RU2573069C2 - Membrane pump provided with leaks compensation inertial-control valve - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: invention relates to pump production, particularly, to membrane pump. Claimed pump comprises pressure chamber 9 separated by membrane 1 from hydraulic chamber 8. Pressure chamber 9 is connected via appropriate check valves with suction and pressure lines. Hydraulic chamber 8 is loaded with pulsating fluid pressure. Hydraulic chamber 8 is connected via leak compensation valve 6 with the working fluid store 15. Leak compensation valve 6 incorporates shutoff element reciprocating between closed position whereat the valve flow section is closed and closed position whereat said flow section is opened, said valve being locked as-closed by the clamp. Said clamp is rated to make said shutoff element 16 displace to opened position at the pressure in hydraulic chamber 8 is smaller than setting pressure p_L. The weight of shutoff element 16 should be such as to make shutoff valve 16 at pressure drop caused by hydraulic sock staying not over one millisecond in hydraulic chamber 8, displace toward opened position by not over 0.2 mm.

EFFECT: decreased leaks, higher reliability.

6 cl, 3 dwg

Description

DESCRIPTION

The invention relates to a diaphragm pump equipped with an inertia-controlled leak replenishment valve, as well as a method for selecting the size of the replenishment leak valve.

Diaphragm pumps generally have a discharge chamber separated by a membrane from the hydraulic chamber, the pressure chamber being connected respectively to a suction connection and a pressure connection. In this case, the hydraulic chamber filled with the working fluid may be loaded with the pulsating pressure of the working fluid. By means of the pulsating pressure of the working fluid, a pulsating movement of the membrane is created, due to which the volume of the discharge chamber periodically increases and decreases. Due to this, it is possible to suck in the injected medium through the suction connection, which is connected with the discharge chamber by the corresponding non-return valve, when the volume of the pressure chamber increases, and through the pressure connection, which is also connected by the corresponding check valve to the discharge chamber, release it again under pressure when the discharge volume camera shrinks.

As a working fluid, hydraulic oil is usually used. In principle, however, other suitable liquids may also be used, such as, for example, water with a water-soluble mineral additive.

With the help of a membrane, the medium to be pumped is separated from the drive, due to which, on the one hand, the drive is protected from the harmful effects of the pumped medium, and on the other hand, the pumped medium is also protected from the harmful effects of the pump, such as contaminants.

The pulsating pressure of the working fluid is often provided by a movable piston that is in contact with the working fluid.

In this case, for example, the piston reciprocates in the hollow cylindrical element, due to which the volume of the hydraulic chamber decreases and increases, which leads to an increase and decrease in pressure in the hydraulic chamber, and also as a result of the movement of the membrane.

Despite the most diverse measures that should prevent the piston from flowing around the piston with working fluid, it cannot be excluded in practice that with each stroke process a small amount of working fluid will be lost through the narrow remaining gap between the piston and the hollow cylindrical element, due to which the amount of working fluid gradually the hydraulic chamber is reduced. As a result of this, the discharge stroke is no longer completely carried out by the membrane, since there is already not enough working fluid available to move the pressure of the membrane.

Therefore, for example, in DE 1034030 it was already proposed to connect the hydraulic chamber through an intermediate valve, the so-called leak replenishment valve, with a supply of working fluid.

Thanks to this replenishment valve, the hydraulic fluid in the hydraulic chamber can be replenished if necessary. In this case, however, it is necessary to ensure that not too much working fluid enters the hydraulic chamber, since then the membrane in the discharge path moves too far into the discharge chamber and, under certain circumstances, gets in contact with valves or other structural elements and is damaged.

To this end, the leak replenishment valve has, as a rule, a closing member that can reciprocate between a closed position in which the valve passage is closed and an open position in which the valve passage is open, for example in the form of a closing ball. This locking body with the help of a pressing element, such as a spring, is pre-tensioned in the closed position. This pressure element is designed in such a way that only when the pressure in the hydraulic chamber is less than the set pressure p _L , the closing member moves in the open direction.

Since during the suction stroke, i.e. while the piston is moving backward, the pressure in the hydraulic chamber is forcibly reduced, the set pressure p _L must be adjusted so that during the suction stroke the liquid cannot enter the hydraulic chamber through the replenishment valve. Only at the end of the suction stroke, when the piston is almost no longer moving, should a possibly lacking working fluid be replenished through the leakage replenishment valve.

In this case, it must be ensured that at the end of the discharge stroke the maximum pressure acts in the discharge chamber. Now, when the suction stroke begins, the membrane will move towards the hydraulic chamber until the pressure in the discharge chamber drops to the static pressure at the suction connection. When the suction stroke continues, this leads to a hydraulic shock, the so-called Zhukovsky shock, since in the discharge chamber the pumped medium is now supplied through the suction connection, which leads to a sharp change in speed in the suction pipe. This water hammer leads to a high-frequency pressure fluctuation in the hydraulic chamber. Briefly, the pressure in the hydraulic chamber decreases excessively.

