DE2556054A1 - HOLLOW CUTTERS AND METHOD FOR MANUFACTURING THESE - Google Patents

Description

Dfpl.-fng. Heinz Bardehfe

Patent attorney

I in «22, Hemisir. 15, Tel. 292553 Posfonsdtfft HQßcbes 26, Postfocb 4

Munich, December 12th, 1975 My reference: ρ 2254 Applicant: R.W.Transmissions Ltd. Lamport Street Hebburn, County Durham / England

Hob and method of manufacturing the same

The invention relates to the hobbing of worm gears and in particular, but not exclusively, waisted hobs for producing worm gears provided with tooth root arcs for double-encompassing worm drive elements.

Known worm gear hobs are produced by cutting one or more threads into a shank blank be, so that a worm is created, which is the counterpart to the worm wheel to be produced, and that then longitudinal slots in it be milled, which divides the worm thread into segments, creating a series of cutting surfaces develop. The hob is then hardened.

609825/0765

A disadvantage of such segmented cutting hobs lies in that the cutting surfaces cannot be provided with a lateral kintering rotation, which is a limitation on certain materials for the production of worm gears and with regard to the surface quality that can be achieved given is.

The object of the invention is therefore to provide a with segments v-.r see worm gear hob, where the snow edges have a kind of lateral relief.

According to the invention, a worm gear hob has a hob shank loaded with a number of cutting knives, each of which:

i) extends in the longitudinal direction of the shaft,

ii> has a sawtooth-shaped cutting edge along four Connection of their front surface with their rear end surface is formed and a longitudinal section of a worm Jc, which is the counterpart to the Scnr. *: ckenrad is, and the front surface lies in a longitudinal plane, üie to a longitudinal radial plane of the cutter shank Assumes an angle so that its Hinterendflache around one corresponding angle from the geometrical location of the tendon edge deviates from inwards to form a kind of lateral undercut.

A method according to the invention for producing a worm gear hobbing cutter consists in that a number of cutting knives are produced in that a corresponding number of knife blanks are fixed in the longitudinal direction of a shank blank, each knife front surface lying in a longitudinal radial plane of this shank blank, and that in the peripheral surface of the shank blank and a worm thread is cut through the outer edges of the cutter, so that a worm is created which is the counterpart to the worm wheel to be produced, whereby the connection of the rear end surface and a front ^f

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surface of the knife have a sawtooth-shaped edge that represent a longitudinal section of the screw and that then

manufactured knife
which are determined in this way / while maintaining the mutual peripheral distance in a hob shank.

The invention is explained in more detail below on the basis of exemplary embodiments with reference to the drawing. In the Drawing show:

Fig. 1 is a perspective view of an inventive waisted worm gear hob,

2 shows the side view of a hob shank,

Fig. 3 shows a section along the line IH-III in Fig. 2, with the knives inserted into the hob shank,

4 shows the side view of a shaft blank,

5 shows a section along the line V-V in FIG. 4 with knife blanks inserted into the shank blank,

6 shows the plan view of a side milling cutter,

FIG. 7 shows a section along the line VII-VII in FIG. 6.

As FIGS. 1, 2 and 3 show, the hob has the shape of a tapered end mill 1 used for finishing, the one with three circumferentially arranged at the same angular distance, longitudinally extending grooves 2 are provided, each of which has parallel sides having milled grooves, one longitudinal side wall 3 of which lies in a plane which is at an angle A of, for example 15 ° deviates from a longitudinal radial plane of the end hob 1.

A knife 4 is inserted into each of these grooves 2 and secured with the aid of wedges 5, which engage in corresponding, not shown, bores in the knife and are fixed with the aid of grub screws 6. One end 7 of the hob 1 is provided with a thread in order to screw on clamping rings 8, 9, so that the

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Knife 4 set in the longitudinal direction of the end mill 1 can be.

The knives 4 are set in the end hob 1 in such a way that that their front surfaces 1o by the angle A from a longitudinal radial plane of the end mill cutter. That means that the Rear end face 11 of each knife, assuming that this and the knife front face start from two mutually perpendicular planes, from the point 12 at which through the meeting of the rear end surface and the front surface the cutting edge is inclined inwards by an angle B, this angle being equal to the deviation angle A.

The outer edge of each of the knives has a sawtooth profile on, wherein the cutting edge 13 forming connection has a longitudinal section in the form of a worm, which the counterpart represents the worm gear to be produced.

The knives are made by having three rectangular Knife blanks 14, each having an inwardly curved rear end surface, are inserted into the grooves 15, which in Umfanysrichtung have the same angular distance and longitudinal of the waisted shaft blank 16 extend. The grooves 15 are milled and each have parallel sides, the longitudinal wall 17 lying in a longitudinal radial plane of the shaft. It a knife blank 14 is now inserted into each of the grooves 15 and with the aid of wedges 18, which are not shown in FIG Engage the corresponding holes in the knife blank and set it with grub screws 19. One end 2o of the shaft blank 16 is provided with a screw thread so that clamping rings 21 are screwed on, which fix the knife blanks in Allow longitudinal direction of the shank blank. The rear end surface 23 each of the knife blanks 14 is flush with the surface of the shank blank 16.

