Patent Publication Number: US-2019185289-A1

Title: String trimmer head with curved trimmer line guide

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 13/213,180, filed Aug. 19, 2011, which is a continuation-in-part of U.S. patent application Ser. No. 11/985,673, filed Nov. 16, 2007, now U.S. Pat. No. 8,025,249, which claims the benefit of U.S. Provisional Patent Application Ser. No. 60/859,246, filed Nov. 16, 2006; the entire specification of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     In general, the present invention relates to string trimmers and the rotating heads of string trimmers. More particularly, the present invention relates to the mechanisms contained within string trimmer heads for winding or adding new lengths of trimmer line to the trimmer head. 
     BACKGROUND 
     Background Information 
     String trimmer machines have been commercially sold for over a quarter of a century. In this period of time, there have been many variations to the design of the string trimmer machine and especially to the trimmer head. 
     The trimmer head is the part of the string trimmer machine that rotates. The trimmer head holds lengths of trimmer line that rotate with the trimmer head. The rotating trimmer line contacts and cuts vegetation as it spins. 
     There are many types of trimmer heads on the market. The most common types of trimmer heads are bump-feed trimmer heads and automatic-feed trimmer heads. Both types of trimmer heads contain an internal spool that holds a reserve of wound trimmer line. As the trimmer line wears away, it can be replaced from the internal spool. In a bump-feed trimmer head, a short length of line is released from the spool when the bottom of the trimmer head is impacted or “bumped” against a hard surface. In an automatic-feed trimmer head, a short length of line is released from the spool when a predetermined change in centrifugal forces occurs that indicates that the existing trimmer line has become too short. 
     Internal combustion engine and electric motor powered vegetation trimmers are commonly used to cut and trim grass, weeds, brush and other vegetation. The typical motorized trimmer comprises an elongate handle to which is connected an internal combustion or electric motor that rotatably drives a trimmer head located at a distal end of the handle. This machine is “hand held”. The trimmer head (i.e., rotary cutting head attachment to drive shaft of trimmer), in turn, carries radially outwardly projecting cutting means which cuts the vegetation as the trimmer head rotates. In addition to “handheld” vegetation cutting machines there is also wheeled type vegetation trimmers which have are gas powered and utilize and engine that generates much greater horsepower than any “handheld” type machine, the trimmer and cutting machines are designed to cut very dense thick vegetation and brush. These DR Trimmer machines use some types of cutting heads that are used with the “hand held” trimmer machines. 
     The trimmer head may include one or more flexible monofilament line or rigid cutting means. Rigid cutting means typically assumes the form of blades fabricated from plastic and or metal and often have corrugations or scalloping about their peripheral cutting edges. They are a unitary one-piece cutting blade molded from a durable high strength plastic/metal material with plurality of cutting arms extending outward from the hub. The pivoting type rigid blades are attached circular pins mounted vertically on peripheral portion of trimmer head body and the body is attached directly to the trimmer machines drive shaft. The pivoting blade yields when they contact hard objects, thereby prolonging the service life of these blades. Other fixed rigid type blades mount directly to the trimmer drive shaft. Both of these above mention vegetation cutting blades are normally used to cut very dense and thick grasses, weeds to include brush. There is one other form of rigid type cutting blade that is used on hand held and wheeled type trimmer machines alike and it is main usage and application is for cutting, highly effective against weeds and small bushes, corn stocks, brush and even saplings up to 3″ thick small diameter etc. This type of rigid blade is a metal disc that attached to the drive shaft of the trimmer machine and mounted around the peripheral of the metal circular plate is a series of chain saw cutting teeth as used on a “Chain Saw”. All of these mentioned types of blades may cause considerable injury to the trimmer operator or other persons should they accidentally be struck by one of these types of blades if made of metal including hard rigid sharp plastic material during operation of the trimmer. Generally, weeds growing on footpaths between rice fields etc. have to be cut several times a year because they tend to be nested by pests. The weed cutting is usually very laborious, and thus various automatic weed cutters have heretofore been proposed and put to practical use, among which shoulder-hung weed cutters are very popular because of their small size and handling ease. In most of the shoulder-hung weed cutters, a driving-force transmission shaft or drive shaft, which is passed through a pipe-shaped handling rod, is rotated via an engine provided at one end of the handling rod so as to rotate a cutter blade provided at the other end of the handling rod. 
