Abstract:
A footwear construction and method for manufacturing the same. The sole include a rigid flexplate suspended within the midsole. The flexplate extends along substantially the entire length and width of the sole. The sole also preferably includes a rear stabilizer molded in place about the heel region of the midsole. Further, the footwear may include a dual-density collar disposed about the ankle region of the upper. The collar includes a relatively soft inner layer that permits the collar to be stitched to the upper and a relatively rigid outer layer that provides the desired level of stability. The sole is preferably manufactured using the general steps of (a) providing a mold with a plurality of flexplate locating pins, (b) positioning a flexplate within the mold, (c) injecting the midsole material into the mold about the flexplate, and (d) attaching an outsole to the midsole. The rear stabilizer is preferably molded prior to and retained within the mold during the midsole molding step. The collar is preferably molded in sequential shots, with the inner and outer materials being molded from the same family of materials to enhance bonding. The molded collar is stitched to the upper and cement to the sole.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to footwear and more particularly to a footwear construction and a method for making the same. 
     In the footwear industry, there is an ongoing effort to produce footwear that provides stability and support while maintaining a high level of comfort. These needs are particularly acute in the design of high performance footwear, such as hiking, mountaineering, multisport and rugged outdoor walking footwear, where one of the primary goals is to reduce fatigue. To minimize the effects of travel over jagged, rugged or uneven surfaces it is important to provide high performance footwear with both torsional stability (e.g. resistance to twisting forces) and longitudinal stability (e.g. resistance to linear forces). 
     Conventionally, the interests of stability and comfort have been competing interests. Efforts to improve stability and support typically result in a reduction in comfort. For example, a common technique for improving comfort is too increase the amount of cushioning material in the sole assembly, such as by manufacturing the midsole from a softer, more resilient material. While this increases comfort, it reduces the stability and comfort of the article of footwear. Likewise, a common technique for increasing stability and support is to provide a rigid insole or a rigid midsole. As both of these components lie close beneath the foot, a rigid insole or midsole typically provides very limited cushioning and therefore results in reduced comfort. Another technique for increasing stability is to sandwich a rigid arch support or heel support between the midsole and the insole. Again, these components lie just below the wearer&#39;s foot and provide little room for cushioning. As a result, there remains a long felt and unmet need for a footwear construction that provides the desired level of cushioning, stability and support. 
     SUMMARY OF THE INVENTION 
     The aforementioned problems are overcome by the present invention which provides an extended structural component, or flexplate, molded in situ within the midsole. The flexplate is preferably disposed centrally within the midsole where it is entrapped within the relatively soft material of the midsole. The flexplate is rigid and extends substantially along the entire length and width of the midsole to provide full support for the wearer&#39;s foot. In a preferred embodiment, the flexplate defines a plurality of openings that permit the midsole material to flow about and thoroughly entrap the flexplate. Further, in a preferred embodiment, the heel portion of the flexplate is cupped to, among other things, aid in centering the wearer&#39;s foot. 
     In another preferred embodiment, the present invention includes a rear stabilizer that provides even further enhanced stability in the heel region. The rear stabilizer is preferably molded in place about the heel portion of the midsole. The rear stabilizer is molded from a relatively rigid polymer, typically from the same family of polymers as the remainder of the midsole. 
     The sole of the present invention is preferably manufactured using the general steps of (a) providing a rigid flexplate, (b) providing a mold with flexplate locating pins, (c) suspending the flexplate within the mold between the locating pins, (d) molding the midsole about the flexplate, (e) molding the rear stabilizer about the midsole, (f) attaching an outsole to the midsole, and (g) attaching the upper to the midsole/outsole combination. 
     The present invention further includes a dual-density collar disposed about the ankle portion of the upper. The collar includes a first relatively soft polymer that permits the collar to be stitched directly to the upper and a second relatively stiff polymer that provides the collar with the desired level of rigidity. The two layers are molded together to form a single, integral unit. In the preferred embodiment, the collar is anchored to the sole and provides a mounting location for a lacing hook. As a result, the lacing pressure on the lacing hook is distributed over a large portion of the footwear, including the sole. 
