You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a drilling rig comprising a mast, a drilling drive mounted for displacement thereon, and a drilling element, which can be rotatably driven and moved along the mast by the drilling drive system, the drilling element comprising a continuous screw auger disposed below the drilling drive system and an extension which is connected to the continuous screw auger and which extends upwardly through the drilling drive. 
     The invention further relates to a drilling method, in which a drilling element is rotatably driven and moved along a mast by means of a drilling drive, the drilling element comprising a continuous screw auger disposed below the drilling drive and an extension which is connected to the continuous screw auger and which extends upwardly through the drilling drive. 
     2. Description of Related Art Including Information Disclosed Under 37 CFR §§1.97 and 1.98 
     The use of so-called continuous screw augers for creating bore holes and, in particular, for creating foundation elements has been known for many years. In a continuous screw auger, a drill helix is disposed along the entire length of the drilling bar for the purpose of conveying loosened earth material out of the bore hole toward the surface by means of rotary motion. A continuous screw auger is driven by means of a drilling drive system, by means of which the continuous screw auger is also moved in the boring direction along a usually vertically positioned mast. In this known method, the depth of the bore hole is restricted by the length of the continuous screw auger and the height of the mast. 
     In order to increase the depth of the bore hole beyond the length of the mast or the length of the continuous screw auger, DE 601 02 255 T2or EP 1 614 853 B1 proposes that an extension bar be disposed at the top of the continuous screw auger, which extension bar extends upwardly through the drilling drive system. The depth of the bore hole can thus be increased by approximately the length of the extension bar. 
     However, feed helixes cannot be mounted on the extension bar for functional reasons. When sinking a bore hole beyond the length of the continuous screw auger, the earth material excavated can thus no longer be conveyed by the feed helixes up to the surface. This earth material thus accumulates in the bore hole above the continuous screw auger in the region of the extension bar. This can lead to undesirable earth compaction or choking of the bore hole, which makes it difficult to subsequently withdraw the drilling element from the bore hole. Furthermore, the wall of the bore hole can be damaged in this region, which can adversely affect the installation of a foundation element in the bore hole by filling the same with filling material. In order to prevent this, the drilling element must be intermittently removed from the bore hole to remove the earth material. This is time-consuming. 
     BRIEF SUMMARY OF THE INVENTION 
     The object underlying the present invention is to provide a drilling rig and a drilling method, by means of which bore holes can also be efficiently created with the aid of continuous screw augers beyond the length of the latter, whilst ensuring good quality of the bore holes. 
     This object is achieved according to the invention with a drilling rig having a mast, a drilling drive displaceably mounted thereon and a drilling element which can be rotatably driven and moved along the mast by said drilling drive, which drilling element has a continuous screw auger disposed below the drilling drive and an extension which is connected to said continuous screw auger and extends upwardly through the drilling drive, wherein a displacement head is disposed between said continuous screw auger and said extension; and by a drilling method in which in a first drilling step, the drilling element is rotated and displaced along the mast by means of the drilling drive to sink a bore hole to the first drilling depth, wherein the first drilling depth is approximately equal to the length of said continuous screw auger and at which depth the drilling drive has reached its lower end position at the bottom end of the mast, a material-transporting step is carried out concurrently with the first drilling step, during which earth material is transported by said continuous screw auger from the upper part of the bore hole to the surface, and in a second drilling step starting from said first drilling depth, the drilling element is rotated and displaced along the mast by means of the drilling drive to sink the bore hole to the second drilling depth and earth material is forced into a wall of the upper part of the bore hole by feeding the earth material transported by said feed helix from the lower part of the bore hole to said displacement head. 
     The drilling rig of the invention is characterized in that a displacement head is disposed between the continuous screw auger and the extension. 
