GB2213354A - Mounting structure for an automatic surface unit temperature sensor - Google Patents

Description

- k t MOUICING STRUCTURE FOR AN AUTOMATIC SURFACE UNIT TEMPERATURE SENSOR

This invention relates to structure for mounting temperature sensors in the central opening of solid disk automatic surface units.

Specifically, this mounting arrangement is an improvement in the counting structure described in U.S. Patent 4,330,701, which is particularly useful in combination with the novel temperature sensor assembly described in co-pending U.S Patent application Serial No. 138583 the priority of which is claimed in our

British application No.6'S-,k4A%k>i.0(9D-RG-17297) which is co-filed herewith and of which the description portion is incorporated herein by reference.

The above-referenced U.S. Patent 4,330,701 discloses a mounting arrangement for supporting an electro-mechanical temperature sensor of the type relying on fluid expansion in a capillary tube, in the central opening of a solid disk type of automatic surface unit.

The primary support member is a relatively complex stamped sheet metal part.

It is a primary object of the present invention to provide an improved mounting structure which is structurally simpler and less costly than previously known in the art for mounting a temperature sensor in the central opening of a solid disk surface unit.

An improved mounting arrangement for supporting a temperature sensor In the central opening of an automatic solid disk surface unit 25. is provided which is particularly suitable for use with a surface unit of the type in which the central opching io lined with a metallic collar having inwardly turned upper and lower lips for retaining a sensor structure in the opening. In accordance with the invention the mounting arrangement includes a temperature sensor assembly comprising a head portion of diameter sufficient to substantially fill the opening 9D-RG-17296 in the surface unit and a generally cylindrical elongated stem portion projecting downwardly from the base of the head portion. Support for the sensor assembly is provided by support member of generally inverted U-shape and a compression spring sandwiched between the sensor assembly and the support imember. The support member comprises a generally flat horizontally extending central portion and two integrally formed downwardly extending legs. An aperture is formed in the central portion to slidably receive the stem portion of the sensor asembly.

Each of the legs has formed thereon a pair of outwardly extending tangs for engaging the lower lip of the collar to limit downward movement of the support member. The legs are self-biased outwardly to bear against the lower lip of the collar.

An annular groove is formed in the base of the head assembly circumscribing the stem for receiving the upper end of the spring member. An annular depression is formed in the support member circumscribing the aperture to receive the other end of the spring to retain the spring in position centered relative to the aperture. When fully assembled, the stem of the sensor assembly extends through the spring and the aperture in the support member. The spring then biases the head portion of the sensor upwardly against the upper lip of the collar which overlaps a portion of the periphery of the head portion to limit upward movement thereof.

Tn the accorn.pany-ing dramings- A h 011 9D-RG-17296 91 FIG. 1 is a perspective view of a solid disk surface unit incorporating the temperature sensor mounting structure of the present Invention; FIG. 2 Is a partial sectional side view of the surface unit of Fig. 1 taken along lines 2-2; FIG. 3 is as ide view with portions removed of the sensor housing incorporated in the surface unit of Fig. 1; and FIG. 4 Is an exploded perspective view of the sensor assembly and mounting structure incorporated in the surface unit of Fig. 1.

Fig. I shows a perspective view of a conventional solid disk surface unit 10 made from cast material with sensor assembly designated generally 12 mounted in the central opening thereof. Surface unit 10 is typically mounted in an electric cooktop or range for heating utensils placed thereon. Temperature sensor 12 senses the temperature of the bottom of the utensil for controlling power to the surface unit.

Referring now primarily to Figs. 2-4, the central opening in surface unit 10 is lined with a metallic, preferably stainless steel, collar 14 which is suitably secured such as by press fitting in the central opening 17 of the surface unit. Collar 14 has inwardly turned upper and lower lips 16 and 18 respectively for retaining the sensor assembly and mounting structure in opening 17.

Sensor assembly 12 comprises an elongated generally cylindrical housing 20 which encloses the temperature sensor. Housing 20 includes an upper hermetically sealed chamber portion 22 for enclosing the sensor and a downwardly extending stem portion 24 which houses the electrical leads connecting the sensor to the power control system. In outwardly extending peripheral retaining flange 26 is formed at the intersection of the chamber and the stem portion which 9D-RG-17296 serves to retain the housing In the sensor assembly as will be hereinafter described.

The chamber portion 22 of housing 20 Includes a top wall 28 and a cylindrical side wall 30 with a peripheral flange 32 formed at the lower edge of side wall 30. When fully assembled and positioned in the surface unit, top wall 28 of housing 20 will contact the bottom surface of the utensil being heated. The temperature sensor is a thermistor 34 (Fig. 3) mounted in close thermal contact with the inner surface of top wall 28. The sensor Is suitably secured to the top wall such as by an appropriate adhesive 35.

