WO1999017924A1

WO1999017924A1 - Method and apparatus for threading a web

Info

Publication number: WO1999017924A1
Application number: PCT/US1998/020657
Authority: WO
Inventors: Charles E. Thomas; Stephen J. Mettee; Gary S. Podhorniak
Original assignee: United Container Machinery, Inc.
Priority date: 1997-10-03
Filing date: 1998-10-02
Publication date: 1999-04-15

Abstract

An apparatus and related method for threading a web through a web processing machine are disclosed. The apparatus of the present invention preferably comprises a double facer (10) including a plurality of heating plates (16) defining a heated surface facing a lower surface of a paperboard web. A weight blanket (78) is provided for exerting pressure against the upper surface of the web wherein a passageway for receiving the paperboard web is defined between the heated surface and the weight blanket. The leading edge of the paperboard web is conveyed over the heating plates (16) by a threading device including a pair of conveyor elements extending along each side of the heating plates. A threading roll (246) is supported by the conveyor elements wherein the threading roll is adapted for wrapping the paperboard web around a portion thereof. A drive moves the conveyor elements wherein the threading roll and the leading edge of the paperboard web are conveyed over the heating plates.

Description

METHOD AND APPARATUS FOR THREADING A WEB

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for processing corrugated paperboard, and more particularly, to a method and apparatus for threading a paperboard web through a web processing machine.

2. Description of the Prior Art

The manufacturing of double face corrugated paperboard typically begins with an apparatus known as a single facer. A conventional single facer includes an upper corrugating roll and a lower corrugating roll wherein each roll has a plurality of longitudinally extending teeth. The corrugating rolls are rotatably mounted adjacent each other such that the teeth of each roll are in a meshing relationship. A medium web typically passes through a preheater for conditioning and is then fed into the nip point of the upper and lower corrugating rolls wherein the medium web conforms to the contour of the meshing teeth to form flutes in the medium web. A gluing roll, arranged to turn in a bath of starch-based glue, applies glue to the tips of the medium web flutes. A top liner web is simultaneously supplied to a preheater of similar design to the medium web preheater.

The conventional single facer further includes a pressure roll arranged adjacent the lower corrugating roll to apply a nip pressure to the corrugated medium web and the top liner web. The pressure roll and lower corrugating roll are typically heated and the combination of heat and pressure gelatinizes the glue between the medium web and top liner web thereby forming a single face web of corrugated paperboard.

The glue typically applied to the flutes of paperboard webs is a suspension of raw or uncooked starch in a suitable liquid carrier. In this state, the starch has little or no adhesive qualities. However, at a certain temperature, dependent upon the type of starch utilized and the kind and amount of additives dissolved in the carrier, the starch granules will absorb the liquid of suspension available and swell, causing gelatinization of the suspension. In this state the starch has superior adhesion abilities and will form a good bond between many substrates, including paper. The temperature at which gelatinization occurs for any particular formulation of glue can be easily determined by heating the particular formulation and observing the changes that occur in its viscosity.

After passing over a single face web preheater drum of design similar to the medium web and top liner preheaters, the single face web is next conveyed to a gluing station where the exposed flute tips are covered with a starch-based glue. A bottom liner is typically trained over a preheater in a manner similar to the single face web and then brought into contact with the glued flute tips of the single face web by an apparatus called a double facer to produce a double face web of corrugated paperboard. In order to heat the bottom liner and assist in the gelatinization of the glue between the bottom liner and single face web. the double face web is pressed against and conveyed over an array of heating plates arranged in the direction of web movement. The heating plates define a heating section of the double facer and are typically comprised of cast iron and have central chambers for containing pressurized steam. Inlet and outlet ports in the lower surface of the heating plates provide for the continuous flow of steam. Double face web travel over the heating plates is conventionally provided by a driven holddown means, usually a continuous holddown belt, in direct contact with the top liner. A series of ballast rollers or the like bear on the inner surface of the holddown belt such that pressure is maintained between the holddown belt and the top liner of the double face web thereby facilitating thermal contact between the web and heating plates.

A significant problem associated with conventional double facers relates to the process of feeding and threading a web through the heating section in preparation for continuous web processing. More particularly, if a stationary holddown means is utilized such that a downstream drawing section is required to pull the web through the heating section, then a pair of human operators must pull the leading edge of the web through the entire length of the heating section, typically 40 feet or more, and into engagement with the conveying elements of the drawing section. This prior art threading method essentially comprises a "brute force" process of human operators gripping each side of a bottom liner web and then manually pulling the liner web downstream between the heating plates and the holddown means. Glued flute tips of the single face web are then manually brought into contact with the bottom liner. Upon start-up of the double facer, the drawing section pulls the bottom liner and single face web through the heating section for continuous processing of the double face web.

As is readily apparent, the prior art threading process is both difficult and time consuming. Further, the traditional threading process creates significant safety concerns. The operators must manually feed the web through pressure nips defined to receive the paperboard web, resulting in crushing hazards for the hands and fingers of the operators. Additionally, if the double facer has been operating, the process is further complicated by extremely hot components, particularly the surface of the heating plates. Operators must come into close proximity with these hot components during the threading process resulting in the possibility of serious burns being inflicted upon the bodies of the operators.

