Abstract:
A microhook and loop fastening and detaching assembly comprising a web including a plurality of malleable loops formed integral with one surface of the web, and a plurality of hooks attached to another surface of the web, wherein the loops are adapted to removably engage the hooks. The hooks are equidistantly-arrayed in a plurality of linear rows on the hook side of the web in a staggered manner across the width of the web, such that each hook in a given row is located between two hooks of an adjacent row. The centerline distance between hooks in adjacent rows in the machine direction of the web is greater than the equidistant centerline dimension between adjacent hooks in the same cross-web row. Each hook includes a pedestal attached to the hook side of the web, and a head portion forming part of the pedestal. The head portion extends in a radial direction beyond the radial extent of the pedestal, and the head portion comprises a flat horizontal underside, or a slightly canted underside extending from a radiused connection between the head portion and the pedestal to a rim of the head portion.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This patent application claims priority to provisional application Ser. No. 60/988,501, filed Nov. 16, 2007, to the extent allowed by law. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to an improved microhook apparatus for use in extruded hook and loop fasteners having a low profile and, more particularly, to the geometry, configuration and spacing of mushroom-shaped hooks that produce a fastener having greater flexibility, reduced flagging, and increased pick and peel resistance. 
     BACKGROUND OF THE INVENTION 
     Extruded hook and loop fasteners having a hook presenting a low profile, or low overall thickness of approximately 0.035 inches, are currently marketed and referred to as microhooks. Flexible webs comprising microhooks are increasingly being used for a variety of purposes, including to tie a plurality of electrical cables together, which require greater holding strength than fasteners used, for example, in disposable hygiene products. Microhook fasteners used for cable management must be designed with the geometry, spacing and structure to provide flexibility to conform to the perimeter of cable bundles, to prevent flagging by providing that the ends of the hook and loop fastener remain attached to the curvature of the cable bundle, while at the same time providing sufficient pick and peel resistance to prevent the fastener from being inadvertently released if bumped or brushed against, or otherwise impacted, after application. 
     SUMMARY OF THE INVENTION 
     A microhook for use in cable management, in an embodiment, includes a plurality of “mushroom” shaped hook elements attached to one side of a web. The mushroom hooks are arrayed on the hook side of the web of the microhook fastener such that the centerline-to-centerline spacing of the mushroom hooks in the lengthwise, or machine, direction is significantly greater than the spacing between mushroom hooks in the cross-web direction. Additionally, the array of mushroom hooks on the hook side of the web is staggered in successive rows in the machine direction such that each hook is aligned with the space between hooks in the adjacent rows in the cross-web direction. In another embodiment, the underside of the head of each mushroom hook is substantially flat, and horizontal or canted slightly downward in the radially outward direction. A limited radius at the junction between the head and the pedestal of each hook provides stress relief. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Certain examples of the present invention are illustrated by the accompanying figures. It should be understood that the figures are not necessarily to scale and that details that are not necessary for an understanding of the invention, or that render other details difficult to perceive, may be omitted. It should be understood, of course, that the invention is not necessarily limited to the particular examples illustrated herein. 
         FIG. 1  is a cross-sectional view of the hook and loop fastener of the present invention showing the shape of the fastener were it assembled around a wire bundle or such other item; 
         FIG. 2  is a perspective detail view of the ends of the hook and loop fastener assembly of  FIG. 1 , showing the loops integrally formed with the loop side of the web and the hooks attached to the hook side of the web, the fastener assembly shown in a partially separated position; 
         FIG. 3  is a cross-sectional view of a single row of hooks attached to the hook side of the web of the present invention, taken along the line III-III in  FIG. 2 ; 
         FIG. 4  is a top plan view of the pattern of hooks mounted to the hook side of the web of  FIG. 1 , shown arrayed in accordance with the present invention; 
         FIG. 5  is a cross-sectional view of a single hook constructed in accordance with an embodiment of the present invention, taken along line V-V in  FIG. 2 ; and 
         FIG. 6  is a cross-sectional view of a single hook having a downwardly and outwardly extending flat surface on the underside of the head of the hook. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , an embodiment of the present invention is illustrated. In the embodiment shown, microhook and loop fastener assembly  10  comprises a flexible web  12  made of a knitted fabric material with a plurality of malleable loops  14  integrally formed on loop side  16  of the web, such that the loops  14  extend generally outward from the loop side  16  of web  12 . The loops  14  are flexible, and are made of material that tends to maintain a random open shape of each loop when in its unstressed configuration. The loops  14  are typically made of a plastic material, such as nylon or a polyester, by way of example. Additionally, the loops could be made of a non-woven textile composed of polypropylene or polyester. The loops  14  are integrally formed at their bases  18  to loop side  16  of the web  12 . 
