US2445515A - Electric motor follow-up type of control - Google Patents

Description

July 20, 1948. c. H. DEDERICK ELECTRIC MOTOR FOLLOW-UP TYPE OF CONTROL Filed NOV. 24, 1943 RAT'Ch ET RELAY Patented July 20, 1948 ELECTRIC MOTOR FOLLOW-UP TYPE OF CONTROL Clinton H. Dederick, Brentwood, Mo., assignor to Ihe Emerson Electric Mfg. Company, St. Louis, Mo., a corporation of Missouri Application November 24, 1943, Serial No. 511,548

6 Claims. 1

The present invention involves a follow-up type of control.

More particularly, it comprises a positioning device that may be used to produce a predetermined and adjustable movement of some apparatus to be displaced.

This application is related to co-pending applications, Serial No. 483,903, filed April 21, 1943, and Serial No. 491,583, now Patent Number 2,- 413,137, filed June 21, 1943.

It is an object of this invention to provide a simplified circuit by which an apparatus to be moved by a motive means may be so moved by a control readily adjustable from a remote point which determines the amount of operation of the motive means.

More particularly, it is an object to provide a simplified circuit of this kind with a control that may be displaced from any position within its range of operation to another position within that range, which control causes the motive means to begin to move to a corresponding position immediately upon initial displacement of the control.

A further object is to provide a mechanism as set forth in the foregoing objects in which a movement can be obtained in either direction.

The drawing represents the invention diagrammatically.

The control generally includes a setting device l0, 9, pair of power relays II and I2, a pair of movement producing relays l3 and M, a motor M and a make-and-break switch mechanism S.

The motor M is caused to rotate in one or the other direction, and such rotation of its shaft is designed to produce movement of the object to be adjusted in one or the other direction, usually between opposite limits. As shown in the copending applications, one use of this control is for the positioning of trimmer tabs on aircraft wings. In such an application, the motor M operates connecting mechanism that moves the trimmer tabs upward or downward. The motor may be located at a convenient point, such as in the wing of the plane with the control operating parts at a place accessible to the pilot.

The control I comprises a movable contact arm I5, that may be displaced about its center. This contact arm I5 is connected to a slip ring l6, engageable by a brush ||,'connected to a power line l8.

The arm l5 has a contact wiper l8 that may be brought into engagement with a contact segment 20 substantially 180 in extent, or a similar segment 2| The two segments are divided at 22 which provides a neutral point or gap for the wiper IS. The two segments and 2| are moved independently of movement of the arm l5. As will appear and as is shown in greater detail in copending application, Serial No. 491,583, these segments are mounted for manual displacement relative to the arm l5 to preset the device, and the arm is attached to a disc that is driven by actuation of the two relays l3 and M.

The segment 20 is connected to a slip ring 23 and the segment 2| is similarly connected to a slip ring 24. The two slip rings 23 and 24 are respectively connected to the opposite sides of the operating mechanism to be described.

The slip ring 23 is in contact with a brush 25, connected to a line 26. This line 26 is connected into the coil 21 of the power relay II, from the other end of which a line 28 leads to a ground connection 29.

Also connected to the line 26 is a line 30 that leads to one contact 3| of a switch 32, operated by the ratchet relay l3. The other contact 33 of this switch is connected to a line IBc that is connected, in turn, to a line |8a that is connected to the line l8 and thus receives power. The line lBa is also connected to the stator winding 35 of the motor M and thence to ground.

The other slip ring 24, connected to the other segment 2|, is engaged by a brush that is connected to a line 46 that leads to the coil 41 of the power relay [2. The other end of the coil 4'1 is connected by a line 48 to the ground connection 29. There is a line 50 connected to the line 46, and this line leads to a contact 5| of another ratchet relay switch 52, operated by actuation of the ratch relay M. The other contact 53 of this switch is connected by a line 54 to the line I80.

The power relay ll operates two double switches, the first of which is indicated at 60. This switch has a contact 6|, connected to a line |8b, receiving power from the line I811. The switch has a double throw contact 62 that is connected by a line 63 to one contact 64 of a limit switch, generally indicated at 65. The limit switch 65 includes a double throw contact 66 that is connected to a line 61 leading into one side of the motor M. The other fixed contact 68 of the limit switch 65 is connected by a line 69 to ground.

The switch 60 has an additional contact 12 engageable by the movable contact 62. The

.contact 12 is connected by a line 13 to the ground connection 29.