Accordingly, there is a need for a method and apparatus for threading a web in an safe and efficient manner through a web processing machine. In particular, there is a need for such a method and apparatus for threading a paperboard web through the heating section and drawing section of a double facer.

SUMMARY OF THE INVENTION The present invention provides a method and apparatus for processing corrugated paperboard and, more particularly, for threading a web through a web processing machine. While the threading device of the present invention may be utilized in any number of web processing machines, it is particularly well-suited for use within a double facer.

The preferred embodiment of the present invention provides for a double facer comprising a heating section including a plurality of heating plates defining a heated surface facing a lower surface of a paperboard web. Holddown means comprising a weight blanket is supported above the heating plates for exerting pressure against an upper surface of the web. The weight blanket includes a plurality of interconnected weight members, preferably rigid shoes, directly contacting the upper surface of the web. The shoes are arranged in a plurality of laterally, or cross- machine, extending rows wherein the shoes of each row are offset from the shoes of an adjacent row. A plurality of longitudinally extending cables interconnect the plurality of rows of shoes and prevent linear movement of the shoes in the direction of paperboard web travel.

Vertically moveable support members are connected to and support the upstream and downstream ends of the cables. Linear actuators are operably connected to the support members for raising and lowering the weight blanket thereby varying the portion of the weight blanket exerting pressure against the web. Further, the weight blanket may be fully elevated to provide clearance for threading the web. A drawing section is provided downstream from the heating section for pulling the paperboard web over the heating plates. The drawing section comprises upper and lower opposing conveyor belts for engaging upper and lower surfaces of the web. Linear actuators support the upper conveyor belt above the lower conveyor belt wherein activation of the linear actuators raises and lowers the upper conveyor belt relative to the lower conveyor belt for providing clearance for threading the web.

The double facer of the present invention further includes a threading device for conveying a leading edge of the paperboard web through the heating section and drawing section. The threading device comprises a pair of flexible conveyor elements extending longitudinally along each side of the heating plates. A threading roll is supported by the conveyor elements wherein the threading roll is adapted for wrapping the paperboard web around a portion thereof. A drive is operably connected to the conveyor elements for moving the threading roll and the paperboard web over the heating plates. In a first embodiment of the threading device of the present invention, the threading roll extends between the conveyor elements and cooperates with a pinch roll which similarly extends between the conveyor elements. The pinch roll is mounted for pivotal movement relative to the threading roll for engaging and securing the web between the pinch roll and the threading roll. During a normal mode of operation the pinch roll is spring biased towards the threading roll, while during a set-up mode of operation the pinch roll is biased away from the threading roll.

A method of threading a web associated with the first embodiment of the threading device includes the steps of wrapping a leading edge of the web around a portion of the outer surface of the threading roll and then pivoting the pinch roll towards the threading roll, thereby securing the web between the pinch roll and the threading roll. The conveyor elements are next driven in motion wherein the threading roll, pinch roll and web are transported downstream through the apparatus. After stopping the conveyor elements, the pinch roll is pivoted away from the threading roll thereby releasing the web from between the pinch roll and the threading roll. The leading edge of the web is unwrapped from the outer surface of the threading roll leaving the web threaded through the double facer and ready for continuous processing.

In a second embodiment of the threading device of the present invention, the threading roll is also rotatably mounted between the conveyor elements. The threading roll is adapted for wrapping the paperboard web around a portion thereof, wherein the threading roll defines upper and lower runs of the web. Clamping means is positioned upstream from the threading roll for selectively securing the web and preventing movement of a leading edge of the web. The threading roll cooperates with the clamping means for pulling one of the lower and upper runs of the web downstream followed by pulling the other of the lower and upper runs of the web downstream. A sensor is positioned downstream from the clamping means for detecting when the threading roll occupies a predetermined position between an entrance and an exit of the double facer.

A method of threading a web associated with the second embodiment of the threading device includes the steps of wrapping a leading edge of the web - around a portion of the outer surface of the threading roll, thereby defining upper and lower runs of the web. The leading edge of the web is next fed through the clamping means which is then activated to secure the web therein for preventing movement of the leading edge of the web relative to the heating plates. The threading roll is conveyed downstream wherein the web is pulled through the double facer. As the threading roll passes a predetermined position, the web is released from the clamping means such that the leading edge of the web is conveyed downstream with continued movement of the threading roll. The threading roll is stopped proximate an exit of the double facer whereby the web is properly threaded through the double facer. Therefore, it is an object of the present invention to provide an apparatus and method for safely and efficiently threading a web through a web processing machine.

It is yet another object of the invention to provide such a threading apparatus which securely grips a paperboard web and pulls the web downstream through a web processing machine with minimal human intervention. It is a further object of the invention to provide such a threading apparatus for pulling a paperboard web through the heating section and into the drawing section of a double facer.

