Abstract:
A pre-compression pump ( 10 ) dispenses microdoses of fluid (F). The pump minimizes pulsing due to pressure fluctuations. The pump is provided with the following to limit pulsing: a low force slow return velocity return spring ( 46 ); enlarged fluid passage ( 58 ); elastic bumper ( 74 ); and, a ratchet tooth ( 76 ) bearing against the stem ( 44 ). Further, a deflectable diaphragm ( 90 ), a splined ( 70 ) stem ( 44 ), no dip tube, and an off-center, gravitational low-point pump inlet ( 62 ) assist in priming the pump. The pump includes a stem ( 44 ) with delfectable fingers ( 92 ) to ensure sufficient momentum in pump operation. Detents ( 118 ) and grooves ( 120 ) selectively lock a nozzle cap ( 14 ) in an inoperative position. To ensure cleanliness, nozzle ( 60 ) cleaning is provided, wiping of the nozzle to remove meniscus (M) therefrom, cuts ( 104 ) formed in a shroud ( 98 ) assist in drawing excess fluid from the nozzle, and an empty volume ( 108 ) for collecting fluid run-off from the nozzle. A handle (H) is mounted to the pump providing a grip.

Description:
This application claims priority of U.S. Provisional Patent Application Ser. No. 60/150,405, filed Aug. 23, 1999. 
    
    
     This invention relates to pumps for dispensing fluids and medications, and, more particularly, to microdispensing pumps. 
     In the prior art, positive displacement and pre-compression pumps are known. In addition, U.S. Pat. No. 5,881,956, to the inventors herein, discloses a positive displacement pump which is capable of dispensing microdoses of fluid, as small as 5–10 microliters. U.S. Pat. No. 5,881,956 is incorporated by reference herein. With such small dosing capability, the pumps of U.S. Pat. No. 5,881,956 are advantageously usable to dispense opthalthmic medication. Although some of the teachings of U.S. Pat. No. 5,881,956 can be applied to the pre-compression pump art, there are significant differences between the pumps which prevent full carry-over of the technology. 
     A pre-compression pump operates on the principle that the pressure build-up within a pump cylinder propels a fluid out of the pump. The ejection of the fluid drains the pump cylinder thereby causing a pressure differential which results in additional fluid being drawn into the pump cylinder. In contrast, a positive displacement pump relies on one dose of fluid literally “pushing” out, and thus causing ejection of, a preceding dose of fluid. 
     As can be appreciated, the consistent dispensing of microdoses (5–10 microliters) of fluid presents a unique set of problems. The problems of priming pumps with such small doses with positive displacement pumps are addressed in U.S. Pat. No. 5,881,956. Because of the difference in operating principles between positive displacement pumps and pre-compression pumps, the disclosure of the aforementioned patent can not be fully applied to pre-compression pumps to achieve microdosing of 5–10 microliters. For example, it has been found that fluids generally pulse upon dispensing from a pre-compression pump because of pressure fluctuations, the pulsing action resulting in atomization of the dispensed fluid. Particularly, pressure fluctuations are generated during pump operation, where a pressure build-up within the cylinder of the pump causes the stem of the pump to separate from the piston, thereby allowing pressurized fluid to rush into, and out of, the nozzle of the pump. However, upon initial separation of the stem from the piston, the pressure within the cylinder quickly decays, with the stem being urged back into sealing contact with the piston by a return spring. The fluid is then quickly re-pressurized in the cylinder, again causing separation of the stem from the piston, thus, achieving further fluid delivery. This repeated “opening” and “closing” of the pump cylinder occurs rapidly with the dose being continuously and interruptedly delivered. The internal pressure of the dose, however, fluctuates as it is dispensed causing the dispensed fluid to pulse. 
     With typical uses of pre-compression pumps, pulsing does not interfere with the required atomization of the dispensed liquid. Typical doses are relatively large, and, thus, are substantially insensitive to the pressure fluctuations; pre-compression pumps generally dispense doses much larger than 10 microliters, with such doses being on the order of at least 70 microliters. Where it is desired to consistently dispense microdoses of fluid without atomization, such as with ophthalmic medication, pressure fluctuations have an adverse effect. Furthermore, medication is ideally delivered in a stable, relatively laminar flow pattern, with little pressure fluctuation throughout dosage delivery. Atomization of the fluid is not desired. 
