Method Of Joining Sheets Of Rigid Deformable Material

Abstract

A method of securing together, as by staking, superimposed strips or sheets of rigid yet deformable material, such as mild steel, having generally planar surfaces. The method includes positioning the superimposed sheets between a driven punch and the working face of a stationary anvil upon sheet-supporting members resiliently urged toward each other mounted laterally of said anvil and providing with said punch and anvil a forming space extending directly as well as laterally above, and laterally below, the anvil working face. By a single stroke of said punch, the punch causes a flow of the material of the strips into the forming space to form therein telescoped hollow bosses, or rivets, with a lower wall portion of the inner boss expanded laterally into interlocking engagement with the corresponding laterally confined wall portion of the outer boss and with the material of the lower transverse end of the outer boss yieldably restrained by said resiliently urged members to a predetermined degree of lateral expansion yet free to flow into the portion of the forming space laterally below said anvil working face to provide downwardly extending lateral flanges. The punch is preferably formed with a pair of opposed lower downwardly converging surfaces and with an intermediate pair of parallel surfaces which together define a generally rectangular striking end, the face of which is arcuate. With this configuration, the striking end of the punch forms hollow bosses that interlock in one plane including the common axis of the bosses, but that are noninterlocking in a plane normal to the first and also including the common axis.

Description

SUMMARY OF THE INVENTION

The invention relates to a method of securing together a plurality of strips, plates, or the like of relatively thin sheets formed of a rigid yet deformable material, such as mild steel or other ductile material. In general, the sheets have planar surfaces which are first superimposed and then subjected to a staking operation in accordance with our invention to secure the sheets together so firmly that they cannot be pulled apart except by the application of very considerable separating forces. The invention also relates to the resulting laminated article with its novel means of joinder.

The securely joined laminated metal sheets made by our invention can be economically used in place of single sheets of heavier gauge for structural purposes, as for instance in reinforcing or backing up weaker structural forms of wood, plastic or the like.

The method of our invention is carried out by means of apparatus that includes a power-driven punch, a die having a stationary anvil aligned with said punch and a pair of rigid members mounted laterally of said anvil and resiliently urged toward each other with the anvil therebetween. For this purpose the rigid members and at least one resilient member are mounted on a through bolt, or the like, that freely passes through one of said rigid members, said resilient member and said anvil, but is threadingly connected with said other rigid member so that said rigid members can be resiliently urged toward the anvil to control the lateral clearance space between the anvil and the opposed ends of said rigid members. Such clearance space is part of the forming space defined between the striking face of the punch and the working face of the anvil. The upper corners of said rigid blocks are beveled to facilitate the flow of metal thereover and prevent excessive thinning or weakening of the wall of the outer boss, as will be explained as the description proceeds.

The punch is an elongated, relatively thin metal strip of rectangular cross section and is tapered toward its striking end. The end is formed with an arcuate face. Resilient stripping blocks are positioned on either side of the punch for resiliently holding the superimposed sheets to be joined against the previously mentioned rigid supporting members and for facilitating the stripping of said sheets after the staking operation.

With the superimposed sheets in place the punch is actuated to apply an impact force against the upper surface of the sheets. In a single stroke of the punch, telescoping hollow bosses, or rivets, are formed in the sheets by the flow of the material of sheets into the forming space. Simultaneously with such downward flow, there occurs a lateral enlargement of the lower wall portion of the inner boss into interlocking engagement with the corresponding wall portion of the outer boss, a thinning of the transverse end walls of both bosses, but especially of the outer boss, and a downward flow of an excess material into the clearance space around the working end of the anvil. Such flow of excess material is yieldingly controlled by the forces necessary to compress the resilient member that urges the rigid members toward the anvil. The amount of such downward flow is usually sufficient to form a pair of lateral flanges projecting downwardly from the longer sides of the lower end of the outer boss. However, the formation of such flanges is relatively unimportant from the standpoint of effecting a secure joinder of the two sheets. The important feature is the latitude of operation afforded by providing clearance space laterally and downwardly of the working face of the anvil if there is any excess material over and above that required for the interlocking of the hollow bosses, or rivets.

