provided between the wall  12  and the end plate  22 , and may be provided similarly in the further embodiments described below. 
     Apertures  24  are defined through the bulkhead  14  through which fluid may be drawn from the reservoir  16 . A solid disc-shaped support plate  26  is defined at the center of the bulkhead  14 , with the apertures  24  being spaced circumferentially thereabout. Splines  28  extend upwardly from the support plate  26  and between the apertures  24 , and a solid wall  30  encircles the splines  28 . The wall  30  terminates in a cantilevered tapered seal ring  32 . A lower pump chamber  34  is defined amidst the support plate  26 , the wall  30 , and the seal ring  32 , which is in fluid communication with the reservoir  16  via the apertures  24 . 
     Casing  36  is mounted onto the wall  30  and is formed with a cylindrical portion  37  and an upper aperture  38 . An upper pump chamber  40  is defined within the casing  36  and is in communication with the lower pump chamber  34 . A valve stem  42  is disposed within the pump chambers  34  and  40  and is urged away from the support plate  26  by a stem spring  44 . A slidable piston cap  46  extends through the aperture  38  and has annular seal members  48  in sealing contact with the cylindrical portion  37  of the casing  36 . The piston cap  46  further includes an inner annular passage  50  formed between the stem  42  and the piston cap  46  which is in fluid communication with an exit aperture  52  located at the upper extremity of the cap  46 . The stem  42  is formed with a top  54  that terminates in a tapered portion  56  shaped to be seated in, and form a seal with, the exit aperture  52 . The stem spring  44  is selected such that the tapered portion  56  is sufficiently acted on to form an acceptable seal with the exit aperture  52 . 
     A nozzle actuator  58  is mounted onto the piston cap  46  so as to move unitarily therewith. Passageway  60  communicates the exit aperture  52  with a discharge chamber  62  in which is located a discharge piston  64 . The discharge piston  64  includes circumferential seals  66  which prevent fluid from leaking beyond the discharge chamber  62 . The discharge chamber  62  is in fluid communication with a discharge nozzle  68 . 
     A stem  70  of the discharge piston  64  has a seal surface  72  formed at an end thereof which coacts with a tapered surface  74  of the actuator  58  to form a seal for the discharge chamber  62 . A discharge spring  76  urges the seal surface  72  into engagement with the tapered surface  74 . To facilitate assembly, an end  77  of the nozzle actuator  58  may be formed open so that the discharge piston  64  and the discharge spring  76  may be mounted therein and covered with a plug  78  which may be fixed using any technique known to those skilled in the art, such as with an interference fit using detents  80 . 
     In use, the nozzle actuator  58  is caused to be pressed downwardly, as represented by the arrow A. As such, the piston cap  46  moves unitarily with the actuator  58 , causing the top  54  to also move downwardly. Upon traversing a stroke distance S, an enlarged portion  82  of the top  54  engages the seal ring  32 , thereby sealing the lower pump chamber  34  from the upper pump chamber  40 . With further downward movement, the seal ring  32  is caused to flex outwardly (forming a seal with the enlarged portion  82 ) and the volume of the upper pump chamber  40  is decreased. With further volume decrease, the pressure of the fluid trapped within the upper pump chamber  40  increases and acts upon upper face  84  of the enlarged portion  82 . As the actuator  58  and the piston cap  46  continue downwardly, pressure builds in the trapped fluid. When pressure overcomes the biasing force of the stem spring  44 , the tapered portion  56  of the stem  42  moves downwardly and away from the cap  46 , thereby exposing the exit aperture  52  (FIG.  2 ). Fluid then is forced into the discharge chamber  62  where pressure therein is increased until the seal members  66  are forced rearwardly against the force of the discharge spring  76 . As a result, discharge nozzle  68  is exposed and pressurized fluid from the discharge chamber  62  is dispensed therefrom. When the enlarged portion  82  goes through, and beyond, the seal ring  32 , the upper pump chamber  40  comes into fluid communication with the apertures  24  via the lower pump chamber  34 , thereby reducing fluid pressure in the upper pump chamber  40  (FIG.  3 ). This allows the stem spring  44  to urge the stem  42  upwardly into sealing engagement with the exit aperture  52 . With the exit aperture  52  closed, fluid pressure in the discharge chamber  62  decays with fluid being dispensed through the discharge nozzle  68 , allowing the discharge spring  76  to shut off the discharge nozzle  68 . The release of the actuator  58  allows the stem spring  44  to return the stem  42  and the piston cap  46  to their original rest positions. As the enlarged portion  82  passes upwardly through the seal ring  32 , it creates a transient vacuum sufficient to draw a volume of fluid through the apertures  24  equal to the amount dispensed. The pressure piston  18  assists the transient vacuum in urging fluid into the lower pump chamber  34 . This assures total fluid replacement. The volume of the reservoir  16  is decreased in response to the fluid which is drawn therefrom as the pressure piston  18  is pushed upwardly responsively by the spring  20 . 
