WO2012084385A1 - Screw anchor - Google Patents

Screw anchor Download PDF

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Publication number
WO2012084385A1
WO2012084385A1 PCT/EP2011/070737 EP2011070737W WO2012084385A1 WO 2012084385 A1 WO2012084385 A1 WO 2012084385A1 EP 2011070737 W EP2011070737 W EP 2011070737W WO 2012084385 A1 WO2012084385 A1 WO 2012084385A1
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WO
WIPO (PCT)
Prior art keywords
screw anchor
thread
cutting spring
screw
spring
Prior art date
Application number
PCT/EP2011/070737
Other languages
German (de)
French (fr)
Inventor
Falk Rosenkranz
Isaiah Freerksen
Ralf Zitzmann
Original Assignee
Hilti Aktiengesellschaft
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hilti Aktiengesellschaft filed Critical Hilti Aktiengesellschaft
Publication of WO2012084385A1 publication Critical patent/WO2012084385A1/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16B—DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING
    • F16B37/00—Nuts or like thread-engaging members
    • F16B37/12—Nuts or like thread-engaging members with thread-engaging surfaces formed by inserted coil-springs, discs, or the like; Independent pieces of wound wire used as nuts; Threaded inserts for holes
    • F16B37/122—Threaded inserts, e.g. "rampa bolts"
    • F16B37/125—Threaded inserts, e.g. "rampa bolts" the external surface of the insert being threaded
    • F16B37/127—Threaded inserts, e.g. "rampa bolts" the external surface of the insert being threaded and self-tapping
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16B—DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING
    • F16B25/00—Screws that cut thread in the body into which they are screwed, e.g. wood screws
    • F16B25/001—Screws that cut thread in the body into which they are screwed, e.g. wood screws characterised by the material of the body into which the screw is screwed
    • F16B25/0026—Screws that cut thread in the body into which they are screwed, e.g. wood screws characterised by the material of the body into which the screw is screwed the material being a hard non-organic material, e.g. stone, concrete or drywall
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16B—DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING
    • F16B25/00—Screws that cut thread in the body into which they are screwed, e.g. wood screws
    • F16B25/0036—Screws that cut thread in the body into which they are screwed, e.g. wood screws characterised by geometric details of the screw
    • F16B25/0094—Screws that cut thread in the body into which they are screwed, e.g. wood screws characterised by geometric details of the screw the screw being assembled or manufactured from several components, e.g. a tip out of a first material welded to shaft of a second material

Definitions

  • the invention relates to a screw anchor, in particular for screwing in concrete.
  • Screw anchors are known from the prior art, which have a threaded shaft.
  • the thread is intended to cut into the wall of a hole in concrete or a similar material, so that an undercut is formed, can be derived directly from the loads (ie without intermediate dowel or other components) in the ground. So that the thread of the screw anchor can reliably cut into the concrete, the hardness on the surface of the screw anchor must be on the order of 650 HV or above.
  • a screw anchor made of a low carbon steel is carbonitrided and quenched. In this way, the necessary hardness is achieved. Subsequently, the screw anchor is stress annealed to reduce or eliminate the stresses generated during quenching.
  • the disadvantage of this method is that the boron, which is contained in the steel, causes a high hardness in the core. In particular, a hardness above 330 HV results in the core of the shaft. This hardness leads to a high risk of hydrogen embrittlement.
  • the screw anchor which consists of a low-carbon steel, is carbonitrided and quenched. Then, the blanks are annealed at a comparatively high temperature to lower the hardness of the screw throughout the shank to a uniform value. Subsequently, the tip of the anchor is induction hardened and quenched to achieve the necessary hardness for cutting the thread into the concrete.
  • This method has the disadvantage that it takes a relatively long time due to the tempering of the material and the overall effort is relatively high, since induction hardening requires an additional process step. However, such a screw anchor is less susceptible to hydrogen embrittlement.
  • the applicant discloses a fastening system known as "coil anchor” which includes a concrete screw and a spring attachment which is placed on the top of the concrete screw Tighten the screw, pressing the spring attachment against the wall of the bore.
  • the object of the invention is to provide a screw anchor, which is characterized by low production costs and high performance.
  • a screw anchor with a head, a shank and a thread at the end facing away from the head end of the shaft is provided according to the invention, and with a cutting spring which is at least partially screwed onto the thread.
