IMPROVEMENTS IN CRANES
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by the said Alexander Grafton at the
Office of the Commissioners of Patents on the 28th August 1882.
ALEXANDER GRAFTON of N° 113 Cannon Street in the City of London.
"IMPROVEMENTS IN CRANES."
33
This Invention relates to certain improvements in the slewing or rotating gear
of either steam haud or power driven cranes and is applicable to cranes which
revolve about a fixed centre. It is of chief use in such cranes as are caused to
rotate by gearing acting upon a horizontal spur wheel or internal or external
toothed rings and consists in making entirely loose and distinct from the bed a
circular roller path and toothed ring or the two combined in one and dispensing
with. all rigid attachments between the bed and the horizontal slewing wheel or
circular toothed ring or roller path and allowing them to revolve subject to certain
resistance applied by friction only,
I obtain the necessary amount of resistance in various ways either by casting
the roller path solid with the bed or foundation plate or securing it thereto, turning
it outside and placing round it a toothed ring which is caused to bind outside the
roller bath and form a friction brake or I reverse it and bore the inside of the
roller path and place an internal toothed ring inside it and cause it to expand
and produce frictional resistance or I turn the roller path conical inside or out and
turn the ring to fit so that its weight will cause it to bind and thus secure the
necessary resistance or I construct the roller path and toothed ring in one or attach
them rigidly together and turn the upper and lower surfaces allowing the roller path
simply to rest on a turned face on the foundation plate carrying the whole or part
Thus secure
of the weight of the crane and load upon it by rollers or other means.
the necessary amount of frictional resistance to turn the crane but not sufficient to
cause any of the gearing to break.
These arrangements have the following advantages.
Firstly. In preventing the breaking of the teeth in the wheel or rack or of the
pinion gearing into it by the sudden stopping or starting of the crane or of the
rotating gear.
Secondly In causing the roller path upon which the crane revolves to be moved
slightly from time to time so as to equalize the wear upon it.
Thirdly. In facilitating the renewal of the parts when worn out without destroying
the whole foundation or bed plate.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Alexander Grafton in the Great Seal Patent Office on the
28th February 1883.
ALEXANDER
GRAFTON of 113 Cannon Street in the City of London
"IMPROVEMENTS IN CRANES."
This Invention relates to certain improvements in the Slewing or rotating gear
of (steam hand or power) cranes and is chiefly applicable to cranes which revolve
upon a roller path and are tied down by a central pin (as distinguished from those
which are suspended from a column) and which are usually slewed by applying
power to the Rollers upon which they turn This mode of slewing is however
defective as the adhesion of the rollers is dependent upon the load on the jib To
avoid this objection it is proposed to cause the crane to slew or rotate by toothed
gearing acting upon a horizontal spur wheel or an internal or external toothed
ring But toothed gear so used is liable to breakage by any sudden strain and to
avoid this liability is the object of my Invention.
With this object the Invention consists in making this toothed wheel or ring
(whether alone or combined in one with the roller path) entirely loose and
distinct from the bed or foundation plate (ie without any rigid attachments
thereto) and allowing the said ring or combined ring and roller path, to revolve on
the bed subject to certain resistance due to friction only.
I may obtain the necessary amount of frictional resistance in various ways.
I prefer to cast the toothed ring and the roller path in one, the upper and lower
sides of the roller path being parallel plane surfaces and allow the roller path
simply to rest on the bed or foundation plate with freedom to rotate thereon, the
rotating superstructure of the crane resting upon it by rollers. Or I may cast the
roller path solid with the bed or foundation plate and the toothed ring separate
therefrom, and apply the toothed ring (which is externally or internally toothed
according to its mode of use) around or within the roller path and cause it to bind
thereto. To cause the ring to bind upon or within the roller path I prefer to make
the roller path of conical form externally or internally as the case may be to form
a seat for the ring and make the ring conical to fit upon or within this conical seat
so that its weight will cause it to bind and produce the desired frictional resistance.
The adjacent surfaces of the toothed ring and roller path might however be
cylindrical (instead of conical as above mentioned) and the binding action be
produced by mechanical devices for tightening the ring upon or in the roller path,
but this mode is not to be preferred.
By either of the above modes of construction I thus obtain the necessary amount
of frictional resistance to enable the crane to be slewed without however opposing
sufficient resistance to sudden or heavy slewing strains which would cause any of
the gearing to break,
This frictional, independent ring, or ring and roller path has the advantage of:-
1st preventing breakage of the toothed gear by the sudden starting or stopping of
the slewing gear or the sudden slewing or stopping of the crane jib by contact with
any external object. 2nd Equalising the wear on the roller path and toothed ring,
by causing the same to be moved round slightly from time to time 3rd Facilitating
the renewal of the roller path and ring when worn out without sacrificing the
whole foundation or bed plate.

page_text: Figure 4 is a cross section of the bed with the roller path cast thereon and the
toothed ring separate and fitting externally on a coned seat on the roller path.
Figure 5 is a cross section of the converse arrangement. The same letters of
reference indicate the same parts in all the figures.
is the
A is the under carriage and B the revolving superstructure of the crane
roller path interposed between the superstructure B and the under carriage A and
upon which the rollers of the superstructure run.
In Figures 1, 2 and 3 the roller path is cast separate from the bed or foundation
plate a of the under carriage and has spur gearing D cast around its outer surface.
This roller path C has its upper and under faces turned plane and parallel, and it
rests loose upon a turned seat a¹ on the bed a which has a raised flange a² that
retains the roller path C in position whilst allowing it to revolve on its seat, the
weight of the superstructure and its load creating sufficient friction to prevent the
roller path being caused to slip by the normal slewing action of the crane. Should
however any undue strain be caused by the swinging of the load or the quick
stoppage or reversing of the gearing, the ring then slips, thus relieving the gear and
preventing breakage This occasional moving of the roller path to different
positions ensures its wearing evenly all round although the crane may not be
required to slew through the complete circle A pinion e on a shaft E gears into
the ring D for the purpose of slewing or rotating the superstructure B. This pinion
receives its motion from the crank shaft through double friction cones, bevel and
spur gear as shown. Referring to Figures 4 and 5, C is the roller path cast solid
with the bed plate a and D is the ring of teeth cast separately and bored or
turned conical to fit upon or in a corresponding conical seat turned or bored
around or within the roller path. In Figure 4 the ring is external and in Figure 5
it is internal, the angle of the cone in each case being such that the necessary
friction is obtained by the mere weight of the ring or the angle may be such that
the weight of the ring requires to be supplemented by a portion of the weight of the
superstructure. Having described the nature of the said Invention and the manner
of performing the same I declare that what I claim as the Invention to be protected
by the herein before in part recited Letters Patent is-1st The combination with
the slewing gear and with the under carriage of a crane, of a horizontal toothed
ring or wheel (whether in one with the roller path or not) resting upon the bed
and prevented by friction from rotating thereon except under sudden or abnormal
strains substantially as and for the purpose herein specified-2nd The employment in
a crane of an independent frictional roller path and toothed ring combined, inter-
posed between the under carriage and the superstructure and combined with the
slewing gear substantially as herein described and illustrated in Figures 1. 2. and 3
for the purpose specified--3rd The employment in a crane of an independent
frictional toothed ring fitting in or on a coned seat upon the roller path,
substantially as herein described and illustrated in Figures 4 and 5 for the purpose
specified.
In witness whereof I the said Alexander Grafton have hereunto set my hand
احمد
AD than und night
ALEXR. GRAFTON (L.S.)