EP3097032A1

EP3097032A1 - Method and apparatus for single feeding of elongate objects

Info

Publication number: EP3097032A1
Application number: EP15737039.6A
Authority: EP
Inventors: Tony GUNNARSSON
Original assignee: C Gunnarssons Verkstads AB
Current assignee: C Gunnarssons Verkstads AB
Priority date: 2014-01-20
Filing date: 2015-01-20
Publication date: 2016-11-30
Also published as: WO2015108481A1; EP3097032A4

Abstract

A method of feeding elongate objects (5) one by one from a conveyor, on which the objects (5) are conveyed with their longitudinal direction substantially transversal to the conveying direction, to a subsequent conveyor. The method comprises the steps that the elongate object (5) is detected and its position and alignment are determined and the determined alignment is compared to a predetermined positioned alignment. Control signals to a number of control drives (3) are calculated, and the object (5) is affected by the control drives to take the predetermined positioned alignment. A device for performing the method according to the above comprises detection means (2) for measuring the position of incoming objects; control drives (3) for alignment and positioning of the objects (5); and a control system for control of said control drives (3) through feed-back.

Description

METHOD AND APPARATUS FOR SINGLE FEEDING OF ELONGATE OBJECTS TECHNIKCAL FIELD

The present invention relates to a method for single feeding of elongate objects from one conveyor, on which the objects are conveyed with their longitudinal direction substantially transversal to the conveying direction, onto a subsequent conveyor.

The invention also relates to a device for performing of the method.

PRIOR ART

It is previously known to convey elongate objects, e.g. wood in the form of sawn or planed battens and planks, as well as bed laths, one by one from one conveyor to another, wherein an alignment of the wood elements takes place before the very transfer so that they end up in exactly a desired position, preferably perpendicular to the conveying direction, e.g. before a subsequent inspection, cutting, packaging or otherwise. In a traditional single feeding process the separate objects are accumulated and a pressure is created between them. A problem occurring in the process can therefor result in very serious consequences, since a large number of objects will pile up before anyone manages to stop the conveyors.

As one example of prior art, there is a device having a rotating drum, on which there are a number of gripping means, which are controlled e.g. through a cam disk. There are also alternative embodiments of the design having pneumatically, hydraulically and electrically actuated gripping means. This design has functioned quite well for single feeding of uniform as well as mixed dimensions of wood products.

However, the construction is quite advanced and expensive and there is a need for in-process maintenance. When feeding of two objects at a time is desired, the driving fingers have to be run with the double velocity in relation to the subsequent conveyor. This will, however, increase the risk of stops and will then affect the efficiency of the machine. Also the sound level will be negatively affected when the machine velocity is increased.

Therefore, there is still a need for an even more improved method for efficient conveying of oblong objects with a high capacity and a high efficiency. THE PROBLEM

Accordingly, one object of the present invention is to provide a method that ensures efficient feeding of elongate objects with a high capacity and a high efficiency.

Another object of the invention is to offer at the same time enhanced degrees of freedom in single feeding, to make it possible to accumulate two or several elongate objects during single object feeding for subsequent release to a subsequent process step with exact positioning of the separate objects, without the creation of a pressure from subsequent objects, thereby reducing the risk for undesired stops.

SOLUTION OF THE PROBLEM The task being the object of the invention is achieved with a method with the features of the main claim.

The object of the device is achieved when the device is characterized by detection means for measuring the position of incoming objects, control means for aligning and positioning of the objects, and a control system for controlling said control means through feed-back. Advantageous embodiments and developments are defined in the sub claims.

DRAWINGS

The invention will now be described with reference to the accompanying drawings. In the drawings:

Fig. 1 shows a perspective view, obliquely from above, of the device according to the invention;

Fig. 2 shows a view from above of the device according to Fig. 1; Fig. 3a shows a straight side view of the device according to Fig. 1; Fig. 3b shows a view of the detail encircled by a ring in Fig. 3a;

Fig. 4a - e show schematic views from above of steps for aligning a batten, which is conveyed using the method according to the invention; and

Fig. 5a shows a cross-sectional view of the device along the line D-D in Fig. 2; Fig. 5b shows a detailed view of the surrounded area in Fig. 5a. PREFERRED EMBODIMENT

Accordingly, the invention relates to a device and a method for single feeding of elongate objects on conveyors, wherein the separate objects lie substantially transverse in relation to the conveying direction. Normally, the individual objects do not lie exactly perpendicular to the conveying direction, they might have different lengths, and some of them may have a wane, etc. At accumulation with pressure between the individual objects many different problems may arise, which in their turn might cause shutdown.

