Note: Descriptions are shown in the official language in which they were submitted.
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TRIMMER HEAD FOR USE IN FLEXIBLE LINE ROTARY TRIMMERS HAVING
IMPROVED LINE LOADING MECHANISM
This is a divisional application of Canadian Patent Application
No.2,578,406 filed on September 1, 2005.
BACKGROUND OF THE INVENTION
The present invention relates to an improved trimmer head for use in flexible
line
rotary trimming devices used to trim grass, weeds and other vegetation. More
particularly,
the invention is directed to an improvement in the line loading of both "bump-
feed" type
trimmer heads such as those disclosed in U.S. Patent Nos. 4,458,419 and
4,959,904 and
the more simple manually operated heads such as that disclosed in U.S. Patent
No.
4,145,809.
Trimmer heads used in flexible line rotary trimmers generally carry one or two
lengths of flexible nylon cutting line wrapped about an interior spool with
the ends of the
line or lines projecting outwardly through opposed. apertures in the side wall
of the
trimmer head. The head is threadably mounted on the end of an elongated shaft
and
rotated at a high velocity by a-gas or electric motor so that the ends of the
cutting line
project radially from the head and sever weeds or other vegetation. When
cutting line
projecting from the head breaks off or becomes overly worn, it must.be severed
and fresh
line extended from the spool through the line outlet eyelets in the side of
the housing.
Bump-feed type heads include a line feed-out mechanism which responds to a
bump on
the ground intentionally applied by the operator to feed out a measured length
of fresh
cutting line which is typically cut to the desired length by a knife blade
projecting from a
shield attached to the trimmer above the cutting head and spaced a
predetermined distance
from the perimeter of the trimmer head housing. Manual heads do not include
any such
line feed-out mechanism. A fastening nut that holds the housing portion of the
trimmer
head to the spool must be loosened so that the spool can be separated from'the
housing and
manually rotated relative to the housing to pay out additional cutting line.
The spool and
housing are then re-secured by the fastening member.
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In both bump-feed and manual heads, the length or lengths of cutting line are
typically wound onto the spool by hand. As most cutting heads employ two
lengths of line
projecting from opposed sides of the cutting head, care must be taken during
the winding
of the spool to avoid crossing or otherwise tangling of the two lines within
the spool which
interferes with the paying out of fresh line. This is particularly important
in bump-feed
heads where centrifugal force is utilized to pull the new lengths of line from
the spool
during use as the head is being bumped against the ground as any line tangle
will interfere
with the proper feeding of the line. Difficulty in properly loading the line
on the spool is
the most common complaint of home users, of flexible line trimmers. It also is
a time
consuming task for the professional user.
The early bump-feed mechanisms typically consisted of a dog or friction clutch
located between the spool of line and the surrounding housing. By bumping an
extension
of the spool on the ground, or other fixed object, the friction clutch was
temporarily
disengaged for a length of time dependant on the duration of the bump. The dog
clutch
released by the bump then abruptly engaged at the next opportunity to feed out
line in
segment lengths which were related to the engagement points of the dog clutch.
Such dog
clutches had outwardly extending ribs which engaged inwardly extending
abutment tangs
and therefore depended upon a skillful bump when it was desired to deliver
only one
segment length. However, friction within such devices and overzealous bumping
often
resulted in two or more line segments being fed out, particularly especially
when the
device has been in use and the comers on the ribs and tangs became worn such
that
positive engagement was no longer assured. The unavoidable abrupt operation of
the dog
clutch caused such wear to occur.
A bump-feed-out mechanism was subsequently developed that automatically fed
out a predetermined length of line with each bump, regardless of the duration
of the bump,
and which did not lose this ability with extended use. That device is
disclosed in
U.S. Patent No. 4,458,419. As described therein
in detail, the improved trimmer head contained a spool holding one or more
coils of
cutting line and a simplified mechanism that selectively allowed relative
movement of the
spool with respect to the housing in response to bumping of the head on the
ground to pay
out measured lengths of line. The simplified pay-out mechanism included a
novel spring-
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loaded cam and cam follower arrangement in which the cam follower included two
pair of
diametrically opposed. and generally inwardly facing abutment surfaces arrayed
about the
__axis_of rotation-of the_trimmer_housing- The_abutment.surfaces_were thus
spaced 90 apart
and were carried by a depending cylindrical wall that circumscribed an
interior chamber.
The cam member was disposed within the chamber in threaded engagement with the
extended lower end of the drive bolt of the trimmer housing and defined two
vertically
adjacent cams, each cam being of a square configuration and defining four
perpendicularly
disposed cam surfaces adapted to engage the abutment surfaces on the cam
follower. The
upper cam was rotationally offset 45 from the lower cam.
In operation, the housing was rotationally driven by the drive bolt through a
connection between the upper end of the bolt and the trimmer drive means. The
housing
and cam member was thus driven by the drive bolt, which in turn drove the cam
follower
and the spool mounted thereon due to the engagement between the cam surfaces
on the
cam member and the abutment surfaces on the cam follower. The line carrying
spool was
disposed about the cylindrical wall of the cam follower and attached thereto
via a pair of
opposed outwardly projecting studs on the cam follower member that extend into
slots
formed in the inner portion of the spool. The spool was provided with a bumper
at its
lower end such that when the bumper was pressed against or bumped on the
ground, the
housing moved downwardly with respect to the spool against the force of a
spring,
disengaged the lower cam from the abutment surfaces on the cam follower and
allowed
the cam member to rotate 45 relative to the cam follower, whereupon the cam
surfaces of
the upper cam would abut the abutment surfaces on the cam follower. That
imparted a
similar degree of relative rotation between the spool and the housing. Once
the force of
the bump was dissipated, the spring loading forced the spool and housing back
to their
relative positions, which released the cam surfaces on the upper cam from the
cam
follower abutment surfaces and allowed another 45 of relative rotation of the
cam
member and cam follower and thus of the spool and housing, for a'total of 90
of rotation
per bump, which provided the predetermined relative rotation between the
housing and
spool needed to pay out a desired length of line through the apertures in the
trimmer
housing. Since the cams interacted with simple, inwardly facing cam follower
surfaces
formed only on a single level, the release mechanism was deemed relatively
economical to
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manufacture and, due to the large abutment surface areas presented between the
cams and
cam follower, the device was durable, trouble free and reliable.
-Because-0f-earl-y--difficulliES-in -moldingsome-of-the--components-of-the--
cutting
head disclosed in Patent No. 4,458,419, the head became more expensive to
manufacture
than anticipated. New material developments subsequently reduced the cost of
manufacture. In the meantime, however, a similar bump-feed drive mechanism was
developed in which large square cams were formed on the upper and lower outer
radial
surfaces of the spool and the corresponding cam followers were formed by upper
and
lower portions of the housing which surrounded the spool. Such a head is
disclosed in
U.S. Patent No. 4,959,904, and is still in production.
Over the years, with increasing competition from offshore manufacturers, it
became clear that even with the development of new materials the earlier bump-
feed
mechanism covered by Patent No. 4,459,419 was not as economical to manufacture
as
earlier believed. It contained several parts, some of which had to be hand
assembled. In
addition, vibration, the threaded engagement between the cam member and the
drive bolt,
and the heat generated by the trimmer required the use of a chemical bonding
agent having
a high melting point to prevent the cam member and cam follower from breaking
loose
from the drive bolt. Such agents, however, had extremely high break way
torques,
rendering the threaded connection effectively permanent. As a result, certain
components
of the head could not be replaced when worn. Thus, that head was significantly
modified
so as to retain all of the advantages of its predecessor yet utilize fewer
component parts
and obviate the need for any hand assembly and use of chemical bonding. That
modification is the subject of a U.S. patent application entitled "Trimmer
Head
for Use in Flexible Line Rotary i"rimmers", filed October 2, 2003 and
identified by
Publication Number 2005/0072007. The bump-feed and
manual heads of the present invention retain all of the advantages of the
above-described
heads and adds thereto the ability to far more quickly and easily uniformly
wind lengths of
cutting line onto the spool without materially increasing the cost of
production-
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SUMMARY OF THE INVENTION
Briefly, the present invention comprises an improved bump-feed-type rotary
trimrrier head_includ ng a housing defining a depending axially-disposed-
tubular extension :
adapted to receive the drive bolt therein and shaped so as to define a first
interference fit
5 with the drive bolt and a second interference fit with a cam member such
that rotation of
the drive bolt effects corresponding rotation of the housing and cam member.
The cam
member defines a pair of vertically adjacent cams, preferably square in cross-
section with
each cam defining four perpendicularly disposed cam surfaces, the upper of
said cams
being rotationally offset 45 with respect to the lower of the two cams. A
generally
cylindrical cam follower defining two pair of diametrically opposed and
inwardly facing
abutment members arrayed about the central axis of the housing channel is
disposed about
the cam member. The abutment members are spaced 90 apart in a common
horizontal
plane and are carried by a cylindrical wall of the cam follower that extends
about the cam
follower. Each of the abutment members defines angularly disposed leading and
trailing
surfaces, the trailing surfaces defining cam abutment surfaces. A coil spring
urges the
cam follower downwardly against the cam member and a slidably disposed
fastener
engages the extended lower end of the drive bolt adjacent the lower end of the
cam
member such that the cam member is vertically moveable against the force of
the coil
spring relative to the cam follower between a first drive position in which
the leading cam
surfaces on the lower cam are in planar alignment with the trailing cam
abutment surfaces
on the cam follower and a second drive position in which the leading cam
surfaces on the
upper cam are in planar alignment with the trailing cam abutment surfaces of
the cam
follower.
In operation, the drive motor on the trimmer rotates the trimmer housing and
cam
member in a first direction that is imparted to the cam follower as a result
of the abutment
of the cam surfaces on the lower cam with the trailing cam abutment surfaces
on the cam
follower. Corresponding rotation of the spool is effected by the projection of
the
engagement lugs on the cam follower in the slots in the inner spool wall. Upon
the cutting
head being bumped upon the ground, a 45 rotation of the cam relative to the
cam follower
is effected and a subsequent 45 rotation occurs upon the head being released
from the
ground so as to effect a relative rotation of 90 between the spool and the
housing and the
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paying out of predetermined lengths of fresh cutting line with each bump of
the head upon
the ground, regardless of the duration of the bump.