     Accordingly, it is an object of the subject application to provide a pre-compression pump capable of consistently dispensing repeated microdoses of fluid and medication without atomization. 
     SUMMARY OF THE INVENTION 
     The aforementioned object is met by a pre-compression pump having various inventive features. It should be noted that some of the features can be carried over to other pump arts beyond the field of pre-compression pumps, such as lift pumps. 
     In a first aspect of the invention, the pump includes features to minimize the pulsing effect caused by pressure fluctuations in a pre-compression pump, thereby avoiding atomization in dispensing a fluid. Specifically, the pump is provided with various elements which restrict the responsive movement of the stem so that the stem does not quickly respond to the pressure fluctuations in the pump cylinder. Accordingly, the stem will respond relatively slowly to the decay of internal pressure of the cylinder, thereby prolonging the uninterrupted delivery of fluid without pulsing and allowing for a laminar delivery. First, a return spring is provided to urge components into a rest position which is formed with a low spring force and/or is wound to have a slow return velocity (typical coil springs are wound to have high return velocities). Accordingly, the spring will react weakly/slowly to pressure decay within the pump cylinder with the stem being urged into a closed position relatively slowly as compared to the rate of pressure decay. Second, portions of the fluid passage communicating the pump cylinder and the nozzle are enlarged so as to reduce restriction to flow, thereby minimizing throttling of the fluid, and to provide a damping effect on the fluid. The reduction in throttling and the damping effect coact to reduce pulsing in the fluid. Third, an elastically-deformable bumper may be disposed on the end of the stem of the pump. The bumper, which may be in the form of a deflectable dome or a solid member, is disposed on an end of the stem so as to absorb, and react to, pressure of the fluid, thereby minimizing the stem&#39;s reaction to fluid pressure. Fourth, an internal seal may be formed with a generally triangular cross-section to increase fluid drag on the stem and further inhibit movement of the stem. Fifth, a ratchet tooth may be disposed on the pump piston which bears against the stem and inhibits movement of the stem, thereby also reducing the stem&#39;s reaction to fluid pressure. 
     In addition, in a second aspect of the invention, priming of the pump is a concern, since a relatively minor air pocket will inhibit, or altogether prevent, the ability of the pump to dispense microdoses. To aid in proper priming, a partially splined stem is preferably used, wherein shallow recesses are formed between the splines. The recesses are sufficiently shallow such that air bubbles may pass between the splines via the recesses, but un-pressurized fluid will not because of its viscosity. As such, air bubbles may escape without hindering operation of the pump. Also no dip tube is utilized, thereby eliminating the possibility of an air pocket being trapped in the dip tube. During priming of a pump with a dip tube, a sufficient amount of fluid must be drawn from the dip tube to ensure no air pockets are therein. Air pockets are compressible and inhibit, or defeat, continuous operation of a pump. Without a dip tube, an inlet is formed in the pump cylinder which is in direct communication with the fluid reservoir of the pump. Preferably, the inlet is located off-center in the pump cylinder and at a low point on a tapered surface. With the off-set location and tapered surface, air bubbles will not become entrapped at the bottom of the cylinder, and the air bubbles will have an unobstructed path up along the outside of the pump cylinder to escape the pump. In addition, a deflectable diaphragm may be provided which is deflectable into the fluid reservoir to reduce the volume thereof. 
     Furthermore, in a third aspect of the invention, the pump includes a stem formed with deflectable fingers that yield under a pre-determined amount of operational force thereby ensuring sufficient momentum is provided in operating the pump. In this manner, the pump can only be operated with sufficient force to ensure full and proper fluid dispensing. 
     In a fourth aspect of the invention, cleanliness of the pump is of concern. Cooperative detents and grooves are formed to selectively lock the nozzle cap in an inoperative, locked position. In a locked position, the nozzle of the pump is covered by a shroud which prevents dirt and debris from collecting on the nozzle. The nozzle cap and shroud are preferably formed with cooperating members which overlap in a locked position to form a seal in proximity to the nozzle to further inhibit the ingress of dirt and debris between the shroud and nozzle cap. The pump also provides for cleaning of the nozzle, with an opening in the shroud wiping the nozzle to remove any meniscus therefrom after dispensing fluid. Additionally, cuts are formed in the shroud facing the nozzle cap which assist in drawing excess fluid from the nozzle, and an empty void is located about the nozzle for collecting fluid run-off from the nozzle. 
