The present invention relates to a coil spring contact connector, i.e., a connector provided with coil spring contacts, to be disposed between two units or circuit boards to electrically connect the respective terminal electrodes thereof.
An elastic-contact connector provided with conducting rubber contacts housed in a case has been used as a connector to be disposed between two units or circuit boards to electrically connect the respective terminal electrodes thereof. The elastic-contact connector has a drawback that the conducting rubber contacts bulge out of the case and make stable contact difficult.
A coil spring contact connector proposed in JP 10-12777 A (1998) is provided with coil spring contacts instead of conducting rubber contacts as shown in FIGS. 12 and 13.
Referring to FIG. 12, a coil spring contact connector 7 includes a plurality of coil spring contacts 70, and an insulating rod 72 extended through the plurality of coil spring contacts 70. A pair of projections 74 and 76 is disposed between the adjacent coil spring contacts 70.
When electrically connecting terminal electrodes 8c and 9c respectively formed on circuit boards 8 and 9, the circuit boards 8 and 9 are pressed against the coil spring contacts 70 so that the coil spring contacts 70 are held between the terminal electrodes 8c and 9c as shown in FIG. 13. Each coil spring contact 70 is deformed elastically such that its coils are tilted with respect to its axis. Consequently, upper and lower circumferential contact parts of each coil spring contact 70 are pressed elastically against the respective contact electrodes 8c and 9c of the boards 8 and 9, respectively, so that the terminal electrodes 8c and 9c are electrically connected.
Another coil spring contact connector disclosed in JP 11-40292 A (1999), similarly to the foregoing conventional coil spring contact connector, includes a coil spring contacts elastically deformable such that coils are tilted with respect to the axis when electrically connecting the terminal electrodes.
Since the coils of the coil spring contacts of the foregoing conventional coil spring contact connectors are elastically tilted with respect to the axis when electrically connecting the terminal electrodes, the axial positions of contact parts of the terminal electrodes with which the coil spring contact comes into contact are dependent on the pressure for pressing the terminal electrodes against the coil spring contact. Thus, there are problems in the accuracy of the positions of the contact parts of the terminal electrodes 8c and 9c with which the coil spring contact 70 comes into contact, and the stability of state of contact between the contact parts of the terminal electrodes 8c and 9c, and the coil spring contact 70.
The present invention has been made in view of the foregoing circumstances. It is therefore an object of the present invention to provide a coil spring contact connector including a coil spring contact, and capable of improving the accuracy of the positions of contact parts of terminal electrodes with which the coil spring contact comes into contact and of improving the state of contact between the coil spring contact and the contact parts of the terminal electrodes.
According to the present invention, a coil spring contact connector includes: a coil spring contact to be brought into elastic contact with first and second terminal electrodes disposed at diametric ends thereof, respectively; and an insulating holder holding the coil spring contact; wherein the coil spring contact has a first contact coil to be brought into contact with the first terminal electrode, and a second contact coil radially offset relative to the first contact coil so as to be brought into contact with the second terminal electrode, and the holder is provided with openings through each of which contact parts of the first and the second contact coils project outside, respectively, and is configured to restrain the coil spring contact from axial deformation and axial movement, and allow the coil spring contact to be deformed in an offset direction.
When the pair of terminal electrodes is pressed in diametrical directions, respectively, against the coil spring contact, the coil spring contact is elastically deformed in the offset direction without being deformed and moved axially. Therefore, the axial position of the coil spring contact with respect to the terminal electrodes is kept unchanged regardless of the magnitude of the pressure pressing the terminal electrodes against the coil spring contact. Thus the accuracy of the positions of contact parts of the terminal electrodes with which the coil spring contact comes into contact and the state of contact between the coil spring contact and the contact parts of the terminal electrodes can be improved.
Since the coil spring contact has the first contact coil and the second contact coil radially offset relative to each other, the coil spring contact of the present invention, as compared with a coil spring contact having coaxially aligned coils, is capable of being sufficiently radially deformed and the diameter of the coils thereof may be small.
Preferably, the coil spring contact further has an intermediate coil connecting the first contact coils and the second contact coils. The intermediate coils further effectively increase the radial deformation of the coil spring contact.
Preferably, the holder has at least a pair of walls disposed on the axially opposite sides, respectively, of the coil spring contact, a distance between the walls being substantially equal to the axial length of the coil spring contact. Thus, the walls of the holder restrain the coil spring contact from axial deformation and axial movement. If the coil spring contact connector is provided with a plurality of coil spring contacts disposed axially side by side, the coil spring contacts can be insulated from each other with reliability by the wall.
Preferably, the holder is provided with a projection axially projecting into the coil spring contact. The projections prevent the coil spring contact from falling out through the openings of the holder.
Preferably, the holder is monolithic. When the holder is monolithic, it is possible to avoid problems arising from dimensional errors that are inevitable when the holder is an assembly of a plurality of members. Thus, the monolithic holder further improves the accuracy of the positions of the parts of the terminal electrodes with which the coil spring contact comes into contact.