GB2249998A - Push/pull paper feeding accessory for selective printers - Google Patents

Abstract

A printer is disclosed in which its paper feeding unit (15) alternatively engagable at either a paper feed-out position or a paper feed-in position, and a pair of guide grooves are formed for guiding the paper feeding unit, which is held by a holding mechanism in either of its in-use locations. Also, a paper supply opening is formed in a lower portion of the printer having the paper feeding unit. An introduction passage in communication with the paper supply opening is formed in a bottom portion of the frame of the printer. The printer may have adjustable feet. <IMAGE>

Description

PRINTER The present invention relates to a printer for performing a printing operation with a print head on a piece of paper to be set while feeding the paper onto a platen by a paper feeding device.

In a conventional printer of this type, a paper feeding device provided with a pin tractor is switchable between a paper feed-out position and a paper feed-in position relative to a platen on the frame of the printer. In each position, the paper feeding device is held so as not to fall away from the frame by the engagement between a hook lever, pivotally supported to the frame, and a fixed part such as a pin.

The conventional printer, however, suffers from the following disadvantages. Since the hook lever for holding the paper feeding device on the frame of the printer is swingably mounted on support plates through a pivot shaft or the like in a position away from an end portion of a rotary shaft supported between the support plates for swingably driving the pin tractor, the mounting structure of the hook lever is unduly complicated. At the same time, it is necessary to project the operating portion of the hook lever in a direction in which the hook lever will not interfere with the end portion of the rotary shaft. Thus, the operating position of the hook lever would be unduly restricted.

Also, in the conventional printer, in particular in the case where the paper feeding device is located on the paper feed-in side relative to the platen, the paper feeding device is to be inserted into a position behind the platen from above the frame through the mounting space defined in the frame.

In the conventional printer, in the case where the paper feeding device is located on the paper feed-in side of the platen, if the paper feeding device is located behind the platen at a level lower than that of the platen, a length of each side actuate contact portion of the paper from the position where the paper starts to contact with an outer peripheral surface of the platen to the position where the printing is performed by the printing head onto the paper on the platen will become short, so that it is possible to reduce the risk of paper jamming at the contact portion and the portion in the vicinity of the inlet of the contact portion.

The conventional printer, however, is constructed so that the paper feeding device is inserted into a direction perpendicular to the paper feeding direction through the mounting space from above the frame. Accordingly, when, as described above, the paper feeding device is located from above the frame at the position lower than the level of the platen and behind it, it is necessary to provide a large and deep mounting space so that an overall size of the frame would be disadvantageously enlarged.

On the other hand, another conventional printer is well known in which a paper feeding device is located on the paper feed-out side relative to the platen on the frame; a paper feeding port for introducing a piece of paper is formed at a bottom portion of the frame; and after the printing has been effected by the printing head onto the paper that has been introduced through the paper feeding port from the bottom side of the frame, the paper is fed out from the platen by the paper feeding device.

In the conventional printer, however, the paper feeding port is formed in the bottom portion of the frame, and in the case where the printer is located on the top surface of the desk or the like, the paper feeding port is closed so that it is impossible to further feed the paper. It is therefore necessary to use a special desk having, in its upper surface, and corresponding to the paper feeding port, an opening for feeding the paper, or to locate a plurality of desks at predetermined intervals and to locate the printer so that the paper feeding port is opened and directed downwardly. This requirement would increase costs and the work would be troublesome.

In the conventional printer, since the paper is fed from the bottom portion as described above, it is possible to reduce the curvature or warpage of the paper in comparison with the case where the paper is fed through the opening portion formed in the rear portion of the frame, and there is no risk that the printing position would be offset or displaced even in the case where a plurality of pieces of paper (including carbon paper) would be used in an overlapping manner.

It should be however noted that, in the conventional printer, the opening portion for feeding the paper is located on the lower portion of the frame. Accordingly, in the case where the paper is to be set onto the paper feeding device by inserting the paper onto the platen from the opening portion where the printer is located on the top surface of the table or the like, the printer must be manually lifted up from the top surface of the table so that the paper feeding opening portion at the lower portion of the frame is separated away from the top surface of the table. This manual work is very troublesome.

In order to avoid this, it is necessary to provide a discrete printer stand for supporting the printer, to locate the printer on the printer stand, and to perform the paper insertion setting when the paper feeding opening portion at the lower portion of the frame is lifted from the top surface of the table, which would increase a running cost.

According to a first aspect of the present invention, there is provided a printer comprising a platen on which a piece of paper is to be set, a printing head for effecting printing on paper on said platen, and a frame on which said platen and printing head are mounted, further comprising: a paper feeding unit detachably mounted on said frame, said paper feeding unit being selectively locatable relative to said platen at a paper feed-out position or a paper feed-in position; guide means formed at the paper feed-in position in said frame for guiding said paper feeding unit from a rear side towards a front side of said frame; and retainer means provided in said frame and said paper feeding unit for retaining said paper feeding unit in an in-use attitude when said paper feeding unit is guided and moved to an inner end side of said guide means.

Advantageously the guide mechanism includes a pair of right and left Ushaped guide grooves formed, in the frame, to be directed obliquely upwardly toward a front side of a rear end portion of the frame.

The paper feeding unit may be located at a position lower than the platen, when the paper feeding unit is located in the paper feed-in position by the guide mechanism and held in the use condition.

