Abstract:
A cable reel structure includes a mobile member including a top guard portion, from which extend at least two (first and second) connector units configured to receive outside circuits. Each of the connector units contains bus bars extending therethrough, such that the bus bars can be bonded to the outside circuits by a welding machine equipped with an anvil and a horn. The connector units are placed in staggered positions to each other, and with respect to a diametrical center line of the cable reel, such that, even after the mobile member has been mounted onto the fixed member, the welding of the bus bars to the outside circuits can be performed, successively in the first connector unit and the second connector unit, by rotating the mobile member after the welding has been performed in the first connector unit. Ultrasonic or resistance welding can thus be effected in those connector units more easily.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a cable reel structure for mounting into a vehicle steering system e.g. for automobiles. The cable reel structure includes a fixed member and a mobile member (rotor part) mounted thereon in a freely rotatable manner. More particularly, the invention concerns a plurality of connector units mounted on the mobile member. In such connector units, connections can easily be established between electrical cables (external circuits) and bus bars (internal circuits).  
           [0003]    2. Description of Background Information  
           [0004]    A steering wheel of a vehicle generally contains an airbag and an inflator for inflating the airbag. In such a construction, the cable reel, i.e. rotary connector, serves as a means for connecting the inflator to the vehicle&#39;s body side circuit. As shown in FIG. 1, the cable reel  1  includes a fixed member  2  that defines an external cylindrical portion and a bottom guard portion, and a mobile member  5  that defines an internal cylindrical portion and a top guard portion, the two members together forming a torus-shaped enclosure having a hollow inner space. As mentioned above, the mobile member  5  is mounted with the fixed member  2  in a freely rotatable manner. The fixed member  2  is then fixed with a combination switch body  3 , which is in turn fixed to a steering column  4 . Conversely, the mobile member  5  is fitted with a steering wheel. The torus-shaped enclosure contains a flat cable  6  in a spiraled condition. One end portion of the flat cable  6  is attached to the fixed member  2 , while the other end portion is attached to the mobile member  5 , so that the latter is connected to an external electrical cable. When the steering wheel is turned in a clockwise or counter-clockwise manner, the flat cable  6  is wound or unwound in conjunction with corresponding rotations of the mobile member  6 .  
           [0005]    The mobile member  5  includes a top guard portion carrying a connector unit  7 , which projects towards the steering wheel. The flat cable  6  is connected to outside electrical circuits through the connector unit  7 . When the number of outside circuits to be connected thereto is rather limited, the connector unit  7  may include only one array of pole cavities. However, when the number of outside circuits must be increased, the connector unit  7  may include two arrays of pole cavities, so as to form a multipolar configuration in the connector unit  7 , as shown in FIG. 2.  
           [0006]    Alternatively, the connector unit  7  may be divided into two subdivisions  7 A and  7 B located on different sites of the top guard portion, as shown in FIG. 3.  
           [0007]    However, when the connector unit  7  is enlarged on a single site and the number of poles therein is increased, the number of electrical cables to be connected will be increased correspondingly. The end portions of the electrical cables will then become more entangled and difficult to handle. The structure of the connector unit  7  thus becomes more complex, and the number of steps for assembling the structure is increased.  
           [0008]    Alternatively, as shown in FIG. 3, the connector unit  7  may be divided into two subdivisions  7 A and  7 B, which are placed at two symmetrically opposed positions on a diametrical center line of the mobile member  5 .  
           [0009]    In the above construction, the mobile member is mounted onto the fixed member which is immobilized at a fixed position. In such a construction, however, a plurality of connector units e.g.  7 A and  7 B cannot be welded successively simply by displacing the mobile member through a rotating action. For instance, a welding machine, equipped with an anvil  10  and a horn  11 , must first be provided (shown in broken lines in FIG. 3). The anvil  10  and horn  11 , once placed over the mobile member  5 , are then reciprocated in a linear direction in the direction of the arrows in FIG. 3 while performing welding. Accordingly, when one of the subdivisions  7 A and  7 B is welded, the other, which is located diametrically opposite, must be placed in a position interfering with the anvil  10 .  
           [0010]    Accordingly, when the mobile member  5  is assembled with the fixed member  2 , which is immobilized in turn, a plurality of subdivisions  7 A and  7 B can no longer be welded by an ultrasonic or resistance welder simply by effecting a rotating displacement of the mobile member  5 .  
           [0011]    Accordingly, the bus bars and electrical cables in the plurality of subdivisions  7 A and  7 B must be welded with the mobile member  5  not yet attached to the fixed member  2  and thus able to move up and down. Alternatively, the electrical cables may be connected to the connector units of the mobile member  5 , before the latter is attached to the fixed member  2 . However, in such a case, the assembling operation of the cable reel  1  will become very complicated.  
         SUMMARY OF THE INVENTION  
         [0012]    In order to solve such problems, the present invention has been contemplated to provide a cable reel structure which includes a torus-shaped enclosure defined by a fixed member and a mobile member mounted thereon, the torus-shaped enclosure containing a flat cable or harness. The above mobile member includes a top guard portion, from which a plurality of connector units extend upwardly. The above flat cable or harness is then connected to bus bars. Subsequently, these bus bars are weld-bonded to the electrical cables in those connector units.  
           [0013]    To this end, there is provided a cable reel structure configured to be mounted into a steering system for vehicles. The cable reel structure includes a fixed member, a mobile member having a top guard portion, and an enclosure having a diametrical center line and storing a flat cable. The flat cable contains several conductor elements respectively including a first end portion to be fixed to the fixed member and a second end portion to be fixed to the mobile member, such that the flat cable can be connected to outside circuits.  
           [0014]    The second end portions of the conductor elements respectively include bus bars bonded thereto.  
           [0015]    Further, the top guard portion of the mobile member includes at least first and second connector units adapted to receive the outside circuits, and each of the at least first and second connector units contains the bus bars extending there through.  
           [0016]    The at least first and second connector units can then be placed in staggered positions with respect to the diametrical center line, such that, even after the mobile member has been mounted on the fixed member, welding of the bus bars to the outside circuits can be performed, successively in the at least first connector unit and the at least second connector unit, by rotating the mobile member after the welding has been performed in the at least first connector unit.  
           [0017]    Preferably, the cable reel structure is defined by a fixed member and a mobile member so as to form a torus-shaped enclosure.  
           [0018]    Preferably yet, the welding is performed by a welding machine including an anvil and a horn. The anvil and the horn form a working zone, within which they are moved closer to, or farther from, each other, while performing the welding in the at least first connector unit, and the staggered positions are defined such that the at least second connector unit is placed outside the working zone.  
           [0019]    Suitably, the at least first and second connector units respectively include the same number of connector poles.  
           [0020]    As mentioned above, a plurality of connector units are placed at staggered positions to one another. Accordingly, when the bus bars and outside circuits (electrical cables) in a first connector unit have been welded, the mobile member can be rotated around a fixed axis. The bus bars and outside circuits in a second connector unit are then welded without being impeded by the first connector unit. In this manner, welding operations can be performed even after the mobile member has been mounted onto the fixed member. Welding operations are thus carried out more efficiently, and are more amenable to automation.  
           [0021]    Further, when the connector units are configured so as to each contain the same number of connector poles, welding can be effected using the same anvil welder body and horn welder body.  
           [0022]    In another aspect of the present invention, a method is provided for assembling a cable reel structure for mounting in a steering system for automobiles. The method includes provision of a cable reel structure including a fixed member, a mobile member having a top guard portion and an enclosure having a diametrical center line and storing a flat cable. The flat cable contains several conductor elements respectively including a first end portion to be fixed to the fixed member and a second end portion to be fixed to the mobile member, such that the flat cable can be connected to outside circuits. The second end portions of the conductor elements respectively include bus bars bonded thereto.  
           [0023]    The method may further include provision of at least first and second connector units on the top guard portion of the mobile member, which are adapted to receive the outside circuits. Each of the at least first and second connector units contains the bus bars extending therethrough. The at least first and second connector units are located at staggered positions with respect to the diametrical center line.  
           [0024]    The method may further include welding of the bus bars to the outside circuits in the at least first connector unit, rotating the mobile member after the welding has been performed in the at least first connector unit and welding the bus bars to the outside circuits in the at least second connector unit.  
           [0025]    In a further aspect of the present invention, the method utilizes a welding machine which includes an anvil and a horn which form a working zone within which they are moved closer to, or farther from, each other, during welding. The at least first connector unit is initially located within the working zone for welding of the bus bars to the outside circuits in the at least first connector unit. The at least second connector unit is initially located outside the working zone so as not to interfere with movement of the anvil and the horn during welding of the bus bars to the outside circuits in the at least first connector unit.  
           [0026]    In a still further aspect of the present invention, rotation of the mobile member locates the at least second connector unit within the working zone for welding of the bus bars to the outside circuits in the at least second connector unit. Rotation of the mobile member also locates the at least first connector unit outside the working zone so as not to interfere with movement of the anvil and the horn during welding of the bus bars to the outside circuits in the at least second connector unit.  
           [0027]    Further, the welding may include ultrasonic welding or resistance welding. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]    The above and the other objects, features and advantages of the present invention will be made apparent from the following description of the preferred embodiments, given as non-limiting examples, with reference to the accompanying drawings, in which:  
         [0029]    [0029]FIG. 1 is a cross-sectional side view of a conventional cable reel, illustrating its general construction;  
         [0030]    [0030]FIG. 2 is a top plan view of a prior art cable reel;  
         [0031]    [0031]FIG. 3 is a top plan view of another prior art cable reel;  
         [0032]    [0032]FIG. 4 is a top plan view of a cable reel structure according to the present invention;  
         [0033]    [0033]FIG. 5 is a cross-sectional side view of the cable reel structure of FIG. 4; and  
         [0034]    [0034]FIG. 6 is a schematic top plan view showing relative positions between connector units and a welding machine.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0035]    A cable reel  20  shown in FIGS. 4 and 5 is mounted into a steering system for a vehicle e.g. automobile, as in the case of the conventional construction shown in FIG. 1. A fixed member  21  including a cylindrical outer wall is fixed to a steering column (not shown in the figures) on an assembly line, while a mobile member  22  including a cylindrical inner wall is fixed to a steering wheel.  
         [0036]    The mobile member  22  is mounted onto the fixed member  21  so as to form a torus-shaped enclosure  23 , in which a flat cable  24  is stored in a spiraled condition.  
         [0037]    The mobile member  22  includes a top guard wall  22   a , which carries first and second connector units  30  and  31 , formed unitarily and in one piece therewith and projecting therefrom. As shown in FIG. 5, each of the first and second connector units  30  and  31  has a substantially rectangular parallelepiped form, having, inter alia, first ( 30   a  and  31   a ) and second ( 30   b  and  31   b ) long sidewalls. Of course, the connector units may have any suitable configuration. The first long sidewalls ( 30   a  and  31   a ) are located diametrically in the outer side, relative to the second long sidewalls ( 30   b  and  31   b ), in the radial direction of the torus-shaped cable reel. Each of the first and second connector units  30  and  31  then contains terminals aligned in a suitable array. The base portion (cable reel side) of the first connector unit  30  includes bottom openings  30   a - 1  and  30   b - 1  which face each other in the corresponding first and second long sidewalls  30   a  and  30   b . Likewise, the base portion (cable reel side) of the second connector unit  31  includes bottom openings  31   a - 1  and  31   b - 1  which face each other in the corresponding first and second long sidewalls  31   a  and  31   b.    
         [0038]    As mentioned above, each of the bus bars  25  includes a first end portion welded to a bared conductor element of the flat cable  24  and a second end portion  25   a  projecting in an array between the openings  30   a - 1  and  30   b - 1  (and,  31   a - 1  and  31   b - 1  in the case of the second connector unit  31 ). The first and second connector units  30  and  31  respectively include a top opening, through which are inserted wire cores  35   a  exposed from the end portions of outside electrical cables  35 . A wire core  35   a  of an electrical cable  35  is then superposed on the second end portion  25   a  of a corresponding bus bar  25 . Subsequently, a welding tip  40   a  of the anvil  40  and a welding tip  42   a  of the horn  42  are inserted through the bottom openings  30   a - 1  and  30   b - 1  (and  31   a - 1  and  31   b - 1 ), and bond the wire cores  35   a  to the second end portions  25   a  of the bus bars  25 . The number of the poles for both connector units  30  and  31  may be set to be the same.  
         [0039]    The ultrasonic welding machine equipped with an anvil  40  and horn  42  is fixed at a predetermined position. The anvil  40  includes a welder body  40   b , and an edge portion where a welding tip  40   a  of the anvil  40  is provided. Likewise, the horn  42  includes a welder body  42   b , and an edge portion where a welding tip  42   a  of the horn  42  is provided. When the welding is to be carried out, a cable reel  20  is installed in a space below the anvil  40  and the horn  42 . In this manner, the welder bodies  40   b  and  42   b  face each other over the mobile member  22  of the cable reel  20 , as illustrated in FIG. 4.  
         [0040]    The welder body  40   b  of the anvil  40  includes a base portion  40   b - 1  having a width S corresponding to about one fourth of the contour length of the mobile member  22 , and a projecting portion  40   b - 2  projecting from one end of the base portion  40   b - 1  and crossing the diametrical center line L (see FIG. 6) of the mobile member  22 . The welder body  40   b  of the anvil  40  reciprocates in the linear direction shown by arrow X in FIG. 6. Conversely, the welder body  42   b  of the horn  42  is placed over the mobile member  22 , but outside the contour thereof, and faces the welder body  40   b  of the anvil  40 . However, its welding tip  42   a  extends from the outside into inside the contour of the mobile member  22 , and reciprocates in the linear direction shown by arrow X′ (FIG. 6).  
