EP3460180B1 - Screw spindle pump - Google Patents

Description

The invention relates to a screw pump with a housing, a housing cover and at least one running spindle accommodated in a bore in the housing, and a bushing arranged on the housing cover with a receiving space delimited by a cylindrical flange into which the running spindle engages with one end, the bushing has an opening on the bottom, via which a fluid supplied via a cover-side supply channel can be supplied with pressure against the end face of the running spindle from the side opposite the running spindle.

Screw pumps are used to pump a wide variety of fluid media. They comprise a housing with at least two spindles, a drive spindle and at least one drive spindle driven by the drive spindle, but often two drive spindles, which are arranged on both sides of the central drive spindle, are also provided. The one or more spindles are driven by the drive spindle after the spindles mesh. Cavities are formed via the engagement, which form the delivery spaces for the fluid to be delivered. In this way it is possible to convey the fluid supplied on one side from this suction side to the pressure side. The structure and function of such a screw pump is basically known.

Since the running spindles are axially movable to a small extent, it is necessary to provide axial thrust compensation, which takes place hydraulically in known screw pumps. For this purpose, a socket is provided on the housing cover, which is designed as a pocket socket. It is fastened on the cover side with several bolt connections, the fixing being such that a slight lateral movement is possible in the unloaded state. The spindle, with its free, cylindrical end, engages in this bushing with little play. This free spindle end as well as the bushing with its cylindrical flange are located in a free space on the housing side, which means that the spindle protrudes from and in the actual housing bore Free space runs into the sack. For hydraulic axial thrust compensation, a fluid, usually the fluid to be conveyed, which is returned from the pressure side, is guided from the socket bottom via an axial bore, which is provided in known screw pumps via an elongated, longitudinally drilled screw, into the receiving space, where the Fluid presses against the front of the spindle. This means that the axial thrust compensation is realized through a hydrostatically depressed space between the bush and the spindle. In the case of known screw pumps, a clear overcompensation of the diameter of the surfaces to be printed is realized in such a way that there is always a resultant force component which presses the bushing against the housing cover. In order to regulate this overcompensation, a very small and long control bore is formed in the spindle, through which the supplied fluid is discharged to the suction side. This arrangement results in a static state depending on the pressure and viscosity of the fluid.

The assembly of the bushings which are floating in the load-free case and their centering is very complex since, especially when two running spindles are provided, the correct alignment of one or both bushings relative to the spindle end is difficult and for this reason the bushing or bushings difficult to push over the spindle ends with several attempts.

The publication DE2828348 discloses a screw machine according to the preamble of claim 1.

From the DE2324967 a generic screw compressor is known.

The invention is based on the problem of specifying a screw pump which is improved in comparison with this.

To solve this problem, the invention provides that the bush engages with a radial flange with radial play in a receptacle in the cover that is open toward the housing, and the radial flange is axially supported on the housing, and that the cylindrical flange of the bush engages in the bore at least in sections and in this is included with game.

The screw spindle according to the invention is characterized by a novel arrangement or mounting of the bush. According to the invention, the socket is no longer screwed to the housing cover, but is only inserted with radial play in a cover-side receptacle. It has a radial flange with which it is supported axially on the front face of the housing. This means that the housing extends right up to the lid. Furthermore, with its cylindrical flange defining the receiving space, the bush engages at least in sections in the bore in which the spindle is received with little play. This bore engagement automatically centers the bush relative to the spindle.

This configuration according to the invention enables very simple assembly. Because it is only necessary to slide the one or the respective bush as a separate component onto the spindle end and thus insert it into the spindle bore. Then only the housing cover has to be put on and positioned in its circumferential orientation so that the bush engages in the corresponding cover-side receptacle. In this final assembly position, in which the housing cover is then screwed to the housing, the bushing-side radial flange is then arranged between the receptacle or the housing cover and the housing, that is to say axially fixed with slight play. At the same time, after the bushing is arranged in the receptacle with play and at the same time is also accommodated in the bore with little play, a lateral offset or tolerance compensation is possible.