Preferably, the paper feeding unit comprises: a pair of right and left support plates; a rotary shaft rotatably supported between both the support plates; pin tractors provided on the rotary shaft and engaged with a feed hole of the paper for performing the feed operation of the paper; and retainer levers mounted on the respective support plates; the retainer levers being swingably and operatively provided between a position where the retainer levers are hooked at a mounting position of the frame and a position where the retainer levers are released away from the mounting position when the paper feeding unit is located at one of the paper feed-in position and the paper feed-out position, and the paper and the paper feed-out position, and the paper feeding unit being prevented from being removed away from the frame under the hook condition.

The retainer levers may be swingably operatively supported on bearings of the rotary shaft at outer surfaces of the respective support plates, springs being interposed between the retainer levers and the support plates and adapted to urge the retainer levers so as to engage the paper feeding unit with the frame.

Favourably, the mounting portions provided on the frame have retainer pins projecting from both outer surfaces of the frame and located on the paper feed-in position; and the guide mechanism includes a pair of right and left U-shaped guide grooves formed in the frame; the retaining mechanism comprising: upper end edges formed in the support plates, for keeping a contact condition at a first contact point with the retainer pins when the paper feeding unit is guided and moved within the guide grooves; and lower edges formed in the guide grooves for keeping a contact condition at a second contact point with the bearings of the rotary shaft when the paper feeding unit is moved and guided within the guide grooves.

The retaining mechanism may further comprise engagement pieces projecting from the retainer levers for keeping an engagement condition at a third contact point with the rear end upper edges of the guide grooves when the paper feeding unit is moved and guided within the guide grooves, thereby swinging in a release direction prior to the engagement with the retainer pins.

The mounting portions provided in the frame preferably have retainer pins detachably engageable with engagement recess portions formed in the support plates, the retainer pins being located between the paper feed-in position and the paper feed-out position and extending from outer surfaces of the frame, the retainer pins having tapered head portions for retaining and guiding the support plates and the retainer levers when the paper feeding unit is switched in position.

With this aspect of the invention a printer may be provided in which the mounting structure for hooking the paper feeding unit to the frame is simplified, thereby reducing the number of parts required.

Another advantage of the invention is that a printer may be provided in which it is possible to make the frame compact and to reduce the risk of jamming of the paper to be contacted with the platen.

According to another aspect of the invention, there is provided a printer comprising a platen on which a piece of paper is to be set, a printing head for effecting printing on the paper on said platen and a frame on which said platen and said printing head are mounted, said printer comprising: a paper feeding unit provided on said frame for feeding, from said platen, the paper on which printing has been effected; a lower paper supplying opening formed in a lower portion of said frame and serving as a passage for supplying the paper onto said platen from a bottom side of said frame; and an introduction passage formed in the bottom portion of said frame, having a front portion in communication with said lower paper supply opening and a rear portion opened rearwardly of said frame for introducing the paper from the rear side of said frame to the lower paper supply opening.

The introduction passage is preferably in the form of a downwardly directed recess formed between right and left side portions of the frame.

Advantageously, a curved guide plate is provided in the deep portion of the introduction passage whereby the paper is guided between the guide plate and the guide surface and is introduced into the lower paper supply opening.

Favorably, the guide plate is provided over a full width of the introduction passage and is made of flexible material.

With the second aspect of the invention a printer may be produced in which it is possible to introduce the paper from the paper supply opening without any trouble when the printer is laid on an ordinary desk or the like without the need for a special desk or the like having an opening for paper feeding on the top surface of the desk corresponding to the supply opening of the bottom portion of the frame.

According to a third aspect of the invention, a stand mechanism is provided on both right and left side portions of the frame and swingably switchable between a use position and a receiving position to thereby have the bottom surface of the frame separable away from a surface on which the printer is laid.

The stand mechanism may comprise: a pair of receiving recesses formed in the lower surface of the frame; support shafts extending in both inner surfaces of the receiving recesses; and a pair of stands swingably supported to the support shafts, the stands being switchably located between a receiving position where the stands are received in the receiving recesses and a use position where the stands project downwardly from the frame.

Preferably, a pair of engagement projections made of flexible material are formed to project from both outer surfaces of the stands, first retainer recesses and second retainer recesses being formed to project from both outer surfaces of the stands, first retainer recesses and second retainer recesses being formed in both side inner surfaces of the respective receiving recesses, the engagement projections being engaged with the second retainer recesses so that the stands are retained and held in the receiving position when the stands are disposed swingably in the receiving position, the engagement projections being engaged with the first retainer recesses so that the stands are retained and held in the use position when the stands are disposed swingably in the use position.

With this last aspect of the invention a printer may be produced in which it is possible to separate the paper feeding opening of the frame lower portion from the top surface of the table or the like without any special printer stand, the paper may be inserted from the opening portion onto the platen for setting the paper with ease.

The invention will further be understood from the following description when taken together with the attached drawings which are given by way of example only, and in which: FIG. 1 is a partial side elevation sectional view showing a first embodiment of the invention; FIG. 2 is a partial front view showing a paper feeding unit shown in FIG. 1; FIG. 3 is a partial , sectional view showing a state in which the paper feeding unit is mounted on a paper feed-out side relative to a platen; FIG. 4 is an enlarged partial sectional view showing a state in which the paper feeding unit is hooked to a frame; FIG. 5 is a partial side elevational sectional view showing a state in which the paper feeding unit is mounted at a paper feed-out position relative to the platen; ; FIG. 6 is a partial side elevational sectional view showing a state in which the paper feeding unit is mounted at a paper feed-in position relative to the platen; FIG. 7 is a partial, side elevational sectional view showing a drive structure in the state in this condition; FIG. 8 is a sectional view showing an introduction passage in communication with the paper supply opening in the bottom portion of the frame; FIG. 9 is a side elevational partial sectional view showing a second embodiment of the invention; FIG. 10 is a partial side-elevational sectional view showing the printer; FIG. 11 is a partial sectional view showing a mounting structure of stands; FIG. 12 is a partial sectional view taken along the line XII-XII of FIG. 11; and FIG. 13 is a partial sectional view showing a state in which the stands are switchably located from a receiving position to a use position.

