CERTAIN IMPROVEMENTS IN CRANES
Year: 1845

page_text: HENDERSON'S SPECIFICATION.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, DAVID.
HENDERSON, of London Works, Renfrew, in the County of Renfrew, Civil
Engineer, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Royal Letters Patent under the Great Seal of the United Kingdom of Great
Britain and Ireland, bearing date at Westminster, the Tenth day of June,
in the eighth year of Her reign, did for Herself, Her heirs and successors,
give and grant unto me, the said David Henderson, Her especial license,
full power, sole privilege and authority, that I, the said David Henderson, my.
exors, admors, and assigns, and such others as I, the said David Henderson,
my exors, admors, or assigns, should at any time agree with, and no others,
from time to time and at all times during the term of years therein expressed,
should and lawfully might make, use, exercise; and vend, within England,
Wales, and the Town of Berwick-upon-Tweed, and also in the Islands of
Jersey, Guernsey, Alderney, Sark, and Man, and in all Her said Majesty's
Colonies and. Plantations abroad, my Invention of " CERTAIN IMPROVEMENTS
IN CRANES;" in which said Letters Patent is contained a proviso that I,
the said David Henderson, should particularly describe and ascertain the
nature of my said Invention, and in what manner the same is to be per-
formed, by an instrument in writing under my hand and seal; and cause the
same to be enrolled in Her said Majesty's High Court of Chancery within
six calendar months next and immediately after the date of the said Letters
Patent, as in and by the said Letters Patent, reference being thereunto had,
will more fully and at large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
David Henderson, do hereby declare that the nature of my said Invention,

page_text: and the manner in which the same is to be performed, are, with the aid
and assistance of the Drawings hereunto annexed, in which similar parts are
marked or referred to by similar letters or figures, ascertained and described as
follows, that is to say :-
My said Invention relates to those kinds of cranes called jib or derrick
cranes, and consists,―
Firstly, of a new construction or arrangement of the machinery attached
to such cranes, which is usually called the crab, and which new arrange-
ment I call a double crab, and, which I have invented for the purpose
of causing the strains upon the different chains or ropes of such cranes
to counteract or balance each other, and also for the purpose of enabling
persons using such cranes to move heavy bodies in the manner required
with greater ease and facility. The nature of my said. Invention will be
best understood from the following description of the several varieties of cranes
made with double crabs, according to my said Invention:-The first variety of
crane constructed with a crab according to my said Invention, which I shall
describe, is shewn at Figures 1, 2, and 3 of the Drawings hercunto annexed.
Figure 1 is a side view of this derrick crane. Figure 2 is a back view of the
stem and crab of the same crane, and Figure 8 is a side view of a portion of
the stem and crab taken on the side of the stem opposite to that represented
in Figure 1. A, A, is a double stem of the ordinary description, with a wheel
or pulley a at the top, and a double crab (herein-after described) attached to
it near the foot, and having pins at the top and bottom placed in suitable
bearings, upon which the stem turns, the top bush or bearing being fastened
by a double shoe to the stays S. B, B, is an ordinary moveable derrick or jib,
having a hinge or joint 6' at the foot, by which it is attached to the stem, and
also having a wheel or pulley 6 at the top, and saddles c, c, c, c, c, on the upper-
side to support the lift chain when there is no strain upon it. D, D, is the
lift chain with an ordinary hook d at the loose end, which passes over the
pulley or wheel 6, at the upper end of the derrick, and down the upper side of
the derrick to one of the barrels of the crab to which it is made fast.
E, E, is the derrick chain, one end of which is attached to the upper end of
the derrick; and I prefer to fasten it at such a distance below the pulley as
will cause the weight to be lifted to assist in counteracting the tendency of the
derrick to bend or deflect. The derrick chain passes over the pulley a and
down the inside of the stem A, A (ás shewn in Figure 2 and also in Figure 1,
at a place where part of the stem is removed for that purpose), to the other
barrel T of the crab, and to which it is made fast. H, H, are winch handles
fixed on the ends of the spindle W, working in bushes fixed to the stems A, A,
and on which is a pinion r, which in the ordinary way works into the spur

