US1306545A

US1306545A - jones

Info

Publication number: US1306545A
Authority: US
Publication date: 1919-06-10
Anticipated expiration: 1936-06-10

Description

- B. w. JONES. SYSTEM OF CONTROL FOR ELECTRIQMOTORS.

'l\PPLlCl-\TH)N FILED MAYZS. 1916- Patented June 10, 1919.

Inventor m Has ffttorneg.

1 Schenectady,

UNITED STATES PATENT orricrz.

BENJAMIN W. JONES, OF SCHE-NECTADY, NEW YORK, ASSIGNOR T0 GENERAL ELECTRIC b COMPANY, A CORPORATION OF NEW YORK.

SYSTEM OF CONTROL FOR ELECTRIC MOTOR To aZZ whom it may concern:

Be it known that I, BENJAMIN W. JONES, a citizen of the United States, residing at county of Schenectady, State of New York, have invented a certain new and useful System of Control for Electric Motors, of which the following is a specification.

My invention relates to the control of hoists and the like, and has for its object the provision of means whereby the hoist may be started, stopped and generally controlled in a safe and effective manner.

My invention is particularly applicable to the control of an electric motor which drives a load, such as a hoist, in two directions, and it provides means for manually and automatically controlling the motor so that accidents due to over-travel may be avoided.

It is customary to provide some means such as limit switches which will automatically denergize theelectric driving .motor and apply a brake to bring the hoist to rest when the hoist passes one of its predetermined limits of travel. p

In the case of hoists and especially of the largersizes it iscustomary to provide a circuit breaking switch which cuts off the motor from the line when either limit switch is operated. It is also desirable to slow down the hoist before it reaches a limit switch so as to reduce the over travel and makethe point at which the hoist will stop more certain. One of the objects of my in vention is to provide means whereby ,after the hoist has been slowed down, theflimit mg the control away from the controlle In order to regain control, the operator must operate a separate-switch which permits the hoist to be returned but not moved forward. When the hoist has beenreturned past the point atvwhich the limit switch o'perated, 'th at both directions of travel is restored.

' In-one form of my invention, ;I employ two. limiting devices, onea limit switch directly geared to the motor through the hoisting drums, hereinafter called a geared limit switch, and another set of limit switches in the path; of travel of the hoistmotor and is, when it is returned within the normal limits of travel, full control for ..vices in case the Specification of Letters Patent. Patented June 10 1919, Application filed May 26, 1916. Serial No. 100,118.

ing buckets, hereinafter called track limit switches. Manually operated switches in the control circuit cooperate with the master controller, the motor reversing switches, the electro-magnetically actuated brake for the hoist, the geared limit switch and the track limit switches to the hoist from dangers which would be pres ent if full control of the motor by means of the controller could be had when the hoist was past either one of its limits. I also provide means for retarding the speed of the hoisting motor by automatically inserting a controlling resistance in the motor circuit before the limit of travel has been reached, with the further provision that the control of this resistance is restored to the master controller when it is desired to return the hoist to the safe limits of travel,

Referring to the drawing, the single figure of which shows one embodiment of my invention, the polyphase induction motor '1 is connected to the supply circuit 2, through the oil switcl 3 and through either one of the electromagnetically actuated reversing switches 4 or 5 depending upon the direction of travel of the hoist desired. The motor 1 is directly and 7 of shown for a balanced hoist which I have purpose of illustration, and directly geared to the hoisting drums is the protect the workmen and geared to the hoisting drums 6 9, and the drum 7 has a hoisting bucket 10 connected to it in a similar manner; the arrangement being such that when the bucket 9 is being raised the bucket 10 is being simultaneously lowered, and vice versa.

