Abstract:
A fishing rod system comprising multiple composite tubes bonded to one another, wherein apertures, or “ports,” are molded between the tubes to improve the stiffness, strength, aerodynamics, comfort and appearance of the fishing rod.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit under 35 U.S.C. §119 to EPO application 08150164.5, filed Jan. 10, 2008. 
       FIELD OF THE INVENTION  
       [0002]    The present invention relates to a fishing rod and, more particularly, to a fishing rod having a composite structure and apertures or “ports” defined therein to improve the performance characteristics. 
       BACKGROUND OF THE INVENTION  
       [0003]    The performance of a fishing rod is determined by a number of factors such as weight, bending flex, bending flex distribution, torsional stiffness, and strength. 
         [0004]    Traditional fishing rods comprise a single tubular structure with a tapered circular cross section. These rods may be solid in construction or may be constructed from a singular, hollow tube. For rods having a singular hollow tube construction, the wall thickness can vary along its length to provide specific performance needs. These rods are typically composed from a lightweight composite material. 
         [0005]    The weight of a fishing rod can be critical feature in determining performance. Generally, the lighter the rod weight, the easier it is to swing the rod, resulting in longer casting distances. Therefore, the lightest materials and designs are used to achieve this performance goal. 
         [0006]    The stiffness and stiffness distribution of a fishing rod are also important factors in determining the performance of a fishing rod. The bending stiffness of the fishing rod needs to match the forces created by the acceleration imposed by the casting motion to have the proper recovery such that the bait is delivered to the intended target. 
         [0007]    There are numerous casting motions and directions. For example, a cast can vary from a vertical casting plane to a horizontal casting plane. These two casting motions will load the rod in directions perpendicular to each other. The vertical, or overhead cast, is capable of a higher acceleration and therefore higher load on the rod. The horizontal cast is a more controlled cast, used, for example, for casting under tree limbs where motion is limited, and therefore would benefit from a more flexible rod. 
         [0008]    A fishing rod is, in fact, subjected to a multitude of stress conditions. There are mainly bending loads from casting or the pull of a fish. There are also impact loads and vibrational loads. In addition, there are high stress concentrations where the reel connects to the rod. The clamping mechanism to attach the reel to the rod can impose a large circumferential compressive stress on the rod in this area. Furthermore, the line guides can exert forces on the rod in these locations. For this reason, the wall thickness of the rod is the greatest in these areas. As a result, the rod can be heavier than desired. 
         [0009]    As mentioned above, the evolution of the fishing rod technology over the past twenty years has focused on improving weight, stiffness, and strength. However, there has not yet been a fishing rod that has meaningfully improved casting distance, or provided anisotropic behavior in different directions. 
         [0010]    The most popular high performance material for modern fishing rod design is carbon fiber reinforced epoxy resin (CFE) because it has the highest strength and stiffness to weight ratio of any realistically affordable material. As a result, CFE can produce a very light weight fishing rod with excellent strength. Because of the anisotropic properties of composite materials, the rods constructed therefrom can be tailored to provide different stiffnesses in different directions and locations along the length of the rod. 
         [0011]    However, there are limitations based on the traditional design of the single tube fishing rod, and further limitations on the carbon fiber based materials used for fishing rod structures when considering strength requirements. A fishing rod made from carbon fiber composite can be susceptible to catastrophic failure resulting from excessive compressive forces, which can cause buckling of the thin walled tube. 
         [0012]    Traditional fishing rods are manufactured with relatively complex and expensive processes. The most common method of producing a traditional composite fishing rod is to start with a raw material in sheet form known as “prepreg”, which is a thermoset resin, such as epoxy, which is impregnated with reinforcing fibers. The resin is in a “B Stage” liquid form which can be readily cured with the application of heat and pressure. The fibers can be woven like a fabric, or unidirectional, and are of the variety of high performance reinforcement fibers such as carbon, aramid, fiberglass, boron, etc. The prepreg commonly comes in a continuous roll, or can be drum wound which produces shorter sheet length segments. The prepreg is cut at various angles to achieve the correct fiber orientation, and these strips are typically overlapped and positioned in a “lay-up” which allows them to be rolled over a mandrel to form a preform. To pressurize and consolidate the prepreg plies, external pressure must be applied. This is commonly done by wrapping a polymer “shrink tape” around the exterior of the preform which will apply pressure upon the application of heat in a curing oven. The mandrel determines the internal geometry of the fishing rod. The thickness of the consolidated laminate plies determines the external geometry of the rod, the cross section of which is generally circular because of the rolling process. 
