EP4390125B1 - Double piston pump with axially displaceable control piston - Google Patents

Description

The present invention relates to a double-piston pump for conveying highly viscous media according to the feature in the preamble of claim 1.

The state of the art is, for example, DE 10 2004 054 606 A1 A double-piston pump is known in which two parallel pistons, also called working pistons, transport a highly viscous medium via the pressure and suction sides.

Such piston pumps are used in particular in agricultural facilities to transport highly viscous media such as animal excrement, liquid manure or solid manure as well as substrate from energy crops. The media to be transported have almost solid properties and also contain clumps, impurities and foreign bodies such as stones.

The range of applications in question for such a pump is tough and adverse. The pump is exposed to high levels of abrasive wear. The pumps must also run almost continuously. Downtime and overhaul times should be avoided wherever possible.

In addition, due to the media to be conveyed, no sieves or filter techniques can be used, as these will become irreversibly blocked in the conveying direction immediately when the medium is present.

For example, from the US 2017/204840 A1 and the DE 195 03 986 A1 piston pumps.

The object of the present invention is therefore to provide a piston pump which has little wear during operation, requires little maintenance and, in particular, enables filtering or separation of foreign bodies during operation.

The above-mentioned object is achieved according to the invention with a double-piston pump for conveying highly viscous media with the feature in claim 1.

Advantageous embodiments are the subject of the dependent claims.

The double piston pump according to the invention is suitable for transporting highly viscous media. It has a base housing. Two pistons, also called working pistons, are arranged on the base housing. These pistons run in a working cylinder. The pistons can accommodate a relatively large volume. One piston always works in suction mode and the other piston in pressure mode. When the top dead center or bottom dead center is reached, the work allocations change. The working piston from suction mode goes into pressure mode and the piston coming from pressure mode goes into suction mode. The high-viscosity medium is sucked in from a suction channel and is then located in the cylinder of the working piston and is pushed out via the pressure side with the next stroke.

In order to ensure that the respective work processes are allocated differently to the pistons, an axially displaceable control piston is provided, which is arranged in the base housing.

The base housing preferably has three adjacent working chambers. The control piston is arranged to be axially displaceable, at least partially, through the working chambers. The working chambers are thereby connected by the control piston separated in such a way that two working chambers are connected to one another in a fluid-technical manner and the third working chamber is separated from this in a fluid-technical manner. If the control piston is moved from an axial movement to the opposite axial position, a middle working chamber, which was initially separated from the third working chamber, is connected to it in a fluid-technical manner. The other working chamber, which was previously connected to the middle working chamber, is separated from it in a fluid-technical manner. This ensures that the suction operation and pressure operation of the working piston are controlled.

The working chambers are preferably arranged next to one another in the base housing in relation to the horizontal direction. The working chambers are arranged above a central intake chamber. The central intake chamber is connected to an external chamber in a fluid-technical manner. The intake chamber is connected to or separated from the central working chamber via the control piston.

In order for the control piston to be mounted in the base housing, cylinder liners are provided, in particular two cylinder liners are arranged axially spaced from each other.

Each cylinder liner preferably has recesses or openings running radially around a central length section, depending on the position of the control piston.

The control piston itself has two piston heads located opposite each other at the axial ends. The piston heads slide in the cylinder liners. This sliding occurs due to the liquid content of the highly viscous medium.

The radially circumferential openings of the cylinder liners are in particular designed to be wave-shaped all the way around. This offers two advantages according to the invention, which are explained below.

A first advantage of the wave-shaped circumferential opening is the fact that when the control piston is moved from one position to the other, Waveform here a scissor mechanism occurs. The highly viscous medium and in particular solids or clumps in the medium are broken down or removed from the liner according to the scissor principle. Clogging or blocking is thus avoided and the abrasive wear that acts on the control piston is also reduced. The double piston pump according to the invention can therefore run error-free and with little maintenance, even in continuous delivery operation.

The horizontally arranged control piston has another fundamental advantage. When the control piston is moved from one position to the other to change the working direction of the respective double piston, a pressure equalization occurs from the pressure side or overpressure side to the suction side or underpressure side. This pressure equalization is controlled in particular according to the invention in such a way that a short pressure pulse occurs. This pressure pulse sediments existing solids, in particular foreign bodies and particularly preferably stones or petrified substances, in such a way that they sink into the suction chamber located below in the vertical direction. This makes it possible to filter solids and foreign substances at the same time with the double piston pump. These foreign substances or stones can then be removed via inspection hatches or by opening the base housing.

Particularly preferably, the pressure pulse can be generated in such a way that the axial distance between the openings of the respective cylinder liner of the piston head of the control piston is slightly greater than the axial length of the piston head. In particular, these are the two maximum deflections of the waveform. When the control piston is transferred from one position to the other and thus a pressure equalization from the suction side to the pressure side occurs, a minimal opening is provided according to the principle of a valve, so that a controlled and regulated pressure pulse is generated in the base housing. When the control piston moves further, the working spaces are already separated from one another again and no further pressure equalization takes place.

The fact that the stones remain particularly at the bottom of the central suction chamber is further supported by the fact that the cross-sectional area of the suction chamber is more than 2 times, preferably more than 2.5 times, in particular 3 times is large compared to the cross-section of the suction line. The inflowing medium will therefore not pass through the entire cross-section of the suction chamber when flowing through the suction chamber into the work chambers above. This allows sedimented or deposited stones to collect on the bottom without being carried away by the flow.

Overall, the pump is designed to be low-wear and insensitive to foreign bodies. It has a high suction power, which always corresponds to 0.6 to 0.8 bar. Overall, pressures of up to 10 bar are possible with low maintenance costs and flow reliability. For example, the double piston pump can provide 55 m ³ /h of highly viscous medium with an 11 kW drive.

Figur 1

eine Doppelkolbenpumpe in perspektivischer Ansicht,

Figur 2

eine Längsschnittansicht durch die erfindungsgemäße Doppelkolbenpumpe mit Steuerkolben in einer Endstellung,

Figur 3

eine Längsschnittansicht gemäß Figur 2 mit Überführen des Steuerkolbens in einer Mittelposition zur Erzeugung eines Druckimpulses,

Further advantages, features, properties and aspects of the present invention are the subject of the following description. Preferred embodiments are shown in schematic figures. These show:

Figure 1

a double piston pump in perspective view,

Figure 2

a longitudinal sectional view through the double piston pump according to the invention with control piston in an end position,

Figure 3

a longitudinal sectional view according to Figure 2 with transfer of the control piston to a middle position to generate a pressure pulse,

In the figures, the same reference symbols are used for identical or similar components, even if a repeated description is omitted for reasons of simplification.

Figure 1 shows the double piston pump 1 according to the invention in a front view. The double piston pump 1 has a base housing 2 arranged centrally at the bottom in relation to the vertical direction V. The base housing 2 has the configuration of a trough. In the base housing 2, a central suction chamber 3 is arranged at the bottom in relation to the vertical direction V. Above this, at least three working chambers 4, 6 are arranged, which are not shown in detail, with a centrally arranged working chamber 5 on a pressure side having a discharge line 7 for discharging of the sucked-in or pumped medium. The two external working chambers are each connected to the suction chamber 3 in a fluid-technical manner. Between them is a control piston 13 (not shown in detail here). The control piston 13 is mounted so that it can be moved axially in the horizontal direction H. Two pistons 8, 9, in particular working pistons, are arranged on the base housing 2. The pistons 8, 9 are used for sucking in and pumping out the sucked-in medium using excess pressure. Stylized hydraulic piston rods are mounted in a housing above the pistons 8, 9 in relation to the vertical direction V, which cause the pistons to retract or extend in the axial direction.

Mounting arms 11 are arranged to protrude from the sides. Hydraulic cylinders 16 are also arranged in the mounting arms 11. The hydraulic cylinders 16 serve for the axial movement of the control piston 13 (not shown in detail) in the horizontal direction H.

The functional principle is now in Figure 2 shown. A medium (not shown in detail) is sucked into the central suction chamber 3 via the suction line 12. The control piston 13 shown here has two piston heads 14 which are axially spaced apart from one another. The piston heads 14 are coupled to one another via a piston rod 15. Hydraulic drives arranged on the left and right cause the control piston 13 to be moved in the horizontal direction H. The right-hand piston 9 relative to the image plane is in pressure mode, the left-hand piston 8 relative to the image plane is in suction mode. A respective cylinder 17 of the pistons 8, 9 is thus either sucked full of a medium in the case of the piston 8 or, in the case of the piston 9, the medium is pushed out of the piston 9. For this purpose, the working chambers 5 and 6 are fluidically connected to one another, so that the medium is pumped out of the cylinder 17 of the piston 9 and conveyed through the working chamber 6 into the central, middle working chamber 5 and then into the discharge line 7. In relation to the image plane, the left piston head 14 separates the left working chamber 4 from the central working chamber 5. At the same time, however, the central suction chamber 3 or the suction line 12 and the piston 8 are fluidically connected to one another, so that suction operation takes place here. In the next stroke of the pump 1, the working direction is changed. The left piston 8 in relation to the image plane then presses the previously sucked medium into the discharge line 7. The Piston 9 sucks in new medium. In this case, the control piston 13 would be moved completely to the left image plane, although this is not shown. In this case, the working chambers 4 and 5 are then fluidically connected to one another and the working chamber 5 is separated from the working chamber 6. So that the control piston 13 is mounted in the intake chamber 3 or in the base housing 2, two cylinder liners 18 are arranged at a distance from one another in the axial direction. These cylinder liners 18 have recesses or holes running radially around a middle length section 19. These holes can also be referred to as slots. Remaining webs 20 connect a left and right part of the cylinder liner 18 to one another. The respective piston head 14 of the control piston 13 passes through these recesses when the control piston 13 is adjusted in the axial direction. For this purpose, the recesses are provided with a wave shape 21 running radially around. If, contrary to expectations, dirt or clumps get between the edge of the recess on the wave form 21 and the piston head 14, they are sheared off according to the principle of scissors. This measure according to the invention prevents the piston 13 from jamming.