Other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side elevational view of a double facer of the present invention;

Fig. 2 is a top plan view of the double facer of Fig. 1 with a partial cutaway of the weight blanket and the upper conveyor belt;

Fig. 3 is a side elevational view of a threading device of the present invention installed on a double facer;

Fig. 4 is a side elevational view of the weight blanket lifting means of the present invention; Fig. 5 is a perspective view of a transfer carriage of the threading - device of Fig. 3; Fig. 6 is a cross-sectional view taken along line 6-6 of Fig. 5 illustrating various positions of the pivot arm of the present invention;

Fig. 7 is a partial side elevational view of an alternative embodiment of the threading device of the present invention installed on a double facer; Fig. 8 is a partial perspective view of the threading device of Fig. 7;

Fig. 9 is an enlarged detail view taken along line 9 of Fig. 8; and

Figs. 10-13 illustrate various positions of threading device of Fig. 7 as the transfer carriage threads a web downstream through the double facer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring initially to Fig. 1 and 2. a double facer 10 constructed in accordance with the preferred embodiment of the present invention is shown as including a heating section 12 upstream from a drawing section 14. The heating section 12 includes a plurality of heating plates 16 arranged in a side-by-side array such that they define a heated surface 18 over which a single face web 20. having a starch-based adhesive applied to its exposed flute tips, is brought together with a bottom liner web 22 to form a double face corrugated web 24. Each heating plate 16 has a width in the cross-machine or lateral direction of approximately 100 inches and a length in the longitudinal direction of approximately 24 inches. The plates 16 are typically arranged to provide a heated surface 18 of approximately 40 feet in length while each plate 16 is spaced apart such that a gap 26 of approximately 1 inch is provided between adjacent heating plates 16 (Fig. 2). The heating plates 16 may be of conventional construction but preferably comprise the heating plates 16 as described in greater detail in U.S. Patent Application Serial No. 08/892,694 (Attorney Docket UCM 101 P2) entitled "Method and Apparatus for Processing Corrugated Paperboard," filed July 15, 1997 and assigned to the assignee of the present invention, such application hereby incorporated by reference.

A stationary holddown means 28 is provided above the heating plates 16 for forcing the single face web 20 towards the liner web 22 and heated surface 18 defined by the heating plates 16. A passageway for receiving the web 24 is obviouslv defined between the heated surface 18 and the holddown means 28. The double face web 24 is conveyed through the heating section 12, in the direction of arrow 30, by the drawing section 14. While Figs. 1 and 2 illustrate a drawing section 14 including upper and lower conveyor belts 15 and 17, respectively, it is to be understood that any suitable conveying elements may be used within the drawing section 14 of the present invention. For example, the drawing section 14 may be of the type disclosed in U.S. Patent Application Serial No. 08/838.150 (Attorney Docket UCM 095 P2) entitled "Web Conveyor," filed April 15, 1997 and assigned to the assignee of the present invention. Referring further to Figs. 1 and 2, the holddown means 28 of the double facer 10 is shown as a weight blanket 78 pressing against the double face web 24 to facilitate heat transfer from the heating plates 16. As the double face web 24 is moved in the direction of arrow 30, the combination of heat from the heating plates 16. and pressure imparted upon the web by the blanket 78, gelatinizes the glue between the bottom liner 22 and single face web 20 to form bonded double face corrugated paperboard 24. The weight blanket 78 includes a plurality of weight members, preferably rigid shoes 80 formed of bent sheet metal. The shoes 80 are arranged in an offset pattern in the direction of web travel, as indicated by arrow 30 in Fig. 1 1, and are interconnected by a series of the metal cables 88 threaded through the apertures formed within each shoe 80. The cables 88 prevent linear movement of the shoes 80 in the direction of travel 30 of the web 24.

Additional detail regarding the rigid shoes 80 and cables 88 is provided in the above incorporated U.S. Patent Application Serial No. 08/892,694 (Attorney Docket UCM 101 P2) entitled "Method and Apparatus for Processing Corrugated Paperboard," filed on July 15, 1997 and assigned to the assignee of the present invention.

As illustrated in Figs. 1 and 2. the upstream and downstream ends 94 and 96 of each cable 88 are supported by upstream and downstream support members or drums, 98 and 100, respectively, such that the plurality of shoes 80 are suspended above the heating plates 16. A curve or catenary of the cables 88 between the support members 98 and 100 permits the shoes 80 to force the web 24 towards the heating plates 16 thereby facilitating heat transfer therebetween. The upstream and downstream support members 98 and 100 may be mounted for vertical movement, as indicated by arrows 102 and 104 in Fig. 1. By raising one or both of the support members 98 and 100. the respective ends 94 and 96 of the cables 88 are likewise raised to vary the portion of the blanket 78 exerting pressure against the web 24. The amount of heat transferred from the heating plates 16 to the web 24 may therefore by adjusted. Additionally, the blanket 78 may be elevated to provide clearance for threading the leading edge of the web 24 as described hereinafter with reference to Fig. 3. It should be noted that a spring (not shown) connects the downstream ends 96 of the cables 88 to the downstream support member 100 for tensioning the cables 88 to counteract cable displacement as the weight blanket 78 is lifted to adjust coverage.

Each support member 98 and 100 has opposing ends 106 and 108 operably connected to linear actuators, preferably conventional lifting screws 110. More particularly, and with reference to Fig. 4, a lifting nut 112 is fixed to a bracket 114 located at each opposing end 106 and 108 of the support members 98 and 100. Activation of a motor 1 16 drives a pair of the lifting screws 1 10 in rotation thereby raising or lowering the respective lifting nuts 112 and support member 98 and 100. It should be noted that the lifting screws 110 on opposing ends 106 and 108 of the support members 98 and 100 are both driven in synchronization by the motor 116 which rotates a transmission shaft 1 18 extending laterally, or in the cross machine direction, across the double facer 10 in parallel relation to the support members 98 and 100 (Fig. 2).