         [0013]    There have been numerous patents describing this manufacturing process, such as U.S. Pat. No. 2,749,643 (Scott), U.S. Pat. No. 3,421,347 (Hubbard) and U.S. Pat. No. 4,061,806 (Lindlerm, et. al). Other notable patents producing a single hollow tube are U.S. Pat. No. 4,178,713 (Higuchi), U.S. Pat. No. 4,653,216 (Inoue), U.S. Pat. No. 6,454,691 (Hsu), U.S. Pat. No. 6,601,334 (Ono, et. al) and U.S. Pat. No. 7,043,868 (Ahn). Of particular note is U.S. patent application Ser. No. 11/971,005 by Davis, et. al., the inventors herein, that describes a fishing rod having a single primary tube with ports that extend through aligned holes on opposite sides of the hollow tube. 
         [0014]    Other notable designs involve the line traveling inside the rod, some of which involve an internal structure to facilitate this feature. Examples are U.S. Pat. No. 5,564,214 (Tsurufuji), U.S. Pat. Nos. 6,048,425 and 6,543,178 (Sunaga, et. al), U.S. Pat. No. 6,243,981 (Komura, et. al) and U.S. Pat. Nos. 6,266,913, 6,334,272, and 6,351,909 (Akiba, et. al). 
         [0015]    Thus, there exists a continuing need for an improved fishing rod that has the combined features of improved aerodynamics, light weight, improved bending stiffness, and improved strength. The objective of the present invention is to provided a fishing rod, which overcomes the identified drawbacks of the prior art. 
       SUMMARY OF THE INVENTION  
       [0016]    The present invention provides a fishing rod representing an improvement over the current state of the art fishing rods. The rod of the present invention utilizes a multiple tube structure, in which multiple tubes are fused together along portions of their lengths, so as to form one or more internal walls. This multi-tube structure also provides for the disposition of apertures or ports at various locations which can vary longitudinally and axially on the rod. 
         [0017]    To form the ports, the tubes are separated from one another at selected locations to form apertures that act as double opposing arches, providing improved aerodynamics, light weight, improved bending stiffness, and improved strength. The number of ports and their locations can be varied to provide different performance characteristics, and the ports also provide an aerodynamic benefit during the casting of the rod. 
         [0018]    The fishing rod, according to the invention, may be designed to have specific stiffness zones at various orientations and locations along the length of the rod. Thus, it is possible to remarkably improve the torsional stiffness of the rod and achieve a superior strength and fatigue resistance, an improved shock absorption and improved vibration damping characteristics. 
         [0019]    The fishing rod, according to the invention, has also a unique look and improved aesthetics and may be easily and efficiently manufactured, at low cost with regard to both materials and labor. 
         [0020]    For a better understanding of the invention and its advantages, reference should be made to the accompanying drawings and detailed description. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is an isometric view of a fishing rod constructed in accordance with one embodiment of the present invention. 
           [0022]      FIG. 1A  is a cross section of the fishing rod of  FIG. 1  along line  1 A- 1 A. 
           [0023]      FIG. 1B  is a cross section of the fishing rod of  FIG. 1  along line  1 B- 1 B. 
           [0024]      FIG. 1C  is an isometric cut away view of a portion of the fishing rod shown in  FIG. 1 . 
           [0025]      FIG. 2  is a side view of a fishing rod constructed in accordance with an embodiment of the present invention. 
           [0026]      FIG. 2A  is a longitudinal sectional view of a portion of the fishing rod taken along line  2 A- 2 A in  FIG. 2 . 
           [0027]      FIG. 3  is an isometric view of a fishing rod constructed in accordance with an alternate embodiment of the present invention. 
           [0028]      FIG. 3A  is a cross section of the fishing rod of  FIG. 3  along line  3 A- 3 A. 
           [0029]      FIG. 3B  is a cross section of the fishing rod of  FIG. 3  along line  3 B- 3 B. 
