System and method of processing timber to make fence posts

Abstract

Method of processing timber comprising steps of: cutting logs and sorting by diameter; removing bark from the logs; machine turning each log to form elongate poles 1; conveying posts to a stacking loc

Description

FIELD OF THE INVENTION This invention relates to an improved system and method of processing timber to make fence posts. BACKGROUND OF THE INVENTION Machine turned round posts are commonly used in fencing, in particular for agricultural, equestrian and landscaping projects, wherein cut portions of a log are debarked and machined to a predetermined diameter to form an elongate pole. With varying lengths and sizes available, these timber poles are ideal for a number of applications. Machine turned round posts are typically manufactured using softwood timber and treated with preservatives to ensure the longevity of the product. Whilst the machining of logs to form round posts of predetermined diameter can be largely automated, the quality control and stacking of the finished posts for subsequent treatment and supply to the customer can be a labour intensive and therefore costly process. A particular problem with round posts is that they can be difficult to stack. When a compressive force is applied around a stack of round posts by a wrapping band, the posts tend to move from a square stack into a round pile as the round posts roll over each other and try to minimise the space between the posts. Prior art attempts to alleviate this problem have typically relied on using retaining planks on the lateral sides of the stack of posts around which the wrapping material is wrapped such that these retaining plants resist the tendency for the poles to slide over each other. However, this places a lot of stress on the retaining planks, which are prone to damage being located on the outer sides of the stack. This problem may be further mitigated by locating spacers between each row of posts in a stack. However, these spacers increases the height the stack and increase costs to the manufacturer. The spacers usually need to be manually placed between each row of posts is placed on the stack, reducing the speed and increasing the labour costs of the palletising process. Another solution is to provide special post support frames having upright side members between which the posts are restrained against lateral movement. However, this increases costs and creates greater logistic problems in relation the need to return the support frames from the customer. SUMMARY OF THE INVENTION According to the present invention there is provided a method of processing timber to make fence posts comprising the steps of: i) cutting logs to a predetermined length and sorting the logs by diameter; ii) removing bark from the sorted logs; iii) consecutively machine turning each log to form elongate poles of a selected diameter; iv) conveying thus formed posts in end to end relationship along a conveying path to a stacking location; v) at the stacking location, laterally rolling the posts from an end of the conveying path onto a first portion of a downwardly sloping support bed to consecutively assemble rows of posts of predetermined number, the lowermost / first post in each row resting against a raised stop defined by a raised end of an adjacent second portion of the support bed; vi) lowering the first and second portions of the support bed to a horizontal configuration with the first and second portions horizontally aligned to form a continuous bed, and transferring the assembled row of posts from the first portion of the support bed onto the second portion of the support bed against associated raised end stops of the second portion, at the same time raising stops at an inlet end of the first portion of the support bed to prevent further posts from passing onto the support bed; vii) raising the first and second portions of the support bed to their downwardly sloping configuration and lowering the end stops of the second portion such that the thus completed row is rolled off the now downwardly sloping second portion of the support bed onto an adjacent post support platform defined by a pair of lifting tines adapted to be raised and lowered to allow the assembled stack of posts thereon to be raised and lowered with respect to the adjacent support bed; viii) after the first row of posts has been delivered onto the post support platform, lowering the platform by the height of one row ready to receive the next row of posts from the support bed; ix) after each second row of posts has been delivered onto the post support platform, operating a spacer dispensing device to place a respective pair of spacer sticks or planks transversely across the upper side of an upper row of posts on the post support platform adjacent the ends of the posts before the next row of posts is passed onto the support platform; and x) applying wrapping bands around the assembled stack of posts; xi) collecting sawdust, bark and wood chips produced during steps (i) to (iii) and converting at least a portion of the collected sawdust into pellets for use as a fuel and burning at least a portion of the collected sawdust, wood chips and bark in a boiler to heat water into steam and using said steam drive a steam turbine coupled to an electricity generator to generate electricity, said electricity being used as a power source for steps (i) to (x). Preferably the number of posts in each odd numbered row (i.e. 1st, 3rd, 5th, 7th) is one greater than the number of posts in each even numbered row (i.e. 2nd, 4th, 6th). The tines defining the post support platform may be located between vertically arranged laterally spaced rows of rollers between which the stack of posts is assembled to laterally retain the posts are they are loaded onto the platform, transversely arranged horizontal support rollers, at least some of which are adapted to be driven, being arranged between the rows of vertical rollers and normally below the tines of the post support platform to define a conveying surface upon which the stack of posts may be conveyed once formed on the platform and once the tines defining the post support platform have been withdrawn. After a first half of the desired number of rows to be formed into a finished