Method Of Expanding Metal

Abstract

A method of expanding a sheet of metal to produce a solid border portion at opposite ends of an expanded mesh portion including first forming a series of slits in the metal sheet at first selected points transverse thereto and disposed inward from a leading end thereof to produce a row of slits; then, shearing the metal sheet at a second series of points transverse to the sheet, each of these points being laterally and longitudinally spaced from a corresponding one of the slits, and, simultaneously expanding the sheet at the second points of shear to form a plurality of mesh openings; and, finally, continuing this simultaneous shearing and expanding for a desired distance along the metal sheet to form an expanded portion. An article of manufacture produced according to the first step of the above method having a series of slits formed in a metal sheet inward from an end thereof and at selected points transverse thereto by vertically shearing the sheet at these points, the sheet being separated into different planes on opposite sides of the slits by the force of the shear.

Description

BACKGROUND OF THE INVENTION

This invention relates to a method of expanding metal, and, in particular, to a method which provides a solid border portion at opposite ends of an expanded portion of a sheet of metal.

Methods of making expanded metal and apparatus for expanding metal have been known for many years. The conventional process used for expanding sheet metal involves shearing the metal transverse to the sheet with a die which, in the same step bends the metal at the point of shear in an oblique direction to the plane of the unsheared metal to expand the mesh openings. The die or the sheet is then moved laterally and longitudinally of the first shear and the shearing action and expanding repeated. The above method is generally disclosed in U.S. Pat. No. 1,448,109 to J. H. Dean et al., and U.S. Pat. No. 1,561,272 to H. C. Nagel.

In expanding metal, it is often desirable to have a solid or imperforate border portion at the leading and terminating ends of the expanded portion. Such a solid border is particularly useful in installations such as lockers to attach the expanded metal or vent portion to the locker assembly. A border will provide additional strength and facilitate assembly in such installations. The methods taught by Dean and Nagel, and in general use today, however, have not been able to provide expanded metal having the desired border portions plus strength and quality characteristics satisfactory in the manufacture of lockers and various other items. This is because these methods of expanding metal, in starting the expanded portion, usually leave a number of mesh openings of odd sizes and tend to overstretch and at least partially sever the strands forming the first row of mesh openings adjacent the border, thereby weakening the junction of the expanded and border portions and presenting a rough, unfinished appearance.

The problem then, in producing what will be called border mesh having acceptable strength and appearance characteristics, is in starting the expanded portion. An attempt to solve this problem has been made by W. B. Agler, in U.S. Pat. No. 3,165,810. Agler teaches a process of forming or punching a row of elongated openings in a metal sheet, then, slitting the sheet along one side of each opening to form a strand, and drawing each strand into the opening to form a half diamond shape. The slitting and drawing, is then continued to form the remaining openings of the expanded portion. Agler, however, requires the formation of a series of definite openings, each wide enough to permit an adjacent strand to be drawn half-way into it, which must be punched completely through the sheet. Each adjacent strand must be then drawn or pushed by a conventional die in the shearing and expanding process into the opening. This process involves a waste of material, since a portion of the sheet is punched out to form each opening, and also results in the junction between the expanded portion and the leading border being of a different appearing design than the junction between the expanded portion and the terminating border.

DESCRIPTION OF THE INVENTION

This invention involves a novel process and article of manufacture to produce expanded metal having border portions at opposite ends of an expanded portion, in which a series of uniform mesh openings are formed adjacent the opposite border portions, without any tearing or weakening of the strands and bonds defining the openings. This invention overcomes the problems of conventional methods of expanding metal to form borders, and also provides uniform appearing mesh openings adjacent each border portion without waste of material. The steps of the invention include:

forming narrow slits or lances in a metal sheet at a first series of selected points transverse to the sheet and disposed inward from a leading end thereof, to produce a row of slits in the sheet;

shearing the metal sheet at a second series of points transverse to the sheet, each of the second points being laterally and longitudinally spaced from a corresponding one of the initial slits, and simultaneously expanding the sheet at these second points of shear to form a plurality of mesh openings in the sheet; and

continuing the simultaneous shearing and expanding of the metal sheet for a desired distance along the sheet to form an expanded portion.

