Abstract:
A deflection compensated roll for a paper/board or finishing machine includes a stationary roll shaft ( 1 ), and a roll shell ( 2 ) structured and arranged to be rotatable around the same and mounted with slide bearing elements ( 3-6 ) upon the roll shaft ( 2 ). The slide bearing elements are provided with hydraulic fluid feeding means for loading the slide bearing elements with a hydraulic fluid. The roll is intended to form a nip together with a counter roll. The hydraulic fluid feeding device is provided with control elements, whereby the slide bearing elements ( 3, 4 ) acting in the direction of a nip load (F) are loadable in such a way that the roll shell ( 2 ) is able to perform a stroke relative to the roll shaft ( 1 ) radially of the roll or to remain substantially immobilized relative to the roll shaft ( 1 ).

Description:
FIELD OF THE INVENTION 
     The present invention relates to a deflection compensated roll for a paper/board or finishing machine, comprising a stationary roll shaft, and a, roll shell adapted to be rotatable around the same and mounted with slide bearing elements upon the roll shaft, said slide bearing elements being provided with hydraulic fluid feeding means for loading the slide bearing elements with a hydraulic fluid, and said roil being intended to form a nip together with a counter roll. 
     BACKGROUND OF THE INVENTION 
     FI patent 98320 describes a slide bearing assembly for a deflection compensated roll, wherein the roll shell is able to shift or perform a stroke relative to the roll shaft both in a main loading plane and in a lateral bearing plane perpendicular thereto. One implementation of such a “movable shell” roll will be described more closely hereinafter in reference to FIGS. 1-3. On the other hand, Finnish patent application No. 990329 discloses a solution for fitting a roll with slide bearings in such a way that the shell is not able to move relative to the shaft, the roll shell bearing assembly allowing substantially no stroke. This type of solution will be described more closely hereinafter in reference to FIG.  4 . 
     FIGS. 1 and 2 show in schematic elevations a prior art tubular roll with slide bearings, such that FIG. 1 is an axial elevation of the roll and FIG. 2 is a sectional view taken along a line II—II of the roll depicted in FIG.  1 . In FIGS. 1 and 2 the deflection compensated roll is generally designated with reference numeral  110  and it comprises a stationary roll shaft  111 , upon which is rotatably fitted a roll shell  112  which is supported on the roll shaft by means of hydraulic loading elements  117 . The hydraulic loading elements  117  work in the direction of a nip plane and enable an adjustment of the roll shell  112  regarding its contour and a control of the roll regarding its axial nip profile. 
     The roll  110  has its bearing system implemented by means of slide bearing elements, whereof the slide bearing elements, acting in the direction of loading, in the case of a roll shown in FIGS. 1 and 2 in the direction of a nip plane, are designated with reference numerals  114  and  114   a . The first slide bearing elements  114  work in the direction of a nip, i.e. against loading, and the second slide bearing elements  114   a  work in the opposite direction. The exemplary embodiment of FIGS. 1 and 2 further shows that the roll  110  is also provided with slide bearing elements  115 ,  115   a  working laterally relative to the loading direction and acting in opposite directions. The roll  110  is a roll totally furnished with slide bearings, which is also provided with slide bearing elements  116 ,  116   a  acting in directions axially opposite to each other and abutting against roll ends  113 ,  113   a  through the intermediary of an oil film. As shown in FIGS. 1 and 2, the radially acting slide bearing elements  114 ,  115 ,  114   a ,  115   a  abut against the inner surface of the roll shell  112  through the intermediary of an oil film. In the representation of FIG. 1, the radially acting slide bearing elements  114 ,  114   a ,  115 ,  115   a  are arranged in pairs, such that there are two specimens of each slide bearing element set side by side in axial direction. From the functional point of view, however, such an arrangement is not an absolute necessity as the bearing system can also be implemented by using just single slide bearing elements. 
     On the other hand, FIG. 2 suggests that the slide bearing elements  114 ,  114   a ,  115 ,  115   a  be adapted to act in the direction of loading and in the direction lateral thereto. However, there could be additional slide bearing elements adapted to work radially in various angular positions. 
