Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
METHOD FOR MANUFACTURING AT LEAST A PART OF A RING GEAR, AND RING GEAR
Document Type and Number:
WIPO Patent Application WO/2017/069626
Kind Code:
A1
Abstract:
The invention relates to a method for manufacturing at least a part of a ring gear (2), particularly for use in heavy industry. The invention also relates to a ring gear component (10) obtained by applying the method according to the invention. The invention further relates to a ring gear (2) obtained by applying the method according to the invention. In addition, the invention relates to an assembly of a ring gear (2) according to the invention and at least one pinion (21) configured to co-act with the ring gear (2). The-invention moreover relates to a rotatable drum (23) comprising a ring gear (2) according to the invention. The invention subsequently relates to a device for manufacturing a part of a ring gear (2) according to the invention by applying the method according to the invention.

Inventors:
VAN DER WEGEN, Dirk Hubert Petrus (Bosweg 160b, 5062 SH Oisterwijk, 5062 SH, NL)
Application Number:
NL2016/050724
Publication Date:
April 27, 2017
Filing Date:
October 21, 2016
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
HOLWEGEN TILBURG B.V. (Lovensekanaaldijk 113, 5013 BJ Tilburg, 5013 BJ, NL)
International Classes:
B23P15/14; B21D7/08; B21D53/28; B23K15/00; F16H55/12
Foreign References:
US0786274A1905-04-04
CA1186529A1985-05-07
US20150239076A12015-08-27
US4118848A1978-10-10
DE8205946U11983-04-28
DE911500C1954-05-17
GB856254A1960-12-14
Other References:
EHRHARDT ET AL: "Elektronenstrahlschweissen ermoeglicht neue Fertigungstechnologien", FERTIGUNGSTECHNIK UND BETRIEB,, vol. 28, 1 January 1978 (1978-01-01), pages 299 - 302, XP009176167
Attorney, Agent or Firm:
SMEETS, Luc (Julianaplein 4, 5211 BC 's Hertogenbosch, 5211 BC, NL)
Download PDF:
Claims:
Claims

1. Method for manufacturing at least a part of a ring gear, comprising the steps of:

A) providing at least one arcuate ring gear segment manufactured at least partially from metal,

B) providing at least one ring gear element manufactured at least partially from metal, and

C) connecting the at least one ring gear element to the arcuate ring gear segment by means of electron beam welding (EBW).

2. Method as claimed in claim 1, wherein the at least one welded connection realized during step C) forms a seam weld.

3. Method as claimed in claim 2, wherein the at least one welded connection realized during step C) forms a fully welded seam weld.

4. Method as claimed in any of the foregoing claims, wherein at least one ring gear segment provided during step B), which is connected by means of electron beam welding during step C), is formed by a radially protruding web plate.

5. Method as claimed in claim 4, wherein the overall length of an outer peripheral edge of the at least one web plate welded to a ring gear segment during step C) substantially corresponds to the length of an inner peripheral edge of the ring gear segment.

6. Method as claimed in claim 5, wherein the curvature of the outer peripheral edge of the at least one web plate welded to a ring gear segment during step C) substantially corresponds to the curvature of the inner peripheral edge of the ring gear segment.

7. Method as claimed in any of the claims 4-6, wherein a plurality of web plates are provided during step B), which are connected to a peripheral edge by means of electron beam welding during step C), such that at least two web plates mutually define a plane.

8. Method as claimed in claim 7, wherein the at least two web plates which mutually define a plane are also mutually connected by means of welding, preferably electron beam welding, during step C).

9. Method as claimed in any of the foregoing claims, wherein an inner peripheral edge of the arcuate ring gear segment is provided with at least one protruding nose.

10. Method as claimed in any of the claims 4-8 and claim 9, wherein the protruding nose forms a radially protruding longitudinal nose and wherein the at least one web plate is connected to the longitudinal nose by means of electron beam welding during step C).

11. Method as claimed in any of the foregoing claims, wherein at least one ring gear segment provided during step B), which is connected by means of electron beam welding during step C), is formed by an axially extending joint-surface.

12. Method as claimed in claim 11, wherein at least one joint-surface is connected to an end surface of the inner peripheral edge of the ring gear segment by means of electron beam welding during step C), wherein the at least one joint-surface is configured to be connected to a joint-surface of another ring gear segment.

13. Method as claimed in any of the claims 4-10 and any of the claims 11-12, wherein at least one web plate is connected to a peripheral edge of the arcuate ring gear segment by means of electron beam welding during step C), after which at least one joint-surface is connected to the above stated peripheral edge of the arcuate ring gear segment by means of electron beam welding and the at least one joint-surface is also connected to a web plate by means of welding, particularly electron beam welding.

14. Method as claimed in claim 13, wherein each end surface of the inner peripheral edge of the ring gear segment is connected to at least one joint-surface by means of electron beam welding during step C).

15. Method as claimed in any of the claims 11-14, wherein at least two joint- surfaces are connected to the same end surface of the inner peripheral edge of the ring gear segment by means of electron beam welding during step C).

16. Method as claimed in claim 13 and 15, wherein at least two joint-surfaces are connected to the same end surface of the inner peripheral edge of the ring gear segment by means of electron beam welding during step C) such that the joint-surfaces mutually enclose a web plate, wherein the above stated joint-surfaces are also welded to the above stated web plate by means of welding, particularly electron beam welding.

17. Method as claimed in any of the claims 10-16, wherein each joint-surface is provided with a plurality of passage openings for bolts for enabling mutual mechanical attachment of joint-surfaces of different ring gear segments.

18. Method as claimed in any of the foregoing claims, wherein the method also comprises step D), which comprises, prior to connecting the at least one ring gear element to the arcuate ring gear segment by means of electron beam welding (EBW) as according to step C), of connecting the at least one ring gear element to the arcuate ring gear segment by means of spot welding.

19. Method as claimed in claim 18, wherein a plurality of ring gear elements are provided during step B), wherein at least two ring gear elements are mutually connected by means of spot welding during step D).

20. Method as claimed in any of the foregoing claims, wherein connecting the at least one ring gear element to the arcuate ring gear segment by means of electron beam welding as according to step C) takes place in a vacuum.

21. Method as claimed in any of the foregoing claims, wherein connecting the at least one ring gear element to the arcuate ring gear segment by means of electron beam welding as according to step C) takes place by applying an electron gun with a power lying between 15 and 45 kW, preferably between 25 and 35 kW.

22. Method as claimed in any of the foregoing claims, wherein a welded connection with a weld depth lying between 50 and 150 mm is realized during the electron beam welding as according to step C).

23. Method as claimed in any of the foregoing claims, wherein the at least one ring gear segment is manufactured at least partially from forged steel.

24. Method as claimed in any of the foregoing claims, wherein the at least one ring gear segment is formed during step A) by:

Al) providing at least one annular and/or arcuate forged basic component with a first diameter, and

A2) bending outward each basic component into an arcuate ring gear segment with a second diameter, wherein the second diameter is greater than the first diameter.

