US2158288A - Thermally controlled switch - Google Patents

Description

May 16, 1939. c. wv KUHN 2,158,288

THERMALLY CONTROLLED SWITCH Filed May 11, 1936 54 m 5 w F 35 711i64 1-11918a 1 W i (7 4g a Patented May 16, 1939 2,158,288

UNITED STATES PATENT OFFICE THERMALLY CONTROLLED SWITCH Clarence W. Kuhn, Wauwatosa, Wis., assignor to Cutler-Hammer, Inc., Milwaukee, Wis.,- a corporatlon of Delaware Application May 11, 1936, Serial No. 78,958

Claims. (Cl. 172-279) This invention relates to thermally controlled switch 2 is arranged below its associated bracket switches, and is particularly applicable to and cooperates with a stationary contact i2 switches for starting alternating current motors cated to the left thereof. The free ends of the and for also protecting the same against overlevers I and 8 of each switch are connected by a 5 leads. tension spring i 3 and each of the levers I has 5 An object of the invention is to provide an ima contact tip I secured thereto for engaging its proved device for controlling single phase alterassociated stationary contact, while each of the nating current motors oi the type having a main leverst has its free end operatively connected to energizing winding requiring continuous enerthe thermally responsive operating element 01' its 10 gization and an auxiliary winding which requires associated switch. 10 temporary energization for starting. The electric heater 6 comprises a vertically Another object is to provide a thermally conarranged coil of resistance wire located between trolled switch for motors of the aforesaid charthe switches I and 2 and having its opposite acter which insures temporary energlzation of ends secured to terminal devices I4 and I5 the starting winding upon establishment of power mounted within casing 3. Eachoi the thermally 15 connections for the motor and which also proresponsive elements 4 and 5 comprises an elonvides for interruption of power connections for gated bi-metallic strip, and said elements are the motor upon given overload current conditions arranged upon opposite sides of the heater 6 in the motor circuit. and adjacent thereto. Operating element 4 has Various other objects and advantages of theits upper and secured toa terminal member I 20 invention will hereinafter appear. fixed within casing 3 and operating element 5 The accompanying drawing illustrates an emhas its lower end secured to a terminal member bodiment of the invention which will now be dell fixed within said casing. Each of the operatscribed, it being understood that the embodiment ing elements 4 and 5 has an insulating plate is illustrated is susceptible of modification without secured to the free end thereof by a rivet I! and 5 departing from the spirit and scope of the apsaid plates are recessed as shown at 20 (Fig. 2)

pended claims. to receive the free end of their associated levers In the drawing, 8. Operating element 4 also has an auxiliary Figure 1 is a front elevational view ofa control heater 2| associated therewith comprising an in- 0 device embodying the invention; sulated resistance wire wound around said ele- Figs. 2 and 3 are sectional views on lines 22 ment and having its lower end electrically conand 33, respectively, of Fig. 1; nected to said element and its upper end elec- Fig. 4 is a diagrammatic view illustrating the trically connected to the terminal 'device I4. circuit connections for the device shown in Fig. Terminal member i8 is electrically connected to 1, and the lever I of switch I by a flexible lead 22 and 35 Fig. 5 is a diagrammatic view illustrating a terminal device i5 is electrically connected to modified form of control. the lever 1 of switch 2 by a flexible lead 23.

