US2425312A

US2425312A - Motor control system

Info

Publication number: US2425312A
Application number: US594623A
Authority: US
Inventors: Gower Thomas Charles
Original assignee: Individual
Current assignee: Individual
Priority date: 1945-05-19
Filing date: 1945-05-19
Publication date: 1947-08-12
Anticipated expiration: 1964-08-12

Description

Aug- 12 1947 l T. c. GQWER MOTOR CONTROL lSYS-TEM Filed May 19, 1945 2 Sheets-Sheet l :Snnentor 7.2" CAL/A51 GWER Cttorneg T. C. GOWER MOTOR CONTROL SYSTEM Aug. y12, 1947.

Filed May 19, 1945 2 Sheets-Sheet 2 IIIII IIIEII llli! IIHIII v :inventor 7T CIJ/JS. GWER /V 0%@ mf Patented Aug. 12, 1947 UNITED STATES PATENT OFFICE MOTOR CONTROL SYSTEM Thomas Charles Gower, Greenville, S. C. Application May 19, 1945, Serial No. 594,623 1'7 Claims. (Cl. 172-279) This invention relates to motor control systems, and more particularly but without limitation to a motor control system adapted for use with automatic door operating mechanisms.

In various industrial installations, processing rooms according to current practice are often airconditioned to maintain a proper atmosphere for theV process being carried out. In certain instances, notably the textile industry, air-conditioning is commonly used in this manner, and is a critical factor affecting the ease withl which the processing is accomplished.

.The problem has arisen in this connection of regulating the use of door openings to such airconditioned processing rooms so as to prevent the opening of doors leadingv from unconditioned areas, or from the outdoors, from dissipating the air-conditioning established in the `processing room. Door openings to processing rooms are normally used at frequent intervals for delivering materials to be processed and removing processed materials, and as such materials are commonly handled with industrial trucks requiring relatively large door openings, the problem oi' regulating the use of the door openings has assumed serious proportions.

A variety of arrangements have heretofore been proposed to serve as door operating mecha- 'nisms, but most of 'the previous arrangements have not been sufficiently automatic to solve the present problem, and, on the whole-they havev been relatively expensive.

The motor control system of the present invention provides a. fully automatic means for controlling a door operating mechanism, and utilizes relatively inexpensive equipment. The control system is arranged so that the door operating mechanism may be set in motion by a single actuation oi a pushbutton, photoelectric cell,`or other similar control, such as might be easily accomplished by a person passing the location of the pushbutton on an industrial truck. Once in motion, the door is operated by my control system to move to open position, to remain in open position fora predetermined time interval, and then vfor disconnecting the starting winding after the ment in my control system.

to return to closed position automatically. Further provision is made to allow the door to be reopened by means of the pushbutton control at any time during its travel to closed position, and to cause the door to reopen if it strikes an obstruction at any time during its closing travel.

My motor control system contemplates the control of a single phase electric motor of the type having a starting winding and associated means Another important feature is an arrangement for bridging the disconnecting means associated with the starting winding so that the starting winding may be connected to reverse the single phase motor while it is running. l,

The foregoing and other features of my invention are illustrated in the accompanying drawing, in which: l

Fig. 1 is a circuit diagram illustrating an embodiment of the motor control system of my invention adapted for use in a door operating mechanism;

Fig. 2 is a fragmentary elevation, mainly diagrammatic, illustrating an arrangement oi a door operating mechanism incorporating my motor control system;

Fig. 3 is a corresponding elevation, partly cut away, of the operating unit;

Fig. 4 is a corresponding right side elevation;

Fig. 5 is a corresponding rear elevation; and

Fig. 6 is a further diagrammatic view illustrating an arrangement of an overhead door for operation according to my invention.

