Note: Descriptions are shown in the official language in which they were submitted.
11~5173
1 This invention relates genPrally to perforating
material by the use of light energy and pertains more part-
icularly to apparatus and systems providing spatially precise
matrices of perforations in sheet material.
In perforating sheet material, a two-dimensional
hole matrix is frequently sought with rigorous limits on per-
foration spacing uniformity as between rows and columns of the
matrix. An illustrative field of current interest is that of
perforating cigarette filter tipping paper, where h~e matrix
1~ unlformity enables consistency of cigarette dilution charac-
ter~stics. In various known mechanical puncture and electric
arc perforating practices, row spacing is rendered precise by
providing an individual perforating device for each row. Uni-
formity in the spacing of perforations made in each row, and
hence precise column spacing is achieved by synchronizing op-
eration of each perforating device. Since the perforating
devices, e.g., pin or electrode pair, are physically limited
in size, these practices can readily accommodate quite close
spacing of adjacent rows of the matrix.
2U The prior art has also encompassed perforating prac-
tices involving lasers providing pulsed or continuous light I ;
energy in row-column perforation. In these efforts, however,
t~ere generally has been an apparent preference, for economic `
and physical size reasons, for use of a single laser serving
~oth row and column perforation. Rnown single laser prac-
tices of type affording spacing uniformity have involved the
splltting of the laser beam into plural ~eams, one for each
rowl and the focusing of light onto a sheet member by use of It
.
,~
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~'
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' , ' ' ' ~.
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1 an individual lens for each row. Spacing of perforations
by precise limits within each row has been sought by inclusion
of a movable reflective element in each of the plural beam
paths. Complexity attends precision movement, e.g., vibra-
tion or pivoting, of such reflective element into and out of
its reference plane, to uniformly locate holes in rows, and
the present state of the art is accordingly limited.
The present invention has, as its primary object,
the provision of improved apparatus and systems f'or perfor-
ating sheet material by the use of light energy.
A more particular object of the invention is toprovide for expeditious perforation of cigarette filter tipping
paper by laser.
In attàining these and other objects, the invention
provides apparatus for generating pulsed light beams from a
continuous light beam, the apparatus including a lens for
focusing the continuous beam and one or more light reflective
devices supported for rotation and having a plurality of
light reflectors disposed in a circular locus and mutually
spaced by light transmissive portions. In the course of
rotation, the reflectors confront the focused beam whereby
light pulses are issued. The reflectors of one such reflec-
tive device are aligned with light transmissive portions of
other participating reflective devices, and vice versa,
such that the light pulses issue successively, or in other
pattern, from the participating reflective devices.
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51'73
In perforating systems of the ~nvention, light pulses
issuing from each pair of participating reflective devices
are received by a common focusing lens, wi`th a prism or like
light deviating member disposed between one of the devices
and such common focusing lens to provide for adjacent rows of
uniformly spaced perforations in a web or like perforatable
member.
In accordance with a broad aspect, the invention
relates to apparatus for generation of pulsed light beams
from a continous light beam, comprising:
(a) lens means f-or receiving said continuous light
beam and issuing a focused continuous beamL
(b) first reflective means arranged to receive said
focused continuous beam and supported for rotation
about a preselected rotational axis;
(1) having light reflective facets mutually spaced in
a circular locus about the periphery of said disc
to confront said focused continuous beam indivi-
dually in the course of rotation of said first
disc; all such light reflective facets being
disposed in mutually identical first attitude
with respect to said rotational axis, and
~2) having apertures between adjacent such light re-
flective elements to define light transmissive
portions; and
(c) second reflective means disposed mutually conti-
gously with said first reflective means, said second
reflective means including a second reflective disc
having light reflective facets mutually spaced in a
circular locus about the periphery of said second
disc to confront said focused continuous beam indivi-
dually in the course of rotation of said second disc,
said light reflective facets of said second disc all
,.,,,~
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~S173
being disposed in mutually identical second
attitude diverse from said first attitude with
respect to said rotational axis, said second
disc further having apertures between adjacent
such light reflective facets defining reflective
portions, said light reflective facets and said
second disc being in alignment respectively with
said apertures and said light reflective ~acets
of said first disc, whereby first and second
~ pulsed light beams issue successively alternately
from said first and second discs;
(d) common focusing means for receiving said first
and second pulsed light beams issuing from said first
and second discs and focusing said pulsed beams at
first and second spaced locations; and
(e) light deviating means disposed between said
second disc and said common focusing means for
controlling the path of said second beam to said
common focusing means, and thereby said second
location relative to said first location.
The foregoing and other objects and features of the
invention will be further understood from the following de-
tailed description of preferred methods and systems and from
the drawings wherein like reference numerals identify like
parts throughout.
Fig. 1 is a block diagrammatic showing of a pre-
ferred system embodiment.
