US 3788515 A
A method for guiding an advancing web of single face corrugated paperboard material and applying tension thereto along its path of advance comprising the steps of applying subatmospheric pressure to a smooth side of the web for tensioning the web, and guiding the web along the path of advance. The preferred apparatus for performing the method comprises a motorized suction device connected to a vacuum chamber for applying the subatmospheric pressure to the smooth side of the web for tensioning the web and guide plates for guiding the web during its contact with the vacuum chamber. By applying suction to the smooth side of the web, flute crush is avoided and no noise is generated by the flutes dragging across a stationary object.
Description (OCR text may contain errors)
nited States Patent [1 1 11] 3,788,515 Middleman Jan. 29, 1974 4] METHOD AND APPARATUS FOR GUIDING AND TENSIONING A WEB Inventor: David Middleman, Baltimore, Md.
Filed: Mar. 20, 1972 Appl. No.: 236,067
References Cited UNITED STATES PATENTS 12/1936 Griggs' 226/199 8/1966 -C ioettsch.... 4/1969 Shields 226/199 X l2/ 1970 Zysman.. 226/95 X 3/1972 Ferara 226/199 Koppers Company, Inc., Pittsburgh,
Primary Examiner-Richard A. Schacher Attorney, Agent, or FirmBoyce C. Dent; Olin Williams; Oskar B. Brumback 5 7 ABSTRACT A method for guiding an advancing web of single face corrugated paperboard material and applying tension thereto along its path of advance comprising the steps of applying subatmospheric pressure to a smooth side of the web for tensioning the web, and guiding the web along the path of advance. The preferred apparatus for performing the method comprises a motorized suction device connected to a vacuum chamber for applying the subatmospheric pressure to the smooth side of the web 'for tensioning the web and guide plates for guiding the web during its contact with the vacuum chamber. By applying suction to the smooth side of the web, flute cr'ush is avoided and no noise is object.
17 Claims, 5 Drawing Figures PATENIEBJANZSMA sum 2 3 PATENTH] JAN29 I974 SHEEI 3 BF 3 METH D. AND APPARATUS FOR GUIDING AND TENSIONING A WEB BACKGROUND OF THE INVENTION In the manufacturing of double faced corrugated paperboard, it is common practice to feed single face corrugated paperboard over a web tensioning device located between the delivery end of a single facer and the input end of a double facer for guiding and tensioning the single faced web prior to entering the double facer.
Conventionally, a number of different guiding and tensioning devices have been utilized in similar fashion.
One such device utilizes a bridge type mechanism in which the web of single face material is fed over a stationary member that spans the width of the web. It usually includes some type of 'guide means attached to the stationary member and tension is created by a mechanical device that presses the moving web against the stauniform and constant web tension, thereby causing warpagein the web and allowing the web to advance at a non-uniform rate. The warpage and non-uniform rate of advance causes many difficulties in manufacturing double face corrguated paperboard. A device ofthis type is illustratedin Bruker US. Pat. No. 2,710,045.
Attempts have been made to overcome the abovenoted difficulties by passing the web of material over a vacuum chamber in which a vacuum is created thus pulling the fluted side of the web against the vacuum chamber as-the web advances. By applying the vacuum to the entire width of web material, a more constant and uniform pressure is applied to the web thereby reducing warpage and allowing the web to maintain a constant speed.
Even though prior art deviceshave attempted to eliminate the tensioning problem, applying very uniform tension still remains a problem. As the web of material passes Over the guiding and tensioning devices, such as illustrated in Shields US. Pat. No. 3,348,559, the fluted surface of the web is the surface in contact with the device. Asa vacuum is applied to thefluted surface, the vacuum not only acts on the tip portion of .the flutes in contact with the device, but it also acts on the valleys of the flutes between adjacent flutes; thus the valleys are pulled inward between the flutes which may cause slight deformations on the smooth side of the web which is undesirable.
Another problem inherent in known prior art devices is the problem of flute crush. As the moving web passes over the guiding and tensioning device the fluted surface of the web is in contact with the device and, as tension is applied to the web, the flutes are pressed against the device. This pressing action often causes the flutes to deform or collapse, thereby weakening the structure of the flutes and causing the corrugated paperboard to be of inferior quality.
