HK1108177B - Liquid discharge method and device - Google Patents

Abstract

CN101107443

Description

Liquid discharge method and apparatus

Technical Field

The present invention relates to a liquid discharge method and apparatus for discharging a plunger in a cylinder by reciprocating the plunger, which can suppress the generation of bubbles and debris and can discharge a desired amount of clean liquid favorably, and more particularly, to a liquid discharge method and apparatus capable of discharging a low-viscosity liquid.

Background

In a conventional liquid discharge apparatus, a cylinder into which a reciprocating plunger is inserted communicates with a suction valve and a discharge valve. In this type of device, when the plunger is reciprocated, the suction valve is opened to supply liquid to the cylinder when the plunger is retracted, and when the plunger is advanced, the discharge valve is opened to discharge liquid from the cylinder and discharge the liquid from a nozzle communicating with the discharge valve (patent document 1).

Further, in a conventional liquid discharge device, there is also a device in which a cylinder having an intake port, an exhaust port, and a plunger is inserted, and communication between the intake port and the cylinder and communication between the exhaust port and the cylinder are switched in a valve chamber by a switching valve in which a valve body is rotated (patent document 2).

Japanese patent laid-open No. Sho 58-178888 of patent document 1

Japanese patent laid-open No. 60-19970 of patent document 2

Disclosure of Invention

In the device of patent document 1, when the liquid passes through a complicated flow path in the discharge valve, turbulence occurs and the discharge becomes disturbed, and bubbles are generated by cavitation (cavitation) or the like and discharged from the nozzle in a large amount, which is a drawback.

In the device of patent document 2, if the gap between the valve body and the valve chamber of the switching valve is too narrow, the switching valve may not slide well, and if the gap is too narrow, the switching valve may be twisted and damaged, the switching valve or the valve chamber may be worn, and the debris may be mixed into the liquid and discharged, or may enter the gap between the valve body and the valve chamber to prevent the sliding of the switching valve.

If the sliding movement of the valve body and the valve chamber is set to be loose, the liquid in the suction port flows into the gap between the valve body and the valve chamber regardless of the reciprocating movement of the plunger, and the liquid is discharged from the nozzle. This phenomenon is likely to occur when a liquid having a low viscosity is used, and particularly, for the convenience of supplying the liquid into the cylinder, it is likely to occur when the liquid on the suction port side is pressurized.

In view of the above problems, an object of the present invention is to provide a liquid discharge device that discharges liquid by the action of reciprocating operation of a cylinder, in which turbulence and bubbles are less likely to occur, the liquid does not flow into a discharge port from an intake port arbitrarily, debris (waste) is not generated, the liquid is less likely to be broken, and the liquid can be discharged satisfactorily, and a liquid discharge method and device.

In order to solve the above problems, the method and apparatus of the present invention are configured based on the technical idea of the following solution.

The liquid discharge apparatus according to solution 1, which has a port 1, a port 2, and a port 3; and a switching valve which can switch between the communication between the 1 st hole and the 2 nd hole and the communication between the 1 st hole and the 3 rd hole by the movement of the valve body in the valve chamber; a cylinder having a plunger inserted into the cylinder and communicating with the 1 st hole; an opening/closing valve connected to the 2 nd hole; and a liquid discharge port communicating to the 3 rd hole.

With the above configuration, the on-off valve can be connected to the liquid storage device or the liquid supply device, the valve body is moved to switch the switching valve body so that the 1 st hole and the 2 nd hole communicate with each other, thereafter, the on-off valve is opened to communicate the liquid storage device or the like with the 2 nd hole, and when the plunger is pulled out in a direction away from the valve chamber by a distance corresponding to the discharge amount, the liquid can be filled into the cylinder through the on-off valve, the 2 nd hole, and the switching valve. Then, the opening/closing valve is closed, the valve body is moved to communicate the switching valve with the 1 st hole and the 3 rd hole, and when the plunger is pressed in a direction approaching the valve chamber, the liquid in the cylinder can be discharged through the switching valve, the 3 rd hole, and the liquid discharge port. In this case, since the discharge port side does not have the opening/closing valve, generation of bubbles can be suppressed and the discharge operation can be performed satisfactorily.