A first embodiment will now be explained with reference to FIGS. 1 through 8.

As shown in FIG. 1, a frame 1 of the printer is composed of an upwardly opened casing 2 made of synthetic resin, a chassis 3 made of steel and disposed within the casing 2, and a cover 4 made of synthetic resin and mounted on the casing 2. A platen 5 is rotatably supported between both side walls of the chassis 3. A guide rod 6 used as a guide member is disposed between both the side walls of the chassis 3 so as to extend in parallel with a longitudinal direction of the platen 5. A carriage 7 is supported on the guide rod 6 so as to be reciprocatingly movable in the longitudinal direction of the rod 6. On the top portion of the carriage 7, there is mounted a printing head 8 for printing on paper P1, P2 for setting on the platen 5. Also, a ribbon cassette 9 is detachably mounted on the carriage 7.

In FIG. 1, the right side and the left side will be referred to as the front side and the rear side of the printer, respectively.

A paper guide 10 is provided on the casing 2 in the vicinity of a lower outer peripheral portion of the platen 5, so that a single piece of paper P1 is supplied onto the platen 5 along the paper guide 10 from an upper paper supply opening 11 formed in the cover 4. A rear paper supply opening 12 and a lower paper supply opening 13 used as an opening are formed as passages in the rear portion and the lower portion of the casing 2, respectively. A continuous paper P2 is supplied from these paper supply openings 12 and 13 onto the platen 5. A paper discharge outlet 14 is formed in the upper portion of the cover 4. The paper P1, P2 on which the printing has been effected by the printing head 8 on the platen 5 is discharged through the paper discharge outlet 14.

A paper feeding unit 15 is detachably mounted on the chassis 3 of the frame 1. The paper feeding unit may be switchably positioned between a position where the unit faces the paper discharge port 14 on the paper feed-out side downstream of the platen 5 as indicated by the solid line in FIG. 1, and another position where the unit faces the rear portion paper supply opening 12 on the paper feed-in side upstream of the platen 5. When the paper feeding unit 15 is located on the paper feed-out side relative to the platen 5, after the continuous paper P2 to be supplied through the lower paper supply opening 13 from the bottom side of the casing 2 has passed through the printing position on the platen 5, the paper is drawn from the paper discharge outlet 14 by the paper feeding unit 15.On the other hand, when the paper feeding unit 15 is located on the paper feed-in side relative to the platen 5, the continuous paper P2 is fed onto the platen 5 from the rear portion paper supplying opening 12 by the paper feeding unit 15 and is discharged from the paper discharge outlet 14 after it has passed the printing position.

As shown in FIGS. 1 and 8, an introduction passage 16 is formed in a concave shape, directed downwardly, while both side portions of the bottom portion of the casing 2 being left, and is in communication with the lower paper supply opening 13 at the front end and opened at the rear end to the rear side of the casing 2. When the paper feeding unit 15 is located on the paper feed-out side relative to the platen 5 for printing, it is possible to introduce the continuous paper P2 from the opening portion of the introduction passage 16 on the rear side of the casing 2 through the introduction passage 16 to the lower portion paper supply opening 13.

As shown in FIGS. 1 and 2, the paper feeding unit 15 is composed of a pair of right and left support plates 19, a support rod 20 provided between both the support plates 19, a rotary shaft 22 rotatably supported between the support plates 19 through bearings 21 so as to extend in parallel with the support rod 20, and a pair of pin tractors 23 movably supported on the support rod 20 and the rotary shafts 22. Under the condition that the pin tractors 23 are engaged with feeding holes of both edges of the paper P1 or the continuous paper P2, the printing paper P1 or the continuous paper P2 is fed through the pin tractors 23 by rotating the rotary shaft 22.

As shown in FIG. 6, respective pairs of upper retainer pins 24 and 25 extend from both outer surfaces of the chassis 3 while facing the paper discharge outlet 14 and constitute the mounting portions for detachably fixing the paper feeding unit 15 at the position on the paper feed-out side relative to the platen 5. Respective pairs of lower retainer pins 26 and 27 extend from both the outer surfaces of the chassis 3 while facing the rear portion supply opening 12, and constitute the mounting portion for detachably fixing the paper feeding unit 15 at the position on the paper feed-in side relative to the platen 5.

Three engagement recess portions 28, 29 and 30 are formed in the tip end portion, the upper portion and the lower portion of both the support plates 19 of the paper feeding unit 15. As shown in FIG. 3, the two engagement recess portions 28 and 30 are engaged with the upper retainer pins 24 and 25 of the chassis 3 so that the paper feeding unit 15 is mounted at the position on the paper feedout side relative to the platen 5. Also, as shown in FIG.

6, the other two engagement recess portions 29 and 30 are engaged with the lower engagement pins 26 and 27 of the chassis 3 so that the paper feeding unit 15 is mounted at the position on the paper feed-in side relative to the platen 5.