To facilitate loading the head with cutting line, the spool is provided with
line
receptor channels, that are preferably tapered and polygonal in cross-section,
that project
into an upper spool flange in a generally radial direction and are adapted to
be radially
aligned with the outlet eyelets in the housing wall by rotating the spool
relative to the
housing. Upon inserting the end portion of a length of cutting line through
each of the
eyelets and pushing the line firmly into the aligned receptor channels, the
line will be
securely held in place by the channel walls when pulled at an acute angle back
toward the
spool. Thus, by holding the housing stationary and rotating the spool in the
same direction
as the spool rotates in the drive mode, the secured lengths of line will be
wrapped about
the rotating spool, obviating the need to separate the spool from the housing
for line
loading purposes.
To provide an even distribution of the lengths of cutting line about the spool
and
prevent tangling within the spool, the trailing surfaces on the lower cam that
are adjacent
and perpendicular to the cam surfaces thereon and the leading surfaces on the
abutment
members on the cam follower are oppositely inclined such that rotation of the
spool in the
drive direction while holding the housing stationary will cause the inclined
leading
surfaces on the abutment members on the cam follower to periodically abut and
slide
upwardly along and over the trailing surfaces on the lower cam, compressing
the coil
spring. Once the cam surfaces clear the cam abutment members, the coil spring
will force
the cam follower downwardly, realigning the cam abutment surfaces with the
lower cam.
As a result, continual manual rotation of the spool relative to the housing
will wrap the
lines about the spool while providing a vertical reciprocating or ratcheting
effect of the
spool with respect to the housing as the line is wrapped thereon so that the
line is
uniformly disposed about the spool. Printed indicia are preferably molded into
the upper
surface of the spool to allow the user to easily orient the spool relative. to
the housing such
that the receptor channels are radially aligned with the exit apertures in the
housing
enabling the line to be readily inserted through the eyelets and into the
receptor channels
to load the line about the spool.
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The line receptor channels and spool ratcheting mechanism of the present
invention that facilitate line loading can also be utilized in other bump and
feed head
configurations and in manual heads. In each case, the line receptors are
provided on the
spool flange radially alignable with the outlet eyelets in the housing. In a
bump-feed head
such as that disclosed in U.S. Patent No. 4,959,904 at least the trailing
surfaces on the
lower cam follower that is defined by lower outer radial surfaces of the spool
is inclined
such that rotation of the spool in the drive direction while maintaining the
housing in a
stationary disposition will cause the spool to periodically ratchet upwardly
and
downwardly within the housing as the line is drawn inwardly through the
eyelets and
wrapped about the spool to effect an even distribution of the lengths of line
about the
spool within the housing. The leading radial surfaces of the lower cam
follower and the
trailing surfaces of the cams formed by the upper and lower portions of the
housing may
also be inclined to provide a smoother ratcheting movement for the head during
the
winding of the line onto the spool.
In a manual feed head such as that disclosed in U.S. Patent No. 4,145,809, a
plurality of pins or drive lugs are disposed about and project upwardly from
the upper
surface of the spool and project into correspondingly sized and spaced
apertures in the
upper surface of the housing such that rotation of the housing will effect
corresponding
rotation of the spool. By providing radially alignable line receptors in the
spool flange and
ramping the interior upper surface of the housing between each of the
apertures therein,
the line ends can be inserted through eyelets into the receptor channels and
gripped by the
spool so that rotation of the spool relative to the housing as above described
will cause the
lugs on the spool to repeatedly travel downwardly along adjacent ramps and
snap
upwardly into the next aperture. Continued relative rotation will thus effect
the desired
reciprocating motion of the spool within the housing to evenly distribute the
cutting line
about the spool.
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In one aspect, the invention provides a trimmer head for use with at
least one length of flexible cutting line in a flexible line rotary trimmer,
said head
comprising: a housing adapted to be operatively connected to a rotary trimmer
to
effect rotation of said head, said housing defining a cylindrical depending
skirt
having at least one line outlet opening therein; a spool operatively connected
to
said housing for rotation therewith in a first direction about a common axis
in a
drive mode and for rotation with respect to said housing in said first
direction in a
line winding mode, said spool including a cylindrical body portion and at
least one
flange projecting radially therefrom so as to define a cutting line storage
area
about said body portion adjacent to said flange; and at least one line
receptor
formed in said flange, said receptor including an inwardly extending walled
channel, said channel defining at least one line engaging surface extending
along
and about said channel and an outer end alignable with said line outlet
opening in
said skirt upon relative rotation of said spool and said housing such that
upon
inserting an end portion of a length of flexible cutting line through said
opening in
said housing and into said channel and rotating said spool with respect to
said
housing in said first direction, said end portion of said line is pulled
against said
line engaging surface and tightly gripped within said channel by said surface
whereby the length of line is pulled inwardly through said line outlet opening
in the
housing skirt toward said body portion of said spool and is wound about said
body
portion as said spool is rotated with respect to said housing.
In another aspect, the invention provides a trimmer head for use with
at least one length of flexible cutting line in a flexible line rotary
trimmer, said head
comprising: a housing adapted to be operatively connected to a rotary trimmer
to
effect rotation of said head, said housing defining an outer wall portion
having at
least one line outlet opening therein; a spool operatively connected to said
housing for rotation therewith about a common axis in a drive mode and for
rotation with respect to said housing in a line winding mode, said spool
including a
cylindrical body portion and at least one flange projecting radially therefrom
so as
to define a cutting line storage area about said body portion adjacent to said
flange; and at least one line receptor formed in said flange, said receptor
including
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an inwardly extending channel and defining a roughened surface extending about
and along said channel, said channel defining an outer end alignable with said
outlet opening in said housing upon relative rotation of said spool and said
housing and wherein said roughened surface grips a length of cutting line upon
an
end portion of the line being inserted into said channel through said line
outline
opening and a portion of the line extending from said channel being directed
toward said body portion of said spool as said spool is rotated with respect
to said
housing.
In another aspect, the invention provides a trimmer head for use with
at least one length of a flexible cutting line in a flexible line rotary
trimmer, said
head comprising: a housing adapted to be operatively connected to a rotary
trimmer to effect rotation of said head, said housing defining a cylindrical
depending skirt having at least one line outlet opening therein; a spool
operatively
connected to said housing for rotation therewith about a common axis in a
drive
mode and for rotation with respect to said housing in a line winding mode,
said
spool including a cylindrical body portion and at least one flange projecting
radially
therefrom so as to define a cutting line storage area about said body portion
adjacent said flange; and at least one line receptor formed in said flange,
said
receptor including an inwardly extending walled channel, said channel defining
an
outer end alignable with said outlet opening in said skirt upon relative
rotation of
said spool and said housing, at least an outer portion of said channel
defining at
least one line engaging surface and wherein said channel is oriented with
respect
to a line tangent to said flange at said outer end of said channel so as to
cause the
length of the flexible cutting line extending therethrough to define an acute
angle
and bear against said line engaging surface for gripping the line upon an end
portion of the line being inserted into said channel through said line outlet
opening
and a portion of the line extending from said channel being directed toward
said
body portion of said spool as said spool is rotated with respect to said
housing.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of a first embodiment of the trimmer
head of the present invention shown secured to the drive bolt of a rotary
trimmer.
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Figure 2 is an exploded perspective view of the various elements
comprising the embodiment of the trimmer head of the present invention
illustrated in
Figure 1.
Figure 3 is a cross-sectional view of the trimmer head housing of the
present invention taken along line 3-3 in Figure 2.
Figure 4A is a top view of the cam member of the present invention.
Figure 4B is a side view of the cam member of the present invention.
Figure 5A is a top view of the cam follower member of the present
invention.
Figure 5B is a side view of the cam follower member of the present
invention.
Figure 5C is a cross-sectional view taken along the line 5C-5C in
Figure 5A.
Figure 6 is a top view showing the relative positioning of the cam
member and cam follower in their normal operating position.
Figure 6A is a cross-sectional view taken along the line 6A-6A in
Figure 6.
Figure 7 is a top view showing the relative positioning of the cam
member and cam follower in the line feeding position.
Figure 8 is a top view showing the relative positioning of the cam
member and cam follower in the line wrapping position.
Figure 8A is a cross-sectional view taken along the line 8A-8A in
Figure 8.
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Figure 8B is a sectional view illustrating the movement of one of the
cam abutment members on the cam follower upwardly along and over one of the
trailing surfaces of the lower cam during the winding of line onto the spool.
Figure 9 is a sectional view of the embodiment of the trimmer head of
the present invention illustrated in Figures 1-8B.
Figure 10 is a perspective view of the spool used in the embodiment of
the trimmer head of the present invention illustrated in Figures 1-9 with a
portion of
the spool broken away to illustrate the configuration of one of the line
receptor
channels therein.
Figure 11A is an enlarged cross-sectional view taken along the line 11A
in Figure 10.
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Figure 11B is an enlarged partial side view showing the guide surface adjacent
the
outlet ends of the line receptor channels.
Figure I 1C is a further enlarged partial side view showing the line receptor
channel
configuration illustrated in Figure 11B in a preferred angular orientation
relative to the line
guide wall surface adjacent the outlet end of the receptor channel.
Figure 11D is an enlarged partial side view showing the preferred angular
orientation of a line receptor channel having a diamond-shaped cross-sectional
configuration relative to the guide wall surface adjacent the outlet end of
the receptor
channel.
Figure 11E is an enlarged partial side view showing the preferred angular
orientation of a line receptor channel having a triangularly-shaped cross-
sectional
configuration relative to the guide wall surface adjacent the outlet end of
the receptor
channel.
Figure 11F is an enlarged partial side view showing the preferred angular
orientation of a line receptor channel having a oval-shaped channel wall
configuration
relative to the guide wall surface adjacent the outlet end of the receptor
channel.
Figure 11G is an enlarged partial side view showing the desired orientation of
a
ribbed channel wall configuration relative to the guide surfaces adjacent the
outlet end of
the line receptor channel.
Figure 1 lH is a perspective view of a portion of a length of particularly
configured
cutting line employable in the trimmer head of the present invention.
Figure 111 is a sectional view taken along the line 111-111 of Figure 11H.
Figure 11J is an enlarged partial side view showing the outlet end of a line
receptor
channel and adjacent guide surface adapted for use with the cutting line
illustrated in
Figures 11H and 11I.
Figure 11K is a perspective view of a portion of a length of another example
of a
particularly configured cutting line employable in the trimmer head of the
present
invention.
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Figure 11L is an enlarged partial side view showing the outlet end of a line
receptor channel and adjacent guide surface adapted for use with the cutting
line illustrated
in Figure 11K.
