US3199172A - Broach - Google Patents

Description

J. A. PSENKA Aug. 10, 1965 BROAGH 2 Sheets-Sheet 2 Original Filed April 10, 1961 INVENTOR. JOSEPH A.PSENKA 7 1 g Jag/" 41 I 7 fATTORNEYS United States Fatent O 3,19,i72 BRUAQH Joseph A. Psenira, Eloorniieid Hills, Mich, assigner to National Breach Machine Qonrpany, Wayne, Mich, a corporation of Michigan Original application Apr. til, 1961, Sci. N 101,887. Divided and this appiication Oct. 21, B64, Scr. No. 405,412

Qiairns. (GE. 29-951) The present invention relates to a breach and is a division of my present application, U.S. Serial No. 101,887, filed April 10, 1961. More particularly this invention relates to a broach comprising a plurality of sections, a leading one which is a roughing section adapted to rough out the teeth of a gear or splined element, and a following one in the form of a finishing section adapted to finish the teeth of the workpiece with extreme accuracy.

Breaches of the type described have been utilized in the industry. However, certain problems have been encountered. One of the main problems is that the side of the part which is produced by the obtuse side of the broach has more stock removed from it than from the side of the part which is produced by the acute side of the breach. This usually results in the acute side not cleaning up fully so that the errors of form introduced into the part by the roughing section of the broach are not entirely corrected or eliminated by the side shaving shell forming the finishing section of the broach.

The present invention relates primarily to means for correcting errors of form in the breach part which are introduced into the part by the roughing section of the broach. This is accomplished by providing an improved side shaving shell which is adapted to be mounted at the rear of the roughing section of the breach so as to conpletely remove the aforesaid errors.

It is an object of the present invention to provide a breach of the character described in which the finishing section is connected to the leading roughing section in such a manner that the finishing section will locate itself accurately in the workpiece and will therefore produce teeth on the workpiece which, for practical purposes, have the same accuracy as the teeth on the finishing section of the breach.

Another object of the present invention is to provide a breach which includes a side shaving shell having the teeth thereon so arranged as to equalize the amount of stock removed from both the acute and the obtuse sides.

A further object of the present invention is to provide a breach wherein the teeth thereon are arranged so that the backotf angle on the acute side is greater than the backoif angle on the obtuse side so as to increase the resistance of the tool to move into the obtuse side of the part.

A still further object of the present invention is to provide a breach having a series of longitudinally aligned finish cutting teeth for finishing a groove in a workpiece, each of the teeth being provided with a front cutting face having an acute side and an obtuse side, each of the sides being inclined or tapered inwardly away from the side walls of the groove from the front face to the rear of the tooth, with the angle of inclination or taper on the acute side being greater than the angle of inclination or taper on the obtuse side.

Another object of the present invention is to provide a breach assembly comprising a leading section having stepped longitudinally aligned series of rough cutting teeth, a following section connected to the leading section, said following section having a series of longitudinally aligned finish cutting teeth for finishing a groove in a workpiece, each of said finish cutting teeth having a steam Fatented Aug. 1%, 1965 front cutting face having an acute side and an obtuse side, each of said sides being inclined or tapered inwardly from the side walls of the groove from the front face to the rear of the tooth, with the angle of inclination or taper on the acute side being greater than the angle of inclination or taper on the obtuse side, and means mounting the following section on the leading section to maintain the teeth in substantial alignment.

it is thus another object of this invention to provide a simplified low cost structure of the aforementioned type having certain advantages contributing to efficiency, reliability and long life as Well as case of maintenance.

Gther objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawings illustrating preferred embodiments of the invention, wherein:

FIGURE 1 is a side elevation of the breach assembly.

FIGURE 2 is a side elevation of the leading roughing section of the breach.

FIGURE 3 is an end view of the leading section of the breach seen from the right in FIGURE 2.

FIGURE 4 is an enlarged view of adjacent teeth illustrated in FIGURE 1 taken on the line 4-4 thereof.

FIGURE 5 is an enlarged view of adjacent teeth illustrated in FIGURE 1 taken on the line 5-5 thereof.

FIGURE 6 is an elevational view of the novel side shaving shell.

FIGURE 7 is an end view of the shell shown in FIGURE 6.

FIGURE 8 is a view of the teeth looking in the direction of line 8-8 of FIGURE 6.

FIGURE 9 is a diagrammatic view of a side shaving finishing tooth.