stack has been assembled on the post support platform, said stacked rows defining a half stack, the tines of the post support platform may be withdrawn and half stack is moved along the support rollers to a wrapping position and wrapped with retaining bands at at least two spaced locations therealong; moving the first half stack to a raised position, using a further pair of lifting tines, as the second half stack is assembled on the tines of the post support platform; once the second half of the stack is completed, withdrawing the tines of the post support platform and moving the second half of the stack is moved to the wrapping position and applying wrapping bands around the second half of the stack; moving the second half of the stack beneath the already wrapped first half and the first half of the stack and lowering the first half onto the second half to form the complete stack of posts; and moving the assembled to the wrapping position and wrapping bands are secured around the complete stack. The method may comprise the further step of operating the spacer dispensing device to place a respective pair of spacer sticks or planks transversely across the upper side of an uppermost row of posts in the second half of the stack before lowering the first half onto the second half. Before the final wrapping bands are applied to the completed stack, the method may include applying timber side support members to the outer lateral sides of the completed stack, each side support member having an outwardly facing elongate channel formed along an outer side thereof, each wrapping band being applied over a respective pair of side support members with the band located within said elongate channel. Preferably the first half stack is assembled with an even number of rows while the second half stack is assembled with an odd number of rows to maintain the alternating odd and even number of posts in each row of the completed assembled stack. The method may further comprise the step of cutting one end of each post to a point subsequent to step (iii). The method may further comprise the step of optically scanning the posts to detect imperfections or remaining bark thereon and, where such imperfections are detected in a post, automatically diverting such post from the main conveying path, as the posts are conveyed along said conveying path towards said stacking location. The method may further comprise the step of, following steps (i) to (x), drying each assembled stack in a drying kiln using heat, from the boiler of step (xi), before placing the thus dried stack of posts in a pressure vessel wherein it is treated with a wood preservative. The method may include the step of forming a series of incisions in at least a portion of the outer surface prior to step (iv) to facilitate penetration of the wood preservative into the post to a consistent depth. BRIEF DESCRIPTION OF THE DRAWINGS A system for processing timber to make fence posts in accordance with a method of the present invention is illustrated, by way of example only, in the accompany drawings, in which:- Figures 1 to 3 illustrate the transfer of posts from a main conveying path onto a post support platform at a stacking location; Figures 5 and 6 illustrate the stacking operation on the tines of the post support platform; Figures 7 and 8 illustrate the placement of spacer sticks or planks between every second row of posts in a stack; Figure 9 to 11 illustrate the wrapping of a first half stack at a wrapping position; Figures 12 and 13 illustrate the wrapping of a second half stack at the wrapping position; Figure 14 illustrates the assembly of the two half stacks; and Figures 15 to 17 illustrate the final wrapping of the completed stack and onward transfer of the stack of posts for further treatment. DETAILED DESCRIPTION OF THE DRAWINGS A method of processing timber to make machine turned round fence posts in a sawmill accordance with an embodiment of the present invention is described below. In a first step (not shown in the drawings) logs are cut to length, preferably from the uppermost portion of logs as supplied from forestry operations, and sorted by diameter. The sized logs are debarked and then machine turned to a predetermined diameter, based on the initial diameter of each log, to produce elongate poles of a selected size. One end of each post may be cut to a tapered point for ease of insertion into the ground. The thus formed posts are conveyed end to end along a conveying path following the above machining steps and are optically scanned to detect any imperfections or remaining bark thereon. Where such imperfections are detected in a post, such post is automatically diverted from the main conveying path. Posts where imperfections are detected may be sold as a cheaper product, further machined to a smaller diameter to remove the imperfections, or may be chipped to form a biomass fuel product for use in the sawmill and / or to manufacture wood pellets for sale as a fuel product in addition to the sawdust, wood chips and bark removed during the machining steps. Once the posts 1 reach the end of said main conveying path at a stacking location 2, they are one by one laterally rolled onto a first portion 4 of a downwardly sloping support bed to assemble a first row of posts 1 of predetermined number, the lowermost / first post in the row resting against a raised stop portion 5 defined by a raised end of an adjacent second portion 6 of the support bed, as shown in Figure 1. Once a first row has been completed, the first and second portions 4,6 of the support bed are lowered to a horizontal configuration with the first and second portions 4,6 horizontally aligned to form a continuous bed, and associated conveying chains 8 are operated to transfer the assembled row of posts 1 from the first portion 4 of the support bed onto the second portion 6 of the support bed against associated raised end stops 10 of the second portion 6, as illustrated in Figures 2 and 3. At the same time stops 12 at an inlet end of the first portion 4 of the support bed are raised to prevent further posts from passing onto the support bed. The first and second portions 4,6 of the support bed are raised once again to their downwardly sloping configuration, the end stops 10 of the second portion are