A tool (2, 102, 202) is constructed from a plurality of tessellating elements (34, 134, 234) to form a mandrel for the deposition of composite fibers.

This invention relates to tools for manufacturing, in particular it relates to tools suitable for use in filament winding processes.

Filament winding machines are well known in the art and essentially comprise a central tool in the form of as mandrel onto which as resin coated filament of a reinforcing fibre is wound to build up a layer of material. The material is then exposed to an elevated temperature for the resin to cure.

A problem with existing winding machines is that they must be constructed for each individual shape of workpiece which is to be produced. For low and medium part volumes this can result in significant tooling costs.

A further problem with such machines is that they can only be used at a uniform temperature (usually determined by the environmental conditions in which the mandrel is placed, e.g. an autoclave). It would be beneficial to achieve greater control over the tool, and hence the workpiece temperature.

It is an aim of the present invention to provide an improved tool for use in a filament winding operation.

According to a first aspect of the invention there is provided a. tool assembly for forming a product, the tool assembly comprising:a tool forming an endless loop in cross-section, the tool having a tool face and a control surface opposite the tool face,a plurality of independently controllable temperature control zones, each comprising heating and/or cooling means arranged to influence the temperature of the tool face.

Advantageously, the cure of material deposited onto the tool (e.g. a mandrel) can be easily controlled.

Preferably the heating and or cooling means are arranged to influence the temperature of the tool face by heating and/or cooling the control surface.

Preferably each heating and/or cooling means comprises a fluid chamber at least partially bounded by the control surface. Alternatively, heating means may be provided in the form of heating mats, e.g. electrical mats, or fluid based heating/cooling mats.

Preferably the heating and/or cooling means comprises a fluid outlet into the fluid chamber. This may be, for example, and inline air heater whose heating element can be switched off to provide cooling (by introduction of air at ambient temperature).

Preferably the fluid outlet is directed towards the control surface.

The tool may be unitary. Alternatively the tool comprises a plurality of radially mounted tool elements that substantially tessellate to form a continuous tool surface.

According to a second aspect of the invention there is provided a tool for forming a product, the tool comprising: a plurality of radially mounted tool elements that substantially tessellate to form a continuous tool surface.

Advantageously, the provision of the plurality of individual elements allows reconfiguration into different shapes.

The provision of a plurality of elements also facilitates the use of individual element control to dynamically control and vary the characteristics (e.g. temperature) of the surface.

Preferably the tool surface forms an endless loop in cross section, allowing use as a mandrel for the winding of filament materials used to form a workpiece.

Preferably the tool is mounted for rotation about a pivot axis. This allows a filament to be wound onto the tool to form a workpiece.

The tool surface may be radially outwardly facing, or radially inwardly facing. The tool may be supported by a support structure, supporting the tool element proximate its periphery. Preferably the support structure comprises a plurality of support members contacting discrete points around the periphery of the tool element.

The support structure may comprise a plate structure defining a volume at least partially bounded by a surface of the tool element. This allows fluid temperature control of each tool element. Preferably the volume comprises a fluid inlet and a fluid outlet. Preferably the tool comprises a plurality of tool element hubs upon which the tool elements are mounted, the tool element hubs being axially aligned on, or stacked along, the pivot axis. Alternatively the tool may comprise a single cylindrical tool element hub extending along the pivot axis.

The tool may have clamping means for axially clamping at least one of the tool element hubs and or the tool elements, from either axial end of the tool. An end bolster may be provided at either axial end of the tool. The clamping means are arranged to force the bolsters towards one another thereby damping said one of the tool element hubs and the tool elements between said bolsters.

In one preferred embodiment each tool hub has a plurality of spokes extending therefrom, each tool element mounted on a spoke. The tool elements may be radially adjustable in relation to the tool element hub. Preferably a central pivot bar is provided and extends along the pivot axis. The tool element hubs are mounted on the pivot bar. The central pivot bar and said tool element hubs can have corresponding location features thereon to prevent rotation of said tool element hubs relative to the pivot axis, for example keys with associated keyways or splines. Alternatively the central pivot bar may comprise a flat in cross section, or may be polygonal in cross section. In this manner rotation of the pivot, axis causes rotation of the tool surface.

The tool elements are preferably substantially rectangular in cross section. In one preferred arrangement the tool elements are orientated such that, in the clamped position. the sides of the cross section are substantially at 45 degrees to the pivot axis.