In the path of travel of the bucket 9 is a track limit switch 11 and in the path of travel of the bucket 10 is a track limit switch 12, provided as additional protective degeared limit switch 8 should fail to operate. Associated with the hoisting drums is an electromagnetically actuated friction brake 13 which exerts a holding friction on the drum shaft when for anv .reason the electromagnet 14 is deenergized.

the segment ,magnet coil 16, the segments 30 and 31 of net coil 16, it is ci rcuit controlled by a hand operated switch lo. The no-volta'ge relay 16 has two

switch members

17 and 18 which open the circuit to all the controlling devices in case the current should fail or the hoist run past one of its limits of tra el. The reversible master controller 19 has two operative positions for each direction of rotation and also has'a contact segment 20 at its neutral or ofi' position. Each of the reversing switches -11 and 5 has mechanically connected thereto an electrical interlock which is adapted to close a circuit through one set of contacts when its respective reversin switch is in the open posit-ion, and through another set or contacts when in the closed position. Associated with these reversing switches is a pivoted mechanical interlock 21 which me chanically prevents both switches being closed at the same time. The no-voltage release magnet 22 has in operative relation thereto a biased pivoted detent 23 which maintains the oil switch 3 in a. closed position against its bias to the open position when the magnet 22 isenergized. The triple pole double throw

protective switches

24 and 25 are connected in the control circuits for a purpose to be hereinafter fully disclosed. The means for varying the speed of the motor comprise resistances 26 and 27 connected in the rotor circuit and controlled by electromagnetically actuated switches 28 and 2t The no-voltage relay 16, and no-voltage release magnet 22 are in multiple so that in case of failure of current or in case one of the supply circuits to these magnets is opened, the

switches

17 and 18 are opened, the oil switch 3 is opened and the reversing switch 4C or 5 which had been closed is opened. The opening of the switch 18 deenergizes thebrake coil 11 and the brake 13 exerts a braking pressure on the drum shaft to stop the hoist. The

switch members

17 and 18, oilvswi-tch 3, reversing switch 4 or 5 and the

resistance controllin switches

28 and 29 will all be automatically opened in case the hoist runs past one of its predetermined limits.

The operation of my lows':' I

' Assho'wn in the drawing, the control circuits and the motor are deenergized, Closin the switch 15 energizes the no-voltage re ay magnet 16, the circuit 'being through 20 of the master controller, the

device is as folthe geared limit switch 8, through the track limit switches 11 and 12 to the other side of the control circuit. Since the no-voltage release magnet 22 is in multiple with the maglikewisc energized through the same circuit. Energization of the magnet 16 causes

switch members

17 and 18 to close, the switch member 17 closing a maintaining circuit for themagnet 16 and the The switch 15, the

switches

17 and 18, and

the oil switch being closed, he would turn the master controller 19 to the first operative position a, making an energizing circuit for the coil of the reversing switch 5 through the switch 17, the master controller 19, the lower interlock contacts 32 and of reversing switch 1, coil of reversing switch 5, through the right blade of switch 25, contacts 3st and 31 ot' the geared limit switch 8 and the track limit switches 11 and 12 to the other side of the control circuit. This will close the motor circuit through'the resistances 26 and 27 and the motor would now run at a low speed due to the resistances in its rotor circuit. In order to cause the motor to run at full speed, the master controller is moved to its second operative position Z), completing an energizing circuit for the coil of resistance controlling switch 28, through the switch 17, upper contacts of the master controller, upper interlock contacts 35 and 36 of reversing switch 5,

segments

37 and 38 of geared limit switch 8, coil of switch 28, lower contacts oi master controller, and the track limit swit hes 11 and 12 to the other side of the co ol circuit. The coil of switch 29 is all at the same time energized through the switch :mcmber 17, coilof switch 29, lov

ments of master controller 19, through limit switches 11 and 12 to the other of the control circuit. Upon the closin switches 28 and 29. the resistances 26 and 27 are short circuitcd and the motor runs at full speed.

