Abstract:
An earth boring machine  10  with a frame and a linearly movable slide  22  on the frame has an apparatus for holding and rotationally driving a boring rod  24 , and a forward feed drive for moving the slide parallel to the boring direction. The machine with especially small space requirement creates a large force for movement of the slide  22  in and opposite to the forward feed direction. Moreover, the forward feed drive of the earth boring machine  10  has a rotationally drivable forward feed spindle  20  arranged on the frame  18 , which spindle is received by a spindle nut non-rotationally connected with the slide  22.

Description:
FIELD OF THE INVENTION 
     The invention concerns an earth boring machine with a frame, a slide linearly movable on the frame, which slide has an apparatus for holding and rotatably driving a boring rod, and a forward feed drive for moving the slide parallel to the boring direction. 
     BACKGROUND OF THE INVENTION 
     In the creation of an earth bore, the forward feed drive of such an earth boring machine moves the slide relatively slowly forwardly against a large force exerted by the earth, which force is transmitted to the slide through the boring rod. Previous earth boring machines have for the forward feed drive a cylinder arranged on the frame from which a piston is moved outwardly in its axial direction to push the slide forwardly. A disadvantage is that in such a drive, during the extension and retraction of the piston respectively, greatly different forces are created. The maximum force can therefore be deployed only either for the creation of a bore or for the pulling of the boring rod from the bore. 
     If the piston becomes fully extended, the boring rod is disconnected from the slide and thereafter the piston is retracted with the slide also being retracted on the frame oppositely to the forward feed direction. Thereafter, an additional rod member is fastened with one end to the slide and with its other end to the boring rod, before the piston is again driven forwardly to extend the bore. The frame of such earth boring machines extends at least over the length of the cylinder with its piston extended, and therefore, at least over double the length of a rod member. Where only little room is available for placement of the frame, such an earth boring machine cannot be used. 
     The frames of such earth boring machines can be built with shorter length. The publication DE 196 45 222 A1 discloses an earth boring machine on the frame of which is arranged a forward feed drive, and chains and chain wheels for driving a slide, which slide is fastened to an upper run of one of the chains. Such a construction requires a forward feed drive of high power for driving the slide at a low rotational speed and a large rotary moment. Therefore, arranged on the frame is an especially high power motor with a speed reducing drive which is expensive and requires a large amount of room. 
     If the chains are driven by an hydraulic motor, there arises the disadvantage that the hydraulic motor when operating at low rotational speeds has a very poor efficiency. This means that, especially in the case of hard earths, which demand a slow forward feed, the maximum rotational moment of the hydraulic motor becomes indeed needed but, because of the slow rotational speed, it cannot be used. 
     Further, during the forward feed of the slide against the resistance of the earth, large forces come into effect between the chain and the slide. This requires the use of especially robust chains and chain wheels likewise requiring much space so they are also disadvantageous in regard to constructional size and/or the space requirement of such compact boring mechanisms. 
     It is the object of the invention to provide an earth boring machine of the above kind which with an especially small space requirement creates in a simple way a large force for moving the slide in and opposite to the forward feed direction. 
     SUMMARY OF THE INVENTION 
     This object is solved by an earth boring machine in which the forward feed drive has a rotationally drivable forward feed spindle arranged on the frame, which spindle is received by a spindle nut non-rotatably fixed to the slide. 
     The use of a forward feed spindle and a spindle nut for the drive of the slide in the earth boring machine of the invention has the advantage that the driving rotational moment by way of the forward feed spindle and the spindle nut is converted directly into a forward feed force exerted onto the slide. A drive motor creates with its power a rotary moment which drives the forward feed spindle in a rotational motion at a given rotational speed. The pitch of the threads of the forward drive spindle, in the case of a given motor power and rotational speed, determines the forward feed force and the forward feed speed of the slide. The smaller the pitch of the thread, the smaller is the forward feed speed and the larger the forward feed force of the slide. 
