EP0605098A2

EP0605098A2 - Serial impact printer

Info

Publication number: EP0605098A2
Application number: EP93309061A
Authority: EP
Inventors: Akira Ninomiya; Yasuo Imoto; Noriyuki Yamada
Original assignee: Brother Industries Ltd
Current assignee: Brother Industries Ltd
Priority date: 1992-11-12
Filing date: 1993-11-12
Publication date: 1994-07-06
Also published as: EP0605098A3

Abstract

A serial impact printer comprises at least two and preferably four platen parts (8A-8D) facing a print head (2) with a printing medium (P) interposed therebetween. One of the platen parts (8A-8D), each having a different arrangement of projections (E), is selected according to the thickness of the printing medium (P). The projections (E) correspond to the print wires (W) on the print head (2). The selected platen part (8A-8D) operates in cooperation with the print head (2) so that stable, high quality printing is performed on the printing medium (P) of varying thicknesses, from a single cut sheet to multiple-sheet paper sets. With optimum projections (E) selected to assist the printing by the print wires (W), the printed sheets are protected from piercing by the print wires (W).

Description

The present invention relates to a serial impact printer having a print head running along the surface of a printing medium and a platen facing the print head and sandwiching the printing medium with the print head.
Conventionally, impact printers are used to print an original and a plurality of copies with pressure sensitive sheets such as carbon paper sandwiched therebetween (called a multiple-sheet paper set.) This type of printer is required to perform quality printing on multiple-sheet paper sets, for example, sets comprising as many as 10 copies each.
Two major disadvantages are commonly experienced in trying to carry out quality printing on multiple-sheet paper sets. One disadvantage is that driving print wires of the print head hard enough to print in a high quality on the bottom sheet of the multiple-sheet paper set often results in piercing the top sheet with the wires. The other disadvantage is that characters are often printed less clearly on the lower sheets in the multiple-sheet paper set. This is because the lower the sheet, the less concentrated the strikina force of the print wires.
An object of the present invention is to provide a serial impact printer capable of providing high quality printing not only on a single sheet but also on a multiple-sheet paper set without piercing the printed sheets by print wires.
According to the invention there is provided a printing apparatus comprising:
a print head movably mounted; and
a platen for supporting a printing medium and mounted for cooperative movement with said print head, said platen having a plurality of platen parts, each platen part having an impact surface facing said print head and said plurality of platen parts includes at least two differently shaped impact surfaces wherein any of said plurality of platen parts can be selectively aligned with said print head.
The invention also provides a method of printing on a printing medium having a thickness within a range of thicknesses and using a printing apparatus having a print head and a platen for supporting the printing medium with a plurality of differently shaped impact surfaces that selectively oppose the print head, comprising the steps of:
measuring the thickness of the printing medium;
selecting one of the plurality of impact surfaces of the platen in accordance with the detected thickness and aligning the selected surface with the print head; and
controlling the print head to print on the printing medium.
With the printing apparatus of the present invention, the printing head and the platen move along the printing medium. The platen has a plurality of platen parts with different shapes, and one of the plurality of platen parts is selectively set to face the printing head.
The serial impact printer of the present invention constructed as described above can ensure clear printing regardless of the number of sheets to be printed simultaneously, from a single sheet to a multiple-sheet paper set. While high quality printing is being carried out, the piercing of printed sheets by the print wires can be prevented.
The invention will be more clearly understood from the following description which is given by way of example only with reference to the accompanying drawings in which:

Fig. 1 is a front view of a serial impact printer in a first embodiment according to the invention;
Fig. 2 is a side view in partial section of the serial impact printer of the first embodiment;
Fig. 3 is a perspective view of a print head of the first embodiment;
Fig. 4 is a block diagram of a controller of the first embodiment;
Fig. 5 is a flowchart explaining steps following paper feed of the first embodiment;
Fig. 6A is a partial view of the print head of the first embodiment;
Fig. 6B is a set of views of platen parts of the first embodiment;
Fig. 7A is a sectional view of a platen part positioned relative to print wires of the first embodiment;
Fig. 7B is a sectional view of another platen part positioned relative to print wires in the first embodiment;
Fig. 7C is a sectional view of another platen part positioned relative to print wires in the first embodiment;
Fig. 7D is a sectional view of another platen part positioned relative to print wires in the first embodiment;
Fig. 8 is a front view of a serial impact printer in a second embodiment according to the invention;
Fig. 9 is a front view of a serial impact printer in a third embodiment according to the invention;
Fig. 10A is a front view of a platen part in a serial impact printer in a fourth embodiment according to the invention;
Fig. 10B is a front view of another platen part in the fourth embodiment;
Fig. 11A is a view showing a platen part positioned relative to print wires in the fourth embodiment;
Fig. 11B is a view depicting another platen part positioned relative to print wires in the fourth embodiment;
Fig. 12A is a view of a prior art platen part positioned relative to print wires;
Fig. 12B is another view of a prior art platen part positioned relative to print wires; and
Fig. 13 is a partially enlarged sectional view of a prior art print head.

