The present invention relates to a method according to the preamble of claim 1 for machining mutually joinable pieces.

According to the present method, the pieces are trans¬ ferred one by one into a machining unit in which the ends of each piece are worked for joint portions corresponding to the desired type of joining system. Subsequent to working, the pieces are transferred to a shaping unit if desired or directly to an assembly station, where they are joined to each other.

Pieces of wood, plastic or soft metal alloy composition are generally worked for joints by mechanically removing material from the pieces to be joined by means of, e.g., rotating cutters. For elongated pieces, the joint portions are formed to the ends of the pieces. To work both ends of the piece, two cutter units are required to this end, or alternatively, the piece must be rotated 180° about its center point.

In a great number of conventional constructions the cutter units are movably and transferrably mounted, whereby dimensional errors readily occur in the machining of the pieces and transfer time losses in the transfer of the cutter unit from one position to the other.

As the first step in the production of door and window jambs, batches of required numbers of suitable jamb members have conventionally been fabricated in the above- described manner by working them in different machines, after which the members have been assembled into ready jambs in assembly jigs. The conventional methods typical¬ ly require several steps of length trimming of material and cutting of blanks, and the overall automation of the

such processes has turned out to be difficult. An auto¬ mated production process to be noted as an example is the DSH 16 machining line by Maschinenfabrik Gubisch GmbH in which the workpieces travel along tracks on which they have to be reversed for working of the other end.

It is an object of. the present invention to overcome the disadvantages of prior-art technology and to achieve an entirely novel method for working elongated workpieces, said method facilitating the automation of the production process.

The method is based on the concept of transferring the workpieces through the machining unit in subsequent longitudinal and lateral movements, whereby the ends of the pieces are worked during the lateral movements in order to work the joint portions. According to this scheme, the machining unit works the leading end of a workpiece on its one side during the first pass, while the trailing end of the workpiece is worked during the second pass. The orientation of the workpieces remains unchanged during working; that is, the workpiece to be worked is not rotated, but rather, the only movements required are comprised of a lateral movement which is followed by a forward movement which is followed by a lateral movement in a direction opposite to that performed first, after which a longitudinal movement follows along the same line or a parallel line to that of the first longitudinal movemen .

More specifically, the method in accordance with the invention is principally characterized by what is stated in the characterizing part of claim 1.

The workpieces can be of any material which is suitable for working by material-removing methods and compatible with mechanical working by means of rotating or moving

cutting tools. The method is particularly suited to wood, plastic and soft metallic materials, in which joints can be fabricated by working. Wood pieces capable of being worked according to the method typically include all members that are joined mutually by means of a joining system such as a tongue-and-groove joint, finger joint or mortise-and-tenon joint, whereby the fabrication of the products involves the mutual joining of pieces for extension or angled joining of pieces for making frames. Exemplifying cases of products whose fabrication is particularly advantageous by virtue of the method can be finally listed:

- door jambs and frames

- window jambs and sashes - parquet floor components

- tongue-and-groove joinable slabs and strips

- log structures and similar prefabricated construction elements and

- tongue-and-groove joinable thermal insulation boards of plastic and mineral wool composition.

To implement the method, an apparatus is employed, called a two-way machining unit within the context of this ap¬ plication. In general, this apparatus has 2 ⁿ machining heads (n being an integer, typically 1, 2 or maximally 4) , said heads being employed to work the desired joint portions into the workpieces by, e.g., milling. The machining heads can be comprised of, e.g., rotating cutters. The apparatus has an input or feed side where the leading edge of the workpieces is worked and an exit side where the trailing edge of the workpieces is worked, and further, a transfer device capable of moving the workpieces from one cutter head to another and from the feed side to the exit side.

A workpiece entering the machining unit is first moved laterally relative to the cutter head and then further

laterally to perform the first working operation. Next, the workpiece is moved forward by at least the length of the piece so as to transfer it to the exit side of the apparatus. Finally, the workpiece is moved laterally to the opposite direction, whereby it is worked on its way at its other end (trailing edge) .

Such two-way machining units which have a single machin¬ ing head or two parallel machining heads, both ends of the workpiece are worked with the same machining head.

