Improvements in the "Helix" or other Screws for Furnace Feeding and in Tilting Bars used in connection with same.
Year: 1889

page_text: Date of Application, 21st Mar.,
1889
Complete Specification Left, 21st Dec., 1889-Accepted, 25th Jan., 1890
Improvements in the "Helix" or other Screws for Furnace Feeding
and in Tilting Bars used in connection with same.
I, THOMAS ANDREWS of Winter Street, Sheffield, in the County of York, Engineer
do hereby declare the nature of this invertion to be as follows:-
My invention relates to improvements in the construction of the screw of the
"Helix Screw Feed" or other screw stokers, and in its application to furnaces of any
description.
The Helix screw and other screws for underfeeding have hitherto been made solid
and to obtain certain advantages in burning the fuel and to give greater strength and
durability to the screw, and to counteract the effect of the fire upon them, I propose
to make such screws with single or double thread hollow, or tubular, or partially
tubular in various ways, and otherwise to improve their construction.
According to one method in casting the screw, I form a longitudinal hole of any
desired length and of suitable diameter up the centre of the screw, the said centre
hole being open at one end and closed at the other or in some cases open throughout
its entire length. According to another method, I cast the thread or threads of
the screw upon a piece of ordinary iron or steel tubing, either passing completely
or partially through the length of the screw, and in either case I provide any
desired number of apertures, holes, nozzles, or similar ports, made through the screw
from the tube, or tubular opening, so that air, steam, gus, or a combination of any of
them can be forced in the tube or hollow part of the screw at the open end and through
the ports (or the end, or both as the case may be) into the fuel, thereby ventilating and
loosening the green and compressed fuel as it passes up by the action of the screw
into the incandescent fuel; thus assisting combustion over the screw case where at
present the fuel lays dead.
This improvement may be applied to the ordinary Helix Screw, but 1 prefer to
make a special form of this screw which I call a stepped screw, consisting of two or
more diameters; for example I may make a screw divided into six parallel lengths of
varying diameters, (somewhat resembling an open telescope) and I cast or otherwise
make the screw hollow to any desired length, or completely tubular, with air ports as
before described. This description of screw is not so likely to become clogged or
obstructed by compressed fuel, as one that is tapered from end to end.
In connection and combination with these hollow screws and the usual arrangement
of furnace bars to which they are adapted, I arrange at the back end of the furnace,
two side longitudinally tilting bars, with a central partition bar, the tilting bars may
be pivotted either centrally or towards the sides, and are tilted from the front. They
are arranged on a lower level than the reciprocating bars, say for example below the
bottom edge of the ends of same, and in this position the tilting-bars being divided as
before described they are of great advantage in side hand firing, and for facilitating
the cleaning one half the fire at once, as will be well understood.
To protect the upper face of the bars from the corrosive action of the fire, I forin
or construct in the said face of each bar, longitudinal undercut recesses or pockets
(say for example four inches long and one inch deep) so that they will hold and retain
fireclay or other refractory material with which I fill them.

