Liquid ejection hole orientation for web guide
A non-contact web guide includes a wall having a curved exterior surface and a hollow interior containing a pressurized liquid. A first row of liquid ejection holes is provided in proximity to the web guide entry position having axes that are inclined toward a downstream direction, and a second row of liquid ejection holes is provided in proximity to the web guide exit position having axes that are inclined toward an upstream direction. An intermediate array of liquid ejection holes is optionally provided. The pressurized liquid flows through the liquid ejection holes to force the web of media away from the bearing surface of the web guide. This configuration of liquid ejection holes provides the advantage that stable web guidance is achieved at low liquid flow rates.
1. A web transport system for transporting a web of media along a web transport path in an in-track direction, the web of media having a width in a cross-track direction, comprising:
at least one web guide for non-contact guidance of the web of media including:
a wall having a curved exterior surface, wherein the web of media travels along the web transport path around a bearing portion of the curved exterior surface from a web guide entry position to a web guide exit position, thereby redirecting the web of media from an input travel direction to an output travel direction;
a hollow interior containing a pressurized liquid;
a first array of liquid ejection holes formed through the wall from the hollow interior to the curved exterior surface, the liquid ejection holes in the first array being distributed across the web guide in the cross-track direction in proximity to the web guide entry position, wherein the liquid ejection holes in the first array have axes that are non-perpendicular to the curved exterior surface and are inclined toward a downstream direction of the web transport path; and
a second array of liquid ejection holes formed through the wall from the hollow interior to the curved exterior surface, the liquid ejection holes in the second array being distributed across the web guide in the cross-track direction in proximity to the web guide exit position, wherein the liquid ejection holes in the second array have axes that are non-perpendicular to the curved exterior surface and are inclined toward an upstream direction of the web transport path;
an intermediate array of liquid ejection holes formed through the wall from the hollow interior to the curved exterior surface disposed along the web transport path between the first array of liquid ejection holes and the second array of liquid ejection holes, the liquid ejection holes in the intermediate array being distributed across the web guide in the cross-track direction, wherein a number of liquid ejection holes in the intermediate array is less than a number of liquid ejection holes in the second array;
wherein the pressurized liquid flows through the liquid ejection holes to force the web of media away from the bearing portion of the web guide so that the web of media does not contact the web guide as it travels around the bearing portion of the curved exterior surface.
2. The web transport system of claim 1 , wherein the first array of liquid ejection holes is a linear array extending along a line in the cross-track direction.
3. The web transport system of claim 1 , wherein the second array of liquid ejection holes is a linear array extending along a line in the cross-track direction.
4. The web transport system of claim 1 , wherein a number of liquid ejection holes in the second array is larger than a number of liquid ejection holes in the first array.
5. The web transport system of claim 1 , wherein the liquid ejection holes in the first array have a first inclination angle relative to a normal to the curved exterior surface and the liquid ejection holes in the second array have a second inclination angle relative to a normal to the curved exterior surface, and wherein the first and second inclination angles have magnitudes between 15 and 45 degrees.
6. The web transport system of claim 5 , wherein the magnitude of the first inclination angle is within 5 degrees of the magnitude of the second inclination angle.
7. The web transport system of claim 1 , wherein at least some of the liquid ejection holes in the intermediate array have axes that are perpendicular to the curved exterior surface.
8. The web transport system of claim 1 , wherein the intermediate array of liquid ejection holes is a linear array extending along a line in the cross-track direction.
9. The web transport system of claim 1 , further including a processing tank containing a reservoir of the liquid, wherein the web transport path carries the web of media through the liquid in the processing tank.
10. The web transport system of claim 9 , wherein the web guide is not submerged in the reservoir of the liquid in the processing tank.
11. The web transport system of claim 9 , wherein the web guide is at least partially submerged in the reservoir of the liquid in the processing tank.
12. The web transport system of claim 9 , further including a pump that pumps liquid from the reservoir of the liquid in the processing tank into the hollow interior of the web guide to provide the pressurized liquid, and wherein the pressurized liquid that flows through the liquid ejection holes is subsequently directed back into the reservoir of the liquid in the processing tank.
13. The web transport system of claim 9 , wherein the liquid is an electroless plating solution.
14. The web transport system of claim 9 , wherein the at least one web guide includes a first web guide positioned at a first height within the processing tank and a second web guide positioned at a second height within the processing tank that is greater than the first height.
15. The web transport system of claim 14 , wherein a single pump is used to pressurize the liquid in both the first web guide and the second web guide.
16. The web transport system of claim 15 , further including a restrictor positioned in a liquid distribution line that carries pressurized liquid from the pump to the first web guide.
17. The web transport system of claim 1 , wherein the wall has a wall thickness and the liquid ejection holes in the first and second arrays have a characteristic diameter, and wherein a ratio of the wall thickness to the characteristic diameter is between about 1.5 and 3.0.
18. The web transport system of claim 1 , wherein a flow rate of the pressurized liquid through the liquid ejection holes is controlled to provide a stand-off distance between web of media and the bearing portion of the web guide of between about 0.5 mm and 1.0 mm.
19. The web transport system of claim 1 , wherein the at least one web guide includes a first web guide and a second web guide, and wherein a configuration of liquid ejection holes in the first web guide is different from a configuration of liquid ejection holes in the second web guide.