Method and apparatus for making expanded metal lead-acid battery grids

Claim 1

A METHOD OF MAKING LEAD-ACID STORAGE BATTERY PLATES COMPRISING: ADVANCING A NARROW LEAD STRIP, HAVING A PREDETERMINED THICKNESS, LONGITUDINALLY BETWEEN TWO ROWS OF PROGRESSIVE DIES AND CUTTERS, SAID STRIP HAVING A CENTRAL, LONGITUDINAL LUG-FORMING PORTION AND TWO EXPANDABLE GRID-FORMING PORTIONS FLANKING THE LUG-FORMING PORTION AND EXTENDING TO BOTH LONGITUDINAL EDGES OF THE STRIP AND SAID ROWS COMPRISING A PLURALITY OF DIES AND CUTTERS WHICH CONVERGE IN INCREMENTAL STEPS ON THE ENTAL LUG-FORMING PORTION OG THE STRIP PASSING BETWEEN THEM; EXPANDING THE GRID-FORMING PORTIONS ALONG THE LONGITUDINAL EDGES THEREOF BY PERIODICALLY SHEARING RECTANGULARLY WIRELIKE SEGMENTS FROM SAID EDGES INTO A PLURALITY OF TIERS OF UNDULARTORY SKELETAL ELEMENTS EXTENDING AT ACUTE ANGLES TO THE PLANE OF SAID LUG-FORMING PORTIONS AND SUCH THAT SUCCESSIVE TIERS ARE OFFSET ONE FROM THE OTHER AND JOINED ONE TO THE OTHER BY A PLURALITY OF NODES WHICH JOIN THE ENDS OF SUCCESSIVE SEGMENTS IN ONE TIER TO THE CENTERS OF LIKE SEGMENTS IN SUCCESSIVE TIERS, SAID NODES HAVING RECTANGULAR, VERTICALLY TRANSVERSE CROSS-SECTIONS AND WIDTHS SIGNIFICANTLY GREATER THAN SAID PREDETERMINED THICKNESS AND EQUAL TO THE SUM OF THE WIDTHS OF THE ADJOINING SKELETAL ELEMENTS, WHEREBY TWO RETICULATED PORTIONS COMPRISING A PLURALITY OF POLYGONAL PASTE-RETAINING CELLS BOUNDED BY SAID SKELETAL ELEMENTS AND NODES ARE FORMED AND EXTEND AT ACUTE ANGLES FROM THE CENTRAL PORTION IN GULL-WING FASHION WHEN VIEWED HEAD-ON; LEVELING THE THUSLY EXPANDED STRIP BY FOLDING SAID RETICULATED PORTONS DOWN INTO NEARLY THE SAME PLANE AS SAID CENTRAL PORTION; UNIFORMLY STRETCHING THE RETICULATED PORTIONS IN DIRECTIONS SUBSTANTIALLY PERPENDICULAR TO THE DIRECTION THE STRIP IS FED THROUGH THE DIES BY URGING EACH TIER OF SKELETAL ELEMENTS IN THOSE DIRECTIONS INDEPENDENTLY OF THE OTHER TIERS TO UNIFORMLY SIZE THE CELLS, TRETCH THE RETICULATED PORTIONS TO A PREDETERMINED WIDTH AND SLIGHTLY ROTATE THE RECTANGULAR NODES SUCH THAT DIAGONALLY OPPOSING EDGES OF THE NODES BECOME SALIENT IN THE PRINCIPAL PLANES OF THE RETICULATED PORTIONS; FLATTENING THE RETICULATED PORTIONS BY FURTHER ROTATING SAID NODES AND COMPRESSING SAID SALIENT EDGES INTO PLATEUS AND THEREBY CONVERT THE RECTANGULAR CROSS-SECTIONS OF SAID NODES TO POLYGONAL CROSS-SECTIONS HAVING TWO OPPOSING SIDES THEREOF LAYING IN PLANES SUBSTANTIALLY PARALLEL TO THE FACES OF THE PASTED PLATE AND SPACED ONE FROM THE OTHER BY A DISTANCE GREATER THAN SAID PREDETERMINED THICKNESS BUT SUBSTANTIALLY LESS THAN TWICE SAID PREDETERMINED THICKNESS; SUBSTANTIALLY ENGULFING THE RETICULATED PORTIONS IN A LEADY ACITIVE MATERIAL PASTE AND SANDWICHING SAME BETWEEN STRIPS OF PAPER WHICH ARE SUBSTANTIALLY COEXTENSIVE WITH SAID RETICULATED PORTIONS; DRYING THE PAPER-BOUND PASTED STRIP; AND FINALLY SEGMENTING THE PASTED STRIP INTO INDIVIDUAL BATTERY PLATES.

