CA1210620A - Die hobber - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

The present invention relates in general to the art of metal shaping wherein a metal work piece is die-cut to a desired shape, and it relates in particular to a new and im-proved die configuration and to a method of using the novel die.

Description

J.2~06Z0 OBJECTS OF THE INVENTION
. _ _ . . . . . .
The principal object of the present invention is, therefore, to provide a new and improved method and means which enables the economical manufacture of metal parts having sides extending perpendicular to the plane of the workpiece, which method permits tl~e holding of extremely close tolerances and daes not result in stress concentrations which would distort the workpiece.
Another object of the present invention is to provide a novel die configuration for use in the said method, which die configuration may be used for shaping very hard, machineable materials, such as high speed tool steel.

SUMMARY OF THE INVENTION
Briefly, there is provided in accordance with the present invention a novel die configuration which may be used in a metal removal operation which is similar to hobbing and which is carried out in a punch preSs. In accordance wlth the novel me~hod of this invention the workpiece is pushed along the cutting edge o ~he die to remove edge material from the work-piece and thus provide the desired shape.
In a preferred embodiment of the invention the die has a three hundred sixty degree cutting edge wherefor the~-entire external or internal edge of the workpiece i9 formed in a single operation. In another embodiment of the invention a plurality of dies are stacked ln mutually spaced relationship and the work-piece is pushed past the dies which progressively remove material from the workpiece to provide a finished part in a single punch press operation.

-2 lZ106Z0 'lhe die of the present invention has a facial contour on the ~ctive side of the die which is mathematically derived to provide the cutting edge of the die with a substantially constant shear angle throughout its entire length. The optimum shear angle is related to the diameter and hardness of the material being worked and may be chosen on the basis of experi-ence or in some other suitable manner.
The active side of the die slopes away from the cutting edge, so that the material which is preferably removed in the form of chips will move freely away from the workpiece as it moves past the cutting edge. In the case where the external edge of the workpiece is being formed, as the workpiece is pushed ~hrough the die the workpiece is outwardly stressed or s~retched as the removed material 18 cut and pulled radially outward. As a result, no stress concentration in the workpiece results, and no distor~ion of the workpiece occurs. In some cases it has been found that the flatness of the workpiece is actually increased when the sides aré~shaped in accordance with the present invention.
Other inherent advantages of the method of the present invention as compared to the use of conven~ional dies and punch press operations are quieter operation and lower maintenance costs. I have found that the die~ of the present invention need be sharpened less than one-third as frequently as conventional punch press dies. Moreover, because of the smooth cutting action of the die, the temperature of the workpiece is not raised as much as it would be in a conventional punch press operation.
Also, the close clearances between the pusher member and the die which would be required to prevent distortion of the workpiece

3~

~2~16ZO

in a normal puncl- press operation are unnecessary when using the method of the present invention.

GENERAL DESCRIPTION OF THE INVENrl`InN
The present invention will be better understood by a reading of the following detailed description taken in con~
nection with the accompanying drawings wherein:
Fig. 1 is a plan view of an external gear which may be made by the method of the present invention;
Fig. 2 is a cross-sectionsl view of the gear of Fig. 1 taken along the line 2-2 thereof;
Fig. 3 is a plan view of an internal gear which may be made by the method o the present invention;
Fig. 4 is a cross-~ectional view of ~ h gear of Fig. 3 taken along the line 3-3 thereof;
Fig. S is a plan view of still another part having a complex peripheral configuration which may be made by the method of the present invention;
Fig. 6 is a plan view showing the gear of Fig. 1 being made by the method of the present invention;
Fig. 7 is a cross-sectional view taken along the line 7-7 of Fig. 6;
Fig. 8 is a cross-sectional view similar to that of Fig. 7 but showing the gear of Fig. 3 being made by the method of the present invention; and Fig. 9 is a framentary, sectional view of a portion of a die embodying the present invention.

