Abstract:
The present invention relates to an expansion anchor, in particular for mining, wherein at least one widenable expansion element is provided on the external side of the expansion anchor including an anchor rod, wherein the expansion element in a retention element fixed to the anchor rod is maintained in an abutment position during the insertion of the expansion anchor into a hole and the expansion element is expansible by the expansion element cooperating with a stop element anchored within the bore hole, wherein the expansion element is expansible through a movement of the anchor rod in the direction towards the opening of the bore hole.

Description:
[0001]    The present invention is a continuation application of PCT/AT00/00202, filed Jul. 21, 2000.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to an expansion anchor, in particular for mining, wherein at least one widenable expansion element is provided on the external side of the expansion anchor including an anchor rod, wherein the expansion element in a retention element fixed to the anchor rod is maintained in an abutment position during the insertion of the expansion anchor into a hole and the expansion element is expansible by the expansion element cooperating with a stop element anchored within the bore hole.  
           [0004]    2. Description of the Prior Art  
           [0005]    In the context of fixing or anchoring an expansion anchor within a bore hole it is known to insert into a previously completed bore hole such an expansion anchor comprising at least one widenable element peripherally arranged in its front portion and, after this, enable the expansion anchor to be fixed within the bore hole and the widenable element to bear against the wall of the bore hole by expanding the widenable element, a settable suspension being additionally introduced in most cases. Embodiments of that type are to be taken, for instance, from AT-B 339 239, EP-A 0 354 760, WO 94/05900 or U.S. Pat. No. 4,305,687. In those known embodiments, the expansion of a plurality of widenable expansion elements peripherally provided on an expansion anchor is effected after insertion of the expansion anchor, for instance by a screwing motion of the anchor, thus causing an element cooperating with the widenable expansion elements and capable of being screwed along the threaded anchor rod of the anchor to cooperate in order to enable the widenable expansion elements to expand into contact on the wall of the previously completed bore hole. Such bearing against the wall of the bore hole results in a provisional securing of such an anchor against falling out so as to enable the introduction of a suspension afterwards. However, by such an expansion of the widenable elements, which, in addition, usually exhibit a respective longitudinal extension in the axial direction of the bore hole and are provided with rib-shaped elevations aimed to enhance the securing or anchoring effect, it is actually feasible, in particular in the event of a loose rock formation, to merely provide provisional and short-term securing that allows for the avoidance of any unintentional extraction, or falling out, of the expansion anchor during application in a vertically upwardly oriented bore hole, yet does not render feasible an anchoring effect of the anchor, that is sufficiently large for taking up major stresses.  
           [0006]    A modified embodiment of an expansion anchor can be taken from U.S. Pat. No. 4,380,407. Furthermore a rock anchor comprising several parts is known from DE-C 916 286, wherein an anchor is biased through a spring effect within a bore hole.  
         SUMMARY OF THE INVENTION  
         [0007]    Departing from an expansion anchor of the initially defined kind, the present invention aims to provide a way of enabling the securing and fixing of such an expansion anchor in a bore hole beyond a provisional anchoring effect by appropriately driving in or inserting said at least one widenable expansion element.  
           [0008]    To solve these objects an expansion anchor of the initially defined kind is essentially characterized in that the expansion element is expansible through a movement of the anchor rod in the direction towards the opening of the bore hole. Due to the fact that according to the invention the widenable expansion element is held in a retention element in an abutting position, the insertion of the expansion anchor along with the at least one widenable element may be accomplished in a simple manner, whereupon the widenable expansion element can subsequently be expanded by a movement of the anchor rod in the direction towards the opening of the bore hole by the expansion element cooperating with a stop element anchored within the bore hole. It is, thus, feasible to do with a structurally simple construction capable of being designed in an accordingly sturdy and stable manner in order to achieve the desired safe anchorage through expansion of the at least one widenable expansion element as the free end of the latter enters the wall of the bore hole, by pulling back the anchor rod together with the widenable expansion element.  
           [0009]    By effecting not only the mere expansion of the expansion element so as to contact the wall of the bore hole, but additionally acting on, or pulling back, the anchor rod and the widenable expansion element in the direction towards the open end of the bore hole as the expansion element is being expanded, not only the safe abutment of the widenable element on the wall of the bore hole is ensured, but that rearward movement additionally causes the free end facing the wall of the bore hole to be inserted or driven into the wall of the bore hole, whereby an accordingly perfect anchoring effect will be obtained. By the free end of the expansible element entering, or eating into, the wall of the bore hole in that manner, a satisfactory anchoring effect of the expansion anchor will be achieved already by merely expanding the widenable element, wherein the anchoring effect may then be appropriately enhanced, for instance, by introducing a settable suspension. An additional anchoring effect, which may be obtained by the rearward movement of the anchor rod and hence of the widenable element at the entry into the wall of the bore hole, for instance, in the event of a provisional walling will enable said walling to be further advanced immediately after having set the anchor and introduced the curable suspension, since jamming of the widenable expansion element brings about a satisfactory anchoring effect and curing of the curable suspension need not be waited for to continue the supporting work such that, in the main, a considerable advantage in terms of time will be achieved in the realization of such a walling.  