Referring at rst to Fig. 2 of the drawing, an operating unit "incorporating my motor control system is indicated generally at III, arranged for operating a sliding door II. The illustration in Fig. 2 is mainly diagrammatic, and Iit will be understood that the door I l is arranged in relation to a door opening (not shown) and may be moved to allow passage through or to close this door opening as desired. The disposition of the door II shown in Fig. 2 is for closed position. The door Il is mounted on an inclined rail hanger ,Y I2 by means of brackets I3 which are attached" to the door Il and iitted with rollers I4 which operate in the inclined rail hanger l2. When moved to open position the door Il travelsup to operate a drive vsprocket II. A sprocket chain IB associated with this drive sprocket I'I is extended across the top of the door Il to an idle sprocket I9. l

The door II is connected with the sprocket chain il by a bracket which is attached to the door and has a cylindrical portion 20a arranged at its upper end through which the sprocket chain i! may be passed. A suitable lug member 2i which will not pass through the hollow cylindrical portion 20a of the bracket 20 is arranged toward the lower inclined end of the rail hanger i2. This arrangement allows the door il to be opened by hand in case of power failure, or in emergencies. or when otherwise desired. y l

The sprocket chain il extends beyond both the drive sprocket I l and the idler sprocket l! in a length sufficient to allow for opening and closing travel of the door li. The ends of the sprocket chain Ill are secured at fixed mountings 22 and 2l. Between these mountings 22 and 2l and the` drive sprocket l1 and idler sprocket i9. respectively, the slack of the sprocket chain Il is disposed in loops 2| and 2l. Counterweights 2l and 21 are arranged on rollers 2l operating in these loops. vided to balance the weight of the door il. and to keepthe sprocket chain Il taut at all times.

The sprocket chain il is actuated for opening and closing th'e door through the drive sprocket i1 by the geared connections to the motor il shown in Figs. 3 and 4. This arrangement comprises a countershaft 29 running from the belt and pulley connection il from the motor il. The countershaf t 29 is mounted in suitable bearings 30 in the operating unit housing, and carries a worm 8i and suitable spacing collars I2 all The counterweights 2B and 21 are pro-v of which are fixed on the countershaft 28 with set screws as shown. Theworm Il is disposed to engage a worm wheel 33 which is fixed on a drive shaft 34 arranged at right angles to counter shalt 28 for driving the drive sprocket il. This drive shaft 34 is also Journalcd in the operating unit housing and also carries a worm 3l disposed to engage a worm wheel 38 fixed on a switch control shaft 3l which in turn is arranged at right angles to drive shaft 34 and parallel to countershai't 29. The drive shaft 3l and switch control shalt 31 are suitably provided with spacing collars similar to the collars 32 arranged on countershaft 29. The switch control shaft 31 is journaled in the operating unit (as at Il) with an extending switch operating portion 39 to be described more in `detail`below.

The manner in which my motor control system may be used for operating a door closure arranged in this manner may be described with reference to the circuit diagram shown in Fig. l.

As mentioned above my motor control system is adapted for controlling a single phase electric motor of the type having a starting winding and associated means for disconnecting the starting winding after the motor has started. A convcnient and readily available motor of this type is a capacitor motor such as is commonly used on electrical appliances of variouskinds. Capacitor motors are characteristically equipped with a centrifugal switch arranged in the circuit of the starting winding to disconnect the starting winding after the motor has started.

A circuit diagram of an electrical motor il oi' this type is indicated generally in Fig.A 1 at l0. The running winding of the motor i! is represented at Il. the starting winding at l2, and the centrifugal switch arranged in the circuit of the starting winding at s3. In arranging the capacitor motor il as at Ill for use with the motor control system 0f my invention, a reversing switch M is also provided in the circuit of the starting winding as indicated in Fig. 1.

Btarting with the operating unit II at rest and the door il in closed position, the capacitor motor il is provided with two line switches ll and Il in series with the running winding Il. of these line switches 4l is initially closed and the other one 4I is open. A low voltage control circuit l'l (suitably 18 to 24 volts) `containing a push-button control ll and a relay ll in series is connected across the line through a transformer l0. The relay ll is arranged so that when it is not energized a connection is made across the line switch 4l referred to above as initially closed.

