US2409895A - Electrical positioning system - Google Patents

Description

Oct. 2z, 194e. G. H. PHELPS 2,409,895

ELECTRICAL POSITIONING SYSTEM F-l'ed Feb. 5, 1943 2 Sheets-Sheet 1 figli WITNESSES: INVENTOR @4W f i @wege/Ww@ BY 74. I I SR YQ Oct. 22, 1946. G, H PH'ELPS 2,409,895

ELECTRICAL PQSITIONING SYSTEM Filed Feb. 5, 1945 2 sheets-sheet 2 ATTORNEY Patented Oct. 22, 1946 UNITEDy vSTATES PATENT OFFICE t ELECTRICAL POSITIONING SYSTEM George H. Phelps, Catonsville, Md., assignor to Westinghouse Electric Corporation, East VPittsburgh, Pa., a corporation of Pennsylvania Application February 5, 1943, Serial No. 474,829

6 Claims. (Cl. 172-239) This invention relates to electrical positioning systems and, more particularly, to a selective control of circuit elements from a remote point.

Positioning systems of the type to which this invention particularly relates include a motor drive rotatable in both directions which is coupled to the driven element in such manner that the movement of the latter can be set to various predetermined positions. In these systems, it is essential that the driven element should be accurately positioned along a circular path to any preselected position, by rotation vin either clockwise or counterclockwise direction. Control systems heretofore used generally employ a. split disc in cooperation with the driving motor which rotates simultaneously with the i driven element. There is also a suitable electricalor mechanical clutch mechanism to disengage the motor when the driven element reaches theselected position. On the split disc are placed a number of contacts, each defining one selectedA position ofthe driven element. The insulating space which separates the two halves forms the dividing line between the ltwo directions of rotation of the motor. The free space between the two segments cooperates with the contacts so that when any one of the contacts through which a circuit is completed to the `motor reaches this space it will open the circuit. f

When a split disc is used the rotation in each direction is confined to 180. If rotation 4beyond' that is desired up to nearly 360 each half of the split disc may be replaced by individual contact discs carrying contact segments which make .a complete revolution for each direction of rotation.

While this type of remote control has been widely used, it has the disadvantage that for very accurate positioning avery accurate and small clearance must exist between the two halves .of thesplit disc segments. The slightest momentum of the turningdisc augmented by the momentum of the motor may cause overriding, whereby upon contact with the other segment a reversal of the motor is effected. This conditioncreates hunting or oscillating around the desired point. Moreover, the accuracy ofvpositioning is limited by the Width of the insulating space between the discs which in practice has to be .wide enough to prevent hunting, and thereby allows appreciable differences in the actual stopping position.

'Ihe present invention overcomes these disadvantages when such systems are used for the positioning of switches or other circuit components,

e 2 wherein each position represents equal angular displacements over the path described by the arc of rotation. This is accomplished by the addition of a cam switch driven by the motor which permits further rotation of the motor after the desired positioning has ybeen established.

Another advantage of the'positioning system herein described is that the usual clutch between the motor and the driven element can be eliminated by utilizing a novel drive inthe form of a Maltese-cross gear, so that the accuracyY of the setting is determined thereby.

A particular feature of the invention resides in an extremely compact v mechanical assembly whichI is easily adapted to effect the positioning of any number of selector switches accurately to any preselected stop. Y

Another feature of the invention, as will be seen when considering its mechanical details, re-

sides in the drive mechanism for the vMaltesecross gear which maintains a rigid contact position for the selector switches driven thereby.

A marked advantage ofthe system herein described is its freedom fromtemperature variationsin that prior tor the movement of the actuated element no actuating motor may start under no-load condition and may run for a definite time freely. In this manner operation is secured when temperature conditions adversely affect the motor speedandpower. v

. Other features and advantages will be apparent from the following description of the invention, pointed out in particularity by the appended claims, and taken in connection with the accompanying drawings, in which:

Figs.A 1, 2-and 3 show three views of the compact driving mechanism-as a unit which can be attached to any desired number of selector switches; Fig. 4 shows` a .schematic circuit arrangementv for thefcontrol of the positioning mechanism in combination, by way of example, with the tuning mechanism of a radio receiver to-a number of preselected frequencies.

