CROSS REFERENCE TO RELATED APPLICATIONSThis application claims priority from U.S. Prov. App. Ser. No. 60/868,512 filed Dec. 4, 2006, the entire contents of which are herein incorporated by reference. This application also claims priority from U.S. Ser. No. 11/758,651 filed Jun. 5, 2007 which in turn claims priority from U.S. Prov. App. Ser. No. 60/803,979 filed Jun. 5, 2006, the contents of each of which are also herein incorporated fully by reference.
FIGURE SELECTED FOR PUBLICATIONFIG. 17
BACKGROUND OF THE INVENTION1. Field of the Invention
The invention relates to footwear and a method of manufacturing same. In particular, the invention relates to a shoe construction having an outsole and upper of footwear stitched together along the forefoot area and glued together along the middle area of the footwear.
2. Discussion of the prior art
The human foot is a combined structure of base and lever, supporting and balancing the body's weight while standing, as well as raising and moving the body. The anatomy of the foot is very complex, but well studied and well know to the shoe industry. Generally, footwear designers tend to construct shoe models that are both comfortable and durable. In addition, of course, the shoes have to be aesthetically appealing and follow the fashion trends.
When even one part of the foot becomes damaged, it can affect every other part of the foot and lead to problems. In very general terms, normal or neutral feet tend to roll off the center of the forefoot (front part of the foot). This motion is associated with substantial stresses upon the forefoot that gradually decrease as the foot rolls towards the heel. Accordingly, in use, if the shoe design ignores both the anatomical and mechanical particularities of the foot, the front of the shoe, if it is not sufficiently reinforced, may wear out rather soon and if not also well designed will appear unattractive. On the other hand, if the shoe has an overly rigid construction, it creates an uncomfortable environment for the foot.
One effort to streamline both the construction of the shoe design and secure the mechanical requirements of the shoe can be found in U.S. Pat. No. 5,203,792 to Kaiser, the entire contents of which are herein fully incorporated by reference. In Kaiser, there is provided a flexible shoe sole member having a lip member extending fully about the top surface. An upper member is then fit, right side in, about the sole such that the upper circumscribes the lip of the sole. Then the upper is secured to the outer wall of the lip and the inner wall of the lip is folded inward and the entire sole flipped right-side-out so as to present a desirable seam surface and a smooth juncture between sole and upper member. Unfortunately, this reference fails to recognize the variants and requirements within the design and construction fields as will be appreciated by one of skill in the art having considered the present disclosure in detail.
In summary, the problems of commercially available manufacturing methods for shoe gluing include at least the following:
Poorly constructed glue joints that easily separate.
Difficult to functionally adhere toe box constructions.
Delicate designs more suitably adapted to hand stitching construction techniques are costly and time consuming.
Non-adaptability of the present glue-joint and stitching construction techniques.
The design aspect is particularly important to consider for fashion conscious woman. Typically, the outsole of the shoe is stitched to the rest of the shoe parts so as to provide a reliable structure capable of withstanding high stresses during use. However, stitching may add to the overall unappealing and bulky look of the shoe and may well create discomfort in use, when stitching is rubbing on a foot portion. Furthermore, as a technological operation, the stitching may be time- and labor-ineffective.
A need therefore exists for footwear that has a reinforced front portion capable of withstanding high stresses while providing the footwear with elegance.
Another need exists for a shoemaking process that is time- and labor-effective.
SUMMARY OF THE INVENTIONThe inventive footwear seam construction and method for manufacturing same meets these proposed needs and multiple variants are provided. In non-technical parlance the phase blind-seam may be employed or stitch and turn depending upon the feature of construction being discussed. In accordance with one aspect of the invention, the inventive method includes juxtaposing an upper with an outer surface of an outsole or with the outer surface of a member extending from tan outsole (attached by stitching, gluing, or other construction). The outsole may be made by a variety of molding methods and has an outer surface and an inner surface and may be generally planer in alternative aspects (as will be discussed). The outer surface is provided with a peripheral edge provided by extending the outer surface or by attaching a secondary outsole member or alternatively called a secondary upper portion. In the juxtaposed position also considered an inside-out position, the inner face of the peripheral edge and the forefront bottom portion of the upper overlap one another. Once the overlapping position is established, the upper is turned upside down over the periphery of the outsole and ends up facing the inner surface of the outsole.
