US2366387A - Modulating condition responsive switch - Google Patents

Description

Jan."2, 1945. w, R|$E 2,366,387

MODULATING CONDITION RESPONSIVE SWITCH Filed June 24, 1941 INVENTOR.

Patented Jan. 2, 1945 I MODULATING connrnon RESPONSIVE swrron George W. Crise, Columbus, Ohio, assignor to Crise Electric Manufacturing Company, Columbus, Ohio, a corporation of Ohio Application June 24, 1941, Serial No. 399,503

' 6 Claims.

This invention relates to improvements in condition responsive switches and more particularly condition responsive switches in which the variation from the condition towhich the switch is adjusted affects not only the direction of movement of the motor controlled by the switch, but also its rateof movement.

The switch is adapted to control a motor such as shown in Figure 1 of Crise et a1. Patent No. 2,134,685, November 1, 1938, or any other motor adapted to be operated in a stalled position that can be reversed by closing a two-wire circuit and stalled by inserting a suitable resistance or inductance in the circuit. The switch could be used where one motor having a greater torque is used in opposition to another or where a motor is reversed by means of gravity or a spring. The switch could also be used to operate a magnet or solenoid controlling a three-position valve or wherever a switch having an open circuit, a circuii; closed through a resistance or inductance and a closed position would be useful.

An object of my invention is to provide a condition responsive switch that will regulate a con- I trol motor to remain stationary under a desired range of condition, to move slowly in a direction to reestablish the desired condition under the influence of a small variation from the desired condition and to move with increasing speed in a direction to reestablish the desired condition as the condition varies more widely from. the desired range.

Other objects of the invention will be apparent from the accompanying specifications, claims, and drawing in which I describe my switch as adapted to regulate temperature, but; it may be used with like effect to control humidity. pres- I sure, light. voltage, current, mechanical movements or other variable conditions.

For a further understanding of my invention, reference is to be had to the following description and the accompanying drawing, wherein:

Fig. 1 is a front elevational view of a thermostat formed in accordance with the present invention;

Fig. 2 is a diagrammatic view of ashaded pole induction motor and associated furnace controls 7 with which my improved thermostat may be employed;

Fig. 3' is a similar view of an electric motor utilizing a direction reversing weight. r

In Figure 1 of the drawing, bimetallic element I 2 carries contact I 6 and is formed as shown. It is fastened to base in by means of post l5. Adjusting arm H which is made 01' an insulating washer 32.

material is pivoted around post it and is frictionally held to base Hi by means of spring Birnetallic strip I3 is fastened to a projection of arm I i by means of rivets 22 and 23. Bimetallic strip M which carries the twosided contact point I8 is fastened to bimetallic strip I3 by means of rivets 24 and 25 as is con nectin-g lug 26. Adjusting screw i9 which carries contact point i! operates in connecting sleeve 3! which is mounted in a projection of arm it as shown.

Resistor 27 is wound around bimetallic strip l3 from which it is electrically insulated but is so placed that heat produced in the resistor will be readily conducted to strip is. Resistor 27? is connected to connecting lug 26 at one end and connecting screw 30 at the other. Resistor 28 is connected between connecting screws 29 and it? as shown. Connecting lead 39 connects connecting screw 29 to connecting sleeve 3i, connecting lead 31 connects connectingscrew 29 to terminal bolt 33 and connecting lead 33 connects post it to terminal bolt 34.

Bimetallic element i2 is formed and assembled to bend in a clockwise direction under the influence of an increase in temperature. Bimetallic strip I3 is assembled to bend counter-clockwise under the influence of an increase in temperature and bimetallic strip i to bend clockwise. Bimetallic strips l3 and M are so proportioned as to counteract each other so that contact point i8 will not move in either a clockwise or counterclockwise direction under the influence of changes in temperature affecting both alike. but will remain substantially stationary with respect to contact-points i6 and IT. The temperature at which contact points l6 and I8 make contact is adjusted by moving adjusting arm i l around post l5. As shown by the position of indicating pointer 20 on scale 2i, it is shown in Figure l. as

- adjusted to The further drop in temperature required to close contacts ll and I it is adjusted by means of adjusting screw it.

Figure 2 shows a diagrammatic view of the motor of Figure 1 of Patent 2,134,685 connected to control the draft door of a furnace. Motor Ml has a primary coil 43 which is adapted to be energized by being connected to any suitable source of alternating current. ll-4i are fixed counterclockwise shading coils, and 4242 are wound clockwise shading coils adapted to be connected through leads 50 and Si to terminal screws 35 and 36 of the thermostat of Figure 1. As shown, motor MI is connected by means of cord 44 to draft door 45 of furnace 46.

