US2643825A - Thermostatic device - Google Patents

Description

June 30, 1953 D. F. DRow 2.6435825 THERMosTATIc DEVICE Filed Feb. 10.` 195o 2 sheets-sheet 1 INVENTOR. 00AM/o F 020W 2 Sheets-Sheet 2 D. F. DROW THERMOSTATIC DEVICE June 30, 1953 Filed Feb. 1o, 195o INVENTOR. 00A/mo F Deow Patented June 30, 1953 UNITED STATES PATENT oFFicE THERMOSTATIC DEVICE Donald F. Drow, Los Angeles, Calif., assignor, by mesne assignments, to Minneapolis-Honeywell Regulator Company, a corporation of Delaware Application February 10, 1950, Serial No. 143,555

'sive to and controlled by a pilot burner which is mounted in proximity to a so-called main burner -for ignition of the gas issuing from the main burner as the condition-responsive thermostat calls for heat. In vsuch an installation, safety of operation depends upon the existence of a iiame at the pilot burner when the operating thermostat turns on the gas to the main burner, so that the gas issuing from the main' burner will be properly ignited and not permitted to escape and accumulate in the appliance or room containing the appliance, to thereby create a hazardous and explosive condition. Accordingly, a so-called pilot safety valve is incorporated in the installation, including a gas valve positioned in the fuel line to the main burner and which functions 'to close this valve and thus shut oli fuel ow on failure or extinguishing of the pilot burner;

An object of the present invention is to provide a device of the character described which is constructed to withstand the high temperature to which it is continuously subjected in the re box of the heat appliance, Without deterioration of its ability to respond to temperature changes occurring on extinguishing of the pilot burner, so that the device will stand ever-ready to function throughout an indefinitely long period of time.

- Another object of the present invention is to provide a device of the character above which will automatically function both to open and clo-se a gas valve as the pilot burner is ignited and extinguished, respectively, thereby automatically providing for so-called safe lighting of the appliance without the use of any form of manual re-setting mechanism, in that gas ilow to the main burner is positively prevented after extinguishing of the pilot burner and until after the pilot burner is again ignited and properly functioning.

A further object of the invention is to provide a device of the character described which will be relatively fast cycling, thereby insuring a minimum delay in shutting off of fuel flow following extinguishing of the pilot burner, and also minimum delay in rre-establishing fueliiow afterre- CIK Figure 1.

ignition of the pilot burner, and in which the cyclingv operation may be conveniently and accurately adjustedto control the on and olfl times of the unit.

Still another object of the present invention Ais to provide a device of the character described 'having an improved snap: action mechanism and operating lOf assembly affording substantially greater valve displacement, thereby permitting the deletion of customary valve adjustments for insuring valve opening and at thev Sametime obtaining greater capacity. 4

Yet a further objectuof` the invention is to provide a device of the character above having an improved unitary mounting and assembly of the snap acting device, thermostat, and valve, and wherein this assembly and its operation is completely independent of the temperature and relative expansion or contraction of the valve body. Yet another object of the present invention is fto provide a deviceo-f the character described which is particularly designed for simplified lowcost construction, utilizing die cast body sections, aminimum machining of parts, and a general elimination of close tolerances in relatively moving parts, thereby obviating the danger of sticking or binding, with resultant failure of the device, when used with gases containing gummy substances or corrosive elements such as sulphur dioxide.

The invention possesses other objects and features of advantage, some of which, with the fcregoing, Will be set forth in the following description of the preferred form of the invention which is illustrated in the drawings accompanying and 'forming 'part of the `speciiication. It is to be understood, however, that variations in the show'- ing made by the same drawings and description may be adopted within the scope of the'invention as set forthV in the claims.

Referring to said drawings:

Figure l is a vertical cross-sectional view of a thermostatic device constructed in accordance with the present invention.

- .Figure 2 is a cross-sectional view of the device taken substantiallyon the plane of line 2 2 of Figure 1.y

Figure 3V is a cross-sectional view on asome- '.Whatfenlarged scale of a portion of the device taken substantially on the plane Ofiline 3f3 of Figure 4 is a cross-sectional view of the device taken substantially on the plane of line 4 4 of 'Figure 3.

Figure' isa perspective exploded View showing the parts and their respective relationships making up the clicker and valve assembly.