     In a fifth aspect of the invention, a handle is also mounted to the pump to provide a comfortable grip for handling the pump. 
     These and other features of the invention will be better understood through a study of the following detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an elevational view of a pump in accordance with the subject invention; 
         FIG. 1A  is a cross-sectional view taken along line  1 A— 1 A of  FIG. 1 ; 
         FIG. 2  is an enlarged view of the nozzle of the pump; 
         FIG. 3  is an enlarged view of an alternative stem of the pump; 
         FIG. 4  is an enlarged view of the stem; 
         FIG. 4A  is a cross-sectional view taken along line  4 A— 4 A; 
         FIG. 5  is an elevational view of the pump with a deflectable diaphragm; 
         FIG. 6  is an enlarged view of the nozzle of the pump; 
         FIG. 7  is an elevational view of the portion of the shroud about the dispensing opening in the shroud; 
         FIG. 8  is a top view showing the locking and operating positions of the nozzle cap; and, 
         FIG. 9  is a plan view of the sealing members. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the FIGS., a pre-compression pump  10  is shown, along with various features thereof. The pump  10  generally includes a body  12 , and a nozzle cap  14 . 
     The body  12  is formed with a generally tubular outer wall  16  with a transverse web  18  which divides the body  12  into two chambers, an upper chamber  20  and a lower chamber  22 , and a web opening  24  communicates the two chambers  20  and  22 . The nozzle cap  14  is disposed in the upper chamber  20 , whereas, the lower chamber  22  cooperates with a bottom wall  26  to define fluid reservoir  28 . The bottom wall  26  may be detachable from the outer wall  16  so as to permit charging of fluid directly into the fluid reservoir  28 . 
     A tubular cylinder  30  is mounted about the web opening  24  and extends into the fluid reservoir  28 . As shown in  FIG. 1 , a rubber washer  32  is disposed over, and presses against, the cylinder  30 . A holding member  34 , disposed to engage and hold the rubber washer  32 , is preferably snap-fitted onto an annular ridge  36  protruding from the web  18 . Also, vent holes  38  extend through the web  18 . It is preferred that the vent holes  38  be out of contact with the rubber washer  32 , so that air may be drawn through the web  18  and into the fluid reservoir  28  during use. 
     A tubular piston  40  is disposed within the cylinder  30  and extends therefrom through the rubber washer  32  and into the upper chamber  20 . The rubber washer  32  is generally circumferentially in contact with, and forms a seal about, the piston  40 . In addition, the piston  40  has an outer surface  42  which is in contact with the cylinder  30 , due to an interference fit being defined therebetween. It must be noted however that the interference fit may not be excessive since the piston  40  must be slidable relative to the cylinder  30 . In addition the nozzle cap  14  is mounted onto the piston  40  such that the two elements move together. 
     A cylindrical stem  44  is disposed within the cylinder  30  and partially telescoped within the piston  40 . The stem  44  is slidable relative to both the cylinder  30  and the piston  40 . Additionally, the stem  44  is urged into contact with the piston  40  by a return spring  46  disposed between the stem  44  and lower end  48  of the cylinder  30 . The interaction of top edge  50  of the stem  44  and lip  52  of the piston  40  limits the upward movement of the stem  44 . 
     A fluid passage  54  is defined in the piston  40  about the stem  44  and above the lip  52 . The fluid passage  54  is in fluid communication with passage  56  formed in the nozzle cap  14 . The passage  56  has a bend  58  which re-directs the passage  56  to nozzle  60 . 