           [0030]      FIG. 3C  is an isometric cutaway view of a portion of the fishing rod shown in  FIG. 3 . 
           [0031]      FIG. 4  shows an isometric cutaway view of an alternative embodiment of the invention. 
           [0032]      FIG. 4A  is a cross section of the embodiment of  FIG. 4  along line  4 A- 4 A. 
           [0033]      FIGS. 5A-5D  show various possible shapes of ports. 
           [0034]      FIGS. 6 and 7  are perspective views illustrating a process for forming yet another embodiment of the rod of the present invention in which a portion of the rod has a multiple tube construction and a different portion of the rod has a single tube construction. 
           [0035]      FIG. 8  is an isometric view of an alternative design of the handle area of the fishing rod, showing a possible method of mounting a reel. 
       
    
    
     DETAILED DESCRIPTION  
       [0036]    As described below, the fishing rod of the present invention is formed of two or more uncured tubes which are molded together to form a common, internal wall (or walls, in the case of more than two tubes) along their facing surfaces. This internal wall improves the bending strength of the fishing rod by acting as a brace to resist the compressive loads which can buckle the structure, causing catastrophic failure. 
         [0037]    At selected locations, the facing surfaces of the tubes are kept apart during molding, to form openings. On either side of the openings, the tubes are joined together to form the internal wall. The openings so formed are referred to herein as “ports” and are apertures which extend through the rod. These ports are formed without drilling any holes or severing any reinforcement fibers, thus improving the strength of the rod. 
         [0038]    The resulting structure is found to have superior performance characteristics for several reasons. First, the ports are in the shape of double opposing arches which allows the structure to deflect, which deforms the ports, and return with more resiliency. The ports also allow greater bending flexibility than can be achieved in a traditional single tube design. Second, the ports improve the aerodynamic performance of the rod, allowing air to pass through the ports, resulting in faster casting speeds and greater casting distances. Third, the internal wall between the hollow tubes adds strength to resist compressive buckling loads. 
         [0039]    With reference to  FIG. 1  of the drawings, the present invention is a composite fishing rod  10 . The rod features ports  20  of various geometric shapes defined in the rod for improving the flexibility, strength and other playing characteristics of the rod. The rod comprises a handle end  12 , about which a grip and reel are normally attached, and a tip end  14 , to which a loop shaped line guide is typically attached. Rod  10  is preferably fabricated of multiple layers of aligned carbon filaments held together with an epoxy binder (i.e., a so-called “graphite” material). The fibers in the various plies are preferably parallel to one another, but the various plies preferably have varying fiber orientations. 
         [0040]    Rod  10  has a long, generally hollow configuration that preferably tapers from handle end  12  to tip end  14 . 
         [0041]    A plurality of ports  20  are formed in rod  10 . Ports  20  extend between opposed walls of the rod, as described further below. Each port  20  is preferably oval in shape, with the long axis of the oval in alignment with the longitudinal axis of rod  10  and the longitudinal axes of ports  20  oriented perpendicular to the longitudinal axis of rod  10 . Ports  20  may have any radial orientation with respect to the longitudinal axis of rod  10 , but preferably are oriented such as to provide the greatest aerodynamic benefit during casting. 
         [0042]    Each port  20  includes a peripheral wall  21  that extends through rod  10 . Peripheral wall  21  is formed from the facing surfaces of tubes  22  which were not allowed to fuse together during the molding process of rod  10 . 
         [0043]    Ports  20  are preferably ovoid or elliptical in shape, forming double opposing arches which allow the structure to deflect, which deforms the ports, and return with more resiliency. Ports  20  therefore allow greater bending flexibility and strength than would traditionally be achieved in a single tube design, because internal wall  24  between the tubes and the peripheral wall  21  of each port  20  help prevent buckling failures of the thin walled tubular rod. If the axes of the ports are in line with the casting direction, they can provide an aerodynamic advantage, allowing air to pass through the rod, resulting in faster swing speeds and further casts. Finally, the ports create a unique appearance to the fishing rod. 
         [0044]    The cross sectional view of  FIG. 1A  shows the two hollow tubes  22  which form the structure of the rod in this embodiment. Hollow tubes  22  are joined together to form an internal wall  24 . Preferably, the plane of internal wall  24  will include the longitudinal axis of rod  10 , but internal wall  24  may also be offset. Both hollow tubes  22  should be about the same size and, when molded, form a “D” shape. 
