US2714807A - Electric circuit control - Google Patents

Description

Aug. 9, 1955 R. w. LELAND ET AL ELECTRIC CIRCUIT CONTROL Filed Jan. 30, 1952 IN VEN TORS 05527- m LELAND 19/10 M2544 E. SP/EES J48. BY M, M

United States Patent Gffiee is? s Fatented Aug. 9, 1955 be engageable with the stationary terminal 22. At-

tached to the free end portion of blade spring 2.5 is the actuator 36;, the end edge thereof having two spaced V- 2,714,87

shaped notches 31 and 32 provided therein. Contact ELECTRTQ QIRCUIT CGNTROL blade 24 has a resilient, biasing finger 34 attached to it a at the area ad'acent contact 23 thereon the free end of Robert W. lueiand and Kreii E. Spires, J23, Dayton, @1110, Said fij a 8831mm in 16 bottom of Shaved rote assignors to General Motors (Iorporation, Detroit, T 1

I I Mldha wrpammm 0f Dslaware 1 in no some or. in a simnar manner, contact acre 26 has a biasing finger 36 attached thereto, the free end Application January 30, @552, Serial No. 269,054 of this finger seating in the notch 32 of the actuator 35 3 Claims. (CL 62 4) These fingers 34 and $6 exert a biasing force upon their respective contact blades 24. and 26 in either one direction or the other, dependent upon which side of the respective blade the actuator 3f: locates the notch engaging end of the finger. 1 shows the notch engaging ends of the fingers and 36 located above the respective com This invention relates to an improved control mechanism for dual electrical devices.

It is among the objects of the present invention to protact blades 24 and 26, or more specifically on the sides of vide a control mechanism adapted to be connected in cirsaid blades opposite the sides on which contact elements cuit with either one or the other of two separate elecare mounted. This causes fingers 34 and 36 to bias their trical devices when the respective device is connected respective blades 24 and 26 so that contact elements 28 with a source of electric power, said control device proand 2? engage the respective terminals 23. and 22. When viding a predetermined time lag for the completion of the notch engaging ends of fingers 34 and 36 are shifted the circuit of the one device when it is connected with to the opposite sides of the respective blades 24 and 2-5, the power source immediately following the disconnection as shown in Fig. 2, then the blades are biased to disof the second device from the source of power. engage their respective contact elements 28 and 29 from The control mechanism is primarily adapted for use in the stationary terminals previously engaged by them. a refrigeration system in which the compressor is driven The notch engaging ends of said fingers are shifted by by an electric motor and the evaporator of the system the movement of the actuator 3d. The blade spring has a heater coil associated therewith for defrosting pursupporting said actuator normally urges the actuator to poses. A selector switch is operative into one or an- M Ward the position occupied by it in Fig. 2 in which the other circuit closing position for rendering either the contact blades 2d and 26 are biased to effect contact discompressor motor or the heater coil active. To provide engagement. for automatic defrosting, the selector switch is time op- The controller has a thermoelectric element 4%, one end erated, that is, an electrically driven timer shifts the of which is electrically and mechanically attached to a selector switch from one circuit making position into the portion of the actuator 38, the other end of said element other at recurrent timed intervals so that the motor being insulatingly and adjustably secured to an angular driven compressor and then the evaporator heater coil are portion of frame 2%. A terminal 42 is electrically rendered active in succession and at timed intervals. in connected to this end of the thermoelectric element. order to obtain most efficient refrigeration especially in This thermoelectric element is shown in the form of domestic refrigerators equipped with automatic defrosta wire predeterminately tensioned to overcome the efing, it has been found highly desirable to provide for a fect of spring blade 25 and thus normally holds the actu time lag or delay between the end of the defrosting peator in the position shown in Fig. 1 in which the riod and the start of the motor which drives the comblades are biased to effect contact engagement. pressor, such a time lag lasting approximately from one The electric motor 5% which provides the motive power to two minutes. The thermoelectric controller of the 45 for the compressor 51, when said motor is installed in present invention and its connections with the compressor a refrigeration system, has a starting winding 52, conmotor and the evaporator heater coil provide for properly nected to stationary terminal 21, and a running winding timed refrigeration and defrosting cycles which tend to- 53, connected to the terminal 22. Both windings 52 and ward most efficient refrigerator operation. 53 are connected to the one terminal 5'4 of the timer Further objects and advantages of the present inven- 5U actuated switch 55 which may be of any suitable type. tion will be apparent from the following description, ref- Another terminal 56 of said switch 55 is connected with erence being had to the accompanying drawings wherein the heater coil 57, associated with the evaporator 58 of a preferred embodiment of the present invention is clear the refrigeration system for heating it during the dely shown. frosting cycle. The movable contact arm 6% of the In the drawings: 55 switch S5 is recurrently actuated at timed intervals to Fig. 1 is a view showing the controller in normal posiengage the respective terminals 54 and 56 and thereby tion and its electrical connections with the source of bring either of the moloi windings i116 11621161 Coll intO electrical energy, the compressor motor, the evaporator circuit with the power line with which said arm 6% is heater d th ele t wit h, connected. The controller terminal 4-2 is connected with Fi 2 is a view showing the controller in the circuit W h other power line and heater is electrically b ki o iti nected to terminal 61 on controller frame 2-9. As pre- Referring to the drawings, the controller is shown con- ViOIlSlY mentioned, Switch 55 may be y P limif sisting of a rigid, metal frame 20 which is mounted on switch of Standard design adapted to p Oil-3 Wofk any suitable insulating base upon which the two tati circuit and close another at timed, successive intervals. ary terminals 21 and 22 are mounted. An upturned car 05 W Switch Contact 69 engages terminal 54 the motor 23 i provided on frame 20, aid ear having one nd of field windings 52 and 53 are brought into circuit connecthe movable contact blade 24, the blade spring 25 and tion with the power line and due to the fact that contact the contact blade 26 attached thereto in any suitable elements 28 and 29 engage their respective terminals 21 manner. Blades 24 and 26 are flexible and each carries and 22, the thermoelectric element 40, as well as the a contact element adjacent its free end, blade 24 carrying 70 engaging contacts will complete the circuit for energizing contact element 28 so as to be engageable with terminal the motor windings and rendering the motor active. As

