US1941921A - Motor operated relay - Google Patents

Description

c. WILHJELM 1,941,921 MOTOR OPERATED RELAY Filed July 22, 1930 ATTORNEY.

Patented Jan. 2, 1934 UNITED STATES MOTOR OPERATED RELAY Christian Wilhjelm, Philadelphia, Pa., assignor to Gustav H. Johanson, trustee Application July 22, 1930. Serial No. 469,836

16 Claims.

This invention relates to motor operated relays, and particularly to relays operable in response to a changing condition of heat or pressure or the like.

Automatic control of variable conditions, such as those attendant upon pressure, light, humidity, temperature, and the like, usually depend on a sensitive instrument pointer for setting in motion anumber of other more or less powerful devices, which, through mechanical operations, in some way or other make the necessary correction, whatever it may be, to maintain the de-- sired conditions.

The most common method of actuating control devices from sensitive instrument pointers is to arrange one or more contacts in the necessary instrument or condition responsive device so that the indicating pointer as it changes position in response to a change in condition touches these contacts and thereby selects one of two or more different passages for an electric circuit, which in turn must set the controlling machinery in action until the changed conditions have been corrected as manifested by a return of the conditions to a normal predetermined condition. However the amount of electric current that can pass through such flimsy instrument contacts, is usually very limited, so it nearly always becomes necessary to introduce one or more stages of relays, the one stage being capable of carrying more current through its contacts than the next previous stage in the series. One of the objects of this invention therefore, is to provide such an intermediate relay device between a contact instrument and the correcting control equipinent, that although it only uses a very faint current for its operation, it can make and break large amounts of electric current and operate electric motors of several horsepower without any additional step-up relays.

Another object is to provide such an intermediate relay between contacts controlled by a mercury colunm and correcting control equipment.

Another object is-to provide a relay to operate from these flimsy instrument contacts in such a manner that the flickering which is due to vibration of the instrument when mounted in a factory building does not pass the relay. Any ordinary solenoid operated relay naturally will carry such flickering through the whole control system and cause almost the destruction of moving parts. Relays are now used which prevent this chattering by self locking features, but when used it becomes necessary for the controlling moving contactor to move far enough back to close another contact in order to make the locked relay fall out, and then close the circuit that in turn makes corrections for variations in the opposite direction. This method makes the control instrument complicated and at the same time less sensitive for control as the required large distance between the two contacts needed for each operation necessary, must be travelled by the moving contactor either way before any change in conditions can be effected through the relays. Therefore, a further object of the invention is to provide a control relay that on the faintest closing of the instrument contact will operate the required correcting mechanism and which also, as soon as this contact is severed will react into some other position causing some other correcting mechanism to operate. Due to the fact that the current consumed by the relay operation is very faint, there is practically no sparking when the instrument contact is broken, hence the faintest move of the moving contactor from the contact will cause a desired change in the operation of the controlling mechanism.

There are many varied means of making the electric contacts in standard measuring or condition responsive instruments. There are also many different mechanical means for controlling the conditions from such gauges or instruments. This invention, therefore, primarily applies to an intermediate device wired in between the sensitive control gauge and the controlling means, therefore, in the description and accompanying drawing, 1 am describing the invention in order to show how it can apply to the now commonly used contact instruments and control means of the different types. The details here shown, however, should by no means confine my invention, but merely show a few of its many applications.

In the accompanying drawing, forming part of this description,

Fig. 1 represents a diagrammatic perspective of one, purely illustrative form of the invention,

Fig. 2 represents an end elevation of the circuit controlling element actuated by the motor, showing the element in one extreme position, and

Fig. 3 represents an end elevation of the circuit controlling element actuated by the motor, showing the element in another extreme position.

This particular design is for use with measuring gauges or devices responsive to conditions of temperature and pressure, and the like, where a mercury column is used as the medium of indieating the changes. This is particularly relevant to those condition responsive mercury columns having three separate control'contacts successively engaged by the moving column and where it is desired to secure the establishment of a plurality of circuits in accordance with the movement of the. mercury column.

The actuating instrument or condition responsive device is, as shown, a mercury thermometer having inserted three contact wires through the glass of the stem in position to be contacted by the mercury column. The glass thermometer bulb is designated as 1, the mercury column or moving contact as 2, the lower contact as 3, the middle contact as 4 and the high contact as 5. For purposes of this description it will be assumed that conditions affecting the thermometer are proper or normal when the mercury 2 contacts with the lower contact 3 and the middle contact 4, but is below the high contact 5.

