1.  Field of the Invention
The present invention relates to a testing unit for a connector testing device. 
2.  Description of Background Information
In general, a connector used for an electric wiring system such as a wire harness or a sub-assembly (hereinafter totally referred to as a "wire assembly") for forming a wire harness includes a plurality of cavities in a molded resin housing, and metal terminals connected with wires are inserted therein.  The metal terminals are fastened within a cavity by a lance system.  With this lance system, by fastening a tongue-shape lance formed on either the metal terminal or the connector (mainly on the connector) to a fastening hole formed in the other, removal from the cavity of the terminal metal is prevented. 
In the above-mentioned wire assembly production process, conductivity testing of electric wiring condition and connecting condition, etc.  of the above-mentioned connectors, as well as testing of the fastening condition of metal terminals and housing are each carried out.  There have been proposed various testing areas on a connector testing device capable of carrying out simultaneously testing the conductivity and the fastening condition. 
The testing unit of a connector testing device normally includes a connector holder which holds a connector and a testing area capable of moving toward and away from a held connector.  The testing area is provided on a block as the main body member, and probe pins are provided on the block and are inserted in a cavity of the connector which is equipped with metal terminals that are electrically connectable to the probe pins.  Various improvements are made for the probe pin and block in order to test a fastening condition between the metal terminals and the connector housing. 
For example, with the prior art as disclosed in Japanese Unexamined Patent Publication No.  HEI 7-113836, the above-mentioned block and probe pin are connected through a spring, structured to be elastically displaceable toward and away from the metal terminals, and provided on the tip of a probe pin with a testing area for incomplete insertion which allows contact with a lance which is incompletely fastened within the cavity.  With this prior art, in the event of normal connection of the lance, contact between the probe pin and the metal terminals electrically causes a circuit in the testing unit to close, thus allowing conductive testing.  While in case of incomplete fastening of the lance, contact of a partially inserted testing unit with the lance causes the spring to compress, which does not allow the probe pin to reach the metal terminals, thereby resulting in a failure of the conductive test where the fastening condition of the lance is incomplete. 
With the prior art as set forth in Japanese Unexamined Patent Publication No.  HEI 8-320355, by providing a molded resin slider integrally with a probe pin, and configuring the probe pin to be movable elastically toward and away from the metal terminal, with this slider integrally formed with lance test pins which are similar to those of the above-mentioned incomplete insertion checking unit, incomplete lance fastening was made testable.  However, with the above-mentioned slider, all the pins corresponding to the number of poles of metal terminals were integrally held in position. 
In the case of the former structure of probe pins, while testing the lance by each metal terminal can be made, damage to the lance may be possible when an incomplete insertion testing area engages a lance which is not completely fastened due to the incomplete insertion testing area being integrally formed with the probe pin.  In order that the incomplete insertion testing area can be maintained in a normal position that enables testing of the lance, providing a mechanism for preventing the probe pin from rotation was necessary, which inevitably increased the number of components and also made the structure complicated. 
On the other hand, in adopting the latter structure, because all of the lance test pins are integrally formed with the same slider, testing the lance by each metal terminal was difficult.  In addition, because all of the lance test pins are integrally formed with the same slider, the load of the spring which biases the slider becomes higher, thereby possibly causing damage to the lance due to greater load applied to the lance when the lance subjected to incomplete fastening engages the lance test pins. 
Furthermore, with such a conductive testing device, in order to provide a switching function for testing the condition of a connector (mainly for conditions of the metal terminal or a lance which fastens the metal terminal), there are devices in which the above-mentioned probe pins are mounted on a slider which is displaceable relative to a block area along a direction opposite to a connector holder, with a predetermined force biased in a direction of the connector holder.  With this kind of testing device, in making the probe pins contact the terminal pins by moving the block close to the connector holder, the devices are formed in such a manner that the condition of a connector was determined by whether the slider displaces or not. 
With the testing device as mounted on a testing unit with a probe pin through a slider which displaces relative to a block area as mentioned above, a lead wire connected with the probe pin also moves in accordance with the displacement of the slider relative to the block area.  Therefore, during continued use of the device, the connected area between the lead wire and probe pin is subjected to wear, thereby causing a deficiency that is likely to break the wires. 
Thus, the present invention was made to overcome the above-mentioned deficiencies, and therefore an object of the present invention is to provide a testing unit of a connector testing device which can carry out comparatively individual testing of lances and which also avoids damage to the lances which are incompletely fastened. 
An additional object of the present invention, in order to overcome the above-mentioned deficiencies, is to provide a testing unit of a connector testing device capable of properly maintaining a connected condition between a probe pin and a lead wire.