CORRUGATED,TOOTHED WEB STRIP FOR CONSTRUCTION ELEMENTS

Abstract: In connection with a corrugated sheet metal strip (30) which is suitable as a web strip in construction elements consisting of an upper and a lower flange (202, 203) taking the form of nailable boards and/or timber bonded together by one or more web strips (204), extending edgeways between the flanges and penetrating the latters with teeth which are mutually spaced on the longitudinal edges of the strip, there are suggested means to ensure a correct predetermined penetration depth of the teeth, independent of the different penetration resistance yielded by either flange. The construction element comprises corrugated sheet metal strips (30) which are provided with penetration stoppers (31) which at a predetermined correct penetration depth of the strip teeth prevent further penetration into the flange (35b). The penetration stoppers (35) can take the form of stationary elements integral with the web strip (30) or consist of separate elements attachable thereto. Further, the stoppers may be constituted by sections or positions of the web strip which during the penetration will have their original shape (32, 33) changed so as to form a stopping foot (35a), the portions then preferably comprising appropriate weakened lines so as to facilitate the folding thereof.

Description: "Corrugated, toothed web strip for construction elements". The invention relates to web strips for construction elements of the type described in Norwegian Patent No. 129 759 and 135 434, i.e. beam- or panel-shaped elements consisting of an upper and lower flange held together in a spaced relationship by one or more webs taking the form of a corrugated sheet metal strip which along the edges are provided with teeth which are pressed into the respective flanges. Panel-shaped elements may be manufactured as a closed box having a bottom and a top made of plywood, par¬ ticle board or similar, and two or more longitudinally extending webs as well as end webs. Beams can be manufac¬ tured with flanges of timber and one or more webs so as to form an I-beam or a tubular beam. For such elements in which the upper and the lower flanges are of the same material, there will normally be used a web strip having the same tooth configuration along the two longitudinal edges. The pressing together of the element is carried out to a controlled total thickness which is equal to the net height of the web (the distance between the tooth root lines) plus the overall thickness of the two flanges. The stopping ability yielded by the plate material when the straight root-line area of the web strip abuts against the surface of the flange, is in connection with such plate materials sufficient to offset the local varia¬ tions of the penetration resistance which otherwise would cause the teeth to penetrate unequally into the respective flanges. However, it is often of current interest to make ele¬ ments in the form of an open box in which the upper flange is a particle board or plywood or chipwood plate, and the lower flange is an open timber framework. This type of ele¬ ment is, inter alia, suited as a storey divider in small houses since the open underside facilitates the emplacement of installations such as electric conductors, water and soil pipes. Such an element is also economic if for reasons of fire proofness or appearance there is wanted a roof of a non-structural material, for example plaster boards or wooden panelling arranged transversely to the lower flanges of the elements and nailed thereto. However, in the manufacturing of such elements it has appeared difficult to ensure correct penetration with the types of web strips described in the above patents. Timber often yields considerably less penetration resistance than the relevant plate materials, and for that part of the web strip which extends in the fibre direction, the resistance is particularly small. This entails that the teeth on the timber sides will not be stopped during their penetration, but continue beyond the root line, whereas the teeth on the plate side will remain partly embedded and "butt" the plate material, causing the element not to be correctly closed. This renders a bad visual impression and furthermore implies that the connection between the web and the plate flange will not obtain its full strength, which in some cases results in the scrapping of the element. This problem can to some extent be reduced by forming the strip with longer and broader teeth on the timber side than on the plate side, but the possibilities here are limi¬ ted. Besides, in the manufacturing of beams having timber flanges it has been observed that the problem of unequal penetration may arise as a consequence of the difference in material quality, the direction of the growth-rings etc. of the two flanges. It has therefore been found that the problem of unequal penetration can be solved most favourably not by increasing the penetration resistance of the tooth but by increasing the stopping ability of the root-line portion thereof. With this recognition as a starting point, the inven¬ tion is to the effect of providing the strip with penetration stoppers along one or both longitudinal edges. Such a stop¬ per may in principle be constituted by a surface or an edge C P portion extending substantially transversely to the longi¬ tudinal direction of the strip, and be so adapted, when the strip is penetrated to the desired depth in the respective flange, as to abut against the surface of the flange and prevent further penetration. An edgewise arranged thin plate which is pressed into timber will meet a small resistance if placed in the fibre direction, but if it is arranged transversely to the fibre direction the resistance is increased several times. The main .principle of such stoppers as will be described in the following, whether they have the shape of a planar surface or a cutting edge, is therefore that they must induce fibre cutting in order to penetrate the timber flange, a fact which renders an abrupt increase in the penetration resis¬ tance and thereby a stopping force which is sufficient to compensate for the difference in hardness between the two flanges. A series of embodiments of the invention will be described in the following, reference being had to the drawing, in which Fig. 1 illustrates a typical corrugation profile of a web strip, Fig. 2 illustrates a section of a stamped but not yet profiled web strip without penetration stoppers , Fig. 3 illustrates a section of a stamped but not pro¬ filed web strip having penetration stoppers on the timber side, Figs. 4 and 5 illustrate in a section taken along the line 4 - 4 in Fig. 3 the edge portion of the finished shaped web strip before and after penetration, respectively, Figs. 6, 7 and 8 illustrate a stamped blank, section 7 -.7 of Fig. 6 and section 8 - 8 of Fig. 7, respectively, of a web strip having an alterna¬ tive penetration stopper, Figs. 9 - 11 illustrate in a corresponding manner as Figs. 6 - 8 a stamped blank, a section 10 - 10 and a section 11 - 11 thereof, respectively, of an embodiment of yet another form of penetration stoppers, Fig. 12 is a perspective view of a penetration stopper designed as a loose stopping foot attachable to the web strip of Figs. 1 and 2, whereas Fig. 13 is a vertical section analogue to the sections 4, 5, 8 and 11, and illustrates the strip having the foot attached thereto, Fig. 14 illustrates an alternative embodiment of a loose stopping foot, Fig. 15 illustrates a part of a longitudinal and hori¬ zontal section through a web strip of alterna tive shape, Fig. 16 illustrates a portion of a stamped blank for the web strip shown on Fig. 15, Fig. 17 illustrates an alternative shape of the stopper shown in Fig. 16, Fig. 18 illustrates a portion of a stamped blank for another, alternative embodiment of the stopper, Fig. 19 is a cross section taken along the line 19 - 19 in Fig. 18, Figs. 20a - 20c are sections taken along the line 20 - 20 in Fig. 18, and illustrate successive stages in the forming of the stopper of Fig. 18 as the web teeth penetrate into the flange, Fig. 21 is a perspective view showing part of a con¬ struction element comprising plate members interconnected by two corrugated web strips. In Fig. 1 there is illustrated a typical corrugation profile of a web strip 10, the tooth configuration of which is illustrated in Fig. 2. The profile of Fig. 1 is in Fig. 2 illustrated as a section 1 - 1 after the blank 10a shown in Fig. 2 has been profiled. The strip 10 has a trapezoi- dally shaped corrugation having a pitch p. The tooth axes are designated x - x, each pitch containing two teeth at either edge of the strip. The shorter tooth 21 with the rippled end edge 25 is designed to be pressed into a plate material, whereas the longer tooth 22 having the cruder tooth prongs 26, 26' and 27 are designed for penetration into wood material. The root lines are designated 23 and 24, respectively. An example of how a web strip of another configuration is to be used for interconnect two plate-like members, is illustrated in Fig. 21, which will be described in more details below. If now a web strip having the shape illustrated in Figs. 1 and 2 is pressed simultaneously into an upper flange of hard particle board and a lower flange of wood material, the situation will in many cases be that the tooth on the plate side will be only partly embedded when the tooth on the wood side is