With the term "elongate objects" particularly, but not exclusively, are meant wood articles in the form of battens and planks, sawn and/or planed, as well as bed laths, e.g. for placement between layers of battens and planks. The method is equally well suited for single object feeding of other forms of elongate objects with the same demands on high capacity and efficiency, such as elements manufactured from cardboard, plastic or composite materials of different kinds, such as laminate flooring, etc. In Fig. 1 a feeding device 1 is shown in a perspective view, which is used in single object feeding of elongate objects, such as battens. The direction of movement of the elongate objects is from left to right in the Fig., each object being positioned so that its longitudinal direction extends substantially in the direction of movement. The elongate objects might be somewhat obliquely placed in relation to the ideal positioning, but the feeding device is intended to align the objects, so that they by the feeding will be aligned completely perpendicular to the conveying direction. For the sake of clarity the conveyor chains, on which the elongate elements are fed up to and away from the feeding device 1 , are not shown.

Accordingly, the present invention relates to a device and a method, wherein individual elongate objects are handled one by one in order to avoid that, e.g. when the length of the individual objects vary, a fan shaped layer is formed during accumulation, which cannot be handled by prior art conveyors, or that, if one object has a wane, subsequent elements slide up onto the object in front, which would cause problems and stops.

With planed wood articles, for example, the spacing between different pieces can be predicted exactly, and accordingly the equipment for feeding, transfer and so on can be controlled when accumulation takes place under pressure. With e.g. sawn wood articles, however, during accumulation of a number of pieces, a displacement of the separation between the pieces might occur because of addition of tolerances, whereby it will be difficult, if not impossible, to arrest the right piece before gripping of a piece lying in front thereof.

By catching, aligning and feeding each individual object according to the invention, without pressure from a subsequent piece, the efficiency is considerably increased and the risk for faults is correspondingly reduced. It is also possible to lower the machine velocities with maintained plant capacity, and thereby having a more calm and safe operation by using the invention.

In the method according to the invention, in a first step there is a feeding of elongate objects with their longitudinal direction substantially transverse in relation to the conveying direction on a first conveyor consisting of a number, individually controllable conveyor elements being mutually aligned in relation to each other, wherein the feeding is controlled in such a way that gaps between the elements are reduced as far as possible by increasing the velocity of the separately controllable conveyor elements when these gaps are identified. When possible gaps have been driven together it is important that the velocity is reduced in order to avoid unnecessary pressure between the pieces.

In Fig. 2 the feeding device 1 is shown from above. In both Figs. 1 and 2 there are a number of detection means 2 for detecting the actual positions of the fed battens/objects in relation to the exactly transversal, ideal position, short before they reach the feeding device 1. Measuring of the position of the piece can, as was mentioned above, take place with a sensor according to the most well suited technology. Examples of such technologies are light-curtain device, camera or a system based on laser beams. Light-curtain is a robust, fast and economical solution.

In order to be able to detect a misalignment of an object the detection means have to be at least two in number. Further, it is advantageous to arrange further detection means 2 in addition, since thereby it is secured, that both shorter and longer objects can be handled with a high accuracy. The distance between two adjacent detection means 2 should be less than half the shortest length of objects, which are expected to be handled by the device. Each object, that is handled, will then be detected by at least two detection means 2, and thereby it is possible to determine a possible misalignment of the respective object, so that this