Overall, the screw pump according to the invention is characterized by a much simpler construction, since fewer components are required after the bushing can no longer be fixed to the housing cover with corresponding fastening screws or bolts. In addition, it is characterized by a high degree of ease of installation, since it is only necessary to simply insert the or each bushing, which can also be referred to as a pocket bushing, into the bore of the spindle, after which only the housing cover has to be put on. Large fit diameters are also eliminated the surrounding structure such as pump body and suction housing due to the simple plug-in solution.

It is particularly preferred if the entire length of the cylindrical flange engages in the bore. This means that the bore in which the spindle is received runs directly to the end of the housing or ends at the front of the housing, so there is no bore extension or the like.

A particularly expedient development of the invention provides that the bushing is designed as an aperture in the region of the opening, that is to say that an aperture opening is provided. A diaphragm or a diaphragm opening is characterized in that the ratio of the length of the opening bore with a small, constant diameter to the diameter itself is approximately 1 or less than 1. This in turn means that the pressure loss built up via the orifice is almost independent of viscosity. The control valve can consequently be used to set and regulate the pressure loss required for axial thrust regulation, this pressure regulation or the axial thrust compensation being largely or completely independent of the viscosity of the fluid, so that the screw pump or the thrust compensation system provided according to the invention can be used to convey fluids with different viscosities , unlike known screw pumps, which show a high viscosity dependency in the thrust compensation system. This results in a thrust compensation system in which the outlet pressure, the pressure loss across the orifice and the selected compensation surface, namely the diameter of the end face of the spindle, interact with one another to the extent that a stable hydrostatic system is formed.

The bushing has an outer diameter which, as described, corresponds to the diameter of the spindle bore in which the cylindrical flange is accommodated with little play. The socket also has an inner diameter in the receiving space, which is the diameter of the compensation surface on the spindle side, i.e. corresponds to the spindle end face. Furthermore, the bushing has the orifice opening or the regulating orifice which regulates the pressure loss required for regulating the axial thrust. In the area of the axial thrust compensation system, however, the running spindle only has a closed diameter, ie it has a cylindrical spindle end with which it engages in the bushing. The diameter of the running spindle in the thrust compensation system, that is to say in the engagement section in the bushing, is selected in such a way that the pressurized surface in the bushing, that is to say the spindle end face, is somewhat larger than the surface to which the fluid is applied. The orifice and the resulting leakage flow, which is discharged from the thrust compensation system to the suction side, is defined in such a way that the pressure loss is set which is required to overcome the overcompensation. This means that a self-regulating hydrostatic thrust compensation system can be implemented that is almost independent of viscosity.

As described, the viscosity independence of the thrust compensation system is ensured by the bush being designed as a diaphragm, that is to say having an opening in the form of a diaphragm opening through which the compensating fluid is supplied. This opening can either have a constant diameter over its entire length, that is to say that the socket base is correspondingly thin, for example has a total thickness of 2 mm with an opening diameter of 2 mm. Alternatively, it is also possible for the opening to have a first section with a constant diameter that adjoins the inlet side, to which a second section that opens toward the end face, preferably in a conical manner, adjoins. In this configuration, the diaphragm base can be designed to be significantly stronger after the diaphragm opening has a number of sections. The first section, which has a constant, small diameter and which defines the degree of pressure loss via the orifice, is provided directly on the fluid inlet side. This opening section is, for example, 2 mm long and has a diameter of 2 mm. The opening widens towards the spindle side, so the first section merges into a second section, this transition, for example can be designed conical. So different types of bushings are conceivable.

Furthermore, it is conceivable that the opening having a constant diameter or the conically widening section merges into a round distribution section which is open towards the end face. This means that a correspondingly large diameter reduction is provided on the socket bottom, towards the spindle side, which forms a distribution section in which either the opening, for example 2 mm long, with the constant diameter, opens out, or in which the conically opening one second section opens.