     The hook and loop fastener assembly  10  also comprises a hook side  20  of web  12 , with a plurality of mushroom-shaped hooks  22  securely fastened to hook side  20  of web  12 . Alternatively, hooks  22  may be integrally formed with web  12 . Referring to  FIGS. 1 ,  2 ,  3  and  5 , each mushroom-shaped hook  22  comprises a pedestal or base  26 , and a disc or head portion  28  formed with or attached to pedestal  26 . The lower segment of each pedestal  26  includes a slightly radiused portion  30  where the pedestal  26  is firmly attached to or formed with, side  20  of web  12 . The limited radius  30  acts to prevent the hooks  22  from breaking off of web  12 , while providing each hook with a slight bending capability. As will be described in further detail, the attachment of the base of each pedestal  26  does not increase the rigidity of the web  12 . This is due to the relatively small radius  30  where the pedestal  26  joins web  12  and the staggering of the mushroom hooks on web  12 , as shown in  FIG. 4  and subsequently described herein. Disc or head  28  is formed at the top of each pedestal  26 , and in the illustrated embodiment, each head  28  is round in plan view, as seen in  FIG. 4 , providing each hook  22  with a three hundred sixty degree loop engaging surface to facilitate engagement of a loop in any direction. The head  28  of each pedestal could also be other shapes, such as generally octagonal, hexagonal, square or the like. The web  12  with integral, or attached, hooks  22  can be made of any moldable plastic resin material, such as but not limited to polypropylene, polyethylene and nylon. Also, flame retardant additives can be incorporated into these resins. The loops  14  and hooks  22  can be laminated into a single web with an adhesive, or can be integrally formed as part of the web. 
     Referring to  FIG. 3 , each head  28  in the illustrated embodiment comprises an upper surface  29 , a rounded outer rim  32 , and a flat lower surface  34  extending in a radial direction from a top portion of pedestal  26  to the rounded outer rim  32 . The flat lower surface  34  can extend horizontally, or can cant slightly downward in the radially outward direction. The junction between each flat surface  34  and pedestal  26  is formed with a limited radius  36  to accomodate stress relief between the head  28  and pedestal  26 . 
     One of the objectives of the present invention is to provide a microhook and loop assembly  10  having optimum flexibility, allowing the assembly  10  to conform to bundles, such as an array of wires, around which the assembly  10  is installed. It has been determined that flexibility of the assembly can be increased by having a thinner flexible web  12 , while at the same time having sufficient thickness to maintain the requisite tensile strength of the web to prevent breaking or tearing. Empirically it has been determined that an optimum thickness of the web  12  is in the range of 0.0045 inches to 0.0061 inches, based on data cable bundling considerations, and using polypropylene as the material for hooks  22 . It is to be understood that other optimum thickness ranges would be applicable were other hook materials used, and the microhook and loop assembly were used for varying purposes. 
     In an embodiment of the present invention and as shown in  FIG. 4 , the flexibility of the microhook and loop assembly  10  is also significantly increased by applying a novel geometry to the placement of hooks on web  12 . The cross-web and machine direction pattern between the mushroom hooks  22  in the present invention is devised to provide greater pick and peeling resistance between hooks  22  and loops  14 , and a virtual elimination of flagging, or the tendency of the end of the hook and loop assembly  10  to become detached due to curvature of the bundle that the assembly is securing. 
     In the embodiment illustrated in  FIG. 4 , alternate rows  38 ,  40  of mushroom hooks  22  are formed on the hook side  20  of web  12  and each row  38 ,  40  comprises four hooks  22  and five hooks  22 , respectively, extending in the cross-web direction designated by the arrow A. It is also within the scope of the present invention that the number of hooks  22  arrayed in the direction A in rows  38 ,  40  can be more or less than the four and five hooks, respectively, shown in  FIG. 4 . In the machine or lengthwise direction of the web  12 , designated by the arrow B in  FIG. 4 , the columns of hooks  22  are staggered between the lengthwise columns of adjacent hooks  22 . Thus, the centerline  23  of each hook  22  in the machine direction is disposed between the centerlines  25  of two hooks in an adjacent row, for reasons to be explained. 
