Screw pump

Abstract

The invention relates to a screw pump comprising a pump housing in which a pump spindle is rotatably mounted with the involvement of a hydrostatic thrust bearing for absorbing the axial thrust which is produced at the spindle during operation, the hydrostatic thrust bearing being formed by a housing-fixed bearing surface, against which an end-face, spindle-fixed bearing surface of the pump spindle is indirectly supported, by virtue of the fact that the housing-fixed bearing surface and the spindle-fixed bearing surface form a bearing gap therebetween, which bearing gap is fed, in its central region, with a pressure fluid which flows out through the bearing gap in the radial direction, preferably into the intake region, and the hydrostatic pressure of which counteracts the axial thrust.

Description

[0001] The invention relates to a screw pump having the features of claim 1. TECHNICAL BACKGROUND

[0002] Screw pumps are powerful positive displacement pumps that enable low-pulsation pumping of liquids or solids. The basic principle of a screw pump will first be explained using the Fig. 1 be explained.

[0003] In Fig. 1 A screw pump 1 is shown as an example in half section. Only the area of ​​the pump housing 2 and the spindles 3 and 4 located therein are shown. The drive of the drive spindle 3 is not shown.

[0004] The drive spindle 3 is driven by a drive at its end protruding from the pump housing 2. The running spindle 4, which is arranged in the pump housing 2 parallel to the drive spindle 3 and is not equipped with its own drive, is driven by the drive spindle 3. In the Fig. 1 In the screw spindle pump 1 shown, there is only one running spindle 4 in the pump housing 2, but it is also conceivable to install a central drive spindle 3 with several running spindles 4.

[0005] Torque is generally transmitted from the drive spindle 3 to the idler spindle 4 via a hydrodynamic lubricating film, thus avoiding direct contact between the drive spindle 3 and the idler spindle 4. When conveying solids, torque is transmitted via an additional gear due to the lack of a hydrodynamic lubricating film. However, since the present invention relates to a screw pump for conveying fluids, the design of a screw pump suitable for conveying solids will not be discussed in detail.

[0006] During operation of the screw spindle 1, delivery chambers are formed between the drive spindle 3, the idler spindle 4 and the pump housing 2. Due to the rotation of the two spindles 3, 4, these move continuously from the suction side in the area of ​​the inlet 5 to the pressure side in the area of ​​the outlet 6. This creates a negative pressure which causes the medium to be pumped to be sucked in.

[0007] Starting from the inlet, which is not visible due to the sectional view, the fluid to be pumped flows through the inlet 5 into the pump housing 2. There, it comes into contact with the spindles 3, 4 and enters the pumping chambers, which move toward the outlet 6. The fluid is transported via the pumping chambers to the threadless area of ​​the spindles 3, 4, where it accumulates. Due to the continuous pumping, the fluid is finally pumped through the outlet 6 toward the outlet 7.

[0008] As a result of the pressure increase during the pumping process, axial forces act on the spindles 3, 4. STATE OF THE ART

[0009] To support these axial forces acting on the spindles, appropriate axial bearings are required. Screw pumps used to pump fluids typically employ hydrostatic axial bearings. The axial bearing must be designed and constructed in such a way that the axial forces acting on the spindle are transmitted to the axial bearing, if possible, only via a lubricating film. Solid friction or mixed friction between the spindle and the axial bearing should be avoided during operation of the screw pump.

[0010] To prevent solid-body friction and mixed friction, a sufficiently thick lubricating film must always be present in the thrust bearing. This is achieved by continuously applying an appropriate lubricant to the thrust bearing. The use of thrust bearings therefore involves high lubricant consumption.

[0011] The fluid being pumped itself is therefore typically used as the lubricant. This also has advantages when screw pumps are used in areas such as the food industry, where the use of lubricants that differ from the fluid being pumped would result in an intolerable risk of contamination. By using the fluid being pumped as the lubricant for the thrust bearing, the risk of contamination, or rather the design effort required to avoid such a risk, is eliminated.

[0012] DE 10 2006 049663 A1 discloses a screw pump with a hydrostatic axial bearing in which the fluid to be pumped is used as a lubricant.

