EP1674221B1

EP1674221B1 - Device for crosscutting lengths of wood

Info

Publication number: EP1674221B1
Application number: EP04030431.3A
Authority: EP
Inventors: Bertil Lindberg; Gunnar Marklund
Original assignee: RENHOLMENS MEKANISKA AB
Current assignee: Renholmens Mekaniska Verkstad AB
Priority date: 2004-12-22
Filing date: 2004-12-22
Publication date: 2013-10-09
Anticipated expiration: 2024-12-22
Also published as: EP1674221A1

Description

The present invention concerns a device according to the preamble to claim 1.
Such a device is known from DE 42 35 240 A1 .
Lengths of wood such as planks and board are normally stacked into packets of standard lengths that are wrapped with plastic on similar packaging material before being distributed to the consumer. Before the lengths of wood are stacked and packaged in layers, they must be cut at the root and/or top end to lengths specified by the buyer or determined by the intended use of the wood, if the wood is to be used for construction purposes or similar for example.
The cutting operation is done in a crosscutting saw through which the layer of wood is fed towards saw blades at right angles to its length axis on a pusher conveyor. Such crosscutting sores are normally be cut with two or more circular saws that can be positioned across the direction of transport of the lengths of wood and whose relative distance from each other can be changed. The lengths of wood are placed on a conveyor comprising a number of continuous chains. These chains are fitted with pushers, which, while in contact with the rear edge of a length of wood, push one piece of wood or an entire layer through the crosscutting saw. One problem with feeding an entire layer of wood using the said pusher conveyor is that individual pieces of wood in the layer are not always maintained at right angles while they are passing through the saw blades. Amongst other things, this is due to the pieces of wood not being ideally rectangular but exhibiting different shapes defects, such as being crooked, warped and twisted, or defects more on the surface, such as wanes. As the lengths of wood are not ideally straight and free from defects, particularly the pieces at the front of the layer tend to turn and move during the cutting operation while the layer is being pushed from behind by the conveyor. That the lengths of wood move while being cut results in a poor surface of the cut and, above all, a very poor cutting precision.
In order to avoid these problems there are known devices for crosscutting in which the lengths of wood are divided into individual pieces before being fed through the crosscutting saw blades on the pusher conveyor. With regard to cutting layers of wood, there are also known devices with a means of clamping positioned above the conveyor intended to hold down or by force drive the layer of wood down against the conveyor in conjunction with the saw blades, compare for example US 3 722 343 . Because the chains of the pusher conveyor are used both to transport the lengths of wood up to the crosscutting saw by means of an input conveyor and to transport them through the same, a problem arises with timing as the crosscutting saw conveyor must be timed in such a way that the pusher is always able to be inserted behind an arriving length of wood in conjunction with the delivery from the input conveyor.
Even if the cutting precision of the currently known devices for crosscutting has improved considerably, there is always a striving for a further improvement and the object of this invention is to achieve a device offering improved cutting precision. Furthermore, the intention is to achieve a device that also allows a simplified method of setting different cutting lengths of the wood. More precisely, the intention is for a device for crosscutting that makes it possible at high speed and independent to the rate of the arriving lengths of wood to feed an entire layer of wood through the saw while maintaining a satisfactory cut quality and precision.
This object of the invention can be achieved with the present device being given the distinctive features and characteristics specified in claim 1.
The invention will be described more fully in the form of an example embodiment with reference to the attached drawings on which;

Fig. 1 shows a side view of a device for crosscutting according to the invention viewed along the line I - I in fig. 3,
Fig. 2 shows a view from above and the device viewed along the line II - II in fig. 1, and
Fig. 3 shows a view from the front viewed in the direction of transport of the wood seen backwards and along the line III - III in fig. 1.

