IMPROVEMENTS IN THE CONSTRUCTION OF INSTRUMENTS OR APPARATUS FOR RULING PARALLEL, ANGULAR, AND CURVED LINES
Year: 1867

page_text: PROVISIONAL SPECIFICATION left by John Garrett Tongue at the
Office of the Commissioners of Patents, with bis Petition, on the 13th
July 1867. A communication from abroad by Thomas Piatti, of Rue
Truffaut aux Batignolles, Paris, in the Empire of France.
I, JOHN GARRETT TONGUE, of the Firm of Tongue and Birkbeck, Patent
Agents and Engineers, of 34, Southampton Buildings, Chancery Lane, in the
County of Middlesex, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN THE CONSTRUCTION OF INSTRUMENTS OR APPARATUS FOR
RULING PARALLEL, ANGULAR, AND CURVED LINES," to be as follows:--
This Invention relates, first, to the construction of an instrument or apparatus
termed a "micrographic" rule. This instrument consists of two rules of
wood, metal, or other material connected at or near their extremities by jointed
arms, which are connected together at the joints by a rod or link which retains
the arms opposite to each other. Upon or near the middle of one of the parts
of the rule a suitably divided transverse bar is mounted, and this bar moves
on a guide piece fixed on the other rule. It is by the aid of this divided bar
that the distance is determined that one of the rules moves in regard to the
other. The equal parallel distances required may be exactly obtained by
means of a small moveable sliding piece which can be fixed when desired upon
the divided bar by a thumbscrew, and the sliding piece is brought against the
connecting rod or link previously described when one of the rules is moved
away from the other, consequently limiting the distance that the other rule
can move. It is evident that this distance will be changed by altering the

page_text: position of the sliding piece. Other forms of stops for arresting the movement
of the rule may be employed for the above purpose. Guides are placed at
the extremites of the two rules to render their parallelism more perfect.
In addition to the instrument previously described apparatus may be com-
bined therewith (or made separate therefrom) for ruling angular and curved
lines, such instrument being termed a "micrographic goniograph." At the
side of one of the parts of the parallel rule previously described is a moveable
ruler arm working upon a joint, the centre of which is placed exactly upon
the exterior edge of the moveable rule, and by preference at the extremity;
this rule can be moved at will upon its centre, and forms when at the
extremity of its movement an angle of 90 degrees, there is therefore the
facility of forming every angle within 90 degrees, and the ruler arm can be
fixed when required by means of a small quadrant fixed upon one end of the
moveable ruler arm, and secured when desired by a thumbscrew to one of the
parallel rules. The ruler arm has a moveable compass branch serving to
trace quarters of circles corresponding to the degrees. The opposite extremity
to the centre of rotation moves upon a divided quadrant indicating all the
degrees. When the ruler arm is in any desired position it can be fixed to the
divided quadrant by means of a thumbscrew placed at its extremity. Upon
the ruler arm a sliding or tail piece may be placed for the purpose of
lengthening it when desired.