X-Y Plotter

Abstract

A chart recording instrument having electromechanical servos which move a pen or stylus in the X-direction along a paper chart, and move the chart with respect to the pen in the Y-direction. A novel mechanism provides for ease in loading and unloading charts, and for accurate relocation of the chart, whereby a chart can be removed from the machine and then replaced accurately without disturbing any of the gain or zero control settings. Thus a curve can be recorded, the chart removed, and then put back to record another curve in the same family. These functions are controlled by a three-position lever which lifts and lowers the pen, raises and lowers pinch rollers in the Y-axis chart drive system, controls a pair of chart positioning stops, and switches appropriate positioning voltages to the servos.

I claim: 
     
       1. An X-Y plotter comprising: a table adapted to support a cut chart slidably thereon;   a fixed carriage guide extending across said table in an X-direction;   a carriage with a marking element, supported by said guide and movable therealong to provide X-deflection of said marking element across said chart;   driving roller means with pinch roller means engageable with said chart to provide bidirectional recording displacement of said chart across said table in the Y-direction orthogonal to said X-direction;   electromechanical X-servo means connected drivably to said carriage; and   electromechanical Y-servo means connected drivably solely to said driving roller means,   said bidirectional displacement of said cut chart being the sole provision for relative displacement of said chart and said marking element for recording in said Y-direction.   
     
     
       2. An X-Y plotter as in claim 1, further comprising: a manual control element adapted to release said pinch roller means to release said chart, and   a retractable chart stop connected to said control element to protrude above said table when said pinch roller means are released and to retract below said table when said pinch roller means are engaged,   said stop serving to position a replaced chart on said table in a calibrated manner, and to permit normal operation of said plotter when it is retracted and said pinch roller means engaged.   
     
     
       3. The structure of claim 2, further comprising: a multi-position switch linked mechanically to said manual control element, and   electrical connections from said switch to cause said Y-servo means to run said driving roller means to a zero position to permit locating said chart in a calibrated manner against said stops.   
     
     
       4. An X-Y plotter comprising: a table adapted to support a chart slidably thereon;   a carriage guide extending across said table in an X-direction;   a carriage with a marking element supported by said guide and movable therealong;   a driving roller engageable with said chart to move it in a Y-direction orthogonal to said X-direction on said table;   electromechanical X-motor means connected drivably to said carriage;   electromechanical Y-motor means connected to said driving roller;   a pinch roller on a pinch roller arm movable between an engaged and a disengaged position with respect to said driving roller;   a chart stop supported movably below said table to have a protruding position above said table and a retracted position;   a marker lifting arm;   a marker lifting cam engageable therewith;   a control lever having a first and a second position;   a connection between said lever and said chart stop; and   a camming element on said control lever engageable with said pinch roller arm and with said marker lifting cam;   said pinch roller being moved to said disengaged position, said chart stop to said protruding position, and said marker being lifted when said control lever is in said first position, and   said pinch roller being engaged and said chart stop retracted when said control lever is in said second position.   
     
     
       5. The structure of claim 4, wherein: said marker lifting arm is disposed for locking engagement with said marker lifting cam to hold said marker in lifted position,   said locking engagement being manually releasable.   
     
     
       6. The structure of claim 4, said control lever having a third position and being mechanically connected to a multi-position switch,   and edge stop means mechanically connected to said Y-motor means,   contacts on said switch connecting said Y-motor means to an electrical source to run them against said edge stop means when said control lever is in said first position,   said contacts disconnecting said Y-motor means when said lever is in said second position, and   said contacts connecting said Y-motor means for normal operation when said control lever is in said third position.   
     
     
       7. The structure of claim 4, said marker lifting cam being pivoted to said pinch roller arm, and   said pinch roller arm having a cam surface adjacent said marker lifting arm,   the engagement of said marker lifting arm and said marker lifting cam being at the end portions thereof by means of a notch.   
     
     
       8. The structure of claim 4, said carriage guide comprising a guide bar, and   said marker lifting arm being fixed to a marker lifting bar extending generally parallel to said guide bar.   
     
     
       9. The structure of claim 4, further comprising: a second driving roller,   a second pinch roller, and   a second chart stop,   said chart stops protruding up through openings in said table in said protruding position,   and the cylindrical surfaces of said driving rollers being knurled. .Iadd. 10. The X-Y plotter as claimed in claim 1, wherein:   said driving roller means includes a drive roller having a peripheral anti-slip surface having a high coefficient of friction frictionally engageable with a surface of said cut chart; and,   said pinch roller means includes a pinch roller engageable with the other surface of said cut chart and   positioned to hold said cut chart against said drive roller. .Iaddend..Iadd. 11. The X-Y plotter as claimed in claim 10, wherein the anti-slip surface of said drive roller is knurled. .Iaddend..Iadd. 12. The X-Y plotter as claimed in claim 11, wherein the anti-slip surface is cylindrical. .Iaddend.