US2843861A - Die cavity with laterally projecting blades for slotting the end of a blank - Google Patents

Description

July 22, 1958 J. E. GANDY DIE CAVITY wnu LATERAL-LY PROJECTING BLADES FOR SLOTTING THE END OF A BLANK Filed April 15, 1956 2 Sheets-Sheet 1 July 22, 1958 J. E. GANDY 2,843,861

DIE CAVITY WITH LATERALLY PROJECTING BLADES FOR SLOTTING THE END OF A BLANK Filed April 15, 1956 2 Sheets-Sheet 2 Fig .II.

all 9 1i" fi1i ii 32' United States Patent DIE CAVITY WITH LATERALLY PROJECTING BLADES FOR SLOTTIEQG THE END OF A BLANK of Chippewa Township, D. C. Fabiani, administrator, Beaver County, Pa., assignor to New Brighton, Pa., a corporation Application April 13, 1956, Serial No. 578,146 3 Claims. (Cl. Ill-11) This invention relates to forming apparatus and partlcularly to apparatus for the forming of slotted blanks. The forming apparatus is adapted, inter alia, for the forming of slotted elongated blanks for use in the manufacture of expandable fasteners and for purposes of explanation and illustration the invention will be described as embodied in such forming apparatus.

The forming apparatus may be embodied in a forming machine which in respect of the general machine structure and operating mechanism is conventional, there being a number of such machines on the market; examples are shown in United States Patents Nos. 2,112,284, 2,170,556 and 2,396,995. The present invention comprises special tools which may be applied to forming machines of the type disclosed in said patents.

There is provided forming apparatus comprising a die cavity open at one end to receive a blank, a slotting blade projecting laterally into the die cavity and adapted to slot a blank forced into the die cavity through the open end thereof and means mounted for movement to force a blank inwardly of the die cavity through the open end thereof and onto the slotting blade to slot the blank. Desirably a blank holder movable into position in alignment with the die cavity is provided and the means mounted for movement to force a blank inwardly of the die cavity through the open end thereof have a portion Within the blank holder and mounted for movement relatively thereto so that a blank held in the blank holder is forced directly from the blank holder into the die cavity. Before the blank is forced into the die cavity the blank holder may be moved to position in contact with the die and in alignment with the die cavity.

The slotting blade preferably has an edge in the die cavity inclined to the die cavity wall in a direction away from the open end of the die cavity generally toward the central portion of the die cavity. Such edge of the slotting blade may have a portion relatively adjacent the die cavity wall and another portion relatively remote from the die cavity wall, the first mentioned portion of said edge being inclined to the die cavity wall at an angle greater than the angle at which the second mentioned portion of said edge is inclined to the die cavity wall.

Preferably a plurality of slotting blades are provided which project laterally into the die cavity. The inner extremities of the slotting blades preferably substantially meet within the die cavity. The number of slotting blades may be varied, but normally the slotting blades are uniformly angularly spaced about the die cavity. In the structure shown in the drawings of the present application four slotting blades spaced 90 apart are shown. Normally the inner extremities of the blades meet at the axis of the die cavity although in special instances the blades may be otherwise arranged.

Preferably the inner extremities of the slotting blades at operative portions of the blades are relatively sharp and substantially meet within the die cavity, the inner extremities of the slotting blades at portions of the blades 2,843,861 Patented July 22, 1958 v 2 generally in alignment with said operative portions of the blades having cooperating surface portions in contact through which the blades are braced against one another.

One form of forming apparatus may comprise a die cavity open at one end to receive a blank, slotting blade means projecting laterally into the die cavity and adapted to slot 2. blank forced into the die cavity through the open end thereof, means extending into the die cavity through the opposite end thereof positionable to form in effect a bottom to the die cavity to limit movement of the blank thereinto and means mounted for movement to force a blank inwardly of the die cavity through the open end thereof and onto the slotting blade means until the blank engages the bottom of the die cavity to slot the blank. Means are desirably provided for moving the means extending into the die cavity through the aforementioned opposite end thereof toward the open end of the die cavity to eject the slotted blank through said open end. The means extending into the die cavity through said opposite end thereof may have slot means to receive the slotting blade means upon movement of the means extending into the die cavity through said opposite end thereof toward the open end of the die cavity.

