METHOD FOR THE MANUFACTURE OF A GRATE

Abstract: The invention relates to a method for the manufacture of a grate comprising longitudinal bars and cross bars involving the following steps: a) feeding at least two parallel oriented longitudinal bars through in the longitudinal direction, the sides of the bars facing each other being provided with an internal recess, of which the height of the opening in the side wall is less than the internal height of the recess inside the bar; b) inserting a longitudinally extending deformable and curable material between the longitudinal bars; c) at least once performing the following steps (c1 and c2): c1) inserting a portion of the deformable material into the recess of the first longitudinal bar, and c2) inserting a following portion of the deformable material into the recess of an adjacent second longitudinal bar such that between said longitudinal bars there is an intermediate portion of the deformable material; d) at least partially curing the deformable material in order to form a cross bar between the longitudinal bars.

Description: Method for the manufacture of a grate The present invention relates to a method for the manufacture of a grate. The invention relates more particularly to a method for the continuous manufacture of composite fibre-reinforced plastics grates comprising longitudinal bars and cross bars. The invention also relates to grates manufactured by this method and to an apparatus for carrying out such a method. In practice it is generally known that grates can be manufactured by interconnecting longitudinal bars through cross bars. Said cross bars are connected as separate parts with adjacent longitudinal bars. The final result is a grate of a desired dimension. Because of the method of manufacture it is generally not possible to make such a grate in any length that may be desired. According to another method of manufacture, openings are provided at regular intervals and aligned with adjacent longitudinal bars through which cross bars are fed which are subsequently connected to each individual longitudinal bar. This is also a laborious method, by which it is not possible to manufacture the longitudinal bars in any length that may be desired. It is the object of the invention to provide an improved method with which it is possible to manufacture grates in every desired length in one single production process. Another object of the invention is to provide a method by which it is possible to manufacture grates in a continuous process. To this end the invention provides a method for the manufacture of a grate comprising longitudinal bars and cross bars involving the following steps: a) feeding at least two parallel oriented longitudinal bars through in the longitudinal direction, the sides of the bars facing each other being provided with an internal recess, of which the height of the opening in the side wall is less than the internal height of the recess inside the bar; b) inserting a longitudinally extending, deformable and curable material between the longitudinal bars; c) at least once performing the following steps cl) and c2) : cl) inserting a portion of the deformable material into the recess of the first longitudinal bar, and c2) inserting a following portion of the deformable material into the recess of an adjacent second longitudinal bar such that between said longitudinal bars there is an intermediate portion of the deformable material; d) at least partially curing the deformable material in order to form a cross bar between the longitudinal bars. By means of said method according to the invention the above mentioned objectives are achieved as well as other advantages, which will become apparent from the following description. The deformable and curable material may suitably be chosen from, for example: a bundle of fibres impregnated with an uncured curable material; a thermoplastic material; or a thermosetting material. Especially when a bundle of fibres impregnated with an uncured curable material is used, the result is a very firm and rigid construction. According to a preferred embodiment, the deformable and curable material is cured immediately after insertion into the recess of a longitudinal bar. This provides a firm link with the longitudinal bar immediately after the material has been inserted into the recess. According to another preferred embodiment, the bundle may be inserted into the recess by means of an apparatus, which simultaneously provides an initial or total cure of the deformable and curable material. According to a particular preferred embodiment this may be carried out by means of a gripper known in the art, for example in the pultrusion technique, which simultaneously aids the longitudinal bar's progression through the machine. When by means of the method according to the invention a grate is manufactured consisting of three or more longitudinal bars, an intermediate bar positioned between two adjacent longitudinal bars is preferably at its two sides facing away from each other and facing adjacent longitudinal bars provided with a recess, and during one of the steps cl) and c2) mentioned above, portions of deformable and curable material are substantially simultaneously inserted into the two recesses formed at both sides of the intermediate bar, and during the other step of cl) and c2) a subsequent portion of the material is inserted into the respective recess of the adjacent longitudinal