A three-dimensional wire structure is for example known from EP-A-0 180 667. The structure comprises a series of plane nettings, which are spaced apart a pre-determined distance by a series of cross wires welded to the nettings. Each netting comprises at least one pair of lengthwise wires and a plurality of brace wires. The structure is used in the building industry for constructing buildings, walls, ceilings or roofs.

A method for assembling such three-dimensional structures is for example known from US-A-4,667, 707. This method comprises the following steps: (a) supplying a plurality of plane nettings to support planes of a support structure, the support planes extending substantially parallel to each other and being spaced from each other by a predetermined netting pitch distance, (b) aligning the plurality of plane nettings in such a way that the lengthwise wires are located in side planes which extend substantially perpendicularly to the support planes, (c) shifting the plane nettings by means of feeding means until welding locations on the plane nettings are located in a welding plane, the welding plane being defined by a pair of welding units for welding the cross wires to the nettings, (d) supplying a pair of cross wires from a pair of supply holders to the welding plane defined by the pair of welding units,

(e) welding the cross wires to the welding locations on the plane nettings by means of the welding units, (f) shifting the plane nettings a predetermined cross wire pitch distance by means of the feeding means until further welding locations on the plane nettings are located in the welding plane, (g) repeating steps (d) to (f) until the plurality of pairs of cross wires have been welded to the lengthwise wires of said series of nettings.

The method of US-A-4,667, 707 has the disadvantage that it is time-consuming. This is due to the fact that step (c) or (f) of shifting the plane nettings and step (d) of supplying a pair of cross wires to the welding units are conducted consecutively. As a result, a certain amount of time passes between the end of the shifting step (c) or (f) and the beginning of the welding step (e), during which time the cross wires are supplied to the welding units in step (d).

It is an aim of the present invention to provide a method for assembling three-dimensional structures which is less time- consuming.

This aim is achieved according to the invention in that the step of shifting the plane nettings and the step of supplying the pair of cross wires are conducted simultaneously. In this way, the pair of cross wires is already present in the welding units when the welding locations on the plane nettings arrive in the welding units. Consequently, step (e) of the welding of the cross wires to the plane nettings can start as soon as the plane nettings come to a stop. In this way, substantially no time passes between the end of the shifting step and the beginning of the welding step (e) and the method according to the invention requires less time for assembling the three-dimensional structures.

Preferably step (d) of supplying the cross wires to the welding units merely comprises rotating the cross wires from a supply position in the supply holders to a welding position in the welding units, the rotation being carried out in a plane which encloses an angle with the welding plane defined by the welding units. In this way, the cross wires are supplied to the welding units in a single operation, namely the rotation. Rotating the cross wires in the plane enclosing an angle with the welding plane makes it possible to supply them in a single operation, without hampering the constructional parts of

the welding units and the movement of the three-dimensional structure under construction. The supplying of cross wires in a single operation can lead to a further speeding up of the method according to the invention.

In order to enable the rotation in the plane enclosing an angle with the welding plane defined by the welding units, the supply holders and the means for supplying the cross wires from the supply holders to the welding units can be directed according to the same angle with respect to the welding plane. This has the advantage that the device for implementing the method of the invention can have a reduced width and take up less space than the prior art device, in which the supply holders and supply means extend sideways of the welding units.

A preferred embodiment of the method according to the invention further comprises the step of setting the predetermined cross wire pitch distance for each individual plane netting. In this embodiment, the feeding means for shifting the nettings are individually adjustable for each plane netting, so that the cross wire pitch distance over which the nettings are moved towards the welding units can be chosen individually for each plane netting. For example, if the cross wire pitch distance is chosen shorter for the uppermost netting than for the lowermost netting with a gradual increase in the cross wire pitch distance from top to bottom, a three-dimensional structure can be obtained which has a bent shape. So by adding this step of individually setting the predetermined cross wire pitch distance, three-dimensional structures can be assembled in a wider variety of shapes.

