Introduction

The present invention relates to a processing line for vacuum bag frame assemblies for the manufacturing of fibre-reinforced composite panels. More specifically the invention relates to a processing line for one or more vacuum bag frame assemblies, where the processing line has a main frame and a pair of furnace half chambers. The main frame supports the vacuum bag frame assemblies, and the furnace half chambers envelopes the composite lay-ups of the vacuum bag frame assemblies. Further the furnace half chambers can move relative the vacuum bag frame assemblies.

Background art

In the art of manufacturing fibre-reinforced composite panels a mould is used for supporting a composite lay-up comprising a removable slip film, a layer of reinforcement fibres, another slip film, a removable breather cloth, and a unilaterally arranged vacuum bag having a seal against a flange on the mould. Resin may be injected under vacuum or integrated as dry thermoplastic fibres in the layer of reinforcement fibres, and the composite lay-up may be baked in an oven. If the mould is to be integrated as a part of the composite product, the mould to be integrated may be added a composite layer on one side at a time, which is time-consuming and provides a non-homogenous rim around the integrated mould. An alternative is to envelope the integrated mould wrapped in the composite lay-up, evacuate it in an integral vacuum bag and baking it in batches in a furnace, one at a time. Using an integral vacuum bag around each product lay-up may be inefficient and may incur shrinking and displacement of fibres near the edges of the integrated mould when the bag is pulled towards the table during vacuum pumping.

From background art it is known that the heating process may be conducted in a large furnace (100) and heated by an electrical heat element (101), as illustrated in Fig. 6, in which one or more vacuum bag frame assemblies (1) are arranged in a rack (110) and connected to a vacuum manifold (120) connected to a vacuum pump. The heating and hold temperature must be above a required melting temperature for the thermoplastic component of the composite lay-up if using a thermoplastic process. The temperature will normally be above 100 degrees Celsius depending on the thermoplastic properties, and the entire vacuum bag system should tolerate a temperature of about 300 degrees Celsius. If vacuum injection moulding and chemical curing is used, the vacuum bag assembly should work cold as well.

The entire vacuum bag frame assembly comprises, as a minimum, first and second rigid vacuum bag frames with first corresponding facing and second vacuum bags and a vacuum outlet from the entire vacuum bag assembly. A main purpose of the frames is for spanning the vacuum bag. Further, the frames comprise a valve or a connector to an external vacuum line as shown in Fig. 6. The vacuum bags are made in a highly flexible silicone material which may adapt to the shape of a variety of mould forms which may be integrated in the lay-up. The vacuum bags will then envelope and retain the composite lay-up. For several reasons the vacuum pump is arranged outside any furnace. The vacuum pump may work more efficiently when arranged outside the furnace both from a thermodynamic and a mechanical point of view. However, with the vacuum bag assembly placed inside the furnace and the vacuum pump arranged outside the furnace the vacuum line must pass through the thermally insulating wall of the furnace. During the heating process the vacuum must be maintained in the vacuum bags so the vacuum bag assembly must be connected to a vacuum line manifold inside the furnace. During the thermal cycling the gaskets in the vacuum bag frame assembly and the vacuum valves and vacuum connectors will thermally wear because the entire vacuum bag frame assembly is subject to the thermal cycle. Further, differential thermal expansion between the frame and the gaskets will contribute to the wear of the vacuum bag frame assembly and reduce the quality of the assembly both with respect to mechanical integrity and the ability of maintaining a sufficient vacuum.

Short summary of the invention

The invention is a processing line for one or more vacuum bag frame assemblies; In one embodiment the invention is a processing line for one or more vacuum bag frame assemblies where;

- the vacuum bag frame assemblies each comprises a first and a second vacuum bag frame spanning corresponding first and second opposite facing vacuum bags, with one or more fibre composite lay-ups arranged between said vacuum bags, each vacuum bag frame assembly having one or more apertures for allowing evacuation of a space formed between said first and second vacuum bags and said vacuum bag frames; and

- the processing line having a main frame and a pair of furnace half chambers, wherein said main frame is arranged for supporting said vacuum bag frame assemblies, and said furnace half chambers are arranged for enveloping one or more of said one or more composite lay-ups and further arranged for moving relative said vacuum bag frame assemblies.

