Abstract:
The invention relates to a precompression pump which includes a feature for opening the outlet valve at the bottom of the pump stroke, to thereby evacuate air and liquid from the pump chamber. The pump includes a gravity-biased inlet valve and a spring-biased outlet valve. Elevated pressure in the pump chamber causes the outlet valve to open against the bias of the outlet valve spring. At least one of the outlet valve or the inlet valve has an engagement end which engages the other valve at the bottom of the pump stroke, to thereby open the outlet valve against the bias of the outlet valve spring and exhaust air and liquid from the pump chamber to the spray nozzle. In this way, the pump chamber is evacuated so that liquid can be drawn into the pump chamber from the bottle or container. The present invention uses a simple design which is easy to mold, does not require close tolerancing, and which operates effectively without the need for difficult-to-mold friction fits.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is directed to the field of precompression pumps. More particularly, the present invention is directed to a precompression pump used for dispensing, e.g., personal care products, from a container or bottle upon which the pump is mounted. 
     2. Description of the Related Art 
     Precompression pumps are known in the art. A precompression pump is a pump in which the outlet valve for the pump chamber opens in response to a predetermined pressure level within the pump chamber. Often, this is accomplished by providing an outlet valve having a surface upon which pressure in the pump chamber acts, and which is biased in a way that the outlet valve only opens when the pressure in the pump chamber is of a sufficiently high level. This type of pump is particularly useful for dispensing personal care products in a fine mist without dribbling. 
     A problem can arise in precompression pumps of the type described above during priming of the pump. When the pump chamber is in an unprimed condition—i.e., is filled with air instead of the liquid to be dispensed—it is necessary to evacuate air from the pump chamber in order to draw the liquid to be dispensed into the pump chamber. However, the air in the pump chamber can act as a compressible fluid. As a result, in certain precompression pump designs air in the pump chamber is compressed during the downstroke of the pump piston, and the pressure in the pump chamber does not achieve a sufficiently high level to open the outlet valve and release the air in the pump chamber through the pump nozzle. It is therefore difficult to evacuate the air from the pump chamber and to draw liquid into the pump chamber for dispensing. The result is that an undesirable number of “strokes to prime” may be necessary to operate the pump, if the air is not released from the pump chamber in some way other than through opening of the outlet valve. 
     Several patents describe mechanisms for assisting in the evacuation of air from a pump chamber to allow the pump to be primed. U.S. Pat. Nos. 3,746,260; 3,774,849; 4,051,983 and 4,144,987 show various mechanisms used to evacuate air from the pump chamber of a precompression pump. However, many of these mechanisms are unsatisfactory in that they can vary the volume of the dose, can cause wear or fatigue in the operating parts of the pump, or are difficult to mold. U.S. Pat. No. 5,192,006 shows a pump which includes a feature for evacuating air from the pump chamber. This pump, however, uses friction-operated inlet and outlet valves which can be disadvantageous for several reasons. First, in order for the friction-operated valves to operate properly, several parts must be closely toleranced to ensure proper frictional fits. In addition, the functional characteristics of the pump can vary depending on variations in the frictional fit between parts. Furthermore, any variations in tolerancing can result in frictional fits which can prevent the valves from opening and/or can cause the valves to remain open when they are intended to be closed. Finally, the design of the parts necessary to achieve the frictional fits involves detailed, and potentially expensive, molding equipment. 
     SUMMARY OF THE INVENTION 
     The present invention is advantageous in that it provides a precompression pump which is of a simple design, which ensures evacuation of air from the pump chamber to the spray nozzle, and which does not require close tolerancing and complicated molded parts to ensure proper and effective operation. 
     The present invention includes a pump housing defining a pump chamber in which a pump piston reciprocates. A pump spring biases the pump piston upwardly or axially outwardly. A gravity-biased inlet valve is located between the inlet or dip tube and the interior of the pump chamber. This inlet valve can be either a conventional ball-check valve or can be a gravity-biased stem valve. A spring-biased outlet valve is located between the interior of the pump chamber and the spray nozzle. This outlet valve opens in response to a specific internal pressure within the pump chamber. The outlet valve can be either a conventional ball-check valve, or a stem valve. The stem valve can have a conical sealing surface which cooperates with a conical sealing surface on the pump piston. In either case, the only contact between the outlet valve and the piston in which the outlet valve is housed is the fit caused by the outlet valve spring bias. At least one of either the inlet valve or the outlet valve has an engagement piece which interacts with the other valve of the pump at the bottom of the downstroke of the pump piston. This interaction opens the outlet valve, against the bias of the valve spring, thereby evacuating any air or liquid trapped in the pump chamber at the bottom of the downstroke of the pump. As a result, any compressed air in the pump chamber is mechanically evacuated from the pump chamber through the outlet valve, and the pump chamber is therefore capable of being filled with liquid from the container or bottle for subsequent spraying through the spray nozzle. 
     Several different variations on the design of the inlet and outlet valves are contemplated, and several variations are disclosed herein, although these variations do not limit the inventions which are contemplated within the scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of a first embodiment of a pump dispenser of the present invention, in a non-depressed position; 
     FIG. 2 is the embodiment of FIG. 2 in the depressed position at the bottom of the pump stroke; 
     FIG. 3 is a cross-sectional view of a second embodiment of a pump dispenser of the present invention, in a non-depressed position; 
     FIG. 4 is the embodiment of FIG. 3 in the depressed position at the bottom of the pump stroke; 
     FIG. 5 is a cross-sectional view of a third embodiment of a pump dispenser of the present invention, in a non-depressed position; 
     FIG. 6 is the embodiment of FIG. 5 in the depressed position at the bottom of the pump stroke; 
     FIG. 7 is a cross-sectional view of a fourth embodiment of a pump dispenser of the present invention, in a non-depressed position; 
     FIG. 8 is a cross-sectional view of a fifth embodiment of a pump dispenser of the present invention, in a non-depressed position; 
     FIG. 9 is a cross-sectional view of a sixth embodiment of a pump dispenser of the present invention, in a non-depressed position; 
     FIG. 10 is a cross-sectional view of a seventh embodiment of a pump dispenser of the present invention, in a non-depressed position; 
     FIG. 11 is a cross-sectional view of an eighth embodiment of a pump dispenser of the present invention, in a non-depressed position; 
     FIG. 12 is a cross-sectional view of a ninth embodiment of a pump dispenser of the present invention, in a non-depressed position; 
     FIG. 13 is a cross-sectional view of a tenth embodiment of a pump dispenser of the present invention, in a non-depressed position; 
     FIG. 14 is a cross-sectional view of an eleventh embodiment of a pump dispenser of the present invention, in a non-depressed position; 
     FIG.  14   a  is a top view of the stem valve of the embodiment of FIG.  14 . 
     FIG. 15 is a cross-sectional view of a twelfth embodiment of a pump dispenser of the present invention, in a non-depressed position; 
     FIG. 16 is a cross-sectional view of an thirteenth embodiment of a pump dispenser of the present invention, in a non-depressed position. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 and 2 show a first embodiment of the present invention. The pump  1  includes a pump housing  2  defining a pump chamber  3 . Sliding within pump chamber  3  is a pump piston  4 . At the lower end of pump chamber  3  is an inlet valve  5 , which in the embodiment of FIGS. 1 and 2 is a gravity-biased ball-check valve. The inlet valve  5  controls the flow of liquid from the inlet tube  6  at the lower end of the pump housing  2 , which inlet tube  6  is normally connected to a dip tube, as is conventional in the art. Inlet valve  5  is encircled completely within pump spring  14 , and is thereby free to move without any interference with pump piston  4 . The dip tube leads to the lower end of a bottle or container (not shown), upon which the pump  1  is mounted by a suitable mounting cup or cap  7 . A pump spring  14  biases pump piston  4  in an upward or axially-outward direction. The pump spring  14  seats at its lower or axially-inward end  20  on a spring seat  21  in pump housing  3 . Lower end  20  of pump spring  14  acts as a cage for inlet valve  5 , restraining it from movement into pump chamber  3 . 