         [0041]    In the conventional construction shown in FIG. 1, the two connector units of the cable reel are placed at symmetrical positions to each other with respect to the center of the mobile member  22 , and the latter is fixed in a predetermined position. In such a case, when one of the connector units is to be welded by the anvil  40  and the horn  42 , the other connector unit is brought in the way of the welder body  40   b  of the anvil  40 , thereby impeding welding operations.  
         [0042]    To solve such problems, the first connector member  30  and the second connector member  31  according to the present invention are placed in staggered positions, with respect to the diametrical center line L of the mobile member  22  (note FIG. 6). Accordingly, when the first connector unit  30  is first welded, it is removed from the reciprocating-movement field of the anvil  40  and horn  42 . This field is illustrated as zone Z 1  shown by oblique lines in FIG. 6, and corresponds to a zone in FIG. 4 where the anvil  40  and the horn  42  are placed. The second connector unit  31  is provided outside the above zone, i.e. at zone Z 2  shown cross-hatched in FIG. 6. The second connector unit  31  may be installed anywhere, so long as it is in zone Z 2 .  
         [0043]    There may be provided a third or further connector unit(s) so long as it is or they are in zone Z 2 .  
         [0044]    The connector units  30  and  31  of the cable reel  20  may be prepared and subjected to a welding operation according to the following steps.  
         [0045]    The cable reel  20  is formed by mounting a fixed member  21  and a mobile member  22 , so as to form a cable enclosure. The cable enclosure stores a flat cable  24 . Then, the mobile member  22  is installed at a given position under the welder body  40   b  of the anvil  40  and welder body  42   b  of the horn  42 .  
         [0046]    A first connector unit  30  is first placed at a welding position P between the anvil welding tip  40   a  and the horn welding tip  42   a , so that the bus bars  25  in the first connector unit  30  can be welded to the wire cores of the outside electrical cables  35 .  
         [0047]    After welding, the welder body  40   b  of the anvil  40  and the welder body  42   b  of the horn  42  are moved back. During the above operation, the connector units  30  and  31  do not interfere with the welder bodies  40   b  and  42   b , and can be rotated at the above given position.  
         [0048]    The already welded first connector unit  30  is moved from zone Z 1  where the anvil  40  and the horn  42  are in operation, away into zone Z 2 . A second connector unit  31  is then placed at the welding position P, as shown in FIG. 4.  
         [0049]    To do this, the mobile member  22  is rotated and placed at the position P shown in FIG. 6. The anvil welder body  40   b  and the horn welder body  42   b  are then mutually approached, and the welding is performed for the second connector unit  31 . When the anvil welder body  40   b  is being advanced, the first connector unit  30  is placed in the zone Z 2 , away from the zone Z 1 . Accordingly, the anvil welder body  40   b  can be advanced up to the welding position P (FIG. 6), without interfering with the first connector unit  30 .  
         [0050]    The above steps can be summarized as follows. The mobile member  22  is mounted onto the fixed member  21 , and the assembly of the cable reel  20  is completed. The cable reel  20  is then placed under the welding machine. The first connector unit  30  is first welded. Then, the mobile member  22  is rotated at a fixed position, and the second connector unit  31  is welded. The number of poles in each of the connector units e.g.  30  and  31  is set to be the same, so that, by rotating the mobile member  22 , welding in a plurality of connector units e.g.  30  and  31  can be performed with a single anvil welder body  40   b  and horn welder body  42   b.    
         [0051]    In the above embodiments, an ultrasonic welding machine was used. Alternatively, a resistance welding machine can be used in the same working configuration involving an anvil and a horn. In such a case, a plurality of connector units are mounted on the mobile member into the same configuration as in the above embodiments. Once a cable reel is assembled, welding is performed in the connector units.  
         [0052]    According to the invention, the mobile member is provided with a plurality of connector units arranged in staggered, but not symmetrical, positions to one another, with respect to the diametrical center line of the mobile member. After the mobile member equipped with a plurality of connector units is mounted onto the fixed member, and the cable reel is thus assembled, a resistance or ultrasonic welding is performed in the connector units.  
         [0053]    Accordingly, when external electrical cables are to be connected to the connector units, the size arrangement of these electrical cables can be made more easily. Further, as welding operations can be performed efficiently in a plurality of connector units, the manufacture of a cable reel becomes easier, and can be automated more easily.  
         [0054]    Although the invention has been described with reference to particular means, materials and embodiments, it is to be understood that the invention is not limited to the particulars disclosed and extends to all equivalents within the scope of the claims.  
         [0055]    The present disclosure relates to subject matter contained in priority Japanese Application No. 200 0 -144430, filed on May 17, 2000, the disclosure of which is herein expressly incorporated by reference in its entirety.