US 1267820 A
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UNITED STATES PATEN oEEIcE.
WILLIAM C. STEVENS, OF SUMMIT, NEW JERSEY, ASSIGNOB TO THE CUTLER- HAMMER MFG. 00., OF MILWAUKEE, WISCONSIN, A CORPORATION OF WISCONSIN.
Specification of Letters Patent. P te ted May 28, 191 8.
Application filed March 2, 1916. Serial No. 81,737.
'To all whom it may concern:
Be it known that I, WILLIAM C. STEvENs, a citizen of the United States, residing at Summit, in the county of Union and State of New Jersey, have invented new and useful Improvements in Hoisting Systems, of which the'following is a full, clear, concise,
and exact description, reference being had to the accompanying drawing, forming a part of this specification.
' This invention relates to hoisting systems. It has been proposed to employ for dock hoists and other purposes a motor drive including a set ofpower transmitting gears, between the driving motor and hoist drum, one gear oi said set having play to apply a mechanical brake to the hoisting drum when the load in descending overhauls the motor and this invention is particularly applicable to such hoisting systems.
One of the oojects of the invention is to provide asystein of thi character with dynamic braking means to assist the mechanical braking means for a more efiicient and accurate contro of: descending loads.
Further. "cots are to provide means whereby dynamic brainng means will be rendered inactive during hoisting operation of the c ng motor and active at all times whe i b r is needed and to provide for regulation. or is dynamic braking action of such means for increased flexibility of control.
@tner obiects and advantages will herein-- after The accompanying drawing schematically and diagram atically illustratesv one em bodiment or invention which will now be described, it being understood that the invention may be embodied in other forms falling within the scope of the appended claims.
The drawing schematically illustrates a winding drum 1, a cable 2 and a weight 3 attached to said cable and representing the load to be controlled. The drum is keyed to a shaft 4 and to be driven through a set of.
toothed ring 1O surrounding the aforesaid pinions and meshing with the pinions 8'. The
ring 10 is carried by a spider l1 revolubly mounted on the hub of spider 9 to have rotary play, limited by a fixed stop 12 in the path of a lug 13 on said spider 11. With the spider ll locked by the stop 12 the gears become effective as a driving medium between the motor and drum, while if the load in descending overhauls the motor, said drum through its pinions 8, will reverse the strain upon and rotate the ring 10, and it is this movement of the ring which is utilized to mechanically brake the drum. As illustrated, the mechanical braking means includes a pivoted brake lever 14- to engage an annular brake surface 15 of the drum and operable by a lever 16 projecting into the path of a lug l? on the spider 11. The arrangement is such that when the s ider 11 occupies its locked position against stop 12 the lug 17 on said spider clears the brake actuating lever 16 whereas said lug is thrown against said lever when the spider moves from its locked position. Such is the hoisting apparatus referred to at the outset and as usual an electromagnetically controlled brake 18 is provided to be set whenever the controller C is set in neutral position.
Referring now to the dynamic brake pro ducing means, the same comprises a generator Gr having its armature coupled to. the shaft 6 of motor M to be driven thereby whenever the motor is in operation or is driven mechanically by a descending load. The field of this generator is supp ied from a direct current line r-Z while its ar nature terminals 19 and 20 are provided with a bridge including a resistance 21, said bridge being controlled by an electro-responsive switch 22. As will hereinafter appear, this switch is utilized to interrupt the armature bridge during hoisting and to close the same during descent of the load, thereby insuring dynamic action of the enerator under the desired conditions whilh relieving the hoisting machine or" the braking action of said generator when not required. Further, the generator is provided with a variable field resistance 23 whereby its dynamic braking action may be regulated at will and this resistance is controllable by the controller C.
