NZ248341A - A press head used in an apparatus for the manufacture of trusses has a platen and a retractable trolley - Google Patents

Description

248141 Priority Datefs): fo.j.sjc,. aa,„ Complete Specification Filed: .sis.j q3 • !v>*i m .cr>."& /??o Publication Date: m '' O. Journal No: PATENTS FORM NO. 5 Fee No. 1 & 4: $340.00 WE PATENTS ACT 1953 COMPLETE SPECIFICATION US FOR MANUFACTURING A TRUSS [NG-NAILr^YSTEMS LIMITED, a British company of Christy Estate, Ivy Road, Alderstitfrl, Hampshire GUI2 4XG, Great Britain hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: (Followed by Page 1 A) 1 1 A L 4 0 6 4 1 M&C FOLIO: 620/5 1 9P6 6 1 6 3 WANGDOC: 03 08o APPARATUS FOR MANUFACTURING A TRUSS The invention relates to apparatus for manufacturing a truss, a press head for use therein and a device for automatically feeding connector plates to the press head.

Until recently, roof trusses have exclusively been manufactured manually. However, over the years, various developments have been made which have assisted in the manufacturing process. For example, machines having a plurality of press heads each having an integral platen have been developed wherein the press heads and platens are manually positioned at the joints of the truss and locked in position. The members forming the truss are positioned on the platens and all of the press heads are then operated simultaneously and from a central control to press connectors into the joints to form a self supporting structure. Another type of known jig consists of separate platens and press heads wherein the platens are first laid out at their required joint locations (often they are strung together to form long continuous sections for ease), and suspended or floor mounted press heads are then individually moved into pfS^ition at each joint and operated. A further type of '■ ki ' consists of a solid roller used to press <- *t d 3 4 1 2 connector plates into the joints. The plates are loosely fixed at the joints by hammering and then the entire truss assembly is fed into the roller mechanism which acts rather like a mangle to press the connectors into the joints and fix the truss members together.

It is also known to provide a large truss table whereon stops are manually located at required positions, continuous platens are laid at and between all joints and then a travelling beam press traverses the truss stopping at each joint under manual control and presses the joints together. US patent No. 4943038 discloses a similar truss assembly table having a plurality of sections in each of which a plurality of jig stops is provided which can be positioned to enable the truss members to be accurately positioned with respect to one another on the table prior to connection. The jig stops are each positioned by means of a lead screw driven by a manually operated drill. However, although each jig stop is positioned by a power-operated device, these devices are manually operated and each jig stop therefore requires individual attention.

The known apparatus for assisting in the manufacture of trusses is therefore time consuming to operate and labour intensive. The average time taken to set up suitable apparatus for manufacturing a run of identical trusses is half an hour to an hour. Pressing a run of 8 \ *48341 3 to 10 trusses will also typically take about half an hour. Thus the setting up of the jig usually occupies at least 50% of the production time and hence a considerable proportion of the cost. It is an object of the present invention to provide apparatus which enables a truss to be accurately and swiftly manufactured. It is a further object of the invention to reduce the labour costs involved in manufacturing trusses.

The invention provides apparatus for manufacturing a truss, comprising a plurality of press heads arranged in a single plane about a fixed datum point and movable within the plane about the datum point, wherein the press heads are each connected to powered driving means and to control means for automatically determining the desired position of each head with respect to the datum point and for controlling the powered driving means such that each head is driven to its desired position.

Preferably, at least some of the press heads are movable both transversely and longitudinally with respect to the datum point, the remainder of the press heads being movable only transversely with respect to the datum point. Such an arrangement allows sufficient freedom of movement of the press heads to allow for any shape or configuration of truss to be manufactured within the practical limits of the apparatus. It is equally preferable that all of the press heads are movable both transversely and longitudinally with respect to the «- *T O 3 4 datum point to give even greater freedom of movement. It is envisaged that at least one press head should be positioned at each junction of the truss members forming the truss.

In an advantageous embodiment, the press heads which are movable both transversely and longitudinally are mounted on a plurality of longitudinally extending support structures so as to be longitudinally movable therealong, the support structures being themselves transversely movable with respect to the datum point. Preferably, the support structures are transversely movable along at least one track which is fixed with respect to the datum point. When press heads which are movable only transversely with respect to the datum point are provided, they are mounted on a transversely extending support structure so as to be transversely movable therealong. This support structure is preferably located parallel to the track. This is a convenient and inexpensive construction of apparatus which fulfils the objects of the invention in an advantageous manner.

