Liquid-Air Switch Valve

Liquid-Air Switch Valve
LAV type

Definitive solution for automatic agricultural chemical spraying

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Liquid-Air Switch Valve

Patented in Japan



Rated pressure


Farming revolution! Easy solution to agrochemical application

Agricultural sprinkler systems have recently seen the widespread use of sprinkler equipment for not only water, but also other agricultural chemicals and liquid fertilizer dispersion from a single sprinkler. This being the case, however, residual liquid in the pipes adds to costs and thus there is a necessity for its efficient use. As for methods of using residual liquid, there is the "collecting" method, where residual liquid is drawn off via separate pipes and collected, or the "pneumatic" method, where pressurized air is pumped into the pipes, dispersing residual liquid out the sprinklers. Of the two methods, it is said that the pneumatic method is the most rational, time-saving approach for complete use of agricultural chemicals over a broad area of dispersion.

However, the use of the pneumatic method, even with its excellent conceptualization, has yet to see widespread use. This has been due mainly to the lack of an appropriate valve to stop air leakage from the sprinkler after the residual liquid has been dispersed (liquid flows, but air is shut off, or the "liquid-air switch valve" as it has been called). Previous "liquid-air switch valves" suffered imprecise operation, with air leakage occurring at shut off, and other frequent problems such as "chattering" or "hunting" noise and vibration at the moment of shut off or when opening. For these reasons, the practicality of the pneumatic method has, for a long time, been viewed as difficult.

Liquid-Air Switch Valve / Concept of pneumatic method

We have now found solutions to all the problems with the previous valves and have successfully developed one with superb operation. This newly developed "Liquid-Air Switch Valve LAV type" carries out a rapid shut off operation when air begins to flow after the residual liquid has been dispersed, together with landmark features that eliminate air leakage, chattering and hunting. As a result, the ideal pneumatic method can be put into practical use for the first time ever in the world.

Precise open/close operation

Accurately detects difference between liquid and air, then instantaneously shuts down at the moment liquid dispersion has finished, stopping air pressure leakage.

Excellent sealing performance

Air leakage is prevented through formation of a seal, utilizing internal pressure, when the valve is shut off.

Silent, no vibration

Valve operation is stable with no chattering or hunting at the moment just before shut off or when opening.

Farm work automation capability

Going from the main dispersion to the residual dispersion requires only switching between liquid and air in the main pipe line, with absolutely no need for working with individual pipes. Furthermore, the switching operation in the main pipe line can be completely automated with a timer. Uses other than agricultural chemical dispersion include the removal of water to prevent pipe-freezing in the winter, which is useful for automated farm work.


It is compact and inexpensive.

Structure & Principle (PAT.)

Liquid-Air Switch Valve


Before the liquid feed starts, the main and 2nd floats descend, the main valve seat shuts off, and the 2nd valve seat opens.


When liquid feed for dispersion starts, residual air in the pipes is exhausted from the 2nd valve seat, and liquid flows into the valve case. The main float ascends as the liquid level begins to rise in the valve case, the main valve seat opens, and dispersion begins. Meanwhile, the 2nd float ascends as the liquid level rises, and the 2nd valve seat shuts off shortly afterward to prevent leakage of liquid.


When the liquid feed stops after dispersion is completed, liquid is retained in the valve case and, consequently, the main and 2nd floats remain ascended, the main valve seat remains open, and the 2nd valve seat remains closed.


Next, air feed is initiated for dispersion of residual liquid in the pipes, and liquid is discharged by air pressure. The main float descends in accordance with the liquid level, the main valve seat shuts off soon afterwards and a tight seal is maintained using the back up of air pressure in the valve case. Meanwhile, the 2nd float remains ascended by upward pressure in the valve case while the 2nd valve seat is closed, and even if the liquid level in the valve case drops, the 2nd float remains fixed to the valve seat, maintaining the shut off condition. Consequently, the main and 2nd valves shut off after the liquid is discharged from the valve case, and air is tightly sealed in.


After all residual liquid in the pipes is dispersed, pressure in the pipes is released by operating an air release valve in the main pipe line. Atmospheric pressure is then restored to the valve case, the 2nd float descends under its own weight, and the 2nd valve seat opens and returns to its original state.


If air is entrained in the liquid in the pipes during main dispersion, it is exhausted through the entrained air exhaust valve, preventing malfunction due to air entrainment.

The above sequence of operations is carried out automatically, and the operator has only to carry out work at a close range with absolutely no necessity of direct or remote operations for each sprinkler.

Example applications
Liquid-Air Switch Valve / Testing condition
Testing in a fruit farm
(hung from a tree)

Liquid-Air Switch Valve / Testing condition
Testing in a fruit farm
(placed on the ground)

Liquid-Air Switch Valve / Testing condition

Tottori Horticultural Experiment Station in Tottori Pref.


Technical data
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