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Патент USA US3097885

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July 16, 1963
|_. G. KAPLAN
3,097,875
CONTROL MECHANISM FOR ELECTRICAL-LY OPERATED LIFTERS
Original Filed Dec. 23, 1957
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July 16, 1963
3,097,875
L- G. KAPLAN
CONTROL MECHANISM FOR ELECTRICALLY OPERATED LIFTERS
Original Filed Dec. 23, 1957
LE’?
2 Sheets-Sheet 2
INVENTOR.
Low 5 G. KAPLAN
BY
United States Patent 0 ” ice
3,097,875
Patented July 16, 1963
1
2
3,097,875
sive speed of the actuating motor for the lifter may be
CONTROL MECHANISM FOR ELECTRICALLY
OPERATED LIFTERS
Louis G. Kaplan, Evanston, IlL, assignor to Cullen
Friestedt ~Company, Chicago, Ill., a corporation of
Illinois
Original application Dec. 23, 1957, Ser. No. 704,385, n'ow
Patent No. 2,959,411, dated Nov. 8, 1960. Divided
and this application Mar. 2, 1959, Set. No. 796,506
1 Claim. (Cl. 294-67)
The improved control mechanism comprising the pres
avoided during closing movements of the lifter jaws.
According to the present invention, and in order to
accomplish the above aims, it is contemplated that auto
matic means be provided for introducing a resistance into
the motor circuit vwhen the motor controls are set for
operation of the motor in one direction only. vWhen
such controls are set for operation of the motor in the
opposite direction, such automatic means is effective to
10 remove the resistance from the motor circuit and allow
the motor to operate at full line voltage. Still further,
ent invention has been designed for use primarily in
according to the invention, it is proposed that the re
connection with lifter mechanisms of the type shown and
sistance element or resistor be mounted directly on or
described in my copending application Serial No. 704,385,
adjacent the motor, or at least that it be mounted on
?led December 23, 1957, now US. Patent No. 2,959,411, 15 and become a permanent part of the lifter assembly.
granted on November 8, 1960, and entitled “Shock Ab
By such an arrangement, a resistor of the proper ohmic
sorbing Linkage Mechanism,” of which ‘application the
value for any given lifter installation may be selected
present one is a division.
The invention is however ca
pable of other uses and the same may, if desired, with
so that it may become individual to that particular lifter
installation and to no other so that intricate control panel
suitable modi?cation where required, be employed for 20 wiring is not necessary where a large variety of litters
other purposes in connection with electrically powered
or other motor-operated instrumentalities are to be op
mechanism, particularly in instances where reversible
erated, for example, from any given overhead crane
electric motors are concerned which require a greater
assembly. The circuit of the present invention contem
torque when the motor is running in one direction than
plates the use of a relay circuit including a high im
when it is running in the opposite direction. The inven 25 pedance magnet coil which is arranged in the circuit in
such a manner that certain recti?er and limit switch
tion has, for illustrative purposes, ‘been illustrated and
mechanism employed in connection with the invention
described herein as being operatively associated with a
will be subject to extremely low current ?ow, thus mak
litter mechanism of the type shown in my copending ap
ing possible the use of small commercial type limit
plication cited above but it will be understood that various
other uses are contemplated and that irrespective of the 30 switches and inexpensive radio type recti?ers.
Yet another advantage accrues from the provision of
particular use to which the invention may be put, the
the present invention. The usual procedure for reducing
essential features of the invention remain substantially the‘
same.