Preferably, each press head comprises a platen and a retractable trolley operable to press connectors into truss members during manufacture of a truss. The operation of each press head can be controlled automatically from a control panel operated by the apparatus operator. Preferably, the platens and trolleys are all simultaneously operable, although it is envisaged that the platens and trolleys can be selectively operable according to the truss to be manufactured. Preferably, each press head is rotatable about an axis perpendicular to the single plane with respect to the support structure on which it is mounted.

In a preferred embodiment, each press head comprises holding means located directly or indirectly on the platen for holding at least one timber member in place with respect to the platen during operation of the press head. More preferably, the holding means are retractable during operation of the press head to a position wherein the holding means do not inhibit the pressing operation. Advantageously, the holding means are retracted to a position beneath the upper surface of the timber member or members. In an advantageous embodiment of the invention, the holding means comprise at least one pneumatically operated cylinder clamp arranged to press against a respective timber member to hold the said timber member in place. This allows the timber members to be held in place during the pressing operation and reduces the risk of the timber members becoming misaligned and thus reducing the efficiency of the apparatus.

In a preferred embodiment of the apparatus, the control means are operable by comparing the actual position of each press head with a desired positi^ii^fBas^ /€ " 6 *48341 that press head, determining the error between these positions and actuating the powered driving means for altering the position of the press head with respect to the datum point until the error is substantially nulled. In this way, the movement of the press heads is accurate and swift; the jig configuration can be changed very quickly and with the minimum operator intervention by means of such a control system. Alternative control means could equally be used, but are preferably computer operated.

Preferably, the apparatus further comprises an automatic feeding device for automatically feeding connectors to the press heads. This also speeds up the operation of the apparatus to manufacture a number of trusses of a given configuration. Advantageously, each press head comprises magnetic means for retaining the connectors in position on the press head between having a pair of connectors automatically fed thereto and operation of the press head.

The invention also provides a press head for use in apparatus as described above, comprising a platen and a retractable trolley, the trolley having a trolley head and being movable between a retracted position wherein the upper surface of the trolley head is level with or below the upper surface of the platen, and an operating position wherein the lower surface of the trolley head... ;/ 7 /: 4 '6 3 4 1 that, when the trolley is in the operating position, the platen can be raised towards the trolley head to carry out a pressing action on any truss members and connectors located therebetween. Preferably, the trolley is located adjacent the platen when in the retracted position and the upper surfaces of the trolley head and the platen are substantially coplanar. Also, it is preferred if frame members are attached to the platen along at least one side thereof to allow connectors to be placed freely between the upper surface of the platen and the truss members to be used to form a truss, the connectors being pressed into the truss members on operation of the press head. More preferably, the frame members are attached to the platen along three sides thereof, the platen being preferably rectangular in shape. This avoids the need for the truss members to rest on the connectors which can lead to instability of the truss members during manufacture and movement of the connectors away from their desired positions before pressing occurs.

It is preferred that the frame members are retractable during operation of the press heads to a position wherein the frame members do not project above the upper surface of the platen.

In an advantageous embodiment, the frame members are releasably attached to the platen. Preferably, the,.. frame members are each releasably attached,%K^/i|^ateri^> /V #1 . / 8 * 8 3 4 1 by means of clamping devices specifically adapted to allow rapid and accurate clamping without overtightening. Each clamping device preferably comprises an abutting member for abutting against either the frame or the platen, and a projecting member extending away from the abutting member, the projecting member carrying at least one radially extending projection for interengagement with cammed groove means and being rotatable about an axis with respect to the cammed groove means, wherein the projecting member is slidably mounted with respect to the abutting member and is biased into a retracted position by means of resilient means acting between the projecting member and the abutting member such that, in use and on interconnection of the at least one projection carried by the projecting member and the cammed groove means and relative rotation therebetween, the projecting member is forced into an extended position against the biasing of the resilient means. Preferably, the respective frame member is permanently carried by the projecting member of the clamping device or devices arranged to connect the frame member to the platen. This reduces the risk that the appropriate clamping device or devices will be mislaid or dropped and also reduces the risk of damage to either the frame or the clamping device by allowing accurate and firm clamping without overtightening.

In an advantageous embodiment of the in*—J-J — 9 248341 holding means are located directly or indirectly on the platen for holding at least one timber member in place with respect to the platen during operation of the press head. Preferably, the holding means are retractable during operation of the press head to a position wherein the holding means do not project above the upper surface of the platen. Furthermore, it is preferable if the holding means comprise at least one pneumatically operated cylinder clamp arranged to press against a respective timber member to hold the said timber member in place. Ideally, the holding means are mounted on the frame members located on the platen.