[0013] However, this in turn leads to problems if a screw spindle pump is to be used for pumping different fluids with different viscosities. If the axial bearing is designed for a high-viscosity fluid, for example, the lubricant may escape from the lubrication point too quickly when a low-viscosity fluid is to be pumped. If the bearing is designed for low-viscosity fluids, however, pumping high-viscosity fluids may result in excessive friction in the bearing because the lubricant escapes from the lubrication point too slowly. Both of these effects lead to increased wear on the bearing or spindle, thus reducing the service life of the spindle and shortening the required maintenance intervals. THE PROBLEM UNDERLYING THE INVENTION

[0014] In view of this, the object of the invention is to provide a screw pump in which the influence of the viscosity of the medium to be pumped on the service life of the screw pump is reduced. THE INVENTIVE SOLUTION

[0015] According to the invention, this problem is solved with the features of the main claim directed to the screw spindle pump.

[0016] Accordingly, the problem is solved with a screw pump with a pump housing in which a pump spindle is mounted with the participation of a hydrostatic axial bearing. The axial bearing serves to absorb the axial thrust generated on the spindle during operation. It is formed by a bearing surface fixed to the housing, against which a front-end, spindle-fixed bearing surface of the pump spindle is indirectly supported. Support is achieved by the housing-fixed and spindle-fixed bearing surfaces forming a bearing gap between them, the central area of ​​which is fed with a pressurized fluid whose hydrostatic pressure counteracts the axial thrust. The pressurized fluid flows radially through the bearing gap. It preferably flows into the suction area of ​​the screw pump. The screw pump is characterized by the fact that the pump spindle comprises an actuating element.The actuator mechanically opens or closes a valve that controls the flow of pressurized fluid into the bearing gap depending on the current axial position of the spindle.

[0017] The axial forces acting on the spindle during operation of the screw pump push the spindle toward the axial bearing. The spindle-mounted bearing surface presses against the pressurized fluid in the bearing gap. If the pressurized fluid has a low viscosity and flows relatively quickly out of the bearing gap, the pressurized fluid in the bearing gap does not develop a sufficiently high static pressure, i.e., no pressure sufficient to hold the spindle in its current axial position. The spindle then moves toward the axial bearing, and the height of the bearing gap filled with pressurized fluid between the spindle-mounted bearing surface and the housing-mounted bearing surface decreases.

[0018] Starting from an initial position of the spindle in which the valve is closed, the axial displacement of the spindle causes the valve to open via the actuator. The opening and closing movement of the valve preferably occurs continuously.

[0019] The valve then opens, allowing a volume flow of pressurized fluid to flow into the bearing gap. As soon as this flow equals the volume flow of the pressurized fluid flowing out of the bearing gap, a force equilibrium is established in the bearing gap. The force resulting from the pressure of the fluid in the bearing gap is equal in magnitude to the axial force resulting from the axial thrust to which the spindle is subjected, which acts in the opposite direction. This stops the spindle's axial movement.

[0020] To achieve the process described in the previous section, the axial bearing, the valve, and the actuating element must be coordinated in such a way that a force equilibrium is established that stops the axial spindle movement before the spindle partially contacts the bearing surface of the axial bearing, which is fixed to the housing. If the spindle partially contacts the bearing surface, which is fixed to the housing, the force is introduced directly and no longer indirectly via the pressurized fluid, which induces wear. This can be achieved by reaching the spindle position required for full opening of the valve earlier than the spindle position in which the spindle contacts the axial bearing, so that even taking the dynamic component of the spindle movement into account, the spindle cannot contact the bearing surface, which is fixed to the housing.If it cannot be completely ruled out that the spindle may occasionally come into contact with the bearing surface fixed to the housing, it is advantageous to provide a corresponding thrust ring on the bearing surface fixed to the housing, which is best made of a bearing metal that can withstand solid or mixed friction, at least temporarily.

[0021] If the axial bearing is also intended to generate a counter-movement of the spindle—away from the axial bearing—when the spindle is already tightly seated against the bearing surface fixed to the housing, the pressurized fluid can be pressed into the bearing gap at increased pressure using an additional pump to force the spindle to initially lift off the bearing surface fixed to the housing. For this purpose, the bearing surface fixed to the spindle and the bearing surface of the axial bearing fixed to the housing should have a gap between them, even when the spindle is in contact with the bearing surface fixed to the housing.

[0022] The term "pump spindle" preferably, but not exclusively, refers to a running spindle. It is also conceivable that the "pump spindle" referred to here refers to the drive spindle.

[0023] Contrary to the above wording, according to which "a" pump spindle is mounted in the pump housing with the participation of a hydrostatic axial bearing, the invention also relates to a screw spindle pump with a drive spindle and one or more idler spindles, of which one, several or all are mounted with the participation of a hydrostatic axial bearing.