     According to the inventive idea, the pitch of the forward feed spindle is so designed that the forward feed speed of the slide is very small and the forward feed force transmitted to it very large. Both of these values can be changed by the use of other forward feed spindles and spindle nuts with other thread pitches, and thereby the particular requirements of a current boring process can be accommodated. These advantageous effects are achieved without the use of a separate speed reducing drive. The frame of the earth boring machine can therefore be made in an especially space-saving way. 
     In a preferred embodiment of the inventive earth boring machine, the slide is movable relative to the spindle nut along an axial extent which is at least so long as the axial length of a thread for connecting two rod members and which axial extent is limited by stops fixed to the slide. During the emplacement and removal of a rod member between the boring rod and the slide, there appears between the boring rod and the slide axially directed tension or compressive forces. During the threading on of an additional rod member, for example, there is exerted on to the threads of the receiver of the slide a force in the forward feed direction and onto the thread of the boring rod an oppositely directed force. Because of the high resistance of the boring rod sticking into the earth on one hand and the spindle nut on the other hand against an axial movement when the forward feed drive is at rest, there exists the danger that the threads on the boring rod and on the receiver are abraded by the high axial forces during the threading of the parts to one another or from one another. In the preferred embodiment, the slide gives way against the tension or compression force applied to it through the receiver and during the making or loosening of the threaded connection is driven relative to the fixed in place spindle nut axially along a stretch of displacement. In this way, damage to the threads is avoided. The length of the movable stretch corresponds about to the length of the threads and is limited by axial stops fixed to the slide. These stops transmit therefore the forward feed force from the spindle nut to the slide when the forward feed drive is in operation. 
     This embodiment can be optimized by pre-tensioning the slide by means of a tension element in one of the axial stop positions. Thereby the movement of the slide relative to the spindle nut either during the threading from one another or the threading to one another of the receiver and the rod member is supported and the tension or compression force is reduced. 
     In this case, it is especially advantageous if the slide is pre-tensioned in the direction of the forward movement of the boring rod, by a helical spring designed as a compression spring surrounding the forward feed spindle and working between the spindle nut and, for example, the axially forward stop. In this way, for one thing, the insertion of an additional rod member is made easier. The slide is first driven in the forward feed direction until the threads of the rod member and the receiver come into contact with one another. Then the spindle nut is moved further against the force of the compression spring for about the length of the threads. The thereby existing tension of the spring is then used itself for the forward pushing of the slide while the threads of the receiver are threaded with those of the rod member by actuation of the rotary drive. An interruption of the actuation of the rotary drive, in order to relieve the slide from tension forces during the threading together of the windings with the help of the forward feed drive, is not necessary. 
     As another thing, the threads of the spindle nut and of the spindle are protected against the direct effect of impacts directed in the forward feed direction, which impacts may appear if the borer encounters relatively large stones. These short-term impulses are conveyed from the boring rod through the slide to the forward axial stop and push the slide against the forward feed direction and against the force of the compression spring, which is thereby compressed. At the same time, the compression spring increases the forward feed force exerted onto the slide and supports the borer in overcoming the encountered obstacle. The spindle nut and spindle do not become loaded with additional axial force. 
     In a further embodiment, a forward feed motor is arranged in line with the longitudinal axis of the forward feed spindle for the direct rotational drive of the forward feed spindle. With this arrangement, the rotational moment of the forward feed motor is transferred directly and without loss to the forward feed spindle. 
     In another preferred embodiment of the inventive boring mechanism, a forward feed motor for the rotational drive of the forward feed spindle is arranged laterally of the longitudinal axis of the spindle and is connected with the spindle through a drive. By this arrangement of the forward feed motor laterally of the forward speed spindle, the extent of the frame of the boring mechanism in the direction of the spindle axis is especially small. 
     In a further preferred embodiment, the forward drive spindle is surrounded by a concave cone spring (telescopic spring) or by a bellows. In this way the forward drive spindle is protected from becoming dirty without the movement of the slide being hindered. 