The invention also provides apparatus for connecting a plurality of timber members comprising a fixed pressing member, a platen movable with respect to the pressing member and means for introducing at least one connector between the pressing member and the platen, wherein the platen and/or the pressing member comprise magnetic holding means for holding the or each connector in place during movement of the platen. Preferably, the holding means comprise electromagnets located in or on the platen and/or the pressing member. The means for introducing at least one connector between the pressing member and the platen are preferably arranged to deliver connectors therebetween in pairs. More preferably, the connectors comprise pairs of gang-nail plates arranged so that the nails of each plate interengano -wi'ffi rfhp *48341 nails of the other plate. When the platen is moved away from the pressing member, one connector of the pair is held on each of the platen and the pressing member until connection of the timber members takes place.

The invention also provides a method of connecting timber members together utilising apparatus as described above comprising the steps of: (a) moving the platen to a connector-receiving position with respect to the fixed pressing member; (b) introducing a pair of gang-nail connectors to the space between the platen and the pressing member; (c) actuating electromagnets located in or on the platen and the pressing member to hold one connector against the platen and one connector against the pressing member; (&) moving the platen and the respective connector held thereagainst away from the pressing member and the other respective connector to a retracted position; (e) introducing the timber members to be connected to the space between the platen and the pressing member; (f) moving the platen towards the pressing member so that the connectors held against the platen and pressing member are pressed into the timber members; (g) deactivating the electromagnets to release the timber members from the apparatus and moving the platen away from the pressing member; and (h) removing the timber members from *48341 11 Embodiments of the invention will now be described with reference to the accompanying drawings wherein: Figure 1 is a schematic diagram of apparatus according to a first embodiment of the invention; Figure 2 is a schematic diagram of apparatus according to a second embodiment of the invention; Figure 3 is a perspective schematic view of a press head forming part of the apparatus of either of Figures 1 and 2; Figures 4a, 4b, 4c and 4d are schematic diagrams showing the operation of the press head of Figure 3; Figure 5 is a schematic sectional view of a clamping, device used in the apparatus of any of Figures 1 to 4; Figure 6 is a schematic sectional view of an alternative clamping device for use in the apparatus of any of Figures 1 to 4; Figure 7 is a plan view of a platen forming part of a press head with frame members mounted on three sides thereof; Figure 8 is a schematic view of a pneumatic clamp for use in the apparatus of any of Figures 1 to 4; Figure 9a is a schematic sectional view of a frame for attachment to the platen of Figure 7; Figure 9b is a schematic front view of part of the frame of Figure 9a; and Figures 10a to lOd are schematic views of apparatus for connecting timber members incorporating a d^^SB^forN-,, //*' 12 /- 4 8 3 4 1 automatically feeding connectors to the press head.

The apparatus illustrated in Figure 1 comprises a transversely extending support structure 2 and a transverse track 4 extending parallel to the support s.tructure 2. A plurality of longitudinally extending support structures 6 are arranged so that one end 6a of each support structure 6 is supported on and movable along the track 4. The opposite end 6b of each support structure 6 is supported on a wheeled carriage (not shown) or other suitable supporting means allowing each support structure to move along the track 4.

A plurality of press heads 8 are mounted upon the support structures 2, 6. The transverse support structure 2 carries a plurality of press heads, a total of eight being illustrated in Figure 1. Each of the longitudinally extending support structures 6 is shown carrying two press heads 8 except for the central support structure 6' which carries only a single press head. However, each support structure 6 can carry any number of press heads (typically between one and three). Furthermore, the press heads are removable from the support structures 6 so that any one support structure 6 can have press heads added or removed to suit any particular design requirement. Each press head 8 located on the longitudinally extending support structures 6 is rotatable about an axis 1 \ #/ substantially centrally of one edge of th£' press hecTdi / '7auGi V E <D ^ 24 8 3 4 1 13 (see Figure 7). The press heads located on the transversely extending support structure 2 need not be rotatable but can be if so desired. Each press head 8 is furthermore slidably movable along the respective support structure 2, 6 so as to vary its position therealong. Driving means for carrying out the sliding movement are provided, but not shown for reasons of clarity. Driving means (not shown) are also provided for moving the support structures 6 along the track 4.

