FI63730B - SUGLYFTANORDNING FOER ARK - Google Patents

Description

63730

Arkkien imunostolaite - Suglyftanordning för ark

The invention relates to a sheet suction lifter, by means of which, for example, stacked sheets can be lifted one by one from the sheet stack and transferred to the next processing object. Such sheet lifting devices are used in particular in plywood production for lifting and moving veneer sheets, and suction lifting devices are known per se for this purpose.

Known suction lifting devices usually consist of a central suction pipe, in which devices are usually placed which provide the suction required for lifting, such as a fan. This central tube can be raised and lowered and the actual suction gripping members are located at its lower end. These suction gripping elements are known to be either open-bottomed boxes extending from the lower end of the central tube in the horizontal plane or suction cups arranged horizontally in the tube or tubes projecting from the suction tube. In a box-like suction member solution, the edges of the box are usually made flexible so that the box can be lowered as tightly as possible over an uneven lifting object, such as a stack of veneer sheets. In the suction cup solution, the suction cups are made movable relative to the suction tube fork so that they can be lowered uniformly on an uneven surface, i.e. the suction cups can be lowered to different heights. However, especially the wood veneers used for plywood production, when stacked on top of each other, form a rather convex pile in the middle area, the shape of which is difficult for the suction gripping members of the lifting device to adapt to. Another inconvenience in handling plywood veneers is that the sheets will hardly ever be stacked on top of each other 30 so that each sheet is stacked exactly on top of the previous sheet, but there is a lateral position variation in the stack between the different sheets. This often results in the gripping member of the lifting device gripping not only the uppermost sheet to be lifted, but also the edge of the next sheet, 35, projecting from the stack. This results in a partial rise of the lower side of the sheet 2 63730 from the stack, which may mix the stack badly, or the sheet may break due to untimely and incorrect lifting · It is also possible that the lower sheet 5 rises completely from the stack with the upper sheet and follows overhead sheet, possibly hanging and interfering with the next step in the process.

Such malfunctions have been substantially eliminated by the suction lift device according to the invention, the features of which appear from the appended claims and which are clarified in the accompanying drawing.

Figure 1 shows a schematic general structure of a suction lifter according to the invention seen from the side.

Figure 2 shows a section of the device from A-A in Figure 15 1, and Figure 3 shows an illustrated operation of the device.

Figure 1 shows a conventional basic structure of a veneer sheet suction lifter, comprising a central suction pipe 3 to which the suction side 20 of the fan generated by the required vacuum is connected or in which the fan 4 itself is located. The central suction pipe with its lifting members can be raised and lowered. To lift the uppermost veneer sheet 5 from the veneer sheet stack, the central suction tube and the lifting members connected thereto are pressed onto the veneer sheet, whereby the sheet is absorbed onto the lower surface of the lifting member. According to the invention, the lifting member is made of a substantially horizontal trough-shaped suction duct member 1 projecting from the central suction pipe in opposite directions, which is open on its underside. In this case, this trough-shaped duct member 1 together with the uppermost veneer sheet forms a flow channel 2 for the intake air. According to the invention, the lifting member is shaped in such a way that the lowering lifting member first contacts the veneer sheet to be lifted at its central part. In this case, the veneer sheet closes the underside of the central area of the lifting member and forms an initial part for the flow channel 2. The flow to the channel creates a pressure difference between the upper and lower veneer sheet points at the channel, which is due to the air velocity Under these conditions, the difference between the static pressure of the channel and the external static pressure of 2 Δρ ^ V V = flow rate in the channel is obtained from Bernoulli's known equation.

The resulting pressure difference thus tends to lift the uppermost veneer sheet 5 towards the lifting member, whereby the sheet rises, respectively, closes the underside of the trough-like lifting member from the rising point, and the contact point advances undulating from the center of the lifting member towards the sheet edge. By shaping the trough-like lifting member so that its flow cross-section decreases from the central region to the end, the air flow rate in the resulting duct 2 remains at least the same as in the central region, eliminating the effect of possible air leaks between the duct bottom and the veneer.

By making the lower edge of the lifting member slightly away from the stack 15 towards its head, the lifted veneer sheet can be raised gradually further away from the lower sheet, so that when entering the edge area the lifted sheet must be raised far enough from the lower sheet so that the lifting effect of outside the edge and thus the sheet stays firmly in place and does not seek to follow the sheet to be removed. In this way, the operation of the device becomes uninterrupted.

When using the suction lifting device according to the invention, it has further been found that the actual lifting step, i.e. the lifting of the lifting member, can be started with a substantially higher initial acceleration than in known devices. This is because the edge areas of the sheet to be removed are raised, so that the suction effect of the sheet on the underlying sheet 30 is substantially less than if the sheets were tightly overlapped in the initial stage of lifting.