Gear cutting – milling – or planing – Gear cutting – Gear tooth shape generating
Patent
1995-11-08
1998-02-24
Pitts, Andrea L.
Gear cutting, milling, or planing
Gear cutting
Gear tooth shape generating
409 32, 409 38, 409 43, 409 48, 409 51, 407 20, 451 47, 451147, B23F 500
Patent
active
057205841
DESCRIPTION:
BRIEF SUMMARY
The invention relates to the field of mechanical engineering in which gear wheels which can mesh with a cylindrical pinion are produced, and in which the axes of the pinion and the gear wheel to be produced form an angle with each other. Such gear wheels are known under the name of crown wheels when the shaft angle is approximately 90.degree..
The method of producing such crown wheels accurately by, for example, milling is known.
However, until now it has only been possible to work crown wheels which can mesh with pinions provided with straight toothing, but there is a need for crown wheels which can mesh with pinions provided with oblique toothing, inter alia because this permits a greater torque to be transmitted between pinion and crown wheel. The shape of the teeth of such crown wheels is complex, in view of the fact that the tooth is spiral and the angle which the tooth space forms with the radius vector towards the centre of the crown wheel is not constant.
The invention relates to a method in which such a crown wheel can be worked by means of a generating tool, and to a tool by means of which said method can be carried out.
The method according to the invention is a method of producing a crown wheel which can mesh with a cylindrical pinion if the axes of rotation of the crown wheel and the pinion are not parallel, in which the workpiece from which the crown wheel is produced and a generating tool rotate at a ratio in the speed of rotation which corresponds to the proportion of the number of passes of the tool and the number of teeth of the crown wheel to be produced, and in which the tool is brought into engagement with the workpiece and is moved in such as way along the workpiece in a direction parallel to the axis of rotation of the cylindrical pinion that the tool works the tooth flanks of the crown wheel to be produced. When the center point of the tool is moved in a direction parallel to the axis of rotation of the cylindrical pinion which can mesh with the workpiece, and the teeth of which form an angle .beta. (described more particularly below) with the axis of rotation of the cylindrical pinion, the workpiece acquires an additional rotation which is proportional to the product of this movement and the tangent of the tooth angle .beta. of the cylindrical pinion. During this movement, the angle between the axis of rotation of the tool and the plane through the axis of rotation of the cylindrical pinion parallel to the axis of rotation of the workpiece is constant.
The angle between the axis of the tool and the radius vector towards the centre of the crown wheel remains constant while this method is being carried out.
It has been found possible to carry out the method according to the invention on existing machines. In this case a tool whose pitch angle is equal to the tooth angle of the pinion can be used, but it has also been found possible to reduce this pitch angle. An advantage of reducing the pitch angle .gamma. is that the number of passes of the tool is reduced, which means that the number of teeth over which the workpiece rotates during one revolution of the tool is reduced. This means that at a given maximum speed of rotation of the turntable on which the workpiece is mounted it is possible to increase the speed of the tool while the working speed between tool and workpiece remains the same, with the result that the working time of the workpiece is reduced.
The invention will be explained in greater detail below with reference to the drawing.
FIG. 1 shows a cylindrical pinion whose tooth direction is the same as the axis direction, so that this is a matter of straight toothing.
FIG. 2 shows a cylindrical pinion whose tooth direction forms an angle with the axis direction, i.e. oblique toothing.
FIG. 3 shows a cylindrical pinion with oblique toothing having therein the transverse plane.
FIG. 4 shows a cylindrical pinion with oblique toothing having therein the normal plane.
FIG. 5 shows the known tool for working crown wheels which can mesh with a pinion with straight toothing.
FIG. 6
REFERENCES:
patent: 1990432 (1935-02-01), Guest et al.
patent: 2304586 (1942-12-01), Miller
patent: 2308891 (1943-01-01), Miller
patent: 2579422 (1951-12-01), Handy et al.
patent: 2711673 (1955-06-01), Miller
patent: 5494475 (1996-02-01), Basstein et al.
Crown Gear B.V.
Kirkman Christopher
Pitts Andrea L.
LandOfFree
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