Each element may comprise an elongate tool pin, which can be tapered along its length. At least some of the tool elements may have heating and/or cooling means associated therewith to locally heat or cool the tool surface and/or a heating and/or cooling means adjacent but spaced from the tool surface and surrounding at least a part of the tool surface. Preferably the tool comprises temperature sensors for detecting the temperature of the tool surface. The individual tool elements may be welded to one another at the tool surface. Optionally the tool surface has had a finishing operation applied to it, such as a cutting or grinding operation. Means may be provided for feeding at least one filament of product material onto the tool surface to form a product. The means for feeding at least one filament of product material may be provided on a carriage that moves parallel to the pivot axis of the tool. The means for feeding may also rotate relative to the tool, allowing the tool to be stationary. This may be beneficial for larger tools where a significant amount of services need to be installed (e.g., heating, cooling, sensing services).

According to a third aspect of the invention there is provided a method of manufacturing a product comprising the steps of:providing a tool forming an endless loop in cross-section, the tool having a tool face and a control surface opposite the tool face,depositing a material onto the tool face to form the product,independently controlling a plurality of temperature control zones, each comprising heating and/or cooling means arranged to influence the temperature of the tool face.

According to a fourth aspect of the invention there is provided a method of manufacturing a product comprising the steps of:assembling a plurality of tessellating tool elements to form a continuous surface,depositing a material onto the continuous surface to form the product.

Preferably the continuous surface forms an endless loop in cross section, and in which the continuous surface is rotated about an axis passing through the endless loop. Preferably the method further comprises the step of heating the continuous surface to cure the material.

Referring toFIG. 1a tool2is shown which comprises a plurality of tool elements4that tessellate to form a continuous tool surface. The tool surface is substantially cylindrical in shape and is arranged about a central pivot axis “A”-“A”, about which the tool2rotates. In use a filament, for example a glass, carbon, or other fibre filament, surrounded by a resin can be wound onto the outwardly facing tool surface formed by the tessellating tool elements4as the tool2rotates. The fibre filaments all become joined to one another as the resin surrounding them comes into contact with the resin of adjacent turns of the fibre elements and cures, thereby forming a product.

The tool elements4are each mounted upon a tool element hub6by means of a spoke8. The tool element hubs each contain a plurality of radial spokes extending therefrom terminating in a tool element4thereby forming a wheel-like section10of the tool2.

A plurality of the wheel-like sections10are arranged adjacent one another along the tool axis “A”-“A” so as to form the continuous tool surface. Although shown aligned so as to form a regular array with tool elements on adjacent tool element hubs aligned with one another it will be appreciated that adjacent tool element hubs may be offset from one another by a fraction of a tool element, e.g. by half of a tool element, so that elements on adjacent tool element hubs are not aligned with one another in the direction of the tool axis. This increases the strength of the tool.

The tool element hubs6are provided with interlocking features, omitted for clarity, so as to prevent the rotational movement of one wheel-like tool section10relative to the next. In this manner the array of wheel like sections10is connected.

The tool element hubs6are arranged on a central pivot bar (16,FIG. 2) such that rotation of the central pivot bar causes the continuous tool surface to rotate about the axis “A”-“A”. The external surface of the pivot bar and the internal surface of the tool element hubs6may be keyed so that the rotational movement of the pivot bar translates into the tool element hubs6, and therefore the tool elements4causing the continuous tool surface to rotate. Alternatively, to give the same effect, the pivot bar may be polygonal in cross section and the interior of the tool element hubs may be correspondingly shaped.

Referring now toFIG. 2an alternative embodiment of the tool2is shown. In the arrangement shown inFIG. 2the tool elements4are rotated 45° compared to those shown inFIG. 1so that the sides of the tool element4are at an angle of approximately 45° to the pivot axis “A”-“A”. In other respects the tool2has the same construction as shown inFIG. 1.

The tool2is further provided with a clamping means which comprises an end bolster12at either end of the continuous tool surface. The end bolsters12have a contoured inner surface14abutting the tool elements4so as to maintain them in their required angular orientation.

The central pivot bar16is provided with a thread at either end and clamps are tightened on the threaded ends of the pivot bar16so as to apply pressure, via the end bolsters12, on the array of tool elements4. It will be noted that the bolsters12also apply an axially compressive clamping force to the hubs6to keep them in position.

As will be appreciated, other clamping methods may be used to apply axial pressure from both ends on the tool surface.

Referring now toFIG. 3a cross-section through a tool element4is shown. The tool elements4are substantially rectangular in cross-section (in the horizontal plane perpendicular to the page) and are tapered along their length to be wider at their radial outer surfaces.