25. Method as claimed in claim 24, wherein the first diameter lies between 1 and 10 metres.

26. Method as claimed in claim 24 or 25, wherein a plurality of forged basic components are provided during step Al) and wherein the forged basic components are bent outward during step A2) into arcuate ring gear segments configured to be mutually coupled, thus forming a ring.

27. Method as claimed in claim 26, wherein a plurality of basic components are bent outward during step A2) into arcuate ring gear segments with a substantially identical, preferably wholly identical, second diameter.

28. Method as claimed in claim 26 or 27, wherein the arc length of the ring gear segments formed during step A2) is substantially identical.

29. Method as claimed in any of the claims 26-28, wherein n ring gear segments are formed during step A2) for forming a ring, wherein n equals an even number.

30. Method as claimed in any of the claims 24-29, wherein the at least one basic component provided during step Al) is formed from a seamless rolled forged steel ring.

31. Method as claimed in any of the claims 24-30, wherein the method also comprises step A3), which comprises, following provision of at least one annular basic component as according to step Al) and before bending outward of the at least one annular basic component as according to step A2), of opening, preferably sawing open, the at least one annular basic component.

32. Method as claimed in any of the claims 24-31, wherein the second diameter is smaller than the sum of the first diameter.

33. Method as claimed in any of the claims 24-32, wherein the method also comprises step A4), which comprises, following forming of the at least one ring gear segment as according to step A2), of shortening at least one end surface, preferably two opposite end surfaces of the ring gear segment.

34. Method as claimed in claim 33, wherein the method comprises step A5), which comprises, following forming of the at least one ring gear segment as according to step A2), of adjusting the measurements of the longitudinal nose.

35. Method as claimed in claim 30 and 31, wherein step A5) is performed after step A4) has been performed.

36. Method as claimed in any of the foregoing claims, wherein the at least one additional ring gear segment is manufactured at least partially from metal, preferably steel.

37. Method as claimed in any of the foregoing claims, wherein the method also comprises step E), which comprises of mutually connecting the ring gear segments, thus forming a ring.

38. Method as claimed in any of the foregoing claims, wherein the method also comprises step F), which comprises of arranging a toothing on a peripheral edge of each ring gear segment.

39. Method as claimed in claim 38, wherein arranging a toothing on a peripheral edge of each ring gear segment as according to step F) takes place by milling away material from said peripheral edge.

40. Method as claimed in claim 38 or 39, wherein the orientation of the toothing arranged in each ring gear segment during step F) and a longitudinal axis of the ring gear which has been formed or is to be formed as such mutually enclose an angle.

41. Method as claimed in any of the claims 4-8, 10, 13-14, 16, wherein the method also comprises step G), which comprises of arranging mounting holes in the at least one web plate for mounting of the ring gear on a rotatable drum.

42. Ring gear component manufactured by applying the method as claimed in any of the foregoing claims, comprising:

an arcuate ring gear segment provided on an outer peripheral edge with a toothing,

at least one radially protruding web plate connected to an inner peripheral edge of the ring gear segment by means of electron beam welding, and at least one axially extending joint-surface positioned on at least one end surface of the inner peripheral edge of the ring gear segment and connected to the ring gear segment by means of welding, preferably electron beam welding.

43. Ring gear manufactured by applying the method as claimed in claim 37 and any of the claims 38-40.

44. Assembly of a ring gear as claimed in claim 43 and at least one pinion configured to co-act with the ring gear.

45. Rotatable drum, preferably for use as rotatable oven, rotatable dryer or rotatable grinding mill, comprising:

a frame,

an axially rotatable drum housing supported by the frame,

at least one ring gear as claimed in claim 43 connected to the drum housing, and

at least one drive co-acting with the at least one ring gear for axially rotating the drum housing.

46. Device for manufacturing at least a part of a ring gear by applying the method as claimed in any of the claims 1-41, comprising:

at least one welding chamber,

extractor means connected to the welding chamber for creating a vacuum in the welding chamber,

at least one electron gun arranged in the welding chamber and configured to realize an electron beam welded connection between at least one arcuate ring gear segment and at least one ring gear element, such as a web plate and/or a joint-surface,

at least one transport element connected to the electron gun and configured to displace the electron gun in the welding chamber, and

a control unit configured to program the transport element and the electron gun for the purpose of realizing an electron beam welded connection between at least one arcuate ring gear segment and at least one ring gear element, such as a web plate and/or a joint-surface.

Description:
Method for manufacturing at least a part of a ring gear, and ring gear

The invention relates to a method for manufacturing at least a part of a ring gear, particularly for use in heavy industry. The invention also relates to a ring gear component obtained by applying the method according to the invention. The invention further relates to a ring gear obtained by applying the method according to the invention. In addition, the invention relates to an assembly of a ring gear according to the invention and at least one pinion configured to co-act with the ring gear. The invention moreover relates to a rotatable drum comprising a ring gear according to the invention. The invention subsequently relates to a device for manufacturing a part of a ring gear according to the invention by applying the method according to the invention.

In heavy industry, such as the mining industry and the cement industry, heavy rotatable drum-shaped installations, referred to in short as rotatable drums, are used among other things to make (mined) materials suitable for further processing. The rotatable drums can for instance serve here as oven, dryer and/or as grinding mill. Each rotatable drum comprises here a housing which can be driven by applying a so-called open gear drive. The open gear drive comprises here at least one ring gear, formed by an annular gear with an external toothing which is mounted on the housing, and a pinion co-acting with the ring gear. The pinion is directly or indirectly coupled to a motor here. Motor driving of the pinion results in rotation of the ring gear and thereby of the housing. In such mills the ring gears which are used have a typical diameter of several metres.

Open gear drives are usually explained according to the applicable AGMA standards (American Gear Manufacturers Association) or DIN standards. The AGMA standards in particular stress the hardness of the material of the ring gear. Increasingly greater hardness is aimed for.

The ring gears were in the past usually manufactured from cast steel (such as

G.35CrMo4 or G.35CrNiMo6.6). Later, the use of nodular cast iron (such as EN-GJS- 700) increasingly superseded traditional cast steel in various applications. Examples hereof are semi-autogenous and autogenous grinding mills, also referred to as SAG and AG mills, which are typically used in the mining industry. Nodular cast iron however has little elongation and is not resistant to impact loads, so that it is still necessary to fall back on (cast) steel in a great number of applications.

The casting of ring gears from cast steel is a difficult process. Expensive (wood or Styropor) models need first be made, while the products are often cast only once. The casting of cast steel is accompanied by many quality problems. The relatively heavy toothing part thus cools much more slowly than the relatively light inner side, often resulting in (shrinkage) cracks. Large risers, which are later removed from the casting, are cast in order to avoid impurities in the final product. This means a great loss of material and energy. Despite all experience and technology, blowholes, (shrinkage) cracks and other imperfections often result in the final casting, which have to be ground out and welded following written permission from the client. A new heat treatment then has to take place. All in all, the process is very time-consuming, and stable production is not possible. Higher Brinell hardnesses (HB) in the order of magnitude of 300-310 can moreover only be achieved by means of additional heat treatments and cooling in liquid. This however causes a greatly increased risk of cracking. Manufacturing (heavy) ring gears from cast steel is therefore expensive, time-consuming, and the final quality is often mediocre.

