Patent Publication Number: US-2007098518-A1

Title: Expansion anchor

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to an expansion anchor which is to be anchored in a borehole and which has a stem having a first end and a second end opposite the first end, load application means provided on the stem and extending up to first end, and an anchoring mechanism provided on the stem.  
      2. Description of the Prior Art  
      German Publication DE 195 41 564 A1 discloses an expansion anchor which is to be anchored in a borehole and which includes a stem having a first and a second end opposite the first end. On the stem, there is provided load application means extending up to the first end. For forming an anchoring mechanism, there are provided, on the stem, an expansion body that widens toward the second end and an expansion sleeve that at least partially surrounds the expansion body and is expandable hereby.  
      Such expansion anchors are used for securing a constructional part to a constructional component formed, e.g., of concrete, with the expansion anchors being preferably, percussively driven in a preliminary formed borehole. The load application means is preferably formed, e.g., as an outer thread on which a nut is screwed. For anchoring the expansion anchor in the borehole, the nut is screwed over the thread until it is supported against the to-be-secured part. With the nut being rotated, the stem, together with the expansion body, are displaced axially, and the expansion body expands, whereby the expansion sleeve is pressed against the borehole wall. Such expansion anchors are set simply and reliably and are economically produced. Therefore, they proved themselves in practice.  
      The drawback of the known expansion anchor consists in that media, e.g., water can penetrate in a gap between the expansion anchor and the borehole wall unhindered, which leads to a corrosion damage of the expansion anchor and, thus, to the reduction of its bearing capacity. In addition, the corrosion damage can affect the concrete reinforcement that was cut during formation of the borehole, which can lead to the reduction of the bearing capacity of the entire construction.  
      German Publication DE 10 204 591 A1 discloses an expansion anchor with a filling channel through which after the anchor has been anchored in the borehole, mortar mass is introduced into the borehole. The mortar mass can exit through an exit opening in a hole disc, which makes possible to control whether a complete filling of the gap in the borehole took place. The gap is, thus, sealed against penetration of media.  
      The drawback of the known solution consists in that several components need be handled, and many steps are necessary for anchoring the anchor. In addition, for as complete as possible hardening of the mortar, certain environmental conditions, e.g., temperature or humidity are necessary, which do not always exist. Further, when mortar is used, in most cases, adherence to particular operational measures is required, which increases operational expenses associated with anchoring of an expansion anchor. Still further, the storage life of the mortar or at least some of its separate components is limited. The use of resins instead of mortar for filling the gap between the expansion anchor and the borehole wall, results essentially in the same drawbacks as with using the mortar.  
      Accordingly, an object of the invention is to provide an expansion anchor that can be easily set in and with which a perfect sealing of the gap between the set anchor and the borehole wall is insured, without the above-mentioned drawbacks.  
     SUMMARY OF THE INVENTION  
      This and other objects of the present invention, which will become apparent hereinafter, are achieved by providing an expansion anchor including a stem having a first end and a second end opposite the first end. On the stem, there is provided load application means which extends up to first end. On the stem, there is further provided an anchoring mechanism for anchoring the expansion anchor in a borehole. A seal is arranged between the anchoring mechanism and the first end of the stem. The seal has, over its axial extent along a longitudinal axis of the stem, different radial dimensions.  
      The maximal radial dimension or the maximal outer diameter of the seal, which is circumferentially arranged on the stem, is advantageously so formed that it is greater than the inner diameter of a borehole in which the expansion anchor is to be set. The seal forms a sheath that at least partially surrounds the stem. The expansion anchor is percussively driven in, e.g., with a hammer, in a preliminary formed bore, whereby at least the region of the seal adjacent to the first end engages a region of the borehole wall, completely sealing thereby the gap between the expansion anchor and the borehole wall. Advantageously, the seal is aggressive medium-resistant.  
      The expansion anchor has an integrated sealing function. For setting the inventive expansion anchor, the number of operational steps is comparable with setting of a conventional expansion anchor without a seal, so that the inventive anchor can be used almost without any limitations. The demands to the environmental conditions of the site are substantially lower than with sealing with mortar or resin, which substantially increases the application region of the inventive expansion anchor. An important advantage of the inventive expansion anchor also consists in that no specific operational measures are required with the use of the expansion anchor. In addition, the expansion anchor can be used without any problems at an overhead work. Overall, it can be concluded that the inventive expansion anchor can be handled and set substantially easier than a conventional expansion anchor, and it can be economically produced.  
      Preferably, the seal is formed as a coating which in order to form a one-piece part, is put on the stem in material-locking manner at a manufacturing plant. E.g., the coating is formed using a polymer-coating process, or a corresponding anchor region is sheathed with a plastic layer in an injection-molding process.  
      Advantageously, the seal has, with reference to the longitudinal axis, an increased radial dimension in a direction of the first end. In this embodiment, the seal has at least one section having a shape of a wedge or cone that widens in a direction opposite the setting direction of the expansion anchor. This provides for an easy driving of the inventive expansion anchor in.  
      Advantageously, the seal is formed as a succession of a plurality of truncated cones having their larger base surfaces located closer to the first end of the stem. This advantageous embodiment of the inventive expansion anchor has not only more sealing regions distributed over the axial extent of the seal but also a very robust construction. The percussive driving of the expansion anchor in a constructional component will be hindered by so-formed seal only to a non-significant extent.  
      Advantageously, the seal has a plurality of radially extending, circumferentially arranged elevations, whereby a plurality of sealing points are available along the axial extent in the direction of the longitudinal axis of the expansion anchor. Because the contact surface between the seal and the borehole wall is reduced to a plurality of separate regions, the inventive expansion anchor is easily driven in. The elevations are formed, e.g., as radially extending circumferential ribs or lamellas with a polygonal cross-section. Alternatively, the elevations can have a lip-shaped profile, with the free end of the elevations advantageously facing toward the first end of the stem. According to another embodiment, the seal can have a plurality of radially extending circumferential elevations having different profiles.  
      Preferably, the seal is formed of a strip wound about the stem of the expansion anchor and having a wedge-shaped cross-section. The strip is wound one or several times about the stem, starting with the smaller edge region, in a region between the anchoring mechanism and the first-end of the stem, forming a cone-shaped seal of the expansion anchor. The expansion anchor is provided with the strip seal either during its manufacturing at the plant or on the construction site. Advantageously, the strip has a glue layer which, on one hand, insures adhesion of the strip to the stem and, on the other hand, insures adhesion of the strip to itself, when necessary. The strip with a glue layer is put on the stem as an adhesive tape. The glue layer is advantageously provided with a removable cover foil. The strip can be arranged on the stem of the expansion anchor at the manufacturing plant or be shipped to the user as a separate component for a subsequent arrangement on the stem. Possible gaps, which may be formed upon winding of the strip, e.g., at the strip end, are compressed upon setting of the anchor, so that no loss of tightness occurs with a set expansion anchor.  
      This embodiment of the inventive expansion anchor is advantageous, e.g., for anchoring the expansion anchor in constructional components which because of their material characteristics, has a tendency to form break-outs in the region of the borehole during formation of the borehole. The sealing function of the expansion anchor can be easily varied with this embodiment. With a corresponding number of strip windings, a necessary or a desired radial dimension of the seal for a satisfactory sealing of the gap between the expansion anchor and the borehole wall can be easily obtained.  
      The storage life of this embodiment of the expansion anchor is limited to a certain extent because of the properties of the glue coating of the strip. However, the storage life of this expansion anchor is still substantially greater than the storage life of a mortar or resin system. Also, in this embodiment, no age hardening of the seal occurs. Likewise, environmental conditions at the construction site should meet only very low demands, which substantially increase the application region of the inventive expansion anchor, and no specific operational measures need be undertaken. This embodiment of the expansion anchor likewise can be used in overhead work without any problems.  
      Advantageously, the seal is formed of a deformable material which, advantageously, is weaker than the material of the constructional component the expansion anchor is to be anchored, and weaker than the steel the expansion anchor is formed of. As a result of the use of the deformable material, the seal is deformed, when the expansion anchor is driven in, and is pressed against the borehole wall.  
      Advantageously, the seal includes elastically deformable components which provide for a perfect sealing of the gap between the expansion anchor and the borehole wall even at a non-uniform shape of the borehole wall.  
      In addition, the elastically deformable components of the seal can compensate possible, thermally induced, dimensional changes of the seal. Advantageously, the seal has, in addition to the elastically deformable components also plastically deformable components.  
      Advantageously, the seal is formed of a thermoplastically treatable material such as, e.g., thermoplast, thermoplastic elastomer, or of elastomer-like thermoplasts. These materials are characterized by economical processing, using established methods such as, e.g., whirl sintering or injection-molding, and by their small price. In addition, many of these materials are resistant to media relevant to building materials, and are available practically with each desired hardness. PE (polyethylene), PA (polyamide), POM (poly-oxymethylene), PP (polypropylene), EVA (ethylenevinylacetate), TPU (thermoplastic polyurethane), TPA (thermoplastic polyamidelastomer), TEEE (polyetheresterelastomer), TPS (SEBS: styrolethylenebuthylenstyrole), or TPV (cross-linked elastomer in a thermoplastic matrix) are examples of such materials. However, these examples are not limiting.  
      Alternatively, the seal can be formed of a cross-linked elastomer. These materials have a high thermal resistance and a high media-resistance, in particular in comparison with thermoplastic elastomers. Further, the cross-linked elastomers have a smaller tendency to creeping and relaxation than thermoplastic elastomers. Also, the cross-linked elastomers are characterized by their low price.  
      An example of a possible cross-linked elastomer is EPDM (ethylene-propylene-dien-resin).  
      According to another alternative embodiment, the seal is formed of metal or alloy which, advantageously, are deformed during setting of the anchor.  
      The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiment, when read with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS:  
      The drawings show:  
       FIG. 1 a  longitudinal cross-sectional view of a first embodiment of an expansion anchor according to the present invention in a set condition;  
       FIG. 2 a  side view of the expansion anchor according to  FIG. 1 ;  
       FIG. 3 a  side view of a second embodiment of an expansion anchor according to the present invention;  
       FIG. 4 a  longitudinal cross-sectional view of a third embodiment of an expansion anchor according to the present invention in a set condition;  
       FIG. 5 a  side view of a fourth embodiment of an expansion anchor according to the present invention;  
       FIG. 6 a  perspective view of a fifth embodiment of an expansion anchor according to the present invention; and  
       FIG. 7 a  longitudinal cross-sectional view of a strip for the expansion anchor according to  FIG. 6 . 
    
    
      In the drawings identical elements are designated with the same reference numerals.  
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      An expansion anchor  11  according to the present invention, a first embodiment of which is shown in  FIGS. 1-2 , has a stem  12 , a first end  14 , and a second end  15  located opposite the first end  14 .  
      On the stem  12 , there is provided an outer thread  17  that extends up to the first end  14  and forms load application means  16 . For forming an anchoring mechanism  21 , there are provided, on the stem  12 , an expansion body  22  that widens toward the second end  15 , and an expansion sleeve  23  that at least partially surrounds the expansion body  22  and is expandable thereby.  
      The expansion anchor  11  further includes a seal  26  located between the anchoring mechanism  21  and the first end  14  of the stem  12 . The seal  26  is formed as a coating and has a different radial extent over its axial extent along an axis  13  of the stem  12 . The sealing  26  has, in a direction of the first end  14  along the longitudinal axis  13  of the stem  12 , a radially increasing dimension. The seal  26  is formed of a deformable, thermoplastically treatable material having elastic and, advantageously, plastically deformable components.  
      For securing a constructional part  1  on a constructional component  2  such as, e.g., concrete floor, in a first step, a borehole  3  is formed in the constructional component  2 . Then, the expansion anchor  11  is driven in the borehole  3  with a hammer, with the seal  26  abutting, at least regionwise, the borehole wall  4 . For anchoring the expansion anchor  11  in the borehole  3 , a nut  28  with a washer  29  are arranged on the outer thread  17 , with the nut  28  tightening the expansion anchor  11  upon rotation. The nut  28  is supported on the constructional component  1  by the washer  29 , with the stem  12  being displaced in the axial direction. The displaceable stem  12  causes the expansion body  22  to expand the expansion sleeve  23  which becomes pressed against the borehole wall  4 . On the stem  12 , there is provided a circumferential stop  18  for the expansion sleeve  23  and which limits the displacement of the expansion sleeve  23  in the direction of the first end  14  and parallel to the longitudinal axis  13  upon sinking of the stem  12  in.  
      An expansion anchor  31 , which is shown in  FIG. 3 , has, between the anchoring mechanism  36  and the first end  34  of the stem  32 , a seal  37  in form of coating and which is formed as a succession of several truncated cones  38 , with their larger base surface  39  located closer to the first end  34  of the stem  32 . The seal  37  is formed of a cross-linked elastomer.  
      An expansion anchor  41 , which is shown in  FIG. 4 , has, between the anchoring mechanism  6  and the first end  44  of the stem  42 , a seal  47  in form of a coating and having a plurality of radially arranged ribs having a rectangular cross-section and forming elevations  48 .  
      An expansion anchor  51 , which is shown in  FIG. 5 , has a seal  57  in form of a coating and arranged between the anchoring mechanism  56  and the first end  54  of the stem  52 . The seal  57  forms radially, circumferentially arranged elevations  58 . The elevations  58  are lip-shaped and have their free ends  59  located closer to the first end  54  of the stem  52 .  
      An expansion anchor  61 , which is shown in  FIG. 6-7 , also has a stem  62  on which there is arranged a seal  67  formed of a strip  68  wound about the stem  62 . The seal  67  is located between the anchoring mechanism  66  and the first end  64  of the stem  62 . The strip  68  has a wedge-shaped cross-section with a first thickness A and a second thickness C that is greater than the thickness A.  
      On one side  69 , the strip  68  is coated with glue  70  which is covered with a cover foil  71  that is removed before arrangement of the strip  68  on the stem  62 .  
      The smaller edge region, which has the first thickness A, is located above the anchoring mechanism  66 , and the strip  68  is wound about the stem  68  several times and is spaced from the first end  64 , whereby a cone-shaped seal  67  of the expansion anchor is formed.  
      Though the present invention was shown and described with references to the preferred embodiment, such is merely illustrative of the present invention and is not to be construed as a limitation thereof and various modifications of the present invention will be apparent to those skilled in the art. It is therefore not intended that the present invention be limited to the disclosed embodiment or details thereof, and the present invention includes all variations and/or alternative embodiments within the spirit and scope of the present invention as defined by the appended claims.