IMPROVEMENTS IN THE MANUFACTURE OF PAVING BLOCKS FROM FURNACE SLAG AND IN APPARATUS FOR THAT PURPOSE
Year: 1883

page_text: LETTERS PATENT to Charles James Dobbs of Middlesbrough in the County
of York for an Invention of IMPROVEMENTS IN THE MANUFACTURE OF PAVING
BLOCKS FROM FURNACE SLAG AND IN APPARATUS FOR THAT PURPOSE
PROVISIONAL SPECIFICATION left by the said Charles James Dobbs at the
Office of the Commissioners of Patents on the 9th August 1883.
CHARLES JAMES DOBBS of Middlesbrough in the County of York "IMPROVE
MENTS IN THE MANUFACTURE OF PAVING BLOCKS FROM FURNACE SLAG AND IN
APPARATUS FOR THAT PURPOSE
"
In the manufacture of paving blocks from slag, as at present carried out, the
slag is run directly from the blast furnace into iron moulds arranged round a
turntable, and when the mass is just set, the blocks are allowed to fall out of the
moulds and are put into a kiln of large dimensions previously heated by fire, where
they are allowed to remain about 15 hours so as to become thoroughly annealed,
whereupon the kiln is opened and the bricks are allowed to cool gradually. The
disadvantages of this arrangement are, firstly the expense of having to heat the
large kilns by fire before introducing the blocks, and secondly the comparatively
large amount of ground space required in close proximity to the blast furnace for
the erection of the kilns, whereby they are rendered inapplicable to a great many
blast furnaces that have only a very limited ground space available in their
vicinity.
Now, according to my present invention, I obviate these disadvantages by
effecting the perfect annealing of the blocks without any preliminary firing of the
kiln, this being rendered possible by constructing the kilas in a different manner
to that heretofore employed; namely, instead of constructing them of one large
chamber requiring a large number of blocks to fill it, I construct them with a series
of separate chambers of smaller size, each of which is charged separately with a
moderate number of blocks, and which are by preferenco made to communicate
with each other by means of flues provided with regulating slides, so that the
sui plus heat given off from the blocks in the one chamber may be led off to another
Pain Car

page_text: chamber in order to heat it to a certain extent before receiving its charge of
blocks. By employing this arrangement, I have found from experiment that the
heat retained by the central portion of the blocks, which is still in a more or less
liquid state when they are introduced into the kiln, is sufficient to effect the perfect
annealing of the blocks without the use of additional firing, as such central heat is
gradually conveyed by conduction to the more or less cooled outer portion of the
block, thus rendering the temperature of the block more or less uniform throughout,
in which condition it is then allowed to cool down gradually.
Although I prefer to construct the kilns with groups of small chambers as
described, yet in cases where only a limited ground space is available near the blast
furnace, I construct the said small annealing chambers or kilns separately, and in
some cases, I mount them upon carriages, so that each chamber may be run near to
the blast furnace to receive its charge and be then removed to a locality where
sufficient ground space is available. By the use of such small sized kilns or
annealing chambers, whether fixed or moveable, I am also enabled to utilise the
slag from smaller furnaces than those to which the process has hitherto alone been
applied with advantage. The said moveable kilns or annealing chambers may also
be used with advantage to supplement the fixed kilns at blast furnaces that are of
such large dimensions that the whole of the available slag supply cannot be utilised
by fixed kilns, on account of the limited space near to the blast furnace.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Charles James Dobbs in the Patent Office on the 6th February
1884.
CHARLES JAMES DOBBS of Middlesbrough, in the county of York
"IMPROVE-
MENTS IN THE MANUFACTURE OF PAVING BLOCKS FROM FURNACE SLAG AND IN
APPARATUS FOR THAT PURPOSE
"
In the manufacture of paving blocks from slag, as at present carried out, the
slag is run directly from the blast furnace into iron moulds arranged round a
turntable, and when the mass is just set, the blocks are allowed to fall out of the
moulds and are put into a kiln of large dimensions previously heated by fire, where
they are allowed to remain about 15 hours, so as to become thoroughly annealed,
whereupon the kiln is opened, and the bricks are allowed to cool gradually.
Now my present invention has for its object to obviate the expense and
disadvantage consequent upon having to heat the large kilns in the first instance,
and it consists in effecting the perfect annealing of the blocks without any
preliminary firing of the kiln, this being rendered possible by constructing the
kilns in a different manner to that heretofore employed; namely, instead of
constructing them of one large chamber requiring a large number of blocks to fill
it, I construct them with a series of separate chambers of smaller size, cach of
which is charged separately with a moderate number of blocks, and which are by
preference made to communicate with each other by means of flues provided with
regulating slides, so that the surplus heat given off from the blocks in the one
chamber may be led off to another chamber in order to heat it to a certain extent
before receiving its charge of blocks. By employing this arrangement, I have
formed experiment that the heat retained by the central portion of the blocks,
which is still in a more or less liquid state when they are introduced into the kiln,
is sufficient to effect the perfect annealing of the blocks without the use of additional
firing, as such central heat is gradually conveyed by conduction to the more or less
cooled outer portion of the block, thus rendering the temperature of the block more
or less uniform throughout, in which condition it is then allowed to cool down
gradually.
Although I prefer to construct the kilns with groups of small chambers as
described, yet in cases where only a limited ground space is available near the blast
furnace, I construct the said small annealing chambers or kilns separately, and in
some cases, I mount them upon carriages, so that each chamber may be run near
to the blast furnace to receive its charge and be then removed to a locality where
sufficient ground space is available. By the use of such small sized kilns or
annealing chambers, whether fixed or moveable, I am also enabled to utilise the
slag from smaller furnaces than those to which the process has hitherto alone been
applied with advantage. The said moveable kilns or annealing chambers may
also be used with advantage to supplement the fixed kilns at blast furnaces, that
aro of such large dimensions that the whole of the available slag supply cannot be
utilised, by fixed kilns, on account of the limited space near to the blast furnace.
The accompanying drawings shew, by way of example, two constructions of
annealing kilns or chambers for carrying out my said invention. Fig. 1 shews a
part front elevation and part section of a series of annealing chambers A A arranged
side by side and fig. 2 shews a longitudinal section of one of the chambers.
The chambers A are formed of brick work with an iron casing, and they are
closed in front by two folding doors B B secured by a bar O and having formed in
them two openings D D closed by slabs E E. The chambers are also provided