The relay Il is energized by momentarily closing the pushbutton Il. When energized in this manner the relay Il is shifted to the position indicated by dotted lines in Fig. i. This causes the above mentioned connection across the line switch Il to be broken while threeother connections are made: one across the line to the capacitor motor Il. which causes it to start rotation in the direction for opening the door Il; another which places a bridging circuit across the centrifugal switch Il arranged in the circuit of the starting winding l2; and a third in series with contacts 0l. 0l, to provide a holding circuit for relay 40.

Shortly after the capacitor motor il is started. mechanical means correlated with the rotation of the motor i5 (see Figs. 3. 4 and 5) close the `initially open line switch 4l so that the motor is then connected and continues to run directly on the line. The mechanical means for closing the line switch I8 comprises an arm Il mounted on the extending switch operating portion Il of the switch control shaft Il. The arm Il turns with rotation of the switch control shaft il to contact the switch arm B2 of line switch Il and shift it to closed position as indicated by thedotted line in Fig. 1. l

At about the same time. further mechanical means also associated with the extending switch operating portion 39 of the switch control shaft 3l effects an opening of the above-mentioned bridging circuit across the centrifugal switch Il. This circuit is opened between two contact points 53 and 5I which are arranged in the nature of a push-button switch as indicated in Fig. 1. The contact points il! and M, as is best shown in Fig. 4, are carried on a suitably insulated mounting Il on the operating unit housing. and the lower contact 54 is arranged to spring away when not held in contact with the upper contact Il. A friction collar 60, fitted with a liningof friction material Il (see Fig. 3), is mounted on the extending switch operating portion I0 of the switch control shaft lll to dispose an operating arm Il in relation to the contacts 53 and Il. With the operating unit Ill at rest and the door Il closed. the operating arm 8l will have assumed a position, as shown in Fig. 4, to close the contacts Il and 53. Rotation of the switch control shaft 21 in the direction corresponding to opening of the door Il, however, will cause the operating arm 58 to shift to the position indicated" by dotted lines in Fig. 4 so that the lower contact Il will spring away from the upper contact Il. This shift is caused by the fact that the friction collar It is fitted on the extending portion Il of shaft." tightly enough to rotate with it when not opposed. The operating arm I0 accordingly turns with rotation of shaft 31 until it is restrained by a stop l extending from the mounting Il. The friction collar 56 will then slip on shaft 31 during continued rotation in the same direction. As explained more'ln detail below, operating arm 5l is shifted back to initial position by rotation of the shaft 31 in the direction corresponding to closing of the door II. A stop 60 for the operating arm 58 in this position is formed in the lower contact 54.

Opening of the

contacts

53 and 54 as described above conditions the bridging circuit across the centrifugal switch 43 so thatthe starting winding 42 may be cut out as soon as the motor I5 attains speed during perationfor opening the door II.

The motor I5 continues to operate under these conditions until the door II has been moved to open position. When the door I I has been opened, the motor I5 is stopped by a second arm 8| mounted on the extending portion 39 of the switch control shaft 31 which engages the switch arm 62 of the initially closed line switch 45 and shifts it to open position. At the same time, arm 8l shifts the switch arm 83 of reversing switch 44 to reverse the connections of the starting winding 42 to condition the motor I5 for reverse operation to close the door II'.

An auxiliary, constant speed, high resistance, timing motor 54 is connected in parallel with the initially closed line switch 45, so that when the line switch 45 is opened to stop the capacitor motor I5 the timing motor 64 is connected in series with the running winding 4I of the motor I5. While the timing motor 64 will operate under these circumstances, its high resistance prevents operation of the capacitor motor I5.

