US2365141A

US2365141A - Power-operated hoist

Info

Publication number: US2365141A
Application number: US446102A
Authority: US
Inventors: Sully John
Original assignee: American Car and Foundry Co
Current assignee: ACF Industries Inc
Priority date: 1942-06-06
Filing date: 1942-06-06
Publication date: 1944-12-12
Anticipated expiration: 1961-12-12

Description

Dec. 12, 1944. J. SULLY 2,365,141

POWER OPERATED HOIST I Filed June 6, 1942 INVENTOR ATTORNEY hoist and injure himself.

Patented Dec. 12-, 1944 UNITED STATES PATENT OFFICE Joim Sully, Joliet, Ill., alaitnor to American Car and Foundry Company, New York, N. Y., a corporation of New Jersey Application June 6,1942, S6118] No. 446,102

This invention relates to power operated hoists 7 Claims.

in general and in particular to electrically operated hoists.

- Throughout industrial plants a large number of power operated hoists are used and mounted in rather inaccessible places but controlled by either ropes or push buttons within easy reach of the operator who is normally located adjacent the object being lifted. Various safety controls have been applied to these hoists which were intendedto prevent either excessive raising or excessive lowering of the load, but quite frequently these safety controls, particularly the one controlling the excessive lowering, would get out of adjustment .or be removed entirely. In cases where the hoists were not equipped with lowering safety devices or were equipped with safety devices which were out of order, it was possible for the operator to seriously damage the Without the lowering safety control the hoist could lower to its full limit, then start rewinding the cable or chain upon the drum in a reverse direction yet without any reversal of the driving motor. In this way an experienced operator would become confused since the control's for the motor would be reversed and damage to the hoist, the operator or the object being lifted would result. Furthermore, with reversal of the direction of winding on the hoist drum the bulk of the lifting limit controls are rendered valueless and the hoist would have absolutely no protection. It is an object, therefore, of the present invention to provide a positive control preventing any reverse winding of the cable upon the drum without a reversal of the motor.

A further object of the invention is the provision of a safety switch located in a part of the motor control circuit and operable to break the motor circuit upon movement of the live cable from one side of the winding drum toward the other side.

A still further object of the invention is the provision of a safety device for power operated hoists which prevents winding of the cable on the hoist drum without a reversal of the motor following an unwinding of the cable from the.

drum.

These and other objects of the invention will be apparent to persons skilled in the art from a study of the following description and accompanying drawing, in which Figure 1 is an elevational view of a powe operated hoist with the improved safety device attached thereto;

Fig. 2 is an end view of the hoist of Fig. 1;

Fig. 3 is a sectional view taken substantially on line 3-3 of Fig. 1 and showing the relationship of the live cable and safety device, and

Fig. 4 is a circuit diagram showing the controls for the hoist motor and component parts.

Referring now to the drawing in detail, it will be seenthat the hoist is of the type driven by an electric motor M carried by a housing 2' sus pended from any suitable structure by means of r a hook I. In order to balance the hoist about hook l the casing 2' has attached thereto a reduction gear case 6 which receives power from' the motor and transmits the same to the hoist drum 8 located in the casing between the 'motor and gear case. The motor operation is controlled" the load, in other words, in anup-direction, while pulling upon the handle designated D in Fig. 2

will cause the lowering or downward movement As shown in Figs. 1 and 2, hoist drum 8 is adapted to wind thereon the live cable l4 anchored at one end to the hoist drum and passing through pulley 46 to which is attached the lifting hook l8. Theopposite or dead end of the cable is anchored, as is customary, to some portion of the hoist housing. The hoist, as shown in Fig. 1, is provided with a lifting limit safety device 20 normally interposed in the path of pulley l6'and adapted to break the circuit preventing excessive lifting of the load. This safety switch is, of course, located from necessity in the lifting side of the motor control circuit and if, due to excessive lowering, the cable is wound on the drum in a reverse direction, the motor controls are reversed and the top limit switch device 20 can no longer operate since it is dead when the load is bein lifted toward it.

In order to prevent reverse winding of the live cable I 4 on the hoist drum 8, a switch S is mounted on the hoist and interposed in a branch of the motor circuit, as clearly shown in Figs. 1 and 4. This switch S is normally closed and has connected to the switch operating arm 24 an operating control 26. This operating control 26, as clearly shown in Figs, 1 and 3, is anchored to a part of the hoist frame through a tension spring 30. The use of this tension spring prevents injury to the switch in the interval between commencement of operation and full stoppage of the hoist drum as. the live cable would be moving from the near side of the drum, as viewed in Fig. 1, to the other or far side of the drum. The switch operating control 26 is stretched across the face of the hoist drum and it becomes impossible for the cable to move from one side of the drum to the other without causing the control 26 t6 operate the switch S thus breaking the motor circuit. This movement of the cable from one side of the drum toward the other is clearly indicated in Fig. 2 which indicates by arrow the lowering direction of drum rotation and indicates by line and dash the position of the live cable l4 as it would move from the left hand toward the right hand side of the drum. The hoist is equipped with a magnetic type brake held in an off position whenever current is fiowing to the motor but moving to an on position preventing rotation of the hoist drum whenever current is not flowing to the motor. The magnet coil of this brake is indicated at 36 in the wiring diagram of Fig. 4.

