EP0036945B1 - Device for delivering fluid materials - Google Patents

Abstract

1. Apparatus for the conveying of fluid media, more particularly of abrasive liquids, thick sludges, suspensions of solid substances, or the like, with a displacement pump (23) which is interposed between two shutoff valves (14, 15) in the conveying conduit (13) and which sucks in the conveyed medium (11) at its suction stroke and delivers it onwards at its compression stroke, and between the conveying conduit (13) and the working side (22) of the pump (23) there is arranged a separating cylinder (19) with a separating piston (20) capable of moving freely axially therein, and at one face (29) of the said piston the conveyed medium (11) is present and at the other face (39) a working medium (40) acted upon by the pump (23), the separating piston (20) having a somewhat smaller diameter (d) than the separating cylinder (19) and being preloaded by at least one spring element (50) in the direction opposite to the compression direction of the pump (23) and being sealed circumferentially against the conveyed medium (11), characterized in that the separating piston (20) is arranged in a separate separating cylinder (19) which it divides into two cylinder chambers (19a, 19b) which in the end positions of the separating piston (20) have a smaller volume than the working medium (40) moved by the pump (23) at the compression stroke and suction stroke, and that the working side (22) of the pump (23) is connected with a storage container (47) which is closed off from the pump (23) at the compression stroke, and that the separating piston (20) has at its circumference at least one lip-type sealing element (34) having a sealing lip (37) which is directed towards the cylinder chamber (19a) filled with the medium being conveyed and which abuts on the inner wall surface (36) of the cylinder, and which not only seals the separating piston (20) at its circumference relatively to the medium (11) conveyed but also allows the working medium (40) to flow past the separating piston (20) towards the conveying conduit (13).

Description

The invention relates to a device for conveying flowable media, in particular abrasive liquids, thick slurries, solid suspensions or the like. With a positive displacement pump connected between two shut-off valves in the delivery line, which sucks in the delivery medium during its suction stroke and conveys it further during its pressure stroke, whereby between the Delivery line and the working side of the pump, a separating cylinder with axially freely movable separating piston is arranged, on one end of which is the pumped medium and on the other end is a working medium acted upon by the pump, the separating piston having a somewhat smaller diameter than the separating cylinder and is loaded by at least one spring element against the pressure direction of the pump and is sealed on its circumference against the pumped medium.

When pumping solid suspensions and abrasive liquids, there is a risk of damage to pump parts that come into contact with the pumped medium. Instead of piston pumps, diaphragm pumps are therefore primarily used for such media. These, in turn, are subject to high wear, since the diaphragm is subjected to very high loads during pumping. Diaphragm pumps cannot be used to pump liquids that have a high temperature.

A device of the type explained in more detail at the outset is known (GB-A-350817) which is used as a petrol pump and in which the working medium is air. In this pump, the separating piston is arranged in the same cylinder as the piston of the working pump, which acts with a strong spring on the separating piston, which is loaded from the opposite side by a weaker spring. The separating piston is very carefully sealed against the cylinder so that on the one hand no petrol escapes and on the other hand no air can get into the delivery line. This known pump is not suitable for conveying abrasive liquids, thick slurries and solid suspensions, since solids can get between the separating piston and the cylinder wall, which prevent the free movement of the separating piston in the cylinder. In addition, cylinder and piston surfaces are subject to very high wear when conveying such media.

A device is also already known (DE-A-1 453 576), in which the separating piston can slide freely in the separating cylinder with play and is not sealed off from the wall of the separating cylinder, so that during operation of the conveying medium, the separating piston passes into the working medium can. In order to avoid that large amounts of the medium to get into the working medium, a long pipeline and an auxiliary pump is provided between the separating cylinder and the positive displacement pump, which continuously pumps working medium into the liquid piston between the positive displacement pump and the separating piston.

In this known pumping device, the fluid that has penetrated into the working medium is kept away from the positive displacement pump with sufficient security, but it is necessary to at least produce the pipeline between the positive displacement pump and the separating cylinder from a material that cannot be attacked by the fluid. In addition, the separating cylinder and the separating piston are subject to high wear when pumping solid suspensions, since the pumped medium constantly flows between the separating piston and separating cylinder and solid particles can become lodged in the intermediate space. Even if thick sludge is to be pumped, difficulties can arise since these clog the gap between the separating piston and the separating cylinder and hinder the free movement of the separating piston. Furthermore, the known pump device only works if the separating piston has approximately the same specific weight as the liquid to be pumped.

