Patent Publication Number: US-2023160168-A1

Title: Rotary driver for a helical pile foundation attached to a boom arm of an excavator forming a counter-support

Description:
The invention relates to a rotary driver for a helical pile foundation that is attached to a boom arm of an excavator forming a counter-support. The helical pile foundation is screwed into or out of the ground using the rotary driver. Power for driving the turning device is provided by the excavator. 
     Rotary drivers of this type which are attached to an excavator arm and by means of which helical pile foundations can be screwed into the ground or screwed out again from the same are known. U.S. Pat. No. 4,199,033 describes a rotary device that is attached to an excavator arm and is capable of driving a helical pile foundation into the ground. The rotary device is fastened to the excavator arm in the form of a hydraulic drive unit on whose lower, groundward-facing side is arranged a chucking device for the helical pile foundation. The helical pile foundation is driven around its longitudinal axis by means of a rotary device. Corresponding pivot axes make it possible for the helical pile foundation to be pivoted in any direction that deviates from a vertical insertion direction and to be screwed into the soil in a desired direction or screwed out again from the same. 
     In the known device, the excavator arm is attached to the upper part of the rotary driver. When a large deflection of the excavator arm occurs, a relatively large tilting moment can occur when screwing in the helical pile foundation, so that the helical pile foundation can wobble or tilt while it is being screwed in. This makes it difficult to screw in the helical pile foundation at a desired, defined angle, which is disadvantageous. If there is an axial offset between the load application point and the screw axis, a feed force creates a skewing moment when the excavator boom arm is pushed down. This skewing moment causes the helical pile foundation that is to be screwed in to deviate from the desired installation direction. During the installation process, the excavator operator can counteract this by attempting to compensate for the degree of skewing. The drawback here is that the installation process is highly dependent on the skill of the excavator operator. When the helical pile foundation is being screwed in using the rotary driver attached to the excavator arm, a torque is exerted on the helical pile foundation, whereby transverse forces are produced which act on the helical pile foundation. In addition, forces arise in the longitudinal direction of the excavator forming a counter-support. The forces exerted on the helical pile foundation as a result, including the torque from the rotary driver, result in a disadvantageous deviation from the desired screw-in angle of the helical pile foundation in the ground during the installation process. 
     It is the object of the invention, in contrast to the known rotary driver for a helical pile foundation attached to a boom arm of an excavator forming a counter-support, is for at least a portion of the acting transverse forces and the skewing moment to be compensated for when there is an axial offset, thus enabling the excavator operator to better control the vertical alignment of the helical pile foundation using the available articulation forces. 
     This object is achieved with a rotary driver for a helical pile foundation which is attached to a boom arm of an excavator forming a counter-support and has the features according to claim  1 . Expedient refinements are defined in the dependent claims. 
     According to the invention, a helical pile foundation is screwed into or out of the ground or soil by means of a rotary driver that is attached to a boom arm of an excavator forming a counter-support. The rotary driver has a rotary drive and a chucking device for the helical pile foundation, the rotary drive being supplied with power from the excavator, being arranged at the front end of the boom arm, and transmitting a drive torque to the helical pile foundation for the purpose of screwing into or out of the ground via the chucking device. The excavator itself forms a counter-support for the installation process, which, depending on the size of the excavator, can often no longer fully compensate for the transverse force resulting from the driving torque. 
     According to the invention, an additional counter-support is therefore provided which acts on the rotary drive, on the front end of the boom arm of the excavator, or on the chucking device for the helical pile foundation and is anchored in the ground. The additional counter-support is designed so as to compensate for the forces acting on the helical pile foundation laterally to the plane of extension of the boom arm of the excavator due to the drive torque. Such an additional counter-support is easy to anchor in the ground—e.g., in the manner of a peg as when anchoring a tent—and likewise easy to fasten to the front end of the boom arm or to the chucking device or to the outer, preferably cylindrical housing of the rotary drive of the rotary driver. This additional counter-support absorbs at least a portion of the forces that arise from the lateral forces and from the skewing moment when there is an axial offset. This enables the excavator operator to better control the vertical alignment of the helical pile foundation while screwing it in. The additional counter-support can also be another vehicle, particularly another excavator, in which case the anchoring in the ground is achieved by means of the drive chains. 
     The additional counter-support is preferably embodied as a tension cable or a tension chain. The tension cable is attached to the side of the helical pile foundation from which the helical pile foundation moves as a result of the skewing relative to the ideal screw axis. Advantageously, the tension cable or tension chain is connected via a winding device to the rotary drive, the front end of the boom arm or the chucking device in such a way that the shortening of the effective length of the tension cable or tension chain as a result of screwing the helical pile foundation into the ground is compensated for, so that the force exerted by the counter-support on the helical pile foundation during installation remains substantially constant. 
     More preferably, the additional counter-support is embodied as a tie rod or push rod, i.e., as a substantially rigid component that can compensate for the tensile forces or compressive forces that occur as a result of the skewing moment. If the additional counter-support is attached to the side of the rotary drive, the front end of the boom arm, or the chucking device in such a way that only tensile forces have to be compensated for by the additional counter-support, the dimensioning of the tie rod can be made smaller than, for example, in the case of a push rod, because the problem of buckling forces does not exist with a tensile load. Preferably, the additional counter-supports are telescopic in the form of the tie rod or push rod, so that both forces can be absorbed and corresponding changes in length can be compensated for in order to maintain a constant counter-support force. 
     The additional counter-support is preferably hydraulically coupled to the drive torque of a rotary drive embodied as a hydraulic motor. The various units that can be connected to an excavator arm are usually supplied with hydraulics, so that the preferred design for the counter-support is for the rotary drive to be embodied as a hydraulic motor that receives the hydraulic power from the excavator. 
     Preferably, the additional counter-support is designed in such a way or is able to absorb such forces that a force component is generated which compensates for the skewing moment, acts counter to the deflection force on the helical pile foundation caused by the drive torque, and is so great that the helical pile foundation does not drift out of its desired installation direction while being screwed into the ground. 
     The counter-support is preferably designed or acts on the rotary drive, on the front end of the boom arm, or on the chucking device in such a way that, in addition to the lateral force component acting counter to the skewing moment, a force component acts in the installation direction, thus enabling the screwing process to be additionally supported. 
     Further advantages, potential applications, and details of the rotary driver according to the invention, which is attached to the boom arm of an excavator forming a counter-support and is used for screwing in a helical pile foundation, are described in the enclosed drawing, in which: 
    
