US2667612A - Thermostatically controlled electric switch - Google Patents

Description

Jan. 26, 1954 A. R. LUCAS THERMOSTATICALLY CONTROLLED ELECTRIC SWITCH Filed Feb. 18, 1950 INVENTOR.

ALFRED R. LUCA S ATTO RNEYS Patented Jan. 26, 1954 UNITED STATES PATENT OFFICE THERMOSTATICALLY CONTROLLED ELECTRIC SWITCH Alfred R. Lucas, Galion, Ohio Application February 18, 1950, Serial No. 144,879 13 Claims. (Cl. 318-221) The present invention relates to electric control switches and specifically to switches adapted to break a circuit automatically under certain heat conditions and re-establish such circuit when such conditions have been eliminated.

Among the objects of the invention is to provide a switch embodying heat afiected elements which will break the circuit therethrough under overload conditions but not be subject to flutter.

Another object is to provide a switch which will break the circuit under excessive ambient temperatures and without flutter.

Another object is to provide a design of a thermally responsive element which will olfer greater operational advantages within limited dimensions.

Another object is to provide a switch which may give a predetermined sequential operation for proper control under multiple loads.

Another object is a switch which may be used as a time relay for sequential operations.

Still other objects and advantages will be apparent to those skilled in the art upon reference to the following description and the accompanying drawings in which Fig. l is a plan view of the switch mechanism,

Fig. 2 is an elevational view thereof from the plane of line 2-2 of Fig. 1.

Fig. 3 is an end view of the mechanism from the left of Figs. 1 and 2.

Fig. 4 is a cross section through the pile showing the anchored ends of the bimetallic arms and the spring arms together with the intervening insulating material.

As shown, the switch comprises a base or support Ill of suitable insulating material which may be rabbeted for the reception of a domed cover MA or other suitable enclosure may be provided.

The switch, as shown, includes two bi-metal arms and three spring arms and the stationary ends of all of these are fixed in a pile at one end of the base. This pile is indicated at II and the parts arranged as follows: At the bottom is a bimetal thermostatic member I5. Immediately above this member is a conducting spring arm IE but with a layer of insulation I50 between the two. Above the arm I6 is a layer of insulating material I! and atop the latter a conducting spring arm I8. Above the latter is a U- shaped or unenclosed grid-like bimetal conducting member I9 and atop of the pile is a spring conducting arm 20.

One leg of the bimetallic member I9 is connected with the spring arm conductor 20 by means 2 of the metal spacer 2IlD. The other leg of I9, designated I9B is connected to the spring arm conductor I 8 by the metal pacer I8C. The spring arm 20 is a rectangular frame in shape, compare Figs. 1 and 4. I6 is of rectangular frame shape, compare Figs. 2, 3, and 4.

The arms IS, IS and 20 carry contacts l6A, I8A and 20A respectively adapted to contact adjustable stationary contacts IBB, I83 and 20B respectively.

Further, between the cross members of arms I5 and I6 is a U-shaped toggle spring 2| adapted, when arm I5 bends upwardly under the infiuence of heat, to snap arm I6 downwardly and separate contacts ISA and I6B.

Also, a similar U-shaped toggle 22 is carried between the cross member of arm I9 and the end of arm I8 while a similar U-shaped toggle 23 is carried between the cross members of arms I9 and 20.

In order to prevent passage of any current through the toggle 2I, the arm I5 is provided on its cross portion with a thin plate I5A of insulation against which the toggle acts. Likewise the arm I9 is provided with a plate I 9A of insulating material coacting with toggles 22 and 23.

These arms I8, I9 and 20 and the toggles 22 and 23 are so proportioned and arranged that when the bimetal arm I9 bends upwardly under the influence of heat, the toggle 22 first snaps the arm I8 downwardly and thereby snaps contact IBA away from contact IBB. Further, heating of arm I9 will cause the toggle 23 to snap arm 20 downwardly and thereby snap the contact 26A away from contact 2013.

As is clearly shown, contacts IBB and 20B are mounted in a conducting bracket 25 while contact I8B is mounted in a conducting bracket 26, and suitable stop screws 27A and 21B are provided to limit the movement of the arms I6, I8 and 2D.

