THERMAL PRINT HEAD CONNECTOR

Abstract: A linear thermal print head used for a printer, for such as a facsimile, and formed so as to improve the quality of a printed product by reducing density differences of parts of a printed product. An ease with which to fix the linear thermal print head and a head connector to each other is improved. A heating resistor (2), a common wiring pattern (3), individual writing patterns (4), driving circuit elements (5) and a ground wiring pattern (7) are provided in a linearly extending manner on a surface of a head base plate (1). A ground writing pattern connecting terminal (8), which is electrically connected to a substantially longitudinally intermediate portion of the ground writing pattern, is provided on the portion of the surface of the head base plate which is at a substantially intermediate part of a ground writing pattern side edge region thereof. A pair of common wiring pattern connecting terminals (12, 13) which are electrically connected to both ends of the common wiring pattern are provided on both of the other sides of the ground writing pattern connecting terminal.

Description: The present invention relates to a thermal print head connector and a line type thermal print head assembly. Background Art A line type thermal print head assembly is a system having a head connector mounted to the line type thermal print head. The head connector is mounted so as to conduct to the connection terminals of the line type thermal print head. External wires (or the terminal connector of external wires) are connected to the head connector. In most cases, the head connector is conventionally mounted to the side edge of the line type thermal print head. The head connector has the connector body made of a hard insulating material, such as a hard synthetic resin, and includes a plurality of terminal metal parts protruding from the connector body. On the other hand, in the line type thermal print head, there are provided through-holes at positions corresponding to the terminal metal parts. The head connector is fixed to the line type thermal print head after its terminal metal parts are inserted into the through-holes of the print head by soldering. In this arrangement, it is necessary to provide the through-holes in the line type thermal print head, and insert the protruding ends of the terminal metal parts into the through-holes. This has been troublesome and a considerably wide space has been required for mounting the head connector. In a system proposed in Japanese Patent Laid-Open Publication Nos. Hei 6-246948 and Hei 6-267620 (Related Art), a terminal metal part protrudes from a connector body made of an insulating material, such as a hard synthetic resin as shown in Fig. 12. In Fig. 12, reference numeral 301 denotes a head circuit board, 303 a head connector, 305 a connector body, and 307 a terminal metal part. The terminal metal part is mounted so as to protrude in a direction toward the surface of the circuit board of the print head (in parallel with the surface of the circuit board). The protruding part of the terminal metal part is shaped in a bifurcated form. The bifurcated portions of the terminal metal parts are fitted over the side edge of the print head. As the terminal metal parts clasp the side edge portion of the print head, the head connector is mounted. In contrast to the conventional system, in this system the head connector can be mounted easily and a smaller space is required for mounting the connector. However, in spite of the advantage mentioned above, the system of Related Art has the following problem. In the above system, the bifurcated portions of the terminal metal parts protrude from one side of the connector body, the head connector is mounted to the line type thermal print head using only the bifurcated portions. Therefore, it is not easy to mount the head connector in a stable condition, to secure sufficient mounting strength or prevent the head connector from becoming shaky. Further, in the above system, the direction of fitting the terminal metal parts of the head connector on the line type thermal print head is in the direction of the flat surface of the circuit board. In other words, this fitting direction is the direction in which the terminal metal parts protrude from the connector body. On the other hand, the direction of inserting and removing the external wires (or the terminal connector of external wires) to and from the head connector is generally the same as the protruding direction of the terminal metal parts. Therefore, when inserting or removing the external wires to or from the head connector, it is necessary to take care that the head connector does not come off the print head. There has been demand for a line type thermal print head system without a possibility of the connector coming off. DISCLOSURE OF THE INVENTION The present invention has been made with a technical object of providing a thermal print head connector and a line type thermal print head assembly structured to improve the mounting strength of the head connector to a line type thermal print head by use of a simple structure, and to preclude the possibility of coming off the head connector when inserting or removing external wires, or the like. In order to achieve the above objects, there is provided a thermal print connector according to claim 1 and a line type thermal print head assembly according to claim 4. With this arrangement, the connector body at its contact surface directly contacts the reverse surface of the line type thermal print head, and is pressed to the reverse surface by the elastic force of the clasp portion. Thus, the connector head can be mounted stably, reliably and firmly without leaving a possibility of becoming loose. Each terminal metal part extends, for example, in a direction substantially at right angles to the top surface of the line type thermal print head. The clasp portion is formed by bending the protruding portion of each terminal metal part sideways. The direction of mounting the head