    
     
         FIG.  1    shows the basic construction of a rotary driver according to the prior art that is attached to a boom arm of an excavator, with indication of the drive torque and lateral forces; 
         FIG.  2    shows an excavator with a rotary driver according to  FIG.  1    attached to the boom arm, with indication of the torque and forces acting in the longitudinal direction of the excavator; 
         FIG.  3   a   ) shows a side view according to the illustration as per  FIG.  1   ; 
         FIG.  3   b   ) shows a plan view of the illustration according to  FIG.  1   ; 
         FIG.  4   a   ) shows a three-dimensional view of an exemplary embodiment according to the invention; 
         FIG.  4   b   ) shows a circuit diagram of the interaction of a hydraulic motor as a drive for the rotary drive, which is controlled with a control plunger; and 
         FIG.  5    shows a front view of an embodiment according to the invention in which the force components of the additional counter-support are indicated. 
         FIG.  1    shows the basic construction of a rotary driver for helical pile foundations attached to an excavator arm, the basic arrangement of the rotary driver being embodied as a hanging attachment on the front side of the excavator arm according to the prior art. The excavator  5  has on its front side a boom arm  3  on whose front end a rotary driver  1  with hanging bracket is provided, with a chucking device  7  for the helical pile foundation  2  being provided at the bottom end facing toward the helical pile foundation  2 . When the helical pile foundation  2  is being screwed in, the excavator  5  exerts a drive torque  11  on the helical pile foundation  2  by means of the rotary drive  6  in order to screw it into the ground. The drive torque  11  is represented by the arrow drawn in a circle around the chucking device  7 . When this drive torque  11  is exerted on the helical pile foundation  2 , the excavator  5  forms a counter-support whose lateral forces are represented by an arrow drawn in the vicinity of the drive chains. The force  9  acting in the direction counter to the lateral force  9  in the vicinity of the chains is shown at the front end of the excavator arm  3  and represents a force couple which is absorbed by the excavator  5  as a counter-support. 
     
    
    
