US2902929A - Electronic loose plate detector for printing press - Google Patents

Description

W. H- STONE Sept. 8, 1 959 ELECTRONIC LOOSE PLATE DETECTOR FOR PRINTING PRESS INVENTOR.

By ?/ZMM 9420M ATTORNEYS.

Filed July 20, 1956 ELECTRONIC LOOSE PLATE DETECTOR FOR PRINTING PRESS Wilfred H. Stone, Des Moines, Iowa, assignor to Meredith PElblISIlillg Company, Des Moines, Iowa, a corporation Iowa Application July 20, 1956, Serial No. 599,240

Claims. (Cl. 101-378) This invention relates to improvements in printing presses and more particularly to improved means for detecting failures in printing plates of the type utilized in high speed rotary printing presses and the like.

Rotary printing presses, as well as operating personnel, are subject to injury due to the failure of the printing plates utilized therewith. One cause of such failure is. cracking of the plates during operation of the printing press with the result that the plates are released from the hooks serving to clamp the plates to the press cylinders and are thrown outwardly therefrom.

Printing plate failure also may be due to the continuous on and on" pressure applied to an electrotype plate during the printing operation as such pressure may cause the clamping hooks to shear through the lead base of the plate and allow it to be thrown by centrifugal force from the cylinder.

Due to the existing dangers of such plate failures some form of protection for both the operating personnel and the printing press must be provided. Several schemes are known in the prior art for stopping the operation of the printing press in the event of plate failure. However, these schemes generally are of a mechanical nature, and, due to the liabilities of mass and energy inherent in mechanical systems, they have proved to be relatively slow acting. Accordingly, in such schemes it is possible that the press may be stopped only after the press or its operating personnel have been damaged or injured. Manifestly such prior art schemes are not entirely satisfactory for use with the high speed rotary presses utilized in modern printing installations.

Accordingly, it is a general object of this invention to provide an improved loose plate detector for use with a printing press which is adapted to detect plate failure while the plate is still on the press cylinder and stop the operation of the printing press prior to the defective condition reaching a stage of danger with regard to the safety of the press and its operating personnel.

It is another object of this invention to provide such an improved loose plate detector which is electronic in nature and therefore is adaptable as a safety device for high speed printing presses.

It is still another object of this invention to provide an improved loose plate detector for a printing press characterized by its high speed of operation, its efficiency and its relative simplicity.

In accordance with features of a specific illustrative embodiment of this invention the loose plate detector comprises a gaseous discharge device which is maintained in a normally nonconducting condition by a suitable negative bias potential applied between its cathode and its control grid. A relay is provided in the anode circuit of the discharge device and is adapted upon discharge of the latter to cause the printing press to be shut down so that its defective condition may be remedied. It is a feature of this invention that the use of electronic detection means enables a plate becoming loose on the press cylinder to be detected and the press stopped before damage can occur.

The cathode of the discharge device is connected to a pluralty of metallic probes disposed in an insulated metallic mounting bar extending over the press cylinder. In accordance with one embodiment of this invention the mounting bar is spaced approximately two inches from the cylinder and the metallic probes protruding from the bar are spaced within .010 inch from the plates so as to come into contact therewith when the plate becomes loose. In the event of such contact the biasing potential is removed from the discharge device and the latter conducts to shut down the printing press. It is a further feature that shut down of the printing press also de-energizes the electronic portions of the detector so that the latter is reset and in condition for further oper- .ation when the press is repaired and is caused to run once again.

The above and other features of novelty which characterize the invention are pointed out with particularity in the claims appended to and forming a part of this specification. For a better understanding of this invention, its advantages and specific objects attained by its use reference is had to the accompanying drawing and descriptive material in which is shown and described an illustrative embodiment of the invention.

In the drawing:

Figure 1 is a perspective view of one embodiment of the press cylinder, printing plate and probe mount construction in accordance with the invention;

Figure 2 is a cross section of a mounted line 2-2 of Figure 1;

Figure 3 is a cross section of the mounting and insulating bars taken on line 33 of Figure 1; and

Figure 4 is a schematic representation of the electronic control circuit embodying the invention.

Referring now to the drawing and particularly Figures 1, 2 and 3, there is shown a specific illustrative embodiment of the sensing probe mounting apparatus of the invention as utilized with a cylinder of a rotary printing press. Although the invention is shown with a printing press cylinder of the type having four plates mounted thereon it will be understood by those skilled in the art that the invention equally is applicable to rotary printing presses having any desired number of printing plates.