     In most cases, a human operator hangs the weed cutter on his or her shoulder using a hanging belt, and cuts weeds with the rotating cutter blade by gripping a U-shaped handle provided on an intermediate position of the handling rod to swing the handling rod in front and-rear and left-and-right directions. In recent years, there have been strong demands for further improvements in agricultural working environment. In the case of the shoulder-hung weed cutters too, there is an increasing demand for reduction in vibrations that are transmitted from the engine via the handling rod to the U-shaped handle, with a view to lowering the load on the human operator. Because the weed or plant cutters are often used in farmland or the like where no AC power source is available, they ordinarily employ, as a prime mover or drive source unit, a small engine that is not equipped with a balancer to attenuate secondary vibrations. The vibrations transmitted from the drive source unit to the drive shaft comprise two major components: one component delivered from the drive source unit via the drive shaft to the handling rod; and the other component delivered from the drive source unit directly to the handling rod. Example: U.S. Pat. No. 0,299,484 Wang; U.S. Pat. No. 6,052,907 Wang; U.S. Pat. Nos. 5,085,113; 4,744,148; 4,922,791; 4,627,322; 4,302,878 Bonforte; Flexible type of cutting means generally are fabricated as a continuous strand flexible monofilament plastic (i.e. Nylon) line wrapped about a spool contained within the trimmer head. In such devices, the plastic line is typically selectively dispensed by the operator of the trimmer apparatus manually. One species of these sorts of devices is semi-automatic in operation and utilizes the centrifugal force generated by rotation of the trimmer head to dispense trimmer line. Commonly known as “bump and feed” trimmers, these apparatus include an internal storage space for a spool of line to be dispensed responsive to an operator tapping the base of the trimmer head against a hard surface. An example of bump indexing trimmer head is shown in Example: Proulx, U.S. Pat. Nos. 6,279,235; 4,458,419. Both in light duty, medium and heavy duty gas &amp; electric powered trimmers, the cutting means may be fabricated as a continuous strand flexible monofilament plastic line wrapped about a spool contained within the trimmer head. In such devices, the plastic line is typically selectively dispensed by the centrifugal force generated by rotation of the trimmer head. A disadvantage common to these sorts of devices is that the line quite frequently becomes jammed when a user attempts to dispense fresh line from the spool and the line prematurely breaks off at the eyelet because the diameter of the line is small and has little tensile strength when making contact with hard objects and heavy vegetation. When this occurs, the user generally must stop the trimming operation, disassemble the trimmer head, fix the jam and or extend line through the eyelet(s) and reassemble the trimmer head before resuming trimming. Such repeated disruption is very frustrating and time-consuming by the end user. It should be noted that spool heads automatic type, semi-auto, include a line cutting blade on the debris shield. When the head is bump on the ground and dispenses the line, the line generally extends more line than needed from the storage spool and this blade on the shield cuts off the extra line. Another species of vegetation trimmer cutting apparatus is an automatic spool trimmer head this type of trimmer cutting head is called “automatic trimmer head. This type requires no tapping on the ground and it always feeds out set length of trimmer line. Examples: Lingerfelt, U.S. Pat. No. 5,901,448; Zatulovsky, U.S. Pat. No. 4,942,664. 
     Another species of vegetation trimmer apparatus where trimmer line is selectively dispensed from a spool by an operator is fully manual in operation. Devices of this sort comprise one or more, typically spring-biased, indexing pins or buttons that are connected to one or more internal trimmer line carrying spools. In order to dispense trimmer line, an operator displaces the indexing pin(s) or button(s) from seating engagement with one or more holes provided in the trimmer head housing. Once the indexing pin(s) or button(s) are separated from the housing, the user either turns the internal spool(s) or pulls on the trimmer line itself from the spool in order to payout the line from the trimmer head. When the desired length(s) of trimmer line have been dispensed, the operator reseats the indexing pin(s) or button(s) into their associated indexing opening(s) in the trimmer head housing. Example: U.S. Pat. No. 4,145,809 Proulx; U.S. Pat. Nos. 4,271,595; 4,172,322; 4,097,991; 3,826,068 and 3,708,967. 
     A new species of spool trimmer heads has surfaced, which is very distinctly and substantially different from prior art examples of spool trimmer head described and reference above. Typically, reloading fresh line into a spool trimmer head is a difficult and time consuming process. All the prior art reference spool trimmer heads reference above “all” do require some form of disassembly of the trimmer head components prior to loading or reloading new trimmer line onto the spool. The reason I feel that this type of spool trimmer head should be considered as a separate species is because this species of trimmer is distinctly and substantially different from the all prior art spool trimmer heads because all of the following prior art patents and or applications. The spool trimmer heads being referenced all have one thing in common, these spool trimmer heads “all” do not require any form of disassembly of the trimmer head components prior to loading or reloading new line onto the spool. This type of spool trimmer head makes loading and reloading of trimmer line onto the spool trimmer head dramatically easier for the end user. Example: Kanou, U.S. Pat. No. 5,345,683; Griffini, U.S. Pat. No. 5,765,287; Everets, U.S. Pat. Nos. 5,659,960; 5,671,536; 5,806,192; 6,148,523; Stark, U.S. Pat. No. 6,263,580; Alliss, U.S. Pat. No. 6,854,185; Pfaltzgraff, U.S. Pat. No. 6,952,877; Proulx, US Patent Application 20050217120; Alliss, US Patent Application 20050252009. All spool type trimmer heads must have some form of anchoring means to secure one or more fixed lengths of line to the hub of the spool prior to commence wrapping the length(s) of line onto and around the spool hub. 
     Another species of vegetation trimmer heads employs finite or fixed cut lengths of monofilament (nylon) plastic line or string that can be quickly and easily replaced as they become broken or worn without need to resort to disassembly and reassembly of the trimmer head. In this category of trimmer heads the finite length(s)} of trimmer line are securely held in a fixed position within the trimmer head body by different methods (i.e. weaving means, different types and forms of clamping means with and without biasing means, special injection molded flails that have special end portion of the cutting flail that holds the finite length of cutting line securely in the body of the trimmer head during cutting operations etc.). All of the these Fixed length type of line vegetation trimmer cutting heads provide the end user a more user friendly trimmer head product vs. the standard spool “bump and feed” product. They are much easier to load and replace worn flexible cutting line. These types of trimmer heads allow the end user the opportunity to be able to use a broad range of flexible line diameters from 0.065″ to 0.155″. These trimmer heads also are typically weigh less and are less expensive in cost to manufacture. And important benefit of the fixed length type vegetation cutting head, because it can receive and hold a wide range of different size line a customer can select the size of line that works best with size (hp) machine that they are using. Too large of a flexible cutting line diameter and too long of a length extending from the exit ports of the head will deplete the rpms and power because of air drag caused by the size of the cutting line. There is a wide variety of electric and gas powered trimmer machines manufactured and they also have wide range of power ratings per machine. It is important to select and use the right cutting attachment with different machines so that they will work efficiently and safety during operation. Examples of such devices are provided: U.S. Pat. Nos. 5,758,424; 5,887,348; 5,896,666 and 6,347,455; U.S. Pat. No. 4,756,146 Rouse; U.S. Pat. Nos. 5,901,448, 4,054,992 Ballas etc. 