motor torque or for stopping the operation of a motor
when a litter mechanism has completed its stroke, or
Lifter mechanisms of the type shown and described in
the above~mentioned copending application, as well as 35 when it has met with an obstruction, is to provide a
limit switch, or a pair of such switches, on the lifter
a wide variety of other ‘lifter mechanisms having opposed
jaws capable of relative outward and upward swinging
motion for jaw opening and jaw closing purposes, fre
mechanism, such switch or switches being electrically
ing closing movements of the jaws. The structures in
power leads including self-winding pulleys and the like,
connected to the motor control panel. ‘Since the con
trol panel is frequently mounted at a remote point, for
quently encounter a condition wherein‘the actuating mo
tor for the jaw mechanism runs at excessive speeds dur 40 example, in the cab of the overhead crane, various
are necessary and greatly increase the cost of the equip
ment. According to the present invention, by mounting
is appreciable and, under no-load conditions when the
ing all of the electrical equipment, including the resistor,
jaws are swinging downwardly and inwardly toward each
other to e?ect their closing movements, the moment of 45 all of the electrical equipment, including the resistor,
limit switch or switches, recti?er, relay devices etc., on
torque which is applied to the rock-shaft or other jaw
volved, being relatively massive, the weight of the jaws
the lifter, with only the reversing switch being retained
actuating member, under the in?uence of gravitational
force, is sufficiently great that this torque will be ap~
plied through the train of driving mechanism leading to
the motor shaft, thus causing excessive motor speed.
This condition is especially prevalent in connection with
a litter mechanism which utilizes a heavy angle bar type
ner indicated being among the principal objects of the
gripping member at the outer ends of the jaw arms
invention, other objects and advantages of the invention,
on the control panel, a very material reduction in equip
ment is attained.
The provision of a control mechanism which will
accomplish the above-noted functions in the novel man
where the gravitational force exerted thereby through
not at this time enumerated, will become more readily
the arms to the rock-shaft or other actuating member 55 apparent as the following description ensues.
is comparatively great by virtue of the distance of the
In the accompanying two sheets of drawings forming
gripping jaws from the pivotal points of the swinging
a part of this speci?cation, one exemplary form of the
invention has been shown.
jaw arms and the relatively large moment of gravita
tional force applied to the arms by virtue of such dis
In these drawings:
FIG. 1 is a fragmentary vertical sectional view taken
tances. Where series wound direct current motors are 60
through a litter assembly in the vicinity of the power actu
concerned, a light load, a zero load, or a negative load
ated gear driving mechanism therefor and showing a limit
such as may be applied to the motor under the condi
switch which forms a part of the control system of the
tions outlined above may allow the motor to “run away”
present invention operatively applied thereto; and
and destroy itself, while at the same time there is likeli
FIG. 2 is a circuit diagram for the electric motor as
hood that the article to be lifted will become damaged 65
sociated with the lifter and illustrating the improved con
due to the relatively high velocity of the jaws at the
trol mechanism ‘of the present invention operatively as
moment of engagement. The present invention is de
sociated therewith.
signed .to overcome the above-noted limitation that is
Referring now to the drawings in detail and in particular
attendant upon the use of litter mechanisms of the type 70 to FIG. 1, for exemplary purposes the control mechanism
described above and, toward this end, it contemplates
of the present invention is shown as being operatively ap
the provision of a novel control means whereby exces
plied to a lifter of the general type shown and described
3,097,875
3
in my abovementioned copending application. Only such
portions of the lifter mechanism as are necessary to a
4
the pivot point 61 and with the inner link member 64
being connected to the pivot point 58. The limit switch
and which may create a condition of mechanical motor
overload have been illustrated herein and for a detailed
62 is ?xedly mounted on the outer link member 66 and
is designed for engagement and actuation under the con
trol of a collar 68 carried by the inner link member 64.
description of the entire mechanism and its mode of
operation, reference may be had to such copending ap
actuating ?nger 76 (see also FIG. 2) which is positioned
general understanding of the conditions which may arise
Toward this end, the limit switch 62 is provided with an
in the path of movement of the collar 68 so that when the
latter moves to the left relative to the link member 64 as
The lifter involves in its general organization an elon
gated supporting element 1t), a pair of jaw assemblies 11 10 seen in FIG. 1, the collar will engage the finger 70 and
actuate the limit switch 62. Such movement of the collar
and 12, a reversible electric motor M, and a power train
into engagement with the actuating ?nger 71) takes place
13 extending between the motor and jaws for conjointly
when compressional forces are applied to the opposite
shifting the latter toward and away from each other in re
ends of the link assembly 60' after an external shock is
sponse to the operation of the motor. At suitable spaced
points along the supporting element 10 there are provided 15 encountered by the lifter jaws 11 and 12, as, for example,
when these jaws [during outward swinging movement there
a series of spaced attachment or pivot lugs 14, only one
of under the motivating in?uence of the motor M en
such lug being disclosed herein. Each lug 14 has pivotally
counter
an adjacent massive object, or when the jaws 11
connected thereto on opposite sides thereof one of the
plication.