a The timing motor 64. which may be of the well known shaded-coil type, is used to time the period during which the door II remains in open position. The timing is accomplished through actuation of contacts 65 and 56 which, like

contacts

53 and 54, are also arranged in the nature of a push-button switch as indicated in Fig. 1. The

contacts

65 and 66 are disposed from a suitable mounting as at 61 in relation to a notched timing element 58 carried on the shaft of the timing motor 64 (see Figs. 4 and 5). The timing element 68 is an electrical conductor, and has a substantially cup-like cylindrical shape in which notches 68a are formed at the open end. .As is best shown in Fig. 4, the contact 65 rides a solid portion of the element 68 as it rotates during operation of the timing motor 64, while the contact 66 is positioned in relation to the notched portion. As a result, the contact 66 will periodically slip across one of the notches 468a in the timing element 68 and momentarily break the connection between contacts 65 and 56 through the element 68. By employing a timing element 68 having notches 68a of suitable size in relation to the speed of the timing motor 64 the periodic breaking of the connection between

contacts

65 and 66 can be arranged to occur at desired intervals corresponding to the length of time it is intended to have the door II remain in open position.

The

contacts

65 and 66 are arranged in the control circuit 41 so that when the connection between these contacts is momentarily broken, as contact 58 slips across a notch 68a in the timing element 58, the relay 49 is de-energized. The relay 49 accordingly assumes its original position to make a connection across the line switch 45 which was opened to stop the capacitor motor I5 y when the doorv II reached open position. As line l. switch 45 is bridged in this manner, and line switch 46 was closed when motor I5 was iirst started to open the door II, motor I5 is again connected on the line and will resume operation:

and as reversing switch 44 was shifted when line switch 45 was opened, motor I5 will resume operation in the direction corresponding to closing movement of the door II.

When the line switch 45 is bridged out at the time that relay 49 is de-energized. the timing movltor 64 is aiso bridged out and consequently will not operate. As the timing motor 64 is stopped in this manner when the contact 66 slips across a notch 68a in the timing element 88, the motor 64 will stop in each instance with the contact 66 resting on the lower edge of a notch 68a in the timing element 68. By arranging the notches 68a regularly in the timing element 58, a uniform timing of the period for holding the door I I in open position can thus be obtained.

Shortly after operation of the capacitor motor I5 vresumes in the direction necessary to close the door II, arm 5I on the extending portion 39 of switch control shaft 31 will again engage switch arms 62 and 63, respectively, to close line switch 45 and again shift the reversing switch 44 to reverse the connections on the starting winding 42. This action of the arm 6I is timed to occur after the capacitor motor I5 has attained speed and the 'starting winding 42 has consequently been cut out by the centrifugal switch 43. At about the same time, the operating arm 58 on the friction collar 56 shifts back to its original position to close

contacts

53 and 54 in the bridging circuit across the centrifugal switch 43. As the relay 49 has been de-energized, however, thisA bridging circuit is open at the relay.

Under these conditions, the capacitor motor I5 may continue operation until the door I I has been closed, the capacitor motor I5 being stopped by the action of arm 5I which will engage switch arm 52 at this time to shift line switch 46 to open poslition and thus open the line on capacitor motor As previously mentioned, further provision is made` to allowv the door I I to be reopened by means of the push-botton control 48 at anytime during its travel to closed position, and to cause it to reopen if an obstruction is met at any time during closing travel. i

Reopening of the door I I with the push-button control 48 iseiected through the bridging circuit from the relay 49 across the centrifugal switch 43. If the push-button 48 is closed at any time during closing travel of the door II, the relay 49 will be energized to close this bridging circuit across the vcentrifugal switch 43 and thus bringthe starting winding 42 into play. As the reversing switch 44 is in position at this time to connect the starting winding 42 for rotation of the motor I5 in the direction for opening the door I I, the starting winding 42 will oppose the running winding 4I and reverse the direction of rotation of the motor I5 to reopen the door II. A resistance element 69 is placed in the starting winding circuit to act as a buier and protect the starting winding 42 during operation in this manner.

When the capacitor motor I5 is reversed as described above to reopen the door I I, the operating arm 58 on the friction collar 56 will shift as opening movement starts to open the

contacts

53 and 54 so that the starting winding 43 may be cut out by the centrifugal switch 43 as soon as motor I5 attains speed in the changed direction.- The motor I5 will be controlled to stop when the door I I reaches open position, the interval in open position will be timed and the motor I5 will be oper ated to close the door II, as noted above in del scribing the operation of the control system under normal conditions.

