Abstract:
A foam core cleaning element of stitch-bonded construction having a multi-surface operative cleaning face. The cleaning element includes at least one fluid absorbing layer of absorptive polymeric foam. At least a first plurality of yarns extends in discontinuous patterned stitched relation through discrete selected zones of the fluid absorbing layer such that the first plurality of yarns forms a patterned array of first surface loop zones projecting outwardly away from a first side of the fluid absorbing layer in a defined patterned arrangement across the operative cleaning face of the cleaning element. A plurality of stitch-free zones of the polymeric foam define outwardly projecting convex curved surfaces at positions adjacent to the first surface loop zones across the operative cleaning face of the cleaning element.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of and priority from U.S. Provisional Application 61/170,304 filed Apr. 17, 2009 and U.S. Provisional Application 61/214,586 filed Apr. 23, 2009 the contents of all of which are hereby incorporated by reference herein in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates generally to cleaning systems for floors and other surfaces, and more particularly, to cleaning systems incorporating a foam body with a plurality of yarn elements stitched through the foam body. The foam body and yarn elements cooperatively provide a cleaning element of variable surface structure that can be used alone or in attached relation to an underlying foam sponge block. Exemplary non-limiting uses may include domestic or industrial cleaning of hard surfaces, floors, bathrooms, kitchens and the like. 
       BACKGROUND OF THE INVENTION 
       [0003]    Fabric formation using so-called stitch bonding techniques is well known. In such processes, a multiplicity of stitching yarns is passed repeatedly in stitching relation through one or more substrate layers in closely spaced rows so as to form a coordinated arrangement of surface stitches in covering relation to the substrate. It is possible to use such stitch bonding techniques to form substantially uniform surfaces covered by the stitching yarns. It is also possible to impart patterns of stitching yarns across the surface by manipulation of the formation process. Such patterns may use upstanding loops, substantially flat stitches or combinations thereof. 
         [0004]    It is also known to use a cleaning element having a cleaning layer defining a scrubbing surface for contacting a floor or other surface to be cleaned and a foam backing for absorption and retention of water or other cleaning fluid. Such prior cleaning elements have typically used adhesive bonding or other attachment techniques to secure the cleaning layer to the foam backing. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention provides advantages and/or alternatives over the prior art by providing a foam core cleaning element of stitch-bonded construction incorporating one or more substrate layers of an absorbent foam and a pattern of outwardly projecting pile elements. 
         [0006]    In accordance with one exemplary aspect, a foam core cleaning element of stitch-bonded construction having a multi-surface operative cleaning face is provided. The cleaning element includes at least one fluid absorbing layer of absorptive polymeric foam. At least a first plurality of yarns extends in discontinuous patterned stitched relation through discrete selected zones of the fluid absorbing layer such that the first plurality of yarns forms a patterned array of first surface loop zones projecting outwardly away from a first side of the fluid absorbing layer in a defined patterned arrangement across the operative cleaning face of the cleaning element. A plurality of stitch-free zones of the polymeric foam define outwardly projecting convex curved surfaces at positions adjacent to the first surface loop zones across the operative cleaning face of the cleaning element. 
         [0007]    In accordance with a further exemplary aspect, loop-forming stitching yarns of differing filament count may be used at different zones in the cross-machine direction during formation such that the formed element incorporates discrete zones of surface loops of micro-fiber yarn characterized by a high filament count in combination with discrete zones of surface loops of yarn characterized by a substantially lower filament count. The low filament count yarn may include, without limitation, monofilament yarns or the like to provide scrubbing action. Unstitched zones of exposed foam are present across the surface between zones of yarn stitching. Such a construction provides a cleaning surface with distinct characteristics at different zones. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The accompanying drawings which are incorporated in and which constitute a part of this specification illustrate exemplary constructions and procedures in accordance with the present invention and, together with the general description of the invention given above and the detailed description set forth below, serve to explain the principles of the invention wherein: 
           [0009]      FIG. 1  illustrates schematically a three bar stitch bonding system adapted to form an exemplary foam core cleaning pad structure; 
           [0010]      FIG. 2  illustrates schematically a cross-section of a segment of an exemplary foam core cleaning element as viewed in the cross-machine direction incorporating zones of micro-fiber stitching yarns with low dpf levels in combination with monofilament or other stitching yarns with relatively higher dpf levels stitched through a foam substrate to provide stitched zones with upstanding loops in combination with unstitched segments of exposed foam substrate; 
           [0011]      FIG. 3  is a schematic elevation plan view of the exemplary foam core cleaning element structure of  FIG. 2 ; 
           [0012]      FIGS. 4A and 4B  are complementary needle point diagrams illustrating exemplary stitch notations for stitching yarns applied through a foam substrate in a stitch-bonding procedure to yield a pattern of stitched yarns as shown in  FIGS. 2 and 3 ; 
           [0013]      FIG. 5  illustrates an exemplary mandrel for a curved surface mop; and 
           [0014]      FIG. 6  illustrates a foam core cleaning element structure of  FIG. 2  in attached relation to a foam backing layer disposed across the surface of the mandrel of  FIG. 5 . 
