FI107070B - Device for making a roof truss - Google Patents

Description

5

Device for making a roof chair Anordning för tillverkning av en takstol

The invention relates to a device for making a roof chair and a press head for use therein.

10 Until recently, roof chairs were made entirely by hand. However, over the years, various developments have been made that have helped in the manufacturing process. For example, machines have been developed which have a plurality of press heads, each containing an integral table, in which the press heads and tables are manually positioned at the joints of the roof chair and locked in place. The components forming the roof chair are positioned on the tables 15 and all the press heads are then operated simultaneously and from the central control device to press the connectors to the joints to form a self-supporting structure. Other types of known guides consist of separate desks and clamping heads, whereby: the desks are first placed at their required joints (often chained to form long continuous sections for ease) and the hanging or floor-mounted clamping heads are then moved individually to each joint and used. Another type of known guide consists of a fixed roller which is used to press the connecting plates to the joining points. Slabs are loosely secured to the joints, not by hammering, and then the entire deck chair assembly is fed to a roller mechanism which acts like a mangle to clamp the connectors to the joints and secure the roof chair members to each other.

From US Re. 27,692 is known as a roof chair making machine comprising a plurality of sleds which can be moved towards and away from the wood material. Each carriage has a · · C-shaped clamp to clamp the nail plates to the lumber wood. The C-30-shaped presses extend below and above the wood material, which results in difficulty in loading timber for the roofing deck.

It is also known to use a large deck chair, where the stops are placed by hand 2 in the required positions, continuous tables are placed on and between all joints, and then a movable boom press passes over the roof chair, stopping at each joint to manually control and press the joints. U.S. Patent No. 4,943,038 discloses a similar roof chair assembly table having a plurality of members, each of which also includes a plurality of guide responses that can be positioned to permit accurate positioning of the roof chair members relative to one another prior to attachment. The guide stops are positioned each by a guide screw that is used by a manual drill. However, even though each controller response is positioned by a machine-driven device, these devices are manually operated and therefore each controller response requires individual attention.

The known device for facilitating the manufacture of roof chairs is therefore time consuming and laborious. The average time to set up a suitable device for making a set of identical roof chairs is half an hour to an hour. It also typically takes about half an hour to squeeze 15 sets of 8-10 sun loungers. Thus, setting up the controller usually takes at least 50% of the production time and thus a considerable part of the cost. The object of the present invention is to provide a device which enables precise and fast manufacture of a roof chair. A further object of the invention is to reduce the labor costs involved in the manufacture of roof chairs.

20

The invention provides a device for manufacturing a roof chair comprising a plurality of press heads disposed in a plane capable of moving in a plane about a datum, each of the press heads being secured to a machine driven device and a guide to automatically control the desired position of each head wherein each end can be automatically moved to its desired position, and wherein each press head comprises a table and a carriage, each carriage including a carriage head, wherein the carriage can be lifted toward the carriage head in an operative position to perform a crimping operation on any roof chair parts and connectors, characterized in that each carriage is retractable and the head of each carriage is movable in a retracted position where the upper surface of the carriage head is at or below the upper surface of the table and the operating position in which the lower surface of the carriage head is located above the upper surface of the table.

Advantageously, the tables and the carriages may be used simultaneously, although it is conceivable that the tables and the carriages may be used according to an optional manufactured roof chair 5. Preferably, each press head may be rotated about an axis perpendicular to a plane relative to the support structure on which it is supported.

Preferably, the device further comprises an automatic feeding device for automatically feeding the connectors to the clamping heads. This speeds up the operation of the device for the production of a series of roof grilles 10 of a certain shape.

