Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27B—SAWS FOR WOOD OR SIMILAR MATERIAL; COMPONENTS OR ACCESSORIES THEREFOR
  • B27B33/00—Sawing tools for saw mills, sawing machines, or sawing devices
  • B27B33/20—Edge trimming saw blades or tools combined with means to disintegrate waste
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27L—REMOVING BARK OR VESTIGES OF BRANCHES; SPLITTING WOOD; MANUFACTURE OF VENEER, WOODEN STICKS, WOOD SHAVINGS, WOOD FIBRES OR WOOD POWDER
  • B27L11/00—Manufacture of wood shavings, chips, powder, or the like; Tools therefor
  • B27L11/007—Combined with manufacturing a workpiece

Definitions

• the present invention relates to a method for forming a round log into a block with two or more flat lateral surfaces, comprising the steps of directly cutting into chips the material which is to be removed, by means of a block-forming assembly of the type having two or more working tools which each have the form of a rotat- able drum or frustoconical body which on its circumferential surface carries a plurality of chipper knives; feeding, after the block-forming assembly, the block to a sawing assembly for resawing the block to produce boards and planks, and, when sawing thick logs, reducing the feed rate of the sawing assembly and, thus, also of the block-forming assembly.
• the invention also concerns a blind knife according to the preamble to claim 5.
• Block-forming assemblies of the type mentioned by way of introduction are often included in a production line of a sawmill.
• a sawing assembly is placed immediately after the block-forming assembly and the logs and blocks are fed at the same rate through the block-forming assembly and through the sawing assembly.
• the block-forming assembly and the sawing assembly it is not unusual for the block-forming assembly and the sawing assembly to be positioned so close to each other that the front end of a log enters the sawing assembly before its rear end has left the block-forming assembly.
• the feed rate of the block-forming assembly will be reduced when cut- ting thick logs, since the feed rate of the sawing assembly must be reduced owing to limitations in capacity.
• the rotary speed of the working tools of the block-forming assembly must therefore be reduced.
• the ratio of the rotary speed to the feed rate is in fact crucial for the length of the cut chips, i.e. how closely the chipper knives hit the log along a given length of the log.
• the thickness of the chips on the other hand is in the first place dependent on their length in such a manner that the chips will be thinner when chopping short lengths and vice versa. In general, when chopping short chip lengths, a larger amount of undesirable short fractions such as shavings and splits is formed.
• the peripheral speed of the chipper knives will decrease, which also applies to a possible saw blade or finishing disc that is usually placed in the upper part of conical working tools to improve the quality of the flat processed surfaces .
• the peripheral speed of chipper knives should normally be between 20 and 30 m/s for the cutting pro- perties of the chipper knives to be optimal. Below the optimal speed, the risk of pick-ups and reduced surface smoothness increases. The speed also has a certain effect on the thickness of the chips in such a manner that a reduced speed gives thicker chips and vice versa.
• the optimal peripheral speed of a saw blade is usually between 40 and 60 m/s below which the quality of the surfaces is deteriorated.
• the present invention aims at obviating problems and drawbacks that are associated with a reduction of the feed rate of a block-forming assembly in the processing of thick logs. More specifically, the invention relates to a new method in which the rotary speed of the working tools can be kept or the otherwise necessary reduction of the rotary speed can at least be limited at a reduced feed rate but with a maintained chip size. At least this object is achieved by a method according to claim 1.
• the invention also concerns a blind knife for use in the application of the inventive method.
• the blind knife aims at enabling the carrying out of the method without any risk of damage to and wear on the working tool and in particular the seats of the chipper knives on the working tool. This object is achieved by a blind knife according to claim 5.
• the invention is thus based on the knowledge that the above objects can be achieved by removing, from a block-forming assembly which is included in a sawing line, one or more chipper knives from each of the working tools to compensate for the reduced feed rate of the sawing assembly and, thus, of the block-forming assembly which is necessary when cutting thick logs, and thus preventing or at least limiting the reduction of the rotary speed which otherwise is necessary to maintain the desir- ed chip size.
• the invention is generally applicable in so far as one or more chipper knives can be removed from an arbitrary block-forming assembly, both those with frustoco- nical working tools and those with cylindrical working tools, for the purpose of keeping a high rotary speed.
• the chipper knives are distributed symmetrically round the circumferential surface of the working tool .
