Patent Publication Number: US-11390485-B2

Title: Yarn tensioner, textile machine, and method for tensioning a continuously running yarn

Description:
The present disclosure relates broadly and generally to the textile industry, and more particularly to a yarn tensioner, textile machine, and method for tensioning a continuously running yarn. In one exemplary embodiment, the pre-tensioner of the present disclosure is utilized in combination with a cannister- (or pot-)yarn tensioning device in a direct-cabling textile machine. One exemplary tensioning device is described in Applicant&#39;s prior published international (PCT) patent application, Publication No. WO 2017/027257 and U.S. Application Pub. 2018/0273338-A1. The complete disclosure of this reference is incorporated herein by reference. 
    
    
     TECHNICAL FIELD AND BACKGROUND 
     Summary of Exemplary Embodiments 
     Various exemplary embodiments of the present disclosure are described below. Use of the term “exemplary” means illustrative or by way of example only, and any reference herein to “the invention” is not intended to restrict or limit the invention to exact features or steps of any one or more of the exemplary embodiments disclosed in the present specification. References to “exemplary embodiment,” “one embodiment,” “an embodiment,” “various embodiments,” and the like, may indicate that the embodiment(s) of the invention so described may include a particular feature, structure, or characteristic, but not every embodiment necessarily includes the particular feature, structure, or characteristic. Further, repeated use of the phrase “in one embodiment,” or “in an exemplary embodiment,” do not necessarily refer to the same embodiment, although they may. 
     It is also noted that terms like “preferably”, “commonly”, and “typically” are not utilized herein to limit the scope of the claimed invention or to imply that certain features are critical, essential, or even important to the structure or function of the claimed invention. Rather, these terms are merely intended to highlight alternative or additional features that may or may not be utilized in a particular embodiment of the present invention. 
     According to one exemplary embodiment, the present disclosure comprises a yarn tensioner (e.g., pre-tensioner) adapted for adjusting tension in a running yarn. The yarn tensioner has a base, an adjustable pin rack, a fixed pin rack, and a fastener assembly. The term “adjustable” refers broadly herein to any movability of the adjustable pin rack relative to the fixed pin rack including, but not limited to, pivoting movement and/or planar movement. The adjustable pin rack is carried by the base and incorporates a first plurality of spaced apart parallel friction pins. The fixed pin rack is carried by the base and incorporates a second plurality of spaced apart parallel friction pins residing alternately between the friction pins of the adjustable pin rack. The running yarn travels across the yarn tensioner by snaking over and under adjacent parallel friction pins of the adjustable pin rack and the fixed pin rack. The fastener assembly attaches the adjustable pin rack to the base, such that the adjustable pin rack is movable relative to the fixed pin rack, thereby controlling frictional drag on the running yarn. 
     The adjustable pin rack is moveable relative to the fixed pin rack. The term “moveable” is used broadly to refer to any pivoting and/or planar movement of the adjustable pin rack relative to the fixed pin rack. The fixed pin rack may be separately formed in a structural manner similar to the adjustable pin rack, or may be integrally formed with the base (e.g., as spaced ridges) and as a single homogenous unit. 
     According to another exemplary embodiment, the adjustable pin rack has opposing distal and proximal ends, and a lift tab located at the distal end adjacent a rounded nose of the fixed pin rack. 
     According to another exemplary embodiment, a pivot block is located at the proximal end of the adjustable pin rack. 
     According to another exemplary embodiment, the pivot block and the base define substantially aligned block and base openings. The fastener assembly comprises an upper spring housing adjacent the block opening, a coiled spring located within the upper spring housing, an interior spacer sleeve extending within the spring, and an assembly bolt. The assembly bolt extends through the spacer sleeve, the block opening, and the base opening. The assembly bolt cooperates with the spring to maintain the adjustable pin rack in a spring-biased condition adjacent the base. 
     According to another exemplary embodiment, the block opening is larger than the base opening, such that the adjustable pin rack is capable of upward pivoting movement from the spring-biased condition adjacent the base. 
     According to another exemplary embodiment, the base comprises a notched base extension and a base plate adjacent the base extension. The assembly bolt attaches the pivot block to the base plate such that upward and downward planar movement of the base plate relative to the base extension effects corresponding upward and downward planar movement of the adjustable pin rack relative to the fixed pin rack. 
