Patent Publication Number: US-2018027731-A1

Title: Wheeled string trimmer mower

Description:
RELATED APPLICATION 
     This application is a Non-Provisional of, and claims 35 USC 119 priority from, U.S. Patent Application No. 62/368,034 filed Jul. 28, 2016, which is incorporated by reference herein. 
    
    
     BACKGROUND 
     The present invention relates generally to lawn and grass trimming machines, and in particular, to a wheeled string trimmer mower. 
     Many conventional wheeled string trimmers only cut what is directly underneath the machine, between a pair of wheels. When it is desired to cut grass or weeds near walled corners, underneath or adjacent fences, including rail type fences, or other obstructions, due to the relation between positions of the two wheels, the trimmer head cannot adequately access the corners or other hard to reach places. 
     Another drawback of conventional string trimmers is that when edging is desired, such as along a driveway or sidewalk, it is relatively difficult to manipulate existing string trimmers units to achieve an even cut appearance. 
     In addition, another drawback of conventional handheld string trimmers is that they do not have the ability to evenly mow areas of grass left behind by larger equipment, such as a riding lawn mower. 
     Thus, there is a need for an improved string trimmer mower that addresses the above-listed operational difficulties of conventional string trimmers. 
     SUMMARY 
     The above-listed drawbacks of conventional trimmers are addressed by the present string trimmer mower featuring a string retention mechanism for releasably retaining a cutting string that accommodates multiple string diameters and also provides for string replacement without the use of tools. Another feature of the present trimmer is a pivoting trimmer head assembly for accessing grass or weeds located outside of the wheel path. More specifically, the trimmer head position is easily adjustable by the operator without moving from an operational position or stopping the engine. Still another feature of the present trimmer is a bevel mechanism for adjusting the angle of the wheels relative to the frame for achieving different angular positions of the cutting head for trimming closer to a substrate and achieving an even cut appearance. In this manner, the present trimmer head is optionally placed at a desired angle for enhanced edging or cutting along sidewalks, driveways or the like. Also featured is an improved throttle control, which is ergonomically designed to interface with a handlebar, requiring reduced operator force for throttle actuation. 
     More specifically, a wheeled string trimmer mower is provided, including a trimmer head with a trimmer head housing having a string retention portion and a coupler portion rotatably attached to the string retention portion, the string retention portion having a first string retainer for releasably retaining a first cutting string. In addition, the string retention portion has a second string retainer for releasably retaining a second cutting string. The second string retainer is preferably circumferentially displaced on the string retention portion from the first string retainer. 
     In a preferred embodiment, the first string retainer has a slidable clamp disposed in the interior and accessible from the exterior. The clamp is constructed and arranged for sliding relative to the base between a clamping position for selectively retaining the string in place in the string retention portion, and a release position for user replacement of the first cutting strings without tools. This clamping position is maintained through centrifugal force generated by rotation of the cutting head which acts on the slidable clamp, gripping the string until released under user control. 
     In another embodiment, a rotary string trimmer is provided, including a pivoting trimmer head mechanism for trimming outside of the wheel path. This mechanism includes a frame having a pair of wheels and a platform. A trimmer head assembly is mounted on the platform, including an engine, a rotating trimmer head, and a powertrain connecting the trimmer head to the engine. A feature of the present trimmer mower is that the trimmer head assembly is rotatable relative to the frame between a plurality of indexed angular positions for enabling adjustment of an operational cutting zone of the trimmer head. 
     Another embodiment of the invention provides a bevel mechanism for a rotary string trimmer mower, including a bevel release lever for adjusting the frame to a plurality of different angular positions. The bevel release lever is connected to the frame and to an adjustable axle associated with one of the wheels. Movement of the bevel release lever relative to the frame adjusts a position of the axle, such that an axis of a first wheel is displaced from an axis of a second wheel, adjusting the first wheel vertically relative to the second wheel and orienting the trimmer head from a parallel position relative to a substrate, to a selected non-parallel position relative to the substrate. 
