Computer input/output equipment

Claim 2

A digitising table unit, comprising a first or digitising table surface, freely movable digitising index member which may be placed at any chosen position within the area of the first table surface, a bug mounted below the first table surface to be movable along x and y axes by means of servo-motors to a position corresponding to the position of the digitising pen when the pen is place on the first table surface, encoding means arranged so that the x and y coordinates of the position of the bug and therefore the pen is converted into electrical signals indicative of that position, a second table surface occupying a plane parallel to that of the first table surface and located in a position below the area of the first table surface, and retractable pen means mounted on the bug and engageable with the second table surface whereby movement of the bug may trace out a representation on the second table surface.

Claim 3

A table unit as claimed in claim 1, including an x axis slideway aligned in said x axis, a gantry arm slidably mounted on said x axis slideway, and a y axis slideway on said gantry arm, said bug being slidably mounted on said y axis slideway.

Claim 4

A table unit as claimed in claim 2, wherein said gantry arm and said bug are slidable on said slideways by means of re-circulating ball bearings.

Claim 5

A table unit as claimed in claim 2, wherein said gantry arm is slideable on said x axis slideway by means of air bearings.

Claim 6

A table unit as claimed in claim 2, wherein said x axis and said y axis servo motors each drive said gantry arm and said bug respectively by way of a flexible looped element extending around a pair of pulleys disposed one at each end of the respective slideway, said looped elements being attached respectively to the gantry arm and the bug, and one of the pairs of pulleys being driven by the respective servo motor.

Claim 7

A table unit as claimed in claim 5, wherein said looped element is a toothed belt.

Claim 8

A table unit as claimed in claim 5, wherein said looped element is a flexible wire.

Claim 9

A table unit as claimed in claim 2, wherein said encoding means comprises an x axis rotary encoder and a y axis rotary encoder, and said encoders are each driven respectively from said gantry arm and said bug by means of a flexible looped element extending around a further pair of pulleys disposed one at each end of the respective slideways, said looped elements being attached respectively to the gantry arm and the bug and one of the respective pairs of pulleys driving the respective encoder.

Claim 10

A table unit as claimed in claim 8, wherein said looped element is a close tolerance steel wire.

Claim 11

A table unit as claimed in claim 8, wherein each said looped element is wound around the respective one of said pairs of pulleys for a plurality of turns.

Claim 12

A table unit as claimed in claim 2, wherein said bug is provided with a moveable counter balance weight.

Claim 13

A table unit as claimed in claim 1 comprising an indexable pen carrier mounted on said bug and a plurality of pens in said carrier, said carrier being indexable under the control of a computer to bring a selected one into operation.

Claim 14

A table unit as claimed in claim 1, wherein said index member is provided with an electric coil arranged to create a magnetic field, and said bug is provided with a sensing coil aligned in said x axis and a sensing coil aligned in said y axis to detect said magnetic field and provide signals indicative of an error in the position of said bug relative to said index member for the control of said servo Motors.

Claim 15

A table unit as claimed in claim 13, including a third electric coil disposed on said bug whereby said bug may be locked magnetically to said index member when in correct relative position thereto.

Claim 16

A table unit as claimed in claim 1, wherein said bug is provided with an electric coil arranged to create a magnetic field, and said index member is provided with a sensing coil aligned in said x axis and a sensing coil aligned in said y axis to detect said magnetic field and provide signals indicative of and error in the position of said bug relative to said index member for the control of said servo motors.

Claim 17

A table unit as claimed in claim 15, including a third electric coil disposed on said index member whereby said bug may be locked magnetically to said index member when in correct relative position thereto.

Claim 18

A table unit as claimed in claim 1, wherein said index member includes a window aperture and a pair of cross wires disposed therein for alignment of the member with a selected position on said digitising table surface.

Claim 19

A table unit as claimed in claim 1, wherein said index member includes three point means for supporting it on said digitising surface and one of said points comprises a pen for indicating a chosen position and drawing on said digitising surface.

Claim 20

A table unit as claimed in claim 1, wherein said index member includes means to support it on said digitising surface and a finely pointed member for indicating a chosen position, and further includes optical magnifying means for a user to view the area of the digitising surface beneath said pointed member.

Claim 21

A table unit as claimed in claim 1 wherein said first or digitising table surface is provided on a transparent sheet.

Claim 22

A table unit as claimed in claim 1, wherein said first and second table surfaces are provided on opposite faces of a single board, said board being pivotally mounted about a horizontal axis whereby said first or said second table surface may be presented uppermost.

Claim 23

A combination comprising a digital computer, an input digitising table and an interface means connecting the table to the computer, the table comprising a first or digitising table surface, a freely movable digitising index member which may be placed at any chosen position within the area of the first table surface, a bug mounted below the first table surface to be movable along x and y axes by means of servo-motors to a position corresponding to the position of the digitising pen when the pen is placed on the first table surface, encoding means connected to the interface, whereby the x and y coordinates of the position of the bug and therefore the pen on the first table surface may be converted to electrical signals indicative of that position and transmitted to the computer, a second table surface occupying a plane parallel to that of the first table surface in a position below the area of the first table surface, and retractable pen means mounted on the bug and engageable with the second table surface whereby movement of the bug may trace out a representation of the second table surface.

Claim 24

A combination comprising a digital computer, an input digitising table and an interface means connecting the table to the computer, the table comprising a first or digitising table surface, a freely movable digitising index member which may be placed at any chosen position within the area of the first table surface, a bug mounted below the first table surface to be movable along x and y axes by means of servo-motors to a position corresponding to the position of the digitising pen when the pen is placed on the first table surface, encoding means connected to the interface, whereby the x and y coordinates of the position of the bug and therefore the pen on the first table surface may be converted to electrical signals indicative of that position and transmitted to the computer, a second table surface occupying a plane parallel to that of the first table surface in a position below the area of the first table surface, and retractable pen means mounted on the bug and engageable with the second table surface whereby movement of the bug may trace out a representation of the second table surface.

Claim 25

A combination according to claim 22, wherein a cathode ray tube is connected to said computer for visual display of digitized information in said computer.