Computer input device

A computer input device comprising a body contacted by only the tips of the thumb and the tips of one or more fingers, with no contact with the palm of the hand, the body having a generally planar base for resting on a work surface and extending away from the base and having a thumb support ledge defining a thumb surface for engagement by only the tip of a thumb of a user, and an opposed finger surface for engagement by only the tip of one or more fingers of the user,

• wherein the thumb support ledge is located a distance in the range 15 to 30 mm above the base, with the spacing between the thumb and finger surface being in the range 8 to 40 mm,
• wherein the body is symmetrical about a plane perpendicular to the base, passing through the thumb surface and finger surface, wherein upper and lower portions of the finger surface extend across the full width of the device and constitute buttons of switch means for operation by finger pressure, with a scroll wheel being provided between the upper and lower portions of the finger surface, for rotation in a horizontal plane,
• wherein the width of the device, in a direction transverse to the spacing between the thumb and finger surfaces, is not more than 70 mm,
• wherein the body tapers inwardly between a front surface including the finger surface and a rear surface including the thumb surface, in an upward direction from the base, over the full height of the device from the base upwards,
• wherein the rear surface is concave in the top to bottom direction, with the thumb surface constituted by a recessed concavity within the rear surface, and wherein the front and rear surfaces are curved in a rearwards direction over the full height of the device.