A pair of right and left retainer levers 31 are swingably supported to the bearings 21 of the rotary shaft 22 in the outer surfaces of both the support plates 19 of the paper feeding unit 15. Each of the retainer levers is provided at one end with a hook portion 32 engaging with the retainer pins 25 and 27, and at the other end with an engagement portion 33 engaging with the retainer pin 26 and with an operating portion 35 facing a finger hook portion 34 on the support plate 19. A spring 36 is interposed between the hook lever 31 and the support plate 19.As shown in FIGS. 3 and 6, under the condition that the paper feeding unit 15 is mounted on the paper feed-out side or on the paper feed-in side relative to the platen 5, the hook lever 31 is swingably biased by the spring 36 to the position where the hook lever 31 is engaged with the retainer pin 25 or the retainer pins 26 and 27, so that the paper feeding unit 15 is retained so as not to be separated away from the chassis 3.

As shown in FIGS. 2 and 4, each of the retainer pins 24, 25 and 27 is provided at its end portion with a large diameter tapered head portion 37. When the paper feeding unit 15 is mounted at the position on the paper feed-in side or the paper feed-out side relative to the platen 5, the mounting of the support plate 19 is guided relative to the chassis 3, and the hook of the retainer lever 31 is guided relative to the retainer pins 25, 26 and 27.

As shown in FIGS. 1, 3 and 6, a pair of left and right guide grooves 38 are formed in U-shapes in both the side walls of the chassis 3 on the rear side of the paper supply opening 12. Each guide groove obliquely upwardly extend from the rear end portion toward the front side. As shown in FIG. 3, when the paper feeding unit 15 is mounted at the position on the paper feed-in side relative to the platen 5, bearings 21 at both ends of the rotary shaft 22 are engaged with the guide grooves 38, and the paper feeding unit 15 is guided to be obliquely upwardly moved from the rear side of the chassis toward the front side. As shown in FIG. 6, when the bearings 21 reach inner ends of the guide grooves 38, the paper feeding unit 15 is located at the position lower than the level of the platen 5 on the rear side of the platen 5.

When such a structure is adopted, it is necessary to mount the paper feeding unit 15 from the rear side of the printer. However, since a number of cables or cords are connected to the printer, it is impossible for the user (who mounts the paper feeding unit 15) to move in the rear side of the printer with ease. For this reason, the user will perform the mounting work of the paper feeding unit 15 by extending his arms toward the rear side of the printer while he is positioned on the front side of the printer. Therefore, according to the first embodiment of the invention, the following structure is adopted for facilitating the mounting work.

Namely, the lower retainer pins 26 located above the guide grooves 38 and the upper edges 39 of both the support plates 19 of the paper feeding unit 15 are formed. As shown in FIG. 3, when the paper feeding unit 15 is guided and moved toward the inner end sides of the guide grooves 38 by the engagement between the bearings 21 and the guide grooves 38, the upper edges 39 of the support plates 19 are engaged with the lower retainer pins 26 to thereby retain the paper feeding unit 15 in the use state. Each of engagement pieces 40 respectively extends toward the inside of each of the operating portions 35 of both the retainer levers 31 in the paper feeding unit 15.As shown in FIG. 3, when the paper feeding unit 15 is guided and moved to the paper feeding unit 15 is guided and moved to the inner end side of the guide grooves 38, the engagement pieces 40 engage with the rear end upper edges of the guide grooves 38, so that the retainer levers 31 are swung to the release position before the levers are engaged with the lower retainer pins 27.

As shown in FIGS. 5 and 7, a drive mechanism 43 is provided on a right side outer surface of the chassis 3 and is composed of a motor 44 and a gear train including a plurality gears 45, 46 and 47. A platen gear 48 is engaged with and fixed to the right end of a platen shaft 49 for supporting the platen 5 and is engaged with the gear 47 of the gear train. When the motor 44 is rotatably driven, the platen 5 is rotated through the gears 45 to 47 and the platen gear 48 to thereby supply the paper P1 or P2.

As shown in FIGS. 2, 5 and 7, a drive gear 50 is fixed to the right end of the rotary shaft 22 at the outer surface of the right side support plate 19 of the paper feeding unit 15. A coupling gear 51 is supported rotatably to the outer surface of the support plate 19 by a support shaft 52 and movable in the axial direction, and is normally biased by a spring 53 to be moved to the position where the coupling gear 51 is engaged with the drive gear 50.

As shown in FIG. 5, when the paper feeding unit 15 is mounted at the position on the paper feed-out side relative to the platen 5, the coupling gear 51 is engaged with the platen gear 48, and the rotational torque of the platen gear 48 is transmitted to the rotary shaft 22 through the coupling gear 51 and the drive gear 50, thereby drivingly rotating the pin tractors 23. Also, as shown in FIG. 7, when the paper feeding unit 15 is mounted at the position on the paper feed-in side relative to the platen 5, the coupling gear 51 is engaged with the gear 47 of the gear train, and the rotational torque of the gear 41 is transmitted to the rotary shaft 22 through the coupling gear 51 and the drive gear 50, thereby drivingly rotating the pin tractors 23.

The operation of the thus constructed printer will be explained.

FIGS. 1, 3 and 5 show the state where the paper feeding unit 15 is mounted at the position on the paper feed-out side relative to the platen 15. Under this condition, the engagement recess portions 28 and 30 on the side of the paper feeding unit 15 are engaged with the upper retainer pins 24 and 25 on both sides of the chassis 3, and at the same time, the hook portions 32 of both the retainer levers 31 are engaged with the upper retainer pins 25 so that the paper feeding unit 15 is retained to the chassis 3. In this state, the coupling gear 51 on the side of the paper feeding unit 15 meshes with the platen gear 48.

