COMPUTER-AIDED LOG BUILDING

Introduction

The present invention relates to log building. More specifically the invention relates to a computer-aided log building process that imitates the quality of log building constructions that can be achieved with traditional handcrafted log building, where traditional handcrafted log building is characterised in exploitation of the natural shape of the logs with curvature and different top and root diameter to create vivacity in the log building walls.

In today's market milled log constructions based on established machine based log building techniques dominates, where the timber is machine-planed to remove natural curvature and roughness, even though most builders could desire more distinctive, traditional constructions that appears to be hand crafted log building. However, this has not been possible to achieve due to the considerable manual effort required by traditional hand crafted log building.

A log building process with selection of logs according to the same criterias as with traditional hand crafted log building may also better the exploitation ratio of the logs compared to known methods for machine based log building because the logs have smaller requirement for shaping.

It is therefore a need for a new type of automated log building process ensuring the distinctive stamp and the advantages of hand crafted log constructions, and at the same time drastically reducing the need for manual work load to reduce the price of the finished log building construction.

Background of the invention

Hand crafted log building has long and rich traditions in Norway. It is likely that the Vikings became familiar with the log building techniques on their journeys to eastern Europe, and that it later has been in extensive use in Norway from the middle age to our modern times. Gradually, different log building techniques have evolved that are distinct from each other. One of the main reasons why the log building technique was so well established in Norway was the use of the groove [NO: meddrag, a longitudinal groove

under the log]. This ensured a precise and tight construction. In addition log building constructions were very durable, and the own weight of the log building construction maintained its characteristics even when the wood dried.

A large part of the log building constructions still characterising our cultivated landscape were raised in a time when there was excess cheap manpower and log building qualifications in Norway. The craftsmen therefore had better time to select the logs that should fit together during the log building process and to perform the craftmanlike adjustments. As a consequence of a method where the logs were selected with great concern, the need for adjustments and shaping of the logs was therefore considerably smaller than it is with e.g. machine based log building that is used today, which resulted in a higher degree of utilization of the timber.

Handcrafted log building is a time consuming process, and with high hourly rates on manual work the hand crafted log buildings become relatively expensive compared to building techniques with less requirements for processing of the raw material. Good hand crafted log building requires knowledge, special tools, practiced technical skills and enough time. Normally, hand crafted log building involves also handling of heavy logs that may often lead to health damages. Good handcrafted log building is therefore costly. As a consequence of the above mentioned limitations, today hand crafted log building constructions that are more prepared from the sawmills are delivered, or simplifications in the log building process itself are made that may be sub-optimal with regard to the quality of the craftsmanship. This implies that natural curvatures and variations between the logs are evened out. Thus, the finished product obtains less character of the natural variations ("vivacity") that older handcrafted log building constructions have. The development described above may imply a danger for the log building tradition and the competence in commercial activity may be diluted in Norway, which means that it no longer can be constructed new log building constructions with the quality expected from traditional handcrafted log building. An important part of the Norwegian heritage may therefore be at risk for disappearing.

By handcrafted log building all the logs are prepared one by one in a sequential physical work process. This implies that any log may be adapted first when the preceding log or logs have been definitely adapted.

During a professional log building adaptation of a given log the next log is selected based on the craftsmans evaluation, approximately, to fit in the best possible way to the

preceding, i.e. as little material as possible should be removed to create a tight fit with the preceding log. In addition it is ensured that the log ends are sufficiently high to overlap well with the crossing logs in the corner connection, i.e. to prevent log building oneself "outwards", or that the height of the following log is too small compared to crossing log(s) to create a secure lock between the crossing logs.

By log building a wall without corner connections, e.g. the upper part of gable walls, a precise adaptation is achieved with hand crafted log building by placing the above log on the underlying position that is as identical as possible to the ultimate desired position in the horizontal plane related to the underlying log. Expressed in another way, the next log is placed based on the craftsmans evaluation to achieve an approximate average vertical wall surface. While the overlying log is put in place in this position in a given vertical distance above the underlying log, a tool called "scriber" is used, - a device with a fixed vertical distance between two measuring points that are run with the opening between the logs such that the lower point follows the shape of the lower log and upper point lay off a mark in the form of a line lying vertically above the lower support point and in the same distance from it. This is done on both sides of the logs laying on top of each other. When the material between the two marked lines is removed from the overlaying log, such that a concave groove on the underside of the overlying log, the logs will, when they are thereafter put on top of each other fit tightly to each other along the before mentioned lines. When hand crafted log building is used the material between the lines [NO: meddragslinje] is removed, such that a cavity appears between the lines where notching wool, wool or in earlier times moss was placed. Usually the logs are smoothened by planing or earlier chipping, but also the peeled timber may in theory be precisely log built.

