GB2309196A - Cover securing arrangment for accurate positioning of discharge rollers in a sheet fed printer - Google Patents

Description

PRINTER The invention pertains to printers. More particularly, the invention is directed to a printer that can not only provide satisfactory printing conditions as quickly as possible but also reduce noise by improving the sheet discharge structure. The invention is further directed to a printer that can provide stable sheet discharge operation with a simple structure for a type of printer in which one of a pair of sheet discharge rollers is mounted on the printer cover.

Figure 5 is a schematic side view showing a printer disclosed as related art in Japanese Unexamined Patent Publication No. 3-53961.

In Figure 5 reference numeral 1 denotes a case of a printer. Within the case 1 are a platen 2 with a sheet P wrapped therearound, a print head H disposed so as to confront the platen 2, and a pair of sheet discharge rollers 3 that discharges the sheet P printed by the print head H.

The pair of sheet discharge rollers 3 include: a drive roller 3a, which is a first sheet discharge roller; and a driven roller 3b, which is a second sheet discharge roller.

The drive roller 3a is mounted on the case main body 1. The driven roller 3b is mounted on a cover 5.

The drive roller 3a receives motive power from the platen 2 and is driven at an increased circumferential speed with respect to the circumferential speed of the platen 2. The driven roller 3b rotates while abutted against the drive roller 3a.

The case 1 has a sheet discharge opening 4. The cover 5 is fixed so as to be turned around a shaft 5b.

According to the thus constructed printer, the sheet P wrapped around the platen 2 and printed by the print head H is forwarded by the pair of sheet discharge rollers 3 and discharged outside the case 1 from the sheet discharge opening 4.

Since the sheet discharge roller 3b, which is one of the pair of sheet discharge rollers 3, is mounted on the cover 5 that can be opened and closed, when the sheet P is jammed at the sheet discharge roller section, the jammed sheet can be removed with ease by opening the cover 5.

However, the above-mentioned printer addresses at least the following problem.

Since the second sheet discharge roller (driven roller) 3b is disposed at a position remote from the cover 5 fixing section 5b of the cover 5 in a printer such as shown in Figure 5, positioning accuracy of the second sheet discharge roller (driven roller) 3b to the first sheet discharge roller (drive roller) 3a is not satisfactory, thereby not ensuring stable sheet discharge operation, which is a problem.

To overcome this problem, a structure characterised as arranging a member on the case main body side for positioning the shaft of the driven roller is disclosed in Japanese Unexamined Utility Model Publication No.4-560.

However, this structure is problematical in that a positioning member other than the cover is required and this makes the structure complicated.

An object of the invention is to provide a printer that can ensure stable sheet discharge operation with a simple structure.

In a first aspect, a printer of the invention includes: a case main body; a first sheet discharge roller mounted on the case main body; a cover fixed on the case main body so as to be opened and closed; a second sheet discharge roller, mounted on the cover, for discharging a sheet in cooperation with the first sheet discharge roller; and a cover fixing section, disposed close to the second discharge roller, for fixing the cover to the case main body.

In a second aspect, a printer of the invention includes: a case main body; a first sheet discharge roller mounted on the case main body; a cover fixed on the case main body so as to be opened and closed; a second sheet discharge roller, mounted on the cover, for discharging a sheet in cooperation with the first sheet discharge roller, a cover fixing section for fixing the cover to the case main body, the cover fixing section beinoformed by a first fixing section and a second fixing section; a regulating section for regulating a fixing position of the cover, the regulating section being provided with the case main body in the first fixing section; and a biasing section for biasing the cover onto the regulating section, the biasing section being provided with the second fixing section, wherein the first fixing section is disposed close to the second sheet discharge roller.

It is preferable that the second sheet discharge roller be biased onto the first sheet discharge roller by a biasing means disposed between the second discharge roller and the cover.

Embodiments of the present invention will now be described with reference to the accompanying drawings, of which: Figure 1 is a segmentary side view of a printer, which is an embodiment of the invention; Figure 2 is a diagram showing the internal structure of the embodiment shown in Figure 1; Figure 3 is a schematic plan view of the embodiment shown in Figure 1 with a part thereof omitted; Figure 4(a) is a general perspective view of a structure in which a cover is going to be fixed to a case main body; Figure 4(b) is a partially enlarged perspective view of Figure 4(a); Figure 4(c) is a sectional view taken along a line c-c in (a); Figure 4(d) is a sectional view taken along a line d-d in (a); and Figure 5 is a diagram illustrative of a conventional example.