In order to compensate for leakage losses in a pump engine, it is also no longer new for a metering pump, the piston of which is actuated by a drive piston via hydraulic fluid, to make the stroke length of the drive piston longer than the stroke distance of the metering piston and the pressure medium space via a suction valve to a reservoir to be connected, from which pressure medium is drawn in during the suction stroke of the drive piston, while excess pressure medium can escape during the pressure stroke through a spring-loaded pressure relief valve (CH-A-420 863).

The object of the invention is to provide a very simple and robust device for conveying flowable media of the type specified in the introduction, in which the conveyed medium does not penetrate into the working medium and does not hinder the movement of the separating piston in the separating cylinder.

This object is achieved with the invention in that the separating piston is arranged in a separate separating cylinder, which it divides into two cylinder spaces, which in the end positions of the separating piston have a smaller volume than the working medium moved by the pump during the pressure stroke and suction stroke, and in that the The working side of the pump is connected to a storage container which is shut off against the pump during the pressure stroke and that the separating piston has at least one lip seal on its circumference with a sealing lip that is directed against the cylinder space filled with the medium to be pumped seals its circumference against the medium, but also allows the working medium to flow past the separating piston in the direction of the delivery line.

This embodiment has the advantage that no medium can get into the working medium and both the pressure stroke and the suction stroke a small amount of working medium flows past the separating piston into the medium, which flushes the annular gap and the seals there. This effect arises from the fact that the pump has to apply a force to overcome the spring pressure in addition to the delivery force during the pressure stroke, so that a pressure difference arises in the working medium and delivery medium, which allows the working medium to flow past the separating piston. On the other hand, during the suction stroke, the spring element leads the separating piston to advance, with the working medium passing through the annular gap between the separating piston and separating cylinder into the conveying medium.

The separating piston divides the separating cylinder into two cylinder spaces, which in the end positions of the separating piston have a smaller volume than the working medium moved by the pump during the pressure stroke and suction stroke. Here, the working side of the pump is expediently connected to a storage container which is shut off against the pump during the pressure stroke. This ensures that the pressure of the working medium increases at the end of the pressure stroke of the pump when the separating piston has reached its end position. As a result of the pressure difference between the working medium and the conveying medium, a certain amount of the working medium can flow past the seal into the conveying medium and flush the seal and the peripheral edge of the separating piston from the conveying medium, so that a perfect seal of the separating piston on the separating cylinder is ensured when the positive displacement pump pumps its Suction stroke begins and the separating piston sucks in the fluid again.

A check valve biased against the reservoir and a check valve biased against the working side of the pump, which is controlled by the separating piston, are expediently arranged between the reservoir and the working side of the pump. This design ensures that the inflow from the reservoir remains blocked as long as the pump executes its pressure stroke and that the check valve is opened at the end of the suction stroke of the separating piston, but the check valve only opens when a negative pressure is created on the working side of the displacement pump that exceeds the force of the spring closing the check valve.

To control the shut-off valve, this can have a tappet which projects into the separating cylinder and is acted upon by the separating piston in the last phase of the suction stroke. It is particularly expedient here if the closure pieces of the check valve and check valve are pressed onto their seats by a valve spring common to both.

A spring can be arranged on the end face of the separating piston facing the displacement pump, which brakes the separating piston during the suction stroke and softens the stop of the separating piston on the separating cylinder housing.

The separating cylinder expediently has stops in both cylinder spaces, which limit the stroke of the separating piston in both directions, and one cylinder space of the separating cylinder can be connected to the delivery line with a pipeline and the other cylinder space can be connected to the working side of the displacement pump designed as a piston pump with a pipeline.

