| 摘要 |
A dispensing pump includes an outer cylinder and an inner piston which cooperate in defining a pump chamber. The cylinder includes an inlet port and an outlet port which are sequentially opened and closed by the piston. In addition, a vent for the container interior to replace discharge product with air is also adapted to be opened and closed incident to the movement of the piston. Sealing rings are provided between the piston and cylinder, the location of which, determines the amount of product and air drawn into the pump chamber as well as the characteristics of the dispensing pattern of the product discharged by the pump. During part of the suction stroke as well as the compression stroke, both the inlet and outlet ports are simultaneously closed by the piston thereby respectively creating a predetermined negative pressure and positive pressure within the pump chamber. A pin, separate from the discharge orifice is adapted to be shiftable into and out of the passageway leading from the pump chamber to the discharge orifice to respectively close and open this passage.
|
