Split type gear and rod and wire rough rolling gearbox
By combining a split gear structure with specific processes, the problems of heavy weight and high cost of traditional gears have been solved, achieving lightweight and low-cost manufacturing and improving maintenance efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- NANJING HIGH SPEED & ACCURATE GEAR GRP
- Filing Date
- 2025-06-06
- Publication Date
- 2026-04-10
AI Technical Summary
The gears in traditional bar and wire roughing gearboxes are heavy, have high manufacturing costs, are difficult to manufacture, and are inconvenient to maintain.
It adopts a split gear structure, with the gear ring and hub being processed separately and then connected by fastening components. It utilizes special-shaped ring rolling technology and casting technology to reduce costs, and weight-reducing holes are set on the hub to reduce weight.
It reduces the difficulty and cost of processing and manufacturing, improves maintenance efficiency, reduces weight, and extends service life.
Smart Images
Figure CN224107629U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to mechanical drive technical field, specifically, relate to a split type gear and bar wire rough rolling gear box. BACKGROUND
[0002] The last stage reduction stage big wheel in the traditional bar wire rough rolling gear box generally adopts two structures, one is solid pie structure gear, one is welded gear structure. The solid pie gear is heavy in weight, large in inertia due to solid structure, and the internal quality of the forging cannot be effectively controlled. The gear ring utilization rate of the welded gear structure is low, and the processing and manufacturing cost is high. In this way, the two conventional structures have a certain influence on the processing and manufacturing difficulty and cost control of the traditional bar wire rough rolling gear box.
[0003] The inventor found in the research that the gear in the prior art bar wire rough rolling gear box at least has the following shortcomings:
[0004] Heavy weight, high processing and manufacturing cost. SUMMARY
[0005] The utility model relates to a split type gear and bar wire rough rolling gear box, which can reduce weight, reduce processing and manufacturing difficulty, and reduce processing and manufacturing cost.
[0006] The embodiments of the utility model can be implemented as follows:
[0007] In a first aspect, the utility model provides a split type gear, which comprises a gear ring, a hub and a fastening assembly.
[0008] The gear ring is provided with an inner hole, and a plurality of helical teeth are arranged on the outer circumferential surface of the gear ring. The plurality of helical teeth are arranged at intervals around the axis of the inner hole. The length direction of each helical tooth has an angle with the axis of the gear ring.
[0009] The hub is provided with a weight reduction hole. The hub is embedded in the inner hole. The hub and the gear ring are fixedly connected through the fastening assembly, so that the hub and the gear ring are relatively fixed in the radial and axial directions of the gear ring.
[0010] In an optional embodiment, a fixing block is protruded on the hole wall of the inner hole. The fixing block has an assembly surface in the extension direction of the axis of the inner hole. The gear ring is attached to the assembly surface. The gear ring and the fixing block are fixedly connected through the fastening assembly.
[0011] In an optional embodiment, the fixing block is arranged in an annular structure, and the fixing block is coaxially arranged with the gear ring. The assembly surface is arranged in an annular surface around the axis of the gear ring.
[0012] In an optional embodiment, a plurality of first fixing holes are arranged on the fixing block; a plurality of second fixing holes are arranged on the gear ring; the first fixing holes and the second fixing holes are in one-to-one correspondence and in communication;
[0013] The fastening assembly is provided with a bolt, a nut and a washer, the bolt is arranged in the first fixing hole and the second fixing hole in communication, the washer is sleeved outside the bolt, the nut is screwed and fixed with the bolt, and the washer is clamped between the hub and the nut.
[0014] In an optional embodiment, a first abutting portion is arranged on the hole wall of the inner hole, the first abutting portion is located on the side of the gear ring close to the assembly surface; a second abutting portion is arranged on the hub, and the first abutting portion and the second abutting portion are clamped and matched to limit the relative rotation of the hub and the gear ring around the axis of the gear ring.
[0015] In an optional embodiment, the hub is arranged eccentrically relative to the gear ring.
[0016] In an optional embodiment, the center of gravity of the gear ring is located on the axis of the gear ring; the center of gravity of the hub is located on the axis of the hub, the axis of the gear ring and the axis of the hub are collinear; the center of gravity of the gear ring and the center of gravity of the hub have a spacing in the extension direction of the axis of the gear ring.
