SE2250817A1

SE2250817A1 - A gripping device for the wood industry

Info

Publication number: SE2250817A1
Application number: SE2250817A
Authority: SE
Inventors: Jonas Gunnarsson
Original assignee: C Gunnarssons Verkst Ab
Priority date: 2022-06-30
Filing date: 2022-06-30
Publication date: 2023-12-31

Abstract

A gripping device for the wood industry, where lumber packages with crosswise arranged stringers (7) on top occur, comprises at least one gripper (22) configured to be lowered onto a lumber package and into contact with a stringer (7) on top thereof and to be lifted off said lumber package after having gripped said stringer (7). Said at least one gripper (22) comprises a number of spaced apart dowels (30), which protrude in a downward direction but, in contact with a stringer (7), are able to individually retract upward. Said at least one gripper (22) is configured to horizontally alter spacings between at least some of its dowels (30), thus that said at least one gripper (22) is enabled to grip a stringer (7) between protruding dowels (30) approaching each other in a horizontal direction.

Description

Technical Field The present invention concerns a gripping device for the wood indus- try, where lumber packages with crosswise arranged stringers on top occur, said gripping device comprising at least one gripper configured to be Iowered onto a lumber package and into contact with a stringer on top thereof and to be lifted off said lumber package after having gripped said stringer.

Prior Art ln the art lumber packages are common comprising pieces of lumber stacked on each other with thin crosswise arranged wooden s|ats in between. To enable easy handling of such lumber packages, e.g. by a forklift, so-called stringers are used, which comprise of pieces of wood substantially thicker than the thin s|ats. Like the s|ats, the stringers are arranged substantially crosswise to the pieces of lumber, and are laid out manually at least in pairs, but mostly in a larger number, below each lumber package. And, when sev- eral lumber packages are stacked on each other, e.g. in a lumber yard, string ers are used between the lumber packages to separate the lumber packages from each other. ln some applications, several lumber packages separated by stringers are handled by a forklift or the like and are fed e.g. into a so-called lumber breakdown hoist. ln such a lumber breakdown hoist each layer comprising of pieces of lumber is gradually removed from top of a lumber package by lifting and tilting the lumber package and having a top layer of pieces of lumber slide off the remainder of the lumber package and into a following apparatus, such as a planer.

Obiect of the Present lnvention Just as the layers of pieces of lumber slide off into a following appa- ratus, layers of s|ats and stringers tend to do so as well. This is no problem when it comes to the thin s|ats, as they easily can be sorted out through grat- ings in said following apparatus. This is, however, not possible with the thicker stringers, which is why they tend to cause disturbances or even stops in said following machinery. Hence, the stringers must be removed before they enter said following apparatus.

One way to remove the stringers is of course to remove them manu- ally, which less convenient out of many reasons. Another way would be to pick the individual stringers by means of a robot or the like after having lo- cated them by optical means. However, individual picking takes time and opti- cal means tend to quickly get disturb in rough and dusty environments, such as sawmills.

Against that background it is an object of the present invention to pro- vide an improved means for gripping stringers on top of lumber packages in the wood industry.

Brief Summary of the Present lnvention According to the present invention the above object is achieved by means of a gripping device according to the preamble, said gripping device comprising at least one gripper with a number of spaced apart dowels, which protrude in a downward direction but, in contact with a stringer, are able to in- dividually retract upward, wherein said at least one gripper is configured to horizontally alter spacings between at least some of its dowels, thus that said at least one gripper is enabled to grip a stringer between protruding dowels approaching each other in a horizontal direction.

Thanks to the retractable dowels, there is no need for the gripping de- vice according to the present invention to exactly locate every single stringer in order to be able to pick it and lift it off a lumber package. lnstead, if sized appropriately, a single gripper with a plurality of retractable dowels can cover an entire lumber package and pick all stringers on top of it at one time without any need of relocation of the gripper. Hence, the gripping device according to the present invention can provide a solution which works faster and more reli- able than other potential automated gripping devices.

