EP3746638B1 - Stator for eccentric screw machine - Google Patents

Description

The invention relates to a stator for an eccentric screw machine, in particular an eccentric screw pump for liquid, pulpy or pasty, homogeneous or inhomogeneous media.

Progressing cavity pumps are generally well known. They typically have a stator with multiple threads and an elastomer lining. Examples include the DE 199 50 257 A1 This document discloses an eccentric screw machine with a stator mounted between an input housing and an output housing. The input housing and the output housing are clamped against each other by tension bolts. It may be necessary to secure the stator in a frame in a rotationally fixed manner. For this purpose, it is common practice to attach a radially projecting arm to the stator. DE 20 2010 016 196 U1 This describes a bracket screwed into a threaded hole in the stator. This bracket may have an external thread at its outer end, which allows for the attachment of a cover and facilitates screwing in the bracket.

Also from the EP 0 987 438 A1 The attachment of a screw pin extending radially from the stator is known, which serves as an anti-rotation device for the stator. The pin engages one of the tie bolts and thus prevents the stator from rotating. To enable shrink-wrapping of the stator, the outer metal casing of the stator is first welded to a nut in a recess into which the screw pin can later be screwed after the shrink-wrapping has been applied.

The utility model DE 20 2014 103 665 U1 discloses an anti-rotation device which is formed by a pin which projects radially from the stator casing and is welded to the stator casing. The utility model proposes, as an alternative, A bushing is welded to the stator casing, into which a round pin is pressed or glued.

From the DE 20 1026 104 173 U1 It is known to provide a stator for an eccentric screw machine with an anti-twist extension that is welded to the casing tube of the stator and protrudes radially from it. The extension can be designed as a bolt with a swaged head that is welded to the casing tube.

The torque support is a critical component. Even under higher loads, it must not be damaged to ensure that the torque support is maintained and the casing tube is not damaged. Furthermore, stators of progressive cavity machines are components that travel considerable distances from the manufacturer to the user and must be prepared for shipping.

Based on this, the object of the invention is to design a stator for an eccentric screw machine with improved torque support.

This object is achieved with a stator according to claim 1:
The stator according to the invention is suitable for eccentric screw machines, in particular eccentric screw pumps for liquid, pulpy or pasty, homogeneous or inhomogeneous media. It has a metallic casing tube, which is provided internally with an elastomer lining. The inner lining defines a longitudinal passage in the form of a two- or multi-start thread. It serves to accommodate a rotor, which has an external thread with a different number of threads. The stator is provided with an anti-twist device in the form of a cantilever that is detachably connected to the casing tube. The anti-twist device is designed as a cantilever that preferably projects radially from the casing tube and is screwed to a pin that is permanently connected to the casing tube. For this purpose, the boom has an opening with an internal thread, which is screwed onto an external thread provided on the pin.

The casing pipe can be cylindrical (round cross-section) or have two (or more) threads (oval cross-section), whereby the spigot can be attached to a point on the casing pipe where the casing pipe has a large outer diameter. This minimizes the forces absorbed by the connection point between the spigot and the casing pipe.

The pin is preferably arranged radially on the casing tube and welded to the casing tube. For this purpose, the pin can have a head whose diameter is larger than the outer diameter of the pin. The connection between the casing tube and the pin can be made by a linear weld, e.g., a ring weld, or by stud welding, thus creating a surface weld. The pin is preferably short compared to the boom, i.e., it is shorter than half, preferably shorter than a third, and particularly preferably shorter than a quarter of the radial length of the boom. This allows the boom to be removed from the stator for transport. Furthermore, the application of protective films, e.g., shrink films, is simplified.

The boom can have a circular cross-section and a threaded blind hole at one end, allowing it to be screwed onto the threaded bolt. Alternatively, the boom can be hollow over its entire length, i.e., designed as a continuous tube. The flexural rigidity is sufficient radially outward. At the radially inner end, the pin screwed into the boom contributes to increasing the flexural rigidity. Apart from its internal thread, the boom can have a constant cross-section over its entire length.

