US2236282A - Controller - Google Patents

Description

March 25, 1941. AYERS 2,236,282

CONTROLLER Filed April 28. 1938.

l/Vd'ULA TIOIY INJULA T/OIY Fi .3. as g l Inventor:-

Fig.4

Belg a? H. Ayers,

y His Attorney Patented Mar. 25, 194i l'TED STATES PATENT 2,236,282 CONTRQLLER Edgar H. Ayers, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application April 28, 1938, Serial No. 204,804 12 Claims. (Cl. 200-122) My invention relates to controllers, more parposition and retains these contacts in disengageticularly to apparatus for controlling the starting ment, until a cooling of the bimetallic strip recircuit of an electric motor of the split-phase closes the starting contacts. Thereafter, the type and for protecting the motor from excessive overload contacts automatically reset and permit current flow therethrough by reason of overload, the motor to start up again with the starting 5 and has for its object the provision of an exwinding in the motor circuit. tremely simple device of this character which has For a more complete understanding of my ina minimum number of parts and which, accordvention, reference should be had to the accomingly, may be cheaply and easily manufactured. panying drawing, in which Fig. 1 is a plan view It is well understood, of course, that it i necesof a controller embodying my invention; Fig. 2 m sary to provide means for insuring that the startis an elevational view of Fig. 1; Fig. 3 is a circuit ing winding of the motor shall be energized durdiagram showing a controller embodying my ining and only during the starting period. It is vention connected in the circuit of a split-phase also highly desirable to protect the motor from motor and Fig. 4 is a perspective view of a magexcessive current both during running and stalled net used in a controller embodying my invention. 15 conditions. For successful operation of a com- Referring to the drawing, I have shown my inbined starting relay and-automatic resetting overvention in one form as applied to the starting and load, the starting contacts of the starting relay running circuits of a split-phase motor, although must be closed ahead of or at the same time the it will be obvious that a controller of this charoverload contacts of the overload relay close. If 'acter has broad application to general circuit 20 this condition was not met, the motor would be control and overload protection. The controller placed on the line without its starting winding is shown mounted on a base Ill of suitable inin the circuit, and the motor-would not be ready sulating material which may form the top or to start when the overload contacts were closed. cover of an insulated wire box or casing H into To efiect the desired control of motors of the which the necessary circuit wires may be led and 25 split-phase type reliably, yet with a device which connected to terminals on the bottom face (not can be cheaply manufactured, I provide a conshown) of the base Ill. Fastened to the base l6 troller having thermally responsive actuating y means of rivets I provide a ar s pmeans, such as a bimetallic strip, arranged to port member l3 having secured at the upper end deflect in accordance with the current inthe strip ther of actuating means h s & imet llic 30 and a heating element in the motor circuit. 0pstrip ld. The bimetallic strip H may be spaced erable by this strip are starting and overload above and may exte l i ly f he b se contacts normally in engagement and adapted "I bein s cu ed a one e ot pp t memto disengage upon a predetermined deflection of y Suitable means, $11611 s y We d and the strip. I provide magnetic mean for r talnmay have its other end free for lateral deflection 35 ing a portion of the bimetallic strip in an und'ein resp s t cha es in e p u e in accordfiected position to hold the overload contacts in I n e with the heatin of a h ter element 15. engagement during normal operating conditions r h in h Strip in accordance w of th mot Th magnetic m a I hav the intensity of the current in the motor circuit,

40 vided, although I do not intend to be limited 1 P de preferably the heating element in 40 thereto, may consist of an armature having two the form of a resistance wire which is electrically arms spaced from but encompassing a permanent connected to the fixed end of the strip 14 and magnet, the armature being attached to the biis arranged adjacen b Spaced from the Strip l4 metallic strip and arranged to be attracted to for the transmission of heat thereto. The strip it of t positions, l I4 is of such material and cross section that heat 45 Another portion of the bimetallic strip is free is also gener ted i it y Passage of current thereto deflect to operate the starting contacts for throu h- T e heater wire 15 is fastened to h removing the starting winding from the motor Support y 8 Screw at O end and Its circuit after suflicient time has elapsed for the other end fastened by a w 13 B terminal motor to come up to speed. In case the motor post l1 secured to the base In. 50 should overload for any reason, the bimetallic The bimetallic strip It may be fastened so that strip will deflect a further amount and overcome its broad faces are substantially perpendicular the magnetic restraint and open the overload to the base It! and so that its deflection is subcontacts. When the overload contacts are stantially parallel to the plane of the base. For

opened, the armature moves to its other attracted switching the starting circuit or the motor, I 55 contact 2Q, thereby causing the starting contacts 59 and it to disengage.

On the opposite face of the strip A l from that Where the starting contact H9 is fastened and seposed adjacent the movable contact 23 but on the other side of the strip, 1 provide an armature 2? which cooperates with a permanent magnet 28 The armature 2? has two arms, one oi which may be secured directly to the strip i by suitable means, such as welding, the armature 27 being C-shaped and having the permanent magnet 28 its face adjacent the armature magnetized as to have a north and a south pole on that face.

