The present invention relates to apparatus for assembling planar structures, such as wooden or metal structures from elongated members, and in particular to apparatus for the assembly of. wooden and steel trusses for the building industry.

Wooden and steel trusses, particularly roof trusses, are assembled on large assembly tables, wherein stops or bobbins are positioned on the table to hold the wooden members in the required position while connector plates are pressed across or into the joints to form the truss or the steel members are fixed together - welded, screwed or clipped to form the truss.

Efforts have been made to improve the positioning of the stops to speed up construction time.

US Patent 5,085,414 - Weaver, describes a jig for forming wooden trusses, which comprises a table transversed by upwardly opening channels along which stop units can slide. The stop units are manually positioned and locked into predetermined positions to locate the wooden members to form the truss. Hence the accuracy of the shape of the truss is dependant on the ability of the operator to align the stops against the scales alongside, next to or in the transverse channels.

An attempt has been made to automate the setting up of the stops on the jig, and is disclosed in US Patent 5,092,028 - Harnden. There is disclosed a jig having a table transversed by a plurarity of parallel elongated openings. Jig stops are positioned in the openings and each jig stop is individually adjustable along the openings by respective lead screw driven by a stepper motor. The motors are controlled from a computer to automatically position the jig stops in accordance with a particular design of truss.

Whilst this jig provides for automatic placement of the jig stops, it is expensive as it requires an individual stepper motor and associated lead screw and drives for each jig stop in each transverse channel and only one stop may be used per transverse channel.

The present invention seeks to ameliorate the disadvantages of the before mentioned prior art apparatus by providing a planar assembly apparatus comprising: an assembly table comprising two parallel spaced apart tracks extending along two opposed sides of said table, and a plurality of upwardly open channels extending, parallel to each other, between said two parallel spaced apart tracks; jig bobbins located in said upwardly open channels and adapted to slide therealong; locking means, located on each jig bobbin, adapted to releasably secure the respective jib bobbin at any position along its respective upwardly open channel; a gantry, bridging said tracks and adapted to travel along said tracks; a gantry carriage adapted to travel across said gantry, between said tracks; engaging means, located on said gantry carriage, adapted to individually engage said jig bobbins and to operate said locking means of said jig bobbin; store means adapted to store positional information, designating the position of each jig bobbin for a predetermined truss design; and operating means adapted to act on said positional information received from said store means, to move said gantry along said track and said carriage across said gantry;

whereby, in use, said operating means moves said engaging means to individually engage respective jig bobbins and to unlock its locking means and to move the respective jig bobbin to a required position where said locking means is activated, and said engaging means then disengages from said jig bobbin, leaving said jig bobbin in its position for a predetermined truss design.

The present invention will now be described by way of example with reference to the accompanying drawings, in which:

FIG. 1 illustrates a truss assembly apparatus according to one embodiment of the present invention, showing a truss in position on the apparatus;

FIG. 2 illustrates a sectional view of a jig bobbin in a channnel;

FIG. 3 illustrates a part view of the embodiment illustrated in Figure 1 , with the engaging head free of the jig bobbin;

FIG. 4 illustrates a part cut-away view of the carriage illustrated in Figure 3;

FIG. 5 illustrates an end view of the gantry with a strut cutaway for clarity sake, showing the engaging means of embodiment shown in Figures 1 , 3 and 4, engaging a jig bobbin.

FIG. 6 illustrates a cut away view of the carriage illustrated in Figure 5;

FIG. 7 illustrates another embodiment of a truss assembly apparatus of the present invention;

FIG. 8 illustrates a section view of a jig bobbin in a channel of the embodiment illustrated in FIG. 7; and

FIG. 9 illustrates a computer flow chart.

An engineering computer, prepares an engineering design based on the requirements of a customer for a wooden or metal truss or other planar structures. Precise positional data for a plurality of jig bobbins (1) corresponding to positions along respective open channel (2) of the table (3), define the exact position of all components of the truss (4) as shown in Figure 1. The components of the truss (4) having been cut to the required shape as specified by the engineering computer.

Normally this data is stored on a diskette which is inserted into a gantry computer to enable the operator to set up each truss for the day. If it is required, however, the gantry operator could directly accesss the engineering computer to obtain the positional data for the new truss.

The assembly table (3), according to one embodiment, as shown in Figure 1 , comprises two parallel tracks (5) which run the length of the table (3). Running between the tracks (5) are a plurality of parallel open channels

(2). These channels (2) are shown substantially at right angles to the tracks (5) but could be at any angle such as 60° or 45°. A support surface (7) can link adjacent channels (2). Located in each channel (2) are, in this case, two jig bobbins (1) although any number of bobbins such as one or more can be used, depending on the truss design.

As shown in Figure 2, the channels (2) comprise a constant cross- section extrusion (6) having an opening (8) with re-entrant shoulders (9).

Each bobbin (1), as shown in Figure 2, comprises stop (10) in the form of a cylinder which sits above the channel (2) and has a bore (11) extending centrally therethrough. A bolt (12) provided with an allan key slot head (16), extends through the bore (11) and engages in a threaded recess (13) in a clamp member (14) located in the channel (2). The clamp member (14) could have recesses to receive the re-entrant shoulders (9) of the channel, so as to prevent rotation of the clamp member (14) within the channel (2). The clamp and the stop can be of any suitable shape as shown in Figure 2 so as the clamp member (14) is restrained from rotation within the channel (2).

