EP2961988B1 - Screw pump with at least two parts - Google Patents

Description

The present invention relates to a screw pump formed from at least two parts.

A screw pump is a so-called positive displacement pump, in which the shape of the rotating displacement resembles that of a spindle screw. The screw pump consists of two or more rotors rotating in opposite directions and a pump housing that encloses the rotors. The rotors are designed with a regular, thread-shaped profile and mesh like a gear. The rotors are also referred to as screw spindles and have at least a first shaft section and a profile section with a helical screw profile. The cavities, which are formed by the three construction elements pump housing, first screw spindle and second screw spindle, form the pumping spaces for the pumping medium. When the screw spindles turn, the pumping chambers migrate in a machine direction and convey the medium within the pump housing from the suction side (= inlet) to the pressure side (= outlet).

This type of pump is particularly suitable for incompressible, also viscous media and for generating high pressures. Screw pumps are used to transport both single-phase and multi-phase liquids. The three-spindle screw pump is mainly used for pumping lubricating fluids that are free from abrasives. It is characterized in particular by the fact that it is possible to generate high pressures of up to 160 bar with it.

In three-spindle screw pumps, the three spindles are usually arranged in such a way that a drive spindle located in the middle (also known as the main rotor) drives two laterally engaging secondary spindles. The drive spindle, for its part, is connected to a drive motor, which can be designed both as an electric motor and as an internal combustion engine. In embodiments known from the prior art, the torque generated by the drive is transmitted from the drive spindle to the driven spindles via the spindle profile. The interlocking spindle profiles create closed pumping chambers in which the pumping medium is enclosed and transported in the axial direction from the suction to the pressure side.

In order to reduce the loads acting on the main rotor, the secondary rotors can be positioned in the pump housing at an angle of 180 ° from the axis of rotation of the main rotor, which balances the radial force acting on the main rotor.

The prior art already knows pumps in which liquid is transported via a stationary inlet to an outlet by means of the pump under pressure.

Such a pump is for example from the WO 2011/063870 A2 known. The WO-Offenlegungsschrift shows a screw spindle pump with a pump housing and a flange section, the flange section being designed as a stationary component of the pump housing. The pump housing must therefore be oriented together with its flange section with regard to the position of a corresponding counter-flange.

Such a screw pump is also disclosed in the document U.S. 2,924,181 A known.

The object of the invention is therefore to provide a screw pump which has increased flexibility with regard to its possible installation.

The above object is achieved by a screw pump which comprises the features in claim 1. Further advantageous refinements are described by the subclaims.

The invention relates to a screw spindle pump formed from at least two parts for pumping conveying media. In preferred embodiments, the delivery media are formed by fluid media, such as lubricants, water, suspensions or the like. In connection with the present invention and the screw spindle pump according to the invention, the term “pumping” is to be understood as a process in which the conveying medium is transported and pressurized.

The first of the at least two parts of the screw pump comprises a housing and at least one spindle system arranged in the housing and drivable in a rotationally movable manner. The spindle system comprises a main drive spindle, which is coupled to one or more further auxiliary spindles which can be driven in a rotationally movable manner by the main drive spindle. In particular, the main drive spindle is coupled to the respective auxiliary spindle via the respective spindle profile that follows the toothing law.

The main drive spindle is preferably driven by one or more actuators. The one or more actuators can be designed, for example, as an electric and / or internal combustion engine. In various embodiments, the rotation frequency of the main drive spindle can be predefined in a defined manner via the one or more actuators and, if necessary, can be adapted to the respective delivery medium and the desired delivery rate.

The first part further comprises a pressure area downstream of the spindle system and at least one outlet opening connected to it, which discharges the conveying medium from the pressure area. The pumped medium is thus conveyed into the pressure area via the spindle system. The outlet opening is designed, for example, as a bore in the housing and / or as a channel in the housing. It is conceivable, for example, that the outlet opening is designed as a through-hole in the housing, which is angled against the axis of rotation of the main drive spindle and opens into the pressure area. According to a further embodiment, the outlet opening is designed as a through-hole which is perpendicular to the axis of rotation of the main drive spindle and opens into the pressure area.

