Apparatus for penetrating a sheet material web carried on a fabric

An apparatus for penetrating a sheet material web being carried on a fabric. The apparatus including a penetrating device and an air flow that separates a portion of the sheet material web from the fabric adjacent the penetrating device so as to bring the web into contact with the penetrating device. In one embodiment, a vacuum lifts a portion of the sheet material web into contact with a slitting member such that it continuously slits the sheet material web longitudinally along its length as the fabric carries the sheet material web beneath it. In an alternative embodiment, a pressurized air stream is directed to a bottom portion of the sheet material web so as to separate the web from the fabric. A method for penetrating a sheet material web as it is carried on a fabric includes the steps of carrying the sheet material web on a fabric in a longitudinal direction, applying an air flow to the web so as to separate a portion of the web from the fabric, penetrating the web as it is separated from the fabric and reapplying the sheet material web to the fabric.

BACKGROUND OF THE INVENTION 
The present invention relates generally to a method and apparatus for 
penetrating a sheet material web, and in particular, to a method and 
apparatus for penetrating a sheet material web, such as by slitting, 
cutting, puncturing or perforating, while the web is being carried on a 
fabric. 
It is well known in the field of paper making, and particularly in the 
field of manufacturing tissue products such as facial tissues, bath 
tissues and paper towels, to provide an apparatus for longitudinally 
slitting a continuous running sheet material web into two or more strips. 
Typically, the sheet material web is slit either as it traverses an "open 
draw" before being wound into rolls, before it is dried or after it is 
wound onto the roll. In the first instance, the area of open draw, where 
the dried sheet is momentarily unsupported before being wound, provides an 
ideal place to slit the web. In particular, the slitting device, often 
configured as a rotary saw blade, can be applied to the web without 
concern about cutting or otherwise damaging an underlying fabric, which 
otherwise carries the sheet material web throughout the forming process. 
Fabrics of this nature can be expensive and difficult to replace. 
However, as described in U.S. Pat. No. 5,591,309, issued Jan. 7, 1997 to 
Rugowski et al., and assigned to Kimberly-Clark Corporation, the same 
assignee as the present application, open draws are a frequent source of 
sheet breaks and associated production delays. As a result, tissue sheets 
often are designed to have high machine direction strengths in order to 
remain intact as they are pulled through the open draw. However, high 
machine direction strengths can adversely affect the quality of the web in 
terms of its desired softness. Therefore, as explained in U.S. Pat. No. 
5,591,309, the elimination of open draws in tissue manufacturing can 
result in a sheet material being made more efficiently at less cost and 
with more desirable properties. 
When the open draw is eliminated, the sheet material web is typically slit 
using a water jet prior to drying the web. However, such "wet slitting" 
can result in a degradation of the throughdrying fabric as it is exposed 
to hot air passing through the slit in the sheet material during the 
drying stage of the process. Moreover, the slit edges of the sheet 
material web may not dry evenly due to the pile up of fibers along the 
slit. Additionally, when the sheet material web is slit prior to drying, 
the various strips of sheet material web are difficult to control and can 
become inadvertently interwoven, or overlapped, as they are further 
carried towards the wind-up reel. Interwoven strips can be more easily 
damaged and can make the winding process particularly difficult. Moreover, 
adjacent rolls having interwoven webs can be particularly difficult to 
separate. Accordingly, the strips of sheet material web are typically 
required to be spread apart so as to prevent interweaving. 
In contrast to slitting the web prior to drying, it is also known in the 
art to slit the sheet material web as it is wound onto the roll, as 
mentioned above. Slitting apparatuses of this nature typically apply a 
pressure or guide roller, or like device, to the outermost surface of the 
roll so as to thereby control the penetration of the slitting device. 
However, facial and bath tissues typically have low densities. 
Accordingly, it usually is not desirable, or even possible, to allow such 
a guide roller to contact the roll as it builds so as to thereby control 
the position of the slitter, and the penetration thereof. Moreover, the 
various strips are necessarily wound onto the same roll and must be 
rewound onto separate rolls after slitting in another manufacturing step 
if desired. 
