DE8906899U1 - Double helical gear - Google Patents

Description

Double helical gear State of the art

Double helical gears require a gap between the two gears for the run-out of the gear cutting tool (G. Nieraann, H. Wintsr? Meaehinenelemesnte, Volume II, 2nd edition, 1933, p. 272/273). If the gears are to be ground, a very wide gap is necessary for the run-out of the grinding wheel. However, the space required for this is not available in the gear housing. In such cases, the arrangement of two individual helical gears arranged next to one another is more space-saving. Problems also arise when these gears are to be pressed or shrunk onto the shaft. BeJ. Due to manufacturing deviations or additional axial forces applied from the outside, the theoretically ideal force distribution of 50:50 in the two press joints is shifted to one side or the other. This then creates the danger of at least one of the two helical gears slipping on the shaft. This innovation is intended to counteract this.

Advantages of the innovation

When the two helical gears are joined together to form a double helical gear, no axial forces are transmitted to the shaft via the interference fit - assuming the same gear teeth but with oppositely directed helix angles - only circumferential forces occur, so that overall there is a higher slip moment.

Even if the forces are unevenly distributed in the gear teeth, the half with the lower load takes on part of the forces in the interference fit.

In the magazine "Schweißen und Schneiden", April 19, 1968, on page 16, a gear wheel made up of two parts joined together by electron beam welding is shown. One part is a disk with involute teeth and a hub section on the side, onto which the second part, a synchronizer ring with short teeth , is placed. This design is used because the synchronizer ring is also used as a standardized part in other gear wheels and, because of the larger quantities this entails, can be manufactured inexpensively using non-cutting manufacturing processes, e.g. as a fine forged or sintered part. The known gear wheel offers no suggestion for solving the problem eliminated by the innovation, since it is not pressed or shrunk onto a shaft.

drawing

The innovation is shown in an exemplary embodiment in the single figure.

Description of the implementation example

A double helical gear 2 is pressed or shrunk onto a tapered section of a shaft 1, which is only indicated. The gear 2 is composed of two rings 21, 22, each of which has a toothing 23, 2k . Both toothings have the same data or dimensions, only the tooth bevel ß is directed in the opposite direction. On the mutually facing end faces 25« 2b, the one

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Ring 21 has a centering mechanism 3 which is received in a corresponding recess in the other ring 22. The two joints 23, 24 delimit a groove 5 located between them which surrounds an area 6 in which the two end faces 25, 26 abut one another. In this area 6, the rings 21, 22 are joined together by electron beam welding. In order not to reduce the quality of the welded connection through the formation of slag, a recess 7 which is present at the transition from the end face 23 to the centering mechanism 3 for manufacturing reasons is vented via bores θ. In the area lying radially inside the centering mechanism 3 and the recess 4, the two rings 21, 22 do not abut one another because of the risk of over-determination, so that an annular gap 9 is present here.

To loosen the gear 2 pressed or shrunk onto the shaft 1, but also to make pressing it on easier, the bore of the gear 2 can be hydraulically expanded. The shaft 1 is provided with at least two threads 11 for this purpose for connecting corresponding pressure devices (not shown). These are used to guide pressure oil via bores 12, 13 to flat annular grooves 1k , from where it spreads out between the shaft 1 and the gear 2, expanding the two rings 21, 22. It can also get into the annular gap 9, with the result that the pressure oil can burst the welded connection in the area. To avoid this, the annular gap is connected to the environment via a bore 10, through which the pressure is reduced and the escaping oil can be collected. Instead of the poorly accessible bore 10 (the gear 2 is moved relative to the shaft 1), it is more expedient to vent the annular gap 9 via an annular groove 15 and bores 16, 17 in the shaft 1.

Instead of the conical press connection shown between the shaft 1 and the gear 2, a cylindrical press connection or similar is also possible.

Claims (2)

Protect speak« 1. Double helical gear, which essentially consists of an annular body having the two toothings and which can be placed on a shaft by means of a press or shrink fit, characterized in that the annular body consists of two rings (21, 22) each having a toothing (23, 2**) which are connected to one another at their mutually facing end faces (25, 26) by electron beam welding. 2. Double, helical gear according to claim 1, characterized by a centering projection (3) on the end face (25) of one ring (21), which is received in a corresponding recess (λ) on the end face (26) of the other ring (22), such that the two rings (21, 22) are only connected to one another in the region (6) of their end faces (25, 26) lying radially outside the centering projection (3) or the recess (k) , while in the region lying radially inside the centering projection (3) or the recess (k), the two rings (21, 22) are axially spaced apart to form an annular gap (9). 3· Poppelt helical gear according to claim 2, characterized in that the annular gap (9) is connected to the free environment via at least one bore (10; l6, 17) after the gear (2) is placed on the shaft (l).