METHOD FOR MANUFACTURING A POST AND POST MANUFACTURED ACCORDING TO SAID METHOD

Abstract: A method for manufacturing a polygonal post including a sheet material jacket and reinforcements provided inside same, and post manufactured according to said method. The new method includes the measures of sizing a thin gauge jacket material sheet (1) so as to have the length of the post and a width corresponding to the circumference thereof, sizing a number of sheet material strips (2) so as to have a length at least corresponding to the length of the jacket material sheet (1) and a width essentially corresponding to the width of each side surface of the polygonal post, placing the sheet material strips at a distance from each other along the jacket material sheet, affixing the strips to the jacket material sheet, folding the jacket material sheet and strips together into a polygonal hollow shape and joining the longitudinal edges (4) thereof.

Description: Method for manufacturing a post and post manufactured according to said method. Technical Field of the Invention This invention relates to posts generally and especially to posts of the kind which give way when hit by e.g. a vehicle. Background of the Invention A number of manufacturing methods for the latter kind of post are known. One known method includes the steps of intermittently securing along each intended longitudinal bending line of a sheet metal jacket, a metal rod and subsequently bend the sheet metal over the rods into a polygonal shape and join the opposing edges thereof. This known method includes welding procedures as each rod is intermittently welded to the jacket, the weld spots adapted to form failure or rupture points causing the collapse of the post when it is hit by a car and also on the closing of the longitudinal joint takes place by welding. This means that rust proofing such as galvanising has to take place after the completion of the post. This causes problems as due to the heating during galvanisation, the posts have a tendency to waφ, which means that they have to be checked and straightened after the galvanisation. The jacket material of the known post - in order to be able to yield when hit by a car - preferably should have a low plasticity strength and accordingly be thin. The buckling tendency of this material however, counteracts this and the thickness can not be too much reduced in order to secure the necessary resistance against normal stresses such as wind One important aspect with this invention is to bring about an new method for producing posts especially such posts which have the ability to give way when hit, which method is highly simplified and facilitates the process. In the new process no temperatures causing warping have to be used and neither any rust proofing damaging measures. Another important aspect is to bring about a new post which has an enhanced ability to give way when hit, but during normal load has the necessary stability. Summary of the Invention The method according to the invention involves the steps of sizing a thin material sheet for the intended length and circumference of the post, placing on top of such sheet a number of thicker material strips discretely arranged with gaps between them, affixing the strips to the sheet, rolling the sheet together into polygon shape by causing the sheet portions between the strips to bend, and joining the free edges outside the outermost strips thus forming a hollow polygonal post. The result will be a composite jacket wall with high buckling resistance. The post according to the invention is characterised by a thin jacket material and thicker material strips affixed thereto for forming a polygonal where the doubled sides have more strength and buckling strength and stiffness than the bent jacket sheet material portions between them resulting in a guided rupture function of the said sheet material portions when a vehicle hits the post and a subsequent collapse of the entire post takes place due to a continuing rupture of at least some of the sheet material portions. This makes it possible to give the post a controlled predeterminable retarding resistance effect. Brief Description of the Drawing. The invention will be further described in the following with reference to the attached drawing, wherein; Fig. 1 is a plan view of a jacket material sheet with a number of thicker material strips placed thereon, Fig 2 is a cross section of a manufactured post according to the invention, and Fig 3 is a side view in smaller sale illustrating a preferred arrangement for manufacturing posts according to the invention, Detailed Description of Preferred Embodiments The basic parts of the post to be manufactured is a jacket sheet 1 and a number of strips 2 affixed to the sheet separated from each other. On manufacturing, a thin gauge metal sheet, preferably a steel sheet, is sized and confectioned so its length meets the intended height of the post and its width corresponds to the intended circumference thereof. As most posts are narrowing upwardly, a method related to the manufacturing of such posts will be described although the method, naturally also can be used for posts having a uniform thickness. In fact the method for manufacturing the latter ones is even simpler as the jacket sheet will have parallel edges and the strips be of constant width throughout. On the sheet 1 are placed, manually or by means of a mechanical device, material strips 2, which are thicker than the sheet material used for the jacket and preferably are made of strip steel. The strips are affixed to the sheet material 1. In a preferred embodiment the sheet 1 as well as the strips 2 are galvanised or otherwise corrosion or rust proofed before assembling. In a preferred embodiment the fixation is achieved by means of heat curable or hardening adhesive material or thermoplastics material applied on the sheet material 1 at least along the areas intended for the strips 2 and/or on the underside of the strips 2. After the strips have been placed in appropriate positions, the combination of sheet and strips is heated or otherwise treated, e.g. by ultrasonic devices, in order to cure the adhesive material or soften the plastics material, resulting in an affixing of