The present invention relates to an arrangement for lifting layers of timber from timber packs.

It occurs in a number of operations performed in sawmills and other timber-handling plants that packs of timber pieces arrive at an intake at which the individual timber pieces shall be mutually separated for later treatment, one at a time. The timber pack comprises a number of layers of timber pieces with the layers either lying directly one upon the other or being separated by means of battens or like spacers. The intake to a trimming mill, to a batten-removing mill and to planing mills are examples of such intakes.

A typical method of drawing one timber layer at a time from a timber pack involves placing the pack on a pack hoist which is inclined to the horizontal plane. The pack rests on a raisable and lowerable bottom and against beams which are slightly inclined to the horizontal plane. When the bottom of the hoist is raised to a level at which the uppermost timber layer is located above the upper edges of the beams, the uppermost timber layer will slide down from underlying layers onto a conveyor in the form of a glide path, and pass to a horizontal lateral conveyor.

The intention is to maintain the relative order and relative parallelism of the timber pieces in a timber layer as said pieces slide down on the lateral conveyor. However, it is normal for the timber pieces to lie across one another and tangle with one another, particularly in the case of leaner timber dimensions.

For this reason, there are included downstream of the lateral conveyor so-called elevators which include conveyors that are provided with dogging devices and which function to lift one

timber piece at a time from a bundle of timber pieces. In this way, there is reproduced a layer of mutually juxtaposed timber pieces which can then be separated individually.

It is also known for the timber pack to be vertical, among other things when separating the timber layers with the aid of spacer battens, and to lift the uppermost timber layer from the pack with the aid of a vacuum lift which comprises a plurality of suction cups, and to move said layer to a position above a lateral conveyor onto which the timber pieces are placed.

Modern sawmills have a high capacity. For instance, individu¬ al timber pieces are divided and transported in a trimming mill at a speed of up to about 120 timber pieces per minute.

The known vacuum lift arrangements are too slow in sawmills of this capacity. Such vacuum lifts are only able to manage about six cycles per minute, i.e. to lift six layers of timber pieces per minute. In the case of broad pieces of timber, each layer may include as few as seven pieces of timber.

If this known vacuum technique were to be applied, another problem would arise involving the recovery of the battens used between each or each alternate layer of timber in a timber pack. When practicing the known vacuum lift technique, a layer of timber pieces is lifted from a pack while battens remain on top of the layer. In addition to it being necessary for the vacuum lift arrangement to firmly suck the layer against a suction plane by virtue of its abutment with the layer between the battens, it is necessary to scrape the battens from the layer in a later stage. This removal of the battens is a troublesome task and requires supervision and manual intervention.

The present invention solves the aforesaid problems by

providing a vacuum lift arrangement which is capable of performing a larger number of cycles per minute while obviating the batten-handling problem.

The present invention thus relates to an arrangement for lifting a timber layer from a timber pack which comprises a vacuum lift device which includes a frame that carries a plurality of suction cups or suction locations forming a suction plane for suction against a layer of timber pieces, wherein the frame can be moved between a first position in which the suction plane is located on the upper side of the timber pack, and a second position in which the suction plane is located above the infeed end of a lateral conveyor, and is characterized in that the arrangement is constructed to coact with a pack hoist of the kind adapted to support a timber pack with said pack inclined to the horizontal plane, wherein the pack hoist is also constructed to hoist the timber pack, after removal of a timber layer, to a level in which the uppermost timber layer is located essentially on the same level as the removed timber layer; in that the frame is carried by a pendulum which is pivotally supported by a stand; in that the pendulum is arranged to be swung relative to the stand between the aforesaid two positions by means of a force-generating means; in that in the first position of the frame the suction plane forms an angle with the horizontal plane and is essentially parallel with an uppermost timber layer in a timber pack carried by the pack hoist; and in that in the second position of said frame the suction plane essentially coincides with the plane of the lateral conveyor.

The invention will now be described in more detail with reference to exemplifying embodiments of the invention and also with reference to the accompanying drawings, in which - Figure 1 is a side view of an inventive arrangement and shows the arrangement in a first position in a working cycle;

Figure 2 shows the arrangement in a second position; Figure 3 shows the arrangement in a third position; and Figure 4 shows the arrangement in a fourth position.