  • the invention is based on the idea of not producing the undercut of a screw anchor by the thread of the screw anchor itself, but by the cutting spring, which cuts into the wall of the bore when screwing the screw anchor. This allows to perform only the cutting spring with the necessary hardness.
  • the actual screw anchor must be subjected to no heat treatment and can therefore consist of a cheaper material.
  • the thread corresponds to a maximum of twice the length of the cutting spring. It has been found that even a very short thread is sufficient to accommodate the cutting spring at the front end of the screw. This results in lower production costs, since only a small part of the shaft must be threaded.
  • the thread tapers conically towards the tip. This ensures that the cutting spring is spread apart when screwing the screw anchor and thus can cut very well into the wall of the bore.
  • the shaft consists of an unhardened steel. This reduces the risk of hydrogen embrittlement.
  • the cutting spring made of hardened steel. This leads to a very high surface hardness, so that the Cutter spring can cut reliably into the wall of the bore and there forms the undercut, which is necessary for load transfer.
  • the cutting spring on about three turns. This embodiment is based on the recognition that even very few Wnditch the cutting spring sufficient to transfer the loads with the desired reliability can.
  • the cutting spring has a teardrop-shaped cross-section, wherein the tip of the teardrop-shaped cross-section points outwards.
  • a cross-sectional shape has been found to be particularly favorable, since on the inside of the cutting spring a uniformly rounded cross section is available, which is suitable for uniform load transfer to the screw anchor, and on the other hand on the outside of the cutting spring a comparatively sharp cross section comparable to Burr of a thread is present, which cuts well into the ground, for example in concrete.
  • the drop-shaped cross section of the cutting spring can have a symmetrical shape with respect to an axis of symmetry; Alternatively, however, a shape is possible which deviates from the symmetrical shape.
  • the tip of the teardrop-shaped cross-section is inclined away from the axis of symmetry.
  • Figure 1 shows a schematic cross section of a screw anchor invention with cutting spring
  • Figure 2 shows schematic cross sections of the cutting spring.
  • FIG. 1 shows a screw anchor 10 which has a head 12 and a shaft 14.
  • a thread 16 is provided, which is formed catchy and in which each thread, viewed in cross section, has a circular-segment-shaped shape.
  • the end of the shaft 14 facing away from the head is conical, so that the thread 16 extends from the conical section to the cylindrical part of the shaft 14.
  • the thread 16 is for the most part on the conical portion of the shaft, and the total thread is shorter than the total length of the shaft. In particular, the thread 16 extends over less than half of the shaft 14.
  • a cutting spring 18 is arranged, which is similar to its structure of a cylindrical coil spring. The cutting spring 18 is much shorter than the shank of the screw anchor 10 and in particular shorter than the thread 16. In the embodiment shown, the cutting spring 18 three turns, while the thread 16 has about six threads.
  • the cutting spring 18 has a teardrop-shaped cross section, with the tip of the teardrop-shaped cross section facing outward. Thus, located on the inside of each turn a circular section-shaped surface whose dimensions are adapted to the dimensions of the threads of the thread 16.
  • the inner diameter of the cutting spring 18 is chosen so that the cutting spring 18 can be screwed one to two threads on the thread 16, but then it comes to a slight jamming.
  • the bolt 10 is preferably made of kaltverform ble steel and is made by mechanical forming.
  • the thread 16 is rolled.
  • a heat treatment is not required.
  • the cutting spring 18 is made of a hardenable stainless steel and is hardened so that its surface has the necessary surface hardness for cutting into concrete or a similar substrate. Suitable hardness values are in the order of 600 HV. But it is also possible to use galvanized carbon steel.
  • the coil spring 18 is shown in various embodiments.
  • FIGS. 2 a) and b) show the cross section of a cutting spring 18 with a symmetrical geometry with respect to the axis of symmetry 22, wherein the tip in FIG. 2 a) is concave and convex in FIG. 2 b).
  • Figure 2 c) shows a cutting spring 18, wherein the cross section has a different geometry from the symmetrical shape.
  • the tip of the spring is no longer on the axis of symmetry 22nd
  • the screw anchor 10 can be inserted with arranged at its tip cutting spring 18 in a well 20 schematically shown here. Then, when the screw anchor 10 is rotated inside the borehole 20, the cutting spring 18 screws onto the thread 16. She is braced against the concrete. Due to the friction between the cutting spring 18 and the wall of the borehole 20, the cutting spring 18 initially remains in its position, so that the screw anchor 10 is screwed into the cutting spring 18. Only when the cutting spring 18 is screwed a certain distance on the thread 16, it reaches a point at which it is prevented by the thread 16 on further screwing. From this point, the cutting spring 18 rotates during further screwing the bolt 10 together with this, so that the now expanded and tensioned against the concrete cutting spring 18 cuts into the wall of the borehole 20 and there forms a mating thread with strong undercut.