     Many problems exist with traditional trimmer head designs that contain internal spools. Primary among those problems are problems concerning the winding of new trimmer line onto the internal spool once the original supply of trimmer line is exhausted. 
     Any trimmer head that has an internal spool also has a housing that surrounds that spool. In order to resupply trimmer line to the spool, the spool must be accessed within the housing. In many early trimmer head designs, the internal spool was accessed by disassembling the trimmer head and removing the spool from the housing. This, of course, required the use of tools and a significant expenditure of labor and time. 
     Recognizing the problem, some trimmer heads have been designed where the trimmer line can be added without any disassembly. In such prior art designs, new trimmer line is threaded through both the housing and the internal spool. The internal spool is then rotated relative the housing to wind the trimmer line onto the spool. This process only works when the eyelet openings in the housing are precisely aligned with a channel in the spool to create a straight open conduit that enables the trimmer line to pass directly through the trimmer head. 
     Many trimmer heads have such straight conduits for the reloading of trimmer line. With such trimmer head designs, the trimmer line often binds as it is advanced through the conduit. The binding occurs because the trimmer line does not lay straight as it is passed into the trimmer head. The trimmer line is almost always coiled when purchased. Consequently, the trimmer line maintains a curved bias when it is removed from its packaging. Accordingly, the trimmer line has a tendency to curve as it is passed through the trimmer head. This causes the trimmer line to bind within the trimmer head or miss the housing eyelet on the far side of the trimmer head. This problem becomes compounded when the conduit through the trimmer head is not straight. 
     Many trimmer heads mount around a drive shaft from the trimmer machine. The drive shaft typically passes through the center of the trimmer head. As a consequence, forming a straight conduit through the center of the trimmer head is not possible. Rather, a curved conduit must be used. The use of a curved conduit in a trimmer head is exemplified in U.S. Pat. No. 7,640,668 to Iacona, and U.S. Patent App. Pub. 2008/0053052 to Cigarini. 
     When a curved conduit is used, the inserted trimmer line approaches the eyelet on the far side of the housing at an angle. This angle in conjunction with the natural curved bias of the trimmer line increases the tendency of the trimmer line to bind inside the trimmer head. Consequently, a user must try multiple times to correctly pass the trimmer line through the trimmer head. This takes time and labor and causes product dissatisfaction. 
     A need therefore exists for a trimmer head assembly with a housing and internal spool that presents a curved conduit that passes around a driveshaft, yet does not cause the inserted trimmer head line to bind. This need is met by the present invention as described and claimed below. 
     SUMMARY 
     The present invention avoids the above referenced problems experienced in the prior art. This is a “bi-directional”, spool trimmer head invention that does not require disassembly of the trimmer head components prior to reloading new trimmer line onto the enclosed storage spool. This invention is somewhat similar to my current US Patent, Non-Provisional Application 20050252009, Nov. 17, 2005, in a couple of aspects (i.e., bi-directional feature, invertible spool and latching and seating means between the spool and housing parts). There is multiple manufactures of handheld weed trimmer machines and models that are offered and sold on the market. There is “no” common or standard specification (i.e., design, type or size) in the industry for drive shaft arbors for attachment of a string trimmer head or other types of vegetation cutting tools to a handheld trimmer machine (gas/electric). 
     Overall the majority of manufactures use a threaded (nut and bolt) fastener means to secure the main body housing of the trimmer head to the threaded drive shaft arbor (male/female types). There are drive shaft arbors that are relatively “short” in length to attach a string trimmer head and then there are “longer” drive shaft arbors that extend through the top center opening of the trimmer head main housing and through the center of the spool and beyond. This invention pertains to the drive shaft arbors that are “longer”. Example of prior art, easy load, spool trimmer heads with “longer” type drive shaft arbors as follows: Everets, U.S. Pat. Nos. 5,659,960; 5,671,536; 5,806,192; 6,148,523; Stark, U.S. Pat. No. 6,263,580; Proulx, US Patent Application 20050217120. All of these, easy load, spool trimmer head inventions require two separate fixed lengths of line for reloading the inner spool. Example of prior art, easy load, spool trimmer head with relative “short” drive shaft arbors as follows: Alliss, US Patent Application 20050252009; Kanou, U.S. Pat. No. 5,345,683; Griffini, U.S. Pat. No. 5,765,287; Alliss, U.S. Pat. No. 6,854,185; Pfaltzgraff, U.S. Pat. No. 6,952,877. Each of these, easy load, spool trimmer head inventions use only one separate fixed length to fully reload line onto the inner spool and each line guiding means through the spool are “linear”. This easy load, spool trimmer head invention uses a trimmer line “continuous” guide passageway that is “nonlinear” for the purpose of by-passing the vertical drive shaft that passes through the center axis of the trimmer head body and spool. Also included in the invention is “insert stop” for the spool to prevent inadvertent misplacement of the spool with the bottom body member and the bump knob components. 
     The present invention is a trimmer head for a trimming machine. The trimmer head assembly includes a spool. The spool has a central tubular hub. The hub is hollow and defines a central opening that extends through the hub. The spool also has a top flange that radially extends from the hub, a bottom flange that radially extends from the hub, and a central flange that radially extends from the hub. 
     A trim line conduit is joined to the central flange. The trim line conduit has a first open end. The first open end leads to a first straight section. The first straight section leads to a curved central section. The curved central section leads to a second straight section. The second straight section leads to a second open end. The curved central section passes around the central opening of the hub without passing into the central opening. 
     A housing is provided that receives the spool therein. Eyelets are formed in the housing on opposite sides. An end cap is provided that connects with the housing and retains the spool within said housing. 
     When loading a new segment of trimmer line into the trimmer head assembly, the shape of the conduit enables the trimmer line to pass around the central opening in the spool without binding. Furthermore, the shape of the conduit reduces binding caused by the curve bias of the trimmer line. 
