Patent Publication Number: US-2016227705-A1

Title: String trimmer head

Description:
FIELD 
     The present invention relates to trimmers and, more particularly, to trimmer heads for string trimmers. 
     SUMMARY 
     Generally, trimmers are used to cut grass and weeds, and are often used to edge around trees, near fences and walls, and along landscape borders. Conventional string trimmers include an elongated shaft with a rotating element or gear head near the end of the elongated shaft, and a spool or string head is attached to the gear head. Typically, the string head includes a monofilament line (i.e., trimmer line) that is rotated by the gear head for cutting and trimming along landscaped areas, fences, and walls. 
     In one independent aspect, a trimmer head may generally include a housing rotatable about an axis; a receptacle in the housing to receive a portion of a trimmer line; and a locking member movable in a radial direction relative to the housing between a first position, in which the locking member engages the trimmer line to axially retain the trimmer line relative to the housing, and a second position, in which the trimmer line is movable relative to the receptacle. 
     In another independent aspect, a trimmer head may generally include a housing rotatable about an axis; a receptacle in the housing to receive a portion of the trimmer line; and a flexible locking member bendable in a radial direction relative to the housing between a first position, in which the locking member engages the trimmer line to axially retain the trimmer line relative to the housing, and a second position, in which the trimmer line is movable relative to the receptacle. 
     In yet another independent aspect, a method of assembling a trimmer head is provided. The method may generally include bending a locking member in a radial direction relative to a housing from a first position, in which the locking member at least partially blocks a receptacle, toward a second position, in which a portion of a trimmer line is insertable into the receptacle; inserting the portion of the trimmer line into the receptacle; and moving, with an intrinsic biasing force, the locking member toward the first position to axially retain the trimmer line relative to the housing. 
     Other independent aspects of the invention will become apparent by consideration of the detailed description, claims and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a trimmer, such as a string trimmer, for use with a trimmer head. 
         FIG. 2  is a top perspective view of a trimmer head for use with the trimmer shown in  FIG. 1 . 
         FIG. 3  is a bottom perspective view of the trimmer head shown in  FIG. 2 . 
         FIG. 4  is an exploded view of the trimmer head shown in  FIG. 2 . 
         FIG. 4A  is a top view of a trimmer line with two strings. 
         FIG. 5  is a perspective view of trimmer lines used with the trimmer head shown in  FIG. 2 . 
         FIG. 6  is a cross-sectional view of the trimmer head shown in  FIG. 2 . 
         FIG. 7  is an exploded view of an alternative construction of a trimmer head for use with the trimmer shown in  FIG. 1 . 
         FIG. 8  is a cross-sectional view of the trimmer head shown in  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION 
     Before any independent embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other independent embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
       FIGS. 2-6  illustrate a trimmer head  10  for use on an exemplary string trimmer T shown in  FIG. 1 . The trimmer T generally includes a shaft S with a handle H toward one end and a motor housing M enclosing an electric motor (not shown) with a motor-driven output or drive shaft (not shown) for connection to a trimmer head on the other end. Various powered trimmers (e.g., battery-powered, gas-powered, etc.) may be used with the trimmer head  10 . 
     As illustrated in  FIG. 1 , the trimmer head  10  includes a housing  14  to at least partially enclose and locking member(s)  16  to selectively retain one or more replaceable trimmer lines  18  for cutting vegetation during operation of the trimmer T. The housing  14  defines at least one opening or slot  22  through which the trimmer line(s)  18  may pass. In the illustrated construction, an entrance passage  24  communicates into each slot  22 . 
     The illustrated trimmer lines  18  include a hub  26  having a protrusion  28  (see  FIG. 5 ) and defining one or more holes  30  to hold cutting string(s)  32 . As shown in  FIGS. 4-5 , the trimmer line(s)  18  used with the trimmer head  10  may include a single cutting string  32 , multiple (e.g., two) cutting strings  32 , a single folded string with opposite ends providing two cutting strings  32 , etc. 
     In other constructions, the cutting string(s)  32  may be molded into the hub  26 . For example (see  FIG. 4A ), for a “two string” trimmer line  18 , a single string may be folded in half, and the hub  26  would be molded around the base of the folded string, with the leg of each half projecting from the hub  26  and providing a string  32 . 
     The cutting string(s)  32  are illustrated with a round cross-section. It should be understood that, in other constructions (not shown), the cutting string(s)  32  may have a different cross-sectional shape (e.g., square, flat, star, etc.). In addition, the outer surface of the cutting string(s)  32  is illustrated as smooth. In other constructions (not shown), the outer surface may be non-smooth (e.g., have teeth, serrations, etc.). 
