US3007062A - Controllers for split-phase electric motors - Google Patents

Description

Oct. 31, 1961 R. H. TEASELL 3,007,062

CONTROLLERS FOR SPLIT-PHASE ELECTRIC MOTORS Filed July 5, 1957 3 Sheets-Sheet 1 Inventor Ems/ALB 19. 72945:

Attorney Oct. 31, 1961 T sELL 3,007,062

CONTROLLERS FOR SPLIT-PHASE ELECTRIC MOTORS Filed July 5, 1957 3 SheetsSheet 2 l v. i 4Z .J Inventor EONALDH 7Z=AsEL L Attorney Oct. 31, 1961 R. H. TEASELL 3,007,062

CONTROLLERS FOR SPLIT-PHASE ELECTRIC MOTORS Filed July 5, 1957 3 Sheets-Sheet 5 Attorney United States Patent 3,007,062 CONTROLLERS FOR SPLIT-PHASE ELECTRIC MOTORS Ronald Harold Teasell, North Wembley, England, as-

signor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed July 5, 1957, Ser. No. 670,278 Claims priority, application Great Britain July 10, 1956 12 Claims. (Cl. 307-112) This invention relates to starting controllers, that is starting relays, for split-phase electric motors.

The function of such controllers is to ensure that the motor starts with both the main (i.e. the running) winding and the phase (i.e. the starting) winding energised, and that the phase winding is switched out, responsive to a current flow in the main winding, when the motor has reached a suitable speed.

Such controllers must respond to two current conditions in the main winding:

(a) The current flowing through the main winding whilst the motor is at a standstill, which must operate the connection of the phase winding, and

(b) The current existing when the motor is running with both windings connected at a balanced speed condition, and from the decay of which current there results the disconnection of the phase winding.

By the use of the present invention, starting controllers may be made which will function even when the current differential, that is the difference between quantities (a) and (b), is very small; such controllers render the motor operable with widely different supply voltages and load conditions.

The scope of the invention is defined by the appended claims; how the invention may be performed is particularly described below With reference to the accompanying drawings, in which:

FIGURE 1 is an enlarged plan view of the starting controller device removed from a case;

FIGURE 2 is a perspective view, enlarged, of part of the device shown in FIGURE 1;

FIGURE 3 is a circuit diagram showing the device of FIGURES l and 2-connected to the motor; and

FIGURE 4 is a plan view of a modified device.

Referring to FIGURE 1 the controller there shown has a moulded phenolic base 1 to which is spun an extrusion from a terminal strip 2, bent upwards to form a contact face by means of a silver inlay 3. This makes contact with a silver contact 5, Welded to a bimetal strip 4, which is formed at right angles and attached to a raised portion 6 of the base by an eyelet 17. This strip 4 is retained by a slot 18 which prevents movement during operation of the bimetal. Adjustment of the bimetal strip 4 is made by a slotted grub screw 62 which is located in the raised portion of the base 6. The eyelet 17 further retains a heater wire 7, which is formed in coils 19 alongside the bimetal strip 4, and retained on a steel bracket 9 secured to the base 1. To provide a sound electrical joint the heater wire is looped around eyelet 10. Two brass eyelets 10 and 11 retain the steel bracket 9 to the base 1, and the bracket is formedupwards to form a stop 20 which can be adjusted to position the bimetal strip 4. This strip is normally positioned with the contacts 3, held in the closed position by a steel toggle spring 12 which exerts a force from its position 21 on the Strip 13, which is a bimetal compensator against ambient temperature variations. This compensator is mounted to the base on a raised leg 16 by means of two eyelets 14 and 15, and is further retained by a ledge 22.

The lower raised end 23 of the steel bracket 9 is formed 3,007,062 Patented Oct. 31, 1961 "ice to provide a mounting, upon which is welded the arm 24A of a U-shaped bimetal strip 24 carrying a silver contact 25 riveted to the end of the other arm 24B. An eyelet 26 riveted to the centre of the U carries a flexible lead 27, soldered at the opposite end 28 to the end of a berylliumcopper blade 29' about .005 thick (see FIGURE 2). Facing the bimetal contact 25 is a silver contact 30 riveted to a Phosphor bronze blade 31, about .006 thick, held to the base by an eyelet 32 and retained at the end by a slot on the base 33. The eyelet 32 also retains a brass terminal tag 34 to which is soldered the end of a solenoid coil lead 35. The Phosphor bronze strip 31 is formed to provide a projecting finger 36 reaching into the bore of the solenoid bobbin 37, and this strip is normally positioned to ensure that the contacts 25, 30 are approximately .030" apart. The solenoid bobbin 37 is held in position to the base 1 by pillars 3-8, 39, 40, which prevent the coil moving up or down, and is further retained by a locking pin 41 which passes through the bobbin. Inside the bore of the solenoid bobbin rests an iron armature slug 42, which is cylindrical, smooth and rounded at the edges to permit free operation movement inside the bore of the solenoid bobbin.

