Liquid pump

Abstract

A liquid pump includes a container body, a vacuuming device, and a liquid-discharging device. The container body has an upper portion, a lower portion, a vent hole formed in the upper portion, a cap mounted removably on the upper portion for closing the vent hole, a liquid inlet formed in the upper portion, a guide tube connected to the liquid inlet, a liquid outlet formed in the lower portion, and a plug mounted removably on the lower portion for closing the liquid outlet. The vacuuming device is mounted on the container body and is operable so as to reduce air pressure within the container body. The liquid-discharging device includes a connecting rod connected to the plug and movable between a closing position and an opening position. The liquid-discharging device further includes a biasing unit connected to the connecting rod for biasing the connecting rod to the closing position.

I claim:  
     
         1 . A liquid pump comprising: 
 a container body confining a receiving space and having an upper portion, a lower portion, a vent hole formed in said upper portion, a cap mounted removably on said upper portion for closing said vent hole, a liquid inlet formed in said upper portion, a guide tube connected to said liquid inlet, a liquid outlet formed in said lower portion, and a plug mounted removably on said lower portion for closing said liquid outlet;    a vacuuming device mounted on said container body and operable so as to reduce air pressure within said container body; and    a liquid-discharging device including a connecting rod connected to said plug and movable between a closing position, where said plug closes said liquid outlet, and an opening position, where said plug is removed from said liquid outlet, said liquid-discharging device further including a biasing unit connected to said connecting rod for biasing said connecting rod to the closing position.    
     
     
         2 . The liquid pump as claimed in  claim 1 , wherein said vacuuming device includes: 
 a barrel mounted on said container body, confining an air passage, and having opposite first and second ends respectively disposed proximate to and distal from said receiving space of said container body;    a first end wall mounted on said first end of said barrel and formed with a first hole for fluid communication between said receiving space and said air passage;    a second end wall mounted on said second end of said barrel and formed with a second hole for fluid communication between said air passage and the atmosphere externally of said barrel;    a check valve mounted on said first end wall for closing said first hole;    a piston disposed in said barrel and movable between said first and second end walls; and    a piston rod having a first end portion connected to said piston, and a second end portion extending through said second end wall;    said check valve opening when said piston is moved toward said second end wall so as to permit air flow from said receiving space into said air passage;    said check valve closing when said piston is moved toward said first end wall so as to block air flow from said air passage to said receiving space.    
     
     
         3 . The liquid pump as claimed in  claim 2 , wherein said piston divides said air passage into a volume-variable first passage portion adjacent to said first end wall, and a volume-variable second passage portion adjacent to said second end wall, said piston including a first piston plate confronting said first end wall and a second piston plate connected to said first piston plate and confronting said second end wall, said first and second piston plates cooperatively forming an annular recess therebetween, said annular recess having a depth in an axial direction of said piston rod, said second piston plate being formed with a third hole to communicate said annular recess and said second passage portion, said vacuuming device further including a seal ring received in and extending along said annular recess, said seal ring having a diameter sufficient to establish sealing contact with said barrel, and further having a thickness in the axial direction of said piston rod that is less than the depth of said annular recess.  
     
     
         4 . The liquid pump as claimed in  claim 2 , wherein said connecting rod extends through said first end wall and into said air passage so as to be capable of being actuated by said piston for movement from the closing position to the opening position.  
     
     
         5 . The liquid pump as claimed in  claim 4 , wherein said biasing unit includes a stop plate disposed in said air passage and connected to said connecting rod, and a spring mounted between said stop plate and said first end wall.