A SET-UP FOR FEEDING TIMBER TO A SINGLE-LOG FEEDER

Abstract: Plant for feeding timber boards to and through a single-board feeder (2) for elongated timber boards (4). The timber boards are conveyed in mutually sequential relationship while lying on a conveyor (1) transversely to the conveying direction. The conveyor (1) advances the boards to the single-board feeder (2) at a speed of Vin and the feeder operates at a feeding speed Vut which is slower than Vin. Arranged upstream of the single-board feeder (2) and the buffer region (3) adjacent thereto as seen in the conveying direction is a regulator means (5, 6) which retards the boards (4) advanced on the conveyor (1) to a speed Vreg which is slower than Vin, prior to passing boards (4) further to the single-board feeder (2) on the conveyor (1).

Description: A SET-UPFOR FEEDING ΗMBERTO A SINGLE-LOG FEEDER The present invention relates to plant for feeding timber boards to and through a single-board feeder in accordance with the preamble of Claim 1. The invention relates in particular to high-speed production plants, i.e. plants in which the boards are fed to different stations at high speeds. The timber boards are normally transported in sawmills with their longitudinal axes transversal to the direction of conveyor belt movement. The boards are not distributed uniformly on the belts and the spacings between the boards can vary widely. However, it is desirable to be able to convey the boards in a uniform and regular array, for instance in conjunction with sorting and cross-laying the boards. The boards are advanced with the aid of so-called single-board feeders which grip boards stored temporarily in a buffer region and advance the boards one by one for further handling. Because the general aim is to increase the rate of production and therewith the speed at which boards are transported through the plant, it is endeavoured to keep the buffer region upstream of the individual board feeder under control, so that the buffer region will neither be too large nor too small. An excessively large buffer region will result in various kinds of disturbances in operation. For instance, the boards will not remain in contact with the conveyor, but will be pressed up and lifted in the buffer region. If the buffer region is too small or when no boards are present in said region, the feeder will stop. Both instances will immediately result in an interruption in production. Because a high production rate is contingent on the continuous outfeed of boards downstream of the board feeder, the buffer region must be kept constantly full of boards above a given lowest level, wherein the feeder output rate V ut , i.e. the number of boards that are fed out per unit of time multiplied by the width of the board, must be lower than the board feeding speed V ιn upstream of the individual board feeder. The buffer region upstream of the board feeder can be said to form a magazine or storage facility and is thus necessary for single-board feeding. In addition to enabling the boards to be dispensed one at a time, the invention also enables boards of different widths and thicknesses carried on the conveyor belt to be dispensed effectively and positively, and also enables two or more boards to be dispensed at one and the same time. Dispensers constructed to this end are known to the art, and reference is made in this regard to Swedish Patent Specifica¬ tion 7700760-7 which teaches a dispensing device for dispens¬ ing timber boards of different widths and thicknesses or heights. Reference is also made to Swedish Patent Application 9403668-8 which teaches a device for dispensing two timber boards at one and the same time. However, this so-called board dispensing function still constitutes a "bottleneck" that limits production rates and therewith the capacity of other plant equipment. Although it is possible to enhance the capacity by double-feeding as proposed in Swedish Patent Application 9403668-8, double-feeding is required only with regard to a part of the sawmill production line. These known devices and arrangements, however, have been found wanting when required to dispense boards of mixed dimensions and when requiring alternating double-feeding and single-feeding of the boards. For instance, these devices must be attended constantly by experienced operators and do not provide the high capacity desired. By utilizing the irregular advancement pattern of the boards on the conveyor to the single-board feeder, with which single-board dispensing of up to three boards per second is possible in single-board feeding operations, the problem presented by the buffer region at high production rates has been solved by the invention, which prevents the buffer region from expanding or decreasing to a lowest level in an uncontrolled manner. This is achieved by virtue of the invention having the characteristic features set forth in the following Claims. The invention will now be described in more detail with reference to exemplifying embodiments thereof and also with reference to the accompanying drawings, in which Fig. 1 is a schematic side view of a conveyor path on which timber boards are placed cross-wise in the vicinity of a single- board feeder; Fig. 2 is a schematic side view of an inventive board dispensing device; Fig. 3 illustrates the device of Fig. 2 with a board gripped for transportation