  • the screw anchor described allows high payloads even in cracked concrete, as the loads are transmitted with a pronounced undercut very deep in the hole. Such an undercut can not be achieved with a conventional concrete screw, since such a concrete screw whose outer diameter would have to be very large in relation to the borehole, would not cut at the borehole mouth. In addition, such a concrete screw with such a large ratio of outer diameter to core diameter would not be economically produced.
  • the described screw anchor with cutting spring with comparatively little effort to produce, since only the cutting spring 18 must be subjected to a heat treatment.
  • the screw anchor 10 can be prepared by conventional cold forming. This also means that there is no risk of hydrogen embrittlement in the shank area of the screw anchor, since it is not hardened.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Geometry (AREA)
  • Dowels (AREA)
  • Joining Of Building Structures In Genera (AREA)

Abstract

The invention relates to a screw anchor (10) having a head (12), a shaft (14), and a thread (16) on the end of the shaft (14) facing away from the head, and a cutting spring (18) threaded onto the thread (16) at least in segments.

Description

Schraubanker  Screw
Die Erfindung betrifft einen Schraubanker, insbesondere zum Einschrauben in Beton. The invention relates to a screw anchor, in particular for screwing in concrete.
Aus dem Stand der Technik sind Schraubanker bekannt, die einen mit einem Gewinde versehenen Schaft aufweisen. Das Gewinde ist dafür vorgesehen, sich in die Wandung einer Bohrung in Beton oder einen vergleichbaren Werkstoff einschneiden, so dass ein Hinterschnitt gebildet ist, über den Lasten unmittelbar (also ohne zwischengeschalteten Dübel oder andere Bauteile) in den Untergrund abgeleitet werden können. Damit das Gewinde des Schraubankers sich zuverlässig in den Beton einschneiden kann, muss die Härte an der Oberfläche des Schraubankers in der Größenordnung von 650 HV oder darüber liegen. Screw anchors are known from the prior art, which have a threaded shaft. The thread is intended to cut into the wall of a hole in concrete or a similar material, so that an undercut is formed, can be derived directly from the loads (ie without intermediate dowel or other components) in the ground. So that the thread of the screw anchor can reliably cut into the concrete, the hardness on the surface of the screw anchor must be on the order of 650 HV or above.
Im Stand der Technik sind insbesondere zwei Verfahren bekannt, um die gewünschte Härte zu erzielen. Bei einem Verfahren wird ein Schraubanker, der aus einem Stahl mit geringem Kohlenstoffgehalt besteht, carbonitriert und abgeschreckt. Auf diese Weise wird die nötige Härte erzielt. Anschließend wird der Schraubanker entspannungsgeglüht, um die beim Abschrecken entstehenden Spannungen zu verringern oder zu beseitigen. Der Nachteil dieses Verfahrens besteht darin, dass das Bor, das im Stahl enthalten ist, eine hohe Härte im Kern hervorruft. Insbesondere ergibt sich im Kern des Schafts eine Härte oberhalb von 330 HV. Diese Härte führt zu einem hohen Risiko von Wasserstoffversprödung. In the prior art, in particular, two methods are known in order to achieve the desired hardness. In one method, a screw anchor made of a low carbon steel is carbonitrided and quenched. In this way, the necessary hardness is achieved. Subsequently, the screw anchor is stress annealed to reduce or eliminate the stresses generated during quenching. The disadvantage of this method is that the boron, which is contained in the steel, causes a high hardness in the core. In particular, a hardness above 330 HV results in the core of the shaft. This hardness leads to a high risk of hydrogen embrittlement.