     The term “planar movement” (and “planar adjustment”) refers herein to upward and downward vertical movement of the adjustable pin rack in a substantially horizontal condition (or 0-degree angle) relative to the fixed pin rack. The term “horizontal” is used herein to refer to a direction, orientation or movement which is generally parallel to the plane of the fixed pin rack. The term “vertical” is used herein to refer to a direction, orientation or movement which is generally perpendicular to the plane of the fixed pin rack. The terms “upward” and “downward” refer to vertical movement relative to the plane of the fixed pin rack. 
     According to another exemplary embodiment, a rotatable tension adjustment wheel resides between the base plate and a top bearing surface of the base extension. 
     According to another exemplary embodiment, at least one ball bearing resides between the tension adjustment wheel and the top bearing surface of the base extension. 
     According to another exemplary embodiment, an underside of the tension adjustment wheel defines a plurality of circumferentially arranged annular bearing races. 
     According to another exemplary embodiment, a second assembly bolt extends through aligned openings formed in the base plate, the tension adjustment wheel, and the base extension. 
     According to another exemplary embodiment, a barrel spacer surrounds the second assembly bolt. 
     According to another exemplary embodiment, a lower spring housing resides adjacent a bottom side of the base extension. A coiled spring is located within the lower spring housing and cooperates with the second assembly bolt to maintain the tension adjustment wheel in a spring-biased condition relative to the at least one ball bearing and the bearing surface of the base extension. 
     According to another exemplary embodiment, adjacent ones of the bearing races are formed at different depths, such that rotation of the tension adjustment wheel locates the ball bearing in a selected bearing race of a particular depth. Locating the ball bearing in one of the relatively deep bearing races moves the adjustable pin rack to an adjusted downward location relative to the fixed pin rack, thereby increasing tension in the running yarn traveling across the yarn tensioner. Locating the ball bearing in one of the relatively shallow bearing races moves the adjustable pin rack to a raised position relative to the fixed pin rack, thereby reducing tension in the running yarn traveling across the yarn tensioner. 
     According to another exemplary embodiment, the tension adjustment wheel includes tension setting indicia. 
     In another exemplary embodiment, the present disclosure comprises a yarn supply canister for use in a direct-cabling textile machine. The supply canister incorporates a canister housing designed for holding a yarn supply package upstream of the textile machine. A yarn guide is located inside the canister housing for receiving running yarn pulled from the supply package at an unwinding tension. A yarn tensioner is located downstream of the yarn guide for adjusting unwinding tension in the running such that the yarn exits the canister housing at an adjusted delivery tension. The exemplary yarn supply canister incorporates embodiments of the yarn tensioner disclosed herein. 
     In yet another exemplary embodiment, the present disclosure comprises a method for adjusting tension in a running yarn. The method includes drawing the running yarn alternatively over and under adjacent parallel friction pins of an adjustable pin rack and a fixed pin rack. The method enables pivoting movement of the adjustable pin rack relative to the fixed pin rack, such that a distal end of the adjustable pin rack is capable of lifting upwardly at a rounded nose of the fixed pin rack. The method further enables planar upward and downward adjustment of the adjustable pin rack relative to the fixed pin rack, such that: 
     a lowered position of the adjustable pin rack relative to the fixed pin rack increases tension in the running yarn; and 
     a raised position of the adjustable pin rack relative to the fixed pin rack reduces tension in the running yarn. 
     Use of the terms “upstream” and “downstream” refer herein to relative locations (or movement) of elements or structure to other elements or structure along or adjacent the path of yarn travel. In other words, a first element or structure which is encountered along or adjacent the path of yarn travel before a second element or structure is considered to be “upstream” of the second element or structure, and the second element structure is considered to be “downstream” of the first. 
     The term “closely spaced” means sufficiently spaced apart to allow snaking passage of yarn between adjacent pins of the adjustable pin rack and the fixed pin rack. One or more yarn-contacting surfaces of the exemplary tensioner may comprise a material coating, such as ceramic and plasma. Additionally, the friction pins may be fabricated of an anodized aluminum, solid ceramic, or other suitable material. 
     The term “sequentially spaced” is defined herein to mean the physical and/or temporal spacing of elements or structure downstream along or adjacent the path of yarn travel. 
