COMPOSITE SHAVING CUTTER

Abstract: A composite shaving cutter having a plurality of thin gear plates superposed in layers to form a serration in each tooth face of the cutter. The serration surface of each thin gear plate is easily finished by grinding in advance to the assembling of the thin gear plates into one body, thereby to obtain an improved precision of the gear processed by the shaving cutter.

Description: BACKGROUND OF THE INVENTION: The present invention relates to a shaving cutter for use in the finish processing of gears. It is well known to effect a shaving on a gear cut and processed from a gear blank by a hobbing machine, in order to further enhance the final precision of the gear surface. This shaving is achieved generally by means of a gear type shaving cutter. The teeth face of the shaving cutter has a serration consisting of a multiplicity of grooves of an extremely small width extending over the root and the top of the tooth, and the finish cutting of the processed gear is made by the serration edge which functions as a cutting edge. FIG. 1 shows in a larger scale the serrations formed on both tooth faces of a tooth of a conventional gear type shaving cutter. In this Figure, the side surface 1 constituting the serration corresponds to a top rake surface of the serration during the cutting. On the other hand, the discontinuous tooth face 2 is referred to as "serration land" and corresponds to a relieving surface during the cutting. A reference numeral 3 designates a serration edge. In this conventional shaving cutter, the serration pitch P is as small as 2 mm, so that it is extremely difficult to finish the serration face (top rake surface) 1 by grinding. In order to improve the cutting quality of the shaving cutter, it is necessary to precisely finish the top rake surface 1. In the conventional shaving cutter, however, the precision of the top rake surface cannot be improved to a level below 6 pm, because the finish grinding cannot be adopted although the top rake surface is finally processed before a heat treatment. SUMMARY OF THE INVENTION: Accordingly, an object of the invention is to make it possible to easily grind the serration surface of the shaving cutter thereby to improve the cutting quality or performance of the shaving cutter and to improve the precision of tooth face of the gear to be processed To this end, according to the invention, there is provided a composite shaving cutter constituted by a plurality of gear thin plates superposed in layers to form a serration in the tooth face of the cutter. The invention will be more fully understood from the following description of the preferred embodiments of the invention taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS: FIG. 1 is a perspective view of the serration portion of a conventional integral type shaving cutter; FIG. 2 is a sectional view of a half part of a shaving cutter in accordance with a first embodiment of the invention, taken along the axis of the cutter; FIG. 3 is a perspective view of the serration portion of the shaving cutter as shown in FIG. 2; FIG. 4 is a perspective view of the serration portion of the shaving cutter in accordance with a second embodiment of the invention; FIG. 5 is a sectional view of a half part of a shaving cutter in accordance with a third embodiment of the invention, taken along the axis of the shaving cutter; and FIG. 6 is a perspective view of the serration portion of the shaving cutter as shown in FIG. 5. DESCRIPTION OF THE PREFERRED EMBODIMENTS: Referring first to FIGS. 2 and 3 showing a first embodiment of the invention, a reference numeral 4 denotes a blade having a portion corresponding to the serration land of the conventional shaving cutter, while a numeral 5 designates a spacer having a portion corresponding to the serration gap. The blade 4 and the spacer 5 are made of a thin plate having a gear-like form. In the illustrated embodiment, the serration is constituted by the combination of the blade 4 and the spacer 5. The thickness of the spacer 5 is smaller than the thickness of the blade 4 by an amount corresponding to the serration depth. Both side faces of the blade 4 and the spacer 5 corresponding to the cutter tooth have been beforehand finished by grinding, and the blade 4 and the spacer 5 are assembled together after the finish grinding. As will be seen from FIG. 2 a plurality of blades 4 and a plurality of spacers 5 are superposed in layers alternatingly, and are held together by means of a tie bolt 6. The gear-shaped spacers 5' which are disposed at both ends of the cutter teeth have a greater thickness (t) than other spacers, in order to provide a sufficient rigidity of the cutter teeth. The blades 4 and the spacers 5 may be united by using, insteadly of the bolt 6, a holder (not shown) in which the blades 4 and the spacers 5 are mounted fixedly. By adopting the construction described above, the blade 4 projects at its both ends beyond the spacer 5 as will be seen from FIG. 3 to form the serration surface 41 corresponding to the top rake surface of the shaving cutter. This surface can easily be finished by grinding in advance to the assembling of the blades 4 and the spacers 5 into one body. Both tooth faces of the blade 4 constitute the serration lands 42 corresponding to the relieving surfaces in the cutting of the gear to be processed. The corners of the blade 4 constitute the serration edges 43, while the side surfaces of the spacer 5 constitute the bottom 51 of the serration. In the illustrated embodiment, the pitch P of the serration is given as the sum of thicknesses of the pair of blade 4 and spacer 5 constructed in the form of gearshaped thin plates. FIG. 4 shows a second embodiment of the invention in which the gear-shaped plates are arranged at an offset in the circumferential direction and are superposed and united by means of a bolt 6 as in the case of the first embodiment. In this case, therefore, one tooth face of each blade 4 constitutes a serration land 42, while the other constitutes the groove bottom 44 of the serration. As in the case of the first embodiment, both side surfaces 41 of the blade 4 have been finished by grinding before the assembling so as to constitute the top rake surfaces. In order to obtain a sufficiently high rigidity of the cutter teeth as a whole, the gear-shaped blades 4' disposed at both ends of the cutter teeth have a thickness greater than that of other blades 4. In this second embodiment, the corners of the outwordly projecting end surface of each blade constitute the serration edges 43. The pitch P of the serration is given as the sum of thicknesses of two blades 4. This second embodiment is advantageous in that the shaving cutter can be constructed simply by superposing the blades 4 of the same gear shape at an offset in the circumferential direction, so that the number of kinds of the parts is reduced, although the outermost blades 4' have to have an increased thickness. A third embodiment of the invention will be described with reference to FIGS. 5 and 6 which are a sectional view of a half part of the shaving cutter of this embodiment and a perspective view of a part of the cutter teeth. In this embodiment, teeth of the same shape as the teeth of the shaving cutter are formed on the periphery of a thin disc-shaped plate of a thickness corresponding to the serration pitch P thereby to form a gear-shaped thin plate. Then, the teeth are cut leaving a thickness necessary for constituting the serration land to form a step 81 and the cut surfaces of the teeth are finished by grinding thereby to form a stepped gear-shaped blade 8 which is an element of the shaving cutter of the third embodiment. The blades 8 thus formed are superposed and united rigidly by means of the bolt 6, thereby to form a composite shaving cutter in accordance with the invention in which the multiplicity of teeth form the serration. In FIG. 6, a reference numeral 9 designates a serration land, while a reference numeral 10 denotes a serration edge (cutting edge). The portion of the teeth from which the material has been removed by the cutting constitute spaces corresponding to the serration gaps as designated at 11. As will be seen from FIGS. 5 and 6, the blades 8' disposed at both ends of the cutter teeth are made to have a thickness (t) greater than that of other blades 8 thereby to ensure a sufficient rigidity of the cutter teeth as a whole. Insteadly of using the bolt 6, it is possible to use a holder (not shown) in which the blades are fixedly mounted, thereby to form the shaving cutter of this third embodiment. In the shaving cutter of this embodiment, the cutting performance during the shaving is improved because both surfaces 12 of the teeth 7 of each blade 8, constituting the top rake surfaces during cutting, have been beforehand finished by grinding. In addition, since vacant space 11 is formed between adjacent teeth 7 without using any spacer as shown in FIGS. 2 and 3 the cutting liquid can flow easily during processing, and the removal of metal chips is facilitated. In addition, the blade thickness, i.e. the pitch P of the serration, is increased as compared with the first and second embodiments shown in FIGS. 2, 3 and FIG. 4, so that the number of the blades can be reduced almost to a half. In consequence, it becomes possible to greatly shorten the production time and to reduce the production cost. In addition, the increased thickness of the blade permits an easier removal or suppression of the stress in the course of the heat-treatment during manufacturing. In the case where the teeth size is increased to reduce its mechanical strength, it is advisable to charge a filler such as a hard resin in the space 11 between adjacent teeth 7 and to harden the filler, thereby to reinforce the teeth. However, it is necessary to dissolve the filler in the region around the cutting edges 10, in order to expose the top rake surfaces 12 by the required shape and size. As has been described, according to the invention, there is provided a composite shaving cutter in which a plurality of gear-shaped thin plates are superposed to form the serration. It is, therefore, possible to beforehand finish by grinding the serration side surfaces corresponding to the top rake surfaces, before assembling the gear thin plates into one body. In consequence, it becomes possible to obtain a shaving cutter having a smoothly finished top rake surfaces and, accordingly, to improve the precision of processing of the gear particularly the precision of the tooth face, when the gear is processed by the shaving cutter of the invention.

Claims: WHAT IS CLAIMED IS: 1. A composite shaving cutter comprising a plurality of gear thin plates superposed in layers to form a serration on each tooth face of said shaving cutter. 2. A composite shaving cutter as claimed in claim 1, wherein said gear thin plates include blades and spacers of different tooth heights, the tooth height thickness of said spacer being smaller than that of said blade by an amount corresponding to the depth of said serration. 3. A composite shaving cutter as claimed in claim 1, wherein said thin gear plates are superposed at an alternating offset in the circumferential direction thereby to form said serration on said tooth face. 4. A composite shaving cutter as claimed in claim 1, wherein each of said thin gear plates has been finished at its teeth by grinding so as to leave a thickness corresponding to the serration land. 5. A composite shaving cutter as claimed in claim 1, wherein thin gear plates disposed at both ends of the serration have a thickness greater than that of the other thin gear plates. 6. A composite shaving cutter as claimed in claim 1, wherein said thin gear plates are united into one body by means of a bolt. 7. A composite shaving cutter as claimed in claim 4, wherein the space between adjacent teeth of said thin gear plate is charged with a filler to reinforce said teeth. Claims (2.) A composite shaving cutter which comprises a plurality of blades and spacers of gear thin-plate shape so super-imposed alternately as to form a serrration on each tooth face of the shaving cutter, the tooth height thickness of said spacer being made smaller than that of said blade by an amount corresponding to the depth of said serration and said spacer being adapted to assume the same involute shape as that of said blade. (4.) A composite shaving cutter which comprises a plurality of blades of gear thin plate shape arranged in a superposed manner, the gear shape portion only of said blade being cut off in width to such an extent as may correspond to the depth of groove of a serration on each tooth face of the shaving cutter.

Inventors: IUCHI, FUMIO C/O KYOTO MACHINERY WORKS, NAKAOKA, SABURO C/O KYOTO MACHINERY WORKS
Applicants: MITSUBISHI JUKOGYO KABUSHIKI KAISHA
Application year: 1981
Main classification: B23F21
IPC codes: B23F21