Bei einem anderen Verfahren wird der Schraubanker, der aus einem Stahl mit niedrigem Kohlstoffgehalt besteht, carbonitriert und abgeschreckt. Dann werden die Rohlinge bei einer vergleichsweise hohen Temperatur geglüht, um die Härte der Schraube im gesamten Schaft auf einen einheitlichen Wert abzusenken. Anschließend wird die Spitze des Ankers induktionsgehärtet und abgeschreckt, um dort die nötige Härte zum Einschneiden des Gewindes in den Beton zu erzielen. Dieses Verfahren hat den Nachteil, dass es aufgrund des Anlassens des Materials relativ lang dauert und der Aufwand insgesamt relativ hoch ist, da mit dem Induktionshärten ein zusätzlicher Verfahrensschritt nötig ist. Allerdings ist ein solcher Schraubanker wenig anfällig für Wasserstoffversprödung. In another method, the screw anchor, which consists of a low-carbon steel, is carbonitrided and quenched. Then, the blanks are annealed at a comparatively high temperature to lower the hardness of the screw throughout the shank to a uniform value. Subsequently, the tip of the anchor is induction hardened and quenched to achieve the necessary hardness for cutting the thread into the concrete. This method has the disadvantage that it takes a relatively long time due to the tempering of the material and the overall effort is relatively high, since induction hardening requires an additional process step. However, such a screw anchor is less susceptible to hydrogen embrittlement.
Von der Anmelderin ist ein Befestigungssystem bekannt, das unter der Bezeichnung„Coil Anchor" vertrieben wird. Dieses enthält eine Betonschraube und einen Federvorsatz, der auf die Spitze der Betonschraube aufgesetzt wird. Nachdem die Betonschraube mit dem Federvorsatz in eine Bohrung eingesetzt wird, wird die Schraube festgezogen. Dabei wird der Federvorsatz gegen die Wandung der Bohrung gedrückt. The applicant discloses a fastening system known as "coil anchor" which includes a concrete screw and a spring attachment which is placed on the top of the concrete screw Tighten the screw, pressing the spring attachment against the wall of the bore.
Die Aufgabe der Erfindung besteht darin, einen Schraubanker zu schaffen, der sich durch geringe Herstellungskosten und hohe Leistungen auszeichnet. Zur Lösung dieser Aufgabe ist erfindungsgemäß ein Schraubanker mit einem Kopf, einem Schaft und einem Gewinde am vom Kopf abgewandten Ende des Schafts vorgesehen, und mit einer Schneidfeder, die zumindest abschnittsweise auf das Gewinde aufgeschraubt ist. Die Erfindung beruht auf dem Grundgedanken, den Hinterschnitt eines Schraubankers nicht durch das Gewinde des Schraubankers selbst zu erzeugen, sondern von der Schneidfeder, die sich beim Einschrauben des Schraubankers in die Wandung der Bohrung einschneidet. Dies ermöglicht, nur die Schneidfeder mit der hierfür nötigen Härte auszuführen. Der eigentliche Schraubanker muss keiner Wärmebehandlung unterzogen werden und kann daher aus einem günstigeren Material bestehen kann. The object of the invention is to provide a screw anchor, which is characterized by low production costs and high performance. To achieve this object, a screw anchor with a head, a shank and a thread at the end facing away from the head end of the shaft is provided according to the invention, and with a cutting spring which is at least partially screwed onto the thread. The invention is based on the idea of not producing the undercut of a screw anchor by the thread of the screw anchor itself, but by the cutting spring, which cuts into the wall of the bore when screwing the screw anchor. This allows to perform only the cutting spring with the necessary hardness. The actual screw anchor must be subjected to no heat treatment and can therefore consist of a cheaper material.
Vorzugsweise ist vorgesehen, dass das Gewinde maximal der zweifachen Länge der Schneidfeder entspricht. Es hat sich herausgestellt, dass bereits ein sehr kurzes Gewinde ausreichend ist, um am vorderen Ende des Schraubankers die Schneidfeder aufzunehmen. Hieraus resultieren geringere Herstellungskosten, da nur ein kleiner Teil des Schafts mit dem Gewinde versehen werden muss. It is preferably provided that the thread corresponds to a maximum of twice the length of the cutting spring. It has been found that even a very short thread is sufficient to accommodate the cutting spring at the front end of the screw. This results in lower production costs, since only a small part of the shaft must be threaded.
Gemäß einer bevorzugten Ausführungsform ist vorgesehen, dass das Gewinde zur Spitze hin konisch zuläuft. Dies gewährleistet, dass die Schneidfeder beim Einschrauben des Schraubankers aufgespreizt wird und sich dadurch besonders gut in die Wandung der Bohrung einschneiden kann. According to a preferred embodiment it is provided that the thread tapers conically towards the tip. This ensures that the cutting spring is spread apart when screwing the screw anchor and thus can cut very well into the wall of the bore.
