GB2205061A

GB2205061A - Circumferential miller for machining, and a method of machining, the running surfaces and/or flanks of rail heads

Info

Publication number: GB2205061A
Application number: GB08811387A
Authority: GB
Inventors: Erwin Fuchs
Original assignee: Mannesmann AG
Current assignee: Vodafone GmbH
Priority date: 1987-05-22
Filing date: 1988-05-13
Publication date: 1988-11-30
Also published as: DE3717702C1; GB8811387D0

Description

1 2205061 1 - CIRCUMFERENTIAL MILLER FOR MACHINING, AND A METHOD OF

MACHINING, THE RUNNING SURFACES AND/OR FLANKS OF RAIL HEADS.

This invention relates to a circumferential miller and to a method of machining the running surfaces and/or flanks of rail heads.

Rails have to be machined on their running surfaces and flanks (said surfaces and flanks are to be found on what are called the "rail heads") and the machining can be carried out both on new rails after the rolling process and on worn rails in order to restore the original rail profile. It is known for rail heads to be machined by grinding, planing, or milling.

The present invention concerns milling of running surfaces. Its advantage over grinding lies above all in the much greater material removal in a given unit of time and its advantage over planing lies in the fact that it only produces small or short chips. Another advantage of milling over planing is the fact that the advance mechanism requires much less driving and braking power.

Rail head milling devices have become known which work by the circumferential milling method and use millers which are hyperbolically curved. In these millers, the hyperbola visible in the longitudinal section through the miller corresponds to the 2 desired profile form of the rail head. The known miller (AT-PS 213196) is fitted with straight cutters which are distributed over the circumference on the hyperbolic tool body and are tangential to the generated surface of the tool body. The straight cutters make it possible to use conventional turnplates with straight cutters.

Although milling has advantages over other methods, as indicated above, rail millers and devices for milling rails have so far only achieved a very limited spread or amount of use in the industry. The main reason for this appears to lie in the fact that tools working by the circumferential milling method leave waviness on the work piece due to the intrinsic nature of the milling method. This waviness is often harmless if the peak to valley height is not excessive but, with the rails concerned here, the waviness of the running surface of the rail heads is extremely disadvantageous because experience indicates that it causes the wheels of a train passing over it to resonate. This resonance tends to increase the waviness rather than to "roll it flat".

This disadvantage also applies to the known milling device with a hyperboloid miller. In addition, the known miller and other profile millers 1 L shaped according to the running surface of the rail have the further drawback that every rail profile must be machined using its own particular miller.

Given the problems and drawbacks described, the underlying object of the present invention is to create a circumferential miller for machining the running surfaces of rail heads with which the problems arising from the waviness of the machined surface will be avoided and which allows adjustment to different rail head profiles within certain limits

