Single Chain Parallel Gear for Overside Cranes and the like.
Year: 1896

page_text: Date of Application, 2nd Mar., 1896
Complete Specification Left, 30th Oct., 1896-Accepted, 2nd Jan., 1897
PROVISIONAL SPECIFICATION.
Single Chain Parallel Gear for Overside Cranes and the like.
I, ALFRED HILLYARD MITCHELL 67 Worfield Street Battersea London, S. W.
Engineers Assistant do hereby declare the nature of this invention to be as
follows:-
In the annexed drawing, the traveller (T) can be made to move backwards or
forwards along the "jib," and by the parallel gear the weight (W) will always
remain at the same distance from T, and travel parallel to it.
The gear chain is fixed by a link to the centre of T, passes under P 3, over P 2,
under B 1 and is fixed at the centre of P 1.
B1 and B2 are two pulleys fixed on one frame, forming a double, single-sheave
block.
After leaving the lifting gear, the lifting chain (LC) passes under P-5 over B 2,
under P 4, & over T, the weight being suspended on the end, at W
B can be lifted by means of a ram, and a chain acting over P 1, or by a ram
acting vertically upwards on the balance weight (B W) direct, and if the lifting
force be removed B will fall in consequence of its own weight.
Let LC be fixed at the power end. If B be lifted 6 feet it will slack out
2 lengths of 6 feet each of chain from under B 1. and over P 2. and since B2 is
fixed to B, B2 will also be lifted 6 feet, and will take up 2 lengths of 6 feet each
of chain. Now the weight W acting over T will tend to pull in the chain given
out over P2 & T will therefore move 12 feet towards P 4.
But B 2 has taken up 12 feet of chain, therefore the length of chain between P 4
and P 3 will not have altered.
Therefore no chain will have passed over T.
That is the distance between T and W will remain the same.
But T has moved along the jib, and W has moved with it, and since the distance
between T and W has not altered, it must have travelled parallel to it.
Dated this 2ud day of March 1896.
ALFRED HILLYARD MITCHELL.
I ALFRED HILLYARD MITCHELL 67 Worfield Street Battersea London S.W.
Engineers Assistant do hereby declare the nature of this invention and in what
mauner the same is to be performed, to be particularly described and ascertained in
and by the following statement :-
In overside cranes the load is generally raised to the required height, and then
the chain which sustains it is pulled nearer to or further away from the crane post,
to travel the load in or out along the iib.

page_text: In those cranes using a single chain for raising the lond, which is suspended on
the end, this travelling in or out drops or raises the load. This latter lift or drop
is generally unnecessary and causes a waste of power.
According to this invention provide a means of keeping the load at exactly
the same height whilst travelling in or out, no matter at what distance from the
jib the load may be suspended, and I can also if necessary lift or lower the lond at
the same time that it is travelling in or out.
In order that my said invention may be more fully understood, and readily carried
into effect, I will proceed to describe the drawings left with the Provisional
Specification.
The figure shews a side elevation of the crane, the post being vertical and the
jib horizontal.
T is a traveller which can be moved along the jib. It consists of a carriage and
such travelling wheels as may be required, and in the centre is fixed one wheel
over which the lifting chain can work.
The gear chain is fixed by one end to the traveller, it then passes under ",
over under B, and is fixed at P
Band B, are two sheaves fixed in one frame, in the positions shewn, and
together they form one compensating block. Or B and 13 could be two soperate
single sheave blocks, connected together by a chain or other method, and provided
always the distance between them does not alter they will have the same compensating
effect as mentioned above and to be referred to hereafter.
The lifting chain, L C, after leaving the lifting gear, passes under P over 13,
unler P, and over the centre wheel of the traveller, as described above, the weight
or load being suspended at the end of the single chain at W.
If the lifting gear be made to take in ten feet of chain, it will lift W also ten
feet.
If the compensating block is then moved up or down, the traveller will move
along the jib.
If the compensating block be pulled down 3 feet, it will in falling take up two
lengths of 3 feet each of the gear chain passing under B, and this will draw the
traveller 6 feet along the jib.
At the same time it will slack out two lengths of 3 feet each of the lifting chain
passing over 13, and this 6 feet of chain will just compeusate the movement of the
traveller, so that the lond will remain suspended at the same height throughout,
and will travel parallel to the jib.
Another method of travelling in or ont would be net on the traveller itself, but
the compensating effect would be the same.
In cases where it is desired to reduce the travel of the compensating block in
proportion to the traveller, the chains may be passed over additional pulleys in the
block and crane post.
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. Overside cranes in which a lond, suspended on the end of a single chain at any
distance from the jib, is made to travel backwards or forwards along the said jib
and parallel to it, by means of a compensating block, connected by chains to the
traveller, substantially as described.
2. Compensating blocks for producing a parallel motion with a load suspended
to the end of a single chain substantially as described.
3. Overside cranes substantially as described and shown in the drawings.
Dated this 29th day of Octalian 1000
ALFRED HILLYARD MITCHELL.