The controller C is schematically illustrated as of the drum type and has two sections 0 and c operable together to respectively control'the alternating current circuits comprises two sets of stationary contact fingers 30 to 34 and 35 to 43, the former havand segments 35 to 43 serve to exclude the resistances R from the secondary circuit 01 the motor in steps upon movement of the controller in hoisting direction for hoisting. Segments 31 to 3t cooperate with contacts 31 to 34: upon reverse or lowering operation of the controller to complete the primary circuit of the motor M for reverse operation thereof, or, in other words, operation to drive the load in its descent. Segments 37", t0" and 43 cooperate with contacts 37, 4:0 and 43 u on such operation of the controller to exclu e all of the resistances R in one step but only when the'controller is moved to its extreme lowering position. The connections are so obvious as to requireno specific description thereof and from the foregoing it will be observed that when the controller is moved in hoisting direction, as indicated by the arrow, it will start and gradually accelerate the motor M and that when the same is moved in lowering direction it will establish power connections for the motor but will maintain all resistance in the primary circuit for slow speed of the motor unless it be thrown to its extreme position. Further, it will he observed that in neutral position of the controller all segments disengage their respective contacts.
The part 0' of the controller has two sets of c0ntacts'44 to 48 and 5051, the former being connected to the field resistance 23 of the generator G and the remaining two con tacts being respectively connected to the coils of the electromechanical brake and switch 22. Contact 44 is connected directly to line L and has a permanently engaging segment :44 while the contacts 45 to 49 have cooperating segments 45" to 48 connected to segment 44* and arranged to short-circuit the resistance 23 in the ofi position of the controller and to include sald resistance in circuit by steps when the controller is moved in lowering direction. When the controller is moved in hoisting direction the contact 48" is immediately withdrawn from enga ement with contact l8 thereb including t e entlre resistance 23 in the fie d circuit of the generator. Contact 50 has cooperating segments 50 and 50 both connected to segment 44* to energize the electro-mechanical brake upon and throughout movement of the controller in either direction from neutral position. Contact 51 has a cooperating segment 51' connected to segment 44 to energize coil of switch 22 upon and throughout movement of the controller in hoisting direction. Also, contact 51 has a cooperatmg segment 51 to engage therewith upon lowering movement of the controller to energize the coil of switch 22 but only in the extreme lowering position of the controller.
More particularly describing the D. C. circuits that of the generator 'eld may be traced from line Z to contact 44, through all or less of resistance 23 according to the position of the controller, by conductor 55 to one field terminal of the generator, while the return may be traced from the other field terminal by conductor 56 to line Z. When the controller is moved to either side of neutral position a circuit is also established from line Z to conductor 44 and segments 44 to segments 50 and 50 and from one of said segments to contact 50 by conductor 57 through the coil of the electromechanical brake to conductor 56 and thence to line Z. Finally the energizing circuit of switch 22 may be tracedlfrom line Z to contact 4:4: and segment 449 to segments 51' and 51 and from one of said segments to contact 51 by conductor 58 through the winding of switch 22 to conductor 56 and thence to line Z.
Considering now the system as a whole,
when the controller is in ed position the motor M is disconnected from circuit while the electro-mechanibal brake is deenergized and hence applied. Also, in the 02 position of the controller the field or the generator is included in circuit with all of its field resistance, excluded and the switch 22 is deenergized to bridge the armature terminals of the generator. Thus connected the generator is in condition to exert its maximum braking force and hence ofi' position of the controller represents the position in which the controller should be set for maximum braking action for a descending load.
Assuming now that it is desired to lower a light load without braking action, the controller is moved to its extreme lowering position to thereby connect the motor M in circuit and exclude all resistance from the rotor circuit. Under such conditions segment 51 coiiperates with contact 51 to energize switch 22 thereby interrupting the bridge across the terminals of the generator and eliminating all braking action of the generator. On the other hand, if the load when started tends to descend too rapidly then the same may be checked to the desired degree by moving the controller toward off position. The first step of movement in this direction disengages segment 51 from contact 51 thereby deenergizing switch 22 with consequent closure thereof to reestablish dynamic braking connections for the generator. However, in this position of the field stren controller the entire resistance 23 is included in the field circuit of the generator whereby the braking efiect of the generator is mate rially curtailed, but by continued movement of the controller the resistance may be gradually excluded from circuit to increase the h of the enerator and hence increase its raking eect. Finally the' controller may be returned to off position with the result of disconnecting the motor from circuit and establishing connections for maximum brakin efiect of the generator.