If the operator should now desire to reverse the motor while the hoist is still within its predetermined limits of travel he would turn the master controller to the off positionfdkanergizing'the reversing switch 5 and opening the motor circuit. the master controller to the first position a. to the right he would energize the coil of By turning moving the controller to the second position b energizing and closing the reslstanceshort.

circuiting switches

28 and 29. The circuit "for the coil of switch 28 is through the switch 17, upper contacts of the master con troller 19, lower interlock contacts 39 and 1S oircrersing switch 5, upper interlock contacts %1 and 12 of reversing switch 4, seg ments 43 and 38 of the geared limit switch, lower contacts of the master controller and track limit switches 11 and 12 to the other side of the control circuit. The circuit for coil of switch 29 is the same as for the other direction of rotation, except for the changes caused by the movement of the master controller to the right.

it the operator should now continue operating the motor 1 to raise bucket 9 and lower the bucket 10, shortly before he reached the limit of travel the segment 43 would separate from its corresponding contact, denergizing the coil of resistance controlling switch 28, inserting the resistance 26 in the rotor circuit of the motor, decreasing the motor speed. If the motor should continue to operate the hoist in this same direction, the bucket 9 will reach its upper limit of travel, deenergizing the control circuits at the track limit switch 11 and also at the segments 30 and d4 of the geared limit switch 8. This will deener ize no-voltage relay 16, the novoltage release magnet 22, the 'coil of reversing switch 4, the coil 14 of the brake 13 and the coil of resistance controlling switch 29. The corresponding switches will open, deenergizingthe motor and the control circuits, the brake will be applied to bring the hoist to rest and the resistance 27 will also be in cluded in the rotor circuit of the motor.

Because of the inertia of the moving parts the hoist necessarily runs a certaindistance beyond the limits determined by the limit switches and it is necessary to provide some means by which the operator may safely return the hoist to its proper limits of travel. If the master controller 19 is moved to the off position, the no-voltagefelay 16 will not be energized as was the case when the hoist was operating within its proper limits of travel, since the circuit. for this relay is open at the contact 30 of the geared limit switch and the track limit switch 11. Neither can the no-voltage release magnet and the brake magnet 14 be energized because they are controlled by the

switch members

17 and 18 of the 'no-voltage relay 16. The operator is in this'way prevented from energizing the motor'to run in either direction, and he can only energize the motor to return by throwing the switch 24 to the right. The no-voltage relay 16 may be energized if the master controller 19 is in the off position, the circuit being through the contact 20 of the master controller, the coil ii"). the middle blade of the switch 24:, segments 3%; and 31 of the geared limit switch, the right blade of switch 24, track limit switch 12 to the other side of the control circuit. The

switches

17 and 18 are thus causedto close energizing the no-voltage rclease magnet 22 and the brake coil releasing the brake 13. From this it can be seen that by moving the switch 24- to the right position the track limit switch 11 has been short circuited and the geared limit switch 8 has been rendered inefiective to deenergize the motor when the bucket 9 is beyond its upper limit of travel, and the control of the motor is independent of the limit switch 11 and that part of the geared limit switch 8 which protects the hoist when raising the bllCntU 9. By moving the master controller 19 to the first position to the right the coil of reversing switch 5 may be energized, this time through the right blade of switch 25, segments 34 and 31 of the geared limit switch 8, the right blade of switch 24, the track limit switch 12 to the other side of the control circuit. The resistances 26 and 27 in the rotor circuit are short circuited when the master controller 29 is moved to the sec ond position in the same manner as p re viously explained.

The operator may continue to lower the bucket 9, and raise the bucket 10, buthe cannot reverse the motor for operation in the other direction by simply reversing the master controller 19 as he was able to do pre-' viously when he was operating the hoist" within its proper limits of travel, because the circuit to the coil of reversing switch '4 has been opened by the movement of the switch 2 I to the right position. If he has returned the hoist to within its proper limits of travel he may reverse the motorby first moving the controller to the oil position and then throwing the switch 24 to the left position. He may then operate "the hoist within the proper limits of travel 111 the same manner as heretoforeexplained. if, however, the operator should attempt "to reverse the motor before the bucket 9 had returned past its predetermined upper limits of travel While the hoist proper limits, he wot kl b closing the .circuit co-the coil of reversing switch 4;, as the circuittothis coil would havejbeeuqopened by the movement of the switch era) the right. He could not complete the circuit for the coil of this reversing switch't by moving the switch at to its left hand position, because that would deenergize the no-voltage relay 16, the no-voltage release magnet 22, the brake magnet 14 and open the oil switch 3 and apply the brake 13, as the control circuit would be open'at track limit switch 11 and segments 30 and 44c of the geared limit switch.