The invention also provides a press head for use in an apparatus for manufacturing a roof chair comprising a table and a wagon including a wagon head, wherein, when in the operating position, the table can be lifted toward the wagon head to perform a crimping operation on any of the characterized in one position: the upper surface of the wagon head is at or below the upper surface of the table, and in the drive position the lower surface of the wagon head is positioned above the upper surface of the table;

Preferably, the trolley is positioned adjacent to the table when in the retracted position and the top surfaces of the trolley head and the table are substantially in the same plane. It is also advantageous if the frame members are joined to the table along at least one side thereof to allow the connectors 25 to be freely disposed between the top surface of the table and the roof chair parts used to form the roof chair. More preferably, the frame members are joined to the table along its three sides, the table preferably being rectangular. This avoids the need for the chair parts to rest on the connectors, which can lead to the unstable part of the roof chair during manufacture and to displace the connectors from their desired locations before being pressed.

4

It is preferable that the frame members are retractable during use of the press heads to a position where the frame members do not protrude above the top surface of the table.

In a preferred embodiment, the frame members are removably attached to a table. 5

In a preferred embodiment of the invention, the holding means is placed directly or indirectly on a table to hold at least one piece of wood relative to the table during use of the press head. Preferably, the holding means are retractable during use of the press head to a point where the holding means do not protrude above the top surface 10 of the table. Further, it is preferred that the retaining means comprise at least one pneumatically actuated cylinder fastener arranged to press against the corresponding wood member to hold said wood member. Ideally, the holding means is mounted on the frame members which are located on the table.

The invention also provides a device for joining a plurality of wood members comprising a fixed clamping member, a table movable relative to the clamping member and means for introducing at least one connector between the clamping member and the table, characterized in that the table and / or clamping member comprises magnetic holding means to hold in place during table movement. Preferably, the holding means 20 comprise electromagnets placed inside or on the table. . and / or clamping member. The means for introducing at least one connector between the clamping member and the table are preferably arranged to divide the connectors between them in pairs. More preferably, the connectors comprise pairs of nail plates arranged such that the nails of each plate are connected to the nails of the other plate. As the table is moved away from the clamping member 25, one pair of the second connector is held over the board and the clamping member until the wood members are joined.

The invention also provides a method of joining wooden members together using the apparatus described above, comprising the steps of: (a) moving a table to a joint receiving position with respect to a fixed press member; (B) introducing a pair of nail plate connectors into the space between the table and the clamping member; (c) activating electromagnets placed inside or on the table and in the clamping member to hold one connector against the table and one connector against the clamping member; (d) moving the table and its corresponding connector away from the clamping member and the other corresponding connector to the retracted position; (E) introducing the joining wood members between the table and the clamping member; (f) moving the table toward the clamping portion such that the clamps held against the table and the clamping portion are clamped onto the wooden portions; (G) deactivating the electromagnets to release the wood members from the device and moving the table away from the press member; and (h) removing wooden parts from the device.

20

Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

Fig. 1 is a schematic representation of a device according to a first embodiment of the invention; 25

Fig. 2 is a schematic representation of a device according to a second embodiment of the invention. . O;

Fig. 3 is a schematic perspective view of a press head forming part of the device of Figs. 1 and 2;

Figures 4a, 4b, 4c and 4d are schematic views showing the operation of the press head 6 of Figure 3;

Fig. 5 is a schematic sectional view of a fastening device used in any one of Figures 1-4; 5

Figure 6 is a schematic sectional view of an alternative fastening device used in the device of Figures 1-4;

Fig. 7 is a plan view of a table forming part of a press head with frame members 10 mounted on three sides thereof;

Figure 8 is a schematic view of the pneumatic fixture used in the device of Figures 1-4; Fig. 9a is a schematic sectional view of a frame for attaching the Fig. 7 to the table; Figure 9b is a schematic front view of a portion of the frame of Figure 9a; and

Figures 10a-10d are diagrammatic views of a device for joining wooden portions including a device 20 for automatically feeding connectors to a press head.

The device shown in Figure 1 comprises a transverse support structure 2 and a transverse rail 4 parallel to the support structure 2. A plurality of longitudinal support structures 6 are arranged such that one end 6a of each support structure 6 is supported on the rail 4 and 25 moves along it. The opposite end 6b of each support structure 6 is supported on a wheel carriage (not shown) or other suitable support means which allows each support structure to move along the rail 4.

