Patent Description:
Known systems for forming deformable materials such as sheet metal into a desired profile include roll forming processes. These involve passing the sheets through a sequence of roll sets each further deforming the sheet beyond the profile achieved at the previous roll set. The disadvantages of roll forming include redundant deformation resulting from nonuniform strain paths as the strip passes each roll set. That leads to high residual stresses which result in product defects such as edge wave, flare, twist, etc. Another disadvantage of roll forming is that the distance between the first roll set and the last roll set is relatively large. Consequently the space needed to house a roll forming assembly is substantial particularly when forming complex profiles. Known systems using multiple roll sets also suffer from significant difficulties associated with initial alignment. A further disadvantage of roll forming is that tooling design is related to the designer's experience. "Trial and error" plays a dominate role in tooling design and alignment and for a new complex profile tooling design, this means the development time is unpredictable. Additionally a large amount of material can be wasted during the period of tooling design and alignment, which contributes to the cost of tooling development.

An apparatus for forming the profile of deformable materials according to the preamble of claim <NUM> is e.g. known from <CIT>.

The present invention seeks to provide a method and apparatus of forming a profile of a deformable sheet material which provides an alternative for overcoming some of the disadvantages of the prior art.

Accordingly, in one aspect the present invention provides an apparatus for forming the profile of deformable materials according to claim <NUM>.

In a further aspect this invention provides a method of forming the profile of deformable materials according to claim <NUM>.

The die elements can be of any suitable shape required to form the desired profile. Where a moving forming surface is used it is preferably formed from an elastic material such as a suitable plastics or rubber material. The moving forming surface can be made up of a series of discrete blocks each corresponding to one or more die elements or an endless band.

Preferably, the dies in each set are arranged for synchronized movement with respect to the dies in the or each other set.

A number of sequential sets of the apparatus can be used to replace the traditional roll sets in a roll forming system. Alternatively, the forming process may partially use roll sets and partly the apparatus of the present invention. The apparatus of the present invention allows the use of a lesser number of distinct forming stations, each of which provide a continuous deformation equivalent to that performed by a subset of the roll sets of the prior art process. The present invention thus provides a hybrid system having a number of distinct forming stages in which continuous forming of the profile takes place. In this regard a large amount of the design processes, for example "flower" diagrams, used in roll forming are applicable to the design of the system. The methods and apparatus of this invention represent significant improvements over conventional roll forming and will result in significantly lower levels of redundant plastic energy and residual stresses in the profile and hence less product defects. Additionally one set of the apparatus of this invention can be used in place of a number of roll sets thus reducing the overall footprint compared to the conventional roll forming approach. The apparatus of this invention additionally have less slippage between dies and material in forming direction, some products having high profile and narrow and deep groves that are difficult to be roll-formed can be produced using this method.

The apparatus of the invention also provides greater control of the material being formed particularly in controlling the stretching in forming direction. This results in the desired profile being formed without the need for straightening as is often required in prior art roll forming processes.

Another advantage of the present invention is a significant reduction in the need for initial alignment required in the prior art processes. The present invention also allows the profile to be changed without undertaking a realignment process. In accordance with the present invention the die sets can be changed, for example, by changing a chain of dies without concern about alignment. This considerably reduces downtime of the apparatus and improves productivity.

The present invention also provides for significantly simpler and improved safety arrangements. Firstly, there are less "pinch points" in the apparatus which need to be shielded against accidental access. Secondly the configuration, being compact, readily lends itself to being enclosed.

The auxiliary operations used in conventional roll forming are also applicable in the method of the present invention in a similar manner. In the case of post forming welding, for example, the present invention provides a more gentle and smooth way to enclose the gap to be welded.

According to the invention at least one of the forming portions of the tracks is formed as a large radius curve. This results in the forming process being comparable to a roll forming process using rolls of very large radius. In accordance with the invention, each of the opposed forming portions can be formed as a large curvature radius. The radius may be the same or different depending upon the application. In some applications one of the radii may be infinite (zero curvature), that is, the path is substantially flat. The curvature centres of radii may be set on respectively opposite sides of the forming portions or may be on the same side of one of the forming portions and different radii used to achieve a convergence between the tracks in the forming portion. In other configurations, the forming portion may be made up of a variable radius. That is, the radius is not constant throughout the forming portion.

The present invention also has application to forming the profile of deformable tubular sections. In particular it is suitable for forming metal tubes of various cross section form tube with a circular cross section.

The dies can be of any desired shape. In one form of the invention flat dies are used in opposed pairs to form a rectangular hollow section. Alternatively, the dies can be respectively concave, convex, male or female in various configurations to provide the desired determined side profile. For example, opposed female and male die profiles may be used to produce a profile with a longitudinally extending groove on one surface. A pair of convex dies could be used to provide an elliptical profile. Other configurations of dies can be used to produce a wide variety of profiles.

