EP0419800A1 - Differential friction media drive - Google Patents
Differential friction media drive Download PDFInfo
- Publication number
- EP0419800A1 EP0419800A1 EP90114394A EP90114394A EP0419800A1 EP 0419800 A1 EP0419800 A1 EP 0419800A1 EP 90114394 A EP90114394 A EP 90114394A EP 90114394 A EP90114394 A EP 90114394A EP 0419800 A1 EP0419800 A1 EP 0419800A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- medium
- drive
- moving
- high friction
- printer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 230000007246 mechanism Effects 0.000 claims description 65
- 239000000463 material Substances 0.000 claims description 3
- 229910000639 Spring steel Inorganic materials 0.000 claims description 2
- 239000003522 acrylic cement Substances 0.000 claims description 2
- 239000002904 solvent Substances 0.000 claims description 2
- 239000004699 Ultra-high molecular weight polyethylene Substances 0.000 claims 3
- 229920000785 ultra high molecular weight polyethylene Polymers 0.000 claims 3
- 239000002783 friction material Substances 0.000 abstract description 2
- 241001131688 Coracias garrulus Species 0.000 description 26
- 230000008901 benefit Effects 0.000 description 10
- 239000004698 Polyethylene Substances 0.000 description 9
- -1 polyethylene Polymers 0.000 description 9
- 229920000573 polyethylene Polymers 0.000 description 9
- 230000009977 dual effect Effects 0.000 description 7
- 230000033001 locomotion Effects 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 230000004075 alteration Effects 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 239000004809 Teflon Substances 0.000 description 1
- 229920006362 Teflon® Polymers 0.000 description 1
- 230000001154 acute effect Effects 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 230000003466 anti-cipated effect Effects 0.000 description 1
- 230000000712 assembly Effects 0.000 description 1
- 238000000429 assembly Methods 0.000 description 1
- 229940000425 combination drug Drugs 0.000 description 1
- 230000002860 competitive effect Effects 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 230000005923 long-lasting effect Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229920000136 polysorbate Polymers 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J13/00—Devices or arrangements of selective printing mechanisms, e.g. ink-jet printers or thermal printers, specially adapted for supporting or handling copy material in short lengths, e.g. sheets
- B41J13/02—Rollers
Definitions
- the present invention relates to medium drive mechanisms for computer hard copy printers.
- the predominant current usage of the improved medium drive mechanism is as a means for causing a medium such as paper to move through the printer and past the printing area in a thermal ink-jet printer.
- This invention relates to a medium drive mechanism for a computer hard copy printer having an extremely low friction surface opposed to a high friction drive surface. This combination provides a positive medium drive formerly available only with dual roller drive systems.
- the preferred embodiment of the present invention is a medium drive mechanism constructed such that a high friction rubber drive roller imparts a motive force to a sheet print medium.
- the medium is held in place against the rubber drive roller by means of a guide plate including a structural backing mechanism and an extremely low friction surface.
- the low friction surface is constructed of ultra-high molecular weight (UHMW) polyethylene.
- UHMW polyethylene has been found by the inventor to provide the best combination of low friction properties and wear resistance. It has been found by the inventor that drive mechanisms so constructed are no more prone to jamming or medium misalignment than are dual roller drive mechanisms.
- the superior drive qualities of the inventive drive mechanism are largely due to the fact that the sum of forces on the medium produced by the inventive drive actually produces a greater total force in the intended drive direction than have similar prior art drive mechanisms.
- the inventive medium drive mechanism subassembly may be placed closer to the printhead in a printer assembly than is possible with a dual roller medium drive mechanism, because the guide surface does not interfere with the movement of the printhead as does a top roller.
- the greater distance the medium has to travel after leaving the drive mechanism and before getting to the printing area of a printer the greater the likelihood that buckling or other medium misalignment may occur.
- the primary advantages of the inventive drive mechanism are that the amount of necessary top and bottom margins are greatly reduced, and that high image quality may be maintained by allowing placement of the printhead close to the medium and to the drive assembly.
- the inventive method is conducive to the highest print quality possible, since medium orientation to the printhead is optimized. That placement of the drive mechanism close to the printhead is desirable has long been known.