[0024] The term "in the radial direction" in which the pressure fluid in the bearing gap flows describes that the pressure fluid, starting from the central area of ​​the bearing gap into which it is fed, initially flows radially outward into the edge area of ​​the bearing gap. However, it is entirely conceivable that the pressure fluid is deflected in the edge area of ​​the bearing gap and then flows in a different direction.

[0025] The "suction area" of the screw pump is the area in which the fluid to be pumped is located, which has not yet reached the pumping chambers.

[0026] According to the claimed invention, the actuating element is a pin. As soon as the bearing gap falls below a certain gap height due to an axial displacement of the pump spindle, the pin opens the valve or opens it further.

[0027] The pin is preferably connected to the spindle-fixed bearing surface of the pump spindle and protrudes through the bearing gap toward the valve. The valve is then actuated by the pin through a corresponding movement of the pump spindle toward the bearing gap. PREFERRED DESIGN OPTIONS

[0028] There are a number of ways to design the invention in such a way that its effectiveness or usefulness is further improved.

[0029] It is particularly preferred that the valve is operated as a throttle valve, the degree of opening of which controls the hydrostatic pressure in the bearing gap.

[0030] Since the valve opens depending on the axial position of the spindle, the displacement of the spindle towards the axial bearing not only results in a continuous opening of the valve, but the pressurised fluid also flows into the bearing gap at higher pressure, which is why the hydrostatic pressure in the bearing gap increases instantly. As soon as the volume flow flowing into the bearing gap and the volume flow of the pressurised fluid flowing out of the bearing gap are in equilibrium, a substantially hydrostatic stress state develops in the pressurised fluid. This in turn results in an equilibrium of the axial forces acting in the axial bearing and the axial spindle movement stops. The valve position then remains constant until the axial force acting on the spindle either increases or decreases as a result of the pumping process.If the axial force increases, the spindle moves further toward the axial bearing, the valve opens further, and, as a result of the processes already described, a force equilibrium is restored, stopping the axial spindle movement. If the axial force on the spindle decreases, the spindle moves away from the axial bearing, so that the valve's opening angle decreases, and a force equilibrium is restored.

[0031] Preferably, the valve consists of a valve ball that is pressed onto a valve seat by the pressurized fluid. The valve ball then blocks the inlet opening located in the center of the valve seat, which leads to the bearing gap. If necessary, the valve ball is lifted or further lifted from its valve seat by the pin that passes through the inlet opening.

[0032] The area into which the valve ball is moved by the pin or actuator when the valve is opened is preferably designed so that the pressurized fluid flowing through the valve flows around the valve ball. As soon as the spindle moves away from the axial bearing and the valve ball is no longer held at a distance from the valve seat by the actuator, the flow ensures that the valve ball is pushed back onto the valve seat.

[0033] In a further preferred embodiment, the housing-mounted bearing surface is formed at the bottom of a bearing cup. A bearing journal of the pump spindle engages the bearing cup at its end, forming a spindle-mounted bearing surface on the front side. The bearing journal engages the bearing cup in such a way that the outer peripheral surface of the bearing journal and the inner peripheral surface of the bearing cup form an annular gap seal. The pressurized fluid flows out of the bearing gap in a throttled manner via the annular gap seal. It preferably flows into the intake area.

[0034] The bearing journal is ideally formed by an area of ​​the spindle whose diameter is smaller than the adjacent section of the spindle due to a shaft shoulder.

[0035] The end face of the bearing journal facing the axial bearing then represents the spindle-fixed bearing surface, which together with the bottom surface of the bearing cup forms the axial bearing.

[0036] Thanks to the annular gap seal, the volume flow of the pressure fluid flowing out of the bearing gap is kept relatively low. As a result, the volume flow required to generate the necessary pressure of the pressure fluid in the bearing gap and flowing into the bearing gap is also relatively low.

[0037] Starting from the suction area, into which the pressure fluid flows from the bearing gap via the annular gap seal, it is mixed with the fluid to be pumped which is fed to the screw spindle pump.

[0038] The term "bearing cup" describes a cylindrical hollow body open on one side, with the side of the hollow body opposite the open side having a closed bottom. In the bottom (preferably in its center) of the bearing cup, there is a bore (a hole, a cutout) through which the pin or actuating element passes.