Referring to figs. 1 and 3, a device for crosscutting lengths of wood comprises a frame consisting of two vertical frame parts 1 located a distance from each other and whose bottom ends are fixed to a surface 2, such as a concrete floor, and a first horizontal frame part 3 of framework type extending between the top ends of the vertical frame parts 1 and a second horizontal frame part 4 in the form of beams positioned below the first horizontal frame part. For vertical movement up and down, the first horizontal frame part 3 is controlled by means of holding and guiding 5, which act between the free ends of the first horizontal frame part 3 and the top ends of the vertical frame parts 1. These means of holding and guiding 5 comprise interacting guide pins 6 and guide rails 7 arranged at each end of the horizontal frame part 3 and the top ends of the vertical frame parts 1 respectively. The first horizontal frame part 3 can be raised to load as illustrated by the double ended arrow 8 in fig. 3 through the action of a means of lifting 9. This means of lifting 9 comprises a respective jack 10 acting on each end of the first horizontal frame part 3 and a respective shaft 11 with which the jacks are linked for synchronous drive from one single motor 12.
As best illustrated in fig. 1, the present crosscutting saw is integrated as a transitional step between on both sides adjoining conventional conveyors, i.e. conveyors comprising a number of adjacent chains fitted with pushers 13 running in channelled rails 14 with which chains the lengths of wood 15 are fed at right angles to their length as illustrated by arrow 16. In the following, that part of the conveyor which, seen in the direction of transport, is positioned before the crosscutting saw is generally designated the input conveyor 17 and that part positioned after the crosscutting saw the output conveyor 18.
Between the two vertical frame parts 1 are a first and a second generally designated 19 combined cutting and transport unit, i.e. a unit that besides a means of cutting 20 the arriving lengths of wood 15 is also equipped with a means of transport 21 providing controlled and regulated feed of the lengths of wood through the means of cutting. The position of each such combined cutting and transport unit 19 can be adjusted in relation to the transport direction of the lengths of wood 15 as illustrated with the double ended arrow 22 in fig. 3, whereby one of the cutting and transport units 19 can be adjusted independently from the other.
As illustrated in fig. 3, each cutting and transport unit 19 comprises an upper part 23 and a lower part 24, each forming a separate unit. The lower part 24 comprises a stand 25, which, via means of holding and guiding 26 comprising guide rails 27, is slide mounted onto the second horizontal frame part 4 extending between the two vertical frame parts 1. The lower part 24 can be offset on the said guide rails 27 across the direction of transport of the lengths of wood 15, i.e. along the said lengths of wood. The lower part 24 on the guide rails 27 is offset through the action of a means of driving 29 comprising a motor 30 mounted in the stand 25 exhibiting a gear wheel 32 arranged on a shaft 31 interacting with a gear rack 33 extending along one of the beams forming part of the second horizontal frame part 4. When activated by the motor 30, the gear wheel 32 engages the gear rack 33 so that the lower part 24 moves along the gear rack and therefore also along the second horizontal frame part 4. For unlocking and fixing the lower part 24 to the horizontal frame parts 4 there are arranged means of locking 34 comprising pneumatic cylinders that can be applied against the long sides of the frame parts 4 for locking.
The means of transport 21 for feeding the lengths of wood 15 through the means of cutting 20 comprise wood transporting parts forming part of both the upper part 23 and the lower part 24. The wood transporting parts comprising principally a parallel running first and second pair of endless transport elements 35 and 36 respectively, of which one pair of transport elements 35 is located above the second pair of transport elements 36 at such a relative distance that the lengths of wood 15 can be fed between the meeting parts of the upper and lower pair of transport elements. Even if the first and the second transport element 35 and 36 respectively are arranged in pairs in the present embodiment of the invention it should be understood that in certain applications, it should be sufficient if each transport element is designed only as a single running element. For example, this will be sufficient when a length of wood is to be cut close to one end, i.e. end cutting.