, From this it can be seen that the operator can in no case render the limiting means ineflective so as to return the hoist to its predetermined limits 1 of travel, and then,

is returning to its;

Qprevented from;

man

an case he should thereafter run the -hoist beyond either one of its limits.

ill)

- by Letters Patent of the Uni-ted States, is p In case the operator should run the hoist x15 beyond the other limit of travel, that is, when the bucket 10 had passed its upper limit', the geared limit. switch at the contacts 30 and 3% and the track limit switch 12 will denergize the control circuits and the motor and apply the brake. The operation of returning the hoist to its proper limits of travel is substantially the same as that when the bucket 9 had passed its upper limit except that in this case the switch 25 must be thrown to its left end position. The protective features above outlined are the same in this case as previously explained in connection with the protective features when the bucket 9 had passed its predetermined limit of travel, as will be readily understood.

In accordance with the provisions of the patent statutes, 1 have described the principle of operation of my invention, to with the apparatus which I now co l to represent the 'best embodiment thereof,

but I desire to have it understood that the apparatus shown is only illustrative, and that the invention can be carried out by other means.

What I claim as new and desire to secure 1.. In combination with a hoist or the like, an electric motor for operating it in two directions and a reversing controller therefor, of a limit switch at each limit of travel,

' means for opening the motor circuit and rendering the controller inoperative to control the motor for operation ineither direction upon the operation of either of said limit switches and means whereby control is restored to the controller to return the hoist beyond the point where the limit switch operated after which full control is restored to the controller.

2. In combination with a hoist or the like,

an electric motor for operating it in two directions, and a reversing controller therefor, of a limit switch at each limit of travel, an electro-magnetically controlled main switch for opening the motor circuit upon the operation of either of said limit switches, connections whereby the operation of either of said limit switches renders the controller inoperative to control the motor for operation in either direction, and means whereby a control circuit for the main switch is established independently of the limit switches to return the hoist beyond the point where the limit switch was operated after which full control of the motor is restored to the controller..

3. In combination'with a hoist or the like, an electric motor for operating it in two directions and a reversingcontroller therefor, of a limit switch at each limit of travel, an electro magnetically controlled main switch for opening the motor circuit UPOT the operation of either of said limit switches, connections whereby the operation of either limit switch renders the controller inoperative to control the motor for operation in either direction, and means inde pendent of the controller whereby a control circuit for the main switch is established through the controller to return the hoist beyond the point where the limit switch operated after which full control of the motor is restored to the controller.

4. The combination with a hoist or the like, an electric motor for operating it in two directions and a reversing controller therefor, of a switch operated to slow down the motor at a predetermined point in each limit of travel, means for opening the motor circuit and rendering the controllerinoperatire to control the motor after it has slowed down and upon the operation of either of said limit switches and means whereby control is restored to the controller to return the hoist beyond the point where the limit switch operated after which full control is restored to the controller through the limit switches and slow down switch.

5. The combination with a hoist or the like, an electric motor for operating it in two directions and a reversing controller therefor, of alswitch operated to slow down the motor at aipredetermined point in each direction of t 'avel, a limit switch at each limit of travel, means for opening the motor circuit and rendering the controller inopera tive to control the motor after it has slowed down and'upon the operation of either of said limit switches and means whereby control is restored to the controller to return the hoist at full speed beyond the point where the limit switch operated after which full control is restored to the controller through the limit switches and slow down switch.

6. The combination with a hoist or the -like, an electric motor for operating it in two directions and a reversing controller down and uponl mit s'wltches, and manually operated the 1 the limit. switch cont1 -o1 is restored operated after which fall own switch. a ciroult through thecontroller In witness whereof, I have hereunto set Independent of the hmit switches and with my hand this 25th day of May, 1916. the slow.dow11 ;switch ineffective whereby 7+ BENJAMIN W. JONES.