1. Field of the Invention
This invention relates to feeding a print medium into a printer and to guiding a print medium through a path in a printer.
2. Related Art
Many printers provide multiple operational modes in which a print medium (e.g., paper, plastic transparency) is fed into a print drive mechanism used to advance the print medium through a printing zone of the printer during printing. For example, the standard mode of operation of many desktop printers is an automatic multi-sheet feeding mode in which individual sheets from a stack of print media (held in, for example, a tray) are, upon appropriate electronic control (e.g., computer control), automatically picked from the stack by a pick mechanism and fed into the print drive mechanism. Many of those printers also include a secondary mode of operation, usually intended for occasional and/or specialized use. The secondary operational mode is often a single sheet mode in which a single sheet of a print medium is fed (often manually) into the print drive mechanism. The secondary operational mode is sometimes a mode in which a small number of sheets of print media are placed in a feed tray, and automatically picked and fed to a print drive mechanism.
Generally, in printers that include a secondary mode of operation in addition to a standard mode of operation, a print medium is fed into the print drive mechanism during the secondary operational mode in the same direction as that in which a print medium is fed during the standard operational mode. For example, in some printers, single sheet mode consists of nothing more than placing a single sheet of a print medium on a stack of print media used in an automatic multi-sheet feeding mode so that the added single sheet is the next sheet picked and fed into the print zone. Even in printers in which a print medium is initially fed into a physically separate loading slot during the secondary operational mode, the print medium is usually eventually directed into the print drive mechanism through the same feed path (i.e., in the same direction) as used during the standard operational mode.
Physical constraints may preclude location of a loading slot for a secondary operational mode so that the feed path for the standard operational mode can be used. For example, a printer designed to be operated within a small area or volume (i.e., a printer having a small form factor) may be restricted so that a user can only access the front of the printer, necessitating that a loading slot for manually feeding a print medium be placed at the front of the printer. If the printer is also designed so that, in the standard operational mode, sheets of print media are fed in a direction from the back of the printer to the front, it becomes, at best, impractical to feed a sheet from the manual feed loading slot into the print drive mechanism in the same direction as that in which sheets are fed during the standard operational mode.
In an inkjet printer, feeding a sheet of a print medium into a print drive mechanism of the printer in a direction opposite that in which sheets are fed into the print drive mechanism during standard operation can be problematic because, just prior to being fed into the print drive mechanism, the sheet must traverse the area (swath gap) through which the print cartridge(s) pass during printing. Since the sheet, which is typically thin and flexible, is not supported in this area, it can be difficult to ensure that the sheet is properly fed into the print drive mechanism. Similar problems (e.g., the necessity for a sheet of a print medium to traverse a gap in the feed path) can exist in other types of printers when a sheet of a print medium is fed into the print drive mechanism in other than the normal feed direction.
One inkjet printer enables a sheet of a print medium to be fed into a print drive mechanism of the printer in a direction opposite that in which sheets are fed into the print drive mechanism during a standard operational mode by providing a sheet feed drive mechanism for such sheet. The sheet feed drive mechanism is positioned opposite the print cartridge swath gap from the print drive mechanism. In a secondary operational mode, a sheet of a print medium is fed into the sheet feed drive mechanism which acts to guide and support the sheet as the sheet traverses the print cartridge swath gap. However, the addition of another drive mechanism significantly increases the cost and complexity of the printer. The additional drive mechanism also necessitates additional space so that the printer is larger than desirable. Additionally, in this printer, a user must effect a special control instruction to cause the sheet feed drive mechanism to operate to feed a sheet of a print medium; the user cannot simply insert the sheet in the feed path. Further, it may not be possible or desirable to feed a sheet of a print medium back through the additional drive mechanism immediately after printing on the sheet, since the ink on the sheet may not be dry. (This problem can be overcome by, for example, pausing during printing to let the ink dry before feeding the sheet through the additional drive roller, or by guiding the sheet through a different exit path using additional structure provided in the printer; neither solution is desirable.) Thus, a better solution is needed for situations in which it is necessary or desirable to provide a second, distinct feed path to a print drive mechanism in addition a first feed path, and, in particular, situations in which such a second feed path is positioned so that a print medium fed therethrough is fed into the print drive mechanism in a direction opposite that in which print media are fed into the print drive mechanism through the first feed path.
In a mode of operation in which a sheet of a print medium is manually fed into a printer, it is often necessary to detect the insertion of a sheet into the print medium feed path associated with that mode of operation. This is typically done by adding an electronic sensor, either an interrupter-type sensor or a reflective-type sensor, that is dedicated to the task of print medium insertion detection. The additional electronics add to the cost and complexity of the printer. An alternative solution to such print medium insertion detection that is more inexpensive and simple is desirable.
