Patent Grant
6854837
1. Field of the Invention
This invention relates to a system for and a method of supplying ink to a stencil printer. This invention also relates to an ink container which is mounted on a stencil printer to supply ink to the stencil printer.
2. Description of the Related Art
There has been known a stencil printer in which print is made by the use of an image-wise perforated stencil. In such a stencil printer, a stencil is made by, for instance, bringing a thermal head having a plurality of heater elements arranged in a row or rows into contact with heat-sensitive stencil material with the heater elements selectively energized according to the image to be printed, thereby imagewise perforating the stencil material. The stencil thus made is wound around a printing drum and a printing paper is pressed against the stencil so that ink is transferred to the printing paper through the perforations. As a means for supplying ink to the stencil printer, there has been employed a mechanism comprising an ink supply roller which is supported for revolution about their respective axes by a pair of opposed plate, a distributor which supplies ink onto the ink supply roller and a doctor roller which is disposed spaced from the ink supply roller to control the thickness of ink film formed on the roller. As the distributor, those comprising a tubular member provided with a plurality of small holes or comprising a plurality of nozzles have been known. Ink in an ink container is sucked by an ink pump and is supplied onto the ink supply roller in the form of drops so that an ink fountain is formed in the wedge-like space between the ink supply roller and the doctor roller. Ink in the ink fountain is supplied into the printing drum through the gap between the ink supply roller and the doctor roller. A predetermined amount of ink is constantly held in the ink fountain so that ink can be uniformly supplied. That is, each time an ink sensor detects shortage of ink in the ink fountain, the ink pump is operated to replenish the ink fountain with ink. When the ink fountain is not replenished with ink after driving the ink pump for a predetermined time, the ink container is considered to be exhausted and the user is prompted to replace the ink container.
As the ink container employed in the stencil printer, there have been known, for instance, those comprising an outer box formed of corrugated board and a flexible inner bag accommodated in the outer box so that an ink discharge pipe formed on one end of the inner bag projecting outside the outer box with the outer end thereof closely sealed with a cap (will be referred to as “a BIC-type ink container”, hereinbelow) and those comprising a cylinder provided with an ink discharge port on the front thereof and a piston inserted into the cylinder (will be referred to as “a piston-type ink container”, hereinbelow). The latter piston-type ink container is advantageous over the former BIC-type ink container in that the amount of ink remaining in the ink container after ink is sucked to the very end is smaller and ink can be effectively used. In this ink container, an ink discharge port is formed on the front end of a small diameter portion and the ink container is sealed by a cap which is screwed on the ink discharge port. When using the ink container, the cap is unscrewed and the ink container is inserted into the stencil printer from the container holder of the stencil printer so that the ink suction port of the stencil printer is fitted with the small diameter portion of the ink container.
When the ink container is exhausted and ink therein comes not to be sucked out, the ink container must be replaced with a new ink container. When replacing the ink container, the vicinity of the ink suction port of the stencil printer can be stained with ink ejected from the ink container unless the ink container is carefully handled. The ink on the vicinity of the ink suction port of the stencil printer can stain the outer surface of the loaded ink container, and the ink on the outer surface of the loaded ink container can stain the user's hand in turn when the loaded ink container is exhausted and removed from the stencil printer.
Even an exhausted ink container is not completely free from ink but some ink remains near the ink discharge port. Further, since ink is sucked from the ink container through the ink suction port, the inside of the ink container and the ink suction port of the stencil printer is under vacuum. When the ink container is rapidly drawn out in this state, ink remaining around the junction of the ink container can be ejected out under the shock of drawing the ink container. This phenomenon is apt to occur in the piston-type ink containers and is less apt to occur in the BIC-type ink containers. It is believed that this is because ink remaining around the ink discharge port is returned inside the inner bag when the inner bag recovers its original shape in the case of the BIC-type ink containers whereas such effect cannot be expected in the case of the piston-type ink containers where the piston is substantially rigid.
In view of the foregoing observations and description, the primary object of the present invention is to provide an ink supply system for and an ink supply method of supplying ink to a stencil printer by the use of a piston-type ink container which can prevent ejection of ink due to a negative pressure inside the ink container during replacement of the ink container.
Another object of the present invention is to provide a piston-type ink container adapted to accomplish the above object.