     The collar of the present invention is preferably manufactured using the general steps of (a) providing a mold having distinct cover molds, (b) molding the first layer of the collar in a first shot of material having a first rigidity, (c) replacing the first cover mold with a second cover mold, and (d) molding the second layer of the collar in a second shot of material having a second rigidity, typically from the same family of polymers as the material of the first shot. 
     The present invention provides a unique footwear construction having a heretofore unachieved combination of comfort, stability and support. The flexplate provides torsional and linear stability over the entire foot. The rear stabilizer provides enhanced stability in the heel region where torsional forces can be particularly damaging. The cupped heel region of the flexplate helps to center the wearer&#39;s heel. The collar provides stability and support to the heel and ankle regions of the upper while simultaneously distributing lacing pressure over the upper and into the sole. Accordingly, the collar helps to anchor the wearer&#39;s foot to the sole to take full advantage of the stability and support provided by the flexplate. 
     These and other objects, advantages, and features of the invention will be readily understood and appreciated by reference to the detailed description of the preferred embodiment and the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of an article of footwear incorporating the flexplate, rear stabilizer and collar of the present invention; 
     FIG. 2 is an exploded perspective view of a sole according to a preferred embodiment of the present invention with portions cut away to show the flexplate; 
     FIG. 3 is a perspective view of the midsole of the present invention; 
     FIG. 4 is a perspective view of the flexplate; 
     FIG. 5 is a side elevational view of the flexplate; 
     FIG. 6 is a top plan view of the flexplate; 
     FIG. 7 is a sectional view of the midsole base mold; 
     FIG. 8 is a sectional view of the first midsole cover mold; 
     FIG. 9 is a sectional view of the second midsole cover mold; 
     FIG. 10 is a perspective view of a portion of the midsole molded in a first injection according to an alternative embodiment; 
     FIG. 11 is a side elevational view of the flexplate disposed above the portion of the midsole molded during the first injection in the alternative embodiment; 
     FIG. 12 is a sectional view of the first midsole cover mold for the alternative embodiment; 
     FIG. 13 is an exploded perspective view of the upper and collar; 
     FIG. 14 is a perspective view of the inner layer of the collar; 
     FIG. 15 is a perspective view of the outer layer of the collar; and 
     FIG. 16 is a perspective view of the collar. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A hiking boot incorporating the sole and collar of the present invention is shown in FIG.  1  and generally designated  10 . The hiking boot  10  generally includes an upper  100 , a sole  12  and a collar  20 . The sole  12  includes a rigid flexplate  14  embedded within a relatively resilient midsole part  16  (See FIG.  2 ). A rear stabilizer  18  extends around the sole  12  in the heel portion to add stability to the heel portion of the sole  12 . The collar  20  extends around the upper  100  to provide improved heel retention and enhanced the lateral stiffness in the ankle region of the upper  100 . The present invention is described in connection with a mid-height hiking boot  10 . The present invention is, however, well suited for us in other types of footwear, including other outdoor footwear, walking footwear, athletic footwear, multisport footwear and work footwear. 
     Referring now to FIG. 2, the sole  12  includes flexplate  14 , midsole part  16 , rear stabilizer  18 , outsole  22  and cushioning insert  24 . The flexplate  14 , midsole part  16  and rear stabilizer  18  are manufactured as a single integrated assembly  26  (See FIG.  3 ). The outsole  22  is secured to the assembly  26  to provide a durable wear surface. The flexplate  14  includes a forefoot portion  32  that is generally planar and extends through the forefoot of the sole  12 , an arch portion  34  that is shaped to curve up through the arch of the sole  12 , and a heel portion  36  that is shaped to form a cup  38  in the heel of the sole  12 . The cup  38  is shaped to accommodate the cushioning insert  24 . The flexplate  14  is manufactured from a rigid material selected to provide the sole  12  with the desired rigidity. A suitable material is polymeric amide, such as nylon, with reinforcing fiberglass. The percentage of fiberglass will vary from application to application depending on the desired stiffness. For example, 15% fiberglass may be used in lighter applications while 20% may be used in heavier applications. The flexplate  14  defines a plurality of circular openings  28  as well as plurality of notches  30  about the periphery of the heel portion that permit the midsole material to flow around and entrap the flexplate  14  during manufacture, as described in more detail below. In the preferred embodiment, a conventional bonding fabric  64  is applied to the upper  60  and lower  62  surfaces of the flexplate  14  to improve the bond between the differing materials of the flexplate  14  and the midsole part  16 . Fabrics of this type are readily available from a variety of suppliers, and their use in molding applications for improved bonding are well-known to those skilled in the art. 