The spigot can be welded to the casing pipe before the elastomer lining is formed. Alternatively, it is possible to weld the spigot to the casing pipe after the elastomer lining has been formed. This is especially true if welding processes that require only minimal local heat are used to attach the spigot.

According to the invention, a shrink film is attached to the stator, which can serve as temporary or permanent protection. The pin breaks through the film at an opening, but the edge of the opening is firmly held on or near the pin or the casing tube between the pin or the casing tube and the cantilever. This ensures that the protective effect of the film is reliably maintained despite the break.

• Figur 1 den erfindungsgemäßen Stator mit Verdrehsicherung, in Perspektivdarstellung,
• Figur 2 den erfindungsgemäßen Stator mit Verdrehsicherung, in Stirnansicht,
• Figur 3 den Stator nach Figur 1 und 2, längs geschnitten auf Höhe der Verdrehsicherung entlang der Linie III-III,
• Figur 4 den Stator nach Figur 1, in quer geschnittener Darstellung, geschnitten entlang der Linie IV-IV,
• Figur 5 den Stator nach Figur 3, in einer ausschnittsweisen Darstellung,
• Figur 6 den Stator nach Figur 3, in ausschnittsweiser Darstellung,
• Figur 7 eine abgewandelte Ausführungsform des Stators mit Zylinderrohr und mit Verdrehsicherung in Querschnittsdarstellung
• Figur 8 einen abgewandelten Ausleger, in Seitenansicht, teilweise geschnitten.

Further details and modifications of the invention will become apparent from the drawings, the description, or the claims. They show:

• Figure 1 the stator according to the invention with anti-twist device, in perspective view,
• Figure 2 the stator according to the invention with anti-twist device, in front view,
• Figure 3 the stator Figures 1 and 2 , cut lengthwise at the level of the anti-twist device along the line III-III,
• Figure 4 the stator Figure 1 , in cross-sectional view, cut along the line IV-IV,
• Figure 5 the stator Figure 3 , in a partial representation,
• Figure 6 the stator Figure 3 , in partial representation,
• Figure 7 a modified version of the stator with cylinder tube and anti-twist device in cross-sectional view
• Figure 8 a modified boom, in side view, partially cut.

In Figure 1 A stator 11 of an eccentric screw machine is illustrated, such as can be used for conveying fluid media, in particular pulpy or pasty, homogeneous or inhomogeneous media, such as concrete, mortar and filler. According to a first embodiment, the stator 11 forms an elongated tube with an internal thread profile of at least two starts. It consists of an outer casing tube 12, the profile of which defines the at least two thread turns 13, 14. Alternatively, the stator can also have a cylindrical casing tube 12, as is shown in Figure 7 emerges.

The stator 11 is provided with an elastomeric coating 15, which preferably has a largely uniform thickness and adheres to the inner surface of the casing 12. The threads 13, 14 are formed accordingly, as can be seen from Figure 2 visible, on the inside of the coating as threads 13', 15`. The thickness of the coating 15 is largely uniform, whereby Figure 3 shows, smaller thickness differences can occur. Larger layer thicknesses can also occur at the inlet and outlet, ie at the two front ends of the stator 11, as Figure 2 It is also possible to form the stator 11 with a less deep profile or to form it cylindrically. In this case, the threads 13, 14 are formed exclusively or predominantly in the coating 15, which then has a locally different thickness. Such an embodiment is shown in Figure 7 illustrated.

While the jacket tube 12 is preferably made of steel, the coating 15 is made of a non-metallic material, in particular a cross-linked plastic material, such as a polymer or an elastomer, rubber, or the like. The material of the coating 15 is typically It is a thermally sensitive material that tends to degrade and decompose at higher temperatures (several 100°C).

