Patent Document

FIELD OF THE INVENTION  
         [0001]    This invention relates to cutting devices primarily used to cut vegetation and more particularly to devices provided with radially projected flexible line referred to as cord or string used as the implement to cut or mow vegetation such as weeds and grass (hereafter such device being referred to as a “string trimmer”).  
         BACKGROUND OF THE INVENTION  
         [0002]    String trimmers have been available and in wide use for many years. It is particularly desirable for trimming along fences, buildings and on grass strips unreachable for the conventional lawnmower. It can also be used to trim borders along sidewalks and driveways and is even desired for cutting small lawns in total. Because the line is flexible, it can impact walls and shrubs with no or minimal damage and is far safer for the user than rigid blades as the cutting implement.  
           [0003]    A common type of string trimmer is one where a housing is mounted to a power tool&#39;s drive line, a spool of line (string or cord) is contained in the housing and a feed mechanism inside the housing is actuated to feed the line from the housing as needed. As the line or string is used up it is necessary for the operator to disassemble the housing, remove the spool and parts associated therewith, wind a new supply of string on the spool and reassemble the components. It is an objective of the present invention to avoid the need for disassembly of the housing to re-supply the trimmer with cutting string.  
           [0004]    Other areas of improvement for the preferred embodiment include the provision of a housing that is less susceptible to penetration from dirt and debris that can cause malfunction or damage, the ability to convert the feed mechanism between automatic and manual feed, and the reduction of vibration. The tool is also adaptable to drive lines regardless of direction of rotation.  
         BRIEF SUMMARY OF THE INVENTION  
         [0005]    One feature of a preferred embodiment of the invention is the provision of a core and not a housing which is connected to the tool&#39;s driveline. The housing is driven by the spool. The core extends down through the spool on which the line is wound and directly drives the spool to reduce the vibration as occurs through indirect or floating connection as typical for prior devices. A two part housing encloses the core and spool but the parting line is closer to the top of the housing and provides minimal opportunity for penetration of debris.  
           [0006]    A spring acts between the housing spool and has alternate positions to urge the spool to the bottom of the housing or to the top of the housing. Either position provides connection between the spool and housing for driving the housing. However, one position allows bump feed of the line from the housing and the other does not. Manual feed is provided for at least the other position.  
           [0007]    The invention and its advantages will be more fully understood with reference to the following detailed description of the preferred embodiment having reference to the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a schematic illustration of an operator operating a string trimmer device as contemplated for the present invention;  
         [0009]    [0009]FIGS. 2A and 2B are section views (offset by 90°) of a string trimmer device representing a preferred embodiment of the invention;  
         [0010]    [0010]FIG. 3 is a horizontal section view of a spool for storing and deploying cutting string as utilized in the device of FIG. 2;  
         [0011]    [0011]FIG. 4 is a section view illustrating the interlock of the spool with the housing;  
         [0012]    [0012]FIG. 5 is a perspective view of the spool of FIG. 3;  
         [0013]    [0013]FIG. 6 is a perspective view of a housing portion in which the spool resides;  
         [0014]    [0014]FIG. 7 is a perspective view of the cover and drive mechanism;  
         [0015]    [0015]FIGS. 8 and 9 are opposing side views of the spool of FIG. 5 and FIG. 10 is a view similar to FIG. 2A but showing an alternate arrangement of parts.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]    Reference is now made to FIG. 1 which schematically represents an operator  10  operating a string trimmer-type cutting device  12 . As typical for such devices, a motor  14  drives a driveline  16  extended from the motor to a trimmer head  18 . A cutting line, cord or string  20  protrudes from the head  18  and is rotated at a high rpm for cutting grass  22 , e.g., as may be located next to a wall  24 . The string  20 , being flexible, will simply bend upon impacting the wall whereas the grass will be severed.  
         [0017]    [0017]FIGS. 2A and 2B illustrate in cross section a trimmer head of a preferred embodiment of the present invention. The driveline  16  rotatably drives a collar  23 . Attached to the collar is a core member  25  which is configured to have a manual turning knob  26 , a bearing portion  28  and a securement head  30 .  