misalignment can be corrected. Obtained measured values are sent to a control system, in which a program processes the measurement values and outputs control signals to a number of control drives 3 in order to position the actual object, which then is released synchronously with the movement of the subsequent conveyor, so that the object is caught and conveyed onwards by this. A number of control drives 3 are arranged in association with the detection means 2 for engagement with any misaligned objects, so that their position can be corrected. In the preferred embodiment each control drive 3 comprises a pair of rolls 3a, 3b, which, when they are brought closer to each other will abut the object on both sides thereof, securely gripping it. Thereby the part being engaged by the control drive 3 can be delayed, which is accomplished by making the rolls 3a, 3b stand still for a time interval. An acceleration forwards, in a direction inwards towards the feeding device, of the engaged part is accomplished by making the rolls 3a, 3b to roll faster than the prevailing velocity of the object. A backward

acceleration, in the direction away from the feeding device, is accomplished by making the rolls 3 a, 3b rotate in a direction which is opposite to the direction of the conveyor. These alternatives for the rolls 3a, 3b being comprised in the control drives 3 together with a choice of time interval for the engagement with the object and the driving velocities of the rolls 3a, 3b produce, in suitable combinations, a small turn, and thereby, alignment of the

object/batten.

The control drive 3 can be one single control drive 3, which catches the object and aligns it in the desired way, but it can also be two or several control drives 3 arranged at a distance from each other, which in cooperation aligns the object so it ends up transversally in relation to the convey direction. At the same time the control drive 3 or control drives 3, acts to release the object synchronously with the movement of the drivers on a subsequent conveyor. The number of control drives 3 and, in the preferred embodiment, the distances between them are decided in a way corresponding to the determination of the number of detection means 2 above.

In the step before alignment the conveyor track is controlled only for feeding the objects to the control drive. This control takes place, in the preferred embodiment, with the aid of a light curtain arranged in parallel with the track with feed-back through a control system to the individual conveyor elements. The control drives 3 may, as has been mentioned already, consist of rubber rolls 3a, 3b, arranged above and/or underneath the conveyor track for the elongate objects, or alternatively bands or belts running over drive rolls, which rolls may be driven by pneumatic, hydraulic or electric servo motors, which are directly coupled back to a control system, or any other types of motors, which are controlled through video cameras, following the object and adjusting it until it is correctly aligned.

I Fig. 3a the conveyor device according to the invention is shown directly from the side, with an enlargement of the encircled area in Fig. 3b. In Fig. 3a and 3b the detection means 2 as well as the control drives 3 are shown. After detection of an incoming object it is captured and fixed, when it is in the working area of the control drives 3. The position of the object is measured in real time with the aid of suitable sensors, and the control system calculates the movement the rolls 3 a, 3b of the respective control drive 3 have to perform in order to align the object, so that it lies exactly transversal in relation to the conveying direction, and so that the object is aligned before the object is released by said control drives 3.

If a subsequent conveyor is a chain of carriers, the movement of the control drives 3 shall also be calculated so that the object is conveyed correctly in between the carriers. This means that the velocity of the aligned object when it is released by the control drives 3 and the time for the release are calculated such that the objects reach the subsequent conveyor just before a carrier of the conveyor moves to a position just behind the object, and can drive the object in front of itself, in a direction away from the conveyor arrangement.

In Figs. 4a - e are shown a sequence of schematic views directly from above of steps for aligning an object in the form of a batten 5, which is handled in the conveyor arrangement 1.

In Fig. 4a the batten 5 is detected by two detection means 2, and its width, position, actual velocity and the extent of misalignment is determined. The front about 10 % of the width of the batten are regarded as a gripping area G, and actual alignment of the batten starts at first when this gripping area G has been passed and the control drives 3 have been engaged with the subsequent working area A, which amounts to about 75 % of the width of the batten 5. The last area, seen in the direction of movement, of the batten, which is an acceleration and retardation area R, is used to give all points along the batten the same velocity, in order to guarantee that the batten continues to move straight forward in the conveying direction without turning itself, and so that the velocity will allow the batten to be captured by carriers on the subsequent conveyor.

If the misalignment is less than the width of the working area A it is possible to correct the position of the batten 5 with the aid of the control drives 3. In other case hooks 4 have to be used, which will be discussed below with reference to Figs. 5a and 5b.

In Fig. 4b the batten 5 has reached the control drives 3, which at the beginning move synchronously with the incoming conveyor. When the centers of both control drives 3 have reached the working area, as is shown in Fig. 4c, the actual positioning can be performed. Hereby, the fact that the control drives can accelerate both forward and backward or at times stand completely still is exploited.