Referring to Fig. 1, the'same illustrates two The aioredescribed control device may be concontrol switches i and 2 mounted within a boxnected as shown in Fig. 4 to control a single phase 40 shaped enclosing casing 2 formed of insulating alternating current motor M having a line switch 40 material. The switches l and 2 are provided with 25 associated therewith for connecting the same thermally responsive operating elements 4 and to asupply circuit indicated by lines L -L. The 5, respectively, both 01 which are under the conmotor shown is of the split phase capacitor type trol of an electric heater 6. and includes a rotor 26, a. main winding 21 and 5 Each of the control switches i and 2 is proan auxiliary starting winding 28 which is convided with a pair of .U-shaped levers I and 8 nected in series with a condenser 29. The arranged in opposed relation upon opposite sides switches I and 2 are normally in closed position of a supporting bracket 9 fixed within casing 3 as illustrated in the drawingand upon closure oi by a screw Ill. The side arms of the levers I switch 25 circuit isestablished from line L and 8 are provided with knife edge portions which through starting winding 28 and condenser 29 to 50 pivotally engage within V-shaped' recesses in stationary contact ll of switch I, through lever their associated brackets 9 and the lever l of "I and flexible lead 22 of said switch to terminal switch lis arranged'above its associated bracket member I6, through operating element 4 and and cooperates with a stationary contact ll 10- auxiliary heater 2i to terminal device l4, through mated to the right thereof, while the lever I of heater 6 to terminal device is, through flexible s5 ill lead 23 and lever l of switch 2 to stationary con tact i2, and thence to line L Also upon closure of the switch 25 circuit is established from line D through winding 2? to terminal device HG, through heater to terminal device i5, through flexible lead 23 and lever i of switch 2 to stationary contact [I2 and thence to line 13. Upon establishment of the aforedescribeol connections motor M starts under the action oi its windings ill] and 28 and the operating elements 6 and 5 the switches i and 2 are both responsive to heat generated by the heater 6 while the operat= ing element t of switch 0 is also responsive to heat generated by the auxiliary heater ill. The auxiliary heater it provides for rapid heating of the operating element 3 and after a predetermined interval said operating element responds to move its associated lever 8 and spring it to wards the left into a position wherein the axis of said spring is located to the left of the pivot of lever l of switch l. The lever I of switch i then moves with a snap action out of engagement with-its associated stationary contact H to interrupt the aforedescribed energizing circuit for starting winding 28. The auxiliary heater 2| is deenergized upon opening of switch I but the heater 6 then acts to maintain operating element 4 sufiiciently heated to maintain switch I in open p s tion.

Switch 2 remains in closed position under normal current conditions in the motor circuit. However, upon predetermined overload conditions in the motor circuit operating element 5 responds under the action of heater 6 to move its associated lever 8 and spring l3 towards the right into a position wherein the axis, of said spring is located to the right of the pivot of lever I of switch 2. The lever 1 of switch 2 then moves with a snap action out of engagement with its associated stationary contact l2 to effect interruption of the motor circuit.

Upon interruption of the motor circuit heater 8 is deenergized and as is apparent the operating elements 4 and 5 will then cool and return to normal position to effect reclosure of switches l and 2 with a snap action. However, switches l and 2 are adjusted so that the operating element 5 requires a greater degree of cooling to effect reclosure of its associated switch than does the operating element 4. Energization of the starting winding 28 is thus insured upon restarting of the motor after an overload.

In connection with the foregoing it should be noted that the operating elements 4 and 5 are elongated to render the same relatively resilient. Each of said elements is therefore adapted to flex until sufiicient energy is stored therein to move the lever 8 of its associated switch out of extreme positions. The levers 8 of switches l and 2 are thus quickly moved between opposite extreme positions under the action of their associated operating elements to render said switches ex 1 ceedingly quick acting and positive in operation.

shown in Fig. 5 isotherwise similar to that shown in Fi 4. i

Each of the switches l and 2 has an eccentric cam 38 associated therewith which is rotatably arteries mounted upon a pin ti within enclosing casing The cam 30 associated with switch i is arranged to the left of operating element t and engages the same adjacent the upper end thereof while the cam iii associated with switch ii is arranged to the right of operating element 5i and engages the same adjacent the lower end thereof. As is apparent, the normal positions oi the operating elements t and 51 can be varied by adjustment oi the cams so toeffect variation of the temperature values at which the switches i and 2 are moved into open position. Each of the levers ll of switches (l and also has a stop 32 associated therewith for limiting opening movement thereof. The stops 33 are adjustably mounted upon Y casing ii and as is apparent adjustment of said stops provides for variation of the temperature values at which the switches i and 2 are adapted to move into closed position.