     When sinking a bore hole beyond the length of the continuous screw auger, the displacement head forces the earth material being conveyed toward the top aside into the wall of the bore hole directly above the continuous screw auger. Thus earth material can no longer accumulate inside the bore hole and therefore lead to choking. Rather, the displacement head forces the earth material aside and in doing so serves to positively compact and additionally stabilize the wall of the bore hole. This improves the stability and quality of the bore hole and actively prevents the bore hole from caving in. In this way, the drilling rig of the invention can be used to sink the bore hole beyond the length of the continuous screw auger in a single continuous operation until the end of the extension has been reached. This considerably accelerates the creation of a bore hole of increased depth and additionally reduces the quantity of excavated material to be hauled away. 
     In principle, the extension can have any form. In particular, the extension can be a telescope bar or a bar composed of several segments. It is particularly preferred, according to the invention, for the extension bar to be designed as a Kelly bar having drive ridges on its outside surface. The drive ridges on the outsides surface of the normally single-piece bar operatively interact with corresponding entrainers of an output device of the drilling drive system in order to transmit a torque from the drilling drive system to the extension. The drive ridges are disposed parallel to the drilling axis so that the former permit axial displacement of the extension through the annular drilling drive system. So-called locking recesses having transversely directed ridge sections can be further provided for transferring axial forces from the drilling drive system to the extension. 
     For achieving particularly large drilling depths it is advantageous, according to the invention, when the length of the continuous screw auger is approximately equal to that of the mast or to a maximum movement distance of the drilling drive. The maximum movement distance of the drilling drive, which is displaceable along the mast, can be utilized in this way. A bore hole, the depth of which corresponds to the length of the continuous screw auger, can thus be created efficiently. 
     For installing a foundation element it is advantageous, according to the invention, when the continuous screw auger and/or the extension comprises a hollow core tube. The hollow core tube thus allows for feeding in a filling material, particularly a solidifying or settable suspension such as concrete, for example, directly through the drilling element after sinking the bore hole. For this purpose, one or more discharge orifices are provided at the bottom end of the continuous screw auger. The bore hole can thus be filled concurrently from the bottom up while withdrawing the continuous screw auger from the bore hole. 
     A wide variety of displacement heads can be used on the drilling element of the invention. It is thus possible to use, between the extension and the continuous screw auger, axially symmetrical displacement heads, displacement heads that are eccentric relative to the drilling axis or other displacement heads. 
     It is particularly preferred, according to the invention, when the displacement head comprises a cylindrical displacement section, the diameter of which is approximately equal to the drilling diameter. The drilling diameter is predetermined by the outside diameter of the drill helixes on the continuous screw auger or by corresponding radial cutting edges at the bottom end of the continuous screw auger. The displacement section can be slightly smaller or larger than this drill diameter, depending on the earth properties. An equally dimensioned diameter is advantageous, since it facilitates both the insertion of the displacement head into the bore hole and the withdrawal of the continuous screw auger from the bore hole. 
     According to the invention, it is advantageous when the displacement head comprises a lower conical section, the diameter of which increases from the diameter of a central tube in the continuous screw auger upwardly to the diameter of the displacement section. Thus, the earth material conveyed up to the displacement head can be gradually forced into the wall of the bore hole. This also facilitates the insertion of the displacement head into the bore hole. 
     The insertion of the displacement head into the bore hole is further improved, according to the invention, by providing said lower conical section with a lower helix, which can convey earth material upwardly to the displacement section during the drilling operation. This lower helix is thus situated on the conical outside surface of the displacement section and has the same conveying direction as that of the feed helix of the continuous screw auger. 
     Furthermore, it is advantageous, according to the invention, when the displacement head comprises an upper conical section, the diameter of which tapers from the diameter of the displacement section upwardly to the diameter of the extension. This arrangement allows for material falling onto the displacement head from above to enter the displacement zone of the displacement section. 
     This effect is assisted, according to the invention, by providing an upper helix, capable of conveying earth material downwardly to the displacement section during the drilling operation, on the upper conical section. This helix thus has a reversed pitch direction compared with the helixes of the continuous screw auger or the helix provided on the lower conical section. The upper helix actively conveys earth material falling from above into the zone of the displacement section. 
