Printer with interchangeable paper-feed modules

Abstract

A data printer having removable, and interchangeable, paper-feed modules, such as may embody a tractor or pin-feed-type paper-feed mechanism. The interchangeable modules each have guide ways which cooperate with and move along complementary guideways supported by the printer main frame to guide the selected module into place and seat it in a particularly defined position. A mechanical latch locks the seated module to maintain it in place. The paper-feed mechanism of each module is driven by a rotatable member, with the power train including a motor-driven worm mounted on the printer and a mating worm-gear carried on the removable paper-feed module. The worm is mounted in an upright position, and the worm-gear moves into mating relation with the worm by travelling an upright path, but with a small acute angle between such paths. The worm and worm-gear have a tooth or thread profile with a rounded nose section.BACKGROUND OF THE INVENTIONIn the use of data printers generally, and particularly in those of sufficiently simple design to be economically feasible for purchase or lease by an average-size business enterprise, which may require a printer capability to complement a data entry terminal, it is often desired to use a variety of different types of business forms as the printing medium. However, such forms are usually so different in nature that they will not fit the same paper-feed mechanism, frequently a tractor, or sometimes a pin-feed mechanism. Nonetheless, in the past, printers have mainly had only a single type of permanently-mounted paper drive, and the needed flexibility to accommodate differently-sized forms has not been available, largely because of the difficulties in obtaining paper-feed module interchangeability while maintaining the needed structural integrity and operational consistency. This is particularly true because the most common type of such printer is an impact device having a reversing or reciprocating carriage of some type, which is subject to substantial vibration and shock during use, which tends to shake, weaken and loosen all but extremely rigid and permanently-anchored components.Thus, the need has been present for some time for greater flexibility in such printers, in the way of convertible or interchangeable paper-feed mechanisms, but this need has of yet remained largely unfilled.BRIEF SUMMARY OF THE INVENTIONThe present invention answers the foregoing need and provides a data printer structure by which ready removeability and complete interchangeability is achieved for the paper-feed apparatus, by means of interchangeable paper-feed modules, each carrying a different type of paper-feed mechanism, as well as preferably carrying its own platen, which is thus changed with the paper-feed module.The printer has an outer housing and a support structure or frame within the housing, for the printer mechanism. This support frame defines or carries a mounting bed for the paper-feed modules. The modules preferably comprise a pair of side plates with at least one interconnecting support member and a paper-feed apparatus mounted between the side plates, such apparatus including a platen, which may or may not be rotatable, and a rotatable element with associated means for engaging paper stock and moving the same lengthwise. The rotatable element comprise a rotary drive element which when the module is seated on the printer frame engages a complementary motor-driven member mounted on such frame. Seating of the module is achieved by complementary guideways cooperating between the module and the printer frame, by which the module may be slid upon a guide into accurately indexed position, where an interlock will hold it securely in position. Most preferably, the printer-mounted power drive comprises a motor-driven worm which is oriented generally vertically, and the paper-feed module has a mating worm-gear which is moved into a position engaging the worm by the guided seating movement of the paper-feed module, which preferably is along a path disposed at a small acute angle relative to the worm axis. Both the worm thread and the worm gear teeth should have a profile with a curved outer tip, so that as the paper feed module is moved toward and into its seated position the worm gear moves toward and engages the worm, with the rounded tips of the engaging gear teeth and worm thread sliding off one another in the event of interfering alignment, to prevent tooth breakage.The many advantages of the invention, together with its objectives, will become more apparent from a study of the ensuing Specification and the attached drawings.

Description

Claims

1. A data printer with removable modular paper-feed assembly, comprising: a main support frame structure for the printer; print head means movable relative to at least portions of said frame structure so as to print lines of characters on paper fed by said paper-feed assembly; means carried on said frame structure defining an elongated guideway having longitudinal guide surfaces and means defining limiting and positioning surfaces for a module guided by said guide surfaces; drive means carried by said frame structure, including a motor and a rotatable output drive member; at least one modular paper-feed assembly having side wall sections, at least one support extending between the side wall sections, and movable paper-engaging-and-feeding apparatus mounted between the side wall sections, said feeding apparatus including a continuously movable member having means for engaging and moving paper stock and a rotational drive element coupled to such member for imparting movement thereto; means for releasably and detachably mounting said modular paper-feed assembly upon said frame structure, said means including a follower structure for said elongated guideway, said follower structure carried with said paper-feed assembly and being complementary to and movable longitudinally along said frame structure guide surfaces, said mounting means also having portions cooperatively seatable against said limiting and positioning surfaces to index the paper-feed assembly in a particularly defined position upon the frame structure said guideway and guideway follower being disposed and positioned to define a path of movement for said paper-feed assembly which brings the drive element of the latter angularly toward and into driving engagement with the output drive member of the drive means motor carried by the frame structure when the said limiting and positioning surfaces have indexed the paper-feed assembly in said particularly defined position; and interlock means having a locking element carried on one of said frame structure and said paper-feed assembly and a locking element-engaging portion carried on the other thereof for mutual locking engagement between said paper-feed assembly and said frame structure in said seated, indexed position, said locking engagement rigidly securing said paper-feed assembly in place upon the frame structure and holding said output drive member of the frame structure drive means engaged with said drive element of the paper-feed module, such that actuation of the motor produces movement of said paper-feeding apparatus through the interengaged output drive member and paper-feed assembly drive element.