In an embodiment of the invention the main frame of the processing line is generally straight linear and comprises;

- an entry section arranged for receiving one or more of said vacuum bag frame assemblies;

- a heating section comprising said furnace half chambers (91);

- an exit section arranged for removal of said vacuum bag frame assemblies (1) having passed said heating section.

The processing line according to the invention may be less costly to build and requires less energy than processing lines according to background art where racks for holding the vacuum bag frame assemblies and other equipment is placed inside a large furnace room and energy is wasted due to the heating of the entire furnace room and the racks and components inside the room.

According to the present invention a processing line is disclosed where only the lay-ups are heated and energy is not wasted to heat other components. Thus, the lay-up may reach the required curing temperature faster and cool down faster after curing, allowing a less costly process and faster throughput of the frame assemblies.

Another advantage is that the fastening of the vacuum line to the centre frame between the vacuum bags provides a mechanically more stable solution than connection of the vacuum line to one of the vacuum bags as seen from background art. The vacuum line may also be connected to the vacuum bag frame assembly during the manufacturing process, and not only during heating.

Further, the vacuum pump can be placed in the same room as the processing line since the furnace is heating only the lay-ups, as opposed to background art where the vacuum line had to be passed through the wall to the vacuum pump to keep it away from the heat.

The stable mechanical processing line guiding the vacuum bag frame assembly renders superfluous the use of clamps or other external devices for keeping the vacuum bag frames in place during the manufacturing process. Thus the time needed for preparations and the finishing process may be considerably reduced compared to manufacturing of composite lay-ups according to background art.

Short figure captions

The invention is illustrated in the accompanying drawing figures, wherein the figures shall not be construed as limiting to the invention.

Fig. 1 is a simplified section view of an embodiment of a processing line for vacuum bag frame assemblies for the manufacturing of fibre-reinforced composites according to the invention, showing the furnace movable relative the vacuum bag frame assembly

Fig. 2 is a side view of the processing line shown in Fig. 1 , showing an external elevation view of a complete and evacuated vacuum bag assembly in a processing line (8) according to the invention, with the outlines indicative of integral moulds with a composite lay-up.

Fig. 3a is an exploded section view of a vacuum bag frame assembly according to the invention, illustrated with a lay-up for a composite fibre-reinforced thermoplastic product including an integrated mould and textiles having antiballistic properties improved during the vacuum moulding process

Fig. 3b is a section view of the same vacuum bag frame assembly according to the invention in which the composite lay-up has been evacuated for air so as for the first and second vacuum bag to bilaterally drape and compress the lay-up to envelope the integrated mould.

Fig. 3c is a section view of a detail of the vacuum-pumped assembled vacuum bag assembly according to the invention, illustrating a section of the vacuum bag frames with the tubular centre frame stabilizing the vacuum bag frames.

Fig. 4 is a side elevation view of the tubular centre frame for the vacuum bag frames.

Fig. 5a is a side elevation view of either of the vacuum bag frames, as seen from the gasket-bearing side which shall encounter the centre frame. Fig. 5b is a section of an embodiment of the frame with the integrated vacuum bag and gasket ribs moulded onto the rigid frame.

Fig. 6 is a front elevation view of a furnace of the background art with an internal rack for vacuum bag assemblies. Such a furnace may use vacuum bag frames according to background art or advantageously novel vacuum bag frames described herein. The vacuum bag frames are connected by vacuum hoses to a vacuum manifold for connecting several vacuum bag assemblies to a common vacuum pump outside the furnace.

Fig. 7 is a perspective view of an embodiment of a processing line according to the invention for thermal processing of a series of vacuum bag frame assemblies for the manufacturing of fibre-reinforced composite panels.

Fig. 8a provides a right elevation view of the same embodiment of the processing line according to the invention, an opposite, left elevation view of the same is shown in Fig. 8b, and further an end view of the same is shown in Fig. 8c.

