Abstract:
A handlebar comprises a transverse extension piece including a first gripping portion. First and second handlebar segments are disposed on opposite ends of the transverse extension piece. Each of the handlebar segments comprises an upper handlebar grip portion and a lower handlebar grip portion. The upper handlebar grip portion includes a first curved section adjoining one end of the transverse extension piece and extending forwardly and inwardly from the transverse extension piece, and a second straight section. The upper handlebar grip portion includes a second gripping portion. The lower handlebar grip portion includes a curved end portion adjoining the end of the second straight section of the upper handlebar grip portion and extends outwardly and then downwardly. The lower handlebar grip portion includes a third gripping portion. The three gripping portions of the handlebar define a plurality of gripping positions in combination with a plurality of riding positions.

Description:
CROSS-REFERENCES 
     This application is a continuation-in-part application of U.S. patent application Ser. No. 13/236,756, filed Sep. 20, 2011, currently pending, the contents of which are incorporated herein by reference in the entirety. 
    
    
     BACKGROUND 
     This specification relates generally to a bicycle handlebar and, more particularly, to an ergonomic bicycle handlebar for use by a casual or recreational rider as well as a racing rider. 
     A conventional bicycle includes a stem coupled to the front fork of the bicycle, and a handlebar comprising a cross-bar rigidly coupled to the stem. The cross-bar is usually a tubular member and may be at least partially linear with curved portions formed at each end of the linear portion. A brake lever assembly can be mounted adjacent each end of the handlebar. The brake lever assembly comprises a grip handle bracket fixable to the handlebar and a brake lever pivotally connected to the grip handle bracket. A brake control cable connected to a corresponding brake lever assembly is introduced into the grip handle bracket for connection to the brake lever. Derailleur operating devices for changing gears, such as a shift lever, may also be located on the bicycle handlebar. 
     Racing bicycles are provided with a drop-type handlebar, which includes an intermediate straight portion centrally connected to a handlebar stem. A pair of U-shaped, downwardly bent drop portions are formed at both ends of the intermediate straight portion. The brake lever assemblies are mounted to the drop portions to enable the rider to conduct a braking operation while the rider grips the drop portion in a running posture. 
     Conventional bicycle handlebars are sometimes uncomfortable and can contribute to increased air drag forces. Moreover, the typical design for the handlebar and brake lever assembly is relatively poorly suited for an anatomically favorable posture of the hand of a rider. Selected fingers, usually the forefinger and middle finger, of the rider must be oriented to engage the brake lever and pull it rearward for a braking operation. However, this arrangement is disadvantageous for conducting a braking operation while gripping the grip handle bracket and is inherently uncomfortable for riding because the rider is required to support her weight mostly on the balls of the thumbs on the handlebar. 
     Riders have attached additional handlebar portions to conventional handlebars in order to increase power transfer, aerodynamics or comfort. Unfortunately, it can be difficult for the rider to control brake operating devices, derailleur operating devices, and the like when using such handlebar attachments. Moreover, the attachments do not always allow efficient power transfer from the rider to the drive train of the bicycle. Furthermore, these attachments do not always minimize air drag forces and can be uncomfortable for the rider. 
     For the foregoing reasons, there is a need for a bicycle handlebar with improved ergonomics. The new handlebar should be configured and oriented so as to provide the rider a comfortable riding position on the bicycle. Ideally the new handlebar will offer improved grip positions for the hands relative to the brake lever and the shift lever. 
     SUMMARY 
     A handlebar is provided for a bicycle including a stem operatively connected to a front wheel for steering the bicycle. The handlebar comprises a transverse extension piece adapted to be connected to the stem of the bicycle at a midpoint of the transverse extension piece. The transverse extension piece has a longitudinal axis and a transverse axis symmetrically bisecting the transverse extension piece and perpendicular to the longitudinal axis. The transverse extension piece includes a first gripping portion. First and second handlebar segments are disposed symmetrically on respective opposite ends of the transverse extension piece. Each of the handlebar segments comprises an upper handlebar grip portion and a lower handlebar grip portion. The upper handlebar grip portion has a longitudinal axis extending in a plane with the longitudinal axis of the transverse extension piece. The upper handlebar grip portion includes a first curved section adjoining one end of the transverse extension piece and extending forwardly and inwardly from the transverse extension piece in a direction toward the transverse axis, and a second straight section extending from the end of the curved section. The upper handlebar grip portion includes a second gripping portion. The lower handlebar grip portion has a longitudinal axis. The lower handlebar grip portion includes a curved end portion adjoining the end of the second straight section of the upper handlebar grip portion and extending outwardly along the longitudinal axis in a direction away from the transverse axis and then downwardly with respect to the plane. The lower handlebar grip portion includes a third gripping portion. The first, second and third gripping portions of the handlebar define a plurality of gripping positions for a rider in combination with a plurality of rider positions. 