Further, since the on-off valve is closed except when the cylinder is filled with the liquid, even if the sliding between the valve chamber and the valve body of the switching valve is set to be relatively loose, the liquid does not flow into between the valve chamber and the valve body and cannot be discharged from the liquid discharge port, and therefore the sliding between the valve chamber and the valve body of the switching valve can be set relatively loose.

In the liquid discharge method, by moving the switching valve in the valve chamber, the plunger in the cylinder can be reciprocated while switching the communication between the passage to the cylinder, the valve chamber and the liquid storage container or the passage to the cylinder, the valve chamber and the discharge port; when the plunger moves backward, it can communicate with the passage toward the cylinder, the valve chamber and the liquid storage container, and can open the on-off valve arranged between the passage and the liquid storage container.

That is, the passage to the cylinder, the valve chamber and the liquid storage container or the passage to the cylinder, the valve chamber and the discharge port is switched by moving the switching valve in the valve chamber, and at this time, when the plunger retreats, the passage to the cylinder, the valve chamber and the liquid storage container is communicated and the on-off valve provided between the communicated passage and the liquid storage container is opened, and the passage to the valve chamber, the cylinder and the discharge port is closed, and when the plunger advances, the passage to the valve chamber, the cylinder and the discharge port is communicated and the passage to the cylinder, the valve chamber and the liquid storage container is closed and the on-off valve is closed.

The liquid discharge apparatus according to claim 2, wherein the opening/closing valve is a check valve provided in a direction in which the liquid flows from the outside toward the 2 nd hole and the flow of the liquid in the opposite direction is blocked.

With the above configuration, the 1 st hole and the 2 nd hole are communicated with each other by the switching valve, and the pressure inside the cylinder is reduced when the plunger is retracted, so that the check valve is opened to fill the liquid into the cylinder. When the opening/closing valve is used as a check valve, the opening/closing valve can be opened by the plunger being retracted and interlocked without requiring special opening/closing control.

In the liquid discharge method, the opening and closing of the opening and closing valve is automatically performed by a check valve provided in a direction in which the liquid flows from the liquid storage container into the valve chamber and blocks the flow from the valve chamber to the liquid storage container.

The liquid discharge apparatus according to claim 3 is characterized in that the switching valve is in sliding contact with the inner wall surface of the valve chamber in close contact with the inner wall surface of the valve chamber, and no contact or excessive friction occurs. With the above structure, the valve chamber or the valve body is not damaged by applying excessive force thereto, and debris generated by friction between the valve chamber and the valve body can be prevented.

In the liquid discharge method, the switching valve is moved while being in sliding contact with the inner wall surface of the valve chamber in close contact therewith, and excessive friction is not generated. The liquid discharge apparatus according to claim 4, wherein the switching valve performs switching of the switching valve by rotation of the valve body, and the 1 st hole is located on a rotation axis of the valve body.

With the above configuration, the amount of liquid in the valve chamber can be minimized, and the influence of the reaction force of the liquid can be minimized, so that the flow path can be switched smoothly at a high speed.

In the liquid discharge method, the movement of the switching valve is performed by rotating the switching valve having a 1 st opening on the rotation shaft and a 2 nd opening communicating with the 1 st opening.

The liquid discharge apparatus according to claim 5, wherein the cylinder is located lower than the 1 st hole, and a front end of the plunger is disposed to face upward.

Since there is no opening and closing valve on the discharge port side (3 rd hole side), although it can suppress the generation of bubbles, minute bubbles are inevitably generated even though it is. Even in this case, since the tip of the plunger is directed upward, bubbles lighter than the liquid flow upward through the 1 st hole, then flow from the 3 rd hole to the discharge port, and are discharged. Since air bubbles do not accumulate in the cylinder, a desired amount can be measured at all times. Further, since the bubbles are discharged immediately when they are minute, it is not necessary to stop the apparatus and perform a task of discharging the bubbles.

In the liquid discharge method, the cylinder is disposed so that the tip of the plunger is directed upward.

According to the present invention, since the liquid does not pass through a complicated structure such as a discharge valve, the liquid can be discharged favorably without causing turbulence in discharge or generating bubbles due to cavitation (cavitation) or the like and discharging a large amount of the liquid from the nozzle.

Since the sliding of the valve chamber and the valve body of the selector valve can be set relatively loosely, the valve chamber and the valve body are not damaged by applying an excessive force thereto, and the occurrence of friction between the valve chamber and the valve body and the occurrence of debris mixing in the liquid can be prevented.

Further, since the opening/closing valve is used as the check valve, it is possible to interlock the opening/closing valve with the plunger retreating to open the opening/closing valve without requiring special opening/closing control.

Further, since air bubbles do not accumulate in the cylinder, a desired amount can be measured at all times. Further, since the air bubbles are discharged immediately when the air bubbles are very small, it is not necessary to stop the apparatus and perform the air bubble discharge operation.

Drawings

Fig. 1 shows a plan sectional view (a) and a side sectional view (b) of the device of the present invention in an initial stage.

Fig. 2 shows a plan sectional view (a) and a side sectional view (b) when the piston is retracted.

Fig. 3 shows a plan sectional view (a) and a side sectional view (b) when the valve body rotates after the piston is retracted.

Fig. 4 shows a plan sectional view (a) and a side sectional view (b) when the piston advances after the switching valve rotates.

Fig. 5 shows a perspective oblique view illustrating the valve chamber.

Figure 6 shows a side cross-sectional view of the device described in example 1.

DESCRIPTION OF SYMBOLS IN THE DRAWINGS

10 switching valve

11 1 st opening

12 nd 2 nd opening

13 cylinder

14 plunger

15 piston

16-stroke adjusting screw

17 discharge port

18-piston cylinder chamber

19 valve seat

20 main body

21 1 st hole

22 nd hole 2

23 rd hole (3 rd)

24 ball valve body

25 spring

26 check valve

27 liquid delivery pipe

28 liquid storage container

29 rotary actuator

30 valve chamber

31 st air opening

32 nd 2 nd air opening

51 slide valve

52 ball screw

53 motor

A. B, C sealing pad

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

As shown in fig. 1, the liquid discharge apparatus of the present invention has a main structure: a valve chamber 30 which is a cylindrical hole formed in the body 20 and the body 20; a switching valve 10 rotatably inserted in the valve chamber 30;

the switching valve 10 has a 1 st opening 11 formed on the axis of the bottom surface at one end, a 2 nd opening 12 formed on the side surface, and the 1 st opening 11 and the 2 nd opening 12 are communicated in an L shape. A circumferential packing a is provided near the opening of the valve chamber 30 to prevent the liquid entering the gap between the valve chamber 30 and the switching valve 10 from leaking to the outside. A port 1 (port)21 is formed at the center of the bottom surface of the valve chamber 30 and communicates with the cylinder 13 formed by a cylindrical hole. The switching valve 10 is rotatably connected to a rotary shaft of a rotary actuator (activator) 29 and can be rotated by a desired angle.

The side surface of the valve chamber 30 is formed with the 2 nd hole and the 3 rd hole, and when the inserted switching valve 10 is rotated, the communication between the 2 nd opening 12 and the 2 nd hole 22 and the communication between the 2 nd opening 12 and the 3 rd hole 23 can be switched. As shown in fig. 5, the space on the cylinder above the dotted line α is a valve chamber, and the portion below the dotted line α is a cylinder 13.

A check valve (check valve) 26 composed of a ball valve body 24 and a spring 25 is provided in the 2 nd hole, and the check valve 26 is connected to a liquid storage container 28 through a liquid sending pipe 27. The check valve 26 is disposed such that the ball valve body presses on a valve seat on the liquid storage container side to allow the liquid to flow from the liquid storage container to the 2 nd hole and to prevent the liquid from flowing in the opposite direction.

The 3 rd hole is connected to the liquid discharge port through the liquid sending tube 27.

In the cylinder 13, the front end of the plunger 14 is inserted toward the valve chamber 30. The rear end of the plunger 14 is connected to a piston 15 which reciprocates in a piston-type cylinder chamber 18 formed inside the cylinder 13. The piston cylinder chamber 18 has a 1 st air opening 31 and a 2 nd air opening 32 near each end of the side surface thereof, and the plunger 14 can be reciprocated by adjusting the air pressure supplied from each air opening. Between the cylinder 13 and the piston cylinder chamber 18 there is a circumferential sealing gasket B which slidably seals against the plunger 14 to separate the cylinder 13 and the piston cylinder chamber 18.