     In operation, fluid F is disposed within the fluid reservoir  28 . With the pump  10  being fully primed, the fluid F is also present within the cylinder  30 . An inlet  62  is formed in the lower end  48  which communicates cylinder chamber  64 , encompassed by the cylinder  30 , and the fluid reservoir  28 . An annular seal  66  is mounted within the cylinder chamber  64  so as to form a seal about the stem  44 . Upon depressing the nozzle cap  14 , the piston  40  is translated downwardly, pressing against the top edge  50  of the stem  44  and against the spring force of the return spring  46 . As the piston  40  and the stem  44  move downwardly, the volume of the cylinder chamber  64  above the annular seal  66  decreases, thereby increasing the pressure of the fluid F trapped therein. The pressure of the fluid F acts on all surfaces in contact with the fluid F, including a tapered actuating surface  68 . With further downward movement, the pressure of the fluid F increases to the point where the fluid F presses down on the actuating surface  68  so as to separate the top edge  50  of the stem from the lip  52  of the piston  40 . The pressurized fluid F then escapes from the cylinder chamber  64  through the fluid passage  54 , into the passage  56 , and out of the nozzle  60 . As the fluid F escapes, the internal pressure of the cylinder chamber  64  decays. The phenomenon of pressure fluctuations described above take effect with the fluid F being dispensed from the nozzle  60 . With the pressure within the cylinder chamber  64  being sufficiently decayed the stem  44  is urged into contact with the piston  40 . 
     The stem  44  is formed with a plurality of longitudinally extending splines  70  which separate recesses  72 . When pressurizing the cylinder chamber  64  during pumping, the splines  70  are located below the seal  66  with the annular seal  66  generally sealing a full circumference of the stem  44 . In this manner, no fluid F by-passes the seal  66 . With the further decrease in pressure in the cylinder chamber  64 , a pressure differential is created across the annular seal  66 , the stem  44  is urged toward the piston  40 , and the fluid F is drawn into the cylinder chamber  66  through the recesses  72  under the annular seal  66 . Consequently, the pump  10  is re-charged, and ready for re-use. 
     The description above generally describes the operation of the pump  10 . Below are various features which elaborate upon different aspects of the invention. 
     Reduction of Fluid Pulsing 
     Various features are provided to minimize pressure fluctuations, in repeated opening and closing of the pump  10  during operation, to avoid repeated engagement and disengagement of the top edge  50  of the stem  44  and the lip  52  of the piston  40 . Accordingly, non-atomized microdoses of fluid may be delivered. First, the interference fit between the piston  40  and the cylinder  30  is reduced from that found in the prior art. Typically, the interference fit is approximately 0.010 inches. With the subject invention, the interference fit is approximately 0.005 inches. Accordingly, the return spring  46  can be formed with a weaker spring force than that in the prior art, since less resistance is presented by the interference fit, and/or the return spring  46  can be wound to have a slower return velocity than that found in the prior art. In either regard, the weaker/slower response of the return spring  46  will retard the spring&#39;s response to pressure decay in the cylinder chamber  64 . With the return spring  46  responding weakly/slowly, the stem  44  will not engage and disengage the piston  40  as repeatedly in the prior art. 
     In addition, as shown in  FIG. 2 , a portion of the passage  56 , preferably the bend  58 , is enlarged relative to other portions thereof. In this manner, the enlarged portions of the passage  56  reduce flow restriction, and, thus, reduce any potential throttling of the fluid F above the stem  44 . In addition, the increased area serves as a pocket or cushion to smooth out pressure fluctuations. 
     Separately, also as shown in  FIG. 2 , a bumper  74  may be mounted to the top edge  50  of the stem  44 . The bumper  74  is elastically deformable to respond to pressure applied thereto by the fluid F. The bumper  74  can be a hollow dome-shaped member which protrudes from the stem  44 , or, alternatively, can be a solid pellet or ball which is partially inserted into the stem  44  and extends therefrom. The bumper  74  will absorb some of the pressure fluctuations in the fluid F and immunize the operation of the pump  10  thereagainst. 
     Referring again to  FIG. 1 , a ratchet tooth  76  may be formed on the piston  40  to bear against the stem  44 . The ratchet tooth  76  is plate shaped with a generally triangular profile. The bearing of the ratchet tooth  76  against the stem  44  creates friction which inhibits relative movement between the stem  44  and the piston  40 . Again, the inhibition of movement of the stem  44  serves to limit the effect of pressure fluctuations. A plurality of ratchet teeth  76  may also be provided. 
