Liner system for forming concrete panels

Abstract

A form for creating a pattern in uncured concrete during a casting process includes a support frame and a perforated reinforcing structure coupled adjacent to at least a portion of the support frame. The perforated reinforcing structure includes a plurality of apertures defined therein. A pliable liner is disposed at least partially within the plurality of apertures and at least partially about the perforated reinforcing structure adjacent the support structure. The pliable liner has a patterned surface formed thereon for creating a corresponding pattern in uncured concrete poured adjacent the form.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a liner system for use in forming concrete panels used in concrete fences, walls and related structure.

2. Related Art

Vertically oriented concrete panels have been used for a number of years in applications including concrete fences, sound walls, partitions, etc. Concrete panels are often poured and cured in a central manufacturing area and shipped as cured panels to job sites, where the panels can be assembled into a fence or similar structure. It is often desirable to apply a textured, decorative finish to such concrete panels to enhance the appearance of the panels. Decorative finishes such as pseudo-brick finishes, pseudo-rock wall finishes, etc., give the concrete panels a more aesthetically pleasing appearance, and in some cases, such as in sound wall applications, can increase the effectiveness of the concrete panels.

One type of system developed to pour concrete panels utilizes vertically-oriented molds between which uncured concrete is poured and allowed to cure. As the concrete panels are formed and cured in a vertical orientation, this type of system is known as a vertical pour system. Some such systems, for example the one described in U.S. Patent Application Publication No. 20050067551, utilize vertically oriented, patterned molds which are secured within a support structure and are filled with uncured concrete. As the uncured (or wet) concrete is poured into the mold, the weight of the wet concrete ensures that the concrete fills indentations in the patterned mold to accurately form a pattern in the finished panel. Such a process produces a decorative pattern on at least one side of the panel. Such systems have been found advantageous over horizontal mold systems because fewer voids appear in the final product, resulting in an aesthetically pleasing product with superior physical integrity.

While systems that pour concrete into vertical forms have been successful in creating decorative patterns on both sides of the vertical concrete panel, the forms used to create such panels have had several operational problems. For example, the forms are quite expensive to make because they must be made of a material that i) won't adhere to the cured concrete, ii) won't deform to a great extent under the weight of uncured concrete, and iii) is sufficiently pliable so as to be easily removable from the pattern created in the cured concrete. Additionally, the forms used to create the decorative pattern in the panels are exposed to, and must be able to withstand, severe environmental conditions such as frequent cyclical loading between concrete pours, rough handling during cured concrete removal, and caustic chemical reactions of curing concrete.

These environmental conditions have caused liners used in vertical concrete forms to prematurely degrade and/or become prematurely separated from adjacent supporting framework structure. Consequently, the relatively expensive liners have had a relatively short useful life and it has been necessary to produce new forms on a relatively frequent basis. Such problems have increased both the material costs associated with vertical pour systems, and with the number of labor hours necessary to maintain a constant fabrication cycle.

SUMMARY OF THE INVENTION

It has been recognized that it would be advantageous to develop forms for use in vertically forming concrete panels that include liner systems that are physically robust and that can withstand the severe environmental conditions involved in vertically forming concrete panels.

The invention provides a form for creating a pattern in uncured concrete during a casting process, including a support frame, and a perforated reinforcing structure, coupled adjacent to at least a portion of the support frame. The perforated reinforcing structure can have a plurality of apertures defined therein. A pliable liner can be disposed at least partially within the plurality of apertures and also about the perforated reinforcing structure adjacent the support structure. The pliable liner can have a patterned surface formed thereon for creating a corresponding pattern in uncured concrete poured adjacent the form.

In accordance with another aspect of the invention, a form system for creating a pattern in uncured concrete during a concrete casting process is provided including a base, and a pair of opposing end wall forms that extend upward from the base and defining end wall surfaces of a vertical mold cavity for uncured concrete. A pair of opposing side wall forms can extend upward from the base and can define side wall surfaces of the vertical mold cavity. Each of the opposing side wall forms can include a perforated reinforcing structure having a plurality of apertures defined therein, and a pliable liner, disposed at least partially within the plurality of apertures and about the perforated reinforcing structure. The pliable liner can have a patterned surface formed thereon for creating a corresponding pattern in uncured concrete poured adjacent the form.

