TECHNICAL FIELD OF THE INVENTION

The invention relates to an end wall of a pulp dryer, a pulp dryer, and a method for observing the inner parts of a pulp dryer according to the preambles of the independent claims presented below.

In a modern pulp dryer, a web formed of pulp, i.e. a pulp web, is conveyed along a multi-layered path by floating it on an air cushion formed with blow nozzles. The blow nozzles are arranged in several superimposed, generally horizontal nozzle levels having almost the length of the pulp dryer. The pulp web is typically introduced into the pulp dryer through its first end, the so-called wet end. Normally, the pulp web enters the pulp dryer at its upper part, through an inlet opening arranged in the upper part of the end of the dryer. Then the pulp web is conveyed along the uppermost nozzle level of the pulp dryer to the second end of the dryer device. At its ends, the dryer is typically provided with turn rolls, over which the pulp web is turned each time to the next, lower nozzle level. After having been conveyed to the lowest nozzle level of the pulp dryer, the pulp web is removed from the pulp dryer, typically through the second end of the pulp dryer. The pulp web is removed from the pulp dryer at its lower part, through an outlet opening arranged in the lower part of the second end of the dryer. A pulp dryer typically comprises 15 - 30 nozzle levels. The gas blown from the blow nozzles is typically hot air, the blow air generally having a temperature of 120 - 170 ⁰ C. When entering the pulp dryer, the pulp web typically has a dry solids content of 48 - 54%. The dry solids content of the pulp web leaving the pulp dryer is typically 85 - 95%, most typically approximately 90%. The pulp web can have a width of 12 m, typically 3 - 1O m, more typically 6 - 10 m. The pulp web is typically conveyed at a speed of 140 - 220 m/min in the pulp dryer.

The pulp dryers are typically provided, at their both ends, i.e. end faces, with several rows of access doors, which rows are one above the other and comprise a number of several adjacent access doors. The access doors are closed in a normal running situation of the pulp dryer, and in a maintenance situation, such as after a web break, the access doors can be opened. Via an access door, it is possible to perform operations for example at the turn rolls. The pulp dryers are typically provided, at both ends, with a moving maintenance bridge having the width of the entire dryer, on which maintenance bridge an operator can work and from which he can reach the inner parts of the pulp dryer when one or more rows of access doors are opened. An access door is normally hinged by its lower part to the end wall of the pulp dryer, and in an open position the access door "hangs" from its hinges and leans on to the end wall.

The access doors are traditionally rather low, i.e. their height is less than a half of the diameter of the turn roll. Due to this, performing of maintenance operations at the turn roll in case of a web break is difficult due to a low and narrow working space, and taking auxiliary equipment to the roll is difficult. At present, the operators need to bring the broke manually from the turn roll to a broke removal device of the movable maintenance bridge. This is time consuming, very unpleasant and hard work. There have been attempts to solve the problem by placing two low rows of access doors at the turn roll, of which rows one is partly above the roll and the other partly below it. However, this does not make it completely easier in all situations to perform the operations taking place inside the pulp dryer.

OBJECT AND BRIEF DESCRIPTION OF THE INVENTION

It is an object of the present invention to reduce or even eliminate the above- mentioned problems appearing in prior art.

An object of the invention is to provide an end wall of a pulp dryer, which end wall enables a simple performing of the service and maintenance operations taking place at the turn rolls of the pulp dryer. An object of the present invention is especially to provide a solution whereby the observing of the turn rolls of the pulp dryer for example during tail threading is considerably easier than at present.

In order to realize the above-mentioned objects, among others, the invention is characterized by what is presented in the characterizing parts of the enclosed independent claims.

Some preferred embodiments according to the invention are disclosed in the dependent claims presented further below.

The embodiment examples and advantages mentioned in this text are in suitable parts applicable to both the device and the method according to the invention, even if this is not always specifically mentioned.

A typical end wall of a pulp dryer according to the invention comprises an upper edge and a lower edge, the distance between which defines the height of the end wall, and between which upper and lower edges there is arranged

- an opening for introducing a pulp web into the pulp dryer or for removing the web from the dryer,

- one or more openable end wall elements for observing the inner parts of the pulp dryer and for performing maintenance operations, the end wall element being arrangeable to a closed and an open position in order to cover or to expose a turn roll located in the inner part of the pulp dryer, whereby the height of the openable end wall element is at least 50% of the distance between the axes of the pulp dryer's two turn rolls that are one above the other, adjacent and closest to each other and exposed in the open position.

