This nonprovisional application claims priority under 35 U.S.C. §119 to Swedish Patent Application No. 1151134-2 filed on Nov. 29, 2011, the entire contents of which are hereby incorporated by reference.
The present invention relates to an edge sawing machine for simultaneously parallel sawing of opposite longitudinal edges and by that width adjustment of a piece of wood, comprising a feed table, which at an upper side defines a feeding plane along which the piece of wood is to be fed in the longitudinal direction during the sawing, as well as a first and a second circular saw blade, which are rotatable in the same direction of rotation but of which the first circular saw blade is rotatably arranged on a rotation shaft, which is located below the feeding plane, while the second circular saw blade is rotatably arranged on a rotation shaft which is located above the feeding plane, having to result that one of the circular saw blades during sawing, affects the piece of wood with a force that acts against a feeding direction for the wood, while the other of the circular saw blades affects the piece of wood with a force that acts in the feeding direction, wherein the position of at least one of the circular saw blades is adjustable in the longitudinal direction of the rotation shaft to allow adjustment of the sawing distance between the two circular saw blades.
Since long time ago it is known edge sawing machines or edging mills of many different types and sizes which by means of at least two sawing members, for example ribbon saws, circular saw blades or frame saw blades, accomplish simultaneously parallel sawing of two opposite longitudinal edges of a piece of wood which is fed in the longitudinal direction through the machine for the purpose of straight or linear sawing of the longitudinal edges and width adjusting of the piece of wood. The type of wood piece that normally, but not exclusively, is a possible choice for sawing in such edge sawing machines are untrimmed boards, girders and planks, which have been produced by rip sawing of whole logs of wood and which for this reason are provided with wanes along their longitudinal edges and whose portions free of wanes have a tapering width towards the top end. Accordingly, such pieces of wood have no straight sawn longitudinal edge which can be brought to bear against a guide and serve as a reference edge during continued straight split sawing of the piece of wood. Therefore, to above all accomplish a linear sawing having a high accuracy, it is necessary to provide such edge sawing machines with strong feeding devices in front of as well as behind the sawing members which guide the piece of wood with a large force during the feeding to prevent lateral displacements. Such strong feeding devices are expensive to manufacture and may cause, particularly by small-scale edge sawing machines, that the costs for the feeding devices will represent an unreasonable large part of the total cost for the machine.
At edge sawing machines which are provided with two or more circular saw blades, each of these are normally rotatably arranged on a rotation shaft which is located below a feeding plane, which is defined at an upper side of a feed table, and is driven in such a direction of rotation that they affect the piece of wood with a force acting against the feeding direction. Hereby arises a great risk for back throw of the piece of wood against the feeding direction and either there have to be arranged special back throw safety devices, which will cause additional costs, or the feeding devices have to be dimensioned to prevent also such back throw which will contribute to additional increase in cost for these.
Through SU 1530445 it is previously known an edge sawing machine, which is provided with two circular saw blades. These rotate in the same direction but are arranged such that one of the circular saw blades is rotatably arranged on a rotation shaft, which is located below a feeding plane of a feed table, while the other circular saw blade is rotatably arranged on a rotation shaft which is located above the feeding plane. The direction of rotation for the circular saw blades is such that the lower saw blade affects the piece of wood with a force that is directed against the feeding direction, while the upper saw blade affects the piece of wood with a force that is directed in the feeding direction and accordingly contributes to the feeding of the wood. By arranging the saw blades in this way the risk for back throw of the wood is decreased considerably in that the saw blades affect the wood with opposite directed forces, which essentially offset each other and possible back throw safety devices or the feeding devices do not need to be dimensioned to take up large back throw forces. Still, the feeding devices have to be so powerful dimensioned that lateral displacement of the wood is prevented during sawing.
The object of the invention is to provide an edge sawing machine, which has a simple and cost saving structure in that the one or more feeding devices can be dimensioned for relatively small forces. At least this object is achieved by an edge sawing machine according to claim 1.
