In the conventional bandsaws, an endless saw blade or saw band runs around two reversing wheels, one of which is driven. The motive power for the saw blade is transmitted in a force-embracing manner, i.e., by the transmission of frictional force, which puts certain limits on the performance of the bandsaw.

Bandsaws having form-embracing driving contact between driving wheel and saw blade are known. For example, FI 10416 teaches a driving pulley for bandsaws, which driving pulley has a rim of fixed teeth of a shape and width such that they are able to rest against and interact with the backs of the saw blade teeth, in order thereby to communicate motion to the saw blade.

US 4,141,142 teaches a bandsaw wherein small pins or similar on the driving wheel engage with the saw blade.

US 3,750,284 teaches a saw wherein when a saw band is driven, a wheel with pins around its periphery is used. These pins engage with holes in the saw blade.

US 5,001,957 teaches a bandsaw wherein rolls having pins which engage with the saw blade are used, but these rolls are not driven. They function as pure guide rolls.

US 1,916,903 teaches a bandsaw wherein the wheels around which the saw blade is trained have pins for engagement with grooves or holes in the saw blade. These pins function only to ensure the position of the saw blade on the respective wheel periphery.

The driving action takes place in a conventional manner with the aid of friction.

DK 1236 teaches a bandsaw having a cutting saw blade section, where on each side, i.e., in front of and behind the cutting area, there is provided a guide unit. A belt runs together with the saw blade. Although the co-driven belt runs through the guide units with the saw blade, the guide units have a pure guide function - in order to produce a desired curvature of the cutting saw blade section. The driving of the saw blade takes place in a conventional manner with the aid of a reversing wheel and driving wheel.

One object of the invention is to make possible concentrated, guided driving of the saw blade in a bandsaw, close to the cutting saw blade section.

According to the invention a bandsaw according to claim 1 is therefore proposed.

The guide and drive units used will provide favourable guiding (spatial fixing) of the saw blade in the cutting area. The guide and drive unit on one side will push the saw blade into the cutting area, whilst the guide and drive unit on the other side will pull the saw blade through the cutting area. Therefore, in the critical cutting or sawing area the saw blade will be actuated in a positive manner, with desired configuration or saw blade course and desired tension.

One advantage is also that virtually any saw blade whatsoever, including heavy-duty, rigid saw blades, could be used, as placing even a heavy-duty, rigid saw blade around the reversing wheels which do not drive, but merely act as direction switching wheels, will not present any particular problems.

In principle, the new bandsaw can saw many different materials in curved or straight sections. The saw blade section, which is the actual sawing area, can be altered both prior to and during a sawing operation by adjusting the drive units relative to one another. Such relative adjustment may be a pure change of position of the drive units relative to one another, but it would also be possible to operate with different drive rates in front of and behind the saw area within certain limits, so as to obtain thereby a sawing saw blade loop or section of varying sizes.

The use of drive units as disclosed in claim 2 is especially advantageous as these will provide good drive control and drive actuation on both saw blade side edges, thus providing very good guiding and drive actuation of the saw blade.

As drive unit it is preferable to use a drive unit as disclosed in claim 3, and a drive unit as disclosed in claim 4 will be particularly advantageous.

A drive unit of this type with chain drive will provide stable fixing of the saw blade and a positive form-embracing multiple drive engagement, although the drive engagement could be achieved with, e.g., one or more drive sprockets in interaction with respective notches or drive grooves in the saw blade.

The invention opens new avenues for simultaneous sawing and planing with the rotating saw blade, when the saw blade, in addition to the saw teeth, is provided with planing bits.

Planing calls for stable guiding of the planing bits. This is achieved in an especially favourable manner with the invention when the saw blade and attached planing bits are guided and driven in a stable manner by means of the drive and guide units according to the invention that are placed and function in front of and behind the cutting saw blade section.

Synchronous driving of the drive units according to the invention is desirable, and this may easily be achieved, for instance, as disclosed in claim 6.

If a curved cutting saw blade section is required, the drive unit is adjusted accordingly and supported preferably pivotally as disclosed in claim 7. In this connection, it would be of particular advantage if the drive units were attached to a common spindle drive as disclosed in claim 8.

Lubrication or flushing of the saw blade may advantageously take place in the drive units, as disclosed in claim 9.

As mentioned, the drive units may be adjusted relative to one another so as to make possible a curved saw section. A particular advantage is that the invention allows a slightly S-shaped saw section, and a special area of application for the new bandsaw is the use thereof for producing sawn timber of an S-shaped cross-section, in particular weatherboards, a board type which provides certain advantages in the case of horizontal, overlapping panelling.

The new bandsaw is also suitable for sawing in a curve along, e.g., a log. The curve can be altered during the sawing operation. Such curved sawing, with or without alteration during the sawing operation, may be useful, for example, for building with logs.

