WO2000001885A1

WO2000001885A1 - Doctor for paper machine

Info

Publication number: WO2000001885A1
Application number: PCT/FI1999/000583
Authority: WO
Inventors: Tuomo Auranen; Mika Saari
Original assignee: Valmet Corporation
Priority date: 1998-07-01
Filing date: 1999-07-01
Publication date: 2000-01-13
Also published as: AU5039599A; FI982358A0; FI104841B

Abstract

A doctor used in a paper machine, which is intended to remove waste pulp from a roll (T1). The doctor (10) is supported on a beam (11). The doctor (10) includes a doctor blade (10.1) and a corresponding blade holder (20.1) that is essentially attached to the front edge of the beam (11). The doctor (10) includes a trough (12) installed on top of the beam (11) after the blade holder (20.1) and a belt conveyor (14). The conveyor belt (14') of the belt conveyor (14) is arranged to travel in the trough (12) and transport the waste pulp removed by the doctor blade (10.1) from the roll (T1) away from the paper machine.

Description

DOCTOR FOR PAPER MACHINE

The present invention relates to a doctor for a paper machine, which is intended to remove waste pulp from the roll and which is supported by a beam attached by bearings to the frame of the paper machine, the doctor includes a doctor blade to be pressed against the roll and a corresponding blade holder essentially attached to the front edge of the beam.

A doctor in a paper machine comprises a doctor blade and a blade holder, which is supported on the frame of the paper machine by means of a beam. Usually there is only a single blade in the doctor, through double-bladed doctors are also used, on account of their effectiveness. In such cases, both blades have their own holders and separate beams, which are set on common frame supports, which are supported by the frame at both ends. The doctor arrangement also often includes devices for turning the doctor blades to the maintenance position and oscillating devices. The oscillating devices are used to move the doctor blade or blades backwards and forwards in the axial direction of the roll.

Doctors are used for purposes such as removing waste pulp from the roll. At the same time, the doctor also cleans the roll surface. During cases of malfunction, for example, in a web break, the waste pulp is guided from the roll over the doctor blade. However, the waste pulp must be immediately moved away from the vicinity of the roll, to avoid further problems. In particular, the transfer of waste pulp using press rolls is problematic, because waste pulp cannot be guided downwards by gravity. Due to this, various kinds of additional devices have been developed for use with a doctor, to move the waste pulp away from the doctor. In one known doctor, a channel is formed at the rear of the doctor behind the doctor blade, in which the broke collects. However, the ability of the channel to move the waste pulp is altogether inadequate in relation to the waste pulp being removed by the doctor, and the channel is very liable to become blocked. In addition, in a malfunction, the cleaning of the doctor and channel is slow. At worst, the operating personnel must clear the channel by hand, which is a highly questionable operation in terms of work safety.

Another solution is to use a separate broke conveyor beneath and after the doctor, installed on its own frame. This solution is complicated and expensive, due to the two separate frames and the equipment connecting them. In addition, there is a considerable number of places requiring later cleaning. The installation of the totality of the doctor and broke conveyor is often difficult, precisely on account of the lack of space. With a double-bladed doctor, the lack of space is emphasized even more. The known doctor and broke conveyor construction is large and its location is often problematical, especially in older machines. For example, there is very little space for a construction of this kind in connection with separate press sections. In addition, the doctor is cleaning using a special lubricating spray, which must be dimensioned to be sufficiently large for possible malfunctions.

The invention is intended to create a new kind of doctor and related arrangement for moving waste pulp away from the roll. The characteristics of this invention are disclosed in the accompanying Claims. According to the invention, the support beams of the doctor are used to support a broke conveyor. This avoids a separate broke conveyor, substantially reducing the space required for the doctor arrangement. In addition, the broke conveyor is located immediately behind the doctor blade, which reduces the number of surfaces requiring cleaning. Besides removing the waste pulp, the broke conveyor can be used to remove the liquid coming with the waste pulp from the paper machine. An auxiliary gutter can be installed between the support beams in the double doctor to remove the waste pulp detached by the second doctor blade.

In the following, the invention is described in detail, by reference to the drawing depicting one embodiment of the invention, in which

Figure 1 shows a rear view of a doctor according to the invention, Figure 2 shows side view of a doctor according to the invention, turned to the maintenance position, Figure 3 shows a cross-section of the doctor in Figure 2, in the operating position,

Figure 4 shows a cross-section of another embodiment of a doctor according to the invention, in the operating position.

Figure 1 shows a doctor arrangement according to the invention. The rolls of the paper machine are not shown. According to the invention, the broke conveyor is a belt conveyor 14, which removes from the roll position the waste pulp detached by doctor blade 10.1 from roll Tl. The drive devices and rollers of the belt conveyor 14 are located outside the frame 19 of the paper machine, where there is generally sufficient space. In the example, the frame structures of the belt conveyor 14 attached to the press are not shown in full in Figure 1. The covers, however, are shown by broken lines. Conveyor belt 14' runs in an unbroken loop around drive roller 15 and, on the opposite side, around guide roller 16' of tensioning device 16. Tensioning device 16 also includes devices for loosening conveyor belt 14' (not shown), so that doctor 10 can be turned to the maintenance position. For this purpose, tensioning device 16 incorporates a quick-release lock on the front side. The quick-release lock also provides locking to prevent the doctor turning. Figure 2 shows doctor 10 turned to the maintenance position.

Doctor 10 is supported in its entirety by means of bearings 23 5 on the frame 19 of the paper machine. In addition, the arrangement includes a conventional oscillating device 21, which is connected to doctor 10 through shaft 22. Doctor 10 also includes channels 26 for transporting the waste pulp from doctor 10 through frame 19. There are similar channels 26 on 10 both sides of doctor 10, so that the direction of movement of belt conveyor 14 can be selected as being towards either the front or the drive side. The oscillating movement of the doctor 10 does not, however, affect the operation of the broke conveyor 14 and channels 26.

15

In Figure 2, the press rolls are marked with the reference numbers Tl and T2. Reference number 10 is used to generally mark a doctor according to the invention, in which there are two doctor blades 10.1 and 10.2 and blade holders 20.1 and

20 20.2. The blade holders 20.1 and 20.2 are installed in support beams 11 and 11', which are supported through common flanges 24 by bearings 23. Figure 3 shows the construction of doctor 10 in greater detail. According to the invention, doctor 10 includes a trough 12 installed on beam 11 after blade holder 20.1, and

25 a belt conveyor 14, which is arranged as a broke conveyor. Conveyor belt 14' of belt conveyor 14 is arranged to travel in trough 12 and transport waste pulp removed from roll Tl by doctor blade 10.1 to the side of roll Tl, from where it can be easily taken to a slusher. In the rear of trough 12, there is

30 a high wall 25, which directs the waste pulp to travel parallel to trough 12. Trough 12 overlaps channels 26, which extend through frame 19, in the manner shown in Figure 1. Channels 26 are fixed in position, but trough 12 forms part of doctor 10 and turns along with doctor 10.

35 Trough 12 also includes a false bottom 13, on either side of which the lower and upper runs 14.1 and 14.2 of conveyor belt 14' are arranged to travel. This construction takes up little space and protects and guides conveyor belt 14'. In trough 12, false bottom 13 preferably forms a closed space 27 open at the ends, essentially over the length of beam 11, in which lower run 14.1 is arranged, with upper run 14.2 travelling on top of false bottom 13. In this case, the belt runs 14.1 and 14.2 do not interfere with each other, so that the waste pulp will travel through trough 12 in the desired direction.

According to the example, a doctor according to the invention may include more than one doctor blade. In this case, there are two doctor blades, the lower doctor blade 10.2 also including holder 20.2 and beam 11', as well as auxiliary gutter 18 set on top of beam 11'. Because the amount of broke removed by the second doctor blade 10.2 is considerably smaller than that removed by the first doctor blade 10.1, the water jets 17 arranged in auxiliary gutter 18 are sufficient to transport the waste pulp along auxiliary gutter 18.

Figure 4 shows an embodiment of a single-beam doctor according to the invention. The same reference numbers are used for the operational components as were used in connection with the double-beam described above. Both of the doctors described operate on the same principle.

The doctor according to the invention is small and has a compact construction. The doctor includes few components, so that it has advantages over previous types, in terms of both cost and operation. The broke coming from the doctor goes straight to the conveyor belt and not onto the beam, as previously happened. This reduces the use of flushing water. In addition, blade lubrication water need no longer be used to flush the doctor beam. Other significant advantages include the reduction of the paper machine cleaning time and the speeding up of the web tail-threading and production stabilization. There are only few parts in the belt conveyor connected to the turning frame of the doctor. Their weight places hardly any stress on the normal frame of the doctor. Thanks to its construction, the drive devices of the belt conveyor can be placed on the frame structures to the side of the rolls, where there is plenty of room for installation and maintenance.

Claims

PATENT CLAIMS

1. A doctor used in a paper machine, which is intended to remove waste pulp from a roll (Tl) and which is supported on a beam (11) attached to the frame (19) of the paper machine by bearings, the doctor (10) including a doctor blade (10.1) that presses against the roll (Tl) and a corresponding blade holder

(20.1) that is essentially attached to the front edge of the beam (11), characterized in that the doctor (10) includes a trough (12) installed on top of the beam (11) after the blade holder (20.1) in the direction of travel of the waste pulp, and a belt conveyor (14), the conveyor belt (14') of which is arranged to travel in the trough (12) and transport the waste pulp removed by the doctor blade (10.1) from the roll (Tl) away from the paper machine.

2. A doctor according to Claim 1, characterized in that the trough (12) has a false bottom (13), on either side of which the lower run (14.1) and upper run (14.2) of the conveyor belt (14') are arranged to travel.

3. A doctor according to Claim 2, characterized in that the false bottom (13) is arranged to form in the trough (12) a closed space open at the ends and essentially extending over the length of the beam (11), in which the lower run (14.1) is arranged, while the upper run (14.2) is arranged to travel on top of the false bottom (13) .

4. A doctor according to one of Claims 1 - 3, characterized in that the doctor (10) includes a second doctor blade (10.2) with a holder (20.2) and a beam (11') and an auxiliary gutter (18) installed on top of beam (11') to transport the waste pulp removed by the second doctor blade (10.2) from the roll (Tl) away from the paper machine.

5. A doctor according to Claim 4, characterized in that water jets (17) are arranged in connection with the auxiliary gutter