US2683844A

US2683844A - Reversing switch for electric motors

Info

Publication number: US2683844A
Application number: US243384A
Authority: US
Inventors: Edward J Schaefer
Original assignee: Individual
Current assignee: Individual
Priority date: 1951-08-24
Filing date: 1951-08-24
Publication date: 1954-07-13
Anticipated expiration: 1971-07-13

Description

July 1954 E. J. SCHAEFER 2,633,844

REVERSING SWITCH FOR ELECTRIC MOTORS Filed Aug. 24, 1951 2 Sheets-Sheet l will I" I, y 32 375i &1

a 7 INVENTOR.

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pm W 7 y 1954 E. J. SCHAEFER 2,683,844

REVERSING SWITCH FOR ELECTRIC MOTORS Filed Afig. 24, 1951 2 Sheets-Sheet 2 RUNNING WINDING 577m TING 73 w/lvowa IN VEN TOR.

Patented July 13, 1954 REVERSING SWITCH FOR ELECTRIC MOTOR-S Edward J. Schaefer, Fort Wayne, Ind.

Application August 24, 1951,

4 Claims.

This invention relates generally to split phase motor control means and more particularly to an instant reversing means therefor.

Split phase motors generally employ an automatic speed responsive switch for cutting out or modifying he starting winding circuit connections as the motor comes up to speed. In certain reversing arrangements in motors of this type it is necessary to wait for the motor to come to a full stop or until the automatic speed responsive switch functions to reconnect the starting winding before throwing the manual reversing switch. Various instant reversing switch arrangements have been proposed to overcome this disadvantage, some of which employ purely mechanical means for varying the relationship of the windings while others utilize electrical actuating elements such as relays. Although the mechanically actuated reversing switches have obvious advantages, they are limited in many cases to use with only a multiple-pole type control switch. For example, one highly satisfactory form of speed responsive instant reversing switch which is currently available requires a three-pole double throw manual reversing switch, and in many applications this limitation constitutes a serious disadvantage, especially where it is necessary or desirable to use only a single-pole double throw switch.

Accordingly, provide a novel ment for split phase motors which offers marked advantages in simplicity and flexibility of use.

A further object of the invention is to provide an instant reversing scheme for split phase motors which comprises a novel combination of a speed responsive mechanical switch, electrical relay means, and a single-pole double throw reversing switch.

Other objects and advantages of the invention will become apparent from the subsequent detailed description of one specific embodiment of the invention as illustrated in the accompanying drawings, wherein:

Fig. l is a fragmentary side elevational view of a motor with portions broken away to show the general arrangement of a, speed responsive switch and its actuating mechanism constituting part of the instant reversing scheme of my invention;

Fig. 2 is a partial sectional view taken along the line 22 of Fig. 1;

Fig. 3 is a side edge view on an enlarged scale of the switch per se;

Fig. 4 is a front elevational View of the switch illustrated in Fig. 3;

one object of my invention is to instant reversing switch arrange- Serial No. 243,384

Figs. 5 to 8 are front end views taken along the line 55 of Fig. 4 and showing successive operating positions of the switch;

Fig. 9 is a schematic electrical circuit diagram of my instant reversing scheme showing the conditions existing during operation of the motor in one direction;

Fig. 10 is a similar circuit diagram at the lnstant of reversal; and

Fig. 11 is a circuit diagram showing the conditions during operation of the motor in the reverse direction.

Referring first to Figs. 1-8 of the drawings, the structure and operation of the speed responsive switch portion of my invention will first be described. A motor i5 is shown having a rotor l6 mounted on a rotor shaft ll. A stationary frictionally set switch unit, indicated generally at I8, is rigidly affixed to the frame structure of the motor i5, and a rotating switch actuating or operating mechanism, indicated generally at i9, is mounted on the rotor shaft I! for rotation therewith during operation of the motor. The rotating switch actuating mechanism 19 is illustrated as being in the form of a centrifugally operated device having a frame member 2| rigidly affixed to the rotor shaft I! and provided with oppositely disposed inturned ends 22. A pair of bent arms 23 are pivoted, as at 24, to the end portions 22 of the frame 2! and are counterweighted, as at 26, at their outermost ends. An axially slidable collar 21 of plastic or other suitable non-conducting material is slidably disposed on the rotor shaft 17 intermediate the fixed switch unit it an i the frame member 2|. The inner ends of the pivoted arms 23 extend through a pair of apertured shoulder portions 28 on the collar 2?, and a pair of thrust springs 29 coact between the arms 23 and the shoulder portions 28 for normally urging the collar 27 away from the frame membar 2! into frictional engagement with a movable member of the switch unit I8, as hereinafter described in detail.

