US2436068A - Follow-up motor control system - Google Patents

Description

Feb. 17, 1948. HEGY FOLLOW UP MOTOR CONTROL SYSTEM INVENTOR. LOUIS HEGY Filed Oct. 9, 1945 ATTORNEY Patented Feb. 17, 1948 2,436,068 FOLLOW-UP MOTOR CONTROL SYSTEM Louis Hen, Burbank, -Caii!., aasignor to Bendix Aviation Corporation, South Bend, bid, a corporation of Delaware Application October 9, 1945, Serial No. 621,347

2 Claims. (CL 318-33) This invention relates to electrical systems for selectively controlling the movements of a motordriven mechanism into any one of a plurality of predetermined positions. and is particularly useful with power-driven multi-position actuators adapted to be stopped in any one of a relatively large number of positions.

An object of the invention is to provide a control system that is positive and reliable in operation over long periods of use, and that is relatively simple and inexpensive to manufacture.

Another object is to reduce the number of conductors required in an electric control system for a multi- -position actuator.

Other more specific objects and features will appear from the detailed description to fellow of a particular embodiment of the invention as illustrated in the drawing.

The invention has application to motor driven devices adapted to be driven either in one or both directions and stopped in any one of a plurality of positions under the joint control of a master selector switch and of a motor-driven switch, both of which switches have a number of positions corresponding to the number of positions in which the device is adapted to be stopped.

In such systems, where multi-position switches having a relatively large number of positions are employed. it is highly desirable from the standpoint of cost, compactness, and weight, to employ what are commonly referred to as wafer switches. Wafer switches employ light contacts riveted or otherwise attached to a light annular plate of insulating material and adapted to be wiped by a light moving contact which is usually also mounted on a thin plate of insulating material. which is adapted to be rotated by a shaft. However, wafer switches have been considered unsuitable for control circuits in which they are required to break appreciable currents. In accordance with the present invention, wafer switches can be employed in multi-position powerdriven actuators, because the arrangement is such that the contacts of the wafer switches are not broken while" they are carrying current. This result is achieved by the use oi special auxiliary switches of snap action type which function to interrupt the current flow in the circuits extending through the wafer switches before the contacts of the latter break, in combination with an extra water switch contact, which reduces the number of leads between the control and controlled station.

Other more specific features of the invention will become apparent from the description to follow with reference to the drawing in which Fig. 1 is a schematic diagram of a control system in accordance with the invention;

Fig. 2 is an end view of a wafer switch assembly employed in the system: and

Fig. 3 is a cross-section taken in the plane III-III of Fig. 2. 1

Referring first to Fig. 1, there is shown a reversible electric motor It having a shaft ll bearing a drive pinion II, which meshes with a driven gear l3, which in turn drives a controlled shaft it through a Geneva mechanism. This Geneva mechanism includes a slotted disk l5 on the shaft H and a locking sector it and drive pin i'l mounted on the side of the gear i3. Whendisk i5 is in any one of six diiierent positions of rest, it is locked in such position by engagement oi the sector IS in one of six arcuate recesses Ilia in the periphery of the disk l5. However, when the disk i5 is to be shifted into a diiierent position, such movement is accomplished by energizing the motor 10 to rotate the gear i3 through one or more revolutions. Rotation of the gear l3 carries the segment i6 out of locking relation with the recess 15min which it was engaged, and simultaneously carries the pin il into one of six radial slots i5b in the disk I5. Continued movement of the pin il rotates the disk l5 through one-sixth of a revolution. after which the pin ll leaves the slot I51), and the sector it simultaneously engages a new recess l5a to lock the controlled shaft 14 in a new position. It will be observed that one revolution of the gear I3 carries the disk I5 through one-sixth of a revolution, and it will be apparent that the disk can be moved in either direction through any desired distance in increments of by driving the gear l3 through a desired number of complete revolutions.

