Method and apparatus for screen printing registered images on opposite sides of a web

Claim 2

Apparatus for screen printing mirror inversion images in registration on opposite sides of a web of material, said apparatus including; a matched pair of ink-receiving screen stencils each presenting a flat printing membrane having an open image area permitting ink transfer therethrough, said image areas being mirror inversions of one another; said pair of stencils being provided with register means for holding said images in mutual registration; a stationary framework fixedly supporting said stencils with said membranes juxtapositioned in parallel, laterally spaced relation to define a printing zone therebetween; means for supplying ink to said stencils; a web support adapted to position said web such that it extends through said printing zone in parallel relation to said flat membranes generally equidistant therefrom; a squeegee assembly including a unitary one-piece carriage mounted on said framework adjacent said stencils for shifting movement along a path of travel extending generally parallel to said web and said membranes, and a pair of opposed squeegees each mounted on said carriage and each normally in printing engagement with one of said membranes outboard of said printing zone; means for shifting said carriage from a first position to a second position along said path of travel while said web is stationary whereby to conjointly sweep said squeegees across said membranes such that opposite sides of the web are printed synchronously; and means to lift said squeegees from said membranes, said means for shifting being operable when said squeegees are lifted from said membranes to move said carriage from said second position to said first position.

Claim 3

Apparatus as claimed in claim 1, said sweeping means including a mechanism for reciprocating said carriage to move said squeegees along a unidirectional printing stroke and an oppositely directed return stroke, said carriage having means for disengaging said squeegees from respective said membranes during said return stroke.

Claim 4

Apparatus as claimed in claim 2, said mechanism being operable to move said squeegees through said printing stroke at a substantially uniform rate of travel.

Claim 5

Apparatus as claimed in claim 1, said membranes being disposed in substantially upright planes, said web drive comprising a pair of vertically spaced, web-engaging roller trains mounted on said framework respectively above and below said printing zone and adapted to support said web therebetween in an upright position parallel to said membranes.

Claim 6

Apparatus as claimed in claim 4, said web drive being adapted to advance said web in an upwardly direction through said printing zone.

Claim 7

Apparatus as claimed in claim 1, each of said stencils having a frame around its respective printing membrane, said register means comprising means for interlocking the frames of said stencils.

Claim 8

The invention of claim 6, said interlocking means including a registration set comprising: an aperture in the frame of each of said stencils, said apertures being correspondingly located relative to respective said image areas; and an alignment pin adapted to be coaxially received within said apertures.

Claim 9

The invention of claim 7, said interlocking means having four of said registration sets.

Claim 10

The invention of claim 6, said membranes being constructed of wire mesh provided with an overcoating.

Claim 11

The invention of claim 9, said overcoating being metal.

Claim 12

Apparatus for screen printing mirror inversion images in registration on opposite sides of a web of material, said apparatus including; a matched pair of ink-receiving screen stencils each presenting a printing membrane having an open image area permitting ink transfer therethrough, said image areas being mirror inversions of one another; said pair of stencils being provided with register means for holding said images in mutual registration; a framework supporting said stencils with said membranes juxtapositioned in parallel, laterally spaced relation to define a printing zone therebetween; means for supplying ink to said stencils; a web support adapted to position said web such that it extends through said printing zone in parallel relation to said membranes generally equidistant therefrom; a pair of opposed squeegees mounted for sweeping movement across respective said membranes in printing engagement therewith outboard of said printing zone; means for conjointly sweeping said squeegees across said membranes whereby to print opposite sides of the web synchronously, said sweeping means including a common carriage for said squeegees; a mechanism for reciprocating said carriage to move said squeegees along a unidirectional printing stroke and an oppositely directed return stroke, said carriage having means for disengaging said squeegees from respective said membranes during said return stroke; and a stencil separator mounted for movement with said carriage through said printing zone, between said membranes said separator being disposed to trail the squeegees during said printing stroke, and being of sufficient thickness to engage the membranes and separate the latter from the web after passage of said squeegees.

Claim 13

Apparatus for screen printing mirror inversion images in registration on opposite sides of a web of material, said apparatus including; a matched pair of ink-receiving screen stencils each presenting a printing membrane having an open image area permitting ink transfer therethrough, said image areas being mirror inversions of one another; said pair of stencils being provided with register means for holding said images in mutual registration; a framework supporting said stencils with said membranes juxtapositioned in parallel, laterally spaced relation to define a printing zone therebetween; means for supplying ink to said stencils; a web support adapted to position said web such that it extends through said printing zone in parallel relation to said membranes generally equidistant therefrom; a pair of opposed squeegees mounted for sweeping movement across respective said membranes in printing engagement therewith outboard of said printing zone; means for conjointly sweeping said squeegees across said membranes whereby to print opposite sides of the web synchronously, said sweeping means including a common carriage for said squeegees; a mechanism for reciprocating said carriage to move said squeegees along a unidirectional printing stroke and an oppositely directed return stroke, said carriage having means for disengaging said squeegees from respective said membranes during said return stroke; and a stencil separator mounted for movement with said carriage through said printing zone, between said membranes said separator being disposed to trail the squeegees during said printing stroke, and being of sufficient thickness to engage the membranes and separate the latter from the web after passage of said squeegees.

Claim 14

Apparatus as claimed in claim 11, said separator being disposed wholly without the portion of said printing zone intermediate said image areas.

Claim 17

The method of claim 13, said sweeping step comprising moving said squeegees rectilinearly at a substantially constant rate of travel.

Claim 18

The method of claim 13; and placing said web under tension during said sweeping step.

Claim 19

The method of claim 13, said stencils and web being disposed in substantially upright planes during said sweeping step.

Claim 20

The method of claim 16, said web being equidistant from said screens during said sweeping step.

Claim 21

The method of claim 16, said web being moved vertically upwardly during said advancing step.

Claim 22

The method of claim 13, said stencils being held stationary during said advancing step.

Claim 23

In a screen stencil printing apparatus adapted to print images on opposite sides of a web of material, the improvement comprising: a pair of juxtaposed, parallel, laterally spaced screen stencils presenting a printing zone therebetween adapted to receive said web; a pair of reciprocable squeegees each printingly engaging a respective said stencil outboard of said printing zone; and means for conjointly reciprocating said squeegees to effect printing on opposite sides of said web synchronously; and a stencil separator movable with said squeegees in offset relation thereto, said separator being disposed to pass between said stencils for maintaining the spacing therebetween.

Claim 24

In a screen stencil printing apparatus adapted to print images on opposite sides of a web of material, the improvement comprising: a pair of juxtaposed, parallel, laterally spaced screen stencils presenting a printing zone therebetween adapted to receive said web; a pair of reciprocable squeegees each printingly engaging a respective said stencil outboard of said printing zone; and means for conjointly reciprocating said squeegees to effect printing on opposite sides of said web synchronously; and a stencil separator movable with said squeegees in offset relation thereto, said separator being disposed to pass between said stencils for maintaining the spacing therebetween.

Claim 25

The improvement of claim 20, said stencils being disposed in upright planes.

Claim 26

The improvement of claim 20, said squeegees being reciprocable along a vertical path of travel.

Claim 27

The improvement of claim 20, said reciprocating means moving said squeegees along a unidirectional printing stroke and an oppositely directed return stroke, said reciprocating means being operable to move the squeegees at a constant speed through said printing stroke.

Claim 28

The improvement of claim 20; said web support including a web drive adapted to apply tension to the web in said printing zone.