US2618722A - Temperature controlling device - Google Patents

Description

NOV. 18, 1952 C Q DE WITT 2,618,722

TEMPERATURE CONTROLLING ,DEVICE Filed Jan. 29, 1949 Patented Nov. 18, 1952 UNITED STATES PATENT OFFICE TEMPERATURE CONTROLLING DEVICE Clyde C. De Witt, Okemos, Mich. Application January 29, 1949, Serial No. 73,487

6 Claims.

This invention relates to new and useful improvements in temperature control devices.

An important object of the present invention is to provide a temperature control device that is exceedingly sensitive in operation.

Another object of the invention is to provide a temperature control device that maintains its sensitivity over a wide temperature range.

Still another object of the invention is to provide a temperature control device having novel means for determining the particular temperature at which it operates Yet another object of the invention is to provide a temperature control device that is simple but rugged in construction and that can be manufactured relatively inexpensively.

,A further object of the invention is to provide a temperature control device that is not affected adversely by exposure to temperatures other than that at which it is set to operate.

Other objects and advantages of the invention will be apparent during the course of the following description.

In the drawing forming a part of this specification and wherein like numerals are employed to designate like parts throughout the same,

Fig. 1 is a longitudinal sectional view, showing parts in elevation, of a temperature control device embodying the invention;

Fig. 2 is an enlarged, fragmentary, longitudio nal sectional view taken on the line 2 2 of Fig. 1 and Fig. 3 is a longitudinalsectional view, showing parts in elevation, of a modified form of the invention.

In the drawing, wherein for the purpose of illustration is shown a preferred embodiment of the invention, the numeral IE) designates a mounting member which carries the operating parts of the device. A pressure-sensitive actuating means I2 depends from the mounting It) and acts through pins I4 and metal disk I6 to flex a resilient metallic strip I8 which in turn operates a micro-switch 2U. The strip I8 and microswitch 2E! are carried by an upstanding support 22 which is adjustably mounted on the mounting It to raise or lower the strip relative to the disk I6 and thus regulate the particular temperature at which the switch is operated. All of the parts disposed above the mounting I0 preferably are enclosed in a housing 24 and a manual actuator 26 is fastened on the upper end of support 22 exteriorly of the housing to facilitate adjustment of the device..

, In use, the temperature-sensitive means I2 (Cl. 20G-137) responds to temperature changes by expanding or contracting. However, this expanding or contracting movement, in itself, is not sufficient to actuate a conventional micro-switch. In the instant construction, the thermal expansion of the means I2 causes pressure to be exerted axially against the iiexib-le strip I8 which multiplies the thermal expansion movement. In practice, I have found that the strip I8 will multiply the thermal expansion movement or more times, and this movement of the strip is sufficient to operate the mi-cro-switch 2U.

While a variety of temperature-sensitive means conceivably could be used to operate the strip I8, I have found the particular mechanism here shown to be far superior to other devices of this type which are known to me. The temperaturesensitive means I2 here show comprises an inner rodlike member 28 which extends axially through and is spaced from an outer tubular member 3d. At the lower ends thereof the rod 28 and tube 3B are rigidly joined together by a threaded annular disk 32. The upper terminal portion of tube 3i) is snugly but slidably received in an axial opening 34 provided in the mounting IU. The rod 28 extends above the tube 3U and the projected portion thereof is threaded into an insert 38 which is set into the top surface of the mounting IU and is fixed to the mounting in any suitable manner as by soldering, welding, or brazing.

It is essential to the present invention that the rod 233 and tube have different coefncients of expansion and it is desirable that the coefcients of expansion `be as far apart as possible. I have found an inner rod of invar metal and an outer tube of aluminum to be satisfactory. The invar rod 23 has a very low coeiicient of heat eXpansion and the aluminum tube has a relatively high coefficient of heat expansion. Thus, while both the rod 28 and tube 3] expand when subjected to an increase in temperature, the tube expands many times faster than the rod. Since the upper end of the rod 23 is anchored in the insert 3S which, in effect, is a part of the mounting I Il and the lower end of tube 30 is attached to the lower end of the rod, the upper end of the tube will advance in opening 34 in response to a rise in temperature and will retract in the opening in response to a drop in temperature.