In a typical method according to the invention for observing the inner parts of a pulp dryer and for performing maintenance operations

- an end wall element located in an end part of the pulp dryer is opened in order to expose a turn roll located in the inner part of the pulp dryer, whereby by opening one end wall element a height that is at least 50% of the distance between the axes of the pulp dryer's two turn rolls that are one above the other and exposed in the open position is exposed from the inner part of the pulp dryer.

A typical pulp dryer according to the invention comprises at least one end wall according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

It has now been surprisingly found out that by enlarging the size of an openable end wall element, the occupational safety, workplace ergonomics and work efficiency can be improved. A higher end wall element offers the operators considerably better possibilities for carrying out the tasks performed in the end part of the pulp dryer, especially at the turn rolls, than the solutions according to prior art. An advantage of the invention is also that each end wall element being larger than before, their number is reduced. At the same time, the thermal loss occurring via the thermal bridges of the openable structures is reduced, as a great part of the thermal loss of a pulp dryer occurs via the edges of the present openable access doors and the gaps between them. As the number of the openable structures is reduced, also the added total length of their edges is reduced. By reducing the thermal losses it is clearly possible to affect the drying capacity of a pulp dryer and to increase its capacity.

An advantage of the invention is also that the possibility for observing the inner parts of a pulp dryer is considerably improved. Thus, for example in case of a web break, it is easier to notice any possible broke that has remained on the drying level of the pulp dryer. By opening an end wall element according to the invention, it is possible to observe an individual drying level even by the entire length and width of the pulp dryer in order to detect any possible additional material that has remained on the drying level.

In this application, by an open position of an end wall element is meant a position in which the end wall element is arranged to expose parts of the inner part of the pulp dryer. Thus, the end wall element in the open position may have been turned or folded away from the plane formed by the end wall, or it may have been transferred above or underneath the end of the pulp dryer, or to the side of the pulp dryer. This allows free observation of the inner part, or at least part of the inner part, of the pulp dryer. In this application, by a closed position of an end wall element is meant a position, in which the end wall element is arranged to cover the inner part of the pulp dryer. In the closed position, the end wall element is arranged to the same plane with other surfaces and/or wall elements forming the end face, so that a uniform end wall surface is formed.

The height of an end wall element is typically at least 65 %, preferably at least 70 %, more preferably at least 75 %, even more preferably at least 80 %, particularly preferably at least 85 %, and even more preferably at least 90 %, even at least 95 % of the diameter of an individual turn roll of the pulp dryer exposed in the open position of the end wall element. According to a preferred embodiment of the invention the height of an openable end wall element is equal or larger than the diameter of the pulp dryer's turn roll exposed in the open position. The height of the end wall element is typically at most 400 %, sometimes at most 300 %, sometimes at most 200 %, preferably at most 175 %, very preferably at most 160 %, more preferably at most 155 %, particularly preferably at most 150 %, even more preferably at most 140 %, typically at most 130 %, even more typically at most 120 %, most typically at most 110 % of the diameter of the pulp dryer's turn roll exposed in an open position. According to an embodiment of the invention, the height of an end wall element is at least 50 cm, typically at least 60 cm, preferably at least 70 cm, even more preferably at least 90 cm, sometimes even at least 100 cm, or at least 200 cm.

According to an embodiment of the invention, the height of an openable end wall element is typically at least 65%, preferably at least 70%, more preferably at least 75%, even more preferably at least 80%, very preferably at least 85%, even more preferably at least 90%, even at least 95% of the distance between the axes of two turn rolls of the pulp dryer that are one above the other an exposed in the open position. Very typically, by opening one end wall element, 1 - 8, more preferably 2 - 5 turn rolls of the pulp dryer are exposed simultaneously. The height of the end wall element can be typically 100%, more typically 150%, even more typically 200%, preferably 300%, more preferably 400%, even more preferably 500%, very preferably even 600% of the distance between the axes of two adjacent turn rolls of the pulp dryer that are one above the other.