Compared to cast steel, nodular cast iron is considerably simpler to use. The casting process in use of nodular cast iron is more predictable and easier to control. Cracks are almost always cut off very quickly, and cannot continue, as a result of the graphite particles present in nodular cast iron. It is therefore readily possible to cast a high- quality casting with reasonably great certainty. Expensive models however also need to be made in the case of nodular cast iron. Large risers, which have to be removed from the casting later by machine, are additionally also cast, this resulting in additional costs. A further drawback of nodular cast iron is that a great hardness is not compatible with the elongation. The loss of elongation with greater hardness ensures that impact loads can lead directly to cracking of the material, making nodular cast iron unsuitable for some applications.

In the manufacture of large ring gears for heavy industry the ring gear is given a modular construction of ring gear components. Each ring gear component comprises an arcuate ring gear segment, generally with an angle at the centre of 90° or 180°, wherein a toothing is arranged on an outer peripheral edge and wherein an inner peripheral edge is generally connected to one or more reinforcing web plates and one or more joint- surfaces in order to enable mutual coupling of the ring gear segments. Connecting the web plates and joint-surfaces to the ring gear segment takes place by means of submerged arc welding (SAW), wherein welding takes place under a layer of flux powder, wherein use is made of a mechanically supplied fusable (welding) electrode which simultaneously also gives off filler material for forming the welded connection. The SAW process becomes much more difficult to perform as the hardnesses increase. Buttering thus has to be applied in order to prevent problems in the weld as far as possible, which means that a strip of welding wire is first arranged on the material to be welded, wherein preheating takes place. If hardnesses exceed 330 HB (Brinell hardness), the SAW generally becomes very problematic. The stress-free annealing, which is absolutely necessary after the SAW, moreover results in a reduction of the hardness of the welded connection, which is undesirable. This is because the annealing temperature during the stress-free annealing is quite close to the tempering temperature of the usually applied forged steel, so that the forged steel is partially 'tempered', the hardness decreasing hereby. The necessary stress-free annealing makes it impossible or almost impossible to guarantee a Brinell hardness above 330 HB, which entails an undesired limitation of the applicability of the ring gears. Apart from the fact that ring gears with higher Brinell hardnesses (> 300 HB) cannot yet be realized at this moment, the production of the known ring gears is also relatively expensive because relatively large amounts of expensive welding electrode (welding wire) are used to generate diverse welded seams, wherein the welded seams moreover have to be generated on two sides, which is disadvantageous from a practical and economical viewpoint. The contact surfaces to be welded further have to be mechanically preprocessed, particularly chamfered, before the SAW in order to be able to realize a cross-sectionally bell-shaped welded connection, heavy machinery generally being required for this purpose on location. During SAW the contact surfaces to be welded have to be preheated and moreover held at temperature (+250°C) in the most stable manner possible during the whole welding process, wherein temperature fluctuations result in imperfections in the weld. The SAW process is moreover time-consuming and generally takes up multiple 24-hour periods because the welded connection has to be generated layer by layer. Continuous deployment of personnel is moreover required in the direct vicinity during the whole SAW process in order to guide the welding process and remove the flux powder. There is an increasing need for very great hardnesses (for instance 350-400 BHN) in the toothing part of a ring gear, which cannot be realized by means of conventional SAW and subsequent stress-free annealing.

A first object of the invention is to provide an improved production process for manufacturing at least a part of a ring gear.

A second object of the invention is to provide an improved production process for manufacturing at least a part of a ring gear whereby hardnesses of more than 330 HB can be achieved for use in heavy industry.

A third object of the invention is to provide a cheaper production process for manufacturing at least a part of a ring gear for use in heavy industry.

At least one of the above stated objects can be achieved by providing a method of the type stated in the preamble, comprising the steps of: A) providing at least one arcuate ring gear segment manufactured at least partially from metal, B) providing at least one ring gear element manufactured at least partially from metal, and C) connecting the at least one ring gear element to the arcuate ring gear segment by means of electron beam welding (EBW). Electron beam welding is a welding technique wherein welding takes place by means of an electron gun whereby a beam of electrons is released, focussed and accelerated, generally to about half the speed of light (150,000 km/s), wherein the beam of electrons is directed at the parts to be welded. Both the metal of the arcuate ring gear segment and the metal of the abutting additional ring gear element will here melt in position-selective manner and can even vaporize, wherein temperatures of up to about 25,000 Kelvin can be reached, whereby the melted parts will fuse, this resulting in a particularly strong welded connection which can extend over the whole depth (full penetration) of the contact surface formed between the arcuate ring gear segment and the at least one additional ring gear element. The achievable weld depth is relatively great here, wherein a weld depth of for instance 120 mm is not a problem, this in contrast to the conventional powder welding technique (SAW) used heretofore in the field. The weld width generally does not vary over the depth of the weld, whereby a linear welded connection is generally realized in cross-section, this in contrast to the form of a conventional submerged arc weld (SAW weld), which is characterized by a double bell-shaped form. The EBW weld is therefore much narrower and more homogeneous, and therefore stronger, generally by about 20%, than a SAW weld.

Because an electron beam is scattered and thereby disrupted relatively easily in gas/air, this increasing the chance of errors during the welding process, step C) preferably takes place in a vacuum environment. Electron beam welding is suitable for mutually connecting metal parts in efficient manner. These parts can be manufactured from the same metal, although it is also possible to envisage the metals and/or the composition of the metals differing from each other. With electron beam welding it is possible to weld together materials which cannot be welded by means of the conventional SAW, resulting in more freedom of choice in materials, and particularly of choice in steel qualities to be applied. In the method according to the invention the arcuate ring gear segment will generally be manufactured from (high-grade and generally high-carbon) forged steel, and at least one additional ring gear segment to be connected to the ring gear segment will be manufactured from steel, such as (rolled) steel plate. In contrast to the SAW technique usual in the field, the EBW technique allows a ring gear segment manufactured from high-carbon steel with a relatively great hardness (> 330 HB) to be welded to another ring gear segment, without this being detrimental to the final hardness of the ring gear. The energy supply (heat input) is moreover much smaller per cm 2 in the case of EBW - typically about 30-35 times smaller - than in SAW, whereby no or hardly any deformation of material occurs. What is even more important is that, owing to the relatively low energy supply, hardly any stresses result in and in the direct vicinity of the weld, whereby the expensive and hardness-reducing step of stress-free annealing is no longer necessary. Because the stress-free annealing can be dispensed with, sandblasting of the formed welded connection after the stress-free annealing is not necessary either, this producing an additional economic and technical advantage. A further advantage of applying electron beam welding during step C) is that the welded connection can be realized much more quickly than in the case of SAW. Much less energy is moreover needed in the electron beam welding, on the one hand because preheating of the components to be welded is no longer necessary and on the other hand because the material is heated very locally during welding, this producing a significant energy saving (>90%) relative to the conventional SAW. This makes it possible to realize an electron beam welded connection by means of an electron gun with relatively limited power of preferably between 15 and 45 kW, more preferably between 25 and 35 kW and typically about 30 kW. In addition, use need not be made during the electron beam welding of relatively expensive welding wire or welding electrode(s). The electron beam welding according to step C) preferably takes place in fully automated manner, whereby it is on the one hand no longer necessary to realize a manual (SAW) welded connection, this considerably reducing the chance of errors, and whereby on the other hand it requires practically no personnel to guide the process, which is particularly advantageous from an economic viewpoint. Automation of step C) will moreover significantly enhance the predictability and reproducibility of the welding process, wherein a particularly high final quality of the product is achieved.