21, and blade 26 carrying the contact element 29 so as to the motor is approaching running speed, current flowing through the thermoelectric element 40 will cause it to be heated and consequently expand, thereby permitting the blade spring to become etfective to move the actuator so that the point of engagement of finger 34 in actuator notch 31 will be shifted and finger 34 will bias contact blade 34 to disengage its contact element 28 from terminal 21 and thereby open the circuit through the starting winding 52. The comparatively heavy surge of current through element 46 during motor starting will cause it to be heated and expand for effecting this controller action. During normal running of the motor 59, current flow through the thermoelectric element 49 remains within predetermined values which do not cause said element 4% to become sufficiently heated as to expand and permit spring 25 to move the actuator so that the point of engagement of finger 36 in the notch 32 of the actuator causes said finger to bias blade 26 and disengage its contact 29 from terminal 22. Thus, during normal motor operation the circuit through the running winding 53 is maintained. However, if, due to overload or for any other reason, current flow through the motor winding 53 and the thermoelectric element becomes excessive, then the said element 40 will be increasedly heated and caused to expand for efiecting disengagement of contact 29 with its terminal 22 and thereby open the running t winding circuit and stop the motor. As the thermoelectric element cools due to no current flow therethrough, it will contract in length and move the actuator 34? in opposition to the effect of blade spring 25. This will again shift the points of engagement of fingers 34 and 36 with actuator notches 31 and 32 respectively so as to permit said fingers to bias their respective blades 24 and 26 and cause reengagement of contact elements 28 and 29 with terminals 21 and 22 respectively for completing both motor winding circuits.

When switch contact 60 is moved to engage terminal 56, heater coil 57 is connected in the power circuit. Now only the thermoelectric element 40 of the controller is in circuit with the heater coil and during this time said element is heated, will expand and thus permit spring 25 to become effective to shift the actuator 30 so that contact elements 28 and 29 are disengaged from their respective cooperating terminals 21 and 22. The heater coil 57, in a refrigerating system heats the adjacent evaporator for defrosting purposes. circuit and being energized, the thermoelectric element due to this current flow therethrough is heated and expanded to effect disengagement of the contacts in the circuits of the motor windings.

