US1397697A - Hob for generating bevel-gears - Google Patents

Description

C. G. OLSON. HOB FOR GENERATING BEVEL GEARS.

2 SHEETS-SHEET I.

Patented N 0V. 22, 1921.

APPLICATION FILED NOV. 24, I920- C. G. OLSON.

HOB FOR GENERATING BEVEL GEARS. APPLICATION HLEb NOV. 24. 1920.

. 397 97; Patented Nov. 22, 1921.

2 SHEETS-SHEET 2.

LOCATION OF Q FJDHiIiT ACTION -LJJJJJ UNITED STATES PATENT OFFICE.

CARL, e. oLsoN,or CHICAGO, ILLINOIS, ASSIGNOR T ILLINoIs TooL woRKs, or dIIIoAeo, ILLINoIs, a CORPORATION or ILLINoIs.

( I HOB FOR GENERATING BEVEL-GEARS.

Specification of Letters Patent.

Patented Nov. 22. 1921.

Application filed November 54, 1920. Serial No. 426,292.

To all whom it may concern: Be it known that I, CARL G. OLsoN, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a 'certain'new and useful Improvement in Hobs for Generating Bevel-Gears,-of which the following is a specification.

My invention relates to hobs and the object is to produce a hobcapable of generating bevel gears. To facilitate an understanding of the principle of the invention, I will call attention to the fact that the type of bevel gears known as skew bevel gears is often used for transmitting motion in various types of machines. -When skew gears cooperate, there is a sliding action of one upon the other lengthwise of the body of the intermeshing teeth and I have discovered that this fact can be taken advantage of to produce a hob capable of generating a bevel gear.

In the accompanying drawings, I have illustrated a hob embodying my invention, a bevel gear producible by the hob, and a machine capable of employing the hob to produce a bevel gear. In these drawings Figure 1 is a face or axial view of a considerable portion of a hob embodying the invent-ion. This figure also shows in dot-anddash lines, the position which the bevel gear blank and arbor will occupy during the generating operation.

Fig. 2 is similar to Fig. 1 except that por-. tions of the hob and of the bevel gear are,

. looking in the direction of the axis .of the latter, and showing in elevation the region of action of the hob upon the gear.

Fig. 5 is a perspective View of the region of action of the hob uponthe gear.

Fig. 6 is an elevation of a machine adapted to employ the hob to produce a bevel gear.

Like numerals denote like parts throughout the several views.

In the form selected to illustrate the invention, the bevel gear produced is an ordinary bevel pinion-that is,', it is a; pinion in which the longitudinal axes of the teeth converge at a common point located on the produced axis of the gear. The hob itself resembles in general, a skew bevel gear such as would mesh and cooperate with such a bevel pinion. As usual in skew-gearing the axes of the two intermeshing elements do not lie in a common plane, but are offset from each other. In the drawings, the bevel gear is indicated by the reference letter G, and the hob in general by the reference letter H. The axis of the gear is oifset from the axis of the hob a distance equal to the radius of the dot-and-dash circle 5, Figs. 1 and 3.

As previouslystated, the hob resembles a skew bevel gear, the longitudinal axes of the teeth, indicated by the light lines 6, Fig. 1, all running tangent to the circle of offset 5. The teeth, however, instead of being continuous from end to end, are traversed by flutes 0r gashes 8, which produce a plurality of hob teeth in longitudinal alinement. The

,gashes are not concentric with the hob, but

are eccentric, and in the illustrated case are struck on radii indicated by the dot-anddash lines 10, shown in Fig. 1. These radii are here shown as being struck from a circle 12 which coincides with the inner diameter of the'hob. The length of the radii is shown as bemg somewhat greater than the radius of the circle 12. These dimensions, proportions and relative locations may, however, be varied.

It is preferable to use a number of gashes or flutes which is prime to the number of rows of teeth in the hob. This provides a condition which produces smoother work, as

a greater number of teeth comes in contact with the work and the cuts are more closely distributed over the surfaces of the work.

