Rotary web chopper

Claim 2

A cutter for a running web comprising: first and second axially co-parallel counter-rotating shafts driven in synchronism one with the other, a first blade mounted on said first shaft and having a straight cutting edge parallel to the axis thereof, a second blade mounted on said second shaft and having a shaped surface defined by generatrices parallel to the axis of said second shaft with the locus of said generatrices being an epitrochoid, said second blade having an outer peripheral surface forming with said shaped surface a second cutting edge, and said blades co-acting along their opposed cutting edges to effect a cut on a web therebetween.

Claim 3

A cutter according to claim 1 wherein said second cutting edge is non-parallel to said second shaft axis.

Claim 4

A cutter according to claim 1 wherein each of said shafts have an equivalent pitch radius and the radial distance of said first blade cutting edge from said first shaft axis is equal to or less than said equivalent pitch radius of said first shaft.

Claim 5

A cutter according to claim 1 wherein each of said shafts have an equivalent pitch radius and the radial distance of said first blade cutting edge from said first shaft axis is greater than said equivalent pitch radius of said first shaft.

Claim 6

A cutter according to claim 4 wherein said first shaft defines at least one peripheral axially extending recess, said first blade being mounted in said recess with its said cutting edge located near the outside periphery of said first shaft.

Claim 7

A cutter according to claim 5 which also includes a retention means for selectively retaining a web on a portion of the periphery of said first shaft at least to the point of web severance.

Claim 8

A cutter according to claim 6 wherein said retention means includes a plurality of vacuum retaining ports in the periphery of said first shaft, and said retention means is adapted to selectively apply vacuum to said ports.

Claim 9

A cutter according to claim 6 wherein said second blade outer peripheral surface contiguous with said cutting edge is tapered along its full length relative to said shaft axis.

Claim 10

A cutter according to claim 6 wherein said second blade cutting edge is located at a radius greater than said equivalent pitch radius of said second shaft.

Claim 11

A cutter according to claim 6 wherein said second blade cutting edge lies in a plane.

Claim 12

A cutter according to claim 3 wherein said first shaft defines at least one peripheral axially extending recess, said first blade being mounted in said recess with its said cutting edge located near the outside periphery of said first shaft.

Claim 13

A cutter according to claim 11 which also includes a retention means for selectively retaining a web on a portion of the periphery of said first shaft at least to the point of web severance.

Claim 14

A cutter according to claim 2 which also includes a retention means for selectively retaining a web on a portion of the periphery of said first shaft at least to the point of web severance.

Claim 15

A shear cutter for a running web comprising: a pair of axially co-parallel counter-rotating shafts power-driven in synchronism one with the other, the first shaft of said pair being provided over a major expanse of its periphery with a multiplicity of web-retaining vacuum ports and at least one peripheral inwardly extending recess within which is mounted a radially disposed straight-edge blade having a cutting edge located near the outside perimeter of said first shaft parallel to the axis thereof, the second shaft of said pair being provided with at least one peripheral inwardly extending recess within which is mounted a blade having a cutting edge located outboard of said shaft shaped in end cross-section over its full length to a generally epitrochoidal curve, said blades interacting along their opposed cutting edges to effect a shearing cut on a web trained over the periphery of said first shaft during a predetermined angular sweep of said shafts when said blades are in proximity one to the other, control means operating in a predetermined time sequence relative to the rotation of said shafts repetitively imposing preselected time durations for vacuum web retention, web end deflection and web stripping cycles of said shear cutter operation, and means responsive to said control means effecting in seriatim, vacuum web retention, vacuum deflection and retention of the leading edge of said web after each cut is completed followed by means stripping said leading edge at a preselected delivery point for severed sheets of said web.

Claim 16

A shear cutter for a running web comprising: a pair of axially co-parallel counter-rotating shafts power-driven in synchronism one with the other, the first shaft of said pair being provided over a major expanse of its periphery with a multiplicity of web-retaining vacuum ports and at least one peripheral inwardly extending recess within which is mounted a radially disposed straight-edge blade having a cutting edge located near the outside perimeter of said first shaft parallel to the axis thereof, the second shaft of said pair being provided with at least one peripheral inwardly extending recess within which is mounted a blade having a cutting edge located outboard of said shaft shaped in end cross-section over its full length to a generally epitrochoidal curve, said blades interacting along their opposed cutting edges to effect a shearing cut on a web trained over the periphery of said first shaft during a predetermined angular sweep of said shafts when said blades are in proximity one to the other, control means operating in a predetermined time sequence relative to the rotation of said shafts repetitively imposing preselected time durations for vacuum web retention, web end deflection and web stripping cycles of said shear cutter operation, and means responsive to said control means effecting in seriatim, vacuum web retention, vacuum deflection and retention of the leading edge of said web after each cut is completed followed by means stripping said leading edge at a preselected delivery point for severed sheets of said web.

Claim 17

A shear cutter for a running web according to claim 14 wherein said means for effecting, in seriatim, vacuum deflection and retention of the leading edge of said web after successive cuts are completed followed by stripping of said leading edge at a preselected delivery point for severed sheets of said web is disposed within said peripheral inwardly extending recess of said first shaft rearwardly of and in close proximity to said straight-edge blade.

Claim 18

A shear cutter for a running web according to claim 15 wherein said shafts are provided with a multiplicity of pairs of peripherally spaced co-acting web cutting blades.

Claim 19

A shear cutter for a running web according to claim 14 in which said counter-rotating shafts are disposed generally horizontally, with said first shaft of said pair located above said second shaft and laterally spaced therefrom a sufficient distance to preclude interference during said interaction of said blades.

Claim 20

A shear cutter for a running web according to claim 15 in which said control means additionally comprises means relieving said vacuum proximal to said leading edge following said shearing cut.

Claim 21

A shear cutter according to claim 14 wherein said blade shaped in end cross-section over its full length to a generally epitrochoidal curve has a shaped expanse in the range of about 0.10 cm to about 40% of the generally radial extent of blade maximum overlap during said blade interaction.

Claim 22

A shear cutter for a running web according to claim 14 wherein said blade shaped in end cross-section over its full length to a generally epitrochoidal curve has an outer surface contiguous with said cutting edge tapered along its full length relative to said shaft axis.