[0017] In an optional embodiment, the hub comprises a center ring, an annular plate body and a plurality of reinforcing plates; the annular plate body is sleeved outside the center ring, each reinforcing plate is connected with the center ring and the annular plate body at the same time, and the reinforcing plates are arranged at intervals around the center ring; the weight-reducing holes are arranged on the annular plate body.
[0018] In an optional embodiment, the center ring, the annular plate body and the plurality of reinforcing plates are made into an integral structure by a casting process.
[0019] In a second aspect, the utility model provides a bar and wire rough rolling gear box, the bar and wire rough rolling gear box includes:
[0020] The split gear of any one of the foregoing embodiments.
[0021] The beneficial effects of the embodiments of the utility model include, for example:
[0022] In summary, the split gear provided by the embodiment can reduce the manufacturing difficulty and cost by separating the gear ring and the hub for processing and then assembling them through the fastening assembly. When the gear ring is worn, the gear ring can be directly detached from the hub without detaching the hub from the bearing, thereby reducing the maintenance difficulty and cost and improving the maintenance efficiency. Since the hub is processed independently, the structure can be adjusted adaptively according to the gear ring, and the hub is processed with the lightening holes to reduce the overall weight while meeting the support strength. BRIEF DESCRIPTION OF DRAWINGS
[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation to the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.
[0024] Figure 1 Fig. 1 is a first perspective view of the split gear of the embodiment;
[0025] Figure 2 Fig. 2 is a second perspective view of the split gear of the embodiment;
[0026] Figure 3 Fig. 3 is a sectional view of the split gear of the embodiment;
[0027] Figure 4 Fig. 4 is a partial enlarged view of the split gear of the embodiment. Figure 3
[0028] Fig. 5 is a schematic view of the split gear of the embodiment.
[0029] 100-gear ring; 101-first end face; 102-second end face; 110-inner hole; 120-fixing block; 121-assembly surface; 122-positioning surface; 123-first fixing hole; 130-first butt joint; 140-helical tooth; 200-hub; 210-center ring; 220-ring plate body; 221-lightening hole; 222-second fixing hole; 230-reinforcing plate; 240-second butt joint; 300-fastening assembly; 310-bolt; 311-end cap; 320-nut; 330-washer. DETAILED DESCRIPTION
[0030] In order to make the purpose, technical scheme and advantages of the embodiments of the utility model clearer, the technical scheme in the embodiments of the utility model will be described clearly and completely in combination with the drawings in the embodiments of the utility model below. Obviously, the described embodiments are part of the embodiments of the utility model, rather than all the embodiments. The components of the embodiments of the utility model described and shown in the drawings can be arranged and designed in various different configurations.
[0031] Therefore, the following detailed description of the embodiments of the utility model provided in the drawings is not intended to limit the scope of the claimed utility model, but only represents selected embodiments of the utility model. Based on the embodiments in the utility model, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the utility model.
[0032] It should be noted that: similar reference numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.
[0033] In the description of the utility model, it should be noted that if the terms "upper", "lower", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship of the product in use, it is only for the convenience of describing the utility model and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore it cannot be understood as a limitation on the utility model.
[0034] In addition, if the terms "first", "second" and the like appear, they are only used for differentiation in description and cannot be understood as indicating or implying relative importance.
[0035] It should be noted that the features in the embodiments of the utility model can be combined with each other without conflict.
[0036] In the prior art, the final stage reduction gear in the gear box for rough rolling of rod and wire has a large diameter, and generally adopts an integral solid structure or is welded together after being processed in parts. The solid gear is heavy and inconvenient to assemble. The welded gear is inconvenient to process and manufacture, and the quality of the weld is not easy to control, resulting in reduced gear processing quality, reduced gear yield, and increased processing and manufacturing cost. In addition, whether the solid gear or the welded gear is an integral structure, the gear is assembled on the bearing, and the gear and the bearing are in interference fit, which is inconvenient to disassemble and inconvenient to replace and maintain.
