Eddy current type digital encoder and position reference

Claim 2

In a digital encoder and position reference, the combination of a scale and a variable reluctance head, said scale including a plurality of channels defining a binary coded pattern which is unique for each position of said head, each channel of said pattern having at least one region of high permeability material and at least one region of low permeabIlity material, said regions of high and low permeability of each channel being different from the regions of adjacent channels, said head comprising a plurality of variable reluctance transducer elements with one element located in alignment with each of said channels, each of said transducer elements including a coil, a yoke having a central portion extending through said coil and having opposite ends located in spaced relationship to each other, first shielding means disposed between portions of said yoke and said coil, second shielding means located between adjacent transducer elements, and means for exciting said coil so that a primary magnetic flux field flows through said yoke and secondary magnetic fields are induced by eddy currents in said first and second shielding means to concentrate the magnetomotive force gradient in the gap between the opposite ends of said yoke to sense the presence or absence of high permeability material in said gap.

Claim 3

The structure of claim 1 in which the gap between opposite ends of the yoke of each transducer element is located in alignment with the gaps of the other transducer elements.

Claim 4

The structure of claim 1 in which said scale includes sharply defined regions of high permeability and low conductivity material in a field of low permeability and high conductivity material.

Claim 5

The structure of claim 1 in which said yoke includes a wide central portion and end portions of reduced size.

Claim 6

The structure of claim 1 in which said first shielding means includes an opening to accommodate said yoke, and a slot extending from said opening to the edge of said first shielding means in the area of said coil to interrupt current flow through said first shielding means.

Claim 7

The structure of claim 1 in which said region of high permeability material in said scale is constructed of mu-metal.

Claim 8

The structure of claim 1 in which said region of high permeability material in said scale is constructed of low carbon steel.

Claim 9

The structure of claim 1 in which said region of low permeability material in said scale is constructed of copper.

Claim 10

The structure of claim 1 in which said coil includes multi-layers in which each pair of layers are connected together at the center of the coil.

Claim 11

A digital encoder and position reference apparatus for measuring precise distances from a known reference point comprising a scale having a plurality of channels defining a binary coded pattern, one of said channels having at least one region of high permeability material, each of the other channels having regions of high permeability material equally spaced in regions of low permeability material, said regions of high and low permeability of each channel being different from the regions of adjacent channels, a variable reluctance head mounted in proximity to said scale, one of said head and said scale being movable relative to the other, said head including a plurality of variable reluctance transducer elements with one element in alignment with each of the channels of said scale, each of said transducer elements including a multi-layer coil connected together at the center of the coil and having outwardly extending peripheral leads, first shielding means located about said coil, a substantially U-shaped yoke having a bight portion extending through said first shielding means and the center of said coil, said yoke having generally parallel arms located adjacent to said first shielding means and terminating in spaced relationship to each other at one edge thereof and defining a gap, second shielding means located between adjacent transducer elements, and means for applying alternating current to the leads of said coil so that a primary magnetic flux field flows through said yoke and a secondary magnetic field is induced by eddy currents in said first and second shielding means and cause the magnetomotive force gradient to be concentrated in the gap between the opposite ends of said yoke to sense the presence or absence of high permeability materiAl in said gap.

Claim 12

A digital encoder and position reference apparatus for measuring precise distances from a known reference point comprising a scale having a plurality of channels defining a binary coded pattern, one of said channels having at least one region of high permeability material, each of the other channels having regions of high permeability material equally spaced in regions of low permeability material, said regions of high and low permeability of each channel being different from the regions of adjacent channels, a variable reluctance head mounted in proximity to said scale, one of said head and said scale being movable relative to the other, said head including a plurality of variable reluctance transducer elements with one element in alignment with each of the channels of said scale, each of said transducer elements including a multi-layer coil connected together at the center of the coil and having outwardly extending peripheral leads, first shielding means located about said coil, a substantially U-shaped yoke having a bight portion extending through said first shielding means and the center of said coil, said yoke having generally parallel arms located adjacent to said first shielding means and terminating in spaced relationship to each other at one edge thereof and defining a gap, second shielding means located between adjacent transducer elements, and means for applying alternating current to the leads of said coil so that a primary magnetic flux field flows through said yoke and a secondary magnetic field is induced by eddy currents in said first and second shielding means and cause the magnetomotive force gradient to be concentrated in the gap between the opposite ends of said yoke to sense the presence or absence of high permeability materiAl in said gap.

Claim 13

In a digital encoder and position reference apparatus having a scale including a binary coded pattern consisting of a plurality of channels, each channel having at least one region of high permeability material and at least one region of low permeability material, said regions of high and low permeability of said channels cooperating to define a predetermined number of unique positions; the improvement comprising a pickup head, said head including a plurality of variable reluctance transducer elements with one element located adjacent to each of the channels of said scale, each of said transducer elements including a coil, a yoke having a central portion associated with said coil and having opposite ends located in spaced relationship to each other, first shielding means located between the opposite ends of said yoke, second shielding means located on the opposite side of said yoke from said first shielding means, and means for exciting said coil so that a primary magnetic flux field flows through said yoke and secondary magnetic fields are induced by eddy currents in said first and second shielding means to concentrate the magnetomotive force gradient in the gap between opposite ends of said yoke to sense the presence or absence of high permeability material in said gap.

Claim 14

In a digital encoder and position reference apparatus having a scale including a binary coded pattern consisting of a plurality of channels, each channel having at least one region of high permeability material and at least one region of low permeability material, said regions of high and low permeability of said channels cooperating to define a predetermined number of unique positions; the improvement comprising a pickup head, said head including a plurality of variable reluctance transducer elements with one element located adjacent to each of the channels of said scale, each of said transducer elements including a coil, a yoke having a central portion associated with said coil and having opposite ends located in spaced relationship to each other, first shielding means located between the opposite ends of said yoke, second shielding means located on the opposite side of said yoke from said first shielding means, and means for exciting said coil so that a primary magnetic flux field flows through said yoke and secondary magnetic fields are induced by eddy currents in said first and second shielding means to concentrate the magnetomotive force gradient in the gap between opposite ends of said yoke to sense the presence or absence of high permeability material in said gap.