         [0018]    The securement head  30  is cylindrical and has opposing configured slots  32 . A housing  34  includes an upper cover  36  mounted to the bearing portion  28  of the core member  25  and is slideable rotatably and axially on said bearing portion as permitted by knob  26  and shoulders  40 . A spool  42  (see also FIGS. 3 and 5) is mounted to the securement head  30 . The spool includes upper and lower flanges  44 ,  46  and a center or dividing flange  48 , all radiating from a cylinder  50 .  
         [0019]    The spool  42  has a tubular post  52  spanning the center of the cylinder  50  and as will be explained in a later section, is extended along the dividing flange  48  as indicated in FIG. 2B. The post  52  (in assembled relation) extends through the securement head  30  as permitted by the configured slots  32  and accordingly, as the securement head is rotated by driveline  16 , that rotation is transmitted to spool  42  via the post  52 . A bottom portion  54  of the housing  34  is releasably locked to the upper cover  36  via lock elements or latches  76 .  
         [0020]    It will be appreciated from the disclosure at this point that drive line  16  is rigidly connected to the core member  25  and rotatably drives the core member. The core member  25  includes a knob  26 , bearing portion  28  and securement head  30 . Because spool  42  has its post  52  extended through the securement head  30 , the spool  30  is rotatably driven when driveline  16  is rotated. Housing cover  36 , as explained, is confined on the bearing portion  28  between the knob  28  and shoulder  40 . This confinement enables limited axial sliding of the cover  36  and thus the housing  34  relative to the core member  25 . A boss  59  of the bottom portion  54  extends into the securement head  30  to facilitate stabilization of the housing  34 . The housing  34  is selectively rotated relative to the core member  30  as will now be explained.  
         [0021]    Extended between the bottom portion  54  of housing  34  and the bottom of securement head  30  (of core member  25 ) is a coil or compression spring  58  seated on boss  59 . Spring  58  urges the housing  34  downwardly relative to securement head  30  and thus urges the cover  36  toward and against the shoulder  40  of bearing portion  28 . The spool  42  has its upper surface of upper flange  44  positioned relative to shoulder  40  so that the cover  36  is urged into engagement with said upper surface of the spool  42 .  
         [0022]    Reference is now made to FIG. 5 which is a perspective view of the spool  42 . As will be noted, the upper surface of flange  44  is provided with ramp detents  60 . Now refer to FIG. 7 and it will be noted that the bottom or inside surface of cover  36  is provided with ribs  62 . Thus as the spring  58  urges the housing downward the ribs  62  are urged into engagement with the ramps  60  of the spool (see FIG. 4). The ramps  60  are arranged so that under the influence of the driveline  16 , the ribs  62  of cover  36  engage the vertical face  64  of ramp  60  to rotatably drive the cover  36  and thus the housing  34 .  
         [0023]    Operation  
         [0024]    With reference to the figures and particularly FIGS. 2A and 2B, it will be understood that the driveline  16  rotatably drives collar  23  and thus the core member  25  and its various portions and particularly having reference to securement head  30 . Because post  52  of spool  42  extends through securement head  30  (FIG. 2B), the spool  42  is also caused to rotate. Because spring  58  forces the cover  36  into engagement with the upper side of flange  44 , the ribs  62  of the cover  36  engage the vertical faces  64  of ramp  60  (FIG. 4) and thus generates rotation of the housing  34 .  
         [0025]    Wound onto the spool  42  is a trimmer line  66  which has an upper winding  66   a  between the upper flange  44  and divider flange  48 . A grommet or eyelet  68  (FIG. 2B) in the wall of the housing  34  allows the line  66   a  to extend through the housing and extends from the housing for cutting of grass  22  as illustrated in FIG. 1. Lower line  66   b  is wound onto the spool between the lower flange  46  and the divider flange  48 . The end of line  66   b  extends from the housing through opposing eyelet  69 . Thus as explained, the trimmer head is operated to cut grass as long as the desired lengths of line  66   a  and  66   b  are extended from the housing  34 .  