         [0045]      FIG. 1B  shows that, at the locations of ports  20 , hollow tubes  22  are separated from one another to form peripheral wall  21  defining ports  20 . It is advisable to have a radiused (i.e., rounded) edge  26  leading into the port so to reduce the stress concentration and to facilitate the molding process. 
         [0046]      FIG. 1C  is an isometric view of rod  10  isolated to one port, which shows hollow tubes  22  and internal wall  24 . Also shown is the port  20  formed by curved peripheral wall  21  which may have the shape of a portion of a cylinder. In this particular example, the axis of port  20  is orthogonal to the longitudinal axis of rod  10 . 
         [0047]      FIG. 2A  is a longitudinal section view taken along line  2 A- 2 A in  FIG. 2 . It shows that, at locations other than where ports  20  are located, hollow tubes  22  are positioned side-by-side and are fused together along their facing sides to form common internal wall  24  that extends across the diameter of rod  10 , (i.e., the wall bisects the rod interior). At selected locations, where ports  20  are to be formed, the facing surfaces  21  of tubes  22  are separated during molding to form apertures  20  in the shape of double opposing arches, which act as geometric supports to allow deformation and return. In addition, internal wall  24  provides structural reinforcement to resist deformations and buckling failures. 
         [0048]      FIG. 3  shows an alternative embodiment in which ports  20  and  20   a  are formed in rod  10 , such that the axes of ports  20   a  are orthogonal to the axes of ports  20 . Such a design requires that rod  10  be constructed of four tubes,  42 ,  43 ,  44  and  45 , shown in  FIGS. 3A-3C . This configuration creates internal wall  46  in the shape of an “X” or cross. 
         [0049]    In this particular example, ports  20   a,  near tip end  14  of rod  10 , are in line with the direction of casting, to provide greater in flexibility in this area. Ports  20  near grip end  12  of rod  10  are oriented perpendicular to the direction of casting, which will provide a traditional stiffness with increased strength. Therefore a fishing rod with this type of design would be considered to have a flexible tip region and a more traditional handle region. It is also possible to have the opposite configuration, or any other configuration desired. 
         [0050]    The  FIG. 3B  cross section, taken along line  3 B- 3 B of  FIG. 3 , is in the region of port  20   a,  which is oriented parallel to the casting direction. In this example hollow tubes  42  and  43  have remained together and hollow tubes  44  and  45  have remained together, forming partial internal wall  46 . Hollow tubes  42  and  43  are separated from hollow tubes  45  and  44  respectively during molding to create port  20   a.  To create port  20 , tubes  45  and  42  would be kept separate from tubes  44  and  43  respectively (not shown in cross section). 
         [0051]      FIG. 3C  is an isometric view of a cutaway portion of rod  10  of  FIG. 3  showing ports  20   a  oriented parallel to the direction of casting, and ports  20  oriented perpendicular to the direction of casting. 
         [0052]      FIG. 4  is an isometric cutaway view showing an alternative embodiment in which ports having orthogonal axes are co-located at the same longitudinal location along rod  10 . This creates port  51  having four openings  51   a - 51   d.  In this example, hollow tubes  47 ,  48 ,  49 , and  50  are all separated in the same location to form the four openings therebetween. 
         [0053]      FIG. 4A  is a cross-sectional view of the tube structure  52  in  FIG. 4  taken along the lines  4 A- 4 A showing the openings  51   a - d.  This particular embodiment would provide more flexibility and resiliency for both in plane and out of plane conditions at the same location. 
         [0054]    In a multiple tube design, there can be any number of ports and orientations of ports, depending on the number of hollow tubes used and how many are separated to form these ports. For example, with a 3 tube design, not shown in any figures, the axis of the port would not necessarily have to pass through the center of the rod. In such an embodiment a “Y” shaped internal wall would be formed and a port having three openings offset by 120 degrees with respect to each other would be formed. 
         [0055]      FIGS. 5A-5D  illustrate some examples of the variety of possible shapes for the ports. Depending on the performance required of the structure at a particular location, more decorative port shapes can be used. The invention is not intended to be limited to these port designs. They are shown here only as examples of possible port configurations. 
