Head with capping facility for an ink jet printer

Abstract: The invention provides a head for an ink-jet printer comprising an ink cartridge (20a) having a nozzle (22), a cap guide (30) having a cap (62) for the nozzle, means for bringing the cap guide and ink cartridge together so the cap approaches the nozzle, and means comprising an interengaging boss (2) and recess (1) for accurately locating the cap (62) over the nozzle (22) when it approaches the nozzle. The means for locating the cap over the nozzle is, preferably, a boss (2) on the cap guide (30) and a recess (1), or groove, on the ink cartridge (20a), or vice versa.

Description: The present invention relates to a head capping unit of an ink-jet printer. In a conventional ink-jet printer, sheets of paper are fed sequentially from a paper feeding tray and are printed one by one when each paper is passed through a printer head. The printer head has a plurality of nozzle holes and is mounted at the lower part of an ink cartridge. The ink cartridge is mounted on a carriage and reciprocates from left to right by means of a shaft. Accordingly, when all the ink in the ink cartridge is consumed, the ink cartridge is easily demounted from the carriage for replacement. The carriage is connected with a timing belt and is mounted to be reciprocated by means of a driving motor. A printing process is performed with ink being ejected from the nozzle holes of the printer head of the cartridge. After finishing the printing process, the printer head operating as described above is situated in a home position. In the home position, a capping unit is normally mounted on the printer head. An object of a conventional capping unit is to prevent clogging by sealing the nozzle holes of the printer head. As shown in Fig. 1, in a conventional capping unit for an ink-jet printer, wipers 60a, 60b typically comprise rubber or material having the properties of rubber. The wipers are mounted so as to wipe off the nozzle holes of two printer heads 22, 24 as the heads move toward the home position within a box-shaped main frame 40. Also, when the wiped heads 22, 24 have passed through the wipers 60a, 60b and are situated in the home position, caps 62a, 62b made of rubber are mounted in a shape opposed to that of the heads 22, 24 so as to seal the nozzle holes of the printer heads 22, 24. One wiper 60a has a longish groove by which it is fixed on a rib 32a of a cap guide 30. The other wiper 60b is fixed on a rib 32b of the cap guide 30. Thus, since the wipers 60a, 60b are made of rubber, they are elastic and can respond accordingly when applied to the head as it passes through. Also, this enables the surface of the nozzle holes to contact the upper surface of the wipers 60a, 60b so as to wipe away ink by sliding over the wipers in a closely adhered state. The caps 62a, 62b are fixedly inserted into cap holders 64a, 64b, and the cap holders 64a, 64b are fixed to the cap guide 30. The cap guide 30 has ribs 32a, 32b for mounting the two wipers 60a, 60b, and fixing parts 34a, 34b are formed to mount the cap holders 64a, 64b. On a most lateral surface of the cap guide 30, supporting shafts 36a, 36b are formed. Accordingly when the cap guide 30 of the main frame 40 is mounted, the supporting shafts 36a, 36b are inserted into sliding grooves 42, 44 formed on the lateral surface of the main frame thereby the cap guide 30 is moved in a horizontal or inclined direction along the grooves 42, 44. As a result, as the wipers 60a, 60b travel to the home position after ink cartridges 20a, 20b, mounted on a carriage 10, finish reciprocating for the printing process, ink on the surface containing the nozzle holes of the printer heads 22, 24 is wiped off by the sliding contact with the upper surface of the wipers 60a, 60b. Subsequently, when the printer heads 22, 24 reach the home position completely, namely, when the cap guide 30 reaches the far right side of the sliding grooves 42, 44, the printer heads 22, 24 are sealed by the caps 62a, 62b to prevent clogging of the ink. In order to perform the printing process again, by means of the carriage 10 being conveyed, the cap guide 30 is moved to the far left side of the sliding grooves 42, 44, as a tension coil spring is mounted in a wiper lever 50 having a projection 52. However, when the printer head reached the home position, there should be some extent of gap between the outer wall of the cap guide and the inner wall of the main frame so that the cap guide can be moved with respect to the main frame. Accordingly, because of the existence of this gap, when the printer head mounted in the carriage has reached the home position, the nozzle surface of the printer head is not accurately sealed. Due to this problem, deterioration of the capping accuracy is apparent. EP 0 313 204 discloses a head capping unit for an ink jet printer. The caps are mounted on a sled which moves on ramps in combination with the print heads, in order to cap the heads. A pen catcher is provided which engages a slot in the print head so that the sled is returned to its initial position when the print head moves from the capping position. Summary of the Invention According to the invention there is provided a head capping unit for an ink-jet printer comprising: a carriage supporting an ink cartridge having a print head; a main frame including a plurality of grooves; a cap guide including at least one cap for a print head, said cap guide being mounted in said main frame to slide on a path determined by said grooves between a first position and a second position at which the cap operatively caps the print head; and a wiper lever which operatively engages the carriage to move the cap guide, with the carriage, towards the second postive and operative to return the cap guide to the first position when said cap guide is released by said carriage; characterised in that the head capping unit further comprises means comprising a cooperating boss and recess for accurately locating the cap over the print head as the cap guide approaches the second position. Preferably the boss and the recess have a tapering cross-section so as to facilitate the location of one on the other. Preferably the recess is on an exposed surface of the ink cartridge facing the cap guide and the boss is on an opposing surface of the cap guide, or vice versa. Preferably the boss and the recess are correspondingly shaped. Preferably the recess is a groove. Preferably the head capping unit further comprises wipers for wiping surfaces of the ink cartridge; In a preferred embodiment, it will be understood that by providing a head comprising an ink cartridge having a guide groove and a cap guide having a boss formed in, preferably, a corresponding shape there is improvement in the accuracy of capping. It will be understood that, to accurately seal the nozzle surfaces of the printer head when the carriage reaches the home position, preferably a guide groove is formed at one side of the lower surface of the ink cartridge, and a boss is formed on the cap guide in a shape opposed to that of said guide groove and the boss is closely inserted into the groove. In a preferred embodiment, there is a head capping unit for an ink-jet printer having a wiper for wiping a surface having a nozzle hole formed on the lower or exposed surface of an ink cartridge. There is a cap for sealing the hole. Preferably, there is a cap holder fixing the cap. Preferably, there is a cap guide mounting the wiper and cap holder. Preferably, there is a main frame on which the cap guide is slidably mounted. Preferably, there is a guide groove formed on the lower surface of the ink cartridge. Preferably, a boss is formed in a shape corresponding to that of the guide groove so as to be closely inserted into the groove when the carriage reaches the home position, so that the cap accurately seals the nozzle surface of the printer head. Brief Description of the Drawings Preferred embodiments of the invention will now be described by way of example only with reference to the following drawings. In the figures, like referenced features indicate the same or similar components. Fig. 1 is a side sectional view illustrating a head capping unit of an ink-jet printer in accordance with the conventional art. Fig. 2 is a side sectional view illustrating a head capping unit of an ink-jet printer in accordance with a preferred embodiment of the invention. Figs 3A and 3B above are side elevation views illustrating the operation of the head capping unit in accordance with one embodiment of the invention. Detailed Description of the Preferred Embodiment(s) As shown in Fig. 2, after the printing process has been performed on sheets of paper, the carriage 10 mounting ink cartridges 20a, 20b is conveyed toward a home position by a timing belt being driven by a driving motor. A capping unit comprises wipers 60a and 60b for wiping a surface containing the nozzle holes of printer heads 22, 24 which are mounted on the underside of ink cartridges 20a, 20b. Caps 62a, 62b are provided for sealing and cap holders 64a, 64b mounting the caps 62a, 62b. A cap guide 30 holds the wipers 60a, 60b and the cap holders 64a, 64b. A main frame 40 is provided with respect to which the cap guide performs a sliding movement. A guide groove 1 is formed on the lower surface of the ink cartridge 20a so that when the carriage 10 reaches the home position, the surfaces containing nozzle holes of the printer heads 22, 24 are accurately located with respect to the caps 62a and 62b so the holes are accurately sealed. Also, on the cap guide 30 a mating boss 2 is formed in a shape corresponding to that of the guide groove 1. As Figs. 3A and 3B illustrate, in the capping unit according to the present invention, when carriage 10 connected with the timing belt is moved toward the home position, one arm of a wiper lever 50 is latched by the carriage and thus the carriage moves it along with it, and the supporting shafts 36a, 36b of the cap guide 30 are moved along the sliding grooves 42, 44 to the right. Since the sliding grooves 42, 44 are inclined, the cap guide 30 is moved upward. In a continuous movement, the nozzle surfaces of printer heads 22, 24 are inserted into the caps 62a, 62b so as to be closely adhered to, by means of the upward movement of the cap guide 30. On the lower surface of the ink cartridge 20a a guide groove 1 is formed, and on the cap guide 30 a boss is formed in a shape corresponding to that of the guide groove 1 such that the boss 2 is accurately inserted into the guide groove 1 when the printer heads touch caps 62a, 62b. Therefore when the carriage arrives at the home position the boss is closely inserted in the groove. The snug fit ensures the accurate location of the cap guide 30 on the ink cartridges and in particular, the printer heads with the caps. In other words, the boss 2 and the guide groove 1 play a role in retaining the ink cartridges 20a, 20b and the cap guide 30 in position when these are engaged with each other, thereby the accuracy of capping is improved. Conversely, when a driving motor is operated to perform a printing operation on sheets of paper, the boss 2 is drifted away from the guide groove 1 and moved to the left. In this case, the supporting shafts 36a, 36b formed on the cap guide 30 are moved along the sliding grooves 42, 44, and after passing through the wiper lever 50, the supporting shafts 36a, 36b are moved to the far left side. As can be seen from the foregoing description, the present invention provides accurate capping when the carriage, having finished the printing process, reaches the home position, by providing a guide groove formed on a conventional ink cartridge and with a corresponding boss formed on a conventional cap guide.