bars, with an intermediate portion of the material being provided between the two longitudinal bars for the formation of the cross bars between the longitudinal bars. The result is a very rigid grate. The invention will now be elucidated with reference to the appended drawings. Figure 1, shows a top view of a grate according to the invention, also showing two means for inserting deformable material into the recess of a longitudinal bar. Figure 2 is a cross-sectional view of a longitudinal bar on the line of the arrows II-II of Figure 1. Figure 3, is a cross-sectional view of a grate according to Figure 1, on the line of the arrows III-III. Figure 4, shows a step during the manufacturing process of a grate according to the invention. Figure 5, shows a side view of a step during the manufacturing process of a grate according to the invention. In the ensuing description particular reference is made to a bundle of fibres impregnated with a curable material for the formation of the cross bars, but any other deformable and curable material, such as a thermoplastic or ther osetting material, may be applied equally well. Figure 1, shows a top view of a portion of a grate 1 according to the invention. The grate 1 comprises longitudinal bars 2 with cross bars 3 provided in-between. By making both the longitudinal bars 2 and the cross bars 3 from a sufficiently rigid material, and by suitably connecting these with each other, a solid grate 1 is obtained. Each longitudinal bar 2 of which a cross- sectional view is shown in Figure 2 on the line of the arrows II-II of Figure 1, comprises at its side 4 facing an adjacent longitudinal bar 2 a recess 5, the height h of the opening in the side wall 4 being less than the internal height H of the recess in the bar 2. In principle, the shape of the recess is not very important, however, it has to comply with the above-mentioned condition. An example of a specific recess shape is a dovetail section. The dotted line 6, shown in the longitudinal bar 2 as represented in Figure 1, indicates to where the recess 5 extends in the longitudinal bars. During the manufacture of the grates, each of the longitudinal bars 2 is conveyed parallel in their longitudinal direction and at a mutually substantially identical speed. During the conveyance of the longitudinal bars 2, a bundle of fibres 3, impregnated with an uncured curable material is guided between two adjacent longitudinal bars . The bundle is thus guided over a certain distance in a recess of one of two adjacent longitudinal bars 2. By means of pressers 7, two of which are shown at each side of the left-most longitudinal bar in Figure 1, the bundle is inserted into the recess 5 at both sides of the longitudinal bar 2. Figure 3, which is a cross-sectional view of a grate as shown in Figure 1 on the line of the arrows III-III, shows how the two pressers 7 guide the bundle 3 into the recesses 5. Advantageously, the pressers 7 simultaneously carry out a possibly partial curing of the curable impregnation material. In this manner a cross-link between the longitudinal bars is obtained. In a subsequent step, the portions of the cross bars 3 located between two adjacent longitudinal bars 2, may be cured. This may be accomplished with ultraviolet light if the curable material can be cured in such a manner, or by means of heat if the curable material is suitable for this method. Of course, any method of curing may be used as long as that method does not adversely affect the strength or the quality of the grate to be manufactured. When manufacturing a grate in a pultrusion device as known in the art, grippers that provide the conveyance of the longitudinal bars 2 through the machine, may simultaneously press the bundle of integrated fibres 3 into the recesses 5 and cure them. In that case, the pressers 7 represented in the Figures 1, 3 are replaced by grippers 7. Figure 4, shows a top view of an apparatus for carrying out the method according to the invention. To this end longitudinal bars 2, which at their sides directed towards adjacent longitudinal bars are provided with recesses 5, are conveyed in a direction of the arrow A. Between the adjacent longitudinal bars 2 feed guides 8,8' are provided, which are connected with control means 9 and 9', respectively. The side 10,10' of the feed guides 8,8' where a bundle of impregnated fibres exits, is directed towards the recess 5 of the longitudinal bars 2. As can be seen from the drawing, in their extreme position as depicted in the figure, the feed guides 8,8' extend slightly into the recesses 5. This results in that the insertable bundle being guided in this position into the recess. The feed guides 8,8' are rotatably attached around a point of rotation 11. The feed guides 8,8' will be controlled synchronously by means of the control means 9 and 9', respectively. When the control means 9 is in the bottom position, as shown in the figure, the control means 9' will be in the respective top position. When subsequently a cross bar is to be formed, the control means 9 will move to the top position, and the control means 9' will preferably simultaneously move to a bottom position. Because the feed guides 8,8' cannot instantly be moved from a first longitudinal bar to an adjacent longitudinal bar, a form of cross bar 3 will be obtained as shown in Figure 1. If each cross bar is to positioned rectangular with respect to the longitudinal bars, it is possible for the feed guides 