Jam detector

• US 4,551,813 A
• Filed: 11/08/1982
• Issued: 11/05/1985
• Est. Priority Date: 11/30/1981
• Status: Expired due to Fees

• Current Assignee: Tokyo Shibaura Denki Kabushiki
• Original Assignee: Tokyo Shibaura Denki Kabushiki Kaisha
• Inventors: Matsumoto, Hiroshi, Sanbayashi, Takeshi
• Primary Examiner(s): Krass, Errol A.
• Assistant Examiner(s): Cosimano, Edward R.
• Application Number:
  US06/439,985
• Time in Patent Office: 1,093 Days
• Field of Search: 271/258, 271/259, 355/14 R, 355/14 TR, 364/569, 377/16, 377/52
• US Class Current: 700/306
• CPC Class Codes: G03G 15/70 Detecting malfunctions relating to paper handling, e.g. jams

Abstract

A jam detector comprising a timer, a comparator for comparing time interval data preset in the timer with time interval data which indicates the time interval required for conveying a transfer paper sheet from a first position to a second position, an operation control device for computing updated time interval data to be reset in the timer, and a RAM for storing the computed data. When a plurality of transfer paper sheets are present along the conveyance path extending from the first position to the second position, the conveying time interval data of the first transfer paper sheet is set in the timer. When the first transfer paper sheet reaches the second position, conveying time for the second transfer paper sheet to reach from the first position to the current position is computed by utilizing the data preset in the timer. The conveying time for the second transfer paper sheet to reach from the current position to the second position is computed, and is reset in the timer. This process is repeated for each succeeding transfer paper sheet.

Claims

1. A jam detector, used in a sheet transfer device, for performing jam detection of first and second transfer sheets on a conveyance path between a first position and a second position by comparing the conveying times of the first transfer sheet and the subsequent second transfer sheet with a predetermined time needed for a transfer sheet to move between the first and second positions, said detector comprising:

a single timer means which can be preset with a value corresponding to said predetermined time, said single timer means begins to count down the preset value to a given value in response to the first transfer sheet passing the first position on said conveyance path, and generates a time-out signal when the given value is reached;

memory means, responsive to the second transfer sheet passing the first position on said conveyance path subsequent to the first transfer sheet, for storing data corresponding to that count value of said timer means which is obtained when the second transfer sheet passes the first position;

detection means for detecting the first transfer sheet at the second position and generating a detection signal;

first judging means for detecting, in response to the detection signal from said detection mens, whether or not the time-out signal is generated and for judging that a paper jam has occurred when it is detected that the time-out signal is generated; and

second judging means for reading the data stored in said memory means, when said first judging means determines that no paper jam has occurred, for computing a preset value for the second transfer sheet based on the read-out data, for setting said timer means with the computed value, and for permitting said timer to count down.

3. A jam detector according to claim 1, further comprising a display unit, connected to said first judging means, for displaying a message indicating a sheet jam when said first judging means judges that a paper jam has occurred.

4. A jam detector according to claim 1, wherein said sheet transfer device includes a main motor, a charger, an exposure lamp, a fixer and a developer, said second judging means is further connected to said main motor, said charger, said exposure lamp, said fixer and said developer to interrupt operation of said main motor, said charger, said exposure lamp, said fixer and said developer when said second judging means receives a signal from said first judging means indicating that a paper jam has occurred.

2. A jam detector according to claim 5, wherein said second judging means comprises a programmable microprocessor which is connected to said timer means, said memory means and said first judging means, and which includes a central processing unit for receiving said time-out signal from said first judging means to control said timer means and said memory means, and a read-only memory device for storing a permanent program executed in said central processing unit, whereby said second judging means controls said timer means, said memory means and said first judging means and computes the value corresponding to the remaining conveying time for the next transfer sheet by subtracting the time it took said next transfer sheet to reach its current position from the first position from said predetermined time, to store said remaining conveyance time for said next transfer sheet in said memory means, and to reset said remaining conveyance time stored in said memory means to said timer means, thereby allowing jam detection of the next transfer sheet after the preceding transfer sheet is detected.