US2489832A - Control circuit for hoisting devices - Google Patents

Description

Filed Oct. 23, 1947 Patented Nov. 29, 1949 UNITED STATES PATENT OFFICE CONTRQL CIRCUIT FOR HOISTING DEVICES Application October 23, 1947, Serial No. 781,738

4 Claims. 1

The present invention relates to hoisting de vices, such as marine Winches, elevators and the like. More particularly, the invention comprises a flexible and accurate control system by means of which the operation of hoisting devices is facilitated, simplified, and rendered much safer than has hitherto been feasible.

In some types of hoisting devices a pawl is provided for holding the cable drum stationary and securing the load in an elevated position. To lower the load from this position it is necessary first to start the motor in a forward, or hoist direction, thus freein the pawl from the pressure of the ratchet wheel caused by the load, then manually to release the pawl, and finally to reverse the direction of the motor and lower the load.

An object of the present invention is to provide mechanism which will permit direct control of the foregoing operation, and to this end a feature of the invention resides in a novel motor and pawl control circuit responsive to a pair of switches so connected through relays that the closing of one switch operates the motor in the hoist direction and simultaneously automatically retracts the pawl, while the closing of the other switch first operates to start the motor in the hoist direction un ll the pawl is disengaged and then automatically reverses the motor while the pawl is still held in disengaged position.

Another feature of this invention comprises a time delay relay circuit, which, in conjunction with a solenoid is adapted for securing the pawl in disengaged position duringthe transition from forward to reverse position in the automatic operation last described.

These and other features of the invention will be best understood and appreciated from the following description of a preferred embodiment, selected for purposes of illustration and shown in the accompanying drawing in which the figure is a schematic wiring diagram for a circuit constructed in accordance with the invention.

The hoisting device to which my invention applies is indicated by a cable drum 16 carrying a ratchet wheel [4 at one end and driven by a motor M, shown diagrammatically. Engaging the ratchet wheel I4 is a pawl l3, pivotally mounted on a lug 28, and connected to the Obviously the drum may be driven in the hoist direction (counter-clockwise in the accompanying drawing) without hindrance from the pawl, but the pressure exerted by the load through the drum and ratchet wheel upon the pawl makes it necessary to rotate the drum in the hoist direction to relieve the pressure on the pawl before the pawl can be disengaged and the motor operated to drive the drum in the lower direction.

In order automatically to accomplish this de sired result, I employ a pair of relays R1 and R2 controlling the supply of current to the motor and the direction thereof. The relay R1 controls four pairs of contacts 30', 49, 5B and 1!), while the relay R2 controls four pairs of contacts 40, 30, and 8!]. A mechanical interlock, shown diagrammatically at 26 serves to prevent simultaneous energization of both relays. Moreover, relay R1, for reasons subsequently explained, is of the 1shaded pole or thermally responsive time-delay ype.

The D. C. service lines are shown at A and B, and a spring-load push-button hoist switch H is connected in series with relay R1. When the hoist switch l l is closed the relay R1 is energized and closes contacts 35!, 49, 5G and It, driving the motor M and the drum 16 in the hoist direction. Simultaneously, the solenoid I0 is energized to retract the pawl 18. The circuits thus established are as follows:

2. Ac0ntacts 3l-junction SS-series wind ing S-contacts it-motor terminal 2l-motor M-motor terminal 22-contacts 5llcontacts ill-Junctions 39-3.

3. Acontacts 3iY-junction 4 lthrough shunt SH and through solenoid ill in parallel-junction 4Zcontacts liljunction 39-3.

As has been mentioned previously, it is necessary, before the lowering operation is accomplished, to remove pressure from the pawl l8 before it can be disengaged from the ratchet wheel. How this is accomplished through the use of only one push button switch will now be explained. When the lower switch 13 is closed, the circuit includes a snap switch 52, the arm 28 of which is carried on the plunger 32 of the solenoid it. Since in the normal or rest position of the solenoid it, the contacts of the switch I 2 are closed, the relay R1 will be energized as the lower switch i3 is depressed. With the energization of the relay R1 the same circuit con ditions prevail as in the hoisting operation above described, namely, the contacts 30', 48, 56 and I0 are closed, the motor M and the drum l6 are started in the hoist direction (counter-clockwise as shown in the accompanying drawing), and the solenoid Ii] is energized to retract the pawl l8. Not, however, until the hoist rotation of the motor M and the drum it releases the load pressure from the pawl 18 will the solenoid ill be efiectual in disengaging the pawl i8. Simultaneous with this disengagement, by the solenoid plunger 52 moving in an upward direction as shown diagrammatically in the drawing herewith, the switch i2 is thrown from rest position to active position, the terminals It!) are bridged, and current is supplied to the relay R2, to reverse the motor M and cause it to. turn in the lower direction.