Figure 3 shows a diagrammatic view of a motor M2 adapted to operate clockwise by means of electrical energy when power supply leads l1 and 49 ar connected to any suitable source of electric current and counterclockwise by means of weight W. v

If leads 50 and 5! of the motor Ml of Figure 2 are connected to terminal bolts 33 and 84 by means of terminal screws 35 and 36 and the sum of the resistance of resistors 21 and 28 is the correct amount to stall the motor, the operation of the thermostatic switch will be substantially as follows: When the temperature drops to 70, contacts l6 and is will close and the control leads of the above-mentioned motor will be connected together through resistors 21 and 28. Terminal bolt 33 connects through connecting lead 31 to connecting screw 29, connecting screw 29 through resistor 28 to connectin screw 30, connecting screw 30 through resistor 21 to connecting lug 26 and through bimetallic strip It to contact points l8 and I6, through bimetallic element l2 to post l5 and through connecting lead 38 to terminal post 34. The heat produced by current passing through resistor 21 will be qu ckly conducted to bimetallic strip l3 and will increase its temperature and cause it to bend counter-clockwise opening contacts l6---l8. Bimetallic strip 13 will then drop in temperature and reclose contacts i6l8. As the temperature affecting the thermostatic switch drops farther below 70, this closing and opening of contacts l6i8 will continue with the time the contacts are open becoming less until when the temperature reaches, say, 68 when the bending of bimetal strip I3, due to the heating of resistor 21, has been overcome by the bending of bimetallic element I2 due to drop in surrounding temperature, contacts l6-|8 will remain closed. If the temperature affecting the thermostatic switch drops still further to, say, 67 contact I8 will be forced against contact l1 by the pressure of contact I6 shorting resistors 21 and 28. Cooling of bimetallic strip l3 will at once begin and contacts i1-l8 will be forced open by the clockwise pressure of bimetallic strip i3. we will then have an intermittent opening and closing of contacts l1l 8 at a temperature below 61 as we had an intermittent opening and closing of contacts l6l8 above 68. If the temperature aflecting the thermostatic switch drops still farther to, say, 65 contacts i1- -I8 will remain in contact and the motor or other device controlled by the thermostatic switch will remain fully energized. At

a temperature just below 67 contacts I1-I8 will remain closed but a very small part of the time as we might have a pressure, produced by a temperature of only affecting bimetallic element l2, effective to close contacts i1l8 and a pressure equivalent. to approximately 2 from the bending of bimetallic strip II, to openthe contacts when .contacts l1l8 close and resistor 21 is de-energized. At a temperature of 66 we.

would have a pressure equal to 1 to close contacts l1-I8 and pressure equal to 2-1 or 1 to open them when resistor 21 is de-energized.

If power supply lead 83 of motor M2 oi-Figure 3 is connected to terminal bolt 84 of the thermostat of Figure 1 and lead 81 is connected to one terminal of a suitable source of electric current and terminal bolt 88 is connected to the other terminal or said source of electric current through lead 48 and if the sum of the resistance of resistors 21 and 28 is the correct amount to stall motor M2 against the urging of weight W. the thermostat of Figure 1 would operate in the same manner when connected to motor M2 as described above when connected to motor Ml.

Under the above set of conditions, the motor of Patent No. 2,134,685, or whatever device the switch-was controlling, would operate the motor in a stalled position at a temperature of 67 to 68, in one direct tm intermittently beginning at a-very small pa oi the time at a temperature just below 6'1" to continuously at and in the opposite direction intermittently beginning at a very small part of the time at a temperature just above 68 to continuously at 70. The range oi temperature when the motor would be stalled could be made any desired amount by adjusting point I1 by means of screw is and ranges of temperature in which movement in either direction would be intermittent can be made anyv desired amount by changing the sensitivity oi compound bimetallic arm li-H and the heat supplied by resistor 21.

A condition responsive element responsive to any other condition could be substituted (or bimetallic element l2 with like operation of the switch. Compensating bimetallic strip I could be omitted if the eflect oi variations in tempera ture in the space around bimetallic strip 18 were not objectionable. Resistors 21 and 28 could be connected in parallel instead of series with like results if proper resistances were chosen and resistor 28 could be omitted it bimetallic strip i8 were made less sensitive and resistance 21 were made the correct amount to stall the device operated, or an inductance could be substituted for resistor 28. A switch arm urged to draw away from the condition-operated contact by magnetic action could be substituted for the heater-operated bimetallic strip l8 and I contemplate such a construction as being a substantial equivalent of a heater-operated bimetallic strip.

It will be seen that a simple two-wire condition responsive switch has been provided capable of controlling a motor or other device to rea main stationary under a desired range of condition and to operate in a direction to correct a variation from the desired range and to do so at a rate that increases as the condition varies farther from the desired range.

