Abstract:
A male punch member is disclosed for use with a female die member to remove a slug in two pieces from a sheet metal workpiece. The working end of the punch member is specially configured to enable punching and splitting of a slug into two pieces from a wide range of materials such as 10-gauge, type 304 stainless steel while providing acceptable punch life.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a punch member and, in particular, to a male punch member for removing a slug in two pieces from sheet metal and the like. 
     BACKGROUND OF THE INVENTION 
     Draw punches useful with a female die member to remove a slug from sheet metal are known in the art. For example, the following United States patents describe various draw punch constructions: 
     U.S. Pat. No. 1,721,007 issued July 16, 1929 
     U.S. Pat. No, 1,754,568 issued Apr. 15, 1930 
     U.S. Pat. No. 1,817,223 issued Aug. 4, 1931 
     U.S. Pat. No. 2,237,069 issued Apr. 1, 1941 
     U.S. Pat. No. 3,269,011 issued Aug. 30, 1966 
     British Pat. No. 1,415,620 and French Pat. No. 851,760 also disclose draw punches. 
     A disadvantage of these known draw punch constructions is that removal of the slug from the female die member, or draw shaft associated with the punch and die members for moving the male member into the female member, is often difficult and time-consuming. Frequently, another tool such as a screwdriver must be used to free the punched slug. None of the aforementioned patents appear to disclose a draw punch construction which splits or cuts the slug into two pieces for easy removal. 
     U.S. Pat. No. 4,353,164 issued Oct. 12, 1982 of common assignee herewith describes an improved draw punch capable of not only punching a slug from soft sheet metal such as mild carbon steel but also splitting the soft slug into two pieces for quick and easy removal. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide a punch member capable of punching a slug from a workpiece and also splitting or cutting the slug into two pieces for easy removal from a cooperating female die member. 
     Another object of the invention is to provide such a punch member which will punch and split a slug from a wide range of metallic, plastic, or composite workpiece materials, in particular from heavier gauge austenitic stainless steels such as for example 10-gauge, type 304 stainless steel which prior art punch members have not been capable of satisfactorily punching. 
     The above objects and advantages of the invention are achieved in a typical embodiment by a novel arrangement of inclined surfaces and associated cutting edges and surfaces on the working face of the punch member. For example, a typical working embodiment of the invention includes a pair of first inclined surfaces oppositely disposed on the punch working face and sloping upwardly in opposite directions. The first inclined surfaces each have an outer peripheral edge forming a first outer cutting edge on opposite sides of the working face, partially around the working face periphery when viewed in plan. A pair of second inclined surfaces intersect the respective first inclined surfaces and also slope upwardly but at a steeper angle of inclination. The second inclined surfaces preferably slope upwardly in a direction transverse to that of the first inclined surfaces. The second inclined surfaces each have an outer peripheral edge forming a second outer cutting edge contiguous with the respective first cutting edges but more steeply inclined. In addition, the second inclined surfaces terminate laterally in respective laterally inclined cutting surfaces which slope upwardly in opposite directions toward and intersecting with the associated second outer cutting edge. The lateral cutting surfaces together form a generally V-shaped lateral cutting means across the working face. Further, the lateral cutting surfaces and second cutting edges together at their junction provide a generally pyramidal cutting section to provide triangular cutting patterns into the workpiece to initially pierce it and initiate lateral cutting or splitting of the slug from the slug periphery toward the slug center before a substantial portion of the slug periphery is cut. This arrangement assures that the slug is adequately supported while it is being split apart. 
     In particularly preferred embodiments of the invention, the first inclined surfaces are inclined planar surfaces and the second inclined surfaces are inclined planar surfaces intersecting the respective first inclined surfaces along a line of intersection parallel with a diameter extending across at least a portion of the working face and sloping upwardly transverse to the first planar surfaces and terminating in inclined lateral cutting surfaces extending across at least a portion of the working face. The lateral cutting surfaces may intersect one another at some location across the working face to, in effect, form a unitary generally V-shaped lateral cutting means or they may terminate in spaced apart ends. 
     The above objects, advantages and features as well as others will be understood in more detail by reference to the accompanying drawings and following detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevation of the punch member and also includes a projection of the inclined surfaces. 
     FIG. 2 is a top plan view of the punch member. 
     FIG. 3 is an elevation of another punch member where the lateral cutting surfaces intersect. 
     FIG. 4 is an elevation of still another punch member. 
     FIG. 5 is a top plan view of the punch member of FIG. 4. 
     FIG. 6 is a top plan view of the workpiece showing the initial triangular cutting pattern into the workpiece. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIGS. 1 and 2 illustrate a preferred version of the present invention. In particular, a male punch member 10 is shown and useful for punching a two inch diameter hole through a sheet metal workpiece, such as 10-gauge, type 304 stainless steel. The male punch member 10 is used with a female die member well known in the art as well as a draw shaft also well known in the art, e.g., the general arrangement of male die member, draw shaft and female die member being shown in the prior art patents cited in the Background of the Invention section hereinabove. In these arrangements, it is apparent that the workpiece is provided with a pilot hole through which the draw shaft extends. 
