Frame of a supercalender

Abstract

 The invention concerns a frame of a super­calender. The frame comprises side frames (10) which are interconnected by trans­verse beams (21) and a support plane (19), on which an unwind stand (17) is placed. Each side frame (10) of the supercalender comprises a first diagonal beam (14), which is fitted with one of its ends at the bottom part of the vertical beam (11) and with the other end at the middle area of said horizontal beam (12). The side frame further comprises a second diagonal beam (15), one of whose ends joins the other vertical beam (13), at its lower part whereas the other end joins the horizontal beam (12), favourably its middle area. The side frame (10) further comprises a third diagonal beam (16), one of whose ends joins the upper part of the vertical beam (11) whereas the other end joins the hori­zontal beam (12) in its middle area.

Description

[0001] The invention concerns a frame of a supercalender.

[0002] The supercalender frames known in prior art are high and narrow constructions. Under these circumstances, they are highly susceptible to vibration. The excitation forces occurring in supercalenders are within, or very near, the ranges of natural frequencies. Thus, at those ranges, problems of vibration are constantly encountered. A super­calender is a machine of a large mass with groups of revolving masses which cause considerable dynamic loads. Such revolving masses are, e.g., the jumbo roll, from which the paper enters into the machine and which is variably eccentric, the upper and lower rolls, whose diameters are larger than those of the other rolls, the fibre rolls, whose diameter becomes smaller in operation and in which eccentricity may arise. Moreover, a supercalender has a great number of iron rolls as well as alignment and spreader rolls. Said revolving masses may be eccentric relative their journalling points, whereby the eccentricity causes harmonic excitation forces in the calender frame. Even little eccentricities of the masses in the rolls cause high forces, because the speeds of rotation are high and the rolls weigh several tons. The weight of a whole stack of rolls, depending on the web width, may be up to 200 tons.

[0003] Also, a paper roll to be unwound, when placed on the unwind stand, may cause a considerable load on the supercalender frame. The maximum diameter of a jumbo roll to be unwound varies from 2000 up to 3000 mm. The mass of a full jumbo roll varies from 30 to 70 tons. In connection with exchange of jumbo rolls, impact loads are produced on the machine. Also, in the acceleration and braking stages of the drives, considerable excitation forces are applied to the machine frame. Likewise, instantaneous openings of the nips in a calender stack produce a series of impact forces. Thus, a supercalender frame may be subjected to numerous excitation forces causing vibration in the frame.

[0004] One basis of dimensioning of supercalender frames is the natural frequencies and the excitation frequencies. It is essential that excitation frequencies do not occur within the range of the lowest natural frequency of a supercalender frame. Excessive vibrations occurring during operation would cause disturbance in the operation of a supercalender. Vibration causes variations in the nip pressure, which again results in deterioration of the paper quality.

[0005] Increased running speeds and increased quality requirements imposed on the product have resulted in a necessity to be able to provide a supercalender frame that is as rigid and as free from vibrations as possible. Thus, the object of the invention is a supercalender frame that is as rigid as possible and in which it has been possible to raise its lowest number of natural vibrations so that it does not occur in the range of the excitation frequencies applied to the supercalender frame. A further object of the invention is to provide a supercalender frame whose construction is of lower weight as compared with the frame constructions of prior art. By means of a frame of lower weight, it is possible to raise the number of natural vibrations of the supercalender frame further. A frame of lower weight is also more advantageous in respect of its cost of manufacture.

[0006] A non-indispensable additional object of the invention is to provide a supercalender frame that offers ample room for working.

[0007] The objectives of the invention have been a­chieved by means of a supercalender frame solution which is mainly characterized in that the supercalender frame comprises a first diagonal beam, which is fitted so that one of its ends joins the vertical beam placed at the side of the calender stack, the bottom part of said vertical beam, and so that the other end joins the horizontal beam that supports the support plane for the unwind stand, favourably the middle area of said horizontal beam, and that the side frame comprises a second diagonal beam, one of whose ends joins the other vertical beam, favourably the lower part of said beam, whereas the other end joins the horizontal beam, favourably its middle area, and that the side frame comprises a third diagonal beam, which is fitted so that one of its ends joins the upper part of the vertical beam of the side frame placed at the side of the calender stack, whereas the other end joins the horizontal beam in its middle area.