Regardless of the specific aperture configuration, it is expedient if the ratio of the opening length with constant diameter to the diameter of the opening is less than or equal to 1. For example, the opening length with a constant diameter is 2 mm, and the diameter is also 2 mm, so that a ratio of 1 is given. However, the diameter can also be somewhat larger, so that a ratio of less than 1 results. The concrete dimensioning of the bore dimensioning depends on the dimensioning of the pressurized surfaces involved and the degree of overcompensation on the spindle side in order to set the pressure loss via the orifice plate that is required to overcome the overcompensation.

The use of the orifice, regardless of how it is specifically designed, and the possibility of generating a viscosity-independent, defined pressure loss via the orifice, makes it possible to set exactly the pressure loss that is required to largely overcome the overcompensation. As described in the introduction, due to the overcompensation of the printed surface on the spindle side, a resultant force is created with which the bush is pressed against the housing cover. In the no-load situation, when the pump is not in operation, the bushing can be moved laterally, that is to say radially, for a certain play compensation or tolerance compensation. If the pump delivers, however, a corresponding pressure builds up, which results in a force with which the bush is pressed against the housing cover. If this force is relatively large, it is lateral or radial The socket no longer moves, the socket is fixed. This in turn means that any lateral movement or lateral migration of the spindle, which takes place during operation, leads to the spindle running against the inner wall of the cylindrical flange of the bush, so that there is abrasion as abrasive wear can.

If a defined pressure loss is set by the thrust compensation according to the invention using the bushing cover, which is such that in connection with the given leakage current the overcompensation and thus the force with which the bushing is pressed against the housing cover is largely reduced, that the bushing can also move laterally or radially when the load is on, i.e. when the pump is working. This in turn leads to the bush also carrying out corresponding lateral compensating movements of the spindle, so that the spindle is always optimally guided in the bush.

As described, the fluid flows onto the socket on the underside of the socket bottom. The socket bottom, in turn, is accommodated in the housing-side receptacle. In order to avoid that the fluid escapes to the side and in some cases does not pass through the aperture, an annular seal is expediently arranged between the housing cover and the bushing. The diameter of the seal is preferably smaller or larger in the interval between +/- 10% than the diameter of the end face of the spindle. The pressure surface against which the fluid presses is defined by this seal. On the one hand, the seal prevents the fluid from flowing off to the side, so that it is ensured that the fluid only flows off through the orifice opening. In addition, by dimensioning the seal appropriately, a dimensioning of this contact surface on the socket bottom side is provided, which approximately corresponds to the counterpressure surface on the spindle, that is to say the spindle end face. This is also useful for setting a low counterforce with which the socket is pressed against the housing cover in the event of a load, in order to ensure the lateral mobility of the socket even in the event of a load.

The seal can either be received in an annular receptacle on the bottom of the socket, that is to say that an annular groove is formed on the socket bottom. Alternatively, such a ring receptacle or annular groove can also be formed on the housing cover.

As described, it is necessary to discharge a leakage flow from the thrust compensation system to the suction side. In the state of the art, as stated, this is done via a very thin, long control bore in the spindle, which has an axial bore section and a bore section which extends radially from it to the side. The formation of this leakage hole is very complex and cumbersome. In contrast, a particularly advantageous development of the invention provides that the receiving space, in which the cylindrical spindle engages with its cylindrical ends, widens conically towards the spindle at least in the region of the free end of the cylindrical flange. The bushing therefore has a cylindrical inner circumference which extends from the bushing base and widens conically towards the free end of the cylindrical bushing flange. The cylindrical spindle engages with the cylindrical spindle end in the bush, it extends into the area of the cylindrical inner circumference. If a corresponding pressure builds up, the spindle is slightly moved away from the bush, which means that the spindle end is slightly moved axially out of the cylindrical inner circumference. Due to the subsequent conical extension section, a narrow annular gap opens between the bush and the spindle end, through which the fluid can then flow as a leakage current. The pressure in the thrust compensation system drops again slightly, the spindle is moved slightly axially into the bush again, the annular gap closes again slightly, a slightly higher pressure builds up. In this way, a hydrostatic state arises in an extremely short time, the thrust compensation system bringing itself into this hydrostatic state in a self-regulating manner.

