Year: 1895

page_text: Date of Application, 8th Jan., 1895-Accepted, 3rd Aug., 1895

page_text: and fitting the convex projections on centre member A thus making a completely
closed, solid and flush joint on all sides when open, see Figures 2, 4, 5 and 7.
The parts F, G and H (Figs. 2, 3, 6 and 8) constitute what is termed one of
the middle knuckles and its construction consists of the parts H H and H H so
formed as to turn on separate centres as couples, fitting into and secured together
by the piece G and the core member F (see Fig. 6); which two members (F fitting
inside of G) have convex curves on their opposite sides concentric with the
turning points of HH and H H and fit corresponding concave curves or apertures
in the abutting members of the rule and the binding on the edges of the legs.
A stop is provided at the bottom of F and G (see K, Figs: 3, 4, 6 and 8) to
prevent the rule being opened beyond a straight line, and this stop is sufficiently
wide in F and G between the members H and H so that the bottom curves in
HH and HH in folding up do not leave the confines of the recesses in which they
fit and thus form a completely closed and dust-tight joint when the rule is folded
up: The sides of the member G are bent in (before assembling) beyond the
position they are to occupy when put together and the inherent spring thus formed
makes this joint always tight even when the rule becomes old.
Of course the middle knuckle construction may be used for the head knuckle,
or vice versa.
It will be noted by the construction of these joints that each turning point only
permits a quarter turn and is then mechanically stopped, so that by turning a leg
of the rule on only one point a true right angle is formed with the other leg running
down to a sharp corner without obstruction of any kind on the inside and by reason
of the natural stiffness in the joints will hold itself as placed rigidly enough for all
practical purposes (see Figures 7 and 8). It will be further noted that the con-
structional sliding curves on the enclosing envelopes A and G in each knuckle if
continued to complete circles, would intersect or overlap one another. The over-
lapping arcs of the parts 'H.H and H H in the smaller knuckles are removed
(Fig. 3) and the stops at the backs or bottom of the joints are prolonged so that
the chords formed by the removal of the arcs do not quite reach the ends of the
stops when the rule is folded up, thus keeping the joints closed and impervious
to dust.
Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed, I declare that what I
claim is :-
Claim 1. In a folding rule, the combination of the rule legs with joints or
knuckles operating within enclosing envelopes formed with intersecting or
overlapping circular ends and prolonged stops at backs, as to make flush and
continuously uniform, flat and unobstructed surfaces on all sides and edges without
projections or recesses when rule is open, substantially as shown and described.
Claim 2. The combination, in a folding rule of the rule legs with a head knuckle
securing them together so formed as to turn on two separate points; provided with
a central member with convex curved ends, said curves struck from the said
turning points intersecting or overlapping each other, and leg members formed to
fit into central member, each provided with concave recesses extending from the
belly of the joint to near the back, the overlapping curves of which are struck from
the turning points of each member, substantially as shown and described.
Claim 3. The combination, in a folding rule, of the rule legs with a head knuckle,
turning on two points, operating within enclosing envelope formed with intersecting
or overlapping circular ends, the leg members of the joint or, knuckle being
provided with pressure springs for making the joint stiff and keeping out dust or
foreign substances when the joint is open or closed, substantially as shown and
described.
Claim 4. The combination, in a folding rule, of the separate legs with middle
knuckles or joints, so formed as to turn on two points each within a central con-
necting member; having a stop prolonged or widened at the back of the middle.

page_text: member to prevent the bottom curves of the leg members of the joint from leaving
the protection of, or covering provided by the said prolongation of the said stop so
as to form a solid and dust-proof joint when the leg members of the rule are closed,
substantially as shown and described.
Claim 5. The combination, in a folding rule, of the legs with the scaling etc.,
described, the pieces or parts A and B and C with their spring lips J, stop D,
side plates E, E, E, E, of the head knuckle and the parts F, G, and "HH"
"HH" of the middle knuckle, all substantially as and for the purposes set forth
and described.
Dated this 8th day of January 1895
ALLISON BROS.,
Agents for the Applicant.