           [0010]    For a particularly simple fixation of the stop element within the bore hole, which is subsequently taken to anchor and expand the widenable expansion element, the stop element may cooperate with a jacket tube, which, after a preceding drilling procedure, is slightly pulled back from the bore hole at least by the length of a retention element with the widenable expansion element and of the stop element, and fixed. It is, thus, readily feasible to utilize a jacket tube used in a preceding drilling procedure directly for positioning the stop element of the expansion anchor so as to enable, after having removed the drill head and drill rod from the jacket tube and slightly pulled back the jacket tube, the setting of the expansion anchor with at least one widenable expansion element through the jacket tube immediately thereafter and, by engagement of the stop element in front of the jacket tube, achieve the safe positioning, and definition of the position, of the stop element for the subsequent procedure of fixing the expansion anchor while expanding the at least one widenable expansion element.  
           [0011]    In order to enable particularly simple positioning and holding of the widenable expansion element on the anchor rod during its insertion, it is proposed according to another preferred embodiment that the retention element for the expansion element is comprised of a sleeve element surrounding the anchor rod.  
           [0012]    For expanding the expansion element after having inserted the expansion anchor into the bore hole, it is contemplated according to a further preferred embodiment that the widenable expansion element is guided or pivotably mounted in the retention element, such an articulation being realizable, for instance, by the aid of a simple joint or an accordingly simple and sturdily designable guiding means.  
           [0013]    In order for the widenable expansion element to readily abut on the anchor rod during insertion of the expansion anchor into the bore hole, it is, moreover, provided according to a further preferred embodiment that the expansion element in the region of the retention element is held by a retaining ring.  
           [0014]    For a proper expansion or swing-out movement of the widenable expansion element, it is additionally provided that the expansion element in its end received within the retention element is designed to include at least one chamfer or bevelment, as in correspondence with a further preferred embodiment of the expansion anchor according to the invention. Such a chamfer or bevelment offers sufficient clearance to the expansion element during the pivotal movement while expanding or swinging out and entering the wall of the bore hole.  
           [0015]    In order to provide for a proper and readily controllable expansion movement during the retraction of the anchor rod along with the at least one widenable expansion element, it is, moreover, preferably contemplated that the widenable expansion element on its end facing the stop element is formed with a further chamfer or profiling which cooperates with a complementary chamfer or profiling provided on the stop element. Such chamfers or profilings provided both on the free end of the widenable expansion element and on the stop element may be designed with appropriate inclinations in order to enable the desired anchoring effect by expanding the expansion element under the simultaneous entry of the free end into the region of the wall of the bore hole, knowing the material of the bore hole.  
           [0016]    In order to ensure the uniform application of high anchoring forces about the periphery of the expansion anchor, it is provided according to a further preferred embodiment of the invention that a plurality of widenable expansion elements are arranged so as to be substantially uniformly distributed about the periphery of the expansion anchor. In addition to such a uniform distribution of the forces to be introduced, about the periphery of the expansion anchor according to the invention, it may be provided with a view to further enhancing the anchoring forces that a plurality of widenable expansion elements are provided on the periphery of the expansion anchor at different distances from the tip of the expansion anchor, as in correspondence with a further preferred embodiment of the expansion anchor according to the invention. Such widenable elements arranged at different distances from the tip of the expansion anchor, thus, allow for the obtainment of an accordingly safe anchorage of the expansion anchor over an extended length, in particular in the tip region of the expansion anchor, during the expansion of the widenable expansion elements such that optionally also at least some of the expansion elements arranged at different distances from the tip of the expansion anchor will ensure a safe and reliable anchorage, in particular in the event of loose rock.  
           [0017]    According to a structurally particularly simple embodiment, it is preferably proposed in this context that expansion elements arranged at different distances from the tip are arranged so as to be mutually offset in the peripheral direction.  