         [0056]    The process of molding with composite materials facilitates the use of multiple tubes in a structure. The most common method of producing a traditional composite fishing rod was described in the background section. 
         [0057]    The present invention, however, requires a different molding technique because the use of multiple tubes and the formation of ports requires internal pressure to consolidate the prepreg plies. For one thing, when molding the fishing rod using two prepreg tubes, each tube should be approximately half the size of the single tube, for four tubes, one forth the size, etc. A polymer bladder is inserted into the middle of each prepreg tube and is inflated and held at a predetermined pressure to generate internal pressure to consolidate the plies upon the application of heat. 
         [0058]    The mold packing process consists of taking each prepreg tube and internal bladder and positioning them into a mold cavity. An air fitting is then attached to the bladder. The process is repeated for each tube, depending on how many are used. Care should be taken for the position of each tube so that the internal wall formed between the tubes is oriented properly. To form the ports, mold pins can be inserted between the tubes to keep the facing walls of the tubes separated at the desired locations of the ports during pressurization. The pins are secured into portions of the mold and are easily removed after the rod has cured. 
         [0059]    The mold is pressed closed in a heated platen press and air pressure for each tube is applied simultaneously to retain the size and position of each tube and the common wall in between. Preferably, each tube should be kept at the same pressure. Simultaneously, the facing walls of the tubes will form around the pins to form the ports. As the temperature rises in the mold, the viscosity of the epoxy resin decreases and the tubes expand, pressing against each other until expansion is complete and the epoxy resin is cross linked and cured. The mold is then opened, the pins removed, and the part is removed from the mold. 
         [0060]    The internal wall of the molded tubular part adds significantly to improving the structural properties of the tubular part. For example, during bending or torsional deflection, the shape of the fishing rod is better maintained, eliminating the tendency to buckle the cross section. 
         [0061]    The orientation of the wall can be positioned to take advantage of the anisotropy it offers. If more bending flexibility is desired, the wall can be positioned along the neutral axis of bending. If greater stiffness is needed, then the wall can be positioned like an “I Beam” at 90 degrees to the neutral axis to improve the bending stiffness. 
         [0062]    Molding the tubular parts using multiple tubes allows greater design options. Separating the hollow tubes at selected axial locations along the rod to mold large oval shaped openings between the tubes, allows the characteristics of the fishing rod to be varied as desired. 
         [0063]    Molding in of apertures, or ports, at selected locations results in a double opposing arch construction. The “double arch effect” of the ports, which are oval in shape, creating two opposing arches, allows the tubular part to deflect, while retaining the cross sectional shape of the tube because of the three dimensional wall structure provided by the port. For example, a ported double tube structure has a combination of exterior walls which are continuous and form the majority of the structure, and ported walls, which are oriented at an angle to the exterior walls, which provide strut like reinforcement to the tubular structure. The cylindrical walls of the ports prevent the cross section of the tube from collapsing, which significantly improves the strength of the structure. 
         [0064]    The stiffness and resiliency of the ported double tube structure can be adjusted to be greater or less than a standard single hollow tube. This is because of the option of orienting the internal wall between the tubes as well as the size, shape, angle and location of the ports. The ports can be stiff if desired, or resilient, allowing more deflection and recovery, or can be designed using different materials or a lay-up of different fiber angles to produce the desired performance characteristics of the structure. 
         [0065]    In another embodiment of the invention, a single composite tube may be combined with the multiple tube design. In this example, the single composite tube can be a portion of the fishing rod made in the traditional method previously mentioned, and co-molded with the multiple tubes to produce a lower cost alternative to a 100% multiple tube construction rod. 
         [0066]    Referring to  FIGS. 6-7 , to make this construction, forward ends  62  of a pair of prepreg tubes  60   a,    60   b,  each having an inflatable bladder  64 , are inserted into one end  65  of a traditional composite tube  66 . The unit is placed inside a mold having the same shape of composite tube  66 , at least at juncture  70  of prepreg tubes  60   a,    60   b  and composite tube  66 . A pin or mold member (not shown) is placed between prepreg tubes  60   a,    60   b  where port  30  is to be formed. The mold is then closed and heated, as bladders  64  are inflated, so that the prepreg tubes assume the shape of the mold, the mold member keeps facing walls  71   a,    71   b  apart so as to form port  30 . As shown, tubes  60   a  and  60   b  will form common wall  72 . After the prepreg tubes have cured, frame member  74  is removed from the mold, and the mold member or pin is removed, leaving port  30 . In this embodiment, the seam between graphite portions  60   a,    60   b  of frame member  74  and composite tube portion  66  should be flush. Tube portion  66  may also be made of metal, plastic, wood, or any other common material. 
