US3604729A

US3604729A - Mounting assembly for a thermostat

Info

Publication number: US3604729A
Application number: US795214*A
Authority: US
Inventors: Henry C Braucksiek; Lloyd R Warner; Wilbur F Jackson
Original assignee: Robertshaw Controls Co
Current assignee: Robertshaw Controls Co
Priority date: 1969-01-30
Filing date: 1969-01-30
Publication date: 1971-09-14
Anticipated expiration: 1988-09-14

Abstract

An assembly for mounting a thermostat on an appliance comprising a flanged member, a coupling member abutting the flanged member and having an annular groove defined by an outer wall and an internally threaded wall for receiving the threaded open end of a copper tube of a thermally responsive device, and an insulator inserted in the groove and shaped so as to form an airspace or pocket with the inner surface of the outer wall of the coupling member whereby galvanic corrosion is prevented and compressive installation forces are insulated from the copper tube.

Description

waited States Patent [72] Inventors Henry C. Braucksiek Buena Park; Lloyd R. Warner, Downey; Wilbur F. Jackson, Rolling Hills, all of, Calif. [21] Appl. No. 795,214 [22] Filed Jan. 30, 1969 [45] Patented Sept. 14, 1971 [73] Assignee Robertshaw Controls Company Richmond, Va.

[54] MOUNTING ASSEMBLY FOR A THERMOSTAT 9 Claims, 4 Drawing Figs.

[52] US. Cl 285/47, 73/3623, 285/158, 285/331 [51] 1nt.Cl F161 11/12 [50] Field of Search 285/47-55, 158, 212, 331, 355, 289, 286; 73/339, 343, 362.3, 374378 [56] References Cited UNITED STATES PATENTS 731,194 6/1903 Lovekin 285/47 X 2,782,806 2/1957 Stambaugh et al. 285/21 1 X 2,842,125 7/1958 Stephany l28/2l8 3,246,501 4/1966 Palmer 73/3623 3,306,109 2/1967 Caparone 285/55 X 2,133,313 10/1938 Weatherhead 285/286 X FOREIGN PATENTS 1,381,469 1l/l964 France 285/55 1,431,797 2/1966 France 285/55 Primary Examiner-Dave W. Arola Attorney-Christen, Sabol & OBrien PATENTEUSEPMISTI 3.604.729

sum 1 or 2 INVENTORS HENRY C. BRAUCKSIEK LLOYD R. WARNER WILBUR F JACKSON WV, Jada/6' (7M ATTORNEYS The present invention pertains to an assembly for mounting a thermostat on an appliance and more particularly to an assembly for mounting a thermostat on the wall of a hot water heater.

The problem of corrosion by galvanic circuits in heating appliances such as hot water heaters has long been sought to be remedied; however, the remedies thus far proposed have not been effective or economically feasible. The galvanic circuits are established in hot water heaters by the use of dissimilar metals in the construction thereof in combination with the water which acts as an electrolyte. In order to reduce galvanic corrosion it is conventional touse fittings, such as the shank for the thermostat, constructed of relatively noble metals such as brass or bronze, to line the steel walls of the hot water heater with a ceramic material such as glass and to envelop the copper tube of the thermostat with a plastic sleeve. Another manner of reducing galvanic corrosion is to insert a sacrificial anode rod in the hot water heater; that is, a rod constructed of a less noble metal such as magnesium so that the sacrificial rod is corroded before the other more noble metals.

The above approaches to the galvanic corrosion problem are not as fully effective as is desirable and are very expensive due to the high cost of brass and bronze and the wasted material in the sacrificial electrode. Furthermore, the brass and bronze fittings must be entirely machined which is an expensive and time consuming process.

Another problem encountered in mounting a thermostat on a hot water heater is that distortion of the thread joint between the copper tube and the coupling member results from compression during installation, and this distortion causes undesired changes in the cooperation of the lnvar rod in the copper tube with the control device which changes adversely affect the calibration of the thermostat. This problem is accentuated by mounting assemblies designed specifically to prevent galvanic corrosion because insulating sleeves are disposed contiguous with the inner surface of the outer wall of the coupling member and thus transfer compressive installation forces to the joint between the copper tube and the inner wall of the coupling member either directly or through adhesives used to fill the area between the outer wall and the inner wall of the coupling member. Until now, no acceptable solution to this problem had been discovered, and the inaccurate operation resulting from installation distortion was accepted as a mandatory disadvantage coexisting with galvanic corrosion prevention.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to mount a thermostat on an appliance in such a manner as to prevent galvanic corrosion and thread-joint distortion.

Another object of the present invention is to utilize a steel shank assembly in mounting a thermostat on the wall of a hot water heater to prevent galvanic corrosion.