To prevent the opening of the replenishment valve during this hydraulic shock and at the same time the possibility of the flow of the working fluid into the hydraulic chamber, the set pressure p _L must be set accordingly small, which means that the pressure element of the replenishment valve must be relatively large.

However, with the known diaphragm pumps this is a drawback, since at the end of the suction stroke it is now difficult to set the pressure below the set pressure of the replenishment valve. Therefore, appropriate design measures must be taken to ensure that at the end of the suction stroke the replenishment valve actually opens when too little hydraulic fluid is contained in the hydraulic chamber. This increases the cost of the diaphragm pump.

US 5,655,894 discloses a hydraulic diaphragm pump with a leak replenishment valve. At the same time, a piston is installed with the possibility of movement, with the help of which the leak replenishment valve can be disconnected from the hydraulic chamber or connected to it.

Therefore, based on the described prior art, it is an object of the present invention to provide a diaphragm pump equipped with a leakage replenishment valve that will reduce or even overcome these drawbacks. In addition, an object of the present invention is to provide a method for selecting the size of a replenishment valve for leaks, which will reduce or even eliminate these drawbacks.

This problem in accordance with the invention is solved with the help of the already mentioned diaphragm pump, in which the mass of the closing element has such a value that the closing element during a lasting no more than one millisecond hydraulic shock due to the pressure drop in the hydraulic chamber moves in the direction of the open position by no more than 0 , 2 mm.

Moreover, it was found that the hydraulic shock, the so-called Zhukovsky shock, which occurs at the moment when the pressure in the discharge chamber drops to the pressure at the suction connection, is high-frequency, i.e. occurs during a time interval of less than one millisecond. According to the invention, the closure body is now made in such a way that its mass and, at the same time, its mass inertia are such that, with such a hydraulic shock, due to mass inertia, the closure body cannot move more than 0.2 mm in the open position. Since after one millisecond the pressure has already risen again, the movement of the closing organ stops. Typically, the movement of the closing member is less than 0.2 mm so small that the resulting open gap for the working fluid is too small to allow a significant amount of working fluid to pass into the hydraulic chamber.

In the event that this small amount is still undesirable, in one of the preferred embodiments it is provided that the closing member with a continuous shock of no more than one millisecond due to a pressure drop in the hydraulic chamber moves no more than 0.1 mm in the open direction.

Of course, as a result of the Zhukovsky shock, a hydraulic shock can lead to a maximum pressure drop in the hydraulic chamber to 0 bar. An example of calculating the mass of the closing member is given below.

In fact, despite the water hammer, the pressure in the hydraulic chamber will not fall to 0 bar, but to some minimum pressure p _min . This minimum pressure p _min depends on the selected process parameters, such as, for example, the static pressure at the suction connection of the pump, the piston speed and the volumes of the hydraulic chamber and discharge chamber.

While in the prior art, typically, the set pressure p _{L is} less than p _min , in one preferred embodiment, now p _L may be greater than p _min . Therefore, the return spring of the replenishment valve can be smaller, which greatly simplifies the handling of the pump.

From the point of view of the method for selecting the size of the replenishment valve of the diaphragm pump leaks, the aforementioned problem is solved due to the fact that the mass of the closing body is selected so that the closing body with a hydraulic shock lasting no more than one millisecond due to pressure drop in the hydraulic chamber moves no more than 0 2 mm, preferably not more than 0.1 mm, in the open direction.

Other advantages, features and applications of the present invention are explained by the following description of one of the preferred embodiments, as well as the corresponding drawings. Shown:

FIG. 1 is a partially cutaway view of a prior art diaphragm pump;

FIG. 2 - pressure change depending on the time in the hydraulic chamber during the suction stroke and

FIG. 3 is a sectional view of a leak replenishment valve according to one embodiment of the invention.

In FIG. 1 shows the main parts of a diaphragm pump in a partially cutaway view. The diaphragm pump has a membrane 1, which separates the hydraulic chamber 8 from the discharge chamber 9. The discharge chamber 9 is connected to the suction connection and pressure connection by means of corresponding check valves. The hydraulic chamber 8 can be loaded with a pulsating pressure of the working fluid using a piston. In the shown embodiment, the membrane 1 is connected to a spring 10 mounted in the mounting space 13, which serves to pre-tension the membrane in the direction of the hydraulic chamber. Due to the pulsating pressure of the working fluid, the membrane also makes a reciprocating movement between the walls, so that the volume of the discharge chamber increases and decreases. When the volume of the discharge chamber decreases, the injection fluid located in the discharge chamber is discharged through the non-return valve to the pressure outlet. When the volume of the discharge chamber due to the reverse movement of the membrane 1 increases, the pumped fluid is sucked through the check valve from the suction connection. Therefore, during periodic movement of the membrane, the pumped fluid is sucked periodically from the suction connection and is discharged through the pressure connection at a higher pressure.