lowered and the completed row is rolled off the now downwardly sloping second portion 6 of the support bed onto an adjacent post support platform, as shown in Figure 4. Further conveying chains may be provided to facilitate movement of the posts onto the post support platform. As shown in Figures 5 and 6, the post support platform may be defined by a pair of lifting tines 14 adapted to be raised and lowered to allow the assembled stack of posts thereon to be raised and lowered with respect to the adjacent support bed. After the first row of posts has been delivered onto the tines 14 of the post support platform, the tines 14 are lowered by the height of one row ready to receive the next row of posts from the support bed. After the second row of posts has been delivered onto the tines 14 of the post support platform, a pair of spacer sticks or planks 16 are placed transversely across the upper side of the upper row adjacent the ends of the posts by means of an associated spacer dispensing device before the next row of posts is passed onto the support platform, as illustrated in Figures 7 and 8. This process of automatically adding spacer sticks or planks 16 is repeated for each second row of posts delivered onto the post support platform, the tines 14 of the platform being lowered after each row is added thereto. Figure 7 actually shows the placement of spacer sticks or planks 16 on the uppermost rows of post of a second half stack 24, with further spacer sticks or planks being visible between said uppermost row and the row below. The system is adapted such that the number of posts in each odd numbered row (i.e. 1st, 3rd, 5th, 7th) is one greater than the number of posts in each even numbered row (i.e. 2nd, 4th, 6th). For example, each odd numbered row (i.e. 1st, 3rd, 5th, 7th) may have an odd number of posts therein (for example 7) and each even numbered row (i.e. 2nd, 4th, 6th) may have an even number of posts therein (for example 6) As shown in Figure 5, the tines 16 defining the post support platform are located between vertically arranged laterally spaced rows of rollers 18 between which the stack of posts is assembled to laterally retain the posts are they are loaded onto the platform. Transversely arranged horizontal support rollers 20 (see Figures 5 and 6), at least some of which are adapted to be driven, are preferably arranged between the rows of vertical rollers 18 and normally below the tines 14 of the post support platform to define a conveying surface upon which the stack of posts may be conveyed once formed on the platform and once the tines 14 defining the post support platform have been withdrawn. After a first half of the desired number of rows to be formed into a finished stack has been assembled on the post support platform, the stacked rows defining a first half stack 22, the tines 14 of the post support platform are withdrawn and the first half stack is moved along the support rollers 20 to a wrapping position, as shown in Figures 9 and 10, and wrapped with retaining bands 21 at at least two, more preferably three, spaced locations therealong. As illustrated in Figure 11, the first half stack 22 is then moved to a raised position, using a further pair of lifting tines, while a second half stack 24 is assembled on the tines of the post support platform. Preferably the first half stack 22 is assembled with an even number of rows while the second half stack 24 is assembled with an odd number of rows to maintain the alternating odd and even number of posts in each row of the completed assembled stack. As with the first half 22 of the stack, the second half stack 24 is assembled with spacer sticks or planks located between each second row of posts. A pair of spacer sticks or plants are preferably place on top of the upper row of posts in the second half stack 24 to be located between the first and second halves of the assembled stack. Once the second half stack 24 is completed, the tines 14 of the post support platform are withdrawn and the second half stack 24 is moved to the wrapping position and wrapped, passing beneath the raised first half stack 22 during such movement, as illustrated in Figures 12 and 13.. After wrapping, the second half stack 24 is moved beneath the already wrapped first half stack 22 and the first half stack 22 lowered onto the second half stack 24 to form the complete stack of posts, as illustrated in Figure 14. As shown in Figures 15 and 16, the assembled stack is then moved to the wrapping position and wrapping bands are secured around the complete stack. Before the final wrapping bands are applied, timber side support members 26 are applied to the outer lateral sides of the completed stack, each side support member 26 having an outwardly facing elongate channel formed along an outer side thereof, each wrapping band 28 being applied over a respective pair of side support members 26 with the band located within said elongate channel. Preferably the length of each side support member 26 is less than the total height of the stack. The assembled and secured stack may then be transferred for further treatment, as shown in Figure 17. Preferably each assembled and wrapped stack of posts is first dried in a drying kiln before being placed in a pressure vessel wherein the stack of posts is treated with a wood preservative. In a preferred embodiment, each post, at least in the region located, in use, in and just above ground level, has a series of incisions formed in the outer surface thereof to facilitate penetration of the wood preservative into the post to a consistent depth. In a preferred embodiment at least a portion of the collected sawdust, wood chips and / or bark is made into wood pellets for use as a fuel. A portion of the collected sawdust, wood chips and / or bark may be used as an energy source for the sawmill, said material being burnt in a boiler to heat water to be used as a heat source, for example for drying kilns, and to drive a steam turbine coupled to an electricity generator to provide power for the various, cutting, control and conveying devices of the system. The invention is not limited to the embodiment described herein but can be 5 amended or modified without departing from the scope of the present invention as defined by the appended claims.

