System for applying vacuum force on web
View Patent ↗Apparatus for causing a vacuum force to be applied across a width of a print medium as it moves through a printing system and for determining whether the edge seals are positioned correctly is disclosed. A vacuum chamber is connected to a vacuum source which provides vacuum to the vacuum chamber. Spaced sealing rollers and the edge seals define an opening in the vacuum chamber, wherein the print medium passes over the opening and is guided by the sealing rollers. A sensor measures a vacuum level in the vacuum chamber. A controller stores a plurality of response curves for different known print media, produces first and second signals indicative of an activation level of the vacuum source and the vacuum level in the vacuum chamber, and compares the first and second signal to appropriate response curves to produce an error signal indicating whether the edge seals are correctly positioned.
1. Apparatus for causing a vacuum force to be applied at a target vacuum level across a width of a web of movable print medium as it moves through a printing system and for determining whether positions of adjustable edge seals of the apparatus do not correspond to edge positions of the movable print medium, comprising:
a vacuum chamber connected to a vacuum source operating at a constant activation level, wherein the vacuum source provides vacuum to the vacuum chamber;
spaced sealing rollers, disposed in relation to the vacuum chamber, that rotate as the print medium moves over each sealing roller, wherein the spaced sealing rollers define an opening in the vacuum chamber, and wherein the movable print medium passes over the opening and is guided by the sealing rollers;
the adjustable edge seals disposed between the spaced sealing rollers at a first position;
a sensor for measuring a vacuum level in the vacuum chamber; and
a controller having controller accessible memory for storing a plurality of response curves for different known print media having different widths, materials, or thickness, responsive to the vacuum source and the sensor, for producing a signal indicative of the vacuum level in the vacuum chamber, and for comparing the signal to an appropriate response curve corresponding to the movable print medium to produce an error signal indicating whether the first position of the pair of edge seals does not correspond to the width of the movable print medium.
2. The apparatus according to claim 1 , further including means for adjusting the position of at least one of the edge seals to at least one new position in response to the error signal.
3. The apparatus according to claim 2 , wherein the new position of the edge seals corresponds to a change in an operating region of the response curve.
4. The apparatus according to claim 2 , wherein the new position of the edge seals corresponds to edges of the movable print medium so that an appropriate vacuum force is applied across the width of the movable print medium.
5. The apparatus according to claim 2 , wherein the means for adjusting the positions of the edge seals includes separate means for adjusting the position of each of the edge seals independently of the position of the other edge seal.
6. The apparatus according to claim 2 , wherein the means for adjusting the positions of the edge seals comprises means to adjust the position of a first edge seal and a second edge seal concurrently such that a midpoint between the first edge seal and the second edge seal is substantially fixed independent of a spacing between the first edge seal and the second edge seal and corresponds to a midpoint of the width of the movable print medium.
7. The apparatus according to claim 1 , wherein the sealing rollers are disposed at two positions in an intrack direction and extending parallel to a crosstrack direction relative to the movement of the movable print medium.
8. The apparatus according to claim 1 , wherein the edge seals are disposed at two positions in a crosstrack direction and extending parallel to an intrack direction relative to the movement of the movable print medium.
9. The apparatus according to claim 1 , wherein the sensor is a pressure sensor used to measure the vacuum level in the vacuum chamber.
10. The apparatus according to claim 1 , wherein the sensor is a vacuum gauge fluidically coupled to the vacuum chamber or to a vacuum duct that connects the vacuum chamber to the vacuum source.
11. The apparatus according to claim 1 , wherein the sensor is a strain gauge attached to a wall of the vacuum chamber to measure the deformation of the vacuum chamber wall produced by the vacuum, a force gauge measuring the force applied to one or more guiding surfaces by the movable print medium as it is pulled into contact with the guiding surfaces by the vacuum, a force gauge measuring the force applied by the vacuum to the edge seals, or a flow gauge measuring the flow rate of the air through a vacuum duct between the vacuum chamber and the vacuum source.
12. The apparatus according to claim 1 , wherein the vacuum source is a blower, a pump, or a venturi-type vacuum source.
13. The apparatus according to claim 1 , further including a clearance gap between the sealing rollers and a wall of the vacuum chamber, the clearance gap extending around a portion of the sealing rollers.
14. The apparatus according to claim 13 , wherein the clearance gap extends around at least an eighth of the circumference of the sealing roller.