To facilitate cutting, the hob teeth are so formed as to afford clearance or relief back of the cutting edges as is the common practice in hobs and cutters. The clearance or relief is illustrated at ,the left portion of Fig. 2. While the manner in which the hob is produced is, strictly speaking, immaterial in this present patent, it may be stated that the forming of the teeth in the blank to first produce the equivalent of a skew bevel gear is preferably accomplished by first removing the greater portion of the stock between the teeth to be formed, with a tool preferably of the rotary cutter type, although a tool of the one point type as used in a planing machine may be substituted. To finish the hob, or practically finish it, there may be used a hob such as the one described and claimed in my copending application filed November 24, 1920, Serial No. 426,293.

t In practice, the hob is used in the manner illustrated in Fig. 6. In the form of the machine there illustrated the hob is secured to an arbor 16, journaled in the machine frame 17 and rotated by a worm wheel 18 which meshes with a worm 20 fastened to a. drive shaft 21. This drive shaft is rotated by a band wheel 22 or other suitable form of power device and has fastened to it a spur gear 24 which meshes with a spur gear 25 for imparting rotation to the work G. In the construction illustrated, gear wheel 25 is fastened to a shaft 26 provided with a bevel gear wheel 28, which meshes with a bevel gear wheel 29, rigidly fastened to a vertical shaft 30. Shaft 30 has splined to it a bevel gear wheel 32 which meshes with a bevel gear wheel 33, the latter being fas tened to or integral with a concentric bevel gear wheel 34 which meshes with a bevel gear wheel 36 splined to the work spindle 3.8. The bevel gear blank or work G is fastened to said spindle and the spindle itself is journaled in a sleeve or housing 40, mounted upon and rotatable with the indexing head 42. Said head is mounted upon the vertically movable carriage 44 of the machine, and is rotatable about an axis concentric withthe axis of the gear wheels 33, 34. This makes it possible to produce bevel gears of different degrees of bevel. The carriage is Vertically movable in guides 46 carried by a horizontally movable carriage 48 mounted upon the main frame 17 Carriage 44 may be raised and lowered by means of a handwheel 50 together with a feed screw and nut (not shown). As mechanisms for causing a carriage to travel along its guides are well known, they need not be described in detail here.

It will be obvious by reference to Fig. 6 and the foregoing description thereof, that the hob H and gear blank G rotate in synchronism about their respective axes as is usual in hobbing machines. In using my hob, however, the work is fed toward the face of the hob in a direction parallel to the hob axis, and the feed causes the tool to sink from top to root of the teeth of the work.

In operation, as the hob and the blank rotate, as soon asthe two come into contact, a sliding action takes place, after the manner of ordinary skew gears. This slid ing action causes the teeth of the hob to cut the metal of the gear blank and as the latter is fed downward the teeth are radually formed. The region of ,action 0 the hob upon the work is indicated by the shaded mately indicated in perspective at 54 l ig. 5. i

From the foregoing, it will be seen that my hob is capable of generating, with a single setting and without any indexing orspacing operation, a bevel gear which is accurate theoretically as well as practically.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent is: 1. A hob having the general configuration of a skew bevel gear, the hob teeth being separated, lengthwise, by cross flutes -or gashes. 2. A hob of the general form of a skew b'evel gear, said hob having cross flutes whereby a plurality of hob teeth occur in alinement with each other, the cross flutes being approximately at right angles to the longitudinal axis of the tooth.

3. A hob having the general form of a skew bevel gear, the hob having arcuate flutes or gashes which are struck from a center remote from the axis of the hob.

4. A hob having the general form of a skew bevel gear, the hob having arcuate flutes which are struck from a center remote from the axis of the hob, the number of flutes being prime to the number of rows of hob teeth. I

5. A hob of the general form of a skew bevel gear in which each tooth of the bevel gear is divided into a plurality of sections interspaced by traversing flutes, said sections being relieved for clearance after the manner of the teeth of an ordinary hob or cutter. I

6. A hob having the general form of a skew bevel gear in which the teeth extend from the outer periphery of the gear to an inner circle remote from the axis, the hob having arcuate gashes struck-upon radii the locus of the centers whereof is a circle of a diameter not less than the offset circle 5.

7". A hob having the general form of a skew bevel gear in which the teeth extend from the outer peripherygof the gear to an inner circle remote from the axis, the hob having arcuate gashes struck upon radii of a length greater than the radius of the offset circle,'the' centers of the radii lying upon a circle having a. diameter at least as great as the diameter of the offset circle.

In witness whereof I have hereunto subscribed my name.

CARL G. OLSON.

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