Each tool element4has a sacrificial area of material20at its outer end. The pins4are adjustable inwards and outwards (i.e. radially) from the spokes8to form the desired shape of the tool surface.

Once the approximate tool surface shape is formed a finishing cut may be applied over the outwardly facing tool surface thereby removing part of the sacrificial layer20and ensuring that a continuous tool surface devoid of any inconsistencies between one tool element4and an adjacent tool element4are avoided.

At least some of the tool elements4may be provided with a tool element heating and/or cooling means by which at least some of the individual tool elements can be heated or cooled. The heating/cooling means may, as shown, include a fluid path30through the tool element4through which a heat transfer fluid can be carried, the heat transfer fluid having a temperature higher than that of the tool element if it is required to heat the tool element and a temperature lower than that of the tool element if it is required to cool the tool element. In one embodiment the spokes8may also have a central heating and/or cooling fluid channel32therein to carry the heat transfer fluid to the individual tool element. Separate channels may be provided, not shown, to carry the heat transfer fluid exiting the pins away. Alternatively, the exhausted transfer fluid could simply vent into the central area of the tool2and be extracted therefrom.

Referring now toFIG. 4a moulding apparatus22is shown comprising three main parts: the tool2, an outer heater24and a means26for feeding a filament28of product material onto the tool2.

In operation as the tool2rotates about its central axis the filament28of product material is fed onto the tool surface by feeding means26. Feeding means26comprises a feeder carriage that can move in a direction parallel to the pivot axis “A”-“A” of the tool. As the carriage moves parallel to the pivot axis of the tool the filament28is wound onto the tool surface to substantially cover it. The speed of movement of the carriage relative to the speed of rotation of the tool will determine the angle at which the filament28is wound upon the tool surface. The angle of winding may increase or decrease by changing the speed at which the carriage moves. In this way the angular alignment of the filament forming the product can be changed so as to modify the structural properties of the finished product.

The outer heater24can be used to heat or cool the product formed on the tool surface, and forms a heating element that substantially surrounds the tool surface. Sensors, not shown, may be embedded within the tool elements4or alternatively may be integrated into the product as it is made. Electrical signals from the temperature sensors can be fed back to a controller to control the temperature of one or both of the tool elements themselves and the heater24so as to closely regulate the temperature of the work piece upon the tool surface. In this way the parts can be cured on the tool without the need for locating a tool or placing a tool, into, for example, an autoclave.

Referring now toFIG. 5, the tool2of the invention is shown in an open state. When the end bolsters12are undamped the tool may separate axially along its pivot axis “A”-“A” so that the individual wheel-like sections10of the tool can he separated from one another. When the sections10are separated from one another the tool elements4can be adjusted on their spokes so as to move them radially towards, or away from, the centre of the tool element hubs. When the tool2is in its open position, as shown, the wheel-like sections of tool elements can be isolated so that they have space on either side thereof. When in this position, as, in the 45° arrangement, only the apexes of the tool elements touch one another. The elements can be rotated so as to change their position.

Although, as stated above, the tooling of this invention is primarily used to make cylindrical or almost cylindrical shapes, the actual shape of the tool surface can be modified by moving the individual tool pins in and out so that a non-symmetrical, non-uniform or otherwise customized shape can be produced. Once the tool elements4have been adjusted to their desired lengths the tool can be closed and the bolsters12can reapply the clamping force to the tool. Once the tool is clamped the lines joining the tool elements4may be welded so as to ensure a continuous metal tool surface. Furthermore, the outer surface of the tool is preferably machined with a sculpting and/or finishing cut so as to remove any discrepancies in the surface.

Once the finishing cut has been applied the tool surface will then be at its required dimensions.

Optionally, in a tool where at least some of the tooling pins are heated the finishing cut may be applied when the tool is at a specific predetermined temperature, for example 70°, and thereafter is allowed to cool down. In this example, when the tool is desired to be used it is initially heated up to the temperature at which the finishing cut was applied so that the shape of the work piece is as fully expected and so that potential sizing problems resulting from the thermal expansion/contraction of the tool material is avoided.

There is a further advantage that, where the moulding is commenced at a slightly elevated temperature, once the moulding process is complete and the resin is set, the tool surface can be cooled so as to make it contract and shrink away from the product, thereby enabling its simple release.

