Abstract:
A recording head for use in a recording apparatus has a plurality of sets of recording electrodes corresponding to a plurality of line densities.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a recording head for use in a facsimile reception apparatus capable of recording in a plurality of line density modes. 
     In the conventional facsimile apparatus, a recording head is provided only with a recording electrode of a size in conformity with the finest line density required and by controlling the use of the recording electrode locally, various line density modes can be set. For example, in the case where simultaneous recording of 32 lines is performed, as shown in FIG. 1, a recording head 1 provided with 32×2 electrodes 2 1  to 2 64  is set at its finest line density, for example, at 8 lines/mm. These electrodes 2 1  to 2 64  are divided into two columns, namely, the odd-numbered electrodes 2 1 , 2 3 , . . . 2 63  and the even-numbered electrodes 2 2 , 2 4 , . . . 2 64  in the sub-scanning direction with a space of 0.25 mm therebetween, and the even-numbered electrodes 2 2 , 2 4 , . . . 2 64  are spaced in the sub-scanning direction by 0.125 mm relative to the odd-numbered electrodes 2 1 , 2 3 , . . . 2 63 , respectively so that the space between the odd-numbered electrodes 2 1 , 2 3 , . . . 2 63  are interpolated by the even-numbered electrodes 2 2 , 2 4 , . . . 2 64 . When recording is performed with 4 lines/mm line density, all of the 64 electrodes 2 1  to 2 64  are used, as shown by the shading in FIG. 2, and the signal voltages are respectively applied thereto by 64 drive circuits. The signals to be applied simultaneously to the 64 electrodes 2 1  to 2 64  are not the same. Referring to FIG. 2, for example, and in particular to an odd-numbered electrode, such as, the electrode 2 1 , a signal is applied to that electrode after a period of time required for the relative movement of the recording head in the main scanning direction by a distance l. This is the distance between the odd-numbered electrode (for example, 2 1 ) and the succeeding even-numbered electrode (for example, 2 2 ) in the main scanning direction. The same thing applies to the other electrodes 2 3  and 2 4 , 2 5  and 2 6  . . . and 2 63   and 2 64 . In other words, with respect to a scanning line, a signal is first applied to an even-numbered electrode and the applied signal is stored in the even-numbered electrode for a period of time which is determined by the distance l and the main scanning speed, and when the preceeding odd-numbered electrode comes to a position corresponding to the original position of the above-mentioned even-numbered electrode, the same signal is applied to the odd-numbered electrode for recording. In this case, when the even-numbered electrodes 2 2 , 2 4 , . . . 2 64  are not used, 32 drive circuits will do for the electrodes, but in the spaces between the odd-numbered electrodes 2 1 , 2 3 , . . . 2 63 , there occur unrecorded blank portions, which reduces the image quality. 
     In the case where recording is performed with 8 lines/mm line density, the electrodes 2 1  to 2 32  are employed as shown in FIG. 3, and respectively different signal voltages are applied thereto by use of 32 drive circuits. 
     However, in the recording head of this type, the electrodes are disposed in conformity with the finest line density mode and by controlling the electrodes locally, each line density mode is set, so that numerous electrodes are required and accordingly, numerous drive circuits are required. Therefore, such recording head becomes expensive. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a recording head using less drive circuits than those of the conventional recording head. 
     According to the present invention, a plurality of groups of recording electrodes corresponding to a plurality of line densities are provided and each recording electrode can be selectively used as desired and a drive circuit can be commonly used for each recording electrode. Accordingly, the number of the necessary drive circuits can be reduced. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1, 2 and 3 are for explaining a principle of the conventional recording head. 
     FIG. 4 is a schematic plan view of an embodiment of a recording head according to the present invention. 
     FIG. 5 is a block diagram of the peripheral circuits for use in the embodiment of FIG. 4. 
     FIG. 6 is part of the block diagram of the peripheral circuits of FIG. 5. 
     FIGS. 7, 8 and 9 are the schematic plan views of another embodiment of a recording head according to the present invention. 