     In a preferred embodiment of the invention, the displacement section and/or at least one of the conical sections thereof is further provided with displacement elements. The displacement elements can be welded-on strips or arcuate segment-shaped elements, which improve the action of forcing or incorporating earth material into the wall of the bore hole. At the same time, the displacement elements can serve as wear parts that can be easily replaced when subjected to heavy-duty earth removal. 
     The drilling method of the invention is characterized in that in a first drilling step continuing to a first drilling depth equal to the length of the continuous screw auger, earth material is conveyed to the surface by the continuous screw auger, and that in a second drilling step starting from the first drilling depth, the drilled material is fed by the continuous screw auger to the displacement head, by means of which the earth material is forced into the wall of a bore hole. 
     The advantages described above with respect to the sinking of the bore hole beyond the length of the continuous screw auger, stabilizing the wall of the bore hole and preventing the accumulation of excavated material are achieved when using this method of the invention. This drilling method makes it possible to create the bore hole in a single continuous operation or intermittently in a number of steps, the drilling element being withdrawn at definite time intervals or at certain depths. Particularly effective stabilization of the wall of the bore hole can thus be achieved by virtue of the fact that the displacement head travels past the wall of the bore hole several times. 
     For creation of a foundation element, it is preferred, according to the invention, that the filling material used to form the foundation element is introduced into the bore hole when the final depth has been reached. The filling material can be a dry material, for example, sand, lime, or the like or a settable suspension such as a concrete mix. The filling material is preferably introduced into the bore hole through a central core tube in the continuous screw auger. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The invention is further explained below with reference to preferred exemplary embodiments illustrated diagrammatically in the attached drawings, in which: 
         FIG. 1  is a diagrammatic side view of a drilling rig of the invention at the commencement of the drilling method of the invention; 
         FIG. 2  is a diagrammatic side view of the drilling rig shown in  FIG. 1  on conclusion of the first drilling step; 
         FIG. 3  is a diagrammatic lateral view of the rig shown in  FIG. 1  and  FIG. 2  in the second drilling step; 
         FIG. 4  is a diagrammatic partial view of the drilling rig of the invention during the first drilling step; and 
         FIG. 5  is a diagrammatic partial view of the drilling rig of the invention during the second drilling step. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A drilling method of the invention together with a drilling rig  10  of the invention is illustrated in  FIGS. 1 to 3 . As shown in  FIG. 1 , the drilling rig  10  comprises an approximately vertically aligned mast  12 , which is pivotally mounted via an adjusting mechanism  13  on a base  14 . The base  14  is in the present exemplary embodiment in the form of a crawler type vehicle having a rotatable superstructure. 
     A slide  18  is mounted in known manner for displacement along the mast  12  via a cable pulley mechanism. An annular drilling drive  16  is provided on the slide  18  for the purpose of driving the bar-shaped drilling element  20 . The lower region of the drilling element  20  comprises a so-called continuous screw auger  22 , which is composed of a mid-conduit or core tube  24 , on the outside surface of which a feed helix  26  extends over virtually the entire length thereof. A cutting unit  28  for removing the earth material is formed in known manner on the bottom end of the continuous screw auger  22 . 
     The length of the continuous screw auger  22  is adjusted to that of the mast  12  and is approximately equal to the length of the mast  12 . In the exemplary embodiment illustrated, the mast has a length of about 20 m, while the length of the continuous screw auger is about 15 m. The length of the continuous screw auger  22  is somewhat shorter than the length of the mast  12 , this being substantially due to the size and length of the drilling drive  16 , including the slide  18 . 
     A displacement head  40 , which will be described below in more detail with reference to  FIGS. 4 and 5 , is connected to the top end of the continuous screw auger  22  below the drilling drive  16 . Adjoining the displacement head  40 , a bar-shaped extension  30  is attached, which extends upwardly through the annular drilling drive  16  from the displacement head  40  disposed below the drilling drive system  16 . Drive ridges  32  extending longitudinally in the drilling direction are disposed on the outside surface of the extension  30  as in a Kelly bar. The torque of the drilling drive system  16  can be transmitted by way of these drive ridges  32  to the extension  30  and thus to the drilling element  20  as a whole. The drive ridges  32  further permit, in known manner, axial displacement of the extension  30  in relation to the drilling drive  16  with concurrent torque transmission. 