The narrow slits are formed in a first operation by vertically shearing the metal sheet at each of the first selected points while the sheet is supported only under its leading imperforate border portion. The shearing force will cause the unsupported portion of the sheet to be separated out of the plane of the solid border portion. When the slit or lanced sheet is moved to a conventional shearing and expanding apparatus, the portion to be expanded is placed flat on a supporting bed or table with the slits slightly overhanging the table, so that when the shearing and expanding operation is performed the shearing die will strike the metal sheet at a series of points laterally spaced about one-half the distance between consecutive first points locating the previously made slits, and longitudinally spaced approximately the width of a single strand of a mesh opening. As the die shears the metal and continues downward, it expands the metal at the points of shear, causing the slits and shear strands to be pushed apart at an angle oblique to the plane of the unexpanded metal sheet to form two rows of mesh openings. The shearing and expanding dies or the metal sheet are then shifted laterally and longitudinally of the second row of openings and the process is repeated and continued for the length of the expanded portion desired.

The forming of narrow slits in a first operation, prior to shearing and expanding, causes the mesh openings later formed adjacent the leading border portion of the metal sheet to be of uniform dimension and also eliminates tearing of the mesh strands at their points of connection to the solid border portion such as occurs using conventional expanded metal processes. This novel process also does not waste material by punching out openings prior to expansion and provides half-diamond shaped openings adjacent both the leading and terminating border portions which are uniform in appearance.

The intermediate article of manufacture produced by the first step of forming narrow slits in a metal sheet, may be used in various types of shearing and expanding operations with different configurations of dies, permitting this article to be produced and used independently of a particular shearing and expanding process.

Accordingly, it is an object of this invention to provide a method of expanding metal which may be used to produce solid border portions at opposite ends of an expanded portion of a metal sheet.

It is a further object of this invention to provide a method of expanding metal which produces an expanded portion of a metal sheet at an inward distance from the leading end of the sheet without tearing or weakening any of the strands forming the openings of the expanded portion.

It is another object of this invention to provide a method of expanding metal which produces an expanded portion having mesh openings adjacent the leading and terminating border portions of the metal sheet which are uniform in dimension and appearance.

It is also an object of this invention to provide an article of manufacture useful in producing expanded metal which allows production of uniform mesh openings adjacent the leading border portion of a sheet of metal without tearing and weakening the strands forming the openings.

It is still one more object of this invention to provide an article of manufacture having a series of narrow slits therein which may be used with any conventional shearing and expanding process to form uniform mesh openings in a metal sheet adjacent a leading border portion without tearing and weakening the strands forming the openings.

These and other important objects of this invention will become apparent from the following description taken in conjunction with the drawings illustrating a preferred embodiment wherein:

FIG. 1 is a top plan view of a sheet of metal following the formation of a row of narrow slits therein according to the method of this invention.

FIG. 2 is a side cross sectional view of the sheet shown in FIG. 1 taken generally along line 2--2 therein;

FIG. 3 is a front elevational view of the sheet shown in FIG. 1, taken generally along line 3--3 therein; and illustrating the separation of the sheet into two planes following the forming of slits therein;

FIG. 4 is a top plan view of a sheet of metal which has been slit, sheared and expanded according to the method of this invention;

FIG. 5 is a front elevational view of the sheet shown in FIG. 4 taken generally along line 5--5 therein;

FIG. 6 is a side cross sectional view of the sheet shown in FIG. 4 taken generally along line 6--6 therein;

FIG. 7 is a fragmentary perspective view showing a sheet of metal formed as in FIG. 1 after a slitting operation according to this invention;

FIG. 8 is a fragmentary perspective view of a sheet of metal formed as in FIG. 7 positioned for shearing and bending according to this invention; and,

FIG. 9 is a fragmentary perspective view showing a sheet of metal formed as in FIG. 4 after the operation shown in FIG. 8.

Referring now to the drawings which show the method of making expanded metal according to this invention, FIG. 1 shows the intermediate article of manufacture which makes possible the production of an expanded portion in a sheet of metal having uniform mesh openings along imperforate border portions without tearing of the metal adjacent these borders.

In FIG. 1 a sheet of metal is shown at 10. This sheet 10 may be of any desired gauge depending upon the use to be made of the expanded metal, and the susceptibility of the sheet to shearing and bending as required in the production of such metal. The sheet 10 has a series of narrow slits or lances 14 formed at a first series of points laterally or across its width by a process which will be explained below. As shown in FIG. 2, the metal sheet 10 of FIG. 1 is separated into diverse planes, containing the leading border portion 16 and the portion of the sheet to be expanded 18, respectively, by the shearing action which produces the slits 14. The shearing and separating action also causes a series of dimples or border bonds 17, shown in FIGS. 1-3, to be formed between the slits 14 in the metal sheet 10.

