The present invention relates to an ink pump selective driver for selectively driving a plurality of tube pumps to supply different kinds of ink. Also, the invention relates to an ink jet printer provided with such an ink pump selective driver.
In recent years, ink jet printers making use of ink of three colors to perform color printing have become widespread. In these kinds of ink jet printers, three or more ink supply passages are arranged for supplying ink of respective colors, and ink pumps disposed in the respective ink supply passages are selectively driven to feed necessary color ink individually with pressure.
With ink jet printers of this construction, there is involved an inconvenience that ink jet printers are made large in size and high in cost, because when rotary drive sources (motors or the like), respectively, for exclusive use are mounted on respective ink pumps selectively driven, the number of the rotary drive sources installed is increased corresponding to the kinds of color ink as supplied. Therefore, it is desirable to provide an ink selector mechanism making use of a single rotary drive source to be able to selectively drive three or more ink pumps.
A related-art selective driver is composed of a single rotary drive source and clutch mechanisms arranged in power transmitting paths between respective ink pumps. Nonetheless, it is required that actuators such as solenoids or the like be attached to the clutch mechanisms to switch over the same. The ink selector mechanism provided with a single rotary drive source and a plurality of clutch mechanisms is advantageous in making an ink jet printer small in size and low in cost, as compared with a mechanism in which rotary drive sources for exclusive use are provided for every ink pump. Since actuators such as solenoids or the like for switching of the clutch mechanisms are required separately, however, there is a limitation in making an ink jet printer small in size and low in cost.
It is an object of the invention to provide an ink pump selective driver capable of selectively driving a plurality of ink pumps, for example, three or more with the use of a single drive source and achieving miniaturization of and cost reduction of an ink jet printer without the separate provision of actuators such as solenoids or the like.
Also, it is an object of the invention to provide a small-sized and inexpensive ink jet printer provided with such an ink pump selective driver.
In order to attain the above and other objects, according to the present invention, there is provided a pump driver for selectively driving at least three pumps, comprising:
a drive source;
a sun gear, rotated by the drive source;
a planetary gear, meshed with the sun gear;
a planetary carrier, which rotatably supports the planetary gear revolvably around the sun gear;
a plurality of driving gears, arranged with respect to the pumps such that the planetary gear meshes with one of the driving gears to selectively drive one of the pumps; and
a revolution limiter, which allows a revolution of the planetary gear in a first direction and restricts a revolution of the planetary gear in a second direction opposite to the first direction at a position where the planetary gear meshes with the one of the driving gears.
With this configuration, when the planetary gear revolves a predetermined angle around the sun gear in the first direction, one of the driving gears is selected. Thereafter, when the planetary gear revolves reversely in the second direction, the revolution limiter puts the planetary gear in a state of meshing with one of the pump drive gears. Accordingly, the pump drive gear is rotationally driven via the planetary gear, so that an ink pump, to which the pump drive gear is attached, is driven.
Preferably, the revolution limiter includes a ratchet mechanism. For example, the ratchet mechanism may include a ratchet lever, provided on the planetary carrier, and ratchet teeth, arranged, for example, in a one-by-one manner with respect to the pumps, to which the ratchet lever engages.
In such a configuration, it suffices that a constituent element, such as a ratchet mechanism, be provided in power transmitting paths from the drive source to the respective pumps without the provision of actuators such as solenoids or the like for switching of the clutch mechanisms. Accordingly, it is possible to realize a small-sized and inexpensive driver.
Preferably, the pump driver further comprises a revolution position detector, which detects a revolution angle of the planetary gears. Here, it is preferable that the revolution position detector includes: a plurality of detection pieces arranged with respect to the pumps; a first detector, which detects a predetermined one of the detection pieces, so that it is detected when the planetary gear meshes with a predetermined one of the driving gears; and a second detector, which detects remaining ones of the detection pieces, so that it is detected when the planetary gear meshes with any one of remaining ones of the driving gears.
In such a configuration, by controlling the drive source on the basis of detection of position by the revolving position detector, it is possible to surely perform selective driving of the pumps. Also, inexpensive motors other than step motors capable of controlling a rotating angular position with accuracy can be used as the drive source.
Preferably, each of the pumps includes a flexible tube. Here, each of the pumps compresses the flexible tube when an associated one of the driving gears is rotated in a forward direction, and releases a compressed state of the flexible tube when the associated one of the driving gears is rotated in a rearward direction.
If the flexible tube in the pump not driven remained in the compressed state, there is caused a bad situation that the ink tube would deteriorate. According to the above configuration, the compressed state of the flexible tube is released when the planetary gear is revolved in the first direction to operatively select an ink pump being driven.
To realize such a releasing operation, the pump driver may further comprise: a plurality of release planetary gears, preferably provided in a one-by one manner with respect to the pumps and meshed with the sun gear; and a release planetary carrier, which rotatably supports the release planetary gears revolvably around the sun gear. Here, the release planetary gears mesh with the driving gears when the planetary gears are revolved in the first direction at a predetermined angle. The release planetary gears are disengaged from the driving gears when the planetary gears are revolved in the second direction.
In this case, the planetary gear is revolved in the first direction, while passing meshing positions in which it meshes with the respective driving gears, which are rotationally driven by the release planetary gears. The respective driving gears thus rotating give a suitable load to the planetary gear when the planetary gear passes the meshing positions, so that the planetary gear can smoothly pass the meshing positions.
In the case where the rotation speed of the respective driving gears is large, there is a probability that revolution of the planetary gear is inhibited in the meshing positions.
Accordingly, it is preferable that a first rotation speed of the driving gears established by the release planetary gears is lower than a second speed of the driving gears established by the planetary gear.
According to the present invention, there is also provided an ink jet printer, comprising:
a print head;
a plurality of tanks, for example, at least three, each storing ink therein;
a plurality of pumps each associated with one of the tanks;
a drive source, and preferably a single drive source;
a sun gear, rotated by the drive source;
a planetary gear, meshed with the sun gear;
a planetary carrier, which rotatably supports the planetary gear revolvably around the sun gear;
a plurality of driving gears, arranged with respect to the pumps such that the revolved planetary gear meshes with one of the driving gears to selectively drive one of the pumps; and
a revolution limiter, which allows a revolution of the planetary gear in a first direction and restricts a revolution of the planetary gear in a second direction opposite to the first direction at a position where the planetary gear meshes with the one of the driving gears.
According to the present invention, there is also provided an ink jet printer, comprising:
a print head;
a plurality of internal tanks, each storing ink therein supplied from a corresponding one of a plurality of external tanks, and to be supplied to the print head;
a plurality of pumps, each associated with one of the internal tanks;
a detector, which detects an amount of ink in each of the internal tanks; and
a pump driver, which selectively drives the pumps in accordance with an output of the detector, the pump driver including:
a drive source, and preferably a single drive source;
a sun gear, rotated by the drive source;
a planetary gear, meshed with the sun gear;
a planetary carrier, which rotatably supports the planetary gear revolvably around the sun gear;
a plurality of driving gears, arranged with respect to the pumps such that the revolved planetary gear meshes with one of the driving gears to selectively drive one of the pumps; and
a revolution limiter, which allows a revolution of the planetary gear in a first direction and restricts a revolution of the planetary gear in a second direction opposite to the first direction at a position where the planetary gear meshes with the one of the driving gears.
With the provision of a small-sized and inexpensive pump driver for selectively driving three or more ink pumps, it is possible to achieve miniaturization and cost reduction of the ink jet printer.