This invention relates to apparatus and methods for incising timber using toothed, rotary incisors.
When treating wood with preservatives, such as fungicide or insecticide, it can be desirable to form a series of incisions in the surface of the wood to enable proper penetration of the preservative. This is especially true of the heartwood of spruce, fir, pine, larch, Douglas-fir, beech, oak and other hardwoods which only allows a surface treatment, without any significant depth of penetration, unless incisions are made.
U.S. Pat. No. 4,836,254 describes a multi-head incising apparatus for incising at least two sides of a piece of lumber or timber in a single pass. It has at least two sets of toothed incisor rolls, each set having an upstream roll and a downstream roll, spaced apart in one plane. Each of these rolls makes a pattern of incisions in the lumber or timber, and the apparatus has means to synchronize rotation of the two rolls in each set to ensure the patterns combine to a predetermined final pattern of closely spaced apart incisions. One reason for using two rolls in each plane is that annular cleaning rings or combs with cleaning teeth between incisor discs impose a minimum spacing between adjacent incisors discs; however, superimposing two patterns from respective rolls enables a final pattern having more-closely spaced incisions than is achievable with just a single roll.
In a main embodiment of U.S. Pat. No. 4,836,254, the two rolls in each set have respective sprockets, and a chain connects these sprockets together so that the two rolls turn at the same rate.
The present applicant has come to realise that the apparatus of U.S. Pat. No. 4,836,254 has a significant shortcoming: namely that, in order to apply the predetermined incision pattern accurately, the timber must always be incised to a constant incision depth, determined by the design of the apparatus. However, different combinations of wood type, size and preservative composition have different optimal incision depths; for example, it may desirable to incise some wood to a depth of 3 mm and other wood to a depth of 8 mm, 15 mm, 25 mm or any depth in between. It is therefore desirable to have an apparatus that can be readily adapted to incise to different depths.
The present invention seeks to overcome this shortcoming.
Thus, from a first aspect, the invention provides apparatus for forming incisions in a timber plank, comprising:
The skilled person will appreciate that such apparatus can be conveniently adjusted to alter the depth of incisions formed in the plank without losing synchronisation between the patterns formed by the respective incisors. In this way, the patterns superimpose to give the same desired formation of interleaved incisions regardless of the determined incision depths.
The incision depth of one or both incisors can be adjusted and compensation can be applied to ensure that a desired synchronisation, or longitudinal alignment, of the incision patterns from each incisor is maintained. This is not possible with the apparatus of the prior art, which does not provide depth-adjusting means, nor means to compensate for the effects of any depth adjustment, were such adjustment possible.
As used herein the spatial period is defined as the length of the pattern formed by one complete revolution of an incisor; i.e. it is the effective circumference of the rotary incisor at the surface of the plank face. In order to maintain a particular alignment between the patterns, this period will need to be the same for both incisors. The axes of both incisors should therefore be at the same distance from the surface of the plank.
In preferred embodiments the same regular pattern of teeth is provided on each incisor. In such embodiments the longitudinal alignment between the patterns is easy to observe and the longitudinal offset between any pair of respective incisions from the two patterns could be used to define it. Clearly the number of teeth on the incisors and hence the spacing distance between the incisions will determine the maximum possible offset distance.
However it is not essential for the patterns on the incisors to be the same or even for either of them to be regular. More generally therefore each of the patterns can be treated as having a longitudinal spatial repetition period which is either equal to, or is an integer fraction of, the spatial period (depending on how the teeth are arranged around the incisor). The lowest common multiple of the two minimum repetition periods of the two incisors defines a spatial repetition period of the combined pattern. The longitudinal alignment may then conveniently be defined as the longitudinal distance between the mid-points of two reference incisions, one from each pattern, divided by the combined spatial repetition period. The reference incisions may be arbitrarily chosen but only occur once in every repetition period of the combined pattern.
However, other suitable definitions of the longitudinal alignment may be used instead, especially in the case where the shapes of the individual teeth are asymmetrical—e.g. saw-tooth shape.