connector to the print head is in the direction of the flat surface of the head circuit body. On the other hand, the direction of inserting and removing external wires (or the connector of external wires) to and from the head connector is the protruding direction of the terminal metal part from the connector body. Therefore, the mounting direction of the head connector differs from the inserting and removing direction of external wires. For this reason, when inserting or removing external wires or the external terminal to or from the head connector, the chances of the head connector coming off the line type thermal print head are greatly reduced. Moreover, by the elastic force of the clasp portion of each terminal metal part, the line type thermal print head is pressed to the contact surface of the connector body. By this pressing action, the warpage of the line type thermal print head can be rectified. In another aspect of the present invention, recesses for mounting terminal metal parts are provided in the contact surface of the connector body, wherein each recess for mounting terminal metal part extends in the longitudinal direction of the clasp portion, and each terminal metal part extends from the recess for mounting a terminal metal part. By this arrangement, the elasticity of the clasp portions can be increased under the condition that the clasp portions are prevented from being bent sideways. Also, it is easy to insert the side edge of the print head between the connector body and the clasp portions. Moreover, the provision of the recesses in the contact surface of the connector body increases the contact pressure of the contact surface to the print head. Therefore, the mounting strength of the head connector to the print head can be further improved. Furthermore, according to yet another aspect of the present invention, a row-direction groove extending in the row direction of the terminal metal parts is formed in the contact surface of the connector body, the press-contact parts of the clasp portions to the line type thermal print head are located so as to face the row-direction groove. With this arrangement, the contact pressure of the contact surface of the connector body to the line type thermal print head can be increased. Since the pressing force of each clasp portion is received by the contact surfaces across the row-direction groove, the mounting strength and the stability of the head connector can be further augmented. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of the whole of an example of a line type thermal print head; Fig. 2 is a plan view of a principal part, on an enlarged scale, of the line type thermal print head in Fig. 1; Fig. 3 is a sectional view, on an enlarged scale, taken along the line III-III in Fig. 1; Fig. 4 is a perspective view of the whole of a line type thermal print head arrangement according to an embodiment of the present invention in which a head connector is mounted on the line type thermal print head; Fig. 5 is a sectional view, taken along the line II-II in Fig. 4; Fig. 6 is a sectional view, taken along the line III-III in Fig. 5; Fig. 7 is a perspective view of the head connector according to an embodiment of the present invention; Fig. 8 is a sectional view taken along the line V-V in Fig. 7; Fig. 9 is a sectional view taken along the line VI-VI in Fig. 7; Fig. 10 is a sectional view taken along the line VII-VII in Fig. 7; Fig. 11 is a sectional view taken along the line VIII-VIII in Fig. 7; Fig. 12 is a sectional view of the line type thermal print head system in Related Art. (1) Example of a line-type thermal print head An example of a line-type thermal print head will be described with reference to Figs. 1 to 3. In Fig. 1, reference numeral 1 denotes a head circuit board formed in a rectangular shape and of a heat-resistant insulating material, such as a ceramic material. On the top surface of the head circuit board, there is formed a heating resistor 2 in a straight line substantially in parallel with one side edge 1a of the head circuit board 1, and the heating resistor 2 has those portions which correspond to a plurality of print dots. A common wiring pattern 3 is formed on that part of the top surface of the head circuit board 1 which is close to the one side edge 1a parallel with the heating resistor 2. The common wiring pattern 3 is formed extending along the heating resistor 2, and conducts to those portions of the heating resistor 2 which correspond to the respective print dots. As shown in Fig. 2, a plurality of individual microcircuits are patterned in that area on the top surface of the head circuit board 1 which is opposite from the common wiring pattern 3 across the heating resistor 2. The patterned individual circuits 4 conduct to the portions of the heating resistor 2 which correspond to the respective print dots. A plurality of driver elements 5 conducting to the patterned individual circuits 4 are mounted in a line along the heating resistor 2. Provided between the driver elements 5 and the other side edge 1b (the side edge opposite from the one side edge 1a) of the top surface of the head circuit board 1 is a ground wiring pattern 7, which is formed extending substantially in parallel with the row of driver elements 5. The ground wiring pattern 7 conducts through metal wires 6, connected by wire bonding, to the respective driver elements 5. A ground connection terminal 8 with a wide width is formed substantially in the central part in the longitudinal direction of, and close to, the other side edge 1b of the top surface of the head circuit board 1. This ground connection terminal 8 conducts to substantially the central portion in the longitudinal direction of the ground writing pattern 7. A plurality of signal connection terminals 9 for supplying various signals to the driver elements 5 are formed on both sides across the ground connection terminal 8. A pair of common-wiring connection terminals 12, 13 wide in width are formed on both sides across the connection terminals 9. The pair of