Alternatively, the sheet material web can be carried on two or more belts 
aligned side-by-side, wherein a slitting blade protrudes through the gap 
between the belts. The sheet material web can become caught or torn in the 
gap, however, and it is not possible to change the lateral position of the 
slitting device without reconfiguring the belts, which can be very 
expensive and time consuming. Moreover, the control of the belts, and the 
alignment thereof, can be difficult to maintain. 
SUMMARY OF THE INVENTION 
Briefly stated, the invention is directed to an apparatus for penetrating a 
sheet material web, such as by slitting, cutting, puncturing or 
perforating, while being carried on a fabric. In a preferred embodiment, 
the apparatus includes a penetrating device positioned above the fabric 
and an air flow, which is applied to a portion of the sheet material web 
adjacent the penetrating device so as to separate the web from the fabric 
and thereby bring the web into contact with the penetrating device above 
the fabric. 
In a preferred embodiment, the apparatus includes a housing disposed around 
a slitting member, preferably configured as a rotary saw blade. The 
housing preferably includes a shoe member attached to a bottom of the 
housing and having an opening forming a mouth of the housing which opens 
towards the sheet material web carried on the fabric. The shoe member 
preferably includes a rearwardly facing nose portion shaped to strip the 
boundary layer of air from the sheet material web as it passes beneath the 
housing. Preferably, a curved plate is mounted to the shoe member at the 
mouth of the housing. The plate has a plurality of apertures and a slot 
formed therein. A vacuum is connected to the housing to apply an air flow 
such that a portion of the sheet material web is separated from the fabric 
at the mouth of the housing and thereby brought into contact with the 
slitting member. 
In an alternative embodiment, an air hose is provided below the fabric. The 
air hose applies a pressurized air stream to a portion of the bottom of 
the web so as to lift it off of the fabric and into contact with the 
penetrating device, preferably including a slitting member. The air hose 
is used with air permeable fabrics, while the vacuum is employed with 
impermeable fabrics. Alternatively, the air hose can be used in 
combination with the vacuum so as to obtain the desired separation of the 
sheet material web when used with an air permeable fabric. 
In one aspect of the invention, a sensor is provided below the fabric. The 
sensor monitors the position of the fabric and signals the retraction or 
stoppage of the penetrating device if the fabric inadvertently approaches 
the penetrating device. Preferably, the penetrating device is made height 
adjustable so as to allow the distance between the blade and fabric to be 
automatically adjusted according to the input from the sensor. 
In yet another aspect, a method is provided for penetrating the sheet 
material web carried on the fabric. The method includes carrying the sheet 
material web on a fabric in a longitudinal direction, applying either a 
vacuum or a pressurized air stream, or both, to the sheet material web so 
as to separate at least a portion of the web from the fabric, penetrating 
the sheet material web as it is separated from the fabric and reapplying 
the separated portion of the sheet material web to the fabric. 
The present invention provides significant advantages over other slitting 
or penetrating devices. Importantly, the apparatus allows for slitting the 
sheet material web while it is being carried by a fabric prior to winding 
the web onto rolls. In this way, the open draw of the forming process can 
be eliminated so as to reduce waste and costs, but without having to slit 
the sheet material web prior to the drying process, wherein the problems 
of fabric degradation, fiber build-up at the slit edges and loss of sheet 
control can be encountered. Moreover, since the apparatus can be 
positioned relatively close to the winding reel, as opposed to wet 
slitting, which is typically performed up stream in the process, the 
problem of interweaving can be greatly reduced. 
In addition, the present invention provides an improved method and 
apparatus for slitting the sheet material web prior to winding the web 
onto rolls. In this way, the various strips of sheet material web can be 
directed to different wind-up reels, rather than rolling the web into a 
single roll, where it is then slit and rewound onto separate, individual 
rolls, if needed. 
Moreover, since the fabric is not split, or otherwise configured to receive 
the slitting device, the apparatus can easily be moved laterally to any 
desired position above the longitudinally moving web without having to 
reconfigure the fabric. In addition, a plurality of slitting apparatuses 
can be positioned above the web so as to enable the operator to make 
multiple strips of sheet material web. In either situation, the desired 
slitting operation can be set up quickly, inexpensively and with little or 
no waste. 
