IMPROVED MACHINERY FOR GRITTING' OR 'GROUNDING' AND POLISHING MARBLE
Year: 1878

page_text: LETTERS PATENT to Robert Clair How, of Carshalton, in the County of
Surrey, for the Invention of "IMPROVED MACHINERY FOR GRITTING' OR
'GROUNDING' AND POLISHING MARBLE."
'
PROVISIONAL SPECIFICATION left by the said Robert Gair How at the
Office of the Commissioners of Patents on the 22nd June 1878.
ROBERT GAIR How, of Carshalton, in the County of Surrey. IMPROVED
MACHINERY FOR 'GRITTING' OR 'GROUNDING' AND POLISHING MARBLE.'
"
My Invention relates to gritting or "grounding" and polishing marble, and it
has for its object to effect these operations by a machine driven by a power as a
substitute for hand labor.
According to my Invention the slab of marble to be "grounded" or polished is
supported on a table or bed, above which works a horizontally reciprocating bar,
to which the grounding blocks and polishing rubbers are attached, The bar is
supported on a friction roller at one end, the other end passes through a guide con
sisting of two vertical rods with a cross pin, the guide being open at the bottom,
so that the bar may be lowered till the polishing blocks rest on the marble; and it
is also provided with means of adjustment for regulating the height of the block
according to the thickness of the slab of marble to be operated on.
Motion is imparted to the bar carrying the blocks or rubbers by means of a con-
necting rod and crank upon a shaft driven by band or other gear, the crank being
slotted to enable the throw of the crank and the movement of the bar to be
regulated to suit the work.
The grounding block is made either of wood or iron, and its under surface is
grooved or channelled for the reception of the stones employed in the operation.
These grooves extend from one side of the block to the other in a diagonal direction
to enable the grounding stones to pass freely over the edges of the slab on the

page_text: return stroke without catching. The stones project from the surface of the block,
and are keyed or otherwise secured in the grooves.
The grounding blocks for long and certain other kinds of slabs may be hinged
or pivotted to a block, which is provided with ears on its upper surface for attach-
ment to the reciprocating bar, this arrangement enabling the grounding blocks to
yield during the operation.
The rubbers for polishing consist of a wooden block faced with felt, woollen cloth,
or list, as usual with the hand rubbers or polishers. The blocks are attached to the
reciprocating bar by a bolt which passes through ears on the back of the blocks, and
secured by a nut or pin, so that the blocks may be readily removed and replaced.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Robert Gair How in the Great Seal Patent Office on the 21st
December 1878.
ROBERT GAIR How, of Carshalton, in the County of Surrey. 'IMPROVED
MACHINERY FOR GRITTING' OR 'GROUNDING' AND POLISHING MARBLE."
My Invention relates to a machine for "gritting" or "grounding" and polishing
marble.
According to my Invention the "gritting" or "grounding" blocks or the
polishing rubbers are attached to a bar having a longitudinal reciprocating move-
ment above and parallel to the slab of marble to be operated on, which is supported
on a table or bed. This bar works in guides at each end, one of which is provided
with a friction roller for the bar to rest on, the other guide being open at bottom,
so that the bar may be lowered until the "gritting or "grounding" block or the
polishing rubber rests on the marble slab.
33
The reciprocating bar is operated by means of a connecting rod from a crank
having an adjustable crank pin to enable the radius of the crank and the stroke of
the bar to be varied to suit the work.
The gritting or grounding block is attached to the reciprocating bar by
ears and a pin or bolt at back, so that the block may be readily removed and re-
placed by another. The said block is preferably inade of wood, but it may be
made of iron or other material, and is grooved on its face to receive the gritting
or grounding stones, which are keyed or otherwise secured therein and stand
out from the face of the block. The stones (technically called "grits") are about
one inch thick and are about the same distance apart, so as to leave spaces between
them to allow the water or water and sand to pass in and ensure an efficient cutting
action of the stones. The grooves extend from one side of the block to the other,
preferably in an obliquo direction (or they may run transversely across); and they
are inclined from top to bottom, those near each end being inclined laterally
towards that end to prevent the block jumping or rattling and ensure a better cut.