     FIG. 3 shows schematically and in partial section one prior art arrangement for supporting a slide-bearing mounted roll and for fitting the same with bearings in a loading direction, i.e. in the direction of a nip plane regarding the roll  110  depicted in FIG.  1 . In FIG. 3, the roll shaft is also designated with reference numeral  111  and the roll shell with reference numeral  112 . The following description deals first with the support system of FIG. 3 in terms of its construction and then with the support system in terms of its function. 
     The roll shell  112  is supported against an inner surface  112 ′ of the roll shell by means of loaded slide bearing elements  114 ,  114   a  which, as shown in FIG. 3, work actively in opposite directions, such that the first slide bearing element  114  loads the roll shell  112  toward an external load applied to the roll shell, i.e. toward a nip, and the second slide bearing element  114   a  in the opposite direction, respectively. In the construction of FIG. 3, the slide bearing elements  114 ,  114   a  are provided with pressurizable cavities  61 ,  61   a , and for each slide bearing element  114 ,  114   a  the roll shaft  111  is fitted with body blocks  63 ,  63   a  which penetrate into said cavities  61 ,  61   a  of the slide bearing elements, the body blocks  63 ,  63   a  being sealed relative thereto by means of packings  63 ′,  63 ′ a  so as to allow a movement of the slide bearing elements  114 ,  114   a  relative to the body blocks  63 ,  63   a . In structural sense, the slide bearing elements  114 ,  114   a  are conventional by having the outer surface thereof provided with oil pockets  64 ,  64   a  which are in communication with the cavities  61 ,  61   a  by way of capillary borings  65 ,  65   a  extending through the slide bearing elements. Thus, the pressurized cavities  61 ,  61   a  release through the capillary borings  65 ,  65   a  a pressure fluid, particularly oil, into the oil pockets  64 ,  64   a  for establishing an oil film between the slide bearing elements  114 ,  114   a  and the inner surface  112 ′ of the roll shell. 
     In the representation of FIG. 3, the first slide bearing element  114  acting in the loading direction is provided with an adjustment means  66 , comprising a bore  76  made in the body block  63  of the slide bearing element and movably fitted with a three-section slide valve  69 ,  70 ,  71 , including a middle slide-valve section  69 , a first end section  70 , and a second end section  71 . The slide-valve sections  69 ,  70 ,  71  are linked by a spindle rod  67 , which holds the slide-valve sections apart from each other and which spindle rod  67  abuts against a floor  62  of the cavity in the first slide bearing element  114 . The bore  76  has its bottom underneath the second slide-valve end section  71  fitted with a spring  68 , which stresses said spindle rod  67  against the cavity floor  62 . Hence, the adjustment means  66  is constituted by a valve, which is supplied with a pressure fluid through a central passage  120   a  and a supply passage  119   a  and which distributes the pressure and flow rate of the supplied pressure fluid at a desired and predetermined ratio through flow paths  72  and  73  defined by the slide-valve sections  69 ,  70 ,  71  of the adjustment means  66 , as well as through a connecting channel  118   a  and pressure passages  75 ,  75   a  made in the body blocks  63 ,  63   a  of the slide bearing elements  114 ,  114   a  into the cavities  61 ,  61   a  of the slide bearing elements. The bore  76  is further provided with an annular groove  74  at a confluence between the supply passage  119   a  and the bore  76 . 
     The roll shell  112  is capable of moving radially relative to the roll shaft  111  also in the direction of loading. In the case of FIG. 3, the roll shell  112  is depicted in a middle position, and from this middle position the roll shell  112  is allowed to travel a certain distance in either direction. For example, when dealing with the deflection compensated roll  110  of FIG. 1, which constitutes a nip with a counter roll, a suitable permissible stroke for the roll shell  112  is for instance 25 mm in either direction. Of course, this distance is only given by way of example. The adjustment means  66  is used to control strokes of the roll shell  112  in the appropriate direction of loading and to limit the stroke to a maximum distance desired therefor. As perceivable from FIG. 3, the middle slide-valve section  69  of the adjustment means  66  has an axial length which exceeds that of the annular groove  74  made in the bore  76 , and this dimensioning, explicitly, has a crucial significance in controlling the roll shell  112  as regards its strokes or movements. 
