METHOD FOR CENTERING VENEER SHEETS IN A PILE

Abstract

A method for centering the settling of veneers on top of each other in a veneer pile, the veneers being cut from a log by slicing and dried. A substantially horizontal pile is, freely supported and having in the lateral direction extreme limits with clearance, subjected to a horizontal swinging motion whereby the extreme limits are reduced during the swinging motion.

Description

The object of the present invention is a method for centering sheet-like veneers in a pile formed after drying, said veneers being separated from a log by slicing.

Sliced veneers are separated from a log as lengthwise plane-sliced layers. Slicing permits acquiring very thin veneer used as coating material in different products leaving the wood pattern visible. For maintaining the uniformity of the wood pattern, the veneers cut sequentially from a log are usually treated as batches per log through the drying and stacked to appropriate piles after the drying. There are usually a constant number of veneers in the piles.

In order to facilitate the further treatment of the veneer piles and to decrease handling damages, it is necessary to pile the veneers as well as possible concerning their position with respect to each other. An apparatus, the operation of which is based on positioning during the piling step, has been used when trying to reach this target. Positioning presents its own difficulties, particularly in guiding thin veneers one by one to a correct position during high-speed production.

In the method according to the present invention, an operation principle is used where veneers can be set substantially centered in a pile, i.e. in a pile narrowing evenly at the opposite sides thereof At the same time the pile will be centered with respect to the apparatus handling it, thus facilitating the positioning of the centered pile during the further treatment.

The substantial characteristic features of the present invention are are apparent from the enclosed claim 1.

The invention will be described in more detail with reference to the enclosed drawing illustrating an apparatus applicable in implementing the method of the present invention.

FIG. 1 shows a general view of the apparatus,

FIG. 2 shows an illustrative drawing of the apparatus' operation at the initial state of the operation cycle corresponding to FIG. 1,

FIG. 3, shows an illustrative drawing of the progression of the apparatus' operation,

FIG. 4 shows an illustrative drawing of further progression of the apparatus' operation, and

FIG. 5 shows an illustrative drawing of the apparatus' operation at the finishing step of the operation cycle.

In an illustrative situation in accordance with FIG. 1, a pile 1 formed from veneers sliced sequentially from a log in a lengthwise plane is brought to the operation area of the apparatus at the beginning of the apparatus' operation cycle. In the described implementation, the veneers have been sliced from a log, dried and stacked in the slicing order, the first acceptable veneer being at the bottom. Depending on the diameter of the log, dozens of such piles will be formed. There is a predetermined number of veneer sheets in a pile, e.g. 24 pcs, depending on the application the apparatus is used to execute. One way of slicing the veneer sheets is to slice the veneer sheets in to stacks, firstly up to the mid-section of the log, and then continuing to form these stacks by turning the log after the mid-section.

The veneer pile is produced after the drying phase with a traditional piling apparatus producing a pile where the veneer sheets are located on top of each other in rather random positions with respect to each other. The pile is on a conveyor 2 which has transferred the pile to the operation area of the apparatus.

The apparatus comprises gripping arms 7, 7′ each of which is connected to actuators 3 lowering/lifting them. The range of the lowering/lifting motion of the gripping arms is dimensioned to extend from above the pile to below the pile. The apparatus further comprises actuators 6 and 6′ coupled to the gripping arms 7, 7′, said actuators enabling the gripping arms 7, 7′ on the opposite sides of the pile to operate in a transversal direction to the pile in pairs as to be pushed towards and pulled away from each other, respectively. With this motion, the gripping elements of the gripping arms 7, 7′ can be placed under the pile and respectively drawn away from below the pile.

The gripping arms 7, 7′ are articulately supported and their tilt angle can be affected by actuators 10, 10′.

Actuators of the gripping arms 7, 7′ further include devices 5 for causing a reciprocating swinging motion of arms, such as piston-cylinder devices with pneumatic or hydraulic operation.

For providing the swinging motion, a crank mechanism can also be used, either so that the motion caused by an eccentric crank is directed to the gripping arm as a direct reciprocating motion, or alternatively as an eccentric rotating motion. An advantage of the last mentioned motion alternative is that it enables to stop the motion at predetermined points of rotation, so that the pile can be positioned in the apparatus with different indentations in the grain direction of the veneers. Thus, the single veneer bundles are separated with staggered endwise relationship in the pile formed by the bundles.

The operation of the apparatus will be described with reference to drawings from 2 to 5.

FIG. 2 shows an initial state of the apparatus' operation, where the conveyor 2 has transported a pile 1 formed from dried veneer sheets stacked in the slicing order. Depending on the construction and operation of the apparatus which stacked the pile, the veneers are located in random positions with respect to each other in the veneer plane in the pile. The gripping arms 7, 7′ have been lowered by the actuators 3 so that their gripping elements are below the veneer pile. In this step, the gripping arms located at the opposite sides of the pile are controllably driven by actuators 6 and 6′ towards each other. The gripping arms 7, 7′ are mounted in an inclined position opening upwards, slightly trailing behind the slicing progression of a half-log's flank shape.