     FIG. 10 is part of a block diagram of a modified peripheral circuit for use in the embodiment of FIGS. 7, 8 and 9. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 4, there is shown an embodiment of a recording head according to the present invention. As shown in FIG. 4, in the facsimile reception apparatus, a recording head 3 has plural groups of recording electrodes 4 and 5 corresponding to each line density mode. The recording electrodes 4 and 5 comprise plural electrodes 4 1  -4 32 , and 5 1  -5 32  arranged with predetermined spaces therebetween in the direction of sub-scanning in conformity with, for example, 4 lines/mm and 8 lines/mm, respectively. The recording electrodes 4 and 5 are changed over in accordance with a required line density rather than by an operation on the transmission side and recording is performed by a main scanning with reciprocal straight-line motion. 
     Referring to FIG. 5, there are shown the peripheral circuits of the recording head 3. In a matrix 6 of the peripheral circuits, four row lines 7 1  -7 4  and 32 column lines 8 1  -8 32  are connected at their respective cross points P 11  -P 131 , P 22  -P 232 , P 31  -P 331 , P 42  -P 432  through series circuits comprising resistors R and diodes D, one of which is shown in FIG. 6. In the cross points P 11  -P 131 , the connecting points of the resistor R and the diodes D are respectively connected to the odd-numbered electrodes 4 1 , 4 3 , . . . 4 31  for 4 lines/mm, and in the cross points P 22  -P 232 , the connecting points of the resistors R and the diodes D are respectively connected to the even-numbered electrodes 4 2 , 4 4 , . . . 4 32  for 4 lines/mm, and in the cross points P 31  -P 331 , the connecting points of the resistors R and the diodes D are respectively connected to the odd-numbered electrodes 5 1 , 5 3 , . . . 5 31  for 8 lines/mm, and furthermore in the cross points P 42  -P 432 , the connecting points of the resistors R and the diodes D are respectively connected to the even-numbered electrodes 5 2 , 5 4 , . . . 5 32  for 8 lines/mm. The change-over of the line density mode is conducted in accordance with the setting on the transmission side. In the case of 4 lines/mm line density mode, AND gates 9 and 10 are opened by a change-over signal A, and in the case of 8 lines/mm line density mode, AND gates 11 and 12 are opened by a change-over signal B. The odd-numbered signals are applied to a drive circuit Y 1  through the AND gate 9 or are applied to a drive circuit Y 3  through the AND gate 11. The even-numbered signals are applied to a drive circuit Y 2  through the AND gate 10 or are applied to a drive circuit Y 4  through the AND gate 12. The odd-numbered signals are pulse signals capable of selecting the electrodes 4 1 , 4 3 , . . . 4 31 , 5 1 , 5 3 , . . . 5 31  of the odd lines of the recording head 3, the even numbered signals are pulse signals capable of selecting and the electrodes 4 2 , 4 4 , . . . 4 32 , 5 2 , 5 4 , . . . 5 32  of the even lines, and the drive circuits Y 1  -Y 4  drive the row lines 7 1  -7 4  corresponding to the pulse signals generated from the AND gates 9-12. The drive circuits X 1  -X 32  apply signal voltage corresponding to image signals to the electrodes 4 1 , 4 3 , . . . 4 31  when the row line 7 1   is driven, and to the electrodes 4 2 , 4 4 , . . . 4 32  when the row line 7 2  is driven, and to the electrodes 5 1 , 5 3 , . . . 5 31  when the row line 7 3  is driven, and to the electrodes 5 2 , 5 4 , . . . 5 32  when the row line 7 4  is driven. When recording is performed with 8 lines/mm line density, 32 electrodes are employed. Accordingly, the sheet feed distance for recording 8 lines/mm is set to one half of the sheet feed density recording by 4 lines/mm line density. In other words, the sub-scanning speed is set at 1/2. Therefore, the drive circuits can be used for 8 lines/mm as well as for 4 lines/mm. 
     In the above-mentioned embodiment of the recording head according to the present invention, the recording electrodes 4 and 5 are arranged in the sub-scanning direction. However, they can be arranged in the main scanning direction as shown in FIGS. 7, 8 and 9. Either an electrostatic recording system or a thermosensitive recording system can be used equally well for the recording head 3. Furthermore, as shown in FIG. 10, the drive circuits Y 1  -Y 4  can be operated by the change-over signals A and B of the line density mode.