The present invention also provides for a method for making a form for vertically molding concrete including positioning a support frame to support a form. A perforated reinforcing structure that can have a plurality of apertures disposed thereon can be coupled to at least a portion of the support frame. A pliable liner can be disposed at least partially within the plurality of apertures. The pliable liner can also be disposed about the perforated reinforcing structure and the support frame. A patterned surface can be created on the pliable liner in order to form a corresponding pattern into uncured concrete poured adjacent the form.

Additional features and advantages of the invention will be apparent from the detailed description which follows, taken in conjunction with the accompanying drawings, which together illustrate, by way of example, features of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a vertical concrete panel form in accordance with an embodiment of the invention;

FIG. 2 is a front, partially sectioned view of the vertical concrete panel form of FIG. 1;

FIG. 3 is a sectional view of the vertical concrete panel form of FIG. 2, taken along section 3-3 of FIG. 2;

FIG. 4 is perspective view of a vertical concrete panel form system in accordance with an embodiment of the present invention, shown in a partially assembled configuration; and

FIG. 5 is a perspective view of the vertical concrete panel form system of FIG. 4, shown in an assembled configuration.

DETAILED DESCRIPTION

Reference will now be made to the exemplary embodiments illustrated in the drawings, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Alterations and further modifications of the inventive features illustrated herein, and additional applications of the principles of the inventions as illustrated herein, which would occur to one skilled in the relevant art and having possession of this disclosure, are to be considered within the scope of the invention.

Illustrated in FIG. 1 is an example of a form, shown generally at 10, for creating a pattern in uncured concrete during a casting process in accordance with one aspect of the invention described herein. As discussed in greater detail below, the form 10 can be used in conjunction with other forms, such as end wall forms and retaining structure, to form concrete panels (e.g., 11 in FIG. 4) that can be used in vertical applications such as fences, retaining walls, and the like. One exemplary system with which the form 10 can be used is described in U.S. Patent Application Publication No. 20050067551, filed Sep. 30, 2003, which is hereby incorporated herein in its entirety.

Vertical concrete panels 11 created by the form 10 of the present invention are used in a variety of applications, including residential and commercial fencing, sound wall applications, etc. Additionally, concrete panels formed in accordance with the present invention generally require little or no maintenance, provide superior strength, and can be relatively quickly assembled on the job site into a fence or other structure. Assembly of the panels into a fence structure is generally accomplished by installing or forming posts (not shown) which include slot structure into which the panels are disposed and held securely.

The form 10 can mold a decorative pattern into sides of the concrete panels 11 to give the concrete panels an aesthetically pleasing appearance such as a rock wall, a brick wall, or other such desirable patterns. As used herein, the term “decorative pattern” is understood to mean a pattern applied to the concrete panels, and may be decorative or functional, or both, in nature. In addition to the decorative pattern applied to the panel, the concrete panel can be stained or dyed in a particular color scheme to enhance the aesthetically pleasing appearance of the panel. In some embodiments, the term “decorative pattern” can refer to a smooth, relatively featureless pattern that is decorative in nature.

As illustrated in FIGS. 2-3, the form 10 can include a support frame 12. The support frame 12 can be a structurally significant material, such as metal, and can be sized and shaped to support loading from uncured concrete poured within a mold system as described below. In one aspect, the support frame 12 can be formed substantially of a plurality of elongate, tubular members 13 that can be welded or otherwise coupled to one another into an integral frame. In one embodiment, the support frame 12 can also be formed of relatively flat, sheet-like materials such as reinforced plywood sheets, metal sheeting, etc. The support frame can be configured in a variety of manners to ensure that sufficient support is provided to allow attachment of a liner (discussed in more detail below) to the support frame. The form 10 can also include a perforated reinforcing structure 14. The perforated reinforcing structure 14 can be coupled adjacent to at least a portion of the support frame 12. The perforated structure can include a plurality of apertures 16 defined therein. The apertures can take a variety of forms, and can include a variety of cross sectional shapes, such as square-shaped, circular, diamond-shaped, etc. Also, the apertures can be spaced from one another and arrayed across the reinforcing structure in a variety of manners and spatial relationships, in both regular, repeating patterns, and in random patterns.