         [0026]    As the line  66   a  and  66   b  as projected through the eyelets  68 ,  69  are worn or broken off, it is necessary to provide for additional lengths to be unwound or fed off of the spool  42 . This can be accomplished in either of two ways as shown in FIGS. 2A and 2B. Automatic feeding of the line can be accomplished by simply bumping the bottom of the housing  34  against the ground. Such bumping produces relative axial movement of the housing and core member  25  as permitted by the tolerance between the knob  26  and shoulder  40  and compression of spring  58 . The ribs  62  on the cover  36  separate from the ramp detents  60  and the friction producing ground engagement of the housing and centrifugal force of the line projected from the spool produces rotative movement of the housing relative to the spool which in turn produces unwinding of the line segments  66   a  and  66   b . As the detents  60  and ribs  62  become disengaged, detents  61  at the bottom of the flange  46  line up with ribs  63  (which are offset from ribs  62 ) and thus allow limited relative rotation before the detents  61  contact ribs  63 . As bumping is but a brief engagement of the housing contacting the ground, the spring  58  effects return axial movement and re-engagement of the ribs  62  and ramp detents  60  following a similar limited relative rotation upon release of ribs  62  from detents  61 . Manual unwinding is accomplished only when the tool is shut down. The operator can unwind the string from the spool by pressing the housing upwardly against the knob  26 , turning the knob  26 , and then pulling on the trimmer lines  66   a  and  66   b.    
         [0027]    Once the line  66  has been completely used up, it is necessary to obtain a new length of line to assemble onto the spool  42 . This is accomplished for the present device (preferred embodiment) with use of the tubular post  52 . With reference to FIGS. 3, 8 and  9 , it will be noted that the post  52  is fully enclosed as it spans the opening of cylinder  50  of the spool. The tube is provided with an open side  72  at the bottom of the post in one direction (see FIG. 9) and an open side  74  at the top of the post in the opposite direction (see FIG. 8). The operator first aligns the tube  52  with the eyelets  68 ,  69  to establish a straight through opening for the string. The string is then threaded through the opening until substantially half of the length of the line is at either side of the housing. The operator then simply turns the knob  26  which is opposite the feed out direction and what is permitted by the ramp detents  60  and the string simply winds onto the spool, one side winding onto the upper portion of the spool and the other to the lower portion of the spool as permitted by the open sides  72 ,  74  of the post  52 . (Note that the spool has been rotated a half turn in FIG. 3.)  
         [0028]    As indicated in the Summary of the Invention, there are occasions where it is preferable that the line is fed out of the eyelets  68 ,  69  only manually. For the preferred embodiment, a conversion to the non-automatic feeding (non-bump feeding) of the line is accomplished by repositioning the spring  58 . The repositioned state is illustrated in FIG. 10. The housing  34  is disassembled by unlatching latches  76  to separate the bottom portion  54  from the cover  36 . The core member  25 , which is screwed into the collar  23 , is unscrewed and thereby separated from the collar  23 . The spring  58  is then placed onto the bearing portion  28  and under the cover  36  as shown in FIG. 10 and the core member  25  is screwed back into engagement with collar  23 . The spool is then assembled back onto the securement head  30  and the bottom portion  54  reattached (latched) to the cover  36 .  
         [0029]    With the bottom portion  54  attached to the cover and the cover urged to its uppermost position, the ribs  63  on the lower portion  54  are in close adjacency to the lower flange  46 . The ribs  63  engage the vertical faces of the ramp detents  61  to prevent turning of the spool relative to the housing in the same manner as FIG. 2. However, now the housing is in the upper position relative to the core member and bumping no longer will release the engagement between the housing and the spool. Yet with the rotation drive stopped, the housing can be manually urged downwardly against the spring  58  to unwind string from the spool. (The movement is permitted as the engagement by the detents  60 ,  61  are transferred between the sets of ribs  62  and  63 .)  
         [0030]    The configured slots  32  are shown as having a T shape which produces nesting of the post  52  in the cross bar of the T to prevent relative axial sliding of spool and core member. This can be accomplished in other ways, e.g., with a straight slot and a locking member, e.g., locking tabs.  
         [0031]    It is submitted that there are a number of unique features in the single embodiment disclosed above and these features may be arranged in a variety of configurations and combinations that will be apparent to those skilled in the art. Accordingly, it is intended that the invention is not limited to any specific configuration or arrangement and instead encompasses the full range of devices as defined by the appended claims.

Technology Category: 1