Improvements in a Means of Lowering the Load of Cranes or Hoists Driven by Electro-motors.
Year: 1898

page_text: Date of Application, 25th June, 1898-Accepted, 24th Sept., 1898
COMPLETE SPECIFICATION.
Improvements in a Means of Lowering the Load of Cranes or Hoists
Driven by Electro-motors.
FREDERICK HENRY ROYCE, and ERNEST ALEXANDER CLAREMONT, both of Cooke
Street, Hulme, Manchester, in the County of Lancaster, Electrical Engineers,
do hereby declare the nature of this invention and in what manner the same is
to be performed, to be particularly described and ascertained in and by the fol-
lowing statement:-
This invention relates to improvements in a means of lowering the load of
cranes or hoists driven by electro-motors.
Heretofore the load on cranes or hoists actuated by electro-motors has been
lowered by means of a brake operated by hand and altogether independent of the
motor and has consequently been jerky and uneven in its action.
The object of this invention is to provide a means of lowering the load on a
crane or hoist driven by electro motors that is dependent on the action of the
motor itself and also to render the operation of lowering less jerky and uneven
in action.
The accompanying drawing is a diagram of the general arrangement.
In applying our invention to cranes or hoists we make use of a suitable switch d
and variable resistances е е for short circuiting the armature 6 of the
lifting motor.
The switch d is so arranged that the contact makers i and i, which are suitably
joined together can be moved in either the direction f or g.
When it is desired to lower the load the contacts and of the switch d are
moved in the direction f and the contact i first connects j to k thus fully exciting
the magnets a of the lifting motor. On being still further moved in the same
direction the contact maker i connects j to exciting the solenoid p of the
magnetic brake c and releasing the same. At the same time or immediately
before the contact maker i, joins m to n thus dead short circuiting the armature b
whereupon the load on the crane or hoist drives the motor as a dynamo and
generates current in the armature windings and the load is lowered by its own
weight slowly.
If it is desired to increase the speed of lowering this can be done by still
further moving the contacts i and 4 of the switch d in the direction f so that
the contact connects m to n, and then successively " and iv as
required thereby inserting the resistances e e₁ and in series with the
lifting motor armature b. The more resistance which is inserted the quicker
will be the speed of lowering.
If a mechanical instead of an electrical brake be used it must not be taken off
until the armature b is short-circuited.
When it is desired to raise the load the contacts
moved in the direction g and the resistances e e₁ en
e naval
and of the switch d are
serve as starting resistances

page_text: Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, we declare that what we
claim is:-
First. The method of lowering the load of cranes or hoists by means of short
circuiting the armature substantially as described.
Second. The insertion of resistance in series with the short circuited armature
in order to increase the speed of lowering substantially as described.
Dated this 23rd day of June 1898.
E. A. CLAREMONT.
F. H. ROYCE.