The central point of the transversely extending support structure 2 is designated the datum point 12. This datum point can be fixed at any suitable point within the overall geometry of the apparatus or, indeed, outside if desired. It is not necessary for the datum point to be fixed as illustrated in Figure 1, but it is convenient to fix the datum point at a specific point along the transverse support structure 2. An X axis and a Y axis have also been illustrated in Figure 1 to assist in the description of the apparatus set out below. The X and Y axes intersect at the datum point and the X axis extends along the transverse support structure 2 and the Y axis extends parallel to the longitudinally extending support structures 6.

The apparatus of the invention also incorporates control means (not shown) which operate to drive the driving means and so to position the press heads 8 appropriately to manufacture a truss 4 8 3 14 shape. The position of all joints in the desired truss relative to the datum point are input into the control apparatus. The control apparatus then determines, by means of monitoring and comparative devices (not shown), the difference between the actual position of each press head 8 and its desired position in order to manufacture the required truss. The control means then actuates the driving means to alter the position and orientation of each press head 8 in response to the value of the error between the actual position of the press head 8 and its desired position. The driving means are arranged to move the press heads 8 located on the transverse support structure 2 along the support structure 2 in the direction of arrow 14 to their desired positions; to drive the support structures 6 in the direction of arrow 16 to locate the press heads 8 mounted thereon in their correct "X axis" positions with respect to the datum point; and to move the press heads 8 mounted on the support structures 6 in the direction of arrow 18 in order to achieve the correct "Y axis" position of each press head 8 with respect to the datum point 12. Once the desired positions of each press head are received by the control means, then each press head 8 can be moved by the control means to its desired position. The press heads can be moved in pairs, in groups or all together which reduces the amount of time required tc apparatus to produce a specific truss. The *4 8 3 means is also capable of rotating the press heads 8 about their axes 10 to align the press 8 heads in the direction of the members which will form the truss.

Once all of the press heads are correctly positioned, they can be held in those positions by an automatic braking system (not shown).

For safety reasons, a system of lights and/or sirens (not shown) can be used to reduce the risk of accident or injury to persons near the jig. Red lights are arranged to light up or flash when the press heads 8 are moving or in operation. Hooters and sirens are also sounded. Also, an automatic stop and reverse system is provided to reduce the risk of accidents. Indicators (not shown) are provided on each press head 8 to show when the respective press head 8 is in the required position. A red light indicates an incorrect position, an amber light indicates that the error is within certain limits and a green light shows that the press head is positioned correctly. This enables the press heads to be manually positioned, if necessary, when for example the driving means are for any reason inoperable.

Figure 2 shows an alternative arrangement according to the invention similar to that shown in Figure 1 but omitting the transversely extending support structure. The only support structures provided are those extending longitudinally 6. As described above, the support structures 6 are movable along the track 4. ^4 8 3 16 point 12 is relocated to the intersection of the track 4 and the centre support structure 6' which may, if desired, be fixed with respect to the track 4. The X and Y axes are also relocated to pass, respectively, parallel and perpendicular to the track 4 and through the datum point 12. As with the apparatus of Figure 1, the datum point can in fact be located at any convenient position with respect to the jig.

Press heads 8 are mounted on the support structures 6 in sufficient numbers for at least one press head 8 to be positioned at each joint of the truss to be manufactured. Press heads are positioned near the track 4 to deal with joints located on the bottom chord of the truss. Alternatively, the truss could be manufactured "upside down"; i. e with the bottom chord extending parallel to the track 4 but adjacent the opposite ends of the support structures 6 to those mounted on the track.

This embodiment is even more versatile than the apparatus described above and facilitates the manufacture of trusses having bottom chords which are angled or which contain non-parallel sections. It is envisaged that this type of apparatus will require a larger number of support structures 6 than would be required by the apparatus of Figure 1 to accommodate the number of joints commonly required along a bottom chord.

Both of the embodiments of Figures 1 and ^utilise •t 8 3 4 1 17 identical press heads 8. Each press head 8 is substantially as shown in Figures 3 and 4. Figure 3 shows a press head in its operational configuration. The press head 8 consists of a platen 20 and a trolley 22. The trolley 22 is movable between a retracted position (shown in Figure 4a) and an operational position (shown in Figures 3 and 4c). Suitable mechanical means by which the trolley 22 can be moved in relation to the platen 20 are well known and will not be described here.