As seen in Fig. l, the motor is at rest and the springs 29 serve to retain the actuating collar 21 in frictional engagement with the switch unit 18. However, it will be understood that when the motor is in operation above a predetermined speed, centrifugal force will cause the counterweighted ends 26 of the arms 23 to swing outwardly thereby compressing the springs 25 and shifting the collar 2'! toward the frame member 2! (to the right as seen in Fig. 1) whereby to disengage the collar 27 from the switch unit l8.

The switch unit !8 comprises a base 3! of insulating material which is attached to the motor frame and has the switch parts mounted there on. A pair of fixed

contact elements

32 and 33 are secured to the base l, and a pair of movable contact arms and 35 carrying contact elements ill and 38 are disposed adjacent the fixed contacts and 33 for electrical engagement and disengagement therebetween. The

arms

34 and 36 are preferably of thin resilient flexible metal and constitute the sides of an integral U-shaped spring member so having a base portion 30 which is secured to the insulating switch base 3!. The arms 3 3 and are bent outwardly (Fig. 3) from the plane the base portion Gil and their inherent resiliency normally urges the

contacts

31 and 33 into engagement with the

fixed contacts

32 and 33. The outermost ends of the arms 3 and 35 have inturned portions H for the purpose described hereinafter.

A frictionally operable pivot arm d2 swingable in both horizontal and vertical planes is pivoted at its inner end to the upright portion of a bracket d3 secured over the base ii] of the U- shaped spring member 39. The outer end of the pivot arm s2 is formed with a curved frictional contact portion i l for actuation by the rotating collar 2'! of the actuating mechanism iii. For coaction with the pivot arm 52, an integral resilient tongue at extends centrally from the base 4!] of the spring member 39 intermediate the arms 34 and 3t and in the plane of the base portion 43 in generally parallel relation with the pivot arm 42. A rockable H-member l'i having side bars 553 and a cross bar as is disposed intermediate the resilient tongue l6 and the pivot arm 42 for transmitting spring pressure to the arm #32 and thereby normally urging the latter outwardly and away from the base 3i. As best seen in Figs. 5-8, the side bars 13 of the H-member i? fit into complementary notched portions in the parallel tongue is and pivot arm 42, and the cross bar :29 of the H -member is formed with rounded outer edges for facilitating rocking movement of the i-l-member relative to the tongue Q3 and the pivot arm 32. A pair of lateral extensions iii are provided integrally on the pivot arm 52 for coaction with the portions ti on the

contact arms

34 and 36.

For limitin the extent of movement of the pivot arm it, a frame member, indicated gen eraliy at 52, is secured at one end portion 53 thereof to the base 3% underlying the spring member 39 and the bracket The opposite end portion of the frame member 52 is bent away from the plane of the attaching portion 53 to provide a parallel outermost portion 5d overlying the pivot arm 12 and the portions El on the movable contact arms 31'; and 35. A pair of abutrients extend inwardly from the frame portion as on opposite sides of the pivot arm 42 for further limiting the pivotal movement thereof.

The various operating positions of the switch are clearly illustrated in Figs. 5-8. In Fig. 5 the pivot arm d2 is shown in its extreme right-hand position during operation of the motor in a given direction. With the motor at full speed, the collar 2? is disengaged from the contact portion 46 of the pivot arm 42 so that the arm 42 is urged upwardly by the spring action of the tongue 45 transmitted through the l-i-member M. In its uppermost right-hand position (Fig. 5) the righthand extension 5! on the arm 42 thus engages the portion ii of the contact arm 36 and thereby lifts the latter to disengage the contact 38 from from the frame 52.

the contact 33. The contacts 3? and 32 remain closed because of the spring action of the resilient contact arm 3 t.