common-wiring connection terminals 12, 13 conduct through the common-wiring connection circuits 10, 11 to each end of the common wiring pattern 3. The line type thermal print head arranged as described above operates in the same manner as the conventional print head under the condition that it is mounted on the printer of a facsimile or the like. More specifically, when a driver element 5 switches from one circuit to another, an arbitrary one of the individual circuits 4 is electrically connected to the ground wiring pattern 7, so that the portion of the heating resistor corresponding to the conducting individual microcircuit 4 generates heat. Consequently, printing is performed at the print dot according to the heat generated. In this example, the ground wiring pattern 7 is not divided about the center into left-side and right-side portions. The ground connection terminal 8 broad in width is connected to about the center in the longitudinal direction of the ground wiring pattern 7. Therefore, electric power for printing can be simultaneously supplied to the left-side and right-side portions of the ground wiring pattern 7 through the ground connection terminal 8. Also, the power supplied to the right-side portion and the power supplied the left-side portion can move from one side to the other. For this reason, when printing takes place for the overall length of the ground wiring pattern 7, even if the number of dots used for printing differs between the right-side and the left-side portion of the ground wiring pattern 7, a voltage difference is prevented from occurring between the left-side and right-side portions. Furthermore, in this example, the ground connection terminal 8 is located substantially in the center of the ground wiring pattern 7. Both common-wiring connection terminals 12, 13 are located at outside positions with respect to the ground connection terminal 8. Therefore, the ground connection terminal 8 as well as both common-wiring connection terminals 12, 13 can be extended up to the other side edge 1b of the head circuit board 1 as shown in Fig. 2. In other words, in contrast to Related Art 1, when the ground connection terminal 8 is mounted by extending it up to the other side edge 1b, there is no chance of its being interfered with the common-wiring connection circuits 10, 11. Accordingly, it becomes easy to mount the connector to the head circuit board 1 and cause the connection terminals to conduct to the connector. For example, a connector 14 for external connection as shown in Fig. 3 can be used to facilitate connection to external wiring. The connector 14 is complete with a plurality of terminal pins 14b fixed in a box 14a. Each terminal pin 1b of the connector 14 has a bifurcated gripper 14b', which is fitted on the other side edge 1b of the head circuit board 1. Thus, the connector 14 is mounted to the head circuit board 1, so that the terminal pins 14b are electrically connected to the ground connection terminal 8, the connection terminals 9 of various signals, or the common-wiring connection terminals 12, 13. According to this example, seven terminal pins 14b are connected to the ground connection terminals 8, three terminal pins 14b to one common-wiring connection terminal 12, and four terminal pins 14b to the other common-wiring connection terminal 13. The bifurcated gripper 14b' of each terminal pin 14b is fitted on the other side edge 1b of the head circuit board 1, and then fixed by soldering or with an electrically conductive paste. In a modification of this example, various external wires may be directly connected to the ground connection terminal 8, connection terminals 9 for various signals, and both common-wiring connection terminals 12, 13. As described above, the ground connection terminal 8, the connection terminals 9 for various signals, and both common-wiring connection terminals 12, 13 are extended up to the other side edge 1b of the head circuit board 1. Therefore, this arrangement enables those connection terminals to be connected simply, easily and firmly to various external wires, a connector for external connection or the like. This effect will become more apparent by comparing the above-mentioned arrangement with the case where there are the common-wiring connection circuits between the ground connection terminal and the other side edge of the head circuit board. In addition, the heating resistor 2, a glass coating 15 covering the common wiring pattern 3 and the individual circuits 4, and a resin coating covering the driver elements 5 are formed on the top surface of the head circuit board 1, as shown in Fig. 3 with a two short and one long dashed line. (2) Embodiment of the invention A line type thermal print head assembly according to an embodiment of the present invention will be described with reference to Figs. 4 to 11. In Fig. 4, reference numeral 101 denotes a line type thermal print head of the same composition as in the above example. More specifically, in this line type thermal print head 102, linear heating resistor 103, a common wiring pattern 104 conducting to the heating resistor 103, a plurality of driver elements 105, and a ground wiring pattern 106 are formed on the top surface of a ceramic head circuit board 102. Furthermore, a plurality of terminal electrodes 107 corresponding to the common wiring pattern 104, the ground wiring pattern 106, and the driver elements 105 are formed on that portion of the top surface of the head circuit board 104 which is adjacent to one side edge 102a. In other words, the terminal electrodes 107 includes the ground connection terminal 8, the signal connection terminals 9, and the common-wiring connection terminals 13, 14 in the above example. Reference numeral 108'denotes a head connector mounted to the side edge portion 102a of the line type thermal print head 101. The head connector 108 includes a connector body 109 and a plurality of terminal metal parts 110 provided in the connector body 109. The connector body 109 is a box-shaped component made of a hard insulating material, such as a hard synthetic resin, and the terminal metal parts are made of leaf springs and have a substantially U-like configuration as shown in Fig. 4. In Fig. 5, a contact surface as one side face of the connector body 109 is that face which comes into contact with the head circuit board 102 when the head connector is mounted. As is clear from Fig. 5, each terminal metal part 110 extends in a direction substantially at right angles to the contact surface 109a when the head connector is mounted, with one end portion of the terminal metal part 110 protruding beyond the contact surface 109a. By bending the protruding end portion sideways to the side of the head circuit board 102, a clasp portion 110a is formed. The shape of the clasp portion 110a is set so that the head circuit board 108 is clasped between the clasp portion 110a and the contact surface 109a when the head connector 108 is in the mounted state. The shape and the position of the clasp portion 110a are set so that the clasp portions 110a contact the terminal electrodes 107 on the surface of the head circuit board 102. A recess 111 is provided at that part of the contact surface 109a of the connector body 109 where a terminal metal part 110 is mounted. The recess 111 extends in the longitudinal direction of the clasp portion 110a. The terminal metal part 110 is so formed as to extend from the inside of the recess 111. In addition, a groove 112 is formed on the contact surface 109a of the connector body 109 so as to extend in the direction of the row of the terminal metal parts 110. In Fig. 5, the contact portion 110a' is that part of each clasp portion 110a which contacts the head circuit board 102. In this embodiment, the contact portion 110a' is set so as to contact the head circuit board 102 where the contact portion 110a' faces the groove 112. Description will now be made of the method of mounting the head connector 108 to the line type thermal print head 101. The head connector 108 is mounted in the direction of the flat surface on the head circuit board 102. In mounting, the edge portion of the head circuit board 102 is clasped between the contact surface 109a of the connector body 9 and the clasp portion 110a. The head connector 108 is positioned so that each terminal metal part 110 can contact the corresponding terminal electrode 107. As shown in Fig. 5, in the mounted condition, the terminal metal part 110 is in contact with the head circuit board 102. A flat part of external wiring is inserted into the connector body 109, and then a key plate 114 is pushed in. Thus, the terminal metal parts 110 are electrically connected to the corresponding wires of external wiring 113. In this embodiment, the contact surface 109a of the connector body 109 is in direct contact with the rear surface of the head circuit board 102, and the contact body 109 is pressed to the head circuit board 102 by elastic force of the clasp portion 110a of each terminal metal part 110. Therefore, the head connector 108 is mounted stably and firmly to the head circuit board 102, leaving no possibility of becoming loose. The connector body 109 is mounted in the direction of the flat surface of the head circuit board 102. On the other hand, the external wiring 113 is inserted into and removed from the connector body 109 is perpendicularly to the head circuit board 102. Hence, the mounting direction of the connector body 109 to the head circuit board 102 and the direction of inserting and removing the external wiring 113 are at right angles to each other. Consequently, there are less chances for the connector body 109 to come off the head circuit board 102. Moreover, the head circuit board 102 is pressed to the contact surface 109a of the connector body 109 by the elastic force of the clasp portion 110a of each terminal metal part 110. Therefore, warpage of the head circuit board 102 can be corrected. Since the wall of the recess 111 is in contact with or close to the terminal metal part 110, the clasp portion 110a is prevented from bending sideways (the left-right direction in Fig. 6). Therefore, the head circuit board 102 can be inserted easily between the connector body 109 and each clasp portion 110a. Because the sideward bending of the clasp portion 110a can be prevented as mentioned above, the elasticity of the clasp portion 110a of the terminal metal part 110 can be increased easily. The provision of the recess 111 decreases the area of the contact surface 109a of the connector body 109, for which reason the contact pressure between the contact surface 109 and the head circuit board 102 is increased. Accordingly, the mounting strength of the head connector 108 can be further increased. Furthermore, due to the provision of the groove 112, it becomes possible to increase the contact pressure of the contact surface 109a of the connector body 109 to the head circuit board 102. The pressing force of each clasp portion 110a is supported by the portions other than the groove 112, in other words, by the portions across the groove 112. This promotes the stable, secure and firm attachment of the head connector 108, obviating any chance of the head connector 108 becoming loose. In this embodiment, the electrical connection end of each terminal metal part 110 is formed in a U-like configuration, and has the contact end of external wiring electrically connected thereto. However, the present invention can be applied to other modes of operation. For example, the end of each terminal metal part 110 to be connected to external wiring may be formed as a straight pin (male type) connector, and the female connector provided at the end of external wiring may be inserted into the male connector. Conversely, the head connector 108 may be formed as a female type and the connector of external wiring may be formed as a male type. INDUSTRIAL APPLICABILITY The present invention can be applied to printers for facsimiles and so on. More specifically, the present invention has wide application as a printer head to be mounted in various types of printers.