     Other details, objects and advantages of the present invention will become apparent as the following description of the presently preferred embodiments and presently preferred methods of practicing the invention proceeds. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       A sample embodiment of the disclosure is set forth in the following description, is shown in the drawings and is particularly and distinctly pointed out and set forth in the appended claims. The accompanying drawings, which are fully incorporated herein and constitute a part of the specification, illustrate various examples, methods, and other example embodiments of various aspects of the disclosure. It will be appreciated that the illustrated element boundaries (e.g., boxes, groups of boxes, or other shapes) in the figures represent one example of the boundaries. One of ordinary skill in the art will appreciate that in some examples one element may be designed as multiple elements or that multiple elements may be designed as one element. In some examples, an element shown as an internal component of another element may be implemented as an external component and vice versa. Furthermore, elements may not be drawn to scale. 
       For a better understanding of the present invention, reference is made to the following description of an exemplary embodiment thereof, considered in conjunction with the accompanying drawings, in which: 
         FIG. 1  is cross section view of the fully assembled trimmer head invention attached to a trimmer machine drive shaft which passes vertically through the center of the spool; 
         FIG. 2  is an exterior isometric view of the fully assembled trimmer head invention; 
         FIG. 3  is a top isometric view of the bottom cap and the knob assembled as shown in trimmer head  FIGS. 1-2 ; 
         FIG. 4  is a top isometric view of the bottom cap as shown in trimmer head of  FIGS. 1-2 ; 
         FIG. 5  is an exploded view all trimmer head parts as shown in trimmer head  FIGS. 1-2 ; 
         FIG. 6  is an isometric view of spool S and the bottom cap assembled as shown in  FIG. 1 ; 
         FIG. 7  is an isometric view of spool S not assembled to the knob as shown in  FIG. 6 ; 
         FIG. 8  is a top isometric view of the knob as shown in trimmer head  FIGS. 1-2 ; 
         FIG. 9  is a top isometric view of 2S spool guide channel cover plate; 
         FIG. 10  is a bottom isometric view of the cover plate; 
         FIG. 11  is a drawings of spool S and the knob assembled and not assembled, drawings Illustrate how to convert the same spool so that the trimmer head can be used on a trimmer machine that has a drive shaft that turns in a clockwise and or counter-clockwise direction; 
         FIG. 12  is a drawing of trimmer head invention attached to a straight shaft, trimmer machine, which typically rotates counter-clockwise and has a vertical drive shaft that passes through the center of the spool; 
         FIG. 13  is a drawing of trimmer head invention attached to a curved shaft, trimmer machine, which typically rotates clockwise and has a vertical drive shaft that passes through the center of the spool; 
         FIG. 14  is a top isometric view of the spool showing the placement of repositionable stop that prevents misplacement and assembly of the knob to the spool once the direction of the trimmer machine drive shaft has been determined; 
         FIG. 15  is a top isometric view of reposition able stop with snap fitting as shown assembled to the spool in  FIG. 14 ; 
         FIG. 16  is a top isometric view of spool guide channel cover plate; 
         FIG. 17  is a top isometric view of the spool showing a non-linear trimmer line U-shaped guide channel; 
         FIG. 18  is a top isometric view of the spool assembled with the spool cover plate; 
         FIG. 19  is a top view of main trimmer head housing body; 
         FIG. 20  is a side isometric view of the main trimmer head housing body shown with metal eyelets and the extended special extension of the main housing capturing the long center drive shaft to secure the main housing body firmly to the machine&#39;s drive shaft arbor; 
         FIG. 21  is a bottom view of main trimmer head housing body; 
         FIG. 22  is a top view of the spool which illustrates on which side of the spool to insert placement of insert stop for a trimmer machine that turns counterclockwise; 
         FIG. 23  is a top view of the spool illustrating that placement of insert stop can be placed on the opposite side of the spool at peg receiver openings on either end; 
         FIG. 24  is a top isometric view of turn bump knob showing extending key to mate and interlock with the spool; 
         FIG. 25  is a side isometric view of turn bump knob that illustrates close up view of the finger grips used for reloading and winding the inner spool; 
         FIG. 26  is a top cross section view of the bottom cap, the spool, the eyelets, the main housing body, showing clearly the linear and non-linear path the trimmer line travels via the guide channel from insertion of the line through a eyelet and exiting the eyelet on the opposite end of the trimmer head; 
         FIG. 27  is a top isometric view of the spool; 
         FIG. 28  is a perspective view of a second exemplary embodiment of a trimmer head assembly; 
         FIG. 29  is an exploded view of the embodiment of  FIG. 28 ; 
         FIG. 30  is a cross-sectional view of the second exemplary embodiment of  FIG. 28 , viewed along section line  30 - 30 ; 
         FIG. 31  is a cross-sectional view of a third embodiment of the present invention trimmer head assembly; 
         FIG. 32  is a cross-sectional view of a fourth embodiment of the present invention trimmer head assembly; and 
         FIGS. 33 a  and 33 b    show a segment of trimmer line being advanced through the exemplary embodiment of  FIG. 32 . 
     
    
    
     Similar numbers refer to similar parts throughout the drawings. 
     DETAILED DESCRIPTION 
     Although the present invention trimmer head can be embodied in many ways, only three exemplary embodiments are illustrated. These embodiments are selected in order to set forth three of the best modes contemplated for the invention. The illustrated embodiments, however, are merely exemplary and should not be considered a limitation when interpreting the scope of the appended claims. 