The present invention, together with further objects and advantages, will 
be best understood by reference to the following detailed description 
taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS 
It should be understood that the term "web," as used herein, is meant to 
include a sheet material made of one or more plies of material so that a 
multiple-ply sheet material is considered to be a "web" of sheet material, 
regardless of the number of plies. In addition, the term "longitudinal," 
as used herein, is intended to indicate the direction in which the web 
traverses through the forming process in the machine direction, and is not 
intended to be limited to a particular length of the web, whether it is 
cut or otherwise. Similarly, the terms "downwardly," "upwardly," 
"forward", "rearward", "left" and "right" as used herein are intended to 
indicate the direction relative to the views presented in the Figures, and 
in particular, from a perspective when viewing the web and fabric as they 
travel away from the drier toward the slitting apparatus and ultimately to 
the wind-up reel. 
Referring to the drawings, FIGS. 1 and 2 show an apparatus 10 having a 
housing 12, a vacuum and a penetrating device, shown as a slitting member 
16. A forward portion of the housing 12 includes a pair of mounting 
flanges 18 bolted to a pivot bracket 20 with a plurality of bolts 21. 
Vertically oriented slots 19 are provided in the mounting flanges 18 so as 
to allow the vertical position of the housing 12 to be adjusted relative 
to the pivot bracket 20. In addition, a pair of adjustment screws 70 
extend through a pair of lug members 72 extending forwardly from the 
flange members 18 and engage a bottom surface 74 of the pivot bracket 20. 
When the bolts 21 are loosened, the adjustment screws 70 can be extended 
or retracted relative to the lug members 72 so as to locate the mounting 
flanges 18 in the desired position relative to the pivot bracket 20, 
wherein the bolts 21 can be tightened so as to securely mount the housing 
to the pivot bracket. In this way, the operator can adjust the exposure of 
the slitting member within a mouth 94 of the housing. 
A pair of lug members 22 extend forwardly from the pivot bracket 20 at two 
locations and are pivotally attached with a pin 64 to a pair of rearwardly 
extending lug members 26 attached to a lower portion 28 of an upwardly 
extending plate member 24. The plate member 24 includes an upper portion 
30 attached to a first mounting plate 40 with a plurality of bolts 34. 
Preferably, the upper portion 30 includes a plurality of slots 32 which are 
adapted to receive bolts 34. A pair of lug members 33 extend forwardly 
from the upper portion 30. A pair of adjustment screws 42 are threadably 
received in the lug members 33 and engage a top surface 39 of the first 
mounting plate 40. In this way, the bolts 34 can be loosened so as to 
allow the adjustment screw 42 to be rotated and thereby raise or lower the 
plate member 24 to a desired height relative to the first mounting plate 
40. In this way, the operator can adjust the position of the slitting 
member relative to the fabric 60 and control the distance therebetween. 
The bolts 34 are then tightened within the slots 32 to mount the plate 
member 24 to the first mounting plate 40. 
As shown in FIG. 1, the first mounting plate 40 is attached to a second 
mounting plate 44 disposed on an opposite side of a laterally extending 
frame member 46. A plurality of bolts 47 are used to clamp the frame 
member 46 between the first and second plate members 40, 44. As shown in 
FIG. 2, the bolts 47 can be loosened so that the entire apparatus can be 
moved laterally along the length of the frame member 46 to a desired 
operating position above the longitudinally oriented fabric 60, which is 
preferably one-piece and spans the entire cross-machine direction of the 
machine. It should be understood by one of skill in the art, that the 
plate member, or first and/or second mounting plates, could also be 
fixedly attached directly to the frame member with fasteners, welding or 
the like. 
