US2713100A - Thermostatic switch - Google Patents

Description

July 12, 1955 A. .1. KERCHER THERMOSTATIC SWITCH Filed March 5, 1951 f? TTU/QN@ YS THEPMOSTATEC SWITCH Arthur J. Kercher, Beriteiey, Calif., assigner of one-half to Wiiliani Wesiey Hicks, San Francisco, Calif.

Application R/iarch 5, 1951, Serial No. 213,899 12 Claims. (Cl. 20G- 139) This invention relates generally to thermostatic switches for etecting control of an electrical circuit in accordance with temperature changes in a given medium, in this particular instance, the medium being air. Particularly, it relates to devices of this character for use in conventional electric space heaters.

In thermostats of the above character it has been common to utilize a thermally responsive element, as for example, a bimetallic strip or a pair of bimetallic strips, which will ex in accordance with temperature changes, connected to a movable electrical contact in such a manner as to move the contact to a full open or full closed position with respect to a stationary contact and thereby either open or close an electrical circuit.

In the past in connection with electrical circuits in which such thermostats have been employed it has been customary to incorporate an electrical switch elsewhere in the circuit. Incorporation of such a switch in an electrical system has increased the cost of electrical heaters and further engineering in connection with their construction.

In my Patent No. 2,512,529 and my copcnding application Serial No. 135,129, now abandoned of which this application is now a continuation in part, I have illustrated a thermostat of the above character in which there is incorporated means for retaining the movable contact of the thermostat in a predetermined fully open position in order that the circuit will remain open and cannot be closed by operation of the thermally responsive elements. However, the thermostatic switches and lockout devices disclosed therein have been for the lsocalled single pole type and have been Vunsatisfactory for two pole or two line operation.

It is an object of this invention to provide a combination thermostat and switch which is in effect a combination double pole switch and single pole thermostat.

It is a further object of this invention to provide a switch of the character described that has high sensitivity. It is well known to those skilled in the art that single pole thermostats have always been superior in their temperature control performance to multiple pole thermostats, but that they lack the electrical advantages of controlling both lines, as is possible with a double pole thermostat. y `-It is-a lfurther object of this' invention to provide a device which has the sensitivity of a single pole thermostat and the convenience of a double pole thermostat yet in which the thermally actuated contact pressure has to be developed on only two points, rather than four.

Further objects and advantages will appear from the following specification taken in conjunction with the accompanying drawings in which:

Figure l is a front elevational view, with a portion or" the frame cut away, showing the switch in full closed position;

Figure 2 is a front elevational view, with a portion of theframe cut away, showing one side of the switch in open position;

nited States Patent Of Z Patented July 12, 1955 Figure 3 is a front elevational view, with a portion of the frame cut away, showing both sides of the switch in open position;

Figure 4 is a rear elevational view of the switch as shown in Figures l, 2 and 3;

Figure 5 is a fragmentary view taken along the line 5 5 of Figure 1; and

Figure 6 is a fragmentary view taken along the line 6 6 of Figure l.

`As shown in the accompanying drawings, the device `consists of a suitable mounting 10 which can conveniently be in the form of a relatively rigid metal plate which may be made in the general U-shape, as shown. The device, as shown, is adapted to control an electric circuit. I have shown two pairs of electrical posts 11, 11a and 12 and 12a. Hereinafter post 11 will be referred to as line 1, post 11a will be referred to as load 1, post 12 asline 2, and post 12a will be referred to as load 2. As particularly illustrated in Figures l, 2 and 3, the stationary posts 11, 11a, 12 and 12a are mounted upon a block 13 which is formed of suitable nonconducting material and each of the posts is provided with an extending arm as is more fully illustrated in Figures 5 and 6. For example, it will be noted that post 11 is provided with an extending rigid arm 14 which is provided with a stationary contact 16. Post 11a is provided with a flexible arm 17 which is provided with a movable Contact 18 which is adapted to move into and out of engagement with the stationary contact 16.

