US1273101A - Overload apparatus. - Google Patents

Description

J. H. HALL.

OVERLOAD APPARATUS.

APPLICATION FILED MAY 2. 1914.

1 ,27 3, 1 O 1 Patented July 16, 1918.

2 SHEETS-SHEET I.

J. H. HALL.

OVERLOAD APPARATUS.

APPLICATION FILED MAY 2. 1914.

1 ,273, 1 O 1 Patented July 16, 1918.

2 SHEETSSHEET 2.

JAY H. HALL, OF CLEVELAND, OHIO.

QVERLOILD APPARATUS.

Application filed may 2, 1914.

To all whom it may concern:

Be it known that I, JAY H. HALL, a citizen of the United States, residing at Cleveland, in the county of Cuyahoga and State of Uhio, have invented new and useful improvements in Overload Apparatus, of which the following is a specification.

My invention relatesito overload apparatus for electric circuits. lln particular, it relates to overload apparatus having various adjustments for causing the overload device or devices to operate at different values of current. More particularly, it relates to apparatus containing one or more of such devices, in which one or more changes in adjustment may be brought about automatically.

In the control of electric motors it often happens that the current required for accelerating the motor is considerably greater than that required for running the motor after it is up to speed. This is particularly true in the case of alternating current mo- .tors. It is also true in many cases where direct current motors are used. Sometimes the value of current at which the overload device should be set during the running period of the motor is so low that the current required in starting will operate the device. To obviate this dilficulty it has been the practice to do away with the overload protection during thestarting period and provide it only durin the running period of the motor. The saving of the motor without overload protection when the current is first admitted to the motor circuit may result disastrously to the apparatus or to thepower circuit. It is often desirable, therefore, to provide an electric circuit with an overload device which affords a high overload protection when current is first admitted to the circuit, and then to change the adjustment to protect the circuit at a lower overload value after the current is reduced tonormal condition. It is also desirable to provide a time element featurefor the operation of .the device which is effective at all times.

One of the objects of my invention isto provide an overload device which will have different settings for different conditions of current in the circuit to be protected. Another ob'ect of my invention is to provide means whereby a change in the setting or calibration of the device may be brought about automatically in accordance with the Specification of Letters Patent.

Patented July 1L6, 3191 8..

Serial No. 835,856.

- specification, in which I have shown my in-.

vention in concrete form for purposes of illustration.

Referring to the accompanymg drawings,

' Figure 1 is an elevation of one form of overload device embodying my invention, parts being in section; Fig. 2, a diagrammatic representation showing my invention as it may be used in connection with a direct current motor; Fig. 3, a diagrammatic representation showing my invention as it may be used in connection with an alternating current motor; Fig. 4, a modification of the device shown in Fig. 1; and Fig. 5, a modification, showing; an optional location for the windin 20.

eferring to Fig. 1, the overload device here shown comprises two magnetizing windings l and 20 which may be connected in series with each other or in any desired suitable manner. The winding 1 has associated with it a magnetic circuit comprising a stationary frame 2, a movable core 3, and a stationary core 4:. The latter may be adjusted at various heights by means of the knurled head 5-. 6 is a lock nut for holding the stationary core in position. 7 is a bushing into which the core 4 is screwed, the

bushing being screwed into the frame 2 andused for clamping the spool of the winding 1 in place.

The movable contact 8 is shown normally closed against the stationary contact '9. These contacts may be used in any suitable manner for opening the circuit to be controlled; this may be the main circuit itself or an auxiliary circuit for controlling the main circuit. It will be understood that the contacts may have any other arrangement, such as being normally open. The movable contact 8 is pivoted at 10 and has a projection 11 which is arranged to be engaged by a non-magnetic pin 12 attached to the movable core 3, and slidable in the stationary core 4. When the winding is suliiciently energized the core 3 rises and causes the pin 12 to engage. the projection 11, thereby opening the contacts 8 and 9.