The following parts are the essentials in a reversing self-starting alternating current motor which is now a standard generally known article on the market. For illustrative and not limitative purposes reference might be made to U. S. Patent No. 1,283,435 for a disclosure of a type of motor that might be usable herein when suitably modifled to comprise a reversing motor. There are numerous reversing motors, made by different manufacturers, that will admirably fill the requirements of this invention, but for further dis closure of a reversing motor of the type preferred with this invention, reference may be made to Bulletin MI3 of the Warren Telechron Company, Ashland, Massachusetts, published in 1930, and particularly to pages 8 and 11, type BX and CX respectively. However for this purpose any electric motor that can conveniently be reversed by sending current to it alternating through one or the other of two wires can be used. The motor has a field winding 6 on an iron core 8 tending to force the motor counter-clockwise, and has an oppositely wound coil 7 on an iron core 9, tending to force the motor in a clockwise direction,

both directions of force being indicated by arrows appropriately placed on the sides of the windings for purposes of clarity. The motor armatures are housed within a tube 10, which is extended to form the enlarged housing 11, within which latter is mounted a reduction gearing of any desired sort, as preferably a train of spur gears (not shown), sufficient to transform the high speed of the motor into the slow speed of a shaft 12, extending from the gear housing 11. This motor as shown is on the market in this general design with drive shaft speed of 1 R. P. M. more or less as may be required. In this description, it may be assumed that the speed of shaft 12 is 1 R. P. M., however, the speed of operation is unimportant although certain shaft speeds may prove more satisfactory in practice than others for certain applications. This particular motor as shown can be operated clockwise or anticlockwise at will, by sending current through either coil 6 or coil 7. In this description as noted, it will be assumed that the passing of current through coil 6, will result in a counterclockwise movement of shaft 12 as indicated by the arrow on the side of coil 6, while passing current through coil 7 will result in a clockwise movement of shaft 12, as indicated by the arrow on coil 7.

The shaft 12 carries a disc 13 which is held by friction on the shaft by means of the spring 14 and the nut 15. On account of this friction the disc 13 will turn with the shaft 12, as long as it is free to move. However, the movement of the disc with the shaft is restricted and limited in clockwise direction by the suitably supported mechanical stop 16 being engaged or abutted by a notch, shoulder, or ear 17 on the disc 13. In the counter-clockwise direction, its movement is restricted by the mechanical stop 18 being engaged by a corresponding shoulder or notch 19 on the disc 13. Two glass bulbs or tubes 20 and 21, respectively, are clamped to the disc 13, preferably toward the upper or top position thereof, with their longitudinal axes out of parallelism or alignment. These two fully enclosed glass bulbs contain each a small amount of mercury. Four electric contacts, two in each end, extend from the inside of each bulb, and bear reference characters respectively from 22 to 28 inclusive, and of which contact 25 is a double contact having a leg in each of the two bulbs 20 and 21.

The outer periphery of the disc, preferably the lower half thereof, between the ears or shoulders 17 and 19, has a contour formed of arcs described about the axis of shaft 12 and the axis of the disc, but on different radii. Thus the right hand side of the disc as shown in the drawing has a cam surface 29 extending from ear 17 to almost the vertical diameter of the disc in the position shown in Fig. 1, of a small radius, while the lefthand side of the disc has a cam surface 30 extending from ear 19 to almost the termination of cam surface of larger radius, while the adjacent ends, of cam surfaces 29 and 30 are separated by an-inwardly extending notch or recess 36 formed in the center of the disc. If the disc is disposed as in Fig. 1, the recess or notch 36 will be disposed with the vertical diameter of the'disc passing through the recess.

The insulated block 31 serves as a support for the three flexible contact arms 32, 33 and 34. The I mechanical arrangement of these contacts in relation to the disc 13 is such that the cam 35 on con.- tact 33 slides on the bottom surface of disc .13. When the disc 13 is-in the mid-position, as shown in the drawing Fig. 1, the cam 35 is received in the recess 36, and contact 33 through its resilient upward urge will engage and make contact with the upper contact arm 34. When the disc is moved from mid-position in a clockwise direction the cam 35 is forced out of the notch or recess 36'and rides upon the cam surface 29, which is formed on an arc of such radius as to depress the contact arm 33 out of engagement with contact 34 but not far enough to establish contact with contact arm 32. From the mid-position with the cam 35 received in the recess or notch 36, as shown in Fig. 1, counter-clockwise movement of the disc 13 forces the cam 35 out of the recess 36 and upon the cam surface 30, which, being formed on an arc of greater radius than is cam surface 29, depresses the spring contact arm 33 to a degree sufiicient toestablish contact of contact arm 33 with the lower contact arm 32. In Figs. 2 and 3 are shown the position of contacts 32, 33 and 34 in the extreme right and left positions, the results respectively from clockwise and counterclockwise movement of the disc 13.

