US2524535A

US2524535A - Electric blanket control with variable compensator

Info

Publication number: US2524535A
Application number: US666032A
Authority: US
Inventors: Heber L Newell
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1946-04-30
Filing date: 1946-04-30
Publication date: 1950-10-03
Anticipated expiration: 1967-10-03

Description

H. L. NEWELL Oct. 3, 1950 ELECTRIC BLANKET CONTROL WITH VARIABLE COMPENSATOR Filed April 30, 1946 7 6 HIGH SETTING OF LEVER 20 LOW 2 3 4 5 Inventor- Haber L.Newell, by

77 ttorney 60 70 ROOM TEMPERATURE, DEGREES FAHRENHEIT Fig.2.

w .w m w .w w u m m =0 Mic tau 5E Patented Oct. 3, 1950 ELECTRIC BLANKET CONTROL WITH VARIABLE COMPENSATOR Heber 1.. Nowell, Fishkill, N. Y., assignor to General Electric Company, a corporation of New York Application April 30, 1946, Serial N0. 666,032

6 Claims. (Cl. ZOO-136.3)

This invention relates to electric blankets, and it has for its object the provision of means for refining the control in electric blankets.

More particularly, this invention contemplates improvements in electric blankets wherein the energy fed to the blanket is varied at a predetermined rate as the room temperature varies so as to compensate for these changes in room temperature and thereby hold a substantially constant temperature in the blanket. This invention contemplates the provision of improved means for adjusting the temperature setting of the controlling elements in order to vary the temperature held in the blanket without affecting the rate of compensation; and also means for varying this rate. This enables different people to obtain different degrees of compensation in their blankets. Thus, for example, different people may desire to obtain the same blanket temperature at a given high room temperature, but obtain higher or lower blanket temperatures as the room temperature drops, and they may have such variations in compensation by means of the control of this invention.

For a more complete understanding of this invention, reference should be had to the accompanying drawing in which Fig. 1 is a diagrammatic representation of an electrically heated blanket provided with control means arranged in accordance with this invention; and Fig. 2 is a chart illustrating the rate at which energy is fed to the blanket as the room temperature varies for different temperature settings of the control device, and also illustrating how the rate of compensation may be varied.

Referring to the drawing, this invention has been shown in one form as applied to an electrically heated blanket having a flexible blanket body I to which there has been attached a heating resistance conductor 2 which as shown is formed into a plurality of convolutions distributed through the blanket body. This heatin resistance 2 is energized from a suitable source of electrical supply 3 which preferably will be alternating current. The energizing circuit of the heater 2 is controlled by the time element cycling type control device described and claimed in the copending application of Jacob W. McNairy, Frank A. Rosenkrans and Arthur E. Coombs, Serial No. 588,014, filed April 12, 1945, now Patent No. 2,- 429,475, issued October 21, 1947, and which patent is assigned to the assignee of the instant application.

This control device comprises a switch 4 having a fixed contact 5 and a coacting movable contact 6 mounted on one end of an operating arm I. It will be observed that when the

contacts

5 and 8 are in engagement the resistance element 2 is energized, whereas when they are separated the resistance element is deenergized. The operating arm I, as shown, has its end opposite the contact 6 pivotally mounted upon a transverse shaft 8 which shaft is mounted in fixed bearings 9.

Also pivoted to the shaft 8 is an actuating arm i0 which is positioned below the operating arm I, lengthwise of it, at an angle thereto-ti"! two arms diverging from each other from their common shaft 8, as shown. The actuating arm I has an end portion i I projecting beyond the shaft 8 and at the extreme end of this end portion there is an upright extension l2 which is engaged by a cam Iii-roughly of heart shape. This cam is driven at a substantially constant speed by means of a time element electric motor I. The cam is shaped so as to periodically oscillate the arm Ill; that is in each revolution of the cam th arm II is oscillated up and down through one cycle.