Thewinding 20 has associated therewith a stationary magnetizable frame 21, a movable .magnetizable core 22, and a relatively stationary magnetizable core 23 having a flange 24 which rests on a boss of the frame 21. The core 23 has a slight upward movement when it is engaged by the core 22. 25 is a bushing surrounding the core 23, and

screwed in the frame 21 to hold in. place the tube 26 comprising a part of the spool of the winding 20. A non-magnetic rod 27, slidable in the core 23, is fastened to the movable core 22 and terminates at its upper end in a hexagonal body 28 and the disk 29, the latter being on the former.

The movable core. 22 is provided at its lower end with a magnetizable extension 30 of reduced cross section. This extension slides in a stationary magnetizable bushing or pole piece 31 screwed into the frame 21 and terminating at its lower end in the head 32, by which it may be adjusted .to var1ous heights. 33 is a lock nut for holdlng the pole piece 31 in place. With this construction there is an operating gap between the movable core 22 and the core 23, which, when the winding is energized, tends to raise the disk'29. There is also a gap between the .lower shoulder of the movable core 22 and the upper end of the bushing or pole piece 31. The latter gap may betermed a lockout gap since 1t tends to prevent the upward movement of the disk 29 when the winding is sufficiently energized. This part of the device operates in a well-known manner in accordance with the principles of the switch shown in Fig.2 of Eastwoods Patent, No. 1,040,292; that is, the disk 29 and the core 22 remain in their unoperated or lower'position when the winding 20 is energized with a current above a predetermined value, and operate to raise the disk when the current is reduced to that value.

Between the disk 29 and the'movable core 3'is preferably interposed a movable system comprising a weighted member 50 pivoted between its ends at 51. The core 3 rests upon a roller 52 mounted on the lighter end of the weighted lever. The weight 53 with the stem 54 is also supported by the same end of the weighted lever 50. The stem 54 slides easily through a hole provided for it in the lever 50, so that, when the disk 29 rises and engages the weight 53, the stem is lifted free from the lever 50. Arraiiged as shown, the core 3 and the weight 53 tend to rotate the weighted lever 50 in a counter clockwise direction, its movement being limited by. the adjustable stop 55. When the disk 29 is raised by the winding 20, itlifts when the core 3 is raised, a smaller current in the winding 1 will, owing to the shortened gap between the cores 3 and 4E, operate the device and open the contacts 8 and 9 than when the core is in its lower position as shown on the drawing.

The lever 50 is constructed with considerable mass. Its inertia is, therefore, comparatively' high and its movement about the pivot 51 is slow whenever the core 3 is lifted by the magnetizing effect of the winding 1. Such a lever is described in H. F. Strattons application, Serial Number 736,907, filed December 16th, 1912. If the current in the winding is just suflicient to lift the core 3, the weight 50 will slowly turn, following up the movement of the core until the ,,core is raised to a point wherethe winding 1 will be enabled to close the gap between the cores 3 and 4: and open the contacts 8 and 9. If the current in the winding is reduced during the movement of the lever 50 and the rising of the core 3, and before the core 3 completes its movement, the weight of the core will return the lever 50 to its original position, as shown in the drawing, and the device will be thereby normally reset and ready to afford uppermost positions due to the lifting of the weight 53 by the lower winding 20.

In Fig. 4 I have shown a modification of my invention, in which the time element feature is omitted. The welght 53 is carried directly by the core 3, being supported on the stem 61. The frame 21 is mounted di rectly beneath the frame 2, so that the disk 29 when raised by its winding 20 lifts the weight 53 free from the core 3' and changes the value of current at which the core 3 can operate. The stem 61 extends through an opening in. the top of the weight 53 and into the hollow therein of larger diameter than that of the said opening. The lower end of the stem 61 has a disk 61 thereon which allows the weight 53' to be lifted independently of the stem 61 and the core 3. With this construction the device 0 crates at a .given' maximum current when t e disk 29 is in its initial position, and it operates at a given lower value when the weight 53 is raised by thedisk 29. It will be obvious to those skilled in the art that many other arrangements can be made by which the movable member, acted upon by the winding 20 when the current in the winding is below a predetermined value, will effect the operation of the movable member acted upon by the windin 1 so as to cause it to operate at a lower va ue.