To overcome at least the two major disadvantages described in the related art above, the following serial impact printer is developed. In general, the printer 1 has a platen 8 that faces a print head 2 and moves parallel to and in synchronism with the print head 2. Printing paper P is held between the platen 8 and the print head 2.
The platen 8 has projections 8A-8D located opposite to the print wires W of the print head 2. When the print wires W strike the printing paper P, the paper P is sandwiched between the print wires W and their corresponding projections 8A-8D on the platen 8. This ensures that the striking force of each print wire W does not disperse but concentrates on a small area of the paper. As a result, high quality printing can be provided on all sheets making up the multiple-sheet paper set.
In the prior art as shown in Figs. 12A, 12B and 13, there are multiple-sheet paper sets comprising various numbers of sheets, for example, from 2 sheets up to 10. During printing, print wires W of a print head 105 dig deeply into a multiple-sheet paper set 101 comprising many sheets, as shown in Fig. 12A. By contrast, the print wires W do not dig very deeply if the paper set includes fewer sheets, as depicted in Fig. 12B with a multiple-sheet paper set 103. As illustrated, the print wires W have longer strokes when printing a paper set of many sheets than when printing a paper set of fewer sheets.
The print wires W are supported by the print head 105 with their tips angled inward, as shown in Figs. 12A and 12B. That is, specifically, as shown in Fig. 13, each wire enters a tip guide G of the print head 105 at an angle ϑ and protrudes therefrom at the same angle. A difference in the stroke of each printing wire depending on the thickness of the paper set causes a displacement 6 of each print wire at the striking position on the printing paper. In the case of Fig. 12A, the amount of stroke L2 of the print wires W is large. In the case of Fig. 12B, the amount of stroke L1 is small.
Suppose that the protruding wire tips are positioned so that they precisely strike the paper set 101 made of many sheets against the corresponding projections of the platen 107, as indicated by arrows A and B in Fig. 12A. In that case, attempts to print the paper set 103 made of fewer sheets can result in a disaccord between the striking position of each print wire W and the position of the corresponding projection on the platen 107, as indicated by arrows A and B in Fig. 12B. The wire-to-projection disaccord makes it impossible to perform high quality printing. The disaccord can also promote piercing of some of the sheets in the multiple-sheet paper set 103.
In addition to multiple-sheet paper sets, thin cut sheets (e.g., from 30 kg type paper lot) are also used one at a time on the serial impact printer. Such thin sheets of paper are vulnerable to piercing by the wires or by projections on the platen.
These difficulties are resolved by the serial impact printer in the first embodiment according to the invention, which is described referring to Fig. 1.
Fig. 1 is a front view of a printer 1 in the first embodiment, showing in particular the vicinity of a print head 2 and a platen 8. Fig. 2 is a side view showing the same portion in the first embodiment. In the printer 1, the print head 2 is furnished opposite to the surface of a printing medium P. The print head 2 is mounted on a carriage 7 supported by a main guide shaft 3 and a subguide shaft 4 and moves in an axially reciprocating manner along the shafts. The main guide shaft 3 is provided rotatably on an axis slightly eccentric from the center of the print head 2.
The platen 8 has four platen parts 8A through 8D each having a different shape and positioned opposite to the print head 2. The platen 8 is attached to a trapezoidal thread part 12 by a platen holder 11, the platen 8 being movable in an axially reciprocating manner with respect to the thread part 12. The torque of a motor 14 is transmitted to the platen 8 via a platen pulley 15, a belt 13 and a motor pulley 16. The motor 14 and platen holder 11 are both mounted on a carriage 17 which in turn is mounted on a main guide shaft 9 and a subguide shaft 10. The shafts are supported by side plates 5 and 6. Thus located, the platen 8 reciprocates along the shafts 9 and 10 facing the print head 2, with the printing medium P sandwiched between the platen 8 and the print head 2. The shafts 3, 4, 9 and 10 are arranged in parallel with one another.
The carriage 7 carrying the print head 2 and the carriage 17 carrying the platen 8 are fixed to timing belts 18 and 19, respectively, so that the print head 2 and platen 8 always face each other. The timing belt 18 is held taut between a driving pulley 23 and an idle pulley 27, and the timing belt 19 is held taut between a driving pulley 24 and an idle pulley 26. The driving pulleys 23 and 24 have the same diameter and are fixedly attached to a driving shaft 20. The driving shaft 20 is positioned perpendicular to the main guide shafts 3 and 9 and is supported by bearings 21 and 22. The driving shaft 20 is in fact the shaft of a motor 25 for driving the two carriages 7 and 17. In this arrangement, the print head 2 and the platen 8 move in the same direction while continuously facing each other.