During step C) the at least one arcuate ring gear segment, usually referred to as outer tyre, and at least one other ring gear element are placed closely against each other, after which the two components are welded to each other by means of electron beam welding, wherein preferably at least one seam weld (continuous weld) and preferably a fully welded (full penetration) seam weld are formed. Use can optionally be made here of one or more mirrors or other means of directing, splitting and/or otherwise manipulating the electron beam, whereby a plurality of joint-surfaces to be welded to each other are simultaneously sandblasted with electrons, which can accelerate and/or improve the welding process further. The ring gear element which is connected to (generally an inner) peripheral edge of an arcuate ring gear segment by means of electron beam welding during step C) can be of diverse nature. The one or more ring gear elements to be connected to an arcuate ring gear segment by means of electron beam welding will however generally be formed by one or more radially protruding (reinforcing) web plates, usually referred to as inner band or web, and/or one or more joint- surfaces for enabling mutual coupling of ring gear components, thus forming a ring gear.

An inner peripheral edge of the arcuate ring gear segment is preferably provided with at least one nose, preferably at least one radially protruding longitudinal nose. The longitudinal nose is in fact a (small) upright ridge which forms an integral part of the inner peripheral edge but which protrudes, typically about 10-40 millimetres, relative to a remaining part of the inner peripheral edge. The longitudinal nose is configured to be able to weld one or more reinforcing radially protruding web plates to the ring gear segment more easily. The longitudinal nose is preferably though not necessarily arranged on a central part of the inner peripheral edge. The longitudinal nose preferably lies at a distance here from the end surfaces of the ring gear segment in question, as seen from a cross-section of the ring gear segment. This gives the ring gear segment a -I- like form.

The overall length of an outer peripheral edge of the one or more web plates welded to a ring gear segment during step C) preferably substantially corresponds to the length of the inner peripheral edge of the ring gear segment. This results in the situation where substantially the whole inner peripheral edge is provided with one or more (reinforcing) web plates. As already indicated, the at least one web plate is preferably welded during step C) to the longitudinal nose forming part of the inner peripheral edge of the ring gear segment. Before the one or more web plates are welded intensively - via seam welds - to the arcuate ring gear segment by means of electron beam welding, it is usually advantageous for the one or more web plates to initially be connected by means of spot welds to the inner peripheral edge of the ring gear segment prior to step C), during a step D). These spot welds are relatively weak, but serve particularly to initially hold the web plates in position relative to the ring gear segment. The at least one web plate is subsequently fully connected by means of electron beam welding (EBW) to an inner peripheral edge of the ring gear segment as according to step C) of the method according to the invention. The previously formed spot welds will generally fully vaporize during the electron beam welding. Substantially wholly connecting the applied web plates to the inner peripheral edge of the ring gear segments is understood to mean connecting the applied web plates to the inner peripheral edge of the ring gear segments more firmly (relative to the spot weld connections). The whole (peripheral) seam enclosed by the web plates and the inner peripheral edge of the ring gear segments is preferably welded here.

A plurality of web plates which mutually define a plane are preferably welded during step C) to an inner peripheral edge of a ring gear segment, wherein end surfaces of connecting web plates are also welded to each other, preferably by means of electron beam welding, optionally preceded by spot welds being realized as according to step D). It is preferred that connecting web plates are finally welded to each other by means of a (continuous) EBW weld for the above stated reasons. As already indicated, it is also advantageous if one or more metal joint-surfaces are provided during step B), which are connected to a preferably inner peripheral edge of the arcuate ring gear segment by means of electron beam welding during step C). The at least one joint-surface, generally extending in axial (longitudinal) direction, is preferably connected here to an end surface of the inner peripheral edge of the ring gear segment. The joint-surface is preferably welded to the arcuate ring gear segment after the one or more web plates have been welded to the ring gear segment. Each end surface of the inner peripheral edge of the ring gear segment is preferably welded to at least one joint-surface. This enables joint-surfaces of adjacent ring gear segments to connect closely to each other and to subsequently be mutually connected, generally by making use of mechanical attaching elements. At least two joint-surfaces will preferably be connected to the same end surface of the inner peripheral edge of the ring gear segment by means of electron beam welding during step C), wherein the above stated joint- surfaces more preferably mutually enclose a web plate. It is also possible to envisage only a single joint-surface being welded to an end surface of an inner peripheral edge of the ring gear segment, wherein a front side of the joint-surface also lies against an end surface of a web plate. The web plate does not extend here to an end surface of the inner peripheral edge of the ring gear segment, but allows some space for placing of the joint- surface. The at least one joint-surface is welded here to the inner peripheral edge of the ring gear segment by means of electron beam welding (EBW) during step C), wherein the at least one joint-surface is also welded to a connecting web plate, preferably by means of electron beam welding. Each joint- surface is generally provided with a plurality of passage openings for bolts for enabling mutual mechanical attachment of joint-surfaces of different ring gear segments. The passage opening is usually adapted here to the type of bolt which will finally be inserted into the passage opening, wherein use is generally made of reamed bolts configured particularly to fix mutually coupled joint-surfaces, and thereby mutually coupled ring gear segments, to each other, as well as of connecting bolts configured particularly to transmit and absorb exerted forces.

