DOUBLE PISTON PUMP WITH AXIALLY SLIDING CONTROL PISTON

Description

[0001] The present invention relates to a double-piston pump for conveying highly viscous media according to the feature in the preamble of claim 1.

[0002] From the prior art, for example, a double-piston pump is known from DE 10 2004 054 606 A1, in which two parallel pistons, also called working pistons, transport a highly viscous medium via the pressure and suction sides.

[0003] Such piston pumps are used primarily 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-like properties and may also contain clumps, contaminants, and foreign matter, such as stones.

[0004] The range of applications in question for such a pump is harsh and adverse. The pump is exposed to high levels of abrasive wear. Furthermore, the pumps must run almost continuously. Downtime and overhaul periods must be avoided whenever possible.

[0005] Furthermore, due to the media to be conveyed, no sieves or filter techniques can be used, as these would irreversibly clog in the conveying direction immediately upon contact with the medium.

[0006] For example, piston pumps are known from US 2017 / 204840 A1 and DE 195 03 986 A1.

[0007] The object of the present invention is therefore to provide a piston pump which has low wear during operation, requires little maintenance and, in particular, enables filtering or separation of foreign bodies during operation.

[0008] The above-mentioned object is achieved according to the invention with a double-piston pump for conveying highly viscous media having the feature in claim 1.

[0009] Advantageous embodiments are the subject of the dependent claims.

[0010] The double-piston pump according to the invention is suitable for conveying 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 switches to pressure mode, and the piston coming from pressure mode switches to suction mode. The high-viscosity medium is sucked in from an intake channel and is then located in the cylinder of the working piston. It is expelled via the pressure side with the next stroke.

[0011] 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.

[0012] For this purpose, the base housing preferably has three adjacent working chambers. The control piston is arranged so as to be axially displaceable, at least partially passing through the working chambers. The working chambers are separated by the control piston in such a way that two working chambers are fluidically connected to one another and the third working chamber is fluidically separated from it. 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 fluidically connected to it. The further working chamber, which was previously connected to the middle working chamber, is fluidically separated from it. This ensures that the suction and pressure operation of the working piston are controlled respectively.

[0013] The working chambers are preferably arranged horizontally, side by side, in the base housing. The working chambers are located above a central intake chamber. The central intake chamber is fluidically connected to an external chamber. The control piston connects or separates the intake chamber from the central working chamber.

[0014] 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 one another.

[0015] Each cylinder liner preferably has recesses or openings radially circumferentially in a central length section, depending on the position of the control piston.

[0016] The control piston itself has two piston heads located opposite each other at its axial ends. The piston heads slide within the cylinder liners. This sliding action is achieved due to the fluid content of the highly viscous medium.

[0017] The radially circumferential openings of the cylinder liners are particularly designed to have a circumferential wave-like shape. This offers two advantages according to the invention, which are explained below.

[0018] A primary advantage of the wave-shaped circumferential opening is the fact that, due to the wave shape, a scissor mechanism is activated when the control piston is moved from one position to another. The highly viscous medium, and in particular solids or clumps in the medium, are broken down and removed from the liner according to the scissor principle. This prevents clogging and blockage, and also reduces the abrasive wear on the control piston. The double-piston pump according to the invention can thus operate reliably and with low maintenance, even in continuous flow operation.

[0019] 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 any solids present, in particular foreign bodies and particularly preferably stones or petrified materials, so that they sink into the suction chamber located at the bottom (relative to the vertical direction). This makes it possible to filter solids and foreign matter simultaneously with the double piston pump. These foreign matter or stones can then be removed via inspection hatches or by opening the base housing.

[0020] Particularly preferably, the pressure pulse can be generated such 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, thus equalizing the pressure from the suction side to the pressure side, 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. Upon further movement of the control piston, the working spaces are already separated from one another again and no further pressure equalization takes place.

[0021] The fact that the stones remain particularly at the bottom of the central intake chamber is further assisted by the fact that the cross-sectional area of ​​the intake chamber is more than twice, preferably more than 2.5 times, and especially three times larger than the cross-section of the intake line. Thus, the inflowing medium will not penetrate the entire cross-section of the intake chamber when flowing through the intake chamber into the working chambers above. This allows sedimented or deposited stones to collect at the bottom without being swept away by the flow.