     The cutting string(s)  32  may be positioned in the slot  22  through the entrance passage  24 . The entrance passage  24  is positioned to be offset from and not aligned with the cutting string(s)  32  during operation to inhibit the string(s)  32  from accidentally exiting the slot  22 . If the cutting string(s)  32  contact an obstruction while cutting, the trimmer lines  18  can rotate to, for example, prevent damage to the trimmer head  10 , the trimmer lines  18 , etc. Each slot  22  allows the cutting string(s)  32  to freely move as the hub  26  pivots relative to the trimmer head  10 . 
     It should be understood that, in some constructions (not shown), an entrance passage  24  may not be provided. In such constructions, each cutting string  32  is inserted through the associated slot  22 . 
     The trimmer head  10  may also include a cap member (not shown) to, for example, limit entry of debris into the trimmer head  10 , avoid an undesirable build-up of vegetative debris within the trimmer head  10 , etc. Mating features (not shown) may be provided for removably coupling the cap member to the housing  14 . For example, a housing mating feature may be associated with a circumferential rim  34  of the housing  14 , and a cover mating feature may be on a complementary portion of the cap member. 
     A cylindrical projection  38  is located at the center of the trimmer head  10  for connection with the drive shaft of the trimmer T. The projection  38  defines an aperture  42  with an attachment feature  46  corresponding to the size and shape of the drive shaft. The drive shaft is connected to the trimmer head  10  via the attachment feature  46  to cause rotation of the trimmer head  10  about an axis A during operation. 
     The housing  14  includes a curved outer wall  50  ( FIG. 2 ) ending at the circumferential rim  34 . The outer wall  50  at least partially defines an inner volume within which the internal end portion of the trimmer line(s)  18  is held. A plurality of support ribs  52  extend from the outer wall  50  to the projection  38  to, for example, provide extra structural support. 
     With reference to  FIG. 3-5 , one or more receptacles  54  are provided in the housing  14 , each defining an aperture  58  to hold the associated trimmer line  18 . In the illustrated construction, each receptacle  54  receives a protrusion  28  of the associated trimmer line  18  and allows pivotal movement of the trimmer lines  18  with respect to the trimmer head  10 . The protrusion  28  may have a different length depending on the desired engagement with the receptacle  54 . The receptacle  54  is sized appropriately to receive the protrusion  28 . 
     Each locking member  16  is selectively engageable with an associated trimmer line  18  to prevent or limit movement of the trimmer line  18  relative to the housing  14 . The illustrated locking members  16  are movable relative to the housing  14  at least partially in a radial direction, toward and/or away from the axis A. In the illustrated constructions, each locking member  16  includes a flexible “finger”  62  bendable toward and/or away from the axis A. In other constructions (not shown), the locking member  16  may include another structure that is movable at least partially in a radial direction (e.g., an at least partially radially-slidable locking member). 
     Each finger  62  is movable between an engaged position (shown in solid lines in  FIG. 5 ), in which the finger  62  engages the trimmer line  18  to inhibit removal of the trimmer line  18  from the trimmer head  10 , and a disengaged position (shown in phantom lines in  FIG. 5 ), in which the finger  62  is disengaged from and allows removal of the trimmer line  18  from the trimmer head  10 . In the illustrated construction, each finger  62  is movable radially outwardly toward the engaged position to prevent axial movement of the trimmer lines  18  and radially inwardly toward the disengaged position to allow axial movement (i.e., entry or removal) of the trimmer lines  18 . In the illustrated construction, rotation of the trimmer head  10  and centrifugal force caused by such rotation thus cooperates to maintain the locking member(s)  16  in the engaged position. 
     As illustrated, each locking member  16  is biased toward the engaged position. In the illustrated construction, the biasing force results from the intrinsic force of the flexible finger(s)  62  tending to move the finger  62  radially outwardly and toward the engaged position. Alternatively or additionally, other forces (e.g., gravity) may bias/contribute to biasing the finger(s)  62 . In such constructions, each locking member  16  is moved radially inwardly (in the direction of the arrow in  FIG. 5 ) toward the disengaged position. In this construction, each locking member  16  is “closed” when the trimmer T is in use or not in use and is “opened” by the user. 
     In the construction shown in  FIGS. 2-6 , each finger  62  prevents or limits axial movement of the trimmer line  18  relative to the housing  14  (e.g., the protrusions  28  from dislodging from the receptacles  54  in an axial direction) while allowing some pivoting movement of the trimmer line  18  relative to the housing  14 . As illustrated, each finger  62  has an engagement surface  66  that, in the engaged position, contacts a surface (e.g., a top surface) of the associated hub  26  to limit axial movement of the hub  26  and, thereby, of the trimmer line  18 . Each finger  62  bends radially inwardly toward the disengaged position so that the protrusion  28  of the trimmer line  18  may be inserted into or removed from the receptacle  54  ( FIG. 5 ). 