     The midsole part  16  is molded about the flexplate  14 . The midsole part  16  preferably completely surrounds the flexplate  14  so that no portions of the flexplate  14  are exposed. The midsole part  16  includes a lower surface  40 , an upper surface  42  and a peripheral surface  48 . The lower surface  40  is shaped to match the shape of the upper surface of the outsole  22  so that the two components can be attached, as described in more detail below. The upper surface  42  of the midsole part  16  is shaped to form a footbed for receiving the wearer&#39;s foot. The upper surface  42  includes a peripheral wall  44  having a curved inner surface that is shaped to wrap slightly around the wearer&#39;s foot. The midsole part  16  defines an insert recess  46  for receiving the cushioning insert  24 . The insert recess  46  includes two concentric, circular regions  49 ,  51  that extend into the midsole part  16  from the upper surface  42 . The upper circular region  49  has a larger diameter than the lower circular region  51 . The midsole part  16  is molded from a relatively resilient polymer to provide the sole  12  with the desired resiliency. A suitable material for the midsole part  16  is Hipren SL 3 , which is available from Goldenplast spa of Potenza Picena, Italy. 
     The rear stabilizer  18  wraps around the heel portion of the midsole part  16  to stiffen and stabilize the sole  12  and particularly the peripheral wall  44  of the midsole part  16 . The rear stabilizer  18  preferably extends along the peripheral surface  48  of the midsole part  16  from a point near the instep portion, around the heel portion of the midsole part  16 , and to a point on the exterior of the peripheral surface  48  approximately opposite of its starting point on the instep portion. In the preferred embodiment, the rear stabilizer  18  extends as close to the flexplate  14  as possible without risking exposure of the flexplate  14 . This reduces the amount of relatively soft midsole part  16  disposed between the flexplate  14  and the rear stabilizer  18 , thereby stiffening the rear stabilizer  18 . The rear stabilizer  18  is preferably contained in the mold at the time the midsole part  16  is molded so that it becomes integrally attached to the midsole part  16 . The rear stabilizer  18  is preferably manufactured from a relatively stiff polymer. A suitable material for the rear stabilizer  18  is Hipren H 2 T, which is available from Goldenplast spa of Potenza Picena, Italy. 
     The cushioning insert  24  is fitted within the upper circular region  49  of the cushioning insert recess  46  leaving the lower circular region  51  vacant. The cushioning insert  24  helps to provide the sole  12  with the desired resiliency and to aid in centering the wearer&#39;s heel within the boot  10 . In the described embodiment, the cushioning insert  24  is manufactured from a resilient material, such as EVA or polyurethane, that is selected to provide the desired level of cushioning beneath the wearer&#39;s heel. The cushioning insert  24  is shaped to fit closely within and complement the shape of the upper region  49  of the insert recess  46 . The illustrated insert  24  is merely exemplary, and may be replaced by an alternative insert having a different size, shape or composition. In some applications, the insert  24  may be eliminated altogether, in which case the insert recess  46  would also be eliminated. 
     The outsole  22  is generally conventional and is secured to the midsole part  16  to provide the sole  12  with a durable and non-slip wear surface. The design and configuration of the outsole  22  will vary from application to application as desired. In the preferred embodiment, the outsole  22  is a polymeric material selected from one of many well-known outsole materials having relatively high durometer. The outsole  22  includes an upper surface  50  that is secured to the lower surface  40  of the midsole part  16 , preferably by cement or other adhesives. The outsole  22  also includes a lower surface  52  that is shaped to define the desired tread pattern. For example, the lower surface  52  may include a plurality of cleats  54  or other tread elements. 