In brief summary, a footwear member is optionally configured with an outer sole and an upper coupled together so as to define a forefoot area of and a rearfoot area of the footwear member. An extending lip member couples the outer sole and the upper member and may extend from either one forming a non-visible or blind seam construction that may be further manipulated in multiple ways. The extending lip member or connection member are stitched together along a forefoot area of the assembled footwear and may optionally allow a portion of a tread member to be glued along a rearfoot area of the assembled footwear. The assembly presented enables optional construction techniques adaptable to a variety of fashion construction options.
In accordance with one aspect of the invention, the forefront bottom region of the upper and the peripheral edge of the outsole are then stitched together but may be adhered in other manners without departing from the scope and spirit of the present invention. As mentioned above, the forefront portion of footwear is always under substantial flexing forces generated by the foot motion of the footwear owner as he or she walks forward. Accordingly, the forefront area of the footwear, which is generally defined by the stitched forefront bottom portion and peripheral edge, provides a reliable structure capable of withstanding the flexing forces as constructed according to the alternative details noted below.
During the stitching step, the peripheral edge and forefront bottom portion of the upper are bent inwards to extend substantially parallel to the inner surface. The stitches may penetrate through to the outer surface of the outsole or the extending flange of the secondary upper where thin-layer constitution requires through stitching, however, where permissible by the layer-thicknesses involved the stitching do not penetrate through the outer surface of the outsole preserving, thus, waterproof characteristics of the flexible polymeric material. Alternatively, the stitching may be replaced by thermal bonding, adhesive-bonding, or other known systems to provide a waterproof seam.
In accordance with another aspect of the invention, the stitching may penetrate a portion of the outsole. In still a further aspect of the invention, the stitched parts of the footwear may be bonded with the inner surface of the outsole. Importantly, regardless of the type of the coupling, the exterior of the forefront area, which is located immediately next to the outsole, does not protrude laterally beyond the periphery of the outsole thereby rendering the forefront area of the footwear elegant and appealing to the eye.
The method continues with tucking the rearfoot bottom portion of the upper so that it lies atop the inner surface of the outsole. In accordance with a further aspect of the invention the bent portion is then glued to the outsole's inner surface. Since the rearfoot area of the footwear is exposed to insignificant bending or flexing forces, gluing the outsole to the upper establishes a reliable stress-resistant structure. To meet aesthetic requirements, the surface of the upper, which is immediately adjacent to the bent rearfoot bottom portion, like the forefront bottom portion, does not protrude laterally beyond the periphery of the outsole the inner to the bet portion. Accordingly, both the forefoot and rearfoot bottom portions of the upper substantially conform to the outer contour of the outsole. The footwear manufactured in accordance with the invention is aesthetically appealing, has a reliable structure that takes into consideration the anatomical particularities of the human foot and cost-effective.
These and other features and aspects of the present invention will be better understood with reference to the following description, figures, and appended claims.
BRIEF DESCRIPTION OF THE FIGURESFIG. 1 illustrates an exploded view of an alternative aspect of the inventive footwear.
FIG. 2 illustrates a top view of an outsole and upper in a disassembled state of the inventive footwear.
FIG. 3 illustrates an initial position of the upper and outsole of the inventive footwear in accordance with the alternative initial step of one aspect of the inventive method, in which the upper is juxtaposed with the outer surface of the outsole or an extended portion affixed to and extending from the outsole.
FIG. 4 illustrates a subsequent step of the inventive method in which the forefront bottom portion of the upper is stitched the outsole and inverted or turned inside-out so that the upper faces the inner surface of the outsole.
FIG. 5 illustrates a following step of the inventive method in which the rearfoot bottom portion of the upper is inverted to the right-side-out configuration so as to face the inner surface of the outsole.
FIG. 6 illustrates a following step of the inventive method in which the rearfoot bottom portion of the upper is glued to the outsole.
FIG. 7 illustrates the inventive footwear in the assembled state thereof.
FIG. 8 is a side view of a shoe constructed according to an alternative aspect of the present invention.
FIG. 8(A) is a sectional view through line I-I inFIG. 8.
FIG. 8(B) is an enlarged view of Area A inFIG. 8(A).
FIG. 8(C) is a partial view of a base member and an upper portion in a blind-seam connection position prior to turning and later constriction.
FIG. 9 is a sectional view through line II-II inFIG. 8.