     The size of the dose dispensed by the pump system  10  is basically a function of four critical dimensions of the pump system  10 . Particularly, the length of the enlarged portion  82  (“x”); the length of flat surface  83  of the seal ring  32  (“y”); the diameter of the enlarged portion  82  (“d”); and, the inner diameter of the casing  36  along cylindrical portion  37  (“z”). By minimizing the tolerances of these four dimensions, high-level of control over doses administered by the pump  10  can be achieved. As will be appreciated by those skilled in the art, dimension “y” (i.e., the flat surface  83 ) can be made so small (0.005 in) that dimensional variation may be practically zero and three dimensions actually control dosage of the pump system  10  (e.g., the flat surface  83  could be made as a small radius making this dimension a point contact with neglible width). 
     With reference to FIGS. 4-6, a second embodiment of a pump system is depicted therein in cross-section and generally designated with the reference numeral  100 . Many of the components of the pump system  100  are the same as, or similar to, that of the pump system  10  described above, and are designated with like reference numerals herein. The pump system  100 , like the pump system  10 , is dependent upon four critical dimensions. The discussion below will focus on the differences from the pump system  10  in structure and operation. 
     A pressure piston  18 ′ is provided which is spring-biased by a spring  20  in the same fashion as the pressure piston  18 . However, the pressure piston  18 ′ is shown to have a generally planar surface in contact with the reservoir  16 , whereas the pressure piston  18  is formed with a tapered portion. The shape of the pressure piston  18 ,  18 ′ is preferably selected to match the shape of the corresponding bulk head. In FIG. 1, the bulkhead  14  is formed with a tapered portion, whereas in FIG. 4, a bulkhead  14 ′ is provided which is generally planar. In this manner, the pressure piston  18 ,  18 ′ may efficiently urge fluid out of the reservoir  16 . 
     A central disc-shaped support plate  26 ′ is formed in the center of the bulkhead  14 ′ with apertures  24 ′ being formed circumferentially thereabout. An inner annular wall  28 ′ extends from the support plate  26 ′, located radially inwardly of the apertures  24 ′. The wall  28 ′ terminates in a seal ring  32 ′. A locator pin  102  may also be provided which extends upwardly from the center of the support plate  26 ′ to provide support for the spring  44 . A lower pump chamber  34  is defined admist the support plate  26 ′, the wall  28 ′ and the seal ring  32 ′. 
     The pump system  100  utilizes a piston  42 ′ which has a different configuration from the stem  42  of the first embodiment. The piston  42 ′ is disposed to extend through an aperture  38  of casing  36  so as to be slidable relative thereto. Piston seals  48 ′ provide a seal against the cylindrical portion  37  of the casing  36  during sliding movement of the piston  42 ′. The spring  44  urges the piston  42 ′ upwardly and away from the support plate  26 ′ with annular shoulder stop  104  defining the upper extent of movement of the piston  42 ′ in contacting the casing  36 . A cylindrical wall  106  extends upwardly from the shoulder stop  104  and through the aperture  38 , and a central passageway  108  is defined within the wall  106 . A check valve seat  10  is defined at an end of the passageway  108  which communicates with an inlet passageway  112 . A check valve  114  is disposed in the passageway  108  so as to seat on the inlet check valve seat  110  and regulate flow through the inlet passageway  112 . A lower annular piston ring  116  is defined about the inlet passageway  112 . The piston ring  116  is formed to engage the seal ring  32 ′ upon sufficient downward movement of the piston  42 ′. 
     A nozzle actuator  58 ′ is rigidly fixed to the piston  42 ′ so as to move unitarily therewith. The nozzle actuator  58 ′ is generally the same as the nozzle actuator  58 . The nozzle actuator  58 ′ is mounted on the piston  42 ′ in any manner so as to move unitarily therewith. In addition, an elongated block  118  is preferably provided which extends from the nozzle actuator  58 ′ and into the passageway  108 . In this manner, a reduced-diameter channel  120  is formed through the block  118  which communicates with passageway  60  and having a much smaller cross-section than the passageway  108 . 