A frame 24 (shown in dotted lines in Figures 3 and 4) is attached to the platen 20. The frame itself and the means of connection will be described below. The purpose of the frame 24 is to allow a space between the upper surface 26 of the platen 20 and the lower surface of a truss member 28 positioned on the press head 8 during the manufacturing process.

The manufacturing process will now be described.

When the press heads 8 have been correctly positioned by the control means, the truss members can be positioned on the apparatus shown in Figure 1 or 2. This involves laying truss members 28 across the frames 24 of each press head 8 and holding them in place by means of pneumatic timber clamps and stops (described below). A connector 30 is positioned on the upper surface 26 of the platen in the space between the..--pl,aten and the truss member 28. 18 248341 positioned on top of the truss member 28. A signal is then given by the operator via the control means to commence the pressing operation and warning sirens and lights are operated. The trolley 22 is initially in its retracted position, being located adjacent the platen 20 with the upper surface 34- of the trolley head 36 substantially level with the upper surface 26 of the platen. The trolley 22 is then moved upward as shown in Figure 4b and subsequently transversely so that the trolley head 36 is located directly above the platen 20. The trolley head 36 is also located above the truss member 2 8 and the two connecting members 30,32. The final step of the pressing operation is to raise the platen 20 with respect to the trolley 22 with sufficient force to press the connectors 30,32 into the truss member 28. The pressing motion is automatically ended when a sufficient force has been applied for a predetermined time. The lifting mechanism by means of which the platen 20 is raised is preferably hydraulically operated and controlled by the same control means used to position the press heads 8. By a reversal of the steps just described, the trolley 22 returns to its retracted position adjacent the platen 20 and the pneumatic timber clamps are automatically released to facilitate rapid handling of the truss ..off the jig.

Each of the press heads 8 is V T- t) 19 c 4 6 3 4 1 identical manner. If all of the press heads 8 are being used to manufacture a particular truss, then all of the press heads will be operated at the same time. If, however, there are a number of press heads which are not required in the manufacture of a particular truss, then the control means will select only the press heads which are required and will not operate those which are not required.

The frame 24 mentioned above is necessary to allow a connector to be positioned beneath the truss member 28 without rendering the truss member unstable with respect to the apparatus. In some cases, it will be necessary for two press heads 8 to be located very close to one another and it may be necessary for part or all of the frame surrounding any particular platen 20 to be removed. For any one platen or group of platens, sufficient frames will be needed to adequately support the timber to be connected. In order to achieve this, a clamping device such as that illustrated in Figure 5 is utilised. The^ device consists of a housing 40 in which is slidably located a cylindrical member 42 carrying a projecting member 44. The projecting member 44 carries bayonet catches 46 which are locatable in cammed grooves 48 formed in the side walls of the platen 20. A disc spring 50 is located between the end wall of the housing 40 and the adjacent face of the cylindrical member 42 -j- '****? ; y A i £• ;-^v and the spring 50 biases the projecting member 44 irito-\a v\> o,.y V. f'i J'' <:4 8 3 4 retracted position. The cylindrical member 42 is retained in the housing by means of a handle member 52 rotatably fixed to the cylindrical member 42; the handle member 52 abuts against a disc shaped member 54 which is securely fixed by means of a split ring in the housing 40. The frame 24 is non-releasably mounted on the projecting member 44 between the housing and the bayonet catches 46. The clamping device and the frame 24 cannot therefore be separated.

In order to securely clamp the frame 24 onto the platen 20, the projecting member 44 and the bayonet catches 46 are introduced into the cammed grooves 48 in the platen 20 to bring the frame 24 into abutment with the platen 20. The handle 52 is then rotated so that the bayonet catches 46 engage with the cammed surface of the grooves 48. As the bayonet catches 46 travel along the cammed grooves 48, the projecting member 44 is forced into an extended position against the bias of the spring 50. The movement involved is, in fact, very slight. This type of clamping device can be used to rapidly achieve a high clamping force without risking damage to the clamping device, or to the components being clamped, by overtightening. The frame 24 can be easily and quickly removed from the platen if desired merely by rotation of the handle 52 in the opposite direction to that required for connection," followed by removal of the projecting member '■ f •? r n u 3 4 1 21 groove 4 8.

Figure 6 shows a variation of the connector shown in Figure 5 adapted for connection to a frame 24 so that the housing 40 can act as a stop member to assist in positioning the timber member on the platen. The connector itself is virtually identical with the connector shown in Figure 5 but has a slightly longer projecting member 44 on which is mounted a clamping member 60 having internal cammed grooves 62. The bayonet catches 46 are arranged at the ends of these cammed grooves 62. The clamping member 60 is rectangular in shape, although any non-circular shape would be adequate.

