US2172270A - Sheet metal joint and securing means therefor - Google Patents

Description

Sept. 5, 1939. H R. ANSEL 2,172,270

SHEET METAL JOINT AND SECURING MEANS THEREFOR Filed July 19, 1937 29.] N v M 7 .3 I Fig.4

' I N V EN TOR. 174147 A. Anse/ BY M A TTORNE Y.

Patented Sept. 5, 1939 UNITED STATES- PATENT OFFICE SHEET METAL JOINT AND SECURING MEANS THEREFOR tion of Ohio Application July 19, 1937, Serial No. 154,369

8 Claims.

The invention to be hereinafter described relates to sheet metal joints and securing means therefor.

Roofs and sheet sidings should, of course, be leak proof, draft proof, capable of withstanding high wind pressures, and positively permanently maintained in place.

The main objects of the present invention are to provide a joint and cooperating securing means by which a readily dismantlable wall, roof, or other structure may be easily, quickly and economically erected and, when erected, will, in a high degree, he leak and draft proof, capable of withstanding high winds and positively permanently maintained in place. A further object is to provide such a structure particularly adapted to the lighter weight or gauge of sheet metal such as is very generally used throughout the agricultural or farming sections.

In order to more clearly disclose the construction, operation and use of the invention, reference should be had to the accompanying drawing forming part of this application. Throughout the several views of the drawing like reference characters designate the same parts in the several views. It will be understood that clearness in the drawing requires, in the enlarged views of the joints, spaced parallel lines for the edge views and that the sheets are, actually, much thinner that appears, but that closer spacing of the lines or finer lines would detract from clearness and would not approximate, appreciably closer to actual dimensions.

In the drawing:

Fig. 1 is a diagrammatic edge view of a sheet, broken out, showing one preferred form and arrangement of bend. crimp or corrugation, without intermediate gutter;

Fig. 2 is a similar view with flat valley bottom and intermediate gutter;

Fig. 3 is a similar view with a convex valley bottom and no stop shoulders;

Fig. 4 is a similar view with a convex valley bottom and inclined stops;

Fig. 5 is a similar view, with concave upper valley bottom;

Fig. 6 is an end elevation of the clip of the securing means;

Fig. '7 is a plan view of Fig. 6;

Fig. 8 is an end elevation of the locking plate, flat;

Fig. 9 is a top plan view of Fig. 8;

Fig. 10 is an enlarged edge view of an assembled joint and securing device, using the sheet of Fig. 1, with the parts in inoperative position, the operative position being shown in dotted lines;

Fig. 11 is a view similar to Fig. 10, using sheets of Fig. 2

Fig. 12 is a view similar to Fig. 10, using sheets of Fig. 3;

Fig. 13 is a view similar to Fig. 10, using sheets of Fig. 5;

Fig. 14 is a View similar to Fig. 10, using sheets of Fig. 4;

Fig. 15 is an end elevation of a different form of clip;

Fig. 16 is a top plan View of Fig. 15,, and

Fig. 17 is a view similar to Fig. 10, showing the gutter in a location other than in the valley between the crimps.

In the drawing a simple V crimp, only, has been shown though it will be clearly understood that other forms of such crimp may be used. A standard and widely used sheet is what is known as the 5V crimp sheet which has two parallel crimps along each side and a fifth running through its center. It will be understood that a pair of spaced V-crimps may be used through the center, like the pairs along the outer edges and that securing clips and cooperating plates may be used with such centrally located pair of V-crimps, just as with those which, assembled, form the joints. It is not believed either necessary or desirable to illustrate or to further describe such construction and arrangement and, of course, while 5V crimp has been specifically illustrated, it is obvious that the sheet may have more crimps and that there may be more pairs of crimps and cooperating'securing devices. In Figs. 10 to 15 of the drawings, the parts are enlarged to about double to more clearly show the parts and their cooperation. In Figs. 1 to 5 the sheet is reduced and shown in diagram as the views are primarily to indicate the outline of the bends.

In the trade, especially for agricultural sections, a sheet known as the 5V crimp is widely used. This sheet is usually of the lighter weights such as 26, 28 or 29 gauge and is formed as previously indicated. The single rib through the middle is, primarily, for stiiiening or strengthening, while the pairs of parallel spaced ribs along the edges are for making joints between sheets. This connection is made by simply seating the pair of Vs of one sheet edge over those of the next adjacent and then nailing through the nested crimps into the wood deck below.