     The piston stem  8  of pump piston  4  includes an inwardly-projecting piston sealing flange  9 . Piston sealing flange  9 , in the embodiment shown in FIGS. 1 and 2, can have a conical sealing surface. Piston sealing flange  9 , on its lower or axially-inward side, acts as a seat for upper or axially-outward end  22  of pump spring  14 . Mounted within piston stem  8  is an outlet valve  10 . Outlet valve  10 , in the embodiment of FIGS. 1 and 2, includes an outwardly-projecting valve sealing flange  11 . Valve sealing flange  11 , in the embodiment of FIGS. 1 and 2, has a conical sealing surface which is shaped to interact with and seal against the conical sealing surface on piston sealing flange  9 . A valve spring  12  biases the outlet valve  10  so that valve sealing flange  10  seats against piston sealing flange  9 . Valve spring  12  cooperates at one end  32  with the piston stem  8  at spring seat  33 , and at the other end  30  cooperates with valve sealing flange  11 , to thereby bias valve sealing flange  11  against piston sealing flange  9 . Valve sealing flange  11  is structured so that its radially-outward edge is spaced from the radially-inward surface of pump piston  4 . As a result, the only contact between outlet valve  10  and pump piston  4  is at the conical sealing surfaces under the bias of valve spring  12 . 
     Outlet valve  10  includes an axially-inwardly projecting outlet valve engagement end  13 . As shown in FIG. 2, outlet valve engagement end  13  is manufactured to be of sufficient distance from valve sealing flange  11  such that, at the bottom of the stroke of pump piston  4 , the outlet valve engagement end  13  contacts inlet valve  5  so as to disengage sealing contact between valve sealing flange  11  and piston sealing flange  9 , against the bias of valve spring  12 . As will be described below, this disengagement of contact or unseating of outlet valve  10  allows trapped air or liquid in the pump chamber  3  to escape out the spray nozzle  15 . The pump  1  can include conventional sealing gaskets  16 ,  17 , spray head  18 , and nozzle  15 , as are well-known in the art. 
     In operation, finger pressure on spray head  18  is applied to the pump in the non-depressed condition shown in FIG.  1 . Downward, or axially-inward, movement of spray head  18  causes pump piston  4  to compress the fluid within pump chamber  3 . When sufficient pressure has built up within pump chamber  3  as a result of downward movement of pump piston  4 , this pressure will act on the downwardly or axially-inwardly facing surfaces on outlet valve  10  to overcome the bias of valve spring  12 , thereby unseating outlet valve  10  by disengaging the conical sealing surfaces on piston sealing flange  9  and valve sealing flange  11 . The resulting gap between these surfaces (shown in FIG. 2) allows pressurized fluid to flow out of pump chamber  3 , and thereafter out of spray nozzle  15 . The outlet valve  10  will remain open throughout the downward, or axially-inward, movement of pump piston  4 , as long as sufficient pressure in maintained within pump chamber  3  to overcome the biasing force of valve spring  12 . 
     FIG. 2 shows the pump  1  of FIG. 1 at the bottom of the pump stroke. In this position, the outlet valve engagement end  13  of outlet valve  10  contacts the upper end of inlet valve  5 . As inlet valve  5  is, in this position, seated against the bottom of pump housing  2 , engagement of outlet valve engagement end  13  and inlet valve  5  causes piston sealing flange  9  and valve sealing flange  11  to disengage from one another, against the bias of valve spring  12 , thereby allowing any trapped air or liquid within pump chamber  3  to flow out of pump chamber  3  and out spray nozzle  15 . The flow of air or liquid out of pump chamber  3  is indicated by arrows F. 