A machining unit with a set of dual cutter heads is used particularly when dissimilar joint portions are desired to be worked to the workpieces. In typical applications every second of the workpieces is required to have the tenon portions, while every other second of the work- pieces must then have the mortise portions. To implement this, the apparatus is designed to function so as to guide every other workpiece in the above described manner past the left-hand machining head of the machining unit and every other second workpiece past the right-hand machining head. The left-hand set of cutter heads works, e.g., a groove or mortise portion to both ends of the workpieces on the left-hand side, while the tongue-and- groove or similar overlapping joint portion is worked to both ends of the workpieces on the right-hand side by means of the right-hand set of cutter heads. The use of two identical machining heads can speed the production throughput and extend the maintenance interval of said machining heads.

The number of the machining heads can be increased to four in a symmetrical configuration, whereby the leading end and the trailing end of the workpiece is worked by a different cutter as the workpiece is transferred on, e.g., the left-hand route past a four-spindle cutter set. If transferred along the right-hand route, the workpiece can equally be worked for a shape of the leading edge

different from that of the trailing edge if so desired. When a set of identical machining heads or groups of two identical heads are used, such a configuration can be employed to extend the maintenance intervals and to increase the production throughput. In a simplified alternative of this embodiment, the machining unit is provided with two successive machining heads which make it possible to work different or identical joint portions to the workpiece ends.

As mentioned above, the method makes it possible to fabricate stock of continuous length from lumber of con¬ ventional lengths by working the lumber ends for joint portion necessary for, e.g., finger joints. The working operation is performed in a two-way machining unit in the same manner as above, however, with the exception that all lumber pieces are worked for both the female and male joint portions. Thus, the one end of each piece is worked for the female joint portion and the other end for the male joint portion, thus permitting the gluing of the pieces together after the working operation in the "head- to-tail" fashion. Both joint portions of the extension joint can be worked in a machining unit equipped with four machining heads, or alternatively, using its si pli- fied version having only two successive machining heads . It is, however, also possible to produce the extension joint in a two-way machining unit having only one machining head so that the machining unit is provided with a phase-shift working facility, which alternately produces the female portion and the corresponding male portion of the finger joint to the workpiece ends by said phasing arrangement, advantageously by altering the elevation of the support table for half finger spacing or similar repeating element of the joint.

In an advantageous embodiment of the invention, the machining unit is used so that during the upward travel

of the piece (outwardly to the side) at the feed end of the machining unit, the preceding piece is moved down¬ wards (inwardly to the side) at the exit side, thus avoiding any discontinuity in the process-like working sequence except for a small temporal phase shift. In this embodiment the machining head can be utilized so as to work productively almost continuously.

All lateral movements of the workpieces in the machining unit are implemented with the help of a transfer car¬ riage. The pieces are clamped to the carriage, whereby the necessary clamping force is actuated by means of, e.g., a pneumatic cylinder. The clamp and the carriage are located on a common frame so as to avoid transmitting the actuating force of the transfer movement as a com- pressive force, but rather, via the rigidity of the transferrable frame. The machining unit has two transfer carriages, one on each side of the support table.

In the machining unit the pieces can be moved vertically relative to the working elevation by controlling the elevation of the machining unit's support table up and down as described above for the fabrication of the extension joint. The machining heads by themselves are mounted on shafts whose orientation can be altered as necessary during the working of the pieces.

When the two-way machining unit is used according to the invention in, e.g., the manufacture of window frame/sash members, it is advantageous but not mandatory, prior to the shaping or other working of these elongated members, to produce continuous stock with extension joints from piecewise material such as lumber or plastic extrusions of limited length. For this purpose, the blanks entering the machining unit are united into continuous stock by a glued extension joint. The extension joint can be fabricated and worked in the two-way machining unit,

whose construction is described above. Prior to the actual working, the stock is cut into pieces of predetermined length.

According to the invention, significant benefits are attained over embodiments used in prior art. The two-way machining unit according to the invention operates in a continuous fashion working the pieces on both the forward and return pass. A parallel configuration of two machin- ing heads .adapted to work compatible joint ends (e.g., female/male) , complemented with an alternating feed arrangement of the workpieces via the machining heads, the pieces with the compatible female and male ends can be worked in correct order, and the joinable pieces are produced without any other length loss except the machined length of one joint portion per one piece.

Thus, the continuous two-way working method can provide process-like production without need for intermediate storage. The knives of the machining head perform an almost continuous work operation, which vastly improves the capacity of such a working line with respect to con¬ ventional methods. Therefore, the embodiment according to the invention can work approx. 16 pieces in a minute at operating speeds of the machining head knives and trans¬ fer speeds of the workpieces comparable to those of the best equipment available on the market described above that manages only approx. 5 pieces/min.

