US885961A - Controlling system for hoists. - Google Patents

Description

No. 885,961. PATENTED APR. 28, 1908. B. R. SHOVBR & A. G. EASTWOOD. CONTROLLING SYSTEM FOR HOISTS.

APPLICATION FILED JUNE 20. 1907.

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A N v c N T 0 R5 TTTTT NEY No. 885,961. PATENTED APR. 28, 1908. B. R. SHOVER & A. U. EA$TWO0D.

CONTROLLING SYSTEM FOR HOISTS.

APPLICATION FILED JUNE 20. 1907.

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vlfi /6 W ATTORNEY No; 885,961. PATENTED APR. 28. 1908.

B. R. SHOVER & A. 0. EASTWOOD.

CONTROLLING SYSTEM FOR HOISTS.

APPLICATION FILED JUNE 20. 1907.

3 SHEETS-SHEET 3.

INVENTORS WITNEEECEI ATTORNEY THE NORRIS PETERS cc WASHINGTON, n. c.

[UNITED STATES PATENT OFFICE.

BARTON R. SHOVER, OF CHICAGO, ILLINOIS, AND ARTHUR, O. EASTWOOD, OF CLEVELAND, OHIO.

CONTROLLING SYSTEM FOR HOISTS.

Specification of Letters Patent.

Patented April 28, 1908 Application filed June 20, 1907. Serial No. 379,885.

To all whom it may concern:

Be it known that we, BARTON ll. Snovnn, a citizen of the United. States, residing at Chicago, in the county of Cook and State of Illinois, and ARTHUR O. Eas'rwoon, a citizen of the United States, residing at Cleveland, in the county of Cuyahoga and State of Ohio, have invented or discovered new and useful Improvements in Controlling Systems for lloists,of which the following is a specification.

Our invention. relates to new and valuable improvements in controlling systems for hoists and is specifically applicable to that class of hoists generally known as skip hoists, though it may also be advantageously applied to hoists of other forms. Skip hoists are commonly used in connection with blast furnaces for elevating the ore, limestone, coke, or other burden for the i'uri'iace from the ground or storage bins to the top of the Furnace. In general, such hoists consist of an inclined runway extending from the grouml to the furnace top and provided with. rails for accomn'iodating a skip-car or bucket, which. is drawn up the runway by means oi cables actuated by a suitable wixiiding engine. Usually and preferably two skip cars are em-- ployed so connected to the drums of the wind ing engine that one car is ascending the incline while the other is descemlii'ig, thus fornn ing a balanced hoist.

It is desirable that the skip cars or buckets be arranged to discharge their contents automatically into the bell or hopper at the furnace top. It is further desirable that the skip car be brought to rest automatically at the proper point when it has discharged its contents, for the reason that not only is labor dispensed with, but additional safety is insured, providing, 01 course, that the automatic system of control is so designed and constr noted as to be safe and reliable in service.

in the past it has been deemed expedient to gradually slow down the speed of travel of the skip-car as the car approached the limit of travel, this being accomplished by gradually reducing the power supplied to the winding engine. The purpose of this slowing down of the car has been to bring it as nearly as possible to a constant slow speed regardless of load before applying a retarding or braking force to the winding eiiigine with the hope that in this way a more accurate stop may be secured with the skip-car always at the same point of travel, To accomplish this result it has been customary (when an electric motor has been employed to drive the winding engine) to gradually cut resistance into the armature circuit of the motor to reduce its speed. If the same amount of resistance is inserted in the armature circuit of the motor irrespective of the load, necessarily the same reduction in speed Will not be secured with varying loads. Thus, for instance, in the case of a direct current shunt wound motor operating on a circuit at 250 volts, if a resistance of ohm be inserted in the armature circuit with a load equivalent to 400 amperes, the voltage a plied to the motor armature will be reducec to volts. If the same resistance be inserted at a load equivalent to 100 ainpercs the voltage will only be reduced to 200 volts, so that necessarily there will be a'wide variation in speed between these voltages. An endeavor to remedy this difficulty has introduced great complication in the controlling apparatus, since with this procedure it becomes necessary to automatically vary the amount of resistance inserted in the armature circuit in accordance with the load or else an automatically graduated retarding or braking force must be provided which will properly interpret variations in speed. By our invention we eliminate this complication and thus render the system of control much simpler and more reliable.

In carrying out our invention, we preferably employ a compound wound motor. The series field winding is employed only in starting and as soon as the load is accelerated the series winding is short circuited and the motor operated as a shunt wound motor. Such a motor will operate at a substantially constant speed within its ran e of loading regardless of the load. Therelore, whether the skip-car be loaded with coke or with ore (which has nearly four times the weight of coke) the skip-car will travel up the incline at the same speed and likewise the armature of the motor and the driven parts of the winding engine will maintain a given speed We do not attempt to slow down the m0 tor by reducing the powersupplied to it as the limit of travel is approached, but at a given point entirely out oh the su ply of power. Since the skip-car invariab y travels at the same speed irrespective of its load, gravity will retard and sto the upward bound skipcar in the same distance invariably, and since the other parts are always moving at the same speed when the power is cut oil, the amount of energy to be dissipated in bringing them to rest is always the same. e automatically cut oif the power from the winding engine at a considerable distance from the limit of travel of the up ward bound skip-car, this distance being dictated by the mass and velocity of the moving parts. In this way a large part of the energy stored in the moving )arts is utilized in completing the travel of the skip-ear with its lead against gravity. Our invention, therefore, provides a system which is highly etlicient and at the same time largely reduces the wear and tear on the hoisting mechanism since, when the filial stop is made, a large part of the energy in the moving parts has already been utilized in performing useful work, so that very little remains to be absorbed in bringing the moving parts completely to rest. Our invention also provides means for ell'ecting the final stop promptly, but in a manner which precludes injurious shock to the hoisting mechanism and cables.

Referring to the accompanying drawings, Figure 1 is a side elevation of a blast furnace showing the inclined runway with skip-cars thereon. Fig. 2 is a plan of the runway and engine. Fig. 3 is a side elevation of our preferred form of automatic cut-oil device. Fig. at is a section on the line i on Fig. 3. Fig. 5 is a side elevation of the switches carried by the base p the switches being reversed from the position of the corresponding switches in Fig. 3. Fig. (Sis a diagram of electrical connections.

In Fig. 1, F is a blast furnace provided with an inclined runway f upon which the skip-cars f and f travel.

f is a machinery house in which are located motor-driven winding drums f and f which, through suitable cables propel the skip-cars on the runway.

As indicated in Fig. 2, one of the cars invariably travels up the incline while the other is traveling down, thus forming a hoist in which the weight of one-ski p car balances that of the other. At the upper end of the inclined runway, it will be seen that the rails f which accommodate the forward trucks of the skip-car deflect downward while the rails f which accommodate the rear wheels of the car are elevated, thus causing the ship-car to assume the position indicated when the limit of travel is reached in which position the skip-car automatically discharges its load f indicates a storage bin from which the skip-cars are alternately filled through ho ers or chutes. The arrangement of t 1e oisting engine is more clearly shown in Fig. 2 in which M is a driving motor. This motor drives through suitable gearing the drums f and f One end of the drum shaft is provided with an extended screw 0 which serves to actuate a cross head C, which is provided with a suitable nut in engagement with the screw. These parts are more clearly shown in Figs. 3 and i and form the actuating means for automatically cutting off the power and subsequently stopping the hoist at a predetermined point.

The cross head C is guided by a guide frame H and through the engagement of the nut 0* with the screw 0 the cross head is driven back or forward along the guide-way in accordance with the rotation of the screw 0 Since this screw is directly attached to the shaft of the hoisting drums, the cross head C will always move in synchronism with the hoisting drum so that de'l'inite points in the travel of the cross head represent delinite travels of the hoisting cable. The cross head C is provided, on either side, with T- shaped slots 0 which accommodate the heads of bolts 0, which in turn serve to adjustably clamp in place suitable actuating cams c, c, 0 0. These cams are arranged in pairs at each end of the cross head, one member of each pair being set somewhat ahead of the other for reasons which will be later explained. Each of the cams cooperates with a cam roller 1/ carried at the extremity of its respective lever 11, pivoted to swing at 1).

