A double-head drilling machine is disclosed, which by changing over or converting small component units can cooperate with drill or drill pipes of different diameters. To this end, drive carriages ( 16 ) operating on drills or drill pipes, for example, comprise a carriage base element ( 32 ), to which a drive unit ( 42 ) is releasably fitted. The drive unit ( 42 ) can thus be replaced by a different drive unit having essentially the same geometry, which is designed for operating with a drill or drill pipe having a different diameter.

CROSS-REFERENCES TO RELATED APPLICATIONS 
     Not applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a drilling machine according to the preamble of claim  1 . 
     Known drilling machines of this type are designed for working with drills or drill pipes having a given diameter and are used successfully in large numbers in order to produce pile foundations for buildings. 
     2. Discussion of Relevant Art Including 
     Information Disclosed under 37 CFR 1.97-1.99. 
     For new buildings in already built-up areas of a locality, it has already been proposed (DE 195 12 109 A1) to construct the drive carriages on the drill or drill pipe so that they are particularly radially compact in the vicinity of their free end, so that a drill hole can be formed in the immediate vicinity of an existing building wall. 
     It would also be possible to make do with piles having reduced diameters in the immediate vicinity of already existing buildings for some applications in which it is unnecessary to provide a foundation which can be subjected to high loading. However, corresponding drilling machines have not been available to date. It would also be conceivable to generally design drilling machines for operation with drills and drill pipes having smaller diameters. However, only partial use would be made of drilling machines of this type, since a large proportion of foundation work which is to be carried out requires the piles having the larger diameters as used to date. 
     SUMMARY OF THE INVENTION 
     By way of the present invention, a drilling machine according to the preamble of claim  1  is therefore to be further developed in such a manner that it can be used equally with drills and/or drill pipes of different diameters. 
     This object is attained by way of a drilling machine having the features disclosed in claim  1 . 
     Advantageous further developments of the invention are to be found in the subclaims. 
     In a drilling machine according to claim  2 , the adaptation to the respective desired diameter of drill and/or drill pipe is effected in that a drive unit operating on the drill or drill pipe is replaced on the drive carriage. In this manner, it is not only the actual drive element which is changed, but also the drive, which consists of motor and reduction gearing. In this manner, the adjustment of the desired drill or drill pipe diameter is attained with a corresponding adaptation of the drive itself. 
     The further development of the invention according to claim  3  is advantageous in view of a simple and nevertheless precise fitting of the drive unit on the carriage body. 
     With the further development of the invention according to claim  4 , it is attained that further auxiliary elements arranged on the drilling machine, such as tackle for moving loads, can be equally used irrespective of the current drill or drill pipe diameter setting of the drilling machine. 
     In a drilling machine according to claim  5 , there is no need to fit any heavy parts in order to change from operating with a drill or drill pipe having a first diameter to operating with a drill or drill pipe having a second diameter. It is merely necessary to replace the drive element operating on the drill or drill pipe by another drill element. 
     Claim  6  discloses a particularly simple bearing for replaceable drive elements of this type. 
     In a drilling machine according to claim  7 , it is automatically ensured that the cylindrical surface of the drill or drill pipe lying furthest from the fault finder remains essentially the same in the case of drill or drill pipes of different diameters. This makes it possible to produce drill holes for rows of piles of different diameters in front of an existing building wall by substantially identical movements of a chassis carrying the drilling machine. If the foundation work is carried out using numerical control of the chassis carrying the drilling machine, then it is unnecessary to fully reprogram the control when the drill or drill pipe diameter is changed; small changes to the program suffice. 
     In a drilling machine according to claim  8 , a single movement allows for the adaptation of the bearing arrangement to the respective diameter of the drill or drill pipe and the engagement of a pinion of the drive unit with a drive toothed rim of the drive element operating on the drill or drill pipe. 
     The further development of the invention according to claim  9  is advantageous in view of good load uptake of the bearing arrangement. 
     In a drilling machine according to claim  10 , a guide element adjacent the soil surface for drills or drill pipes can be easily adapted in its operating diameter. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be explained in further detail in the following with the aid of embodiments with reference to the drawings. In the drawings: 
     FIG.  1 : is a side view of a double-head drilling machine for producing drill holes in the immediate vicinity of a building wall; 
     FIG.  2 : is a similar view to FIG. 1, although in this case the drilling machine drives a drill having a smaller diameter and a drill pipe having a smaller diameter; 
     FIG.  3 : is a top view of the drill pipe drive of the drilling machine according to FIG. 1, partially shown in section; 
     FIG.  4 : is a top view of the drill pipe drive of the drilling machine according to FIG. 2, partially shown in section; 
     FIG.  5 : is a top view of a modified drill pipe drive in the setting for drill pipes having large diameters; 
     FIG.  6 : is a similar view to FIG. 5, although in this case the drill pipe drive is adjusted for a drill pipe with a small diameter; 
     FIG.  7 : is an axial section through the drill pipe drive of FIG. 7 taken along the line of section VII—VII in FIG. 7, 
     FIGS.  8  and  9 : are views similar to FIG. 6, although in these cases a modified drill pipe drive is again shown; and 
     FIG.  10 : is a similar view to FIG. 3, although in this case a modified drill pipe drive is again reproduced. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     In FIG. 1, the reference  10  designates an excavator chassis in its entirety. The latter supports a fault finder  14 , which is adjustable via a steering arrangement indicated in its entirety by the reference  12 . 