Claims: A head capping unit for an ink-jet printer comprising: a carriage (10) supporting an ink cartridge having a print head (22, 24); a main frame (40) including a plurality of grooves (42, 44); a cap guide (30) including at least one cap (62) for a print head (22, 24), said cap guide (30) being mounted in said main frame (40) to slide on a path determined by said grooves (42, 44) between a first position and a second position at which the cap (62) operatively caps the print head (22, 24); and a wiper lever (50) which operatively engages the carriage (10) to move the cap guide (30), with the carriage (10), towards the second postion and operative to return the cap guide (30) to the first position when said cap guide (30) is released by said carriage (10); characterised in that the head capping unit further comprises means (1,2) comprising an cooperating boss and recess for accurately locating the cap (62) over the print head (22, 24) as the cap guide (30) approaches the second position. A head capping unit according to claim 1, in which the boss (2) and the recess (1) have a tapering cross-section so as to facilitate the location of one on the other. A head capping unit according to claim 1 or 2, in which the recess (1) is on an exposed surface of the ink cartridge (20) facing the cap guide (30) and the boss (2) is on an opposing surface of the cap guide (30).

Inventors: LEE YONG-DUK, LEE, YONG-DUK
Applicants: SAMSUNG ELECTRONICS CO LTD, SAMSUNG ELECTRONICS CO., LTD.
Application year: 1997
Main classification: B41J2
IPC codes: B41J2