The particular construction here shown has the advantage that the temperature-sensitive means i2 works equally well at high and low temperatures. For example, the means I2 will function as well at -l0 F. as it will at 800 F. or 1G00 F. Further, the device is in no way affected adversely by sudden or abrupt changes in temperature. Thus, the device can be employed in one instance to maintain a heating oven at 800 F. and then used in another instance to maintain a refrigerating system at temperatures in the order of 100 F. without any change or adaptation of the device other than to adjust the strip I8 relative to the pressure-sensitive means I2. Also, the device will withstand considerable rough treatment and abuse without damage and without getting out of adjustment. Ruggedness of this order is in sharp contrast to conventional bellows-type refrigerator controls, for example, which frequently rupture if the refrigerator is merely permitted to stand at normal summer temperatures for a period of time.

Other advantages of the particularconstruction here shown reside in the extreme sensitivity of the device and in the fact that the sensitivity can be regulated or controlled by using metals or metal alloys having different thermal expansion characteristics for thefrod 28 and tube 30 and also by varying the length of these elements. For example, an invar rod 28 and an aluminum tube 30 approximately 10 in length is sensitive to within ve hundredths of one degree Fahrenheit. Extreme sensitivity of this character is essential for some purposes. On the other hand under circumstances where a less sensitive contro1 is satisfactory and Vcompactness is important, it may be possible to use a much shorter rod and tube. For example, an invar rodl 28 and a stainless steel tube 30 approximately 4" in length is sensitive to within one-third of one degree Fahrenheit. A unit of this type is small, compactand suiciently sensitive for Vmany domestic'and commercial uses.

Any desired number of pins I4 may be employed. Inpractice I haveused an annular series of five pins which rest upon the inner end of tube Sand support the disk I6, as shown. All of the pins are mounted to slide `readily in the insert 36 so that they.y transmit exceedingly slight movement readily from( the tube to the strip I8.

The particular Vsupport 22 here shown has an upright member 38 and an annular base member 481. Also, it will be observed that the insert 38 has an upstanding central embossment l2 and the base is threaded onto the embossment. The lower end of upright member 38 extends diametrically across the base member d8 andl is welded or otherwise fastened thereto as at Il (Fig. 2)

The flexible metallic strip I8 is mounted on one side of the upright member 38 and the upper end of the strip isv welded or otherwise iixed to the member asat 46. Thelower terminal portion of strip I8 projects slightly below the support 38 and is held flatly against the support member by an overlying band 48. In this connection it should be notedthat the band 48 holds strip I8 relatively loosely so as not to bindvor in any way restrict fiexure of the latter. The projecting lower portion of strip I8 rests upon the disk I8v so that the strip responds instantlyY to vertical uctuations of the disk in response to movement of the temperature-sensitive means I 2. A small stop 50 dise posed behind and substantially midway between the ends of the strip I8,` holds the latter bowed slightly in the directionof switch 28. The rate of multiplication fallsvoif rapidly as the spring strip I8 is bowed from an initial straight position. Consequently, the initial bow caused by the stop 50 should be just enough to assure directional bowing and preferably is about 0.0i inch. As

suggested, the particular arrangement of strip I8 multiplies the vertical movement of the temperature-sensitive tube as much as times or more. In practice, however, the particular multiplication ratio may vary somewhat depending upon the size and shape of the spring strip I8 and upon the elasticity characteristics of the metal from which it is made.

To raise the temperature at which the device operates micro-switch 20, it is merely necessary to unscrew the base 40 on boss 42. This action moves the strip I8 away from temperature-sensitive means I2 and thus increases the distance the latter must expand before it iiexes spring I8 sumciently to operate switch 28. On the other hand, tolower thev temperature at which the device operates switch 20 it is merely necessary to screw the support 22 downwardly on the embossment lgsoasto move the flexible strip I8 closer to the temperature-sensitive means I2.

In one device actually constructed, one` full rotation ofthe support-22 varied the operating temperature of the device 200. Howevenit will be readily apparent thatthe amount of temperature variationvper rotation of the support 22 depends upon the'leadof thethreads which connect thebase of thesupportto the embossment 32. Manifestly,A the latterA factor Canbevaried within wide limits. 4 e 4 While the above construction is operative over an exceedingly widetemperature range, I have found that it is slightly lesssensitive at exceedingly low temperaturesfin the orderof 100 F. than at higher temperatures intheorder of 800 F. or 1000 F. Thediiference in sensitivity1 at low temperatures isso small as to be nonsigniiicant in most. cases. However, where extreme sensitivity is imperative, the lossinY sensitivity may be significant. I have found, however, that if the construction is modiedas-shownin Fig. 3, there is no loss in sensitivity at low temperatures. In general it may be stated'that the formof the invention shown in Figs. land 2 has maximum sensitivity at high temperatures andthe form of the invention shown in Fig, 3haslmaximum sensitivity at low temperatures, although both forms are suciently sensitive for most purposes at both high and low temperatures.