Embodiments of the invention

The invention will in the following be described referring to the attached figures and will describe a number of embodiments according to the invention

Referring firstly to Fig. 1 of the drawings in which is shown a simplified section view of a processing line (8) according to an embodiment of the invention. A vacuum bag frame assembly (1) is arranged within a main frame (79) and the furnace half chambers (91a, 91 b) envelope one or more of the fibre composite lay-ups (70). At least one of the furnace half chambers (91a, 91b) are arranged to be moveable relative the vacuum bag frame assemblies (1) to allow vacuum bag frame assemblies (1) to be inserted or removed from the processing line (8). In an embodiment of the invention the furnace half chambers (91a, 91b) envelopes only a subset of the composite lay-ups (70) of the vacuum bag frame assembly (1), and the furnace half chambers (91a, 91b) and the vacuum bag frame assembly (1) may move relative each other to move the furnace half chambers (91a, 91b) from a subset of the composite lay-ups (70) to the next. The furnace half chambers (91) may comprise symmetrical contact frames (93) arranged for bearing against opposite sides of the vacuum bags (30, 40) within an inner perimeter of the first and second vacuum bag frames (3,4) and for enveloping the one or more composite lay-ups.

In an embodiment of the invention the furnace half chambers are arranged for providing radiant heat from one or more electrical coils or windings comprised by the furnace half chambers. Radiant heat may also be provided by one or more Infrared transmitters comprised by the furnace half chambers as understood by a person skilled in the art. In Fig. 2 the section view from which the section A-A of Fig. 1 is made is seen from the side. It shows the top and bottom of the vacuum bag frames (3, 4) guided by the main frame (79). Further, one of the furnace half chambers (91 a or 91 b) is seen covering one of the lay-ups (70).

In an embodiment of the invention the vacuum bag frame assemblies (1) handled by the processing line (8) each comprises a first and a second vacuum bag frame (3, 4) spanning corresponding first and second opposite vacuum bags (30, 40), with one or more fibre composite lay-ups (70) arranged between the vacuum bags (30, 40), each vacuum bag frame assembly (1) having one or more apertures (23, 24) for allowing evacuation of a space formed between the first and second vacuum bags (30, 40) and the vacuum bag frames (3, 4). The processing line (8) has a main frame (79) and a pair of furnace half chambers (91), wherein the main frame (79) is arranged for supporting the vacuum bag frame assemblies (1), and the furnace half chambers (91) are arranged for enveloping one or more of the one or more composite lay-ups (70) and further arranged for moving relative the vacuum bag frame assemblies (1). In this embodiment of the invention the furnace half chambers (91) may be arranged to move laterally to enclose the subset of the fibre composite lay-ups (70) before heating and release the vacuum bag frame assemblies (1) after heating.

In an embodiment of the invention the vacuum bag frame assemblies (1) are fixed relative the main frame (79) during processing. In this embodiment the furnace half chambers (91a, 91b) are, in addition to the lateral movement, arranged for a longitudinal and/or vertical movement to allow processing of more than one subset of fibre composite lay-ups (70) by moving from one subset of the fibre composite lay-ups (70) to the next subset without moving the vacuum bag frame assembly (1). The furnace may also be arranged to be movable from one vacuum bag assembly to the next in line.

In an embodiment of the invention the vacuum bag frame assemblies (1) are movable relative the main frame (79) during processing in the processing line (8). In this embodiment the lateral movement of the furnace half chambers (91a, 91b) described above may be sufficient, provided that the furnace half chambers (91a, 91b) are able to envelope the composite lay-ups (70). Thus, in this embodiment of the invention the longitudinal position of the furnace half chambers may be fixed.

In Fig. 7 a perspective drawing of a processing line (8) for vacuum bags is shown. In this embodiment of the invention the main frame (79) being generally straight linear comprises;

- an entry section (89) arranged for receiving one or more of said vacuum bag frame assemblies (1);

- a heating section (90) comprising said furnace half chambers (91); - an exit section (99) arranged for removal of said vacuum bag frame assemblies (1) having passed through said heating section (90).

In an embodiment of the invention the un-evacuated or evacuated vacuum bag frame assembly (1) is initially arranged in the entry section (89) of the processing line (8). The vacuum bag frame assembly (1) is supported by the bottom sliding rail (85) and the top sliding rail (87), and further arranged for sliding from one section to the next supported by the sliding rails (85, 87).

