IMPROVEMENTS IN THE ART OF RECOVERING TIN FROM SCRAP TIN PLATE AND IN APPARATUS THEREFOR."
Year: 1877

page_text: LETTERS PATENT to Wells David Walbridge, of Jermyn Street, in the County
of Middlesex, for the Invention of IMPROVEMENTS IN THE ART OF RECOVERING
TIN FROM SCRAP TIN PLATE AND IN APPARATUS THEREFOR." A communication
from abroad by Nathaniel Shepard Keith, of Brooklyn, State of New York,
United States of America.
Sealed the 29th September 1877, and dated the 6th April 1877.
PROVISIONAL SPECIFICATION left by the said Wells David Walbridge at
the Office of the Commissioners of Patents on the 6th April 1877.
WELLS DAVID WALBRIDGE, of Jermyn Street, in the County of Middlesex.
"IMPROVEMENTS IN THE ART OF RECOVERING TIN FROM SCRAP TIN PLATE AND IN
APPARATUS THEREFOR." A communication from abroad by Nathaniel Shepard
""
Keith, of Brooklyn, State of New York, United States of America.
The improvements in the said art consist of certain processes in which the
agency of electricity is made use of, and which are based upon the following
discoveries, viz. :—
First. That if scraps of tin plate are separated and extended the tin can be
removed from all parts of each scrap simultaneously, and consequently the separation
and the recovery of the tin and iron can be effected with great rapidity.
Second. That the scraps may be moved progressively through a liquid electro-
lyzing bath while under the action of the electricity and the solution constituting
the bath, and consequently that the tin scraps can be entered into and removed from
the electrolyzing bath in continuous progression as distinguished from charging a
multitude of scraps simultaneously into the bath, leaving all of them therein
during the same period, and then removing them therefrom simultaneously.
Third. That if the scrap tin plate in the bath be subjected simultaneously to the
action of electricity and heat exceeding 160° Fahrenheit or thereabout, while in the
electrolyzing bath the tin may be dissolved and removed without material solution
or oxidation of the iron which forms the body of the scraps.
The improvements in the apparatus for practicing the said processes consist of
certain combinations of the following devices, viz:-A vat for holding the electro-

page_text: lyzing bath; an endless chain conveyer or some substitute or equivalent therefor
for holding and moving the scrap tin plate through the said vat; a central electrical
cathode; means for heating the liquid in the vat; and a galvanic battery or some
equivalent or substitute therefor for the purpose of furnishing an electric current.
.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Wells David Walbridge in the Great Seal Patent Office on the
5th October 1877.
WELLS DAVID WALBRIDGE, of Jermyn Street, in the County of Middlesex.
"IMPROVEMENTS IN THE ART OF RECOVERING TIN FROM SCRAP TIN PLATE AND IN
APPARATUS THEREFOR." A communication from abroad by Nathaniel Shepard
Keith, of Brooklyn, State of New York, United States of America.
The improvements in the said art consist of certain processes in which the
agency of electricity is made use of, and which are based upon the following
discoveries, videlicet :-
First. That if the scraps of tin plate are separated and extended the tin can be
removed from all parts of each scrap simultaneously, and consequently the separation
and recovery of the tin and iron can be effected with great rapidity.
Second. That the scraps may be moved progressively through a liquid electro-
lyzing bath while under the action of the electricity and the solution constituting
the bath, and consequently that the tin scraps can be entered into and removed from
the electrolyzing bath in continuous progression as distinguished from charging a
multitude of scraps simultaneously into the bath, leaving all of them therein during
the same period, and then removing them therefrom simultaneously.
Third. That if the scrap tin plate in the bath be subjected simultaneously to the
action of electricity and heat exceeding 160° Fahrenheit or thereabout, while in
the electrolyzing bath the tin may be dissolved and removed without material
solution or oxidation of the iron which forms the body of the scraps.