A plurality of press heads 8 are mounted on support structures 2.6. The transverse support structure 2 30 supports a plurality of clamping heads, of which a total of eight are shown in Figure 1. Each longitudinal support structure 6 is shown to support two clamping ends 8 except for a central support structure 6 'which supports only one clamping head 7. However, each support structure 6 can support any compression purpose (usually between one and three). Further, the press heads can be removed from the support structures 6 so that any support structure 6 can be added to or removed from the support structures for any particular structural requirement.

Each clamping head 8 disposed in the longitudinal support structures 6 is pivotable about an axis 10 located substantially in the middle of one edge of the clamping head (see Figure 7). The press heads, which are disposed in the transverse support structures 2, need not be rotatable, but may be if desired. Each press head 8 further slides along the respective support structure 2, 6 10 to change its position along it. The actuators are used to effect the sliding movement but are not shown for clarity. The actuators (not shown) are also used to move the support structures 6 along the rails 4.

The center of the transverse support structure 2 is designated as datum 12. This datum 15 may be attached to any suitable position in the overall geometry of the device, or, indeed, externally if desired. It is not necessary to attach the datum as shown in Fig. 1, but it is convenient to attach the datum to a specific location along the transverse support beam 2. Fig. 1 also shows the X axis and the Y axis for ease of explanation of the device shown below. The X and Y axes intersect at zero, and the X axis is transverse to the support structure 2 and the Y axis is parallel to the longitudinal support structures 6.

The device of the invention also includes a control device (not shown) which operates to drive actuators and thereby position the press heads 8 conveniently to produce a certain shape of the roof lattice. The position of all junctions at the desired roof chair relative to the datum is fed to the control device. The control device then determines, by means of monitoring and reference devices (not shown), the difference between the actual position of each press head 8 and its desired position to produce the desired roof chair. The actuator then activates the actuator to change the position and position of each compression head 8 in response to an error value between the actual position of the compression head 8 and its desired position. A drive means is arranged to move the press heads 8 which are located on a transverse support structure 2 along the support structure 2 δ in the direction of arrow 14 to their desired positions; to drive the support structures 6 in the direction of arrow 16 to the ends of the pressing 8 which their correct "X axis" places of datum; and to move the press heads 8 mounted on the support structures 6 in the direction of arrow 18 each purustuspään 8 from the right "Y-axis 5" to obtain a slot 12 with respect to the zero point. Once the guide means has received the desired positions of each press head, each press head 8 can then be moved by the guide means to its desired position. The clamping heads can be moved in pairs, groups, or all together, which reduces the installation time required to produce a particular roof grille. The guide means is also capable of rotating the press heads 8 around their axes 10 to position the press heads 8 in the direction of the roof lattice-forming parts. Once all the clamping heads are correctly positioned, they can be held in place by the automatic brake system (not shown).

For safety reasons, a light and / or siren system (not shown) can be used to reduce the risk of accident or injury to 15 people near the controller.

•; The red lights are arranged to light or blink when the press heads 8 are moving or in operation. Horns and sirens are also played. The automatic stop and turn system is also used to reduce the risk of accidents. A pointer (not shown) is provided at each clamping head 8 to indicate when the clamping head 8 is in the required position. A red light indicates the wrong position, a yellow light indicates that the error is within certain limits, and a green light indicates that the press head is correctly positioned. This allows for manual positioning of the press heads if necessary, for example when the actuators are not working for some reason.

Figure 2 illustrates an alternative arrangement according to the invention, similar to that shown in Figure 1 but lacking a transverse support structure. The only mounted support structures are longitudinal 6. As described above, the support structures 6 move along the rail 4. The zero point 12 is disposed at the intersection of the rail 4 and the central support structure 6 ', which structure 6' may be fixed to the rail 4 if desired. The X and Y axes are also disposed to run parallel and perpendicular to the rail 4 and through the datum 12, respectively. As in the device of Fig. 1, the datum can in fact be located at any of the 9 appropriate positions relative to the guide.