completely embedded, i.e. when the tooth root line edge 24 abuts against the wood or timber flange. This edge portion 24 extends substantially parallel to the fibre direction of the timber flange and therefore meets a small penetration resistance against further penetration, since the cutting of fibres develops the substantial part of the penetration resistance. Further compression of the element will therefore only have as a consequence that the tooth on the timber side together with its root portion will penetrate further, whereas the tooth on the plate side will remain only partly embedded. Fig. 3 illustrates a web strip 30 by which it is possible to achieve an increase of the stopping force of the root portion by making a "stopping foot" having the form of a tongue or a lip 31 which is prefolded about lines 32 and 33 as illustrated in the vertical section 4 - 4 (Fig. 4) of the finished strip. As the tooth penetrates the wood flange, the front edge 35 of the lip will abut thereagainst, where¬ after the tongue will be further bent or folded about the lines 32 and 33 till it forms a flat foot 35a abutting against the wood flange 35b as illustrated in Fig. 5. For this foot 35a to penetrate into the wood material there must take place fibre cutting as well as a compression of the material below the foot, and the increase of the stopping force which thereby arises, has proved sufficient to ensure correct penetration as regards the materials in question, i.e. construction plywood, particle board and spruce or pine timber. A stopping foot in the form of a bent or folded tongue can also be implemented with three bending lines rather than two, so as to obtain three layers of sheet-metal rather than two in the finished flat foot. Since the foot in this way becomes stiffer, it can have a somewhat larger extension in the transverse direction of the strip, and thereby be made more effective. Further, it is evident that the stopping foot can take the form of a tongue which can only be folded about the root line 32, or the tongue can be divided in several portions which are folded alternatively to the one and the other side. Figs. 6 - 8 illustrate a penetration stopper designed as stamped triangular flaps 61, 61' which are folded about lines 62 and 62", respectively, so that the edge portions 63, 63' will be arranged transversely to the longitudinal direction of the strip and thereby cause fibre cutting upon penetration. The increase of the stopping force which is thereby achieved will usually be sufficient for counter¬ balancing the difference in hardness between two wood flanges and thereby ensure correct penetration. This embodiment is therefore well suited for web strips designed for beams having timber flanges. . Figs. 9 - 11 illustrate an alternative embodiment of a penetration stopper, similarly based on the principle disclosed above. In this case the fibre cutting edge por¬ tions are formed by tongue-shaped portions 91 which are twisted around their axes 92 so that the front edge 93 of the tongue will be standing transversely to the longitudinal direction of the strip and thereby account for an abrupt increase in the penetration resistance of the strip, so as to give the root portion the necessary stopping force to ensure correct penetration. Instead of shaping the penetration stopper integrally with the web strip as illustrated in the above examples, it can be designed as a separate element which can be attached to the root portion of the strip. Such an embodiment is illustrated in Figs. 12 and 13, taking the form of a stopping foot formed from a plate 120 which is folded in such a way that there is formed a flat foot 121 and two vertical walls 122, 122', by means of which it is clamped to the edge por¬ tion of the web strip. For further anchoring the stopping foot is provided with a lock taking the form of a triangular lip 123 stamped in the wall 122 and bent inwardly perpen¬ dicularly thereto, whereas in the edge of the opposite wall 122 * there is provided an opening 124 giving room for the lip 123. The lip 123 co-operates with a hole 131 (Fig. 13) provided in the web strip 132 so as to prevent the foot from sliding off. Such a stopper which is manufactured sepa¬ rately, can be made from a thicker material than the web strip itself and thereby be made broader and more effective than stoppers formed integrally with the strip. Fig. 14 illustrates an alternative embodiment of a separate stopping foot which is somewhat simpler to make than the one shown in Fig. 12. The foot in Fig. 14 consists of a plate 140 bent in such a way as to prowide two vertical end walls 142, 142' having an intermediate planar foot por¬ tion 141. The walls 142, 142' are provided with slots 143, 143' so