Accordingly, under such a condition, when the printer is operated after the continuous paper P2 has been set at the pin tractors 23 of the paper feeding unit 15 through the paper discharging outlet 14 and the printing position on the platen 5 from the lower paper supply opening 13, the platen 5 is rotated through the gears 45 through 48 and the platen shaft 49 by the motor 44 of the drive mechanism 43 while the printing is effected on the continuous paper P2 by the printing head 8 at the printing position on the platen 5, and at the same time, the pin tractors 23 are rotated through the gears 51 and 50 of the paper feeding unit 15 and the rotary shaft 5, thereby drawing the continuous paper P2 from the printing position on the platen 5.

In this case, since the introduction passage 16 in communication with the lower paper supply opening 13 is provided in the bottom portion of the casing 2, even if the printer is located on a top surface of a normal desk or the like, the lower paper supply opening 13 of the bottom portion of the casing 2 is opened to the rear side of the casing 2 through the introduction passage 16. Therefore, it is unnecessary to use a special desk or the like having an opening for the paper supply in the ceiling plate portion corresponding to the lower paper supply opening 13 of the bottom portion of the casing 2. It is possible to introduce the continuous paper P2 from the rear side of the casing 2 through the introduction passage 16 and the lower paper supply opening 13 without interfering with the printing position on the platen 5.

In the case where the paper feeding unit 15 is moved from the paper feed-out position to the paper feed-in position relative to the platen 5, when the operating levers 35 of both the hook levers 31 of the paper feeding unit 15 is swingably operated toward the rear side (i.e., in the counterclockwise direction in FIG. 3) under the condition shown in FIGS. 3 and 5, the hook portions 32 of the retainer levers 31 are released away from the upper retainer pins 25, thereby releasing the hook of the paper feeding unit 15 relative to the chassis 3. Accordingly, when in this condition the paper feeding unit 15 is upwardly lifted from the chassis 3, the retainer recess portions 28 and 30 of both the support plates 19 are separated away from the upper retainer pins 24 and 25 so that it is possible to remove the paper feeding unit 15 from the printer.

Thereafter, when the paper feeding unit 15 is moved forwardly as shown by the imaginary lines in FIG. 3 under the condition that both the bearings 21 of the paper feeding unit 15 are engaged with the guide grooves 38, the paper feeding unit 15 is obliquely upwardly guided from the rear side to the front side of the chassis 3 along the guide grooves 38. As shown in FIG. 6, when the bearings 21 reach the inner ends of the guide grooves 38, the paper feeding unit 15 is located at a position lower than a level of the platen 5 on the rear side of the platen 5.

Also, when the paper feeding unit 15 is guided to the inner ends of the guide grooves 38, in FIG. 3, the engagement pieces 40 are in contact with the rear end upper edges of the guide grooves 38 at a contact point A (i.e., a third contact point), the upper edges of the support plates 19 are in contact with the retainer pins 26 at a contact point B (i.e., a first contact point), and the bearings 21 are in contact with the lower edges of the guide grooves 38 at a point C (i.e., a second contact point). In this condition, since the paper feeding unit 15 is supported and retained by the above-described three points, the paper feeding unit 15 is maintained in its posture.

Furthermore, the paper feeding unit 15 is maintained at the posture (i.e., at the same angle as that of the use condition), and at the same time, the engagement pieces 40 of the hook levers 31 are engaged with the rear end upper edges of the guide grooves 38, so that the hook levers 31 are swung to the release position before the levers are engaged with the lower retainer pins 27. At this time, since the paper feeding unit 15 is also moved under the contact condition at the three points A, B and C, the posture of the paper feeding unit 15 is not displaced or offset. Accordingly, when the paper feeding unit 15 is mounted from the rear side to the front side relative to the chassis 3, it is unnecessary to keep the posture of the paper feeding unit 15 under the use condition, and it is possible to extremely readily perform the mounting work of the paper feeding unit 15.Also, when the paper feeding unit 15 is mounted at the paper feed-in position in a normal manner, it is unnecessary for the user to operate the retainer levers 31. Incidentally, it is unnecessary for the user to move to the rear side of the printer, and the mounting operation is performed without a visual confirmation. Even in such a case, it is possible to perform the operation in a rapid and easy manner.

As described above, when the paper feeding unit 15 reaches the inner ends of the guide grooves 38, the engagement recess portions 29 and 30 of both the support plates 19 on the side of the paper feeding unit 15 are engaged with the lower-retainer pins 26 and 27 on both sides of the chassis 3 as shown in FIG. 6, and at the same time, the hook portions 32 and the engagement portions 33 are in engagement with the lower retainer pins 27 and 26, so that the paper feeding unit 15 is maintained and hooked at the position on the paper feed-in side relative to the platen 5 and relative to the chassis 3. Also, in this case as shown in FIG. 7, the coupling gear 51 on the side of the paper feeding unit 15 is engaged with the gear 41 of the gear train of the drive mechanism 43.

Accordingly, under this condition, when the printer is operated after the continuous paper P2 has been set at the pin tractors 23 of the paper feeding unit 15 from the rear paper supply opening 12 through the printing position on the platen 5 and the paper discharge outlet 14, the platen 5 is rotated through the gears 45 through 48 and the platen shaft 49 by the motor 44 of the drive mechanism 43, and at the same time, the pin tractors 23 are rotated through the gears 51 and 50 of the paper feeding unit 15 and the rotary shaft 22. As a result, while the continuous paper P2 is fed into the printing position on the platen 5, the printing is performed onto the continuous paper P2 by the printing head 8.

In this printing operation, since the paper feeding unit 15 -is located at a position lower than the platen 5 on the rear side of the platen 5, the contact length in the circumferential direction from the position where the continuous paper P2 fed by the paper feeding unit 15 starts to contact against the platen 5 to the position where the printing is performed onto the continuous paper P2 by the printing head 8 on the platen 5 is shortened. Thus, it is possible to reduce a fear of generation of jamming of the continuous paper P2 in contact with the platen 5 in the contact portion and in the vicinity of the inlet portion of the contact portion.

