CONTROLLING THE TREATMENT OF FIBROUS MATERIAL

Abstract

A method for controlling a device for treating a fibrous material includes the steps of: providing that the device includes a housing in which at least a first treatment tool and a second treatment tool are arranged; mounting at least one of the first base plate and the second base plate in an axially movable manner in order to compensate for a wear of the first treatment profile and the second treatment profile; measuring a distance between the first base plate and the second base plate respectively of the first treatment tool and the second treatment tool of a treatment nip during an operation of the device; and selecting a value of a total power depending on the distance between the first base plate and the second base plate of the at least one treatment nip.

Claims

1. A method for controlling a device for treating a fibrous material, the method comprising the steps of: providing that the device includes a housing in which at least a first treatment tool and a second treatment tool are arranged, the first treatment tool and the second treatment tool: being mounted on a first base plate and a second base plate respectively; having a rotationally symmetrical shape; being arranged coaxially relative to each other in that the first treatment tool and the second treatment tool rotate relative to one another about a common axis; delimiting at least one treatment nip through which the fibrous material flows; and having respectively a first treatment profile and a second treatment profile facing toward the at least one treatment nip; mounting at least one of the first base plate and the second base plate respectively of at least one of the first treatment tool and the second treatment tool in an axially movable manner in order to compensate for a wear of the first treatment profile and the second treatment profile; measuring a distance between the first base plate and the second base plate respectively of the first treatment tool and the second treatment tool of the at least one treatment nip during an operation of the device; and selecting a value of a total power depending on the distance between the first base plate and the second base plate of the at least one treatment nip.

2. The method according to claim 1, wherein the value of the total power is selected depending solely on the distance between the first base plate and the second base plate of the at least one treatment nip.

3. The method according to claim 1, wherein the value of the total power is selected in conjunction with a plurality of additional values, depending on the distance between the first base plate and the second base plate of the at least one treatment nip.

4. The method according to claim 1, wherein the value of the total power is adjusted at least when a change in the distance between the first base plate and the second base plate of the at least one treatment nip of at least 1 mm is detected.

5. The method according to claim 1, wherein the value of the total power is adjusted at a plurality of predetermined time intervals, which is at least every 1 to 2 weeks, depending on the distance between the first base plate and the second base plate of the at least one treatment nip.

6. The method according to claim 1, wherein, after replacing at least one of the first treatment tool and the second treatment tool, a no-load power is measured and is stored in a memory as a starting value for a control system.

7. The method according to claim 6, wherein, for a desired treatment intensity, a relevant specific power of the device, which results from a difference between the total power and the no-load power, is kept constant over an operating period, taking into account a changing no-load power.

8. The method according to claim 1, wherein, after replacing at least one of the first treatment tool and the second treatment tool, a no-load power is measured – when the at least one treatment nip is closed – and is stored in a memory as a starting value for a control system.

9. The method according to claim 1, wherein, in determining the value of the total power depending on the distance between the first base plate and the second base plate of the at least one treatment nip, a plurality of values are accessed.

10. The method according to claim 9, wherein the plurality of values are a plurality of characteristic diagrams stored in a memory of a controller.

11. The method according to claim 1, wherein the method is used in a refiner.

12. The method according to claim 11, wherein the refiner is an LC refiner.

13. A device for treating a fibrous material, the device comprising: a first base plate; a second base plate; a first treatment tool; a second treatment tool; a housing in which at least the first treatment tool and the second treatment tool are arranged, the first treatment tool and the second treatment tool: being mounted on a first base plate and a second base plate respectively; having a rotationally symmetrical shape; being arranged coaxially relative to each other; rotating relative to one another about a common axi; delimiting at least one treatment nip through which the fibrous material flows; and having respectively a first treatment profile and a second treatment profile facing toward the at least one treatment nip, at least one of the first base plate and the second base plate respectively of at least one of the first treatment tool and the second treatment tool being mounted in an axially movable manner in order to compensate for a wear of the first treatment profile and the second treatment profile; a sensor configured for determining a position of an axially movable one of at least one of the first treatment tool and the second treatment tool; and a memory, in which a characteristic diagram is stored, the characteristic diagram containing a dependency of a no-load power depending on a change in a distance between the first treatment tool and the second treatment tool.

14. The device according to claim 13, wherein the device includes a wear indicator configured for treating the first treatment tool and the second treatment tool, wherein the device is configured for triggering a signal when a value associated with the signal falls below a predetermined distance value or a predetermined distance change.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of at least one embodiment of the invention taken in conjunction with the accompanying drawings, wherein:

[0041] FIG. 1 is a schematic cross section through a refiner; and

[0042] FIG. 2 is the change in no-load power P.sub.L and the adjustment of the total power PG over time t and over the distance s between base plates 7,8.

[0043] Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate at least one embodiment of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

[0044] According to FIG. 1, fibrous material 1 is pressed directly into the central, that is the radially inner, region of the refiner fillings, which is formed by the two treatment tools 3,4.

[0045] While one treatment tool 3 is fixed and is thus designed as a stator, the other treatment tool 4 is rotatably mounted in housing 2 of the refiner.