     A bicycle is provided comprising a frame, a rear wheel rotatably mounted to the frame, a seat connected to the frame, a stem journaled to the frame forward of the seat, a fork connected to the stem, and a front wheel rotatably mounted to the fork. A handlebar comprises a transverse extension piece connected to the stem of the bicycle at a midpoint of the transverse extension piece. The transverse extension piece has a longitudinal axis and a transverse axis symmetrically bisecting the transverse extension piece and perpendicular to the longitudinal axis. The transverse extension piece includes a first gripping portion. First and second handlebar segments are disposed symmetrically on respective opposite ends of the transverse extension piece. Each of the handlebar segments comprises an upper handlebar grip portion and a lower handlebar grip portion. The upper handlebar grip portion has a longitudinal axis extending in a plane with the longitudinal axis of the transverse extension piece. The upper handlebar grip portion includes a first curved section adjoining one end of the transverse extension piece and extending forwardly and inwardly from the transverse extension piece in a direction toward the transverse axis, and a second straight section extending from the end of the curved section. The upper handlebar grip portion includes a second gripping portion. A lower handlebar grip portion has a longitudinal axis. The lower handlebar grip portion includes a curved end portion adjoining the end of the second straight section of the upper handlebar grip portion and extends outwardly along the longitudinal axis in a direction away from the transverse axis and then downwardly with respect to the plane. The lower handlebar grip portion includes a third gripping portion. The seat and the first, second and third gripping portions define a plurality of gripping positions for a rider in combination with a plurality of rider positions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present invention, reference should now be had to the embodiments shown in the accompanying drawings and described below. In the drawings: 
         FIG. 1  is a top perspective view of an embodiment of a handlebar for use with a bicycle. 
         FIG. 2  is a top plan view of the handlebar as shown in  FIG. 1 . 
         FIG. 3  is a bottom plan view of the handlebar as shown in  FIG. 1 . 
         FIG. 4  is a front elevation view of the handlebar as shown in  FIG. 1 . 
         FIG. 5  is a rear elevation view of the handlebar as shown in  FIG. 1 . 
         FIG. 6  is a right side elevation view of the handlebar as shown in  FIG. 1 , the left side view being a mirror image thereof. 
         FIG. 7  is a top perspective view of the handlebar as shown in  FIG. 1  with one of the brake lever assemblies exploded from the end of the handlebar. 
         FIG. 8  is a front elevation view of the handlebar as shown in  FIG. 4  including brake lever assemblies disposed on the ends of the handlebar. 
         FIG. 9  is a side elevation view of a bicycle including the handlebar as shown in  FIG. 1 . 
         FIG. 10  is a top plan view of one side of the handlebar as shown in  FIG. 8  and a hand of a user in a first position on the handlebar and the brake lever assembly. 
         FIG. 11  is a top plan view of one side of the handlebar as shown in  FIG. 10  and a hand of a user in a second position on the handlebar and the brake lever assembly. 
         FIG. 12  is a top perspective view of another embodiment of a handlebar for use with a bicycle. 
         FIG. 13  is a top plan view of the handlebar as shown in  FIG. 12 . 
     
    
    
     DESCRIPTION 
     Certain terminology is used herein for convenience only and is not to be taken as a limitation on the invention. For example, words such as “upper,” “lower,” “left,” “right,” “horizontal,” “vertical,” “upward,” and “downward” merely describe the configurations shown in the FIGs. Indeed, the components may be oriented in any direction and the terminology, therefore, should be understood as encompassing such variations unless specified otherwise. 
