JPS63312840A - Offset preventive device for printer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to reducing ink transfer or "offset" between newly printed sheets transferred to a stacking station or other output area of a printing press.
” relates to a device used in printing presses to prevent In particular, the present invention relates to an improved control system for anti-offset means.

Printing press offset prevention methods are commonly used,
Disclosed in U.S. Pat. No. 3,550,552 and U.S. Pat. No. 4,332.198. Such means include pressurized o
-, typically includes a spray assembly that dispenses an anti-offset material, typically in powder form, onto the newly printed sheet passing from the impession roll to the stacking station of the printing press.

Additionally, the anti-offset means prevents the material spraying operation of the spray assembly from dispensing the anti-offset material only when it is impacted onto a newly printed sheet and not when passing between successive sheets. It may also include an electrical control system that defines the cycle of. A deficiency in existing control systems is that this desired result follows automatically as long as the printing speed is maintained constant. If the print speed changes, the control system must be manually readjusted. In addition to being time consuming, such realignment may be overlooked by the print operator, and in such cases the munch offset material may not be sprayed on all required sheet portions and/or the gap between adjacent sheets may be is sprayed on. Both of these results are highly undesirable.

With the foregoing in mind, the present invention provides an inexpensive but highly reliable control means whereby the operation of an anti-offset material spraying device of the type described above is responsive to and responsive to changes in the operating speed of the printing press. automatically adjusted in a manner that compensates for In its preferred embodiment, the control means of the present invention dispenses anti-offset material from a spray nozzle upwardly onto each newly printed sheet at several preselected locations along its travel path. seat position indicating means for generating an electrical trigger signal indicative of the arrival of the vehicle. This trigger signal is converted into a pulse signal by a pulse generator, which includes a pair of adjustable timing devices whose timing periods determine, respectively, when each cycle of operation of the anti-offset material spray apparatus begins and ends. and then received by the electrical control means. The set of pulse signals is directed from the aforementioned pulse generator to a fixed pulse generator which generates synchronization pulses of fixed duration. Integrating means, preferably in the form of a capacitor and an operational amplifier, convert the aforementioned pulses into a control voltage signal which is inversely proportional to the pulse frequency and therefore inversely proportional to the printing speed. A control voltage signal is continuously transmitted to the first and second timing devices and performs an inversely proportional compensating change in the duration of the device's timing in response to changes in speed of the printing press. The means of spraying the anti-offset material may be of the pneumatic type, including an air compressor, as is often the case.
e), the control system of the invention includes means for effecting automatic termination of compressor operation after a time interval sufficient for passage of the final printed sheet through the location where the anti-offset material is sprayed. It is also desirable to include.

In addition to those previously cited, the following U.S. Pat.
No. 16.790, No. 4.198.907, No. 4.21
No. 1.258 and No. 4.500.937 are relevant to the present invention.

The invention will now be described in detail by way of example with reference to the accompanying drawings.

Referring specifically to the drawings, number 10 indicates its printing station (schematically bracket and pressure roll 14.16).
from its sheet stack or sheet receiving station (represented by
ction 5tation) 18 The sheet delivery mechanism of the printing machine
ism) 12 is shown being transported by a newly printed sheet. The delivery mechanism 12 is a roll 14.16
A gapped gripper bar (
exemplified by the known endless chain type with a gripper bar). However, several other types of sheet delivery mechanisms could be used in place of the one shown.

To minimize the possibility of ink transfer or "offset" occurring between newly printed sheets at the stacking station 18, the material spraying device or means 21 is configured such that the sheets are transported by the mechanism 12 to the stacking station. Spray anti-offset material powder onto the sheet 10. Apparatus 21 includes a material dispensing nozzle 22 located in close overlapping relation to the path traveled by sheet 10 between roll 14.16 and stacking station 18. Nozzle 22 is connected to a hopper 23 or other suitable source of anti-offset material by a conduit 24 containing an electrically actuatable valve 26. A branch conduit 28 also connects the nozzle 22 with an air compressor 30.

Anti-offset material from hopper 23 is sprayed from nozzle 22 when compressor 30 is operating and valve 26 is open. even compressor 3
Closure of valve 26 terminates the material spraying operation of spray device 21 even though zero is energized and compressed air is continuously directed into conduit 24.