The present invention intended to be preferably used in modern pulp dryers, the web width of which is typically 7 - 10 meters, sometimes even 11 - 13 meters, and the height of which may even be 20 meters. The height of an end wall element can thus even be several meters, usually > 2 meters, even 5 - 10 meters. Other details of a modern pulp dryer, such as drying i.e. nozzle levels, have also been described earlier in this application. A pulp dryer thus comprises a number of drying levels which in turn comprise drying sections formed of drying means. A pulp web is led to an air dryer normally at its upper part, the dry matter content of the web being approximately 45 - 55, typically 50% by weight. The web is carried on a drying level preferably in a contact-free manner, for example by means of air blows generated by drying means. The web is removed from the lower part of the air dryer, when its dry matter content is approximately 90% by weight. Typically, one or two lowermost levels of the air dryer function as cooling levels of the web to be dried. Typically, an air dryer has 15 - 30 drying levels.

Typically, to an end face of a pulp dryer it may also have been arranged a maintenance bridge extending over the width of the pulp dryer, which bridge can be moved in the height direction of the pulp dryer and from which necessary maintenance operations of the inner parts and turn rolls of the pulp dryer can be performed.

Generally, a dryer suitable for drying a pulp web or the like comprises

- an actual drying area, in which the pulp web is dried in air-float drying by means of hot air jets or the like,

- blow towers arranged adjacent to the actual drying area, by blowers of which towers moist circulation air is removed from the actual drying area and by means of which heated circulation air is blown to the actual drying area, and - heating devices by means of which removed moist circulation air is heated before returning it as drying air to the actual drying area.

So-called roll towers are located at the ends of a pulp dryer, to which towers mainly superimposed turn rolls have been arranged, by means of which turn rolls the web to be dried is turned from one drying level to the next. At the same, the travel direction of the web changes by 180°. The axes of the rolls have been arranged to be parallel in the roll towers. The turn rolls are usually of the same size, i.e. their diameters are equal.

In an embodiment of the invention the height of an end wall element can be substantially the same as the height of an end wall of the pulp dryer. An individual end wall element then extends, in practice, from the lower edge or from near the lower edge of the pulp dryer's end part to the upper edge or near the upper edge of the pulp dryer. The height of the end wall element can then be at least 65 %, preferably at least 75 %, more preferably at least 80 %, even more preferably at least 85 %, most preferably at least 90 %, even more preferably at least 95 %, even at least 97 % of the height of the end wall of the pulp dryer.

To an end of the a pulp dryer, one or several openable end wall elements can be arranged. Separate end wall elements can be arranged one above the other in the height direction of the end of the pulp dryer or they can be arranged side by side in the width direction of the end of the pulp dryer. The end wall elements can be arranged to cover the entire end wall of the pulp dryer or they can be arranged at a distance from one another so that there is free end wall surface between them. The end wall elements can all be of same size, or the end wall may comprise several end wall elements, for example on several levels one above the other, whereby the height of the end wall elements in different levels differs from one another, the height being, however, uniform on one level. In one embodiment, the end wall of the pulp dryer comprises several end wall elements of the same height. According to an embodiment of the invention, all of the end wall elements being in an open position, at least 55 %, typically at least 60 % of the area of the end wall is arranged to be open to the machine room. This enables opening of the end wall of the pulp dryer by its major part or even entirely. According to a preferred embodiment, at least 65 %, preferably 75 %, most preferably 80 %, more preferably 85 %, even 90 %, sometimes even 95 % of the total area of the end wall of the pulp dryer can be arranged to be openable. This enables, inter alia, a faster cooling of the inner parts of the pulp dryer for example in case of a malfunction, whereby the maintenance operations taking place at the pulp dryer become quicker and easier to perform. The size of individual end wall elements being larger than at present enables guiding of larger amounts of cooling air into the inner parts of the dryer. "Cool" machine room air can also be guided, if needed, to a desired location of the end wall, towards certain opened end wall elements in order to cool a certain location inside the end part of the pulp dryer. In this manner, possible energy losses from the pulp dryer to the machine room can be minimized and at the same time safe working conditions at required locations of the pulp dryer can be ensured.

In a preferred embodiment of the invention, the entire outer surface of the end wall of the pulp dryer is formed by openable end wall elements. Then the end wall of the pulp dryer can be entirely opened for example during tail threading or during broke removal and cleaning after a web break. It has been estimated that performing of such operations becomes much quicker when the operators have the possibility to work freely in the vicinity of the turn rolls and when the events inside the dryer can be better observed as a whole. It is clear that, when the entire outer surface of the pulp dryer's end wall is formed of end wall elements, it is not always necessary to open the entire end wall of the pulp dryer. For example during tail threading, the process can be monitored by arranging a required number of the end wall elements to be in the open position.

An end wall element can be arranged to open in the sideward, i.e. width direction of the end wall against the height direction of the end wall. One end wall element can comprise at least two, preferably more partial elements, such as three, four, five, six, eight or ten separate partial elements, which can be arranged in a closed or open position. The partial elements can be arranged into connection with each other so that they are arranged to open simultaneously. In an embodiment of the invention, the partial elements of the end wall can be arranged into connection with each other, i.e. with adjacent partial elements, at the edges parallel with the height direction of the end part of the pulp dryer, so that they can be arranged to open in the manner of a folding door. Then the end wall element opens in the width direction of the end of the pulp dryer, i.e. the opening movement of the elements occurs substantially horizontally in the direction of the upper and lower edges of the end. An individual partial element of the end wall can be perceived to form an individual door leaf of the created "folding door". The partial elements can be fixed to each other by suitable hinge means in order to open the end wall of the pulp dryer. The end wall can comprise one end wall element, whereby substantially all of the turn rolls located in the end of the pulp dryer are exposed by moving said end wall element into an open position in the width direction of the end wall. The end wall can also comprise two end wall elements, which are arranged to open into opposite directions in the width direction of the end wall.

In another embodiment of the invention individual partial elements of the end wall element can be arranged into connection with each other so that when opening the end wall the partial elements form a tambour door -like end wall element. A tambour door -like end wall element can be arranged to open either in the height or the width direction of the end wall. The partial elements that are in contact with each other can be moved into an open position for example on top of or under the pulp dryer, for example into the spaces located under the machine room space. An end wall element can also be moved in the width direction of the end wall, whereby it is in an open position on the side of the pulp dryer. Individual partial elements can also form two tambour door -like end wall elements, the first of which is moved into an open position on top of the pulp dryer and the other under the pulp dryer, or alternatively on both sides of the pulp dryer. According to an embodiment of the invention it is also possible to arrange the partial elements of the end wall to open in the manner of a lever gear door in the height direction of the end wall. The end wall elements can be connected with suitable connection means to each other at the edges parallel with the width direction of the end wall, and an end wall element comprising partial elements can be arranged in an open position in the upper or lower part of the pulp dryer's end wall.

The end wall of a pulp dryer can also be divided into several separate sections, such as for example into two, three or four, sometimes even five sections, whereby an end wall element covering an individual section can be opened independently from the end wall elements covering the adjacent or other sections.

The end wall can be divided into sections either in the height or in the width direction of the end wall. An individual section can be covered by one end wall element, which can comprise several partial elements, or an individual section can be covered by two end wall elements opening into opposite directions, which can both comprise several partial elements.

According to an embodiment of the invention, the end wall comprises at least two end wall elements one above the other, of which each end wall element comprises an equal number of partial elements. Then the partial elements located one above the other of the end wall elements can be arranged to be opened simultaneously in the height direction of the end wall. In this manner, a desired part of the turn rolls located in the end part of the pulp dryer can be exposed, for example during tail threading.

In an embodiment of the invention, the end wall comprises guides for moving the end wall elements or the partial elements. The end wall elements can be arranged to move along the guides so that they can be glided from a closed position to an open position or vice versa. Thus, the edges of the end wall elements or of the partial elements can be provided with disc means of the like, which can be fitted in a recess, a groove or a corresponding guide means of the guides, and with which the elements can be moved. In another alternative the end wall element or its individual partial elements can be provided with hinges, which can be fixed to said guides. By means of the hinges the elements can be closed to a closed position, whereby they cover the turn rolls located in the end part of the pulp dryer and form a substantially planar surface, and opened to an open position, whereby the turn rolls located in the end part of the pulp dryer are exposed. In an open position the end wall elements or the partial elements can be for example in an angle of 90 degrees with respect to their closed position.

According to a preferred embodiment of the invention, the end wall elements or the partial elements of an end wall element can be arranged against each other, the main surfaces of the partial elements against each other in the open position.

It is also possible that the upper and lower edges of the end wall elements be provided with leading means, which are arranged to travel along the upper and lower guides arranged in the end part of the pulp dryer. The end wall elements are moved away from the front of the turn rolls along the upper and lower guides in the width direction of the end part of the pulp dryer. When the end wall elements are arranged on the side of the end part, they can be arranged in an open position so that the leading means of the first upper and lower edge of the end wall elements are released from the upper and lower guides, whereby the end wall elements are connected to the upper and lower guides only via the leading means of their second edge. The end wall elements can then be arranged for example against each other, the main surfaces against each other perpendicular to the height and width directions of the end wall.

According to an embodiment of the invention the leading means can be arranged in the upper and lower edge of an end wall element or of a partial element so that the element/elements can be turned by, for example, 90 degrees around the axis traversing the leading means. The turned elements can be arranged along a guide means away from the turn rolls for example into the edge of the dryer. Then the element/elements are arranged partly inside the pulp dryer in an "open" position, which saves space in the machine room. Typically and advantageously in the present invention end wall elements are not entirely detached from the supporting structures of the end wall of the pulp dryer or from the guide or supporting structures. End wall elements can for example be moved along different guides or guide means, or they can be folded to an edge of the end wall, but usually, some part of the end wall element remains in contact with the end wall or the supporting structure and connected to it. With the present invention, it is thus possible to allow easy and light moving of considerably large end wall elements between open and closed positions. This improves the ergonomic working conditions of the operating personnel, especially when the work is done on a maintenance bridge moving in the height direction of the end wall.

The end wall element can be made of two parts, i.e. it can be double-walled, whereby the end wall element comprises an outer surface or wall parallel to the end wall, and an inner surface or wall parallel to the outer surface or wall, between which walls or surfaces heat insulation medium is arranged. In this manner the insulation of the warm inner parts of the pulp dryer from the machine room can be intensified and possible thermal losses can be minimized. The thermal insulation medium can be an insulation material made from mineral fibers, such as glass wool or rock wool, stationary insulating gas, such as air, or a vacuum. There may be several parallel walls in the end wall element, if needed, i.e. it is possible to arrange a required number of partition walls between the outer wall and the inner wall. It is possible to arrange a similar or a different medium between the inner, outer and partition walls of the end wall element.

In an embodiment of the invention, gas, preferably dry and cool air from the machine room, can be blown into the space located between the inner and outer walls of the double-walled end wall element. When air from the machine room is blown to the space located between the walls of the double-walled end wall element, this air cools the inner wall in contact with the inside of the pulp dryer. Thus, the surface of the inner wall is cool. When the moist and hot air that is in the inner part of the pulp dryer comes into contact with this cool wall surface, a controlled condensation takes place, and a part of the moisture of the indoor air of the pulp dryer condenses on the wall surface wherefrom it can be removed with suitable removal arrangements. To the lower part of the end wall element may have been arranged for example a trough-like guide to which the condensed moisture flows along the wall surface and along which trough the condensed moisture can be removed from the inner part of the pulp dryer. In this way, indoor air of a pulp dryer can be dried and cleaned in a simple manner, because usually also some amount of dust and other small particles inside the pulp dryer are bound to the condensed moisture. By adjusting the temperature and quantity of the air to be led between the inner and the outer walls of the end wall element, the amount of water condensing on the surface of the inner wall can be adjusted in a simple manner.

Preferably, air is led to the outer wall facing the machine room of the double- walled end wall element through an inlet slot or opening arranged at a first height into the end wall element, to the intermediate space between its inner and outer walls. The air is led in the intermediate space towards an outlet slot or opening arranged to the inner wall, facing the inner part of the dryer, of the end wall element, which slot or opening is arranged at a different height from the inlet slot or opening, preferably higher than the inlet slot or opening. As the air travels in the intermediate space defined by inner and outer walls of the end wall element, it cools down the inner wall and simultaneously itself warms up, so that the air entering through the outlet slot to the inner part of the pulp dryer is warmer than the air in the machine room. Thus, pre-heating of the drying and replacement air to be introduced to a pulp dryer and drying of the indoor air of a pulp dryer by means of a controlled condensation on the inner surface of the end wall element can easily be achieved simultaneously. It is also possible to lead cooled air into a double-walled end wall element, the temperature of which air is substantially lower than the temperature of the air in the machine room. Typically, the temperature of the air in the machine room is 20 - 3O ⁰ C, and the temperature of the air in the inner part of a pulp dryer is approximately 100 ⁰ C. The temperature of the cooled air can for example be 10 - 15°C. Materials in use at present, such as steel, can be used as the material of the end wall element. In a preferred embodiment of the invention, the end wall element or its individual partial elements are however made, at least partly, of a substantially transparent material, such as glass or plastic. Of the surface of the end wall element, at least 45%, preferably at least 55%, more preferably 65%, even more preferably 75%, sometimes even 90% can be made of transparent material. In an embodiment of the invention, the end wall of a pulp dryer comprises one or several end wall elements that are made of entirely or almost entirely transparent material. This enables observing of the pulp dryer's turn rolls also during the operation of the pulp dryer. Thus, the operators are able to react faster and at an earlier stage to possible problems arising at the turn rolls. In a problem situation it is also possible to faster locate the problematic location, and any unnecessary opening of the end wall element or its partial elements can be avoided. The end wall element can also be made of a flexible material, such as plastic or rubber, whereby it can be rolled up into an open position.