Throughout the drawing this 5V crimp sheet has been shown merely because it is a simple,

practical and widely used type in the field in which the invention will find its greatest application. The regular standard V crimp is some- What modified to adapt it to the present; invention, as will later appear. In the present invention, the crimps may be Vs, Us, or other bends or corrugations which, as later explained,

, will properly cooperate with other features of corrugated sheets.

the invention. And of course, the sheets may be corrugated throughout as in the regular standard The invention also maybe used with other weight sheets, of course.

The simplest form of the invention is shown in Figs. 1 and 10. In this form, the gutter intermediate of the crimps is not involved. A sheet which maybe used for siding, roofing or other purposes, is provided along opposite edges with pairs of crimps 2. These crimps of each sheet are substantially identical with those of every other sheet and are adapted tonest upon or within those of every other sheet, in usual and well known manner.

Heretofore, these sheets with nested joints have 7 been secured by nails driven through the nested crimps of the joints and into the frame work beneath. The number of nails and corresponding nail holes, even in a very small area, is large and every nail hole is an actual or potential leak. Thesev holes rust rapidly, with corresponding rapid enlargement and no practical preventative "has, so far, been devised. This not only greatly mated by the present invention. Instead of nailincreases leakage but frees the sheets from the nails so that they are no longer secured in place.

All nailing through the sheet, and consequently, all puncturing of the sheet is entirely eliming, a simple clamping or gripping device is used,

comprising two cooperating elements working on opposite sides of the sheet, as will'later appear.

Referring to Figs. 1 and 10, when the joint is completed, there are no nail holes to provide and arrangement renders the joint substantially draft proof.

Assume that it is desired to lay a roof of the sheets. First a suitable starting point for. laying the sheets will be selected and the first sheet laid. Where the double crimp along one edge falls, to nest with the corresponding crimp along the oppositeedge of the next sheet, a series of clips will be disposed beneath and fitting up into the crimps. These clips, in a preferred form, comprise a base 3 adapted to setfiush and even on the usual wood deck or frame work. This base is cut out or channeled to provide two inwardly directed ribs, branches or arms 4, extending the full length of opposite sides of the 'base' and arching'inwardly .toward each other over the base channel. This provides arcuate grooves or recesses 5 beneath the arms or ribs, extending the full length of the base. These grooves are so formed, in one type of the clip, as to leave small shoulders 6 between the grooves and the channel of the base, "for a purpose to be later disclosed.

In-order to secure the clip in place, it may be provided with a nail hole 1 through which a nail maybe driven into the frame work, or it may be formed with integral prongs 8, indicated in dotted lines, which may be driven into the frame work. These clips are mounted at desired inter vals along the length of the double crimp in such position that, with the arms fitting up into the crimps, the base falls below the portion connecting the crimps. In forming the crimps, the outer valley-bottom between crimps of the under sheet edge is raised above the plane of the sheet a distance equal to the thickness'of the base 3, so that it will not be sprung or'pushed up by the clip base when in place, but will be level throughout. As each clip is positioned and secured in place by nail or prong, its respective location is clearly marked by a chalk or other line on the sheet. Then, when the crimps of the next sheet are nested on those of the'preceding sheet, the marks are repeated on the second sheet. These clips may be stamped, forged or cast, according to circumstances and preference. For each clip 3 a looking plate!) is provided. This plate, whenflattened out, may be a small rectangle of heavy gauge metal, of such size that the two opposite edges are spaced a distance approximately equal to that of the sheet crimps when and where crowded into thegrooves 5, as will later appear. These plates, in manufacture, are made concavoconvex, the curvature being such that the edges tion, its edges engage the side walls of the crimps and force them into the grooves 5. This bends the sheet around and under the hooks or arms 4, as at H, all as clearly shown in Figs. 10 to 14 and 17 thereby positively'and securely locking the sheets to the clip 3, by the clip 3 below and lock plate 9 above. This very short and very narrow bend, made by the thin short edge ll] of plate 9 when struck, or by other suitable means, has exactly the same type construction as would be provided or produced by a hammer blow having a similar edge. It is a short narrow indentation or depression in the wall of the crimp or corrugation, below the surrounding surface of the same and has approximately a width equal to the thickness of the p-1ate9 and a length approximately equal to the width of said plate. A special tool or a machine may, of course, make the same indentation. Since the crimps are steeply oppositely inclined, the cooperating sides of the locking plate 9 are reversely inclined to avoid slipping. This provides edges In which, after pickling and galvanizing, are not sharp. The four corners are rounded off as at l6, toavoid piercing points and, also, to allow the plates to be struck with a'hammer and driven lengthwise of the crimps and "out of the recesses 5. a