Figure 12 is a sectional exploded view showing a modification of the housing
5 portion of a trimmer head of the present invention and the drive bolt used
with the
modified housing.
Figure 13 is a sectional view of one of the trimmer head eyelets.
Figure 14A is a sectional view of the spool showing the inner end portion of a
length of cutting line being held within one of the line receptors and being
wound about
10 the spool.
Figure 14B is a sectional view of the spool having an inwardly inclined line
receptor channel and showing the inner end portion of a length of cutting line
being held
within one of the line receptors and being wound about the spool.
Figure 14C is a partial sectional view of a spool having a single line guide
wall
surface and showing the inner end portion of a length of cutting line exiting
the adjacent
line receptor channel and being pulled against the guide wall surface.
Figure 15 is a bottom plan view of the spool showing the eyelet alignment
indicia
thereon.
Figure 16 is a bottom plan view of an alternate embodiment of the spool
employing a second opposed pair of line receptors for accommodating different
sized line.
Figure 17 is an enlarged exploded view of portions of an alternate embodiment
of
housing and cam member employable in the present invention.
Figure 18 is an enlarged exploded view of another alternate embodiment of the
housing and drive cam of the present invention similar to that shown in Figure
17 but with
the elements creating the interference fit between the housing and the cam
member being
reversed.
Figure 19 is an enlarged partial exploded view of yet another alternate
embodiment
of the housing and drive cam employable in the present invention.
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Figure 20 is a perspective view of a second embodiment of the trimmer head of
the
present invention as seen from below.
Figure 21 is a perspective view of a second embodiment of the trimmer head of
the
present invention as seen from above.
Figure 22 is an exploded perspective view of the various elements comprising
the
second embodiment of the trimmer head of the present invention illustrated in
Figures 20
and 21.
Figure 23 is a top plan view of the trimmer head housing of the second
embodiment of the present invention.
Figure 24 is bottom plan view of the trimmer head housing of the second
embodiment of the present invention.
Figure 25 is a cross-sectional view taken along the line 25-25 in Figure 24.
Figure 26 is a perspective view of the underside of the housing of the second
embodiment of the present invention showing the interior surface of the upper
wall of the
housing and the ratcheting ramps formed therein.
Figure 27 is a sectional view of the spool of the second embodiment of the
present
invention.
Figure 28 is a top plan view of the spool of the second embodiment of the
present
invention.
Figure 29 is a sectional view of the of the second embodiment of the trimmer
head
of the present invention illustrating the spool and trimmer head housing in
the drive mode.
Figure 30 is a sectional view of the of the second embodiment of the trimmer
head
of the present invention illustrating the spool and trimmer head housing in
the initial line
winding mode.
Figure 31 is a cross-sectional view of the trimmer head spool of the second
embodiment of the present invention taken along line 31-31 of Figure 27 and
showing the
inner end portions of the cutting line being wound about the spool.
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Figure 32 is a perspective view of a third embodiment of the trimmer head of
the
present invention as seen from below.
Figure 33 is a perspective view of a third embodiment of the trimmer head of
the
present invention as seen from above.
Figure 34 is an exploded perspective view as seen from below of the various
elements comprising the third embodiment of the trimmer head of the present
invention
illustrated in Figures 20 and 21.
Figure 35 is an exploded perspective view of the various elements comprising
the
third embodiment of the trimmer head similar to Figure 34 but as viewed from
above.
Figure 36 is a sectional view of the of the third embodiment of the trimmer
head of
the present invention illustrating the spool and trimmer head housing in the
line loading
and bump-feed modes.
Figure 37 is a sectional view of the of the third embodiment of the trimmer
head of
the present invention illustrating the spool and trimmer head housing in the
initial line
loading and drive modes.
Figure 38 is a bottom plan view of the upper portion of the housing of the
third
embodiment of the present invention.
Figure 39 is a cross-sectional view taken along the line 39-39 in Figure 38.
Figure 40 is a top plan view of the lower portion of the housing in the third
embodiment of the present invention-
Figure 41 is a cross-sectional view taken along the line 41-41 in Figure 40.
Figure 42 is a top view of the spool of the present invention showing the
relative
positioning of the lower cam follower with respect to the upper cam follower
with the
lower cam follower and line receptors being shown in dotted lines.
Figure 43 is a cross-sectional view taken along the line 43-43 in Figure 42.
Figure 44 is a bottom plan view of the spool of the third embodiment of the
trimmer head of the present invention showing the relative positioning of the
upper cam
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follower with respect to the lower cam follower with the upper cam follower
and line
receptors being shown in dotted lines.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now in detail to the drawings, a first embodiment of a bump-feed
type
trimmer head 10 of the present invention is shown in Figure I mounted on the
extended
end of a rotatable drive shaft 12 on a gasoline or electric powered rotary
trimmer (not
shown). The trimmer head 10 generally comprises a housing 14, a spool 16 for
carrying
one or more lengths of coiled monofilament nylon cutting line 17, a cam member
18, a
cam follower 20, a coil spring 22, a drive bolt 24 and a retaining nut 25. The
trimmer
housing 14 is preferably formed by injection molding a nylon 6 copolymer and
defines a
circular upper wall 26, a cylindrical depending skirt 28 and a centrally
disposed tubular
extension 30 depending from upper housing surface 26 into the interior of the
housing
about the central axis of rotation "Y" of the head. The tubular extension 30
in the trimmer
head housing 14 defines an annular outer shoulder 32 for coil spring 22 and an
axial
channel 34 through which the drive bolt 24 extends. Channel 34 is configured
to create a
mating fitment with both the drive bolt 24 and cam member 18. The upper end
portion 36
of channel 34 is preferably square in cross-section; the central portion 38 is
of a constant
radius and the lower portion 40 is hexagonal in cross-section.
As seen in Figures 2 and 9, the drive bolt 24 defines a square head portion
24a
which is received within the correspondingly configured upper portion 36 of
channel 34, a
cylindrical body portion 24b that extends through the central cylindrical
portion 38 of
channel 34, and a lower shaft portion 24c that projects from the larger
diameter body
portion 24b and extends through and projects from the lower hexagonal portion
40 of
channel 34. The drive bolt also defines an internally threaded cylindrical
bore 24d
extending axially through the head portion 24a and a substantial part of
central portion 24b
for threaded engagement with the drive shaft 12 of the trimmer. Thus, with the
drive bolt
24 disposed in channel 34 and in threaded engagement with the drive shaft 12,
rotation of
the drive shaft imparts corresponding rotation to the drive bolt 24 and
housing 14 due to
the interference fit between the square head portion 24a of the drive bolt and
the upper
portion 36 of channel 34 defined by housing extension 30.
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It should be noted that the head portion of the drive bolt and the cross-
section of
the upper portion of the axially depending tubular member could be formed of
shapes
other than square to form the desired interference fit. For example, they
could both be
hexagonally shaped and rotation of the drive bolt would still be imparted to
the trimmer
head.
The cam member 18 is preferably molded of nylon 6 glass reinforced material,
is
of single-piece construction and, in the preferred embodiment, defines a
hexagonally-
shaped head portion 42, an upper cam 44, a lower cam 46 and a lower skirt
portion 48.
Head portion 42 is sized and shaped so as to be received within the lower
portion 40 of
channel 34 in extension 30 such that rotation of the housing 14 in a
counterclockwise
direction (as seen from above and indicated by arrow D in Figures 6 and 7)
will impart
corresponding rotation to the cam member 18. In the preferred embodiment, the
head
portion 42 of the cam member 18 and the cross-section of the lower portion 40
of channel
34 are hexagonal. It is to be understood, however, that other non-circular
shapes (e.g.
square) could be used to provide the desired interference fit between the
tubular extension
30 in the housing and the cam member.
In alternative embodiments of the housing and cam member, the head portion 42A
of cam member 18A and the cross-section of the lower portion 40A of the
tubular
extension 30A in the housing 14A is cylindrical and the interference fit
between the
housing and the cam member is provided by means of a plurality of ribs or lugs
45A
projecting vertically from the extended end 47A of the tubular extension 30A
and a
corresponding plurality of receiving slots or apertures 49A formed in upper
surface 51A of
cam 44A as seen in Figure 17. While at least one complimentary pair of ribs
and slots or
lugs and apertures would be required to prevent relative rotational movement
between the
housing and cam member, a greater number is preferable and, from a
manufacturing and
operational standpoint, four equally spaced pairs of ribs and slots or lugs
and apertures
would appear to be ideal. Such a configuration is illustrated in Figure 17. It
is to be
understood that the male element of such an interference fit (e.g., rib or
lug) could be
provided on either the extended end 47A of the tubular housing extension 30A
as shown in
Figure 17 or on the upper surface 51A of the cam 44A. In either case, and the
corresponding female elements (e.g., slot or aperture) would be provided in
the other
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component. Such a reversal of parts is shown in Figure 18. In yet another
alternative
embodiment, the head portion of the cam member could be eliminated altogether
and the
required interference fit provided by the same or similar plurality of ribs or
lugs 45A' and
receiving slots or apertures 47A'. Such a variation is illustrated in Figure
19. Again, the
5 corresponding male and female elements could be reversed.
The upper and lower cams 44 and 46 are preferably each of a square
configuration
so as to define four identical perpendicularly disposed surfaces, 44' and 46'
on each cam.
That portion of each of those surfaces that is adjacent a corner of one of the
cams 44 or 46
on the drive or leading side of the cam, as the cam rotates in a
counterclockwise direction
10 D (as seen from above), defines a cam surface 44a or 46a. Each cam surface
on each cam
is parallel to the axis of rotation Y of the head. The upper cam 44 is
rotationally offset 45
from the lower cam 46 as seen, for example, in Figure 4A. Those portions of
lower cam
surfaces 46' that are perpendicular to and adjacent cam surfaces 46a (and thus
on the
trailing sides of the cam 46 as the cam member 18 rotates counterclockwise)
are inclined
15 upwardly as seen, for example, in Figures 2 and 4B and define slide
surfaces 46b. Slide
surfaces 46b can be formed by an inclined linear surface or a curvilinear
surface. In the
embodiment of the invention illustrated in Figures 1-9, the slide surfaces are
preferably
radiused. By way of example, in a cam member 18 in which the upper and lower
cams 44
and 46 each define surfaces 44' and 46' of about .90 in. in length and the
lower cam 46 has
a thickness of about .20 in. The inclinations on trailing slide surfaces 46b
define a circular
segment having a radius of .125 in. Alternatively, surfaces 46b could be
upwardly
inclined at an angle of about 25 degrees.
