BEARING UNIT WITH THREE BEARINGS INCLUDING A PRELOAD BEARING, IN PARTICULAR FOR A PAPER PROCESSING TOOL

Abstract

This invention discloses a very compact play-free bearing unit. The bearing runs without play while having a reasonably large play when assembling and disassembly the bearing unit from its axle. The bearing unit uses three bearings, one of which is mobile, and thanks to a preloading mechanism the play is removed when loaded. Thanks to an amplification lever, the preloading unit is able to function either with a pneumatic actuator or with a hydraulic actuator.

Claims

1. A bearing unit, for a rotary processing tool, comprising: two outer bearings; an intermediate bearing; and a preloading unit adapted for displacing one of the two outer bearings or the intermediate bearing with respect to the other of the two outer bearings or the intermediate bearing, wherein the intermediate bearing is accommodated in a slider which is received within a recess in a main body of the bearing unit, and wherein the preloading unit comprises an amplification lever arranged for converting an actuation force into a greater preloading force and whereby the amplification lever is configured to amplify the actuation force created by an actuator, into a greater preloading force acting on the slider and the intermediate bearing.

2. The bearing unit of claim 1, wherein the lever cooperates with the intermediate bearing.

3. The bearing unit of claim 1, wherein the amplification lever is a one-armed lever.

4. The bearing unit of claim 1, wherein the amplification lever extends parallel to an axis of rotation of the two outer bearings or the intermediate bearing.

5. The bearing unit of claim 1, wherein an end of the amplification lever engages behind a support provided at the bearing unit.

6. The bearing unit of claim 5, wherein the support is a separate element fastened to the bearing unit.

7. The bearing unit of claim 5, wherein the end of the amplification lever engaging behind the support is formed in a fork-like manner.

8. The bearing unit of claim 1, wherein the preloading unit comprises a pneumatic actuator adapted for pivoting the amplification lever with respect to the bearing unit.

9. The bearing unit of claim 8, wherein the actuator comprises a piston/cylinder arrangement in which the piston is held stationary with respect to the bearing unit.

10. The bearing unit of claim 9, wherein the cylinder is formed by a through-hole in the amplification lever.

11. The bearing unit of claim 10, wherein a cover is associated with the through-hole.

12. The bearing unit of claim 9, wherein two pistons are provided which are arranged in two cylinder openings arranged along a centerline of the amplification lever.

13. The bearing unit of claim 12, wherein a connection opening is formed in the lever for establishing a pressure connection between the cylinder openings.

14. The bearing unit of claim 9, wherein a sealing element is provided for sealing between the inner wall of the cylinder and the piston arranged therein and for centering the piston within the cylinder.

15. The bearing unit of claim 9, wherein the piston rests on an abutment plate.

16. A method for changing the mechanical characteristics of a drum engaged into a bearing unit as claimed in claim 1, comprising varying the amplitude of the actuation force applied to the amplification lever of the preloading unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The invention will now be explained with reference to an embodiment shown in the drawings. In the drawings,

[0032] FIG. 1 shows a rotary processing tool provided with a bearing unit;

[0033] FIG. 2 is a first side view of the bearing unit;

[0034] FIG. 3 is a second side view of the bearing unit;

[0035] FIG. 4 is a sectional view of the bearing unit of FIG. 3 along the plane IV-IV of FIG. 2;

[0036] FIG. 5 is a view similar to the view of FIG. 4, sectioned along plane V-V of FIG. 2;

[0037] FIG. 6 is a plan view of the amplification lever with the pneumatic actuator; and

[0038] FIG. 7 is a cross-section through the amplification lever and the actuator of FIG. 6 along plane VII-VII.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0039] A bearing unit 6 according to the invention is shown in detail in FIGS. 2 to 7. It comprises a main body 10 adapted for being connected to machine frame 2 and carrying three bearings.