Claims

These principal objects are achieved by a circumferential miller according to Claims 1 and 2 and by a method of machining according to Claim 3. It has been shown that the object of the invention can be achieved by producing an oblique waviness on the workpiece by positioning the known miller at an oblique angle and adapting the body of rotation the generating lines of which are the miller cutting edges, to take account of this oblique position. Because of the oblique waviness, the wheel of the vehicle can never get into a wave valley but only rolls over the wave peaks. As a result, no resonance can be produced in the wheel. In addition, the oblique waviness means that in spite of a large milling advance per tooth a very narrow waviness is produced which means a very 4 shallow waviness (minimal peak to valley depth). Lastly, another advantage is a very long cutter when the curvature of the generated surface of the miller is adapted to the profile of the miller positioned at an oblique angle, increasing the life of the tool. The reason for this lies in the fact that the ratio of the length of cutter used to the material-removing work is much greater than in the case of millers in accordance with the state of the art the axis of which lies at right angles to the direction of advance. Another significant advantage of the invention lies in the fact that in accordance with another feature of the invention it is proposed that the inclination of the axis of rotation of the circumferential miller to the longitudinal axis of the rail be adjustable. The radius to be machined on the head of the rail can be altered by swivelling the correspondingly profiled or hyperbolically shaped miller about an axis at right angles to the axis of rotation of the miller so that different rail profiles can be produced with one and the same miller. Some embodiments of a circumferential miller according to the present invention, and of a method of machining according to the present invention, will - now be described with reference to the accompanying drawings. In said drawings:- Figure 1 shows a miller in accordance with the present state of the art, in elevation, plan and side views; Figure 2 shows a circumferential miller in accordance with the present invention, in elevation, plan and side views; Figure 3 shows a side view of a wheel rolling on a rail which has been prepared using the miller shown in Figure 1; Figure 4 shows a cross-section through a wheel and a rail machined with a circumferential miller in accordance with the present invention; Figures 5 and 6 are diagrammatic views showing the alteration of the radius which can be machined with one and the same miller according to the present invention; and Figures 7 and 8 show the miller in accordance with the present invention when machining the rail flanks. In Figure 1, there is illustrated a miller 1 in accordance with the state of the art. The rail 2 is indicated in cross-section under the miller 1 and it can be seen that the hyperbola bounding the miller in the elevation view roughly corresponds to the radius of the running surface of the rail head. The miller can be rotated about the axis of rotation 3 which runs at right angles to the median perpendicular X of the rail 2. A milling pattern is produced on the running surface of the rail 2 with a waviness 5 according to the oblique position of the cutters or cutting edges 11 on the circumference of the miller. As the axis of the miller is so disposed as to make a right angle with the direction of advance (which direction is indicated by the large arrow), the individual waves almost form a right-angle with the direction of advance (longitudinal axis 4 of the rail). The essential purpose of the oblique attitude of the cutters or cutting edges on the miller is not to produce an oblique milled pattern; the obliquely positioned straight cutters produce a hyperboloid form. On the right-hand side of the illustration the waviness or the spacing of two wave peaks is denoted by a; the height h of the waviness depends on a and the diameter d of the miller and can be calculated roughly using the brief formula h = 0.25 x a/d. Moreover, this figure clearly shows that the spacing a between two wave peaks is the same as the advance per tooth b. Figure 2 is a grossly simplified illustration of a circumferential miller 6 according to the present invention and, here again, the miller 6 is shown in elevation, plan and side views with the rail 2. The axis of rotation 7 of the miller 6 is inclined at an angle 0C which is less than 80 0 with respect to the longitudinal axis 4 of the rail, and the milled pattern 8 has a waviness which is inclined rigidly at an angle 6 with respect to said longitudinal axis 4 of the rail. The inclination of said waviness is obtained by joining the extreme left-hand and the extreme right-hand points of contact 9 and 10 between the miller 6 and the rail 2 by an imaginary line. Figure 2 clearly shows that the spacing a' between two neighbouring wave peaks is much smaller than the advance per tooth denoted by b, in Figure 1. This can be described by the formula a' = b x sin 13. This means that a much smaller wave spacing a' is obtained with the same advance per tooth b and, on the basis of the above relationship, a much smaller wave height h results. This clearly shows that, with the same speed of advance and the same diameter of miller, a much smoother surface can be obtained with the miller 6 in accordance with the present/invention than was possible with a miller (Figure 1) in accordance with the present state of the art. Conversely, this means that much greater advance speeds can be used while producing a surface with the same waviness. A comparison of Figure 1 with Figure 2 also shows that the length of the cutters or cutting edges 11 in the circumferential miller in accordance with the present invention is much greater than is the case with a miller whose axis of rotation is not tilted in relation to the longitudinal axis 4 of the rail. This means that the ratio of the length of the milling edge 11 to the material-removing work carried out by the miller 6 positioned at an oblique angle (Figure 2) is much greater than the ratio of the length of the milling edge 11 to the materialremoving work carried out with the conventional miller 1 (Figure 1). Thus, the tool can be expected to have a much longer life due to the oblique position in which it is used. Figures 3 and 4 show, diagrammatically, in each case, a wheel 12 of a train on the milled rail 2. Figure 3 shows the wheel 12 rolling over the rail surface which has a wavy pattern produced by a straight miller as in Figure 1. It can be clearly seen that the movement of the wheel is totally exposed to the waviness of the rail which (experience indicates) causes resonance at certain 1 1 9 - speeds which, in turn, increases the waviness of the running surface of the rail. Figure 4 shows the wheel 12 rolling over the surface of the rail 2 which has a milled pattern produced by a miller, in accordance with the present invention, positioned at an oblique angle. The cross- section through the rail (Figure 4) clearly shows that the wheel is not exposed to the waviness of the milled pattern but only rolls over the wave peaks. With a large radius of curvature r for the running surface of the rail and a small wave length a, it can be assumed that the wheel simultaneously rests on a plurality of wave peaks and so never gets into a wave valley. Consequently, wheel resonance can be prevented in accordance with the invention very simply. Figures 5 and 6 show one associated or resultant advantage which is obtained from the use of a method according to the present invention and from the use of a circumferential miller according to the invention. The radius r which can be produced with one and the same miller 6 can be changed by altering the angle OC. (which angle was discussed with reference to Figure 2). In Figures 5 and 6, the miller 6 is shown as being mounted together with the milling drive 13 in a housing 14. This housing 14 is so 12 - 10 mounted in or on the base frame 16 as to be pivotal about an axis 15 standing perpendicularly with respect to the surface of the workpiece. In Figure 5, the miller together with the housing and drive are tilted at a fairly small angle CC, which produces a fairly small radius r at the workpiece whereas, in Figure 6, the miller and the housing and drive are tilted at a larger angle oCwhich produces a larger radius r at the workpiece. Figures 7 and 8 again show a miller 6 in accordance with the invention and the rail 2 to be milled; the two illustrations show that the miller in accordance with the invention is also suitable for milling flanks. In addition, the two illustrations also show the pivot axis 15 about which the miller can be tilted to vary the radius.

