IMPROVEMENTS IN HOISTS OR COMPOUND PULLEY BLOCKS
Year: 1884

page_text: I, WILLIAM Box at the Office for Patents 6, Lord Street, Liverpool, in the
County of Lancaster, Engineer do hereby declare the nature of my said invention
for "IMPROVEMENTS IN HOISTS OR COMPOUND PULLEY BLOCKS" to be as follows:-
:-
Pulley blocks as usually manufactured present several serious drawbacks.
The arrangement of the gearing involves very considerable friction, and there is
great danger of the chains slipping off the wheels and letting the load down
suddenly.
Now my invention is designed for the purpose of achieving a maximum efficiency
with a minimum expenditure of power, combined with perfect safety to the user,
and to the goods lifted, thereby, securing moreover a lessened strain on portions
of the mechanism by a more equal distribution of the strains caused by the weight
of the load. The surging, twisting, or slipping of the chains are also greatly
prevented, and greater regularity and smoothness of motion attained.
My compound pulley blocks are constructed as follows:-
The hand driving chain passes over a wheel of the usual construction and of
suitable diameter, keyed onto the screw shaft which actuates the lifting wheels.
A double bar, the ends of which overlap the screw shaft on each side of the driving
wheel and which passes over the rim of the same, bears a bell or guide which
directs the chain correctly on to the wheel, at whatever angle it is held. The screw
shaft bears two screws or worms, of opposite revolution, right and left respectively,
which actuate two wheels, adjusted so as also to engage in each other, and over
one of which the lifting chain passes. The left screw is preferably nearest the
hand chain wheel, and actuates the lifting wheel over which the lifting chain
passes, delivered on to it through a suitable guide, and engaging in sprocketts so as
to prevent slipping or surging This lifting wheel engages by teeth into the second
worm wheel, which is revolved by the left worm on the shaft. The two worm
wheels thus geared together on the rims opposite form a lock to prevent the end
or sliding motion of the worm shaft and dispense with the end thrust. The
arrangement also conveys the power of the right screw back to the lifting wheel.
The worms revolve in oil chambers and the distribution of the work and of the
strain over two opposed motions in this manner reduces the friction to a minimum,
whilst the gain of power enables the hoist to be worked at a greater speed than the
ordinary construction with the same motive power.
0

page_text: I, WILLIAM Box, Office for Patents, 6 Lord Street Liverpool, Lancashire,
Engineer do hereby declare the nature of my said invention for "IMPROVEMENTS
IN HOISTS OR COMPOUND PULLEY BLOCKS, and in what manner the same is to
be performed, to be particularly desoribed and ascertained in and by the following
statement:-
Pulley blocks as usually manufactured present several serious draw backs.
The arrangement of the gearing involves very considerable friction, and there is
great danger of the chains slipping off the wheels, and letting the load down
suddenly.
Now my invention is designed for the purpose of achieving a maximum efficiency
with a minimum expenditure of power, combined with perfect safety to the user
and to the goods lifted, thereby securing moreover a lessened strain on portions of
the mechanism by a more equal distribution of the strains caused by the weight
of the load. The surging, twisting or slipping of the chains are also greatly
prevented and greater regularity and smoothness of motion attained.
The invention is best described by aid of the accompanying drawing, in which
g is the hand driving chain. This passes over a wheel E¹ of the usual construction
to fit the chain, and of suitable diameter keyed on to the screw shaft E which also
actuates the lifting wheels. I is a double bar, the centre of which is pivoted on
the shaft E while its ends H overlap on each side the rim of the driving wheel E¹.
Each end bears a bell or guide H which directs the chain correctly on to the wheel,
at whatever angle it is held. The screw shaft bears two screws or worms CD of
opposite revolution, right and left respectively, which actuate two wheels A, B,
adjusted so as also to engage in each other. The left screw C is preferably nearest
the worm wheel A to which is attached the hand chain wheel, and actuates the
lifting wheel over which the lifting chain passes. The chain is delivered on to
the lifting wheel through a suitable guide, and engaging in sprockets so as to
prevent slipping or surging. The two worm wheels are geared together on the
rims opposite, and form a complete lock, to prevent the end or sliding motion
of the worm shaft dispensing with the end thrust. It also conveys the power of
the right screw back to the lifting wheel.
Thus each screw must at all times do an equal amount of work, as each one
pushes directly to the other, and therefore the weight is at all times borne by both.
The two worm wheels thus geared together on the rims of the opposite worm
wheels also geared together, form a lock to prevent the end or sliding motion of
the worm shaft, and dispense with the end thrust. The arrangement also conveys
the power of the right screw back to the lifting wheel.
The worms revolve in oil chambers, which are shown partially broken away in
the drawings, and the distribution of the work and of the strain over two opposed
motions in this manner reduces the friction to a minimum and enables the hoist
to be worked at a greater speed than the ordinary construction with the same
motive power.
In lowering any reasonable load there is really nothing to do but start the load
down by a sudden pull of the hand chain, and the weight will lower rapidly; the
operator then being simply required to allow the chain to run through his hand,
and stop the hoist instantly when required. This is a great advantage over the
old block, which sometimes requires almost as much power to pull down the weight
as to raise it.

page_text: Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is
1st The combination of the hand wheel (E') with the bells (H) guiding the chain
of the hand wheel, and swivelling about the handwheel (E) upon the same centre (E),
substantially as and for the purposes described.
2nd The combination in a hoist of the lifting wheel and its rigidly attached
spur-wheel (A) and a second spur-wheel geared to it with right and left hand
worms on the same driving shaft, driving the two worm wheels respectively,
substantially as described.