It is particularly expedient if the size of the throughflow opening between the separating cylinder and the separating piston is adapted to the amount of working medium which is to be pressed into the conveying medium with each pressure stroke. Such a design is particularly advantageous if a particular medium is to be added to the pumped medium in a metered amount with each pump stroke. In this case, the working medium consists of this additional medium, which is always refilled from the storage container. If the conveying medium is, for example, a bauxite slurry to which sodium hydroxide solution is to be added during the pumping process, the storage container can contain the sodium hydroxide solution to be added to the conveying medium. In other cases, the reservoir contains a rinsing liquid or the working medium, which can be any suitable hydraulic fluid, for example an oil or water, which does not have any harmful influence on the conveying medium if it is added to it in small quantities during the conveying process.

• Figur 1 eine Pumpvorrichtung nach der Erfindung in einer schematischen Schnittdarstellung und
• Figur 2 die Einzelheit II der Fig. 1 in vergrößertem Maßstab, welche die Abdichtung des Trennkolbens am Trennzylinder zeigt.

Further features and advantages of the invention result from the following description, in which a preferred embodiment of the invention is explained in more detail using an example. It shows:

• Figure 1 shows a pump device according to the invention in a schematic sectional view and
• Figure 2 shows the detail II of FIG. 1 on an enlarged scale, which shows the sealing of the separating piston on the separating cylinder.

In the drawings, 10 denotes a pumping device for conveying flowable media, in particular an abrasive liquid, such as a bauxite sludge, which is hereinafter referred to as "conveying medium" and is designated in the drawing with 11. The conveying medium flows in the direction of the Arrow 12 in a delivery line 13, in which there are two check valves 14 and 15, which are designed as ball check valves and are accommodated in a valve housing 16. Between the two check valves 14 and 15 there is a pipe connection piece 17, to which a pipe 18 is connected, which leads to a separation cylinder, which in its entirety with 19 be is drawing.

In the separating cylinder 19 there is a separating piston 20 which is freely displaceable in the axial direction and which divides the separating cylinder 19 into a lower cylinder space 19a and an upper cylinder space 19b. The already mentioned pipeline 18, which leads to the valve housing 16 of the delivery line 13, is connected to the lower cylinder chamber 19a. A pipeline 21, which is filled with a working medium 40 and communicates with the working side 22, of a displacement pump 23, which in the exemplary embodiment shown is a piston pump, opens into the upper cylinder space 19b. The pump housing is designated by 24 and the pump piston bears the reference number 25. The piston rod 26 is attacked by the piston rod 26, which is only schematically indicated here, which is moved by the crankshaft 27 and gives the piston 25 a moving up and down movement.

As can be seen from FIG., The separating piston 20 has a circumferential edge 28 which is thickened in the axial direction and which projects beyond the lower end face 29 of the separating piston and strikes one end face 30 of the separating cylinder during the pressure stroke. On the opposite end face 39 of the separating piston, a hump 31 is provided which can abut the upper end face 32 of the separating cylinder and thereby limits the suction stroke of the separating cylinder.

It can be seen from FIG. 2 that the separating piston 20 has a diameter which is somewhat smaller than the diameter D of the separating cylinder, so that an annular gap 33 remains between the separating cylinder 19 and the separating piston 20. This annular gap is sealed by two lip seals 34 arranged one behind the other in the axial direction, each of which lies in a circumferential groove 35 of the separating piston and has a sealing lip 37 which bears against the inner wall 36 of the cylinder and is directed against the cylinder space 19a filled with pumped medium 11. The ring groove has a very specific size, which is explained in more detail below.

In the upper end wall 38 of the separating cylinder 19 there is a bore 41 through which the tappet 42 of a poppet valve 43 projects into the upper cylinder chamber 19b of the separating cylinder. The poppet valve 43 is located together with a check valve formed by a ball 44 in a valve housing 45 which is fastened to the upper end wall 38 of the separating cylinder 19 and belongs to a line 46 which leads to a reservoir 47 in which working medium or a special one Flush liquid 48 is located.

As is apparent from Fig., The spherical closure piece of the check valve 44 and the valve plate of the poppet valve 43 are pressed onto their seats and held closed by a valve spring 49 common to both valves. The poppet valve 43 is lifted from its seat when the annular thickening 28 of the separating piston 20 abuts against the end of the valve tappet 42 projecting into the cylinder space 19b and displaces it in the axial direction when the separating piston 20 moves upward in FIG. 1.