The variety of shapes obtainable with the method of the invention can further be enhanced by including a step of setting the predetermined netting pitch distance and/or a step of adjusting the position of the alignment means of each support holder of the support structure and the distance between the welding units to the width of the plane nettings.

The invention will be further elucidated by means of the following description and the appended figures.

Figures 1-3 respectively show a side view, a top view and a front view of a preferred embodiment of a device for implementing the method of the invention.

Figures 4 and 5 respectively show a side view and a front view of feeding means comprised in the device of figures 1-3.

Figure 6 shows a top view of a welder of one of the welding units comprised in the device of figures 1-3.

Figure 7 shows a cross-sectional view of a supply holder comprised in the device of figures 1-3.

Figures 8 and 9 show perspective views of three- dimensional structures obtainable with the device of figures 1-3.

The assembling method according to the invention is intended for the manufacture of for example, but not exclusively, three- dimensional wire structures 1 (figure 8) of the kind described in EP-A-0 180 667.

These three-dimensional structures 1 comprise a plurality of plane nettings 2 to which a plurality of pairs of cross wires 3 are welded. The plane nettings 2 comprise at least a pair of lengthwise wires 4 to which a plurality of brace wires 5 are welded. The brace wires 5 are spaced apart by a predetermined brace wire pitch distance D1, the nettings 2 by a predetermined netting pitch distance D2 and the cross wires 3 by a predetermined cross wire pitch distance D3.

Preferably, the predetermined cross wire pitch distance D3 is twice the predetermined brace wire pitch distance D1, but different values are possible.

The device for implementing the method of the invention comprises a first assembly device (not shown) for constructing the plane nettings 2 by welding the brace wires 5 to the lengthwise wires 4 and a second assembly device 10 (figures 1-3) for assembling the three-dimensional structure 1 by welding the cross wires 3 to the plane nettings 2. The device is further provided with an electronic control group (not shown) for controlling the various assembly and welding steps, a control panel (not shown), an air unit (not shown) for performing the commands of the control group and a cooling unit (not shown) for cooling welding electrodes in the first and second assembly machines.

The assembly device 10 shown in figures 1-3 is intended for welding the pairs of cross wires 3 to the plurality of plane nettings 2.

The device 10 comprises a support structure 11 having a plurality of support holders 12. The support holders 12 define a plurality of substantially parallel support planes for bearing the plane nettings 2, which are spaced from each

other by the predetermined netting pitch distance D2. The device 10 further comprises a pair of welding units 21 for welding the pairs of cross wires 3 to the plane nettings 2, feeding means 31 for shifting the plane nettings 2 on the support structure 11 towards the welding units 21 and a pair of supply holders 41 with supply means 42 for holding and supplying cross wires 3 to the welding units 21. Finally, the device 10 is preferably provided with receiving means 51 for receiving the assembled three-dimensional structure 1.

The support holders 12 of the support structure 11 are mounted on uprights 14 in such a way that the mutual distance between superimposed support holders 12 is adjustable in height direction. In this way, the predetermined netting pitch distance D2 can be adjusted. Preferably, the mutual distance between each two superimposed support holders 12 is chosen substantially equal, but the mutual distance may also differ. Each support holder 12 is provided with alignment means 13 for aligning the plurality of plane nettings 2 in such a way that the lengthwise wires 4 are substantially coplanar. The alignment means 13 on each support plane preferably comprise, on the one hand, a longitudinal flat plate 15 which is mounted on a pair of rotatable arms 16 which are fixed to rotatable uprights 17 and, on the other hand, an upstanding edge (not shown) of the support holders 12. All the rotatable arms 16 are fixed to the rotatable uprights 17 in the same angle, so that all the flat plates 15 are provided to remain parallel to each other and to the lengthwise wires 4 of the nettings 2. In this way, the alignment means 13 on all support planes are adjustable simultaneously. By providing these adjustable alignment means 13, the support structure 11 is suitable for supporting plane nettings 2 of different widths.