Referring further to Fig. 4, a linear rail guide 120 is located adjacent each lifting screw 1 10 for guiding the support members 98 and 100 in vertical movement. The linear rail guide 120 includes a rail member 122 supported on a lifting tower 124 and a guide block 126 engaging the rail member 122. Each guide block 126 is fixed to one of the brackets 114 so that, as the respective support member 98 and 100 is vertically moved, its motion is guided linearly along the rail member 122. Referring again to Figs. 1-3, continuous processing of the double fac^~e web 24 occurs as the web 24 is pulled through the heating section 12 by the drawing section 14 which includes upper and lower opposing continuous conveyor belts 15 and 17. Each belt 15 and 17 defines an outer surface 152 for engaging a surface 154 and 156 of the double face web 24. More specifically, in a normal mode of operation, the conveyor belts 15 and 17 define a passageway wherein the outer surfaces 152 of the upper and lower belts 15 and 17 are adapted for engaging the upper and lower surfaces 154 and 156 of the web 24, respectively. Both the upper and lower conveyor belts 15 and 17 are driven by motors 158 and 160, respectively, in a manner as is well known in the art. The motors 158 and 160 are electronically coupled to ensure that each belt 15 and 17 is driven at the same speed such that the upper and lower surfaces 154 and 156 of the web 24 are likewise driven at the same speed. This prevents a speed differential between the upper and lower surfaces 154 and 156 of the web 24 which could damage the fresh bond between the single face web 20 and the bottom liner web 22.

The upper conveyor belt 15 is supported by a vertically moveable frame 162. A plurality of weight rolls 164 are rotatably mounted within the frame 162 for exerting pressure against an inner surface 166 of the upper belt 15 thereby forcing the upper belt 15 towards the lower belt 17. The weight rolls 164 therefore facilitate frictional contact between the outer surfaces 152 of the upper and lower conveyor belts 15 and 17 and the upper and lower surfaces 154 and 156 of the web 24.

A bracket 168 is attached proximate each corner of the moveable frame 162. A lifting nut (not shown) and guide block 170 (Fig. 3) are fixed to each bracket 168 in a manner similar to the lifting nut 1 12 and guide block 126 of the support members 98 and 100 as described above with reference to Fig. 4. A lifting screw 174 threadably engages the lifting nut wherein activation of a motor 176 drives the lifting screw 174 in rotation, thereby raising or lowering the lifting nut and the upper conveyor belt 15. A linear guide member 178 of the type described above with respect to Fig. 4 is provided wherein the guide block 170 engages a rail member 180 fixed to a lifting tower 182. The linear guide member 178 ensures that the moveable frame 162 is raised in substantially linear vertical movement. A single ^* motor 176 operates a pair of lifting screws 174 by rotating a laterally extending transmission shaft 184 between the pair of lifting screws 174 (Fig. 2).

Turning now to Figs. 3-5, a web threading device 200 according to the present invention is illustrated for threading a leading edge 202 of the bottom liner 22 through the double facer 10. The web threading device 200 includes a transfer carriage 204 supported between a pair of flexible conveyor elements, preferably roller chains 206 and 208 (Fig. 2). The roller chains 206 and 208 extend downstream from proximate an entrance end 210 to proximate an exit end 212 of the double facer 10 along each side thereof. Each chain 206 and 208 has an upper run 214 and a lower run 216 wherein the chains 206 and 208 wrap around driven sprockets 215 proximate the exit end 212 and return sprockets 217 proximate the entrance end 210. The upper runs 214 are partially supported by support rails 218 having a nylon bearing strip 220 for contacting a respective roller chain 206 and 208 (Fig. 4). Each support rail 218 is located exterior to the heating plates 16 and between adjacent support legs 222 for the heating plates 16. A pair of idler sprockets 224 are located adjacent each support rail 218 wherein the idler sprockets 224 guide the upper and lower runs 214 and 216 of each chain 206 and 208 when they are driven in motion by driven sprockets 215. The driven sprockets 215 are operably connected to a motor 226 located proximate the exit end 212 of the double facer 10 in a manner as is well known in the art. A plurality of support pins 228 are positioned between the idler sprockets 224 below the support rails 218 for supporting the lower run 216 of each roller chain 206 and 208. When the motor 226 is activated, the chains 206 and 208 and transfer carriage 204 are driven in motion longitudinally through the double facer 10.

Referring to Figs. 5 and 6, the transfer carriage 204 includes a pair of mounting plates 230 and 232. each mounted to one of the roller chains 206 and 208 are extending outwardly therefrom. One of the roller chain links 234 of each chain 206 and 208 is replaced by a mounting link 236 having outwardly extending tabs 238 which straddle one of the mounting plates 230 and 232. A pin 240 secures the tabs 238 to a respective mounting plate 230 and 232. Opposing ends 242 and 244 of a threading roll 246 are secured to mounting plates 230 and 232. respectively, wherein the threading roll 246 extends in a lateral or cross machine direction across the double facer 10 between the conveyor chains 206 and 208. A pivot arm 248 is pivotally mounted to an inside surface 250 of each mounting plate 230 and 232 by a pivot bolt 252. At least one of the pivot arms 248 includes a handle 254 fixed thereto for utilization by an operator in pivoting the pivot arm 248 about the pivot bolt 252 as indicated in Figs. 6 and 7 by arrow 255.