The press heads 8 are mounted on the support structures 6 with a sufficient number of at least one press head 8 positioned at each junction of the roof chair to be manufactured. The ends 8 of the compression-5 are positioned near the rail 4 to handle the junctions which are located at the base of the roof chair. Alternatively, the roof chair could be made "upside down"; i. the bottom tendon parallel to the rail 4 but adjacent to the opposite ends of the support structures 6 relative to those mounted on the rail.

This embodiment is even more versatile than the apparatus described above and facilitates the manufacture of roof chairs having base tendons that are angled or which contain non-parallel parts. It is conceivable that this type of device requires a large number of support structures 6 which would be required by the device of Figure 1 to accommodate the number of junctions that are usually required along the bottom tension.

15

Both embodiments of Figures 1 and 2 use identical press heads 8. Each press head 8 is substantially as shown in Figures 3 and 4. Figure 3 shows the press head in its operating mode. The clamping head 8 consists of a table 20 and a carriage 22. The carriage 22 may be moved between a retracted position (shown in Figure 20 4a) and an operating position (shown in Figure 3 and 4c). Suitable mechanical devices for moving the carriage 22 relative to the table 20 are well known and will not be described herein.

Frame 24 (shown in broken lines in Figures 3 and 4) is connected to table 20. Frame 25 itself and the connecting means are described below. The purpose of the frame 24 is to allow space between the upper surface 26 of the table 20 and the lower surface of the deck chair portion 28 which is disposed on the press head 8 during the manufacturing process.

The manufacturing process will now be explained.

30

When the press heads 8 are correctly positioned by the control means, the parts of the roof chair can be located on the device shown in Figs. This includes positioning portions of the roof chair 28 10 across the frames 24 of each press head 8 and holding them in place by means of wooden pneumatic clips and stops (explained below). The connector 30 is disposed on the upper surface 26 of the table in the space between the table 20 and the portion 28 of the roof chair. Auxiliary connector 32 is disposed on the upper surface of the roof chair portion 28. The user then gives a 5 signal through the control means to initiate the compression step and the warning sirens are triggered and the lights are on. The carriage 22 is initially positioned in a retracted position adjacent to the table 20 with the top surface 34 of the carriage head 36 substantially in alignment with the top surface 26 of the table. The carriage 22 is then moved upwards as shown in Figure 4b and then transversely with the carriage end 36 directly above the table 20 10. The end 36 of the carriage is also above the roof member 28 and the two connecting members 30, 32. The final step of the crimping operation is to raise the table 20 relative to the carriage 22 to compress the terminals 30, 3.2 with sufficient force to the roof member portion 28. The crimping motion is automatically stopped when sufficient force has been applied for a predetermined time. The lifting mechanism by which the table 20 is raised is preferably hydraulically actuated 15 and is controlled by the same control device used to position the press heads 8. In the inverse of the steps just explained, carriage 22 returns • <. in its retracted position next to table 20, and the pneumatic wood clips are automatically released to facilitate rapid removal of the roof chair.

20

Each press head 8 is operated in the same manner. If all press heads 8 are used to make a particular roof chair, then all press heads 8 are used simultaneously. However, if there is a plurality of press heads that are not needed in the manufacture of a particular roof chair, then the control device selects only the press heads that are needed and does not use those that are not needed.

The aforementioned frame 24 is necessary to allow the connector to be located under the roof chair part 28 without making the roof chair part unstable with respect to the device. In some cases, it is necessary to locate the clamping heads 8 very close to one another, and it may be necessary to remove some or all of the frame surrounding any particular table 20. For any table or group of tables, a sufficient number of frames will be required to properly support the timber to be joined. To achieve this, a fastening device such as that shown in Fig. 5 is used. The device consists of a body 40 with a slidably disposed cylindrical member 42 which supports a protruding member 44. The protruding member 44 supports bayonet connectors 46 which are lockable by is formed in the side walls of table 20. The spring 50 of the disc 5 is disposed between the end wall of the body 40 and the adjacent surface of the cylindrical portion 42, and the spring 50 pushes the protruding portion 44 into the retracted position. The cylindrical portion 42 is held in the body by a handle portion 52 that is pivotally secured to the cylindrical portion 42; the handle portion 52 rests against a disk-shaped portion 54 which is firmly secured by a ring connector to the body 40. The frame 24 is non-removable 10 mounted on a projecting portion 44 between the body and bayonet connectors 46. The mounting device and the frame 24 are therefore indistinguishable.