     The state shown in  FIG.  1    is that in which the helical pile foundation  2  is in a vertical orientation on a soil domain, which represents the usual installation direction. During installation, the arm of the excavator  5  exerts a downward force on the helical pile foundation  2 , so that, in conjunction with the effect of the drive torque  11  through the rotary drive  6 , the helical pile foundation  2  is screwed into the ground while the height of the front end of the excavator boom arm  3  changes. When the excavator boom arm  3  is pushed down by a feed force, a skewing moment occurs as soon as there is an axial offset between the load application point and the screw axis. Lateral forces are also generated by the torque exerted on the helical pile foundation while it is being screwed in. The skewing moment and transverse forces cause the helical pile foundation  2  that is to be screwed in to move out of the desired vertical installation direction shown in  FIG.  1   . This is disadvantageous in principle and cannot be compensated for without the device according to the invention of an additional counter-support  4 , which is not shown in  FIG.  1    because it represents the state of the art. With the use of an additional counter-support according to the invention, it is possible to use a significantly smaller device, because the excavator only has to form a counter-support with a substantially smaller effect. 
       FIG.  2    shows a known arrangement of a rotary drive  6  for screwing in helical pile foundations  2  on an excavator boom arm  3  of an excavator  5  according to  FIG.  1   , the drive torque  11  that is introduced through the rotary drive  6  via the chucking device  7  being represented by the circular arrow that is drawn in.  FIG.  2    illustrates the situation of a sufficiently heavy excavator  5  as a counter-support. A force couple  10  compensating for driving torque is formed in the longitudinal direction of the excavator  5 . Lateral forces are not introduced into the foundation. This figure is intended to show that the torque can only be compensated for by a considerable dead weight on the part of the excavator  5 . 
       FIG.  3    shows the known arrangement according to  FIGS.  1  and  2    in a side view ( FIG.  3   a   )) and top view ( FIG.  3   b   )). The arrangement and the individual elements are identical to those according to the three-dimensional representations according to  FIG.  1    and  FIG.  2    and are therefore not explained separately again. 
       FIG.  4   a   ) shows an exemplary embodiment according to the invention in a three-dimensional view. Here again, the basic construction is identical to that according to  FIGS.  1  to  3   , according to which a boom arm  3  is attached to the excavator  5  and a rotary drive  6  is suspended from the front end thereof. The rotary drive  6  has a chucking device  7  for a helical pile foundation  2  at its end opposite the hanging attachment on the excavator arm. In order to compensate for the skewing moment that occurs during installation, an additional counter-support  4  is attached to the outer circumference of the rotary drive  6  in this exemplary embodiment and is embodied as a tie rod  4 . 3 , the end of which opposite the attachment to the rotary drive  6  has an anchorage in the soil domain. This tie rod ensures that any skewing of the helical pile foundation  2  is compensated for while it is being screwed in. The forces  9  acting laterally as a result of the skewing moment when the axis is offset and the transverse forces are thus absorbed by the additional counter-support  4  in the form of the tie rod  4 . 3 . This enables the excavator operator to better control the vertical alignment of the helical pile foundation while screwing it in. Since the length of the tie rod  4 . 3  shortens during installation when the helical pile foundation  2  is being screwed in along its longitudinal axis, the tie rod  4 . 3  is designed so as to have a telescopic effect that shortens the length in the compression direction, meaning that, during the installation process, the tie rod  4 . 3  arranged on the hypotenuse of the triangle adapts to the respective screw depth while preventing skewing in the pulling direction of the tie rod  4 . 3 , i.e., compensating for the deflection of the helical pile foundation  2  as a result of the skewing moment. 
       FIG.  4   b   ) shows that the rotary drive  6  is embodied as a hydraulic motor and is appropriately controlled in terms of the drive torque  11  via a control plunger. The advantage of using a hydraulic motor as a rotary drive  6  is that a hydraulic supply from the excavator  5  is already available for the tools of the excavator  5 , which can be attached to the excavator arm  3  and exchanged for different purposes. 
       FIG.  5    shows a front view of the rotary driver  1  that is attached to the boom arm  3  of the excavator  5  and has a rotary drive  6  with a hanging attachment at the front end of the boom arm  3  and is embodied at the opposite end with a chucking device  7  for the helical pile foundation  2 . The additional counter-support  4  according to the invention and the forces  9  acting laterally on the excavator  5  are shown in the form of force effects. The lateral forces  9  are absorbed by the excavator  5 , which in turn forms a counter-support. In order to prevent skewing caused by the skewing moment, the additional counter-support  4  absorbs a force in the direction of the existing tie rod  4 . 3  consisting of two force components. One force component is a lateral force component, which additionally compensates for the lateral force  9 . An advantage of the tie rod  4 . 3  as an additional counter-support  4  is that, due to the laterally inclined attachment of the additional counter-support  4 , there is also a force component in the direction of the insertion of the helical pile foundation  2  which additionally supports the insertion of the helical pile foundation  2  into the ground. 
     It will readily be understood that the additional counter-support  4  can be embodied not only as a tie rod  4 . 3  (see  FIG.  4   a   )), but also as a tension cable or tension chain. The embodiment of the additional counter-support  4  as a tension cable or tension chain is provided in such a way that the tensile force can of course be absorbed by the tension cable or tension chain when the additional counter-support  4  is attached, thus preventing the helical pile foundation  2  that is to be inserted into the ground from migrating out of the desired direction, but that in the course of installation the shortening of the effective length is achieved by winding up the corresponding length representing the shortening of the effective length of the additional counter-support  4 , for example around the rotary drive  6 . Attaching an additional counter-support  4  is a simple way to compensate for the skewing moment without requiring the excavator operator to have any special skills. 
     LIST OF REFERENCE SYMBOLS 
     
         
           1  rotary driver 
           2  helical pile foundation 
           3  boom arm, excavator 
           4  additional counter-support 
           4 . 1  tension cable 
           4 . 2  tension chain 
           4 . 3  tie rod 
           5  excavator 
           6  hydraulic motor 
           7  chucking device 
           8  housing of hydraulic motor 
           9  lateral forces 
           10  longitudinal forces/force couple 
           11  drive torque of hydraulic motor 
           12  control plunger