IMPROVEMENTS IN CUTTING OR DRESSING STONE, AND IN THE MACHINERY OR APPARATUS EMPLOYED THEREFOR
Year: 1869

page_text: LETTERS PATENT to Andrew Mitchell, of Leith, in the County of
Mid Lothian, North Britain, for the Invention of "IMPROVEMENTS IN
CUTTING OR DRESSING STONE, AND IN THE MACHINERY OR APPARATUS
EMPLOYED THEREFOR."
Sealed the 24th August 1869, and dated the 8th March 1869.
PROVISIONAL SPECIFICATION left by the said Andrew Mitchell at the
Office of the Commissioners of Patents, with his Petition, on the.
8th March 1869.
I, ANDREW MITCHELL, of Leith, in the County of Mid Lothian, North
Britain, do hereby declare the nature of the said Invention of "IMPROVE-
MENTS IN CUTTING OR DRESSING STONE, AND IN THE MACHINERY OR APPARATUS
EMPLOYED THEREFOR," to be as follows, that is to say :-
This Invention which relates to improved arrangements of mechanism
whereby stone is rapidly and efficiently cut or dressed, consists of an

page_text: upright framing in which cross slides centred on pivots or bearings and
adjustable to any required height are contained. The cross slides carry
in an adjustable frame one or more hammers which may be actuated by
steam or compressed air or gas which is admitted into the cylinders for
that purpose. These hammers act upon one or more chisels or dressing
tools, which are carried in boxes so arranged that when the hammer acts
upon a tool the tool is moved to approximate the action of a dressing
tool or chisel as it is used in the ordinary stone dresser's hands, the
special movement being effected by causing the tool box or holder to
slide or travel in suitably shaped guides. The tool holder by preference
consists of a piston, in the lower end of which a socket is formed for
holding the tool, and the upper part fits into a cylinder filled with com-
pressed air, which acts like a spring, and causes the return stroke of the
piston and tool in readiness for the next blow of the hammer, but in place
of compressed air a spring may be employed. The framing which carrics
the tool driving mechanism is made adjustable to any angle which may
be required. The stone to be dressed is placed on an adjustable table
carried on a truck or carriage. which traverses on rails or guides.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Andrew Mitchell in the Great Scal Patent Office
on the 7th September 1869.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ANDREW
MITCHELL, of Leith, in the County of Mid Lothian, North Britain,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Eighth day of March, in the year of
our Lord One thousand eight hundred and sixty-nine, in the thirty-
second year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Andrew Mitchell, Her special licence
that I, the said Andrew Mitchell, my executors, administrators, and
assigns, or such others as I, the said Andrew Mitchell, my executors,
administrators, and assigns, should at any time agree with, and no
others, from time to time and at all times thereafter during the term
therein expressed, should and lawfully might make, use, exercise, and

page_text: vend, within the United Kingdom of Great Britain and Ireland, the
Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS. IN
CUTTING OR DRESSING STONE, AND IN THE MACHINERY OR APPARATUS EMPLOYED
THEREFOR," upon the condition (amongst others) that I, the said Andrew
Mitchell, my executors or administrators, by an instrument in writing,
under my, or their, or one of their hands and seals, should particularly
describe and ascertain the nature of the said Invention, and in what
manner the same was to be performed, and cause the same to be
filed in the Great Seal Patent Office within six calendar months next and
immediately after the date of the said Letters Patent..
NOW KNOW YE, that I, the said Andrew Mitchell, do hereby declare
the nature of my said Invention, and in what manner the same is to.
be performed, to be particularly described and ascertained in and by
the following statement in writing, reference being had to the accom-
panying Drawings, that is to say :-
My said Invention has. for its object the rapid and effectual cutting:
or dressing of stone by means of machinery or apparatus which whilst
it dispenses with manual labor is contrived to operate with dressing
tools or chisels, and to actuate these instruments in a manner closely.
approximating to that in which the mason works them.. The chisels.
in connection with hammers for striking them are arranged so that
they may be adjusted at any inclination to the surface of the stone
to suit the varying qualities of the stone, and their motion when struck
is regulated by specially arranged guides in such a way, that their
points move as nearly as possible in lines coinciding with the intended
surface of the stone. The guides may however be adjusted to give other
movements to the chisels if wished..
And in order that my said Invention and the manner of performing
the same may be properly understood, I have hereunto appended a
Sheet of explanatory Drawings to be herein-after referred to and
representing by way of example certain modifications of my improved
machinery or apparatus.
Figure 1 is a front elevation, and Figure 2 is a transverse vertical
section showing one modification of the general machinery, which is
designed for operating with three tools or chisels 1 simultaneously.
The machine may however be arranged to work with any convenient

