Abstract:
The invention is a silt screen fence assembly which combines the use of a polymeric silt screen fabric with or without a plastic reinforcement member and a thermoplastic support stake with a hot melt adhesive to attach the silt screen fabric with or without the reinforcement member to the support stake to provide an extremely durable and tenacious bond of the screen fabric to the support stake so as to overcome the inherent problems with prior art silt screen fences wherein the mechanical bond is initially significantly weakened due to penetrating, cutting, punching, or thinning out the silt screen or reinforcement material upon assembly.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation-in-part of U.S. patent application Ser. No. 11/724,876, filed on Mar. 16, 2007 which claims the benefit of U.S. Provisional Patent Application Ser. No. 60/783,562, filed on Mar. 17, 2006. 
     
    
     FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not applicable.  
       REFERENCE TO A SEQUENCE LISTING  
       [0003]     Not applicable.  
       BACKGROUND OF THE INVENTION  
       [0004]     1. Field of the Invention  
         [0005]     The present invention relates generally to a system for minimizing erosion of a site of soil, more particularly, the invention pertains to the provision of a material and system for minimizing the erosion of soil during a construction period.  
         [0006]     2. Description of the Related Prior Art  
         [0007]     In excavating and grading work, such as in the construction of golf courses, highways, shopping centers, or other commercial and residential construction, the work often results in large areas of mounds of soil which may lay undisturbed for several months until the project is completed and graded. Often, these areas are subjected to severe weather conditions such as rain or storms resulting in severe run-off as a result of the surface water carrying the soil to various unwanted areas. The run-off water contains fine soil, small stones, and a large amount of silt. The run-off will often block drains, as in a subdivision, contaminate streams as in the construction of golf courses as well as ponds, and kill vegetation, depending on the flow of the run-off and the length of time such action occurs.  
         [0008]     The natural way to prevent this type of run-off is to seed the area to provide growth of vegetation which will then hold the soil in place. However, the time it takes to seed the area and grow appropriate vegetation to contain or prevent the run-off is often long term and under the present environmental regulations, run-off during the period of time that it takes to grow the vegetation is generally not acceptable. Temporary seeding is also an unneeded expense.  
         [0009]     To solve this well known problem, the prior art has proposed the use of straw bales selectively placed to avoid the acceleration of the water run-off thereby preventing the erosion of the soil. The bales are maintained in place by driving a stake into the ground through the straw bale. This form of solution is strictly temporary since water will find new paths and the problem will often reappear shortly after the bales of straw have resided in one place for a period of time. Other solutions are known to exist in the prior art. For example, Olsen, U.S. Pat. No. 2,872,161, discloses the use of a fencing structure wherein a flexible sheet formed fencing material supported in a generally vertical spread condition, by means of plural element post units which may be suitably spaced apart throughout the length of any particular fence. The object of the improved fencing structure is to provide a relatively inexpensive fencing structure wherein flexible sheet material of suitable width may be utilized as a barrier medium; the flexible sheet material being engaged between and around the posts of suitably spaced plurality of posts supporting units between which the sheet material extends in a tensioned condition and by which the sheet material is maintained in generally fully spread conditions.  
         [0010]     Another method which has been used in the prior art is disclosed in Gagliardy et al., U.S. Pat. No. 4,279,535, which proposes a fabric material that has special characteristics of strength and porosity to minimize the flow of silt suspended in ground water while having the requisite strength to resist abrasion and tearing occasioned by the field conditions. Such fabric consists of a lamination of one or more webs of a relatively fragile non-woven fabric of relatively uniform porosity and formed from filaments of relative cross-section to a web formed from filaments arranged in a grid pattern, the later filaments being of relatively larger cross-section relative to the cross-section of filaments to the non-woven material. In installation, one edge of the fabric is buried in a trench in the ground and the other edge is supported above the ground in a fence like configuration on a series of posts or stakes which are driven or otherwise secured in the ground. To facilitate the attachment of the upper edge of material to the post, one edge of the strip of the laminated material is folded over to form a hem which is securely stitched to provide a longitudinally extending pocket wherein a cord, cable, or the like, is disposed to provide means for readily supporting the upper edge of the fabric in a taut condition. Grommets are utilized to tie the fabric fence to the individual posts.  