Another problem created by such prior art devices is the problem of noise. The advancing web moves at a high rate of speed and as the fluted surface of the web is dragged over the guiding and-tensioning device, noise levels created by this dragging action are extremely Objectionable; sometimes the noise levels may exceed maximum levels permitted by present regulations of the Occupational Safety and Health Administration, particularly when the device is used near other noisy equipment and expensive shielding is not provided.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method and apparatus for guiding and tensioning an advancing web that will overcome the aforementioned disadvantages and others; particularly for reducing flute crush and for reducing noise levels to within acceptable limits. Thus, this invention provides a guiding and tensioning device that will apply a uniform but adjustable constant tension to an advancing web, and in addition, this invention substantially reduces flute crush and will effectively reduce the noise level between the delivery end of the single facer and the input endof the double facer.
This is generally accomplished by-the method of guiding an advancing web-Of single face corrugated paperboard material and applying tension to the web along its path of advance comprising the steps of applyi'ng subatmospheric pressure to a vsmooth side of the web for tensioning the web and guiding the web along its path of advance.
The preferred apparatus for performing the method comprises a vacuum means for applying subatmospheric pressure to a smooth side of the advancing web to create a dragging force thereon for tensioning the web, and a guide means for guiding the edges of the web along the path. of advance.
The above and further objects and novel features of the invention will appear more fully from the following detailed description when the same is read in connection withthe accompanying drawings. It is to be expressly understood, howeventhat the drawings are not intended as a definition of the invention but are for the I purpose. of illustration only.
BRIEF DESCRIPTION OF THE DRAWINGS In the drawings wherein like parts are marked alike:
FIG. 1 is a schematic side view of a single factor and a double facer showing a moving single face webs path of advance from the single facer, through the'guiding and tensioning device of the present invention, and into the double facer;
DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention is shown in FIG. 1 as it is applied to a corrugated paperboard making machine having a conventional single facer noted generally by numeral 11 wherein a web 20 to be corrugated is first fed over a pre-steamer 22 and then between corrugating rollers 24 and 26. A facing sheet 28 passes partially around a pressure roll 30 where it is pressed into contact with the peaks of the corrugations in web 20, to which adhesive has been applied to the peaks in a known manner (notshown). Since single facer 11 may be of known construction and mode of operation, it will not be described; however, it should be understood that web 12 of single faced corrugated paper travels upwardly from single facer 11 to pass between sets of feed belts 32 and 34 which deliver the web progressively onto the entrance end of an overhead guide bridge indicated generally at 36. The arrangement is such that the single face web advances along the bridge 36 with its smooth side on top and its corrugated side on the bottom against a suitable flooring 40 on bridge 36. This overhead bridge 36 extends horizontally toward the double facing section 51 ofthe machine, later to be described, and is provided with an appropriate number of traveling belts 38 to feed the single faced corrugated web 12 progressively right to left as the parts appear in FIG. 1, bridge 36 being shown with flooring 40 supporting web 12 beyond the travel of belts 38.
It has long been customary in operation to maintain on bridge 36 an excess length of web 12 so that web 12 travels along bridge 36 largely in the form of more or less loose folds or loops 42 which do not lie flat against belts 38. Since the above parts of the machine may be assumed to be of known form they are not described in greater detail herein.
At the delivery end of bridge 36 is located the web guiding and tensioning apparatus of the present invention generally denoted by numeral 10. Apparatus is used for guiding web 12 into alignment with a second facing sheet 48 so that a minumum of edge cutting will later be necessary and for applying tension or a dragging force to smooth surface 16 of web 12 between vacuum means 14 and the entrance to the double facer 51 The amount of tension needed will vary depending on several factors such as the amount of wrap around roll 44 to apply the proper amount of heat to web 12, the web weight, and the like. A preferred construction of apparatus '10 islater described in detail. From apparatus 10, web 12 is shownas passing partially around the preheater roller 44 used in connection with double facing section 51 of the machine. Web 12 is then fed past an appropriate and conventional adhesive applying mechanism 46 where adhesive is applied to the peaks of the corrugations of web 12. The second facing sheet 48 is shown as being fed partially around a preheater roller 50 to the entrance end 52 of double facer section 51 of the machine where the second facing sheet 48 is pressed into contact with the adhesive coated peaks of the corrugations of web 12. Since the above described parts may be assumed to be of known construction, they are not further described in greater detail.
