PROCEDURE AND MEANS FOR GUIDING THE END CONDUCTION STRIP OF A PAPER WEB FORWARD FROM A SMOOTH-SURFACED ROLL OR EQUIVALENT IN THE PRESS

Abstract: A procedure and a means for guiding the end conduction strip (R) of a paper web from a smooth-surfaced roll (35;45) of a press and for directing it. The end conduction strip (R) is detached from the smooth surface (35′;45′) of the roll (35;45) and guided further, utilizing a guide plate (16) and air blow actions (P₁, P₂). Against the end conduction strip (R) on the roll surface (35′;45′) is directd an air jet (P₁) having great enough impulse and directed. The end conduction strip (R) is cut with the aid of the air jet (P₁) and its end on the incoming side is detached with said air jet (P₁) from the roll surface (35′;45′). The detached end conduction strip (R) is conducted to be further guided and conveyed forward by a transfer blowing action (P₂). The transfer blowing action (P₂) is directed along the guide plate (16). In conjunction with the guide plate (16) an under-pressure field is pro­ duced, by effect of the blowing action (P₂), the effect of this under-pressure field causing the end conduction strip (R) to be further guided in the direction determined by the guide plate (16).

Description: The present invention concerns a process for cutting and guiding the end conduction strip of a paper web from a smooth-surfaced roll or equivalent in the press section and directing it to the desired location, e.g. to the beginning of the drying section following after the press section, the end conduction strip being detached from the smooth surface of said roll and being guided forward, making use of a guide plate and of air blow actions. In addition, the present invention concerns an apparatus for implementing the process of the invention, said apparatus being disposed in the vicinity of the paper machine press roll or equivalent, and said means comprising blowing members which have been connected to a blow air source and from which blow actions guiding the end conduction strip can be directed and which are provided with nozzles. The process and apparatus of the invention are intended to be used at such points in the paper machine where end conduction of the web is carried out by cutting from the margin of the full-width web a narrow band, e.g. 150 to 500 mm in width, or a so-called end conduction strip, which is driven forward with the aid of air jets and various guide plates. Such points are for instance those where the web is transferred from a smooth-surfaced central roll of the press to the drying section. As to the state of art pertinent to the invention, reference is made to GB-A-2 098 912. Said GB patent discloses cutting and guiding means in a paper machine for the marginal strip separated from a paper web in connection with the paper web lead-in operation. Said means comprises jet tubes connected to a compressed air supply, nozzle apertures provided on said jet tubes and plates guiding the running of the marginal strip. Said nozzle apertures or a nozzle slit of a first jet tube are/is directed to blow air jets parallel to the first guide plate. The nozzle apertures of a second jet tube are similarly disposed to blow air jets parallel to the other guide plate. The planes of said guide plates are disposed at a given angle (180°-α) with reference to each other, so that the orientation of the first guide plate is consistent with the direction in which the cut-off end of the marginal strip is conducted onward. The orientation of the second guide plate is consistent with the direction in which the marginal strip is conducted into a pulper or equivalent. Said guide plates are arranged with the aid of air jets provided in their conjunction to operate as guiding and air transporting surfaces so that as said air jets pull the marginal strip in opposite directions in the region of the guide plates, the marginal strip is severed by rupture between the guide plates or at the nozzle apertures. The new end obtained upon severing or cutting off the marginal strip is conducted onward under guidance by the first guide plate. Further, according to the GB patent, the guide plates guide air jets so that said air jets pull the marginal strip in opposite directions in the region of the guide plates so that the marginal strip is severed by rupture between the guide plates or at the nozzle apertures. According to the present invention, an air jet having relatively high impulse and sharpness is directed against the end conduction strip on the roll surface, and the end conduction strip is cut off by said air jet, after which the end of the end conduction strip