Steering mechanism for trencher

Claim 1

A self-propelled trencher and back-filler comprising: a front frame portion having thereon a power operated back-fill blade generally transversely across the front end of said front frame portion, a power plant, a transmission connected to said power plant, a pair of laterally spaced steerable wheels having a front drive axle connected therebetween, and a universal joint drive shaft connecting said transmission to said front drive axle; a rear frame portion having thereon a pair of laterally spaced wheels having a rear drive axle connected therebetween, and trenching means extending rearwardly and being shiftable from a lower trench digging position to a raised transport position; pivot means connecting said front and rear frame portions together for swinging movement about a generally vertical axis; a universal joint drive shaft connecting said transmission to said rear drive axle; power means connected between said front and rear frame portions for changing the relative angular positions of said portions about said generally vertical axis to provide articulated frame steering; and a connection between said steerable wheels on said front frame portion and said rear frame portion to cause turning of said steerable wheels when said power means is actuated to cause a combined steering effect; said pivot means connecting said front and rear frame portions together being located to position said generally vertical axis a substantial distance rearwardly of the midpoint of the wheel base length to permit said wheels on said rear frame portion to substantially track said wheels on said front frame portion during turns induced by said comBined steering effect.