As shown in FIGS. 1 and 2, a mounting bracket 48 is attached, with 
fasteners, or by welding and the like, to a rear surface 36 of the upper 
portion 30 of the plate member 24. The bracket 48 includes a pair of 
rearwardly extending lug members 50. A pneumatic cylinder 54 includes an 
upper end 56 which is pivotally attached to the lug members, and a shaft 
62 having a lower end 58 pivotally attached to a pair of lug members 52 
extending rearwardly from the pivot bracket 20. In operation, the 
pneumatic cylinder 54, preferably configured as a gas spring, can be 
extended or retracted so as to pivot the pivot bracket 20 about the axis 
of pin 64. Alternatively, a hydraulic cylinder can be used to actuate the 
pivot bracket. In addition, a pair of horizontally oriented adjustment 
screws 76 extend through the lower portion 28 of the plate member 24 and 
engage a forward surface 38 of pivot bracket 20. The adjustment screws 76 
act as a stop against the pivot bracket 20 and can be extended or 
retracted relative to the plate member so as to limit the rotation of the 
pivot bracket 20, and attached housing 12 and slitting member 16, relative 
to the fabric 60. In this way, the slitting member is prevented from being 
rotated into contact with the fabric, especially in the event of a failure 
in the pneumatic cylinder 54. 
As shown in FIGS. 1 and 2, an electric motor 80 is also attached to the 
pivot bracket 20. A suitable motor is the 1.1 KW, 50 Hz, 2840 RPM AC motor 
commercially available from ABB Industrie as Type M2JA 80L. In a preferred 
embodiment, the horizontally oriented shaft 82 of the motor extends 
laterally into the housing 12. Preferably, the slitting member 16 is a 
rotary saw blade. The slitting member 16 is disposed in the housing 12 and 
is mounted to the shaft 82 of the motor. A commercially available saw 
blade suitable for use is the 3/4 inch inner diameter, 12 inch outer 
diameter tool steel blade sold by Otter-Kinetic Co. as Part No. 3074-5A. 
Preferably, the saw blade rotates clockwise, or in the same direction as 
the travel of the fabric and sheet material web, and a greater speed, 
preferably at about a 2:1 ratio. 
Alternatively, the penetrating device can be configured as one of a 
stationary, fixed knife blade positioned within the housing, a water jet, 
a laser or any other known and conventional slitting devices. In addition, 
the apparatus can be used to modify the moving sheet material web as it is 
carried on the fabric such as by cutting the web in a transverse, 
cross-machine direction, by puncturing or perforating the web, or by 
similarly acting upon the web so as to change its size, shape or makeup. 
In such embodiments, one of skill in the art should recognize that the 
apparatus would include a penetrating device capable of making the cuts, 
perforations or punctures, including for example, but not limited to, 
rotary cutter or perforation heads. 
As shown in FIGS. 1 and 2, the vacuum includes a conduit 15 attached to the 
rear portion of the housing. A conventional vacuum is connected to the 
conduit 15 so as to apply a vacuum to the housing 12. Depending on the 
weight of the sheet material web and the permeability of the underlying 
fabric, vacuum levels of from about 4 inches water column ("WC") to about 
25 inches WC can be applied to the housing so as to provide an adequate 
separation of the sheet from the material web fabric without also drawing 
the fabric toward the housing. 
As shown in FIGS. 1-5, the housing 12 preferably includes a shoe member 90 
having flange portion 103 attached to a lower portion 66 of the housing. 
The shoe member 90 has a cavity 92 and a mouth 94 opening downwardly 
towards the underlying fabric 60 and sheet material web 100 traversing 
beneath it. The shoe member 90 also includes a rearwardly facing nose 
portion 96 which is shaped to strip the boundary layer of air from the 
sheet material web 100 so as to allow the web to be more easily separated 
from the underlying fabric. Preferably, the shoe member is made of 
aluminum. 
Referring to FIGS. 6-9, a perforated vacuum plate member 102 is shown. 
Preferably the vacuum plate member 102 is curved so as to have a 
downwardly facing concave surface 104 overlying the sheet material web 100 
and fabric 60. The concave curved surface extends substantially 
continuously along the longitudinal length of the plate member. A pair of 
mounting flanges 106 extend longitudinally along the side portions of the 
plate member. Each mounting flange 106 includes a plurality of holes 108. 