The slug 42 is positioned by an adjustable stop screw 43, consisting of a screw 43 of insulating material which can be moved through a threaded pillar 44 to move the slug into the bore. The slug 42, by virtue of its weight, presses a springy contact blade 29, 45 against the stop screw 43, keeping a contact 46, which is riveted to the beryllium copper strip 29, in the open circuit position. The strip 29 is formed such that contact 46 would press against a contact 47 and make electrical contact, were the weight of the slug 42 not applied to the end 45 of the strip. Contact 47 is riveted to a brass bracket 48 which has an extrusion 49 spun to the base 1. The beryllium copper strip 29 is riveted to a pillar 50, projecting from the base 1, by an eyelet 51 before extending to a soldering point 28 where both the flexible lead 27 and a solenoid coil lead 52 are soldered to make electrical contact. The coil lead 52 commences the solenoid coil 53 wound around the bobbin 37, and which is tapped by extending a loop 54 soldered to a terminal tag 34 at a point 35, as shown in FIGURE 1. The end of coil 53 is brought from the lower end of the bobbin at 55 and is soldered to a terminal strip 56, which is spun to the base 1 by an extrusion 57. Five wiring points are made by tapping the extruded tags 2, 49, 57, and nuts and screws 5859 and 60-61.

Referring to FIGURE 3 which is a wiring diagram of the motor and control circuit, a switch is mounted in the supply line and closure of the contacts 71 and 72 connects a circuit through the starting relay i.e., the controller described above, through the main winding 74 of the motor 75 and back to neutral. This current flows through the contacts 3 and 5 and along the bimetal strip 4, which increases in temperature as a result of its resistance and through the heater coil 19. It then flows through the bracket 9, through the thin leg 24A of the U-shaped bimetal strip 24 which increases in temperature as a result of its resistance, through the solenoid coil 53 from end to end, and into the main winding 74 of the motor. This current flow, is sufficient to create a flux in the solenoid coil 53 which attracts the slug 42 into the coil, and this movement allows the switch formed by the contacts 46 and 47, to close and connect the phase winding 85. As the slug 42 is pulled to the centre of the coil 53 it strikes the projecting finger 36 and forces the conand, together with a decrease in current as the motor 3 accelerates and a downward force applied by the finger 36 of the blade 31 (which may be called the armaturereturning blade), the slug is dropped clear of the coil 53.

As the slug 42 is dropped clear and the finger 66 is released, the contacts 25 and 30 are held temporarily to the closed position by the thermal deformation of the bimetal strip 24, the thin arm 24A of which has flexed as a result of the current and the resistance of the strip. The slug 42 opens the contacts 46, 47 thus disconnecting the phase winding 85. The low current which exists when the motor is running normally allows the contacts 25, 30 to separate and the relay is then in a position to re-start the motor when required. The current flow through the overload bimetal strip 4 and the heater 19 whilst the motor is starting, does not remain for a sufficient time to flex bimetal strip 4 appreciably, but should the motor run on an overload or fail to start correctly, the current flow through these parts creates sufficient heat and, therefore causes flexure of the bimetal 4 to separate the contacts and 3' by the snap action of toggle spring 12, and disconnect the voltage supply. These will normally reset after a short interval of time and the motor will then attempt to re-start.