     Furthermore, with reference to  FIG. 3 , the annular seal  66  may be formed with a generally right-triangular cross-section, having a pointed edge  78  for engaging the stem  44 . With this structural arrangement, a generally planar lower surface  80  is defined which is generally perpendicular to the axis of the stem  44 . This perpendicular arrangement creates more fluid drag during use against upward movement of the stem  44 , thereby inhibiting the movement of the stem  44  and further reducing the effects of pressure fluctuations. 
     Typically in the pump art, a seal in a seal/shaft arrangement is sized so that the seal diameter is a little smaller than the shaft to ensure a good seal. Often, the seal is 0.010 inches smaller than a shaft diameter in seals typically used in hand-held pre-compression pumps, such as the annular seal  66 . Referring to  FIG. 4 , a constant-diameter portion  82  is formed in the stem  44  above the splines  70  which may be 0.010 inches larger than the inner diameter of the annular seal  66 . Alternatively, as shown in  FIG. 3 , the constant-diameter portion may be substituted for by conical portion  84 . The conical portion  84  is preferably made with an upper diameter  86  slightly greater, e.g. 0.002 inches, than the inner diameter of the annular seal  66 . Also, preferably a lower diameter  87  is provided of 0.005 inches. The conical portion  84  provides a progressively looser fit in the seal  66  as it progresses down through the seal  66  with the movement of the stem  44 , thereby allowing the stem  44  to move downwards with less resistance from the seal  66  throughout the dispensing stroke. This reduction in resistance from the seal  66  reduces the creation of pulses. 
     Priming 
     The elimination of air pockets and bubbles, especially upon initial use of the pump  10  is critical to ensure proper priming is achieved, especially where microdoses are concerned. 
     Most prior art pump dispensers house fluid to be dispensed at the bottom of the dispenser; the dispenser then pulls, or lifts, the fluid upwards via a dip tube which dips into the liquid. In contrast, the pump  10  houses the fluid F around the cylinder  30  and does not utilize a dip tube. Instead, the inlet  62  is in direct communication with the fluid reservoir  28 . As shown, the inlet  62  may be coextensive with the cylinder  30 , or may be formed to extend slightly therefrom. Costs are saved by removing the dip tube component. Also, priming is enhanced, because the fluid F is disposed at a higher elevation with respect to the cylinder  30  as compared to the elevation of fluid in prior art pumps utilizing dip tubes. With the subject invention, the fluid F at least partially engulfs the stem  44  with the cylinder  30  substantially being coextensive with the fluid reservoir  28  and the inlet  62  being located in proximity to the bottom wall  26 . 
     The recesses  72  allow air to leak freely out of the cylinder chamber  64  during priming. The splines  70  are relatively shallow, preferably 0.001 to 0.005 inches, which allows air to pass downwards with the pump  10  not in use. The annular seal  66  is disposed about the splines  70  with the pump  10  not in use. In addition, because of the shallowness of the splines  70 , fluids will be generally too viscous to pass through the recesses  72 , and, thus, will remain above the seal  66  in an unactuated state. In re-charging the cylinder chamber  64  after a dispensing operation, the fluid F is urged through the recesses  72  under force of the aforementioned pressure differential. 
     Additionally, as shown in  FIG. 1 , it is preferred that the inlet  62  be located off-center in the lower end  48  of the cylinder  30 . Preferably, the inlet  62  will be located off-center in a direction away from the nozzle  60 . Since the pump  10  will often be inclined slightly towards the nozzle  60  in use, the off-center location will encourage entrapped air to be expelled into the fluid reservoir  28 , where it can rise freely up to the vent holes  38 . 
     Furthermore, the inside surface  88  of the lower end  48  is preferably inclined, relative to the cylinder  30 , so as to encourage the fluid F to spread evenly across the inside surface  88  upon entry. This ensures that pockets of air do not become trapped at this point. 