When placing the switch in circuit with a motor having both starting and running windings, one of the power supply lines 30 is connected to the stationary or fixed end of arm I6 as by means of a suitable binding post or screw 30a. The starting winding 3| of the motor is connected to the bracket 26 (Fig. l), and thereby to contact I8B, and the running winding 32 is connected to the fixed end of arm I8 by means of a screw 32A fixed thereto. This is shown diagrammatically by the lead line from the winding 32 in Fig. 2. From the other ends of the windings 3| and 32 the leads connect with the return power line 33.

When the main switch (not shown) is thrown to complete the circuit, flow is through line 38, terminal screw 30A which screws into a lateral extension (Fig. 1) of the metal bar 16C which lies over the end of arm It in the pile (Fig. 4), to arm H5. The current passes then to contacts [BA and [63, through bracket 25 to contact 293. From contact 20B flow is through the spring arm 20 to the pile H in which arm 20 contacts one side of the open bimetal loop l9. From Fig. 4 it will be seen that the loop I9 is separated from arm 20 by a layer of material, part of which 20D is conducting and the other part 28E insulating, so that one leg of the loop 18 is insulated from arm 20 and flow must be through the loop itself to the other leg IBB. This leg [9B is separated from arm l8 by a layer of conducting material [80 while the other leg I9 is insulated therefrom by the insulating layer 18D. From spring arm 18 flow is through contact i813 and thence to starting winding 3i. The running winding 32 is connected to arm 18 in the pile H.

Due to current flow through the bimetal arm l9, heat is developed therein and cause the arm to bend upwardly, first breaking the starting circuit by separating contacts 18A and i813 but maintaining the circuit through the running winding. The time of opening may be varied through the adjustability of contact i833.

If, due to overload conditions, an excessive current flow occurs while the motor is running, the arm l9 will further heat and bend up still more to cause the toggle 23 to separate contacts 20A and 203 to stop all fiow. When the flow stops, arm I9 will cool and re-establish both the starting and running circuits. It should be noted, however, that both make and break" are due to snap action of the parts so there can be no flutter.

In the present switch, the current fiow as above stated, is also subject to ambient temperature, whatever the cause may be that may raise it to an excessive degree. If the ambient temperature should be too elevated, the thermostatic arm [5 is caused thereby to bend upwardly and through toggle 2|, breaks the lead-in circuit by separating contacts ISA and EB, thus discn tinuing operation as long as such high ambient temperature continues and for a period beyond.

Further, by mounting the stop screws 21A and 213 in the arm l as shown, the circuit off period may not only be varied due to screw setting, but is also varied by ambient temperature.

The use of the adjustable stops 21A and 21B on the ambient temperature arm I5 is for the purpose of controlling the throw of the spring arms i8 and 23 so that the cooling time for the bimetallic member will always be substantially the same so that the switch will snap back to its normal running position after the same lapse of time independent of the ambient temperature. In the manufacture of the switches it is not possible to have the parts and the assembly absolutely the same in each switch so that the snap back time will be the same in all the switches with the same ambient temperature. Consequently these adjustable screws are put on the ambient temperature bimetallic arm so that at the factory these may be adjusted so as to get the snap back time in cooling substantially the same on all the switches.

One of the features of my switch is that the starting switch first opens with a snap over center toggle action and then sequentially or perhaps not at all during the running time of the motor the running winding switch opens whenever there is an overload that should cause a break in the circuit. This second overload switch is also a snap over center switch with a toggle action but only one bimetallic member is required to control sequentially both switches. On the other hand when on cooling of the bimetallic member the switches close substantially simultaneously and not consecutively as when opening. This is an important feature because if the running winding switch closed at any appreciable time prior to the closing of the starting switch the running winding current would be sufficiently high to cause the running winding switch to reopen before the closure of the starting winding switch, hence the motor would not start. The same would hold true if the starting winding switch closed any appreciable time before the energization of the running winding during the existence of an overload condition. This substantially simultaneous closing of the circuits is due to the arrangement of the U springs 22 and 23 and the position of the stops 21A and 21B relative to the bimetallic member l9. Both the running winding switch at contact 29A and the starting winding switch at ISA are now closed as shown in Fig. 2. Suppose. contrary to the showing in Fig. 2, that both circuits are open with the starting winding arm l8 forced against stop 27B by U spring 22 and the running winding arm 20 forced against stop 27A by U spring 23, this described condition being the result of an overload of the motor which caused bimetallic member 19 to bend upward. Upon the opening of both contacts [8A and 29A the bimetallic member l9 cools to a point where either or both contacts I8A and 20A close but the high overload current will cause a repeated cycle as outlined above to protect the motor for the deleterious eifects of this high overload current. If it is further supposed that while contacts IBA and 20A are in the opened condition, due to an overload, and this overload condition were removed, the series of events would be such that on the cooling of bimetallic member l9 whichever of the two of members l8 or 20 were to cross center first would aid in cansing the other to cross center due to the arrangement of the U springs 22 and 23 and the position of the stops 21A and 213 relative to the bimetallic member 19 thus causing a substantially simultaneous closure of both the starting and running circuits.