FIG. 10 is a plan view of a flexible tread or sole member optionally containing a tread pattern (not shown).
FIG. 11 is a plan view of a separate flexible tread lip or upper lip member that is later connected between the flexible tread or sole members and an upper member.
FIG. 11(A) is a plan view of a stitched together or connected assembly between the flexible tread or sole member inFIG. 10 and the separate flexible tread lip or upper lip member inFIG. 11.
FIG. 12(A) is a plan view of a stitched together upper member containing a tongue portion.
FIG. 12(B) is a partially folded-over or juxtaposed plan view of the stitched together upper member ofFIG. 12(A).
FIG. 13 is a side elevational view of the pre-assembly ofFIG. 11 andFIG. 12(A) prior to juxtaposition, flipping, or inversion by both members to formFIG. 14.
FIG. 14 is a side elevational assembly view of the juxtaposed, flipped, or inverted assembly of the separate flexible lip member and tread/sole inFIG. 11 with the inverted upper assembly inFIGS. 12(A) and 12(B).
FIG. 15 is a side elevational view of the assembly inFIG. 14, rejuxtaposed or flipped right-side-out exposing the tread member with the insertion of an insole portion.
FIG. 16 is a side elevational view of the assembly ofFIG. 15 in combination with an external foot-shaped last member to provide a rigid support for later assembly steps.
FIG. 17 is a side elevational view of a complete assembly combining the assembly ofFIGS. 15 and 16, with a heal body.
DETAILED DESCRIPTIONReference will now be made in detail to a sequence of inventive steps illustrating manufacturing of the inventive footwear in accordance with the inventive method. The drawings are in simplified form and are not to precise scale. For purposes of convenience and clarity only, directional terms, such as top, bottom, left, right, up, down, over, above, below, beneath, rear, front and beyond may be used with respect to the drawings. These and similar directional terms should not be construed to limit the scope of the invention in any manner. The words “connect,” “couple,” and similar terms with their inflectional morphemes do not necessarily denote direct and immediate connections or particular methods of connecting, unless specifically identified, but also include connections through mediate elements or devices.
In coping with the problems noted above, the present invention provides a system for manufacturing footwear, particularly ladies shoes that combines a stitch and turn method utilized by this invention and a conventional glue construction.
Referring toFIGS. 1-6, and in particular toFIG. 1, aninventive footwear10 is configured with aoutsole12, upper14,midsole16,insole18 andheel42. Each of the above-identified parts has a forefront portion extending from the front end of the footwear and terminating substantially midway between the front and rear ends of the footwear. Portions of footwear components extending from the midsection to the rear end of the footwear are generally denoted as rearfoot portions. Coupled together, the forefront portions and rearfoot portions of the footwear components define aforefront area20 andrearfoot area22, respectively, of footwear10 (FIG. 7).
During construction, upper14 is initially juxtaposed with anouter surface24 of outsole12 (FIGS. 3 and 4) and subsequently stitched thereto (FIGS. 3 and 4). The stitching step is accomplished by juxtaposing, turning, flipping the upper with the outsole so that abottom edge32 of a forefoot bottom portion44 (FIGS. 1,3 and4) overlaps an outer face48 (FIG. 3) of aperipheral flange28 ofoutsole12. Theflange28 is formed oninner surface26 ofoutsole12 and defines its outer extremity while extending along the forefront portion of the outsole or optionally a greater or lesser portion of the outsole (or as will be discussed an alternative portion of the upper that is affixed separately, as will be discussed). As a result of molding,peripheral flange28 extends transversely toinner surface26 rendering positioning of upper14 labor- and time-effective.
Having juxtaposed upper14 andouter surface24 ofoutsole12 in the desire position, the overlapped segments offlange28 and forefrontperipheral edge32 are stitched together, as better illustrated inFIG. 4. Then, upper14 is inverted so as to faceinner surface26 ofoutsole12, as shown inFIG. 4.
Thereafter, a rearfootperipheral portion46 is bent inwards so that its edge34 (FIG. 3) lies atopinner surface26 ofoutsole12. To completely couple the outsole and upper, a layer of glues is inserted between the opposing surfaces of the upper and outsole. Inserting aweight40 or foot-last (a rigid foot-shaped body) (FIG. 6) and pressing there against so that it, in turn, brings the opposing surfaces to be glued in close contact with one anther complete the coupling step. Accordingly, the outsole/upper combination is characterized by the stitchedforefoot area20 offootwear10 and its gluedrearfoot area22. The variously coupled forefoot and rearfoot areas of the footwear allow it to withstand greater stresses usually imposed on the forefront area, while leaving the rearfoot area sufficiently reinforced to withstand relatively insignificant stresses during the use of the footwear. On the other hand, the gluing operation, as compared to the stitching operation, is time-effective which renders the entire coupling step of the inventive method to be time-effective as well.
