US3061707A - Pressure-temperature operated electrical switching apparatus - Google Patents

Description

'r. H. STIEBEL 3,061,707

TEMPERATURE OPERATED ELECTRICAL SWITCHING APPARATUS Oct. 30, 1962 PRESSURE- 2 Sheeis-Sheet 1 uv l/EN TOR THEOOO H. S 776' BE L.

Filed Oct. 20, 1959 Oct. 30, 1962 T. H. STIEBEL 3,061,707

PRESSURE-TEMPERATURE OPERATED ELECTRICAL SWITCHING APPARATUS Filed Oct. 20, 1959 2 Sheets-Sheet 2 3,061,707 Patented Oct. 30, 1962 Free 3,061,707 PRESSURE-TEMPERATURE QPERATED ELECTRI- CAL SWITCHING APPARATUS Theodor Hermann Stiebel, Luchtringer Weg 11, Holzminden (Weser), Germany Filed Oct. 20, 1959, Ser. No. 847,509 Claims. (Cl. 219-41) This invention relates to an electrical switching arrangement within a casing or head actuatable by a hydraulic drive by way of a force transmitting member. The drive per se consists of a probe tube terminating in a pressure sensitive element, the probe tube preferably containing a thermally expansive liquid. The pressure variations are transmitted to the pressure responsive element either directly by way of the temperature acting on the free, closed end of the probe tube or indirectly, in the manner known from the manometer art, by way of an open probe tube end.

Temperature disconnect switches or control devices employing these principles are used, for example, in im mersion heaters. In such heaters it is prior knowledge to house the electrical switch and the pressure sensitive element (a membrane or a bellows) separately, each in one of the half-shells of the handle casing or in one of the handle casing portions, and to separate them by means of an insulating plate clamped between the parts of the handle casing, the plate having an aperture or recess for a pressure transmitting element. Such immersion heater is, for example, shown in Patent 2,902,581 for Miniature Immersion Heater With Electric Controller Sealed in Handle, issued to me on September 1, 1959.

The predetermined relative position of the pressure responsive element and the electrical switch for obtaining positive switching sequences is assumed thereby only after assembly of the handle casing in immersion heater handles so constructed. Consequently, only after assembly of the complete device can it be ascertained whether the switching temperature is the required temperature. Subsequent justification is then practically impossible, particularly where the half-shells of the handle, or the casing components, are joined, as by welding them together, as occurs extensively in making handles for immersion heaters of synthetic materials.

It is, of course, conceivable that the actuating mechanism of a justifying arrangement, in the form of a regulating screw, be brought out through the handle housing; but by so doing the immersion heater handle is no longer watertight. Furthermore, in such a construction, the point at which the switch operates to open the heater circuit might be irresponsibly altered by an unauthorized person. Thus, an excess temperature disconnect switch, adjusted to above the boiling point, might, in the least objectionable case, be actuated during ordinary heating, that is, below the boiling point; or vice versa, a temperature regulating arrangement normally operating at below the boiling point may fail completely, that is, not be actuated at all when the disconnect point is adjusted to a temperature above the boiling point.

Likewise, in the case where a temperature disconnect arrangement is housed in the immersion heater handle, the

. predetermined relative position of the parts housed in the individual half-shells of the handle or in the individual portions of the handle housing will not be ob- .tained positively, where these handle portions are, wholly or partially, of a material of perceptible elasticity, preferably synthetics. In the course of reclosing the switch by thumb-pressure on the portions of the handle provided therefor, below which the temperature and pressure responsive switching element is located, undesirable deformations of the casing may occur, causing sticking of the movable components of the switch.

However, in accordance with this invention, these disadvantages can be avoided by no longer housing the pressure responsive element and the electrical switch mechanism each in separate regions of the handle casing.

An object of the invention is to eliminate the need for justification of the relative positions of the pressure responsive element and the switch per se by permanently fixing their relative positions before assembling them with the housing or handle.