The separating piston 20 is held by two springs 50 and 51 approximately in the middle of the separating cylinder 19 when the displacement pump 23 is not working, one spring 50 being located in the lower cylinder space 19a and the spring 51 being located in the upper cylinder space 19b of the separating cylinder 19.

• Wenn der Kolben 25 der Verdrängepumpe 23 von der Pleuelstange 26 in Fig. 1 nach unten bewegt wird und seinen Druckhub ausführt, drückt das in der Leitung 21 befindliche Arbeitsmedium 40 auf die obere Stirnseite 39 des Trennkolbens 19, so daß dieser ebenfalls in Fig. 1 nach unten gedrückt wird und auf das in der Rohrleitung 18 und im Ventilgehäuse 16 befindliche Fördermedium 11 einen Druck ausübt. Bei dieser Druckerhöhung wird das Rückschlagventil 15 im Ventilgehäuse 16 geschlossen gehalten, während sich das Rückschlagventil 14 öffnet und das Fördermedium in Richtung des Pfeiles 12 in der Förderleitung 13 weiterbefördet wird.

The device works as follows:

• When the piston 25 of the displacement pump 23 is moved down by the connecting rod 26 in FIG. 1 and executes its pressure stroke, the working medium 40 in the line 21 presses on the upper end face 39 of the separating piston 19, so that this is also shown in FIG. 1 is pressed down and exerts a pressure on the conveying medium 11 located in the pipeline 18 and in the valve housing 16. With this pressure increase, the check valve 15 in the valve housing 16 is kept closed while the check valve 14 opens and the conveyed medium is conveyed further in the direction of arrow 12 in the conveying line 13.

Since the separating piston 20 is under the action of the spring 50, the liquid pressure generated in the line 21 by the piston 25 of the positive displacement pump must be higher than the pressure for conveying the conveying medium located in the pipeline 18 and the conveying line 13 when the separating piston 20 is in the separating cylinder 19 is pressed down. As a result of the pressure difference in the lines 21 and 18, working medium 40 flows through the annular gap 33 between the separating piston 20 and separating cylinder 19 past the sealing lips 37 into the conveying medium and thereby flushes the seals 34. The same effect also occurs if the separating piston 20 strikes the end wall 30 of the separating cylinder 19 before the piston 25 of the displacement pump 23 reaches its bottom dead center, i.e. if the cylinder spaces 19a and 19b have a smaller volume in the end positions of the separating piston 20 than the working medium displaced by the pump 23 during the pressure stroke and suction stroke.

When the piston 25 has reached its bottom dead center and the piston pump 23 begins its suction stroke, the separating piston 20, which in turn generates a negative pressure in the line 18 and in the valve housing 16, is carried upward by the vacuum created in the line 21, whereby the check valve 14 is closed and the check valve 15 in the delivery line 13 is opened and the medium is sucked out of the delivery line 13.

Before the separating piston 20 comes into contact with the upper end wall 32 of the separating cylinder 19, the outer annular bead 28 abuts on the separating piston 20 against the tappet 42 of the plate valve 43 and lifts it off its seat. Since the separating piston 20 by the spring 51 at its As the upward movement is braked, but the piston 25 of the displacement pump 23 continues its suction stroke after the separating piston 20 has struck the upper end wall 32 of the separating cylinder 19, a vacuum is created in the line 21. Since the sealing lips 37 of the lip seals 34 are directed against the lower cylinder space 19a filled with the conveying medium 11, the sealing lips 37 are pressed firmly against the inner wall 36 of the separating cylinder by the conveying medium 11. The check valve 44 is lifted from its seat by the vacuum which simultaneously becomes effective inside the valve housing 45, so that the liquid 48 in the reservoir 47 can flow through the valve housing 45 into the cylinder space 19b and replenish the working medium 40, while the piston 25 of the Displacement pump 23 continues its suction stroke. The cylinder space 19b and the line 21 are then completely filled with liquid again when the piston 25 reaches its top dead center.