The membrane is held between the clamping edges 11, 12. Due to the return spring 10, the membrane 1 can bulge.

During operation, under known circumstances, the working fluid may flow out through the clearance 5 at the piston. In order to ensure that the hydraulic chamber 8 always has a sufficient amount of working fluid, a leakage replenishment valve 6 is provided through which the hydraulic chamber 8 is connected to the working fluid supply 15. This leak replenishment valve has a small ball that is pressed against the valve seat by means of a spring. By means of the spring of the replenishment valve 6, the set pressure p _{L is set} . If the pressure in the hydraulic chamber 8 drops below the set pressure p _L , then the ball of the replenishment valve rises from the valve seat, and additional working fluid from the reserve 15 of the working fluid, which is generally under atmospheric pressure (1 bar), can flow into the hydraulic chamber 8, until the pressure in the hydraulic chamber 8 rises above the set pressure p _L , since then the spring of the replenishment valve 6 will press the ball against the valve seat again and thereby block the valve passage.

In the drawing of FIG. 2, the pressure in the hydraulic chamber at the time of suction inlet is schematically shown. At the beginning of the suction stroke, the pressure in the hydraulic chamber corresponds approximately to the pressure with which the pump releases the pumped fluid from the pressure connection. This pressure is much higher than the static pressure of the suction pipe. Of course, the pressure in the hydraulic chamber is additionally determined by the return spring 10. This pressure difference is not further considered, however, since it is not essential for the invention.

The suction stroke starts when the piston moves backwards, i.e. shown in FIG. 1 of the embodiment moves to the right. This first leads to the fact that the pressure in the hydraulic chamber decreases slowly, and since the pressure in the discharge chamber is greater, the membrane will move to the right, i.e. in the direction of the hydraulic chamber. In this case, the pressure in the discharge chamber will slowly drop until it reaches the static pressure at the suction connection p _so . When the pressure drops even more, the corresponding check valve that connects the discharge chamber to the suction connection will open and the pumped fluid will leak through the suction connection. At that moment in which the pressure in the discharge chamber thus reaches the static pressure at the suction connection, a sharp change in the fluid velocity will occur in the suction pipe. This change in the velocity Δv leads to the so-called Zhukovsky shock Δp _st = ρ · a · Δv, where ρ is the density of the injected medium and a is the wave propagation velocity in the suction pipe filled with liquid.

This Zhukovsky shock in the discharge chamber leads to a hydraulic shock in the discharge chamber, since both chambers are connected by means of a membrane.

It can be seen that after a certain time after the start of the suction stroke s, the pressure p _n in the hydraulic chamber suddenly drops to a short time interval (Δp _st ). Shortly thereafter, it rises again strongly, so that a high-frequency, rapidly decaying pressure oscillation is obtained. It is immediately clear that water hammer can lead to a decrease in pressure to a maximum of p = 0. In fact, however, the pressure in the hydraulic chamber will not drop to 0, but to a certain minimum pressure p _min , which is set by the operating parameters and design of the diaphragm pump.

In order to prevent the opening of the replenishment valve when a hydraulic shock drops to p _min , it is provided in the prior art that the set pressure p _{L is} less than p _min .

Due to the measure proposed by the invention, the set pressure p _L can, however, be selected significantly more than p _min , while p _{L is} less than the average pressure p _m in the hydraulic chamber.

The basis of the invention is the well-known fact that water hammer occurs only within a very short time interval Δts <1 millisecond.

The mass of the locking member according to the invention is selected such that such a water hammer only results in a stroke of less than 0.2 mm or, accordingly, preferably less than 0.1 mm.

One of the leak replenishment valves of the invention is shown in FIG. 3.

This leakage replenishment valve has a closure member 16 located in the valve body 18, which has a closure member 20 that closes in the closed position the opening in the valve housing 18 so that the hydraulic fluid conduit 19 is separated from the hydraulic chamber 8. The closure member by means of the spring member 17 is preloaded to the closed position, which is shown in FIG. 3. The pressure of the working fluid in the volume of the working fluid, and at the same time, the pressure in the conduit 19 remains substantially constant. When the pressure in the hydraulic chamber 8 falls below the set pressure p _L , which is essentially set by the spring 17, then the closing member 16 in FIG. 3 position moves up, so that the connection between the pipe 19 and the hydraulic chamber 8 is opened. In principle, it is assumed that when the locking member moves only 0.2 mm, that the gap between the valve body 18 and the locking member 20 is not enough to release a significant amount of working fluid through the pipe 19 into the hydraulic chamber.