Various adjustments are provided to adapt the use of the device to varying conditions. The operating gap above the core 3 can be adjusted by moving the core a up or down or by changing the position of the lever 50 by means of the adjustable stop 55, so that the core 3 will be raised or lowered. The operating value or" the lower winding 20 can be adjusted by raising or lowering the pole piece 31,.by -the head 32. The amount by which the operating gap of the core 3 is lengthened or shortened by movement of the core 22 and the disk 29 can be adjusted by means of the nut 56. The maximum movement of the lever 50 can be limited by means of the adjustable gap 57. The center of gravity of the lever 50 can be shifted horizontally by means of the eccentric bushing 51' about the pivot 51, whereby the time element of the device may be adjusted. Other adjustments may be provided as desired.

The stationary parts of the device are mounted in the well-known way on an insulating base 60 composed of wood, marble, or slate.

To more clearly describe the operation of the device ll will refer to Fig. 2, wherein the device K, representing the overload device of Fig. l or Fig. 4:, is incorporated in a motor control system for the motor with the armature A and the shunt field F. Current is admitted to the motor circuit through the main switch M, the circuit of whose operating winding passes through the contacts 8 and 9 of the overload device. The current in the motor circuit, upon closure of the switch M, is limited by means of the resistances R, R and R which are cut out in the well-known way by the series wound switches S, S S to bring the motor up to speed. The switch M is closed by short circuiting the resistance E by closing the normally open starting switch B. The resistance E is so proportioned that it prevents sufiicient current from flowing through the winding of the switch M to close the switch,

but permits sufficient current to flow to maintain the switch closed after it is once closed. After the switch M has closed, the starting switch B maybe opened. To stop the motor at will, the main switch M is caused to open by opening. the normally closed stopping switch C.

Assuming that the initial current for starting the motor is say 300 amperes, and that the peaks of current during the acceleration of the motor are approximately 300 amperes,

the overload device can be adjusted to operate in its normal position at about 350 amperes, to protect the motor during the acceleration period. If, after the motor has accelerated, the running current of the motor is only 100 amperes, it is desirable to reduce the overload protection in the device K to about 150 amperes. In such a case the winding 20 would be adjusted to hold its movable plunger 22 in normal position until the cur rent has diminished to, say 120 amperes. The core 22 then rises, lifts the weight 53, and allows the lever 50 to raise the core 3 to a new position which should be adjusted to operate on an overload value of say, 150 amperes. After this operation has taken place any value of current in the motor circuit above 150 amperes, due to an overload or other cause, will operate the overload device K, which opens the contacts 8 and 9, thereby causing the main switch M to open and out the motor ofi the line. It is seen that in this particular case the motor has an overload protection of 350 amperes during the accelerating period and 150 amperes during therunning period. When the main switch M opens, due to an overload, the windings 1 and 20 are denergized and the device returns to its initial position with all parts in readiness for ire-starting the motor.

It is obvious that the winding 20, instead of being connected directly in series with the winding 1, can be connected into any other part of the system as desired. For instance,

it can be included in the connection 71 between the points 7 2 and 73, as shown on Fig. 5. In this case the winding 20 is not energized until the closure of the last resistance cutting out switch S and the change in the setting of the overload device cannot occur until the motor is connected directly across the source of supply by the closure of the last resistance switch S The change in the setting of the overload device then occurs as soon as the motor current has diminished below the value at which the winding 20 is adjusted to raise its movable core 22 and the weight 53.

As before explained, the time element feature is efiective to operate the device K in a shorter time on a high overload value than in the case of a long continued application of a moderate overload value of current. For instance, during the running period of the motor 150 amperes will cause the operation of the device in, say five seconds, whereas a sudden overload of 200 amperes will cause the operation of the device in a much shorter time, and the variation in the time limit can be adjusted by various means, as already explained.