- prior attempts to design mechanisms which could be placed closer to the printhead have failed because all such attempts have resulted in mechanisms that were more prone to jamming or other problems than were the conventional dual roller drive mechanisms. Therefore, prior to the present invention, dual roller mechanisms have been incorporated into ink-jet printer assemblies.
- a drive mechanism constructed according to the invention may be made smaller than conventional medium drive mechanisms, thereby facilitating a reduction in overall printer size.
- An advantage of the present invention is that the size of top and bottom margins on the print medium may be decreased.
- Another advantage of the present invention is that a sprinter medium drive mechanism may be placed horizontally closer to an ink-jet printer printhead.
- Yet another advantage of the present invention is that image quality is improved by allowing placement of the printhead vertically closer to the medium.
- a further advantage of the present invention is that a tendency of medium to jam in the drive mechanism is reduced.
- a still further advantage of the present invention is that the unsupported area between a drive mechanism and a printhead wherein a medium might buckle is reduced.
- Yet another advantage of the present invention is that overall printer size may be reduced.
- the best presently known mode for carrying out the invention is a thermal ink-jet printer incorporating a conventional printer pen and pen traversing mechanism, but also using a medium drive mechanism in accordance with the present invention, wherein motive force is transferred to the medium via a high friction surface and the medium is held against the high friction surface by an opposing low friction surface.
- the medium drive mechanism of the present invention is more compact then comparable prior art drive mechanisms, and also provides for more accurate medium placements than has been considered to be feasible using compact drive mechanisms.
- the friction differential necessary to the success of the invention is achieved by use of an ultrahigh molecular weight (UHMW) polyethylene tape on the low friction surface.
- UHMW ultrahigh molecular weight
- the predominant expected usage of the inventive medium drive mechanism is in thermal ink-jet printers, wherein clearance of the drive mechanism to the printhead pen is critical, and especially in applications, wherein the height of the combined assembly is a concern, such as in a portable or small desk top units, and in applications wherein minimal top and bottom margins are required.
- thermal ink-jet printer assembly of the presently preferred embodiment of the present invention is illustrated in diagrammatic form in a side view in FIG. 1 and is designated therein by the general reference character 10. In most of its substantial components, the printer 10 does not differ significantly from conventional thermal ink-jet printers.
- the conventional elements of the printer 10 include a printhead 12 and a printhead traversing mechanism (not shown) for moving the printhead 12 across a piece of medium 14, thus positioning the printhead 12 for printing upon the medium 14.
- the medium 14 is moved through the printer by means of a high friction drive surface 16.
- the drive surface 16 is made of high friction rubber and constitutes the surface 16 of a drive roller 18.
- a drive plate 20 is provided to hold the medium 14 firmly against the drive surface 16.
- a means for pressing the drive plate 20 toward the drive surface 16 in a force direction 22 is provided in the presently preferred embodiment of the invention by constructing the drive plate 20 of spring steel and tensioning it against the drive roller 18 in force direction 22.
- the tangent point 24 of the drive roller 18 to the drive plate 20, according to the present invention transfers motive force to the medium 14 in a medium advance direction 26 as the drive roller 18 rotates in a rotational direction 28. Therefore, normal force in force direction 22 must be sufficiently great to prevent slipping and mishandling of the medium 14. The actual amount of necessary normal force in force direction 22 may vary depending upon the type of medium 14 used and other variables, but this can be quickly and easily adjusted according to the exact application to which the present invention is applied.
- an ul trahigh molecular weight (UHMW) polyethylene tape 30 is applied to the drive plate 20.
- UHMW polyethylene tape 30 friction differential as between the first junction 32 of the high friction drive surface 16 to the medium 14, and the second junction 34 of drive plate 20 to the medium 14, sufficient to prevent problems previously believed to be unavoidable in such an application, may be created.
- UHMW polyethylene tape may be obtained from 3M Company, Industrial Tape Division, St. Paul, Minnesota, under their part number 5425. The tape is provided with a solvent-resistant acrylic adhesive backing (not shown) for adhering the UHMW polyethylene tape 30 to the drive plate 20.
- the polyethylene tape of the presently preferred embodiment of the present invention allows the printhead 12 (FIG. 1 and FIG. 2) to be placed closer to the tangent point 24 while not necessitating raising the printhead 12 higher above the medium.