Vorzugsweise ist vorgesehen, dass der Schaft aus einem ungehärteten Stahl besteht. Dies verringert das Risiko einer Wasserstoffversprödung. Gemäß der bevorzugten Ausführungsform ist vorgesehen, dass die Schneidfeder aus gehärtetem Stahl besteht. Dies führt zu einer sehr hohen Oberflächenhärte, sodass sich die Schneidfeder zuverlässig in die Wandung der Bohrung einschneiden kann und dort den Hinterschnitt ausbildet, der zur Lastübertragung notwendig ist. It is preferably provided that the shaft consists of an unhardened steel. This reduces the risk of hydrogen embrittlement. According to the preferred embodiment it is provided that the cutting spring made of hardened steel. This leads to a very high surface hardness, so that the Cutter spring can cut reliably into the wall of the bore and there forms the undercut, which is necessary for load transfer.
Gemäß einer Ausgestaltung der Erfindung weist die Schneidfeder etwa drei Windungen auf. Diese Ausgestaltung beruht auf der Erkenntnis, dass bereits sehr wenige Wndungen der Schneidfeder ausreichen, um die Lasten mit der gewünschten Zuverlässigkeit übertragen zu können. According to one embodiment of the invention, the cutting spring on about three turns. This embodiment is based on the recognition that even very few Wndungen the cutting spring sufficient to transfer the loads with the desired reliability can.
Gemäß der bevorzugten Ausführungsform der Erfindung ist vorgesehen, dass die Schneidfeder einen tropfenförmigen Querschnitt hat, wobei die Spitze des tropfenförmigen Querschnitts nach außen weist. Eine solche Querschnittsform hat sich als besonders günstig herausgestellt, da zum einen auf der Innenseite der Schneidfeder ein gleichmäßig abgerundeter Querschnitt zur Verfügung steht, der zu gleichmäßigen Lastübertragung zum Schraubanker hin geeignet ist, und zum anderen auf der Außenseite der Schneidfeder ein vergleichsweise scharfer Querschnitt vergleichbar dem Grat eines Gewindes vorhanden ist, der sich gut in den Untergrund einschneidet, beispielsweise in Beton. Der tropfenförmige Querschnitt der Schneidfeder kann dabei eine bzgl. einer Symmetrieachse symmetrische Form aufweisen; alternativ ist jedoch auch eine Form möglich, die von der symmetrischen Form abweicht. Bevorzugt, indem die Spitze des tropfenförmigen Querschnitts von der Symmetrieachse weggeneigt ist. According to the preferred embodiment of the invention it is provided that the cutting spring has a teardrop-shaped cross-section, wherein the tip of the teardrop-shaped cross-section points outwards. Such a cross-sectional shape has been found to be particularly favorable, since on the inside of the cutting spring a uniformly rounded cross section is available, which is suitable for uniform load transfer to the screw anchor, and on the other hand on the outside of the cutting spring a comparatively sharp cross section comparable to Burr of a thread is present, which cuts well into the ground, for example in concrete. The drop-shaped cross section of the cutting spring can have a symmetrical shape with respect to an axis of symmetry; Alternatively, however, a shape is possible which deviates from the symmetrical shape. Preferably, the tip of the teardrop-shaped cross-section is inclined away from the axis of symmetry.
Die Erfindung wird nachfolgend anhand einer Ausführungsform beschrieben, die in den beigefügten Zeichnungen dargestellt ist. In diesen zeigen: The invention will be described below with reference to an embodiment shown in the accompanying drawings. In these show:
Figur 1 einen schematischen Querschnitt eines erfindungsgemäßen Schraubankers mit Schneidfeder; Figure 1 shows a schematic cross section of a screw anchor invention with cutting spring;
Figur 2 schematische Querschnitte der Schneidfeder. Figure 2 shows schematic cross sections of the cutting spring.
