Method of and apparatus for detecting abnormal paper feeding

A method and apparatus for detecting an abnormal paper feed such as a paper jam in a printing press which can reduce the work load for an operator and prevent productivity and printing quality from being lowered by detecting the elapsed time of travel of a first sheet of paper from a paper feeder to a register, with the time corresponding to the number of sheets reaching the register. This number is compared to a number of paper sheets stored in a memory. When there is an agreement between the compared sheet numbers, normal paper feeding is indicated. When the detected number of sheets is more or less than the number stored in memory, abnormal paper feeding is indicated and further paper feeding is interrupted. A number less than the required number is indicative of paper remaining on a feeder board from a previous printing operation. A number larger than the required number is indicative of a paper jam.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a method and apparatus, acting as a safety
 device, for detecting abnormal paper feeding in a sheet printer and, more
 particulary, for detecting abnormal paper feeding in a sheet printer from
 a paper feeding portion to a printing unit portion thereof.
 2. Description of the Prior Art
 When performing a printing operation on a rotary printing press such as
 shown and described in assignee's U.S. Pat. No. 5,983,796, Ishida et al.,
 Nov. 16, 1999, an operator operates the apparatus to feed printing papers
 piled on a paper feeding portion to a printing unit portion to start the
 printing operation. However, there are times when paper feeding is not
 performed normally due to "an improper setting of the paper feeding
 portion in various kinds of apparatuses" or "problems with the papers" or
 the like occurs. In response to such abnormal paper feeding, various kinds
 of safety apparatuses are provided in a paper register portion or the
 paper feeding portion itself so as to automatically detect this
 malfunction.
 For example, as disclosed in Japanese Utility Model Publication No.
 2-39808, there is shown apparatus for detecting abnormal paper feeding
 having a luminescent element and a photoreceptor element provided near a
 front lay in a feeder board of the sheet printer for detecting whether an
 abnormal paper feeding state with respect to the front lay of a sheet
 paper is large or small. The apparatus includes a control circuit which
 transmits a cylinder disengagement signal in synchronism with an operation
 of the printer and a control signal for discharging sheet paper as a
 special state when the abnormal paper feeding state is large on the basis
 of a detected output from the photoreceptor element, and transmits only
 the control signal in synchronism with an operation of the printer when
 the abnormal paper feeding state is small. In accordance with the
 foregoing apparatus, there is an advantage if the number of interruptions
 of operation can be reduced and the sheet paper, in a small abnormal paper
 feeding state, can be discharged as the special state after being printed
 so as to be easily separated from a normal sheet paper.
 However, conventional safety apparatus including the apparatus mentioned
 above performs a function as a safety device by directly detecting "a
 positional shift of paper" or "overlapping papers" or the like.
 Accordingly, the following problems can occur during a printing operation.
 (1) In the situation where paper does not reach a plurality of safety
 devices provided in the register portion even when a timing for feeding a
 paper is shifted, an accurate detection and judgement as to whether the
 paper feeding state can or not can not performed.
 (2) Generally, since the safety device performs the foregoing detection at
 a fixed timing (within a time period),there is a case where the detection
 of the abnormal paper is delayed when the timing of the fed paper is
 shifted, and the safety apparatus cannot perform the function as the
 safety device.
 (3) There are times when the fed paper is interrupted by the register
 portion or a member provided on the feeder board, resulting in too many
 papers flowing into the printing unit portion, and causing damage or
 trouble in the apparatus or a blanket or the like.
 (4) When a malfunction mentioned above is generated, it is necessary for
 the operator to always observe whether or not the paper fed from the paper
 feeding portion properly enters the register portion.
 (5) When a malfunction mentioned above is generated, not only is some
 damage caused, but also a loss time for a post operation is generated
 therewith, so that not only are productivity and printing quality reduced,
 but also the work load for the operator is increased.
 SUMMARY OF THE INVENTION
 Accordingly, an object of the present invention is to provide a method and
 apparatus for detecting an abnormal paper feed which can increase the work
 load on an operator and lessen productivity and printing quality by
 improving a detecting function with respect to a timing shift of fed paper
 to avoid various kinds of malfunctions previously caused by abnormal paper
 feeding.