Claims

1. A method of processing timber to make fence posts comprising the steps of:i) cutting logs to a predetermined length and sorting the logs by diameter;ii) removing bark from the sorted logs;iii) consecutively machine turning each log to form elongate poles of a selected diameter;iv) conveying thus formed posts in end to end relationship along a conveying path to a stacking location;v) at the stacking location, laterally rolling the posts from an end of the conveying path onto a first portion of a downwardly sloping support bed to consecutively assemble rows of posts of predetermined number, the lowermost / first post in each row resting against a raised stop defined by a raised end of an adjacent second portion of the support bed;vi) lowering the first and second portions of the support bed to a horizontal configuration with the first and second portions horizontally aligned to form a continuous bed, and transferring the assembled row of posts from the first portion of the support bed onto the second portion of the support bed against associated raised end stops of the second portion, at the same time raising stops at an inlet end of the first portion of the support bed to prevent further posts from passing onto the support bed;vii) raising the first and second portions of the support bed to their downwardly sloping configuration and lowering the end stops of the second portion such that the thus completed row is rolled off the now downwardly sloping second portion of the support bed onto an adjacent post support platform defined by a pair of lifting tines adapted to be raised and lowered to allow the assembled stack of posts thereon to be raised and lowered with respect to the adjacent support bed;viii) after the first row of posts has been delivered onto the post support platform, lowering the platform by the height of one row ready to receive the next row of posts from the support bed;ix) after each second row of posts has been delivered onto the post support platform, operating a spacer dispensing device to place a respective pair of spacer sticks or planks transversely across the upper side of an upper row of posts on thepost support platform adjacent the ends of the posts before the next row of posts is passed onto the support platform; andx) applying wrapping bands around the assembled stack of posts;xi) collecting sawdust, bark and wood chips produced during steps (i) to (iii) and converting at least a portion of the collected sawdust into pellets for use as a fuel and burning at least a portion of the collected sawdust, wood chips and bark in a boiler to heat water into steam and using said steam drive a steam turbine coupled to an electricity generator to generate electricity, said electricity being used as a power source for steps (i) to (x).