     Referring again to  FIG. 4 , the cross-web centerline distance in the direction A between individual hooks is designated as X. In each adjacent row  38 ,  40 , the centerline-to-centerline distance in the cross-web, or A, direction is designated as one-half X (½ X), whereby the centerline of each hook  22  in a given row is centrally disposed and directly in the middle of the centerlines of two side-by-side hooks  22  in adjacent cross-web rows. 
     In addition, the centerline distance between two adjacent hooks  22  in the machine, or B, direction is designated Y in  FIG. 4 . To provide the advantages in increased flexibility, reduced flagging and greater pick and peel resistance mentioned above, the distance Y is greater than the distance X. It has been determined in one embodiment that the distance Y should be in the range of about twenty-five percent greater than the distance X. However, under certain circumstances depending on materials the hooks  22  and loops  14  are made of, the dimensions of the hooks  22 , the thickness of web  12 , and the intended use of the hook and loop assembly  10 , the dimension Y may vary, but is always greater than the dimension X. The Y direction is the direction the loops  14  engage the hooks  22  when the hook and loop assembly  10  is applied to a bundle. The increased spacing in the Y direction provides the web  12  with larger empty or hinge areas on the web between the rows  38 ,  40 , which increases the ability of the web  12  to bend between the rows  38 ,  40  of hooks, resulting, in increased flexibility of the web  12  when in use. 
     Empirically, it has been determined that a cross-web centerline spacing X between hooks  22  of approximately 0.0263 inches provides the necessary number of hooks to prevent flagging with polypropylene as the hook material. Under other circumstances, contemplating differences in material and web thickness, the optimum cross-web centerline spacing X between hooks  22  may vary. 
     Empirically, it has also been determined that the dimension Y, the centerline distance between hooks in adjacent rows  38 ,  40  measured in the machine direction B ( FIG. 4 ), should be approximately 0.0328 inches to provide increased flexibility to the web  12 . This figure was obtained by multiplying the empirical 0.0263 inch dimension for X by 125%. Using these representative dimensions for X and Y in the above description results in an array of one hundred eighty mushroom hooks  22  per square centimeter, and simultaneously increases the flexibility of web  12  compared to an array of hooks  22  where the X and Y dimensions are substantially the same. 
     As seen in  FIG. 4 , the machine direction centerlines of hooks  22  in each sequential adjacent row  38 ,  40  are staggered or offset in the cross-web direction A by a distance of one-half X (½X) from the centerlines of hooks  22  in the prior and subsequent row  38 ,  40 . This staggering increases the tangential edge distance between rims  32  of the hooks  22  in an adjacent row, compared to unstaggered rows of hooks. This increased distance allows more loops  14  to enter the spaces between the mushroom hooks  22 , such that an increased number of loops  14  are captured by the array of hooks  22  when the hook and loop assembly  10  is in use, such as engaging a bundle of wires. The increased amount of loops  14  becoming engaged with hooks  22  provides additional peel strength, which is generally defined as the force required to separate the ends of web  12 , as will be explained. The staggering of the mushroom hooks  22  also provides a greater pick resistance at the edge of the hook and loop assembly  10  when wrapped around a bundle, thereby preventing the condition known as flagging and keeping the ends of web  12  engaged around the curvature of the bundle. 
     As described above, and referring to  FIGS. 3 ,  5  and  6 , the underside of head  28  of each hook  22  comprises a substantially flat, and horizontal or canted lower overhanging surface  34  extending outward from a relatively small radius  36  at the junction of the flat surface  34  and pedestal  26 . This novel structure provides an increase in overhang beneath the head portion  28  of each hook  22 , allowing each loop or loops  14  engaging a hook  22  to have a firm grip on the flat underside  34  of a corresponding hook  22 . The flat underside reduces the tendency of a loop  14  to slip off of a captured hook  22 , and provides a stronger grip between the ends of the web  12 , thereby adding to the force required to separate the two web ends. The combination of a mushroom hook  22  having a flat horizontal ( FIG. 5 ) or canted ( FIG. 6 ) underside  34  for engaging a loop or loops  14  also provides greater pick resistance, whereby loop assembly  10  resists separation if the hook and loop assembly is inadvertently bumped or brushed after being applied to a wire bundle or the like. 