Fig. 3 shows the application of my overload device to the control of an alternating current induction motor G. M is the main switch, arranged to connect the motor cir- &

' is not permitted to pass to hold the switch M closed, but a small amount of current is allowed to flowfor deenergizing the winding M insuring an immediate opening of the switch. I have indicated the well-known form of starting device for the motor, comprising a compensator or auto-transformer C and a double-throw starting and running switch H. I have indicated the overload devices K and K in two of the leads supplying current to the motor, but it is obvious that they could be used in all three leads, or only one. It is not necessary to trace the circuits in the diagram as they are easily followed upon inspection.

It is well known that the current for starting an induction motor is much greater than the current required during the running period. The overload devices shown may be adjusted to accommodate the currents required 'in the particular apparatus with which they are associated. The motor is protected at a high overloadvalue during the starting period, the winding 20 being adjusted tolock its movable core in its initial position while the current is above a certain value. After the switch H has been thrown to the running position and the motor cur rent is reduced to the normal running value of the motor, the winding 20 is adjusted to operate its core 22, lift the weight 53, and change the setting of the overload devlce. so that the devices K and K will then operate at a suitable value to protect the motor. The winding 20 may be connected in one of the running circuits if so desired.

I have shown and described my invention as used in connection with the control of electric motor circuits, but it will be obvious to those skilled in the art that it may be used in connection with other circuits in which a change in the value of overload protection is desired.

I claim 1. In an electromagnetic device, an electric circuit, a winding therein, an armature, a magnetic circuit energized by current in the winding and movable thereby from a normal position of rest to close an air-gap in the magnetic circuit when the current exceeds a predetermined value, and means whereby, when the current in the circuit is below a lower predetermined value, the armature is moved to a second position of rest at which the air-gap ispartially closed.

2. The combination of an electric circuit, an overload. device including a winding in series with the circuit, an armature adapted to be attracted by the winding to open the circuit when the current in the winding exceeds a certain value, a second winding in the said circuit, and an armature operated by the second winding when the current therein is below acertain lower value only, the operation of the second armature moving the first armature to a position from which it moves and opens the circuit when the current exceeds a predetermined value less than the first.

3. The combination of an electric circuit, an overload device including a winding responsive to current in the circuit, an armature adapted to be moved from rest by the winding to open the circuit when the current in the circuit exceeds a certain value,

a second winding in series with the circuit, and an armature operated thereby only when the current in the winding is below a C(l'l in lower value, the said second armature being adapted when operated to move the first armature to a second position of rest, from which the first armature will be moved to open the circuit when the current exceeds a predetermined value less than the first.

l. The combination with an electric circuit, of a magnetically-operated device, including an operating winding connected in the circuit, an armature moved from its normal position thereby when the current in the circuit exceeds a predetermined value, and means controlled by a reduction of the current in the circuit for moving the armature to a second position of rest and lowering the value at which the said armature ,operates.

. cluding a winding 1n the circuit, an armature. operated thereby when the current in the circuit exceeds a certain value, a second winding in the circuit, and means operated by the second winding upon a reduction of current therein for causing the first winding to operate its armature at a predetermined value less than the said first value.

6. The combination with an electric circuit, of an overload device for opening the circuit when the current exceeds a predetermined value, and means including a winding in series with the circuit and controlled by a reduction of current in the winding, for causing said device to open the circuit when the current exceeds a second predotermined value less than the first.

when the current in the circuit exceeds a predetermined value, and means for governing the movement of the armature in accordance with the current in the circuit, the said means including means operated by a reduction of current in the circuit for automatically moving the armature to a position where it will be operated when the current in the circuit exceeds a second predetermined value less than the first.

9. The combination with an electric circuit, of a magnetically-operated device including a winding in the circuit, an armature operated thereby when the current in the circuit exceeds a certain value, a pivoted weight cooperating with the armature to cause the speed of movement of the armature to vary with the current, and a second winding in the circuit for automatically changing the position of the center of gravity of said weight when the current reduces below a predetermined value.