In any event stop means, which may extend into the die cavity through the aforementioned opposite end there-. of or otherwise, may be provided limiting the extent of movement of the blank into the die cavity and thereby determining the extent of slotting of the blank, and a plurality of elements may be provided adapted. to act on the blank in the die cavity and selectively positionable to act thereon, one of said elements being mounted for movement to force the blank inwardly of the die cavity through the open end thereof and onto the slotting blade means to slot the blank and the other of said elements being mounted for movement to engage and head the slotted blank while in the die cavity. Means are preferably provided for moving the stop means toward the open end of the die cavity to eject the slotted and headed blank.

The forming apparatus may comprise two die cavities, the first die cavity being shaped to reduce the end of a blank forced thereinto and the second die cavity having therein slotting blade means to slot a blank forced thereinto, means for forcing a blank into each of the die cavities and means for transferring the blank from i the first die cavity to the second die cavity so that the reduced end of the blank formed in the first die cavity may be slotted in the second die cavity. Means are preferably provided for ejecting the blank from each of the die cavities.

The forming apparatus in its present preferred form comprises two die cavities each open at one end to receive a blank, the first die cavity being shaped to reduce the end of a blank forced thereinto through the open end thereof, slotting blade means projecting laterally into the second die cavity and adapted to slot 21 blank forced thereinto through the open end thereof, means for limiting the extent of movement of the blank into each of the die cavities and ejecting the blank therefrom, means for forcing a blank into the first die cavity to reduce the end of the blank, means for transferring the blank from the first die cavity to the second die cavity and a plurality of elements adapted to act on the blank in the second die cavity and selectively positionable to act thereon, one of said elements being mounted for movement to force the blank inwardly of the second die cavity through the open end thereof and onto the slotting blade means to slot the reduced end of the blank and the other of said elements being mounted for movement to engage and head the slotted blank while in the second die cavity.

The slotting blade means may be shaped and positioned in the die cavity to slot the blank from the mouth of the die cavity inwardly so that-the slots in the blank extend substantially to the head of the blank when the blank is headed as above set forth.

' Other details, objects and advantages of the invention will become apparent as the following description of cer tain present preferred embodiments thereof proceeds.

In'th'e accompanying drawings there are shown certain present preferred embodiments of the invention and there are illustrated successive steps in making an expandable fastener using the apparatus of the invention, in which Figure 1 is a side view of a starting blank;

Figure 2 is a side View of the blank after the first operation which provides the blank with a zone at one end tapering to reduced transverse dimension toward that end;

Figure 3 is an axial cross-sectional view of the blank after the second operation in which the blank is slotted;

Figure 4 is an axial cross-sectional view of the blank after the third operation in which the blank is headed;

Figure 5 is an axial cross-sectional view of the blank after the fourth operation in which the expanding pin receiving opening is drilled through the headed end of the blank, the end of the drill being shown;

Figure 6 is an axial cross-sectional view of the finished fastener including the expander pin taken on the line VIVI of Figure 7, the fastener as shown being ready for application but not yet applied;

Figure 7 is an end view of the fastener shown in Figure 6 as viewed from the shank end, or the left-hand end in Figure 6, before the fastener is applied;

Figure 8 is a view similar to Figure 6 showing the fastener applied to fasten together two pre-drilled plates;

Figure 9 is an axial View of the slotting blades;

Figure 10 is a side view of three of the slotting blades, the slotting blade nearest the eye being omitted so that the edges of the other blades may be clearly seen;

Figure 11 is a fragmentary cross-sectional view through the forming apparatus;

Figure 12 is a fragmentary cross-sectional view showing the portion of the apparatus for heading the blank; and

Figure 13 is a fragmentary cross-sectional view of a modified form of apparatus for forming a slotted and headed blank with the slots extending substantially to the head.

It should be explained at the outset that the method of making an' expandable fastener herein disclosed is largely the same as the method of copending application Serial No. 465,071, filed October 27, 1954, and Figures 1-10 of the drawings of the present application are similar to Figures 1-10 of the drawings of said copending application. In connection with the explanation of the forming apparatus which is the subject of the present application the steps of making an expandable fastener will be described since the forming apparatus is, as above explained, here embodied for purposes of explanation and illustration in forming apparatus for performing operations on a blank which is to become the body of an expandable fastener.