I claim:

1. In a thermally controlled electric switch a spring current conducting arm fixed at one end and carrying a contact at the free end, a bimetal heat flexible U-shaped arm surrounding but spaced from the spring arm and having its legs fixed adjacent the fixed end of the first arm with its cross member opposite the end thereof, a toggle pivoted to the end of said spring arm and to said cross member, a second U-shaped or looped spring current conducting arm surrounding said bimetal arm and spaced therefrom and having its legs fixed adjacent the fixed ends of the first two arms, a toggle pivoted between the cross members of said second spring arm and said bimetal arm, said second spring arm carrying a contact at its free end, a third conducting U- shaped or looped spring arm having its legs fixed adjacent the fixed ends of the other arms but insulated therefrom and carrying at its free end a contact, stationary contacts adapted to cooperate with each of the arm carried contacts to make and break circuits therethrough, the

stationary contacts for the second and third spring arms being electrically connected, a bi metallic heat flexible arm within said third arm and having one end adjacent the fixed end thereof, and a toggle pivoted between the end of said latter bimetal arm and the cross member of said third spring arm.

2. In a thermostatically controlled electric switch having in combination with a motor having a starting and a running winding, a bimetallic heat flexed arm adapted to be heated by resistance to current flowing therethrough, said arm for inclusion in two circuits, one including said starting winding, the other including said running winding, means connected to said arm for breaking said starting circuit after a predetermined time, means also connected to said arm iorbreaiing said running circuit when an excessive current flows through said arm, and a second heat flexible bimetal arm closely adjacent with the first mentioned bimetallic arm adapted to be heated solely by ambient temperatures and adapted to break both said circuits when ambient temperature reaches a predetermined degree.

3. In a thermostatically controlled electric switch having in combination with a motor having a starting and a running winding, a bimetallic heat flexed arm adapted to be heated by resistance to current flowing therethrough by means of a starting circuit and a running circuit each including the corresponding motor winding and each including said arm and a snap over center opening and closing toggle switch, means connected to said arm for breaking said starting circuit after a predetermined time, means also connected to said arm for breaking said running circuit toggle switch when an excessive current flows through said arm, and a second heat flexible bimetal arm adapted to be heated solely by ambient temperatures and adapted to break both said circuits when ambient temperature reaches a predetermined degree, and adjustable stops carried by said second bimetal arm for varying the 01TH circuits in accordance with ambient temperatures by limiting the throw in the opening of said toggle switches.

4. In a thermostatically controlled electric switch for use in multiple circuits, a plurality of conducting flexible arms all of which are anchored at one end and at the same location when viewed in plan, one of said arms being U-shaped and surrounding the others, a second. arm being also U-shaped and surrounding a third arm, said second arm having its ends insulated from each other but having one end in conducting relation to the first arm and its other end in conducting relation to the third arm, said second arm being of material capable of flexing under heating due to its resistance to current flow, a toggle spring between the first and second arms and adapted to move quickly and suddenly the first arm when said second arm is flexed a predetermined amount due to heat, a second toggle spring between the second and third arms and adapted to move the latter quickly and suddenly when said second arm is flexed a lesser amount due to heating, said springs being insulated from. said second arm, a fourth flexible conducting U-shaped arm surrounding, in plan view, a second heat flexible arm, a toggle spring between the latter and said fourth arm and adapted to move quickly and suddenly said fourth arm when said second heat flexed arm is moved a predetermined distance periods of said starting and running panion contact with said under heating, an insulating base member, all of said arms being anchored in a vertical pile at the same location on said base, the last mentioned two arms being insulated from the others, contacts carried by the non-heat-flexing arms, stationary contacts cooperating therewith, conducting means connecting the stationary contacts cooperating with the contacts on the first and fourth arms, means for connecting the fourth arm to a source of current supply, means connecting the third arm to a suitable circuit and means connecting the stationary contact coopcrating with the contact carried by said third arm to another suitable circuit, and a common return lead from said circuits to said source of pply.

