EP1294567B1 - Printer module with a dot-matrix printhead - Google Patents

Abstract

The invention relates to a printer module, comprising a chassis (10), with a guide (32, 34) for a printhead carrier (36), a printhead (38) arranged thereon, a carrier motor for moving the printhead carrier (36) back and forth on the guide thereof (32, 34), a mounting (26) for an ink ribbon cassette and an ink ribbon drive (28). Said guide comprises two guide rods (32, 34) which are parallel to each other on which the printhead carrier (36) runs in a displaceable manner, whereby a drive mechanism (48) which may be driven by the carrier motor engages with a section of the printhead carrier (36) lying between the two guide rods (32, 34). The printhead (38) is arranged on one side of the printhead carrier (36) in relation to the connection point of the drive mechanism (48) and on the other side of the printhead carrier in relation to the connection point of the drive mechanism (48) a balance weight (58) for the printhead (38) is arranged.

Description

The invention relates to a printer module according to the preamble of claim 1.

A printer module of this type dispenses with a record carrier transport. With him therefore adapted to specific tasks printers of all kinds can be constructed, for example, printers in writing devices, for printing receipts and journal rolls in cash registers or for printing bank documents in ATMs. According to their purpose, the printing width of the entire printer module also changes. In all applications, a very high printing speed is sought. This requires on the one hand a correspondingly powerful printhead and, on the other hand, a strong carrier motor in order to be able to reciprocate the printhead in a correspondingly fast and uniform manner.

From US 3,726,381 a printing device is known with a dot matrix print head, which is arranged on a print head carrier, which in turn on two mutually parallel guide rods back and forth is herverschiebbar. The drive of the print head carrier is effected by a carrier motor and a drivable by this tension member which engages a located between the guide rods portion of the print head carrier.

From DE 694 23 406 T2 a printing device with a printhead and a printhead carrier holding it is known, which is guided displaceably on a guide rod and has a portion extending away from the printhead to which a flexible printed circuit board is connected is, which transmits the signals required for the operation of the printhead.

The invention has for its object to provide a printer module of the type mentioned, in which with low-cost means a high printing speed, a uniform print image and low wear can be achieved.

This object is achieved by a Drukkermodul with the features of claim 1.

By inventively provided measures it is achieved that the print head carrier can be accelerated and moved practically tilt-free with the print head arranged eccentrically on him. This achieves a very uniform movement of the printhead carriage and the printhead, which ensures a higher operating speed with high print quality and less wear on the guide rods and the bearings of the printhead carriage. The low wear in turn ensures that the high print quality is maintained over a longer period of time than conventional printers.

Usually printers of the type mentioned are designed specifically for the applications already mentioned, since the print width is different according to the particular application. The manufacturers have thus kept a large number of printers ready for the different application purposes. This increases the effort for the production of the printer and storage. This disadvantage is at in a printer module of the above ge called type eliminated by the fact that the chassis has a side rail and two perpendicular to the longitudinal direction directed transverse walls on which the parallel to the longitudinal direction of the longitudinal member directed guide rods are held. The longitudinal member may be rigidly, preferably integrally connected to one of the transverse walls, while the other transverse wall is preferably detachably connected to the longitudinal member, for example screwed. The inventive design of the chassis makes it possible to vary the printing width of the printer module in a very simple manner. For this purpose, only the length of the longitudinal member and the guide rods need to be selected accordingly. This is manufacturing technology easy to do. All remaining parts of the printer including most mounting holes and openings on the chassis remain virtually unchanged. As a result, the same parts and mounting devices can be used for printer modules with different print width largely.

Preferably, the carrier motor is arranged at one end of the longitudinal member, while a deflection roller for the tension member is mounted on the transverse wall at the other end of the longitudinal member. The tension member, for example, a toothed belt can be stretched in this solution in a simple manner by adjusting the position of the carrier motor on the side rail. Preferably, the carrier motor is arranged at the end of the longitudinal member which is rigidly connected to a transverse wall. This area of the chassis has the highest rigidity and remains unchanged regardless of the length of the longitudinal member, so that here offer the best mounting options for the relatively heavy carrier motor.