The improvements in the apparatus for practicing the said processes consist of
certain combinations of the following devices, videlicet:-A vat for holding the electro-
lyzing bath; an endless chain conveyer or some substitute or equivalent therefor
for holding and moving the scrap tin plate through the said vat, and for small scrap
a cage or basket which may or may not be made to revolve; a central electrical
cathode; means for heating the liquid in the vat; and a galvanic battery or some
equivalent or substitute therefor for the purpose of furnishing au electric current.
In practicing the Invention the scrap tin plate is immersed in an electrolyzing
bath contained in a suitable vat, and is connected with a galvanic battery or other
means of furnishing a current of electricity in such manner that the said scrap
constitutes the anodo for the current, while the vat itself or some suitable conductor
contained in it constitutes the cathode for the current.
Various liquids may be used for the electrolyzing bath, in fact, any liquid may
be used that will dissolve the tin when excited by electricity; I prefer, however,
solutions which contain a quantity of free alkali, such as caustic potash or caustic
soda.
Any galvanic battery may be used to generate or furnish the electricity or any
of the magneto-electric machines, the requisite in this particular being a quantity
current of sufficient amount. A current of intensity may be used; but I do not
recommend the use of such a current.
The vat or tank containing the liquid may be of iron or of any other metal or
substance which will not be affected by its contents, but it is preferable that the
vat should be of a material which will conduct electricity.
Scrap tin plates as usually found in the market, are curled or bent, and are
tangled together in masses, so that some parts of each scrap are overlapped by

page_text: •
adjacent scraps, or frequently by other parts of itself. On the other hand the
currents of electricity pass directly or thereabout from the surfaces of the anodo in
the electrolyzing bath to those of the cathode. Hence, if the scraps of tin plate
remain in the mass while they are subjected in the bath to the action of electricity,
the tin will be removed most rapidly from those parts of the scraps which aro
opposite the surfaces of the cathode, while the overlapped surfaces of the mass will
be but slightly, if at all, affected. Therefore, according to my Invention, the scraps
arc first separated and extended to such extent that their surfaces are not over-
lapped to any material extent, and they are subjected in this separated and
extended condition to the electric action. For the latter purpose the scraps,
according to one part of my Invention, are placed upon the cross bars of an endless
chain of rods or other moving frame connected electrically with the positive polo of
the source of electricity, and this chain or frame is moved progressively into,
through, and out of the vat, so that the scraps may be entered progressively into
the bath and removed progressively therefrom, and that the operation may go on
continuously.
According to another part of my Invention the bath in which the scraps are
immersed while under the action of electricity, is heated, by preference, to the
boiling point of the liquid or thereabout, either by applying heat to the bottom or
walls of the vat by means of a furnace and flues suitably arranged, or by means of
a coil of steam pipe immersed in the vat.
The several improvements which constitute my Invention are set forth in detail
at the close of this Specification; but in order that the same may be fully under-
stood, I will proceed to describe the form of apparatus, and the mode of troating
the scrap tin plate which I have used with success in practicing my Invention.
Figure 1 of the accompanying Drawings represents a plan of the apparatus used
by me; Figure 2 represents a central vertical transverse section of the same;
Figure 3 represents a partial side view of the same with the side of the vat removed.
The vat or tank A of the said apparatus is made, by preference, of boiler iron.
It is open at its top, and is fitted at the bottom with a faucet F, by means of which
its contents can be drawn off. This tank is traversed by the endless chain of rods B
which consists of two parallel endless wire ropes or chains connected by rods C, C.
The endless chain of rods is supported by and suspended from a pair of pulley
wheels D, D, that are secured to a shaft E which is constructed to turn in suitable
bearings H above the tank. The rims of the pulleys are grooved or otherwiso
formed so as to retain the ropes or chains in their places and cause them to move
with the pulleys, so that the turning of the pulley shaft by means of a crank g or
by power applied to a belt pulley G causes the chain of rods to move progressively
through the tank, its rods descending successively into the tank at one side thereof,
and being successively raised from the tank at the opposite side.
