Patent Application
20120288809
The present invention relates to a burner/hot air generator device with a riser usable, in particular but not exclusively, for low-temperature heating of a plastic film, for example a polyethylene film for the retraction thereof using a gas flow coming from the combustion of a combustible gas such as propane or air or to place thermoplastic material on the ground.
The invention more particularly relates to a burner of the type previously described equipped with a riser consisting of a generally tubular element, potentially telescoping, able to insert itself between the injection device and the burner head, of the device.
Such a device is in particular described in patent FR 2 907 882.
One problem results from the fact that the riser is made from an electrically conductive material and is connected to the ground of the electric generator (piezoelectric). As a result, the conductor, which passes into the riser to connect the outlet of the electric generator to a lighting electrode (spark plug) arranged in the lighting chamber of the burner, constitutes, with the riser, a capacitor whereof the capacity depends on the length of the riser and the arrangement of the conductor inside said riser. This capacitor has the drawback of absorbing a significant fraction of the electric charge delivered by the electric generator at the time of the lighting. The charge applied to the spark plug is therefore weakened. To increase the voltage at the terminals of the spark plug, the manufacturer is led to increase the shock on the lighter and/or the operator is led to strike the lighter several times, which considerably reduces its lifetime.
The invention more particularly aims to eliminate these drawbacks. Furthermore, the invention must in particular have a reduced weight and bulk, so as to preserve the portability of the device, and to allow it to be used during long working periods.
To that end, the invention proposes a hot air generating device of the type comprising an injection device capable of producing a flow of a combustible gas mixture at a high speed and a burner head in which the flow is ignited via a spark plug positioned in said burner and electrically connected to a lighter, preferably a piezoelectric lighter, said device also comprising means to reduce the capacitive losses between the lighter and the spark plug.
This device also may or may not comprise a riser tube between the injection device and the burner.
The means for reducing losses comprise means to make the increase in the voltage at the terminals of the spark plug more gradual; in particular, they can be a transformer, of the autotransformer type, mounted in parallel with the lighter.
Preferably, the transformer is mounted as a step-down transformer. A piezoelectric lighter can easily produce a voltage peak of 14 kV, or even 20 kV, whereas a voltage of 8 kV is generally sufficient at the terminals of the spark plug to ignite the gaseous mixture.
Advantageously, the transformer is mounted near the lighter. In particular, if the device comprises a riser tube, the transformer is preferably mounted at one end of the tube opposite the burner.
Several embodiments of the invention are described hereafter, as non-limiting examples, in reference to the appended figures, in which:
In the example shown in
In the illustrated example, the device 1 comprises a spark plug 6, arranged in the burner, to make it possible to ignite the gaseous mixture. The spark plug 6 is supplied with a voltage generated by a piezoelectric lighter 7 arranged in the body of the gun 2. An electric connection between the lighter 7 and the spark plug 6 is ensured on the one hand by the riser tube 4, connected to the ground of the lighter 7, and on the other hand by a linear conductor 8, kept at a distance inside the tube 4.
According to the invention, a transformer 9, of the autotransformer type, is mounted in parallel with the lighter 7. In the example illustrated in
It will be noted that in the usage made thereof, the transformer has not been provided to operate at a constant rating, but rather only according to a regular pulse rating, upon each ignition. The transformer is advantageously calculated so as to include an equivalent “parallel” capacity sufficient to make the voltage “creep,” i.e. to make the increase of the voltage T6 more gradual at the terminals of the spark plug 6, so as to reduce the capacitive losses, in particular between the conductor 8 and the tube 4. For better effectiveness, the transformer is mounted in the gun 2, as close as possible to the lighter 7.
Of course, the invention is not limited to the preferred embodiments just described, but on the contrary is defined by the claims that follow.
One skilled in the art will in fact see that various modifications can be made to the embodiments described above, in light of the teaching just disclosed.
Thus, the transformer can be mounted in a step-up voltage version.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1154143 | May 2011 | FR | national |