     In still another embodiment, a rotary string trimmer mower is provided, including a throttle control for mounting to a handlebar. Included on the throttle control is a paddle coupled between a first throttle control cover and a second throttle control cover, a throttle cable having a first end connected to the first throttle control cover, and a second end connected to a powertrain, and a lever return spring captured inside the throttle control housing. Rotation of the paddle pushes the cable to overcome the biasing force of the return spring, actuating the throttle control. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top perspective view of the present trimmer in a standard mowing position; 
         FIG. 2  is a top plan view of the present trimmer of  FIG. 1 ; 
         FIG. 3  is a top perspective view of the present trimmer in a first trimmer head pivoted position; 
         FIG. 4  is a top plan view of the present trimmer of  FIG. 3 ; 
         FIG. 5  is a top perspective view of the present trimmer in a second trimmer head pivoted position; 
         FIG. 6  is a top plan view of the present trimmer of  FIG. 5 ; 
         FIG. 7  is a fragmentary side view of the present trimmer; 
         FIG. 8  is a fragmentary enlarged side view of the trimmer of  FIG. 7 ; 
         FIG. 9  is a fragmentary top perspective view of the present trimmer frame in a straight mowing position; 
         FIG. 10  is a fragmentary top perspective view of the present trimmer frame in a pivoted position; 
         FIG. 11  is a fragmentary side perspective of the present trimmer showing the bevel mechanism; 
         FIG. 12  is a fragmentary side perspective of the trimmer of  FIG. 11  with the wheel removed; 
         FIG. 13  is a fragmentary side perspective of the trimmer of  FIG. 11  with the wheel removed and in a first bevel position; 
         FIG. 14  is a side perspective view of the present trimmer in a pivoted, level trimmer head position; 
         FIG. 15  is a front view of the trimmer of  FIG. 14 ; 
         FIG. 16  is a fragmentary side perspective of the present trimmer with the wheel removed and in a second bevel position; 
         FIG. 17  is a side perspective view of the present trimmer in a pivoted, second bevel position; 
         FIG. 18  is a front view of the trimmer of  FIG. 17 ; 
         FIG. 19  is a fragmentary side perspective of the present trimmer with the wheel removed and in a third bevel position; 
         FIG. 20  is a side perspective view of the present trimmer in a third bevel position; 
         FIG. 21  is a front view of the trimmer of  FIG. 20 ; 
         FIG. 22  is a top perspective view of the present trimmer head with narrow gauge trimmer strings held by a narrow string retainer; 
         FIG. 23  is a top perspective view of the present trimmer head with larger gauge trimmer strings held by a large string retainer separate from the narrow retainer; 
         FIG. 24  is a fragmentary top view of the head with the narrow string retainer; 
         FIG. 25  is a fragmentary bottom view of the narrow string retainer, including a slidable locking member; 
         FIG. 26  is a bottom perspective view of the retainer of  FIG. 25  with a string attached; 
         FIG. 27  is a bottom view of the retainer of  FIG. 26  showing the direction of string movement when the head is operationally rotated; 
         FIG. 28  is a side perspective view of the present trimmer head with narrow strings showing the direction of movement of strings under rotational load; 
         FIG. 29  is a fragmentary top perspective view of the present trimmer head with narrow strings showing the direction of movement of strings under rotational load; 
         FIG. 30  is top perspective view of the present trimmer head with large gauge strings in the respective retainer, showing the strings under rotational load; 
         FIG. 31  is a rear perspective view of the present trimmer with the throttle control mechanism; 
         FIG. 32  is an enlarged fragmentary rear perspective of  FIG. 31  showing the throttle control mechanism; 
         FIG. 33  is a rear perspective view of the present trimmer with the throttle control in an actuated position; 
         FIG. 34  is an enlarged fragmentary rear perspective of  FIG. 33  showing the throttle control in an actuated position; 
         FIG. 35  is a rear perspective view of the present trimmer with the throttle control in an idle position; 
         FIG. 36  is an exploded perspective view of the throttle control shown in  FIG. 35 ; 
         FIG. 37  is a top perspective view of the present throttle control in an idle position; 
         FIG. 38  is a fragmentary top perspective view of the throttle control of  FIG. 37 ; 
         FIG. 39  is a front view of the inside of the throttle control cover showing the spring in a relaxed position; 
         FIG. 40  is an enlarged top perspective view of the throttle control of  FIG. 38  in an idle position; 
         FIG. 41  is a front view of the inside of the throttle control cover showing the spring in a tensioned position; and 
         FIG. 42  is a fragmentary top perspective of the present throttle control in the actuated position. 