As previously mentioned, at the delivery end of bridge 36 is located the web guiding and tensioning apparatus 10 whose purpose is to guide and tension web 12 as it leaves bridge 36 and enters double facer 51. Conventional web guiding and tensioning mechanisms have some distinct disadvantages, as previously mentioned, and it is an object of the present invention to provide a novel means for overcoming the aforementioned disadvantages.
Referring to FIG. 1, this invention generally comprises a method of guiding an advancing web of single face corrugated paperboard material 12 and applying tension to web 12 along its path of advance between the web guiding and tensioning apparatus denoted generally by numeral 10 and the entrance into double facer 51. The method comprises the steps of applying subatmospheric pressure to a smooth side 16 of web 12 (FIGS. 2 and 4) for tensioning web 12 and guiding web 12 along its path of advance. Preferably, web 12 is advanced above its normal support path along bridge 36 to a position above it prior to applying subatmospheric pressure to web 12. The apparatus 10 for performing this method generally comprises a vacuum means 14, FIG. 2, for applying subatmospheric pressure to a smooth side 16 of web 12 for tensioning web 12, and a guide means 18, FIG. 5, for guiding web 12 along its path of advance.
As shown in FIGS. 2-5, for the purpose of clarity, the long dimensions of the guiding and tensioning apparatus 10 across the width of web 12 will be considered its Width and the short dimensions along the path of advance of web 12 will be considered its length. Vacuum means 14 includes a vacuum chamber 54 (FIGS. 2 and 4) that spans the width of bridge 36 at its delivery end. The vacuum chamber 54 is generally rectangular in shape bounded on the front and back by two spaced parallel supports 56 which span the width of bridge 36 and provide the necessary support and strength for the rest of the parts that make up the vacuum means 14, which are to be described in detail later. Vacuum chamber 54 is bounded on the sides by supports 58 which in turn are attached to bridge 36 by supports 60. Supports 56 are attached to supports 58 by any suitable means, for example, a pair of brackets 62 are spaced and attached to each support 58 such as by welding. Supports 56 are placed between each pair of spaced brackets 62 and secured thereto such as by bolting the flanges 64 of supports 56 to brackets 62. The vacuum chamber 54 is covered on the top by a cover 66 which spans the width between the two upper brackets 62 and spans the space between the two supports 56 to include flanges 64 so that top 66 may be secured to flanges 64 by any suitable means, such as by screws (not shown). The bottom of vacuum chamber 54 is covered by a perforated plate 68 (see Fig. 2) which spans the width between the two lower brackets 62 and spans the space between the two supports 56 to include the flanges 64 so that the perforated plate 68 may be secured to the flanges 64 by any suitable means such as by screws (not shown). It is to be understood that the aforementioned construction of vacuum chamber 54 is preferred although other methods of construction may be used, for example (not shown) the top cover may be rounded to form the shape of a half cylinder whose edges attach directly to the bottom perforated plate thereby eliminating the front and rear supports.