Still a further object is to facilitate the installation of the heating element and the pressure-temperature responsive switching mechanisms in cooking utensils and vessels, and to permit ready replacement thereof with a minimum or simple assembly and disassembly operations.

I accomplish the foregoing, and other, objects by providing an insulating plate upon which both the pressure responsive element and the electrical switch are mounted, which mounting plate is readily insertable in a housing or handle. So to mount the pressure-temperature responsive member, the latter is provided with tongue-like projections which preferably are inserted through corresponding apertures or grooves in the mounting plate and are bent over, and/or twisted, to the rear thereof while the electrical switch and the line connections are supported on the face of the mounting plate remote from a flexible wall or membrane of the pressure-temperature responsive member. The so assembled parts provide a structure which is as simple as possible, is fully selfcontained and independent of the position of the casing portions relative to each other, is positively operable at the predetermined desired temperature of the heated contents of the cooking utensil, and completely and readily interchangeable. If desired, this structure can be at tached to a handle or housing portion by means of a screw simultaneously serving as a portion of a line connector.

Where the handle casing consists of a bell-shaped housing into the open end of which a flanged plate is insertable which supports both of the end regions of the tubular heater and the probe tube and simultaneously serves as the sealing cover, such as shown in my copending application for patent, Serial Number 812,935, filed May 13, 1959, for Watertight Handle for Immersion Heaters, it is recommended that the mounting plate be anchored to the tubular heater connecting terminals which, for this purpose, are made rigid and preferably in the form of lugs of known type, and are mechanically con nected rigidly to the line connector supported on the mounting plate.

To increase the stability of the switching arrangement according to the invention within elastic handle housings, indirectly mechanically supporting the same by way of the temperature probe tube on the flanged plate, has been found to be appropriate. Hence, the instant invention further proposes to make the temperature probe tube rigid at least from the flexible membrane of the pressuretemperature responsive member to its exit portion beyond the flanged plate, or to reinforce the per se readily defortmable temperature probe tube with an enveloping rigid sleeve or tube at such region. In addition, the mounting plate can advantageously be secured in its position by providing tongue-like extensions at the edge thereof toward the flanged plate and providing corresponding re: cesses in the flanged plate. The mounting plate, prior to making the electrical connections, is then forcibly and positively inserted into the recesses. Furthermore, it has been found advantageous, in addition to supporting the structure (switch, pressure-temperature responsive member, and mounting plate) at one side of the flanged plate,

to push the mounting plate drawerlike, with its lateral sides in grooves provided therefor Within a portion of the housing, into the housing, or, vice versa, to push the housing provided with grooves over the assembled complete mounting plate. By so doing damage to the electrical switching arrangement either on pushing the mounting plate in, or on manual reconnection of the switch because the mounting plate has too great a bending moment exerted upon it, is avoided.

Two illustrative embodiments of the invention are now descraibed in detail with the aid of the annexed drawing, in which:

FIGURE 1 shows a top view, partially in section, of a first embodiment of the invention comprising a heating element combined with a temperature-responsive disconnect switch installed in a container for heating liquids;

FIGURE 2 an exploded perspective view or" the switching head of the embodiment of FIGURE 1 in the order in which the head is assembled;

FIGURE 3 a section along line III-III of FIGURE 2 showing the temperature responsive member and the dis connect switch assembled with the mounting plate as a unitary component;

FIGURE 4 a section along line IV-IV of FIGURE 1;

FIGURE 5 a section along line V-V of FIGURE 1;

FIGURE 6 a longitudinal view, partially in section, of a second embodiment of the invention in an electric immersion heater handle with the handle casing open;

FIGURE 7 a section along line VII-VII of FIG- URE 6;

!FIGURE 8 a section along VIIIVIII of FIGURE 6;

FIGURE 9 a view of the second embodiment similar to the view of F-IGURE 6 but with the handle casing closed.