A gasket C is provided in a portion that slides against the inner wall of the piston cylinder chamber 18 on the outer periphery of the piston 15, and prevents air on the 1 st air opening 31 side or air on the 2 nd air opening 32 side from leaking to the opposite side. Further, a stroke adjusting screw 16 is provided at the rear end of the piston cylinder chamber 18. Since the piston 15 can move backward only in contact with the tip of the screw 16, the amount of movement of the piston 15 and the connected plunger 14 is determined by setting the amount of advance of the stroke adjustment screw 16, and the amount of discharge can be set accordingly.

The device may act as follows.

First, as shown in fig. 1, the advance/retreat position of the stroke adjustment screw 16 is set in accordance with a desired discharge amount. The switching valve 10 is rotated by rotating the actuator 29, and the 2 nd opening 12 of the switching valve 10 is communicated to the 2 nd hole 22, that is, the 2 nd opening 12 is brought to a position opposed to the 2 nd hole 22. The 1 st air port 31 is opened, and air is sucked into the piston cylinder chamber 18 from the 2 nd air port 32, so that the plunger 14 is advanced.

In this state, as shown in fig. 2, air in the piston cylinder chamber 18 is discharged from the 2 nd air opening 32, air is sucked into the piston cylinder chamber 18 from the 1 st air opening 31, and the piston 15 is retracted to abut on the tip end portion of the stroke adjustment screw 16. The plunger 14 connected to the piston 15 also retreats to reduce the volume occupied by the plunger 14 in the cylinder 13, and the internal volume of the cylinder 13 increases. At this time, since the switching valve 10 is in a state where the 2 nd opening 12 and the 2 nd hole 22 are opposed to each other, that is, the cylinder 13 and the 2 nd hole 22 are communicated with each other, the volume in the cylinder 13 increases and the pressure in the cylinder 13 decreases, the ball valve body 24 in the check valve 26 upstream of the 2 nd hole 22 is separated from the valve seat 19 by the compression spring 25, the liquid flows from the liquid reservoir tank 28 to the 2 nd hole 22 side through the check valve 26, and the liquid is filled in the cylinder 13 through the 1 st opening 11 via the 2 nd opening 12 of the switching valve 10 and then through the 1 st hole 21.

When the liquid is filled in the cylinder 13, as shown in fig. 3, the pressure reduced in the cylinder 13 returns to its original state, and the pressure difference of the liquid before and after the check valve 26 becomes small, so that the ball valve body 24 is pressed against the valve seat 19 by the spring to close the check valve 26. When the switching valve 10 is rotated by rotating the actuator 29, the 2 nd opening 12 and the 3 rd hole 23 of the switching valve 10 communicate with each other, that is, the 2 nd opening 12 is located opposite to the 2 nd hole 22.

In this state, as shown in fig. 4, when air in the piston cylinder chamber 18 is discharged from the 1 st air opening 31 and air is sucked into the piston cylinder chamber 18 from the 2 nd air opening 32, the piston 15 moves forward to abut against the end of the piston cylinder chamber 18. The plunger 14 connected to the piston 15 also advances, thereby increasing the volume occupied by the plunger 14 in the cylinder 13 and decreasing the volume in the portion of the cylinder 13. At this time, since the switching valve 10 is in a state where the 2 nd opening 12 and the 3 rd opening 23 are in a relative position, that is, the cylinder 13 and the 3 rd opening 23 are in a communicating state, the volume in the cylinder 13 is reduced, and therefore, the liquid in the cylinder 13 is pushed out, and the liquid is discharged from the discharge port 17 through the 1 st opening 11, the 2 nd opening 12 and the 3 rd opening 23.

The discharge operation was completed 1 time as above.

In the device of the present invention, since the check valve 26 is provided on the liquid supply side, that is, on the 2 nd hole 22 side, even when the switching valve 10 and the valve chamber 30 are provided to slide loosely, the liquid on the liquid reservoir 28 side is blocked by the check valve 26, and therefore the liquid on the liquid reservoir 28 side does not flow into the gap between the switching valve 10 and the valve chamber 30 and is discharged from the discharge port 17. In particular, in this case, it is preferable to pressurize the liquid in the liquid storage container 28 for the purpose of facilitating the liquid supply.

Further, since the liquid supply side is closed by the check valve 26 when the plunger 14 advances, the liquid in the cylinder 13 does not flow between the switching valve 10 and the valve chamber 30 but flows back toward the liquid reservoir 28.