When the reversing or control switch in the motor circuit is thrown, as hereinafter described, a negative torque is developed by reason of the connected relation of the motor windings and the motor slows down. When the speed falls below a predetermined level, the action of the springs 29 overcomes centrifugal force and forces the collar 21 into rotating frictional engagement with the contact end ie of the pivot arm 42 whereby to press the latter downwardly while still in its extreme right-hand position, as seen in Fig. 6. In this position both pairs of contacts 32-3l and 33-38 are closed.

When the motor finally stops and reverses its direction of rotation, the collar 2'! hich is still in frictional contact with the arm also begins to rotate in the reverse direction and thereby frictionally pivots or resets the arm :32 to its lowermost extreme left-hand position as seen in Fig. '7. Gradually, the motor picks up speed in its reverse direction of rotation and finally the centrifugal action of the actuating mechanism I9 causes retraction of the collar and consequent disengagement thereof from the arm =32. Thereafter, the arm 42 is forced upwar'ly again by the tongue it acting through the H-niember 47, and the contact arm 34 is lifted upwardly by the left-hand extension 55 engaging the corresponding portion ll of the arm 32 whereby to break the contacts 32-47.

It will be seen that the arm as undergoes so" quential pivotal movement first in a vertical plane, thence in a horizontal plane, and final y in a vertical plane, as viewed in Figs. 5-8. The H-member 4'1 pivots or rocks about the cross bar 69 to accommodate horizontal pivoting of the arm -42 and also provides a direct connection between the spring tongue 45 and the arm 52 to pivot the latter in a vertical plane. Vertical movement of the arm i2 is limited in one direction by the forward portion 54 of the frame member 52 and in the opposite direction by engagement of the outer end 54 of the arm 32 with the base 3|. Horizontal pivotal movement of the arm 42 is limited by engagement of the side edges of the arm 52 with the abutments 5% depending It will also be apparent that the resilient nature of the

contact arms

36 and 33 normally tends to urge the contacts 32-6? and 33-38 into closed relation but that the lateral extensions 5! of the arm 32, when the collar 21 is disengaged therefrom, function to lift one or the other of the contacts 3i and 38 away from its corresponding fixed contact 3'2 or 33. Upward movement of the contact arms 3 and 36 is, of course, limited by engagement of the actuating portions ii of the arms with the for ward portion 54 of the limiting frame 52.

Referring now to Figs. 9-11, the electrical characteristics of my instant reversing scheme will be described. The invention as illustrated in these circuit diagrams is shown as applied to a single phase motor in which a capacitor at is used for splitting the phase for starting purposes. A pair of primary windings 62 and $3 are disposed in axially displaced relation, preferably at in the usual manner. It will be understood that a rotor, not shown, which is usually of the inductance squirrel cage type, is disposed in operating relation adjacent the primary windings. A speed responsive switch comprising the unit l8, as hereinbefore described, is included in the circuit and has a permanent electrical contact or connection 64 in addition to the two sets of disruptible contacts 323l' and 33-48. The circuit is also provided with a relay 65 having contacts 6'! and 68 and a control switch 59 of the single pole double throw type having a pair of contacts H and 12.

The line terminals of the motor are indicated at 13 and 14, the line connection 13 going directly to one end of both

primary windings

52 and 53 and the other line connection 74 going to the movable blade of the control switch 69 which serves both as an energizing switch and as a reversing switch. The contact ll of the switch 69 is connected to the other end of the primary Winding 63, and the contact 12 connects through the coil of the relay 66 with the other end of the primary winding 62. The phase splitting con denser GI and the centrifugal switch 18 are also connected in series through the movable arm of the relay 66 between the last two mentioned ends of the

primary windings

62 and 63.