The second part of the screw pump further comprises at least one low-pressure chamber arranged upstream of the spindle system and at least one inlet opening for the fluid medium into the low-pressure chamber. With regard to their diameter, it is conceivable that the at least one outlet opening and the at least one inlet opening are designed to be identical or different. The second part and the first part are preferably connected to one another in a sealed manner, so that no conveying medium can inadvertently escape from the low-pressure chamber of the screw pump.

According to the invention, it is provided that the first part and the second part of the screw pump are coupled to one another so as to be rotatable in order to assume at least two different relative positions.

For example, it is conceivable that the inlet opening and the outlet opening are designed as an inlet channel and as an outlet channel, with a parallel course of the inlet channel and the outlet channel in a first relative position. It can further be the case that in a second relative position a skewed course of the inlet channel and of the outlet channel is formed.

It is also conceivable that the first part and the second part are releasably connected to one another in the respective relative position. For example, it is conceivable that the detachable connection takes place via screw connections or the like. In addition, it is conceivable that during the operation of the screw pump, the first and the second part are held in the respective relative position, for example by means of shrink and / or adhesive and / or welded connections. In preferred embodiments, it can be the case that the first part and the second part are releasably connected to one another in their respective relative positions during operation of the screw pump.

In preferred embodiments, the first part and the second part are rotatably coupled to one another. For example, it is conceivable that the housing has a cylindrical shape, at least in sections, and the relative rotational movement of the first and second parts about a longitudinal axis of the cylindrically shaped housing or housing part can be produced.

It is also conceivable that the second part of the screw pump sits rotatably on the first part. For example, one of the two parts has contact means for this purpose and the other of the two parts has corresponding mating contact means, the contact means and mating contact means possibly engaging with one another.

It is also conceivable that a change from a first of the at least two relative positions to a second of the at least two relative positions can be brought about by means of a relative rotational movement of the first part with respect to the second part about a longitudinal axis, which longitudinal axis is designed as the axis of rotation of a main drive spindle of the spindle system. As already mentioned above, the main drive spindle can be defined as that spindle which is coupled to an actuator, such as an electric motor and / or internal combustion engine, for driving purposes. Alternatively, embodiments are possible in which the longitudinal axis is designed as the axis of rotation of another of the spindles.

In particular, embodiments have proven themselves in practice in which the low-pressure chamber of the second part has a shell-like shape at least in some areas. Such a shape improves the flow behavior of the delivery medium in the second part of the screw pump.

It is also conceivable that in the area of the inlet opening and / or in the area of the outlet opening a flange section for fixing to a corresponding counter flange is formed. The flange section in the area of the inlet opening or the flange section of the second part is thus preferably rotated together with the first part when the second part is rotated relative to the first part.

In order to limit overpressure in the pressure area, it is possible in various embodiments that the first part comprises at least one return channel, which at least one return channel is fluidically connected to the pressure area and to the low-pressure chamber. For example, it is conceivable that the return channel is designed to guide the conveying medium from the pressure area into the low-pressure chamber. In further embodiments, for example, there are several return channels of this type, which optionally run parallel to one another. In practice, embodiments in which one or more return ducts are oriented parallel to an axis of rotation of one or more drive spindles have proven particularly useful. It is also conceivable that the return channel leads from the pressure area in the direction of the low-pressure chamber and is closed at an end pointing in the direction of the low-pressure chamber. It is also conceivable that the return channel has, for example, a branching and / or deflection, which deflection leads in the direction of one or more means, which are described in more detail below, for limiting a predefined setpoint pressure level in the pressure area.

In order to be able to integrate the at least one return channel in the simplest possible manner during the manufacture of the screw pump, there is, for example, the possibility that the at least one return channel is formed by the housing of the first part. For example, the at least one return channel is designed as a bore in the housing which extends from the pressure area to the low-pressure chamber.

According to the invention, the screw pump comprises one or more means which are brought into operative connection with the low-pressure chamber and the pressure area in such a way that when a predefined pressure level in the pressure chamber is exceeded, a predefined maximum pressure level in the pressure chamber can be set via one or more means. It is conceivable that such means are arranged in the area of the low-pressure chamber. The means comprise one or more pressure relief valves.