Thus it wil be observed that under descending load conditions the braking duty is divided between the mechanical and dynamic brakes and that with the dynamic regulation desc ed an exceedingly elect, reliable ii ib-le control is prohile it is unnecessary to specifically consider the conditions obtained by moving the cost oller in hoisting direction, it should noted that upon such movement of controller the segment 4:8" disengages seg ct 4&8 thereby inserting the entire resistan e 23 in circuit with the generator field, This effect-s an economy of current and protects the generator which on er hoisting conditions operates Without arena-- ture comiections.
rat I claim as new and desire to secure ters Patent is:
hoisting system, in combination, machine, a generator to driven normally dynamic l means said machine and ater insuring interruption of said dyo braking circuit upon starting of said for hoisting and insuring reestabiisnment of said dynamic braking circuit upon starting of-said machine for lo-Werin in a hoisting system, in combination, 'ng machine, a generator to be driven a normally closed dynamic braking 7. for said. generator and jointly opercontrol means for said machine and ge rator insuring interruption of said dyic braking circuit upon starting of said machine for hoisting and insuring reestablishment of said dynamic braking circuit upon starting of said machine for lowering but enabling subsequent interruption of said dynamic braking circuit for unretarded lowering operation of said machine.
8. a hoisting system, in combination, hoisting machine, a generator to be driven thereby, a normally closed dynamic braking circuit for said generator and jointly operable control means for said machine and generator insuring interruption of said braking circuit upon starting of said machine in hoisting direction and reestablishment of said circuit upon startin a r said generator and gointl of said j machine in lowering dlrection, sai control means further providing for regulation of said generator to vary its dynamic braking eifect and for interruption of said dynamic braking circuit while said machine is continued in operation in a lowering direction.
4. In a hoisting system, in combination,
jointly operable control means for said ma chine generator.
5. a hoisting system, combination, a hois ng mechanism, a driving'fmachiue therefor, a mechanical brake for said mechanism, driving connections between said machine and said mechanism acting upon said brake to apply the latter under overhauling load conditions, a generator to be driven by said machine, a normally closed dynamic braking circuit for said 'generator, and jointly operable control means for said machine generator insuring interruption mic circuit upon start hoisting and endirection witn said dynamic braking said meclninicai relieve said machine 'Dliillcfi to rupted to e it the combination, drawing ier said etween said acting upon said der overhauling or to be driven by chine and said mes brake to apply the lat load conditions, a geneia said machine, a normal hraln'ng circuit for said generator, and jointly operable cont: 1 chine and generator, insuring interruption of said dynamic braking circuit upon start ing of said machine for hoisting and enabling operation 0 machine in lowering direction with said dynamic braking cir cuit ither completed to assist said mechanical brake or interrupted to relieve said machine of its retarding efiect, leaving the braking duty to said mechanical brake, said control means also providing for regulation of said generator, when its dynamic braking circuit is closed, to vary th dynamic brak ing effect thereof. Q
7. In a. controller for hoisting machines, in combination, a reversible power controller for the hoisting machine, a generator to be driven by the machine and having a dynamic braking circuit, a switch biased to close the braking circuit of said generator andhavingawindingtooperatethesameto achine in lcwer v r i means for said y closed dynamic interrupt said circuit and control means for said switch operable with said power controller, said switch controlling means insuring energization of said switch in all hoisting positions of said power controller and insuring deenergization of said switch in the'neutral position ofsaid power controller and upon movement of said controller to its first lowering position.
8. In a controller for hoisting machines, in combination, a reversible power controller for the hoisting machine, a generator to be driven by the machine and having a dynamic braking circuit, a switch loiased to close the braking circuit of said generator and having a winding to operate the same to interru t said circuit and control means for sald switch operable with said power controller,
said switch controlling means insuring energization of said switch in all hoisting positions of said power controller and msurmg denergization of said switch in the neutralposition of said power controller While providing for selective energization and define!- gization of said switch in lowering position of said power controller,
ln witness whereof I have hereunto subscribed my name.
WM. (1 STEVEN S.