The bifurcated armature 2? is adapted to be attracted to two positions relative to the magnet 28 which is encompassed by the armature arms.

Normally, the armature 2? is magnetically held L in a first position in which the overload contacts 3 and 26 are engaged. Upon a predetermined deflection of the strip M, however, the armature 2?? moves to a second attracted position for holding the contacts 23 and 243 in disengagement.

Near the top of the support 29 I provide a projection 39 for limiting the movement of the armature 27/ in its second position out of contact with the magnet 28, the fixed overload wish to be limited to the construction shown.

Referring now to Fig. grammatically a controller embodying my invention connected in the circuit of'a split phase motor M having a starting winding S and a running winding R connected in a well-known manner. The moto'r M may be supplied from a source of alternating current, 32 through the conductors 33 and 36. The running circuit of the motor M comprises the conductor 33 connected in series circuit with the supporting member 25, the overload contacts 23 audit, the bimetallic strip'l l, the heater wire 115, the running Winding R, and the conductor 36. The starting circuit oi the motor M is electrically connected in parallel to I the running circuit from the strip i l starting contacts 149 and 2&3 and through the I winding S to-the conductor 35.

In operation, when the motor M is disconnected V from, the source 32, the strip it remains in an unheated and undeflected condition. The overe, I have shown die-- the starting tacts 29 and 23 slightly oil? the line the strip Mi would normally assume in its undefiected condi- After sumcient time has elapsed for the motor M to come up to speed, the strip i l bows up or deflects to disengage the starting contacts 69 and 28. movement of the strip Ml is one of pivoting on the fixed contact 25, the overload contacts 23 and 2 3 being magnetically retained in engagement.

and-2S disconnected and the overload contacts 23 and 24 still in engagement.

It will be understood that ii the magnet 28 were removed and the left hand end of the bimetallic strip. l6 would move downward,

a certain extent.

When the intermediate portion of the'strip M bows or. curves upon heating, the movable conto slip across the surface of the magnet 28 such as contacts had rounded tips.

were entirely free, this end mechanical load might stall before Should for any reason a condition of overload :ome on the motor M, either in the stalled or unning condition, the heater l5 and the strip I will heat up accordingly. Upon an abnorrnal heating of the strip ll, it will build up force sufficient to overcome magnetic force on the armature 21 on its first position and will snap the overload contacts 23 and 24 apart. The armature 21 is then magnetically restrained in the second position awaiting automatic resetting when the strip l4 cools down.

With the main circuit broken, the strip M will cool down and again cause the starting contacts l9 and 2D to reclose before the magnetic restraint on the strip in the second position is overcome. After the starting contacts l9 and 20 have reclosed, a further cooling and deflection of the strip ll will cause the overload contacts 23 and 2A to snap engage in the first position, and the motor M will be ready for starting with the starting winding S connected in the motor circuit.

In a motor circuit such as I have shown, it is conceivable that the motor pulling a sluggish the strip M cooled sufficiently to reclose the starting contacts 69 and 20. Under these circumstances, if the current were again turned on, the motor would be unable to start since the starting circuit s would be still disconnected. However, the high current through the heater element l5 and the strip l4 would quickly cause flect suificiently to actuate the overload contacts 23 and 24, and automatic resetting of both the starting and the overload contacts would occur in the normal and correct sequence before any damage was done to the motor.

Although I have shown my invention in one form with magnetic restraining and resetting means, I do not intend to be limited thereto, since it will be obvious to those skilled in the art that spring means, such as an overcenter spring arrangement, or other means may be used as well without departing from the spirit of my invention.

While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not wish to be limited thereto since many modifications may be made, and I therefore contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A motor controller comprising a starting switch and an overload switch, means including a thermo-responsive element arranged for lateral deflection in response to a change in temperature for actuating said starting switch and said overload switch, means for heating said thermo-responsive element, and means associated with said thermo-responsive element for causing said overload switch to be operated only in a predetermined sequence with respect to the operation of said starting switch.

2. A thermo-responsive device comprising a thermo-responsive element arranged for a deflection in response to changes in temperature, means for heating said thermo-responsive element, switching means operable by. a deflection of an intermediate portion of said element, switching means operable by another portion of said element, and restraining means for retain-v ing said last mentioned switching means in a given position during a predetermined -deflection the strip 14 to deof said element while said first mentioned switching means is operated.

3. A thermo-responsive device comprising a thermo-responsive element fixed at one end having the other end free for lateral deflection, means for heating said thermo-responsive element, switching means including a first pair of contacts in normal engagement operable by the deflection of said free end of said thermo-responsive element, switching means including a second pair of contacts in normal engagement operable by the deflection of an intermediate portion of said thermo-responsive element,- and restraining means for retaining said first pair of contacts in engagement during a predetermined deflection of said element while said second pair of contacts are caused to disengage, said first pair of contacts being disengaged by a further deflection of said element, and said restraining means retaining said first pair of contacts in disengagement thereafter until said second pair of contacts are caused to re-engage.