the strips to the sheet. The sheet and strips unit is then rolled together and in this procedure the sheet material portions 3 between the strips 2 will be bent resulting in the shaping of a polygonal hollow pipe with a number of flat sides. Finally, the longitudinal edges 4 of the sheet 1 are joined in an appropriate way e.g. by folding, bending and squeezing or the like method. It is possible, when using galvanised sheet material and strip steel to achieve an affixation by heating the sheet and strip combination so as to make the zinc melt and join the materials. This method, however, could involve problems by causing warping. In another embodiment the sheet and/or the strips are provided, preferably already on the production thereof, with a coating of thermoplastics type and upon arranging the strips on top of the sheet a rather moderate, i.e. 100 - 250° C heating takes place. The plasticizing of the plastics material followed by a setting thereof results in a very stable connection of the strips to the sheet. Spot welding and riveting could also be used but the cost aspect speaks against such methods. A preferred way of arranging the production described below is regarded to be both cost and production efficient. On a stable table T, which, as shown, is movable by means of stationary rollers R, a first sheet 1 of thin gauge steel sheet. On the sheet 1 are placed in the appropriate positions, the required number of steel strips 2. The length of the strips is preferably, as indicated, somewhat greater than the length of the sheet 1 so that ends 5 project outside the ends of the sheet. If the adhesive method is used the selected type of curable adhesive is spread on the appropriate areas of the sheet and/or on the underside of the strips. If precoated sheets and/or strips are used only the positioning of the strips is necessary. Upon the first sheet 1 with its number of strips 2 placed thereon, a second sheet 1 is placed and a number of strips 2 placed upon it and then a third and fourth sheet with strips up to a pre-set number are stacked upon each other. On stacking the correct positioning of the strips is facilitated by aligning the ends 5 of each added strip 2 with the projecting ends 5 of already positioned strips. As well as on the first sheet and set of strips, the curable or heat hardening adhesive material or coating is provided on the upwardly facing strip receiving side portions of each sheet and/or on the downwardly facing surface of each strip. Over the stack of sheets and strips is placed a flexible airtight cover C e.g. of tarpaulin type and the edges of the cover are pulled down towards the supporting table T surface and in an appropriate way sealingly tightened to the table surface. A vacuum pump is used for evacuating the air inside or below the cover C so that the outside atmospheric pressure, in per se known fashion, is allowed to press the stack downwardly towards the table T and press the strips against their sheets. The heating necessary in most cases can be achieved in several different ways. In one embodiment the entire stack of sheets and strips is heated by hot air before the compression, the air made to pass along the stack and through the multitude of slot like channels formed between each pair of adjoining strips and sheets defining channel top and bottom. In the drawing a special heating or curing enhancing device D shown. After being activated the device is arranged to heat the stack or otherwise bring about a curing as the table T with the stack passes the device. The table T can, naturally, also be stationary and the heating device D movable. As only a comparatively low temperature is needed the heating has no detrimental effect on the stacked material such as warping or bending. After the curing period is over the vacuum is released and the cover C removed. The sheets with affixed strips are then ready for bending and edge joining. The heating of the stack can also be achieved by heating a specific type of stationary table so that the heat dissipates upwardly into the stack. A preferred way of heating is by means of a device D of electromagnetic type shown in the drawing. By utilising inductive heating, the steel material of the sheets 1 and the strips 2 will be heated on the passage of the table T and the compressed stack thereupon between the electromagnetical devices D. The heating, although rather low, of the steel material, will cause the adhesive to cure or harden and thermoplastics material to plasticize, respectively. Another way of causing the necessary heating is by means of ultrasonic devices tuned at the structure of the adhesive or plastics and causing it to cure or soften. Naturally, also self curing or hardening adhesives or sticky sheets may be used as long as the necessary compression of the strips and sheets is ensured. Above is stated that the strips are placed upon the sheet. It is, however, obvious that the method also can be performed the opposite way, i.e. by placing the strips 2 at a set distance from each other on an appropriate table and place the sheet upon the strips. The bending of the sheet with strips affixed thereto and the joining of the longitudinal edges of the sheet takes place in an appropriate per se known device. The joining is preferably a rather conventional folding, bending and squeezing procedure, similar with the procedure used for sheet metal. This method can be used as the thickness or gauge of the sheet is very thin. The resulting post is very stable and able to withstand normal stresses, but will give way when hit by say a vehicle. The giving way ability is achieved thanks to the construction of the post, and more in detail because of the thin bent corner portions joining the intermediary flat areas stabilised by the strips. It is very important that the forces influencing a post are transferred to the ground in an appropriate way so that the root end of the post is off-loaded detrimental forces. To secure an even distribution of stress a short end or stub of a steel pipe or the like, normally is inserted into the root end portion intended to be received into a foundation. The strip ends projecting outside the end of the sheet metal jacket are preferably welded to such pipe stub.