[0046] Treatment tools 3,4 each have a rotationally symmetrical shape, whereby the two circular refining surfaces are arranged parallel to one another. Treatment nip 6 between the refining surfaces is adapted via an axial movement in order to achieve a predetermined total power. The treatment intensity of fibrous material 1 – also referred to as fibrous suspension –flowing into the nip is established by the nip width of treatment nip 6. The axial extent of said nip width of treatment nip 6 is negligible in comparison with the height of treatment profiles 9 of treatment tools 3, 4.

[0047] Rotating refining surface 9 is herein moved in the direction of rotation by a shaft rotatably mounted in housing 2. This shaft is driven by a drive, also provided in housing 2. In the illustrated example, fibrous suspension 1 passes via an inlet through the center into treatment nip 6 between the refining surfaces of both treatment tools 3,4.

[0048] Fibrous suspension 1 passes the interacting refining surfaces in a radially outward direction and exits the adjoining annular space through an outlet.

[0049] Both refining surfaces are formed respectively by several refining plates, each of which extends over a peripheral segment of the corresponding refining surface. Arranged side-by-side in peripheral direction, the refining plates provide a continuous refining surface.

[0050] The refining plates and thereby also the refining surfaces have a treatment profile 9, facing toward treatment nip 6, wherein said profile is generally formed by a multitude of essentially radially progressing refining bars and grooves between them.

[0051] The already known ways with which non-rotating treatment tool 3 is axially moved is not shown. The extent of this axial movement is measured by a displacement sensor. Rotating treatment tool 4 does not change its axial position.

[0052] It can also be measured by way of an incremental encoder on the drive for setting the axial position of the non-rotating but axially movable treatment tool 3 (not shown).

[0053] Furthermore, treatment tools 3,4 are attached to corresponding base plates 7,8.

[0054] In contrast to the example shown here, treatment nip 6 can progress not only perpendicular, but also – as in the case with cone-refiners – inclined toward axis of rotation 5. In addition, housing 2 can also include several, in particular two treatment nips 6.

[0055] FIG. 2 illustrates the change in the real no-load power P.sub.L of the refiner over distance S, which decreases with increasing operating time t and thereby also with increasing wear of treatment profile 9 of treatment tools 3,4.

[0056] The total power P.sub.G, which is supplied to the treatment device consists of the no-load power P.sub.L and the specific power P.sub.S responsible for the treatment intensity, that is the refining power of fibrous material 1.

[0057] The total power is set to a predetermined value that corresponds to the desired treatment intensity at a known no-load power. In order to avoid that the specific power Ps becomes significantly higher over the service life of treatment tools 3, 4 than would be required for the desired treatment intensity of fibrous material 1, the assumed no-load power P.sub.L is adapted accordingly depending on measured distance s between base plates 7, 8 and/or the distance between treatment tools 3,4 by accessing the stored values or the stored characteristics diagram.

[0058] By changing the distance s between base plates 7,8 of treatment tools 3,4 of treatment nip 6 during operation, the total power P.sub.G consumed by the device can be controlled easily and efficiently. It is essential to the present invention that the value of the total power P.sub.G is selected depending on distance s between base plates 7,8 of treatment nip 6.

[0059] The value of total power P.sub.G is herein optionally chosen so that the specific power Ps of the device, which is relevant for the desired treatment intensity, is as constant as possible over the operating time.

[0060] When selecting the value of total power P depending on distance s between base plates 7,8 of treatment nip 6, values stored in the memory of the controller are accessed which are specified by the manufacturer of the device or were determined by the operator of the device during tests.

[0061] The value of total power P specified for the control of the device can be continuously adapted to distance s between base plates 7,8 of treatment nip 6, as shown in FIG. 2 as a dashed line.

[0062] Alternatively, according to the solid line for total power P.sub.G in FIG. 2, it is also possible to readjust the value of total power P.sub.G to distance s between base plates 7,8 of treatment nip 6 at certain time intervals. Alternatively it may also be provided that the total power is adapted depending on change s. The adaptation is based on the no-load power assigned to distance s. The specified value of total power P.sub.G remains constant between the respective adjustments. The slight increase in specific power P.sub.S that has occurred in the meantime can be tolerated.

[0063] The no-load power P.sub.L relevant for the control of the treatment device is updated via the measured distance.

[0064] A no-load power P.sub.L is verified when fibrous material 1 is present during opening and/or closing of treatment nip 6 at normal operating parameters, such as pressure, flow rate and stock consistency. This verification can be scheduled every 1-2 weeks, up to once daily.

[0065] For this purpose, the no-load power P.sub.L of the treatment device is measured when the treatment nip is opened and/or closed, and it is checked whether the assumed value of the no-load power P.sub.L is consistent with the measured value. As a result, a malfunction in the distance measurement can also be reliably detected if the measured value of the no-load power deviates clearly from the value stored for the respective distance.

[0066] Also, on start-up of the treatment device or when treatment tools 3, 4 or their fillings are replaced, the no-load power P.sub.L is measured when treatment nip 6 is closed and is stored in the memory as a starting value for the controller.

[0067] The knowledge of the at least approximately real no-load power P.sub.L not only has an influence on the specific power and the corresponding total power to be regulated, but if a specified, minimum no-load power P.sub.L is not reached a correspondingly high level of wear on treatment tools 3, 4 can be concluded, making replacement of the latter necessary. Provision can also be made for informing the user if a predetermined distance value is not met, so that the user can plan and prepare for an imminently needed replacement of the refining fillings.

[0068] While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.