In Fig. 4d, the batten 5 has taken a correct, transversal position. The center of the control drives 3 are now at the end of the working area A. However, the batten 5 does not necessarily perform a purely transversal movement in the longitudinal direction of the conveyor, but different points on the batten 5 might have different velocities, both regarding size and direction. If the batten 5 would be released without control in this position, the risk for the batten to pivot is large, since its different points continue to move with different velocities in different directions.

In order to remedy this risk, the magnitude and direction of the velocities are synchronized in the different points of the batten 5, while the acceleration and retardation area R passes past the control drives 3. At the same time a synchronizing with the subsequent conveyor is done. In Fig. 4e the batten 5 is released, and it can continue forwards towards the subsequent conveyor correctly positioned.

In e.g. a wood handling plant there are velocities of up to 220 pieces per minute. With these velocities the risk for a stop is high and a stop will cause large problems and a time- consuming reset. By feeding two pieces at a time, the velocity can be reduced to be half as high with retained capacity, with the proviso that the subsequent conveyor or otherwise, can handle two pieces in the same way as a single piece. Then the machines would work more calmly and more stable, while at the same time less air is transported, i.e. fewer non-used interstices between the drivers on the driver chains, which comprise the other conveyor. According to the invention, as with single piece feeding, one works with fixation of a front piece with the aid of at least two control drives, whereupon, after measuring a position and calculation of the movement of the control drives, a positioning of the piece takes place, after which the next piece is guided with pressure against the fixed piece, and finally the two, now positioned pieces are placed on the subsequent conveyor, which now works more calmly and more stable with half the velocity that would be needed in order to achieve the same machine capacity when feeding one piece at a time.

The invention also comprises accumulation of two or several elongate objects in a so called layer on a subsequent conveyor, which is not provided with drivers. Earlier, it has been difficult to build up wide layers, because it was easy to pinch the wrong object, and, as has already been pointed out, it is risky to build up layers using pressure.

Besides the above mentioned problems, if the objects are long, a fan shaped layer might form, which inevitably will lead to a stop of the operation. All of these drawbacks are eliminated by using the method according to the present invention. In order to build up such a layer, consisting of a number of elongate objects lying adjacent to each other, according to the prior art the desired number of objects is accumulated using a hook, which stops a first piece and holds it by friction, the desired number of object is accumulated by pressure, whereupon a layer is released and the hook is controlled to grip the first object of a subsequent layer. By gripping with the aid of pressure from above or from underneath it is difficult to achieve the desired accuracy, since with sawn timber the tolerances of the wood dimensions add up, and it is difficult to grip the right object. There may also be objects with wanes, resulting in a risk for that objects run up onto each other. With planed timber a better accuracy can be upheld, but since there are often shape defects with sawn wood, there are problems with formation of layers also with such pieces. The more narrow pieces and the wider layers, the more difficult it will be to clamp or grip the right piece.

In order to create a layer according to the invention, each object is fixed and positioned, subsequently to be transferred onto a second conveyor without drivers, which conveyor is controlled to move corresponding to the width of a transferred element, which is repeated until the layer contains a desired number of objects, whereupon the layer is sent off to a subsequent conveyor and/or process step. Accordingly, the objects are still conveyed according to the same method as when objects are conveyed one by one, and they are transferred to the conveyor where the layer is collected. When the layer is finished, this conveyor sends the layer onwards as a unit.

Fig. 5a shows the conveyor means according to the invention from the side as a cross section along the line D-D in Fig. 2 with an enlargement of the encircled area in Fig. 5b. If the misalignment of one object is very large, it will be difficult or impossible to correct the position of the object only with the aid of the control drives 3. In such a case at least one hook 4 is utilized, which hook is raised and is pivoted around the upper side of the object, catches and retain the object until it takes up a correct, transversal position and until it can be released synchronously with the movement of the subsequent conveyor.

The essential novelty of the invention is accordingly, with the aid of control drives, a measuring system for measuring of the position of elongate objects and a control system, to catch the elongate objects in said control drives, measure the position of the elongate objects, and thereupon control said control drives through feed-back to position the object to be exactly transversal to the conveying direction, so that, when the elongate object leaves said control drives, the elongate object when necessary also has been synchronized with a subsequent conveyor.