At least the above object can be achieved by an edge sawing machine, which is provided with circular saw blades, at which the circular saw blades are arranged in such a way that a first saw blade is rotatably arranged on a rotation shaft, which is located beneath a feeding plane for the wood and a second saw blade is rotatably arranged on a rotation shaft, which is located above the feeding plane, and the saw blades have the same direction of rotation. Thereby, one of the saw blades, the counter feed sawing saw blade, will affect the piece of wood with a force that is directed against the feeding direction for the wood, while the other, the down feed sawing saw blade, will affect the piece of wood with a force which is directed in the feeding direction. The basis of the invention is the insight that the piece of wood which is sawn in the machine will be affected, due to the combination of one counter feed sawing and one down feed sawing blade, by a turning moment, which will strive to carry the sawn part of the wood towards the side of the machine where the counter feed sawing saw blade is located. In accordance with the invention, this condition is utilized to achieve, in a simple way, a very stable, straight-lined feeding and thereby straight sawing with high precision of the piece of wood in that a guide, which at least in an operative portion has a thickness which do not exceed the thickness of the saw blade, is arranged in alignment with and behind at least the counter feed sawing saw blade. In the following description and claims the saw blade which is rotatably arranged on a rotation shaft that is located beneath the feeding plane, will for simplicity's sake normally be called first and/or lower saw blade. In a corresponding way the saw blade which is rotatably arranged on a rotation shaft that is located above the feeding plane will normally be called second and/or upper saw blade.
Within the technology for sawing by means of circular saw blades it is known to arrange so called cleavers in the area immediately behind the respective saw blade which in most cases are formed as an upward directed and upward tapering fin of sheet metal, which conforms to the curvature of the saw blade and has a thickness that approximately corresponds the thickness of the saw blade. However, such cleavers have nothing to do with guiding of the sawn wood but aims only for to prevent that the wood is squeezed around the saw blade from each side during the sawing or that the saw teeth of the blade can grip the wood at the upward motion of the rear portion of the saw blade, which both can lead to overheating of the saw blade and/or that the wood is thrown upwards. Such cleavers are not sufficient rigid and/or are not sufficient firmly fixated sideways in relation to the saw blade to be able to serve as a wood directing guide, which they neither have to be to be able to fulfill their function as the cleaver will be self-centering in the saw cut behind the saw blade. Neither do they have sufficient large length in the feeding direction so that they could be serving as a wood directing guide since the length in most cases is no more than 5-10 cm. A guide according to the present invention on the other hand has sufficient rigidness, is securely fixated in the correct position in relation to the saw blade and has a sufficient length in the feeding direction to be able to allow straight-lined sawing of pieces of wood. It is evident that the ability of the guide to accomplish a straight-lined feeding of pieces of wood through the machine is increased the larger length the guide has and as a rule the guide ought to have a length that is at least as large as the half diameter of the saw blade, preferably at least 30 cm and most preferred have a length between 0.5-2 m to achieve an acceptable straight-lined feeding of the pieces of wood. As a rule it is preferred that the guide is positioned with its forward end with a small distance immediately behind the counter feed sawing saw blade but the distance could also be considerably longer and possible up to 10-20 cm. However, the bigger the distance is the bigger will the risk be that the forward end of the sawn wood will get caught on the forward edge of the guide. In the hereinafter described and illustrated exemplary embodiments the operative portion of the guide has the form of a continuous metal plate. It should however be understood that it also could be composed of several separate elements, which are arranged with a little spacing from each other in the feeding direction. For example several metal plates, each having a relatively short length in the feeding direction or several vertically after one another arranged pins having a circular cross section.
