US2940159A - Apparatus for broaching spiral gears - Google Patents

Description

June 14, 1960 K. E. EKLUND APPARATUS FOR BROACHING SPIRAL GEARS 8 Sheets-Sheet 1 Filed April 7, 1955 IN VEN TOR.

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APPARATUS FOR BROACHING SPIRAL GEARS Filed April 7. 1955 8 Sheets- Sheet 2 ,1 ,1 4 INVENTOR.

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APPARATUS FOR BROACHING SPIRAL GEARS Filed April 7. 1955 8 Sheets-Sheet 8 United States Patent 1 2,940,159 APPARATUS FOR BROACHING SPIRAL GEARS Karl E. Eklund, 14333 Prairie, Detroit, Mich. Filed Apr. 7, 1955, Set. No-,499,780 16 Claims. (Cl. 2995.1)

This invention relates to a method and apparatus for breaching individual spiral gears.

:In many applications for gears, especially in the automotive industry, it is important that the cost be reduced to a minimum for use especially in window raising assemblies and other similar applications. It is important to have a low-cost gear which will be serviceable. It is also desirable to have a spiral gear which, of course, provides a smoother operation.

It is an object of the present invention to provide a method and apparatus for breaching spiral gears. I have previously developed the breaching of straight-tooth gears, such as spur gears and the like, and breaching dies having internal teeth are known in the art in such patents as 1,070,561 to W. R, Walker, August 19, 1913. Some of these dies use special rings cut to shape and heat treated. With this type, warping and distortion frequently change the shape of the ring, causing inaccuracies. Also, chip removal is difiicult because of lack of clearance.

It is an object of the present invention to provide an improved breaching die which can be manufactured and assembled at considerably less expense than an ordinary breaching cutter which may be especially made for a particular job out of a solid piece.

It is a further object to provide a breaching die in which the teeth may be simultaneously ground in a special type of holder, and a further object to provide an assembly wherein the damaging of one tooth will not destroy the entire cutter. Also, it is an object to provide a die assembly in which chip removal is possible with out packing of the chips in the tool.

Another object is the provision of a breaching die with internal teeth which will cut a spiral gear without the necessity of independent lead control, the spiral resulting from the inherent nature of the teeth and the arrangement in the die or breaching holder. The result is an apparatus and method of breaching spiral gears which permits their production from prepared blanks at the low est possible cost at which any machineahle gears may be produced and yet with an accuracy which is maintained equal to or better than gears made in a hobbing operation. Other objects and features of the invention relating to details of construction and operation will be apparent in the following description and claims.

Drawings accompany the disclosure, and the various views thereof may be briefly described as:

Figure 1, an assembly view of the device showing the relationship of the parts.

Figure 2, a sectional view on line 22 of Figure 1.

Figure 3, a longitudinal section adjacent the feed end of the device taken on line 3-3 of Figure 2.

Figure 4, a sectional view of the die with the blank nearing completion taken on line 44 of Figure 1.

Figure 5, an elevation of thedie head at the feed end taken on line 55 of Figure 1.

Figures 6, 7 and 8, an end view and side elevations of an individual tube used in the die assembly.

Figure 9, a view of the breach body showing the helical position lines for the cutter plugs.

Figure 10, an end view of a completed spiral gear.

Figure 11, a side view of a completed gear.

Figure 12, a top view of a fixture used in grinding the cutting teeth.

Figure 13, a side view of the grinding fixture showing the manner in which the teeth are graduated.

. to conform to the cutter body 2%. The body can be 2,940,159 Patented June 14, 1960 Figure 14, a diagrammatic view of an enlarged groove showing the progressive cuts taken in the breach assembly.

Figure 15, an elevation of one end of a breach assembly showing a ring-type clamp.

Figure 16, a sectional view showing the manner in which the ring clamp acts on the breach plugs.

Figures 17 and 18, bottom views of a grinding fixture showing the manner in which the teeth are interspersed with aligning plugs for grinding.

Figures 19, 20 and 21, diagrammatic views showing the various dimensions on the grinding plugs.

Figures 22, 23 and 24, charts corresponding respectively to Figures 19, 20 and 21 showing relative dimensions on the diagrammatic views.

Figure 25, a modified body construction illustrating an alternative way of aligning the tooth plugs independent of each other.

Figure 26, a fragmentary section showing the body construction of Figure 25.

Figure 27, a section on line 27- 27 of Figure 26.

Figure 28, a perspective view of a modified body con struction.

Figure 29, a view of a tooth plug to be used in the body of Figure 28.

Referring to the drawings, attention is drawn first to Figure 9, which shows a breach cutter body as a cylinder 20 having a manifold groove 22 for distributing coolant around the body to passages which lead to the center thereof. In Figure 9, lines 24, 26, 28, 30, and so. forth, show the helical path for the various cutter plugs. which are to be inserted in the body.