It is clear that the first, second or both end walls of the pulp dryer can comprise any of the solutions according to the invention.

It is also an advantage of the invention that the sizes of the end wall elements or their partial elements can be standardized. Thus, in practice only a few different element sizes can be manufactured, whereby their manufacturing processes can be more easily automatized and streamlined. The end wall of the pulp dryer can be made by combining standardized end wall elements or their partial elements. Pulp dryer ^' s end walls of a different size can therefore be made of individual elements of a same size by combining them- in an appropriate manner. Then it is not any more necessary to tailor a suitable end wall for each pulp dryer right from the beginning, which naturally provides savings in the planning and manufacturing costs.

According to a preferred embodiment of the invention, the end wall elements or their partial elements are arranged to open so that in the open position they will not hinder the opening of the adjacent or other end wall elements or partial elements. In the open position, the end wall elements or their partial elements do not preferably also cover the view into the inside of the pulp dryer exposed from behind the adjacent end wall elements or their partial elements, which are in the open position.

In an embodiment of the invention, sealing means are arranged to the edges of an end wall element or of its partial element, with which sealing means a gap-like space possibly located between the edges of adjacent elements or partial elements can be sealed and closed for minimizing the thermal losses. In this case, partial elements forming one end wall element have not been connected fixedly to each other, but they are sealed to each other with sealing means.

BRIEF DESCRIPTION OF THE FIGURES

The invention is described in more detail below with reference to the enclosed schematic drawing, in which

Figure 1 shows a part of an end wall according to an embodiment of the invention,

Figure 2 shows a part of an end wall according to another embodiment of the invention,

Figures 3A - 3E show an end wall element's opening mechanism according to a further embodiment of the invention as seen from above,

Figure 4 shows an end wall element's opening mechanism according to still a further embodiment of the invention as seen from above,

Figures 5A and 5B show a pulp dryer, which is provided with ends according to an embodiment of the invention as seen from the side, and Figures 6A - 6C show an end wall element's opening mechanism according to a further embodiment of the invention as seen from above.

DETAILED DESCRIPTION OF THE EXAMPLES OF THE FIGURES

Figure 1 shows a part of a pulp dryer's end wall according to an embodiment of the invention. The figure shows two end wall elements 2, 2', of which the first end wall element 2 can be arranged into an open position to the tending side of the pulp dryer and the second end wall element 2' can be arranged into an open position to the driving side of the pulp dryer. The opening directions of the end wall elements 2, 2' are indicated by arrows a, a' in figure 1. The end wall element 2 comprises four partial elements 3, 3', 3", 3'", which are arranged to open into the tending side in the manner of a folding door. Two partial elements 3, 3" are provided with transfer means 4, 4', such as gripping handles, with which the partial elements can be transferred from a closed position to an open position. Respectively, the second end wall element 2' comprises six partial elements opening in the manner of a folding door. The individual partial elements are fixed to each other by hinge means 5, 5', 5". The partial elements are arranged to travel along the guiding means 6, 6' arranged at the upper and lower edges of the partial elements. The upper and/or lower edges of the partial elements are provided with leading means (not shown), which are arranged into connection with the guiding means 6, 6' so that the partial elements can be moved along the guiding means.

In an open position the end wall elements 2, 2' enable servicing measures at two turn rolls 7, 7' of the pulp dryer one above the other. In the case presented, the height of the end wall elements 2, 2' is about two times the distance b between the axes of rolls that are one above the other.

Figure 2 shows a part of an end wall 1 according to another embodiment of the invention, comprising four end wall elements 22, 22', 22", 22'". Each of the individual end wall elements 22, 22', 22", 22'" comprises two partial elements 23, 23'. The end wall elements are arranged one above each other in two levels 11 , 11' so that the partial elements 23', 23' of the first upper 11 and the second lower 11' levels are one above the other. The end wall elements 22, 22" can be arranged simultaneously into an open position, if necessary, whereby the second edge of the pulp dryer is exposed for observing. The end wall elements 22, 22" can be arranged into an open position on the tending side of the pulp dryer and the end wall elements 22', 22'" can be arranged into an open position on the driving side of the pulp dryer. The opening directions of the end wall elements 22, 22' of the first level 11 are indicated by arrows a, a' in figure 2. The end wall elements 22", 22'" of the second level 11 ' are opened in a corresponding manner. Each individual end wall element 22, 22', 22", 22'" can also be arranged into an open position independently from each other. The partial elements 23, 23" are provided with transfer means in a manner corresponding to that of figure 1. In an open position the end wall elements 22, 22' enable service operations at four turn rolls 27, 27', 27", 27'" of the pulp dryer one above the other. In the case presented, the height of the end wall elements 22, 22', 22", 22'" is about four times the distance b between the axes of rolls that are one above the other.

In figures 1 and 2 the partial elements of the end wall elements can be made of a substantially transparent or translucent material. Thus, it is possible to observe the turn rolls by visual inspection without arranging the end wall elements into an open position.

Figures 3A - 3E show an end wall element's opening mechanism according to a further embodiment of the invention as seen from above. Figure 3A shows an end wall element 32 comprising several partial elements 33, 33', 33", 33'" in a closed position, i.e. the end wall element is arranged to cover at least a part of the inner part of the pulp dryer. The partial elements 33, 33', 33", 33'" are connected to each other by hinge means 35, 35', 35", 35'" via their lateral edges, which are parallel with the height direction of the pulp dryer. In connection with some hinge means 35, 35" there are arranged transfer means 34, 34' with which it is easier to move the partial elements 33, 33', 33", 33'" when arranging the end wall element into an open position.

In figure 3B arranging of the end wall element 32 into an open position has been started by moving the partial elements 33, 33' so that they start to group against each other. The movement of the partial elements thereby takes place in the width direction of the pulp dryer. At the hinge means 35', 35"' there are arranged leading means, with which the partial elements can be moved along the guides suitably arranged in the end of the pulp dryer. The leading means and guides are not presented for the sake of clarity of the figure.

In figure 3C the partial elements 33, 33' are completely grouped into an open position. It can be noticed that the end wall element 32 is partly open.

In figure 3D the final arranging of the end wall element 32 into an open position has been started by moving the partial elements 33", 33'" in the width direction of the pulp dryer towards the partial elements 33, 33', which are already arranged in an open position.

In figure 3E the end wall element 32 is entirely arranged in an open position their main surfaces against each other, preferably on the side of the pulp dryer, on the tending side or on the driving side.

It is clear that the solution presented in figures 3A - 3D also suits for situations, where the end wall element is arranged in an open position in the height direction of the pulp dryer. In such case the hinge means are fixed in the upper or lover edges of the partial elements, and the guiding means travel in the height direction of the pulp dryer.

Figures 4A and 4B show an end wall element's opening mechanism according to a further embodiment of the invention as seen from above. In figures 4A and 4B the end wall element 42 comprises four partial elements 43, 43', 43", 43'", which are connected to each other by hinge means 45, 45', 45". The end wall element 42 also comprises transfer means 44, 44'. In the embodiment shown in figures 4A and 4B the guiding means 48, 48', 48", 48'" are however arranged in the upper and/or lower edge of the partial element 43, 43', 43", 43'", however not at the hinge means 45, 45', 45". In figures 4A and 4B the guiding means 48, 48', 48", 48'" are arranged in the middle of the edge of an individual partial element 43, 43', 43", 43'", but it is clear that they can be arranged also to some other location in the edge of the partial element, if desired.