In this embodiment, as shown in FIG. 4, since the large diameter tapered head portions 37 are provided at the tip end portions of the upper retainer pins 24 and 25 and the lower retainer pins 26 and 27, when the paper feeding unit 15 is to be mounted on the chassis 3 of the frame 1, the engagement recess portions 28, 29 and 30 of the support plates 19, the hook portions 32 and the engagement portions of the retainer levers 31 are engaged with the tapered head portions 37 to thereby ensure the engagement with the retainer pins 24 through 27. Accordingly, it is possible to avoid the displacement or offset of the paper feeding unit 15 relative to the chassis 3.

Incidentally, for instance, it is possible to modify, as required, the structures of the mounting portions for mounting the paper feeding unit 15 and the fixture portions for hooking the retainer levers 31 of the paper feeding unit 15. Also, it is possible to modify the structures of the retainer means or to provide rails or the like as the guides for guiding the paper feeding unit 15 into the guide grooves 38.

In the first embodiment, since the retainer levers for hooking the paper feeding unit 15 to the frame of the printer are swingably supported to the rotary shaft on the support plates, it is possible to simplify the mounting structure of the retainer levers to thereby reduce the number of the mechanical parts, and to project the operating portions of the retainer levers in any desired direction without any restriction in operating position of the retainer levers.Since the mounting portions provided on the frame side so as to engage with or to be disengaged from the retainer levers are made of retainer pins having tapered head portions, the retainer recess portions of the support plates and the retainer levers are positively engaged with the tapered head portions by the effect of the tapered head portions, and it is possible to maintain and hook firmly the paper feeding unit to the frame without any displacement or offset.

Also, since the pair of right and left guide grooves for engaging with a part of the paper feeding unit and guiding the paper feeding unit from the rear side to the front side is provided in the frame, and the paper feeding unit is located at a position lower than the height level of the platen on the paper feed-in side relative to the platen, it is possible to make compact the frame, and at the same time, the length of the contact portion having, in cross section, an arcuate shape, from the position where the printing paper starts to contact with the outer peripheral surface of the platen to the position where the printing is effected onto the printing paper by the printing head on the platen, so that it is possible to suppress a fear of the generation of the jamming in the paper in the contact portion and in the vicinity of the contact portion inlet portion.

FIG. 9 shows a second embodiment of the invention. In this embodiment, as indicated by imaginary lines in FIG. 9, a guide plate 17 which is made of flexible material and curved is provided over the full width of the introduction passage 16 on the deep portion of the introduction passage 16, so that the continuous paper P2 introduced into the introduction passage 16 may be guided to the lower paper supply opening 13 by the guide plate 17.

The deep portion of a paper guide surface 16a of the introduction passage 16 is curved with a large curvature to extend to the lower paper supply opening 13. The paper P2 is guided between the paper guide surface 16a and the guide plate 17 to be supplied to the lower paper supply opening 13. Incidentally, the other structure is substantially the same as that shown in the first embodiment and hence will not be explained in detail.

In the case where the continuous paper P2 is inserted through the introduction passage 16 from the position indicated by an arrow DA into the lower paper supply opening 13 under the condition where the paper feeding unit 15 is located on the position on the paper feed-in side, the continuous paper P2 is introduced substantially in the tangential direction with respect to the surface of the platen 5 from the introduction passage 16 by being guided by the guide surface 16a. As a result, the distance of the circumferential contact portion from the contact position of the continuous paper P2 with the surface of the platen 5 to the printing position is shortened, so that it is possible to reduce jamming at the contact portion even if a plurality (three or four) of pieces of continuous paper are used in an overlapping manner.

Furthermore, in the case where the continuous paper P2 is supplied from the position indicated by an arrow DB, the paper P2 is guided by the guide plate 17 and is inserted into the lower paper supply opening 13. In this case, the curvature of the paper is much smaller than that in the case where the paper P2 is supplied from the position indicated by the arrow DA and the radius of curvature is elongated.

Thus, it is possible to further reduce the risk of the jamming in the contact portion. As described above, in the second embodiment, it is unnecessary to provide a special desk or the like having an opening for paper supply at the ceiling plate corresponding to the lower paper supplying opening of the frame bottom. Under the normal condition of the desk located on the top of the desk or the like, it is possible to introduce the paper from the lower paper supply opening without any trouble.

FIGS. 10 to 13 show a third embodiment of the invention, in which the components and members indicated by the same reference numerals as used in the first and second embodiments have like structures or functions and hence the explanation therefor will be omitted.

As shown in FIGS. 10 to 12, a pair of receiving recesses 120 are formed in a lower surface of a casing 102 on both right and left sides of the introduction passage 116 formed in the bottom portion of the frame. Support shafts 121 extend within both inner surfaces- of the receiving recesses 120. The support shafts 121 may be made of a single rodlike member laid over both the inner surface. A pair of stands 122 are supported swingably to the support shafts 121 within the respective receiving recesses 120 and are positioned switchably between the receiving position received in the receiving recesses 120 as shown in FIG. 13 and the use position where the stands project from the receiving recesses 120 downwardly of the casing 102 by hooking the user's fingers to finger hook portions 123.