       
    
    
       [0015]    While the invention has been illustrated and will hereinafter be described in connection with certain exemplary embodiments and practices, it is to be understood that in no event is the invention to be limited to such illustrated and described embodiments and practices. On the contrary, it is intended that the present invention shall extend to all alternatives and modifications as may embrace the general principles of this invention within the full and true spirit and scope thereof. 
       DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0016]    Turning now to the drawings,  FIG. 1  illustrates one method utilized to form an exemplary foam core stitch-bonded material  20  including loop elements  22  projecting outwardly from zones of a cleaning surface using a stitch bonding apparatus. In the illustrated practice, a layer of foam substrate material  30  such as a polyurethane foam or the like is conveyed to a stitch-forming position in a stitch-bonding apparatus as will be well known to those of skill in the art. As will be appreciated, in the stitch-bonding apparatus, a pattern of rows of stitches is formed by passing stitching yarns through the substrate material  30  such that the stitching yarns cooperatively form at least a partial covering of stitches across the substrate. 
         [0017]    By way of example only, one foam substrate material  30  that may be used is a 3/16 inch thick polyester polyurethane foam sold under the trade designation S82JJ by William T. Burnett &amp; Company having a place of business in Jessup, Md., USA. According to exemplary embodiments, such material may have a density in the range of 20 to 37 kg per cubic meter and more preferably 25 to 32 kg per cubic meter. According to exemplary embodiments, such foam substrate material will preferably have a tensile strength of greater than about 120 kPa and more preferably at least 170 kPa. According to exemplary embodiments, such foam substrate material will preferably have an elongation at break of at least 300% and more preferably at least 450%. According to exemplary embodiments, such foam substrate material will preferably have a tear resistance of greater than about 500 N/m and more preferably about 700 N/m. According to exemplary embodiments, such foam substrate material will preferably have a 25% compression force deflection of at least 2.8 kN/square meter and more preferably about 3.4 KN/square meter or greater and a 50% compression force deflection of at least 2.8 KN/square meter and more preferably about 3.8 KN/square meter or greater. Such foam substrate material will preferably have at least 70% tensile strength retention after 3 hours of steam autoclave at 150 degrees Celsius. In this regard, evaluation of foam properties may be carried out according to ASTM test method D3574 entitled “Standard Methods of Testing Flexible Cellular Materials—Slab, Bonded and Molded Urethane Foam” the contents of which are hereby incorporated by reference in their entirety. Of course foam materials of different character may also be used if desired. Likewise, while only a single layer of foam substrate material  30  is illustrated, it is also contemplated that multiple layers may be used if desired. 
         [0018]    The stitch forming position is defined by a row of reciprocating needles  34 , extending in adjacent relation to one another across the width of the foam substrate material  30  substantially transverse to the direction of movement of the foam substrate material  30 . As will be appreciated, while only a single needle has been illustrated, in actual practice a large number of such needles are arranged in close relation to one another in the cross machine direction between the fingers  37  of a sinker bar. It is contemplated that the so called gauge or needle density in the cross machine direction may be adjusted as desired. By way of example only, and not limitation, it is contemplated that the needle density in the cross-machine zones where the loop elements  22  are formed may be in the range of about 7 to about 28 needles per inch and more preferably about 14 needles per inch although higher and lower needle densities may likewise be used if desired. In these zones, the stitch bonding apparatus may be set to produce a stitch density of about 17 cpi, although higher or lower stitch densities may be used if desired. At the cross-machine locations where no surface loop elements  22  are desired, the needles  34  are preferably removed such that the foam in those zones is not perforated during the manufacturing process. The absence of perforation aids in maintaining the resilient character of the foam substrate material  30  in those locations. 