1 CLAIMS:

Circumferential miller the cutting edges of which are generating lines of a body of rotation, in particular of a hyperbolic body of rotation, the axis of which is the milling axis and the contour of the projection of the generated surface of which viewed in the longitudinal direction of the rail corresponds to the curvature of the running surface or the flank of the head of the rail, the axis of the miller being disposed so as to run in a plane parallel with the longitudinal axis of the rail, characterised in that the axis (7) of the miller is disposed so as to run at an angle (oe,) to the longitudinal axis (4) of the rail (2) such that the imaginary straight connecting line between the two outermost (in the axial direction of the circum ferential miller) contact points of the generated surface of the body of rotation on the finished machined rail head profile encloses.an angle (13) of between 20 and 40 0 with the longitudinal axis (4) of the rail.

2. Circumferential miller as in Claim 1, characterised in that the inclination of the rotational axis (7) of the circumferential miller (6) to the longitudinal axis (4) of the rail is adjust able.

3. A method of machining the running surfaces and/or flanks of a rail head, said method comprising the step of positioning a circumferential miller with its rotational axis at an angle (oC-)of less than 80 0 with respect to the longitudinal axis of the rail whose head is to be machined, such position- ing being for the purpose of ensuring that the milled pattern on the rail head surface has a waviness whose inclination with respect to said longitudinal axis is at an included angle of 0 0 from 2 to 40

4. Circumferential miller constructed, arranged and adapted to operate substantially as hereinbefore described with reference to and as illustrated in Figures 2 and 4 to 8 of the accompanying diagramma tic drawings.

5. Method of machining the running surfaces and/ or flanks of a rail head substantially as herein before described with reference to any of Figures 2 and 4 to 8 of the accompanying diagrammatic drawings.

6. Any features of novelty, taken singly or in combination, of the embodiments of the invention hereinbefore described with reference to Figures 2 and 4 to 8 of the accompanying diagrammatic drawings.

Published 1988 at The Patent Office. Etate House, 66'71 I-Tigh Ho2born. London WClR 4TP. Further copies maybe obtained from The Patent Office, Sales Branch, St Mary Cray, Orpington, Kent B-115 3RD. Printed by Multiplex techniques ltd, St Maxy Cray, Kent. Con. 1187.

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