EP0419800B1 - Entraînement différentiel à friction pour documents - Google Patents

Entraînement différentiel à friction pour documents Download PDF

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Publication number
EP0419800B1
EP0419800B1 EP90114394A EP90114394A EP0419800B1 EP 0419800 B1 EP0419800 B1 EP 0419800B1 EP 90114394 A EP90114394 A EP 90114394A EP 90114394 A EP90114394 A EP 90114394A EP 0419800 B1 EP0419800 B1 EP 0419800B1
Authority
EP
European Patent Office
Prior art keywords
medium
drive
moving
printhead
low friction
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.)
Expired - Lifetime
Application number
EP90114394A
Other languages
German (de)
English (en)
Other versions
EP0419800A1 (fr
Inventor
John A. Underwood
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
HP Inc
Original Assignee
Hewlett Packard Co
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Hewlett Packard Co filed Critical Hewlett Packard Co
Publication of EP0419800A1 publication Critical patent/EP0419800A1/fr
Application granted granted Critical
Publication of EP0419800B1 publication Critical patent/EP0419800B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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 an assembly for moving a print medium through a printer according to the preamble of claim 1 and to a print medium feeder according to the preamble of claim 5.
  • 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.
  • 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.
  • the JP-A-57/120 476 discloses a paper feeding mechanism comprising a round drive roller as a high friction moving surface, a low friction stationary surface for causing the medium to be pressed against the roller and means for tensioning said stationary surface toward said moving surface.
  • the JP-A-62/100 342 discribes a non-rotating path idler which is provided with an arcuate member positioned closely adjacent to a drive roller for the paper feeding mechanism, said arcuate member being made from an ultra-high molecular weight polyethylene.
  • the object of the invention is to provide a mechanism for driving medium through a printer which can successfully meet 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.
  • the medium drive mechanism of the invention should avoid the problems of medium buckling, and also avoid the problems of medium misfeed and jamming, and further cause the medium to exit the drive mechanism in a straight line parallel to the printhead. Further, the mechanism for driving medium through a printer shall allow 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.
  • 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 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.
  • 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 .
  • 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 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 ultrahigh 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)
  • Ink Jet (AREA)
  • Handling Of Cut Paper (AREA)
  • Feeding Of Articles By Means Other Than Belts Or Rollers (AREA)
  • Handling Of Sheets (AREA)

Claims (5)

  1. Un ensemble destiné à déplacer un milieu d'impression (14) à travers une imprimante (12), comprenant:
       une surface en déplacement (16) à friction élevée servant à transmettre une force motrice au milieu (14), ladite surface en mouvement (16) à friction élevée étant fixée à un rouleau d'entraînement (18);
       un moyen d'amener ledit rouleau d'entraînement à tourner;
       une surface stationnaire (30) à friction extrêmement basse qui sert à amener le milieu (14) à être appuyé contre ladite surface en déplacement (16) à friction élevée; et
       un moyen (20) de mise en tension de ladite surface stationnaire à friction extrêmement basse vers ladite surface en déplacement (16) à friction élevée,
       caractérisé en ce que
       ladite surface stationnaire (30) à friction extrêmement basse est une matière de polyéthylène à poids moléculaire extrêmement élevé; et ledit moyen de mise en tension de ladite surface stationnaire (30) à extrêmement basse friction vers ladite surface en déplacement à haute friction inclut une plaque de renfort (20) sur ladite surface stationnaire (30) à friction extrêmement basse.
  2. L'ensemble destiné à déplacer un milieu d'impression selon la revendication 1,
       caractérisé en ce que ladite surface (30) à faible friction est un côté d'un ruban attaché à ladite plaque d'entraînement (20) au moins à une zone tangente audit rouleau d'entraînement (18).
  3. L'ensemble à déplacer un milieu d'impression selon la revendication 1 ou 2,
       caractérisé en ce que ladite matière à poids moléculaire extrêmement élevé est amenée à adhérer à ladite plaque d'entraînement au moyen d'un adhésif acrylique résistant aux solvants.
  4. L'ensemble à déplacer un milieu d'impression selon la revendication 1, 2 ou 3,
       caractérisé en ce que ladite plaque de renfort (20) est en acier à ressorts.
  5. Un dispositif d'alimentation de milieu d'impression, comprenant
       un moyen propulseur (20) pour propulser un milieu d'impression (14);
       et un moyen (16, 18) de maintien du milieu (14) contre ledit moyen propulseur;
       caractérisé en ce que ledit moyen de maintien du milieu (14) contre ledit moyen propulseur comprend une surface de polyéthylène à poids moléculaire extrêmement élevé; et ledit moyen propulseur inclut:
       une plaque plate;
       une surface à friction élevée sur ladite plaque plate;
       un moyen servant à déplacer ladite plaque plate parallèlement à ladite surface de polyéthylène à poids moléculaire extrêmement élevé.
EP90114394A 1989-09-29 1990-07-26 Entraînement différentiel à friction pour documents Expired - Lifetime EP0419800B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US414829 1982-09-03
US41482989A 1989-09-29 1989-09-29

Publications (2)

Publication Number Publication Date
EP0419800A1 EP0419800A1 (fr) 1991-04-03
EP0419800B1 true EP0419800B1 (fr) 1994-12-14

Family

ID=23643149

Family Applications (1)

Application Number Title Priority Date Filing Date
EP90114394A Expired - Lifetime EP0419800B1 (fr) 1989-09-29 1990-07-26 Entraînement différentiel à friction pour documents

Country Status (4)

Country Link
EP (1) EP0419800B1 (fr)
JP (1) JPH03152039A (fr)
CA (1) CA2015021A1 (fr)
DE (1) DE69015082T2 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4220175C2 (de) * 1991-06-21 1994-12-01 Ricoh Kk Druckmechanismus für einen Drucker

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62100342A (ja) * 1985-10-24 1987-05-09 ゼロツクス　コ−ポレ−シヨン シ−ト案内装置

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62100342A (ja) * 1985-10-24 1987-05-09 ゼロツクス　コ−ポレ−シヨン シ−ト案内装置

Also Published As

Publication number Publication date
EP0419800A1 (fr) 1991-04-03
JPH03152039A (ja) 1991-06-28
CA2015021A1 (fr) 1991-03-29
DE69015082D1 (de) 1995-01-26
DE69015082T2 (de) 1995-08-03

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