At the completion of the stroke, the resilient stripping members tend to expand and push the punch upwardly away from its engagement with the formed inner boss, thereby facilitating stripping of the sheets from their supporting surfaces.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric elevational view of a pair of sheets securely joined together as a laminated article in accordance with our invention;

FIG. 2 is an enlarged fragmentary sectional view taken along the line II-II of FIG. 1;

FIG. 3 is a sectional view taken along the line III-III of FIG. 2;

FIG. 4 is a broken longitudinal vertical sectional view of apparatus suitable for carrying out the method of our invention;

FIG. 5 is a sectional view taken along the line V-V of FIG. 4 with parts in section and broken away;

FIG. 6 is an enlarged fragmentary sectional view illustrating the superimposed sheets in their relation to the supporting members therefor and anvil of the die, at an initial stage in the stroke of the punch during the carrying out of our method;

FIG. 7 is a view similar to that of FIG. 6 at an advanced position of the punch; and

FIG. 8 is a view similar to that of FIG. 6 at the final position of the punch in its working stroke.

DETAILED DESCRIPTION OF THE DRAWINGS

As shown in FIG. 1, the reference numeral 10 indicates a finished article formed of a pair of sheets 11 and 12 joined together by a plurality of spaced, interlocked, telescoped hollow boss, or rivet assemblies 13 and 13a formed integrally from the material of the respective sheets 11 and 12. As illustrated, the sheets 11 and 12 are relatively thin, elongated plates of rectangular shape with substantially planar extended surfaces. The inner confronting surfaces are in full mating contact at the plane of joinder 14 of the laminated sheets.

By way of example only, the sheets 11 and 12 may be formed from mild steel strips or plates that have been galvanized to provide corrosion-resistant surfaces. In some instances the sheet 11 can be a low carbon steel sheet of about 0.09 percent carbon maximum, and in the neighborhood of 0.105 inch in thickness; and the sheet 12 can be a similar mild steel sheet of about 0.083 inch in thickness. These are merely for illustrative purposes, since other relatively rigid, ductile or deformable metal alloys or other materials, and various thicknesses of sheets can be used. The number and spacing of the hollow bosses, or rivets, 13 will depend upon the length of the strips to be joined and other factors including the strength of securement of the strips against separation that is required.

As illustrated in FIGS. 2 and 3, each hollow boss assembly 13 presents a different shape depending upon the plane of the section that is taken. In FIG. 2 the sectional plane is along the longer centerline of the hollow boss assembly, while in FIG. 3 the sectional plane is at right angles, namely, along the shorter centerline of the assembly. Both sectional planes pass through the common axis, A-A, of the boss assembly. The boss assembly does not provide positive interlocking of the material of the sheets 11 and 12 in the plane of FIG. 2 but does provide positive interlocking in the plane of FIG. 3. This is for a reason that will be explained as the description proceeds.

As shown in FIG. 2, the upper sheet 11 provides an inner hollow boss 15, the sidewalls 15a of which have generally planar downwardly converging inner surfaces 16 and 16a smoothly joined to a transverse inner surface 17 of a bottom wall 18. The sidewalls 15a are of gradually diminishing thickness toward the bottom wall 18 as a result of a thinning of sheet 11 during the forming of the hollow boss 15.

In the same forming process, the lower sheet 12 is shaped into an outer hollow boss 19 into which the inner boss 15 telescopes with full mating surface contact along the now deformed initial plane of joinder 14. Like the sidewalls of the inner hollow boss 15, the sidewalls 19a of the outer boss 19 thin down toward the thinned bottom wall 20 of said outer boss. Both bottom walls 18 and 20 have substantially planar surfaces, but the lower surface of the bottom wall 20 has lateral flanges 21 projecting downwardly therefrom for a relatively small distance. The reason for this flange will become apparent later on in the description of the forming operation.