The operation of the clamping device as a stop is as follows: The projecting member 44 and clamping member 60 are introduced into a slot 64 running the length of an appropriate frame 24 by means of one of two keyways 66 appearing at either end of the slot 64 (see Figure 7). The stop is then slid along the slot 64 with the frame member 24 located between the clamping member 60 and the housing 40. When the desired position has been reached, the handle 52 is rotated to cause the bayonet catches 46 and the clamping member 60 rotate as well. The clamping member 60 will, after a certain amount of rotation, abut against the frame 24 due to the non-circular shape of the clamping member. Further rotation of the handle 52 will cause the bayonet catches v £• ni c t b 3 4 1 22 46 to travel along the cammed grooves 62 and thus force the projecting member 44 into an extended position against the bias of the spring 50. A high clamping force between the housing 40 and the clamping member 60 is thereby achieved without undue effort and without a risk of overtightening. The stop is thereby accurately and easily located on the frame 24 and can, if required, be accurately and easily relocated.

The connector described above in relation to Figures 5 and 6 is extremely versatile. For example, the connector can be adapted to receive pneumatic holding stops for assisting in the location and gripping of timber members in relation to the platen. Ideally, pneumatic cylinder stops as illustrated in Figure 8 are connectable to the upper surface of the stop shown in Figure 6 so that the pneumatic stops can be easily positioned at any suitable point around the platen. The platens of the apparatus shown in Figures 1 to 4 will ideally have at least two pneumatic holdings stops located along at least one side of the platen and mounted on the appropriate frame. Fixed stops may also be provided on the frame members to provide an abutment for the timber members against which the pneumatic holding stops may press the timber members. The pneumatic holding stops are controlled by the control means described above so that, when the press heads have all been correctly positioned and the timber members c 4 8 3 4 1 23 introduced to the jig assembly, the pneumatic holding stops can then be acuated to grip the timber members in place for the duration of the pressing operation.

In order to achieve an effective pressing operation, the platen must be able to press the lower connector into the lower surface of the timber members located on the press head. The frame members which support the timber members and also the stops and holding means should therefore be retractable to a position wherein they do not impede the pressing operation. This can be achieved by providing a retractable frame as shown in Figures 9a and 9b. These figures show a frame 24 having two parts; an upper part 24a and a lower part 24b. The lower part 24b is releasably connected to the platen 20 by means of at least one connector as shown in Figure 5 and described above. The upper part 24a of the frame 24 is connected to the lower part 24b by means of a bolt 70 which passes through a circular aperture in the lower part 24b but through an elongated slot 7 2 in the upper part 24a. A retention bolt 74 extends between the upper part 24a and the lower part 24b with a helical spring 76 arranged therealong. The action of the spring 7 6 biases the upper part 24a away from the lower part 24b so that the bolt 70 is retained at the lower end of the slot 72. The biasing force of the spring 76 4..s sufficient to keep the upper part 24a of the frame member 24 rn<the position shown in Figure 9a even when 24 c. h 8 3 4 1 supported thereon. Only when the pressing action takes place and the platen 20 is forced towards the trolley head (see Figure 3), is the upper part 24a forced downwardly so that the upper part 24a retracts beneath the upper surface 78 of the platen 20.

The apparatus of the present invention may also incorporate a projection system (not shown) to assist in the manufacture of a specific truss. The projection system projects an image of the truss to be manufactured onto the remainder of the apparatus located substantially in the plane of the press heads. This assists the operator by displaying exactly which components are required at each specific location and illustrates the positioning of the timber members required to form the truss. Stops and clamps can then be easily and conveniently located in appropriate positions by the operator. The projection means are preferably laser projection means.

The apparatus described above can be enhanced by the provision of automatic feed apparatus for supplying connectors direct to the press heads. An automatic feeding device is described below in conjunction with apparatus for connecting timber members.

The apparatus, shown in Figures 10a - 10d, comprises a press head having a movable platen 100 and a fixed pressing member 102. The platen 100 is movable in a vertical direction towards and away from 248341 member 102 as shown by the arrow 104. The apparatus also comprises a store 106 wherein pairs of gang-nail plates or other suitable connectors 108 are stacked ready for supply to the press head. The store 106 terminates at its lower end in a feed tunnel 110 along which a pair of connectors 108 can be pushed by means of a rod 112. Each of the platen 100 and the pressing member 102 contain electromagnets (not shown) which enable the connectors 108 to be held against the platen and pressing head 100, 102 when the electromagnets are operated.

