GB2087846A - Forming regular stacks from irregular piles - Google Patents

Abstract

A timber handling apparatus wherein one or more timber setts (A, B), in irregular piles, at a pick-up station can be dismantled layer by layer using a suction head (7) mounted on an overhead trolley (3) which moves at a constant speed to transfer the or each sett from the pick-up station for reassembly at one or more deposit stations (C, D) in regular stacks. The apparatus includes a timer by means of which the operator can manually control the set down position at the or each deposit station to ensure that the stacks formed are in alignment. The timer is triggered when the trolley reaches a position upstream of the or each set down position thereby delaying the signal to apply a brake to stop the trolley by the time increment selected by the operator on the timer. <IMAGE>

Description

SPECIFICATION Vacuum lifting apparatus The invention relates to a vacuum lift apparatus and more particularly to an apparatus suitable for handling timber in sheet or plank form. It may however be used for the handling of other materials having at least one planar surface.

In the timber industry, once a tree has been falled, it is taken to a processing station where it is normally sawn up to provide the optimum number of planks of varying lengths and widths depending on the size of the trunk. They are then arranged into setts or bundles, the planks being arranged one on top of each other in such a manner that the overall cross section of the sett is generally square or rectangular.

Any one layer of the sett will therefore have a series of planks therein of differing widths and each layer may well be different to its adjacent layer either above or below it.

These setts of timber are shipped from abroad in this form to their final destination where they are dismantled and reassembled in generally the same configuration but with "sticks" between each layer, the sticks being laths or small pieces of timber arranged across the longitudinal axis of the sett to permit air to circulate throughout and thereby allow thetimbertoseason and dry. In the past, this "sticking" process has normally been done by hand which is labour intensive and back-breaking work because some of the planks, particularly if hardwood setts are being handled, can be extremely heavy.

Indeed, an individual plank of hardwood which is 9 inches by 15 feet can be too heavy for two men to lift so an overhead crane may have to be used to move it to its new location for "sticking" and this is very time consuming. Seasoning the timber naturally by allowing the circulation of air between the individual planks is unacceptable these days because of the time involved which may be many months. Accordingly, it is now more usual to kiln dry it and to do this, the sett on arrival is dimantled in the traditional way and reassembled on a wheeled bogie or trolley which is then wheeled into the drying kiln where it is seasoned for a much shorter period of time, e.g. a few days.The capacity of the drying kiln is dictated by the width of its access doors and, in order to use the full capacity of the kiln, two or more setts of timber are normally arranged on the bogie in side-by-side relationship.

Timber setts imported into the UK normally come in widths of between 39 and 41 inches. The standard width of a kiln bogie is normally 84 inches and the standard width of the kiln door aperture is usually 7' 6". It will be seen therefore that two standard 41 inch wide timber setts can be loaded onto a bogie side-by-side but this will only leave a clearance of 8 inches on the overall width, i.e. 4 inches clearance at each side if it is to fit in the kiln. Whilst it might appear that it would be a fairly simple job to load the bogie accurately to give the required clearance, it must be remembered that a space of about 3 inches also has to be left between the two setts of timber stacked side-by-side on the bogie. Accordingly, only 21/2 inches clearance on either side of the bogie can be left if the kiln doors are to be cleared.One of the problems is that even if the timber setts can be stacked on the bogie accurately enough to give the required clearance on either side, once the timber is in the drying kiln, due to the natural properties of the wood during drying, it may well warp or move with the result that the whole sett may lean outwardly to such a degree such that it extends beyond the available clearance and prevents the bogie from being withdrawn from the kiln. As the height of the bogie load may be of the order of 10 feet or more, it will be appreciated that a small deflection or movement at the bottom of the load can well result in a movement at its top region of several inches so it is critical that the timber be arranged very accurately on the bogie prior to kilning.The accurate stacking of the timber on the bogie is also important to ensure even distribution throughout the bogie load of the vertical pressures thereof. Also, if a board is left projecting beyond the outer edge of the load, it can interrupt the airflow if the kiln has overhead fans and thereby restrict proper air circulation throughout the kiln.