As shown in Fig. 2, a pair of paper feed rollers 28A and 28B are furnished upstream of the direction in which the print medium P is fed. Another pair of paper feed rollers 29A and 29B are provided downstream of the same feed direction. A printed circuit board 30 is connected to the print head 2. A controller of the printer sends print data through the printed circuit board 30 to the print head 2.
As shown in Fig. 6A, a face 2A of the print head 2 has a plurality of print units arranged in a diamond shape. Each print unit has a print wire W that strikes the printing medium P. As shown in Fig. 6B, 7A and 7B, the surfaces of the platen parts 8A through 8D each have a diamond-shaped arrangement E of projections corresponding to the print units provided on the face 2A of the print head 2.
The tips of the projections E have different impact surfaces or areas facing the print head 2 from one platen part to another. Where the printing medium is thick, projections of small tip areas are used so that the plurality or thick copies are printed clearly. Where the printing medium is thin, projections of large tip areas are used so that the displacement at the striking position of each print wire is absorbed by the corresponding projection tip. Thus, the thin paper is better protected against getting pierced by the print wires.
More specifically, the projections E of the platen part 8A have the smallest tip areas opposite to the print wires W. The projections E of the platen part 8B have tip areas greater than those of the platen part 8A. The platen part 8C has four large projections corresponding to the four sides of the diamond-shaped print unit arrangement. The platen part 8D has no projections; it has the same area as the bed of each platen part. Preferably, the projections E of the platen part 8A or 8B correspond one on one to the print wires W. Alternatively, the individual projections E of these platen parts 8A and 8B may be formed into four large projections, like those of the platen part 8C except smaller, the four projections corresponding to the four sides of the diamond-shaped print unit arrangement.
Driving the carriage 7 carrying the print head 2 is described with reference to Fig. 3. The driving mechanism is disclosed in detail in U.S. Patent No. 4,990,004, which is incorporated herein by reference.
A fan-shaped oscillating gear 76 is attached to the tip of the shaft 3. A first gear 72 is provided to engage with the oscillating gear 76. A second gear 79 is furnished alongside the first gear 72, the two gears being mounted rotatably on a rotary shaft 77. The second gear 79 meshes with a motor gear 71 fixed to an output shaft 80 of a stepping motor 70.
Between the first gear 72 and the second gear 79 is a latch pin 82. The second gear 79 has an arcuate hole 73 formed along an arc of a circle whose center coincides with the axis of rotation of the gear 72. The latch pin 82 is inserted in the arcuate hole 73. A torsion coil spring 74 is attached to the tip of the rotary shaft 77. One end of the torsion coil spring 74 is latched by the latch pin 82 and the other end thereof by a projection 79A of the second gear 79.
A slit plate 86 having a plurality of radial slits is provided on one side of the first gear 72. A photo-interrupter 75 is mounted in a pinching manner over an outer circumference of the slit plate 86. The photo-interrupter 75 outputs pulses by detecting a plurality of slits on the slit plate 86 and the intermediate portions between the adjacent slits.
When the print head 2 comes into abutting contact with the platen parts 8A through 8D, the rotation of the shaft 3, oscillating gear 76, first gear 72 and second gear 79 is suppressed. There occurs a rotary displacement between the first gear 72 and the second gear 79, contracting the torsion coil spring 74 therebetween. The force of the spring 74 pushes the print head 2 against the printing medium at a constant pressure level. When the print head 2 stops, the first gear 72 and the slit plate 86 also stop, whereupon the photointerrupter 75 no longer detects slit-based changes. This terminates the driving of the stepping motor 70. The amount of drive of the stepping motor 70 is detected in terms of the output from the photointerrupter 75.
The print head 2 is controlled by a control circuit MC shown in Fig. 4. The control circuit MC is connected to the stepping motor 70 that rotates the main guide shaft 3 on its eccentric axis of rotation.
The thickness of the printing medium P is measured as follows. Before the printing medium P is inserted, the stepping motor 70 is driven to move the print head 2 from its home position to the platen 8. When the edge of the print head 2 comes into contact with the wire-receiving portion of the platen 8, the amount of drive required of the motor 70 to go out of step until its current value changes is measured and stored. Then, with the printing medium P inserted in the head-to-platen gap, the stepping motor 70 is driven likewise and its amount of drive is measured.
Comparing the amount of motor drive between two cases, before the printing medium P is inserted and after it is inserted, provides the thickness of the printing medium P. The larger the amount of motor drive, the thinner the printing medium P is determined to be.
When determined to be thick, the printing medium P is generally considered a multiple-sheet paper set containing carbon paper. The greater the number of sheets involved, the larger the measured thickness. Depending on the measured thickness of the printing medium P, one of the four platen parts 8A through 8D is selected to ensure optimum printing quality. The platen parts are mounted on the platen holder 11, which moves in an axially reciprocating manner.