     Referring now to FIGS.  1  and  13 - 16 , the collar  20  is fixed to the upper  100  and the sole  12  to provide support in the ankle region. The collar  20  is manufactured from polymeric materials, and includes an inner layer  70  and an outer layer  72  that are molded together to form an integral, one-piece collar  20 . The inner layer  70  is manufactured from a relatively soft polymeric material, such as thermoplastic polyurethane (TPU) LPR 8520 available from Goldenplast spa, which has a hardness of approximately  86  shore A. This material permits the collar  20  to be secured to the upper  100  using conventional stitching techniques and apparatus. The outer layer  72  is manufactured from a harder polymeric material, such as TPU LPR 5725 available from Goldenplast spa, which has a hardness of approximately  56  shore D. This layer  72  provides the collar  20  with the desired rigidity and stiffness. When the two layers are combined, the collar  20  provides significant stability while still being readily securable to the upper using conventional stitching techniques and apparatus. The inner layer  70  includes a marginal portion  73  that extends beyond the outer layer  72  in the integrated collar  20 . The marginal portion  73  provides a stitching allowance through which the collar  20  can be stitched to the upper  100  such that the stitching  75  passes only through the soft and flexible inner layer  70 . 
     The collar  20  includes a cup portion  74  that extends around the heel of the boot and upwardly along the rear of the ankle portion of the boot. The collar- 20  further includes a lacing portion  76  having a somewhat horizontal span  78  that extends forwardly from the cup portion  74  and a somewhat vertical span  80  that extends downwardly to the sole  12 . The lacing portion  76  defines a pair of holes  82   a-b , which permit a lacing hook  83  to be secured to the collar  20  by rivets or other conventional fasteners. The collar  20  improves the function of the lacing system by distributing the lacing pressure over a large portion of the boot  10 , including the sole  12  and heel region of the boot  10 . With conventional systems, the pressure of the lacing system is centralized at the location at which the lacing hook is secured to the upper. 
     MANUFACTURE AND ASSEMBLY 
     Manufacture of the boot  10  will now be described with reference to FIGS. 7-17. The upper  100  is generally conventional and will not therefore be described in detail. Suffice it to say the that upper  100  is manufactured from conventional upper materials using conventional techniques and apparatus. In the preferred embodiment, the upper  100  is provided with an allowance permitting it to be secured to the sole  12  using conventional adhesives. 
     The sole  12  is manufactured by first molding the flexplate  14  from fiberglass reinforced nylon. As noted above, the proportionate amount of fiberglass will vary from application to application, but is preferably within the range of 10-30%. The flexplate  14  is manufactured using conventional injection molding techniques and apparatus. The fabric  64  is cut to the shape of the flexplate  14  and is placed in the base and cover molds of the flexplate mold (not shown) in a conventional manner. The flexplate mold is closed and the flexplate material is injected into the mold where it fills the mold cavity and comes into direct contact with the fabric  64 . The material is then permitted to cure such that the fabric  64  is disposed on the upper and lower surfaces of the flexplate  14 . Once the flexplate  14  is sufficient cured, it is removed from the flexplate mold (not shown) and is ready for incorporation into the midsole part  16 . 
     The midsole part  16  is manufactured using a midsole mold having a base mold  110  (See FIG. 7) and a pair of interchangeable cover molds  112  (See FIG. 8) and  114  (See FIG.  9 ). The base mold  110  defines a cavity portion  116  that is shaped to define the majority of the midsole part  16  as well as the rear stabilizer  18 . The base mold  110  includes a plurality of flexplate locating pins  118  that extend upwardly to retain the flexplate  14  in position within the mold cavity during the midsole part  16  injection step. The first cover mold  112  is used during molding of the rear stabilizer  18 . Accordingly, it includes a male portion  120  that extends into and cooperates with cavity portion  116  to define a cavity in the shape of the rear stabilizer  18 . The male portion  120  defines a series of openings  121  adapted to receive the flexplate locating pins  118  when the first cover mold  112  is closed onto the base mold  110 . The remaining portion of the mold cavity is separated from the rear stabilizer  18 . The appropriate material is then injected into the rear stabilizer cavity, where it is permitted to cure to define the rear stabilizer  18 . 
     Once the rear stabilizer  18  is sufficiently cured, the first cover mold  112  is removed and the mold  110  is prepared for molding of the midsole part  16 . The rear stabilizer  18  is left in place within the base mold  110  so that it will become integrally attached to the midsole part  16  during molding of the midsole part  16 . In addition, the previously molded flexplate  14  is inserted into the cavity portion  116  of the base mold  110  atop the locating pins  118 . The second cover mold  114  closes the base mold  110  and includes a male portion  122  that extends into and cooperates with the cavity portion  116  to define a cavity in the shape of the midsole part  16 . The male portion  122  includes a protrusion  124  that defines the insert recess  46  as well as a plurality of flexplate locating pins  126  that extend down into the cavity portion  116  to locate the flexplate  14 . 