Opposing ends 256 and 258 of a pinch roll 260 are supported by each pivot arm 248 wherein the pinch roll 260 is selectively engageable with the threading roll 246. A spring 262 connects the pivot arm 248 with respective mounting plate 230 and 232 for biasing the pinch roll 260 towards the threading roll 246 during a normal mode of operation, which is represented by reference letters A and B in Fig. 6. When the spring 262 travels "over center", i.e. to a position where a spring connection point 263 on the pivot arm 248 is above the pivot bolt 252 as represented by reference letter C in Fig. 6, a set-up mode of operation is defined. In this set-up mode of operation, the pinch roll 260 is biased away from the threading roll 246 and remains locked in an open position. The clockwise movement of the pivot arm 248 and pinch roll 260, as shown in Fig. 6, is limited by a stop pin 264 which engages a bearing surface 266 of the pivot arm 248.

In operation, the operator first elevates the weight blanket 78 and upper conveyor belt 15 to provide adequate clearance for the transfer carriage 204 to move longitudinally through the double facer 10 as illustrated in Fig. 3. As described above, the upstream and downstream support members 98 and 100 for the blanket cables 88 are operably connected to lifting screws 110. The motors 116 are activated to rotate the lifting screws 110 and raise the support members 98 and 100 to a position where the transfer carriage 204 will clear the catenary of the weight blanket 78. Similarly, the lifting screws 174 for supporting the moveable frame 162 of the upper conveyor belt 15 are rotated thereby raising the upper conveyor belt 15 such that the transfer carriage 204 will clear the upper conveyor belt 15.

Once the weight blanket 78 and upper conveyor belt 15 are elevated, the operator positions the transfer carriage 204 adjacent the entrance end 210 of the double facer 10 by selective activation of the motor 226 driving the roller chains 206 and 208. Next, the operator pulls the handle 254 and pivot arm 248 of the gripping device 204 upwardly thereby pivoting the pinch roll 260 away from the threading roll 246 until the pivot arm 248 engages the stop pin 264. At this point, the pinch roll 260 is locked open in the set-up mode of operation. The leading edge 202 of the bottom liner 22 is then pulled towards the transfer carriage 204 and wrapped from beneath the threading roll 246 upwardly around a substantial portion of an outer surface 268 of the threading roll 246 until positioned for clamping engagement between the threading roll 246 and the pinch roll 260.

The operator next pulls the handle 254 downwardly towards the threading roll 246 so that the pivot arm 248 travels "below center", i.e. where the spring connection point 263 of the pivot arm 248 is below the pivot bolt 252. This returns the transfer carriage 204 to its normal mode of operation wherein the pinch roll 260 is spring biased towards the threading roll 246. As clearly illustrated in Fig. 6, the bottom liner web 22 is locked between the pinch roll 260 and the threading roll 246 at this point. The operator activates the motor 226 to drive the roller chains 206 and 208 such that the transfer carriage 204 and web 22 are conveyed downstream through the heating section 12 and drawing section 14 of the double facer 10. The motor 226 is stopped once the transfer carriage 204 is located proximate the exit end 212 of the double facer 10. The operator pulls the handle 254 upwardly and away from the threading roll 246 until the pivot arm 248 engages the stop pin 264 and the pinch roll 260 is locked open in the set-up mode of operation.

The paperboard web 22 is then unwrapped from the outer surface 268 of the threading roll 246 and the transfer carriage 204 is conveyed just beyond the driven sprocket 215 of the double facer 10 where it will not interfere with the continuous processing of the double face web 24. The weight blanket 78 and upper conveyor belt 15 are then lowered to the positions illustrated in Fig. 1. The single face web 20 having glued flute tips is brought into adhering contact with the bottom liner web 22. The drawing section 14 is activated to pull the webs 20 and 22 together through the heating section 12 to form the double face web 24.

Turning now to Figs. 7 and 8. an alternative embodiment of a web threading device 300 according to the present invention is illustrated for threading a leading edge 302 of the double face web 24 through the double facer 10. It should be appreciated that in the following description, identical reference numerals represent identical components as described above.

The web threading device 300 includes a transfer carriage 304 supported between the pair of roller chains 206 and 208. As with the previous embodiment of Fig. 2, the roller chains 206 and 208 extend along each side of the double facer 10 from proximate an entrance end 210 to proximate an exit end 212. Driven sprockets 215 proximate the exit end 212 and return sprockets 217 proximate the entrance end 210 serve to define upper and lower runs 214 and 216, respectively, of the chains 206 and 208. As with the previous embodiment of Fig. 4, support rails 218 having a nylon bearing strip 220 are provided for engaging and supporting the upper run 214 of each chain 206 and 208. A pair of idler sprockets 224 are located adjacent each support rail 218 for guiding the upper and lower runs 214 and 216 of the chains 206 and 208. Referring further to Fig. 7, a motor 226 drives the driven sprockets 215 in motion thereby moving the roller chains 206 and 208. As the motor 226 is activated, the chains 206 and 208 convey the transfer carriage 304 longitudinally through the double facer 10 over the heating plates 16 and lower conveyor belt 17.