Their motion towards each other to a light contact with the sheet's edges protruding from the pile is controlled with photoelectric sensors 9, 9′ monitoring the opposite edges of the pile.

After this approaching motion, the gripping arms will be somewhat distanced from each other and the veneer pile is subjected to a transversal reciprocating shaking and swinging motion with actuators 5. The gripping arms are moved towards each other, maintaining the shaking motion and simultaneously monitoring the pressing effect subjected to the pile by the actuators 6, 6′. Thereby a situation according to FIG. 3 is produced, where the veneers on top of each other have aligned with each other. A part of the veneers in the pile are arched depending on the anticipated tilt of the arms 7, 7′. Press elements 8 are lowered on top of the pile, and the gripping angle of the arms 7, 7′ to the sides of the pile can be tightened with actuators 10, 10 for improving the shape-up of the pile (FIG. 4), after which the gripping arms 7, 7′ are distanced from each other as shown in FIG. 5.

In the exemplary implementation, it is assumed that the veneers from a half-log are stacked in the sequence of slicing. The tilting of the gripping arms 7, 7′ is meant to trail the inclination of the flank profile of the log. The stacking sequence can also be reverse, which must be taken into account when adjusting the inclination direction of the gripping arms. The trailing of the log flank profile is not, however, necessary for the operation of the apparatus. The gripping arms can also be in a vertical position, in which case the apparatus is applicable for handling of veneer piles sliced from a half-log, regardless of the stacking sequence, or for handling veneer sheet piles sliced from a whole log, depending on the application the apparatus is used to execute.

It is also possible to make the veneers set in a pile in their longitudinal direction, in other words, in the grain direction, one end being aligned, using an apparatus implementing the method of the present invention. Alignment of the log's butt end is preferred. This can be achieved by adjusting the gripping arm pair 7, 7′ supporting the butt end of the veneers to operate on a lower plane than the corresponding gripping arm pair supporting the top end of the veneers. Thereby the veneers on top of each other can slide during the initial phase of the shaking in the grain direction against a stopper mounted on the apparatus at the butt end of the veneer pile.

Claims

1. A method for centering the settling of veneer sheets on top of each other forming a pile after drying and being separated from a log by slicing, characterized in that a substantially horizontal pile, freely supported and having extreme limits with clearance in the lateral direction, is subjected to a horizontal swinging motion, and that during the swinging motion the extreme limits are reduced.

2. A method according to claim 1, characterized in that the veneer pile is subjected to the swinging motion as an eccentric rotating motion having an amplitude exceeding the clearance of the lateral extreme limits.

3. A method according to claim 1, characterized in that the veneer pile is subjected to the swinging motion as a reciprocating motion in the reduction direction of the extreme limits, having an amplitude exceeding the clearance of the lateral extreme limits.

4. A method according to claim 1, characterized in that the swinging motion is used with an amplitude of ca. 50 mm.

5. A method according to claim 1, characterized in that the swinging motion is used with a frequency of ca. 2 Hz.

6. A method according to claim 1, characterized in that the veneer pile is supported slightly inclined in the grain direction of the veneers.

7. An apparatus for implementing the method according to claim 1, characterized in that the apparatus comprises at least two gripping arm pairs (7, 7′) setting on the opposite sides of the veneer pile, that the apparatus comprises actuators (3) for controllably moving the gripping arms to directly support the veneer pile, that the apparatus comprises actuating elements (6, 6′) for moving the gripping arms at the opposite sides of the veneer pile towards each other, respectively apart from each other, and that the apparatus comprises actuating elements (5) for causing a reciprocating shaking motion of the gripping arms.

8. An apparatus according to claim 7, characterized in that the supporting planes of the gripping arms (7, 7′) are on different heights at the opposite ends of the veneer pile (1).

9. A method according to claim 2, characterized in that the swinging motion is used with an amplitude of ca. 50 mm.

10. A method according to claim 3, characterized in that the swinging motion is used with an amplitude of ca. 50 mm.

11. A method according to claim 2, characterized in that the swinging motion is used with a frequency of ca. 2 Hz.

12. A method according to claim 3, characterized in that the swinging motion is used with a frequency of ca. 2 Hz.

13. A method according to claim 4, characterized in that the swinging motion is used with a frequency of ca. 2 Hz.

14. A method according to claim 2, characterized in that the veneer pile is supported slightly inclined in the grain direction of the veneers.

15. A method according to claim 3, characterized in that the veneer pile is supported slightly inclined in the grain direction of the veneers.

16. A method according to claim 4, characterized in that the veneer pile is supported slightly inclined in the grain direction of the veneers.

17. A method according to claim 5, characterized in that the veneer pile is supported slightly inclined in the grain direction of the veneers.

18. A method according to claim 9, characterized in that the veneer pile is supported slightly inclined in the grain direction of the veneers.

19. A method according to claim 10, characterized in that the veneer pile is supported slightly inclined in the grain direction of the veneers.

20. A method according to claim 11, characterized in that the veneer pile is supported slightly inclined in the grain direction of the veneers.