Preferably, said at least one gripper is configured to horizontally alter spacings between some of its dowels by a linear or rotary displacement of a first gripper part in relation to a second gripper part. Such a solution is easy to accomplish and can for instance comprise a slider or a rotor with a protruding dowel that pushes a stringer against a protruding stationary dowel on the sec- ond gripper part.

At least one of said gripper parts of the gripping device according to the present invention can be displaceable by means of a pneumatic, hydrau- lic, or electric means. lrrespective of the displacement means chosen, a per- son ski||ed in the art can easily devise an easy way to provide the required lin- ear or rotational movement.

Preferably, at least one of said gripper parts is displaceable against a mechanic or pneumatic spring force. Such an extra displacement possibility is very useful when it comes to gripping several stringers at one time, especially if their dimensions differ, since a spring can compensate for deviations.

According to a preferred embodiment the first gripper part comprises a first horizontal bar, which is arranged to be substantially in parallel with a lon- gitudinal lumber package direction and comprises a row of said spaced apart dowels along the first bar. A bar solution is easy to accomplish and to control and fits the shape of lumber packages perfectly.

Further, according to the preferred embodiment the second gripper part comprises a second horizontal bar, which is arranged substantially in parallel with said first horizontal bar and comprises a row of said spaced apart dowels along the second bar, wherein said first bar and said second bar form a first pair of cooperating bars. Again, even this more advanced bar solution is easy to accomplish and to control and fits the shape of lumber packages perfectly.

Further, according to another embodiment the second bar of said first pair of bars can be subdivided into a plurality of separate bar pieces, which al- ternately are placed on either side of said first bar and are displaceable against spring forces in a direction opposite to the one in which dowels ap- proach each other. An advantage of this solution is that it renders it possible to safely grip especially a plurality of stringers at one time, since each sepa- rate bar piece potentially needs to contribute to gripping just one stringer at a time.

Preferably, two pairs of cooperating bars are arranged along each other in spaced apart parallel rows. Such a pair solution brings about the ad- vantage that gripped stringers cannot rotate horizontally in any larger extend, whereby safety and reliability is improved.

Preferably, the dowels are forced to protrude from the bars by a me- chanic or pneumatic spring means. Although gravity can suffice to make the dowels protrude in a downward direction, given the environment at hand in for instance a sawmill, a mechanic or pneumatic spring means is clearly benefi- cial to ensure proper operation.

Brief Description of the Drawinqs ln the drawings a preferred embodiment of the gripping device accord- ing to the present invention is shown schematically in perspective views, wherein: Fig. 1 shows a forklift on its way to pick up a lumber package with a couple of stringers on top; Fig. 2 shows the forklift on its way to unload the picked-up lumber package on an input conveyor of a lumber breakdown hoist; Fig. 3 shows that the input conveyor has fed the lumber package onto a lift of the lumber breakdown hoist and underneath a gripping device accord- ing to the present invention; Fig. 4 shows parts of the gripping device and of the lumber package with stringers on top; Fig. 5 shows how the parts shown of the gripping device interact with the stringers while said parts are lowered; Fig. 6 shows how the lowered parts of the gripping device act to squeeze the stringers by horizontal displacement; Fig. 7 shows how the squeezed stringers are lifted off the lumber pack- age by means of the gripping device; and Fig. 8 shows how the stringers are released on a discard conveyor and the lumber package, freed of stringers, is tilted into the lumber breakdown hoist.

Description of a Preferred Embodiment ln the drawings Fig. 1 shows a forklift 1 which picks up a lumber pack- age 2 resting on another lumber package 3 in a lumber yard. Each lumber package 2, 3 comprises of a plurality of lumber pieces 4, which form layers 5 separated by thin horizontal slats 6 which extend substantially perpendicular to the lumber packages 2, 3 and the lumber pieces 4 and are illustrated for in- stance in Fig. 4.