           [0018]    As already indicated above, regulation or control of the expansion procedure, for instance as a function of the rock formation into which the expansion anchor is to be inserted, is feasible by providing chamfers or profilings both on the free ends of the widenable expansion elements and on the expansion elements respectively cooperating therewith. In this context, it is contemplated according to a particularly preferred embodiment that expansion elements arranged at different distances from the tip are provided with different chamfers or profilings for cooperation with complementary chamfers or profilings of the associated stop elements so as to allow for the obtainment of a selective anchoring effect by different opening movements of the individual widenable elements depending, for instance, on the distance from the tip of the expansion anchor. Thus, it may, for instance, be aimed to provide widenable expansion elements located in the tip region with steeper chamfers or profilings to allow for proper securing with shorter widenable expansion elements, while widenable expansion elements arranged at larger distances from the tip of the anchor, by being provided with flatter chamfers, allow for an altogether slower opening movement and additional securing without affecting the entry of the widenable expansion elements in the tip region. With those flatter chamfer inclinations it is also feasible to use accordingly longer widenable expansion elements.  
           [0019]    In order to enable further coordination with an anchoring effect sought, in particular in loose rock, it is proposed according to a further preferred embodiment that the expansion element is variable in terms of length, in particular telescopic, so as to ensure a safe anchoring effect partially irrespective of the nature of the rock formation and even despite the presence of previously not readily known hollow spaces in the region of the bore hole.  
           [0020]    In order to further equalize the forces to be applied on the periphery of the expansion anchor, it is proposed according to another preferred embodiment that an expansion element which is divided in the peripheral direction surrounds the anchor rod in an umbrella-like manner and is comprised of plate-shaped elements connected, in particular articulately, with one another. Such an umbrella-like element is able to allow for the abutment of the widenable expansion element substantially continuously about the total periphery of the expansion anchor in a manner similar to a screening structure, likewise by pulling back the anchor rod as well as the expansion element, through cooperation with a stop element.  
           [0021]    In order to enable the particularly simple fixation of the stop element within the bore hole, it is contemplated according to another preferred embodiment of the expansion anchor according to the invention that the stop element via a spring washer cooperates with a jacket tube from a preceding drilling procedure arranged within the bore hole, enabling the simple insertion of the expansion anchor through such a jacket tube by using a spring washer of this type, wherein, upon complete insertion of the expansion anchor, the exact positioning of the stop element on the jacket tube within the bore hole is immediately effected by the spring washer expanding automatically, whereupon the anchorage of the expansion anchor is realized immediately after this by screwing back the anchor rod and hence expanding, and driving into the wall of the bore hole, the widenable expansion elements. 
       
    
    
     SHORT DESCRIPTION OF THE DRAWINGS  
       [0022]    In the following, the invention will be explained in more detail by way of exemplary embodiments schematically illustrated in the accompanying drawing, of expansion anchors according to the invention for carrying out the method of the invention. Therein:  
         [0023]    [0023]FIG. 1 is a partially sectioned schematic side view of a first embodiment of an expansion anchor according to the invention for carrying out the method of the invention;  
         [0024]    [0024]FIG. 2 is an illustration similar to that of FIG. 1, of a modified embodiment of an expansion anchor according to the invention for carrying out the method of the invention, comprising a plurality of widenable expansion elements arranged at different distances from the tip of the expansion anchor; and  
         [0025]    [0025]FIG. 3 is a front view of the expansion anchor according to the invention including partially extended widenable expansion elements in the direction of the arrow III of FIG. 2. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]    [0026]FIG. 1 generally illustrates the foremost portion of an expansion anchor  1  which has been inserted into a bore hole  2 , wherein a plurality of widenable expansion elements  3  are arranged about the periphery of the expansion anchor, one of which is depicted in detail in FIG. 1. The expansion anchor  1 , in addition, comprises an anchor rod schematically indicated by  4 , which is provided with a thread  5  as is also schematically indicated. In the fold-in position of the widenable expansion elements, which is illustrated in FIG. 1 by full lines, the insertion of the expansion anchor  1  is effected through a jacket tube  6  located within the bore hole  2 , which, after completion of a preceding drilling procedure and removal of the rod assembly plus drill head, was slightly pulled back from the tip  7  of the bore hole in accordance with the foremost portion of the expansion anchor. After having passed the expansion anchor through the jacket tube  6 , the fixation of a stop element  9  to the end face  10  of the jacket tube  6  and hence the exact positioning of the expansion anchor in the insertion position represented in FIG. 1 by full lines are feasible by the automatic expansion of a spring washer  8 .  