     Referring now to the drawings, wherein like reference numerals designate corresponding or similar elements throughout the several views, an embodiment of a handlebar for use with a bicycle is shown in  FIGS. 1-7  and generally designated at  20 . The handlebar  20  comprises a transverse connecting portion  22 , a pair of first upper handlebar portions  24 , and a pair of second lower handlebar portions  26 . The transverse connecting portion  22  is a linear elongated member having first and second ends  28 ,  29 , a short intermediate mounting section  30  and a central longitudinal axis  32  ( FIG. 2 ). The transverse connecting portion  22  extends substantially transversely from each side of the intermediate section  30  a distance of about 7 to about 10 inches, although it is understood this distance may vary to accommodate the size of the rider. The transverse connecting portion  22  preferably has an aerodynamic cross-sectional shape. In one embodiment, the transverse connecting portion  22  is circular in transverse cross-section, and a central section of the transverse connecting portion has a clamp diameter D 1  ( FIG. 2 ). D 1  may vary from about 25 mm to about 26.4 mm for standard handlebars, and up to about 32 mm for handlebars having oversized clamp diameters. The remainder of the transverse connecting portion  22  and the upper handlebar portions  24  and the lower handlebar portions  26  are substantially formed with a diameter D 2 . D 2  is typically slightly smaller than the clamp diameter, for example, slightly less than about 25 mm. The transverse connecting portion  22  forms a first continuous gripping surface for the hands on each side of the intermediate section  30 . 
     Each of the pair of first upper handlebar portions  24  is coupled to an end  28 ,  29  of the transverse connecting portion  22 . As best seen in  FIGS. 2 and 3 , the upper handlebar portions  24  extend outwardly from the ends  28 ,  29  of the transverse connecting portion  22 . The upper handlebar portions  24  comprise a curved section  34  bending forwardly and inwardly relative to the transverse connecting portion  22 . The curved section  34  is followed by a straight section  37 . The curved section  34  of each upper handlebar portion  24  has a radius of curvature R 1  of about one inch. Each upper handlebar portion  24  has a central longitudinal axis  36  in the same plane as the central longitudinal axis  32  of the transverse connecting portion  22 . The longitudinal axes  36  at the inner end of the upper handlebar portions  24  extend tangentially to the longitudinal axis  32  of the transverse connecting portion  22 . The central longitudinal axes  36  of the upper handlebar portions  24  are angled inwardly relative to the central longitudinal axis  32  of the transverse connecting portion  22 . The inward angle (I) may be from about 45 degrees to about 90 degrees. The overall length of the upper handlebar portions  24  is variable, particularly with respect to the length of the straight section  37 . Preferably, the upper handlebar portions  24  have an overall length sufficient to provide a second gripping surface for the hands. The second gripping surface may be used to accommodate the hands in an upright standard riding position or extended further to provide a tucked aero-position, as will be described below. 
     Each of the pair of second lower handlebar portions  26  adjoin an end of the straight sections  37  of the first upper handlebar portions  24  in a continuing manner. The lower handlebar portions  26  curve downwardly and outwardly relative to the upper handlebar portions  24 . The lower handlebar portions  26  have an outward radius of curvature R 2  of about two inches, which is the curvature of drop portions of conventional drop-type handlebars and is configured to fit the grip handle brackets of brake-shift lever units. Each lower handlebar portion  26  has a central longitudinal axis  38 . The longitudinal axes  38  at the inner end of the lower handlebar portions  26  extend tangentially to the longitudinal axes  36  of the upper handlebar portions  24 . The longitudinal axes  38  of the lower handlebar portions  26  are angled outwardly with respect to the longitudinal axes  36  of the upper handlebar portions  24  at an angle (θ) of about 10 degrees to about 40 degrees. Referring to  FIG. 6 , the longitudinal axes  38  of the lower handlebar portions  26  also extend tangentially to the common plane of the transverse connecting portion  22  and the upper handlebar portions  24 . The longitudinal axes  38  of the lower handlebar portions  26  are angled downwardly with respect to the common plane of the transverse connecting portion  22  and the upper handlebar portions  24  at an angle (Π) of about 0 degrees to about 45 degrees. The lower handlebar portions  26  have a length along their longitudinal axis  38  sufficient for a brake-shift lever mounting section  40  to allow grip handle brackets  52  to be clamped adjacent the ends of the handlebar  20 . In combination, the lower handlebar portions  26  and brake-gear shift lever units  50  form a third gripping surface for the hands. 