     In another preferred embodiment, the threads of the forward drive spindle and of the spindle nut are formed in profile like ball bearing races and in the interior of the spindle nut are filled with balls. Because of the relatively low rolling frictional forces between the balls and the threads of the spindle nut and the forward drive spindle, the loss of rotational drive moment is reduced, in comparison to the substantially higher sliding frictional forces which would exist between the threads of the forward drive spindle and the spindle nut in the absence of this bearing. 
     In a further embodiment, a ball bearing is provided for supporting each of the ends of the forward feed spindle on the frame. The ball bearings absorb axial as well as radially-directed forces and are especially saving in space. 
    
    
     Further features and advantages of the invention will be apparent from the following description of an exemplary embodiment of the inventive earth boring machine taken in connection with the accompanying drawings: 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawings are: 
     FIG. 1 a simplified side view of the boring machine. 
     FIG. 2 a perspective illustration of the boring machine. 
     FIG. 3 a plan view of a pit carriage of the boring machine. 
     FIG. 4 an axial partial section of the slide shown in its rear stop position. 
     FIG. 5 a radial section taken along the line V—V in FIG.  4 . 
     FIG. 6 an axial partial section of the slide in its forward stop position. 
     FIG. 7 a radial section taken along the line VII—VII in FIG.  6 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a simplified side view of an earth boring machine  10  with a pit carriage  12 , which is set up in a dug starting pit  16  in the earth  14 . The pit carriage  12  has a frame  18  with a forward feed spindle  20  connected with a slide  22  to which the rear end of a boring rod  24  is fastened. The boring rod  24  extends with its boring head  26  essentially horizontally outwardly from the frame  18  into the earth  14 . 
     FIG. 2 shows a detailed perspective view of the earth boring machine  10  without the boring rod  24 . The frame  18  of the pit carriage  12  has a forward wall  28  and a rear wall  30 . These walls are rigidly connected, at their lower lateral sections, by two rectangular profile bars  32  and  34  extending between the walls, and at their upper lateral sections by two adjustable length tension struts  36  and  38 , which with their dish-shaped end surfaces  40  brace the frame  18  of the earth boring machine  10  against the walls of the starting pit  16  (see FIG.  1 ). The forward feed spindle  20  is rotatably supported on the walls  28  and  30 . 
     Further, two cylindrical guide rails  44  and  46  extend between the forward wall  28  and the rear wall  30  on both sides of and somewhat above the forward feed spindle  20 , which guide rails, as illustrated in FIG. 2, are surrounded by a cover  42  in the form of a concave cone spring. A slide  22  of nearly rectangular shape is supported on the guide rails  44  and  46  for sliding movement along the length of the spindle axis. Two hollow cylinders  48  and  50 , which receive the guide rails  44  and  46 , and which are rigidly connected with the body of the slide, extend in the axial direction through the slide  22  near the lower lateral ends of its body. The connection of the slide  22  with the forward drive spindle  20  is described below in connection with FIG.  4  through FIG.  7 . 
     On the slide  22  above the forward feed spindle  20  is arranged a rod receiver  52  with a rotatable threaded pin  56  fastened to a bearing  54  and extending in the forward feed direction. The boring rod  24  is tightly screwed onto the threaded pin  56 . For the rotary drive of the boring rod  24 , the rod receiver  52  is connected with a rotary drive motor  58  by means of a non-illustrated drive, which motor is fastened to the side of the slide facing in the forward feed direction laterally of the rod receiver  52 . 
     For the rotary drive of the forward feed spindle  20 , on the side of the forward wall  28  facing in the forward feed direction is provided a chain drive  60  with a drive wheel  62 , a chain  64 , and drive wheel  66 . The drive wheel  66  is non-rotatably connected with the forward end of the forward feed spindle which extends forwardly through and beyond the forward wall  28 . To avoid dirt, the chain drive  60  is surrounded from outwardly in by a protective cover  68  fastened to the forward wall  28 . 