Forming the slits 14 in the sheet 10 prior to a normal sharing and expanding operation accomplishes two unique objects:

it provides a starting point in the sheet 10 which allows an expanding operation to produce a sheet of expanded metal in which the mesh openings 20 adjacent the leading border portion 16 are uniform in dimension; and, most importantly, it prevents the strands 24 which are later developed as a result of these slits 14 from being partially severed, sheared or weakened in any manner near their junction with the leading border portion 16 at bond 17, as would be likely to occur if normal expanding methods were immediately used on a plane metal sheet.

FIGS. 4-6 show the metal sheet 10 of FIG. 1 after the first hit of a shearing and expanding die has been made in a second operation. As is shown in FIG. 4, the sheet 10 is sheared at a second series of points transverse to it, each of these second points being longitudinally spaced a distance 32 approximately equal to the width of a mesh strand 24 from a corresponding narrow slit 14, and laterally spaced a distance 30 equal to approximately one-half the distance between the consecutive first points at which a corresponding narrow slit 14 has been formed. As shown in FIGS. 5 and 6, the shearing and expanding operation forms a series of half-diamond shape mesh openings 20 alternating with the border bonds 17 adjacent the inward edge of the leading solid border portion 16 of the sheet 10. The operation also forms a series of temporary half-diamond mesh openings 22 and mesh bonds 26 which begin the normal expanded portion of the sheet. Upon the next hit of the shearing and expansion die, the mesh openings 22 will be enlarged to the normal full-diamond shape with mesh strands 24 serving to form two sides of the diamond shape.

The half-diamond mesh openings 20 are of uniform dimension along the entire leading border portion 16. Likewise, the mesh openings which will be formed along the terminating border portion (not shown) will be the same uniform half-diamond shape. It is also to be noted that the mesh strands 24, as shown in FIG. 5, are not severed or otherwise weakened by the expanding process at the point where they join the leading border portion 16 through the bonds 17. Thus, there is no loss of strength in the expanded portion encountered in the production of expanded metal with a border portion when using the article shown in FIG. 1 and the method of expanding metal according to this invention.

The method of expanding metal to produce a solid border portion 16 at opposite ends of an expanded portion of a sheet of metal 10 is shown more clearly in the perspective views of FIGS. 7-9. FIG. 7 shows the sheet 10 after the narrow slits 14 have been formed in it in a first operation. Prior to the formation of the slits 14, however, the solid metal sheet 10, which is then lying in a single plane, is positioned with respect to the slit forming die 36 on a slitting bed or table 34 which serves to support a portion of the sheet 10 during the slit forming operation. A length of the metal sheet 10 is placed flat upon this table according to the length of leading border portion 16 desired. The die is then moved downwardly to form one or more slits or lances 14 in the sheet 10 and the intervening dimples or border bonds 17 between these slits 14. Thus, the slits 14 are located inward from the leading edge 42 of metal sheet 10 a distance equalling the desired length of the leading border portion 16. The slitting action of die 36 causes the portion to be expanded 18 of the metal sheet 10 to be separated out of the plane of the leading border portion 16. It is obvious that the die 36 used to form the narrow slits 14 in the sheet 10 could be a progressive die which moves laterally across the sheet forming successive slits or could, as shown, be a series of dies mounted in a die carrying member 50 so as to form simultaneously, a row of slits 14 laterally across the sheet 10.

When the intermediate article shown in FIG. 1 has been formed, the sheet of metal 10 is placed in a conventional shearing and expanding machine 52 for formation of the expanded portion 18 of the sheet 10. This operation is shown in FIGS. 8 and 9. In FIG. 8, it is seen that the sheet 10 is reversed when placed in the shearing and expanding machine 52 so that the leading border portion 16 is unsupported during the subsequent shearing and expanding operation, while the majority of the portion of the sheet to be expanded 18 is firmly supported by a shearing and expanding bed 38. The sheet 10 is positioned on this bed 38 so that the shearing and expanding dies 40, upon descending, will shear the unexpanded portion 18 of the sheet 10 at a second series of points transverse to the sheet and laterally and longitudinally spaced from the slits 14 as described above. These second points of shear are located on a length of the portion of the sheet to be expanded 18 which extends over the edge of bed 38, and, like the leading border portion 16, is unsupported. Thus, as the dies 40 shear the sheet 10 at these points and continue their downward descent, they also push the leading border portion 16 downwardly below and oblique to the plane of the portion to be expanded 18 severing the dimples or border bonds 17 from the portion to be expanded 18 and producing a series of mesh openings 20 and 22, as shown in FIG. 9. The sheet 10 or the die 40 is then moved laterally and longitudinally of the second shear points and the shearing and downward expanding process again repeated to produce further strands 24 and bonds 26 and enlarge openings 22 to full diamond shape. This process is continued longitudinally along the sheet 10 for whatever length expanded portion 18 is desired.