[0008] By means of the supercalender frame in accordance with the present invention, considerably more favourable vibration properties have been obtained as compared with the prior-art frames. The vibration levels in the super­calender frame of the invention are throughout lower than in the prior-art frames. Vibration calculations have been carried out at a certain calculation point on the frame, whereby it has been possible to draw the vibration curves as a function of running speed. The vibration amplitude has been determined as a function of running speed at a certain calculatory dimensioning point on the frame. Further, the speed of vibration of the dimensioning point has been determined as a function of the running speed of the paper web.

Figure 1 is an axonometric view of a super­calender frame of the invention.

Figure 2A is a side view of a supercalender shown in Fig. 1 seen in the direction of the arrow K in Fig. 1.

Figure 2B shows a section I-I of Fig. 2A.

Figure 3 shows a solution that is more rigid than the basic frame form shown in Fig. 1.

Figure 4A shows a graph of running-speed/vibra­tion-amplitude for a supercalender frame of the invention shown in Fig. 1 as well as a corresponding reference curve for a prior-art frame.

Figure 4B shows a curve of running-speed/vibra­tion-speed for a supercalender frame of the invention shown in Fig. 1 and a corresponding reference curve for a prior-art frame.

[0009] Fig. 1 shows a supercalender frame in accordance with the invention. The supercalender frame comprises sub­stantially equivalent side frames 10 at both sides of the machine-direction longitudinal axis X of the supercalender. Each side frame 10 is formed as a trussed construction in accordance with the invention. Each side frame 10 of the supercalender comprises a first vertical beam 11 placed at the side of the vertical calender stack 20 and support­ing said stack of rolls, as well as a horizontal beam 12, which joins said vertical beam 11 in the middle area of its length. At, or at the proximity of, the end of the hori­zontal beam 12, there is a second beam 13 of vertical central axis. The vertical beams 11 and 13 are placed so that their central axes are substantially parallel to each other, and, correspondingly, the horizontal beam 12 is placed so that its central axis is substantially perpen­dicular to said two vertical beams 11 and 13.

[0010] In accordance with the invention, diagonal beams are fitted in the area between the vertical beams 11 and 13, the horizontal beam 12, and the base level T. Accord­ing to the invention, diagonal beams 14,15 and 16, whose central axes run diagonally relative the vertical plane, join the horizontal beam 12 substantially in its middle area.

[0011] In the embodiment of the invention shown in Fig. 1, there are three diagonal beams. The first diagonal beam 14 and the second diagonal beam 15 are fitted in the area between the first vertical beam 11, the second vertical beam 13, the horizontal beam 12, and the level T. The first diagonal beam 14 is fitted to pass from the lower part, preferably from the proximity of the base plate T, of the vertical beam 11 of the side frame 10, placed at the side of the calender stack 20, to the middle area of the horizontal beam 12, in respect of the length of said horizontal beam 12.

[0012] In Fig. 1, reference numeral 17 denotes the unwind stand of the supercalender, and reference numeral 18 denotes the reel-up of the supercalender. The support plane 19 of the unwind stand 17 is placed between the side frames 10. The side frames 10 are interconnected by means of transverse beams 21. The paper web is denoted with broken lines and with the letter W in Figs. 2A and 3.

[0013] As is shown in Fig. 1, the vertical beams, the horizontal beam, and the three diagonal beams define tri­angular frame areas D₁, D₂,D₃ and D₄ in the side frame 10. Thus, besides rigid, the construction in accordance with the invention has also become of low weight. By means of the frame of the invention, it has been possible to raise the lowest natural vibration number of the whole super­calender frame as compared with the prior-art frame con­structions. By means of the triangular intermediate spaces D₁ to D₄, the weight of the construction has become low. In this way, ample room for working has also been provided in connection with the supercalender. The rigidity that has been obtained by means of the construction has also permitted a reduction in the constructional dimensions, and thereby the cost of manufacture of the supercalender frame of the invention is lower than that of the prior-art frame solutions. Further, the reduced weight of the frame construction has raised the lowest natural vibration number of the frame. Under these circumstances, by means of the frame construction of the invention, it is possible to run at very high speeds while the vibration level of the frame of the machine, nevertheless, remains low. The running speed may be up to 1000 m/min, or even higher.

[0014] Fig. 2A shows the side frame 10 shown in Fig. 1 as seen in the direction of the arrow K in Fig. 1. Fig. 2A is a plane view of the formation of the trussed construc­tion of the side frame.

[0015] In the figure, the central axis of the first diagonal beam 14 is denoted with X₁. The central axis of the vertical beam 11 placed at the side of the calender stack 20 is denoted with X₂. The angle between the central axes of the vertical beam 11 and the diagonal beam 14 is α₁, being advantageously 30 to 60°, preferably about 45°. The central axis X₁ of the diagonal beam 14 inter­sects the central axis X₃ of the horizontal beam 12 sub­stantially in, or at the proximity of, the middle area of the horizontal beam 12. Said intersection point is de­noted with P₁′. The solution in accordance with the in­vention shown in Fig. 1 further includes a second diagonal beam 15, which is fitted to pass from the lower area, pre­ferably from the proximity of the base T, of the second vertical beam 13 substantially to the middle area of the horizontal beam 12 or to the proximity of said middle area. The vertical beam 13 is fitted to run so that its central axis runs in a vertical plane, and it is fitted to join the end of the horizontal beam 12 in the area between the centre point of the horizontal beam 12 and the end of the horizontal beam 12, and preferably at the proximity of said outer end.

[0016] The angle between the central axes X₄ and X₅ of the second diagonal beam 15 and the second vertical beam 13 is denoted with α₂. The angle α₂ is advantageously also within the range of 30 to 60°, preferably about 45°. At one of its ends, the diagonal beam 15 joins the lower part of the second vertical beam 13 substantially at the proximity of the base level T, and at its other end it joins the horizontal beam 12 while, besides said horizontal beam 12, also joining the first diagonal beam 14 passed to said junction point. The intersection point P₁˝ between the central axis X₄ of the second diagonal beam 15 and the central axis X₃ of the horizontal beam 12 is advantageously placed in the middle area of the horizontal beam 12, in respect of the length of said horizontal beam 12. Accord­ing to the invention, a further, third diagonal beam 16 is passed to the junction or node point between the hori­zontal beam 12 and the diagonal beams 14 and 15. The diagonal beam 16 is fitted to join the horizontal beam 12, its upper face, substantially at the same point in re­spect of the length of the horizontal beam 12 as the diagonal beams 14 and 15 join said horizontal beam 12. At one of its ends, the third diagonal beam 16 is connected with the upper part of the first vertical beam 11, and at its other end it is fitted to join the horizontal beam 12 in the middle area of the horizontal beam 12. The central axis X₆ of the third diagonal beam 16 intersects the central axis X₃ of the horizontal beam 12 at the point P₁′˝. The angle α₃ between the central axis X₆ of the third diagonal beam 16 and the central axis X₂ of the first vertical beam 11 is advantageously also within the range of 30 to 60°, preferably about 45°.

[0017] In the embodiment of the supercalender frame of the invention shown in Figs. 1 and 2A, the longitudinal central axes X₁,X₄,X₆ of the diagonal beams 14,15 and 16 intersect each other at the same point, which is denoted with the letter P₁. Said intersection point is further placed on the longitudinal central axis X₃ of the hori­zontal beam 12.

[0018] In Fig. 2A, a set of coordinates is fixed by means of which a supercalender frame construction in accord­ance with the invention that has good rigidity properties is defined. A plane illustration of the side frame 10 is shown. Thereat, when an intersection point of the central axes X of beams is spoken of, this means equally well the intersection points of the central planes (X_T) of the longitudinal central axes of said beams (Fig. 2B). Thus, in the present specification, when central axes are spoken of, longitudinal central main planes of the beams can also be meant equally well.

[0019] The starting point of the dimensioning consists of said central axes or central planes of the beams. The starting point for the dimensioning of the horizontal dimensions has been the line parallel to the central axis X₂ of the first vertical beam 11, placed at the side of the calender stack 20. The starting level for vertical dimen­sioning has been the level of the base T.

