Cutters – for shaping – Gear cutting tool – Rotary – gear shaving cutting tool
Patent
1987-02-17
1989-07-18
Schmidt, Frederick R.
Cutters, for shaping
Gear cutting tool
Rotary, gear shaving cutting tool
407 28, B23P 1544
Patent
active
048489760
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to laminated gear shaving tools.
A tool of this type is used for a finishing operation only, the gear to be finished having already been produced by some other method, and is a gear-like member usually with a large number of teeth and having channels formed down each tooth flank to provide cutting edges on the serrations left therebetween. As shown in FIG. 1 of the accompanying drawings, which is an isometric view of two teeth 10,12 of conventional prior art tool, formed from a solid blank, these channels 14 run down each flank of each tooth from crown to root to form serrations 16 therebetween, usually terminating in a drilled hole or slot 18 at the root of the tooth. An accepted method of producing the channels 14 is to progressively feed a slotting tool 20 to the required depth; while in some cases the tool 20 is moved in a straight line (so the depth d of the channel 14 is not constant) in others it follows the involute curve giving a constant depth.
It has been proposed in U.S. Pat. No. 2,119,298 (Simowski) to form a gear shaving tool by laminating a plurality of similarly formed toothed discs (which term is similarly used throughout this specification to include discs having a central aperture, i.e. of annular form), the flanks of the teeth being relieved from one or both side faces of the disc to form a land, the lateral edges of which are spaced inwardly from the sides of the disc and constitute cutting edges. Configurations of disc teeth to form both helical and spur gear shaving tools are described.
FIG. 2 of the accompanying drawings is a partial axial section through a prior art laminated gear shaving tool 22 of the above type fabricated from a series of annular discs 24 (edge reliefs omitted) which are assembled together on a body 26 and clamped together mechanically by bolts 28 co-operating with end plates 30,32 which are typically of different radial extent. An alignment pin or keyway not shown is provided in each individual disc 24 in order to ensure that the discs can be assembled in the correct alignment and to resist the forces which will be applied to the serrations during cutting.
There are certain techniques of gear shaving commonly referred to as `plunge` or `underpass` which require the serrations to be staggered with respect to each other around the tool periphery so that the cutting edges are not in line with each other in the plane of rotation of the tool. Such a requirement cannot be met by teeth formed in the manner described in the above U.S. Patent and it is an aim of the invention to provide this facility.
SUMMARY OF THE INVENTION
According to the first aspect of the present invention there is provided a laminated gear shaving tool comprising a stack of toothed discs, a land being formed on the flanks of each tooth of a disc by cutting away the tooth from one or both sides of the disc to form a serration terminating in a land in each flank face, such that the land on each flank of one tooth is offset with respect to the corresponding land on each adjacent tooth. Preferably the lands on successive teeth are laterally displaced around the periphery of the disc from a position adjacent one side of the disc to a position adjacent the other side of the disc.
Preferably the discs are inclined to the axis of rotation to provide a further overlap of the serrations from one plate disc to another.
In crossed axis gear shaving the sliding velocity is the resultant of the sliding velocity down the flanks and the velocity across the flanks and it changes speed and direction from tip to root of the teeth. An improvement in cutting efficiency is obtained according to a second aspect of the present invention by cutting the teeth so that the lateral cutting edges of the land on each flank are inclined to the plane of a face of the disc and preferably lie in opposite directions on the corresponding flanks of alternate teeth.
The shaving process is not efficient and involves high pressures to ensure that the cutting serrations penetrate th
REFERENCES:
patent: 1807665 (1931-06-01), Miller
patent: 2137146 (1938-11-01), Simmons
patent: 2171325 (1939-08-01), Hagwood
patent: 2329284 (1943-09-01), Mentley
patent: 2356868 (1944-08-01), Miller
patent: 3169447 (1965-02-01), Hurth
patent: 3685112 (1972-08-01), Lohrer
Schmidt Frederick R.
Showalter Robert
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