An Improved Method of and Means for the Manufacture of Leads for Lead-pencils.
Year: 1897

page_text: Date of Application, 4th May, 1897-Accepted, 19th June, 1897
COMPLETE SPECIFICATION.
An Improved Method of and Means for the Manufacture of Leads
for Lead-pencils.
1, FREDERICK WILLIAM MUSSON of 1410 Marquetto Building, Chicago, County
of Cook and State of Illinois, U.S.A., Gentleman, 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 :-
My invention relates to the method and means for the manufacture of leads for
lead-pencils, and has for its object to provide for use in certain automatic or
moveable-lead lead-pencils the screw-threaded or circumferentially grooved leads
necessary for that purpose. There have been at different times automatic or
moveable-lead lead-pencils made or attempted to be made in which a screw-threaded
or circumferentially grooved lead was designed to be employed; but so far as I am
advised it does not appear that any such lead-pencil has ever become commercially
satisfactory. I have for sone time past been engaged in developing and inventing lead
pencils of this character; and having succeeded in securing and patenting what
appears to be successful forms of such lead pencils, I have encountered the difficulty
of providing leads for the same commercially. In some of my pencils a spiral groove
in the surface of the lead is required. In others a circumferential groove or series of
grooves might be employed. But in neither case have I been able to find such leads.
commercially available. The attempt to cut the thread or grooves on the finished lead
proved highly unsatisfactory. It would require more or less expensive machinery, and
involve certain dangers to the lead itself; so that by increased cost of manufacture
and deterioration of the leads, the advantages of my improvements in the pencil are
overcome in great part. I have found that by following a certain process satisfactory
grooves or screw-threads or spirals can be cut or formed in the lead. This process I
will now describe :
The lead material, suitably ground and mixed, and of a consistency something like
putty, is preferably placed in a receptacle and there exposed to a very high pressure.
An aperture of substantially the cross-section of the finished lead is provided, and
through this aperture the lead material is forced by such pressure. It comes out in a
plastic condition and is cut into pieces of the proper length. These plastic lead rods
so produced, or produced in any other manner, are placed either upon a flat plate or
upon a plate having a die surface whereby the screw-tbread or groove is to be formed,
and a corresponding flat surface or die plate is then placed upon these lead rods. It
is understood, of course, that these lead rods will first be gently rolled upon a flat
surface and brought so that the last one of them is against a straight-edgo, whereupon
they will all be found to lie parallel with each other, each thus being brought into the
form of a straight rod. Having now been exposed to the dies (and upon the form
and construction of these dies, I lay no great stress, as there may be great latitude in
their construction), such dies being formed upon the surface of one or both of the
plates between which the rods are now seated, one of these plates will be moved slightly
forward so as to roll or press into the surface of the leads the desired grooves. Since
these leads are to be thus rolled, it is necessary that there should be, at least in
the first instance, a flat surface, and hence the first operation of the die, or the
first rolling of the leads in the process of forming the grooves or screw-threads involves
no more thin pressing the grooves in such manner that there will be left a flat
surface of a relatively considerable extent between the successive grooves or spirals.

page_text: These leads so formed are now subjected in the usual manner to proper heating
and curing processes until they are formed into hardened leads fit for use, having
thus formed on their surfaces these grooves or spirals or screw-threads which fit
them for use in my pencils. Of course the groove can be deepened and thus the
flat surface of the lead between the successive spirals be narrowed by successive
rollings or exposure to the dies, so that in fact, though this I do not consider the
best form of the lead, the lead may be brought into practically the condition of
a screw-threaded rod.
As previously suggested I do not attach any particular importance to the particular
form of the devices used to bring about these results, but I have in the accompanying
drawing illustrated some features of my invention.
Figure 1 is a view of a series of plastic load rods brought into parallelisin on a
proper surface.
Figure 2 is one of the said rods after the groove has been first or partially formed
as the case may be.
Figure 3 is a view of one of said rods in which the groove has been so far doveloped
as to make the ordinary form of a screw thread.
Figure 4 is a view of the die whereby said grooves can be formed in the leads.
Figure 5 is a view of a series of leads in position between the two die plates.
Figure 6 is a transverse section through Figure 5.
Like parts are indicated by the same letter in all the figures.
AA are the leads in their plastic condition before treatment. B is a lead with a
spiral having a wide flat surface between its successive grooves. C is a screw-threaded
lead. D is the die plate. E is the smooth surface plate opposed to the die plate.
One of the great practical difficulties which I encountered in rolling the grooves,
spirals or screw-threads into the leads grew out of the fact that the leads being
plastic, the attempt to cut or roll a deep groove or continuous screw thread in
its surface was unsatisfactory. I found that it was necessary that during this
process of first forming the groove the lead itself must have a bearing surface
because of its plastic condition, and hence I begin by rolling the groove into and
beneath the surface of the lead so as to leave an exposed smooth outer surface of
the lead of considerable extent between the grooves or successive spirals.
"
I have in the description and also in the claims for convenience used the term
"lead
and "lead pencil." By this, however, I do not wish or intend to be
limited to graphite, or to what in the narrowest sense might be included in the
term "lead" or "lead poncil." My invention is applicable to all such forms of
marking materials. Thus there are colored crayons, wax crayons, pastel crayons,
oil crayons, paint crayons, slate crayons, and other such like marking materials;
and doubtless some if not all of them could be used in a similar manner and
treated in a similar manner to that indicated herein. I wish, therefore, to have it
understood that by the term "lead" and "lead pencil" as used in the description
and in the claims I mean broadly to include and cover any and all such marking
materials as can be treated in the manner herein described as being applied to the
specific marking material which I have made the base of my description.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed 1 declare that what I
claim is :
1. The method of forming leads for moveable-lead, lead-pencils which consists
in producing the leads in a series of plastic rods, rolling these while arranged in
a series side by side in association with a straight edge so as to bring them all
into parallelism and straightness, then rolling them between die plates so as to
roll circumferential grooves therein with broid flat bearing surfaces between such
grooves, then drying and curing said leads to form the finished product.
2. The method of forming leads for moveable-lead lead-pencils which consists in
reducing the lead substance to a plastic mass, then producing therefrom a series of
plastic leads, then bringing such leads in a inass or series into straightness and

page_text: parallelism on a proper surface, then subjecting said leads en masse to the rolling
action of die. plates so as to form on each circumferential grooves, said successive-
grooves separated in the first instance by a broad flat bearing surface to permit such
rolling process then successively rolling said leads in like dies until the grooves are
properly formed, then drying and curing the leads.
3. The method of forming leads for moveable-lead lead-pencils which consists in
reducing the lead substance to plastic rods, then bringing such rods in a mass or series.
into straightness and parallelism on a proper surface or a die, then subjecting the
entire series of rods. to the rolling action of die plates so as to force on each
circumferential grooves substantially along its entire length, thie grooves on all of the
series being formed simultaneously by a single rolling of the die plates, then drying
and curing the rods.
4. The method of forming leads for moveable-lead lead-pencils which consists in
producing the leads in a series of plastic rods, then rolling a series of these rods in.
association with a straight edge so as to bring them all into parallelism and straightness,
then rolling them between die plates.so as to roll circumferential grooves therein and
without changing the length of said leads, said circumferential grooves extending
substantially the entire length of said leads and being formed by one operation of
the dies.
H. D. FITZPATRICK,
70 Wellington Street, Glasgow, Agent..