Improvements in the Preparation of Selenium for, and the Manufacture of, Selenium Cells for Electrical Purposes, and Apparatus therefor.
Year: 1884

page_text: Improvements in the Preparation of Selenium for, and the
Manufacture of, Selenium Cells for Electrical Purposes, and
Apparatus therefor.
I WILLIAM ROBERT LAKE of the firm of Haseltine Lake & Co Patent Agents
Southampton Buildings London do hereby declare the nature of said invention for
"IMPROVEMENTS IN THE PREPARATION OF SELENIUM FOR, AND THE MANUFACTURE
OF, SELENIUM CELLS FOR ELECTRICAL PURPOSES, AND APPARATUS THEREFOR
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 the preparation of selenium for, and the manufacture of,
selenium cells."
The said invention primarily consists of a new method of utilizing substances
sensitive to radiant energy, and in the construction and methods of application of
apparatus whose active elements possess such properties as selenium.
In carrying out my invention I so manufacture and form the selenium that
substantially the whole of its mass responds to, or is affected by, the motion of
light rays to change its electrical resistance and to cause it to exhibit its other
characteristic properties in such an intensified manner over what has been
heretofore done as to virtually admit certain properties of selenium as exhibited
under the new condition to be classified as new phenomena. In accomplishing
this and demonstrating the peculiar physical properties of this substance I place in
contact therewith a material which is both pervious to the radiant energy and
offers a free passage for electric currents, the said material being arranged on one
or both sides of selenium formed in thin sheets so that the radiant energy, as light,
acts on the surfaces or through the entire mass of the selenium in the same plane
as, or general direction of, the electric current produced, controlled, or affected, by
the action of the radiant energy on the selenium.
This exaltation of the characteristic properties of selenium due to the new
method of manipulating and utilizing it, opens innumerable fields for the
application to useful purposes of devices or cells made according to my invention,
which could not be suggested by the properties of selenium as made manifest by
selenium cells of ordinary make, such being entirely inadequate for practical

page_text: application. A few of these applications will be hereinafter -mentioned and
described, after a description of the form of, and method of, making my improved
selenium cells is given.
To produce good effects it is desirable that the selenium should be as pure as
possible. I form the same into thin sheets of any desired form, and anneal them
by a new process the old known processes for annealing to convert the vitreous or
non-conducting form of selenium being less adapted to my purpose.
The process consists in enclosing the selenium between blocks or plates, of the
desired form having smooth polished surfaces, of a material to which the selenium
will not adhere; applying heat till it softens; pressing the plates together to bring
the selenium into the required shape; continuing the heat until the second melting
point is reached; again applying pressure to reduce the selenium to the required
thickness; and then allowing the whole to cool slowly.
If the first application of pressure brings the selenium to the desired thickness,
then the second pressing may be omitted, and the heat regulated so that the
selenium barely reaches the second melting point, it being allowed to cool slowly
as before while under pressure. Thus the melting, forming, annealing, and cooling
of the selenium are performed at one continuous operation.
When thin sheets of selenium are to be thus formed and removed from the
pressing plates, cracks will sometimes occur during such removal, which would.
allow the electric current to break at such places and so destroy their value for
use in a cell. To prevent this I sometimes place thin sheets of mica or other
suitable smooth material on each side of the selenium, between the plates, the
said sheets being readily removed when the selenium is cold. Or thin sheets of
metal may be used which can be readily removed by a solvent therefor which will
not affect the selenium.. I sometimes press and form the selenium for use on a
permanent metal backplate.
The thickness of the selenium plates can be varied to suit the particular mode
of its application, but when it is desired that it should be very sensitive to light,
then it should be made thin enough to have a blood-red color in transmitting light,
before being annealed.
The invention is illustrated in the accompanying drawing the views of which
are hereinafter described.
.