The at least one ring gear segment is preferably formed during step A) by the steps of Al) providing at least one annular and/or arcuate forged basic component with a first diameter, and A2) bending outward each basic component into an arcuate ring gear segment with a second diameter, wherein the second diameter is greater than the first diameter. Steps Al) and A2) of the method according to the invention are aimed at manufacturing one or more ring gear segments by bending outward one or more forged basic components. The ring gear segments formed by means of steps Al) and A2) of the method according to the invention can then be processed further and be mutually coupled, thus forming a ring gear, which is further described in the following. Because the basic components provided during step Al) are forged instead of cast, these basic components can be provided in relatively simple and inexpensive manner, wherein the forged basic components are moreover practically always completely solid and thus comprise no (core) cavities, this having a beneficial effect on a desired constant and high quality, defined inter alia by the material hardness. A further advantage of using a forged starting material compared to a cast starting material is that a forged material is better suited to being welded. In addition to the starting material being more

advantageous than cast steel or cast iron, the method according to the invention has the additional advantages that the forged basic components used have a sharper curvature than the ring gear segments to be formed on the basis of these basic components. This has on the one hand the logistical and economic advantage that the basic components can be transported and stored more easily. This has on the other hand the technical advantage that bending outward of the basic components to form the ring gear segments results in a thickening of material on an outer peripheral edge (outer periphery) of the ring gear segments, and thereby of the ring gear as such, this resulting in a further improvement of the good mechanical properties of the outer periphery of the formed ring gear segments in particular, and thereby of the ring gear to be finally formed as such. The toothing of the ring gear will otherwise generally be arranged in the above stated outer peripheral edge, this resulting in a relatively high load-bearing capacity of the toothing and thereby of the ring gear as such. Forming the ring gear segments with a relatively large second diameter on the basis of basic components with a relatively small first diameter, typically between 1 and 10 metres, has the additional advantage that use is made of annular (or arcuate) (standard) basic components, which are generally particularly widely available on the market at a relatively low cost price and which are moreover of relatively compact nature, which has a beneficial effect on transport and storage. Ring gears with different diameters can be manufactured in relatively simple manner on the basis of the (standard) basic components. A plurality of forged basic components will generally be provided during step Al). Providing can be understood to mean both purchasing and/or manufacturing. The applied basic components are preferably identical, which is most efficient from a practical viewpoint. It is however possible to envisage different kinds or types of basic component being provided during step Al) of the method according to the invention, wherein the (first) diameters of the different basic components can differ from each other. In this latter case the applied - mutually differing - first diameters of the different basic components are however smaller than the second diameter of the ring gear (with external toothing) to be manufactured, so that the above stated technical advantage associated with the bending outward of the basic components remains guaranteed. As stated, a basic component can be arcuate or annular. An annular basic component has a closed (continuous) annular or circular body and, from a three-dimensional viewpoint, generally a (flat) hollow cylindrical body, while an arcuate basic component has a finite circle segment-shaped geometry and, from a three-dimensional viewpoint, generally has a (flat) hollow cylinder segment-shaped body. The height of the basic components generally lies between 10 and 150 centimetres. The wall thickness of the basic component generally lies between 2 and 25 centimetres. The diameters (and associated curvatures) of an annular basic component and an (other) arcuate basic component can be identical herein. It is however also possible to envisage oval, elliptical or other non-circular ring gears being desired for determined applications, whereby such varying forms can also be taken into consideration during the bending outward of basic components as according to step A2). The basic components preferably have a rectangular and optionally square geometry in cross-section (section along a longitudinal plane), which considerably facilitates the processing of the basic components into a ring gear as compared to the situation in which the basic components were to have a round cross- section.

The ring gear manufactured by means of the method according to the invention is intended particularly, though not exclusively, to be applied in heavy industry, such as the cement industry and the mining industry, as part of a drive of an axially rotatable mill housing, as already noted in the preamble of this patent publication. For application of the ring gear in such heavy equipment the diameter of the ring gear is advantageously sufficiently large, and it is moreover advantageous that use is preferably made of a limited number of basic components to manufacture the ring gear, which generally enhances the strength and other mechanical properties of the ring gear. It is therefore preferred that during step A2) n ring gear segments are formed for forming a ring, wherein n equals an even number, n will generally equal 2 or 4. An even number of ring gear segments is generally easier to mount on a rotatable drum. The ring gear segments are here arranged on the drum in uncoupled state and then mutually coupled in situ - on location - so that a closed ring gear results.

The second diameter of the ring gear segments is greater than the first diameter of the basic components. This means that the (first) curvature of the basic components is greater than the (second) curvature of the ring gear segments. The first diameter is otherwise interpreted as the maximum distance between two points on a (real or virtual) circle defined by an outer peripheral edge of the arcuate or annular basic component. The second diameter is interpreted as the maximum distance between two points on a virtual circle defined by an outer peripheral edge of an arcuate ring gear segment or as the maximum distance between two points on a real circle defined by an outer peripheral edge of the ring gear to be finally formed.

The basic components will generally be manufactured from (high-grade) forged steel, whereby the final ring gear will generally also be manufactured at least partially from forged steel. Forged steel generally has a particularly good strength to weight ratio, which is particularly advantageous for the primarily intended application in heavy equipment. The ring gear segments (obtained from the basic components) - which are finally provided with a toothing - will be loaded most heavily during use, whereby it is preferred that precisely these relatively heavily loaded parts of the final ring gear are manufactured from (high-grade) forged steel. Other parts of the ring gear, such as for instance web plates optionally used as inner band (inner web), which are loaded less heavily during use, are generally of (rolled) steel plate.

The basic components provided during step Al) are more preferably manufactured from a rolled forged material, preferably a seamless rolled forged material, and each basic component is more preferably formed by a seamless rolled ring manufactured from forged steel. Seamless rolled rings with diameters of up to about 8 metres are (currently) relatively readily obtainable on the market. These seamless rolled rings are generally manufactured from a solid block of cast steel, also referred to as ingot, which is compressed (flattened) at high temperature - typically about 1100 °C - by means of a hydraulic press, wherein the steel is forged (compacted), this resulting in a higher material quality because imperfections (seams, cracks, cavities and so on) can in this way be obviated almost wholly. After forging of the steel a hole will be arranged in the forging, after which the then resulting ring is further formed by rolling the rough ring into the correct general shape by means of a rotating movement, thus forming the seamless rolled forged steel ring. The formed ring will generally subsequently be cooled rapidly to about 600 degrees Celsius, whereby the material structure is more or less fixed (frozen), which enhances the final material hardness. The advantage of a seamless rolled forged steel ring is that the material is relatively homogenous and solid, with a high material density, wherein the material fibres are moreover oriented in the same direction, which significantly enhances the (uniform) strength of the annular basic component.

The method preferably also comprises step A3), which comprises, following provision of at least one annular basic component as according to step Al) and before bending outward of the at least one annular basic component as according to step A2), of opening, preferably sawing open, the at least one annular basic component. In contrast to alternative techniques, such as opening the annular basic component by means of cutting or severing, interrupting of the preferably seamless rolled annular basic component by means of sawing will have no or practically no influence on the material properties of the annular basic component, whereby a high-grade material quality can be maintained, which also enhances the quality of the final ring gear.