Referring now more particularly to the drawings, Figure 1 shows the starting blank which is designated B. It is an elongated cylindrical blank of the material of which the fastener body is to be made. The material may be metal or other material suitable for the manufacture of an expandable fastener. Fasteners of the type in question may, for example, be made of aluminum alloy, and for purposes of explanation and illustration the blank B may be considered as a solid cylindrical length of aluminum alloy such as may be produced by shearing from aluminum alloy wire. Normally the fasteners are of small size, the diameter of the cylindrical blank B beinga small fraction of an inch. However, the fasteners may be made of larger size.

While the blank B is shown as being of circular cross section it may be of other cross section, as, for example,

'4' elliptical or polygonal. The cross-sectional shape of the blank is not a limitation upon the invention and expandable fasteners of the type in'question may be made using blanks of various cross sections. However, for purposes of explanation and illustration the blank B will be deemed to be a right circular cylinder.

The blank B may be sheared from a length of wire 31 (Figure 11) which is fed, for example from a reel, into a guide 32 in the forming apparatus, the guide 32 being carried within a holder 33 which also carries a sleeve 34 coaxial with the guide 32 as shown. The internal diameter of the sleeve 34 is such as to snugly receive the wire 31.

A shearing member 35 is mounted in the forming apparatus to move in the right and left direction viewing Figure 11. The shearing member 35 carries a sleeve 36 of the same transverse size and shape as the sleeve 34, the sleeves 34 and 36 abutting end to end as shown in Figure 11 when the shearing member 35 is disposed with the sleeves coaxial, whereby the sleeves 34 and 36 constitute cooperating shearing elements. The shearing member 35 carries a downward extension 37 in which is positioned a stop pin 38. The stop pin 38 is coaxial with the sleeve 36. The upper end of the stop pin 38 serves to stop the leading end of the wire 31 when it is fed forwardly (downwardly viewing Figure ll) with the sleeves 34 and 36 in coaxial relationship as shown in Figure 11.

In operation the shearing member 35 is disposed in the position shown in Figure 11 with the sleeve 36 coaxial with the sleeve 34 and the stop pin 38 in operative position as shown, whereupon the wire 31 is fed forwardly as above mentioned by any suitable feeding mechanism until its leading end strikes the stop pin 38. When the forward movement of the wire 31 is stopped by the stop pin 38 a measured length of the wire is disposed below the plane of contact between the upper surface of the sleeve or shearing element 36 and the lower surface of the sleeve or shearing element 34 viewing Figure 11. Thereupon the shearing member 35 is moved at right angles to the axis of the sleeve 36 and the blank B is sheared off of the length of wire 31. The blank )3 is then advanced for the succeeding operation as will presently be described, the wire 31 remaining stationary until the shearing member 35 with the sleeve 36 empty returns to the position shown in Figure 11 when the cycle of operations just described for shearing the blank B from the length of wire 31 is repeated.

The next step after shearing the blank B from the length of wire 31 is to provide the blank with a zone at one end tapering to reduced transverse dimension toward that end. Figure 2 shows the blank provided with the tapered zone, the blank of Figure 2 being des ignated B and the tapered zone at an end of the blank being designated T. The purpose of providing the tapered zone T is to enable the blank to be die-slotted without loss of material and so that as a consequence of the die-slotting the transverse dimension of the zone T will be increased to substantially the transverse dimension of the blank beyond that zone. The tapered zone T may be formed in a die 39 shown in Figure 11 having a die cavity illustrated as having a portion 40 of relatively small circular cross-section, a portion 42 of relatively great circular cross section and an intermediate portion 41 of tapering circular cross section tapering from the cross section of the portion 40 at its smaller end to the cross section of the portion 42 at its larger end. When the blank B is forced into the die cavity of the die 39 its leading end (the upper end viewing Figure 11) is die-formed to provide the tapered zone T at the end thereof.

