JPH07317665A - Fluid distribution pump - Google Patents

Abstract

PURPOSE: To improve the distributing characteristics of a pump, in a liquid distributing pump provided with a pump chamber whose volume increases in a suction stroke and decreases in a pressurization stroke and with a hydraulically-operated exhaust valve device which determines response characteristics depending upon the accumulated condition of circulating medium or gas and is positioned on the end of the pump chamber. CONSTITUTION: Check-valves 16, 18 are disposed in the upstream of exhaust valves 17, 18 when viewed from a flowing direction from a pump chamber, so that counter-flow into the pump chamber of eliminated gas is prevented. A distance between the exhaust valves 17, 18 sharing one valve element 18 and the check-valves 16, 18 is small, therefore the amount of flow-out liquid with exhaust is negligible. During exhaust from the exhaust valves 17, 18, a liquid exhaust valve is kept closed. The liquid exhaust valve does not open until the exhaust valves 17, 18 close, and after it opens, the distributed supply of liquid starts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid metering pump provided with a pump chamber whose volume increases in the suction process and decreases in the pressurization process.
The present invention relates to a liquid metering pump having a fluid actuated exhaust valve device whose response characteristic is determined by the state of accumulation of a medium or gas flowing therethrough.

[0002]

2. Description of the Related Art As a known liquid metering pump of this type, German Published Patent No. 42 1
No. 9 663 discloses a pump using a membrane as a valve body of an exhaust valve. This membrane can adhere to the sealing surface and seal the exhaust valve device portion at the pump chamber outlet.
However, the force that causes the film to adhere to the film occurs only when the liquid is present there. The closing force during the outflow of gas is not great enough to create a sufficient sealing action on the membrane.

A pump of this kind is described in Swiss Patent No. 390 686.
It is also known from U.S. Pat. No. 5,968,027, and instead of a membrane a ball is used as the valve body of the exhaust valve. Also in this case, the force exerted on the ball by the gas flow at the time of gas outflow is not so large as to cause a sealing action on the ball. The force sufficient to cause the ball to seal is only produced when the liquid flows out.
Further, this structure cannot be applied to a pump that performs the suction operation peculiar to the metering pump.

In the liquid dispensing pumps of the type mentioned at the beginning,
Exhaust behavior can be controlled relatively accurately. The amount of liquid discharged from the exhaust valve is relatively small. However, this has another consequence. That is, even if the pump chamber is completely filled with the liquid during the pressurizing process, that is, even if the gas existing in the pump chamber before the pressurizing process is exhausted from the exhaust valve, the residual gas is again present in the next inspiring process. Has been found to enter the pump chamber. This is despite the fact that the inhaled liquid does not contain that much gas. It is considered that the reason for this phenomenon is that the gas reaches only the back side of the membrane when the pump chamber is evacuated. When the liquid flows out, the membrane virtually closes immediately, so that the gas that was there remains. Therefore, when the membrane is opened again in the next suction step, the gas existing on the back side of the membrane is sucked into the pump chamber. This situation does not change if a check valve is placed after the exhaust valve. Such a check valve only prevents air or gas from being sucked in from the outside, and prevents gas existing between the exhaust valve and the check valve from being sucked into the pump chamber again. You can't do that. This encapsulation of gas in the pump chamber changes the metering action of the pump and is undesirable.
The enclosed gas is pushed out of the pump chamber during the next pumping cycle, but remains behind the exhaust valve. The presence of such a dead space, especially in the known construction, leads to a reduction in the accuracy of the metering of the pump, when operating with low liquid delivery, as can be seen in the typical operation of the metering pump.

An object of the present invention is to improve the pump performance of a liquid metering pump having an exhaust valve.

[0006]

[Means and Actions for Solving the Problems]
For a liquid metering pump of the type mentioned at the outset, it is solved by placing a check valve upstream of the exhaust valve in the direction of flow from the pump chamber as described in claim 1.

This makes it possible to prevent the fluid discharged from the pump chamber during the exhaust operation from entering the pump chamber again during the next suction process. This prevention is
It does not matter whether the fluid is a gas or a liquid. Since the exhaust valve is arranged downstream of the check valve, virtually only liquid is present in the portion sandwiched between the check valve and the check valve when the exhaust operation is completed. In addition, this can prevent gas from being inhaled during the inhalation process. Thus, the possibility that parasitic residual gases are re-inhaled is completely closed off and the occurrence of undesired dead spaces can be avoided.

