Electric resistance heating devices – Heating devices – Continuous flow type fluid heater
Reexamination Certificate
2000-01-10
2001-11-20
Walberg, Teresa (Department: 3742)
Electric resistance heating devices
Heating devices
Continuous flow type fluid heater
C392S475000, C392S466000
Reexamination Certificate
active
06321037
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to herbicidal apparatus and methods for use, more particularly to of hot water and/or steam for use in destroying vegetation, and to a hand-held device for dispensing heated water.
BACKGROUND
A weed is generally defined as a plant growing where it is not required. Destruction of weeds can be by a number of means; physical removal, covering, herbicidal chemicals, burning, or scalding with hot water, steam, or both. These methods have their own particular disadvantages for particular applications; for example herbicidal chemicals may leave residues harmful to other life forms or drift from the target plant on to a valuable plants. Burning can start destructive fires.
The preferred method; using hot water, does not leave residues and although it does require energy at the point of use there is no particular energy requirement involved in supplying the raw material: water.
There is a good deal of merit in minimizing the amount of heat energy used by a hot-water applicator means, because water has a high specific heat and the act of boiling water consumes even more heat. Energy consumption is always seen as a disadvantage of hot-water weed control though it must be remembered that it is highly visible whereas the energy cost of preparing or disposing of a weed killer is invisible.
OBJECT
It is an object of the present invention to provide an improved means for the provision of heated water by a portable herbicidal appliance, or one which will at least provide the public with a useful choice.
STATEMENT OF THE INVENTION
In one aspect the invention provides a portable water heater capable of generating a flow of water at around its boiling point, suitable for use in killing plants, having a water inlet for connection to a source of water, water heating means, and an outlet nozzle, wherein there is means for restricting the flow of water through the water heating means; the water heating means comprises an electrical heating means and means for sensing at least the outlet water temperature and means to control the amount of power applied to the water heating means to regulate the temperature of the heated water leaving the outlet.
Preferably the portable water heater is fabricated in the configuration of a wand, capable of being held, using a handle on a first end, by a standing person, the outlet nozzle being situated at a second end of the wand, and the water inlet being situated on or close to the handle.
Preferably the water heating means includes a first heating element for raising the water temperature from that at an inlet, and a second heating element capable of receiving the flow of water from the first heating element, Preferably the second heating element at least is controllable by means of a temperature-sensitive control device in thermal contact with an outlet for heated water so that the second heating element is capable of further heating as required and holding the outlet water temperature at a desired temperature.
Preferably the first heating element raises the inlet water temperature to about 75-85 degrees C. at typical rates of flow.
Preferably the second heating element further raises the temperature of the flow of water to between 95 and 100 degrees C. within a range of typical rates of flow and/or within a range of inlet water temperatures.
Preferably the means to control the amount of power applied to the water heating means comprises an electronic controller capable regulating the power level supplied to the electrical heating means in response to the sensed water outlet temperature.
Preferably the controller applies maximum power if the outlet water temperature is below a predetermined first limit and less than full power if the outlet water temperature is above this predetermined first limit.
Preferably the flow of water through the wand is arranged so that when in use, water flows from the handle towards the outlet end and then flows upwards through the electrical heating means and exits the electrical heating means near the handle, and the resulting hot water is then piped to the outlet nozzle.
Preferably the electrical heating means comprises a single resistance heating element of about 2 kW rating surrounded by a co-axial tube through which the water can flow.
More preferably the format of the electrical energy consumed is compatible with household mains supplies, for instance 2 kW at 230V AC.
Preferably the flow rate of water is constrained so that available power levels are capable of raising the outlet temperature to lie within the preferred range of temperatures.
Preferably the invention is provided with safety devices capable of interrupting the flow of electricity in the event of overheating.
Preferably the invention is provided with safety devices capable of interrupting the flow of electricity in the event of a hazardous amount of current leakage into the water system.
REFERENCES:
patent: 5078123 (1992-01-01), Nagashima et al.
patent: 5265318 (1993-11-01), Shero
patent: 5385106 (1995-01-01), Langshaw
patent: 2122511 (1984-01-01), None
Reid David Garth
Weatherly John Deane
Campbell Thor
Waipuna International Limited
Walberg Teresa
Young Law Firm P.C.
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