Referring to the drawing, the first illustrative embodiment of my invention is shown in FIGURES 1 through 5. Through an aperture 1 defined in the cylindrical wall of a vessel '2 for heating liquids, for example a water kettle, a tubular heating element 3, of known construction per se, projects into the interior of the vessel and is provided, exterior to the vessel wall, with a temperature responsive disconnect switching arrangement 4. The heater end of heating element 3, broken away and not shown in FIGURES 1 and 3, maybe in the form of a hollow cylinder or an open helical coil, the latter being shown in FIGURES 6 and 9. The switching arrangement 4 is provided with a temperature probe tube 5 extending into the vessel and containing a thermally expansible liquid 6. The probe tube 5 is enveloped by protective pipe 7 which is connected by heat conductive bridge 8, at its region extending into vessel 2, to tubular heating element 3. The shanks of the heating element 3, together with pipe .7, pass through plate flange 9, on the interior surface of the wall of vessel 2, to rigid base body 10 of a material non-conductive both thermally and electrically, positioned on the exterior surface of the wall of the vessel of a switch housing or head. Obviously, the end of protective pipe 7 within vessel 2 is closed to prevent leakage of the liquid being heated into the switching arrangement. Base body 10 and rim region 12 of the vessel wall defining aperture 2 are rigidly and tightly sealed, by bolts 13 and packing 14, to plate flange 9, with the baseiody serving as the housing for temperature re sponsiveswitching arrangement 4 (FIGURES 2 and 3), as also for terminal pins 15 and 16 (FIGURES 4 and 5) connectable to the electric line, and is provided with slidable cover 17.

The switching arrangement 4 per se is afiixed to mounting plate 18 of electrically insulating material and consists of a relatively flat, pressure casing 19, connected to the temperature probe tube 5, and the pressure casing wall facing the mounting plate is provided with a resilient membrane 20. The pressure casing is provided also with tongues 21 which pass through corresponding slots 22 (FIGURE 3) in mounting plate 18 and are twisted or bent over on the other side against the mounting plate to support the casing thereon. A hollow rivet 23 fastens one end of a contact spring 24 to the other face of the mounting plate, that is, to its surface opposite membrane 2%, a button 25 of electrical insulating material being carried by the contact spring. Button 25 extends through an aperture 26 defined by the mounting plate with one end of the button engaging resilient membrane 2t) and its other end engaging a soft, manually depressible region 27 of cover 17 (FIGURE 4). The free end of contact spring 24 carries a contact 29 which is juxtaposed to a fixed strip contact 31 on the mounting plate, which in turn is connected to an elongated contact lug 31 (FIGURES l and 4) which at its opposite end electrically connects with a bow or loop 32 in recess 41 of body 141 into which one rigid terminal 33 (FIGURE 4) of heating element 3 is slid on assembly of the heating element with base 1% to electrically connect that side of the heating element to strip contact 30.

The electrical connection of terminal pin 15 to contact spring 24 is by way of a conductor 34 in base 10, conductor 34- terminating in a metal nut 35 sunk in supporting surface 36 of base It) for mounting plate 15}. A metal bolt 37 is threaded into nut 35 and in conductive contact extends into the hollow rivet 23 which holds mounting plate 18 and contact spring 24 together. Thus metal bolt 37 serves in a first aspect as a current supply member, and in second aspect to affix temperature switching arrangement 4 to body 11). The electrical connection of terminal 16 to the other end of heater coil 3 is by way of a direct connection in the form of a metal tube 39 embedded in body It and end 28 of body 11) adjacent to vessel 2, into which the corresponding connecting pin 33 of the heater coil slides on assembly exactly as does connecting terminal pin 33 into loop 32.