Feeding means 31 are associated with each of the support holders 12 and are mounted substantially in the middle on the support planes. The position of the feeding means 31 on the support planes can be varied according to the width of the plane nettings 2 which are to be assembled, so that the feeding means grip the nettings 2 substantially in the middle. The feeding means 31, shown in greater detail in figures 4 and 5, each comprise a feeding tooth 32 which is provided to perform a reciprocating movement and to shift the plane netting 2 on the corresponding support holder 12 by gripping behind the brace wires 5 of the netting 2. For this purpose, the feeding tooth

comprises a gripping edge 33 and a slanting edge 34 and is pivotally mounted on a tooth actuator 35 which can shift forwards and backwards to move the feeding tooth 32 along forward and backward strokes of the reciprocating movement.

The feeding tooth 32 is provided with a stop 36 which rests on the tooth actuator 35 during the forward stroke, so that the tooth is held in an active position in which the gripping edge 33 of the tooth 32 extends through the plane defined by the plane netting 2 and is able to engage one of the brace wires 5. The slanting edge 34 is provided to lift the feeding tooth to an inactive position above the plane defined by the netting 2 during the backward stroke when it contacts the subsequent brace wire 5 of the netting 2, for positioning the tooth 32 behind the following brace wire 5. Preferably, the feeding tooth 32 comprises two pairs of gripping and slanting edges 33 and 34, so that it is provided to simultaneously grip two brace wires 5.

In a preferred embodiment of the device 10 shown in figures 1-3 the reciprocating movement of each feeding tooth 32 can be adjusted individually by setting the rotation angle of the tooth actuators 35, so that the cross wire pitch distance D3 can be chosen individually for each plane netting 2.

The pair of welding units 21 is located in front of the support structure 11. Each welding unit 21 comprises a plurality of welders 22 for forming a plurality of welding spots, on which the cross wires 3 are welded to welding locations on the lengthwise wires 4 of the nettings 2. All welding spots are coplanar and define a welding plane, which preferably extends substantially perpendicularly to the support planes and the side planes of the nettings.

On the opposite side of the welding units 21, the pair of supply holders 41 are located, which are provided to hold and supply the cross wires 3 to the welding units 21. Each supply holder comprises a container 44 for receiving a supply of cross wires 3. The wires are pulled one by one by gravity into an outlet channel 45 at the bottom of the container 44, which is dimensioned such that it can receive only one wire at a time. Below the outlet channel a set of wheels 46 is provided on a common spindle 47, the wheels having cut-outs for gripping the wire in the outlet channel 45. The wheels are provided to drop the wire from the outlet channel onto permanent magnets 43 on a rotatable arm 42. The permanent magnets 43 are provided for holding the wire

which is dropped onto the arm 42. The arm 42 is mounted in such a way that it can freely rotate the cross wire into the adjacent welding unit 21 without hampering the elements of the welding unit 21 and the movement of the three- dimensional wire structure 1 under construction. For this purpose, the supply holder 41 and the arm 42 are preferably arranged in an angle a of 15 to 45°, more preferably about 20°, with respect to the welding plane defined by the welding units 21. The mounting in said angle a has the advantage that the width of the assembly device 10 is reduced with respect to the prior art device, in which the supply holders and supply means extend sideways of the welding units.

The supply holders 41 can each be provided with partitioning elements (not shown), to each receive a plurality of cross wires 3 of lengths smaller than the total width of the supply holder 41. As the wheels 46 are mounted on a common spindle 47 and the rotatable arms 42 are provided with permanent magnets 43, they are in themselves suitable for handling said plurality of cross wires simultaneously, so that the need for further partitioning elements between the wheels 46 and on the arms 42 can be avoided. By providing such a plurality of pairs of cross wires 3 to the welding units 21 instead of one cross wire on each side, a corresponding plurality of three-dimensional structures 1 can be assembled simultaneously above each other. Of course, the height of each of the plurality of structures will be smaller than a three-dimensional structure having the maximum possible height achievable with the assembly device 10.

