US3467813A - Sauna steam generators - Google Patents

Description

Sept. 16, 1969 u. RAABE SAUNA STEAM GENERATORS Filed Feb. 1s, 1967 Wll m 25' mvENToR Ulo Raabe by United States Patent O M 3,467,813 SAUNA STEAM GENERATORS Ulo Raabe, 459 Gaulet St., St. Boniface 6,

Manitoba, Canada t Filed Feb. 13, 1967, Ser. No. 619,882 Int. Cl. F22b 27/14 U.S. Cl. 219-275 3 Claims ABSTRACT OF THE DISCLOSURE A generator composed of porous composition stone molded with anouter reinforcing mesh shell and positioned within a sheet metal container; the stone is spaced from the container walls and rests on a spacing pad to protect the container against buckling by heat; an electric element is imbedded in the stone for high temperature heating thereof, so water can be sprayed on the stone to generate `steam for shock-treatment of bathers in a sauna; the element is tube-covered to eliminate shorting, and also has a cutout thermostat in the power circuit therefor to prevent overheating of the stone; and a shielding is positioned over the thermostat to deect Water therefrom. i

This invention relates to sauna bath heaters, and is an improvement over the heater in my former patent, No. 3,277,274, dated Oct. 4, 1966, for Electric Sauna Bath Heating Unit. In this patent, two upper electric elements are adapted to heat a box of stones for generation of steam when water is sprayed thereon, and the amount of steam is regulated by manual valve control of the water. Surplus water, if any, falls on a lower tray and is suitably drained.

As the above heating elements are below the box of stones, and the stones themselves have spacing therebetween, hot air passes up through said stones from the elements and tend to have a cooling effect thereon, so extra time is required to heat the stones to high steam generating temperatures, and these temperatures quickly lower when the water is sprayed on the stones. Accordingly, the steam generation is erratic.

The principal object of the present invention is: to provide a steam generator wherein a molded composition stone is provided within a container for the heat transfer medium, and an electric element is imbedded in the stone for the heating of the stone.

A further object of the invention is: to provide a porous composition stone for water retention thereon, and provide passages through the stone for distribution of the water over both the upper and lower surface areas of the stone.

A further object of the invention is: to provide a covered electric element for imbedment in the stone as a safety feature to prevent shorting.

A further object of the invention is: to form the composition stone from material having high heat conductivity and a low co-etlicient of expansion, so the stone will have good spalling resistance.

A further object of the invention is: to provide a coating over the covered element before molding in the stone, to permit a closer bond between the element covering and the stone.

A further object of the invention is: to mold the cornposition stone within and to an encircling metallic mesh shell to protect the outer walls of the stone.

A further object of the invention is: to provide a thermostat control operable by the temperature of the stone to regulate the electric current to the heating element for the stone.

Patented Sept. 16, 1969 A further object of the invention is: to provide a spacing pad under the composition stone and air spacing therearound to prevent the container from warping with the heat.

A further object of the invention is: to provide a shielding over the thermostat control to protect it from the spraying water.

A further object of the invention is: to provide a drain for the container to prevent undue cooling of the stone.

With the above important and other minor object in view, which will `become more apparent as the disclosure proceeds, the invention consists essentially in the construction and arrangement of the various parts hereinafter more particularly described, reference being had to the accompanying drawings wherein:

FIGURE 1 is a side view of a sauna unit wall-installed in a bathroom with parts broken away to expose construction.

FIGURE 2 is an enlarged perspective view of the new steam generator for the sauna unit.

FIGURE 3 is a vertical cross section through the steam generator on the line 3-3 of FIGURE 2.

FIGURE 4 is a detailed perspective view of the thermostat probe.

FIGURE 5 is a lengthwise vertical section through the steam generator on the line 5-5 of FIGURE 2.

FIGURE 6 is a horizontal section taken on the line 6 6 of FIGURE 5.

FIGURE 7 is a diagram of the sauna unit wiring.

In the drawings like characters of reference indicate corresponding parts in the several gures.

The sauna heating unit described in my former patent mentioned is also shown in FIGURE 1 of the present drawings, and is positioned within a bathroom wall 10. The heating side 11 of this unit is in the bathroom proper, and the opposite control side 12 is located in an adjoining room. An insulated partition 13 in the unit separates the two sides. In operation of this unit, a lower fan 14 draws air in from the bathroom under a front baille 15 and directs it up and over a covered heating element 16 for passage back to the bathroom over the baille. All the electric controls -of this unit are operated from the control side in the adjoining `room so no injury can occur to the undressed wet bathers.