Apparatus for melting, forming annealing and cooling the selenium at one
continuous operation is shown in Figure 9, which apparatus consists of a muffle or
heating chamber a having a door a¹ and a rigid shelf or platform b provided with
guides between which is fitted the slide b¹; a hand screw c, or other pressure-
applying device passing down through the centre of the roof; and a bridge or
brace-piece c¹, whicir extends down the sides of the chamber and under the shelf b.
d indicates a gas-burner or other source of heat, d' a thermometer, and d² scrap
iron or other suitable material placed in the lower part of the chamber to equalize
and retain the heat. The pressing plates 6 and 63, with the selenium between
them, are placed on the slide b', and adjusted thereon by means of pins, so as to
come centrally under the screw c. The said slide itself, when pushed in the
chamber between the guides on the shelf b, always assumes the same position
under the screw, so that an even pressure is applied to the selenium as it melts.
To ensure the plates coming together parallel, a frame or pieces of sheet metal of
the thickness it is desired to make the selenium film may be placed between
them. The plate 6', may also represent the back plate of a cell to which the
selenium is permanently attached during its formation thereon.
Thin plates of selenium made and annealed in apparatus as before described may
be applied to cells in various ways, and of any desired form. In Figure 1, which
shows a selenium cell in section, the selenium plate Se is held in the centre of a
frame e of vulcanite or other suitable material, with metal frames f, f¹, on either
side of it, but separated therefrom by strips of insulating material.
The whole is enclosed by the glass covers g, g which, by suitable cement or
otherwise, are made watertight at their connections to the frame e. The two

page_text: frames f, f¹, are connected to the wires f³, and f³, respectively which wires
convey the electric current to or from the cell. Both sides of the cell are
provided with a suitable conducting fluid, through the pipes e¹, e', which pipes
also permit the escape of gases. produced by the decomposition of the liquid.
Figure 2 represents a similar cell, in section, provided with wires or strips of
metal f*, f* stretched across the metal frames ƒ ƒ¹, to more evenly distribute the
electric current from these frames through the liquid to the surfaces of the
selenium Se. This cell is also shown provided with shutters e, e³, adapted to be -
moved over the faces of the cell to regulate and govern the amount of light
allowed to impinge on one or both of the surfaces of the selenium to regula'e and
control the resistance of the same as desired. These shutters may also be applied
to any form of cell and be held and moved by any mechanical means adapted to
such purpose. The cell shown in Figure 3, is also a fluid one, but adapted to
receive the light on one side only of the selenium, which is attached to the plate
of metal h. Similar letters of reference indicate similar parts in all these views.
These thin plates of annealed selenium can be used in what may be termed dry
cells, by conting them on one or both sides with a metal adapted to be made
sufficiently attenuated to permit light rays to pass through it to the selenium.
Platinum; silver, or gold-is suitable for this purpose, to be applied to both sides
of thin sheets of selenium, or to the surface of the selenium when it is formed on,
or attached to, a metallic plate as before described; but I generally use gold leaf,
which I apply by first flooding it with alcohol, then placing the selenium film on
it, turning the whole over, and blowing or forcing air on the gold leaf, thereby
pressing it into close contact with the selenium over the whole of its surface.
The gold, after having the proper electrical connection made to it, is then covered
with a piece of glass or suitable transparent varnish to protect it from injury.
Figure 4 indicates a dry cell in which the selenium Se, is coated on both sides
with a transparent metallic conductor i, arranged to have the light rays act on
both sides of the selenium. The metal frames f, f¹, are shown provided with
strips of metal in contact with the surface of the transparent metallic conductors i,
to equally distribute the electric current to said conductors i.
The cell shown at Figure 5 is a form from which high results have been
obtained in practice. The selenium Se is melted, pressed and annealed on the
metal back plate h¹ as before described, over which is subsequently placed the film
of gold i, to which one end j of the circuit is attached; the other end j' being
secured to the metal plate h¹.
The current in this case passes from the whole surface of the plate h¹, to the
gold covering i, through the whole mass of the selenium, which, if made very thin,
allows the light to pass through so as to act on the back plate h¹, thus bringing
under the action of the radiant energy the whole mass of the selenium. The
gold may be covered with glass or suitable transparent varnish; and what is here
said about this cell applies also to the forms shown at figures 6, 7 and 8.
