Drill boom with hydraulic parallel motion means

Claim 1

A drill boom arrangement with hydraulic parallel motion means for positioning an elongated rock drilling apparatus to different drilling positions with respect to a boom support, comprising in combination therewith: a first cross shaft on said boom support, a drill boom having forward and rear ends, said drill boom being pivoted at the rear end thereof on said first cross shaft, a second cross shaft at the forward end of said drill boom for pivotally supporting said rock drilling apparatus, an hydraulic elevating cylinder means pivotally connected at one end thereof to said drill boom and at the other end thereof to said boom support for selectively elevating and lowering the rock drilling apparatus to given elevation angles, an hydraulic tilt cylinder means pivotally connected at one end thereof to said drill boom and at the other end thereof to said rock drilling apparatus for selectively tilting said rock drilling apparatus relative to said drill boom independently of said hydraulic elevating cylinder means, said hydraulic tilt cylinder means having a pair of hydraulic chambers, an hydraulic pilot cylinder means having a pair of chambers and pivotally connected to said drill boom and to said boom support for sensing the elevation angle of said drill boom, and an hydraulic circuit including fluid conduit means connecting one chamber of said hydraulic pilot cylinder means with one chamber of said hydraulic tilt cylinder means to selectively transfer hydraulic fluid therebetween to provide hydraulic slave coupling between said hydraulic pilot cylinder means and tilt cylinder means to concurrently operate same in order to tilt said rock drilling apparatus while maintaining parallel displacement of the rock drilling apparatus during operation of said hydraulic elevating cylinder means to change the drilling position; a common hydraulic control valve coupled to said hydraulic pilot, tilt and elevating cylinder means for alternately pressurizing the other chambers of said hydraulic pilot cylinder means and said hydraulic tilt cylinder means simultaneously with the chambers of said hydraulic elevating cylinder means during elevating and lowering of the rock drilling apparatus, respectively; a second control valve coupled to said hydraulic tilt cylinder means for actuation thereof independently of said hydraulic elevating and pilot cylinder means; first isolating valve means for isolating said hydraulic elevating and pilot cylinder means from said second control valve during actuation of said second control valve; and second isolating valve means for isolating said second control valve from said hydraulic tilt cylinder means during actuation of said common control valve, whereby said hydraulic pilot cylinder means assists the elevating movement of said drill boom and said hydraulic tilt cylinder means assists the lowering movement of said drill boom.