The apertures 16 can be holes 18 that extend through the perforated reinforcing structure 14 and form the perforations in the reinforcing structure. In one aspect, the perforated reinforcing structure 14 can be a sheet of expanded metal. As is known in the art of metal manufacturing, expanded metal is a product generally formed from a single sheet of metal which is cut or slit and stretched to “expand” the slits into diamond-shaped perforations in the metal sheet. A series of “knuckles” are formed at the edges of each of the perforations as a result of the stretching and serve to distribute loads applied to the metal throughout the sheet. The expanded metal can be formed from a variety of materials, such as steel, stainless steels, brass, aluminum, etc. As expanded metal can be relatively easily manufactured and obtained at a relatively low cost, it has been found to an effective reinforcing structure for liner 20 (discussed in more detail below). Also, as the expanded metal can be easily tack-welded or otherwise attached to the support frame (e.g., stapled in the case where the support frame includes wood), it can be easily and securely attached to the support frame.

As discussed above, the form 10 can also include a pliable liner 20 that can be disposed at least partially within the plurality of apertures 16. The pliable liner 20 can also be disposed at least partially about the perforated reinforcing structure 14 adjacent the support structure 12. The pliable liner 20 can include a compliant polymer material, such as polyurethane or 2070 SX polymer. In one aspect of the invention, the pliable liner is applied about the reinforcing structure adjacent the support frame while in an uncured, liquid state. As the liquid fills between and around each of the perforations or apertures 16 when applied adjacent the support frame, an excellent bond is achieved between the liner and the perforated reinforcing structure (and between the liner and the support structure). In this embodiment of the invention, the pliable liner substantially encompasses the perforated reinforcing structure.

As the perforated reinforcing structure 14 can be independently attached to the support frame 12, the reinforcing structure aids in retaining the liner 20 securely attached to the support frame so that repeated casting and tear-down cycles can be achieved without requiring that the liner be frequently replaced. It has been found that the present invention can produce a form that is capable of sustaining up to 1,000 casting cycles before requiring that the liner be replaced or discarded. As the liner need not be replaced at frequent intervals, a higher quality polymer, which is generally more expensive than lower quality materials, can be used to provide a superior finish to the concrete panels without significantly increasing the cost of each concrete panel.

The pliable liner 20 can also be sufficiently stiff to mold uncured concrete into a decorative pattern. The pliable liner can also be flexible to allow the form 10 to flex when being assembled into a form system, as described below. Advantageously, the flexibility of the pliable liner can extend the usable life of the form 10 since the form can flex instead of breaking during rough handling of the form when during assembly and disassembly procedures.

Advantageously, the support frame 12 and perforated reinforcing structure 14 can minimize the amount of compliant polymer that is needed, such that sufficient polymer is present to seal the mold cavity, but is prevented from deforming to an undesirable level by the reinforcing structure. In addition to the embodiment shown, the reinforcing structure can be disposed on, over, or adjacent to the support gasket to provide reinforcement to the support gasket.

The perforated reinforcing structure can also be formed of perforated metal, woven wire sheets, welded mesh sheets, and the like. As such materials can be relatively easily obtained and cut to preferred sizes, they have been found suitable as reinforcing structure. In addition, conventional sheet material can also be utilized, with perforations formed in the sheet material in a variety of manners, such as drilling, punching, etc.

The pliable liner 20 can have a patterned surface 22 formed thereon. The patterned surface can be an inverse decorative pattern that can form a corresponding decorative pattern on a surface of a cast concrete wall. Specifically, the patterned surface 22 can create a corresponding pattern in uncured concrete poured adjacent the form 10 when the form is used in a form system as described below. The inverse decorative pattern 22 can be of a variety of inverse patterns, including brick, rock, or other pseudo structure that provides the concrete panel with a decorative or functional advantage.

The inverse decorative pattern 22 can be formed on or in the form 10 by a number of methods. In one aspect, the inverse decorative pattern 22 is provided on the form 10 by application of the pliable liner 20 to the form 10. The pliable liner 20 can be formed by preparing a “master” form in which the support frame and reinforcing structure can be disposed. An uncured polymer can be poured over the support frame, reinforcing structure and master form. The uncured polymer can flow around and through the support frame and the apertures or perforations in the perforated reinforcing structure. When the viscous polymer cures, the resulting pliable liner can be removed from the master form and will be bonded or cured around the reinforcing structure. Once prepared, the form 10 can be used numerous times to apply the decorative pattern to a number of concrete panels poured in cavities at least partially defined by the forms 10. By preparing many such forms 10 from the same master form, multiple panels having identical surfaces can be concurrently formed.