     As yet another additional feature, the pump  10  of the subject application can be provided with a deflectable diaphragm  90  for accelerating the priming operation. Currently, prior art pumps prime themselves prior to dosing liquid by stroking up and down several times. Once fully flooded with liquid they then begin to dose. The problem with very low dose pumps (any below 70 micro-liters) is that the number of strokes required to prime can be high, simply because the internals of the pump are of relatively high volume compared to the dose volume of the pump. Referring to  FIG. 5 , the diaphragm  90  protrudes from the outer wall  16  prior to initial use of the pump  10 . Instead of priming the dispenser by pressing the cap several times, the user presses the diaphragm  90 , which deflects inwards into the fluid reservoir  28  and remains in that position. The indenting of the diaphragm  90  decreases the volume of the fluid reservoir  28 , thereby raising the pressure in the fluid reservoir  28  which spontaneously drives the fluid F into the cylinder  30 . In order for the fluid F to be driven into the cylinder  30 , the stem/piston interaction of the top edge  50  and the lip  52 , when in a dry condition, and allowing air in the pump  10  to pass therethrough. It should be noted that the rubber washer  32  should not leak at a lower pressure than the stem/piston interaction because the deflection of the diaphragm  90  would result in fluid leaking through the vent holes  38 , without the pump  10  being actually primed. 
     Sufficient Operating Momentum 
     The basic operation described above is sufficient to dispense fluid out of the pump  10 . But, if the pump  10  is operated very slowly, it is possible to dispense the fluid F so slowly that it dribbles down the outside of the nozzle  60  instead of leaping clear of the nozzle  60  as is desired for reliable operation. U.S. Pat. No. 5,881,956 describes a latch mechanism which is utilized to ensure a minimum amount of velocity is applied to actuate a pump. The pump  10  is also provided with a mechanical latch in the form of a plurality of fingers  92  which are cantilevered to, and extend downwards from, the stem  44 . The fingers  92  bear against and slide freely against an upstanding pin  94  during downward movement of the stem  44  and the piston  40 . In an unactuated state of the pump  10 , it is preferred that the fingers  92  be located clear of and above the pin  94 . 
     The pin  94  has a tapered end  96 , with increasing diameters from smaller to larger. Preferably, the end  96  makes initial contact with the fingers  92  just prior to the point at which the upper end of the splines  70  on the stem  44  enter the seal  66  (which is the point at which the pump is about to dispense fluid). 
     The point at which the fingers  92  engage the tapered end  96  may be slightly in advance of the point at which the splines  70  enter the seal  66 . To further advance the stem  44  downwardly, sufficient force must be applied to deflect the fingers  92  and cause yielding thereof. The increased downward force required to deflect the fingers  92  past the tapered end  96  provides sufficient momentum needed to ensure a minimum velocity is provided to the pump  10  to properly dispense a full dose of the fluid at an acceptable velocity. 
     Cleanliness 
     With respect to another aspect of the invention, to achieve reliable and safe dosing of fluid, the nozzle  60  and free space around the nozzle cap  14  must remain clean and free from any accumulation of excess fluid, or the dried remnants of fluid. 
     Cleanliness of the nozzle  60  may be managed in several ways. 
     The portion of the outer wall  16  disposed about the upper chamber  20  defines a shroud  98  which shields the nozzle cap  14  and the nozzle  60  from dirt and debris. A dispensing opening  100  is defined in the shroud  98  which is located to register with the nozzle  60  during dispensing, so that dispensed fluid may pass through the shroud  98 . When the pump  10  is not in use, and is in a rest position, the nozzle  60  is positioned behind a portion of the shroud  98 . The nozzle  60  is disposed to be relatively close to a snout  102  formed about the opening  100 . The snout  102  is used to aim the pump  10  when in use. The nozzle  60  is brought close enough to the snout  102  so that any liquid meniscus M which might remain on the nozzle  60  after dosing is wiped against the snout  102 . As shown in dashed lines in  FIG. 6 , the meniscus M overlaps with portions of the snout  102 . The wiping action has the tendency to transfer some of the excess fluid onto, or adjacent to, the shroud  102 , thus reducing the height of the meniscus M. It is preferred that the liquid be transferred to the snout  102 , rather than to other portions of the pump  10 . 
     When the pump  10  is not in use, the nozzle cap  14  is rotated, preferably by about 40 degrees, into a locking position to prevent inadvertent operation. During this locking operation, any slight meniscus of liquid which might have gathered will not be wiped around the inside of the shroud  102  which surrounds the cap  14  because of the prior wiping action against the inside of the snout  102 . 
