U.S. patent application number 09/740023 was filed with the patent office on 2001-09-27 for string trimmer head.
Invention is credited to Beafore, John L., Brant, Ronald G..
Application Number | 20010023542 09/740023 |
Document ID | / |
Family ID | 26868242 |
Filed Date | 2001-09-27 |
United States Patent
Application |
20010023542 |
Kind Code |
A1 |
Brant, Ronald G. ; et
al. |
September 27, 2001 |
String trimmer head
Abstract
A string trimmer head is provided for receiving and retaining
separate lengths of string supplied from outside the head. String
lengths passing through openings in the periphery of the head are
held by clamping members provided within the head. The clamping
members are selectively opened by activation of respective slidable
members provided on the upper surface of the head in order to
release short lengths of previously supplied string and/or to
permit the receipt of new string lengths. On release of the
slidable members, the respective clamping members move towards one
another for clamping purposes under the influence of springs.
Inventors: |
Brant, Ronald G.; (Smyrna,
TN) ; Beafore, John L.; (Franklin, TN) |
Correspondence
Address: |
Pillsbury Madison & Sutro LLP
Intellectual Property Group
Ninth Floor, East Tower
1100 New York Avenue , N.W.
Washington
DC
20005-3918
US
|
Family ID: |
26868242 |
Appl. No.: |
09/740023 |
Filed: |
December 20, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60172578 |
Dec 20, 1999 |
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Current U.S.
Class: |
30/347 ;
30/276 |
Current CPC
Class: |
A01D 34/416
20130101 |
Class at
Publication: |
30/347 ;
30/276 |
International
Class: |
A01D 034/416 |
Claims
What is claimed is:
1. A head for a string trimmer of the type which receives lengths
of string introduced from outside the head, comprising: a base
portion; a cover portion removably secured to the base portion to
form a trimmer head body having a central axis of rotation; a
plurality of spaced openings provided in said head body radially of
said central axis for receiving respective lengths of string
introduced within the head body from outside said body; a plurality
of openings on an upper surface of the cover portion, each being
aligned with a respective one of said radially spaced openings; a
plurality of slidable members positioned within respective ones of
the openings in the upper surface of the cover plate, each slidable
member being movable towards and away from the central axis of the
head body; a plurality of springs, each associated with a
respective one of the slidable members to normally urge the
slidable members towards the respective radially spaced openings in
the head body; a plurality of pairs of clamping members mounted
within the head body, each pair underlying a respective slidable
member; a plurality of camming arrangements, each operatively
joining a respective slidable member with its associated pair of
clamping members and being operative to separate its associated
clamping members when the slidable member is moved towards the
central axis of rotation of the head body and to allow the clamping
members to move towards one another when the slidable member moves
towards its respective radially spaced opening in response to force
applied to the slidable member by its associated spring, the
clamping members being configured to engage respective lengths of
string within the head body and to clamp said string with increased
force in response to centrifugal force occurring when the head is
rotated about said central axis of rotation.
2. A head according to claim 1, wherein each of said slidable
members is retained in position and is guided by a pair of spaced
ribs projecting from an underside of the cover portion.
3. A head according to claim 1, wherein said clamping members are
pivotally mounted to the base portion, each clamping member having
a clamping surface which is eccentric to an axis about which the
clamping member is pivotally mounted.
4. A head according to claim 3, wherein said camming arrangement
for each clamping member comprises a roller provided on one of
either the clamping member or the respective slidable member, and a
rib provided on the other of either the clamping member or the
respective slidable member, said rib being disposed at an acute
angle relative to a line from the central axis of rotation to the
respective radially spaced opening whereby when the rib and the
roller engage as the respective slidable member is moved towards
the central axis of rotation, the clamping members separate.
5. A head according to claim 4, wherein each of said slidable
members is retained in position and is guided by a pair of spaced
ribs projecting from an underside of the cover portion.
6. A head according to claim 5, further comprising openings
provided in said base portion substantially underlying the slidable
members for permitting discharge of loose string from within the
head.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an improved head for a
string trimmer of the type which does not use a spooled or coiled
supply of string.
[0003] 2. Prior Art
[0004] String trimmers are well known wherein a spool or coil of
string is retained within the head of the trimmer. Such arrangement
requires that the head be disassembled when a new supply of string
becomes necessary. Additionally, when the string breaks, the head
often must be disassembled in order to correct the problem and to
adjust the string supply for resumption of operation. Such
disassembly of the head is cumbersome and requires a certain amount
of dexterity by the operator of the trimmer.
[0005] To overcome deficiencies of the type just described,
attempts have been made to supply string to a trimmer head from
outside the head.
[0006] An example of such an arrangement is disclosed in U.S. Pat.
No. 5,758,424 wherein a pair of spring-loaded cams are disposed
within the trimmer head at locations adjacent openings in the
sidewall of the head through which string ends may be inserted. The
sidewall includes an inwardly extending deflection at each opening
towards which the respective cams are urged by their springs. As a
result, a string passing through an opening is pressed against a
sidewall deflection by the associated cam to retain the string.
SUMMARY OF THE INVENTION
[0007] The present invention represents an improvement over the
arrangement disclosed in the aforesaid U.S. Pat. No. 5,758,424 by
providing an arrangement wherein the string is more easily inserted
or removed from the trimmer head and is more securely held in
operation position. The arrangement also permits simplified removal
of broken string, is more durable than known arrangements and
minimizes wear on the string during operation.
[0008] More particularly, the improved arrangement employs a pair
of clamping jaws for each strand of string to be held by the
trimmer head. A slidable actuator is associated with each pair of
jaws. Each actuator is easily accessible to the operator to permit
the jaws pairs to be selectively opened and closed. This feature is
particularly useful when worn or broken string is being replaced.