10. The combination with an electric circuit, of a magnetically-operated device, including a winding energized by current in the circuit, an armature operated thereby when the current exceeds a certain value,.

inertia means cooperating with the armature to vary its movement in accordance with the value of current, and means for automatically changing the effect of said inertia means when the current in the circuit is below a predetermined value.

11. In a magnetically-operated device, a winding, an armature operated thereby when the current in the circuit eXceeds a predetermined value, a second winding energized by current in the circuit, and means operated by the second winding efi'ective only when the current in the circuit is reduced to a certain value for causing the operation of said armature at a second predetermined value less than the first.

12. In a magnetically-operated device, a winding, an armature operated thereby when the current exceeds a predetermined value, a pivoted weight cooperating with the armature for regulating the movement thereof, and means operated by a reduction of current in the circuit for changing the position of the center of gravity of the said weight.

13. The combination with an electric circuit, of a magnetically-operated device including a winding in said circuit, an armature moved from its initial position by said winding only when the current is below 'a certain value. a second winding in said circuit, a member movable thereby for opening the said circuit when the current therein exceeds a certain value. and means whereby the armature moved by the first winding changes the magnetic relation between the second winding and its movable member.

14:. The combination with an electric circuit, of a magnetically-operated device ineluding an armature, a winding for holding the armature in its initial position when the current in the circuit is above a certain value and operating to move the armature from its initial position when the current is reduced, and means associated with the armature for opening the circuit at one value therein when the armature is in its initial position, and at a lower value when the armature is moved to its operated position.

15. In an electromagnetic device, a winding, a movable member, means controlled by current in the winding whereby the movable member occupies one position of rest when ,the current is below a predetermined value only, whereby the movable member is moved to a second position of rest when the current in the winding is below a second predetermined value, and whereby the movable member remains in the second position of rest only when the current in the winding is below a third predetermined value.

16. The combination of an electric circuit, an electromagnetic overload device having a magnetic circuit, an energizing winding therefor energized by current in the electric circuit, a movable member in the magnetic circuit, the movable member being adapted to be moved by the winding "from its normal position when the current in the electric circuit is above a predetermined overload value, and means whereby, when the current in the circuit is below a second predetermined value, the movable member ismoved from its normal position to a position of rest, from which it is adapted to be moved by the energizing winding when the current in the circuit is above a second predetermined overload value less than the first predetermined overload value.

17. In an electromagnetic overload device for opening a circuit, an energizing winding and a movable member occupying a nor-' mal position of rest when the winding is deenergized, and means whereby the movable member is moved from its normal position of rest to open the circuit when the current in the circuit is above a first predetermined overload value, and whereby when the current in the circuit falls below a predetermined value, the movable member is moved to a second position of rest without opening the circuit, and whereby it remains in the latter position while the current in the circuit is below a second predetermined overload value only.

18. In electromagnetic overload device for opening a circuit, an energizing winding and a movable member occupying a normal position at rest when the winding is deenergized, and means whereby the movable member is moved from its normal position of rest to open the circuit the current in the circuit is above a first predetermined overload value, and whereby when the current in the circuit falls below a predetermined value, the movable member is moved to a second position of rest without opening the circuit, and whereby it remains in the latter position while the current in the circuit is below a second predetermined overload value only, the said means including a time interval device for producing a relatively slow movement of the movable member to the second position of rest.

19. Means for protecting electrical apparatus requiring a larger current for starting than for running, comprising a switch, an electromagnetic overload device controlling the switch, the overload device having a magnetic movable member adapted to 00- ,mined running current for opening the switch, and electromagnetic means controlled by the reduction of the current from the starting to the running value for moving the movable member from one position to the other.

Signed at Cleveland, Ohio, this 28th day 3 0 of April, A. D. 1914,

- JAY H. HALL. Witnesses:

RUTH H. BENNETT, H. M. DIEMER.

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