Improvements in Incandescent Lamps for Electric Lighting.
Year: 1892

page_text: COMPLETE SPECIFICATION.
Improvements in Incandescent Lamps for Electric Lighting.
I, FREDERICK HERBERT PRENTISS, of Bergen Point, State of New Jersey,
United States of America, Manufacturer, do hereby declare the nature of my
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 electric incandescent lamps, and consists in constructing
the lamp so as to facilitate the repairing of the same by the substitution of a new
filament in the place of a burned out or broken filament, without the destruction of
the lamp; and also in providing the lamp with a detachable cap which may be
readily removed when it is desired to repair the lamp, or for any other reason.
In the accompanying drawing
Figure 1 shows a lamp constructed according to any improvement with a section
of soft glass below the metal cap.
Figure 2 is a view of the upper portion of the lamp with the metal cap removed
showing the section of soft glass at the top of the glass bulb.
Figure 3 is a longitudinal sectional view of a lamp with my improved detachable
cap.
Figure 4 is a plan view of the neck of a lamp with the detachable cap in place.
Figure 5 is a view of the cap detached from the lamp.
Figure 6 is a view of the neck of the lamp with the cap removed, and provided
with a threaded collar or band to engage with the cap or with a connecting sleeve.
Figure 7 is a sectional view of the connecting sleeve.
Figure 8 shows the upper part of a modification wherein the thread is formed
directly upon the glass bulb so that the collar may be dispensed with.
Figure 9 is a view of the neck of a modification wherein the movable and fixed
parts of the cap are joined by screws passing through flanges on each.
It is well known that the ordinary life of a carbon filament seldom reaches two
thousand hours of actual use. That upon the failure of such filament the remaining
parts of the lamp, including the metal cap, glass globe and platinum wires, are
practically in as good condition as when first made. It follows that if a lamp can
be so constructed as to admit of its being repaired by replacing a broken or burned
out filament by a new one, a great saving in the cost of manufacture will be
effected.
I accomplish this by making a portion of the globe of a softer glass than the
rest of the globe; that is to say, a glass which will melt or fuse at a lower
temperature than the glass of the other parts of the globe, so that the glass bulb
being separated into two parts on a line passing through the section or portion of
softer glass by means of a diamond, file, revolving wheel, saw, or other suitable
method, or by cracking, may be reunited by fusing, after the substitution of the
new filament. The portion of softer glass may form a section of the bulb below
the metal cap so placed that after separation through such section easy access can
be obtained to the points of connection between the filament and the platinum, as
is shown in Figure 1 where the section of soft glass is represented by the band c-c
a short distance below the fixed or permanent cap H; or the upper part of the
neck of the globe, covered by the cap may be composed of the softer glass as shown
at c Figure 2, or a portion of such neck may be made of softer glass, and the
separation be made through that portion of the bulb uncovered by the removal of
the metal cap, as at .-c.
I do not confine myself to the exact location of this section of softer glass
described above, and shown in the drawing, as such softer glass may be placed at

page_text: .
any portion of the bulb which would give convenient access to the platinum wires
and filament.
In the construction shown in Figure 2 where the section of softer glass is at the
neck or top of the bulb, and the separation is made at that part of the bulb covered
by the cap, in order to effect such separation it is necessary to remove the cap, and
afterwards, when the repairs are made and the severed portions of the bulb
reunited, to replace and again secure the cap on the lamp. It is, therefore, very
desirable in this construction, that the cap should be made removable.
The second part of my improvement refers to a construction of cap and bulb
whereby the cap may be readily detached from and secured to the bulb whenever
desired. Such construction is shown in the drawing in Figures 3 to 9.
The principal feature of my invention consists in an easily removable cap, or a
cap in two parts, one of which parts is easily removable so as to give ready access
to the neck of the glass bulb covered by the cap. The modifications cover the
various means of fastening the cap or the removable part thereof to the lamp.
Figure 5 shows a cap provided with screw thread a upon its lower outer surface.
In Figure 6 B is a band or collar fastened to the neck of the glass bulb.
The band or collar B is shown with screw-thread upon its outer surface. Such
threads are necessary when the union of the two parts of the cap is made by means
of the threaded sleeve I as in Figure 4. When the union is made by other means
as described the construction of the collar must be adapted to such method.
me,
This collar may be fastened to the glass bulb in a variety of ways; for example,
by the use of plaster of paris, or cement. The process adopted and preferred by
is to provide the collar B upon its inner surface with corrugations or indentations.
I then place it upon the neck of the bulb while the glass is in a plastic condition,
and by means of an air pressure through the tube at the lower end of the bulb,
force the glass into the corrugations or indentations of the collar, whereby, as the
glass cools, the collar becomes firmly fastened to the bulb.
Figure 3 shows a connecting sleeve I with screw-threads i upon its inner surface.
This sleeve is first engaged with the cap H and screwed thereon until its lower
edge is flush with the lower edge of the cap. The cap is then placed over the neck
of the bulb and in contact with the collar B. The sleeve I is screwed down until
it firmly engages with the collar B when the cap becomes securely fastened to the
lamp.
The collar B may be of any suitable material preferably of thin sheet metal.
The sleeve I may be of metal, hard rubber, vulcanized fibre or other suitable
material. In practice and to avoid danger of loosening the sleeve in handling, it
may be found desirable to use vulcanized fibre or some similar material and to aid
the union of the parts by treating the inner surface of the sleeve with a slight
coating of cement or other adhesive material, in which case the sleeve may be
removed, in the process of removing the cap, by cutting, and substituting a new
sleeve in the repaired lamp.
I do not, however, confine myself to the above described collar and sleeve, as a
connecting or fastening device. The cap H may be fastened to the bulb by
any mechanical means, some of which I show and claim in combination with the
removable cap.
Figure 8 shows the glass bulb with a screw-thread d of the same material
pressed or blown thereon, against which the cap H will rest when placed in position.
In this form of construction the sleeve I will engage with the thread upon the
bulb instead of with the collar B.
Figure 9 shows a form of construction whereby the sleeve I is omitted and the
cap H and collar B are provided with flanges and the cap H is then held in
position by screws e e passing through the flanges. The cap H may also be
fastened by means of one or more springs placed therein or thereon, which
springs engage with the collar B or with lugs or projections thereon or on
the glass bulb, or by a readily fusible solder or soft glass which will cement the
cap H to the collar B or to the glass bulb without the interposition of the collar in