Referring toFIG. 6an alternative tool element detail is shown. As the tool elements have a curved outer surface34and, as for ease of machining it is simpler to manufacture a tool element with a flat inner end surface36, the material thickness of the end of the tool element is greater towards its centre and less towards its edges. If even heating is applied to the inside surface36of the end of the tool element the outer edges of the outside surface34of the tool element will rise in temperature more quickly that the centre of the tool element due to their lower thermal mass. The element therefore has a heating fluid inlet38that is comprises an opening40that directs heating and/or cooling fluid at the centre of the flat inner end surface36. As the heating/cooling fluid impinges on the tool element at the thickest point of the inner end surface more heat is transferred into the area with the higher thermal mass. In this way a substantially constant heating of the outer surface34of the end of the tool element, and therefore the tool surface, can be achieved. The position of the opening40in relation to the inner end surface36of the tool element, in particular its spacing therefrom, the size of the opening and the velocity of the heating/cooling, fluid can be varied depending on the particular geometries of the tool element so as to achieve substantially constant cooling.

The element ofFIG. 6has walls44which extend from the inside surface36to a spoke42defining the opening40. A chamber is thereby formed bounded in part by the inside surface36.

The walls14are non load bearing but are supported by a number of support members (not shown) extending from the spoke42to the inside surface36. The support members contact the element at its edges (specifically each of its four comers) and transfer the axial load from the tool surface34to the spoke42. The provision of a support structure which supports the tool element proximate its periphery is advantageous because it allows even contact of the hearing fluid with the inside surface36whilst providing a stable platform to react the incident loads from the winding operation.

In particular the frame-like structure comprising a series of panels or plates defining the fluid space, being supported by a plurality of support members, is lightweight thus reducing the moment of inertia of the complete tool (and therefore making it easier to rotate compared to, say, a tool made up from the elements ofFIG. 3).

Turning toFIG. 7, a side view of a tool102is shown being similar to the tool2. The tool102comprises a plurality of tool elements134which are similar to the elements34each having connectors144similar to connectors14. Each element134is connected to a spoke142which is in trim connected to a hub106as discussed in the embodiments described above.

As shown inFIG. 7, the tool elements134do not have a sacrificial portion, and instead are made relatively thin in order for a heating/cooling system (not shown) at the inner surface of the elements to easily influence the surface temperature of the tool element with minimum delay. The outer surface of the tool102is thereby made as responsive as possible to heating and cooling. This provides the user with improved control over the curing behaviour of the material wound onto the tool.

It will be noted that only two of the elements134inFIG. 7are shown with the connectors144and spokes142, but it is understood that each element134has a corresponding arrangement.

According to a further embodiment of the invention as shown inFIG. 8, a tool202has a tool surface203which faces radially inwards. The filament is deposited on the radially inner surface of tool elements234. Each tool element has a connector244disposed on a radially outer surface having a spoke242extending to a support ring250. Each of the support rings acts as an “outer hub” and may be compressed in place by an appropriate clamping arrangement.

It is within the abilities of the notional skilled person to construct a mechanism for rotating the tool202about a central axis A whilst depositing filament on the inner surface. It is also possible in this embodiment (or any of the preceding embodiments) for a filament deposition head to be moved (rotated about axis A) with a stationary tool.

A further embodiment may provide a unitary tool component similar in shape to the assembly of the elements134. The unitary tool component has a number of connectors defined on the inner face, and each connector is connected to a spoke which is in turn connected to a hub as discussed in the embodiments described above.

Each connector defines a fluid chamber at least partially bounded by the inner surface of the unitary tool component. Therefore the component is divided into a number of temperature control zones. By varying the fluid temperature in each of the chambers the temperature of the corresponding (outer) tool face can be varied to influence the properties of the material deposited on the tool.

The structure of the connectors is substantially similar to the connector14shown inFIG. 6, that is fluid at a predetermined temperature is injected towards the inner control surface (opposite the tool face) to heat and/or cool the tool face as desired.

In a further embodiment, a tool may be provided having a tool face which faces radially inwards. The filament is deposited on the radially inner surface of unitary tool component. A plurality of connectors are disposed on a radially outer surface having a spoke extending to a support ring. Each of the support rings acts as an “outer hub” and may be compressed in place by an appropriate clamping arrangement.

Each connector defines a fluid chamber which can be used to influence the temperature of the outer control surface and hence the inner tool face.

It is also envisaged that the tools of the above embodiments may be used for the deposition of alternative forms of materials, e.g. prepregs, fibre mats etc.

As will be appreciated by the skilled person, where applicable the various features described in relation to one embodiment may equally be applied to the other embodiment.

Amendments to the design of the invention will be apparent to the skilled person and are within the scope of the invention as defined by the claims.