Also, the actuators may be used when inserting a new length of
string into the trimmer head.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The invention will be described in greater detail with
reference to the accompanying drawings wherein:
[0010] FIG. 1 is a perspective view of a trimmer head according to
the invention;
[0011] FIG. 2 is a top plan view of a segment of the base portion
of the trimmer head shown in FIG. 1; and
[0012] FIG. 3 is a partial cut-away view of the base portion of the
trimmer head shown in FIG. 2.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION
[0013] Referring to FIG. 1, a trimmer head 10 comprises a base
portion 12 and a cover portion 14. The base and cover portions are
held together by fasteners 16, such as screws. The mating sidewalls
of the base and cover portions are provided with aligned
semi-circular notches so as to define a plurality of openings 18
providing access to the interior of the head. The openings are
arranged at spaced locations about the periphery of the head. In
the embodiment illustrated, openings 18 are disposed at 90.degree.
spacings about the head. Each opening receives an eyelet or grommet
20 which provides a smooth surface for string passing through the
openings thereby reducing wear on the strings during operation.
[0014] A collar or hub 22 is mounted on the upper surface of the
cover portion 14 to surround and shield a drive arrangement (not
shown) which extends to the trimmer head from a conventional
trimmer motor and handle (also not shown for convenience of
illustration). The base of hub 22 is provided with openings 24 to
permit tools to be inserted within the hub. The upper surface of
cover portion 14 also is provided with openings 26 which are
radially aligned with openings 18 and through which respective
actuator bars 28 project to permit their being accessible to the
operator for the purpose now to be described.
[0015] Referring to FIGS. 2 and 3, the upper surface of the base
portion 12 is formed with a pair of projecting ribs 30 between
which a slidable member 32 is disposed. The actuator bar 28 is
fixed to the upper surface of member 32. Ribs 30 guide member 32 as
it slides on the upper surface of portion 12 towards and away from
the rotational axis of the trimmer head 10. A compression spring 34
is secured to the base portion 12 in contact with the inner end of
member 32 so as to urge the outer end of member 32 into engagement
with the mating sidewalls of the base portion 12 and cover portion
14.
[0016] A pair of mirror-imaged clamping jaws 36 and 38 are
pivotally connected to the base portion 12 at respective axes 40
and 42 equally distanced from a line extending from the center of
opening 18 to the center of the trimmer head. Jaws 36 and 38 are
provided with complementary serrated edges 44 and 46 which face one
another. These edges line along a line curvature which is eccentric
to the respective axes 40 and 42.
[0017] The upper surfaces of the jaws 36 and 38 are provided with
upwardly projecting ribs 48 and 50 having longitudinal axes each of
which is disposed at an acute angle relative to a line from the
center of opening 18 to the center of head 10. A pair of rollers 52
and 54 are joined to the underside of the slidable member 32 and
are positioned to engage projections 48 and 50, respectively.
[0018] The operation of the trimmer head just detailed will now be
described.
[0019] When the actuator bar 28 is displaced by the operator
towards the center of the trimmer head to move member 32 in the
direction indicated by the arrowhead in FIG. 2, rollers 52 and 54
transmit such displacement, via ribs 48 and 50, the rotation of the
jaws 36 and 38 about their respective pivotal axes 40 and 42 to
spread apart the complementary serrated edges 44 and 46 of the
jaws. This permits a length of string 56 to be inserted within the
trimmer head 10 through an eyelet or grommet 20 from outside the
head. When the actuator bar 28 is released, the force of spring 34,
which was compressed when the jaws were separated, causes the
slidable member 32 to move in the opposite direction whereby the
jaws rotate about their respective pivotal axes in the direction
indicated by the arrowheads in FIG. 3 to clamp the string between
the serrated edges 44 and 46. The string thus is easily loaded into
the trimmer head by an operation which requires minimum dexterity
on the part of the operator.
[0020] By the operational steps just described, the string can be
removed from the head or repositioned relative thereto.
[0021] When the trimmer head is rotated during a cutting operation,
its centrifugal force urges the serrated surfaces 44 and 46 towards
one another thereby increasing the gripping force on the string
ensuring that it remains in its desired position. With the
arrangement described, the gripping force on the string is
increased as compared with an arrangement of the type described in
the above-identified U.S. Pat. No. 5,758,424. Additionally, the
stresses experienced during cutting are distributed through the
jaws over a larger area of the base plate thereby making the
trimmer head more durable.
[0022] A further feature of the present invention is the provision
of an opening 60 in the bottom of the base portion 14 (see FIG. 2)
located between the jaws and the inner end of slidable member 32.
In the case where a string breaks, the release of the jaws on the
remaining string segment, by movement of bar 28 followed by inward
displacement of the released segment caused when a new string is
inserted through opening 18, results in such segment dropping from
the trimmer head through opening 60.
[0023] In the description of operation just presented, the actuator
bar is displaced by the operator while loading new string into when
removing broken string segments. It will be understood, however,
that the insertion of a string end through an eyelet or grommet 20
into engagement with jaws 36 and 38 causes the jaws to spread as
the string is further advanced. When such advancement is stopped,
the bias of spring 34 locks the string in position. If a broken
string segment is gripped by the jaws when a new length of string
is inserted into the head, the new string engages and advances the
broken segment so as to release the jaws' clamping force thereby
allowing the broken segment to be discharged from the head through
opening 60 and the new string to be inserted into the head in
replacement of the broken segment.
* * * * *