     The term “housing” refers broadly herein to any open, closed, or partially open or partially closed structure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The description of exemplary embodiments proceeds in conjunction with the following drawings, in which: 
         FIG. 1  is an environmental view of an exemplary yarn tensioner (“pre-tensioner”) located inside a supply canister between an upstream yarn feed package and a downstream textile machine; 
         FIG. 2  is an enlarged view of the area designated at reference numeral  2  in  FIG. 1 ; 
         FIG. 3  is a further enlarged view of the exemplary yarn tensioner mounted inside the supply canister; 
         FIG. 4  is a perspective view of the exemplary yarn tensioner; 
         FIG. 5  is an exploded perspective view of the exemplary yarn tensioner; 
         FIGS. 6A and 6B  are side views of the exemplary yarn tensioner with portions shown in cross-section; 
         FIGS. 7, 8, and 9  are perspective views demonstrating sequential movement of the adjustable pin rack when threading the yarn tensioner; 
         FIG. 10  is an environmental view of an exemplary yarn tensioner mounted at the creel outside of the supply canister; 
         FIG. 11  is an enlarged view of the area designated at reference numeral  11  in  FIG. 10 ; 
         FIGS. 12 and 13  are perspective views of the exemplary yarn tensioner; 
         FIG. 14  is an exploded perspective view of the exemplary yarn tensioner; 
         FIG. 15  is a side view of the exemplary yarn tensioner with a portion shown in cross-section; 
         FIG. 16  is a further perspective view of the exemplary yarn tensioner shown in cross-section; 
         FIGS. 17, 18 and 19  are views showing an underside of the exemplary tension adjustment wheel; 
         FIGS. 20A-20F  are cross-sectional views of the exemplary tension adjustment wheel with the  2  ball bearings seated in respective bearing races and shown in broken lines; 
         FIG. 21  is a topside view of the exemplary tension adjustment wheel; and 
         FIGS. 22A-22C  are views illustrating an uppermost planar position of the adjustable pin rack, an intermediate planar position of the adjustable pin rack, and lowermost planar position of the adjustable pin rack. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS AND BEST MODE 
     The present invention is described more fully hereinafter with reference to the accompanying drawings, in which one or more exemplary embodiments of the invention are shown. Like numbers used herein refer to like elements throughout. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be operative, enabling, and complete. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalents thereof. Moreover, many embodiments, such as adaptations, variations, modifications, and equivalent arrangements, will be implicitly disclosed by the embodiments described herein and fall within the scope of the present invention. 
     Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. Unless otherwise expressly defined herein, such terms are intended to be given their broad ordinary and customary meaning not inconsistent with that applicable in the relevant industry and without restriction to any specific embodiment hereinafter described. As used herein, the article “a” is intended to include one or more items. Where only one item is intended, the term “one”, “single”, or similar language is used. When used herein to join a list of items, the term “or” denotes at least one of the items, but does not exclude a plurality of items of the list. 
     For exemplary methods or processes of the invention, the sequence and/or arrangement of steps described herein are illustrative and not restrictive. Accordingly, it should be understood that, although steps of various processes or methods may be shown and described as being in a sequence or temporal arrangement, the steps of any such processes or methods are not limited to being carried out in any particular sequence or arrangement, absent an indication otherwise. Indeed, the steps in such processes or methods generally may be carried out in various different sequences and arrangements while still falling within the scope of the present invention. 
     Additionally, any references to advantages, benefits, unexpected results, or operability of the present invention are not intended as an affirmation that the invention has been previously reduced to practice or that any testing has been performed. Likewise, unless stated otherwise, use of verbs in the past tense (present perfect or preterit) is not intended to indicate or imply that the invention has been previously reduced to practice or that any testing has been performed. 
     Referring now specifically to the drawings, an adjustable yarn tensioner according to one exemplary embodiment of the present invention is illustrated in  FIGS. 1-4 , and shown generally at reference numeral  10 . The exemplary yarn tensioner  10  is located inside a supply canister  11  between an upstream yarn feed package  12  (e.g., single ply filament) and a downstream textile machine—indicated diagrammatically at  14 . The exemplary yarn tensioner  10  (also referred to as a “pre-tensioner”) may be used in combination with a second yarn tensioner “T” such as that described in Applicant&#39;s prior published international (PCT) patent application, Publication No. WO 2017/027257 and U.S. Application Pub. 2018/0273338-A1. The complete disclosure of this reference is incorporated herein by reference. The textile machine  14  may be a conventional direct-cabling machine used to form high-quality pile in the manufacture of rugs and carpets. In other applications, exemplary yarn tensioners of the present disclosure may also be used in the creel on the cabler, in other types of creels, and in other various textile machines and processes. One alternative exemplary yarn tensioner  100  is shown in  FIGS. 10-13  and described further below. 