As described in claim 2, the check valve is normally closed and is opened only when there is a flow of fluid from the pump chamber. Therefore, backflow is not required to close the check valve. The check valve closes when there is no flow from the pump chamber, so residual gas does not enter the pump chamber.

As described in claim 3, the exhaust valve and the check valve share one valve body. This allows the flow path between the check valve and the exhaust valve to be relatively short. Although the backflow prevention valve prevents the liquid in the valve from being used directly, the amount of liquid flowing out with the exhaust is reduced. This is particularly advantageous if the liquid to be dispensed is toxic or corrosive. This is because the amount of liquid that requires treatment is reduced.

As described in claim 4, the valve body is freely movable between the first valve seat which constitutes the check valve and the second valve seat which constitutes the exhaust valve. The flow through of the valve device is possible only if the valve body is between the first valve seat and the second valve seat. With this arrangement, the check valve opens as soon as an outflow from the pump chamber occurs. The force exerted by the flow on the valve body when the gas flows out is not so great as to bring the valve body into close contact with the second valve seat. The valve body stays in a so-called equilibrium state, that is, an intermediate position between the first valve seat and the second valve seat.
Only when the liquid flows out, the force acting on the valve body becomes large enough to bring the valve body into close contact with the second valve seat. This ensures that the exhaust valve closes. As a result, the liquid is delivered from the metering port, which is normally closed by the pressure valve, without flowing out of the pump chamber through the exhaust valve in the next pressurization step. As described above, the dispense accuracy of the pump can be improved by a relatively simple measure.

As described in claim 5, the valve body is formed of a ball. If the valve body is spherical, the orientation of the valve body does not matter in practice. The ball can always come into close contact with the first or second valve seat no matter which orientation it rotates. Rather, it is desirable to rotate the ball. This is because the valve seat contact position on the ball surface changes due to the rotation, so that the possibility of leakage due to local wear can be kept low.

According to the sixth aspect of the present invention, the valve body provided in the exhaust valve device has the valve body arranged inside thereof and the inside of the second valve seat arranged inside the discharge port. It becomes narrower toward the direction. This valve body can be realized in a simple form of the entire exhaust valve device including the exhaust valve and the check valve. The valve body restricts the role of guiding the valve body, that is, the movement of the valve body in the direction intersecting with the flow. As a result, the valve body can always be brought into close contact with each valve seat with high reliability. Since the inside of the valve body is narrowed toward the second valve seat, the occurrence of dead space is suppressed, and as a result, gas is less likely to accumulate. Even if gas accumulates in the dead space, the gas is almost harmless because the check valve prevents the gas from being re-sucked into the pump chamber. Such a dead space poses a serious problem when the medium contains solid matter. Solid matter settles and eventually blocks the discharge path,
This is because the function of the exhaust valve may be impaired thereby.

As described in claim 7, the internal volume of the valve body is 1.5 to 3 times the volume of the valve body. That is, the volume inside the valve body is larger than that of the valve body so that the valve body can move freely. However, the volume inside the valve body is limited so that an excessive amount of liquid cannot exist here. This improves the operating characteristics of the exhaust valve device.

As described in claim 8, when the valve body is in close contact with the first valve seat, the end of the valve body on the side away from the first valve seat is almost at the starting end of the second valve seat. Match. That is, the reciprocating distance between the valve body and the first valve seat and the second valve seat is limited to the sum of the depths of engagement of the valve body into both valve seats. This allows the exhaust valve to be controlled very finely. There is only a very small gap between the valve body and the second valve seat. This gap becomes smaller as the valve element moves away from the first valve seat. At this time, the gas passes through this gap without any problem, but the liquid passing around the valve body exerts on the valve body a force of a size that presses the valve body against the second valve seat almost immediately.

According to a ninth aspect of the present invention, at least the first valve seat is formed with a chamfered portion forming a contact surface with the valve body. The chamfered portion improves the contactability of the valve body and the maintainability of the center thereof, and accordingly improves the sealing performance of the check valve.

Further, as described in claim 10, at least the second valve seat is formed with a rough finishing edge having a constant roughness. This prevents the valve body from sticking to the second valve seat. By doing so, backflow of air or gas from the outside is prevented. However, the gas trapped between the first valve seat and the second valve seat may re-enter the pump chamber during the suction process, so it is desirable to prevent this.

As described in claim 11, it is desirable that the valve body has a constant surface roughness and / or a constant roundness. This measure also contributes to prevention of sticking to the valve seat, particularly sticking of the valve body to the second valve seat. Thus, the check valve closes reliably as soon as the throughflow through the exhaust valve device is finished. No backflow is required to close it.