page_text: whcel F attached to the spindle of the lift barrel z, or into the spur wheel G,
at pleasure,.according as the weight to be lifted is great or small, and which
spur wheel G. is fixed on another spindle N, on which is another pinion I,
which works into the spur wheel F. By turning the handle H (the clutch
herein-after described being out of gear) the spindle and lift barrels only
will be put in motion, and a weight attached to the end of the chain at d may
be thus raised or lowered at pleasure in the same way as by an ordinary crane,.
the arrangement just described (usually called a crab) being the ordinary and
well-known arrangement generally attached.to. cranes. On the other end of
the spindle of the lift barrel is a loose spur wheel K. formed with a clutch V on
the outside. of it, through which the spindle will turn without turning the
wheel K. To the end of the spindle is attached another clutch X, which
revolves with the spindle, and which, when closed or pushed into gear
with the clutch .formed on the outside of the wheel K, fixes that wheel
upon the spindle and causes it to turn with it. To one end of the spindle
of the derrick chain barrel T is fixed a spur wheel M which works.
into the spur wheel K. The left chain and derrick chain must in every case.
be wound upon their respective barrels in such a way, that when the clutches
are in gear and the crab in motion, the derrick chain will be wound on to its
barrel when the lift chain is wound off its barrel, and vice versa. The derrick.
chain barrel T is made tapering, as shewn in Figure 2, and in this and in
every variety of my crane, it is to be tapered in such a way that when the
clutches are closed and the two barrels are in gear with each other and in motion,
and the derrick is thereby raised by winding up the derrick chain, the space
through which the raising of the derrick would lift the weight if the lift
barrel were stationary shall be equivalent to the space through which the lift
chain, which is at the same time unwound from off the lift barrel, would
lower the weight if the derrick were not raised, in order that the weight may
inove in a horizontal direction towards the stem, or as nearly so as may be,.
and also in such a way that when the clutches are closed and the two barrels.
are in gear with each other and in motion, and the. derrick is thereby lowered
by letting out the derrick chain, the space through which the lowering of the
derrick would lower the weight if the lift barrel were stationary shall be
equivalent to the space through which the lift chain, which is at the same
time wound up on the lift barrel, would raise the weight if the derrick were
not lowered, in order that the weight may move outwards from the stem in a.
horizontal direction. O is a catch or pall for fixing or locking the derrick
barrel, so as to support the derrick when the derrick barrel is not kept in
gear by the clutch. X. This catch will allow, the derrick.to be raised without

page_text: its being turned out; but when the derrick is to be lowered the catch must be
turned back. In order to use this crane the derrick is to be turned towards
the weight to be lifted, and then the derrick must be lowered or raised so as
to bring the hook d directly above the weight, and then the derrick is to be
fixed in that position by the catch O and the clutch thrown out of gear.
The lift chain is then to be drawn out, and the hook being fastened to the
weight, it is to be drawn up to the required height by means of the crab
worked in the ordinary way. If the weight is to be deposited at the same
distance from the stem of the crane as it is taken up, it is only necessary to
turn the crane round to the proper position and lower the weight in the
ordinary manner. But when the weight is required to be deposited in a place
nearer to or further from the stem of the crane, the clutch must be closed so
as to bring the derrick chain barrel into gear with the lift barrel, and then
the derrick is to be raised or lowered as the case may require. If the weight
is to be deposited nearer to the stem (in which case the catch need not be
turned out) the derrick must be raised until the weight is brought into the
required position. If the weight is to be deposited further from the stem the
catch must be thrown back and the derrick lowered, so as to remove the
weight to the required distance from the stem. The intention of this is, that
the tendency of the motion of the derrick to communicate a perpendicular
motion to the weight in one direction may be counteracted by the winding or
unwinding of the lift chain, so that a horizontal motion only, in the direction
required, may be communicated to the weight which has been lifted.
A second variety of crane constructed with a crab, according to my said
Invention, is shewn in Figures 4, 5, and 6. Figure 4 is a side view of this
derrick crane, Figure 5 is a back view of the stem and crab of the same
crane, and Figure 6 is a side view of a portion of the stem and crab taken on
the side of the stem opposite to that shewn in Figure 4. The several parts of
the crane shewn in these three latter Figures are marked with the same letters
as the corresponding parts of the crane shewn in Figures 1, 2, and 3; and
the first and second varieties of cranes with my double crab are the same,
with the exception of the differences which I shall now describe. These.
differences consist in this, that the end of the derrick chain E, E, E, is not
fastened directly to the derrick near the top, but is fastened to the pin at the
top of the stem, and passes round a pulley e, which is fastened to the derrick
near the top, and then passes to the pulley a at the top of the stem, and
from thence down the inside of the stems to the derrick barrel T, as shewn
in Figure 5. The spur wheels K and M (shewn at Figure 5) are of different
dimensions and in different proportions to each other from those shewn in