Fig. 2 is a perspective view of the reflective discs
of Fig. 1, the discs being shown side-by-side for purposes of
explanation.
Fig. 3 is an optical diagram applicable to the Fig.
1 system.
Fig. 4 is an optical diagram applicable to the
.^ Fig. 1 system as expanded to include additional reflective
discs. ~
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5~73
Fig. 5 is a plan elevation of such expanded system.
Fig. 6 shows the respective configurations of the
xeflective discs of the expanded system.
Fig. 7 is a geometric drawing explanatory of
perforating activities with the expanded system set as in
Fig. 5.
Referring to Fig. 1, a web 10 of sheet material is
collected by take-up drum 12 following horiæontal transport
from a payout drum, not shown. Take-up drum 12 is rotated by
3b -
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ll~S173
1 drive unit 14 with drum speed being established by a control
signal provided on line 16 as furnished by potentiometer 18
or like settable device. A further control signal, derived
on line 20 from potentiometer 22 controls drive unit 24 of
light-reflector assembly 26, which comprises shaft 28, rotated
by drive unit 24 and light-reflective discs 30 and 32 keyed to
shaft 28 for rotation therewith.
Laser 34 generates a continuous output beam ~6 which
is focused by lens 38 at a location adjacent discs 30 and 32.
Light beams reflected ~y the discs are conducted by a common
focus~ng element, shown as lens 40, to web 10.
~ ig. 2 shows in side-by-side perspective disc 30
and disc 32, as the latter would be seen rightwardly of disc
30 in Fig. 1. T~e discs are keyed to shaft 28 in position
wherein lines 42 and 44 are in common plane with shaft axis
46. In the illustrative embodiment wherein two discs are used
and are intended to confront beam 36 (Fig.l) alternately, the
discs have light-transmissive uniformly spaced peripheral por-
tions 48 and 50 which are mutualiy staggered, defining reflec-
tive facets 52 and 54 therebetween. Forty-five such facets
are typically employed with each facet subtending four degrees
of arc ~angles 56 and 58) and each transmissive portion also
subtending four degrees o~ arc (angles 60 and 62). With
transimissive portion 48a having its leading edge aligned
with line 42 and transmissive portion 50a spaced from line 44
b-~ ~acet angle 58, the discs are properly aligned for alter-
nate reflectron of the laser beam, the beam passing through
tXansmiss~ve portlon 48a to be reflected by the facet clock-
~-~se of transmissive portion 50a. The light-transmissive
ll.1 ~5~7;3
1 portions are typically opening in the discs of size sufficient
to freely pass the laser beam. While disc 32 might be con-
structe`dwith no light-transmissive portions since it is the
last disc from the laser, the described construction mitigates
against spurious reflection of the laser output beam by disc
32 during confrontation of facets of disc 30 with the laser
beam, i.e., laser output beam spillage beyond disc 30 simply
passes through disc 32 openings. In this respect, such beam
spillage may be desired in applications wherein different
spacing lengths are required in adjacent rows and beam usage
is not strictly alternate as in the practice under discussion.
Referring to Fig. 3, each confrontation of a facet
of disc 30 with beam 36 will give rise to the propagation of
a modified version of the laser output beam, such modified
beam being shown at 64 and having central axis 64a, which is
incident on lens 40 at angle set by the selected orientation
of disc 30. Beam 64 has outer rays 64b and 64c, which diverge
respectively oppositely from ~eam central axis 64a. Where
~eam 36 converges and then di~erges between discs 30 and 32,
~o the beam is then con~ergent as to disc 30, and modified beam
64 will be convergent at the outset and then divergent.
Lens 40 also has within its fiald of view, through
prism 33, the facets of disc 32 and hence collects further
modified versions o laser output beam 36 on each confronta-
: tion of a facet of disc 32 with beam 36. Such fur~her modi-
fied beam 66, as it issues from disc 32, has central axis 66a
and divergent outer rays 66b and 66c.
In copending, commonly-assigned application Serial
No.329,184, filed onJune 6/79 and entitled "Method and Appar-
3U atus for Perforation of Sheet Material by Laser", all reflec-
11~5~73
1 tive discs couterpart to discs 30 and 32 herein have theirreflective facets disposed at one identical attitude with
respect to the axis of rotation thereof. Accordingly, beams
counterpart to beams 64 and 66 herein issuing from such
counterpart discs are each inclusive of an axis of symmetry
parallel to the optical axis ~axis 40a) of the common focusing
element. Based on optical considerations discussed in said
copending application, such counterpart beams thereof are
processed directly by such common focusing element without
1~ other intervening optics.