The preferred construction of the internal parts of vacuum chamber 14, is shown in FIGS. 2 and 5. A pair of laterally spaced restraining plates 70 are secured to supports 56 at substantially the midpoint of vacuum chamber 54, and are constructed so that there is a space between the top of plates 70 and top cover 66. A pair of laterally spaced stop plates 72 are secured to supports 56 at each end of vacuum chamber 54. Located between each restraining plate 70 and stop plate 72 is a piston 74. Piston 74 consists of a rectangular plate 76 whose circumference around the outside periphery is less than the circumference around the inside periphery of vacuum chamber 54. Around the outside periphery of plate 76 is attached a flexible seal 78, such as rubber, whose outer periphery is in contact with the inner periphery of vacuum chamber 54, that is to say, seal 78 on each plate 76 is in contact with cover 66, front and rear supports 56, and the bottom perforated plate 68 to form a slidable but substantially air-tight connection. Attached to the outboard surface of each rectangular plate 76 is a rectangular block 80 which serves as additional support for piston 74. A hollow tube 82 is placed through each rectangular plate 70 at substantially the midpoint of each plate 70 with the length of tube 82 being greater than the distance between the outboard surfaces of each plate 70; thus the ends of tube 82 will extend beyond the outboard surface of each plate 76. A control shaft 84 extends through substantially the midportions of stops 72, blocks 80, plates 76, and through hollow tube 82. Control shaft 84 is supported for rotation at one end by conventional bearings (not shown) which are mounted in one of the end supports 58; the other end of shaft 84 extends through and beyond similar bearings (not shown) mounted in the other support 58, and is attached to a mechanism capable of rotating shaft 84, such as a control motor 86 as shown in FIGS. 2, 3, and 5. Control motor 86 is supported by attaching it to a platform 88 which is in turn attached to end support 58. Control shaft 84 has left hand male threads on substantially one-half of its length and right hand male threads on substantially the other half of its length.
Each piston 74 has either .right or left hand female threads engageable with the corresponding male threads of shaft 84; therefore, when shaft 84 is rotated, each piston 74 will move simultaneously toward the center of vacuum chamber 54 or away from the center of vacuum chamber 54 depending on which way shaft 84 is b'eingrotated. Movement of pistons 74 toward or away from the center of vacuum chamber 54 decreases or increases the volume of the space in chamber 54 between each piston 74, thereby regulating the operating width of vacuum chamber 54 by limiting the application of subatmospheric pressure to web 12 through perforations 67 in plate'68 located between pistons 74.
Each piston 74 has a support bar 90 on each side of control shaft 84 extending through each piston 74. Each bar 90 is supported at one end by restraining plates 70 and at the other end by stop plates 72. These support bars 90 are provided as guides and supports for pistons 74 as pistons 74 move along their respective paths when control shaft 84 is rotated. A flexible dust cover 83 preferably surrounds control shaft 84 extending from each piston 74 to each restraining plate 70 for protecting the threads on control shaft 84 from dust contamination when subatmospheric pressure is applied to vacuum chamber 54.
Referring now to FIG. 2, perforated plate 68 is preferably flat and includes a central slot 92 extending along the width of perforated plate 68 and at substantially the center of its length. Slot 92 is preferably formed by spacing two similar plates 68a and 68b a short distance apart rather than by cutting a slot 92 in a single plate 68. Attached to surfaces 93 of block 80, which is adjacent to perforated plate 68, and at substantially the center of its length, are support plates 94 which extend laterally at a right angle from the outboard surface of each plate 76 to a point beyond the width of blocks 80. Attached to the surface of support plate 94 adjacent perforated plate 68 are struts 96 which extend through slot 92 and to the exterior of perforated plate 68. Attached to the inside surface of struts 96 at a point exterior of perforatedplate 68 are guide plates 98. Guide plates 98 extend at right angles from struts 96 back towards the center of vacuum chamber 54 as shown in FIGS. 2 and 5. The function of guide plates 98 will be explained later.
In order for the above described vacuum chamber 54 to guide and tension advancing web 12, subatmospheric pressure must be applied to vacuum chamber 54. To accomplish this, a motorized suction device 100 is utilized. The preferred suction device 100, and the one illustrated, is a centrifugal blower, but it should be understood that any number of different types of suction devices may be used for applying suction to the interior of chamber 54 between pistons 74. Suction device 100 is supported by two parallel support beams 102 which span the width between bridge supports 60 and are attached thereto. A base 104 spans the two beams 102 and is attached thereto. The suction device 100, which includes a power motor 106 for creating the suction, is attached to base 104. A flexible hose 108 (or rigid pipe if desired) is attached at one end to the input nozzle 101 of suction device 100 and the other end of flexible hose 108 is attached to an opening 110 in one of the supports 56 which leads to the interior cavity 55 (FIG. 2) of vacuum chamber 54. Opening 110 is preferably located at substantially the midportion of support 56 so that an even and uniform suction is applied on either side of opening 110 inside vacuum chamber 54. Flexible hose 108 is routed where it will not interfere with tensioning and guiding web 12. For example, hose 108 may be secured along support 56 and then along support 58 by hose clamps 112. Suction device 100 also contains an exhaust nozzle 114 which is preferably connected to a conventional muffler and exhaust system 103 by flexible hose for reducing the noise generated by suction device 100.