In Figur 1 ist ein Schraubanker 10 gezeigt, der einen Kopf 12 und einen Schaft 14 aufweist. Am vom Kopf abgewandten Ende des Schafts 14 ist ein Gewinde 16 vorgesehen, welches eingängig ausgebildet ist und bei dem jeder Gewindegang, im Querschnitt betrachtet, eine kreisabschnittsförmige Gestalt hat. Das vom Kopf abgewandte Ende des Schafts 14 ist konisch ausgeführt, sodass sich das Gewinde 16 vom konischen Abschnitt bis auf den zylindrischen Teil des Schafts 14 erstreckt. We in Figur 1 zu sehen ist, befindet sich das Gewinde 16 dabei zum größten Teil auf dem konischen Abschnitt des Schafts, und das Gewinde insgesamt ist kürzer als die Gesamtlänge des Schafts. Insbesondere erstreckt sich das Gewinde 16 über weniger als die Hälfte des Schafts 14. Am Schraubanker 10 ist eine Schneidfeder 18 angeordnet, die von ihrem Aufbau einer zylindrischen Schraubenfeder ähnelt. Die Schneidfeder 18 ist sehr viel kürzer als der Schaft des Schraubankers 10 und insbesondere kürzer als das Gewinde 16. Beim gezeigten Ausführungsbeispiel weist die Schneidfeder 18 drei Windungen auf, während das Gewinde 16 etwa sechs Gewindegänge aufweist. FIG. 1 shows a screw anchor 10 which has a head 12 and a shaft 14. At the end facing away from the head of the shaft 14, a thread 16 is provided, which is formed catchy and in which each thread, viewed in cross section, has a circular-segment-shaped shape. The end of the shaft 14 facing away from the head is conical, so that the thread 16 extends from the conical section to the cylindrical part of the shaft 14. As can be seen in Figure 1, the thread 16 is for the most part on the conical portion of the shaft, and the total thread is shorter than the total length of the shaft. In particular, the thread 16 extends over less than half of the shaft 14. At the screw anchor 10, a cutting spring 18 is arranged, which is similar to its structure of a cylindrical coil spring. The cutting spring 18 is much shorter than the shank of the screw anchor 10 and in particular shorter than the thread 16. In the embodiment shown, the cutting spring 18 three turns, while the thread 16 has about six threads.
Die Schneidfeder 18 weist einen tropfenförmigen Querschnitt auf, wobei die Spitze des tropfenförmigen Querschnitts nach außen weist. Somit befindet sich auf der Innenseite jeder Windung eine kreisabschnittsförmige Fläche, deren Abmessungen an die Abmessungen der Gewindegänge des Gewindes 16 angepasst sind. Der Innendurchmesser der Schneidfeder 18 ist dabei so gewählt, dass die Schneidfeder 18 ein bis zwei Gewindegänge auf das Gewinde 16 aufgeschraubt werden kann, es anschließend jedoch zu einem leichten Verklemmen kommt. The cutting spring 18 has a teardrop-shaped cross section, with the tip of the teardrop-shaped cross section facing outward. Thus, located on the inside of each turn a circular section-shaped surface whose dimensions are adapted to the dimensions of the threads of the thread 16. The inner diameter of the cutting spring 18 is chosen so that the cutting spring 18 can be screwed one to two threads on the thread 16, but then it comes to a slight jamming.
Der Schraubbolzen 10 besteht vorzugsweise aus kaltverform barem Stahl und ist durch mechanisches Umformen hergestellt. Das Gewinde 16 ist dabei gewalzt. Eine Wärmebehandlung ist nicht erforderlich. Die Schneidfeder 18 besteht dagegen aus einem gut härtbaren nichtrostenden Stahl und ist gehärtet, so dass ihre Oberfläche die nötige Oberflächenhärte zum Einschneiden in Beton oder einen ähnlichen Untergrund aufweist. Geeignete Härtewerte liegen in der Größenordnung von 600 HV. Möglich ist aber auch die Verwendung von galvanisch verzinktem C-Stahl. In Figur 2 ist die Schraubfeder 18 in verschiedenen Ausführungsformen gezeigt. So zeigen die Figuren 2 a) und b) den Querschnitt einer Schneidfeder 18 mit einer bzgl der Symmetrieachse 22 symmetrischen Geometrie, wobei die Spitze in Figur 2 a) konkav und in Figur 2 b) konvex ausgebildet ist. Im Gegensatz hierzu zeigt Figur 2 c) eine Schneidfeder 18, bei der der Querschnitt eine von der symmetrischen Form abweichende Geometrie aufweist. Somit liegt die Spitze der Feder nicht mehr auf der Symmetrieachse 22. The bolt 10 is preferably made of kaltverform ble steel and is made by mechanical forming. The thread 16 is rolled. A heat treatment is not required. By contrast, the cutting spring 18 is made of a hardenable stainless steel and is hardened so that its surface has the necessary surface hardness for cutting into concrete or a similar substrate. Suitable hardness values are in the order of 600 HV. But it is also possible to use galvanized carbon steel. In Figure 2, the coil spring 18 is shown in various embodiments. Thus, FIGS. 2 a) and b) show the cross section of a cutting spring 18 with a symmetrical geometry with respect to the axis of symmetry 22, wherein the tip in FIG. 2 a) is concave and convex in FIG. 2 b). In contrast, Figure 2 c) shows a cutting spring 18, wherein the cross section has a different geometry from the symmetrical shape. Thus, the tip of the spring is no longer on the axis of symmetry 22nd
