Abstract:
A finger-operated spray pump assembly including a tank, a primary piston slidably fitted inside the tank, having a liquid passageway, a secondary piston slidably fitted inside the primary piston, and a spring fitted inside the primary piston and the secondary piston for biasing the primary piston away from the secondary piston.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to liquid atomizer pumps. In particular, the invention relates to small, hand-held, finger-operated dispensers involving pump assemblages as distinguished from pressurized aerosol containers and valves. 
     Pumps of the type with which the present invention is concerned include a piston arranged to be driven into the pump housing against a spring pressure so as to deliver the liquid to the nozzle. It is known that in order to obtain the highest possible degree of atomization it is preferable to provide at the pump outlet a so-called turbulence nozzle. 
     However, it has been found that even the use of a nozzle of this type in prior art atomizing pumps does not completely preclude the occurrence of an insufficient atomization and the formation of droplets in the vicinity of the nozzle, particularly when the pump is subjected to a relatively slow depression movement. 
     U.S. Pat. No. Re. 28,366, reissued Mar. 18, 1975 to Pechstein discloses an atomizing pump which has as its object the elimination of some of these drawbacks. The Pechstein patent discloses a pump that has a first piston and a second piston, the first piston having a liquid flow passage. A valve which moves relative to the first piston and the second piston is disposed for closing the liquid flow passage in the first piston. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention there is provided a finger operated spray pump assembly including a tank, a primary piston slidably fitted inside the tank having a liquid passageway, a secondary piston slidably fitted inside the primary piston, and a spring fitted inside the primary piston and the secondary piston for biasing the primary piston away from the secondary piston. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an enlarged fragmentary sectional view showing details of the pump; 
     FIG. 2 is an enlarged fragmentary sectional view of the pump as the primary piston is being depressed; 
     FIG. 3 is an enlarged fragmentary sectional view of the pump as the primary piston is rising; and, 
     FIG. 4 is an enlarged fragmentary perspective view of the primary piston. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, the spray pump assembly of the present invention can be seen in FIG. 1 to include a tank which is generally indicated by the numeral 25. Tank 25 houses a primary piston generally indicated by the numeral 15 and a secondary piston generally indicated by the numeral 30. 
     At the bottom of tank 25 is circular valve 27. Circular valve 27 makes a seal with circular ridge 25b when actuator button 10 is depressed, as can be seen in FIG. 2. Circular valve 27 is held between tank 25, and post 25c and ridge 25b. Post 29c has channels 25d therein through which liquids may flow as indicated by the arrows in FIG. 3. If desired, circular valve 27 can be replaced with a conventional ball check valve. 
     At the lower end of tank 25 is an inlet passageway 28 to which is attached suction tube 42. The suction tube 42 is arranged to extend substantially to the bottom of container 23 to which the pump assembly may be connected. 
     Primary piston 15 is slidably contained within tank 25 by means of closure 22 which can be seen in the drawings to be a threaded cap screwed onto the threaded top of container 23. Closure 22 could also be attached to a suitable container by crimping, or the like. Closure 22 limits the upward movement of primary piston 15 when shoulders 15b of primary piston 15 strike shoulder 22a of closure 22. Closure 22 bears against flange 25a which is formed integrally with tank 25. The edge of the tank flange 25a may be snapped into the closure to prevent disassembly prior to placement on the container. Preferably a gasket 20 is placed between the flange 25a and the top of container 23 to prevent leakage around the spray pump assembly. 
     A circular cup 22c, having a slot 22d for receipt of tab 10a on button 10 is preferably integrally molded with closure 22. Button 10 can be depressed only when tab 10a is aligned to be received in slot 22d. To prevent actuation during shipment, tab 10a is turned from alignment with slot 22d. A flat portion or key 15e may be provided on primary piston 15 to assure alignment between outlet 12 and chamber 11c. 
     Primary piston 15 is generally hollow inside and has a hollow stem 15a which projects upwardly therefrom and which contains a liquid outlet passageway 16. As can best be seen in FIG. 4, passageway 16 permits liquid to flow into a mechanical break up swirl chamber generally indicated by the numeral 11 which is integrally molded on primary piston 15. The swirl chamber 11 includes a circular channel 11a which is connected to round chamber 11c by radial channels 11b. 
     Stem 15a is slidably received in circular opening 22b in closure 22. Vent 25e is located in tank 25 to permit air to flow into container 23. A cylindrical guide 15d extends downwardly from the inside of piston 15 into spring 40. At the lower end of primary piston 15 is scaling collar 18 which forms a seal with the inner wall of tank 25. 
     Attached at the top of stem 15a is actuator button 10. Outlet 12 in actuator button 10 forms an exit for liquids passing outwardly through passageway 16 and channel 11. 
     Secondary piston 30 can be seen in the drawings to be hollow inside and to be slidingly received in primary piston 15. At the upper end of the secondary piston 30 is located an annular scaling collar 31 which forms a seal with the inner wall of stem 15a. Piston 30 has a series of ridges 30a inside, the ends of which serve as a lower seat for spring 40. 
     In the free-standing normal position shown in FIG. 1, the spring 40 forces secondary piston 30 against the bottom of tank 25 onto valve 27. In operation, the actuator button 10 is first depressed moving primary piston 15 downwardly, compressing spring 40. As piston 15 moves downwardly the fluid trapped in tank 25 transmits a pressure which keeps valve 27 closed as shown in FIG. 2. At a certain point during the downward travel of piston 15, the pressure within tank 25 reaches a point sufficient to overcome the spring pressure being exerted downwardly on secondary piston 30. At this point, secondary piston 30 begins to travel upward due to the upward force exerted against scaling collar 31 by the fluid in tank 25. Secondary piston 30 continues to move upward as the actuator button is depressed until the scaling collar 31 moves above liquid outlet passageway 16. At this point the fluid within tank 25 flows out of passageway 16 and channel 11 outwardly through exit 12 of actuator button 10. Then, once a sufficient pressure drop caused by escape of fluid is obtained, the spring returns so to its original rest position. 
     In FIG. 3, actuator button 10 is shown moving upwardly by spring pressure. The reduced pressure within compression chamber 26 caused by the upward movement of primary piston 15 draws liquid from container 23 through suction tube 42 and inlet 28 upward between valve 27 into tank 25, thus filling tank 25 with a new charge of liquid. 
     Having fully described the invention, it is desired that it be limited only within the spirit and scope of the attached claims.