on the incoming side is detached by said air jet from the roll surface and the end conduction strip detached in the above fashion is guided by the transfer air jet onward. An object of the present invention is to provide a margin strip guiding and cutting means which requires no moving parts and no cutting blades. An additional object of the invention is to provide an apparatus which can be arranged to be controllable from the operating desk of the paper machine so that it is not necessary on connection with end conduction to approach e.g. the immediate neighbourhood of the press, whereby the labour safety is also improved. In order to attain the objects described above, and others which will become apparent later on, the process of the invention as defined in the preamble of claim 1 has the features set forth in the characterizing clause of claim 1. The apparatus of the invention as defined in the preamble of claim 8 has the features set forth in the characterizing clause of claim 8. In a particularly advantageous embodiment of the invention, it is also an essential feature that the forward transporting direction of the end conduction strip after detaching from the roll surface subtends an acute angle with the direction in which the strip arrives at the point of detachment, which contributes to stable further guiding of the end conduction strip and to its accurate aiming at the desired location. The invention is described in the following in detail, referring to certain embodiment examples of the invention, presented in the figures of the drawing attached, to the details of which the invention is not confined. Fig. 1 presents, in a schematic elevational view, a typical application area of the invention: that is, the closed press section of a paper machine. Fig. 2 presents, in a way similar to that in Fig. 1, another application area of the invention: a separate press nip, which may operate, for instance, after the closed press section depicted in Fig. 1. Fig. 3 presents, in a vertical section in the machine direction, the end conduction means of the invention applied in the environment of Fig. 1. Fig. 4 presents the same as Fig. 3, viewed in the direction IV-IV indicated in Fig. 3. Fig. 5 presents the placement of the apparatus of the invention in conjunction with the smooth-surfaced central roll of a paper machine press. Fig. 6 presents graphically the mutual phasing and timing of the various blowing actions applied in the apparatus of the invention. Fig. 7 presents the pneumatic control system associated with the apparatus of the invention. To begin with, two typical application environments of the process and means of the invention are described, reference being made to Figs 1 and 2. As shown in Fig. 1, the end conduction strip guiding apparatus 10 of the invention has been placed in conjunction with the smooth-surfaced central roll 35 of a closed press section, on the lower sector thereof before the doctor blade 39. The press section shown in Fig. 1 is in all other respects the Sym-Press II (TM) press section of the same applicant, known in the art, to which now the web W to be pressed is carried with a pick-up felt 34 serving as press fabric in the first and second nips N₁ and N₂. The first nip N₁ is a two-felt nip, and it is defined between the suction roll 33 and the roll 30 having a recessed surface 31. The web separates from the lower felt 32, following along with the pick-up felt 34 and the surface of the suction roll 33 to the second nip N₂, where the web W is detached from the felt 34 and is transferred onto the smooth surface 35′ of the central roll 35, such as a stone roll, on which the web W moves to a third nip N₃ provided with a felt 38, said nip being defined between the press roll 36 with recessed surface 37 and the central roll 35. The full-width web W is detached in the free draw W o and transferred to the drying wire 41 passing over the guide roll 40, said wire guiding the web W on its underside over the roll 42 to the drying section (not depicted). The apparatus of the invention has been placed in conjunction with the second lower quadrant of the central roll 35, before the doctor blade 39 and on the level of the transfer nip defined by rolls 40 and 42, or equivalent. The apparatus of the invention for the end conduction strip R, which is cut from the side of the full-width web W, may also be applied in association with the separate press nip N₄ shown in Fig. 2. The press nip N₄ is defined between the lower press roll 43 with recessed surface 44 and the upper press roll 45 with smooth surface 45′. The full-width web W is detached as a free draw W o , transferred over the guide roll 46 to the drying wire 48 passing over the roll 47 and on the underside of the latter, further to the drying section. The apparatus 10 of the invention has been placed on the upper sector of the upper roll 45, on the level of the transfer nip defined by the rolls 46 and 47 or close to this level. In the following, an advantageous structural and functional example of the apparatus 10 mentioned in the foregoing is described, reference being made primarily to Figs 3 and 4. The apparatus of the invention comprises a blow box 11 disposed adjacent to the shell 35′ of the roll 35, spaced therefrom at a small distance, said blow box extending in the cross-machine direction at least over the whole width L of the end conduction strip R (Fig. 5). The wall of the blow box 11 is provided with a set of nozzle apertures or with an equivalent nozzle slot 12. Adjacent to the blow box 11 has been disposed a blow tube 14, from which nozzle apertures 15 directed against the smooth surface 35′ of the roll 35, or an equivalent slit nozzle, open(s). Adjacent to the wall of the blow box 11 facing the nozzle apertures 12, and spaced therefrom by a narrow gap 17, is provided a guide plate 16 featuring, commencing at the nozzle gap 12, an upward slanting section 16R having a fairly large radius of curvature radius R o and thereafter a planar portion 16T. In Figs 5 and 7 is seen the placement of the apparatus of the invention in conjunction with the central roll 35 of a press or with another equivalent press roll 45. Adjacent to the support beams 52 of the bearing housings 51 for the journal pins 50 of the central roll 35 has been disposed a cantilever beam 22, whereto an arm 20 has been attached with a pivot axle 21. On said arm 20, the blow box 11 and the blow tube 14 of the means 10 of the invention have been mounted, to which the compressed air tubes 23 lead from the compressed air system depicted in Fig. 7. The apparatus 10 is turnable, carried on the arm 20, about the pivot axle 21 by means of a power cylinder 18 through the arc indicated by arrow S so that the apparatus 10 will not interfere with any other operation after the end conduction has been completed. Similarly, the apparatus 10 can be run out into operating position by remote control from the central control room of the paper machine to initiate the end conduction process. In Fig. 7 is shown the pneumatic system associated with the invention, compressed air being supplied to this system by the input pipe 25, which includes a control and/or shut-off valve 25a if such is needed. The operation of the power cylinder 18 is controlled by the valve 26. From the compressed air supply pipe 25, pipes 23a and 23b branch off, through valves 27a and 27b to the blow box 11 and the blow tube 14. In the pipes 23a and 23b throttling means or pressure controllers 29a have been inserted, by means of which the pressures P₂ and P₁ in the box 11 and the tube 14 can be regulated. In Fig. 7 is shown schematically the control system as a block 100, with which the various functions of the apparatus of the invention are controlled, most appropriately from the central control room of the paper machine. In the following are described, referring to all of Figs 1-7, the functional steps of the process and the apparatus 10 of the invention in various situations. Prior to end conduction, the full-width paper web W is guided as a run W₁, detached by the doctor blade 39, to a pulper provided below (not depicted). The end conduction is started, either automatically under control by the control unit 100 or by a control pulse from a control switch manipulated by the operator. Hereby, the power cylinder 18 is pressurized and turns the arm 20 about the pivot 21 so that the apparatus 10 assumes the operating position depicted in Figs 3, 4 and 5. From one side of the web W a narrow end conduction strip R is now cut with an oblique known in the art (not depicted). At the time T o indicated in Fig. 6, the valves 27a and 27b open and admit compressed air into the blow box 11 and the blow tube 14. From the blow tube 14, a powerful and sharp detaching blow P₁ is directed with rather high pressure p₁, this jet cross-cutting the end conduction strip R and at the same time detaching it from the smooth surface 35′ of the roll 35, to which the strip R is rather strongly adherent. The blowing angle of the blow action P₁ can be controlled to suit the running conditions, etc. After the end of the end conduction strip R has been detached from the surface 35′ of the roll 35, it enters immediately the action area of the curved initial section 16R of the guide plate 