Abstract:
Flexible cables are connected to a movable member at a first end and a fixed member at a second end, each having a curve in between the first end and the second end. The flexible cables each include a first positioning system near the first end in the curve and a second positioning system near the second end in the curve, and they have different distances between the first positioning system and the second positioning system. The first positioning system and the second positioning system are fixed to a first positioning portion and a second positioning portion respectively. The flexible cables are spaced from each other to define clearances thereamong at the curve.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of Invention  
           [0002]    The invention relates to a flexible cable harness for use in an image forming apparatus. In particular, the invention relates to a flexible cable harness with a plurality of flexible cables that transmit electrical signals from a main body to a carriage in an image forming apparatus, such as a printer, a facsimile machine, and a copier.  
           [0003]    2. Description of Related Art  
           [0004]    Conventionally, there exists ink jet image forming apparatuses, such as a printer, a facsimile machine, and a copier, in which a carriage mounted in an ink cartridge thereon reciprocates in a main scanning direction to perform printing on a recording medium. In such an apparatus as shown in FIG. 6, a round guide shaft  211  is disposed between a left side plate  212   e  and a right side plate  212   f , and a carriage  210  is slidingly guided onto the guide shaft  211  to reciprocate in an X direction. The carriage  210  includes a recording head  215  that ejects ink. When the recording head  215  is designed for color printing, it communicates with a control part  200  fixed to a main body of the image forming apparatus to transmit drive signals via four flexible flat cables (hereinafter referred to as flexible cables) FFC 1 -FFC 4 .  
           [0005]    The flexible cables FFC 1 -FFC 4  are connected to corresponding connectors  201  of the control part  200  at one end and corresponding connectors  203  of the recording head  215  at the other end. The flexible cables FFC 1 -FFC 4  drawn from the connectors  201  are tied in a bundle to a rear frame  212  near the connectors  201  by a binding plate  202  so as to prevent entanglement. The flexible cables FFC 1 -FFC 4  are bent at a curve A and tied in a bundle near the connectors  203  by a binding plate  204 .  
           [0006]    When the carriage  210  reciprocates in the X direction, the flexible cables FFC 1 -FFC 4  also move while bending more at the curve A. Especially, the flexible cables located more inward at the curve A may suffer more stress. Further, while the adjacent cables rub against each other, they are also subjected to stress. For these reasons, the flexible cables may be prone to damage or breakage at an early stage.  
           [0007]    Japanese Laid-Open Patent Publication No. 4-133780 proposes that, as a method for fixing a plurality of flexible cables in a bundle, each flexible cable has the same length between two connectors. Each cable is also provided with its own positioning hole thereon, so as to fit around a protrusion provided on the carriage.  
           [0008]    However, as the length between the connectors is the same on each cable, arranging the connectors separately restricts the connector positions, greatly affects the arrangement of other element parts, and affects the size of the apparatus. Further, as the positioning hole is disposed at one place in the direction of the length of each cable, the conventional problem in that the length between two points to fix each flexible cable by adjusting the position of each cable is not solved.  
         SUMMARY OF THE INVENTION  
         [0009]    The invention thus provides a flexible cable harness whose cables, which have different lengths, are set in place easily and free from undue stress at a curve without having to place a restriction on connector positions, and an image forming apparatus using such a flexible cable harness.  
           [0010]    According to one exemplary aspect of the invention, a flexible cable harness may include a plurality of flexible cables. Each of the cables has a first end connected to a first object and a second end connected to a second object, and at least one of the cables contributes to an electrical connection between the first object and the second object. Each cable includes a curved portion that curves between the first end and the second end, a first positioning system provided near the first end in the curved portion, and a second positioning system provided near the second end in the curved portion. A distance from the first positioning system to the second positioning system is different in each of the plurality of flexible cables such that the more inward the flexible cables are located at the curved portion, the shorter the distance is between the first positioning system and the second positioning system. The first positioning system of each of the plurality of flexible cables is fixed to a first positioning part provided on or near the first object. The second positioning system of each of the plurality of flexible cables is fixed to a second positioning part provided on or near the second object. Each cable is spaced in the curved portion.  
