US2403895A - Thermostatic metal - Google Patents

Description

` M? Ey 346 c. F. ALBAN ETAL 2,403,895

THERMOSTATIC METAL Filed Feb. 2s, 1942 2 sheets-sheet 1 J'O /50 35,0 450 o 650 TEM/D. o CENT/@F1905 C'arence Hfoneys.

July 16, 1946. y c. F. ALBAN ErAL 2,403,895

THERMOSTATIC METAL Filed Feb. 2a; 1942 2 sheets-sheet 2 Manganese Copper:- N/cke/ 6V/orf INV NTOR Va/ence' Hian BY 5am @y 22 00d,

Hfen/reqs- Patented July 16, 1946 Clarence F. Alban, Pontiac, and Stanley R. Hood, Birmingham, `Mich., assignors to W. M. Chace Company, Michigan Detroit, Mich., `a 'corporation of Application February 28, 1942, Serial No. 432,832

2 Claims.

This invention relates to thermostatic metal. 'Ihis application is a continuation-impart of our application Serial No. 315,130, iiled January 22, 1940, now abandoned.

Itis a common expedient in temperature responsive mechanisms and controls to utilize the diiference in expansion of two metals or alloys to effect mechanical movement. The mechanical movement is usually vobtained by usingone metal having a vhigh coeircient of expansion and another metal having a low coeliicient of expansion which are either fused together to form thermostatic bimetal or mechanically arranged as, for example, a rod within a tube. The degree of movement obtained and the amount of work produced depends in general on three factors: the strength of the materials used, the temperalture chang and the difference in expansion coefficients of the two metals.

The following metals and alloys having high coefficients ofi-expansion are commonly used in temperature responsive mechanisms and controls: copper, brass (60% copper, 40% zinc) and iron-nickel alloys to` which may be added chromium, for example, .an alloy containing 22% nickel, 3% chromium, 75% iron. Upto the present no alloy has ben developed which has both an expansionrate higher than a 60-40` brass and good strengthcharacteristics at temperatures as high as 500 C. For a` low expansive element iron-nickel alloys containing between 35% and 50% 'nickel are commonly used. Invar (36% nickel, 64% iron) is one such alloy commonly used for the low expansive element. The low expansive element `can also be made from an alloy of 17% chromium, `4% aluminum, balance iron.

It is an object of this invention toproduce a laminated thermostatic metal which has a higher electrical resistivity and which will produce a remarkably lhigher strain energy per degree temperature difference than any other known thermosta'tic metal.

This invention also contemplates a laminated thermostatic metal having an appreciably higher deilection rate than any other known thermo- Vstatic metal.

jThis object has been vachieved by utilizing a binary yalloy of manganese and copper or a ternary alloy of manganese, copper andone o-f the iron group metals, as the high expanding lamina of the thermostatic metal. Manganese, both commercially pure .manganese and electrolytic manganese, has properties which make it desirable as the high expanding lamina of thermostatic metal, such as a Vhigh melting point, a high coefficient of expansion 4and high strength at high temperatures, but since manganese Ais brittle it alone cannot be used for `the high expanding lamina of thermostatic metal. Because of `this manganese is alloyed with copper which produces a ductile alloy having a high melting point, high strength at high temperatures and a remarkably vhigher coeiiicient of expansion than either Vpure manganese or copper and a remarkably higher electrical resistivity.

According to Mechanical Engineers Handbook by Lionel S. Marks, fourth edition, 1941, page 624, manganese has a linear coeiiicient of thermal expansion per degree F. at about 70 F. of 12.8 10-5,nickel 7.2 1'0T6, and copper 9.12X'l0r6. This remarkable increase .in -thermal expansion of the Aalloy in contrast to manganese is remarkably demonstrated, `by way of example, if one considers the coeflicient of expansion of an alloy consisting of 72% manganese, 18% copper, and 10% nickel. According to the law of mixtures, one would expect a low linear coefficient of expansion forthis alloy 0f 11.57 10-6 per degree F. at about '70 F. Actually one gets the remarkably high linear coefficient `of expansion of l5.5 l06. Because of this property of the manganese alloy, the thermostatic metal, which is the subject of this invention, Vhas a remarkably high deflection rate.