Interposed between the two arms I and I0 is a motion transmitting element ii in the shape of an elongated bar, as shown, and which bar is formed of a suitable electrically insulating material. It will be observed that when the arm is is close to the shaft 8 the arm I will be picked up at an early point in the movement of the cam II and will open the

contacts

5 and 6 at an early point, as compared with the operation when the element It is more removed from the shaft 8 when the switch arm 1 is picked up at a later point in the operation of the cam. That is, when the element i5 is close to the shaft 8 the proportion of time that the contacts are closed to the time that they are open is relatively small, as compared to the operation when the element i5 is more removed from the shaft 8 when the proportion of time that the contacts are closed to the time that they are open is greater. In other words, by varying the position of the element I5 lengthwise of the arms it is possible to control the amount of energy which is fed to the heating circuit 2 and thereby control the temperature of the blanket body I.

The motion transmitting element ii is mounted upon the outer end of a room temperature responsive thermostatic helix i8 which preferably is formed as a bimetallic element, the two metals of the element having different temperature coefficients of expansion. The element 16 is so arranged that it unwinds so-to-speak to move the transmitter l5 toward the left responsive to lower room temperatures, and winds up to move it toward the right as the temperature of the element increases. The inner end of the bimetallic element is fixed to a post or standard II which is rot-atably mounted intermediate the ends of a lever I8, but which is normally held in fixed relation with the lever by means of a friction and spring clutch It. The shaft I1 can be adjusted on its axis by means of a lever Ill and will b held by the spring friction device It in its adjusted the control lever is in its mid position shown in Fig. 1, and transmitter I5 is in its position there shown it will be understood that a. portion of the oscillatory motion of the actuatingarm III will be imparted to the switch operating arm I and that the

contacts

5 and 8 will be opened and closed, the proportion of time that they are closed to the time that they are open determining the amount of electrical energy fed to the heating circuit 2. If the room temperature should drop with the control in its setting shown in Fig. l, the element 'I5 will be moved toward the left which operation will increase the proportion of time the contacts are closed to the time that they are open and thereby increase the amount of energy fed to the blanket thereby to compensate for the falling room temperature. Conversely, if the room temperature should rise the bimetal element I6 will move the motion transmitter I5 toward the right thereby to decrease the amount of time that the contacts are closed during each revolution of the cam I3. This decreases the amount of energy fed to the blanket again to compensate for the room temperature change. Likewise, the element I5-may be manually shifted in either direction from its Fig. 1 position by the lever 20 in order to change the temperature setting of the control device to hold different temperatures in the blanket. If the lever 20 is moved toward the position indicated Low" the element I5 will be moved toward the right which will decrease the energy fed to the blanket and thereby decrease the blanket temperature; conversely, if the lever 20 be moved toward the position indicated High," the element I5 will be moved toward the left and increase the amount of energy fed to the blanket thereby elevating the blanket temperatureit being remembered that for any given setting of the lever 20 the thermostat I6 will shift the element I5 in accordance with room temperature variations so as to vary the proportion of time the switch is closed to hold the set temperature irrespective of these room temperature variations. As pointed out in the aforementioned McNairy, Rosenkrans and Coombs application, the cam I3 is shaped so that once each revolution the cam releases the transmitter I 5 in order to let it assume any position it should take either when lever 20 is adjusted or the bimetal thermostat I6 winds or unwinds.

The foregoing operation may be understood more clearly by reference to Fig. 2 which is a chart showing how the per cent Time on" of the switch 4 varies with room temperature variations for various settings of lever 20. For example, suppose that the lever 20 is set at point 5 which is midway between the Low and High positions, then if the room temperature is 70 the motion transmitting element II will be so far in the right that it will always hold the switch contact 6 out of engagement with contact I during the oscillations of the actuating lever II (see curve a). In other words, the switch will be on zero per cent time, and no electrical energy will be fed to the blanket. Now if the temperature of the room falls the percentage of Time on" will increase along curve a until when the temperature of the room falls to approximately 48' the element I! will have been moved so far to the left that the switch contact 6 will not be opened at all; in other words, the switch will be on 100% of the time of operation of the cam I3, and maximum energy will be fed to the blanket. That is, as the room temperature changes from to 48 the thermostat I6 will have progressively shifted the element I from a right-hand position at which the switch did not close at all to a left-hand position at which the switch remains closed all the time. The characteristics of the bimetallic element It determine the rate of variation of the per cent Time on" of the switch, that is, the rate of variation of the energy feed to the blanket to compensate for room temperature variations. It will be observed by reference to Fig. 2 that this rate determines the slope of the compensation curve a for setting 5. And that the rate is the same for each knob setting. That is, irrespective of what position the temperature adjustment knob 20 is in between its Low and High" positions, the rate at which the device compensates for room temperature variations remains constant.