The system of Fig. 1 includes a circuit controlled jointly by a master selection switch 18 and by a follow switch l9 driven by the controlled shaft l4. Movement of the master selection switch l8 into a different position completes a circult through the follow switch l9 to start the motor running in one direction or the other, to drive the controlled shaft it into the desired new position, and the follow switch It functions to interrupt the energizing circuit of the motor iii when the controlled shaft it .has reached its desired position.

The master switch l8 comprises a shaft Ida on which are mounted: a handle l8b; a cam disk llc actuating a snap action switch ltd; and the retatable element lie of a wafer switch having a movable contact l8] which is permanently connected to a fixed contact I80, and is movable into six different positions, in which it contacts with six different fixed contacts lBh which are connected respectively to six conductors I, 2, 3, 4, I and I extending to the follow switch it.

The shaft |8a is connected through a friction drag switch I 81 with a continuing shaft l8]: on which is mounted an arm l8p adapted to operate switch contacts lBm and l8n, according to the direction of rotation of the shaft Ho.

The follow switch I8 is a double wafer switch comprising two rotatable contacts l9a and lab mounted on an insulating support I90, which is connected to the controlled shaft l4 for rotation therewith. The rotatable contact I90. makes contact at all times with a stationary contact i911 and has an extension lee which is adapted to connect with different ones of six stationary contacts l9f in six different positions of the controlled shaft I I. The movable contact [91), in= stead ofhaving a finger thereon, has a recess or gap I99, and in any position of rest of the controlled shaft M, the contact l9b contacts with five of six contacts lQh, but is open with respect to the remaining contact l9); because of the gap lag.

The different stationary contacts lth and i9) are connected respectively to the lines l, 2, 8, t, and 6, and it will be observed that the recess We in the rotatable contact lab and the extension nected to a contact l97, which is connected by a,

conductor to the contacts 2i and 22 of the reversing switch. This line 20 is also connected to one terminal of a cam-actuated switch 23, the other terminal of this switch being connected to the contact I911. The switch 23 is closed by a' cam 24 on a shaft 25 extending from the gear l3, which functions to close the switch 23 while the pin I1 is in driving relation with any one of the slots [5b of the driven member it.

The motor I0, as shown, is of the series type having an armature Illa, brushes lllb and tile, and two field windings ltd and lile respectively, these field windings being oppositely poled so that the motor runs in one direction when one field winding is energized and in the other direction when the other field winding is energized. One of the brushes lilo is connected by a conductor 27' to one terminal of a current source 28. other brush lllb is connected to a common terminal oi the two field windings llid and llle, the

other terminals of these field windings being connected by conductors 23 and 2a to the reversing switch contacts lllm and lan respectively. The other terminal of the current source 28 is connected by a conductor 38 to one terminal of the switch ltd, the other terminal of this switch being connected to the contact lag.

It will be observed that in any position of the master selection switch it, one terminal of the current source 28 is connected through the conductor 30 and the switch ltd, and thence through the contact Mg and the contact lBf to one of the lines i, 2, 3, 4, 5 or 6, and, when the system is at rest, the contact l9h of the switch it associated with this line will be juxtaposed to the recess lag, while the contact l9! that is connected to this line will be closed on the extension lee and will be connected through contact IM to one terminal of the switch 28, which is normally and the movable contact llib and the stationary 7 contact H91 to the conductor 26 through the contacts 2| and 22. If the handle lab was moved clockwise, then the arm lBp was rocked clockwise by the friction clutch I81 to open contact I8m away from contact 2| and close contact lBn on contact 22, thereby completing a circuit from conductor 20 over contacts 22 and Ian and through the field winding llld and armature its of the motor ill, and thence through conductor 21 back to the other side of the current source 28. The field winding llld is so poled that it causes the motor ill to rotate in such direction as to drive the controlled shaft id in the same direction that the handle lBb was turned (clockwise, in this instance).