The base member of chamber 22 is a generally flat circular metallic disk 36. Two small openings are provided in the disk to accommodate the electrical wires 38 for the sensor which project from the chamber for connection to the sensor circuitry (not shown). Each opening receives a glass electrical insulation bead 40 apertured to receive a wire. Base member 26 is suitably secured to the flange 32 of side wall 30, such as by welding, to form the hermetic seal.

Cylindrical stem portion 24 of housing 20 extends downwardly from the base of chamber 22. An annular flange 42 formed at the upper edge of stem 24 is suitably secured to the lower surface of base member 26 such as by welding. The lower end 44 of stem 24 is crimped to provide a tight fit to the glass wool sheath 46 which encloses the electrical wires 38. Strain relief for the wires may be provided by either a band crilisped around the wires, or a knot tied in the wires above the crimp 44 which exceed the diameter of the crimped stem.

The resultant annular retaining flange 26 at the juncture of chamber 22 and stem 24, comprising flange 32, disk 36 and flange 42, serves to axially retain housing 20 In the sensor assembly as will be hereinafter described.

-5 0 9 9D-RG-17296 Centrally apertured upper and lower insulating disks 50 and 52 thermally isolate sensor housing 20 from surrounding surface unit 10. Disks 50 and 52 are formed of porcelain ceramic material or other suitable material capable of withstanding temperatures on the order of 7500F. The chamber portion 22 of housing 20 projects through central aperture 54 in upper insulating disk 50 for contact with the utensil. The stem portion 24 of housing 20 projects downwardly through central aperture 56 in lower insulating disk 52. A recess 58 on the upper surface 60 of lower disk 52 circumscribing central aperture 56 receives retaining flange 26. When fully assembled, upper surface 60 of lower disk 52 abuttingly engages the bottom surface 62 of upper disk 50 sandwiching flange 26 therebetween. Flange 26 is sufficiently vertically spaced from top wall 28 of chamber 22 to enable chamber to project above upper surface 64 of disk 50 sufficiently for good thermal contact with the utensil.

A metallic outer skirt 66 conforms to the peripheral contour of the upper and lower porcelain disks to hold the disks together and to protect the edge of the porcelain from utensil impact damage. The upper inwardly turned portion 68 of skirt 66 extends radially inwardly overlapping the outer portion of upper surface 64 of upper porcelain member 50. The upper edge 70 of skirt 66 is radially spaced from side wall 30 of housing 20 defining a gap 72 therebetween. Upper surface 64 of upper disk 50 is slightly raised in this region to provide a surface essentially flush with the outer surface of skirt 66. The exposed porcelain surface in gap 72 is covered with a thin layer of glaze material to seal the porcelain against the absorption of food stains and cooking odors.

Four tabs 74 of equally spaced intervals formed (2 not shown) at the lower edge of skirt 66 are bent inwardly against the lower 9D-RG-17296 surface 76 of bottom porcelain disk 52. The inwardly extending upper portion 68 of skirt 66 and the bottom tabs 74 cooperate to hold upper and lower disks 50 and 52 together.

The upper disk 50 and the reduced diameter upper portion 78 of lower disk 52 are of a diameter slightly less than the diameter of the central opening defined by the upper lip 16 of collar 14. The outer diameter of the lower portion 80 of lower disk 52 is slightly greater than the central opening at upper lip 16. The resultant peripheral shoulder 82 acts as a stop and seal against the upper collar lip 16.

Four raised knobs 84 are provided on the upper surface 60 of lower disk 52. Corresponding circular depressions 86 are formed in the lower surface 62 of upper disk member 50. Knobs 84 project into depressions 86 thereby preventing relative rotational movement between upper and lower disks 50 and 52.

Rotational movement of housing 20 relative to disks 50 and 52 is prevented by a retaining means in the form of a push nut 88 which tightly engages the side wall of stem portion 24. Push nut 88 is snugged up against the lower surface 76 of bottom porcelain disk 52 tightly securing lower disk 52 between push nut 88 and housing flange 26.

in the description of the mounting structure to follow, the term "head portion" of the sensor assembly refers to the portion of the assembly having the sensor and substantially filling the central opening. In the illustrative embodiment the bead portion comprises chamber 22, porcelain disks 50 and 52, and skirt 66.

It will be recalled that a primary object of the present invention is to provide a structurally simple, relatively inexpensive mounting structure for supporting a temperature sensor in the central opening of a solid disk surface unit.

1 - 1 -11 9D-RG-17296 in accordance with the present invention as illustratively embodied In Figs. 2 and 4, the central element of the support structure Is support bracket 90. Bracket 90 is of generally Inverted U-shape with a generally horizontal central portion 92 and downwardly extending legs 94. Bracket 90 Is Integrally formed from sheet metal stock such as by stamping and lanced and bent to the desired configuration. Each of legs 94 includes a pair of outwardly projecting tangs 96, for abuttingly engaging the lower lip 18 of collar 14 to prevent downward movement of support bracket 90. Ugs 94 are self-biased outwardly to bear against lower lip 18 of collar 14. Portions 98 of the legs extending beneath the tangs project below the collar when fully assembled. This extended portion of the legs 94 may be easily manually or mechanically grasped and flexed thereby facilitating Insertion and removal of the bracket from the collar.

