Patent Publication Number: US-2010126112-A1

Title: Method of anchoring fastening element

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a method of anchoring a fastening element and a method of forming a cleaned borehole for anchoring a fastening element. 
     2. Description of the Prior Art 
     At a chemical anchoring, fastening elements such as, e.g., threaded rods, reinforcing irons, or dowels are anchored in a borehole preliminary formed in a constructional component, e.g., wall or ceiling, e.g., of a mineral material such as, e.g., concrete or brickwall. In order to be able to achieve high anchoring values of a fastening element in the constructional component or underground, preferably, a substantial cleaning of the borehole is important because drillings or drilling dust, which still remain in the borehole, disadvantageously influence adhesion of the hardenable mass to the borehole wall. 
     For cleaning a borehole, mechanical devices have already been proposed with which the borehole, after being drilled, is brushed or blown off. The drawback of the known solution consists in that the degree of cleaning depends on the fastidiousness of the user of the device. 
     German Publication DE 29 12 396 A1 discloses a borehole cleaning process or method using a hollow drill and according to which during drilling of the borehole, air is blown into the borehole through the hollow drill. The produced drillings and drilling dust is blown out of the borehole. With this method, drillings and dust contaminate the borehole environment. 
     German Publication DE 198 10 193 A1 discloses a borehole-cleaning process or method with a hollow drill and according to which for improved cleaning during the drilling of the borehole, the produced drillings and drilling dust are aspirated through the hollow drill with a vacuum source such as a vacuum cleaner. 
     The object of the invention is to provide a reliable method of anchoring a fastening element. 
     Another object of the invention, is a method of forming a cleaned borehole in a constructional component for chemical anchoring a fastening element in the constructional component. 
     SUMMARY OF THE INVENTION 
     These and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a method including the steps of drilling a borehole in a constructional component with a percussively-rotationally driven hollow drill, aspirating produced drillings and drilling dust with a vacuum source between an outer side of the hollow drill and a borehole wall during drilling of the borehole, immediately after formation of the suction-cleaned borehole, filling the borehole with a self-hardenable mortar, and inserting the fastening element into the self-hardenable mortar. 
     The desired pull-out loads in the range of over 1,000 Newton are transmitted by the self-hardenable mortar only to the constructional component when the drillings are removed by cleaning. In addition, it has been found that the smooth borehole walls, which we formed by sawing or grinding, can be cleaned very well by suction but, however, do not enable any satisfactory adhesion of the mortar to the wall. A partially chiseling tool, which the percussively driven hollow drill forms, provides a sufficient roughness and insures formation of fissures in the borehole wall which provide for an adequate adhesion of the mortar to the borehole wall. 
     According to one of the embodiments of the inventive method, the borehole is filled with a two-component mass. The self-hardenable mortar can be based on epoxyresin and/or polymethacrylat. 
     The self-hardenable mortar fills the borehole without any further cleaning of the borehole. The method according to the present invention insures that a fastening element, which is anchored in the self-hardenable mortar, can withstand pull-out loads of at least 1,000 Newton. 
     According to the invention, during drilling of the borehole with a hollow drill, the drillings and the drilling dust are aspirated by the vacuum source through the gap between the outer side of the hollow drill and the borehole wall. 
     The foregoing measures provide for drillings and drilling dust constantly being aspirated starting from the drilling head or from the cutters of the hollow drill, outside of the drilling head. Simultaneously, passive air flows through the hollow drill into the borehole, providing for an advantageous air flow pattern in the borehole for removal of the drillings and drilling dust out of the borehole. Thereby, the produced drillings and, in particular, the produced drilling dust are prevented, from the start, from being pressed onto the borehole wall during the drilling process which would have made it very difficult to remove it from the borehole. The inventive method is particular advantageous for anchoring fastening elements in underground and constructional components formed of porous material with respect to the achievable degree of cleaning. 
     The inventive method enables in a simple manner to integrate the operational steps of drilling and cleaning the borehole, which eliminates a separate and expensive cleaning procedure, and a noticeable increase of the drilling speed. 
     This permits to achieve a noticeably improved productivity simultaneously with increase of safety and reliability of the chemical anchoring. The reduction of operational expenses for forming a cleaned borehole in comparison with a subsequent cleaning of a borehole by brushing and/or blowing off amounts up to 50% or even more. 
