IMPROVEMENTS IN PULLEY BLOCKS, AND OTHER LIKE HOISTING APPARATUS
Year: 1883

page_text: PROVISIONAL SPECIFICATION left by Thomas Henry Ward at the Office of
the Cominissioners of Patents on the 16th April 1883.
THOMAS HENRY WARD, of the firm of Lee Howl Ward and Howl of Tipton, in
the County of Stafford, Engineers IMPROVEMENTS IN PULLEY BLOCKS, AND
OTHER LIKE HOISTING APPARATUS
"
My Invention has for its object to produce a pulley block or like apparatus,
which shall be more efficient and compact and less bulky for a given load and
cheaper in cost of production, than such apparatus as hitherto constructed.
My said Invention is especially adapted for use with the pulley blocks or like
apparatus arranged with the differential sheaves below as described in the
Specification of Letters Patent N° 5311 granted to me as of the 5th Dec AD 1881,
but is also applicable to pulley blocks or like apparatus otherwise arranged as
hereinafter mentioned
I will describe my invention as applied to a pulley block, such as is described in
my before mentioned Specification and in connection with the top single pulley or
snatch block thereof. The wheel over which the chain passes is in the form of a
ring or wheel, without boss or spokes and is situated between the limbs of the
frame carrying the hook or other attachment.
In the said frame are mounted two shafts which are threaded through the said
chain wheel which rests or hangs upon the upper of these shafts.
In raising the load the lower shaft drives the upper shaft by means of a pinion
on the former gearing with an internally toothed wheel on the latter, the said lower
shaft being provided with a sprocket wheel or its equivalent, for imparting motion,
to the said shaft. In order to retain the load suspended when the pulley block is
unoperated I combine with the said block apparatus constructed upon the principle
described in the Specification of Letters Patent. N° 4012 granted to me conjointly
with Edmund Howl, as of the 17th Sept 1881 but consisting in the present instance
as follows. The sprocket wheel is carried by or formed with a screw nut running
upon a screw on the lower shaft, the said nut being mounted in bearings in the
frame, and capable of being caused to bear at its inner part against a wheel or
roller, threaded upon the said lower shaft, and situated within the ring like chain
wheel. The said lower shaft is mounted in such a position that the said roller

page_text: thereon is situated excentrically to the said chain wheel, and a loose roller is
dropped into the space between the interior of the said chain wheel and the
exterior of the roller on the lower shaft. In raising a load with an apparatus
constructed as hereinbefore described, the sprocket wheel and nut on being rotated
move along the screw thread on the lower shaft, until the said nut bears upon the
roller carried by the said shaft and pinches the said roller firmly between itself and
a collar on the said shaft so that the said roller rotates with the said shaft which
shaft through the pinion and internally toothed wheel hereinbefore described
imparts motion to the upper shaft, and consequently to the chain wheel, resting or
hung thereon. The hereinbefore mentioned loose roller, during the raising of the
load is rotated by the contact with the roller carried by the lower shaft, in a
direction the reverse of that, in which the chain wheel rotates the said loose roller
by the said movement, of the chain wheel being raised slightly so as to run idly.
If now the pull upon the chain be discontinued, the tendency of the chain wheel is
to run back but this is prevented by the counteracting forces exerted in opposite
directions namely in the one direction through the upper shaft and its toothed
wheel and the pinion and lower shaft and in the other direction through the loose
roller, and the roller on the lower shaft, which is virtually in one therewith, by the
binding action of the sprocket wheel nut thereon. In lowering the load the
sprocket wheel is rotated in the opposite direction to that in which it is rotated in
raising when the binding nut releases the roller on the lower shaft, and the load
consequently descends, but if the operation of the sprockett wheel be discontinued,
the downward movement of the load operating through the upper shaft and the
toothed wheel thereof, and the pinion upon the lower shaft rotates the said lower
shaft sufficiently to draw the sprocket wheel nut into position to bind upon the
roller carried by the said lower shaft, and thereupon prevent the further descent of
the load by bringing into action the opposite forces as hereinbefore explained.
It will be evident that if the sprocket wheel were fixed to the shaft and that the
pinion or the roller formed the nut to the screwed shaft that the results would be
the same.
If it be found necessary to increase the friction between the ring-like
chain wheel and the upper shaft, toothed or frictional gearing or surfaces may be
employed which may consist for example of inclined surfaces, at the sides of the
internal periphery of the said chain wheel, engaging with a recess in the shaft,
with correspondingly inclined sides.
The same arrangement may be employed between the loose roller, the chain
wheel, and the roller carried by the lower shaft, or the loose roller may be replaced
by a pawl, engaging with ratchet teeth formed on the roller or wheel on the lower
shaft. The arrangement described may be applied to either the single pulley or
snatch block onto the differential sheaves of pulley blocks or like apparatus
whether they be situated above or below, and the lowering gear may or may not
be used, in combination with the purchase gear described. The lowering gear
when used instead of being arranged as hereinbefore described, may be arranged
as described in the Specification of the before named Letters Patent N° 4012
A.D. 1881
When the Invention is applied to certain of the modifications there described it
will be advantageous to provide the shaft upon which the ring like differential
sheaves are mounted with a roller upon which the said sheaves run to which roller
the screw gear will be applied. The differential sheaves may be so proportioned as
that the resistance in raising is less than the friction or adhesion of the chain wheel
on the upper shaft whereby I am enabled to employ plain frictional surfaces at
these parts which surfaces may be rough castings or unturned surfaces.
I have herein before described a double purchase pulley block but it will be
evident that the Invention is equally applicable to single or to treble or greater
purchase blocks all the shafts being preferably threaded through the ring like chain
wheel. With treble purchase I may carry the first motion shaft through the axis
of the main shaft or as a sleeve on the said shaft.
A simple and efficient form of single purchase pulley block may be provided

page_text: wherein the ring-like chain wheel or upper pulley hereinbefore described rests upon
a shaft carried by the framing of the block the said shaft and block being provided
with lowering gear generally resembling that shewn at Figure 3 of the Drawings
of my aforesaid Specification N° 4012 in the year of Our Lord One thousand eight
hundred and eighty one but the centred pawl which engages with the ratchet wheel
may be replaced by one which is capable of rising and falling between guides
formed on the frame I may cast on the framing a projection which carries a curved
guard piece over the upper part of the sprocket wheel which guard piece while
serving to retain the chain in place acts as a stop to limit the sideway movement'
of the sprocket wheel when the load is released so as to prevent it running down
too far before being retained suspended In order to bring the pull of the chain on
the sprocket wheel as close to the centre line of the block as possible. I may dispense
with the flange of the chain wheel or snatch block and form the framing with a
quick curve above preferably cast in the hook thereto and make the sprocket wheel
of a cup like form so that its periphery is situated inwards of its boss and near to
the centre line of the block.
In place of the pawl and ratchet wheel in the lowering gear I may provide a
brake arrangement consisting of a wheel on the screwed shaft (in place of the
ratchet wheel shewn in the said Figure 3) and a curved projection on the framing
the curve of which projection is excentric with that of the wheel and in the space
between this wheel and projection a ball or roller is placed to act as a brake in
substantially the same manner as does the loose roller in the arrangement herein
first described. The differential sheaves may replace the single ring-like chain
wheel but I prefer to use the latter above and the differential sheaves beneath.
It will be readily understood that the herein before described arrangement of
ring-like chain wheel or pulley (single or differential) may be employed in combi-
nation generally with the various modifications of pulley blocks forming the subject
matter of my hereinbefore mentioned Letters Patent.