In particular in the case of embodiments with the at least one return channel described above, there is the possibility that the means are brought into operative connection with the low-pressure chamber and the pressure area and are designed as part of the second part of the screw pump. Thus, in this embodiment, the means can be moved together with the second part as part of the second part when the first part and the second part are rotated relative to each other.

It is conceivable, for example, that the previously mentioned at least one return channel has a branch, with one branch continuing the conveying medium to the one or more means.

The one or more means can have a base body with a cavity, in which a piston is mounted such that it can move in a stroke against the restoring force of a compression spring, and have at least one bore arranged on the end face in the base body. A bolt coupled to the piston can be guided through the bore, preferably coaxially to the piston, and can be in contact with the respective conveying medium. The maximum cross section of the bolt is preferably designed to be reduced in area compared to the maximum cross section of the piston. Preferably, the maximum cross-section of the bolt is designed to be reduced in area to the minimum cross-section of the piston.

In addition, it is possible that the bore is designed as part of a front cover of the base body and the cover has one or more further openings, preferably arranged radially around the bore, for the delivery medium to enter the cavity of the base body. After entering via the one or more further bores, the conveying medium can come into direct contact with the piston and in particular with a head section of the piston described further below and push the bolt away from the one or more bores in a supporting manner against the restoring force of the spring.

If the piston moves or the piston executes a stroke movement, the delivery medium can penetrate into a cavity of the base body that becomes accessible from the stroke movement, which results in a pressure reduction in the pressure area or in the low-pressure chamber.

In principle there is the possibility of designing the one or more means as a valve, the valve being composed of a base body, a piston, a compression spring and a so-called pilot system. The pilot system is used to increase the pressure in a pressure range when a maximum pressure level is exceeded by opening and closing the valve. In this embodiment, the opening takes place under pressure from a control bolt. If there is pressure at an opening bore of the valve, pressure relief in the pressure area is achieved by opening the valve via the control bolt. The control bolt is connected to the aforementioned piston and preferably has a smaller cross-sectional area than the piston, which results in a reinforcing effect when the valve is opened.

If the pressure in the pressure range decreases, the piston in the described embodiment is moved into a seat of the valve by the force of the compression spring and closes a pressure opening through which the control pin is guided. At the same time, an opening or channel arranged laterally in the base body is opened, which is connected to the low-pressure chamber. The pressure level in the base body is thus reduced when the opening or the channel is opened and adapted to the pressure level of the low-pressure chamber.

There is thus the possibility that, if necessary, the one or more means comprise a base body with a cavity in which a piston is mounted so as to be movable against the restoring force of a compression spring and a bolt connected to the piston, whose maximum cross-section is reduced in area to the maximum cross-section of the Piston is formed when a predefined maximum pressure level is exceeded, is guided in the base body in a stroke-movable manner. As a result of the lifting movement, a lateral opening of the base body is preferably released for the return flow of the conveying medium from the pressure area into the low-pressure chamber.

It is therefore also conceivable that if the maximum pressure level in the pressure area is not exceeded, a head section of the piston is guided into a seat by means of the compression spring and the cavity of the base body is fluidically connected to the low-pressure chamber via the opening formed on the side of the base body, see above that the pressure level in the cavity of the base body is essentially identical to the pressure level in the low-pressure chamber.

It is also conceivable that the one or more means are designed as a component of the second part and have a rear cover which can be removed via one or more screw connections and which is arranged on an outside of the second part.

There is also the possibility that the one or more means have one or more setting means, accessible from the outside and preferably actuatable by means of a tool, for specifying the restoring force of the compression spring. For example, an external square or the like. Advantageously, the maximum pressure level in the low-pressure chamber or in the pressure area is adjusted by simply actuating the one or more setting means from outside, without having to replace components.

• Figur 1 zeigt eine schematische Perspektivansicht einer Ausführungsform einer erfindungsgemäßen Schraubenspindelpumpe;
• Figur 2 zeigt eine schematische Perspektivansicht des zweiten Teils der Schraubenspindelpumpe aus Figur 1;
• Figuren 3 zeigen eine schematische Draufsicht sowie eine schematische Seitenansicht des zweiten Teils aus Figur 2;
• Figuren 4 zeigen eine schematische Frontalansicht auf das zweite Teil aus den Figuren 2 und 3 sowie einen Querschnitt durch das zweite Teil;
• Figur 5 zeigt ein Ventil zum Einstellen eines Maximal-Druckniveaus indem Druckbereich der Schraubenspindelpumpe aus Figur 1;
• Figuren 6 zeigen eine Möglichkeit der Anordnung des Ventils aus Figur 5 in einem zweiten Teil einer Ausführungsform einer erfindungsgemäßen Schraubenspindelpumpe.