• the expression symmetrical distribution thus comprises also a single chipper knife in a rotary plane of the working tool since this will hit the log at the same intervals.
• a symmetrical distribution is most easily obtained by removing exactly half of the chipper knives, i.e. by removing every second chipper knife, but can also be achieved in other ways.
• a working tool is shown in the form of a frustoconical disc with the chipper knives arranged in two separate circumferential rings or rotary planes, an inner and an outer. Each of the rings has four chipper knives.
• two opposite chipper knives are removed from the inner ring while two opposite chipper knives are kept. In such a case, the feed rate of the logs can thus be reduced by half while keeping the same rotary speed and the same size of chips.
• the working tool is provided with a feed limiter which limits the maximum feed rate of the block between the chipper knives by preventing what is called power feed.
• the feed limiter has the form of a ring which along its outer circumference has stepped cam curves and is arranged between the top surface of the cone and a saw blade which performs finishing of the lateral surfaces of the block.
• the feed limiter need not have the form of a ring but could consist of short arcuate sections to facilitate an exchange of the feed limiter, for instance by allowing an exchange without first having to remove an exteriorly positioned saw blade or finishing disc.
• this feed limiter must be replaced with one having a corresponding number of cam curves.
• Such a feed limiter is advantageous by limiting the maximum feeding of logs so that the chips will have a uniform size. In practice, it is therefore preferred to use such a feed limiter on the working tools, but it would also be possible to ensure the correct feed rate in other ways, for instance by accurate control by means of feeding rolls.
• the working tools have the form of frustoconical discs or bodies which each have chipper knives arranged in two rings or rotary planes along the circumference of the circumferential surface. More specifically, one ring with four symmetrically distributed chipper knives at the top surface of the truncated cone and one ring with four symmetrically distributed chipper knives at a longer distance from the top surface of the truncated cone. In the shown embodi- ment, two opposite chipper knives are removed from the inner ring located closest to the top surface when reducing the feed rate, while all chipper knives in the outer ring spaced from the top surface are kept.
• the invention is not restricted to this and could be varied in many ways within the scope of the claims.
• half of the chipper knives could be removed also from the outer ring.
• many different types of working tools are available on the market, for instance those with more than two rings of chipper knives or those with only one ring of chipper knives, which then usually have a greater length than those shown in this embodiment.
• the basic principle of the invention is applicable to all these types of working tool and, as mentioned above, also to working tools that are not frustoconical but cylindrical.
• Fig. 1 is a top plan view of a round log which is formed into a block with two flat lateral surfaces in a prior-art block-forming assembly and which is then resawn in a sawing assembly,
• Fig. 2 is a perspective view of a working tool in the block-forming assembly according to Fig. 1
• Fig. 3 is a side view of the working tool in Fig. 2
• Fig. 4 is a top plan view of a round log which is form- ed into a block with two flat lateral surfaces in a block-forming assembly, which is modified according to the present invention, and then resawn in a sawing assembly
• Fig. 5 is a perspective view of a working tool in the block-forming assembly according to Fig. 4
• Fig. 6 is a side view of the working tool in Fig. 5
• Fig. 7 illustrates a feed limiter for the working too ⁇ L according to Figs 2 and 3
• Fig. 8 illustrates a feed limiter for the working tool according to Figs 5 and 6.
• FIG. 1 is a schematic top plan view of the procedure of block-forming and sawing of a round log.
• the round log 1 is fed longitudinally first through a block-forming assembly which is generally designated 2 and which in the shown embodiment consists of two opposing frustoconical working tools or chipper discs 3, 3'.
• a plurality of chipper knives 4 are arranged, which during rotation of the working tool and simultaneous longitudinal feeding of the round log cut the material to be removed from the round log into chips so that the round log is formed into a block with two flat lateral surfaces 5, 5'.
• a sawing assembly is arranged, which is schematically shown in the Figure in the form of two circular saw blades 6. As is evident, the distance between the block forming assembly and the sawing assembly is so small that the front end of the block enters the sawing assembly before its rear end has left its block-forming assembly.
• Figs 2 and 3 illustrate the more precise construction of a working tool 3.
• the working tool has a frusto- conical form with chipper knives 4 mounted on its circumferential surface.
• the chipper knives are arranged in two separate circumferential rings with four chipper knives in each ring.
• the chipper knives are sym- metrical arranged, equidistantly spaced from each other along the circumference of the working tool as is best seen in Fig. 3.
