Thermal record apparatus

Abstract: A thermal record apparatus comprising a roller (28) for transfer­ ring thermosensible recording paper (31); a thermal head (29) inclu­ ding a heating resistance element; a flat spring (30) for biasing the thermal head (29) to press the thermosensible recording paper (31) on the roller (28); a cam (50,51) provided in the thermal head (29) and having a cam face; contact members (57,58) keeping the thermal head (29) at a distance from thermosensible recording paper (31) and the roller (28) against the biasing force of the flat spring (30) under the condition where the heating resistance element of the thermal head is positioned on the line including the shaft of the roller (28) and the contact point with the cam face.

Description: BACKGROUND OF THE INVENTION (1) Field of the Invention The present inverition relates to a thermal record apparatus, and more specifically, to a thermal record apparatus well applied to a recording apparatus of a facsimile. (2) Description of the Prior Art Fig. 6 is a side view showing a major portion of the basic structure of a thermal record apparatus termed "thermal printer" or the like. Usually, in a thermal printer, a thermal head 1 is tightly pressed against a thermosensible paper 3 on a roller 2 to prevent the irregularity of density in printing. The thermal head 1 is fixed to a receiving portion 5 of a supporter 4, and pushing means 6 such as a spring urges the thermosensible paper 3 against the roller 2. At this time, vertical portions 8 of the supporter 4 hold a rotation shaft 9 of the roller 2 therebetween to keep the thermal head 1 in position. The thermal head 1 is composed of many heating resistance elements 7 disposed in parallel to the line of the rotation axis of the roller 2. The pushing means 6 applies force at the point on a plane P1 including the line corresponding to the rotation axis 9 and the heating resistance elements 7. The roller 2 has a shape of a right circular cylinder, and is driven by a driving mechanism (not shown) such as a stepping motor synchronously with the recording operation of the thermal head 1. This causes the thermosensible recording paper 3 to move in a direction shown by an arrow A2. With the above-mentioned thermal printer, when the thermal head 1 must be kept off the roller 2 to supply further thermosensible recording paper or to get rid of a paper jam, the operator manipulates an operating portion 10 so that a projection 11 formed in the operating portion 10 displaces the thermal head 1 against the force applied by the pushing means 6. As an example of the prior art embodiments, Unexamined Japanese Patent Publication No. 176075/1984 discloses an apparatus in which an operating portion is not separate from a supporter of a thermal head. In the thermal printer shown in Fig. 6, the projection 11 applies force to the thermal head 1 at a point which is not on the plane P1, and the thermal head 1 may sometimes be distorted in keeping the thermal head 1 off the roller 2. Such a distorted thermal head 1 would be ununiformly pressed against the roller 2; that is, the heating resistance elements 7 is ununiformly pressed on the thermosensible recording paper 3 to cause irregularity in density of printed characters. There also arises the problem that larger operating force is required because the projection 11 applies the force to the thermal head 1 at the point which does not exist on the plane P1. An object of the present invention is to solve the above-mentioned problems and to provide a thermal record apparatus with improved operability and enhanced quality of printing. SUMMARY OF THE INVENTION A thermal record apparatus according to the present invention comprises a body; a roller rotatably held in the body, for transferring thermosensible recording paper; a thermal head held in the body, capable of moving in the radial direction of the roller and including a heating resistance element; the thermosensible recording paper intervening between the heating resistance element and the roller; pushing means for biasing the thermal head to press the thermosensible recording paper on the roller; a cam provided in the thermal head, capable of angular movement that results in a linear movement of said thermal head and having a cam face; contact members provided in the body, coming in contact with the cam face by the angular displacing operation of the cam and keeping the thermal head at a distance from the thermosensible recording paper and the biasing roller against the force of the pushing means under the condition where the heating resistance element of the thermal head is positioned on the line including the shaft of the roller and the contact point with the cam face. In accordance with the present invention, a cam angularly displaced related to the thermal head and a contact member coming in contact with the cam face of the cam are provided to position the heating resistance element of the thermal head on the straight line including the axial line of the roller and the contact point of the cam face with the contact member. Thus, since the force is applied to the thermal head at a point on the straight line, the distortion of the thermal head is prevented, and the thermal head can uniformly press on the roller in recording. This considerably improves the printing quality of this thermal record apparatus. Additionally, the force required for keeping the thermal head off the roller is prevented from increasing, and the operability is improved. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram presented for explaining a structure of a facsimile 21 of an embodiment of the present invention; Fig. 2 is an exploded schematic view showing a structure related to a thermal head 29; Fig. 3 is a block diagram showing an electric structure of the facsimile 21; Fig. 4(1) is a side view showing a major portion of the facsimile 21 under the recording condition; Fig. 4(2) is a perspective view of Fig. 4(1); Fig. 5(1) is a side view showing a major portion of the facsimile 21 under the reception release condition; Fig. 5(2) is a side view of Fig. 5(1); and Fig. 6 is a side view showing a major portion of a typical embodiment of a prior art facsimile under the recording condition. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1 is a diagram presented for explaining a structure of a facsimile 21 of an embodiment according to the present invention. Original supply rollers 24 are placed within a body (side plates of the same) of the facsimile 21 to draw originals in an original tray 23 one after another into the body. A guide member 25 and a reader 26 composed, for example, of a CCD (charge connecting device) and the like are disposed in the downstream part from the original supply rollers 24 with regard to a sheet feeding direction shown by an arrow A1. A pushing means 27 such as a spring biases the reader 26 to press against a roller 28. The reader 26 may include a plurality of rod lenses disposed in parallel to the axial line of the roller 28 and a line image sensor extending along the axial line of the roller 28, for reading the image of an original. On the other hand, a thermal head 29 is placed opposite to the reader 26 related to the roller 28 intervening therebetween. A pushing means 30 such as a spring biases the thermal head 29 to press on the roller 28. A body 22 houses a roll 32 of thermosensible recording paper 31 used for the recording by the thermal head 29. The thermosensible recording paper 31 drawn from the roll 32 is lead through the guide member 33 and passes between the thermal head 29 and the roller 28 for recording. In the downstream part of the reader 26, roller 28 and thermal head 29 with regard to the paper feeding direction shown by the arrow A1, guide members 34, 35 and rollers 36, 37 are disposed to discharge the used original and the thermosensible recording paper 31 having a record from outlets 38, 39 to the outside of the body 22. Fig. 2 is an exploded perspective view showing the relations among the body 22, roller 28 and thermal head 29. Opposite lateral ends of the thermal head 29 are fixed to receiving portions 43, 44 of supporting portions 41, 42. The pushing means 30 such as a flat spring urges the thermal head 29 to press the thermosensible recording paper 31 on the roller 28. Vertical portions 45, 46 formed in the supporting portions 41, 42 hold the rotation shaft of the roller 28 therebetween to keep the thermal head 29 in position. The thermal head 29 includes a plurality of heating resistance elements 54 disposed in parallel to the line of the rotation shaft of the roller 28. Portions 47, 48, which are formed in the supporting portions 41, 42 extending downward, hold a rotation shaft 49 therethrough. Opposite ends of the rotation shaft 49 protrude from elongate openings 55, 56 formed in the body 22, and cam members 50 51 are fixed to the opposite ends of the rotation shaft 49. The cam member 50 is provided with an operating arm 52, and a cam 53 is composed of these two components. Contact members 57, 58 are formed in the upper portion of the elongate openings 55, 56. The roller 28 has a shape of a right circular cylinder, and is driven by a driving mechanism (not shown) such as a stepping motor synchronously with the recording operation of the thermal head 29. This causes the thermosensible recording paper 31 to move in the direction shown by the arrow A1. Fig. 3 is a block diagram showing an electric structure of the facsimile 21. The facsimile 21 has a network controller 12 connected to a telephone line ℓ1. The network controller 12 controls line communication between the telephone line ℓ1 and the facsimile 21. A telephone 14, which is provided with a handset 13 having telephone transmitter and receiver for telecommunication, is connected to the network controller 12. The telephone 14 is provided with a hook-up detecting unit 15 connected to a controller 16. A facsimile unit 17 and a dial pulse generator 18 are provided between the controller 16 and the network controller 12. The facsimile unit 17 modulates or demodulates image data which the facsimile 21 transmits or receives through the telephone line ℓ1. The dial pulse generator 18 generates dial signaling pulse according to a telephone number inputted from an operating unit 19 stated hereinafter. The operating unit 19 including dial keys, a "start" key and the like, the reader 26 for optically reading the image