4. A motor controller comprising a starting switch and an automatic resetting overload switch, said starting switch and said overload switch being normally closed for completing a circuit, means including a bimetallic strip adapted to deflect in response to changes in temperature for actuating said starting switch and said overload switch, means including a heater element for heating said strip, electrical connections for connecting said heater element in the circuit of a motor to be controlled, and means associated with said strip for retaining said overload switch in said normally closed position after said starting switch has opened, for snapping said overload switch to an open position after a predetermined deflection of said bimetallic strip, and for causing said overload switch to reset in a predetermined sequence relative to the closure of said starting switch after said strip has cooled.

5. A motor controller comprising a starting switch and an overload switch having a plurality of fixed and movable starting and overload contacts in respective normal engagement, means including a bimetallic strip for actuating said movable contacts, means for heating said bimetallic strip for causing said strip to deflect, electrical connections for connecting said heating means in the circuit of a motor to be controlled, and means associated with said strip including a permanent magnet and an armature for causing said overload contacts to disengage and re-engage in a predetermined sequence with respect to the operation of said starting contacts.

6. A motor controller comprising fixed and relatively movable starting contacts in normal engagement, fixed and relatively movable overload contacts in normal engagement, means for actuating said movable starting and overload contacts including a bimetallic strip, means including a heater element for causing said strip to deflect, and magnetic means cooperating with .said strip adapted to be attracted to either of two positlons for retaining said overload contacts in engagement in a first of said positions when said starting contacts are caused to disengage by a deflection of said strip and for snapping said armature to said second position after a predetermined deflection of said bimetallic strip for causing said overload contacts to disengage.

'7. A motor controller comprising fixed and relatively movable starting contacts in normal engagement, fixed and relatively movable overload controlled, and said strip adapted to be attracted to either of two positions for retaining said overload contacts in 10 mined deflection of said bimetallic strip for causing said overload contacts to disengage, said last mentioned means being adapted to restrain said armature in said second position for holding said overload contacts in disengagement until said bimetallic strip has cooled suiiiciently to permit has cooled, said last mentioned said starting contacts to re-engage.

8. A motor controller comprising fixed and movable starting and overload contacts, means including a bimetallic strip fixed at one end the of an intermediate portion means including a permanent magnet cooperating with an armature on said other end of said bimetallic strip for retaining said overload conduring a predetermined deflection of said intermediateportion of said strip, said predetermined deflection of said strip being suificient to disengage said starting contacts.

9. A motor controller comprising fixed andmovable starting and including a bimetallic overload contacts, means strip fixed at one end the other end being adapted to deflect in response to changes in temperature for actuating said contacts, said movable starting contact being in normal engagement with said fixed starting contact and operable to disengage by the deflection of an intermediate portion of said strip, able overload contact being in normal engagesaid fixed overload contact and operable to disengage by said other end of said strip, and means including a permanent magnet cooperating with an armature secured to said strip for retaining said overload contacts in engagement during a predetermined deflection of said intermediate portion of said strip, ing said overload contacts after said predetermined deflection of said strip, andfor retaining said overload contacts in disengagement until said starting contacts have re-engaged ai'ter said strip means thereafter causing said overload contacts to snap re-engage.

10. A motor controller comprising a bimetallic strip fixed at one end the other end being arranged for lateral deflection changes in temperature, a movable starting contact secured to of said strip, and

for snap disengag-' in response to an intermediate portion of said strip for movement therewith normally in engagement with a fixed starting contact, a movable overload contact secured to said other end of said strip for movement therewith normally in engagement with a fixed overload contact, a heater element for heating said strip, and means including an armature secured to said strip having two arms spaced apart and a permanent magnet positioned between said arms, said armature adapted to be attracted to a first position for holding said overload contacts normally in engagement while said starting contacts are caused to disengage and adapted to be attracted to a second position after a predetermined deflection of said strip for disengaging said overload contacts, I

whereby said overload contacts engagement until said strip has cooled sufiiciently for re-engaging said starting contacts and there-.

during a predetermined deflection of said strip and thereby causing said intermediate'portion of said strip to deflect in a negative direction for disengaging said starting contacts.

12. A thermo-responsive device comprising a bimetallic strip fixed at one end having a movable starting contact secured to an intermediate portion of said strip and a'movable overload contact secured to the free end of said strip, a pair of stationary contacts in respective normal engagementwith said movable contacts in a first position when said strip is in an undeflected position, a heater element for heating said strip, said being heated, and magnetic means for restraining said free end of said strip in said first position for holding said overload contacts in engagement during a predetermined deflection of said strip and'thereby causing said intermediate portion of said strip to deflect in a negative direction for disengaging said starting contacts, said magnetic means being adapted to snap said free end of said strip to a second position in a positivedirection for disengaging said overload contacts upon a further deflection of said strip w e said intermediate portion of said strip is caused to retain its negative deflection for holding said starting contacts in disengagement.

EDGAR H. AYERS.

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