Turning now to Figs. 8 and 9. the transfer carriage 304 includes a pair of mounting plates 330 and 332, each mounted to, and extending outwardly from, one of the roller chains 206 and 208. A mounting link 236 replaces one of the roller chain links 234 in each chain 206 and 208. The mounting link 236 includes a pair of outwardly extending tabs 238 which are secured to one of the mounting plates 330 and 332 by a pin 240 (Fig. 9).

A threading roll 346 is rotatably mounted between the mounting plates 330 and 332. The preferred mounting arrangement for the threading roll 346 is often called a "dead shaft idler," wherein the threading roll 346 comprises a cylindrical sleeve concentrically and rotatably supported on a fixed shaft 348. Opposing ends of the fixed shaft 348 are rigidly mounted to mounting plates 330 and 332 wherein the fixed shaft 348 extends in a lateral or cross machine direction across the double facer 10 between the conveyor chains 206 and 208. Bearings 350 are supplied on opposing ends of the threading roll 346 such that the threading roll 346 is supported for rotation about the fixed shaft 348.

Clamping means 352 is provided upstream from the transfer carriage 304 proximate the entrance end 210 of the double facer 10. The clamping means 352 is supported between a pair of clamping towers 354 wherein a stationary clamp bar 356 is fixed to an inside surface 358 of each tower 354.

The stationary clamp bar 356 includes a substantially planar upper surface 360 facing a substantially planar lower surface 362 of a moveable clamp bar 364. An upstream end of the stationary clamp bar 356 includes an arcuate portion 366 adapted for wrapping a portion of the web 24 therearound. The arcuate portion 366 prevents a sharp bend and resulting cracking or weakness in the web 24 as the web 24 wraps around the stationary clamp bar 356.

The moveable clamp bar 364 is operably connected to a pair of air cylinders 368 to provide linear vertical movement of the moveable clamp bar 364 relative to the stationary clamp bar 356. More particularly, a body portion 370 of each air cylinder is supported by a bracket 372 fixed to the inside surface 358 of one of the clamping towers 354. A rod 374 of each air cylinder 368 is fixed to an upper surface 376 of the moveable clamp bar 364 wherein the upper surface 376 is substantially planar in a manner parallel to the lower surface 362 of the moveable clamp bar 364. While two air cylinders 368 are illustrated in Fig. 8, additional air cylinders 368 may be provided along the moveable clamp bar 364 to prevent undesirable flexing of the bar 364 and thereby facilitating clamping engagement of the web 24 between clamp bars 356 and 364.

Referring further to Fig. 7, a sensor 378 is positioned downstream from the clamping means 352 for detecting when the transfer carriage 304 occupies a predetermined position between the entrance end 210 and exit end 212 of the double facer 10. The predetermined position is preferably centrally located between the clamping means 352 and the exit end 212 of the double facer 10 for facilitating the complete threading of the double face web 24 through the double facer 10, as will be described in greater detail below. The sensor 378 preferably comprises a proximity switch for sensing one of the mounting plates 330 and 332 as it occupies ^" the predetermined position. While a proximity switch is preferred, it may be readily -lo-

appreciated that other electronic and mechanical switches may be substituted therefore, including photo sensors and limit switches of the type well known in the art. Upon sensing one of the mounting plates 330 and 332, the sensor 378 sends a signal to a controller (not shown) which then deactivates, or retracts, the air cylinders 368 thereby releasing the web 24 from between the moveable clamp bar 364 and the stationary clamp bar 356.

Turning now to Figs. 10-13, the operation of the threading device 300 will be described in greater detail. The operator initially elevates the weight blanket 78 and upper conveyor belt 15 to provide adequate clearance for the transfer carriage 304 to move longitudinally through the double facer 10 in an identical manner as described above with reference to Fig. 3. Once the weight blanket 78 and upper conveyor belt 15 are elevated, the operator positions the transfer carriage 304 adjacent the entrance end 210 of the double facer 10, as illustrated in Fig. 10, by selective activation of the motor 226 driving the roller chains 206 and 208. The operator then pulls the leading edge 302 of the double face web 24 towards the transfer carriage 304 and wraps the web 24 around a substantial portion of an outer surface 382 of the threading roll 346. The leading edge 302 is next wrapped around the arcuate portion 366 of the stationary clamp bar 356. A sufficient portion of web 24 is wrapped around the arcuate portion 366 until the leading edge 302 of the web 24 extends downstream from the moveable clamp bar 364 such that the entire lower surface 362 of the moveable clamp bar 364 is directly above the upper surface 154 of the web 24.

After the web 24 has been positioned as described above, the operator activates, or extends, the air cylinders 368 such that the moveable clamp bar 364 moves linearly downwardly in the direction of arrow 383 until the double face web 24 is secured between the stationary clamp bar 356 and moveable clamp bar 364. More particularly, the lower surface 362 of the moveable clamp bar 364 engages the upper surface 154 of the web 24 while the upper surface 360 of the stationary clamp bar 356 contacts the lower surface 156 of the web 24. As clearly seen in Fig. 10, the threading roll 346 defines an upper run 384 and a lower run 386 of the double face^* web 24 as the web 24 is wrapped thereabout. Tuming now to Fig. 1 1, the operator next activates the motor 226 to drive the driven sprocket 215 and roller chains 206 and 208 such that the transfer carriage 304 is conveyed downstream over the heating plates 16 of the double facer 10. As may be readily appreciated, the leading edge 302 of the double face web 24 is fixed from moving since it is secured within the clamping means 352. As such, when the transfer carriage 304 is conveyed downstream, the upper run 384 of the web 24 does not move relative to the heating plates 16. However, the lower run 386 will be pulled through the double facer 10 over the heating plate 16 in the direction of arrow 388. While the upper run 384 does not move relative to the heating plates 16. the upper run 384 does increase in length as the web 24 rotates around the threading roll 346. Since the threading roll 346 is rotatably mounted, friction between the web 24 and the threading roll 346 is reduced thereby reducing the resulting tension within the upper and lower runs 384 and 386 of the web 24.