The four positions shown in respective Figures 1 to 4 are included in a full working cycle of the arrangement.

Figure 1 shows an arrangement for lifting a timber layer 1 from a timber pack 2. The arrangement includes a vacuum lift device of appropriate known kind. It includes a frame 3 which carries a plurality of suction cups 4 or suction locations forming a suction plane for firmly holding a layer of timber pieces by suction. The frame 3 is movable between a first position, in which the suction plane is located on the upper side of the timber pack, and a second position, in which the suction plane is located above the infeed end of a lateral conveyor 5.

Several designs of such vacuum lift devices are known to the art. In the case of one known design, the suction cups are comprised of a dense pattern of cells with one valve to each cell. The cells have the form of cavities punched in a soft rubber foam slab having a thickness of about 25 mm. The slab is connected to a vacuum pump which generates the requisite subpressure.

The inventive arrangement is constructed for coaction with a well-known pack hoist 6 of the kind intended to support a timber pack 2 with the pack inclined to the horizontal plane. The pack hoist is also constructed to raise the timber pack after removal of the uppermost timber layer so that the timber layer which is now uppermost is located on the same level as the removed timber layer. This well-known pack hoist is collapsed so that the bottom beams 7 of the hoist will be located on a level beneath the upper surface of a pack conveyor 8, whereafter a timber pack is conveyed in over the bottom beams and the hoist is then returned to the position

shown in Figure 1. The bottom beams then raise the pack successively.

Conventionally, the hoist works to lift the pack to a level at which the uppermost timber layer passes the upper ends of the upstanding beams 9 of the hoist, wherewith the timber layer slides from the pack obliquely down to the right in Figure 1. The pack is then hoisted up through a distance corresponding to the thickness of a timber layer and the thickness of any layer-separating battens that may be pres¬ ent.

The timber pieces lie in the timber pack with their longitu¬ dinal axes at right angles to the plane of the paper in Figure 1. On the other hand, battens, ie spacer boards, lie perpendicular to the timber pieces. As a timber layer slides from the pack, the underlying battens will also slide from the pack and fall into a batten receiver 10 from which they are transported by means of a batten conveyor 11.

The frame 3 of the inventive arrangement is carried by a pendulum 12 which is pivotally mounted on a stand 13 by means of a pivot 14. The pendulum 12 is arranged to be swung between the aforesaid two positions relative to the stand 13 by means of a force generator 15, of which positions the first position is shown in Figure 1 and the second position is shown in Figure 4. When the frame 3 is in its first position, the suction plane 4 will define an angle with the horizontal plane and is parallel with an uppermost layer of timber in a timber pack, as will be seen from Figure 1. When the frame 3 is in its second position, the suction plane will coincide essentially with the horizontal plane, as will be seen from Figure 4.

The force generator 15 has the form of a hydraulic piston- cylinder device and is suitably activated by a proportional valve. By using a hydraulic piston-cylinder device and a

known microprocessor for activating the valve, movement of the pendulum can be caused to accelerate and decelerate opti¬ mally to reduce the cycle time without the timber pieces loosening from the suction plane.

When the device by means of which the timber pieces are moved from the timber pack to the lateral conveyor merely executes a single movement, namely a pendulating movement, a much shorter cycle time is obtained than that obtained with known arrangements, which require several different movements patterns in order to achieve a transfer operation.

By pendulum is meant a device which swings between the aforesaid two positions. It is obvious that such a pendulum can be designed in different ways. For instance, the frame or the suction plane can be caused to follow a curved guide rail, wherein said movement is effected by the frame or the suction plane following the guide rail and therewith moving in a manner corresponding to the frame in the illustrated embodiment. Such a device or other devices that have the same function are included in the term "pendulum".

A working cycle commences with the pendulum in the position shown in Figure 1, whereafter the uppermost timber layer is sucked firmly to the suction plane. In the case of one embodiment, the pack hoist is lowered slightly after the timber layer has been sucked firmly against the suction plane, so as to separate the layer from the remainder of the pack and to enable the pendulum to move to the position shown in Figure 4. When the pendulum is positioned above the lateral conveyor, the subpressure is removed and the timber pieces placed on the lateral conveyor 5. The lateral conveyor 5 conveys the timber pieces to the right in Figure , to a possible downstream lateral conveyor 16.