     In the condition shown in FIG. 3, wherein the roll shell  112  is in its middle position, the middle slide-valve section  69  covers the annular groove  74  completely. When the roll shell  112  commences its stroke from the position of FIG. 3 in either direction, for example downward in FIG. 3, the first slide bearing element  114  loaded through an oil film against the inner roll shell surface  112 ′ accompanies the roll shell  112  in its stroke and uses the spindle rod  67  to press the slide valve of the adjustment means  66  in the same direction against the loading force of the spring  68 . The middle slide-valve section  69  has its axial length dimensioned such that, as the roll shell  112  approaches its permissible extreme position, the slide valve  69 ,  70 ,  71  has shifted to such a position that pressure fluid is allowed to flow from the supply passage  119   a  through the annular groove  74  past the middle slide-valve section  69  into the first flow path  72  and thence further along the pressure channel  75  into the cavity  61 . This develops a braking pressure for the stroke of the roll shell  112 , which ultimately stops the roll shell  112  in its permissible extreme position. This preferably results in a closure of pressure channels used for a regular setting pressure and extending to the slide bearing elements  114 ,  114   a . An advantage offered by this configuration is that it enables controlled strokes for the roll shell  112  without external control and, furthermore, it protects the oil films of the slide bearing elements  114 ,  114   a  also in the extreme positions of the roll shell  112 . The arrangement has naturally an equivalent operation when the roll shell  112  performs its stroke in the opposite direction. 
     The representation of FIG. 3 is incomplete in the sense that said figure only discloses the way of controlling and decelerating strokes of the roll shell  112 . It is quite obvious, however, that, in addition to pressure connections depicted in FIG. 3, the cavity  61 ,  61   a  of each slide bearing element  114 ,  114   a  must be supplied, also in the middle position shown in FIG. 3, with a normal setting pressure for loading the slide bearing elements  114 ,  114   a  against the inner roll shell surface  112 ′ also in the condition shown in the figure. As perceivable from FIG. 3, the supply of a setting pressure cannot be handled through the supply passage  119   a  as the annular groove  74  is completely covered by the middle slide-valve section  69  blocking the flow of a pressure fluid to either flow path  72 ,  73 . For the introduction of setting pressures, each body block  63 ,  63   a  must simply be provided with an extra channel connected to a pressure source, the pressure fluid supplied thereby not passing through the adjustment means  66 . 
     FIG. 4 illustrates an arrangement according to application 990329 for fitting a roll shell with bearings without stroke. The figure depicts a stationary roll shaft  1 , around which is rotatably mounted a roll shell  2 , the external load applied thereto being designated with reference symbol F. The bearing assembly acting in a plane of loading comprises a slide bearing element  3  working against the load, as well as a slide bearing element  4  working in the loading direction. These slide bearing elements  3 ,  4  of the load bearing assembly are controlled by a control valve  7 , which is supplied with a hydraulic fluid pressure along a feed line  8 , the valve  7  distributing the pressure for a cavity  12  of the slide bearing element  3  and along a line  9  for a cavity  13  of the slide bearing element  4 . The cavities  12 ,  13  have pressure measuring/standby lubricating lines  11  and  10 , respectively, connected therewith. The operation of such a non-stroke bearing assembly has been described in more detail in the above-mentioned FI application 990329 and the operation of such a non-stroke bearing assembly is old and well known in the art and no further explanation is needed for the understanding of the non-stroke bearing assembly by a person of ordinary skill in the art. The roll, shell has its lateral bearing system implemented by means of lateral bearing elements  5  and  6  as described for example in FI patent 98320 and the operation of such a lateral bearing system implemented by means of lateral bearing elements is old and well known in the art and no further explanation is needed for the understanding of the non-stroke bearing assembly by a person of ordinary skill in the art. 
     In certain calendar applications there is a need to run two movable shell rolls oppositely to each other, whereby one of the rolls must be securely immobilized. In this case, the nip forces are created by loading the movable shell roll against a counter roll having its shell immobilized. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is one object of the present invention to provide a solution, whereby, if necessary, the bearing system of a movable shell roll can be converted into a non-stroke system in a relatively simple fashion, the shell becoming immobilized relative to the roll shaft in the loading direction. 
