Patent Publication Number: US-10774592-B2

Title: Pipe ramming system with hydraulic crowd

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a Divisional of U.S. patent application Ser. No. 14/935,315, which was filed on 6 Nov. 2015, now U.S. Pat. No. 10,316,587, which claims priority from Canadian Application No. 2891805, which was filed on 15 May 2015, which are each incorporated herein in its entirety by this reference thereto. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to pipe ramming. In particular, this invention relates to a system for accommodating a hydraulic percussive hammer and applying crowd to it in a pipe ramming system. 
     BACKGROUND OF THE INVENTION 
     In one conventional approach to pipe ramming, a percussive pneumatic hammer is used to drive the pipe horizontally or at an angle into the ground. The hammer housing is attached to the end of the pipe by means of a suitable fitting and is sometimes further secured by cables. A piston-actuated ram strikes a plate inside the housing and the percussive force is transmitted to the end of the pipe through the housing, thereby causing the pipe to advance into the ground. Friction between the soil and the pipe prevents backward displacement of the pipe while the piston retracts for the next strike. A typical small pneumatic hammer offers 0.17 kJ of energy and delivers 580 blows per minute, weighing less than 10 kg. A typical large hammer has 40 kJ of energy, weighs 12 metric tons and delivers 180 blows per minute. 
     Hydraulic (rather than pneumatic) hammers are often used in vertical drilling. Hydraulic hammers generally operate at fewer strokes per minute but delivering much more per blow. One hydraulic hammer weighs 4 metric tons, delivers  65  blows per minute at 30 kJ, while a 242 metric ton hammer delivers 2300 kJ at 30 blows per minute. In many hydraulic hammers, the energy per stroke and the strike rate are adjustable. The strike piston extends outside the hammer housing to strike the casing. In vertical drilling, the hammer housing is maintained in contact against the casing principally by means of gravity, though a winch crowd system may also be used for enhanced crowd. 
     It is also known to use hydraulic percussive hammers disposed horizontally for pipe ramming. Hydraulic hammers provide greater force and the ability to adjust the impact force of a hydraulic hammer allows for tailoring of the system to the soil conditions. However because the ram extends outside the hammer housing, it is not practical to secure the housing to the pipe. It therefore becomes essential to provide crowd of the hammer against the pipe. One approach to doing so is disclosed by Verkyk, U.S. Pat. No. 6,652,190, who relies on a cable winch crowd system (illustrated in  FIG. 1A  of Verkyk and reproduced as  FIG. 1  herein). While the system is reasonably effective in operation, it is unwieldy to set up, taking about a week to do so. The highly tensioned cables also present a significant danger to personnel. 
     It is an object of the present invention to provide a horizontal pipe ramming system with hydraulic crowd. 
     It is a further object of the invention to provide a horizontal pipe ramming system that uses a hydraulic hammer and that has an improved crowd system. 
     These and other objects of the invention will be better understood by reference to the detailed description of the preferred embodiment which follows. Note that the objects referred to above are statements of what motivated the invention rather than promises. Not all of the objects are necessarily met by all embodiments of the invention described below or by the invention defined by each of the claims. 
     SUMMARY OF THE INVENTION 
     The pipe ramming system of the invention comprises providing a hydraulic crowd to a percussive hammer aligned against the pipe (or against a strike plate, anvil or pipe adaptor interposed between the hammer and the pipe). The hydraulic crowd may be provided by means of one or more hydraulic cylinders. 
     In the preferred embodiment, the hydraulic cylinders act on a rail-mounted carriage that carries the percussive hammer. 
     The system allows the hammer harness to remain in close contact with the pipe for more effective delivery of the strike force. 
     In another aspect, the invention comprises a pipe ramming system that uses a hydraulic hammer aligned with a substantially horizontal pipe. 
     In a more specific aspect, the hammer comprises a housing carried by a rail-mounted carriage and hydraulic cylinders urge the carriage along the rails toward the pipe. 
     In yet a more specific aspect, the hydraulic cylinders are mounted on the carriage and act against an abutment that is stationary in relation to the rails. The abutment may comprise a stationary push block. 
     In another aspect the invention is a pipe ramming system that includes a horizontally disposed hydraulic hammer, hydraulic cylinders to urge a carriage carrying the hammer toward the pipe, and a compressible resilient assembly interposed between the carriage and the hammer. The assembly is compressed by the combined action of the hydraulic cylinders urging the carriage and a hammer harness toward the pipe and of the hammer and associated strike assembly that are braced against the pipe by the crowd force. The resilient assembly decompresses upon the displacement of the pipe resulting from an impact of the hammer. 
     In another aspect of the invention, the assembly is bounded on the pipe side of the assembly by an assembly abutment surface that is fixed in relation to a housing of the hammer and the assembly is bounded on a side that is distal from the pipe by an assembly abutment surface that moves toward the pipe as the hydraulic cylinders displace the carriage toward the pipe. 