FIGURE 4 shows a modified and somewhat simple starting controller, which is substantially the same as the one according to FIGURES l-3 except that the U-shaped bi-metallic strip 24 is omitted, and the Phosphor bronze spring blade 31 is replaced by a thin bi-metallic springy blade 31A. This is fixed to a steel bracket 9A (corresponding to bracket 9) and at starting carries the combined current flowing in the main and phase windings. To the end of the blade 31A is fixed a copper rivet 36A forming a finger adapted to be struck by the attracted armature slug 42. A flexible copper lead 27A (compare lead 27 in FIGURE 1) connects rivet 36A to a point 28A (compare 28 in FIGURE 1) on a U-shaped metal bracket 50A. At 28A the circuit divides, the current to the main winding passing by the wire 52 to the solenoid winding (compare description of FIGURE 1), and the current to the phase winding passing through the bracket 50A to the beryllium-copper blade 29A (equivalent to the blade 29 in FIGURE 1), fixed by rivets 29B. The remaining parts are substantially the same as the corresponding parts in FIGURE 1, and have the same reference numerals as those parts. 44A is a stop corresponding to the adjustable stop screw 44 in FIGURE 1.

The action on starting is that current flows through the over-load heater 19 to the bracket 9, through the bi-metal blade 31A, along the flexible lead 27A, to bracket 50A, through lead 7 and around the solenoid coil 53, leaving it by lead 55 which connects to the main winding by terminal bracket 56. The current flow through coil 53 results in a flux which attracts the armature slug 42 upwards allowing the beryllium-copper strip 29A to move upwards, so that the phase-winding switch formed by contacts 46, 47 is closed. Thus both motor windings are energized. The slug 42 strikes the copper rivet 36A and thus applies pressure to the bi-metal blade 31A which is deflected slightly upwards. The slug 42 then commences to move back towards the centre of the solenoid bobbin acting under the force of gravity, the spring deflection of the bi-metal blade 31A, and the downward flexure of the bi-metal resulting from its temperature rise due to the current flow. This augments its spring force. At this moment the motor, which has been accelerating, will apply a decay of current though the main winding and this also will assist in allowing the slug to drop clear of the bobbin. The slug will then strike the end 45A of the beryllium-copper blade 29A and open the contacts 46, 47 controlling the phase winding. If the slug 42 should fail to leave the bobbin cleanly, the bi-metal blade 31A will continue to deflect downwards and the copper rivet 36A will force the slug into a position at the lower end of the coil, the relative position of which decreases the current required to hold the slug into the bobbin.

I claim:

1. A starting controller for an electric motor, including in the combination, an electrically energizable solenoid, an armature attracted to the solenoid by energization of the solenoid, a switch for controlling an electric circuit including spring means urging the switch toward closed position, said switch being normally held open by the gravity applied weight of the armature as unattracted to the unenergized solenoid and closed by the spring means when the armature is attracted to the solenoid when energized, and an armature return spring means normally disengaged from the armature when the solenoid is unenergized but engaged by said armature in solenoid attracted position with the solenoid energized thereby to partially oppose the attracting force of the solenoid by the force of said spring means to spring aid thereby gravity release of the armature from the solenoid on decay of electric current in said solenoid.

2. A starting controller including the structure set forth in claim 1 wherein said spring means is thermally sensitive and electric current responsive and in series circuit with said solenoid to increase thereby the spring effectiveness of said spring means during energization of said solenoid.

3. A starting controller including the structure set forth in claim 1 wherein said spring means is thermally sensitive and electric current responsive and is in series circuit with said solenoid and has one position with the solenoid de-energized and a second position with the solenoid energized to increase thereby the spring effectiveness of the said spring means during energization of said solenoid.

4. A starting controller for an electric motor, including in the combination, a fixed contact, a movable contact closable on the fixed contact and adapted to close an electric circuit, a spring blade bearing said movable contact and urging it toward closure with said fixed contact, an electrically energizable solenoid having a hollow bore located above the free end of said blade, a loose armature in said solenoid bore normally resting its gravity applied weight on the end of said blade to hold said movable contact away from said fixed contact, said armature being adapted to be lifted from said blade by energization of said armature to permit said movable contact to close on said fixed contact, and an armature return spring blade located above said solenoid normally disengaged from said armature and adapted to be engaged and bent by the said armature when in attracted position by energization of said solenoid to exert thereby a spring force operating against the armature attracting force to spring aid gravity release of the armature from the solenoid on decay of electric current in said solenoid.

5. A starting controller constructed and arranged in accordance with the structure set forth in claim 4 wherein said spring blade is a bimetal electric current sensitive member in series circuit with said solenoid to bend under the heating effect of electric current passing to said solenoid to increase thereby its armature returning force in proportion to the current flowing through said solenoid.