In order to increase and decrease the amount of tension that is applied to moving web 12 negative pressure applied to the interior cavity 55 of vacuum chamber 54 may be increased or decreased. To accomplish this a damper device 116 or preferably a conventional air relief valve, may be used and can be mounted on top cover 66 with an access port extending to the interior of vacuum chamber 54. It is preferable to mount damper 116 at substantially the midportion of top cover 66 in order to maintain a substantially uniform subatmospheric pressure inside vacuum chamber 54. Damper 116 may be of any suitable type which will provide proper regulation of the magnitude of subatmospheric pressure applied to vacuum chamber 54. For example, the damper 116 may be progressively opened to vent the interior of chamber 54 to atmosphere thereby reducing the magnitude of the pressure. However, the pressure may also be controlled by increasing or decreasing the speed of suction device 100.
Referring now to FIGS. 2, 3, and 4, a pair of rotatable rollers 118, preferably bearing mounted in the conventional manner, spans the width between end supports 58, one of which is attached thereto slightly below and at the input and the other at the output side of vacuum chamber 54. The rotatable rollers 118 may be motor In operation, web 12 moves from the single facing 8 operation 11 to overhead bridge 36 where belts 38 move web 12, which is folded into loops 42, toward the delivery end of bridge 36. At the delivery end of bridge 36 is the guiding and tensioning device of the present invention. The vacuum means 14 may be spaced just slightly above bridge 36 with the bottom of perforated plate 68 in contact with the top smooth surface 16 of web 12 as the web advances horizontally along bridge 36 so that web 12 may be guided almost directly horizontally into the apparatus, but the preferred method is to have vacuum means 14 spaced a substantial distance above bridge 36 as shown in FIG. 1 so that loops 42 are pulled upward out of web 12 prior to its entering the apparatus. Vacuum means 14 is supported above bridge 36 by end supports 58, as previously described.
Web 12 is fed over input roller 118 and under perforated plate 68 so that the smooth surface 16 of web 12 is in contact with perforated plate 68 and the fluted surface of web 12 is in contact with input roller 118. Web 12 is then fed over output roller 118, around preheater roller 44, and into double facer 51. Motor 86 is energized by suitable conventional controls (not shown) thereby rotating control shaft 84 in the desired direction. Since pistons 74 are engaged with control shaft 84, rotation of control shaft 84 will simultaneously move pistons 74 toward each other, thus, toward the edges of web 12. As illustrated in FIGS. 2 and 5, strut 96 is connected to piston 74 by support plate 94, and strut 96 extends through slot 92 to the exterior of perforated plate 68. Guide plates 98 in turn are connected to struts 96 exterior of perforated plate 68. Therefore, when pistons 74 advance or retract along their path of advance, guide plates 98 will also advance and retract. The machine operator, by activating motor 86, can move guide plates 98 along their path of advance until they are in contact with the edges of web 12, at which time motor 86 is deenergized by the operator, which stops any further advance of guide plates 98. The guide plates 98 are then in a position to guide web 12 along its path of advance by being in contact with the edges of the web.
As guide plates 98 are positioned, pistons 74 are also positioned since both are interconnected, by motor 86 and control shaft 84. As pistons 74 advance, flexible seals 78 contact the inner periphery of vacuum chamber 54, thereby defining the active volume of chamber 54 between each piston 74 subjected to subatmospheric pressure. When guide plates 98 are in contact with the edges of web 12, the separation distance between each piston 74 will be substantially the same as the width of web 12. Thus, no, suction is lost through the perforations lying outside the width of web 12.