The shear member 35 with the blank B therein is moved into position with the sleeve 36 coaxial with the die 39 whereupon the pin 38 is actuated to move upwardly viewing Figure 11 to eject the blank B from the shearing member 35 into the die 39. The blank B is thus ejected into the lower portion of the die 39 and into the portion 42 of relatively great cross section of the die cavity of the die 39. When the blank B is thus ejected into the die 39 the lower end of the blank is only slightly above or substantially in transverse alignment with the lower extremity of the die. The stop pin 38 thus serves as an ejector. After ejection of the blank B into the die 39 the shearing member 35 and the stop pin 38 return to the position shown in Figure 11 A pin 43 serving similarly to the pin 38 as both a stop pin and an ejector projects downwardly into the upper end of the die 39 as shown in Figure 11. In the position in which it is shown in Figure 11 the pin 43 has its extremity substantially at the junction between the portions 40 and 41 of the cavity of the die 39. The pin 43 is maintained in that position and a plunger 44 is introduced through the bottom of the die 39 and forces the blank up into the die, deforming the blank by pro viding the tapered zone T thereon as shown in Figure 11. The tapered zone T is formed by forcing the forward or upper end of the blank against the tapered portion 41 of the cavity of the die 39, the forward movement of the blank being limited by the end of the pin 43. With that operation the blank B is transformed into the blank B.

After formation of the blank B the plunger 44 is withdrawn and a transfer device, not shown in the drawings but well known to those skilled in the art, is moved into coaxial relationship with the die 39. The pin 43 is moved downwardly to eject the blank B into the transfer device, whereupon the transfer device is moved into coaxial relationship with the die cavity 9 of a die 7. In the die 7 the blank B is die-slotted and becomes the blank B" shown in Figure 3. In transformation of the blank from the form B to the form B the tapered zone T is slotted and increased in transverse dimension to substantially the transverse dimension of the blank beyond that zone. The slots are designated by reference numeral 2. They are formed within the die cavity 9 by the slotting blades shown in Figures 9 and 10 which, together with the die 7, are mounted in a die structure 47 shown in Figure 11.

As shown in Figures 9 and 10 there are four slotting blades each of which is designated 3. There may be more or less than four blades. Each of the blades has a generally planar body 4 and a tapered or sharpened forming edge having an inclined portion 5 and a portion 6 adapted to extend axially of the blank and disposed at an angle to the portion 5. At its extremity remote from the portion 6 the portion 5 of the forming edge of each slotting blade 3 has a part of limited length designated 5a which is inclined to the portion 6 at an angle somewhat greater than the angle of inclination of the portion 5. The blades are assembled with the portions 6 of their forming edges together in line contact as shown in Figure 9 and, in the structure illustrated by Way of example, with opposed blades coplanar, the blades of the respective pairs of opposed blades being at right angles as shown in Figure 9.

Each of the slotting blades 3 has beyond the edge portion 6 thereof and above that edge portion viewing Figure 1G and edge portion 60 having in cross section as evidenced by Figure 9 a point in line with that of the edge portion 6 and having opposed faces 6b disposed at an angle of 90 to each other so that when the four blades 3 are assembled as shown in Figure 9 the surface portions 6b of the blades cooperate with one another to brace the blades against one another.

As above stated the blades 3 are mounted in the die 7 having the central cylindrical die cavity 9. The die 7 is provided with radial slots 8. There are four such slots at 90 intervals, the slots 8 respectively receiving the four slotting blades 3. The die 7 maintains the blades 3 in proper cooperative relationship and provides the 6 cylindrical die cavity 9 into which the blank B is to be projected with the tapered zone T leading.

Entering the upper portion of the die 7 viewing Figure 11 is a cylindrical ejecting pin 11, the end of the ejecting pin 11 being provided with four slots 12 to re ceive the respective slotting blades 3 when ejecting the slotted blank from the die 7.