In the following, exemplary embodiments are intended to explain the invention and its advantages in more detail with reference to the accompanying figures. The proportions of the individual elements to one another in the figures do not always correspond to the real proportions, since some forms are simplified and other forms are shown enlarged in relation to other elements for better illustration.

• Figure 1 shows a schematic perspective view of an embodiment of a screw pump according to the invention;
• Figure 2 FIG. 11 shows a schematic perspective view of the second part of the screw pump from FIG Figure 1 ;
• Figures 3 show a schematic top view and a schematic side view of the second part from FIG Figure 2 ;
• Figures 4 show a schematic front view of the second part from FIG Figures 2 and 3 and a cross section through the second part;
• Figure 5 shows a valve for setting a maximum pressure level in the pressure area of the screw pump from Figure 1 ;
• Figures 6 show one way of arranging the valve Figure 5 in a second part of an embodiment of a screw pump according to the invention.

Identical reference symbols are used for identical or identically acting elements of the invention. Furthermore, for the sake of clarity, only reference symbols are shown in the individual figures which are necessary for the description of the respective figure. The illustrated embodiments merely represent examples of how the screw pump according to the invention can be designed and do not represent a final limitation.

Figure 1 shows a schematic perspective view of an embodiment of a screw pump 1 according to the invention. The screw pump 1 is formed from a first part 3 and a second part 5. The first part 3 comprises a housing 7. In the housing 7, a spindle system 4 is arranged, which in the present case is composed of a main drive spindle 9 and two further auxiliary spindles, of which one auxiliary spindle 10 in Figure 1 is recognizable. The first secondary spindle 10 and the further secondary spindles are coupled to the main drive spindle 9 in a rotationally movable manner and form moving conveying chambers for transporting a conveying medium in the conveying direction FR, with an operative connection with the main drive spindle. The main drive spindle 9 is coupled to an actuator (not shown), such as an electric motor, at its free end 11 emerging from the housing 7 of the first part 3. The axis of rotation R of the main drive spindle 9 is also indicated.

The first part 3 comprises a pressure area 15 and an outlet opening 13, which is brought into connection with the pressure area 15 in a way that removes the conveying medium from the pressure area 15. The delivery medium thus flows out of the pressure area 15 and out of the housing 7 of the first part 3 via the outlet opening 13. In the present case, the pressure area 15 is defined as that area via which the conveying medium is passed on from the spindle system 4 to the outlet opening 13. In further embodiments, a screw pump 1 can also have one or more pressure chambers which are arranged upstream of the outlet opening 13.

The embodiment of the Figure 1 also knows a return channel 21 as part of the screw pump 1. The return channel 21 is formed by the housing 7 of the first part 3 and is made as a bore in the housing 7 during a manufacturing process of the housing 7. Only one such return channel 21 is shown, but in further embodiments several such return channels 21 can also be introduced into the housing 7.

The return channel 21 connects the pressure area 15 of the first part 3 with the low-pressure chamber 16 of the second part 5, but is closed in the area of the low-pressure chamber 16 so that the conveying medium cannot flow back from the pressure area 15 into the low-pressure chamber 16. As below in Figure 6 Described in more detail below, the delivery medium is guided through the return channel 21 into a pressure chamber 43 or 43 ', which is designed as an annular channel, with a valve 2 (cf. Figure 5 ) is in communication.

Figure 1 shows an embodiment in which the outlet opening 13 is designed as an outlet channel, the return channel 21 having an orthogonal orientation to the outlet channel or to the outlet opening 13 and being connected to the outlet opening 13 or the outlet channel. The pressure area thus extends into the outlet opening 13 or into the outlet channel. The return channel 21 runs as a bore parallel to the axis of rotation R of the main drive spindle 9.