Preferably, the ink ribbon drive has a releasably coupled to the internal tape transport of a ribbon cassette drive shaft, which is coupled via a reversing gear with the deflection roller for the tension member. A reduction of the parts of the reversing gear can be achieved in that this has a coaxial with the guide roller bearing pivot carrier with two arms, in each case with the pulley constantly in driving connection intermediate wheels are mounted, which is dependent on the direction of rotation of the pulley pivoting movement of the Swivel carrier optionally be coupled to the drive shaft of the ribbon drive.

A ribbon cassette insertable into the holder of the printer module comprises a housing having a storage chamber for the ink ribbon, a transport mechanism for withdrawing the ink ribbon from the storage chamber and for introducing the ink ribbon into the storage chamber, and two ribbon guide arms parallel to and spaced from each other the. Stand housing and the free ends of the ribbon on its way between an outlet opening and an inlet opening of the storage chamber to form a insertable between the print head and the platen abutment work section is stretched. The length of the working portion of the ink ribbon usually corresponds to the printing width of the printer, ie the travel of the print head in the printer. For printers with different print width, therefore, different width ribbon cartridges must be kept ready. This requires an increased effort in the production and storage of this required in large quantities consumable. Preferably, therefore, at least one the tape guide arms parallel to the longitudinal direction of the working portion of the ink ribbon adjustable. As a result, the length of the working section can be set to the printing width of the respective printer. This only requires one ribbon cartridge type for printers of different print widths.

Preferably, the tape guide arm closest to the outlet opening of the storage chamber is adjustable. Since the ink ribbon cassette transport mechanism of this type is usually arranged immediately in front of the entrance opening of the storage chamber, the position of the transport mechanism within the cassette housing is not affected by the adjustability of the ribbon guide arm in this embodiment of the ink ribbon cassette. Thus, the position of the drive shaft for the transport mechanism in the printer need not be changed.

Preferably, the adjustable band guide arm is arranged on a frame part, which is guided displaceably in the housing. According to an embodiment that is easy to manufacture and to operate, the frame part can have a transverse web forming a housing side wall and the guide arm, and two slide rails which are perpendicular to the latter and which are displaceably guided in complementary guide grooves of the housing.

Conveniently, the frame part relative to the housing in predetermined positions can be locked, which correspond for example to the usual paper sizes, to which the printing widths of the printer are set.

According to a simple and inexpensive to manufacture solution for locking the frame part to the housing to the Slide rails and the walls of the guide grooves for mutual engagement with each other certain latching means provided, for example, recesses in the one part (slide rail, groove wall) and at least one projection on the other part (groove wall, slide rail). The necessary for the engagement and disengagement elastic deflection of the parts intended for engagement with each other is often already given due to the inherent elasticity of the housing material (usually plastic) and the game of interleaved housing parts. If this is not sufficient or a safer locking is desired, for example, the projection may be formed on a resiliently deflectable tongue.

Figur 1

eine perspektivische Ansicht der Vorderseite eines erfindungsgemäßen Druckmoduls,

Figur 2

eine perspektivische Ansicht der Rückseite des erfindungsgemäßen Druckmoduls,

Figur 3

eine perspektivische Ansicht des erfindungsgemäßen Druckmoduls mit senkrecht gestelltem Druckkopf,

Figur 4

eine schematische Draufsicht auf den Farbbandantrieb,

Figur 5

eine perspektivische Draufsicht auf eine geöffnete Farbbandkassette in einer ersten Stellung des verstellbaren Bandführungsarmes und

Figur 6

eine der Figur 1 entsprechende Ansicht der Farbbandkassette in einer zweiten Stellung des verstellbaren Bandführungsarmes.

Further features and advantages will become apparent from the following description, which explains the invention with reference to an embodiment in conjunction with the accompanying drawings. It shows:

FIG. 1

a perspective view of the front of a printing module according to the invention,

FIG. 2

a perspective view of the back of the printing module according to the invention,

FIG. 3

a perspective view of the printing module according to the invention with vertical printhead,

FIG. 4

a schematic plan view of the ribbon drive,

FIG. 5

a top perspective view of an opened ribbon cassette in a first position of the adjustable Bandführungsarmes and

FIG. 6

1 corresponding view of the ink ribbon cassette in a second position of the adjustable Bandführungsarmes.