As described in claim 12, the first and second valve seats have the same shape. This simplifies assembly and storage of spare parts. In principle, the same parts can be used for both the exhaust valve and the check valve.

According to a thirteenth aspect, in a particularly advantageous embodiment, the exhaust valve device is connected with a return line for directly guiding the liquid flowing out of the exhaust valve device to the outside of the pump.

Therefore, the liquid that may change the opening / closing behavior of the exhaust valve device does not flow out from the outlet of the exhaust valve device. The liquid that flows out with the exhaust gas is directly carried away. This advantage is great especially when dealing with toxic or corrosive liquids. This is because there is no concern that these liquids act on the pump area downstream of the exhaust valve device for a long time.

As described in claim 14, the valve body has a larger specific gravity than the liquid to be metered. Unless the difference is too great, the valve body also responds to the slight liquid flow and sticks to the second valve seat. As a result, the exhaust valve is closed. When the specific gravity of the valve body is further increased, that is, when the self-weight is large with the same size,
Although it is a liquid with high viscosity and a large specific gravity in most cases, it can be reliably exhausted.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a side sectional view of the liquid metering pump of the present invention, and FIG. 2 is an enlarged view of the exhaust valve device portion.

The liquid dispensing pump 1 of the present invention comprises a pump chamber 2 defined by a casing 3 and a membrane 4. Instead of the membrane 4, it is also possible to use a piston. The membrane 4 is driven back and forth via a drive rod 5 by means of a drive device not shown in the figure. When the membrane 4 moves to the left, the volume of the pump chamber 2 decreases. Hereinafter, such a motion is referred to as a pressurizing process (motion). When the membrane 4 moves to the right, the volume of the pump chamber 2 increases. Hereinafter, such a motion is referred to as an inhalation process (operation). An inlet connection pipe 6 is connected to the pump chamber 2, and this connection pipe is connected via a threaded portion 7 to a liquid supply pipe (not shown). A gravity-actuated check valve type liquid suction valve 8 is arranged between the pump chamber 2 and the inlet connection pipe 6. In the suction step, the valve element (ball) indicated by a ball floats up from the valve seat and opens the flow path from the inlet connection pipe 6 to the pump chamber 2. In the pressurizing process, the balls are pressed against the valve seat, preventing the backflow of the fluid in the pump chamber 2 to the inlet connection pipe 6. The pump chamber 2 is also connected to a metering pipe, not shown in the figure, and to an outlet connecting pipe 6 which can be connected via a thread 10. A liquid discharge valve 11 is arranged between the outlet connection pipe 9 and the pump chamber 2, and this valve opens in the discharge direction against the force of the spring 12. The opening pressure depends on the force of the spring 12. When the pressure in the pump chamber 12 exceeds the valve opening pressure, the liquid discharge valve 11 opens. When the pressure in the pump chamber 12 falls below the valve opening pressure, the liquid discharge valve 11 closes again.

An exhaust path 13 extends from the top of the pump chamber 2. The exhaust path 13 is connected to the exhaust valve device 14. The exhaust valve device 14 includes a valve body 15 having a first valve seat 16 on the exhaust path 13 side and a second valve seat 17 on the other side. Both valve seats 16 and 17 have the same shape,
The valve bodies 15 are mounted on opposite sides of each other.

A ball 18 as a valve element is arranged between the first valve seat 16 and the second valve seat 17 so as to be freely movable. The first valve seat 16 and the bolt 18 together form a check valve, and the second valve seat 17 and the ball 18 together form an exhaust valve. The ball 18 can move freely inside the internal space 20 of the valve body 15. The valve body 15 limits the range of motion of the ball 18 in the direction intersecting with the flow, and
-Between both valve seats 16 and 17-Ball in the direction of flow
The range of motion of 18 is also limited.

The ball 18 and the valve seats 16 and 17 can be made of metal, particularly non-ferrous metal, plastic, or elastomer (elastic material such as synthetic rubber). However, it is desirable to use ceramics for these. This is because this material has high chemical durability and also has abrasion resistance.

The internal space 20 narrows toward the second valve seat 17. In order for the exhaust valve device 14 to exert its function, it is important that the second valve seat 17 is disposed above as viewed from the direction of gravity, and the gas flowing through the narrowed portion 21 is dead space. Exhaust valve device 14 without accumulating in
Emitted from.

A chamfer on both the first valve seat 16 and the second valve seat 17.
22 are formed. These chamfered portions 22 become contact surfaces with the balls 18. Since the ball 18 is not accurately guided and can move in the direction intersecting with the flow, forming the chamfered portion 22 facilitates maintaining the center of the ball 18 at the time of contact with each valve seat 16, 17.

