Porous supports and vacuum hold down device using said supports

Abstract

The present invention relates to a porous support intended to be removably positioned on a top side of a perforated plate of a table of a vacuum hold down device, the perforated plate having a bottom side connected to a vacuum system for producing reduced pressure on the bottom side, wherein the porous support comprises a perforated tray provided on one side with outer reliefs and on the other side with a blade penetrable porous structure fixed thereon. The invention further relates to a vacuum hold down device comprising such a support. The invention also relates to a process for replacing a first porous support by a second porous support in such a device.

Claims

1. A vacuum hold down device comprising: a table comprising a perforated plate, the perforated plate having a bottom side connected to a vacuum system for producing reduced pressure on the bottom side, and a porous support removably positioned on a top side of the perforated plate of the table, wherein the porous support comprises a perforated tray and a blade penetrable porous structure, the perforated tray including a top side, a bottom side, and a plurality of traversing holes extending therebetween, the perforated tray further including side walls and a plurality of outer reliefs, the side walls extending upwardly from opposite ends of the top side of the perforated tray to form an integral, substantially rigid structure having a substantially U-shaped cross section, and the plurality of outer reliefs distributed on the bottom side of the tray and between the traversing holes, wherein the blade penetrable porous structure is fixed on the top side of the perforated tray between the side walls, wherein the outer reliefs create a space between the top side of the perforated plate of the table and the bottom side and side walls of the perforated tray, whereby an airflow generated by the reduced pressure of the vacuum system will pass through the blade penetrable porous structure, through the perforated tray, through the space, and through the perforated plate, and wherein the porous support as a unit is removable from and replaceable on the perforated plate.

2. The vacuum hold down device of claim 1, further comprising releasable fixing means for temporarily fixing the porous support to the top side of the perforated plate.

3. The vacuum hold down device of claim 1, further comprising a cutting device configured for cutting a sheet of workpiece material laid on the porous support and positioned on the top side of the perforated plate.

4. The vacuum hold down device of claim 3, wherein the cutting device is a blade and is supported by a movable carriage.

5. The vacuum hold down device of claim 4, wherein the movable carriage vertically moves the blade through a thickness of the blade penetrable porous structure, and at a lower extent of a vertical distance that the blade is movable, the blade does not contact the perforated tray.

6. The vacuum hold down device of claim 1, wherein the side walls of the perforated tray have a height which is greater than a thickness of the blade penetrable porous structure.

7. The vacuum hold down device of claim 6, wherein the side walls are spaced from of the table.

8. The vacuum hold down device of claim 1, further comprising a film of substantially air-impervious material positioned on a top side of the blade penetrable porous structure for covering an exposed surface of a sheet of workpiece material, wherein the film cooperates with the vacuum system connected to the bottom side of the perforated plate to apply a compacting force to the sheet of workpiece material.

9. The vacuum hold down device of claim 1, further comprising screws extending from the bottom side of the perforated tray and removably mounted in respective threaded holes provided in the top side of the perforated plate of the table to temporarily fix the porous support to the perforated plate.

10. The vacuum hold down device of claim 9, wherein the screws extending from the bottom side of the perforated tray are spaced apart from the outer reliefs along the bottom side of the perforated tray.

11. The vacuum hold down device of claim 10, wherein the screws extending from the bottom side of the perforated tray extend across the space between the top side of the perforated plate and the bottom side of the perforated tray.

12. The vacuum hold down device of claim 1, wherein a top side of the porous structure includes a porosity that allows air from the vacuum system to pass therethrough.

13. The vacuum hold down device of claim 1, wherein the outer reliefs have a substantially constant height.

14. The vacuum hold down device of claim 1, wherein opposite ends of the bottom side of the perforated tray beneath the side walls are not directly attached to the top side of the perforated plate of the table.

15. The vacuum hold down device of claim 1, wherein the porous structure is a foam plastic with open cells.

16. The vacuum hold down device of claim 15, wherein the foam plastic is a low density cellular polyethylene or polypropylene material.