With the four slotting blades 3 arranged in. the die 7 as above described and with the pin 11 in the position shown in Figure 11 with its end surface in the same transverse plane as the ends of the faces 6b of the blades 3 the blank B carried in the above-mentioned transfer device is brought into alignment with the die cavity 9 and is forced into the die cavity 9 by a pin 46 in a sleeve 45. The sleeve 45 is spring loaded and moves to and remains in the position shown in Figure 11 butting against the die 7 and assists in guiding the blank as the pin 46 forces the blank into the die cavity 9. The tapered zone T of the blank B enters the die cavity first. The diameter of the cylindrical die cavity 9 is such as to receive the portion of the blank B other than the zone T so that after the zone T has passed through the mouth of the die cavity the blank is guided by the cylindrical wall of the die cavity to move axially thereinto. Adjacent what may be termed the bottom of the die cavity (the upper portion thereof viewing Figure 11) the operative edge portions 6 of the slotting blades 3 project inwardly and are in contact with one another along the axis of the die. As the blank B is projected into the die cavity the zone T thereof is slotted and simultaneously expanded to increase its transverse dimension to substantially the transverse dimension of the remainder of the blank. This is done Without loss of material, the space within the slots being equal in volume to the difference in volume between the portion of the blank B at the zone T and a solid of the same length as the zone T having the same diameter as the portion of the blank B other than the zone T.

The blank as slotted by the slotting blades 3 in the die cavity 9 is designated B and is shown in Figure 3. The slotting blades form the slots 2 so that each of the slots is relatively wide at the transverse outer surface of the blank and relatively narrow inwardly of such surface. Opposed slots collectively extend completely through the blank at the extremity of the blank Where the portions: 6 of the slotting blades come together. At the point 13 indicated in Figure 10 where the portions 5 of the slotting blades meet the portions 6 the blades begin to recede outwardly and consequently the slots formed by the portions 5 and 5a of the blades are of gradually decreasing depth radially of the blank. This is clearly shown in Figure 3. In that figure each slot 2 is clearly shown as having a depth equal to the radius of the blank at the slotted end of the blank designated a, that depth of slot being maintained to the point b whereafter each slot decreases uniformly in depth to the point c, whereafter each slot decreases uniformly in depth to the point d, the rate of decrease in depth from c to a being greater than the rate of decrease in depth from b to c.

The die slotting has numerous advantages over the formation of slots by sawing. Not only is there a saving in material, for sawdust is entirely eliminated, but by reason of the fact that the slots are die-formed instead of being sawed they can be made of varying width as shown in Figure 7. Actually the slots are formed with pointed inner extremities which has the advantage of increased holding efiiciency of the fastener when it is applied. Also, the die-slotting provides in a very simple manner for forming of the slots of varying depth as above explained. Still further, the die-forming of the slots imparts to the slotted end of the fastener the added strength of cold work which increases the holding efiiciency of the fastener.

After formation of the blank B as above explained the sleeve 45 with the pin 46 therein is withdrawn from the blank B", leaving that blank in the position shown in Figure 11 partially within and partially without the die 7. The pin 11 remains in the position in which it is shown in Figure 11. A punch 14 shown in Figure 12 is then driven axially against the blank B" to head the blank. This is done while the blank is in the die 7. The punch 14 has therein a cavity 14a for forming the head on the blank, the head being designated H. The headed blank is designated B' and is shown in Figure 4. The heading punch 14 in addition to forming on the blank the head H also has a projection 14b which forms in the head H a cavity 15 with a tapered bottom 16 as clearly shown in Figure 4. In the form shown the cavity 15 above the tapered bottom 16 is substantially cylindrical. The tapered bottom 16 of the cavity 15 provides a centering point for the drill in the performance of the drilling operation presently to be described in forming the expander pin receiving opening 19.

After the blank is headed by the punch 14 the blank B is ejected from the die cavity 9 by the ejecting pin 11 which is operated to move downwardly viewing Figure 12, pushing the blank ahead of it, the slots 12 in the ejecting pin receiving the blades 3 as the ejecting pin moves forward.

While the slotting and heading of the blank have been shown as being performed in successive steps it might be possible in some cases to simultaneously slot and head the blank by using only the punch 14 in connection with the die 7. The punch would drive the blank into the die to slot it until the blank would be stopped by the pin 11, whereafter the blank would be headed as shown in Figure 12. For certain materials the two-step process is preferable while for other materials the simultaneous slotting and heading of the blank might be preferred.