The thermostatic device of the present invention is illustrated in the accompanying drawing in an adaptation of such device to a pilot safety valve of the character above described. As will be clear from an understanding of the mechanism, variousessential parts of .the devicemay be used in other types of thermostatic devices, such as, for example, thermostats for controlling water temperature of an automatic gas fired water heater.

The device includes a casing 6 made up oflthree sections, l, 8 and 9, providinga valve body and dening an interior valve chamber I Ihavinginlet and discharge passages Iland .I3'iandia-valve seat I4 controlling the gas now through the chamber. In the design of the casing; the section 8 forms a central portion of the bodyiandis of generally tubular orm-having open upper and Y lower kends which are engaged andsealed .ofi by `thetop and bottom cover sections 1. .andhseal- .ing gaskets `I6 and I'I being positioned between flat contacting surfaces of these sections .andthe .assembly being clamped togetherin a. .rigid gasvvtight ^enclosure .by a screw IIlextendinginto the interior ofthe casing through anaperture I!!` in Y.the bottom cover Band threadedinto adepend- .ingilug 2I onthe-top coverl. Threaded tubular extensions or bosses v22 and 23 are formed on. the A.top and bottom covers 'l .and 9 forproviding the inlet and discharge passages I21and I3 and for connection to supply iand'discharge conduits 24 ,.and.26. ..-Also, the valve seat I4 is .formed inthe f bottom cover VSl in surrounding relation .to the -discharge passage I3.

The L casing construction asdescribed .and as will bemoreapparent with reference. to the parts-of the device, .has .been

specially designed for low-.cost die 'casting of the sections anda simple;rapid,.and yet highly eiTectiverattachment of the sections .todene a .gas-

tight body-with buttheuse cfa single attaching .Thermostatic operation ofthe deviceis obtained by means of arod-.and-tube type thermoi statincluding telescopic tube 2l andfrod 28 hav- .ing .diierent coefficients of thermalexpansion, connected lat .their endsr29 .and .3| .-to provide differentialmovementof their opposite ends-32 and 33 with temperature changes. As .here

opening 31 adapted to slidably receive .thersmooth cylindrical portion of a screwy38 having .amend portion 39 threaded intothe inner Yend33 tof the rod '23, ithe screw-extending axially .from Athe rod through the bearing openingi 3l and. provided with an enlarged headI 4I spaced inwardly Ain the chamber-.from .thexjbearing` member L36. .Carried on the screw 38 in abutment with its head 4 I -isra hub :member 42 having ra central kaperture for axial mountingon the'screw and which 'supports in an outer .peripheralgroove the inner..periph ery'43 of a concavo-convex, dish-shaped .snap

.ringmember'fAL `Themembery 4.4;,is preferably constructed -of lthin.l spr-ingwmaterial such as vappropriate spring steel used for this purpose and capable Of-providing an: over-center snap action concentric .knife- edged fulcrums 48 and 49 thereon into pressure contact with the outer periphery of the ring 44. The levers may be formed, as best shown in Figure 5, from sheet unstressed position as shown in Figure l. In

.IiLmounted through'an opening V62 in the arm metal stock with the several levers radiating outfwardfrom a ring-like center portion 5I having aY centraiopening -52.mounted on the screw 38 so as to-support the levers 41 symmetrically about -.the.centralzaxisof the assembly with the outer extremities of the lever-s contacting the outer periphery-46 of the ring member 44 on its normally concaveside. As will be seen from Figures l and 5, the fulcrum 49;on the stationary bearing member .3E surrounds the opposed fulcrum 48 on the". hub`42 so Athatupon movement of the. hub 142 inlthe direction ofr the member"36-the levers will .beswung againstthe outer .periphery of thering .member .44 in a direction tending to attenthe ring4 andeiect .snap action. Contra-wise,...on movement .of the hubV 42 away from the bearing .member 36 the levers will be swung awayirom the outer `periphery of the. ring membenthereby permitting. the latter .tosnapback toits original the construction of the ring memberfitsconcavoconvex deformity is suchas to cause the ringto snap overcenter as pressureisapplied .to-its inner ,and outer peripheries asA above 'described-butthe extent of its original curvatureissuch that the .ring will snap back to itsfnormal position as such pressure is released.