     The drive wheel  62  of the chain drive  60  is connected with a forward feed motor  70  which, in the illustration of FIG. 2, is not visible and which is described in more detail below in connection with FIG.  3 . 
     On the frame  18  of the pit carriage  12  is a vertically extending carrier  72  for a control console  74  for controlling the functions of the earth boring machine. The carrier  72  is hollow and carries the non-illustrated control conductors for connecting the operating elements  76  of the control console  74  with the drive apparatuses of the pit carriage  12 . 
     FIG. 3 shows in a simplified plan view the pit carriage  12 , to which the forward feed motor  70  for rotatably driving the forward feed spindle  20  is fastened laterally of the forward feed spindle on the side of the forward wall  28  facing opposite to the forward feed direction. 
     FIG. 4 shows by way of an axial partial section of the slide  22  its support on the forward feed spindle. First one sees in non-sectional illustration the upper section of the slide body having on its forward side the rod receiver  52  extending in the forward feed direction as well as the rotary drive motor  58 , and on its rear side having a housing  78  for connection with flushing water conductors. The housing  78  has a sealed, rotatably supported inner shaft (not illustrated) which is connected with the boring rod through the rod receiver. The hollow cylinder  48  extends in the axial direction to both sides of the slide  22 . In sectional illustration is shown a support housing  80  arranged on the lower section of the slide  22 , which housing  80  surrounds the forward speed spindle  20 , a spindle nut  82  supported on the spindle, and a helical spring  84 . The support housing  80  has a cylindrical outer profile and is made up of three housing parts; namely, a forward housing body  86  rigidly formed on the slide  22 ; an intermediate ring  88 ; and a rear housing body  90 . The three housing parts are connected by screws  92 . 
     At both axial ends of the support housing  80  are formed tubular supports  94  and  96 , which extend in the axial direction. During operation of the earth boring machine on each of the supports  94  and  96 , a portion of the cover  42 , illustrated in FIG. 2, is supported. 
     The forward housing body  86  has a forward wall  98  with a circular shaped opening in its middle, the edge of which closely surrounds the forward feed spindle  20 . Forwardly of the intermediate ring  88 , the outer and inner profile of the forward housing body widens step-wise to a flange  100 . The intermediate ring  88  lies on the flange  100 , and the intermediate ring in turn, lies on outer ring flange  100  fixedly formed on the rear housing body  90 . The flange  100 , the intermediate ring  88 , and the ring flange  102  have bores  103  for receiving the screw  92 . The rear housing body  90  has a rear wall  104  with a circular opening in its middle, which closely surrounds the forward feed spindle  20 . With its side wall  106 , the rear housing body  90  is received in the interior of the forward housing body  86  and forms together with this a stepless inner profile of the support housing  80 , which closely surrounds the spindle nut  82  at its circumference. In the axial direction, the support housing  80  has play room for movement of the spindle nut  82  between the forward wall  98  and the rear wall  104 . A movement of the spindle nut  82  in the direction toward the forward wall  98  takes place against a force of the intermediately supported helical spring  84  which is formed as a compression spring. 
     FIG. 5 shows a radial section of the support housing  80  and of the forward feed spindle along the line V—V of FIG.  4 . The support housing  80  as seen in this transverse section has a nearly rectangular inner profile. 
     FIG. 6 shows a partial axial section of the slide  20  in its forward stop position. FIG. 6 differs from FIG. 4 in regard to the position of the spindle nut  82  inside of the support housing  80 . The spindle nut is contact with the rear wall  104  so that the helical spring  84  is unloaded. 
     FIG. 7 shows a radial section along the line VII—VII in FIG.  6 . The inner profile of the support housing  80  surrounds the spindle nut  82  so that it is supported in rotatably fixed condition but is axially movable with rotation of the forward feed spindle  20 .