     Each finger  62  also includes an actuation surface engageable to move the finger  62  toward the disengaged position. In the illustrated construction, the actuation surface includes a sloped surface  70  engageable by the hub  26  of the trimmer line  18  during insertion to “automatically” cause the finger  62  to bend toward the disengaged position to uncover and allow insertion of the trimmer lines  18  into the receptacles  54 . The illustrated surface  70  is curved to better conform to the illustrated cylindrical hub  26  and/or to be more comfortable for engagement by a user&#39;s finger. 
     In an alternative construction, each locking member  16  may be biased (e.g., by an intrinsic force, gravity, etc.) toward the disengaged position (in the direction of the arrow in  FIG. 5 ) so that the associated receptacle  54  is uncovered when the trimmer T is not in use (e.g., when the trimmer head  10  is not being rotated). In such a construction, the user can simply insert the hub  26  of the trimmer line  18  without manipulating the locking member  16 . Rotation of the trimmer head  10  and centrifugal force caused by such rotation moves the locking member(s)  16  toward and maintains the locking member(s)  16  in the engaged position during use of the trimmer T. In this construction, each locking member  16  is “open” when the trimmer T is not in use and “closed” only when the trimmer T is in use. 
     In other constructions (not shown), a separate biasing member (e.g., a spring) may be used, alternatively or additionally, to apply a biasing force. For example, such a biasing member may be used with a locking member which does not have an intrinsic biasing force (e.g., a sliding locking member). 
     The components of the trimmer head  10  (i.e., the outer wall  50 , the projection  38 , the ribs  52 , the finger(s)  62 , etc.) may be formed as a single unit using, for example, an injection molding process. Alternatively, components of the trimmer head  10  may be separate pieces that are coupled (e.g., screwed, adhered, welded, etc.) together to form the trimmer head  10 . 
       FIGS. 7-8  illustrate an alternative construction of a trimmer head  10   a  for use with a powered trimmer, such as the trimmer T. Common elements have the same reference character with the letter “a”. The description of the common elements, components and features is similar to the corresponding above description, except as contradicted below. 
     In the illustrated construction, the trimmer lines  18   a  are not pivotable relative to the housing  18   a . The hubs  26   a  of the trimmer lines  18   a  and/or the receptacles  54   a  are constructed to limit such pivoting movement. In the illustrated construction, each hub  26   a  is non-cylindrical, and the receptacle  54   a  has a complementary non-cylindrical shape. In other constructions (not shown), the hub  26   a  may be provided with a protrusion that is non-cylindrical so that the hub  26   a  remains non-pivotally coupled to the trimmer head  10   a.    
     In this alternative construction, the trimmer lines  18   a  will not pivot with respect to the trimmer head  10   a  upon impact with an obstruction while cutting vegetation. The illustrated “fixed” connection shown in  FIGS. 7-8  may be more secure than the pivoting connection shown in  FIGS. 2-5 . However, the trimmer lines  18   a  may be subject to greater force during cutting and/or when impacting obstacles and, as a result, may break more easily. 
     In operation of the trimmer heads  10 ,  10   a , a user may insert the trimmer line  18 ,  18   a  into the corresponding receptacle  54 ,  54   a  by pressing inwardly on the finger  62 ,  62   a  (either with the hub  26 ,  26   a  or with a finger). The user may then operate the trimmer T using the cutting string(s)  32 ,  32   a  of the trimmer line  18 ,  18   a  to cut vegetation. The user may then remove the trimmer line  18 ,  18   a  by again pressing inwardly on the finger  62 ,  62   a  and pulling the hub  26 ,  26   a  out of the receptacle  54 ,  54   a  in the axial direction. 
     For non-round cutting strings  32  (e.g., square, flat, star-shaped, toothed, serrated, etc.), proper orientation of the cutting string  32  relative to the trimmer head  10  and the direction of cutting may be important (e.g., cutting teeth on leading edge rather than on trailing edge, etc.). To ensure proper orientation, the trimmer line  18  and/or the housing  14  may be constructed so that the trimmer line  18  is received by the housing  14  in only the proper orientation(s). For example, in the construction of  FIGS. 1-6 , orienting structure is provided by the protrusion  28  on the hub  26  and the cooperating aperture  58  in the associated receptacle  54 . 
     In the construction of  FIG. 7-8 , the hub  26   a  and/or the receptacle  54   a  are shaped (e.g., tapered) so that the hub  26   a  is received in the receptacle  54   a  in only the illustrated proper orientation of the cutting string  32   a . Insertion of the hub  26   a  in a different orientation (e.g., inverted, pivoted about its axis 90°, etc.) is inhibited by the shape of the hub  26   a /receptacle  54   a.    
     It should be understood that, in other constructions (not shown), other structure (e.g., inter-engageable projection and groove, blocking structure, other non-uniform outer shape, marking or other indication (“This side up”, “This side visible”, “Proper”, etc.) may be provided additionally or alternatively to ensure proper orientation of the cutting string(s)  32 . 
     One or more independent features and independent advantages of the invention may be set forth in the following claims: