US1243767A - Method of cutting a worm. - Google Patents

Description

C. H. SCHURR & E. J. LEES.

METHOD OF CUTTING A WORM.

APPLICATION FILED NOV. 5. 1914.

Whiz/95555 Patent-ed oat; 1 917.-- 1- 2 5 CHARLES 1H. SCHURR AND ERNEST J. LEES, OF CLEVELAND, OHIO, ASSIGNORS TO THE I LEES BRADNEB COMPANY, OF CLEVELAND, OHIO.

METHOD OF CUTTING A WORM.

Specification of Letters Patent.

Application filed November 5, 1914. Serial No. 870,393.-

, Methods of Cutting Norms, of which the following is a specification, the principle of the invention being herein explained and the best mode in which I have contemplated applying that principle, so as to distinguish it from other inventions.

Our invention relates, more particularly than its title indicates to a method of generating a worm of absolutely precise predetermined pitch line form, whereby the prodnot is adapted to constitute a cooperating or truly mating part for the transmission of power with consummate nicety of operation.

We fulfil the desired object by establishing between the work and a cutter, a manufacturing relation which is precisely similar to-the relation it is desired to present between the coacting units of what is commonly known as a worm drive. A cutting tool is presented to the work in precisely the manner and direction that the spaces between the teeth are to be intersected by such surfaces as are to engage the workingsurfaces of the threads. The configuration at the pitch line is the factor upon which the efficiency depends. A

The distinguishing features of our in vention are four in number, viz:

1. Fixed center distance.

2. Tangential relation of Worm axis.

3. Cutting in a parallel plane.

4. Cutter having a transverse motion.

The drawings exemplify in Figure. 2 a worm drive of the side engagement type so that the worm engages the mating member by intersection in the direction parallel to the axis of the latter, and in Fig. 1 they exemplify a resort to an end mill to acco plish the cutting operation.

Fig. 1 shows end mills of conical surface, whereas Figs. 7 and 8 show the coaction and result respectively of a unit of cylindrical outline.

The inventive conception is associated with means which are hereinafter explained and variously combined in the claims. While the annexed drawings and particular demription thereof, set forth an arbitrarily preferred and one modified form based upon our invention, it should be understood that such means only exemplify two of many di- Patented Oct. as, ram.

versified mechanical forms with which the principle of our invention may be properly applied.

Fig. 1 is a diagrammatic View showing the manner in which our invention may be practised.

Fig. 2 is a section on line XX of Fig. 1 looking in the direction of the arrows and showing the manner in which the worm is employed as a lateral drive.

Fig.3 is a diagrammatic View of a single cutter seen looking in the opposite direction to that of Fig.

., Fig. 4c is a section on line YY of Fig. 3.

Fig. 5 is a section on line Z-Z of Fig. 3 looking downwardly.

Fig. 6 is a vertical axial section of the worm gear seen in Fig. 3.

Fig. 7 is a View corresponding to Fig. 4 showing the application of a cutter 0f modified outline.

Fig. 8 is a view corresponding to Fig. 6 and pertaining to the product resulting from the employ of such a modified tool.

Adverting to Fig. 1, it will be noted that only so much has been drawn as will indicate to one sufficiently skilled in the art how the required movements are carried out. driving member 1 to be considered as connected with a source of power, serves to 1'0- tate in proper ratio both the work 2 through the agency of a gear 3, and the tool disk 4 through the agency of a gear 5 keyed there- 'to at 6. \The independent rotation of, the

end mills 7 simultaneously with their revidual splined tool shafts13. The proper feed or movement of the shafts 13 in the parallel directions of their axes will be presumed as imparted to the circumferential series of tools by means of the spline connections, such that owing to what is in effect an approach toward and recession from the axis of the work, the thread develops shal lower toward the ends and at the same time gradually thicker at the top. In other words such development is owing to the arc of movement seen in Fig. 3. Such are meets with the axis of the work at. its middle so that such axis is tangential thereto. Fig. 2 nicely shows the tangential relation of the axis of the worm to the cylindrical surface generated by an axis of a cutter.

The type of cutter 7 which has been arbitrarily chosen as preferred for the exemplifying purpose of Figs. 1, 4, and 5 is conically surfaced and produces a worm such as is shown in Figs. 2 and 3. Such outer surface or outline of the cutter or end mill 7 would in practice correspond to the outlines of circumferentially arranged beveled rollers or truncated conical rolls such for ex ample as were shown described and claimed in a joint application of R. H. Rosenberg and Ernest J. Lees filed November 15, 1912, Serial No. 731,518. It will be noticed in Figs. 3 and' fi that the root 14 develops as an are depressed toward the axis, the tops of the teeth lying in a straight line. In Fig. 5 as viewed, it is furthermore made clear that the completed cut is perfectly true both with the root and side faces whereby the latter taken on the pitch line conform to the outline [of the end mill which has in turn been premised as conforming to the working faces of the worm gear with which the Worm is to roll. The top of the thread in such Fig. 5 is disposed in an are because dill the blank is a true cylinder, whereas the roots in this figure owing to the fact that it is a developed projection appear to lie in a straight line parallel to the axis. 'The pitch line is caused to follow or be parallel with the bottom.

It should be understood from the claims that this method is independent of a fixed type of cutting tool as it is also of the opera tion of an end mill of definitely prescribed shape, and to demonstrate this We have added in Fig. 7 a view of a cutter 7 of cylindrical as distinguished from conical outline.

. Such a cutter would produce a worm whose axial section is depicted in Fig. 8, wherein it will be seen that the roots 16 of the teeth I lie in an arc. The tops 17 in this instance also lie in an arc either because the blank was so formed in the beginning or because .the cutter carried side edges capable of reaching and trimming the tops. The faces 18 of the product shown in Fig. 8 furthermore difit'er from the faces of the teeth seen in Fig. 6 in thatthey are perpendicular to the axis, while those in Fig. 6 are inclined relative to the axis. This method necessitates cutters slightly larger than the outline of the rollers or other working faces, with which our worm product is to roll. Otherwise opposed rolling actions. on both sides of the assumed rollers with a hindering friction would ensue. In the case of the conical end mill the in and out adjustment compensates sufficiently to avoid this happening, since it depends merely on how far such tool is set in.

cording to the drawings, the plane of rotation of the cutters.

(b) The plane to which the axis of the wvork is perpendicular, or what is the same thing, the plane of gear 3, will be consist: ently called the transversely vertlcal plane.

(c) That axial plane of the Worm or work which is perpendicular to the generating plane shall be considered as the horizontal plane.

We claim 1. The method of cutting a worm which consists in efl'ecting cuts from the work along an arc of movement corresponding to that described by the working faces of a gear wheel with which the worm is to roll, establishing a fixed distance between the centers of the working units and feeding'in a direction at an angle to the plane of the generating circle. 7

2. The method of cutting a worm which consists in rotating the work and simultaneously rotating and revolving a cutter in engagement with such work, the axes of said cutter and work being disposed at right angles, and feeding said cutter in a direction parallel to its own axis.

3. The method of cutting a worm which consists in rotating the work, rotating a cutter in proper ratio to and in operative engagement with said work, revolving the cutter in a plane parallel to one axial plane of allel to another axial plane of the work.

a. The method of cutting a worm whichconsists in rotating the work, rotating and revolving a cutter in proper ratio and in operative relationship to the work, and constantly feeding the cutter transversely to the generating circle.

5. The method of cutting a worm which consists in rotating the work, revolving a series of cutters in predetermined operative relationship to the work, simultaneously rotating said cutters, and feeding the latter transversely to the generating plane thereof.

6.'The method of cutting a worm which consists in rotating the work, simultaneously revolving and rotating a cutter in e11 gagement therewith and constantly feeding the cutter axially of itself.

7. The method of cutting a worm which consists in rotating the work, rotating a cutter, effecting between the work and cutter an operative engagement, theiaxes of said cutter and Work being constantly disposed 8. The method of cutting a worm which consists in rotating the work in operative proximity to a cutter, revolving the cutter in a plane parallel to'one axial plane of the work, and feeding the cutter parallel to a transverse axial plane of the Work.

9. The method of cutting a Worm which consists in rotating a Work piece, revolving a series of cutters in engagement therevyith, and simultaneously feeding the said series of cutters in the same direction.

' CHARLES H. SCHURR.

E. J. LEES.

Attested by MARIE WAGNER, G. F. FRANKE.

Signed by us, this 4th day of November, 15

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