The lumber packages 2, 3 themselves are separated by means of hori- zontal stringers 7, which also extend substantially perpendicular to the lumber packages 2, 3 and the lumber pieces 4. The stringers 7 are thicker than the slats 6 to provide easy access for forks 8 of the forklift 1.

When, in a step previous to the one illustrated in Fig. 1, a lumber pack- age (not shown) that was resting on the top lumber package 2 is removed, the stringers 7 that separated the removed lumber package from the top lum- ber package 2 do remain in place, just as shown in Fig. 1. Hence, when the top lumber package 2 is picked up and moved away by the forklift 1, the stringers 7 on top of the lumber package 2 come along. This is illustrated in Fig. 2, where the forklift 1 delivers the lumber package 2 with stringers 7 on top to an inlet conveyor 11 of a lumber breakdown hoist 10.

A lumber breakdown hoist 10 generally serves to gradually remove lay- ers 5 of lumber pieces 4 from top of a lumber package 2 by lifting and tilting the lumber package thus that a top layer 5 of pieces of lumber 4 slides off the remainder of the lumber package 2 and into a following apparatus, such as a planer (not shown). For this purpose, the inlet conveyor 11 of the lumber breakdown hoist 10 moves, as illustrated in Fig. 3, the lumber package 2 onto a lifting platform 12 of the lumber breakdown hoist 10.

As can be seen, the lifting platform 12 is bridged by a portal 13, which extends sideways over an output conveyor 14 of the lumber breakdown hoist 10. The output conveyor 13 leads to a recycling bin 15, which serves to col- lect stringers 7 removed from top of the lumber package 2.

The removal of the stringers 7 is important, because stringers 7 fed into said following machinery are likely to cause severe production disturb- ances. Of course, the removal of the stringers could be performed manually.

That would, however, be time consuming and thus not very effective. There- fore, a gripping device, generally depicted 20, according to the present inven- tion comes into play.

The gripping device 20 is suspended on said portal 13 by means of a carriage 21 that enables the gripping device 20 to move sideways from the lifting platform 12 to the output conveyor 14 and back again. Further, the car- riage 21 enables the gripping device to move down and up again by means of pneumatic, hydraulic, or electric means (not shown), thus that it can be low- ered onto stringers 7 resting on a lumber package 2 on the lifting platform 12 and lifted after having gripped these stringers 7.

The main features of the gripping device 20 are illustrated in greater detail in Figs. 4 to 6 and are described in the following while interacting with stringers 7 in order to grip these. ln Figs. 4 to 6 two layers 5 on top of a lumber package 2 are shown. These layers 5 are, as indicated before, separated by thin slats 6, which ex- tend substantially transversely to the layers 5 and the lumber pieces 4 they comprise of. On top of the uppermost layer 5 four stringers 7 rest. They ex- tend substantially transversely to the to the layer 5 but can, as shown, be placed in a somewhat erratic way with different spacings in between.

To grip and remove the stringers 7 the gripping device 20 according to the preferred embodiment comprises two parallel grippers 22, each compris- ing a first gripper part 23 and a second gripper part 24.

The first of these gripper parts 23 comprises a first horizontal bar 25, which is arranged substantially in parallel with the lumber pieces 4, and the second of these gripper parts 24 comprises a second horizontal bar 26, which is arranged close to and in parallel with said first bar 24. The bars 25, 26 are displaceable in relation to each other in their longitudinal direction (c.f. arrows in Fig. 6) by means of pneumatic, hydraulic, or electric means (not shown).

Each of the two bars 25, 26 comprises a number of vertical bores 27, which are arranged along the bars 25, 26. The bores 27 are stepped and comprise a narrow through hole 28 at the bottom and a wider circular cham- ber 29 on top. ln the through hole 28 a stem 31 of a plunger-shaped dowel 30 is seated in a sliding way thus that the stem 31 can easily be moved in and out of the through hole 28.

On top the dowel 30 is provided with a circular disk 32, that fits the cir- cular chamber 29 of a bore 27 in an easy going way. On top of the circular disk 32 a he|ica| spring 33 is arranged vertically, which is confined into the cir- cular chamber 29 by a cap 34, thus that the stem 31 of the dowel 30 is biased and pushed out of the narrow through hole 28 on the bottom of a bar 25, 26.