The printer module shown in Figures 1 to 3 comprises a generally designated 10 chassis, which consists essentially of a longitudinal beam 12, a first transverse wall 14, a second transverse wall 16 and a longitudinal wall 18 directed parallel to the longitudinal beam 12. The longitudinal member 12 consists of an angle section with a first leg 20 parallel to the longitudinal wall 18 and a second leg 22 oriented in a right angle thereto.

The first transverse wall 14 is formed integrally with the longitudinal member 12. The longitudinal member 12 is punched together with the transverse wall 14 of sheet steel and bent into the shape shown. The second transverse wall 16 is connected to the longitudinal member 12 and the longitudinal wall 18 via screws 24. On the leg 20 of the longitudinal member 12 and on the transverse wall 16 two tabs 26 are arranged, which serve in a conventional manner for holding a ribbon cassette, not shown, the internal transport mechanism for the ink ribbon with a drive shaft 28 can be coupled, through a slot 30th protrudes in the leg 20 of the longitudinal member 12. The ribbon drive will be discussed in more detail below.

Between the transverse walls 14 and 16 extend parallel to the longitudinal beam 12, two guide rods 32 and 34, on where a print head carrier generally indicated at 36 is slidably mounted to which a dot matrix print head, generally designated 38, is mounted. For reciprocating the print head carrier 36 and thus the print head 38 is a drive motor 40 which is fixed to the longitudinal member 12 and projects with its shaft 42 through an opening 44 in the second leg 22 of the longitudinal member 12. The shaft 42 of the drive motor 40 carries a pinion 46, which drives a tension member 48 in the form of a toothed belt. The toothed belt 48 is guided on the end of the longitudinal member 12 remote from the drive motor 40 via a deflection roller 50, which is mounted with a shaft 52 in lugs 54 bent from the material of the transverse wall 16. The toothed belt 48 is fixedly connected to a lying between the guide rods 32 and 34 portion of the print head carrier 36. The toothed belt 48 can be tensioned by a displacement of the drive motor 40 in the longitudinal direction of the longitudinal member 12.

With the shaft 52 of the guide roller 50, an encoder disk 56 is connected, which allows in conjunction with a light barrier, not shown, a detection of the movement of the print head carrier 36.

As can be seen in the figures, the print head 38 is attached laterally outside the guide track formed by the guide rods 32 and 34 on the print head carrier 36. As a result, at least in a position of use of the printing module, in which the print head 38 prints up or down, a tilting moment on the print head carrier 36, which leads to increased friction in the bearing of the print head carrier on the guide rod 34. In order to exclude or reduce this tilting moment and thus the friction, a dashed line is drawn on the print head carrier in FIG Balancing weight 58 arranged, which ensures that both bearings of the print head carrier 36 are charged approximately equal. In conjunction with the point of application of the toothed belt 48 between the guide rods 32 and 34 on the printhead support 36, this helps to reduce the risk of jamming of the printhead support on its guide rods 32 and 34, thereby providing a smoother and smoother running of the printhead support 36 obtained on the guides 32 and 34, which ensures less wear and a cleaner print image at high printing speeds.

In Figure 2 can be seen two plug contact strips 60 and 62, which are connected to the leg 20 of the longitudinal member 12, on the one hand to connect the print head and the other hand, the drive motor 40 and the encoder 56 with a power supply and control, not shown.

According to Figure 4, the drive shaft 28 of the ribbon drive is driven by a worm 64, a worm gear 66 and a generally designated 68 reversing gear from a seated on the shaft 52 gear 70 ago. The reversing gear 68 comprises a freely rotatably mounted on the shaft 52 pivot carrier 72 with two radially projecting at an angle arms 74, 76, which are permanently mounted with the gear 70 in engagement intermediate gears 78 are mounted. Depending on the direction of rotation of the gear 70 and thus depending on the direction of the print head 38 either the arm 74 or the arm 76 is brought into engagement with the worm gear 66, so that the direction of rotation of the drive shaft 28 regardless of the direction of rotation of the gear 70 and thus the direction the printhead 38 always remains the same.