Claim 2

A METHOD OF MAKING LEAD-ACID STORAGE BATTERY PLATES COMPRISING: ADVANCING A NARROW LEAD STRIP, HAVING A PREDETERMINED THICKNESS, LONGITUDINALLY BETWEEN TWO ROWS OF PROGRESSIVE DIES AND CUTTERS, SAID STRIP HAVING A CENTRAL, LONGITUDINAL LUG-FORMING PORTION AND TWO EXPANDABLE GRID-FORMING PORTIONS FLANKING THE LUG-FORMING PORTION AND EXTENDING TO BOTH LONGITUDINAL EDGES OF THE STRIP AND SAID ROWS COMPRISING A PLURALITY OF DIES AND CUTTERS WHICH CONVERGE IN INCREMENTAL STEPS ON THE ENTAL LUG-FORMING PORTION OG THE STRIP PASSING BETWEEN THEM; EXPANDING THE GRID-FORMING PORTIONS ALONG THE LONGITUDINAL EDGES THEREOF BY PERIODICALLY SHEARING RECTANGULARLY WIRELIKE SEGMENTS FROM SAID EDGES INTO A PLURALITY OF TIERS OF UNDULARTORY SKELETAL ELEMENTS EXTENDING AT ACUTE ANGLES TO THE PLANE OF SAID LUG-FORMING PORTIONS AND SUCH THAT SUCCESSIVE TIERS ARE OFFSET ONE FROM THE OTHER AND JOINED ONE TO THE OTHER BY A PLURALITY OF NODES WHICH JOIN THE ENDS OF SUCCESSIVE SEGMENTS IN ONE TIER TO THE CENTERS OF LIKE SEGMENTS IN SUCCESSIVE TIERS, SAID NODES HAVING RECTANGULAR, VERTICALLY TRANSVERSE CROSS-SECTIONS AND WIDTHS SIGNIFICANTLY GREATER THAN SAID PREDETERMINED THICKNESS AND EQUAL TO THE SUM OF THE WIDTHS OF THE ADJOINING SKELETAL ELEMENTS, WHEREBY TWO RETICULATED PORTIONS COMPRISING A PLURALITY OF POLYGONAL PASTE-RETAINING CELLS BOUNDED BY SAID SKELETAL ELEMENTS AND NODES ARE FORMED AND EXTEND AT ACUTE ANGLES FROM THE CENTRAL PORTION IN GULL-WING FASHION WHEN VIEWED HEAD-ON; LEVELING THE THUSLY EXPANDED STRIP BY FOLDING SAID RETICULATED PORTONS DOWN INTO NEARLY THE SAME PLANE AS SAID CENTRAL PORTION; UNIFORMLY STRETCHING THE RETICULATED PORTIONS IN DIRECTIONS SUBSTANTIALLY PERPENDICULAR TO THE DIRECTION THE STRIP IS FED THROUGH THE DIES BY URGING EACH TIER OF SKELETAL ELEMENTS IN THOSE DIRECTIONS INDEPENDENTLY OF THE OTHER TIERS TO UNIFORMLY SIZE THE CELLS, TRETCH THE RETICULATED PORTIONS TO A PREDETERMINED WIDTH AND SLIGHTLY ROTATE THE RECTANGULAR NODES SUCH THAT DIAGONALLY OPPOSING EDGES OF THE NODES BECOME SALIENT IN THE PRINCIPAL PLANES OF THE RETICULATED PORTIONS; FLATTENING THE RETICULATED PORTIONS BY FURTHER ROTATING SAID NODES AND COMPRESSING SAID SALIENT EDGES INTO PLATEUS AND THEREBY CONVERT THE RECTANGULAR CROSS-SECTIONS OF SAID NODES TO POLYGONAL CROSS-SECTIONS HAVING TWO OPPOSING SIDES THEREOF LAYING IN PLANES SUBSTANTIALLY PARALLEL TO THE FACES OF THE PASTED PLATE AND SPACED ONE FROM THE OTHER BY A DISTANCE GREATER THAN SAID PREDETERMINED THICKNESS BUT SUBSTANTIALLY LESS THAN TWICE SAID PREDETERMINED THICKNESS; SUBSTANTIALLY ENGULFING THE RETICULATED PORTIONS IN A LEADY ACITIVE MATERIAL PASTE AND SANDWICHING SAME BETWEEN STRIPS OF PAPER WHICH ARE SUBSTANTIALLY COEXTENSIVE WITH SAID RETICULATED PORTIONS; DRYING THE PAPER-BOUND PASTED STRIP; AND FINALLY SEGMENTING THE PASTED STRIP INTO INDIVIDUAL BATTERY PLATES.