The second power relay switch of the power relay II is generally indicated at I5. It comprises a movable contact I6 connected to the line I8b. There is a fixed contact 11 that is connected by a line 78 into the coil I9 of the ratchet relay I4. The other end of the coil I9 is connected by a line 89 to a contact 8| of the make-and-break switch S. The other contact 82 of this switch, which is moved by a cam 83, driven by the shaft of the motor M, is connected to ground.

The switches operated by the power relay I2 are symmetrical. The first of these is the switch 90 which has a contact 9|, connected to the line I8b. The movable contact 92 is connected by a line 93 to the first fixed contact 94 of a limit switch 95, having a double throw movable contact 96. The contact 96 is connected by a line 91 into the other side of the motor M. The other fixed contact 98 of the limit switch 95 is connected by a line 99 to ground.

The. other fixed contact I02 of the switch 90 is connected by a line I03 to the line 29, and thence toground.

The other power relay switch I05 includes a movable contact I96, connected to the line I'Bb. It has a fixed contact I01, connected by a line I 8into the coil I09 of the ratchet relay I3. The other end of this coil I09 is connected by a line [I0 to the line 80,

The circuit set out above. is designed to be used with a mechanism such as is shown in the co-pending application, Serial No. 495,183. A convenient handle or knob is provided for rotatingv the, disc carrying the slip rings 20 and 2I. The ratchet relays, in addition to operating their switches, operate pawls that effect displacement of the arm I a predetermined distance for each energization of a relay, the displacement being in the direction in which the gap. 22 between the segments 29 and 2I has been moved, so that the arm is ultimately operated to engage in the gap 22" which, as Will be seen, stops the mechanism.

The motor M is reversible, its direction of rotation being determined by the direction of flow of current through the rotor. In other words, the motor operates in one direction if the current flows from theline 51 through the rotor, and in the other direction if the current flows from the line. 9! through the rotor. The limit switches 65 and 95, as shown in the co-pending applications,

determine the maximum amount of rotation in both directions that is permitted. Each limit switch will be shifted from the position shownto engagement with its other fixed contact after the motor has rotated a predetermined amount in the particular direction forwhich such switch is'used.

The switch S is driven from the motor and acts as means to count the number of energizations of the ratchet relays per rotation of the motor, since the cam 83 is driven from the motor shaft.

Operation through the arm, the segment 20 to the slip ring 23, whence it flows through the line 26 and the power relay coil II to the line 29 and ground. (Ground in this case means the return power connection.) At this time no circuit is closed from the line I80 through the line 30 because the ratchet relay switch 32 is open.

The coil 21 of the power relay II shifts the switches and :5. When the switch 60 is closed to engage the contacts BI and 82, power from the line I8 through the connections I8a and I9b is introduced into the line 63. With the limit switch in its normal position, the current from the line 63 fioWs from left to right through the rotor of the motor M by the line 61, thence by line 91 through the limit switch 95, and by the line 93 through the other power relay switch 90, which is released, passing through the contacts 92 and I02 into the line I03 and the line 29 to ground. This circuit starts the motor to rotate in a forward direction.

When the switch 60 is closed, the switch I5 is opened. However, at this time, the power relay I2 is released so the switch I05 is closed, which introduces power from the line I82) through the line I98, the coil I09 of the ratchet relay I3, and the line H9 to, line and to the switch S. This switch is intermittently closed by the rotation of the motor. Each time it closes it completes the circuit through the ratchet relay I3 and causes an operation thereof. As shown in co-pending application, Serial No. 491,583, this action steps. the arm I 5 one unit clockwise, bringing the movable arm I5 toward the gap 22.

At the same time the ratchet relay coil I09 is energized the switch 32 i closed. This introduces power from the line I8a by way of the line Iilc to the line 30, which, during the interval that.

the switch 32is closed,provides a parallel circuit,

for the power relay, II, independent of the seg: ment 20.

It will be noted that the field winding 35. of the motor M is constantly in circuit. Thisv not only permits the motor to operate whenever the rotor winding is energized, but also provides a dynamic braking effect each time the rotor is deenergized, andshorted on itself.

After the ratchet relays have been energized a number of times, corresponding to the initial displacement of s gment 20, the brush. I9 will come into the gap 22,which breaks the circuit through the segmentv 20 ,for the power relay I I. It will be noted that the power relay controls the motor circuit. However, in order to insure a complete break and dispositionof the brush I9 in the middle of the gap 22. at the end of each operation.

the parallel circuitthrough the switch 32 of the.

ratchet relay, I3 is employed. It will be noted that the operation of the ratchet relay I3 is independent of the power relay II except indirectly in so far. as the operation of the switch S is dependent upon operation of the motor. If the switch S were to be stopped-the instant of a break between the segment 20 and the, brush I'9, a very,v

relay, by which it brings the brush I9 into thev gap 22, is ,inpart controlled by the parallel circuit through the switch 32. In other words, this step, is. completed after the brush I9 has withdrawn from the segment 20, through this parallel circuit. The brush is thereby brought to neutral position between the two segments, and the mechanism always is stopped with the switch S open.