The operation of the apparatus will now be described. Referring first to Fig. 9, the circuit is shown with the various elements in their re spective positions when the motor is running in a clockwise direction, the contacts H and T2 of the control switch 69 being designated as the clockwise (CW) and the counterclockwise (CCW) terminals, respectively, and the sets of contacts 32-3'l and 33-38 of the centrifugal switch I8 likewise having the respective CW and CCW designations. The blade or the hand switch 69 is closed on contact H thereby disrupting the circuit through the coil of the relay 8B for deenergizing the same in which condition the arm of the relay is biased into engagement with the contact 67. However, the pivot arm 42 of the centrifugal switch 18 is in its right-hand position during clockwise rotation of the motor, corresponding to the position shown in Fig. 5, so that when the motor is up to speed the contacts 33-48 are broken thereby cutting out the primary winding 52. Although the contacts 32-37 are closed to establish a connection with the fixed terminal 64 of the switch l8, as indicated diagrammatically by a dotted line 76, it will be seen that during deenergization of the relay 56 the contact 68 is open thereby interrupting the circuit through the switch 18 and the condenser F 65. Thus, during clockwise operation of the motor at full speed, the primary winding 63 is connected directly across the line terminals '53 and 14 through the control switch 69. Consequently, winding 63 is the running winding while winding 62 has functioned only as a starting winding in a manner which will become clear hereinafter.

Assuming now that it is desired to reverse the direction of the motor to counterclockwise rotation, the control switch 69 is moved directly to contact 72, as seen in Fig. 10, without the necessity of any delay or hesitation in so doing. The instant the blade of the switch 69 closes against the contact 72, the quick acting relay 66 becomes energized and the arm of the relay is closed against the contact 53. This happens before the motor can slow down to any appreciable extent, and hence both

primary windings

62 and 63 are momentarily connected in parallel directly across the line terminals 13 and 14, the winding 62 being connected through the coil of relay 56 and switch '59, and the winding 63 being connected through condenser 6!, connection 64, closed contacts 32 3'1, contact 68, the coil of relay 66, and the switch 69. As thus connected the motor has a substantial negative or reversing torque tending to slow it down. The magnitude of this negative torque and the speed to which the motor will slow down depends primarily upon the resistance of the rotor winding and the capacity of the condenser Bl. However, it is only necessary that the negative torque be sufficient to reduce the speed of the rotor to the point where the speed responsive switch [8 will return to its low speed or starting position.

Hence, the motor reduces speed very quickly with the result that the actuating mechanism 5 9 of the centrifugal switch 3 as hereinbefore described, depresses the pivot arm 42 to permit closing of the contacts 3338 in addition to the already closed contacts 32-31, thereby corresponding to the condition illustrated in 6. Thus, a connection is established between the fixed terminal 64 of the switch I8 and the closed contacts 33-38, as indicated diagrammatically by a dotted line 77 in Fig. 10. Subsequently, as the motor begins to rotate in a counterclockwise direction under the influence of the negative or reversing torque, the pivot arm 42 is frictionally reset by being shifted to its left-hand position while still depressed inwardly from the movable contact arms of the switch, as previously described in connection with Fig. 7.

Referring now to Fig. 11, the motor gradually counterclockwise direction mechanism of the switch I 8 releases the pivot arm 42 of the switch wher by to break the contacts 3231 and thereby cut the winding 63 and the condenser 65 out of the the winding 53 functions as the the running winding, the circuit through the latter being established through the line terminal 13,

the usual manner.

The reversing of the motor back to a clockwise direction may be accomplished by throwing the control switch 59 from contact 72 to H, and it will be readily understood that the reversion to the circuit conditions illustrated in Fig. 9 takes place in a manner similar to the operation alread described with the winding 82 functioning as the starting winding and the winding 63 as the running winding. If the primary windings of the motor are alike, the reversing characteristics of the motor will be similar for both directions. However, the scheme will still be operative even if there is a substantial difference in the two windings. It will also be understood that in order to stop the motor the switch 69, which is also an energizing as well as a reversing switch, is merely moved to an intermediate position between the contacts "II and '12.

