Gas appliance such as a thermal weed sprayer

Details Gas appliance such as a thermal weed sprayer Gas appliance such as a thermal weed sprayer

1999-12-22

2001-02-20

Yeung, James C. (Department: 3743)

Combustion

Electrical or mechanical igniter correlated with burner feed

Having electric current producer

C431S258000

Reexamination Certificate

active

06190161

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATION
The present application is related to and seeks priority for related information from PCT International Application No. PCT/IB98/00935, International Publication No. WO 98/59199, entitled APPAREIL A GAZ DU TYPE DESHERBEUR THERMIQUE, filed on Jun. 15, 1998, having a priority of date of Jun. 23, 1997 from French Patent Application No. 97/08068. The present application incorporates these related applications by reference in their entireties.
1. Field of the Invention
The present invention relates to gas combustion appliances, in particular electric ignition systems of gas torch appliances, such as flame throwers used in burning weeds.
2. Background Information
Gas combustion appliances such as blowtorches and flame throwers are well-known in the art. Publication EP-A-0 415 824 describes one such blowtorch for use in welding as comprising a fuel gas flow control device, a burner, and a piezoelectric ignition. The fuel gas control device may be, for example, a pressure-reducing valve. The burner may include an air/fuel mixer for the introduction of oxidizing air into the controlled flow of fuel gas, a metal pipe for transferring the air/fuel mixture, and a combustion device for burning the air/fuel mixture. The piezoelectric ignition may include a grounded piezoelectric generator coupled by an insulated wire to an electrode that is next to but offset from the metal pipe.
Traditionally, the electrode constitutes a part or component whose installation requires accurate positioning, because beyond the discharge distance, no ignition of the combustible mixture occurs. The accurate positioning of the electrode during installation may require, on the one hand, one or more precision-machined parts, and on the other hand, a controlled assembly operation.
SUMMARY OF THE INVENTION
The present invention relates to gas combustion appliances having piezoelectric ignition systems, such as flame throwers used in burning weeds. In particular, the subject of the present invention is a piezoelectric ignition assembly that is particularly simple in its construction and in its layout, but nonetheless facilitates the precise positioning required for the electrode. An exemplary embodiment of the electrode according to the present invention comprises a stripped end formed by and arranged at the end of a semi-rigid electric wire located inside a transfer pipe, the wire having been shaped to form a bent part braced inside the pipe and a terminal branch that diverges from the transfer pipe to leave a predetermined discharge distance between the stripped end and the pipe.
Moreover, a preferred embodiment of a gas appliance according to the present invention includes a fuel gas flow control device, a burner assembly, and a piezoelectric ignition assembly. The fuel gas flow control device comprises a fuel regulator valve assembly. The burner assembly includes a transfer pipe assembly having an assembly proximal end and an assembly distal end, an air/fuel mixing assembly at the assembly proximal end, and a combustion nozzle at the assembly distal end. The transfer pipe assembly has an inner tube at the assembly proximal end and an outer tube at the assembly distal end. The piezoelectric ignition assembly includes a grounded piezoelectric generator coupled by a thermally and electrically insulated, semi-rigid electric wire to an electrode comprising a stripped end of the wire arranged inside and at a distal end of the inner tube, the wire having been shaped to form a bent part braced inside the pipe and a terminal branch that diverges from the inner tube to leave a predetermined discharge distance between the stripped end and the inner tube.
In addition, the outer tube preferably has a length adapted to a maximal path of inflammation at the moment of ignition of the burner, to facilitate transferring a flame forward from the proximal end of the outer tube to the combustion nozzle and thereby lighting the nozzle. Furthermore, the outer tube can be made to telescopically slide over the inner tube to vary the length of the transfer pipe assembly. Thanks to the arrangement of the assemblies of the present invention, it is therefore possible to vary the length of the transfer pipe assembly without the piezoelectric ignition assembly hampering the sliding of the outer tube over the inner tube, and at the same time ensuring piezoelectric ignition independent of the effective length of the transfer pipe assembly.


REFERENCES:
patent: 4292021 (1981-09-01), Miyagawa
patent: 4526532 (1985-07-01), Nelson
patent: 4666399 (1987-05-01), Nelson
patent: 5123837 (1992-06-01), Farnham et al.
patent: 5626471 (1997-05-01), Howie et al.
patent: 0 415 824 (1991-03-01), None
patent: 0 821 197 (1998-01-01), None

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