The invention accomplishes print medium feed functions, at least in part, by making use of pre-existing printer apparatus that is used to accomplish other functions of the printer. For example, the invention can enable the use of a single print drive mechanism to accommodate multiple print medium feed paths within a printer and, in particular, feed paths through which print media are fed into the print drive mechanism in different (e.g., opposite) directions. Additionally, the invention can enable a rotatable media guide that can be positioned in one position to guide a sheet of a print medium during a print operation and in another position to release the sheet of the print medium after the printing operation, to be positioned in still another position to facilitate guiding a sheet of a print medium into a print drive mechanism after the sheet has traversed a gap in the feed path. The invention can also enable sensing of print medium insertion into a print medium feed path using pre-existing sensing apparatus within a printer that is used for other sensing purposes.
In a printer having two completely distinct feed paths to a single print drive mechanism, the invention can enable a sheet of a print medium to be guided to the print drive mechanism via at least one of the feed paths without using a drive mechanism, such as the sheet feed drive mechanism of the printer described above. For example, one of the feed paths of the printer can be one in which a print medium is manually introduced into the feed path, while the other feed path can be one in which a print medium is automatically introduced into the feed path. In particular, the feed paths can enable print media to be fed to the print drive mechanism in opposite directions. The invention can enable, if necessary, a sheet of a print medium fed through a feed path that does not contain a drive mechanism to traverse a gap in the feed path in which the sheet is unsupported. In particular, the invention can enable the sheet to traverse such a gap that is proximate to the print drive mechanism, while maintaining adequate guidance of the sheet to ensure that the sheet is directed into a nip region of the print drive mechanism. As explained further below, the invention can enable such sheet feeding to be accomplished with one or more simple and inexpensive mechanisms that necessitate the addition of little or no additional space to a printer in which the invention is used.
To enable a print medium to traverse a gap in a path (which can be, in general, any path) in a printer, the invention can make use of a guiding mechanism positioned on a first side of the gap past which the print medium travels to begin traversing the gap, as well as a print medium receiving mechanism positioned on a second side of the gap to which the print medium travels to finish traversing the gap. The former can be a guide surface for bending the print medium prior to crossing the gap. The latter can be a media guide having a media contact surface which slopes downward, relative to the path, from a first location to a second location that is near the first side of the gap than the first location. The latter can also be a movable media guide that can be placed in a specified position to facilitate directing the print medium along the path. The invention can enable gaps of greater than 0.25 inches to be traversed.
As indicated above, the invention can enable a movable (e.g., rotatable) media guide proximate to a print drive mechanism to be moved to a first position when the print drive mechanism is operated to advance a print medium over the media guide through the print zone during a printing operation, and to a second position when a print medium is being fed over the media guide into the print drive mechanism. The first position is specified to maintain a desired spacing within the print zone between the print medium and an apparatus for printing on the print medium, while the second position is specified to facilitate directing the leading edge of a print medium into the print drive mechanism. Typically the second position is a position at which the media guide has been moved such that a media contact surface of the media guide is lower, relative to a feed path into the print drive mechanism, than at the first position. For example, the second position can be a position at which the media guide has been rotated through an angle of about 18xc2x0 to the lower position.
As mentioned above, the invention can also enable sensing of the insertion of a print medium into a feed path by making use of a sensor that is adapted to perform a sensing function other than sensing insertion of a print medium into the feed path. The invention can accomplish this by activating a sensor that senses the presence of an object in a space outside of the print medium path, and causing the introduction of an object into that space in response to insertion of a medium into the feed path. The latter function can be accomplished by disposing an object in the feed path so that a print medium inserted into the feed path will contact the object, then transmitting a signal, either mechanically or electrically, in response to contact in the feed path to cause the object to be moved into the space being monitored by the sensor. The sensor can be, for example, a sensor that is positioned on the print carriage of the printer to enable detection of the leading edge of a print medium during a printing operation. Since an existing sensor is used, print medium insertion detection is accomplished in a more inexpensive and a simpler fashion.
When print medium insertion is detected, as described above, by disposing an object in the feed path so that a print medium inserted into the feed path will contact the object, the invention can further provide compliant support of the object so that when a print medium is removed from the feed path after having been inserted, the object can move in response to a force exerted by the print medium, thereby preventing buildup of force between the object and the print medium that may result in marking or scarring of the print medium.