In the broaching of internally toothed members, such as internal gears, spline members or the like, it is possible to produce broaching elements having substantially any required degree of accuracy. However, in use, such a breaching element can reproduce itself with substantially perfect accuracy only when it is not subjected to negative factors occasioned by an earlier stage of the breaching operation. The present invention relates to a broach which has a roughing section and a finishing section, with the finishing section taking the form of a replaceable side shaving shell which is afiixed to and lo cated on the rear end of the breach body following the roughing section, such as disclosed in my Patent 2,987,801 which issued on June 13, 1961. Certain aspects of the invention may be embodied in a finishing broach construction whether formed as a part of a breach including the finishing construction or formed as a separate broach.

Referring now to the drawings, the leading section of the breach assembly it) is shown in FIGURES 1 and 2 and is designated by the numeral ill and comprises a head 1?; adapted to be connected to a suitable device for pulling the broach through a hole in a workpiece. Conveniently, the roughing section of the broach is indicated generally at 14 and includes a series of continuous interrupted annular blades or ribs 16 adapted to form separate cutting teeth 29. The rear part of the roughing section includes alternate round and spline teeth. The round teeth or blades 18 are adapted to machine the hole in the workpiece to true cylindrical formation. The spline cutting teeth 26 are progressively stopped from front to rear and are backed off on the top at an angle phi and the sides thereof are relieved to within x inch to 6 inch of the top of the profile. The round teeth 13 are also backed off at an angle alpha.

it will be appreciated that the cutting teeth 26 are arranged in axial alignment if the breach it? is for the purpose of producing spur teeth, or in helical alignment if the broach is for the purpose of producing helical teeth. The

U term longitudinal alignment or the like is intended'to cover arrangemerns for producing both spur and helical ears.

At the following end of the roughing section 14 of the broach assembly 10 is a cylindrical support 22 having a reduced portion 24 which forms a shoulder 26. Roan wardly of the reduced portion 24 a support portion 22 is threaded as indicated at 23. Rearwardly of the threaded portion 28 is provided a cylindrical support portion 3%.

Directly to the rearof the final blade of the roughing section 14 there is a cylindrical surface 32, the opposite sides of which are machined away as indicated toforrn rearwardly facing fiat abutment surfaces 34 and radially outwardly facing flat surfaces 36. This arrangement provides a fiat transversely extending key 38'. As shown in FIGURE 1,.the following finishing broach section or side shaving shell db is assembled on the support portion 22 of the leading section 11. Rearwardly of the finishing section'or shell id is located a spacer 41 followed by a round shell 42 comprising a plurality of continuous round uninterrupted blades or ribs 44. The finishing shell 4%, spacer land side shaving shell 42 are retained on the support portion 22 of the leading section 11 in assembled relation by nut 48 threaded to the threaded portion '23 of the leading broach section 11. v

1 The finishing section or shell 49 is essentially tubular in shape having toothed cutting blades 59 forming longitudinally aligned series of cutting teeth 52. Again, the cutting teeth extend in axially disposed series if the broach id is tO fOIITl a spur member and the series are helically aligned if the broach 10 is used to produce helical'teeth on the workpiece. At the leading end of the finishing section at a notch or keyway is provided which extends diametrically across the leading end thereof and is dimensioned to receive the key 33 at the following end of the roughing section of the broach. The finishing section it? is generally provided with a central opening,'the intermediate portion of which is enlarged to provide clearance and the ends of which are of slightly reduced size to provide guide surfaces which are guidingly received on the cylindrical surface of the support portion 22 of the leading section 11 of the broach lit It will be observed inFlGURE 1 that the nut 48 has the front portion or forward end thereof engageable with the rear end of the round shell ;2 so as to urge the spacer 41 into engagement with the shoulder 26. With such a key and keyway construction between the roughing and finishing sections a small clearance in the amount of .002 inch is sufiicient to permit limited circumferential relative movement between the roughing and finishing broach sections. In addition, the key and keyway constructions of the sections are properly related with respect to the cutting teeth thereon so that the cutting teeth 52; on the finishing section are in substantial true alignment with the teeth 29 of the roughing section. Nevertheless,

as the finishing section db moves into action, it is per- The widths of the side shaving teeth increase from front a to rear. The broach assembly just described is disclosed in the aforesaid Patent 2,987,801.

Certain problems have been encountered with the use of side shaving shells 40 of the type just described in that the side of the part which is produced by the obtuse side of the broach has more stock removed from it than from V the side of the part which is produced by the acute side not eliminated by the side shaving shell in a practical length of shell.

