In traditional techniques for cutting to size a stack of veneer layers, use is made of a cutting machine comprising a cutting knife (knives), a pres¬ sure beam, a worktable, parallel stops and angular stops. For performing the cutting operation, one long side of the stack of veneer layers is first cut clean. Then, the desired size is set by means of a parallel stop against which the clean-cut side of the stack is maintained while the opposite side of the stack is cut clean. For longitudinal adjustment, the stack of parallel-cut veneer layers is placed against an angular stop where one short side is first cut clean, after which the clean-cut short side of the stack is placed against a longitudinal stop as at the same time the initially cut long side is maintained against the angular stop, whereupon the fourth short side is cut clean.

This technique means that the stack of veneer layers must be moved many times. Further, when using angular stops, parallel stops and longitudinal stops, it is very difficult to manually ascertain that all veneer layers in the stack are actually maintained against the respective stop. In actual practice, this means that a substantial part of the layers will ex- hibit relatively large dimensional variations.

The object of the invention is to overcome this drawback. According to the invention, this object is achieved in that use is made of a cutting device comprising four separate cutting members two of which are moved through the stack from one flat side there¬ of for producing two opposed edge surfaces on the sheets and the remaining two cutting members of which are moved through the stack from the opposite flat

side thereof for producing the other two opposed edge surfaces on the sheets.

The essential difference between traditional cutting techniques and the invention is that the lat- ter makes it possible to work (cut) the veneer layers in the stack on all sides without moving the veneer layers out of their position in relation to the cutting knives.

This ensures angular accuracy and reduced dimen- sional tolerances.

The invention will now be described in greater detail hereinbelow with reference to the accompanying drawings in which Fig. 1 (perspective view). Fig. 2 (part sectional side view), and Fig. 3 (end view) illustrate parts of a machine for carrying out the method according to the invention.

The machine comprises four cutting knives which are arranged in pairs B, B ¹ and C, C, a specially designed worktable E, and a pressure beam D for holding down and compressing the stack of layers, e.g. veneer layers. The two knives B, B', which are here parallel, are rigidly interconnected with a mutual spacing which corresponds to the desired width of the layers to be manufactured and which is slightly greater than the width of the pressure beam D, and are mounted on a frame (not shown) so as to be movable above the table E towards and away from it. The two knives C, C, which are here parallel and the mutual spacing of which corresponds to the length of the layers to be manufactured, are also mounted on a frame and adapted to move simultaneously underneath the table and through slots F provided therein, in a vertical plane contain¬ ing the end surfaces of the knives B, B' when these knives are in a position in which they have cut through the stack. The knives B, B' will occupy this posi¬ tion after a pattern of motion which in a downward stroke contains a first vertical phase which, when

the knives B, B' have encountered the layers, is fol¬ lowed by an oblique phase of movement through the layers. This pattern of motion is known per se, e.g. from U.S. 3,174,375, and is here achieved by pendulum suspension of the knives B. For the strokes of the knives B, B ¹ and C, C, respectively, use may be made of hydraulic or pneumatic means. G designates a hydraulic cylinder for the knife C.

The method of the invention is carried out in the following manner.

A stack A of veneer layers with a length and width oversize (in relation to the spacing between the knives B, B' and C, C*, respectively, are placed in the machine on the worktable E, such that the di- rection of the fibres of the layers coincides with the longitudinal direction of the knives B, B' . The veneer layers are then compressed by means of the pressure beam D and any unevenesses in the layers are leveled out. The two cuttings knives B, B' are caused to make a downward-forward movement or stroke so as to cut through the veneer layers, the worktable E serving as abutment. The two cutting knives C, C, which are disposed underneath the worktable transverse¬ ly of the fibre direction, are thereafter caused to execute a straight upward movement- or stroke so as to cut through the veneer layers, the pressure beam D then serving as abutment. These two cutting operations are performed without lifting the pressure beam D.

The veneer layers are thus clamped in relation to the cutting knives B, B" and C, C during the entire working operation, thus ensuring high angular and dimen¬ sional accuracy on the veneer layers cut to size.

It will be appreciated that the knives C, C* can be curved or otherwise profiled. Instead of knives, saws can be used as cutting members. The knives B, B' and C, C, respectively, need not necessarily be con¬ nected to each other for simultaneous movement.