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Патент USA US2404415

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July 23, 1946.
2,404,415
F. _F. TURNER
vOVERLOAD SAFETY SWITCH FOR ELEVATORS
Filed June 24, 1945
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Patented July 23, 1946
2,404,415
UNITED STATES PATENT OFFICE
2,404,415
OVERLOAD SAFETY SWITCH FOR
ELEVATORS
Floyd F. Turner, Toledo, Ohio, assignor to The
Haughton Elevator Company, Toledo, Ohio, a
, corporation of Ohio
Application June 2-4, 1943, Serial No. 492,117
1 Claim.
1
(Cl. 187—29)
2
This invention relates to a safety device to
which the car is suspended from the usual cables
prevent the starting of an overloaded elevator.
l3. Beneath beam Hi there is a switch beam
The object of the invention is to avoid the start
l4, securely fastened to beam I2 at its ends. A
ing of an elevator car when overloaded.
micro-switch I5 is mounted upon beam l4 and
When an elevator car is overloaded, and it is 6 is opened by relative movement of the central
started in the down direction, there is danger
portions of beams 12 and I 4. If necessary, the
that it cannot be stopped at the desired floor
micro-switch may comprise desirable and suit
but will continue downward into the pit, from
able means for multiplying the relative move
which it cannot be raised by the regular elevator
ment of the beams.
motor. This involves much trouble and delay 10
It will be readily understood that as soon as
an excessively loaded car is suspended from the
before the elevator is in use again, even where
no injury to the apparatus is inflicted.
cables, beam 12 is sprung slightly and its central
In speeding up production for war purposes,
portion moves upward relatively to beam l4,
heavy loading of elevators is unusually common,
which is not affected by the weight in the car.
In Fig. 2 there is shown an arrangement where
so that some safety device is needed. A device 15
in plate 16 is directly suspended from cables l3
which would in itself render the elevator inoper
and the distance between that plate and beam
ative upon there being exerted upon the floor of
I2] is governed by the degree of compression of
the car and excessive weight would not produce
springs l1. Switch I 8 is opened when the springs
the desired results. When an elevator is started
or accelerated upward, the inertia of the load in 20 are compressed unduly.
the car adds to the pressure due to the weight
Fig. 3 indicates another arrangement wherein
of load, so that the lifting device is normally
the ends of beam I22 are attached to the car by
arranged to have a starting or accelerating lift
bolts l9 and the springs 20 about bolts l9 are
ing force greater than the dead weight of the
compressed by the weight of the car, opening
maximum permissible load. For this reason, a 25 switch 2| on crossbeam 22 when the weight is
device set to render the elevator motor inoper
excessive.
ative when a downward pressure was exerted
These different arrangements do not exhaust
on the car equal to the weight of a normal load
the possibilities, but are by way of illustration
would stop the car immediately after starting
only. However, the arrangement shown in Fig. 1
even though the dead weight of the load was 30 is preferred because it is most easily applied to
much under that permissible, while a device set
many elevators now in use, and it operates sub
for the maximum permissible downward pressure
stantially independently of the location of weight
on the car would permit its starting when greatly
in the car.
overloaded, and would not even stop the motor
If the safety switch located and operated as
after the car started in the downward direction. 35 described was in a circuit necessary for both the
The purpose of this invention is to avoid these
starting and the continued operation of the motor,
di?iculties and prevent the starting of an over
it would be open to the objection noted above,
loaded car in either the upward or downward
because it would stop the motor when accelerat
direction while not interfering with the normal
ing with normal load, or else allow the starting
operation of the car when the load is not eX 40 of the motor with excessive load. To avoid this,
cessive.
the safety switch is located in a circuit the clos
Minor objects and the details of the invention
ing of which is necessary for starting the motor
will appear as the description proceeds.
but not necessary for the continued operation of
In the accompanying drawing forming a part
the car. One way in which this can be done is
of this speci?cation, Fig. l is a diagrammatic 45 indicated in Fig. 4.
In that ?gure the safety switch [5 is shown
elevation, partly in section, of an elevator car
showing one mounting of my safety switch.
located in a circuit 25 leading from power line
25 to power line 21 through switch coil 28 and‘
Figs. 2 and 3 are views similar to Fig. 1, but
starting switch 29. With safety switch 15 nor
showing different mountings of the switch. Fig.
4 is a wiring diagram indicating the relation of 50 mally closed, the closing of starting switch 29
my new safety device to the normal operating
energizes coil 28 and closes power line switches
30 and 3|, thereby energizing the motor of the
In the form shown in Fig. 1 there is indicated
elevator. At the same time switch 32 is closed
an elevator car In containing a load ll. At the
in bypass circuit 33, so that the current continues
top of the car there is shown a crossbeam l2 by 55 through coil 28, regardless of whether switch
mechanism of an electric elevator.
2,404,415
,
3
I5 is opened or closed, until the motor is stopped
in the normal manner.
In this way, it will be seen that the safety
switch operates to prevent the starting of the
4
In an electric elevator apparatus, a car having
a top cross member to which suspension cables
are centrally attached, said member being at
tached at its ends to rigid car frame parts and
being capable of ?exing intermediate its ends to
elevator motor when the car is overloaded, With Ci
assume a longitudinal bow when the car is sub
out interfering in any way with the operation of
jected to a predetermined overload condition, a
the car after the motor has started.
second cross member ?xedly connected at its ends
It will be readily understood that changes may
to the ?rst member near the ends of said ?rst
be made to adapt the arrangement to the wiring
system otherwise in use with the elevator, the 10 member and remaining substantially rigid during
?exing of the ?rst member, and a normally closed
essential feature illustrated being that there is a
micro switch in a circuit which must be closed
safety switch normally closed in a circuit essen
for the elevator to operate, said switch being dis
tial to the starting of the motor, and a bypass
circuit for the safety switch, the bypass being
provided with a normally open switch which is
closed by the starting of the motor.‘
Having disclosed the invention so that those
skilled in the art can make and use the same, ,
what I claim is:
posed adjacent to the longitudinal center of said
cross members and being operable by a ?exing of
the ?rst cross member relative to the other under
predetermined overload conditions to open the
switch.
FLOYD F. TURNER.
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