A further object of the present invention is to mount a thermostat on an appliance by disposing a resilient insulator in a groove in a threaded portion of a shank assembly to prevent galvanic corrosion.

The present invention has another object in that a mounting assembly for a thermostat includes an insulator disposed in a coupling member to provide an air space or pocket therebetween to prevent calibration distortion of the thermostat.

Some of the advantages of the present invention are that a thermostat may be installed on an appliance without adversely affecting calibration of the thermostat, the shank assembly for a thermostat mounting assembly can be conveniently formed by stamping a flanged member and welding it to a coupling member, a dielectric seal is formed between the copper tube of a thermal-response device and the shank assembly and the mounting assembly may be formed quickly and inexpensively with maximum galvanic corrosion prevention.

The present invention is generally characterized in a mounting assembly for a thermostat of the type having an elongated tube with an open end, the mounting assembly comprising mounting means having a first wall for receiving the open end of the elongatedtube and a second wall spaced from the first wall, and insulating means disposed adjacent the second wall to form an air space whereby compressive installation forces are insulated from the elongated tube.

Other objects and advantages of the present invention will become apparent from the following detailed description of the accompany drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a broken view, partially in section, of a control unit connected with a thermostat in a hot water heater in accordance with the present invention.

FIG. 2 is ,a broken front elevation, partially in section, of an insulator for use with the present invention.

FIG. 3 is a partially broken exploded view, in perspective, of the mounting assembly of the present invention.

FIG. 4 is an enlarged broken front elevation, partially in section, of another insulator for use with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT While the present invention is shown and described as used with a hot water heater, the present invention is not limited to use with hot water heaters and may be used with any appliance in which it is desirable to prevent calibration, distortion and/or galvanic corrosion.

With reference to FIG. 1, a part of a hot water heater 10 is shown and includes a wall 12 having an aperture therein for accommodating an internally threaded nut 14 that is secured to wall 12 by welding or brazing. A flanged member 16 and a coupling member 18 comprise a mounting or shank assembly for mounting a conventional control device 20 and a conventional thermally responsive rod and tube device 22 on hot water heaterlO.

Control device 20 has a valve therein for controlling flow in conduits 24 and 26 in accordance with movement of an lnvar rod 28 in thermally responsive device 22 to control the operation of hot water heater 10 as is conventional. Device 22 further includes a copper tube 30 having an externally threaded open end 32 and a closed end welded to lnvar rod 28. A plastic sleeve 34 is disposed around tube 30 and extends the entire length thereof to insulate tube 30 from galvanic action.

Flangedmember 16 is constructed of steel and formed by a stamping process and is secured to the body of control device 20 in any conventional manner, such as by screws inserted through holes 36 shown in FIG. 3. Flanged member 16 includes a flange 38 and a hemispherical bulge 40, and a slot 42 is cut into member 16 to permit the passage of electrical wires if a switch for sensing high limit temperatures is included in device 22. Bulge 40 has an annular shoulder 44 which defines a bore 46 to permit lnvar rod 28 to extend therethrough to connect, with control device 20.

Coupling member 18 is constructed of steel and may be formed by machining. An outer cylindrical wall 48 of coupling member 18 is externally threaded to engage nut 14, and coupling member 18 has an inner cylindrical wall 50 which is internally threaded to accommodate the externally threaded end 32 of tube 30. The outer and inner cylindrical walls of member 18 are joined with an annular base 52 which has a lower surface 54 adapted to abut shoulder 44 of flanged member 16 and a transverse surface 56 adapted to abut the inner surface of bore 46. An angled lip 58 on base 52 is provided adjacent inner wall 50 to act as a stop for externally threaded end32 of tube 30. The inner and

outer walls

48 and 50 of coupling. member I8 form an annular groove 60 for receiving the annular bottom edge of an insulating sleeve 62 in abutting fashion on an upper support surface 64 of base 52. Coupling member 18 is secured to flanged member 16 to form the shank or mounting structure by welding; however, the weld is not required to be a watertight seal since the external threads for engaging nut 14 and the internal threads for receiving the threaded end 32 of tube 30 are both on the coupling member 18.

Insulating sleeve 62 is shown in broken section in FIG. 2 and includes a cylindrical wall 66 having a slightly larger inner diameter at the upper end than at the lower end due to an offset portion 68 of the inner surface. On the outer surface of the bottom of sleeve 62 is an annular upwardly tapered ridge 70 which abuts surface 64 and the inner surface of outer cylindrical wall 48 of coupling member 18. The outer surface of cylindrical wall 66 is angularly offset at 72 and has a vertically aligned segment 74 connected with an annular lip 76. As can be seen from FIG. 1, ridge 70 and vertical segment 74 abut the inner surface of wall 48, and lip 76 extends over the end of wall 48. In order to assure a watertight fit, the outer diameters of insulator 62 at ridge 70 and segment 74 are slightly greater than the inner diameter of wall 48, and lip 7 snugly fits the top of the wall.