When the control is in such a position, the relative positions of its parts are the same as they were at the starting position, shown in the drawings, although displaced bodily, in space. It may be moved thereafter'in either direction from the new neutral position. If it is moved in the other direction to bring the segment 2| under the brush [9, thepower relay [2 is energized and the circuit to the motor this time moves from the line [8b through the switch 99, the line 93, the limit switch 95, and from right to left by way of the line 91, through the rotor of the motor M. It then passes through the line 61, the line 53, the contacts 62 and 12 of the switch 69, and the line 13 to ground. Also the ratchet relay i4 is energized through the switch 15 inreleased position of .the coil 21, and ultimately through the switch S, which, in this case, steps the arm l counterclockwise, rather than clockwise as before, which again brings the arm 19 toward the newly positioned gap 22. In like manner, the switch 52, operated by the ratchet relay l4, provides a parallel circuit around the segment 2| to insure a clean break at the end of the segment, and to insure that the switch S is opened for a complete deenergization of both ratchet relays.

Itwill be observed that when the control is in the neutral position, in which the gap 22 registers with the brush l9, the system is entirely deenergized except for the field winding 35. This field "winding, of course, may be controlled by a master switch, but, for the dynamic braking effact, it is desirable that it be constantly energized.

The limit switches 65 and 95 operate in the same manner as those of the co-pending applications. When the motor is operating in the forward direction, after a predetermined maximum movement in such direction, it will shift the contact 66 over against the contact 58. This breaks the motor circuit for the forward direction. It will be observed that the motor circuit is always normally completed through one of the power relay switch mechanisms energized, and through the other released. When the limit switch 65 shifts to the contact 68 to terminate forward rotation of the motor, it supplies a substitute ground circuit for the reverse circuit, the normal grounding of such reverse circuit being through the switch 60 released, which has been broken by shifting of the limit switch.

Consequently, when the limit switch 65 moves, the motor stops, but the control may operate again when it is moved in the other direction, so as to bring the segment 2| under the brush l9, instead of the segment 29. In such case, the relay coil 41 of the power relay l2 will be energized, the switch 90 lifted, and power introduced into the line 93. This passes through the limit switch 95, which is, of course, closed at this time, as shown in the drawings, and the current flows through the line 91, the rotor, the line 51, the contact 68, and the line 69 to ground. The motor is then operated in the reverse direction to back off the limit switch 65 and permit it to shift to its initial position, which reestablishes the normal ground circuit through the line 63, the switch 69 released, and the line 13.

The limit switch 95 for the reverse circuit operates in the same manner.

The interlocking of the motor circuits through both sets of power relay switches prevents improper operation when the switch S sticks in closed position. It will be seen that, when the switch S is closed and both power relays released, both ratchet relay circuits will be held closed and thereby both power relay coils energized through the parallel circuits passing through the two switches 32 and 52. However, when both power relays are energized at once, both motor circuits are broken and both ratchet relay circuits are broken.

What is claimed is:

1. In a control, a setting device having a setting contact and a pair of opposite contacts comprising a second and a third contact from between which the setting contact may be moved to selectively engage one of them by relative movement of the devices, a reversible power means, a pair of power relays, a pair of control relays adapted to actuate mechanism to reestablish starting relationship between the main contact and the pair of contacts wherein the setting con' tact is between the pair of contacts, power relay circuits, one adapted to be closed through each of the second and third contacts and the main contact, a circuit for each control relay adapted to be established through one power relay in deenergized position, a switch in both control relay circuits, said switch being intermittently closed by the reversible power means during operation thereof, circuit means for the reversible power means, said circuit means being connectable to ground or to power at each power relay, whereby when one power relay is energized and the other released, the circuit through the reversible power means delivers power in one direction, and when the other power relay is energized and the one released, the circuit delivers power in the other direction, and means to insure opening of the switch of the control relay circuits when the main contact is between the second and third contacts.

2. In a control, a setting device having a setting contact and a pair of opposite contacts comprising a second and a third contact from between which the setting contact may be moved to selectively engage one of them by relative movement of the devices, areversiblepower means, a pair of power relays, a pair of control relays adapted to actuate mechanism to reestablish starting relationship between the main contact and the pair of contacts wherein the setting contact is between the pair of contacts, power relay circuits, one adapted to be closed through each of the second and third contacts and the main contact, a circuit for each control relay adapted to be established through one power relay in deenergized position, a switch in both control relay circuits, said switch being intermittently closed' by the reversible power means during operation thereof, circuit means for the reversible power means, said circuit means being connectable to ground or to power at each :power relay, whereby when one power relay is energized and the other released, the circuit through the reversible power means delivers power in one direction, and when the other power relay is energized and the one released, the circuit delivers power in the other direction, and means to insure opening of the switch of the control relay circuits when the main contact is between the second and third contacts, said means comprising a switch in each power relay circuit, each of said switches being closed upon operation of its respective control relay, and a shunt circuit established through each of said switches to connect the corresponding power relay to power independently of the set= ting device.

3. In a control, a setting device, comprising a main contact and second and third contacts between which the main contact may be disposed in non-cohtacting relationship, and with either of which the main contact may selectively be engaged, a pair of power relays, a pair of control relays, a reversible power device, the direction of operation of which is determined by the direction of current flow therethrough, the first power relay having a pair of switches, the first switch being of the single pole double throw type, and the second being of the single pole single throw type, the second power relay having third and fourth switches corresponding to the first and second respectively, one contact of each of the four switches being connected to power, the releasedeposition contacts of the first and third switches being connected to ground, the energized-position contacts thereof being connected to opposite sides of the reversible motive means, the released-position of the second and fourth switches being connected respectively through the coils of two control relays, a switch operated by the motive means, the control relays being connected through said switch to ground, and means toinsure that the motive means switch is opened when the setting contact is between the second and third contacts.

7 4. In acontrol, a setting device, comprising a main contact and a device comprising second and third contacts between which the main contact may be disposed in non-contacting relationship, and with either of which the main. contact may selectively be engaged, a pair of power relays, a pair of control relays, a reversible power device, the direction of operation of which is determined by the direction of current flow therethrough, the first power relay having a pair of switches, the first switch being of the single pole double throw type, and the second being of the single pole single throw type, the second power relay having third and fourth switches corresponding to the first and second respectively, one contact of each of the four switches being connected to power, the released-position contacts of the first and third switches being connected to ground, the energized-position contacts thereof being connected to opposite sides :of the reversible motive means, the released-position of the second and fourth switches being connected respectively through the coils of two control relays, a switch operated by the motive means, the control relays ibeing connected through said switch to ground, means to insure that the motive means switch is opened when the main contact is between the second and third contacts, said means comprising a switch operated by each control relay when energized, and a circuit through each switch to the corresponding power relay to shunt the setting device for said power relay.

5. In a control of the kind described, a power relay having a coil and switch means, a motive means, a circuit breaker operated thereby, a preset switch means selectively closable, mechanism energizable to return the pre-set switch means to open position, said mechanism being operable to effect return of the pre-set switch in steps, by intermittent energization, circuit means for the motive means, closed through the relay switch means when the coil is energized, circuit means for the return mechanism, including the circuit breaker, whereby the said circuit means for the return mechanism is intermittently energized, and means to hold the power relay coil energized when the circuit means for the return mechanism is energized.

6. In a .control of the kind described, a reversible power means, a forward power relay having a coil and a switch means closed when the coil is energized, a reverse power relay having a coil and a switch means closed when the coil is energized, pre-set switch means movable oppositely from an intermediate open position to forward or reverse contact, a circuit for the forward coil including the forward pre-set contact, a circuit for the reverse icoil including the reverse pre-set contact, a circuit breaker operated by the power means, a forward circuit for operating the power means forward, including the forward power relay switch, a reverse circuit for operating the power means in reverse, including the reverse power relay switch, forward return means energized when the circuit breaker is closed to return the pre-set switch means from its forward contact to open position, reverse return means energized when the circuit breaker is closed to return the pre-set switch means to open position from its reverse contact, and shunt circuit means closed by energization of each return means to hold its power relay coil energized when the said return means is energized, regardless of the return of the pre-set means to open position, until the power means opens the circuit breaker.

CLINTON H. DEDERICK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 993,814 Barnum May 30, 1911 1,669,112 Winter May 8, 1928 2,077,086 Adair Apr. 13, 1937 2 ,079,492 Courtin May 4, 1937 2,351,451 Obszarny June 13, 1944

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