To secure the frame 24 to the table 20, the protruding portion 44 and the bayonet connector 46 are inserted into the lug 48 of the table 20 to bring the frame 24 into contact with the table 20. The handle 52 is then rotated such that the bayonet connectors 46 engage. grooves 48 in the cam surface. As the bayonet connectors 46 move along the cam grooves 48, the projecting portion 44 is forced into the extended position against the force of the spring 50.

The movement involved is actually very small. This type of clamping device can be used to provide high clamping force quickly without the risk of damaging the clamping device, or attachment parts, by over-tightening. The frame 24 can be easily and quickly removed from the table, if desired, by simply turning the handle 52 in the opposite direction to the attachment, followed by removing the protruding portion 44 from the cam groove 48.

Fig. 6 shows a modification of the connector shown in Fig. 5, which is adapted to be attached to a frame 24 such that the body 40 can act as a retaining part to assist in positioning the wooden part on the table. The connector itself is apparently identical to that shown in Fig. 5, but has a slightly longer protruding portion 44 fitted with a fastening portion 60 having internal cam grooves 62. Bayonet connectors 46 are provided at the ends of these cam grooves 30 62. The fastener 60 is rectangular, even if any non-circular shape is suitable.

12

The engagement of the clamping device in response is as follows: The protruding portion 44 and the clamping portion 60 are introduced into a notch 64 extending along a suitable frame 24 by one of the keyways 66 at both ends of the groove 64 (see Figure 7). The stop is then pushed along the notch 64 with the frame portion 24 between the fastening portion 60 and the body 40.

5 When the desired point has been reached, the handle 52 is rotated to cause the bayonet connectors 46 and the mounting member 60 to rotate. After a certain number of turns, the securing member 60 is against the frame 24 due to the non-circular shape of the securing member. Further rotation of the handle 52 causes the bayonet connectors 46 to move along cam 62, thereby forcing the projecting portion 44 into the extended position against the action of the spring 50. 10 A high clamping force is thus obtained between the body 40 and the clamping member 60 without excessive effort and without the risk of over-tightening. The response is thus precisely and easily positioned in the frame 24 and can be relocated accurately and easily if necessary.

The connector described above with reference to Figures 5 and 6 is extremely versatile. For example, the connector may be adapted to receive pneumatic gripping responses: to assist in positioning and engaging the wooden members with respect to the table.

Ideally, the pneumatic cylinder stops, as shown in Fig. 8, can be attached to the upper surface of the stub shown in Fig. 6 so that the pneumatic stops can be easily placed anywhere on the table. At least two pneumatic retaining means are disposed on the table of the device shown in Figures 1-4, which are disposed along at least one side of the table and mounted in a suitable frame. Fixed stops may also be mounted on the frame members to effect contact of the wooden members against which the pneumatic retaining means may compress the wooden members. The pneumatic gripping paths 25 are controlled by the above-described control device such that, when all of the clamping heads are correctly positioned and the wood members are positioned within the guide device, the pneumatic gripping responses can then be activated to grip the wooden members in place during the pressing operation.