The screw pump 1 further comprises at least one low-pressure chamber 16 arranged upstream of the spindle system 4, which is shown in FIG Figure 1 Is shell-shaped. By means of the shell-shaped configuration, the flow behavior of the conveying medium entering the low-pressure chamber 16 as a volume flow and its transfer to the spindle system 4 are optimized.

An inlet opening 14 of the second part 5 is also shown. The conveying medium enters the low-pressure chamber 16 via the inlet opening 14. In the area of the inlet opening 14 and in the area of the outlet opening 13, a respective flange section 18 or 19 is formed for fixing to a corresponding counter-flange (not shown).

The first part 3 and the second part 5 are rotatably coupled to one another in order to assume two different relative positions. For this purpose, the second part 5 sits on the first part 3 in the present case.

Figure 1 shows a first relative position of the first and second parts 3 and 5, in which the conveying medium flows in a first flow direction SR1 through the inlet opening 14 into the low-pressure chamber 16 and flows out in a second flow direction SR2 through the outlet opening 13 from the housing 7 of the first part 3 , wherein the first flow direction SR1 and the second flow direction SR2 run parallel to one another. The axis of rotation R of the main drive spindle 9 is also designed as an axis of rotation D for the relative rotation of the first and second parts 3 and 5. The flange sections 18 and 19 of the first and second parts 3 and 5 can thus be adapted to the position of a corresponding counter flange by means of a relative rotation of the first and second parts 3 and 5. A higher flexibility with such a configuration of a screw pump 1 according to the invention is guaranteed.

Figure 2 FIG. 10 shows a schematic perspective view of the second part 5 of the screw pump 1 from FIG Figure 1 . It is easy to see in Figure 2 Again the flange section 18 and the inlet opening 14 of the second part 5. In addition, a valve 2 is shown, which is also designed as a component of the second part 5 and to which valve 2 is shown in detail below in Figure 5 is received. The valve 2, the inlet opening 14 and the flange section 18 are in the relative rotational movement of the first part 3 (cf. Figure 1 ) to the second part 5 as part of the second part 5 together with the second part 5.

Figures 3 show a schematic top view ( Figure 3A ) and a schematic side view ( Figure 3B ) of the second part 5 Figure 2 . Are shown in Figure 3A The flange section 18 and the inlet opening 14 of the second part 5 are again clearly visible in FIG Figures 3 a rear cover 23 and adjustment means 25 of the in Figure 5 valve 2 shown in detail. The rear cover 23 is arranged on an outside of the second part 5 and can optionally be fixed there via connections such as screws or the like and / or received in the second part 5 in a form-fitting manner. Via the setting means 25, which is accessible from the outside and designed as an external square, a restoring force of the in Figure 5 illustrated compression spring 27 of the valve 2 can be specified or adjusted.

Figures 4 show in Figure 4A a schematic front view of the second part 5 from FIG Figures 2 and 3 . Next is in Figure 4B a cross section through the second part 5 along the section line BB Figure 4A shown.

The cross section of the Figure 4B again clarifies the arrangement of the valve 2 in the second part 5. As in FIG Figure 4B the low-pressure chamber 16 and the valve for the transfer of the conveying medium are shown fluidically connected to one another. The conveying medium can, for example, via a return channel 21 (comparatively Figure 1 ) are passed on to valve 2.

Figure 5 shows a valve 2 for setting a maximum pressure level in the pressure area 15 of the screw pump 1. The valve 2 is designed as a so-called overpressure valve or safety valve. The valve 2 is part of the second part 5. When the first part 3 and the second part 5 are rotated relative to each other, the valve 2 also rotates together with the second part 5.

With regard to its function, the valve 2 is designed in such a way that when a predefined pressure level is exceeded in the pressure area 15, a predefined maximum pressure level can be produced in the pressure area 15 via the valve 2.

In the embodiment of Figure 5 the valve 5 comprises a base body 35 with a cavity H. In the cavity H, a piston 31 is mounted such that it can move in a stroke against the restoring force of a compression spring 27. A plurality of bores 44 are shown in a front cover 41 of the base body 35, a control bolt 39 guided through the cover 41 guiding the piston 31 coaxially over the bore provided at the end. In the present case, the control bolt 39 is fastened through a central bore 44 in the cover 41, several further openings or bores 44 being provided radially around the central bore in the cover 41 of the base body 35.