In claim 1 it is stated that an operative portion of the guide has a thickness which do not exceed the thickness of the saw blade. By the expression “an operative portion of the guide” is meant a portion of the guide which is located within a vertical area where pieces of wood that are sawn passes by the guide, i.e. at least within an area from the feeding plane that is defined by the feed table, up to an upper edge of the guide, in the case the guide is fixated only in its lower part and has a height that is lower than the thickest pieces of wood which are intended to be sawn in the machine, or to a height over the feeding plane which corresponds to the maximum thickness of the pieces of wood that are intended to be sawn in the edge sawing machine in the case the guide also or only is attached in its upper part. In most cases the guide does not need to reach high above the feeding plane since it usually is sufficient that the guide directs a lower part of a side edge surface of the pieces of wood. Above a height which corresponds to the maximum thickness of the pieces of wood that are intended to be sawn in the edge sawing machine, the guide may according to the invention comprise for example stiffening flanges and/or fastening devices such that the guide will be able to withstand relatively large lateral forces without bending, despite the fact that it has so thin cross section in its operative portion such that it do not exceed the thickness of the saw blade, for the purpose of being able to in a reliable way direct pieces of wood without lateral displacement and accomplish a straight-lined sawing.
In the hereinafter described and in the drawings illustrated exemplary embodiments, the single guide is arranged in alignment with and behind the lower saw blade, which has a direction of rotation such that it affects the wood with a force which is directed towards the feeding direction of the wood (a counter feed sawing saw blade), i.e. the sawing upper portion of the saw blade has a component of motion which is directed against the feeding direction. Moreover, this saw blade is stationary arranged such that it cannot be displaced in the direction of the rotation shaft. The other, upper saw blade has the same direction of rotation as the first saw blade and will accordingly affect the wood with a force which is directed in the feeding direction of the wood (a down feed sawing saw blade), since it is sawing with its lower portion which has a motion component which is directed in the feeding direction. Moreover, this saw blade is adjustable in the direction of the rotation shaft by displacement of the motor in order to allow adjustment of the distance between the saw blades and thereby enable sawing of the wood in different widths. However, it should be understood that the displaceable characteristics in the direction of the rotation shaft could be achieved in some other way than displacement of the entire motor, e.g. by displacement of the rotation shaft in relation to the motor or displacement of the saw blade along the rotation shaft.
However, an edge sawing machine according to the invention can be modified and designed in many different ways within the scope of the overall inventive idea. For example, a guide could be mounted also behind the down feed sawing saw blade, which affects the wood with a force in the feeding direction, but such a guide should probably not have any larger practical function, at least not for ensuring a straight-lined sawing as with the first guide. In case a guide is arranged behind a saw blade which is adjustable in the longitudinal direction of the rotation shaft, irrespective of if it is arranged behind a saw blade which affects the wood with a force directed against or in the feeding direction, it has to be adjustable together with the saw blade which necessitate special arrangements to be able to accomplish this and therefore causes cost increasing design solutions.
Moreover, the direction of rotation of the saw blades could be such that the first, lower saw blade affects the wood with a force acting in the feeding direction while the other, upper saw blade affects the wood with a force acting against the feeding direction and accordingly should a guide be arranged at least in alignment with and behind the upper saw blade. However, such an embodiment is not preferred while in this case both of the saw blades will additionally affect the piece of wood with a component force acting in a direction upwards from the feed table in that the sawing portion of the respective saw blade also has a component motion directed upwards such that the wood tend to be lifted from the feed table. Therefore, the feeding devices must in such a case be designed to be able to prevent such a lifting of the wood. With the direction of rotation of the saw blades according to the exemplary embodiments described hereinafter and illustrated in the drawings, the force from the saw blades acts downwards since the sawing portion of the respective saw blade also has a component motion which is directed downwards such that the piece of wood will be forced towards the feed table.
In the following exemplary embodiments it is the second, upper saw blade that is adjustable in the longitudinal direction of the rotation shaft. However, alternatively the first, lower saw blade could be adjustable instead. This would however lead to the disadvantage that a groove, which is formed in the feed table to be able to displace the saw blade in the longitudinal direction of the rotation shaft, has to be made considerably wider than if it is the upper saw blade that is adjustable. An alternative to this would be to arrange the entire feed table displaceable together with the saw blade, but such an embodiment is probably considerably more complicated and expensive to achieve.