As described above, according to the apparatus of the present invention, the sliding movement between the switching valve 10 and the valve chamber 30 can be set relatively loosely, and when debris is generated by friction between the switching valve 10 and the valve chamber 30, the debris is mixed into the liquid and discharged from the discharge port 17, and the debris does not get caught between the switching valve 10 and the valve chamber 30 and interfere with the sliding movement.

Since the sliding of the selector valve 10 and the valve chamber 30 can be set relatively loosely, the rotation thereof becomes smooth, and therefore, it is possible to prevent the selector valve 10 from being damaged or the like by applying an excessive force such as twisting or the like.

Since the check valve 26 is not provided at the 3 rd hole 23 side, that is, at the discharge port 17 side, it is possible to prevent the occurrence of turbulence in the liquid flow and the occurrence of bubbles due to cavitation and the like.

Although this device can be used by being disposed in any direction of up, down, left, and right, the front end of the plunger 14 is disposed upward, and thus even when air bubbles are inevitably generated, the air bubbles are not accumulated in the cylinder 13. Therefore, the amount of liquid filled in the cylinder 13 can be reduced without accumulating air bubbles in the cylinder 13, and a stable discharge amount can be always maintained without changing the discharge amount. Further, since the air bubbles are discharged at any time, the efficiency of the operation can be improved without particularly discharging the air bubbles.

The turning actuator 29 may be any mechanism as long as it can turn and switch the 2 nd opening of the switching valve 10 to the 2 nd hole 22 at a predetermined angle between the 2 nd opening 12 and the 2 nd hole 22, and an air type or a motor may be used.

The plunger 14 and the inner wall of the cylinder 13 may have a gap even if they are closely attached. When there is a gap, the sliding is smooth and the generation of chips during friction can be prevented.

In the figure, the angle between the 2 nd hole 22 and the 3 rd hole 23 is 180 °, but may be other angles such as 90 °. Further, the connection portion, the sliding portion, and the like of each component may be sealed with a sealing agent such as an O-ring, thereby preventing leakage of liquid or air. By pressurizing the liquid in the liquid storage container 28, the supply of the liquid can be promoted, and the liquid can be filled into the cylinder 13 easily by the retraction of the plunger 14.

The shape of the discharge port 17 is not particularly limited, and a plurality of discharge ports 17 or a single discharge port 17 may be used, and may be appropriately selected depending on the purpose of the work.

Although a cylinder and a piston are used to reciprocate the plunger 14 in the drawing, other mechanisms may be used as long as they can reciprocate. For example, a mechanism such as a cam or a ball screw (ball screw) may be used. In the case of a mechanism using a ball screw, the amount of movement can be set according to the number of rotations of the ball screw, and thus setting of an adjustable screw or the like is not necessary.

The check valve 26 may be opened when the plunger 14 retreats, and other opening/closing valves having such a function may be used; a valve of a control mechanism that can be interlocked and opened when the plunger 14 retreats may be used.

Although the present invention is described in detail with reference to the embodiments, the present invention is not limited to any one of the embodiments.

Example 1

The basic configuration of the device of the present embodiment is the same as that of fig. 1 to 4, but as shown in fig. 6, a slide valve 51 is used instead of the switching valve 10, and a ball screw 52 is used instead of the piston mechanism of the driving device for reciprocating the plunger 14. In the present embodiment, the check valve 26 on the 2 nd port 22 side is closed, whereby the sliding between the spool 51 and the inner wall of the valve chamber 30 is gently formed, and the same effect as that of the structure of fig. 1 to 4 is obtained.

The plunger 14 is reciprocated by the mechanism of the ball screw 52 rotated by the motor 53, and the stroke amount of the plunger 14 can be set according to the number of rotations of the motor 53. Therefore, by changing the number of revolutions of the motor 53 at each discharge, the stroke amount of the plunger 14 can be changed at each discharge.

The present invention is not limited to discharge, application, and the like, and can be applied to all kinds of apparatuses for liquid transport.