As in Figure 5 It can also be seen that the maximum cross section of the bolt 39 is designed perpendicular to the respective longitudinal axis with a reduced area in relation to the maximum cross section of the piston 31.

In addition, the piston 31 comprises a head section 33 at a free end pointing in the direction of the bore 44. When the valve 2 or the pressure relief valve is assembled, the head section 33 is received in the cavity H of the base body 35 without play. In addition, a lateral opening 37 is shown in the base body 35, through which the head section 33 of the piston 31 is guided when a lifting movement is carried out.

Until the maximum pressure level is reached in the pressure area 15, the piston 31 does not perform any stroke movement. The head section 33 is arranged in a seat S of the front cover 41 resulting from a restoring force of the compression spring 27. For example, the seat S of the front cover 41 can be such that the head section 33 can be received in the seat S essentially without play.

The conveying medium can penetrate through the lateral opening 37. The pressure level of the delivery medium penetrating into the lateral opening 37 is always identical to the actual pressure level in the low-pressure chamber 16 or in the pressure region 15. If the piston 31 executes a stroke movement by exceeding the maximum pressure level and the head section 33 of the piston 37 leaves the seat S, the conveying medium with excess pressure can penetrate through the return duct 21, the bore 44 and the radially attached openings of the control pin 39 and the stroke movement of the Support piston 31 against the restoring force of the compression spring 27 in addition to to open the path into the cavity H of the base body 35 via the opening 37 into the low-pressure chamber 16 following the conveying medium.

As mentioned before and also in the Figures 3 and 4th As can be seen, the rear cover 23 is arranged on an outside of the second part 5. The restoring force of the compression spring 27 can be specified via the setting means 25.

About the next in Figure 5 The fixing means 29 shown - in the present case designed as screw connections - the individual components of the valve 2 can be assembled.

Figures 6 show one possibility of the arrangement of the valve 2 from Figure 5 in a second part 5 of an embodiment of a screw pump 1 according to the invention.

First clarified Figure 6A a possible option for the flow of the pumped medium by means of an arrow representation. The conveyed medium enters the low-pressure chamber 16 of the second part 5 as a volume flow via the inlet opening 14 and is then transferred in the direction of the arrow via the spindle system 4 (cf. Figure 1 ) transported to the outlet opening 13.

The embodiment of the Figures 6 has two return channels 21 and 21 ', which return channels 21 and 21' have a parallel course. Each of the return channels 21 and 21 'leads in the direction of a pressure chamber 43 and 43', respectively, with each pressure chamber 43 and 43 'having a valve 2, as in FIG Figure 5 exemplified, is in connection.

Figure 6B also shows that the pumped medium is transferred directly to the in Figure 5 The opening 37 of the valve 2 shown can flow into the low-pressure chamber 16 of the second part 5. Next is the cavity H of the valve 2 respectively. of the base body 35 is fluidically connected directly to the low-pressure chamber 16 via the opening 37.

The invention has been described with reference to a preferred embodiment. However, it is conceivable for a person skilled in the art that modifications or changes can be made to the invention without departing from the scope of protection of the following claims.

Reference list

1

Screw pump

2

Valve

3

First part

4th

Spindle system

5

Second part

7th

casing

9

Main drive spindle

10

Secondary spindle

11

Free end

13

Outlet opening

14th

Inlet opening

15th

Pressure area

16

Low pressure chamber

18th

Flange section

19th

Flange section

21st

Return channel

23

Rear lid

25th

Adjustment means

27

Compression spring

29

fixer

31

piston

33

Head section

35

Base body

37

Side opening

39

Control pin

41

Front lid

43

Pressure chamber

44

drilling

D.

Axis of rotation

FR

Conveying direction

H

cavity

R.

Axis of rotation

S.