In Figures 10 and 11, the spur gear 32 is shown which is to be cut, this gear having nine teeth with a helical shape. The blank from which the spur gear is made is of cylindrical shape having the diameter of the spur gear. tral passage 40 of the breach body 20. The breach body 20, as shown in Figure 2, is bored radially around its circumference with a plurality of holes 42, each successively spaced along the helical lines of Figure 9. There are nine rows of holes spaced around the body, each on a helical line which runs the length of the body. each of the roles there is inserted a cylindrical toothed cutter plug 44 having a head 46 at one end and a tooth formation 50 at the other end. The particular formation of the cutter teeth will be described later, it being suificient to say at this time that they vary in length and configuration from one end of the breach body to the other.

Beneath the head of each tooth cutter is a spacer 52 having a fiat top surface and a curved bottom surface ground with a fiat outer surface, in which case, fiat shims could be used. These spacers or shims 52 simplify themanufacture of the plug heads and also permit a re-grind on the teeth by substituting spacers of a lesser thickness. This permits a re-use of the expensive teeth after a wear period. One manner of holding the teeth in place is shown in Figure 2, in which an anchor yoke 54, held in place by a bolt 56, has projecting points 58 which reach to the center of each plug to hold it securely in place.

The plugs are held in place in pairs throughout the length.

, flats on the cutter teeth will contact each other in assem- This blank is to be pushed through a can tion.

bly, each tooth thus locating and stabilizing the next adjacent tooth and so on throughout the entire construc- The broach body is suitably mounted in a head 60 (see-Figure 1.) through which cooling fluid may be furnished to the manifold groove 22. Associated with the head is a plunger 62 having a plunger rod 64 rotatably mounted thereon so that it may turn as it pushes the blank through the breach. A coolant fluid passage 65in head 60 furnishes coolant to the manifold groove 22, whererit passes to tangent holes 66 which tend to move coolant in the direction of the spiral and insure chip flow to the discharge 'end.

The head 60 (Figure 5,) has a feedchannel 67 to receive gear blanks from a hopper feed (not shown). A pltmger 68 is periodically actuated to move a blank up to position where the rod 64 can start it on its path through the breach.

In order to broach spiral teeth on a gear, it is necessary that the gear be properly guidediand turned. It will be recognized that the lead angle of a spiral gear tooth changes from its root to its outer diameter. .It is necessary, therefore, to get this varying angle from the inner diameter to the outer diameter. In the present case, this is accomplished by grinding the teeth with varying cutting depths and angles and providing an unusual tooth design which imparts the necessary spiral motion to the gear as it moves through the broach. The grinding can also be done in this fixture to provide the necessary back-oil angles and contour. For example, in Figures 6, 7 and 8, a typical tooth is shown. The tooth is ground away to provide a gullet at 70 to provide chip space and is ground on the side at 72 and 74 to provide side clearance. The tooth may be hollow ground on top at 76, and the sides are'ground at an angle so that the leading edge 78 has a leading corner 8%) and a trailing corner 82. The edge 78 is at a shear angle which tends to move the blank in proper rotative action for spiral cutting. The direction of the work relative to the tooth is shown on the dotted line AB in Figure 6, and from this it will be seen that there is a back-oil clearance on the edge 84 behind the lead corner 80.

The edge 86 behind the trailingcorner 82 is not backedoff but actually forms a slight heel which also moves the leadcorner 80 into the work md creates the spiral motion of the work as it progresses. In Figure 2 the shape of the teeth used for the introductory cuts on the blank is shown. In Figure 4 the shape of the teeth for the final cuts is shown.

The blank is pushed through the lead portion of the body 20 by therod 64, and the blank turns in response A to the cutting action of the teeth, being'uncontrolled in its turning except by the teeth which are acting on it.

In- Figure 14 the progress of the cuts is shown by dotted lines. The first teeth in the series will make curved cuts, as indicated in the area from 1 to 15m Figure 14. These curved teeth take a side cut immediately on the cylindrical surface and thus cause movement of the blank'in the spiral direction. The teeth from 15 to 24 are straight in their outer contour, since it is less expensive 'to form a tooth in this way and the guidance can come out the sides as these teeth progress into the tooth form. The cuts from 24 to 32 gradually narrow following the tooth form. The cutsfrom 32 to 44 also follow the tooth form approaching the root diameter and also start'cu-ttingthe final outer contour of the tooth adjacent the OD. The-final four teeth are guided on the sides of the iteeth adjacent the pitch line and are also curved to further insure accurate spiral progress and clean out the root of the teeth to finish the job. Teeth from about 43 to 52 start shaving the sides of the tooth to the final form along'the'heavy black line. .It is desirable'that the final teeth have a slight back-off oneachside to insure a finish cut on both sides of the'gear teeth. 7 V

The lead angle of the teeth must vary as the cut gets deepersince in a; spiral cut the lead may be close 'to.

