Sheet media feeders are widely used in a variety of devices such as in printers, copy machines, facsimile machines and the like. In general, sheets of media, such a paper, and the like, are stored in a stack of media, and the sheet media feeder includes engaging structures, such as a roller or the like, for separating one sheet from the stack and urging it along a media path of the device.
In order to ensure consistent and reliable separation of the sheet of media from the stack of media, the sheet of media typically engages the engaging structure within a predefined range of force between the sheet of media and the engaging structure. If too much force is applied, the sheet may not separate from the stack, and if too little force is applied, the sheet may not properly engage the engaging structures.
In many situations, it is undesirable to apply a large biasing force to a large stack of media. For example, where the individual sheets of media form a vertical stack of media, and those sheets of media are relatively massive and/or fragile, such as when they are individual polymer identification cards or the like being fed through an identification card printer, the weight of the large stack of media tends to urge the lowest sheet of media within that stack toward the engaging structure. Accordingly, it may be unnecessary to apply any additional biasing force to the stack of media, and such additional force creates extra load to the engaging structure and ultimately to the driving mechanism causing system stall.
Similarly, as the sheets of media are consumed from the stack of media, the weight of the stack of media is reduced. Accordingly, the remaining stack of media cannot contribute significantly to the biasing of the bottom most sheet of media toward the engaging structure.
Therefore, the force applied to the stack of media is desirably sufficient to urge the bottom most sheet of media in the stack of media toward the engaging structure when the stack of media is nearly depleted, while still preventing excessive force from being applied when the stack of media is large. In practice, this characteristic tends to limit the size or height of the stack of media allowed within the frame.
A biasing device 20 for a sheet media feeder 22 that allows the amount of force applied to a stack of media 10 to be optimized as the stack of media 10 is depleted is disclosed in
1. Exemplar Media-Path Bearing Device
Referring to
In one implementation, the inkjet printer 24′ includes a chassis 30, the sheet media feeder 22 for supplying sheets of media 32 to the printer 24′ via a media path 34, and a movable print carriage for moving one or more printheads relative to the sheet of media 32 at a print zone. The sheets of media 32 may be any type of suitable sheet material, such as paper, card-stock, transparencies, mylar, foils, and the like, but for convenience, the illustrated embodiment is described using a substantially planar, polymer card that includes a planar surface 36 (
The sheet media feeder 22 moves the sheet of media 32 into the print zone from a storage chamber 38 along the media path 34, using a series of motor-driven rollers or the like, here rollers 40a, 40b, which are secured to the printer so as to engage the detachable sheet media feeder, are shown in
In the print zone, the sheets of media 32 receive ink from a printhead, which is operably secured to the carriage (not shown). The carriage is usually driven by a conventional drive belt/pulley and motor arrangement along a guide rod or the like. The guide rod defines a scanning direction or scanning axis along which the printheads traverse over the print zone. The printheads selectively deposit one or more ink droplets on the planar surface of the sheet of media located in the print zone in accordance with instructions from a printer controller, such as a microprocessor, which may be located within chassis 30.
The controller may receive an instruction signal from the microprocessor based on sensors along the media path 34, and from a host device (not shown). The printhead carriage motor and the media delivery system drive motor operate in response to the printer controller, which may operate in a manner well known to those skilled in the art.
In other embodiments, a laser print engine or other suitable print engine may be used instead of an inkjet print engine.
2. Sheet Media Feeder
As shown in
The frame 44 can have at least one side 46 and the stack of media 10 rests within the storage chamber 38 adjacent to the at least one side 46. In one implementation, the frame 44 has a lower side 46′ and an upper side 48 and the stack of media 10 is stacked substantially vertically on the lower side 46′ with the media engaging structure 12 positioned adjacent to the lower side 46′ as shown in
The biasing device 20 operably engages the stack of media 10 to bias the stack of media 10 towards the media engaging structure 12. In the illustrated example embodiment, the biasing device 20 applies a force substantially normal to a planar surface 54 on the stack of media 10, and the amount of force applied by the biasing device 20 to the stack of media 10 is adjustable so that the amount of force applied may be optimized as the stack of media 10 is depleted from the storage chamber 38.
