IMPROVEMENTS IN FIXING THE DRILLS OF ROCK DRILLING MACHINES IN THEIR HOLDERS
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by John Swaine at the Office of the
Commissioners of Patents on the 8th June 1882.
JOHN SWAINE of Handsworth in the County of Stafford Mechanical Engineer
"IMPROVEMENTS IN FIXING THE DRILLS OF ROCK DRILLING MACHINES IN THEIR
HOLDERS
"
In the ordinary method of fixing the drills of rock drilling machines in their
holders, two parallel screw bolts and screw nuts are employed. These screw bolts
pass through holes crossing the holder on each side of the socket, and also through
a cap or plate crossing the holder. This cap or plate has a rib on its under side
which rib passes through a slot in the holder and engages in a corresponding
depression or recess in the shank or rear part of the stem of the drill. By tightening
the screw nuts on the screw pins the rib on the cap is made to bear with the
required amount of pressure upon the stem of the drill and to fix the drill in the
socket of the holder
This the ordinary method of fixing the drill in its socket, is attended with some
inconveniences. There is nothing to prevent the turning of the bolts in the holes
in the socket and the loosening or slackening of the drill consequent thereon
necessitates frequent stoppages of the machine for the purpose of tightening the
screw nuts on the said bolts. In consequence of the inelasticity of the ordinary
means of fastening there is a great tendency to the slackening of the screw nuts
which results in great wear and tear of the bolts and nuts and their renewal
involves considerable expense.
The object of my invention is to remedy these defects and to provide means of
fixing the drills in their holders inore efficient more durable and less costly than
the ordinary means.
In fixing the drills of rock drilling machines in their holders according to my
invention, I take a cylindrical rod of iron or steel of a length somewhat greater
than the combined lengths of the two bolts commonly employed and of about the
same diameter. I form a screw thread on each end of the said rod and bend the
said rod at its middle into a nearly semi-circular figure. There is thus produced
a strap or staple having the figure of the letter U its ends being formed into screws.
The two branches of this U shaped staple are passed through the holes in the
21

page_text: holder in the same way as the separate screw bolts ordinarily employed and screw
nuts on their screwed ends are similarly made to hold the cap and fix the drill
As the arms of the strap or staple cannot turn, the risk of the slackening of the
screw nuts is reduced to a minimum. The curved part of the strap or staple gives
a slight elasticity to the fastening and diminishes the wear and tear. The part of
the socket on which the curved part of the strap or staple bears is recessed so that
the said curved part may embed itself on the said recessed part of the socket.
For the purpose of giving the cap a greater bearing on the shank of the drill
when desirable, I dispense with the recess in the shank of the drill and make a
flat plane on the said shank. The rib on the underside of the cap has in this case
a breadth equal to the breadth of the said plane on the shank of the drill.
Or the ordinary cap may be dispensed with and the drill may be fixed by a block
carried in the bend of the U shaped strap, the flat inner face of the said block being
made to bear against a plane on the shank of the drill. The shank of the drill
may be made triangular.
The screw nuts are conical on their undersides and seat themselves in conical
seats in the holder. The screw nuts are prevented from coming off the screws and
being lost by means of cotters passed through the screws near their ends.