[0020] In the following table, the frame dimensions and some advantageous index number ranges for same are given:
L₁ - horizontal distance between the centre line of the vertical beam 11 placed at the side of the calender stack 20 and the longitudinal central axis of the second vertical beam 13. L₁ is advantageously within the range of 4 m to 7 m.
L₂ - is the illustrated horizontal distance of the point P₁ from the centre line X₂. L₂ is advantageously within the range of 2 m to 4 m, and L₂ is advantage­ously within the range of 0.3 x L₁ to 0.7 x L₁ . The most advantageous range for L₂ is about 0.5 x L₁.
L₃ - is the distance of the end of the horizontal beam 12 from the coordinate line X₂. L₃ is advantageously within the range of 5 m to 9 m.
H₁ - is the distance of the centre line X₃ of the horizon­tal beam 12 from the base level T. H₁ is advantage­ously within the range of 3 m to 7 m.
H₂ - is the distance of the upper end of the vertical beam 11 from the horizontal level T. H₂ is advan­tageously within the range of 9 m to 11 m.
H₃ is the distance of the intersection point P₂ of the centre line X₆ of the diagonal beam 16 and the centre line X₂ of the vertical beam 11 from the horizontal level T. H₃ is advantageously within the range of 6 m to 10 m.
α₁ - is the angle between the centre line X₁ of the first diagonal beam 14 and the centre line X₂ of the ver­tical beam 11, and the intersection point between said central axes of the beams is denoted with P₃. α₁ is advantageously within the range of 30° to 60°.
α₂ - is the angle between the central axis X₄ of the second diagonal beam 15 and the central axis X₅ of the second vertical beam 13, and the intersection point between the central axes of said beams is denoted with the letter P₄. α₂ is advantageously within the range of 30° to 60°.
α₃ - is the angle between the central axis X₆ of the third diagonal beam 16, placed above the horizon­tal beam 12, and the central axis X₂ of the verti­cal beam 11 placed at the side of the calender stack 20; the intersection point between the central axes X₆ and X₂ of the diagonal beam 16 and the vertical beam 11 is denoted with the letter P₂. α₃ is advan­tageously within the range of 30° to 60°.
H₄ - distance between the point P₃ and the basic hori­zontal level T. H₄ is advantageously within the range of 0.5 m to 1 m.
H₅ - distance between the point P₄ and the basic hori­zontal level T. H₅ is advantageously within the range of 0 to 1 m.
Moreover, L₁/H₃ is within the range of 0.4 to 1.5, and preferably within the range of 0.6 to 1.

[0021] Fig. 2B shows a section I-I in Fig. 2A. The central axis of the beam is denoted with X₄. The longi­tudinal central main plane of the beam is denoted with X_T. The plane passes substantially through the mass centre point of the beam and is parallel to the top and bottom planes of the beam. The width L₄ of the beam is advan­tageously within the range of 200 mm to 400 mm, and the height L₅ of the beam is advantageously within the range of 500 mm to 1000 mm.

[0022] Fig. 3 shows an even more stable frame construc­tion, which differs from the basic form of a supercalender frame in accordance with the invention described above. The solution of Fig. 3 is in the other respects fully similar to the solution shown in Figures 1 and 2A except that the frame construction includes a third vertical beam 22, which is fitted in the area between the first vertical beam 11 and the second vertical beam 13 halfway in the distance between them. Said third vertical beam 22 is fitted to join the diagonal beams 14 and 15 so that the central axis X₇ of the vertical beam 22 intersects the central axis X₃ of the horizontal beam 12 substantially at a corresponding point as the central axes X₁ and X₄ of the diagonal beams 14 and 15 intersect the central axis X₃ of the horizontal beam. In the figure, said common inter­section point is denoted with P₅. Such an embodiment of the invention is also possible that the third vertical beam 22 of the side frame joins the horizontal beam 12 directly without contacting the diagonal beams 14 and/or 15.

