GLIDE-SHOE ARRANGEMENT FOR A VARIABLE-CROWN ROLL

Abstract: Glide shoe arrangement for a variable-crown roll (10). The said roll (10) comprises a non-revolving massive central axle (12), on which a cylindrical roll mantle (11) is journalled (13a,13b) as revolving, between which said axle (12) and the inside face (11′) of the said roll mantle (11) piston-glide-shoe-­ combinations (20₁...20 N ) loaded by means of hydraulic pressure fluid are fitted. Their glide shoes (22) can be loaded by the intermediate of pistons (15) by means of pressures against the inside face (11′) of the roll mantle (11) for the purpose of controlling the distribution of the nip pressure in the nip (N). The piston-glide-shoe combinations (20₁...20 N ) include bores (16) made into the axle (12), in which said bores there are loading pistons (15). Bearings (31,32) provided with spherical bearing faces (33) are fitted between the loading pistons (15) and their glide shoes (22), the center of rotation (0) of the said bearings being located at the side of the glide shoe (22). A pin-shaped projection part (25) is fitted in the said loading pistons (15), which said projection part extends through the spherical bearing (31,32,33). Between the said projection part (25) and the glide shoe (22) or a projection part (36) attached to the glide shoe (22), there is a sealed articulation arrangement (30). The pressure fluid is passed from the loading space (16p) of the pistons (15) through the said pin-shaped projection part (25) into the hydrostatic lubrication spaces (23a,23b) on the glide shoes (22).

Description: The present invention concerns a glide-shoe arrangement for a variable-crown roll, which said roll comprises a non-revolving massive central axle, on which a cylindrical roll mantle is journalled as revolving, between which said axle and the inside face of the said roll mantle piston-glide-shoe combinations loaded by means of hydraulic pressure fluid are fitted, whose glide shoes can be loaded by the intermediate of pistons by means of the pressures of the hydraulic fluid against the inside face of the roll mantle for the purpose of con­ trolling the distribution of the nip pressure in the nip placed facing the said loading shoes, and which said piston-glide-shoe combinations include cylindrical bores or equivalent made into the said axle, into which said bores cylindrical or equivalent pistons are fitted. In prior art, several different variable-crown or adjustable-crown rolls for paper machines are known. As a rule, these rolls comprise a massive, stationary roll axle and a roll mantle arranged as revolving around the said axle. Between the said axle and the mantle, a series of glide shoes and/or chambers of pressure fluid, acting upon the inner face of the mantle, are fitted. As a rule, the nips formed by such rolls, such as press nips or calendering nips, are loaded by means of loading forces applied to the axle journals of the variable-crown roll and of its counter-roll. The present invention relates to such variable-­ crown or adjustable-crown rolls as include a series of glide shoes whose glide faces act upon the inner face of the roll mantle and whose glide faces are at least partly hydrostatically lubricated by means of pressure fluid passed onto the glide face. In respect of the prior art related to the invention, reference is made, by way of example, to the US Patent No. 4,241,482, to the Finnish Patents Nos. 56,252 and 69,684 as well as to the Finnish Patent Application No. 792,712. A great number of different functions are required from the supporting and loading members used in variable-crown rolls and acting upon the inner face of the roll mantle and loaded by means of pressure fluid, and an integration of all of these functions in one and the same member has not been quite successful by means of the arrangements known in prior art. In the following, a list is given of some of the properties required from the said supporting and loading members: - the hydrostatic lubrication of the support shoes as well as the loading-shoe/cylinder must be sufficiently well sealed even with varying load forces, and even when changes in angle take place between the mantle and the inner part, - the loading pistons of the support shoes must receive lateral forces, which are forces caused by friction, - the loading equipment for the support shoes must be capable of acting as an articulated joint, because the relative positions of the mantle to