page_text: number of tools. Figure 3 is. a section of the tool holder 2. and tool
box 3.
The main framing of the machine consists of two end
standards 4 which are bolted down upon a sole plate 5 and suitable
foundation, and which are connected at the top by a pair of tie rods 6.
The standards 4 are fitted with bearings for two journals or trunnions 7,
which are fixed to and serve as centres for two frame plates 8, which
are connected by four horizontal rods 9 extending across the machine.
The rods 9 serve as guides and supports for a carriage or slide 10.
fitted with eyes to slide on the rods, and comprising three hammer
cylinders 11 to be actuated by steam or compressed air supplied to
them by a flexible pipe 12 and carrying three corresponding tool
boxes 3. Any convenient self-acting valve gear may be applied to
the hammer cylinder. The piston rods are fitted with hammer
heads 13 which strike on the upper ends of the tool holders 2. Each
tool holder 2 is a rod or bar with a socket at its lower end for the
chisel 1 and having fixed near its upper end a piston or ring 14 which
bears on a steel spring 15 held in a box 16 carried in the tool box 3
upon trunnions indicated by a dotted circle at 17. On one side of
the lower end of the tool holder 2 there is fixed a pin indicated by
a dotted circle at a and which works in a guide groove in a guide
piece 18. This guide piece has on its further side a pin (which may
also be considered as indicated by the dotted circle u, and) which is
entered into a socket in the downwardly projecting cheek of the tool
box 3, so that the guide piece can be adjusted at different inclinations
to the box, and for the purpose of such adjustment it has jointed to it
a rod 19 which is connected by a screw and nut to a bar 20 held in
slots in the frame plates 8 and in slots 21 in the standards 4, the
action of which latter slots 21 will be herein-after explained. The
action of the guide piece 18 is shown by the red lines, it causes the
tool holder 2 and tool 1 when struck to move downwards and angularly
in such a way that the centre line passes from the full red line to the
dotted one, the guide pin moving to b and the point of the tool to c.
The tool holder 2 and tool 1 are shown in an inclined working position
in Figure 3, but in Figures 1 and 2 the parts are shown in a vertical
position for convenience in delineation. The tools can be set to work
at any angle by turning the frame plates 8 on their trunnions 7, and
for the purpose of so setting. them a hand wheel 22 is keyed outside
of the standard upon one of the trunnions, such hand wheel being