page_text: with openings F at top closed by slabs G, and in the partition walls are formed
other openings H, provided with a slide 1, on raising which the one chamber can
be made to communicate with the contiguous one.
The slag blocks having become set in the moulds as before stated, they are at
once charged into the chambers, first through the lower openings D and afterwards
through the upper one. The chamber having been filled, the openings D are closed,
whereupon the greater heat contained in the central portions of the blocks will be
gradually conveyed by conduction to the outer surfaces thereof, thereby rendering
the block of a more or less perfectly uniform temperature throughout. In this
condition, the blocks are allowed to cool down gradually, whereby they become
perfectly annealed without any additional heating of the chambers being required
beyond that which is obtained by radiation from the blocks themselves. During
the cooling, the slide 1 is opened so as to allow a portion of the heat given off to
pass by radiation into the next chamber, so as to heat this to a certain extent
before receiving its charge of blocks, and the openings F may also be opened more
or less if found necessary, to accelerate the passage of heat. The block having
cooled down to a sufficient extent, the doors B B are opened for the removal
thereof, after which the chamber can be at once charged with fresh blocks.
Fig. 3 shews an end clevation and fig 4 a longitudinal section of an annealing
kiln or chamber mounted on wheels, so as to be capable of being brought near the
blast furnace to receive its charge of blocks, and then removed to a convenient
place, as above described. The chamber A. is here shewn of cylindrical shape for
obtaining the requisite strength without staying; it may however be made of a
rectangular or other convenient shape. The construction of the chamber is other-
wise the same as at figs. I and 2, the parts being designated by the same letters of
reference, and therefore requiring no further description.
Having thus described the nature of my invention and in what manner the same
is to be performed, I-claim :-
First In the manufacture of paving blocks from furnace slag, the method of
annealing the blocks exclusively by means of their own initial heat by enclosing
them immediately after they have solidified, in kilns or chambers of moderate
dimensions that are only healed by the heat radiated from the blocks.
Second-The use for annealing paving blocks made from slag of a series of kilns
or chambers arranged side by sido and communicating with each other by means
of openings, flues or passages so that the heat of the slag blocks contained in one
chamber may be conveyed into the contiguous chamber or chambers so as to heat
it or them preparatory to receiving a charge of slag blocks, substantially as herein
described with reference to the accompanying drawings.
In Witness whereof I the said Charles James Dobbs have hereunto set my hand
and seal this fourth day of February in the year of our Lord, one thousand,
eight hundred and eighty-four.