The improved steam generator comprising this invention is positioned in the upper part of the heating side of the unit, as shown at 17, and three suitably perforated lengthwise pipes 18 thereabove, fed by a supply line 19, are adapted to spray streams of water into the generator under the control of a manually operable valve 20 which i is located on a wall of the bathroom in the supply line.

This steam generator will now be described.

The generator itself is best shown in FIGURE 2 and presents a rectangular-shaped box 21 as a container having a handle 22 at each end and a drain connection 23 at one lower corner. A pair of spaced vertical slots 24 are provided in one side of the box for passage of terminals 25 and 25'. A thermostat control 26 is centrally positioned on the same side, between the slots, and presents a control stem 27 and a lower vertical pair of terminals 28 and 29. When this generator is Ifitted into the sauna unit the drain connection 23 is passed through a hole in the inner wall thereof, the hole being indicated in dotted outline at 30, so surplus water, if any, from the generator can drop therefrom to the bottom of the unit and removed. Brackets (not shown) will be provid-ed on each end wall of the unit to receive and support the handles 22 of the box while the terminals 25 and 25 and the thermostat control 26 will pass`4 through suitable holes (not shown) the insulated partition 13 for terminal connection and operation of the stem 27. It will also be noted that a spacing 31 is left between the generator and the partition for passage of heated air from the fan 14.

The interior of the box 21 receives a rectangularshaped pre-cast composition stone 32 having a tubularcovered element 33 molded therein, as shown in FIGURES 3, and 6. The essential component of this stone is silicon carbide in a refractory cement mix which when molded has a high heat conductivity, including porosity. It has been found that such a stone lwill stand temperatures up to 3,500" F. without apparent effect while at the same time it has a low co-eflicient of expansion which gives a good spalling resistance (cracking due to sudden cooling after heating). The porosity permits 'a larger heat surface in contact with the water and accordingly provides an ideal heat transfer medium for the purpose. It -will also be noted that four slots 35 are centrally molded vertically through the stone from the upper surface to bottom so water can quickly pass from the upper to the lower surface. The tubular covering over the element 33 insures that live wires will not come in contact with moisture and cause short circuits. This tubular covering is pre-coated cold with a heat conducting compound known in the trade as Thermon T 63. It will stand 1250 F., the normal maximum heat for the element. This coating not only improves the heat transfer but permits a degree of elasticity -for the expansion 0f the element when heating. The element 33 is formed in a serpentine-shape to present a flat grid, as shown in FIG- URE 6, the ends projecting out the stone to pass through the slots 24 of the box 21 and provide the terminals 25 and 25. The composition stone 32 is also molded within `and to an encircling wire mesh 36, preferably expanded metal, which protects the outer walls of the stone from damage. This shell of wire imesh is chrome plated to prevent rust. The bottom of the stone rests on a sheet metal spacing pad 37 to protect the bottom of the box from the heat, and at the same time a spacing 38 is left between the mesh and the box 21 for the same purpose.

When the composition stone 32 is placed in the box a pair of metal screws 39 are threaded through the front wall of the box and are long enough to cross over the spacing 38 (see FIGURE 3) to contact the stone surface and prevent lift of that side. Similarly, a sheet metal shield 40 centrally nests over the upper rear edge of the box and is secured by a screw 41. The inner side of the shield projects downward at a 45 angle and contacts the stone surface, to prevent any lifting at this side.

It should be mentioned at this time that a horizontal opening is centrally molded in the rear wall of the stone 32, above and adjacent the element 33, for the recept1on of a thermostat probe 42. This probe is shown in FIG- URE 4 and consists of a solid copper rod welded at right angles to a vertical copper plate 43. The plate is centrally received against the outer -rear wall of the box 21 and on lan insulation pad 44 while the rod of the probe passes through the insulation and the box and into the opening in the stone. The thermostat control 26 rests against the plate 43 for heat contact therewith and is secured to the box by screws which pass through both. The rod and plate being copper quickly communicate the stone temperature to the thermostat control. It will also be seen that the shield 40 protects the thermostat control from the spraying water.

