Patent Application
20050212197
The present invention relates generally to duplex media sheet handling systems for printers. Specifically, it relates to a duplex system for an inkjet printer having small form factor for printing duplex media sheets with zero bottom of form margin.
Duplex printing is a desirable feature in printing systems. The advantages of duplex printing include reducing the amount of paper required as compared to one-side (simplex) printing, and generating print sets with layouts resembling that of professionally printed books. Modern duplex printing is typically accomplished by using one of two types of duplex system employed in printing systems, such as inkjet printers. The two types of duplex systems are back and front duplex systems as shown respectively in
Although the back duplex module 102 may be installed only when duplex printing is required, the duplex system 100 suffers from not being able to print all the way to the trailing edge 124 of the media sheet 112. The portion of the unprintable area on the media sheet is commonly referred to as “bottom of form” 108 as shown in
The front duplex system has a duplex module typically housed inside the base of the printer. Thus, the overall size or form factor of the printer remains the same even when the duplex module is removed. The front duplex system overcomes the bottom of form limitation but suffers from large form factor which consumes valuable table space as described herein with reference to
As the printhead 206 prints, the media sheet 212 is progressively advanced forward and eventually received by the output roller assembly 208. Once printing on the first side of the media sheet 212 is completed, the output roller assembly 208 further advances the media sheet 212 forward until the trailing edge 218 of the media sheet 212 reaches the duplex media path entry 214 area. The output roller assembly 208 then reverses the rolling direction and rolls the media sheet 212 into the duplex media path entry 214. The media sheet 212 is advanced along a duplex media path 216 to the linefeed roller assembly 204 where the media sheet 212 is received and subsequently fed to the printhead 206 for printing on a second side of the media sheet 212.
In the front duplex system 200, the transmission (i.e. the set of gears and belts that drives the rollers) of the output roller assembly 208 is coupled to the transmission of the linefeed roller assembly 204 in order to maintain media sheet 212 feeding accuracy.
Thus, during duplexing (i.e. the process of flipping the media sheet), the trailing edge, which is the leading edge 220 during duplexing, of the media sheet 212 must leaves the output roller assembly 208 before the media sheet 212 is further advanced along the duplex media path by a transfer roller assembly 222 to the linefeed roller assembly 204. This is so because the turning direction of the rollers of the two roller assemblies 204 and 208 are in opposite directions to each other.
This requirement causes the front duplex system 200 to have a large form factor. The form factor is dependent on the size of the media sheet the printer is designed to accommodate. For example, if the media sheet is of A4 size, then the reverse duplex media path length (i.e. the duplex media path entry 214 and the duplex media path 216) between the linefeed roller assembly 204 and the output roller assembly 208 must be longer than the length of the A4 size media sheet. However, if the transmissions of the linefeed roller assembly 204 and output roller assembly 208 can be decoupled, the form factor can be reduced and is only limited by the loop of the media sheet path starting and ending at the output roller assembly 208. Thus, the form factor of the printer of the decoupled transmissions of the linefeed roller assembly 204 and output roller assembly 208 is smaller but still has substantial impact to the base printer size. Further, decoupling the transmissions of the two roller assemblies 204 and 208 is difficult and may be costly.
Therefore, there is clearly a need to provide a duplex system for an inkjet printer that addresses the above-outlined shortcomings of existing duplex systems.
The present invention is directed to a duplex system for an inkjet printer having a printhead for printing a media sheet. The duplex system includes a front duplex module and a back duplex module detachably coupled to the front duplex module. The front duplex module includes a first roller assembly for advancing the media sheet to the printhead along a simplex media path and a second roller assembly disposed along the simplex media path for handling the media sheet.
Embodiments of the invention are herein described, purely by way of example, with reference to the accompanying drawings, in which:
A duplex system for an inkjet printer having substantially small form factor and a method for printing a media sheet on both sides with zero bottom of form margin using the inkjet printer are described hereinafter.
A duplex system 300 according to an embodiment is shown in
Typical operation of the front duplex module 302 is such that the media sheet 312 is fed to the linefeed roller assembly 308 via a media sheet path entry 314. The linefeed roller assembly 308 subsequently advances forward the media sheet 312 along a simplex media path 324 to the printhead 306 for printing on a first side of the media sheet 312. When the leading edge 316 of the media sheet 312 reaches the output roller assembly 310, the linefeed roller assembly 308 and the output roller assembly 310 advances the media sheet 312 together. Once the trailing edge 318 of the media sheet 312 leaves the linefeed roller assembly 308, the output roller assembly 310 takes over the task of further advancing forward 320 the media sheet 312 until printing on the first side of the media sheet 312 is completed. If the transmission between the output and linefeed roller assembly are not coupled together, complicated (if possible at all) control is needed to ensure the two roller assemblies 308 and 310 synchronize with each other and advance the media sheet 312 with substantially identical motion profile in order to achieve good feeding accuracy. Accordingly, in an embodiment, the transmissions of the two roller assemblies 308 and 310 are coupled to provide coordinated control for handling the media sheet 312.
If printing on the second side of the media sheet 312 is not needed, the output roller assembly 310 simply rolls out the printed media sheet 312 to an output tray of the printer (not shown). Thus, base size of the printer is minimized and not restricted to the length of a media sheet. However, if duplex printing is needed, the media sheet 312 is fed back into a reverse duplex media path (i.e. a duplex media path entry 326 and a duplex media path 328) as described hereinafter.
The back duplex module 304 can be easily attached to the printer and operates in conjunction with the front duplex module 302 to provide duplex printing capability. Means for such detachable connection between two mechanical modules are well known in the art. The back duplex module 304 includes a duplex roller 332 for receiving and advancing the media sheet 312 along the duplex media path 328 to the linefeed roller assembly 308. The exit portion of the duplex media path 328 is aligned to the simplex media path 324. It is possible to change the number of duplex rollers, the diameters and positions thereof to achieve the required media path length.
Once the trailing edge 318 of the media sheet 312 leaves the linefeed roller assembly 308, the output roller assembly 310 takes over the task of advancing forward 320 the media sheet 312 as the printhead prints on the first side thereof. Thus, printing to the end of the length of the media sheet 312 is possible since the output roller assembly 310 is located downstream from the printhead 306 along the simplex media path 324.
Once printing on the first side of the media sheet 312 is completed and duplex printing is not needed, the output roller assembly 310 rolls out the printed media sheet 312 to an output tray of the printer (not shown). However, if duplex printing is needed, the media sheet 312 is flipped in a step 406.
In the step 406, the output roller assembly 310 advances forward 320 the media sheet 312 until the trailing edge 318 of the media sheet 312 reaches the duplex media path entry 326 area. The output roller assembly 310 then reverses the rolling direction and advances the printed media sheet 312 backward 322 into the duplex media path entry 326. As the media sheet 312 advances backward 322, a transfer roller assembly 340 advances the media sheet along the duplex media path 328 to the duplex roller 332. The duplex roller 332 subsequently advances the media sheet 312 to the linefeed roller assembly 308 with the media sheet 312 being flipped for printing on the second side thereof. In a step 408, once the second side of the media sheet 312 is printed in the same manner as the first side described in the foregoing, the output roller assembly 310 rolls out the printed media sheet 312 to the output tray (not shown) of the printer.
Although an embodiment of the invention is described in the foregoing, it is anticipated that individuals skilled in the art may make other modifications and equivalents thereto. Therefore, the foregoing description should not be taken as limiting the scope of the invention which is defined by the appended claims.