         [0011]     Wright, III, U.S. Pat. No. 4,756,511, discloses a web wherein the web of the fencing material is mounted to stakes in a simple and economical manner. Wright teaches the use of a mounting strip which is secured against the stake with the fabric therebetween. The mounting strip makes contact with the fabric over an extended width of the fabric so that there is a surface securement instead of the simple space point securement as in the prior art. The mounting strips and fabric may be secured to the stakes in any suitable manner such as by conventional fasteners, including staples, nails, and the like. Wright further points out that conventional means of securement is unsatisfactory whereby fasteners and staples are used because the staples tend to tear through the fabric web when exposed to environmental conditions such as high winds, snow drifts, and the like. Accordingly, the use of a contact strip avoids these difficulties.  
         [0012]     Because the construction of silt fences is susceptible to adverse effects produced by the wind, Shea, U.S. Pat. No. 5,758,868, discloses and teaches a means for securing a flexible plastic fencing material to a fence post element which provides a silt fence which is more wind resistance and maintenance free. The fence consists, in combination, of a plurality of post units, a flexible plastic fencing material having rigid rod means at two opposing ends wherein each of the post units consist of about three continuous hollow elongated tubes, the central tube contains a retractable stabilizing means for ground insertion; and wherein the outer tubes have a slit along their longitudinal length to accommodate the rod means of the fencing material. The three continuous hollow elongated tubes provide appropriate fastener elements and secure the flexible fencing material in position to eliminate damage to the fence material caused by wind effects.  
         [0013]     Finally, Root, U.S. Pat. No. 6,824,332 discloses a production method for a silt fence flat pack wherein silt fabric is attached to a number of evenly spaced stakes, the stakes then being bunched together so that the silt fabric hangs between the stakes in descending loops. The bunching is continued until all of the stakes lie close together in one plane. The loops of silt fabric are then wrapped tightly around the stakes. Securing bands are then placed around the assembly to create a flat pack.  
         [0014]     What is needed however is a method of securing a silt fence fabric material to a support stake that does not penetrate, cut, break, or thin the silt screen or reinforcing surfaces to avoid tearing of the fabric web when exposed to environmental conditions, such as high winds, snow drifts, and the like. Further, where fasteners are used, the puncturing of the material by the fastener tends to provide a weak point where tears and holes are started and continue as a result of environmental conditions.  
       BRIEF SUMMARY OF THE INVENTION  
       [0015]     The present invention relates to an improvement in the manner of securing the flexible plastic silt fencing material to a fence post or stake which provides a silt fence which is desirable, maintenance free, less subject to damage due to wind conditions, and much more economical to build and maintain. The invention completely avoids the shortcoming of the mechanical methods of attachment (i.e. staples, hog rings, nailing, or sandwiching between posts, etc.) where strength reduction is caused by the penetrating, cutting, tearing, breaking or thinning of the silt screen material or reinforcement surfaces due to the attachment procedure used.  
         [0016]     Many of the prior art shortcomings due to mechanical attachment are remedied by the use of a non-mechanical method of assembly by directly bonding the screen and/or reinforcement surfaces to the post or support surfaces with an adhesive thereby creating an infinite number of fastening points. The invention does not penetrate, cut, break, or thin the silt screen or reinforcement member surfaces, and thus, does not mechanically reduce the initial strength of the bond or material strength of the silt screen fabric or reinforcing member surfaces.  
         [0017]     The invention proposes the use of thermoplastic stakes with a thermoplastic silt screen fabric. The silt screen fence is manufactured in rolls which are formed by a plurality of thermoplastic stakes attached to the silt fabric at preselected intervals. After the first stake is adhesively attached to the thermoplastic silt screen fabric, the stake is rotated to wind the silt fabric around itself on the stake. At preselected intervals, another stake is adhesively attached to the silt fabric and the winding continues until a complete roll of preselected size is formed. The roll can be made of any size, generally  100  foot rolls are typical.  
         [0018]     If a reinforcement member is required, the same technique is used, except both the reinforcement member and the silt fabric are adhesively attached to the first stake and wound together until subsequent stakes are adhesively attached at selective intervals during the winding process.  
         [0019]     The bonding of the stakes to the silt screen with or without the reinforcement member is accomplished by the use of a hot melt adhesive, when using an adhesive that has a surface tension lower than the surface tension of the outer surface of the stake members. The bonding is almost instantaneous and requires just a few seconds of time to cure so that the technique of manufacturing by rolling the silt screen, with or without the reinforcement member upon an attached stake and winding the silt screen material upon itself with additional stakes bonded at preselected intervals, can be a continuous process because the hot melt adhesive requires a very short curing period. The curing of the molecular bond is almost instantaneous.  