The speed of movement of the chain of rods determines the duration of the period
of immersion of the articles in the electrolyzing bath contained in the vat or tank;
consequently, if the chain be driven by power, its speed should be regulated by
some one of the well-known mechanical governors or regulators of speed, and the
power should be transmitted to the shaft through the intervention of a belt and
reversed cone pulleys or other means that will enable the speed to be varied, as
found expedient to lengthen or shorten the period of immersion of the articles,
according to the rapidity with which the operation of removing the tin proceeds,
the general rule being that the period of immersion should be only long enough to
permit the tin to be removed from the iron basis of the scraps. The length of
time required for this purpose depends upon the character of the solvent or solution,
the amount of scraps or other articles under treatment, the thickness of the coating
to be removed, and the density of the current of electricity in use.
The complete solution and removal of the tin from scrap tin may be effected in a
few minutes. A conductor h from the positive pole of the battery should be con-
nected electrically with the shaft E or with one of the wheels D, D, and a
conductor ¹ from the negative pole of the battery should be fastened at some con-

page_text: venient point on the vessel or tank A.
The shaft E, wheels D, D, ropes or
chains a, a, and rods C, C, should be insulated from or not in electrical connection
with the vat or tank A, so that the current of electricity may pass through the
solvent or solution. Thus the vat or tank becomes the cathode, and the wire ropes
or chains, rods, and pieces of scraps or other articles to be operated on the anode
for the current of electricity. The vat or tank is filled nearly to its brim with the
electrolyzing solution constituting the bath.
The solutions which I have used with success are the following, videlicet:-Caustic
soda, three pounds, and nitrate of soda, one pound, to overy gallon of water contained
in the vat; or caustic potash, three pounds, and nitrate of potash, one pound, to
every gallon of water; or caustic soda, one-fifth pound, and chloride of sodium
(common salt), two pounds, to every gallon of water. The proportions and con-
stituents of the solution may, however, bo varied as circumstances or the views of
different users may render oxpedient. The rods C may be plain iron or copper
rods, or may be fitted with projections, hooks, or other appliances upon which the
scraps may be hung, the only requisite being that when the scraps are on the rods
the scraps are in electrical connection with the battery or its substitute.
Heat is applied to the contents of the vat, either by building it in brickwork,
forming flues like those of a steam boiler, and communicating with a furnace, or by
immersing in the tank a coil of iron steam pipes, supplied with steam from a steam
boiler. The chain of rods being put in motion, the tin plate scraps are separated
from the mass of scraps by being picked up one at a time by children, are pulled
lengthwise, so as to extend them partially or wholly, and aro hung upon the rods
of the chain above the vat at the descending side of the chain, one end of each
scrap being bent into a hook form for the purpose. The scraps thus separated
and extended are by the movement of the chain carried progressively down into the
bath, and upward at its opposite side, and when they are raised above the vat they
are removed by children.
During the immersion of the scraps in the bath they are treated by the conjoined
agencies of the solution forming the bath, electricity and heat. The tin is dissolved
from the scraps and separates at the cathode, and it is deposited in the vat in the
condition of crystals of metallic tin. The materials thus deposited may be with-
drawn from the vat through the faucet F without removing the cathode, or may be
scooped out, and the tin matter thus recovered from the scrap tin plates is washed,
and either reduced to the form of block tin by the usual metallurgic processes, or is
otherwise utilized. The iron of the scraps being cleansed of the tin, is rendered
useful for the purposes for which scrap iron is used. The process being a continuous
one, though but a comparatively small amount of scrap is under treatment at once,
a large quantity can be disposed of in a given time, and much valuable metal,
which is now worthless, can be utilized at a comparatively trifling cost.
The solution constituting the bath remains practically permanent, it being
necessary only to replace such water as may be dissipated by evaporation, and
to add from time to time enough of the other constituent to replace the small
quantity unavoidably removed with the iron scraps, and not saved by washing
them.
For the purpose of increasing the surface of the cathode, and bringing it into a
position to work more satisfactorily in connection with the anode, a division plate K
of sheet iron or other suitable material is arranged in the vat or tank between the
entering and receding portions of the chain of rods, so as to present an antagonistic
surface to both the ascending and descending portions of the chain of rods when
in motion. I find it expedient so to proportion the breadth of the vat that the
chain of rods is about one foot distant from the surface of the cathode at each side
of them.
In place of constructing the vat or tank, of iron, it may be constructed of some
non-conductor of electricity, and may have sheets or plates of iron, copper, or brass
suspended in it at both sides of the chain of rods, and connected electrically with the
negative pole of the battery, so as to form the cathode.

page_text: In place of having the rods permanently secured to the chains or wire ropes, it is
convenient to have them hung upon hooks or other appliances attached to the chains
or ropes. In such case the rods may be charged with scraps when separated from
the chains or ropes, and then applied to them. The rods also may be removed from
the chains, so as to facilitate the stripping of the scraps from the rods.
The chains or rods may be moved continuously, or at short intervals as found
most convenient, and if some parts of my Invention are used without others, the
scraps may be applied in a separated condition to a rack or frame of rods, which is
lowered into the vat, left there long enough to permit the tin to be separated, and
then withdrawn from the vat.
I do not limit my Invention to the employment of a certain kind of solvent or
solution, but prefer those which, under the conditions employed, have no dissolving
or injurious effect upon the iron of the scrap.
I do not limit my Invention to the described apparatus, as various devices may
be used, continuous and intermittent, horizontal and perpendicular, with wire ropes,
chains, or frames, operated by hand or acting automatically, but I prefer the
apparatus represented in the Drawing and above described.
I am aware that tin has been dissolved by various solvents excited by
electricity in galvano-plastic operations, and for the purpose of plating with that
metal.
I am also aware that scrap tin plates have been treated by various acid solvents,
and also by solutions of caustic alkalies.
I am also aware that it has been proposed to treat scrap tin plate in mass in a bath
by electricity. Therefore I do not claim, broadly, the treatment of scraps of tin
plate by solvents, nor the treatment of them by solutions of caustic alkalies, nor
the treatment of them in every condition by electricity while in an electrolyzing
bath.
I am also aware that in galvano-plastic operations copper and gold solutions are
heated, but in this case the metal is plated upon the cathode instead of dropping free
thereof in the vat. Therefore I do not claim the heating of solutions from which
metals are to be separated by electricity.
I claim as my Invention,―
1. The improvement in the art of recovering tin from scrap tin plate, consisting
in the treatment of the same, substantially as before set forth, in a separated
and extended condition in an electrolyzing bath by the agency of electricity.
2. The improvement in the art of recovering tin from scrap tin plate, consisting
of the treatment of the same, substantially as before set forth, in a separated con-
dition, and progressively in an electrolyzing bath by the agency of electricity.
3. The improvement in the art of recovering tin from scrap tin plate, consisting
of the treatment of the same, substantially as before set forth, in a separated con-
dition by the joint agencies of electricity and heat.
4. The combination, substantially as before set forth, of the vat, the endless chain
of rods or baskets, and the electric battery.
5. The combination, substantially as before set forth, of the vat, the endless chain
of rods or baskets, the supplementary cathode arranged within said chain of rods and
the electric battery.
6. The combination, substantially as before set forth, of the vat, the means of
heating the contents thereof, the endless chain of rods with or without baskets and
the electric battery.
In witness whereof, I, the said Wells David Walbridge, have hereunto
set my hand and seal, this Fourth day of October, in the year of our Lord
One thousand eight hundred and seventy-seven.
WELLS D. WALBRIDGE, (L.S.)