GB2300832A

GB2300832A - Timber processing

Info

Publication number: GB2300832A
Application number: GB9510081A
Authority: GB
Inventors: William Grainger
Original assignee: MAYBOLE Ltd
Current assignee: MAYBOLE Ltd
Priority date: 1995-05-17
Filing date: 1995-05-18
Publication date: 1996-11-20
Anticipated expiration: 2015-05-18
Also published as: IES950358A2; GB9510081D0; IES66131B2; GB2300832B

Abstract

Two opposite sides of a graded debarked log 1 are canted in a first stage canter 2 and the other two sides are canted in a second stage canter 3. Wood chips from the canters 2, 3 are delivered along a main wood chip conveyor to a vibrating screen unit 30 which divides the chips into over-size wood chips 31, fines 32, and wood chips 33 of desired size. End trimmers 10 and resaws 15, 18 provide a finished timber 25. Waste slivers from edgers 17, 20, waste timber ends 12, and the oversize wood chips 31 are delivered to a main waste timber conveyor 29. From the conveyor 29 the timber is chopped by a chopper 35 into wood chips which are delivered up a pipe 36 to a cyclone 37 which delivers the chips to the screen unit 30 for sorting.

Description

wTlaber Processing The invention relates to timber processing and in particular to a method for producing wood chips in timber processing.

According to the invention there is provided a method for producing wood chips comprising the steps of: debarking logs; scanning the debarked logs to establish the major dimensions of the logs; grading the logs into a range of log sizes; delivering the graded logs on demand to a first stage canter; canting two sides of the graded debarked logs in the first stage canter; canting the other two sides of the graded debarked logs; delivering unsorted wood chips from the first and second stage canting to a wood chip conveyor; end trimming the canted log to provide a canted log of desired length and a waste timber end; resawing the canted and trimmed logs forming side slivers and finished timber of desired width and length; edging at least some of the side slivers removed on resawing; delivering waste slivers from the resawing and edging to a waste timber conveyor;; delivering unsorted wood chips from the wood chip conveyor to a vibrating screen unit; dividing the wood chips in the vibrating screen unit into over-size chips, fines and chips of desired size; delivering the over-size chips from the vibrating screen to the waste timber conveyor; chopping the wood pieces from the waste timber piece conveyor into wood chips; delivering the wood chips from the wood chopper to the vibrating screen to divide the wood chips into over size chips, fines and chips of desired size; collecting the wood chips of desired size, collecting the fines, and re-chopping over-size chips.

The invention provides a highly efficient method for producing wood chips of desired size which are a very valuable by-product. In addition, the timber processing is optimised to recover as much useful timber as possible, while ensuring that any waste is converted with maximum efficiency to the relatively high value wood chips.

In a preferred embodiment of the invention, the method includes the step of delivering the waste timber ends from the end trimming to the waste timber conveyor for chopping into wood chips. In this way the optimum use of the waste timber ends is achieved.

In an especially preferred embodiment of the invention the unsorted wood chips from the wood chopper are passed through a cyclone before being delivered to the vibrating screen unit. The cyclone ensures that fines generated in the wood chopping process is removed and that the chopped wood chips are delivered in an optimum manner to the vibrating screen unit.

For maximum processing efficiency, the two opposite sides of the graded debarked logs are canted in a first stage canter and the other two sides are subsequently canted in a second stage canter arranged in series with the first stage canter.

In a preferred embodiment of the invention, the resawing comprises first stage resawing two opposite sides of the canted and trimmed logs and subsequently second stage resawing the other two sides of the canted and trimmed logs. Resawing in sequential stages ensures maximum timber processing efficiency and optimum collection and conversion of waste timber into wood chips.

In a preferred arrangement at least some of the side slivers removed in the first stage resawing are edged in a first stage edger, and at least some of the side slivers from the second stage resawing are edged in a second stage edger. The use of separate edgers for the first and second stage resawing assists in maximising the throughput and operating efficiency of the timber processing while also optimising the collection and usage of waste timber.

In a particularly preferred embodiment of the invention the vibrating screen unit has at least three vibrating screens for dividing the wood chips into fines, over-size chips and chips of a desired size. This construction of vibrating screen unit ensures that optimwii separation of the wood chips into chips of desired size, over-size and fines is achieved.

The invention also provides wood chips whenever produced by the method of the invention The invention will be more clearly understood from the following description thereof, given by way of example only with reference to the accompanying drawings in which:- Fig. 1 is a block diagram illustrating the method of producing wood chips according to the invention, Fig. 2 is a perspective view of part of the timber processing apparatus used in the method of the invention; and Fig. 3 is a perspective view of another part of the apparatus used in the method of the invention.

Referring to the drawings, there is illustrated a method for producing wood chips of a desired size range comprising the steps of debarking logs and scanning the debarked logs to establish the major dimensions of the logs. Logs that do not conform to preset parameters are rejected. The logs are then graded into a range of log sizes. The graded logs 1 axe delivered on demand to a first stage canter 2 in which two sides of the graded debarked logs 1 are canted to roughly flatten two opposite side edges of the log 1. The other two sides of the graded debarked logs 1 are then canted in a second stage canter 3 to provide a canted debarked log 5. Unsorted wood chips from the first and second stage canters 2, 3 are delivered along input conveyors 6, 7 to a main wood chip conveyor 8.

The canted logs 5 are trimmed in an end trimmer 10 to provide a canted log 11 of desired length and waste timber ends 12. The canted and trimmed logs 11 are resawed in a first stage resaw 15 which forms side slivers 16 which are delivered to a first edger 17. In a second stage resaw 18 side slivers 19 are also produced which are delivered to a second edger 20. The resaws 15, 18 provide a finished timber 25 of desired width and length which may be further processed to form the required sizes of timber. Edging of the side slivers by the edgers 17, 20 provides some lower quality timber pieces which may be used for some applications. The waste slivers from the edgers 17, 20 are delivered along conveyors 26, 27, respectively, to a main waste timber conveyor 29.Waste timber ends 12 from the end trimmer 10 are also delivered by a conveyor 12A to the main waste timber conveyor 29.

Unsorted wood chips from the main wood chip conveyor 8 are delivered to a vibrating screen unit 30 which divides the wood chips into over-size wood chips 31 which are delivered to the waste timber conveyor 29, undersized wood chips or fines 32 which is collected in a storage area and used for example as a fuel supply for a boiler. Wood chips 33 of desired size from the vibrating screen unit 30 are collected to provide a relatively high value byproduct.

Waste timber delivered onto the waste timber conveyor 29 from the vibrating screen unit 30, from the waste conveyors 26, 27, from the edgers 17, 20 and waste timber ends 12 from the trimmer 10 are all delivered to a chopper 35 which chops the waste timber into unsorted wood chips which are delivered up a pipe 36 to a cyclone 37 above the vibrating screen unit 30. The cyclone 37 removes fines generated on chopping the waste timber and delivers the unsorted wood chips for grading to the upward screen of the vibrating screen unit 30.

In more detail, the vibrating screen unit 30 comprises at least three screens through which the wood chips are passed to divide them into over-size, fines and chips of desired size. The screen unit 30 is mounted for vibratory movement on a support frame 40.

The support frame 40 comprises structural tubing with steel plate sides. The screens are of punched plate and woven wire, the screen being sloped at an angle of typically 70. The screens are suspended by four hangar assemblies, each equipped with a pair of anti-friction universal joints.

An electric rotor induces a full length flat rotary action. Because of the balanced mounting minimal forces are transmitted to the support frame 40.

The vibrating screens are operated at preferably approximately 300 revolutions per minute which we have found to be the optimum speed for high volume sorting of wood chips and fines removal. The high speed agitates the flow of chips to fluidise the entire chip bed allowing the fines to tumble unhindered through the mass of chips. In addition, the high speed prevents chips from clinging to the surface of the screen thus reducing blockages.

It will be appreciated that screens may be added or removed to facilitate sorting into different size ranges.

In more detail, the cyclone 37 causes the wood chips to decelerate as they are blown from the wood chopper 35 by the fan draught developed by the blades of the =.hopper 35 This facilitates orderly evacuation of wood chips from the chopper unit 35. The cyclone 37 also funnels the wood chips to the upper end of the vibrating screen unit 30, thus utilising the full length of the screen and facilitating optimum segregation of the wood chip.

The invention provides a highly efficient and optimised process for producing wood chips of desired size.

The invention is not limited to the embodiments hereinbefore described which may be varied in both construction and detail.

Claims

CLARIS

1. A method for producing wood chips comprising the steps of: debarking logs; scanning the debarked logs to establish the major dimensions of the logs; grading the logs into a range of log sizes; delivering the graded logs on demand to a first stage canter; canting two sides of the graded debarked logs in the first stage canter canting the other two sides of the graded debarked logs; delivering unsorted wood chips from the first and second stage canting to a wood chip conveyor; end trimming the canted log to provide a canted log of desired length and a waste timber end; resawing the canted and trimmed logs forming side slivers and finished timber of desired width and length; edging at least some of the side slivers removed on resawing; delivering waste slivers from the resawing and edging to a waste timber conveyor;; delivering unsorted wood chips from the wood chip conveyor to a vibrating screen unit; dividing the wood chips in the vibrating screen unit into over-size chips, fines and chips of desired size; delivering the over-size chips from the vibrating screen to the waste timber conveyor; chopping the wood pieces from the waste timber piece conveyor into wood chips; delivering the unsorted wood chips from the wood chopper to the vibrating screen to divide the wood chips into over-size chips, fines and chips of desired size, collecting the wood chips of desired size, collecting the fines, and re-chopping over size chips.

2. A method as claimed in claim 1 including the step of delivering the waste timber ends from the end trimming to the waste timber conveyor for chopping into wood chips.

3. A method as claimed in claim 1 or 2 wherein unsorted wood chips from the wood chopper are passed through a cyclone before being delivered to the vibrating screen unit.

4. A method as claimed in any preceding claim wherein two opposite sides of the graded debarked logs are canted in a first stage canter and the other two sides are subsequently canted in a second stage canter arranged in series with the first stage canter.

5. A method as claimed in any preceding claim wherein the resawing comprises first stage resawing two opposite sides of the canted and trimmed logs and subsequently second stage resawing the other two sides of the canted and trimmed logs.

6. A method as claimed in claim 5 wherein at least some of the side slivers removed in the first stage resawing are edged in a first stage edger, and at least some of the side slivers from the second stage resawing are edged in a second stage edger.

7. A method as claimed in any preceding claim wherein the vibrating screen unit has at least three vibrating screens for dividing the wood chips into fines, over-size chips and chips of a desired size.

8. A method for producing wood chips substantially as hereinbefore described with reference to the accompanying drawings.

9. Wood chips whenever produced by a method as claimed in any preceding claim.