The aforesaid pair of transport elements 36 is located in the lower part 24 and therefore comprises transport chains 37, the parts of which that are active in transporting the wood are arranged an elastomeric friction material. For example, the parts are covered with a friction material such as rubber and which transport chains 37 driven by a motor 38 run in parallel pairs over a number of wheels 39. The speed of the motor 38 is adapted so that the speed of the second pair of transport elements 36 is synchronous with the speed of the input and output conveyors 17 and 18 respectively. To offer a certain degree of control and to support the weight of the lengths of wood 15 passing through the crosscutting saw, the upper parts 40 of the second pair of transport elements run along grooves 41 arranged in a plate 42 included in the lower part is 24 stand 25. The lower part 24 means of cutting 20 comprises a motor 43 that drives a saw blade 44 positioned parallel to the direction of transport 16 and so at right angles to the lengths of wood 15. As best illustrated in fig. 2, the upper parts 40 of the second pair of transport elements 36 run at a relatively small distance from each other on both sides of an active part of the saw blade 44 extending up through a slit 45 arranged in the plate 41. It should be understood that the closer both the upper parts 40 of the pair of transport elements 36 are to the saw blade 44, the more secure and fixated can the length of wood 15 be held during the cutting operation.
The upper part 23 has a stand 46, which, via means of holding and guiding 47, is slide mounted to the horizontal beam 3 of the frame for moving along the first horizontal frame part 3. The means of holding and guiding 47 comprise interacting means of holding 48 and guide rails 49, whereby the said guide rails run parallel and at a distance from each other along the bottom of the second horizontal frame part 3. The means of holding and guiding 47 also comprise pneumatic locks to secure the upper part 23 relative to the horizontal frame part 3. The upper part 23 comprises a means of clamping 50 in the form of a cradle 52 suspended from a link arm system 51 that is used to hold down the lengths of wood 15 against the upper parts 40 of the lower part's second pair of transport elements 36. This cradle 52 supports in turn the aforesaid first pair of transport elements 35, which hereby comprise two endless straps 53 running in parallel pairs over several wheels 54 mounted on the cradle. For efficient transport of the lengths of wood 15, the conveyor belts comprise a suitable elastomeric friction material such as rubber.
The bottom parts 55 of the first pair of transport elements 35 run on the outside of a plate 56 arranged on the lower part of the cradle 52 that in a supporting manner absorbs forces from the passing lengths of wood 15. The cradle 52 also supports a motor 57 used to drive one of the said wheels 54 and thereby the first pair of transport elements 35 synchronously with the lower part's 24 second pair of transport elements 36 of chain type. For stretching and adjustment of the belt tension, one of the wheels 54 can be adjusted via a means of adjustment 58.
The link arm system 48 comprises a front and a rear pair of swivel arms 59 and 60 respectively, which are so pivoted with the stand 46 and cradle 52 respectively that the said cradle, which should be understood if fig. 1 is studied closely, can be swung vertically downwards in a clockwise direction towards both the upper parts 40 of the second pair of transport elements 36. That is to say, so that both lower parts 55 of the first pair of continuous transport elements 35 are moved in a downwards direction towards both upper parts 40 of the second pair of continuous transport elements 36. See also fig. 1.
As the thickness of the individual length of wood 15 in a layer can vary, the distance between both lower parts 55 of the first pair of transport elements 35 and both upper parts 40 of the second pair of transport elements 36 must be adaptable to allow such random variations. To maintain the constant clamping force on the lengths of wood 15 passing between the meeting upper and lower parts 55, 40 of the pairs of transport elements 35, 36, there is a spring pressure device 61 in the former pneumatic cylinder pivot mounted between the cradle 52 and the upper part's 23 stand 46. Besides the flexible spring clamping force provided by the chosen means of pressure 61, the clamping capability can be further improved by the choice of continuous belts with suitable elastic properties for the first pair of transport elements 35. In this part, it could be considered to use hose-like belts filled with air or gas to offer the same clamping force on the lengths of wood even when they exhibit considerable variations in thickness.