Cam member 18 further defines an axially disposed channel 50 extending
vertically therethrough. Channel 50 has a first upper constant radius portion
50a adapted
to receive the first constant radius portion 24b of drive bolt 24 and a second
smaller
diameter constant radius portion 50b adapted to receive in a slip fit the
second and smaller
constant radius portion 24c of drive bolt 24, which extends therethrough.
The cam member 18 is disposed within trimmer head 10 interiorly of the cam
follower 20, the configuration which is best seen in Figures 5A and 5B. To
properly align
the cam member 18 with respect to the line outlet eyelets 78 in the trimmer
head housing,
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a key 42' is molded into the side of the head portion 42 of the cam member
which is
received in a slot 40' in lower portion 40 of the central housing channel 34.
The cam follower 20 is preferably molded of the same material as cam member
18,
is of single-piece construction and defines a cylindrical wall portion 52
circumscribing a
chamber 54 and four equiangularly disposed projections defining abutment
members 56
extending radially inwardly of chamber 54 from the upper interior end portions
of
cylindrical wall 52. Each of the abutment members 56 defines an angularly
disposed cam
abutment surface 56a and an inclined slide surface, 56b. Relief areas 60 are
disposed
between members 56. The abutment surfaces 56a are on. the trailing side of
each abutment
member, extend parallel to the axis of rotation Y of the cutting head and are
angled at 135
with respect to an adjacent slide surface 56b. A plurality of outwardly
projecting radial
lugs 62 (four being shown) are equiangularly disposed about the cylindrical
wall portion
52 of the cam follower 20 for the releasable securement of the spool 16 to the
cam
follower.
The spool 16 defines an upper annular flange 70 and a lower annular flange 72
carried by a hollow cylindrical body portion 74 so as to define an annular
area 76 between
flanges 72 and 74 for carrying coils of flexible nylon cutting line 17 wrapped
about body
portion 74 such that upon assembly, the end portions 17' of the cutting line
extend
outwardly through eyelets 78 which are press fit through opposed apertures 80
in the
sidewall of the head formed by housing skirt 28. In the preferred head
configuration
shown in Figure 1, the portions of the housing skirt 28 adjacent the eyelets
78 are raised or
ramped radially outwardly to protect the eyelets during use from foreign
objects.
The body portion 74 of spool 16 further defines a rounded bumper 81 at its
lower
end, an interior cylindrical chamber 82, a pair of diametrically opposed and
identically
configured vertical locking channels 84 in the interior side wall thereof and
a pair of
diametrically opposed and identically configured vertical guide channels 88
transversely
aligned with respect to locking channels 84. As seen in Figure 10, locking
channels 84
terminate at their lower ends in somewhat shallower offset portions 90 that
terminate in a
pair of opposed securement apertures 92 extending through the cylindrical body
portion
74. The locking and guide channels are each adapted to slidably receive one of
the
outward projecting radial lugs 62 on the cam follower 20. The guide channels
88 differ
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17
from locking channels 84 in that they are wider, of a constant length and do
not terminate
in apertures. The guide channels preferably have a width equal to the width of
the locking
channels plus the length of the offset portions 90 of the locking channels 84.
The spool 16 is secured to the cam follower 20 upon aligning the lugs 62 with
the
locking and guide channels 84 and 88 such that the end portions 17' of the
cutting line 17
project radially from the spool 16 proximate eyelets 78, the spool is pressed
over the cam
follower until the lugs 62 reach the lower ends of the guide and locking
channels. The
spool is then rotated such that the lugs in the two locking channels 84 pass
into the slightly
shallower offset portions 90 thereof, slightly compressing the cam follower
until the two
lugs reach the apertures 92 whereupon the resiliency in the cam follower
material causes
the lugs to snap into apertures 92, securing the spool to the cam follower. In
the locked
position, the two lugs in apertures 92 are disposed adjacent the aperture
walls and the two
lugs in the guide channels 88 are adjacent the leading walls of the channels
such that
during use, all four lugs will abut their adjacent walls to effect
corresponding rotation of
the spool 16 with the cam follower 20. To remove the spool, one need only
twist the spool
relative to the cam follower and when the lugs are pulled back into the
vertical portion of
the locking channels, the spool can be easily axially withdrawn from the
housing.
The above-described lug and channel configuration allows the spool 16 to be
used
with cam followers having either four equally-spaced drive lugs 62 (as shown)
or two
opposed lugs if desired. In addition, the driving force is evenly distributed
among the four
lugs 62 on the cam follower 20. Guide channels 88 are provided in lieu of a
second pair of
locking channels 84 for mold forming purposes only. Otherwise, four identical
locking
channels could be employed. If desired, the two guide channels in the spool
could be
widened so as to each define an arcuate length of about 95 such that the
spool could
accommodate cam follower configurations having six equally-spaced projecting
lugs.
Again, the guide channels would be sized such that two of the lugs in each of
the guide
channels would be adjacent a leading wall of the channel such that during use,
four lugs
will again function as drive lugs to effect rotation of the spool.
To provide rapid loading of the trimmer line about spool 16, the upper spool
flange
70 is provided with a pair of opposed line receptors 91 for gripping inner end
portions 17"
of two separate lengths of cutting line 17. Each of the receptors 91 comprises
a line
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18
receptor channel 93 that extends radially inwardly from an enlarged outer
flared portion
93' adjacent the outer edge of the spool to the spool's cylindrical body
portion 74. The
receptor channels 93 are configured and oriented so as to tightly grip the
cutting line 17
when an end portion of the line is inserted therein, through the aligned
eyelet, and pulled
at an acute angle back toward the spool, as will be described. Examples of
channels 93 are
shown in detail in Figures 11A-G, IN, 11L, 14A and B. A preferred channel
configuration is polygonal in cross section, most preferably hexagonally
shaped, and
tapers inwardly from the enlarged flared portion 93' to body portion 74 at an
angle of
about 5 . The size of the receptor channels depends on the size of the line to
be secured
therein. By tapering the channel walls inwardly at an angle of about 5 , the
channels can
accommodate variations in line size.
By way of example, a tapered channel 93, hexagonal in cross-section and having
a
length (exclusive of flared portion 93') of about .650 in., a transverse
dimension measured
across the two parallel sides adjacent the enlarged flared outlet end of about
.130 in. and a
transverse dimension across the inner channel end of about .075 in. (see,
e.g., Fig. 11A),
has been successfully employed in trimmer head 10. Conventional nylon cutting
line
having diameters of .080 in., .095 in. and .105 in. can be received therein
and tightly
gripped by the receptor channel walls as the line is pulled from the outer end
of the
channel and wrapped about the spool as shown in Figures 14A and 14B.
To properly direct the line inwardly upon exiting the receptor channel, the
downstream or left side of the enlarged flared portion 93' of each receptor 91
is cut away
so as to define flat guide wall surfaces 94a and 94b as shown in Figures 11B
and 13-15.
Surface 94a is substantially perpendicular to the central axis of the receptor
channel and
inclined slightly downwardly such that the central longitudinal axis "X" of
the guide wall
surface defines an angle declination of about 5 -10 , depending on the
configuration of the
spool, with respect to the horizontal. Adjacent surface 94b is inclined
inwardly to direct
the line toward the center of the spool. Thus, when the cutting line is
inserted into one of
the receptor channels 93 and pulled laterally against guide surface 94a and
inwardly
against guide surface 94b, the line effectively forms an acute angle with the
central
channel axis. In addition, the lower inner surface 95 of the flange extending
under channel
93 is rounded so as to avoid any abrupt surface deviations on the spool
adjacent the line
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19
receptors 91 which could interfere with the proper winding of the line and to
direct the line
downwardly toward the lower flange 72. The channel 93 is preferably oriented
about its
central axis such that opposed corners of the channel align with the central
axis X of guide
wall surface 94a as shown in Figure 11C.
By aligning opposed channel corners with the central axis "X" of guide wall
surface 94a, the cutting line is pinched by the converging channel walls as
the line is
pulled from the channel and along the adjacent guide wall surface 94a. Due to
the
inherent stiffness in the nylon cutting line, this pinching of the cutting
line occurs not only
at the channel wall corner 93" adjacent guide surface 94a (see Fig. 11C), but
also at the
opposed corner at the inner end of the line receptor channel, enhancing the
gripping of the
line. While a line receptor channel having a hexagonally configured cross-
section that is
not aligned with the central axis of surface 94a as above described (see,
e.g., Fig. 11B),
will still grip the line, the alignment illustrated in Figure 11C takes better
advantage of the
pinching effect created by the hexagonal cross-sectional configuration of the
channel and
is thus preferred. Further, by inwardly inclining the central axis of the
receptor channel 93
at about 5 toward guide wall 94a, as seen in Figure 14B, as opposed to
radially aligning
the central axis of the channel with the center of the spool as seen in Figure
14A, the
central channel axis forms an acute angle with respect to a line tangent to
the flange at the
outlet end of the channel. As a result, cutting line is caused immediately to
form an acute
angle with respect to the central channel axis as it exits the receptor
channel and is pulled
against the adjacent guide wall surface 94b. This further increases the
pinching effect of
the channel wall on the line, further enhancing the gripping of the cutting
line. The more
securely the receptor channel grips the line, the easier it is for the user to
effect the initial
winding of the line about the spool without the line being inadvertently
pulled from the
receptor channel. However, the acute angle formed adjacent to the outlet ends
of the
receptor channels by inclining the central axis of the channels inwardly as
described, may
be too tight for .105 in. diameter line. Accordingly, in trimmer head designed
to
accommodate such larger line, a radially directed channel may be preferred.
Additional line receptor channel configurations are illustrated in Figures 11D-
G.
Figures 11D and E illustrate other polygonal configurations particularly
suited for use with
the present invention. Figure 11D illustrates a line receptor channel 93a
having a
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diamond-shaped cross-section. To maximize the line pinching effect of such a
channel,
the channel should be oriented such that the opposed comers lying on the minor
axis of the
cross-section lie on the longitudinal axis "X" of the guide wall surface as
shown in the
drawing. Figure 11E illustrates a line receptor channel 93b having a
triangularly-shaped
5 cross-section. To maximize the line pinching effect of such a channel
configuration, one
of the apexes of the triangle defined by the channel at the outlet end thereof
is positioned
on the longitudinal axis of the guide wall surface adjacent the guide wall
surface as shown
in Figure 11E. Other polygonal cross-sectional configurations could also be
employed in
the formation of the line receptor channels 93 of the present invention.