In particular, the chamfered portion 22 of the valve seat 17 is formed with a rough finishing edge 23, which has a certain roughness for preventing the ball 18 from sticking to the second valve seat 17. Has been given. The surface of the ball 18 itself is also provided with a certain roughness to prevent the ball 18 from sticking to the valve seats 16 and 17.

The volume of the internal space 20 is about 1.5 to 2.5 times the volume of the ball 18. Also the first valve seat
The distance between the first valve seat 16 and the ball 16 is
The ball 18 on the side away from the first valve seat 16 when
Is selected so that the end (upper end) of is substantially coincident with the start end (lower end) of the second valve seat 17. This is shown in FIG. In other words, the reciprocating distance between the first valve seat 16 and the second valve seat 17 of the ball 18 is limited to the extent that the ball 18 fits into both valve seats 16 and 17 at the sum of the depths of engagement. There is. This allows the gap 24 between the ball 18 and the second valve seat 17 to be kept relatively small. Immediately after the fluid has flowed through the valve body 15, the balls 18 are lifted from the first valve seat 16 and the gap 24 is further reduced.

A discharge space 25 is formed above the valve body 15, and a return line 19 is connected to the discharge space 25. The return line 19 prevents liquid from practically collecting in the discharge space 25. The liquid that has passed through the valve body 15 is directly discharged to the outside of the pump through the return line 19.

The function of the exhaust valve device 14 will be outlined below.
During the pressurizing operation of the membrane 4, the gas in the pump chamber 2 is compressed. Since the gas has a high compressibility, the pressure in the pump chamber 2 does not rise until it exceeds the closing force of the spring 12 of the liquid discharge valve 11.

Since gas has a smaller specific gravity than liquid, it always gathers at the highest reachable point. When viewed in the direction of gravity, the exhaust path 13 branches at the uppermost point of the pump chamber 2, so that the gas collects in the exhaust path 13. Thus, during the pressurizing operation of the membrane 4, the pressure in the exhaust path 13 increases, and therefore the force on the ball 18 in the direction of the second valve seat 17 increases and the ball
18 is lifted from the first valve seat 16 by this force. Then, a gap is created between the ball 18 and the first valve seat 16, and the pressurized gas flows around the ball 18 and flows out through the gap 24 between the ball 18 and the second valve seat 17. To do.

Before the end of the membrane pressing operation, that is, before the next inhalation process, the ball 18 is moved by its own weight to the first valve seat.
Returning to 16. That is, no reverse flow is required for the ball 18 to return to the first valve seat 16. During the inhalation action of the membrane 4, the ball 18 remains on the first valve seat 16 and prevents backflow of gas on the first valve seat 16 into the pump chamber 2. The same applies to prevention of backflow of gas from the return line 19 into the internal space 20 of the valve body 15.

Therefore, during the suction operation of the membrane 4, gas cannot return to the pump chamber 2. On the other hand, during the pressurizing operation, all the gas in the pump chamber 2 is gradually pushed out of the pump chamber. That is, the gas is an exhaust valve device
As long as it can flow out of 14, the pressure in the pump chamber 2 does not rise too much. Therefore, liquid that may contain gas is not pumped from the liquid discharge valve against the force of the spring 12.

Rather, all of the pumping power is spent pumping gas out of the pump chamber 2. This operation is repeated until the gas in the pump chamber 12 and the exhaust channel 13 is completely discharged.

When the pump chamber 2 is completely filled with liquid, the balls 18 float above the first valve seat 16 during the pressurizing operation. A part of the liquid is sent out and discharged to the outside of the pump via the return line 19. However, this partial flow is relatively small. Under optimal conditions, this partial flow can be almost zero. That is, the liquid in the exhaust path 13 presses the ball 18 against the second valve seat 17 very quickly. This causes the exhaust valve device 14 to close. Further membrane 4
Continues to pressurize, and the pressure in the pump chamber 2 rises. This pressure is then applied to the spring 12 inside the liquid discharge valve 11.
Only when the valve opening pressure is exceeded, the liquid is metered and delivered. The ball 18 returns to the first valve seat 16 by its own weight before the end of the pressurization process, that is, before the start of the suction process.