The slotted and headed blank is next drilled as shown in Figure to provide an expander pin receiving opening. The drill used is designated 17 and has a tapered end 18 terminating in a curved nose 18a. The diameter of the drill 17 is less than the diameter of the cavity as clearly shown in Figure 5. The drill 17 drills in the blank an expander pin receiving opening 19 extending through the head H and into the shank, the shank being designated S in Figure 5. The taper of the end 18 of the drill 17 is the same as the taper of the bottom of the slots from b to c as indicated in Figure 3. The drilling is continued until the expander pin receiving opening 19 intersects the slots 2 as shown in Figure 5. As soon as the expander pin receiving opening 19 has intersected the slots 2 the drilling is stopped and the drill is removed. Because of the curved or blunt nose 18a of the drill there is left an integral portion or web 20 of the material of the fastener which connects the portions of the fastener intermediate the slots 2. Those portions may be designated prongs and are marked P in Figures 6, 7 and 8. The provision of the web 20 prevents the prongs P from spreading at any time during manufacture or heat treatment of the fastener and obviates the necessity of an additional operation to restore the prongs to their desired relative positions as shown in Figures 6 and 7.

Figure 6 shows the completed fastener ready for application. The body of the fastener comprising the shank S and the head H slotted and drilled as above described receives an expander pin E. The expander pin E has an enlarged head 21 receivable within the cavity 15 at the mouth of the expander pin receiving opening 19. The enlarged head 21 of the expander pin E is, as shown in Figure 6, relatively narrow at its extremity and relatively wide a short distance removed from its extremity. The edge of the extremity of the head is designated 22 and the head widens from the edge 22 to the zone designated 23. The annular surface from the edge 22 to the zone 23 is inclined toward the axis of the pin E toward the right viewing Figure 6. When the pin is driven home the zone 23 lies within the cavity 15 as shown in Figure 8. This enables the material of the head H at the outer periphery of the cavity 15 to bepeened over against the inclined portion of the pin between the edge 22 and the zone 23 to lock the pin in place. The peened over portion of the head is clearly shown at 24 in Figure 8 positively locking in place the expander pin E.

The expander pin E may be provided with generally axially extending spaced apart radial projections 25 adapted when the expander pin E is introduced into the body of the fastener to insure tight frictional engagement between the expander pin and the body. In this way the initial assembly of the expander pin and body as shown in Figure 6 is maintained. The fasteners may be assembled to the extent shown in Figure 6 at the factory where they are made. Also, when the expander pin is driven home the projections 25 maintain it in tight frictional engagement with the body as shown in Figure 8. Thus the projections 25 after the expander pin has been driven home act cooperatively with the peened overmaterial at 24 to insure locking of the expander pin E in place and continued holding by the fastener of the parts which are being held together.

In Figure 8 the fastener is shown as fastening together two plates 26 and 27. The plates are assembled in faceto-face relation as shown and are pre-drilled as shown at 28, the diameter of the drilling being such as to snugly receive the shank of the fastener. The fastener with the body and expander pin assembled as shown in Figure 6 is introduced through the drilling 28 until the bottom of the head H engages the outer surface of the plate 26 as shown in Figure 8 whereupon the pin E is driven home and the material at the outer periphery of the cavity 15 is peened in as shown at 24 against the inclined edge portion of the head 21 of the expander pin to lock the expander pin in place. When the expander pin is driven home it ruptures the web 20 and spreads apart the prongs P as shown in Figure 8, thus fastening together the plates 26 and 27. v

The extremity of the pin E opposite the head 21 may be formed with a tapered zone as shown at 29. The taper of the zone 29 may be the same as the taper of the inner portion of the expander pin receiving opening as formed by the end 18 of the drill 17. When the expander pin is first introduced into the body of the fastener at the factory to form the assembly as shown in Figure 6 the expander pin may be introduced until the tapered zone 29 engages the tapered inner portion of the expander pin receiving opening as shown in Figure 6. The inward taper of the slots 2 results in maximum outward movement of the prongs for the amount of material employed in manufacture of the fastener.

It may be desired to have the slots 2 of the headed fastener body extend substantially completely to the under face of the head in contradistinction to the form of fastener shown in Figures 5, 6, 8 and 12 in which there is a substantial length of the shank which is unslotted between the under face of the head and the slotted portion of the shank. Figure 13 shows a modified form of apparatus in which the blades 3' are similar to the blades 3 previously described but extend completely to the mouth of the die cavity 9. Other elements shown in Figure 13 are designated by the same reference numerals as corre sponding elements in Figures 11 and 12, but each with a prime afllxed. The fastener body formed by the apparatus of Figure 13 has slots of the same shape as the slots of the previously described fastener body, the difference being that the slots are positioned to extend substantially completely to the under face of the head of the fastener body. Consequently, the shank of the fastener body formed by the apparatus of Figure 13 will be shorter than the shank of the previously described fastener body.