A preferred stamped form of clip, has a base 3 with one or more nail holes or integral prongs and two spaced arms 4 formed by simply bending the plate at right angles. Each arm is notched as at 5. In this form, the length of the groove or channel 5 equals the thickness of the metal plate, whereas, in the form previouslydisclosed, the arms and grooves are the full length of the base. Both operate in the same way and accomplish the same results.

In the form of the invention just described, the crimps are of'the same depth and, therefore, the

intervening valleys are of the same depth so that, when nested there is a metal-to-metal contact throughout the crimpsand valleys. When the locking plates 9 are positioned to bespread, their inclined sides and lower edges will engage the angle formed by the junction of the crimp and valley. In making the clips, they are so proportioned that their recesses, grooves or notches 5 are directly in line with the above mentioned junction, when the sheets have been assembled, as abovementioned. Consequently, as the plate is flattened, it forces the metal of the crimp. into the recesses 5. course, follows this bend I? in the sheets and, its edges extend into the recesses 5, forcing the sheet in ahead of it. This provides a secure permanent lock binding the sheets to the clip. This plate may be driven out lengthwise to release the sheets for dismantling. A plain wedge may be used, forced down to the proper depth and then driven longitudinally into locking position. Such wedge may be removed by simply driving in the opposite direction. After the plate or wedge is removed, the sheet crimps may be 5 easily sprung enough to remove them from the clips. They will be in perfect, wholly undamaged condition for immediate reuse. In this form, it will be noticed that the edges of plate 9 seat or bottom directly in the junction angle of crimp and valley. This junction is a definite and positive stop of two thicknesses of metal of the sheet, beyond which the plate can not go. For that reason no stop or limit shoulders are required in this form, as in some other forms. Since the plate has reached a stop against movement perpendicular to the plane of the sheet, when it is struck to flatten it out, it is forced to move in a direction parallel to the plane of the sheet and, in doing so, force the metal of the crimps into the recesses. The metal for these bends I1 is drawn from the valleys or gutters and not from the crimps, as will be clear. The recesses may be curved and approximately semicircular. This is not essential. They may be rectangular, elliptical or other shape, provided that they extend inwardly under the upper ends of the arms so that there is a wall or edge projecting beyond or overhanging and engaging the metal which has been forced into the recesses, and preventing removal of the sheet, as long as the plate 9 is in operative position. Logically, the recess will be such as to leave greatest strength in the arms 4 of the clips.

Referring to Figs. 2 and 11, the invention includes an internal gutter between the two sheets. For that purpose, the valleys of the sheets are spaced or separated. This is done by making the valley of the top sheet shallower than the valley of the under sheet and that, in turn, is accomplished by having each sheet provided with a shallower valley between the crimps along one edge and a full depth valley between the crimps along the other edge, as in Fig. 2, so that, when the joint is assembled it will be as in Fig. 11. It will be noticed that the valley of the underlying sheet is deepest and that the bottom of that valley is above the plane of the sheet. It is probable that a single thickness of metal might be ruptured by the straightening of the plate. So, to avoid this, the valley of the under sheet is provided with shoulders II and the clip is provided with cooperating shoulders 6, the parts being so proportioned that, when the sheets are assembled on the clip, shoulders ll seat on shoulders 6 and the bottom wall of the valley The plate, of i of the top sheet rests on shoulders ll. At this point which is also the junction point between the crimp and valley-bottom of both sheets, the thrust of plate 9 will be amply met by a double sheet thickness of metal and the shoulders 6. It will be solidly bottomed on the shoulders and, when hit, will be forced to straighten out with no danger of rupturing the sheet. The sheet will be forced into the grooves 5 under the arms of the clips and securely held by the plate 9, just as in the form of Figs. 1 and 10. Of course, the other type of wedge may be used, as in the construction of Figs. 1 and 10.