In Fig. 1, 37, 38 and 39 designate, respectively, three electric lights which may be of different colors, say 37 is green and stands for low temperature or negative condition, 38 is white and stands for right temperature or neutral or normal condition, and 39 stands for red and means too high temperature or positive condition. These three lights enable an operator to manually make the necessary manipulation of valves or other regu-' lating devices, in order to try to maintain the .proper temperature or normal condition with the white light burning. If automatic control is desired the current that lights the three lights respectively can be used to manipulate valves, dampers, or other devices mechanically, thus eliminating the human element. The lights will be designated broadly, therefore, as electric devices.

The glass'bulbs 20 and 21 as willbe noticed are so arranged that when cam on contact 33 rests on notch or step 36, the globule of mercury in each bulb lies in that end of each'bulb,

that meet in the center in this position owing to the angular divergence of two tubes. .It will be noticed that a metallic connection is completed from contact 24 through mercury in bulb 21 to contact 25 from contact .25 to mercury in bulb 20 to contact 26. If disc 13 is tilted counter-clockwise, the mercury in both bulbs will take the position as shown in Fig. 3. It will be noticed that the mercury in bulb 21 remains'in the same position as shown in Fig. 1, but the mercury in bulb 20, due to the tilting of disc 13, shifts to the other end of the bulb, thereby opening the metallic connection between 24 and 26, but establishing a new connection between 27 and 28. In Fig. 2, the disc .13 is tilted clockwise and in this case the mercury in bulb 21 shifts and opens the connection from 24 to 26 whereas it makes a connection between 22 and 23, thus the three different positions of the disc 13; left tilted position Fig. 3, mid-position Fig. 1, and right tilted position Fig. 2, each closes aseparate set of contacts and automatically breaks any one of the two other connections that were closed ;in the previous position. The angular relation betweenthe two bulbs 20 and 21 is generally such (as shown) that only one of these contacts can be made and one circuit completed at any one time, although there may be occasions when the bulbs may have to be so mounted in relation to each other that the concontact 3 and the middle contact 4, but, Obviously has not been elevated to such a degree as to cause it to engage also upper contact 5. The light or control circuit, therefore, is as follows: from line 40 current will pass through wire 41 to wire 42 -to contact 24, through mercury in bulb '21 to contact 25, through mercury in bulb 20,

to contact 26, to wire 43, to lamp or electric device 38, to wire 44, and wire 46, back to the other side of the line 47, and the lamp or device will burn or function indicating that the temperature or condition where responsive indicator 1 is located is within the desired limit.

With the disc in mid-position, while the condition-responsive circuit controller is establishing contact with the lower contact 3 and middle contact 4, and with the conditions affecting the bulb 1 being normal, the following circuits are established in the motor. There is first a permanent fractional circuit or circuit of reduced or less current strength through the coil 6, as follows: line 40, wire 41, wire 42, coil 6, wire 48, resistor 49, wire 50, to the other line 47. Owing to the fact that cam 35 onspring contact arm 33 is received in the recess or notch 36 on disc 13, so that am 33 engages contact arm 34, there is, secondly, a balanced fractional circuit or circuit of reduced or less current strength through the opposite coil 7 of the motor, as follows: line 40, wire 51, contact 3, mercury column 2, contact 4,, wire 52, contact arm 33, contact arm 34, resistor 53', (equal in ohms resistance to resistor 49) wire 54, coil 7, wire 55, wire 50, back to the other side of the line 47. with a fractional circuit or circuit of reduced or less current strength in coil 6, and an equal and balancing fractional circuit of equal reduced or, less current strength in coil 7, it will be observed that the motor is stationary, and therefore the disc 13 remains in its normal mid-position.

