Improvements in Insulating Lining for Electrical Apparatus and Process of Making same.
Year: 1899

page_text: Date of Application, 22nd Mar., 1899-Accepted, 20th May, 1899
COMPLEIE DIECIFICATION.
Improvements in Insulating Lining for Electrical Apparatus and
Process of Making same.
We, THE BRITISH THOMSON-HOUSTON COMPANY, LIMITED, of 83, Cannon Street,
in the City of London, Electrical Engineers, do hereby declare the nature of this
invention (which has been communicated to us from abroad by George B.
Painter, residing at Schenectady, in the County of Schenectady, State of New
York, United States of America, Electrical Engineer) and in what manner the
same is to be performed to be particularly described and ascertained in and by
the following statement:-
This invention relates to that class of electrical apparatus in which a metallic
shell surounds other metallic parts serving to carry or regulate an electric cur-
rent, and will be described with particular reference to sockets for incandescent
lamps, though it is useful in various other relations.
In such apparatus it is highly desirable that the metallic shell should be lined
with an insulating sheath, for obvious reasons, and it has hitherto been the customi
to stamp out from sheets of fibre, or other similar material, curved pieces which
would when assembled form an approximately cylindrical lining of the proper
shape. But this arrangement was objectionable, both because of the cost of manu-
facturing and assembling such pieces, and because of the imperfection of the
lining thus formed.
This invention contemplates forming a single lining, of the proper shape, made
in one piece, and highly suitable for the purpose for which it is intended. The
invention also comprises a new process of working insulating material.
It has been discovered that it is possible to work insulating material such as
fibre, hard rubber, and the like, by a treatment that is not applicable to metal,
and to work a simple cylinder into fairly complex forms by dies suitably shaped.
Therefore in the practice of this invention. tubes of insulating material are taken
and cut to suitable lengths and then submitted to the action of dies in a manner
to be explained further on.
The invention will be more clearly understood from the accompanying draw-
ings, which illustrate one of the linings, suitable for lamp sockets, and the method
of making it.
Fig. 1 is a perspective view of the parts of the outer shell of the lamp socket
and the insulating lining ready to be applied; Figs. 2 and 5 show the die and
the lining in various stages of the process of manufacture.
In Fig. 1, A is a lining, which is composed of two cylindrical portions A¹, A²
The upper portion is designed to fit the larger part of the socket and is provided
with notches a³, a³, through which the securing screws pass, and with a deeper
cut at in which the key of the socket (not illustrated) may rest. It is manifest
that in a keyless socket the cut at may be omitted. the lining otherwise being
the same.
B is the cap of the socket and C the shell.
In Fig. 2, A¹ is a section of tube from which the lining A is made. This may
be of any suitable fibrous or similar insulating material both rubber and insu-
lating fibre, made by any of the processes now well known in the art, have been
used with good effect. The diameter of the upper portion of the female die D¹
makes a working fit with the tube A', and the upper part of the male die D
similarly fits the inside of the tube. The female die D¹ has shoulders which are
curved so that, as illustrated especially in Fig. 3, the ends of the tube when turned

page_text: over in the process of manufacture, will not strike at too obtuse an angle upon
the die D. The top of the female die is slightly countersunk, so that the tube
may readily enter it.
In Fig. 3 the process of manufacture is shown at a further stage. Here the
dies have been pressed together and the ends a¹ of the tube have begun to turn
over against the shoulders of the lower die. The material flows, as shown, urged
forward by the shoulder of the male die D³, until it assumes successively the
positions and form shown in Figs. 3, 4 and 5. This process of working an open-
ended tube is not, so far as we are aware, known or used in metal working, and
indeed, its operativeness depends upon the peculiar characteristics of the material
used.
Subsequently the notches a², a³, ut are cut in any desired way, usually by a
milling cutter, and the lining is complete.
It will be seen from an examination of the figures, that the lower part 3 of
the male die so nearly fits the inner bore of the lower die that the lower part of
the tube A¹ has no room to crimp or buckle, but it is compressed and upset so
that the lining forms a smooth inner and outer surface. When made of fibre,
this compression is considerable, and the lining is stronger and more substantial
than the tube from which it is made.
It will be obvious that the invention is not limited to use in connection with
a circular tube, or to the production of a lining of the form shown.
Having now particularly described and ascertained the nature of our said
invention (as communicated to us from abroad) and in what manner the same is
to be performed, we declare that what we claim is: ---
1-A lining for a lamp socket consisting of an integral sheath of insulating
material shaped to fit the inside of the shell.
2As a new article of manufacture, a lining for the socket of an incandescent
electric lamp, consisting of a removable integral sheath of insulating material
shaped to fit the inside of the shell, and having the slots a², a³, through which
the securing screws may pass.
As a new article of manufacture, a lining for the socket of an incandescent
electric lamp, consisting of a removable integral sheath of insulating material
shaped to fit the inside of the shell, having slots a, a³, for the screws, and the
slot for the key of the socket.
4 The process described of making insulating linings, which consists in form-
ing the selected insulating material into a tube, and then forcing the tube into a
dia and upsetting a part of it to a less diameter.
5-The process of making an insulating lining, an open tube, upsetting the
end of a tube of insulating material to a small diameter, and confining the end
while being upset between relatively moving surfaces so that crimping or buck-
ling is prevented.
6 The process of making an insulating lining, which consists in radially com-
pressing a portion of an open tube of insulating material by longitudinally exerted
pressure and confining the portion under compression between relatively moving
surfaces.
Dal 011 1
1000
THE BRITISH THOMSON-HOUSTON CO. LTD.
Applicants.
A. R. MONKS,
W. MARTINDALE,
Directors.
ALFRED CLEMENTS.
Assistant Secretary.