     A further embellishment to encourage liquid to transfer from the nozzle  60  to the snout  102  is provided by a series of angled cuts  104  on the inside face  101  of the snout  102 . These cuts  104  are angled such that tapered lands  106  are defined which accommodate the excess liquid on the snout  102 . The lands  106  diverge and becomes broader, and as the cap  14  is rotated to a lock position, the nozzle  60  wipes past the broadening region of a land  106 . The broadening land  106  tends to pull the liquid outwards to its boundaries, defined by the cuts  104 , which draw more liquid away from the nozzle  60  as the cap  14  is rotated to the locked position. Also, the cuts  104  act to break surface tension of the meniscus M, as the meniscus M is passed thereover. 
     Given that the inside of the snout  102  wipes the meniscus M on the nozzle  60 , some of the excess liquid may partly transfer onto the snout  102 , but can also be pushed downwards from the mouth of the nozzle  60  and roll over and down the outside of the protruding nozzle. A void  108  is provided around the nozzle  60  where any excess liquid can be transferred. In this way, the excess fluid can dry without interfering with the mouth of the nozzle  60 . 
     To further encourage any meniscus M to roll over and onto the outside conical section of the nozzle  60  and be deposited within the void  108  defined about the nozzle  60 , the front edge of the nozzle is rounded with a full radius, of typically 0.005 inches. This small radius tends to reduce any meniscus formation by encouraging the rolling over mechanism to occur. 
     As a further embellishment to all the features mentioned above regarding meniscus elimination, all the surfaces which are designed to receive excess liquid from the nozzle  60  can be roughened during manufacture, on the basis that roughened surfaces will more readily attract liquid. 
     As previously mentioned the cap  14  is rotated relative to the body  12  of the pump  10  in order to lock it against unintended operation. To facilitate rotation, grooves  110  are cut into the outside of the cap  14  to provide a grip to provide for this rotation. The pump  10  provides for the outer surfaces of these grooves  110  to be roughened to improve the quality of the grip. 
     The rear part of the cap has flat faces  112  which can also be used to rotate the cap  14  into and out of its locked position. Pushing on one of the faces  112  will rotate the cap to lock, while pushing on the other face  112  will rotate the cap to unlock. 
     A pair of slotted faces  114  cut into the outside diameter of the cap  14  work in conjunction with a pair of protrusions  116  on the inside diameter of the shroud  98  to define the position at which the cap is permitted to descend and also the extremes of rotational travel of the cap  14 . A detent  118  is added to each of the protrusions  116  within the shroud  98  which is formed to snap into a groove  118  when the cap  14  is rotated into the lock position. The detents  118  indicate that the lock position has been achieved by holding the cap  14  in that position. Similar shaped grooves  120  are formed to correspond to the operating position of the cap  14 , thus providing clear indications as to the locked and operating positions. 
     Once the locked position is achieved it is desirable to provide an intimate seal between the periphery of the cap  14  adjacent to the nozzle  60  and the inside of the shroud  98 . This is achieved by introducing three bands  122  of reduced diameter on the inside of the shroud  98 , preferably equi-spaced, and three bands  124  of increased diameter on the cap  14 , also preferably equi-spaced. One of the bands  124  on the cap  14  is preferably centered upon the nozzle  60 . The diameters of the inside bands on the shroud  122  and outside bands  124  on the cap  14  are approximately equal in diameter, to provide a seal when overlapped. It is preferred that the overlapping occur when the pump  10  is locked, with the bands of the cap  124  being in pressing engagement with the bands of the shroud  122 , preferably with transition fits. When the pump  10  unlocked and the cap  14  is urged into an operating position, the diameter bands on the shroud  122  and the cap  124  are spaced apart to allow unrestricted downward operation of the cap  14 . 
     Handle 
     Since the fluid reservoir  28  is generally coextensive with the cylinder  30 , the overall length of the pump  10  is relatively short. Accordingly, a handle H is provided for convenient handling and gripping. The handle H both provides an ergonomic grip for the user and also serves to buffer the fluid reservoir  28 . Preferably, the pump  10  will be filled in an inverted position, and the handle H will be snapped into place. The pump  10  will then be inverted to the normal upright position for further manufacturing operations. 
     The discussion set forth above is with respect to a pre-compression pump. Those skilled in the art will understand that the disclosure herein is exemplary and the inventive features may be applied to other types of pumps. 
     The invention is not intended to be limited to the embodiments discussed herein, but only limited by the scope of the appended claims.