The form of the invention shown in Fig. Bis identical to the formfrst. describedexceptY that the inner rod 28- is used to actuate the flexible metal strip I8 instead of the outer tube 30. In the latter form ofthe invention, the upperend of tube 30 is threaded into the'inserty 36 and the insert is provided with a relatively large central opening 52 throughwhich therod 28.extends. Thepins Id. and disk I6. areomitted and the upper. end of rod 28 bears directly' against the lower endof thestrip I8.l Thus, variations in length ofvtheouter tube 30 moves the rody 28 against orawayfrom the strip I8 to operate the micro-switch 28 in the same manner as the form of the invention first described.

Havingthus described the invention, I` claim:

1. A temperature controllingv device comprising a micro-switch, an elongated, flexible and inherently resilient metallic strip mounted in front and longitudinally arched only slightly from a straight rectilinear conditionland inthe direction of the switch and operable to actuate, the switch by iiexure thereof Aas 4a result of pressure imposed longitudinally, thereagainst, temperature-sensitive means arranged to impose longitudinal pressure against said strip in response. to temperature changes, and means for adjusting said strip bodily relative to said temperature-sensitive means to regulate the specific temperature at which said strip operates said switch.

2. A temperature controlling device comprising a micro-switch, switch actuating means including an elongated eXible and inherently resilient metallic strip mounted in front of and longitudinally arched in the direction of the switch and operable to actuate the switch by flexure as a result of pressure imposed longitudinally thereagainst, temperature-sensitive means for flexing said strip to operate the switch, and manually operable means for adjusting said switch actuating means to move said strip bodily relative to said temperature-sensitive means to regulate the specic temperature at which said switch is actuated by said strip.

3. A temperature control device comprising a micro-switch, an elongated flexible and. inherently resilient metallic strip mounted in front and longitudinally arched in the direction of said switch and operable to actuate the switch by ilexure as a result of pressure imposed longitudinally thereagainst, a. pair of essentially rigid metallic elements having different coeflicients of expansion, one of said elements being rigidly supported at one end and rigidly supporting the other of said elements in longitudinal alignment with said strip, freely slidable means establishing contact between said other element and said strip whereby the dierential in thermal eXpansion of said elements exes the strip to actuate said switch, and means for adjusting said strip bodily longitudinally relative to said other element whereby to regulate the specific temperature at which, said switch is operated.

4. A temperature controlling device comprising a mounting, temperature-sensitive means including a pair of individual, essentially rigid metallic elements having different coeiiicients of expansion, one of said elements being rigidly secured at one end to said mounting, the other of said elements being supported by said one element and freely movable relative to the mounting, a micro-switch, an elongated flexible and inherently resilient metallic strip mounted in front and normally longitudinally arched in the direction of said switch, said strip operable to actuate the switch by pressure imposed longitudinally thereagainst by thermal expansion movement of said freely movable element, and a support for said strip adjustable on the mounting to move the strip bodily relative to said freely movable element whereby to regulate the specic temperature at which said switch is operated.

5. A temperature controlling device comprising a mounting having an externally threaded upstanding embossment thereon, a pair of essentially rigid metallic elements having different coefficients of expansion, one of said elements being fastened at its upper end to said mounting and fastened to the other of said elements at the lower end thereof, the upper terminal portion of said other element being journaled for sliding movement in said mounting, a support having an annular base portion threaded on said embossment, a micro-switch carried by said support, and an elongated flexible and inherently resilient metallic strip mounted on the support in front of said switch, said strip being normally fastened at one end to the support, being longitudinally arched in the direction of said switch and being operable by thermal expansion movement of said slidable element to aotuate said switch.

6. A temperature-controlling device comprising a micro-switch, an elongated, flexible and inherently resilient metallic strip mounted in front and longitudinally arched only slightly from a straight rectilinear condition and in the direction of the switch and operable to actuate the switch by flexure thereof as a result of pressure imposed longitudinally thereagainst, temperature-sensitive means arranged to impose longitudinal pressure against said strip in response to temperature changes, and adjustable means for effecting relative movement between the strip and said temperature-sensitive means to regulate the specific temperature at which said strip operates said switch.

CLYDE C. DE WITT.

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

UNITED STATES PATENTS Number Name Date 1,859,605 Schaefer May 24, 1932 2,033,417 Dezotell Mar. 10, 1936 2,185,623 Beam Jan. 2, 1940 2,270,738 Lightfoot Jan. 20, 1942

Images