Press cylinder 11 is supported by frame 13 of the printing press in such a manner as to be freely rotatable therein when rotary driving power is applied to shaft 15 of the cylinder. Many devices for rotating cylinder 11 are known and it will be understood by those skilled in the art that any of these devices suitable for the purpose of driving cylinder 11 may be utilized therewith. In accordance with a preferred embodiment of the invention, however, cylinder 11 is driven by means of an electric motor connected to shaft 15 through suitable transmission means.

A plurality of arcuate printing plates such as plates 17, 19, 21 and 23, are secured to the surface of cylinder 11 by suitable clamping means such as books and the like. A plurality of probes of conductive material are supported in spaced relation from the plates by means of an elongated mounting bar 25 disposed substantially parallel to the axis of rotation of cylinder 11. Thus, mounting bar 25 supports probe 27 above plate 17, probe 29 above plate 19, probe 31 above plate 21, and probe 33 above plate 23. Mounting bar 25 is supported by means of an insulating bar 35 which advantageously may be formed of rubber, plastic or the like, secured to the press frame 13. Each probe is adapted by means of a threaded insert 37 and a nut 39 to be positioned a desired amount above the surface of its associated printing plate.

As shown in greater detail in Figure 2, each probe, as for example probe 29, is inserted through a bore provided Patented Sept. 8, 1959' probe taken on probe'is spaced avdesired amount from the surface of the printing plate 19; A threaded nut 39, which also is tapered at its inner surface to accommodateferrule 41, is.screwed on insert 37 to increase the clamping pressure of ferrule 41 on probe 29 to maintain the probe in a fixed manner at the desired position.

Thus it will be appreciated that there is a highly conductive electrical pathfrom tip 43 of the probe throughv insert 37 and mounting bar 25. In the absence of a defective'printing'plate there is no electrical path between the press frame 13 and the probes, since, as shown in Figure 3, mounting bar 25 is supportedby means of an insulating bar 35 disposed between press frame 13 and the mounting bar. Advantageously this is brought about by means of a stud 45 inserted through mounting bar 25 and insulating bar 35 and threaded into press frame 13. Electrical insulation is provided by a layer of insulating material 47 completely surrounding stud 45 so as to be disposed between the stud and the adjacent portions of mounting bar 25.

Referring now to Figure 4, the electronic control circuit there shown comprises a gaseous discharge device 10 which advantageously may be of the type generally known as a thyratron and which comprises a heater filament 12, a cathode 14, a control grid'lo, a screen grid:18 and an anode 20. In the operation of the invention discharge device 10 normally is maintained in its nonconducting condition by a biasing potential applied between control grid 16 and cathode 14 and is placed in its conducting condition by the removal of this biasing potential due to a printing plate becoming loose on the press cylinder and contacting one or more of plates 17, 19, 21 and 23.

Operating potentials are supplied to the discharge device 10 by a full wave rectifier circuit which comprises a power transformer 22 having a primary winding 24 con nected through a power switch 26 and a current limiting fuse 28 to a source of A.C. voltage 30. One secondary winding 32 of power transformer 22 has its windings connected to heater filament 12 of discharge device 10 and supplies heater current thereto.

Secondary winding 34 of power transformer 22 has one terminal thereof connected to anode 36 and the other terminal thereof connected to anode 38 of a full wave rectifier tube 40. Secondary winding 34 has a conductor 42 which is connected to a center tap thereon and also advantageously is connected to ground. Heater filament 44 of rectifier tube 40 is connected to the terminals of heater winding 32 of transformer 22.

Cathode 46 of rectifier 40 is connected to a filter network which comprises a pair of condensers 48 and t! connected across the rectifier tube output and a filter choke 52 connected in series with the tube cathode and between condensers 48and 50 in network fashion.

A-voltage dividing resistance network comprising resistances 54 and 56- is connected across the rectifier output'at condenser 50. Anode 20 of gaseous discharge is connected through the windings of a relay 58 to the rectifier output at the junction of choke 52 and condenser 50% In accordance with one specific embodiment of the invention the rectifier output at this point may have a potential of approximately 200 volts. Cathode 14 of gaseous discharge 10 is connected to the junction of resistances 54 and 56. In accordance Wit-hsaid specific embodiment these resistances are chosen such that the output potential at their junction is approximately 30 volts. Cathode 14 also is connected to screen grid 18 of dischargedevice 10.