Figure 6, represents a cell, as at figure 5, provided with a shutter k, adapted to
be moved over and adjusted to cut out as much of the active element of the cell
as desired from the action of the light, by means of the screw ³, which is held in
bearings on the shutter k and works in a fixed nut on the back plate h¹.
Figure 7 shows a dry cell having the active element cut into equal parts i and i¹,
either by separating the metallic conductor and selenium or the conductor only,
connected respectively to the branch circuit l, and l. The current entering by
line j, is seen to be divided into two equal parts, so that the branches 1, 1 are
equally affected by the action of the light on the two cells, by reason of the two
cells being made at one and the same operation.
Any number of cells having exactly the same characteristics may be made in
this manner, four such cells being shown in figure 8. The back plate in this case
is divided, and secured to a plate of non-conducting material h, and the selenium
on the parts h³, h³, divided into cells i, is, and i, respectively The value of
such divided cells for various purposes will be readily seen by those skilled in

page_text: the science of electricity, and I only mention their application to controlling
currents used to actuate instruments connected up on the Wheatstone bridge
principle, or in other analogous manners.
A few other applications to practical purposes are shown in the remaining
views of the drawings. Figure 10 shows a condenser m placed in a circuit
derived from the cell Se, in circuit with battery n. The cell Se in this case is
supposed to be one of the kind represented in Figures 1, 2, 3 and 4, the object of
the condenser being to prevent or lessen the polarization of the cell whenever the
current passing through it ceases Figure 11 shows the cell Se, arranged for
sending the currents from two independent batteries n n¹ through it at the same
time, so that variation of the light falling on the cell may vary both currents
equally, thus simultaneously controlling and modifying in exactly the same manner
the action of any number of electrical instruments as o, o, o¹, o¹, which may be of
any kind requiring identical variations in the currents actuating them. The cell
shown in Figure 12 is one which offers little resistance to a current passing through
it in one direction, and a great resistance to currents in the opposite direction it
being adapted for use with a to and fro current where it is desired to obliterate or
destroy the positive or negative current.
Figure 13 shows two such cells in multiple circuit with instruments p'p¹, which
require direct currents to operate them the source of electricity producing a to and
fro current; the cells being arranged so that the one in circuit with p, allows the
negative current only to pass in one direction, and the one in circuit with p', allows
the positive current only to pass in the same direction; viz:-from cells to earth,
as shown by the signs and +.
-
Figure 14 shows a selenium cell Se, arranged in a circuit containing a magnet q,
or other apparatus in which induced currents are troublesome. The cell is so
placed as to favor the passage of the positive current; for example. Then any
positive induced currents could pass freely through the cell and circuit with the
primary or inducing current, while the negative induced currents would be quenched
or prevented from appearing; and vice versa. In case the primary current is an
alternating one, the two induced currents may be separated and each one sent
through the same branch as the primary current of the same name, by two cells
arranged as in Figure 13.
Figure 15, shows the cell Se, arranged in a circuit containing an apparatus adapte 1
to vary the strength of the current passing through the circuit as by a telephone
transmitter t. In this case a cell may be used which offers about the saine resistance
to currents of both polarities, or not, as preferred. But as the resistance of the
cell increases when the battery power becomes less, the effect of the cell will be to
exaggerate the variations in the strength of the current, by still further opposing
the weak currents, and favoring the passage of the strong ones, in proportion to
their varying strength.
Figure 16 shows a method of regulating a current and maintaining its strength
uniform. The circuit is divided into two branches, one containing the selenium
cell Se (or a number in series, if necessary, to increase the resistance, or for any
other purpose) while in the other is the electrical instrument 8. A variable
resistance r, may be used, if necessary, for adjusting the relative resistances of the
two branches. When the main current weakens in the circuit, the tendency is. to
lessen the current proportionately in these two tracks, but as the cell offers greater
resistance to the weakened current, a portion of it is forced through the other
branch, thus making up for the loss which would otherwise be sustained by the
lectrical instrument S, and keeping its current uniform. When the main current
becomes stronger the cell allows more than its share of it to pass, thus again
keeping the current through the instruments uniform. With to and fro currents
this result may be had to two instruments by following the arrangement shown in
Figure 13.