     The handlebar  20  as described herein can be constructed in a conventional manner of a one-piece, unitary member formed of lightweight metallic material, such as aluminum or titanium alloy or any other known suitable material, such as carbon fiber. In the embodiment shown in the FIGs., the handlebar  20  is formed of tubing with a crimped external groove  31  ( FIG. 4 ) for receiving wires or cables, as needed. 
     The mounting sections  40  on the lower handlebar portions  26  are configured to receive standard combination brake-gear shift lever units  50 . Brake-gear shift lever units  50  are well known, being available commercially from Campagnolo SRL of Vicenza, Italy, and Shimano Inc. of Osaka, Japan. Referring to  FIG. 7 , a typical brake-gear shift lever unit  50  comprises a grip handle bracket  52  adapted to be removably attached to the corresponding mounting section  40  of the lower handlebar portion  26  by a circular collar  54  or other suitable means. The collar  54  is split so that the ends of the collar can be compressed tightly in a gripping relation with the mounting section  40  upon tightening of a threaded element such as a screw (not shown), which is screwed into a threaded hole in the collar  54 . A brake shift lever  56  is pivotally connected at one end to the grip handle bracket  52  for movement toward the handlebar  20 . The brake shift lever  56  is pivotable bidirectionally laterally of the handlebar  20 . More specifically, as best seen in  FIG. 8 , the brake shift lever  56  pivots for braking in a plane that extends through the handlebar  20  and the pivots bi-directionally in a plane that is at a right angle to the plane of movement for braking. It is understood that the structure of the combination brake-gear shift lever unit  50  is not critical to the invention and a different form of combination brake-gear shift lever unit may be used. Although not shown, it is understood that operating cables are connected to, and extend between, the brake shift levers  56  and a brake mechanism and a derailleur, respectively, for controlling the bicycle in a conventional manner. The connections between the brake-gear shift lever units  50  and the brake and derailleur are not critical, thus these connections will not be discussed or illustrated in detail herein. Rather, it will be apparent to those skilled in the art that any suitable connections could be utilized as needed. 
     As shown in  FIG. 8 , the brake-gear shift lever units  50  are mounted, in one embodiment, so that the brake shift levers  56  are located directly in front of the end of the lower handlebar portions  26 . The downwardly and outwardly curved ends of the lower handlebar portions  26  are configured so that the brake-gear shift lever units, when mounted, may extend upwardly and inwardly as shown in  FIG. 8 . The length of the lower handlebar portions  26  can vary to allow different angles of orientation of the grip handle brackets  52 . For example, a short overall length of the lower handlebar portions  26  will provide a more inwardly directed angle of the grip handle brackets  52  and a longer length of the lower handlebar portions  26  will provide a more forwardly directed angle of the grip handle brackets  52 . A plane aligned along the longitudinal axis of the grip handle brackets  52  and brake shift levers  56  and passing through the central longitudinal axis  38  of the lower handlebar portions  26  extends inwardly and upwardly in an inclined fashion at an angle with respect to the common plane of the transverse connecting portion  22  and the upper handlebar portions  24  of about 0 degrees to about 45 degrees. 
     The lower handlebar portions  26  and the brake-gear shift lever units  50  together form a gripping section. Specifically, as shown in  FIGS. 10 and 11 , the grip handle bracket  52  has an upper surface  58  workable as a palm rest and a lower surface  60 , which may be suitably shaped to facilitate gripping by the fingers. Each grip handle bracket  52  is sufficiently elongated such that the handlebar  20  and the grip handle bracket  52  form a saddle to provide a stable support for the rider&#39;s palm. This specific arrangement, along with the inward angle of the upper handlebar portions  24 , provides an ergonomic gripping position for the hands. The hands rest primarily on the upwardly facing upper surface  58  of the brake-gear shift lever units  50 . The variable angle of the brake-gear shift lever units  50  relative to the vertical allows the hands to rest on different portions of the grip handle brackets  52 . For example, at about 0 degrees the hands are completely on the upper surface  58  of the grip handle brackets  52 . At about 45 degrees, the hands rest approximately equally on the upper surface  58  and the outer portions of the grip handle brackets  52 . In addition to supporting the hands, this arrangement also provides for comfortable use of the brake shift levers  56  by the hands. As shown in  FIGS. 10 and 11 , when assuming either riding posture with a hand resting on the grip handle bracket  52 , selected fingers, normally at least the forefinger and the middle finger, can conveniently reach and engage the brake shift lever  56  while gripping the grip handle bracket  52 . The fourth and fifth fingers can conveniently reach the ends of the lower handlebar portions  26  below the grip handle brackets  52 . As a result, the rider can pivotally pull the brake shift lever  56  in a natural grasping manner to operate the brake shift levers  56  without taking the hands off of the grip handle brackets  52 . 
     The handlebar is adaptable to any type of bicycle that uses brake-gear shift lever units  50 . Referring to  FIG. 9 , a bicycle  80  is illustrated with an embodiment of the handlebar  20  described herein. The bicycle  80  comprises a frame  82 , with a stem  84  and front forks  86 , a front wheel  88 , a rear wheel  90 , a drive train  92 , and a seat  94 . The bicycle  80  and its various components are well known in the art and will not be discussed in detail herein, except for the components that relate to the handlebar  20 . It is understood that various conventional bicycle parts, such as brakes, drive trains, etc., can be used in conjunction with the handlebars. 
     In use, the intermediate section  30  of the transverse connecting portion  22  is fixedly coupled to the stem  84  of a bicycle  80  by a stem clamp (not shown) in a conventional manner, such that the transverse connecting portion  22  extends substantially horizontally when the bicycle is upright. It is understood that the stem  84  may be raised or lowered relative to a head tube of the bicycle. Because the stem  84  is fixedly coupled to a front fork  86  of a bicycle  80 , the handlebar  20  is utilized to steer the front wheel  88  via the front fork  86  in a conventional manner. 
     The bicycle handlebar is represented with a right half in  FIGS. 10 and 11 . The left half of the handlebar  20  (not shown) is designed symmetrically to the right half relative to a center plane (not shown) bisecting the transverse connecting portion  22 . Thus, since they are mirror images of each other, only an outer portion of the right half of the handlebar  20  will be described in detail herein. However, it is understood that the description of the right portion also applies to the left portion since these parts are substantially identical. 
     The handlebar  20  is configured so that at least three gripping sections are provided for a variety of different hand positions for the rider. Moreover, the hand positions are available in different riding postures, including an upright posture, a tucked or aerodynamically favorable sprinting posture, and an out-of-the-saddle posture, as well as various other riding positions. Referring to  FIG. 10 , the lower handlebar portions  26  can be grasped by a rider along with the grip handle brackets  52  when the rider is upright, whether in the saddle or out of the saddle. In this posture, the forearms are not directed in the running direction of the bicycle, but rather the forearms extend substantially upwardly. In the tucked posture ( FIG. 11 ), the rider naturally assumes a position in which the forearms are supported by the transverse connecting portion  22  and the upper handlebar portions  24  while the hands engage the grip handle brackets  52  and lower handlebar portions  26 . Forearm rests (not shown), or other padding material, may be mounted to the handlebar  20  and positioned to increase comfort of the rider when in the tucked position. In all riding postures, the rider has direct access to the brake-gear shift levers while the wrist is in a comfortable, natural position. Thus, the brake-gear shift levers can be conveniently operated when the rider assumes any of the different riding postures. 
     In another embodiment, the handlebar  20  may be rotated about the longitudinal axis  32  of the transverse connecting portion  22  when connected to the stem  84  such that the common plane through the transverse connecting portion  22  and the upper handlebar portions  24  is angled upwardly from the bicycle stem relative to the horizontal. This upward tilt provides for a more upright riding posture, which many casual riders may find more comfortable. Moreover, it is understood that variations in the length, radii of curvature, and relative angles of the handlebar  20  described herein can be manufactured to suit individual riders&#39; preferences. 
     In yet another embodiment, the lower handlebar portions  26  may be adjustably attached to the handlebar  20  and independently moved to a desired location relative to the position of the upper handlebar portions  24 . The lower handlebar portions  26  may then be fixed, for example by a screw (not shown), and the rider can maintain that position until a change is desired. The change is brought about by merely loosening the screw and moving the lower handlebar portions  26  to the desired location relative to the position of the upper handlebar portions  24  and then re-tightening the screw. By the use of an adjustable connection mating the upper handlebar portions  24  and the lower handlebar portions  26 , the lower handlebar portions  26  can be moved about multiple axes in order to provide multiple adjustable positions as desired by the rider. 