Asan important feature of the ipresentfconstruction, the ring member is formed-withfan integral army eXtension=53 which projects from the outer periphery46 of thering member tol provide an amplified, abrupt*snapactionmovement of the outer free end 54 of the. arm A,uponsnap action of thering Ymember as above described. In the present construction, the-arm 53 .is bent fromfthefgeneral plane of the ring membepso'as .to lie `atl substantially Aright angles thereto;.with

the outer .end of the.` armin opposed relation to -the-valve seat 44. The. construction is alsosuch that upon snapping of ;the;ring,bythelevers 41 -the free-.end of the arm will be abruptly swung .in the direction of .the valve seat and upon reversexsnap action V-of'the ring to its normal unstressed position ther arm end will be swung away .f rom the valve seat.

In the present deviceand as an important feature thereofyvalve jsmounted directly on the .outer end 54 of `the arm and is carried `lthereby `for movement into and out of engagement with v the valve seatl. The valve construction-and its .mountingonzthe arm is seen best fromFigures 3 land 5. `The Valve body is here composed of a flat disc washer 5Irigidlysecured to the head end 58 uffa-screw 59 threaded into a sleeve-type nut end'll. A valve disca ofsuitable compressible andsealing-.material such. as rubber; neoprene or tained on Ythe arm by an enlarged head-end64 of the'nut at one .sideof .thearm 54 and a spring .nation of movement.

retainer washerl 66 at the opposite side of the arm, and supported on a shoulder 61 on the nut.

Normally, the valve assembly is urged to a closed vpassage l2. It is important to note that the action of this spring is to constantly urge the valve to a lpassage-closing position, so that in the event of a failure of the device for any reason other than failure o-f spring 68, the fuel flow will be lpositively shut off.

Since an abundant movement is available at the outer end 54 of the arm for the purposes desired, a limited lost motion connection between the arm and valve is preferred in order to obtain a clean snap movement oi the valve without grad- 'o accomplish this, the spring retainer washer S5 is supported on its shoulder t1 at a suiicient distance from the head end @4 of the nut so as to .permit any graduation of movement of the arm occurring while the snap ring is displaced to and from its critical snap acting positions, to take place between the retainer washer and the head. rIhe threading or" the screw 59 into the sleeve nut 6l permits an easy and accurate initial setting oi the valve, and preferably the shank of the screw is split and spread as illustrated to :provide a tight nt to v- -maintain the initial setting, Due to the large amplitude of movementat the outer end of the arm, the initial setting of the valve is not critical, and full valve opening and maximum fuel. now is at all times provided.

As another -feature .of the present construction, the rotative position of the snap ring llt to mainw ,tain proper alignment of the valve and seat is insured and retained by utilizingthe screw i8 as a positive guide for the arm. `As will be seen kfrom Figures 1, 2 and 5, the arm 53 is lprovided with a guide opening 'H intermediate its length through which is inserted the shank of the casing assembly screw I8, the axis of the screw being generally Iparallel to the axis of movement of the valve.

As hereinabove noted, the device herein disclosed is particularly designed for use with a pilot burner, and preferably such burner is mounted yon the casing for insuring a precise relationship between the thermostat 21 and the pilot burner.

-As here shown, a pilot oriiice fitting i2 is threaded into the side wall of the casing section 8 adjacent to the thermostat tube 27 and in generally parallel relation thereto. A conventional type pilot burner tube i3 is here tted over the outer end of the fitting 'l2 and is formed with a .primary air opening 14 adjacent the aperture discharge of the fitting to provide a usual Bunsen burner construction. The tube 'I3 extends axially from the fitting 'i2 in underlying parallel relation to the thermostat tube 21 and then curves upwardly at its outer end 'IS to project somewhat above the -outer end of the thermostat into proximity to the vformed in a boss 82 on the side of the section. vAn intake conduit for pilot gas may be Vsecured as here shownin the inlet opening 8| by a con-1 ventional fitting 84. Desirably, a needle type -valve 86 (see Figure 4) is provided in the ,passage 'I9 for regulating the gas flow to the pilot burner, and a removable plug 8l is provided in the wall of the section to permit access to the' head 88 of the valve, the latter being threadably mounted in the body for adjusting action, as shown in Figure 4.