8,8' during their movement between two adjacent longitudinal bars 2, as shown in Figure 4, to move together with the longitudinal bars in the direction of arrow A in order to thus obtain a rectangular link (not shown) . During the insertion of the bundle 3 into the recess 5, the feed guides may be moved counter to the direction of the arrow A to their starting position. This operation may be repeated at a subsequent movement between the adjacent longitudinal bars, thereby forming rectangular links . Figure 5 finally shows a side view of an apparatus for the manufacture of a grate according to the invention. To this purpose a longitudinal bar is formed in an apparatus 12 by means of a moulding die (not shown) , which leaves said apparatus at the side 13. The longitudinal bar is conveyed in the direction of the arrow A. Shortly after leaving the apparatus 12, a bundle of fibres 3 impregnated with a suitable curable material is fed by means of a feed guide 8 into a recess 5 of the longitudinal bar 2. By means of pressers (not shown) the bundle of fibres fed into the recess 5 will subsequently be pressed firmly into the recess 5 and cured, producing a firm link between the bundle 3 and the longitudinal bar 2. Preferably, a curing device (not shown) is provided downstream from the direction of conveyance A in which the cross bars 3 may be thoroughly cured. As already mentioned, this device may consist of a UV-light radiation device or a thermal oven. Any other suitable device may also be used, provided it is suitable for the curable impregnating agent. According to a further embodiment it is preferred for the longitudinal bars 2 to be manufactured in a moulding device immediately upstream from a device shown in Figure 4. In this case both the longitudinal bars 2 and the cross bars in-between can be formed quite easily in one operational run, so as to allow the manufacture of a grate of any desired dimension. Moreover, if sufficient feed guides 8,8' as well as moulding devices for moulding the longitudinal bars 2 are positioned next to one another, it is possible to form grates of widely varying widths by adjusting the number of moulding devices for the longitudinal bars 2 and the number of feed guides 8 that are actually active, accordingly. Instead of the shape represented in the figures, the longitudinal bars may also have, for example, a round cross section. It is further possible not to position the longitudinal bars in the same plane when manufacturing the grate but to position them such as to create a column with a circular cross section, which is formed in the longitudinal direction by longitudinal bars interconnected by cross bars. Figure 6 shows a schematic representation of a cross section of such an embodiment. Square or triangular columns as well as any other cross-sectional shape is possible. According to a particular preference, the longitudinal bars are adapted to that desired shape by adapting the cross section of the longitudinal bar to the shape to be produced. The longitudinal bars and the cross bars may be made of any desired material. For example, the longitudinal bars may be manufactured from a synthetic fibre- or fibre glass-reinforced plastic. The materials known in the art are eligible for this purpose. The plastic may, for example, be a polymerizable or a thermosetting material, but a thermoplastic that is still hard at a sufficiently high temperature and that sufficiently strengthens the grate is just as possible. Similarly, the cross bars may be made of any desired material, provided it is suitable to be used in the present method. A person skilled in the art is well able to choose a suitable material from the available materials. This material may, for example, be any polymerizable or thermosetting material that can be cured in a suitable manner. To this end, it must not negatively affect the grate according to the invention, e.g. it must not negatively affect the strength of the grate to be manufactured to the extent of rendering it unsuitable for use. It is also possible to use a thermoplastic material. However, it must still be hard at a sufficiently high temperature and provide the grate with sufficient rigidity. For reinforcement, any desired fibre material that is effective in combination with the respective curable material, may be added. For obtaining a tight connection, it is especial- ly preferred that the deformable and curable material is wedged into the recess of the longitudinal bars. It will be obvious that the invention is not limited to the above description and to the representations in the figures, which merely show preferred e bodi- ments of the invention. More particularly, the longitudinal bars 2 may be conveyed at any desired distance from one another, and the feed guides 8,8' may be formed in any way desired. The grates that may be manufactured according to the invention may be used, among other things, as grates for walking on. However, they may also be used as partitions, e.g. as fencing. The grates may also be used as reinforcement in concrete, or as packing in filter systems. Finally, the grates according to the invention may be used as any material that requires an open character. The strength and rigidity may be adapted as desired by a suitable choice of starting materials. After reading this specification and studying the drawings, other adaptations and alternative embodiments will be apparent to a person skilled in the art.