     A drive carriage  16 , which operates via a drive pipe  18  on a drill pipe  20 , is displaceable in the vertical direction on the fault finder  14 . 
     Lying above the drive carriage  16 , a further drive carriage  22 , which operates on a drive rod  24 , is displaceable on the fault finder  14 . The drive rod  24  supports a drill  26 , which extends through the drill pipe  20 . 
     Provided at the lower end of the fault finder is a pipe guide head  27 , which forms a radial bearing for the drill pipe  20 . 
     In order to produce a drill hole in the immediate vicinity of a schematically indicated building  28 , the drill  26  is rotated and forced into the soil. According to the advance of the drill  26 , the drill pipe  20  is also forced with rotation into the soil. The drill  26  constantly conveys the loosened soil upwards into the drill pipe  20 , whence it can fall downwards via openings  30  in the drive pipe  18 . 
     Once the drill  26  has reached the desired depth, it is withdrawn from the drill pipe by moving the drive carriage  22  upwards. If the pile which is to be produced is to be armoured, then an armouring is let down into the drill pipe  20 , and the drill pipe  20  is then filled with local concrete and withdrawn rotating from the drill hole. 
     The procedure described above is repeated in such a manner that a row of adjacent local concrete piles is obtained, which can thus form a building foundation which lies in the immediate vicinity of the building  28 . 
     The drilling machine described above can be converted from operation with a drill pipe  20  having a large diameter and a drill  26  having a large diameter, as shown in FIG. 1, to operation with a drill pipe having a small diameter and a drill  26  having a small diameter, as illustrated in FIG.  2 . 
     In order to carry out this conversion simply, the drive carriages  16  and  22  each have the construction shown in FIGS. 3 and 4, these drawings showing the drive carriages for the drill pipe, the drive carriages for the drill and the pipe guide head being similarly designed. 
     As a modification, the upper drive carriage  22  can be constructed in such a manner that it is suitable for use together with the drill having the smallest diameter, the drive rods for the drills having larger diameters remaining the same in this case. 
     As shown in FIG. 3, the drive carriage  16  has a carriage base element  32 , which with lateral cheeks  34  engages around guide strips  36 , which are provided in the corners of the fault finder  14 . Resting on a shoulder  38  of the carriage base element  32  is a rear end section  40  of a box frame  41  of a drive unit designated in its entirety by the numeral  42 . The latter has a downwardly hanging plate  44 , which rests against the front side of the carriage base element  32 . 
     Provided on the shoulder  38  are positioning rods  46 , which cooperate with positioning apertures  48 , which are provided in the end section  40  of the drive unit  42 . Screws  50 , which cooperate with threaded bores  52  in the shoulder  38 , are used for the releasable connection of the drive unit  42  with the carriage base element  32 . Further screws  54  extend through the vertical plate  44  and are screwed into the front boundary surface of the carriage base element  32 . 
     The drive unit  42  supports two hydromotors  56 ,  58 , which operate via pinions  60 ,  62  on an intermediate pinion  64 . The latter meshes with a toothed rim  66 , which is constructed on the outer surface of a drive sleeve  68 , and this is mounted via a radial/axial bearing, not shown in further detail in FIG. 3, in the front section of the drive unit  42 . In this respect, the thickness of the drive sleeve  68  and the web of the box frame  41  of the drive unit  42  enclosing the drive sleeve  68  are selected to be as small as is still acceptable in respect of the mechanical loading. In this manner, the drive unit  42  projects only slightly in the radial direction beyond the outer surface of a drill pipe  20  connected to the drive sleeve  68 , as is shown in FIGS. 1 and 2. 
     The drive carriage  22  for the drill is similarly constructed, with the exception that a drive disc is provided instead of the drive sleeve  68 , the drive disc comprising in its centre a polygonal (usually square) opening for a drill rod. 
     The pipe guide head  27  is also constructed similar to the drive carriage  16 , but comprises a radial bearing unit, which can be removed from the carriage base element and cooperates with the outer surface of the drill pipe. 
