Tray Assembly of a Printer

This invention relates to printers such as thermal transfer type printers, and more particularly to a tray assembly of printers in which a sheet of printing paper is moved forward and backward over a roller platen several times to effect a full color printing.

Recently, thermal transfer type printers have come into wide use, in which a thermal head is pressed against a sheet of printing paper supported on a roller platen to transfer dye materials carried on an ink sheet or ribbon to the sheet of paper. Some of these thermal transfer type printers are capable of printing full color images; in such case, a sheet of printing paper must undergo several printing operations in each of which a different primary color is printed thereon so that several primary colors are superposed on each other to produce a full color image. In some of these full color printers, the sheet of paper undergoing printing operation is moved forward and backward several times over the roller platen to effect a superposition of several primary colors.

FIG. 1 shows a conventional printer disclosed in Japanese Laid-Open Patent Application No. 61-154866. The structure of this printer is as follows: To the main body 1 of the printer is detachably attached a paper cassette 3 accomodating sheets of printing paper 2 therein; the sheets of paper 2 are fed from the cassette 3 one by one. An ink sheet 4 carries dye materials thereon that are transferred to the sheet of paper 2a under the printing operation; to effect the transfer, a thermal head 5 is pressed against the roller platen 6 with the sheet of paper 2a and the ink sheet 4 interposed therebetween. The roller platen 6 opposes the thermal head 5 and rotates in the forward direction (i.e. clockwise as viewed in the figure) during a printing operation to move the sheet of paper 2a forward (toward left in the figure), and in the backward direction during the time when the sheet of paper 2a under printing is moved backward to the initial printing position. Sheets of paper which are fed manually are supplied from the manual feed tray 7 detachably attached to the main body 1 of the printer. Sheets of printing paper which have been printed with the primary colors are received in the discharge tray 8 which is also detachably attached to the main body 1 of the printer. A feed roller 9 rotates in the direction indicated by the arrow to feed the sheets of paper 2 in the cassette 3 one by one to the printing mechanism including the platen 6. The pair of forwarding rollers 10 are disposed between the feed roller 9 and the roller platen 6 to forward sheets of paper either from the cassette 3 or from the manual feed tray 7. A pair of discharge rollers 11 are disposed to discharge the sheets of paper which has finished printing of the primary colors to the discharge tray 8. The sheet of paper 2a under printing is moved forward during printing of a primary color into the front paper passage 12; it is moved backward into the return paper passage 13 when it is returned to the position at which the printing of the next color is started. The direction of the first guide plate 14 is determined according as a sheet of paper is being fed or moved backward by the roller platen 6 rotating in the backward direction. The second guide plate 15 is disposed in the front paper passage 12 to guide the sheet of printing paper 2a which has finished printing operations to the discharge tray 8.

Next, the operation of the printer of FIG. 1 is supplemented. When a sheet of paper is fed from the paper cassette 3 or the manual feed tray 7, the first guide plate 14 is changed-over to secure the passage for the sheet of paper to the roller platen 6 in response to a signal from a paper sensor (not shown); the sheet of paper is thus fed to the roller platen 6. Thereafter, the thermal head 5 is pressed on the roller platen 6, the sheet of paper 2a and the ink sheet 4 being interposed therebetween. Thus, images, such as characters and figures, are printed on the sheet of paper 2a wrapped around the roller platen 6 in response to a signal from a figure processing device implemented in a microcomputer (not shown); namely, the dye material carried on the ink sheet 4 is selectively transferred to the sheet of paper 2a in accordance with the signal from the figure processing device. During a printing operation, the sheet of paper 2a is moved to the left in the figure and the front end portion of the sheet of paper 2a is thus moved into the front paper passage 12.