     Once the second cover mold  114  is closed on the base mold  110 , the material of the midsole part  16  is injected into the mold. The material fills the mold cavity surrounding and entrapping the flexplate  14  while also engaging and bonding to the rear stabilizer  18 . Because the rear stabilizer  18  and midsole part  16  are molded from materials in the same family (e.g. Hipren) a good bond between the two components is achieved. The second cover mold  114  remains in place until the material is sufficiently cured. The second cover mold  114  is then opened and the midsole part  16  is removed. 
     The outsole  22  is preferably manufactured using conventional techniques and apparatus. In the illustrated embodiment, the outsole  22  is compression molded using conventional compression molding machinery. The outsole  22  is molded from material having the desired resiliency and wear characteristics, such as a relatively high durometer polyurethane material. The outsole  22  is preferably attached to the midsole part  16  using conventional techniques and apparatus. In the preferred embodiment, the outsole  22  is secured to the lower surface of the midsole part  16  by cement or other adhesives using conventional techniques and apparatus. 
     The cushioning insert  24  is preferably manufactured using conventional techniques and apparatus, and therefore will not be described in detail. Suffice it to say that the cushioning insert  24  is manufactured from a material such as EVA using conventional techniques and apparatus. The insert  24  is fitted within the insert recess  46  to complete assembly of the sole  12 . The cushioning insert  24  can be cemented, frictionally fitted or otherwise secured in place as desired. 
     The collar  20  is manufactured using a mold (not shown) having a base mold and interchangeable first and second cover molds. The base mold and first cover mold cooperatively define a cavity having the shape of the inner layer  70 . The appropriate material is then injected in the mold cavity to form the inner layer of the collar  20  (See FIG.  14 ). The first cover mold is removed from the base mold once the inner layer  70  is sufficiently cured. While the inner layer  70  remains in place on the base mold, the second cover mold is moved into place on the base mold. The second cover mold cooperates with the outer surface of the inner layer  70  to define a cavity corresponding in shape to the outer layer  72 . The appropriate material is then injected into the cavity in a second shot to form the outer layer  72  (See FIG.  15 ). As the material of the second shot cures, it bonds to the inner layer  70  providing an integral, dual density collar  20  (See FIG.  16 ). The lacing hook holes  82   a-b  can be formed as part of the molding process or they can be punch, drilled or otherwise formed in the collar  20  after the molding process is complete. 
     Once manufacture of the collar  20  is complete, it is attached to the upper  100  with stitching  75  using conventional stitching techniques and apparatus. If desired, stitching holes (not shown) can be preformed in the inner layer  70  prior to stitching, for example, by drilling, punching or as part of the molding process. The lacing hook  83  is secured to collar  20  at holes  82   a-b  using rivets or other conventional fasteners. The rivets may extend just through the collar  20 , typically both inner and outer layers, or may extend through the collar  20  and the upper  100 . The collar  20  is also cemented or otherwise attached to the sole  12  using conventional techniques and apparatus. 
     The combined upper  100  and collar  20  are then attached to the sole  12 . Preferably, the upper  100  and collar  20  are direct attached to the sole using conventional techniques and apparatus. In the preferred embodiment, the upper  100  and collar  20  are cemented directly to the upper surface  42  of the midsole part  16  using conventional cement or other adhesives. A sock lining or other conventional insert can be placed within the footwear  100  as desired. 
     ALTERNATIVE METHOD OF MANUFACTURE FOR MIDSOLE 
     In an alternative embodiment, the midsole part  16 ′ is molded in several injections. The first injection forms the lower portion  17  of the midsole part  16 ′ with a platform  250  and integral locating pins  252  for supporting the flexplate  14 . The second injection forms the rear stabilizer  18 . And, the third injection forms the upper portion  19  of the midsole part  16 ′. FIG. 10 shows the flexplate  14  disposed above the lower portion  17  with the upper portion  19  illustrated in phantom lines. 
