IMPROVED MEANS AND APPARATUS FOR EFFECTING REDUCTION OR ENLARGEMENTS OF DRAWINGS OR PLANS
Year: 1877

page_text: PROVISIONAL SPECIFICATION left by Robert Sharland at the Office of the
Commissioners of Patents on the 17th March 1877.
ROBERT SHARLAND, of Marwood House, Sydenham, in the County of Kent.
"IMPROVED MEANS AND APPARATUS FOR EFFECTING REDUCTION OR ENLARGEMENTS
OF DRAWINGS OR PLANS."
This Invention relates to improved means and apparatus for effecting reduction
or enlargements of drawings or plans, and is carried out in the following manner.
A sheet of paper, parchment, or any suitable woven fabric has drawn, printed, or
otherwise produced upon its surface a series of lines not parallel to one another, but
such that any straight line drawn at right angles to the length of the sheet shall be
divided into equal parts by the series. Of the said series of lines, one which may
be called the base line, is straight throughout its length, and the others vary in their
distances from this base line and from each other in such a manner that a straight
line drawn at right angles to the base line at one of its two extremities shall be
divided by the series into inches or other units of length, and a perpendicular to
the base at its other extremity shall be divided into tenths, twelfths, or other frac-
tional parts of the inch or other unit adopted.
From the above it follows that any intermediate scale may be found by a
perpendicular to the base line at some intermediate point between these two
extremes.
By the process described any scale of equal parts between any desired limits may
be formed and may be used as follows.
Method 1. The simple sheet may be folded or doubled on the line perpendicular
to the base corresponding to the scale required, and then used as an ordinary
plotting scale.
Method 2. The sheet may be carried on two rollers in a suitable frame or box,
and the folded sheet supported by a blunted knife edge. In this and other methods
where rollers are used a clamp screw is provided to fix the rollers, and thus to bold
the sheet as required for use. Rachets inay also be used to prevent the rollers from
being turned in the wrong direction.
Method 3. The sheet may be made of some transparent material, such as tracing
paper or tracing cloth, and may be carried on two rollers set at such a distance
apart in their frame that a sufficient portion of the drawing to be measured can be
seen between the straight edges or guides used to keep the sheet in position. Ono
Pavion 911

page_text: of the straight edges may thus be used as a perpendicular to the base line of the
series of lines on the sheet, and its length may therefore be divided into any
required number of parts for use as a scale; but this method is not so convenient
for plotting as for measuring, since for the plotting it is necessary to transfer the
dimensions to the plan by means of compasses or other equivalent device. A fine
thread or wire in tension may be used to define the line of scale between the
guides, and the angular guides in that case can be replaced by rollers.
a
Method IIII. Here a frame and rollers are used, but instead of the knife edge
third roller is used, and a permanent sloping scale, with any convenient markings,
perpendicular to its length on its surface, is used to transmit the readings of the
scale at the upper edge to the lower edge, or vice versa.
Either the permanent scale or the roller adjacent to it may be capable of slight
adjustment, lengthways, so as to bring a given mark on the permanent scale to
coincide with the base line of the series on the sheet.
A pair of indices may be made capable of sliding on the face of the per-
manent scale to mark any points required from edge to edge of the said permanent
scale.
In the methods III. and IIII. the straight edge or permanent scale has its markings
made by preference to show some one or more standards of length, such as the metre,
foot, inch, link, or other measure and fractional parts of the same, thus giving at a
glance the value of any scale on the sheet.