However,-it is.
10 believed that a channel formed by more than about eight side walls would be
sufficiently
round so as to not provide the desired gripping force on the line. Round
radial channels
have been found not to provide adequate grip on the line as have channels
defining a
square cross-sectional configuration when the flat sides of the square lie on
the
longitudinal axis of the guide wall surface. Other channel configurations
could also be
15 employed. For example, as illustrated in Figure 11F, a line receptor
channel 93c having
an oval-configuration wherein the minor axis of the oval lies on the
longitudinal axis of
the guide wall channel surface should provide adequate gripping force for the
line.
Irregularities in channel wall surfaces could also be employed. For example,
Figure IIG
illustrates a line receptor channel configuration in which a plurality,
preferably four,
20 longitudinally extending ribs 93"'are provided in an otherwise round
channel wall to grip
the line. To prevent excessive wear on the ribs and/or line, the ribs are
preferably spaced
such that the line would bear equally against two of the ribs both at the
inner and outer
ends of the channel as seen in Figure 11G. Other such irregularities in the
side wall(s) of
the receptor channel could include roughened surfaces and helically extending
ridges on
channels (not shown).
While the above discussed line receptor channel configurations have been
described and illustrated as extending the full length of the channel, and
indeed such
configurations are preferred, it should be noted that the gripping
characteristics of the
channel, need not extend the length of the channel. Acceptable gripping of the
line may
be obtained by providing the line gripping cross-sectional configuration only
at the outer
end portions of the channels. By way of example, the outer end portion of the
channel
CA 02714878 2010-09-14
21
could be hexagonally or diamond-shaped in cross-section, while the remainder
of the
channel could be round. As the line is pulled laterally from the channel and
against the
adjacent guide surface 94a and then inwardly against surface 94b, the line
would be
retained in the receptor channel by the converging walls in the outer end
portion of the
channel. The outer portion of the channel in such configurations should be at
least about
_150 in. in length. Similarly, when utilizing a tapered line receptor channel
to
accommodate multiple line sizes, only the inner portion of the line, needs to
be tapered.
Preferably, at least about fifty percent of the axial length of the channel
(exclusive of
flared portion 93') should be tapered in such channel configurations.
In addition to retaining the end portions of the cutting line by configuring
the
cross-sections of at least the outer portions of the line receptor channels so
as to grip the
line as above-described, the channels could be configured to cooperate with a
particular
line configuration to effect securement of the line by a mating or keying
effect as the line
is wrapped about the spool. For example, a flexible noise attenuating trimmer
line
marketed by Proulx Manufacturing, Inc. of Rancho Cucamonga, California, under
the
name Ultra Quiet, is formed by extruding two non-filament polymer strands in
close
disposition and twisting the two strands together about a longitudinal axis in
a cooling
bath. Upon curing, the formed line defines two overlapping cylindrical strands
joined
together in two opposed substantially V-shaped troughs that extend helically
along and
about the line. Such a line configuration has been found to provide
substantial noise
attenuation as compared to comparably sized conventional line rotating at the
same speed
and is the subject of U.S. patent application, Publication Number
2002/0069303, filed
August 29, 2001. An example of such noise attenuating trimmer line 517 is
illustrated herein in
Figure IIH and its cross-sectional configuration is illustrated in Figure 11J.
By
configuring the line receptor channel 593 (see Figure IJJ) so as to have a
corresponding
cross-section helically extending along at least the outer portion of the
channel, the
channel wall will mate with the line as the line is inserted into the channel
through the
aligned line outlet opening in the housing skirt and rotated, effectively
threadably
engaging the line in the channel and securing the end portion of line to the
spool.
Another example of a keyed line and receptor channel is illustrated in Figures
11K
and 1IL. As seen therein, a length of the cutting line 617 is provided with
protruding
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22
locking feature 617a proximate one end of the line. Feature 617a could be of
any
convenient configuration. At least the end portion of the line receptor
channel 693 (see
Figurel1L) is correspondingly configured to receive the line with its
protruding feature
and an offset channel area is provided within the channel to allow the line to
be rotated
such that the protruding feature is received in the offset area. Thus, upon
aligning the
feature 617a with the outer end of the receptor channel 693, inserting and
twisting the line,
the length of line is secured to the spool by the trapped locking feature,
whereupon the line
can be wrapped about the spool body as previously described. In all such
embodiments
the circular holes in the eyelets 78 in the side of the trimmer housing are
sufficiently larger
than the diameter of the cutting line, that the locking feature will not
interfere with the
extension of the line through the eyelets.
Figure 14C illustrates yet another modified line receptor which employs a
single,
inwardly inclined guide wall surface 94c disposed adjacent to the outlet end
of the
receptor channel. The single inwardly inclined surface 94c, like the inwardly
inclined
channel 17" illustrated in Figure 14B, creates an acute angle between the
central axis of
the receptor channel and the guide surface adjacent to the channel outlet.
This single
guide surface 94a is preferred for use in smaller heads as it directs the line
inwardly
toward the center of the spool more quickly than the previously described
guide surface
comprised of laterally extending portion 94a and inclined portion 94b and the
smaller
diameter spools tend to reciprocate upwardly and downwardly more quickly than
the
larger spools. As the smaller spools are not generally designed to accommodate
the larger
diameter line, the acute bend created by the guide surface 94c is generally
not an issue.
With each of the above-discussed variations in the line receptors, the line
winding
process is essentially the same. To wind the cutting line on the spool 16, the
line receptor
channels 93 in the spool are first aligned with the eyelets 78 in the side of
the housing 14.
Printed indicia such as an arrow 85 are preferably provided on the lower
surface of the
spool to facilitate alignment as shown in Figure 15. The inner end portions
17" of two
separate lengths of cutting line 17 are then inserted through the opposed
eyelets 78 in the
housing and pushed securely into the aligned receptor channels 93 in the spool
flange 70.
With the line and channel configurations illustrated in Figures 1IJ-l 1L, the
line must also
be twisted as above-described. The lengths of line are then bent at acute
angles and pulled
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23
toward the spool body portion 74 against lateral guide walls 94. The spool is
then
manually rotated in a counterclockwise direction using the bumper 81 as a
handle while
maintaining the housing in a stationary disposition. The preferably tapered
and angularly
disposed walls defining the receptor channels will tightly grip the inner ends
of the cutting
line, preventing their withdrawal from the channel. As rotation of the spool
in a
counterclockwise direction continues, the two lengths of cutting line will be
wound about
the spools.
Manual rotation of the spool in a counterclockwise direction with respect to
the
housing 14 also will cause corresponding rotation of the cam follower 20 with
respect to
the cam member 18, bringing the inclined slide surfaces 56b on abutment
members 56 into
abutment with the oppositely inclined slide surfaces 46b on the lower cam 46
(see Fig.
8A). Because surfaces 56b and 46b are inclined in opposite directions,
continued
counterclockwise rotation of the spool while maintaining the housing
stationary will cause
the abutment members 56 on the cam follower to ride upwardly on and over the
slide
surfaces 46b on the lower cam 46. As the cam follower 20 moves upwardly with
respect
to the cutting head housing 14 so does the spool 16. This movement is
illustrated in
Figure 8B. When the cam follower 20 is rotated to the point that the trailing
corners of the
lower cam 46 become aligned with relief areas 60 in the cam follower, the cam
follower
and thus spool 16 will snap downwardly under the force of coil spring 22 to
their original
elevations with respect to the housing wherein the cam surfaces 46a on the cam
member
are aligned with the cam abutment surfaces 56a on the cam follower. Thus,
continual
manual rotation of the spool with respect to the housing in the
counterclockwise direction
will effect continual vertical ratcheting or reciprocation of the spool within
the housing as
the two lengths of cutting line are pulled inwardly through eyelets 78 and
wound about the
spool.
This reciprocating movement of the rotating spool provides for an even
distribution
of the cutting line about the spool, even though the vertical distance
traveled by the spool
relative to the housing is less than the distance between the upper and lower
spool flanges
70 and 72 as the two lengths of line enter the spool area from opposed sides
of the spool
and are separately directed toward the center of the spool by the outlet ends
of the line
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24
receptors. As a result, the lengths of line tend to roll over themselves and
fill the spool
without becoming entangled on the spool.
The above description of the trimmer head 10 and its components is based on
using
the head on a conventional rotary trimmer in which the gear box (not shown)
typically
imparts a counterclockwise rotation to the drive shaft 12 and thus to the
trimmer head. If
the head were used on a trimmer without a gear box or with one that imparted a
clockwise
rotation to the head, the leading and trailing surfaces on the cams and cam
follower
abutment members would simply be reversed. Accordingly, it would simply be
necessary
to reverse the orientation of the cam and slide surfaces on the lower cam 46
and on the
abutment members 56 on the cam follower 20. The cam surfaces 46a on the lower
cam
would then still be on the leading surfaces 46' of cam 46 and the slide
surfaces 46b on the
trailing sides. Similarly, the cam abutment surfaces 56a would then still be
on the trailing
side of each abutment member and the slide surfaces 56b would still be on the
leading
sides.
While the spool 16 has been described and illustrated comprising two
diametrically
opposed line receptors 91, one such receptor could be employed if a single
line head was
desired or, alternatively, multiple equally spaced receptors could be
utilized. In addition,
two pair of opposed receptors of different sizes could be employed to provide
additional
versatility for the cutting head. For example, in addition to the receptors
shown in the
drawings and described above, a second pair of line receptors slightly larger
in cross
sectional dimension could be employed with each pair of opposed receptors
being
perpendicular to the other pair to balance the head. Through such a
configuration, one pair
of opposed receptors could be sized to accommodate, for example, small
diameter cutting
line such as .065 in., .080 in. and .095 in. line, while the second pair of
receptors could
accommodate larger diameter line such as .095 in., .105 in. and .130 in. For
such
applications, a second pair of indicia would be imprinted on the upper surface
of the spool
to assist in the alignment of the second pair of line receptors with the line
outlet eyelets
and indicate which pair of receptors accommodated the larger and smaller line
sizes. For
example, a pair of smaller or narrower arrows 85' could be perpendicularly
disposed with
respect to an opposed pair of layer arrows 85" as shown in Figure 16 to
identify the
channel size and align the lengths of cutting line.