The operation of the spray device is defined by adjustable control elements which will now be described. Such elements are placed at a number of preselected locations along the seat travel path.
A sensor 3 that directly or indirectly detects the presence of the leading edge of each successive sheet of the moving sheet 10 and converts it into a signal.
Contains 2.

While the aforementioned locations are anywhere along the sheet path of travel, it is illustratively located at the upwardly facing end of the sheet delivery mechanism 12 (
relative to the direction of sheet travel). As illustrated in the figures, the sensor 32 consists of a snap switch that can be activated by the leading edge of each sheet IO and/or some element of the sheet delivery mechanism 12 that is movable therewith. Can be done. Upon each such engagement, sensor 32 transmits an electrical trigger signal to pulse generator 34, which forms part of the primary control means of device 21.

In response to an electrical trigger signal transmitted thereto from sensor 32, pulse generator 34 generates two sets of synchronous electrical pulses. One set of pulses generated by the pulse generator 34 passes through an electronic timer 36,38 to the valve controller 40.
The valve controller 40 is connected to a valve 26 whose opening and closing initiate and end each cycle of anti-offset material spraying operation of the device 21, respectively.
control the behavior of

Potentiometers 36', 38', associated with timers 36, 38, respectively, allow manual adjustment of the timing period. The timing of timer 36 determines the delay that occurs between actuation of seat position sensor 32 and the start of the spray cycle of operation of device 21.

This delay is caused by the leading edge of each sheet 10 being at the designated position A.
(where sensor 32 is activated) to compensate for the time required to go from vertically aligned position with nozzle 22 of device 21. Manual adjustment of the delay time of the timer 36 using the attached potentiometer 36' is only required when the device 21 and/or the sensor 32 are first set up, or if they change the distance between positions A, B. This is typically required for situations that are adjusted in a changing manner.

The timing period of the other timer 38 defines the time of completion of each cycle of material spraying operation of the device 21, and thus its duration. If there is a change in the actual length of the sheet 10 being printed, or if it is desired to spray the anti-offset material onto only a portion of each sheet, then the "effective" length of the sheet may vary. If there is,
Potentiometer 38' is used to manually and compensatedly adjust the aforementioned timing periods and spray cycle durations.

The cycle of material spraying operation of the device 21 will no longer be correct due to the movement of the sheet 10 under the spray nozzle 22 if the printing speed is changed and there is no compensating change in the time delay period of the timer 36,38. There will be no synchronization. To avoid this highly undesirable result, means are provided to automatically adjust the timing of the timers 36,38 to respond to and compensate for changes in printing speed. The aforementioned speed compensation control means includes a speed pulse generator 35 which receives a second set of pulses generated by the pulse generator 34 in response to a trigger signal from the sheet sensor 32. In response to reception from the aforementioned pulse signal generator 34, the frequency of which is proportional to the printing speed,
The speed pulse generator 35 generates and transmits fixed length electrical pulses of the same frequency to a charging capacitor 42 and an integrating means in the form of an operational amplifier 44. After a short period of time, the pulses then charge the capacitor to a voltage that is proportional to the pulse frequency and therefore the printing speed. The capacitor charge forms the input of operational amplifier 44, which responsively transmits an inverse proportional control voltage signal to timer 36.38. Such a control signal does not change the duration of the timer as long as the printing speed remains constant. However, if the print speed changes, the control signal will cause a change that compensates for the timing of both timers. In this way, if the printing speed is for example 10
When increased by a percentage, the times of timers 36,38 are each automatically decreased by 10%. Similarly,
If the printing speed is decreased by a certain percentage, the duration of timer 36,38 is automatically increased by the same percentage.

Electrical control signals transmitted from tie 36.38 to solenoid valve controller 40 are transmitted to compressor controller 46, which controls the energization and deactivation of a motor (not shown) associated with air compressor 30.

The controller 46 causes the compressor motor to remain energized during each cycle of material spraying operation of the spray device 21 and for a preselected short period of time following the completion of each cycle of such operation. . The aforementioned time limit is
The compressor motor is operated continuously while the printing sheet 10 passes under the spray nozzle 22, but is automatically shut off when the last seed in the printing "run" passes under the nozzle. It is long enough so that it can be used.