that the foot 140 can be pressed or clipped onto the root portion between the teeth of the web strip, whereby triangle-shaped peaks 144, 144' at the one edge of the slots snap into holes in the web strip for locking the foot thereto. Figs. 15 and 16 illustrate a further development of the embodiment shown on Figs. 1 - 5, in as much as the longi- tudinal portions 151 of the corrugation profile 150 are shaped with a gentle curvature as opposed to the flat por¬ tions shown on Fig. 1. The main object of this curved shape is to stiffen the web strip and prevent local buckling of the thin sheet material when subjected to compressive stresses arising when the teeth are being pressed into the flanges. In order to enable the stopper to fold neatly along the lines 162, 163 (corresponding to the lines 32, 33 of Figs. 3 - 4) the stopper 161 proper is connected to the root por¬ tion of the web through a narrow portion 164. The web strip is manufactured with the stopping foot prefolded along the lines 162, 163 as shown correspondingly in Fig. 4, and will after completed tooth penetration appear in the plane of the flange as shown in Fig. 15. The root line edge portion of the web thus abuts the flattened stopping foot along a cur¬ ved line 151, which serves to stabilize the stopping foot and prevent it from rotating or bending about the root line when the stopper is being pressed slightly into the flange. As the stopping foot thus achieves better stability, it can be made somewhat broader (larger in the direction trans¬ versely to the web length) , whereby its stopping force will be increased. A further stiffening of the stopping foot can be achieved by folding its two side edges 171, 171' as shown in Fig. 17. These edges will cut into the flange material and may therefore advantageously be shaped with small teeth 172. When these have been pressed into the flange they are able to transmit horizontal and longitudinally directed forces between the web and the flange (horizontal shear) and thus give a contribution to the capacity of the web in this respect. Figs. 18, 19 and 20a - 20b illustrate an embodiment in which the prefolding of the tongue forming the stopping foot is avoided. As shown in Fig. 18, the tongue 181 is formed with three parallel weakened lines 182, 183 and 184, in the form of narrow slots. As shown in section in Fig. 19 the tongue, as produced, lies in the plane of the web strip proper and hence has the form of a cylinder segment. When penetration has proceded to the point where the leading edge 185 of the tongue abuts the flange surface, see Fig. 20a, the ensuring pressure against that edge causes the tongue to be bent along the weakened lines as shown in Fig. 20b because the cut-out slots form hinges which are placed excentrically, in alternating directions, to the line of contact pressure passing through the centre of gravity CG of the tongue cross section. As penetration proceeds, the tongue continues to bend about the hinges until a flat foot 186 is formed as shown in Fig. 20c. The embodiment of a web strip with stoppers shown on Figs. 18 - 20 is simpler to manufacture than the previously described forms since no special operation for pre-bending the tongue is called for. Although the tongue of Fig. 19 is shown as having the shape of a circular cylindrical segment, it is understood that the term cylindrical segment also includes other shapes, e.g. a cylinder, the generating curve of which is a broken line. Although the various embodiments of the invention have been described in connection with a web strip having a trapezoid-shaped corrugated profile it is evident that other profiles as e.g. those illustrated in the abovementioned patent specifications and provided with stoppers, are covered by the invention, the scope of which i limited only by the patent claims. Further, it is evident that the invention comprises combinations of the various embodiments, e.g. web strips having one type of stoppers along the one longitudinal edge and another type of stoppers along the other edge, or a com¬ bination of two different stoppers along one and the same longitudinal edge. In Fig. 21, there is in a perspective view illustrated ; o.MPi a construction element in the form of a box-shaped beam 201. The beam comprises an upper plate-like member 202 and a lower plate-like member 203 and two corrugated web sheets 204 interconnecting the members. The element is ready for use and the edge teeth of the web sheets 204 are embedded in the respective surfaces of the upper and lower members. The correct penetration depth is effected by penetration stop¬ pers 205, of which a few are shown in Fig. 21. The stoppers may be of the type shown in Fig. 12 or 14, i.e. of the attachable type.