     In order to accomplish this object, a roll of the invention is characterized in that the hydraulic fluid feeding means are provided with control elements, whereby the slide bearing elements acting in the direction of a nip load are loadable in such a way that the roll shell is optionally able to perform a stroke relative to the roll shaft radially of the roll or to remain substantially immobilized relative to the roll shaft. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described in more detail with reference to the accompanying drawings, in which 
     FIGS. 1 and 2 show in schematic elevations one tubular roll of the prior art fitted with slide bearings, 
     FIG. 3 shows in a schematic view one arrangement of the prior art for supporting a roll shell in a loading direction, said arrangement allowing the roll shell to perform a stroke relative to the roll shaft, 
     FIG. 4 shows in a schematic view another arrangement of the prior art for supporting a roll shell in a loading direction, which maintains the roll shell immobilized relative to the roll shaft, and 
     FIG. 5 shows in a schematic view a solution of the invention for supporting a roll shell in a loading direction. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 and 2 show in schematic elevations a prior art tubular roll with slide bearings, such that FIG. 1 is an axial elevation of the roll and FIG. 2 is a sectional view taken along a line II—II of the roll depicted in FIG.  1 . In FIGS. 1 and 2 the deflection compensated roll is generally designated with reference numeral  110  and it comprises a stationary roll shaft  111 , upon which is rotatably fitted a roll shell  112  which is supported on the roll shaft by means of hydraulic loading elements  117 . The hydraulic loading elements  117  work in the direction of a nip plane and enable an adjustment of the roll shell  112  regarding its contour and a control of the roll regarding its axial nip profile. 
     The roll  110  has its bearing system implemented by means of slide bearing elements, whereof the slide bearing elements, acting in the direction of loading, in the case of a roll shown in FIGS. 1 and 2 in the direction of a nip plane, are designated with reference numerals  114  and  114   a . The first slide bearing elements  114  work in the direction of a nip, i.e. against loading, and the second slide bearing elements  114   a  work in the opposite direction. The exemplary embodiment of FIGS. 1 and 2 further shows that the roll  110  is also provided with slide bearing elements  115 ,  115   a  working laterally relative to the loading direction and acting in opposite directions. The roll  110  is a roll totally furnished with slide bearings, which is also provided with slide bearing elements  116 ,  116   a  acting in directions axially opposite to each other and abutting against roll ends  113 ,  113   a  through the intermediary of an oil film. As shown in FIGS. 1 and 2, the radially acting slide bearing elements  114 ,  115 ,  114   a ,  115   a  abut against the inner surface of the roll shell  112  through the intermediary of an oil film. In the representation of FIG. 1, the radially acting slide bearing elements  114 ,  114   a ,  115 ,  115   a  are arranged in pairs, such that there are two specimens of each slide bearing element set side by side in axial direction. From the functional point of view, however, such an arrangement is not an absolute necessity as the bearing system can also be implemented by using just single slide bearing elements. 
     On the other hand, FIG. 2 suggests that the slide bearing elements  114 ,  114   a ,  115 ,  115   a  be adapted to act in the direction of loading and in the direction lateral thereto. However, there could be additional slide bearing elements adapted to work radially in various angular positions. 
     FIG. 3 shows schematically and in partial section one prior art arrangement for supporting a slide-bearing mounted roll and for fitting the same with bearings in a loading direction, i.e. in the direction of a nip plane regarding the roll  110  depicted in FIG.  1 . In FIG. 3, the roll shaft is also designated with reference numeral  111  and the roll shell with reference numeral  112 . The following description deals first with the support system of FIG. 3 in terms of its construction and then with the support system in terms of its function. 
     The roll shell  112  is supported against an inner surface  112 ′ of the roll shell by means of loaded slide bearing elements  114 ,  114   a  which, as shown in FIG. 3, work actively in opposite directions, such that the first side bearing element  114  loads the roll shell  112  toward an external load applied to the roll shell, i.e. toward a nip, and the second slide bearing element  114   a  in the opposite direction, respectively. In the construction of FIG. 3, the slide bearing elements  114 ,  114   a  are provided with pressurizable cavities  61 ,  61   a , and for each slide bearing element  114 ,  114   a  the roll shaft  111  is fitted with body blocks  63 ,  63   a  which penetrate into said cavities  61 ,  61   a  of the slide bearing elements, the body blocks  63 ,  63   a  being sealed relative thereto by means of packings  63 ′,  63 ′ a  so as to allow a movement of the slide bearing elements  114 ,  114   a  relative to the body blocks  63 ,  63   a . In structural sense, the slide bearing elements  114 ,  114   a  are conventional by having the outer surface thereof provided with oil pockets  64 ,  64   a  which are in communication with the cavities  61 ,  61   a  by way of capillary borings  65 ,  65   a  extending through the slide bearing elements. Thus, the pressurized cavities  61 ,  61   a  release through the capillary borings  65 ,  65   a  pressure fluid, particularly oil, into the oil pockets  64 ,  64   a  for establishing an oil film between the slide bearing elements  114 ,  114   a  and the inner surface  112 ′ of the roll shell. 
     In the representation of FIG. 3, the first slide bearing element  114  acting in the loading directions is provided with an adjustment means  66 , comprising a bore  76  made in the body block  63  of the slide bearing element and movably fitted with a three-section slide valve  69 ,  70 ,  71 , including a middle slide-valve section  69 , a first end section  70 , and a second end section  71 . The slide-valve sections  69 ,  70 ,  71  are linked by a spindle rod  67 , which holds the slide-valve sections apart from each other and which spindle rod  67  abuts against a floor  62  of the cavity in the first slide bearing element  14 . The bore  76  has its bottom underneath the second slide-valve end section  71  fitted with a spring  68 , which stresses said spindle rod  67  against the cavity floor  62 . Hence, the adjustment means  66  is constituted by a valve, which is supplied with a pressure fluid through a central passage  120   a  and a supply passage  119   a  and which distributes the pressure and flow rate of the supplied pressure fluid at a desired and predetermined ratio through flow paths  72  and  73  defined by the slide-valve sections  69 ,  70 ,  71  of the adjustment means  66 , as well as through a connecting channel  118   a  and pressure passages  75 ,  75   a  made in the body blocks  63 ,  63   a  of the slide bearing elements  114 ,  114   a  into the cavities  61 ,  61   a  of the slide bearing elements. The bore  76  is further provided with an annular groove  74  at a confluence between the supply passage  119   a  and the bore  76 . 
     The roll shell  112  is capable of moving radially relative to the roll shaft  111  also in the direction of loading. In the case of FIG. 3, the roll shell  112  is depicted in a middle position, and from this middle position the roll shell  112  is allowed to travel a certain distance in either direction. For example, when dealing with the deflection compensated roll  110  of FIG. 1, which constitutes a nip with a counter roll, a suitable permissible stroke for the roll shell  112  is for instance 25 mm in either direction. Of course, this distance is only given by way of example. The adjustment means  66  is used to control strokes of the roll shell  112  in the appropriate direction of loading and to limit the stroke to a maximum distance desired therefor. As perceivable from FIG. 3, the middle slide-valve section  69  of the adjustment means  66  has an axial length which exceeds that of the annular groove  74  made in the bore  76 , and this dimensioning, explicitly, has a crucial significance in controlling the roll shell  112  as regards its strokes or movements. 
     In the condition shown in FIG. 3, wherein the roll  112  is in its middle position, the middle slide-valve section  69  covers the annular groove  74  completely. When the roll shell  112  commences its stroke from the position of FIG. 3 in either direction, for example downward in FIG. 3, the first slide bearing element  114  loaded through an oil film against the inner roll shell surface  112 ′ accompanies the roll shell  112  in its stroke and uses the spindle rod  67  to press the slide valve of the adjustment means  66  in the same direction against the loading force of the spring  68 . The middle slide-valve section  69  has its axial length dimensioned such that, as the roll shell  112  approaches its permissible extreme position, the slide valve  69 ,  70 ,  71  has shifted to such a position that pressure fluid is allowed to flow from the supply passage  119   a  through the annular groove  74  past the middle slide-valve section  69  into the first flow path  72  and thence further along the pressure channel  75  into the cavity  61 . This develops a braking pressure for the stroke of the roll shell  112 , which ultimately stops the roll shell  112  in its permissible extreme position. This preferably results in a closure of pressure channels used for a regular setting pressure and extending to the slide bearing elements  114 ,  114   a . An advantage offered by this configuration is that it enables controlled strokes for the roll shell  112  without external control and, furthermore, it protects the oil films of the slide bearing elements  114 ,  114   a  also in the extreme positions of the roll shell  112 . The arrangement has naturally an equivalent operation when the roll shell  112  performs its strokes in the opposite direction. 
