US3194074A

US3194074A - Thermally-operated control means

Info

Publication number: US3194074A
Authority: US
Inventors: Maynard E Anderson; Chapa John; Melvin W Polkinghorn
Original assignee: American Radiator and Standard Sanitary Corp
Current assignee: American Radiator and Standard Sanitary Corp
Priority date: 1961-11-16
Filing date: 1961-11-16
Publication date: 1965-07-13
Anticipated expiration: 1982-07-13
Also published as: GB998050A; FR1340422A

Description

United States Patent 3,194,074 THERMALLY-OPERATED CONTROL MEAN Maynard E. Anderson and John Chapa, Birmingham, and Melvin W. Polhinghorn, Livonia, Mich, assignors to American Radiator 8: Standard Sanitary (Iorporatiou, New York, N.Y., a corporation of Delaware Filed Nov. 16, 196i, Ser. No. 152,723 8 Claims. (53*. 73363) This invention relates to thermally-operated control devices, as for example electric switches and fluid valves. The invention, among its features, includes the use of a recently developed crystalline material comprised of manganese, chromium and antimony, said material having the unusual property of having little or no dimensional change in a low temperature range, but undergoing a substantial dimensional change per unit temperature change in a higher transition temperature range. The sharp nature of the dimensional change makes the material partic ularly advantageous as an operator for varioustherinally actuated control devices, particularly control devices which are required to have snap-action in response to small temperature change.

One object of the present invention is to provide improved control devices which utilize the advantageous characteristics of the aforementioned manganese-chromium-antimony compound.

Another object of the invention is to provide a thermally actuated control device which is operated by a relatively small temperature change.

A further object of the invention is to provide a thermally operated control device which can easily be manufactured to operate at precise temperatures and which will retain its manufactured operating characteristics after prolonged service.

Other objects of this invention will appear from the following description and appended claims, reference being had to the accompanying drawings forming .a part of this specification wherein like reference characters designate corresponding parts in the several views.

In the drawings:

FIGURE 1 is a view of one embodiment of the invention with parts thereof shown in section;

FIG. 2 is a view partly in section of a second embodiment of the invention;

FIG. 3 is a sectional view through a third embodiment of the invention;

FIG. 4 is a sectional view taken on line 44 in FIG. 3;

FIG. 5 is a right end elevational view of the FIG. 3 embodiment; and

FIG. 6 is a sectional view through another embodiment of the invention.

Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways, Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Referring to FIG. 1, there is shown a thermally-operated electrical switch comprising a conventional snap action switch housing having mounting holes 12, a tubular cylindrical guide structure 14, and a switch-operating plunger 16 slidably disposed within the guide structure. The .switch'housing .10 may have any suitable form of snap action'switch blade therein, as for example a blade constructed as shown in U.S. Patent 2,669,618. -Preferab'ly the switch is made so that only a relatively small movement of plunger 16, as for example .0005 inch, is required to actuate the switch.

For plunger actuation purposes there is provided a thermally responsive power means comprising a fixed tubular sleeve element 18 and a slidable cylindrical rod element 20. Element 18 may be constructed of any suitable material which undergoes negligibledimensional change per unit temperature change, while element 20 is preferably formed of a crystalline material having the formula 'Mn Cr Sb ln where 0.025x0.20 and og goos According to an article entitled Evidence for an Antiferromagnetic-Ferrimagnetic Transition in Cr-Modified Mn Sb appearing at pages 509 through 511 in Physical Review Letters, volume 4, Number 10, issued May 15, 1960, the indium in the compound acts principally to retend the precipitation of Mn Sb and does not otherwise affect the characteristics of the compound. It is therefore contemplated that the compound can be employed without the indium. The manganese-chromium-antimony material is advantageous in that in certain temperature ranges it experiences a relatively large dimensional change per unit temperature change. The temperature range in which the large dimensional change occurs may be varied by varying the chromium concentration within the limits above specified.

One crystalline material within the above specified composition range experiences a relatively small linear dimensional change of approximately .001 percent per degree until the temperature reaches a transition value of approximately C., whereupon the material then undergoes a linear dimensional change of approximately .2 percent during the next five degree temperature rise. By varying the chromium concentration in the compound the transition point can be lowered from the 100 C. value. It can be seen that the material has negligible linear expansion per unit temperature change below its transition temperature but has substantial linear expansion of about .04 percent per degree in its transition temperature range so that it can be advantageously used as the material for element 20. In an actual construction wherein plunger 16 requires a movement of .0005 inch for actuation of the switch blade,-elernent 2-0 may have a length of approximately one inch, in which case the switch is actuated by a temperature change of one or two change per unit temperature change since element 20 has.

sufficicut expansion properties in its transition temperature range to provide a satisfactory net movement. Thus, operation of the control device of this invention depends primarily on the characteristics of element 20, which operation is distinct from the usual operation of prior art devices which depended on the differential expansion characteristics of two telescoped elements, each having a relatively small thermal expansion characteristic.