A plurality of fasteners are received in the holes and securely fasten the 
plate member 102 over the mouth 94 of the shoe member. In addition, an end 
plate 107 is attached to a forward portion 109 of the shoe member. Each of 
the mounting flanges 106 have a bottom surface 112. Preferably, the vacuum 
plate member is made of # 14 gauge stainless steel. 
The curved portion 114 of the plate member is received within the cavity 92 
of the shoe member and forms a downwardly facing recess 116 opening 
towards the sheet material web as shown in FIG. 13. A plurality of 
apertures 118 are positioned in the curved portion 114 of the plate 
member. Preferably, the apertures 118 are configured as holes, rather than 
slots, so that the sheet material web is prevented from being drawn 
through the plate member and into the housing, or vacuum plenum. In 
addition, the plate member includes a longitudinal elongate slot 120 
positioned approximately along the centerline of the plate member. The 
apertures 118 are positioned both on the sides of and rearwardly of the 
slot 120, but not forward of the slot. Preferably, the apertures do not 
extend the full length of the shoe member 90 so as to allow the raised 
portion of the sheet material web 100 to settle back onto the fabric 60 as 
it travels toward the wind-up reel. 
As shown in FIG. 13, the shoe member 90 and vacuum plate member 102 allow 
the relatively more flexible sheet material web 100 to be drawn into the 
recess 116 and into contact with the slitting member 16, but prevent the 
relatively inflexible fabric 60, which is stretched tight over reel drum 
174, from being drawn into the recess as it contacts the bottom of the 
shoe member and/or plate member flanges. In this way, the shoe member 90 
and vacuum plate member 102 prevent the slitting member from contacting 
and thereby damaging the fabric 60. In addition, screw 70 can be adjusted 
to expose more or less of the slitting member 16 within the recess 116. 
In addition, as shown in FIGS. 1-2 and 9-12, a laser displacement sensor 
130 is mounted to a frame member 132 below the fabric 60. In particular, a 
cross member 134 is adjustably mounted to a bracket 136 attached to the 
vertical frame member 132. The cross member 134 includes flange member 138 
at about a midpoint of the cross member. The laser sensor 130 is mounted 
on a bracket member 140 which includes a flange member 141 attached to 
flange member 138. In operation, the cross member 134 can be moved 
laterally beneath the fabric 60 by sliding the cross member between the 
support brackets 136 mounted on opposite sides of the machine as the 
apparatus 10 is moved laterally above the fabric 60 such that the laser 
sensor 130 is directed at the fabric immediately below the slitting 
member, preferably at the approximate centerline of the rotary saw blade 
at its lowest point adjacent the fabric. A lock-down bolt 137 is mounted 
on each bracket 136 and engages the cross member 134 to releasably lock 
the cross member in a desired position. Alternatively, the laser can be 
slid to the operator side of the machine to allow for angular adjustment 
or maintenance of the sensor. The sensor 130 monitors the position of the 
fabric 60 and automatically signals the operator or adjusts the slitting 
apparatus if the fabric is lifted upwardly towards the slitting member. In 
a preferred embodiment, the signal from the sensor 130 triggers an upward 
retraction of the slitting member or a stoppage of the vacuum so as to 
ensure that the fabric is not damaged by the slitting device. In 
particular, the pneumatic cylinder is actuated so as to pivot the slitting 
apparatus upwardly about pin 64 and away from the fabric. A commercially 
available sensor 130 is the Nippon Automated LAS-8010 laser sensor 
available from Adsens Tech. Inc. 
Also as shown in FIGS. 1 and 2, a support tube 142 or bar is attached to 
bracket 144 and supports a bottom surface 146 of the fabric immediately 
behind the housing 12. Preferably, the support tube is rotatably mounted 
beneath the fabric so as to not wear the fabric. The support tube impinges 
slightly on the fabric so that the fabric wraps around the tube and 
thereby further helps to prevent the fabric from being drawn to the 
slitting device. An adjustment screw 147 threadably engages a flange 
extending rearwardly from bracket 136 and engages a bottom surface of 
bracket 144. The screw 147 can be rotated to adjust the vertical position 
of the support tube, and the relative impingement against the fabric. 