In order to obtain an effective clamping operation, the tables must be able to clamp the lower connector 30 to the underside of the wooden parts at the clamping end. Frame members which support the wooden members and also the stops and the retaining means should therefore be retractable to a point where they do not obstruct the pressing operation. This can be achieved by using 13 retractable frames as shown in Figures 9a and 9b. These figures show a frame 24 having two parts; upper portion 24a and lower portion 24b. The lower portion 24b is removably connected to table 20 by at least one connector shown in Figure 5 and described above. The upper portion 24a of the frame 24 is connected to the lower portion 24b by a bolt 70 passing through a circular opening in the lower portion 24b but through an elongated notch 72 in the upper portion 24a. The retaining bolt 74 is disposed between the upper portion 24a and the lower portion 24b with a helical spring 76 disposed along it. The action of the spring 76 pushes the upper part 24a away from the lower part 24b so that the bolt 70 is retained at the lower end of the notch 72. The thrust of the spring 76 is sufficient to hold the upper part 24a of the frame member 24 in the position 10 shown in Fig. 9a, even when the wood member is supported thereon. Only when compression occurs and the table 20 is forced toward the end of the carriage (see FIG. 3), is the top portion 24a forced down so that the top portion 24a retracts below the top surface 78 of the table 20.

The apparatus described above can be improved by using an automatic feeder 15 for feeding the connectors directly to the clamping heads. The automatic feeder is explained; - underneath, in combination with a joining device for wooden parts.

The device shown in Figures 10a-10d comprises a press head having a movable table 100 and a fixed press member 102. The table may be moved vertically towards and away from the press member 20 102 as shown by arrow 104. The device also comprises a storage 106, where nail plate pairs or other suitable connectors 108 are stacked ready for feeding the press head. The storage 106 terminates at its lower end in a supply tunnel 110 through which a pair of terminals 108 can be pushed by a rod 112. Each of the tables 100 and the clamping ends 102 includes electromagnets (not shown) that permit clamps 108 to hold against the table and clamping head 100,102

The operation of the device will now be explained.

Initially, the table 100 is moved upwardly toward the clamping portion 102 to the connector receiving position 30 as shown in Figure 10a. The distance between the table 100 and the clamping portion 102 is approximately the width of the pair of connectors 108 or slightly greater. Then the push rod 112 along the lower terminal pair of the feed tunnel 110 in the direction of arrow 114, until the connectors 14, 108 are in the table 100 and the pressing portion 102 of the slot. Then, the rod 112 is pulled back to its original position in the direction of arrow 116 to permit connectors 108 additional pair of drop by gravity to the point that previously held the pair of terminals, which is now located between the table 100 and the pressing member 102 (see Figure 5 10c). The electromagnets are now activated by pulling the connectors 108 between the table 100 and the clamping portion 102. The connectors, which are in the form of nail plates and which are initially disposed with their respective nails in relation to each other, are thus securely held in the position shown in Fig. 10c. The table 100 may then be moved away from the clamping portion 102, resulting in a disconnection of the clips 108 which are then held firmly against the upper surface of the table 100 and the lower surface 102 of the clamping portion, as shown in Fig. 10d.

The device can now be used to interconnect the wood members by bringing the corresponding wood members between the table 100 and the clamping member 102 in the required position and clamping the connectors 15 to the wooden members by moving the table 100 upwardly against the clamping member 102. Then. the electromagnets are deactivated to release the connectors from the table Ϊ00 and the clamping member 102, and then the table 100 may be moved away from the clamping member 102 to permit removal of the wood members.

It is conceivable that the table and clamp portion of the device described above can be made permanently magnetic, if desired. In addition, the connectors can be of any type and need not be nail plates. It is preferable that the warning mechanism is connected to the device to indicate when the supply of connector pairs is decreasing. Safety devices such as guards and warning signals that operate during use reduce the number of accidents and injuries caused by clamping the connectors onto wooden parts. The table is preferably moved by a hydraulic press, but could alternatively be moved by any suitable means.

This type of automatic feeder can be applied to devices other than the roof chair manufacturing device shown in Figures 1-4 and described above. Various embodiments and uses will be apparent to those skilled in the art.