           [0011]    Thus, the flexible cable harness is structured wherein the flexible cables located more inward at the curve have a shorter distance from the first positioning system to the second positioning system. This structure can prevent breakage or damage to the cables caused by deflection at the curve area and sets the cables in place without the need for measuring the distance between the first positioning system and the second positioning system that varies according to each cable.  
           [0012]    Specifically, the first object is a fixed member such as a frame, and the second object is a movable member such as a carriage. The flexible cable harness may be structured where the first positioning system of each flexible cable may be fixed to a first positioning part provided fixedly with the fixed member, and the second positioning system of each flexible cable may be provided on or near the movable member and fixed to a second positioning part, which is movable with the movable member.  
           [0013]    In an image forming apparatus including the flexible cable harness structured as above, a frame may include left and right side plates supporting a guide shaft that guides the carriage in a movable direction and a rear frame provided between the left and right side plates. The carriage may have a substantially box shape and two sides for positioning the recording head. The first positioning part is disposed at a substantially central portion of the rear frame with respect to a left to right direction thereof, and the second positioning part is disposed on one of the two sides of the carriage. The flexible cable harness is kept curved when the carriage reciprocates sideways in the frame, however, the flexible cables are spaced from each other to define a clearance thereamong and free from stress caused by collision against each other. Thus, with this structure of the harness, its durability increases and a burden on maintenance of the image forming apparatus is reduced, thereby increasing the useful life of the image forming apparatus. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    An embodiment of the invention will be described in detail with reference to the following figures wherein:  
         [0015]    [0015]FIG. 1 is a right side view of a printer also serving as a facsimile machine as an example of an image forming apparatus applied to an embodiment of the invention;  
         [0016]    [0016]FIG. 2A is a top view of a recording part in which flexible cables are arranged;  
         [0017]    [0017]FIG. 2B is a front view of the FIG. 2B;  
         [0018]    [0018]FIG. 3 shows a film cable and flexible cables which are provided with positioning systems;  
         [0019]    [0019]FIG. 4 is a perspective view seen from a rear of the printer showing a first positioning part disposed on a rear frame;  
         [0020]    [0020]FIG. 5 is a left side view of a carriage showing a second positioning part disposed on the carriage; and  
         [0021]    [0021]FIG. 6 is a schematic top view showing an image forming apparatus for use with a conventional flexible cable harness. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0022]    An embodiment of the invention will be described in detail with reference to the accompanying drawings. As shown in FIG. 1, a printer  1  includes a normal facsimile machine function that does the following according to a key input through an operation panel  6 : sets various operations; reads a document image(s) by a document reading unit  5 ; converts document images into transmission data; encodes the transmission data; transmits or receives facsimile data to or from other facsimile machines via a communications line; decodes the received data; and performes recording of the decoded facsimile data to a sheet of paper P in the recording unit. The printer  1  further includes a copier function that scans in a document by a contact image sensor (CIS) of the document reading unit  5  to form a color image on a sheet P by each unit of a recording part, a printer function that receives print data transmitted from an external device such as a personal computer via a printer cable or by wireless such as infrared radiation to form a color image onto a recording sheet P according to the received data, and a scanner function that uses the document reading unit  5  to send the read image to the external device.  
         [0023]    A main case of the printer  1  is made up of a main lower case  1   a  and a main upper case  1   b , which are both made from synthetic resin. The lower case  1   b  accommodates an ink jet recording part  2  and includes a backward-leaning paper feed tray  3  disposed at an upper rear part. Recording sheets P for image formation are supplied from the paper feed tray  3  into the printer  1 . The lower case  1   a  is covered with the upper case  1   b . On an upper surface of the main upper case  1   b , a document loading part  4  is disposed toward the rear and the document reading unit  5  is disposed toward the front. The document reading unit  5  is covered with an operation panel  6  having an operation key part  6   a  and a display  6   b . The operation key part  6   a  includes function keys and a ten-key numeric pad. The document loading part  4  is provided, on both sides, with a pair of document guide members  8  that guide both side edges of a document to be conveyed into the document reading unit  5 .  
