Patent Application
20110291348
This invention relates generally to sheet feeders for use with devices having an externally accessible feed mechanism that pulls a sheet from a stack of sheets. It has particular but not exclusive usefulness in feeding sheets to a bypass tray of a high speed digital printer (such as a laser printer, an LED printer, or an ink jet printer) which prints an image based on a digital file downloaded to the printer.
There are thousands of digital printers sold each year by many different manufacturers. Digital printing technology has been widely used for several decades. Typically, digital printers are used to print on standard thickness paper, commonly known as “copy paper” of common sizes such as 8.5″×11″ or A4. Since the majority of usage on these printers consists of this type of paper, the feed systems on these printers are designed to handle this specific material well. A stack of paper is placed in a hopper that is incorporated into the body of the printer. The printer takes one sheet of paper at a time by pulling the top sheet off a stack of paper in the hopper with a feed roller or “feed tire” that is resting on the top of the stack.
Although this method works very well on standard paper, it is not capable of feeding difficult or thick sheets, such as envelopes, postcards, folded pieces, and other thick materials. The term “sheet” is used herein to encompass not only single sheets of paper, but also such things as envelopes, postcards, CDs, credit cards, labels, calendars, or any other object, generally on the order of a few thousandths of an inch to about ⅜ of an inch thick, and sufficiently flexible to flex on the order of 1/16 to ⅛ inch, that can be fed from a stack and that can be printed by the printer into which it is fed.
To accommodate occasional feeding of these thick or difficult sheets, many digital printers include a “manual feed tray” or “multi-purpose feed tray” or “bypass tray” that is open to the exterior of the digital printer when in use and is most often hinged to one side of the printer. In this tray (hereinafter called a “manual feed tray”), the user can normally place a few envelopes, cards or other thick sheets for printing when not printing on standard paper. Although these manual feed trays work reasonably well, they have very small limits on the size of the stack of sheets, and therefore cannot be used for large volumes of printing without constant re- loading of media. In addition, these manual feed trays also incorporate a top feed design, meaning that they have a feed roller that pulls the top document off the stack in the manual feed tray. This means that the operator cannot load documents into the feed tray until the prior stack is depleted.
Attempts have been made to solve this problem by providing a separate sheet feeder that feeds envelopes to the feed roller of the manual feed tray. However, they require that changes be made to the printer's manual feed tray to accommodate the feeder. The manual feed trays of most existing digital printers are attached to one end of the digital printer, and typically are hinged to the printer. The manual feed tray typically rests at a slight angle, rising upwards as it extends away from the hinged point. The manual feed tray also incorporates media guides and other components that are positioned near the feed roller area. For these reasons, the manual feed tray blocks access to the feed roller and feed area on the printer. The manual feed tray therefore must be removed from the printer when using prior art add-on feeders. This eliminates the ability to use the manual feed tray without the use of the add-on feeder or for its normal purposes completely, unless the manual feed tray is re-attached to the printer.
The present invention provides a friction feeder assembly that is designed to be positioned near a printer's manual feed tray, and feed sheets, one at a time, to the manual feed tray feed roller, increasing dramatically the production capability of the printer when printing envelopes or other difficult sheets. Most commonly, the printer will be a digital printer, and the sheets will be envelopes or cards, but the invention is not limited thereto. Preferably and advantageously, no modification of the printer's manual feed tray or of the printer's sensors and electronics is required. The feeder assembly of the present invention may also be used with devices other than printers which incorporate a top-feed mechanism that draws sheets from the top of a stack.
The feeder is of top-load, bottom-feed design, meaning that a stack of sheets is placed in the feeder's hopper, and the bottom sheet is pulled away from the stack and delivered to the printer. With this construction, the operator can load more sheets in the feed hopper and continue to load on top of the stack, while the system is running. The feeder is conventionally driven by an electric motor. It is desirable but not essential in the present invention that the motor be a variable speed motor.
The feeder assembly of the present invention obviates the need to remove the manual feed tray from the printer by incorporating a delivery table that is attached to the feeder, and extends laterally away from the feeder in the direction of the printer. One end of this table is pivotally attached to the feeder, leaving the end closest to the printer vertically movable, so that it can be raised up while the feeder is moved into position adjacent the printer to clear the upwardly tilting manual feed tray described above and then tilted back down onto the manual feed tray to allow the end of the table to be positioned under the feed roller of the printer. When the feeder is placed in the proper position, the exit end of the delivery table is positioned just below the feed roller of the digital printer. When the printer is started, the manual feed tray is raised slightly by internal components of the printer. When this tray which is underneath the delivery table of the feeder rises, it lifts the pivoting delivery table up until it, or a sheet at its free end, activates the printer's top-of-stack sensor. By allowing the printer to lift the delivery table to the proper height, the delivery table is positioned exactly as needed to deliver the documents to the printer without interference.