In accordance with the present invention, an ink container comprising a cylinder provided with a substantially cylindrical body portion and a small diameter portion which is formed on one end of the body portion and is provided with an ink discharge port on its free end, a piston inserted into the body portion of the cylinder to be slidable in the axial direction of the body portion along the inner peripheral surface thereof toward the small diameter portion, and ink filled in the space formed between the inner surface of the body portion and the surface of the piston facing the small diameter portion is inserted into an ink container holder of a stencil printer so that the small diameter portion of the ink container is fitted with an ink suction nozzle which sucks the ink in the ink container through the ink discharge port, and vacuum in the space evacuated by the ink suction nozzle is at least partly released by a vacuum release means before the tip of the nozzle and the tip of the small diameter portion are aligned with each other when the ink container is drawn from the ink container holder.
The ink suction nozzle may be either fitted in or on the small diameter portion of the ink container. That is, the ink suction nozzle may be inserted into the small diameter portion, or the small diameter portion may be inserted into the ink suction nozzle.
It is preferred that a sealing means for sealing the joint between the nozzle and the small diameter portion be provided between the nozzle and the small diameter portion. The sealing means may be an annular elastic sealing member which may be, for instance, an O-ring. The annular elastic sealing member may be provided either on the nozzle or on the small diameter portion.
For example, “the tip of the nozzle and the tip of the small diameter portion are aligned with each other” when they are in the relative position shown in FIG. 5D.
The vacuum release means may be any means so long as it can at least partly release the vacuum in the space between the inner surface of the body portion of the cylinder and the surface of the piston facing the small diameter portion but need not be limited to those which completely release the vacuum.
The vacuum release means may comprise, for instance, a projection provided on one of the outer surface of the ink container and the inner surface of the ink container holder (which is substantially cylindrical in shape) and a guide groove formed on the other of the outer surface of the ink container and the inner surface of an ink container holder to engage with the projection to guide the projection when the ink container is drawn from the ink container holder so that the ink container drawing speed is reduced or the ink container is once stopped to allow the vacuum in said space to be at least partly released before the tip of the nozzle and the tip of the small diameter portion are aligned with each other.
For example, the guide groove includes a helical portion through which the projection is moved between a time point at which sealing of said space is broken and a time point at which the tip of the nozzle and the tip of the small diameter portion are aligned with each other and which is inclined so that the ink container drawing speed is reduced to allow the vacuum in said space to be at least partly released before the tip of the nozzle and the tip of the small diameter portion are aligned with each other. Otherwise, the guide groove may be provided with a bent portion through which the projection is moved between a time point at which sealing of said space is broken and a time point at which the tip of the nozzle and the tip of the small diameter portion are aligned with each other and which is bent so that the ink container is once stopped to allow the vacuum in said space to be at least partly released before the tip of the nozzle and the tip of the small diameter portion are aligned with each other.
The “time point at which sealing of said space is broken” is a time point at which sealing of said space is broken during drawing the small diameter portion away from the nozzle.
Further, the projection may be provided on a ring member mounted on the outer surface of the body portion of the cylinder of the ink container for rotation about the axis of the body portion whereas the guide groove to be engaged with the projection is formed on the inner surface of the ink container holder and is provided with a helical portion so that the ink container drawing speed is reduced to allow the vacuum in said space to beat least partly released before the tip of the nozzle and the tip of the small diameter portion are aligned with each other. In this case it is preferred that a predetermined friction be produced between the outer surface of the body portion of the cylinder and the ring member or between the projection and the guide groove.
In one embodiment, the projection extends on the outer surface of the body portion of the cylinder in the axial direction of the body portion by a length not smaller than the radius of the body portion whereas the guide groove is formed on the inner surface of the ink container holder. In this case, the front end (the end nearer to the discharge port) of the projection abuts against an end face of the guide groove to guide the projection when the ink container is drawn from the ink container holder so that the ink container drawing speed is reduced or the ink container is once stopped.
It is preferred that the front end of the projection be at a distance from the front face of the body portion of the cylinder in the range not smaller than 0 mm and not larger than 35 mm.
Further it is preferred that the body portion of the cylinder be smaller than 100 mm in its diameter and the projection be not larger than 120 mm in its length when.
Further, the vacuum release means may comprise a plurality of small vent holes formed along the small diameter portion of the ink container in the case of where the ink suction nozzle is fitted in the small diameter portion.
In accordance with the present invention, splash of ink can be prevented since the vacuum in the space filled with the ink is at least partly released before the ink suction nozzle is entirely drawn away from the small diameter portion of the ink container (before the tip of the nozzle and the tip of the small diameter portion are aligned with each other) and accordingly, ejection of ink due to that the space which has been kept under a vacuum is abruptly subjected to the atmospheric pressure.
