Improvements in & relating to pile and post driving equipment

Abstract

The present invention is directed to an impact driver, which relies on multiple connected piston and cylinder assemblies which sequentially fire; a first auxiliary piston assembly charged to compress a compressible fluid with a piston rapidly releases the charge on said piston allowing the compressed fluid, which is typically a gas, to accelerate said auxiliary piston. This auxiliary piston is connected to a second travelling primaty piston assembly which it accelerates. Within the primary piston assembly a primary piston can be charged to compress a compressible fluid. The charge on the primary piston can also be rapidly released to accelerate the primary piston. The primary piston may be connected to a striking element, or successive travelling piston and cylinder assemblies which ultimately connect to a striking element.

1 - 15 . (canceled) 
     
     
         16 . Impact driving apparatus comprising an auxiliary piston assembly comprising an auxiliary piston and cylinder, and in which one side of the auxiliary piston can be charged to pressurise a compressible fluid on the other side thereof;
 said auxiliary piston being connected to a primary piston assembly in turn comprising at least a primary piston and associated cylinder assembly; said primary piston being able to be charged to pressurise a compressible fluid on the other side thereof; and wherein said primary piston assembly is able to slide within an outer housing;   said primary piston being connected to a striking element for delivering energy to a target.   
     
     
         17 . Impact driving apparatus as claimed in  claim 16  in which charging a piston comprises introducing hydraulic fluid into a reservoir bounded at least partly by a said piston and its associated cylinder. 
     
     
         18 . Impact driving apparatus as claimed in  claim 16  in which the charge on a piston can be rapidly released. 
     
     
         19 . Impact driving apparatus as claimed in  claim 18 , in which hydraulic fluid can be released through a port having a relatively large effective cross-sectional area. 
     
     
         20 . Impact driving apparatus as claimed in  claim 19  in which a said port comprises a seated valve under bias towards a closed position. 
     
     
         21 . Impact driving apparatus as claimed in  claim 16  in which the charge on the auxiliary piston is released prior to the charge on the primary piston. 
     
     
         22 . Impact driving apparatus as claimed in  claim 16  in which the charge on the primary piston is released after its associated cylinder assembly has acquired velocity due to the release of the charge on the auxiliary piston. 
     
     
         23 . Impact driving apparatus as claimed in  claim 16  in which the parameters for timing of charge release, extent of pressurisation of compressible fluid, and component masses, are selected so that recoil on the travelling primary piston assembly after release of the charge on the primary piston causes said primary piston assembly to any one of slow, stop, and change direction. 
     
     
         24 . Impact driving apparatus as claimed in  claim 17  which includes means for slowing the striker element after it has travelled a predetermined distance. 
     
     
         25 . Impact driving apparatus as claimed in  claim 24  which comprises preventing further rapid release of hydraulic fluid acting on the primary piston. 
     
     
         26 . Impact driving apparatus as claimed in  claim 16  in which the compressible fluid is a gas. 
     
     
         27 . Impact driving apparatus as claimed in  claim 26  in which the gas is nitrogen, or an inert gas mixture. 
     
     
         28 . Impact driving apparatus as claimed in  claim 16  in which the striker element allows different heads to be attached or substituted. 
     
     
         29 . Impact driving apparatus as claimed in  claim 16  including mounting means for a vehicle.