8de'gre es at the O. D., 6% deg're'es at thepitch' line, and

5 degrees at the root of the tooth. In fact, as the out begins-it is desirable to have the blades at greater angle than true lead to compensate for lag or slippage in the rotation of the part. The lead at the cutting edges, except at the start, is about equalto that ofthe gear tooth at the cut audit: is possible to back off the remainder of the cutting tooth so it will not interfere at; the higher angles at the outer ends of the gear teeth. With the disclosed method ofg'riii'dingocf teeth, it will be seen, a backoil can be readily provided at any point.

It is desirable when poss'ble to have-two teeth in the gear grooves atany one time, and this assists in thelead turn of the blank although'it is possible to control this lead turn without such a condition. a H

In Figures 12 and 13 and 17 to 24, there" is shown a method of arranging the teeth for proper grinding in a fixture. The tooth plugs are arranged in side by-side position aligned in a fixture. They are disposedatan angle by the ends of the fixture and at angles. to. each other by dummy plugs interposed as shown. With this arrangement a straight pass of the grinding wheel will put the proper side angle on the teeth. As shown inFigure 12, it is desirablethat the centerline of the plugs coincide V withthe centers of the cutting corners of the teeth; Then;

when the teeth are arranged in the spiralled holder, the cutting. edges will fall in a proper spiral.

The lay-out of Figures 17 to 24 shows a set-up for a 6 /2 degree helix, nine tooth RH. gear form. The various teeth from T1 to T52 are set at'varying angles by end plates 100 and dummy plugs R-1, R2', and so forth. The charts and plug ends'show the varying angles used in the grinding operation.

With the teeth ground as above described, the gear 1 blank can be pushed through the'broach and it will turn at the proper rate to'produce an accurate helix gear; With respect to'the method of operation, it should be further stated that concentricity can be perfectly malntairled, ifdesired, by inserting circumferentially spaced dummy guide plugs,z-three, for example, for the first pass, so that six teeth could be cut. The last three teeth could then be cut using guide plugs in the cutrecsses to maintain concentricity.

In Figures 15 and 16, a modified construction is shown wherein the teeth 44 are held in body"20 b'y'a-plurality ofsolid rings 110, which are'driven'on the assembly over In Figures 25'to' 27, there is showman alternative body construction in which heads 46" of the broach teeth are received iii'surface' slots -on thefbody 122 at the outer ends ofholes"124:= These slots 129' are spaced axially to leave I circumferential ridges1 26 which lock theflat sides of the heads'46in a defined position. This permits independentpo'sitioning of'e'acl'rtooth. V

In Figures 28 and 29, amodified'body construction is shown wherein the body is provided with spiral surface slots 134. which receive flat sides 132 urine hadnd of the tooth plugs 134 to locatethe same; Hereagainue teeth may be pos'ition'ed independentlyand clamped as previously described.

When the term spi ral gear is' used herein, it maybe taken to mean "any body having spaced spiral' slots and spiral flutes regardless of'the particular tooth formation. The method and apparatus herein actually form's spiral sl'o'tsin a leavingspiral gear teethor splines or'othr shapes'o'f 'tootli-likfiiit's; t

I claim:

1. An apparatus for forming and finishing external gears by broaching operation, which comprises a cylindrical broach body of one piece integral elongate construction having a central axial opening, a plurality of radial round recesses in said body spaced circumferentially and axially along and intersecting said opening, a plurality of broaching teeth each externally insertable and removably positioned independently of the other in a recess in said broach body and each comprising a cylindrical body shank portion snugly fitted in one of said radial recesses having one end projecting into said opening as a tooth form, another portion of each of said teeth being acircular in shape to serve as a locator to prevent rotation of the teeth within the recesses, means positively to position said teeth in a defined position radially of said holder, and releasable means to hold said teeth in said radial position.

2. An apparatus for forming and finishing external gears by a broaching operation, which comprises a broach body of elongate construction having a central axial opening, a plurality of radial recesses in said body spaced circumferentially and axially along and intersecting said opening, a plurality of broaching teeth each removably positioned independently of the other in a recess in said broach body and each comprising a body shank portion snugly fitted in one of said radial recesses having one end projecting into said opening as a tooth form, another portion of each of said teeth being acircular in shape to serve as a locator to prevent rotation of the teeth within the recesses, means positively to position said teeth in a defined position radially of said holder, and releasable means to hold said teeth in said radial position.

3. A device as defined in claim 2 in which the means to positively position the said teeth comprises on each tooth a head at the outer end to limit the inward radial movement of the tooth form in the axial opening.