The sets of dies can be driven substantially at the same rate. However, a use of appropriate dies and adjusting the phase of movement of the respective sets of dies can be used to control the deformation of the material to be formed in order to get a better quality of product.

In accordance with the invention the pitch between each die in the forming portion of the track is small compared to the radius of the track, the pitch-radius ratio being over <NUM>:<NUM>. That is the maximum gap between the adjacent dies is only <NUM>/500th of the height or even smaller. The pitch height is also proportional to the pitch-radius ratio of the pitch.

The die elements can be driven so as to draw a section to be formed through the forming portion. In the case of die elements configured in a chain arrangement this can be achieved by drive sprockets operating on the chain. In an alternative, separate driving rolls or other suitable mechanisms can be employed to either drive the sections through the apparatus or pull the section through the apparatus.

The apparatus can produce a tubular section of constant profile in a continuous process. The profile of the sets of dies can correspond to a section having a varying profile. This is a batch process in which lengths of the section having for example tapered profile or formed with ribs or grooves or even profiles varying in shape along the length of the section can be produced.

Embodiments of the invention will now be described, by way of example only with reference to the accompanying drawings.

Referring to the <FIG> a schematic configuration of the apparatus for forming the profile of deformable sheet material is shown. The apparatus <NUM> includes two track frames <NUM>, <NUM> that mount respective sets <NUM>, <NUM> of die elements <NUM>. The die elements <NUM> have any suitable profile determined by the profile desired to be formed. In the illustrated embodiment respective male and female die sets suitable for forming a channel or a top-hat profile are shown. Each die element <NUM> is mounted on a chain link <NUM> respectively connected to the adjacent chain link <NUM> by a pin <NUM> in a conventional manner to form a roller chain. The track frames <NUM>, <NUM> define respective endless paths or tracks around which the links <NUM> travel. Each of the paths has a forming portion <NUM>, <NUM> in which the die elements <NUM> of each set are opposed to define a forming space <NUM>. Other than in the forming portion, it is not necessary for the chain links <NUM> to contact the track frame. The forming portions <NUM>, <NUM> are configured so that the dimensions of the space <NUM> between the forming portions reduce along its length. In this way transverse forces are simultaneously applied to a section passing through the forming portion. The die elements <NUM> move with the material synchronisely and the distance between the sets of elements <NUM> gradually reduces.

<FIG> shows an embodiment of the invention for forming the profile of a deformable hollow section from a pre-formed tubular section. The same reference numerals as used in relation to <FIG> have been used to identify corresponding integers. The apparatus <NUM> includes four track frame elements <NUM>, 2a, <NUM>, 3a arranged in opposed pairs. Each track frame element mounts respective sets <NUM>, 4a, <NUM>, 5a of die elements <NUM>. The die elements <NUM> have any suitable profile determined by the profile desired to be formed in the material. Each die element <NUM> is mounted on a chain link <NUM> respectively connected to the adjacent chain link <NUM> by a pin <NUM> in a conventional manner to form a roller chain. The track frames <NUM>, 2a, <NUM>, 3a define respective endless paths around which the links <NUM> travel. Each of the paths has a forming portion <NUM>, 9a, <NUM>, 10a in which the die elements <NUM> associated with each pair of track frames are opposed to define a forming space <NUM>. The forming portions <NUM>, 9a, <NUM>, 10a are configured so that the dimensions of the space <NUM> between the forming portions reduce along its length. In this way transverse forces are simultaneously applied to a section passing through the forming portion. This can be visualised as the section to be formed being forced through a progressively smaller aperture as it progresses through the forming portion.

<FIG> show three different configurations of die elements <NUM> profiles at respective locations along the formed portion <NUM>. <FIG> shows a configuration applicable to the embodiment shown in <FIG> for forming the profile of a deformable sheet material m. The die sets are made up of respective male and female opposed dies. As the dies move along the forming portions <NUM>, <NUM> the distance between them decreases to reduce the forming space in the direction from right to left. This progressively forms the material to a desired profile.

<FIG> show a configuration of die sets used in the embodiment generally described in relation to <FIG>. In <FIG> four die sets arranged in opposed pairs are used to form a circular section h into a square section as the dies move together along the forming space. <FIG> shows an arrangement in which three sets of dies displaced at <NUM>° to form a circular section h to a triangular profile.

<FIG> shows an alternative to the apparatus shown in <FIG>. In this configuration one lower set <NUM> of die elements <NUM> have the profile of the final die profile. Three upper sets <NUM> of progressive shaped complimentary die elements upon track frames <NUM> are sequentially positioned. In the same manner as described in relation to <FIG> this provides forming portions <NUM>, <NUM> at three spaced apart locations. In the same way as described above the forming portions of the tracks are configured to progressively reduce the dimensions to the space <NUM> between the dies. The material m to be formed progressively proceeds from right to left as shown in the drawings and is formed to the desired profile by the sequential operation of the die sets.

