Improvements in Apparatus for Drawing to Scale in Class Teaching.
Year: 1894

page_text: Date of Application, 20th Sept., 1894
Complete Specification Left, 8th May, 1895-Accepted, 6th July, 1895
PROVISIONAL SPECIFICATION.
Improvements in Apparatus for Drawing to Scale in Class Teaching.
I ANDREW GEORGE ASHCROFT of University College London do hereby
declare the nature of this invention to be as follows:-
A frame of wood, or other material supporting two horizontal rollers, one at the
top and the other near the bottom.
Over these rollers is stretched canvas, or other material in the form of a
continuous band, coated with paint, or otherwise prepared for writing, or drawing
upon with chalk, charcoal, crayons, or paint.
The lower roller is mounted on bearings, to which are attached screws, whereby
any desired vertical tension of the canvas can be obtained.
Narrow strips of wood or metal are placed in horizontal pockets, at intervals on
the inside of the canvas to keep it flat.
Attached to the frame is a parallel ruler, to take the place of the T square,,
ordinarily used in drawing.
This parallel ruler consists of seven bars of wood, or other material, pivoted on
the frame, as shown on the accompanying drawing, at points marked A and B,.,
and to each other at points marked C, D, E, F and G.
By this arrangement the top bar, which has a straight edge on its upper side,
can move freely upwards or downwards, the straight edge always being parallel to
a straight line passing through the centres of the pivots A and B.
This parallel ruler can be used with any drawing board, blackboard, or slate.
The weight of the parallel ruler is balanced by a weight attached to a cord
passing from the point marked F on the drawing, to which it is fixed, over a pulley
attached to some convenient part of the frame.
Dated this Twentieth day of Sentember in the year 1894.
COMPLETE
SPECIFICATION.
Improvements in Apparatus for Drawing to Scale in Class Teaching.
ANDREW GEORGE ASHCROFT University College London, Engineer, do hereby
declare the nature of this invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement :-
A frame of wood, or other material supporting two horizontal rollers, one at the
top and the other near the bottom of it.
Over these rollers is stretched canvas, or other material, in the form of a
continuous band, coated with paint, or otherwise prepared for writing upon with
chalk, charcoal, crayons or paint.
The lower roller is mounted on bearings, to which are attached screws, whereby
any desired vertical tension of the canvas can be obtained by tightening nuts
marked H K on the accompanying drawings.

page_text: Narrow strips of wood or metal are placed in horizontal pockets at intervals on
the inside of the canvas, to insure its remaining flat.
Attached to the frame is a parallel ruler, to take the place of the T square,
ordinarily used in drawing.
This parallel ruler consists of seven bars of wood, or other material pivoted on to
the frame, as shown on the accompanying drawing, at points marked A and B, and
to each other at points marked C, D, E, F, & G; so that the upper bar can move
freely upwards or downwards, always being parallel to a straight line drawn through
the centres of the pivots A and B.
This parallel ruler can be used with any drawing board, blackboard, or slate.
The weight of the parallel ruler is balanced by a weight attached to a cord
passing from the point marked F on the drawing, to which it is fixed, over a pulley
attached to some convenient part of the frame.
A wooden board is attached to the frame behind the canvas to take the pressure
of the hand or of the point of a pair of compasses.
The invention is used for drawing to scale, working geometrical problems or for
any of the purposes for which an ordinary drawing board is used, the top bar of the
parallel motion taking the place of the ordinary T square.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be used I declare that what I
claim is
1. The arrangement of the seven bars forming the parallel ruler for the purpose
described.
2. The use of strips of wood or metal to insure the canvas remaining flat.
3. The construction of the apparatus for the purpose specified, substantially as
described.
Dated this Eighth day of May 1895.
ANDREW GEORGE ASHCROFT.