When the projection is provided on a ring member mounted for rotation on the outer surface of the body portion of the cylinder of the ink container, it is not necessary to rotate the ink container itself when the ink container is drawn out from the ink container holder.
When the length of the projection is not smaller than the radius of the body portion, the projection and the guide groove are engaged with each other over a larger area and the posture of the ink container is stabilized during insertion and drawing of the ink container into and from the ink container holder, whereby workability is improved and the projection is improved in strength and durability. As the front end of the projection is nearer to the front end of the ink container, displacement of the front end of the projection due to swelling of the ink container becomes less and can guide the ink container more accurately when the ink container is drawn from the holder. Especially, when the front end of the projection is at a distance not larger than 35 mm from the front face of the body portion of the cylinder, change in dimensions due to swelling of the ink container can be suppressed, and splash of ink can be suppressed even in an aged ink container.
When the projection is not larger than 120 mm in its length when the cylinder is smaller than 100 mm in its diameter, change in dimensions due to swelling of the ink container can be suppressed.
An ink supply system for a stencil printer in accordance with a first embodiment of the present invention comprises an ink container 1 shown in FIG. 1. As shown in
The ink container 1 is inserted into an ink container holder provided on the stencil printer (not shown). As shown in
The ink suction nozzle 31 is fitted, as shown in
Operation of the ink supply system of this embodiment will be described, hereinbelow. When the ink container 1 is replaced, the old ink container 1 is first drawn out from the ink container holder 2 before a new ink container 1 is inserted into the ink container holder 2. At this time, since the space 15 between the inner surface of the body portion 13 and the surface of the piston 14 is sealed and the ink in the space 15 has been sucked by the ink suction nozzle 31, the inside of the old ink container 1 is kept under a vacuum. While the ink container 1 is drawn out from the ink container holder 2, the projection 16 of the ink container 1 is kept in engagement with the guide groove 21 on the inner surface of the ink container holder 2 and is moved along the guide groove 21. When the ink container 1 is drawn out from the ink container holder 2, the ink container 1 is pulled rearward in a state shown in
In the ink supply system of this embodiment, since the ink container 1 is once stopped and the vacuum in said space 15 is allowed to be at least partly released before the ink suction nozzle 31 is moved outside the small diameter portion 12, the ink suction nozzle 31 restrains the ink from being ejected outside under the shock of drawing the ink container 1.
The shape of the guide groove 21 formed on the inner surface of the ink container holder 2 need not be limited to that shown in
In the modification shown in
In the modification shown in
A guide groove 21c in accordance with the modification shown in
Though, in the embodiment and the modifications described above, the projection 16 is provided on the ink container 1 and the guide groove 21 is provided on the ink container holder 2, the projection 16 may be provided on the ink container holder 2 with the guide groove 21 provided on the ink container 1. The guide groove 21 need not be a groove in the strict sense but may be, for instance, a groove-like portion between a pair of rows of projections or a row of projections which abuts against the projection 16 to guide insertion and drawing of the ink container 1.
The old ink container 1 is drawn out from the ink container holder 2 in the following manner. In a state where the ink suction nozzle 31 is hermetically engaged with the small diameter portion 12 of the ink container 1 as shown in
The protrusion 50 need not be formed of a pair of parallel sub-protrusions as shown in
The guide groove which guides the protrusion 50 need not be limited to that shown in
The vacuum release means may comprise at least one vent hole 41 as shown in
In the vacuum release means shown in
The projection 16 may be provided on a ring member 18 mounted on the outer surface of the body portion 13 of the cylinder of the ink container 1 for rotation about the axis of the body portion 13 as shown in FIG. 14. In this case it is preferred that a predetermined friction be produced between the outer surface of the body portion 13 of the cylinder and the ring member 18 or between the projection 16 and the guide groove 21 on the inner surface of the guide groove 21. Further, in this case, the guide groove 21 for guiding the projection 16 is preferably in the form of a guide groove 21b shown in FIG. 6C. In the vacuum release means, since the ring member 18 is rotated with respect to the body portion 13 as the projection 16 moves along the helical portion of the guide groove 21b, it is not necessary to rotate the ink container 1 by hand.
In order to prove the effect of the present invention, experiments 1 and 2 were carried out.