From the foregoing, it will be seen that the dismantling of a timber sett and its reassembly on a kiln bogie is both labour intensive and highly skilled because the operatives not only have to insert the "sticks" between the individual layers of the reassembled sett on the kiln bogie but they also have to make sure that the dimensions of the reassembled setts are pecisely within the pre-defined limits dictated by the kiln doors and the sides of the bogie.

One of the problems to be solved by the present invention therefore is to provide an apparatus which can transfer timber from a sett and place it on a kiln bogie very accurately so that all the operator then has to do is to place the "sticks" on top of each deposited timber layer on the kiln bogie and judge where the next layer should be deposited toenable the reassembled sett to have the required dimensions to fit in the kiln.

French Patent Specification No. 2,273,748 discloses a timber handling system having a suction head which may be lowered onto a stack or sett of timber to lift off the top layer therefrom. An apparatus is known incorporating this suction head in which it is mounted by means of a scissor lift on a trolley which moves on an overhead gantry. The apparatus includes means enabling the suction head to be lowered to pick up the top layer from a sett of timber at one location, raised and then transported laterally to another location where it is lowered and released when the vacuum supplied to the suction head is switched off. The positional performance of this apparatus is governed by limit switches provided on the overhead gantry directly above the location at which the timber layer is to be picked up and put down.Because of the design of the suction head and the manner in which it operates in conjunction with the gantry arrangement and limit switches, it can only be used to dismantle a timber sett and reassemble it at a different location in exactly the same configuration as it was originally. In other words, if a plank in the original settto be reassembled is out of position when it is picked up by the suction head, it will be deposited in the same wrongly orientated position when it reaches its alternative location. For the reasons already explained, the consequence of such misalignment can prove to be disastrous because it could mean that the wrongly positioned plank extending beyond the outside edge of the timber sett assembled on the kiln bogie would prevent its admission into the drying kiln.

Due to varying widths of setts and varying widths of layers in a sett, it is sometimes desirable to alter the stop position of the suction head by a positive or negative dimension in order to obtain a straight edge on either of the outside faces of the made up load with its "sticks" in position on the kiln bogie.

The way to achieve this at present is to climb up onto the gantry and adjust the position of the limit switches which, due to the time involved, and the frequent times it is necessary to makes changes, in unacceptable in practice.

It is therefore an object of the invention to provide mans whereby the precise positioning of the suction head of a timber handling apparatus can be controlled during its travel so that, even if it picks up a plank which is wrongly positioned from the sett to be broken down, appropriate compensating adjustments can be made by the operator so that it may be put down in exactly the required position.

According to one aspect of the present invention, there is provided a computer controlled timber handling apparatus operable and programmed to dismantle, layer by layer, a timber sett at a pick-up station and transfer it to one or more deposit stations where it is reassembled as a whole sett or as a plurality of part setts, the apparatus including an overhead trolley movable at a constant speed between said pick-up and the or each deposit station, the trolley having mounted thereon a suction head lowerable into engagement with the upper layer of a timber sett at the pick-up station to remove said layer therefrom and transfer it to the or one of the deposit stations where it is set down on release of a vacuum applied to the suction head, the movement sequence of the trolley between the pick-up and the or each deposit station being controlled by a computerfed with signals generated by the cooperation of the trolley with limit switches associated therewith, a limit switch being located upstream of the or each deposit station and being connected to the computer via a timer device on which an operator can select a required time delay, a time signal being generated when the trolley reaches said limit switch and used to initiate application of a brake to stop movement of the trolley only after the time increment selected on the or each timber has elapsed.

By the addition of appropriate timers and limit switches, the apparatus can be adapted to handle the transfer of one or more setts from the pick-up station to the deposit station where they are reassembled side-by-side or alternatively the reassembly of the setts can be as a single sett of increased height, the original setts from the pick-up station being stacked on top of each other.

One or more timers and associated limited switches may also be provided at the pick-up station so that the apparatus can be adapted to dismantle one or more setts at the pick-up station and reassemble it or them at the deposit station and vice versa.

Whilst it is preferred that the deposit station be one or more kiln bogies, it will be appreciated that the setts can be reassembled on the ground for natural seasoning or latertransporation elsewhere.