Im Ausgangszustand, wie er in Figur 1 gezeigt ist, kann der Schraubanker 10 mit an seiner Spitze angeordneter Schneidfeder 18 in ein hier schematisch gezeigtes Bohrloch 20 eingeschoben werden. Wenn dann im Inneren des Bohrlochs 20 der Schraubanker 10 gedreht wird, schraubt sich die Schneidfeder 18 auf das Gewinde 16 auf. Dabei wird sie gegen den Beton verspannt. Aufgrund der Reibung zwischen der Schneidfeder 18 und der Wandung des Bohrlochs 20 verbleibt die Schneidfeder 18 zunächst in ihrer Position, so dass der Schraubanker 10 in die Schneidfeder 18 eingeschraubt wird. Erst wenn die Schneidfeder 18 eine bestimmte Strecke auf das Gewinde 16 aufgeschraubt ist, erreicht sie einen Punkt, an welchem sie vom Gewinde 16 am weiteren Aufschrauben gehindert wird. Ab diesem Zeitpunkt dreht sich die Schneidfeder 18 beim weiteren Einschrauben des Schraubbolzens 10 gemeinsam mit diesem, sodass sich die nun aufgeweitete und gegen den Beton verspannte Schneidfeder 18 in die Wandung des Bohrlochs 20 einschneidet und dort ein Gegengewinde mit starkem Hinterschnitt bildet. In the initial state, as shown in Figure 1, the screw anchor 10 can be inserted with arranged at its tip cutting spring 18 in a well 20 schematically shown here. Then, when the screw anchor 10 is rotated inside the borehole 20, the cutting spring 18 screws onto the thread 16. She is braced against the concrete. Due to the friction between the cutting spring 18 and the wall of the borehole 20, the cutting spring 18 initially remains in its position, so that the screw anchor 10 is screwed into the cutting spring 18. Only when the cutting spring 18 is screwed a certain distance on the thread 16, it reaches a point at which it is prevented by the thread 16 on further screwing. From this point, the cutting spring 18 rotates during further screwing the bolt 10 together with this, so that the now expanded and tensioned against the concrete cutting spring 18 cuts into the wall of the borehole 20 and there forms a mating thread with strong undercut.
Der beschriebene Schraubanker ermöglicht hohe Traglasten auch in gerissenem Beton, da die Lasten mit einem ausgeprägten Hinterschnitt sehr tief im Bohrloch übertragen werden. Ein solcher Hinterschnitt kann mit einer herkömmlichen Betonschraube nicht erzielt werden, da eine solche Betonschraube, deren Außendurchmesser sehr groß im Verhältnis zum Bohrloch sein müsste, am Bohrlochmund nicht anschneiden würde. Außerdem wäre eine solche Betonschraube mit einem derart großen Verhältnis von Außendurchmesser zu Kerndurchmesser wirtschaftlich nicht herstellbar. Dagegen ist der beschriebene Schraubanker mit Schneidfeder mit vergleichsweise geringem Aufwand herstellbar, da nur die Schneidfeder 18 einer Wärmebehandlung ausgesetzt werden muss. Der Schraubanker 10 dagegen kann durch herkömmliches Kaltverformen hergestellt werden. Hieraus resultiert auch, dass es kein Risiko von Wasserstoffversprödung im Schaftbereich des Schraubankers gibt, da dieser nicht gehärtet ist. The screw anchor described allows high payloads even in cracked concrete, as the loads are transmitted with a pronounced undercut very deep in the hole. Such an undercut can not be achieved with a conventional concrete screw, since such a concrete screw whose outer diameter would have to be very large in relation to the borehole, would not cut at the borehole mouth. In addition, such a concrete screw with such a large ratio of outer diameter to core diameter would not be economically produced. In contrast, the described screw anchor with cutting spring with comparatively little effort to produce, since only the cutting spring 18 must be subjected to a heat treatment. The screw anchor 10, however, can be prepared by conventional cold forming. This also means that there is no risk of hydrogen embrittlement in the shank area of the screw anchor, since it is not hardened.