6. A starting controller constructed and arranged in accordance with claim 1 wherein said spring means is thermally sensitive and electric current responsive and is in series circuit with said solenoid to increase thereby the spring effectivenessof the said spring means during energization of said solenoid to spring aid thereby gravity release of the armature from the solenoid on decay of electric current in said solenoid, and wherein said spring means includes a second switch circuit connected with said solenoid to short circuit a part of the solenoid when said second switch is closed by attraction of said armature to reduce thereby the flux eifect holding the armature in attracted position.

7. A starting controller for an electric motor constructed and arranged according to claim 1 that includes a short circuiting switch in series circuit with said solenoid to short circuit a part of said solenoid when closed and includes a thermally deformable element actuating said short circuiting switch as heated by the eifect of current flow to the solenoid, said thermally deformable element holding the short 'circuiting switch temporarily closed when the armature is released.

8. In a starting controller, an electrically energizable solenoid, an armature attracted by energization of the solenoid, a switch for controlling an electric circuit including spring means urging the switch toward closed position, said switch being normally held open by gravity applied weight of said armature to said spring means when unattracted by the solenoid and closed by said spring means when said armature is attracted by energization of said solenoid to remove the gravity applied weight of the armature from the spring means, and an armature return spring in the form of an electric current sensitive bimetallic blade electrically in series with the solenoid and electrically in series with the said switch to conduct thereby the combined currents conducted to the said solenoid and to the circuit containing the said switch, said armature being normally disengaged from said return spring when unattracted by said solenoid and engaging said return spring when unattracted by said solenoid, said return spring deforming under the heating eifect of the combined currents flowing through the same to spring aid thereby gravity release of the armature to open said switch on decay of current flow through the solenoid and the circuit containing said switch, said solenoid continuing to receive current through said bimetallic blade after opening of said switch by said armature with the current flow thereby through said bimetallic blade being reduced by the value of the current removed upon opening of said switch.

9. Apparatus constructed and arranged in accordance with claim 8 wherein said armature return spring includes a short circuiting switch closable by the attraction movement of the armature to the solenoid to short circuit a part of the solenoid whereby to reduce the flux effect of the solenoid on the armature in attracted position.

10. Apparatus constructed and arranged in accordance with claim 8 wherein said solenoid has a hollow bore with said armature movable in said bore, said armature return spring having a finger projecting into the bore of said solenoid in the path of the armature as attracted into the bore of the solenoid to engage thereby one end of said armature return spring and flex the same upwardly by the said attracting movement of said armature to render said armature return spring effective for release of the armature.

11. In a starting controller, an electrically energizable solenoid, an armature attracted by energization of the solenoid, a switch for controlling an electric circuit including spring means urging the switch toward closed position, said switch being normally held open by gravity applied weight of said armature to said spring means when unattracted by the solenoid and closed by said spring means when said armature is attracted by energization of said solenoid to remove the gravity applied weight of the armature from the spring means, and an armature return spring means comprising a first spring blade and a second spring blade in the form of an electric current sensitive bimetallic blade electrically in series with the solenoid and electrically in series with the said switch to conduct thereby the combined currents conducted to the said solenoid and to the circuit containing the said switch, said first blade being engageable by said armature when attracted by said solenoid and normally disengaged from said first blade to retain said switch means open by gravity applied weight of the armature to the spring means for the said switch, said second blade of said return spring means deforming under the heating effect of the combined currents flowing through the same to spring aid thereby together with said second blade gravity release of the armature to open said switch on decay of current flow through the solenoid and the circuit containing said switch.

12. Apparatus constructed and arranged in accordance with claim 11 wherein said first and second blades form a short circuiting switch to short circuit a part of the current flow through said solenoid and reduce thereby the flux effect of the solenoid on said armature, the heating effect of said bimetallic blade retaining said short circuiting switch closed temporarily after the armature is released.

References Cited in the file of this patent UNITED STATES PATENTS 1,716,389 Starr June 11, 1929 2,338,250 Logan Jan. 4, 1944 2,513,986 Woodson et a1. July 4, 1950 2,711,503 Elliott June 21, 19*53 2,801,312 Clark July 30, 1957 FOREIGN PATENTS 631,696 Great Britain Nov. 8, 1949

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