The operation of the apparatus will now be described.

Initially, the platen 100 is moved upwardly towards the pressing member 102 to a connector-receiving position as shown in Figure 10a. The distance between the platen 100 and the pressing member 102 is approximately the width of a pair of connectors 108 or a little larger. The rod 112 then pushes the lowermost pair of connectors along the feed tunnel 110 in the direction of arrow 114 until the connectors 108 are located between the platen 100 and the pressing member 102. The rod 112 is then retracted to its original position in the direction of arrow 116 to allow a further pair of connectors 108 to fall under the influence of gravity to the position previously held by the pair of connectors now positioned between the,platen 100 and the pressing member 102 (see Figurie'CfcOc.iT^^The ' "Z // ■- •» > A •V-I 26 648341 electromagnets are now activated so that the connectors 108 positioned between the platen 100 and the pressing member 102 are attracted thereto. The connectors, which are in the form of gang-nail plates initially positioned with their respective nails interengaging, are thus held firmly in the position shown in Figures 10c. The platen 100 can then be moved away from the pressing member 102 which results in the separation of the connectors 108 which are then held firmly against the upper surface of the platen 100 and the lower surface of the pressing member 102 as shown in Figure lOd.

The apparatus can now be used to join timber members together by introducing the respective timber members between the platen 100 and the pressing member 102 in the required orientation and pressing the connectors 108 into the timber members by upward movement of the platen 100 towards the pressing member 102. The electromagnets are then deactivated to release the connectors from the platen 100 and the pressing member 102 and the platen 100 can then be moved away from the pressing member 102 to allow the timber members to be removed from the apparatus.

It is envisaged that the platen and pressing member of the apparatus described above can be made permanently magnetic if desired. Furthermore, the connectors can be of any suitable variety and need not be gang-haiJL^ plates. It is preferred that a warning me f- h d 3 4 1 27 incorporated into the apparatus to indicate when the supply of connector pairs is becoming low. Safety apparatus such as guards and warning signals operable during the pressing operation will reduce the number of accidents and injuries caused by pressing the connectors into the timber members. The platen is preferably moved by means of a hydraulic press, but could alternatively be moved by any other suitable means.

This type of automatic feeding apparatus can be applied to devices other than the truss manufacturing device shown in Figures 1 to 4 and described above. Various embodiments and uses will be apparent to one skilled in the art. 248 34 1 28

Claims (30)

1. Apparatus for manufacturing a truss, comprising a plurality of press heads arranged in a single plane about a fixed datum point and movable within the plane about the datum point, wherein the press heads are each connected to powered driving means and to control means for controlling the powered driving means and for automatically determining the desired position of each head with respect to the datum point such that each head can be automatically driven to its desired position, and wherein each press head comprises a platen and a retractable trolley, each trolley having a trolley head and being movable between a retracted position and an operating position wherein the lower surface of the trolley head is located above the upper surface of the platen so that, when the trolley is in the operating position, the platen can be raised towards the trolley head to carry out a pressing action on any truss members and connectors located therebetween, characterised in that, in the retracted position, the upper surface of the trolley head is level with or below the upper surface of the platen.

2. Apparatus as claimed in claim 1, wherein the control means are computer operated. 6 N - c 24 8 34 1 29

3. Apparatus as claimed in claim 1 or 2, wherein each press head is rotatable about an axis perpendicular to the plane.

4. Apparatus as claimed in any one of claims 1 to 3, wherein the press heads are connected to the control means for automatic operation of the platens and trolleys to press the connectors into the truss members.

5. Apparatus as claimed in claim 4, wherein the platens and trolleys are all simultaneously operable.

6. Apparatus as claimed in claim 4 or 5, wherein the platens and trolleys are selectively operable.

7. Apparatus as claimed in any one of the preceding claims, further comprising an automatic feeding device for automatically feeding connectors to the press heads.

8. A press head for use in apparatus for manufacturing a truss, comprising a platen and a retractable trolley, the trolley having a trolley head and being movable between a retracted position and an operating position, characterised in that, in the retracted position, the upper surface of the trolley head is level with or below the upper surface of the platen and, in the operating position, the lower surface of the trolley head is &. W f 248 34 1 30 located above the upper surface of the platen so that, when the trolley is in the operating position, the platen can be raised towards the trolley head to carry out a pressing action on any truss members and connectors located therebetween.