Central portion 92 of bracket 94 has formed therein an aperture 100 for slidably receiving the stem portion 24 of the sensor assembly 12. Stem 24 also projects through a helical coil spring member 102 which is interposed between bracket 90 and the head portion of the sensor assembly to vertically bias the head portion against the utensil. The spring force of spring member 102 is selected to provide sufficient force to insure good contact with the utensil bottom for sensing, while limiting the force sufficiently to prevent lifting of lightweight utensil loads from the surface unit surface.

The diameter of spring 102 Is sufficiently large to aid In maintaining a generally horizontal alignment of the sensor head portion while allowing sufficient tipping to enable the upper wall 28 of sensor housing 20 to align with warped utensil surfaces.

A groove 104 Is formed in the lower surface 76 of bottom porcelain disk 52 to receive the upper end of spring 102. An annular 9D-RG-17296 recess 106 in central portion 92 of bracket 90 receives the lower and of spring 102. Groove 104 and recess 106 serve to maintain spring 102 in position centered about stem portion 24. It is important to retain the spring in this centered position. Should the spring move off center, the spring force could bias the sensor head in a cocked or tilted position resulting in poor contacts with the utensil. In addition, the combined depth of groove 104 and recess 106 are sufficient to fully contain the spring 102 when fully compressed. This permits the central portion 92 of bracket 90 to act as the lower stop for the sensor assembly when fully assembled, greatly simplifying the mounting bracket structure.

As hereinbefore described, legs 94 are self-biased outwardly.

In addition, the shape of the support bracket 90 with legs 94 slightly outwardly flared also converts some of the downward force of spring 102 against the central portion 92 of support bracket 90 to an outward force further aiding in pressing tangs 96 into engagement with the lower collar lip 18.

To facilitate assembly of the combined sensor assembly and support structure a second push nut 108 is secured to stem 24 beneath bracket 90. Push nut 108 retains the sensor assembly and support structure in assembly when the sensor is not installed in the surface unit.

While --a specific embodiment of the present invention has been illustrated and described herein, it is realized that numerous modifications and changes will occur to those skilled in the art. For instance other forms of stemmed sensor assembly could be supported by the mounting arrangement.

i a 9D-RG-17296

Claims (5)

1. I. An improved mounting arrangement for supporting a temperature sensor In the central opening of an automatic solid disk surface unit of the type in which the opening is lined with a metallic collar having inwardly turned upper and lower lips for retaining a sensor structure therein, said mounting arrangement comprising: a temperature sensor assembly comprising a head portion of diameter sufficient to substantially fill the opening in the'surface unit configured to contact the bottom of a utensil being heated on the surface unit, and a generally cylindrical elongated stem portion extending downwardly from the base of the head portion generally centrally thereof, the base of said head portion having formed therein coaxially with and generally circumscribing said stem portion a downward opening groove; a support member of generally inverted U-shape having a generally flat horizontally extending central portion and two integrally formed downwardly extending legs, said central portion having formed therein an aperture for slidably receiving said stem portion of said sensor assembly and a circular depression bordering said aperture, each of said legs having formed thereon a pair of outwardly extending tangs for engaging the lower lip of the collar to limit downward movement of the support member relative to the collar, said legs being self-biased outwardly to ear against the lower lip of the collar; a helical compression spring member sandwiched between the base of sgid head portion of said sensor assembly and said central portion of said support member, said spring being captured at one end thereof in said groove in said base of said head portion and at the 9D-RG-172 96 other end thereof in the annular depression surrounding said aperture, said stem extending throu gh said spring member and said aperture, said spring biasing said head portion upwardly against the upper lip of the collar, the collar overlapping a portion of the periphery of the head portion to limit upward movement of the head portion relative to the collar.
2. 2. The mounting arrangement of Claim 1 wherein said legs extend downwardly from the lower lip of the collar to facilitate insertion and removal of the mounting structure from the collar.
3. 3. The mounting arrangement of Claim 2 further comprising retaining means secured to said stem portion beneath said central portion of said support member to limit movement of said sensor assembly relative to said support structure.
4. 4. The mounting arrangement of Claim 3 wherein said support member is stamped from a single piece of flat steel stock and lanced and bent to the desired configuration.
5. 5. A temperature sensor mounting arrangement substantially as hereinbefore described with reference to Figure 2 of the accompanying drawings, Published 1989 atThePatentOMee, State House, 6671 High HOlbom, LondonWCIR4TP- Further copies maybe obtained from The Patent Oince Was Branch, St Maxy Cray, Orpington. Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent, Con. 1/87