PRINT HEAD PRESSURE CONTACT DEVICE

Abstract: A print head pressure contact device for use in a printer comprising a head holder (3) for holding a print head (4); a platen (24) for supporting a medium (25) to be printed; and resilient means (6) for urging the head holder (3) and the platen (24) relatively towards each other characterised in that the head holder (3) is pivotally mounted on a lever (2) which is itself pivotally mounted on a head carrier (1) whereby good printing contact may be maintained between the print head (4) and the medium (25).

Description: This invention relates to a print head pressure contact device for use in a printer. In a printer for printing a tag or label by pressing it against a print head of the printer, there is liable to be uneven contact between the print head and the tag or label with the result that blurring of the print can occur. This is due to the fact that uniform pressure is not applied over the entire surface of the print and that even if the print head is initially designed not to cause blurring, any mechanical displacement taking place in the printer as time lapses is liable to cause the uneven contact. In order to solve the abovementioned problem, Nozaki et al, Japanese Laid-Open Utility Model No. 51-154211 discloses a print head pressure contact device having a platen which is rotatably mounted with respect to the frame, whereby the platen and the print head can be brought into close contact with each other. Since the platen is arranged to rotate and oscillate resiliently with respect to the surface of the print head, when the platen presses a tag or label against the print head, a substantially uniform pressure is applied so that blurring of the print does not occur. However, when the material which is to be printed is so hard that it does not closely contact the platen, the ability of the platen to rotate does not produce close contact between the print head and the print material, and hence adequate contact therebetween cannot be obtained. It is therefore difficult to obtain good printing quality when hard print materials are used. In DE-A-3,226,194 there is disclosed a head support mechanism in which the head is resiliently urged towards the platen. The required parallelism between the head and the platen, however, is not automatic and involves the use of adjustment screws. According to the present invention, there is provided a print head pressure contact device for use in a printer comprising a head holder for holding a print head; a fixed platen for supporting a medium to be printed; and resilient means for urging the head holder and the platen relatively towards each other, the head holder being movably mounted on a lever which is itself pivotally mounted on a head carrier whereby good printing contact may be maintained between the print head and the medium, characterized in that the head holder is pivotally movable, the head holder being rotatably mounted on a spindle fixed to the said lever, the resilient means acting between the head carrier and the said lever. The axis of the resilient means preferably passes through the spindle. The head holder may have a print head bonded thereto. The head carrier may be slidably mounted in a frame, drive means being provided for effecting movement of the head carrier in the frame. Thus the print head pressure contact device of the present invention is capable of adequately allowing for the disposition of the printing surface of the print material, and enables good printing quality to be achieved even with hard print materials. The platen is fixed and consequently manufacturing costs can be reduced by eliminating the use of an adjustable rotating unit for the platen. The invention is illustrated, merely by way of example, in the accompanying drawings, in which:- Figure 1 is a sectional view of an embodiment of a printer provided with a print head pressure contact device in accordance with the present invention, and Figure 2 is a perspective view of the printer shown in Figure 1. This invention will now be explained with reference to the accompanying drawings. As indicated above, Figure 1 and Figure 2 respectively show a sectional and a perspective view of a printer provided with a print head pressure contact device in accordance with the present invention. A head carrier 1 is slidably mounted on head carrier guide spindles 8, 9 which extend through respective lateral holes which are formed in the head carrier 1 and are spaced from each other. The guide spindles 8, 9 are secured to a frame 5 of the printer. A head carrier transfer spindle 7 extends loosely through a lateral hole 21 formed in the head carrier 1 so as to be out of contact with the hole 21. A head carrier driving pin 10 is supported by a stopper 11 which is mounted on the head carrier 1. The pin 10 engages an helical recess in the head carrier transfer spindle 7. The stopper 11 prevents the head carrier driving pin 10 from breaking away from the head carrier transfer spindle 7. A head pressure contact lever 2 is pivotally mounted on a spindle 22 which is fixed to the head carrier 1. A head holder 3 is rotatably mounted on a spindle 23 fixed to the head pressure contact lever 2. A print head 4 is adhesively bonded to the head holder 3. One end of a spring 6 engages in a groove 6 a provided in the head carrier 1, the other end of the spring 6 engaging in a groove 6 b provided on the top side of the head pressure contact lever 2. The axis of the spring 6 passes through the spindle 23. The spring 6 provides, through the head pressure contact lever 2, a downward pressure on the print head 4 which is bonded to the head holder 3 so as to force the print head 4 against a platen 24. The platen 24 extends from the face of the frame 5. Paper or other record medium 25 may be placed on the platen 24. The cross-section of the platen 24 has, at the printing section, a flat face 24 a protruding from its surrounding surface, the flat face 24 a being adapted to be contacted by the print head 4. This feature facilitates easy contact between the print head 4 and the medium 25 placed on the printing section. Electric power is supplied to the print head 4 by a flexible printed circuit 15 having a plurality of signal lines thereon. The operation of the head carrier 1 having the above-mentioned construction is described hereunder. If a hard record medium 25 is inserted onto the printing section, the medium may be at an angle with respect to the flat face 24 a of the platen and may not evenly contact the flat face 24 a . In such a case, when the hard record medium 25 pushes up the print head 4, the head pressure contact lever 2, which pivots about the spindle 22, automatically adjusts the angle of the print head 4 to fit it to the angle and position of the hard record medium 25. Simultaneously, the print head 4 pivots about the spindle 23 and automatically adjust its angle to the angle of the hard record medium 25. Consequently, the print head 4, which automatically adjusts its position and angle in response to the angle of the hard record medium 25, makes close contact with the hard record medium 25. The drive of a motor 13 is transmitted through reduction gears 14A, 14B, 14C and 14D to the head carrier transfer spindle 7. As a result of the rotation of the head carrier transfer spindle 7, the head carrier 1 and the head carrier driving pin 10 engaged with the helical groove provided in the head carrier transfer spindle 7, shift longitudinally of the head carrier transfer spindle 7. If a hard record medium has undulations extending in the direction of its width, the head pressure contact lever 2 and the head holder 3 pivot about the spindle 22 and the spindle 23 respectively during travel of the head carrier 1, and the print head 4 shifts while in contact with the surface of the record medium. As described above, the printer shown in the drawings may be used not only for ordinary printing media but also for hard printing media because its print head follows any tilt angles of the printing media and therefore makes good contact with them, as a result of which high quality print is obtained.

