WO1998038380A1

WO1998038380A1 - Rib for a water draining device in a paper machine

Info

Publication number: WO1998038380A1
Application number: PCT/FI1998/000165
Authority: WO
Inventors: Samppa J. Salminen; Aimo NÄRVÄINEN
Original assignee: Valmet Corporation
Priority date: 1997-02-26
Filing date: 1998-02-25
Publication date: 1998-09-03
Also published as: FI970798A0; DE29823850U1; FI100811B

Abstract

The invention relates to a rib for a water draining device in a paper machine, which rib is used to support and/or to load a wire or wires in a paper machine and/or to doctor water from the face of a wire or wires. The rib (41) is loaded by means of the pressure of a medium. A pressure space defined by a flexible belt (46) is formed between a rib part (41A) of the rib (41) placed against the wire (10) and a frame part (43) of the rib attached to other frame constructions of the machine, into which pressure space a loading pressure is passed, and which flexible belt (46) defines the pressure space such that the area of effect of the loading force is independent from the movement of the rib (41). The rib part (41A) is supported in relation to the frame part (43) by means of a linkage mechanism (44) which comprises two articulation arms (74, 76) interconnected by means of an articulated joint (75), of which arms one articulation arm (76) is attached to the rib part (41A) by means of an articulated joint (77) and the other articulation arm (74) is attached to the frame part (43) by means of an articulated joint (72). The linkage mechanism (44) is placed in the pressurized spaced defined by the flexible belt (46).

Description

Rib for a water draining device in a paper machine

The invention relates to a rib for a water draining device in a paper machine, which rib is used to support and/or to load a wire or wires in a paper machine and/or to doctor water from the face of a wire or wires, which rib is loaded by means of the pressure of a medium, wherein a pressure space defined by a flexible belt is formed between a rib part of the rib placed against the wire and a frame part of the rib attached to other frame constructions of the machine, into which pressure space a loading pressure is passed, and which flexible belt defines the pressure space such that the area of effect of the loading force is independent from the movement of the rib, and which rib part is supported in relation to the frame part by means of a linkage mechanism.

In web formers of paper machines, a number of different forming members are used. The primary function of these members is to produce compression pressure and a pressure pulsation in the fibrous layer that is being formed, by means of which pressure and pulsation, dewatering of the web that is being formed is promoted and, at the same time, the formation of the web is improved. Said forming members include various forming shoes which are usually provided with a curved ribbed deck and over which the forming wires, placed one above the other with the web placed therebetween, are caused to curve. In the area of these forming shoes, water is removed through the wire placed at the side of the outside curve by the effect of its tensioning pressure, and this draining is promoted further by a field of centrifugal force. Draining of water also takes place through the wire placed at the side of the inside curve, which draining is generally intensified by means of negative pressure present in a chamber of the forming shoe. The ribbed deck of the forming shoe produces pressure pulsation, which both promotes the dewatering and improves the formation of the web. Further, from the prior art, so-called MB units are known, through which two wires run usually as a straight run. In the prior-art MB units, there is a pressure loading apparatus inside the loop of one of the wires and a draining apparatus provided with a set of guide and draining ribs is arranged inside the loop of the other, opposite wire. In a manner known from the prior art, said MB unit is usually placed either in the fourdrinier wire portion so that the MB unit is preceded by a single-wire portion, in which a substantial amount of dewatering takes place before the web runs as a straight run in the plane of the fourdrinier wire through the MB unit or into a gap former, in which the dewatering starts immediately through both of the wires.