Seat

SR

Direction of flow

Claims (14)

1. A screw pump (1) formed from at least two parts (3, 5) for pumping conveyed media such as lubricating fluids, water, suspensions or suchlike, wherein

   - the first part (3) comprises a housing (7) and at least one spindle system (4), which spindle system (4) is arranged in the housing (7) and can be driven in rotation, a pressure region (15) located downstream of the spindle system (4) and at least one outlet opening (13), which outlet opening (13) is connected to the pressure region (15) in a manner that removes the conveyed medium from the pressure region (15) and wherein

   - the second part (5) comprises at least one low-pressure chamber (16) located upstream of the spindle system (4) and at least one inlet opening (14) for the entry of the conveyed medium into the low-pressure chamber (16), wherein the first part (3) and the second part (5) are preferably rotatably coupled to one another so as to occupy at least two different relative positions, the screw pump (1) characterised in that
   the screw pump (1) comprises one or more means (2), which comprise one or more pressure relief valves and which are brought into an operative connection with the low-pressure chamber (16) and the pressure region (15), in such a way that, when a predefined pressure level in the pressure region (15) is exceeded, a predefined maximum pressure level in the pressure region (15) can be adjusted by the one or more means (2).
2. The screw pump (1) according to claim 1, wherein the second part (5) of the screw pump (1) sits rotatably on the first part (3).
3. The screw pump (1) according to claim 1 or claim 2, wherein a change from a first of the at least two relative positions into a second of the at least two relative positions can be brought about by means of a relative rotary motion of the first part (3) with respect to the second part (5) about a longitudinal axis (D), which longitudinal axis is constituted as a rotary axis (R) of a main drive spindle (9) of the spindle system (4).
4. The screw pump (1) according to one or more of claims 1 to 3, wherein the low-pressure chamber (16) of the second part (5) has a bowl-shaped design at least in sections.
5. The screw pump (1) according to one or more of claims 1 to 4, wherein a flange section (18, 19) for fixing to a corresponding counter-flange is constituted in the region of the inlet opening (14) and/or in the region of the outlet opening (13).
6. The screw pump (1) according to one or more of claims 1 to 5, wherein the first part (3) comprises at least one return channel (21), which return channel (21) is brought into fluidic connection with the pressure region (15) and with the low-pressure chamber (16).
7. The screw pump (1) according to claim 6, wherein the at least one return channel (21) is passed through the housing (7) of the first part (3).
8. The screw pump (1) according to claim 6 or claim 7, wherein the at least one return channel (21) runs parallel to the rotary axis (R) of one or more spindles (9, 10) of the spindle system (4).
9. The screw pump (1) according to claim 1, wherein the means (2) are constituted as a component of the second part (5) of the screw pump (1).
10. The screw pump (1) according to any one of claims 1 to 9, the one or more means (2) comprising a base body (35) with a hollow space (H), in which a plunger (31) is mounted capable of a stroke motion against the restoring force of a compression spring (27) and at least one control pin (39) connected to the plunger (31), the maximum cross-section of which control pin in terms of area is constituted reduced with respect to the maximum cross-section of the plunger (31) and which, when a predefined maximum pressure level is exceeded in the pressure region (15), guides the plunger (31) with a stroke motion in the base body (35) against the restoring force of the compression spring (27), wherein as a result of the stroke motion a lateral opening (37) of the base body (35) is freed for the return flow of the pumping medium from the pressure region (15) into the low-pressure chamber (16).
11. The screw pump (1) according to claim 10, wherein the at least one bore (43) is constituted as a component of a front cover (41) of the base body (35) and wherein the front cover (41) comprises one or more further apertures preferably arranged radially around the bore (43) for the entry of the pumping medium into the hollow space (H) of the base body (35).
12. The screw pump (1) according to claim 10 or 11, wherein, when the maximum pressure level is not exceeded in the pressure region (15), a head section (33) of the plunger (31) is guided by means of the compression spring (27) into a seat (S) and the hollow space (H) of the base body (35) is brought into a fluidic connection with the low-pressure chamber (16) via the opening (37) constituted laterally in the base body (35), so that the pressure level in the hollow space (H) of the base body (35) is constituted essentially identical to the pressure level in the low-pressure chamber (16).
13. The screw pump (1) according to one or more of claims 1 to 12, wherein the one or more means (2) are constituted as a component of the second part (5) and wherein the base body (35) comprises a rear cover (23), which can be removed by means of one or more screw connections (29) and which is arranged at an outer side of the second part (5).
14. The screw pump (1) according to one or more of claims 10 to 13, wherein the one or more means (2) comprise an adjustment means (25) for selecting the restoring force of the compression spring (27), said adjustment means being accessible from the exterior and preferably able to be operated by means of a tool.

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