     Because the inventive method insures uniform, reproducible cleaning with a high degree of cleaning, high specific loads can be applied to a chemically anchored fastening element. The inventive method permits to achieve a smaller decrease of reference load values, so that at the same dimensional characteristics of the chemical anchoring, additional applications become possible. 
     Advantageously, there is provided a suction hood for covering the borehole and having a through-opening for the hollow drill and a connection union for the vacuum source. Thereby, an underpressure is produced around the hollow drill in a region outside of the borehole. This insures an almost complete removal or aspiration of drillings and drilling dust produced by drilling through a gap between the outer side of the hollow drill and the borehole wall. This measure further improves cleaning of the borehole and specific loads for chemically anchored fastening elements can be increased further. In addition, contamination of the environment is prevented to a most possible degree. 
     Advantageously, during drilling of a borehole, additional air is blown into the borehole through the hollow drill. Thereby, removal or aspiration of produced, during drilling, drillings and drilling dust through a gap between the outer side of the hollow drill and the borehole wall is further improved. 
     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 schematic view illustrating views of a hollow drill according to the inventive method; and 
         FIG. 2  a cross-sectional view showing an anchored fastening element. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A device  11 , which is shown in  FIG. 1 , is used for carrying out a process according to the present invention for forming a cleaned borehole  7  in a constructional component  6 , e.g., in a concrete ceiling for chemically anchoring a fastening element  46  in the constructional component  6 . The device  11  includes a hollow drill  12 , a suction hood  21 , and a vacuum source  26 , e.g., a vacuum cleaner. 
     The hollow drill  12  has a shaft  16  having, at its first, front end, a drilling head  13  with outlet openings  14  and at its other rear end, a shank  15  for insertion of the hollow drill  12  in a chuck  8  in a percussion-rotary drilling tool, not shown in the drawing. 
     At a distance from the shank  8 , there is provided an inlet opening  17  that opens radially outwardly and is connected with the outlet opening  14  in the drilling head  13  by a circumferentially closed elongate channel  18  provided in the shaft  16 . 
     The suction hood  21  is bell-shaped and is provided with a through-opening  22  for the hollow drill  12  and a connection union  23  for connection with a suction conduit  27  that connects the suction hood  21  with the vacuum source  26 . The through-opening  22  can be provided with sealing means, e.g., with projecting radially inwardly, brush elements or flexible sealing elements for partially sealing the through-opening  22 . 
     For forming the cleaned borehole  7  in the constructional component  6 , the hollow drill  12  is rotated by the drilling tool, as shown by arrow  9 , and is percussively driven in the axial direction, with the hollow drill penetrating into the borehole  7  in the constructional component  6  up to a desired depth of the borehole  7 . Simultaneously, the vacuum source  26  is actuated. During the drilling of the borehole  7  with the hollow drill  12 , air and, thus, drillings and drilling dust, which are produced during drilling, are aspirated by the vacuum source  26  through the gap between the outer side of the hollow drill  12  and the wall of the borehole  7 . Simultaneously, air continuously flows in the borehole  7  through the inlet opening  17  of the hollow drill  12 . This insures an advantageous air flow for removing drillings and drilling dust (see flow arrow  28 ). 
     Optionally, e.g., a feed adapter  31  can be provided in the region of the inlet opening  17 . During the drilling of the borehole  7  additional air can be actively blown in through the hollow drill  12 , if needed, through the adapter  31 . 
     After a desired depth of the borehole  7  has been reached, the device  11  is removed. The formed borehole  7  is already adequately cleaned. Thus, no further operational step for cleaning the borehole  7  is needed before filling the borehole  7  with a hardenable mass  41 . A fastening element  46 , e.g., a threaded rod is pushed into borehole  7  filled with the hardenable mass  41 . After hardening of the hardenable mass  41  in the borehole  7 , the anchored fastening element  46  has noticeably higher pull-out value then a fastening element chemically anchored in a conventionally formed borehole that was not subsequently optimally cleaned. 
     Also, mechanically anchored fastening elements, which were anchored in a borehole produced by the inventive process, achieved higher pull-out value than they are anchored in a conventionally formed borehole. 
     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.