In contrast to the disc structure and practice of
such copending application, system use herein of the apparatus
for generation of pulsed light beams involves diverse attitudes
for the facets of different discs and the use of intervening
optics. Referring to Fig. 3, surface 30a of disc 30 is fully
planar across t~e diameter of the disc. Surface 32a of disc
32 is ~eveled at t~e disc periphery. Thus, the facets of
disc 30 are each at first identical attitude with respect to
the disc rotational axis and the facets of disc 32 are each
at second ldentical attitude, aiverse from such first attitude,
with respect to such rotational axis.
Beam 64 is collected airectly by lens 4U and focused
at locatlon ~8. ~eam 66 is incident o~ prism 33, and upon
de~iation by the prism is focused at location 7U, both such
locations being outward of focal plane FP40 of lens 40. In its
functlon, prism ~3 confronts beam 66 and modifies the place and
angle of incidence of the beam on lens 40, effectively dis-
placing beam lncidence place rightwardly in Fig. 3, from that
;bta~ning if beam 6~ were directly applied to the lens, and
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accordingly controlling the position of location 70. For
var~able control of the position of location 70, the prism is
cemented as at 33a to ring 35, which is supported for rotation
about the ring axis~ Locations 68 and 70 may accordingly be
arranged to be in juxtaposition ~ith a plane through which web
10 is conveyed, thereby to effect perforations therein.
Beam axis 36a and shaft 28 are positioned at a common
acute angle to the Fig. 3 plane and lens 40 and prism 33 are
moved throu~h such angle outwardly of the Fig. 3 plane into
registry with discs 30 and 32. Web 10 has a marginal edge co-
inciding with the Fig~ 3 plane~ Operation of the system then
gives rise to a first ro~ of perforations created by modified
beam 64 at locations 68 and a second perforation row spaced
therefrom and created by modified beam 66 at locations 70. Such
practice will be understood further by detailed consideration
of an expanded syste~ embodiment, shown and explained in Figs.
4-.7~
In Fig~ 4, four reflective discs, 30~. 32', 72 and 74,
are spa.ced along shaft 28 by spacer 76.. An additional prism is
s~bwn at 78 and a further focus~ng element for modified beams is
; sho~n as lens 80~ Modified beams 82 and 84 are propagated re-
spect~.~ely by the facets of disas 72 and 74~ Modified beam 82
has central axis 82a and outer divergent rays 82b and 82c~
; Discs 72 and 74 h~ve. their reflective facets arranged
at attitudes to the rotational axis respectively as in the case
of discs 30 and 32 discussed above. Lens 80 is positioned closer
to web 10 than.lens 40~ based on the increased extent of diver-
gence of beam 36 as it is confronted by discs 72 and 74. Lens
80 position and prism 78 position are adjusted to provided for
disposition of focus locations 86 and 88 of beams 82 and 84
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1~ ~5173
Closely adjacent web 10, and generally juxtaposed with locations
68 and 70, as indicated. Spacing Dl exists between locations
68 and 70 based on the selection of facet attitudes of discs
30 and 32 and optics (lens 40 and prism 33) therefor. Spacing
D2 between locations 70 and 86 is set by the length of spacer
76~ Spacing D3 exists between locations 86 and 88 based on the
selection of facet attitudes of discs 72 and 74 and optics (lens
80 and prism 78) therefor.
In Fig. 5, the plane of Fig. 4 is orthogonal to web 10
and coincident with web maxgin lOa and laser output beam axis
36a makes acute angle Z therewith. The axis of shaft 28 is in
a common plane with beam axis 36a orthogonal to web 10. By set-
ting of system parameters as discussed below, the illustrated
four row-column matrix may be reached with column spacings D4
and D5 applicable to respective upper and lower adjacent row
pairs and spacings Sl-S3 applicable as between the rows.
Fig. 6 shows the configurations of discs 30', 32', 72
and 74. With all discs keyed to common plane keying lines 90,
92, 94 and 96, and assuming forty-five facets per disc as in
the system of Figs. 1-3, facets of all discs each subtend two
degrees of arc and openings thereof each subtend six degrees of
arc. Facet 98 of disc 32' has its leading clockwise edge
coincident with keying line 92. Facets 100, 102 and 104 of
discs 30', 72 and 74, have their leading clockwise edges spaced
from keying lines 90, 94 and 96 respectively by two, six and
four degree angles 106, 108 and 110. By this configuration, it
will be seen that clockwise rotation of shaft 28 will give
rise to successive propagation of modified beams 66, 64, 84
~ and 82 (Fig. 4). Such firing order is chosen for convenience
of explanation since it gives rise to time-successive perfora-
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1145173
tions in rows 112, 114, 116 and 118 of Fig. 5. The firing order
ca~ be changed, as desired, from such convenient order. As
noted for the two disc embodiment above, the last successive
disc may be arranged without light-transmissive portions, but
same are preferred to mitigate against spurious light energy
reflections from such last disc. The laser beam is focused to
its divergence origin 360 (Fig. 4), such that the beam cross-
section clears the openings of the penultimate disc (disc 72),
thereby assuring that the full beam can be incident on each disc.