In the transition between the crosscutting machine and the input and output conveyors 17, 18 respectively is arranged a set of first up and down folding flaps 62 across the direction of transport of the lengths of wood 15. These first flaps 62 are operated via means of actuation and control 63 in the form of pneumatic cylinders, whereby the flaps are shown in lowered position with a dotted line in fig. 1. See also fig. 2. Around each flap 62 runs a conveyor chain 65 on wheels 64 that is driven by a motor 66. Seen in the direction of transport and as best shown in fig. 2, the flap's 62 conveyor chains 65 and the conveyor chains 13 of the input and output conveyors 17, 18 respectively overlap each other like interlocking fingers when the flaps 62 are in their raised positions. Hereby, the lengths of wood 15 can be conveyed from the input conveyor 17 to the crosscutting saw and on from the same to the output conveyor 18. When the flaps 62 are in the lowered positions, i.e. in the positions shown with a dotted line in fig. 1, the lower part 24 of the crosscutting saw goes free from the input and output conveyors 17, 18 and is allowed to move sideways along the first and second horizontal frame parts 3, 4.
To facilitate service and maintenance on the means of sawing 20, the crosscutting saw is equipped with other types of folding flaps 67, which, like the flaps described above, exhibit a synchronous motor-driven continuous conveyor chain 69 running around wheels 68 facing towards the input conveyor 17 and intended to be operated by hand. This second type of flap 67 is essentially longer than the flaps 62 described above and has, for swinging between a lowered normal position and a raised alternative position illustrated by a dotted line in fig. 1, one end pivot mounted to the lower part's 24 stand 25. In this longer flap's 65 raised position, the means of cutting 20 becomes very easy to access for service and maintenance.
The present crosscutting saw also includes a means of coupling 70, which allows the upper 23 and lower 24 part respectively in each cutting and transport unit 19 to be coupled for a common instantaneous movement along the first and second horizontal frame parts 3, 4 of the frame 2 through the action of the means of driving 29 described above. The means of coupling 70 is described in more detail with reference to the detailed enlargement shown in fig. 3 and as is evident herein, the means of coupling comprises matching pins 71 and recesses 72 that are arranged to the upper 23 and the lower 24 part respectively. The said pins and recesses can be engaged with each other by the upper part 23, using the means of lifting 9, being lowered so it makes contact with the lower part 24 and essentially rests on the same. To further secure the coupled upper and lower parts 23, 24 to each other, the means of coupling 70 has a means of locking 73 comprising a locking arm 74 pivot mounted to the lower part with a hook section and a pin 75 arranged on the upper part to which the hook section can engage in an interlocking position. The locking arm 74 is swung by the action of a means of actuation and control 76 in the form of a pneumatic cylinder.
With both cutting and transport units 19 set at a suitable distance from each other to obtain the necessary cutting length for the passing lengths of wood and with the flaps 62 in their raised positions, the layers of wood 15 arriving on the input conveyor 17 are made to pass between the meeting upper and lower parts 40, 55 of the pairs of transport elements 35, 36. The lengths of wood 15 are fed through the saw blades 44 and conveyed, after passing between the upper and lower parts 55, 40 of the pairs of transport elements 35, 36, to the output conveyor 18 for further handling.
When changing the cutting lengths of the crosscutting saw, the flaps 62 are lowered by the means of actuation and control 63 so that the bottom part 24 of the crosscutting saw goes free from the input and output conveyors 17, 18 respectively. Hereafter, the upper 23 and lower 24 parts are coupled together by the upper part 23 being lowered by the means of lifting 9 so that it makes contact with the lower part 24 and the pins 71 and recesses 72 of the means of coupling are brought to engage with each other. The coupling together is completed by the locking arm 74 of the means of locking 73 being moved to its locked position. The crosscutting saw is hereby reset by the means of driving 29 being activated and both the cutting and transport units 18 being moved sideways to their desired positions along the first and second horizontal frame parts 3, 4 and secured in the desired positions by the means of locking 34. In order for the crosscutting saw to be taken into operation again, the upper 23 and lower 24 parts must be disengaged and separated from each other vertically. This is so that the lengths of wood are able to pass between the meeting upper and lower parts 40, 55 of the pairs of transport elements 35, 36.
The separation of the upper 23 and the lower 24 parts from each other takes place in a manner that is the reverse of the one described above for changing the cutting lengths of the crosscutting saw.
The present invention is not limited to the above description or as illustrated in the drawings but can be changed and modified in a number of different ways within the scope of the following claims.

