Improvements in Mechanism for Operating the Scrapers of Flue Heat Economizers for Steam Boilers.
Year: 1895

page_text: Date of Application, 23rd Mar., 1895
Complete Specification Left, 22nd Jan., 1896-Accepted, 7th Mar., 1896
PROVISIONAL SPECIFICATION.
Improvements in Mechanism for Operating the Scrapers of Flue
Heat Economizers for Steam Boilers.
I, THOMAS ROLAND WOLLASTON, Consulting Engineer, of 12 Dutton Street
Manchester in the County of Lancaster do hereby declare the nature of, this
invention to be as follows:-
The economizers to which these improvements are adapted consist of a number
of vertical pipes suitably arranged within the flue through which the hot gases
from a boiler furnace pass on their way to the chimney.
The water to be heated is passed through the interior of these pipes, while the
hot gases, in passing around their exterior surfaces, impart a certain proportion of
their heat to it. To prevent an accumulation of soot upon the exterior surfaces
of the pipes it is usual to provide scrapers of annular form surrounding them,
which are caused to continually travel upwards & downwards alternately. The
object of my invention is to provide a mechanism for imparting this motion to the
scrapers, & it may be described as follows:-
In a convenient position upon or near to the economizer I mount a shaft which
may be rotated by means of a pulley & belt or other well known means.
Upon
this shaft I place a worn which gears into a worm wheel upon a second shaft.
Upon this second shaft is a spur wheel which is rigidly attached to the worm wheel
and rotates with it. This spur wheel drives another of the same size and number
of teeth, on a third shaft, which will consequently rotate at the same speed but in
the opposite direction. Upon the shafts called second and third are two segmental
spur wheels each of which has teeth round only about half its circumference.
These segmental wheels are rigidly attached to the spur wheels upon their
respective shafts and rotate with them. Upon a fourth shaft running parallel with
the second and third shafts previously mentioned I affix a spur pinion in such a
way that it may gear with either of the segmental wheels. The segmental wheels
are so arranged on their shafts that the portions of their circumferences carrying
teeth will come into gear with the pinion alternately and will thus rotate it first in
one direction for a given number of revolutions and then in the reverse direction
for the same uumber of revolutions and so on. The shaft which carries and is
rotated by the pinion passes over the top of the economizer, being carried in
suitable bearings.
::
The scrapers are arranged in sets, the number in each set varying with the size
of apparatus, and two sets may be worked by a chain, one end of which is attached
to each. The chains pass over revolving chain pulleys mounted above' the
economizer. In one arrangement these chain pulleys are affixed directly to the
pinion shaft previously mentioned, or in another arrangement they are mounted on
shafts at right angles to the pinion shaft and driven from it by mitre or bevel
wheels or other suitable gearing.
I may arrange the worm on the driving shaft to work directly into the wheel on
the second shaft, thus dispensing with the separate worm-wheel, but in this case the
teeth of all the wheels are made angular or skew to suit the worm.
I may also make the spur wheels and segmental wheels on the second and third
shafts respectively in one and the same piece, or as independent wheels bolted or
otherwise secured together to form one wheel. In this case the path of the worm

page_text: on the first shaft occupies half the width of the wheel on the second shaft, and the
path of the pinion on the chain shaft occupies the other or segmental half of the
width of the wheels on the second and third shafts before described.
The action of the mechanism is as follows:-The first or worm shaft, being
driven by external power at the desired speed and constantly in one direction the
wheels on the second and third shafts, (which also carry round the segmental
wheels) are caused to rotate, each one constantly in one direction, but opposite
directions the one to the other. Assuming that the segmental wheel on the second
shaft is in gear with the pinion on the fourth shaft the latter is driven in a given
direction thereby, as the portion of the segmental wheel on the third shaft which
is without teeth is at that time adjacent to the pinion. As soon as the toothed
segment on the second shaft has passed the pinion & ceases to gear with it the
latter comes to rest and immediately thereafter the approaching toothed segment
on the third shaft, (which as previously described rotates in the opposite
direction to that on the second shaft) enters into gear with the pinion, and rotates
it in the direction opposite to that of its previous rotation, & this reversing of the
pinions motion is continued constantly by the two toothed segments alternately
coming into gear with it. By these means intermittent and alternate rotation is
imparted to the chain wheel shaft and thence to the scrapers.
Dated this Twenty-first day of March 1905
Improvements in Mechanism for Operating the Scrapers of Flue
Heat Economizers for Steam Boilers.
I, THOMAS ROLAND WOLLASTON, of 12 Dutton Street, Manchester, in the
County of Lancaster, Consulting 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 :-
The economisers to which these improvements are adapted consist of a number of
vertical pipes suitably arranged within the flue through which the hot gases from
a boiler furnace pass on their way to the chimney. The water to be heated is
passed through the interior of these pipes, while the hot gases, in passing around
their exterior surfaces, impart a certain amount of their heat to it. To prevent
an accumulation of soot upon the exterior surfaces of the pipes it is usual to
provide scrapers of anuular form surrounding them, which are caused to continually
ravel upwards and downwards alternately.
The object of my invention is to provide a mechanism for imparting this alternate
motion to the scrapers and in. order to describe it more clearly I refer to the
accompanying drawings in which
Fig. 1 is a front elevation of the mechanism, Fig. 2 a side elevation ;
Fig. 3 illustrates one arrangement and disposition of the scraper pulleys and
chains, and Fig. 4 an alternative arrangement of the same.
The shaft A is mounted in a convenient position upon or near to the economiser.
It may be driven by a belt running on the pulley a or by other suitable means.
I rigidly key a worm a¹ upon this shaft gearing into and driving a worm wheel b
which may run loosely upon a stud B.
A spur wheel not shewn in the drawings is in one form of my invention rigidly
attached to the worm wheel b, rotating with it and gearing into and driving an
equal spur wheel also not shewn and which may run loosely upon the stud C.
But in the form I prefer and as illustrated in the drawings I make use of the
worm wheel b itself as a spur wheel and cause it to gear with and drive a similar
wheel c running on the stud C. It will be understood that the studs B and C