page_text: fixed in any position by means of a small wheel and screw spindle 23
carried by the hand wheel 22 and entering one of a series of set holes
formed in the standard for the purpose. Grooves or slots 24 concentric
with the trunnions 7 are made in the upper parts of the standards 4
to receive blocks formed upon or attached to the frame plates 8, and
to thereby guide and steady those plates and the parts carried by them.
The slots 21 hercin-before referred to for receiving and guiding the
bars 20, to which the guide pieces 18 are connected, are made eccentric
from the trunnions 7 (the centre being a little above that of the
trunnions), whereby when the inclination of the tool is altered such a
corresponding relative alteration of the position of the guide pieces 181
is produced as will cause the point of the tool to still move in a
horizontal line, and so that no separate adjustment for that purpose
will be required. Each guide piece 18 may also be adjusted separately
by screwing the nuts connecting the rod 19 to the bar 20.
Figure 4 is a diagram showing a modification in which tilt hammers
are substituted for piston hammers, one of the frame standards 4 being
shown in end elevation. The tilt hammers 25 are centred on a
horizontal shaft 26 carried in frame plates 8 inside each frame
standard 4, and are worked by cams 27 on a revolving shaft 28 carried.
by the same plates 8. On one end of the shaft 28 there is a spur
wheel indicated by a red circle 29 which gears with a similarly
indicated spur wheel 30 turning on the trunnion 7 and which has
fixed to or formed in one piece with it a pulley 31 driven by a belt
from a pulley 32 on a shaft carried at the top of the frame and driven
in any convenient way. The arrangements just described admit of
the frame plates 8 with the parts carried by them being set round
to any desired inclination, and for the same purpose slots 24 are
formed in the frame standards 4 concentric with the trunnions 7 to
receive and guide blocks upon the outer ends of the frame plates 8.
Figure 5 is a sectional elevation of a modification of piston hammer
in which instead of using a steel spring (15, Figure 3,) to return the
tool after each blow that action is obtained from the steam or com-
pressed air in the cylinder 11: The cover of the cylinder has a small
cylindrical recess 33 formed in it, in which there works a piston 34,
the piston rod of which passing out through a stuffing box is fixed to

page_text: a cross head 35. Rods 36 are fixed to the ends of the cross head 35.
and have their lower ends jointed upon trunnions 37 formed or fixed
upon the tool holder 2. The steam or compressed air entering the
cylinder by a port 38 between the small piston 34 and the hammer
piston forces down the latter, and. by acting 'on the former holds the
tool up to receive the stroke. The concussive action of the stroke is.
however sufficient to force down the small piston 34 with the movement
of the tool, but that piston afterwards draws up the tool again in
readiness for the succeeding stroke. Compressed air or other spring
may be used instead of the steel spring 15 in the arrangement shown
in Figure 3.
My present Invention does not include any novel or particular mode.
of carrying and moving the stone block 39, but it must be moved
along under the stone at a rate suited to the action of the tool. The
block may be fixed on any convenient slide or carriage, and it may
be moved by means of a screw, or by a rack and pinion, or by a chain
and winding barrel. It is represented in Figures 1 and 2 as fixed
upon a wheeled carriage 40 running on rails 41, and the parts of the
rails immediately below the cutting or dressing tools are upon a movable
plate or table 43 which can be raised. to or adjusted at any convenient
height by means of a hydraulic press 44 set in the foundation below it.
Or the hydraulic press 44 may be fixed in the carriage 40, as shown
in Figure 4, and act upon an upper plate or table 45 on which the
block of stone is placed. With either modification of hydraulic press
lifting apparatus the machinery may be arranged to cut or dress a
vertical face of the stone, the tools with their carrying and actuating
details being set at a suitable inclination, and the stone block being
raised gradually upwards as the action proceeds. Also by combining
the vertical and horizontal movements the machine may be made to
cut or dress faces at various inclinations.
Having thus particularly described my said Invention, and the manner
in which the same is to be performed I have to state that I do not
restrict myself to the precise details herein described or delineated, but
that what I believe to be novel and original and claim as the Invention
secured to me by the hercin-before in part recited Letters Patent is,
the cutting or dressing of stone by means of machinery or apparatus
in which the tools in connection with hammers for striking them

page_text: can be set at various inclinations, and have their motion regulated
by specially arranged guides, all substantially as herein-before described.
In witness whereof, I, the said Andrew Mitchell, have hereunto
set my hand and seal, this Fourth day of September, in the year
of our Lord One thousand eight hundred and sixty-nine.
A. MITCHELL. (L.S.)