In fabricating the high expanding lamina the best analysis having the highest strength, highest expansion rate and highest .electrical `resistivity is a ternary alloy consisting of 72% Amanganese, 18% copper and 10% nickel. Although the above is the preferred analysis, other excellent alloys can be obtained for use as the high expanding lamina wherein the manganese ranges from `60% to 85% of thealloy by weight, `wherein the copper ranges from 10% to `35% by weight of the alloy, and wherein the nickel ranges -from 5% to 30% by weight oi the alloy. yAlthough the above are the preferred ranges Yof the constituents of the alloy, these ranges can be widened somewhat to include other analyses which produce a material much 'better suited as vthe high expanding lamina of thermostatic `metal than other known materials. In this enlarged range the constituents by weight would comprise the 'following percentages of the alloy: manganese 15% t0 95%, copper 85% to 5%, nickel 0% to 30%. Cobalt or iron can be substituted Wholly or in part for .nickel 1in the ranges above specilied. However, nickel is preferred over either cobalt or iron. Nickel when alloyed with copper 3 and manganese raises the elastic limit of the alloy and improves the physical properties in general of the alloy. The nickel also gives the alloy stability, that is, causes the alloy upon cooling One of the best thermostatic bimetals available on the market is known as Chace #2400. The Chace #2400 bimetal has a low side of Invar (36% nickel, balance iron) and a high expandto travel along the same curve that it traverses 5 ing side of 22% nickel, 3% chromium, balance While being heated. In other Words, nickel iron by weight. It is interesting to compare the causes the alloy when its expansion and contrac'- 2400 thermostatic bimetal with the herein pretion characteristics, due to thermal change, are ierred bimetal; namely, that having a low explotted on a graph, to travel along the same panding lamina of Invar and a high expanding curve upon a fall in temperature that it travlamina of 72% manganese, 18% Copper, 10% eled upon a corresponding rise in temperature. Y nickel by weight. A very careful and exhaustive Manganese having a purity of 99.98% can be study of these two bizmetals has been made which produced electrolytically. So-called commershows that the thermostatic metal, which is the cially pure manganese usually contains about 3% subject of this invention, is surprisingly superior to 5% of impurities, such as iron, carbon, alu- 15 to the best of the known bimetals. A summary minum and silicon. In the above analyses it is of this study is set forth below: preferred to use electrolytically pure manganese throughout the entire range. However, commer- Advantage-gained through use cially pure manganese can be used up to a point of?? Mn, tig?, cit a12% gril M f at which the commercially pure manganese ap- 2o tafggrglormggtauc anne Se proximates about 35% of the alloy. Where the bimetal Y f manganese comprises more than 35% of the alloy, then to avoid brittleness it is essential that all y 50% constant temperature difference: amounts of manganese over about 35% of the 1' Smm energy Identcalslze' alloy should be electrolytically pure manganese. 58% Constant temperature dierence:

The following expansion data is characteristic 2' Smm energy Identcalweght' Of the OHOWIlg allOYSZ Constant electrical current: Identi- 3. Temperature rlse cel size.

X10-e orX10-t X10-o X10-a 156% Constant eletrical current: Identi- 4. Strain energy cal slze. Tnp" 23% Mn,4% 27% Mn, 4% 32% Mn, 5% 9% Mn,5% 30 Fe, balance Fe, bsleuee Ni, 5% Fey Ni, balance 170% Constant electrical current: Identi- Cu Cu balance Cu Cu 5. Strain energy cal welght.

Strain energy is the force developed by restrain- 3002221: 224 2310 2413 2dr 35 ing thermal deilection of the rbimetal and is the 400 23'4 23-9 25-2 22-2 measure of the work which the bimetal cando.

TheV above summary showsk (1) On the basis of Expansion data and representative resistance a given temperature difference for pieces of the data is herewith set forth of the below specified same size, the ratio of the strain energy availalloys: able through the use of the new manganese thermostatic bimetal and the 2400 bimetal is 1.5 to 1; Temperature range .Resistance (2) This relationship, as mentioned immediately Alloy gzfgsiggegfl; above in paragraph (l), for pieces of the same em.per degree C. foot at 20 C. Weight of the new manganese thermostatic bimeta1 and the 2400 bimetal is 1.58 to l. (3) The QSXHH 900 fact that the electrical resistivity of the new material is considerably higher than that of the older 28X1' 11140 #2400 results in an added advantage in those sexie- 1,140 cases where the temperature change is accom- ,IOXMH 950 plished from the passage of electric current. The ratio of the temperature diierentials of pieces of 38X10' 780 the same size of several materials when heated mms, at 20 Q 1,200 by the passage of the same quantity of electric `current will, in the general case where temperature difference 1s a linear function of heat input, The above described binary and ternary alleysa be proportional to the ratio of the electrical redue t0 their high coefficient 0f expansion and SiStiVity for the materials in question. It OllOWS high electrical resistance are Very useful in the then that-the ratio of the temperature rise of the fabrication of thermostatic metals, particularly new thermo-static bimetal '00 the #2400, when those thermostatic metals such as bimetal, tripieces 0f the Same Size are heated by the passage mel-,el and other plural laminae thermostatie of equal amounts of electric current is 1.308 to l. metals. In the fabrication of such thermostatic (4) The raf/i0 0f Strain energy 01 WOrk resulting metals a lamina of the above manganese alloy is from the passage 0f equal amounts 0f electric fused or Otherwise bonded to a lamine, of a current through pieces of the same size of the new metal 0ralloy having a, 10W coelcient of expam 65 manganese Inval' thermostatic bimetal and the Sion Such as Invar or nickel r0n alloys contain #2400 bimetal is 2.566 to l. (5) The relationship ing between 35% and 50% nickel. If desired, the mentioned directly above in paragraph (4) for low expansion lamine, een be made from e, terpieces of the new manganese Invar thermostatic nary alley of iron, nickel and titanium In such bimetal and the #2400 bimetal of identical Weight case thenickel content will range from 35% to 70 iS 2-70 t0 1- 50%, lelle titanium content from 1% to 4%J kand In the above described bimetal the difference the remainder iron" The preferred jr0n nicke1 between the COemCeIlS Of eXpallSOIl Of the high titanium alloy for the low side contains from 35% and 10W 'eXpal'ldng lamina@ iS greater than in to 42% nickel, about 2.5% titanium, and the those bimetals heretofore known. The advanremainder iron. tages of increasing the diierence in the expansion rates of the two laminae are evident, For example, where such bimetal is used in temperature responsive mechanisms and controls, for a given size of control element the deflection or strength of the element is increased compared with )a control element of other known bimetals of such given size, thus making the instrument or device in which it is used more positive or sensitive. Further, because of the high deection rate and strength of such bimetal, where a given combination of strength and deection is needed in a control element, smaller amounts can be used than is possible where the control element is made from other known bimetals, thus effecting a saving in the cost of the control element. Since this high electrical resistance bimetal has a higher deection rate than any other known bimetal, it lends itself to great utility in the manufacture of low amperage circuit breakers.