Activation of suction device 100 causes subatmospheric pressure to be applied in inner cavity 55 between pistons 74 in vacuum chamber 54. The smooth side 16 of web 12 is thereby lifted and pressed against perforated plate 68, thereby causing tension orv a dragging force to be applied to the smooth surface 16 of web 12 between vacuum means 14 and the entrance to the double facer 51. The amount of tension needed will vary depending on several factors such as the amount of wrap around roll 44 to apply the proper amount of heat to web 12, the web weight, and the like. Damper 116 can be adjusted to regulate the magnitude of the tension applied to web 12, by controlling the amount of atmosphere that is allowed to return to vacuum chamber 54 through damper or valve 116.
Activation of single facer 11 and double facer 51 causes web 12 to move along its path of advance. As the fluted surface of web 12 moves over input roller 118, input roller 118 will begin to rotate at the same speed as advancing web 12 due to the flutes being pulled over input roller 118. As the flutes are not dragged over a stationary object, but are allowed to flow over a free-wheeling rotatable roller, very little noise is created at this point. As web 12 passes under perforated plate 68, tension is applied to the smooth surface 16 of web 12. Since the smooth surface 16 of web 12 is sliding across perforated plate 68 rather than the fluted surface, the noise level at this point is greatly reduced because the individual flutes are not being dragged over perforated plate 68. Also, since the tension is applied to smooth surface 16 of web 12, and smooth surface 16 is in contact with perforated plate 68 rather than the fluted surface, the fluted surface is not subjected to flute crush while web 12 is being tensioned nor is any force present tending to pull the corrugated medium away from the smooth liner 16. Web 12 then passes over output roller 118 causing it to rotate which again creates little or no noise. The passage of web 12 over input and output rollers 118 is helpful for guiding and supporting web 12 along a straight flat path under flat perforated plate 68 thereby reducing the possibility of web 12 becoming disengaged from perforated plate 68 by tension in the portion of web 12 between roller 118 and wrap roll 44 while tension is being applied to web 12. Rollers 118 also keep web 12 in position in the event suction pressure is temporarily lost.
To process a different width web, motor 86 is activated to either advance or retract guide plates 98 until they contact the edges of the new web. Regulation of damper 116 applies the correct amount of tension to the new web, and the process begins anew.
It should be pointed out that a conventional overload relay (not shown) may be connected to motor 86 so that in the event the pistons 74 are advanced until they contact restraining means 70, the overload relay will activate and cause motor 86 to shut down, thereby stopping the rotationof shaft 84 and advancing pistons 74. Also, a conventional limit switch 120 may be positioned on the inboard surface of stop 72 to deactivate motor 86 should pistons 74 be separated to their maximum limit thereby stopping the rotation of shaft 84 and retracting pistons 74. These features prevent the possibility of binding thecooperating threads on the pistons 74 and shaft 84.
The foregoing has presented a novel web guiding and tensioning device which is capable of guiding an advancing web along its path of advance and at the same time applying a controlled tension to the smooth surface of the web thereby greatly reducing flute crush and noise levels created when flutes are caused to pass over a conventional guiding and tensioning device.
The apparatus for guiding and tensioning the web has been illustrated as being positioned above the bridge because as the web moves along the bridge, the smooth surface of the web is facing up and in order to apply tension to the web, the webs top smooth surface must contact the bottom perforated plate of the apparatus. Should the single faced web material be processed so that the smooth surface of the web is facing down when the web is moving along the bridge, the apparatus may be inverted so that the perforated plate facing up and substantially coplanar with the support surface of the bridge. As the web moves along the bridge the smooth surface of the web can then pass over the perforated plate for applying tension thereto. It should be noted that additional devices may have to be used, such as air blowers or mechanical guides, to straighten the loops prior to the web passing over the perforated plate.