Claims: A print head pressure contact device for use in a printer comprising a head holder(3) for holding a print head(4); a fixed platen(24) for supporting a medium(25) to be printed; and resilient means(6) for urging the head holder(3) and the platen(24) relatively towards each other, the head holder(3) being movably mounted on a lever(2) which is itself pivotally mounted on a head carrier(1) whereby good printing contact may be maintained between the print head(4) and the medium(25), characterized in that the head holder(3) is pivotally movable, the head holder(3) being rotatably mounted on a spindle(23) fixed to the said lever(2), the resilient means(6) acting between the head carrier(1) and the said lever(2). A device as claimed in claim 1 characterized in that the axis of the resilient means(6) passes through the spindle(23). A device as claimed in claim 1 or 2 characterized in that the head holder(3) has a print head(4) bonded thereto. A device as claimed in any preceeding claim characterized in that the head carrier(1) is slidably mounted in a frame(5), drive means(10) being provided for effecting movement of the head carrier(1) in the frame(5). A device as claimed in claim 4 in which the drive means comprises a head carrier driving pin(10) which engages a head carrier transfer spindle(7).

Inventors: FUJIHIRA, HAJIME
Applicants: SEIKO INSTRUMENTS INC.
Application year: 1988
Main classification: B41J25
IPC codes: B41J2, B41J25