Referring to the drawings, in the viewsof Figs. 1, 2 and 3, the driving motor I is shown to be mounted in a frame 2the motor having a shaft 3 carrying a worm 4. The latter drives the worm gear 5, the shaft 6 of which runs transverse to the frame 2 in bearings I and 8. Secured to the shaft 6 and driven thereby is the lock wheel 9 carrying the pin I 0 .for driving the Maltesecross wheel I2. On the other'y side of the gear 5, the shaft 6 carries the cam I3, the surfaceY of which engages the movable member I4 of the holdlover switch I 5. 'I'he Maltese-cross wheel I2 drives the shaft I1 at one end, and at the other end it rotates the circuit control switch I8 and the connecting switch 20 for the hold-over switch I5. The shaft I1 protrudes sufficiently to permit coupling thereto the selector switches which the device is intended to position. In other words, to the shaft I1 is connected the driven element of the positioning system.

The mechanical features should be observed in these figures for a clearer understanding of the system when considering the operation thereof in connection with the various electrical controls. It is seen, taking particularly Figs. 2 and 3 into consideration, that as the motor shaft 3 revolves the lock wheel 9 is turned by the worm gear 5.

The lock wheel 9 carries the locking member II which engages the corresponding peripheral face of segment IB, of the Maltese-cross wheel I2.. As long as the member II engages the surface of the segment I6, the Maltese-cross wheel I?. is locked in position. At every revolution oi the lock wheel 9, the pin I engages the slot I9 between the segments IB and will drive the wheel I2 one segment in either direction depending upon the direction of rotation oi the wheel 9. When the pin Hl engages the slot I9, the cutout portion of the member II unlocks the wheel I2, permitting movement thereof. It is to be noted that once the pin I0 leaves the slot I9, the wheel 9 is free to rotate Without affecting the firm position of the Maltese-cross I2. In this manner, as will be explained later, the -motor may continue its rotation over a comparatively long segment in the circular -path of the pin I0, and may be stopped anywhere along this segment without interfering with the succeeding positioning of the Maltese-cross I2. This is an important feature and instrumental in the absolute accuracy of each step in the positioning of the shaft I1.

Referring now to the operation of the system and observing the circuit shown in Fig. A4, it is seen that the important mechanical elements are shown in vperspective and the electrical circuit is schematically represented. For the purpose of clear illustration, the control switches and the various mechanical elements are spaced far apart, and particularly the shaft I1 is shown extended. Coupled to the shaft is shown, by way of example, a set of rotary switches for the remote actuation of the tuning of a radio receiver. The electrical positioning device in accordance with this invention is well adapted for use in connection with radio receivers, and for this reason it was chosen to illustrate its operation in connection with a radio receiving system. It is to be understood and can readily be seen that, in place of the tuning arrangement of the radio receiver, other types of rotary switches may be actuated for a variety of purposes, such as selecting different electrical circuits. While there are only two switches shown, any number may be employed as long as they are to be actuated simultaneously. The switches may also have any number of contacts provided that the Maltese-cross wheel segments are accordingly proportioned and the size of the circuit control switch I8 allows the placement of the number of riding contacts desired side-by-side along the two operating segments 22 and 22 respectively. To avoid unnecessary complication of the circuit, there are only three contacts shown, sufficient it is believed for a `thorough understanding of the operation of the system.

The terminals A and B indicate the connection to a source of power for driving the motor I. This source may be either alternating or direct current. The motor is of the dual* iield type, having iields 23 and 24. One terminal of each iield connects to one side of the incoming supply line in series with the armature or rotor which contacts brushes 25 and 2E. The other terminal of field 23 connects through lead 21 to the rider 28 of the circuit control switch I8 engaging the segment 22, and also through lead 29 to the upper contact of the hold-over switch I5. Similarly, the other terminal of field 24 .connects through lead 30 to the rider 3| which engages segment 22' of the circuit control switch I8, and also to the lower contact of the hold-over switch I5. Displaced around the switch I9 are the contacts 32, 33 and 3d, equidistantly placed corresponding to the number of steps which the positioning system is to make in its intended operation. Connected in parallel with the abovementioned contacts are the contacts 35, 36 and 31 of the connecting switch 29, the rider of which is connected through lead 38 to the moving contact I4 of .the hold-over switch I5. The contacts 39, 40 and 4I of the manual selector switch 42 connect also to contacts 32, 33 and 34, respectively. The manual selector switch 42 may be placed at any desired location and completes the current path to the source in that its rider 43 is connected to the terminal B of the supply.

The radio receiver shown here comprises a simple ampliiier and detector circuit tunable by means of the iiXed condensers 41, 48 and 49 in the ampli-lier stage and the fixed condensers 50, 5I and 52 in the detector stage. Each of these condensers is indicated to be variable for a particular setting to tune the receiver to a desired station. Selector switch 53 connects any one of the condensers 41, 48 or 49 to the grid `55 of the Vacuum tube `56, tuning thereby the grid circuit comprising the secondary 51 oi the radio frequency input transformer 58. Similarly, the selector switch 54 connects any one of the condensers 5I), `5I or 52 in shunt with the secondary 59 of the coupling transformer 60. The various circuit elements of the radio receiver have no bearing on the invention herein described and need not be considered in detail. Suffice it to say that when switches 53 and 54 connect corresponding contacts, the radio receiver is tuned to receive a selected station.

Describing the operation, let us assume that the entire system is at rest. It is seen that following the circuit from the A terminal, the motor iields 23 or 24 are not energized, since the connection to the field is broken in that neither switch I8 nor switch I5 is closed to the contacts selected by switch 42. Thus the center contact 40 of the switch 42 was chosen as the desired position when the system was last operated. Following the connection to the center contact 33 of the switch I8, We see that the circuit is broken by the insulation between the segments 22 and 22. Furthermore cam I3 is in such position that the moving contact I4 of the switch I5 is between the upper and the lower contacts.

Let us now turn the manual selector switch 42 to the position whereby its rider 43 engages the contact 4I. Following the circuit from the B terminal, we see that the current will flow through the contact 34 of the switch I8 and finds a path along the segment 22 to the contact 3| and through lead 39 to the field 24 and through the motor to the terminal A. It should be noted also that the rider of the switch 2D does not engage the contact 31, so that the moving arm I4 of the switch I5, is not connected to the current source.4 The purpose of the switch 20 will be better understood when the` operation ofthe system becomes clear and will be explained hereafter in greater detail'.

We have seen that the field 24 become'fene'rgized, when the switch 42 was moved to energize contact 4I. The connections of the motor elds are so made that when the eld 24 is energized, the motor will turn the worm 4 so as to rotate the worm-gear 5 in the proper direction whereby the Maltese-cross wheel I2 moves the shaft I1 so that the contact 34 of the circuit control switch lI8 shall be placed between the segments 22 and 22. In accordance with the operation in the manner chosen it is seen that the rotation of the worm gear 5 must be counterclockwise as indicated by the arrow,` since movement of the drive pin I I) in this direction will rotate the Maltese-cross wheel I2 in a clockwise direction. It should be noted here that as the worm gear 5 rotates and the pin IIJ approaches the Maltese-cross wheel I2, the cam I3 will lift the moving arm I4 of the switch I5 so that it engages the upper contact thereof. However, this in no way inuences the rotation of the motor I in the direction indicated in that, as can be seen in tracing the circuit, the field 23 is not connected to the source, because the circuit through contact I4 and upper contact I5 is broken at contact arm 20 of the switch 20 and also at contact 39 of the switch 42. As the drive pin I 0 moves the Maltese-cross wheel I.2 one step and shaft I1 is turned thereby, the switch I8 will be moved so that the segment 22 no longer engages the Contact 34. The latter` will be now in the same position as .the contact 33 was previously, that is, the circuit therethrough will be broken. At

the same time, the switch 2D will engage con-A tact 31. rI'he switches 53 and 54 are now also positioned so that condensers 41 and 50 are placed across the respective circuits of ythe receiver. The instant when this occurs the drive pin IU will be just ready to leave the slot, and the motor would stop since the contact 34 is not in engagement with the segment 22', and the circuit is broken between contacts 34 and 3|. However, the operation' of the hold-over switch I3 assures continued rotation of the motor and also, of course, of the pin Il) of the lock wheel 9. The reason for this is that the cam I3 will now oier the smaller diameter of its contours to the moving arm I4 of the hold-over switch I5, so that the lower Contact thereof is in engagement. In tracing the circuit, we see that the current starting from the terminal B will iiow through contact 4I of the switch 42, contact 31 of the switch 20, through lead 38 and the lower contacts of the hold-over switch I5 through the iield 24. The rotation will continue until the cam I3 reaches the original starting position shown, whereby the arm I4 of the hold-over switch I5 is again in the mid-position between the upper and lower contacts. Whatever momentum the motor may have had, including the momentum of the worm gear '5 and lock wheel 9 which would tend to continue rotation of the motor even after the arm I4 of. the hold-over switch I5 breaks the circuit, will not affect the accuracy of the setting of the driven elements in that the Maltese-cross wheel stays in locked position over a substantial travel of the drive pin I0. The stopping surface 44 of the cam I3 has sufficient length to allow for the movement due to momentum when the arm I4 is lifted from 6 the lower contact toi break the circuit to the motor.

Considering now the operation of the switch 2li, it will be seen thatit is intended to control theconnection'of the arm I4 of the hold-over switch I5 to the supply circuit in such manner thatwhen the manual selector switch 42 is placed to any desired contact for the next ensuing operation, connection `to the arm I4 of the hold- 4over switch I5 is broken until the shaft I1 is moved tothe selected position. Then contact of the hold-over switch arm I4 is again established through the new setting of the switch 20.

I claim as my invention: Y

1. In an electrical positioning system, switchingA means adapted to be positioned in denite steps over a series of contacts, a motor for driving said means, an energizing circuit for said motor including a current source and a circuit control switch in series therewith operated in conjunction with the positioning of said means,

'said circuit control switch determining also the direction offrotation of said motor, a selector switch adapted to be placed at a remote point for selecting at will the positioning of said switching means to any one of the number of said series of contacts, said selector switch completing the energizing circuit through said control switch to said motor and a hold-over switch maintaining said energizing circuit closed until the positioning of said switching means is fully completed and after said control switch reaches its open circuit position.

2. In an electrical positioning system, switching means adapted to be positioned in denite steps over a series of contacts, a motor for driving said means, an energizing circuit for said motor including a current source and a circuit control switch in series therewith operated in conjunction with the positioning of said means, said circuit control switch determining also the direction of rotation of said motor, a selector switch adapted to be placed at a remote point for selecting at will the positioning of said switching means to any one of the number of said series of contacts, said selector switch completing the energizing circuit through said control switch to said motor and a hold-over switch operated by a cam driven by said motor for maintaining said energizing circuit closed until the positioning of said switching means is fully completed and after said control switch reaches its open circuit position.

3. In an electrical positioning system, switching means adapted to be rotatably positioned in definite angular steps over a series of contacts, a reversible motor for driving said means, an energizing circuit for said motor including a current source and a circuit control switch in series therewith operated in conjunction with the rotation of said means, said circuit control switch determining also the direction of rotation of said motor, a selector switch adapted to be placed at a remote point for selecting at will the positioning of said switching means to engage any one of the number of said series of contacts, said selector switch in series with said control switch completing the energizing circuit to said motor, and a hold-over switch operated by a cam driven by said motor for maintaining said energizing circuit closed until the rotation of said switching means is fully completed to the selected contact and after said control switch reaches its open circuit position.

4. In an electrical positioning system, switching means adapted to be rotatably positioned in denite equidistant steps over a series of contacts, va reversible motor for driving said means, an energizing circuit `for said motor including a current source and a "circuit control switch in series Vtherewith operated in conjunction lwith the rotation of said means, said circuit control switch Ydetermining also the direction of rotation of said motor, a selector switch adapted to be placed at a remote point for selecting at will the positioning of said switching means to any one of the number of said series of contacts, said selector switch completing the energizing circuit in series with said Icontrol switch to said motor and a hold-over switch `in `shunt with said control switch for maintaining said energizing circuit closed until the positioning of said switch means is fully completed and after said control switch reaches its open circuit position.

5. In an electrical positioning system, driving means comprising a reversible motor, driven means, a drive between said motor and said driven means including `means for positioning said driven means to a fixed step of `angular displacement for each complete revolution of said drive in either direction, an electrical control circuit for said motor includinglmeans for determining the direction oi' rotation of said driven means and for selecting a particular step of displacement .thereof, and control `means for completing the revolution of said drive to substantially the same stopping point after said driven means vis positioned to a selected step.

6. In an electrical positioning system, driving means comprising a reversible motor, driven means, `a drive between said motor and said driven means including a Maltese-cross coupling for positioning said driven means to a fixed step of 'angular displacement for each complete revolution of said drive in either direction, an electrical control circuit for said motor including switching means actuated by said driven means for determining the direction of rotation of said driven means and for selecting a particular step of displacement thereof, and control means for said motor for completing the revolution of said drive to substantially the same stopping point after said driven means is positioned to a selected step.

GEORGE H. PHELPS.

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