[0040] As can be seen in particular in FIGS. 4 and 5, a first group of bearings 12 is provided, which here consists of bearings which are held stationary within main body 10. Further, a second group is provided which here consists of a bearing 14. Bearing 14 is arranged in between bearings 12 and is mounted within main body 10 so as to be displaceable in a radial direction (see the arrow A in FIGS. 4 and 5). To this end, bearing 14 is accommodated in a slider 16 which is received within a recess 18 in main body 10.

[0041] Because of their position with respect to each other, bearings 12 can be referred to as being outer bearings while bearing 14 is an intermediate bearing.

[0042] In order to displace slider 16 and therewith bearing 14 with respect to main body 10 and outer bearings 12, a preloading unit is provided, of which the main components can be seen in FIGS. 6 and 7.

[0043] The preloading unit comprises an amplification lever 20 and an actuator 22. Amplification lever 20 serves for amplifying an actuation force created by an actuator 22, into a greater preloading force acting on slider 16 and intermediate bearing 14.

[0044] As can be seen in particular in FIG. 6, amplification lever 20 is formed at its end comprising the axis of pivot P, in a fork-like manner in that there are two spaced engagement portions 21. The line of engagement E between amplification lever 20 and slider 16 is arranged between the pivot axis P around which amplification lever 20 pivots with respect to main body 10, and the location of actuator 22. Thus, amplification lever 20 is a one-armed lever.

[0045] The basic structure of amplification lever 20 is a solid metal plate which at one end (in FIGS. 6 and 7 on the left side) is supported at bearing unit 6 and at the opposite end carries actuator 22. The metal plate of the amplification lever 20 extends and is held so that a centerline C of the amplification lever 20 is parallel to the axis of rotation R of bearings 12 and 14 and to the rotation axis of the bearing stud 5. As an example shown in FIGS. 4 and 5, the amplification lever 20 is placed under the main body 10. The bulkiness of the main body 10 with the amplification lever 20 is reduced.

[0046] Advantageously, the amplification lever 20 may be connected to the main body 10 thanks a flexible plate (not shown) that acts as a flexible blade, and allows the amplification level to pivot around axis P. The function of the plate is to keep the amplification lever in place when the preloading unit is idle. As an alternative to the plate, one could use a hinge that pivots around axis P, but since the amplitude of the pivoting is low and the forces in play are big, the plate solution is preferred.

[0047] In order to obtain a high amplification factor, the line of engagement E is arranged close to pivot axis P. Thus, an amplification ratio in the order of 5 to 10 can be obtained. In the particular embodiment, amplification factors in the order of 6 to 7 have been proven effective.

[0048] The high amplification factor is made possible along with the compactness of the setup thanks to the fact that the necessary displacement of the slider is of the order of 1 mm, maximum 2 mm.

[0049] The actuator 22 is formed as a pneumatic actuator to which pneumatic pressure can be supplied via a pneumatic connection 24.

[0050] For transferring a pneumatic pressure into a displacement of amplification lever 20, actuator 22 comprises a piston/cylinder unit 26 having two pistons 28 arranged within cylinders 30 formed in amplification lever 20.

[0051] Cylinders 30 are formed by circular holes which extend entirely through amplification lever 20 from one of its major side surfaces towards the other. On one of their sides, cylinders 30 are closed by means of a cover 32 which is connected to one of the major outer surfaces of amplification lever 20. A seal 34 seals between cover 32 and amplification lever 20. Four mounting screws 36 serve for evenly compressing seal 34 so as to tightly seal cylinder chambers 38.

[0052] Pistons 28 are arranged freely floating within the cylinder chambers 38. Their position in a radial direction is determined by a circular seal 40 which seals between the inner wall of the respective cylinder 30 and the outer contour of the respective piston 28.

[0053] Pistons 28 rest with their end face opposite cover 32 on an abutment plate 42 which is held at bearing unit 6 by means of anchors 44.

