Writing instrument projectable by fluid pressure

Claim 1

A pen having longitudinally opposed first and second ends, comprising: a writing element comprising a longitudinal tube having ink therein and longitudinally opposed ends, one of said ends being a writing tip; actuating means for producing a projecting force in response to lateral pressure applied at any point about the entire outer periphery of said pen between said longitudinally opposed ends and for enabling a pen user to write with said pen when said pen is grasped and positioned in the hand of a user in the normal manner for the intended purpose of writing with said pen; said actuating means comprising: a generally tubular outer pen casing having a resilience such that said outer casing is substantially deformed with the normal amount of force created between the fingers and thumb of a pen user when the user is writing with said pen; a generally tubular inner rigid casing having opposed ends; a fluid reservoir, said reservoir being located substantially between said outer casing and said inner casing and having longitudinally opposed means for sealing said reservoir; and a fluid contained in said reservoir; said writing element being disposed longitudinally within said inner casing with said writing tip adjacent said first end and supported for longitudinal sliding movement; biasing means coacting with said inner casing and said writing element for biasing said writing element longitudinally in a direction toward said second end; projecting means responsive solely to said projecting force produced by said actuating means for projecting said writing tip longitudinally against said biasing means in a direction toward said first end to project said writing tip longitudinally outwardly from said first end a distance sufficient to expose said writing tip, said projecting means comprising expansible chamber means disposed within one of said ends of said inner casing near said second end in fluid communication with said reservoir such that when said projecting force is produced the volume of said fluid in said reservoir is reduced and said fluid is caused to expand said expansible chamber means toward said first end to thereby expose said writing tip, said writing element being positively engaged with said expansible chamber means by said biasing means.