The post 12 is provided with a rigid arm 21 which is provided with a stationary Contact 22 while the Contact 12a is provided with a similar rigid arm 23 provided with a stationary contact 24.

A movable contactor 26 which is adapted to establish and close a circuit between the stationary contacts 22 and 24 is provided and is loosely mounted upon one end of a lever arm 25 which, in turn, is connected to a pair of temperature responsive elements 27 and v28 in a manner to be presently described. `v

-As indicated, when the movable contact 26 is in engagement with the two contacts 22 and 24, a circuit-be- Itween posts 12 and 12a', or line 2 and load 2, is completed. 1t is also-'obvious that when the movable con- .tact 26 is not in engagement with the contacts 22 and 24 the circuit between line 2 and load 2 is interrupted.

It willalso be apparent that when the stationary contact 16 and the movable contact 18 upon the flexible .arm 17 are in engagement, a circuit is completed between the posts 11 and 11b, or between line 1 and load 1.

acter v are well known in thev art and are-generally formedA of layers of material having diierent temperature co5- eiiicients of expansion. ln this instance these strips are preferably formed spirally as shown. @ne end of theV strips 27 and 28 is mounted upon similar axles 31 and 32 which are rotatably mounted in suitable openings in the base 10. The ends of the bimetallic strips 27 and 28 remote from the axles 31 and 32 are arranged so as to be in spaced relationship. The bimetallic layers of these elements are preferably arranged so that each strip tends to uncoil in response to an increase in temperature and, since the elements 27 and 2S are coiled in opposite directions, their ends 36 and 37 likewise move in opposite directions responsive to changes in temperature,

Ends 36 and 37 are provided with transverse grooves 38 and 39 which cooperate with ridges 41 and 42 upon the toggle member i3 thereby supporting toggre member 43,. Member 43 is formed of nonconducting material and entirely surrounds the lower end of lever 25 and is rigidly connected therewith whereby any motion 'trans-- mitted to the member 43 will be transmitted to the lever 25. The member i3 is engaged in the grooves 38 and 39 by frictional engagement therewith.

I have provided means in connection with the foregoing to adjust the device forV eiecting a control over a wide range of temperatures. This is done by rotating the axles 31 and 32 and changing or adjusting the ends 36 and 37 of the strips 27 and Z8 with respect to the base 10. Thus the axles 31 and 32 are provided with lever arms 46 and 47. The ends of the lever arms i6 and 47 remote from the axles 31 and 32 are provided with identical projecting portions 4S and 459 which are rotatably mounted with respect thereto. A threaded member 51 cooperates with both said members d8 and 49 and maintains the same in predetermined spaced relationship. A nut 52 is provided upon member 51 and abuts against the member 4S thereby preventing rotation o the member 51 once the spaced relationship between the members 4S and d@ has been determined. Between the members 48 and 49 on the threaded member Si there is a flanged member S3 whose purpose will hereinafter be described. lt is apparent that upon movement of the anged member 53 in one direction or another, a sintilar movement of the arms 46 and 47 occurs, thereby rotating the axles 31 and 32 as has previously been described to adjust the device for effecting control at any point over the range of temperatures.

The arms 46 and 47 are provided with similar notches 56 and 57 and as shown in Figures l and 2 a coil spring 58 engages the notch 56 in the arm 46 and the notch 57 in the arm 47 thereby urging the same to the positions shown generally in Figure l, the position in which a higher temperature is required to open the circuit, or, in other words, to move the contacter 26 away from the contacts 22 and 24. To oppose normal biasing of the spring 58 I have provided a cam 5.9 as shown, which engages the anged member 53. Upon rotation of the cam 59 the anged member 53 and the threaded member 51 are urged to the right as illustrated in Figure 2, thereby overcoming the bias of the spring 58 and urging the arms 46 and 47 to the position shown in Figure 2. It will be appreciated that the rotation of the cam 59 may be halted at any point between the extremes shown in Figures l and 3, thereby eiecting a control at any point over the range o t' temperatures provided between the positions of the temperature responsive elements as illustrated in Figures l and 2.