Thus, in use, as wet concrete is poured adjacent the form 10, the weight of the wet concrete ensures that the concrete fills in and around the textured surface of the inverse decorative pattern 22. After cure of the concrete, the textured surface appears in the cured concrete panel as a decorative pattern, such as a brick wall appearance, a rock wall appearance, etc.

The form 10 of the present invention can also be utilized to form concrete panels of a variety of sizes. For example, forms can be sized to create concrete panels with a length of 12 feet, a height of 6 or 8 feet, and a thickness of 4 inches. As described in more detail below, the forms can be used in a form system to create panels of varied width, including panels with 4, 5 or 6 inch widths. The forms can be adapted to fit into form systems that can create a number of variously sized and shaped vertical concrete panels with minimal adjustments to the form system being necessary to effectuate formation of differently sized panels.

Referring now to FIG. 4, a form system, shown generally at 100 is shown with a pair of forms 10 at least partially forming a mold cavity for creating a pattern in uncured concrete during a concrete casting process in accordance with the present invention. The form system 100 can have a base 130 that is disposable on a support surface, such as the ground or a casting floor. The form system 100 can also have a pair of opposing end wall forms 140 that each extend upward from the base 130 and define end wall surfaces 142 of a vertical mold cavity (150 in FIG. 5) for uncured concrete. The end wall forms 140 can have a perforated reinforcing structure 144 with a plurality of apertures (not shown). A pliable liner 148 can be disposed at least partially within the plurality of apertures, and about the perforated reinforcing structure 144.

A pair of forms 10, described above, can define opposing side wall forms 110 that extend upward from the base 130. The side wall forms 110 can define side wall surfaces 112 of the vertical mold cavity. The side wall forms 110 can be spaced a desired distance apart, corresponding to a desired thickness of the concrete panel to be formed. As described above, each form 10 can have a perforated reinforcing structure 14 having a plurality of apertures (not shown) and a pliable liner 20 disposed at least partially within, or through the plurality of apertures and about the perforated reinforcing structure 14. The pliable liner 20 can have a patterned surface 22 formed thereon for creating a corresponding pattern in uncured concrete poured adjacent the forms 10.

The form system 100 can also have a lower support gasket 160 disposable over the base 130 to at least partially define a bottom surface 162 of the vertical mold cavity. The lower support gasket can have a perforated reinforcing structure 164 with a plurality of apertures (not shown). A pliable liner 168 can be disposed at least partially within the plurality of apertures, and about the perforated reinforcing structure 164.

Together the end wall forms 140, the side wall forms 110, and the lower support gasket 160 can be operably positionable to form a tetragonal mold cavity 150, as best seen in FIG. 5. The vertical mold cavity 150 can correspond to a substantially vertical concrete panel. In one aspect, the tetragonal vertical mold cavity 150 can have a smaller rectangular cross section across a top surface 152, and a larger rectangular cross section across a front surface 154.

Advantageously, the compliant polymer of the pliable liners 20, 148 and 168 can provide an effective seal between the lower support gasket 160, and each of the end wall forms 140 and side wall forms 110. As the mold cavity 150 fills with wet concrete, the various forms are allowed to slightly bend outwardly to form a seal that increases in effectiveness with the addition of more wet concrete. Thus, wet concrete can be held within the mold cavity 150 even when larger panels are poured that may generally require greater amounts of wet concrete.

Referring to FIG. 5, the form system 100 can also have securing structure, shown generally at 170, associated with the end wall forms 140 and the side wall forms 110 that retains and secures the end wall forms 140 and the side wall forms 110 in the tetragonal mold cavity configuration in order to receive concrete in an uncured state within the vertical mold cavity 150. The securing structure 170 can include various tensioning and restraining devices, as known in the art, to ensure that the mold forms are not displaced by the introduction of uncured, or “wet” concrete in the mold cavity. Once each mold cavity is defined, and any retaining or securing structure 170 has been applied, wet concrete can be poured into each mold cavity. Vibrators or other agitating devices can be utilized when pouring the wet concrete to minimize voids and ensure the wet concrete fills each cavity to the extent desired.

Thus, the mold cavity 150 can be defined by moveable concrete forms restrained by the securing structure 170 in order to maintain the vertical mold cavity 150. As an example of the present invention in use, first side wall form 110 can be positioned in a desired location within the securing structure 15. Lower support gasket 160 can be positioned adjacent the side wall form 110, abutting against the side wall form 110. End wall form 140 can then be placed within the securing structure associated with side wall form 110. A second side wall form 110 can then be moved into position such that end wall form 140 is oriented within the securing structure 170 associated with the second side wall form 110. In this manner, the end wall form 140 is secured in place between the side wall forms 110 by the securing structure 170.

If desired, additional side wall forms 110 can be similarly positioned with end wall form 140 and lower support gaskets 160 forming ends and a bottom, respectively, of a vertical mold cavity 150. The width of the concrete panels thus formed can be easily altered by the use of alternate end wall forms and lower support gaskets. If a wider panel is required, wider end wall forms and support gaskets can be utilized. If a panel with a narrower width is required, narrower end wall forms and support gaskets can be used.

Once each end wall form 140, side wall form 110 and lower support gasket 160 are positioned, the forms can be restrained in position in a number of manners. Due to the substantial weight of uncured concrete, the various forms will tend to move outwardly from the defined mold cavity upon introduction of wet concrete into the cavity. As discussed above, end wall forms 140 can be secured in place by securing structure 170. Further, as illustrated in FIG. 5, side wall tensioning members 240 can be coupled to the various side wall forms 110 to restrain the side wall forms from moving in reaction to forces introduced by wet concrete poured in the mold cavity.

The tensioning members 240 can be a variety of those known in the art, and can include threaded end 242 which can be secured in place by nut 244. An opposing threaded end 246 can similarly be secured by nut 248. Each of the nuts 244, 248 can be tightened to tension the side wall forms together. To provide for variation in the number of mold cavities formed, threaded end 246 can include a length of threads that allow nut 248 to be attached in a variety of positions to facilitate tensioning of a varying number of concrete forms.

The tensioning members 240 can be disposed outside of the mold cavity so as to retain the side wall forms in position without displacing the wet concrete in the mold cavity. In this manner, the forms are securely held in position without adversely affecting the finished panel by introducing foreign matter into the wet concrete and without leaving cavities in the concrete, as has been done in previous methods. In this manner, the concrete forms are maintained securely in place prior to curing of the concrete without compromising either the structural integrity or aesthetic appearance of the finished concrete panel.

Thus, in use, as wet concrete is poured into the mold cavity 150 and adjacent the forms 10, the weight of the wet concrete ensures that the concrete fills in and around the patterned surface of the inverse decorative pattern 22. After cure, the inverse of the patterned surface 22 appears in the cured concrete panel as a decorative pattern, such as a brick wall appearance, a rock wall appearance, etc. Because the present invention advantageously forms concrete panels in a vertical orientation, the wet concrete can fill the textured surface of inverse decorative patterns on both sides of the mold cavity 150 equally well, in contrast to horizontal mold systems which can generally only apply a well-defined pattern to a lower surface of the concrete panel.

After pouring, the wet concrete in the form system 100 can be allowed to cure, after which the various retaining structure and forms can be removed. The cured panel can then be removed, and the process can be repeated a number of times to create a number of concrete panels. In the case where the proper concrete mix is used, the system can form panels on a one day cycle, that is, panel can be poured in the morning and allowed to cure through the night. The following morning, the cured panel can be removed, the forms can be reassembled, and the process begun again.

The present invention also provides for a method for making a form for vertically molding concrete including positioning a support frame to support a form. A perforated reinforcing structure having a plurality of apertures disposed thereon can be coupled to at least a portion of the support frame. The perforated reinforcing structure can include a substantially planar sheet of expanded metal. A pliable liner can be disposed at least partially within the plurality of apertures. The pliable liner can also be disposed about the perforated reinforcing structure and the support frame. A patterned surface can be created on the pliable liner in order to form a corresponding pattern into uncured concrete poured adjacent the form. The pliable liner can be a compliant polymer that can be poured into the plurality of apertures and about the perforated reinforcing structure and support frame. The compliant polymer of the pliable liner can be cured to form a mold surface for retaining uncured concrete.