     Together, body members  7  and  11  are referred to herein as the trimmer cutting head housing. A threaded fastener (bolt or nut)  6  is used to attach the main housing body  7  to drive shaft  3 . In order to secure body member  7  to the trimmer machine apparatus, a threaded fastener (bolt or nut)  6  is inserted through a central opening  14  of an extended housing to accommodate a drive shaft that extends through and beyond the center of a spool. As used herein, spatial terms such as “top”, “bottom”, “upper”, “lower”, etc. refer to the relative positions that the various structural components described herein would assume when trimmer cutting head  1  is “in use,” i.e., when attached to the rotating drive shaft of a conventional internal combustion or electric powered grass/weed trimmer machine. 
     Referring to  FIG. 1  there is shown an assembled cross section view of a first presently preferred embodiment of a trimmer cutting head  1  according to the invention that is used for cutting vegetation in conjunction with an internal combustion engine or electric motor powered trimmer apparatus commonly known as handheld grass/weed trimmer or brush cutting machine. Trimmer head  1  preferably comprises a rigid molded plastic first or “top” body member  7  and a rigid molded plastic second or “bottom” body member  11 . Together, body members  7  and  11  are referred to herein as the trimmer head housing. Body members  7  and  11  may be releasably fastened to one another by a snap, threaded, J•slot or other releasable connection. For example, suitable fastening means may include generally stiff yet resilient tabs  22  ( FIGS. 2, 3, 4 ) upwardly projecting from the body member  11 . 
     Tabs  22  are adapted to pass through correspondingly shaped apertures  52  ( FIGS. 2, 19, 20, 21 ). At their upper ends tabs  22  preferably have radially outwardly directed lips. As tabs  22  are inserted through apertures  52 , the tabs flex radially inwardly until such time that lips pass completely through the apertures whereby the tabs assume their unflexed positions and the lips latchingly engage body member  11  with body member  7 . 
     Alternatively, it will be understood that the lipped tabs or similar structure may be carried by the first body member  7  and corresponding slots may be provided, where appropriate, in the circumferential wall or the end wall of the second body member  11  in order to achieve the desired latching engagement between the first and second body members of the trimmer head housing. 
     Also shown in  FIGS. 1, 2, 20, 26  are trimmer line metal eyelets  5  through which trimmer line passes when loading trimmer line into and discharging trimmer line from trimmer head  1  in the manner described hereinafter. The diametrically opposed metal eyelets  5  are securely mounted between the circumferential wall of the first and second body members  7  and  11 . 
     Metal eyelets  5  are preferably provided with a gently curved contour to reduce breakage of the trimmer line during operation of trimmer head  1 . As depicted in  FIGS. 19, 20 and 21  main body member  7  includes a central opening  50 . Prior to assembly of trimmer head  1 , the threaded arbor of a trimmer apparatus drive shaft is inserted through opening  50  and a fastener (nut/bolt)  6  is threaded onto the drive shaft arbor which secures body member  7  to the threaded drive shaft arbor. Trimmer head  1  further includes a trimmer line spool  8  that is rotatably supported in the trimmer head housing. Spool  8  comprises a cylindrical core bounded on its first and second (upper and lower) ends by circular disc-like flanges  17  and  16 . According to this embodiment, spool  8  comprises a multiple chamber spool, that is, it is divided into two chambers or compartments by the provision an intermediate flange  32  located between flanges  17  and  16 . Intermediate flange  32  is preferably coplanar with abutment means  37  ( FIGS. 18, 23, 22 ), discussed below, provided within the core of spool  8 . Abutment means  37  serves as an abutment or seat for resilient biasing means  9  e.g., a compression spring or the like, in a manner described below. In addition to biasing means  9 , the latch means according to the embodiment of trimmer head  1  illustrated in  FIGS. 1-26  comprise at least one projection  18 ,  15  carried by one of the trimmer head housing and or spool  8 . The projection(s) cooperate with seat means in the form of at least one recess carried by the other of the trimmer head housing and the spool. Together the latch means and seat means function as indexing means to enable a user to selectively discharge trimmer line from the spool when desired or necessary. According to a presently preferred embodiment most clearly illustrated in  FIGS. 1, 6, 7, 11, 14, 17, 18, 22, 23  and projection(s)  18  and  15  assume the form of generally arcuate wedge shaped formation(s) provided on the outer faces of both of the trimmer spool end flanges  17 ,  16 . Each formation includes a substantially vertical stop surface and a sloped or inclined cam or glide surface. Preferably, the formation(s) are molded integrally into spool  8  at the time of its manufacture. In a presently preferred embodiment most clearly illustrated in  FIGS. 6, 7 and 11  projection(s)  18 ,  15  are adapted to cooperate with seat means in the form of generally arcuate and or vertical depressions  26 ,  58  provided on the inner face of both first and second housing body member  11 ,  7 . A projection  18 ,  15  received in a depression  26 ,  58  is shown in  FIG. 1 . It will be understood that the relative positions of the projection(s)  18 ,  15  and depression(s)  26 , 58  may be reversed. That is, suitable sloped projection(s) may be provided in the inner faces of the first and second body member  7 ,  11  and cooperating depression(s) may be formed in the outer faces of both of the trimmer spool end flanges  17 ,  16 . Projection(s)  18 ,  15  are normally retained in depression(s)  26 ,  58  under the influence of the compression force of biasing means  9 . 
     In order to maintain biasing means  9  in stable orientation during operation of trimmer head  1 , it is desirable that the bottom surface of first body member  7  be provided with a protruding ring or collar  251  the function of which is described below. In presently available spool trimmer head assemblies wherein the trimmer line may be wound onto a spool without disassembly of trimmer head housing to reload line onto the inner spool that easy load, these spool trimmer heads are “uni-directional” and can only function properly on a trimmer machine which drive shaft arbor turns in one (1) specific direction (clock-wise or counter clockwise). 