~Z1~620 DETAILED DESCRIPTION OF A PREFERRED
EMBODIME;NT OF THE INVENTION
... ..
The present invention may find application where-e~er it is desired to form a vertical edge on a part, but it is particularly suited for cutting vertical side edges on relatlvely thin, hard metal parts. For example, the invention has been used to cut both internal and external involute teeth on thin flat parts sueh as gears and splines formed of high speed tool steel, and parts having an external diameter of more than nine inches and a thicknes~ of less than one-eighth inch have been made in~accordance with the teaching~ of the present invention. Therefore, although the invention ls described here-in in connec~ion with th~ manufacture of a few representative parts, its use i8 not 80 limited.
Referring to Fig~. 1 and 2, there iR shown a thin, flat member 10 of generally annular shape having a plurality of external teeth 12. The teeth 12 are iden~ical and equally spaced, and they have sides 12A in the ~ape of a partial in-volute. The memb¢r 10 may function as an external gear or spline and may be seen from an ~nspection of Flg. 2 to be relatively thin in cross-section. The con~inuous external side edge of the member 10 i8 identified at 13 and may be seen to be perpendicular to the principal plane and faces 14 and 15 of the member 10.
Referring to Figs. 3 and 4, there is shown a thin, flat member 18 of generally annular shape having a plurality of equally spaced internal teeth 20 having the sides 20A thereof each in the shape of a partial involute. As best shown in Fig.

4, the internal side edge of the member is identified at 21 and is perpendicular to the principal plane and faces 23 and 24 of the member 18.

-5-Referring to Fig. S there is shown a thin flat member 26 having an external perpendicular edge 27 of relatively complex confi~uration in the plane of the member 26. The external edge 27 may be formed in accordance with the teach-ings of this invention.
Referring now to Figs. 6 and 7 there is shown a die 30 for removing metal from the external side 32 of a flat metal plate or workpiece 33 as the plate 33 is pushed past the cutting edge 35 of the die through the center opening 36 therein by mesns of a pusher member 38 The side 39 of the pusher member 38 is complimentary to the cutting edge 35 of the die 30 although a substantial clearance of a few thousandths of an inch or more may be provided between the pusher member and the die. The lower face 40 of the pusher ~ember i8 complimentary to the upper face of the workpiece 33. The die 30 and the pusher member 38 are preferably mounted to the base and upper platen respectively of a conventional punch press whereby the pùsher member 38 i9 driven down toward the die 30 to pus4 the workpiece 33 there-through as in a conventional punch pressoperation. Preferably the workpiece 33 is a blank having its outer edge more or less conforming to the external shape of the final part thereby to facilitate removal and dlsposition of the metal from the workpiece in the form of 8mall chips.
In accordance wlth an important aspect of the present invention the die 30 has a particular facial contour 42 on the working si~e of the die, which contour, in associaiton with the vertical side 36, provides a cutting edge 35 having a sub-stantially constant shear angle throughout its entire length.
The optimum shear angle will vary with the hardness and thick-3~ ness of the part being made, but whatever shear angle is selected, ~21(~62~

it is sul~stantially the same along the entire cutting edge of the die. I`or example, for most applications where high speed tool steel is to be worked, a shear angle between six degrees and fifteen degrees will generally be used. The facial contour of the die can, as more fully described hereinafter, be math-ematically computed when the planar shape of the part to be formed is given mathematically, and the computation necessary for developing this facial contour can best be made using a general purpose computer. However, since the facial contour 42 is uniform for all radii of the die the contour can be shaped in any preci~e metal working process such as turning or milling.
The working contour of the die 30 extends from the innermos~ portions of the edge 35, identi~ied in Fig. 6 as Rl, to a location a short distance outward of the maximum external radius of the cutting edge 35. The reference character Ro ln~icates the latter location or radius. The upper face of~
the die between the locations RI and Ro has a cross-sectional profi which in combina~ion with the involute tooth configuration shown in Fig 6 provides the cutting edge 35 with a constant shear angle throughout it~ entire 360 length. The shape of the con-tour between the radii RI and Ro can be mathematically computed as described hereinafter. I have found, however, that for some applications the contour between the radii RI and Ro can be a portion of a cone closely approximating the actual contour as mathematically computed and still maintain the shear angle substantially constant throughout the entire length of the cutting edge.
The portion of the die which is exterior to the radius ~Z~6;i~0 Ro does not have a critical facial contour, but it preferably slopes downwar~lly s~ that the removed chips will fall by gravity away from the workpiece and away from the die itself.
Referring to Fig. 8 there lS shown a novel die 46 for cutting the internal edge of the part 18 shown in Figs. 3 and 4.
In Fig. 8, a blank 48 rests on ~he upper face 50 of an annular support piece 52 adapted to rest on the base platen of a punch press. The support piece 52 has an internal vertical wall 54 which is similar in horizontal cross-section to the internal edge of the part to be formed. The lower face of the die 46 is the working face thereof and is contoured to provide a cutting edge 56 having ~ constant shear angle throughout its entire 360 length. The edge 56 lies in a horizontal plane and correspondR
to the internal edge of the part lB as shown in Fig. 3.
When forming the internal edge of a part in accordance with this aspect of the invention, a flat, annular blank 48 is placed on the support member 52 in a punch press and the die 46 ls fixedly mounted to the upper platen~ The press i8 then operated to push the die 46 into the central opening ln the support member 52 thereby to cut the metal from the interior edge of the blank 48 to precisely form the internal edge of the finished part. The metal is removed in the form of chips and falls by gravity into the central opening in the support member 52.
The optimum speed at which the die is moved past the workpiece during the cut~ing operation will vary with the hardness and thickness of the workpiece, but I have produced acceptable parts at the rate of thirty-five per minute.