         [0067]    There is a very distinguished appearance to a fishing rod made according to the invention. The ports are very visible, and give the tubular part a very light weight look, which is important in rod marketing. The ports can also be painted a different color, to further enhance the signature look of the technology. 
         [0068]    There are unlimited combinations of options when considering a double opposing arch structure. The ports can vary by shape, size, location, orientation and quantity. The ports can be used to enhance stiffness, resilience, strength, comfort and aesthetics. For example in a low stress region, the size of the port can be very large to maximize its effect and appearance. If more deflection or resilience is desired, the shape of the aperture can be very long and narrow to allow more flexibility. The ports may also use designer shapes to give the product a stronger appeal. The ports may also have axes that are not orthogonal to the longitudinal axis of the rod, for example, a port may be defined in the rod to allow a fishing line to pass therethrough from one side of the rod to the other. 
         [0069]    If more vibration damping is desired, the ports can be oriented and shaped at a particular angle, and constructed using fibers such as aramid or liquid crystal polymer. As the port deforms as a result of rod deflection, its return to shape can be controlled with these viscoelastic materials which will increase vibration damping. Another way to increase vibration damping is to insert an elastomeric material inside the port. 
         [0070]    Although only rods having circular cross sectional shapes are shown herein, the invention also allows for other cross sectional shapes to be molded in the rod, because the rod is formed by internal pressurization inside a mold with a cavity that defines the external shape of the rod. For example, the rod may have an oval or polygonal shaped cross section, or may be irregularly shaped, as in a teardrop shape. 
         [0071]    In addition, the rod may have ridges molded in the surface thereof. The rod can be made stiffer by adding one or more ridges on the external surface of the rod. For example, the placement of the ports in the rod will tend to decrease the rod stiffness in the areas defining the ports. The stiffness in these areas can be increased by defining ridges in the vicinity of the ports. Such ridges can be longitudinally or circumferentially disposed, and can be of limited length or can run the entire length of the rod. 
         [0072]    Additionally, the cross-sectional shape of the rod can also affect stiffness, particularly when the cross-sectional shape of the rod defines comers, such as with a polygonal or teardrop cross sectional shape. Note that if uniform stiffness is not desired, ridges may be added to increase the stiffness in some areas, while leaving other areas unaltered. Absent any ridges or corners, the stiffness of the rod will be defined by the manner and angle at which the prepreg strips were laid out to form the basic hollow rod, as previously discussed. The invention is therefore meant to encompass rods having any cross sectional shape. 
         [0073]    Another advantage of the invention could be to facilitate the attachment of the reel. Having one or more ports at the handle portion of the rod that where the reel will attach provides a mechanical means of attachment to the reel to better secure it to the rod. 
         [0074]      FIG. 8  shows such an example of handle end  12  of rod  10  molded with two tubes  22  that form internal wall  24  therebetween. Recessed area  78  is formed in the rod by the shape of the mold to accommodate foot  80  of reel  82 . Ports  84  are formed in the recessed area  78  that line up with holes  86  in foot  80  of reel  82 . A fastening means attaches foot  80  to the recessed area  78  going through holes  86  and ports  84 . 
         [0075]    One advantage of recessed area  78  is that it reduces the distance of the axis of the reel to the center of the rod. This facilitates releasing the line through the guides for increased casting distances as well as enhanced feel. 
         [0076]    Another option is for the fishing line to travel from the reel through a port in the rod to the opposite side of the rod. This would provide an advantage for reel designs that operate on the top side of the rod, yet position the line and guides on the bottom side of the rod, which is a preferred location because it is more stable. This is not possible with conventional rod designs. 
         [0077]    With respect to the above description then, it is to be realized that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, may vary without departing from the scope of the invention. Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.