As mentioned above, the patterns formed by the two incisors are preferably identical, but this is not essential. In particularly preferred embodiments, for each incisor the teeth at any given axial distance along the incisor are uniformly distributed around the circumference. The minimum spatial repetition period of the pattern formed by such an incisor is then simply equal to the distance between adjacent teeth at the surface of the plank.
In one set of embodiments of the present invention, the compensating means comprises means for adjusting the distance between the axes of the two rotary incisors. This preferably comprise means whereby one of the incisors can be slidably moved towards and away from the other incisor. Both incisors may be slidably movable relative to a housing or frame, but in some preferred embodiments one incisor is fixed relative to a housing or frame and the other incisor is movable. The movable incisor may be held in a given position by secure retaining means, such as a notch or a clamping nut and bolt, ratchet etc. One or both incisors may be acted on, directly or indirectly, by one or more springs.
Additionally or alternatively the means for compensating comprises means for adjusting the rotational offset of the teeth of one of the incisors relative to the teeth of the other incisor. Thus in some embodiments, the means for compensating comprises both means for adjusting the distance between the two incisors and means for adjusting the rotational offset of one of the incisors relative to the other. These means may be the same, or may share some components in common, or may be wholly distinct.
The compensating means may act automatically; that is, it may be such that adjusting the depth causes the compensating means to apply appropriate compensation without further human input. This automation may be purely mechanical, or it may involve use of one or more electronic controls, such as a computer processor.
The incisors could take the form of single discs but preferably they each comprise a plurality of coaxial, toothed incisor discs, effectively forming a roller structure. The separation distance between adjacent discs along the roller may be selected appropriately depending on the kind of wood, the treatment product, and/or the kind of process being used. It might, for example, be between 1.6 mm and 6.0 mm. The discs may be polygonal, but are (except for the teeth) preferably substantially circular or annular, forming a cylindrical roller. For each incisor, the discs are preferably fixed to an axle or shaft, for example by interfacing with splines formed along the axle, thereby enforcing a common rotation rate. The discs may be identical to one another, or may differ; in particular, they may have the same or different numbers and spacing of teeth around their circumferences. For economy of manufacturing, every incisor disc is preferably the same. However, as explained below, the teeth of each disc are not necessarily identically rotationally-aligned between adjacent discs along the axle, instead being rotationally staggered along the axle. An advantage of a roller made up of individual discs is that allows discs to be replaced separately if they become worn. It also allows the width of the roller to be altered. However in an alternative set of embodiments an integral roller having an equivalent pattern of teeth could be provided.
The depth-controlling means in some embodiments may comprises a guide, such as a roller, acting on one of the faces of the plank. In some embodiments it could control the depth relative to the face being incised, which is advantageous as the depth is then independent of any variation in the thickness of the plank. In other embodiments the depth-controlling means acts on an opposite face of the plank to the toothed incisors. In either case there is preferably provided a fixed, but adjustable, spacing between the guide and the toothed incisors. In one set of embodiments, rather than a dedicated depth guide, the depth-controlling means may comprise one or more further incisors, acting on a parallel opposed face. The incision depth on both faces for a given thickness of plank may therefore be controlled through the mutual separation of the respective sets of incisors.
Although in preferred embodiments both incisors are arranged to incise to the same depth below the surface of the plank, this is not essential and they may incise to different depths. The depths may be adjustable in unison or may be adjustable independently. Typically the incisor making the deeper incision would have longer teeth compared to the other one but the axis of rotation would be at the same height above the plank to ensure rotation at the same speed.
As mentioned above, in some preferred embodiments, the apparatus comprises further incisors arranged to form incisions on a second face of the plank; for example, on a face parallel to the first face, or perpendicular thereto. In such embodiments, the depth-controlling means may comprise means for holding the two pairs of incisors at a fixed separation distance from each other; for example by means of a variable-length strut. This separation distance is adjustable, by the means for adjusting the depth of penetration, both to cater for varying sizes of plank and to alter the depth of incision. The plank may self-centre between the opposed incisors, or may be guided, for example by guide rollers. The distance may be changed manually or the apparatus may comprise means for receiving an indication of a desired incision depth and controlling the apparatus so as to produce incisions of the indicated depth; this control may be purely mechanical or may comprise electronic circuitry; for example, a computer which receives as input a desired incision depth and a dimension of the plank (either manually entered, or measured by the apparatus) and outputs a signal to an actuator to adjust the spacing between a pair of incisors and a guide or another pair of incisors.
