EP3268616A1 - Self-priming pump - Google Patents

Abstract

The invention relates to a self-priming pump (1) having a housing (9), an inlet (4) and an outlet (5), having a first impeller (15) with a first pump section (17) that is arranged in a first chamber (18), and a second impeller (16) with a second pump section (19) that is arranged a second chamber (20), and a shaft section (25) that is arranged between the pump sections (17, 19), which shaft section (25) comprises a shaft end (26) and passes through an opening (24) of a housing wall (23). According to the invention, in order to improve the net positive suction head of the pump (1), the shaft section (25) is formed in a tapering manner from the shaft end (26) to a necking (27) between the necking (27) and the shaft end (26), and the first impeller (15) and shaft section (25) have a smooth course between the necking (27) and the first pump section (17).

Description

 Self-priming pump

The invention relates to a self-priming pump according to the preamble of claim 1.

Self-priming pumps are well known in the art and have been used successfully in the process industry for many years. Process industry means in particular the beverage technology, food technology, pharmacy and

Biochemistry.

Such pumps are designed, for example, as self-priming centrifugal pumps. Between the inlet and outlet of such a centrifugal pump, a first

Chamber and a second chamber may be provided, in each of which an impeller is arranged. Each impeller is part of a pumping stage, with the pumping stage closer to the inlet producing the self-priming property.

A first self-priming centrifugal pump of this type is proposed in EP 1 191 228 A2. Another self-priming centrifugal pump is shown in DE 10 2007 032 228 A1.

These two centrifugal pumps have one in addition to the centrifugal pumping stage

Liquid ring pumping stage, which receives fluid to be pumped directly from the inlet of the centrifugal pump. By means of the liquid ring pumping stage, a negative pressure can be generated, which sucks fluid from the line connected to the inlet.

A return line connects the overpressure region of the centrifugal pumping stage to the inlet of the liquid ring pumping stage. As a result, a liquid template is guaranteed, which when starting the centrifugal pump for generating the

Liquid ring is necessary.

The impeller of the centrifugal pumping stage is connected to the impeller of the liquid ring pumping stage via a shaft portion which passes through an opening of a housing wall. In both cases, the shaft portion is designed to be cylindrical up to its impeller of the centrifugal pump facing shaft end. An important characteristic of such self-priming centrifugal pumps is the NPSH value. NPSH stands for "Net Positive Suction Head" and is often equated with the term "Haitruckhöhe". This parameter indicates which overpressure of the fluid to be pumped at the inlet of the pump must prevail above the vapor pressure of this fluid in order to avoid cavitation inside the pump. This pressure increase must be generated in the process plant. Therefore, a pump is sought, which has the lowest possible NPSH value. It is therefore an object of the invention to provide a self-priming pump with an improved Haitesruckhöhe.

This object is achieved by a pump having the features of the first

Claim. The dependent claims 2 to 12 indicate advantageous developments of this invention.

The self-priming pump has a housing with an inlet and an outlet. A first impeller has a first pump portion disposed in a first chamber. A second impeller carries a second pump section which is arranged in a second chamber. Between the pump sections, a shaft section is provided, which shaft section comprises a shaft end and passes through an opening of a housing wall. The flow of the fluid to be pumped, in particular a liquid with gas fractions, along the

Shaft portion is improved by the shaft portion between a constriction and the shaft end is tapered from the shaft end to the constriction and the first impeller and shaft portion between the constriction and the first pumping portion have a smooth course.

A smooth course in the sense of this text is a surface form of

Shaft section and impeller, in which steps, creases, heels and similar structures are designed and reduced in number as much as possible, that vortex in the

passing fluid to a minimum, or in a no longer detectable area, are reduced. This design of the pump improves the flow conditions between the pump sections. By the rejuvenation of the shaft section of the Reduced flow resistance at the bottleneck. By the enlarged

Cross-section, the flow velocity is reduced in the region of the shaft portion, whereby the static pressure loss is reduced. The smooth course reduces the risk of eddies. Both effects in interaction a reduction in the risk of the occurrence of cavitation, so that a lower

 Pressure increase is necessary. The NPSH value of the pump is thus improved over the prior art. These advantages achieved outweigh the disadvantage in terms of the stability of the second impeller, which results from the constriction and which initially prevents the idea of a constriction of the shaft.

The flow path between the shaft sections is improved when the thinnest point of the shaft section is arranged in the second chamber.

