US2319563A - Thermostat - Google Patents

Description

May 18, 1943 B. E. SHAW THERMOSTAT Filed June so, 1941 INVENTOR. fiuribwfi? 5 720111 BY 1? 1 w Patented May 1?, 1943 ZEN? GFFICE THERMGSTAT of Iowa mplication June 30, 1941, No. 469,428

(Cl. Zita-139) 9 Jiainis.

My present invention relates to a room thermostat having an adjusting dial provided with an off position and an on position.

One object of my invention is to provide a thermostat wherein a graduated dial may be used for adjusting the range of the thermostat, but at, opposite limits of movement of the dial the thermostat is set for a sudden decrease and increase, respectively, in the temperatures to which it is adjusted.

A further object is to provide means at one of these limits to serve as a stop for the switch arm to positively prevent it from assuming a closed circuit position.

Still another object is to provide a room thermostat in which the on position is truly an on position only until such time as the thermostat is subjected to an excessively high temperature, whereupon the thermostat opens.

With these and other objects in view, my invention consists in the construction, arrangement and combination of the Various parts of my device whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in my claims and illustrated in the accompanying drawing. Although the invention is susceptible of a variety of embodiments, it is unnecessary to fully describe and illustrate more than one in order to give a full understanding of the invention both from its structural and functional stand-points. Accordingly, I have illustrated a preferred and desirable embodiment of the invention in the accompanying drawing, in which:

Figure 1 is a front elevation of a thermostat embodying my invention, the cover thereof being removed;

Figure 2 is a side elevation of Figure 1 showing the cover in section, and

Figure 3 is a View similar to Figure 1 showing the thermostat in a different position.

On the accompanying drawing, I have used the reference numeral iii to indicate a thermostat base. A stud i2 is mounted in the base it and on the stud I pivotally mount a bell crank lever I3. The bell crank lever l3 has an upstanding arm I4 bent back toward the stud i2 at its upper end to form a perforated ear l5, also pivoted on the stud. A coiled bimetal element l6 has one end secured to the vertical part it of the lever An adjusting dial ii is rotatable on a stud i3 mounted in the base iii. The dial Ii carries a cam having a spiral face It, a lobe and a depression 21. The lever l3 carries an adjusting screw 22 to coact with the cam C. A spring 23 is coiled around the stud I2 and has one end 2!: located in the base Iii. Its other end is hooked as at 25 to coact with the lever l3 and thereby bias it in a clockwise direction to retain the adjusting screw 22 in engagement with the cam C. The bimetal element 16 carries a switch arm 26 provided with a contact 27. The contact 21 is adapted to cooperate with a stationary contact 28 carried by a bracket 29. A horseshoe magnet 38 cooperates with an armature portion SI of the switch arm 26 to alford snap action.

The bell crank lever l3 carries a second adjusting screw 32 adapted at times to coact with the bimetal element i6, as shown by its dotted position in Figure 1. The stud 18 has a pointer 33 carried thereby to cooperate with the graduation marks and the indicia on and off of the dial IT. A cover 34 is provided for the thermostat mechanism on the base Iii. Th cover 35 may carry a mercury column 35, if desired, for indicating actual room temperatures. The cover 34, together with the base l0, constitute a casing for the thermostat, and air may circulate up through the casing by entering openings 35 at the bottom of the cover 34 and issuing from openings 31 at its top. Such air, in passing through the cover, efiects coiling or uncoiling of the bimetal element 16 depending on whether the temperature lowers or rises.

Practical operation In the operation of my thermostat, the dial I! may be adjusted anywhere from to which will cause the spiral portion [9 of the cam C to gradually swing the bell crank lever l3, thereby coiling or uncoiling the bimetal element It to make it control the switch contacts at different temperatures. When the dial I1 is adjusted to one extreme position, indicated as Off in Figure 1, the cam lobe 20 will engage the adjusting screw 22, thus causing the supporting arm [3 to be suddenly adjusted to an extreme low temperature position. Such position, for instance, might be as low as 25 below zero before the switch contacts would engage. Thus the temperature afiecting the bimetal element 16 may go extremely low Without imposing any strains on the bimetal element.

If, however, it is desirable to have the switch positively insured against closing of the contacts at such low temperature, the adjusting screw 32 may be set as illustrated, so that when the temperature approaches the low extreme it will stop the switch arm, as in the dotted position of Figure 1.

At the other extreme of adjustment, On, as shown in Figure 3, the bimetal element l6 has been adjusted to an extreme high temperature position. For instance, the supporting lever 13 might assume the full line position illustrated when the notch 2| of the cam C registers with the adjusting screw 22. The temperature then, might rise, which would first effect movement of the lever I3 to the dotted position and thereafter, upon continued rise, would swing the switch arm 26 to its dotted position, thus opening the circuit. Such open circuit condition might occur in the neighborhood of 115 on an installation where the furnace is gas fired. Thus, although the thermostat indicates an on position rather than an automatic position, as indicated by the graduations from 40 to 80, it actually has a safety feature in that when the temperature around the thermostat becomes exceptionally high, it will automatically open the switch contacts.