A pair of flexible engagement projections 124 are provided to extend from both outer surfaces of the respective stands 122. First and second retainer recesses 125 and 126 are formed so as to face and engage the engagement projections 124. As shown in FIG. 11, when the stands 122 are swingably located at the receiving positions, the engagement projections 124 are in engagement with the second retainer recesses 126 so that the stands 122 are retained in the receiving position. When the stands 122 are swingably located in the use position as shown in FIG. 13, the engagement projections 124 are in engagement with the first retainer recesses 125 so that the stands 122 are retained in the use position.

The operation of the printer in accordance with the third embodiment will be explained.

In the case where the paper feeding unit 15 is located in the paper feed-in position relative to the platen, the stands 122 should be located in the receiving position for the reason of avoiding the noise problem or the like, and the lower paper supply opening 13 is closed by the surface S of the table or the like.

In the case where the paper feeding unit 15 is located in the paper feed-out position relative to the platen 5 as indicated by the solid lines in FIG. 10, the continuous paper P2 is inserted from below the casing through the introduction passage 116 into the lower supply opening 13 as indicated by the arrow DA, and at the same time, is set by the pin tractors of the paper feeding unit 15. The pair of the stands 122 provided in the lower surface of the casing 102 are swung from the receiving position shown in FIG. 11 to the use position shown in FIG. 13. Then, the engagement projections 124 are elastically deformed and separated from the second retainer recesses 126. Thereafter, the projections 124 are engaged with the first retainer recesses 125 so that the stands 122 are projected from the lower surface of the casing 102 and retained in the use position.

As a result, the paper supply opening 13 and the introduction passage 116 of the lower portion of the casing 102 are separated away from the surface S of the table or the like. Therefore, it is unnecessary to specially prepare a separate printer stand for supporting the printer in the lifted condition. It is possible to insert and set the continuous paper P2 onto the platen 5 from the lower paper supply opening 13 of the casing 102 with ease.

When the printer is operated in the set condition of the continuous paper P2, the printing is effected onto the continuous paper P2 by the printing head 8, and the continuous paper P2 is drawn from the printing position on the platen 5 by the paper feeding unit 15. In this case, if the printing is effected while the stands 122 are in the use position, since the lower paper supply opening 13 and the introduction passage 16 of the lower portion of the casing 102 are separated away from the surface S of the table of the like, it is unnecessary to use a special table having a special insertion hole for feeding the paper in the ceiling plate corresponding to the lower paper supply opening 13, and it is possible to perform the printing operation by supplying the continuous paper P2 from the lower paper supply opening 13 under the condition that the printer is laid on the top surface of the ordinary table or the like.

At this time, the curvature of the paper is smaller than that in the case where the paper is supplied from the upper paper supply opening or the rear paper supply opening. For this reason, even if a plurality of pieces of papers (copying paper, carbon paper or the like) are used in an overlapping manner, there is less offset or displacement of the pieces of paper.

Subsequently, in the case where the paper feeding unit 15 is switched to the position on the paper feed-in side relative to the platen 5 as shown in FIG. 10, the continuous paper P2 is set at the pin tractors of the paper feeding unit 15 by passing the paper through the printing position on the platen and the paper discharge outlet 14 from the rear paper supply opening 12. At the time of insertion setting of the continuous paper P2, when the stands 122 of the lower surface of the casing 102 are swung from the use position shown in FIG. 13 to the receiving position shown in FIG. 11, the engagement projections 124 are elastically deformed and released away from the first retainer recesses 125 and then are engaged with the second receiving recesses 126, so that the stands 122 are retained and held at the receiving position within the receiving recesses 120. When the printer is operated under the set condition of the continuous paper P2, the printing is effected onto the continuous paper P2 by the printing head 8 while the continuous paper is being fed into the printing position on the platen.

Incidentally, it is possible to provide the guide plate 117, which is made of flexible material and curved, over the full width of the introduction passage 116 in the deep portion of the introduction passage 116 as indicated by the imaginary lines in FIG. 10, so that the continuous paper P2 is guided to be inserted by the guide plate 117 when the continuous paper P2 is introduced from the introduction passage 116 to the lower paper supply opening 13.

Claims (27)

1. A printer comprising a platen on which a piece of paper is to be set, a printing head for effecting printing on paper on said platen, and a frame on which said platen and printing head are mounted, further comprising: a paper feeding unit detachably mounted on said frame, said paper feeding unit being selectively locatable relative to said platen at a paper feed-out position or a paper feed-in position; guide means formed at the paper feed-in position in said frame for guiding said paper feeding unit from a rearside towards a front side of said frame; and retainer means provided in said frame and said paper feeding unit for retaining said paper feeding unit in an in-use attitude when said paper feeding unit is guided and moved to an inner end side of said guide means.

2. A printer according to claim 1, wherein said guide means includes a pair of right- and left- hand Ushaped guide grooves formed in said frame, directed obliquely upwardly toward a front side of a rear end portion of said frame.

3. A printer according to claim 1 or 2 wherein said paper feeding unit is located at a position lower than said platen when said paper feeding unit is located in the paper feed-in position by said guide means.

4. A printer according to claim 1, 2 or 3 wherein said paper feeding unit comprises: a pair of right and left support plates; a rotary shaft rotatably supported between said support plates; pin tractors provided on said rotary shaft and engageable with a feed hole of said paper for feeding the paper; and retainer levers mounted on the respective support plates; said retainer levers being swingable between a position where they engage a mounting portion of said frame and a position where they are released away from said mounting position when said paper feeding unit is located at said paper feed-in position or said paper feed-out position, said paper feeding unit being prevented from being removed from the frame when the retaining levers are engaged with the mounting portion of the frame.