With regard to the prior art, reference is made to FI Patent Application No. 2563173, which describes a water draining device for paper machines, which device comprises a support member intended to be fixed substantially transversely underneath a fourdrinier wire of a paper machine and a water draining wing disposed in a longitudinal direction on it by means of a sliding joint, the support member comprising a rail supporting the water draining wing and being U-shaped in cross- section, and said rail comprising a locking part which is adjustable in a height direction and which is a rail substantially T-shaped in cross-section, and there being provided members for moving these parts in a vertical direction relative to each other such that the lower part of the water draining wing can be pressed between the supporting part and the locking part. The lower side of the water draining wing is provided with two flanges directed towards each other in the longitudinal direction of the wing, which flanges are arranged to extend underneath the branches of the T- shaped rail such that the flanges lie on the supporting part. The members for moving the supporting part and the locking part relative to each other are arms that are pivotally joumalled on the locking part at their upper end and on the U-shaped rail at their lower end, which arms convert the reciprocating movement of the locking part into a movement in a height direction. In this arrangement, there remains a clearance between the ribs and the T-rail provided for the attachment thereof, which T-rail is locked and presses the lower edge of the water draining rib locking the rib in place. Because of the clearance, the movement of the rib is not precise. With regard to the prior art, reference is also made to FI Patent No. 69 885, which discloses an arrangement comprising a forming shoe in a twin-wire former of a paper machine, which forming shoe comprises a curved area which guides wires and which is defined by a guide face formed by blade ribs. In the area of the forming shoe, draining of water takes place through both or one of the wires, and the rib-like or plate-like guide and water draining members of the forming shoe are attached to attachment members that can be adjusted rectilinearly relative to a frame part of the forming shoe in order to adjust the shape of the guide face of the forming shoe. Furthermore, said blade ribs are attached by means of quick-release fasteners to attachment members that can be turned about axles situated transverse to the running direction of the web, and said blade ribs can be replaced either with new blade ribs of the same kind or with different blade ribs for the purpose of regulating the quality of the guide face and/or the free gaps between the blade ribs. In the arrangement described here, the ribs move in a longitudinal direction.

With respect to the prior art, reference may also be made to US Patent 5,262,010, which describes a water draining device for the web-forming or wet end of a paper machine comprising ribs arranged transverse to a wire to extend in the cross direction of the machine. Loading elements operate together with the ribs producing a force against the wire, thereby bringing about dewatering and forming of the web. The loading element is constructed and positioned such that an additional moment is generated in which a counteracting force is produced by a frictional force acting between the ribs and the wire. In certain embodiments, the loading elements may also be interconnected with one another. This US patent describes many different arrangements for constructing loading ribs. In some embodiments, in place of an attachment member there is a linkage mechanism or a spring, which holds the rib in place. This arrangement does not include a relief or compensation arrangement.

In the prior-art loading elements, it has been a problem that the loading force has not been sufficiently independent from the length of the movement of the rib in the direction of loading. Moreover, problems may have been caused by contamination of the loading elements as paper machine waters have access between the parts of the rib construction, which has resulted in problems in keeping the loading at a desired level. Moreover, these loading elements have been difficult to manufacture because of their high precision of manufacture. In the prior- art solutions, problems have also been caused by the fact that the rib construction has been quite rigid in the cross direction of the machine.

With regard to the prior art more closely related to the invention, reference may be made to the applicant's FI patent 95 935, which describes a rib for a water draining device of a paper machine used to support and/or to load a wire or wires in the paper machine and/or to doctor water from the face of the wire or wires, which rib is loaded by means of the pressure of a medium. In the arrangement described here, it has been considered novel that a pressure space defined by a flexible belt is formed between the rib and its frame part, a loading pressure being passed into said pressure space, which is defined by the flexible belt such that the area of effect of the loading force is independent from the movement of the rib. This arrangement provides the advantage that the loading force can be made sufficiently independent from the length of the movement of the rib, and moreover, in the construction, the glide faces of the rib construction are placed in a closed space, so that the paper machine waters cannot contaminate them. The clean glide faces permit supporting of the element substantially free of play, and, at the same time, the problems arising from contaminations for the movement of the glide faces can be minimized. The object of the invention is to develop this arrangement further.

With a view to achieving the objectives stated above and those that will come out later, the rib in accordance with the invention is mainly characterized in that a linkage mechanism comprises two articulation arms interconnected by means of an articulated joint, of which arms one articulation arm is attached to the rib part by means of an articulated joint and the other articulation arm is attached to the frame part by means of an articulated joint, and that the linkage mechanism is placed in a pressurized space defined by a flexible belt. The arrangement in accordance with the invention provides significant advantages over the prior art arrangements. For a start, all the movable parts are placed in a pressurized and protected space, and thus it does not comprise any points that are contaminated, thereby eliminating the need for cleaning. The arrangement in accordance with the invention is also such as to allow the ribs to be used either individually or in pairs during the loading stage.