     In this embodiment, the mold includes a base mold (not shown) and three interchangeable cover molds, only the first  204  of which is shown in the drawings. The base mold of this embodiment is generally identical to the base mold  110  of the embodiment discussed above, except that it does not include flexplate locating pins  118 . The base mold includes a cavity portion that defines the majority of the midsole part  16 ′ as well as the rear stabilizer  18 . The first cover mold  204  includes a male portion  212  that extends into and cooperates with the cavity portion of the base mold to define a cavity  214  in the shape of a lower portion  17  of the midsole part  16 ′. The first cover mold  204  also defines a platform recess  215  and a pair of locating pin recesses  216 . The platform recess  215  and locating pin recesses  216  create support elements in the lower portion  17  of the midsole part  16 ′ that support the flexplate  18  within the mold during molding of the upper portion of the midsole part  16 ′. 
     The lower portion  17  of the midsole part  16  is molded by closing the first cover mold  204  onto the base mold (not shown). This defines a cavity in the shape of the lower portion  17  of the midsole part  16 ′. The midsole part material is then injected into the mold in a conventional manner to fill the cavity, including platform recess  215  and locating pin recesses  216 . The material is permitted to cure as desired and then the first cover mold  204  is removed. The platform recess  215  and locating pin recesses  216  have defined a platform  250  and a pair of locating pins  252  to support the flexplate  14  during molding of the remainder of the midsole part  16 ′ (See FIG.  10 ). The lower portion  17  of the midsole part  16 ′ is left in the base mold during the remaining molding steps as described in more detail below. As with the midsole part  16  of the preferred embodiment, the lower portion  17  of the midsole part  16 ′ is preferably manufactured from a relatively soft polymer, such as Hipren SL 3 . 
     The rear stabilizer  18  is molded next using the base mold and the second cover mold. The second cover mold (not shown) is generally conventional and it includes a male portion that extends into and cooperates base mold to define a cavity in the shape of the rear stabilizer  18 . The desired material is then injected into the rear stabilizer cavity in a conventional manner, where it is permitted to cure to define the rear stabilizer  18 . As with the preferred embodiment described above, the rear stabilizer is preferably manufactured from a relatively rigid and durable material, such as Hipren H 2 T. 
     Next, the second cover mold (not shown) is removed to provide access to the lower portion  17  of the mold part  16 ′ and the rear stabilizer  18 , both or which are retained on the base mold (not shown) for the upcoming final injection. The flexplate  14 , which is preferably pre-molded as in the previously described embodiment, is then placed in the mold atop the lower portion of mold part  16 ′. The flexplate  14  is supported atop the platform  250  and locating pins  252  defined in the lower portion  17  of the midsole part  16 ′ (See FIG.  11 ). The first portion of the midsole part  16 ′ and the rear stabilizer  18  are left on the base mold where they remain trapped during the next injection molding step. The third cover mold (not shown) is then closed on the base mold. The third cover mold is not illustrated in the drawings, but it is generally identical to the second cover mold  114 , except that it does not include the flexplate locating pins  126 . The third cover mold cooperates with the base mold, the first portion  17  of the midsole part  16 ′ and the rear stabilizer  18  to define a cavity in the shape of the remaining, or upper portion  19 , of the midsole part  16 ′ yet to be formed. The appropriate material is then injected into the mold cavity in a conventional manner. In the preferred embodiment, the upper portion of the midsole part  16 ′ is manufactured from the same material as the lower portion of the midsole part  16 ′, which in this alternative embodiment is Hipren SL 3 . Although the two midsole parts  17  and  19  need not be manufactured from the same material, it is desirable for the two midsole parts  17  and  19  to be manufactured from materials of the same family of materials so that they readily bond to one another. As the material from this injection cures, it bonds to the lower portion of the midsole part  16 ′ and the rear stabilizer  18 . As a result, the material cures to provide an integral midsole part  16 ′. Once cured, the mold is opened and the midsole part  16 ′ is removed for incorporation in the boot  10  as described above in connection with the preferred embodiment. 
     The above description is that of one or more preferred embodiments of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law including the doctrine of equivalents. Any reference to claim elements in the singular, for example, using the articles “a,” “an,” “the” or “said,” is not to be construed as limiting the element to the singular.