Figure 4A shows the end wall element 42 in a closed position, whereby it covers the turn roll or turn rolls located in the end of the pulp dryer. In figure 4B the end wall element 42 is arranged in an open position, which enables observing of the inner parts of the pulp dryer. The partial elements 43, 43', 43", 43" are arranged in the end part of the guiding means 46 by moving the leading means 48, 48', 48", 48'" along the guiding means 46 in the width or the height direction of the pulp dryer. At the same time, the partial elements 43, 43', 43", 43" are turned in the open position partly into the pulp dryer. This is advantageous if there is very little space around the pulp dryer, whereby the end wall element in an open position could disturb working in the end of the pulp dryer.

Figures 5A and 5B show a pulp dryer, which is provided with ends according to an embodiment of the invention as seen from the side.

In figure 5A the pulp web A is taken into the pulp dryer 1 , into its wet first end 1' via an inlet opening 51 located in the upper part of the dryer. In the dryer 1 the pulp web A travels form the first end 1' of the dryer to the second end 1", where its travelling direction is turned by 180° by means of a turn roll 57. In both ends 1', 1" of the dryer 1 there are arranged a plurality of parallel turn rolls 57' one above the other, by means of which the web A is turned so that it travels back and forth inside the pulp dryer 1. The web A is removed from the pulp dryer 1 by its second end 1" via an outlet opening 51' located in the lower part of the pulp dryer. A movable maintenance platform 59, 59' is arranged in both ends 1', 1" of the pulp dryer 1. The maintenance platform 59, 59' can be moved in the end 1', 1" of the pulp dryer 1 in the height direction of the pulp dryer, and maintenance operations required by the pulp dryer can be performed from it. In figure 5A the end wall elements 52, 52' of the pulp dryer are arranged in a closed position.

In figure 5B the end wall elements 52, 52' of the pulp dryer 1 are arranged in an open position so that the end wall element 52 of the wet first end 1' of the pulp dryer is arranged under the bottom level 12 of the pulp dryer 1 , in a storage space 61 arranged between the bottom level 12 of the pulp dryer and the floor 60. The end wall element 52' of the second end 1" of the pulp dryer 1 is, in turn, arranged above the roof level 13 of the pulp dryer. This way, the end wall elements 52, 52' which are in an open position do not occupy the valuable machine room space and do not substantially disturb the maintenance and service operations performed around and in the ends of the pulp dryer 1. In this embodiment it has been possible to arrange the end wall elements 52, 52' to open preferably in the manner of a tambour door.

Figures 6A - 6C show an end wall element's opening mechanism according to an embodiment of the invention as seen from above. Figure 6A shows an end wall element 62 comprising several partial elements 63, 63', 63" in a closed position, whereby the end wall element 62 is arranged to cover at least a part of the inner part of the pulp dryer. The partial elements 63, 63', 63" are not connected to each other in an fixed manner, but they are provided with sealing means 69, 69', 69" with which a gap-like space 64, 64' eventually between the lateral edges of the partial elements 63, 63', 63" can be sealed and closed. An individual partial element 63, 63', 63" is formed of two parallel sides 70, 70' the space 71 between which sides can be filled with an insulating medium, such as for example gas, such as air. The parallel sides can be arranged to be substantially transparent in order to enable the observing of the inner parts of the pulp dryer.

The partial elements 63, 63', 63" are provided with hinge means 65, 65', 65" with which the partial elements 63, 63', 63" can be moved along a guiding means (not shown) while the end wall element is arranged into an open position. Thus, the hinge means are arranged to move along a guiding means. With the aid of the hinge means 65, 65', 65" the partial elements 63, 63', 63" can also be turned by 90 degrees, whereby they can be arranged on the side of the pulp dryer, on the tending or driving side, as efficiently as possible with regard to use of space.

In figure 6B arranging of the end wall element 62 into an open position has been started. The partial element 63 is turned by 90 degrees and glided on the side of the pulp dryer along a guiding means (not shown). The movement of the partial element 63 thereby takes place in the width direction of the pulp dryer. The partial elements 63', 63" are still in a closed position.

In figure 6C the partial elements 63, 63', 63" are completely grouped into an "open" position next to each other their main surfaces against each other. It can be noticed that the end wall element 62 is partly open.

It is apparent to a person skilled in the art that the invention is not limited exclusively to the examples described above, but that the invention can vary within the scope of the claims presented below.