It is understood that other methods of performing the second operation of shearing and expanding could be used in the production of an expanded portion according to this invention, other than that described and shown in FIGS. 8 and 9, so long as the narrow slits 14 are formed prior to shearing and expanding and are laterally and longitudinally spaced from the points of shear in the subsequent shearing and expanding.

It is obvious that a knife or series of knives may be substituted for the die 36 shown in FIG. 7, or that other shapes and forms of dies may be used to produce the narrow slits or lances 14 in the sheet of metal 10. It is also clear that variations may be made in the widths and lengths of the slits 14 or the location of the second series of shear points at which shearing and expanding is begun. Thus, while the invention has been described in relation to a preferred embodiment thereof, it will be apparent to those skilled in the art that the details of the structure and process described herein are capable of wide variation without departing from the principles of the invention.

Claims

We claim:

1. A method of expanding metal to produce a solid border portion at opposite ends of an expanded portion of a metal sheet, providing uniform mesh openings adjacent the border portions and eliminating tearing of the strands of the expanded portion adjacent the leading border portion, characterized by the steps of:

forming slits in the metal sheet at a first series of selected points transverse to the sheet and disposed inward from an end thereof to produce a row of slits therein;

shearing the metal sheet at a second series of points transverse thereto, each of said second points being laterally and longitudinally spaced from a corresponding one of said slits, and simultaneously expanding said sheet at said second points of shear to form a plurality of mesh openings in the sheet; and,

continuing the simultaneous shearing and expanding of the metal sheet for a desired longitudinal distance along the sheet to form said expanded portion of the metal sheet.

2. The method of expanding metal set forth in claim 1 wherein said slits are formed by shearing the metal sheet vertically at each of said first selected points while supporting only the solid border portion from below, thereby simultaneously separating the solid border portion of the metal sheet and the portion of the metal sheet to be expanded out of a common plane.

3. The method of expanding metal set forth in claim 1 wherein each of said slits is formed successively, transverse to the metal sheet.

4. The method of expanding metal set forth in claim 1 wherein all of said slits are formed simultaneously, transverse to the metal sheet.

5. The method of expanding metal set forth in claim 1 wherein each of said second series of points at which the metal sheet is sheared and expanded is generally located one-half the distance between consecutive ones of said first points, laterally, and a desired width of a mesh-forming strand longitudinally, of each corresponding slit on the metal sheet.

6. In a method of expanding metal to produce a solid border portion at opposite ends of an expanded portion of a metal sheet, and including the steps of shearing the portion of the sheet to be expanded at a series of shear points transverse to the sheet and simultaneously expanding the sheet at these shear points to form mesh openings, and continuing such simultaneous shearing and expanding to form further mesh openings for a desired longitudinal distance of the sheet to produce said expanded portion of the metal sheet, the improvement comprising the step of:

forming slits in the metal sheet at first selected points transverse to the sheet and disposed inward from a leading end thereof, prior to the initial shearing and expanding of the sheet at said shear points, to produce a row of slits therein, said slits being effective, upon the subsequent shearing and expanding of the sheet at said shear points, which are laterally and longitudinally spaced from said slits, to provide uniform mesh openings adjacent the border portions of the sheet and to eliminate tearing of the strands forming the mesh openings of the expanded portion of the sheet adjacent the leading border portion.

7. The improvement in the method of expanding metal set forth in claim 6 wherein said slits are formed by shearing the metal sheet vertically at each of said first selected points while supporting only the solid border portion from below thereby simultaneously separating the solid border portion of the metal sheet and the portion of the metal sheet to be expanded out of a common plane.

8. The improvement in the method of expanding metal set forth in claim 6 wherein each of said slits is formed successively, transverse to the metal sheet.

9. The improvement in the method of expanding metal set forth in claim 6 wherein all of said slits are formed simultaneously, transverse to the metal sheet.

10. The improvement in the method of expanding metal set forth in claim 6 wherein each of said shear points at which the metal sheet is sheared and expanded is generally located one-half the distance between consecutive ones of said first points laterally, and a desired width of a mesh strand longitudinally, of each corresponding slit on the metal sheet.