Accordingly, the invention having been described in its best embodiment and mode of operation, that which is desired to be claimed by Letters Patent is:
1. Apparatus for guiding an advancing web of single face corrugated paperboard material and applying tensionthereto along its path of advance, comprising:
vacuum means for applying subatmospheric pressure to a smooth side of said web for tensioning said a web, said vacuum means including: a perforated plateadjacent said smooth side for applying said subatmospheric pressure thereto; and
' a vacuum chamber having at least one laterally adjustable piston means therein for limiting the volume of said chamber subject to evacuation and; for limiting the area of said perforated plate exposed to said subatmospheric pressure to apply said pressure to within the edges of said web; and
guide means "for guiding said web along said path of advance.
2. The apparatus of claim 1 wherein said guide means are laterally adjustable along the edges of said web for guiding webs of various widths. I
. 3. The apparatus'of claim 1 wherein said vacuum means includes 'a damper means for regulating the magnitude ofsubatmospheric pressure applied to said vacuum means for regulating tension in said web.v
4. The apparatus of claim 1 wherein said vacuum means includes a motorized suction means for creating said su-batmosphericprjessure in said vacuum means.
5. The apparatus of claim 1 wherein said piston meansincludes two simultan eously adjustable laterally opposedpistons at opposite sides of said chamber movable into'alignment with the edges of said web to limit the application of subatmospheric pressure to the width of said smooth side of said web. v
6. The apparatus of claim 5 wherein said pistons include:
a control shaft means extending laterally through substantially the midportion of each of said pistons,
said shaft means having left hand male threads on substantially one-half of said shaft means and right hand male threads on substantially the other half of said shaft means, I
said male threads engageablewith corresponding female threads in each of said pistons,
said shaft means being rotatable for simultaneously adjusting each of said pistons toward and away from one another thereby regulating the operating width of said vacuum chamber. 7. The apparatus of claim 6 wherein said shaft means is connectedto a power means for remotely rotating said shaft means. i
8. The apparatus of claim 7 wherein said power means is remotely shut down by a relay means when said pistons reach their minimum closed position for stopping the rotation of said shaft means before said pistons contact each other.
9. The apparatus of claim 7 wherein said power means is remotely shut down when said pistons engage a switch means connected to one end of said vacuum chamber for stopping rotation of said shaft means when said pistons reach their maximum opened position.
10. The apparatus of claim 5 wherein said vacuum chamber includes:
two piston restraining means secured to said vacuum chamber and laterally spaced at substantially the midpoint of said vacuum chamber with said shaft means extending through each of said restraining means for restraining said pistons from contacting each other;
two piston stop means secured to said vacuum chamber and laterally spaced at each end of said vacuum chamber with said shaft means extending through each of said stop means for stopping said pistons when said, pistons are at their maximum separation;
and 1 4 1 piston support means on each side of said shaft means for each of said pistons extending through each of said pistons and supported at one end by said restraining means and at the otherv end by said stop means for guiding and supporting said pistons along their respective paths'when said shaft means is rotated.
11. The apparatus of claim 5 wherein said pistons include a flexible seal means around the outer periphery of said pistons for contacting the inner periphery of said vacuum chamber thereby preventing vacuum loss around said pistons.
12'. The apparatus of claim 7 wherein:
said perforated plate includes a slot extending along the width thereof and substantially at the center of its length; each of said pistons includes a strut means connected thereto and extending through said slot to the exterior of said plate; andsaid guide means includesa plate means connected to each of said struts and movable with said pistons into contact with corresponding edges of said web for guiding the same during its contact with said perforated plate.
13. The apparatus of claim 12 further including remotely operable power means connected to said pistons for simultaneously positioning said pistons and said plate means to correspond to the width of said web being advanced. a
14. The apparatus of claim 1 wherein said plate is substantially flat.
15. The apparatus of claim 1 wherein said apparatus further includes: a
support means attached to each of said vacuum means for spacing saidvacuum means above the path of said advancing web; and a pair of rotatable roller means attached to said supperforated port means below and at the input-and output of i chamber and through a perforated plate to a smooth side of said portions in said position above said path of advance for causing tension in said web following the application of said pressure thereto; and
laterally adjusting at least one piston within said vacuum chamber for limiting the volume of said chamber and limiting the area of said perforated plate exposed to said subatmospheric pressure to apply said pressure to within the edges of said web.