Completion of the method entails providing a compartment, which is formed as a result of coupling between the upper and outsole, withmidsole18 that is, typically, made from rigid material such as wood, cork, plastic or even metal. The midsole spans the width of the outsole and, thus, is configured as a stiffening member preventing unintended distortion of the forefront area offootwear10 during shipping and use.
After the midsole is placed atop the inner surface ofoutsole12 and attached parts of upper14, it is fixedly attached thereto so as to prevent relative displacement between the midsole and the rest of coupled components. To soften the supporting structure of the footwear, a cushionedinsole16 is removably inserted into the compartment atopmidsole18. Finally, aheel42 is attached to the rearfoot portion of the outer surface ofoutsole14.
The final product is thus is manufactured by a simple, time- and cost-effective blind seamed process involving in part a turning process benefited by a highly flexible outsole and upper portions. In addition,footwear10 is elegant because not a single area of the upper protrudes beyond the periphery of the outsole, as will be evidenced during the rest of the disclosure.
As mentioned above, the molded outsole is made withflange28 extending inwardly from and transversely toinner surface26 ofoutsole12. Theforefront bottom portion44 of upper14 is juxtaposed withouter face48 offlange28 and stitched to this flange. When these parts are subsequently flexed toward the inner surface ofoutsole12, the bottom region of upper14 adjacent to itsedge32 offorefront area20 does not extend laterally beyond the periphery ofoutsole12, thereby providing the forefront area of the footwear with an elegant look.
Therearfoot portion46 of upper12 extending along the midsection of the footwear is wider than itsforefoot portion44 and has respective portions of itsbottom edge34 tucked inside so that the rearfoot portion of the upper also does not extend laterally beyond the periphery ofoutsole12. Like the forefoot area, the rearfoot area is, thus, elegant, but both the forefoot and rearfoot areas are still sufficiently reinforce to withstand respective stresses upon the footwear.
Theinner surface26 ofoutsole12 has an elevated region36 (FIG. 2) having its periphery spaced from aninner face50 offlange28. Thus, opposing sides of the elevated region and flange delimit atrough38 coextending withflange28. Thetrough28 is dimensioned to receive the full width offlange28 and, of course, edge32 of upper14, when these parts get stitched. Preferably the depth of the trough is sufficient to receive the stitched parts so as to haveedge32 of upper14, which upon bending forms an outer layer of the stitched parts, flush with the top surface of the elevated region. Thus, the inner surface offootwear10 supporting the midsole andinsole18 and16 (FIG. 1), respectively, is substantially flat and provides the owner of the footwear with a comfort. The stitched parts may be glued to the trough during gluing of the rearfoot portions of the upper and outsole. Alternatively, the stitching may be extended into the outsole without, however penetrating the full width thereof.
Thefootwear10, as illustrated inFIGS. 1-7 is shown to be designed for women, and, thus, the elegance of the footwear is particularly important. However, the same method and structure may be implemented for manufacturing footwear for men and children. Theinsole16, often constructed of natural or synthetic leather is positioned on foam cushion. Commonly an adhesive glue, often a clue compatible with a PVC basedoutsole12, is used between the outer andmidsole12,18, respectively.
Materials used for manufacturing upper14 can vary in accordance with any given design, but, preferably, the upper is made from leather.
Referring now toFIGS. 8 through 9 an alternative construction discussion is present according to another aspect of the present invention.
A shoe100 includes a toe portion200 and a healportion300 joined by a continuoussole portion500 as shown and supported by a healmember400. A series of decorative cutouts60,60 enhance the visual appearance of shoe100.Sole member500 is constructed of PVC (polyvinyl chloride), but may be constructed from any suitable material both organic (leather/rubber) and in-organic/man-made (PVC and related elastomeric materials).