 In order to achieve the object mentioned above and in accordance with the
 present invention, there is provided a method of detecting an abnormal
 paper feed comprising the steps of detecting the number of papers fed to a
 printer based on a paper feeding signal generator generating a signal in
 response to paper feeding after the start of paper feeding, detecting
 whether or not paper exists on a feeder board by a paper existence
 detector located on the feeder board, and detecting an abnormal paper feed
 state in accordance with a relation between the number of the papers fed
 and the existence or non-existence of detected paper.
 In the method of detecting abnormal paper feeding according to the above,
 an abnormal paper feed is judged to exist in the case where said paper
 existence detector does not detect the existence of paper on the feeder
 board when said number of the fed papers is equal to a preset fixed
 number.
 In the method of detecting an abnormal paper feeding according to the
 above, an abnormal paper feeding is judged to exist in the case when said
 paper existence detector detects the existence of paper when said number
 of the fed papers is less than a preset fixed number.
 Further, in accordance with the present invention, there is provided an
 apparatus for detecting abnormal paper feed, which is used for the method
 of detecting an abnormal paper feed according to the above comprising, a
 paper feeding start signal generator, a paper feeding signal generator
 generating a signal in response to paper fed to a printer, a paper
 existence detector located on a feeder board, and a control apparatus
 having number of fed paper memory means for storing a number of papers fed
 to the printer until a first paper comes to the paper existence detector
 after the paper feed is started, and detecting an abnormal paper feed from
 a relation among the number of fed papers from said paper feeding signal
 generator, the number of the fed papers stored in said number of fed paper
 memory means and the detected signal of said paper existence detector so
 as to output a paper feed stop signal.
 In the apparatus for detecting an abnormal paper feed according to the
 above, the control apparatus outputs a paper feeding stop signal by
 judging an abnormal paper feeding in the case when the paper existence
 detector does not detect the existence of paper when the number of the fed
 paper for the printer, after the paper feeding is started, equals to the
 number of the fed paper stored in said number of fed paper memory means.
 In the apparatus for detecting an abnormal paper feed according to the
 above, the control apparatus outputs a paper feeding stop signal by
 judging abnormal paper feed in the case that the paper existence detector
 detects the paper existence when the number of the fed paper for the
 printer, after the paper feeding is started, is less than the number of
 the fed paper stored in said number of fed paper memory means.
 In accordance with the method of and the apparatus for detecting abnormal
 paper feed mentioned above, an abnormal paper feed due to a timing shift
 from the paper feeding portion to the register portion can be
 automatically and accurately detected, so that a paper feed to the
 printing unit thereafter can be securely stopped.

DESCRIPTION OF THE PREFERRED EMBODIMENT
 A method and apparatus for detecting an abnormal paper feed in accordance
 with the present invention will be described in detail on the basis of an
 embodiment shown in the accompanying drawings and where:
 FIG. 1 is a side elevational view of a four color printing sheet paper
 rotary printer depicting an embodiment of the present invention; FIG. 2 is
 a detailed view of a main portion of a register portion; FIG, 3 is a plan
 view of a control panel; FIG. 4 is a flow chart of the operation of the
 control apparatus of the present invention; and FIG. 5 is a timing chart
 illustrative of a normal time and an abnormal time of apparatus of the
 control apparatus.
 As shown in FIG. 1, a four color printing sheet paper rotary printer 1 is
 structured such that it includes a paper feeding portion 2, a register
 portion 3, a printing unit portion 4, and a paper discharging portion 5
 and which are successively arranged in the order from the right and where
 a pile of sheet paper 6 placed on the paper feeding portion 2 is printed
 and discharged to the paper discharging portion 5 after being successively
 fed to a first to fourth color printing units 4a to 4d through the
 register portion 3.
 Any changes in the paper feed time of the sheet paper 6 fed from the paper
 feeding portion 2 to the register portion 3 is automatically detected by a
 control apparatus (a control circuit), not shown located within a control
 table 7 mounted on a side surface of the paper feeding portion 2,
 whereupon paper feeding to the printing unit portion 4 is thereafter
 stopped.