     
    
    
     DETAILED DESCRIPTION 
     As shown in  FIGS. 1 and 2 , a preferred embodiment of the present wheeled string trimmer, generally designated  10 , includes a frame  12  and a pair of wheels  14  rotatably connected to the frame. A platform  16  is a component of the frame  12  between the wheels  14 . An important feature of the present trimmer  10  is that a trimmer head assembly  18  is rotatably mounted on the platform  16 . Included with the trimmer head assembly  18  is an engine  20 , typically an internal combustion engine, however other power sources, such as rechargeable electric motors, are contemplated. A rotating trimmer head  22  is connected to the engine  20  via a powertrain or driveshaft  24  as is well known in the art. A handlebar  26  is connected to the frame  12  and includes a throttle control  28  preferably secured to a gripping portion  30 . As is known in the art, a throttle cable  32  connects the throttle control  28  to the engine  20 . 
     The above-identified rotatability of the trimmer head assembly  18  is achieved in part through an operator-actuated lever  34  mounted on the handle bar  26 , and connected to the trimmer head assembly  18  via a Bowden cable  36  or the like. As discussed below in greater detail, the trimmer head assembly  18  is rotatable relative to the frame  12  between a plurality of indexed angular positions for enabling adjustment of an operational cutting zone of the trimmer head  22 . 
     Referring now to  FIGS. 1-6 , the trimmer  10  is adjustable under operator control so that the trimmer head assembly  18  is movable between a plurality of angular positions including a first position ( FIGS. 1-2 ) wherein the trimmer head  22  is centered on an axis “A” projecting forwardly of the frame  12 , a second position ( FIGS. 3-4 ), such that the trimmer head is offset from the axis “A” of the frame at a first angle α, and a third position ( FIGS. 5-6 ), such that the trimmer head is further offset from the axis at a second angle β larger the first angle. While the size of angles α and β may vary to suit the application, in the preferred embodiment, they are oblique, and more preferably are acute. 
     As shown in  FIGS. 7-10 , the trimmer head assembly  18  further includes a rotating engine bracket  42  mounted to the platform  16  using a pivot pin or bolt  44 . A spring-biased locking pin  46  is mounted to platform  16 , and is configured for releasably securing the bracket  42  in one of the desired positions through operator control of the actuator lever  34 . A plurality of holes  48  is located on the rotating engine bracket  42  in an arc, each hole being in selective alignment with the locking pin  46  and a corresponding hole  49  in the platform  16  for retaining the various positions of the trimmer head assembly  18  relative to the frame  12 . 
     In operation, when the operator desires to change the position of the trimmer head assembly  18  relative to the frame  12 , the lever  34  is pulled, which, through the Bowden cable  36 , retracts the locking pin  46  by overcoming biasing force generated by a biasing element  50 . The biasing element  50  retains the pin  46  in a default locking position. Retraction of the locking pin  46  from the holes  48  and  49  allows adjustment of the trimmer head assembly  18  relative to the frame. 