- This is an important advantage in thermal ink-jet printers, since maintaining the printhead 12 at a minimal height above the medium 14 is necessary to print quality, and since placement of the printhead 12 close to the drive tangent point 24 allows printing on a greater portion of the medium 14, thereby reducing the size of top and bottom margins (not shown).
- the normal forces 50 are produced, in the best presently known embodiment of the present invention, by tensioning of the drive plate 20 toward the drive roller 18. Since the drive plate 20 and the drive roller 18 are immobile in the plane of the normal forces 50, the two normal forces 50 are necessarily equal in magnitude and opposite in direction.
- the drive force 44 in medium advance direction 26 acting on the medium 14 is a function of the product of the normal force 50 and a friction factor between the high friction drive surface 16 and the medium.
- the drag force 46 acting in a direction opposite to medium advance direction 26 is a function of the product of the normal force 50 and a friction factor between the low friction surface 30 and the medium 14.
- greatly reducing the friction factor between the medium 14 and the drive plate 20 by addition of the low friction surface 30, causes the ratio of the drive force 44 to the drag force 46 to be greatly increased.
- the sum of forces acting on the medium 14 in a plane parallel to the medium drive direction 26 is the drive force 44 minus the drag force 46.
- the normal force 50 can be increased, in accordance with the present invention, to a value necessary to provide sure and positive handling of various types of medium 14 without slippage or other mishandling of the medium 14.
- the high friction drive surface 16 may be part of a flat sliding plate, rather than a roller.
- Another conceivable alteration would be to use another very low friction surfacing material as a substitute for the UHMW polyethylene tape 30.
- Thermal ink-jet printers have found wide acceptance in the marketplace. Among the many desirable qualities of thermal ink-jet printers are the high print quality and the ease of use of these printers. The present invention has been found to enhance both of these qualities.
- the print quality of thermal ink-jet printers is enhanced through use of the drive mechanism of the present invention by virtue of the fact that the printhead may be placed at a height which is relatively close to the medium as compared with prior art arrangements, and because the height relationship of the medium to the printhead is held relatively constant by virtue of the fact that the medium is supported close to the printhead by the inventive drive assembly.
- the top and bottom margins may be greatly reduced. These margins are a function of the distance from the drive assembly to the printhead, since the medium must necessarily be supported in the drive assembly when printing is being accomplished, and since the absolute minimum margin would be the distance from the printhead to point at which the medium is supported by the drive assembly. It is thought that this factor alone will provide a major benefit to the users of printers employing the inventive drive mechanism.
- medium drive mechanisms of the present invention may be readily constructed and are easily incorporated into printer designs, it is expected that they will be accepted in the industry as substitutes for conventional medium drive mechanisms.
Landscapes
- Delivering By Means Of Belts And Rollers (AREA)
- Feeding Of Articles By Means Other Than Belts Or Rollers (AREA)
- Handling Of Cut Paper (AREA)
- Handling Of Sheets (AREA)
- Ink Jet (AREA)
Abstract
Description
- The present invention relates to medium drive mechanisms for computer hard copy printers. The predominant current usage of the improved medium drive mechanism is as a means for causing a medium such as paper to move through the printer and past the printing area in a thermal ink-jet printer.
- A number of various means have been employed to move a medium such as paper through computer hard copy printers. The first of these was the traditional typewriter roller arrangement. This arrangement proved unsatisfactory for automated computer printers, however, because it was not well suited for automatically accepting single sheets of medium as they were fed into the printer.
- Other methods that have been tried have included tractor feed mechanisms wherein drive sprockets engage holes in the medium. This method works well for form-feed type documents and other media; however, it is not adaptable for use with single sheets of media.
- Current drive mechanisms for thermal ink-jet printers frequently include roller mechanisms wherein the medium is passed between two opposing rollers as in the rollers of an old fashioned washing machine. This arrangement works well because it provides a positive feed for the medium and allows the medium to exit the drive area in a straight line. However, the problem with this arrangement is that there is frequently insufficient room to easily include a pair of opposed rollers. This problem is particularly acute as regards the top roller, as it may interfere with the movement of the printhead if it is placed too near.