As has previously been pointed out, I desire to provide a device for locking the movable contacter 216 in open position with respect to contacts 22 and 24 and for locking movable contact 13 in open position with respect to contact 16.

It is apparent that when the lever arm 25 which supports the movable contacter 2d is moved to the right, as illustrated in Figure 2, the circuit between line 2 and load 2 .is Opened, thereby terminating the Operation of the heater by terminating the supply Gt current thereto.

Under normal condition the Opening of this circuit is sucient. However, there arise conditions when it is desirable to terminate the connection 'between posts 1i. and 11a or, in other words, to open the circuit between line 1 and load 1, and for locking the device in this condition.

To this end I have provided a member 66 which is movably mounted upon the base it) generally as illustrated in Figures l and 4 by means of a grooved plate 67. The member 66 is provided with arms 68 and 69. As shown in Figures l and 2 the arm 69 is adapted to be engaged by the anged member 53. When `the flanged member 53 is urged to the position illustrated in Figure 3 by means of rotation of the cam 59, this motion is transmitted to the arm 68 which engages the toggle member 43 as is likewise shown in Figure 3. When the arm 6B engages the member 43 as shown in Figure 3, it is obvious that the pin 25a will be urged into contact with the flexible arm 17 to overcome the pressure of the flexible arm l? and the temperature responsive elements 27 and 2S. i have so constructed the device that when the arm 65 is urged to the position shown in Figure 3 no change in temperature would be sufficient to operate the members 31 and 32 to overcome the pressure of the member 55. in this manner the device is locked against operation and both circuits are kept open regardless of temperature variations. It will be obvious, therefore, that this lock-out device obviates the necessity of the insertion of a sw' ch at any point in the circuit and that the handle 71 which operates the cam ESR opern ates both as a means to effect control of the device over substantial ranges of temperature and also as a means of effecting a lock-out for directly opening the circuit between line l and load l.

vWhen the device is in operation the member d3 is subiected to a turning torque to rotate the same in one di- 'on or the other, depending upon the temperature of the bimetallic strips 27 and 28, and upon the position or the hanged member 53. The turning torque is created by the tendency of the ends 36 and 37 to move in opposite directions in response to change in temperature in the strips 27 and 28. A toggle effect which makes positive movement of the contactor 26 is produced by virtue of the normally sprung condition of the bimetallic strips 27 and 2S, whereby their ends 36 and 37 in the grooves and 39 are normally biased together upon the ridges nd 42. For a given setting of the flangedmember S3 a ertain temperature variation is required to eiect move ment of the contacter 26 from open to closed position or vice versa. Assuming now for a given adjustment of the device that the temperature of the elements 27 and 25 is midway between certain upper and lower units, the contactor 26 will remain in either open or closed position. Furthermore, for such conditions the member 45 will move to a dead center position when the contacts are open or closed. Therefore, as the temperature varies between such limits, the contacter 26 is caused to move rapidly to either closed or open position, and the rapidity of the movement is caused by upsetting the toggle formed by the member 43. Ii, for one setting of the member 53, the contacts will close at a given temperature, resetting :v1 the member 53 to change the angular position of the arms 46 and d'7 with respect to the member 43 will require a diierent temperature of the strips 27 and 28 to close the contacts. Thus by varying the setting of the member 53 the contacts can be caused to open or close for any desired temperature over a substantial range.

However, when it is desired that the circuit from line 1 to load likewise be opened, it is obvious that the handle crank may be operated in such a manner that the toggle effect is overcome by urging the arm 68 to the extreme right as illustrated in Figure 3 with the efcct that the pin 25a engages and moves the iiexible con'- ductor 17 causes the contacts i6 and i to become disengaged. Since this action is a mechanically positive one, no change in temperature will cause any movent or the toggle arm 25' with the eiect that both circuits will remain open.