The stroke length of the closing body Δs is calculated:

In this case, Δt is the duration of the water hammer, and b is the acceleration that the closing member acquires due to the water hammer. Acceleration is calculated:

where F is the force acting on the closure organ, and m is the mass of the closure organ. Thus, it turns out:

or respectively

Based on the fact that the water hammer lasts no more than 1 millisecond, i.e. Δt _s = 1 millisecond that the movement of the closing organ should be a maximum of 0.1 mm, i.e. Δs _s = 0.1 mm, and that water hammer causes a decrease in pressure to 0 bar, i.e. water hammer has a setting pressure p _L , for example, 0.7 bar, it is obtained with a diameter of the closing element equal to 8 mm, i.e. a corresponding area of approximately 0.5 cm ² :

and thus

Therefore, in the example shown, the mass of the locking member must be at least 17.5 g in order to prevent the movement of the locking member by more than 0.1 mm.

If the mass of the locking member is chosen of such a magnitude, then even a water hammer up to 0 bar cannot move the locking member so far that a significant amount of the working fluid flows into the hydraulic chamber.

The described method can be further improved, given that the hydraulic shock generally reduces the pressure not to 0 bar, but only to a certain minimum pressure p _min . In the above equality (5), then, instead of the set pressure p _{L, we can} substitute the difference p _L -p _min between the set pressure p _L and the minimum pressure p _min due to water hammer, due to which the mass can be further reduced. Alternatively, the set pressure p _L may increase, so that the spring 17 can be made weaker, which simplifies the handling of the pump.

LIST OF REFERENCE NUMBERS

1 Membrane

5 clearance

6 Leak-up valve

8 hydraulic chamber

9 Pressure chamber

10 Return spring

11 clamping edge

12 clamping edge

13 Installation space

15 Stock of working fluid

16 trailing organ

17 spring

18 valve body

19 Pipeline

20 Locking element

Claims (6)

1. A diaphragm pump, which includes a discharge chamber (9) separated by a membrane (1) from the hydraulic chamber (8), the discharge chamber (9) being connected to the suction connection and pressure connection, and a hydraulic chamber filled with working fluid (8) can be loaded with pulsating pressure of the working fluid, while the hydraulic chamber (8) is connected to the supply (15) of the working fluid through the leakage replenishment valve (6), while the leakage replenishment valve (6) has a closing element, which can be made the reciprocating movement between the closed position in which the valve passage is closed and the open position in which the valve passage is open and which is held in the closed position by the pressure element, the pressure element is designed so that when the pressure in the hydraulic chamber (8) is less than the set pressure p _L , the locking member (16) moves in the open direction, characterized in that the mass of the locking member (16) is such that the locking member (16) and the pressure drop to 0 bar lasting no more than one millisecond, due to water hammer in the hydraulic chamber (8), moves in the direction of the open position by no more than 0.2 mm. 2. A diaphragm pump according to claim 1, characterized in that the mass of the closing member (16) is selected so that the closing member (16) with a pressure drop lasting no more than one millisecond due to water hammer in the hydraulic chamber (8) does not move more than 0.1 mm in the open direction. 3. A diaphragm pump according to claim 1 or 2, characterized in that the closing element (16) with a pressure drop lasting no more than one millisecond to a minimum pressure p _min due to water hammer in the hydraulic chamber (8) moves no more than 0.2 mm, preferably not more than 0.1 mm, in the open direction, with p _min representing the minimum pressure arising in the hydraulic chamber due to water hammer when the fluid velocity changes through the suction connection during the stroke suctioning. 4. A diaphragm pump according to claim 1 or 2, characterized in that p _{L is} greater than the minimum pressure in the hydraulic chamber (8). 5. A diaphragm pump according to claim 3, characterized in that p _{L is} greater than the minimum pressure in the hydraulic chamber (8). 6. The method of selecting the size of the valve (6) to replenish the leaks of the diaphragm pump, which includes a discharge chamber (9) separated by a membrane (1) from the hydraulic chamber (8), while the discharge chamber (9) is connected respectively to the suction connection and pressure connection, and the hydraulic chamber (8) filled with the working fluid can be loaded with the pulsating pressure of the working fluid, while the hydraulic chamber (8) is connected through a leakage replenishment valve (6) to the working fluid reserve (15), while the replenishment valve (6) The kidney has a locking member, which is configured to reciprocate between a closed position in which the valve passage is closed and an open position in which the valve passage is open, characterized in that the mass of the locking member (16) is selected so that the locking the body (16) with a continuous hydraulic shock lasting no more than one millisecond due to the pressure drop in the hydraulic chamber (8) moved no more than 0.2 mm, preferably no more than 0.1 mm, in the direction of open position.

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