Claims (19)

Apparatus for the manufacture of a roof chair comprising a plurality of press heads (8) arranged in a single plane and movable in the plane about a zero point (12), each of the press heads (8) is fixed to a machine-driven device and to a control device for controlling the machine-driven device and for automatically determining the desired position of each head (8) with respect to the zero point (12) in such a way that each head (8) automatically can be driven to the desired position, and wherein each press head (8) comprises a table 10 (20) and a carriage (22), each carriage (22) including a carriage end (36) such that when the carriage (22) is in position In the position of use, the table (20) can be lifted towards the carriage end (36) for performing a pressing operation on which hoist roof parts (28) and coupling pieces (30,32) arranged between the table (20) and the carriage end (36). characterized in that each carriage (22) is t and the carriage end 15 (36) of each carriage (22) is slidable between a retracted position where the upper surface (34) of the carriage end (36) is in alignment with the upper surface (26) of the table: - (20) or below it, and a position of use, wherein the lower surface of the carriage (36) is above the upper surface (26) of the table (20). 2. Device according to claim 1, characterized in that the control device is computer controlled. Device according to Claim 1 or 2, characterized in that each press head (8) is rotatable about a shaft (10) relative to the plane. 25 4. Device according to which as claimed in claims 1 to 3, characterized in that the press heads (8) are connected to the control device for automatic operation of the tables (20) and the carriages (22) for pressing the coupling pieces (30, 32) into the roof. chair parts. 30 Device according to claim 4, characterized in that the tables (20) and the carriages (22) can be operated simultaneously. 19 Device according to claim 4 or 5, characterized in that the tables (20) and the carriage area (22) can be selectively driven. 7. Apparatus as claimed in any of the preceding claims, characterized in that it further comprises an automatic feeding device for automatic feeding of couplings (108) to the press heads (8). Pressing head for use in a device for manufacturing a roof chair, comprising a table (20) and a carriage (22) comprising a carriage end (36) such that when the carriage (22) is in the operating position, the table (20) can be lifted towards the carriage end (36) for performing a pressing operation on those hoisting roof parts (28) and coupling pieces (30,32) arranged between the table (20) and press head (36), characterized therein. that in one position the upper surface (34) of the carriage end (36) is in line with the upper surface (26) of the table (20) or below it, and in the position of use the lower surface of the carriage end (36) is above the upper surface (26) of the table (20), the carriage end being slidable between the position of use and said one position, the latter position being a retracted position. Pressing head according to claim 8, characterized in that the carriage (22) in the retracted position is adjacent to the table (20) and the upper surfaces * 'of the carriage end (36) and the table (20) are substantially in the same pane. Pressing head according to claim 8 or 9, characterized in that fastening means are arranged directly or indirectly on the table (20) for holding at least one wooden part (28) in place with respect to the table (20) using the press head (8). . Pressing head according to claim 10, characterized in that the retaining means are retractable using the press head (8) at a position below the plane of the upper surface of the wooden part (28) or the parts. 20 Pressing head according to claim 10 or 11, characterized in that the retaining means comprise at least one pneumatically operating cylinder clamp which is arranged to press against a corresponding wooden part (28) for holding said wooden part in place. 5 Pressing head as claimed in claims 8 to 12, characterized in that frame members (24) are connected to the table (20) along at least one side thereof to allow placement of couplings (30) between the upper surface (26). of the table (20) and the roof chair parts (28) used to form a roof chair, the coupling pieces (30) being pressed into the roof chair parts (28) using the press head (8). Pressing head according to claim 13, characterized in that the frame parts (24) are retractable using the press head (8) in a position where the frame parts (24) do not protrude above the upper surface (26) of the table (20). • · * f 9 9 Device according to which as claimed in claims 10 to 12 and either of claims 13 and 14, characterized in that the fastening means are mounted on the frame parts (24). 20 16. Press head as claimed in claims 13 to 15, characterized in that the frame parts (24) are detachably connected to the table (20). Pressing head as claimed in claims 8 to 16, characterized in that the table (20) and the carriage (22) comprise magnetic means for holding coupling pieces (108) therebetween between the feeding of coupling pieces to the press head and the use thereof. . Pressing head according to claim 17, characterized in that the magnetic devices are electromagnets. 19. Apparatus for the manufacture of a roof chair according to which the hoist of claims 21 1 to 7, characterized in that the press heads (8) are the press heads according to the hoist of claims 8-18. • r • <- «