In the rib in accordance with the invention, the loading force remains the same and the foil angle remains unchanged better than before. Moreover, all the guide faces of the ribs are placed in a closed pressurized space, thereby preventing their contamination.

In accordance with the invention, the loading force can be made independent from the length of the movement of the rib, and moreover, in the construction in accord- ance with the invention, the glide faces of the rib construction are placed in a closed space, so that paper machine waters cannot contaminate them. The clean glide faces allow the element to be supported substantially free of play, and, at the same time, the problems arising from contaminations for the movement of the glide faces can be minimized.

In the following, the invention will be described in more detail with reference to the figures in the accompanying drawing, to the details of which the invention is, however, by no means intended to be strictly confined.

Figure 1 is a vertical sectional view in the machine direction of an exemplifying embodiment of an environment of the application of the invention,

Figure 2 is a schematic vertical sectional view of an exemplifying embodiment of a water draining rib in accordance with the invention,

Figure 3 is a schematic longitudinal sectional view of an exemplifying embodiment of a water draining rib in accordance with the invention, and Figure 4 is a schematic longitudinal sectional view of another exemplifying embodiment of a water draining rib in accordance with the invention.

Fig. 1 is a schematic illustration of an environment of the application of the inven- tion which includes a former comprising a lower- wire loop 10 and an upper- wire loop 20. In connection with the lower- wire loop 10, after the headbox (not shown), there is a single-wire initial portion 10a of the web forming zone, in which initial portion, owing to draining elements 1 la placed in said portion, the stock web W₀ attains a certain dry solids content, and at least its lower face receives a certain couching degree before the web enters into a twin- wire zone which is formed between the wires 10 and 20. The twin- wire zone starts at a breast roll 21 of the upper- wire loop 20. After the breast roll 21, inside the lower- wire loop 10, the twin- wire zone includes a pre-loading board 12 which is followed by a loading unit/loading units 32 of an MB unit 30 in the twin-wire zone, in which loading unit/units 32 there are several loading ribs 41 placed one after the other, which ribs extend across the entire width of the wires 10,20.

The upper wire 20 is arranged to run over turning rolls 16, 17,18and over the breast roll 21, and the lower wire 10 runs substantially parallel to the upper wire 20 underneath the upper wire 20. The wires 10 and 20 form a wedge-shaped inlet gap K in which the web W₀ placed on the lower wire 10 is pressed continuously between the wires 10 and 20 as the wires make progress. After the wedge-shaped inlet gap K, in a transfer direction F, there is the MB unit 30 which comprises an upper dewatering box 31. The bottom of the dewatering box 31 comprises ribs 52 and water is sucked out of the web W₀ through gaps between said ribs into the dewatering box 31 by means of a vacuum and air. On its run, the upper wire 20 rests against said ribs 52. The MB unit 30 also includes loading units 32 which permit dewatering to take place in a downward direction, and there are loading ribs 41 on the top face of the loading units 32. Further, Fig. 1 shows a number of other parts and support structures included in the former, which parts and structures are known in themselves and will not be described in further detail in this connection. The loading rib 41 shown in Fig. 2 comprises cross-direction frame parts 43 on which a rib part 41 A is supported by means of a mechanism 44. The rib part 41 A of the loading rib 41 comprising a longitudinal groove 54 is arranged to move vertically while supported by the mechanisms 44. The planar top side A of the rib part 41 A of the loading ribs 41 drags against the face of the wire 10; 20 and loads the wire while water operates as lubricating fluid. Water to be drained out of the web W₀ is doctored by means of the loading ribs 41 from that face of the wire which is opposite to the web. The mechanism 44 of the loading rib 41 is linked by means of an articulated joint to the frame part 43. A flexible belt 46 is attached to the rib part 41 A of the loading rib 41, preferably to the lower edge thereof, and at its opposite end, the flexible belt is attached preferably to the top portion of the frame part 43 so that U-shaped loops 48 are formed in a downward direction. Shield plates 55 restricting the movement of the belt 46 in the lateral direction are fixed to the sides of the rib 41, outside the belt 46. The belts 46 are attached to grooves 59 formed in the rib 41 and in the frame part 43, respectively, preferably by means of a shaped- profile joint whose interior space 56 has been shaped so that it can be pressurized when necessary, thereby providing a simple, sealed joint. The frame part 43 of the rib 41 is fixed to other frame constructions of the machine by means of a fastening groove 58.