Assembly of pressure-temperature switching arrangement 4 with heater element 3, and the installation thereof, proceed as follows: The above described pressuretemperature switching arrangement 4 constructed as a completely independent structural element, with mounting plate 18 positioned on supporting surface 36 and laterally in guide grooves 40 of body 10, is slid into the base body whereby contact lug 31 and loop 32 are positioned in a suitably formed recess 41 provided, as has been stated, in the base body. Thereupon metal bolt 37 is tightly screwed through metal nut 35, and cover 17, with its dove-tailed shaped lateral edges 42 in corresponding grooves 43 of the base body, is slid into the base body as previously was the mounting plate, whereby the rim of recess 44 in end 38, adjacent to vessel 2, of cover 17, slides on the temperature probe tube until a longitudinal extension 45 of the mounting plate, towards the end of the insertion, enters into, and terminates in, a corresponding opening 46 in such cover end 38, so that mounting plate 18, which is subjected to a bending stress on re-connection of the switch, as below described, also has a support at its forward end which otherwise is not supported on supporting surface 36. The assembled switch head is so placed in front of aperture 1 and plate flange 9 positioned in back thereof, while simultaneously inserting the probe tube 5 projecting therefrom into protective tube 7, that metal tube 39 and loop 32 of contact lug 31 on pushing it further forward in the direction of plate flange 9, will push over the terminal pins 33, 33 of heater 3. switch housing-as initially stated-is bolted to plate flange 9. Dismantling and disassembly of the switchhousing is obviously in the reverse order.

The switching sequence is as follows: Spring membrane 21), as the result of the increasing pressure applied to it with increasing temperature of the liquid in vessel 2 by thermally expansible liquid 6 in temperature probe tube 5, which liquid 6 can be of such type that when the Thereupon the g liquid to be heated or the heating coil reaches the predetermined switching temperature it evaporates, is distended to such a degree that it snaps into its convex position (FIGURES 3, 4) thereby lifting insulating button 25 in impact-like manner, by which action contact 29 is moved away from fixed contact strip 30 with the result that the heating circuit is opened. Such snap-action membranes for pressure casings are shown and described in detail in my copending application above mentioned. Reconnection of the current is obtained manually by depressing soft portion 27 of cover 17. When so doing, the insulating button 25 is depressed to such extent as to exert sufiicient pressure on the resilient membrane 20 that the latter will spring back into its opposite, or concave (and connect) position, shown in FIGURES 3 and 4 by the dashed or broken lines. Simultaneously, prebiased contact spring 24 will spring back into its connecting position when contact 29 presses tightly against fixed contact strip 30.

The immersion heater of FIGURES 6 through 9 is, with minor variations, provided with the same switching arrangement as shown in FIGURE 3. Like reference characters in this embodiment denote the same elements as in the first, and above described, illustrative embodiment. Specifically, the following changes in construction are involved in this second illustrative embodiment of the invention. The protective tube 7 for probe tube 5 is dispensed within the switch housing, constructed in the form of the handle for the immersion heater, is not, as in the first embodiment, adapted for incorporation or building into a heating vessel and thus need not, even temporarily, be separated from the heating element. The form of the handle housing of this second embodiment renders inadvisable the use of the threaded connection of a conductive bolt 37 and a conductive nut 35 as in the first embodiment.

Furthermore, the form of the direct connection made by metal tube 39 from the connecting line 47 to the terminal prong of the heater 3 is, in this embodiment, in the form of a conductor 89' directly supported on mounting plate 18 to maintain bell-shaped, thin handle 48, free of all conductors. Handle housing 48 is made of a per ceptibly elastic thin walled synthetic material in order to obtain the soft portion 27 by thinning the wall thickness of the handle housing, and, as below described, to connect the handle housing with the flanged cover plate 9'. Loop 32 (32') and contact lug 31 (31), in this embodiment, are provided at each connecting terminal 33 (33') of heating element 3 with such terminal pins being of rigid material to function as supports for mounting plate 18 and being soldered to the loops upon previously having inserted extension 45 of the mounting plate into aperture 49 of flanged cover plate 9. The two last-mentioned expedients, together with sleeve 50 extending through cover plate 9' and reinforcing temperature probe tube 5, function to stabilize the interconnection of mounting plate assembly 18, having switching arrangement 4 mounted thereon, with flanged cover plate 9. Such immovable and rigid disposition of the switching arrangement relative to the flanged cover plate is absolutely required also for the reason that on assembling bell-shaped handle housing 48, which guides the lateral edge regions of mounting plate 18 in grooves 51 during such assembly, the housing on further advancement must be positioned in a predetermined relation to flanged cover plate 9' when the bell-shaped housing, automatically distending its open rim end 52., tightly engages rim 53 of flanged cover plate W with internal annular projection 54 of the bell-shaped housing.

