| 摘要 |
The present invention resides in an apparatus (8) and method for maintaining a print head (10) at a substantially constant, closely spaced working distance (22) from a surface (17) of a printing receiver (16) during relative translational movement between the print head (10) and the receiver (16) along a predetermined path of movement for depositing liquid or ink droplets (12) onto the surface (17), the apparatus (8) including an actuator (20) connected to the print head (10) and controllably actuable for moving the print head (10) toward and away from the receiver (16), an element (35,36) for detecting a representative distance between the print head (10) and locations on the surface (17) of the receiver (16) along the path of movement and generating a signal having a value representative of or related to the representative distance, an element (46) for comparing the signal value to a reference; value representative of the working distance (22) for determining a difference between the signal value and the reference value and generating a control signal representative of the difference, and a control element (24) for receiving the control signal and responsively controllably actuating the actuator (20) to move the print head (10) toward or away from the receiver (16) to locate the print head (10) at the working distance (22) from the locations on the surface (17) of the receiver (16) when the print head (10) is positioned for depositing the liquid or ink droplets thereon. The method of the present invention includes the steps of(a) generating signals representative of distances between the print head (10) and the locations on the surface (17) of the receiver (16) along the path of movement prior to the print head (10) being positioned for depositing liquid or ink droplets onto the locations on the surface (17), respectively; and(b) responsively to the signals, as required, moving the print head (10) toward or away from the receiver (16) to locate the print head (10) at substantially the closely spaced working distance (22) from the locations on the surface (17) of the receiver (16) when positioned for depositing the liquid or ink droplets thereon, respectively.
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