Claim 3

A method of making lead-acid storage battery plates comprising: advancing a narrow lead strip having a predetermined thickness longitudinally between two rows of progressive dies and cutters, said strip having a central, longitudinal lug-forming portion and two expandable grid-forming portions flanking the lug-forming portion and extending to both longitudinal edges of the strip, and said rows comprising a plurality of dies and cutters which converge in incremental steps on the central lug-forming portion of the strip passing between them; expanding the grid-forming portions along the longitudinal edges thereof by periodically shearing rectangular wire-like segments from said edges and stretching said segments to about 1.2 times their original length into a plurality of tiers of Undulatory skeletal elements extending at acute angles to the plane of said lug-forming portions and such that successive tiers are offset one from the other and joined one to the other by a plurality of nodes which join the ends of successive segments in one tier to the centers of like segments in successive tiers, said node having rectangular, vertically transverse cross-sections and widths significantly greater than said predetermined thickness and equal to the sum of the widths of the adjoining skeletal elements, whereby two reticulated portions comprising a plurality of polygonal paste-retaining cells bounded by said skeletal elements and nodes are formed and extend at acute angles from the central portion in gull-wing fashion when viewed head-on; plowing said reticulated portions down into a position more nearly in the same plane as said central portion, but with a residual hump near where the reticulated portion joins the central portion; rolling out said hump so as to bring said reticulated portions into nearly the same plane as said central portion; uniformly stretching the reticulated portions in directions substantially perpendicular to the direction the strip is fed through the dies by urging each tier of skeletal elements in those directions independently of the other tiers to uniformly size the cells, stretch the reticulated portions to a predetermined width and slightly rotate the rectangular nodes such that diagonally opposed edges of the nodes become salient in the principal planes of the reticulated portions; flattening the reticulated portions by further rotating said nodes and compressing said salient edges into plateaus and thereby convert the rectangular cross-sections of said nodes to polygonal cross-sections having two opposing sides thereof laying in planes substanntially parallel to the faces of the pasted plate and spaced one from the other by distance greater than said predetermined thickness but substantially less than twice said predetermined thickness; substantially engulfing the reticulated portions in a leady active material paste and sandwiching same between strips of paper which are substantially coextensive with said reticulated portions; drying the paper-bound pasted strip; and finally segmenting the pasted strip into individual battery plates.

Claim 4

A method of making lead-acid storage battery plates comprising: advancing a narrow lead strip having a predetermined thickness longitudinally between two rows of progressive dies and cutters, said strip having a central, longitudinal lug-forming portion and two expandable grid-forming portions flanking the lug-forming portion and extending to both longitudinal edges of the strip, and said rows comprising a plurality of dies and cutters which converge in incremental steps on the central lug-forming portion of the strip passing between them; expanding the grid-forming portions along the longitudinal edges thereof by periodically shearing rectangular wire-like segments from said edges and stretching said segments to about 1.2 times their original length into a plurality of tiers of Undulatory skeletal elements extending at acute angles to the plane of said lug-forming portions and such that successive tiers are offset one from the other and joined one to the other by a plurality of nodes which join the ends of successive segments in one tier to the centers of like segments in successive tiers, said node having rectangular, vertically transverse cross-sections and widths significantly greater than said predetermined thickness and equal to the sum of the widths of the adjoining skeletal elements, whereby two reticulated portions comprising a plurality of polygonal paste-retaining cells bounded by said skeletal elements and nodes are formed and extend at acute angles from the central portion in gull-wing fashion when viewed head-on; plowing said reticulated portions down into a position more nearly in the same plane as said central portion, but with a residual hump near where the reticulated portion joins the central portion; rolling out said hump so as to bring said reticulated portions into nearly the same plane as said central portion; uniformly stretching the reticulated portions in directions substantially perpendicular to the direction the strip is fed through the dies by urging each tier of skeletal elements in those directions independently of the other tiers to uniformly size the cells, stretch the reticulated portions to a predetermined width and slightly rotate the rectangular nodes such that diagonally opposed edges of the nodes become salient in the principal planes of the reticulated portions; flattening the reticulated portions by further rotating said nodes and compressing said salient edges into plateaus and thereby convert the rectangular cross-sections of said nodes to polygonal cross-sections having two opposing sides thereof laying in planes substanntially parallel to the faces of the pasted plate and spaced one from the other by distance greater than said predetermined thickness but substantially less than twice said predetermined thickness; substantially engulfing the reticulated portions in a leady active material paste and sandwiching same between strips of paper which are substantially coextensive with said reticulated portions; drying the paper-bound pasted strip; and finally segmenting the pasted strip into individual battery plates.