- It is desirable to place the drive mechanism as close to the printhead as possible, because the less distance the medium has to travel from the drive mechanism to the printhead, the less chance there is of it buckling in that interval. Further, if the printhead could be placed nearer to the drive area, necessary top and bottom margins could be greatly reduced. This is considered to be a highly desirable feature. Therefore, printer designers have been faced with the dilemma of having to place the drive mechanism as close as possible to the printhead to avoid buckling and to reduce necessary top and bottom margin sizes, and also having to remove the drive mechanism from the printhead sufficiently far to provide room for a top roller. This dilemma has been compounded by the fact that the height of the printhead above the medium must also be minimized, as this is an important factor in print quality.
- Obviously, it would be desirable to provide a means for driving media through printers which did not include a top roller and therefore could be placed as close as is desired to the printhead. However, previous attempts to design such a mechanism have been less than successful. For instance, if the top roller is replaced with a flat surface, the medium has tended to feed improperly and to jam in the drive mechanism unless an additional pair of drive rollers is provided, thereby allowing for a clearance between the drive roller and the flat surface.
- To the inventor's knowledge, no prior art mechanism for driving medium through a printer has successfully met desirable size restrictions so as to reduce the overall size of the printer and also to allow the drive mechanism to be placed very close to the printhead. All successful medium drive mechanisms to date have used either a combination of rollers or other complex mechanisms in order to avoid the problems of medium buckling, and also to avoid the problems of medium misfeed and jamming, and further to cause the medium to exit the drive mechanism in a straight line parallel to the printhead. Further, no prior art mechanism for driving medium through a printer has allowed for producing top and bottom margins as small as 2 to 3 millimeters.
- This invention relates to a medium drive mechanism for a computer hard copy printer having an extremely low friction surface opposed to a high friction drive surface. This combination provides a positive medium drive formerly available only with dual roller drive systems.
- Briefly, the preferred embodiment of the present invention is a medium drive mechanism constructed such that a high friction rubber drive roller imparts a motive force to a sheet print medium. The medium is held in place against the rubber drive roller by means of a guide plate including a structural backing mechanism and an extremely low friction surface. In the preferred embodiment of the present invention, the low friction surface is constructed of ultra-high molecular weight (UHMW) polyethylene. Although other very low friction materials such as Teflon could be used in the manufacture of the inventive drive mechanism, UHMW polyethylene has been found by the inventor to provide the best combination of low friction properties and wear resistance. It has been found by the inventor that drive mechanisms so constructed are no more prone to jamming or medium misalignment than are dual roller drive mechanisms.
- The superior drive qualities of the inventive drive mechanism are largely due to the fact that the sum of forces on the medium produced by the inventive drive actually produces a greater total force in the intended drive direction than have similar prior art drive mechanisms.
- The inventive medium drive mechanism subassembly may be placed closer to the printhead in a printer assembly than is possible with a dual roller medium drive mechanism, because the guide surface does not interfere with the movement of the printhead as does a top roller. Of course, the greater distance the medium has to travel after leaving the drive mechanism and before getting to the printing area of a printer, the greater the likelihood that buckling or other medium misalignment may occur. But the primary advantages of the inventive drive mechanism are that the amount of necessary top and bottom margins are greatly reduced, and that high image quality may be maintained by allowing placement of the printhead close to the medium and to the drive assembly.
- Therefore, the inventive method is conducive to the highest print quality possible, since medium orientation to the printhead is optimized. That placement of the drive mechanism close to the printhead is desirable has long been known. However, prior attempts to design mechanisms which could be placed closer to the printhead have failed because all such attempts have resulted in mechanisms that were more prone to jamming or other problems than were the conventional dual roller drive mechanisms. Therefore, prior to the present invention, dual roller mechanisms have been incorporated into ink-jet printer assemblies.
- Another desirable factor of the present invention is that a drive mechanism constructed according to the invention may be made smaller than conventional medium drive mechanisms, thereby facilitating a reduction in overall printer size.
- An advantage of the present invention is that the size of top and bottom margins on the print medium may be decreased.
- Another advantage of the present invention is that a sprinter medium drive mechanism may be placed horizontally closer to an ink-jet printer printhead.
- Yet another advantage of the present invention is that image quality is improved by allowing placement of the printhead vertically closer to the medium.
- A further advantage of the present invention is that a tendency of medium to jam in the drive mechanism is reduced.
- A still further advantage of the present invention is that the unsupported area between a drive mechanism and a printhead wherein a medium might buckle is reduced.
