Method for manufacturing a stator or machining the inner wall of a stator

Abstract

Disclosed is a method for manufacturing a stator for an eccentric screw motor where at least two milling heads are used for machining the inner wall of the stator tube, wherein, at the start of the machining, one of the milling heads is brought to a predetermined position near the stator with respect to the end of the stator tube, the milling head is fed into the tube interior along its linear axis from this predetermined position, and a thread is machined until the milling head reaches at least the longitudinal center of the stator tube or exceeds a predetermined value, and the second milling head starts its machining of the inner wall surface of the stator tube at this point, wherein the milling head is moved along its linear axis and rotated about its rotary axis until the milling head reaches the centre of the stator tube.

Claims

1. A device for machining a stator tube comprising: a chuck, configured to receive and hold the stator tube; two movable milling heads, comprising a first milling head and a second milling head, positioned on opposite ends of the chuck, and a control unit configured to control the two movable milling heads to machine the stator tube by: first moving the first milling head to a first position relative to the chuck; accelerating the first milling head to a first machining speed after moving the first milling head to the first position; moving the first milling head at the first machining speed along a first linear axis relative to the stator tube to a first predetermined point, to form a first interior thread; determining an exit point of the first interior thread; moving a second milling head to a second position on the opposite side of the stator tube based on the determined exit point of the first interior thread; accelerating the second milling head to a second machining speed, after moving the second milling head to the second position; moving the second milling head along a second linear axis relative to the stator tube to a second predetermined point, to form a second interior thread; wherein the first interior thread and the second interior thread form a continuous thread.

2. The device according to claim 1, wherein the control unit is configured to machine the stator tube, the stator tube having an inner wall surface is lined with an elastomer the stator tube having a dimension or inner contour with a ratio V of the length L to the diameter D of V=L:D30:1.

3. The device according to claim 1, wherein the first milling head and the second milling head are both supported by a tool-holder, both tool-holders comprising a tool drive and/or a centring device and/or supporting means and/or a chip outlet and/or a coolant supply.

4. The device according to claim 3 wherein each tool holder comprises an inner ring configured for stable hydraulic guidance of the milling head to the inner wall surface of the stator tube via a supporting cone.

5. The device according to claim 4, wherein the coolant supply is supplied via a drive train of the respective milling head, wherein an outlet opening for the coolant supply is located by the respective milling head.

6. The device according to claim 2, wherein the ratio V is greater than or equal to 40:1.

7. The device according to claim 1, wherein each of the two milling heads comprises a plurality of adjacent milling heads located on a carrier.

8. The device according to claim 1, wherein the first predetermined point and the second predetermined point are both at a longitudinal center of the stator tube.

9. The device according to claim 1, wherein the control unit is further configured to determine an exit contour of the first interior thread.

Description

(1) Exemplary, but non-limiting, embodiments of the invention based on the drawings are explained in detail below:

(2) FIGS. 1 and 2 show schematic views of known stator tubes.

(3) FIG. 3 shows a view of a stator tube formed according to the invention.

(4) FIG. 4 schematically shows a machining machine or device according to the invention.

(5) FIG. 5 shows a milling head.

(6) FIG. 6 shows a tool holder.

(7) FIG. 7 schematically shows a milling head inside or in front of the end surface or opening of a stator tube.

(8) At the start of manufacturing of a stator, a prefabricated metal tube with the finished length of the component, for example 6000 mm, is introduced into a machining machine 1 and centrally clamped by a chuck 2. The machining machine 1 comprises respectively on both sides of the chuck 2 or its carrier 20 a milling tool 3, 3 which carries a milling head 4 in its front end region close to the workpiece. The axis of rotation V of the milling head 4 protrudes laterally from a tool holder 24, which is adjustable and rotatable about its longitudinal axis L in the longitudinal direction of the tube 6. FIG. 4 shows the basic structure of a machining machine 1.

(9) The machining machine or device 1 according to the invention comprises a carrier 20 or a frame 20, which carries a chuck 2, in which the stator tube 6 to be machined can be firmly clamped. Milling stations F1, F2 are formed on both sides of the carrier 20, wherein each has a tool holder 24 carrying a milling head 4, 4. The milling heads 4, 4 arranged on the tool holder 24 are shown schematically in greater detail in FIG. 5. This shows milling heads attachable to a rotating drive which can rotate them about its rotational axis V. The tool holder 24 of the milling head 4 is movable along a longitudinal axis Z1, while the tool holder 24 for the milling head 4 is movable along a longitudinal axis Z2, allowing the clamped stator tube 6 to be displaced linearly in the longitudinal direction. At the same time, the milling heads 4, 4 carried by the tool holders 24 with the respective tool holder 24 can be rotated about a rotary axis C, C or the longitudinal axis of the stator tube 6, so that a helical thread 10 can be milled inside the stator tube 6 by the milling heads 4, 4. The rotational speed of the milling heads 4, 4 can be controlled by means of the schematically illustrated control unit 23, or the tool holder 24 along the axes Z1, Z2 and only the rotary axes C, C moved or adjusted. FIG. 4 shows the milling heads 4, 4 in their starting position, i.e. in a position before the start of machining of a stator tube 6 clamped in the carrier 20.