Referring to FIG. 15, a schematic diagram for forming a sheet material web 
without an open draw is shown. The apparatus and method for making such a 
web is set forth in U.S. Pat. No. 5,593,545, issued Jan. 14, 1997 and U.S. 
Pat. No. 5,591,309, issued Jan. 7, 1997, both of which are herein 
incorporated by reference. However, it should be understood by one of 
skill in the art that the present invention could be used with other paper 
forming processes which utilize fabrics and/or belts to carry the sheet 
material without an open draw, and can be used for slitting other types of 
sheet materials other than paper products. 
As explained in U.S. Pat. Nos. 5,593,545 and 5,591,309, and as shown in 
FIG. 15, a representative throughdrying process for making uncreped 
throughdried tissues is shown. Shown is the headbox 148 which deposits an 
aqueous suspension of papermaking fibers onto inner forming fabric 150 as 
it traverses the forming roll 152. Outer forming fabric 154 serves to 
contain the web while it passes over the forming roll and sheds some of 
the water. The wet web 156 is then transferred from the inner forming 
fabric to a wet end transfer fabric 158 with the aid of a vacuum transfer 
shoe 160. This transfer is preferably carried out with the transfer fabric 
traveling at a slower speed than the forming fabric (rush transfer) to 
impart stretch into the final sheet material web. The wet web is then 
transferred to the throughdrying fabric 162 with the assistance of a 
vacuum transfer roll 164. The throughdrying fabric carries the web over 
the throughdryer 166, blows hot air through the web to dry it while 
preserving bulk. There can be more than one throughdryer in series (not 
shown), depending on the speed and the dryer capacity. The dried tissue 
sheet is then transferred to a first dry end transfer fabric 168 with the 
aid of vacuum transfer roll 170. The sheet material web shortly after 
transfer is sandwiched between the first dry end transfer fabric and the 
second dry end transfer fabric 60 to positively control the sheet path. 
Suitable fabrics for use as the first dry end fabric include without 
limitation, a wide variety of fabrics such as Asten 934, Asten 939, Albany 
59M, Albany Duotex DD207, Lindsay 543 and the like. After the sheet 
material web is compressed between the first dry end transfer fabric and 
the second dry end transfer fabric 60, which, in one embodiment, has a 
greater air permeability than that of the first dry end transfer fabric, 
the web is wrapped around the reel drum 174. Suitable second dry end 
transfer fabrics include, without limitation, Asten 960 (air permeability 
of about 300-400), Appleton Mills style Q53F (air permeability of about 
400), Appleton Mills style Q53KY (air permeability of about 200). Because 
of the air flow through the lower fabric caused by roll, the sheet 
transfers to the second dry end transfer fabric. It is retained on the top 
surface of the second dry end transfer fabric by air pressure generated by 
the presence of an air foil on the underside of the fabric. The sheet 
material web is then carried to the winding nip formed between the reel 
drum 174 and the reel 178 and wound into a roll 180. 
In an alternative embodiment, the permeability of the second transfer 
fabric 60 is much lower than the corresponding fabric used for the 
above-described method. By lowering the permeability of the second dry end 
transfer fabric, the need for an air foil is eliminated because with the 
lower permeability of the second fabric, the sheet tends to naturally 
adhere to that fabric. At the point of separation the sheet follows the 
lower permeability fabric due to vacuum action. No air is pumped through 
the fabric by the various rolls and no foils are required. Suitable low 
air permeability fabrics for this embodiment include, without limitation, 
Asten 960 dryer fabric (air permeability of about 50-100), COFPA Mononap 
NP 50 dryer felt (air permeability of about 50) and Appleton Mills dryer 
felt style H53FH (air permeability of about 75). 
As shown in FIG. 15, the apparatus 10 is positioned over the second dry end 
transfer fabric 60 between the first dry end transfer fabric 168 and the 
reel drum 174. Preferably, the apparatus of FIGS. 1-2 is used in 
conjunction with the second dry end transfer fabric of the second 
embodiment described above, which has a low permeability. 