2. The data printer of claim 1, and including a second modular paper-feed assembly also having side wall sections, at least one support extending between the side wall sections, and a paper-feeding apparatus mounted between the side walls and including a rotatable member having a second and different means for engaging paper stock and moving same lengthwise, said member having a rotary drive element coupled thereto for imparting rotation to the member; means for detachably mounting said second paper-feed assembly upon said frame structure and including a follower for the guideway of said frame structure and portions cooperatively seatable against said limiting and positioning surfaces for indexing the second paper-feed assembly in a similar particularly defined position upon the frame structure; said rotary drive element of said second paper-feed assembly engaging said rotatable output drive member of said frame-carried drive means when said second paper-feed assembly is brought into said indexed position, such that actuation of the drive means then produces rotation of said rotatable member through the interengaged output drive member and drive element, said second modular paper-feed assembly having interlock means substantially like those of the first paper-feed assembly for substantially the same locking engagement with the frame structure in the seated, indexed position of the second paper-feed assembly wherein the drive element of the latter is held engaged with the output drive member of the frame structure drive means, whereby said two modular paper-feed assemblies are interchangeable with one another upon said frame structure.

3. The apparatus of claim 1, wherein said paper-engaging-and-feeding apparatus of said one paper-feed assembly comprises a tractor mechanism driven by said rotational drive element, said motor and interengaged output drive member and rotational drive element imparting driving power to said tractor mechanism.

4. The apparatus of claim 2, wherein said paper-feeding apparatus of said second paper-feed assembly comprises a pin-feed mechanism driven by said rotary drive element, said motor and said interengaged output drive member and rotary drive element serving to drive said pin feed mechanism.

5. The apparatus of claim 4, wherein said paper-engaging-and-feeding apparatus of said one paper-feed assembly comprises a tractor mechanism driven by said rotational drive element, said motor and said interengaged output drive member and rotational drive element serving to drive said tractor mechanism.

6. The apparatus of claim 5, wherein said output drive member of said motor means comprises a worm element coupled to said motor, said rotational drive element of said paper-feed apparatus comprising a worm-gear engageable with said worm element.

7. The apparatus of claim 1, wherein said output drive member of said motor means comprises a worm element coupled to said motor, said rotational drive element of said paper-feed apparatus comprising a worm-gear which engages and disengages with said worm element when said removable modular paper-feed assembly is moved into and out of seated and indexed position upon said frame structure.

8. The apparatus of claim 7, wherein at least one of said worm-gear and worm element has a tooth or thread profile with a rounded tip section.

9. The apparatus of claim 8, wherein both of said worm-gear and worm element have a tooth or thread profile with a rounded tip section.

10. The apparatus of claim 7, wherein said worm element is mounted with its axis of rotation disposed generally vertically relative to the normal position of use of said data printer.

11. The apparatus of claim 10, wherein said worm-gear has an axis of rotation disposed generally horizontally relative to said normal position of use.

12. The data printer of claim 1, wherein said interlock means includes a clamping member which applies force to hold the paper-feed assembly clamped against portions of the frame structure.

13. A data printer with removable modular paper-feed assembly, comprising: a main support frame structure for the printer; removably mounted modular paper-feed assembly; print head means for printing characters on paper fed by said paper-feed assembly; means defining a guideway along which said removable paper-feed assembly is movable to an indexed operating position upon said support frame structure; said paper-feed assembly having means for engaging and moving paper stock in response to driven movement of a rotational gear element carried with the paper-feed assembly; a drive motor carried on said support frame structure and a driving worm element coupled to said motor to be rotated thereby, said worm element being fixed in position and having an axis of rotation disposed at an acute angle relative to at least portions of the said guideway for the removable paper-feed assembly; said paper-feed assembly being mountable upon said frame for printing operation by movement along said guideway, such movement carrying said gear element toward and into driving engagement with said worm along a path converging with the rotational axis of the worm element at said acute angle thereby substantially precluding clashing of the tooth tips on the gear element with the tip of the thread on the worm element.

14. The apparatus of claim 13, wherein said worm element is mounted with its axis of rotation at an acute angle relative to true vertical when said printer is in its normal position of use.

15. The apparatus of claim 14, wherein at least said portions of said guideway are disposed at an acute angle relative to true vertical when said printer is in its normal position of use.

16. The apparatus of claim 15, wherein said guideway portions are disposed at an acute angle relative to the axis of rotation of said worm element.

17. The apparatus of claim 14, wherein said acute angle of said worm element axis is on the order of from about 5.degree. to 25.degree..

18. The apparatus of claim 17, wherein said acute angle is on the order of about 15.degree..

19. The apparatus of claim 15, wherein said acute angle of said guideway portions is on the order of from about 2.degree. to 20.degree..

20. The apparatus of claim 19, wherein said acute angle is on the order of about 10.degree..

21. The apparatus of claim 16, wherein said acute angle is on the order of about 1.degree. to 10.degree..

22. The apparatus of claim 21, wherein said acute angle is on the order of about 1.degree. to 5.degree..

23. The apparatus of claim 13, wherein said guideway portions are disposed at an acute angle relative to the axis of rotation of said worm element, and wherein said acute angle is on the order of from about 1.degree. to 10.degree..

24. The apparatus of claim 23, wherein said acute angle is on the order of about 1.degree. to 5.degree..

25. The apparatus of claim 23, wherein at least one of said worm-gear and worm element has a tooth or thread profile with a rounded tip section.

26. The apparatus of claim 25, wherein both of said worm-gear and worm element have a tooth or thread profile with a rounded tip section.

27. The apparatus of claim 26, wherein said rounded tip section has a generally circular radius on the order of about one-third the average width of the tooth or thread.