In a set of embodiments four pairs of incisors are provided, each pair arranged to act on a different face of a plank of rectangular cross section. The apparatus preferably comprises depth-controlling means, depth-adjusting means and compensation means in respect of every pair of incisors. In other embodiments, any number of incisors may act on any one or more faces of the plank.
Incisors arranged to act on a common surface, for example a pair of incisors, may be independently rotatable or may be linked, for example by gears or a chain.
Preferably at least one incisor of the apparatus is powered, e.g. by an electric motor, so as to propel the plank through the apparatus. However, this is not essential, and alternative propulsion means may be used such as manual pushing of the plank through the machine, or separate drive rollers or a conveyor belt. Using one of the incisors to propel the plank is advantageous in that the incising teeth provide a secure grip on the plank, which may not be so readily achievable by other means. In some embodiments, at least one incisor of every set of incisors acting on respective common faces of the plank is driven; this can provide additional power for timber species that require it, and may help facilitate a smooth passage of the plank through the apparatus, since reduced torque is applied to the plank.
All the incisors acting on a common face of the plank are preferably synchronised so that the regular patterns of incisions from each incisor interleaves those of the other incisors in a predetermined manner to yield a desired final pattern.
Synchronisation between the incisors may be achieved by in several ways. In some embodiments the apparatus comprises synchronised motors driving the respective axles of at least some of the incisors. In one set of embodiments a timing belt or chain is provided connecting between sprockets or wheels mounted on, or communicating drive to, an axle of each incisor. A single motor may then be sufficient. In some embodiments, particularly where the spacing between the incisors is variable, the apparatus further comprises a tensioning means, e.g. sprocket, roller or wheel, acting on the chain or belt to maintain a desired tension when the distance between two or more incisors is increased or decreased. The timing belt may be a toothed belt, for example.
Alternatively or additionally, tensioning means can enable the belt or chain to be slackened sufficiently that the rotational and/or lateral position of one or more of the incisors may be changed by disengaging the belt or chain from the respective incisor, rotating and/or laterally moving the incisor, and re-engaging the chain with the incisor. This may be done manually or by mechanical actuating means. Where there are more than two incisors forming mutually overlapping patterns on a single face of the plank, the incisors may be linked by a plurality of belts or chains, with a plurality of tensioners; for example, one between every adjacent pair of incisors.
In some preferred embodiments, compensation for the altered period of the pattern of incision is applied to two incisors by moving the tensioner relative to one or both incisors so as to alter the length of a section of chain or belt extending directly between the respective incisors, thereby simultaneously altering the separation distance between the incisors and the relative rotational offset between the incisors; i.e. one of the incisors is effectively rolled towards or away from the other, rather than being translated purely laterally, or being rotated in place, which are alternative adjustment mechanisms. In such embodiments, one or both incisors may be movable, and may be biased away from the other incisor of the pair by spring means. Alternatively, one or both incisors may be releasably fixed in position and can be released when an adjustment is being made, and secured in position subsequently.
As explained above, by the use of a tensioning means such as a sprocket, the spacing between the incisors and/or the relative rotational angles of the incisors may be easily adjusted. The tensioner may be temporarily locked in position, for example by frictional retention with a nut and bolt acting on a slotted frame member, or it may be tensioned by resilient means, acting against tension in the chain.
Where a timing belt or chain is used, advantageously only one incisor of the pair need be directly driven, e.g. by a motor; the other can be driven indirectly by the timing chain.
Any sprocket or wheel associated with a incisor need not necessarily be coaxial with the incisor, but could be operably connected to it by any number of intermediate gears, shafts, etc.