lZ10620 Wi L1- re fer~?nce to Fig . 9, the facial contour of the work-ing area of the die for cutting radial teeth of involute config--` uration may be computed using the following formula:

A = Arc Tan _ _ Tan B
~ Rl Co s 1 ~ 2 + (~ + INV01 - INV02 ) wherein A - angle of contour at radius R2 B = shear angle of cutting edge ~ Rl - pltch radius - R2 ~ radius at each point in the die Tl = arc thickness of tooth at Rl T2 = arc thickness of tooth at R2 01 = pressure angle at Rl This equation can best be solved for a plurality of incremental values R2 by means of a digital computer. The angular values A can be plotted in the associated computer printer to provide the plot shown in Fig. 9, which contour is a radial section taken at all circumferential points of the die. It will be apparent that for the parts 10 and 18 , ~
the contour profile i8 the same even though one die is for cutting radial involute teeth on the external edge of the workpiece and the other die is for cutting identical involute teeth in the internal edge of the workpiece.
It will be understood that other equations ~ay be used for determining the contours necessary for providing constant ~: :
shear angles for cutting edges of other shapes such, for example, as those shaped to form a complex configuration such as the ex-ternal profile of the part 26 shown in Fig. 5 or of square ~Z106Z0 ~eeth (not shown) or of any other configuration.
Whi le the present invention has been described in connection with particular embodiments thereof, it will be understood by those skilled in the art that many changes and modifications may be made without departing from the true spirit and scope of the present invention. Therefore, it is intended by the appended claims to cover all such changeQ
modifications which come within the true spirit and scope of this lnvention.

Claims (6)

WHAT IS CLAIMED:

1. A method of shaping a plate by removing material from an edge thereof, comprising the steps of providing a die having a cutting edge corresponding to said edge and a facial contour sloping away from said cutting edge, said facial contour being convex and configured to provide a substantially constant shear angle along said entire cutting edge, positioning said plate against said die and said cutting edge, positioning a rigid pusher member having an edge complementary to the shape of said cutting edge against the side of said plate opposite said die, and pushing said pusher member and said plate past said cutting edge of said die to move said plate past said cutting edge to form said edge thereon.

2. A method according to claim 1 wherein said continuous edge is on the exterior of said plate, and said cutting edge is on the interior of said die.

3. A method according to claim 1 wherein said shear angle and said facial contour cause said cutting edge to remove material from said plate in the form of chips.

4. A method according to claim 1 wherein said continuous edge is a plurality of involute teeth and the cross-sectional configuration of said facial contour is defined by the following equation:

wherein:
A = angle of contour at radius R2 relative to the horizontal B = shear angle cutting edge relative to the horizontal R1 = pitch radius R2 = radius at each point on the die T1 = arc thickness of tooth at R1 INV0 = tan 01 - 01 INV0 = tan 02 - 02 01 = pressure angle at R1 02 = pressure angle at R2

5. A die for removing metal from a metallic workpiece, said die having a continuous cutting edge having a shear angle within the range of six degrees to fifteen degrees throughout the entire length of said cutting edge.

6. A die for removing metal from a-metallic workpiece, said die having a cutting edge having a facial contour substantially defined by the following equation:

wherein:
A = angle of contour at radius R2 relative to the horizontal B = shear angle of cutting edge relative to the horizontal R1 = pitch radius R2 = radius at each point on the die T1 = arc thickness of tooth at R1 INV0 = tan 01 - 01 INV0 = tan 02 - 02 01 = pressure angle at R1 02 = pressure angle at R2