17. The vacuum hold down device of claim 1, wherein the perforated tray including the outer reliefs and the side walls are metal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The porous support, vacuum hold down device and process of the invention will now be further described in reference to the following description and attached drawings in which:

(2) FIG. 1 is an exploded cross section view of an embodiment of a vacuum hold down device of the invention showing a porous support of the invention and a table,

(3) FIG. 2 is a cross section view of the vacuum hold down device of FIG. 1 with the porous support positioned on the perforated plate,

(4) FIG. 3 is a bottom perspective view of the tray of the porous support of the device of FIGS. 1 and 2,

(5) FIG. 4 is a perspective view of the porous support of the device of FIGS. 1 and 2,

(6) FIG. 5 is a cross section view of another embodiment of a porous support of the invention,

(7) FIG. 6 is a cross section view of a vacuum hold down device of the invention with the porous support of FIG. 5 positioned on the perforated plate,

(8) FIG. 7 is a cross section view of the device of FIG. 2 during the step of cutting of a sheet of workpiece material.

DETAILED DESCRIPTION OF EMBODIMENTS

(9) With reference to FIG. 1 is shown in cross section a vacuum hold down device 1 according to the invention, comprising a table 10 and a removably positionable porous support 20. As will appear from the description below and more particularly with further reference to FIG. 7, such a vacuum hold down device 1 may be used in the cutting of a sheet of workpiece material 100, in order to maintain the sheet of workpiece material in a spread configuration and in a fixed position during the cutting process. Anyway, irrespective of the fact that the vacuum hold down device 1 of the invention is illustrated in the present application with reference to a cutting process, it should be kept in mind that the vacuum hold down device of the invention may be used in any situation where it is desirable to maintain a sheet of workpiece material in a spread configuration and in a fixed position.

(10) The table 10 comprises a perforated plate 11 having a generally horizontally rectangular shape supported by four feet 12 (two only being visible on FIG. 1). The perforated plate 11 has a bottom side 11a and a top side 11b. The bottom side 11a is connected to a vacuum system 13. The vacuum system comprises a duct 13a linking a suitable vacuum source (not shown) to the bottom side 11a of the perforated plate 11. When the vacuum system 13 is switched on, reduced pressure is applied on the bottom side 11a of the perforated plate 11.

(11) The perforated plate 11 has a plurality of traversing holes 14 formed therein for passage of the airflow generated by the vacuum system 13 from the top side 11b of the plate 11 to its bottom side 11a. The perforated plate 11 is made from a material having mechanical properties allowing it to be used as a support for the porous support 20 and sheet of workpiece material 100 (see FIG. 7) intended to be laid on the porous support 20. The perforated plate 11 is for example formed of a metal. Examples of suitable metals for the perforated plate are aluminum, stainless steel and combinations thereof.

(12) Still with reference to FIG. 1, the porous support 20 comprises a perforated tray 21 and a blade penetrable porous structure 22 fixed thereon. The porous support 20 has globally a rectangular shape and is intended to be positioned on the perforated plate 11 and to serve as a supporting surface for the sheet of workpiece material 100 to be cut.

(13) The perforated tray 21 has a bottom side 21a and a top side 21b. FIG. 3 is a perspective view from the bottom of the perforated tray 21 of FIG. 1 on its own. As clearly shown on this Figure, the bottom side 21a of the perforated tray 21 is provided with a plurality of outer reliefs 23. As shown on FIG. 2, the outer reliefs 23 are configured so as to create a space 30 between the top side 11b of the perforated plate 11 of the table 10 and the tray 21, once the porous support 20 is positioned on the perforated plate 11, with the outer reliefs 23 facing the top side 11b of the perforated plate 11. Such space 30 allows the passage of the airflow generated by the vacuum system 13 from the porous support 20 to the perforated plate 11. The outer reliefs 23 may be distributed regularly or not regularly on the surface of the bottom side 21a of the tray 21, and they may show different heights, as long as they create the space mentioned above. Anyway, in embodiments, such as shown on FIG. 3, the outer reliefs 23 are distributed regularly on the surface of the bottom side 21a of the tray 21 and they show a substantially constant height.