` As will be seen from the foregoing, the thermostat tube end 32 and the associated inner end of the thermostat rod provide the sole means of sup'- port for the clicker or snap action assembly and the valve. Thus, a unitary thermostat, clicker and valve assembly is provided independent of the casing' of the unit. Accordingly, the operation of this assembly is independent of the temperature or relative expansion or contraction of the casing. Preferably, the tube 21 is constructed of a material having a relatively large coeiiicient of thermal expansion and at the same time being resistant to high operating temperatures. Certain stainless steels available in the market are quite satisfactory for this purpose. Some are capable of withstanding constant temperatures in excess of 1,000 F. without scaling or developing brittling grain growth or inner granular carbide precipitation, and have a coeii'lcient of thermal expansion of approximately 9.45 10-6 in. per degree F. The rod 28 may be made of invar steel or even cold rolled steel having a coeicient of expansion of approximately 6.'7 106 in. per degree F. Preferably, the rod 28 is madeof tubular construction throughout its length, or provided with an end bore over a majority of its length, las here shown, so as to reduce its mass and thereby render it more responsive to temperature changes. An over-all length of the tube and rod thermostat of about two and one-half inches is sumcient to provide adequate relative movement to operate` the device. VOf course, longer lengths of the rod and tube thermostat increase the amount of activating movement available. Up to about eight inches in length is more or Vless standard for water heater installations. Y

The assembly above described is thus capable of use in very high ambienttemperatures which would lpreclude the use of other types of safety pilots. It is also highly sensitive to temperature changes and can be constructed with a minimum cycling time. A setting of the snap action'mechanism for a iullv on and oi operating cycle of about twenty to thirtyseconds is preferred Iin order that minor variations in the pilot flame will not operate the device and yet the device will be rapidly responsive upon extinguishing or the pilot burner. The respective on and foff times in such a cycle can be set by adjusting the screw 38 controlling the tension and pre-setting of the clicker assembly. In the present construction, access to the head end 4I oi the screw is provided by a removable closure plug 39 threaded into the wall of section 8 in alignment with thev screw 38.

- Also, an opening 9! is :formed in the lug 2| in alignment with the screw and plug 89. On re,- moval of the plugr 89, a screwdriver or Allen wrench or the like (depending upon the type of socket formed in the screw head) may be insertedv erating cycle of twenty-four seconds, the device may be set to afford a 6 seconds on time andlS seconds ofi time, or any other" combination of ,.7 -,,onand olf times-'making uprthe =operating cycle. This adjustmentmay beieasily ymade'in thezeld vby first shutting o'ffthe :main gas lvalve .leading to the appliance.

:The-normal cold position ofthe device is illustrated in Figure 1,1vvhereinrthe valve-56 is in shut- 01T position. Toplacerthe device inoperation, the pilot burner is ignited and-heat-is-applied to the thermostat tube 21, causing its expansion. `As `the tube 21 expands, the hub 42 is displaced to- `wardthe bearing member 36, fulcruming the levers-41 vagainst the outer periphery of the snap `ring and causing it to snap to an over-center position, thereby-swinging the integral arm 43 away from'valve seat I4, and opening the valve. If thereafter the pilot-burnerbecomes extinguished, 'theucooling of the thermostat tube 21 provides a reversecoperation Nwherein the snap ring returns toits unstressed position, vthereby abruptly displacing the valve to closed position, 'as illustrated iriFigure l. -Since the device functions automatically toopen'and close the valve as `above described; depending upon the presence or absence of -pilot flame, noV manual re-setting mechanism -is requiredas in the case of other types of pilot safety'valves. Also, due to this automatic open- 'ingiand closing action, the unit inherently provides yso-calledsafe lighting, in that no ow of gas to theV mainV burner is permitted while the pilot burner .isfbeing ignited and until after `the pilot burner is in proper operation.

