1. Electric water heating apparatus comprising first and second electric water heaters each having a tank adapted to hold a quantity of water to be heated, thermal insulation arranged to insulate a portion of said tank, an electric heating structure for heating water disposed in said tank, an electrical control circuit for controlling said electric heating structure, and electrical wiring, the electrical control circuits of the first and second water heaters and the electrical wiring forming a control unit, wherein the control unit is arranged to the electric heating structure of the second electric water heater to be powered only if the electric heating structure of the first electric water heater is not powered, said first and second electric water heaters being in a vertically stacked end-to-end relationship in which top and bottom ends of said first and second electric water heaters, respectively, are interfittingly interlocked with one another,
wherein the first and second water heaters comprise junction boxes and a vertical wiring passage extending between the junction boxes and through the thermal insulation, the vertical wiring passage containing the electrical wiring, the junction boxes being arranged to be vertically aligned when the first and second water heaters are interfittingly interlocked with one another to electrically connect said electric wiring of said first and second electric water heaters.
2. The electric water heater apparatus of claim 1 wherein:
said first and second electric water heaters have identical configurations.
3. The electric water heater apparatus of claim 1 wherein:
each of said first and second electric water heaters has a projection on its top end and a recess in its bottom end, with the projection of one of said first and second electric water heaters being complementarily received in the recess of the other one of said first and second electric water heaters.
4. The electric water heater apparatus of claim 3 wherein:
said projections and recesses are centrally disposed respectively on said top and bottom ends of said first and second electric water heaters.
5. The electric water heater apparatus of claim 4 wherein:
said projections and recesses have frustroconical configurations.
6. The electric water heater apparatus of claim 1 wherein:
neither of said first and second tanks has a volume exceeding fifty five gallons, and the total volume of said first and second tanks exceeds fifty five gallons.
7. The electric water heater apparatus of claim 1 wherein each of said first and second electric water heaters has:
a jacket structure outwardly circumscribing its tank and forming an insulation space between its jacket structure and its tank;
an insulation material disposed in said insulation space;
upper and lower electrical junction boxes respectively disposed on its top and bottom ends; and
a wiring passage extending through said insulation material between said upper and lower electrical junction boxes.
8. Electric water heating apparatus comprising a plurality of electric water heaters having top and bottom ends configured to permit said plurality of electric water heaters to be vertically stacked in an end-to-end relationship in which each facing pair of said top and bottom ends interfittingly interlock with one another, each of said plurality of electric water heaters having thermal insulation arranged to insulate a portion of said tank, an electric heating structure and an electric control circuit for controlling said electric heating structure, wherein said electrical control circuits are interconnectable such that the electric heating structure of a first electric water heater of the plurality of electric water heaters is to be powered only if the electric heating structure of a second electric water heater of the plurality of water heaters is not powered;
Wherein the plurality of water heaters comprise junction boxes and a vertical wiring passage extending between the junction boxes and through the thermal insulation, the vertical wiring passage containing the electrical wiring, the junction boxes being arranged to be vertically aligned when the first and second water heaters are interfittingly interlocked with one another to electrically connect said electric wiring.
9. The electric water heating apparatus of claim 8 wherein:
the electric water heaters in said plurality thereof have identical configurations.
10. The electric water heating apparatus of claim 8 wherein:
each of said plurality of electric water heaters has a projection on its top end and a recess on its bottom end, and
when said plurality of electric water heaters are vertically stacked in an end-to-end relationship, the projections and recesses in each facing pair of said top and bottom ends are configured to be complementarily telescoped with one another.
11. The electric water heating apparatus of claim 10 wherein:
said projections and recesses are centrally disposed respectively on said top and bottom ends of said plurality of electric water heaters.
12. The electric water heating apparatus of claim 10 wherein:
said projections and recesses have frustroconical configurations.
13. The electric water heating apparatus of claim 8 wherein:
each of said plurality of electric water heaters has a tank for holding water to be heated,
none of said tanks of said plurality of electric water heaters has a volume exceeding fifty five gallons, and
the total tank volume of said electric water heating apparatus exceeds fifty five gallons.
