Screw for mounting sandwich panels on a supporting wooden substructure

Abstract

A screw (1) for mounting sandwich panels on a supporting wooden substructure, comprising a screw head (5) and a screw shaft (15), at the end of which a screw tip (50) is formed opposite the screw head (5), and a thread (41) extends at least partially along the screw shaft (15), wherein the screw head (5) and the adjoining screw shaft (15) are made of stainless steel, and the screw tip (50) and a short section of the overlying screw shaft (15) are made of carbon steel and are welded to the overlying stainless steel screw shaft (15), characterized in that the transition between the screw shaft (15) and the screw tip (50) is formed by a conical shoulder (45),which widens the core diameter (d3) of the screw shaft (15) in the region of a threaded section (40) to the diameter (d4) of an annular collar (46) adjoining below the conical shoulder (45).

Description

The invention relates to a screw for mounting sandwich panels on a supporting substructure made of wood.PRIOR ARTWhen assembling sandwich panels on a supporting substructure, the fastening means are subject to the most difficult requirements, since these are faced with a wide variety of materials. On the one hand, the sandwich panel has a metallic shell around its insulating material core. On the other hand, the supporting substrate can have a further characteristic different from the other materials. For example, when the supporting base is a wood construction. If several working steps are to be dispensed with, i.e. no pre-drilling is possible, a screw used for mechanical fastening must be suitable for penetration of metal and wood.In addition, further requirements regarding corrosion resistance are also required. The penetration of certain materials leads to abrasion of the corrosion protection layer surrounding the screws, so that a merely coated and pure carbon steel screw would be subject to premature corrosion attack.DE 10 2012 215 645 C5 describes a bi-metal screw. This consists of a screw head and a screw shank, at the end of which opposite the screw head a screw tip is formed and a thread extends at least partially on the screw shank. While the screw head and the screw shank adjoining it are made of stainless steel, the screw tip with a short piece of the screw shank consists of carbon steel and is welded to the screw shank made of stainless steel lying above it. It is thus possible to combine a hardened screw tip with improved cutting and drilling performance in a screw, so that the corrosion resistance of the screw is given in a desired section and the drill tip enables penetration and anchoring in materials which a pure stainless steel screw could not afford.In order to obtain the best possible drilling performance, a two-start thread formation is selected in the known screws, wherein different types of thread may engage in the different materials. This can lead to the insulation material located in the sandwich profile being attacked too much. In the case of screws with different thread geometries, the thread leading during screwing in is generally predominant. This can have a disadvantageous effect on the holding or anchoring force in the other materials.TASKThe object of the present invention is to propose a screw by means of which the disadvantages indicated of the known screws for this purpose are eliminated. In particular, the proposed screw is intended to allow it to penetrate all the materials to be penetrated without deforming, tearing or excessively compressing them, so that an optimum anchoring effect is achieved in all the components.This object is achieved by a screw according to the proposed claim 1.ADVANTAGES OF THE INVENTIONAccording to the invention, a screw for mounting sandwich panels on a supporting substructure made of wood is proposed, comprising a screw head and a screw shank, at the end of which opposite the screw head a screw tip is formed and a thread extends at least partially on the screw shank, wherein the screw head and the screw shank adjoining the latter are made of stainless steel, and the screw tip and a short piece of the screw shank lying above it are made of carbon steel and are welded to the screw shank lying above it made of stainless steel.The invention is distinguished in that the transition between the screw shank and the screw tip is formed by a conical shoulder which widens the core diameter of the screw shank in the region of a threaded section towards the diameter of an annular collar adjoining below the conical shoulder.The invention allows the use of the screw in substrates which consist of different materials and therefore place differentiated requirements on the screw, which are now fulfilled by the screw according to the invention.The widening at the end of the tip also widens the pre-screwed hole and reduces the screwing-in force, since the core of the thread no longer has any points of contact.The tip geometry according to the invention ensures rapid screwing into sheet metal and reduced splitting action in the wood, wherein the thread geometry in the lower region ensures good retention in the wood and thus higher extraction values. The screw can be screwed into wood as well as into steel or light metal without producing chips. This eliminates the need for roof cleaning.A particular advantage of the invention is that the screw shank is divided into the following functional sections: a neck section starts directly under the screw head, which neck section is adjoined by a thread-free section and which neck section is adjoined by a thread section, which in turn is adjoined by the shank tip. The functional sections can be equipped with different performance features.It has been found to be particularly advantageous if a supporting thread is arranged on the neck portion, whereby a good hold in the sheet metal and a step safety are effected.The invention advantageously provides that the transition between the neck portion and the thread-free portion is formed by a conical shoulder which widens the core diameter of the neck portion towards the diameter of the thread-free portion, wherein the further course has a particular significance by providing that the transition between the thread-free portion and the thread portion lying thereunder is formed by a further conical shoulder which in turn reduces the diameter of the thread-free portion towards the core diameter of the thread portion.In a sandwich panel, the thread-free section with the larger diameter then comes to lie in the region of the insulating material, wherein the drilled-up insulating