The receiving space can open at an angle between 5 ° -15 °, in particular between 8 ° -12 ° and preferably with 10 °.
The area of the conical widening should expediently extend at least over half the length of the flange and then merge into the cylindrical inner circumferential area or an area with a cylindrical inner circumference.

A particularly expedient development of the invention provides that an annular collar reducing the diameter of the flange is provided in the region of the bottom of the bush. This ring collar serves as a contact surface or contact collar against which the face of the spindle runs when the spindle is moved into the bushing. In this case there is too little pressure in the thrust compensation system to axially push back the spindle. If the end face of the running spindle now runs against the ring collar, the counterpressure area on the running spindle suddenly decreases after there is only a reduced end face on the running spindle against the fluid against which the fluid presses with its constant fluid pressure. As a result of the fact that no more fluid can flow out through the axially closed gap, the correspondingly high pressure builds up, which axially pushes the spindle back again. Suddenly, a correspondingly high pressure builds up in the thrust compensation system, which axially pushes back the spindle. Should such a situation arise when the screw pump starts up or during operation, the hydrostatic state will immediately be restored.

The socket itself is secured against rotation by a securing element on the housing cover, so that it is ensured that the socket is not rotated by the rotating spindle. The securing element can be a pin which engages in a bore on the cover side and in a receptacle formed on the end face on the housing base or on the radial flange. Either an end blind hole or a lateral recess in which the pin engages can thus be formed.

As already described, a screw spindle can only have one running spindle and one drive spindle. However, it is also conceivable that two or more running spindles are provided in the respective bores, each of which is assigned a bushing, and which are driven by a common drive spindle.

If two or more sockets are provided, they preferably communicate via a common supply line, so that they are supplied simultaneously via a supply line with the fluid, as described, with the medium to be conveyed, so that overall a closed fluid circuit also results within the thrust compensation system .

Fig. 1

eine Explosionsdarstellung, perspektivisch, eines Teils einer erfindungsgemäßen Schraubenspindelpumpe,

Fig. 2

eine Teilschnittansicht durch eine erfindungsgemäße Schraubenspindelpumpe,

Fig. 3

eine Schnittansicht entsprechend Fig. 2 mit zusätzlich geschnittenen Buchsen und Laufspindeln,

Fig. 4

eine Schnittansicht in einer Ebene 90° zur Ebene gem. Fig. 3,

Fig. 5

eine Perspektivansicht einer Buchse der Schraubenspindelpumpe,

Fig. 6

eine Schnittansicht durch die Buchse aus Fig. 5,

Fig. 7

eine vergrößerte Detailansicht des Bereichs VII aus Fig. 6,

Fig. 8

eine Schnittansicht durch eine Buchse einer zweiten Ausführungsform, und

Fig. 9

eine erfindungsgemäße Schraubenspindelpumpe, teilgeschnitten, in gesamter Länge.

Further advantages and details of the present invention result from the exemplary embodiments described below and from the drawings. Show:

Fig. 1

2 shows an exploded view, in perspective, of part of a screw pump according to the invention,

Fig. 2

2 shows a partial sectional view through a screw pump according to the invention,

Fig. 3

a sectional view accordingly Fig. 2 with additionally cut bushings and spindles,

Fig. 4

a sectional view in a plane according to 90 ° to the plane. Fig. 3 ,

Fig. 5

a perspective view of a socket of the screw pump,

Fig. 6

a sectional view through the socket Fig. 5 ,

Fig. 7

an enlarged detail view of area VII Fig. 6 ,

Fig. 8

a sectional view through a socket of a second embodiment, and

Fig. 9

a screw pump according to the invention, partially cut, in full length.

