Pressure roller plate with force distribution
Printer (1) feeds paper or other media sheets (5) to pinch rollers (9a, 9b), which further feed the sheets into an imaging station (7). Pressure rollers (9b) are held by plate 22 which is biased by a spring (33) and pivots on extensions (37a, 37) to moves pressure rollers (9b) into nip relationship with nip roller (9a). To evenly distribute the forces across pressure rollers (9b), plate 22 is weakened by depressed lines (27a, 27b) located between the spring and the pressure rollers (9b).
This invention relates to apparatus to apply pressure evenly to rollers forming a nip with a drive roller for sheet feed, such as in printers and other imaging devices,
BACKGROUND OF THE INVENTIONAdvancing of paper and other sheets through two rollers forming a nip is highly conventional in printers and other imaging devices. Typically one of the rollers is driven from a motor and the second roller turns freely while it applies pressure to keep the rollers nipped against the sheets. Typically, the pressure rollers are supported by cantilevered plate or the like which is rotated toward the nip by a spring. It is known to bevel or weaken the ends of rollers to reduce damaging forces.
It has been discovered in accordance with this invention that the pressure roller plate may induce significant pressure differences on the pressure roller along it length. The tends to skew sheets being fed. When the second or driven roller is compliant enough to absorb differences in a pressure roller pressures, along its length, such pressure differences have been tolerable. However, reliable, forward sheet feeding can be improved by eliminating such differences. This permits the drive roller to be less compliant, which contributes to the reliable sheet feeding.
The pressure roller plate of the disclosed embodiment of this invention in general form and in primary function is essentially the same as pressure plates previously employed in printers constituting prior art to this invention. This invention differs in the plate having different bending characteristics between the pressure application point and the part of the plate at which rollers are supported.
DISCLOSURE OF THE INVENTIONThis invention includes a pressure plate for supporting one or more pressure rollers. The pressure plate connects to a spring at one location and has pivot locations which contact frame members at opposite locations spaced from the spring-connection location. The plate is weakened at location intermediate the spring-connection location and locations supporting the pressure roller or rollers.
In an embodiment, the plate is generally rectangular, with a spring-connection location generally central on one side (the spring connection side). Two pivot surfaces are somewhat forward of the spring-connection and are spaced from the spring connection to locations generally near the two sides of the plate leading away from the spring connection side (the lateral sides of the plate). Two rollers are held on the side of the plate opposite the spring-connection location, each roller being positioned generally from the center of the plate to the lateral side of the plate. The two rollers are held in resilient, C-shaped elements partially surrounding their shafts to be parallel to the roller holding side. The plate is of a single material which has a thinned portion beginning generally near the center and connecting to the sides leading from the spring connection. In an embodiment this weakened part is a depression located from generally near the center of one side to generally near the far ends of the other sides in a somewhat V shape when viewed from the top.
DESCRIPTION OF THE DRAWINGSThe details of this invention will be described in connection with the accompanying drawings, in which
Imaging station 7 is located past nip rollers 9a, 9b (see
With reference to
The printer of
A C-shaped paper guide 17 is made up of rear guide surface 17a and spaced, generally parallel, front guide surface 17b. Both surfaces have spaced ridges (not shown), as is common. Guide 17 directs a sheet 5 to nip rollers 9a, 9b. Intermediate in guide 17 is drive roller 19a, which is a part of an autocompensating swing-mounted system 19. Sensor arm 21 is moved by a sheet 5 to detect the sheet 5 at system 19.
Pick roller 15a at tray 13 and drive roller 19a combine to move sheets 5 from tray 13 to nip rollers 9a, 9b. Drive roller 19a is effective to move short media into rollers 9a, 9b, when pick roller 15a is no longer in contact with the sheet 5.
Operational control is by electronic data processing apparatus, shown as element C in
Frame 23 where it supports plate 22 is of thin, rigid sheet metal. It has tabs 23a folded to form ledges on which plate 22 pivots as will be described. Plate 9a is a molded, generally rectangular single piece of rigid polycarbonate which is generally of at least one thickness, except at depressed lines 27a and 27b. Depressed lines 27a and 27b are to weaken plate 22 for bending.
Spring 33 is connected between frame 23 and a spring connecting bar 35 which is generally central on the side of plate 22 spaced from the side holding rollers 21. Also shown in
This invention recognizes that spring 33 operates to bow the center of plate 22 upward, thereby providing the highest forces of the lateral sides of plate 22. By weakening plate 22 between the center of plate 22 and the roller holding part, the plate tends to flatten, which more evenly distributes the forces on rollers 9b.
Clearly, the pressure plate can take many forms which are pivoted by spring action or the like and which are subject to being bowed by that spring action. The weakening can be in any manner including employing more still material near the spring connection and less stiff material between the more stiff material and the pressure rollers.
Claims
1. An imaging device comprising
- a sheet feed path,
- a drive roller in said sheet feed path,
- a pressure roller,
- a plate holding said pressure roller by spring force for rotation in nip relationship with said drive roller, said plate comprising a spring connection location to receive a spring to provide said spring force, a pressure roller holding location on a side opposite side spring connection location, said pressure roller being held at said pressure roller hold location in nip with said drive roller, and a weakened portion between said print connection location and said pressure roller holding location.
2. The imaging device as in claim 1 in which said plate holds two pressure rollers and said spring connection location is located generally intermediate said two pressure rollers.
3. The imaging device as in claim 1 in which said weakened portion is a depressed portion in said plate.
4. The imaging device as in claim 3 in which said depressed portion in said plate is a line extending generally between the center of said pressure roller holding location to one lateral side of said plate and a line extending generally between the center of said pressure roller holding location and the other lateral side of said plate, thereby forming a somewhat V shape when viewed from the top of said plate.
5. An imaging device comprising
- a sheet feed path,
- a drive roller in said sheet feed path,
- two pressure rollers,
- a plate holding said pressure rollers by spring force for rotation in nip relationship with said drive roller, said plate comprising a spring connection side having a generally central spring connection location, a pressure roller holding side opposite said spring connection side holding said two rollers generally from the center of said plate to the lateral sides of said plate, and a weakened portion between said print connection side and said pressure roller holding side.
6. The imaging device as in claim 5 in which said weakened portion is a depressed portion in said plate.
7. The imaging device as in claim 6 in which said depressed portion in said plate is a line extending generally between the center of said pressure roller holding location to one lateral side of said plate and a line extending generally between the center of said pressure roller holding location and the other lateral side of said plate, thereby forming a somewhat V shape when viewed from the top of said plate.
Type: Application
Filed: Aug 11, 2004
Publication Date: Apr 6, 2006
Inventors: William Klein (Richmond, KY), Bhaskar Ramakrishnan (Lexington, KY)
Application Number: 10/916,351
International Classification: B65H 5/02 (20060101);