According to a development is proposed the thinnest point of the

Shaft section to arrange in the opening. This results in a large passage cross-section for fluid, so that a large amount of fluid with reduced flow velocity and a greatly reduced number of vortices can flow between the pumping stages. The pump has a structurally simple drive, if according to another

Continuing first impeller and second impeller are mounted together flying.

After yet another development is provided that the

Shaft section is formed on the second impeller. This results in additional advantages of a simple manufacture of the pump and the ability to produce a modular system self-priming and non-self-priming pumps, in which the different types have many common parts.

Another development relates to the connection of the wheels. The shaft portion is therefore shaped so as to receive a threaded portion of a drive shaft supporting the first impeller. This is an advantageous simple structure, which also deepens the advantages in terms of a modular system.

An embodiment of the pump according to the invention is that the first impeller has a first clamping surface, which cooperates with a second clamping surface, which is formed on the second impeller, and via the clamping surfaces a clamping force for clamping the first impeller on a truncated cone, which is formed on a drive shaft carrying the first impeller, is introduced into the first impeller. This is a simple, inexpensive construction, which advantageously simultaneously causes the attachment of both wheels.

According to a further development, it is proposed that the second impeller comprises a blade arranged in a thread-like manner on a cylinder. This means a simple, cost-effective production of the second impeller, for example according to DE 20 2004 013 752 U1.

The pumping stage with the at least one thread-like blade can be additionally improved in its pumping action, the blade at her the

Shaft portion facing end has an extension. For the aforementioned applications in the hygienic to aseptic area, it is advantageous to design the pump so that the first impeller part of a

normal suction centrifugal pump is.

Also in view of the application and especially in cooperation with a Zentrifugalpumpstufe an advantageous embodiment is a pump in which the second impeller is part of a liquid ring pumping stage.

The vortex formation in the pumped fluid is advantageously reduced, whereby the occurrence of cavitation is also reduced when the pump is so

is further developed that an end face, which is formed on the second impeller on the side facing the shaft portion smoothly merges into the shaft portion.

Reference to an embodiment and its developments, the invention will be explained in more detail and the representation of the effects and benefits to be deepened.

Show it:

 Fig. 1: Perspective view of a self-priming centrifugal pump;

 2 shows a longitudinal section through a self-priming centrifugal pump;

 3 shows a section through detail view A;

Fig. 4: Perspective view of the second impeller. In Fig. 1 is a self-priming centrifugal pump 1 in a perspective

Illustration shown. This centrifugal pump 1 comprises a liquid ring pumping stage 2 and a normal suction centrifugal pump 3. The liquid ring pumping stage 2 is associated with an inlet 4 of the self-priming centrifugal pump 1. Fluid, in particular liquid, which is possibly admixed with gas, enters through the inlet 4 of the centrifugal pump 1 and first enters the liquid ring pumping stage 2.

Subsequently, the fluid is transferred to the centrifugal pump 3. The fluid ejected from there leaves through the outlet 5 the self-priming

Centrifugal pump 1. A return line 6 branches off from the centrifugal pump 3. Fluid flows through this return line 6 from the centrifugal pump 1 back into the

 Liquid ring pumping stage 2 and is there for the formation of the liquid ring already when starting the centrifugal pump 1 available.

The self-priming centrifugal pump 1 rests on feet 7 and has a cover 8, are housed under the drive and control means, with these drive and control means, the pumping action of the self-priming centrifugal pump 1 is controllable.

In Fig. 2, the self-priming centrifugal pump 1 is shown in a longitudinal section.

A multi-part housing 9 houses the

Liquid ring pumping stage 2 and the normal suction centrifugal pump 3. The housing 9 is supported by a lantern 10, which connects to a motor 1 1 manufactures. This engine 1 1 is typically designed as an electric motor and is controlled by an electronic control unit 12. Engine 1 1 and control electronics 12 are arranged under the cover 8 and are supported by the feet 7.

The motor 1 1 has a motor shaft 13, with which a drive shaft 14 is releasably connected and rotationally fixed. This drive shaft 14 carries a first impeller 15 and a second impeller 16. The impellers 15 and 16 are by means of motor shaft 13 and

Drive shaft 14 mounted in a cantilevered manner and are rotatably supported by the bearings of the motor shaft 13.