If now the temperature or condition affecting the mercury column 2 changes to the negative, so that the column moves downwardlyiout of engagement with contact 4, such movement immediately disrupts the fractional or reduced current strength circuit through coil 7, leaving the permanent fractional or reduced current strength a position such as shown in Fig. 3, as a result of the counter-clockwise movement thereof, two things occur in substantial synchronism. First. the movement of the disc from its mid-position forces the cam 35 out of the recess 36 on the periphery of disc 13, and out upon the cam surface 30. The spring contact arm is thus forced downwardly into engagement with the lower contact arm 32, in position to complete a full circuit through coil ,7 as will be later described. The second occurrence is that tilting of disc 13 causes the mercury globule in tube 20 to move gravitationally out of engagement with contacts 25 and 26, thus disrupting the circuit through the lamp or ,device 38, and then immediately subsequently the globule engages contacts 27 and 28 in said tube 20, thus establishing a difierent circuityas through lamp or device 37, as follows: from line 40, wire 41, contact 27, mercury in tube 20, contact 28, wire 60, lamp or device 37, wire 46, back to the other side of the line 47. Lamp or device 37 will burn or function to indicate that the temperature 'or condition affecting mercury column 2 is low or negative, or to make proper correction to change the condition or temperature.

The parts will remain in the position shown in Fig. 3, untilremedial measures have again changed conditions affecting mercury column 2, so that the movable contact (2) will approach and ultimately establish contact with the middle contact 4. Immediately thereupon a full current circuit, sufficient to overpower the urge of the circuit of less current strength in coil 63 will be established in coil 7, as follows: from line 40, through wire 51, contact 3, mercury 2, middle contact 4, wire 52, contact arm 33, contact arm 32, wire 61, wire 54, coil 7, wire 55, wire 50 back to the other side of the line 47. As this last described circuit has no interposed resistance, and as the circuit is sufficiently strong as .to rotate the motor in a clockwise-direction against the repelling urge of the circuit of less current strength through coil 6, it will be clear that the disc will be rotated in a clockwise direction until the cam riding on cam surface 30 drops into the recess or notch 36 on said disc. This immediately disrupts the full current circuit through coil 7, through disengagement of spring arm 33 from spring contact arm 32, but at once establishes a fractional circuit through coil 7, as described heretofore, by the engagement of spring arm 33 with spring arm 34, thus interposing the resistor 53 in the circuit through coil 7, as will be clear. The disc is now in the mid-position where the circuits through the respective coils are balanced and this condition maintains until a further movement of the mercury column occurs. Obviously the clockwise movement of the disc has through movement of the mercury in tube 20, broken or severed the circuit through lamp or device 37, and re-established the circuit through the lamp or device 38, which, as noted indicates the normal condition surrounding or afiecting the mercury column.

With the parts in the mid-position shown in Fig. 1, and assuming that the mercury column rises so as to establish an engagement with the upper contact 5, then immediately a full circuit is established in coil 7 to cause it to overbalance the fractional circuit in coil 6 to cause the clockwise rotation of the motor and disc, as follows: from line 40, through wire 51, contact 3, mercury colunm 2, upper contact 5, wire 62, wire 54, coil 7,

. wire 55, wire 50 and back to the other side of the line 47. The clockwise movement of the disc 13 is continued until ear or lug 17 abuts stop 16, after which the motor may continue to run while the disc 13 is stationary. During the clockwise movement of the disc from its neutral or mid-position two things occur. First, cam 35 on spring arm 33 is forced out of the recess or notch 36 on disc 13, and rides on cam surface 29. As noted, this disengages spring arm 33 from contact arm 34, and holds the spring arm 33 out of contact with either spring arm 34 or 32; and secondly, movement of the disc causes the mercury globule in tube 21 to gravitationally move from engagement with contacts 24 and 25, thus disrupting the circuit through lamp or device 33, and then engages with the contacts 22 and 23 to establish a circuit through lamp or device 39 as follows: from line 40, wire ,41, contact 22, mercury in tube 21, contact 23, wire 63, lamp or device 39, wire 64, 44, 46 and back to the other side of the line 47. The parts remain in the position shown in Fig. 2, until there is a further change in the position of the mercury column 2. Assuming corrective measures to have been taken or applied either manually in response to the burning of lamp 39, or automatically by. the circuit to lamp 39, the correction of the conditions will be indicated by the disengagement of the mercury column 2 from the upper contact 5. This obviously disrupts the full current circuit through the coil 7 of the motor, which being severed leaves the permanent fractional or reduced current strength circuit through coil 6 free to rotate the motor and disc in an antior counterclockwise direction, until the mid-position of the disc is reached, upon which the cam 35 on spring arm 33 will drop or move into the recess or notch 36 on disc 13, and thus establish an engagement of spring arm 33 with contact arm 34. As previ ously noted this closes a fractional or reduced current strength circuit through the coil 7, be-

cause of the interpositioning of the resistor 53, which circuit, being just balanced by the permanent fractional or reduced current strength circuit through coil 6, stops the motor with the disc in the mid-position.

