OOR FOR FURNACES
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by James Shepherd at the Office of the
Commissioners of Patents on the 14th December 1882:
JAMES SHEPHERD of the City of Manchester, Engineer
FIRE GRATES AND DOORS FOR FURNACES
"
"IMPROVEMENTS IN
This Invention relates to improvements in fire grates and doors for the furnaces
of steam boilers, and for smelting, converting chemical and other purposes, and the
objects of construction according to the improvements are to obtain a large area
opening for the admission of air to the fuel, and to obviate the liability of the
parts regulating the admission of the air becoming: inoperative from choking or
sticking fast with ashes etc, and to provide an efficient rocking bar apparatus for
the fire grate, which may be actuated by hand or machinery. The upper portion
of the front of the furnace door is cut away except a narrow strip of metal up
each side and across the top. On the back of the door grooves or recesses are
formed up each side, into which the spindle of a flat lever, valve or lid is fitted in
manner to allow the valve to work freely up and down.
Into the same recess is fixed at an angle a plate of metal termed a deflector that
extends across the width of the door and rests upon the ends of the valve spindle
aforesaid, and acts as a cap or weight to keep the same in position.-The deflector
is not so deep as the door opening by several inches, thus allowing ample clearance
of space between the bottom edge of the deflector and the dead plate of the
furnace. The upper part of the deflector is fitted with a series of louvre bars or
equivalent arrangement which are opposite to and kept in constant and free
communication with the opening at the top of the door through which the air
necessary for the ordinary requirements of the fire passes. When the fire is in an
incandescent state, the regulating valve lies in an inclined position against the
deflector, thereby closing the communication between the atmosphere and the low
level passage to the fire, but when the fire is freshly coaled, the valve should be
raised to a vertical position against the back of the door, which opens the lower.
passage and admits an adequate quantity of air to the grate, the duration for which
supply is governed by the weight of fuel laid thereon.-The valve is opened and
closed by a suitably shaped lever attached to the valve or flap, and projecting
through an opening in the front of the door. The fire grate is composed of cast
steel or iron bars The bars are constructed with a centre rib, taper or wedge

page_text: shaped in section, and of single fish rail form with spacing pieces along the top
sides of the web at regulated distances, and joined to strips of metal up either
side parallel to each other, so as to form a triple-headed bar.-The spacing pieces
which form the air races between the centre web and the outer strips are by
preference of triangular shape so as to offer the least resistance to the ingoing air
or to the falling dust and ash from the grate.
The surface or top of the bars may be flat, convex, or concave in form, to suit
the character of the work for which they are intended-In constructing the grate,
the bars are arranged so that every other one can be rocked or moved upon its
axis either by hand or by machinery, in which latter case its action may be
constant and automatic. The cross bearers that support the bars are suitably
prepared for this purpose.-The fast or stationary bars have flat or otherwise
shaped ends, that fit into correspondingly formed recesses on the top of the bearers.
The movable or rocking bars have circular or semicircular shaped ends that fit
into suitable recesses or steps in the bearer.-To obtain an easy and sufficient
action for the movable bars, the axis upon which they move is kept near to or
below the mid-centre of the bar.
This method of obtaining motion differs materially from those systems where
the point of suspension is near to the top of the bar, whereby the amount of
oscillation of the top of the bar is extremely limited, thus reducing the usefulness
of such arrangements for self cleaning purposes.
Motion is communicated to the movable bars by means of a swing bar or rod
that hangs below the grate, and is bolted or secured to the outer movable bar on
either side. Upon the upper edge of the swing bar there is a series of notches or
slots, corresponding in number to the movable bars; the bottom edge of each bar
fitting loosely into one of the slots.-On the lower.side of the swing bar is, cast or
formed an opening to receive an eccentric disc, which is actuated by a shaft
carrying the same, which runs along one side of the grate-The end of the shaft
may project a convenient distance in front of the fire place, and can be actuated
either by a lever or a handle worked by hand, or be driven by suitable machinery
In operation, each movable bar oscillates between the stationary bars, producing
on one side an increased opening of the air-space, and on the other side a reduction
in the same area, thus producing a crushing action as the edges of the bars
approach each other.-By this means the dirt, ashes or dust in contact with the
bars are cleared away and discharged into the ash pit.
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