The first impeller 15 is part of the normal-suction centrifugal pump 3 and has a first pumping section 17. This is arranged in a first chamber 18. Upon rotation of the drive shaft 14 fluid flows in the region of a rotation axis of Drive shaft 14 and thus of the first impeller 15 and is ßen from the first pump section 17 radially outward and there moved in the circumferential direction and pressurized. The second impeller 16 is part of the liquid ring pumping stage 2 and comprises a second pumping portion 19. This second pumping portion 19 is disposed in a second chamber 20 and formed so that in this upon rotation of the

Drive shaft 14, a liquid ring is generated, wherein an axis of symmetry of the liquid ring is offset radially to the axis of rotation of the drive shaft. By the liquid ring and the eccentrically arranged to him second impeller 16 creates a negative pressure within the liquid ring pumping stage 2, which causes a suction of fluid through the inlet 3.

The detailed view A is shown enlarged in Fig. 3 and shows a section of the wheels and the region of the connection of both wheels together.

The drive shaft 14 passes through the housing 9 in the area in which housing 9 and lantern 10 are connected to each other. The lantern 10 surrounds the

Drive shaft 14. The sealing of an interior of the housing 9 against the atmosphere by means of a mechanical seal. This mechanical seal comprises a rotating seal ring 21, which is arranged co-rotating with the drive shaft 14. The rotating seal ring 21 is in sliding contact with a stationary seal ring 22 which is mounted in the housing 9 so as not to rotate with it. A development of the mechanical seal is a flushed design according to DE 203 16 570 U1.

The first chamber 18 is separated from the second chamber 20 by a housing wall 23. In this housing wall 23, an opening 24 is provided, which is penetrated by a shaft portion 25.

The shaft portion 25 is made in this example as part of the second impeller 16 and includes a shaft end 26 and a constriction 27. Das

Shaft end 26 is in mechanical contact with the first impeller 15. The transition point between the first impeller 15 and shaft portion 25 is sealed by means of a seal 28. The seal 28 is designed as an O-ring, which is accommodated in an adapted contour such that no gap between it and the recording remains. This is advantageous for hygienic application, since deposits of dirt are prevented.

The shaft portion 25 is formed between the constriction 27 and the shaft end 26 tapered from the shaft end 26 to the constriction 27. A diameter of the shaft portion 25 decreases from the transition to the first impeller 15 for constriction 27 out. At the same time have second impeller 15 and shaft portion 25 between constriction 27 and the first pump section 17 on a smooth course. The constriction 27 causes together with the smooth course of a

more uniform distribution and reduction of the flow velocity in this area of the centrifugal pump. In particular, tips of the

Flow velocity is reduced to largely avoided, there is a reduction in speed over the entire cross section. This reduces the NPSH value.

The smooth course is given in the mathematical sense, if the intersection curve in Fig. 3 follows a curve with a steady slope. This means that kinks, steps or heels are avoided as far as technically feasible. In the context of this invention smooth is also given when the seal 28 has an exposed portion which interrupts the surface of the shaft portion 25 and the first impeller 15 and is exposed piecewise with a curvature. As long as a predominantly laminar flow along the surface of shaft portion 25 and the first impeller 15 remains educable, a sufficiently smooth course is given. A further improvement of the flow path is given if, as in the example shown, an end face 29 of the second impeller merges with a groove 30 and thus with a smooth course in the shaft section 25. If the shaft portion 25 is made in one piece with the second impeller 16, the groove 30 is particularly simple and smooth to produce.

The shaft portion reaches in the constriction 27 its thinnest point

preferably in the second chamber 20 and / or in the opening 24 in the

Housing wall 23. The constriction 27 may, as shown, have an extension in the longitudinal direction of the shaft portion. Through this placement and

If necessary, expansion of the constriction 27, it is possible in large

Flow passage to keep the opening 24 small, so that the functions of Liquid ring pumping stage 2 and normal-suction centrifugal pump 3 are not impaired despite increasing the flow-through cross-sectional area.

The embodiment shows a connection of the drive shaft 14 with the first impeller 15 and the second impeller 16, which for receiving the flying from

Storage resulting forces is very well suited and allows high accuracy and low gap to the housing 9.

