JPH0380960A - Method for preventing liquid dripping - Google Patents

Abstract

PURPOSE:To certainly prevent liquid dripping of a liquid by making suction quantity stable by a method wherein a diaphragm is held at the max. deformation position before the start of suction and the min. volume of a flow chamber is fixed even when fluctuation is generated in the pressure of a liquid to be emitted. CONSTITUTION:A suction valve 6 is interposed between a pressure feed source 5 of a liquid to be discharged and a nozzle 7 opened downwardly so that the volume of a flow chamber 18 through which a liquid to be discharged flows is increased and decreased by the pressure of the pilot air supplied to the pressure chamber 25 demarcated from the flow chamber 18 by a diaphragm 26. The liquid to be discharged in the nozzle 7 after the pressure feed of the liquid to be discharged is stopped is sucked by the increase of the volume of the flow chamber 18 of the suction valve 6 to prevent liquid dripping. At his time, the min. volume of the flow chamber 18 is set to a definite value by prescribed the max. deformation positions of diaphragms 16, 20 and the pressure of the aforementioned pilot air is controlled so that the diaphragm 16, 26 before the start of suction are held to the max. deformation positions. As a result, liquid dripping can be certainly prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a method for discharging a liquid such as a reagent from a nozzle that opens downward, when the liquid to be ejected is stopped from discharging the liquid to be ejected from the nozzle. The present invention relates to a drip prevention method that prevents the liquid to be ejected from dripping after the ejection is stopped by suctioning the liquid inward.

Problems to be Solved by the Prior Art and the Invention As a method for preventing dripping, a suction valve that increases or decreases the volume of the flow chamber by deforming the diaphragm is interposed in the flow path in front of the nozzle, and the flow of the liquid to be discharged is prevented. There is a method of minimizing the volume of the flow chamber during flow, and then increasing the volume after stopping discharge to suck in the liquid to be discharged from the nozzle.However, the amount of deformation of the diaphragm depends on the pressure of the pilot air and the volume of liquid to be discharged within the flow chamber. Since it is determined by the pressure balance of the liquid, the minimum volume of the flow chamber changes due to pressure fluctuations caused by stopping the ejection of the liquid to be ejected, and as a result, the suction amount becomes unstable and drip prevention is uncertain. There was a drawback.

Means for Solving the Problems The present invention solves these problems by regulating the maximum deformation position of the diaphragm so that the minimum volume of the flow chamber is set at a constant value, so that the diaphragm reaches its maximum deformation before the start of suction. The configuration is such that the pressure of the pilot air is controlled so that it is held in position.

Functions and Effects of the Invention The present invention has the above configuration, and the diaphragm is held at the maximum deformation position before the start of suction.
Even if the pressure of the liquid to be discharged varies, the minimum volume of the flow chamber is kept constant, the amount of suction is stabilized, and dripping is reliably prevented.

Example An embodiment of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, l is a sequencer, 2 is a control device, 3 is a pressure air source, 4 is an electropneumatic proportional valve, 5 is an inlet of liquid to be discharged, and 6
is a suction valve, and 7 is a nozzle. The control device w2 outputs a voltage for controlling the electro-pneumatic proportional valve 4, and air having a pressure proportional to the voltage is supplied from the electro-pneumatic proportional valve 4 to the suction valve 6.

As shown in FIG. 2, this suction valve 6 has an inlet 14 and an outlet of the main body 13! 5, a flow chamber 18 whose upper surface is airtightly partitioned by a first diaphragm 16 is formed. A lifting rod 22 is provided which is fixed to the diaphragm 16. The accommodation chamber 19 is a service hole having a lower step 20 and an upper step 21, and includes a disk 23 fixed to the upper end of the lifting rod 22 and a lower step.
A coil spring 24 is installed between the lifting rod 22 and the disc 20 to bias the lifting rod 22 and the disc 23 upward, and the peripheral edge of the lower surface of the disc 23 can come into contact with the step 21 on the upper side of the storage chamber 19. It corresponds to The disk 23 sandwiches the center of a second diaphragm 26 that partitions the storage chamber I9 and the pressure chamber 25, and the pressure chamber 25 has a boat 27 connected to the electropneumatic proportional valve 4. Further, the storage chamber 19 communicates with the atmosphere through a through hole 28.

The suction valve 6 configured as described above has a second
The lifting rod 22 and the first diaphragm 16 fixed thereto stop at a position where the downward force of the diaphragm 2G and the elasticity of the coil spring 24 are balanced.
The higher the pressure of the air in the pressure chamber, the lower the diaphragm I6 and the smaller the volume of the circulation chamber 18. As shown by the chain line in FIG. When the lower surface hits the upper step 2I of the storage chamber 19, the elevating rod 22 and the first diaphragm 16 remain stopped even if the pressure of the air in the pressure chamber 25 increases further.

Therefore, by making the voltage output from the control device 2 sufficiently high according to the signal from the sequencer 1 and inputting it to the electro-pneumatic proportional valve 4, the air pressure that will be output from this will become sufficiently high and will flow into the pressure chamber 25 of the suction valve 6. act, and the disc 23 enters the storage chamber 19.
The flow chamber 18 is held in a state where it is strongly pressed against the upper step 21, and at this time, the volume of the flow chamber 18 is at its minimum value.

Therefore, in this state, even if the liquid to be discharged 5 is closed by the signal from the sequencer 1 and fluctuations occur in the circulation chamber 18, the diaphragm I6 does not fluctuate, and the voltage decreases due to the decrease in the output voltage from the control device 2. After the pressure of the air supplied from the air proportional valve 4 has decreased to a certain extent, the disc 23 moves to the stage P.
It rises away from the IS 21, and the first diaphragm 16 also rises, increasing the volume inside the circulation chamber 18, causing suction in the nozzle 7 and preventing dripping. In this way, since the air pressure acting on the pressure chamber 25 is made sufficiently high in the suction standby state so that the disc 23 is pressed against the upper step 21, pressure fluctuations in the circulation chamber 18 cause the first diaphragm to I6 does not operate, and stable suction can be performed to reliably prevent liquid dripping.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a drip prevention device used in carrying out the method of the present invention, and FIG. 2 is a sectional view of its suction valve. 4: Electro-pneumatic proportional valve 5: Discharged liquid population 6: Suction valve 7
: Nozzle 16: First diaphragm 8 : Step part 22 on the upper side of circulation chamber 2: Lifting rod 23: Disc 24: Coil spring 25: Pressure blade chamber 26: Second diaphragm

Claims (1)

[Claims] The volume of the flow chamber through which the liquid to be discharged flows between the pressure source of the liquid to be discharged and the downwardly opened nozzle is equal to the pressure of the pilot air supplied to the pressure chamber partitioned by the flow chamber and the diaphragm. In this method, a suction valve that increases and decreases is interposed, and the liquid to be discharged in the nozzle is sucked after the pressure-feeding of the liquid to be discharged is stopped by increasing the volume of the circulation chamber of the suction valve to prevent dripping, The minimum volume of the circulation chamber is set to a constant value by regulating the maximum deformation position of the diaphragm, and the pressure of the pilot air is controlled so that the diaphragm is held at the maximum deformation position before the start of suction. How to prevent dripping