In operation, a vacuum is continuously applied through the apertures 118 in 
the plate member 102 so as to apply a negative pressure to a portion of 
the sheet material web and thereby lift the web from the fabric 60 and 
thereafter be drawn into the recess 116 and into contact with the concave 
surface 104 of the plate member. The slitting member 16, or saw blade, 
extends through the slot 120 in the plate member and into the recess 116 
formed by the plate member. Preferably, slitting member 16 does not extend 
below the bottom surface 98, 112 of the shoe member or vacuum plate 
member. Accordingly, as the sheet material is carried by the fabric, a 
portion of the web is lifted from the fabric 60 and carried past the 
slitting member which makes a slit in the sheet material web 100, thereby 
forming separate strips of sheet material web. As the sheet material web 
strips traverse past the slitting member 16 and beyond the apertures 118 
applying the vacuum, the raised portions of the strips settle back onto 
the fabric 60, or are reapplied thereto, and are thereafter transferred to 
the wind-up reel 178 and wound into rolls 180. 
It should be understood by those of skill in the art that a fixed knife, 
water jet, laser or like slitting member could be positioned in the 
housing. Alternatively, the vacuum can be applied to the sheet material 
web without a housing. Moreover, other penetrating devices, capable of 
cutting, puncturing and/or perforating the web can also be positioned 
adjacent the fabric and web and act upon the web as it is separated from 
the fabric without contacting or otherwise damaging the fabric. 
In an alternative embodiment, shown in FIG. 14, the slitting apparatus 
includes a flexible air line 182 and nozzle 184 positioned beneath the 
second dry end transfer fabric 60 of the first embodiment described above, 
i.e., a fabric having a relatively high permeability, and beneath the 
mouth 194 of the housing and the slitting member 16. In this embodiment, 
the nozzle 184 continuously emits a stream of pressurized air which passes 
through the relatively permeable fabric and provides a positive pressure 
which lifts a portion of the sheet material web off of the fabric and into 
contact with the slitting member. As with the first embodiment, the raised 
portions of the strips of sheet material web settle back onto, or are 
reapplied to, the fabric after being slit. 
It should be understood by one of skill in the art that the vacuum and 
pressurized air can be used either separately, or in conjunction, 
depending on the thickness of the sheet material web being slit and the 
permeability of the fabric carrying the sheet material web. For example, 
when using only a vacuum applied to a relatively impermeable fabric having 
a basis weight of about 800 to 1100 g/m.sup.2, a 4 inch WC to 25 inch WC 
vacuum is sufficient to lift a portion of the sheet material web having a 
basis weight of from about 18.6 g/m.sup.2 to about 32.0 g/m.sup.2 off of 
the fabric and into contact with the slitting member, but without drawing 
the fabric into contact with the slitting member. 
The slitting apparatus and method of slitting provides significant 
advantages. First, the invention provides for slitting the web, or similar 
modification such as by cutting or puncturing, while being supported on a 
fabric, which allows the manufacturer to do away with open draws. 
Accordingly, sheet breaks and the like are reduced, while simultaneously 
allowing for the manufacture of a softer, more desirable sheet material 
product. In particular, the shoe member and vacuum plate, in conjunction 
with the sensor, and adjustment screws ensure that the fabric is prevented 
from being drawn into the slitting device. In addition, the invention 
eliminates the need for wet slitting which helps to preserve the 
throughdrying fabric, improves the control of sheet web and provides a 
more uniform web. Moreover, the lateral position of the slitting apparatus 
can be easily adjusted and changed. 
In addition, the slitting apparatus can be used with a one-piece fabric 
which extends laterally across substantially the entire cross-machine span 
of the machine. This avoids the problems of the web being caught between 
multiple, adjacent fabrics or belts, and the associated problems with 
keeping such belts properly aligned. Moreover, the slitting operation can 
be moved laterally along the transverse direction of the web without 
having to reconfigure the underlying fabrics or belts. 
Although the present invention has been described with reference to 
preferred embodiments, those skilled in the art will recognize that 
changes may be made in form and detail without departing from the spirit 
and scope of the invention. As such, it is intended that the foregoing 
detailed description be regarded as illustrative rather than limiting and 
that it is the appended claims, including all equivalents thereof, which 
are intended to define the scope of the invention.