Now it is possible that different people would like to have a different degree of compensation. It is for this reason and in accordance with this invention that the bimetallic element It support I1 is mounted upon the lever ll. This lever II is mounted to pivot in a fixed support 2i, and is held in any position of adjustment by a friction washer 22. Adjustment of the lever I8 away from and toward the switch arms I and HI varies the effective radius of operation of the element I5 from the central axis of the spiral l6 and this will vary the slope of the curve shown in Fig. 2, that is, will vary the rate of compensation. Putting it differently and as a specific example, it is possible that two people would like to have the switch Time on" equal to 0% when the room temperature is at 70 and the control lever 20 is at its midpoint 5, as in the example given above. It is further possible that the first person would like th compensation rate denoted by line a in the manner described above. whereas the second would like to have less compensation, that is, would like to have the Time on occur at a lower temperature-in other words, at some compensation rate indicated by the line b. This change in rate is effected by moving the lever ll counterclockwise which causes the element It to operate on a smaller radius. It will be observed that if the element I I be so adjusted its move ment leftward will be less than before for any given room temperature drop, and its compensation, therefore, will be less. That is, the new setting requires a lower room temperature in order to move th transmitter I! so far to the left that the contacts will remain 100% "Time on." In the example chosen, it will be necessary for the room temperature to fall to about 40' before the switch remains on 100% of the time. Conversely, if the lever I8 is moved clockwise, it increases the effective radius of operation of the element II and therefore its movement leftward will be greater for a given temperature drop. In this case, the blanket will be heated a greater percentage of the time for the temperature drop and the compensation will be greater.

Thus lever adjusts blanket temperature, whereas lever l8 adjusts rate of compensation tor room temperature variations.

While I have shown a particular embodiment of my invention, it will be understood, 0! course, that I do not wish to be limited thereto since many modifications may be made, and I, therefore, contemplate by the appended claims to cover any such modifications as tall within the true spirit and scope oi my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In an electric blanket having a heating circuit, means for controlling the energy ted to said circuit comprising, a switch connected in said circuit, a periodic operator i'orsaid switch for supplying a predetermined average power to said circuit at a given room temperature, a thermostat responsive to room temperature variations and carrying an element of variable efiectiveness which is interposed between said switch and said operator for controlling the operation of said switch by said operator to vary the proportion of time said switch is open to that during which it is closed thereby to vary said average power supplied to said blanket in a predetermined proportion to variations in the magnitude of said room temperature to compensate therefor and thereby hold a substantially constant temperature in said blanket, means for changing the effectiveness of said element to change said predetermined average power and thereby to change the temperature held in said blanket without changing said proportion in which the average power is varied in response to room temperature variations, and a manually adjustable member carrying said thermostat and element movable for changing the eifective radius of movement of said element between said switch and said operator in response to changes in temperature so as to change said proportion.

2. In an electric blanket having a heating circuit means for controlling the electric energy fed to said circuit comprising, a switch connected in said circuit, an actuator for said switch, a time element device for operating said actuator periodically, a motion transmitter connected between said actuator and switch for imparting opening and closing motions to said switch from said actuator as it is periodically driven for supplying a predetermined average power to said circuit at a given room temperature, a thermostat responsive to room temperature connected with said motion transmitter for controlling the position of the same so as to control the proportion of time said switch is open to that which it is closed thereby to vary said average power supplied to said circuit in predetermined proportion to variations in the magnitude of said room temperature, means for adjusting said thermostat to change the position of said motion transmitter and thereby to change said predetermined average power and thus the temperature held in said blanket without effecting said proportion in which said thermostat varies the average power in response to room temperature variations, and a manually adjustable member supporting said thermostat and transmitter movable in a direction to change the effective radius of heat responsive motion of said transmitter with respect to said actuator and switch to change said proportion.