page_text: Figure 2, the spur wheel K, Figure 5, upon the end of the lift barrel, being
twice the diameter of the spur wheel M upon the end of the derrick barrel,
so that when the two barrels are working together the derrick barrel shall
make two revolutions for one revolution of the lift barrel, so as take up the
extra length of chain which must be used to lift the derrick in consequence of
the additional pulley es being introduced in this variety of my crane. The same
effect may however be produced by any other arrangement of the machinery of
the double crab, which will cause the derrick barrel, when working in conjunc-
tion with the lift barrel, to take up the extra length of chain, which must be
used to lift the derrick in consequence of the additional pulley being
introduced. In this second variety of crane the thrust on the stem from the
chain E, E, E, is much reduced, as with the same load the strain on the chain.
E, E, E, Figure 4, would be about one half of the strain on the chain E, E,
in Figure 1. This arrangement of the derrick chain is well known, and
therefore I do not claim the same as of my Invention, and I have only
described it in order to shew the manner in which the same may be applied
to my derrick crane constructed with my double crab.
A third variety of crane constructed with a crab according to my said
Invention, is shewn in Figures 7, 8, and 9 of the Drawings hereunto annexed.
Figure 7 is a side view of this derrick crane, Figure 8 is a back view of the
stem and crab, and Figure 9 is a side view of a portion of the stem and crab,
taken on the side of the stem opposite to that shewn in Figure 7. The
several parts of the crane shewn in these three latter Figures are marked
with the same letters as the corresponding parts of the two varieties of cranes
shewn in Figures 1, 2, and 3, 4, 5, and 6, and this third variety of cranes is.
the same as the first variety herein-before described, except in the respects
herein-after mentioned; that is to say, that in this third variety of crane the
derrick chain E, E, E, is fastened to the pin at the top of the stem and passes
round the pulley e², which is fastened to the derrick in the same way as in
the second variety of crane shewn at Figure 4. But in this third variety the
spur wheels K and M of the crab are to bear the same proportions to each
other as the spur wheels K and M of the first-described crane. And in this
third variety of crane the lift chain D, D, D, is differently arranged, being
fastened to the upper end of the derrick and passing from thence downwards
and round a pulley or snatch block d, Figure 7, to which is attached a hook-
for supporting the weight; and from the snatch block the chain is carried up
to and over the pulley 6 at the top of the derrick, and from thence it passes
along the upper side of the derrick to the lift barrel z, as already described in
Figures, 1 and 4. In this construction the thrust on the derrick from the lift

page_text: chain is much reduced, as with the same load the strain on the chain
D, D, D, in Figure 7 would be about half of the strain on the chain D, D,
in Figure 1. This arrangement of the chain D, D, D, although not known
or used in derrick cranes, yet is well known and in common use on other
cranes, and therefore I do not claim the same as of my Invention, and I have
only described it in order. to shew the manner in which it may be applied to
derrick cranes constructed with my double crab.
A fourth variety of derrick crane constructed with my double crab is shewn
in Figures 10; 11, and 12 of the Drawings hereunto annexed. Figure 10 is
a side view of this fourth variety of derrick crane.; Figure 11 is a back view of
the stem and crab; and Figure 12 is a side view of a portion of the stem and
crab, taken on the side of the stem opposite to that shewn in Figure 11:
And this fourth variety of crane differs from the first variety herein before
described in the following particulars :-Instead of the single pulley a at the
top of the stem in Figure 1, there must be two pullies a and a³, as shewn at
the top of the stem A, A, Figure 10. The derrick chain fastened to the
derrick, in the same way as mentioned in the first described crane, is to. pass
over the pulley a, Figure 10, and down to the derrick barrel, to which it is be
fastened, as before described. The derrick barrel of this crane must be tapered
in a greater degree (as shewn at T, Figure 11) than the derrick barrel shewn
in Figure 2. The lift chain is to be fastened to the upper end of the derrick
and passed downwards round a pulley or snatch block d*, Figure 10, and over
the pulley b³, Figure 10, in the same manner as in Figure 7.. The lift chain
then (instead of being carried down the upper side of the derrick) passes
direct to the top of the stem and over the pulley a³, and from thence down
the inside of the stem to the lift barrel z (Figure 11), to which it is fastened
in the same manner as in Figure 1. The effect of this arrangement is to
free the derrick entirely from that part of the thrust upon it occasioned by
passing the lift chain down its upper side, and it also frees the derrick chain
E, E, from as much of the strain on it as is equal to the strain on the lift
chain D. In this arrangement the snatch block on the lift chain is necessary,
as it reduces the strain on the lift chain, which strain, when no snatch block is
used, as in Figure 1, would be greater than the strain on the derrick chain
when the derrick is in an elevated position; besides which, if the lift chain
were carried (as in Figure 1) from the top of the derrick to the top of the
stem, the derrick would run up to the stem; but when a snatch block is used,
the-strain on the lift chain is reduced one half, so that its amount is less than.
the strain on the derrick chain E, when the derrick is in the highest position
required in practice, and the derrick will not run up to the stem. The same