page_text: ¡may be replaced by shafts in which case the wheels b and c would be rigidly keyed
to them.
Segmental spur wheels b¹ and c¹ are rigidly attached to the wheels b and c or
rigidly.keyed to shafts B and C respectively and rotate with them.
Upon a fourth shaft D a spur pinion d is rigidly keyed gearing into and driven
by the segmental wheels b and c alternately. The wheels and ci have each
only a sufficient number of teeth, to allow one of them to clear the teeth of the
pinion d before the teeth of the other of them engages with the pinion teeth and
so drives it in the opposite direction. The teeth shewn blocked out in solid black
in the drawings are intended to be omitted in the segmental wheels. The
directions of rotation of the wheels b, b and c, c' are indicated by arrows.
The shaft D passes over the top of the economiser of which E are the top
boxes and F the pipes. G is the bracket carrying the bearings of the shafts
and the studs.
The scrapers are arranged in sets, the number in each set varying with the size
of apparatus, and two sets may be worked by a chain one end of which is attached
to each. The chains H pass over the revolving pulleys I mounted above the
economiser.
In one arrangement the pulleys I are mounted directly upon the shaft D as
shewn in Figs. 2 and 3 and in another arrangement they are mounted on shafts K
at right angles to the shaft D as shewn in Fig. 4 and driven from it by suitable
bevil or mitre gearing L. In this latter case if desired I insert a handle M in
order to operate the scrapers by hand by disconnecting the gearing L.
I may make the segmental wheels b₁ and the worn wheel B in one piece and c¹
and C similarly in one piece, in which case the teeth on one-half the breadth of
the wheel are angled to form a worm wheel and the other half are straight to form
the segmental spur wheels the path of the worm a¹ occupying the first half and the
path of the pinion D the second half width.
The action is as follows:-
The worm shaft A being driven by external power at the desired speed and
constantly in one direction the wheels b and c on the second and third shafts are
caused to rotate, each one constantly in one direction, but in opposite directions the
one to the other. Assuming that the segmental wheel b' is in gear with the
pinion D the latter is driven in the direction of the full arrow thereby, as
the portion of the segmental wheel c¹, which is without teeth is at that time
adjacent to the pinion D. As soon as the toothed segment has passed the
pinion D, and ceases to gear with it, the latter comes to rest and immediately
thereafter the approaching toothed segment c' (which as previously described
rotates in the opposite direction) enters into gear with the pinion D and rotates it
in the direction of the dotted arrow, and this reversing of the pinion's motion is
continued constantly by the two toothed segments alternately coming into gear
with it.
By these means intermittant and alternate rotation is imparted to the chain
wheel shaft D and thence to the scrapers.
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. The combined gearing consisting of worm and worm wheel, one pair of
complete spur wheels and one pair of segmental spur wheels, the latter operating a
pinion alternately and hence rotating it in opposite directions substantially as and
for the purposes hereinbefore described and illustrated in the accompanying
drawings.
2. Obtaining alternate rotatory motion by means of a pair of segmental wheels
constantly rotating in opposite directions and alternately gearing with the same
pinion, substantially as and for the purposes herein before described and illustrated
in the accompanying drawings.i

page_text: 3. Obtaining alternate rotatory motion by the combination of four shafts, one
worm, one pair of worm wheels gearing together, one pair of segmental spur
wheels rigidly attached to the worm wheels and one pinion operated alternately by
the segmental wheels substantially as and for the purposes herein before described
and illustrated in the accompanying drawings.
4. Obtaining alternate rotatory motion by one pinion driven by the teeth of
two spur wheels gearing alternately with the said pinion and having a sufficient
number of the teeth of each of them omitted to ensure that only one shall gear at
one time substantially as and for the purposes herein before described and illustrated
in the accompanying drawings.
5. The chain pulleys mounted direct on the pinion shaft in combination with the
worm, worm wheel, and segmental gearing substantially as and for the purp es
hereinbefore described and illustrated in the accompanying drawings.
6. The chain pulleys mounted on shafts at right angles to the pinion shaft and
driven therefrom by bevil gearing in combination with the worm, worm wheel, and
segmental gearing substantially as and for the purposes hereinbefore described
and illustrated in the accompanying drawings.
Dated this 21st day of January 1896.
EDGAR CONISTON MILLS,
Agent to the Applicant.