While a specific embodiment of this invention has been described, it will be understood that this is for the purpose of illustration only, and that the invention is to be limited only by the scope of the appended claims.

I claim as my invention:

1. In a control system of the character disclosed, a shaded pole induction motor having a shading coil adapted to operate the motor in one direction and a second shading coil adapted to operate thev motor in the reverse direction in opposition to the first-mentioned shading coil, 8. heat sensitive control instrument including two sets of contacts arranged for both sets of contacts to be disengaged in one limit position, for the first setof contacts to be engaged in an intermediate position and connected to energize the said second shading coil through a resistance to a degree substantially equal to that of the first-mentioned shading coil,1or both sets of contacts to be energized in the other limit position and the second set 01' contacts connected to energins said second shading coil to a degree pro dominating the first-mentioned shading coil and aheaterincircuit withsaidsetsoicontactlao connected as to be energized only when said instrument is in an intermediate position and adapted when energized to assist in opening said first set of contacts.

2. A device adapted to operate normally in one direction, a heat sensitive control instrument having two sets of contacts arranged for both sets of contacts to be disengaged in one limit position, for the first set of contacts to be engaged in an intermediate position and connectedthrough a means to energize said device to op- 1 erate it in a substantially stalled condition, for

both sets of contacts to be engaged in the other limit position and the second set of contacts connected to energize said device to operate it in a direction opposite to its normal direction of operation and a heater in circuit with said sets of contacts so connected as to be energized only when said instrument is in an intermediate position and adapted when energized to assist in opening said first set of contacts.

3. A thermostat comprising a base, an indicator movably supported by said base, a normally stationary contact member carried, by said indicator, a temperature deformable bimetallic element fixed at one end to said base and having its free end spaced from said stationary contact member and disposed for movement toward and away from the latter in response to variations in am bient temperature, a compounded bimetallic member composed of two linearly arranged and united sections, one of said sections deforming in response to temperature variations in a manner opposite to that of the other of said sections, one of said sections being carried by said indicator and the other of said sections being arranged between said stationary contact member and the outer end of the bimetallic element, and electrically energized heating means for supplying supplemental heat to the section of said compounded member which deforms in'a manner opposite to that of the bimetallic element.

4. A thermostat comprising a base, an indicator supported by said base for pivotal movement about a fixed axis, a single temperature deformable bimetallic element fixed at one end to said base at a position in registration with the pivotal axis of said indicator, a normally stationary contact member carried by said indicator in spaced relation from the outer defiectible end of said bimetallic elemen t,, a compounded bimetallic and said stationary contact member, and means,

for applying supplemental heat to the section of said compounded bimetallic member which deflects in a manner opposite to that of the bi-.

metallic element when the compounded bimetalno member is in physical engagement with said single bimetallic element.

5. A thermostat comprising a base, an indicator supported by said base for pivotal movement, a normally stationary contact member carried by said indicator contiguous to its outer end, a temperature deformable bimetallic element having one end thereof secured to said base and the opposite end thereof disposed in spaced order from said stationary contact member and adapt,- ed for movement toward and away from'the latter in response to temperature variations ambient thereto, a compounded bimetallic member composed of two linearly arranged and united sections, one of said sections deflecting in response to temperature variations in a manner opposed to that of the otherhif said sections, one of said sections being secured to said indicator and the other of said sections having its free end disposed between the outer end of said bimetallic element and said stationary contact member, electrically energized heating means for supplying supplemental heat to the section of said compounded bimetallic member which deflects in a manner opposite to that of the bimetallic element, spaced terminals carried by said base for connection with a source of electrical energy, current conducting means extending from one of said terminals' to said single bimetallic element, and second current conducting means extending from said heating means and said stationary contact member to the other of said terminals,

6. A thermostat comprising a base, an indicator supported by said base for pivotal movement, a normally stationary contact member carried by said indicator, a temperature deflectable bimetallic element fixed at one end oi said base and having its free end spaced from said stationary member, said element being disposedfor movement toward and away from the stationary contact member in response to variations in the ambient temperature, 'a compounded bimetallic member composed of two linearly arranged and united sections, one of said sections deforming in response to temperature variations in an opposite manner to that of the other of said sections, means for securing one of said sections to said indicator whereby to maintain the outer end of the other of saidsections in an operating position between the outer end oi said bimetallic element and said stationary contact member, spaced terminals carried by said base for connection with a source of electrical energy, current conducting means extending from one of said terminals to said single bimetallic element, electricaliy energized heating means for supplying supplemental heat to the indicator united section of said bimetallic member which deforms in a manner opposite to that of the bimetallic element, a resistance mounted on said indicator and connected in series with said electrically energized heating means, and second current conducting means extending from the second of said terminals to said resistance and to said stationary

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