Where incisors act on multiple faces of the plank, these may all be synchronised, or synchronisation may be effected for each face independently.
In other embodiments, the incisors are each directly driven, e.g. by respective electric motors, with the apparatus comprising means to ensure that the rotation of the drive incisors is synchronised at the same rate as each other. This may be accomplished for example by an incremental position encoder and a servo-motor. By setting a starting position (feather key), the incisors can be positioned in relation to each other in such a way that the incisors create a desired interleaved pattern. Servo-motor positioning may be accomplished manually or by automatic positioning means which receives an input of a desired perforation depth and controls the servomotor accordingly.
The teeth of the incisors may be of any suitable shape, such as pointed, rounded or spiked. Preferably they are each symmetrical about a central radial line. In a set of preferred embodiments the teeth are three-sided, preferably tapering in width towards their distal edges—e.g. presenting a truncated triangular shape.
The teeth are preferably substantially laminar although this will typically include some tapering in thickness towards their tips. Preferably such thickness taper is not to a knife-edge. This serves to reduce stress in the timber compared with a sharp edge, by primarily compressing the wood inwards rather than separating the fibres. This reduces the tendency for the timber to expand against the tooth as it is pulled out, which would otherwise result in tearing of the wood. It also avoids surface cambers forming between adjacent incisions. However, this is not essential, and apparatus of the invention may use sharp edges.
The described essentially laminar, truncated triangular teeth will create slot-like incisions in the wood, the length of which is dependent on the chosen depth of penetration.
A single incisor disc may carry any number of teeth. The preferred number is generally dependent on the diameter of the incisors and the depth of incision. The number of teeth might, for example, be between 1 and 100, possibly 20 to 30. In one set of embodiments every disc has 24 teeth.
The apparatus preferably has a mechanism for removing debris from the incisor discs and/or for preventing ripping of the timber surface. Such a mechanism may comprise floating rings mounted between adjacent incisor discs along the incisor axis, or combing or tooth-pick devices, hold-down bars, pressure plates, or a combination of these. In one set of embodiments, the apparatus comprises a guide having one or more through slots arranged such that the slots are aligned with respective incisor discs so as to form pressure plates between adjacent discs. These pressure plates can apply a force to the wood in a direction so as to resist ripping or splintering of the surface of the wood. The guide may comprise a cylinder through which the plank passes during the incising.
In some embodiments, the apparatus comprises means for lubricating the plank as it passes through the apparatus. This preferably comprises a nozzle for spraying a liquid lubricant or wetting agent onto some or all of the plank. The lubricant is preferably water or a preservative, such as a suitably-diluted sap-stain product. It may be applied by means of a spray, water curtain, brushes, rollers or other suitable wetting devices.
When viewed from second aspect, the invention provides a method of operating a machine for forming incisions in a timber plank, comprising:
Adjusting said incisors to compensate for the altered spatial period in said patterns may comprise moving one of the incisors of the pair towards or away from the other incisor. Such moving may involve directly moving the incisor, or may involve moving a tensioning wheel which acts on a belt or chain connected to the incisor so as to move the incisor.
Alternatively or additionally, the adjusting step may comprise changing the rotational position of one or the incisors relative to the other incisor. This may comprise adjusting a control connected to a servo-motor, or it may comprise changing the position of the teeth of the incisor relative to a chain or belt; for example by disengaging the chain or belt from a sprocket or wheel connected to the incisor, changing the rotational position of the incisor, and re-engaging the chain or belt; or by disengaging a sprocket, shaft or axle from another part of the incisor, adjusting the relative rotational position of the incisor, and re-engaging the sprocket, shaft or axle.
From a further aspect, the invention provides an apparatus for forming incisions in a timber plank, comprising:
From a further aspect, the invention extends to use of apparatus as described herein for incising a timber plank.