[0037] Therefore, the designer provides a split gear which not only reduces the processing and manufacturing difficulty, but also reduces the weight, is convenient for subsequent disassembly and maintenance, and has low use cost.
[0038] Please refer to Figures 1-4 The embodiment provides a split gear, which comprises a gear ring 100, a hub 200 and a fastening assembly 300.
[0039] The gear ring 100 is provided with an inner hole 110, and a plurality of helical teeth 140 are arranged on the outer circumferential surface of the gear ring 100, the plurality of helical teeth 140 are arranged at intervals around the axis of the inner hole 110, and the length direction of each helical tooth 140 has an angle with the axis of the gear ring 100.
[0040] The hub 200 is provided with a lightening hole 221, the hub 200 is embedded in the inner hole 110, and the hub 200 and the gear ring 100 are fixedly connected through the fastening assembly 300, so that the hub 200 and the gear ring 100 are relatively fixed in the radial direction and the axial direction of the gear ring 100.
[0041] As described above, the processing mode of the split gear provided by the embodiment is as follows:
[0042] First, the gear ring 100 and the hub 200 are independently processed, the gear ring 100 can be processed and manufactured by adopting a special-shaped rolling ring process, the utilization rate of the gear ring 100 can be greatly improved, material waste is reduced, and cost is saved; the hub 200 can be provided with an integrated structure by adopting a casting method, batch production can be realized, and mold opening cost is reduced. When the gear ring 100 and the hub 200 are both processed, the hub 200 is inserted into the inner hole 110 of the gear ring 100, and the two can be gap fit, which is beneficial to assembly. Then, the gear ring 100 and the hub 200 are fixedly connected by using the fastening assembly 300, and assembly is completed.
[0043] Since the gear ring 100 and the hub 200 are independently processed and then assembled together, the processing and manufacturing difficulty can be reduced, and the processing and manufacturing cost can be reduced. Meanwhile, when the gear ring 100 is worn, the gear ring 100 can be directly disassembled from the hub 200, without the need of disassembling the hub 200 from the bearing, so that the maintenance difficulty and the maintenance cost are reduced, and the maintenance efficiency is improved. Since the hub 200 is independently processed, the structure can be adaptively adjusted according to the gear ring 100, and the lightening hole 221 is processed on the hub 200, so that the overall weight can be reduced while the supporting strength is met.
[0044] The following embodiment describes the details of the split gear of the application in an exemplary manner.
[0045] Please refer to Figures 1-4In the embodiment, the split gear includes a gear ring 100, a hub 200, and a fastening assembly 300. The gear ring 100 and the hub 200 are fixedly connected by the fastening assembly 300. It should be understood that the number of the fastening assembly 300 can be multiple, and the fastening assembly 300 can be used to fix the gear ring 100 and the hub 200, thereby improving the firmness of the combination of the gear ring 100 and the hub 200 and prolonging the service life.
[0046] For reference Figures 2-4 In the embodiment, the gear ring 100 is manufactured by a special-shaped rolling ring process, has high structural strength, high material utilization rate, and low cost. The outer circumferential surface of the gear ring 100 is provided with a plurality of helical teeth 140, each of which has an included angle with the extension direction of the axis of the gear ring 100, and the included angle is an acute angle or an obtuse angle. The plurality of helical teeth 140 are uniformly and spacedly arranged in the circumferential direction of the gear ring 100, and the included angles of all the helical teeth 140 with the axis of the gear ring 100 are the same. It should be noted that the number of the helical teeth 140 on the gear ring 100 is designed as required, and is not specifically limited in the embodiment.
[0047] Meanwhile, the gear ring 100 is provided with an inner hole 110 in the thickness direction, the thickness direction is consistent with the extension direction of the axis of the gear ring 100, the cross-sectional profile of the inner hole 110 is circular, and the cross section is a plane perpendicular to the axis of the gear ring 100. That is, the gear ring 100 has a first end surface 101 and a second end surface 102 arranged in the extension direction of the axis thereof, and the two ends of the inner hole 110 penetrate the first end surface 101 and the second end surface 102, respectively.
