GB1601225A - Alternating current energized printing system utilizing a dielectric covered resilient impression roller - Google Patents

Description

(54) ALTERNATING CURRENT ENERGIZED PRINTING SYSTEM UTILIZING A DIELECTRIC COVERED RESILIENT IMPRESSION ROLLER (71) We, tII !RLETRON ALTAIR, INC.

a Corporation organised and existing under the laws of the State of Illinois of 1938 East Fairchild Street, Danville, State of Illinois, 61832, United States of America, do hereby declare the invention, for which I pray that a patent may be granted to me, and the methcd by which it is to be performed, to be particularly described in and by the following statement: This invention relates to an apparatus for assisting the transfer of ink.

According to the present invention there is provided an apparatus for assisting the transfer of ink, carried on a metal printing cylinder connected to ground potential, to a web of substantially non-conductive material as the web paasses along a web path through a nip between the grounded printing cylinder and the outer perimeter of a resiliently covered impression roller said apparatus comprising a metal printing cylinder connected to ground potential an impression roller comprising a core, an electrically conductive layer of resilient material on said core a sleeve of dielectric material on said layer of resilient material, said sleeve being of homogeneous continuous annular cross section and having a resistivity substantially greater than that of said conductive layer, means mounting said impression roller for rotation on its central axis and insulating said electrically conductive layer of resilient material on said core from ground potential, and means comprising an electric circuit connected with said electrically conductive layer for applying an alternating electric potential between said electrically conductive layer and said grounded printing cylinder, the entire operative width of the outer perimeter of the impression roller being formed entirely by said dielectric material of said sleeve, said dielectric material having a thickntss less than one-eighth of an inch and having a dielectric constant between twenty and one hundred, and said electric circuit cimprising an alternating potential source for applying an alternating current electric potential between said electrically conductive layer of resilient material and said grounded printing cylinder to produce an alternating reactive current from said electrically conductive layer through said dielectric material of said sleeve over the entire width of said impression roller.

The sleeve of dielectric material may have a width substantially equal to the width of the outer perimeter of the core.

Alternatively, the width of the sleeve of dielectric material may be less than the width of the outer perimeter of the core, the sleeve forming the outer perimeter of the impression roller and being disposed directly at said web path for direct contact with Ihe web at said nip over the operative width of the outer perimeter of the impression roller.

A preferred embodiment of the invention will now be described with reference to the accompanying drawing.

The single figure of the drawing is a somewhat diagrammatic end elevational view of a form of apparatus according to the invention including an electrically assisted printing system utilizing an impression roller.

The electrical printing roller, for example in an electrically assisted gravure printing system, is considered to be the most critical component because of the stringent and relatively narrow electrical requirements for such roller.

Conventional gravure impression rollers used in presses without the application of electrical potential are limited in their advantageous characteristics because of the need for solvent resistance in the printing environment. Accordingly, optimum thermal conduction and resilience, for example, have not been achieved in the conventional gravure impression roller. It is conceived that the provision of a sleeve cover, for example formed of heat shrinkable material, will enable the use of a covering with excellent chemical and abrasion resistance, while the underlying substrate of the roller can have optimum thermal conduction and resilience. For example, the outer covering sleeve may be of neoprene, while the material of the substrate may be of natural rubber or other material with thermal conductivity and resilience substantially equivalent to that of natural rubber. This permits not only longer life, but higher press speeds. When excessive wear or catastrophic failure takes place, the covering sleeve is simply replaced. Such replacement can take place at the user's plant, thus avoiding the delay due to shipping and the like which is generally the case at present.

In an electric printing roller, in addition to conventional parameters, one needs an elecrical parameter critically related to the printing system. Such printing systems include those utilizing direct current potential and alternating curent potential, for example, as will hereinafter be explained.

By way of example, in an electrically assisted gravure printing system, printing conditions are encountered whereby portions of the impression roller contact the design cylinder to print a partial web. Using an applied direct current potential, for example, such contact interferes with the electrical function and the amount of assist becomes a compromise. The present invention employs an alternating current potential and with the use of the extruded sleeve configuration contemplated herein, it is entirely practical to use a partial sleeve covering of the impression roller, thus permitting an adjustment of the width of the conducting surface to correspond to that of the web without any change of the basic impression roller.

In the case of electrically assisted printing, when an electrical property is required of the sleeve, the present invention provides an optimized geometry enabling precise control of the parameter in manufacture and in auditing. Conventional rollers must be refaced frequently to extend the life of the rollers with a consequent progressive reduction in diameter. This change adversely affects the electrical properties.

When the covering sleeve configuration of the present disclosure is replaced, satisfactory control for the electrical parameters is maintained simply by the proper selection of the thickness of the replacement covering sleeve. Although the sleeve cover may be refaced, one has a satisfactory control for the electrical parameters by maintaining a defined thickness.

Replacement of the sleeve for any roller may be done locally and in a few hours.