As soon as the timer mechanism of switch shifts contact out of engagement with terminal 56 and into engagement with terminal 54 of said switch, the heater coil 57 is disconnected from the source of power as is also the thermoelectric element 40. When element 40 is disconnected from the source of energy it will cool and gradually contract and in a predetermined time, a minute or two in a system of refrigeration, will permit spring 25 to become effective to shift the actuator 34 again to reestablish engagement of contact elements 28 and 29 with terminals 21 and 22 respectively thereby closing these gaps in the circuits of the motor starting and running windings 52 and 53 and consequently rendering the electric motor operative. Thus the controller, or more particularly the thermoelectric element 40 of the controller provides the time lag between cessation of the heater energization and the starting of the electric motor which in refrigeration systems is highly desirable and sometimes very necessary for complete efficiency in the operation of the refrigerator. Thus the thermoelectric element 40 of the controller acts not only as a protective device for the electric motor during its operation, but also as a time lag device for the starting of the compressor driving motor following a defrosting cycle.

While the embodiment of the present invention as While the heater coil is in herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. Control apparatus for an electric motor and a second electric work device to render the electric motor inactive in response to an overload on the motor or in response to activation of the second electric work device for a delayed period after termination of activation of the second device, comprising in combination, an electric motor and a second electric work device for connection to a source of electric power, a controller switch consisting of cooperating contacts normally yieldably urged toward disengagement and thermal electric means operably connected therewith normally holding the contacts engaged and operative in response to predetermined current flow therethrough to effect contact disengagement for a predetermined time period with resultant inactivation of the motor, said electric motor being in circuit with said contacts and rendered ineffective upon opening of the contacts and in circuit with said thermal electric means to effect actuation thereof in response to current flow through the motor to effect opening of said contacts thereby to render the motor ineffective and effect reciosing of the contacts a predetermined time interval thereafter to reenergize the motor, said second work device being in circuit with said thermal electric means only to effect actuation thereof in response to current flow through the second device to effect thereby opening of said contacts with resultant inactivation of the motor so long as said second device is active with subsequent closing of said contacts with resultant reactivation of said motor a predetermined time period after said device is rendered ineffective, and a selector switch operative to connect either said motor or said second work device with the source of power, said thermal electric means providing the sole means to effect a time lag for energization of the electric motor when the selector switch is actuated from the second work device activating position immediately into the motor activatlng position.

2. Control apparatus for an electric motor and a second electric work device to render the electric motor inactive in response to an overload on the motor or in response to activation of the second electric work device for a delayed period after termination of activation of the second device, comprising in combination, an electric motor having starting and running windings and a second electric work device for connection to a source of electric power, a controller switch consisting of pairs of cooperating contacts controlling the starting and running winding circuits of the motor, said contacts normally yieldably urged toward disengagement and heat sensitive thermal electric means operably connected therewith normally holding the pairs of contacts engaged, said thermal electric means being expansible in response to current fiow therethrough to first effect disengagement of the pair of contacts in circuit with the starting winding and thereafter effect disengagement of the pair of contacts in circuit with said running winding and maintain both said pairs of contacts open for a predetermined time period to render the said motor fully inactive for the said time period, said second work device being in circuit with said thermal electric means only to effect actuation thereof in response to current flow through the second device to effect thereby opening of said pairs of contacts with resultant inactivity of the motor so long as said second device is active with subsequent closing of said pairs of contacts at predetermined time period after said second device is rendered inactive, and a time selector switch operative to connect either said motor or said second device selectively with a source of power, said thermal means providing the sole means to eifect a time lag for energization of the electric motor when the selector switch is actuated from a position activating the said second electric device immediately to a position activating the electric motor.

3. In an electric refrigeration system including an evaporator, a condenser and a compressor connected in fluid flow circuit with the compressor being driven by an electric motor and wherein the evaporator is defrosted periodically by an electric heater thermally associated with the evaporator, the control system comprising, a control switch including contact means making electric circuit for said motor and actuated by a thermo-electric element connected therewith responsive to current flow to the motor to eifect actuation of the contacts thereby to control the starting of the motor and for rendering the motor inactive in response to an overload condition of the motor and for a determined time period thereafter, said thermal electric element being also responsive to current flow to said heater when rendered active to effect thereby opening of the contacts with resultant motor inactivity during activity of the heater, said thermal electric element maintaining inactivity of said motor for said determined time period after said heater is rendered inactive irrespective of any extraneously imposed References Cited in the file of this patent UNITED STATES PATENTS 2,196,291 Clancy Apr. 9, 1940 2,278,575 Werner et al Apr. 7, 1942 2,313,390 Newton Mar. 9, 1943 2,317,630 Menzies et al Apr. 27, 1943 2,333,906 Werner Nov. 9, 1943 2,492,970 Curry Ian. 3, 1950 2,500,298 Smith Mar. 14, 1950 2,505,201 Peterson Apr. 25, 1950 2,601,466 Thomas June 24, 1952

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