• each chipper knife has a processing cutting edge, and is screwed into a recessed seat in the working tool .
• through holes 7 are formed in the working tool through which the chips leave the block-forming assembly.
• a saw blade 8 is arranged, which performs finishing of the lateral surfaces of the block. Moreover there is in the area between the saw blade 2 and the upper surface of the cone a feed limiter 9, whose outer circumferential edge forms a stepped cam curve with a height decreasing from one chipper knife to the next.
• the feed limiter is shown and described in more detail in connection with Figs 7 and 8.
• Figs 4-6 illustrate a preferred embodiment of a method according to the present invention, which obviates the problems and drawbacks that are associated with the reduction of the feed rate of the logs when sawing thick logs.
• two opposite chipper knives are removed from the working tool from the inner circumferential ring of chipper knives and are replaced with blind knives 10 which are screwed into the ordinary chipper knife seats 11.
• the blind knives protect the chipper knife seats from wear and can be arbitrarily designed, provided that they can be mounted in the chipper knife seats and have no cutting edge or other protruding parts that can interfere with the feeding of logs .
• the blind knives have the same mass as the ordinary chipper knives so as not to change the balancing of the working tool independently of how many chipper knives are removed and replaced with blind knives.
• the blind knives could have such a form as to cover also the openings 7 of the working tool.
• the feed limiter has a number of cam curves 12 along the outer periphery of the feed limiter. More specifically, the feed limiter has in Fig. 7 four cam curves while the feed limiter in
• Fig. 8 has only two cam curves. Each cam curve has a gradually decreasing radial distance between the axis of rotation and its outer peripheral edge from the area immediately behind a chipper knife to the area immediate- ly in front of the next chipper knife.
• the feed limiter depicted in Fig. 7 is intended for use in a working tool which has four cutting knives in the inner circumferential ring, i.e. one chipper knife in each recess along the periphery of the feed limiter as shown in the Figures. If, according to the invention, two of the chipper knives are then removed to be able to reduce the feed rate of the logs but keep a high rotary speed of the working tool, the feed limiter in Fig. 7 must be replaced with a feed limiter according to Fig. 8 which has two cam curves 12 and two recesses for the chipper knives along its periphery.
• the radial distance between the centre of rotation and the periphery of the feed limiter is to decrease to the same extent from the front end to the rear end of each cam curve both in the embodiment according to Fig. 7 and in the embodiment according to Fig. 8.
• the difference is that in Fig. 8 the change of the radial distance between the centre of rotation and the outer periphery of the feed limiter is to occur along about twice the distance in Fig. 7.
• the function of the feed limiter will be most easily understood from Fig. 4. As is evident, the outer peripheral edge of the cam curve of the feed limiter abuts against the surface last cut by the chipper knives . As a result, the feed limiter will limit the maximum feeding of the log to be processed by the feeding being limited to the reduction of the radial distance between the centre of rotation and the outer peripheral surface of the cam curve that occurs from one chipper knife to the next chipper knife.
• the feed rate of the logs can thus be reduced to half, without the rotary speed of the working tools needing to be reduced or the size of the chips being changed.
• the number of chipper knives is maintained in the outer circumferential ring but this is not very important since, as illustrated in Fig. 4, it is usually only the inner circumferential ring of chipper knives that processes the round log while the outer circumferential ring of chipper knives will process the logs only in case of unusually large dimensions, such as in connection with root swellings and the like. The amount of chips that is cut by the outer circumferential ring of chipper knives and that will be smaller than the chips that is cut by the inner circumferential ring of chipper knives will thus be small .

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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Wood Science & Technology (AREA)
• Forests & Forestry (AREA)
• Manufacturing & Machinery (AREA)
• Debarking, Splitting, And Disintegration Of Timber (AREA)
• Chemical And Physical Treatments For Wood And The Like (AREA)

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• 2001
  • 2001-11-28 SE SE0103967A patent/SE0103967L/ not_active IP Right Cessation
• 2002
  • 2002-11-28 DE DE60217913T patent/DE60217913T2/de not_active Expired - Fee Related
  • 2002-11-28 AT AT02789121T patent/ATE352403T1/de not_active IP Right Cessation
  • 2002-11-28 EP EP02789121A patent/EP1458531B1/de not_active Expired - Lifetime
  • 2002-11-28 WO PCT/SE2002/002199 patent/WO2003064126A1/en not_active Ceased

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