(Ink Container)
Two kinds of ink containers (equivalent to a GR-series ink container available from RISO KAGAKU CORPORATION) were prepared. One (container 1) of them was in accordance with an embodiment of the present invention and was provided with a projection, and the other (container 2) of them was not in accordance with the present invention and was provided with no projection. The projection was 20 mm in the distance from the front end of the body portion 13 of the cylinder to the front end of the projection and 105 mm in length. Both the ink containers were formed of polypropylene, and were 16.0 mm, 15.5 mm, 79.5 mm and 1.5 mm as shown in
(Ink Container Holder)
A guide groove 21e shown in FIG. 11 and adapted to be engaged with the projection on the ink container 1 was formed on the inner surface of the ink container holder. Since the guide groove was designed so that the ink container was helically drawn out from the holder from the point A to the point E by way of the point C, the ink container was helically drawn when the vacuum is broken (point C) irrespective of backlash between the guide groove and the projection. The ink container holder was 107.5 mm in axial length of the guide groove 21e, 17° in the circumferential rotating angle and 135° in the drawing angle θ3.
(Ink)
Ink A (6.13 Pa·s in viscosity), Ink B (3.18 Pa·s in viscosity), Ink C (2.86 Pa·s in viscosity), Ink D (1.07 Pa·s in viscosity) and Ink E (0.87 Pa·s in viscosity) were prepared by diluting RP-HD ink (available from RISO KAGAKU CORPORATION) with solvent AF-6 (NIPPON OIL CORPORATION). The viscosity of ink was measured by the use of a stress-control type rheometer (RHEO-STRESS RS75 available from HAAKE). That is, a cone which was 1° in cone angle and 20 mm in diameter was employed and the viscosity at 100 sec−1 was measured while the stress was increased 20Pa per second from 0Pa at 23° C.
(Way of Experiment)
The ink containers filled with ink A to ink E were set in sequence to a jig provided with the ink container holder and an ink pump (RP3790 available from RISO KAGAKU CORPORATION). When the ink container was exhausted and ink came not to be discharged from the ink container, the ink pump was stopped and drawing test was carried out three times (n=3) and the state of stain with ink was visually evaluated. The result was as shown in the following table 1. In the drawing test, the container 1 was drawn out from the ink container holder 2 while the ink container 1 was rotated with the protrusion guided by the guide groove, and the container 2 was drawn out from the ink container holder 2 by pulling straight rearward in the axial direction of the ink container holder 2. When the ink container holder 2 was stained with even a drop of ink, the ink container was marked with X in table 1 and when the ink container holder 2 was stained with no ink, the ink container was marked with ∘ in table 1. The experiment was carried out at 23° C. As can be seen from the following table 1, by drawing out the ink container from the ink container holder while guiding the ink container by the guide groove, no ink is ejected from the ink container irrespective of ink employed.
The piston-type ink container is generally formed of polypropylene, and accordingly, it is known that the ink container is swollen to some extent when left alone for a long time with ink remaining in the inner space 15.
A plurality of ink containers of the present invention which were different in the distance of the front end of the projection or protrusion from the front end of the body portion of the cylinder (105 mm long) were prepared and the state of stain with ink was evaluated after a swelling test. The ink containers were 79.5 mm in diameter of the body portion. The swelling test was carried out by measuring change of the distance of the front end of the projection or protrusion from the front end of the body portion of the cylinder after each ink container is left alone for 7 days at 70° C. with each ink container filled with ink A. A guide groove 21e shown in
A plurality of ink containers of the present invention which were different in the length of the protrusion (the distance between the front end of the protrusion and the rear end of the protrusion) were prepared and stability in inserting the ink container into the ink container holder before swelling and interference between the protrusion and the guide groove after swelling were evaluated. The ink containers were 79.5 mm in diameter of the body portion. The protrusion on each ink container was shown in
As can be seen from the table 3, when the length of the protrusion is not smaller than 40 mm and not larger than 120 mm (preferably not smaller than 60 mm and not larger than 100 mm), interference between the protrusion and the guide groove can be prevented after swelling, and stability in insertion of the ink container into the ink container holder can be ensured.
From tables 2 and 3, it can be found that when a protrusion such as shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2002-165552 | Jun 2002 | JP | national |
| 2003-019852 | Jan 2003 | JP | national |
| 2003-134168 | May 2003 | JP | national |
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| 6192797 | Rea et al. | Feb 2001 | B1 |
| 20010003953 | Wakayama et al. | Jun 2001 | A1 |
| Number | Date | Country |
|---|---|---|
| 1 153 754 | Nov 2001 | EP |
| Number | Date | Country | |
|---|---|---|---|
| 20030227523 A1 | Dec 2003 | US |