(10) The manufacturing process is, for example, as follows:

(11) Each milling tool 3, 3 comprises a tool holder 24, a tool drive, a centering device, a chip outlet, a coolant supply and the milling head 4, and is initially moved close to the tube 6 or its end face or inserted in the tube 6 until the milling head 4 is at a predetermined distance from the tube 6, as shown in FIG. 4.

(12) An inner ring 25 that is also carried by the tool holder 24 is then hydraulically applied to the inner wall of the tube 6, to ensure stable guidance of the milling head 4 inside the tube 6. Further, the coolant supply, which is guided via the drive train or the tool holder 24 directly past the milling head 4, is brought into operation.

(13) Thereafter, the CNC rotary axis C and the CNC linear axis Z1 is brought into operation, in particular at the same time, and given the pitch direction and the pitch angle of the thread 10 to be formed. The milling head 4 is accelerated to machining speed.

(14) The tool holder 24 with the milling head 4 now moves at a constant feed rate along the axis Z1+ in the tube 6, and the milling head 4 thereby forms part of the thread 10 to be produced in the tube 6, for example a part of the flank 20 or 21 of the thread 10.

(15) The path which the milling head 4 travels during manufacture depends on the tube length, the milling diameter, the distance of the milling head 4 to the tube end before commencing milling, and the tolerance. Thus the path of the milling head 4 may be calculated as follows: Workpiece length: 6000 mm Milling diameter: 20 mm Distance of milling head to workpiece: 10 mm Tolerance: 10 mm

(16) $\mathrm{Axis}Z1-\frac{6000}{2}+\frac{20}{2}+10+10-3030\mathrm{mm}$

(17) After reaching the calculated or predetermined starting point of the milling head 4 to commence milling, the axis Z1 stops. The axis C is rotated until the milling head 4 contacts or lies in front of the end face or the inner wall surface of the tube 6 in the region of the flank 20 of the thread 10 to be formed or machined. The starting point of this thread 10 is selected or specified. Alternatively, it may be provided that a prefabricated thread 10 is already present in the tube 6 to be milled before commencing milling.

(18) Based on this contact point located in the end region of the tube 6, there results a defined exit point of the thread 10 at the end face II, i.e. the opposite end face of the tube 6 on a secondary imaginary spiral line in the tube, which corresponds to the thread to be formed.

(19) Thereafter, the axis Z1 and the axis C start with a predetermined direction of rotation and constant feed and move the milling head and its tool holder 24. If the milling head 4 overshoots the centre of the tube or by a predetermined amount, it is turned off or moved out of the tube 6 again.

(20) FIG. 6 schematically shows a tool holder 24 carrying a milling head 4. The cooling fluid conduit and the chip output unit are carried in the tool holder 24. The tool holder 24 can be supported on the inner wall of the stator tube by means of the supporting part or the inner ring 25.

(21) FIG. 7 shows a schematic section through a stator tube 6 with a tool holder 24 in section, wherein the milling head 4 is in a position at which it is placed against the flank 20, 21 of an already partially machined thread 10, or to which the milling head 4 is moved following a milling operation as a starting point for a further milling process.

(22) If the axes Z1 and C have each travelled the minimum path which results from the matching of the determined or calculated spiral line at Point II, then the milling head 4 with its axis Z2 is moved to the left in FIG. 4 in fact with the same speed as the axis Z1. When the tool holder 24 with the milling head 4 with the axis Z1 reaches its starting point, the axis Z1 is stopped and waits until the tool holder 24 with the milling head 4 with the axis Z2 and the rotary axis C reaches its inner position, and is rotated with the axis C to the position or has reached the flank 21 of the thread 10, and has travelled with the axis Z2 until that point is reached, travels this time in the opposite direction on a predetermined secondary spiral line to the flat surface I at the left end of the tube.

(23) This principle is now repeated until all threads have been machined multiple times and the chip volume and the geometry of the profile prevents entire machining by a milling tool 4, 4 in one step. Thus, as many surface milling passes are performed with the milling heads 4, 4, possibly with different geometries, as are necessary to achieve the desired profile and number of passes.

(24) All movements of the milling heads 4, 4 are controlled by the control unit 23. The linear axis and rotary axis of the respective milling head 4, 4 correspond to the longitudinal axis and rotary axis of the tool holder 24 carrying the respective milling head 4, 4 in its movement relative to the stator 6.