         [0024]    An under surface of the main lower case  1   a  is covered with a metal bottom cover plate  7 , and a control part  100  is disposed in an internal space of the main lower case  1   a . The control part  100  includes a control circuit board, a power supply circuit board, and a network control unit (NCU) circuit board that allows transmission and reception of conversation or facsimile data with the party on the end of the telephone or facsimile machine by telephone lines (which are not shown). A handset (not shown) for two-way conversation with another telephone is placed on a cradle outwardly projecting from a side of the main lower case  1   a . A speaker for issuing alarms and monitoring calls is secured to the right rear side of the main lower case  1   a.    
         [0025]    The sheets P stacked on the paper feed tray  3  are separated from the top of the stack one by one by a sheet feed roller  21  and a separator disposed at a rear portion of the main lower case  1   a . The sheet feed roller  21  and the separator are structured as a known paper feed mechanism. The separated sheet P is fed to a conveying roller  22  such that the position of the leading edge of the sheet P is adjusted. The sheet P is then fed between a recording head  15  (FIG. 2) and a platen  25 , and pinched between a pair of ejecting rollers  23  and  24  disposed vertically on a downstream side of a sheet conveying direction. While the sheet P is pinched and conveyed between the ejecting rollers  23  and  24 , ink drops are ejected onto the sheet P in accordance with printing commands to form an image, and the sheet P where the image is formed is ejected to a discharged tray  26 .  
         [0026]    As shown in FIGS. 1 and 2, a round guide shaft  11  is disposed between a left side plate  12   e  and a right side plate  12   f , and a carriage  10  in a recording part  2  is slidably mounted to the guide shaft  11  at its lower rear end. The recording head  15  of a cartridge type is detachably mounted in the carriage  10  such that the recording head  15  faces downward and is pinched between left and right side plates  32  of the carriage  10 . To perform color printing, the recording head  15  has four nozzle portions  15   a  for ejecting four ink colors of cyan, yellow, magenta, and black respectively, on its lower surface. Ink cartridges  16 , each containing a corresponding ink which is to be supplied to the recording head  15 , are attached to the recording head  15  so as to be detachable from the top of the recording head  15 . The ink cartridges  16  are held downward by presser levers  17 , which are rotatable frontward and disposed on the top end of the carriage  10 .  
         [0027]    A timing belt (not shown) extending parallel with the guide shaft  11  is looped around a driven pulley (not shown), which is disposed to one side of the rear frame  12 , and a driving pulley (not shown), which is fixed to an output shaft of a driving motor, such as a stepping motor, that can rotate both clockwise and counterclockwise. The timing belt placed on the pulleys is connected to the carriage  10 , thereby enabling the carriage  10  to reciprocate parallel with the guide shaft  11 .  
         [0028]    Printing operations by the carriage  10  will be described with reference to FIG. 2. A maintenance portion  27  is provided on the right side of the platen  25  outside the recording area. A nozzle wiping device that wipes ink drops adhered to the surface of the nozzle portions  15   a  of the recording head  15  and a purge device  28  that recovers the state of the ink to be ejected from the recording head  15  are disposed in the maintenance portion  27 . The purge device  28  is provided with suction caps  28   a . The purge device  28  is constructed such that the nozzle portions  15   a  of the recording head  15  are covered with the corresponding suction caps  28   a , a negative pressure generated by a pump is applied to the nozzle portions  15   a , poor quality ink remaining in the recording head  15  is removed by suction, and the state of ink ejection is recovered. The purge device  28  in the maintenance portion  27  is positioned at the home position (at the right end in FIG. 2), and the purge device  28  also serves as a capping device that covers all the nozzle portions  15   a  of the recording head  15  of the carriage  10  to prevent drying of ink. The suction caps  28   a  also serve as protective caps. A flushing portion  29  that causes ink to be ejected tentatively from each nozzle portion  15   a  of the recording head  15  in order to prevent ink clogging is provided on the left end of the platen  25 .  
