Tool driving or impacting – With work engaging means supporting drive – Structure extends between opposed points
Reexamination Certificate
1999-02-22
2001-03-20
Smith, Scott A. (Department: 3721)
Tool driving or impacting
With work engaging means supporting drive
Structure extends between opposed points
C173S141000, C173S152000
Reexamination Certificate
active
06202758
ABSTRACT:
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 d
McCormick Paulding & Huber LLP
Smith Scott A.
Terra AG fuer Tiefbautechnik
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