Fig. 7 shows four solid line perforations 120, 122,
124 and 126 made in time succession. The time spacing between
each successively made perforation is readily calculated since
the propagation rate of modified beams is determined solely by
reflector assembly parameters, i.e., for one revolution of shaft
28 in the given embodiment, four times forty-five, or one
hundred eighty, modified beams are propagated. The time spacing
(t) between successively-made perforations, i.e., perforations
120 and 122, is thus 1/180R, where R is the number of revolutions
of shaft 26 per unit time.
Perforations 120 and 122 are spaced in distance by the
measure (Fig. 7) Dl cos Z plus D6. Dl is the spacing in the
Fig. 4 plane between the perforations 120 and 122, with web 10
stationary. The cast image separation of Dl is greater in Fi~.
7, based on angle Z and is the measure Dl cos Z. D6 represents
the distance travelled by web 10 during the interperforation
time period (t) and is simply web speed (distance- travelled
per unit time) multiplied by t, derived as above. Since per-
forations in row 112 are all made at the same location (68 - Fig.
4) with respect to lens 40, and do not have cast image spacing,
they may all be spaced by a distance (D4j which is shown as
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1~ 5173
being fractional to the spatial measure Dl cos Z plus D6, and a
multiple of D6 times the number of discs.
In the Fig. 7 example, on rightward movement of web 10, -
row 112 perforations 128 and 130 are made spatially prior to,
and row 112 perforation 132 is made spatially coincident with,
row 114 perforation 122, but later in time than row 114 perfor-
ation 122. Such phenomena is attributable to the combined
effects of cast image separation as between time-successive per-
forations and angle Z.
One may define a number N indicating the number of row
112 perforations made spatially prior (or coincident with) and
timewise later than the ~ow 114 perforation made time successive
to an initial row 112 perforation, and establish the following
relation, for a four disc arrangement:
,. N D4 = Dl cos Z + D6 (1)
N = Dl cos Z + D6 (2)
D
or
Dl cos Z = D4 N - D6 (3)
or
Dl = D4 N D6 ~4)
', cos Z
In the given instance, N is three and D4 is four times
D6. In such instance:
1 11 D6 (5)
cos Z
In expression (4) with Dl, Z and N preselected constants, D4 and
D6 may be established as mutually variable to effect the same
pattern. Since D4 is proportional to t and since D6 is deter-
mined by web speed, one may establish a series of respective
values for drive unit 24 (reflector assembly speed, line 20
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signal of Fig. 1) and drive unit 14 (web transport speed, line
16 of Fig. 1) which will yield the Fig. 7 configuration for rows
112 and 114. A common control input may adjust the wiper
positions of pots 18 and 22.
The number N is integral in the foregoing example and
is selected as the number three. Any integer may be selected to
provide for column perforation registry. Lower values of N, i.e.,
lesser perforations in row 112 between time successive (row 112-
row 114) perforations will give rise to a lesser number of per-
forations per unit distance in web 10. Conversely, higher values
of N will increase perforation density in the web.
If N is selected to be non-integral, the above-noted
column registration is not provided. By way of example, if N is
selected as three and one-half, perforation density as between
rows 112 and 114 decreases from the N equals three situation and
the perforations in rows 112 and ll4 are mutually uniformly
staggered, i.e., are 180 out of phase, as is the case with all N
values which have a one-half fractional part.
In the N equals three situation above, column registry
in rows 116 and 118 also applies, and column registry as among
all of rows 112 through 11~ may be achieved by making D2 cos Z
plus D6 an integral multiple of D6 times the number of discs and
by making D3 equal to Dl. On the other hand, non-uniform ma-
trices may be achieved by other parameter selections however,
with consistency of both row spacing uniformity and uniformity
in intrarow perforation spacing. The spacing parameters may
likewise be modified to compensate for optics aberrations to
attain desired perforation matrices.
In its embodiments depicted in the drawings, the ap-
paratus for pulsed beam generation involves plural discs or the
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like which are disposed mutually contiguously, with facet atti-
tude diversity enabling generation of non-interfering pulsed
beams. In the above-noted copending application, such discs
are spaced from one another along the common rotational axis. The
apparatus hereof will thus be seen to be changeable in various
manners in leading to the generation of pulsed beams. Further,
while system usage of the apparatus disclosed herein and in said
above-noted copending application look to the use of common fo-
cusing of beams issuing from plural discs, individual processing
of such beams may be undertaken. As will be clear, beams in
number greater than two may be collected by a common focusing
element, giving rise to a corresponding number of perforation
rows greater than the two rows obtained in the illustrated
practice for each lens.
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