[0048] Optionally, the hole wall of the inner hole 110 is provided with a fixing block 120 and a first butt joint portion 130. The fixing block 120 protrudes from the hole wall of the inner hole 110, that is, the fixing block 120 protrudes from the hole wall of the inner hole 110 in the direction of the radial direction of the gear ring 100. The fixing block 120 can be an annular structure arranged around the axis of the gear ring 100, and the cross-sectional profile of the fixing block 120 can be circular, and the fixing block 120 is coaxially arranged with the inner hole 110.
[0049] It should be understood that the fixing block 120 can be integrally formed with the gear ring 100 by a rolling ring process, and has high structural strength.
[0050] Optionally, the fixing block 120 has an assembly surface 121 and a positioning surface 122 oppositely arranged in the extension direction of the axis of the ring gear 100, the assembly surface 121 and the positioning surface 122 are both circular annular surfaces, the assembly surface 121 has a spacing with the first end surface 101, and the positioning surface 122 has a spacing with the second end surface 102, so that both sides of the fixing block 120 can provide mounting space for the wheel hub 200. At the same time, the fixing block 120 is provided with a first fixing hole 123, the first fixing hole 123 can be a circular hole, the first fixing hole 123 penetrates the fixing block 120 along the extension direction of the axis of the ring gear 100, the axis of the first fixing hole 123 is the same as the extension direction of the axis of the ring gear 100, that is, both ends of the first fixing hole 123 are located on the assembly surface 121 and the positioning surface 122 respectively. The number of the first fixing hole 123 can be multiple, and the multiple fixing holes are uniformly spaced around the axis of the ring gear 100.
[0051] Optionally, the first connecting part 130 can be arranged as a connecting groove, the connecting groove is arranged on the hole wall of the inner hole 110, and the side of the connecting groove away from the fixing block 120 extends to the end surface of the ring gear 100, so that one end of the connecting groove is in communication with the end surface of the ring gear 100. Obviously, in other embodiments, the first connecting part 130 can also be arranged as a connecting protrusion or the like.
[0052] In addition, the number of the first connecting part 130 can be one or more, and in the embodiment, the number of the first connecting part 130 is taken as one for example.
[0053] Please refer to Figures 1-2In this embodiment, optionally, the hub 200 can be made into an integrated structure in a casting manner, which is beneficial for batch processing, has low processing cost and high structural strength. For example, the hub 200 includes an integrated center ring 210, an annular plate body 220 and a plurality of reinforcing plates 230. The annular plate body 220 is sleeved outside the center ring 210, each reinforcing plate 230 is connected with the center ring 210 and the annular plate body 220 at the same time, and the plurality of reinforcing plates 230 are arranged at intervals around the center ring 210. The number of reinforcing plates 230 is designed as required, the reinforcing plates 230 can be distributed on both sides of the annular plate body 220, which can improve the structural strength of the hub 200, so that the hub 200 can better support the gear ring 100. At the same time, a plurality of lightening holes 221 and a plurality of second fixing holes 222 are arranged on the annular plate body 220. At least one lightening hole 221 is arranged between adjacent reinforcing plates 230, in other words, the plurality of reinforcing plates 230 and the plurality of lightening holes 221 are alternately arranged in the circumferential direction of the annular plate body 220, which is reasonably distributed, can reduce the weight, and can ensure sufficient strength. The number of second fixing holes 222 is set as required, which is equal to and one-to-one corresponding with the number of first fixing holes 123. The second fixing holes 222 can be set as the same circular through holes as the first fixing holes 123. All the second fixing holes 222 are uniformly arranged around the axis of the center ring 210, and all the second fixing holes 222 are located on the outer side of the reinforcing plate 230, which can reduce the thickness of the fixing block 120, that is, reduce the size of the fixing block 120 in the radial direction of the gear ring 100, thereby reducing the weight.
[0054] Optionally, a second butt joint portion 240 is arranged on the outer circumferential surface of the annular plate body 220, and the second butt joint portion 240 can be arranged as a butt joint protrusion. The butt joint protrusion protrudes outwardly from the outer circumferential surface of the annular plate body 220 along the radial direction of the annular plate body 220. The butt joint protrusion can be clamped into the butt joint groove, thereby guiding the assembly of the hub 200 and the gear ring 100, ensuring that all the first fixing holes 123 can be one-to-one corresponding with all the second fixing holes 222, and the step of relatively rotating the gear ring 100 and the hub 200 is omitted, thereby reducing the assembly difficulty and improving the assembly efficiency.