Claims: CLAIMS 1. Method for manufacturing a polygonal post including a sheet material jacket and reinforcements provided inside same, c h a r a c t e r i z e d in that it includes the measures of sizing a thin gauge jacket material sheet (1) so as to have a length essentially corresponding to the intended height of the post and a width essentially corresponding to that of the intended circumference of the post, sizing a number of sheet material strips (2) preferably of thicker gauge material so as to have a length at least corresponding of the length of the jacket material sheet (1) and a width essentially corresponding but not exceeding the intended width of each side surface of the polygonal post, providing an triggerable affixing adhesive substance at the face of the jacket material sheet (1) and/or the one face of the sheet material strips (2), placing the sheet material strips at a distance from each other along the jacket material sheet, triggering the affixing adhesive substance in order to secure the strips to the jacket material sheet, folding the jacket material sheet together by bending same along the elongated portions (3) separating the strips (2) into a polygonal hollow shape and joining the longitudinal edges (4) of the jacket material sheet (1) to form a closed polygonal post unit. 2. Method according to claim ^characterized in shaping the jacket material sheet (1) so as to have a decreasing width towards it one end and shaping each of the strips (2) so as to have a correspondingly decreasing width towards it one end. 3. Method according to claim 1 or 2, characterized in selecting an adhesive affixing substance, which is activatable or curable by allowing it to be influenced by an external means. 4. Method according to claim ^characterized in, selecting as jacket sheet material a thin gauge steel sheet material, and as strip material a steel sheet material at least as thick as and preferably thicker than the jacket sheet material. 5. Method according to claim ^characterized in selecting as adhesive affixing substance, a substance able to cure when under the influence of heat. 6. Method according to claim ^characterized in that a number of sized jacket sheet material pieces (1), each with a set of sized sheet material strips (2) and with affixing adhesive substance arranged between the jacket sheet material piece and each strip, are stacked the one upon the other up to a predetermined height, that the stack resting on an airtight support (T) is covered by a flexible, air tight cover (C), together with the support forming an air tight enclosure, that the air is evacuated from the interior of the enclosure in a per se way to cause the atmospheric pressure to compress the stack of sheet pieces and set of strips, that a triggering means (D) influencing the adhesive affixing substance is made active to bring about a permanent amalgamation between the jacket sheet pieces (1), and the sets of strips (2), that the stack is uncovered, each sheet piece with a set of strips secured thereto is separated from the other such pieces, bent or folded together and having its longitudinal edges (4) joined to form a hollow post unit. 7. Polygonal post having a sheet material jacket and internal stiffening means, characterized in, that the jacket sheet (1 ) material is a thin gauge foldable metal material, that the stiffening means are constituted by elongated strips (2) of thicker gauge sheet metal material having a width smaller than the internal width of each side of the polygonal post and that the elongated strips (2) each having a length at least corresponding to the length of the jacket sheet material are affixed to the said sides of the post leaving at each corner of the post an uncovered portion (3) of the jacket sheet material. 8. Polygonal post according to claim 7, characterized in that the width of the jacket sheet material in its unfolded state is decreasing towards its one end and that each of the strips has a width also decreasing towards the one end of the strip. 9. Post according to claim 7 or 8, characterized in that the elongated strips (2) are affixed to the face of the jacket material (1) sides facing inwardly. 10. Post according to claim 8 or 9, characterized in that the end portions (5) of the strips (2) extend beyond the jacket sheet material (1) at the lower end of the post and form connections means for securing a pipe stub thereto.

Inventors: SVENSSON LARS, SVENSSON, LARS
Applicants: SVENSSON LARS, SVENSSON, LARS
Application year: 1998
Main classification: E01F9
IPC codes: B21C37, E01F9, E04H12