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Fully assembled, and loaded with cutting line, the cam member 18 is located
within the chamber 54 in the cam follower 20 with its hexagonally-shaped head
portion 42
disposed within the correspondingly configured portion 40 of channel 34
defined by the
housing tubular extension 30. The coil spring 22 is disposed between and bears
against
5 the shoulder 32 formed by the housing extension 30 and the upper surface of
the cam
follower 20 defined by cylindrical wall 52 and projections 56, urging the cam
follower 20
downwardly about the cam member 18 such that the undersides of abutment
members 56
on the cam follower about the upper surface of the skirt portion 48 of the cam
member. A
5/16-inch or other suitably sized push-type retainer or pal nut 25 (also
referred to as a push
10 nut or bolt retainer) is slid onto the cylindrical lower end of the shaft
portion 24c of the
drive bolt 24 snugly against the underside of skirt 48 on the cam member 18.
The shaft
portion 24c of the drive bolt can be threaded or smooth and push-type
retainers, such as
those shown and described in the 2003 edition of the McMaster-Carr Catalog at
page
2982, are available for threaded as well as unthreaded bolts. By providing the
shaft
15 portion 24c of the drive bolt with threads, a conventional threaded hex nut
could be used
for repairs in the field, if necessary, and if a push-type retainer were not
available. The
use of a push-type retainer, however, allows for simple and totally automated
assembly of
trimmer head 10 which is an object of the present invention.
The spool 16 is disposed within the interior of housing 14 with two of the
lugs 62
20 thereon being disposed in the offset portion of locking channels 82
projecting through
apertures 92 and the remaining two lugs being disposed at the bottom of the
two guide
channels 88. The bumper 81 on the bottom of spool 16 projects downwardly from
the
lower end of the housing 14 as seen in Figure 1 and the extended ends of the
cutting line
17 project through the opposed eyelets 78 in the housing skirt 28.
25 The eyelets 78 preferably employed with the present invention are
constructed of
aircraft grade aluminum and each define annular retention flanges 100 at their
inner ends
and radially extending channels 102 for the passage of the cutting line
therethrough and
into receptors 91. As seen in Figure 13, the inner and outer end portions 104
and 106 of
channels 102 are radiused to eliminate any sharp corners and accommodate
bending of the
line about the eyelets without crimping or overly stressing the line. This
eyelet
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26
configuration allows the eyelets 78 to be attached to the head 10 in an
automated process
and be held in place by flange 100 and the centrifugal force generated thereon
during use.
In operation, the rotating drive shaft 12 on the trimmer effects corresponding
rotation of the housing 14 and the cam member 18 due to the fitment between
the drive
bolt 24, drive shaft 12 and the tubular extension 30 of housing 14. The cam
follower 20 is
pressed downwardly about the cam member 18 such that the undersides of
projections 56
on the cam follower abut the skirt portion 48 of the cam member 18 and the cam
surfaces
46a on the lower cam 46 are aligned with and bear against the abutment
surfaces 56a
defined by the abutment members 56 on the cam follower 20 to effect
corresponding
counterclockwise rotation of the cam follower and the spool carried thereby as
seen from
above in Figure 6. By providing the skirt portion 48 of the cam member 18 with
a vertical
length of about .5 inches, as opposed to using a thinner disc configuration,
any wobble of
the cam member within the cam follower during use is minimized.
Upon pressing the rotating bumper 81 on the bottom of the spool 16 against the
ground or other rigid surface, the trimmer housing 14 and the cam member 18
which is
secured thereto by drive bolt 24 and retainer 25 are forced downwardly,
compressing coil
spring 22 and disengaging the lower cam 46 from the abutment surfaces 56a on
the cam
follower. As the cam member 18 moves downwardly until the lower end of 30' of
the
tubular extension 30 abuts the upper surface of the upper cam 44, the lower
cam passes out
of the path of engagement with the cam abutment surfaces on the cam follower
and the
cam surfaces 44a on the upper cam 44 are brought into the path of cam abutment
surfaces
56a. This causes a slowing of the rotation of the cam follower 20 relative to
the cam
member 18 and thus of the spool 16 relative to the cam member 18 and housing
14. When
the upper cam surfaces 44a strike the abutment surfaces 56a, corresponding
rotation of the
cam and cam follower resumes (see Figure 7). However, during the interim the
cam
member and housing rotate 45 relative to the cam follower and spool.
Once the force of the bump is dissipated, the coil spring 22 forces the spool
and
housing back to their initial positions, releasing the engagement of cam
surfaces 44a on
the upper cam 44 from the cam follower abutment surfaces 56a, re-engaging cam
surfaces
46a and allowing another 45 of relative rotation of the cam member and cam
follower and
thus of the spool and the housing for a total of 90 of rotation during the
bump, regardless
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27
of the time duration of the bump. During these periods relative rotation in
which the spool
lags behind the housing, centrifugal force causes a predetermined amount of
fresh cutting
line to be paid out through the opposed eyelets 78 in the trimmer housing. The
worn line
is then severed by a conventional cutting blade (not shown) carried by a
protective cover
(not shown) mounted on the trimmer above and radially spaced from the rotating
head 10.
It should be noted that the cam follower 20 includes relief areas 60 between
projections 56 so that the cams 44 and 46 can slide vertically with respect to
the cam
follower 20 when the cams 44 and 46 are in the line feeding positions relative
to the cam
follower shown in Figures 6 and 7, and to allow spool reciprocation during
line loading
but at no other times. In the position illustrated in Figure 7, the cams 44
and 46 are free to
slide upwardly to disengage the cam surfaces 44a and in Figure 6, free to
slide
downwardly to disengage the cam surfaces 46a. Cams having three or more or
differently
configured cam surfaces are also possible, with four-sided cams 44 and 46
being a
practical comprise between the surface area contact, ease of manufacture, and
the desired
line feed out. Also, in lieu of square cams defining the cam and slide
surfaces adjacent the
corners thereof, the angularly offset upper and lower cams could each have
four recessed
side walls and define four equally-spaced radial projections or tangs at the
four corners.
The leading and trailing edges of the tangs would then define the cam and
sliding surfaces.
Such a cam member would be operable without the need to modify the cam
follower 18.
In the preferred embodiment of cutting head housing 14, a recessed area 99 is
provided in the housing skirt 28 to define a "window" for a label. As the
surface 99' on
which the label would be affixed is offset from the remainder of the housing
skirt, the
label is protected during use.
Alternate embodiments of the housing and drive bolt usable in the present
invention are illustrated in Figure 12. These embodiments differ from the
prior
embodiments in that the drive bolt 124 is pushed upwardly through the lower
hexagonally-
shaped portion 140 of the interior housing extension 130 for assembly. The
tubular
extension 130 of the modified housing 114 defines a cylindrical upper portion
136 having
a raised annular ridge 137 extending about the interior side wall thereof and
an extended
hexagonally-shaped lower portion 140. The drive bolt 124 defines a cylindrical
upper
portion 124a having an annular groove 124e formed therein, a hexagonally-
shaped mid-
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28
portion 124b and a reduced diameter cylindrical shaft portion 124c, which, as
with the
shaft portion 24c of drive bolt 24 can be threaded or smooth. Upon inserting
drive bolt
124 into tubular extension 130, the ridge 137 in the upper portion of the bolt
provide an
interference fit to retain the bolt within the housing. If the bolt is pushed
into place just
after the housing has been formed, the nylon material will shrink about the
bolt as it cools,
enhancing the securement. However, even if the bolt is inserted into the
housing
extension long after the housing is formed and cooling, the snap fitment
between the bolt
and housing extension will retain the bolt in place.
The cylindrical upper portion 124a of drive bolt 124 has a threaded
cylindrical bore
124d extending axially therethrough and into the hexagonal portion 124b for
threaded
engagement with the drive shaft 12 of the trimmer, similar to the prior
embodiment.
However, if desired, the bolt 124 could be provided with a threaded extension
(not shown)
adapted to engage a trimmer drive shaft having a threaded female end. This
same change
could, of course, be employed with drive bolt 24. The hexagonally-shaped
portion 124b
of the drive bolt is received within an upper portion of the hexagonally-
shaped portion 140
of the housing extension 130 and, upon securement of the cam member 18 and cam
follower 20 is disposed immediately adjacent the hexagonally-shaped head
portion 42 of
the cam member. As in the prior embodiment, the shaft portion 124c of drive
bolt 124
projects downwardly beyond the end of the housing extension 130 and through
the cam
member 18 for engagement with a push retainer 25. The remainder of the
elements also
are identical to the corresponding elements of the prior embodiment. As with
the prior
embodiment, this embodiment can be assembled in a totally automated process
with a
minimal number of parts and without the need for chemical bonding elements
which are
susceptible to heat and/or prevent part replacement.
A second embodiment of the present invention is illustrated in Figures 20-31
wherein the line loading mechanism is employed in a manual trimmer head 100.
Head
100 is also mounted on the extended end of a rotatable drive shaft on a
gasoline or electric
powered rotary trimmer. The trimmer head 100 generally comprises a housing
114, a
spool 116 for carrying one or more lengths of coiled monofilament nylon
cutting line 17, a
coil spring 122, drive bolt 124 and a wing nut 125 for securing the spool 116
to the
trimmer head housing 114.
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29
The trimmer housing and spool are preferably formed of the same material as
the
corresponding components of the prior embodiment. The housing 114 defines an
upper
circular wall 126, a cylindrical skirt 128 depending therefrom and a centrally
disposed
tubular extension 130. Extension 130 is axially aligned with the central axis
of rotation
"Y" of the head and includes a depending portion 130a and an upwardly
projecting portion
130b. The tubular extension 130 is configured to receive the drive bolt 124
with the
upwardly projecting portion 130b preferably being square in cross section to
mate with the
square head portion 124a of the bolt and the depending portion 130a being of a
reduced
constant radius to receive the cylindrical body portion 124b of the drive
bolt. The lower
shaft portion 124c extends downwardly into and through the interior of the
housing and
into the spool where it is threadably engaged by the wing nut 125 as will be
described
(see, e.g. Fig. 29).