     The punch member 10 includes a generally cylindrical punch body 12 having a threaded bore 13 extending axially therethrough for threadably receiving the threaded end of the draw shaft (not shown) in conventional fashion. The punch member 10 also includes a working face 14 transverse to its axis and having a novel arrangement of inclined surfaces and associated cutting edges and surfaces for not only punching but also splitting apart of the slug to be removed from the workpiece. For example, the working face 14 includes a pair of first inclined planar surfaces 20 and 22 on opposite sides of diameter D and bore 13. The first planar surfaces 20, 22 slope upwardly from the working face in opposite directions at an angle α of for example 13° in the particular embodiment shown. The first planar surfaces 20, 22 have outer circumferential or peripheral edges which form first outer cutting edges 20a, 22a around a large portion of the working face periphery when viewed in plan (FIG. 2). The planar surfaces 20, 22 also have inner chordal ends 20b, 22b parallel with and spaced from diameter D across the working face in plan view. These chordal ends 20b, 22b are intersected by a pair of second inclined planar surfaces 30, 32 extending laterally across the working face and sloping upwardly in a direction transverse to the direction of slope of the first planar surfaces as shown in FIG. 1. The second inclined planar surfaces 30, 32 slope upwardly from the lines of intersection at a steeper angle of inclination θ (for example, 20°) than the first planar surfaces 20, 22. 
     The inclined planar surfaces 30, 32 include outer peripheral edges forming second outer circumferential edges 30a, 32a and third cutting edges 30c, 32c around a small portion of the working face periphery when viewed in plan (FIG. 2). Importantly, the second inclined planar surfaces also terminate laterally across the working face on one side of the bore between the first inclined planar surfaces 20, 22 in narrow lateral cutting surfaces 30b, 32b which are generally flat across and in vertically and radially oriented third surfaces 31,33 on the other side of the bore between the first inclined planar surfaces. The third surfaces 31, 33 each extend vertically upward at a 90° angle from the respective second inclined planar surface and terminate at the respective lateral cutting surface 30b, 32b in spaced relation to the second inclined planar surface terminating at the cutting surface. From FIG. 1, it is apparent that the lateral cutting surfaces 30b, 32b extend generally toward one another and incline upwardly in opposite directions toward the associated second outer cutting edges 30a, 32a of the inclined planar surfaces 30, 32. The lateral cutting surfaces thus form a generally V-shaped lateral cutting means across the working face when viewed in elevation (FIG. 1). 
     Furthermore, the lateral cutting surfaces 30b, 32b at their junction P 1 , P 2  with the respective second cutting edges 30a, 32a form a generally pyramidal-shaped piercing section S (FIG. 1) on diametrically opposite sides of the working face periphery to initially pierce the workpiece in a triangular pattern and initiate lateral cutting across the slug diameter before a substantial portion of the slug circumference is cut. The uppermost height, H, of the second cutting edges 30a, 32a above the respective first cutting surfaces 20a and 22a as well as their angle of slope and length (circumferential) is correlated with similar parameters for lateral cutting surfaces 30b, 32b to achieve this effect. The intersection of the lateral cutting surfaces 30b, 32b with the second cutting edges 30a, 32a in this manner insures that the slug will be peripherally supported during most of the time the lateral cutting or slug splitting is occurring. This feature prevents unwanted tearing and twisting of the slug during punching. 
     FIG. 3 shows another embodiment of the invention where there is no axial bore in the punch member 10&#39; and where the lateral cutting surfaces 30b&#39;, 32b&#39; intersect centrally on the working face. In FIG. 3, like features are represented by like numbers primed. It is apparent that the lateral cutting surfaces 30b&#39;, 32b&#39; form a V-shaped lateral cutting or splitting means across the working face in elevation. As used hereinabove and hereinafter, &#34;V-shaped&#34; merely means an elevational profile generally resembling a full V or open-ended (partial) V including a profile wherein the lateral cutting surfaces might be concave or convex across the working face. The choice of the particular shape for the lateral cutting means may be varied to suit specific applications so long as the lateral cutting surfaces 30b, 32b are upwardly divergent away from the working face as shown for example in FIGS. 1, 3 and 4. 
     FIG. 4 shows still another embodiment of the punch member for punching and splitting a smaller slug such as a 1/2-inch diameter slug from a workpiece. In FIG. 4, like features are represented by like numerals double primed. 
     As a result of the particular construction of the present punch member, in particular the working face thereof, thicker, stronger material such as 10-gauge, type 304 stainless steel can be punched to remove a slug in two pieces. And, the punch life under such cutting conditions is adequate from a commercial product standpoint. 
     In operation, the male punch member 10 is placed opposite the female die member (not shown) with the sheet metal workpiece therebetween. The male punch member and female die member are then brought together so as to progressively move the punch member working face into the workpiece. Initial penetration is by the pyramidal section S formed by the lateral cutting surfaces 30b, 32b at their juncture with second cutting edges 30a, 32a and this penetration constitutes a piercing action into the workpiece. As the pyramidal sections penetrate further, lateral cutting or splitting of the slug is initiated from the slug periphery toward the slug center before a significant part of the slug periphery is cut. FIG. 6 shows the initial triangular cutting pattern wherein radial cuts R progress toward center hole B in workpiece W while circumferential cuts C progress from the junction of the second cutting edges 30a, 32a and lateral cutting surfaces 30b, 32b. With further penetration, lateral splitting of slug Z continues and preferably is substantially complete before the first cutting edges begin cutting their portion of the slug periphery. Final cutting proceeds as the third cutting edges 30c, 32c and first cutting edges 20a, 22a cut toward one another. The entire slug periphery is thus cut and the slug is split apart into two pieces for easy removal. 
     While there have been described what are considered to be certain preferred embodiments of the invention, other modifications, changes, additions and the like may be made within the spirit and scope of the invention. For example, instead of the inclined surfaces being planar, helical or curvilinear inclined surfaces may be employed. The third cutting edges 30c, 32c formed by the second planar surfaces may instead be formed by the first planar surfaces 20, 22. The shape of the outer periphery of the punch may be such as to punch a hole other than circular, such as elliptical or rectangular. It is intended to cover in the appended claims all such modifications and the like as fall within the spirit and scope of the invention.