be supported and the central axle in respect of each other vary to a considerable extent with varying load forces, - the pistons of the support shoes must provide a suffi­ cient radial force, whose range of variation must be sufficiently large in view of supporting and loading the mantle, - it must be possible to control the thickness of the oil film that lubricates the glide face of the support shoes, and - the loading pistons of the support shoes and the bores provided in connection with the central axle must permit even considerable radial movements of the pistons. In the loading and supporting members known in prior art, the functions listed above are not carried into effect satisfactorily, at least not all of them. It is an object of the present invention to avoid the above drawbacks and to provide a novel arrangement of fastening for the glide and support shoes so that the properties mentioned above can be accomplished. It is an object of the invention to provide such an arrangement of support for the glide shoes in which the glide shoes can be made to be positioned freely in all directions in relation to the pistons that load them. It is a particular object of the invention to provide such an arrangement of support for the glide shoes in which the pivot point of the glide shoes in relation to the loading pistons can be placed as near the lubricated glide face of the glide shoes as possible so that the moment of the friction forces that tends to turn the glide shoes, which said friction forces are produced by the friction of the glide face, should be as little as possible. It is an essential object of the present inven­ tion to provide such a relative support arrangement between the glide shoes and their support pistons wherein pressurized fluid can be passed from the loading space of the loading pistons into the lubrication spaces of the glide shoes through a simple and tight support-joint construction. In view of achieving the objectives stated above and those that will come out later, the invention is mainly characterized in - that bearings provided with spherical bearing faces are fitted between the loading pistons and their glide shoes, the center of rotation of the said bearings being located at the side of the glide shoe, - that a pin-shaped projection part is fitted in the said loading pistons, which said projection part extends through the said bearing, - that between the said pin-shaped projection part and the glide shoe or a projection part attached to the glide shoe, there is a sealed articulation arrangement, and - that the pressure fluid can be passed from the loading space of the pistons through the said pin-shaped projection part into the hydrostatic lubrication spaces on the glide shoes. In accordance with the invention, the centres of rotation of the glide shoes become placed near the inner face of the roll mantle, i.e. near the glide face of the glide shoes, whereby the friction between the roll mantle and the glide shoes causes a minimum of a moment inclining the shoes. In accordance with the invention, when the seal ring between the pin of the loading piston and the glide shoe or a component attached to the glide shoe is placed, in a preferred embodiment of the invention, in the plane of the centre of rotation of the glide shoes, the seal moves in operation as little as possible, and thereby it can be sealed reliably and its construction can be made simple. It is a further advantage of the invention that between the glide shoes and the loading pistons, it is possible to use standard bearings, whose friction is low and whose cost is favourable. In the support arrangement of the invention, it is possible to use bearings of relatively little radius of rotation, whereby the moment tending to prevent inclination of the shoe becomes as little as possible. In the following, the invention will be de­ scribed in detail with reference to an exemplifying embodiment of the invention, illustrated in the figures of the accompanying drawing, the invention being not restricted to the details of the said embodiment. Figure 1 is a schematical view of a variable-­ crown roll in accordance with the invention when it forms a nip with a counter-roll. Figure 2 shows a section II-II in Fig. 1. Figure 3 is a partial sectional view along line II-II in Fig. 1, on a larger scale than Fig. 2. To begin with, the general construction of the variable-crown roll adjustable in zones illustrated in Figures 1, 2 and 3 will be described, which said con­ struction is largely known in prior art. The roll 10, e.g. a press roll or calender roll for a paper machine, comprises a revolving cylinder mantle 11, within which there is a stationary massive axle 12. Between the inner face 11′ of the mantle 11 and the axle 12 a sufficiently large free space 13 remains. The mantle 11 is journalled on axle journals 12a and 12b, which constitute extensions of the axle 12, by means of bearings 13a and 13b. The mantle 11 is closed by end flanges 14a and 14b. The roll mantle 11 is driven by the intermediate of a drive mechanism not shown. Opposite the roll 10, another roll 50 is pro­ vided, which said rolls 10 and 50 together form, e.g., a press nip N. Between the axle 12 and the inner face 11′ of the mantle 11, a piston-loading-shoe combination 20₁...20 N in accordance with the invention is provided, by whose means the linear load in the nip N can be adjusted in zones and compensated to the desired level, e.g. so as to make a uniformly distributed linear load. In the following, the principal construction of the piston-shoe arrangement in accordance with the invention, placed between the axle 12 and the roll mantle 11, will be described. Into each of the said cylinders 16, a separately adjustable pressure of appropriate magnitude is passed from an external pressure source (not shown) through fluid ducts. In each cylinder, there is a piston 15 of, e.g., circular section. To each piston 15, a loading shoe 22 of its own is connected. The loading shoes 22 are identical with each other, and they are spaced axially as densely as possible so that a uniform load is provided on the cylinder mantle 11 even with high compensation forces. The shoes 22 include, e.g., two hydrostatic lubrication chambers 23a and 23b, between which and at whose edges there are ridges 24, which form a lubricated glide face against the smooth inner face 11′ of the mantle 11. Into the hydrostatic lubrication chambers 23a and 23b, lubrication oil has been passed out of the pressure space 16p in the piston 15 through the bore 26 in the piston 15 as well as through a support joint arrangement 30 in accordance with the present invention, which will be described in more detail below. In the following, a preferred exemplifying embodiment will be described in detail, reference being made mainly to Fig. 3. At the same time, the support joint arrangement 30 in accordance with the invention, placed between the glide shoes 22 and the loading pistons 15, operates as a pressure-tight fitting, by means of which the pressurized fluid is passed from the pressure spaces 16p in the cylinders 16 of the loading pistons 15 into the lubrica­ tion chambers 23a and 23b on the glide shoes 22. To the plane face of the glide shoes 22 placed opposite to the glide face, a projection piece 36 is attached, which is placed with a sufficiently wide play inside the cylinder bores 16. To a shallow bore 37 in the lower side of the projection pieces 36, a bearing piece 32 is fixed. A second bearing piece 31 is fixed to a bore 21 in the end face of the piston 15. The bearing pieces 31 and 32 have spherical bearing faces 33 facing each other, whose journalling centre is, in Fig. 3, denoted with 0, and the journalling radius with R. The pistons 15 have a central bore 26, to whose wider part a pin 25 is fixed, which extends cen­ trally through the bearing 31,32,33 into a central bore 38 in the projection piece 36 of the glide shoe 22. In the part of the said pin 25 that is placed inside the projection piece 36, there are two ring flanges 28, an elastic seal ring 39, e.g. of rubber, being fitted in a groove 29 between the said flanges. A bore 27 passes through the pin 25, one end of the said bore being connected with the bore 26 in the piston 15, and the other end with the space 40 in the projection piece 36 of the glide shoe 22. The bores 22p in the glide shoe 22 open into the said space 40. From the pressure space 16p of the cylinder bores 16 loading the piston 15, the pressure fluid is passed along the route 26-27-40-22p into the spaces 23a and 23b on the glide shoes 22 so as to lubricate the glide face between the glide shoes 22 and the inner face 11′ of the roll mantle 11 hydrostatically. The route of the said pressure fluid is sealed at the joint of the com­ bination 30 by the ring seal 39 of the pin 25 against the inner face of the bore 38 in the projection part 36. According to the invention, the centre of