As will be obvious to the skilled worker in the art, the

temperature disconnect switch in both switch head 11 and in handle housing 48 may house a temperature regulating arrangement, that is, a controller, in place of the disconnect switch shown in both embodiments. In such case, there is no need for a soft portion 27 in either the constructed that it has but a single normal position, at which the switch is closed, to which at all times it tends to restore even when distended sufficiently to open the switch.

What I claim is:

I. A switching arrangement for electrical heaters in direct heat transferring contact with liquids to be heated comprising an electrical heating element having a pair of terminals, a fixed first contact, a spring of electrically conductive material of which one end is spatially fixed, a second contact supported at the free end region of the spring end movable to engage with the first contact, a pair of line supply conductors of which one is connected to one of the first and second contacts and the other to one terminal of the heating element, the other of the first and second contacts being connected to the other terminal of the heating element, a hollow housing of electrical and thermal insulating material, a longitudinal internal shoulder in each of a pair of opposite longitudinal walls of the housing, a support plate of insulating material slidably supported on the housing shoulders, the first contact and the spatially fixed end of the spring being attached to one longitudinal face of the support plate, a heat probe tube in heat transfer relation with the heating element, a thermally expansive liquid within the heat probe tube, a closed reservoir into which the heat probe opens having one wall which is flexible, a pin of insulating ma terial supported in and extending through the spring, one end of the pin engaging the flexible wall of the reservoir, the support plate defining a central aperture through which the pin extends, and means mounting the heat probe tube and the reservoir on the longitudinal face of the support plate opposite to that to which the first contact and the fixed end of the spring are attached.

2. The switching arrangement according to claim 1 in which the support plate is mechanically positioned in the housing by a metallic threaded member threaded into and through the spatially fixed end of the spring, through the support plate and into the housing wall, the threaded member electrically connecting to one of the line supply conductors.

3. 'In combination with a vessel for heating liquids, an immersion heater of which the heating coil of the immersion heater extend through an aperture defined in the heating vessel wall, means sealing the heating coil liquid tight within the vessel with its terminals external to the vessel, a housing of electrical and thermal insulating material external to the vessel, the housing defining a cavity into which the terminals of the immersion heater extend, a heat probe extending through the sealing means and containing a thermally expansive liquid, a closed container into which the end of the probe external to the vessel connects, one wall of the container having a flexible region, a support plate of insulating material within the housing cavity, an electrical switch having a spring throw biased to closure and connectable to a line supply of electrical potential, means supporting the switch and the con tainer on the plate, an insulating member supported in and extending through the spring throw of the switch and extending through an aperture defined in the plate to engage the container flexible wall, and a flexible portion in a wall of the housing aligned with insulating member for depressing the insulating member manually to restore the container flexible region and the switch each to its preoperated condition after operation thereof by the expansion of the thermally expansive liquid at a predetermined temperature.

4. The combination of claim 3 in which the heat probe is removably within a protective pipe integral with the sealing means and extending into the vessel, and a heat conductive bridge connects the protective pipe to the heating coil.

5. The combination of claim 3 in which the housing consists of a body defining a longitudinal recess extending from one end of the body to close its other end, and a cover having an integral flange at one end to close the open end and the top of the recess when slid into the body, the body has a pair of grooves in opposite longitudinal walls for guiding the support plate with the switch and the container mounted thereon into the cavity of the recess, a conductive threaded member passes through one contact of the switch and the insulating plate into the body when the plate is in its predetermined position within the cavity, a line conductor is embedded in the body and electrically connected to the threaded member, a longitudinal projection is integral with the trailing end of the support plate, the projection extending into an aperture defined in the integral flange of the cover on closing the cover on the body with the plate in its predetermined position, and means secure the body with its cover closed to the sealing means.

