Abstract:
The inventions relate generally to devices for trimming grass, such as string trimmers, that are attachable to a lawn mower and usable while mowing a lawn. More particularly, the inventions relate to a light-duty string trimmer wand attachable to a walk-behind lawn mower and independently operable to trim small areas of grass. Detailed information on various example embodiments of the inventions are provided in the Detailed Description below, and the inventions are defined by the appended claims.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This Application claims the benefit of the U.S. Provisional Application Ser. No. 60/662,422 filed Mar. 16, 2005 (hereinafter “the Provisional Application”) which is hereby incorporated by reference in its entirety.  
       BACKGROUND OF THE INVENTIONS  
       [0002]     A conventional homeowner lawn maintenance solution includes a push or walk-behind mower and a full-size string trimmer. The homeowner mows the accessible areas of the grass with the mower, however there are some areas the mower cannot reach, which are typically alongside fences and objects surrounded by grass. Following mowing, a typical homeowner stows the mower and takes up a string trimmer to tidy these inaccessible areas.  
         [0003]     An ordinary, full-size string trimmer is designed to trim large areas of grass. For example, a homeowner having grass planted abutting a fence may trim the grass at the fence by sweeping the full-size trimmer generally along the length of the fence. While the homeowner has the trimmer out, he will trim central areas around trees, poles, flowerbeds and the like. Commonly, a string trimmer will be designed and marketed to trim not only small patches of relatively short grass, but also to clear weeds and tall grass. For this, a typical full-size string trimmer includes a relatively large power plant to drive its string through thick stems, leaves and cut debris while continuing to rotate its head at an acceptable speed. These power plants are conventionally either two-cycle combustion engines or electric motors.  
         [0004]     A number of years ago string trimmers were commonly electric, connectible to ordinary AC power through an extension cord. The homeowner dragged the cord with him as he went, but that was preferable to trimming the grass by hand. This burden was relieved somewhat by the availability of portable gas-powered string trimmers, but due mainly to the size and weight of the engine required these are not comfortably used or carried in tandem with other yard-care equipment. Gas-powered trimmers also require some maintenance, mainly in relation to fuel replenishment and engine care.  
         [0005]     One additional homeowner burden introduced by conventional string trimmers is that of making two passes across the yard: one to mow and one to trim. Some attempts have been made to combine a mowing operation with a trimming operation, generally by incorporating a string trimmer into a lawn mower powered thereby. Of these, many incorporate a trimmer head fixed to a mower deck, such as that described in U.S. Pat. No. 4,170,099 to Owens. Mowers of that type might be conveniently used near fences, as the operator would likely pass alongside a fence anyway. However, for trimming around small objects such a mower would need to be moved from side to side, which would require maneuvers against the generally forward mower motion for which it is principally designed. Solutions of this kind also introduce new moving parts and maintenance issues, and although several examples of solutions of this type have appeared in issued patents, mowers that incorporate a string trimmer have not attained popularity perhaps for these reasons.  
         [0006]     Other designs have incorporated a string trimmer to a lawn mower, not fixably mounted. For example, U.S. Pat. No. 4,242,855 to Beaver describes a string trimmer powered through a flexible shaft coupled to the mower engine&#39;s crankshaft. Apparently, there are few solutions to providing driving power to a portable string trimmer head from a mower engine, and thus these designs appear infrequently. Furthermore, it seems likely that maintenance issues would outweigh the advantages; a flexible shaft would rotate at a fairly high rate and could suffer from cable breaks due to kinking or loss of lubricant over seasonal use.  
         [0007]     Other aspects of combining a lawn-mower with a string trimmer have challenged prior designers. Most, if not all, of the prior designs incorporate essentially a full-sized trimmer or trimmer head as described above. Thus one might categorize the prior designs as either a string-trimmer head mounted to a mower deck, or a full-sized trimmer mounted to a riding mower/tractor such as that described by Aldrich in U.S. Pat. No. 5,802,824. Although many of the riding mower designs incorporate a fixed trimmer on a mower base, Aldrich cleverly adds removability of his trimmer for use apart from the riding mower. Aldrich&#39;s solution, however, is not suitable for the majority of homeowners who occupy a lot size of well less than one-half acre and do not have a substantial outbuilding large enough to store a riding mower. Thus in order to serve the majority of homeowners, a trimming product must be combinable with a walk-behind self-propelled or push mower.  