As shown in Fig. 1, the platen bed bearing the projections differs in thickness from one platen part to another. The platen part thickness including the projections is the smallest for the platen part 8A having the smallest tip areas; the thickness is the largest for the platen part 8D having the flat surface. When one of the platen parts 8A through 8D is selected according to the paper thickness, an optimum gap is ensured between the print head 2 and the platen 8 without the need for changing the positional relation therebetween.
The operation of the printer 1 of the above construction is described with reference to Fig. 5. A paper feed command causes two pairs of paper feed rollers (28A and 28B; 29A and 29B) to feed the printing medium P in the paper feed direction through the gap between the print head 2 and the platen 8. For printing, a plurality of print wires W on the print head 2 strike through an ink ribbon IR at the printing medium P positioned where appropriate. When the printing medium P is a multiple-sheet paper set, the top sheet is printed by the ink ribbon; the next and subsequent sheets are duplicated by the carbon paper sandwiched therebetween under the impact from the wires W of the print head 2.
In the above state, the amount of drive of the stepping motor 70 required to bring the print head 2 from its home position into abutting contact with the printing medium P is counted. At this point, the print head 2 is driven in such a manner that no printing is made on the printing medium P.
In step 1 (S1) of Fig. 5, the thickness of the printing medium P is measured according to the amount of motor drive thus counted. In step 2 (S2), the print head 2 is retracted to ensure an optimum head gap according to the measured thickness. In step 3 (S3), one of the four platen parts 8A through 8D is selected to provide optimum printing quantity based on the thickness of the printing medium P. The selected platen part is positioned to face the print head 2. In step 4 (S4), the selected platen part and the print wires W operate in cooperation to perform printing on the printing medium P.
In the first embodiment described above, an optimum head gap is obtained by selecting one of the platen parts 8A through 8D having varying thicknesses. Alternatively, the print head 2 may be brought back to a predetermined position without regard to the thickness of the printing medium P. Details of the head gap adjustment procedure are disclosed in U.S. Patent No. 4,990,004 and Japanese Patent Publication No. 4-14634.
In synchronism with print data transmitted by a host computer, the motor 25 rotates the driving shaft 20 which in turn rotates the driving pulleys 23 and 24. This causes the carriage 7 carrying the print head 2 to travel on the timing belt 18 along the surface of the printing medium P. In conjunction with the movement of the carriage 7, the carriage 17 carrying the platen 8 travels on the timing belt 19 over the back of the printing medium P.
Since the driving pulleys 23 and 24 have the same diameter, the speed of movement of the carriages 7 and 17 is the same. That is, the platen 8 moves along the back of the printing medium P in synchronism with the print head 2 traveling over its surface, the printing medium P being sandwiched between the platen and the print head. After each line of printing, the printing medium P is fed by a predetermined distance by the paper feed rollers 28A, 28B, 29A and 29B in the paper feed direction.
A second embodiment of the invention is described referring to Fig. 8, which is a front view of a serial impact printer. Fig. 8 highlights the vicinity of the print head 2 and the platen of the printer. In the first and second embodiments, the same reference numerals designate the corresponding parts. Therefore, repetitive descriptions of the parts are omitted.
In the second embodiment, the print head 2, like that of the first embodiment, is furnished to face the surface of the printing medium P located where appropriate for printing. The print head 2 moves in an axially reciprocating manner, as in the first embodiment. Platen parts 41A through 41D are mounted 90 degrees apart on a platen table 40, which is preferably circular, that rotates on a shaft 50. One of the platen parts 41A through 41D is rotated selectively on the shaft 50 to face the print head 2. The platen table 40 corresponds to the platen of the first embodiment. The torque of a motor 48 is transmitted to the platen table 40 via a pulley 42, a belt 51 and a pulley 47 mounted on the table 40.
Because any one of the platen parts 41A through 41D may be selected by rotating movement, the axial length of the platen as a whole is reduced. This in turn contributes to making the printer more compact than before.
In the first and the second embodiment, the carriage 7 carrying the print head 2 and the carriage 17 carrying the platen 8 or the platen table 40 are driven by a single driving shaft 20 of the motor 25 via the timing belts 18 and 19. In this arrangement, the print head 2 and the platen 8 or the platen table 40 travel in a reciprocating manner while continuously facing each other. To select one of the platen parts, the arrangement requires installing suitable known mechanisms to axially move the platen parts 8A through 8D on the platen 8 or to rotate the platen parts 41A through 41D on the platen table 40.