[0022] Overall, the pump is designed to be wear-resistant and resistant to foreign matter. It has a high suction capacity, consistently between 0.6 and 0.8 bar. Overall pressures of up to 10 bar are achieved with low maintenance costs and continuous flow. For example, the double-piston pump can deliver 55 m³ / h of highly viscous fluid with an 11 kW drive.

[0023] Further advantages, features, properties, and aspects of the present invention are the subject of the following description. Preferred embodiments are illustrated in schematic figures. These show: Figure 1 shows a double-piston pump in perspective view, Figure 2 shows a longitudinal section through the double-piston pump according to the invention with control piston in an end position, Figure 3 shows a longitudinal section according to Figure 2 by moving the control piston to a central position to generate a pressure pulse,

[0024] 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.

[0025] Figure 1shows a front view of the double-piston pump 1 according to the invention. The double-piston pump 1 has a base housing 2 which is arranged centrally at the bottom with respect to the vertical direction V. The base housing 2 has the configuration of a trough. A central suction chamber 3 is arranged at the bottom with respect to the vertical direction V in the base housing 2. At least three working chambers 4, 6 are arranged above this, which are not shown in detail, with a centrally arranged working chamber 5 being coupled on a pressure side to a discharge line 7 for discharging the sucked-in or pumped medium. The two outer working chambers are each fluidically connected to the suction chamber 3. A control piston 13, not shown in detail here, is located between them. The control piston 13 is mounted so as to be axially displaceable in the horizontal direction H. Two pistons 8, 9, in particular working pistons, are arranged on the base housing 2.Pistons 8 and 9 serve to draw in the medium and, using overpressure, pump it out. Above the pistons 8 and 9, stylized hydraulic piston rods are mounted in a housing, relative to the vertical direction V, which cause the pistons to retract and extend in the axial direction.

[0026] Mounting arms 11 are arranged laterally. Hydraulic cylinders 16 are also arranged in the mounting arms 11. The hydraulic cylinders 16 serve to axially move the control piston 13 (not shown in detail) in the horizontal direction H.

[0027] The functional principle is now in Figure 2shown. 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 spaced axially 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 respectively 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 piston 8 or, in the case of 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 (relative to the image plane) then pushes the previously sucked-in 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 fluidically connected to one another, and the working chamber 5 is separated from the working chamber 6. In order for the control piston 13 to be mounted in the intake chamber 3 and 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 their middle lengths in a 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 their entire length.Should, contrary to expectations, dirt or clumps get caught between the edge of the recess in the waveform 21 and the piston head 14, they are sheared off according to the scissors principle. This inventive measure prevents the piston 13 from tilting.

[0028] A second aspect essential to the invention is Figure 3shown. 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 generates a pressure pulse 22. This pressure pulse 22 makes it possible to press any impurities present in the medium, in particular sediments 23 or stones, out of the medium or into a lower corner shown here. From here, these impurities can be removed via an inspection hatch (not shown in detail). This makes it possible to still 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 downstream processing stations or in the tank of the biogas plant itself.To ensure that the pressure pulse 22 is generated 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. During a movement in the horizontal direction H of the control piston 13, a pressure equalization is thus 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 located in the intake are thus pushed back by the pressure pulse 22 and sink sediment by sediment to the bottom of the intake chamber 3. Reference symbol:

[0029] 1 - Double piston pump 2 - Base housing 3 - Suction chamber 4 - Working chamber 5 - Central working chamber 6 - Working chamber 7 - Discharge 8 - Piston 9 - Piston 10 - Hydraulic drive 11 - Mounting arm 12 - Suction line 13 - Control piston 14 - Piston head 15 - Piston rod 16 - Hydraulic cylinder 17 - Cylinder 18 - Cylinder liner 19 - Middle section 20 - Web 21 - Wave shape 22 - Pressure pulse 23 - Sediment / stone 24 - Distance 25 - Axial length to 14 V - Vertical direction H - Horizontal direction

Claims

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).