         [0008]     For a homeowner with large areas of fence line to trim, use of a full-sized string trimmer may be acceptable. For him, the inconveniences of equipment care and the additional time to stow his mower and retrieve a string trimmer may be compensated with the efficiency with which his full-sized trimmer trims his many areas not reachable by his mower. However, there are some homeowners who have little trimming to do. Lawn areas abutting a sidewalk, driveway or other flat surface level with the lawn can be entirely cut by passing the mower over the lawn interface, although some seasonal edging may be required. Some homeowners deliberately place such mow-strips under fences to permit the mower to ride on the strip on one side, while preventing grass from growing directly under a fence. Traditionally, homeowners have also edged their grass with objects buried partially in the ground, providing a barrier to the expansion of grass. These objects have often had a substantial vertical profile, preventing a lawn mower to pass over these edges without substantial damage. Recently a product has become available that provides both an edging and a mow strip in the same block, and can be used to surround flowerbeds, trees or placed alongside fences to provide a mow strip and reduce or eliminate the need to trim grass.  
         [0009]     A homeowner utilizing mow-strips, blocks and other products may have very few areas to trim, which might be reduced to the area around a few trees, or the legs on a child&#39;s swing set. For such a homeowner prior grass trimmers become cumbersome.  
       BRIEF SUMMARY OF THE INVENTIONS  
       [0010]     The inventions relate generally to devices for trimming grass, such as string trimmers, that are attachable to a lawn mower and usable while mowing a lawn. More particularly, the inventions relate to a light-duty string trimmer wand attachable to a walk-behind lawn mower and independently operable to trim small areas of grass. Detailed information on various example embodiments of the inventions are provided in the Detailed Description below, and the inventions are defined by the appended claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  depicts a first exemplary trimmer wand.  
         [0012]      FIG. 2  depicts the internal components of the first exemplary trimmer wand.  
         [0013]      FIG. 3A  shows an assembled first exemplary interlock.  
         [0014]      FIG. 3B  shows an exploded view of the first exemplary interlock.  
         [0015]      FIGS. 4A and 4B  depict the coupled state of the first exemplary trimmer wand and the first exemplary interlock.  
         [0016]      FIG. 5A  depicts the first exemplary trimmer wand mounted to a walk-behind lawn mower by way of the first exemplary interlock.  
         [0017]      FIG. 5B  depicts the operation of the first exemplary trimmer wand.  
         [0018]      FIG. 6  depicts an alternative exemplary sabre form of a trimmer wand.  
         [0019]      FIG. 7A  depicts a second exemplary interlock in exploded view.  
         [0020]      FIG. 7B  depicts the second exemplary interlock in an open or unclamped state.  
         [0021]      FIG. 7C  depicts the second exemplary interlock in a closed or clamped state.  
         [0022]      FIG. 8A  depicts a third exemplary form of a trimmer wand.  
         [0023]      FIG. 8B  depicts the third exemplary trimmer wand in exploded view.  
         [0024]      FIGS. 9A and 9B  show a non-spooling, threading rotating head and a section of trimmer string threaded in operational condition.  
         [0025]      FIG. 10  depicts an exemplary guard that may be used with some trimmer wands.  
         [0026]      FIG. 11A  depicts an exemplary retractable guard in an extended position.  
         [0027]      FIG. 11B  depicts an exemplary retractable guard in a retracted position.  
         [0028]     Reference will now be made in detail to some embodiments of the inventions, examples of which are illustrated in the accompanying drawings. 
     
    
     DETAILED DESCRIPTION  
       [0029]     Disclosed herein are trimmer products attachable to a push mower, the first example of which is shown in  FIG. 1 . The trimmer products disclosed herein may be referred to as a wand, as generally these products are small and light enough to operate comfortably with one hand. The first exemplary wand  10  shown in  FIG. 1  includes a body or housing  24 , a grasping portion or handle  17 , and a rotating head  12  distally disposed from the handle  17 . Also in wand  10 , head  12  is maintained at an angle relative to handle  17  to provide for a comfortable manual grip while maintaining head  12  level to the ground and away from the operator&#39;s body. Wand  10  is operated on or off through pressure on switch  16 , which in this example is located at the underside of housing  24  at about the position of contact of an operator&#39;s index finger. In an alternative configuration, housing  24  at handle  17  may incorporate a flexible area over a switch, thereby closing the circuit while an operator applies squeezing pressure to the handle.  