A second aspect essential to the invention is Figure 3 shown. Here, the control piston 13 is in a middle position, so that a transition from the suction side to the pressure side can be seen on the respective piston 8, 9. This creates a pressure equalization between the suction side and the overpressure side, which creates a pressure pulse 22. This pressure pulse 22 makes it possible to press impurities present in the medium, in particular sediments 23 or stones, out of the medium or into a lower corner shown here. Here, these impurities can be removed via an inspection flap (not shown in detail). This makes it possible to filter this highly viscous medium of a biogas plant. Sediments 23 or stones are not fundamentally transported along, so that no oversaturation of stone material occurs during continuous operation of a biogas plant at the subsequent processing stations or in the container of the biogas plant itself. In order to generate the pressure pulse 22 in a targeted manner, a distance 24 of the maximum deflection of the waveform 21 is slightly larger, preferably 1.01 to 1.1 times, particularly preferably 1.01 to 1.02 times, than the axial length 25 of the piston head 14. When the control piston 13 moves in the horizontal direction H, a pressure equalization is created between the pressure side and the suction side for a short period of time, so that the pressure pulse 22 is generated. Sediments 23 or stones in the suction are thus pushed back by the pressure pulse 22 and sink sediment by sediment to the bottom of the suction chamber 3.

Reference symbol:

• 1 - Double piston pump
• 2 - Base housing
• 3 - Intake chamber
• 4 - Workspace
• 5 - central workspace
• 6 - Workspace
• 7 - Derivative
• 8 - piston
• 9 - piston
• 10 - hydraulic drive
• 11 - Mounting arm
• 12 - intake line
• 13 - Control piston
• 14 - Piston head
• 15 - Piston rod
• 16 - Hydraulic cylinder
• 17 - cylinder
• 18 - Cylinder liner
• 19 - Middle section
• 20 - Steg
• 21 - Waveform
• 22 - Pressure pulse
• 23 - Sediments/Stone
• 24 - distance
• 25 - axial length to 14
• V - vertical direction
• H - horizontal direction

Claims (10)

1. Double piston pump (1) for conveying highly viscous media, having two arranged pistons (8, 9), wherein each piston (8, 9) is driven by a drive and an axially displaceable control piston (13), which is arranged in a base housing (2), and three working chambers (4, 5, 6) are provided in the base housing (2), characterized in that the working chambers (4, 5, 6) are separated by the control piston (13) such that two working chambers (4, 5) are connected to one another in a fluidically conductive manner and the further working chamber (6) is separated from these in a fluidically conductive manner, and in that the control piston (13) has two piston heads (14) located opposite one another at the axial ends, wherein the piston heads (14), depending on their position, separate or connect the working chambers (4, 5, 6).
2. Double piston pump (1) according to claim 1, characterised in that the two pistons (8, 9) are arranged parallel to one another, in particular in vertical alignment.
3. Double piston pump (1) according to any one of claims 1 or 2, characterised in that the control piston (13) is arranged perpendicular to the pistons (8, 9), in particular in horizontal direction.
4. Double piston pump (1) according to any one of claims 1 to 3, characterised in that the three working chambers (4, 5, 6) are arranged above a central suction chamber (3), wherein the two outer working chambers (4, 5) are connected in a fluidically conductive manner to the suction chamber (3).
5. Double piston pump (1) according to any one of claims 1 to 4, characterised in that two cylinder liners (18) are arranged spaced apart axially from one another in the base housing (2), wherein the control piston (13), in particular the piston heads (14), is/are mounted in a sliding manner in the cylinder liners (18).
6. Double piston pump (1) according to claim 5, characterised in that a cylinder liner (18) has openings around it in a central longitudinal section (19).
7. Double piston pump (1) according to claim 6, characterised in that a transition from an end section of the cylinder liner (18) to the openings is configured to be radially circumferentially undulating.
8. Double piston pump (1) according to claim 6 or 7, characterised in that a distance (24) of the openings, in particular a distance (24) of the maximum deflection of the waveform (21) is greater than the axial length (25) of a piston head (14) of the control piston (13).
9. Double piston pump (1) according to any one of the preceding claims, characterised in that when the control piston (13) is transferred from one position to an opposite position, the working chambers (4, 5, 6) of a suction side are fluidically connected to the working chambers (4, 5, 6) of a pressure side, such that a pressure pulse (22) is produced by the pressure equalization from the suction side to the pressure side.
10. Double piston pump (1) according to any one of the preceding claims, characterised in that a cross-sectional area of the suction chamber (3) is at least 2 times, preferably 2.5 times, in particular 3 times as large in comparison to the cross-section of the suction line (12).

Images