Of course, during the counter-clockwise motion of the disc 13, the mercury globule in tube 21 has disengaged contacts 22 and 23, thus disrupting the circuit through the lamp or device 39, and has thereupon engaged contacts 24 and 25 and re-established the previously described circuit through lamp or device 38.

It will be obvious that the voltage of the lines supplying the circuits through lamps or electric devices 37, 38 and 39, may readily be much higher than that necessary to secure the operation of the reversible motor, although for purposes of illustration only all circuits are shown as arising from a common line.

The above described motor relay is but one of the applications and modifications of my invention, particularly designed for use with contact measuring gauges or conditionresponsive devices where it is essential to arrange to do something in any one of the three cases when the temperature is low or condition negative, when it is normal, and when it is high or the condition is positive. It prevents chattering action of the circuits it controls through its mercury contacts because the flickering of the thermostat contacts only makes the disc oscillate minutely back and forth without being able to influence the position of the mercury in the bulbs before a firm make or break is established on or by the instrument gauge.

In the above described design of my invention the small amount of the current required by the motor coils 6 and 7 must be made and broken by the contacts on theinstrument, however, this current can be made very small and most control instrument contacts can withstand the breaking of this faint current.

I claim as my invention:

1. In a motor operated relay in combination with a primary and a secondary group of circuits a reversible motor having two opposing fields, secondary circuit controllers operatively associated with the motor means establishing a circuit of reduced current strength through one field of the motor to urge the motor in one direction, a condition responsive circuit maker, and means automatically. selectively establishing a circuit in the other field of said motor to urge it in the opposite direction, said means further selectively determining whether the second mentioned circuit is of full current strength or of reduced strength for the purpose of closing said secondary circuits in proper predetermined rela tion to the corresponding primary circuits.

2. In a motor operated relay in combination with a primary and a secondary group of circuits a reversible motor having two fields, secondary circuit controllers operatively associated with the motor means establishing a circuit of reduced current strength in one field of the motor, a condition responsive circuit maker arranged to establish a full current circuit in the other field of said motor to overbalance the circuit of reduced current strength to cause the motor to run against the force of the circuit of reduced current strength, said circuit maker also arranged to establish an equal circuit of reduced current strength in the said other field of the motor to balance the circuit of reduced current strength in the first mentioned field to hold the 150.

motor stationary and toclose the secondary circuit corresponding to the particular condition oi the primary circuits.

, 3. In a motor operated relay in combination with a primary and a secondary group of circuits a reversible .motor having two fields, secondary circuit controllers operatively associated with the motor means establishing a circuit of reduced current strength in one field of the motor, a con-'- dition responsive circuit maker arranged to establish a full current circuit in the other field of said motor to overbalance the circuit of reduced current strength to cause the motor to run against the force of the circuit of reduced current strength, said circuit maker also arranged to establish. an equal circuit of reduced current strength in the said other field oi the motor to balance the circuit of reduced current strength in the first mentioned field to hold the motor stationary, and supplemental means moditying the last mentioned function of the circuit maker to cause the establishment of a full current circuit in said other field of said motor to close the secondary circuit corresponding to the particular condition of the primary circuit.

4. In a motor operated relay in combination with a primary and 'a secondary group oi. circuits a reversible motor having two opposing fields, secondary circuit controllers operativelyassociated with the motor means for establishing balanced circuits in both fields oi the motorsimultaneously, and means for modifying one circuit to unbalance the circuits to cause the motor to operate in one direction in order to establish a predetermined relation of the secondary circuits corresponding to the electrical relation of the primary circuits.

5. In a motor operated relay in combination with a primary and a secondary group of circuits a condition responsive mercury column, contacts in the path of the mercury column, a

reversible motor having two opposite fields, secondary circuit controllers operatively associated with the motor means for establishing a circuit of reduced current strength in one field oi the motor, the mercury column establishing a circuit in the other field, and means for modifying the last mentioned circuit to render the last mentioned circuit either of full current strength or of reduced current strength in order to move or stop said motor in positions predeterminedly relative to the existing conditions in the primary circuits and thereby establishing corresponding conditions of the secondary circuits.