The drive bolt 124 also defines an internally threaded cylindrical bore (not
shown)
extending axially through the head portion and a substantial part of the
central portion
124b of the bolt for threaded engagement with the drive shaft of the trimmer
as in the
bump-feed head of the prior embodiment. Thus, with the drive bolt 124 disposed
in the
tubular extension 130 of the trimmer head housing 114 and in threaded
engagement with
the drive shaft, rotation of the drive shaft imparts a corresponding rotation
of the drive bolt
and housing (generally counterclockwise) due to the interference fit between
the square
head portion 124a of the drive bolt and the upper portion 130b of extension
130. Again,
the head portion of the drive bolt and the cross section of the upper portion
of the tubular
extension in the housing could be formed of different shapes other than square
to form the
desired interference fit.
The trimmer head housing 114 also defines a pair of opposed slots 180 in the
depending cylindrical housing skirt 128. Slots 180 are open at their lower
ends and are
adapted to slidably receive a pair of opposed outlet eyelets 178 in a press
fitment.
Alternatively, the eyelets could be press fit through apertures in the housing
skirt as in the
prior embodiment. Again, the portions of the housing skirt 128 adjacent the
eyelets
preferably are raised or ramped outwardly to protect the eyelets from foreign
objects
during use. A plurality of radially projecting heat dissipation ribs 115 are
formed on the
upper wall 126 of housing 114 that extend upwardly along the upper portion
130b of
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tubular extension 130. The heat dissipation ribs 115 are preferably provided
with
sharpened surfaces 117 for severing weeds that may wrap about the drive shaft
adjacent
the trimmer head housing during use. A plurality of equally-spaced drive lug
receiving
apertures 119 extend axially through the upper wall 126 of the trimmer housing
which are
5 adapted to receive the upwardly extending projections defining drive lugs
121 on the spool
116 as will be described.
The trimmer head spool 116 defines an upper annular flange 170 and a lower
annular flange 172 carried by a cylindrical upper body portion 174 so as to
define an
annular area 176 between flanges 170 and 172 for carrying coils of flexible
nylon cutting
10 line 17 wrapped about body portion 174 such that upon assembly, the end
portions 17' of
the cutting line will extend outwardly through the outlet eyelets 178. The
spool also
includes a lower body portion 175 depending from the lower flange 172. Spool
116
further includes a depending cylindrical extension 131 which, upon assembly,
is axially
aligned with the tubular extension 130 on the trimmer head housing 114 as seen
in Figure
15 39 such that the threaded lower shaft portion 124c on the drive bolt 124
extends
therethrough and into the area circumscribed by the lower body portion 175 of
the spool
where the shaft portion is threadably engaged by the wing nut 125.
A coil spring 122 extends about the depending extension 131 in the spool,
bears
against and extends between the underside of the upper spool flange 170 and an
annular
20 recessed surface 125' in the upper portion of wing nut 125. So secured, the
spool 116 and
trimmer head housing 114 are urged together by the coil spring 122. In the
secured
position, the drive lugs 121 project upwardly from the upper surface of flange
170 into the
drive lug receiving apertures 119 in the trimmer head housing, securing the
spool to the
trimmer housing such that rotation of the housing by the drive bolt is
imparted to the
25 spool. To remove the spool from the trimmer head housing it is simply
necessary to
threadably disengage the wing nut 125 from the threaded lower shaft portion of
the drive
bolt.
To enable the trimmer line to be wrapped about the spool 116 without having to
remove the spool from the housing, the upper spool flange 170 is provided with
a pair of
30 opposed line receptors 191 for gripping the inner end portions 17" of two
separate lengths
of cutting line 17. Spool 116 is sized and configured such that flange 170 is
in planar
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31
alignment with the line outlet eyelets 178. Each of the line receptors 191,
including the
line receptor channels 193, is of the same configuration and functions in the
same manner
as the line receptors 91 in the prior embodiment. The dimensions may vary
slightly
depending on variations in the sizes of the respective spools and the diameter
or diameters
of the cutting line for which the head is designed.
In addition to the inclusion of the line receptors 191 on spool 116, the
interior
surface 126' of the upper wall 126 of the trimmer head housing 114 is provided
with a
plurality of arcuate inclined ramps 123. One such ramp is adjacent and extends
from each
lug receiving apertures 119 to the next aperture as seen in Figure 26. In the
embodiment
of trimmer head 100 illustrated in the drawings, ramps 123 are configured such
that they
each extend along an arcuate path and at a downward inclination from a
position laterally
adjacent and slightly below the inner surface 126' of the upper housing wall
126 so as to
define vertical steps 119' at the trailing sides of the lug receiving
apertures. The ramps
123 then smoothly transition back into the inner surface 126' of the upper
housing wall
proximate the next in line of the lug receiving apertures 119. Thus, upon
gripping the
lower body portion 174' of the spool 116 and rotating the spool in a
counterclockwise
direction while holding the trimmer head housing stationary, the drive lugs
will translate
from their respective apertures 119 in the upper wall of the trimmer head
housing about
steps 119' onto and downwardly along the ramps to the inner surface 126' of
the upper
housing wall and then upwardly under the force of the spring 122 into the next-
in-line lug
receiving apertures. Thus, continual rotation of the spool relative to the
housing will
provide the same ratcheting or reciprocal movement of the spool within the
housing as
described above in discussing the first embodiment of the invention.
The steps 119' defined by the vertical spacing between the outer surface of
the
housing upper wall 126 and the upper ends of ramps 123 prevent any whipping or
backlash in the line during use from causing a reverse rotation of the spool
and inadvertent
paying-out of line. Vertical steps of about .015 in. - .025 in. in height have
been
employed for this purpose. To enable the drive lugs 121 to smoothly negotiate
steps 119'
under manual rotation of spool 116, the upper surfaces of the lugs (which are
substantially
flush with the upper surface of housing wall 126 in the drive position) are
rounded at 121'.
A radius of about .030 in. for surfaces 121' has been employed. While ramps
123
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32
vertically align the upper spool flange 170 and thus the line receptors 191
therein with the
eyelets 178 when the drive lugs 121 are rotated off the ramps and onto the
inner housing
wall surface 126', it may be preferable to size the spool 116 relative to the
trimmer housing
114 such that the opposed line receptors would be radially aligned with the
eyelets when
the drive lugs 121 are disposed within lug receiving apertures. In either
case, radial
alignment between the receptors and eyelets is easily achieved.
Thus, as with the prior embodiment, the lengths of cutting line 17 are wound
about
the spool by pressing the extended ends of the line into the line receptors
and rotating the
spool relative to the housing as above described. As the spool is rotated, the
lengths of
line are bent acutely toward the inner portion of the spool as the line exits
the receptor
channels and is pulled against the flat lateral guide walls adjacent the
channel outlets. As
rotation of the spool continues, the spool reciprocates vertically with
respect to the
housing as a result of the drive lugs repeatedly moving along the downwardly
inclined
ramps and snapping upwardly into the next receiving aperture. As a result, the
line is
caused to be wound uniformly on the spool while avoiding line tangling as in
the prior
embodiment.
Finally, as in the prior embodiment, various changes in the configuration,
number
and sizes of the line receptors can be employed in the manual head 100 to
provide the
desired gripping of the line and accommodate different line sizes and, of
course, the
number of cutting lines extending from the cutting head. In addition, the
orientation of the
drive lugs 121, apertures 199 and ramp 123 could be altered or reversed. For
example, the
drive lugs could be formed on the interior of the upper housing wall and the
apertures and
adjacent ramps could be formed in the upper surface of the spool.
A third embodiment of the present invention is illustrated in Figures 32-44.
The
trimmer head 200 shown therein is a bump-feed type head having the drive and
line
feeding mechanism disclosed in U.S. Patent No. 4,959,904 but modified to
include the
rapid line loading feature of the present invention. As will be seen, trimmer
head 200
primarily differs from the bump-feed head 10 of the first embodiment in that
the cam, cam
abutment and slide surfaces defined by the axially mounted cam member 18 and
cam
follower 20 in head 10 are molded directly into the spool and trimmer head
housing in
trimmer head 200.
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Trimmer head 200 comprises a housing 214, spool 216, coil spring 222 and drive
bolt 224. The housing comprises an upper portion 214a and a lower portion 214b
that are
releasably secured together about the spool. The trimmer head housing and
spool are
again preferably formed of the same material as the corresponding elements of
the prior
embodiments. The upper housing 214a defines an upper circular wall 226, a
cylindrical
skirt 228 depending therefrom and a centrally disposed tubular extension 230.
Extension
230 is axially aligned with the central axis of rotation of the head and
includes a
depending portion 230a and an upwardly projecting portion 230b. The tubular
extension
230 is again configured to receive the drive bolt 224 with the upper portion
224a of the
bolt being cylindrical in cross section and the lower portion 224b being
hexagonal in cross
section to mate with the hexagonal lower portion 230a of the tubular
extension. The lower
portion of the drive bolt and the tubular extension in the housing could also
be square or
otherwise configured to provide the desired interference fit between the drive
bolt and
housing. The drive bolt 224 is secured within the tubular extension 230 by
heat shrinking
the extension 230 about the bolt. An annular groove 224e is provided about the
drive bolt
to create an interference fit between the bolt and housing upon the shrinkage
of the plastic
housing material, to enhance the securement of the bolt to the housing. Other
means for
securing the drive bolt to the housing also could be employed. The drive bolt
224 also
defines an internally threaded cylindrical bore 224f extending axially
therethrough for
threaded engagement with the drive shaft of the trimmer as in the prior
embodiments. A
second tubular extension 211 radially spaced from the depending portion 230a
of
extension 230 extends downwardly from the inner surface of the upper housing
wall 226
to define at its lower end an upper annular seat 213 for the coil spring 222.
The upper portion of housing 214 also defines a pair of opposed slots 277 in
the
depending cylindrical housing skirt 228. As in the prior embodiment, the slots
280 are
open at their lower ends and are adapted to receive a pair of opposed metal
outlet eyelets
278 in a press fitment. Alternatively, the eyelets could be press fit through
apertures in the
housing skirt as in the first embodiment. Again, portions of the housing skirt
adjacent the
eyelets are preferably raised or ramped outwardly to protect the eyelets from
foreign
objects during use and a plurality of radially projecting heat dissipation
ribs 215 are
formed on the upper wall 226 of the upper housing. A plurality of
equiangularly disposed
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34
and outwardly projecting radial tabs 233 also are provided at the lower end of
the skirt 228
for the securement of the lower housing portion 214b to the upper portion 214a
as will be
described.
The upper wall 226 of the trimmer head housing has a raised central portion
227 so
as to define an interior recessed area 229 therein. As shown in Figure 38, the
perimeter
wall surface 231 extending about the recessed area 229 defines four
equiangularly
disposed projections 244 that project radially inwardly from wall surface 231.