A preferred apparatus of the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings in which: Figure lisa front elevation of an apparatus of the invention, Figure 2 is an end elevation of the apparatus of Figure 1, Figure 3 is a schematic diagram of the various stopping points of the overhead trolley of the apparatus of Figures 1 and 2, Figure 4 is a chart showing the preferred movement programmes of the apparatus of Figures 1 and 2, and Figure 5 is a wiring diagram for the timer device which provides a fine adjustment control for the positioning of the trolley and suction head attached thereto shown in Figures 1 and 2.

Referring to the drawings, there is shown in Figure 1, a timber handling apparatus comprising an overhead gantry 1 supporting rails 2 on which a wheeled trolley 3 runs. The trolley moves back and forth along the rails 2 in the direction of the arrow. A structure 4 is suspended from the wheeled trolley and this carries a scissor lift 5 to which is attached a suction head 6 of the kind described and claimed in French Patent Specification No. 2,273,748. The suction head comprises two separate suction pads 7 curved across their width provided with a plurality of regularly spaced suction apertures (not shown) across its surface.The suction head 6 is arranged to operate so that when it is lowered into contact with the upper layer of one or more timber setts D1 D2 (see Figure 2), the valves controlling the vacuum supply to the apertures not covered by a plank are automatically closed so that only those apertures which are wholly or partially covered by a plank will have the suction vacuum applied thereto and thereby attach the plank to the suction pad. The operation of the suction head 6 is known from the aforementioned French Patent Specification and is fully described therein so no further description thereof will be given here as it does not form part of the present invention.

As can be seen from Figure 1, a timber sett to be dried in kiln 20 is deposited at one side of the gantry structure at position A or B. From either of these locations, it is dismantled and moved laterally to be reassembled on bogie 9 either as a single sett C with "sticks" or as two separate setts C and D with "sticks", the separate setts being generally half the height of of sett A or B.

The wheeled trolley 3 is driven in the direction of the arrow along the overhead rail 2 by means of a motor (not shown) and similarly the scissor lift 5 is raised and lowered by appropriate means not shown. The vacuum supplies to the suction head 6 are also not shown. None of these parts of the apparatus form part of the present invention so no further detailed description thereof will be given here.

The positioning of the suction head 6 at locations A, B, C or D is controlled by limit switch abutments 10, 11, 12, and 13 respectively (see Figure 3), each abutment or stop 10, 11 being centrally located above the sett position A and B. Switch abutments 14 and 15 are also provided at each end of the gantry rail 2 to limit the full tranverse of the trolley 3. It will be noted that the abutments 12 and 13 are not centrally located over the sell positions C and D but instead are off-set by a distance c and d before their nominal or zero positions C' and D' for reasons which will become apparent shortly. The distances c and dare approximately 6.25" but they can be of a different value if desired.

The operation of the illustrated apparatus is controlled from a control box 18 which houses the electrical circuits and computer (not shown) for controlling the programme which enables the suction head to follow a number of different preselected movements, full details of which are given in Figure 4. From Figure 4, it will be appreciated that the apparatus can be made to operate automatically to break down one or more timber setts (A, B) and reassemble it or them as one, two or three sells (C, E, D) on a kiln bogie. The movements in accordance with these programmes are determined by the positions ofthe limit abutments 10,11,12 and 13.

Accordingly, the suction head 6 will be lowered, for instance, at a location corresponding to abutment 10 and it will pick up the planks on top of the set A in the orientation it finds them in. As it is the external limits y (see Figure 3) of the setts C and/or D which determine if the trolley will fit into the kiln 20, it is desirable for the suction head 6 to be able to deposit the planks taken from set A or B on the kiln bogie in the desired location and orientation determined by said external limits which may well be different to that in which they were picked up.Accordingly, the operator needs to be able to control the put down stopping point of the suction head 6 to vary it, on either side of the nominal put down points C' and D', to ensure that the outer faces C" and D" of the stacked timber sells C and/or D is within the limits defined by the width of the kiln doors.