- Yet another advantage of the present invention is that overall printer size may be reduced.
- These and other objects and advantages of the present invention will become clear to those skilled in the art in view of the description of the best presently known mode of carrying out the invention and the industrial applicability of the preferred embodiment as described herein and as illustrated in the several figures of the drawing.
-
- FIG. 1 is a diagrammatic representation of a side view of a portion of a printer including the drive mechanism of the present invention;
- FIG. 2 is a diagrammatic representation similar to FIG. 1, showing the low friction surface of the present invention replaced with a prior art pinch roller; and
- FIG. 3 is a representation of the various forces exerted on a print medium by a drive mechanism.
- The best presently known mode for carrying out the invention is a thermal ink-jet printer incorporating a conventional printer pen and pen traversing mechanism, but also using a medium drive mechanism in accordance with the present invention, wherein motive force is transferred to the medium via a high friction surface and the medium is held against the high friction surface by an opposing low friction surface. The medium drive mechanism of the present invention is more compact then comparable prior art drive mechanisms, and also provides for more accurate medium placements than has been considered to be feasible using compact drive mechanisms. In the best presently known embodiment of the present invention, the friction differential necessary to the success of the invention is achieved by use of an ultrahigh molecular weight (UHMW) polyethylene tape on the low friction surface. The sum of the resultant forces produced on the medium by the inventive drive mechanism is greater in a desired drive direction than that which is produced by comparable prior art drive mechanisms.
- The predominant expected usage of the inventive medium drive mechanism is in thermal ink-jet printers, wherein clearance of the drive mechanism to the printhead pen is critical, and especially in applications, wherein the height of the combined assembly is a concern, such as in a portable or small desk top units, and in applications wherein minimal top and bottom margins are required.
- A portion of the thermal ink-jet printer assembly of the presently preferred embodiment of the present invention is illustrated in diagrammatic form in a side view in FIG. 1 and is designated therein by the general reference character 10. In most of its substantial components, the printer 10 does not differ significantly from conventional thermal ink-jet printers.
- The conventional elements of the printer 10 include a
printhead 12 and a printhead traversing mechanism (not shown) for moving theprinthead 12 across a piece ofmedium 14, thus positioning theprinthead 12 for printing upon themedium 14. - The
medium 14 is moved through the printer by means of a highfriction drive surface 16. In the presently preferred embodiment of the present invention, thedrive surface 16 is made of high friction rubber and constitutes thesurface 16 of adrive roller 18. Adrive plate 20 is provided to hold themedium 14 firmly against thedrive surface 16. A means for pressing thedrive plate 20 toward thedrive surface 16 in aforce direction 22 is provided in the presently preferred embodiment of the invention by constructing thedrive plate 20 of spring steel and tensioning it against thedrive roller 18 inforce direction 22. - The
tangent point 24 of thedrive roller 18 to thedrive plate 20, according to the present invention, transfers motive force to the medium 14 in amedium advance direction 26 as thedrive roller 18 rotates in arotational direction 28. Therefore, normal force inforce direction 22 must be sufficiently great to prevent slipping and mishandling of the medium 14. The actual amount of necessary normal force inforce direction 22 may vary depending upon the type ofmedium 14 used and other variables, but this can be quickly and easily adjusted according to the exact application to which the present invention is applied. - Contrary to previous beliefs about printer drive mechanisms, the inventor has found that sufficient normal force in
force direction 22 may be applied to prevent slippage and resultant jamming of the medium 14 whentangent point 24 is the point of transfer of motive force from the highfriction drive surface 16 to the medium 14. In the best presently known embodiment of the present invention, an ul trahigh molecular weight (UHMW)polyethylene tape 30 is applied to thedrive plate 20. - Using the
UHMW polyethylene tape 30, friction differential as between thefirst junction 32 of the highfriction drive surface 16 to the medium 14, and thesecond junction 34 ofdrive plate 20 to the medium 14, sufficient to prevent problems previously believed to be unavoidable in such an application, may be created. UHMW polyethylene tape may be obtained from 3M Company, Industrial Tape Division, St. Paul, Minnesota, under their part number 5425. The tape is provided with a solvent-resistant acrylic adhesive backing (not shown) for adhering theUHMW polyethylene tape 30 to thedrive plate 20. - As opposed to prior art mechanisms, as depicted in FIG. 2, wherein a