As will be understood from the foregoing description, when changing the displacement path of the print head carrier 36, i. when changing the printing width, only the guide rods 32, 34, the legs 20 and 22 of the longitudinal member 12 and the timing belt 48 to be changed in length. All other parts and their mounting locations can remain unchanged. As a result, the production of similar printer modules with different print widths can be substantially simplified and made less expensive.

The ribbon cassette shown in Figs. 5 and 6 includes a flat cuboidal housing, generally designated 80, having a bottom 82, longitudinal walls 84 and 86, and transverse walls 88 and 90. A top surface occluding the cassette cavity is removed in the figures to provide insight into the cassette cavity grant.

The cartridge cavity has a storage chamber 92 in which an endless ribbon 94 is stored in loops. On the exit side closes, separated by an intermediate wall 96 of the storage chamber 92, a space 98, in which the ink ribbon 94 passes through an exit gap 100 and in which it is turned before it leaves the cassette cavity through a second exit slit 102.

In a chamber 104 upstream of the storage chamber 92 in the direction of travel of the strip, there is a transport mechanism 106 for extracting the ink ribbon 94 from the storage chamber 92 through the discharge gap 100 and pushing it back into the storage chamber 92 through an entrance slit 107. The transport mechanism 106 consists of two intermeshing gears 108, 110, of which the gear 108 is coupled to a drive shaft of a printer, not shown.

The side or transverse walls 88, 90 of the cassette housing 80 are extended by tape guide arms 112, 114, each having a tape guide channel 116 through which the ink ribbon 94 extends so that between the free ends of the tape guide arms 112 and 114, the ink ribbon 94 to form a is stretched parallel to the longitudinal wall 84 extending working portion 118. The length of the guide arms 112 and 114, i. the distance between the housing longitudinal wall 84 and the working portion 118 of the ink ribbon 94 is such that in this space the printhead of the printer can move. The length of the working section 118 corresponds to the printing width of the printer.

In order to be able to use the same ink ribbon cassette on printers with different print width, the tape guide arm 114 according to the invention relative to the rest of the cassette housing 80 is adjustable. For this purpose, the transverse wall 80 and the tape guide arm 114 are connected to two slide rails 120 which are directed perpendicular to them and which are displaceably guided in guide grooves 122 which are formed in the longitudinal walls 84 and 86 of the housing 80. The transverse wall 90, the tape guide arm 114 and the slide rails 120 together form a frame part 123 which is pulled out as a whole in the direction of the double arrow A from the housing 80 (Figure 6) or can be inserted into the housing 80 to the length of the working portion 118 of Changing the ribbon in accordance with the printing width of the respective printer.

In order to lock the frame member 123 in the respective desired position, 120 recesses 124 are provided in the slide rails, in each of which a projection 126 can engage, which is formed on a resiliently deflectable wall portion 128 of a groove wall of the two guide grooves 122. As a result, the frame part can be latched in a position corresponding to the standardized printing width of the respective printer.

The housing parts of the ink ribbon cassette can be inexpensively injected in a conventional manner of plastic. The possibly slightly larger costs for the production and assembly of the ribbon housing of two parts are more than compensated by the savings that result from the fact that only one type of cassette must be manufactured and stored.

Claims (15)