<FIG> show some exemplary ways in which the apparatus can operate. In <FIG> the system is provided with driving sprockets which drive the two sets of die elements in phase so as to draw a section through the forming portion. In <FIG> a separate set of driving rolls is provided to propel this section through the forming portion. <FIG> shows a similar configuration in which a separate set of driving rolls are used to push a section through the forming portion.

<FIG> show some of the possible configurations of the track in the forming portion of the apparatus. In <FIG> each of the opposed forming portions has a large radius and the centre of the radii are respectively on the opposite sides of the forming space. <FIG> shows configuration in which one of the forming portions has a large radius and another has an infinite radius or in other words is flat. <FIG> shows a configuration in which the centres of the radii are both on one side of the forming space and large radii are used for the respective forming portions to provide converging paths between the opposed dies. <FIG> shows a configuration in which the radii of the forming portion is not constant to provide a converging track between the opposed dies.

Figure <NUM>(a) schematically shows the relationship between the maximum gap between adjacent dies on the chain and the radius of the portion of the track. In accordance with the invention the pitch to radius ratio is large and preferably over <NUM>:<NUM>. As shown in the diagram the maximum gap between the adjacent dies is approximately the product of the height and the length divided by the radius of the track. The distance s the chord height between cord c extending through the mid point of the upper die surface and the adjacent die corners is a measure of the relative angle between the die blocks. It is approximately equal to the square of the length of each die divided by quad the radius. It will be apparent that larger gaps may occur in portions of the track other than the forming portion without in any way affecting the operation of the apparatus.

<FIG> schematically shows some of the profiles that can be formed from a circular section using the apparatus of this invention. <FIG> shows a triangular profile. <FIG> shows a rectangular profile and <FIG> a stepped profile. It will be apparent however that appropriate selection of die shapes can produce a wide range of profiles.

<FIG> shows a modified form of the die sets suitable for use in the invention as described in <FIG>. As shown in the drawings the die elements <NUM> are not uniform but form a taper. By arranging these dies in sections on corresponding parts of the respective tracks a profile having a longitudinal taper or other desired non linear form can be formed.

Embodiments of this invention can be in the form of standalone equipment lined before or after a forming process such as roll forming to process auxiliary operations such as blanking, punching, dooming, coining, shearing and the like. Because the forming dies' velocity is so close the strip's velocity, the auxiliary operation is processed continuously without the interference with the strip that occurs in the rotary punching or dooming.

<FIG> schematically show die configurations for performing punching and dooming respectively. As in the other embodiments opposed dies corresponding shaped to perform the operation more through a forming function in which the dimension of the forming space reduce along the length of the forming portion.

In the embodiments discussed above, one part of the die elements (for example, male die elements), are rigid to ensure the profile to be formed but the another can be elastically deformable such as using polyurethane. The deformable die elements can provide adequate compressing force to the material to be formed and/or compensate the variation of material properties and thickness.

Embodiments of the invention can also be used to form a part having limited length that requires multiple passes to form. As schematically shown in <FIG> the forming dies for each pass (for example, <NUM> passes as shown) are arranged in one set and the motions of the sets are synchronised. The blank is fed into the former a corresponding number of times to achieve the final profile in one machine. One advantage of this arrangement is to save the capital and space, and another is this type former can be placed beside an assembly line for multi component product and after forming a workpart on-site, the part can be assembled to the product directly.

Claim 1:
An apparatus (<NUM>) for forming the profile of deformable materials, said apparatus (<NUM>) including:
opposed track frames (<NUM>, <NUM>) that mount respective sets (<NUM>, <NUM>) of die elements (<NUM>), the die elements (<NUM>) of said sets (<NUM>, <NUM>) being respectively arranged to travel along corresponding endless paths;
said paths each including a forming portion (<NUM>, <NUM>) in which die elements (<NUM>) of each set (<NUM>, <NUM>) are opposed to define a forming space (<NUM>) therebetween,
wherein a distance between the forming portion (<NUM>, <NUM>) of each said path decreases along the length of the forming portion (<NUM>, <NUM>) in the direction in which material travels so that the dimensions of the forming space (<NUM>) between the forming portions (<NUM>, <NUM>) reduce along the length of the forming portion (<NUM>, <NUM>) to simultaneously apply lateral forces to material progressing through the forming portion (<NUM>, <NUM>) to shape said material to a determined profile, wherein at least one of the forming portions (<NUM>, <NUM>) of the paths is formed as a large radius curve,
wherein the pitch between each die element (<NUM>) in the forming portion (<NUM>, <NUM>) of the path is small compared to the radius of the path, characterised in that
the ratio of the pitch between adjacent die elements (<NUM>) in the forming portion of the path and the radius of the path is over <NUM>:<NUM>.