The platinum, silver or gold may be formed on the selenium to produce cells, as
shown in Figures 5 to 8, by means of electrical or chemical deposition Aud where

page_text: I use the auxiliary conducting strips in contact with the transparent metal
conductore, I propose, in some cases, to ensure perfect contact between them, to
electro-deposit a little of the metal at the points of contact, covering with a
suitable varnish the parts of the metal surface where it is desired not to deposit
any metal.
In the formation of cells as before described imperfect places will sometimes
occur in selinium. In such cases I cover the said imperfections with a film or patch
of a non-conducting cement or varnish before applying the gold thereto, or, after
the gold has been applied thereto, I cut away the gold from the imperfect parts, so
that the current is not allowed to pass through or near said imperfections.
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
First. The method of utilizing substances sensitive to light or radiant energy,
by means of a material in contact therewith capable of allowing the radiant energy
to pass through it to the sensitive substance and at the same time being a conductor
for an electric current produced controlled or affected by such radiant energy.
Second. The method of utilizing substances which under the action of light
produce or affect an electric current passing through them, by causing the light to
act on such substances in the same plane as or general direction of the electric
current.
Third. The method of increasing the action of light upon a substance electrically
sensitive thereto, by forming the said substance into thin sheets or films, and
causing the light to act on one or both of the sides of said sheet or film, through
electrical conductor or conductors.
Fourth. The method of increasing the action of light on a substance electrically
sensitive thereto, by forming such substance into films sufficiently thin that the
light acting on one or both sides thereof affects the whole mass.
Fifth. The method of varying the electrical resistance of a device embracing a
substance sensitive to light by allowing light rays of different intensities to act
thereon on one or both sides thereof.
Sixth. The method of balancing or adjusting resistances of different electrical
circuits, which consists in including in two or more of such circuits different parts
of a device whose active member is a substance electrically sensitive to radiant
energy.
Seventh. A selenium cell composed of a thin sheet of selenium covered by
a transparent conductor or conductors substantially as, and for the purpose, set
forth.
Eighth. A selenium cell composed of a thin sheet of selenium covered by a
metallic transparent conductor.
Ninth. A selenium cell composed of a sheet of selenium covered by a transparent
conductor or conductors, and conducting wires to equally distribute the current to,
or convey it away from, the transparent conductor or conductors.
Tenth. A selenium cell composed of a sheet of selenium covered by a metallic
transparent conductor or conductors, in combination with supplemental wires or
conductors secured in contact with the transparent conductor or conductors by
means of electrical or chemical. deposition of a metal at their points of contact
substantially as set forth.
Eleventh. The method of utilizing imperfect plates of selenium or other similar
substances by cementing over the imperfect places a non-conducting film or patch,
or removing therefrom the transparent conductor, to prevent access of the electric
current to such places.
Twelfth. The method of making selenium cells by melting, pressing, annealing
and cooling the selenium at one continuous operation.
Thirteenth. The application of thin films of platinum, silver or gold as solid
transparent conductors of electricity for selenium cells.

page_text: Fourteenth. The method of making two or more selenium cells having the same
characteristics, which method consists in forming a sheet of selenium by melting,
pressing, annealing and cooling it, and then dividing it into the desired number
of separate cells.
Fifteenth. The method of making selinium cells having the same characteristics,
and one electrode of a circuit common to all, which method consists in pressing
and annealing the selenium on a metal plate, dividing the said selenium into the
desired number of parts, and coating them with a transparent conductor,
either before or after making the division, substantially as, and for the purpose,
set forth.
Sixteenth. Apparatus for making thin plates of selenium and selenium cells,
comprising means for applying heat, means for controlling the temperature and
means for applying pressure to the selenium when melted, and mainting pressure
upon it while annealing and cooling.
Seventeenth. Thin plates of annealed selenium having smooth polished surfaces.
Eighteenth, A selenium cell adapted to receive the radient energy in the same
plane as or general direction of the current flowing through the selenium.
Nineteenth. A selenium cell adapted to receive the action of radient energy on
both surfaces of the selenium.