It will of course be understood that the delivery table can be any structure which receives sheets from a sheet feeder and delivers them one at a time to a top-feed mechanism, and that the “table” need not incorporate a flat horizontal plate.
Since varying digital printers incorporate various manual feed tray designs and specifications, including height, the pivoting delivery table of the feeder of the present invention offers the ability to use it with a wide variety of printers. As described earlier, the manual feed tray of the digital printer typically rises a bit to push documents up to the feed roller. Since the rising force of these manual feed trays will vary, the pivoting delivery table may include an adjustable counter-balance or spring-loaded mechanism that reduces the effective weight of the delivery table and aids the feed tray in lifting the end of the delivery table to the proper height of the feed roller. The balance mechanism used in the preferred embodiment of the present invention is an adjustable spring, but it can also be an adjustable weight or shock absorbing device, for example. Preferably, the adjustable balance mechanism is capable of reducing the effective weight of the delivery table on the feed tray by at least 10%, desirably by at least 25%, and preferably by at least 50%.
The delivery table of the preferred embodiment includes a drive roller at its rearward, or upstream, end. The drive roller is conveniently driven by a timing belt trained around a pulley on a drive roller of the feeder. This arrangement ensures that movement of sheets across the delivery table is synchronized with ejection of sheets from the sheet feeder. The delivery table drive roller pulley is preferably somewhat smaller than the drive roller of the feeder, so that the delivery table belts travel faster than the feeder belts, thereby separating the sheets on the delivery table from each other. Delivery table feed belts are trained around the delivery table drive roller and around an exit shaft at the downstream, exit, end of the delivery table. These delivery table feed belts are used to advance the sheets away from the feeder's hopper area and toward the printer's manual feed tray feed roller. The exit shaft has a one-way bearing of sufficient diameter to urge the sheet into the digital printer top-feed pulling roller; the one-way bearing spinning freely when the top-feed roller accelerates the sheet into the printer. A sensor, illustratively a photo-eye, at the exit end of the delivery table detects the leading edge of the foremost advancing sheet and signals the feeder to stop advancing the sheet once it has reached the proper position under the printer's feed roller. When the printer's feed roller advances the foremost sheet into the printer, the sensor detects the absence of a sheet and calls for the feeder assembly to deliver another sheet to the exit end of the delivery table.
With the freely pivoting delivery table of the present invention, the user of the digital printer can slide the feeder into position next to the digital printer without removing any components of the digital printer or circumventing any of the electronic sensors or switches on the printer. An additional advantage is that the operator can also easily move the feeder away from the printer and use the manual feed tray normally, since it does not need to be re-attached.
Although the pivoting delivery table is described herein as a feeder for a digital printer, it will be appreciated that its usefulness is not limited thereto. It may also be used for feeding other types of machines having their own friction feeds, including, for example, copying machines, offset printers, thermal printers, and material handling machines such as envelope stuffers or paper folders.
Referring to the drawings, reference numeral 1 indicates a sheet feeder assembly including a sheet feeder 3 having pivotably attached thereto a delivery table 5. The sheet feeder assembly 1, in this mode of carrying out the invention, interacts with a digital copying machine/printer 7 as described below.
The sheet feeder assembly 1 is mounted on a stand 9 having wheels 11 and adjustable feet 13. The stand 9 has telescoping legs 15 with locks 17 for setting the height of the sheet feeder assembly 1. If the floor on which the stand 9 rests is always expected to be level with the section of floor on which the digital printer 7 rests, the locks 17 may be pins which lock into holes in the legs 15. Otherwise, the locks 17 may be frictional locks of well-known design, to allow slight variance in the heights of the legs 15.
Sheet feeders 3 useable with the present invention are well known in the art. Although the structure of the sheet feeder 3 is not critical to the invention, it is preferably of top-load, bottom-feed design, allowing several hundred sheets to be loaded, and allowing more sheets to be loaded while the feeder is running. The sheet feeder 3 is preferably made in accordance with Kaiping, U.S. Pat. No. 7,624,978, hereby incorporated by reference. In brief, the sheet feeder 3 includes a hopper 31 designed to hold up to five hundred sheets 32 in the form of envelopes or cards, a drive shaft 33, and feed belts 35 trained on the drive shaft 33 and on an idler shaft 37 at the downstream end of the feeder 3. As shown in
The delivery table 5 portion of the feeder assembly 1, as best seen in
A table lift mechanism 75 is provided as a balance mechanism to reduce the effective weight of the delivery table. The lift mechanism 75 includes an arm 77 bolted to one of the mounting plates 51. The free end of the arm 77 includes a bore 79 sized to allow free passage of a threaded spring rod 81. A coil spring 83 is held at its upper end by the spring rod 81 and at its lower end by a bolt 85 threaded into a side plate 53. An adjustment knob 87, threaded on the spring rod, permits adjustment of the spring tension, hence of the effective weight of the delivery table. If desired, the table can be adjusted to be effectively weightless, although it is preferred that the table exert some downward pressure, simulating a stack of sheets, as discussed hereinafter.