[0039] Ideally, the bearing cup rests axially against a wall of the pump housing, but is not positively fixed to the pump housing in the radial direction.

[0040] The axial force acting on the spindle as a result of the pumping process, supported in the thrust bearing, presses the bearing cup directly or indirectly against the pump housing. Due to the resulting static friction between the bearing cup and the pump housing or the element located between the pump housing and the bearing cup, the bearing cup is sufficiently secured against slipping.

[0041] The fact that the bearing cup rests axially against "a wall of the pump housing" does not exclude the possibility that there is another element between the pump housing and the bearing cup, into which the valve seat of the valve ball described above is inserted. In this case, the additional element is considered a component of the pump housing.

[0042] In a further preferred embodiment, the bearing cup rests axially against a wall of the pump housing and is positively secured in the radial direction relative to the pump housing. The positively secured radial direction is achieved, for example, by pins or screws.

[0043] This further reduces the risk of the thrust bearing slipping. This is particularly advantageous when the pressure fluid has a high viscosity. Highly viscous pressure fluids can sometimes cause shear stresses in the area of ​​the pressure fluid in the bearing gap adjacent to the spindle-fixed bearing surface. In an unfavorable case, this can lead to a flow within the pressure fluid in the bearing gap, which, due to fluid friction in the area between the housing-fixed bearing surface and the pressure fluid, causes a rotational movement of the bearing cup. This is prevented by a positive-locking fixation of the bearing cup to the pump housing.

[0044] The positive locking of the bearing cup relative to the pump housing does not preclude the provision of an additional element between the pump housing and the thrust bearing, such as a plate containing the valve seats. In this case, the additional element is considered a component of the pump housing.

[0045] Preferably, the outer peripheral surface of the bearing journal and the inner peripheral surface of the bearing cup form a hydrodynamic radial bearing.

[0046] The pressure fluid flowing out of the bearing gap via the gap between the outer peripheral surface of the bearing journal and the inner peripheral surface of the bearing cup forms the necessary lubricating film to prevent solid or mixed friction.

[0047] In a further preferred embodiment, the pressure fluid is the fluid pumped by the screw pump, which is taken from the pressure side of the screw pump.

[0048] For this purpose, a portion of the pressurized fluid from the discharge side of the screw pump is ideally directed back toward the suction side via a channel in the pump housing. There, after flowing through the valve, it is fed to the bearing gap.

[0049] Preferably, the bearing journal has a reduced diameter compared to the immediately adjacent pump spindle area.

[0050] This ensures that, in the unfortunate event that the spindle comes into contact with the thrust bearing, the shaft shoulder between the bearing journal and the remaining spindle area rests against the thrust bearing. This ensures that the housing-mounted and spindle-mounted bearing surfaces of the thrust bearing never touch each other and wear out. Furthermore, a certain bearing gap is always kept open, into which the pressure fluid can flow.

[0051] In addition, the response behavior of the axial bearing can be adjusted via the selected diameter of the bearing journal.

[0052] Further optional modes of operation, advantages and design possibilities arise from the description of the embodiment based on the figures. LIST OF FIGURES

[0053] Fig. 1 shows a typical screw pump in half section. Fig. 2shows the area of ​​the axial bearing in a sectional view, whereby the spindle is not yet subjected to an axial force. Fig. 3 shows the area of ​​the axial bearing in a sectional view, with the spindle subjected to an axial force. EXAMPLE OF IMPLEMENTATION

[0054] The basic functionality of the generic screw pumps is already explained at the beginning using the Fig. 1 explained, reference is made to this.

[0055] The inventive further development of the screw pump is exemplified by the Figures 2 and 3 explained, but also with a side view of the starting point Fig. 1 .

[0056] First, the principle of the axial bearing 8 according to the invention and of the valve 15 will be explained in general terms.

[0057] During operation of the screw pump 1, a pressure acting on the fluid to be pumped is generated on the pressure side of the screw pump 1. This results in an axial force acting on the impeller spindle 4, which, in Fig. 2 from right to left, towards the axial bearing 8.

[0058] The axial bearing 8 comprises a housing-fixed bearing surface 9 and a spindle-fixed bearing surface 10.

[0059] The housing-fixed bearing surface 9 is formed here by the bottom of a bearing cup 12. The spindle-fixed bearing surface 10 is usually formed by the end face of a bearing journal 13. A bearing gap 11 is always present between the two bearing surfaces 9 and 10. Even if the spindle 4 were to rest against the axial bearing 8 with its shoulder 25, which is usually not the case during fault-free operation of the screw spindle pump 1, the two bearing surfaces 9 and 10 do not normally touch each other.