         [0030]      FIG. 2  depicts the internal components of exemplary wand  10  and its attachment bracket interlock  20 . Housing  24  separates into two halves, one of which  24   a  is shown. Wand  10  incorporates an electric motor  13 , the output shaft of which is attachable to rotating head  12 , the shaft of which thereby is directly coupled to head  12 . The housing of motor  13  attaches to or communicates with housing  24  and thereby rotates head  12  with respect to housing  24  when power is applied. Motor  13  is electrically connected to batteries  15 , affixed to housing  24  inside or otherwise, through wires  14  that run the length of housing  24 ; motor  13  is interruptably controllable through switch  16  thereby controlling powered rotation of head  12 . Motor  13  may be permanently or semi-permanently mounted to one of the housing halves to maintain position on disassembly of the wand. Housing portion  24   a  may include clips or other attachments holding wires  14  in position, easing assembly of the wand and also reducing vibrations and thereby wear. In exemplary wand  10  batteries  15  are positioned near grasping area  17 , reducing the lever-arm of the working end of the product relative to the hand of an operator and thereby improving control. Batteries  15  may be selected to be a common type, such as a 1.2 to 1.5 volt dry cell battery. Batteries  15  maybe disposable types, alkaline or otherwise. Batteries  15  may also be a rechargeable type, such as NiMH or NiCd, and terminals may be provided in housing  24  to engage a charging circuit if desired. Also in  FIG. 2 , a length of trimmer line, which may be of the ordinary nylon type for string trimmers, is attachable to rotating head  12  through a threading operation, described hereinafter.  
         [0031]     The exemplary trimmer wand  10  is designed to be attached to the tubular portion of a walk-behind mower handle, and wand  10  can be coupled to a mount securable to a tubular handle, which in this example is by a clamping interlock  20 . Best viewed in  FIGS. 3A and 3B , interlock  20  includes two halves  21  and  22 , which together form a cylindrical channel  25  through which a steel handle tube may pass through. In this example, halves  21  and  22  are clamped by machine screws  23 , although other arrangements maybe used as discussed below. Interlock  20  further includes a coupling channel  26  receiving housing  24 . Referring now to  FIG. 4A  and further in this example, the shape of housing  24  includes a keyed portion  19  shaped to fit closely in channel  26 . The profile of the key expands outward, thereby restraining the keyed portion  19  from exiting channel  26  and thereby forming a keyed interlock. As best viewed in  FIG. 4B , housing  24  includes a widening key termination  28  preventing interlock  20  from moving beyond a resting position. Housing  24  may escape interlock  20  by a sliding motion through channel  26  downward  27  beyond key termination  29 . A keyed coupling is but one example, and other coupling types may also be used. Looking again to  FIG. 3A , the end of channel  26  is flared to ease alignment of housing  24  into channel  26 . Keyed channel  26  and cylindrical channel  25  may be made symmetrical, which allows the interlock  20  to be installed in either direction on the tubular handlebar and thereby providing goof-proof installation for non-mechanically inclined homeowners. Alternatively as shown in figure SA, channel  26  may be angled with respect to channel  25  to set the grasping end of the wand at some distance from a mower handle providing clearance for a control lever or other handlebar-attached part.  
         [0032]     Use of the trimmer wand  10  and interlock  20  is depicted generally in  FIGS. 5A and 5B  in relation to a walk-behind push mower  30  including a mower deck, engine, cutting blade and handle  31 . First in  FIG. 5A , interlock  20  is clamped to handlebar  31  as described above. As shown, clamp  20  is attached on handlebar  31  to position trimmer wand  10  at the side of the handle  31 , with wand  10  positioned generally below interlock  20  and the downward sloping side portion of handle  31 . This position may serve to reduce interference with the movements of the lawn mower operator, and conveniently places the grasping portion near the operator. This position may also avoid interference with lawn mower controls, which are commonly mounted above the handle for the operator&#39;s convenient reach. Even so, interlock  20  may be positioned at other locations on handle  31  if desired.  
         [0033]     As the operator  32  mows his lawn he may encounter an obstruction  33 , which might in this drawing be a post, which prevents the mower  30  from cutting the grass nearby the obstruction. Momentarily, the operator stops the motion of mower  30 , which may or may not involve stopping its engine. Operator  32  then withdraws wand  10  from interlock  20  by lifting it generally in the direction marked  34 , or by pulling generally toward the operator standing behind mower handle  31 . Operator  32  grasps the wand  10  and depresses switch  16  activating rotation of head  16  and thereby trimming around post  33 . Note that because wand  10  is powered internally, it operates independently of mower  30  without any connection to the mower required. The length of wand  10  may be made to be approximately 30 to 38 inches, placing head  12  at a comfortable level with respect to the ground when held out at an angle and away from the operator&#39;s body. When finished, operator  32  replaces wand  10  back into interlock  20 , in this configuration also by a sliding motion, and continues to mow as before. Note that because wand  10  is available to the operator  32  when an obstacle  33  is encountered, he need not move from the immediate vicinity of lawn mower  30  to trim the grass around the obstacle.  