     Referring now to  FIGS. 11 and 12 , another feature of the present wheeled string trimmer  10  is a bevel lever mechanism  54  which is constructed and arranged for enabling adjustment of an angle of attack of the trimmer head  22  to the grass or plants for enhanced edging cutting action. More specifically, a bevel release lever  56  is connected to the frame  12  and to an adjustable axle  58  associated with each of the wheels  14 . Pivotal movement of the bevel lever  56  relative to the frame  12  adjusts a position of the axle  58 , such that an axis “T” of a first wheel  14   a  is displaced from an axis “V” of a second wheel  14   b.  The bevel mechanism  54  further includes a bevel bracket  62  fixed to the frame  12  that releasably receives the bevel lever  56  in a locking relationship, such that the bevel lever and the adjustable axle  58  move relative to the bevel bracket about a pivot pin or bolt  64 . An index bracket  65  on the frame  12  has at least one bevel tab  66  and the bevel lever  56  has a complementary bevel slot  68  releasably accommodating one of the tabs  66  for adjusting the position of the axle  58  relative to the frame  12 . It is contemplated that, depending on the application, the position of the tab  66  and slot  68  are reversible on the respective lever  56  and bracket  65 . 
     Turning now to  FIGS. 13-15 , the present string trimmer  10  is shown in a pivoted trimmer head position and a level first bevel position, such that the trimmer head  22  is parallel relative to a substrate  72 . 
     Referring now to  FIGS. 16-18 , the present string trimmer  10  is shown in a pivoted trimmer head position and a second bevel position, such that the bevel lever  56  has been raised relative to  FIGS. 13-15  and the axle  58  has been lowered relative to the frame  12  to move the wheel  14   a  relative to the other wheel  14   b  and orients the trimmer head  22  from a parallel position relative to the substrate  72 , to a selected non-parallel position at an angle θ relative to the substrate. 
     As seen in  FIG. 19-21 , the present string trimmer  10  is shown in a pivoted head position and a third bevel position, such that the bevel lever  56  adjusts the frame  12  moving one wheel axis vertically relative to the other wheel axis and orients the trimmer head  22  from a parallel position relative to the substrate  72 , to a selected non-parallel position Ω relative to the substrate. In the above discussion of the bevel feature, it will be understood that only one wheel  14   a  was moved relative to the frame  12 . However, it is contemplated that the other wheel  14   b  could easily be moved in a similar manner to achieve desired angular modification of the position of the trimmer head  22 . 
     Referring now to  FIGS. 22 and 23 , another feature of the present wheeled string trimmer  10  relates to a common problem of string trimmers, the retention and replacement of the grass-cutting string. Another common problem of string trimmers is converting operation between various string diameters, including but not limited to 0.095, 0.105 and 0.155 inch diameter string. In the present trimmer  10 , this feature is found in the rotatable trimmer head  22  having a trimmer head housing  82  with a coupler portion  84  a string retention portion  86  rotatably attached to the coupler portion. As is known in the art, the coupler portion is secured to an end  85  of the powertrain  24 . 
     The string retention portion  86  has a first string retainer  88  for releasably retaining a first cutting string  90  and a second string retainer  92  for releasably retaining a second cutting string  94 . The second string retainer  92  is circumferentially displaced on the string retention portion  86  from the first string retainer  88 . Thus, the present trimmer head  22  is configured for accommodating multiple strings  90 ,  94 . Alternatively, an operator has the option of using only one type of string  90 ,  94  at a time. Also, it is contemplated that the first and second strings  90 ,  94  will have distinct diameters, and it is preferred that the first string  90  has a smaller diameter (0.095, 0.105 inch), and the second string  94  has a larger diameter (0.155 inch), the latter used for heavier duty operation. The focus of the present trimmer head  22  will be on the retention of the first string  90 . As is known in the art, the powertrain  24  is preferably provided with a clippings guard  96  for directing the flow of cut grass and plants. 
     Referring now to  FIGS. 22 and 24-27 , the first string retainer  88  has a cover  100  with an exterior surface  102  facing the operator during normal operation, and an opposite interior surface  104 . The interior surface  104  includes a curved track  106  defined by at least one boss  108  and a preferably curved wall  110 . The first cutting string  90  follows the curved track  106  to reduce stress concentration. A slidable clamp  112  is disposed relative to the cover  100  so that it is operationally captured between the cover and the trimmer head housing  82 . The clamp  112  is accessible from the exterior surface  102  and slides relative to the cover  100  between a clamping position ( FIG. 26 ) for selectively retaining the first cutting string  90  in place against the bosses  108 , and a release position ( FIG. 25 ) where the clamp slides away from the bosses for user replacement of the first cutting string  90  without tools. 