In order for the FIG. 1 device to properly operate with snap action, element 18 must be adjusted on tubular guide 14 so that the high expansion period for element 20 occurs when plunger 16 is being actuated. Calibration may be accomplished by maintaining element 20 at the actuation temperature, mechanically forcing sleeve 18 onto tu Ibular guide structure 14 as a press fit, and halting the press fit movement when plunger 16 is actuated. With this arrangement the plunger 16 will thereafter always be actuated during the period when element 20 is undergoing its sharp increasein linear dimension.

Referring now to the FIG. 2 construction, tubular ele ment 18 thereof enjoys a non-adjustable press fit on tubular guide structure 14, and screw 22 is threaded into the enlargement 24 of element 18. Calibration of the device may be accomplished by holding element 20 at the desired actuation temperature and turning screw 22 until plunger 16 is operated. After calibration the FIG. 2 device operates in the same manner as the FIG. 1 device.

The embodiment of the invention shown in M68, 3, 4 and 5 comprises a rigid frame 26 having two arms 23 and St). The portions of the arms adjacent their free ends are notched, asat 31, to form fulcrum areas for the oppositely facing edges and 34 of the resilient lade As best shown in HG. 4, blade 36 is provided with an elongated cut away area 38 which defines two longitudinally extending blade arms 4% and 42 and two facing blade edges and 4d. Elongated arm portions ill 42 are interconnected by a raised bridge portion which, as shown in FIG. 3, engages the plunger 5b of a conventional snap action switch housing 52. The raised nature of bridge 4-8 provides a free space between blade edges and for reception of the thermally responsive power means generally designated by numeral 5 The illustrated power means comprises a sleeve-like support element 56 and a rod-like thermal expansion element 2t) preferably formed of the chromium-manganese-antimony material previously specified.

The right end of element Zt'l abuts against the right end wall of element 5-6, and the left end of element 2% abuts against a slidable plug 58 which retained against rotary motion by means of a ltey-lilte extension to operating in a slot 62 which is formed in the enlarged end portion of element 5d. Plug 53 is of hollow construction and threadedly accommodates a screw 64, the left end of which is notched to have fulcrum engagement with the aforementioned edge 46 of blade 35. Members 53 and together function as a slack take-up device for ensuring that the opposite extremities of power means 54 will operatively engage the blade edges and 4d and will cause a deflection of blade 36 when element Ed is undergoing its period of high expansion.

Blade 36 is preferably formed with a slight downward bow as shown, and is installed so that its edges 32 and are spaced slightly away from the adjacent surface areas of arms 28 and 3d. As a result, any tendency of power means 54 to expand will cause the blade to move towar a flattened condition, with consequent upward movement of bridge In its PK}. 3 position power means 54 is in a low temperature COI'l't'llfiBCl condition wherein blade 3-5 is bowed downwardly and plunger 56 is extended from the switch housing 52. Raising of the ambient temperature through its transition temperature range causes element to undergo a substantial linear expansion, whereupon blade 36 moves toward a flattened condition with the central bridge portion 43 of the blade moving upwardly to thus actuate plunger 59.

The FIG. 3 construction is advantageous in that a relatively small linear dimensional change of element 21? results in a relatively large flexing of blade 3%; thus a switch 52 having a relatively long plunger operating stroke can be employed. Such long stroke switches are less expensive than the switches required in the PEG. 1 and FIG. 2 constructions wherein small plunger motions are relied on to actuate the switch blades.

Because the dimensional change per unit temperature change for element 2% has a relatively great effect on plunger 5% any undesired tolerance variations in the axial dimension of the thermally responsive power means 54 or blade 36 will have a magnified error-producing tendency. However, adjustment structure 64 may be turned to properly calibrate the construction in spite of such manufacturing tolerance variations.