pinch roller 44 is used to reduce drag, the polyethylene tape of the presently preferred embodiment of the present invention allows the printhead 12 (FIG. 1 and FIG. 2) to be placed closer to thetangent point 24 while not necessitating raising theprinthead 12 higher above the medium. This is an important advantage in thermal ink-jet printers, since maintaining theprinthead 12 at a minimal height above the medium 14 is necessary to print quality, and since placement of theprinthead 12 close to the drivetangent point 24 allows printing on a greater portion of the medium 14, thereby reducing the size of top and bottom margins (not shown). - Referring now to FIG. 3, wherein is depicted a
drive force 46, adrag force 48, and twonormal forces 50 acting on aprint medium 14, it can be seen that the sum offorces medium advance direction 26. Thenormal forces 50 are produced, in the best presently known embodiment of the present invention, by tensioning of thedrive plate 20 toward thedrive roller 18. Since thedrive plate 20 and thedrive roller 18 are immobile in the plane of thenormal forces 50, the twonormal forces 50 are necessarily equal in magnitude and opposite in direction. Thedrive force 44 inmedium advance direction 26 acting on the medium 14 is a function of the product of thenormal force 50 and a friction factor between the highfriction drive surface 16 and the medium. Thedrag force 46 acting in a direction opposite tomedium advance direction 26 is a function of the product of thenormal force 50 and a friction factor between thelow friction surface 30 and the medium 14. As can be appreciated by one skilled in the art, greatly reducing the friction factor between the medium 14 and thedrive plate 20 by addition of thelow friction surface 30, causes the ratio of thedrive force 44 to thedrag force 46 to be greatly increased. The sum of forces acting on the medium 14 in a plane parallel to themedium drive direction 26 is thedrive force 44 minus thedrag force 46. Thenormal force 50 can be increased, in accordance with the present invention, to a value necessary to provide sure and positive handling of various types ofmedium 14 without slippage or other mishandling of the medium 14. - Various modifications may be made to the invention without altering its value or scope. For example, the high
friction drive surface 16 may be part of a flat sliding plate, rather than a roller. Another conceivable alteration would be to use another very low friction surfacing material as a substitute for theUHMW polyethylene tape 30. - All of the above are only some of the examples of available embodiments of the present invention. Those skilled in the art will readily observe that numerous other modifications, alterations, and adaptations may be made without departing from the spirit and scope of the invention. Accordingly the above disclosure is not intended as limiting and the appended claims are to be interpreted as encompassing the entire scope of the invention.
- Thermal ink-jet printers have found wide acceptance in the marketplace. Among the many desirable qualities of thermal ink-jet printers are the high print quality and the ease of use of these printers. The present invention has been found to enhance both of these qualities. The print quality of thermal ink-jet printers is enhanced through use of the drive mechanism of the present invention by virtue of the fact that the printhead may be placed at a height which is relatively close to the medium as compared with prior art arrangements, and because the height relationship of the medium to the printhead is held relatively constant by virtue of the fact that the medium is supported close to the printhead by the inventive drive assembly.
- Since printing is accomplished in a thermal ink-jet printer by ejecting droplets of ink onto the medium, any variations in the plane of the medium relative to the surface of the printhead from which the ink is ejected will result in a reduction of print quality. Since the marketplace for thermal ink-jet printers is quite competitive and since one of the major differentiating factors of such printers is the print quality, any innovation such as the present invention which will enhance quality will greatly enhance the utility of the printer in the marketplace.
- Furthermore, since the printhead may be placed very close to the drive assembly, according to the present invention, the top and bottom margins (unprinted areas) may be greatly reduced. These margins are a function of the distance from the drive assembly to the printhead, since the medium must necessarily be supported in the drive assembly when printing is being accomplished, and since the absolute minimum margin would be the distance from the printhead to point at which the medium is supported by the drive assembly. It is thought that this factor alone will provide a major benefit to the users of printers employing the inventive drive mechanism.
- Ease of use of thermal ink-jet printers is greatly reduced by any jamming or mishandling of medium within the printer. Minor variations in medium handling will result in print being improperly placed upon the medium. Major mishandling problems require operator intervention and are considered to be extremely detrimental to user satisfaction. For this reason, dual roller type medium drive mechanisms have been used in spite of the fact that they are less than ideal for other reasons discussed herein.
