Self propelled reversible boring ram
AssigneeBritish Telecommunications plc
InventorsWilliam E. Cox, Kenneth L. Hemmings
Life of this patent
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Abstract
A reversible boring ram having a tubular body containing a reciprocable hammer is provided with a pneumatically balanced control member which allows the direction of operation of the ram to be reversed without halting the hammer's reciprocation. The pneumatically balanced control member also allows easy starting of the device. The control member includes a balance piston situated in a balance cylinder which is attached to the body of the ram, the balance cylinder being connected to an inlet channel in such a manner that forward pressure on the balance piston counteracts the backward pressure in the main cylinder. The control member may be spring biased into the position for forward motion.
Claims10
A self-propelled reversible boring ram comprising a tubular body which contains a reciprocable hammer and a pneumatically balanced reciprocable control member for supplying working fluid to the hammer in either a forward motion mode position or a reverse motion mode position,
- said control member having oppositely directed piston surfaces which are at all times subjected to substantially balanced pneumatic forces from said working fluid in both said reverse and forward mode positions.
A self-propelled reversible boring ram comprising:
- a tubular body;
- a hammer contained within the body, said hammer being reciprocable by working fluid supplied to the ram;
- and
- a pneumatically balanced control member movable between a forward position for advancing the ram and a reversing position, rearwards of the forward position, for reversing the ram;
- wherein said control member includes oppositely directed surfaces which are both subjected to the pressure of the working fluid such that the net pneumatic fluid pressure on said member is substantially balanced at both said forward and reversing positions of the control member and during motion of the control member between said forward and reversing positions.
Dependencies are inferred from the claim text.