I claim:

l. in a double pole electric switch to control two lines, means for opening one of the lines comprising a contacter movable into and out of engagement with a pair of contacts in said line, means for moving said contactor comprising a contactor arm adapted to be actuated by a pair of temperataure responsive strips, manually cam operated means associated with said strips to determine the temperature at which they actuate said arm,

means associated with said arm to open a pair of contacts in the second line, and a lock-out means actuated by said cam operated means adapted to engage said arm and move said contactor out of engagement with said contacts and to lock the pair of contacts in the second line in open position.

2. In a double pole electric switch, means for opening one line comprising a contactor movable into and out of engagement with a pair of contacts in said one line, means for moving said contactor comprising a toggle arm adapted to be actuated by a pair of temperature responsive strips, cam operated means associated with said strips to determine the temperature at which they actuate said toggle arm, a manually operated handle for positioning said cam operated means, means actuated by said cam operated means associated with said toggle arm adapted to open a pair of contacts in a second line, and a lock-out means actuated by Vsaid cam operated means, said lockout means being adapted to position said toggle arm whereby both said lines are opened.

3. In a double pole switch having iirst and second lines, a movable contactor in said first line adapted to be actuated by a pair of temperature responsive strips, manually cam operated means associated with said strips to determine the temperature at which they actuate said movable contactor, a handle for positioning said cam operated means, a lock-out means actuated by said cam operated means adapted to prevent movement of said movable contactor from full open position, a movable contact in said second line and means associated with said first movable contact whereby when the same is actuated by said lock-out means to prevent its movement from full open position, said contact in said second line is also held in full open position.

4. in a double pole switch, two pairs of contacts controlling rst and second lines respectively, a contact arm movable between three positions, in the iirst of said positions closing both said pairs of contacts, in the second position opening the said pair of contacts in said first line, and in the third position opening both of said pairs of contacts, temperature responsive means adapted to move said contact arm between said irst and second positions and to thereby open and close the rst of said lines, and manually operable means for moving said contact arm between the second and third positions to thereby open and close the second or' said lines, said manually operable means also serving to control said temperature responsive means.

5. In a double pole thermostatic switch, a pair of contacts in one line, a contactor arm, temperature responsive means for controlling said contactor arm to engage and disengage said pair of contacts in said line, a pair of contacts in the second line and manually operable means for actuating said contactor arm to control the opening and closing of said second pair of contacts in said second line, said manually operable means also serving to control said temperature responsive means.

6, In a thermostatic switch, two pairs of contacts each of which is adapted to open and close a circuit, a contacttor arm movable to three positions, both pairs of contacts being closed when said contactor is in the i'irst position, the i'irst of said pairs of contacts being open and the second pair of contacts being closed when said contactor arm is in said second position and both pairs of contacts being open when said contact arm is in said third position, temperature responsive means adapted to move said contact arm between said iirst and second positions, manually operable means adapted to move said contactor arm to said third position and also serving to prevent said contactor arm from being moved by said temperature responsive means to said irst or second position when said contactor arm is in said third position, said manually operable means also serving to control said temperature responsive means.

7. In a thetmostatic switch, a movable contact adapted to be actuatedv by' a pair of temperature responsive spiral strips, means associated with said strips to determine the temperature at which they actuate said movable contact, said means comprising a pair of vertically disposed axles each being ailixed to the inner end of one of said strips, a pair of horizontally disposed arms each having one end rigidly aiiixed to one of said axles, a pair or vertical rotatably mounted projections each having one end fitted to one of said arms, a threaded horizontal rod screwed into tapped holes in said projections, a nut for locking said threaded rod onto said projections, a movable ange mounted between said projections on said threaded rod, a rotatable cam member engaging said iiange, a spring diagonally connected between said arms to force said flange against said cam and a handle for actuating said cam member.