In the form shown in Figs. 3 and 12, the valley or gutter of the top sheet-i. e. the shallower valley or gutteris formed to function, also, as a pair of shoulders to resist the thrust of the locking plate as it is straightened out to operative position. In this construction, the sides of. the Vs are full length, substantially the same as the sides of the Vs of the contiguous sheet over and on which they are adapted to be nested. However, instead of being flat, this valley-bottom is convexed as at [2. By such construction, the side walls of the Vs nest snugly full length, the junction point or angle of each side wall of the overlying sheets, with its convexed bottom, nesting in the corresponding junction point or angle of each side wall of the underlying sheet. The underlying sheet rests firmly on the clip. Consequently, when the two sheets are assembled, the nested valleys will be securely seated on the clip and, also, there are two thicknesses of sheet at the point of thrust of the plate 9. In this form, as in the two forms previously described, the locking plate, when hit with a hammer to flatten it or straighten it out to operative position, it will be compelled to straighten out for the simple reason that downward movement perpendicular to the sheet has been stopped. It, therefore, must straighten out, or move in a direction parallel to that of the plane of the sheet, thereby forcing the sheet into the recesses 5. This construction provides an ample gutter, while eliminating the shoulders B and II. The convex valley-bottom may also be used where shoulders 6 and H are used. In such cases, the junction points between side walls of the crimp and convex bottom would simply seat on the shoulders ll of the under sheet. That would give an increased depth of gutter between sheets and the increased stiffness of the corrugation in the gutter of the upper sheet. This increased stiifness due to corrugation exists also in the form (Figs. 3 and 12) where shoulders are eliminated. Instead of plate 9, a plane wedge may be used, as in the other forms.

In the preferred form of the invention, also,-Figs 5 and l3-shoulders 6 and II are eliminated. In this construction, the valleybottom of the overlying sheet is concaved as at crimp to the concave. This, in turn, provides an abrupt junction or angle between crimp sidewall and valley-bottom into which the edges of the plate 9 seat. Due to the bottom support of concave I3, the junction points without shoulders,v offer ample resistance to avoid rupture as the plate 9 is flattened out. The locking action is the same asin the other forms .and the locking plate is placed and removed in the same way.

In Figs. 4 and 14, the construction is very much the same as in the construction of Figs. 3 and 12, except as to the stop shoulders. These are made as short inclined planes or surfaces inclined at about 30. vided with such inclines. In the sheet, they are formed, of course, at thejunction between sides and bottom of the crimps,,as at -l4'. And, when nested and assembled on the clips, these inclines will seat on the corresponding incline l5 of the clips. Inclines l5 lead upwardly into recesses 5. In this form, as each plate 9 is positioned, it will be solidly bottomed on. the nested inclines, M and I5, at the entrance to'the recesses .5. When flattened or spread by a blow, it will force the sheet into the recesses and lock the joint, as in the other forms. The other form of locking wedge may,,also, be used. Because of the inclined l4 and I5, there will be less binding and strain on the sheet and the plate will flatten more easily and quickly.

In every form so far described, in which a gutter is embodied, the gutter isintermediate'of or,

in other words, between two spaced parallel crimps and each crimp is separate and complete,

independently, of the gutter. Though such is the preferred arrangement, it is not essential or compulsory. Instead, the gutter may be made as an integral part of the crimp wall or crimp.

;A preferred construction of this modification is shown in Fig. '17. In that construction, each crimp of the under sheet, atthe turn of the crimp, as it approaches the top, is provided with a concave channel or gutter ll. This gutter, extending longitudinally of the sheet, as shown in this form, lies wholly on the near side of each crimp and extends downwardly from a point slightly beyond the beginning of the bend of the V as it approaches the apex. Any capillary seepage which may crawl up between the free edge of the overlying sheet and the V of the underlying sheet will fall into the first of these gutters thereby breaking the capillary feed. Before it can continue further, that channel must be complete: ly filled or flooded. When the flood reaches the capillary exit at the other and higher side of the gutter, capillary feed will have to travel com-L pletely through the full wall-height of the first crimp, across the valley between crimps and the full wall-height of the second crimpand then empty into the second gutter. This second gutter, then, must be filled and flooded before the seepage can again resume capillary feed toward the inside of the building and'possible leak. It is very improbable that the first gutter will ever crimps, or wholly one in the top of one crimp and one in either side-wall of the other crimp, or. .both formed in the same crimp, one each wholly in each side wall or one wholly in the top and the other in a side wall; or they may be Both the sheet and the'clip are proformed in either or both side walls of either or both crimps and extendingpartly into the tops of the crimps, being arranged in any desired manner above indicated; or, instead of two gutters, a single gutter may beused in any of the locations above indicated; or the free edge of the underlying sheet may be bent up to form a trough either with or without other gutter formation. It is believed that all above variant constructions and arrangements will be clear from the single illustration of Fig. 17 and that further illustration and corresponding description would merely encumber the record to no useful purpose.