Bending outward of a basic component, thus forming a ring gear segment, as according to step A2) preferably takes place by applying a device for outward bending. The device for outward bending generally comprises at least one inner pressing element configured to realize at least two inner pressure points on an inner peripheral edge of the basic component, and at least one outer pressing element configured to realize an outer pressure point on an outer peripheral edge of the basic component, wherein the outer pressure point lies between at least inner pressure points and wherein the at least one inner pressing element and the at least one outer pressing element are mutually displaceable. During clamping and bending outward of the basic component as according to step A2) the basic component is retained by the pressing elements by displacing the at least one inner pressing element and the at least one outer pressing element toward each other. The basic component is subsequently carried through a space formed between the pressing elements, whereby at least a large part of the basic component is bent outward by means of pressing. Each pressing element can here comprise one or more axially rotatable roller straightening machines. At least one roller straightening machine will generally be actively driven (in motorized manner) here to displace a basic component in a space formed between the pressing elements. The end surfaces of the basic component generally cannot be deformed by the device for outward bending, whereby the end surfaces generally retain the original curvature. It is therefore advantageous for the method also to comprise step A4), which comprises, following forming of the at least one ring gear segment as according to step A2), of shortening at least one end surface, preferably two opposite end surfaces of the ring gear segment, preferably by means of sawing. By shortening a ring gear segment on two sides the ring gear segment acquires a uniform curvature (uniform second diameter), this facilitating the subsequent manufacture of an annular ring gear. The shortening of the ring gear segments results in some reduction of the circumference of the ring gear. This must be taken into consideration during bending outward as according to step A2).

The circumference of the final ring gear is generally equal to or smaller than the sum of the circumferences (or arc lengths) of the applied basic components for manufacturing the above stated ring gear, particularly if the ring gear segments formed from the basic components are shortened as according to step A4). In other words, the (second) diameter of the ring gear will generally be equal to or smaller than the sum of the (first) diameters of the applied (annular) basic components of the above stated ring gear, since the circumference and the diameter of an annular body are directly proportional to each other. The second diameter is already determined during step A2) of the method according to the invention.

Since the longitudinal nose, if applied, also deforms during bending outward, which generally influences the dimensioning (measurements) of the longitudinal nose, it is preferred for the method to comprise step A5), which comprises, following forming of the at least one ring gear segment as according to step A2), of adjusting the

measurements and optionally forming the longitudinal nose. Adjusting of the longitudinal nose as according to step A5) preferably takes place by means of milling. The longitudinal nose can in this way be provided with the (most constant possible) radius, which allows one or more curved web plates to be positioned against the longitudinal nose as tightly as possible (preferred step G#) of the method according to the invention; see below). The radius formed by an inner peripheral edge of the longitudinal nose will here correspond substantially wholly to the radius of an outer peripheral edge of the one or more web plates.

Step A5) preferably takes place after step A4) has been performed in order to be able to prevent new damage to or degradation of the longitudinal nose while step A4) is being performed.

The method preferably also comprises step E), which comprises of mutually connecting the ring gear segments, thus forming a ring. As already indicated above, the mutual coupling preferably takes place by mechanically connecting adjoining joint-surfaces of different ring gear segments. Mutual coupling of the ring gear segments usually, though not necessarily, takes place while forming a ring, and a toothing is subsequently arranged on a peripheral edge of each ring gear segment during step F) of the method according to the invention. Arranging a toothing on an outer (or inner) peripheral edge of the ring gear segments as according to step F) will generally take place by milling away material from the above stated peripheral edge. The toothing therefore preferably forms an integral part of the assembly of coupled ring gear segments, this considerably enhancing the strength of the toothing and therefore of the ring gear as such. The orientation of the toothing arranged during step F) and a longitudinal axis of the ring gear as such can mutually enclose an angle, this generally enhancing the absorption and transmission of greater forces during later application. The above stated angle preferably lies here between 0 and 45 degrees.

The method according to the invention preferably also comprises step G), which comprises, preferably following mutual connection of the ring gear segments, thus forming a ring, as according to step E), of arranging mounting holes in the web plates for subsequent mounting of the ring gear on a rotatable drum.

The ring gear is usually disassembled after arranging of the toothing (step F)) and optionally the mounting holes (step G)) for transport to a location where a rotatable drum is disposed on which the ring gear is then once again assembled and in fact formed, wherein the ring gear components are connected to the drum as well as mutually connected. A ring gear component is defined here as an assembly comprising: an arcuate ring gear segment provided on an outer peripheral edge with a toothing, at least one radially protruding web plate connected to an inner peripheral edge of the ring gear segment by means of welding, and at least one upright joint-surface positioned on at least one end surface of the inner peripheral edge of the ring gear segment and connected to the ring gear segment by means of welding.

The invention also relates to a ring gear component manufactured by applying the method according to the invention, comprising: an arcuate ring gear segment provided on an outer peripheral edge with a toothing, at least one radially protruding web plate connected to an inner peripheral edge of the ring gear segment by means of electron beam welding, and at least one joint-surface which is positioned on at least one end surface of the inner peripheral edge of the ring gear segment, extends in axial direction and is connected to the ring gear segment by means of welding, preferably electron beam welding. The ring gear component is deemed here to be a semi-manufacture for manufacturing a final ring gear.

The invention also relates to a ring gear manufactured by applying the method according to the invention. The ring gear generally has a modular construction of a plurality of ring gear components according to the invention, which are mutually attached by means of mechanical attaching elements, particularly bolts and nuts.

The invention further relates to an assembly of a ring gear according to the invention and at least one pinion configured to co-act with the ring gear.

The invention then relates to a rotatable drum, preferably for use as rotatable oven, rotatable dryer or rotatable grinding mill, comprising: a frame, an axially rotatable drum housing supported by the frame, at least one ring gear according to the invention connected to the drum housing and at least one drive co-acting with the at least one ring gear for axially rotating the drum housing.

In addition, the invention relates to a device for manufacturing at least a part of a ring gear by applying the method according to the invention, comprising: at least one welding chamber, extractor means connected to the welding chamber for creating a vacuum in the welding chamber, at least one electron gun arranged in the welding chamber and configured to realize an electron beam welded connection between at least one arcuate ring gear segment and at least one ring gear element, such as a web plate and/or a joint-surface, at least one transport element, also referred to as manipulator, connected to the electron gun and configured to displace the electron gun in the welding chamber, and a control unit configured to program the transport element and the electron gun for the purpose of realizing an electron beam welded connection between at least one arcuate ring gear segment and at least one ring gear element, such as a web plate and/or a joint-surface. The welding chamber has to be sufficiently large to wholly enclose the components to be welded to each other. The at least one transport element preferably comprises a plurality of substantially parallel stationary guide rails, at least one mobile guide rail connected displaceably to the stationary guide rails, this mobile guide rail extending substantially transversely relative to the longitudinal direction of the stationary guide rails, and at least one engaging element connected displaceably to the mobile guide rail and configured to engage on an object to be displaced. The stationary guide rails are here preferably oriented substantially horizontally. Such a construction for displacing an electron gun is also referred to as an X-Y crossbar, i.e. a displacing device in the substantially horizontal plane. It is also, and optionally additionally, possible to envisage that the components to be welded are disposed displaceably in the welding chamber, wherein the components to be welded can for instance be supported by an endless conveyor and/or a different type of support structure whereby one or more components can be supported in mobile manner. It is also possible to envisage that the components to be welded are disposed in stationary position in the welding chamber. The floor area enclosed by the welding chamber will generally amount to (much) more than 10 m 2 in order to enable the components to be wholly enclosed. It is possible to envisage the welding chamber being sufficiently large for simultaneously enclosing a plurality of arcuate ring gear segments and/or for a plurality of electron guns to be applied in the welding chamber, wherein welding can take place at different locations in the welding chamber simultaneously, which can be particularly favourable from a production engineering viewpoint and thereby from a logistical and financial viewpoint.