Fig. 1 shows an inventive screw pump 1 in a partial view as an exploded view. A housing 2 is shown, in which a first bore 3 for receiving a drive spindle and, to the side, two bores 4, 5 for receiving a running spindle each, which mesh with the drive spindle, are formed in the center. The spindles are not shown here. The bores 4, 5 receiving the running spindles extend directly to the end face 6 of the housing 2.

Also shown is a housing cover 7, which is screwed onto the housing 2 by means of suitable fastening screws, finally.

Also shown are two bushings 8, 9 which are part of a hydraulic thrust compensation system via which the two running spindles are axially supported. The structure and function of the sockets 8, 9 will be discussed below. For the rotationally fixed fixing of the bushings, two pins 10, 11 are used, which on the one hand are inserted into corresponding blind bores 12, 13 on the housing and which on the other hand pass through corresponding lateral recesses 14, 15 on the bushings 8, 9. This prevents the bushings 8, 9 from being set in rotation by the spindles engaging in them.

Fig. 2 shows a partial sectional view of the screw pump 1 from Fig. 1 , wherein the housing 2 is shown cut here. On the one hand, the drive spindle 16 and the two running spindles 17, 18 can be seen, the spindles meshing with one another with their corresponding screw profiles. The housing cover 7 is placed on the housing 2 and screwed to it. The two bushings 8, 9 are pushed onto the running spindles 17, 18, that is, the spindle ends engage in the bushings 8, 9. The sockets clearly catch 8, 9, each with a cylindrical flange 19, 20 with little play in the bores 4, 5, in which the running spindles 17, 18 are received, by means of which the bushings 8, 9 are centered. With their other end they are received in corresponding receptacles 21, 22 which are formed on the cover side. The socket base 23, 24 is each provided with a radial flange 25, 26 which, as will be discussed below, is supported on the end face 6 of the housing 2.

Also shown is an inlet duct 34, which is formed on the housing cover 7 and from which two branch ducts 35, 36 extend, which run to the sockets 8, 9, and thus thus open into the corresponding receptacle 21, 22. This can be used to supply a pressure compensation fluid via which the axial thrust compensation is implemented.

Fig. 3 shows a sectional view through the screw pump 1 accordingly Fig. 2 , here also the drive spindle 16 and the two running spindles 17, 18 and the bushings 8, 9 are shown in section.

The sockets 8, 9 can be seen in the corresponding receptacles 21, 22. With their radial flanges 25, 26 they rest on the end face 6 of the housing 2, which is possible after the bores 4, 5 extend directly to the end face 6, the housing cover 7 being in direct contact with the end face 6.

The respective cylindrical spindle ends 28, 29 of the two running spindles 17, 18 are shown. It can also be seen that the spindle ends 28, 29 engage in the bushings 8, 9. They are accommodated in the sockets 8, 9 with minimal play, with a receiving space 32, 33 being formed between the socket base 23, 24 and the respective end face 30, 31 of the running spindles 17, 18, in which the receiving channel 34 and the fluid supplied to both branch channels 35, 36, which is the fluid to be pumped. For this purpose, each bushing in the respective bushing base 23, 24 has an aperture 37, 38 through which the inlet channel 34 and the fluid channels 35, 36 supplied fluid can enter the receiving space 32, 33. The fluid flow is indicated by the corresponding arrows in Figure 3 shown.

As far as the respective openings 37, 38 are concerned, the bushes 8, 9 are designed as screens, which will be discussed in more detail below. This means that a defined, viscosity-independent pressure drop from the inlet side with the feed channel 34 to the outlet side to the respective spindle 17, 18 can be realized via these orifices or orifices.

