Semi-conductive electrical heating device with voids

An electrical heating device including a layer of semi-conductive material carried on an insulating surface and defining a semi-conductive pattern, and a pair of spaced-apart conductors electrically connected to said semi-conductive pattern, said device being characterized in that

• a first heating portion of said semi-conductive pattern intermediate said conductors includes a two-dimensional array of areas devoid of semi-conductive material ("voids") within a mesh of semi-conductive material, and
• said conductors and said voids being arranged such that the centers of the voids forming sets of three adjacent voids are positioned at the corners of triangles, and the overall direction of current flow between said conductors is not parallel to the sides of said triangles.

An electrical heating device including a layer of semi-conductive material carried on an insulating surface and defining a semi-conductive pattern, and a pair of spaced-apart conductors electrically connected to said semi-conductive pattern, said device being characterized in that

• a first heating portion of said semi-conductive pattern intermediate said conductors includes a two-dimensional array of areas devoid of semi-conductive material ("voids") within a mesh of semi-conductive material, said voids being hexagons arranged such that the centers of the voids forming sets of four adjacent hexagons are positioned at the corners of parallelograms.

An electrical heating device including a layer of semi-conductive material carried on an insulating surface and defining a semi-conductive pattern, and a pair of spaced-apart conductors electrically connected to said semi-conductive pattern, said device being characterized in that

• first and second heating portions of said semi-conductive pattern intermediate said conductors each include a respective regular two-dimensional array of areas devoid of semi-conductive material ("voids") within a mesh of semi-conductive material, and
• said second heating portion of said semi-conductor pattern is contiguous to said first heating portion and has a resistivity (ohms per square) different from that of said first portion.