The door ll is caused to reopen if it meets an obstruction by a safety switch 1li mounted on springs on the leading edge of the door ll as illustrated in Fig. 2. The safety switch 1li is arranged in the manner of a push-button to close auxiliary contacts a in the control circuit 41 as shown in Fig. 1. Closing of these auxiliary con` tacts 10a eiiects reopening of the door il in the same way that actuation of the push-button control 48 accomplishes this result as described above. The safety switch 10 may be of the contact pressure type. or of any other conventional design adapted, for this purpose.

A further safety provision is included in my motor control system to guard against damage to the operating unit lli in the event of a power failure. If a power failure interrupted operation during opening movement of the door ll. the relay 49 would of course be de-energized; but, as

both line switches 45 and 46 would be closed at this time, operation to open the door ll would be resumed when the power failure was remedied. With relay 49 de-energized. however, the opening of line switch 46 would not be effective to stop motor l5 when door il reached open position because switch 4B would be bridged out at de-energized relay 49. As a result. motor lli would con tinuc to operate until the transmission became locked. To avoid this possibility in the event of a power failure, an auxiliary switch 45a (see Fig. 1) is arranged to control a bridging circuit connected directly across the centrifugal switch 4l. The switch 4lia4 is arranged so that it is closed and opened simultaneously with opening and closing, respectively. of line switch 4D. Consequently. if relay 49 is deenergized for any'reason so as to allow motor IB to continue operation in opening direction, switch 45a will bring the starting winding 42 into play as line switch 4! is opened; and as reversing switch 44 will be shifted to reverse the connections of starting winding 42 when line switch 45 is opened, the capacitor motor l! will be reversed so that door I l will return immediately to closed position, thus avoiding the possibility of damage to the operating unit lll. Any danger resulting from sudden resumption of movement of the door ll in thisvmanner is obviated by the provision o f the above described safety switch 10.

To arrange the door ll for operation from either sidel a second push-button control 1l may be placed in parallel with the push-button 48 as shown in Fig. 1. If desired. photoelectric cells i not shown) or other means for automatically actuating the relay 49 may be substituted for the push-buttons 48 and 1l.

An adaption of my motor control system for operating an overhead door is illustrated diagrammatically in Fig. 6. The overhead door is represented at 12 as the well known type composed of hinged panels and adapted to be raised overhead to open position on rollers operating in curved guideways (not shown). Tension springs 13 are commonly used on a door installation o! this type to carry the major portion of the weight of the door 12 when it is moved to open position but not to resist closing movement of the door unduly. In adapting such a door for operation according to my invention, the springs 13 are tightened so that they will raise the door 12 to open position unaided if not resisted. The pull of the springs 13 is exerted on the door" 12 through lines 14 whichvhave a nxed mounting at 1I and run over pulleys 10 which are movable with the springs 1I and fixed pulleys 11 to a point of attachment 18 at the bottom of the door 12.

The door 12 is held in closed position against the pull of springs 13 through a line 1l running from a fixed mounting lli over rollers Il mounted at the bottom of the door. It will be seen that the door 12 may be readily opened in emergencies with this arrangement by cutting the line 1l.

Beyond the rollers 0i the line 18 is led around a fixed pulley 82 and over a movable pulley Il to a fixed mounting B4. The movable pulley Il is carried at the end of a line Il, s uitably a sprocket chain, engaged by the point of drive Il of the door operating unit represented in this instance at l1. A counterweight Bl is arranged on the other end of the line I5 to balance the pull of springs 13 approximately.

An operating unit 81 which is in all respects identical with the embodiment described above for operating a sliding door ll may be used to operate the overhead door 12. As the operating unit v81 'is started for opening movement of the door 12, the effect is to pay out the line IU so that the door may be raised by the springs 13. The counterweight B8 insures smooth operation as this opening movement occurs. After the door 12 has been timed in open positionI the operating unit l1 is caused to start in closing direction and the door 12 is closed against the pull oi springs 13 with the aid of counterweights 88.