Figure 1 is a segmentary side view of a printer, which is an embodiment of the invention; Figure 2 is a diagram showing the internal structure of the printer as a whole; Figure 3 is a plan view of the printer with a part thereof omitted; and Figure 4 is a diagram illustrating the structure for fixing a cover to a case main body.

In Figure 2 reference numeral 10 denotes a case main body of the printer. The case main body 10 includes a lower case 11 and an upper case 12.

Reference numeral 13 denotes a cover, which is fixed to the upper case 12 so as to be opened and closed. The case main body 10 and the cover 13 are made of synthetic resin.

Reference numeral 20 denotes a sheet feed cassette attached to the bottom of the case main body 10.

Reference numeral 14 denotes a sheet feed roller, which feeds sheets P (not shown in Figure 2) placed in the sheet feed cassette 20 on a single sheet basis.

The fed sheet P is not only wrapped around a platen 15 via a sheet feed path 10a but also further fed while nipped between a sheet feed roller 16 and the platen 15 and printed through an ink ribbon (not shown) by a print head 17 of a wire dot type.

The printed sheet is discharged to a sheet discharge tray 19 from a sheet discharge opening 18 via a sheet discharge path 10b and a pair of sheet discharge rollers 30. As shown by a three-dot chain line in Figure 1, a discharged sheet P3 is piled up in the sheet discharge tray 19 with the trailing end thereof supported by a support section 12s formed on the inner surface of the upper case.

As shown in Figure 2, the sheet discharge opening 18 is arranged in the form of a slit (see Figure 3) that extends in the sheet width direction at an intersection between an upper surface 13a of the cover and a back surface 12a of the upper case.

An edge portion 1 8a located on the print head 17 side is linear.

The sheet discharge tray 19 constitutes a sheet guide. The sheet discharge tray 19 guides a sheet P1 that is in the course of being discharged so as to come in slidable contact with the edge portion 18a on the print head side of the sheet discharge opening 18.

As shown in Figure 1, the pair of sheet discharge rollers 30 include a first sheet discharge roller 31 mounted on the case main body 10 side and a second sheet discharge roller 32 mounted on the cover 13 for discharging the sheet in cooperation with the first sheet discharge roller 31. In this embodiment the first sheet discharge roller 31 is adrive roller, and the second sheet discharge roller 32 is a driven roller that rotates while abutted against the drive roller.

The drive roller 31 is made of a material whose friction coefficient with respect to the sheet P is large, e.g., of rubber, and disposed on the side of a nonprinting surface Pb of the sheet P.

As shown in Figure 3, this drive roller 31 has a gear 31b on one end of a shaft 31a and is driven with the gear 31b meshed with an intermediate gear 33 that rotates while abutted against the platen 15. The shaft 31a and the gear 31b of the drive roller 31 are made of synthetic resin. The drive roller is formed by firmly fixing a cylindrical body made of rubber to the shaft 31a.

Reference numeral 34 denotes a holder that is C-shaped when viewed from top. The holder 34 supports the shaft 3 la of the drive roller 31 and a shaft 33a of the intermediate gear 33 rotatably. The holder 34 is pivotably supported by fitting holes 34b, 34b with projections 12b, 12b, the holes 34b, 34b being arranged on lateral plates 34a, 34a of the holder 34 and the projections 12b, 12b being disposed on the upper case 12. A compression spring 35 disposed between a bottom plate 34c of the holder 34 and the upper case urges the intermediate gear 33 in such a direction as to be abutted against the platen 15 at all times.

The intermediate gear 33 operates as a one-way clutch with the shaft 33a thereof being supported by a long hole 34d formed on the holder 34. The intermediate gear 33 transmits motive power to the drive roller 31 only when the platen 15 rotates in a direction indicated by the arrow a in Figure 1. Therefore, the drive roller 31 does not rotate reversely, and the trailing end of the once discharged sheet P3 will no longer be nipped back into the pair of sheet discharge rollers 30.

The driven roller 32 is made of a material to which ink is hard to adhere, e.g., of synthetic resin, and is disposed on the side of the printing surface Pa of the sheet P.