pairs of jaw assemblies 11 ‘and 12. The two jaw assem
and 12 become wedged between two opposed immobile
jaw section 16 is comprised of a pair of laterally spaced
described presently.
blies are identical in construction and each is in the form 20 adjacent objects. The limit switch 62 is provided with a
pair of normally open contacts 01 (FIG. 2) adapted to
of a composite assembly including an upper or proximate
become closed under the in?uence of the actuating ?nger
jaw section 16 and a lower or distal jaw section 18 hinged
70. The circuit connections for the limit switch will be
ly connected as ‘at 20 to the upper section. The upper
As previously stated, the reversible electric motor M is
?at metal bars 22 and 24, the upper ends of which strad 25
of the series wound, direct current type wherein reversal
dle the pivot lugs 14, while the lower section 118 is in the
of the direction of current ?ow through the motor armature
form of a single ?at metal bar, the upper region of which
will effect reversal of the direction of rotation of the motor
extends between the bars 22 and 24. Toothed sector
shaft, this shaft being designated at 74 in FIG. 2. Re
means 26 on the lower section =18 is adapted to cooperate
with a locking bar 28 in such a manner that the angular 30 versal of the direction of rotation of the motor shaft 74
will, of course, cause reversal of the output shaft 38 of the
position of the lower jaw section relative to the upper jaw
gear reduction device 36 and of the entire power train
section may be adjusted. The lower ends of the lower
mechanism 13. Such selective reversal of the current ?ow
jaw sections 18 carry opposed angle bar gripping mem
through the armature circuit will control the direction of
bers 30.
The electric motor M by means of which the jaws 11 35 movement of the lifter jaws 11 and 12.
In order to prevent excessive motor speeds during in
and 12 are actuated is preferably of the reversible direct
ward swinging movement of the jaws '11 and .12 under the
current type. The motor includes a casing 32 which is
in?uence of gravitational forces acting on the jaws, means
secured as at 34 by welding to the supporting member 10.
The motor M has operatively associated therewith a gear 40 are provided whereby full line current will be applied to
the armature circuit with the current ?owing through the
reduction mechanism 36 having an ‘output shaft 38 carry
circuit in a direction to cause clockwise rotation of the
ing a pinion 40‘ constituting one element of the previously
rock-shaft as viewed in FIG. 1 and consequent opening
mentioned power train 13. The power train 13 which ex
movement of the jaws 11 and :12. The motor M will
tends between the output shaft 38 of the gear reduction
thus be ‘driven under full power. However, when the
device 36 and the jaws 11 and ‘12 is comprised of a set of
gearing including the pinion 40 and a linkage mechanism 45 direction of current flow through the armature circuit is
42. The gearing, in addition to the pinion 40, comprises
a gear segment 44 which meshes with the pinion 4t} and
which is keyed to a rock-shaft 46. Also keyed to the
rock shaft 46 are a pair of bifurcated crank arms 50 and
52 which extend radially outwardly from the rock shaft
46 in opposite directions. The distal end of the crank
arm 50 is pivotally connected as at 53 to one end of a
thrust link 54, the other end of the link being pivotally
connected as at 56 to a medial region of the upper jaw
section 16. The distal end of the crank arm 52 is pivotally
connected as at 58 to one end of a spring biased lost mo
tion link assembly designated in its entirety at 60", the
other end of the link assembly being pivoted as at 61 to
a medial region of the upper jaw section 16 of the jaw 11.