     The foregoing may cover only some of the aspects of the invention. Other aspects of the invention may be appreciated by reference to the following description of at least one preferred mode for carrying out the invention in terms of one or more examples. The following mode(s) for carrying out the invention is not a definition of the invention itself, but is only an example that embodies the inventive features of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       At least one mode for carrying out the invention in terms of one or more examples will be described by reference to the drawings thereof in which: 
         FIG. 1  is a prior art set up for pipe ramming using a hydraulic hammer and a cable winch crowd system; 
         FIG. 2  is a perspective view of a pipe ramming installation according to the preferred embodiment of the invention; 
         FIG. 3  is a side elevation of the installation of  FIG. 2 ; 
         FIG. 4  is a plan view of the installation of  FIG. 2 ; 
         FIG. 5  is a perspective view of a rail and carriage set up used in the preferred embodiment and showing hydraulic cylinders used to provide crowd; 
         FIG. 5A  is a perspective side view of a rail and carriage set up used in the preferred embodiment showing apertures in the rails; 
         FIG. 6  is a perspective view of a harness for holding a hydraulic hammer according to the preferred embodiment; 
         FIG. 7  is a hydraulic hammer used in the preferred embodiment; 
         FIG. 8  is an exploded perspective view of the cushion assembly of the preferred embodiment and also showing a hammer and portions of the hammer harness; 
         FIG. 8A  is an exploded side view of the cushion assembly; 
         FIG. 9  is a perspective view of the system of the invention showing the hammer housing in a forward position at the moment of hammer strike; 
         FIG. 9A  is an enlarged view of the cushion assembly in the position shown in  FIG. 9 ; 
         FIG. 10  is a perspective view of the system of the invention showing the hammer housing in a cocked position immediately prior to a hammer strike; and, 
         FIG. 10A  is an enlarged view of the cushion assembly in the position shown in  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS AND OF AT LEAST ONE MODE FOR CARRYING OUT THE INVENTION IN TERMS OF EXAMPLE(S) 
     The preferred embodiment of the invention uses substantially the same rail  12  and carriage  16  set up as does a standard boring machine. 
     Referring to  FIGS. 2-4 , a hydraulic hammer  20  is disposed axially and aligned with a substantially horizontal pipe  24 . Hammer  20  includes hammer housing  26  to the end of which is rigidly attached a pipe adaptor  22 . A strike plate (not shown) is secured within the pipe adaptor  22 . Pipe adaptor  22  serves to maintain the hammer and the strike plate in alignment with the pipe  24 . As it is fixed to the hammer housing  26 , the pipe adaptor  22  moves along with the hammer housing  26 . 
     During an impact cycle, the forward end of the hammer  20 , namely the strike plate and the pipe adaptor  22  should be in contact with the pipe  24  such that when the hammer  20  strikes the strike plate, the percussive force is transmitted to the pipe  24 . 
     In the preferred embodiment, the hammer  20  is an IHC S90 Hydrohammer hydraulic hammer available from IHC Hydrohammer B.V. It offers an adjustable energy of 9 to 90 kJ per stroke. 
     Hammer housing  26  is cradled by a harness  28  that is secured to the carriage  16 . 
     The hammer harness  28  comprises a rear portion  30  ( FIG. 6 ) affixed to the hammer housing  26  ( FIG. 7 ) and that is translatable in relation to a forward portion  32  of the hammer harness that is fixed to the carriage  16 . Relative movement between them compresses a rubber cushion assembly  34  located at the rear of the harness  28 . The cushion assembly  34  is interposed between the carriage  16  and the hammer. 
     An adjustable push block  35  is secured by dogs  38  inserted into apertures  40  (see.  FIG. 5A ) in the rails  12  to provide an abutment for hydraulic cylinders. Hydraulic cylinders  36  mounted in the carriage push against the push block  35  to urge the carriage  16  along the rails toward the pipe  24  at a steady pressure and pace to cause the carriage  16  to advance. The supply of such hydraulic crowd to the hammer  20  is one aspect of the present invention. 
     Referring to  FIG. 5 , as the carriage  16  is urged forward by the action of the hydraulic cylinders  36  against the push block  35 , the reaction force of the hammer assembly abutting against the pipe  24  causes the hammer housing  26  and the rear portion  30  of the harness  28  to which it is attached to be held in place against forward movement while the carriage  16  and the forward portion  32  of the harness  28  that is attached to it are urged forward. This causes relative translation between the rear portion  30  and the forward portion  32  of the harness  28  that in turn causes the cushions  42  in the cushion assembly  34  to be compressed. Without the cushion assembly  34 , once the hammer hits the strike plate and transmits the percussive force to the pipe  24  and thereby moves the pipe  24  forward, a gap would be introduced between the hammer  20  and the pipe  24 . The hydraulic crowd offered by the cylinders  36  would eventually cause the hammer  20  to catch up to the displaced pipe  24 . A further impact of the hammer would then need to wait for the carriage  16 , the harness  28  and the hammer  20  to be brought back into contact with the pipe  24 . However, the presence of the cushion assembly  34  provides a nearly instantaneous release of the tension in the cushions  42  to urge the hammer  20  forward in relation to the carriage  16  and to thereby closely track the forward movement of the pipe  24  and to maintain the hammer assembly in contact with the pipe. 