         [0020]     If required for the application, an alternate arrangement can be made. For example, the stake can be manufactured from a highly-glass-filled polypropylene with the use of a polyolefin silt screen with or without reinforcement, attached to the stake by the use of hot melt adhesive. The same method can be used for manufacturing rolls of this extremely durable material.  
         [0021]     Accordingly, it is an object of the invention to provide a relatively inexpensive silt fence capable of being readily installed by relatively unskilled labor, and utilizing silt fencing material of flexible sheet material which may be conveniently supplied in rolls of desired width and length. The sheet material, with or without a reinforcing member, is supported and maintained by adhesively bonded plastic posts.  
         [0022]     It is a further primary object of the invention to provide a silt fencing system which can be readily installed so that its effectiveness in impeding the flow of ground water to minimize the run-off of the silt and soil is readily utilized.  
         [0023]     It is a further object of the invention to provide a silt fence which includes means for securely mounting the web to the stakes without the reduction of the strength of the web by penetrating, cutting, breaking, or thinning the silt screen web or reinforcing material.  
         [0024]     It is yet a further object of the invention to provide a silt fence wherein the web may be mounted to the stakes in a simple and economical manner.  
         [0025]     It is yet a further object of the invention to provide a silt fence which is readily recyclable.  
         [0026]     These objects and other features, aspects, and advantages of this invention will be more apparent after a reading of the following detailed description, appended claims, and accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0027]      FIG. 1  is a perspective view of the silt fence assembly components using only the woven silt fabric without a reinforcement member;  
         [0028]      FIG. 2  is a perspective view of the silt fence assembly components including the use of a reinforcement member;  
         [0029]      FIG. 3  is a perspective view of the silt fence assembly using only the woven silt fabric without a reinforcement member; and  
         [0030]      FIG. 4  is a perspective view of the silt fence assembly including the use of a reinforcement member. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0031]      FIGS. 1-4  illustrate a silt fence assembly  10  in accordance with the invention. The silt fence assembly  10  includes a plurality of support stakes  12 , preferably made from plastic, each of which consists of a longitudinal body portion  14  terminating in a pointed end  16  so that the pointed end  16  may be penetrated into the ground surface for anchoring the plurality of support stakes  12  in an upright position. Although the preferred embodiment is a plastic material for the support stake  12 , it is understood that the support stake  12  may be fabricated of any plastic, metal, wood, or wood composite material or size of any convenient cross-section as dictated by the specific application.  
         [0032]     As also illustrated in  FIGS. 1-4 , the silt fence assembly  10  includes a web or silt fabric screen  18  of any suitable woven polymeric fabric. Woven silt fabrics using synthetic yarns have been used increasingly in recent years to prevent soil run-off at construction sites. These fabrics are generally designed to have predetermined water flow capacity per square foot of area, while also having the capability of retaining soil particles of predetermined size. Some woven fabrics have been known to use yarn with substantial flat and rectangular cross-sections, sometimes called tape or ribbon yarn which are woven together using a plain weave while others employ very wide, flat tape yarns in the warp and weft which are woven together with a twill-type weave in a highly compacted fashion in each of the warp and weft. Still others are woven from tape yarns and either bulked continuous filament yarns or spun yarns for specialty applications. The specific construction is selected as dictated by the need to achieve appropriate water flow rates through the fabric while at the same time retaining relatively smaller soil particles.  FIGS. 1-4  illustrate the mounting means used for securing the polymeric fabric to the support stakes  12  without the deleterious effect of penetrating the silt fabric screen  18 . A bead of hot melt adhesive  20  is laid along the longitudinal body portion  14  of the support stake  12 . The silt fabric screen or web  18  is then pressed against the bead of hot melt adhesive  20  with or without an applicator tool. An applicator tool is preferred so as to provide a cooling effect to the hot melt adhesive  20  and the instant cooling solidifies the hot melt adhesive  20  in a few seconds to create a permanent bond. If a reinforcement member  22  is required, as shown in  FIGS. 2 and 4 , the silt fabric screen  18  is placed in contact with the reinforcement member  22  before both layers are pressed against the bead of hot melt adhesive  20  on the support stake  12 . Again, an applicator tool may be used to press both layers of the silt fabric screen  18  and reinforcement member  22  against the support stake  12  and after a few seconds; the hot melt adhesive  20  solidifies to bond both the reinforcement member  22  and the silt fabric screen  18  to the support stake  12 .  