     In contrast, trimmer line spool  8  may be received in the trimmer head housing with either spool flange  16  or spool flange  17  in operative engagement with the inner surface of body member  11 . That is, spool  8  may be selectively placed in a desired disposition in body member  11  depending on the direction of rotation of the drive shaft of the trimmer apparatus with which trimmer head  1  is intended to be used ( FIG. 11 ). Once the desired disposition of spool  8  has been determined a small removable (i.e., friction fit) semi-permanent type insert “stop”  19  ( FIGS. 1, 5, 14, 15, 22 ) can be placed in receiver openings  31 , 48  provided in spool center non-circular opening which acts as a “block” for misplacement of the spool  8  in the trimmer head housing  11 , incorrectly. This insert “stop” can be permanently placed or non-permanently placed (i.e. removable). It would be made from plastic or rubber type material but not limited to. Accordingly, the cam surface(s) of the projection(s)  18 ,  15  on the flanges  17 ,  16  are inclined in such a way that spool  8  is capable of practical rotation in one direction (e.g., counterclockwise) when first flange  17  faces upwardly and practical rotation in the opposite direction (e.g., clockwise) when second flange  16  faces upwardly ( FIG. 11 ). 
     With this capability, this spool trimmer head may be effectively used with essentially any powered vegetation trimmer, regardless of whether the trimmer&#39;s drive shaft rotates clockwise or counterclockwise. Referring to  FIGS. 6, 7, 14, 17, 18, 22, 23 and 27 , it will be seen that, extending inwardly from the outer surfaces of spool flanges  16 ,  17  and terminating at abutment means  37  is a pair of opposed sockets  64 . In the illustrated embodiment, sockets  64  have a generally noncircular shape. Referring to  FIGS. 3, 8, 24, 25  there is shown a trimmer spool turning member  12  suitable for enabling a user to wind trimmer line onto spool  8 . Trimmer spool turning member  12  comprises a knob portion  12  that is adapted to project through a central aperture  65  ( FIGS. 3, 4 ) provided in the second body member  11 . Knob portion  12  is preferably provided with a plurality of raised grip enhancing formations about its periphery. Trimmer spool turning member  12  further comprises a drive portion  37  which is separated from knob portion  12  by a radially outwardly directed flange  35 . Flange  35  is adapted to rest against the inner face of the closed end of the second body portion  11 . Preferably, the inner face of the closed end of the second body portion surrounding central aperture  65  is provided with a circular seat  66  ( FIGS. 3 and 4 ) which is dimensioned to closely receive knob flange  35  in the manner shown in  FIG. 3 , drive portion  37  is sized and shaped to essentially matingly cooperate with sockets  64  of trimmer line spool  8 . In the illustrated embodiment, therefore, the drive portion  37  of trimmer spool turning member  12  is generally a non-circular symmetric shape to permit its insertion into either of the spool sockets  64 . It will be appreciated, however, that the mating spool sockets  64  and drive portion  37  are not limited to any particular shape. Indeed, they may assume any mating shape other than a purely circular configuration that will effectuate rotation of spool  8  by rotation of knob portion of  12 . It should be noted that spool cover plate  28  ( FIGS. 9, 10, 16, 17, 18 ) is placed in spool socket  64  of spool  8  by an assembly person/worker at plastic injection mold factory.  28  and  8  to be sold as preassembled. 
     Cover plate  28  has insert pegs  38  that are to be joined with receiver openings  67  within the spool socket that has open face U shaped “non-linear” portion of trimmer line guide channel exposed. Spool cover plate is a friction fit assembly and this part once placed cannot easily be removed and when the trimmer head is fully assembled this part is held in place either being biased by spring  9  and or abutment to  37  of bump/turn knob  12  which is also biased by spring  9 . Metal Eyelets  5 , ( FIGS. 1, 2, 5, 20 ) are fixed and preassembled to main housing body  7  by an assembly person/worker. The eyelets simply slide in to a tapered side wall of main housing body  7  with a friction fit. The eyelets can be installed by hand without the use of tools and removed and replaced by hand as well. Assembly of trimmer head  1  is as follows. A user first inserts the knob portion of trimmer spool turning member  12  until knob flange  35  comes to rest against the inner face of the closed end of the second body portion  11 . He or she then places trimmer line spool  8  into the second body portion  11  while bringing one of the spool sockets  64  into mating engagement with the drive portion of trimmer spool turning member  12 . When inserting the spool, the user must take care to face either spool flange  17  or spool flange  16  upwardly depending on whether they have trimmer machine that has a drive shaft arbor that turns either clockwise or counterclockwise onto the spool (the direction of winding is dictated by the direction of rotation of the trimmer apparatus drive shaft: if the drive shaft rotates counterclockwise, then the trimmer line winding direction is clockwise, and vice versa). Instructional message and directional symbols  29  ( FIGS. 14, 17, 18 ) are molded on spool flanges  17 ,  16  to aide user from misplacement of spool with  11  and  12 . Biasing means  9  is then placed into the open upwardly facing socket  64  and first body member  7  is brought into closing engagement with second body member  11 . 
     Each socket  64  is preferably provides for placement a small removable (i.e. friction fit) semi-permanent type insert “stop”  19  ( FIGS. 1, 5, 14, 15, 22 ) can be placed in receiver openings  31 , 48  provided in spool center non-circular opening which acts as a “block” for misplacement of the spool  8  in the trimmer head housing  11 , incorrectly. If an end user does not use or loses “stop”  19  and errors in properly placing the spool within the trimmer housing, the body member  7 ,  11  may be separated to permit the spool to be inverted into the proper disposition. 