9. A press head as claimed in claim 8, wherein, in the retracted position, the trolley is located adjacent the platen and the upper surfaces of the trolley head and the platen are substantially coplanar.

10. A press head as claimed in claim 8 or 9, wherein holding means are located directly or indirectly on the platen for holding at least one timber member in place with respect to the platen during operation of the press head.

11. A press head as claimed in claim 10, wherein the holding means are retractable during operation of the press head to a position beneath the level of the upper surface of the timber member or members.

12. A press head as claimed in claim 10 or 11, wherein the holding means comprise at least one pneumatically operated cylinder clamp arranged to press against a respective timber member to hold the said ti "1" ~ " in place. 24 8 3 4 t 3 1

13. A press head as claimed in any one of claims 8 to 12, wherein frame members are attached to the platen along at least one side thereof to allow connectors to be placed between the upper surface of the platen and the truss members to be used to form a truss, the connectors being pressed into the truss members on operation of the press head.

14. A press head as claimed in claim 13, wherein the frame members are retractable during operation of the press head to a position wherein the frame members do not project above the upper surface of the platen.

15. A press head as claimed in any one of claims 10 to 12 and either of claims 13 and 14, wherein the holding means are mounted on the frame members.

16. A press head as claimed in any one of claims 13 to 15, wherein the frame members are releasably attached to the platen.

17. A press head as claimed in any one of claims 8 to 16, wherein the platen and trolley comprise magnetic means for retaining connectors thereon between having the connectors fed to the press head and operation thereof. 16 AUG 1995 24834 1. 32

18. A press head as claimed in claim 17, wherein the magnetic means comprise electromagnets.

19. A press head substantially as hereinbefore described with reference to the accompanying drawings.

20. Apparatus for manufacturing a truss as claimed in any one of claims 1 to 7, wherein the press heads are press heads according to any one of claims 8 to 19.

21. Apparatus for manufacturing a truss as claimed in any one of claims 1 to 7 and 20, wherein each platen and/or trolley head comprises magnetic holding means for holding the said connectors in place during movement of the trolley head.

22. Apparatus as claimed in claim 21, wherein the holding means comprise electromagnets located in or on the platen and/or the trolley head.

23. Apparatus as claimed in claim 21 or 22, wherein means are provided for automatically introducing connectors between the platen and the trolley head.

24. Apparatus as claimed in any one of claims 21 to 23, wherein the means for introducing connectors between the trolley head and the platen are arranged to deliver AUG 1995 248 3 4 1 33 connectors therebetween in pairs.

25. Apparatus as claimed in claim 24, wherein each pair of connectors is a pair of nail plates arranged so that the nails of each plate interengage with the nails of the other plate.

26. Apparatus as claimed in claim 24 or 25, wherein the platen is movable to a connector-receiving position with respect to the trolley head, the distance between the platen and the trolley head being substantially equal to the width of a single pair of connectors.

27. Apparatus as claimed in claim 26, wherein, when the platen is moved out of the connector-receiving position away from the trolley head, one connector of the pair is held on each of the platen and' the trolley head until manufacture of the truss takes place.

28. Apparatus for manufacturing a truss substantially as hereinbefore described with reference to the accompanying drawings.

29. A method of manufacturing a truss utilising apparatus according to any one of claims 21 to 27, comprising the steps of: (a) moving each platen to a connector-recei / V *16 AUG 1995;«■» 248 341;34;position with respect to each trolley head ;;(b) introducing a pair of nail plate connectors (108) to the spaces between the platens and the trolley heads ;;(c) actuating electromagnets located in or on the platens and the trolley heads to hold one connectors against each platen and one connector against each trolley head ;;(d) moving the platens and the respective connectors held thereagainst away from the trolley heads and the other respective connectors to a retracted position;;(e) introducing the truss members to be connected into the spaces between the platens and the trolley heads;;(f) moving the platens towards the trolley heads so that the connectors held against the platens and trolley heads are pressed into the truss members;;(g) deactivating the electromagnets to release the truss members from the apparatus and moving the platen away from the trolley heads ; and;(h) removing .'the truss members from the apparatus.;

30. A method of manufacturing a truss substantially as hereinbefore described with reference to the accompanying drawinqs. \ 1.4-;r „ _rv><*\ Sterns LvwTe "5 vU> E»uTW FtufcoriOoI RtWne-y& ^ 1G AUG jj a m