Method of connecting terminal fitting to flat conductor and terminal fitting for flat conductor

A terminal fitting (20) is provided for an FFC (10). The FFC (10) includes a conductive path (11) that has upper and lower surfaces covered with an insulation sheet (12). The terminal fitting (20) includes bottom plate (22) with contact blades (25) erected on both side edges of the bottom plate (22). A ceiling plate (23) confronts the bottom plate (22) and can penetrate into the space between the opposed contact blades (25). When the ceiling plate (23) is closed, it moves downward, with both side surfaces thereof in sliding contact with an inner surface of each contact blade (25), while the ceiling plate (23) presses the terminal of the FFC (10) toward the bottom plate (22). Consequently, the contact blades (25) pierce through the terminal of the FFC (10). The contact blades (25) pierce into the conductive path (11) and the ceiling plate (23) prevents floating of the FFC (10). Thus, it is possible to allow a cut surface (11A) of the conductive path (11) located inward from the contact blades (25) to properly confront the inner surfaces of the contact blades (25).

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a method of connecting a terminal fitting
 to a flat conductor and a terminal fitting for the flat conductor.
 2. Description of the Related Art
 Prior art flat conductors include an FFC (flexible flat cable) and an FPC
 (flexible print circuit board). The prior art FFC includes a plurality of
 conductive paths arranged in parallel with one another and sandwiched
 between insulation sheets. The FFC is flexible and formed in the shape of
 a ribbon.
 Terminal fittings are connected to the conductive paths of the FFC by
 embedding portions of the terminal fitting in the insulation sheet or by
 tearing off a section of the insulation sheet of the FFC to expose
 sections the conductive paths on one surface of the FFC.
 The former method of connecting a terminal fitting to an FFC is called a
 through type method, and has an advantage of omitting the stage of tearing
 off the insulation sheet. This method is disclosed in Japanese Patent
 Application Laid-Open No. 50-100585, which is shown in FIG. 12A. The
 method of FIG. 12A includes providing a terminal fitting 1 with contact
 blades 2 erected on both side edges of the terminal fitting 1. Both
 contact blades 2 pierce a conductive path 4 of an FFC 3 to bring cut end
 surfaces of the conductive path 4 into contact with side surfaces of the
 contact blade 2.
 However, in the above-described method, when the contact blade 2 pierces
 through the conductive path 4, as shown in FIG. 12B, the FFC 3 is liable
 to curve between the opposed contact blades 2. Therefore, there is a
 possibility that a cut surface 4A of the conductive path 4 does not
 confront the side surfaces of the contact blade 2 properly or only a part
 (corner) of an insulation sheet 5 is in contact with the side surfaces of
 the contact blade 2. Thus, the method is not reliable in electrical
 contact.
 The present invention has been completed in view of the above-described
 situation. Thus, it is an object of the present invention to allow a
 reliable contact between a contact blade of a terminal fitting of through
 type and a cut surface of a conductive path of a flat conductor.
 SUMMARY OF THE INVENTION
 The subject invention is directed to a method of connecting a terminal
 fitting to a flat conductor. The flat conductor includes at least one
 conductive path embedded in an insulation layer. A terminal fitting is
 provided with a base plate and at least one contact blade projecting from
 the base plate. The contact blade is pierced into the conductive path,
 such that a surface of the flat conductor is in contact with the base
 plate. A pressing plate then presses the flat conductor toward the base
 plate.
 The pressing plate remains on the flat conductor, with the flat conductor
 being sandwiched between the base plate and the pressing plate.
 The invention also is directed to a terminal fitting connected to a flat
 conductor whose conductive path is embedded in an insulation layer. The
 terminal fitting includes a base plate from which at least one contact
 blade is erected. The contact blade is pierced through the conductive
 path, such that a surface of the flat conductor is in contact with a base
 plate. The terminal fitting further comprises a pressing plate for
 pressing the conductive plate toward the base plate, and thus causing the
 contact blade to pierce into the conductive path. The pressing plate
 remains on the flat conductor, such that the flat conductor is sandwiched
 between the base plate and the pressing plate after the contact blade is
 pierced into the conductive path. The pressing plate further includes an
 insertion hole through which a projected end of the contact blade is
 inserted. The insertion hole fits on the contact blade tightly in a
 thickness direction thereof and has a clearance in a widthwise direction
 thereof.
 The contact blades pierce into the conductive path, and the ceiling plate
 prevents float of the conductive path. Thus, the cut surface of the
 conductive path confronts the inner and outer surface of the contact
 blades to obtain a good contact state.
 The ceiling plate is left on the flat conductor after the ceiling plate
 presses the flat conductor against the bottom plate. Thus, it is possible
 to keep the cut surface of the conductive path in confrontation with the
 contact blades properly.
 The front end of the contact blade is pierced into the flat conductor and
 is inserted into the insertion hole of the pressing plate. The insertion
 hole is dimensioned to provide a clearance. Chips generated when the
 contact blade pierces into the flat conductor are introduced into the
 clearance formed for the contact blade at the outer side of the widthwise
 direction thereof. That is, it is possible to prevent the chips from being
 introduced into the space between the cut surface of the conductive path
 and the inner and outer surfaces of the contact blade. This construction
 allows a preferable contact between the cut surface of the conductive path
 and the contact blade.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 The first embodiment of the present invention will be described below with
 reference to FIGS. 1 through 8.