     In  FIG. 5 , the dimension Z designates the radial distance of the overhang provided by flat surface  34 . The dimension Z has been empirically determined to be 0.0037 inches, considering use of the assembly  10  as a cable tie, and using polypropylene as the hook material. Dimension Z will vary as the dimensions of hook and loop assembly  10  change, and as the material of composition of the assembly changes. 
       FIG. 1  illustrates the hook and loop assembly  10  of the present invention, showing the relative position of the loops  14  and mushroom hooks  22  when one end of web  12  is fastened to another portion of web  12 . In this condition, when bringing the loops  14  into contact with hooks  22  to fasten the loop and hook assembly  10  together around a wire bundle or other device, single or multiple loops  14  come into contact with each hook  22 , whereby some of the loops extend over the head portion  28  of each hook  22 , and each loop  14  engages the flat lower surface  34  of each head portion  28 . Each hook is a 360° hook, and can engage a single loop or a plurality of loops in any direction. Since the hooks  22  are staggered in the cross-web direction A by ½ X, as explained above, the distance between the tangential edges of rims  32  is increased relative to a non-staggered hook array. This increased distance allows more loops  14  to enter the space between the mushroom hooks, increasing the ability of the loops to positively engage the flat underside  34  of each mushroom hook  22 . As the multitude of loops  14  engages the plurality of hooks  22 , one end of web  12  becomes removably but firmly attached to another portion of web  12 . The construction of the hook and loop assembly, as described above, provides optimum flexibility, peel resistance, pick resistance and the reduction or elimination of flagging when the hook and loop assembly  10  is wrapped around a wire bundle, or other object. 
     When it is desired to disengage the hook and loop assembly, the respective attached ends of loop web  12  are manually or otherwise separated, as illustrated in  FIG. 2 , by lifting and peeling away one of the web ends upward and away from the other web end. The web ends will then be in the position shown in  FIG. 2 . Each loop  14  that previously engaged the under surface  34  of a hook  22  is stretched until the loop  14  extends around rim  32  of a corresponding hook  22 , and the loop becomes detached from the hook as the loop slips off of the hook. During this detaching process, it has also been observed that disc or head portion  28  of an engaged hook  22  will deform in an upward direction under the force of a loop  14  being removed from the hook  22  and disengaging from flat underside surface  34  of the hook. Additionally a loop  14  may break and release itself from a corresponding hook  22 . This process continues until all of the loops  14  are disengaged from a corresponding hook  22 , and the respective ends of web  12  are separated from each other. 
     Utilizing the staggered hook array of the present invention shown in  FIG. 4 , the hook and loop assembly  10  has increased peel capability, resulting in a smoother separation of one end of web  12  from the other end of the web. This is due to the fact that during the disengagement process, no mushroom hook  22  is directly ahead of a loop  14  disengaged from a previous row of hooks  22 . Additionally, the distance Y between hooks  22  ( FIG. 4 ) is increased as previously described. Thus, a loose loop  14  is not in an advantageous position to re-engage with another hook  22  during the peeling process. 
     Additionally, the density of hooks  22  in the cross-web direction A exceeds the density of hooks  22  in the machine direction B, since Y≈X+0.25X. This provides a greater space in which more loops  14  can fall between and become engaged with hooks  22  during the fastening process, thus adding to the peel resistance strength of the fastened ends of web  12 . Additionally, the staggered array of hooks between rows  38  and  40  provides an increased linear distance between the mushroom hooks of adjacent rows  38  and  40 , making it easier for loops  14  to enter the space between mushroom hooks  22  and become engaged with the hooks, increasing peel strength. 
     While the invention has been shown and described in conjunction with specific exemplary embodiments, the invention is not limited to these. It will be obvious to those skilled in the art that changes and modifications may be made without departing from the teachings of this invention and that the matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. The actual scope of the invention is intended to be defined in the following appended claims.