     After the pump  1  is in the position shown in FIG. 2, finger pressure is released from spray head  18 . Piston spring  14  biases pump piston  4  upwardly, increasing the volume of pump chamber  3  and thereby decreasing the pressure in pump chamber  3 . As a result, outlet valve  10  closes, as the bias of valve spring  12  causes valve sealing flange  11  to seal against piston sealing flange  9 . Inlet valve  5  opens, as the decreased pressure in pump chamber  3  unseats inlet valve  5  against the force of gravity, allowing liquid to be drawn into pump chamber  3  through inlet tube  6  and any attached dip tube (not shown). Pump chamber  3  fills, and pump piston  4  continues to move upwardly, until it reaches the position shown in FIG.  1 . 
     FIGS. 3 and 4 show a second embodiment of the pump of the present invention. The design of the pump  101  of the embodiment of FIGS. 3 and 4 is very similar to that of the embodiment of FIGS. 1 and 2, except that the pump structure of the embodiment of FIGS. 3 and 4 is of a modular design (i.e., the pump components fit together to form a modular unit for insertion into mounting cup or cap  107 ), and the upper end of outlet valve  110  is slightly different in shape. In all other respects, however, the embodiment of FIGS. 1 and 2 and FIGS. 3 and 4 are identical in structure and operation. Similar elements in the embodiment of FIGS. 3 and 4 are designated with identical reference numerals to those used with the embodiment of FIGS. 1 and 2, except for the addition of the “100” prefix in the embodiment of FIGS. 3 and 4. 
     FIGS. 5 and 6 show a third embodiment of the pump of the present invention. The design of the pump  201  of the embodiment of FIGS. 5 and 6 is very similar to that of the embodiment of FIGS. 1 and 2, except that the design of the upper end of the outlet valve  210  is different. The outlet valve  210  of FIGS. 5 and 6 includes an opening  220  into which valve spring  212  is received, and pump piston  204  includes a pin  221  for receiving the other end of valve spring  212 . The bottom of opening  220  acts as a spring seat for the lower or axially-inward end  230  of valve spring  212 , and upper end  232  of valve spring  212  engages a spring seat  233 . The valve sealing flange  211  of the embodiment of FIGS. 5 and 6 is not conically shaped, and the valve sealing flange  211  interacts with a rounded piston sealing flange  209  to form a seal for the outlet valve  210 . A spring seat  223  restrains the upper or axially-outward end  222  of pump spring  214 . The valve sealing flange  211  seals against the interior wall of the pump piston  204 . A series of axial slots  251 , which provide a fluid bypass around valve sealing flange  211 , are in pump piston  204  upper end. In all other respects, however, the embodiment of FIGS. 1 and 2 and FIGS. 5 and 6 are identical in structure and operation. Similar elements in the embodiment of FIGS. 5 and 6 are designated with identical reference numerals to those used with the embodiment of FIGS. 1 and 2, except for the addition of the “200” prefix in the embodiment of FIGS. 5 and 6. 
     In operation of the embodiment of FIGS. 5 and 6, finger pressure on spray head  218  is applied to the pump in the non-depressed condition shown in FIG.  5 . Downward, or axially-inward, movement of spray head  218  causes pump piston  204  to compress the fluid within pump chamber  203 . When sufficient pressure has built up within pump chamber  203  as a result of downward movement of pump piston  204 , this pressure will act on the downwardly or axially-inwardly facing surfaces on outlet valve  210  to overcome the bias of valve spring  212 , thereby pushing outlet valve  210  up until the valve sealing flange  211  lifts from the piston sealing flange  209  and clears the lower end of slots  251 . After valve sealing flange  211  clears slots  251 , pressurized fluid can escape through slots  251  around valve sealing flange  211 , and thereafter out of spray nozzle  215 . The outlet valve  210  will remain open throughout the downward, or axially-inward, movement of pump piston  204 , as long as sufficient pressure in maintained within pump chamber  203  to overcome the biasing force of valve spring  212 . 