FIGURE 6 shows a finishing shell designated by the numeral 54 which is constructed and designed to correct the aforesaid condition. Shell 54 has a series of longitudinally aligned. side cutting teeth 56 which progressively increase in width. 'In order to prevent the obtuse side of the broach shell Sdfrom removing more material from the part on circular tooth thicknesses than the acute side, it has been found that changing the backoff angle on the acute side will be of some benefit in correcting the errors of form. FlGURE 9 shows a tooth 56a having a cutting edge 58, with the acute side backed off at an angle phi and the obtuse side backed off at an angle alpha, with the angle phi being greater than the angle alpha. Withsucn a construction, the greater the backoff angle on the acute side, the freer will be the cutting action thereon and the less tendency there will be to pull the part into the obtuse side and conversely, the lower the backoff angle on theobtuse side, the greater will be the tendency for resistance of the broach to move into the obtuse side of the part. i f

Originally, finishing shells of the type described had a three-quarter degree backoff angle on both the acute and obtuse sides of the teeth for both spur and helical. However, due to size reduction of the tool with successive face grindings that produce'd'undersized parts in a relatively short time, the backoff angles were decreased to one-half degree on both sides of the'teeth on both spurand helical applications. found that the aforesaid problem is substantially eliminated by decreasing the obtuse backoff angle to onequarter degree and increasing the acute backoif angle to three-quarter degree. The net result is a broach that has as much tool life as if both sides were backed off to onehalf of a degree. V

The drawings and the foregoing specification constitute a description of the improved broach in such full, clear, concise and exact terms as to enable any person skilled in the art to practice the invention, the scope of which is indicated by the appended claims.

What I claim as my invention is:

l. A broach having a series of longitudinally aligned finish cutting teeth for finishing a groove in a workpiece, each of said teeth having a front cutting face having an acute side and an ob-tuseside, each of said sides being inclined inwardly away from the side walls of the groove from the front face to the rear of the tooth, withthe angle of inclination on the acute side being greater than the angle of inclination on the obtuse side.

2. A broach assembly comprising a leading section having stepped longitudinally aligned series of rough cutting teeth, a following section connected to the leadingsection,

said following section having a series of longitudinally aligned finish cutting teeth for finishing a groove in a workpiece, each ofsaid finish cutting teeth having a front cutting face having an acute side and an obtuse side, each of said sides being inclined inwardly from the side walls of the groove from the front face to the rear of the tooth, with the angle of inclination on the acute side being greater than the angle of inclination on the obtuse side, and means mounting said following section on said leading section to maintainsaid cutting teeth in substantial alignment.

3. A broach having a series of longitudinally aligned finish cutting teeth for finishing a groove in a workpiece,

. each of said teeth having a front cutting face having an of the broach. This results sometimes in the acute side not cleaning up entirely so thatthe errors of form introduced into the broach part by the roughing section are acute side and an obtuse side, each of said sides being tapered inwardly away from the side Walls of the groove from the front face to the rear of the tooth, with the angle of taper on the acute side being'greater than the angle of taper on the obtuse side.

t. A broach assembly comprising a leading section having'stepped longitud-inally aligned series of rough cuttingf With the present invention, it has been teeth, a following section connected to the leading section, said following section having a series of longitudinally aligned finish cutting teeth for finishing a groove in a workpiece, each of said finish cutting teeth having a front cutting face having an acute side and an obtuse side, each of said sides being tapered inwardly from the side walls of the groove from the front face to the rear of the tooth, with the angle of taper on the acute side being 6 greater than the angle of taper on the obtuse side, and means mounting said following section on said leading section to maintain said cutting teeth in substantial alignmerit.

Noreferences cited.

ANDREW R. JUHASZ, Primary Examiner.

Claims (1)

1. A BROACH HAVING A SERIES OF LONGITUDINALLY ALIGNED FINISH CUTTING TEETH FOR FINISHING A GROOVE IN A WORKPIECE, EACH OF SAID TEETH HAVING A FRONT CUTTING FACE HAVING AN ACUTE SIDE AND AN OBTUSE SIDE, EACH OF SAID SIDES BEING INCLINED INWARDLY AWAY FROM THE SIDE WALLS OF THE GROOVE FROM THE FRONT FACE TO THE REAR OF THE TOOTH, WITH THE ANGLE OF INCLINATION ON THE ACUTE SIDE BEING GREATER THAN THE ANGLE OF INCLINATION ON THE OBTUSE SIDE.

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