In every form, the metal which is forced into the recesses 5 is drawn from the valley portion of the sheet, between the crimps, leaving the crimp apex undisturbed. Since only a slight in-- dentation of the sheets is made, the take-up of metal in the valley. section is inconsequential and has no effect on the operation of the device.

N0 sharp creases or abrupt bends are involved.

They-are all gradual, rounded, and on relatively large radii. Consequently, there is no puncture, cracking or injurious stressing of the galvanization. And, because of the character and relative size of the bends orindentations, they may be very easily disengaged from the clip when once the locking plate has been removed. The total take-up is distributed through the valley portion of the sheet and except at the locking bends, where the total is gathered, can not be practically shown and, therefore, no'actual attempt has been made to illustrate such distribution, except at said locking points.

The sheets with the various slightly different crimps of this inventionmay 'be very readily and economically made in quantity by stamping or pressing, A simple set of dies for each variation is all that is required. The fastening device com prising the clip and, either the bent locking plate or the plane wedge, may be produced in quantity the free, exposed, outer edge of the top, upper' or overlying sheet crimp terminates far up on the side of the underlying crimp distantly removed from the plane of the sheet and from the junction of sheet and crimp. Before any water may reach the inside of the joint on its way toward establishing a leak, it must enter beneath that free edge and between it andrthe crimp. 'That is the entrance point and the only possible beginning or origin of a leak in the construction of this invention. By keeping that point remote from all drainage water, the main cause of leaks is reduced to a minimum and almost eliminated.

The steepness or near-approach to the vertical,

. of the crimps, adds resistance to possible capillary attraction. This minimum is further greatly reduced by the gutter formation. Whatever capillary leakage does reach the gutter, flows into the near side of the gutter. By appreciably spacing the metal surfaces, as is done in the gutters, the capillary feed is broken and capillary attraction can carry the water no further. Its capillary travelis stopped. 'It runs into the gutter and drains off. If the seepage should be great enough to fill the gutter, it still can not resume capillary feed until it again rises high enough to reach the entrance of the next capillary passage or spacebetween sheets. After'that, it must still crawl through that entire passage to the free edge of the under sheet before there is any chance of a leak. So, capillary action is, as far as practical, prevented at the start, what does get started is completely broken down, and restarting is as far as practical, prevented. Without capillary action in such construction there can be no leakage, just as without vacuum, in appreciable degree, there can be no delivery of water in a suction pump, And, like such a pump, the entrance end of the capillary passage must receive water in order to transmit it. Either it must be below the surface or water must be driven into it by wind and rain or otherwise. And, in this invention, that entrance is as far removed from probable supply as is practical, in every modiflcation.

In every form of the invention it will be noticed that there is a very snug nesting fit between the crimps of the nested joint portions of the sheets, greatly restricting any seepage and that, even then, any seepage must completely cross two high crimps and a wide intervening valley or space, before it can possibly result in a leak. In addition, in every form which includes an intervening gutter, the gutter would have to be so filled or flooded by such seepage that the water would rise, by capillary attraction from the far edge of the gutter into the succeeding crimp. In every gutterincluding form except that of Fig. 12, the side Walls of the overlying crimps are spaced considerably above the valley-bottom of the underlying crimps so that the exit point of drainage water from the gutter is high and can be reached only when the gutter is flooded, which is a very improbable condition. In the form of Fig. 13, this safe guard is increased by the concave I 3 which acts as a barrier or dam extending lengthwise through the center of the gutter and, in effect, making two gutters of it. The half nearest the free edge of the overlying sheet must fill to the flooded stage before it can work through to the other half and that in turn, must flll before capillary action can start to climb up the second crimp.

While several variations in crimp constructions for the joint have been illustrated and described it is obvious that a considerable range of variations may be resorted to all well within the scope of this invention.