         [0029]    A flexible cable harness  109 , which is made by tying flexible cables in a bundle and transmits electrical signals between the recording head  15  and a control part  100 , will be described. The flexible cable harness  109  electrically connects the control part  100 , that is usually fixed to a bottom plate or a frame of the printer  1  and sends image signals for recording and control signals, to the recording head  15  that reciprocates from side to side with respect to FIG. 2 and ejects ink from the nozzle portions  15   a  in accordance with the image signals and the control signals. One end of each of the flexible cables (FFC 1  to FFCn in FIG. 3), that make up the flexible cable harness  109 , is connected to a corresponding connector  101  provided in the control part  100 , and the other end is connected to a corresponding connector  103  of the recording head  15 .  
         [0030]    As described above, the flexible cable harness  109  is connected to a fixed part at one end and a movable part at the other end. If the flexible cable harness  109  is not fixedly held at any place, it may unnecessarily contact or rub against other structural elements in the printer  1  with the movement of the flexible cable harness  109  attached to the movable part, and may resultantly become damaged. Therefore, the flexible cables coming from the connectors  101  are fixed to the rear frame  12  via a first positioning part  105 . The flexible cables are sent from the rear of the rear frame  12  (where the control part  100  is placed) to the front along a first guide part  105   a  of the first positioning part  105 , bent at the front to form a curve A, inserted into a second positioning part  106  and fixedly held therein.  
         [0031]    In detail, the flexible cables are inserted and guided between a second guide part  106   a  and a third guide part  106   b  of the second positioning part  106 , and are held in the second positioning part  106 . The flexible cables are further guided inside the carriage  10  along an internal surface of a fourth guide part  106   e , and connected to the connectors  103  of the recording head  15 . Thus, the flexible cable  109  is fixed not only to the connectors  101  and  103  but also at the first and second positioning parts  105  and  106 . Accordingly, the flexible cable harness  109  is fixed at the first positioning part  105 , which is the fixed part, and moved by the second positioning part  106  that is moved with the travel of the carriage  10 . Even when the position and the state of the curve A are changed, the flexible cable harness  109  can communicate electrical signals without unnecessarily rubbing against the other structural elements.  
         [0032]    The more internally placed the flexible cables are relative to the curve A, the length of a cable from the first positioning part  105  to the second positioning part  106  should be set shorter. However, to fix the flexible cables, measuring the length from the first positioning part  105  to the second positioning part  106  every time each one of the flexible cables is arranged is inefficient and may cause an error. Therefore, in the embodiment, a mechanism that can fix and hold the flexible cables with a single motion without the necessity of measuring the length for each cable is adopted. The details of the mechanism will be described as follows.  
         [0033]    Appropriate spacing among the adjacent flexible cables at the curve A is determined by various factors such as the cable elasticity, the number of cables, the cable thickness, width, length, the size of the curve, and the shape of the curve. When the flexible cable harness  109  is given an appropriate elasticity to form an optimum curve or the cables are likely to rub against the other structural elements of the printer  1 , a film cable FC 1  (FIG. 3, described later in detail) that does not contribute to the electrical connection may be used as an interference or protective cable and is arranged along other cables so as to be placed at the outside, inside, or each side of the curve A. Based on the spacing among the adjacent flexible cables determined by the above factors, the distance from the first positioning part  105  to the second positioning part  106  required for each cable is calculated in such a manner that the more outward at the curve A the flexible cables are located, the distance becomes correspondingly longer. The calculated length is assigned to each one of the flexible cables.  
         [0034]    The distance between the two positioning places, which varies according to each cable, will be described in detail with reference to FIG. 3. In FIG. 3, the film cable FC 1  is made of a film that does not contribute to an electrical connection and has a length L between the two positioning places. A flexible cable FFC 1  is located outside the flexible cable FC 1  at the curve A and has a length L1 between the two positioning places. A flexible cable FFC 2  is located outside the cable FFC 1  at the curve A and has a length L2 between the two positioning places. A flexible cable FFCn is placed outermost at the curve A and has a length Ln between the two positioning places. Flexible cables FFC 3  to FFCn- 1  are not shown in FIG. 3. As shown in FIG. 2, the flexible cables FFC 1  to FFCn are connected to the control part  100  at their left ends and to the recording head  15  at their right ends, thereby contributing to an electrical connection between the control part  100  and the recording head  15 . A beginning of the film cable FC 1  is at the first positioning part  105  and an end of the film cable FC 1  is at the second positioning part  106 .  
         [0035]    The film cable FC 1  is provided with a first positioning system  107  at the left end (shown in FIG. 3). The first positioning system  107  includes a pair of positioning holes  107   c  aligned vertically across the width of the film cable FC 1 . Projections  105   c  (FIG. 4) of the first positioning part  105  are to be inserted into the positioning holes  107   c . The film cable FC 1  is provided with a second positioning system  108  at the right side (shown in FIG. 3) thereof. The second positioning system  108  includes a pair of positioning holes  108   c  aligned vertically across the width of the film cable FC 1 . Projections  106   c  (FIG. 5) of the second positioning part  106  are to be inserted into the positioning holes  108   c . The first positioning system  107  and the second positioning system  108  are integrally formed with the film cable FC 1 . In this case, a length between the first positioning system  107  and the second positioning system  108 , in other words, a length between a center line of the positioning holes  107   c  and a center line of the positioning holes  108   c , is set to the length L.  
         [0036]    Similarly, the flexible cables FFC 1  to FFCn each have a first positioning system  107  with a pair of positioning holes  107   c  aligned vertically across their width near their left ends. The projections  105   c  of the first positioning part  105  are to be inserted into the positioning holes  107   c . Further, the flexible cables FFC 1  to FFCn each have a second positioning system  108  with a pair of positioning holes  108   c  aligned vertically across their width near their right ends. The projections  106   c  of the second positioning part  106  are to be inserted into the positioning holes  108   c.    
         [0037]    In the embodiment, the first positioning system  107  and the second positioning system  108  provided on each of the flexible cables FFC 1  to FFC are formed by bonding tab-shaped sheets  107   a  and  108   a , which have been punched separately, to bonded surfaces  107   b  and  108   b  at both ends of the cable using adhesive or double-faced tape. Not being limited to this, however, the first positioning system  107  and the second positioning system  108  may be integrally formed with the flexible cable FFC 1  to FFCn during manufacturing, as is the case with the film cable FC 1 .  
         [0038]    When the first and second positioning systems  107  and  108  are attached to each cable FFC 1  to FFCn, the manufacturing of various flexible cables is simplified. When the first and second positioning systems  107  and  108  are integrally formed with each cable, it is necessary to provide production facilities with a plurality of presses in order to make the first and second positioning systems  107  and  108  at different positions. On the other hand, when the first and second positioning systems  107  and  108  are attached, new facilities that do not include the machine that make the tab-shaped sheets  107   a  and  108   a  are not necessary.  
         [0039]    When the first and second positioning systems  107  and  108  are integrally formed with each cable FFC 1  to FFCn, manufacturing processes can be reduced, production costs can be reduced, and positioning fluctuations can be minimized.  
         [0040]    When the tab-shaped sheets  107   a  and  108   a  are bonded to a specific place on each of the flexible cables FFC 1  to FFCn, the use of a jig, where the lengths of the flexible cables for bonding are indicated beforehand, may facilitate bonding precisely and smoothly without the need to measure such lengths as occasion demands.  
         [0041]    In any of these instances, the length between the first positioning system  107  and the second positioning system  108  (the length between the center line of the positioning holes  107   c  and the center line of the positioning holes  108   c ) is set to any of the lengths L1 to Ln which are allocated to the cables. In the example shown in FIG. 3, the length L is the shortest, and the length Ln is the longest. In other words, the following equation holds: L&lt;L1&lt;L2&lt; . . . &lt;Ln-1&lt;Ln. A difference of each length between L and L1, between L1 and L2, . . . between Ln-1 and Ln is set such that a curvature radius at the curve A is reduced by a specified amount as the flexible cables FFC 1  to FFCn are located more inward at the curve A. However, it can be changed according to the shape of the curve A and the material used for the cable.  
         [0042]    Specifically, in the embodiment, each of the cables FC 1 , FFC 1  to FFCn is made of a 0.15 mm-thick and nearly 20 mm-wide flame-retardant polyester film sheet (for cables FFC 1  to FFCn, further done with conductor wiring). The difference in length between the adjacent cables, that is, between L and L1, between L1 and L2, . . . between Ln-1 and Ln is set to 1.5 mm. However, it is not limited to this value. It should be taken for granted that an optimum cable length difference may vary according to the cables thickness and materials to be used. In the case of flexible cables used in general printers, when the length difference is from 1 mm to 3 mm, problems caused by cable deflection, such as cable breakage or frequent contacts between the cables can be prevented, and damage or breakage at an early stage can be also prevented.  
         [0043]    The first positioning part  105  where the first positioning system  107  for each of the flexible cables FC 1  and FFC 1  to FFCn is fixedly maintained will be described in detail with reference to FIG. 4. The first positioning part  105  is inserted into a substantially rectangular opening  12   g  provided in a specified position of the rear frame  12  from the rear of the rear frame  12  (the side where the control part  100  shown in FIG. 2 is located). The first positioning part  105  has the projections  105   c , which are vertically aligned with respect to the cable width direction so as to be engaged in the positioning holes  107   c  formed in the first positioning system  107  provided on each of the flexible cables FC 1  and FFC 1  to FFCn. In the embodiment, the film cable FC 1  to be positioned inner mostly at the curve A (FIG. 2) is first placed in the first positioning part  105 , and the flexible cables FFC 1  to FFCn are overlaid on the film cable FC 1  in this order. Finally, a lid  105   b  is closed in a direction of arrow C, thereby the first positioning system  107  of each cable can be reliably fixed to the first positioning part  105 . Ends extending leftward from the first positioning systems  107  of the flexible cables FFC 1  to FFCn shown in FIG. 3, exclusive of the film cable FC 1 , are connected to the control part  100  (FIG. 2), and the right ends of the flexible cables FFC 1  to FFCn inclusive of the film cable FC 1  (shown in FIG. 3) are sent along the first guide part  105   a  from the opening  12   g  to the front of the printer  1 , curved to form the curve A, and taken in the carriage  10  (FIG. 2).  
         [0044]    In the carriage  10  as shown in FIG. 5, the film cable FC 1  and the flexible cables FFC 1  to FFCn are attached to the third guide part  106   b  of the second positioning part  106 , which is formed in a ribbed shape on the left side plate  32  of the carriage  10 . The two positioning holes  108   c  of the second positioning system  108  provided on each of the film cable FC 1  and the flexible cables FFC 1  to FFCn are fitted over the two projections  106   c  formed on the left side plate  32  of the carriage  10 , so that the cables are positioned in place. The second positioning part  106  is mounted on the left side plate  32  so as to cover the second positioning system  108  of each cable. The flexible cables FFC 1  to FFCn are inserted into the second positioning part  106  with a specified angle θ (FIG. 2) relative to a direction perpendicular to the travel direction of the carriage  10  by the guide of the second guide part  106   a  and the third guide part  106   b . The flexible cables FFC 1  to FFCn are brought inside the carriage  10  as shown in FIG. 2, a presser lid  106   d  is closed in such a manner as to fold into the direction of arrow D in FIG. 5, thereby the second positioning system  108  of each cable is reliably fixed on the carriage  10 . Thereafter the flexible cables FFC 1  to FFCn are connected to the connectors  103  of the recording head  15 . Then, the recording head  15  is mounted on the carriage  10 .  
         [0045]    In the conventional structure shown in FIG. 6 where the binding plates  204  allow the flexible cable harness  207  to be sent in parallel with the direction X of which the carriage  210  moves, the flexible cable harness  207  may heavily collide against the left side plate  212   e  at the curve A and may swing from the binding plates  204  greatly and vertically, and reaction stress may focus on the curve A of the flexible cable harness  207  or around the binding plates  204 , causing breakage of the cables at an early stage. Although it is not shown, for the sake of scattering the reaction stress applied to the curve A and the binding plates  204  around, it can be considered that the binding plates  204  may be modified to guide the harness in a lower-left direction in FIG. 6. However, when the carriage  210  moves toward the left end in FIG. 6, the arc of the curve A will expand and a great space to the left side plate  212   e  or to the lower-left part of the figure will be needed. If there is no space for it, the curve A may be pushed into or collide against the left side plate  212   e , thereby increasing the stress applied to the curve A and the binding plates  204  around.  
         [0046]    In the embodiment, as shown in FIG. 2, the second guide part  106   a  and the third guide part  106   b  of the second positioning part  106  pinch the flexible cable harness  109  from both sides thereof so as to guide it with a specified angle θ toward the first positioning part  105 , relative to the direction perpendicular to the travel direction of the carriage  10 . In this case, the angle θ for example is an angle with which each cable can be bent toward the first positioning part  105  without suffering undue stress even when the carriage  10  moves to the left end or the center in the figure. As the angle θ becomes a part of the curvature of the curve A, even when the carriage  10  moves to the left end (a position indicated by a double dashed chain line), each cable is set with such an angle so as to be free from undue stress capable of forming the curve A with the necessary curvature and eliminates the need for a great space in a main scanning direction. Thus, this prevents the cables from being broken by stress fatigue generated by colliding against the left side plate  12   e  at the curve A. To obtain the above effect, it is desirable that the angle θ is within the range of 35° to 60°. In the embodiment, the second guide part  106   a  and the third guide part  106   b  are formed such that the angle θ is 50°. However, the optimum value for the angle θ varies depending on the material used for the flexible cables FFC 1  to FFCn, their thickness, a positional relationship between the control part  100  and the carriage  10 , and the movable range of the carriage  10 .  
         [0047]    In FIGS. 4 and 5, the diameter of the positioning holes  107   c  and  108   c  provided on the first and second positioning systems  107  and  108  is shown larger than the diameter of the projections  105   c  and  106   c  provided on the first and second positioning parts  105  and  106 , however it can be decreased. Especially when the positioning holes  107   c  and  108   c  are provided on the resilient tab-shaped sheets  107   a  and  108   a  or integrally provided with the film cable FC 1  or the flexible cables FFC 1  to FFCn, decreasing the diameter of the positioning holes  107   c  and  108   c  smaller than the diameter of the projections  105   c  and  106   c  makes the positioning holes  107   c  and  108   c  tightly fit around the projections  105   c  and  106   c , thereby reliably engaging each other. This prevents the cables from loosening and coming apart when the cables are attached to the first and second positioning parts  105  and  106  or the structural elements of the first and second positioning parts  105  and  106  are mounted.  
         [0048]    The flexible cables FFC 1  to FFCn in the embodiment are set and kept in place with a two-point attachment, the two positioning holes  107   c  and  108   c  are each provided on both ends thereof. Compared with a single-point attachment, cables do not rotate around a positioning point as a pivot and are not inclined and displaced.  
         [0049]    As described above, the tab-shaped positioning systems  107  and  108  are integrally formed with or separately attached to each cable at the two specified places with respect to its length. However, other shapes or mechanisms can be used without departing from the scope of the invention. The above embodiment has been described with a case where the cables are connected to the fixed part at one end and the movable part at the other end, however both ends of the cable harness can be connected to the fixed part or different movable parts as long as the harness is curvedly connected between two points. Further, the embodiment has been described with a flexible cable harness made of a plurality of flexible flat cables, however, it is not limited to this. The invention can be put into practice as long as a harness is made of similar flexible cables.  