In the full color printing, three primary colors, e.g. yellow, magenta, and cyan, must generally be superposed on each other on the sheet of paper 2a at predetermined densities to obtain desired colors; thus, the above printing operation must be repeated several times. As a result, when a printing operation of a first primary color is over, the thermal head 5 is raised from the roller platen 6, and, forwarding the ink sheet 4 to the inital position at which the front end of the next primary color lies thereon, the roller platen 6 is rotated in the reverse direction to move the sheet of paper 2a under printing backward into the return passage 13 to the position at which the printing of the next primary color is started. The printing of the next color is effected thereafter in a way similar to the printing of the first primary color described above. By the way, when the sheet of paper 2a under printing is moved backward, the first guide plate 14 is changed over the guide the end portion of the sheet of paper 2a to the return paper passage 13.

Thus, the printing operations are repeated a number of times equal to the number of primary colors; the sheet of paper 2a which has finished these printing operations is discharged by the discharge rollers 11 to the discharge tray 8, following the course determined by the changed-over second guide plate 15.

The tray portion of the above printer have the following disadvantages. Namely, the manual feed tray 7 and the discharge tray 8 form separate parts which are detachably attached to the main body 1 of the printer 1 independently of each other; thus, the attachment portions of these trays 7 and 8 have structural weakness, and are prone to failures. Further, the paper return passage 13 is formed within the main body 1 of the printer; thus, the length of the passage 13 is limited by the dimension of the main body 1; it is therefore difficult to form a return passage 13 long enough to accommodate sheets of paper of longer sizes.

In view of the above disadvantages of the trays of the printer of FIG. 1, a structure of the printer shown in FIG. 2 has been developed, wherein the manual feed tray 7 and the discharge tray 8 are formed integrally to enhance its structural strength; further, the paper return passage 13 is extended to the extension passage in a paper guide 18 formed between the trays 7 and 8. (In FIG. 2, the reference numerals 1 through 13 represent parts or portions similar to corresponding parts or portions in FIG. 1.) The trays 7 and 8 and the paper guide 18 constitute an integrally formed tray assembly.

The tray assembly of FIG. 2, however, also suffers from problems. Namely, the size of printing paper used in printing is not always the same; it may differ from one set of sheets of paper to next. The size of the manual feed tray used in each occasion must be adapted to these sheets of paper of various sizes. Thus, the whole tray assembly, including the discharge tray 8 and the guide 18, must be moulded separately according to the paper sizes. The necessity of moulding a number of whole tray assemblies adapted to different paper sizes results in a high cost of production.

The primary object of this invention is therefore to provide a tray assembly for use with a full color thermal transfer type printers which is structurally strong, allows room for extending the paper return passage, and yet is adaptable to different sizes of sheets of printing paper.

It is an additional object of this invention to provide such a tray assembly which is inexpensive.

It is a further object of this invention to provide such a tray assembly which is easy to handle and wherein the adaptation to different sizes of paper can be effected easily and quickly.

The above objects are accomplished in accordance with the principles of this invention in a tray assembly comprising a discharge tray, a paper guide integral therewith, a manual feed tray detachably attached to the underside of the paper guide, and a pair of plate-shaped adapters detachably attached to the manual feed tray. The printer to which the tray assembly is attached moves the sheet of printing paper under printing forward and backward during the printing operations, to effect a full color printing, as described above. The printer thus comprises a return paper passage into which the sheet of paper enters which is moved backward in the steps of operation in which the sheet of paper is returned to the print starting position. The paper guide of the tray assembly forms an extension of this return paper passage. The pair of plate-shaped adapters are attached to the interior side surfaces of the side walls of the manual feed tray; thus, the interior side surfaces of the adapters, when attached to the manual feed tray, determines the lateral position of the sheet of paper that is fed into the printer from the manual feed tray.

The features which are believed to be characteristic of this invention is set forth with particularity in the appended claims. This invention itself, however, both as to its structure and operation, may best be understood from the detailed description of the preferred embodiment taken in connection with the accompanying drawings, in which:

FIG. 1 is a sectional side view of a conventional printer comprising trays formed separately of each other;

FIG. 2 is a view similar to that of FIG. 1, but showing a printer comprising an integrally formed tray assembly, which is related to this invention;

FIG. 3 is a sectional end view of a tray assembly according to this invention which may be used with the printer shown in FIG. 2, the view showing its section along line III--III in FIG. 4; and

FIG. 4 is a sectional side view of the tray assembly of FIG. 3, showing its section along line IV--IV in FIG. 3.

In the drawings. like reference numerals represent like or corresponding parts or portions.

Referring now to FIGS. 3 and 4 of the drawings, a tray assembly according to an embodiment of this invention is described. Before beginning the description thereof, it is noted that a tray assembly according to this invention shown in FIGS. 3 and 4 has, when assembled, a form substantially similar to that of the integrally formed tray assembly in FIG. 2 consisting of the trays 7 and 8 and the guide 18; thus, the tray assembly of FIGS. 3 and 4 may be attached to and used with the printer of FIG. 2, instead of the integral tray assembly thereof.

The tray assembly of FIGS. 3 and 4 comprises four portions: a discharge tray 8 at the top, a paper guide 19 formed under the tray 8 to be integral therewith, a manual feed tray 7 detachably attached to the underside of the paper guide 19, and a pair of plate-shaped adapters 20 detachably attached to the interior of the manual feed tray 7. In the following, these portions are described in the above order.

The discharge tray 8 comprises a bottom plate 8a, a pair of side walls 8b formed at both sides of the bottom plate 8a, and an end wall 8c formed at the front end (i.e. the left end in FIG. 4) of the bottom plate 8a. Thus, the discharge tray 8 is open at the top and at the rear side. The rear end portion of the side walls 8b are slanted downward, as shown in FIG. 4, for easier handling of the discharged sheets of paper. By the way, the position of a discharged sheet of paper is indicated by a dot and dash line 16b in FIG. 3.

The paper guide 19, which corresponds to the guide 18 of FIG. 2, and, when the tray assembly of FIGS. 3 and 4 are attached to the printer of FIG. 2, forms an extension passage for the paper return passage 13 thereof, comprises a pair of side walls 19a each forming an extension of the respective one of the side walls 8b of the discharge tray 8, and a pair of horizontal extensions 19d extended horizontally inward toward each other; thus, the side walls 19a and the horizontal extensions 19dof the guide 19 form at each side an L-shaped integral extension of the wide walls 8b of the discharge tray 8. At the bottom of the guide 19 is thus formed an opening defined at each lateral sides by the interior sides of the horizontal extension 19d; the sheet of paper which is moved backward (i.e. toward right in FIG. 4) in a paper returning operation is guided on the horizontal extensions 19d. The position of the sheet of paper in the guide 19 is indicated by a dot and dash line 16 in FIG. 3. The front end of the horizontal extensions 19d are slanted downward toward the front, to provide an easier entrance for the returned sheet of paper 16; the rear end portion of the horizontal extensions 19d, on the other hand, are bent upward to be joined to the bottom plate 8a of the discharge tray 8 (see FIG. 4). Further, the guide 19 is provided with structures for the attachment of the manual feed tray 7 described below. Namely, a substantially plate-shaped dowel 19b of an elastic material having a hook-shaped enlarged top is formed on the underside of each horizontal extension 19d (or rather under each side wall 19a) to extend vertically downward therefrom. Further, a pair of rectangular holes 19c are formed in each horizontal extension 19d to extend vertically therethrough horizontally in alignment with side walls 7a of the manual feed tray 7 described below. The above discharge tray 8 and the return paper guide 19 are formed integrally of a synthetic resin by a moulding process, etc.