2. A method as claimed in claim 1, wherein the number of posts in each odd numbered row (i.e. 1st, 3rd, 5th, 7th) is one greater than the number of posts in each even numbered row (i.e. 2nd, 4th, 6th).

3. A method as claimed in claim 1 or claim 2, wherein the tines defining the post support platform are located between vertically arranged laterally spaced rows of rollers between which the stack of posts is assembled to laterally retain the posts are they are loaded onto the platform, transversely arranged horizontal support rollers, at least some of which are adapted to be driven, being arranged between the rows of vertical rollers and normally below the tines of the post support platform to define a conveying surface upon which the stack of posts may be conveyed once formed on the platform and once the tines defining the post support platform have been withdrawn.

4. A method as claimed in claim 3, wherein, after a first half of the desired number of rows to be formed into a finished stack has been assembled on the post support platform, said stacked rows defining a half stack, the tines of the post support platform are withdrawn and half stack is moved along the support rollers to a wrapping position and wrapped with retaining bands at at least two spaced locations therealong;moving the first half stack to a raised position, using a further pair of lifting tines, as the second half stack is assembled on the tines of the post support platform;once the second half of the stack is completed, withdrawing the tines of the post support platform and moving the second half of the stack is moved to the wrapping position and applying wrapping bands around the second half of the stack;moving the second half of the stack beneath the already wrapped first half and the first half of the stack and lowering the first half onto the second half to form the complete stack of posts; andmoving the assembled to the wrapping position and wrapping bands are secured around the complete stack.

5. A method as claimed in claim 4, comprising the further step of operating the spacer dispensing device to place a respective pair of spacer sticks or planks transversely across the upper side of an uppermost row of posts in the second half of the stack before lowering the first half onto the second half.

6. A method as claimed in claim 4 or claim 5, wherein, before the final wrapping bands are applied to the completed stack, applying timber side support members to the outer lateral sides of the completed stack, each side support member having an outwardly facing elongate channel formed along an outer side thereof, each wrapping band being applied over a respective pair of side support members with the band located within said elongate channel.

7. A method as claimed in any of claims 4 to 6, wherein the first half stack is assembled with an even number of rows while the second half stack is assembled with an odd number of rows to maintain the alternating odd and even number of posts in each row of the completed assembled stack.

8. A method as claimed in any preceding claim, further comprising the step of cutting one end of each post to a point subsequent to step (iii).

9. A method as claimed in any preceding claim, further comprising the step of optically scanning the posts to detect imperfections or remaining bark thereon and, where such imperfections are detected in a post, automatically diverting such post from the main conveying path, as the posts are conveyed along said conveying path towards said stacking location.

10. A method as claimed in any preceding claim, further comprising the step of, following steps (i) to (x), drying each assembled stack in a drying kiln using heat, from the boiler of step (xi), before placing the thus dried stack of posts in a pressure5 vessel wherein it is treated with a wood preservative.

11. A method as claimed in claim 10, comprising the step of forming a series of incisions in at least a portion of the outer surface prior to step (iv) to facilitate penetration of the wood preservative into the post to a consistent depth.1015

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