page_text: COMPLETE SPECIFICATION.
Improvements in the "Helix" or other Screws for Furnace Feeding
and in Tilting Bars used in connection with same.
1, THOMAS ANDREWS of Winter Street, Sheffield in the County of York, 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:—
My invention relates to improvements in the "Helix" and other similar serews for
furnace feeding. and also tilting bars used in connection with same.
::
The "helix screw and of her screws used for underfeeding in furnaces have hitherto
been made solid, and in order to obtain certain advantages in burning fuel, and to
increase the strength and durability of the screw, and to counteract the effect of
the fire upon them, I propose to inake such screws with either single or double
thread, hollow or tubular, or partly tubular, in various ways, and in order that my
invention may be clearly understood in all its details, I annex a sheet of drawings
illustrating same.
Fig 1, represents a plan and an end view of tilting bars constructed and arranged
according to my invention.
Fig. 2, represents a side elevation and a plan of a firebar with undercut pockets to
be filled with refractory material.
Fig. 3, represents a tubular "helix" screw with perforations for the escape of air.
Fig. 4, represents a different class of screw with a conical body, and partly tubular
Fig. 5, represents a screw made in sections, and fitted upon a square rod, or upon
a tube.
In carrying out my invention so far as relates to the screws, I form a longitudinal
hole up the centre of the screw, of any desired length and diameter, that in Fig. 3, is
shown passing completely through the screw, and that in Fig. 4 extends about half
way; or the thread portion of the screw may be cast upon a piece of tubing, either of
the full length of the screw or not as preferred.
In either case, I provide any desired number of holes, nozzles, or apertures, made
through the body of the screw into the longitudinal hole.
A is the screw thread, B the longitudinal hole or tube, C the apertures communi.
cating with the interior. The object of the mode of construction is, that air, steam,
gas, or a combination of any of them may be forced or admitted into the said
longitudinal bole or tube at its open end, and pass through the ports or apertures C,
and the opposite end of tube or hole B, if open, into the fuel, and thereby ventilate
and loosen the green and compressed fuel as it is passed upwards by the action of
the screw into the incandescent fuel, thus assisting combustion over the screw case,
where at present the fuel usually lies dead.
This improved construction is applied to the ordinary "Helix" screw, but I also
apply it to special forins of screws, one of which is shown in Fig. 4, in which the screw
thread does not taper, but is parallel throughout its entire length; the body of the
screw increases in diameter from the front end, and thus gives a direct vertical lift to
the fuel, a tubular hole B is made through a portion of its length with holes C, as
before described.
The screw shown in Fig. 5, is also of a special construction; it consists of screwed
sections, or any desired number of short lengths of screw put upon either a solid
bar or tube D, so that any part of the screw that may get broken may be replaced at
a small cost. When a round rod or bar is used the sections are made to clutch into
each other at their end faces, but if square bars or tubes are used, the ends of the
sections may be plain. The sections may be made tapered so as to form a taper screw,
or they may be made parallel, but of different diameters so as to form a stepped screw,
somewhat resembling an open telescope. It is to be understood that this screw made
in sections may either be made with ports opening into a tube, or solid, that is without
such ports.

page_text: The second part of my invention which is used in combination with the specially
constructed screws before described, refers to an arrangement of tilting bars, to be
used with other furnace bars, and a plan of protecting the upper faces of furnace bars
from the corroding action of the fire.
I arrange at the back end of the furnace as shown in Fig. 1, two side tilting
bars E&E, with a central partition bar F; the said tilting bars may be pivotted
either centrally as E, or towards the side as E, and they are operated by the rods (i
and G1, which extend to the front of the furnace. These tilting bars are arranged
preferably on a lower level than the bars H, say for example below the bottom edge
or face of such bars, and in this position the tilting bars, being divided as before
described, by bar F, they are of great use in side hand firing, and in facilitating the
cleaning one half the fire at once, as will be well understood by engineers.
To protect as far as possible the upper face of the fire bars froin the destructive
action of the fire, I construct in the faces of such bars, longitudinally arranged undercut
recesses or pockets Pas shown in Fig. 2, which represents an ordinary fire-bar as an
example, and I fill these pockets with fireclay or other like refractory inaterial.
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-In Furnace Feeding Screws, a tubular hole B made partially or completely
through the screw, and provided with openings or ports C, of any shape or construction
to permit the passage of air, steam, or the like, to the fuel, for the purpose specified
and substantially as herein before described and shown.
2-A Furnace Feeding Screw built up in parallel or tapered sections (or a number of
short lengths) and secured upon a hollow rod or tube or upon a solid bar, either with or
without openings or ports for the passage of air, steam or the like, for the purpose
specified.
3-In Furnaces, the arrangement at the back end of the usual bars of two tilting
bars E, E, pivotted at each end either centrally, or nearer to the outer side, for the
purpose specified, and substantially as hereinbefore described and shown in Fig. 1 of
the drawings.
4-In Furnace bars, the undercut longitudinal openings or pockets formed in the
upper faces of such bars, filled with fire-clay or other like refractory material, for the
purpose specified.