| 摘要 |
PURPOSE:To eliminate the need for detaching a hammer unit when measuring the hammer flight time and thereby avoid time-consuming operations such as fitting and detaching of a substrate, by measuring the hammer flight time on the basis of the difference between the moment a hammer collides against a platen to generate vibration and the moment a hammer-driving trigger pulse is impressed. CONSTITUTION:With an address signal ADj impressed on a terminal 68, a trigger pulse Tpj for operating a j-th hammering mechanism (j) in a hammer unit 25 is sent from an address circuit 62 to a hammer-driving unit 61, whereby the j-th hammer 5 is caused to fly out, thereby giving an impact on the platen 11 at a point pj. The acoustic shock wave generated at this moment is transmitted through the platen 11, and is detected by an acoustic sensor DTE to form an electrical signal SP (SPj). The period of time from the moment the trigger pulse Tpj is generated to the moment the electrical signal SP is detected is measured by a counter 30, and the period of time required for propagation of the sound wave is subtracted from the measured period of time by a calculating means 305, thereby obtaining the hammer flight time. |