         [0019]    According to the illustrated practice, three bars are used to form stitches through the substrate material  30 . In the illustrated three bar practice, a multiplicity of ground yarns  38  is threaded through moveable back bar yarn guides  40  carried by the back guide bar (not shown) for engagement with selected needles  34 , across the width of the substrate material  30 . By way of example only, in one exemplary construction the ground yarns  38  may be threaded in a so called “6 miss 3” pattern ( FIG. 4A ) such that ground yarns engage 6 needles and then skip 3 needles in a repeating pattern across the machine. However, it is also contemplated that other patterns may be used if desired. As will be described further hereinafter, the pattern of ground yarn stitches acts to lock in the loop elements  22  across the surface of the stitch-bonded material  20 . 
         [0020]    In the illustrated exemplary construction, the ground yarns  38  are threaded at one end of ground yarn per engaged needle. In practice, the ground yarns  38  are moved into engagement with the selected needles which, in turn, carry the ground yarns in a reciprocating manner through the foam substrate material  30  without engaging finger elements  37  of the sinker bar so as to form an arrangement of flat ground yarn stitches. According to one exemplary practice, the ground yarn stitches are applied in a chain stitch configuration. By way of example only, one suitable construction for the ground yarns  38  is a 63/40/12 draw warped polyester applied in a chain stitch notation of (1-0,1-0). However, other yarn constructions, and other stitching arrangements may likewise be utilized if desired. 
         [0021]    According to the illustrated practice, a multiplicity of first pile yarns  44  is carried through moveable front bar yarn guides  46  (only one shown) carried by a front guide bar in a pattern for cooperative engagement with selected needles  34  across the width of the foam substrate material  30 . According to the illustrated exemplary practice, a multiplicity of second pile yarns  48  of different character than the first pile yarns  44  may be threaded through middle yarn guides  50  (only one shown) which are carried by the middle guide bar for cooperative engagement with a different group of the needles  34 . Thus, the first pile yarns  44  and the second pile yarns  48  may cooperatively form a patterned repeat across the width of the machine to yield stitch zones of different character based on the character of the yarns in those stitch zones. 
         [0022]    In accordance with the exemplary practice, the ground yarns  38  and the pile yarns  44 ,  48  are each threaded in cooperative patterns so as to leave stitch-free zones  60  across the surface between the zones covered by loop elements  22  ( FIG. 2 ). As best seen through joint reference to  FIGS. 4A and 4B , in one exemplary construction the ground yarns  38  may be threaded in a so called “6 miss 3” pattern such that ground yarns engage 6 needles and then skip 3 needle locations in a repeating pattern. The first pile yarns  44  may be threaded in a so called “4 miss 14” pattern such that the first pile yarns  44  follow a repeating pattern of engaging 4 needles and then skipping 14 needle locations. The second pile yarns  48  may be threaded in a so called “skip 9, 4 miss 14” pattern such that the second pile yarns  48  initially skip 9 needle locations, and then follow a repeating pattern of engaging 4 needles and then skipping 14 needle locations. However, it is also contemplated that other patterns may be used if desired. 
         [0023]    In forming the loop elements  22 , the pile yarns  44 ,  48  are moved back and forth between adjacent needles over intermediate sinker fingers  37 . By way of example only, a pile sinker height of about 2-5 millimeters may be desirable. However, other heights may be used if desired. According to one exemplary practice, the first pile yarns  44  and the second pile yarns  48  are each applied in a tricot stitch configuration with a stitch notation of (1-0,3-2) as shown in  FIG. 4B . However, other stitching arrangements may likewise be utilized if desired. 
         [0024]    In the final construction, the loop elements  22  project outwardly across the so called “technical back” of the stitch-bonded material  20  with flat locking stitches  52  across the so called “technical face”. As will be appreciated, the repeating 4 miss 14 pattern of the pile yarns  44 ,  48  is contained within the boundaries of the 6 miss 3 pattern of the stitches formed by the ground yarns  38 . Accordingly, the chain stitch of the ground yarns  38  serves to lock down the loop elements  22 . 
         [0025]    As previously noted, the complimentary partial threading arrangement of the ground yarns  38  and the pile yarns  44 , 48  yields stitch-free zones  60  at intermediate positions in the cross-machine direction. As best seen in  FIG. 2 , these stitch-free zones  60  provide openings across the surface where the underlying foam substrate material  30  is uncovered and may bulge outwardly. In this regard, according to the potentially preferred practice, at the needle locations skipped by the ground yarns  38 , the needles are physically removed to avoid perforation of the foam substrate material  30 . This absence of perforation aids in maintaining the resilient character of the foam substrate material at the stitch-free zones  60  and enhances the bulging character at those locations. 
         [0026]    Following stitching, the resultant stitch-bonded structure may be segmented in the machine and cross-machine directions to yield a cleaning element  62  ( FIG. 3 ) with desired dimensions and having a cross section corresponding to that shown in  FIG. 2 . In the final construction, the loop elements  22  and convex foam bulges at the stitch-free zones  60  cooperatively define a cleaning face. As will be appreciated, while the cleaning element  62  is shown as generally rectangular, the stitch-bonded structure  20  may be segmented to provide virtually any shape as may be desired. 
         [0027]    The use of two or more different pile yarns may be used to form loop elements of different surface character across the width of the formed stitch-bonded material  20  and the resulting cleaning element  62 . According to one exemplary embodiment, the first pile yarns  44  carried at the front bar may be so called “micro-fiber yarns” of multi-filament construction. Such micro-fiber yarns are formed from ultrafine fiber of less than 1 denier per filament (dpf). Such yarns are characterized by a soft feel and very high effective surface area. In this regard, such micro-fiber yarns may be made up of at least a predominant percentage of fiber with a dpf level of less than 0.8 and will more preferably be made up of at least a predominant percentage of fiber with a dpf level of less than 0.6 and will most preferably be made up of at least a predominant percentage of fiber with a dpf level of less than 0.4 when evaluated on a weight basis. That is, according to the potentially preferred practice, 51% or more of the fiber weight in the first pile yarns  44  may made up of fibers with these dpf levels. In accordance with one exemplary embodiment, such micro-fiber yarns may be formed substantially entirely from fiber with a dpf level of about 0.4 or less. By way of example only, and not limitation, one micro-fiber yarn construction for use as the first pile yarns  44  is a 1/150/408 (i.e. 150 denier, 408 filament) textured polyester yarn. While polyester may be potentially desirable for the micro-fiber yarns, other natural or synthetic materials including nylon, polypropylene, cotton or blends of any identified materials also may be used if desired. 
         [0028]    According to one exemplary embodiment, the second pile yarns  48  are monofilament yarns or multi-filament yarns incorporating at least a predominant percentage of fiber with a dpf level of greater than about 2. Such yarns will be substantially stiffer and more abrasive than the low dpf micro-fiber yarns. The second pile yarns  48  will preferably be made up of at least a predominant percentage of fiber with a dpf level of greater than 3 and will most preferably be made up of at least a predominant percentage of fiber with a dpf level of greater than 4 when evaluated on a weight basis. That is, according to the potentially preferred practice, 51% or more of the fiber weight in the second pile yarns  48  may be made up of fibers with these dpf levels. In accordance with one exemplary embodiment, the second pile yarns may be formed substantially entirely from fiber with a dpf level of greater than 4. By way of example only, and not limitation, one yarn for use as the second pile yarn  48  is a monofilament yarn with a linear density of about 200 to 800 denier. One such yarn is a 300/1 PE (i.e. 300 denier monofilament). However, multi-filament yarns may also be used if desired. 
         [0029]    According to a potentially desirable practice, the second pile yarns  48  are made up predominantly (on a weight percentage basis) from fibers characterized by a dpf level which is at least 5 times greater than the dpf level of the ultrafine fibers in the first pile yarns  44 . More preferably, the second pile yarns  48  are made up predominantly (on a weight percentage basis) from fibers characterized by a dpf level which is at least 10 times greater than the dpf level of the ultrafine fibers in the first pile yarns. Most preferably, the second pile yarns  48  are made up predominantly (on a weight percentage basis) from fibers characterized by a dpf level which is at least 100 times greater than the dpf level of the ultrafine fibers in the first pile yarns. As described below, the use of first pile yarns  44  and second pile yarns  48  with substantially different dpf levels results in loop zones of different abrasive character across the surface of the final cleaning element  62 . 
         [0030]    As will be recognized by those of skill in the art, the threading pattern of first pile yarns  44  and the second pile yarns  48  provides a first set of rows  66  of loop elements formed by the high filament count micro-fiber first pile yarns  44  and a second set of rows  68  of loop elements formed by the coarse dpf second pile yarns  48 . The first set of rows  66  is separated from the second set of rows  68  by rows of exposed foam defined by the stitch-free zones  60 . This exemplary striped patterned arrangement is best illustrated in  FIGS. 2 and 3 . 
         [0031]    As will be appreciated, the first set of rows  66  of loops formed by the high filament count micro-fiber first pile yarns  44  are relatively soft and are characterized by a very high surface area. During a cleaning operation, such character is believed to be beneficial in attracting and retaining particulate matter. Thus, the first set of rows  66  define particle retention zones across the cleaning surface of the cleaning element  62 . Conversely, the second set of rows  68  of loops formed by the coarse second pile yarns  48  have a more abrasive character with lower surface area. During a cleaning operation, such character is believed to be beneficial in loosening matter from a surface to be cleaned by scrubbing action. Thus, the second set of rows  68  define scrubbing zones across the cleaning surface of the cleaning pad cleaning element  62 . 