of the original set in the facsimile 21 and the thermal head 29 for recording the image data received through the telephone line ℓ1 are connected to the controller 16. Fig. 4 is a diagram showing the facsimile 21 under the recording condition. Since the constitution related to the lateral opposite ends of the thermal head 29 is the same as in Fig. 2, an explanation about the cam member 50 which is provided with the operating arm 52 will be given. As shown in Fig. 4(1), the operating arm 52 is moved in the direction shown by an arrow R5, the cam member 50 is also angularly displaced in the direction shown by the arrow R5. This causes a cam face 50a of the cam member 50 to keep off the contact member 57 as shown in Fig. 4(2), and the pushing means 30 urges the thermal head 29 to press against the roller 28. The position where the thermal head 20 comes into contact with the roller 28 through the thermosensible recording paper 31 exists on a plane P2 including the line corresponding to the rotation shaft of the roller 28 and the line corresponding to the rotation shaft of the cam member 50. The roller 28 is rotated under the condition to feed the thermosensible recording paper 31 between the roller 28 and the thermal head 29, and the image data received is recorded on the thermosensible recording paper 31. Fig. 5 is a diagram showing the facsimile 21 under the condition where the thermal head 29 is kept off the roller 28, that is, the reception release condition. As shown in Fig. 5(1), the operating arm 52 is driven in the direction shown by an arrow R7, and the cam member 50 is also angularly displaced in the direction of the arrow R7. This causes the cam face 50a of the cam member 50 to come into contact with the contact member 57 as shown in Fig. 5(2), and the rotation shaft 49 to which the cam member 50 is attached, the supporting portion 41 and the thermal head 29 are displaced altogether against the force of the pushing means 30 in the direction shown by an arrow R9 to keep the thermal head 29 at a distance from the roller 28 through the thermosensible recording paper 31. At this time, the position where the cam face 50 comes in contact with the contact member 57, is on the plane P1. As has been described, according to the present invention, the distortion of the thermal head 29 is prevented, and the thermal head 29 can be uniformly pressed against the roller in recording. This prevents the occurrence of irregularity of the density in recording image data, and the high quality of data recording can be attained. Reduced force may be required for keeping the thermal head 29 off the roller 28 compared with the conventional embodiment because the thermal head 29 is never distorted, and hence the operability is improved. According to the facsimile 21 of the present invention, no distortion is caused in the thermal head in keeping it off the roller, and the thermal head can be uniformly pressed against the roller in recording. This prevents the occurrence of irregularity of the density in recording image data, and the high quality of data recording can be attained. Additionally, reduced force may be required for keeping the thermal head off the roller, and the operability is improved.

Claims: A thermal record apparatus, comprising: a body (22); a roller (28) rotatably held in said body, for transferring thermosensible recording paper (31); a thermal head (29) held in said body, capable of moving in the radial direction of said roller and including a heating resistance element; said thermosensible recording paper (31) intervening between said heating resistance element and said roller; pushing means (30) for biasing said thermal head (29) to press said thermosensible recording paper (31) on said roller (29); a cam (50,51) provided in said thermal head, capable of angular movement that results in a linear movement of said thermal head and having a cam face; contact members (57,58) provided in said body, coming in contact with said cam face by the angular displacing operation of said cam and keeping said thermal head at a distance from said thermosensible recording paper and said roller against the biasing force of said pushing means under the condition where said heating resistance element of said thermal head is positioned on the line including the shaft of said roller and the contact point with said cam face. An apparatus according to claim 1, wherein said body includes side plates having elongate openings, a shaft sliding through said elongate openings (55,56) to move in the radial direction of said roller, and a supporting portion for fixing and supporting said shaft and said thermal head. An apparatus according to claim 1, wherein said cam includes a cam member having a cam face, and an operating arm (52) extending from said cam member and capable of angularly displacing said cam portion related to said thermal head. An apparatus according to claim 1, wherein said pushing means is a flat spring. An apparatus according to claim 1, wherein it is used as a thermal printer for a facsimile.

Inventors: SAKAI KATSUYUKI, SAKAI, KATSUYUKI
Applicants: SHARP KK, SHARP KABUSHIKI KAISHA
Application year: 1990
Main classification: B41J25
IPC codes: B41J2, B41J25