Material advance tracking system

Details Material advance tracking system Material advance tracking system

1999-05-13

2001-03-27

Mansen, Michael R. (Department: 3653)

Advancing material of indeterminate length

With material-responsive control means

To regulate longitudinal movement of material

C226S045000

Reexamination Certificate

active

06206263

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to friction drive systems such as printers, plotters and cutters that feed strip material therethrough for generating graphic images and, more particularly, to friction drive systems which accurately track the longitudinal position of the strip material.
2. Background Art
Friction, grit, or grid drive systems for moving strips or webs of sheet material longitudinally back and forth along a feed path through a plotting, printing, or cutting device are well known in the art. In such drive systems, friction (or grit or grid) wheels are placed on one side of the strip of sheet material (generally vinyl or paper) and pinch rollers, of rubber or other flexible material, are placed on the other side of the strip. Spring pressure urges the pinch rollers and material against the friction wheels. During plotting, printing, or cutting, the strip material is driven by the friction wheels back and forth in the longitudinal or X-coordinate direction in accordance with a commanded position for the strip material. As the strip material is advanced back and forth in the longitudinal direction, a pen, printing head, or cutting blade is driven over the strip material in the lateral or Y-direction.
These systems have gained substantial favor due to their ability to accept plain (unperforated) strips of material in differing widths. However, the existing friction feed systems experience several problems. One problem is that the existing systems do not compare the commanded position of the strip material and the actual position of the strip material. Thus, if a longitudinal slippage or creep error in the X-coordinate direction occurs with the strip material moving either too slowly or too fast, respectively, the system is not aware of the discrepancy between the commanded position and the actual position of the strip material. This potential discrepancy is not detected until the plot is completed and results in inaccurate final work product. This problem is most pronounced in long plots, i.e. those two or more feet in length, and those in which the strip material moves back and forth in the X-coordinate direction with respect to a tool head such as a plotting pen, print head, or cutting blade.
SUMMARY OF THE INVENTION
It is an object of the present invention to ensure that the actual longitudinal position of the strip material is substantially identical to the commanded longitudinal position of the strip material in a friction drive system.
According to the present invention, a friction drive apparatus for feeding strip material in a longitudinal direction along a feed path includes a motor encoder secured to a drive motor that rotates friction wheels for advancing the strip material longitudinally and a detecting means for detecting the longitudinal position of the strip material. The motor encoder generates a motor encoder signal, indicative of the rotational movement of the drive motor and friction wheels. The detecting means generates a detecting encoder signal indicative of the actual longitudinal position of the strip material. The motor encoder signal is compared with the commanded position signal and the difference is filtered and defined as a filtered motor encoder position error signal or a short-term error signal component. The detecting encoder signal is also compared to the commanded position of the strip material with the difference filtered to remove high frequencies to result in a filtered detecting encoder position error signal or a long-term error signal component. The short-term error signal component and the long-term error signal component are then combined to result in a position error signal that is used as a feed back for the closed loop control system.
In the preferred embodiment of the present invention, the strip material includes an encoder pattern printed on the strip material and the detecting means includes an illuminator and a sensor to track the encoder pattern of the strip material to provide the microprocessor with the detecting encoder signal.
One advantage of the present invention is that the position error signal has improved accuracy over both the low frequency and the high frequency ranges because the short term accuracy of the friction wheels and the long term accuracy of the longitudinal feed provide highly reliable signals under all feed conditions.
Another advantage of the present invention is that the actual longitudinal position of the strip material is compared with the commanded position of the strip material.
The foregoing and other advantages of the present invention become more apparent in light of the following detailed description of the exemplary embodiments thereof, as illustrated in the accompanying drawings.


REFERENCES:
patent: 3949856 (1976-04-01), Ulber et al.
patent: 4147078 (1979-04-01), Bishop
patent: 5027993 (1991-07-01), Ferguson
patent: 5138341 (1992-08-01), Kobayashi
patent: 5405069 (1995-04-01), Duncan et al.
patent: 5695106 (1997-12-01), Bauknecht
patent: 5766389 (1998-06-01), Brandon et al.
patent: 5930139 (1999-07-01), Chapdelaine et al.
patent: 6033502 (2000-03-01), Coenen et al.
U.S. application No. 09/069,392, Rich et al., filed Apr. 29, 1998.

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