In order to further assure a watertight fit between coupling member 18 and insulator 62, which is constructed of a relatively firm, yet resilient, dielectric material such as a polypropylene plastic, groove 60 is filled with an adhesive 78, such as fluid epoxy, which has dielectric characteristics in order to prevent the establishment of galvanic circuits.

With insulating sleeve 62 positioned in coupling member 18, as shown in FIG. 1, an annular airspace or pocket 80 is formed in the area between segment 74 and ridge 70 of insulator 62 and the inner surface ofwall 48 of coupling member 18, and airspace 80 serves to insulate compressive forces from installation of coupling member 18 on wall 12 of the hot water heater from copper tube 30.

To combine the mounting assembly of the present invention, coupling member 18 is first welded to flanged member 16 and insulator 62 is forced into groove 60. Thermally responsive device 22 is then secured to the shank or mounting structure by screwing externally threaded end 32 of copper tube 30 into the internally threaded portion of inner wall 50 of coupling member 18, and groove 60 is filled with adhesive 78. Plastic sleeve 34 is then subjected to air pressure to increase its diameter and is forced over copper tube 30 until it abuts adhesive filler 78 to completely cover copper tube 30.

Adhesive 78 is flexible so that it will not crack from compression during installation of the mounting assembly or from the stress due to the thermal response of the materials to which it is bonded. For instance, the operation of device 22 is such that when the temperature of the water in the hot water heater increases Invar rod 28 is retracted due to the great coefficient of thermal expansion of copper as compared with lnvar and similarly when the water temperature decreases lnvar rod 28 is extended. Since the coefficient of thermal expansion of steel is less than copper, there is stress applied to the adhesive, and therefore, it must be flexible.

Another embodiment of an insulating sleeve 82 for use with the present invention is illustrated in FIG. 4 and includes a cylindrical wall 84 having a plurality of longitudinal ribs 86 running from the bottom thereof to an annular lip 88 which extends over ribs 86. The outer diameter of lip 88 is slightly greater than the inner diameter of wall 48 of coupling member 18, and insulator 82 is constructed of a relatively firm, yet resilient, dielectric material such as a polypropylene plastic so that insulator 82 may be forced into groove 60 to form a watertight seal between the outer edge of lip 88 and the inner surface of wall 48. Ribs 86 are also in contact with the inner surface of wall 48 and form a plurality of air spaces or pockets bounded by ribs on either side, lip 88 at the top and surface 64 at the bottom.

In the same manner as previously described, groove 60 is filled with an adhesive after insertion of insulating sleeve 82 to further assure the provision of a watertight seal that will not break or crack during installation or operation. The airspaces or pockets formed between ribs 86 serve the same purpose as the airspace illustrated in FIG. 1; that is to cushion or insulate compressive installation forces from copper tube 30.

Clearly other insulators may be designed to cooperate with the inner surface of wall 48 to form airspaces and pockets; and, consequently, the present invention is not meant to be limited to the insulators illustrated in FIGS. 2 and 4. Similarly, other conventional techniques for preventing galvanic corrosion in thermostat-mounting assemblies may be utilized with the present invention such as coating the threaded end 32 of copper tube 30 withan adhesive so that as the copper tube is screwed into coupling member 18 the adhesive is extruded to further provide a watertight seal.

In as much as the present invention is subject to many variations, modifications and changes in detail, it is intended that all matter described in the foregoing specification or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. A mounting assembly for a thermally responsive device comprising mounting means including an inner wall for engaging the thermally responsive device, an outer wall having an inner surface radially spaced from said inner wall and a base connecting said inner and outer walls to define a support surface; and

insulating means disposed adjacent said inner surface of said outer wall and having a first end abutting said support surface, a second end abutting said inner surface of said outer wall and a central portion spaced from said inner surface of said outer wall to form an airspace therebetween whereby compressive forces on said outer wall are insulated by said airspace.

2. The invention as recited in claim 1 wherein said insulating means is a cylindrical wall of dielectric material having an annular ridge disposed at said first end abutting said inner surface of said outer wall and an annular lip disposed at said second end abutting said inner surface of said outer wall.

3. The invention as'recited in claim 1 wherein said insulating means is a cylindrical wall of dielectric material having a plurality of longitudinal ribs disposed on said central portion abutting said inner surface of said outer wall.