An alternative to the above arrangement is the third embodiment of the invention wherein one motor drives the carriage 7 carrying the print head 2 and another separate motor drives the carriage 17 carrying the platen 8. The two-motor arrangement eliminates the need for equipping the carriage 17 with the traveling or rotating mechanisms that are characteristic of the first or the second embodiment. Without these mechanisms, one of the platen parts is selected optimally to face the print head 2 according to the thickness of the printing medium.
The third embodiment outlined above is described with reference to Fig. 9, which is a front view of a serial impact printer. In the third embodiment as well as in the first and second embodiments, the same reference numerals designate the corresponding parts, and repetitive descriptions of the parts are omitted.
In the third embodiment, the print head 2, like that of the first embodiment, is furnished to face the surface of the printing medium P located where appropriate for printing. On a platen 60, platen parts 60A through 60D having different shapes are arranged to face the print head 2. The platen 60 is mounted on the carriage 17 that moves in an axially reciprocating manner over the printing medium P sandwiched between the platen 60 and the print head 2.
A motor 62 drives the print head 2 axially via the timing belt 18 and driving pulley 23. A motor 64 drives the platen 60 axially via the timing belt 19 and the driving pulley 24. With the motors 62 and 64 operated separately, changing the position of the carriage 17 allows one of the platen parts 60A through 60D to be selected to face the print head 2. During printing, the two motors 62 and 64 run in synchronism so that the print head 2 and one of the platen parts 60A through 60D travel facing each other.
As described, using two motors to separately drive the print head 2 and the platen 60 eliminates the need to equip the carriage 17 with mechanisms for axially moving or rotating the print head 2. Without these mechanisms, any one of the platen parts 60A through 60D is selected as needed to face the print head 2.
A fourth embodiment of the invention is described referring to Figs. 10A and 10B. This embodiment is the same in mechanical structure as the first embodiment except for the platen. Thus, only the platen of the fourth embodiment is described hereunder, and those parts that also appeared in the first embodiment are designated by the same reference numerals with their descriptions are omitted.
As depicted in Figs. 10A and 10B, the fourth embodiment includes two platen parts 70A and 70B having projections G of different shapes. The arrangement of the projections G corresponding to the print wires W varies depending on the thickness of the multiple-sheet paper set. Illustratively, the projections G on the platen part 70A are intended for a multiple-sheet paper set comprising many sheets (e.g., 6 to 10 sheets); those of the platen part 70B are intended for a multiple-sheet paper set including fewer sheets (e.g., 2 to 5 sheets).
The projections G on the platen part 70A are somewhat shifted inward (by δ in Fig. 13) compared with those on the other platen part 70B. Because the print wires W have their tips angled inward, the projections G for long-stroke multiple-sheet paper sets are positioned differently relative to the platen center from those for short-stroke multiple-sheet paper sets.
By use of the same selecting mechanism as that of the first embodiment, one of the platen parts 70A and 70B is selected according to paper thickness. When the amount of stroke of the print wires W varies with the thickness of multiple-sheet paper sets, the striking position of each print wire W coincides precisely with the tip of the corresponding projection G on the platen part 70A or 70B, as illustrated in Figs. 11A and 11B. Unlike the first embodiment, the fourth embodiment preferably assigns the same tip area to each projection G on both platen parts 70A and 70B. Alternatively, the platen parts 70A and 70B may each have a different projection tip area, as in the first embodiment.
As described, the first through the third embodiments of the invention allow an optimum platen part to be selected according to the detected paper thickness. Thus, high quality printing is made available regardless of the number of sheets constituting the multiple-sheet paper set. Where thin cut sheets are used individually for printing, they are protected from piercing by the print wires.
The fourth embodiment of the invention allows one of the furnished platen parts to be selected according to the paper thickness so that the striking position of each print wire will not shift from its corresponding projection. This makes it possible to perform high quality printing regardless of the number of sheets constituting the multiple-sheet paper set. Furthermore, thin printing paper is protected during printing from being pierced by the print wires.
Although the description above contains many specifics, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments according to this invention. For example, there may be more or fewer than four platen parts for the first through the third embodiments. The fourth embodiment may have more or fewer than two platen parts.
Thus, the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.