The manual feed tray 7 comprises a bottom plate 7e and a pair of side walls 7a formed a predetermined distance laterally inward from the lateral sides of the bottom plate 7e. The bottom plate 7a has a width slightly greater than that of the discharge tray 8 and the guide 19. On the other hand, the longitudinal length of the bottom plate 7e is substantially longer than that of the bottom plate 8a of the discharge tray 8; thus, the rear end portion of the bottom plate 7e of the manual feed tray 7, when attached to the guide 19, extends backward (to the right in FIG. 4) from the rear end of the tray 8 and the guide 19. The rear half of the rear end portion of the manual feed tray 7 extending from the discharge tray 8 and the guide 19 is bent downward for easier insertion of a sheet of printing paper into the tray 7. Side walls 7a of the manual feed tray 7 each have a pair of rectangular projections 7b extending vertically upward from the top surface thereof horizontally in registry with the rectangular holes 19c formed in the horizontal extensions 19d of the guide 19; the dimensions of these projections 7b are such that they fit into respective holes 19c to determine the position of the manual feed tray 7 with respect to the guide 19 and the tray 8. The rear end portion 7f of the side walls 7a, which lies outside of the guide 19 when the tray 7 is attached thereto, has a height substantially greater than that of their portions under the guide 19. Further, a stepped hole 7c each is formed in each portion of the bottom plate 7e extending sideways outward from respective one of the side walls 7a; each stepped hole 7c extend vertically through the bottom plate 7e, being horizontally in registry with the associated one of the pair of dowels 19b formed on the horizontal extensions 19d of the guide 19. Thus, when the manual feed tray 7 is attached to the underside of the guide 19. the dowels 19b extend into the stepped holes 7c, the hook-shaped enlarged top of the dowels 19b engaging with the stepped portion of the stepped holes 7c. By the way, at the bottom of the interior side of each side walls 7a are formed a pair of rectangular recesses 7d, into which projections 20a of an adapter 20 are fitted as described below.

The pair of plate-shaped adapters 20 each have a length substantially equal to that of the straight portion of the bottom plate 7e of the manual feed tray 7. The adapters 20 each comprise a pair of rectangular projections 20a extending from the underside thereof in registry with the rectangular recesses 7d formed on the bottom plate 7e of the manual feed tray 7. Before the manual feed tray 7 is attached to the guide 19, the adapters 20 are attached to the interior sides of the side walls 7a of the tray 7, as best shown in FIG. 3, the projections 20a being fitted into respective recesses 7d. When the manual feed tray 7 is attached to the guide 19, the top portion of the adapters 20 are each fitted into the groove formed between the interior side of the side walls 7a of the tray 7 and the longitudinally extending projections 19f formed on the underside of the horizontal extensions 19d of the guide 19. Thus, the lateral position of the sheet of manually fed paper on the tray 7 is determined by the interior side surfaces of the adapters 20, as shown in FIG. 3, wherein the position of the sheet of paper on the manual feed tray 7 is indicated by a dot and dash line 16a.

When the above described tray assembly is mounted to the printer of FIG. 2, the sheet of paper fed from the manual feed tray 7 is forwarded toward the roller platen 6 by the forwarding rollers 10. Then it is held, together with an ink sheet 4, between the thermal head 5 and the platen roller 6. In a printing operation, the platen roller 6 rotates forward (i.e. clockwise in FIG. 2) and the sheet of paper 2a under printing is moved gradually forward into the front paper passage 12. After each printing of a primary color, the thermal head 5 is raised from the platen 6, and the sheet of paper 2a is moved backward by the platen 6 rotating in the reverse direction. Thus, the sheet 2a is returned to the print starting position, the front end of the sheet of paper 2a entering, via the return passage 13, into the guide 19 of the tray assembly of FIGS. 3 and 4. Thereafter, the printing of the next primary color is effected in manner similar to the above. When the printing of all the primary colors are finished, the sheet of paper 2a is discharged to the discharge tray 8 by the discharge rollers 11. Otherwise than above, the operation of the printer of FIG. 2 provided with the tray assembly of FIGS. 3 and 4 is similar to that of the printer of FIG. 1 described above.

While I have described and shown the particular embdiment of my invention, it will be understood that many modifications may be made without departing from the spirit thereof; I contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.