Claims (16)

1. A liquid discharge method characterized by providing a liquid discharge apparatus comprising: a plunger, a drive mechanism for reciprocating the plunger by a desired stroke, a cylinder into which the plunger is inserted, a nozzle having a discharge port, a liquid storage container, the cylinder, a valve chamber for communicating the liquid storage container with the discharge port, and a switching valve disposed in the valve chamber, wherein an on-off valve is provided in a passage for communicating the liquid storage container with the valve chamber, and the liquid discharge device has no on-off valve between the valve chamber and the discharge port; a switching valve moving in the valve chamber, which can switch the path towards the cylinder, the valve chamber and the liquid storage container or the path towards the cylinder, the valve chamber and the discharge port, and can reciprocate the plunger in the cylinder to discharge;

when filling the cylinder with liquid, moving the switching valve to a position where the passages to the cylinder, the valve chamber, and the liquid storage container are communicated, and the opening and closing valve is opened;

when discharging the liquid from the discharge port, the switching valve is moved to a position at which the passages toward the cylinder, the valve chamber, and the discharge port are communicated, and the opening and closing valve is closed.

2. The liquid discharge method according to claim 1, wherein opening and closing of the on-off valve is automatically performed by a check valve provided in a direction in which the liquid can flow into the valve chamber from the liquid storage container and the flow of the liquid from the valve chamber to the liquid storage container is blocked.

3. The liquid discharge method according to claim 1 or 2, wherein the switching valve is moved so as to be in sliding contact with the inner wall surface of the valve chamber in close contact therewith without generating excessive friction.

4. The liquid discharge method according to claim 1 or 2, wherein the switching valve is moved by rotating a switching valve having a 1 st opening on the rotation shaft and a 2 nd opening communicating with the 1 st opening in the valve chamber.

5. The liquid discharging method according to claim 1 or 2, wherein the cylinder is disposed so that a front end of the plunger faces upward.

6. A liquid discharge method according to claim 1 or 2, characterized in that the rear end of the plunger is connected to a piston sliding back and forth in a piston cylinder chamber formed inside the cylinder, the piston being able to advance until abutting the end of the piston cylinder chamber.

7. The liquid discharging method according to claim 1 or 2, wherein the plunger is thick and thin with a gap from an inner wall of the cylinder.

8. The liquid discharging method according to claim 1 or 2, wherein the switching valve is a spool valve disposed in the valve chamber.

9. A liquid discharge apparatus, comprising: a plunger, a drive mechanism for reciprocating the plunger by a desired stroke, a cylinder into which the plunger is inserted, a nozzle having a discharge port, a liquid reservoir, a valve chamber having a 1 st hole communicating with the cylinder, a 2 nd hole communicating with the liquid reservoir, and a 3 rd hole communicating with the discharge port, a switching valve disposed in the valve chamber, an on-off valve provided in a passage communicating the valve chamber and the liquid reservoir, and no on-off valve between the valve chamber and the discharge port;

when filling the cylinder with liquid, moving the switching valve to a position where the passages to the cylinder, the valve chamber, and the liquid storage container are communicated, and the opening and closing valve is opened;

when discharging the liquid from the discharge port, the switching valve is moved to a position at which the passages toward the cylinder, the valve chamber, and the discharge port are communicated, and the opening and closing valve is closed.

10. The liquid discharge apparatus according to claim 9, wherein the opening/closing valve is a check valve provided in a direction in which the liquid flows from the liquid storage container toward the 2 nd hole and the flow of the liquid from the 2 nd hole toward the liquid storage container is blocked.

11. The liquid discharge apparatus according to claim 9 or 10, wherein the switching valve moves while being in sliding contact with an inner wall surface of the valve chamber in close contact with the inner wall surface of the valve chamber, and excessive friction is not generated.

12. The liquid discharge apparatus according to claim 9 or 10, wherein the switching valve has: a 1 st opening on the rotating shaft and a 2 nd opening communicated with the 1 st opening;

and the 1 st and 2 nd holes or the 1 st and 3 rd holes are communicated in the valve chamber by the rotation of the switching valve.

13. The liquid discharge apparatus as claimed in claim 9 or 10, wherein the cylinder is configured such that a front end of the plunger is directed upward.

14. A liquid discharge apparatus as claimed in claim 9 or 10, characterised in that the rear end of the plunger is connected to a piston which slides back and forth in a piston cylinder chamber formed in the interior of the cylinder, the piston being able to advance until it abuts the end of the piston cylinder chamber.

15. The liquid discharge apparatus as claimed in claim 9 or 10, wherein the plunger is thick and thin with a gap from an inner wall of the cylinder.

16. The liquid discharge apparatus as claimed in claim 9 or 10, wherein the switching valve is a spool valve disposed in the valve chamber.