1. Printer module having a matrix printing head, comprising a chassis (10) with a guide (32, 34) for a printing-head carrier (36), a printing head (38) which is arranged on the latter, a carrier motor (40) for moving the printing-head carrier (36) to and fro on its guide (32, 34), a holder for an ink-ribbon cassette (36) and an ink-ribbon drive (28), the guide comprising two guide rods (32, 34) which are parallel to one another and on which the printing-head carrier (36) is guided displaceably, and a pulling element (48) which can be driven by the carrier motor (40) acting on a section of the printing-head carrier (36) which lies between the guide rods (32, 34), characterized in that, with regard to the point of action of the pulling element (48), the printing head (38) is fastened to the printing-head carrier (36) on one side of the guide rods, laterally outside the guide track which is formed by the guide rods (32, 34), and in that a compensating weight (58) for the printing head (38) is arranged on the other side of the printing-head carrier (36) with respect to the point of action of the pulling element (48), which compensating weight (58) precludes or reduces a tilting moment which acts on the printing-head carrier (36) in a use position of the printing module.
2. Printer module according to Claim 1, characterized in that the chassis (10) has a longitudinal carrier (12) and two transverse walls (14, 16) which are oriented perpendicularly with respect to its longitudinal direction and on which the guide rods (32, 34) which are oriented parallel to the longitudinal direction of the longitudinal carrier (12) are held.
3. Printer module according to Claim 2, characterized in that the longitudinal carrier (12) is connected rigidly, preferably in one piece, to one of the transverse walls.
4. Printer module according to Claim 2 or 3, characterized in that the longitudinal carrier (12) is bent from sheet metal.
5. Printer module according to one of Claims 2 to 4, characterized in that the carrier motor (40) is arranged at one end of the longitudinal carrier (12), and in that a deflection roller (50) for the pulling element (48) is mounted on the transverse wall (16) at the other end of the longitudinal carrier (12).
6. Printer module according to Claim 5, characterized in that the carrier motor (40) is arranged at the end of the longitudinal carrier (12) which is connected rigidly to a transverse wall (14).
7. Printer module according to either of Claims 5 and 6, characterized in that the ink-ribbon drive has a drive shaft (28) which can be coupled releasably to the internal ribbon transport of an ink-ribbon cassette and is coupled to the deflection roller (50) for the pulling element (58) via a reverse gear mechanism (68).
8. Printer module according to Claim 7, characterized in that the reverse gear mechanism (68) has a pivoting carrier (72) which is mounted coaxially with respect to the deflection roller (50) and has two arms (74, 76), on which intermediate wheels (78) are mounted which are drive-connected in each case permanently to the deflection roller (56) and can be coupled optionally to the drive shaft (28) of the ink-ribbon drive by a pivoting movement of the pivoting carrier (72), which pivoting movement is dependent on the rotational direction of the deflection roller (50).
9. Printer module according to one of Claims 1 to 8, characterized by an ink-ribbon cassette which is arranged in the printer module, comprising a housing (80) with a storage chamber (92) for the ink ribbon (94), a transport mechanism (106) for pulling the ink ribbon (94) out of the storage chamber (92) and for inserting the ink ribbon (94) into the storage chamber (92), and with two ribbon-guiding arms (112, 114) which protrude from the housing (80) parallel to one another and at a spacing from one another, and the ink ribbon (94) being tensioned over the free ends of said ribbon-guiding arms (112, 114) on its path between an outlet opening (102) and an inlet opening of the storage chamber (92), with formation of a working section (118) which can be introduced between the printing head and the printing abutment, it being possible for at least one of the ribbon-guiding arms (112, 114) to be adjusted parallel to the longitudinal direction of the working section (118) of the ink ribbon (94).
10. Printer module according to Claim 9, characterized in that the ribbon-guiding arm (114) which lies closest to the outlet opening (102) of the storage chamber (92) can be adjusted.
11. Printer module according to Claim 9 or 10, characterized in that the ribbon-guiding arm (114) is arranged on a frame part (123) which is guided displaceably in the housing (80).
12. Printer module according to Claim 11, characterized in that the frame part has a transverse web which forms a housing side wall (90) and the guide arm (114) and two sliding rails (120) which are perpendicular with respect to the said transverse web and are guided displaceably in complementary guide grooves (122) of the housing (80).
13. Printer module according to Claim 11 or 12, characterized in that the frame part (123) can be locked in predefined positions with respect to the housing (80).
14. Printer module according to Claim 13, characterized in that latching means (124, 126) which are intended for mutual engagement with one another are provided on the sliding rails (120) and the walls (128) of the guide grooves (122).
15. Printer module according to Claim 14, characterized in that the latching means comprise cutouts (124) in one part (sliding rail (120), groove wall (128)) and at least one projection (126) on the respective other part (groove wall (128), sliding rail (120)).

Images