     FIG. 6 shows the pump  201  of FIG. 5 at the bottom of the pump stroke. In this position, the outlet valve engagement end  213  of outlet valve  210  contacts the upper end of inlet valve  205 . As inlet valve  205  is, in this position, seated against the bottom of pump housing  202 , engagement of outlet valve engagement end  213  and inlet valve  205  causes piston sealing flange  209  and valve sealing flange  211  to disengage from one another and for valve sealing flange  211  to move past the bottom end of slots  251 , against the bias of valve spring  212 , thereby allowing any trapped air or liquid within pump chamber  203  to flow out of pump chamber  203  and out spray nozzle  215 . The flow of air or liquid out of pump chamber  203  is indicated by arrows F. 
     After the pump  201  is in the position shown in FIG. 6, finger pressure is released from spray head  218 . Piston spring  214  biases pump piston  204  upwardly, increasing the volume of pump chamber  203  and thereby decreasing the pressure in pump chamber  203 . As a result, outlet valve  210  closes, as the bias of valve spring  212  causes valve sealing flange  211  to seal against piston sealing flange  209 . Inlet valve  205  opens, as the decreased pressure in pump chamber  203  unseats inlet valve  205  against the force of gravity, allowing liquid to be drawn into pump chamber  203  through inlet tube  206  and any attached dip tube (not shown). Pump chamber  203  fills, and pump piston  204  continues to move upwardly, until it reaches the position shown in FIG.  5 . 
     FIG. 7 shows a fourth embodiment of the pump of the present invention. In this embodiment, similar elements to those in the embodiment of FIGS. 1 and 2 are designated with identical reference numerals to those used with the embodiment of FIGS. 1 and 2, except for the addition of the “300” prefix in the embodiment of FIG.  7 . In the embodiment of FIG. 7, the inlet valve  305  is a gravity-biased stem valve. Inlet valve  305  includes an inlet valve engagement end  330 , which engages with outlet valve engagement end  313  on outlet valve  310  when the pump piston  304  is at the bottom of its stroke. This engagement disengages valve engagement flange  311  from piston engagement flange  309 , releasing air or liquid from pump chamber  303  so that it may flow through spray nozzle  315 . In all other respects, the structure and operation of the embodiment of FIG. 7 is identical to that of the embodiment of FIGS. 1 and 2. 
     FIG. 8 shows a fifth embodiment of the pump of the present invention, which is similar in design and operation to the embodiment of FIG. 7, but which uses an outlet valve  410  and piston sealing flange  409  similar in design to those used in the embodiment of FIGS. 1 and 2. In all other respects, however, the embodiment of FIG. 8, in design and operation, is identical to that of the embodiment of FIG.  7 . In the embodiment of FIG. 8, elements similar to those in the embodiment of FIG. 7 include identical reference numerals, except in the embodiment of FIG. 8 a “400” prefix is used instead of the “300” prefix of FIG.  7 . 
     FIG. 9 shows a sixth embodiment of the pump of the present invention, which is similar in design and operation to the embodiment of FIG. 7, but which uses a spring-biased ball-check inlet valve  510  which seals against piston sealing flange  509 . At the bottom of the pump stroke, the inlet valve engagement end  530  of inlet valve  505  engages the bottom of outlet valve  510 , disengaging outlet valve  510  from piston sealing flange  509 , thereby allowing air and liquid in pump chamber  503  to escape out spray nozzle  515 . In all other respects, the embodiment of FIG. 9 operates in a manner identical to that of the embodiment of FIG.  7 . The embodiment of FIG. 9 uses the prefix “500” for those elements that are similar to those elements designated with the prefix “300” in the embodiment of FIG.  7 . 
