Improvements in Galvanising Iron, and Apparatus therefor.
Year: 1892

page_text: Date of Application, 16th Apr., 1892
Complete Specification Loft, 16th Jan 1803 Accented 4th Mar 1893
PROVISIONAL SPECIFICATION.
Improvements in Galvanising Iron, and Apparatus therefor.
I, GUSTAVE RETTERER of 31 Rue du Commerce, Paris, in the Republic of
France, Engineer, do hereby declare the nature of this iuvention to be as
follows:-
This invention relates to an improved galvanising bath and its method of
employment for galvanising iron whereby the formation of hard spelter, so prejudicial
with the processes heretofore employed is in a great measure prevented.
At present sheet iron is generally galvanised by immersing the sheets, previously
pickled and scoured by an acid bath, in a bath of melted spelter covered with
sal-ammoniac where they become covered with a superficial coating of spelter. This
operation requires two workmen to operate the sheets and a third to spread (spatuler) ·
the surface of the bath when the sheets are withdrawn.
By this process hard spelter is largely produced and an excessive evaporation
results from the frequent and considerable oxidation of the surface of the spelter
from contact with the atmosphere for, it will be understood, that for each sheet
the upper surface of the spelter has to be spread whereby it is uncovered more
than is expedieut and is put directly and for a certain length of time in contact
with the atmosphere. This method of galvanising possesses the further disadvantage
of charging the immersed sheets with spelter to too great an extent, doubtless owing
to the length of time occupied in immersing them in and removing them from the
bath.
By another method, also well known, the sheets are first dipped in a bath of
melted lead and are afterwards immediately immersed in another bath of melted
spelter. This method only possesses the advantage of better preparing the sheet to
receive the covering of spelter the process otherwise having the same defects as
exist with the single bath process.
The
According to my invention the galvanising bath at its upper part is divided by
means of a longitudinal partition into two compartments which communicate with
each other below the partition; one of these compartments which forms the
continuation of the lower part of the bath is filled, as well as such lower part, with
melted lead and the other compartment with melted spelter which floats on the lead.
which has free access through the bottom of this second compartment.
sheets to be galvanized are first immersed in the lead bath sufficiently deep to allow
of the upper longitudinal side to descend somewhat below the dividing partition and
in any suitable manner caused to pass to the other side of the thickness of the said
partition when by reason of the difference of the densities of the lead and the sheet
the latter will be automatically projected through the spelter bath until it arrives
within the reach of the the workmen who grasp it with their lifting tongs and withdraw
it perfectly galvanised. Oscillating guides are provided in the spelter bath arranged
on two bars which float on the surface of the zinc, which guides direct the automatic
upward movement of the sheet and the bars spread the insulating layer which
re-covers the surface of the spelter in the necessary manner and at the moment
required. By my invention the oxidation of the spelter takes place only on the
withdrawal of each of the sheets and not during the whole of the operation as with
the processes hitherto employed, the formation of, hard spelter and evaporation are
reduced to a minimum, the charge of spelter is as small as possible and is uniformly
applied and inally the spreading being effected automatically the workman charged
with this duty in the well known processes can be dispensed with whereby an
economy of labour is effected:

page_text: The surface of the lead is covered with sal-ammoniac and the surface of the
zinc with a layer of fine powder, such as powdered coke.
Dated the 16th day of April 1892.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Galvanising Iron, and Apparatus therefor.
I, Gustave RETTERER, of 31, Rue du Commerce, Paris, in the Republic of
France, Engineer, 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 :—
This invention relates to an improved galvanizing bath and its method of
employment for galvanising iron whereby the formation of hard spelter so prejudicial
with the processes heretofore employed is in a great measure prevented.
At present sheet iron is generally galvanised by immersing the sheets, previously
pickled and scoured by an acid bath, in a bath of melted spelter covered with
sal-ammoniac where they become covered with a superficial coating of spelter.
This operation requires two workmen to operate the sheets and a third to spread
(spatuler) the surface of the bath when the sheets are withdrawn.
By this process hard spelter is largely produced and an excessive evaporation
results from the frequent and considerable oxidation of the surface of the spelter
from contact with the atmosphere for, it will be understood, that for each sheet the
upper surface of the spelter has to be spread whereby it is uncovered more than is
expedient and is put directly and for a certain length of time in contact with the
atmosphere. This method of galvanising possesses the further disadvantage of
charging the immersed sheets with spelter to too great an extent, doubtless owing
to the length of time occupied in immersing them in and removing them from the
bath.
By another method, also well known, the sheets are first dipped in a bath of
melted lead and are afterwards immediately immersed in another bath of melted
spelter. This method only possesses the advantage of better preparing the sheet.
to receive the covering of spelter, the process otherwise having the same defects
as exists with the single bath process.
According to my invention the galvanising bath at its upper part is divided
by means of a longitudinal partition into two compartments which communicate
with each other below the partition; the lower part of the bath and one of these
compartments contains melted lead and the other compartment contains melted
spelter which floats on the lead which has free access through the bottom of this
second compartment. The sheets to be galvanized are first immersed in the lead
bath sufficiently deep to allow the upper longitudinal edge to descend somewhat
below the dividing partition and in any suitable manner caused to pass
to the other side of the thickness of the said partition when by reason of
the difference of the densities of the lead and the sheet the latter will be
automatically projected through the spelter bath until it arrives within reach of
the workmen who grasp it with their lifting tongs and withdraw it perfectly
galvanised. Oscillating guides are provided in the spelter bath arranged on two
bars which float on the surface of the zinc, which guides direct the automatic
upward movement of the sheet and the bars spread the insulating layer which
re-covers the surface of the spelter in the necessary manner and at the moment
required. By my invention the oxidation of the spelter. takes place only on the
withdrawal of each of the sheets and not during the whole of the operation as
with the processes hitherto employed, the formation of hard spelter and evaporation
are reduced to a minimum, the charge of spelter is as small as possible and is.