Control grid 16 of discharge device 10 is connected to ground. Thus, it will be appreciated that when the circuit is inthe condition shown in the drawing there is a negativebiasing potential of 30. volts between control grid 16 and cathode 14 of discharge device 10. This potential serves to maintain discharge device 10 in its nonconducting condition in the normal operation of the detector control circuit.

Cathode 14 of discharge device 10 also is connected to a plurality of metallic probes such as probes 27 and 29 supported by mounting bar 25 above press cylinder 11 in the manner described above. In accordance with the specific embodiment of the invention mounting bar 25 is positioned approximately two inches above the surface of the arcuate printing plates, such as 17 and 19, secured to thesurface of press cylinder 11: In this embodiment sensing. probes 27 and 29 were set into bar 25 so as to protrude therethrough to Within .010 of an inch of the surface of the printing plates. Press cylinder 11 is connected by means of conductor 70 to ground.

It now is clear that if, during the operation of the printing'press, a plate becomesaloose and moves as little as .010 of an inch so as to come into contact with a sensing probe a circuit will be completed between cathode 14 of discharge device 10 and ground through the probe, the loose printingplate, press cylinder 25 and conductor 70. This action results inthe removal of the negative biasing potential from discharge device 10 and the latter is'triggered to conduction. Relay 58 in the anode circuit of discharge device It) thereupon is energized to close its contacts 72'and '74. This causes latching relay '78 to be energized by battery to open its contacts 82 and 84 and break the circuit between A0. source 86 and press cylinder motor 88. Consequently, the printing press is shut down to permit repair or replacement of thede= fective plate.

Advantageously, a pilot light 76 is connected'in series with contacts 72 and 74 of relay 58, battery 80 and relay 78 to indicate by its lighted condition the operation'of the detector circuit. This signals the printing press personnel to investigate for a loose plate condition as the cause of the press shut down.

Advantageously, power switch 26 is operatively asso-' ciated with latching relay 78 and is opened by the opera-;

tion of the latter to de-energize the detector circuit and reset discharge device 10. When the'defective condition of the press is remedied the operator presses the reset button the latching relay to start the press cylinder motor 88-and to close power switch 26 of the detector circuit for further operation.

It will be understood by those skilled in the art that modifications may be made in the construction and ar rangement of the parts of the above described loose plate detector without departing from the real spirit and purpose of the invention and that it is intended to cover' by the appended claims any modified forms of struc tures or use of equivalents which reasonably may be included within their scope.

What is claimed is:

1. Means for detecting a defective plate on a printing press comprising the combination of a printing press cylinder, drive means for causing said cylinder to rotate, a press plate adapted to be secured to said cylinder, sens ing means associated with said press plate and held in closely spaced relation therewith, electronic circuit means connected to said sensing means and said cylinder adapted to be operated whenever said press plate becomes loose on said cylinder and comes into electrical contact with said sensing means, said electronic circuit means including a discharge device, a source of potential, means for' to the energization of said relay means for stopping said drive means to terminate rotation of said cylinder and,

circuit means responsive to the press plate coming into electrical contact with said sensing means for removing the cut-ofi bias from said discharge device and causing the latter to conduct to energize said relay means.

2. The combination of a printing press cylinder, means for causing said cylinder to rotate, a plurality of press plates adapted to be secured to said cylinder, sensing means associated with said press plates and held closely spaced therefrom, electronic circuit means including a discharge device, means for applying a cut-ofi potential to said discharge device to maintain the latter in a normally nonconducting condition, means connected in circuit with said discharge device adapted to be energized only upon conduction of the latter for shutting off said drive means, and circuit means responsive to said sensing means being placed into electrical contact with any one of said plurality of press plates as a result of said press plates becoming loose on said cylinder for removing the cut-ofi potential from said discharge device and causing the latter to conduct.

3. Apparatus for detecting a loose plate on a printing press comprising in combination a printing press cylinder, drive means for causing said cylinder to rotate said drive means including an electric motor and switch means for applying operating potentials to said motor, a plurality of plates adapted to be secured to said cylinder, sensing probe means associated with said plates and held closely spaced therefrom, electronic means including a discharge device connected to said sensing probe means, said discharge device being normally nonconductive and adapted to be rendered conductive whenever a plate becomes loose on said cylinder and comes into electrical contact with said sensing probe means, and means connected in circuit with said discharge device adapted to be energized only upon conduction of the latter to open said switch means to stop rotation of said motor and said cylinder.