For example and as shown in
In order to prevent the second end 70 of the compression spring 56 from adversely impacting the upper most sheet of media 32b of the stack of media 10, a spring engaging structure 72 can be positioned between the stack of media 10 and the second end 70 of the compression spring 56. In one possible implementation, the spring engaging structure 72 has a substantially planar member 74 that engages the upper most sheet of media 32b of the stack of media 10 on a first side 76, and has a protrusion 78 extending from its opposite second side 80 toward the threaded opening 64. A disk 82 that is sized to engage the second end 70 of the compression spring 56 is rotatably secured to the protrusion 78. Accordingly, when the adjustment control 60 is rotated within the threaded opening 64, the compression spring 56 will necessarily rotate and cause the second end 70 to spin the disk 82 about the protrusion 78 and thereby prevent the second end 70 from digging into the stack of media 10 or otherwise hindering rotation of the compression spring 56 and adjustment control 60. The disk 82 can also include a strain gauge 84 or the like thereon which is visible through the frame 44 thereby allowing the amount of force applied by the compression spring 56 to the stack of media 10 to be monitored and tuned accordingly.
The treaded adjustment control 60 can include a knob portion 90 that allows a user to easily grasp and rotate the adjustment control 60. In one possible implementation, the knob portion 90 includes a position indicator 92 such as an elongate needle portion or the like to provide a user with a visual indication of the position of the knob portion 90 relative to the frame 44.
The threaded opening 64 can be a threaded and tapered collar 64a received within the upper side 48 of the frame 44. The collar 64a can have a threaded length 94 that provides the adjustment control 60 sufficient range of movement therein so as to allow the compression spring 56 to provide an optimal force between the stack of media 10 and the engaging structure 12, even when the stack of media 10 is substantially depleted or even if only one sheet of media 32 is remaining from the stack of media 10.
As shown in
The difference in pitch 104 (
The adjustability of the biasing device 20 allows a full stack of media 10′ (
Moreover, the rectractability of the spring 56 within the threaded opening 64 also allows the biasing force applied to the stack of media 10 to be minimized when not needed, such as during storage and/or shipment of the media feeder 22 containing the stack of media 10. Common biasing structures usually store and ship the media feeder containing the stack of media with the compression spring fully compressed against the stack of media, thereby applying the maximum biasing force to the stack of media for extended periods of time. Accordingly, such forces can tend to damage the sheets of media within the stack, particularly, where the media are sheets of resilient, polymer cards used for identification badges and the like.
3. Use and Operation
A user activates the adjustable biasing device 20 by turning the adjustment control 60 as needed to apply the necessary force to the stack of media 10. The position indicator 92 and, if installed, the transparent cover 44b and strain gauge 84 allow the user to see if the second end 70 of the spring is operably engaging the stack of media 10 and adjust the biasing force applied as needed. Moreover if desired, the frame 44 includes surface ornamentation thereon relative to defined aligned positions of the position indicator 92 thereby allowing a user to position the knob portion 90 of the adjustment control 60 for a known stack size or the like.
In an example embodiment, the sheet media feeder 22 is a pre-packaged cartridge-style structure that contains a full stack of media therein. The structure can arrive with the biasing device 20 in its retracted position 100 so as to prevent excessive force from being applied to the stack of media 10 during initial transport and storage of the structure. A user obtains a new sheet media feeder 22 and turns the adjustment control 60 to a defined position so as to extend the spring 56 from the threaded opening 64 and apply a biasing force to the stack of media 10. The user then installs the sheet media feeder 22 on the media-path bearing device 24, such as a printer 24′ or the like.
As the printer 24′ is used and the sheets of media 32 are depleted one-by-one, from the stack of media 10, the user turns the adjustment control 60, so as to maintain a desirable biasing force on the stack of media 10. If available, the user can align the position indicator 92 on the adjustment control 60 to defined positions for the detected stack height 42 of the stack of media 10. This process of adjusting the adjustment control 60 is repeated as needed during depletion of sheets of media 32 from the stack of media 10 thereby maintaining optimal biasing force on the stack of media 10 as it is being depleted.
Alternatively, in cases where the strain gauge 84 is installed, the user can position the adjustment control 60 so as to maintain the force applied to the strain gauge 84 within a predetermined range. As the detected force drops below a predefined limit, the user readjusts the position control 60 accordingly so as to return the force applied to the strain gauge 84 to within the predetermined range.
Also, in cases where a transparent cover 44b is installed, the user can view through the transparent cover 44b the engagement between the second end 70 of the biasing device 20 and the substantially planar member 74. Should the second end 70 ever become disengaged from the substantially planar member, the user can position the adjustment control 60 so as to move the second end 70 toward the substantially planar member 74, thereby increasing the biasing force applied to the stack of media.
In view of the wide variety of embodiments to which the principles of the invention can be applied, it should be apparent that the detailed descriptions of exemplar embodiments are illustrative only and should not be taken as limiting the scope of the invention. For example, exemplar type of media-path bearing device is for illustrative purposes only. Accordingly, the claimed invention includes all such modifications as may come within the scope of the following claims and equivalents thereto.