In laying the sheets, in well known manner, the ends of the adjacent rows will overlap the ends of the next adjoining rows. Where two joints overlap they will, of course, nest in the joints of the other sheets. Wherever that occurs there will be four thicknesses of metal which will be forced into the recesses 5 of the clips.

It is thought that the construction, operation and use of the invention will be clear from the preceding detailed description.

Many changes may be made in the construction, arrangement and disposition of the various parts of the invention, within the scope of the appended claims, without in any degree departing from the held of the invention, and it is meant to include all such within this application wherein only a preferred form with several modifications have been disclosed, purely by way of illustration and with no thought of in any way or degree limiting the claims by such disclosures.

Having thus described my invention, what I claim and desire toprotect by Letters Patent is:

1. A sheet metal structure comprising a sheet having a pair of spaced parallel folds or corrugations extending upwardly therefrom along one edge thereof and each provided with a sheet securing indentation in the side wall nearest the other corrugation, said indentations extending longitudinally of and inwardly of the respective corrugation and one indentation of one corrugation being located opposite a corresponding indentation of the other corrugation, a sheetsecur-l:

corrugation of one sheet and a corrugation ofs.

the other sheet, each corrugation of each sheet being provided with a sheet securing indentation in the side wall of that corrugation nearest a side Wall of the other corrugation of the same sheet, said indentations extending longitudinally of and inwardly of the side wall of the respectivecorrugation and one indentation of one corrugation of each sheet lying opposite a corresponding indentation of the other corrugation of the same sheet, a sheet securing clip in assembled relation mounted within said corrugations, and a locking plate cooperating therewith and in assembled relation disposed between said corrugations and seated in looking position within said sheet securing indentations, securing said sheets, clip and plate together.

3. A metal joint sheet provided with a pair of spaced parallel corrugations along one edge thereof extending outwardly from the same side of the sheet, a pair of cooperating longitudinally extending securing indentations of relatively short length one formed in each corrugation wall on the near side of the intervening space and projecting inwardly of the respective corrugation, each being opposite the other relatively to said intervening space, said indentations being disposed in the same plane relatively to the plane of the base of the corrugations, said sheet being adapted, in assembled relation, to nest the corrugations and indentations of a cooperating sheet, and an expansible securing plate seated in said indentations to secure said sheet.

4. A joint for metal sheets comprising pairs of spaced, parallel corrugations, each pair car ried by a separate sheet and extending upwardly from its respective sheet and from the same side of its sheet along one edge thereof, and a drainage gutter within said joint between said sheets, each corrugation provided with sheet securing indentations in its adjacent side wall, the corrugations and securing indentations of one sheet being removably nestable relatively to those of the cooperating sheet.

5. A sheet metal structure comprising a sheet having a pair of spaced parallel folds or corrugations extending upwardly therefrom along one edge thereof and each provided with a sheet securing indentation in the side wall nearest the other corrugation, said indentations extending longitudinally of and inwardly of the respective corrugation and one indentation of one corrugation being located opposite a corresponding indentation of the other corrugation and cooperating locking devices disposed on opposite faces of the sheet, cooperating with said indentations and securing said sheet between them.

6. A sheet metal structurecomprising a pair of sheets each having a pair of spaced parallel folds or corrugations extending upwardly therefrom along one edge thereof and each provided with a sheet securing indentation, the corrugations and indentation of one sheet nesting those of the other, and locking devices disposed on opposite sides of said sheet, one of said devices being within said corrugations, said locking devices cooperating with said nested indentations and securing between them said sheets.

'7. A sheet metal structure comprising several 'sheets each having a pair of spaced parallel folds corrugation being opposite a corresponding indentation of the other corrugation, said sheets having'formed between them a gutter, and means for securing said sheets in assembled relation.

8. A metal joint sheet provided with a pair of permanently appreciably spaced parallel corrugations extending upwardly from the same side thereof along one edge with a relatively wide valley extending from corrugation to corrugation between the corrugations, each corrugation being provided in its inner side wall with a longitudinally extending securing indentation, the valley, corrugations and indentations of one sheet being removably nestable in those of another,

whereby the resiliency of the sheets yieldingly retains said indentations in nested sheet-interlocked relation releasable by springing said sheets;

against their resiliency to separate said indentations.

HARRY R. ANSEL.

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