page_text: uniformly applied and finally the spreading being effected automatically the
workman charged with this duty in the well known processes can be dispensed
with whereby an economy of labour is effected.
The surface of the lead is covered with sal-ammoniac and the surface of the
spelter with a layer of fine powder, such as powdered coke.
In order to enable the invention to be fully understood I will describe the
same by reference to the accompanying drawings, in which :-
Figure 1 is a longitudinal section of the galvanizing bath on the line 1-2 of
Figures 2 and 3:
Figure 2 is a plan; and,
Figure 3 is a transverse section on the line 3-4 of Figure 1:
Figure 4 is a detail.
The masonry of the bath is of known construction; the grate a is provided
with a furnace mouth a¹ opening into a heat chamber a², the gases of combustion
pass into flues of progressively increasing size formed in an arch b' upon which
the galvanizing bath c rests. Cast iron supports of progressive heights maintain
the bottom of the galvanizing bath in a horizontal position notwithstanding the
incline given to the arch for the purpose of collecting in a gutter d any metal
which may escape by leakage and which passes into a vessel placed at any
suitable point within the heating chamber.
The gases of combustion after passing through the flues b, on each side of
the fire-bridge e, rise to a point a little more than half the height of the lateral
sides of the galvanizing bath then pass to the end abutting on the heat chamber a²
and return to heat the upper part of the lateral sides and thence pass to a draught
flue communicating with a flue f.
As shewn in the drawing the workmen stand upon the gratings g, on a level with
the ground or upon plates g¹ on a level with the edges of the bath.
The upper part of the bath is divided longitudinally by an iron partition h making
a tight joint at each end so as to form with the sides of the bath two bottomless
compartments o, o³, equal or unequal in size. Two bare k, k¹ placed. edgewise in
the middle of the compartment o are respectively carried by two series of
supports m, m pivotting respectively upon two horizontal rods n, n', one being
near the partition and the other near the side of the bath. The ends of the
rods n, n' turn in bearings n², n². This arrangement allows of the bars k, k¹ being
brought as near together as possible in their normal position and of being moved
away from each other by pivoting on their supports m, m³. Figure 4 is a view
shewing this arrangement.
In the bath c and the compartment o' is placed pure melted lead and in the
compartment o melted spelter.
In consequence of the difference in density of the lead and the spelter the levels
of the lead in o' and o will be about those shewn in Figure 3. The surface of the
lead in the compartment o' is covered with sal-ammoniac, muriate of ammonia or a
salt of zinc such as chloride of zinc and upon the surface of the spelter is a layer of
coke powder or other suitable powder.
In carrying out the invention the sheet to be galvanized is taken by two workmen
and immersed in the compartment o' to a sufficient depth to allow its upper edge to
descend somewhat below the partition h, the sheet is then inclined and its upper
edge pushed towards the compartment o, the workmen then releasing their hold
"pon it.
By the difference of densities of the lead and the sheet metal the latter rises into
the compartment o and pushes apart the bars k, k'. The sheet metal is then
again taken hold of by the workmen and removed from the bath.
It will thus be seen that according to my invention sheets of metal are passed
into the lead bath and then without any further operation passed into the spelter
bath. In this latter stage of the process the bars &, & act as spatulas as in opening
under the thrust of the sheet metal plate they only uncover sufficient of the zinc to
allow of the withdrawal of the sheet metal from the bath.

page_text: Sheet metal thus trented is more brilliant; has a better appearance, is more
malleable and is of greater commercial value than sheet metal galvanized by hitherto
known methods. To these advantages must be added the great reduction in the
production of hard spelter and the slight evaporation in consequence of the automatic
spreading of the covering of powder on the zinc; the suppression of the oxides
whereby a minimum quantity of spelter is required and finally the economy of
manufacture by reason of the automatic spreading. It is further to be noted that
the volume of spelter is as small as possible and therefore the stock of spelter
required is reduced.
The destructive action of the spelter only takes place in the upper part of the
bath and this action may be watched and when needful it can be limited in a great
measure as when the compartment o is damaged after a certain time of service the
spelter bath and its automatic arrangement, which is removable, can be placed in
the compartment o. In this way the durability of the bath is practically considerably
increased.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. A galvanizing bath for sheet metal comprising an ordinary bath in the upper
part of which is a vertical partition dividing the bath into two bottomless
compartments, the lower part of the bath and one of the compartments com-
municating therewith containing melted lead, the other compartment containing
melted spelter resting on the lead in the bath, the latter compartment being
provided with two longitudinal bars so arranged as to be normally held near
together and capable of being automatically moved away from each other by the 2
thrust of the galvanised sheet, substantially as hereinbefore described and illustrated
in the accompanying drawing.
2. A process of galvanizing sheet metal by the use of a melted lead and spelter
bath such as is claimed in Claim 1 consisting in immersing the sheets of metal in a
bath of lead to a depth such that they can then pass automatically through the 3
spelter bath and causing an arrangement of bars to be operated, whereby the
necessity of employing a workman to spread the surface as required in the ordinary
process is obviated substantially as hereinbefore described.
3. The use of the apparatus and the employment of the process herein before
described and forming the subjects of Claims 1 and 2 for galvanizing other objects 3
for which such apparatus and process may be adapted.
Dated this 16th day of January 1893.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.