away from a timber board buffer facility; Fig. 4 illustrates the device subsequent to the board having been "spat away" from the board buffer facility; and Fig. 5 illustrates a somewhat different embodiment of the device illustrated schematically in Fig. 2. The conveyor belt of the embodiment illustrated in Fig. 1 has the form of a belt conveyor 1 whose board-feeding rate is referenced V in . The reference numeral 2 identifies a single- board feeder whose board-feeding rate is referenced V ut and which will be described later on. Thus, the conveyor 1 moves the boards 4 at the speed V ιn , said boards lying cross-wise to thβ' conveying direction. The boards 4 will not normally be distributed regularly on the conveyor 1, but may be spaced unevenly therealong. This is indicated on the left of the Figure. Since the single-board feeder 2 is intended to feed the boards one by one on a forwarding conveyor provided with dogging means, as indicated on the right of the Figure, it is necessary to obtain a given temporary storage or buffer 3 upstream of the single-board feeder. This buffer is obtained by ensuring that V ιn is greater than V ut , as earlier indicated. The aforedescribed forms part of the known technology and a more detailed description is thereof unnecessary. The invention enables the buffer region 3 upstream of the single-board feeder 2 to be maintained within a controlled size. There is provided upstream of the single-board feeder 2 a regulator which includes endless belts 5 disposed across the width of the conveyor 1, each of said belts being guided over respective guide wheels or rollers 6, of which one is driven. The upper run of the endless belt 5 is located above the upper transporting plane of the conveyor 1 and will thus engage the timber boards 4. As indicated in the drawings, the upper run of the belt 5 shall move in the transporting direction of the conveyor 1. The speed of the belt 5 is V reg , which is lower than the speed V ln of the conveyor 1. The unevenly distributed boards 4 transported on the conveyor 1 will either be gripped or retarded by the belt 5 as a result of the difference between the speeds v\ n and V. eg . Thus, a pre- buffer 3' will be built-up with boards on the upper run of the belt 5 at the same time as the regulator device will deliver the boards that collect thereon in a delayed rate ? to the conveyor 1 upstream of the single-board feeder 2 when so required by the feeder buffer 3. The pre-buffer 3' can be allowed to grow or expand to a given extent upstream of the regulator. Thus, despite the boards being forwarded to the single-board feeder 2 on the conveyor 1 at the speed V ιn , enlargement of the buffer region 3 upstream of the single- board, feeder 2 will be equalized in accordance with the timing of the conveyor 1, i.e. an enlargement which keeps within largest and smallest permitted limits. Retardation of the boards and feeding of the boards to the single-board feeder 2 is made possible by utilizing the gaps between the boards on the conveyor 1 upstream of the regulator device. The invention thus enables building-up of the pre-buffer 3' and of the buffer 3 upstream of the single-board feeder 2 to be continued for given shorter periods, even if the feeder 2 is stopped due to a halt in production of the feeder, for instance. The regulator can be constructed to adapt to different speeds of the conveyor 1, and also to different board dimensions and feeder capacities. The regulator speed V reg will normally lie between V ιn and V ut . The invention thus provides a highly flexible arrangement which can be installed in existing plants to solve an existing serious problem, particularly in the case of high-production plants. In principle, the conveyor belts may be of any appropriate kind and made from any suitable material, including high friction chains, provided that they will lower the rate of feed of the boards the speed V reg . The conveyor belt 1 advances the boards 4 in the arrowed direction, up to the location of a stop means in the form of a stop shoulder 300, so as to create the board buffer region 3. The boards 4 have mutually different dimensions with regard to width and height, or thickness, as indicated in the drawings. A first belt conveyor or chain conveyor is refer- enced 400 and, when seen in the feed direction, includes a rear belt guide wheel 500 and a belt guide wheel 600 which is larger than the rear guide wheel 500. A conveyor belt runs around the guide wheels so as to provide lower and upper belt runs 700. The upper belt run 700 of the conveyor 400 runs in generally the same plane as the conveyor path 1 and a downstream conveyor path 800. The conveyor path 800 includes suitably spaced dogging means 900 and runs over a guide wheel 1000. The upper run of the dogging conveyor path 18 moves in the arrowed direction. Mounted above the first belt or chain conveyor 400 is a second belt or chain conveyor 1100, which runs over a rear wheel 1200 and a wheel 1300 which is larger than the wheel 1200. The lower run 1400 of the second conveyor belt moves above the upper run of the first conveyor belt 400, with the belt guide wheel 1200 located essentially above the belt guide wheel 500 of the first conveyor. The two belt or chain conveyors 400 and 1100 together form a separate unit which, in the illustrated embodiment, can swing about the shafts 1500 and 1600 of