'I claim:

1.1'A1thermostatic device comprising,- a casing formed with aninterior chamber having inlet and Adischarge openings and provided with a valve 'seat between said openings, a concavo-convex ring formed to snap through a center position in said chamber,.a hub member supporting the inner periphery of -said ring, means engaging the'outer periphery of lsaid ring on the concave side to afford snap action of said ring upon displacement relative tosaid hub member, thermostat elements `having different coefficients of thermal expansion connected to said hub member and means for effecting relative displacement thereof and snap action of said ring means with temperature changes, an arm formed integrally with said ring and extendingfrom the outer periphery thereof, thetouter end of said arm being' mounted in `juxtaposition to said'seat and being abruptly displaced to and from'said seat uponv snap action of said ring, a valve mounted for movementV to and from said seat and actuated by the outer end of said armyand guide means "carried*by1s`aid casingand coacting with said arm to maintain alignment of said: arm and valve seat.

2.A thermostatic device-'comprising a casing `forrnedwith an interior chamber having inlet and discharge openings and provided with a valve seat between said openings, a dish shaped mem- 'ber having an over-center snap action mounted in said chamber, opposed and concentric means engaging said member at radially spaced posi- `tions for displacing said member intoand out o its-over-center position upon relative movement ofsaid means, thermostat means connected to said first means for displacing said first means and actuating said member in accordance with temperature changes, an arm formed integrally :withl'said dish shaped member and extending from the outer periphery thereof, the outer end `of said arm being arranged in juxtaposition to said valve seat and being abruptly displaced upon snap action of said member to and from said seat, a valve mounted for movement to and from lsaid :seat-'and actuated by "the outer'end-of--said arm, said arm being formed intermediate fits length f with4 an opening, .and meansA carried -by .said casing and extending through said-opening to prevent V'rotative displacement of saidarm away from said valve seat.

3. A thermostaticdevice comprisingacasing Yformed withan interior chamber and a valveseat therein, -a dish shaped vmember having anfoverlcentersnap actionmounted in said chamber with the planeof said member substantially perpendicular to theV plane of said valve seat, Yopposed and concentric means engaging said-'memberlat radially spaced positions for "displacing said member into and out of itsover-center position -uponA relative movement of'said means, thermo- `stat means connected to -said rst-meansfifor effecting relative displacement thereof and actuation of said .member in accordance ,with temperature changedfan arm formedintegrallywith said dish shapedmember'and extending from'the .nected at one end to :providefdifferential movement of their opposite ends with temperature changes, a bearing member secured to the-'last mentioned end :of said outer Amember :and concentrically supporting said `inner L member "for relative longitudinal movement, screw y=means carried Vby said innerrmember and-providedlwith a hub in opposedposition to said bearing. member, a dish shaped ring formed to snap Sthrougha center position and mounted on said hub Vwith vthe inner periphery of Ysaid ring lsupported thereby in` concentricity with said bearing member, a plurality of `radially extending levers mounted between said hub and bearing member and displaced thereby against the outer'peripheryof said ring to effect snap actionvthereof, an arm formed integrally with said ring and extending from the outer periphery thereof, `the-outer end of said arm being abruptly displaced upon snap action of said ring, and mea-ns, adapted to `be ithermostaticallyoperated connected to -and actuated by the outer end of: said arm.

' 5.. A Athermostatic device comprising, inner and outer -telescopically arranged members of :different coeflicients of thermal expansion connected Vat one end to provide diierentiation of movement-of their opposite ends with .temperature changes, a bearing member secured to'the last mentioned end of said outermembena screw slidably mounted for reciprocation in` said bearing member concentrically of said outer member and threaded into the adjacentfend of said inner member, a hub carried by the outerend ofsaid screw in opposed position to said bearing member, a dish shaped ring formed to'l snap through a center position mounted on saidA hubwith'zthe inner periphery of said ring supported by said hub in concentricity with said bearing member, a plurality of radially extending levers mounted between said `hubzand bearing member and'displaced thereby against .the outer periphery of said ring to. eiect snap laction V,of l saidsringzupon displaced upon snap action of said ring, and

means adapted to be thermostatically operated connected to and actuated by the outer end of said arm.