     In a direct-cabling machine, the feed package  12  is loaded into the cannister  11  and the yarn Y 1  unwound and tensioned using a tensioning device or “yarn brake”, such as the tensioner “T” disclosed in Publication No. WO 2017/027257 and U.S. Application Pub. 2018/0273338-A1. The tensioner “T” may be suspended above the package  12  inside the canister  11  by mounting bracket  15  or other suitable structure. The mounting bracket  15  has a yarn guide  16 . The present pre-tensioner  10  is carried by the mounting bracket  15  upstream of the yarn tensioner “T”, and functions to tension the running yarn immediately prior to its passage to the second tensioner “T”. An annular guide  18  is located at a top wall of the cannister  11  downstream of the second tensioner “T”. 
     A second feed package  12 A is loaded into a creel, unwound, and slightly tensioned utilizing the yarn tensioner  100 , shown in  FIGS. 10 and 11 , before it enters a lower hollow shaft of a spindle. This yarn end Y 2  wraps around a storage disc  19  and forms a balloon around the cannister  11 . At the balloon apex outside of guide  18 , both yarns Y 1 , Y 2  meet and wrap around each other, which thus dissolves the false twist in the balloon yarn Y 2 . At the meeting point  20 , both yarns Y 1 , Y 2  should have substantially the same tension in order to form a balanced composite yarn with no or limited residual torque and substantially equal lengths of component yarns. Consequently, whenever the spindle speed is altered, tension in the cannister yarn Y 1  is adjusted by the exemplary pre-tensioner  10  and yarn tensioner “T” to compensate for a consequent increase or decrease in tension of the balloon yarn Y 2 . 
     As yarn is pulled from the feed package  12  and fed through pre-tensioner  10 , the yarn tensioner “T” interposed between the package  12  and downstream textile machine  14  applies predetermined (e.g., calibrated) frictional resistance to the running yarn Y 1 , such that the delivery tension is maintained at a generally uniform, constant and predictable level. This process is described and illustrated in detail in Applicant&#39;s Publication No. WO 2017/027257 and U.S. Application Pub. 2018/0273338-A1. 
     Exemplary Yarn Tensioner  10   
     Referring to  FIGS. 3-9 , the exemplary yarn tensioner  10  (or “pre-tensioner”) comprises a base  21  which attaches to a mounting arm  22  of canister bracket  15 , an adjustable (e.g., pivotable) pin rack  24 , a fixed pin rack  26 , and a fastener assembly  28 . The adjustable pin rack  24  is carried by the base  21  and incorporates a first set of spaced apart parallel friction pins  31 . The friction pins  31  extend between and are affixed at respective opposite ends to a distal lift tab  32  and a pivot block  34 . The fixed pin rack  26  is carried by the base  21  and incorporates a second set of spaced apart parallel friction pins  35  residing alternately between the friction pins  31  of the adjustable pin rack  24 . Opposite ends of friction pins  35  are affixed to base posts  37 ,  38  formed at a rounded nose end of the pin rack  26  and adjacent the pivot block  34  of pin rack  24 . The running yarn Y 1  travels across the yarn tensioner  10  by snaking over and under closely-spaced adjacent parallel friction pins  31 ,  35  of the adjustable pin rack  24  and the fixed pin rack  26 . 