     The representation of FIG. 3 is incomplete in the sense that said figure only discloses the way of controlling and decelerating strokes of the roll shell  112 . It is quite obvious, however, that, in addition to pressure connections depicted in FIG. 3, the cavity  61 ,  61   a  of each slide bearing element  114 ,  114   a  must be supplied, also in the middle position shown in FIG. 3, with a normal setting pressure for loading the slide bearing elements  114 ,  114   a  against the inner roll shell surface  112 ′ also in the condition shown in the figure. As perceivable from FIG. 3, the supply of a setting pressure cannot be handled through the supply passage  119   a  as the annular groove  74  is completely covered by the middle slide-valve section  69  blocking the flow of pressure fluid to either flow path  72 ,  73 . For the introduction of setting pressures, each body block  63 ,  63   a  must simply be provided with an extra channel connected to a pressure source, the pressure fluid supplied thereby not passing through the adjustment means  66 . 
     FIG. 4 illustrates an arrangement according to application 990329 for fitting a roll shell with bearings without stroke. The figure depicts a stationary roll shaft  1 , around which is rotatably mounted a roll shell  2 , the external load applied thereto being designated with reference symbol F. The bearing assembly acting in a plane of loading comprises a slide bearing element  3  working against the load, as well as a slide bearing element  4  working in the loading direction. These slide bearing elements  3 ,  4  of the load bearing assembly are control by a control valve  7 , which is supplied with a hydraulic fluid pressure along a feed line  8 , the valve  7  distributing the pressure for a cavity  12  of the slide bearing element  3  and along a line  9  for a cavity  13  of the slide bearing element  4 . The cavities  12 ,  13  have pressure measuring/standby lubricating lines  11  and  10 , respectively, connected therewith. The operation of such a non-stroke bearing assembly has been described in more detail in the above-mentioned F1 application 990329 and, thus, shall not be explained further in this context. The roll, shell has its lateral bearing system implemented by means of lateral bearing elements  5  and  6  in a per se known manner as described for example in FI patent 98320 and, thus, its operation shall not be described in further detail, either. 
     FIG. 5 depicts one preferred embodiment of the invention, wherein the pressure feed line  8  shown in the solution of FIG. 4 is provided with a shut-off valve  14 , by means of which the feed pressure control valve  7  can be closed. At this time, the pressure measuring/standby lubricating lines  11 ,  10  extending to the cavities of the load bearings  3 ,  4  are actively deployed. Pressure regulating valves are used for supplying the lines with bearing pressures by using a control system similar to what is employed in a normal movable-shell roll. Thus, the control valve  7  functions as a shuttle valve, which isolates the bearing zones to function separately from each other. By means of this solution, the non-stroke bearing assembly of FIG. 4 can be designed as a stroke performing assembly, whereby the roll must naturally be provided with bearing mounting elements and a control valve in such a way that for example a + −20 mm stroke relative to the middle position becomes possible. When the shut-off valve  14  is re-opened and the lines  11 ,  10  are set in a regular pressure measuring/standby lubricating operation, the roll becomes a non-stroke shell roll, wherein the shell position in radial direction relative to the roll shaft can be selected by means of a piston fitted in the control valve  7  underneath the load bearing  3 . The control valve  7  can also be designed to have its position adjustable relative to the roll shaft. 
     The locking of a movable-shell roll in one extreme position is also conceivably effected by running so much overload on the slide bearing elements on one side of the loading bearing zones that the shell does not commence its stroke in response to a nip load. In this type of function, however, the calendar may be subjected to such a loading condition that the shoes on the opposite side relative to shell holding shoes will be subjected to maximum pressures through a brake valve, the shell being subjected to a major stretching force, which may damage the shell.