respective wheels 600 and 1300. The arrangement includes a pneumatic or hydraulic piston-cylinder device 1700 and a link system 1800 by means of which the first conveyor 1400 can be swung about the shaft 1500, i.e. the rear end with the guide wheel 500 and the upper belt run 700 can be raised above the top edge of the stop shoulder 300. The second conveyor 1100 can be swung correspondingly about the shaft 1600, with the aid of a link system 1900 that is driven by a pneumatic or hydraulic piston-cylinder device 2000. The link system 1900 also includes a gas spring means 2100. The arrangement includes a sensor means 2200, for instance a light cell. The conveyor paths 1 and 800 work continuously when the arrangement is in operation, and the conveyors 400 and 1100 are driven continuously at a speed which is substantially greater than the speed of the conveyor path 1. When the sensor means 2200 detects the presence of a board (Fig. 2), the first conveyor 400 is swung up about the shaft 1500, so as to lift the board. At the same time, the second conveyor 1100 is rotated about the shaft 1600 so as to lower the lower belt run 1400 with the wheel 1200. As the first conveyor 400 lifts the board to the upper edge of the stop shoulder 300, the conveyor 1100 is, at the same time, lowered so that the board will be clamped between the two conveyors 400 and 1100 and their respective guide wheels 500 and 1200 (Fig. 3). As a result of the high speed of the belt conveyors, the board clamped between the conveyors will be "spat out" over the conveyor 800 provided with said dogging means (Fig. 4) and dispensed through the medium of said dogging means by said conveyor. By using belt or chain conveyors 400 and 1100 that have a given length, the timber boards will be "spat away" in a controlled and damped fashion, through the gap formed between the conveyors. The intention of clarifying the drawings, it is emphasized that the conveyor paths 1 and 800 are comprised of conveyor chains and that the conveyor path 1 is guided around wheels that are coaxial with the illustrated guide wheel 1000 of the conveyor path 800. The arrangement includes a plurality of belt or chain conveyors 400 and 1100 respectively between the conveyor chains of the conveyor paths 1 and 800 in the width direction of said paths. These conveyors 400 and 1100 may be five in number, as can also the stop means 300. Although only one dogging means 900 is shown in the drawings, it will be understood that dogging means are provided on the conveyor path 800 with a determined spacing, or pitch, therebetween. As soon as the sensor means 2200 fails to register the presence of a board, due to the fact that the board has been jerked away by the conveyors 400 and 1100 and the difference in belt speeds and in belt inertia has prevented following boards from filling out the space downstream of the board that has been jerked away, the first conveyor 400 is lowered and the second conveyor 1100 raised so that the arrangement will return to the starting position shown in Fig. 2. This procedure is repeated and if it is the board shown to the right in Fig. 2 that is to be dispensed, the second conveyor 1100 will adapt automatically to the right-hand board through the function of the air springs 2100, with the same positive feeding function as a result. When it is intended to dispense boards of mutually the same dimensions or boards whose heights only marginally vary, the piston-cylinder device 2000 can be regulated so as to enable the second conveyor 1100 to be adjusted with the guide wheel 1200 located above the top edge of the stop shoulder 300 at a height which corresponds to or slightly less than the height or thickness of the boards to be dispensed. Deviations in the height of the boards are taken up by the air springs 2100 also in this case. As will be evident from Fig. 5, the stop shoulder 300 can be moved to a forward position 300' in the feed direction, so as to enable two boards to be dispensed from the buffer zone 3. When the stop shoulder is located in position 300', two boards will be fed forwards in the region above the upper run 700 of the belt conveyor 400. When the conveyor 400 and its upper run 700 are raised, two boards will be lifted to a level above the stop shoulder, therewith providing space for two further boards. Movement of the stop shoulder 300 between its two positions (300, 300') is automatic and controlled in dependence on a downstream stacking machine, for instance. An alternative to the provision of a movable stop shoulder 300 is to provide two stop shoulders 300, 300' that can be lowered or swung out of the transportation plane. In this case, the stop shoulder 300' is moved out of the feed plane when feeding one board at a time, while the stop shoulder 300 is moved out of said feed plane when feeding two boards at a time. This also takes place automatically, of course. It will be understood that it lies within the scope of the invention to dispense forwards three boards at a time, by commensurate displacement or positioning of the stop shoul¬ ders. The second belt conveyor or chain conveyor 1100 is shown swung to a relatively high position in broken lines 2300. This indicates the possibility of opening the "gap" between the two conveyors 400 and 1100 so as to provide ready access to this region for taking any steps or measures that need to be taken.

Claims: CLAIMS 1. Plant for feeding boards of timber (4) to and through a single-board feeder (2) for elongated boards of timber (4) which lie sequentially on a conveyor (1) transversely to the longitudinal axis of said conveyor, wherein the conveyor advances the boards to the single-board feeder (2) at a speed V ιn , said feeder (2) operating at a board-feeding speed V ut that is lower than V ιn , characterized by a regulator means (5, 6) mounted upstream of the board feeder (2) and the buffer region (3) in the proximity thereof as seen in the conveying direction, wherein said regulator means retards the boards (4) advanced on the conveyor (1) to a speed V reg which is slower than V ιn prior to the boards (4) being conveyed further to the board feeder (2) on the conveyor (1). 2. Plant according to Claim 1, characterized in that the regulator means comprises high friction endless belts (5) or chains disposed across the width of the conveyor (1) and each passing over at least two guide wheels (6), wherein the upper runs of the belts in the regulator means are located above the conveying plane of the conveyor ( 1) and move at a speed V reg which is slower than V in . 3. Plant according to Claim 1 or 2, characterized in that the speed V rβg of the regulator means is greater than the speed V ut of the single-board feeder (2) but slower than the feeding speed V ιn of the conveyor. 4. Plant for guiding dispensing advancement of timber boards (4) carried sequentially and cross-wise along a first conveyor path (1) in a board buffer region, wherein movement of the boards to a second conveyor path (800) having dogging means and located downstream of the first conveyor path is obstructed by a height-limited stop means (300), character¬ ized in that there extend between the first and the second conveyor paths transversely to the longitudinal axes thereof first belt conveyors or chain conveyors (400) whose upper runs (700) move essentially on level with the conveying planes of the conveyor paths (1, 800) and extend rearwardly in the feed direction slightly beyond the stop means (300), and a plurality of second belt conveyors or chain conveyors (1100) disposed above the first conveyors (400) transversely to the transverse extensions of the conveyor paths, wherein the lower runs (1400) of the belt conveyors or chain convey¬ ors (1100) extend rearwardly essentially on level with the first conveyors (400); and in that the upper runs (700) of respective first conveyors (400) can be raised above the upper edge of the stop means (300) therewith lifting the board (4) that lies against said stop means above said stop means and into engagement with the lower run (1400) of the second conveyor (1100). 5. Plant according to Claim 4, characterized in that the lower run (400) of the second conveyor (1100) can be lowered towards the first conveyor (400)? and the board (4) located thereon, at the same time as the first conveyor (400) rises and lifts the board (4). 6. Plant according to Claim 4 or 5, characterized in that the stop means comprises a stop shoulder (300); and in that the first and second conveyor (400, 1100) extend rearwardly beyond the stop shoulder (300) through a distance which corresponds to the width of some of the boards advanced on said conveyors. 7. Plant according to Claim 4 or 5, characterized in that the stop means comprises first and second stop shoulders (300, 300') which are located mutually sequentially in the board feeding direction; and in that the first and second conveyors (400, 1100) extend rearwardly beyond the first stop shoulder by an extent which corresponds to the width of some of the boards advanced by said conveyors; and in that the second stop shoulder (300") is located at a distance from the first stop shoulder (300) that corresponds to the width of the advancing boards. 8. Plant according to Claim 7, characterized in that the first and second stop shoulders (300, 300' ) can be lowered to a level beneath the conveying plane of the first conveyor (400) . 9. Plant according to Claim 4 or 5, characterized in that the stop means comprises a stop shoulder (300) that can be moved in the feed direction (300' ) through a distance corresponding to the width of the advancing boards. 10. Plant according to any one of Claims 4-9, characterized in that the first and second conveyors (400, 1100) can be raised and lowered with the aid of piston-cylinder means (1700, 2000); and in that an air spring (2100) is provided between the second conveyor (1100) and coacting piston- cylinder means (2000). 11. Plant according to any one of the preceding Claims, characterized by sensor means (2200) for sensing the presence of a board upstream of the stop means (300). 12. A method of controlling the feed of timber boards to and through a single-board feeder (2), wherein the boards are transported to said the single-board feeder (2) in mutually sequential relationship transversely to the feed direction on a .conveyor (1) having a board-feeding speed V ln , wherein the feeder (2) operates at a board-feeding speed V ut that is slower than V ιn , characterized by causing the boards (4) upstream of the single-board feeder (2) and the buffer region (3) adjacent thereto, as seen in the conveying direction, to move at a speed V reg which is slower than the speed V ιn , prior to forwarding the boards to the single-board feeder (2) on the conveyor ( 1) .

Inventors: MARKLUND ERLAND, MARKLUND, ERLAND
Applicants: MARKLUND ERLAND, RENHOLMENS MEK VERKSTAD AB, MARKLUND, ERLAND, RENHOLMENS MEKANISKA VERKSTAD AB
Application year: 1997
Main classification: B65G47
IPC codes: B27B31