         [0034]     Now the use of the exemplary wand  10 , or others disclosed herein, provides several benefits. First, as most walk-behind mowers incorporate a tubular handle, a wand can be added as an attachment to virtually all walk-behind mowers. Because the wand is relatively small, it may be stored beneath a typical walk-behind lawn mower handle, and no additional storage space in a garage or shed is needed. Additionally, the weight of the wand can be reduced to the point that the wand can be controlled with one hand. If a homeowner can operate a trimming wand with one hand, he can keep a safety control lever depressed with the other and potentially avoid restarting his lawn mower while trimming. A typical walk-behind lawn mower weighs about 70 to 100 lbs., and a wand weighing about 5 lbs. or less is comparatively light and is not likely to be an encumbrance to a lawn mower operator. With careful choice of a motor, batteries and other components, a wand might be constructed weighing about two to three lbs or even less.  
         [0035]     The components of the wand contributing the most to the weight are the batteries and motor, as the housing and other components can be made from plastics or other light-weight materials. The housing of a wand can also be constructed with thinner walls, due to its lighter-duty requirements. In one implementation, a wand is constructed having about a 2 cm diameter with walls about 2 mm in thickness, permitting AA size batteries to be housed therein.  
         [0036]     A wand may utilize a DC motor having a sufficient torque and rotational speed for the desired use. One implementation utilizes an HC783LG or similar motor available from Johnson Electric of Tai Po, Hong Kong (www.johnsonelectric.com), having a speed of about 14,000 to 16,000 RPM at a current of about 1.8A at 12 V and no load. Alternatively, a Stinger motor manufactured by Traxxas of Plano, Tex. (www.traxxas.com), requiring 1.2 A at 12 V and rotating at 17,500 RPM may also be used. A motor in the Havoc line from Team Orion of Yorba Linda, Calif. (www.teamorion.com) is also a suitable choice. A rotational speed of about 10,000 to 20,000 RPM may provide good performance: a high RPM or high power motor may provide improved trimming efficiency although depleting batteries more quickly. Should a high-current motor be chosen, it may be necessary to provide venting in the housing near the motor. Generally, motors manufactured for remote-controlled cars or boats are suitable due to their high power and/or speed and light weight, which may be under 2 lbs. If desired, a motor may be placed toward the handle portion through the use of a straight or geared shaft coupled to the motor, which may improve the balance of a wand by moving the center of gravity toward the handle. Also, a wand housing might be made to fit motor magnets, armatures, contacts and other parts, taking the place of an independent motor housing and potentially reducing weight and/or cost.  
         [0037]     As suggested above, dry cell batteries are an acceptable choice for some applications. For the 12V Johnson motor above, it may be useful to use 8 or 9 C or D cells providing up to several hours of use per charge. In such a configuration, it may be expected that a set of batteries might last sufficiently long for some users to make battery replacement a start-of-the-season maintenance activity. AA cells might also be acceptable if a lower-current motor is used. Other battery configurations may be used consistent with the desired portability and use of the trimmer product. With the use of C size batteries and a motor as suggested above, a wand could weigh as little as five or six lbs and not encumber an operator&#39;s control of a lawn mower to which it may be attached. With AA size batteries, a further weight reduction could be made at the expense of available current for the motor and battery life.  
         [0038]     The shape of a trimmer wand may be almost infinitely varied. In the example shown in  FIG. 6 , a wand takes a form more like a sabre. The angle between the rotating head and the handle, rather than being introduced by a bend near the head as shown in  FIG. 1 , is introduced by a gentle curve in the housing. About a thirty-degree angle is generally suitable for the trimming products disclosed herein. Holsters or other attachments may be provided for securing a wand to a lawn mower conforming to the selected form. Further in the example of  FIG. 6 , the housing of this wand is telescoping, providing a reduced storage profile.  
         [0039]     A handle or gripping portion of a wand may have incorporated therein texturing, finger recesses, serrations or other shaped features to improve control or comfort. A handle may also include additions, such as a surrounding rubber or foam grip.  
         [0040]     The interlock shown in  FIGS. 3A and 3B  is a good choice where it is not expected that a homeowner will need to relocate the trimmer wand product to a different lawn mower. A quick-release interlock version is depicted in  FIGS. 7A, 7B  and  7 C. The components of this version are depicted in  FIG. 7A , which are an interlocking half  43 , a clamping half  44 , pins  45 , threaded stud and bushing  46 , and knurled thumbscrew  47 . Pins  45  secure the assembled parts of this interlock as shown in  FIG. 7B . To use, halves  43  and  44  are positioned around the tubing of a handle, stud  46  is swung between the forked portion of clamping half  44 , and thumbscrew is tightened accordingly as depicted in  FIG. 7C . Again, this exemplary interlock may ease the transition and mounting of a trimmer between two or more lawn mowers.  