The FIG. 6 embodiment comprises a support structure having a cylindrical side wall "ill, a radial wall '72, and a tubular sleeve-like wall 74. Disposed within the support structure is a rod element 2% preferably formed of the aforementioned manganese-chromium-antimony material. The upper end of element engages the bottom wall portion '76 of a cup-shaped thrust element 78. The knife edge portion Ell of the thrust element engages a curved disc 82 on an annular line of contact disposed inwardly of the annular fulcrum line of contact 34 for the curved disc. is preferably not importer-ate; instead it is preferably formed with radial notches extending inwardly from its periphery so that may better mechanically expand or breathe when it is axially actuated by rod 2b. In operation, thermal expansion of element 29 causes thrust element '18 to push disc 32 upwardly from its deeply bowed condition toward but not necessarily to a flat condition (not shown).

The on tral portion of disc 32 en ages the operating movement of rod produces a magnified movement of plunger fill. in this way a relatively small length of material 26 may be used to actuate the conventional snap switch which requires approximately .005 inch of plunger stroke for actuation. FIG. 6 is semi-schematic in character, and it is contemplated that suitable adjustment devices (not shown) may be incorporated in commercial forms of the device to insure that element 253 will undergo its period of highest expansion when disc 82 is being operated.

Tie drawings show the invention as incorporated in therrnaliy operated electric switci e it is contemplated, however, that the invention in certain of its aspects can e incorporated in other thermally operated control devices such as fluid valves and electrical potentiometer devices, this being particularly the case with respect to the use of the chrorniunvmanganese-antimony material as a thermally responsive power means. lt will be understood that variations in construction and arrangement may be resorted to as come within the scope of the appended claims.

We claim:

In combination, a thermally responsive power means, including a support structure having a negligible coelhcient of thermal expansion, and a thermal lenient carried by said support structure; said thermal element being formed of a material comprising the compound lvin Cr Sb ln wr ere 9.8255935020 and Oydfli n combination thermally responsive power means,

a including a support structure having a negligible coeilicient of therml expansion, and a thermal element carried by said upport struesre; said thermal element being formed of a material comprising the compound Mn Cr;,Sb where 0.025X0.2Q and Cyg lfii 3. The combination of claim 2 wherein the thermal element comprises an eion ated rod formed of the aforementioned material, the support structure comprises a sleeve-like support structure su 'onnding said rod in intimate thermal engagement therewith along a substantial portion or the rod length.

i. In combination, a thermally responsive power m ans, comprising an elongated support st" ture having a negligible dimensional ch age p unit temperature change, and an elongated rot. carried thereby; said rod being formed of a material which in a low temperature range has a dimensional change per urlt temperat e change on the order of .fiill percent per degree and which in a higher temperature range experiences a dimensional change on the order of .04 percent per degree.

5. In combination, an elongated flexible blade having two facing edges arra= ged so that a longitudinal force acting thereagainst is eicctive to flex the blade in a direc- 5 compound Mn Cr Sb Where 0.025x0.20 and OyilOS.

7. The combination of claim 5 wherein the power means is adjustable in length independently of temperature to take up potential slack between the power means I and the facing edges of the blade.

8. In combination, a curved disc; support means engaging the peripheral edge of said disc to locate same for axial movement of its central area; and thermally responsive power means for operating said curved disc, includ ing a thrust element having an operating line of contact With the disc located radially inwardly from its peripheral edge, a substantially non-expansihle tube rigid With the support means and disposed on the line of action of the thrust element, and a thermal expansion rod disposed Within the tube in pressure relation With the thrust element; said expansion rod being formed of a material comprising the compound Mn Cr Sb where 0.025 x020 and 0. .y0.05.

References Cited by the Examiner UNlTED STATES PATENTS OTHER REFERENCES Swoboda et al.: Evidence for an Antiferromagnetic-Ferrimagnetic Transition in Cr-Modified M11 51), Physical Review Letters, vol. 4, No. 10, May 15, 1960, pages 509-511. Pages 5 09-511 relied on.

ISAAC LISANN, Primary Examiner.

20 B. A. GELHEANY, P. K. SCHAEFER, Examiners.

Claims

0.025<X<0.20 AND 0<Y<0.05
1. IN COMBINATION, A THERMALLY RESPONSIVE POWER MEANS, INCLUDING A SUPPORT STRUCTURE HAVING A NEGLIGIBLE COEFFICIENT OF THERMAL EXPANSION, AND A THERMAL ELEMENT CARRIED BY SAID SUPPORT STRUCTURE; SAID THERMAL ELEMENT BEING FORMED OF A MATERIAL COMPRISING THE COMPOUND MN(2-X)CR(X)SB(1-Y)IN(Y)