Next, a vacuum pump is connected to the vacuum outlet (23), and the space formed between the vacuum bag frames (3, 4) is evacuated. This step may, in an embodiment of the invention, performed in or ahead of the entry section. However, it may also be performed in the heating section (90) or during the movement from the entry section (89) to the heating section (90). Once in the heating section (90), one or more of the fibre composite lay-ups (70) of the vacuum bag frame assembly (1) is enveloped by the furnace half chambers (91a, 91b). In an embodiment of the invention the furnace half chambers (91a, 91b) are moved from an open position relative said vacuum bag frames (3,4) to a closed position to envelope only the targeted area of the vacuum bag frames (3,4), i.e. one or more fibre composite lay-ups (70) and to approach or seal against the vacuum bag frames (3,4). In the closed position the vacuum bag frames (3, 4) are heated by the furnace half chambers to melt the thermoplastic component(s) of the composite lay-up.

In an embodiment of the invention the processing line (1) is provided with a cooling section (95) arranged subsequent to said heating section (89) and preceding said exit section (99) to cool the vacuum bag frame assembly (1) before it reaches the exit section. The cooling section may comprise fans arranged for directing a flow of air, water or any cooling media as known to a person skilled in the art towards one or more of the composite lay-ups (70).

Finally the vacuum bag frame assembly (1) reaches the exit section (99) where the final assembly is ready for removal from the processing line (8) Fig. 8 illustrates an embodiment of the invention where actuators (92) are arranged for moving the furnace half chambers (91), arranged in the heating section (90), laterally relative the processed vacuum bag frame assembly (1). Actuators (97) may also be arranged for moving the fan assembly (96) of the cooling section (95) laterally relative the processed vacuum bag frame assembly (1 ).

Additional processing equipment, for e.g. cutting, polishing and packaging as understood by a person skilled in the art may be part of the same process line.

In an embodiment of the invention the longitudinal main frame (79) of the processing line (1) comprises one or more longitudinal rails (85) extending from the entry section (89) to the exit section (99) for guiding the one or more vacuum bag assemblies (1) through the processing line.

The processing line may comprise one or more of the entry, heating, cooling, exit or additional sections described above, where the sections may be arranged along the processing line in sequence, or be arranged in the same physical location.

In an embodiment where the sections are arranged in the same physical location the furnace half chambers (91a, 91b) are arranged to move laterally in and out relative the combined entry section, heating section, and exit section to allow easy insertion and removal of the vacuum bag frame assemblies (1). In another embodiment of the invention where the sections are arranged in the same physical location the furnace half chambers (91a, 91b) are fixed relative the combined entry section, heating section and exit section and the production line (8) is arranged for insertion and removal of the vacuum bag frame assemblies (1) by entering or removing then into/from the processing line (8) without moving the furnace half chambers (91a, 91b).

In an embodiment of the invention the entry section (89) is arranged for receiving the vacuum bag frame assemblies (1) in a vertical position, and the furnace half chambers (91) are arranged horizontally moveable in the transverse direction relative to the longitudinal main frame (79) for engaging the outward facing surfaces of the vacuum bags (30, 40).

In an embodiment of the invention the furnace half chambers (91) comprises symmetrical contact frames (93) (See Fig. 1) arranged for bearing against opposite sides of the vacuum bags (30, 40) within an inner perimeter of the first and second vacuum bag frames (3,4) and for enveloping the one or more composite lay-ups. In an embodiment of the invention the longitudinal main frame (79) of the processing line (1) is arranged with a longitudinally extending free gap (86) as illustrated in Fig. 6 and Fig. 7 between a first and a second longitudinal guide rail (83, 84) connected to said main frame (79), the gap (86) allowing lateral passage of vacuum lines connected to said vacuum bag frames (1) during their passage from said entry section (89) to said exit section (99), so as for easing the maintenance of the vacuum during the processing of the composite lay-up.

In Fig. 7 a control box (100) is shown. The control box may be arranged for controlling the progress of the manufacturing process of the processing line (8). This may include controlling the movement from one section to the next, controlling the movement of the furnace half chambers (91) in one, two or three dimensions, controlling the heating of one or more thermoplastic components by the furnace half chambers (91) for melting or curing layers of the composite lay-ups (70).