The details of the link assembly 60 constitutes the sub
ject matter of my above-mentioned patent and no claim is
made herein to any novelty associated therewith. Since
reversed so that the power [train 13 is actuated to cause
counterclockwise rotation of the rock-shaft 46 to effect
closing movement of the jaws '11 and 12, automatically
operable means are provided for introducing a resistance
50 element into the armature circuit so that the motor will
be driven under reduced power. The circuit diagram of
FIG. 2 illustrates schematically the manner in which such
a resistance is automatically introduced into the arma
ture circuit of the motor and it also illustrates the man
ner in which the limit switch 62 is capable of reducing
the ?ow of current through the armature circuit when the
lifter jaws L11 and 12 encounter opposition as previously
outlined.
Referring now in detail to FIG. 2, full line current may
be applied to the armature circuit of the motor M from
the positive side of the line, through lead 17, ?eld winding
F of the motor M, lead 19, a reversing switch 80, leads
21, 23, armature A of the motor M, leads 25, 27, a pair
of normally closed contacts c2 associated with a relay
the link assembly involves in its general organization a
certain limit switch mechanism, designated in its entirety 65 magnet M1, leads ‘31, 33, 35 and reversing switch 80 to
at 62, which is pertinent to the control mechanism of the
the negative side of the line. Current ?owing through
present invention, only this switch mechanism and such
the armature of the motor M in this direction will move
portions of the link assembly as serve to actuate the same
the rock-shaft 46 in a clockwise direction as seen in FIG.
will be described herein and reference may be had to such
1 so as to cause opening movements of the jaws :11 and
patent for a more detailed description of the link assembly. 70 12. Upon operation of the reversing switch 80 in such
It is deemed su?icient for purposes of disclosure herein
a manner as to reverse the direction of current flow
to state that the link assembly 60 includes an inner link
through the armature of the motor M, a circuit will exist
member 64 and an outer encompassing link member 66.
from the positive side of the line, through lead :17, ?eld
The two link members bear a telescopic relation to each
winding F of the motor M, lead 19', the reversing switch
other with the outer link member 66 being connected to 75 80, leads 35, ‘37, relay magnet M1, leads 39, 41, a unidi
3,097,875
rectional device SR which may be in the form of a seleni
um recti?er, leads 4'7, 49, 21, and reversing switch 80 to
the negative side of the line. Energization of the relay
magnet M1 will cause opening of the contacts 02, thus
establishing a circuit extending from the positive side of
the line, through the reversing switch 80, leads 35, 33, 51,
resistance R, leads S3, 25, armature of the motor M, leads
6
contemplated. The form illustrated herein is only one
which has been developed for commercial application of
the system.
The invention is not to be limited to the details de
scribed, since these may be modi?ed within the scope
of the appended claim without departing from the spirit
of the invention.
23, 21 and ‘reversing switch 80 to the negative side of the
Having thus described the invention what I claim as
line. The ohmic value of the resistor R may be selected
new and desire to secure by Letters Patent is:
according to engineering requirements to produce a de 10
In a lifter construction of the character described, a
sired voltage drop across the resistor and reduce the cur
lifter framework, a pair of cooperating lifter jaws pivoted
rent ?ow through the motor armature to such an extent
to said framework and each swingable about a horizontal
that over-speeding of the motor M under the in?uence of
axis from an elevated open jaw position to a lowered
gravitational forces acting upon the jaws V311 and 12 during
closed jaw position wherein they may engage an article
closing movements thereof will be avoided.
