Impact printer temperature control device

Claim 2

In an impact printer in which a plurality of printing hammers operable by an electromagnetic unit are arranged linearly, and a printing operation is carried out at a first predetermined printing speed L 1 with a printing cycle and a sheet-feeding cycle conducted repeatedly, a control device comprising: a temperature sensing means positioned to detect the temperature of said electromagnetic unit by one of direct detection and indirect detection, said temperature sensing means having a hysteresis characteristic such that said temperature sensing means produces a signal in response to a first predetermined temperature and is restored at a second predetermined temperature lower than said first predetermined temperature; and a controller means for limiting said printing speed to a second printing speed L 2 lower than said first printing speed in response to said signal produced by said temperature sensing means in response to a first predetermined temperature and for returning said printing speed to said printing speed L 1 when said temperature sensing means is restored, and for limiting said printing speed to a third printing speed L 3 lower than said second printing speed L 2 when said temperature sensing means produces said signal for a duration greater than a first predetermined period of time.

Claim 3

A control device as claimed in claim 1, in which said temperature sensing means is provided in a power source unit which supplies electric power to a driver adapted to drive said electromagnets.

Claim 4

A control device as claimed in claim 1, in which a dummy period of time is provided between said sheet-feeding cycle and said printing cycle to achieve said limits of said printing speed.

Claim 5

A control device as claimed in claim 3, including means for setting said second printing speed L 2 and said third printing speed L 3 with said dummy period of time changed.

Claim 6

A control device as claimed in claim 1, in which said first predetermined period of time is the sum of a marginal period of time and a period of time which, when said printing operation is continued at said second printing speed L 2 at an ambient temperature, is required for the temperature of said electromagnetic unit to become lower than said second predetermined temperature sensing means.

Claim 7

In an impact printer in which a plurality of printing hammers operated by an electromagnetic unit are arranged linearly, and a printing operation is carried out at a first predeermined printing speed L 1 with a printing cycle and a sheet-feeding cycle conducted repeatedly, a control device comprising: a temperature sensing element provided at a position where a temperature of said electromagnetic unit can be detected by one of direct detection and indirect detection, said temperature sensing element having a hysteresis characteristic whereby said temperature sensing element is operated at a first predetermined temperature and is restored at a second predetermined temperature lower than said first predetermined temperature; and a controller means for limiting said printing speed to a second printing speed L 2 lower than said first printing speed L 1 in response to the operation of said temperature sensing element, for returning said printing speed to said first printing speed L 1 when said temperature sensing element is restored, and for limiting said printing speed to a third printing speed L 3 lower than said second printing speed L 2 when said temperature sensing element is maintained in operation for a duration greater than a first predetermined period of time, and, when said printing operation is continued at said third printing speed L 3 for a duration greater than a second predetermined period of time, for alternately permitting a first cycle in which said printing operation is carried out at said first printing speed L 1 for a duration equal to a third predetermined period of time and a second cycle in which said printing operation is carried out at said third printing speed L 3 for a duration equal to a fourth predetermined period of time.

Claim 8

In an impact printer in which a plurality of printing hammers operated by an electromagnetic unit are arranged linearly, and a printing operation is carried out at a first predeermined printing speed L 1 with a printing cycle and a sheet-feeding cycle conducted repeatedly, a control device comprising: a temperature sensing element provided at a position where a temperature of said electromagnetic unit can be detected by one of direct detection and indirect detection, said temperature sensing element having a hysteresis characteristic whereby said temperature sensing element is operated at a first predetermined temperature and is restored at a second predetermined temperature lower than said first predetermined temperature; and a controller means for limiting said printing speed to a second printing speed L 2 lower than said first printing speed L 1 in response to the operation of said temperature sensing element, for returning said printing speed to said first printing speed L 1 when said temperature sensing element is restored, and for limiting said printing speed to a third printing speed L 3 lower than said second printing speed L 2 when said temperature sensing element is maintained in operation for a duration greater than a first predetermined period of time, and, when said printing operation is continued at said third printing speed L 3 for a duration greater than a second predetermined period of time, for alternately permitting a first cycle in which said printing operation is carried out at said first printing speed L 1 for a duration equal to a third predetermined period of time and a second cycle in which said printing operation is carried out at said third printing speed L 3 for a duration equal to a fourth predetermined period of time.

Claim 9

A control device as claimed in claim 6, in which said second predetermined period of time is the sum of a marginal period of time and a period of time which, when said printing operation is continued at said second printing speed L 2 of an ambient temperature higher than room temperature, is required for the temperature of said electromagnet unit to become lower than the restoration temperature of said temperature sensing element.

Claim 10

A control device as claimed in claim 6, in which said third predetermined period of time is shorter than said fourth predetermined period of time.

Claim 11

A control device as claimed in claim 6, including means for setting said third predetermined period of time to a value with which, when said printing operation is continued at said first printing speed, the temperature of said electromagnet unit will not exceed an allowable value.

Claim 12

A control device as claimed in claim 6, including means for setting said fourth predetermined period of time to a value with which, when said printing operation is continued at said third printing speed, the temperature of said electromagnet unit is sufficiently decreased.