[0054] As can be seen in particular in FIGS. 6 and 7, two pistons 28 are arranged in two cylinders 30 positioned adjacent each other on the centerline C of amplification lever 20. Pneumatic pressure can be applied to the cylinder chamber 38 adjacent pneumatic connection 24 via an internal channel 46 formed within amplification lever 20. A connection opening 48 is formed in amplification lever 20 between the two cylinders 30 so as to ensure that the pneumatic pressure established in the first cylinder chamber 38 is also present in the second cylinder chamber.

[0055] The manner in which the preloading unit formed from amplification lever 20 and actuator 22 is mounted to bearing unit 6, can, in particular, be seen from FIGS. 3 to 5.

[0056] Amplification lever 20 engages with its free end opposite actuator 22 behind a support 50 provided at main body 10. Support 50 is here formed as a separate element which is fastened to main body 10 by means of a plurality of fastening screws 52.

[0057] Support 50 forms a mechanical abutment for amplification lever 20 and defines the pivot axis. However, no pivoting hinge is formed. Rather, amplification lever 20 is simply slid into a recess formed between support 50 and main body 10 so as to be mechanically held in a direction which is perpendicular to the axis of rotation R of bearings 12 and 14. In a direction parallel to the axis of rotation R, amplification lever 20 can be disengaged from support 50 by being displaced towards the right (with respect to FIGS. 3 to 5).

[0058] Abutment plate 42 is mechanically connected via anchors 44 to bearing unit 6. Thus, any reaction force acting on pistons 28 is transmitted to bearing unit 6.

[0059] The anchors 44 extending on opposite sides of amplification lever 20, a very compact configuration is achieved. Anchors 44 can serve for mechanically guiding amplification lever 20.

[0060] The operation of bearing unit 6 will now be described with reference to FIG. 4. In a starting condition in which bearing stud 5 is to be inserted into bearing unit 6, intermediate bearing 14 is in a position in which its axis of rotation coincides with the axis of rotation of outer bearings 12. Bearing stud 5 can then easily be inserted in an axial direction into bearing unit 6.

[0061] After bearing stud 5 is in the correct axial position, pressure is supplied to cylinder chambers 38. The pressure in cylinder chambers 38 tends to expel pistons 28 from the cylinder chambers. As the pistons 28, however, rest on abutment plate 42 which in turn is held stationary with respect to main body 10, the reaction force acting via cover 32 on amplification lever 20 results in the entire amplification lever 20 being rotated in a counterclockwise direction around pivot axis P (see arrow B in FIG. 4).

[0062] As amplification lever 20 cooperates with slider 16, the rotation of amplification lever 20 in a counterclockwise direction results in intermediate bearing 14 being displaced with respect to outer bearings 12. With reference to FIG. 4, intermediate bearing 14 is displaced upwardly, thereby exerting a force F1 on bearing stud 5. Corresponding reaction forces F2 are created at outer bearings 12. As a consequence, bearing stud 5 is held without play in bearing unit 6. Bearing unit 6 allows creating the necessary magnitude of radial thrust at intermediate bearing 14 while being very compact. In particular, actuator 22 has a height, measured in parallel with the direction of displacement of pistons 28 with respect to amplification lever 20, which is not more than three times the thickness of amplification lever 20.

[0063] Also, the external footprint of the complete bearing, including the preloading unit, is of the order of 10% to 20%-25% larger in one of the radial directions, than the very same bearing without any preloading unit. Thus, the system can be adapted for systems where there is little space available, like the one depicted in FIG. 1.

[0064] When the rotary processing unit is running, with a drum 4 inserted into the bearing unit 6, and a preloading force applied to one of the bearings, the unit exhibits a given natural frequency. The unit cannot be run at the natural frequency without affecting the output quality. Thus, is may be advantageous to be able to change the natural frequency of the unit. This can be done by changing the preloading force applied to the amplification lever 20, and thus to the bearing. In a particular embodiment of the invention, similar to the one depicted in the Figures, by changing the preloading force applied to the bearing from 4 kN to 8 kN, the natural frequency shifted from 230 Hz to 233 Hz. Also, by increasing the preload, we increase the deformation applied to the drum 4 (also outside from the bearing).