When a cam comes into engagement with the corresponding cam roller the lever 1) actuates a corresponding cross head p in such manner as to multiply the motion of the cam, the lever 29 being pivoted near its upper end and in engagement with the cross head p near its lower end. The cross head 1) moves upon a suitable guide 12 mounted upon a slate or other insulating base, 1). The cross head carries two brushes, p, p, the brush 19 being adapted to connect together the strips 2), p and the brush p being adapted to electrically connect the strips p", p. Each of the outermost strips are provided with short sections or tips p by suitably connecting which the electrical length of the corresponding strip may be adjusted. Then, for instance, the brush 7) passes to the left beyond the last one of these adjustable tips 19 which is in circuit, the connection between strips p, p is opened. When the direction of motion of the cross head C is reversed by reversing the direction of rotation of the hoisting drum, the lever 29 is returned to the vertical position by the spring 2).

Fig. 6 shows the various electrical connections in our invention as used in connection with a compound wound, direct current motor. While we find such a motor well adapted to the purpose, it is to be understood that our invention is not limited to the use of such a motor as certain broad features of our invention are equally applicable to hoists driven with other forms of motors, or with steam engines or other prime movers.

switch is energized.

In Fig. 6, A is the armature of the driving motor. F is the series-field winding, and f, the shunt field winding of the motor. Z) is the winding of the releasing magnet of the friction brake B, this brake being of well known construction wherein the brake is released when the magnet is energized and applied bymeans of aweight or si iring 7) when the magnet is deenergized. It is to be noted that the magnet winding Z) is coi'mected in parallel with the switch coil S. U, U, D, D are reversing switches which close in p airs to give one or the other direction of rotation to the armature A in the well known way, the switches U, U giving one direction of rotation, and the switches D, D, the reverse di rection. r r 1' are sections of starting resistance wl'iich are controlled by the magnet ically operated switches R R, R in automatically starting the motor. F is a mag netically operated. switch, which, when closed short circuits the series field winding F and allows the motor to operate as a simple shunt wound motor. A series relay or throttle O automatically governs the successive closure of the switches R R it and F in the man u er clearly described in. Arthur C. Eastwoods L[')}')ll6tttl011 for United States Patent, Serial No. 352,408 We do not, however, confine ourselves to this precise system of automatically cutting out the starting resistance, but we consider this a preferable arrai'igement. r is a resistance in shunt with. the winding of the series relay 0 and may be used for ad justing the proportion of current which flows through the winding of the relay, thereby adusting the amount of current to be taken in accelerating the motor. S is a magnetically operated switch which controls a circuit through the armature of the motor, the contacts of the switch S, and the resistance The winding of the switch S is connected. directly across the terminals of the armature so that it tends constantly to close while the armature is running. It is, however, normally prevented from closing by the mechanical interlocking levers Z" and. Z which are so arranged that switch S cannot close when either of the neighboring switches U or D is closed. S is a second dynamic braking switch whicl'i is normally closed by a spring S and which is opened when. the winding of the This switch is also mechanicall y interlocked by means of the levers Z," and Z with its neighboring switches U, D so that it cannot close when either of the said. switches is closed. The switch 8- controls a circuit through. the armature of the motor A, and the winding I, which is of low ohmic resistance, but of high inductance. The winrh ing I is preferably inclosed in a complete, or practically complete, magnetic circuit of heavy section. Ne make use of this construction to provide what might be termed a magnetic cushion which. is made use of in chokes back the ilow of current due to the.

inductive action of the increasing magnetic field. As the magnetismbuilds up this choking action is reduced but the speed of the armature has also been reduced through the work which it has performed in forcing current through the closed circuit. Conse quently, as the choking action of the inductive winding l: reduced, the voltage available for forcing current through the closed.

circuit is also reduced. Excessive rush of current is, therefore, prevented when the dynamic braking action is first instituted. and by this construction such a low ohmic resistance may be made use of in the winding I that the braking action will still remain very powerful even when the armature A has been brought down to a very slow speed.

K is the operating controller which is shown with the operating lever in the vertical, or off-position. This controller is operated manually in one direction or the other by the operator to start the hoist either up or down. Merely the throwing of this switch is required on the part of the operator, as the starting resistance is automatically cut out and wl'ien the limit of travel is rcacl'icd the hoist is automatically stopped.