The delivery table 5 further includes a drive shaft 89, best shown in
A top plate 101 is mounted between the side plates 53 and secured by flat-head bolts to drive shaft bearing blocks 93 and exit shaft bearing blocks 69. The top plate 101 supports the upper run of delivery belts 103 and sheets 32 as they are advanced from the feeder section to the printer by the delivery table feed belts 103.
The delivery table 5 also includes an exit shaft 105 around which delivery table belts 103 are trained. The exit shaft 105 is rotationally driven by the delivery table belts 103. The exit shaft 105 is held in position by the two exit shaft bearing blocks 69 equipped with bearings 107 which allow free rotational movement of the exit shaft 105.
The exit shaft 105 is sized to permit the exit end of the delivery table, including the belts 103, to be less than 1.5″ (5.1 cm) high, preferably one-half inch to one inch (1.2-2.5 cm) high, to permit the delivery table to fit into the printer's roller area without disturbing its manual feed tray. In the illustrative embodiment, the shaft 105 is 0.375″ (0.95 cm) in diameter, turned down to 0.25″ (0.635 cm) at its ends to fit bearings 107, and the height of the side plates 53 and bearing blocks 69 is 0.5625″ (1.43 cm) at the exit end of the delivery table. The height of the exit shaft 105 plus the belts 103 is about 0.5″ (1.27 cm).
The width of the delivery table 5 is selected to fit a range of digital printers and to allow use with a range of sheet sizes. It will be understood that this requires a compromise. A general-purpose feeder assembly should have a width of at least 8.5″ (21.5 cm) to handle U.S. letter-sized paper and should not be wider than about 14″ (35.6 cm) to fit most digital printer manual feed trays. The illustrative embodiment has a width of 12.5″ (31.8 cm) and can handle sheets 3″ (7.6 cm) wide minimum up to 12″ (30.5 cm) wide, and from 4″ (10 cm) long minimum to 18″ (46 cm) long. The envelopes or sheets can be run in portrait or landscape orientation.
A one-way bearing 109 is mounted in the center of the exit shaft 105 and is driven by the exit shaft 105 in the proper direction so as to advance sheets 32 into the printer's feed roller area. The one-way bearing 109 is positioned in use directly below the manual feed tray's feed roller. The one-way bearing 109 rotates freely in the direction of the printer when the printer's feed roller is activated to advance a sheet 32 into the printer; it therefore does not impede advancement of the sheet 32 into the printer.
The delivery table drive shaft pulley 97 is preferably of smaller diameter than the pulley 47 on the feeder section drive shaft 33, thereby causing the delivery table drive shaft to rotate at a higher rate than the feeder section drive shaft 33. This results in the delivery table belts 103 having a higher advancing rate than that of the feeder section feed belts 35 and results in a gap between sheets as they advance toward the printer on the delivery table 5, as shown in
The delivery table top plate 101 includes paper guides 111 which are movable laterally toward and away from each other to accommodate sheets 32 of varying widths. These paper guides 111 serve to align the sheets 32 as they are advanced toward the printer 7 so that each sheet 32 is presented to the printer straight and in uniform position allowing for accurate print registration. Transverse slots 113 in the plate 101 carry adjustment blocks 115 attached to the paper guides, for fixing their position.
The outermost delivery table belts 103 are movable laterally toward and away from the center of the delivery table top plate 101 so as to accommodate sheets of varying widths. This is accomplished by means of the two manually movable belt guides 61 shown in
The delivery table top plate 101 includes a photo sensor 117 secured to the bottom of the delivery table top plate 101 near the exit end of the delivery table 5 in a position between two adjacent delivery table belts 103 and directly underneath an opening cut into the delivery table top plate 101. The upward facing photo sensor 117 detects the presence or absence of sheets 32 at the exit end of the delivery table. The photo sensor 117 is electronically attached to the motor control mechanism to signal the motor to start running, advancing the sheets 32 toward the printer when the photo sensor 117 detects the absence of a sheet 32 at the exit end of the delivery table 5. When a sheet 32 has advanced sufficiently to cover the photo sensor 117, the photo sensor 117 signals the motor controller to stop the motor. The sheet 32 therefore stops in the proper position for the printer's feed roller to advance it into the printer.
