| 摘要 |
A viscous material dispenser (for liquid soap and the like) comprises a piston in fluid communication with an air chamber. Depressing the piston increases the pressure in the air chamber and this pressurized air is conducted through a duct to a reservoir. Depressing the piston also opens a nozzle leading from the bottom of the reservoir. In one embodiment the duct terminates in a portion which turns back on the remainder of the duct which portion incorporates a one-way non-return valve so that the pressure in the reservoir may be built up with consecutive strokes of the piston due to the non-return valve. When air is pumped through the duct, a bubble of air is trapped between the valve and the mouth of the duct which prevents fouling of the valve by the viscous material. In another embodiment, the reservoir may contain a sac of a viscous material; in this embodiment a one-way valve to admit air to the air chamber may be locked closed during a portion of the return stroke of the piston to suck viscous material at the basal dispensing opening of the unit back into the unit thereby preventing drips.
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