     FIG. 10 shows a seventh embodiment of the pump of the present invention. The design of the pump  601  of the embodiment of FIG. 10 is similar to that of the embodiment of FIGS. 5 and 6, except that the design of the upper end of the outlet valve  610  is different. The outlet valve  610  of FIG. 10 includes a sealing skirt  650 . The top of sealing skirt  650  acts as a spring seat for the lower or axially-inward end  630  of valve spring  612 , and upper end  632  of valve spring  612  engages spring seat  633 . The sealing skirt  650  of the embodiment of FIG. 10 seals against the interior wall of the pump piston  604 . Along the distance S, the sealing skirt  650  seals around its entire periphery. Above the distance S are a series of axial slots  651 , which provide a fluid bypass around sealing skirt  650  when sealing skirt  650  is above the lower end of slots  651 . Similar elements in the embodiment of FIG. 10 are designated with identical reference numerals to those used with the embodiment of FIGS. 5 and 6, except for the addition of the “600” prefix in the embodiment of FIG.  10 . 
     In operation of the embodiment of FIG. 10, finger pressure on spray head  618  is applied to the pump in the non-depressed condition shown in FIG.  10 . Downward, or axially-inward, movement of spray head  618  causes pump piston  604  to compress the fluid within pump chamber  603 . When sufficient pressure has built up within pump chamber  603  as a result of downward movement of pump piston  604 , this pressure will act on the downwardly or axially-inwardly facing surfaces on outlet valve  610  to overcome the bias of valve spring  612 , thereby pushing outlet valve  610  up until the sealing skirt  650  clears the lower end of slots  651 . After sealing skirt  650  clears slots  651 , pressurized fluid can escape through slots  651  around sealing skirt  650 , and thereafter out of spray nozzle  615 . The outlet valve  610  will remain open throughout the downward, or axially-inward, movement of pump piston  604 , as long as sufficient pressure in maintained within pump chamber  603  to overcome the biasing force of valve spring  612 . The remaining operation of the embodiment of FIG. 10 is identical to the operation of the embodiment of FIGS. 5 and 6. 
     FIG. 11 shows an eighth embodiment of the pump of the present invention. The design of the pump  701  of the embodiment of FIG. 11 is very similar to that of the embodiments of FIGS. 10 and 2, except the embodiment of FIG. 11 includes conical sealing surfaces on piston sealing flange  709  and valve  210 , similar to the conical sealing surfaces in the embodiments of FIGS.  1 - 4  and  7 - 8 . It has been found that this embodiment provides particularly advantageous results, in that the pressure to disengage the conical sealing surfaces on piston sealing flange  709  and valve  710  is greater than the pressure necessary to move the sealing skirt  750  upward by a multiple of 2 to 10—depending on the angle of the conical surfaces and the diameters of the conical surfaces on the piston and on the stem. As a result, upon actuation of the pump, the pressure which is placed on the sealing skirt  750  at the moment the conical sealing surfaces disengage is much more than is necessary to push the valve  710  up, thereby rapidly opening the outlet valve and providing a more uniform exit pressure and better spray dispersion. This result is preferred by consumers. The use of the conical sealing surfaces also ensures that a lighter valve spring  712  may be used. The remainder of the operation of the embodiment of FIG. 11 is identical to the operation of the embodiment of FIG.  10 . Similar elements in the embodiment of FIG. 11 are designated with identical reference numerals to those used with the embodiment of FIG. 10, except for the addition of the “700” prefix in the embodiment of FIG.  11 . 
     FIG. 12 shows a ninth embodiment of the present invention. The design of the pump of the embodiment of FIG. 12 is very similar to that of the embodiment of FIG. 11, except in the design of the interface between the valve  810  and the pump piston  804 . In the embodiment of FIG. 12, the outlet valve  810  includes a sealing skirt  850 . The top of sealing skirt  850  acts as a spring seat for the lower or axially-inward end  830  of valve spring  812 , and upper end  832  of valve spring  812  interacts with spring seat  833 . The valve spring  812  of the embodiment of FIG. 12 includes several “dead coils”—i.e., coils which touch an adjacent coil on its upper and lower surfaces—at both the upper end  832  and the lower end  830 . This type of valve spring  812  provides several advantages. First, the valve spring  812  with dead coils reduces tangling of springs when used in high-speed automatic assembly equipment. Second, the dead coils provide a rigid metallic column at the top and bottom of valve spring  812 . In addition, the spring seat  833  of pump piston  804  can be made to have an inner diameter which is equal to the outer diameter of the valve spring  812 . As a result, when the spray head  818  is assembled onto the pump piston  804  the piston, specifically spring seat  833 , is squeezed between the rigid steel column and the inner diameter of the actuator, resulting in good retention of these parts. As a result, the piston top can be made of thinner and softer materials, giving greater design flexibility and increasing the ability of the pump piston  804  to seal. 