Claim 5

A method of making lead-acid storage battery plates comprising: advancing a narrow lead strip having a predetermined thickness longitudinally between two rows of progressive dies and cutters, said strip having a central, longitudinal lug-forming portion and two expandable grid-forming portions flanking the lug-forming portion and extending to both longitudinal edges of the strip, and said rows comprising a plurality of dies and cutters which converge in incremental steps on the central lug-forming portion of the strip passing between them; expanding the grid-forming portions along the longitudinal edges thereof by periodically shearing rectangular wire-like segments from said edges into a plurality of tiers of undulatory skeletal elements extending at acute angles to the plane of said lug-forming portions and such that successive tiers are offset one from the other and joined to the other by a plurality of nodes which join the ends of successive segments in one tier to the centers of like segments in successive tiers, said nodes having rectangular, vertically transverse cross-sections and widths significantly greater than said predetermined thickness and equal to the sum of the widths of the adjoining skeletal elements, whereby two reticulated portions comprising a plurality of polygonal paste-retaining cells bounded by said skeletal elements and nodes are formed and extend at acute angles from the central portion in gull-wing fashion when viewed head-on; leveling said strip by folding said reticulated portions down into nearly the same plane as said central portion; advancing said reticulated portions longitudinally between coacting male and female stretching and forming rollers in which the male roller has alternate rows of aligned truncated pyramidal projections for engaging the cells and the female roller has a resilient surface layer having alternate rows of aligned recesses for receiving said projections and ridges between said recesses for pressing said skeletal elements and nodes toward the bases of said projections and uniformly stretch each tier in directions perpendicular to the direction the strip is fed through the rollers to substantially uniformly size the cells, stretch the reticulated portions to a predetermined width and slightly rotate the rectangular nodes such that diagonally opposed edges of the nodes becomes salient in the principal planes of the reticulated portions; flattening the reticulated portions by further rotating said nodes and compressing said salient edges into plateaus and thereby convert the rectangular cross-sections of said nodes to polygonal cross-sections having two opposing sides thereof laying in planes substantially parallel to the faces of the pasted plate and spaced one from the other by a distance greater that said predetermined thickness but substanttially less than twice said predetermined thickness; substantially engulfing the reticulated portitons in a leady active material paste and sandwiching same between strips of paper which are substantially coextensive with said reticulated portions; drying the paper-bound pasted strip; and finally segmenting the pasted strip into individual battery plates.

Claim 6

A method of making lead-acid storage battery plates comprising: advancing a narrow lead strip having a predetermined thickness longitudinally between two rows of progressive dies and cutters, said strip having a central, longitudinal lug-forming portion and two expandable grid-forming portions flanking the lug-forming portion and extending to both longitudinal edges of the strip, and said rows comprising a plurality of dies and cutters which converge in incremental steps on the central lug-forming portion of the strip passing between them; expanding the grid-forming portions along the longitudinal edges thereof by periodically shearing rectangular wire-like segments from said edges into a plurality of tiers of undulatory skeletal elements extending at acute angles to the plane of said lug-forming portions and such that successive tiers are offset one from the other and joined to the other by a plurality of nodes which join the ends of successive segments in one tier to the centers of like segments in successive tiers, said nodes having rectangular, vertically transverse cross-sections and widths significantly greater than said predetermined thickness and equal to the sum of the widths of the adjoining skeletal elements, whereby two reticulated portions comprising a plurality of polygonal paste-retaining cells bounded by said skeletal elements and nodes are formed and extend at acute angles from the central portion in gull-wing fashion when viewed head-on; leveling said strip by folding said reticulated portions down into nearly the same plane as said central portion; advancing said reticulated portions longitudinally between coacting male and female stretching and forming rollers in which the male roller has alternate rows of aligned truncated pyramidal projections for engaging the cells and the female roller has a resilient surface layer having alternate rows of aligned recesses for receiving said projections and ridges between said recesses for pressing said skeletal elements and nodes toward the bases of said projections and uniformly stretch each tier in directions perpendicular to the direction the strip is fed through the rollers to substantially uniformly size the cells, stretch the reticulated portions to a predetermined width and slightly rotate the rectangular nodes such that diagonally opposed edges of the nodes becomes salient in the principal planes of the reticulated portions; flattening the reticulated portions by further rotating said nodes and compressing said salient edges into plateaus and thereby convert the rectangular cross-sections of said nodes to polygonal cross-sections having two opposing sides thereof laying in planes substantially parallel to the faces of the pasted plate and spaced one from the other by a distance greater that said predetermined thickness but substanttially less than twice said predetermined thickness; substantially engulfing the reticulated portitons in a leady active material paste and sandwiching same between strips of paper which are substantially coextensive with said reticulated portions; drying the paper-bound pasted strip; and finally segmenting the pasted strip into individual battery plates.