The overhead door 12 may be reopened automatically, or as desired during closing movement, in the same manner as was described in detail above inconnection with the operation of the sliding door l I.

While my motor control system has been described above in connection with its embodiment for use in a door operating mechanism. it will be understood that my invention is not limited in this respect and that the motor control system described is of general application as defined in the appended claims.

I claim:

1. A motor control system comprising a single phase electric motor of the type including a starting winding and associated means for automatically disconnecting the starting winding after the motor has started, means for starting said motor for rotation in a given direction, means for automatically stopping said motor when a predetermined degree of rotation in said given direction has been obtainedpmeans Iorautomatically restarting said motorafter a predetermined time interval for rotation in reverse direction with respect to said first mentioned direction of rotation, means for automatically stopping said motor when it has returned to initial position by virtue of said reverse rotation, and controllable means for changing the direction of rotation of said motor to said first mentioned direction of rotation at any time during said reverse rotation.

2. A motor control system comprising a single phase electric motor of the type including a starting winding and associated means for automati-.

cally disconnecting the starting winding after the motor has started, means f or starting said motor for rotation in a given direction. means for automatically stopping said motor when a predetermined degree of rotation in said given direction has been obtained. an auxiliary. constant speed. high resistance, electric timing motor, means for automatically connecting said timing motor in series with said single phase motor simultaneously with the stopping of rotation of said single phase motor in said given direction, means associated with said timing motor for automatically restarting said single phase motor after a predetermined time interval, means for automatically conditioning said single phase motor for rotation upon restarting in reverse direction with respect to said ilrst mentioned direction of rotation, and means for automatically stopping said single phase motor when it has returned to initial posi tion by virtue of said reverse rotation.

3. A motor control system comprising a single phase electric motor of the type including a starting winding and associated means for automatically disconnecting the starting winding after the motor has started, means for starting said motor for rotation in a given direction, means for automatically stopping said motor when a predetermined degree of rotation in said given direction has been obtained, an auxiliary, constant speed, high resistance, electric timing motor, means for automatically connecting said timing motor in series with Isaid single phase motor simultaneously with the stopping of rotation of said Isingle phase motor in said given direction, `means associated with said timing motor ior automatically restarting said single phase motor after a predetermined time interval, means for automatically conditioning said single phase motor for rotation upon restarting in reverse direction with respect to said ilrst mentioned direction of rotation, means for automatically stopping said single phase motor when it has returned to initial position by virtue of said reverse rotation, and controllable means for changing the direction of rotation of said motor to said first mentioned direction of rotation at any time during said reverse rotation.

4,. In a motor control system for a single phase electric motor of the type including a starting winding and associated means for automatically disconnecting the starting winding after themotor has started, a means for automatically interru'pting the operation oi' said single phase motor for a predetermined time interval comprising means for automatically stopping said single phase motor, an auxiliary, constant speed, high resistance, electric timing motor, means for automatically connecting said timing motor in series with said single phase motor simultaneously with the stopping of said single phase motor, and means associated with said timing motor for automatically restarting said single phase motor ai'ter said predetermined time interval.

5. In a motor control system for a single phase electric motor of the type including a starting winding and associated means for automatically disconnecting the starting winding after the motor has started, a means for automatically"inter rupting the operation of said single phase motor for a predetermined time interval comprising a line switch in the operating circuit to said single phase motor, means for automatically opening said line switch, an auxiliary, constant speed, high resistance, electric timing motor connected in parallel with said line switch, and means associated with said timing motor for automatically closing the operating circuit to said single phase motor after a predetermined time interval.

6. In a motor control system for a single phase electric motor of the type including a starting winding and associated means for automatically disconnecting the starting winding after the motor has started, a means for automatically interrupting operation of said single phase motor for a predetermined time interval comprising means for automatically stopping said single phase motor, an auxiliary, constant speed, high resistance, electric timing motor, means for automatically connecting said timing motor in series with said single phase motor simultaneously with the stopping of said single phase motor, and means associated with said timing motor for auto matically restartingsaid single phase motor after said predetermined time interval, said "associated -means including an element mounted for rotation on the shaft of said timing motor and adapted to close the operating circuit to said single phase motor after said predetermined time interval.