Claims

A printing apparatus (1) comprising:
a print head (2) movably mounted; and
a platen (8) for supporting a printing medium (P) and mounted for cooperative movement with said print head (2), said platen (8) having a plurality of platen parts (8A-8D), each platen part having an impact surface facing said print head (2) and said plurality of platen parts (8A-8D) includes at least two differently shaped impact surfaces wherein any of said plurality of platen parts (8A-8D) can be selectively aligned with said print head (2).
The printing apparatus of claim 1 wherein said print head (2) is mounted on a print head carriage (7) and said print head carriage (7) is coupled to a drive mechanism (19-27,62).
The printing apparatus of claim 1 or 2 wherein said platen is mounted on a platen carriage (17) and said platen carriage (17) is coupled to said drive mechanism (19-27), or to an independent drive mechanism (19,24,26,64) independent from said drive mechanism (18,23,27,62) for said print head.
The printing apparatus according to any of the preceding claims wherein said print head comprises a plurality of printing wires (W) which are arranged in a configuration and each impact surface has a matching configuration.
The printing apparatus of claim 4 wherein said configuration is a diamond shape.
The printing apparatus according to any of the preceding claims wherein each of said platen parts (8A-8D) has a different thickness.
The printing apparatus according to any of the preceding claims wherein at least one of said platen parts (8A-8D) has at least one projection (E) thereon, each projection (E) having an end extending toward said print head (2) and said impact surface being disposed on said end.
The printing apparatus of claim 7 wherein at least two of said platen parts (8A-8D) each has a plurality of projections (E) thereon, each projection having an end extending toward said print head (2), a said impact surface being disposed on said end, and wherein said plurality of projections (E) on each platen part (8A-8D) are arranged differently with respect to said projections (E) on the other platen parts (8A-8D).
The printing apparatus of claim 7 or 8 where the projections (E) on each platen part (8A-8D) have different sizes.
The printing apparatus according to any of the preceding claims wherein said platen (8) includes a plate supporting said platen parts (8A-8D) in linear alignment.
The printing apparatus according to claim 10 wherein said plate is movably supported on a threaded shaft (12) for selectively aligning one of said platen parts (8A-8D) with said print head (2).
The printing apparatus according to any of the preceding claims further comprising a controller (MC,14) coupled to said platen (8) for controlling selective alignment of said platen parts (8A-8D) with said print head (2).
The printing apparatus according to any of the preceding claims further comprising a selecting mechanism coupled to said platen (8) that selects one of said plurality of platen parts (8A-8D) according to the thickness of the printing medium (P).
The printing apparatus according to any of the preceding claims further comprising a detecting mechanism coupled to said print head (2) for detecting the thickness of the printing medium (P).
A method of printing on a printing medium (P) having a thickness within a range of thicknesses and using a printing apparatus having a print head (2) and a platen (8) for supporting the printing medium (P) with a plurality of differently shaped impact surfaces that selectively oppose the print head (2), comprising the steps of:
measuring the thickness of the printing medium (P) ;
selecting one of the plurality of impact surfaces of the platen (8) in accordance with the detected thickness and aligning the selected surface with the print head (2); and
controlling the print head (2) to print on the printing medium (P).
The method of claim 15 wherein the step of measuring the thickness of the printing medium comprises the steps of
driving the print head (2) from a home position to the platen (8) prior to insertion of the printing medium (P) and measuring a first drive amount;
inserting the printing medium (P) between the print head (2) and the platen (8), driving the print head (2) from the home position to the platen (8), and measuring a second drive amount; and
comparing the first drive amount and the second drive amount to determine the thickness of the printing medium (P).