page_text: effect (or nearly so) may, however, be produced without the snatch block, by
making the derrick not less than twice the length of the stem.
A. fifth variety of crane, constructed with a crab according to my said.
Invention, is shown in Figures 13, 14, and 15 of the Drawings hereunto
annexed. Figure 13 is a side view of this variety of derrick crane..
Figure 14 is a back view of the stem and crab; and Figure 15 is a side view.
of a portion of the stem and crab, taken on the side of the stem opposite to
that shewn in Figure 13. This crane is the same as that shewn in Figures
10, 11, and 12, except that there is a snatch block e³, Figure 13, used on the
derrick chain E, E, in the same manner as shown in Figures 4 and 7, whereby'
the strain on the derrick chain is reduced one half..
.. A sixth variety of crane constructed with a crab, according to my said'
Invention, is shewn in Figures 16, 17, and 18 of the Drawings hereunto.
annexed. Figure 16 is a side view of this variety of derrick crane. Figure 17.
is a back view of the stem; and Figure 18 is a side view of a portion of the
stem and crab, taken on the side of the stem opposite to that shewn in
Figure 16. In this form of crane the stem is to be held up by four guy or:
tie rods (or they may be ropes or chains); and the stem is of such a height
as to allow the end or top. of the derrick to pass beneath the guy rods or
:cords, whereby the derrick is permitted to revolve freely round under them.
The form of the crane shewn in Figure 16 is nearly the same as that shewn
in Figure 1, with the exception of the relative heights of the stem and derrick,
and the manner in which the stem is supported.
Either of the six forms of crane herein-before described may be fixed to a
wall, or under a horizontal beam of a building by a bracket, or shoe, instead of
being fixed by stays or guys, as before described. And either of the six
arrangements of chains and crabs may be applied to a pillar or column of a
building; in which case the double stem described may be used or it may be
dispensed with, and the pulley or pullies at the top of the stem may be
fastened to the pillar or column, and the bottom of the derrick fastened to, the
foot of the pillar or column; but in this case the pulley or pullies and crab
must be so fixed as to be moved freely round the top and bottom of the pillar
or column by the action of the derrick. Either of the plans described may
also be applied to a fixed post. and used as post cranes, but in that case a
collar must be added to the bottom of the stem through which the post can
pass up to the top of the stem. My improved double crab, or arrangement
for producing the horizontal traverse of the weight above described, may be
separated from the stem and placed at a distance from it, the chains passing
under pullies below the stem from the crane to the crab. It is also to be

page_text: understood that my improved crab for cranes may be worked by steam or any
other description of motive power. And note, that ropes may be used in
place of the lift and derrick chains herein-before described. And note also,
that the proportions of the barrels of the crab must always bear relation to the
proportions of the crane. And I would further observe, that the arrangement
and construction of the double crab for producing the effects herein-before
mentioned may be varied without altering the principle of my said Invention,
but that in every case in which a derrick crane is constructed with a crab,
according to my said Invention, the machinery of the double crab must
be constructed and arranged with the wheels and barrels thereof of such
sizes and proportions and in such manner that when the derrick and
lift barrels are both working in gear, the effect will be to produce
a motion of the lifted weight in a horizontal direction, as herein-before
described.
And I hereby declare that I do not claim as of my Invention any of the
parts of the machinery herein-before mentioned separately or apart from the
combination thereof herein-before described.
And I also declare that I claim to have invented the mode herein-beforo
described and shewn in various forms, whereby the lift and derrick barrels of
a derrick crane are made to move simultaneously, and by their combined
action produce a simple horizontal motion of the weight lifted, in manner
herein-before described.
In witness whereof, I, the said David Henderson, have hereunto set my
hand and seal, this Sixth day of December, in the year of our Lord
One thousand eight hundred and forty-five.