[0060] A pressure fluid flows into the bearing gap 11 via the return channel 23 as well as the chamber 24 and the inlet opening 18 of the valve 15, which in this embodiment is a part of the fluid to be pumped on the pressure side of the screw spindle pump 1.

[0061] At the same time, the pressure fluid in the bearing gap 11 initially flows radially outward. It then flows out of the bearing gap 11 via the gap between the bearing cup 12 and the bearing journal 13.

[0062] As long as the volume flow flowing into and out of the bearing gap 11 are equal, an at least approximately hydrostatic stress state will arise in the pressure fluid, at least in the central region of the bearing gap 11, when the impeller spindle 4 experiences axial thrust as a result of the pressure prevailing on the pressure side of the screw pump 1 and is thereby pressed toward the axial bearing 8. The spindle-fixed bearing surface 10 can then be supported indirectly via the pressure fluid on the housing-fixed bearing surface 9.

[0063] Without the actuating element in the form of the pin 14, the valve ball 16 would be moved toward the valve seat 17 by the pressurized fluid flowing through the chamber 24, closing the inlet opening 18 of the valve 15. As soon as the volume flow into the bearing gap 11 is reduced due to the valve ball 16 approaching the valve seat 17, more pressurized fluid flows out of the bearing gap 11 than flows into it.

[0064] In combination with the axial force acting on the spindle 4, this results in a movement of the spindle 4 in the direction of the axial bearing 8 and consequently a reduction in the distance between the bearing surfaces 9 and 10. However, the actuating element, in the form of the pin 14 located on the spindle-fixed bearing surface 10, is also moved together with the spindle 4 in the direction of the valve ball 16. During this process, the pin 14 eventually comes into contact with the valve ball 16 and prevents the valve ball 16 from completely closing the inlet openings 18, or pushes the valve ball 16 further into the chamber 24.

[0065] The movement of the spindle 4 and the pin 14 as a result of the pressure on the pressure side of the screw pump 1 in the direction of the axial bearing 8 continues until the valve ball 16 has been pushed by the pin 14 far enough into the chamber 24 that the volume flow flowing into the bearing gap 11 and the volume flow flowing out of the bearing gap 11 are in equilibrium. Then, an approximately hydrostatic state is again established in the pressure fluid in the bearing gap 11, and the spindle-fixed bearing surface 10 is supported indirectly via the pressure fluid on the housing-fixed bearing surface 9. The movement of the spindle 4 in the direction of the axial bearing is thereby stopped.

[0066] The volume flow flowing into the bearing gap 11 is therefore always automatically adjusted depending on the pressure prevailing on the pressure side of the screw spindle pump 1 and the position of the spindle 4 in such a way that a state of equilibrium is created.

[0067] In Fig. 2 a state of the screw spindle pump 1 is shown in which no pressure is yet exerted on the pressure side on the fluid pumped by the screw spindle pump 1. Therefore, no axial force pushing the idler spindle 4 in the direction of the axial bearing 8 acts on the idler spindle 4. Furthermore, the fluid located in the return channel 23 is not yet under pressure. As long as no axial force acts on the idler spindle 4, the distance between the bearing cup 12 of the axial bearing 8 and the shaft shoulder 25 at the transition between the bearing journal 13 and the rest of the idler spindle 4 is still relatively large. Furthermore, the actuating element designed as a pin 14 is not yet in contact with the valve ball 16 of the valve 15. Since there is no flow in the return channel 23 and the chamber 24, the valve ball 16 rests on the bottom of the chamber 24 due to gravity and not on the valve seat 17 of the valve.

[0068] In Fig. 3The state of the spindle pump 1 is shown in which the spindle 4 has already been moved towards the axial bearing 8 as a result of a pressure prevailing on the pressure side of the spindle pump 1. There is only a minimal gap between the shaft shoulder 25 and the bearing cup 12, which Fig. 3 cannot be seen. The pin 14 is already in contact with the valve ball 16 and lifts it off the valve seat 17.