4. The invention as recited in claim 1 wherein said inner and outer walls extend from said base to form a groove therebetween receiving said insulating means, and an adhesive is disposed in said groove between said insulating means and said inner wall.

5. An assembly for mounting a thermally responsive device and a control device on a wall of an appliance comprising a steel coupling member having an externally threaded outer cylindrical wall for engaging the wall of the appliance, an internally threaded inner cylindrical wall for engaging the thermally responsive device, and a base integrally formed with said inner and outer walls;

said inner and outer walls of said steel coupling member extending from said base to form an annular groove therebetween; a cylindrical insulator of dielectric material disposed adjacent said outer wall in said annular groove defined by said inner and outer walls of said steel coupl ng member; and l a steel flanged member for supporting the cqntrol device and having a shoulder welded to said base of said coupling member whereby the weld between said coupling member and said flanged member need not be a watertight seal.

6. The invention as recited in claim 5 wherein said shoulder of said flanged member is annular to define a bore in said flanged member, and said base of said coupling member is annular and includes a portion extending into said bore.

7. The invention as recited in claim 5 wherein said outer wall has an inner surface spaced from said inner wall, and said insulator has an end engaging said inner surface of said outer wall and a central portion spaced from said inner surface of said outer wall to form an airspace therebetween.

8. An assembly for mounting a control device and a thermally responsive device on a wall of a water heater, the thermally responsive device having an elongated tube with a fixed open end and a rod extending through the open end to engage the control device, said mounting assembly comprising a steel coupling member having a base, an internally threaded inner cylindrical wall extending from said base for threadedly engaging the open end of the elongated tube, and an externally threaded outer cylindrical wall extending from said base for threadedly engaging the wall of the water heater, said outer wall having an inner surface spaced from said inner wall to form an annular groove therebetween with said base defining a support surface in said groove;

a steel flanged member for supporting the control device and having a shoulder welded to said base of said coupling member; and

a cylindrical insulator disposed in said groove adjacent said 9. The invention as recited in claim 8 wherein said shoulder of said flanged member is annular to define a bore in said flanged member, and said base of said coupling member is annular and includes a portion extending into said bore.

Claims

1. A mounting assembly for a thermally responsive device comprising mounting means including an inner wall for engaging the thermally responsive device, an outer wall having an inner surface radially spaced from said inner wall and a base connecting said inner and outer walls to define a support surface; and insulating means disposed adjacent said inner surface of said outer wall and having a first end abutting said support surface, a second end abutting said inner surface of said outer wall and a central portion spaced from said inner surface of said outer wall to form an airspace therebetween whereby compressive forces on said outer wall are insulated by said airspace.

3. The invention as recited in claim 1 wherein said insulating means is a cylindrical wall of dielectric material having a plurality of longitudinal ribs disposed on said central portion abutting said inner surface of said outer wall.

5. An assembly for mounting a thermally responsive device and a control device on a wall of an appliance comprising a steel coupling member having an externally threaded outer cylindrical wall for engaging the wall of the appliance, an internally threaded inner cylindrical wall for engaging the thermally responsive device, and a base integrally formed with said inner and outer walls; said inner and outer walls of said steel coupling member extending from said base to form an annular groove therebetween; a cylindrical insulator of dielectric material disposed adjacent said outer wall in said annular groove defined by said inner and outer walls of said steel coupling member; and a steel flanged member for supporting the control device and having a shoulder welded to said base of said coupling member whereby the weld between said coupling member and said flanged member need not be a watertight seal.

8. An assembly for mounting a control device and a thermally responsive device on a wall of a water heater, the thermally responsive device having an elongated tube with a fixed open end and a rod extending through the open end to engage the control device, said mounting assembly comprising a steel coupling member having a base, an internally threaded inner cylindrical wall extending from said base for threadedly engaging the open end of the elongated tube, and an externally threaded outer cylindrical wall extending from said base for threadedly engaging the wall of the water heater, said outer wall having an inner surface spaced from said inner wall to form an annular groove therebetween with said base defining a support surface in said groove; a steel flanged member for supporting the control device and having a shoulder welded to said base of said coupling member; and a cylindrical insulator disposed in said groove adjacent said inner surface of said outer wall and having a first end abutting said support surface, a second end abutting said outer wall and a central portion spaced from said inner surface of said outer wall to form an airspace therebetween whereby compressive forces on said outer wall developed during threading engagement with the wall of the water heater are insulated from the threaded joint of the open end of the elongated tube and said inner wall by said airspace.

9. The invention as recited in claim 8 wherein said shoulder of said flanged member is annular to define a bore in said flanged member, and said base of said coupling member is annular and includes a portion extending into said bore.