Extensible beam arrangement

Rock drilling equipment includes a boom carrying an extensible beam arrangement supporting a drilling mast, the extensible beam arrangement comprising a support pivotally mounted on the boom, a first elongated element slidably mounted on the support for movement longitudinally of the first element, a second elongated element slidably mounted on the first element for movement longitudinally of the first element, and drive transmission means sensitive to movement of the first element and adapted to move the second element relative to the support upon sensing relative movement between the support and first element.

This invention relates to extensible beam arrangements. 
In particular, although not exclusively, the present invention relates to 
extensible beam arrangements for use with drilling and like equipment 
where typically the extensible beam arrangements support, for example, a 
drilling mast. 
In the drilling of bore holes in a rock face to receive explosive charges 
for rock removal it is known to mount a drilling mast on a suitable 
carriage, such carriage being disposed adjacent the rock face to be 
drilled and the drilling mast being reciprocable relative to the carriage 
to and from an operative position. 
One object of the present invention is to provide an extensible beam 
arrangement upon which at least one drilling mast is mounted and which is 
itself supported on the carriage, thereby to allow of the drilling of 
holes in rock faces in circumstances wherein the carriage cannot be moved 
close to the rock face in question. 
According to the present invention, there is proposed an extensible beam 
arrangement comprising a support, a first element mounted on the support 
for movement relative thereto, a second element supported by and movable 
relative to the said first element, displacement means connected with and 
operable between the support and the first element and adapted, upon 
actuation, to effect a relative shift therebetween, and a drive 
transmission means connecting the support and said second element, the 
said drive transmission means being sensitive to relative movement between 
the support and the said first element and being adapted, upon such 
relative movement, to impart relative movement as between the first and 
second elements. 
Preferably, the first and second elements are elongated elements and the 
movements are longitudinally of the elements. 
According to a preferred feature, the drive transmission means comprises a 
pulley or the like on the first element and a draw cable or the like 
which, in use, is trained around the pulley, the ends of the said cable 
being connectable to the support and second element respectively. 
According to a preferred feature, the drive transmission means is adapted 
to effect relative movement between the first and second elements for both 
directions of movement of the first element relative to the support.

Referring now to the drawings, an extensible beam arrangement 11 for 
supporting a drilling mast 12 comprises a support platform 13 pivotally 
mounted on the forward end of a carriage (only a forwardly direct boom of 
which is shown in FIG. 1), a first elongated beam element 14 slidably 
mounted on the said support platform 13 for motion relative thereto in the 
longitudinal direction of such element, a second elongated beam element 15 
slidably supported on the first such element 14, a displacement means 16 
connecting the support platform and first beam element and adapted, upon 
actuation, to effect a relative shift therebetween, and a drive 
transmission means 17 connecting the second beam element 15 and the 
platform 13 and cooperable with the first beam element to impart an 
amplified motion to the second beam element relative to the first beam 
element upon motion of the latter relative to the support platform. 
The support platform 13 consists of a generally horizontal support surface 
having an inwardly lipped guide means 18 at each longitudinal edge 
thereof, there being an upstanding trunnion 19 generally centrally of the 
support surface of a purpose hereafter to be made apparent. 
The first beam element 14 comprises two channel members 14a arranged in 
outwardly facing, spaced disposition, the lower flanges 14b of the element 
being engaged with the guide means 18, thereby to locate such element 
transversely of the support platform. The upper face of the outwardly 
directed flanges 14c of channel members 14a carry inwardly lipped guide 
means 20. 
The second beam element 15 likewise comprises two outwardly facing channel 
members 15a arranged in spaced parallel disposition, the lower flanges 15b 
of element 15 being slidably engaged with guide means 20 and being located 
in the transverse direction of element 14 by such guide means. 
A drill mast 21 is slidably supported on the second beam element 15 in a 
manner analogous to the mounting of such element 15 on the first beam 
element, and is movable longitudinally of the second beam element by an 
hydraulic piston and cylinder arrangement 22 positioned within the second 
beam element 15 and operating between such element 15 and a lug 23 
depending from the underside of the drill mast 21. 
The displacement means 16 for effecting longitudinal shift of the first 
beam element 14 relative to the support platform comprises an hydraulic 
cylinder arrangement disposed within the first beam element 14, the 
cylinder 16a of such arrangement being pivotally mounted in trunnion 19 
and the piston 16b being secured to the beam element 14 adjacent the 
forward end thereof. Upon actuation of the cylinder arrangement 16 the 
first beam member will be caused to move longitudinally of the guide means 
18 provided on the support platform 13. 
The drive transmission means 17 comprises a draw cable 17a (only one of 
which is shown) at each end of the first beam element, one end 17b of such 
cable being secured to the second beam element 15, as at 24, and the other 
end 17c being secured to the platform 13, as at 25, each such cable being 
trained around a roller or pulley 17d provided at each respective end of 
the first beam element. 
As will be appreciated, actuation of the hydraulic cylinder in an 
appropriate sense will advance the first beam element relative to the 
support platform. Such relative movement will cause the cable at the 
forward end of the first beam element to move around the pulley at such 
end and will thus advance the second beam element relative to the first 
such element, the arrangement being such that the second beam element 
moves, relative to the first beam element, twice the distance moved by the 
first beam element relative to the support platform. Accordingly, there is 
a 3:1 amplification of the piston movement at the drilling mast. 
By means of the arrangement as hereinproposed we are able to obtain an 
appreciable extension of the beam arrangement for only a limited stroke of 
the piston of the hydraulic cylinder, and, furthermore, are able to 
optimize on overall length of structure. 
The invention is not limited to the exact features of the embodiment 
hereinbefore described, since alternatives will readily present themselves 
to one skilled in the art. Thus, while it is convenient to provide a draw 
cable at each end of the first beam element for co-operation with a 
related pulley, thereby to provide for movement of the second beam element 
for both directions of operation of the cylinder arrangement, a drive 
transmission means may, if desired, be provided at one end only, 
alternative provision being made for the return motion of the second beam 
element. 
In addition to being of ready application in the context of the specific 
drilling machine shown in the drawings, the extensible beam is of use in 
other machines, such as, for example, that machine described and 
illustrated in the specification and drawings of the assignee's co-pending 
application Ser. No. 970,166 filed simultaneously herewith. 
The invention is not limited to use in the context of drilling machines, 
since other analogous uses are possible.