Although the invention has been described with reference to timber planks, the skilled person will appreciate that apparatus of the invention could be used to incise materials other than wood, or boards made from processed wood such as chipboard, plywood, medium-density fibreboard, veneers, etc. Suitable modifications, within the grasp of the skilled person, may be made to the apparatus to enable such uses. The apparatus may be adapted to incise wood that is not in the form of a finished plank, but is in an irregular shape or, for example, still carries bark on at least one surface. The term plank is not to be understood as limited to any particular shape of wood; rather, it is intended to encompass any board or other cut piece of wood. Timber and lumber are both used herein to refer to wood from a felled tree.
Although the description has referred primarily to two rotary incisors acting on a given face, any greater number could be provided.
Features described herein with reference to one embodiment or aspect of the invention may, where appropriate, be used with any other embodiment or aspect.
Certain preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:
The upper horizontal pair comprises an upper leading roller 10A and an upper trailing roller 12A; similarly the lower horizontal pair comprises a lower leading roller 10B and a lower trailing roller 12B, while the left and right vertical pairs (as viewed looking in through entrance port 18) respectively comprise left and right leading rollers 10C, 10D, and left and right trailing rollers 12C, 12D.
The lower and left pairs of rollers 10B, 10C, 12B, 12D are secured in a fixed position within the framework 2, while the upper and right pairs 10A, 10D, 12A, 12D are secured temporarily against notched racks 14, 16 within the framework 12. The notches allow the position of the upper and right pairs to be adjusted to alter the spacing between the pairs of rollers of each set of rollers 6, 8.
The framework 2 and cover 4 cooperate to define a rectangular entrance port 18 and a rectangular exit port 19. A plank of wood can be inserted through the entrance port 18, passing between the pairs of horizontal rollers 6, then between the pairs of vertical rollers 8, before leaving the apparatus through the exit port 19.
The apparatus illustrated in
The upper leading cleaning comb 20 comprises a rod 41 of square cross-section which carries an array of cleaning prongs 43 along part of its length. The rod 41 is secured through square holes in the framework 2 so as not to rotate. It is positioned by the framework 2 such that each prong 43 extends upwardly into a gap between a respective pair of incising discs in the upper leading roller 10A (
The upper trailing cleaning comb 22 is identical to the leading cleaning comb 20, but is installed with its cleaning prongs arranged to point downwardly between the incising discs of the trailing roller 12A.
In use, the cleaning combs scrape wood dust and debris away from the incising discs, so that the incising action of the discs is not impaired by an accumulation of waste material.
The incising disc 50 has six through-holes 54 spaced in a coaxial ring of approximately half the diameter of the whole disc 50, which can be used to secure it to a plate located on an axle of a roller; this is an alternative securing mechanism to that shown in the embodiment above.
The tensioning sprocket 79 is also slidably movable, in order to take up or release any slack in the chain 77 when the trailing incising roller 72′ is adjusted.
An identical, inverted arrangement of rollers, chain and tensioning sprocket acts on the opposite face of the plank 70. Additional, similar arrangements may be provided to act on the other faces of the plank.
Slots through the faces of the guide 80 are aligned with respective incising discs, one slot for each disc. These slots allow the teeth of the incising discs to penetrate the plank 44 unimpeded; however, they are dimensioned such that the guide 80 comprises strips of material in contact with the surface of the plank 44 between each adjacent pair of slots. These strips resist tearing and splintering of the plank 44 as the teeth leave the wood by providing an opposite force on the wood where necessary. The guide 80 may be used in addition to or instead of the combs described previously.
Also shown are two spray bars which surround the plank 44: a plank spray bar 84 and a roller spray bar 86. The plank spray bar 84 is arranged to spray a liquid lubricant 88, such as water or diluted sap-stain product, onto the surface of the plank 44 as it passes. The roller spray bar 86 is arranged to spray a liquid lubricant 90, which may be the same as or different from that sprayed by the plank spray bar 84, onto the incising rollers. This lubrication aids the incising process.
Number | Date | Country | Kind |
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1004735.5 | Mar 2010 | GB | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/GB2011/050557 | 3/21/2011 | WO | 00 | 4/2/2013 |