The drive shaft 14 has at its end remote from the motor shaft 3 a truncated cone 31 which terminates in a cylindrical threaded portion 32. This threaded portion 32 is received in a thread in the shaft portion 25 under formation of a screw connection. The first impeller 15 has a first clamping surface 33 which can be brought into mechanical contact with a second clamping surface 34 formed on the shaft section 25. Making the

Screw connection with participation of the threaded portion 32 causes clamping forces which are introduced from the second impeller 16 via first clamping surface 33 and second clamping surface 34 in the first impeller 15 and cause a clamping on the truncated cone 32. The second impeller has a base 35 to a cylinder. On this at least one thread-like encircling blade 36 is provided. This blade 36 serves to create and maintain a liquid ring in the second chamber 20 and the screw-like passage of the gas phase through the second chamber 20. This at least one blade 36 forms the second

Pump section 19. At its end, the blade may have an extension 37 which projects beyond the end face 29 in the axial direction. This runs in the gap which exists between the end of the blade 36 and the housing wall 23 and there improves the formation of the liquid ring. A perspective view of the second impeller 16 is shown in FIG. 4. The second

Impeller 16 in this figure has three blades 36 and each of the blades has at its end extensions 37 which are oriented in the axial direction.

Extensions 37 are provided on both the inlet 4 side facing as well as on the side of the shaft portion 25. The cylinder 35, which is closed with an end plate 38, has an extract 39 arranged with Wrench surfaces with which the second impeller 16 can be screwed onto the threaded portion 32.

LIST OF REFERENCE NUMBERS

1 self-priming centrifugal pump

 2 liquid ring pumping stage

 3 normal suction centrifugal pump

 4 inlet

 5 outlet

 6 return line

 7 feet

 8 cover

 9 housing

 10 lantern

 1 1 engine

 12 control electronics

 13 motor shaft

 14 drive shaft

 15 first impeller

 16 second impeller

 17 first pump section

 18 first chamber

 19 second pump section

 20 second chamber

 21 rotating seal ring

 22 stationary sliding ring

 23 housing wall

 24 opening

 25 shaft section

 26 shaft end

 27 constriction

 28 shaft seal

 29 face

 30 coving

31 truncated cone Thread portion first clamping surface second clamping surface

cylinder

 shovel

 renewal

end disk

abstract

 detailed view

Claims

claims 1 . Self-priming pump (1) having a housing (9), an inlet (4) and an outlet (5), with a first impeller (15) having a first  Pump section (17) which is arranged in a first chamber (18) and a second impeller (16) with a second pump section (19), which is arranged in a second chamber (20), and one between the  Pump portion (17, 19) provided shaft portion (25), which shaft portion (25) comprises a shaft end (26) and an opening (24) of a housing wall (23) passes through, characterized in that the  Shaft portion (25) between a constriction (27) and the shaft end (26) is tapered from the shaft end (26) to the constriction (27) and the first impeller (15) and shaft portion (25) between constriction (27) and first pump section (17) have a smooth course. 2. Pump according to claim 1, characterized in that the thinnest point of the shaft portion (25) in the second chamber (20) is arranged. 3. Pump according to claim 1, characterized in that the thinnest point of the shaft portion (25) in the opening (24) is arranged. 4. Pump according to one of the preceding claims, characterized  in that the first impeller (15) and the second impeller (16) are mounted together in a floating manner. 5. Pump according to one of the preceding claims, characterized  characterized in that the shaft portion (25) on the second impeller (16) is formed. 6. Pump according to one of the preceding claims, characterized  characterized in that the shaft portion (25) receives a threaded portion (32) of a drive shaft (14) supporting the first impeller (15). 7. Pump according to one of the preceding claims, characterized characterized in that the first impeller (15) has a first clamping surface (33) has, with a second clamping surface (34) formed on the second impeller (16) cooperates and on the clamping surfaces (33, 34) a clamping force for clamping the first impeller (15) on a truncated cone (31), the a drive shaft (14) carrying the first impeller (15) is introduced into the first impeller (15). Pump according to one of the preceding claims, characterized  in that the second impeller (16) comprises a blade (36) arranged in a thread-like manner on a cylinder (35). Pump according to claim 8, characterized in that the blade (36) has an extension (37) at its end facing the shaft section (25). 10. Pump according to one of the preceding claims, characterized  characterized in that the first impeller (15) is part of a normal suction centrifugal pump. Pump according to one of the preceding claims, characterized  characterized in that the second impeller (16) is part of a  Liquid ring pumping stage is. 12. Pump according to one of the preceding claims, characterized  characterized in that an end surface (29) formed on the second impeller (16) on the side facing the shaft portion (25) smoothly merges into the shaft portion (25).