Referring now more directly toFIG. 8A-9, toe portion200 includes a ofsole member500 stitched at extendinglip members140 toupper member portion90 in a type of blind-seam, as will be discussed. In this embodiment,uppers90 are joined byupper members110,110 at decorative stitchings111,111, as shown to enhance an overall attractive appearance. In alternative embodiments, upper90 in upper member200 may be continuous from side to side or otherwise alternatively constructed according to the related arts. A pair ofopposed stitches116,116 on each extendinglip member140 securely join bottom portions ofuppers90 as shown.Sole member500 additionally includestread portions70 for gripping during walking and for enhancing flexibility as desired.
A stiffening member or insolesupport board member80 is generally provided for additional support and spans generally the width ofsole member500 to provide stiffening support and prevent unintentional distortion of toe portion200 during shipping and later use. Stiffeningmember80 is inserted after the blind-seam stitching process as the flexibility required to achieve the same prevents prior insertion of stiffeningmember80.
Afoam cushion member112 is positioned on insolesupport board member80, as shown and increases user comfort. Aninsole member113, often constructed of natural or synthetic leather is positioned oncushion member112 and provides a pleasing visual appearance. Commonly, anadhesive glue115, often a glue compatible with a PVC basedsole member500, is used between the layers to secure each respective layer tosole member500 andinsole support board80, and is used as would be otherwise expected by one of skill in the art having read and considered the entire disclosure. In this way, the respective members are secured and shoe100 is provided in a suitable form for secure consumer use. This construction also is adapted to bind extendinglip140 to respective locations on sole500 securely lockingstitchings116 in place while providing a pleasing blind-seam outward appearance.
While not mandated by the present construction, alternative variants are envisioned by the present disclosure as noted in expanded view A inFIG. 8(A), an additionaladhesive layer115′ is positioned between stitched or bonded portions ofupper member90 and extendinglip members140 to improve security.
Referring additionally now toFIG. 8(C) a portion ofsole member500 is shown with an extendinglip member140 stitched to upper90 in a blind seam manner prior to a turning and optional gluing. It will be understood by those of skill in the art that variants of the present invention are within the bounds of the present disclosure, including those variants whereinlip members140 are provided as separate members, or the stitched portion of upper90 is provided in a separate upper or separate lip member body, as will be discussed without departing from the scope and spirit of the present invention.
Referring now directly toFIG. 9, healportion300 of shoe member100 is more fully discussed. As shown,sole member500 is joined to upper90 employingadhesive115. Thereafter, insolesupport board member80′ (which may be an extension of support board member80) is positioned and secured allowing later insertion of a reinforcingmetal shank member117 bounded bysupport board members118,118 on either side. Thereafter, foam member112 (likely a closed cell based foam) is layered withinsole member layer113 and adhered in place using adhesive115 (not shown). Finally, healmember400 is secured to the bottom portion of sole500 to complete construction.
In another manufacturing method discussed, after toe portion200 is constructed and flipped/inverted (creating a joining or stitching method creating a blind seam), healportion300 of shoe100 is constructed by inserting an external last (shown later) to form a foot-shape and gluing the insole board in place and thereafter finishing and polishing the shoe in a conventional manner. In this way, an alternative embodiment of the present invention provides both a blind-seam construction method for a portion of a shoe construction and a partial stitch-and-turn construction method for a second portion of a shoe construction without departing from the scope and spirit of the present invention.
Referring collectively now toFIGS. 10 through 17 an additional alternative seam construction method employs a lip extending member is provided in assembly600. Shoe assembly600 includes a flexible tread member orsole member601 that may be optionally formed with treads or friction enhancing protuberances or flexibility enhancing undulations (both not shown) so as to enable use as a shoe tread or sole member while being sufficiently flexible to enable the proposed method of assembly as outlined the proposed invention.
A separate flexible tread lip orupper lip member602 is provide in a shape partially extending about a corresponding portion of tread member orsole member601, and is shown in a generally “U” or “N” configuration (FIG. 11). It is noted, that the proposed alternative flexible tread lip or upper lip member is functional to flexibly join portions of the flexible tread orsole members601 and an upper member assembly603 (as will be discussed), and may be a wholly separate member prior to assembly, may alternatively extend from anupper member assembly603 or may alternatively extend from flexible tread orsole member601 according to aspects of the present invention without departing therefrom as will be recognized by those of skill in the art having considered the entire disclosure herein.