     Referring again to  FIGS. 26, 27, 17, 11, 14, 7 and 6 , it will be seen that spool  8  when joined with spool cover plate  28  includes a continuous closed “non-linear” trimmer line guide passageway formed coplanar with intermediate spool flange  32 . Trimmer line guide means is a continuous closed “non-linear” passageway passing from a first enlarged portion  10  of intermediate spool flange  32  through abutment means  33  ( FIGS. 7, 6 ) and through a second (opposite end of spool) enlarged portion  10  of intermediate spool flange  32 . As seen in  FIGS. 26, 27 , the passageway of trimmer line guide means communicates with oppositely oriented guide openings in the first and second enlarged portions  10  of intermediate flange  32  that are constructed and arranged to ensure that trimmer line is properly wound on both upper and lower chambers of spool  8  equally during reloading of trimmer line onto the spool  8 . Also, it is preferable that the opposite open ends of the passageway of trimmer line guide means be funnel or flare shaped, as at  10  ( FIGS. 6, 7, 11 ,) to facilitate insertion of trimmer line into the passageway. In order to load trimmer line  4  into trimmer head  1 , the passageway of trimmer line guide means  10  is first brought into alignment with trimmer line exit ports (metal eyelets)  5 . Then, using one fixed length of line long enough to fully load the inner spool  8  (note: use manufactures recommended length), take one end length of trimmer line and insert it into either eyelet  5  and by feed/push the line through trimmer line guide means of spool  8  until it passes out of the opposite exit eyelet  5 . The trimmer line should then be adjusted so that approximately equal lengths of line project from each exit port. The user then winds the bump/turn knob portion  20  of the trimmer spool turning member  12  in the direction that is free to turn which turns the inner spool and the line is drawn into the housing and wound upon the upper and lower chambers of spool  8 . The sloped surfaces of projections  18 ,  15  allows a person to be able to easily turn knob  12  which ratchets in one direction and cannot move in the opposite direction. As knob  12  is turned projections  18 ,  15  makes contact with indexing ribs  26  in bottom housing  11  that glide upward and over the rib and then drop in to the depression which locks the spool from turning in the opposite direction. As is known in the art, the substantially vertical stop faces of projections  18 ,  15  prevent uncontrolled discharge of trimmer line during vegetation trimming. Trimmer head  1  is a bump indexing variety of trimmer head. That is, it permits user-controlled discharge of trimmer line utilizing the centrifugal force generated by the rapidly rotating head. More particularly, when the bottom of knob portion  60  of the trimmer spool turning member  12  is tapped against a hard surface, the biasing force of biasing means  9  is momentarily overcome, whereby the substantially vertical stop faces of projections  18 ,  15  are momentarily displaced from contact with the corresponding substantially vertical stop faces of depressions  26 . During this brief instant, centrifugal force cause trimmer line  4  to be discharged through metal eyelets  5 . Thereafter, the biasing means  9  re-seats the spool into engaging contact between the stop faces of projections  18 ,  15  and their counterparts in depressions  26 . It is also possible to use trimmer head  1  in a fully manual mode. As such, when the user desires to extract trimmer line from the head, he or she brings trimmer head to a complete stop, pushes the knob portion  60  inwardly against the biasing force of the biasing means while turning the knob and pulling on the line to extract the desired length of line from the spool. When sufficient line has been discharged, the user releases the knob and resumes trimming. 
     Referring simultaneously to  FIG. 28 ,  FIG. 29 , and  FIG. 30 , a first exemplary trimmer head assembly  110  is shown. The trimmer head assembly  110  attaches to the drive shaft of a string trimmer machine (not shown), which may rotate the trimmer head assembly  110  either clockwise or counterclockwise depending upon the model of the string trimming machine being used. The trimmer head assembly  110  is comprised of three major molded plastic parts. The major plastic molded parts include a primary housing  112 , a spool  114  and an end cap  116  that holds the spool  114  within the primary housing  112 . 
     The primary housing  112  defines an open interior  118 . The top surface  119  of the housing  112  is closed, except for a mounting hole that permits the passage of the drive shaft into the housing  112 . The bottom of the housing  112  is open, therein providing easy access to the open interior  118  of the housing  112 . The periphery of the open interior  118  of the housing  112  is defined by a cylindrical wall  119  that extends downwardly from the periphery of the top surface  119 . 
     At least two string eyelets  120  are formed through the cylindrical wall  119 . The string eyelets  120  are diametrically opposed. The housing  112  may contain thickened regions about each of the string eyelets  120  to compensate for the wearing of the plastic at the string eyelets  120 . Furthermore, optional wear rings  122  may be provided within the string eyelets  120 . The wear rings  122  can be made from metal, ceramic, or a hard plastic that resists contact wear better than does the plastic material of the remainder of the housing  112 . 
     The spool  114  has a central hub  124 . The central hub  124  is tubular in shape and has three primary flanges  126 ,  128 ,  130  that define two trimmer line winding areas  132 ,  134 . A trimmer line conduit  136  is coupled to the central flange  130 . The conduit  136  has a first open end  138  and an opposite second open end  139 . The details of the conduit  136  are later explained. 
     The spool  114  passes into the interior  118  of the housing  112 . The end cap  116  holds the spool  114  in place. The spool  114  has a projecting knob  140  that extends through an opening  142  in the end cap  116 . Accordingly, when the spool  114  is assembled within the trimmer head assembly  110 , the spool  114  can be manually rotated within the housing  112  by grasping and turning the projecting knob  140 . 
     To load a length of trimmer line  144  onto the spool  114 , the spool  114  is manually rotated until the two open ends  138 ,  139  of the conduit  136  align with the two eyelets  120 . A free end  145  of the trimmer line  144  is then advanced into the conduit  136  through one of the eyelets  120 . The advancement of the trimmer line  144  is continued until the trimmer line  144  emerges out of the opposite open end  139  of the conduit  136  and passes through the opposite eyelet  120 . The trimmer line  144  can then be wound onto the spool  114  by rotating the protruding knob  140 . 