In the construction shown in Fig. 2, the loading force is produced by passing the loading pressure by means of a medium, such as air, into the space defined by the flexible belt 46, the rib part 41 A and the frame part 43. The loading is relieved by reducing the pressure, and the force of gravity returns the rib part 41A down. The belt 46, which has a thickness, for example, from 0.1 mm to 3 mm, preferably from 1 mm to 2 mm, and is made of rubber or an equivalent resilient material, is attached from its top edge to the rib part 41 A and from its lower edge to the frame part 43 by means of fastening parts 56, so that U-shaped loops 48 are formed downwards, which loops 48 permit movements of the rib part 41 A in the direction up and down. The lateral supports 55 restrict widening of the belt 46 in the lateral direction so that the area of effect of the pressure is not changed when the rib part 41 A is shifted in the loading direction. As shown in Figs. 2-4, linkage mechanisms 44 are placed in the loading rib 41 of the invention so that they are spaced from one another in a cross-machine direction and placed inside the pressurized and protected space defined by the flexible belt 46, whereby the linkage mechanisms 44 are not contaminated. The linkage mechanism 44 comprises a first articulation arm 74 attached, at one end thereof, to the frame part 43 by means of an articulated joint 72 and a second articulation arm 76 attached to the other end of the first articulation arm by means of an articulated joint 75 and to the rib part 41A by means of an articulated joint 77. As shown in the figures, spaces 81 are provided in the frame part 43 in the form of notches, grooves, recesses or equivalent to serve as a path for movement of the linkage mechanism 44. In the embodiment illustrated in Fig. 3, the linkage mechanisms 44 of the rib 41 move in the same direction, and in the embodiment shown in Fig. 4, the adjacent linkage mechanisms 44 move in opposite directions with respect to one another.

The loading angle of the rib part 41 A provided by means of the linkage mechanisms 44 remains unchanged and the force remains as desired. The linkage mechanism 44 does not affect the loading pressure produced by pressure, but, instead, maintains the rib part 41A fixedly in place in a cross direction, preventing possible rocking. The distance L_j between the linkage mechanisms 44 is from about 100 mm to about 500 mm, preferably from about 200 mm to about 300 mm, and the length of the opening L2 made for them in the frame part 43 is from 30 mm to 150 mm, preferably from 50 mm to 80 mm.

Each rib 41 can be loaded individually but, when desired, they can also be intercon- nected in pairs, as described, for example, in the applicant's FI Patent 95 935.

In the following, claims are presented, and the various details of the invention may vary within the scope of the inventive idea defined in the claims and differ from what has been stated above by way of example only.

Claims

1. A rib for a water draining device in a paper machine, which rib is used to support and/or to load a wire (10) or wires in a paper machine and/or to doctor water from the face of the wire (10) or wires, which rib (41) is loaded by means of the pressure of a medium, wherein a pressure space defined by a flexible belt (46) is formed between a rib part (41 A) of the rib (41) placed against the wire (10) and a frame part (43) of the rib attached to other frame constructions of the machine, into which pressure space a loading pressure is passed, and which flexible belt (46) defines the pressure space such that the area of effect of the loading force is independent from the movement of the rib (41), and which rib part (41 A) is supported in relation to the frame part (43) by means of a linkage mechanism (44), characterized in that the linkage mechanism (44) comprises two articulation arms (74,76) interconnected by means of an articulated joint (75), of which arms one articulation arm (76) is attached to the rib part (41 A) by means of an articulated joint (77) and the other articulation arm (74) is attached to the frame part (43) by means of an articulated joint (72), and that the linkage mechanism (44) is placed in the pressurized space defined by the flexible belt (46).

2. A rib as claimed in claim 1, characterized in that the ribs (41) are interconnected in pairs and one after the other in the machine direction.

3. A rib as claimed in claim 1 or 2, characterized in that the ribs (41) are individually supported.

4. A rib as claimed in any one of claims 1 to 3, characterized in that the linkage mechanisms (44) of the rib (41) are spaced from one another in the cross direction.

5. A rib as claimed in any one of claims 1 to 4, characterized in that the linkage mechanisms (44) are placed in the cross direction thereof at a distance of from about

200 mm to about 300 mm from one another.