- However, the inventive mechanism has been found to be as conducive to error-free medium handling as have prior art dual roller mechanisms. Therefore, it is anticipated that medium drive mechanisms according to the present invention will greatly enhance the usability of thermal ink-jet printers.
- Another factor which may increase the acceptance and usefulness of the inventive drive mechanism is that the need for smaller printers is increasing. In fact, portable printers to accompany portable computers may be a future application.
- Since the medium drive mechanisms of the present invention may be readily constructed and are easily incorporated into printer designs, it is expected that they will be accepted in the industry as substitutes for conventional medium drive mechanisms.
- For these and other reasons, it is expected that the utility and industrial applicability of the invention will both significant in scope and long lasting in duration.
Claims (10)
a high friction moving surface (16) for transmitting motive force to the medium (14);
means for imparting motive force to said high friction moving surface;
an extremely low friction stationary surface (30) for causing the medium (14) to be pressed against said high friction moving surface (16); and
means (20) for tensioning said extremely low friction stationary surface toward said high friction moving surface (16).
said high friction moving surface (16) is affixed to a round drive roller (18); and
said means for imparting motive force to said high friction moving surface is a means for causing said round drive roller to rotate.
said extremely low friction stationary surface (30) is an ultrahigh molecular weight polyethylene material.
said means for tensioning said extremely low friction stationary surface (30) toward said high friction moving surface includes a backing plate (20) on said extremely low friction stationary surface (30).
an ultrahigh molecular weight polyethylene surface (30) for holding the medium (14) against said means for propelling the medium.
a flat plate;
a high friction surface on said flat plate;
a means for moving said flat plate parallel to said ultrahigh molecular weight polyethylene surface.
a round drive roller;
a high friction surface on said round drive roller;
and
a means for causing said round drive roller to rotate.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US41482989A | 1989-09-29 | 1989-09-29 | |
US414829 | 1989-09-29 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0419800A1 true EP0419800A1 (en) | 1991-04-03 |
EP0419800B1 EP0419800B1 (en) | 1994-12-14 |
Family
ID=23643149
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP90114394A Expired - Lifetime EP0419800B1 (en) | 1989-09-29 | 1990-07-26 | Differential friction media drive |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0419800B1 (en) |
JP (1) | JPH03152039A (en) |
CA (1) | CA2015021A1 (en) |
DE (1) | DE69015082T2 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE4220175A1 (en) * | 1991-06-21 | 1992-12-24 | Ricoh Kk | Paper printing mechanism - has low friction coating e.g. of PVC on roller covering allowing paper to slip |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4938468A (en) * | 1985-10-24 | 1990-07-03 | Xerox Corporation | Non-rotating paper path idler |
-
1990
- 1990-04-20 CA CA 2015021 patent/CA2015021A1/en not_active Abandoned
- 1990-07-26 DE DE1990615082 patent/DE69015082T2/en not_active Expired - Fee Related
- 1990-07-26 EP EP90114394A patent/EP0419800B1/en not_active Expired - Lifetime
- 1990-09-27 JP JP25879190A patent/JPH03152039A/en active Pending
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4938468A (en) * | 1985-10-24 | 1990-07-03 | Xerox Corporation | Non-rotating paper path idler |
Non-Patent Citations (2)
Title |
---|
PATENT ABSTRACTS OF JAPAN vol. 10, no. 304 (M-526)(2360), 16 October 1986; & JP - A - 61116567 (SANWA K.K.) 04.06.1986 * |
PATENT ABSTRACTS OF JAPAN vol. 6, no. 216 (M-168)(1094), 29 October 1982; & JP - A - 57120476 (SHINSHIYUU SEIKI K.K.) 27.01.1982 * |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE4220175A1 (en) * | 1991-06-21 | 1992-12-24 | Ricoh Kk | Paper printing mechanism - has low friction coating e.g. of PVC on roller covering allowing paper to slip |
Also Published As
Publication number | Publication date |
---|---|
CA2015021A1 (en) | 1991-03-29 |
EP0419800B1 (en) | 1994-12-14 |
DE69015082D1 (en) | 1995-01-26 |
JPH03152039A (en) | 1991-06-28 |
DE69015082T2 (en) | 1995-08-03 |
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