There is a disc milling cutter 24 (Figures 6 and 7) with interchangeable Teeth 25 used to cut into the peripheral surface of the

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Shank blank to mill an involute worm thread, so that a tapered worm shape is created, which is the counterpart to the worm wheel to be produced. The outer edge of the knife 14 is in each case cut saw-tooth, so that the connection of the rear end surface and the front surface of each blade is a longitudinal section of the screw, which has been milled by the milling cutter 24th

The cutting edges are then removed from the shank 16 and deburred and have a rake angle of 1o on their front surface

in this example ground 15 °. Then they are hardened.

Care must be taken to keep the knives in the same Sequence and are used again in the end mill 1 at the same angular distance that they were used during their manufacture had taken in the shaft blank.

The knives fixed in the shank hobs thus form a segmented cutting hobs during operation, in which the inward deviation of the knife rear end surfaces 11, i.e. the angle B, gives the knives a kind of undercut, so that the segmented cutting hobs produce a more precise worm wheel with a smoother surface can.

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Claims (14)

Expectations ι 1. JSchneckenradschneidwälzfraser, characterized / that it has the shape of a shank hobs (1), in which a number of each extending in the longitudinal direction of the shank cutting knives (4) are used, which are sawtooth-shaped and through the connection of the front surface (1o) and the Rear end face (11) of the knife have cutting edge (13) formed, which are longitudinal sections of a worm representing the counterpart of the worm wheel to be produced, and that the knife front side is at an angle to a longitudinal radial plane of the shank / so that the rear end face of each knife is around one corresponding angle deviates inward from the geometrical location (12) of the cutting edge and a kind of undercut is achieved. 2. Milling cutter according to claim 1, characterized in that the Fräserscnaft (1) with a row of along the circumference at the same angular distance and extending in the longitudinal direction extending milled grooves (2) is provided, the front longitudinal wall (3) lies in a plane which deviates by a given angle (A) from a longitudinal radial plane of the cutter shank. 3. Milling cutter according to claim 2, characterized in that in each of the grooves (2) a cutting knife (4) with the aid of in the hob shank (1) inserted parts (5), which engage in corresponding bores of the knife, set is. 4. "Milling cutter according to claim 2 or 3, characterized in that one end of the hob shank (1) is provided with a screw thread (7) onto which the clamping rings (8, 9) are screwed can be to set the knife (4) in the longitudinal direction in their grooves (2). 609825/0 7 65 5. Hob according to one of the preceding claims, characterized in that the hob shank (1) and the Cutting (4) can be tapered in order to be able to produce worm gears provided with tooth root arches. 6. worm wheel, characterized in that it is produced with the aid of a cutting hob according to one of claims 1 to 5 is. 7. A method for producing worm gear hobs, characterized in that a number of cutting knives (4) be generated that a corresponding number of knife blanks (14) set in the longitudinal direction of a shank blank 06) are, with their front surface in a longitudinal radial plane of the shank blank, that then in the outer surface of the shank blank and a worm thread is cut through the outer edges of the knife blanks, so that a worm is created, which is the counterpart to the worm wheel to be produced, whereby the connection (13) of the Rear face (11) and the front face (1o) of each knife a sawtooth-shaped edge is obtained, which represents a longitudinal section of the worm, and that finally the machined in this way Knives are inserted into a hob shank (1) while maintaining the angular distance. 8. The method according to claim 7, characterized in that the knife blanks (14) are rectangular and curved inward Have rear end surfaces. 9. The method according to claim 7 or 8, characterized in that the knife blanks (14) along the periphery of the shank blank (16) having the same angular distance and extending in the longitudinal direction of this shaft, each milled grooves are set, whose one wall (17) extending in the longitudinal direction lies in a longitudinal radial plane of the shaft blank. 609825/0 7 65 · "8 ■ - 10. The method according to claim 9, characterized in that the Knife blanks (14) fixed in the respective groove (15) with the aid of wedges (18) inserted into the shank blank (16) that engage in corresponding holes in the knife. 11. The method according to claim 9 or 1o, characterized in that that one end of the shaft blank (16) with a screw thread (2o) is provided, which is used to screw on clamping rings (21, 22), with the help of which the knives (14) in The longitudinal direction of the shank blank can be set in the relevant grooves (15). 12. The method according to any one of claims 7 to 11, characterized in that that a side milling cutter is used to cut into the peripheral surface of a waisted shank blank (16) Cut an involute worm thread to form a waisted worm that is the counterpart to the worm gear to be generated and provided with a tooth root arch. 13. The method according to claim 7 or 12, characterized in that in the front surface (1o) each of the knives (4) in front of them Hardening a rake angle «.xn is ground. 14. Worm wheel, characterized in that it has a cutting edge hob is produced, which is produced in a method according to any one of claims 7 to 13. 609825/0765 Blank page