It will be seen that by the inclusion of the small uncalibrated relay 66 in the circuit in the manner described, my invention permits a centrifugal reversing switch of the type shown to be used with a three lead reversible motor while requiring merely a single-pole double throw control switch for energizing and instant reversing purposes. The relay 66, as described, is so connected in the circuit that it is energized when the motor is running in one direction but is deenergized when the motor is running in the opposite direction.

Although the invention has been described in connection with one specific embodiment thereof, it will be understood that various modifications and equivalents may be resorted to Without departing from the scope of the invention as de fined in the appended claims.

I claim:

1. In a split phase reversible motor, a pair of axially displaced motor windings, a main control switch for selectively connecting either of said motor windings across a source for running in either direction, phase displacing means con nected in series with one or said motor windings, a switch mechanism including two sets of switch contacts each connected in series with said phase displacing means, and auxiliary control means responsive to the operation of said main control switch and cooperating with said switch mechanism for selectively connecting either or said motor windings across the source in series with said phase displacing means and with one of said sets of switch contacts and for connecting the remaining motor Winding across the source in parallel circuit, said switch mechanism including switch operating means responsive to the speed and direction of rotation of the motor for subsequently opening said one set or switch con tacts when the motor attains running speed.

2. In a split phase reversible motor, a pair of axially displaced motor windings, phase displacmg means connected in series with one of said motor windings, relay means including a pair or relay contacts and also including a relay winding connected in sales with the other of said motor windings, a main control switch for selectively connecting said one motor winding or said other motor winding and said relay winding across a source, and a switch mechanism including two sets of switch contacts each connected in series with said phase displacing means and with one of said relay contacts, said relay means being operative in cooperation with said switch mechanism for selectively connecting either of said motor windings across the source in series with said phase displacing means and with one of said sets of switch contacts and for connecting the remaining motor winding across the source in parallel circuit, and said switch mechanism including switch operating means responsive to the speed and direction of rotation of the motor for subsequently opening said one set of switch contacts when the motor attains running speed.

3. In a split phase reversible motor, a pair of axially displaced motor windings, a main control switch for selectively connecting either of said motor windings across a source for running in either direction, phase displacing means connected in series with one of said motor windings, switch means connected to said phase displacing means and including a pair of spaced contacts, said switch means being operative to con nect said one motor winding across the source in a first series circuit with said phase displacing means and with one of said contacts and said switch means also being operative to connect the other of said motor windings across the source in a second series circuit with said phase displacing means and with the other of said contacts, and relay means cooperating with said contacts and adapted to be energized and deenergized in response to operation or" said main control switch for selectively closing either of said series circuits and for connecting the motor winding not included in the series circuit across the source in a parallel circuit, said switch means including switch operating means responsive to the speed and direction of rotation of the motor for subsequently opening the series circuit when the motor attains running speed.

a. In a split phase reversible motor, a pair of axially displaced motor windings adapted to be connected to one side of a line, a main control switch adapted to be connected to the other side of the line for selectively connecting one or said motor windings across a source for running in one direction and the other of said motor windings across the source for running in the oppcsite direction, and means for connecting said other motor winding in parallel with said one motor winding for starting in said one direction and for connecting said one motor winding in parallel with said other motor winding for starting in said opposite direction, said means comprising a relay including a relay winding connected in series with said oth motor winding and with said control switch and also including a pair of relay contacts adapted to connected respectively to said relay winding and to said other motor winding upon operation of the relay, a switch mechanism connected to said one motor winding and including two sets of switch contacts respectively connected to said relay contacts, and a phase displacing means connected in series with said switch mechanism said one motor winding, said switch mechanism being adapted to close both or" said sets or switch contacts on starting in either direction and being responsive to the direction of rotation and to the speed or the motor for selectively opening one of said sets of switch contacts when the motor attains running speed, and said relay being operative to connect one of said sets of switch contacts with said relay winding when the relay is energized and to connect the other of said sets of switch contacts with said other motor winding when the relay is deenergized.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,195,287 Schaeier Mar. 26, 19-40 2,586,734 Sprague et al. 19, 1952