The adjusting dial I! may be limited to its extremebn and ofi positions as by a stop lug 38 projecting downwardly from the dial into an arcuate slot 39 of the base Ill. The adjusting screws 22 and 32 are provided for factory adjustment, after which only the dial H is adjusted by the user.

Some changes may be made in the construction and arrangement of the parts of my device with-- out departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims any modified forms of structure or use of mechanical equivalents which may be reasonably included within their scope without sacrificing any of the advantages thereof.

I claim as my invention:

1. A thermostat of the character described comprising a movable switch member, a thermostatic element operating said switch member, an adjustable support for said thermostatic element, manually operable means for moving said support to adjust the switch member throughout a predetermined range and adapted when the means is moved to one extreme position to hold said switch member in open circuit position against closing except at an exceptionally low temperature, and stop means to stop said switch arm at a position short of closed circuit position when said means is at said extreme position, said dial, at its opposite extreme position, holding said switch member closed until only an exceptionally high temperature opens it.

2. A thermostat of the character described comprising a movable switch member, a thermostatic element operating said switch member, an adjustable support for said thermostatic element, manually operable means for moving said support and thereby said thermostatic element to adjust the switch member throughout a predetermined range and adapted when the means is moved to one extreme position to hold said switch memher in open circuit position against closing except at an exceptionally low temperature well beyond such range, said manually operable means, at its opposite extreme position, holding said switch member closed until only an exceptionally high temperature opens it.

3. A thermostat comprising a casing, a movable switch member, a thermostatic element carrying said switch member, an adjustable support for said thermostatic element, manually operable means for moving said support to adjust the switch member including a dial projecting from the casing, a lever connected with said thermostatic element, a cam carried by said dial and coacting with said lever and adapted when the dial is moved to one extreme position to suddenly move the lever and thereby hold said switch member in open circuit position against closing except at an exceptionally low temperature, said dial, at its opposite extreme position, suddenly positioning said switch member in its closed circuit position under such tension of said thermostatic element as to permit the thermostatic element to open the switch only at an exceptionally high temperature.

4. In a thermostat, a movable switch member, a thermostatic element for operating said switch member, an adjustable support for said thermostatic element, means for moving said support to adjust the switch member, said thermostatic element, when said means is moved into one extreme position thereof, suddenly assuming a position that permits said switch member to function only after an appreciable change in temperature beyond the limit of range adjustment of said means.

5. A thermostat comprising a pair of switch contacts, a thermostatic element normally operable to move one of said contacts relative to the other in response to changes in temperature, manually operable cam means operatively associated with said element to adjust the movable contact, said cam means having a sudden change in contour to coast with said element and hold said contacts spaced from each other until an exceptional change in the temperature affecting said element takes place.

6. In a room thermostat of the character disclosed, a temperature responsive element, switch contacts controlled thereby, cam means for adjusting said temperature responsive element to secure different ranges of temperature responsive for the operation thereof, said cam means having a sudden change in contour to adjust said temperature responsive element to an extreme low temperature position at one extreme position of adjustment, said cam means, at the other extreme position of adjustment, having a second sudden change in contour to close said switch and permit its opening in response to only an exceptionally high temperature affecting said temperature responsive element,

7. In a room thermostat, a supporting arm pivotally mounted, a temperature responsive element mounted thereon, a switch arm carried by said temperature responsive element, switch contacts under control of said switch arm, a cam for pivotally adjusting said supporting arm gradually throughout a predetermined range of movement of the cam and thereby changing the temperature to which said temperature responsive element responds in controlling said switch contacts from one position to another, means biasing said supporting arm toward said cam, said cam having a lobe at one extreme position and a depression at its other extreme position to eiiect respe tively a sudden low temperature adjustment of said temperature responsive element and a sudden high temperature adjustment of said temperature responsive element with uniform rotation of said cam at its extreme limits of movement, whereby at one extreme the switch tends to close only at an exceptionally low temperature position, the other limit of adjustment of the cam effecting response of said temperature responsive element to open the switch only at an exceptionally high temperature.

8. In a thermostat of the class described, a

supporting arm pivotally mounted, a temperature responsive element mounted thereon, a switch arm carried by said temperature responsive element, switch contacts under control of said switch arm, means for pivotally adjusting said supporting arm and thereby said temperature responsive element throughout a predetermined range, means at the ends of such range for effecting relatively quick adjustment of said temperature responsive element to low and high temperatures respectively, and means carried by said supporting arm and constituting a stop for said switch arm in a position where said contacts are slightly separated when said supporting arm is adjusted to its extreme low temperature position.

9. In a thermostat of the character disclosed,

a base, a supporting arm pivotally mounted thereon, an adjusting screw carried by said supporting arm, a cam rotatable on said base having a spiral cam surface terminating at its respective ends in a lobe and a depression, said cam surface, lobe and depression being coactable with said supporting arm to effect sudden changes in the angle of the supporting arm in opposite directions at the limits of rotary movement of said cam, a spring biasing said supporting arm to engage said cam, a coiled bimetallic element mounted on said supporting arm, a switch arm carried thereby, switch contacts controlled by said switch arm, and means carried by said supporting arm and having an adjusting screw serving as a stop for said switch arm to hold the same in a predetermined open circuit position when said cam is adjusted to one of its extreme positions.

BURTON E. SHAW.

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