         [0027]    In order to expand the widenable expansion elements  3  peripherally provided in a regularly spaced-apart relationship, threading of the anchor rod  4  within the stop element  9  is effected in the sense of arrow  11 , thus causing a terminal element  12  connected with the foremost portion of the anchor rod  4 , which is connected with the anchor rod in a rotationally fast manner, to directly act on a retention element or sleeve element  13  provided for the pivotable and widenable expansion element  3 . Screwing out of the anchor rod  4  in the sense of arrow  11  causes the widenable expansion element to fold out or spread due to the sliding of a chamfer or profiling  14  of the widenable expansion element on a complementary chamfer  15  of the stop element  9 , thereby reaching not only the contact of the free end or tip  16  of the widenable element at the bore hole wall  2  but, as the screwing motion proceeds in the direction of arrow  11 , also the penetration of the tip into the material in the region of the bore hole wall  2 , as is indicated in FIG. 1 in broken lines by the tip  16 ′ of the spread or folded-out expansion element  3 ′. The widenable expansion element is mounted in the retention element  13  about a joint schematically indicated by  17 .  
         [0028]    By the free tip  16 ′ respectively penetrating deeply into the surrounding material particularly as a function of the material in which the bore hole  2  has been formed, the safe anchorage of the widenable expansion elements  3  can be realized through a rearward movement of the foremost portion by screwing the anchor rod  4  in the sense of arrow  11  in the stop element, which is stationarily fixed within the bore hole  2 .  
         [0029]    In the modified embodiment represented in FIG. 2, a plurality of widenable expansion elements  3  are fixed at different distances from the tip of the expansion anchor  1 . In addition to the different distances of the widenable expansion elements  3  from the front portion  12  of the expansion anchor, it is apparent, in particular, from FIG. 3 that the expansion elements arranged in different radial planes also are arranged in a mutually offset relationship, wherein in FIG. 3 the expansion elements that are located closer to the tip, which are each denoted by  3 ′ in the widened state in FIG. 2, in the system of coordinates chosen in FIG. 3 are arranged at 0°, 90°, 180° as well as 270°, while the widenable expansion elements that are located at a larger distance from the tip  12 , which are denoted by  3 ″ in FIG. 2, are each arranged between elements  3 ′. In the illustration according to FIG. 2, the widenable expansion elements  3 ′ and  3 ″, which are illustrated in section, are, thus, shown to be twisted relative to one another by 45°.  
         [0030]    Also in this embodiment, the expansion of the individual widenable expansion elements  3  into the positions again illustrated in broken lines and denoted by  3 ′ and  3 ″ is effected upon insertion of the expansion anchor  1  into a bore hole  2  and stationary positioning of a stop element again denoted by  9  via a spring washer attached to a jacket tube, by screwing back the anchor rod  4  in the sense of arrow  11 . The joint  17  depicted in FIG. 1 for each individual widenable expansion element has been replaced with retaining rings  18  in FIG. 2, which enable the widenable expansion elements  3  to be properly inserted by engaging at the respective retention elements  13 , whereupon, due to a suitable guidance in retention elements  13  during the movement of the anchor rod  4  with the foremost portion  12 , a reduction of the respective distances between the retention elements  13  and the stop elements  9  and an expansion of the widenable expansion elements is effected.  
         [0031]    In this respect, it is apparent from FIG. 2 that the expansion elements located closer to the tip, which are denoted by  3 ′ in the spread state, include chamfers  14 ′ each having a larger inclination as compared to the farther remotely located expansion elements  3 ″ including chamfers  14 ″, wherein the associated stop elements  9  naturally have corresponding chamfers with different inclinations. Due to said different inclinations, accordingly different extraction or fold-out movements of the expansible elements  3  may be obtained during screwing of the anchor rod such that anchoring, for instance, of the elements located closer to the tip and having shorter lengths in position  3 ′ is effected first and of the larger-length expansion elements in position  3 ″ is effected by an accordingly delayed movement.  
         [0032]    From FIG. 3 it is apparent that the offset arrangement of expansion elements arranged in different radial planes allows for the obtainment of a substantially complete overlap of the total periphery of the expansion anchor by the widenable expansion elements  3  and hence the introduction of accordingly high anchoring and securing forces distributedly about the total periphery of said expansion anchor.  
         [0033]    Instead of the above arrangement of a plurality of expansion elements both in a spaced-apart relationship in the peripheral direction and at different distances from the tip of the expansion anchor, accordingly divided expansion elements may be arranged substantially in a radial plane  1  in the manner of a screen, wherein, again by screwing out of the anchor rod  4  according to arrow  11  and cooperation with a stationary stop element, the expansion of a screen-like expansion element and its simultaneous abutment about the total periphery of the expansion anchor with the expansion elements entering the material of the wall  2  of the bore hole is effected.