A shaft 32a of the driven roller 32 is rotatably supported by a holder 36 that is C-shaped when viewed from top. The holder 36 is movable in and out with respect to the drive roller 31 with projections 36b, 36b slidably fitted into a long hole 38b of a support plate 38, the projections 36b, 36b being respectively disposed on lateral plates thereof 36a, 36a and the support plate 38 being attached to the cover 13 with engaging pawls 38a, 38a. A compression spring 37 serving as an urging means disposed between an upper plate 36c of the holder 36 and the cover 13 urges the driven roller 32 in such a direction as to be abutted against the drive roller 31 at all times.

As shown in Figure 3, two pairs of sheet discharge rollers 30 are arranged in the sheet width direction.

Reference numeral 40 denotes a guide piece integrally on the lower surface of the cover 13. A guide surface 41 has such an angle as to guide the sheet P that has been sent from the platen 15 while slightly bent so that the leading end Pc of the sheet P will be abutted against the drive roller 31 earlier than the driven roller 32.

A portion 42 of the guide piece 40 that is on a lateral side of the drive roller 31 is located inward with respect to the circumferential surface of the drive roller (i.e., toward the shaft 31a).

Further, the guide surface 41 of the guide piece 40 is not only designed to guide the sheet so that the leading end of the sheet does not touch the support plate 38 and the like, but also formed into a recess 41c in the vicinity of the sheet discharge opening 18 so that the slidable contact of the edge portion 18a with the sheet will not be disturbed.

As shown in Figures 3 and 4, the section at which the cover 13 having the above-mentioned driven roller 32 and guide piece 40 is fixed to the case main body 10 includes a first fixing section 51 and a second fixing section 52. A pair of first fixing sections 51 are disposed at a position close to the driven rollers 32, i.e., in the rear of the printer. A pair of second fixing sections 52 are disposed in the front of the printer.

In each first fixing section 51, a regulating section 12k that regulates the cover 13 fixing position is formed on the upper case 12.

The regulating section 12k has a regulating surface 12c and an opening 12d.

The regulating surface 12c is substantially L-shaped when viewed from the front and is abutted against an end 13c of the rear end corner of the cover 13. The opening 12d receives therein an engaging piece 13d that projects rearward at a position slightly inward from the lateral surface of the rear end corner of the cover 13. Reference character 12e denotes a guide surface continuing from the regulating surface 12c; and 12f, a guide surface continuing from the regulating surface 12c and the guide surface 12e. These guide surfaces 12e, 12f are designed to guide the lower surface 13e and inner surface of the lateral plate of the cover 13.

Each second fixing section 52 has an engaging section 52a as shown in Figure 4 (c) and a biasing section 52b shown in Figure 4 (d).

The engaging section 52a includes an elastic pawl 13g formed integrally with the lower surface of the cover 13 and an engaging hole 12g formed on the upper case 12, so that when the cover 13 is attached to the upper case 12, the elastic pawl 13g clicks the engaging hole 12g.

The biasing section 52b includes: a recess 12h formed on the upper surface of the upper case 12; and a slightly bent projection 13h formed integrally on the lower surface of the cover 13. When the cover 13 is attached to the upper case 12, a front surface 13i of the projection 13h gets abutted against the inner surface 12i that is on the front side of the recess 12h strongly as the projection 13h enters the recess 12h.

This force biases the cover 13 toward the above-mentioned regulating section 12k.

With respect to the engaging sections 52a and the biasing sections 52b, only those on the right side are shown in the drawing in enlarged form. It goes without saying that those on the left side are formed similarly (so as to be symmetrical) (see Figure 3).

The following steps will be taken to attach the thus constructed cover 13 to the case main body 10. First, as shown in Figure 4 (b), the engaging pieces 13d on the rear end of the cover are inserted into the openings 12d of the upper case 12. Then, as shown in Figure 4(a), the cover 13 is turned downward. As a result, the elastic pawls 13g of the cover 13 get fitted into the engaging holes 12g of the upper case 12; the projections 13h of the cover 13 enter into the recesses 12h of the upper case 12; and the cover 13 is attached and, at the same time, fixed to the upper case 12 while biased toward the regulating sections 12k. With the cover fixed in this way, the rear end corner of the cover 13 gets abutted against the regulating section 12k so strongly that positioning accuracy of the cover 13 with respect to the case main body 10 (the upper case 12) in the first fixing section 51 becomes quite high.

According to the thus constructed printer, the following advantages can be obtained.

