An Improved Process of Producing Moulded Articles having a Metallic Core or Strengthening Piece.
Year: 1889

page_text: Date of Application, 27th Aug., 1889-Accepted. 26th Oct., 1889
COMPLETE SPECIFICATION.
[Communicated from abroad by CHARLES TENNANT LEE, of Starey Place, Jamaica
Plain, Boston, Massachusetts, United States of America, Chemist.]
An Improved Process of Producing Moulded Articles having a
Metallic Core or Strengthening Piece.
I, HENRY HARRIS LAKE of the firm of Haseltine, Lake & Co. Patent Agents,
Southampton Buildings in the County of Middlesex, 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 the manufacture of many articles, such for example as handles for electrical
switches, which it is desired shall be of considerable strength, a core or strengthening
piece of metal is used which is enveloped wholly or partially in an insulating
composition.
Mica compositions consisting chiefly of mica or similar laminated material in a
comminuted state bound together with a resinous gum such for example as shellac,
are largely used as insulators. They are good non-conductors and may be moulded
when in a plastic condition to produce an object of any form desired. Many of the
articles so made require to be strengthened as, if made of the composition alone, they
would be liable to break. To strengthen them, a metal core or strengthening piece is
inserted, as above stated, and the plastic mass moulded around it into the shape
desired. Hitherto difficulty has been experienced in securely uniting the metal core
to the composition and so the composition was liable to come off the core or piece of
metal with which it was in contact and thus destroy the value of the article.
The object of my invention is a process by which articles moulded from a compo-
sition of mica or similar material and a resinous gum can be secured firmly to a metal
core or strengthening piece; and it consists in the process hereinafter described and
which is set forth in the claim hereof.
One of the mica compositions which is employed, as above referred to, in making
moulded objects consists of ground mica mixed and incorporated with shellac by the
aid of heat. The mass after being thoroughly mixed and while it is in a plastic con-
dition, is placed in dies of the proper shape to mould it to the shape desired in the
object which is to be produced and the moulding is accomplished by the compression
of the plastic mass in the dies. These dies are warın. Before the plastic mass is
placed in them, the core or piece of metal which it is desired shall be attached to the
inohlded object, is heated until it is hot, that is, has reached a temperature of say
three hundred degrees Fahrenheit which is considerably higher than the temperature
of the dies or the plastic mass. This core or piece of metal is then placed in proper
position within the dies together with the mass of plastic material and the dies closed
under pressure, compressing the mass and moulding the article to shape around the
metallic core. The object is allowed to remain in the dies to cool under pressure and
is then ready for use or further manipulation. Such cooling under pressure prevents
expansion of the moulded object and enables the production of an article of exact size
and shape with a close uniform surface and the composition part of said article even
if fractured into many pieces will still remain firmly secured to the metal.
I am aware that it is not new to produce objects made from plastic material
enclosing metallic cores or strengthening pieces but, so far as I know, the cores or
strengthening pieces are not heated in the process of securing them in place and if the
composition he fractured, it will easily detach from the metal rendering the article
worthless.

page_text: Having now particularly described and ascertained the nature of
my
said inven-
tion, and in what manner the same is to be performed, as communicated to me
by my foreign correspondent I declare that what I claim is :-
The process of producing moulded objects consisting of mica or similar material
incorporated with a resinous gun and having a core or strengthening piece of metal
secured therein, consisting in first warming the dies, which are to give the exterior
shape to the article to be moulded, then heating the core or strengthening piece to a
much higher degree of heat than the dies or the plastic mass and placing said core and
said plastic mass together within the dies, then moulding and compressing into shape
and allowing the object thus formed to cool before removing the pressure, sub-
stantially as described.
Dated this 27th day of August. 1889.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.