     In a first drilling step illustrated in  FIG. 2 , a bore hole  6  is sunk until the top end of the continuous screw auger  22  is reached. During this first drilling step, earth material removed by the cutting unit  28  is conveyed by the feed helixes  26  upwardly out of the bore hole  6 . On conclusion of the first drilling step, the drilling drive  16  is moved until it reaches its maximum movement distance, that is to say, from its upper initial position shown in  FIG. 1  to its lower end position at the bottom end of the mast. In order to sink the bore hole  6  further, the drilling element  20  is moved further down by way of the extension  30  with the drilling drive  16  now stationary. The downward advance of the drilling rig in the drilling direction can significantly be brought about substantially by the weight of the drilling element  20  and the propelling action of the feed helixes  26 . However, the drilling drive  16  can alternatively be reset and the extension  30  can be actively moved in the drilling direction. 
     In this second drilling step, the removed earth material can no longer be conveyed by the feed helixes  26  of the continuous screw auger  22  toward the surface. In order to prevent choking in the region of the bar-shaped extension  30 , which has now entered the bore hole  6 , the displacement head  40  forces this removed earth material, aside into the wall of the bore hole as proposed by the invention. On conclusion of the second drilling step, in which the bar-shaped extension is moved into its bottom end position as shown in  FIG. 3 , filling material can be fed into the bore hole  6  at the bottom end of the continuous screw auger  22  from a suspension port  34  at the top end of the extension  30  via the inner cavity of the extension  30  and the core tube  24 . 
       FIG. 4  illustrates the drilling method of the invention during the first drilling step. Here, a bore hole  6  is formed in the ground  2  by the continuous screw auger  22 . Feed helixes  26  convey the removed earth material  4  upwardly out of the bore hole  6  toward a surface  3 . The excavated earth material  4  can be removed from here and hauled away in known manner. 
     At the top end of the core tube  24  of the continuous screw auger  22  there is disposed a tube connection  25 , to which the displacement head  40  (not illustrated here) is coupled non-rotatably. 
     On conclusion of the first drilling step, when the maximum movement distance of the drilling drive  16  has been reached and the continuous screw auger  22  penetrates the ground  2  over its entire length, the displacement head  40  forces the earth material  4  being conveyed upwardly aside into the wall of the bore hole  7 , as shown in  FIG. 5 . 
     In the preferred exemplary embodiment, the displacement head  40  comprises an approximately central, cylindrical displacement section  42 , on the outside surface of which strip-shaped displacement elements  44  are disposed. A lower conical section  46 , the outside surface of which is provided with a lower helix  48 , is disposed below the displacement section  42 . The lower helix  48  serves to convey the removed earth material  4  into the region of the displacement section  42 . 
     The inverted cone-shaped lower conical section  46  is non-rotatably connected to the continuous screw auger  22  with the aid of the conduit connection  25 . The diameter of the lower conical section  46  continuously increases from the diameter of the core tube  24  to the diameter of the cylindrical displacement section  42 . 
     Conversely, an upper conical section  50  comprising an upper helix  52  is disposed above the displacement section  42 . The upper helix  52  has a counter-conveying direction in relation to that of the lower helix  48  so that earth material is conveyed by the upper helix  52  downwardly to the central displacement section  42  in the usual drilling direction. 
     The upper conical section  50  is of a regular conical shape, the diameter of which uniformly tapers from the diameter of the displacement section  42  upwardly to approximately the diameter of the bar-shaped extension  30 . The bar-shaped extension  30  is connected non-rotatably to the displacement head  40  via an upper tube connection  54 .

Summary:
A drilling rig and a drilling method, in which the drilling element is caused to rotate and is displaced along a mast by means of a drilling drive, which drilling element has a continuous screw auger disposed below the drilling drive, and an extension, which is connected to the continuous screw auger and extends upwardly through the drilling drive. A displacement head is disposed between the continuous screw auger and the extension and is adapted to force earth material into the wall of a bore hole.