6. In a motor operated relay in combination with a primary and a secondary group of circuits a reversible motor having two opposing fields, secondary circuit controllers operatively associated with the motor, a constant circuit of reduced current strength energizing one coil of the motor and urging it in one direction, a conditionresponsive circuit maker to establish a circuit in the other coil of the motor, and means operatively associated with the motor for regulating the strength of the last mentioned circuit to determine whether the circuits are balanced or unbalanced to'move or stop said motor in position predeterminedly relative to the existing conditions in the primary circuits and thereby establishing corresponding conditions of the secondary circuits.

7. In a motor operated relay in combination with a primary and a secondary groupof circuits a reversible motor having two opposing fields, secondary circuit controllers operatively asso- 8. In a motor operated relay in combination with a primary and a secondary group of circuits a reversible motor having two opposing fields, secondary circuit controllers operatively associated with the motor means having a lost motion connection with the motor and having a limited driven relation with the motor, a circuit controller establishing a primary circuit of reduced current strength in one field of the motor when said means is in a predetermined position, and means establishing a balanced primary circuit of reduced current strength in the other field of the motor so arranged asto establish a predetermined relation between the secondary circuits and the primary circuits.

9. In a motor operated relay, a reversible motor having .two opposing fields, means having a lost motion'and limited driving connection with the motor, a circuit controller responsive to conditions for establishing aprimary circuit in one field of the motor, a circuit controller responsive to the position of said means for selectively establishing a resistor in said circuit, and

motor, a circuit controller selectively out of contact or engaging a primary or secondary contact according to the position of said element, a resistor, and connections establishing a circuit through the resistor the primary contact of the mercury column and the other field of said motor to balance the circuit in the first mentioned field of the motor to stop the motor in a predetermined position of the element, said mercury column contacts alsoarranged to establish a lull current strength circuit in said other field of the motor.

11. In a motor operated relay, a reversible motor having two opposing fields, an oscillatable element having a lost motion connection with said motor to be oscillated thereby, a mercury columnhaving a plurality of contacts, connections establishing a circuit of reduced current strength through one field of the motor, connections establishing a full current circuit through the otherfield of said motor and through certain contacts of the mercury column, and means operable by the oscillatable element to establish a balanced equal circuit in said last mentioned field of the motor uponthe disruption of the full circuit through the contacts of the mercury column.

12. In a motor operated relay, an element oscillatable about an axis, circuit makers mounted on the element and controlling a plurality of secondary circuits selectively according to the OScillated' position of the ,element, a reversible motor having two field coils, a three contact circuit maker having a movable contact element successively engageable with the first, second and third contacts, and overlapping said contacts so as to engage them all simultaneously or the first and second simultaneously, or the first alone, means establishing a circuit of reduced current strength in one field of the motor which is effective to turn the element to one predetermined position in the absence of a counter circuit in the other field, means establishing a circuit of reduced current strength in the other field of said motor when the moving contact engages the first and second contacts to balance the circuit of reduced current strength in the first mentioned field to stop'the motor, engagement of the moving contact with the third contact of the three contact circuit maker establishing a full current circuit in said other field oi the motor to overcome the circuit of reduced current strength in the first mentioned field to turn the motor in the other direction to return said element to a predetermined position.

13. Ina motor operated relay, a circuit controller, a reversible motor for operating the circuit controller, means establishing a permanent primary circuit of reduced current strength through one field oi. the motor to urge it in one direction to control the circuit controller, and a condition responsive circuit maker arranged to establish a full strength primary circuit in the other field of said motor, and also arranged to establish a circuit of reduced current strength in said other field of said motor to balance the permanent primary circuit in the other field to hold the motor stationary according to conditions.

.run the motor in the opposite direction to return the circuit controller to neutral position.

15. In a motor operated relay, a, reversible motor, a positionable circuit maker having a neutral position and two extreme positions and operably associated with the motor, condition responsive means establishing a drivingcircuit in the motor to move the circuit maker from its neutral position to an extreme position, and

means efiective thereafter to establish a driving "circuit to run the motor in the other direction to return the circuit maker to neutral position.

16. In a motor operated relay in combination with two primary operating circuits and three secondary operated circuits, means in connection with the primary circuits to maintain one of the secondary circuits closed while none of the primary circuits are closed, means for opening said secondary circuit when one of the primary circuits is closed and sequentially to close another of the secondary circuits, further means for opening said second secondary circuit and closing the third secondary circuit when both primary circuits are closed, with still further means for closing in reverse sequence said secondary circuits as first one then the other primary circuit is broken.

CHRISTIAN WILHJELM.

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