5. A printer according to claim 4, wherein said retainer levers are supported by bearings in said rotary shaft at outer surfaces of said respective support plates, springs interposed between the retainer levers and said support plates being adapted to urge the retainer levers so as to engage the paper feeding unit in said frame.

6. A printer according to claim 5, wherein the mounting portions provided on said frame have retainer pins projecting from outer surfaces of said frame and located adjacent the paper feed-in position; and said retaining means comprise: upper end edges or in said support plates, for keeping a contact condition at a first contact point with said retainer pins when said paper feeding unit is guided and moved within said guide grooves; and lower edges formed in said guide grooves for keeping a contact condition at a second contact point with the bearings of said rotary shaft when said paper feeding unit is moved and guided within said guide groves.

7. A printer according to claim 6, wherein said retaining means further comprises engagement pieces projecting from said retainer levers for keeping a contact condition at a third contact point with the rear end upper edges of said guide grooves when said paper feeding unit is moved and guided within said guide grooves, thereby swinging in a release direction prior to the engagement with said retainer pins.

8. A printer according to claim 4, 5, 6 or 7 wherein the mounting portions provided in said frame have retainer pins detachably engageable with engagement recess portions formed in said support plates, said retainer pins being located between the paper feed-in position and the paper feed-out position and extending from outer surfaces of the frame, said retainer pins having tapered head portions for retaining and guiding said support plates and said retainer levers when said paper feeding unit is switched in position.

9. A printer according to any preceding claim, further comprising a lower paper supply opening formed in a lower portion of said frame and serving as a passage for supplying paper to said platen from a bottom side of said frame; and an introduction passage formed in the bottom portion of said frame, and having a front portion in communication with said lower paper supply opening and a rear portion opened rearwardly of said frame for introducing the paper from the rear side of said frame to the lower paper supply opening.

10. A printer according to claim 9, wherein said introduction passage is in the form of a downwardly directed recess formed between right- and left- hand portions of the frame.

11. A printer according to claim 9 or 10, wherein a deep portion of a paper guide surface of said introduction passage is curved with a large curvature and extends to the lower paper supply opening.

12. A printer according to claim 11, wherein a curved guide plate is provided in the deep portion of said introduction passage whereby the paper is guided between said guide plate and said guide surface and is introduced into the lower paper supply opening.

13. A printer according to claim 12, wherein said guide plate is provided over a full width of said introduction passage and is made of flexible material.

14. A printer comprising a frame and stand means provided on both right- and left- hand portions of said frame and swingable, between a use position and a receiving position for lifting the bottom surface of the frame away from a surface on which the printer is laid.

15. A printer according to claim 14, wherein said stand means comprise: a pair of receiving recesses formed in the lower surface of the frame; support shafts extending across the inner surfaces of said receiving recesses; and a pair of stands swingably supported on said support shaft and switchable between a receiving position where said stands are received in said receiving recesses and a use position in which the stands project downwardly from said frame.

16. A printer according to claim 15, wherein a pair of engagement projections made of flexible material are formed to project from both outer surfaces of said stands, first retainer recesses and second retainer recesses being formed in the inner surfaces of said respective receiving recesses, said engagement projections being adapted to engage respective second retainer recesses when said stands are disposed in said receiving position, and adapted to engage said first retainer recesses when said stands are disposed in the use position.

17. A printer according to any one of claims 1-13 and any one of claims 14-16.

18. A printer comprising a platen on which a piece of paper is to be set, a printing head for effecting printing on the paper on said platen and a frame on which said platen and said printing head are mounted, said printer comprising: a paper feeding unit provided on said frame for feeding, from said platen, the paper on which printing has been effected; a lower paper supplying opening formed in a lower portion of said frame and serving as a passage for supplying the paper onto said platen from a bottom side of said frame; and an introduction passage formed in the bottom portion of said frame, having a front portion in communication with said lower paper supply opening and a rear portion opened rearwardly of said frame for introducing the paper from the rear side of said frame to the lower paper supply opening.

19. A printer according to claim 18, wherein said introduction passage is in the form of a downwardly directed recess formed between right- and left- hand portions of the frame.

20. A printer according to claim 18 or 19, wherein a deep portion of a paper guide surface of said introduction passage is curved with a large curvature and extends to the lower paper supply opening.

21. A printer according to claim 20, wherein a curved guide plate is provided in the deep portion of said introduction passage whereby the paper is guided between said guide plate and said guide surface and is introduced into the lower paper supply opening.

22. A printer according to claim 21, wherein said guide plate is provided over a full width of said introduction passage and is made of flexible material.

23. A printer according to claim 20, 21 or 22 wherein stand means are provided on both right- and lefthand portions of said frame and swingable between a use position and a receiving position for lifting the bottom surface of the frame away from a surface on which the printer is laid.

24. A printer according to claim 23, wherein said stand means comprise: a pair of receiving recesses formed in the lower surface of the frame; support shafts extending across the inner surfaces of said receiving recesses; and a pair of stands swingably supported on said support shafts and switchable between a receiving position where said stands are received in said receiving recesses and a use position in which the stands project downwardly from said frame.

25. A printer according to claim 24, wherein a pair of engagement projections made of flexible material are formed to project from both outer surfaces of said stands, first retainer recesses and second retainer recesses being formed in the inner surfaces of said respective receiving recess, said engagement projections being adapted to engage respective second retainer recesses when said stands are disposed in said receiving position, and adapted to engage said first retainer recesses when said stands are disposed swingably in the use position.

26. A printer according to any one of claims 18 to 25 and according to any one of claims 1 to 13 and/or 14 to 16.

27. A printer constructed and arranged to operate substantially as hereinbefore described with reference to the attached drawings.