Patent Application
20100276868
Disclosed herein is a system and method for controlling the application of vacuum in a vacuum transport.
An example of an application for a vacuum transport is an image production device using direct marking print heads. The flatness and motion control requirements for direct marking print heads are extremely demanding. One strategy is to use a vacuum transport belt with ¼″ hole spacing over a 28″ vacuum plenum. To limit the leakage at the uncovered holes in the process and cross-process directions, the plenum can be divided into a number (for example four) chambers with a separate controllable blower at each chamber. The cost of these blowers is extremely high and there can be a large amount of leakage present. There are also issues related to how a sheet will pass from one chamber to another without losing its suction hold to the belt. In addition, plenum deflection can result, which may require ribbing or other supports to be added.
A vacuum control assembly for use in an image production device is provided. The assembly has a plenum, a perforated plate, a plurality of valve assemblies, and a controller. Each valve assembly has a rotating valve having a vacuum passage, and a chamber body having a plurality of chambers. Each valve is rotatable between a first position that fluidly connects the vacuum passage with at least one of the chambers to complete a fluid path between the plenum and the perforated plate, and a second position at which the vacuum passage connects the plenum with none of the chambers. The controller controls the plurality of valve assemblies to provide vacuum to a first predetermined portion of the perforated plate while also providing no vacuum to a second predetermined portion of the perforated plate.
Aspects of the embodiments disclosed herein relate to a system and method for controlling the application of vacuum in a vacuum transport system.
The disclosed embodiments may include a vacuum control assembly for use in an image production device. The assembly has a plenum, a perforated plate, a plurality of valve assemblies, and a controller. Each valve assembly has a rotating valve having a vacuum passage, and a chamber body having a plurality of chambers. Each valve is rotatable between a first position that fluidly connects the vacuum passage with at least one of the chambers to complete a fluid path between the plenum and the perforated plate, and a second position at which the vacuum passage connects the plenum with none of the chambers. The controller controls the plurality of valve assemblies to provide vacuum to a first predetermined portion of the perforated plate while also providing no vacuum to a second predetermined portion of the perforated plate.
The disclosed embodiments may further include an image production device having a vacuum control assembly, a transport belt for transporting a sheet of medium across a perforated plate, and a media storage compartment for storing sheets of the media. The vacuum control assembly has a plenum, the perforated plate, a plurality of valve assemblies, and a controller. Each valve assembly has a rotating valve having a vacuum passage, and a chamber body having a plurality of chambers. Each valve is rotatable between a first position that fluidly connects the vacuum passage with at least one of the chambers to complete a fluid path between the plenum and the perforated plate, and a second position at which the vacuum passage connects the plenum with none of the chambers. The controller controls the plurality of valve assemblies to provide vacuum to a first predetermined portion of the perforated plate while also providing no vacuum to a second predetermined portion of the perforated plate.
The disclosed embodiments may further include a method of controlling a vacuum transport in an image production device. The method provides a plurality of valve assemblies, each valve assembly having a rotating valve having a vacuum passage, and a chamber body having a plurality of chambers. The method rotates at least one of the valves between a first position that fluidly connects its corresponding vacuum passage with at least one of the chambers in its corresponding chamber body to complete a fluid path between a plenum and a perforated plate, and a second position at which the vacuum passage connects the plenum with none of the chambers. The method controls the rotation of the valves to provide vacuum to a first predetermined portion of the perforated plate while simultaneously preventing the application of vacuum to a second predetermined portion of the perforated plate, and passes a transport belt carrying a sheet of media over the perforated plate.
The image production device 10 can include a vacuum control assembly 100, a media stack 20, and a controller 30. Image production device 10 may have other elements that are not shown.
Although the following description is directed toward an image production device, it will be understood that the teachings herein can be applied to any transport system using vacuum.
The use of plenum 170 makes it possible to use only one blower to provide the required vacuum to valve assemblies 110. Using a plenum also provides uniform vacuum to the valve assemblies, which can be difficult to obtain using multiple blowers.
The operation of vacuum control assembly 100 will be described with reference to
Rotating valve 120a is positioned so that its passage 130 does not align with any chambers 150. As a result, the perforations in vacuum plate 160 associated with rotating valve 120a are not fluidly connected to plenum 170 and do not see negative pressure −P.
Rotating valve 120b is positioned so that its passage 130 aligns with only the right hand side chamber 150 in its chamber body 140. As a result, only half of the perforations in vacuum plate 160 associated with rotating valve 120b are fluidly connected to plenum 170 and see negative pressure −P.
Rotating valve 120e is positioned similarly to rotating valve 120b, except that its passage 130 aligns with only the left hand side chamber 150 in its chamber body 140. As a result, only half of the perforations in vacuum plate 160 associated with rotating valve 120e are fluidly connected to plenum 170 and see negative pressure −P.
Rotating valve 120c is positioned so that its passage 130 aligns with both chambers 150 in its chamber body 140. As a result, all the perforations in vacuum plate 160 associated with rotating valve 120c are fluidly connected to plenum 170 and see negative pressure −P. Rotating valve 120d is in a position similar to that of rotating valve 120c.
In
The leakage allowed by the vacuum control assembly can be reduced by decreasing the length of the chambers. For example, a vacuum control assembly having a length of 28 inches can have fourteen 2 inch valve assemblies. If each valve assembly has two chambers, each chamber is approximately one inch long. In this example, proper control of the rotating valves results in a maximum leakage of less than two inches. If, however, a 28 inch vacuum control assembly has twenty-eight 1 inch valve assemblies (each having two chambers), each chamber is approximately ½ inch long. As a result, proper control of the rotating valves results in a maximum leakage of less than one inch.
Each chamber body 140 in the example shown in
Other advantages of possible embodiments of the disclosure are (1) leading edge and trailing edge leakage is easily controlled regardless of paper size and inner document gap, (2) multiple sheets can be handled simply on the transport while maintaining a small amount of leakage, (3) the modular design gives the ability to increase or decrease the length of the vacuum transport as needed for different projects or changes that may occur during the design phase of any given product, (4) the low profile of the vacuum control assembly helps reduce machine space, belt length, and chamber ducting, (5) the chamber bodies can stiffen the top of the plenum, the deflection of which is a concern in conventional systems, (6) the short paths between the plenum and the vacuum plate create near instant suction at the plate when the valves are opened, (7) drag force between the belt and vacuum plate can be reduced by turning off suction in the inner document gap, and (8) drag can be further reduced by turning off the valves that lie under the sheet, keeping only the leading edge and trailing edge valves open at any given time.
It will be appreciated that variations of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