The new bandsaw may also to advantage be used for straight sawing in coarse timber, inter alia because the drive units can transmit greater power to thicker saw blades and the saw blade can be flushed, and because of this, better tooth bite.

The new bandsaw may also be used with very thick saw blades in which tungsten tips are embedded, also replaceable recessing types of cutters.

One area of application is also the cutting of stone, the saw blade preferably having a diamond coating embedded therein.

As mentioned, it is also a great advantage of the invention that sawing and planing with the same saw blade is made possible.

The invention will now be explained in more detail with reference to the drawings, wherein: Figs. 1, 2 and 3 show various types of cutting saw blade sections which can be achieved by means of the invention; Fig. 4 is a purely schematic view of a bandsaw according to the invention; Fig. 5 is a purely schematic view of a bandsaw according to the invention; Fig. 6 shows a variant of the embodiment in Fig. 5, the figure merely illustrating the cutting saw blade sections of interest; Fig. 7 is an end view of a drive unit according to the invention; Fig. 8 is a lateral view of the drive unit in Fig. 7; Fig. 9 is the opposite lateral view of the drive unit in Fig. 7 (from the driving side); Fig. 10 is a section of a so-called triple chain used in a drive unit according to the invention; Fig. 11 is a schematic illustration of the driving interaction between triple chains and saw blade in a drive unit; Fig. 12 is a section of a saw blade with planing bits; Fig. 13 is a cross-section of the saw blade in Fig. 12 during the sawing of a piece of wood, with simultaneous planing; and Fig. 14 is a section of a panel wall with slightly S-shaped panels which have been cut using a bandsaw according to the invention.

Figs. 1, 2 and 3 show examples of saw sections which can be obtained and implemented by means of the invention. Thus, Fig. 1 shows a straight cutting saw blade section 1, provided between two drive units 2, 3 for a saw blade 4, which forms part of a bandsaw.

In Fig. 2 the two drive units 2, 3 are positioned relative to one another such that the saw blade 4 forms a curved cutting saw blade section 1'.

In Fig. 3 the two drive units 2, 3 are positioned relative to one another such that the saw blade 4 in the cutting saw blade section between the drive units 2, 3 forms an S-shaped saw section 1".

Figure 4 is a purely schematic illustration of a bandsaw according to the invention. The bandsaw has a saw blade 4 which runs around two reversing wheels 5, 6. On each side of a saw area 1 there is provided a drive unit 2, respectively 3. The drive units 2, 3 are driven synchronously from a motor M via a transmission mechanism comprising synchronisation gears 7, 8. The drive units 2, 3 have, in a way which will be discussed in more detail below, driving contact with the saw blade 4 and drive this, the drive unit 2 pushing and the drive unit 3 pulling the saw blade 4.

A log 10 is shown on a conveyor belt 9 whilst being cut with the bandsaw.

Fig. 5 is a purely schematic illustration of an embodiment of a bandsaw according to the invention, having only one reversing wheel 11. The saw blade 4 runs around the reversing wheel 11 and through two angularly positioned drive units 2, 3. The saw blade 4 therefore forms a curve between the drive units 2, 3, thereby producing a curved saw section 1'. The bandsaw in Fig. 5 cuts a curved section in a log 10 lying on a conveyor belt 9. The drive units 2, 3 are driven in this case from a common motor M.

The drive units 2, 3 are pivotally supported about the centres of rotation 12, 13. By pivoting the drive units 2, 3, the curved cutting section 1' can be altered with respect to size and shape.

Fig. 6 shows a variant of Fig. 7, wherein the two drive units 2, 3 are driven from a common motor M via a common spindle 14. In the drive spindles in Figs. 5 and 6, necessary links are built in according to need to allow movements of adjustment of the drive units 2, 3. A spindle drive 58 is provided for simultaneous turning of the drive units 2, 3 in opposing directions about their respective axis 12, 13.

An example of a drive unit according to the invention is shown in Figs. 7, 8 and 9. The drive unit is constructed to have a sturdy frame or housing 15 which basically is U- shaped in the lateral view. The legs of the U have a respective slot 16 for feed-through of the non-illustrated saw blades. The non-illustrated saw blades run between two guide chocks 17, 18. These guide chocks 17, 18 are supported in the housing 15 by means of fixing screws 19, 20 which run freely in bores in the housing. Between each set of fixing screws 19, 20 there is provided an adjusting screw 21 which is screwed into a threaded bore in the housing and runs against the respective guide chock 17, 18. With the aid of the adjusting screws 21 the guide chocks can be pressed against the non- illustrated saw blade, which runs in the slot 16, or to be more precise in the slot 22 between the guide chocks 17, 18.

A chain drive including a so-called triple chain is supported in the frame or housing, see Figs. 10 and 11.

