Radially firing igniter

1. A spark igniter comprising a plurality of electrodes and an insulator, which are configured to form an elongated body having a first end, a second end and an outer surface extending between the first end and the second end;

wherein the outer surface comprises a side surface and an end surface,

wherein the end surface is located at the first end, and the side surface extends between the first end and the second end,

wherein the spark igniter is configured to form a spark gap on the side surface, which produces a radially-directed spark,

wherein the plurality of electrodes comprises a first electrode and a second electrode and at least a portion of the second electrode forms an electrode shell, which surrounds at least a portion of the first electrode and forms at least part of the side surface;

wherein the insulator is between the first electrode and the electrode shell,

wherein a portion of the side surface is adjacent to the end surface and the electrode shell defines an open end and the first electrode extends through the inside of the electrode shell and out the open end to form a cap forming the end surface and the portion of the side surface adjacent to the end surface, and

wherein the spark gap is between the side surface of the cap and the open end of the electrode shell.

2. The spark igniter of claim 1 wherein the side surface is a cylindrical surface and the spark gap is a circumferentially extending gap.

3. The spark igniter of claim 2 wherein the circumferentially extending gap extends completely around the cylindrical surface.

4. The spark igniter of claim 1 wherein the first electrode forms a first edge of the circumferentially extending gap and the open end of the electrode shell forms a second edge of the circumferentially extending gap.

5. The spark igniter of claim 1 wherein the end surface offers at least partial protection for the spark gap from flame radiation.

6. The spark igniter of claim 5 wherein the end surface has an end diameter and the electrode shell has an outer diameter and the end diameter is greater than the outer diameter.

7. The spark igniter of claim 1 wherein the side surface of the cap includes a first side surface portion extending longitudinally toward the second end and having a first length and a tab portion extending longitudinally toward the second end and having a second length, wherein the first length is less than the second length and the spark gap extends around the tab portion.

8. The spark igniter of claim 7 wherein the tab portion has two longitudinal edges and a circumferential edge and the electrode shell is a cylindrical surface having a notch with the open end forming an edge spaced from and opposing the tab so that the spark gap is a circumferentially and longitudinally extending gap.

9. A spark igniter comprising a plurality of electrodes and an insulator, which are configured to form an elongated body having a first end, a second end and an outer surface extending between the first end and the second end;

wherein the outer surface comprises a side surface and an end surface,

wherein the end surface is located at the first end, and the side surface extends between the first end and the second end,

wherein the spark igniter is configured to form a spark gap on the side surface, which produces a radially-directed spark,

wherein the plurality of electrodes comprises a first electrode and a second electrode and at least a portion of the second electrode forms an electrode shell, which surrounds at least a portion of the first electrode and forms at least part of the side surface;

wherein the insulator is between the first electrode and the electrode shell,

wherein the electrode shell forms the end surface,

wherein the electrode shell has a first gap edge defining an aperture in the side surface, and

wherein the first electrode forms at least part of the side surface and forms a second gap edge within the aperture such that the first gap edge and second gap edge define the spark gap.

10. The spark igniter of claim 9 wherein the first gap edge and the second gap edge are the same shape and are concentric.

11. The spark igniter of claim 10 wherein the first gap edge and the second gap edge are an elongated closed curve and are confined to one-half of the circumference of the side surface.

12. The spark igniter of claim 10 wherein the first gap edge and the second gap edge are circular and are concentric and where there is a plurality of spark gaps formed on the side surface.