The invention moreover relates to a device (for outward bending) for manufacturing a part of a ring gear, comprising: at least one inner pressing element configured to realize at least two inner pressure points on an inner peripheral edge of an annular or arcuate basic component to be bent outward, at least one outer pressing element configured to realize an outer pressure point on an outer peripheral edge of the above stated basic component, wherein the outer pressure point lies between at least inner pressure points, wherein the at least one inner pressing element and the at least one outer pressing element are mutually displaceable in order to determine the degree of outward bending of the basic component. The pressing elements are configured here to mutually retain and preferably guide a basic component to be bent outward. The pressing elements can be configured here to retain a basic component such that the basic component extends in a horizontal or vertical plane when being retained, which is generally most

advantageous from a practical viewpoint.

A plurality of inner pressing elements is preferably applied, wherein each inner pressing element is configured to realize one pressure point on the inner peripheral edge of the basic component to be bent outward. It is possible to envisage at least one or even each pressing element being formed by an axially rotatable roller. In a preferred embodiment at least one axially rotatable roller is coupled to a motorized drive for motorized axial rotation of the axially rotatable roller. The outer pressing element is preferably formed by an axially rotatable roller driven in motorized manner. Since the basic component to be bent outward extends during the process of outward bending in a direction remote from the outer pressing element, it is precisely in this direction that there is generally the most space for positioning a drive for axially rotating the roller which functions as outer pressing element, and optionally also space for displacing the outer pressing element from and toward the at least one inner pressing element. The at least one inner pressing element can be disposed here in substantially stationary position. It is however also possible to envisage also giving the at least one inner pressing element a mobile (displaceable) configuration. All pressing elements are generally supported by a, preferably shared, support structure. It is noted for the sake of clarity that it is not necessary to apply axially rotatable rollers. It is also very well possible to envisage non- rotatable pressing elements being applied instead of rotatable rollers to press the basic components into a desired outward bent orientation. The three (or more) pressure points realized by the pressing elements press the forged steel of the basic components beyond the yield point, whereby the forged steel is plastically deformed to have a desired second diameter. The invention will be elucidated on the basis of non-limitative exemplary embodiments shown in the following figures. Herein:

figures 1-14 show successive method steps for manufacturing a ring gear according to the invention,

figure 15 shows a perspective view of an assembly of a pinion and a ring gear manufactured by means of the method according to the invention, figures 16a- 16f are successive method steps for manufacturing an annular basic component for use in the method for manufacturing a ring gear as shown in figures 1-14,

figure 17 shows a comparative image of a conventional SAW weld and an EBW weld, and

figure 18 shows a perspective view of a rotatable oven comprising a ring gear according to the invention.

An example of the method according to the invention will be described step by step hereinbelow, wherein reference is also made to the figures.

Step 1: Providing basic components (figure 1)

Step 1 consists of providing annular basic components 1 for manufacturing a ring gear 2 according to the invention. For manufacturing the ring gear use can be made of 2 or 4 seamless rolled forged rings (seamless rolled rings), depending on whether a two-part or a four-part ring gear 2 is desired. In order to achieve a ring gear circumference of 8 metres, rings 1 in principle have to have a diameter of + 4 metres. A ring gear with a diameter of 8 metres has a circumference of 25.13 metres, this requiring a

circumference of 12.56 per ring gear component in the case of a ring gear constructed from two equal parts (ring gear components). Since each end surface of each ring gear component is shortened by about 50 centimetres during the production process due to rolling loss (pressing loss), which is described in further detail hereinbelow, a starting circumference of about 13.5 meters is necessary, which can be realized with seamless rolled rings with a diameter of 4 meters which function as basic components. The general rule of thumb is that a ring gear 2 with an external diameter smaller than or equal to 8 meters is constructed from two parts and that a ring gear 2 with an external diameter greater than 8 metres is constructed from four parts. In the case of a seamless rolled ring 1 the starting point is cast material 3, which is heated and is compacted by means of pressing. This process step is also referred to as the forging of material 3. A hole 4 is subsequently pressed into material 3. Forging 5 is then rolled out to the desired diameter from this hole 4. This process is also shown in figures 16a-16f. Directly after the rolling there follows a thermal treatment (refining) and quenching in liquid in order to bring the material to the desired hardness. The quality of this type of ring is normally very high. Seamless rolled rings in this order of magnitude are readily available. These rings can moreover be supplied preprocessed, so that extensive and comprehensive NDT research (Non-Destructive Testing research) can already be carried out by the supplier in order to guarantee the initial quality.

Step 2: Preprocessing the basic components (figure 2)

In order to enable the subsequent welding process to be performed, a (longitudinal) nose 6 preferably has to be formed on the inner side of these seamless rolled rings 1 by turning. As shown, the inner side of each ring 1 is hollowed out on two sides, whereby a ridge protruding inward about 30 mm remains on the inner side, which ridge is referred to as nose 6. The width of nose 6 substantially corresponds to the thickness of web plates 7 to be attached to nose 6 later (see figure 8).

Step 3: Opening the basic components (figure 3)

The basic components formed by rings 1 are then sawn through by means of a sawing machine so that an opening (interruption) is created.

Step 4: Bending the basic components outward (figures 4a-4f)

Each interrupted ring 1 is then arranged in a device for outward bending 8 comprising a plurality of roller straightening machines 9 (or non-rotatable pressing elements

(pressure points)) displaceable relative to each other (and in vertical direction) for bending outward (bending open) the interrupted ring 1 into a ring gear segment 10 with a greater diameter (see figures 4a-4f). The original radius of r=2.25m (04.5m) will be bent outward here to achieve the desired radius of the ring gear, for instance a radius of r=4m (on the basis of a two-part ring gear with a diameter of 08m). The shells or shell parts (arches) formed during this outward bending function as ring gear segment 10 for manufacturing the final ring gear 2. In this exemplary embodiment ring gear segments 10 each cover an angle of 180 degrees for manufacturing a two-part ring gear 2. If a four-part ring gear were for instance desired, ring gear segments 10 can be configured as quarter segments (90-degree segments). It is noted for the sake of completeness that the ring gear segments can differ from each other in a ring gear with a toothing with an odd number of teeth. In the case of for instance a two-part ring gear with 201 teeth a first ring gear segment can be provided on a peripheral side with 100 teeth, while the other, second ring gear segment is provided on a peripheral side with 101 teeth. In practice the first ring gear segment covers in that case a first angle at the centre smaller than 180°, while the second ring gear segment covers an angle at the centre greater than 180°. The total of the first and second angle at the centre forms 360°, this enabling a closed annular ring gear to be formed. The same can generally apply to each n-part ring gear if the number of teeth of the toothing cannot be divided by n.

