Improvements in Safety Devices for Electrically Operated Hoisting Apparatus.
Year: 1899

page_text: Date of Application, 13th Sept., 1899-Accepted, 4th Nov., 1899
COMPLETE SPECIFICATION.
Improvements in Safety Devices for Electrically Operated Hoisting
Apparatus.
I, HANS VON KRAMER, Electrical Engineer, of Clun House, Surrey Street,
Strand, in the County of London, 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 following statement: —
In electrically driven hoisting apparatus, such as electric lifts and cranes, the
electro-motor is usually so connected with the drum or other mechanical hoist-
ing gear, that when the load is allowed to descend, it will turn the motor back-
ward and cause it to act as a dynamo, and the electric current thus generated by
the descending load, may be utilized to prevent the mechanical hoisting gear
from running at a dangerous speed, which might cause injury to the entire lift.
To obviate this danger, I provide a safety or locking device, which prevents the
controlling lever of the starting and regulating resistances belonging to the
hoisting motor from being placed in such a position in lowering the load, that the
motor would be fed with current from the supply circuit in the same sense or
direction, (as regards its rotary effect) as that produced by the descending load,
which position of the controlling lever should be used only for commencing the
downward motion of an empty hook or of a very light load.
In the accompanying drawings, Fig. 1 is a section of a controlling apparatus
and locking device embodying my invention. Fig. 2 is a partial section at a right
angle to Fig. 1.
B, represents a hoisting motor,
RW, the starting and regulating controller belonging to the same.
A, the controlling lever having its fulcrum at E.
G, a mechanical brake acting on the armature shaft of the hoisting motor.
F, the brake lever situated between the said brake and the controlling lever.
When the controlling lever A is turned from its mid-position C (shown by
the drawing) to the left, it lifts the brake lever F and thereby releases the brake.
Consequently the load works the hoisting gear, the motor is short circuited by
means of a suitable switching device in the regulating controller, and current is
sent through the solenoid or magnet I of the locking device V.
This device chiefly consists of a solenoid H containing an iron core J and small
friction rollers a to facilitate smooth working. The lower end of the iron core J carries
a locking pin or bolt K passing through a radial opening L of the rail M. The
upper end of the core J is connected with a draw spring 6 fixed at m to the in-
terior of the casing c which covers and protects the locking device.
When the load is allowed to descend, and thereby to turn the hoisting motor,
the current generated by the same passes through the exciting coils d and draws
the core J into the solenoid H, thereby causing the pin K to pass through the
opening L and to enter the recess N of the stationary lug or attachment 0, Fig. 2.
As the locking pin K is now in the way of the arm P fixed to the controlling
lever A, the latter cannot pass beyond the line ES, when it is turned to the left
for lowering a load.

page_text: When the load has been lowered, and the controlling lever has returned to its
normal position C, current ceases to flow through the wire d, and the locking or
stop pin K is withdrawn by the spring b.
If the attendant now wishes to lower the empty hook, he can immediately
turn the controlling lever A. into its extreme left hand position, so as to occupy
the notch 6 or 7, and to cause current from the main to flow through the motor.
In this case the projecting arm P is allowed to pass the lug 0, because when the
motor is at rest, no current will flow through the wires d, and the controlling
lever will not start the motor until it has reached the notch 6 or. 7.
This arrangement therefore excludes the possibility of a load being lowered by
means of current from the main.
....
Fig. 1 includes also a diagram showing the connection of the solenoid wire d
with the hoisting motor. T indicates the armature, and U the field magnet of
the same, e the connecting wires.
Although the drawing shows an example of a mechanical brake acting on the
armature shaft of the hoisting motor, it will be understood that other known
forms of brake, including magnetic and electric brakes, may be used, and con-
nection established with the controlling lever A in such a manner, that the turn-
ing of the latter will apply or release the brake.
Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed, I declare, that what
I claim is
1. An electro-magnetic safety device for the controlling lever of the starting
and regulating apparatus belonging to an electric hoisting motor, said safety
device comprising a locking mechanism adapted to act when a load is being
lowered, so as to prevent current from the mains to flow through the motor in a
manner to co-operate with that produced in the motor by the descending load,
substantially as described.
2. In electrically driven hoisting apparatus of the type described, the combi-
nation of the starting and regulating apparatus, with a controlling lever adapted
to operate the same, an electro-magnetic bolt adapted to prevent the controlling
lever from being turned into the position serving to lower the empty hook by
means of the supply current, and means for placing the said bolt in its locking
position by utilizing the current produced by the hoisting motor when working
as a dynamo under the influence of the descending load.
3. In electrically operated hoisting apparatus, the method of preventing the
supply current from turning the hoisting motor during the descent of a load,
substantially as described.
Dated this 13th day of September 1899
FAIRFAX & WETTER,
Agents, 37 and 39, Essex Street, Strand, London.