Screw Pump

Abstract

A screw pump for transporting a fluid, with a drive spindle having a drive spindle profile and with at least one running spindle having a running spindle profile, the running spindle engages with its running spindle profile at least partially in the drive spindle profile of the drive spindle, the drive spindle profile and/or the running spindle profile is formed as a rolled profile, and a method for producing a spindle for such a screw pump, and a method for producing a groove in such a spindle are disclosed.

Claims

1. A screw pump for transporting a fluid, the screw comprising: a drive spindle having a drive spindle profile, and at least one running spindle having a running spindle profile, wherein the running spindle engages with its running spindle profile at least partially in the drive spindle profile of the drive spindle, and wherein at least one of the drive spindle profile and the running spindle profile is formed as a rolled profile.

2. The screw pump according to claim 1, wherein at least one of drive spindle profile and the running spindle profile is at least one of a rolled involute profile and an epicycloid profile and a profile without undercut.

3. The screw pump according to claim 1, wherein at least one of the drive spindle and the running spindle provides on its outer edge a lubricant groove extending substantially radially inward.

4. The screw pump according to claim 1, wherein the screw pump has a single thread.

5. The screw pump according to claim 1, wherein the screw pump has multiple threads.

6. The screw pump according to claim 1, wherein the drive spindle profile and running spindle profile intermesh without play.

7. The screw pump according to claim 1, wherein the drive spindle profile is formed complementary to the running spindle profile.

8. A method for producing a spindle profile of a spindle of a screw pump, comprising: forming the spindle profile in a cold rolling process.

9. The method according to claim 8, wherein the spindle profile is at least one of a rolled involute profile and an epicycloid profile and a profile without undercut.

10. A method for producing a lubricant groove with a first groove wall and a second groove wall and a groove base arranged in-between, wherein the lubricant groove is formed on an outer edge of at least one of a drive spindle and a running spindle of a screw pump, and the groove base is offset substantially radially inwardly from the outer edge of the spindle, wherein the method comprises: a. creating a first spindle profile flank by rolling; b. forming a first groove wall by displacement of material on rolling of the first profile flank; c. creating a second spindle profile flank by rolling; d. forming a second groove wall by displacement of material upon rolling of the second profile flank.

11. The method according to claim 10, further comprising a lubricant groove being formed in a screw pump, the screw pump including a drive spindle having a drive spindle profile, and at least one running spindle having a running spindle profile, wherein the running spindle engages with its running spindle profile at least partially in the drive spindle profile of the drive spindle, and wherein at least one of the drive spindle profile and the running spindle profile is formed as a rolled profile.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0017] The drawings show:

[0018] FIG. 1: a diagrammatic section view through a screw pump;

[0019] FIG. 2: a diagrammatic radial section view through a spindle of the screw pump shown in FIG. 1;

[0020] FIG. 3: a diagrammatic depiction of the machining of a spindle; and

[0021] FIG. 4: a diagrammatic section view through a flank of the spindle shown in FIGS. 1 and 2.

DETAILED DESCRIPTION OF THE INVENTION

[0022] In the description below, the same or equivalent elements carry the same reference numerals.

[0023] FIG. 1 shows a longitudinal section through a multiple-thread screw pump 1 with a drive spindle 2 which drives at least two running spindles 4, 6. The drive spindle 2 is rotated in the known manner via a motor. The drive spindle and the running spindles 4, 6 are in turn arranged in a housing 8, wherein the running spindles 4, 6 contact the housing 8 directly.

[0024] As further shown in FIG. 1, the drive spindle 2 and the running spindles 4, 6 intermesh so that on rotation of the drive spindle 2, the running spindles 4, 6 also rotate. Furthermore, the drive spindle 2 and the running spindles 4, 6 have drive spindle and running spindle profiles 10, 12 which are configured complementary to each other, so that on rotation of the spindles, a fluid can be screwed from a first chamber 14 into a second chamber 16. The flanks 18, 20 of the running spindles and drive spindle 2 are curved complementarily accordingly, wherein usually the flank curvature of a flank 18 of the drive spindle 2 is substantially convex, and the flank curvatures of flanks 20 of running spindles 4, 6 are substantially concave.

[0025] Such a running spindle profile 10 is shown diagrammatically in FIG. 2. As shown from the figure, the profile 10 is formed as a profile without undercut which follows an epicycloid curve 22. Alternatively, other profiles without undercut, such as for example an involute profile, may be formed. Such profiles are ideal for screw pumps 1 and can advantageously be rolled.

[0026] As FIG. 3 shows, for the formation of a rolled profile 10, a rolling tool 24 is guided along the spindles 2; 4; 6. Because of the pressure exerted by the tool 24, the material of the spindles 2; 4; 6 is pressed into the corresponding form for the profile 10. The rolling process indeed requires great experience and correspondingly configured tools 24, but no extra material need be provided for the formation of the profile itself, since this is pressed at the corresponding points during the rolling process. Since in addition, multiple passes of the profile 10 are not required, the drive or running spindles 2; 4; 6 can be produced as endless spindles which are then shortened to the corresponding lengths. Furthermore, the rolling process has the advantage that no surface roughness occurs because of material compression, so that further treatment such as for example grinding can be largely omitted. Also, the rolling process gives surfaces with constant quality within a very narrow tolerance range. A further advantage of the rolled profile 10 is that spindle profiles 10 with particularly hard flanks 20 can be provided.

[0027] The profile 12 of the drive spindle 2 can be produced similarly.

[0028] As FIG. 1 further shows, the running spindles 4, 6 lie with their outer edges 26 directly on the housing 8. Consequently, friction occurs between the housing 8 and the outer edges 26, which can be reduced ifas shown in FIG. 4a groove 28 is produced in the outer edge 26. This groove has two groove walls 30, 32 and a groove base 34 lying in-between.

[0029] This lubricant groove may advantageously be made directly on rolling of the profile 10, since the material displaced during rolling can be built up as the groove walls 30, 32. Thus there is no need for the difficult milling of the groove 28. The groove base 34 may however still be optionally reworked.

[0030] As a whole, with the screw pump with rolled profile, a screw pump can be provided which is simpler and faster to produce. It also constitutes a cost saving since no additional material need be provided for the material removal process. Also, with the rolled profile, tolerances can be achieved which are difficult to achieve with material removal processes. In particular, involute profiles, epicycloid profiles or profiles without undercut are easy to produce with the rolling process and at the same time offer good pumping properties for a fluid transport.

LIST OF REFERENCE NUMERALS

[0031] 1 Lubricant pump

[0032] 2 Drive spindle

[0033] 4, 6 Running spindle

[0034] 8 Housing

[0035] 10 Running spindle profile

[0036] 12 Drive spindle profile

[0037] 14 First receiver region for a fluid

[0038] 16 Second receiver region for a fluid

[0039] 18 Profile flank of drive spindle

[0040] 20 Profile flank of running spindle

[0041] 22 Epicycloid curve

[0042] 24 Rolling tool

[0043] 26 Outer edge of running spindle

[0044] 28 Lubricant groove

[0045] 30, 32 Groove wall

[0046] 34 Groove base