In an embodiment the control box (100) controls the connection and disconnection of vacuum lines to the vacuum outlet (23) of the vacuum bag frame assemblies (1) and controlling the vacuum pressure during the manufacturing process.

In an embodiment of the invention the processing line is provided with a process control box (100) arranged for controlling the progress of the vacuum bag frame assemblies (1) from the entry section (89) to the exit section (99), and for controlling the movement and heating of the furnace half chambers (91).

Fig. 3a is an exploded section view of a vacuum bag frame assembly, illustrated with a lay-up for a composite fibre-reinforced thermoplastic product including an integrated mould and textiles, said textiles providing antiballistic properties. A vacuum bag frame assembly (1) according to the invention is made for use in the manufacturing of fibre- reinforced composite panels. The vacuum bag frame assembly (1) comprises the following main features: A rigid, tubular centre frame (2), a first, rigid vacuum bag frame (3) arranged for holding and spanning a perimeter of a first vacuum bag (30), and a similar and oppositely arranged second, rigid vacuum bag frame (4) arranged for spanning a perimeter of a corresponding second vacuum bag (40). The tubular centre frame (2) is provided with a vacuum inlet from the internal of the assembly and an outlet to a vacuum pump. The vacuum bag frame assembly (1) is arranged for holding a composite lay-up and an integrated mould, said mould preferably for being integrated in said moulded composite lay-up after vacuum baking, or for being removed from the moulded composite product after vacuum baking. A proposed lay-up of the composite to be vacuum-moulded will be described below.

The composite lay-up (70) illustrated in Fig. 3a and Fig. 3b is a so-called dry lay-up for making a composite product, and comprises the following components: - a first, removable breather cloth (32) for leading air from the lay-up to the vacuum apertures (24) of the central frame (2);

- a first disposable slip film (34) so as for releasing the baked lay-up from the enveloping vacuum bags (30, 40);

- a first, dry fibre layer (35) of one or more sheets of composite reinforcement and thermoplastic fibres;

- a first, optional adhesive film (36) for binding the fibre layer (35) to a subsequent integrated mould (50);

- the above-mentioned integrated mould (50);

- a second, optional, adhesive film (46) for binding the integrated mould (50) to a subsequent layer;

- a lay-up of fibres (60), possibly interfoliated with glue nets or thin binder films,

- a third, optional, adhesive film (47) for binding the fibres (60) to a subsequent layer,

- a second, dry fibre layer (45) of composite reinforcement and thermoplastic fibres,

- a second, disposable, slip film (44), and, - a second, optional, removable breather cloth (42).

The integrated mould (50) may in one embodiment be an antiballistic ceramic plate shaped to fit a body part. Likewise, the fibres (60) may be of an antiballistic type. With such a lay-up, an antiballistic panel is formed.

Fig. 3b is a section view of the same vacuum bag frame assembly where the composite lay-up has been evacuated so as for the first and second vacuum bag (30, 40) to bilaterally drape and compress the lay-up to envelope the integrated mould (50). Please notice that the first and second vacuum bags (30, 40) are free to follow and drape the edge of the mould and the fibre cloth lay-up, and also able to exert an edge-on pressure, better than a single one-sided vacuum bag is capable of laid against a static mould form. The central frame (2) and the vacuum bag frames (3, 4) are preferably, but not necessarily planar.

As is shown in Fig. 4, the rigid, tubular centre frame (2) has a first flange surface (21) and a second flange surface (22) at an opposite side of the centre frame relative to said first flange surface (21). Fig. 5a shows a first, rigid vacuum bag frame (3) arranged for holding and spanning a perimeter of a first vacuum bag (30). The first vacuum bag frame (3) has a first flange gasket (31) arranged for closing against said first flange surface (21) of the centre frame (2). Further, the vacuum bag frame assembly comprises a similar second, rigid vacuum bag frame (4) arranged for spanning a perimeter of a corresponding second vacuum bag (40). As for the first vacuum bag frame, the second vacuum bag frame (4) has a second flange gasket (41), please see Fig. 3a and Fig. 5a, arranged for closing against said second flange surface (22) of the centre frame (2).