After having removed a timber layer from the timber pack, the pack hoist lifts the timber pack to a position in which the

bottom surface of the uppermost timber layer is located adjacent to but slightly beneath the upper ends of respective upstanding beams 9. The timber layer is retained on the pack in this way. As the timber layer is sucked firmly against the suction plane, it comes closer to the frame so that its bottom surface will lie above the upper surface of the beams 9, so as to enable the layer to be transported away.

Alternatively, arms (not shown) may be placed at the upper ends of respective beams, these arms in one position project¬ ing to a level above the upper ends of the beams 9 and in another position, a collapsed position, being located beneath the upper ends of said beams. In the case of this embodiment, the timber pack is raised to a height at which the arms retain the uppermost timber layer before said layer is firmly sucked against the suction plane. When the timber layer has been sucked firmly against the suction plane, the arms are lowered and the timber pack is lowered by the hoist so as to enable the timber layer to be transported away.

In the case of a preferred embodiment, however, the frame 3 of the inventive arrangement is suspended from the pendulum 12 by means of parallel struts 17, 18 which are pivotally mounted on both the frame and the pendulum so that the frame 3 can be moved in parallelism towards and away from the pendulum between a third position, see Figure 1, furthest from the pendulum and a fourth position, see Figure 2, nearer the pendulum. In the case of this embodiment, the timber layer is thus lifted from the timber pack after having been sucked firmly against the suction plane. This obviates the need of lowering the hoist after the timber layer has been sucked firmly to the suction plane, and also obviates the need for arms which retain the uppermost timber layer. The aforesaid parallel movement can be achieved very quickly. According to this embodiment, a force generator 19 acts between the pendulum 12 and the frame 3 and functions to produce the aforesaid parallel movement.

As the layer of timber pieces is sucked firmly to the suction plane and lifted slightly, battens will slide from underlying layers and fall down into the batten receiver 10. Thus, when practicing the present invention, no battens will be present on the upper side of the layer that is lifted by the suction device. In addition, the arrangement includes a sufficiently wide gap 20, formed by a horizontal distance between the lower front edge of the pack hoist and the infeed end of said lateral conveyor 5, for battens and bolsters to pass through the gap and down into the batten receiver 10 irrespective of their positioning in relation to the timber layers. Bolsters are larger timber-pack separating battens which enable the tines of fork-lift trucks to be inserted between stacked timber packs. Battens will slide down into the batten receiv- er 10 without problem from an underlying timber layer as the uppermost layer is lifted.

The fact that the vacuum lift device can be made totally independent of the positioning of battens and like spacers between the timber layers constitutes an important advantage.

The aforesaid force generator 19 is preferably a hydraulic piston-cylinder device, see Figure 1.

According to one preferred embodiment, the frame 3 is ar¬ ranged to be located in its third position when firmly sucking a timber layer against the suction plane and when delivering a timber layer onto said lateral conveyor. The frame is located in its fourth position, see Figure 2, after the timber layer has been sucked firmly to the suction plane and approximately until the position in Figure 4 has been reached.

It will be evident that the present invention solves the problems mentioned in the introduction. The fundamental concept of the invention is to transport a timber layer from an inclined timber pack to a lateral conveyor in one single

movement, a swinging movement, and therewith achieve very rapid transport with a cycle time that enables at least ten to fifteen timber layers to be transported each minute. Furthermore, dislodgement of the layer-separating battens or like spacers is achieved in a highly advantageous manner with the aid of a sloping pack hoist. The arrangement is also completely independent of the positioning of said battens.

Although the invention has been described above with refer- ence to several exemplifying embodiments thereof, it will be obvious that the arrangement can be modified substantially without departing from the inventive concept. For instance, the frame may be seated firmly in the pendulum by means of a hydraulic piston-cylinder device at each corner of the frame, such as to move the frame towards and away from the pendulum, as an alternative to the parallel strut arrange¬ ment.

The present invention shall not therefore be considered limited to the aforedescribed and illustrated exemplifying embodiments thereof, since modifications can be made within the scope of the following Claims.