     The slidable clamp  112  has a peripheral surface  114 , such that the clamping position is achieved by a squeezing action exerted on the first cutting string  90  by the peripheral surface against an opposing curved surface  115  of the at least one and preferably both bosses  108 . 
     Referring now to  FIGS. 26-29 , the slidable clamp  112  has a tab  116  that slides reciprocally in a slot  118  in the cover  100  for securing the first cutting string  90  and for allowing the user to move the slideable clamp  112  during string installation for tool-less string replacement. Also included on the clamp  112  is an elongate aperture  120  that receives a fastener  122  such as a bolt or the like that passes through a mounting hole  123  to secure the cover  100  to the trimmer head housing  82 , and at the same time retaining the clamp within the cover. 
     During operation, as the trimmer head  22  rotates relative to the powertrain  24 , rotation force “F 1 ” is generated which causes the first string  90  to bend relative to the trimmer head ( FIGS. 27 and 29 ). The bending of the string  90  occurs around the radiused bosses  108  and the radiused feature of slideable clamp  112 , thus reducing the stresses in the string. In addition, the centrifugal force “F 2 ” causes the clamp  112  to slide in the slot  118  towards the bosses  108 , thus pinching the first string  90  in position and holding the string in the retainer  88 . 
     Referring now to  FIG. 30 , the trimmer head  22  is shown with the second cutting string  94  attached to the second string retainer  92 , showing the direction of string movement when the trimmer head  22  is operationally rotated. As is the case with the first string retainer  88 , the second string retainer holds a single length of string in a doubled over or looped orientation, which presents two lengths of string to the plants for enhanced cutting action. 
     As shown in  FIGS. 31, 32 and 36 , another feature of the present wheeled string trimmer  10  is that the throttle control  28  includes a throttle control housing  126  mounted on the handlebar  26  and having a throttle paddle  128  for actuating the engine  20  for powering the trimmer head  22 . The paddle  128  is coupled between a first throttle control cover  130  and a second throttle control cover  132 , these latter components defining the throttle control housing  126 . In addition, the paddle  128  is affixed to the base of a cylinder casing  134 , which rotatably engages the first throttle cover  130 , rotating about the handlebar  26 . 
     The throttle control  28  has at least one fastener  140  extending through the second cover  132  into the first cover  130 , to both retain the throttle control on the handlebar  26 , and also creates a space in which the paddle  128  moves under operator control. More specifically, the first and second covers  130 ,  132  each have at least one curved raised wall or fin  142  on inside surfaces  144  configured for defining a guiding track, rotatably engaging and complementary ribs  146  on the cylinder casing  134 . 
     Referring now to  FIGS. 36, 38, 39 and 41 , a lever return spring  148  is captured inside the throttle control housing  126 , preferably on the inside surface  144  of the second throttle control cover  132  by engagement of a short free end  150  of the spring  148  in a socket  152  formed in the cover. Upon assembly of the throttle control housing with the captured paddle cylinder casing  134 , a spring actuator formation  154  on the casing engages a long free end  156  of the spring  148 . As the user presses on the paddle  128 , causing the cylinder casing  134  to rotate in the track formed by the fins  142 , the actuator formation  154  tensions the return spring  148 . Upon user release of the paddle  128 , the return spring  148  is allowed to return to its rest or idle position ( FIGS. 32, 38 ). 
     Referring now to  FIGS. 33-35 and 37 , a feature of the above-described throttle control  28  is that the user can actuate the paddle  128  with either or both thumbs, providing a more ergonomic relationship than seen in conventional trimmers of this type. 
     While a particular embodiment of the present wheeled string trimmer has been described herein, it will be appreciated by those skilled in the art that changes and modifications may be made thereto without departing from the invention in its broader aspects and as set forth in the following claims.