IMPROVEMENTS IN POCKET RULES
Year: 1866

page_text: PROVISIONAL SPECIFICATION left by William Robert Lake at the Office
of the Commissioners of Patents, with his Petition, on the 21st February
1866. A communication from abroad by Benjamin Green Martin, of
Philadelphia, Pennsylvania, United States of America..
I, WILLIAM ROBERT LAKE,. of "the International Patent. Office," No. 8,
Southampton Buildings, Chancery Lane, in the County of Middlesex, .Con-
sulting Engineer, do hereby declare the nature of the said Invention for.
"IMPROVEMENTS IN POCKET RULES," a communication, to be as follows:-
The nature of the said Invention chiefly consists in providing the ordinary
pocket rule with a pointed swinging arm to adapt the same for use as a plumb.
level, and also in providing the said rule with an index and pointer in such a
manner that any angle of inclination to a plane may be readily ascertained
thereby..
By this construction and combination of parts the instrument. answers the
purposes of a plumb level, and also a square and level, without lessening its
utility as a pocket rule or materially increasing its cost. The pocket rule is
constructed two feet long with joints to fold into a length of six inches. The
swinging arm, formed of a piece of metal four inches in length, has one end
pivoted near one of the first folds of the rule in such a manner that the said
arm will vibrate freely on the pivot, the other end of the said arm being
unconfined and made wider and heavier than the pivoted end. For conveni-
ence however the extremity of the free end is pointed. The index pointer also
formed of a piece of metal five inches in length is about seven-eights of an

page_text: inch from the centre of the main or middle joint of the rule and close to the
inner edge of the section to which the said swinging arm is pivoted, and upon
the same side of the said section, while the opposite end of the index pointer
is attached to the corresponding section of the rule by means of a double
headed screw passing through a slot or aperture cut longitudinally in the latter
section of sufficient length to allow the two sections to close together and to
open out, forming a straight line with each other, as in the ordinary rule.
The index formed on the same section and face as the pointer is pivoted con-
sists of a curved line and a series of equidistant radial lines, whose centre of
radiation is the pivot of the index pointer, and the first of which is made to
coincide with the end of the said pointer when the rule is closed, and is
marked with a cypher. For illustration, the curved line is divided by the
radial lines into parts of fifteen degrees each, consequently when the pointer
coincides with the second radial line the rule is open fifteen degrees, with the
fourth forty-five degrees, and when it coincides with the seventh radial line it
is open ninety degrees, forming a square. Upon the index pointer is fixed a
pointed block in such a position that its upper point will coincide with the
point on the lower end of the swinging arm when the rule is open forty-five
degrees and held upright with the section on which the longitudinal slot is
formed on a horizontal plane. When the rule is closed the unconfined end of
the swinging arm is secured by means of a stay piece fixed to the section to
which the said arm is pivoted. When closed this rule can be carried con-
veniently in the pocket; when open forty-five degrees, as before mentioned, it
answers the purpose of a plumb level, and when open ninety degrees it
answers the purpose of both a square and level, and any angle may be
measured with accuracy. The additions to the ordinary rule are simple and
readily applied to those rules in use at a trifling cost.