material is compacted again in this region.The invention provides that the thread extending over the threaded section and the screw tip is a continuous wood thread. A wood thread has a flank angle of 40° by default and a greater thread pitch than a sheet metal thread. Damage to the wood is thereby avoided and an optimum anchoring force is achieved. According to the invention, the thread is of single-start design, which has a material-saving effect on the anchoring substrates and, in addition, improves the anchoring property.It is preferably provided that the screw tip carries a mandrel at its front outlet. The sheet is thereby grained at its surface and the grooving performance of the screw tip is supported.Further advantages and advantageous embodiments of the invention can be derived from the following description, the drawing and the claims. There are various possibilities for advantageously configuring and further developing the teaching of the present invention. For this purpose, reference is made on the one hand to the subordinate claims and on the other hand to the following explanation of an exemplary embodiment of the invention on the basis of the drawing.EMBODIMENTIn conjunction with the explanation of the preferred exemplary embodiment of the invention on the basis of the drawing, preferred embodiments and developments of the teaching are also generally explained.In the drawing, the following are shown: FIG. 1 shows the screw according to the invention in a side view, FIG. 2 shows an enlargement of the screw between the screw head with the upper supporting thread and the non-threaded section, FIG. 3 shows an enlargement of the screw at the transition between the non-threaded section and the lower threaded section, FIG. 4 shows the screw tip FIG. 5 is a top view of the screw head; and FIG. 6 shows an installation situation.The screw denoted in its entirety by 1 has a screw head 5 and a screw shank 15, which in turn is divided into individual functional sections. These are a neck section 20 adjoining immediately below the screw head 5 and having a supporting thread 21, and the screw shank 15 continues at the lower end of the supporting thread 21 with a thread-free section 30. The transition between the neck portion 20 and the non-threaded portion 30 forms a frustoconical shoulder 25 so that the core diameter d 1 of the neck portion 20 increases slightly towards the diameter d 2 of the non-threaded portion 30.The length of the non-threaded portion 30 depends on the profile thicknesses of the structural elements encountered in the construction object. Accordingly, the overall length of the screw 1 according to the invention is selected such that the next functional section comes into effect. In the present case, this is a threaded section 40 with a single-start thread 41 which adjoins below the thread-free section and is therefore a wood thread and has a relatively large pitch and a flank angle of approximately 40°. The transition between the unthreaded section 30 and the threaded section 40 again forms a frustoconical shoulder 35, wherein the diameter d 2 again reduces toward the core diameter d 3 of the threaded section 40.The threaded section 40 carries the continuous thread 41, which also extends over the screw tip 50 arranged at the end opposite the screw head 5.The transition between the threaded portion 40 and the screw tip 50 forms a further frustoconical shoulder 45, the collar 46 lying below the shoulder 45 having a larger diameter d 4 than the core diameter d 3 of the threaded portion 40.The screw tip 50 terminates conically as far as the end and is surrounded by the thread 41 which is continued above it, the thread diameter of which continuously decreases. Slightly above the shoulder 45, at the dotted parting line marked "T", is the weld where the carbon steel screw shank and the stainless steel shank are joined together. In order to be able to cure the screw tip, this section is made of carbon steel, while the fraction lying above it, including the screw head, consists of stainless steel.In summary, the screw 1 according to the invention consists of the screw head 5, the screw shank 15 with its described functional sections and the screw tip 50.In this exemplary embodiment, the screw head 5 has an external hexagonal force drive with a load distribution disk 6 formed on the bottom side of the head. However, other suitable force application points are also possible here, such as an internal drive in the form of a Torx bed.The screw 1 according to the invention does not produce any chips, but continuously expands the hole produced when it penetrates into the metal. A drilling power is also generated in the wood, which leads to a sudden increase in the anchoring force.FIG. 6 shows an installation situation of the screw 1 according to the invention. A sandwich panel 60 rests on a wood carrier 70. The sandwich panel 60 has a metal shell 61, 62 which surrounds an insulating core 63, usually a hard foam.The sandwich panel 60 has a trapezoidal cross section with alternating high beads 64 and low beads 65. The shell 61, 62 can consist of aluminum or else of steel sheet, each of which makes a different requirement for the screw used. Although the insulating core 63 does not require any drilling performance of the screw, it is intended to avoid the possibility of the insulating material being retanned or ground as much as possible, since the particles then produced could escape from the drilling site or impair the property of the thread 41. According to the invention, the screw tip 50 which leads during the screwing process has the same drilling performance and displacement performance when passing through the high bead as is the case when it hits the lower shell 62. The penetration of the metallic shell 61, 62 takes place without machining, so that the entry into the underlying wood carrier can take place without impairment. That is, no drill chips are dragged along.LIST OF REFERENCE CHARACTERS1 Screw 5 Screw head 6 Load distribution disk of 5 15 Screw shank 20 Neck portion 21 Supporting thread on 20 25 Shoulder between 20 and 30 30 Non-threaded portion 35 Shoulder between 30 and 40 Threaded portion 41 Thread on 40 45 Shoulder between 40 and 50 46 Collar between 40 and 50 Screw tip 51 Mandrel on 50 60 Sandwich panel 61 Shell of 60 62 Shell of 60 63 Insulating core of 60 64 High bead of 60 65 Low bead of 60 70 Wood carrier d 1 Core diameter of 20 d 2 Diameter of 30 d 3 Core diameter of 40 d 4 Diameter of 46 T Parting line between carbon steel and stainless steelReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2012 215 645 C5

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Claims

A screw (1) for mounting sandwich panels on a supporting substructure made of wood, comprising a screw head (5) and a screw shank (15), at the end of which opposite the screw head (5) a screw tip (50) is formed and a thread (41) extends at least partially on the screw shank (15), wherein the screw head (5) and the screw shank (15) adjoining the latter are made of stainless steel, and the screw tip (50) and a short piece of the screw shank (15) lying above it are made of carbon steel and is welded to the screw shank (15) lying above it made of stainless steel, characterized in that the transition between the screw shank (15) and the screw tip (50) is formed by a conical shoulder (45), which widens the core diameter (d 3) of the screw shank (15) in the region of a threaded section (40) towards the diameter (d 4) of an annular collar (46) adjoining below the conical shoulder (45).Screw (1) according to claim 1, characterised in that the screw shank (15) is divided into the functional sections neck section (20), thread-free section (30) and the threaded section (40), which is adjoined by the shank tip (50).Screw (1) according to Claims 1 and 2, characterized in that a supporting thread (21) is arranged on the neck portion (20).Screw (1) according to claims 1 to 3, characterised in that the transition between the neck portion (20) and the thread-free portion (30) is formed by a conical shoulder (25) which widens the core diameter (d 1) of the neck portion (20) towards the diameter (d 2) of the thread-free portion (30).Screw (1) according to claims 1 to 3, characterised in that the transition between the thread-free section (30) and the thread section (40) is formed by a conical shoulder (35), which reduces the diameter (d 2) of the thread-free section (30) towards the core diameter (d 3) of the thread section (40).Screw (1) according to claims 1 to 5, characterised in that the thread (41) extending over the threaded section (40) and the screw tip (50) is a continuous wood thread.Screw (1) according to claim 6, characterised in that the thread (41) is of single-start designScrew (1) according to claims 1 to 7, characterised in that the screw tip (50) carries a pin (51) at its front outlet.

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