         [0032]    While the use of micro-fiber yarns in combination with mono-filament and/or standard filament yarns may be desirable in many environments of use, it is also contemplated that the first pile yarns  44  and second pile yarns  48  may each be formed predominantly from fibers with dpf levels greater than 1. That is, no micro-fiber yarns are used. In such a construction, patterning providing relatively softer and coarser zones may still be achieved by use of yarns with different dpf levels in various zones even if those dpf levels are all greater than one. Likewise, it is also contemplated that first stitching yarns  44  and second stitching yarns  45  may each be formed from predominantly from fibers with dpf levels less than 1. That is, only, micro-fiber yarns are used. In such a construction, patterning providing relatively softer and coarser zones may still be achieved by use of yarns with different dpf levels in various zones even if those dpf levels are all less than one. 
         [0033]    While the use of a two loop yarn system is illustrated, it is also contemplated that three or more loop yarns of different character may be used at different zones in the cross-machine direction to provide desired performance characteristics. By way of example only, and not limitation, it is contemplated that a third yarn (not shown) such as an intermediate stiffness multi-filament or the like may be threaded to needles at selected zones to provide further pattern diversity. Likewise, yarns of other character may be placed as desired. Moreover, while striped patterns may be desirable, it is also contemplated that other pattern arrangements may be used with zones of micro-fiber yarn loops and coarse filament yarn loops at different locations if desired. By way of example only, and not limitation exemplary techniques for forming various patterns in a stitch-bonded product are described in U.S. Pat. No. 6,855,392, the contents of which are incorporated by reference herein in their entirety. In this regard, it is contemplated that in applying such techniques to the present invention, yarns with different dpf levels may be applied in different loop zones to provide a desired pattern of coarse and soft loop zones across the surface of the cleaning element  62 . 
         [0034]    It is also contemplated that a single yarn system may be used if desired such that only yarns of either micro-fiber construction or coarse dpf construction are used. By way of example, in such a construction, a common yarn type may be used in all loops interposed by stitch-free zones to define a striped pattern. Alternatively, two or more different microfiber yarns may be used to provide a patterning effect with zones of different character. 
         [0035]    In addition to the cleaning benefits, the use of multi-filament stitch zones in combination with stitch-free zones of exposed foam also may aid in securing a resultant cleaning element  62  to an adjacent structure such as an absorptive structure. Specifically, the high surface area of the yarns aids in the ability of the relatively flat locking stitches formed by yarn segments across the side of the pad facing away from the loop elements to attach to adjacent structures. Thus, the cleaning element  62  may be used as formed or can be adjoined to another underlying surface. By way of example only, and not limitation, the surface of the cleaning element  62  facing away from the loop elements may be attached to a layer or block of foam or other material. This attachment may be by any suitable technique including adhesive bonding, flame lamination or the like as may be desired. 
         [0036]    In accordance with one contemplated use, the cleaning element  62  may be secured across a flat or curved mop head to define a cleaning surface. In this regard,  FIG. 5  illustrates an exemplary curved mop head mandrel  70  which is operatively connected to a handle  72 . The mandrel  70  may be formed from metal, plastic or other suitable material. As shown in  FIG. 6 , an exemplary cleaning element  62  incorporating spaced rows  66 ,  68  of loop elements of different character and convex zones  60  of stitch-free foam maybe disposed across a lower surface of the mandrel  70 . In the illustrated exemplary arrangement, an intermediate layer  76  of foam or other material is adjoined to the cleaning element  62  to provide additional absorptive capacity. However, such an intermediate layer is not essential. Attachment to the mandrel may be by adhesives or any other suitable technique as may be desired. 
         [0037]    As will be appreciated, with the cleaning element  62  in place, the alternating stripes of different character are arranged along the length dimension of the mandrel generally transverse to the direction of movement during a cleaning operation. Thus, the cleaning element  62  presents a pattern of zones of different character to the floor or other surface to be cleaned thereby promoting an efficient and thorough cleaning operation. 
         [0038]    Of course, variations and modifications of the foregoing are within the scope of the present invention. Thus, it is to be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the invention. The embodiment described herein explain the best modes for practicing the invention and will enable others skilled in the art to utilize the invention. The claims are to be construed to include alternative embodiments and equivalents to the extent permitted by the prior art. 
         [0039]    The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
         [0040]    Various features of the invention are set forth in the following claims.