C represent the switches actuated by the automatic stop mechanism. The switches D D control the circuits of the operating clectro-magncts of reversing switches D, D. Switches U [7 control the circuits of the operating electro-magncts of switches U, U. Switches S S control the operating circuit of the dynamic l1 raking switch S. in the drawing switches D+, D-, C S are indicated as open, in which position the hoist will have reached its upward limit of travel and have been automatically stopped. if the operating lever of the contmller K be now moved to the right so that the contact brush 7.? connects the contact rings 71:, fig, 7t and brush 7r connects the rings 7r", 7.1", 7c, the control circuits will b as follows: from the positive main to the contact ring 1: to the contact ring 75 thence through the switch 8 the winding of the dynamic braking switch. 8, the switch S3 the contact ring 1: brush 7r to the negative main. This causes switch S to open. The coil 6 of the brake being in parallel with the winding of switch S is also excited and the brake conse quently released. Current also flows from the positive main to the contact ring brush it, ring A, switch U+ through the windings of the reversing switches U, U in parallel, thence through switch U the contact ring is", brush 7., and ring It to the negative main. This causes the reversing switches U, U to close. The main circuit through the motor is then established as follows: from the positive main, through the switch U, the armature A, the switch U the sections of resistance r r 1' the current then dividing, a portion passing through the resistance 'r and the remainder through the winding of the overload relay 0, this current re-uniting and llowing through the series lield F to the negative main.

It is to be noted that the shunt field winding of the motor f is constantly connected across the supply mains. The motor should, therefore, start under the influence of both its shunt and series field, with the brake B released. As the motor speeds up the series relay 0 will permit the switches R, R, R, and F to consecutively close, thereby short circuiting the sections of resistance 1, 1", r and the series lield winding F. As the armature speeds up the winding of the switch S, which as has been previously mentioned is connected directly across the terminals of the armature, is energized and tends to cause the switch S to close. It is, however, )revented from closing by the interlocking lever Z which will not permit switch 5 to close while switch U is closed. The switch S, however, tends to close and all of its parts are under a. strain in what may be called an endeavor to close.

'hen the limit of upward travel is approached, the cam in Fig. 3 comes into contact with the cam roller 2) of switches U ll, thus automatically opening these switches, which in turn opens the circuit through the magnets of switches U, U, thus causing these switches to open, thereby cutting oll' the supply of power to the armature of the motor. Switch S closes concurrently with the opening of the switch U with which it is interlocked. As previously stated, this switch is under strain in an endeavor to close so that an exceedingly brief period elapses between. the opening of switch U and the closing of switch S. The closure of switch S establishes a circuit including the armature A and the resistance 1" in which the armature immediately generates current due to its rotation under the influence of the shunt field windingf It is not intended that a material amount of energy shall ordinarily be absorbed and dissipated in the resistance 1 it being the intention that the moving parts of the hoist should be slowed down by continuing to lift the upward bound skip-car with its load against gravity. The amount of resistance r in circuit may be adjusted to meet conditions of operation. For instance, where the handling of material at very high speed is required there may not be suflicient time allowable for slowing down the hoisting 70 mechanism purely through the action of gravity on the upward bound skip-car. In such cases a minimum amount of resistance T will be used, thus rendering the dynamic braking action more intense. time is allowable the resistance 1 may be increased or may be entirely dispensed with. \Vhen the moving parts have been sul'licie'ntly slowed down in this way the cam 0 comes into contact with its cooperating cam roller p thus automatically opening switches 3 3 This opens the circuit of the magnetizing coil of switch S and allows this switch to instantly close and at the same time opens the circuit of the brake magnet b, 35

thus causing the brake to be applied. This establishes a second dynamic braking circuit through the armatiu'e of the motor A, the switch S and the inductive winding 1. As

previously described a powerful, though Consequently, when the upward limit of 00 travel has been reached these switches are closed and the hoist maybe started down by simply reversing the position of the operating lever of the controller K. .[n this case the reversing switches D, place of 'thc reversing switches U, U. In other respects the cycle of operations is the same as that described above in connection with the reverse direction of motion.

It is to be noted that the final dynamic braking switch S is opened by a magnet and is closed by a spring. Therefore, in case the supply of current fails at an intermediate position of the hoist, this switch will instantly close thereby connecting the armature of the motor in a dynamic braking circuit and bringing it to rest under the influence of the shunt 'licldf which dies out slowly owing to the high self-induction of the field winding.