     In use, the nozzle actuator  58 ′ is caused to translate downwardly (as shown by the arrow A), causing commensurate movement of the piston  42 ′. With sufficient movement, the piston ring  116  engages the seal ring  32 ′ and causes the lower pump chamber  34  to be sealed from the upper pump chamber  40 . With further downward movement of the piston  42 ′, the seal ring  32 ′ is caused to deflect outwardly, maintaining the seal between the pump chambers  34  and  40  intact. Further downward movement of the piston  42 ′ causes volume reduction of the lower pump chamber  34 , and an increase in pressure therein. With a sufficient increase in pressure, the check valve  114  is caused to lift from the valve seat  110  and pressurized fluid is forced through the inlet passageway  112 , the channel  120  and the passageway  60  to act on the discharge piston  64  (FIG.  5 ). The fluid is discharged form the discharge chamber  62 , in the same manner as described with respect to the pump system  10 . When the piston ring  116  goes through, and beyond, the seal ring  32 ′ (FIG.  6 ), pressure decays, the discharge piston  64  returns to its closed state, and the check valve  114  returns to its seated position on the valve seat  110 . With release of the nozzle actuator  58 ′, the spring  44  urges the piston  42 ′, and the nozzle actuator  58 ′, upwardly to the rest state shown in FIG.  4 . As the piston  42 ′ separates from the seal ring  32 ′, fluid is drawn from the reservoir  16 . 
     The four critical dimensions in the pump system  100  are the outer diameter x of the piston  42 ′; the diameter y of the seal ring  32 ′; the length t of the diameter x; and, the length z of flat surface  83 ′ on the seal ring  32 ′. The “z” dimension can be a radius or a small flat (0.005 inches); as such, dimensional variation is practically zero making three dimensions control dosage. 
     With reference to FIG. 7, a possible external configuration of a pump system is shown, which may be either the pump system  10  or the pump system  100 . Although the discharge nozzle  68  is shown to be covered in both FIGS. 1 and 4; it is in fact exposed, as shown in FIG.  7 . It is critical that the nozzle  68  not be covered by the wall  12  at a location where fluid is to be discharged therefrom. 
     With reference to FIGS. 8-9, a third embodiment of a pump system is depicted therein in cross-section and generally designated with the reference numeral  200 . The pump system  200  has the same basic structure and operates in the same basic manner as the first embodiment described above. However, the pump system  200  is an “in-line” dispenser having an exit aperture extending along the longitudinal axis of the pump system, such as in the manner of a nasal spray. Like reference numerals refer to identical or similar components described above. 
     The pump system  200  includes the exit aperture  52  formed in the piston cap  46  as with the first embodiment. However, the exit aperture  52  acts as a dispensing aperture for this embodiment in contrast to the first embodiment. Thus, fluid dispensed from the pump system  200  is dispensed along the longitudinal axis of the pump system  200  (which is coincident with the longitudinal axis of the stem  42  as shown in FIG.  8 ). To provide for actuation of the pump system  200 , actuator  202  is provided having finger grips  204  formed to be depressed by the pointer and middle fingers of a user. The actuator  202  is rigidly mounted to the piston cap  46  about shoulder  206 . With downward movement of the actuator  202 , the pump system  200  works in the same manner as described above. For illustrative purposes, as shown in FIG. 9, with downward movement of the actuator  202 , the stem  42  engages the seal ring  32  to form a seal therewith resulting in eventual separation of the stem  42  from the cap  46 , with exposure of the exit aperture  52  for dispensing pressurized fluid from the upper pump chamber  40 . Further downward movement of the actuator  202  results in pressure decay after a dose has been administered and full passage of the enlarged portion  82  beyond the seal ring  32  results in subsequent recharging of the pump system  200 . A release of the actuator  202  allows for return of the valve stem  42  to its rest position as shown in FIG.  8 . 
     FIG. 10 shows a fourth embodiment of the subject invention which is a variation of the third embodiment. Pump system  300  is also an “in-line” pump system which utilizes valve stem  42 , as in the first and third embodiments described above. Here, however pressure piston  302  applied to the reservoir  16  is applied in a downward motion to urge fluid up through tube  304 , having a passage  306  formed therein, and into the lower pump chamber  34 . Also, a swirl plug  308  may be provided between the piston cap  46  and actuator  310 . Various swirl plug configurations are known in the prior art. As an exemplary embodiment, as shown in FIGS. 11A-11C, the spray plug  308  may include radiating channels  312 . When fluid goes through the channels  312  and into the center of the plug  308 , a swirling motion is imparted to the discharging fluid, causing the fluid to break up into a spray pattern through nozzle  314 . In all other respects, the pump system  300  is essentially the same as the third embodiment. 
     As is readily apparent, numerous modifications and changes may readily occur to those skilled in the art, and hence it is not desired to limit the invention to the exact construction operation as shown and described, and accordingly, all suitable modification equivalents may be resorted to falling within the scope of the invention as claimed.