Before the lowering circuits so established are traced in detail, the time-delay feature of relay R1 must be noted. A time-delay relay is so constructed as to provide a predetermined lag interval between the opening of the relay circuit and the resumption of rest position by the relay armature. Here the requisite delay period is equal to the time required for the contact member 28 of switch i2 to leave the contacts 90 and engage the contacts Hi5. This delay is essential to insure the continued energization of solenoid is during the brief period required for the switch-over action of switch arm 28 from the contacts 90 to the contacts we. Otherwise, the

relay Rz-B-energizing the relay R2.

2. A-contacts Silk-junction 38series winding Scontacts 6il--motor terminals 22motor M-motor terminals 2lcontacts 8ilcontacts 3l--junction 39-3. It will be observed that current fiow through the motor armature is in a direction opposite to that obtaining when the hoist circuit is closed. This circuit drives the motor M and the drum it in the lower direction.

3. A-contacts Nt -junction ilthrough shunt SH and through solenoid it! in paralleljunction t2contacts 40junction 39B.' This circuit maintains the pawl in retracted position.

The total efiect of depressing lowering switch 13 is first to cause the motor M and the drum [6 to start up in a hoist direction (corresponding to counter-clockwise in the accompanying diagram) while the energized solenoid ill disengages the pawl it from the ratchet wheel l4;

and then through the automatic action of the solenoid It to cause the motor to reverse and turn in a lower direction (clockwise in the diagram) as the solenoid It continues to hold the pawl i8 disengaged from the ratchet wheel l4.

Variations in the organization of the circuit components will suggest themselves to those skilled in 'theart, but it should be borne in mind that the foregoing description relates to one preferred embodiment of an invention and that the scope of the invention is to be measured by reference'to the appended claims.

Having now described and illustrated a preferred embodiment of my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

l. A control circuit for hoisting devices, comprising a ratchet wheel, a pawl movable to and from engagement with the ratchet wheel, a solenoid controlling the position of the pawl, a motor having a driving connection with said ratchet wheel, a first relay, a plurality of contacts and connections operated by said relay to actuate said solenoid and simultaneously to drive said motor in one direction, a first switch controlling said first relay, a second relay, a plurality of contacts and connections operated by said second relay to actuate said solenoid and drive said motor in the other direction, a second switch actuated by said solenoid, and a third switch in series with said second switch, said second switch being so connected to the first and second relays that the third switch is normally connected to the first relay through said second switch but automatically disconnected from the first relay and connected to the second relay when the solenoid is operated and the pawl disengaged irom the ratchet wheel.

2. A control circuit for hoisting devices comprising a reversing motor having power supply 7 connections, a ratchet wheel driven by said motor, a pawl movable to and from engagement with said ratchet wheel, a solenoid operatively connected with the pawl to disengage the same when the solenoid is energized, a first switch connected to operate the motor in one direction, a second switch operated by the solenoid and connected to drive the motor in the same direction in the rest position of the s0lenoid, a third switch controlling the power supply to said second switch, said second switch being connected to drive the motor in the opposite direction when the first switch is open, the third switch closed, and the solenoid in energized condition with the paw! disengaged from the ratchet wheel.

3. In an electrically operated hoisting device including in its structure a reversing motor, a drum driven thereby, a ratchet wheel attached to said drum and a pawl serving to lock said ratchet wheel against rotation in one direction; a control circuit comprising a time-delay relay for controlling rotation by said motor in one direction, a second relay for controlling rotation by said motor in. the opposite direction, a switch, a solenoid connected for energization selectively by either of said relays and serving to control the switch and when actuated to release the pawl from engagement with the ratchet wheel, said switch being connected to the time delay relay in the rest position of the .solenoid and to the second relay in the energized position of the solenoid, the time delay period being sufficient to maintain the solenoid energized during the time the switch is being shifted by the solenoid, a second switch connecting a source of current to the time delay relay whereby the motor is driven in one direction, a third switch connecting the source of current to the first switch whereby the motor is first driven in one direction while the first switch is connected to the time delay relay and the solenoid is inactive and'the motor is driven in the other direction when the solenoid is energized and the first switch is connected to the second relay.

4. A control circuit for hoisting devices comprising a reversible motor, a drum driven by said motor, a ratchet wheel attached to said drum.

5 and a pawl movable to and from engagement with the ratchet; wheel; a first relay possessing time delay characteristics and having connections for driving th motor in one direction, a first switch controlling the flow of current to the first relay, a second relay having connections for driving the motor in a reverse direction, a solenoid connected for energization when either relay circuit is closed, said solenoid being connected to said pawl to disengage the samewhe'n said solenoid is actuated, a second switch connected to a source of current, and means operated by said solenoid for connecting said second switch to the first relay when the solenoid is de-energized and to the second relay when the solenoid is energized, whereby the second switch REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 4 1,499,735 Hynes July 1, 1924 1,693,293 Gittings Nov. 27, 1928 2,086,030 Hodgson et a1 July 6, 1937

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