rotation 0 of the spherical bearing 31,32,33 of the pistons 15 and of the glide shoe 22 is placed at the level of the seal 39 of the piston 15 pin 25 so that, when the glide shoe 22 and its fixed projection part 36 pivot relative the piston 15, the seal 39 moves very little relative the walls of the bores 38 in the pro­ jection part 36, and hereby a simple and reliable seal construction is obtained. According to the invention, in the combinations 20₁...20 N , the centres of rotation 0 of the pistons 15 and of the glide shoes 22 are placed as near the glide face between the glide shoe 22 and the mantle 11 as possible, out of the reasons mentioned above. As is shown in Fig. 3, the bore 26 in the piston 15, the projection part 25, and the bore 27 in it are placed on the centre line K-K of the cylinder bores 16. In their cylinder bores 16, the pistons 15 are sealed by seal rings 17. The joint arrangement 30 guarantees that, in spite of relative changes in posi­ tion between the central axle 12 and the mantle 11, the glide contact of the glide shoe remains correct, and, moreover, the pistons 15 are not stuck in their bores 16. The glide-shoe arrangement in accordance with the invention is intended for use in connection with such glide shoes in which a partly, preferably mainly, hydrostatic lubrication is used. In the glide shoes, it is also possible to use partly hydrodynamic lubri­ cation, which is implied by the chamferings 41 at the edges of the glide faces on the glide shoes 22, which said chamferings, together with the inner face 11′ of the mantle 11, define wedge spaces, in which a dam pressure of lubricant is produced, by means of which the glide face may, if necessary, also be lubricated partly hydrodynamically. In Fig. 3, the glide-shoe arrangement is shown with the correct proportions and in the scale 1:1.5. In Fig. 3, the length of the glide shoe in the direction of rotation of the roll mantle 11 is denoted with L, the diameter of the loading piston 15 with D, the radius of the spherical bearing with R, and the perpendicular distance of the journalling centre 0 of the said spherical bearing from the glide face of the mantle 11 with E. Within the scope of the invention, the said dimensions are, as a rule, within the ranges of D = 50 to 200 mm; E = 20 to 80 mm; L = 100 to 300 mm; R = 20 to 50 mm. When the dimensions R and E essential for the invention are proportioned to the width L of the glide shoe 22, it can be ascertained that favourably L/R > about 3, preferably L/R = about 4...6, and L/E > about 2, preferably L/E = about 2.5...4. If the said dimensions R and E are proportioned to the diameter D of the loading piston 15, it can be ascertained that D is favourably several times larger than the dimensions R and E. The construction described above operates mainly as follows. The axle 12 is pressed by the inter­ mediate of articulated bearings (not shown) attached to its axle journals 12a and 12b against the counter-roll 50 so as to load the nip N, whereby the axle 12 is, at the same time, deflected. In order to control the distribution (profile) of the nip pressure N in zones, a fluid pressure of adjustable magnitude is applied through the ducts 18 so as to load the glide-shoe-piston combinations 20₁...20 N , which said pressure presses the pistons 15 and the shoes 22 attached to the pistons within the area of the nip N against the inner face 11′ of the roll mantle 11. The shoes 22 receive their lubrication oil from the loading oil and pressure of the pistons 15, so that the pressure of the lubrication oil in the spaces 23a and 23b is proportional to the loading pressure of the pistons 15 and the shoes 22 attached to same. As the axle 12 is deflected because of the loading forces, the shoes 22 are able to be positioned in accordance with the mantle 11 and the pistons 15 in accordance with the central axle, because the pistons 20 and the shoes 22 are interconnected by the support joint arrangement 30. The shoes 22 are also capable of being positioned in the cross-sectional plane of the roll 10 around the spherical joints 31,32,33, and this positioning is not interfered with by the sealed passage of the lubrication oil into the chambers 23a and 23b on the shoes 22. In the following, the patent claims will be given, whereat the various details of the invention may show variation within the scope of the inventive idea defined in the said claims and differ from the details given above by way of example only.