As illustrated in Fig. 4, the rigid, tubular centre frame (2) is provided with a one or more vacuum inlets from the internal of the assembly and an outlet to a vacuum pump.

Specifically, a first, peripherally arranged vacuum outlet (23) is arranged external relative to said first and second flange gaskets (31 , 41) shown in Fig. 3, for connection to the vacuum pump. One or more second vacuum apertures (24) are directed internally relative to said first and second flange gaskets (31 , 41), arranged for evacuating air from a space formed between said first and second vacuum bags (30, 40) and said tubular centre frame (2).

In Fig. 3c the rigid tubular centre frame (2) illustrated further comprises a tubular, auxiliary centre frame (25) attached onto and preferably within an inner perimeter of the rigid tubular centre frame (2). The auxiliary frame (25) is made to be in vacuum communication via auxiliary evacuation apertures (27) with the surrounding centre frame (2). The auxiliary frame provided with said vacuum apertures (24) along the inner rim portion extending inwards between the vacuum bags when assembled and holding the composite lay-up.

The auxiliary centre frame (25) illustrated has a cross-section larger than the cross- section width of the centre frame (2), i.e. wider than a separation between said first and second flange surfaces (21 , 22). The auxiliary centre frame (25) has a generally triangular cross-section and is arranged for forming a shoulder (26) for positioning and holding said first and second rigid vacuum bag frames (3, 4) in place during an assembly process, and for preventing the gaskets (31 , 41) from being displaced during vacuum pumping and subsequent handling in the heating and cooling process.

The integrated mould (50) has a perimeter generally smaller than and fitting generally within the perimeter of said tubular centre frame (2). In an embodiment of the invention the vacuum bag frame assembly (1) may envelope an array of two, four, six or any number of separate integrated moulds (50), each carrying their lay-up to be vacuum moulded. Each mould (50) is arranged for being arranged flexibly held by and held between said first and second vacuum bags (30, 40). The integrated mould (50) may have a 3-D shape with a dimension extending out of the plane formed by the otherwise empty vacuum bags (30, 40), and may even provide some undercut, because undercut will not provide a significant problem as the vacuum bag material is highly flexible and easily removed from the final product. The integrated mould (50) should be a rigid piece of material having the desired base shape of the composite product to be formed. As mentioned above, the integrated mould (50) may form a base for forming and being draped by a lay-up of antiballistic fibres (60). Thus the integrated mould may have antiballistic properties in itself, such as one or more antiballistic ceramic tiles, or a plate of hardened steel or hardened aluminium, or a combination thereof. One of the important features of the vacuum bag frame assembly of the invention is that the vacuum bags are literally very flexible and may very closely drape even rather angled mould forms with significant fidelity. Using the vacuum bag frame assembly one may thus manufacture not only doubly curved antiballistic chest panels and back panels and shoulder plates, but also more complex shapes as antiballistic front upper chest/neck shields for personnel to be protected, and complexly formed antiballistic panels for following the shape of car body parts for cars to be antiballistically protected.

In an embodiment the invention is a method for processing a vacuum bag frame assembly (1) in a processing line (8) wherein the vacuum bag frame assembly (1) comprises a first and a second vacuum bag frame (3, 4) spanning corresponding first and second opposite vacuum bags (30, 40), with one or more fibre composite lay-ups (70) arranged between the vacuum bags (30, 40), each vacuum bag frame assembly (1) having one or more apertures (23, 24) for allowing evacuation of a space formed between the first and second vacuum bags (30, 40) and the vacuum bag frames (3, 4), comprising the following steps;

- connecting a vacuum line to the vacuum bag frame assembly (1) and evacuate the space between the first and second vacuum bag frame (3, 4) by applying pressure to the vacuum line,

- enveloping the vacuum bag frame assembly (1) with furnace half chambers (91) comprised by the vacuum line and heating one or more of the composite lay-ups (70),

- disconnecting the vacuum line from the vacuum bag frame assembly (1) and removing the vacuum bag frame assembly (1) from the processing line (8). In an embodiment of the invention the method for processing a vacuum bag frame assembly (1) in a processing line (8) as described above further comprises the steps of;

- entering the vacuum bag frame assembly (1) into an entry section (89), and

- cooling the vacuum bag frame assembly (1), in a cooling section.