In order to give the apparatus the desired flexibility of adjustment that is required regarding its put down operation, a timer device is provided on the control box 18 which is activated when the trolley 3 reaches abutment 12 for put down position C and abutment 13 for put down position D. Because the trolley 3 is driven at a constant speed of 11/4' in 1/10 of a second, it will travel 1/8" in 1/100 of a second.

Thus, the distance travelled is directly related to a time increment so it is possible to calibrate a dial for the timer on the control box in increments of 1/100 of a second or 1/8".

Steel sensing strips are used on the gantry to trigger the timer device and since these are positioned, preferably 6.25" before the nominal put down positions, this can be shown on a dial on the control box 18 as -6.25", the delays then being increased across the range 0 - 1 second to give travel settings of from -6.25" to +6.25". The zero position would correspond to the optimum or nominal stopping position so that it is possible, using the timber dial, to arrange for the trolley 3 to stop up to 6.25" before or 6.25" beyond the optimum stopping positions C', D'.

If the layer of planks removed from sell A is to be deposited directly beneath the nominal put down position C' i.e. 6.25" beyond abutment 12, the operator would dial in the appropriate distance on the timer dial i.e. he would set it at zero. The trolley 3 would then activate the timer when it reached abutment 12 which would allow the trolley to continue its forward travel only for 1/2 a second (the time equivalent of 6.25"). After the elapse of this time interval, the nomal programme of the computer would come into operation and the brake would be applied to the trolley 3 to stop it at location C' and the suction head 6 would be lowered to deposit its load in the desired location at set down put C on the bogie 9.

If one of the planks picked up by the suction head 6 at A is seen by the operator to be sticking out on the left as viewed in the drawings, for instance by a distance of 3", beyond the outer faces of the sell A, unless some adjustment is made, the picked up timber will be deposited on the kiln bogie at location C with this plank still sticking out by the same 3" which would prevent the bogie from fitting in the kiln doors.Using the timer device, the operator would dial up a 3" increment on the dial on the control box 18 which would mean that, when the timer was triggered by the trolley 3 when it reached abutment 12, the trolley would travel on for a further 6.25" plus 3" (74/100 seconds) after which time the brake would be applied in the normal way in accordance with the computer controlled programme to stop the trolley at the desired location 3" beyond the nominal lay down position C' whereby the out-of-line plank would line up with the outer face C" of the planks in sell C on the bogie 9. The suction head would then be lowered in the normal way in accordance with the computer programme and the timber layer released from the suction head in the manner already described.

If the misaligned plank had been 3" inside the left outer limit of the timber sett A, then the operator would dial up on the timer dial on the control box 18 a negative distance of 3" (24/100 seconds). Thus, when the trolley reached the abutment 12, it would trigger the timer device which would allow it to travel for a further 6.25" less 3" (i.e. 26/100 seconds) after which time, the brake would be applied and the trolley 3 would stop as before in a position where the out-of-line plank could be deposited on the other planks at position C in line with their outer face C".

From the foregoing, it will be seen that the range covered by the illustrated timer dial is -6.25" to +6.25" and that this would correspond to time delay settings on the timber which would have a range of 0 - 1 seconds in increments of 0.01 seconds, each 0.01 second time delay allowing a travel distance by the trolley 3 of 0.125". Greater time/distance ranges can however be provided for using different timers.

If sells A and B are to be reassembled on the bogie 9 as two sells C and D, then an additional timer and abutment 13 are provided, the abutment being located 6.25" upstream of nominal put down point D' as before. As the critical positioning limit on sell D is its outer face D", the timer device will work in the reverse way to that associated with abutment 12. In other words, if a plank removed from sell A extends 3" beyond the right outer edge of the sell as viewed in the drawings, the operator will have to dial up a negative 3" on the timer device which will mean that the trolley 3 will travel beyond abutment 13 for a distance of 6.25" less 3" (i.e. 26/100 seconds).Thus, when trolley stops after the elapse of the 26/100 second time interval on the timer, the outer edge of the misaligned plank will be lined up with the outer face D" of the reassembled "sticked" sell D on the kiln bogie 9. If the plank was 3" inside the right outer edge of the sell A as viewed in the drawings, then the operator would dial 3" on the timer on control box 18 which would mean that the trolley would travel beyond abutment 13 to 6.25" pius 3" (i.e.