3. In an electric blanket having a heating circuit, means tor controlling the energy input to said circuit comprising, a switch connected in said circuit, a pivoted operating arm for said switch ior operating it to opened and closed positions, a pivoted actuating arm arranged lengthwise of said operating arm and at an angle thereto, a time element device for oscillating said actuating arm, a motion transmitting element interposed between said arms for transmitting motion from said actuating to said operating arm, said element being movable about an axis ior shitting it lengthwise of said arms thereby to control the proportion of time said switch is opened to that which it is closed. means responsive to room temperature for moving said element on said axis to adjust its position lengthwise oi said arms so asto control said time periods whereby the switch operates to supply a predetermined average power to said circuit which average power is varied in a predetermined proportion to variations in room temperature to compensate for such variations, means for manually adjusting the position of said element lengthwise of said arms to change said predetermined average power and thereby to change the temperature held in said blanket, and a manually adjustable member supporting said transmitting element and mounted for movement in a plane perpendicular to said axis for varying the effective radius of movement of said transmitter with respect to said operating and actuating arms to change said proportion.

4. In an electric blanket having a heating circuit, means for controlling the electrical energy input to said circuit comprising, a switch, an operating arm for said switch for operating it to opened and closed position, an actuating arm arranged lengthwise of said operating arm spaced from it, means supporting said arms to move about a given pivot axis, and said arms diverging away from each other from said axis, a time element device for oscillating said actuating arm, a motion transmitting element interposed between said arms for transmitting motion from said actuating to said operating arm, a spiral bimetallic thermostat connected to and supporting said element in its position between said arms and for moving said element about the axis of said thermostat to shift the element lengthwise of said arms thereby to control the proportion of time said switch is opened to that during which it is closed to supply power to said blanket at a predetermined average rate varying in a predetermined proportion to room temperature variations to compensate for such variations, means for manually adjusting the angular position of said thermostat on said axis and thereby to adjust the position of said element lengthwise of said arms to change said average predetermined rate of power supply and thus change the temperature held in said blanket, and a movable support for said thermostat and element for manually adjusting the position of said axis toward and away from said arms tovary the efiective radius of operation of said element with reference to said arms to change said predetermined proportion of variation of power supply in response to variation in room temperature.

5. In an electric blanket having a heating circuit, means for controlling the electrical input to said circuit comprising a switch in said circuit, a pair of relatively movable arms, movement of one of said arms operating said switch, means for periodically oscillating said other arm, a motion transmitting element adjustably positioned beasses tween said arms for transmitting the oscillatory movement of said other arm to said one arm and hence for periodically operating said switch, said transmitting element being rotatably adjustable about an axis, which adjustment varies the extent of motion transmission iron: said oscillated arm to said switch operating arm and hence the proportion or total time said switch remains closed, means responsive to room temperature and independent oi blanket temperature operatively connected to rotate said transmitting element about said axis, said transmitting element being turther adjustable laterally with respect to said arms by lateral movement of said axis thereby varying the eitective radius oi! the rotative adjustment, and a pivoted arm manually adjustable to eflect said lateral adjustment.

6. In an electric blanket having a heating circuit, means for controlling the electrical input to said circuit comprising a switch in said circuit, a pair of relatively movable pivotally mounted arms, movement oi! one of said arms operating said switch, means for periodically oscillating said other arm, a motion transmitting element adjustably positioned between said arms for transmitting the oscillatory movement of said other arm to said one arm and hence for periodically operating said switch, said transmitting element being rotatably adjustable about an axis, said rotative adjustment varying the extent of motion transmission from said oscillated arm to said switch 8 operating arm and hence the proportion oi total time said switch remains closed, means responsive to room temperature and independent cs blanket temperature operativeiy connected to retate said transmitting element about said axis, manual means to rotate both said element and said temperature responsive means about said axis, said transmitting element being mrther adjustable laterally with respect to said arms by movement of said axis thereby varying the cites-- tive radius of the rotative adjustment, and a pivoted arm manually adjustable to eilect said lateral adjustment.

HEBER L. NEWELL.

REFERENCES CITED The following references are of record in the die of this patent:

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