8. A device as in claim 7 together with a manually operated lock-out means comprising an elongated member longitudinally disposed along said device hav'ng a vertical arm at each of its two ends, one of said arms adapted to engage said ange and the other arm adapted to engage said movabie contact so that said movable contact will no longer be responsive to said temperature responsive spiral strips.

9. In a thermostatic switch having two pairs of contacts, a movable contact adapted to be actuated by a pair of temperature responsive spiral strips, means associated with said strips to determine the temperature at which they actuate said movable contactor, said means comprising a pair of vertically disposed axles each being aflixed to the inner end of one of said strips, a pair of horizontally disposed arms each having one end rigidly affixed to one of said axles, a pair of rotatably mounted projections having one end iitted to one of said arms, a threaded horizontal rod that is screwed into tapped holes in said projections, a nut for locking sai-d threaded rod onto said projections, a movable ange mounted between said projections on said threaded rod, a rotatable cam member engaging said ange, a spring diagonally connected between said arms to force said flange against said cam, and a handle for actuating said cam member.

l0. A device as in claim 9 together with a means to actuate said movable contact to open said second pair ot contacts and also serving to maintain said movable contact in such a position that both pairs of contacts are retained in an open position when said movable contactor is no longer responsive to said spiral strips, said means comprising an elongated member having a vertical arm at each of two ends, one of said arms being adapted to engage said iiange and the other of said arms being adapted to engage said movable contactor.

l1. In a thermostatic switch adapted to control two lines, a U-shaped mounting plate, an insulated mounting block aixcd to said plate, a pair of stationary contacts in the iirst line mounted on said block, one stationary contact in the second line mounted on said block, a exural arm mounted on said block, a movable contact in the second line carried on said iiexural arm, a pair of axles vertically and rotatably disposed between said U- snaped mounting plate, a pair of oppositely spiraled resilient bimetaliic strips each having the inner end of said strip aflixed to one of said axles, a pair of horizontally disposed arms each having one end rigidly affixed to one of said axles, a pair of vertically rotatably mounted projections each having one end fitted to one of said arms, a

threaded horizontal rod screwed into tapped holes in said projections, a nut for locking said threaded rod onto said projections, a movable ange mounted between said projections on said threaded rod, a rotatable cam member engaging said ange, a spring diagonally connected between said arms to force said tlange against said cam, a handle for actuating said cam member, a pair of grooved ends iitted on the outer ends of said spiral strips, a toggle member supported by said grooved ends, an arm carried by said toggle member adapted to move into three positions, a contacter having a pair of contacts capable of engaging said pair of stationary contacts in said rst line be,- ing carried on one side of the outer extremity of said arm, a pin carried by the other side of said arm adapted to engage said exural arm, a grooved plate mounted on said mounting plate, an elongated member having a vertical arm at each of its two ends carried by said groove plate so that said elongated member is longitudinally disposed along said mounting plate, one of said arms adapted to engage said flange, and the other of said arms adapted to engage the arm on said toggle member.

12. In a thermostatic switch, two pairs of contacts each of which is adapted to open and close a` circuit, a contacter arm movable to tnree positions, both pairs of contacts being closed when said contactor arm is in the first position, the first pair of contacts being open and the second pair of contacts being closed when said contactor arm is in second position and both pair of contacts being open when said contactor arm is in said third posi tion, temperature responsive means adapted to move said contacter arm between said first and second positions, manually controlled means to move said contactor arm between said second and third positions and also to prevent said arm from being moved to said rst or second positions while locked in said third position, and means associated with said temperature responsive means to determine the temperature of which said temperature responsive means will act to move said contactor, said manually controlled means also serving to control said last named means.

References Cited in the lile of this patent UNITED STATES PATENTS

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