Claims: CLAIMS 1. A method for the manufacture of a grate comprising longitudinal bars and cross bars involving the following steps: a) feeding at least two parallel oriented longitudinal bars through in the longitudinal direction, the sides of the bars facing each other being provided with an internal recess, of which the height of the opening in the side wall is less than the internal height of the recess inside the bar; b) inserting a longitudinally extending deformable and curable material between the longitudinal bars; c) at least once performing the following steps cl) and c2) : cl) inserting a portion of the deformable material into the recess of the first longitudinal bar, and c2) inserting a following portion of the deformable material into the recess of an adjacent second longitudinal bar such that between said longitudinal bars there is an intermediate portion of the deformable material; d) at least partially curing the deformable material in order to form a cross bar between the longitudinal bars. 2. A method according to claim 1, in which the deformable material comprises a bundle of fibres impregnated with an uncured curable material. 3. A method according to claim 1, in which the deformable material comprises a thermoplastic material. 4. A method according to claim 1, in which the deformable material comprises a thermosetting material. 5. A method according to one of the claims 1-4, in which step d) is carried out after every step cl) and c2) . 6. A method according to one of the claims 1-4, in which step d) is carried out substantially simultaneously with every step cl) and c2) . 7. A method according to one of the claims 1-6, in which said material is wedged into said recess. 8. A method according to one of the claims 1-7, in which the recess comprises an internal dovetail section. 9. A method according to one of the claims 1-8, in which the insertion of a bundle into the recess of a longitudinal bar is carried out simultaneously as the bundle is being guided between the longitudinal bars. 10. A method according to one of the claims 1- 9, in which at least three longitudinal bars are being conveyed, in which an intermediate bar positioned between two adjacent longitudinal bars at its two sides facing away from each other and each facing an adjacent longitudinal bar is provided with a recess, and in which during one of the steps cl) and c2) , a portion of the deformable and curable material is substantially simultaneously inserted into the two recesses formed at both sides of the intermediate bar, and during the other step of cl) and c2) a subsequent portion of the material is inserted into the recess of the adjacent longitudinal bars, such that an intermediate portion of the material is provided between the two longitudinal bars for the formation of the cross bars between the longitudinal bars. 11. A grate comprising longitudinal bars and cross bars attached between them, the cross bars between two adjacent longitudinal bars being comprised substantially of a continuous bundle of material, and which may be manufactured by means of a method according to one of the preceding claims . 12. A grate comprising longitudinal bars and cross bars attached between them, the cross bars being positioned at an angle of approximately 90° in relation to the longitudinal bars. 13. An apparatus for carrying out a method according to one of the claims 1-10, comprising: means for feeding at least two parallel oriented longitudinal bars through in the longitudinal direction, the sides of the bars facing each other being provided with an internal recess; means for inserting a bundle of impregnated fibres; and means for inserting the bundle into the recess of a first longitudinal bars, and subsequently inserting the bundle into the recess of the adjacent longitudinal bar in order to form a cross bar between the longitudinal bars.

Inventors: KETEL JACOB HERMEN, KETEL, JACOB, HERMEN
Applicants: KETEL CONSULTING AGENTS B V, KETEL JACOB H, KETEL CONSULTING AGENTS B.V., KETEL, JACOB, HERMEN
Application year: 2001
Main classification: B29C67
IPC codes: E04C2