As will be noted inFIG. 11A,flexible lip member602 is connected withflexible tread member601 with partial perimeter or edge stitching800 (as shown) but may be connected in any other known bonding, adhering, or affixing method known to those in the shoe construction arts without departing form the scope of the present invention. A toe region602A of the lip-tread assembly602B is opposite a lose heal region602C of tread orsole member601 that is not connected to tread orsole member601, as shown. Aloose portion609 opposite toe region602A is provided whereconnection800 ends for the remaining portion offlexible lip member602.
Referring directly toFIGS. 12(A) and 12(B) anupper assembly603 contains a continuousupper loop604 joined alongseam605. Continuousupper loop604 contains atoe portion604A and a healportion604B including seam605. Anupper tongue portion605A is joined or connected to continuousupper loop604 intoe portion604A in astitching region606 or by other connection methods known to those of skill in the art. To invert or juxtaposeupper assembly603 an operator grasps continuousupper loop604 proximaterear seam605 and twists alongdirection arrows607 and607A inFIGS. 12A and 12B until ultimatelyupper assembly603 is juxtaposed or inverted as will be understood by those of skill in the art.
It will be noted that the top plan view inFIG. 12A is represented in the top part of the view inFIG. 13 prior to the juxtaposition or inside-out switch for assembly inFIG. 14.
InFIG. 13 a relationship is recognized prior to juxtaposition or inversion of bothupper assembly603 and lower assembly602A noting the general alignment of a stitching or connection interface between connection edges608,608 on respectiveupper assembly603 and lower assembly602A. It will be recognized by study of the image that non-connected portion602C of tread orsole member601 includes aloose region609 opposite toe portion602A.
InFIG. 14, bothupper assembly603 andlower assembly602B have been juxtaposed or inverted or turned inside-out and are brought into close association alongedges608 and affixed or connected together by stitching610 or by other methods known to those of skill in the art, such as thermal bonding, adhesive bonding, and combinations thereof. It will be appreciated by those of skill in the art that the surfaces visible inFIG. 14 are what would be the inner surfaces of the complete shoe assembly600 (FIG. 17) and that the view is of what would be considered an inside-out view.
It will also be appreciated by those of skill in the art having studied the present disclosure thatflexible tread portion601 is hidden from view and is within the inverted assembly, with it's surface-contacting tread portion (if any) facing the outerfinished surface605A′ oftongue member605A. As connected alongedges608 by stitching or otherwise, it will be recognized that upon further juxtaposition or inversion the connection will be a blind seam or hidden-from view seam similar to that shown earlier inFIGS. 8(A)-8(C), although unlikeFIGS. 8(A)-8(C) the lip extension portion is not re-joined to the tread or sole member in a further assembly step.
InFIG. 15, the assembly noted inFIG. 14 is re-juxtaposed or turned right-side-out again hidingseam edges608 joined byconnection610 forming a type of partial blind-seam between the upper assembly and lower assemblies, as shown. As will also be appreciated, the non-connected portion602C of tread orsole member601 remains non-connected. As shown an inner rigid foot support member611 is inserted and inFIG. 16 is followed by insertion of a rigid foot-shapedlast member612 inside the assembly. Thereafter, adhesive (not shown) is employed to join portions of continuousupper member603 proximate unsealed tread or sole portion602C along adhesive orconnection juncture613 forming a continuous connection betweenupper assembly603 andlower assembly602B withlip member602 there between having ablind seam610 for by a blind seam or seam creation system or method.
InFIG. 17 healmember615 is assembled in a manner recognized by those of skill in the shoe assembly arts involving pressure and adhesive to form full shoe embodiment600 employing the present alternative embodiment of the present invention. It will be recognized by those of skill in the art that multiple connection methods (including stitching, bonding, and adhesive) may be employed to form the connections discussed herein without departing from the scope of the present invention.
In the claims, means- or step-plus-function clauses are intended to cover the structures described or suggested herein as performing the recited function and not only structural equivalents but also equivalent structures. Thus, for example, although a nail, a screw, and a bolt may not be structural equivalents in that a nail relies on friction between a wooden part and a cylindrical surface, a screw's helical surface positively engages the wooden part, and a bolt's head and nut compress opposite sides of a wooden part, in the environment of fastening wooden parts, a nail, a screw, and a bolt may be readily understood by those skilled in the art as equivalent structures.
It will be understood that the invention may be embodied in other specific forms without departing from the spirit or central characteristics thereof. The present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein.