Sheet binding apparatus having needle detection means, and image forming apparatus

An image forming apparatus having an image forming means, and a sheet binding apparatus for effecting a stapling operation in which a needle is pressed into a sheet stack by moving a head by operation of a motor, comprising:

• first timing output means for outputting a signal at a timing of the needle pressing operation;
• second timing output means for outputting a signal at a timing other than the timing of the needle pressing operation;
• electrical load measuring means for measuring an electrical load value on the motor when the head moves, in response to the signals from said first and second timing output means;
• base value setting means for setting an electrical load base value on which a judgement of the presence and absence of the needle is based;
• and
• judging means for calculating a difference value between electrical load values measured by the electrical load measuring means in response to signals from said first and second timing output means, and for comparing the difference value with the value set by said base value setting means to judge the presence and absence of the needle.

A sheet binding apparatus for effecting a stapling operation in which a needle is pressed into a sheet stack by moving a head by operation of a motor, comprising:

• first timing output means for outputting a signal at a timing of the needle pressing operation;
• second timing output means for outputting a signal at a timing other than the timing of the needle pressing operation;
• electrical load measuring means for measuring an electrical load value on the motor when the head moves, in response to the signals from said first and second timing output means;
• base value setting means for setting an electrical load base value on which a judgment of the presence and absence of the needle is based;
• and
• judging means for comparing a difference value between electrical load values measured by the electrical load measuring means in response to signals from said first and second timing output means with the value set by said base value setting means to judge the presence and absence of the needle.

An image forming apparatus having an image forming means, and a sheet binding apparatus for effecting a stapling operation in which a needle is pressed into a sheet stack by moving a head by operation of a motor, comprising:

• first timing output means for outputting a signal at a timing of a needle pressing operation;
• second timing output means for outputting a signal at a timing other than the timing of the needle pressing operation;
• electrical load measuring means for measuring an electrical load value on the motor when the head moves, in response to the signals from said first and second timing output means;
• base value setting means for setting an electrical load base value on which a judgement of the presence and absence of the needle is based;
• and
• judging means for comparing a difference value between electrical load values measured by the electrical load measuring means in response to signals from said first and second timing output means with the value set by said base value setting means to judge the presence and absence of the needle.

A sheet binding apparatus for effecting a stapling operation in which a needle is pressed into a sheet stack by moving a head by operation of a motor, comprising:

• timing output means for outputting a first signal at a first timing of a needle pressing operation, and for outputting a second signal at a second timing before the needle pressing operation, during one stapling operation;
• electrical load value measuring means for measuring an electrical load value on the motor at each of the first and second timings when the head moves, in response to the first and second signals from said timing output means;
• and
• judging means for comparing a difference value between electrical load values measured by the electrical load value measuring means in response to the first and second signals from said timing output means with a previously-set, adjustable reference value, on which a presence and absence of the needle is based, to judge the presence and absence of the needle.

An image forming apparatus having an image forming means, and a sheet binding apparatus for effecting a stapling operation in which a needle is pressed into a sheet stack by moving a head by operation of a motor, comprising:

• timing output means for outputting a first signal at a first timing of a needle pressing operation, and for outputting a second signal at a second timing before the needle pressing operation, during one stapling operation;
• electrical load value measuring means for measuring an electrical load value on the motor at each of the first and second timings when the head moves, in response to the first and second signals from said timing output means;
• and
• judging means for comparing a difference value between electrical load values measured by the electrical load value measuring means in response to the first and second signals from said timing output means with a previously-set, adjustable reference value, on which a presence and absence of the needle is based, to judge the presence and absence of the needle.

A sheet binding apparatus for effecting a stapling operation in which a needle is pressed into a sheet stack by moving a head by operation of a motor, comprising:

• first timing output means for outputting a signal at a timing of a needle pressing operation;
• second timing output means for outputting a signal at a timing other than the timing of the needle pressing operation;
• electrical load value measuring means for measuring an electrical load value on the motor when the head moves, in response to the signals from said first and second timing output means;
• base value setting means for setting an electrical load base value on which a judgement of the presence and absence of the needle is based;
• and
• judging means for calculating a difference value between electrical load values measured by the electrical load value measuring means in response to signals from said first and second timing output means, and for comparing the difference value with the value set by said base value setting means to judge the presence and absence of the needle,
• wherein said first and second timing output means comprises in combination a rotary means, which is rotated synchronously with the rotation of the motor for pressing the needle into the sheet stack, with a sensor for detecting a position of said rotary means, the signal output by said first timing output means being output at a timing when the needle is clinched, the signal output by said second timing output means being output immediately before the timing of a needle clinching operation, and the judgement that the needle is present being made when the difference value is larger than the base value.

An image forming apparatus having an image forming means, and a sheet binding apparatus for effecting a stapling operation in which a needle is pressed into a sheet stack moving a head by operation of a motor, comprising:

• first timing output means for outputting a signal at a timing of a needle pressing operation;
• second timing output means for outputting a signal at a timing other than the timing of the needle pressing operation;
• electrical load value measuring means for measuring an electrical load value on the motor when the head moves, in response to the signals from said first and second timing output means;
• base value setting means for setting an electrical load base value on which a judgement of the presence and absence of the needle is based;
• and
• judging means for calculating a difference value between electrical load values measured by the electrical load value measuring means in response to signals from said first and second timing output means, and for comparing the difference value with the value set by said base value setting means to judge the presence and absence of the needle,
• wherein said first and second timing output means comprises in combination a rotary means, which is rotated synchronously with the rotation of the motor for pressing the needle into the sheet stack, with a sensor for detecting a position of said rotary means, the signal output by said first timing output means being output at a timing when the needle is clinched, the signal output by said second timing output means being output immediately before the timing of a needle clinching operation, and the judgement that the needle is present being made when the difference value is larger than the base value.