 A flexible ribbon-shaped FFC (flexible flat cable) is identified generally
 by the numeral 10 in FIG. 1. The FFC 10 has a plurality of conductive
 paths 11 arranged in parallel with one another at predetermined intervals.
 The conductive paths 11 are embedded in insulation sheets 12 disposed on
 upper and lower surfaces of the conductive paths 11.
 A terminal fitting 20 of the first embodiment is formed as a male terminal
 fitting by press-molding a highly electrically conductive metal plate. As
 shown in FIGS. 1-3, the terminal fitting 20 includes a tab 21 with a front
 end to be fitted on a mating terminal and an opposed rear end. A bottom
 plate 22 is extended rearward from the rear end of a tab 21, and a ceiling
 plate 23 confronts the bottom plate 22 vertically.
 The bottom plate 22 is slightly narrower than the conductive path 11 and
 has opposite left and right side edges. Two contact blades 25 are formed
 at the left side edge of the bottom plate 22, and two contact blades 25
 are formed at the right side edge thereof. The contact blades 25 are
 erected on the bottom plate 22 such that they alternate with one another
 along the length of the bottom plate 22. The upper end of each contact
 blade 25 is tapered to a point.
 The ceiling plate 23 has a width equal to the width of the space between
 the contact blades 25 on the left side edge of the base plate 22 and the
 contact blades 25 on the right side edge. The metal blank for forming the
 terminal fitting 20 has the ceiling plate 23 formed parallel with the
 bottom plate 22 and connected to the base plate 22 by a bending part 26
 that projects sideways from a location substantially where the tab 21 and
 the base plate 22 meet. The bending part 26 then is bent to be in close
 contact with the tab 21. Thus, as described above, the ceiling plate 23
 confronts the bottom plate 22 and is integral with the tab 21 and the base
 plate 22. As a result, the rear end of the ceiling plate 23 can be opened
 and closed relative to the base plate 22.
 A piercing piece 28 that can be inserted into the FFC 10 is formed at the
 rear end of the ceiling plate 23, and defines a width of about the half of
 the entire width of the ceiling plate 23. The lower end of the piercing
 piece 28 is tapered off to a point that is directed downward toward the
 bottom plate 22 and substantially perpendicular to the ceiling plate 23.
 The terminal fitting 20 is connected to the FFC 10 by initially opening the
 ceiling plate 23 of the terminal fitting 20 upward, as shown in FIG. 1.
 Next, as shown in FIGS. 3 and 4, the terminal of the FFC 10 is placed on
 the contact blades 25 formed on side edges of the bottom plate 22 by
 adjusting the mating position of the conductive path 11 to the location of
 the terminal fitting 20. Then, as shown by the arrow of FIG. 4, the
 ceiling plate 23 is pivoted into a closed position. As a result, as shown
 in FIG. 5, the side edges of the ceiling plate 23 move downward in sliding
 contact with the inner surface of each contact blade 25, such that the
 ceiling plate 23 presses the FFC 10 toward the bottom plate 22.
 Consequently, the contact blades 25 at the left and right side edges of
 the bottom plate 22 pierce into the lower surface of the FFC 10 at
 positions located slightly inward from the left and right side edges of
 the conductive path 11 and project from the upper surface of terminal of
 the FFC 10.
 When the terminal of the FFC 10 contacts the bottom plate 22 by the
 pressing operation of the ceiling plate 23, the projected end (upper end)
 of each contact blade 25 is bent inward and crimped to both side edges of
 the ceiling plate 23. Consequently, as shown in FIGS. 6 through 8, the
 terminal fitting 20 is connected to the FFC 10, with the ceiling plate 23
 and the bottom plate 22 placed in the closed state.
 The piercing piece 28 formed at the rear end of the ceiling plate 23
 pierces the conductive path 11 of the FFC 10 and projects from the lower
 surface of the FFC 10.
 As described above, the contact blades 25 pierce the conductive path 11,
 and the ceiling plate 23 is interposed between the contact blades 25 at
 both side edges of the bottom plate 22. As a result, the ceiling plate 23
 prevents the FFC 10 from floating, and it is possible to allow a cut
 surface 11A of the conductive path 11 located inward from the contact
 blades 25 to properly confront the inner surfaces of the contact blades
 25. Thus, it is possible to obtain a preferable contact state and thereby
 it is possible to obtain a stable electrical performance.
 The ceiling plate 23 is left on the FFC 10 after the ceiling plate 23 is
 used to press the FFC 10 against the bottom plate 22. Thus, it is possible
 to keep the cut surface 11A of the conductive path 11 in confrontation
 with the contact blades 25 properly.
 The FFC 10 is used with the terminal fitting 20 connected with the terminal
 of the FFC 10 and accommodated in a cavity of a connector housing (not
 shown). A tensile force may be applied to the FFC 10 in a rearward
 direction (to the right in FIG. 6). However, the piercing piece 28 formed
 at the rear end of the ceiling plate 23 pierces the FFC 10 in a direction
 perpendicular to the direction of the applied tensile force, thus hooking
 the terminal fitting 20 firmly in resistance to the tensile force.
 Therefore, the terminal fitting 20 is not easily removed from the terminal
 of the FFC 10.
 Further, because the piercing piece 28 pierces the conductive path 11, it
 is possible to increase the contact area between the terminal fitting 20
 and the conductive path 11.
 The second embodiment of the present invention is directed to a terminal
 fitting 20A, as shown in FIGS. 7 through 9. The terminal fitting 20A of
 the second embodiment has a bottom plate 22A that is narrower than the
 bottom plate 22 of the first embodiment and is formed with a leftward
 offset when viewed from the front. The bottom plate 22A includes left and
 right side edges. Two contact blades 25 are formed on the left side edge
 of the narrow bottom plate 22A and two contact blades are formed on the
 right side edge, such that the contact blades 25 on the left and right
 side edges alternate with one another.
 The terminal fitting 20A further includes a ceiling plate 23A, and two
 slit-shaped insertion holes 31 are formed on the ceiling plate 23A. The
 contact blades 25 at the right side in a front view can be inserted
 through the insertion holes 31. Each insertion hole 31 is formed to
 contact the respective contact blade 25 closely in the thickness
 direction, but each insertion hole 31 has a clearance for the contact
 blade 25 in the widthwise direction.
 The other constructions are similar to those of the first embodiment. Thus,
 parts of the second embodiment that have the same functions as parts of
 the first embodiment are denoted by the same reference numerals and
 symbols. Therefore, the descriptions of those parts are omitted herein.
 In the second embodiment, the FFC 10 is placed on the contact blades 25,
 and the ceiling plate 23A is pivoted downward to a closed position. As a
 result, the ceiling plate 23A presses the FFC 10 toward the bottom plate
 22A, and the contact blades 25 formed at the left and right side edges of
 the bottom plate 22A are pierced into the lower surface of the FFC 10.
 More specifically, the left-side contact blades 25 in a front view pierce
 into positions slightly inward from the left side edge of the conductive
 path 11 and project from the upper surface of the FFC 10, whereas the
 right-side contact blades 25 pierce into positions slightly inward from
 the right side edge of the conductive path 11 and project from the upper
 surface of the FFC 10 through the insertion hole 31 of the ceiling plate
 23A.
 When the FFC 10 contacts the bottom plate 22A by the pressing operation of
 the ceiling plate 23A, the projected end (upper end) of each contact blade
 25 is bent inward and crimped to the upper surface of the ceiling plate
 23A. Consequently, as shown in FIG. 10, the bottom plate 22A and the
 ceiling plate 23A are connected to each other in a closed state.
 As described above, the contact blades 25 of the second embodiment are
 pierced into the conductive path 11, and the ceiling plate 23A prevents
 floating of the FFC 10. Therefore, it is possible to allow the cut surface
 11A of the conductive path 11 to confront the inner and outer surface of
 the contact blades 25 properly, and it is possible to obtain a preferable
 contact state.
 The contact blade 25 is inserted into the insertion hole 31 of the ceiling
 plate 23A, as shown in FIG. 11A, and the FFC 10 is pressed at the inner
 and outer sides of the contact blade 25 as shown in FIG. 11B. Thus, it is
 possible to allow the cut surface 11A of the conductive path 11 to
 confront the inner and outer surfaces of the contact blade 25 properly.
 There is a possibility that when the contact blade is pierced into the FFC
 10, the insulation sheet and the like are torn and chips X thereof remain.
 However, there is a clearance formed in the insertion hole 31 for the
 contact blade 23 at the outer side of the widthwise direction thereof.
 Thus, as shown in FIG. 11B, the chips X are introduced into the clearance.
 That is, it is possible to prevent the chips X from being introduced into
 the space between the cut surface 11A of the conductive path 11 and the
 inner and outer surfaces of the contact blade 25. This construction
 contributes to a preferable contact between the cut surface 11A of the
 conductive path 11 and the contact blade 25.
 The present invention is not limited to the embodiment described above with
 reference to the drawings. For example, the following embodiments are
 included in the technical scope of the present invention. Further, various
 modifications can be made without departing from the spirit and scope of
 the present invention.
 The ceiling plate may be separate from the bottom plate and may be removed
 from the FFC after the ceiling plate is used to press the FFC against the
 bottom plate, with the contact blade pierced into the FFC.
 It is possible to penetrate the contact blade at one side edge of the
 bottom plate into the conductive path and crimp the contact blade at the
 other side thereof to the ceiling plate.
 It is possible to form the contact blade on the ceiling plate and function
 the bottom plate as the pressing plate.
 The present invention can be used to connect the female terminal fitting to
 the FFC.
 It is possible to apply the present invention to not only the FFC
 exemplified in the first embodiment, but also terminal fittings to be used
 in connection with the flat conductor such as an FPC in which the
 conductive path is covered with the insulation layer.