The actual triple chain 23 runs about two chain wheels 24, 25. The chain wheels 24, 25 are by means of known bearing technique supported in a lower support plate 26, secured between the legs of the U by means of fixing screws 27, 28. One of the chain wheels 25 can be tensioned or slackened with the aid of an adjusting screw 29. To allow an adjustment of this kind, the chain wheel 25 is supported in an elongate hole 35 in the lower support plate 26, see Fig. 9. The triple chain 23 has driving interaction with the saw blade 4 guided into the slot 22, as is shown in Fig. 11 where the lower triple chain 23 is shown to the right.

The opposite side edge of the saw blade is driven by an upper triple chain 23, This is supported in the same manner as the lower triple chain 23 in an upper support plate 30, which constitutes a part of an upper frame 31. The upper frame 31 consists of two end plates 32 and the upper support plate 30 fixed therebetween. The fixing takes place with the aid of the indicated screws 33, 34.

The upper triple chain 23 runs in the same way as the lower triple chain about two chain wheels 24, 25, both supported in the upper support plate 30. In this upper support plate 30 there is an elongate hole 36, corresponding to the elongate hole 35, so that also one chain wheel 25 in the upper triple chain assembly can be tensioned or slackened by means of a tensioning screw 29 (not illustrated in the case of the upper triple chain).

The upper triple chain 23 interacts with the adjacent saw blade edge, as, for example, is shown in Fig. 11.

In Fig. 11 it can be seen that the saw blade 4, in addition to the saw teeth 37, has small indentations 38 with which pins 39, see also Fig. 10, have driving engagement. The pins 39 constitute parts of a triple chain, see, for example, Fig. 10, where it can be seen that a triple chain 23 is built up of two chains 40, 41 of the bicycle chain type. Only every fourth pin 39 between the two chains 40, 41 is retained as a through-going pin.

The use of the triple chains 23 causes the saw blade 4 to run very smoothly. The arrangement of the drive units also allows greater forces to be transmitted to the saw section as a pushing force is exerted on one side and a pulling force on the other side of the saw section. An advantage of the invention is also that the large tensile strains

associated with previously known bandsaws, where the drive takes place via one of the reversing wheels, are avoided.

The saw blade 4 can be lubricated or flushed. For this purpose, there are provided in the respective guide chocks schematically illustrated connection pieces 42, 43. Suitable hoses for the supply of flushing agent can be connected here.

Each triple chain assembly is driven by a suitable drive shaft 44, 45 which drives respectively upper and lower chain wheel 24.

As mentioned, the upper triple chain assembly with the upper triple chain 23 is supported in a frame 31 consisting of end plates 32 and an upper support plate 30 fixed therebetween. This unit 31 is located on the frame or housing 15 as shown in Fig. 7, and is connected to the frame 15 by means of two arms 46, 47. The arms 46, 47 are pivotally connected to respectively the upper frame 31 and the frame 15 by means of tensioning screws 48, 49, 50, 51, see especially Fig. 9. By respectively tensioning and slackening these screws, the frame part 31 can respectively be secured in the position shown in Fig. 7, and be pivoted outwards and upwards about the screws so that the upper triple chain 23 can thereby be pivoted towards the left in Fig. 7, and the saw blade 4 (not shown in Fig. 7) can be pulled up from the slot 22 between the guide chocks 17, 18 and guided into the slot 22, respectively.

In Figs. 12 and 13 a possible saw blade shape is shown. Here, the saw blade is indicated by means of the reference numeral 4, as in the preceding exemplary embodiment. It has been modified somewhat relative to the saw blade shown in Fig. 11 in that the saw teeth 37 are shaped somewhat differently, although in a known way. In the saw blade 4 in Fig. 12 indentations 38 are provided for interaction with the pins 39 in the respective triple chains 23. Owing to the somewhat "flatter" shape of the saw teeth 37, the location of support chocks between the chain wheels 24, 25, in supporting contact with the inner side of the triple chain, is made possible. Support chocks of this kind are well known and are not illustrated. Since they support the driving chain, they will help to further stabilise the drive. The saw blade 4 in Fig. 12 is also distinguished by planing bits 52 secured thereto. When sawing with the saw blade 4 in Fig. 12, it is possible to achieve simultaneous planing, as is shown in more detail in the section in Fig. 13 where the saw blade 4 is shown whilst cutting in a workpiece 53.

Fig. 3 shows in a purely schematic manner how an S-shaped saw section 1" can be provided by displacing the drive units 2 and 3 in relation to one another as shown. This displacement can be brought about in a simple manner, e.g., with the bandsaw shown in Fig. 4, with corresponding design of the drive connections and so forth. With an S- shaped saw section of this kind it is possible, e.g., in an advantageous manner to cut a panel 54 of S-shaped cross-section. A panel of this kind may be used, as shown in Fig.

14 as horizontal, overlapping panelling on a house wall 55. The individual panel boards 54 can advantageously be secured with the aid of special nails 56. These special nails 56 are designed as angle nails and so have a small leg 57 which grips about the lower edge of the overlying panel.

Teeth on both sides of the blade will allow operation in any direction according to choice.