As stated, the bushings 8, 9 each have a cylindrical flange 19, 20. With this they engage, as stated, directly with little play in the respective bore 4, 5. The respective flange 19, 20 is provided on its inside in the region of the socket base 23, 24 with a cylindrical inner circumferential region 39, 40, see among others Fig. 6 , which in turn is followed by a conically widening region 41, 42 (see again Fig. 6 ). Pressure control can be implemented in this way. Depending on how deep the respective spindle end 28, 29 dips into the respective bushing 8, 9, a more or less large annular gap is formed, through which the supplied fluid can flow off to the suction side of the pump. If the respective spindle end 28, 29 is inserted deeply, then the respective end face 30, 31 is located in the region of the cylindrical inner circumference, that is to say in the circumferential region 39, 40. If the running spindle 17, 18 is formed or generated by the pressure formed in the receiving space 32, 33 pushed out again somewhat, the respective end face 30, 31 moves into the conical widening area 41, 42, so that an annular gap results which increases the further the spindle 17, 18 is pushed out. The fluid in the receiving space 32, 33 can flow through this annular gap to the suction side, via which the pressure drops again and the respective spindle 17, 18 migrates somewhat into the bushing 8, 9 again. Overall, a static equilibrium state arises in an extremely short time, in which the respective spindle 17, 18 is hydraulically thrust-balanced.

The 3 and 4 furthermore show the fluid supply of the thrust compensation system comprising that in the manner according to the invention formed and mounted bushings 8, 9. In the housing 2, a fluid channel 43 running from the pressure side to the suction side and to the housing cover 7 is formed, which opens via a branch channel 44 into a cover-side fluid channel 45, which in turn opens into the supply channel 34. If necessary, the corresponding channels are closed by means of sealing plugs 46, 47. The fluid, via which the hydraulic thrust compensation takes place, is therefore supplied from the pressure side with the corresponding pump pressure. This pressure acts on the bottom surface 48, 49 of the respective bushing 8, 9. This bottom surface 48, 49 is sealed off by a sealing element 50, 51 for receiving 21, 22. For this purpose, corresponding annular grooves 52 are formed in the socket bottoms 23, 24, see here Fig. 6 , where an exemplary sectional view through the bushing 8 is shown, the bushing 8 and the bushing 9 being of identical design.

The bushings 8, 9 are received in the corresponding receptacles 21, 22 with little radial play, so they are floating and laterally movable. They are also accommodated with little play with their respective flanges 19, 20 in the bores 4, 5, so that overall there is a floating bearing.

This floating bearing is also retained in the event of a load, ie when fluid is being pumped. In this case, a defined pressure drop results via the opening 37, 38 of the bushings 8, 9, which is designed in such a way that it is due to the overcompensation resulting from the size of the respective end face 30, 31 of the spindles 17, 18 resulting force that presses the bushings 8, 9 against the housing cover 7, as far as is reduced or minimized and compensated for, that in the load case the bushings are pressed firmly against the housing cover 7 while compressing the respective sealing elements 50, 51, but still since this resulting force is largely balanced, can be moved laterally. This makes it possible to compensate for any lateral migration of the respective spindle 17, 18, that is to say that the respective bushing 8, 9 is carried along and displaced laterally via the respective spindle end 28, 29, whereby this lateral offset naturally takes place in the range of a few hundredths of a millimeter. In any case, however, the bushings 8, 9 can also deflect to the side in the event of a load, so that they follow the running spindles 17, 18 and do not abrasively attack the cylindrical flanges 19, 20.

The Fig. 5-7 show a first embodiment of a socket used according to the invention, socket 8 being shown here by way of example. The bushing 9 is of course identical to this. It has a cylindrical flange 19, as well as a radial flange 25, which extends the bottom 23 of the bushing laterally.

The sectional view according to Fig. 6 and the enlarged detailed view according to Fig. 7 show the further construction of the bushing 8 in detail. As can be seen, the conically widening region 41 of the inner circumference extends to almost or somewhat more than half the axial length of the flange 19, followed by the cylindrical inner circumferential region 39 which has a constant diameter.

Also shown is the opening 37, which is designed as a diaphragm. This area is enlarged in Fig. 7 shown.

