Improvements in Rheostats or Electric Heaters.
Year: 1898

page_text: Date of Application, 11th Oct., 1898-Accepted, 5th Aug., 1899
i
COMPLETE SPECIFICATION.
Improvements in Rheostats or Electric Heaters.
I, EDWIN OTTO RASTER, of 1029, North Clark Street, in the City of Chicago,
County of Cook, and State of Illinois, United States of America, Manufacturer,
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 a novel construction in a rheostat or electric heater,
the object being to provide a device of this kind in which a plurality of high
resistance mediums are employed so that the device will occupy small space,
and further so connecting said resistances as to overcome all variations in resist-
ance, besides so constructing the device that the parts thereof can be readily
and easily assembled and taken apart for repairs, and consists in the features
of construction and combinations of parts, hereinafter fully described and
claimed.
In the accompanying drawings, illustrating my invention:
Fig. 1 is a view in elevation of a rheostat face plate of the kind known as
automatic release, though it should be understood that I do not claim this as a
part of my invention.
Fig. 2 is a view in front elevation of my rheostat without the face plate.
Fig. 3 is a top plan view of same.
Fig. 4 is a detail sectional view on an enlarged scale, on the line 4-4 of
Fig. 2.
Fig. 5 is a fragmentary end elevation of the frame in which the resistance
sticks are mounted.
One feature of my invention consists in providing a plurality of parallel
carbon or graphite sticks of high resistance divided by air spaces and connecting
each two adjacent sticks electrically together at one end, and insulating them
from each other at their other ends, so as to cause the current to pass through
the combined lengths of all of said carbons.
Another feature of my invention consists in providing posts at intervals so
that all or only a part of the total number of carbons can be thrown into the
circuit, each of said binding posts being adapted also to serve as an electrical
connection between two adjacent carbons.
Another feature of my invention consists in providing non-oxydizable elec-
trical connections between said carbons, whereby variation in resistance is
avoided.
My invention consists primarily in providing a metallic frame A comprising
end plates 1 connected together by means of cross pieces 2. Said plates 1 are
enlarged or flanged adjacent the points of connection with said cross pieces 2,
as indicated at 3, and through said flanges 3, set-screws or clamping screws 4
pass which are adapted to bear against iron plates 4" which in turn bear against
and clamp a set of parallel carbon or graphite resistance sticks 5 in said frame.
Said iron plates 4ª each bears directly against a piece of insulating material 6
consisting of mica or a similar hard substance, which in turn bears against one
of said resistance sticks. This again bears at one end against an electrical con-
necting piece 7 consisting of a small piece of carbon or of aluminum or similar