The aforementioned automatic shutdown of compressor operation contributes significantly to compressor life.

Although preferred embodiments of the invention have been specifically shown and described, this is for purposes of illustration and not for purposes of limitation.

(Summary) A newly printed sheet is being sprayed with an anti-offset material while being transferred from the printing station of the printer to the sheet stacking station. The spray equipment control circuit detects the position of each successive sheet and
It includes a signaling sensor and a timer whose timing determines when each cycle of operation of the spray device begins and ends. The time limit is made manually adjustable by a potentiometer associated with the timer and is automatically and compensatingly adjusted in response to changes in printing speed. Operation of the air compressor element of the spray device automatically ends after spraying the last printed sheet of the printing run.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the control and configuration of an offset prevention device for a printing press according to the present invention. 1 Misaki... Sheet 12... Sheet delivery mechanism 14, 16...
... Pressure roll 18 ... Sheet stacking (or receiving) station 20 ... Gripper bar 21 ... Spray device (or means) 22 ... Nozzle 23 ... Hopper 24 ... Conduit
26... Valve 28... Branch conduit 30.
・・Air compressor Nosa 32・・Seat sensor
34...Pulse generator 35...Speed pulse generator 36, 38...Electronic timer 36', 38'...Potentiometer 40...
・Solenoid valve controller 42...Charging capacitor 44...Operation amplifier 4
6... Compressor controller patent applicant Airtic Company, Inc.

Claims (1)

[Claims] 1. Sheet delivery means for guiding a newly printed sheet along the path of the trip from the printing station to the sheet receiving station of the printing press, and an anti-offset material along the path of said trip. In an apparatus combined with a printing press having cyclically operable sheet spraying means for spraying each successive sheet in motion, in preparation for each cycle of operation of said sheet spraying means, one of said sheets is seat position indicating means for generating electrical trigger signals indicative of a position along said path of travel; 1 for causing motion by said spray means for one cycle of said motion in response to each said trigger signal;
secondary electrical control means, said primary control means comprising: timer means having adjustable timing periods for defining the end time of each cycle of operation of said spraying means; Apparatus comprising: adjustable means for performing the adjustment; and speed-responsive control means for automatically adjusting said timing periods in a manner responsive to and compensating for changes in speed of said printing press. 2. said primary control means comprising second timer means having an adjustable timing period defining a set time for each said cycle of operation of said spraying means; and said second-mentioned timing period; and wherein said speed-responsive control means is responsive to and compensates for changes in the speed of said printing press at said first-mentioned timing intervals. Apparatus as claimed in claim 1, for automatically adjusting both of the second-mentioned timing periods. 3. The speed responsive control means is effective to include pulse generating means for generating electrical pulses at a frequency proportional to the speed of the printing press, and for receiving the pulses and adjusting timing periods accordingly. 3. Apparatus as claimed in claim 2, including integrating means for directing a control signal to said first and second timing means. 4. said integrating means comprises capacitor means for receiving said pulses and generating a control voltage proportional to the pulse frequency; and operational amplifier means for receiving said control voltage and generating said control signal; 4. The apparatus of claim 3, wherein said control signal is inversely proportional to said control voltage. 5. The spraying means includes an air compressor;
further comprising air compressor control means for maintaining energization of said air compressor during each said cycle of operation of said spraying means and for a preselected time period following the end of each said cycle of operation. Apparatus according to claim 4. 6. The speed responsive control means includes pulse generating means for generating electrical pulses at a frequency proportional to the speed of the printing press, and capacitor means for receiving the pulses and generating a control voltage proportional to the pulse frequency. and operational amplifier means for receiving said control voltage and responsively directing an inversely proportional electrical control signal to said timer means. 7. Apparatus according to claim 6, wherein said seat position indicating means comprises a switch element actuable by engagement of a leading edge portion of each successive seat. 8. said primary control means including second timer means having an adjustable timing period defining a set time for each cycle of operation of said spraying means, said electrical control signal also said second timer means; 8. A device according to claim 7, which is directed to the timer means as described in . 9. said spraying means comprises an air compressor, and during each said cycle of operation of said spraying means;
and air compressor control means for maintaining energization of said air compressor for a preselected period of time following the end of each said cycle of operation.
Equipment described in Section.