Each of the
projections defines a pair of angularly disposed surfaces 244' that offset by
135 and are
parallel to the axis of rotation of the head. These projections are similar in
configuration,
albeit larger, to the projections 56 on the cam follower 20 of the first
embodiment. Here,
however, these projections will define cam surfaces as opposed to cam abutment
surfaces.
The leading surface on each of the projections 244 defines an upper cam 244a
(counterclockwise rotation as seen from above). The trailing surfaces each
define an
upper slide surface 244b. The surface of each of the cams is again parallel to
the axis of
rotation of the head. The upper slide surfaces 244b may be downwardly
inclined,
preferably radiused, particularly on smaller sized heads, to facilitate line
loading as will be
discussed.
The lower housing portion 214b of the trimmer head 200 defines an enlarged
circular opening 235 in the underside thereof, an annular horizontal surface
237 disposed
about opening 235, and a plurality of equiangularly disposed slots 239 (four
being shown)
adjacent the upper surface 241 of the lower housing portion 214b for receiving
a
corresponding number of locking tabs 233 on the upper housing portion 214a.
Slots 239
are provided with narrow offset portions 239' as seen in Figure 35 and at
least one of the
locking tabs 233a is mounted on a cantilevered portion 228' of the housing
skirt so as to be
resilient such that upon inserting the rigid locking tabs 233 into three of
the slots in the
lower housing portion, pressing the resilient tab 233a radially inwardly and
into the
remaining aligned slot and rotating the upper portion of the housing
counterclockwise with
regard to the lower portion, the locking tabs will translate into the offset
portions of the
slots, releasably securing together the two housing portions.
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The lower housing portion 214b further defines four equiangularly disposed
projections 246 on the annular surface 237 adjacent opening 235 as seen in
Figure 40. The
angularly disposed surfaces 246' on projections 246, like the surfaces 244' in
the
projections 244 in the upper housing portion, define angularly disposed lower
cams 246a
5 and lower slide surfaces 246b. The lower cams 246a are on the leading
surfaces of the
projections, extend parallel to the axis of rotation of the cutting head and
again can be
angled at 135 with respect to the adjacent slide surfaces. The slide surfaces
246b also can
be radiused upwardly in the same manner as the slide surfaces 46b on the lower
cam 46 in
the first embodiment. In a preferred embodiment, however, the slide surfaces
246b on the
10 lower projections 246 are not angled at 135 with respect to the cam
surfaces 246a but at a
lesser angle as seen in Figure 40 to accommodate a preferred ramping
configuration on the
leading sides of the lower cam follower which is defined by the spool as will
be described.
The spool 216 in trimmer head 200 defines an upper flange 270 and a lower
flange
272 carried by a cylindrical upper body portion 274 so as to define an annular
area 276
15 between flanges 270 and 272 for carrying coils of flexible nylon cutting
line 17 wrapped
about body portion 274 such that upon assembly, the end portions 17' of the
cutting line
will extend outwardly through the outlet eyelets 278. A cylindrical chamber
243 is
disposed about the central axis of rotation that is open at its upper end. An
annular
upstanding wall 245 is disposed in the lower end of chamber 243 so as to
define an
20 annular spring receiving area 247 and lower spring seat 247'. The lower
body portion 275
of the spool terminates in a bumper 281 and a radial flange 249 extends
outwardly from
the lower spool body portion to prevent debris from becoming lodged between
the spool
216 and the lower housing portion 214b (see Fig. 36). When head 200 is
assembled, the
coil spring 222 extends about extension 230 and bears against and extends
between the
25 upper seat 213 formed by the upper housing portion 214a and the lower
spring seat 247' in
the spool 216 as seen in Figures 36 and 37. The bumper 281 on the bottom of
the spool
projects through the opening 235 in the bottom of the lower housing portion
214b such
that it can be bumped against the ground to pay out additional cutting line
through the
opposed eyelets 278 as in the first embodiment.
30 The upper flange 270 on spool 216 defines an upper cam follower 256 on its
upper
surface and the lower spool flange 272 defines a lower cam follower 257 on its
lower
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36
surface as seen in Figures 42-44. While other configurations could be
employed, both
cam followers are preferably of a square configuration, defining four
perpendicular
surfaces 256' and 257' respectively, and are offset by 45 with respect to the
central axis of
rotation of the trimmer head. The cam abutment surfaces 256a and 257a defined
by the
trailing surfaces of the upper and lower cam followers are again parallel to
the axis of
rotation of the head. The leading surfaces of the lower cam follower which
define sliding
surfaces 257b may be inclined upwardly proximate the corners thereon so as to
provide
smoother ratcheting if needed. Also, the leading surfaces of the upper cam
follower may
also be inclined downwardly to facilitate line feeding. Such a downward
inclination of the
trailing edges 256b is believed to be particularly necessary on the smaller
heads where the
length of each of the cam follower surfaces is shorter which otherwise might
make the
relative rotation of the spool and housing during line winding more difficult.
It may also
prove desirable to incline the trailing surfaces of the upper and lower cams.
In the preferred configuration, the sliding surfaces 257b on the lower cam
follower
are defined by inclined ramps as seen in Figures 34, 42 and 44 to provide a
smoother
ratcheting of the spool during the winding of the cutting line thereon due to
the more
gradual incline than that which would be provided by radiused surfaces. As
noted earlier,
the corresponding slides surfaces 246b on the projections 246 defined by the
lower
housing portion are inclined inwardly more sharply than the corresponding
surfaces on the
projections 244 on the upper housing portion 214a to provide more space
adjacent the
slide surfaces on the projections 246 to accommodate these inclined ramps on
projections
224 when the spool 216 translates upwardly as occurs when the trimmer head is
bumped
against the ground to pay out fresh line and during the manual rotation of the
spool to
effect the winding of the cutting line thereon.
The operation of the bump-feed mechanism provided by the upper and lower cams
and cam followers is explained in detail in the referenced Patent No.
4,959,904. It should
be noted, however, that the cam followers carried by the upper and lower spool
flanges in
head 200 are identified as upper and lower cams in the referenced patent and
the upper and
lower cams in head 200 are referred to as cam followers in the referenced
patent. As
explained in the cited reference in more detail, during use, the lower cams
246a on the
lower housing portion 214b are aligned with and abut the lower cam abutment
surfaces on
CA 02714878 2010-09-14
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37
the trailing surfaces of the lower cam follower 257. Accordingly, as the
housing is rotated
in a counterclockwise direction by the trimmer drive, the spool is rotated
with the housing.
In this drive position, the upper cams 244a are upwardly spaced from upper cam
follower
256 so that the driving force is generated solely by the lower cams. When the
bumper 281
is pressed against the ground, the spool 216 is forced upwardly within the
housing
disengaging the lower cam abutment surfaces 257a on the lower cam follower
from the
lower cams 246 and bringing the upper cam abutment surfaces 256a on the upper
cam
follower 256 into alignment and immediate abutment with the upper cams 244a
whereupon the driving force is effected solely by the upper cams. When the
bumper 281
is lifted from the ground, the coil spring 222 forces the spool downwardly,
disengaging the
upper cam follower from the upper cams and re-engaging the lower cam follower
with the
lower cams. Thus, as with the first embodiment of the invention, with each
bump on the
ground effects a relative rotation of the spool and housing of 90 results,
regardless of the
duration of the bump. During this relative rotation, centrifugal force causes
a
predetermined amount of fresh cutting line to be paid out through the opposed
eyelets 278
in the trimmer head housing.
To provide the rapid loading of the trimmer line about spool 216, the upper
spool
flange 270 is provided with a pair of opposed line receptors 291 for gripping
the inner end
portion 17" of two separate lengths of cutting line 17. Spool 216 is sized and
configured
such that the upper flange 270 thereon is in planar alignment with the eye
outlets apertures
278. Each of the line receptors 291, including the line receptor channels 293,
comprises
the same configurations and functions in the same manner as the line receptors
in the prior
embodiments. Again, the dimensions may vary slightly depending on the
variations in the
sizes of the respective spools and the diameter or diameters of cutting line
for which the
head is designed. The cams, cam abutment surfaces and sliding surfaces
described above
cooperate in essentially the same manner as the cams, abutment and sliding
surfaces in the
first embodiment of the bump-feed head to effect the reciprocal movement of
the spool
within the housing to uniformly distribute the line on the spool. When the
spool 216 is
gripped by the bumper 281 and rotated in a counterclockwise direction relative
to the
housing, the lower slide surfaces 257b on the lower cam follower 257 will abut
the trailing
surfaces 246b on the lower projections 246 causing the spool to translate
upwardly with
CA 02714878 2012-04-24
72044-62D
38
respect to the housing, compressing the coil spring 222. As the manual
rotation of
the spool continues, the corner portions of the lower cam follower 257 will
ride over
and clear the projections 246 in the lower portion of the housing whereupon
the
spring will cause the spool to snap downwardly such that the lower projections
and
lower cam abutment surfaces are again in planar alignment. Because the upper
slide
surfaces on the upper projections 244 and the leading (slide) surfaces 256b on
the
upper cam follower 256 are in abutment to wind the cutting line thereon at the
very
time the coil spring 222 will snap the spool 216 downwardly, it may prove
desirable to
incline the trailing surfaces 244b of the upper projections 244 and/or the
leading
(slide) surfaces 256b of the upper cam follower 256 to provide smoother
rotation of
the spool with respect to the housing during the loading of the line.
As noted in referenced Patent No. 4,959,904, the bump-feed
mechanism provided by the cams and cam abutment surfaces need not be limited
to
square cam followers (or cams as they are referred to in the referenced
patent). The
same is true of trimmer head 200. The upper and lower cam followers formed the
upper and lower spools, for example, could be three or five sided as shown in
Figures 12-15 of the referenced Patent No. 4,959,904. Three and five sided cam
followers would cooperate with an equal number of cam abutment members in the
upper and lower housings as shown in the referenced drawings. The function,
cooperation and operation of such cams and cam followers would be otherwise
essentially unchanged from that described above and in the referenced patent.
Various changes and modifications also may be made in carrying out
the present invention without departing from the scope thereof. For example,
the
spools employed with the present invention could be formed with a single
flange and
the line would be wound about the spool body between that flange and a portion
of
the housing. The line receptor or receptors would continue to be provided in
the
single flange. Insofar as these and other changes and modifications are within
the
purview of the appended claims, they are to be considered as part of the
present
invention.