Claim 7

A method of making lead-acid storage battery plates comprising: advancing a narrow lead strip, having a predetermined thickness, longitudinally between two rows of progressive dies and cutters, said strip having a central, longitudinal lug-forming portion and two expandable grid-forming portions flanking the lug-forming portion and extending to both longitudinal edges of the strip, and said rows comprising a plurality of dies and cutters which converge in incremental steps on the central lug-forming portion of the strip passing between them; expanding the grid-forming portions along the longitudinal edges thereof by periodically shearing rectangular wire-like segments from said edges into a plurality of tiers of undulatory skeletal elements extending at acute angles to the plane of said lug-forming portions and such that successive tiers are offset one from the other and joined one to the other by a plurality of nodes which join the ends of successive segments in one tier to the centers of like segments in successive tiers, said nodes having rectangular, vertically transverse cross-sections and widths significantly greater than said predetermined thickness and equal to the sum of the widths of the adjoining skeletal elements, whereby two reticulated portions comprising a plurality of polygonal paste-retaining cells bounded by said skeletal elements and nodes are formed and extend at acute angles from the central portion in gull-wing fashion when viewed head-on; leveling the thusly expanded strip by folding said recticulated portions down into nearly the same plane as said central portion; uniformly stretching the reticulated portins in directions substantially perpendiculalr to the direction the strip is fed throught the dies by urging each tier of skeletal elements in those directions independently of the other tiers to uniformly size the cells, stretch the reticulated portions to a predetermined width and slightly rotate the rectangular nodes such that diagonally opposing edges of the nodes become salient in the principal planes of the reticulated portions; flattening the reticulated portions by further rotating said nodes and compressing said salient edges into plateaus and thereby convert the rectangular cross-sections of said nodes to polygonal cross-sections having two opposing sides thereof laying in planes substantially parallel to the faces of the pasted plate and spaced one from the other by a distAnce greater than said predetermined thickness but substantially less than twice said predetermined thickness; substantially engulfing the reticulated portions in a leady active material paste; drying the pasted strip; and finally segmenting the pasted strip into individual battery plates.

Claim 8

A method of making lead-acid storage battery plates comprising: advancing a narrow lead strip, having a predetermined thickness, longitudinally between two rows of progressive dies and cutters, said strip having a central, longitudinal lug-forming portion and two expandable grid-forming portions flanking the lug-forming portion and extending to both longitudinal edges of the strip, and said rows comprising a plurality of dies and cutters which converge in incremental steps on the central lug-forming portion of the strip passing between them; expanding the grid-forming portions along the longitudinal edges thereof by periodically shearing rectangular wire-like segments from said edges into a plurality of tiers of undulatory skeletal elements extending at acute angles to the plane of said lug-forming portions and such that successive tiers are offset one from the other and joined one to the other by a plurality of nodes which join the ends of successive segments in one tier to the centers of like segments in successive tiers, said nodes having rectangular, vertically transverse cross-sections and widths significantly greater than said predetermined thickness and equal to the sum of the widths of the adjoining skeletal elements, whereby two reticulated portions comprising a plurality of polygonal paste-retaining cells bounded by said skeletal elements and nodes are formed and extend at acute angles from the central portion in gull-wing fashion when viewed head-on; leveling the thusly expanded strip by folding said recticulated portions down into nearly the same plane as said central portion; uniformly stretching the reticulated portins in directions substantially perpendiculalr to the direction the strip is fed throught the dies by urging each tier of skeletal elements in those directions independently of the other tiers to uniformly size the cells, stretch the reticulated portions to a predetermined width and slightly rotate the rectangular nodes such that diagonally opposing edges of the nodes become salient in the principal planes of the reticulated portions; flattening the reticulated portions by further rotating said nodes and compressing said salient edges into plateaus and thereby convert the rectangular cross-sections of said nodes to polygonal cross-sections having two opposing sides thereof laying in planes substantially parallel to the faces of the pasted plate and spaced one from the other by a distAnce greater than said predetermined thickness but substantially less than twice said predetermined thickness; substantially engulfing the reticulated portions in a leady active material paste; drying the pasted strip; and finally segmenting the pasted strip into individual battery plates.