At the same time the brake Bis automatically applied and serves to safely hold the load until the supply of current is again established at which time the motor will again automatically be started, will drive the load to the limit of travel and will then be automatically stopped.

1. In a balanced. skip-hoist, an inclined runway, a pair of skip-cars having travel thereon simultaneously in reverse directions,

Where more 75 D are energized in 105 a winding engine for propelling either of said 1skip-cars up said inclined runway, and autodumping said skip-car at a predetermined. point on sa1d runway, sa d automatlc dumping means deriving the energy required to dump said skip-car from the energy stored in the moving parts of said hoisting mechanism.

3. In a hoisting mechanism, an inclined runway, a skip-car traveling thereon, and means for causing the energy stored in the moving parts of said hoisting mechanism to dump said slrip-car at a predetermined point on said runway.

4:. In a hoisting mechanism, an inclined runway, a skip-car traveling thereon, a wind ing engine for drawing said skip car up said runway, means for automatically cutting oil the power from said winding engine when said skip-ear reaches a predetermined point on said runway, and for causing the energy stored in the moving parts of said hoisting mechanism to automatically dump said skipcar.

5. In a hoisting mechanism, an inclined. runway, a skip-car, a motor driven hoisting engine for propelling said skip-car up said runway, and automatic means for cutting oil the supply of power from said motor before the limit of travel of said skip-car is reached and for causing energy due to the motion of the parts of said hoisting mechanism to be absorbed in completing the travel 01 said. skip-car against gravity.

(3. In a system of control for hoists, a load to be hoisted against gravity, a hoisting engine ior hoisting said lead, automatic means for supplying power to said hoisting engine to aece crate said load, automatic means for cutting oil the )ower from said hoisting engine when the load has reached a predetermined point of travel and causing the moving parts of said hoisting engine to slow down through giving up the energy due to their motion in continuing to hoist said load against gravity, and automatically acting means for absorbing the residue of saidenergy when a second predetermined point of travel is reached.

7. In a system of controller hoists, a load to be hoisted against gravity, a hoisting enine for hoisting said load, automatic means for sup lying power to said hoisting engine to acce erate said load, automatic means for cutting off the power from said hoisting engine when the load has reached a predetermined point of travel, thus causing the moving parts of said hoistingengine to slow down through giving up the energy due to their motion in continuing to hoist said load against gravity, automatically acting means for absorbing the residue of said energy when a second predetermined point of travel is reached, and. a holding brake automatically applied when the moving parts have substantiaily come to rest. r

8. In a hoist, the combination of a load to be hois ed, a hoisting engine, a brake for said hoisting en 'ine, automatic means for cutting oil the supply of power 'from said engine when a predetermined point of travel is reached, and means for automatically applying said brake when. a second further point of travel is reached.

9. In an electric hoist the combination of a load to be hoisted, a motor driven hoisting engine, a mechanically applied brake for said. motor, automatic means for entirely cutting oil the power from said motor before the limit of upward travel is reached, and automatic means for causing said brake to be applied when the limit oi travel is reached.

10. In an electric hoist the combination of a load to be hoisted, a motor driven hoisting engine, an automatic controller for starting said motor, automatic means for entirely cutting oli'the supply of power to the armature of the motor before the limit of travel of said load is reached, without previously slowing down the motor, a brake on said motor normally released when power is supplied to the armature ol said motor, and automatic means -for preventing the application of said brake after power has been cut ofl from the armature of said motor till said arm ature has substantially come to rest.

11. The method of slowing down and stopping a motor-driven hoist at a predetermined point which consists in automatically cutting oh the supply of power from the armature of the motor when a given position of travel is reached, thereby permitting the moving parts to be slowed down by lifting the load against gravity and, at a second given point of travel, automatically connecting the mechanical brake to the hoisting mechanism.

Signed at Chicago, 111., this 15th day of June, 1907.

BARTON R. SHOVER.

Witnesses as to Barton R. Shaver:

AUG. F. JoBKn, E'rnnnrnen G. Boone.

Signed at Cleveland, Ohio, this 21st day of

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