Claims: A thermal print head connector (108) which is mountable on a line type thermal print head (101) having connection terminals (107) arranged on a side edge portion (102a), said head connector (108) including: a connector body (109) made of a hard insulating material, such as a hard synthetic resin, and when mounted, being in contact at a contact surface (109a) thereof with the reverse surface of said line type thermal print head (101); and a plurality of terminal metal parts (110) provided in a row at positions corresponding to said respective connection terminals (107) in such a manner as to extend from the contact surface (109a) of the connector body, wherein a clasp portion (110a) of each terminal metal part (110) is formed by bending the protruding end portion of said terminal metal part sideways for holding the line type thermal print head (101) between said clasp portion (110a) and the contact surface (109a) of said connector body of the head connector. A thermal print head connector according to claim 1, wherein recesses (111) for mounting terminal metal parts (110) are provided in the contact surface (109a) of said connector body (109), and wherein each recess (111) extends in the longitudinal direction of said clasp portion (110a), and each terminal metal part (110) extends from the recess (111). A thermal print head connector according to claim 1, wherein a row-direction groove (112) extending in the row direction of said terminal metal parts (110) is formed in the contact surface (109a) of said connector body, and wherein press-contact parts (110a') of said clasp portions (110a) for contacting said line type thermal print head (101) are located so as to face said row direction groove (112). A line type thermal print head assembly including a line type thermal print head (101) having connection terminals (107) arranged on a side edge portion (102a) and a thermal print head connector (108) according to any of the preceding claims which is mounted on said line type thermal print head. A line type thermal print head assembly according to claim 4, wherein said line type thermal print head (101) comprises: a head circuit board (1); a heating resistor (2) extending in a line on the surface of said head circuit board (1); a common wiring pattern (3) extending along said heating resistor (2) and conducting to portions of said heating resistor which correspond to respective print dots; a plurality of individual printed wires (4) formed on the surface of said head circuit board (1) in an area on an opposite side of said heating resistor (2) to said common wiring pattern (3), and conducting to those portions of said heating resistor which correspond to said respective dots; a ground wiring pattern (7) extending along said heating resistor (2) on the surface of said head circuit board (1), and connected to said individual printed wires (4) through a plurality of driver elements (5); a ground connection terminal (8;107) provided substantially in the center of said edge portion (1b) on the side of said ground wiring pattern (7) with respect to said heating resistor (2) on the surface of said head circuit board (1), and conducting to substantially the central portion in a line direction of said ground wiring pattern (7); and a pair of common-wiring connection terminals (12,13;107) in said side edge portion (1b), conducting to both ends of said common wiring pattern (3), and wherein the clasp portions (110a) of said terminal metal parts (110) of the thermal print head connector (108) are connected to at least said ground connection terminal (8;107) and said common-wiring connection terminals (12,13;107) of the line type thermal print head (101). A line type thermal print head assembly according to claim 5, wherein said pair of common-wiring connection terminals (12,13;107) is provided across said ground connection terminal (8;107) in said line direction.

Inventors: NAGAHATA TAKAYA, SATO TADAYOSHI, NAGAHATA, TAKAYA, SATO, TADAYOSHI, NAGAHATA, TAKAYA, C/O ROHM CO., LTD., SATO, Tadayoshi, c/o Rohm Co., Ltd.
Applicants: ROHM CO LTD, ROHM CO., LTD.
Application year: 1996
Main classification: B41J2
IPC codes: B41J2