The welding units 21, which are opposed on either side of the support structure 11, each comprise a plurality of welders 22, one for each support holder 12. The mutual distance between superimposed welders 22 is adjustable according to the predetermined netting pitch distance D2. The distance between the welding units 21 is adjustable along with the width of the support holders 12.

Figure 6 shows a welder 22 of the welding unit 21 shown on the right side of figure 3. The welders 22 in the welding unit 21 on the left side are symmetrical to that shown in figure 6. The welder 22 comprises a body 201 in the shape of a hollow parallelepiped, on which a transformer 202, an air actuator 203, a movable electrode 204 and an opposing electrode 205 are mounted.

The movable electrode 204 is secured to a piston 207 of the air actuator 203. The piston 207 is guided in sleeves 206 which insulate the piston 207 from body 201. The opposing electrode 205 has an L- shaped body 208 and is electrically connected to the body 201. The electrodes 204 and 205 are provided with contact surfaces 213 for contacting the wires of the three-dimensional structure during welding. The transformer 202 is fitted partly inside the parallelepiped-shaped body 201 and is provided with a primary winding of which the terminals are connectable to a source of electric energy.

The secondary winding of the transformer 202 is provided with two terminals 209 and 210 which are respectively connected to the electrodes 205 and 204.

Terminal 209 is directly connected to electrode 205, whereas the connection between electrode 204 and terminal 210 is obtained by means of a flexible U- shaped member 211, which enables the movements of the piston 207 and the movable electrode 204 relative to the transformer 202 and the opposing electrode 205. The electrodes 204 and 205 are provided with cooling ducts (not shown) which are connectable to the cooling unit.

All welders 22 of each welding unit 21 are mounted on plates a plate 212 which extends in a direction substantially perpendicular to the support planes of the support structure 11. This plate 212 is slidably mounted on a vertical upright and is provided with means (not shown) for moving the plate 212 and the welders 22 mounted thereon between an active and an inactive position. In the inactive position, the electrodes 204 and 205 are located between two superimposed support planes, so that they do not hamper the shifting of the nettings 2. In the active position, the contact surfaces 213 of the electrodes 204 and 205 are coplanar with the nettings 2, so that they are in a position suitable for clamping the cross wire 3 and the lengthwise wire 4 and subsequently welding them together. The means for moving the plate 212 are provided to move the welders 21 upward to the active position and downward to the inactive position.

The receiving means 51 for receiving the assembled structure 1 comprises a carriage 52 mounted on rails 53. This carriage 52 comprises a lower base 54 for supporting the assembled structure 1 and can be provided with at least one further base 55 above the lower base 54

for supporting simultaneously constructed wire structures 1 of reduced height above each other.

The assembly device 10 is provided with a plurality of sensors (not shown), for example for sensing the presence of nettings 2 on the support holders 12 and cross wires 3 on the rotatable arms 42, for sensing the beginning and end positions of the feeding means 31, the rotatable arms 42 and the plates 212 on which the welders 22 are mounted, etc. The sensors are all connected to the control unit for conveying the information to the control unit, so that it can control the sequence of movements and operations to be conducted by the device 10.

The control unit comprises a microprocessor provided with a series of input-output interface units. The input interfaces receive the data from the sensors; the output interfaces are connected to relays for enabling the movement of the components of the device. The microprocessor is provided to operate a power unit, which is connected to the source of electrical energy of the primary windings of transformers 202 in the welding units 21, and the air unit for controlling the movements of the feeding means 31, the welders 22 and the rotatable arms 22. The microprocessor is provided with a programme which controls the sequence of movements and operations. In this programme, different parameters can be set according to the desired shape of the three- dimensional structure, such as for example the predetermined pitch distances D1, D2 and D3.

The method of assembling used with the assembly device 10 will be described in the following.