Where rollers must be returned to the vendor and revulcanized as with prior art impression rollers a time loss of several weeks commonly results. Rollers are heavy and consequently shipping costs are high.

A preferred apparatus for applying a heat-shrinkable sleeve to a roll is shown in MacCallum, Toward and Coberley U.S.

Patent No. 3,677,856 issued July 18, 1972, and may comprise an impression roller support which is rotatable on a vertical axis and which is so shaped as to receive the lower journal of the roller and to support the roller during insertion into a sleeve. A means to rotate the roller at a variable speed is provided fixed to the rate of rise of a circumferential heater. The heater is so constructed as to permit convection to preheat the sleeve and to provide a maximum average radiant watt density of 80 watts per square inch (variable). A belt is wrapped for at least 360" about the lower part of the sleeve and is tensioned to exert uniform pressure about the entire perimeter of the sleeve. Energy is then applied, for example heat energy by means of the aforesaid heater, tending to cause the sleeve to constrict onto the roller.

The rotation of the roller serves to drive the belt and also to cause the belt to move progressively along the axis of the roller to smoothly apply the sleeve to the roller and to progressively remove entrapped gases. In one embodiment, a reservoir of adhesive is formed between the roller and sleeve at the lower portion thereof, the belt serving to progressively move the reservoir upwardly to distribute the adhesive over the interface betwen the roller and the sleeve.

Referring to the drawing there is illustrated an alternating current printing system including a design cylinder 30 having a grounded shaft 31 and cooperating with an impression roller 32 which receives an alternating current potential from an alternating potential source 33. A web 34 is indicated as moving in the direction of arrow 35 through a printing zone or nip region between the design cylinder 30 and impression roller 32. In this embodiment an insulated bearing 34' journals a metal shaft 35' which serves to supply the alternating current potential to brush means such as indicated at 36 and 37 in sliding contact with the metal core 38 of the roller.

The roller 32 further includes a resilient electrically conductive substrate layer 39 and an outer covering sleeve 40 of dielectric material. By way of example, the dielectric material of sleeve 40 may have a dielectric constant between 20 and 40. By way of example where the sleeve 40 is of a heat shrinkable elastomer dielectric material, the thickness thereof is not more than about 1,8 inch. Preferably the sleeve 40 is bonded to the substrate 39 by means of an adhsive as previously described, the substrate 39 being bonded or vulcanized to the core 38. As an example, the sleeve 40 may be made of a heat shrinkable irradiated elastomer material such as neoprene. Neoprene has the advantage of being ozone resistant, to a substantially greater degree than natural rubber, for example.

As another example, the sleeve 40 may comprise a sleeve of homogeneous continuous annular cross section and of dielectric elastomer material having a thickness between about 1/16 inch and about 1/8 inch, and a dielectric constant of for example substantially forty (40). The sleeve may be of vulcanized rubber or the like rather than being formed of heat shrinkable material. Further the sleeve preferably has a resistivity substantially greater than the resistivity of the conductive layer 39 and preferably in the range from 108 ohm-centimetres to 1(Y ohmcentimetres, or greater.

WHAT WE CLAIM IS: 1. An appartus for assisting the transfer of ink. carried on a metal printing cylinder connected to ground potential, to a web of substantially non-conductive material as the web passes along a web path through a nip between the grounded printing cylinder and the outer perimeter of a resiliently covered impression roller said apparatus comprising a metal printing cylinder connected to ground potential an impression roller comprising a core, an electrically conductive layer of resilient material on said core a sleeve of dielectric material on said layer of resilient material, said sleeve being of homogeneous continuous annular cross section and having a resistivity substantially greater than that of said conductive layer, means mounting said impression roller for rotation on its central axis and insulating said electrically conductive layer of resilient material on said core from ground potential, and means comprising an electric circuit connected with said electrically conductive layer for applying an alternating electric potential between said electrically conductive layer and said grounded printing cylinder, the entire operative width of the outer perimeter of the impression roller being formed entirely by said dielectric material of said sleeve, said dielectric material having a thickness less than oneeighth of an inch and having a dielectric constant between twenty and one hundred, and said electric circuit comprising an alternating potential source for applying an alternating current electric potential between said electrically conductive layer of resilient material and said grounded printing rent electrical potential to the interior side of said electrically conductive layer and cylinder to produce an alternating reactive current from said electrically conductive layer through said dielectric material of said sleeve over the entire operative width of said impression roller.

2. An apparatus as claimed in claim 1 in which the sleeve of dielectric material has a width substantially equal to the width of the outer perimeter of the core.

3. An apparatus as claimed in claim 1 in which the width of the sleeve of the dielectric material is less than the width of the outer perimeter of the core, the sleeve forming the outer perimeter of the impression roller and being disposed directly at said web path for direct contact with the web at said nip over the operative width of the outer perimeter of the impression roller.