(14) The perforated tray 21 further comprises a plurality of traversing holes 24 formed therein for passage of the airflow generated by the vacuum system 13 from the top side 21b of the tray 21 to its bottom side 21a. The perforated tray is made from a material allowing it to show sufficient mechanical properties for being used as a support for the porous structure 22 and sheet of workpiece material 100 intended to be laid on the porous support 20 on one hand, and to be light enough so as to be easily transportable on the other hand. The perforated tray 21 is for example formed of a metal. Examples of suitable metals for the perforated plate are aluminum, stainless steel, and combinations thereof.

(15) The outer reliefs 23 may be formed directly from the raw sheet of material forming the tray 21 and in such case are formed of the same material as the tray 21. In other embodiments, the outer reliefs may be formed of a material different than that of the tray and may be added to the bottom side of the tray by any appropriate fixing means, such as screwing, gluing, fusing, or welding.

(16) With reference to FIGS. 1, 2 and 4, the blade penetrable porous structure 22 is fixed on the top side of the tray 21. The top side 21b of the tray 21 is preferably smooth. However, in embodiments, the top side of the tray may be textured.

(17) The blade penetrable porous structure 22 can be easily cut by a cutting device 40 usually used for cutting sheets of workpiece material such as textile. The cutting device 40 may for example be an elongated blade 41 (see FIG. 7) or a cutter. The penetrable porous structure 22 is intended to provide support for a sheet of workpiece material 100 to be cut and its porosity should allow the air from the vacuum system 13 to pass therethrough. The penetrable porous structure 22 may be formed of a foam plastic with open cells, like for example a low density cellular polyethylene or polypropylene material.

(18) The thickness of the porous structure 22 is preferably greater than the vertical distance on which the blade or cutter is intended to penetrate in order to perform an accurate and efficient cutting of the sheet of workpiece material 100, so that the blade or cutter does not contact the perforated tray 21.

(19) The porous structure 22 is fixed to the top side 21b of the tray 21 in a permanent way. The porous structure 22 is for example glued to the top side 21b of the tray via discrete points of glue, in order not to close the traversing holes 24 of the perforated tray 21. Whatever means used for permanently fixing the porous structure 22 to the top side 21b of the perforated tray 21, care should be taken not to close the traversing holes 24 of the tray 21 during the fixing operation.

(20) As shown on FIGS. 1-3, the perforated tray 21 may be provided with side walls 21c, the height of which being slightly greater than the thickness of the porous structure 22 fixed to the tray 21. Anyway, with the porous structure 22 being fixed to the top side 21b of the tray 21, such side walls 21c may be optional. In embodiments not shown, the perforated tray 21 is free of any side walls 21c.

(21) With reference to FIG. 2, the porous support 20 may be simply laid on the top side 11b of the perforated plate 11 of the table 10 of the vacuum hold down device 1. As shown in FIG. 2, the outer reliefs 23 face the top side 11b of the perforated plate 11, thereby creating the space 30 between the top side 11b of the perforated plate 11 and the bottom side 21a of the tray 21. This space 30 allows the airflow generated by the vacuum system 13 to pass therethrough when the vacuum system 13 is operated.

(22) With reference to FIGS. 5 and 6, a vacuum hold down device 1 having another embodiment of a porous support of the invention, similar to that of FIGS. 1-4, is shown. The porous support 120 of FIGS. 5 and 6 comprises a penetrable porous structure 122 and a tray 121 with outer reliefs 123 and traversing holes 124 similar to the porous support 20 of FIGS. 1-4. The porous support 120 of FIGS. 5-6 is further provided with screws 125 intended to be screwed in corresponding threaded holes 15 provided in the perforated plate 11 of the table 10 of the vacuum hold down device 1. For example four screws 125 are provided (only two of them being visible on FIGS. 5 and 6). Such screws 125 form fixing means for temporarily fixing the porous support 121 to the perforated plate 11.

(23) With reference to FIG. 7 is shown the vacuum hold down device 1 of FIGS. 1-4, further provided with the cutting device 40 and ready to be operated.

(24) The sheet of workpiece material 100 has been laid on top of the porous structure 22 of the porous support 20.

(25) The sheet of workpiece material 100 may be porous or non porous such as a fabric layup, textile, knits, woven, nonwovens, . . . .

(26) A film 50, or thin flexible panel, of substantially air-impervious material has been provided for substantially covering the exposed surface of the sheet of workpiece material 100. For example, the film 50 may be a plastic film, such as a polyethylene film. The film 50 cooperates with the vacuum system 13 connected to the bottom side 11a of the perforated plate 11 in order to apply compacting force thereto. The film 50 is preferably of a size allowing it to be spread over the entire exposed surface of the sheet of workpiece material 100 to be cut, such as a textile. When the vacuum system 13 is applied and the cutting step proceeds, the film 50 holds down the sheet of workpiece material 50 to the porous support 20 and maintains it firmly in position, regardless from the lateral forces applied on the sheet of workpiece material 100 by the movements of the cutting device 40.

(27) The cutting device 40 comprises the elongated blade 41, supported by a movable carriage 42 capable of traversing the surface of the table 10 in two coordinate directions, for example in response to position signals supplied by a controller. Alternatively, the movable carriage 42 could be operated manually. The blade 41 is supported for vertically reciprocating movement in cutting engagement with the sheet of workpiece material 100, e.g; a textile, and film 50. The blade 41 is movable along any line, straight or curved, as required by the final shape desired for the cut textile.

(28) At the beginning of the cutting step, the blade 41 is elevated with respect to the film 50, as shown on FIG. 7, so as to be moved to a starting position. The blade 41 is then lowered to penetrate the film 50, the sheet of workpiece material 100, such as a textile, and part of the penetrable porous structure 22 of the porous support 20, and the cutting step proceeds. The porous structure 22 has a thickness greater than the distance on which the blade 41 may be lowered so that the blade 41 never contacts the top side 21b of the perforated tray 21 of the porous support 20. The blade 41 is adjusted to penetrate the porous structure 22 so as to ensure efficient and accurate cutting of the sheet of workpiece material 100 such as a textile.

(29) The removably positionable porous support 20 of the invention allows providing a plurality of porous supports to be used in combination with the table 10. In particular, a first porous support of the invention may be dedicated to the cutting of a first specific textile, having either a specific color, nature, density. A second porous support of the invention may be dedicated to the cutting of a second specific textile, having either a specific color, nature, density, different from that of the first specific textile. In case where these textiles are intended to be used for the manufacture of implantable prosthesis, it is not acceptable that bits of the first specific textile, produced by the cutting step, be mixed to the second specific textile. The porous supports of the invention allow preserving the quality of the cut textiles.

(30) Indeed, once the cutting operations relative to a first specific textile are over and proceeding to the cutting operations relative to a second specific textile is contemplated, the process for replacing the first porous support dedicated to the cutting of a first specific textile by a second porous support dedicated to the cutting of a second specific textile may be performed very easily and in a limited time. Actually, such a process comprises the simple following steps: i) removing the first porous support, and ii) positioning the second porous support on the top side of the perforated plate, with the outer reliefs of the perforated tray of the second porous support facing the top side of the perforated plate.

(31) In case the positioning of the first and second porous supports requires that these porous supports be simply laid on the top side of the perforated plate, such operations may be performed in a very limited time. In the same manner, in such a case, the removal of the first porous support may also be performed very rapidly.

(32) In embodiments where the device comprises screwing means, for example screws 125, for temporarily fixing a porous support to the top side of the perforated plate, step i) comprises unscrewing the first porous support from said perforated plate and step ii) comprises screwing said second porous support on said perforated plate. In this embodiment also, the various operations to be performed may be completed very rapidly. In particular, these operations may be completed significantly more rapidly than in devices of the prior art where the porous bed to be removed must be unglued from the perforated plate and the porous bed to be installed must be glued to the perforated plate.

(33) As a result, the removably positionable porous supports and vacuum hold down device of the invention allow gaining significant time during the maintenance operations of the device. The time necessary for the maintenance of the vacuum hold down device is therefore significantly lowered and the device may be used for production for a longer time. The rate of the production line is therefore increased.