When the transfer carriage 304 reaches the predetermined position. the sensor 378 is triggered by one of the mounting plates 330 and 332 as illustrated in Fig. 12. A signal indicative of the position of the transfer carriage 304 and the threading roll 346 is thereby sent from the sensor 378 to the controller (not shown) which instructs the air cylinders 368 to deactivate, or retract, and move the moveable clamp bar 364 away from the stationary clamp bar 356. More particularly, the moveable clamp bar 364 moves linearly upwardly in the direction of arrow 390. The web 24 is thereby released from the clamping means 352 such that the leading edge 302 of the web 24 is free to move.

Turning now to Fig. 13. the transfer carriage 304 continues its downstream movement uninterrupted as it passes the sensor 378. After the leading edge 302 of the web 24 is released from the clamping means 352. the lower run 386 of the web 24 remains substantially stationary, while the upper run 384 of the web 24 is conveyed downstream through the heating section 12 and drawing section 14 as indicated by arrow 392. The lower run 386 remains substantially stationary since the frictional forces resisting its movement are considerably greater than the frictional forces acting against the upper run 384. Therefore, it may be readily appreciated that the leading edge 302 of the web 24 is conveyed downstream until the transfer carriage 304 is located proximate the exit end 212 of the double facer 10.

The motor 226 is stopped once the transfer carriage 304 moves just beyond the driven sprocket 215 of the double facer 10 where it will not interfere with the continuous processing of the double face web 24. At this point, the leading edge 302 of the web 24 has been completely threaded through both the heating section 12 and drawing section 14 of the double facer 10 as illustrated in phantom in Fig. 13.

As discussed above, after the clamping means 352 releases the upper run 384 of the web 24, the upper run 384 is free to move downstream through the double facer 10. The predetermined position of the transfer carriage 304 where the clamping means 352 releases the web 24 is preferably defined as the center point between the clamping means 352 and the exit end 212 of the double facer 10. Therefore, when the clamping means 352 releases the web 24. the length of the upper run 384 at that time is substantially equal to the distance remaining to be threaded through the double facer 10, i.e., the distance between the predetermined position and the exit end 212 of the double facer 10. Therefore, as the transfer carriage 304 reaches the exit end 212 of the double facer 10, the web 24 is completely threaded through both the heating section 12 and drawing section 14 of the double facer 10.

After threading has been completed and the transfer carriage 304 stopped beyond the driven sprocket 215. the weight blanket 78 and upper conveyor belt 15 are lowered to the positions illustrated in Fig. 1 with respect to the first embodiment of the invention. The drawing section 14 is then activated to pull the double face web 24 through the heating section 12 wherein continuous operation of the double facer 10 for the processing of double face web 24 may commence.

From the above description, it should be apparent that the present invention provides an apparatus and method for safely and efficiently threading a web through a web processing machine. Furthermore, the present invention provides such a threading apparatus and method which require minimal human intervention. While the methods herein described, and the forms of apparatus for carrying these methods into effect, constitute preferred embodiments of this invention, it is to be understood that the invention is not limited to these precise " methods and forms of apparatus, and that changes may be made in either without departing from the scope of the invention, which is defined in the appended claims.

Claims

-CLAIMS-

1. A double facer for the continuous processing of a paperboard web. said double facer comprising: a plurality of heating plates defining a heated surface facing a lower surface of the paperboard web; a holddown means for applying pressure against an upper surface of the paperboard web; a passageway for receiving the paperboard web and defined between said heated surface and said holddown means: and a threading device for conveying a leading edge of the paperboard web over said heating plates.

2. The double facer of claim 1 wherein said threading device comprises: a conveyor element; a threading roll supported by said conveyor element wherein said threading roll is adapted for wrapping the paperboard web around a po╧Çion thereof; and a drive for moving said conveyor element wherein said threading roll and the paperboard web are conveyed over said heating plates.

3. The double facer of claim 2 wherein said threading roll defines upper and lower runs of the paperboard web.

4. The double facer of claim 3 further comprising clamping means positioned upstream from said threading roll for selectively preventing movement of the leading edge of the paperboard web.

5. The double facer of claim 1 wherein said holddown means comprises at least one weight member directly contacting the web. said at least one weight member restrained from linear movement in a direction of travel of the paperboard web.

6. A web threading device for a web processing machine, said threading device comprising: a pair of conveyor elements extending along each side of said web processing machine; a threading roll extending between said conveyor elements; a pinch roll extending between said conveyor elements and cooperating with said threading roll: wherein said pinch roll is mounted for pivotal movement with respect to said threading roll for engaging and securing a web between said pinch roll and said threading roll: and a drive for moving said conveyor elements whereby said threading roll and the web are moved downstream through said processing machine.