4. An apparatus as claimed in claim 1 or claim 2 with said impression cylinder having an electrically conductive metal core electrically insulated from ground potential and in electrical contact with the inner periphery of said electrically conductive layer of resilient material, and said alternating potential source being electrically connected with said electrically conductive metal core for supplying alternating current electrical potential to the interior side of said electrically conductive layer and thereby to produce an alternating reactive current through said electrically conductive inner layer and through said dielectric material of said sleeve over the entire operative width of said impression cylinder.

5. An apparatus as claimed in claim 1 or claim 2 with said mounting means for said impression cylinder comprising an electrically conductive shaft mounting said impression cylinder and electrically insulated from ground potential, said alternating potential source being electrically connected with said electrically conductive shaft for supplying alternating current electrical potential to the interior side of said electrically conductive layer and thereby to produce an alternating reactive current from said electrically conductive layer through said dielectric material of said sleeve over the entire operative width of said impression cylinder.

6. An apparatus as claimed in claim 3 with said alternating potential source having a metallic conductive path connecting it with the inner periphery of said electrically conductive material of annular cross section for supplying alternating cur

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. the core 38. As an example, the sleeve 40 may be made of a heat shrinkable irradiated elastomer material such as neoprene. Neoprene has the advantage of being ozone resistant, to a substantially greater degree than natural rubber, for example. As another example, the sleeve 40 may comprise a sleeve of homogeneous continuous annular cross section and of dielectric elastomer material having a thickness between about 1/16 inch and about 1/8 inch, and a dielectric constant of for example substantially forty (40). The sleeve may be of vulcanized rubber or the like rather than being formed of heat shrinkable material. Further the sleeve preferably has a resistivity substantially greater than the resistivity of the conductive layer 39 and preferably in the range from 108 ohm-centimetres to 1(Y ohmcentimetres, or greater. WHAT WE CLAIM IS:

1. An appartus for assisting the transfer of ink. carried on a metal printing cylinder connected to ground potential, to a web of substantially non-conductive material as the web passes along a web path through a nip between the grounded printing cylinder and the outer perimeter of a resiliently covered impression roller said apparatus comprising a metal printing cylinder connected to ground potential an impression roller comprising a core, an electrically conductive layer of resilient material on said core a sleeve of dielectric material on said layer of resilient material, said sleeve being of homogeneous continuous annular cross section and having a resistivity substantially greater than that of said conductive layer, means mounting said impression roller for rotation on its central axis and insulating said electrically conductive layer of resilient material on said core from ground potential, and means comprising an electric circuit connected with said electrically conductive layer for applying an alternating electric potential between said electrically conductive layer and said grounded printing cylinder, the entire operative width of the outer perimeter of the impression roller being formed entirely by said dielectric material of said sleeve, said dielectric material having a thickness less than oneeighth of an inch and having a dielectric constant between twenty and one hundred, and said electric circuit comprising an alternating potential source for applying an alternating current electric potential between said electrically conductive layer of resilient material and said grounded printing rent electrical potential to the interior side of said electrically conductive layer and cylinder to produce an alternating reactive current from said electrically conductive layer through said dielectric material of said sleeve over the entire operative width of said impression roller.

2. An apparatus as claimed in claim 1 in which the sleeve of dielectric material has a width substantially equal to the width of the outer perimeter of the core.

3. An apparatus as claimed in claim 1 in which the width of the sleeve of the dielectric material is less than the width of the outer perimeter of the core, the sleeve forming the outer perimeter of the impression roller and being disposed directly at said web path for direct contact with the web at said nip over the operative width of the outer perimeter of the impression roller.

4. An apparatus as claimed in claim 1 or claim 2 with said impression cylinder having an electrically conductive metal core electrically insulated from ground potential and in electrical contact with the inner periphery of said electrically conductive layer of resilient material, and said alternating potential source being electrically connected with said electrically conductive metal core for supplying alternating current electrical potential to the interior side of said electrically conductive layer and thereby to produce an alternating reactive current through said electrically conductive inner layer and through said dielectric material of said sleeve over the entire operative width of said impression cylinder.

5. An apparatus as claimed in claim 1 or claim 2 with said mounting means for said impression cylinder comprising an electrically conductive shaft mounting said impression cylinder and electrically insulated from ground potential, said alternating potential source being electrically connected with said electrically conductive shaft for supplying alternating current electrical potential to the interior side of said electrically conductive layer and thereby to produce an alternating reactive current from said electrically conductive layer through said dielectric material of said sleeve over the entire operative width of said impression cylinder.

6. An apparatus as claimed in claim 3 with said alternating potential source having a metallic conductive path connecting it with the inner periphery of said electrically conductive material of annular cross section for supplying alternating cur

thereby to produce an alternating reactive current through said electrically conductive layer and through said dielectric material of said outer sleeve over the entire operative width of said impression cylinder.

7. An apparatus as claimed in claim 3 with said outer sleeve of dielectric material having a thickness between 1/16 inch and 1/8 inch and a resistivity in the range from 102 ohm-centimetres to 1012 ohmcentimetres

8. An apparatus as claimed in claim 1 and substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.