14. The electric water heating apparatus of claim 8 wherein each of said plurality of electric water heaters further comprises:
a tank adapted to hold a quantity of water to be heated;
a jacket structure outwardly circumscribing said tank and forming an insulation space between said jacket structure and the tank;
an insulation material disposed in said insulation space;
upper and lower electrical junction boxes respectively disposed on said top and bottom ends of the electric water heater, and
a wiring passage extending through said insulation material between said upper and lower electrical junction boxes.
15. A water heating apparatus comprising:
a first water heater having:
a first thermal insulation;
a first tank;
a first junction box;
a first electric heating structure; and
a first control unit connected to the first electric heating structure;
a second water heater having:
a second thermal insulation;
a second tank;
a second junction box;
a second electric heating structure; and
a second control unit connected to the first electric heating structure; and
electrical wiring interconnecting the first control unit and the second control unit, said electrical wiring extending through a vertical wiring passage through the first thermal insulation and the second thermal insulation, between said first junction box and said second junction box are vertically aligned when the first and second water heaters are interfittingly interlocked with one another to electrically connect said electric wiring;
wherein the first control unit, second control unit, and electrical wiring are arranged such that the second electric heating structure is to be powered only if the first electric heating structure is not powered.
16. The water heating apparatus of claim 15, wherein the first control unit, second control unit, and electrical wiring are further arranged such that the second electric heating structure cannot be powered while the first electric heating structure is powered.
17. The water heating apparatus of claim 15, wherein the first tank comprises an upper end, a lower end, a projection extending upwardly from said upper end, and a recess formed in said lower end and having a configuration complementary to that of said projection.
18. The water heating apparatus of claim 17 wherein:
said projection and said recess have frustroconical configurations.
19. The water heating apparatus of claim 17 wherein:
said projection and said recess are centrally positioned respectively on said top and bottom ends of said electric water heater.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A composite material of a base body with a multilayer coating which has at least one multiphase layer of aluminum, zirconium andor hafnium oxides and a single phase layer of Al2O3, ZrO2 or HfO2.
2. A composite material according to claim 1 characterized in that the multiphase layer contains an additional proportion of MgO andor the single phase layer contains up to 1% of an additional titanium oxide proportion.
3. The composite material according to claim 1, characterized by at least two, preferably at least three, layers which are comprised each of a multiphase layer of oxides of Al, Zr, Ti andor Al, Hf, Ti, andor Al, Zr, Ti, Mg andor Al, Hf, Ti, Mg and of a three phase oxide layer of Hf, Zr or Al.
4. The composite material according to claim 1 characterized in that the base body is composed of a hard metal, steel, cermet or ceramic.
5. The composite material according to claim 1 characterized in that between the substrate body and a first oxide layer, which preferably is a multiphase oxide layer, at least one layer of TiCN, HfCN or ZrCN is provided which preferably has a thickness of 1 to 15 \u03bcm, especially 3 to 8 \u03bcm.
6. The composite material according to claim 1 characterized in that between the multiphase oxide layer and the single phase oxide layer, preferably between each two such layers, one or more intermediate layers are provided of TiCN, HfCN, or ZrCN, each of which preferably has a thickness between 0.2 \u03bcm to 3 \u03bcm, especially 2 \u03bcm.
7. The composite material according to claim 1 characterized in that the total thickness of all of the multiphase oxide layers and all single phase oxide layers is 6 to 20 \u03bcm, preferably 10 \u03bcm, whereby further preferably the thickness of an individual multiphase oxide layer is 2 to 6 \u03bcm, preferably 4 \u03bcm, andor the thickness of the individual single phase oxide layer is 1 to 5 \u03bcm, preferably 3 \u03bcm.
8. The composite material according to claim 1 characterized in that the multilayer coating is produced by means of CVD.
9. The composite material according to claim 1 characterized in that the composite material is subjected to a final dry blast treatment with using a granular blast agent composed of a high metal granulate and which at least in major part has a rounded grain configuration with a maximum diameter of 150 \u03bcm preferably with a maximum of 100 \u03bcm.