Initially the following parameters are set: (i) the netting pitch distance D2 is set by adjusting the support holders 12 in height direction, along with the feeding means 31 and the welders 22; (ii) the device 10 is adjusted to the width of the nettings by adjusting the position of the alignment means 13 of the support holders 12 and the mutual distance between the welding units 21 along with the mutual distance between the supply holders 41; and (iii) the cross wire pitch distance D3 is set for each support holder 12 by adjusting the stroke of the feeding means 31. Preferably, the mutual distances between the superimposed support holders 12 are chosen substantially equal, but they may also differ. In the following it is assumed that the cross wires 3 are

of maximum length. For using shorter cross wires 3 and assembling a plurality of three-dimensional structures 1 simultaneously, partitions are inserted in the containers 44 of the supply holders 41, but the operation of the device 10 remains substantially the same.

In the following it is further assumed that the cross wire pitch distance D3 is chosen the same for all plane nettings 2, so that a three-simensional structure 1 is achieved acoording to figure 8. The cross wire pitch distance D2 is preferably chosen twice the brace wire pitch distance D1 of the nettings 2, which implies that the stroke of the feeding means 31 is slightly larger than twice the distance between two subsequent brace wires 3.

In a first step, plane nettings 2 are placed on the support holders 12 and cross wires 3 are placed in the containers 44 of the supply holders 41. The plane nettings 2 are aligned so that their outer lengthwise wires 4 are substantially coplanar and moved towards the welding units 21 until their front brace wires 5 are located beyond the feeding teeth 32.

At this point, the device 10 is ready to assemble the structure 1 under control of the control unit. By pressing the start key, the tooth actuators 35 are started, which shift the not yet assembled nettings 2 towards the welding units 21, by means of the feeding teeth 32 which grip the front brace wires 3, until first welding locations on the plane nettings 2 are located between the electrodes 204 and 205 of the welders 22. During this shifting step, a cross wire 3 is supplied to each welding unit 21 by operating the supply means (gripping wheels 46 and rotatable arms 42) of the supply holders 41. In this way, the cross wires 3 are already present between the welding electrodes 204 and 205 when the first welding locations on the plane nettings 2 arrive.

Subsequently, the plates 212 on which the welders 22 are mounted are moved upwards for bringing the welding electrodes 204,205 into the planes of the nettings 2, after which the pistons 207 are operated, bringing the movable electrodes 204 towards the fixed electrodes, thereby clamping the cross 3 and lengthwise wires 4 between the contact surfaces 213.

At this point, the rotatable supply arms 42 are rotated back for collecting a subsequent pair of cross wires 3 from the supply holders 41. Next, the welding of the cross wires 3 to the lengthwise wires 4 is performed by providing power to the primary windings of the transformers 202. While the electrodes 204 and 205

are retaining the wires 4 and 3, the tooth actuators 35 are operated to move the feeding teeth 32 back in the backwards stroke of their reciprocating movement.

The feeding teeth 32 are thus brought backwards until they project slightly rearward of the subsequent brace wires 5 to be gripped during the next forward stroke. When the end position of the feeding teeth 32 is sensed by the sensors, the control unit operates the pistons 207 to remove the welding electrodes 204 and causes the plates 212 to be moved downwards, to remove the electrodes 204,205 from the path of the brace wires 5. The device is now in its original condition and ready for the following shifting and welding steps.

In order to achieve a three-dimensional structure 1 having a bent shape according to figure 9, the cross wire pitch distance D3, i. e. the stroke of the reciprocating movement of the feeding means 31, is chosen different for each individual netting 2, namely a shorter distance for the top netting and a longer distance for the bottom netting with a gradual increase from top to bottom for the intermediate nettings 2. The brace wire pitch distance D1 of the nettings correspondingly differs in this case, gradually increasing from top to bottom. The assembly method is similar to the one described above, but as the stroke of the feeding means 31 gradually increases from top to bottom, the shift of the nettings increases from top to bottom, i. e. the bottom netting is pushed further in each stroke than the top netting. This has the effect that, during each shifting step, the portion of the three-dimensional structure 1 coming out of the welding units is bent upwards, so that in the end the bent shape of the structure is achieved.

The device and method for assembling the plane nettings 2 from lengthwise 4 and brace wires 5 is substantially the same as the one described in US-A-4,667, 707.