     The sealing skirt  850  of the embodiment of FIG. 12 seals against the interior wall of the pump piston  804 . Along the distance S, the sealing skirt  850  seals around its entire periphery. Above the distance S is a widened-diameter section  851 , which provides a fluid bypass around sealing skirt  850  when sealing skirt  850  is above the lower end of widened-diameter section  851 . Widened diameter section  851  could alternatively be a series of axial slots. In addition, a stem sealing skirt  880  on pump piston  804  seals against the outer diameter of the outlet valve  810 . Outlet valve  810  includes a series of axial valve slots  881 . After the axial valve slots  881  pass through stem sealing skirt  880 , fluid communication is established between the pump chamber  803  and the sealing skirt  850 . After this is accomplished, the embodiment of FIG. 12 operates in a manner identical to the operation of the embodiment of FIG.  11 . The embodiment of FIG. 12 provides the same advantageous performance results as the embodiment of FIG. 11, but is easier to tolerance, mold, and assemble in high volume. Similar elements in the embodiment of FIG. 12 are designated with identical reference numerals to those used with the embodiment of FIG. 11, except for the addition of the “800” prefix in the embodiment of FIG.  12 . 
     FIG. 13 shows a tenth embodiment of the present invention. The design of the pump of the embodiment of FIG. 13 is very similar to that of the embodiment of FIG. 12, except in the design of the upper portion of the valve  910 . Valve  910  includes a valve sealing flange  911  which is structured so that its radially-outward edge is spaced from the radially-inward surface of pump piston  904 . Valve sealing flange  911  seats against a piston sealing flange  909 , thereby sealing spray nozzle  915  from pump chamber  903 . Downward, or axially-inward, movement of spray head  918  causes pump piston  904  to compress the fluid within pump chamber  903 . When sufficient pressure has built up within pump chamber  903  as a result of downward movement of pump piston  904 , this pressure will act on the downwardly or axially-inwardly facing surfaces on outlet valve  910  to overcome the bias of valve spring  912 , thereby unseating outlet valve  910  by moving the axial valve slots  981  past the stem sealing skirt  980  and disengaging the sealing surfaces on piston sealing flange  909  and valve sealing flange  911 . The resulting passages though axial valve slots  981 , the gap between the surfaces on piston sealing flange  909  and valve sealing flange  911  and slots  970  in valve sealing flange allow pressurized fluid to flow out of pump chamber  903 , and thereafter out of spray nozzle  915 . A widened diameter section or axial slots  951  can also be provided to allow passage of fluid from the pump chamber  903  to the spray nozzle  915 . 
     FIG. 14 shows a different configuration of the embodiment of FIG.  13 . In the embodiment of FIG. 14, the flange  1011  does not create a seal against the flange  1009 . The slots  1070  in outlet valve  1010  bridge the flange  1011 , creating a flow path around flange  1011  even when flange  1011  is seated against flange  1009 . In all other respects, however, the embodiments of FIG.  13  and FIG. 14 are identical in structure in operation. FIG.  14   a  shows a top view of the upper portion of outlet valve  1010 , and specifically the configuration of the slots  1070 . 
     FIG. 15 shows a twelfth embodiment of the present invention. The design of the pump of the embodiment of FIG. 15 is very similar to that of the embodiment of FIG. 12, except in the design of the interface between the valve  1110  and the pump piston  1104 . In the embodiment of FIG. 15, the outlet valve  1110  includes a sealing skirt  1150 . The top of sealing skirt  1150  acts as a spring seat for the lower or axially-inward end  1130  of valve spring  1112 , and upper end  1132  of valve spring  1112  interacts with the actuator  1118 . The bottom of sealing skirt  1150  engages and seals against a seat  1109  in the lowermost or axially-inwardmost position. The valve spring  1112  of the embodiment of FIG. 15 can include “dead coils”—i.e., coils which touch an adjacent coil on its upper and lower surfaces—at both the upper end  1132  and the lower end  1130 . 