At an embodiment according to the claims 6 and 7, the feed table is so designed that it at a longitudinal edge of the feed table lacks any forms of delimiting devices in an area above the feeding plane within which pieces of wood to be sawn are to be fed, preferably at the longitudinal edge of the feed table that is located closest to the upper saw blade. This is done with the object to allow sawing of pieces of wood having a larger width than the width of the feed table and is particular advantageous at small-scale edge sawing machines to restrict the total width of the machine and minimize the need for material and thereby also costs.
Furthermore, the feed table can be formed in many different ways. In the following exemplary embodiments the feed table includes a plate, which in the area before and after the saw blades is provided with rotational drivable rolls whose upper peripheries are located somewhat above the plate and moves the wood forward during the sawing. Accordingly, the feeding plane is in this case a plane which interconnects the upper peripheries of the rolls. However, the feed table could also be completely constituted of driven or not driven, rotatable rolls. Also feed tables in form of chain or belt conveyors could be conceivable, wherein a first conveyor could end immediately in front of the saw blades and a second conveyor could begin immediately behind the same.
In the hereinafter illustrated and described first embodiment, the guide has the form of a 90° angle section, wherein a horizontal part of the angle section is attached on the underside of the feed table plate while a vertical part of the angle section is reaching up through a slot in the feed table plate to a height of about 20-50 mm above the feed table and has a free upper edge. However, many other embodiments of the guide could be conceivable within the scope of the inventive idea. Normally, the guide need not reach particular high above the feeding plane since it usually is sufficient if the guide directs only the lower edge portion of the respective piece of wood.
In the second embodiment the guide is attached to a connecting device above the feed table. Such a connecting device has to be arranged on a distance above the feed table which is larger than the thickest pieces of wood to be sawn in the edge sawing machine. Attaching the guide only in its upper edge and not in its lower, e.g. in the feed table, can be particular advantageous in case the guide is arranged in alignment with and behind a saw blade which is displaceably adjustable in the longitudinal direction of its rotation shaft since the guide then can be displaced entirely independent from the feed table.
Due to the fact that the counter feed sawing and the down feed sawing saw blades affect the wood with forces that essentially cancel each other out, an edge sawing machine according to the invention could be designed without any specially arranged back throw safety device, which normally is a requirement from public authorities. By this the manufacturing costs could be reduced.
Embodiments of the invention will hereinafter be described with reference to de accompanying drawings, in which are schematically shown in:
Reference is first made to
The box formed casing 1 is consequently formed by an upper part 1′ and a lower part 1″, which are interconnected along the left edge as seen in the feeding direction. In the lower part 1″ a first, lower circular saw blade 6 is arranged, which is driven by a stationary mounted first motor 7 via a rotation shaft 8 which consequently are located below the feed table 3. An upper portion of the saw blade projects upwards above the feed table through a not shown slot in the same, for sawing from beneath of pieces of wood which are fed along the feed table. A second, upper circular saw blade 9, which is parallel to the first saw blade, is arranged in the upper part 1′ of the casing. This saw blade is driven by a second motor 10 via a rotation shaft 11, which consequently is located above the feed table and the sawing of the wood is accordingly performed from above by a lower portion of the saw blade. The very lowest portion of the saw blade extends a bit downward below the feeding plane of the feed table through a not shown recess in the feed table. This second motor is, in contrast to the first, displaceably arranged in the direction of the rotation shaft, in a not closer shown way, to allow adjusting of the distance between the first and second saw blades and by this sawing of the wood in different widths. Consequently, the recess in the feed table for the second saw blade must have a width which at least corresponds to the maximum displaceable distance for the saw blade.
From the longitudinal section in
In
One condition for being able to use a guide 16 in the above described way to achieve a secure and reliable straight-lined guiding of the wood, is that the guide has a thickness which do not exceed the thickness of the saw blade in at least an operative portion of the guide. By an operative portion of the guide is meant the portion of the guide which comes into contact with and guides the wood. In
Referring now to
The upper part 1′ of the box formed casing 1 is partly cut-through in
The function of and the principle for the second embodiment of the edge sawing machine, according to
Number | Date | Country | Kind |
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1151134-2 | Nov 2011 | SE | national |