     As best shown in  FIGS. 5, 6A, and 6B , the pivot block  34  of adjustable pin rack  24  and the base  21  define substantially aligned block and base openings  41  and  42 . The exemplary fastener assembly  28  comprises a generally cone-shaped upper spring housing  44  adjacent the block opening  41 , a coiled spring  45  located within the upper spring housing  44 , an interior spacer sleeve  46  extending within the spring  45 , and an assembly bolt  48 . The assembly bolt  48  extends through the spacer sleeve  46 , the block opening  41 , and the base opening  42 , and has a threaded end which fastens to complementary-threaded lock nut  49  on a bottom side of the base  21 . When threaded through the lock nut  49 , the assembly bolt  48  cooperates with flat washer  51  and spring  45  to maintain the adjustable pin rack  24  in a spring-biased condition adjacent the base  21 . As best shown in  FIGS. 6A and 6B , the block opening  41  is larger than the base opening  42 , such that the adjustable pin rack  24  is capable of upward pivoting movement (as indicated by arrow  52 ) from the planar spring-biased condition adjacent the fixed pin rack  26 . The adjustable pin rack  24  is slightly pivotable at the assembly bolt  48 , and can be lifted (manually at lift tab  32  or otherwise) against the normal biasing force of the spring  45 . This enables convenient threading of the yarn tensioner  10  as demonstrated in  FIGS. 7, 8, and 9 . In an alternative embodiment, the biasing force generated by the spring  45  may be increased or decreased by tightening or loosening the assembly bolt  48 , thereby controlling frictional drag on the running yarn Y 1 . 
     Exemplary Yarn Tensioner  100   
     Referring to  FIGS. 10-13 , the exemplary yarn tensioner  100  is carried by a creel bracket  101  mounted to the creel and comprising spaced apart yarn guides  102 ,  103 . The yarn tensioner  100  is located between the yarn guides  102 ,  103  and functions to adjust tension in the running yarn Y 2  drawn from the creel package  12 A. 
     Like tensioner  10  described above, the yarn tensioner  100  comprises a base  111 , an adjustable pin rack  112 , a fixed pin rack  114 , and a fastener assembly  115 . The exemplary base  111  comprises a separate base plate  118  and a notched base extension  119 . The adjustable pin rack  112  is carried by the base plate  118  and incorporates a first set of spaced apart parallel friction pins  121 . The friction pins  121  extend between and are affixed at respective opposite ends to a distal lift tab  122  and a pivot block  124 . The fixed pin rack  114  is also carried by the base  111  and incorporates a second set of spaced apart parallel friction pins  126  residing alternately between the friction pins  121  of the adjustable pin rack  112 . Opposite ends of friction pins  126  are affixed to base posts  127 ,  128  located at a rounded nose end of the pin rack  114  and adjacent the pivot block  124  of pin rack  112 . The running yarn Y 2  travels across the yarn tensioner  100  by snaking over and under closely-spaced adjacent parallel friction pins  121 ,  126  of the adjustable pin rack  112  and the fixed pin rack  114 . 
     As best shown in  FIGS. 14, 15, and 16 , the pivot block  124  of adjustable pin rack  112  and the base plate  118  define substantially aligned block and base openings  131 ,  132 . The exemplary fastener assembly  115  comprises a cylindrical upper spring housing  135  adjacent the block opening  131 , a coiled spring  136  located within the upper spring housing  135 , an interior spacer sleeve  137  extending within the spring  136 , and an assembly bolt  138 . The assembly bolt  138  extends through the spacer sleeve  137  and the block opening  131 , and has a threaded end which fastens to a complementary internal screw thread formed with the base opening  132 . When operatively screwed into the base opening  132 , the assembly bolt  138  cooperates with a flat washer  141  and spring  136  to maintain the adjustable pin rack  112  in a spring-biased planar condition adjacent the fixed pin rack  114 . As best shown in  FIGS. 14 and 15 , the block opening  131  is larger than the base opening  132 , such that the adjustable pin rack  112  is capable of upward pivoting movement from its normally planar spring-biased condition. The adjustable pin rack  112  is slightly pivotable at the assembly bolt  138  and can be lifted (manually using lift tab  122  or otherwise), as indicated by direction arrow of  FIG. 15 , against the biasing force of the spring  136 . This enables convenient threading of the yarn tensioner  100 , as previously described. The biasing force generated by the spring  136  can be slightly increased or decreased by tightening or loosening the threaded assembly bolt  138 , thereby controlling frictional drag on the running yarn Y 2 . 