As shown in FIG. 3, the inner surfaces 22 of the sidewalls 15a of the inner boss 15 are substantially normal to the planar strip surfaces, and the inner surface 23 of the transverse bottom wall 18 is segmental circular, or at least arcuate in profile. Toward the bottom wall 18, the sidewalls 15a are first thinned, as at 24, and then thickened, as at 25, to provide a lateral interlock between the inner boss 15 and the outer boss 19, resisting separation of the telescoped bosses by forces acting in a plane including the axis A-A. In effect, the inner and outer bosses assume the form of telescoped headed hollow rivets having interengaging peripheral surfaces that are so interlocked as to resist axially applied separating forces. Sufficient wall thickness is maintained even at the thinned wall portion 24 to insure the desired degree of securement of the laminated strips 11 and 12 against separation.

The apparatus illustrated more or less diagrammatically in FIGS. 4 and 5 includes a die assembly 30 mounted on a bedplate 31. The die assembly comprises a stationary anvil 32 having flanged lower end 33 secured in said bedplate 31, and an upstanding web portion 34. A pair of die members 35 and 36, comprising blocks of metal on opposite sides of the anvil web portion 34, is mounted for sliding movement on the surface 37 provided by the upper surfaces of the bedplate and anvil end 33. A block 38 of resilient material, such as polyurethane is mounted also on the surface 37 to abut against one of the die blocks, such as block 35. An elongated headed bolt 39 extends through smooth bores in a washer 40, in the blocks 38 and 35 of the anvil web portion 34, and is threaded into an internally threaded bore 41 in the block 36. Application of a turning force to the head 42 of the bolt serves to adjust the amount of compression of the resilient material of block 38 and correspondingly the amount of resilient pressure tending to urge the blocks 35 and 36 toward each other and toward the intervening web 34 of the anvil 32. When the die assembly is not in use, the confronting end surfaces 43 and 44 of the die blocks 35 and 36 are resiliently held in abutment against the corresponding surfaces of the web 34, but free to move away from said web 34 against the resilient action of the block 38 during the boss-forming operation.

An upper reciprocating punch assembly, designated generally by the reference numeral 45, is mounted for vertical reciprocating movement on posts 46, of which only one is shown. Suitable driving mechanism (not shown) serves for the operation of the punch assembly in a manner later to be described. The punch assembly 45 includes a crosshead 47 having bores 48 for slidably receiving the upper ends of the posts 46, and a punch proper 49 dependent from and secured to the backup pad 50. The backup pad 50 is, in turn, secured in or made a part of the crosshead 47. A heavy plate or rigid block 51 is mounted about the upper portion of said punch 49 up against the backup pad 50, and a plastic block 52 of suitable material, such as polyurethane, is freely mounted about the lower portion of the anvil 32. The resilient block 52 serves as a stripper for facilitating the removal of the laminated strips from the die assembly after the forming operation.

In the form of punch shown in FIGS. 4 and 5, the upper portion 53 of the punch 49 is rectangular in cross section, and the lower portion 54 is formed with a pair of opposed downwardly converging plane surfaces 55 and intermediate parallel plane surfaces 56 (FIGS. 6--8). The striking end 57 of the punch is generally planar in profile, as viewed in section as in FIG. 4, and is arcuate as viewed in section in FIG. 5, (and also FIGS. 6--8).

The resilient block 52 is suitably formed of polyurethane and is provided with a vertical bore 58 so shaped and dimensioned as to freely receive the lower end 54 of the punch 49 with a conforming clearance space 59 therebetween. The normal height of the block 52 in its free state is such that the block is placed under compression between the rigid block 51 and the upper surfaces of the superimposed sheets 11 and 12, when the punch 49 is at a lower position of its stroke (FIGS. 4 and 5), acting thereby to resiliently hold the superimposed sheets in position supported by the upper surfaces 60 of the die blocks 35 and 36. When the punch assembly is again raised to the upper limit of its stroke, the resilient block 52 expands and acts as a stripper aiding in the removal of the laminated strips from the lower die assembly. The urethane block 52 has suitably a 95A durometer reading, as does also the resilient block 38.