Claims: P a t e n t C l a i m s 1. Corrugated sheet metal strip suitable as a web strip in construction elements (201) consisting of an upper and a lower flange (202, 203) taking the form of nailable boards and/or timber bonded together by one or more web strips (204) extending edgeways between the flanges and penetra¬ ting the latters with teeth which are mutually spaced on the longitudinal edges of the strip, c h a r a c t e r i z e d i n that between the consecutive teeth along at least one longitudinal edge the strip is provided with penetration stoppers (205) which upon penetration of the strip to the desired depth in the respective flange will abut there- against and thereby prevent further penetration of the web strip into the flange. 2. Corrugated sheet metal strip as claimed in claim 1, c h a r a c t e r i z e d i n that the penetration stop¬ pers take the form of a tongue (31) protruding between the teeth (22) and being folded about one or more lines parallel to the root line of the teeth for thereby providing a foot (35a) having planar abutment against the flange surface (35b) . 3. Corrugated sheet metal strip as claimed in claim 2, c h a r a c t e r i z e d i n that the tongue (31) is pre-folded in one direction substantially about the root line (32) and in the opposite direction about a line (33) parallel thereto but therebeyond, so that the front edge (35) of the tongue upon penetration of the teeth into the flange (35b) will abut against the flange surface and the tongue thereby being further folded about the two lines (32, 33) to a total angle of approximately 90° about the root line (32) and approximately 180 about the other line (33) , whereby a foot (35a) is shaped which have a planar abutment against the flange between the latter and the root portion of the web strip. 4. Corrugated sheet metal strip as claimed in claim 1, c h c h a r a c t e r i z e d i n that the penetration stoppers take the form of flap- or tongue-shaped portions (61, 91) which are bent or twisted out from the strip sur¬ face, so that between the teeth there are formed edge por¬ tions (63, 93) extending substantially transversely to the main direction of the strip. 5. Corrugated sheet metal strip as claimed in claim 1, c h a r a c t e r i z e d i n that the penetration stoppers are constituted by separate elements (120, 140) attached to the web strip between the teeth and forming a planar foot (121, 141) underneath the edge portion of the strip. 6. Corrugated sheet metal strip as claimed in claim 3, c h a r a c t e r i z e d i n that the root line (151) is curved in a plane perpendicular to the tooth axis , and that the tongue (161) is joined to the root line through a narrow neck-like portion (164) which can fold along a short length (162) of the root line, whereby the latter retains its curved shape and upon completed penetration abuts the flat foot (161) along a curved edge (151) which stabilizes the foot (161) against bending or rotation about the root line. 7. Corrugated sheet metal strip as claimed in claim 6, c h a r a c t e r i z e d i n that the tongue (161) is shaped with preferrably toothed lateral edges (171, 171') which are bent approximately 90 to the plane of the tongue so that said toothed edges during the final stage of web penetration penetrate a short distance into the flange. 8. Corrugated sheet metal strip as claimed in claim 2, c h a r a c t e r i z e d i n that the tongue is shaped as a segment of a cylinder, the generating curves of which are parallel to the tooth axes, and that the tongue (181) is formed with a number of weakened lines (182, 183, 184) parallel to the root line, said weakened lines forming hinges which lie with alternating excentricity relative to a line (P) parallel to the tooth axes and passing through the centre of gravity (CG) of the tongue cross section, thus causing the tongue to fold along the weakened lines in alternating directions as the leading edge (185) of the tongue is pressed against the flange. 9. A construction element (201) consisting of an upper and a lower flange (202, 203) of nailable plates and/or tim¬ ber held together in a spaced and substantially parallel relationship by one or several corrugated sheet metal strips (204) extending edgeways between the flanges and penetrating the latters with teeth provided on the edges of the strips, c h a r a c t e r i z e d i n that the construction ele¬ ment comprises corrugated sheet metal strips (204) which are provided with penetration stoppers (205) which at a predeter¬ mined correct penetration depth of the strip teeth into the respective flanges will halt further penetration of the strip teeth. 10. A method for manufacturing a construction element (201) consisting of an upper and a lower flange (202, 203) made of nailable material which yield a varying penetration resis¬ tance, c h a r a c t e r i z e d i n that the flanges (202, 203) are bonded together in a spaced and substantially parallel relation by means of one or more corrugated edge toothed sheet metal strips (204) which are provided with penetration stoppers (205) , the penetration stoppers preven¬ ting further penetration of the toothed edges when the strip teeth penetration has reached a predetermined depth, so as to ensure correct parallel relation between the flanges of the finished construction element.

Inventors: FALKENBERG J
Applicants: FALKENBERG J
Application year: 1980
Main classification: E04C3
IPC codes: E04C2, E04C3