Electric resistance heating devices – Heating devices – Tank or container type liquid heater
Reexamination Certificate
2001-12-13
2003-09-30
Campbell, Thor (Department: 3742)
Electric resistance heating devices
Heating devices
Tank or container type liquid heater
C392S441000, C392S444000
Reexamination Certificate
active
06628894
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is directed to a warm water system incorporating a portable water heater, and in particular to a system water heater used in combination with a portable toilet
2. Description of the Prior Art
Hand washing facilities have been provided in portable toilets for a number of years, using cold water. Under cold weather conditions the provision of a brine solution enables such facilities to operate effectively down to as low as zero F degrees (minus 20 C degrees). Also, heaters and heater lights may be used in such circumstances.
Electric water heaters have been in household use for many years, most usually consisting of a heating element immersed within a water storage tank. Other, continuous flow, tankless systems are known, having through-flow arrangements that operate at mains pressure, with an outlet shutoff, and which utilize high temperature plastic components.
Known ones of these are complex in structure, requiring costly specialty injection moldings in their construction.
SUMMARY OF THE INVENTION
The present invention provides a warm water system having a compact, low cost in-line water heater mainly constructed from off-the-shelf component parts.
The subject heater includes a tubular plastic body having closure end caps welded thereto forming a casing.
This construction renders the water heater substantially tamper and vandal proof, being thus safe for children.
The thermal gradient across the thickness of the plastic walls substantially precludes any hot outer surfaces. This is particularly true when a thermostat setting for warm water is selected, in the range of about 68 to 100 F degrees, as opposed to the more usual household setting of some 120 to 130 F degrees.
It will be understood that the warm water is used directly, and does not require blending with cold water, as in the more usual practice.
The heater plastic body, being of polyvinylchloride (PVC) is fire retardant, such that, in the event of the heater becoming dried out, there is an extremely low probability of a fire ensuing from overheating of the heating element that would follow such a dry-out.
In the preferred embodiments, the subject system operates at atmospheric pressure. The water supply may be admitted by way of a hand or foot operated pump, or as a gravity feed, thus enabling the outlet (or “demand end”) to operate without a shut-off tap or other valve, so that the system remains substantially unpressurized at all times.
However, the casing is sufficiently strong to withstand normal household pressures of up to about 100 psi gauge.
The subject system provides a compact, low temperature installation that can be readily mounted on a wall, by way of a U-shaped plastic pipe support bracket or brackets.
The adoption of an all-plastic heater construction, combined with an electric immersion heater element, provides full electrical insulation. Safety may be further enhanced by the use of a ground-fault protected electrical outlet. Such further provision may be considered redundant. The heater is preferably suspended vertically, with the heating element depending downwardly from the upper end of the heater and projecting well into the heating chamber of the heater. The cold water supply is directed to the lower end of the chamber, to flow upwardly, past the heater element to the unrestricted warm water outlet adjacent the upper end of the heater casing. By locating the warm water outlet somewhat below the top of the heating chamber, there is provided an air cushion zone where entrained air and water vapor collects. This cushion zone facilitates a smooth flow of warm water when further cold water is admitted to the heater. Also, under severe freeze-up conditions that may be encountered, the cushion zone provides an expansion space as ice forms within the heater chamber, thus mitigating the adverse effects of such freeze-up.
In a preferred embodiment, the cold water supply is connected to the top outer end of the heater casing, having a transfer tube within the chamber to pass the cold water downwardly towards the bottom of the heating chamber.
A bleed hole in the wall of the transfer tube, located adjacent its upper end, serves as a siphon-break, in the event that the cold water supply line should become drained, which otherwise would tend to siphon out the contents of the heater. In such an eventuality of supply line drain-down, any consequential siphoning is terminated by the bleed hole, which admits air into the line, thereby breaking the vacuum and terminating the siphoning action, such that the heater chamber remains substantially full, thus protecting the heater element against rapid burn-out.
Without such protection, an energized but dry heater element would probably burn out within three or four minutes.
The size of the heating chamber and the rating of the heating element are such that an adequate individual hand washing supply is provided. A recovery time of about 90 seconds between washings has been found to be practical. This value can be varied by changes in the respective parameters of water temperature, heating chamber capacity, and the power rating of the heating element.
The use of a foot pump by the user enables warm water to be dispensed in spurts, consonant with the washer's requirements, while conserving water.
The use of a brine solution to off-set freezing of the cold water supply has the added advantage of improved anti-septic conditions.
A number of variants of the system include a free-standing combination unit incorporating a water tank with a built-in foot pump, surmounted by a wash hand-basin, having the water heater unit secured to the side of the water tank.
Other uses of the system, as for camping, may involve a tree-mounted tank with a variable outlet valve, feeding a subject heater that supplies warm water to a bowl on a picnic table, by way of a molded hook-over delivery tube.
REFERENCES:
patent: 4185187 (1980-01-01), Rogers
patent: 6161228 (2000-12-01), Wietecha
patent: 6321036 (2001-11-01), Huang
Winter Ken S
Winter Roger S.
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