[0069] The valve seat 17 of the valve 15 and the inlet opening 18 are incorporated into a wall element 19, which is located between the remaining pump housing 2 and the bearing cup 12. The bearing cup 12 is secured against slipping or twisting along the wall element 19 by a pin 20. Axial securing of the bearing cup 12 relative to the wall element 19 is not necessary, since the forces resulting from the axial bearing 8 always push the bearing cup 12 toward the wall element 19. An O-ring seal 22 is located between the wall element 19 and the remaining pump housing.

[0070] The bearing cup 12 and the bearing journal 13, in interaction with the pressure fluid, which flows out of the bearing gap 11 through the gap between the bearing cup 12 and the bearing journal 13, form a hydrodynamic radial bearing 21 for the spindle 4. LIST OF REFERENCE SYMBOLS

[0071] 1Screw pump 2Pump housing 3Drive spindle 4Idler spindle 5Inlet 6Outlet 7Outlet 8Thrust bearing 9Housing-fixed bearing surface 10Spindle-fixed bearing surface 11Bearing gap 12Bearing cup 13Bearing journal 14Actuator / pin 15Valve 16Valve ball 17Valve seat 18Inlet opening 19Wall element of the pump housing 20Pin for fastening the bearing cup 21Radial bearing 22O-ring 23Return channel 24Chamber 25Shaft shoulder

Claims

1. A screw pump (1) with a pump housing (2), in which a pump spindle (3, 4) is rotatably mounted in cooperation with a hydrostatic thrust bearing (8) for absorbing the axial thrust, which is produced at the spindle (3, 4) during operation, wherein the hydrostatic thrust bearing (8) is formed by a housing-fixed bearing surface (9), against which an end-face, spindle-fixed bearing surface (10) of the pump spindle (3, 4) is indirectly supported, in that the housing-fixed bearing surface (9) and the spindle-fixed bearing surface (10) form a bearing gap (11) therebetween, which, in its central region, is fed with a pressure fluid, which flows out through the bearing gap (11) in the radial direction - preferably into the suction region - and the hydrostatic pressure of which counteracts the axial thrust, wherein the pump spindle (3, 4) comprises an actuating element (14), which, as a function of the current axial position of the spindle (3, 4), mechanically opens or closes a valve (15), which controls the inflow of pressure fluid into the bearing gap (11), characterized in that the actuating element (14) is a pin, which opens or further opens said valve (15) as soon as the bearing gap (11) falls below a certain gap height due to an axial displacement of the pump spindle (3, 4).

2. The screw pump (1) according to claim 1, characterized in that the valve (15) is operated as throttle valve, the opening degree of which controls the hydrostatic pressure in the bearing gap (11).

3. The screw pump (1) according to claim 1 or 2, characterized in that the valve (15) consists of a valve ball (16), which is pushed onto a valve seat (17) assigned thereto by means of the pressure fluid and then blocks the inflow opening (18), which is located in the center of the valve seat (17) and which leads to the bearing gap (11) and which, if necessary, is lifted off its valve seat (17) by means of the pin (14), which engages through the inflow opening (18), or is further lifted off its valve seat (17).

4. The screw pump (1) according to one of the preceding claims, characterized in that the housing-fixed bearing surface (9) is formed on the bottom of a bearing pot (12), with which an end-side bearing journal (13) of the pump spindle (3, 4), which forms a spindle-fixed bearing surface (10) on the end face, engages in such a way that the outer circumferential surface of the bearing journal (13) and the inner circumferential surface of the bearing pot (12) form an annular gap seal, via which the pressure fluid flows out of the bearing gap (11) in a throttled manner -preferably into the suction region.

5. The screw pump (1) according to claim 4, characterized in that the bearing pot (12) rests axially against a wall (19) of the pump housing (2), but is not fixed in a positive manner with respect to the pump housing (2) in the radial direction.

6. The screw pump (1) according to claim 4, characterized in that the bearing pot (12) rests axially against a wall (19) of the pump housing (2) and is fixed in a positive manner with respect to the pump housing (2) in the radial direction, for instance by means of pins (20) or screws.

7. The screw pump (1) according to claim 6, characterized in that the outer circumferential surface of the bearing journal (13) and the inner circumferential surface of the bearing pot (12) form a hydrodynamic radial bearing (21).

8. The screw pump (1) according to one of the preceding claims, characterized in that the pressure fluid is the fluid pumped by the screw pump (1) and which is removed from the pressure side of the screw pump (1).

9. The screw pump (1) according to claim 4, characterized in that the bearing journal (13) has a decreased diameter with respect to the immediately adjacent pump spindle region.

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