(i) Since the section for fixing the cover 13 to the case main body 10 includes the first and second fixing sections 51, 52, stable conditions for fixing the cover 13 to the case main body 10 can be ensured.

(ii) The upper case 12 in the first fixing section 51 has the regulating sections 12k for regulating the cover 13 fixing position and the second fixing section 52 has the biasing sections 52b for biasing the cover 13 toward the regulating sections 12k.

Therefore, when the case main body 10 and the cover 13 are fixed together by the first and second fixing sections 51, 52, positioning accuracy of the case main body 10 and the cover 13 in the first fixing section 51 becomes improved. Since the first fixing section 51 is disposed close to the driven roller 32, positioning accuracy of the drive roller 31 and the driven roller 32 can in turn be improved.

As a result, positioning accuracy of the driven roller 32 with respect to the drive roller 31 can be improved without requiring any other positioning member than the cover 13, which in turn ensures stable sheet discharge operation.

(iii) High positioning accuracy of the driven roller 32 with respect to the drive roller 31 can be obtained despite the fact that the driven roller 32 is mounted on the cover 13 as described above. As a result, inconsistencies in contact pressure of the compressionspring 37 with respect to the drive roller 31 are reduced, thereby ensuring stable sheet discharge operation.

If the driven roller 32 were positioned with respect to the drive roller 31 with low accuracy, then the contact pressure by the compression spring 37 would become inconsistent, thereby not ensuring stable sheet discharge operation.

On the other hand, according to the printer, which is the embodiment of the invention, high positioning accuracy can be obtained despite the fact that the driven roller 32 is mounted on the cover 13 as described above. Therefore, inconsistencies in the contact pressure of the compression spring 37 can be reduced, thereby ensuring stable sheet discharge operation.

That is, the fixing structure of this type is particularly effective when the second sheet discharge roller disposed on the cover is urged toward the first sheet discharge roller by an urging means disposed between the second sheet discharge roller and the cover.

(iv) Since the cover 13 is fixed stably with respect to the upper case 12 and the edge portion 18a of the sheet discharge opening 18 is formed at the edge portion of the cover located close to the first fixing section 5 1 whose positioning accuracy is high as described above, the sheet P comes in slidable contact with the edge portion 18a stably, which in turn contributes to stable noise reduction.

(v) Since the cover 13 is fixed stably with respect to the upper case 12 and the guide piece 40 is formed close to the first fixing section 51 whose positioning accuracy is high as described above, the leading end Pc of the sheet can be guided toward the pair of sheet discharge rollers 30 certainly as well as stably, which in turn contributes to further stable noise reduction.

The embodiment of the invention has been described in the foregoing. How the invention is embodied is not limited to the above-mentioned embodiment, but may be modified as appropriate within the scope of the invention.

For example, while the case where the first and second fixing sections constitute thgfixing section has been described in the above embodiment, the number of fixing sections may be one as long as the fixing section is disposed close to the second sheet discharge roller in order to obtain the above-mentioned advantages.

Claims (5)

CLAIMS:

1. A printer comprising: a case main body; a first sheet discharge roller mounted on the case main body; a cover fixed on the case main body so as to be opened and closed; a second sheet discharge roller, mounted on the cover, for discharging a sheet in cooperation with the first sheet discharge roller; and a cover fixing section, disposed close to the second discharge roller, for fixing the cover to the case main body.

2. A printer comprising: a case main body; a first sheet discharge roller mounted on the case main body; a cover fixed on the case main body so as to be opened and closed; a second sheet discharge roller, mounted on the cover, for discharging a sheet in cooperation with the first sheet discharge roller; a cover fixing section for fixing the cover to the case main body, the cover fixing section being formed by a first fixing section and a second fixing section; a regulating section for regulating a fixing position of the cover, the regulating section being provided with the case main body in the first fixing section; and a biasing section for biasing the cover onto the regulating section, the biasing section being provided with the second fixing section, wherein the first fixing section is disposed close to the second sheet discharge roller.

3. A printer according to claim 1, wherein the second sheet discharge roller is biased onto the first sheet discharge roller by a biasing means disposed between the second discharge roller and the cover.

4. A printer according to claim 2, wherein the second discharge roller is biased onto the first sheet discharge roller by a biasing means disposed between the second discharge roller and the cover.

5. A printer substantially as hereinbefore described with reference to either one of Figures 3 and 4 of the accompanying drawings.