7. Means for automatically interrupting the operation of a capacitor motor for a predetermined `time interval comprising a line switch in the operating circuit to said capacitor motor, means for automatically opening said line switch, an auxiliary, constant speed, high resistance, electric timing motor connected in parallel with said line switch, and a bridging circuit and means associated with said timing motor for connecting said bridging circuit across said open line switch after said predetermined time interval.

8. In a control system for a capacitor motor, an operating line circuit to said capacitor motor, a. control circuit in parallel with said operating circuit, a relay in said control circuit, means for closing said control circuit to energize said relay. means closing the operating circuit to start said capacitor motor when said relay is energized, a, line switch in said operating circuit, means for automatically opening said line switch to stop said capacitor motor, an auxiliary, constant speed, high resistance, electric timing motor connected in parallel with said line switch, means associated with said timing motor to deenergize said relay after a predetermined time interval, and means for closing the operating circuit to restart said capacitor motor when said relay is de-energized.

9. A motor control system comprising a, single phase electric motor of the type including a starting winding and associated means for automatically disconnecting the starting winding after the motor has started, means for starting said motor for rotation in a given direction,

means for automatically stopping said motor when a, predetermined degree of rotation in said given direction has been obtained, means for automatically restarting said motor after a. predetermined time interval for rotation in reverse direction with respect to said first mentioned direction of rotation, means for automatically stopping said motor when it has returned to initial position by virtue of said reverse rotation, and controllable means for changing the direction-of rotation of said motor to said first mentioned direction of rotation at any time during said reverse rotation, said controllable means comprising a bridging circuit across the means for automatically disconnecting the starting winding after the motor has started and means for closing said bridging circuit to connect said starting Winding.

10. In a motor control system for a capacitor motor having a centrifugal switch for disconnecting the starting winding of said capacitor motor after said motor has started, an operating circuit for said motor, a control circuit in parallel with said operating circuit, a relay in said control circuit, means for closing said control circuit to energize said relay, a, bridging circuit across said centrifugal switch, said bridging circuit being connectedfor closing at said relay when said relay is energized. means for reversing said motor, means for maintaining said bridging circuit open while said motor is operating in one direction of rotation but conditioning said bridging circuit to be closed by energizing said relay during reverse rotation oi' said motor with respect to said first mentioned direction of rotation. whereby the starting winding maysbe connected to change the direction of rotation oi' said motor to said ilrst mentioned direction of rotation at any time during the reverse operation of said motor.

11. In la motor control system for a single phase electric motor of the type including a starting winding and associated means for disconnecting the starting winding after the motor has started, means for reversing said motor, a bridging circuit across the means for disconnecting the starting winding, means maintaining said bridging circuit open while said motor is operating in one direction of rotation but conditioning said bridging circuit for closing during reverse operation oi said motor with respect to said rst mentioned direction of rotation, whereby the starting winding may be connected to change the direction of rotation of said motor to said rst mentioned direction of rotation at any time during the reverse operation of said motor. said last mentioned means comprising a collar member mounted in i'rictional engagement with the shaft of said single phase motor for rotation with said shaft except when opposed. contacts arranged in said bridging circuit in normally open position, means associated with said collar member for closing said contacts, said associated means being moved by said collar member upon rotation of said motor in said ilrst mentioned direction to a position allowing said contacts to assume an open position and being moved to a position closing said contacts upon reverse rotation of said motor, and means for opposing rotation oi said collar member to limit movement of said associated means between positions correspending to open and closed positions of said contacts.

12. A door closure means comprising a door movable to open and closed positions and a single phase electric motor, of the type including a starting winding and associated means for disconnecting the starting winding after the motor has started, connected for moving said door between open and closed position, means for starting said motor to move said door to open position, means for automatically stopping said motor when said door has been moved to open position, and means for automatically restarting said motor to move said door to closed position after a predetermined tine interval.