Material on an outer side of rings 1 is compressed and compacted during deformation by the outward bending of original rings 1, which will result in improved mechanical properties and thereby a higher load-bearing capacity of final ring gear 2.

Step 5: Removing end surfaces (figure 5)

During the bending outward of rings 1, thus forming ring gear segments 10, as shown in figures 4a-4f, it will generally not be possible to bend the outer ends of the ring fully into the correct radius (run-in and run-out of device for outward bending 8). These insufficiently deformed end surfaces 10a, 10b are removed by means of milling or sawing.

Step 6: Precisely milling longitudinal nose (figure 6)

Design and dimensioning of longitudinal nose 6 can then be milled to achieve exactly the desired radius. This milling operation generally takes place on a "Computerized Numerical Control"-controlled (CNC-controlled) milling machine, whereby the radius can be followed precisely. For the subsequent welding process it is important that the welded seam is preprocessed very precisely.

Step 7: Processing web plates (web) (figure 7)

In order to reinforce the final ring gear 2 diverse web plates 7 are applied, which are attached to an inner side of ring gear segments 10, as will be discussed hereinbelow. The assembly of web plates 7 is also referred to as web. Each web plate 7 is here burnt as cutting piece from steel plate. These segments are preprocessed on a CNC processing machine such that all welded seams are prepared as well as possible and fit onto the inner peripheral edge of the ring gear segments 10 functioning as outer tyre.

Step 8: Placing of the web plates (web) (figure 8)

Web plates 7 (web) are then placed in the formed ring gear segments 10. Several small spot welds 11 can be arranged for fixing purposes, so that the components are temporarily fixed to each other.

Step 9: Manufacturing the main weld (figure 9)

Electrons are moved from a gun 12 in the direction of the welded seam at very high speed by means of electron beam welding (EBW). Enormous heat is created when these electrons collide with the surface (welded seam) at very high speed. This heat development is concentrated in a very small area, whereby a high temperature results such that the steel not only melts at the location of the welded seams, but even partially vaporizes. This creates a slot, whereby welding can take place through and through, to a very great depth (120 mm in steel is no problem). By moving the electron beam the molten steel of the outer tyre fuses with the molten steel of the web, and a very strong connection results over the whole thickness of the web. This step corresponds to step C) of the appended claims. The previously formed spot welds 11 will vaporize during the electron beam welding.

This process must take place in a vacuum. Without vacuum, the atmosphere would comprise too many spurious particles, which impedes the electron beam and causes a diffuse beam. The ring gear to be welded therefore preferably has to be welded in a vacuum chamber. The temporarily fixed ring gear parts 7, 10 are placed in a vacuum chamber, after which the door of the vacuum chamber is closed and a vacuum is created by means of pumps in about 20-30 minutes, depending on the volume of vacuum chamber 13 and the power of the pumps.

Figure 17 shows a cross-section of a normal SAW weld on the left-hand side, wherein it is clearly visible that a bell-shaped weld is generated from many different layers from both sides. Shown on the right-hand side is an EBW weld which is obtained by means of electron beam welding (EBW). The EBW weld is much narrower in comparison to the SAW weld. The SAW weld is generated in one movement and need only be welded from one side. The energy supply (heat input) is much smaller per cm 2 in electron beam welding than in all other welding techniques, whereby hardly any deformation occurs. Even more important is that hardly any stresses result owing to the low energy supply, whereby stress-free annealing after the welding is probably no longer necessary.

Omission thereof results in large energy, time and cost savings. Even more important however is the fact that a final product with a much greater hardness can be produced because of the omission of the stress-free annealing. The weld depth realized by means of electron beam welding for the purpose of manufacturing a sufficiently strong weld, which is suitable for application in heavy industry, preferably lies between 50 and 150 mm, wherein the weld depth amounts to 100 mm in the exemplary embodiment shown in figure 17.

As shown in figure 9, the main weld is welded in the vacuum chamber fully automatically from one side. Figure 9 shows only one ring gear half, although it is of course possible to weld a plurality of halves or quarters (simultaneously) in one vacuum operation, depending on the dimensioning of the vacuum chamber and the size of ring gear segments 10, which can considerably enhance efficiency.

The main weld can thus be welded fully automatically and under vacuum. The result is a very high-quality weld. The chance of errors is practically negligible as a result of the degree of automation and the absence of atmospheric influence. The strength of the weld is about 20% greater than the conventional SAW weld.

It is moreover not necessary to use an electrode or welding wire because the types of steel of outer tyre 10 and web 11 simply fuse together. External preheating (preheating is done by the electron beam) is not necessary.

Step 10: Placing the joint-surfaces (figure 10)

After web plates 7 have been connected to ring gear segments 10 by means of EBW welds the vacuum is released and coupling flanges 14 are temporarily attached to web plates 11 and ring gear segments 10 by means of spot welds 15. Each end surface of each ring gear segment 10 is provided here with two coupling flanges 14 which mutually enclose a web plate 11. Step 11: Welding coupling flanges 14 (figure 11)

After a new vacuum has been created the coupling flanges 14 can be fully connected to ring gear segments 10 and web plates 11 by means of EBW welds. The same electron gun 12 can be applied for this purpose, although gun 12 will generally be rotated over 90° or a similar angle here so that the welded seam is perfectly accessible to gun 12. The use of EBW will significantly reduce the chance of errors and will greatly improve the quality of these heavily loaded welds.

Step 12: Perforating coupling flanges 14 (figure 12)

Each coupling flange 14 is then provided with a plurality of holes 15, for instance by means of drilling. Holes 15 serve to guide bolts 16 (see figure 13).

Step 13: Forming ring gear 10 (figure 13)

Ring gear segments 10 are mutually connected by means of bolts 16 and nuts 17. Step 14: Arranging toothing (figure 14)

Web plates 11 are then provided with holes 18, which facilitates subsequent mounting of ring gear 2. A toothing 19 is furthermore arranged on an outer peripheral edge of the assembly of ring gear segments 10 by means of milling (removing material from) the outer peripheral edge.

Ring gear 2 is then ready for use and can subsequently be received in a (gear wheel) housing 20, of which only ring gear 2 and a pinion 21 are shown in figure 15. Housing 20 can then for instance be applied in a rotatable oven 22 (see figure 18), wherein an oven housing 23 is enclosed by the ring gear 2 which is connected to oven housing 23 in fixed manner, and wherein housing 20 is configured to rotate housing 23. Housing 20 is driven here by a motor 24.

It will be apparent that the invention is not limited to the exemplary embodiments shown and described here, but that within the scope of the appended claims numerous variants are possible which will be self-evident for the skilled person in this field. It is possible here to envisage that different inventive concepts and/or technical measures of the above described embodiment variants can be wholly or partially combined without departing from the inventive concept described in the appended claims.

The verb "comprise" and conjugations thereof used in this patent publication are understood to mean not only "comprise", but are also understood to mean the phrases "contain", "substantially consist of, "formed by" and conjugations thereof.