It is to be understood that the above-referenced arrangements are illustrative of the application for the principles of the present invention. Numerous modifications and alternative arrangements can be devised without departing from the spirit and scope of the present invention while the present invention has been shown in the drawings and described above in connection with the exemplary embodiments(s) of the invention. It will be apparent to those of ordinary skill in the art that numerous modifications can be made without departing from the principles and concepts of the invention as set forth in the claims.

Claims

1. A form for creating a pattern in uncured concrete during a casting process, comprising:

a support frame;

a perforated reinforcing structure, coupled adjacent to at least a portion of the support frame and having a plurality of apertures defined therein; and

a pliable liner, disposed at least partially within the plurality of apertures and at least partially about the perforated reinforcing structure adjacent the support structure, the pliable liner having a patterned surface formed thereon for creating a corresponding pattern in uncured concrete poured adjacent the form.

2. The form of claim 1, wherein the support frame includes a plurality of elongate, tubular members.

3. The form of claim 1, wherein the reinforcing structure is formed of a substantially planar sheet.

4. The form of claim 1, wherein the pliable material further includes a compliant polymer.

5. The form of claim 1, wherein the pliable material further includes polyurethane.

6. The form of claim 1, wherein the perforated reinforcing structure further includes expanded metal.

7. The form of claim 1, wherein the perforated reinforcing structure further includes a material selected from the group consisting of: perforated metal, woven wire sheets and welded mesh sheets.

8. A form system for creating a pattern in uncured concrete during a concrete casting process, comprising:

a base;

a pair of opposing end wall forms, extending upward from the base and defining end wall surfaces of a vertical mold cavity for uncured concrete; and

a pair of opposing side wall forms, extending upward from the base and defining side wall surfaces of the vertical mold cavity, the opposing side wall forms each including at least: a perforated reinforcing structure having a plurality of apertures defined therein; and a pliable liner, disposed at least partially within the plurality of apertures and at least partially about the perforated reinforcing structure, the pliable liner having a patterned surface formed thereon for creating a corresponding pattern in uncured concrete poured adjacent the form.

9. The system of claim 8, further comprising a lower support gasket disposable over the base to at least partially define a bottom surface of the vertical mold cavity.

10. The system of claim 8, wherein the end walls each include:

a perforated reinforcing structure having a plurality of apertures defined therein; and

a pliable liner, disposed at least partially within the plurality of apertures and at least partially about the perforated reinforcing structure.

11. The system of claim 8, wherein the side walls and end walls are operably positionable to form a tetragonal mold cavity.

12. The system of claim 8, further comprising securing structure associated with the end wall forms and the side wall forms, and being configured to retain the end wall forms and the side wall forms in a secure configuration to receive concrete in an uncured state within the mold cavity.

13. The system of claim 12, further comprising a plurality of side wall forms, end wall forms and lower gaskets disposed within the securing structure, to define a plurality of vertical mold cavities to enable simultaneous vertical casting of multiple concrete panels.

14. The system of claim 8, wherein the perforated reinforcing structure further includes a material selected from the group consisting of: expanded metal, perforated metal, woven wire sheets and welded mesh sheets.

15. A method for making a form for vertically molding concrete, comprising the step of:

a) obtaining a support frame;

b) coupling a perforated reinforcing structure to at least a portion of the support frame, the reinforcing structure having a plurality of apertures disposed therein; and

c) disposing a pliable liner at least partially within the plurality of apertures and at least partially about the perforated reinforcing structure adjacent the support frame.

16. The method of claim 15, comprising the further step of:

curing the pliable liner to form a mold surface for retaining uncured concrete.

17. The method of claim 15, wherein the support frame includes a plurality of elongate, tubular members.

18. The method of claim 15, wherein the step of coupling the perforated reinforcing structure further comprises coupling a substantially planar sheet of expanded metal to at least a portion of the support frame.

19. The method of claim 15, wherein the pliable liner includes a compliant polymer.

20. The method of claim 15, wherein the perforated reinforcing structure further includes a material selected from the group consisting of: perforated metal, woven wire sheets and welded mesh sheets.