     The cushion assembly  34  thereby allows the hammer  20  to almost instantaneously track the displacement of the pipe  24  and helps to maintain crowd even though the hydraulic crowding of the carriage  16  toward the pipe  24  may be delayed as it catches up to the displaced pipe. The built up pressure in the cushions  42  effectively accelerates the repositioning of the hammer forward against the pipe  24  while the carriage  16  catches up. 
     Once the carriage  16  has been advanced beyond the extension capacity of the cylinders  36  (typically after several impact cycles of the hammer), the system is reset by removing the push block  35  from its last position and advancing it to a new position on the rail  12 , and securing the dogs  38  in new apertures  40 . The operation of the hydraulic crowd from cylinders  36  and the reciprocating percussion of the hammer  20  may then be resumed. 
     Referring to  FIGS. 8 and 8A , the cushion assembly  34  comprises a centering rod  50  mounted in cantilever fashion from a back plate  52  extending between opposed forward mounting plates  54 ,  56 . A plurality of rubber ring cushions  42  are installed about the rod  50 . The forward mounting plates  54 ,  56  are secured by bolts  58  to the forward portion  32  of the harness (more particularly to an attachment flange  59 ). As a result, when the carriage  26  and its dependent forward portion  32  of the harness are urged forward by the hydraulic cylinders  36  toward the pipe  24 , the forward mounting plates  54 ,  56  and the back plate  52  are also urged forward. 
     The rear portion  30  of the harness includes forwardly extending connectors  60 ,  62  which are attached to an abutment plate  64  by means of bolts  66 . The abutment plate  64  is dimensioned so as to be displaceable between and inward of the forward mounting plates  54 ,  56 . Such relative displacement and sandwiching between the abutment plate  64  on the one hand, and the forward mounting plates  54 ,  56  and the back plate  52  on the other hand, results in a compression or a relaxation of the cushions  42  of the assembly. 
     In the preferred embodiment, the system includes two opposed cushion assemblies, one on each side of the hammer  20 . 
     As a result of the arrangement described above, the cushion assembly is bounded on the pipe side of the assembly by an assembly abutment surface that is fixed in relation to a housing of the hammer and the assembly is bounded on a side that is distal from the pipe by an assembly abutment surface that moves toward the pipe as the hydraulic cylinders displace the carriage toward the pipe. 
       FIGS. 9 and 9A  show the positions of the components of the cushion assembly  34  with the hammer housing  26  in its extended position, the hammer  20  having just delivered a blow to the strike plate. The cushions  42  are relaxed and fully extended so that the forward  32  and rear  30  portions of the harness  28  are both in an advanced position in relation to the pipe  24 . The hammer  20  is in contact with the pipe  24  and the carriage  16  remains some distance from the pipe  24 . The crowd of the hydraulic cylinders  36  urges the carriage  16  and the forward portion  32  of the harness  28  toward the pipe  24  (against which the hammer  20  is already braced). As shown in  FIGS. 10 and 10A , the pressure is taken up by the cushions  42  which compress, allowing the carriage to progress toward the pipe  24  and causing the forward portion  32  of the harness to also advance in relation to the relatively stationary rear portion  32  of the harness. 
     Once the hammer  20  is triggered to strike the strike plate, the hammer within the hammer housing  26  is propelled forward of the housing  26  and strikes the strike plate, jolting the pipe  24  forward. The displacement increases the distance between the pipe  24  and the carriage  16  but the steady crowd pressure applied by the hydraulic cylinders  36  is not sufficient to cause the carriage  16  to instantaneously reposition the hammer assembly against the pipe. The cushions  42  react more quickly, releasing their energy to drive the rear portion  32  of the harness and the hammer  20  forward into contact with the pipe. 
     By the system of the preferred embodiment, the inventors have achieved an approximate nearly constant minimum crowd of the hammer on the pipe of 40 tonnes during the impact cycle of the hammer. 
     The invention therefore provides a hydraulic crowd for a reciprocating percussive hammer in a horizontal pipe ramming system. 
     The effectiveness of the hydraulic crowd is further enhanced by the use of a compressive resilient assembly (the cushion assembly in the preferred embodiment) that is effectively interposed between the hammer and the carriage against which hydraulic crowd is applied. 
     It will be appreciated that the resilient assembly need not necessarily be rubber cushions. Other compressive resilient devices may be as effective, such as metal springs, or very high pressure pneumatic systems. 
     Other structural alterations to the preferred embodiment may also be made without departing from the inventive aspects. 
     In the foregoing description, exemplary modes for carrying out the invention in terms of examples have been described. However, the scope of the claims should not be limited by those examples, but should be given the broadest interpretation consistent with the description as a whole. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.