page_text: non-oxydizable conductor interposed between said resistance stick and the next
adjacent resistance stick, while at its other end, said first carbon bears against
a piece of glass or other insulating material 8 interposed between said end
resistance sticks. Between the second and third resistance sticks 5ca piece of
conducting material 7 and a piece of insulating material 8 are likewise inter-
posed but their positions reversed so that the second conducting piece 7 is in
line with the first insulating piece 8, and the second insulating piece 8 is in line
with the first conducting piece 7. In this manner said insulating and con-
ducting pieces are alternated so as to cause the electric current to traverse the
entire length of one carbon before being conducted to the second, and traverse
the entire length of the second before, being conducted to the third, and so on.
At certain intervals in each set of said resistance sticks, said conducting pieces
are extended, outwardly to form binding. posts 9 by means of which a part of
said resistance can be thrown into an electric current without throwing in the
entire number....
1
01.04.
Said frame A is.preferably made of-metal and-said' set of resistance 'sticks 5
clamped between said flanges 3 lie parallel with said cross pieces 2: To insulate
said resistance. sticks from said cross pieces.2, I interpose a layer 10 of insu-
lating material consisting of mica and asbestos or like substances. As" said
sets of resistance sticks are clamped together with great pressure which would
tend to cause them to spring outwardly, I have provided retaining strips 11
which are secured at their ends to said flanges 3 and between which and said.
resistance sticks I interpose a layer 12 of insulating material.
At the middle portions of said cross pieces 2 I provide flanges 13 against
which said sets of resistance sticks 5 are clamped, insulating material being
interposed between said flanges 13 and the adjacent resistance sticks..
To electrically connect said "sets of resistances on opposite sides of said.
flanges 13, I provide bridges 14 of aluminium which rest against resistance
sticks next adjacent to said flanges 13, the ends of said bridges being inserted
between said resistance sticks and the insulating material between the latter.
and the resistance sticks next behind the same."
To hold said set screws 4 against becoming loose, I tap said flanges. 3. trans-
versely to the openings in which said set screws move and insert. set screws 15
therein which bear against and lock said set screws 4 in an obvious manner.
As stated in the description of Fig. 1, I do not claim the device there shown
as part of my invention, but in view of the demand for automatic release for
switch levers, I have adopted this device, of which I will insert a short
. description.
The switch board or face plate there shown and with which my rheostat is
connected, is provided with a lever 16, controlled by a spring at its pivot which
holds it normally on the first button of the switch as shown. An electro-
magnet 17 is mounted on said face plate above said first button and is always
in the circuit, so that when the dynamo is started said electro-magnet is excited
and attracts the lever 18 pivoted on said face plate at 19. A small lever 20, is
also pivoted at 19 and this projects into the path of the lever 16, as said lever 18
is attracted by said magnet.
By advancing the lever 16 from the first button to the second, all the resistance
is inserted-in the circuit:
By further advancing the lever 16 the resistance is gradually thrown out of
the circuit, until the entire rheostat is out of the circuit, thus starting the motor
gradually. When this is accomplished the lever 16 rests upon the last button,.
having passed lever 20 which thereupon returns into the path of the lever 16
and prevents the latter from returning.
When the dynamo is stopped the electro-magnet is obviously demagnetized
and consequently the lever 18 drops and thereby throws the lever 20 out of the
path of the lever 16, thus permitting the latter to return to the first button,
and throwing the motor out of the circuit.

page_text: This device prevents the motor from being started under a full current, as
might otherwise occur.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:
1. A rheostat or heater comprising a frame adapted to receive a plurality of
resistance sticks alternately electrically connected with each other and insulated
from each other, and means for clamping said resistances in said frame and in
close contact with the connecting and insulating pieces, substantially as
described.
2. A rheostat or heater comprising a frame adapted to receive a plurality of
sets of resistances, each of which comprises a plurality of resistance sticks
alternated with contact and insulating pieces, and means for clamping said sets
of resistances in said frame comprising devices mounted in one member and
adapted to bear against said sets of resistances and clamp same against another
member of said frame, substantially as described.
3. A rheostat or electric heater comprising a frame adapted to receive a
plurality of practically parallel resistances divided from each other by means
of contact and insulating pieces, and means for securing said resistances in said
frame and holding same in close contact with said contact pieces, consisting
of a set-screw in one member of said frame adapted to bear upon one member
of said set of resistances to clamp said set against each other and another
member of said frame, substantially as described.
4. A rheostat or heater comprising a plurality of resistance sticks laid practi-
cally parallel with each other, each of said resistances being electrically con-
nected at one end with the adjacent resistance and at its other end insulated
therefrom by means of conducting and non-conducting pieces respectively
interposed between said adjacent resistances at opposite ends, and clamping
devices for holding said resistances and said pieces interposed between the
same in close contact with each other, substantially as described.
5. A rheostat or heater comprising a plurality of resistance sticks laid practi-
cally parallel with each other, each of said resistances being electrically con-
nected at one end with the adjacent resistance and at its other end insulated
therefrom by means of conducting and non-conducting pieces respectively
interposed between said adjacent resistances at opposite ends, means for con-
necting said resistances with a face plate or switch board comprising projections
on said conducting pieces interposed between said resistances to which wires
are adapted to be connected and clamping devices for holding said resistances
and said pieces interposed between the same in close contact with each other,
substantially as described.
6. A rheostat or heater comprising a plurality of resistance sticks of rectan-
gular cross section laid practically parallel with each other, each of said resist-
ances being electrically connected at one end with the adjacent resistance and
at its other end insulated therefrom by means of conducting and non-conducting
pieces respectively interposed between said resistances at opposite ends, a frame
adapted to receive said resistances, and means for clamping said resistances in
said frame and in close contact with the interposed pieces, substantially as
described.
Dated this 1st day of September 1898.
EDWIN O. RASTER.
Haseltine, Lake & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.