[0055] Obviously, in other embodiments, when the first butt joint portion 130 is a butt joint protrusion, the second butt joint portion 240 is correspondingly arranged as a butt joint groove, which is flexible in processing.
[0056] In addition, in some embodiments, optionally, the annular plate body 220 can be arranged as an arched plate, and all the reinforcing plates 230 are arranged on one side of the concave arc surface of the arched plate. During assembly, the convex arc surface of the arched plate faces the inner hole 110 and is inserted into the inner hole 110 as the front end. The arched plate can not only improve the strength, but also play a guiding role in assembly.
[0057] Please refer to Figures 3-4In the embodiment, the fastening assembly 300 can include a bolt 310, a nut 320 and a washer 330. The bolt 310 has an end cap 311 at one end. The washer 330 is sleeved on the bolt 310. The nut 320 is screwed and fixed with the bolt 310. The washer 330 is located between the end cap 311 and the nut 320.
[0058] It should be understood that the washer 330 can be an NL washer 330 or the like.
[0059] The assembling method of the split gear provided in the embodiment is as follows:
[0060] The gear ring 100 can be laid flat with the first end face 101 of the gear ring 100 facing upward. Then, the second joint part 240 on the hub 200 is aligned and clamped with the first joint part 130 on the gear ring 100. Under the guidance of the first joint part 130 and the second joint part 240, the hub 200 is clamped into the inner hole 110, and one side plate face of the annular plate body 220 is in contact with the assembling face 121. The center ring 210 and part of the annular plate body 220 can pass through the fixing ring and protrude from the positioning face 122. The second fixing hole 222 on the annular plate body 220 is in correspondence and communication with the first fixing hole 123 on the fixing block 120. The bolt 310 is inserted into the first fixing hole 123 from the side of the positioning face 122, and then is inserted out of the second fixing hole 222. The washer 330 is sleeved on the bolt 310. The nut 320 is screwed on the bolt 310. The nut 320 is tightened, so that the end cap 311 is in contact with the positioning face 122. The nut 320 and the annular plate body 220 cooperate to clamp the washer 330, and the fixing of the gear ring 100 and the hub 200 is completed.
[0061] Meanwhile, the gear ring 100 has a first center of gravity located on its own axis, and the hub 200 has a second center of gravity located on its own axis. After the assembling of the gear ring 100 and the hub 200 is completed, the axis of the gear ring 100 is collinear with the axis of the hub 200. The gear ring 100 and the hub 200 are arranged in an eccentric structure, that is, the center of gravity of the gear ring 100 and the center of gravity of the hub 200 have a spacing in the extension direction of the axis of the gear ring 100 or the hub 200. In this way, since the outer peripheral surface of the gear ring 100 is provided with the helical teeth 140, when the gear ring 100 is engaged with the power input gear, the engagement position of the helical teeth 140 and the power input gear is gradually engaged from the first end face 101 to the second end face 102 (or gradually engaged from the second end face 102 to the first end face 101). This causes the gear ring 100 to be subjected to an axial force. By arranging the gear ring 100 and the hub 200 in an eccentric structure, the axial force acting on the gear ring 100 can be reduced, the wear of the gear ring 100 can be reduced, and the service life of the gear ring 100 can be prolonged.
[0062] The split gear provided by the embodiment can reduce the manufacturing difficulty and cost by disassembling and processing the gear ring 100 and the hub 200 and then assembling them through the fastening assembly 300. When the split gear is assembled to the gear box, the central ring 210 of the hub 200 is sleeved outside the rotating shaft, and the rotating shaft and the central ring 210 are provided with a bearing and are in interference fit. When the gear ring 100 needs to be replaced due to wear, the fastening assembly 300 is disassembled, and then the gear ring 100 is disassembled from the hub 200, without the need to disassemble the hub 200, thereby reducing the maintenance difficulty, improving the maintenance efficiency, and reducing the maintenance cost.