         [0041]     Now turning to  FIG. 8A , another trimming wand  50  is depicted, illustrating further possible variations. This example includes no angle between head  12  and gripping portion  59 . The housing is fashioned in two parts, which are a tubular battery portion  51  and a wider motor housing  52 . In this example portion  51  may be either molded plastic or may be formed from extruded aluminum, bent sheet steel or other metal, providing additional durability. Portion  51  has an inner diameter slightly larger than batteries  15 , permitting the batteries to be inserted inside to become serially connected while restricting rattling. Spring contact  56  is incorporated into endcap  53 , providing an electrical battery connection. Another contact, not shown, is implemented in motor housing completing a battery circuit. Motor  13  is securable inside housing  52 , and is further wired to the battery terminals described above and also to switch  63 . Note that if housing  51  and endcap  53  are conductive, these may be used as conductors for the battery/motor circuit. Housing portion  51  may implement inner or outer threads receiving threaded portions of motor housing  52  and endcap  53 , as desired. O-rings  55  may be used to resist water penetration, and may also keep the housing parts assembled. Indeed, the construction of a trimmer wand may borrow from techniques for manufacturing flashlights, as desired.  10043 ] Rather than utilizing an interlock, this example utilizes a securing clip  58 . Housing  51  is cylindrical in shape, and clip  58  includes a matching clip. The other side of clip  58  maybe sized for the handlebar of a particular lawn mower, as desired. Also provided with this wand is a hanging loop  54 , by which wand  50  may be carried or hanged from a utility hook if desired. The reader may look to the Provisional Application for other devices for securing a trimming wand to a handle; note that other interlocks such as holsters, clips, hooks, elastic ropes and virtually any others that restrain or secure a trimming wand to a lawn mower handle can be used.  
         [0042]     Conventional string trimmer heads utilize a string spool and a mechanism to release additional string as it wears under use. Although such techniques may be employed with a trimmer wand, it may be desired to use a non-spooling trimmer head as depicted in  FIGS. 9A and 9B  to keep the weight of the product minimal. This trimmer head includes a disc-like portion  60  that rotates against wand body  61 . This head utilizes a 10 to 12 inch length of 0.065 length of nylon line  62 , threaded through 6 mm holes as shown, leaving about a four-inch length free on both sides. Other operational lengths of string may be utilized for a particular head design and trimming use. The exit holes  64  are placed oppositely around the axis of rotation, thereby providing balance and minimizing vibration from the rotating line ends. This configuration is very good for light-duty use, i.e. where the homeowner does not need to change the line generally more than one time per mow. Now although this method is functionally simple, it may be desired to provide other string retaining devices for securing a length of string to a head, which devices come within the scope of the inventions described herein.  
         [0043]     A trimmer wand as disclosed herein may also include a guard, for example the one depicted in  FIG. 10 . A guard may serve to protect the operator from contact with a rotating string or debris flung out thereby. The guard of  FIG. 10  includes an outer arc of about fifteen degrees, with an outer lip extending down about one inch. That guard includes a shield portion  72  and a clamp  71 . Shield portion  72  might, for example, be made of molded plastic, or alternatively might be fashioned from sheet metal through a stamping process. Clamp  71  might be metal and susceptible to crimping or otherwise tightening; alternatively clamp  71  might be fashioned from rubber or other elastomer. An attachment for a shield might take any other form, for example integral to a trimmer wand housing.  
         [0044]     A guard may also be retractable or fixed. Shown in  FIG. 11A  is a retractable guard  72  fastened by clamp  71 , guard  72  being in an extended (operational) position. Guard  72  may be swung toward wand  10  and thus be positioned in a minimally obstructive position. Guard  72  and clamp  71  may be jointed with a rivet, screw and thumbnut, cam and spring, or any other connection with desirable operational characteristics.  
         [0045]     While the present systems, products and methods have been described and illustrated in conjunction with a number of specific configurations, those skilled in the art will appreciate that variations and modifications may be made without departing from the principles herein illustrated, described, and claimed. The present invention, as defined by the appended claims, may be embodied in other specific forms without departing from its spirit or essential characteristics. The configurations described herein are to be considered in all respects as only illustrative, and not restrictive. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.