The steam generator 17 is connected into the circuit of the sauna unit in the manner shown in FIGURE 7, the terminals 25, 25', 28 and 29 being shown in the upper part. Three main power wires (not shown) are adapted to be connected to contacts 45, 46 and 47 at the bottom of the circuit, the central contact 46 being grounded to the unit. The three contacts are carried on a main knife switch 48 which, when closed, connects the contacts 4S and 47 with a pair of fuses 49 and 50 respectively, The opposite end of the fuse 50 connects to a Wire S1 which through a wire 52 connects to the terminal 29 of the thermostat control 26. A wire 53 then connects the terminal 28 of the control with the terminal 25 of the element 33 of the steam generator stone. The other terminal 25 of this element connects through ya pair of wires 54 and 5S -With a temperature switch 56 of the original sauna unit. A yfurther wire 57 from this latter switch completes the circuit back to the fuse 49.

In the operation of the sauna unit, the element 33 heats the composition stone 32 to a high temperature (normally between 500600 F.) and assists the regular element 16 in heating the bathroom. When the occupant thereof desires to receive steam shock-treatment, the valve 20 is manually turned on. This causes water to spray from the pipe 18 onto the heated stone 32 thus creating steam which is indicated at 58. The steam is directed into the bathroom by that portion of the fan blast which passes up the spacing 31. As this water comes into contact with the upper porous surface `of the stone and passes down the slots 35 to the bottom it is promptly vaporized to carry out the -principle of a Finnish sauna; instant steam. Any surplus water, if any is quickly carried away by the drain' pipe 23 so heat is not lost in raising its temperature. AsA live wires are not exposed short circuits cannot occur- While the steam generation removes heat from the stone 32 the close bond of the heating element 33 therewith soon restores the high temperature and a continuous supply of steam is assured. Expansion of the metallic shell 36 by the heat is neglible due to the open mesh and the spacing between the heated stone and `the box container insures that the box will not be damaged. Should the temperature of the composite stone rise too high, the thermostat control 26 will shut-01T the current to the element 33 until it cools down. This control always operates etiiciently as it is protected from water by the shield 40.

Should the temperature of the sauna unit itself rise dangerously and go beyond the setting of the te-mperature switch 56, this switch will automatically stop all current to the elements, as explained in my former patent, and so posiitvely prevent any serious accident.

What I claim as my invention is:

1. A steam generator for a heating unit, comprising: an open-topped container receivable by said unit and having means for draining into said unit; a porous composition stone receivable by said container; said stone having an imbedded element therein with the ends of said element protruding as terminals; means for connecting a source of electric power to said terminals for element-heating of the stone; said stone molded with a surrounding metal mesh for reinforcement of the sides thereof; a vertical passage through the stone for water flow therethrough; a control in contact with said stone for thermo regulation of said terminal electric power by the temperature of the stone; and said open-topped container presenting means for directing a spray of water onto said stone.

2. A steam generator as defined in claim 1 wherein said stone is supported on a spacing plate on the bottom of the container and is spaced from the walls of the container therearound to prevent warping of said container by the heat of said stone.

3. A steam generator for a sauna heating unit, comprising: an open-topped container receivable by said unit and having means for draining into said unit; a. porous composition stone receivable by said container in spaced relation from the container Walls; said stone having a grid-formed element horizontally im-bedded therein with the ends of said element protruding as terminals therefor; means for connecting a source of electric power to said terminals for heating said element; said stone supported on a spacing pad within the container and having a mesh of expanded metal molded therewith therearound for reinforcement of the stone walls; a vertical passage through the stone for water flow therethrough;

a control carried by the container with a probe extending therefrom and entering the stone for thermo-regulation of the power to said terminals by the temperature of the stone; said open-topped container presenting means for directing a spray of water onto said stone; and guard means carried by the container for protecting said control from said water.

References Cited UNITED STATES PATENTS 1,828,702 10/1931 F00 219-273 2,180,602 11/1939 Morgan 219--457X 6 2,365,243 12/1944 Boren 219-362 X 3,309,503 3/1967 Dow et al. 219--275 X 3,349,224 10/1967 Jaeger l 219-457 X FOREIGN PATENTS 202,491 5/ 1939 Switzerland.

JOSEPH V. TRUHE, Primary Examiner C. L. ALBRITTON, Assistant Examiner U.S. C1. X.R.

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