It can be seen that the pump device according to the invention can also be used as a metering device with which a liquid 48 located in the storage container 47 can be mixed in a metered amount with the conveying medium 11, the force of the spring 50, the cylinder spaces 19a and 19b and the The width of the annular gap 33 can be coordinated with one another in such a way that a specific quantity of the liquid 48 reaches the line 21 with each suction stroke and is pressed past the lip seals 34 into the conveying medium 11 during the pressure stroke. In this case, the additional liquid 48 can be the same liquid as the working medium 40, but it is also possible to use an additional liquid which is different from the working liquid, since in the arrangement of the injection opening for the additional liquid shown in the diagram, which is not insignificant for the invention upper end wall 38 of the separating cylinder 19, a mixture between the working liquid located in the line 21 and the additional liquid injected into the upper cylinder chamber 19b hardly occurs.

The invention can be used commercially for conveying flowable materials, in particular aggressive and abrasive slurries, such as bauxite suspensions or coal slurries. A hydraulic fluid, for example a mineral oil, but also water, sodium hydroxide solution or another additional liquid, which is to be injected into the conveying medium and can be added from the additional container 48, can serve as the working medium.

The invention is not restricted to the exemplary embodiment. For example, it is also possible to use other trained and controlled valves for injecting the additional liquid, without thereby exceeding the scope of the invention.

Claims (7)

1. Apparatus for the conveying of fluid media, more particularly of abrasive liquids, thick sludges, suspensions of solid substances, or the like, with a displacement pump (23) which is interposed between two shutoff valves (14, 15) in the conveying conduit (13) and which sucks in the conveyed medium (11) at its suction stroke and delivers it onwards at its compression stroke, and between the conveying conduit (13) and the working side (22) of the pump (23) there is arranged a separating cylinder (19) with a separating piston (20) capable of moving freely axially therein, and at one face (29) of the said piston the conveyed medium (11) is present and at the other face (39) a working medium (40) acted upon by the pump (23), the separating piston (20) having a somewhat smaller diameter (d) than the separating cylinder (19) and being preloaded by at least one spring element (50) in the direction opposite to the compression direction of the pump (23) and being sealed circumferentially against the conveyed medium (11), characterised in that the separating piston (20) is arranged in a separate separating cylinder (19) which it divides into two cylinder chambers (19a, 19b) which in the end positions of the separating piston (20) have a smaller volume than the working medium (40) moved by the pump (23) at the compression stroke and'suction stroke, and that the working side (22) of the pump (23) is connected with a storage container (47) which is closed off from the pump (23) at the compression stroke, and that the separating piston (20) has at its circumference at least one lip-type sealing element (34) having a sealing lip (37) which is directed towards the cylinder chamber (19a) filled with the medium being conveyed and which abuts on the inner wall surface (36) of the cylinder, and which not only seals the separating piston (20) at its circumference relatively to the medium (11) conveyed but also allows the working medium (40) to flow past the separating piston (20) towards the conveying conduit (13).

2. Apparatus according to claim 1, characterised in that between the storage container (47) and the working side (22) of the pump (23) there are arranged a non-return valve (44) preloaded towards the storage container (47) and a shutoff valve (43) preloaded towards the working side (22) of the pump (23), and that the shutoff valve (43) is controlled by the separating piston (20).

3. Apparatus according to claim 2, characterised in that the shutoff valve (43) has a stem (42) which projects into the separating cylinder (19) and is acted upon by the separating piston (20) in the last phase of the suction stroke.

4. Apparatus according to claim 2, characterised in that the closure members of the shutoff valve (43) and the non-return valve (44) are pressed against their seats by a valve spring (49) common to both valves.

5. Apparatus according to claim 1, characterised in that on that side (39) of the separating piston (20) which is directed towards the displacement pump (23) there is situated a spring (51) which brakes the separating piston (20) at the suction stroke.

6. Apparatus according to claim 1, characterised in that the size of the throughflow aperture (33) between the separating cylinder (19) and the separating piston (20) is adapted to the quantity of medium (40, 48) which is to be forced into the conveyed medium (11) at each compression stroke.

7. Apparatus according to claim 1, characterised in that the storage container (47) contains a liquid (48) which is to be added to the medium (40) to be conveyed, or contains a special rinsing or scavening liquid.

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