6. A thermostatic device comprising, a casing formed of a plurality of sections and providing an interior chamber and a valve seat therein, a dish shaped member having an over-center snap action mounted in said chamber, opposed and concentric means engaging said member for overcenter actuation thereof, thermostatmeans connected to said rst means for effecting displacement thereof and actuation of said member in accordance with temperature changes, an arm formed integrally with said dish shaped member and extending from the outer periphery thereof, the outer end of said arm being abruptly displaced upon snap action of said member, means adapted to be thermostatically operated actuated by the outer end of said arm, said arm being formed with an opening intermediate its length, and a member engaging said sections for clamping said casing together and being formed with a portion extending through said chamber and passing through said opening in said arm in alignment with the direction of displacement of said arm to provide a guide for maintaining alignment of said outer end of said arm with said last named means. t

7. A thermostatic device comprising, a casing formed of a plurality of sections and providing 10 named member end, a screw slidably mounted for reciprocation in said bearing member with the head end of said screw in said chamber and the opposite end threaded to the adjacent end of` said inner member, a hub carried by said screw at the head end thereof in opposed position to y said bearing member, a dish shaped ring formed to snap through a Icenter position mo-unted at its inner periphery on said hub, levers mounted beftween said hub and bearing member and displaced thereb-y against said ring to effect snap,v

action thereof, an arm formed integrally with said ring and extending therefrom substantially perpendicular to the plane of said ring with the outer end of said arm in juxtaposition to said seat, a valve carried by said arm end for movement to and from said seat, a helical spring normally urging said valve to said seat and mounted with its axis extending across the axis of said screw in spaced relation to the head end thereof, a removable part for said casing substantially aligned with said screw axis affording access through the coils of said spring to the head end of said screw for adjustment of the relative positions of said -hub and bearing member.

9. A thermostatic device comprising, inner and outer telescopi'cally arranged membersl having different co-eiiicients of thermal expansion pro'- viding a differential movement of adjacent ends of -said Vmembers with temperature changes,

- screw means carried by said inner member end and provided with a hub, an overcenter snapacting ring member mounted on said hub for movement therewith, means mounted in fixed an interior chamber and a valve seat therein, a v

dish shaped member having an over-center snap action mounted in said Ichamber with the plane of said member substantially perpendicular to the plane of said valve seat, opposed and concentric means engaging said member for overcenter actuation thereof, thermostat means connected to said rst means for effecting displacement thereof and actuation of said member in accordance with temperature changes, an arm formed integrally with said dish shaped member and extending from the outer periphery thereof, said arm being bent from the plane of said dish shaped member to lie in a plane substantially perpendicular thereto and with the outer end of said arm in juxtaposition to said seat and being abruptly displaced to and from said seat upon snap action of said member, a valve carried by the outer end of said arm for movement to and from said seat, said arm being formed with an opening intermediate its length, and a screw member engaging said casing sec'- tions for clamping said casing together, said screw member extending into said chamber and passing through said opening in said arm to provide a guide for maintaining alignment of said valve with said seat.

8. A thermostatic device comprising, a casing formed of a plurality of sections and providing an interior chamber and a valve seat therein, a thermostat consisting of inner and outer telescopically arranged memibers of different coeiiicients of thermal expansion connected at one end to provide differential movement of their opposite ends with temperature changes, the last named end of said outer member being secured to and supported by said casing and extending into said chamber along an axis sub-- stantially perpendicular to the axis of said valve seat, a bearing member secured to said last relation to said vouter member end and engaging said ring member to provide snap action thereof upon relative movement of said hub, said screw means providing adjustable positioning of said hub relative to said last named means, and means kadapted to be thermostatically operated connected to and actuated by said ring member.

10. A thermostatic device comprising, a casing providing an interior chamber with a valve seat therein, inner and outer telescopically arranged members having different co-efcients of thermal expansion providing a differential movement of adjacent ends of said members with temperature changes, said outer member end being secured 'to said casing, screw means carried by said inner member end and projecting axially therefrom into said chamber and provided with a hub movable in said chamber in accordance with temperature changes, an overcenter snapring member mounted on said hub for movement therewith, means in said chamber providing a fixed support engaging said ring member concentrically to said hub to provide overcenter snap action of said ring member upon said movement of said hub, a valveconnected to said ring member and being abruptly displaced thereby to and from said seat, said screw means being formed with a tool engaging portion exposed in said chamber, and a removable part for said casing alfording access therethrough for engagement with said tool portion of said screw means for adjustingv the position of said hub relative to said fixed support means.

DONALD F'. DROW.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,901,881 Vaughn Mar. 21, 1933 2,084,982 Anderson et al. June 29, 1937 2,238,837 Vaughn et al Apr. 15, 1941

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