In the corner connections, the notches, the same principles for tightening applies as for log over log. A number of corner styles are available. The shape that has been made by the previous crossing log is transferrred to the overlying log such that they fit tightly together. The transfere of shape from one log to another in a corner may be performed by different measurement techniques, including scriber line techniques [NO: meddragsteknikk]. NUsually the notches are prepared by making inclined plane surfaces called saddle surfaces [NO: kinninger]. Plane saddle surfaces contributes to achieving a relatively good adaptation or imperviousness between crossing logs when the logs are forced together and settles in the finished construction.

A particular challenge with log building applies to logs that has not yet dried to the final dryness it will achieve after many years of use, or that the timber has a different and an uneven dryness when the log building process is ongoing. Such timber will usually not remain tight in the notches for a longer term. A precise and tightly notched construction requires correct drying (such as drying from the pith and outwards) related to future dryness. Making a log building that is precisely adapted both between the logs in a wall and especially in notches when it is log built is demanding, but it is even more challenging to maintain such tightness after the logs have dried to a stable state. Very often log building constructions will depart from the precise adaptation due to drying of the logs after completion.

The particularity with handcrafted log building is the achievement of a building construction in principle comprising only logs. Precise adaptation between every log both in walls and in every corner ensures tightness and stable placing.

Pegs [NO: dymling]: It is also common to ensure the broadwise position by using pegs (more names exist), implying to place wooden pegs in drilled holes mainly centric between two logs, wherein one of the logs rests on the other.

Spline: [NO: beitski] In window and door openings the relative position of the logs are ensured by a so called spline. (Figure) This involves the making of a vertical groove approximately centric between several logs where a spline is placed.

Purlin: Purlins can be notched into the walls or inserted into this. When log building the purlins the wall and purlins are adapted analogous to a corner connection.

Log building with staves [NO: Stavlaft]: Log building with staves involves combining notched logs with vertical posts or "staves". Such staves may be round trunks, squared or shaped with different ornamentation. The ends of the staves are usually log built, or notched (precisely adapted) perpendicularly into horizontal logs.

As a consequence of the before mentioned limitations hand crafted constructions that are more prepared from the saw mill than earlier are delivered today. This implies that natural curvatures and variations between the logs are evened out. Thus, the finished product obtains less character of the natural variations ("vivacity") that older handcrafted log building constructions have.

A counterpart to the handcrafted log building is the milled or machine log building. In

milled log building the logs are usually prepared such that the cross-section surface along the logs between the corner connections are about the same. Initial difference in shape between the logs are usually planed off. Also the corner connections, the notches are made the same such that the logs in principle may be placed arbitrary and still ^' tighten well both in the corners and between logs that are resting on top of each other.

Short summary of the invention

The invention makes possible the provision of log building constructions by means of mainly automated processing that approximately has the same qualities as log building constructions made with traditional handcrafting techniques. This applies specifically to the exploitation of the natural shape of the logs such that the log building construction obtains its characterising distinctive stamp, that is obtained by handcrafted log building by utilizing the curvatures and roughness that is undesired for machine log building, by selecting logs that fit together as well as possible before the logs are prepared, and thereby adapt the logs individually.

Another advantage of the invention is that the material loss may be substantially reduced when the determination of how to assemble the logs is done before the shaping of the log instead of planing the logs to the same shape.

The method according to the invention may be exploited both for providing log building constructions with traditional shapes and appearance with a narrowing in the groove and for providing log building constructions with new exterior shapes and appearance for use in modern architecture, e.g. flat wall without narrowing in the groove, but with non- straight lines.

The invention is a methode for log building of logs (1) with natural shapes and different top and root diameters where the method comprises the following steps; - the shape of the logs are measured (11) and converted (12) to digital images (2),

- the required shape of the logs (5) and their required assembly (4) is calculated (13) based on the desired shape of the log building construction (3) and the digital images (2) so that the required shape of the logs (5) and the required assembly of said logs (4) imitates handcrafted log building, - the logs (1) are shaped (14) such that said shaped logs (6) obtain approximately said required shape of said logs (5),

- the shaped logs (6) are log built (15) as indicated in the required assembly (4).