In the operation of the punch (FIGS. 6,7 and 8), the lower striking face 57 of the punch 49 initially deforms the affected portions of the sheets 11 and 12 into a downwardly convex profile, as at 61 (FIG. 6), projecting slightly into the forming space S defined by spaced opposed surfaces 62 and 63 of the die blocks 36 and 35 and partially by the working face 64 of the anvil web 34. The upper corners of the die blocks 36 and 35 are beveled, as at 65 and 66, so as slope downwardly toward the working face 64. A suitable angle of bevel is about 20.degree.. With this amount of bevel, a suitable heading action takes place in the subsequent forming of the telescoped hollow boss assembly 15, resulting in a lateral radially inward bulging of the metal of the lower sheet 12 to cause a thinning of the wall of the upper sheet 11 at 24 (FIG. 3), as already described.

The forming space S (FIG. 6) not only includes the space above and laterally above the working face 64 of the anvil but also the space 67 laterally of the anvil web 34 below said working face 64. This space 67 is provided by the initially slight spacing between the vertical end faces of the die blocks 35 and 36 and the corresponding vertical faces of the anvil web 34. Due to the resiliency of the block 38, this lateral space 67 is susceptible of enlargement during the subsequent stages of the forming operation, as best shown in FIG. 8 and explained in connection therewith.

FIG. 7 represents a further downward position of the punch 49 as compared with the position of the punch shown in FIG. 6. At this intermediate position of the punch, the forming space S above the working face 64 of the anvil has been contracted axially of the punch and anvil but still exists since the lower surface of the transverse end of the deformed portion of the lower sheet 12 has not yet come into contact with the anvil working face 64. In the plane of the section shown in FIG. 7, which is a plane corresponding to that of the the section shown in FIG. 3, no interlocking of the telescoped portions of the partially formed boss assembly 15 has as yet taken place, nor has there occurred any widening of the lateral downwardly extending portions 67 of the clearance space S. The deformed portions of the sheets 11 and 12 have simply been further displaced downwardly by the punch 49 to form a partially completed telescoped hollow boss assembly formed about the common axis of the punch and anvil.

FIG. 8 shows the punch 49 at the lowermost position of its stroke in positive cooperation with the anvil working face 64. The boss assembly is now complete and in the state of the boss assembly 13 illustrated in FIG. 3. Due to the downward and lateral forces exerted by the striking face 57 of the punch and the counter force exerted by the stationary anvil 34, a necking-in and a heading action have simultaneously occurred to cause the thinning at 24 and the thickening at 25 (FIG. 3) that have previously been described. Also, some of the metal of the deformed portion of the lower sheet 12 has been forced downwardly into the lateral spaces 67, causing a widening of these spaces and the extruding of metal in their upper open ends to form lateral downwardly projecting flanges such as the flanges 21 (FIG. 3), already described. In addition, FIG. 8 shows the axial thinning of the transverse end wall 20, due partly to the flow of metal therefrom into the formation of the peripheral flange 21. The formation of the flanges 21 along the sides of the end wall is due to the greater length than width of the punch 49. The flanges are not functionally necessary to the carrying out of our method, but as previously stated they allow a certain amount of latitude as to the selection of sheets of predetermined composition, characteristics and dimensions and as to the design of the apparatus and its manner of operation.

The showings of FIGS. 6 and 7, and 8 illustrate the stages of operation of the apparatus during a single, continuous downward thrust of the punch for the full extent of its length of travel. The punch is thereafter raised to its uppermost position, ready for another downward thrust to carry out a further staking operation. It will be obvious to one skilled in the art that a plurality of staking operations can be carried out simultaneously to produce in the same set of superimposed sheets a plurality of telescoped, interlocking hollow bosses or rivets.