16, where the transfer blows P₂ guide the strip R in the manner shown in Fig. 3, for instance into the throat defined by the first drying cylinder and the drying wire 41, into a rope throat or, alternatively, from the third to the fourth press. Through the blow nozzle 12 of the guide plate 16 facing the blow box 11, air is blown at high velocity in the direction of the plate 16, whereby an under-pressure field is produced, by action of which the running of the end conduction strip R becomes stabilized so that it is guided by the plate 16 without contact and assumes the direction determined by the planar portion 16T of the plate 16. When the initial part 16R of the plate 16 is made to have a suitable, fairly large radius of curvature R, the strip R is swiftly stabilized to be governed by the effect of the transfer blow P₂ and the guidance of the plate 16, and it is pulled taut so as to prevent bagging between the press roll 35 and the means 10. The guide plate 16 and the blow box 11 define a narrow gap space 17, through which air is ejected in the direction of arrow E₁ to join the blow jets P₂, which promotes the stable operation of the apparatus 10. As can be seen in Fig. 6, the detaching blow P₁ is active during a comparatively short period of time t₁ only. counting from the starting time t o , whereafter the valve 27a closes under control by the control unit 100 and/or the timer 28. As shown in Fig. 6, the transfer blow P₂ is active a period t₂, its length being selected to be sufficient so that the running of the end conduction strip R can be stabilized. The operation of the valves 27a and 27b can either be controlled by means of a separate timing unit 28, or the respective function can be located in the central unit 100. An essential feature in the operation of the apparatus 10 of the invention is that the initial direction M of the end conduction strip R is at an acute angle in relation to the tangential plane T of the roll 35 at the detaching point K. Thereby the detaching force which the strip needs is at its minimum. The size of said angle a is as a rule in the range a = 5° - 60°, most advantageously in the range a = 10° -40°. In this manner the strip R can be efficiently detached from the smooth surface 35′ of the roll 35, to which the strip is quite firmly adherent, and with the aid of the blow actions P2 efficient guiding entrainment of the end of the strip R is achieved, which can be aimed at the desired goal. The blow actions P₁ and P₂ are arranged to be as close together as possible so that the cutting/detaching blow P₁ and the guiding blow P₂ act on the same side of the strip R, that is on that side which was against the surface 35′ of the roll 35. Usually no angulations are required on the guide plate 16. After the guide plate 16, additional guide plates known per se may be used. The radius of curvature R o of the initial part 16R of the guide plate 16 is usually in the range R o = 100 - 500 mm, most appropriately R o = 200 mm, and the centre of curvature O is located on the side of the plate 16 opposite to that on which the end conduction strip R arrives and leaves. It is important in view of the operation of the apparatus 10 that the pressures p1 and p2 are appropriately selected. As a rule, p₁ > p₂. The range of the pressure p₁ is usually 4-6 bar, and p₂ = 2-3 bar. The impulse of the blow action P₁ has to be high enough so that the somewhat wet strip will positively break and that its end will be guided with the aid of the blowing P₁ into contiguity with the plate 10 for further guidance by the blow actions P₂. Through the gap 12 between the plate 16 and the blow box 11 air is ejected (arrow E₁) into the region of the plate 16 and the nozzle 12 so that the strip R cannot adhere to the plate 16. The length of the plate 16 in the travel direction of the strip R is usually 150 - 500 mm, most suitably 200 - 300 mm. It is a characteristic of the orientation of the plate 16 that it determines the direction of propagation of the end conduction strip and its further aiming. In the embodiment examples presented in the foregoing, the application environment of the invention is the press section of a paper machine. As has been initially observed, the invention may in special cases also be applied elsewhere, e.g.in calenders or in other paper after-processing apparatus, although the invention is not believed to be equally well suited for use in these applications as it is on the press section, where the strength of the web has not yet fully developed, by which token it can advantageously be severed and guided onward with the blow actions P₁ in the way taught by the invention.