     Referring now to  FIG. 12 , another embodiment of a handlebar for use with a bicycle is shown and generally designated at  100 . The handlebar  100  comprises a transverse connecting portion  102 , a pair of first upper handlebar portions  104 , and a pair of second lower handlebar portions  106 . The transverse connecting portion  102  is an elongated member having first and second ends  108 ,  109 , a short intermediate mounting section  110  and a central longitudinal axis  112  ( FIG. 13 ). The portions of the transverse connecting portion  102  extend substantially transversely from each side of the intermediate section  110  such that the overall length of the handlebar from the outermost edge of each of the upper handlebar portions is about 18 inches to about 22 inches, although it is understood this distance may vary to accommodate the size of the rider. As best shown in  FIG. 13 , the portions of the transverse connecting portion  102  extending from each side of the intermediate section  110  are directed rearwardly. The rearward distance, or the “reverse offset”, in the plane of the central longitudinal axis  112  of the transverse connecting portion  102  from the midpoint of the transverse connecting portion  102  to an imaginary line joining the ends of the central longitudinal axis  112  is about 15 mm to about 25 mm. 
     The transverse connecting portion  102  preferably has an aerodynamic cross-sectional shape. In one embodiment, the transverse connecting portion  102  is circular in transverse cross-section, and a central section of the transverse connecting portion has the clamp diameter D 1  ( FIG. 12 ). The remainder of the transverse connecting portion  22  and the upper handlebar portions  24  and the lower handlebar portions  26  may be substantially formed with the diameter D 1  or the slightly smaller diameter, D 2 . The transverse connecting portion  102  forms a first continuous gripping surface for the hands on each side of the intermediate section  110 . 
     Each of the pair of first upper handlebar portions  104  is coupled to an end  108 ,  109  of the transverse connecting portion  102 . As best seen in  FIGS. 12 and 13 , the upper handlebar portions  104  extend outwardly from the ends  108 ,  109  of the transverse connecting portion  102 . In one embodiment, the upper handlebar portions  104  comprise a curved section  114  bending forwardly and inwardly relative to the transverse connecting portion  102 . In another embodiment, shown in phantom in  FIG. 13 , the curved section  114  is followed by a straight section  117 . The curved section  114  of each upper handlebar portion  104  has a radius of curvature R 1  of about one to about two inches. Each upper handlebar portion  104  has a central longitudinal axis  116  in the same plane as the central longitudinal axis  112  of the transverse connecting portion  102 . The longitudinal axes  116  at the inner end of the upper handlebar portions  104  extend tangentially to the longitudinal axis  112  of the transverse connecting portion  102 . The central longitudinal axes  116  of the upper handlebar portions  104  are angled inwardly relative to the central longitudinal axis  112  of the transverse connecting portion  102 . The inward angle (α) may be from about 45 degrees to about 90 degrees. In one embodiment, the inward angle (α) may be about 60 degrees. The overall length of the upper handlebar portions  104  is variable, particularly with respect to the length of the straight section  114 . In one embodiment, the distance in the plane of the central longitudinal axes  112 ,  116  of the transverse connecting portion  102  and the pair of first upper handlebar portions  104  from the ends  108 ,  109  of the transverse connecting portion  102  to the forwardmost end of the lower handlebar portions  106  is about 10 mm to about 15 mm. Preferably, the upper handlebar portions  104  have an overall length sufficient to provide a second gripping surface for the hands. The second gripping surface may be used to accommodate the hands in an upright standard riding position or extended further to provide a tucked aero-position, as will be described below. Each of the pair of second lower handlebar portions  106  adjoins an end of the first upper handlebar portions  104  in a continuing manner, as described hereinabove. 
     Although the present invention has been shown and described in considerable detail with respect to a few exemplary embodiments thereof, it should be understood by those skilled in the art that I do not intend to limit the invention to the embodiments since various modifications, omissions and additions may be made to the disclosed embodiments without materially departing from the novel teachings and advantages of the invention, particularly in light of the foregoing teachings. Accordingly, I intend to cover all such modifications, omission, additions and equivalents as may be included within the spirit and scope of the invention as defined by the following claims. In the claims, 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.