Claims

PATENTANSPRUECHE cLAIMS
1. Schraubanker (10) mit einem Kopf (12), einem Schaft (14) und einem Gewinde (16) am vom Kopf abgewandten Ende des Schafts (14), und einer Schneidfeder (18), die zumindest abschnittsweise auf das Gewinde (16) aufgeschraubt ist. 1. screw anchor (10) having a head (12), a shaft (14) and a thread (16) facing away from the head end of the shaft (14), and a cutting spring (18) at least partially on the thread (16 ) is screwed on.
2. Schraubanker nach Anspruch 1 , dadurch gekennzeichnet, dass das Gewinde (16) maximal der zweifachen Länge der Schneidfeder (18) entspricht. 2. Screw anchor according to claim 1, characterized in that the thread (16) corresponds to a maximum of twice the length of the cutting spring (18).
3. Schraubanker nach Anspruch 1 oder Anspruch 2, dadurch gekennzeichnet, dass das Gewinde (16) zur Spitze hin konisch zuläuft. 3. screw anchor according to claim 1 or claim 2, characterized in that the thread (16) tapers towards the tip.
4. Schraubanker nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass der Schaft (14) aus einem ungehärteten Stahl besteht. 4. screw anchor according to one of the preceding claims, characterized in that the shaft (14) consists of an uncured steel.
5. Schraubanker nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass die Schneidfeder (18) aus gehärtetem Stahl besteht. 5. screw anchor according to one of the preceding claims, characterized in that the cutting spring (18) consists of hardened steel.
6. Schraubanker nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass die Schneidfeder (18) etwa drei Windungen aufweist. 6. screw anchor according to one of the preceding claims, characterized in that the cutting spring (18) has approximately three turns.
7. Schraubanker nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass die Schneidfeder (18) einen tropfenförmigen Querschnitt hat, wobei die Spitze des tropfenförmigen Querschnitts nach außen weist. 7. screw anchor according to one of the preceding claims, characterized in that the cutting spring (18) has a teardrop-shaped cross-section, wherein the tip of the teardrop-shaped cross section has to the outside.
PCT/EP2011/070737 2010-12-21 2011-11-23 Screw anchor WO2012084385A1 (en)

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DE102013219013A1 (en) 2013-09-20 2015-03-26 Böllhoff Verbindungstechnik GmbH Spring connecting element
EP3869051A1 (en) 2020-02-18 2021-08-25 Hilti Aktiengesellschaft Bimetallic stainless screw
EP4184021A1 (en) 2021-11-18 2023-05-24 Hilti Aktiengesellschaft Tri-component screw

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US1230603A (en) * 1914-07-21 1917-06-19 Julian Richmond Screw-anchor.
GB179144A (en) * 1921-04-23 1923-05-24 Belge Pour La Fabrication De R A reinforcement for holding-down bolts
DE839692C (en) * 1950-05-21 1952-05-23 Christof Sturm Screw connection for wooden parts
EP1498618A2 (en) * 2003-07-15 2005-01-19 Adolf Würth GmbH & Co. KG Screw for hard materials
US20100180541A1 (en) * 2009-01-20 2010-07-22 Chong Ming Lee Reusable Expansion Anchoring Assembly and Setting Method Thereof

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DE102013219013A1 (en) 2013-09-20 2015-03-26 Böllhoff Verbindungstechnik GmbH Spring connecting element
WO2015039997A1 (en) 2013-09-20 2015-03-26 Böllhoff Verbindungstechnik GmbH Spring connection element
US9909603B2 (en) 2013-09-20 2018-03-06 Böllhoff Verbindungstechnik GmbH Spring connection element
US10626900B2 (en) 2013-09-20 2020-04-21 Böllhoff Verbindungstechnik GmbH Spring connection element
EP3869051A1 (en) 2020-02-18 2021-08-25 Hilti Aktiengesellschaft Bimetallic stainless screw
WO2021165094A1 (en) 2020-02-18 2021-08-26 Hilti Aktiengesellschaft Bimetallic stainless screw
US12110919B2 (en) 2020-02-18 2024-10-08 Hilti Aktiengesellschaft Bimetallic stainless screw
EP4184021A1 (en) 2021-11-18 2023-05-24 Hilti Aktiengesellschaft Tri-component screw
WO2023088724A1 (en) 2021-11-18 2023-05-25 Hilti Aktiengesellschaft Tri-component screw

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