Claims: A process for cutting and guiding the end conduction strip (R) from a smooth-surfaced roll (35; 45) in a press, or equivalent, and for aiming it toward a desired location, e.g. to the beginning of the drying section following after the press section, the end conduction strip (R) being detached from the smooth surface (35′; 45′) of said roll (35; 45) and being further guided utilizing a guide plate (16) and air blow actions (P₁, P₂), a transfer blowing action (P₂) being used as one of said air blow actions and being directed along said guide plate (16), in conjunction with said guide plate (16) being produced an under-pressure field by effect of said blowing action (P₂), the end conduction strip (R) being further guided by the action of said under-pressure field in the direction determined by said guide plate (16), characterised in that (a) an air jet (P₁) having sufficient impulse and sharpness is directed against the end conduction strip (R) on the roll surface (35′; 45′); (b) the end conduction strip (R) is cut off with said air jet (P₁) and its end on the incoming side is detached by said air jet (P₁) from the roll surface (35′; 45′); and (c) the end conduction strip (R) which has been detached in the preceding step (b) is further guided and conveyed by said transfer blowing action (P₂). A process according to claim 1, characterised in that the cutting and detaching jet (P₁) is directed substantially at right angle against the smooth-surfaced (35′) central roll (35) of a closed press in a paper machine, on the surface of said press (35), after the intended detaching point (K). A process according to claim 1, characterised in that the process is applied in association with the smooth-surfaced (45′) press roll (45) of a separate press in a paper machine, most suitably of its fourth press nip (N₄). A process according to any one of claims 1-3, characterised in that the end conduction strip (R) is further guided by the guide plate (16) at an acute angle (a) in relation to the entrance direction (T) of the end conduction strip (R), and that the size of said angle (a) is selected to be in the range a = 5°-60°, most properly in the range a = 10°-40°. A process according to any one of claims 1-4, characterised in that the process and its various steps are controlled from the central control room of the paper machine by a control system (Fig. 7). A process according to any one of claims 1-5, characterised in that the detaching/cutting air jet (P₁) and the transfer blow actions (P₂) are connected to operate substantially simultaneously, and that the detaching/cutting jet (P₁) is discontinued and the transfer blow actions (P₂) are kept operative for such a period (t₂) that the running of the end conduction strip (R) is stabilized. A process according to any one of claims 1-6, characterised in that an apparatus (10) applying the process is moved with an actuating means (19) and under control by a control system (100) into operating position, and after accomplished end conduction moved into a non-operative position on one side, where the apparatus (10) is no obstacle. An apparatus (10) for applying the process according to any one of claims 1-7 and disposed adjacent to a paper machine press roll (35; 45) or equivalent, said apparatus comprising blowing members which are connected to a source of blow air, blow actions (P₁, P₂) guiding the end conduction strip (R) being directable from said members, said apparatus further comprising a first blow tube or blow box and a second blow tube or blow box (11), a blow nozzle arrangement (12) of said second blow tube or blow box (11) being, at least to some extent, directed against the direction in which the end conduction strip (R) arrives, and a guide plate (16) commencing adjacent to the blow nozzle (12) of said second blow tube or blow box (11) and extending in the direction of propagation of the end conduction strip (R) at an acute angle (a) with respect to the tangent plane (T) placed at the detaching point (K) of the end conduction strip (R) against the roll surface (35′), characterised in that the first blow tube (14) or blow box is situated, in the direction of rotation of the press roll (35; 45), after the second blow tube (11) or blow box adjacent thereto, and that a blow nozzle arrangement (15) of the first blow tube (14) or blow box is directed substantially at right angles against that roll surface (35′; 45′) from which the end conduction strip (R) is being detached. Apparatus according to claim 8, characterised in that between said second blow box or blow tube (11) and the front edge of the guide plate (16) is provided a gap space (17) adjacent to the nozzle (12), through which air is ejected (E1) to join the transfer blow actions (P₂) blown from said nozzle (12) parallel to the guide plate (16). Apparatus according to claim 8 or 9, characterised in that said guide plate (16) presents an initial part (16R) with a relatively large radius of curvature (R o ) starting from the blow nozzle (12), its centre of curvature (O) thereof being located on the side opposite to the run of the end conduction strip (R), that after said curved part (16R) the plate (16) presents a substantially straight part (16T), which determines the aiming of the end conduction strip (R) toward the intended location. Apparatus according to any one of claims 8-10, characterised in that the blow tubes and/or blow boxes (11, 14) are connected to a frame component (20), most suitably an arm disposed, most advantageously pivoted, in conjunction with the frame structures (52) on the operating side of the paper machine, and that said frame component (20) is arranged to be movable with an actuating means (18) into operative position and inoperative position, in which latter position it will not interfere with any other function (Figs 5 and 7).

Inventors: ILVESPAEAE, HEIKKI, LIEDES, ALLAN, VIITANEN, OLAVI, Ilvespää, Heikki
Applicants: VALMET PAPER MACHINERY INC.
Application year: 1989
Main classification: D21G9
IPC codes: D21G9