     In order for the rewinding process to work, the open ends  138 ,  139  of the conduit  136  must be aligned with the eyelets  120  of the housing  112 . Furthermore, the curved bias of the trimmer line  144  cannot cause binding within the conduit  136 . In order to reduce the likelihood of binding, the curved bias in the trimmer line  144  is compensated for by the structure of the conduit  136 . 
     Referring now solely to  FIG. 30 , it can be seen that the conduit  136  generally has an omega shape. That is, the conduit  136  has two straight sections  146 ,  148  and a curved central section  150 . The first straight section  146  extends from the first open end  138  of the conduit  136  to the curved central section  150 . Likewise, the second straight section  148  extends from the second open end  139  of the conduit  136  to the curved central section  150 . The combined length of the straight sections  146 ,  148  is at least as long as the distance D 1  between the straight sections  146 ,  148  that is occupied by the curved central section  150 . 
     Each straight section  146 ,  148  is linearly aligned with each other and lays perpendicular to the exit planes of the open ends  138 ,  139 . The curved central section  150  begins at an upward bend  151  having a first radius of curvature R 1 . The upward bend  151  transitions into a downward bend  152  having a second radius of curvature R 2 . Lastly, the downward bend  152  transitions into a lateral bend  153  that reorients the conduit  136  back onto its original direction. The lateral bend  153  has a third radius of curvature R 3 . The radii of the various bends  151 ,  152 ,  153  depend upon the radius of the central opening  142  in the spool  114 . It is preferred that the various radii be between  5  percent and  20  percent larger than the radius of the central opening  142 . In this manner, the curved central section  150  remains relatively close to the exterior of the central opening  142 . 
     When the trimmer line  144  enters the first straight section  146 , the first straight section  146  guides the trimmer line  144  into the curved central section  150 . When the trimmer line  144  exits the curved central section  146 , the trimmer line enters the second straight section  148 . The second straight section  148  has a long enough length to eliminate any bias curvature embedded within the plastic of the trimmer line  144 . Accordingly, when the trimmer line  144  exits the second straight section  148 , the trimmer line  144  has been set on a straight path and reaches the second housing eyelet  120  without any binding. 
     In the embodiment described, a curved central section  150  is shown. If the incoming trimmer line  144  has a downward curve bias and the curved central section  150  curves upwardly, there is potential for the trimmer line  144  to bind. To eliminate this potential problem, two curved central sections can be made, wherein one is on either side of the central opening  142 . Such an embodiment is shown in  FIG. 31 . 
     Since the alternate embodiment shown in  FIG. 31  has many of the same features as the originally described embodiment, the same reference numbers will be used to describe the same features. Referring to  FIG. 31 , it can be seen that two curved sections  150 ,  160  can be created between the two straight sections  146 ,  148 . When a segment of trimmer line  144  is inserted onto one of the straight sections  146 ,  148  and that segment reaches the two central curved sections  150 ,  160 , the natural curved bias of the trimmer line  144  will cause the trimmer line  144  to enter either the first central curved section  150  or the second central curved section  160 . Since the natural curved bias of the trimmer line  144  creates the selection, the trimmer line  144  is not guided against its bias and the potential for binding is removed. 
     In the embodiments previously described, the conduits are completely enclosed between their open ends  138 ,  139 . This need not be the case. Parts of the conduit can be fabricated in an open fashion. Such fabrication may also result in simplified and less expensive molding tools. 
     Referring to  FIG. 32 , a third alternate embodiment of the present invention is shown. In this embodiment, a spool  170  is provided having a flange  172 . A relief  174  is formed in the flange  172  of the spool  170  around the central opening  176 . The relief  174  has a general rhombus shape with rounded corners. The central opening  176  is disposed in the center of the relief  174 . Two deflectors  178 ,  179  are set within the relief  174 . Both deflectors  178 ,  179  have an offset salient point  180 . The offset salient point and the angles of the deflectors  178 ,  179  act to deflect the trimmer line  144  to the right of the salient point  180  as the trimmer line  144  approaches the salient point  180 . 
     The relief  174 , being generally shaped as a rhombus, has a long axis  182  between corners  183 ,  184  and a short axis  185  between corners  186 ,  187 . Straight sections  188 ,  190  of the conduit lead into the relief  174  in the same line as the long axis  182 . The straight sections  188 ,  189  of the conduit extend to open ends  192 ,  193  at the edge of the flange  172 . These open ends  192 ,  193  are aligned with the eyelets  120  in the surrounding housing  112  of the trimmer head assembly when new trimmer line  144  is loaded into the trimmer head assembly. 
     Referring to  FIGS. 33 a  and 33 b   , it can be seen that when a length of trimmer line  144  is inserted through the eyelet  120  of the housing  112  and through a straight section  188  of conduit, the free end  145  of the trimmer line  144  enters the relief  174 . The trimmer line  144  advances until the trimmer line  144  contacts the salient point  180  of the deflector  178 . The deflector  178  deflects the trimmer line  144  to the right of the deflector  178 . The trimmer line  144  then contacts the peripheral wall  194  of the relief  174  and follows the path of that wall  194 . The wall  194  of the relief  174  guides the trimmer line  144  into the opposite straight section  190 . 
     It will be understood that two deflectors  178 ,  179  are provided, so it does not matter in which direction the trimmer line  144  is inserted into the trimmer head. A left-to-right insertion and right-to-left insertion operate in the same manner. 
     As with the earlier embodiments, the combined length of the straight sections  188 ,  190  of the conduit are preferably longer that the distance D 2  between the straight sections  188 ,  190  of conduit. In the shown embodiment, this distance corresponds to the long axis  182  of the relief  174 . 
     It will be understood that the embodiments of the present invention that are illustrated and described are merely exemplary and that a person skilled in the art can make many variations to those embodiments. For instance, radius of curvatures used in the curved section of the conduit path can be varied to accommodate different spool diameters with different sized central openings. All such embodiments are intended to be included within the scope of the present invention as defined by the claims.