     Referring to  FIGS. 12, 13, 14 and 16 , a rotatable tension adjustment wheel  150  resides between the base plate  118  and a top bearing surface  119 A of the base extension  119 . A pair of identical steel ball bearings  151 , best shown in  FIG. 14 , are located on the top bearing surface  119 A and directly engage an underside of the tension adjustment wheel  150 . The ball bearings  151  are held within respective identical annular indents  152  on opposite sides of an extension hole  154  formed through the base extension  119 . The extension hole  154  vertically aligns with holes  155 ,  156 ,  157 , and  158  formed respectively in the base plate  118 , the tension adjustment wheel  150 , a barrel spacer  161 , a cylindrical lower spring housing  162 , and through flat washers  164 A,  164 B,  164 C and  164 D and a coiled spring  165 . A second threaded assembly bolt  168  extends through the vertically aligned holes  154 - 158  and through washers  164 A- 164 D, and fastens to a complementary-threaded locking nut  169  inside the lower spring housing  162 . When tightened, the threaded assembly bolt  168  urges the flat washer  164 C against the coiled spring  165  inside the lower housing  162 . This compresses the spring  165  causing the tension adjustment wheel  150  to closely and firmly engage the two ball bearings  151  in a spring-biased condition. 
     As best shown in  FIGS. 16-18, 19 and 20 , an underside of the tension adjustment wheel  150  defines a plurality of circumferentially arranged, individual, annular bearing races  171 . As indicated above, the tension adjustment wheel  150  is sandwiched between the base plate  118  and ball bearings  151 , and the base plate  118  is attached directly to the pivot block  124  of adjustable pin rack  112  by the first assembly bolt  138 . The underside of tension adjustment wheel  150  is shown in  FIGS. 17, 18 and 19 . The bearing races  171  located at opposite ends of respective diameter lines A, B, C, D, E, and F (See  FIG. 19 ) comprise a set having an identical depth, and are intended to align with the two ball bearings  151  to temporarily secure the adjustable pin rack  112  at a desired planar depth relative to the fixed pin rack  114 . 
     Referring to  FIGS. 19 and 20A-20F , the exemplary tension adjustment wheel  150  has 6 different sets of bearing races  171  corresponding to 6 different planar depth settings of the adjustable pin rack  112  relative to the fixed pin rack  114 . Manually rotating the tension adjustment wheel  150  positions the two ball bearings  151  in a selected set of bearing races  171  of a particular depth. Locating the two ball bearings  151  in a set of relatively deep bearing races  171  (e.g.,  FIGS. 20A and 20F ) moves the adjustable pin rack  112  to a lowered planar position relative to the fixed pin rack  114 , thereby increasing tension in the running yarn Y 2  traveling across the yarn tensioner  100 . Locating the two ball bearings  151  in a set of the relatively shallow bearing races  171  (e.g.,  FIGS. 20C and 20E ) moves the adjustable pin rack  112  to a raised planar position relative to the fixed pin rack  114 , thereby reducing tension in the running yarn Y 2  traveling across the yarn tensioner  100 . The tension adjustment wheel  150  may also comprise tension setting indicia  180  shown in  FIG. 21 . In one embodiment, the exemplary tensioner  100  includes available settings within a graduated tension range of approximately 0 grams to 300 grams, and up to 2000 grams.  FIGS. 22A-22C  show the adjustable pin rack  112  located in an uppermost planar position relative to the fixed pin rack  114 , an intermediate planar position relative to the fixed pin rack  114 , and a lowermost planar position relative to the fixed pin rack  114 . 
     Either of the exemplary yarn tensioners  10  and  100  described above may be used inside the canister or may be mounted on the creel, and either may be used alone or in combination with other yarn tensioners or pre-tensioners, and either may be used in any other application requiring any degree of yarn tensioning in a textile machine. 
     For the purposes of describing and defining the present invention it is noted that the use of relative terms, such as “substantially”, “generally”, “approximately”, and the like, are utilized herein to represent an inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. These terms are also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue. 
     Exemplary embodiments of the present invention are described above. No element, act, or instruction used in this description should be construed as important, necessary, critical, or essential to the invention unless explicitly described as such. Although only a few of the exemplary embodiments have been described in detail herein, those skilled in the art will readily appreciate that many modifications are possible in these exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the appended claims. 
     In the claims, any means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. Unless the exact language “means for” (performing a particular function or step) is recited in the claims, a construction under 35 U.S.C. § 112(f) [or 6th paragraph/pre-AIA] is not intended. Additionally, it is not intended that the scope of patent protection afforded the present invention be defined by reading into any claim a limitation found herein that does not explicitly appear in the claim itself.