Once the liquid to be dispensed is determined, the weight of the ball 18 can be adjusted accordingly. By using a ball that has a heavy weight, even a highly viscous liquid can be exhausted. In general, it is desirable that the specific gravity of the ball, that is, its own weight divided by its volume is within the range of the specific gravity of the liquid to be metered. The specific gravity of the ball may be slightly higher or lower than this. In that case, the ball 18
The strength of the flow required to move the slab changes accordingly.

[0040]

As described above, in the liquid metering pump of the present invention, the exhaust valve device at the upper end of the pump chamber does not sufficiently lift the valve body due to the flow of gas, and the valve body immediately moves due to the flow of liquid. This is an exhaust valve that is lifted up and is in close contact with the valve seat to close the flow. Since the check valve is arranged on the upstream side of the check valve, the gas in the exhaust valve is prevented from flowing back to the pump chamber. Further, since the distance between the exhaust valve sharing one valve body and the check valve is small, the amount of liquid discharged with the exhaust is small. In addition, the liquid discharge valve remains closed because the pressure inside the pump chamber does not rise so much during exhaust, and the exhaust valve closes immediately after the exhaust ends, and the liquid discharge valve opens due to the increase in pressure inside the pump chamber, and the liquid distribution valve opens. Since the metering is started, the liquid metering characteristic of the liquid metering pump which requires an accurate liquid metering is improved.

[Brief description of drawings]

FIG. 1 is a side sectional view of a liquid dispensing pump of the present invention.

FIG. 2 is a partially enlarged sectional view of the exhaust valve device of FIG.

[Explanation of symbols]

 1 ... Liquid dispensing pump 2 ... Pump chamber 3 ... Casing 4 ... Membrane 11 ... Liquid discharge valve 14 ... Exhaust valve device 15 ... Valve body 16 ... First Valve seat 17 ... second valve seat 18 ... valve body 19 ... return line 22 ... chamfer 25 ... discharge space

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Walther Hetzel Germany 69226 Nusloch Theodor-Hus-Strasse 11 (72) Inventor Joseph Brown Germany 68804 Altruthheim Goethestrasse 41

Claims (14)

[Claims] 1. A fluid-operated exhaust valve having a pump chamber whose volume increases in the suction process and whose volume decreases in the pressurization process, and the response characteristic of which is determined at the upper end of the pump chamber by the accumulated state of the medium flowing therethrough. In a liquid dispensing pump equipped with a device, a check valve (16, 1) is provided upstream of the exhaust valve (17, 18) when viewed from the flow direction from the pump chamber (2).
Liquid dispensing pump characterized by having 8). 2. The check valve (16, 18) is closed regardless of the backflow of liquid and is opened only when there is a flow of fluid from the pump chamber (2). 1. The pump according to 1. 3. The exhaust valve (17, 18) and the check valve (16)
, 18) share one valve body (18) with the pump according to claim 1 or 2. 4. The check valve (16, 18) is the valve body (18).
Is freely movable between the first valve seat (16) forming part of the valve and the second valve seat (17) forming part of the exhaust valve (17, 18). 4. The pump according to claim 3, characterized in that the exhaust valve device (14) is able to flow through only if () is between the first valve seat (16) and the second valve seat (17). 5. Pump according to claim 3 or 4, characterized in that the valve seat (18) is a sphere. 6. The exhaust valve device (14) comprises a valve body (15) having a valve body (18) arranged in an internal space (20), and the internal space (20) thereof.
Is narrowed in the direction of the second valve seat (17) arranged on the outlet side, The pump according to any one of claims 3 to 5. 7. The volume of the internal space (20) is 1.5 to 3 times the volume of the valve body (18).
Pump. 8. When the valve body (18) is in close contact with the first valve seat (16), the end of the valve body (18) remote from the first valve seat (16) is the second valve. Pump according to any one of claims 3 to 7, characterized in that it is substantially coincident with the starting end of the seat (17). 9. A valve body (18) on at least the first valve seat (16).
The pump according to any one of claims 3 to 8, characterized in that a chamfered portion (22) serving as a contact surface with is formed. 10. A pump according to any one of claims 3 to 9, characterized in that at least the second valve seat (17) is provided with a rough finishing edge (23) having a constant roughness. 11. A pump according to any one of claims 3 to 10, characterized in that the valve body (18) has a constant surface roughness and / or a constant roundness. 12. The first and second valve seats (16, 17).
3 have the same shape as each other.
The pump according to any one of 1. 13. A return line (19) for directly discharging the effluent from the exhaust valve device (14) is connected to the exhaust valve device (14). 1
The pump according to item. 14. The pump according to claim 3, wherein the specific gravity of the valve body (18) is larger than that of the liquid to be metered.