[0023] Fig. 4A illustrates an examination of the vibra­tion of a supercalender in accordance with the invention, corresponding to Figs. 1,2A,2B. The figure shows the vibration amplitude of a measurement point on the super­calender frame as a function of the running speed of the paper. The figure also shows corresponding vibration values of a frame in accordance with conventional technol­ogy. In the figure, the prior-art frame construction and its vibration are represented by the curve a, and the curve b represents the vibration/running-speed curve of a frame corresponding to the embodiment of the invention shown in Figs. 1,2A,2B. In the figure, the running speed was increased by 200 m/min up to the upper limit 1000 m/min of the running speed. The vibration amplitude of a con­ventional frame increases steeply when the upper limit of the running-speed range is approaching. At the upper limit of the running-speed range, 1000 m/min, the difference between the vibration amplitudes of the supercalender frame of the invention and that of prior art is more than 50 per cent. For example, the vibration amplitude of a frame in accordance with the invention at the running speed of 1000 m/min is about 0.13 mm, and correspondingly the vibration of a prior-art frame at the running speed of 1000 m/min is about 0.33 mm.

[0024] The vibration amplitudes and vibration speeds are horizontal (direction of the x-axis), and the calcu­lation point is point E (in Fig. 1).

[0025] In a corresponding way, Fig. 4B shows the vibration speed of a supercalender frame in accordance with the invention (curve b) and of a prior-art frame (curve a) at a certain measurement point as a function of running speed. In regard to the prior-art frame, the vibration speed increases steeply when the upper limit of the running-speed range approaches. At the upper limit of the running-speed range, 1000 m/min, with a supercalender in accordance with the invention, a vibration speed is attained for the measurement point which is, for example, about 7 mm/s. Correspondingly, with a prior-art reference frame, with the corresponding running speed, a vibration speed is attained which is about 18 mm/s. Thus, the difference between the vibration speeds is higher than 50 per cent.

Claims

1. Frame of a supercalender, comprising side frames (10) placed at both sides of the machine-direction longitudinal axis (X) of the supercalender, transverse beams (21) interconnecting the side frames (10), a support plane (19) fitted between the side frames (10) and an unwind stand (17) placed on said plane (19), a calender stack (20) fitted at the side of the vertical beams (11) of the side frames (10), characterized in that the side frame (10) of a supercalender comprises a first diagonal beam (14), which is fitted so that one of its ends joins the vertical beam (11) placed at the side of the calender stack (20), the bottom part of said vertical beam, and so that the other end joins the horizontal beam (12) that supports the support plane (19) for the unwind stand (17), favourably the middle area of said horizontal beam (12), and that the side frame comprises a second diagonal beam (15), one of whose ends joins the other vertical beam (13), favourably the lower part of said beam (13), whereas the other end joins the horizontal beam (12), favourably its middle area, and that the side frame (10) comprises a third diagonal beam (16), which is fitted so that one of its ends joins the upper part of the vertical beam (11) of the side frame (10) placed at the side of the calender stack (20), whereas the other end joins the horizontal beam (12) in its middle area.

2. Supercalender frame as claimed in claim 1, characterized in that the longitudinal central axes (X₁,X₄,X₆) of the diagonal beams (14,15,16), or the central planes of said beams, intersect each other at the same point (P₁) of a side.

3. Supercalender frame as claimed in claim 1 or 2, characterized in that the angle (α₁ and/or α₂ and/or α₃) between the central axes or central planes of a diagonal beam (14 and/or 15 and/or 16) and a connected vertical beam (11 and/or 13) is advantage­ously within the range of 30 to 60°.

4. Supercalender frame as claimed in any of the preceding claims, characterized in that the side frame (10) comprises a third vertical beam (22),which is fitted in the area between the vertical beam (11) of the side frame placed at the side of the calender stack (20) and the second vertical beam (13) connected to the horizontal beam (12), and that said third vertical beam is fitted to join the horizontal beam (12) and/or the first and/or the second diagonal beam (14 and/or 15).

5. Supercalender frame as claimed in any of the preceding claims, characterized in that the distance(L₁),of the intersection point (P₁) between the longi­tudinal axis of a diagonal beam (14 and/or 15 and/or 16) and the longitudinal axis of the horizontal beam from the centre line of the vertical beam (11) placed at the side of the calender stack (20) is within the range of (0.3...0.7) x L₁, wherein L₁ is the distance between the centre lines of the vertical beams (11 and 13).

6. Supercalender frame as claimed in any of the preceding claims, characterized in that L₁/H₃ is within the range of 0.4 to 1.5, wherein H₃ is the distance of the intersection point (P₂) of centre lines of the diagonal beam (16) and vertical beam (11) from the horizontal level (T).

Drawing