74/100 seconds).

Ifthree timber sells C, D and E are to be assembled and "sticked" on the kiln bogie 9, then of course a further timer and abutment similarly located upstream of a nominal set down location would be needed.

As a further refinement, timber devices may be used in conjunction with the pick up points for the timber sells A and B in which case appropriate abutments would be provided on the overhead gantry.

With the illustrated timer device, which can be set in increments of 1/00 seconds, it will be appreciated that the fine control of the movement of the trolley can be accurate to 1/s" at each side of the reassembled sells C and D on the bogie. Thus an accuracy across the whole width y of " can be obtained with the illustrated apparatus.

A preferred wiring diagram for the addition of a timer 21 into the normal computer control of the apparatus can be seen in Figure 5 which shows a 0-1 second timer 21 of the kind which is triggered by an associated relay 22, although other kinds of timer not requiring an associated relay and which can be triggered directly by the signal from the limit switch could be used instead. The timer 21, which is in effect located in the signal line from the limit switch to the computer, can delay the limit switch signal by a chosen period up to one second. Accordingly, the trolley brake application signal, fed out of the computer in accordance with its programme when a limit switch signal is received, is delayed by the chosen period set on the timer 21, and the trolley can therefore be stopped at any selected position up to 12.5 inches after the position in which the trolley has activated the limit switch, i.e.

in a range extending 6.25 inches on either side of the nominally correct set down position.

It will be appreciated that the overhead trolley can be arranged to operate at a constant speed other than that just described by either gearing its drive differentaly or by incorporating a multiple speed gearbox and drive arrangement.

Claims (9)

1. A computer controlled timber handling apparatus operable and programmed to dismantle, layer by layer, a timber sell at a pick-up station and transfer itto one or more deposit station where it is reassembled as a whole sell or as a plurality of part sells, the apparatus including an overhead trolley movable at a constant speed between said pick-up and the or each deposit station, the trolley having mounted thereon a suction head lowerable into engagement with the upper layer of a timber sett at the pick-up station to remove said layer therefrom and transfer it to the or one of the deposit stations where it is set down on release of a vacuum applied to the suction head, the movement sequence of the trolley between the pick-up and the or each deposit station being controlled by a computer fed with signals generated by the cooperation of the trolley with limit switches associated therewith, a limit switch being located upstream of the or each deposit station and being connected to the computer via a timer device on which an operator can select a required time delay, a time signal being generated when the trolley reaches said limit switch and used to initiate application of a brake to stop movement of the trolley only after the time increment selected on the or each timer has elapsed.

2. Timber handling apparatus as claimed in claim 1 wherein two sells are located side-by-side at the pick-up station the apparatus being operable to dismantle said sells at the pick-up location and transfer and re-assemble them side-by-side at the deposit station.

3. Timber handling apparatus as claimed in claim 1 wherein two sells are located side-by-side at the pick-up station, the apparatus being operable to dismantle said sells alternately at the pick-up station and deposit each layer as a single sett at the deposit station.

4. Timber handling apparatus as claimed in claim 1 or claim 2 wherein a timer device and associated limit switch is provided at the pick-up station, the apparatus being adapted to dismantle a sell at the pick-up station and reassemble it at the deposit station and vice versa.

5. Timber handling apparatus as claimed in claim 4 wherein one or more additional timers and associate limit switches are provided at the pick-up station, the apparatus being adapted to dismantle more than one sell at a pick-up station and reassemble them at the deposit station or vice versa.

6. Timber handling apparatus as claimed in any one of the preceding claims wherein the trolley runs along rails provided on an overhead gantry.

7. Timber handling apparatus as claimed in any one of the preceding claims wherein the suction head is mounted on a scissor lift attached to the trolley.

8. Timber handling apparatus as claimed in any one of the preceding claims wherein the suction head comprises two separate suction pads which are curved across their width i.e. laterally with respect to the timber to be picked up thereby.

9. Timber handling apparatus substantially as herein described with reference to the accompanying drawings.