 Accordingly, in the above control apparatus, the following signals are
 input: signals such as an ON signal from a product switch 10 (described
 below), provided by a paper feed start signal generator; a reference pulse
 of a rotary encoder, provided by a paper feed signal generator which
 generates a signal in accordance with a paper feed in the four color
 printing sheet paper rotary printer 1; and a paper existence/non-existence
 signal from a cylinder engagement sensor 11 (described later), generated
 by a paper existence/non-existence detector. The control apparatus also
 includes a paper feed number memory means which stores a number of fed
 paper sheets in the four color printing sheet paper rotary printer 1, to
 which the first sheet of paper from the pile 6 is supposed to be delivered
 to and thus passes over the cylinder engagement sensor 11 following the
 beginning of paper feed. When the cylinder engagement sensor 11 does not
 output a paper existence signal at the time when the number of paper feed,
 from the beginning of the paper feed, is equal to the number stored in the
 paper feed number memory means, or when the cylinder engagement sensor 11
 outputs the paper existence signal at the time when the number of paper
 feed, from the beginning of the paper feed, is less than the number stored
 in the paper feed number memory means, the control apparatus determines
 that an abnormal paper feed has occurred, illuminates a pilot lamp 12
 (described later), and turns the product switch 10 OFF.
 The product switch 10 mentioned above is disposed on an operation control
 panel 13 provided in the paper discharging portion 5, as shown in FIG. 3,
 and outputs the ON signal, a signal for starting a paper feed by pushing a
 start button by the operator. Further, the pilot lamp 12 and a printer
 stop button 14 are provided on the operation control panel 13.
 The cylinder engagement sensor 11 is fixed to a feeder board 15, provided
 in the register portion 3, by a fixing screw 16, as shown in FIG. 2, and
 is structured to detect whether or not the paper exists by a quantity of a
 reflected ray. Further, the cylinder engagement sensor 11 is threaded to a
 holder 17, and is structured such that a height of a detecting surface can
 be adjusted by a nut 18. Element 19 comprises an intermediate element
 located between the feeder board 15 and a convey board, not shown.
 Further, the rotary encoder is provided on a rotary shaft in a drive system
 of the four color printing sheet paper rotary printer 1, and generates a
 pulse signal for each rotation of the shaft.
 Being structured in the above manner, a printing operation can be started
 by the operator performing a drive operation of the four color printing
 sheet paper rotary printer 1 by turning on the product switch 10. When the
 printing operation is started, the paper sheets 6 piled on the paper
 feeding portion 2 are automatically fed to the register portion 3 from the
 paper feeding portion 2, and are conveyed to the paper discharging portion
 5 and piled there after being printed in each of the printing units 4a to
 4d.
 Normally, the printing operation is performed in accordance with the
 procedure mentioned above. However, due to various reasons, there is an
 instance where the feed timing for the sheet paper 6 shifts from the
 normal paper feed timing at a time of starting the feeding of the paper
 sheet 6. In such an instance, in this embodiment, the control apparatus in
 the control table 7, mentioned above, detects this, thereby turning on the
 pilot lamp 12 on the operation panel 13, outputting a paper feeding stop
 signal, and turning off the product switch 10.
 A control operation of the control apparatus will now be described below on
 the basis of the operation flow chart shown in FIG. 4 with reference to
 the timing chart in FIG. 5.
 At first, when the product switch 10 is turned on by the operator in step
 P1, whether or not sheet paper 6 exists is detected by the cylinder
 engagement sensor 11 in step P2. When the sheet paper 6 printed at the
 preceding time is left on the feeder board 15, the product switch 10 is
 turned off in step P16. That is, the control is maintained until the
 remaining paper is removed.
 When the remaining paper no longer exists on the feeder board 15 in step
 P2, the controls such as "turning on a feeder", "turning of a feeder
 pump", "opening a feeder valve" and the like are continuously and
 automatically performed in steps P3 to P5.
 Next, after paper feeding in the feeder is started in step P6 and a counter
 is reset to zero in step P7, whether or not sheet paper 6 exists is again
 detected by the cylinder engagement sensor 11 in step P8, and when the
 sheet paper 6 printed in the preceding time remains on the feeder board
 15, the pilot lamp 12 is turned on in step P17, the feeder is stopped in
 step P18 and, successively, the product switch 10 is turned off in step
 P16.
 When the remaining paper does not exist on the feeder board 15 in step P8,
 a reference pulse of the rotary encoder is input in step P9, and the
 counter starts a counting operation of the reference pulse in step P10.
 That is, the number of the fed paper for the four color printing sheet
 paper rotary printer 1 from the beginning of the paper feeding until the
 first sheet paper 6 comes to the cylinder engagement sensor 11 is
 calculated by the reference pulse of the rotary encoder mentioned above.
