US2512055A - Safety load limiting means for hoists and the like - Google Patents

Description

June 20, 1950 R. R. DILLON 2,512,055 SAFETY LOAD LIMITING MEANS FOR HoIsTs AND LIKE Filed .June 1947 @f 65W il Patented June 20, 1950 SAFETY LOAD LIM'ITING MEANS FOR HOISTS AND THE LIKE Ralph R. Dillon, Chicago, Ill., assigner to W. C.

Dillon & Company, Inc., Chicago, Ill., a corporation of Illinois Application June 4, 1947, Serial No. 752,326

6 Claims. 1

This invention relates to a means to make safe the operation of hoists and the like by positively preventing any overloading of the hoist.

One object of the invention is to provide a load limiting means in the form of a device that weighs the load, and if the load exceeds a predetermined safe weight the means for operating the hoist is rendered inoperative thereby notifying the operator of the hoist of such fact and at the same time preventing any possibility of unsafe operation due to an overload on the hoist.

Another object is to provide means which is simple and inexpensive in construction and readily adaptable for connecting in the electric circuit of the hoist operating motor for serving to limit the load, thus preventing any possibility of either accidental or intentional overloading of the hoist.

Still another object is to provide an element interposed at any point between a stationary support and the load being hoisted for the purpose of controlling an electric circuit that renders the hoist operating motor inoperative to further lift the load whenever the load causes the safety load limiting means to assume its operative position.

A further object is to provide a special link interposed between a support and the load, which link is extensible in proportion to load, which carries an electric switch and which so operates the switch as to move it to hoist motor de-energizing position at a predetermined loading of the hoist.

Still a further object is to provide the switch carried by the special link connected in the lifting circuit of the hoist motor but so connected with anrelectric switch for the motor that the switch can be operated to the reverse position for lowering the load independent of the load limiting switch, thereby making it possible to lower the load suiciently to release all or part of it upon the lifting circuit of the hoist motor being rendered inoperative by the load limiting switch.

With these and other objects in view, my invention consists in the construction, arrangement and combination of the various parts of my device whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in my claims and illustrated in the accompanying drawings, wherein:

Figure 1 shows a motor driven chain hoist (Cl. S18-488) switch, the switch being adjusted to lift a load,

Figure 5 is a similar .view showing the control switch adjusted for lowering the load, and

Figure 6 is a sectional view on the line 6-6 of i Figure 5 showing ythe -switch in neutral position.

On the accompanying drawing I have used the reference character LS to indicate a limit switch of a safety load limiting means indicated in general at A. AThe switch LS comprises terminals Il and I2 and a switch blade 22 adapted tovnor= mally establish a circuit across the terminals.

The blade 22 is normally held in the downwardlyl bowed position of Figures 2 and 4 by an actuating pin 24 against which an adjusting screw 25 rests.

The screw 25 is carried by a U-shaped frame 23 having an arm 26 extended from the upper leg toward the lower-,leg of the U. This frame is preferably made of tool steel cut to the shape shown and then hardened so that it will carry a substantial load without breaking when inter-- posed in a hoist line. It may be connected in the line by means of studs 21 .and 28 which by way of example are shown connected with a supporting hook 29 and a hoist H respectively in Figure 1. A support 30 is shown for the hook 29 and the hoist H has extended therefrom a lifting chain 32 terminating in a load engaging hook 30.

The safety load limiting means A may be placed instead just above the hook 3| and can be connected with the hoisting cable of a `crane or elevator as it is applicable to any type of hoisting mechanism. The type of hoist shown in Figure 1 .is merely for the purpose of illustration.

'I'he limit switch LSk may be supported onthelowerleg of the U frame by means of a plate 39 riveted at 40 to the arm, screws 4| being provided to mount the switch housing on the plate. The

switch terminals Il and l2 are connected in a.

circuit with the motor M and a control switch therefor which is shown diagrammatically in.

Figures 4 and 5. The control switchr consists o f .a rotor 2| rotatable about one-fourth turn be- 3 tween upper brushes I, 2, 3 and 4 and lower brushes 5, 5 and l.

The motor M has a starting coil SC connected with the brushes 2 and il, a centrifugal switch CS being in the circuit or any suitable switch may be used for cutting out the starting coil after the motor gets up to speed. The motor also includes a running coil RC connected to the brushes 3 and 6. The brush I is connected with terminals 8 and I 2 with the circuit branching at a terminal I0, and the brush 5 is connected with the terminal II ofthe limit switch. The terminal B is a current supply terminal and a second one is provided indicated at 9. The terminal 9 is con.- nected with the brush 1.