Claims: 1. Glide shoe arrangement for a variable-­ crown roll (10), which said roll (10) comprises a non-revolving massive central axle (12), on which a cylindrical roll mantle (11) is journalled (13a,13b) as revolving, between which said axle (12) and the inside face (11″) of the said roll mantle (11) piston-glide-shoe combinations (20₁...20N) loaded by means of hydraulic pressure fluid are fitted, whose glide shoes (22) can be loaded by the intermediate of pistons (15) by means of the pressures of the hydraulic fluid against the inside face (11″) of the roll mantle (11) for the purpose of con­ trolling the distribution of the nip pressure in the nip (N) placed facing the said loading shoes (22), and which said piston-glide-shoe combinations (20₁...20N) include cylindrical bores (16) or equivalent made into the said axle (12), into which said bores cylindrical or equivalent pistons (15) are fitted, characterized in - that bearings (31,32) provided with spherical bearing faces (33) are fitted between the loading pistons (15) and their glide shoes (22), the center of rotation (0) of the said bearings being located at the side of the glide shoe (22), - that a pin-shaped projection part (25) is fitted in the said loading pistons (15), which said projection part extends through the said bearing (31,32,33), - that between the said pin-shaped projection part (25) and the glide shoe (22) or a projection part (36) attached to the glide shoe, there is a sealed arti­ culation arrangement (30), and - that the pressure fluid can be passed from the loading space (16p) of the pistons (15) through the said pin-shaped projection part (25) into the hydrostatic lubrication spaces (23a,23b) on the glide shoes (22). 2. Variable-crown roll as claimed in claim 1, characterized in that the said pin-shaped projection part (25) is a cylindrical body of revolution whose centre axis substantially coincides with the centre axis (K-K) of the cylinder bores (16) in the pistons (15). 3. Variable-crown roll as claimed in claim 1 or 2, characterized in that in the part of the pin-shaped projection part (25) that is placed at the side of the glide shoe (22), there are two ring flanges (28), between which there is a groove (29), in which a seal ring (39) is fitted, which seals the joint arrangement (30) between the loading pistons (15) and the glide shoes (22). 4. Variable-crown roll as claimed in claim 3, characterized in that the said seal ring (29) is placed substantially in the same plane in which the center of rotation (0) of the said bearing (31,32) that has spherical bearing faces is placed. 5. Variable-crown roll as claimed in any of the claims 1 to 4, characterized in that the plane outer end of the said loading pistons (15) is provided with a bore (21) or equivalent to which the bearing ring (31) of the spherical bearing is fixed that has a concave bearing face (33), and that the other bearing ring (32), which has a convex spherical bearing face (33), is fixed to the inner plane face of the glide shoes (22) or to the inner side of the projection part (36) of the glide shoes or to a bore (37) in same, and that the said pin-shaped projection part (25) extends through the inner holes (35) in the said bearing rings (31,32). 6. Variable-crown roll as claimed in any of the claims 1 to 5, characterized in that the inside face of the said glide shoes (22) is pro­ vided with a projection part (36), which fits with a wide play into the outer part of the said cylinder bores (16) or equivalent, and that the said projection part (36) is provided with a central bore (38), into whose interior the said pin-shaped projection part (25) extends and against the inner face of which said bore (38) the seal ring (39) on the pin-shaped projection part (25) seals the said joint arrangement (30). 7. Variable-crown roll as claimed in claim 6, characterized in that in the side of the bore in the said projection part (36) facing the glide shoe (22) there is a space (40) into which the bore (27) in the said pin-shaped projection part (25) opens, the opposite end of the said bore (27) being connected to the loading pressure space (16p) in the piston (15) via the bore (26) in the piston (15), and that out of the said space (40) bores (22p) or equivalent pass into the hydrostatic lubrication spaces (23a,23b) on the glide shoe (22). 8. Variable-crown roll as claimed in any of the claims 1 to 7, characterized in that the ratio of the length L of the said glide shoe (22) in the direction of rotation of the roll mantle (11) to the journalling radius R of the said spherical bearing and to the perpendicular distance E of its journalling center (0) from the glide face of the glide shoe (22) is L/R > about 3, preferably L/R = 4...6, L/E > about 2, preferably L/E = 2.5...4, and that the diameter (D) of the said loading piston (15) is substantially larger, preferably several times larger than the said journalling radius R and the said distance E.

Inventors: NISKANEN, JUHANI
Applicants: VALMET OY
Application year: 1987
Main classification: F16C13
IPC codes: F16C13, D21F1, D21F3, D21G1, B21B27