Printer having head gap adjusting device

A printing apparatus comprising:

• a platen for supporting a recording medium;
• a print head disposed movably in a transverse direction toward and away from said platen;
• a head advancing and retracting device for moving said print head in said transverse direction;
• automatic head gap adjusting means for controlling said head advancing and retracting device to advance said print head until the print head comes into contact with said recording medium and then retracting the print head by a predetermined distance to adjust a head gap between said recording medium and said print head;
• said head advancing and retracting device comprising a drive source, a power transmission mechanism for transmitting a drive force of said drive source to said print head to move the print head in said transverse direction, and a clutch mechanism having a connecting state for transmitting said drive force of said drive source smaller than a preset value in a forward direction to advance the print head toward said platen, and a disconnecting state for inhibiting the transmission of said drive force exceeding said preset value to said print head;
• and
• said automatic head gap adjusting means comprising clutch release detecting means for detecting said disconnecting state of said clutch mechanism, and stopping means for stopping an operation of said drive source that produces the drive force in said forward direction, when said disconnecting state of said clutch mechanism is detected by said clutch release detecting means.

A method of adjusting a head gap in a printing apparatus, said apparatus comprising a platen for supporting a recording medium;

• a print head disposed movably in a transverse direction toward and away from said platen;
• a head advancing and retracting device for moving said print head in said transverse direction;
• automatic head gap adjusting means for controlling said head advancing and retracting device to advance said print head until the print head comes into contact with said recording medium and then retracting the print head by a predetermined distance to adjust a head gap between said recording medium and said print head;
• said head advancing and retracting device comprising a drive source, a power transmission mechanism for transmitting a drive force of said drive source to said print head to move the print head in said transverse direction, and a clutch mechanism having a connecting state for transmitting said drive force of said drive force smaller than a preset value in a forward direction to advance the print head toward said platen, and a disconnecting state for inhibiting the transmission of said drive force exceeding said preset value to said print head;
• and
• said automatic head gap adjusting means comprising clutch release detecting means for detecting said disconnecting state of said clutch mechanism, and stopping means for stopping an operation of said drive source that produces the drive force in said forward direction, when said disconnecting state of said clutch mechanism is detected by said clutch release detecting means, comprising the steps of:
• positioning said print head at a predetermined position which is spaced from said platen by a known distance;
• operating said automatic head gap adjusting means to advance said print head until the print head comes into contact with said platen, with no recording medium placed on said platen, and determining a first advancing distance of said print head between said predetermined position and a position at which the print head contacts said platen;
• calculating a difference between said known distance and said first advancing distance, as a specific value inherent to the printing apparatus;
• retracting said print head and placing the recording medium on said platen;
• operating said automatic head gap adjusting means again to advance said print head, until the print head comes into contact with the recording medium placed on said platen;
• and
• retracting said print head by a distance equal to a sum of said specific value and a nominal head gap value.

A method of adjusting a head gap in a printing apparatus having a platen for supporting a recording medium, (b) a print head disposed movably in a transverse direction toward and away from said platen, (c) a head advancing and retracting device for moving said print head in said transverse direction, and (d) automatic head gap adjusting means for controlling said head advancing and retracting device to advance said print head until the print head comes into contact with said recording medium and then retracting the print head by a suitable distance, to thereby adjust said head gap between said recording medium and said print head, said method comprising the steps of:

• positioning said print head at a predetermined position which is spaced from said platen by a known distance;
• operating said automatic head gap adjusting means to advance said print head until the print head comes into contact with said platen, with no recording medium placed on said platen, and determining a first advancing distance of said print head between said predetermined position and a position at which the print head contacts said platen;
• calculating a difference between said known distance and said first advancing distance, as a specific value inherent to the printing apparatus;
• retracting said print head and placing the recording medium on said platen;
• operating said automatic head gap adjusting means again to advance said print head, until the print head comes into contact with the recording medium placed on said platen;
• and
• retracting said print head by a distance equal to a sum of said specific value and a nominal head gap value, said sum consisting of said suitable distance.

A printing apparatus comprising:

• a platen for supporting a recording medium;
• a print head disposed movably in a transverse direction toward and away from said platen;
• a head advancing and retracting device for moving said print head in said transverse direction;
• said head advancing and retracting device comprising a drive source, a power transmission mechanism for transmitting a drive force of said drive source to said print head to move the print head in said transverse direction, and a clutch mechanism having a connecting state for transmitting said drive force of said drive source smaller than a preset value in a forward direction to advance the print head toward said platen, and a disconnecting state for inhibiting the transmission of said drive force exceeding said preset value to said print head;
• and
• said clutch mechanism comprising a drive member, a driven member, a first and a second engaging portion which are provided on one and the other of said drive and driven members, respectively, and an elastic member, said first and second engaging portions engaging each other such that a movement to retract said print head is transmitted from said drive member to said driven member while a movement to advance the print head is inhibited from being transmitted from the drive member to the driven member, said elastic member having a predetermined pre-load biasing said first and second engaging portions of said drive and driven members for engagement of said first and second engaging portions with each other, said pre-load being smaller than said drive force of said drive member.