4. Apparatus for stopping the rotation of a printing press cylinder upon the detection of a defective plate thereon comprising an elongated support member positioned above the cylinder in parallel with its axis, said support member being formed of a conductive material, at least one conductive finger disposed in said support member and maintained in closely spaced relation to said plate, a discharge device including an anode, a cathode and a control grid, means for applying a cut-01f potential between said control grid and said cathode to maintain said discharge device in a normally nonconducting condition, means for connecting said cylinder to said control grid, means for connecting said cathode to said finger whereby any contact between a defective plate and said finger causes said cut-off potential to be removed from said discharge device to enable it to conduct, and actuating means connected to said anode of said discharge device adapted to be energized in response to the conduction of the latter for stopping the rotation of said press cylinder.

5. Apparatus for stopping the rotation of a printing press cylinder upon the detection of a defective plate thereon comprising a cylinder drive means for rotating said cylinder, an elongated support member of conductive material positioned above the cylinder in parallel with its axis of rotation, a bar of insulating material securing said support to the printing press frame, at least one metallic finger disposed in said support member and maintained closely spaced from said press plate, a discharge device including a pair of electrodes, means for applying a cut-ofif potential to said pair of electrodes of said discharge device to maintain it in a normally nonconducting condition, means for connecting said cylinder to said one of said electrodes, means for connecting said metallic finger to the other of said electrodes whereby any contact between a plate and said finger causes said cut-off potential to be removed from said discharge device to enable said discharge device to conduct, and actuating means connected to said discharge device adapted to be energized in response to the conduction of the latter for de-energizing said drive means stopping the rotation of said press cylinder.

6. Safety apparatus for a printing press comprising a press cylinder, drive means for rotating said cylinder, an elongated support member of conductive material positioned above the cylinder in parallel with its axis of rotation, a plurality of plates positioned on said cylinder, a plurality of metallic fingers disposed in said support member and maintained in closely spaced relation to said plates, a discharge device, bias means for applying a cutoif potential to said discharge device to maintain it in a normally nonconducting condition, means for connecting said discharge device to said cylinder and said fingers such that any contact of a plate with said fingers causes said cut-oft" potential to be removed from said discharge device to enable said discharge device to conduct, and actuating means connected to said discharge device adapted to be energized in response to the conduction of the latter for de-energizing said drive means and stopping the rotation of said cylinder.

7. Safety apparatus for a printing press in accordance with claim 6 wherein said drive means for rotating said cylinder comprises an electric motor, and further comprising a source of power connected to said motor and a switch responsive to the operation of said actuating means connected between said motor and said source of power whereby energization of said actuating means opens said switch to de-energize said electric motor.

8. Safety apparatus for a printing press in accordance with claim 7 further comprising a second source of power, and a second switch connected between said second source of power and said bias means, said second switch being responsive to the energization of said actuating means for opening the circuit between said second source of power and said bias means to de-energize the latter.

9. Safety apparatus for a printing press in accordance with claim 6 further comprising an indicator in circuit with said actuating means and responsive to the energization of the latter for signalling a defective plate condition.

10. Safety apparatus for stopping the rotation of a printing press cylinder upon the detection of a loose plate thereon comprising a press frame, a press cylinder rotatably mounted in said frame, a plurality of printing plates on said cylinder, a support member of conductive material positioned adjacent the cylinder and in parallel with its axis of rotation, an insulating bar adapted for mounting said support member to said frame, a plurality of sensing fingers in said support member and extending therethrough in closely spaced relation to said press plates, means for enabling the spacing between said fingers and said plates to be adjusted as desired, a discharge device including an anode, a cathode and a control grid, means for applying a cut-elf potential between said control grid and said cathode to maintain said discharge device in a normally nonconducting condition, means for connecting said cylinder to said control grid, means for connecting said cathode to said fingers whereby any contact between a loose plate and said fingers causes said cut-oil potential to be removed from said discharge device to enable said discharge device to conduct, and actuating means connected to said anode of said discharge device adapted to be energized in response to the conduction of the latter for stopping the rotation of said press cylinder.

References Cited in the file of this patent UNITED STATES PATENTS 1,057,134 Evensen Mar. 25, 1913 1,257,833 Fankboner Feb. 26, 1918 1,257,834 Fankboner Feb. 26, 1918 1,340,355 Wood May 18, 1920 1,708,196 Wood Apr. 9, 1929 1,856,162 Isbell May 3, 1932 2,200,316 Wieking May 14, 1940 2,431,316 Dudley Nov. 25, 1947

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