The mechanism for mounting, timing and operating the various tools for acting on the blank as above described will be clearly understood by those skilled in the art and hence is not shown in detail. While examples of machines which may be employed have been cited above other machines available in the market may also be used,

any slight modification of the machine structure necessary to perform the operations above described in the desired sequence being within the skill of the machine designer. The advantages of the invention derive from the special tools and their action on the blank and not from the specific mechanisms employed ot mount, time and operate the tools.

The improved expandable fastener is claimed in copending application Serial No. 629,320, filed December 19, 1956, which is a continuation of copending but now abandoned application Serial No. 452,500, filed August 27, 1954.

While certain present preferred embodiments of the invention have been illustrated and described it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied Within the scope of the following claims.

What is claimed is:

1. Forming apparatus comprising a die cavity open at one end to receive a blank, slotting blades projecting laterally into the die cavity and having cutting edges inclined to the axis of the die cavity and extending inwardly of the die cavity away from said open end of the die cavity and meeting substantially at the axis of the die cavity at a point spaced from the bottom of the die cavity so as to form in the end of a blank forced into the die cavity through the open end thereof slots of progressively increasing depth away from said open end of the die cavity and meeting each other substantially at the axis of the die cavity and means mounted for movement to force a blank inwardly of the die cavity through the open end thereof and onto the slotting blades to slot the blank.

2. Forming apparatus comprising a die cavity open at one end to receive a blank, slotting blades projecting laterally into the die cavity and adapted to slot a blank forced into the die cavity through the open end thereof, the slotting blades each having a cutting edge in the die cavity inclined to the die cavity wall in a direction away from the open end of the die cavity generally toward the central portion of the die cavity, said edge having two immediately contiguous portions both inclined to the die cavity wall, one relatively adjacent the die cavity wall and also relatively adjacent the open end of the die cavity and the other relatively remote from the die cavity wall and also relatively remote from the open end of the die cavity, the first mentioned portion of said edge being inclined to the die cavity wall at an angle greater than the angle at which the second mentioned portion of said edge is inclined to the die cavity wall, the cutting edges meeting substantially at the axis of the die cavity at a point spaced from the bottom of the die cavity, and means mounted for movement to force a blank inwardly of the die cavity through the open end thereof and onto the slotting blades to slot the blank.

3. Forming apparatus comprising a die cavity open at one end to receive a blank, slotting blades projecting laterally into the die cavity and having cutting edges inclined to the axis of the die cavity and extending inwardly of the die cavity away from said open end of the die cavity and meeting substantially at the axis of the die cavity at a point spaced from the bottom of the die cavity so as to form in the end of a blank forced into the die cavity through the open end thereof slots of progressively increasing depth away from said open end of the die cavity and meeting each other substantially at the axis of the die cavity, each of the slotting blades having an edge in the die cavity inclined to the die cavity wall in 'a direction away from the open end of the die cavity generally toward' the axis of the die cavity, said edge having two immediately contiguous portions both inclined to the die cavity wall, one relatively adjacent the die cavity wall and also relatively adjacent the open end of the die cavity and the other relatively remote from the die cavity wall and also relatively remote from the open end of the die cavity, the first mentioned portion of each of said edges being inclined to the die cavity wall at an angle greater than the angle at which the second mentioned portion thereof is inclined to the die cavity wall, and means mounted for movement to force a blank inwardly of the die cavity through the open end thereof and onto the slotting blades to slot the blank.

References Cited in the file of this patent UNITED STATES PATENTS 1,388,566 Hinchclifi Aug. 23, 1921 1,730,954 St. Pierre Oct. 8, 1929 2,114,420 Freter Apr. 19, 1938 2,251,201 Purtell July 29, 1941 2,396,995 Friedman Mar. 19, 1946 2,799,027 Hatebur July 16, 1957

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