page_text: For long slabs, or slabs having an uneven surface, two gritting or grounding
blocks may be hinged or pivoted to the ends of a bar attached to the reciprocating
bar in the way above described for the single block.
The rubber to be used in place of the gritting block when polishing is of the
usual kind, consisting of a wooden block faced with felt, woollen cloth, or list,
and is attached to the reciprocating bar in the same way as the gritting or
grounding block.
Figure 1 is an elevation of the machine.
Figures 2 and 3 are side views of the guides for the reciprocating bar.
Figures 4 and 5 are back and face views of the gritting or grounding block;
Figure 6 is a face view of a similar block, with the stones in an oblique direction;
and Figure 7 shows a double block for long or uneven slabs.
A is the slab of marble to be operated on, resting on a movable table B, supported
on transverse rails C, C, upon a strong frame D, so that it may be shifted back-
wards and forwards by hand to bring all parts of the slab under the action of the
machine. There would be several slabs side by side on the table, and these would
by moving the table be brought successively under the action of the grounding
block without stopping the machine. E is the gritting or grounding block;
and F, the reciprocating bar, to which it is attached by a cross pine passing
through ears fixed to the back of the block and to the bar; G, H, are the guides
in which the bar F works. The guide G serves merely to guide the bar in a
straight line; it is of the form shown in Figure 2, being open at the bottom to
allow the bar to accommodate itself to the thickness of the marble, and the wholo
weight of the bar and block to bear thereon; this guide is attached to any con-
venient support, and is also provided with a row of holes, in which a cross pin may
be inserted to hold up the bar F whilst the grounding block is being changed;
M is a cord passing over a pulley and attached to bar F. by which to raise it.
The guide H (shown separately in Figure 3) is also attached to a suitable support,
and einbraces the top side of bar F, and a friction roller is situated beneath for
the bar to rest upon. K is the connecting rod, jointed at one end k to about the
middle of the length of the reciprocating bar F, and at the other end to a crank
pin fixed adjustably at a radius suited to the work in a slotted crank arm L on a
shaft driven by power or by hand.
The stones of the block E may either be at right angles to the line of motion of
the block, as in Figure 5, or they may be oblique thereto, as in Figure 6; but in
either case they would preferably be set in a slanting position, one half of them
slanting in one direction and the other half in the other direction, as shown in
Figure 1; the grooves in which they are fixed being made to give the stones this
"set" or inclination.
In Figure 7 two blocks E are hinged at e' to the ends of a bar E¹, which is con-
nected to bar F, as above described; and in this case the stones or "gritts” are
inclined towards the outer ends of their respective blocks.
The sand and water used in gritting or grounding can be supplied by any
suitable means.
Having described the nature of my Invention, and the manner of performing tho
same, 1 declare that what I claim as my Invention to be protected by the herein-
before in part recited Letters Patent is,―
1st. In a machine for gritting or grounding and polishing marble, attaching
the gritting or grounding block or the polishing rubber, as the case may be, to a
bar having longitudinal reciprocating motion in guides, substantially as shown and
described.
2nd. The combination of adjustable crank, connecting rod, reciprocating bar,
and grounding block or polishing rubber, substantially as shewn and described.

page_text: 3rd. The combination of a reciprocating bar working in guides and carrying
the block or rubber and a table moving at right angles to the bar to carry the slabs
to be operated on and bring them under the operation of the machine, sub-
stantially as shewn and described.
4th. The construction of block for gritting or grounding marble, and consisting
of strips of stone set in grooves in a block, from which they project, substantially
as shown and described.
5th. The employment of a pair of double blocks for gritting and grounding
hinged to a bar, which is itself hinged to the reciprocating bar, substantially as
shown and described,
In witness whereof, I, the said Robert Gair How, have hereunto set my
hand and seal, this Twentieth day of December, in the year of our Lord One
thousand eight hundred and seventy-eight.