Apparatus for expressing writing fluid from a plotting pen

Claim 2

Apparatus for expressing writing fluid from a plotting pen onto a recording medium while the pen and the recording medium are moved relative to one another in a plotting device in accordance with plotting commands supplied to the plotting device comprising: velocity signal generating means connected with the plotting device for producing a velocity signal representative of the rate of movement of the pen and the recording medium relative to one another in the plotting device; and fluid pumping means connected to the plotting pen and the velocity signal generating means and responsive to the velocity signals for forcing writing fluid from the plotting pen at a flow rate proportional to the rate of movement of the pen and recording medium relative to one another in the plotting device, the fluid pumping means including a fluid piston pump having a rotatably driven drive shaft, fluid displacement pistons, piston drive means interconnecting the shaft and the pistons for displacing at least one piston by an amount directly proportional to the shaft rotation at each rotational position of the shaft and a fluid discharge duct receiving the displaced fluid and connected to the plotting pen; and pump motor means connected to the drive shaft of the pump and to the velocity signal generating means for rotating the drive shaft at a rate proportional to the velocity signal.

Claim 3

Apparatus for expressing writing fluid from a plotting pen as defined in claim 1 wherein the velocity signal generating means includes a rate sensing circuit connected to receive the plotting commands supplied to the plotting device.

Claim 4

Apparatus for expressing writing fluid as defined in claim 1 wherein the piston drive means comprises drive cams interconnecting the rotatably driven drive shaft and the pump pistons.

Claim 5

Apparatus for expressing writing fluid as defined in claim 3 wherein the rotatably driven drive shaft is connected between the pump motor and the drive cams, and the drive cams are rotatable in the pump and have cam profile segments selected to displace the pistons within the cylinders by amounts directly proportional to rotation of the drive shaft.

Claim 6

In a plotting device in which a plotting head and a recording medium are moved relative to one another along first and second mutually perpendicular axes in response to plotting commands supplied to first and second transport mechanisms associated respectively with the relative movements of the head and the recording medium along the first and second directions, the improvement comprising: first drive motor means connected in the first transport mechanism for receiving plotting commands and actuating the first transport mechanism; second drive motor means connected in the second transport mechanism for receiving plotting commands and actuating the second transport mechanism; first rate sensing means for providing a first rate signal representative of the relative movement of the head and recording medium along the first axis; second rate sensing means for producing a second rate signal representative of the relative movement of the head and the recording medium along the second axis; computing means connected with the first and the second rate sensing means for producing a rate signal representative of the combined rates of relative movement of the head and recording medium along the first and second axes; a writing fluid reservoir; a plotting pen mounted to the plotting head and having a writing tip carried by the plotting head in close proximity to the recording medium; a piston pump connected between the writing fluid reservoir and the plotting pen and having a drive train including a pump drive shaft and means for displacing the individual pistons in the pump in direct proportion to the shaft rotation or fraction thereof while the pistons are expelling fluid from the pump; and pump drive means connected to the computing means and drive shaft of the pump foR controlling the pump to produce a flow of writing fluid from the writing tip of the recording pen at a flow rate proportional to the rate signal from the computing means.

Claim 7

In a plotting device in which a plotting head and a recording medium are moved relative to one another along first and second mutually perpendicular axes in response to plotting commands supplied to first and second transport mechanisms associated respectively with the relative movements of the head and the recording medium along the first and second directions, the improvement comprising: first drive motor means connected in the first transport mechanism for receiving plotting commands and actuating the first transport mechanism; second drive motor means connected in the second transport mechanism for receiving plotting commands and actuating the second transport mechanism; first rate sensing means for providing a first rate signal representative of the relative movement of the head and recording medium along the first axis; second rate sensing means for producing a second rate signal representative of the relative movement of the head and the recording medium along the second axis; computing means connected with the first and the second rate sensing means for producing a rate signal representative of the combined rates of relative movement of the head and recording medium along the first and second axes; a writing fluid reservoir; a plotting pen mounted to the plotting head and having a writing tip carried by the plotting head in close proximity to the recording medium; a piston pump connected between the writing fluid reservoir and the plotting pen and having a drive train including a pump drive shaft and means for displacing the individual pistons in the pump in direct proportion to the shaft rotation or fraction thereof while the pistons are expelling fluid from the pump; and pump drive means connected to the computing means and drive shaft of the pump foR controlling the pump to produce a flow of writing fluid from the writing tip of the recording pen at a flow rate proportional to the rate signal from the computing means.

Claim 8

In a plotting device, the improvement as defined in claim 5 wherein: the first rate sensing means has an input receiving plotting commands received by the first drive motor means; and the second rate sensing means has an input receiving plotting commands received by the second drive motor means.

Claim 9

In a plotting device, the improvement as defined in claim 5 wherein the plotting pen has a capillary tube forming the writing tip of the pen, a writing fluid supply conduit connected with the fluid pump and a housing having a bore leading from the writing piston supply conduit to the capillary tube.

Claim 10

In a plotting device, the improvement as defined in claim 5 wherein the writing piston reservoir and the fluid pump are mounted to the plotting head with the plotting pen.

Claim 11

In a plotting device, the improvement as defined in claim 5 wherein the drive train of the pump has at least two rotatable drive cams mounted on a common axis and two cam-operated pumping pistons associated respectively with the two drive cams, and two drive cams each having cam profile segments subtending arcs about the common axis greater than 180* and providing positive piston displacements directly proportional to the cam rotations, the cams being mounted on the common axis and rotated together so that at least one of the cam profile segments displaces an associated piston during each phase of the cam rotations.

Claim 12

In a plotting device, the improvement as defined in claim 9 wherein the pump drive means includes a pump motor driven at a speed proportional to the rate signal from the computing means and connected in driving relationship with the two rotatable drive cams.