Claims

Device for crosscutting lengths of wood (15) transported at right angles in relation to their lengths comprising a frame (1, 3, 4) carrying a number of from each other separate cutting and transport units (19) arranged across the direction of transport of the lengths of wood (15), where each cutting and transport unit comprises an upper part (23) and a lower part (24) positioned at a distance from each other above and below the transported lengths of wood respectively, the means of transport (21) forming part of both the upper and the lower part and which through relative interaction feed the lengths of wood in the direction of transport between the upper and the lower parts, a means of cutting (20) for cutting the lengths of wood passing between the upper and the lower part, whereby the means of transport (21) comprises a first and second continuous running transport element (35, 36) that are positioned one on top of the other and running parallel with each other, the second transport element (36) is mounted on and supported by the lower part (24) and whereby the continuous running transport elements are positioned by the side of the active cutting part of the means of cutting (20), characterised in that the first transport element (35) is supported by a cradle (52) which is pivot mounted on the upper part (23) to facilitate varying the distance between meeting upper and lower parts (55, 40) of the transport elements (35, 36) and that each of the first and second transport elements (35, 36) comprises an elastomeric friction material in which the lengths of wood (15) are fed forward between the meeting upper and lower parts (55, 40) of the transport elements under the influence of the said friction material.
Device according to claim 1, whereby the first and second transport elements (35, 36) are arranged as a pair whose parallel running upper and lower parts (55, 40) are positioned on each side of the active cutting part of the means of cutting (20).
Device according to claim 2 whereby one of the continuous running transport elements (35) is positioned in the upper part (23) and comprises elastic belts or straps while the second transport element (36) is positioned in the lower part (24) and comprises transport chains covered in a friction material such as rubber.
Device according to claim 3 whereby the belts or straps are covered or coated with a friction material such as rubber.
Device according to claim 3 whereby the belts or straps are made as hose-like hollow elements filled with a gas or air in order to provide good elasticity and compliancy on the lengths of wood.
Device according to any one of the claims 1 -5, characterised in that the means of cutting (20) comprises a saw blade (44), the active part of which used for cutting the lengths of wood (15) is located between the lower part's (24) pair of transport elements (36).
Device according to any one of the claims 1 - 6, whereby the continuous and with each other parallel running transport elements (35, 36) in the means of transport (21) are supported by plates (42) at their meeting upper and lower parts (55, 40).
Device according to any one of the claims 1 - 5, whereby the upper part (23) comprises a link arm system (51) in which the cradle (52) is pivot mounted supporting both one of the transport elements (35) and a motor (57) for driving the same as well as a means of spring pressure (61) for rotating the cradle clockwise to the upper part/s (40) of the second transport element (36).
Device according to claim 8, whereby the means of spring pressure (61) is compliant in an upward direction from the lower part (24) for taking up the variations in thickness of the transported lengths of wood (15).
Device according to any one of the previous claims, comprising a means of holding and guiding (26, 47) with which the upper part (23) and the lower part (24) respectively are movable on the frame (1, 3, 4) across the direction of transport of the lengths of wood, means of locking (34, 47) with which the upper part and the lower part respectively can be locked in determined positions to the frame.
Device according to any one of the previous claims, whereby the frame comprises a first horizontal frame part (3) supporting the upper part (23) of the cutting and transport unit (19), a second horizontal frame part (4) located below the first frame part and supporting the lower part (24) of the cutting and transport unit, means of holding and guiding (5) with which the first horizontal frame part is guided for vertical movement up-and-down on vertical frame parts (1) in the frame, means of lifting (9) for raising and lowering the first horizontal frame part and thereby varying the relative distance between the upper and lower parts of the cutting and transport unit, means of coupling (70) allowing the upper and the lower parts to be brought together to make contact and be coupled together for instantaneous joint movement of the parts along the horizontal frame parts.
Device according to claim 11, comprising a means of driving (29) with which the upper part (23) and the lower part (24) in their, via the means of coupling (70), linked position can be moved along the first and second horizontal frame parts (3, 4).
Device according to claim 12, whereby the means of driving (29) comprises a motor (30) supported by the lower part (24) with a gear wheel (32) arranged on a shaft (31) that interacts with a gear rack (33) arranged on the lower second horizontal frame part (4).
Device according to any one of the previous claims 12 - 13, whereby a first group of up and down folding flaps (62) is arranged in conjunction with the means of transport (21) on both sides of the same and which flaps each comprise a continuous running motor driven transport element (69) in which the flaps in one of their control positions allows the lengths of wood (15) from an adjoining conveyor to be conveyed to the means of transport (21) and with the flaps in their second control position the cutting and transport units (19) are allowed to go free from the adjoining conveyors so that the said cutting and transport units, via the means of driving (29), can move freely on the first and second horizontal frame parts (3, 4) of the frame.
Device according to claim 14, comprising other up and down folding flaps (67) located between one of the first or second groups of up and down folding flaps (62) and the means of transport (21), which other flaps are hinge fastened to the lower part (24) and each comprise a motor driven continuous running transport element (69) in which the means of cutting (20) is accessible with the flaps folded up.