15 to be lifted therebetween, a crank arm interposed between
The contacts c1 of the limit switch 62 are disposed in
said lifter jaws for actuating the same, a lost motion con
shunt relationship with the unidirectional device SR so
nection between said crank arm and one of said lifter
that when the actuating ?nger 70‘ is engaged by the collar
jaws, ‘a limit switch operable under the control of said
68, and the contacts 01 ‘become closed, the unidirectional
lost motion connection, said limit switch including a pair
device SR will be bypassed and a shunt circuit passing 20 of normally open contacts adapted to become closed when
through lead 43, contacts 01, leads 45, 39, and magnet M1
the limit switch is operated by said lost motion connec
will be completed, thus opening the contacts c2 and re—
tion, a reversible series wound direct current motor car
storing the circuit through the resistor R and motor
ried by the tramework :for moving said jaws between their
armature so as to reduce the power output of the motor
open and their closed positions, a power train operatively
M. Such a condition will obtain, for example, when
connecting said motor and jaws, an armature circuit for
compressional forces are applied to the ends of the link
said motor, a source of direct current for energizing said
assembly 60 due to the lifter jaws becoming wedged be
circuit, -a reversing switch remote ‘from the lifter and
tween two adjacent objects during opening of the jaws
operable to selectively energize said armature circuit with
under full motor power in the manner previously indi
current of opposite polarity from said source, a pair of
cated.
30 normally closed relay-actuated contacts in said armature
According to the present invention, the electrical com
circuit, a relay magnet operable upon energization thereof
ponents including the motor M, magnet M1, contacts 02
to open said normally closed contacts, a circuit for the
and limit switch 62 including the contacts (:1 are opera
magnet operatively connected to said source through said
tively carried by the lifter assembly while the reversing
reversing switch, a unidirectional device in said magnet
switch '80 may be disposed at a remote location, for ex
circuit, and ‘a current limiting resistance disposed in said
ample in a control panel CP disposed in the cab of an
armature circuit and arranged in shunt relation across the
overhead crane. The lifter-contained components have
pair of normally closed contacts, said unidirectional de
been enclosed within a dotted line rectangle in FIG. 2
vice establishing current ?ow in the magnet circuit when
labelled LM and representing the lifter mechanism, while
the polarity current applied to the armature is of such
the reversing switch 80 has been enclosed by a dotted line 40 polarity as to cause said motor to move said jaws toward
rectangle labelled CP and representing the control panel
which, as previously stated, may be positioned in the
cab of an overhead crane.
The disposition of the limit switch 62 and motor M on
their closed positions through the medium of said power
train, said limit switch being disposed in said magnet
circuit in shunt relation to the unidirectional device, said
normally closed relay-actuated contacts, relay magnet,
the lifter assembly has previously been described. The 45 unidirectional device, and current-limiting resistance be
other electrical components, namely the resistor R, relay
ing mounted on and bodily movable with the lifter ?ram'e
magnet M1 and the contacts 01, may conveniently be dis
work.
posed within a shield housing 90 conveniently positioned
References Cited in the ?le of this patent
on the lifter framework, as for example on one of the
pivot lugs v14 associated with the supporting element 10. 50
UNITED STATES PATENTS
The resistor R thus becomes a permanent part of the lifter
assembly where it is available for introduction into and
908,251
Haldy _______________ __ Dec. 29, 1908
removal from the motor circuit. Since the resistor R is
individually identi?ed with the motor M, no circuit
changes or resistor substitutions need be made when the 55
particular lifter assembly becomes associated with the
control panel of an overhead crane.
While one speci?c and preferred form of the motor
control system by means of which the principles of the
invention may be carried out has been illustrated and 60
described herein, it will be understood that this form of
the system does not by any means indicate the only form
1,079.345
Hogre'be et a1 _________ __ Nov. 25, 1913
1,245,264
Peck _______________ __ Nov. 6, 1917
1,545,433
1,555,020
Lee et al. ____________ __ July 7, 1925
iParvin ______________ _.. Sept. 29, 1925
1,750,892
1,817,797
2,275,074
Kennedy _____________ __ Mar. 18, 1930
Baker _______________ __ Aug. 4, 1931
Carr ________________ __ Mar. 3, 1942
2,841,434
2,985,481
Hooker et al. _________ __ July 1, 1958
Janoff ______________ __ May 23, 1961
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