     If it is intended to convert the drilling machine to operation with drills having a smaller diameter and drill pipes having a smaller diameter, then the screws  50  and  54  are released and with the aid of a lifting tool schematically indicated  70  in FIGS. 1 and 2, the drive unit  42  of the drive carriage  22  and then the drive carriage  16  are raised and placed onto the ground. The radial bearing unit of the pipe guide head  27  is then removed. A new radial bearing unit and new drive units  72  are then accommodated and again secured in reverse sequence to the carriage base elements  32  of the pipe guide head  27 , the drive carriage  16  and the drive carriage  22 . The new radial bearing unit and the new drive units have the same geometry as the replaced units with the proviso that they are designed for different diameters of drill or drill pipe. For example, if the drive sleeve  68  now has the desired smaller diameter on the drive carriage  16 , then the size of the intermediate pinion  64  is accordingly increased. 
     Since drills and drill pipes having smaller diameters can be rotated into the soil with reduced torque, it is also possible to provide smaller hydromotors  56 ,  58 . 
     It can be seen that a drilling machine as described above can be very rapidly converted for the drilling of drill holes of different diameters. 
     In the embodiment illustrated in FIGS. 5 and 6, parts of the drive carriage which correspond in their function to parts already explained with reference to FIGS. 3 and 4 are again provided with the same reference numerals. These parts are not described again in detail in the following. 
     In this case, an upper plate of the box frame  41  of the drive unit  42  has a rectangular opening  74 . The edges of the opening  74  extending towards the free ends of the drive unit simultaneously act as guide rails for guide grooves  76 , which are provided in lateral surfaces of a motor plate  78 . The motor plate  78  supports the hydromotors  56 ,  58  as well as the intermediate pinion  64 . In order to move the motor plate  78  in a horizontal direction perpendicular to the fault finder, two hydraulic cylinders  80  are used, which are supported against the rear end section  40  of the housing  41  of the drive unit  42 . 
     The intermediate pinion  64  has a bearing collar  82 , which lies beneath the toothed rim of the intermediate pinion, projects radially beyond the pinion toothed rim  66  and runs axially beneath the pinions  60 ,  62 . The bearing collar  82  has a trapezoidal cross section. A bearing groove  84 , which has a cross section matching the bearing collar  82 , is cut into the drive sleeve  68  beneath the toothed rim  66 . 
     In the case of the free end of the drive unit  72 , bearing rollers  86 ,  88  having small diameters are mounted, whose contour also matches the bearing groove  84 . The drive sleeve  68  is thus mounted by the intermediate pinion  64  with its bearing collar  82  and the bearing rollers  86 ,  88 . 
     By moving the motor plate  78  in the direction of the fault finder  14 , the bearing collar  82  can be moved away from the drive sleeve  68  to such an extent that the latter is released from the bearing rollers  86 ,  88  and can be removed from the box frame  41 . A drive sleeve  68  having a smaller diameter can then be inserted and the motor plate  78  can be moved away from the fault finder to such an extent that the bearing sleeve  68  simultaneously engages again with the bearing collar  82  and the bearing rollers  86  and  88 . A correct engagement between the toothed rim of the intermediate pinion  64  and the toothed rum  66  of the drive sleeve  68  is then simultaneously produced, since all drive sleeves which are to be used together with the drive carriage comprise toothed rims consisting of teeth having the same shape. 
     The engagement relationships between the intermediate pinion  64  and the bearing rollers  86 ,  88  on the one hand and the drive sleeve  68  on the other hand can be clearly seen from the angled sectional view of FIG.  7 . 
     The further modified embodiment according to FIG. 8 differs from that according to FIG. 7 only in that two intermediate pinions  64   a  and  64   b  are used instead of a single intermediate pinion  64 , the two intermediate pinions being arranged symmetrical to the vertical centre plane of the drive carriage  16  in FIG.  8 . 
     In the embodiment according to FIG. 9, the bearing rollers  86 ,  88  are supported by a bearing plate  90 , which with guide shoes  92  engages over the lateral edges of the box frame  41 . The bearing plate  90  is adjustable and lockable by hydraulic cylinders  80 . Also in this manner, the drive carriages  16  can bear and drive drill pipes having different diameters. 
     It is, of course, also possible to use sliding bearing elements instead of the bearing rollers  86 ,  88  shown in FIGS. 5 to  9 , the sliding bearing elements cooperating with the bearing groove  84  and only extending over a small circumferential region, so that they can cooperate equally well with circular bearing grooves of different diameters. 
     In the case of the drive carriage according to FIG. 10, the hydromotors  56 ,  58  are fitted to support plates  94 ,  96 , which are fitted to the carriage base element  32  independent of the housing  41  and are accommodated in recesses  98 ,  100  in the housing  41 . The adaptation of the drive carriage to the respective drill pipe diameter is effected merely by exchanging the bearing and gearing unit, which is formed by the components  41 ,  64 ,  66 ,  68 . In this manner, the unit which is to be replaced is cheaper, and the connections to the hydromotors do not need to be released in order to convert the drill pipe diameter.