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Title:
A METHOD AND APPARATUS FOR DRYING LUMBER AS WELL AS DRYER
Document Type and Number:
WIPO Patent Application WO/2009/112630
Kind Code:
A1
Abstract:
The present invention relates to a method and an apparatus for drying lumber. Furthermore it relates to a dryer consisting of said apparatus. The pieces of sawn wood are during drying placed into the drying container in the direction of air flow. The drying modules are transferred into different drying stations, where air flow is led through the container. During drying the pieces of sawn wood are squeezed against the walls of the container. The weight of the sawn wood and/or the weight of the drying module is transmitted into tightening force fighting against the warp of the sawn wood.

Inventors:
LAMMI, Matti (Kaasmarkuntie 129, Vanha-Ulvila, FI-28450, FI)
LAMMI, Antti (Sammakontie 8, Pori, FI-28220, FI)
Application Number:
FI2009/000030
Publication Date:
September 17, 2009
Filing Date:
March 03, 2009
Export Citation:
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Assignee:
PAPROTEC OY (Kaasmarkuntie 129, Vanha-Ulvila, FI-28450, FI)
LAMMI, Matti (Kaasmarkuntie 129, Vanha-Ulvila, FI-28450, FI)
LAMMI, Antti (Sammakontie 8, Pori, FI-28220, FI)
International Classes:
F26B9/04; F26B3/04
Foreign References:
FI106982B1
US20050223590A1
Other References:
See also references of EP 2252848A1
Download PDF:
Claims:

CLAIMS

1. A method for drying lumber, when pieces of sawn wood (1) are placed for drying into the drying container (2) in the direction of air flow, and air flow is led through the drying container (2), characterized in, that the weight of the sawn wood is transmitted into tightening force fighting against the deformation of the sawn wood.

2. A method according to claim 1, characterized in, that in addition of the weight of the sawn wood substantially also the weight of drying container (2) is transmitted into tightening force fighting against the deformation of the sawn wood.

3 A method according to one of the previous claims, characterized in, that during the drying the sawn timber (1) is squeezed against the walls of the container (2).

4 A method according to one of the previous claims, characterized in, that the compression force directed to the bundle of sawn wood from one part of wall of the drying container and/or from the cover is transmitted into squeezing between the bundle of sawn wood and the other parts of the walls of the container.

5 A method according to one of the previous claims, characterized in, that the force fighting against the warp is increased in the course of drying.

6. A method according to one of the previous claims, characterized in, that in order to engage the drying module at a drying station to the air circulation pipeline (11) and in order to sealing the coupling, the engagement of the coupling member and sealing is achieved by means of air flow/pressure.

7. An apparatus for drying lumber, comprising a drying container (2), in which the pieces of sawn wood (1) are placed for drying in the direction of air flow, and air flow is led through the drying container (2), characterized in, that the drying module (3)

accommodates equipment which transmits the weight of sawn wood (1) into tightening force which fights against warp of the sawn wood (1).

8. An apparatus according to claim 7, characterized in, that the drying module accommodates equipment which transmits, in addition to the weight of the sawn wood, substantially also the weight of the drying container (2) into tightening force fighting against the warp of the sawn wood.

9. An apparatus according to one of the previous claims, characterized in, that the drying apparatus consists of a portable drying module (3), which at drying stations is engaged to air pipeline, and that the drying module (3) accommodates equipment for generating pressure between the sawn wood (1) and the drying container (2).

10. A dryer, characterized in, that the dryer accommodates transfer members (6, 10) for transferring the drying module from previous drying station to the next one, and that the dryer consists of one of the apparatuses according to claims 7 - 9.

Description:

A METHOD AND APPARATUS FORDRYINGLUMBERAS WELL AS ADRYER

The present invention relates to a method in accordance with the preamble of claim 1 and an apparatus according to preamble of claim 7 for drying lumber. Furthermore it relates to a dryer consisting of said apparatus.

Prior art technology used for drying timber has been discovered for example in publications mentioned below.

The present invention relates especially to drying sawn wood cut about small size timber. Sawn wood means below various types of lumber which have been cut into drying profile by sawing, planing, milling, turning or by similarly profiling or by combination of said cutting methods. According to the invention the sawn wood is dried as bundled, without stickers.

One major problem related to drying is the deformation, the living of the sawn wood which progresses in the course of drying. With small size log the tendency for warp is especially enforced, and called juvenile timber problem. This is one of the reasons which have hindered the utilization of small size log for example in the production of laminated wood, even though the raw material would be considerably cheaper than normal size log. The forces contributing for warp increase in the course of drying. Green timber is yet practically free from stresses. In case the slender sawn wood would be dried in a traditional way, the stickers should be spaced at tight pitch. Otherwise the sawn wood could extend in the space between the stickers.

Regarding to prior art technology the patent publication FI 106982 is especially referred to. It, as well as the publications referred to in it, comprehensively discovers the shortages related to the prior art technology.

In the referred solution the drying takes place without stickers. Essential has been keeping the bundle in a tight grip through the drying process. It is known from prior art to fill the gap between the bundle of shrinking sawn wood and embracing vessel with along shrinking elastically living pneumatic actuators, such as fire hoses, air bags or similar. The life span of hoses at temperature exceeding 100 C-degrees, has proven to be about one year only.

The prior art technology entails even other problems. Firstly, for composing the bundle of sawn wood and transferring it into the dryer, closing the drying enclosure and maintaining the tight grip of the bundle, actions are required, which are difficult to automate and therefore the operator is needed to be present.

Due to shrinking of wood in course of drying due compliance is required of the tensioning elements. When drying down to carpenter moisture level, the shrinking averages 5%. As an example with the dryer discovered by the publication FI 106982 and with 1500 mm bundle diameter, almost all the compression range of the embracing fire hose by diameter 200 mm is used. In order to reach one year life span, the compression range of the hose must be limited down to ca 150 mm. Consequently, in the beginning the hose is almost fully flattened, and then the compression force is at the maximum. At the latest stage of the drying the hose is quite round, and compression force at the minimum. From the point of view of the forces behind the deformation it should be just the opposite. Of course the problem can be lessened by regulating the pressure, but expensive arrangements are needed, energy wasted, and it is difficult to realize with mobile vessels.

A substantial problem is related to the turbulence of air flow, which is created at the outer sphere of bundle when passing the sealing area. In order to reach the shortest possible drying time the speed of air flow must be fastest possible. It is obvious, that when air flow is colliding against about 150 mm wide ring-shaped barrier, turbulence is generated. Therefore must be accepted lower speed of air flow than could be reachable without the barrier. The consequent lengthening of drying time has significant economical affect.

In order to restrain the sawn wood in shape during the drying process, it is also known to place weights upon the wood stack, such as concrete plates. This practice suits for normal lumber, stacked with stickers, but worse for bundled sawn wood. For handling of weights due equipment and labor are needed. Such a solution has been disclosed in publication US 2005223590. Such constructions are complicated and expensive. Furthermore the direction of air flow is transverse in relation to the longitudinal axis of sawn wood. It is difficult to achieve high speed for the air flow due to several barriers triggering turbulence.

In the publication WO 2006099737 has been disclosed a press arrangement for eliminating the sawn wood warp in the course of drying. The solution is massive and expensive. Other dryers have been disclosed in publications WO 02081992 and FI 20012267.

The present invention presents a solution with several improvements for problems related to dryers of prior art. Firstly the drying module according to present invention is simple by structure. Functionally no actuators attached to the module itself are needed. Therefore dryer modules are easily and automatically shifted from one drying station to the next one. Unloading and loading of the container are simple to execute and can be easily automated. The dryer according to present invention requires minimal handling, and the whole dryer can be realized as unmanned. Manual share may be limited to camera monitoring.

No tightening-/sealing element is needed between sawn wood and container. The force required for tightening is generated by the weight of drying container and timber bundle, i.e. quite for free. Tightening force may be easily set at appropriate level. Tightening force shall increase by itself in the course of drying substantially in relation to the amount of shrinking. Owing to modular construction dryers with varying sizes can be built about the same components.

The invention is characterized by what is stated in the characterizing parts of independent claims.

In the following, the invention is described in more details referring to the appended drawings in which

Fig. 1 shows a drying module at loading-╬╗inloading station according to one embodiment of the invention, front view in middle section.

Fig. 2 shows a drying module filled with sawn wood at the beginning phase of drying, front view in middle section.

Fig. 3 shows the drying module at the final phase of drying, front view in middle section.

Fig. 4 shows a top view of two in transfer direction consecutive drying modules, where in partial drawing 4a the module is in transfer state and in partial drawing 4b the module is in drying state connected to air circulation system.

Fig. 5 shows two other embodiments of connecting the drying module to air circulation pipeline.

The dryer consists of several drying apparatuses and of an apparatus for transferring the drying modules 3. The drying apparatus consists of a portable drying module and of stationary apparatuses for circulating, heating and humidifying the air. At first the container 2 of the module is filled with sawn wood 1, which is in a bundle, without stickers. The pieces of sawn wood 1 are placed in the container 2 in the direction of air flow and kept there through the drying. The drying module 3 is furnished with equipment for generating pressure between sawn wood 1 and container 2 as well as equipment by means of which the weight of sawn wood and/or substantially the weight of the drying module is transmitted into a tightening force which opposes the warp of sawn wood. The force fighting against the warp of sawn wood increases in the course of drying.

The tightening force for the mechanism is generated by the counterforce F of the gravity G directed to the support wheel 6, which multiplied by distance x is the tightening torque. In the course of drying the sawn wood is shrinking, and the cover 4 bends down. By this way the torque generating tightening increases in the course of drying. According to fig. 2 in the beginning of the drying, when the forces tending to cause warp, are at the minimum, the distance xl is at the shortest. And according to fig.3, at the final stage of drying, when the forces tending to cause warp, are at the maximum, the distance x2 is at the longest.

The function of the right side power transmission mechanism 5 is as follows. When lowering the drying module 3 down, the lever 7 is forced by the guide 28 to turn counterclockwise until the support roller 6 has moved to right beyond the vertical line crossing the axis of swivel 8. Next the support roller 6 reaches the guide beam 10 and while lowering continues, moves to right and forces the lever 7 to turn counterclockwise. The turning movement of the lever 7 is transmitted to the cover turn lever 25 by means of connecting rod 23 which has joints 22, 24 at the ends. The cover turn lever turns around the joint 26 and pushes the cover 4 attached to its upper end against the sawn wood 1. hi drying ca three meter long sawn wood, there are preferably two power transmission mechanisms, one after another. With longer sawn wood there are more of them. The angular positions and lengths of levers are preferably chosen so, that the mechanism allows for movement corresponding to at least 5% shrinking in the bundle of sawn wood, and at the end the tightening force is increased by 10 - 20%. Power transmission mechanism 5 is preferably parallelogram or similar.

The form of the drying container 2 is such, that when its moving part/cover/covers 4 protrude down, the sawn wood is squeezed against other wall parts of the container. Vertical tightening is converted also into tightening in horizontal direction in ratio according to the wedge angle at the cross section of the bundle of sawn timber. By this way the whole bundle of sawn wood is kept in grip which is tight enough through the whole drying process.

Furthermore, the drying module accommodates transfer members 6 for transferring the drying module from previous drying station to the next one. Transfer members are preferably known wheels of cast iron, which move along guide beams 10.

Drying module and/or pipeline 11 accommodates joining members, by means of which the container 2 is joined to become a part of air circulation system. Joining member 15 consists preferably of elastic, heath resistant material, such as silicon rubber or similar. In Fig. 5a the joining member, including for example an actuator ring 20 fillable with pressurized media, has been shown as non-pressurized state, enabling transfer of the drying module to next drying station. In Fig. 5b the joining member has been engaged by means of media led into actuator ring 20.

The engagement of the drying module at a drying station to the air circulation pipeline and sealing is, according to one embodiment of the invention, achieved by means of air flow/pressure. According to Fig. 5c there is no air flow and joining member is at by pass state. At state according to Fig. 5d the air flow forces the bellows-like moving member to push the sealing member against its counter site 16. When the air flow is cut, the sealing members retract, and the drying module may freely be transferred to the next drying station. According to other embodiment of the invention the engagement is carried out by an actuator, such as an air cylinder.

After loading the drying module goes through several drying stations, where the drying module is coupled to air pipeline and air with moisture and temperature values dedicated to each stage is circulated through the container 2. Finally the sawn wood is unloaded from the drying module. At unloading- and/or loading station the drying module is lifted by lifting elements 18. Lifting elements may be powered for example by hydraulic cylinders 19 as power elements. When lifting the container the covers open at the same time automatically. The bundle is lifted preferably by lifting members 14 formed according to the cross sectional form of the container, for which in the container is appropriate mating space 17.

It is obvious that the invention is not limited to the disclosed embodiments, and several other solutions are possible. For example converting the weight of sawn wood and/or embracing structures into pressure against the sawn wood can be achieved by many varying ways. According to one embodiment of the invention the bundle of sawn wood can be hanging in an array of grippers similar to halters. So the weight of the sawn wood is converted into force opposing the deformation of sawn wood. Furthermore the pressing force can be divided between sawn wood and different parts of walls of the container 2 by many different ways.




 
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