Our invention thus provides a method and apparatus whereby and wherein two or more sheets of rigid yet ductile material can be securely joined together as a laminated unit by a single stroke of a plunger relative to a fixed or stationary anvil. As a result of said stroke, telescoped interlocked hollow boss or rivet assemblies are formed from the material of superimposed sheets or strips in a headed strongly interlocked relationship that resists separation of the laminates of the resulting unitary laminated article.

One use of our invention is in securing together two parts of an overhead door track for garages and the like. This has previously been accomplished by riveting, but our method is believed more positive than welding and less troublesome than riveting or welding and to be more economical than either. The two parts of a track so secured are called the cover and the tread in ordinary parlance.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

Claims

We claim:

1. In a method of securing together by staking at least two generally planar, rigid strips of deformable material, including superimposing said strips on a die having a fixed anvil, positioning strip-supporting members on either side of said anvil resiliently urged toward said anvil to provide a forming space above and laterally below the working face of said anvil, and aligning a punch with and above said anvil for movement theretoward with said strips therebetween, the improvement which comprises

in a single stroke of said punch forcing material of said strips toward said anvil to cause flow of some of the material of the strip nearer said die into said space laterally of and below the working face of said anvil to form a hollow boss, and to cause flow of material of the strip further from said anvil into the material of said strip nearer said anvil to displace the same and laterally interlock therewith and thereby secure said strips together.

2. The method as defined by claim 1, wherein

said strips are formed of mild steel and are of substantially uniform thickness in the neighborhood of 0.1 inch.

3. The method as defined by claim 2, wherein

the forming space laterally of said anvil working face is defined by surfaces sloping toward each other and in the direction of said working face.

4. The method as defined by claim 3, wherein

the flow of material in said space laterally of and below the working face of said anvil forms lateral downwardly presented flanges at the lower end of said hollow boss.

5. The method as defined by claim 4, wherein

the lower portion of said punch is provided with a pair of opposed downwardly sloping faces converging toward the striking end thereof and with a pair of parallel plane faces terminating at said striking end.

6. The method as defined by claim 5, wherein

the strip-supporting members are resiliently urged toward said anvil to resist the lateral enlargement of said forming space during flow of material thereinto while permitting downward flow of material laterally of said anvil working face.

7. The method as defined by claim 6, wherein

the striking end of said punch is formed with an arcuate working face and is of generally rectangular configuration in cross section.

8. A method of interconnecting two sheets of deformable material, which comprises

in a single stroke of a punch relative to the anvil of a die member including laterally opposed members supporting said sheets and resiliently urged toward each other to provide with said anvil a resiliently confined forming space above, laterally of and below the working face of said anvil,

forming two hollow bosses with transverse end walls in the two sheets respectively with the inner hollow boss dimensioned to telescope into the outer hollow boss, telescoping the two hollow bosses together with the two confronting transverse end walls of said bosses in coextensive surface engagement, subjecting said end walls to axial compression against said anvil to cause a downward flow of material into said forming space, and

resiliently resisting lateral flow of said downwardly flowed material to effect an interlock of the material of said telescoped bosses laterally of and above said anvil working face and to extrude any excess of said downwardly flowed material into downwardly projecting lateral flanges on the end wall of said outer boss.

9. A method as defined by claim 8, wherein

said laterally opposed members are provided with beveled surfaces sloping downwardly toward said anvil working face to facilitate flow of material into said forming space and limit the thinning of the lateral wall of said outer boss.

10. The method as defined by claim 9, wherein

the strips are formed of mild steel and are of substantially uniform thickness in the neighborhood of 0.1 inch.

11. The method as defined by claim 10, wherein

said sheet-supporting members are urged toward each other sufficiently to resist and control the lateral flow of said material to provide a thinned but strong wall on the outer boss and a secure interlock of the material of said two bosses.

12. The method as defined by claim 11, wherein

the lower portion of said punch is provided with a pair of opposed downwardly sloping faces converging toward the striking end thereof and with a pair of parallel plane faces terminating at said striking end.

13. The method as defined by claim 12, wherein

the striking end of said punch is formed with an arcuate working face and is of generally rectangular configuration in cross section.