'Ihe thermostatic laminated metal which is the subject matter of this invention gives a greater work output for a given electrical input than those thermostatic laminated metals heretofore known. This is important, particularly in electrical devices where the electrical resistance of the thermostatic metal element is important. In such an electrical device Where a thermostatic element having a given electrical resistance and deflection is desired, it is necessary to use a relatively small piece of the heretofore known thermostatic metals. This was disadvantageous because such a small piece of thermostatic metal gave correspondingly small power. On the other hand in such an electrical device, due to the high electrical resistance of the instant thermostatic metal, to satisfy such given electrical resistance and deflection a piece of the instant thermostatic metal can be used which is larger than the usable piece of heretofore known thermostatic metals. Due to the fact that a relatively larger piece of the instant thermostatic metal can be used, such piece of thermostatic metal will give more power.

In the drawings:

Fig. 1 shows the temperature expansion coeiiicient data of two copper-manganese alloys compared with standard materials.

Fig. 2 shows a bimetal strip having a high expanding lamina of manganese, copper and nickel and a low expanding lamina of Invar. The two laminae are welded together.

Fig. 3 is an illustrative showing of a portion of a water heater, the burner of which is controlled by a tube and rod type thermostat.

The gas supply is admitted through pipe I into valve chamber 2 and passes through pipe 3 into the burner (not shown). The valve housing 2 is provided with a valve 4 pivoted as at 5 and backed up by a compression spring E which tends at all times to hold valve 4 in the closed position shown, thereby cutting off the ow of gas through pipe 3 to the burner. The hot Water tank is designated 1.

Valve 4 is controlled by a thermostat in the form of a tube 8 secured to the tank 1 as at 9 and a rod I0 mounted within the tube 8 and contacting the tube 8 at Il. Tube 8 is made of the above described high expansion alloy of manganese, copper and nickel. The rod I0 can be any suitlow expansion alloy such as Invar. In the position shown, the water in the tank is at the elevated temperature desired. As the temperature of the water in the tank 1 falls, tube 8 will contract thereby raising rod l0 which swings valve 4 about its pivot 5 thereby opening valve 4 and permitting gas to flow through line 3 to the heater. As the temperature of the water rises, rod 8 will expand thereby lowering rod I0 which permits spring 6 to close valve 4 and thereby stop the iiow of gas through line 3 to the heater.

We claim:

1. Thermostatic metal comprising a plurality of joined metallic laminations, one of said laminations having a relatively high coeicient of expansion and comprising an alloy of the following constituents by weight: manganese from 20% up to 50%, nickel 4% to 20%, balance substantially all copper; the other lamination having a relatively low coefcient of expansion.

2. In a device responsive to temperature changes to perform work or mechanical movement, a plurality of metallic members, one of said members having a relatively high linear coefficient of thermal expansion and comprising analloy of the following constituents by weight: manganese from 20% to 50%, nickel 4% to 20%, balance substantially all copper; the other member having a relatively low linear coefficient of thermal expansion and comprising essentially Invar, an alloy of iron and nickel.

CLARENCE F. ALBAN. STANLEY R. HOOD.

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