5. The combination claimed in claim 12 in which the toggle springs are each a U spring.

6. The combination claimed in claim 12 in which the control arm is an open U bimetallic arm which deflects upon being heated.

7. The combination claimed in claim 12 in which the control arm is a loop bimetallic member of U-shape in plan view and one spring arm is a similar shape and encloses the control arm.

8. The combination claimed in claim '7 in which the toggle springs are a U spring connecting the control arm loop with the spring arm loop on the outside and a U spring connecting the control arm loop on the inside to the other spring arm.

9. The combination claimed in claim 12 in which the thermally responsive member is a bimetallic arm which deflects under heat and in which is added an ambient temperature controlled switch with a bimetallic arm with a stop thereon for controlling the other bimetallic arm when that arm swings over center in opening the switch, the ambient temperature controlled bimetallic arm under heat swinging toward the other bimetallic arm to thereby shorten the are that the other bimetallic arm has to swing to initiate the swing over center and snap the switch closed.

10. The combination claimed in claim 12 in which the two toggle switches open only in one sequence or only the first-opening switch opens and in which after both switches have opened the two switches, upon cooling of the thermally responsive member, close substantially simultaneously.

11. The combination claimed in claim 12 in which the control arm is an open U bimetallic arm and the toggle springs are U springs so placed and so stressing as to open the switches in one sequence and close the switches substantially simultaneously.

12. An automatic electric switch for controlling multiple circuits having in combination a base, a spring conductor arm supported thereon and provided with a contact, a companion contact, the two contacts for connection with an electric circuit, a second spring conductor arm supported on said base and provided with a contact, a comlast mentioned contact for connection with a second circuit, a control arm held by said base and responsive to the flow of current through said arm to both circuits for a short time to move said control arm a given distance, and responsive to abnormal flow of current through the control arm and the second circuit or both circuits to move said arm a second prescribed distance, a toggle spring member for connecting the end of said control arm with o conductor spring arm and arranged to throw over center and break the first mentioned set of contacts after the control arm has moved the said given distance, and a second toggle spring member for connecting the control arm with the other spring arm and arranged, on abnormally large flow of current through the control arm and through the second circuit or both circuits, to flex the control member the second prescribed distance and thereby throw over center to separate the second set of contacts and break the second circuit.

13. A thermally controlled multiple electric switch having in combination a base, a motor starting switch thereon, an overload switch thereon, each having a pair of contacts controlling a separate circuit, and an ambient temperature controlled switch on said base cuttir out the circuit to both previously mentioned switches when the ambient temperature of the switch rises above a set point, the ambient temperature controlled switch carrying a bimetallic actuating arm with a stop thereon, and the starting and overload switches having a common bimetallic actuating arm which is arrested by said stop, whereby the ambient temperature controlled switch arm when acted upon by the am-- bient temperature cuts down the are through which the starting switch arm must throw to close the switch after cooling.

ALFRED R. LUCAS.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,680,773 Dumler et-al. Aug. 14, 1928 2,068,374 Carlson Jan. 19, 1937 2,237,705 Kohl Apr. 8, 1941 2,311,048 Harrold Feb. 16, 1943 2,414,778 'Iratsch Jan. 21, 1947 2,418,235 Menzies Apr. 1, 1947 2,475,039 Lucas July 5, 1949 2,477,408 Gross July 26, 1949 2,505,689 Richmeyer Apr. 25, 1950 2,568,373 Dales Sept. 18, 1951

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