With the invention, there is a possibility to control the feeding in a machine so that in one and the same machine one elongate object can be fed at a time, or, in case a number of objects is accumulated upstream from said control drives, these can be conveyed together as one single wide object. If for example two elongate objects are fed at a time, this means that a subsequent conveyer with drivers can be operated at half the velocity.

ALTERNATIVE EMBODIMENTS

The subsequent conveyor is normally a conveyor with drivers, but it can be a flat conveyor as well in order to build up layers with a larger number of elongate objects. In this case the subsequent conveyor is operated synchronously with said control drives when feeding takes place.

In the description above, handling of sawn and planed wood articles is referred to as an example, however, the method can of course also be applied on other types of elongate objects, as was discussed in the introduction. The control drives 3 have, in the preferred embodiment been described as pair of rolls 3 a, 3b.

As an alternative, one or several hooks 4 can also be used in order to build up units, wherein a number of objects are positioned adjacent to each other in a so called layer. The first object is retained with the aid of the hook or hooks 4, and a number of subsequent objects, which when necessary are aligned by the control drives 3, are fed into abutment with the earlier fed objects. When a predetermined number of objects have been fed, alternatively when the layer built up in this way has achieved a predetermined width (i.e. the layer covers a certain distance, seen in the conveying direction), the layer is released from the hooks at such a time and with such a velocity, that the layer can be conveyed onwards, an a unit, by drivers on the subsequent conveyor.

The invention can be modified further within the scope of the appended claims.

Claims

A method of feeding elongate objects (5) one by one from one conveyor, on which the objects (5) are conveyed with their longitudinal direction substantially transversal in relation to the conveying direction, to a subsequent conveyor, characterized by the steps that the elongate element (5) is detected and its position and alignment are determined, the determined alignment is compared with a predetermined, positioned alignment, in that control signals to a number of control drives (3) are calculated, and in that the object (5) is affected by the control drives (3) to take the predetermined, positioned alignment.

The method according to claim 1 , characterized in that the steps are repeated in a feed-back method.

The method according to claim 1 or 2, characterized in that the alignment is performed during the engagement of a middle part of the object (5) by the control drives (3), seen in its width direction, and in that a synchronization of the velocities and movements in all points of the object (5) is performed during the engagement of a rear part of the object (5) by the control drives (3).

The method according to any of the claims 1 - 3, characterized in that the feeding in a machine is controlled in such a way that one elongate object (5) is conveyed at a time to a subsequent conveyor.

The method according to any of the claims 1 - 3, characterized in that the feeding in a machine is controlled in such a way that two or several elongate elements (5) with a known width are aligned according to the method and in that a corresponding number of elongate objects (5) then are conveyed as one broad object to a subsequent conveyor.

The method according to any of claims 1 - 3, characterized in that for build-up of a layer on a subsequent conveyor a number of aligned objects (5) are conveyed in rapid succession to the conveyor.

A device for performing the method according to any of claims 1 - 6, characterized by detection means (2) for measuring the position of incoming objects, control drives (3) for aligning and positioning the objects (5) , and a control system for control of said control drives (3) through feed-back.

8. The device according to claim 7, characterized in that at least two control drives (3) are arranged at a distance from each other.

9. The device according to claim 7 or 8, characterized in that at least two detection means (2) are arranged at a distance from each other.

10. The device according to any of claims 7 - 9, characterized in that the respective control drive (3) comprises a pair of rolls (3a, 3b), which can be driven in either direction and which are stoppable.

11. The device according to any of claims 7 - 9, characterized in that the respective control drive (3) comprises a pair of belts (3a, 3b), which can be driven in either direction and are stoppable.

12. The device according to any of claims 7 - 10, characterized in that the respective control drive (3) can be driven to a synchronous movement with the subsequent conveyor.

13. The device according to any of the claims 7 - 11, characterized in that the

subsequent conveyor is a conveyor with carriers.

14. The device according to any of claims 7 - 11, characterized in that the subsequent conveyor is a flat conveyor.