4. A device as defined in claim 2 in which the releasable means to hold said teeth in said radial position comprises clamping blocks bearing on the outer ends of said teeth and means anchored in said broach body exerting inwardly radial force on said blocks and said teeth.

5. A device as defined in claim 2 in which the said I acircular portion of each of the plurality of teeth comprises radial mating surfaces on the outer ends of said teeth positioned outside said recesses to interengage adjacent teeth.

6. A device as defined in claim 2 in which the said acircular portion of each of the plurality of teeth comprises a head larger than said recesses to position outside said recesses, having planer mating surfaces perpendicular to the axis of said body positioned axially to interengage similar surfaces of adjacent teeth.

7. A device as defined in claim 2 for cutting of spiral tooth gears in which the radial recesses in the body are arranged along a plurality of spiral lines axially of said body, said lines being spaced circumferentially to correspond with the number of teeth to be formed.

8. A device as defined in claim 7 in which the tooth form on each tooth projecting into the axial opening and thus into the path of portions of the gear blank comprises a straight sided, quadrilaterally outlined plateau area gradually ensmalled from the body shank, having a forward shear edge at an angle to the path of the blank, the lead corner of said shear edge being followed by a side edge relieved to permit cutting, the trailing corner of said shear edge being followed by a side edge forming a heel to move the lead corner into the work to impart a relative rotation between a gear blank and the body as the blank passes the tooth forms.

9. A device as defined in claim 7 in which the tooth form on the broach teeth is shaped with a quadrilateral form having a lead corner and a trailing corner at a forward cutting edge which is angled from the lead corner to the trailing corner, the side edge of the form adjacent the lead corner being relieved and the side edge of the form adjacent the trailing corner being disposed in approximate parallel relation to the other side edge wherein the tooth imparts a relative rotative motion between the body and a gear blank moving through the body.

10. A device as defined in claim 8 in which the surface between the shear edge and the shank of the tooth is undercut to provide a slight hook at the shear edge.

11. An apparatus as defined in claim 8 in which the tooth forms are shaped progressively from one end to the other of the body to gradually remove the metal between the teeth of the finished gear, the initialteeth being dimensioned to remove material spaced from the sides of the finished teeth and progressively to move radially inward and circumferentially outward to the final tooth form.

12. An apparatus as defined in claim 11 in which a plurality of teeth at the entrance to said opening have the face surface of the cutting edges curved concavely to create side edges projecting radially beyond the center of the tooth form.

13. An apparatus as defined in claim 11 in which a first group of teeth at the entrance to said opening are located at a spiral lead angle greater than the desired lead of the tooth, and a plurality of teeth beyond said first group are positioned at a lead angle substantially equal to the desired lead of the tooth at the point of cut.

14. An apparatus as defined in claim 11 in which the forward cutting edges of the tooth form are shaped to conform approximately to the spiral angles of the teeth being cut radially at the point of cutting, the other form below the cutting edge being backed off to permit clearance of that portion of the formed tooth outside the point of cutting which has a greater spiral angle.

15. A broach tooth to be held in a breaching body for use in cutting spiral slots on a blank to be used as a spiral gear, which comprises an elongate body to be held radially in a broach holder, said body having a locating shank portion, a tooth formation at one end comprising a straight sided, quadrilaterally outlined plateau area gradually ensmalled from the body shank, the sides of said plateau lying in a plane substantially perpendicular to the axis of the tooth body, said tooth having a forward shew edge connecting said side edges, forming a lead corner and a trailing corner, the side edge adjacent said lead corner being angled to a relief position, the side edge adjacent said trailing corner being angled to a heel position in approximately parallel relation to the first side edge.

16. A broach tooth as defined in claim 15 in which the end of the tooth opposite the tooth form is shaped with fiat surfaces lying in a plane outwardly from the shank portions and parallel to the axis of the shank to engage with similar surfaces on adjacently positioned spaced teeth.

References lite-d in the file of this patent UNITED STATES PATENTS 772,841 Smith Oct. 18, 1904 1,089,376 Hanson Mar. 3, 1914 1,986,793 Chapman et a1. Jan. 8, 1935 2,102,071 Hart Dec. 14, 1937 2,161,901 Praeg June 13, 1939 2,282,193 Lambrix May 5, 1942 2,304,185 Lee Dec. 8, 1942 2,346,851 Lloyd Apr. 18, 1944 2,374,890 Pelphrey May 1, 1945 2,511,298 Schinnerer June 13, 1950 2,536,864 Strickland et a1. Jan. 2, 1951 2,641,822 Sampson June 16, 1953 2,644,369 Praeg July 7, 1953 2,674,780 Nielsen Apr. 13, 1954 2,683,919 Psenka July 20, 1954

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