     The sealing skirt  1150  of the embodiment of FIG. 15 seals against the interior wall of the pump piston  1104 . Along the distance S, the sealing skirt  1150  seals around its entire periphery. Above the distance S are a series of slots  1151 , which provides a fluid bypass around sealing skirt  1150  when sealing skirt  1150  is above the lower end of slots  1151 . In addition, a stem sealing skirt  1180  on pump piston  1104  seals against the outer diameter of the outlet valve  1110 . Outlet valve  1110  includes a series of axial valve slots  1181 . After the axial valve slots  1181  pass through stem sealing skirt  1180 , fluid communication is established between the pump chamber  1103  and the sealing skirt  1150 . After this is accomplished, the embodiment of FIG. 15 operates in a manner identical to the operation of the embodiment of FIG.  12 . Similar elements in the embodiment of FIG. 15 are designated with identical reference numerals to those used with the embodiment of FIG. 12, except for the addition of the “1100” prefix in the embodiment of FIG.  15 . 
     FIG. 16 shows a different configuration of the embodiment of FIG.  14 . In the embodiment of FIG. 16, the flange  1211  does not create a seal against the flange  1209 . The slots  1270  in outlet valve  1210  bridge the flange  1211 , creating flow paths F around flange  1211  even when flange  1211  is seated against flange  1209 . In the embodiment of FIG. 16, the top  1232  of spring  1212  seats against actuator  1218 . The embodiment of FIG. 16, like the embodiment of FIG. 14, is particularly useful for thicker liquid products, as these embodiments do not require that two seals be bypassed by the exiting liquid product. 
     Both the embodiments of FIGS. 15 and 16 are shown using a screwcap  1107 ,  1207  for mounting to a container, and therefore may be used in larger dosage size applications. A retaining element  1117 ,  1217  is used to retain the pump components within the screwcap  1107 ,  1207 . The retaining element  1117 ,  1217  allows the pump to be assembled by pushing the pump components down into the screwcap  1107 ,  1207 . In the embodiments of FIGS. 15 and 16, the retention of the spring  1112 ,  1212  against the actuator  1118 ,  1218  increases the ease by which the pump may be assembled. 
     In each of the embodiments in FIGS.  1 - 16 , both the inlet and outlet valves for the pump chamber are retained in their sealing positions only by the force of gravity or the force of a spring bias. In the embodiments of FIGS.  1 - 16 , no frictional or other forces caused by interaction of the two sealing parts are used to effect the outlet valve seal, and disengagement of the seal is only effected by the pressure of fluid within the pump chamber. Although the embodiments of FIGS.  5 - 6 ,  10 - 12  and  15 - 16  include interacting sealing surfaces at the outlet valve which slide relative to one another, the forces between these surfaces are uniform throughout the movement of the valve, and do not vary depending on the position of the valve. This design ensures that the parts need not be closely toleranced to ensure good sealing or that tolerance variations do not materially affect pump performance characteristics. As a result the pump of the present invention is much easier to manufacture, while providing advantageous operational characteristics and long-term reliability. Furthermore, in each of the embodiments of FIGS.  1 - 16 , the inlet valve is spaced from, and does not interact with, the pump piston, thereby ensuring that it operates only in response to the force of gravity or pressure within the pump chamber. As a result, much more reliable operation of the inlet valve can be assured. Finally, since the pump spring surrounds the inlet valve, the pump spring acts to both align, and act as a valve cage, for the inlet valve. 
     While the forgoing represents a description of several preferred embodiments, it is to be understood that the claims below recite the features of the present invention, and that other embodiments, not specifically described hereinabove, fall within the scope of the present invention.