US2298110A - Thermostat - Google Patents

Description

Oct. 6, 1942. s. cRUM v 21,298,110 Y 4 THERMOSTAT I Filed April 11, 1940 Fig. 4-

v hmmkn?- Sephen.. Crum- Patented Octi `6., 1942 UNITED STATE THERMOSTAT stephen cram.. mnneipnua man.,

Regulator Minneapolis-Honeywell Minneapolis, Minn., a corporation of Delaware adgnor to4 Company.

Application April 11, 194s, serial No. 329,121

z claims. (ci. zar-1s) The present invention relates to a compensated condition responsive element, and more particularly to such an element, and the construction' thereof, which is compensated vfor angular movement.

Condition responsive devices, particularly biof metals having high expansion oeilcients, and the strips 2| and 23 have low coefcients.

It is a well known fact that bimetal helices expand and contract axially and wrap and unwrap in response to'temperature changes. It

is alsowell known that, up to a certain angle Ior metallic elements, are often wound into helices and utiliedv to rotate control devices upon changes temperature. Many devices cannot be readily adapted to the use of rotary motion, v and still others could not possibly use it.

An object of the present invention is to provide a simpliiied temperature responsive element for obtaining straight line motion.

Another object is to provide a compact elemen as set forth in the preceding object which is formed of bimetallic helices. A further object is to provide a plurality of suitably mounted bimetallic helices which are oppositely wound as to angular direction and exterior or interior position of the diierent metals of the bimetallic helices to thereby obtain a thermal element which will expand and contract axially and he' compensated `for rotary motion.

Other objects will be apparent in the accom- Y variation to which the helices I0 and ii are suh-y jected because cf this pitch, Vthere will befsubil will unwrap and elongate, thus moving the Y panying specification and the appended claims.

In the drawing: l

Fig. l is an elevational view of one form of my device, Fig. 2 is a view looking at the right-hand end .of Fig. 1,

Fig. 3 is an elevational view of a second form of my device, and v Fig. 4 is a view looking at the right-hand end of Fig. 3.

' .Referring now more in detail to the drawing. in Fig. 1A a bimetallic temperature responsive element for practical purposes is shown as com- ;prising bimetal helices generally indicated at III and Ii. The helices ili'and Il are fastened together at i2 by a rivet i3.' The helix it has a mounting end il which is provided with a screw hole i5 by which the entire element may be `mounted to a suitable support. The helix Il has a motion takeoi! end Il which has a screw hole l i1 which may receive ascrew to secure a suitable takeoil device. 1

The two helices Il andli are eachcomposed of two metals having dierent expansion coeiilcients. yAs shown in Fig. 2, the helix i! has an internal strip 2B and an external strip. 2i.

'I'he helix Ii has an external strip 22 and an internal strip 23. For purposes of illustration,

it may be assumed that the strips 2l and V22 are' pitch, the axial movementv is increased as -the pitch is increased.

YThe convolutions of -the are shown as being spaced from each other. In other words, the angle'of the. pitch of these convolutions is quite great. Upon a temperature stantial axial movement of these helices as -well las rotative or angular movement thereof.

.Asinning now that the device is suitably moimted by the mounting end il and there is a temperature rise towhichthe device is subjected. Because'the strip 20 has a higher coeilicient of expansion than' the strip 2i, the helix end I2 toward the right. Because the strip 22 has a higher coelclcnt oi expansion than strip 2l, the helix Ii will wrap up and shorten, thus moving the motion takeo end i6 toward the right. Therefore, because the ends joined at i2 were also moved toward the right by the helix il, the movement of both helices-lli and Il is added to eet a substantial axial movement of the end AII. When the helix Iii expands to move axially due to its right-hand wind, there is also.

an imwrapping rotation thereof. When the helix il contracts to move axially due to its lefthand wind. there -ls a wrapping rotation thereof.

-Hencaitissemthatthetwo helices Il an'd Il will rotate onposltely. By properly selecting 'the helices Il vand Il any eilective tationthereoi mi! be completely compensated.- with lthe re 14o suit that only axial movement will be taken ofi at the end il. Upon cooling, exactly the reverse o! the above dcribed action is eilected. It will be obvious thatthe siz'lps 20,22 and 2l, 23 could be reversed without altering the practical oper,-

# ation o! the .device except to reverse the movement.

Referring now to Fig. 3, La temperature responsive element is shown as comprising a righthand woimd bimetal helix 3 0 and a left-hand woimd bimetal helix Il. The helices-3l and Il are secured'together at n by a rivet 33. 'The helix Il has a molmting end 3l in which there is v a screw hole 3i which may receive a screw to suitably mount the -entire thermostatic element.A Thehelix has amotiontak'eoi! end 3i inwhich two helices in and n a hole 31 is provided to which a takeo device may be secured.

The helices 30 and 3| are each made of metals having different coefcients of expansion. Referring to Fig. 4, the diierent strips of metal I and 4| are clearly shown. For purposes of illustration, it may be assumed that the strips 40 are of high expansion material and the strips 4| have a low coeilicient of expansion.

Upon a temperature rise, the high expansion metal 40 will expand at a greater rate than the low expansion metal 4| to thereby cause the end 32 of the helix 3| to Wrap up and also to contract in length. The helix 30 is also adapted to have its high expansion strip on'the outside so that it also will contract when being heated. However, the strip 30 because it is right-hand wound,

whereas the strip 3| .is left-hand wound, will wrap up in the, opposite direction, and in an equal amount to which the helix 3| is rotated. Therefore, it is seen that an element is provided in which similar expansive metals are wound on the` exterior of both helices but the'two helices have right and left-hand wound convolutions to thereby compensatefthe angular rotations of each, thus leaving only the additive axial movement of each to move a device. It will be obvious that Aupon cooling of the entire sensitive element, just,the reverse of the above described action will be effected. It will also be understood that the sensitive metals, that is the high and low expansive metals, may be reversed in both of the helices without changing the mode of operation of the device.

' While I have shown two forms which my invention may take, it`wi11 be clearly understood that many modiiloations will occur to those skilled in the art. For example, it will be readily apparent that the elements could be formed from a singlejpiece of material rather than from two pieces secured together. Therefore I wish not to be limited by the forms shown and described but by the spirit of the appended claims.

I claim as my invention:

1. In a control element, in combination, a rst helicallyA wound bimetal adapted to expand and contract axially and rotate angularly upon a change in temperature, means for securing one end of said first bimetal to a support, a second helically wound bimetal also adapted to expand and contract axially and rotate angularly upon a change in temperature, Isaid rst and second bimetals being wound in opposite directions so that they will rotate oppositely in the same degree for a given change in temperature, said bimetals4 being in axial alignment one within. the other, one end of the second bimetal being secured to the free end of said rst bimetal Whereby the other end of said second bimetal will move in a straight line on temperature changes.

2. A device of the character described comprising, a first bimetal helix coiled in a right-hand direction having its high expansive metal on the outside to cause it to expand and contract axially and rotate angularly upon changes in temperature, a second bimetal helix coiled in a left-hand direction having its high expansivemetal on the inside to cause it to -expand and contract similarly to said rst bimetal but to rotate angularly in an opposite direction to a similar degree, one of said bimetals being arranged within the other bimetal, means securing said first and second bimetals together, mounting means at the distal end of said rst bimetal, and straight line motion takeoff securing means at the distal end of said second bimetal.

STEPHEN CRUM.

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