As shown in Figure 1 , and 3 to 6, a gantry (17) straddles the table (3) and is connected by struts (13) to wheeled feet (18) which runs along the tracks (5). As shown in Figure 3, the wheeled feet (18) have a motor (36) which drives a pinion (37) which engages on a rack (38) extending along the length of the tracks (5). A gantry carriage (19) runs along the gantry (17).

The gantry carriage (19) comprises a U-shaped base (20) which is supported on the gantry beam (21) by bearings (22). A rack (23) extends along the gantry beam (21 ) and is engaged by a pinion (24) driven by a motor (25) located on the U-shaped base (20). A bearing (26) locks the pinion (24) into intimate engagement with the rack (23), such that the gantry carriage (19) is moved along the gantry (17), by the motor (25).

Located on the vertically extending arm (27) of the base (20), is a plate (28) which rides vertically between guide rollers (29) and is controlled by cylinder (30) to move the head (31) from a position where it is free of a jig bobbin (1) (Figures 3 and 4) to an engaging position where it engages the jig bobbin (1), (Figures 5 and 6).

The head (31) has a coupling means (32) which engages over the bobbin stop (10). An allan key (33) engages the head (16) of the bolt (12). The motor (34) via a single direction clutch (35) rotates the allan key (33) to loosen or tighten the bolt (12) and hence the jig bobbin (1).

The motors (36, 34, and 25) and cylinder (30) are all controlled by the gantry computer. The motor cable (57), resolve cable (58), signal cable (59) and the air line (60) are carried in the cable flex (15).

More than one gantry can be used to increase the speed of setting up the jig bobbins.

A further embodiment of a truss assembly apparatus is shown in Figures 7 and 8. In this embodiment the formation of the channels (62) and the table (3) differ from that illustrated in Figures 1 and 2.

The table (3) comprises transversely extending supports (63) over which the table top sections (64) are affixed in any suitable manner, such as drill and tap. The edges (65) of adjacent table top sections (64) overhang the supports (63) to form the channels (62), with the opening (8) of the channels (63) being smaller in width than the width of the channels (63) between the adjacent supports (63).

This form of channel is stronger than, cheaper than and relatively maintenance free, as compared to the channel illustrated in figure 1 and 2.

A flow diagram of the operation steps of assembling a wooden truss using one embodiment of the present invention is shown in Figure 7.

At start (39) the diskette containing the design data is inserted into the gantry computer. The design data is converted into positional references for jig bobbins (1) located in the open channel (2) to position the components of the wooden truss (4). The positional references are in conversion step (40) converted into an X direction along the table (3), with predetermined positions for each channel (2) and a Y direction along a respective channel (2).

On receiving this information the motor (36) located in this embodiment, in an each wheeled feet (18) of the gantry (17), is operated by

the gantry computer to move the gantry to align the head (31) with the first channel (2); gantry movement step (41). The gantry (17) stops its movement and the gantry carriage (19) moves across the gantry (17) in a Y direction (42), positioning the head (31) above the first jig bobbin (1); Y movement step (42).

The carriage (19) stops, in aligning step (43) and the cylinder (30) moves the engaging head (31) to cover the stop (10) of the jig bobbin (1), wherein the alien key tool (33) of head (31) fits into the slot head (16) of the bolt (12). In loosening step (44) the tool (33) is rotated by its motor (34) to loosen the bolt (12).

With the engaging head (31) locked over the stop (10) of the jig bobbin (1) the carriage (19) in carriage movement step (45), moves along the channel (2), (Y axis movement), to position the jig bobbin (1 ) in its new position. The jig bobbin is locked in place, in locking step (46). The head (31) is raised in the disengaging step (47), proud of the bobbin stop (10), and the carriage (19) moves, in Y movement step (48), to the next jig bobbin (1). In verifying step (49), the positions of the jig bobbins (1 ) are checked, if all jig bobbins (1) on that particular channel (2) have been positioned as required, the programme moves to verifying step (50). If not, the programme returns to step (42).

If, in verifying step (50), all of the jig bobbins (1) are not in their correct position the programme returns to step (41). If all jig bobbins (1) are in their correct position the gantry (17), in park step (51), moves back to its parking station, allowing full access to the table (3).

The truss components are then assembled (assembly step (52) ) and the connector plates are then located and pressed across or into the joints by any suitable means, such as a roller press in press step (53), and the press moves to a park station. The air operated ejection rollers (54) are then activated (roller activation step (55) ) and the truss (4) slide off the table (3) in removal step (56). It will be appreciated that hydraulically operable elements may be used.

If the run is finished the programme ends. If not, the programme returns to step (41 ) to complete the next truss.

The invention could also be used to assemble other planar shaped structures, which could be constructed of any suitable materials such as wood, plastics or metals.

Thus, in the example of the construction of a wooden truss as described with reference to the computer flow diagram illustrated in figure 9, the press step (53) would be altered to a connecting step such as welding, ultrasonic welding etc. depending upon the material of the planar structure to be assembled.

The particular shape or profile of the particular components shown in the embodiment can be altered without departing from the spirit or scope of the present invention.