Referring specifically to Fig. 4 it will be seen that the controller consists of aplurality of fixed contacts and a plurality of movable contacts. The movable contacts located at the left of Fig. 4 are indicated as up and those at the right side of the fixed contacts as down. If an operator pulls handle U the up-contacts ar moved into engagement with the-centrally located fixed contacts, while if the handle marked D is pulled the contacts marked down are moved into contact with the fixed contacts. 'Assuming. the handle marked D has been pulled, the contacts marked down will have been shifted to the left in Fig. 4 and will engage the fixed contacts and the motor circuit can be traced as follows: Current flows into line 40 to fixed contact 42 thence into movable contact 44 and by jumper 46 into contact 48. From contact t8 the current flows through fixed contact ill and wire 52 into normally closed safety switch S. From this switch the current flows through wire 54 to the motor armature and through the armature into wire 55 and fixed contact 58. From fixed contact 55 the current flows to contact 60 and through jumper 62 into

contacts

64, 6G and 58. These latter three contacts, as clearly shown, are of different lengths and progressively engage contacts l, 2 and 3, thus progressively cutting out the field resistance R. Tracing the first contact step it will be seen that current will flow from contact 64 to contact l, thence through the entire field resistance R to wire 10, thence through motor field 72. wire 14 and brake coil 36 to the main supply line marked 80. Thus it will be seen that when the controller is active lowerin the live hoist cable the switch S is in the circuit and any break occurring at S interrupts the circuit and causes the brake 3G to engage and the motor M to stop and it becomes impossible to operate the motor until the up-controller is moved into contact with the fixed segments by pulling the handle marked U. Movement of the controller to the up position will permit current to flow from 40 to 42, thence through the up-contacts to 58 and wire 56 and through the armature in a reverse direction to that in which it previously flowed and into wire 54. From wire 54 the current flows to fixed contact 90 and

movable contacts

92, 93, 94 and 95, with the latter three progressively cutting out the 'field resistance.

From the preceding description of the mechanical and electrical location of the switch S and its controlling cable or arm 26 it will be seen that it is absolutely impossible under any condition for the cable to wind upon the hoist drum in a reverse direction while the motor is still operating in a lowering direction. Since this is the only way in which the live cable could cross from one side of the drum to the other, such crossing is absolutely prevented;

While the safety device has been described more or less in detail, it will be obvious to persons skilled. in the art that various modifications and rearrangements of parts are possible and all such modifications and rearrangements of parts are contemplated as will fall within the scope of the appended claims defining my invention.

What is claimed is: I

1. In a power operated hoisting apparatus, a motor, a control circuit for the motor, a hoisting drum driven by said motor, a live hoist cable normally winding on and unwinding from one side of said drum, and means operating to break said control circuit and stop said motor upon sidewisc movement of said live hoist cable toward the other side of said hoist drum.

2. In a power operated hoisting apparatus, a motor, a control circuit for the motor, a hoisting drum driven by said motor, a live hoist cable normally winding on and unwinding from one side of said drum, and means operating to break said control circuit and stop said motor and hoist drum after full lowering of said live hoist cable and upon sidewise movement thereof toward the other side of said hoist drum.

3. In a power operated hoisting apparatus, a reversible motor, a control circuit including reversing connections for said motor, a hoisting drum driven in either direction by said motor, a live hoist cable normally positioned on one side of said hoist drum, and means operating to break the circuit to said motor upon movement of said live hoist cable when fully unwound toward the other side of said hoist drum.

4. In a power operated hoisting apparatus, a reversible motor, a control circuit including reversing connections for said motor, a hoisting drum driven in either direction by said motor, a live hoist cable normally positioned on one side of said hoist drum, and means operating to break the circuit to said motor upon movement of said live hoist cable toward the other side of said hoist drum when fully unwound from the drum, said means rendering a portion of said control circuit ineffective until said motor has been reversed and said live hoist cable again positioned on said one side of the hoist drum.

5. In a power operated hoisting apparatus, a motor, a control circuit for the motor, a hoisting drum driven by-said motor, a live hoist cable normally winding on and unwinding from one side of said drum, and means operating to break saidcontrol circuit and stop said motor upon movement of said live hoist cable when fully unwound toward the other side of said hoist drum, said means comprising a switch located in a part of the motor circuit and operable by a control cable extending across the face of said hoist drum.

6. In a power operated hoisting apparatus, a motor, a control circuit for the motor, a hoisting drum driven by said motor, a live hoist cable normally winding on and unwinding from one side of said drum, and means operating to break said control circuit and stop said motor upon movement of said live hoist cable toward the other side of said hoist drum, said means comprising a normally closed switch located in a "1' part of :the motor circuit and operablelby a control device extending across the face of said hoist drum and positioned in the path of sidewise movement of said hoist cable in moving from one side of the drum to the other.

'7. In a power operated hoisting apparatus, a reversible motor, a control circuit including a controller for the motor having one position for reversing the motor, a hoist drum driven by said motor, a live hoist cable normally unwinding from said drum during reverse rotation of said