page_text: which case the solder or equivalent material may be fused by a gas flame or hot
tool applied to the outer surface of the cap and thereby the cap loosened and
removed. The drawings show the lower part of the cap H, the sleeve I and the
collar B to be threaded. The cap may, however, be held in position by the
friction of the sleeve against the cap and collar, or by shrinking the sleeve on to
increase the friction, or by placing sockets or indentations in the cap H and
pressing it over corresponding lugs or projections on the collar B or on the glass
bulb, without the interposition of the collar, in which case the screw threads will
be unnecessary.
From the foregoing description it will be seen that the principal feature of this
part of my invention is a cap for an incandescent lamp constructed in two parts H
and B, one of which parts, B, shall be securely fastened to the glass of the bulb,
and the other part, H, attached or fastened thereto in such manner that it may be
easily removed, for the purpose of uncovering the neck of the glass bulb in the
process of separating the bulb into two parts, and so as to be readily reattached
and refastened, after the lamp shall have been repaired by the substitution of a
new filament.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed declare that, what I
claim is :-
I-An incandescent lamp for electric lighting having a section of the glass
bulb composed of a softer glass than the glass of the other parts of the bulb,
whereby the bulb may be divided as set forth, substantially as and for the purposes
described.
II An incandescent lamp for electric lighting having a section of the glass
bulb below the metal cap composed of a softer glass than the glass of the other
parts of the lamp, in combination with the metal top, platinum wires and filament,
substantially as and for the purposes described.
III An incandescent lamp for electric lighting having a portion of the glass
bulb covered by the metal cap, composed of a softer glass than the glass of the
other parts of the lamp, in combination with the metal top, platinum wires and
filament, substantially as and for the purposes described.
IV An incandescent lamp for clectric lighting with an easily removable and
replacable cap in combination with the glass bulb, electrical conductors, and
filament, substantially as and for the purposes described.
V: In an incandescent lamp for electric lighting, a cap composed of two parts,
one of which parts is permanently fastened to the glass bulb; said two parts being
easily attachable and detachable to and from each other, in combination with the
glass bulb, electrical conductors and filament, substantially as and for the purposes
described.
VI In an incandescent lamp for electric lighting, a cap composed of two parts,
one of which parts is permanently fastened to the glass bulb, the removable part
being held in position by a threaded sleeve connecting the two parts in combination
with the glass bulb, electrical conductors and filament, substantially as and for the
purposes described.
.
VII In an incandescent lamp for electric lighting a removable cap H, a
collar B fastened to the glass bulb and a connecting sleeve I in combination with
the glass bulb, electrical conductors and the filament, substantially as and for the
purposes described.
VIII In an incandescent lamp for electric lighting a cap composed of two
parts, one of which parts is permanently fastened to the glass bulb, said two parts
being connected by one or more screws in combination with the glass bulb,
electrical conductors and the filament, substantially as and for the purposes
described.
IX: In an incandescent lamp for electric lighting a glass bulb having thereon
screw threads d of the same material, a removable cap H having screw threads a

page_text: upon its lower exterior surface, and a threaded sleeve I connecting the cap with the
glass bulb, in combination with the electrical conductors and filament, substantially
as and for the purposes described.
Dated this 16th day of November 1892.
FREDERICK HERBERT PRENTISS.
Haseltine, Lake & Co.,
45, Southampton Buildings, London, Agents for the Applicant.