7. The web threading device of claim 6 further comprising a plurality of support rails for supporting said conveyor elements.

8. The web threading device of claim 6 further comprising a plurality of idler sprockets along each side of said processing machine for guiding said conveyor elements.

9. The web threading device of claim 6 wherein each said conveyor element comprises an endless roller chain.

10. The web threading device of claim 6 wherein said pinch roll is spring biased towards said threading roll.

11. The web threading device of claim 10 further comprising: a pair of mounting plates, each said mounting plate connected to one of said conveyor elements and supporting an opposing end of said threading roll; a pair of pivot arms, each said pivot arm supporting an opposing end of said pinch roll and mounted for pivoting movement relative said mounting plate; and a spring connecting said mounting plate and said pivot arm for biasing said pinch roll towards said threading roll.

12. The threading device of claim 10 wherein said pinch roll is alternatively biased towards said threading roll and away from said threading roll.

13. The threading device of claim 6 wherein said web processing machine comprises a double facer including a heating section and a drawing section downstream from said heating section.

14. The threading device of claim 13 wherein said heating section comprises a plurality of heating plates defining a heated surface facing a lower surface of said web and a holddown means for applying pressure against an upper surface of said web, said holddown means vertically moveable relative said heating plates for providing clearance for said pinch roll and said threading roll.

15. The threading device of claim 13 wherein said drawing section comprises upper and lower opposing conveying elements facing upper and lower surfaces of said web. said upper conveying element vertically moveable relative said lower conveying element for providing clearance for said pinch roll and said threading roll.

16. A method of threading a web through a double facer, said method comprising the steps of: wrapping a leading edge of a web around a portion of the outer surface of a threading roll; securing said web to said threading roll; conveying said threading roll downstream wherein said web is pulled through said double facer; stopping said threading roll proximate an exit of said double facer; releasing said web from said threading roll; and unwrapping said leading edge of said web from said outer surface of said threading roll.

17. The method of claim 16 wherein: said step of securing said web to said threading roll comprises pivoting a pinch roll towards said threading roll thereby securing said web therebetween; and said step of releasing said web from said threading roll comprises pivoting said pinch roll away from said threading roll thereby releasing said web from therebetween.

18. A web threading device for a web processing machine, said threading device comprising: a first conveyor element; a threading roll supported by said conveyor element, said threading roll defining upper and lower runs of the web; clamping means positioned upstream from said threading roll for selectively preventing movement of a leading edge of the web; and a drive for moving said conveyor element and said threading roll wherein said web is moved downstream through the processing machine.

19. The web threading device of claim 18 wherein said threading roll cooperates with said clamping means for pulling one of the lower and upper runs of the web downstream followed by pulling the other of the lower and upper runs of the web downstream.

20. The web threading device of claim 18 further comprising a sensor positioned downstream from said clamping means for detecting when said threading roll occupies a predetermined position between an entrance and an exit of the web processing machine.

21. The web threading device of claim 18 further comprising a plurality of support rails for supporting said conveyor element.

22. The web threading device of claim 18 further comprising a plurality of idler sprockets for guiding said conveyor element.

23. The web threading device of claim 18 wherein said conveyor element comprises an endless roller chain.

24. The web threading device of claim 18 wherein said threading roll is rotatably supported by said conveyor element.

25. The web threading device of claim 18 further comprising a second conveyor element, said first and second conveyor elements extending along each side of the web processing machine.

26. The web threading device of claim 25 further comprising a pair of mounting plates, each said mounting plate connected to one of said conveyor elements and supporting an opposing end of said threading roll.

27. The web threading device of claim 26 further comprising a fixed shaft rigidly mounted between said mounting plates and rotatably supporting said threading roll.

28. The web threading device of claim 18 wherein said web processing machine comprises a double facer including a heating section and a drawing section downstream from said heating section.

29. The web threading device of claim 28 wherein said heating section comprises a plurality of heating plates defining a heated surface facing a lower surface of said web and a holddown means for applying pressure against an upper surface of said web. said holddown means vertically moveable relative said heating plates for providing clearance for said threading roll.

30. The threading device of claim 29 wherein said drawing section comprises upper and lower opposing conveying elements facing upper and lower surfaces of said web, said upper conveying element vertically moveable relative said lower conveying element for providing clearance between said pinch roll and said threading roll.

31. A method of threading a web through a web processing machine, said method comprising the steps of: wrapping a leading edge of a web around a portion of the outer surface of a threading roll thereby defining upper and lower runs of said web; feeding said leading edge of said web through a clamping means; securing said web within said clamping means thereby preventing movement of said leading edge of said web; conveying said threading roll downstream wherein said web is pulled through said web processing machine; releasing said web from said clamping means when said threading roll passes a predetermined position; and stopping said threading roll proximate an exit of said web processing machine.

32. The method of claim 31 wherein said step of releasing said clamping means comprises the steps of: providing a sensor proximate said predetermined position; producing a signal from said sensor when said threading roll occupies said predetermined position; and deactivating said clamping means in response to said signal.

33. The method of claim 31 wherein one of said upper and lower runs is pulled downstream prior to said step of releasing said web from said clamping means and the other of said upper and lower runs is pulled downstream after said step of releasing said web from said clamping means.