Claim 9

A method of making lead-acid storage battery grid stock from strips of lead alloy comprising: advancing a narrow strip of said lead alloy, having a predetermined thickness, longitudinally between two rows of progressive dies and cutters, said strip having a central, longitudinal lug-forming portion and two expandable grid-forming portions flanking the lug-forming portion and extending to both both longitudinal edges of the strip, and said rows comprising a plurality of dies and cutters which converge in incremental steps on the central lug-forming portion of the strip passing between them; expanding the grid-forminng portions along the longitudinal edges thereof by periodically shearing rectangular wire-like segments from said edges into a plurality of tiers of undulatory skeletal elements extending at acute angles to the plane of said lug-forming portions and such that successive tiers are offset one from the other and joined one to the other by a plurality of nodes which join the ends of successive segments in one tier to the centers of like segments in successive tiers, said nodes having rectangular, vertically transverse cross-sections and widths significantly greater than said predetermined thickness and equal to the sum of the widths of the adjoining skeletal elements, whereby two reticulated portions comprising a plurality of polygonal paste-retaining cells bounded by said skeletal elements and nodes are formed and extend at acute angles from the central portion in gull-wing fashion when viewed head-on; leveling the thusly expanded strip by folding said reticulated portions down into nearly the same plane as said central portion; uniformly stretching the reticulated portions in directions substantially perpendicular to the direction the strip is fed through the dies by urging each tier of skeletal elements in those directions independently of the other tiers to uniformly size the cells, stretch the reticulated portions to a predetemined width and slightly rotate the rectangular nodes such that diagonally opposing edges of the nodes become salient in the principal planes of the reticulated portions; and flattening the reticulated portions by further rotating said nodes and compressing said salient edges into plateaus and thereby convert the rectangular cross-sections of said nodes to polygonal cross-sections having two opposing sides thereof laying in planes substantially parallel to the faces of said central portions and spaced one from the other by a distance greater than said predetermined thickness but substantially less than twice said predetermined thickness.

Claim 10

A method of making lead-acid storage battery grid stock from strips of lead alloy comprising: advancing a narrow strip of said lead alloy, having a predetermined thickness, longitudinally between two rows of progressive dies and cutters, said strip having a central, longitudinal lug-forming portion and two expandable grid-forming portions flanking the lug-forming portion and extending to both both longitudinal edges of the strip, and said rows comprising a plurality of dies and cutters which converge in incremental steps on the central lug-forming portion of the strip passing between them; expanding the grid-forminng portions along the longitudinal edges thereof by periodically shearing rectangular wire-like segments from said edges into a plurality of tiers of undulatory skeletal elements extending at acute angles to the plane of said lug-forming portions and such that successive tiers are offset one from the other and joined one to the other by a plurality of nodes which join the ends of successive segments in one tier to the centers of like segments in successive tiers, said nodes having rectangular, vertically transverse cross-sections and widths significantly greater than said predetermined thickness and equal to the sum of the widths of the adjoining skeletal elements, whereby two reticulated portions comprising a plurality of polygonal paste-retaining cells bounded by said skeletal elements and nodes are formed and extend at acute angles from the central portion in gull-wing fashion when viewed head-on; leveling the thusly expanded strip by folding said reticulated portions down into nearly the same plane as said central portion; uniformly stretching the reticulated portions in directions substantially perpendicular to the direction the strip is fed through the dies by urging each tier of skeletal elements in those directions independently of the other tiers to uniformly size the cells, stretch the reticulated portions to a predetemined width and slightly rotate the rectangular nodes such that diagonally opposing edges of the nodes become salient in the principal planes of the reticulated portions; and flattening the reticulated portions by further rotating said nodes and compressing said salient edges into plateaus and thereby convert the rectangular cross-sections of said nodes to polygonal cross-sections having two opposing sides thereof laying in planes substantially parallel to the faces of said central portions and spaced one from the other by a distance greater than said predetermined thickness but substantially less than twice said predetermined thickness.