The rotor 2l of the control switchhas thereincurrent conducting bars I3, I4, I5, I6, 11, I8, I9 and for connecting the various brushes I to l with each other in a desired iriiit path,

Normally the conductors I3 to 2D are out of contact with all the brushes I to 'I and the rotor is in the position of Figure 6. The rotor has a cross bar 33 normally retained in the position shown in Figure 6 by opposing springs 34and 35. It can be rotated an eighth of a turn in either direction however by pull wires 36 and 3g?, extend'- ing to a control bar 38, rI lhis bar maybe manipulatedlfer causing rotation of the motor `Min either i direction for either raising or lowering the :load

as desired, and when the control bar is released the rotor '2I returns to theneutral position,

Whenthe control bar 38 is lowered at its right hand end in Figure 1 the rotor 2| assumes the p osi-tion shown Figure 4. The circuit may n ow If such load exceeds the predetermined safe load for the particular hoist y in question, as soon as the .load is almost sulllciently supported licy the hook 3| the link 23 .will open enough to per'- mit ,the switch blade 2 2 to .move away iroin the contact connected with the terminal Ii in the limtswitch thus breaking the cirouitto the ning coil RC.y the circuit usually having been broken to the starting coil SQ 4hy the motor corningun to sneedaud due to thecentriiugal .switch Cshavingonenedlf. the load is. imposed the hoist before the starting coil .has hoerige-energized by opening of the centrifugal switch. the opening oi the limit switch will breals the oircuit to the starting coil alsoi hoth thestarting coil .and the running coil in the un circuit oftheinotor which includes thelimitswitcn vlilith the limit .switch oneri the rnotor can he reversed yhowever,as the-,limit switch is not the downcircuit which may he traced in Figure 5 from-li through l0, l, I 1, 2, .CSpSGA 2i! and l to 9, part oiithe current dividing at Zand passing through i3., 6., upwardly through RC, sand -I 9- 'lhus the starting coil islenergized in the saine direction as in the up circuit, .but the running .coil isenergiged in the reverse direction for-revers: ing the .motor ,and the current from. the supply terminal does not have to go through the limit switch Whlh Would be open vas illustrated in Figure 5 due to having operated in its safety capacity by reason oi aload., imposed on the hoist After the load is released, all or part of it may be removed and the hoist again operated in the normal manner. The arrangement is such however that when the hoist is rendered inoperative by an overload it can still be operated in the lowering direction for releasing the load. In order to prevent the U-shaped link 23 from being opened excessively, I provide a screw 39 threaded into the arm and adaptable to engage a shoulder 40 of the lower arm of the U- shanedmeinher 23 after the arrn has been spread sufficiently toopen the V limit switch T-1S. The operating point of the limiting switch may be adjusted by means of the screw 25 and the screw 39 is then adjusted to a point where it permits opening of the limit switch and a slight addiltional amount oi' opening movement of the U.

Some changes ,may be made in the construction and arrangement of the parts of my device withoutdeparting from the real spirit and purpose o f my invention, and it is my intention to `'cover by my claims any modified forms of structure 2or use of mechanical equivalents which may be reasonably included within their scope.

25 l claim as my invention.:

l. ty load limiting ineens .for hoists and the l c comprising a mechanical connecting link of erna ihle character, a switch carried. thereby ve to the weight oi the load on. ,said being physically interposed the ist and connected in the un circuit of th hoisting motor independent of the down oircuit thereoft 2. Safety load limiting means of the character switch yheine normally ,closed and havingan actuating elerneiit responding to spreading of `said loon underload, to be opened when the load is greater than a. predetermined value.

3: Eoruse a hoist motor or the like having a switch provided withindenendent un and-down circuits: a load. responsive linhmechanically con.- nected between the hoist and a support therefor, a safety load limiting switch Supported by said linkv and normally closed unon normal loads andonened hy imposing excessive loads on the hoisty said switch heine: electrically connected in the.,

hoist. being operative to open a circuit therethrough and being electrically connected in .the

ative.

5. A safety load limiting -switchv electrically in terposed in theV lifting circuit only of a hoist, ,and means for operating said switch comprising a Cs. shaped element which isrextensible in proportion to the load imposed thereon, normally cooperates with said'limiting switch toretain the same closed4 and permits the same toopen upon the load e x. ceeding a predetermined value.

5 c. n saiety ieee limiting switch nir the. uam

disclosed ,comprising loon shaped frame onen` .te same unen an attempt being made to hoist greater than a predetermined load, said.

up circuit of .the hoist motor to render it inlopencircuit only of a hoist, and means for operating said switch comprising a loop element open at one side and extensible in proportion to the load imposed thereon, normally cooperates with said limiting switch to retain the same inoperative, and permits the same to operate to render `the lifting circuit inoperative upon the load exceeding a predetermined Value. Y

RALPH R. DILLON.

REFERENCES CITED The following references are of record in the file of this patent:

6 UNI'I'ED STATES PATENTS Number Name Date Darlington Aug. 21, 1906 Johnson Feb. 24, 1925 Hallenbeck Dec. 13, 1932 Nelles Apr. 24, 1945 Manney et al Oct. 9, 1945 Roy Nov. 12, 1946

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