An anti-rotation device 16 is attached to the stator 11, which serves to absorb and divert torques acting around the longitudinal axis 17 of the stator 11. Such torques can be dissipated during operation by rotating the rotor 18 (see Figure 2 , 4 or 7 ) appear.

The anti-rotation device 16 is formed by a cantilever 19, which preferably projects radially from the casing tube 12 and may, for example, have a round cross-section. The cantilever 19 may be formed by a round rod with a solid cross-section or, as shown, by a round tube. In any case, it may have a constant cross-section over its entire length. At its radially inner end, facing the stator 11, the cantilever 19 has an opening with an internal thread 20, by means of which the cantilever is attached to a pin 21 projecting radially from the casing tube 12.

It is also possible to provide a boom 19 with a cross-section that varies along the radial. For example, the boom 19 can Figure 8 have a head whose diameter is larger than the diameter of the remaining, radially outwardly extending portion. The head may be provided with a threaded blind bore to receive the pin 21. The outwardly extending portion may have a round cross-section or a cross-section suitable for the attachment of a tool, e.g., a wrench.

The boom 19 can have a non-circular structure on its outer side. For example, the boom 19 can have a tool coupling structure at its radially outer end, at its radially inner end, or in an intermediate region. For this purpose, a cross-sectional shape deviating from the circular shape, For example, an oval shape with two parallel straight sections, or a hexagonal shape for attaching a wrench or another torque-exerting tool can be provided. It is also possible to design the entire boom 19 with an outer contour that allows the attachment of a wrench. The boom can have a rectangular cross-section that is unchanged along its entire length, longitudinally continuous flattened areas, or another polygonal cross-section. It is also possible to provide different cross-sections for different wrench widths along the length of the boom 19. Additionally or alternatively, tool coupling structures, e.g. an Allen key shape, can be provided on the radially outer end face or in the interior of the boom 19.

The pin 21 is preferably made of solid material in the manner of a screw bolt and is provided with an external thread 22 on its outer circumference (see in particular Figure 5 ), which fits the internal thread 20. The basically cylindrical pin 21 has a preferably flat, disc-like head 23 at its end facing the casing tube 12, the outer diameter of which is preferably not smaller than the outer diameter of the boom 19. The head 23 is firmly connected to the casing tube 12 by a material fit, preferably welded, for example over the entire surface by a pressure weld or friction weld. Alternatively, an annular, uninterrupted weld seam 24 in the form of a fillet weld can be provided around the head 23. Alternative welded connections between the head 23 and the casing tube 12, in particular welded connections that lead to a surface connection between the head 23 and the casing tube 12, can also be provided.

The welded connection between the threaded pin 21 and the casing pipe 12 is located outside the thread 22 and is limited to the front end of the threaded pin 21, in particular on its head 23. Therefore, it is ensured that the thread 22 applied before welding the threaded pin 21 to the casing pipe is not damaged by the welding process and, in particular, is not deformed.

In all embodiments of the stator 11 according to the invention described above and below, the boom 19 is preferably arranged at a point on the casing tube 12 where the latter has a large radius, as can be seen from the Figures 1, 3 and 5 This has the advantage that the forces to be transmitted from the connection point between the boom 19 and the casing tube 12 are lower than if it were mounted in a threaded valley due to the greatest possible distance from the longitudinal axis 17.

The outer surface of the casing pipe 12 can be provided with a lacquer and/or a plastic coating. The plastic coating can be formed by a shrink film 25, as shown in Figure 5 This shrink film can be applied to the casing pipe 12 after the attachment of the spigot 21, but before the boom is screwed on. It can span the spigot 21 and tightly enclose it. Alternatively, it can be perforated by the spigot 21.

Applying the shrink film 25 to the stator 11 initially causes the shrink film 25 to envelop the journal 21. If the shrink film 25 is severed on the journal 21 when the extension arm 19 is screwed on, it may have a tendency to creep away from the journal 21 due to the inherent tension. However, since a supply of film is present on the journal 21, this does not lead to an exposure of the weld seam. This thus remains protected. The stator 11 according to the invention can therefore also be used safely in adverse environments. The hole edge of the film created when the extension arm 19 is screwed on and thus when the shrink film 25 is broken can be located between the internal thread 20 and the external thread 22 and/or between the head 23 and the The end face of the boom 19 is clamped. This ensures corrosion-proof enclosure of the casing pipe 12, particularly in the area of the weld seam 24.

Numerous modifications to the invention described so far are possible. For example, the cross-section of the boom 19 does not necessarily have to be round, hexagonal, or oval. Different configurations are possible. For example, the boom 19 can have a cross-shaped cross-section or a symmetrical or asymmetrical angular cross-section, a T-shaped cross-section, a profile tube cross-section, or the like. The boom 19, regardless of its cross-section, can also be designed to taper away from the casing tube 12. In other words, the cross-section of the boom 19 can be constant or decrease radially outward in steps or smooth transitions.

Reference symbol

11 stator 12 jacket pipe 13, 14, 13', 14' threads 15 Coating 16 anti-twist device 17 Longitudinal axis 18 rotor 19 boom 20 internal thread 21 cones 22 external thread 23 Head of the pin 21 24 Weld seam 25 shrink wrap

Claims (14)

1. A stator (11) for an eccentric screw machine, in particular an eccentric screw pump for liquid, pulpy, or pasty, homogeneous or non-homogeneous media, comprising:

   a metallic casing pipe (12) which is provided on the inside with an elastomer lining (15) and defines an axial direction (17),

   an anti-rotation device (16) in the form of an extension arm (19) which has an opening provided with an internal thread (20),

   a pin (21) which is non-detachably connected to the casing pipe (12) and is provided with an external thread,

   wherein the internal thread (20) of the extension arm (19) is engaged with the external thread (22) of the pin (21), and

   wherein the casing pipe (12) is provided on its outside with a shrink film (25), the shrink film (25) being held between the pin (21) or the casing pipe (12) and the extension arm (19).
2. The stator for an eccentric screw machine according to claim 1, characterized in that the casing pipe (12) is cylindrical or has a non-circular, preferably oval cross-section and in that the pin (21) is attached to a location on the casing pipe (12) at which the casing pipe (12) has a large outer diameter.
3. The stator according to claim 1 or 2, characterized in that the pin (21) is arranged on the casing pipe (12) in a radial orientation and is welded to the casing pipe (12).
4. The stator according to claim 3, characterized in that the pin (21) has a head (23) whose diameter is larger than the outer diameter of the pin.
5. The stator according to anyone of the preceding claims, characterized in that the pin (21) is connected to the casing pipe (12) via a surface welded connection or via an annular seam (24).
6. The stator according to anyone of the preceding claims, characterized in that the extension arm (19) has a round cross-section.
7. The stator according to anyone of the preceding claims, characterized in that the extension arm (19) has a hollow cross-section.
8. The stator according to claim 7, characterized in that the extension arm (19) is formed as a continuous tube.
9. The stator according to anyone of the preceding claims, characterized in that the radially inner end of the extension arm (19) is provided with the internal thread.
10. The stator according to anyone of the preceding claims, characterized in that the extension arm (19) has a constant cross-section over its entire length.
11. The stator according to anyone of the preceding claims, characterized in that the pin (21) is welded to the casing pipe (12) on the end face by stud welding, pressure welding, friction welding, resistance welding or spot welding.
12. The stator according to anyone of the preceding claims, characterized in that the pin (21) has been welded to the casing pipe (12) prior to formation of the elastomer lining (15).
13. The stator according to anyone of the preceding claims, characterized in that the pin (21) has been welded to the casing pipe (12) after the formation of the elastomer lining (15).
14. The stator according to anyone of the preceding claims, characterized in that the casing pipe (12) is painted on its outside.

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