 Next, an actual number of the fed paper is compared with a predetermined
 fed paper number (for example seven), previously stored in the number of
 fed paper memory means in step P11. In the case where the cylinder
 engagement sensor 11 outputs a paper existence signal when the number of
 the fed paper is less than the number of the fed paper stored in the
 number of fed paper memory means, it signifies that abnormal paper
 feeding, caused by the paper feeding timing being shifted to an early
 side, is judged in step P19, the pilot lamp 12 is turned on in step P17,
 the feeder is stopped (turned off) in step P18, and the product switch 10
 is successively turned off in step P16.
 In the case where the cylinder engagement sensor 11 does not output a paper
 existence signed in step P19, it signifies that normal paper feeding is
 being performed, so that the step is returned to step P9 and the counting
 is continued.
 Next, in the case when it is determined, in step 11, that the cylinder
 engagement sensor 11 does not output a paper existence signal when the
 actual number of the fed paper and the predetermined number of the fed
 paper, previously stored in the fed paper memory means, are equal, it is
 determined that an abnormal paper feeding caused by the paper feed timing
 being shifted to a delay side, so that the pilot lamp 12 is turned on in
 step P17, the feeder is stopped (turned off) in step P18, and the product
 switch 10 is successively turned off in step P16.
 In reality, as shown in FIG. 5B, since the paper existence signal from the
 cylinder engagement sensor 11 is not output therefrom during the seventh
 detecting gate pulse, a feeder stop signal is output. In this case the
 detecting gate pulse is output during a fixed rotary angle of the printer
 with reference to the reference pulse (the timing pulse) from the rotary
 encoder.
 In the case where the cylinder engagement sensor 11 outputs a paper
 existence signal in step P12, normal paper feeding is being performed.
 Therefore, a cylinder engagement signal of the printing unit 4a for a
 first color is output in step P13. Thereafter, a printing operation in
 each of the printing units 4b to 4d for a second color to a fourth color
 is continued in step P14, and a printing is complete in step P15. In this
 case, the pilot lamp 12 illuminated in step P17 is automatically turned
 off when "the feeder is again turned on" after taking necessary steps for
 the sheet paper that has been abnormally fed.
 As mentioned above, in the present embodiment, the steps necessary due to
 the timing shift of the paper feeding can be omitted. Accordingly, a
 typical watch operation for preventing a malfunction from occurring can be
 omitted. As a result, the work load of the operator can be reduced and the
 time can be reduced, so that a productivity can be improved and a printing
 quality can be stabilized. Further, since the conventional cylinder
 engagement sensor 11 and rotary encoder can be used, it is advantageous in
 cost.
 In the embodiment mentioned above, the reference pulse of the rotary
 encoder is used as means for detecting the number of paper sheets 6 fed to
 the register portion 3 from the paper feeding portion 2. However, a sensor
 can be provided in a part of a sucker main body such that the number of
 the papers is counted at a position at which the sheet paper 6 is sucked
 by a first suction port so as to be lifted up, or a sensor for detecting a
 pressure change can be provided within a passage of a pipe of a sucker
 valve such that the number of the papers is counted by detecting the
 pressure change in a state that the sheet paper is sucked.
 Further, the present invention is not limited to the embodiment mentioned
 above, and it is needless to say that various kinds of modifications can
 be made within the scope of the invention.
 As mentioned above, in accordance with the method and apparatus for
 detecting abnormal paper feed of the present invention, the control
 apparatus is provided with a signal from a paper feed start signal
 generator. A signal from a paper feed signal generator which generates a
 signal in accordance with a paper feed in the printer, and a paper
 existence/non-existence signal from paper existence/non-existence detector
 provided on the feeder board. Further, the control apparatus has a paper
 feed number memory means which stores a predetermined number of fed paper
 in the printer, to which the first paper sheet is supposed to be delivered
 to the paper existence/non-existence detector. When the paper
 existence/non-existence detector does not output a paper existence signal
 at the time when the number of paper feed, from the beginning of the paper
 feed, is equal to the number the predetermined number stored in the memory
 means, or when the paper existence signal at the time when the number of
 paper feed, from the beginning of the paper feed, is less than the
 predetermined number stored the memory means, the control apparatus
 determines that an abnormal paper feed has occurred, and generates a paper
 feed stop signal. Therefore, abnormal paper feed between the paper feed
 portion and the register portion due to the shift in the timing can be
 automatically detected with high accuracy, thus preventing various
 malfunctions due to abnormal paper feed. This reduces the workload of an
 operator and prevents reduction in manufacturing efficiency and printing
 quality.