13, A door closure means comprising a door movable to open and closed positions and a singie phase electric motor, of the type including a starting winding and associated means for disconnecting the starting winding after the motor has started. connected for moving said door between open and closed position, means for starting said vmotor to move said door to open position, means for automatically stopping said motor when said door has been moved to open position. means for automatically restarting said mo'- tor to move said door to closed position after a predetermined time interval, and means i'or reversing said motor to reopen said door at any time during operation of said motor to close said door.

14. A door operating mechanism for controlling the movement of a door normally maintained in closed position comprising a single phase electric motor, of the type including a starting winding and associated means for disconnecting the starting winding after the motor has started. connected for moving said door between open and vclosed position, means for operating said motor in` one direction of rotation to move said door to open position, means for maintaining said door in open position for a predetermined time interval, means for operating said motor in reverse direction with respect to said rst mentioned direction of rotation to move said door to closed position after said predetermined time interval, and means for changing the direction of rotation of said motor to said ilrst mentioned direction of rotation to return said door to open position at any time during operation of said motor to move said door to closed pition.

l5. A door operating mechanism for controlling the movement of a door normally maintained in closed position comprising a capacitor motor having a centrifugal switch lor disconnecting the starting winding of said capacitor motor after said motor has started, an operating circuit for said `motor, a control circuit in parallel with said operating circuit, a relay in said control circuit, means for closing said control circuit to energize said relay, means closing said operating circuit when said relay is energized, whereby said capacitor motor is operated to move said door to open position, a line switch in said operating circuit, means for automatically opening said line switch to stop said capacitor motor when said door reaches open position, means for automatically reversing the connections oi' the starting winding of said capacitor motor when said door reaches open position, an auxiliary, constant speed. high resistance, electric timing motor connected in parallel with said line switch, whereby said timing motor is connected in series with said capacitor motor and operates when said line switch is open, means associated with said timing motor to de-energize said relay after a predetermined time interval, means lor bridging said line switch to close said operating circuit when said relay is de-energized, whereby said capacitor motor is operated in reverse direction to close said door after said predetermined time interval, means for automatically reversing the connections of said starting winding t0 condition said capacitor motor for operation to open said door alter said reverse operation has started, and means ,to connect said starting winding to cause said capacitor motor to reopen said door at any time during reverse operation of said motor to close said door.

i6. In a control system for a capacitor motor of the .type having a starting winding and a ccntrifugal switch for disconnecting the starting winding alter the motor has started, an operating line circuit to said capacitor motor, a control circuit in parallel with said operating circuit, a relay in said control circuit, means for closing said control circuit to energizel said relay, means closing the operating circuit to start said capacitor motor when said relay is energized, a line switch in said operating circuit, means for automatically opening said line switch to stop said capacitor motor and associated means for concurrently conditioning said capacitor motor for reverse operation, an auxiliary, constant speed, high resistance, timing motor connected in parallel with said line switch, means associated with said timing motor to de-encrglze said relay after a prede- .termiri'ed time interval, a bridging circuit across said open line switch and means closing said bridging circuit when said relay is deenergized. and a second bridging circuit across said-centrifugal switch and means i'or closing said second bridging circuit simultaneously with opening of said line switch, whereby operation of said capacitor motor is automatically reversed when said line switch is opened if said relay has previously been accidentally de-energized.

17. In a motor control system for a single phase electric motor of the type having a starting winding and associated means for disconnecting the starting winding after the motor Ahas started, an operating line circuit to said single phase motor, a control circuit in parallel with said operating circuit, a relay in said control circuit, means for closing said control circuit to energize said relay, means closing the operating circuit to start said single phase motor when said relay is energized, a line switch in said operating circuit, means for automatically opening said line switch to stop said single phase motor and associated means for concurrently conditioning said single phase motor for reverse operation, means for deenergizing said relay alter a predetermined time REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 2,205,787 Brongersma June '25, 1940 2,253,170 y Dunham. Allg. 19, V1941 2,315,582 Blodget Apr. 6, 1943 2,380,270 Suhr et al July 10, 1945