[0063] The embodiment further provides a bar wire rough rolling gear box, and the bar wire rough rolling gear box has at least the advantages of light weight, stable and reliable operation, and low use cost.
[0064] The above is only a specific implementation manner of the utility model, but the protection scope of the utility model is not limited to this, any skilled person in the art can easily think of changes or replacements within the technical range disclosed by the utility model, which should be covered in the protection scope of the utility model. Therefore, the protection scope of the utility model should be subject to the protection scope of the claims.
Claims
1. A split gear, characterized by, The split gear comprises a ring gear (100), a hub (200) and a fastening assembly (300); The ring gear (100) is provided with an inner hole (110), and a plurality of helical teeth (140) are arranged on the outer circumferential surface of the ring gear (100) and are spaced around the axis of the inner hole (110), and the length direction of each helical tooth (140) forms an angle with the axis of the ring gear (100); The hub (200) is provided with a weight-reducing hole (221), the hub (200) is embedded in the inner hole (110), and the hub (200) and the ring gear (100) are fixedly connected through the fastening assembly (300), so that the hub (200) and the ring gear (100) are relatively fixed in the radial and axial directions of the ring gear (100).
2. The split gear according to claim 1, wherein: A fixing block (120) is protruded on the hole wall of the inner hole (110), the fixing block (120) has an assembly surface (121) in the extension direction of the axis of the inner hole (110), the ring gear (100) is attached to the assembly surface (121), and the ring gear (100) and the fixing block (120) are fixedly connected through the fastening assembly (300).
3. The split gear according to claim 2, wherein: The fixing block (120) is arranged in an annular structure and coaxially arranged with the ring gear (100); and the assembly surface (121) is arranged as an annular surface around the axis of the ring gear (100).
4. The split gear according to claim 2, wherein: A plurality of first fixing holes (123) are arranged on the fixing block (120); a plurality of second fixing holes (222) are arranged on the ring gear (100); and the plurality of first fixing holes (123) and the plurality of second fixing holes (222) are in one-to-one correspondence and in communication; The fastening assembly (300) comprises a bolt (310), a nut (320) and a washer (330), the bolt (310) is arranged in the first fixing hole (123) and the second fixing hole (222) in communication, the washer (330) is sleeved outside the bolt (310), the nut (320) is screwed and fixed with the bolt (310), and the washer (330) is clamped between the hub (200) and the nut (320).
5. The split gear according to claim 4, wherein: A first abutting portion (130) is arranged on the hole wall of the inner hole (110), and the first abutting portion (130) is located on the side of the ring gear (100) close to the assembly surface (121); a second abutting portion (240) is arranged on the hub (200), and the first abutting portion (130) and the second abutting portion (240) are clamped and matched to limit the relative rotation of the hub (200) and the ring gear (100) around the axis of the ring gear (100).
6. The split gear according to any one of claims 2-5, characterized in that: the hub (200) is arranged eccentrically relative to the ring gear (100).
7. The split gear according to claim 6, characterized in that: a center of gravity of the ring gear (100) is located on an axis of the ring gear (100); a center of gravity of the hub (200) is located on an axis of the hub (200), the axis of the ring gear (100) is collinear with the axis of the hub (200); the center of gravity of the ring gear (100) and the center of gravity of the hub (200) have a spacing in an extension direction of the axis of the ring gear (100).
8. The split gear according to any one of claims 2-5, characterized in that: the hub (200) comprises a center ring (210), an annular plate body (220), and a plurality of reinforcing plates (230); the annular plate body (220) is sleeved outside the center ring (210), each of the reinforcing plates (230) is connected with the center ring (210) and the annular plate body (220) at the same time, and the plurality of reinforcing plates (230) are arranged at intervals around the center ring (210); the weight-reducing holes (221) are arranged on the annular plate body (220).
9. The split gear according to claim 8, characterized in that: the center ring (210), the annular plate body (220), and the plurality of reinforcing plates (230) are made into an integral structure by a casting process.
10. A bar wire roughing gear box characterized by, the bar wire rough rolling gear box comprises the split gear according to any one of claims 1-9.