The workpieces exit the machining unit according to the above described method in the order they are intended to be joined, which makes the automation of the joining assembly easier than in prior-art technology for automated on-line joining by, e.g., gluing.

The invention is next examined in detail with the help of the appended drawings, in which

Fig. 1 shows in a top view the diagrammatic construction of a two-head machining unit designed to operate according to the invention.

Fig. 2 shows in a top view each step of the travel of the workpieces through the machining unit illustrated in Fig. 1.

Fig. 3 shows also in a top view the construction of a four-head machining unit according to the invention.

The production of a frame, such as a window frame, is examined closer in the following exemplifying embodiment. For those versed in the art it is, however, evident that the same operations can be adapted to the working of pieces having an elongated as well as other kind of shape.

The lengths of workpieces to be machined are computed in the control unit of the production line from the dimen¬ sions H x W of the frame to be manufactured. An elongated blank made from, e.g., piecewise stock by extension joints is trimmed by a cross-cut saw into piecewise blanks 1 of the desired lengths H and W, which are fed alternating (in the order H - W - H - W - etc.) to a conveyor 2. The conveyor can be of any conventional type such as a band or roller conveyor, or any other kind of suitable transfer device such as a pneumatic transfer actuator. The blank 1 arrives from the cross-cut saw to the feed side of the machining station 3, where its longitudinal movement is stopped by a mechanical fence 4 in order to bring the workpiece end to a correct position for working. At this stage, the blank 1 has been trans¬ ferred onto a movable carriage 5, on which it is clamped in place by means of, e.g., a pneumatic cylinder. Under the compression of the clamp and supported by the carriage 5, every second blank is transferred to the left and every other second to the right. As is evident from Fig. 1, the carriage has two clamping stations 6, 7, of

which one station 6 is intended for transfer to the left and the other station 7 for transfer to the right .

The machining station 3 has two cutter heads 8, 9 mounted on rotatable spindles, whereby the spindles are mutually spaced to both sides of the extended line of longitudinal axis of the conveyor of the blank 1. The planes of the cutter knives are parallel with the lateral movement of the blanks 1 and the cutter knives are aligned level with the blanks resting on the carriage. When necessary, the distance of the cutter heads 8, 9 to the machining table 21 can be altered by adjusting the machining table height, thus making it possible to work blanks of various thicknesses. The function of the machining unit here is to work the female and male joint portions for the assem¬ bly, respectively, to the ends of the blanks 1, whereby the first cutter head 8 is used for cutting the female joint portion to the H-blank, while the second cutter head 9 produces the male joint portion to the W-blank (or vice versa) . The cutter knives and their tips can be of any conventional type. A movable fence 10 of the feed side is controlled against the ends of the blanks 1 during their lateral movement, said fence being adapted to move between the feed-side cutter heads 8, 9 of the machining station 3. The fence 10 has slots for the cutter knives 8, 9, said slots being marked with a dash line on the diagram of Fig. 1. The trajectory of the fence 10 is symmetrical with respect to the extended line of the longitudinal axis of the above-mentioned conveyor. The other extreme position of the fence is evident from the diagram, which shows that the position of the fence end in the lateral direction of the machining unit is located at least approximately level with the center point of the cutter head 8. The purpose of the fence 10 is to support the end of the workpiece 1 during working, thus achieving an improved accuracy of the cutting result .

When the blanks pass by the cutter heads 8, 9 during their lateral movement, the indentations necessary for joining are worked to the ends of the blanks 1.

The lateral movement of the blanks 1 is further extended for some length past the cutter heads until the blanks meet the controllable fences 11, 12 of the machining table, each end of the table having one fence. The lateral movement of the carriage 5 is stopped at these fences, after which the blanks 1 are released from the carriage and brought to a longitudinal movement directed along the side of the fences 11, 12 crosswise over the table of the machining station 3. The longitudinal movement is continued until the rear end, or trailing end, of the blanks 1 is located at the exit side of the machining station 3 in the same position and at the same distance from the cutter heads 8, 9 as the front ends of the blanks were at the feed side of the machining station. Next, the blanks 1 are brought to a new lateral movement supported by the exit-side carriage 15, said movement being in an opposite direction relative to that of the first lateral movement. The carriage has clamping means 16, 17 equivalent to those of the feed-side carriage. When passing by the cutter heads 8, 9 for the second time, the rear end of the blank is worked for slotted joint portions identical to the that worked as the joint portion to the front end of the blank. During the working, the trailing end of the blank is supported by fences 13, 14 of the exit side of the machining station, said fences being movable in the longitudinal direction of the machining station between the work¬ station ends and a vertical plane coincident with the center point of the cutter head 8 and 9, respectively for each fence. After working, the blanks are released from the carriage 5 and transferred onto an exit conveyor 20, which is located on the same longitudinal axis with the feed conveyor 2.