The motor it drives the gear l3, which in turn drives the controlled shaft Hi through the Geneva mechanism until the recess 69g in the movable contact l9b is carried into registration with the contact l9h that is connected to the energized line. However, the motor ill is not stopped immediately upon movement of the recess l9g into the disconnect position with respect to the live contact lilh, because the corresponding contact lBf issimuitaneously connected to the extension We and thence through the contact ltd to one terminal of the switch 23. As has been previously pointed out, the switch 23 is closed by the cam 2% whenever the controlled shaft it is being rotated. Therefore, prior to the breaking of the connec= tion from the energized line by the recess leg, the conductor 20 is connected by the switch 23, the contact ISd, the moving contact l9a and the extension thereof Hie, to the energized line so that the circuit to the motor in is not interrupted by the opening of the connection between the movable contact wt; and that one of the stationary contacts l9h that is connected to the energized line. However, the motor is stopped when it has reached the desired position, by opening of the switch 23 by the cam 26.

If the control handle lSb is turned clockwise into still another position, the operation described is repeated to move the controlled member it into the new position.

If the control handle ldb is turned counterclockwise, the system functions as described except that the motor ill then runs in the opposite direction because the friction clutch l87' will then open the contacts i811. and 22 and close the contacts 2i and ltlm to energize the field winding We of motor it]. The switch l9 and the switch 23 function in the same manner regardless of the minal of the switch 23 back to the current source 28. This feature is highly desirable in control systems for use on airplanes in which the current source 28 may be located a substantial distance from the motor I and its associated switches,

because the weight of the extra contacts provided on the wafer switch i9 may be substantially less than the weight of an additional conductor ex-.

tending from the switch 23 to the current source 28.

It is also to be noted that the 'use of the auxiliary switch I8d in series with the wafer switch contact I8g has the important advantage of eliminating any possibility of the wafer switch contacts breaking while current is flowing, which would produce destructive arcing in a wafer switch. As is previously indicated, both the switch l8d and the switch 23 can be of the snap action type, although for simplicity they are indicated only schematically in the drawing.

Although for the purpose of explaining the invention a specific embodiment thereof has been described in detail, the invention is to be limited only to the extent set forth in the appended claims.

I claim:

1. In a control system of the type described: a controlled member movable into a plurality of predetermined different positions, and electrically controlled power means for driving it; a current source; a follow switch driven by said controlled member, and a master switch, said switches each having a plurality of different positions corresponding to said predetermined positions of said controlled member; a plurality of lines extending from said master switch to said follow switch; said follow switch comprising a first selector contact connecting with all of said lines except one and having a second selector contact connecting with only that line that is discontinued from said first selector contact in any of said positions of member approaches each of said positions and into open position as said controlled member reaches each of said positions, said auxiliary switching means being connected in series between said first and second selector contacts.

2. In a system of the type described: a controlled member movable into a plurality of predetermined diiferent positions and electrically controlled power means for driving it; a current source; a master switch for completing a circuit to said power means for driving said controlled member into a new position, and a follow switch driven by said controlled member for stopping the controlled member in the selected position, said switches each having a plurality of different positions and contacts corresponding to said predetermined positions of said controlled member; a plurality of lines extending from said master switch to said follow switch; means including said master switch and follow switch for completing a current path including said current source and said power means in series relation for driving said controlled member into a new position corresponding to a, new position of said master switch, and for opening said current path in response to movement of said controlled member into said new position; in which said master switch comprises a multi-position selector switch having separate line contacts connected to said respective lines and a. selector contact movable over said line contacts, and an auxiliary single circuit make and break switch connected in series with said selector contact, with means for opening said auxiliary switch prior to opening of said selector contact from each line contact and closing it following closure of said selector contact on the next line contact.

LOUIS HEGY.

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

UNITED STATES PATENTS Number Name Date 654,130 Buck July 24, 1900 1,798,044 Somajni Mar. 24, 1931 2,409,895 Phelps Oct. 22, 1946

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