The way in which the thus described dowel arrangement works is now described in detail with reference being had to Figs. 5 and 6 and especially the detail views shown in these.

First, as shown in the detail view to the left in Fig. 5, a gripper 22 is lowered onto a stinger 7 in a random way, which means it does not have to be centered in any way in relation to the stringer 7. Then, as shown in the de- tail view to the right in Fig. 5, in contact with the stringer 7, some of the dow- els 30 along the adjacent bars 25, 26 are pushed upward into the bars 25, 26, while the remaining dowels 30 are not affected by the stringer 7 and remain protruding.

Now, as shown in the detail view in Fig. 6, at least one of the bars 25, 26 is moved in its longitudinal direction in relation to the other bar, whereby downwardly protruding dowels 30 of both bars 25, 26 come into contact with sides of the slat 7 and squeeze the slat 7 in between.

The next step performed by the gripping device 20 according to the present invention is illustrated in Fig. 7 and comprises of lifting slats 7 squeezed in the way described off the lumber package 2 on the lifting plat- form 12 of the lumber breakdown hoist 10.

Then, in a final step the stringers 7 are released on the output con- veyor 14 of the lumber breakdown hoist 10 and the lifting platform 12 of lum- ber breakdown hoist 10 is tilted and lifted to gradually release layers 5 of lum- ber pieces 4 into said following machinery.

Claims

1. A gripping device (20) for the wood industry, where lumber packages (2, 3) with crosswise arranged stringers (7) on top occur, said gripping device (20) comprising at least one gripper (22) configured to be lowered onto a lumber package (2, 3) and into contact with a stringer (7) on top thereof and to be lifted off said lumber package (2, 3) after having gripped said stringer (7), c h a r a c t e r i z e d in that at least one gripper (22) comprises a number of spaced apart dowels (30), which protrude in a downward direction but, in contact with a stringer (7), are able to individually retract upward, wherein said at least one gripper (22) is configured to horizontally alter spacings between at least some of its dowels (30), thus that said at least one gripper (22) is enabled to grip a stringer (7) between protruding dowels (30) approaching each other in a horizontal direction.

2. The gripping device (20) according to claim 1, wherein said at least one gripper (22) is configured to horizontally alter spacings between some of its dowels (30) by a linear or rotary displacement of a first gripper part (23) in re- lation to a second gripper part (24).

3. The gripping device (20) according to claim 2, wherein at least one of said gripper parts (23, 24) is displaceable by means of a pneumatic, hydraulic, or electric means.

4. The gripping device (20) according to claim 2 or 3, wherein at least one of said gripper parts (23, 24) is displaceable against a mechanic or pneumatic spring force.

5. The gripping device (20) according to any of claims 2 to 4, wherein said first gripper part (23) comprises a first horizontal bar (25), which is arranged to be substantially in parallel with a longitudinal lumber package direction and comprises a row of said spaced apart dowels (30) along the first bar (25).

6. The gripping device (20) according to claim 5, wherein said second gripper part (24) comprises a second horizontal bar (26), which is arranged substan- tially in parallel with said first horizontal bar (25) and comprises a row of said spaced apart doweis (30) along the second bar (26), wherein said first bar (25) and said second bar (26) form a first pair of cooperating bars.

7. The gripping device (20) according to claim 6, wherein said second bar (26) of said first pair of bars (25, 26) is subdivided into a plurality of separate bar pieces, which alternately are placed on either side of said first bar (25) and are displaceable against spring forces in a direction opposite to the one in which doweis (30) approach each other.

8. The gripping device (20) according to claim 6 or 7, wherein two pairs of co- operating bars (25, 26) are arranged along each other in spaced apart parallel rows.

9. The gripping device (20) according to any previous claim, wherein said doweis (30) are forced to protrude from the bars by a mechanic or pneumatic spring means (33).