Pipe propelling device

DETAILED DESCRIPTION Accordingly, an object of the present invention is to overcome said conventional problems.
That is, the present invention aims to enable pipes to be propelled from a small-dimensioned vertical shaft without interposing any struts while providing a sufficient operative space within the vertical shaft.
A pipe propelling device according to the present invention comprises fundamentally two sets of jack assemblies supported spaced from each other in the vertical shaft and extending laterally of said vertical shaft, each jack assembly comprising a plurality of first stage jacks having a rod end contacting said reacting shaft wall and at least one second stage jack having cylinders connected to the respective cylinders of the first stage jacks and directing the rod end forward in the direction of propelling said pipe.
According to the present invention, the total length of the jack assembly prior to the propulsion of pipe can be minimized while the operative stroke of the jack assembly can be made longer than the length of the pipe by extending operatively said first and second stage jacks.
Accordingly, the size of the vertical shaft can be minimized and further the pipe can be forced entirely into the ground by one operation of the jack assembly without interposing the strut, thereby the efficiency of operation can be remarkably improved.
Further, the present device is made of two sets of jack assemblies spaced from each other, and portions at which the pipes to be propelled against the respective jack assemblies are limited only to the rod end of the second stage jack so that the jacks are not arranged in the form of a box like prior ones.
Thus, an instrument for measuring the direction of propelling the pipe forced into the ground can be disposed easily between the jack assemblies or rods.
Also, a gap between the rod end of the second stage jack and the reacting shaft wall can be lessened by locating the front end of said first stage jack in front of the rod end of said second stage jack when all said jacks are under the contracted condition