Figure captions

The invention is illustrated in the accompanying drawings, meant to illustrate embodiments of the invention that is defined by the accompanying claims.

Fig. 1 shows a flow chart for a computer aided log building process according to the invention. Resources that are used in the sub-processes and results of the sub- processes are shown to the left in the figure.

Fig. 2 shows a flow chart for selection, assembly and calculation of desired shape of the logs in a computer aided log building process according to the invention. Figure 2 shows block (13) in Fig. 1 in more detail.

Fig. 3 shows a flow chart for calculation of quality in the log building construction and degree of utilization and the need for shaping of the logs. Figure 3 shows block (136) in Fig. 2 in more detail.

Fig. 4 shows marking of a log with identification and direction parameters that are used during calculation of the desired shape of the log, and preparation of the log in the final log building process.

Fig. 5 shows a log building construction where the original shape of the logs clearly can be recognized. This gives constructions that are handcrafted and constructions log built according to the present invention more vivacity and more flexibility in the degree of utilization of the logs than for a machine milled construction.

Detailed description of the invention

Below is a description of preferred embodiments of the invention.

a methode for log building of logs (1) with natural shapes and different tip and butt diameters where the method comprises the following steps;

- the shape of the logs are measured (11) and converted (12) to digital images (2), - the required shape of the logs (5) and their required assembly (4) is calculated (13) based on the desired shape of the log building construction (3) and the digital images (2) so that the required shape of the logs (5) and the required assembly of said logs (4) imitates handcrafted log building,

- the logs (1) are shaped (14) such that said shaped logs (6) obtain approximately said required shape of said logs (5),

- the shaped logs (6) are log built (15) as indicated in the required assembly (4).

Fig. 1 shows a flow chart for a computer aided log building process according to the invention. The process with its sub-processes is shown to the right in the figure and resources used in the sub-processes are shown to the left in the figure. In Fig. 1 the shape and the characteristics of the log are read and the log is marked (11). The read shape and characteristics of the log are converted (12) to digital images (2). Reading, marking and converting is repeated for the desired logs. Afterwards a set of digital images that are a detailed 3-dimensional representation of each logs shape and characteristics exist. After this the logs is not needed before later in the process where they will be shaped and log built, because all subsequent calculation will be based on the digital images.

Then suitable logs are selected (13) from the digital images (2) based on a drawing of a desired log building construction (3). This could for instance be an architect drawing of the construction to be log built. Such a drawing would typically indicate the walls and the roofs to be log built, dimensions of theese and technical requirements to be fulfilled, however, not necessarily anything about how the log building technique should be performed. The selection of a log has to comply with the area in the drawing of the desired log building construction (3) that one intend to build, e.g. the selection of a log on a specific level will have to consider the windows and doors in the drawing. A log that is selected will have to be prepared to fit with other logs, and to fit with the drawing (3). This could involve adaptation of the length of the log according to the drawing (3), adaptation of the saddle [NO laftehals] and dovetail [NO: laftehode] to the already selected logs, and adaptation of the groove. In an embodiment of the present invention this adaptation will first be made computerwise, i.e. a digital required desired shape (5) of the log is calculated. The digital required desired shape (5) of the log is a digital, modified description of the image of the log (2).

In relation to the selection of the logs (13) and the calculation of a required shapes of the logs (5) a required assembly of the logs with the required shapes (4) is also calculated. Since every log in this method is individually adapted, the log will only fit in one place in the log building construction. The assembly (4) declares the logs unique position in the log building construction and can be seen as a construction drawing for the log building construction where each log is identified. A more detailed description of how the logs are selected, how the required shape is calculated and how the assembly is calculated in an

embodiment of the invention is given in Figure 2.

Next, the logs will be prepared (14) according to the required calculated shape of the logs (5). This preparation may be accomplished by mounting the log in an automated planer or milling machine that prepares the log according to the parameters given in the description of the required calculated shape for each of the logs (5), where data, automatically, semi-automatically or manually is transferred to the planer or milling machine from the required calculated shape (5).

After the logs have been prepared, the construction is log built (15) according to the required assembly (14).

The trunks may be scanned and marked before cutting, peeled or unpeeled after cutting, or in any state or combination of cut/ not cut or peeled unpeeled as it is understood by a person skilled in the art.

Depending of how the logs are prepared, it may be necessary to mark the logs again if the marking or parts of the marking has been lost.

The method according to the invention described above may be carried out in different locations. For instance may the measuring and marking be done in the forest, the calculation somewhere else, the preparation of the logs a third place, and the log building a fourth place, such that the process can be made more effective according to the needs.

In an embodiment of the invention the selection of the next log in addition is based on the required shape of one or more neighbouring trunks (5) that have already been added to the required assembly of logs (4).

Fig. 2 shows in a flow diagram a more detailed description of how the logs are selected, how the required shape of the logs is calculated, and how the assembly is calculated in an embodiment of the invention.

In an embodiment of the invention, an iteration is performed for each log to be selected. For each iteration a new log is selected from the digital images (2) based on that the log, represented by the digital images (2), should fit with the logs already selected in earlier iterations.

In Fig. 2 it is in block (131) shown in an embodiment of the invention that desired

properties for the next log is analysed based on the logs that have already been added to the assembly of logs (4) and the drawing of the desired log building construction (5). Parameters that may be analysed before the selection of the next log is e.g.; length of wall, curvature and shape of the previous log, height of each end of the log wall after the previous log, and height and width of the neighbouring logs in the neighbouring wall that is to have a common cogging joint.

In block (132) it is further shown that the function of the log in the log building construction is analysed before the log is selected. Some of the relevant parameters to analyse are whether the log is a sill log, whether the log is in connection with a window, door or other openings, whether it is a rafter, purlin etc. In an embodiment of the invention the analysis comprises look-up in a library (10) comprising desired parameters for each type of log. The library may be adapted to a specific log building technique, or comprise information about desired properties for different types of log building techniques, such as cog building from Rauland [NO: Raulandslaft], log building with staves [NO: stavlaft] etc.

According to the selection criteria's described above, a log corresponding mostly to the desired properties after performing the analysis described above in (132 and 133) will be selected.

Next, a required shape for the log (134) will be calculated, which implies that it will later have to be somewhat shaped before it will fit with the neighbouring logs. The log with the calculated required shape will then be added to the required assembly (135) together with the already selected logs. Therefore, before the first iteration, no required shape of the log (5) or any elements in the required assembly of logs with required shape (4) exist. For every iteration a new log will be added to the assembly (4) based on that it has been calculated a required shape (5) for the log .

In an embodiment of the invention the quality of the log building construction, the total material loss and the need for preparation of the logs (136) is analysed. It is an objective of the invention to reduce the material loss and the need for preparation as compared to known machine log building techniques. By utilising the natural curvature and shape instead of planing the logs alike, a substantial improvement can be achieved, possibly 10-20% reduction of the number of logs compared to machine based log building. In an embodiment of the invention whole or parts of the log building construction may be optimised with regard to the deviations that have been found in the analysis (136). This

may apply to analysis of whether it is expedient to interchange logs that resemble each other, improve the characteristics of cogging joints, improve the strength properties in some parts of the construction and other improvements that will be understood by a person skilled in the art.

In Fig. 2 it is shown in an embodiment of the invention how one log after another are selected based on existing logs. The selection of logs are done level by level until a complete digital log building drawing (3) and required shape for the logs (5) exist, such that the log building construction later can be log built. However, the selection of logs may be performed for one wall at the time, or in other sequences as can be understood by a person skilled in the art. In addition Fig. 2 shows that the optimizing (136) is performed after the selection of all the logs. In an embodiment of the invention the analysis of the quality, material loss and the need for preparation of the log in every iteration related to the selection of each of the logs (133) is performed in each iteration.

In Fig. 3 it is shown in more detail how the analysis in block (136) is performed in an embodiment of the invention. In block (136) the quality is calculated based on expected shrinking in the timber and setting in the log building construction, stability and carrying capacity for the log building construction or for single points in the log building construction. During this analysis the available resources may be used, such as the digital images (2), the drawing of the desired log building construction (3), required assembly of logs with required shape (4) and required shape of log (5). If the quality appears not to be satisfactory the selection process is performed completely or partially again as described in Fig. 2.

Likewise the material loss and need for preparation of the logs will be analysed based on the available resources. If the result is not satisfactory the selection process may be performed completely or partially again as described in Fig. 2.

Fig. 4 shows the direction of the log (1) indicated with a set of direction parameters (x, y, z), and an identifier (8).

In an embodiment of the invention every log (1) is marked (11) with a unique identifier (8) and initial direction parameters (x,y,z) indicating the direction of the log during the measurement (11) of the shape of the log (1). The unique identifier (8) and the direction parameters (x,y,z) are used to retrieve and determine the direction of the log when it should be prepared and used in log building later, such that the log (1) can be prepared

(14) to its required calculated shape (5) and log built. The identifier (8) may be a visual and /or machine readable identification, such as a bar code. The direction parameters may be marking of each end point in each end, insertion of directional markers or similar as will be understood by a person skilled in the art.

Fig. 5 shows an example log building construction (7) resulting from a computer aided log building process according to the invention. As illustrated in the figure the logs have kept their original shapes, giving the construction more vivacity than constructions build according to known machine based logging techniques. In addition there is less requirement for preparation of the log, resulting in an improved utilisation factor for the timber.

In an embodiment of the invention the required shape of the logs (5) is calculated (131- 136) based on that the adaptation of the logs should resemble the adaptation of logs used during hand crafted log building.

In an embodiment of the invention the material quality in the log is measured (11) and converted to a set of material quality parameters (2) and, the adaptation of the log is calculated based on that the required shape (5) of the log complies with a set of predefined material quality requirements. Such material quality requirements may be e.g. rot, knots etc.

In an embodiment of the invention the moisture in the log is measured (11) and the adaptation of the log is calculated (13) based on the final required shape (5) of the log at the desired moisture level, such that the log building walls appears tight and adapted after drying of the logs, and that the calculation of other structural and non-structural elements also takes into account the vertical shrinking of the log building construction.

In an embodiment of the invention the logs are measured (11) before the logs (1) are peeled. Such a method may be labour-saving, since the peeling and preparation can be performed at the same time later in the process.

In an embodiment of the invention the calculation (13) of the required shape of the logs (5) and the assembly (4) comprises the use of pegs [NO: dymlinger] for log building walls according to pre-defined standards. The use of pegs may be used where there are long spans between the cogging joints, and are important for maintaining the shape of the log building wall during the lifetime of the log building construction.

In an embodiment of the invention the invention the calculation (13) of the required shape of the logs (5) and the assembly (4) comprises the use of stiffening splines [NO: Beitski] for log building walls according to pre-defined standards. Stiffening splines are inserted into the ends of the logs to terminate and support the log building walls in connection with door and windows openings.

In an embodiment of the invention the invention the calculation (13) of the required shape of the logs (5) comprises cut outs and sockets for open or concealed installations. This may be electrical installations, such as wall boxes, roof boxes and conduits. It may also be HVAC installations for concealed pipe installations or other open or concealed installations as will be understood by a person skilled in the art.

In an embodiment of the invention the groove of the logs has one or more internal groove channels in the longitudinal direction of the log. The groove channels may e.g. be made as one or more additional tracks in the form of milled tongue and groove shapes inside the V-groove. In this way one may achieve an improved tightening and thereby reduce the draft through the wall if small openings should appear without affecting the outer or inner shape of the wall. The grooves may be continued all the way into the cogging joints.

In an embodiment of the invention an external edge of a groove [NO: medfar] in a cross-section of a log building wall is approximately equal to the external edges of the logs above and below said groove in the same cross-section for at least one of the sides of the log building wall. The outer edge of the groove may here be the contact line between the logs above and below the groove. This may be utilised to provide log building constructions with new exterior shapes and appearance for use in modern architecture, e.g., flat wall without narrowing at the groove, but with non-straight groove lines [NO: medfarslinje]. For instance would it be possible to provide external walls with appearance and quality according to traditional hand crafted logging techniques, and inner walls that are flat with evident grooves that are not straight. In an embodiment of the invention the calculated offcut after calculation of the required shape of the logs (5) be represented as digital images (12), such that the digital images (12) of the offcut may be utilised in the log building construction in the same way as the logs (1). This would further reduce the material loss. Calculated offcut may here be a result of too long logs that have to be cut in length, or as a result of specific adaptations, such as e.g. cutting in the longitudinal direction for providing a bottom sill.