6. The combination according to claim in which the body defines a second recess, a pair of line terminals is disposed within the second recess of which one terminal is connected to the line conductor embedded in the body, a conductive tube is embedded longitudinally in the body and connected at one end to the other line terminal, and a conductive rod embedded transversely in the body connected at one end to the other switch contact with the plate in its predetermined position, the other end. of each conductive tube and the conductive rod electrically engaging the terminals, respectively, of the immersion heater.

7. A switching arrangement actuatable at a predetermined temperature to disconnect an electrical supply line in which it is connected comprising an enclosure having at least one pressure-sensitive wall, a thermally expansive liquid filling the enclosure, an electrical heating element for connection to the electrical supply line, a portion of the enclosure remote from its flexible wall being exposed to heat from the heating element, a fixed electrically conductive contact electrically connected to one side of the heating element, the other side of the heating element being connected to one side of the line supply, a movable electrical contact electrically connected to the other side of the line supply, the movable contact normally engaging the fixed contact, a support plate of electrical insulating material on one face of which the fixed and movable contacts are mounted while the enclosure is mounted on the opposite face thereof, an interconnection of electrical insulating material passing through an aperture defined in the support plate between the flexible wall of the enclosure and the movable contact, an opentop housing of electrical insulation material, a pair of spaced longitudinal shoulders on opposite walls of the housing adjacent the open top of the housing, and a cover of electrical insulating material for the housing supported on the shoulder the nearer to the open top of the housing, the support plate being slidably supported on the other shoulder.

8. The switching arrangement according to claim 7 in which a plurality of elongated projections integral with the enclosure extend through apertures defined in the supporting plate and are deformed at their ends project- .ing beyond the plate securely to attach the enclosure to the plate, and a rivet attaches one end of the movable contact to the support plate.

9. The switching arrangement according to claim 7 in which a hollow, electrically conductive, rivet afi'ixes one end of the movable contact to the support plate and has an externally threaded portion extending through the support plate, the other side of the line supply being connected to an internally threaded, electrically conductive, member embedded in the housing into which the extending portion of the rivet is screwed, to mechanically position the support plate at the predetermined position within the housing and to attach the support plate to the housing.

10. The switching arrangement according to claim- 1 in which the housing consists of a bell-shaped body and a cover fitted over the open end thereof, the spring is biased to closure of its free end on the first contact and is movable by the pin moved by the flexible Wall of the reservoir at a predetermined elevated temperature of the liquid within the reservoir to disengage the free spring end from the first contact, and one wall of the body has a flexible portion registering with the insulating pin when the cover is secured to the body with the plate at a predetermined position within the housing for manually depressing the fiexible body portion to depress the insulating pin after the liquid within the reservoir has cooled from the predetermined elevated temperature to restore both the flexible wall of the reservoir and the flexible portion of the body to their preoperated positions, both the flexible portion of the body and the flexible wall of the reservoir being sufliciently stiif that with pressures thereon in either the outward or the inward direction of magnitudes less than that corresponding to the predetermined elevated temperature they each retain the position determined by the last applied pressure and the direction thereof.

References Cited in the file of this patent UNITED STATES PATENTS 1,620,183 Bersted Mar. 8, 1927 1,833,996 Johnstone et al Dec. 1, 1931 2,024,060 Peralta Dec. 10, 1935 2,369,986 Schaefer Feb. 20, 1945 2,432,169 Morgan et al. Dec. 9, 1947 2,576,688 Landgraf Nov. 27, 1951 2,732,478 Stiebel Jan. 24, 1956 2,902,581 Stiebel Sept. 1, 1959 2,977,456 Stiebel Mar. 28, 1961

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