The opening 37 comprises a first section 53, which has a constant diameter. The axial length of this section 53 preferably corresponds to the diameter of this cylindrical opening, so that there is a ratio of opening length to diameter of 1. Alternatively, the ratio can also be less than 1, which means that the diameter is greater than the opening length.

In the example shown, this first section 53 is followed by a conically widening second section 54. The pressure drop begins in this area and continues in a subsequent distribution section 55.

Fig. 6 shows, as already described, the annular groove 52 in which the corresponding ring seal 50 is received. The annular groove 52 and thus the ring seal 50 in the case of assembly have a diameter which approximately corresponds to the diameter of the inner circumferential region 39, and consequently also the diameter of the end face 30 or 31. This means that the inflow face on the bushing base approximately corresponds to the end face 30, 31 corresponds to the counter pressure area. The entire surface defined by the respective ring seal 50, 51 can be seen as the inflow surface, since in operation the respective bushing 8, 9 is pressed against the housing cover 7, but due to the defined pressure drop and thus force equalization, the respective bushing 8, 9 is possibly minimally spaced from the housing cover 7 and consequently the fluid can be distributed over the entire area delimited by the respective seal 50 and 51.

In operation, as described, the fluid is guided to the respective orifice bushing 8, 9 via the respective channel geometry and enters the respective receiving space 32, 33. It flows against the respective end face 30, 31, ie the counter pressure surface. Due to the defined pressure drop across the respective orifice design, there is an extensive balancing of forces, so that only a relatively small resulting force with which the respective orifice 8, 9 is pressed against the housing cover 7 results, so that a floating bearing also remains is given in the case of load or pressure.

Due to the inner circumferential geometry according to the invention of the respective bushing 8, 9, a static equilibrium state with respect to the spindle axial position is established quickly and easily. Because due to the pressure applied to the respective end face 30, 31, the respective spindle 17, 18 is moved axially relative to the bushing 8, 9, resulting in a corresponding variation of the respective gap cross-section, via which the fluid as a leakage flow from the respective receiving space 32, 33 can flow away, so that a corresponding static state is established.

The installation of this thrust compensation system is very easy. After the housing 2 has been fitted with the drive spindle 16 and the two running spindles 17, 18, it is only necessary to push the two bushings 8, 9 onto the spindle ends 28, 29 and in doing so with the corresponding flanges 19, 20 into the respective bores 4, 5 introduce. Automatic centering is provided here. At the same time, when the pins 10 engage in the corresponding lateral recesses 14, 15, the anti-rotation device is implemented. Then only the housing cover 7 has to be attached and positioned in the circumferential direction so that the bottoms 23, 24 of the bushings 8, 9 engage in the corresponding receptacles 25, 26, after which the housing cover 7 can be screwed on.

Fig. 8 finally shows an embodiment of a bushing 8 according to the invention (the same applies to the bushing 9), in which an annular collar 56 is additionally formed on the inner circumference in the region 39, which reduces the diameter there. The respective end face 30, 31 can run against this annular collar 56 if the spindle, for whatever reason, is immersed axially to such a depth. If the respective end face 30, 31 runs against the respective annular collar 56, the counter pressure surface against which the fluid works is reduced. As a result of the fact that no more fluid can flow out through the axially closed gap, the correspondingly high pressure builds up, which axially pushes the spindle back again. There is an increase in pressure in the respective receiving space 32, 33, which means that the respective spindle 17, 18 is immediately pressed out of the system on the respective ring collar 56 and the static equilibrium state is then established again.

Fig. 9 finally shows a sectional view through a screw pump 1 according to the invention, the housing 2 here consisting of a plurality of separate housing elements 57 which are axially assembled and connected to one another. Shown is the housing cover 7 and the axial thrust compensation system implemented via the bushings 8, 9, via which the two running spindles 17, 18 are hydraulically thrust balanced.