The enclosing casing 3 has an extension on one side thereof which is formed to provide a termi nal compartment 33 having wiring openings 34 in one side thereof. The terminal compartment 33 has binding posts 35, 36 and 31 mounted therein, and the binding posts 35 and 36 are connected to contacts II and II, respectively, by connecter strips 38 and 39 and the binding post 3'! is connected to terminal l4 by a connecter strip 40. Also the enclosing casing 3 is provided with a cover 4| which is secured thereto by screws 42.

What I claim as new and desire to secure by Letters Patent is:

l. The combination with an alternating current motor having main and auxiliary energizing windings, of a pair of normally closed switches, one for controlling power connections for said motor and the other for establishing an energiz ing circuit for said auxiliary winding through the medium of said former switch, an operating thermostat associated with each of said switches, a main electric heater traversed by the current supplied to said motor and arranged in heat transferring relation to said thermostats and an auxiliary electric heater traversed by the current supplied to said auxiliary winding and arranged in heat transferring relation to the opcrating thermostat of said second mentioned switch.

2. The combination with an electric motor having a starting winding and a running winding, of

a pair of normally closed snap switches, one for controlling power connections for said motor and the other for establishing an energizing circuit for said starting winding through the medium of said former switch, a single electric heater connected in the energizing circuit of said motor, a pair of bi-metal operating elements each subjected to control by said heater, one of said bimetal operating elements being responsive under the action of said heater to open said second mentioned switch after a predetermined interval upon establishment of power connections for said motor, and the other 01' said bi-metal elements being responsive under the action of said heater to open said first mentioned switch upon a predetermined overload on said motor, and means for adjusting said bi-metal elementswith respect to said heater to separately vary the conditions under which said switches are opened under the action 01' said heater.

3. The combination with an electric motor having a starting winding and a. running winding, of a pair of normally closed switches each having a snap operating mechanism ass( ciated therewith including an over-center spring, one of said switches being arranged to establish power connections for said motor, and the other being arranged to establish an energizing circuit for said starting winding through the medium of said former switch, an elongated bi-metal operating element associated with each of said switches, each of said bi-metal elements having one end fixed and its opposite end operatively connected to the over-center spring of its associated switch, and a single electric heater connected in the energizing circuit of said motor and associated with said bi-metal'elements to effect opening of said first mentioned switch after a given interval upon establishment of power connections for said motor and opening of said second mentioned switch upon a predetermined overloadcondition in the motor circuit.

4. The combination with an electric motor having a starting winding and a running winding,

of a pair of normally closed switches each having a snap operating mechanism associated therewith including an over-center spring, one of said switches being arranged to establish power connections for said motor, and the other being arranged to establish an energizing circuit for said starting winding through the medium of said former switch, an elongated bi-metal operating element associated with each of said switches, each of said bi-metal elements having one end fixed and its opposite end operatively connected to the over-center spring of its associated switch, and a single electric heater connected in the energizing circuit said motor and associated with said bi-metal elements to effect opening oi! said first mentioned switch after a given interval upon establishment of power connections for said motor and opening of said second mentioned switch upon a predetermined overload condition in the motor circuit, said bi-metal elements acting upon interruption of power connections to reclose their associated switches and to insure reclosure of said second mentioned switch prior to reclosure of said first mentioned switch.

5. The combination with an electric motor having a starting winding and a running winding, of a pair of normally closed switches each having a snap operating mechanism associated therewith including an over-center spring, one of said switches being arranged to control power connections for said motor, and the other being arranged to establish an energizing circuit for said starting winding through the medium of said former switch, a bi-metal operating element associated with each of said switches, each of said bi-metal elements having one end fixed and its opposite end operatively connected to the overcenter spring of its associated switch, and a single electric heater connected in the energizing circuit of said motor and associated with said bimetal elements to effect opening of said first mentioned switch after a given interval upon establishment of power connections for said motor and opening of said second mentioned switch upon a predetermined overload condition in the motor circuit, each of said bi-metal elements being adjustable with respect to said heater to vary the conditions under which said switches are opened under the action of said heater.

CLARENCE W. KUHN.

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