As mentioned above, the elevation of the machining table can be altered during the working operation if necessary. For this purpose, the apparatus is provided with support and guide rods 18, 19 beside the fences 11 and 12, said rods facilitating the vertical elevation of the machining table to accommodate workpieces of different thicknesses.

The above-described process achieves H- and W-members worked according to the method, the members having identical joint portions at their ends. Fig. 2 shows in detail the manner in which the blanks fed in a queue are transferred through the machining unit 3.

The blanks A...J are received one by one from a cross-cut saw to the feed side of the machining station 3, where they are clamped in place and transferred under the clamping force every second of them (blanks B, D, F, H and J) to the left and every other second (blanks A, C, E, G and I) to the right. The female portion of the joint is worked against the feed-side fence. After the first blank A has passed the machining head, the next blank B is fed into the machining station to the waiting posi¬ tion. The blank A is transferred forward by a longitu¬ dinal movement simultaneously as the blank B is being worked against the feed-side fence for the male portion of the joint. The third blank C is already at this stage transferred to the waiting position. The blank C is controlled to the right simultaneously while the blank A is controlled to the left on the exit side and the blank B is controlled forward. The blanks A and C pass by the same machining head simultaneously but on different sides, so an identical joint portion is worked on both of them, one to the front end of the blank C and one to the rear end of the blank A. During this working operation, the next blank D is transferred to the machining station in the waiting position. Finally, the blank A is removed

from the station just prior to the working of the rear end of the blank B and the front end of the blank D.

Fig. 2 shows a few typical operations of the method intended for speeding the handling the pieces. For instance, the next piece in sequence is brought to the waiting position already at the stage the preceding piece is being worked in the first pass, and two blanks (one for the front end and one for the rear end) are advanta- geously worked simultaneously by the same cutter head.

In the embodiment illustrated in Fig. 2 the blanks are worked one by one, thus retaining their mutual order during the eed, working and exit operations. As men- tioned above, the present method differs in this respect from conventional processes in which the required members are produced in batches of desired size and the members worked in different apparatuses are then assembled into ready frames of windows or doors, for instance, at a separate assembly site. The method according to the present method makes it possible to produce the required succession of short and long members in a desired order.

Fig. 3 shows a machining station comprised of four machining heads. The construction of the apparatus corresponds to that shown in Fig. 1 for all other parts except that the machining heads 31, 32, 33 and 34 are placed to the corners of a rectangle so as to be located symmetrically with respect to the extension of the longitudinal axis of the blank conveyor 35. The cutter heads can all be identical, or alternatively identical in groups of two, whereby the greatest benefit of this arrangement is in extending the intervals between routine maintenance and increasing the production capacity. However, all cutter heads can be different or pairwise different, whereby each member can be worked for a different joint portion at its front and rear ends, and

furthermore, pieces passing via the left-hand route can have joint portions different from those worked on the pieces passing via the right-hand route.

The embodiments of the invention can be varied in their details within the scope of the enclosed claims from those of the exemplifying embodiments described above. For instance, the invention makes it possible to produce pieces having different joint portions at their ends by, e.g., altering the elevation of the machining station's support table along the support and guide rods 18, 19 after the first working pass by an offset of approxi¬ mately half finger spacing of the joint. Alternatively, the cutter head can be moved up or down. For a finger joint, the elevation control is easy to implement for the support table. By contrast, when the working of a frame or sash joint must be performed, the cutter head up/down control is more advantageous, since the elevation differences required are too large for the height control of a conventional support table.

To conclude the description, it can be noted that in an advantageous embodiment of the invention the transfer carriage is formed by a frame having linear guides at its bottom rail and clamping devices (with clamping pads) at its upper rail. The stiles at the ends of the frame structure are outdistanced so as to remain exterior to the longitudinal travel of the workpiece along its path at both sides of the apparatus. At the release of the clamps from the workpiece after the completion of the lateral movement so as to allow the start of the longitudinal movement, this carriage construction makes it possible to start a new lateral/return movement without waiting for the completion of the longitudinal movement. In Fig. 1, the left-side conveyor referenced by numeral 22 and the right-side conveyor referenced by numeral 23, respectively, are such conveyors that can

perform the longitudinal transfer of the workpieces past the machining heads.