         [0033]     The reinforcement member  22  is made of any convenient woven material with a woven texture creating substantially larger interstitial distances than the woven silt fabric screen  18  so as to function as a support to the silt fabric screen  18  with no other function.  
         [0034]     The use of an adhesive bond avoids the deleterious effect of reducing the initial strength of the woven fabric layer by penetrating, cutting, breaking, or thinning the fabric material when using a mechanical fastener or stretching the fabric between adjoining stakes. In the preferred embodiment, the bonding of the silt fabric screen  18  with or without the reinforcement member  22  is accomplished by the use of a hot melt adhesive No. 4199 available from Hot Melt Technologies, Inc., Rochester Hills, Mich. However, it is not intended to limit the adhesive to this specific composition. The invention proposes to use any rapid curing adhesive that is wettable with the substrates to be bound and has a surface tension equal to or lower than the substrates to be bound. With this arrangement, low surface energy materials such as the support stakes will become molecularly bound with the woven polymeric fabric screen and requires a permanent bond with the silt fabric screen as well as the reinforcement member, when used. In general, adhesives that can wet a surface of a substrate that have a surface tension below 40 dynes/cm maybe used, although the ability to wet a substrate that has a surface tension below 35 dynes/cm is preferred. Such adhesives are commercially available from adhesive manufacturers. The preferred embodiment further proposes the use of a thermoplastic support stake  12  with a thermoplastic silt fabric screen  18  with or without a thermoplastic reinforcement member  22  attached to the thermoplastic support stake  12  with a thermoplastic hot melt adhesive  20 .  
         [0035]     Such combination yields an extremely durable and tenacious bond of the silt fabric screen  18  to the support stake  12 . Also, such assembly of the preferred method of construction is readily recyclable. Again, the preferred embodiment is not intended to be limiting in that the support stakes  12  can be made of wood, metal, plastic, or wood composite and of any convenient cross-section including the square cross-section illustrated in  FIGS. 1-4 .  
         [0036]     It is foreseen that for some applications, the support stake  12  may be made from a highly glass-filled polypropylene with a silt fabric screen  18  and/or reinforcement member  22  made of polyolefin, polyester, nylon, or other woven or non-woven materials.  
         [0037]     The silt fence assembly  10  is generally manufactured in rolls of specified lengths. This is accomplished by transversely attaching a first support stake  12  to the silt fabric screen  18  and thereafter rotating the support stake  12  to wind the silt fabric screen  18  around itself on the support stake  12 . At preselected intervals, a second support stake  12  is adhesively attached to the silt fabric screen  18  and the winding continues until a complete roll of preselected length is formed. The roll can be made of any size; generally  100  foot rolls are typical.  
         [0038]     If a reinforcement member  22  is required, the same technique is used except both the reinforcement member  22  and the silt fabric screen  18  are adhesively attached to the first support stake  12  and wound together on the first support stake  12  until subsequent support stakes  12  are adhesively attached at selected intervals during the winding process.  
         [0039]     The silt fence assembly  10  is installed in the field or at the construction site by unrolling the roll of preassembled support stakes  12  and silt fabric screen  18  transverse to the anticipated direction of water flow. The beginning support stake  12  is then placed upright and the pointed end  16  of the support stake  12  is anchored into the ground until the bottom edge of the silt fabric screen  18  comes into contact with the ground. Subsequent support stakes  12  are then mounted into the ground also across the direction of anticipated water flow, at a distance from the beginning support stake  12  that is sufficient to hold the silt fabric screen  18  taut between the support stakes  12 . The supplied roll is unwound as additional support stakes  12  are mounted in place. After installation, the silt fabric screen  18  with or without the reinforcement member  22  will allow the passage of water but encourage the deposition of sediment being carried by the water such that the sediment builds up on the upstream side of the silt fabric screen  18 , resulting in the bottom edge of the silt fabric screen  18  ultimately tending to bury itself. For some applications, a small shallow trough can be made in the soil immediately underneath the silt fabric screen  18  as it is spanned between support stakes  12 . After the shallow depression or trough is in place, the support stakes  12  are pounded to a slightly deeper position so that the silt fabric screen  18  is in contact with the bottom surface of the depressed ground so that the bottom edge of the silt fabric screen  18  is slightly below the ground level of the run-off water. Such arrangement will greatly assist in the quick sediment buildup on the upstream side to ultimately bury the bottom edge of the silt fabric screen  18  in the ground.