The delivery table 5 includes a bridge 119, best shown in
Referring now to
When using the sheet feeder assembly 1 of the present invention, the manual feed tray 203 is first emptied of any envelopes, causing the feed table 204 to drop to its lowest position. Paper guides on the tray are moved laterally outward to make maximum room for the delivery table 5 of the sheet feeder assembly 1. The exit end of the sheet feeder assembly's delivery table is then positioned into the manual feed tray 203, with the exit shaft just under the manual feed roller. Height adjustments may be made by loosening the locks 17 on the legs 15 of the stand 9 and then tightening the leg locks 17 when the proper height is reached. The locking lever on the left (operator) side of the delivery table is loosened so the delivery table can pivot freely. The delivery table 5 is lifted over the opened manual feed tray 203 and slid into position so the delivery table goes in above the manual feed tray 203 and between the manual feed tray 203 paper guides. The end of the delivery table 5 is allowed to drop gently onto the feed table 204 of the manual feed tray 203, and the feeder assembly 1 is pushed forward until the exit end of the delivery table 5 bumps into the front wall of the manual feed tray 203 and the one-way bearing 109 on the delivery table exit shaft is positioned just below, but not contacting, the manual feed tray 203 feed roller 205.
In normal operation, the feed table 204 will push the delivery table 5 up until the one-way bearing contacts the manual feed tray 203 feed roller 205. The one-way bearing will press the first envelope 32 against the manual feed tray 203 feed roller 205, but will spin freely as the feed roller pulls the envelope away.
Because the feed table 204 will be required to lift the sheet feeder assembly delivery table up to the feed roller, it is desirable to minimize the force it is required to exert, using the balance mechanism 75. Once the feeder assembly 1 is in position with the printer 7, and the printer has not been started, the adjustment knob 87 is turned clockwise until the delivery table just starts to lift toward the feed roller. The one-way bearing 109 should not be lifted up to the feed roller; this is to be done by the feed table 204. The lift assist should only be strong enough to aid the feed table 204.
When the printer is activated, the feed table 204 lifts normally, which simply lifts the sheet feeder assembly's floating delivery table 5 up to the feed roller 205, simulating a stack of envelopes. When the delivery table is pushed up it raises the feed roller 205 or its sensor to the proper height, and the feed table 204 stops rising. The sheet feeder assembly then feeds a single envelope 32 to the feed roller 205, and on an internal signal from the printer 7 the feed roller 205 pulls the envelope into the printer. The photo sensor 117 mounted at the end of the delivery table detects when the first envelope 32 has left the delivery table 5, and signals the feeder assembly 1 to advance another envelope 32 to the manual feed roller 205. This process is repeated for each envelope required, with the feeder assembly being activated only when the photo sensor 117 detects the absence of a sheet at the forward (exit) end of the delivery table 5.
Numerous variations in the construction of the feeder assembly of this invention, within the scope of the appended claims, will occur to those skilled in the art in light of the foregoing disclosure. Merely by way of example, other feeders may be used with the pivoting table. Although not preferred, the entire feeder assembly, including the table, could be pivotably mounted on a vertically adjustable stand. The balance mechanism which reduces the effective weight of the delivery table may include other types of springs, counterweights, or other known mechanisms. The top-feeding device into which the feeder assembly feeds may include different feed mechanisms. For example, the entire manual feed tray may lift when the printer calls for a sheet from the manual feed tray. The top-feeding device may be a simple vertically floating top-feed roller with a sheet sensor, adapted to handle a small stack of only a few sheets on a fixed sheet support. Rather than utilizing two different size pulleys to create different belt speeds between the feeder section and the delivery table section, the speed difference can be created by utilizing two different size shafts as well as utilization of a separate, independently controlled motor for the delivery table. Other devices, such as offset printing presses, utilize vacuum pickups, rather than feed rollers, as feeds, to move the top sheet of a stack into the device; the feeder assembly of the invention may be used with such devices, although the one-way roller is less important.
These variations are merely illustrative.
Applicant claims priority to U.S. provisional application 61/241,209, filed Sep. 10, 2009, and U.S. provisional application 61/372,745, filed Aug. 11, 2010, both of which are hereby incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US2010/048425 | 9/10/2010 | WO | 00 | 8/4/2011 |
| Number | Date | Country | |
|---|---|---|---|
| 61241209 | Sep 2009 | US | |
| 61372745 | Aug 2010 | US |