Claims (16)

1. Screw spindle pump having a housing (2), a housing cover (7) and at least one running spindle (17, 18) received in a bore (4, 5) in the housing (2), and a bushing (8, 9) which is arranged on the housing cover (7) and which has a receiving space (32, 33) bounded by a cylindrical flange (19, 20) and in which one end (28, 29) of the running spindle (17, 18) engages, wherein the bottom of the bushing (8, 9) has an opening (37, 38) via which, from the side opposite the running spindle (17, 18), it is possible to supply a fluid, supplied via a cover-side supply duct (34), with pressure against the end face (30, 31) of the running spindle (17, 18), characterized in that the bushing (8, 9) with a radial flange (25, 26) engages with radial play in a recess (21, 22) in the cover (7), this recess being open towards the housing (2), and the radial flange (25, 26) is supported axially on the housing (2), and in that at least a portion of the cylindrical flange (19, 20) of the bushing (8, 9) engages in the bore (4, 5) and is received with play therein.
2. Screw spindle pump according to Claim 1, characterized in that the cylindrical flange (19, 20) engages with its entire length in the bore (4, 5).
3. Screw spindle pump according to Claim 1 or 2, characterized in that the bushing (8, 9) takes the form of a diaphragm in the region of the opening (37, 38) .
4. Screw spindle pump according to Claim 3, characterized in that the opening (37, 38) has a constant diameter over its entire length, or in that the opening (37, 38) has a first, constant-diameter portion (53) adjoining the inlet side, adjoining which portion there is a second portion (54) that opens, preferably in a conical manner, towards the end face (30, 31).
5. Screw spindle pump according to Claim 4, characterized in that the constant-diameter opening (37, 38) or the conically-widening portion (54) transitions into a round distribution portion (55) that is open towards the end face (30, 31).
6. Screw spindle pump according to Claim 4 or 5, characterized in that the ratio of the constant-diameter opening length to the diameter of the opening is ≤ 1.
7. Screw spindle pump according to one of the preceding claims, characterized in that between the housing cover (7) and the bushing (8, 9) there is arranged an annular seal (50, 51) whose diameter is between +/- 10% smaller or larger than the diameter of the end face (30, 31) of the running spindle (17, 18).
8. Screw spindle pump according to Claim 7, characterized in that the seal (50, 51) is received in an annular recess (52) on the bottom (23, 24) of the bushing (8, 9) or on the housing cover (7).
9. Screw spindle pump according to one of the preceding claims, characterized in that the receiving space (32, 33), in which the running spindle (17, 18) engages with its cylindrical end (28, 29), widens conically towards the running spindle (17, 18), at least in the region of the free end of the cylindrical flange (19, 20).
10. Screw spindle pump according to Claim 9, characterized in that the receiving space (32, 33) opens with an angle of between 5°-15°, in particular between 8°-12° and preferably 10°.
11. Screw spindle pump according to Claim 9 or 10, characterized in that the region (41, 42) of the conical widening extends over at least half the length of the flange (19, 20).
12. Screw spindle pump according to one of Claims 9 to 11, characterized in that an annular collar (56) which reduces the diameter of the flange is provided in the region of the bottom (23, 24) of the bushing (8, 9).
13. Screw spindle pump according to one of the preceding claims, characterized in that the bushing (8, 9) is prevented from rotating by means of a securing element (10, 11) on the housing cover (7).
14. Screw spindle pump according to Claim 13, characterized in that the securing element is a pin (10, 11) which engages in a cover-side or housing-side bore (12, 13) and in a recess (14, 15) formed on the end face of the bottom (23, 24) or on the side of the radial flange (25, 26).
15. Screw spindle pump according to one of the preceding claims, characterized in that two or more running spindles (17, 18) are provided in respective bores (4, 5), each being assigned a bushing (8, 9).
16. Screw spindle pump according to Claim 15, characterized in that all of the bushings (8, 9) communicate with a common supply line (34) and are supplied simultaneously with fluid.

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