Improvements in Flexible Rulers.
Year: 1891

page_text: COMPLETE SPECIFICATION.
Improvements in Flexible Rulers.
We KARL AUGUST LINGNER and GEORG WILHELM KRAFT trading as
Lingner and Kraft of Dresden, Kingdom of Saxony, German Empire, Manu-
facturers, 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:—
In drawing lines with an ordinary ruler as hitherto in use there is a difficulty in
drawing straight lines if the object does not offer a level surface, such as is the
case for example in large account books for business &c. on the curved surfaces of
the sheets of which the ruler cannot evenly be pressed down.
The production of a flexible ruler has met with these difficulties, that in con-
structing it of hard material, the ruler had in order to be really flexible, to be made
too thin, whereby the drawing edge of the ruler comes too near the paper, causing
blotting on the paper; if the ruler was made of a soft and flexible material such
for example as india rubber, the soft edge of such material does not offer resistance
enough against the pen.
The object of the present invention is to construct a ruler which combines the
following qualities and advantages of, 1, having a hard or resisting drawing edge;
2, being high enough to offer the necessary distance between 'the paper and the
drawing edge; and 3, being so flexible that it easily yields to curved surfaces withi
the slighest pressure. The ruler according to the present invention offers all these
desired qualities as will readily be seen by the following Specification.
The ruler according to this invention consists of two clastic plates of the suitable
length and width of a ruler and of the very minimum of thickness, such as for
example, the thickness of the spiral spring of a clock of moderate size. These
two elastic plates are connected together in such manner that they lie with their
flat sides parallel to each other, and if desired at such a distance apart from each
other as to constitute the thickness of an ordinary ruler, the connection being such
that the parallelism is always kept up, whereas the two elastic plates may be shifted
independently from each other in the lengthwise directions. We thus preserve the
full elasticity of each plate, and thereby of the ruler composed of such plates.
The construction will be more fully understood by referring to the annexed
drawing in which Figure 1 is a side view and Figure 2 is a top view of the ruler,
Figure 3 showing a section on the line X X of Figure 2 and Figure 4 showing
the ruler in use on au account book or ledger.
a a¹ are two elastic and flexible plates of suitable size and of very little thick-
ness. We prefer to make these plates of steel, but we reserve to ourselves the
right of using any material which in very thin plates combines the necessary
flexibility, hardness and resistance.
The lower plate a is provided with studs or projections d at its upper surface,
said studs ending in a round head and having an annular recess of below the head.
The upper plate al is provided with long slots c, each slot having at one end an
opening for the head of the studs d to enter, whereas the slots are of smaller
dimensions, to allow the recesses of the studs to enter into said slots. In the
middle or near the middle of the lower plate u and on its upper surface a nut i with
inner thread is fixed, the upper plate a¹ at the corresponding place being provided
with a hole for the screw with a milled head to enter and to combine the two
plates a and a rigidly at or near their middle part. We prefer to make the lower
plate a smaller in its width as indicated in dotted lines in Figure 2, so as to prevent
the lower plate being touched by the ink of the pen, thus imitating the hollow
recess usual in wooden rulers.

page_text: In using the ruler the protruding edge of the upper plate a' serves as the
drawing edge for the pen to rest against, whereas the lower plate a rests on the
paper to be ruled. and preserves or protects the paper from. being soiled or blotted
by the ink which in the act of drawing adheres to the edge of the upper plate and
dries up between the two plates.
The space or room between the two plates may if desired be filled up with a soft
substance such as paper, which in long strips of the width of the lower plate or of
less width, is provided with elongated holes to pass over the studs d; such strips
preserving the parallelism between the two plates, but being able to shift longi-
tudinally independently from each other. If an absorbent material is used to fill up
the space between the plates, such material will take up the ink adhering to the
drawing edge of the upper plate.
Such an elastic and flexible ruler may be composed of more than two plates con-
nected together and being capable of shifting independently in lengthwise
direction; the elasticity and flexibility, however, of such ruler being inferior to
those composed of two plates only.
If the ruler is laid for use on a surface of a certain curvature, the ruler will by
the slightest pressure on the top plate, accommodate itself to, the surface by bending
so that it rests on all parts of the surface in the line to be drawn, thus insuring a
straight line without necessitating the rocking of the ruler, as is the case if the
latter is stiff and rigid in all its parts. With our improved ruler the plates
and a will always, even if bent, remain parallel, whereas the plates are capable of
shifting independently of each other, to yield while the ruler is bent.
We may connect the two plates a and a¹ in any suitable manner such as by means
of hinged parts arranged between the two plates a and a', allowing these two plates
to shift independently of each other in lengthwise direction, but maintaining all
the while their parallelism. But we have found the stud and recess construction
in combination with the elongated slots to be preferable, said construction affording
the possibility of easily detaching the two plates by simply unscrewing the middle
screw g and shifting the upper plate so as to allow the stud heads to escape through
the holes provided for them.
We do not limit ourselves to the exact construction of the ruler as explained
above; we reserve to ourselves the right to vary the parts according to will, always
maintaining in an elastic or flexible ruler the parallelism of the upper and lower
thin plates and. their capability of lengthwise shifting independently from each,
thereby constituting a ruler capable of. yielding to the curved surface of the object
to be.ruled, and yet being of the sufficient height or thickness and resistance, and
offering, a stiff and rigid edge for the pen to rest against in the act of ruling.
We may mention that instead of the studs with recesses under their head, rivets
may be used which with their stem are fixed to the one plate, while the rivet head
passes through the hole of the other plate and the stem of the rivet slides in the
elongated slots of this latter plate.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is:-
1: A flexible ruler composed of two or more elastic plates of metal or other
hard material superposed and.combined in such a manner that the plates may shift
independently of each other in lengthwise directions in order to ensure the easy
flexibility of the ruler independently of its thickness.
2. A flexible ruler composed of two (or more) flexible plates a and a¹ provided
with. studs or rivets d and with elongated slots e for the studs or rivets to enter into
and to slide in,,the two plates being fastened rigidly or detachably together in the
middle part or near the middle part, substantially as described with reference to the
drawings.
3. In a flexible ruler composed of two elastic plates, which at a distance, apart
from each other are so combined together as to keep up their parallelism and to shift

page_text: lengthwise independently of each other, filling up the room or space between the
two plates with strips of flexible and soft material, substantially as and for the
purpose set forth.
Dated this 8th day of June 1901
J. C. MEWBURN,
55 & 56, Chancery Lane, London, Patent Agent.