         [0050]    According to the embodiment, the flexible cable harness  109  is connected to the fixed part (the control part  100 ) at one end and the movable part (the carriage  10 ) at the other end and includes a plurality of flexible cables FFC 1  to FFCn tied in a bundle, and at least one of the cables contributes to the electrical connection between the fixed part and the movable part. Each of the flexible cables FFC 1  to FFCn is bent between one end and the other end thereof to form the curve A, and includes the first positioning system  107  near one end and the second positioning system  108  near the other end. The distance between the first positioning system  107  and the second positioning system  108  varies depending on the flexible cables FFC 1  to FFCn. As the first and second positioning systems  107  and  108  are attached to the first and second positioning parts  105  and  106  respectively, the flexible cables FFC 1  to FFCn are spaced from each other at the curve A. Thus, there is no need to set the flexible cables FFC 1  to FFCn in place by measuring the length between the two positioning systems (L, L1, L2, . . . , Ln) that varies according to each cable. Upon manufacturing or maintenance of an apparatus using the flexible cable harness  109 , the flexible cables FFC 1  to FFCn can be set in place easily.  
         [0051]    Further, the flexible cable harness  109  is structured wherein the flexible cables located more inward at the curve A have a shorter distance from the first positioning system  107  to the second positioning system  108 . This structure can prevent breakage or damage to the cables FFC 1  to FFCn caused by deflection at the curve A and sets the cables FFC 1  to FFCn in place without the need for measuring the distance varying according to each cable.  
         [0052]    The flexible cable harness  109  is structured wherein the distance between the first positioning system  107  and the second positioning system  108  is set in each cable such that a curvature radius at the curve A is reduced by a specified amount as the flexible cables FFC 1  to FFCn are located more inward at the curve A. With this structure, as long as the distance from the first positioning system  107  to the second positioning system  108  is determined for the outermost and innermost cables, it is easy to determine the distance for other cables between the innermost and outermost cables.  
         [0053]    In the flexible cable harness  109 , the flexible cables FFC 1  to FFCn are set in position by engagement with the first and second positioning systems  107  and  108  and the first and second positioning parts  105  and  106 . This structure enables a snap attachment of the cables, and is extremely effective even when maintenance is performed where a number of adjustment tools can not be prepared. Further, the first and second positioning systems  107  and  108  are provided on the shorter side (i.e., inner side) of each of the flexible cables FFC 1  to FFCn, and the positioning holes  107   c  and  108   c  thereof, which are provided outside across the width of each cable, are fitted around the corresponding projections  105   c  and  106   c  provided on the first and second positioning parts  105  and  106 . Thereby the flexible cables FFC 1  to FFCn are set in place. In other words, with a simple engagement of holes and projections, the first and second positioning systems  107  and  108  can be reasonably manufactured and the necessary positioning accuracy can be also ensured.  
         [0054]    In the printer  1  using the flexible cable harness  109 , the fixed part is the control part  100 , the movable part is the carriage  10  mounting the recording head  15  thereon, the flexible cable harness  109  is connected between the control part  100  and the carriage  10 . Thus, it is possible to provide an image forming apparatus that is compact in size, highly durable, and facilitates manufacturing and maintenance. The first positioning part  105  and the second positioning part  106  include the projections  105   c  and  106   c , and lids  105   b  and  106   d  that cover and fix the first positioning system  107  and the second positioning system  108  engaged with the projections  105   c  and  106   c , respectively. Thus, in the printer  1 , the flexible cables FFC 1  to FFCn can be attached with a snap, and it is extremely effective even when maintenance is performed where a number of adjustment tools can not be prepared.  
         [0055]    While the invention has been described in detail with reference to a specific embodiment thereof, it should be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention.