Note: Descriptions are shown in the official language in which they were submitted.
2362
APPAR~TUS FOR CUTTING VEGETATION
BACKGROUND OF THE INVENTION
This invention relates to the cutting of vegetation,
and more particularly, it relates to the cutting of vegetation
uslng a flexible, non-metallic cutting line extending from
a rotating head into a cutting plane.
Various types of devices have been proposed for
many years to facilitate the removal of vegetation by mowing,
trimming, edging and like cutting operations. In general, these
devices have emFloyed a metal blade to effect vegetation removal.
Devices of this nature employ prime movers such as electric and
gasoline motors. As a result, rotating metal blades can inflict
serious and terrible injury upon the user.
In the United States of America, practical vegetation
~5 cutting devices using flexible, non-metallic lines carried upon
a rotating head were developed. Examples of devices are shown
in U.S. Patents 3,708,967, 3,826,068, 4,052,789, 4,054,992,
4,067,108 and 4,104,797. These patented devices have met out~
; standing success in that these American developments provide
safer electrical or gasoline-powered tools for vegetation cutting,
edging and trimming operations.
The dcvices shown in these patents employ a
flexible cutting line, such as manufactured from Nylon~
polymer. The cutting line is carried usually upon a spool
internally of a rotating head. When desired to replenish
the line or to extend an additional length of it, the rotation
of the head was stopped and line manually extended from the
spool. This line extension procedure in the patented devices
has been found to be convenient~, simple and reliable. In
many of the more powerful devices, especially those powered by
DC electric motors, a system to extend the cutting line
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~I from the head without interrupting eutting operations was desired~
~ A most desirable system would be capable of feeding cutting line
¦l as needed form the head 80 that line feeding is independent of operator I
action during grass cutting. Structures directed toward this purpose are
~ shown in U. S. Patents 3,895,440, 4,020,550 and 4,035,915. These
IJi structures have in common a basket-weave supply of cutting line carried
on the periphery of a disc with the line feeding from behind special post
memberæ. These post members have a cutting-abrading edge so that
cutting line from the weave supply is bent about such edge in the free ¦
traveling end portion extending into the cutting plane. The combination f~
¦ function of the edge , line ~ angular speecl , etc ., is arranged so that the l~
line posts with such edge sever the free end of the cutting line when it is,
worn to an ineffective length. In practice, these structures are found to ¦
~ waste about 25 per cent of the cutting line because of the excessive length
~ of line severed at the post's edge, e.g., l:hree inches. I
I Other line feeding structures are shown in 4,118,864 and li
¦ 4,138,810. These mechanisms control spool rotation in line feeding I
functions by worm and spur gears having complex action in the vegetation 'f
1~ cutting~ environment.
20 ~¦ The present invention provides a rotating head with a simple
mechanism that maintains the cutting line at its maximum present length in ~
the cutting plane irrespective of rates of cutting line wear or loss and I
without interrupting vegetation cutting or requiring independent operator
action. However, the operator can selectively activate the mechanism if I
~ additional length of cutting line extensionæ are desired.
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~I SUMMARY OF THE INVENTION
In accordance with this invention, there is provided an
apparatus for cutting vegetation, comprising a head rotatable about an axis
I of rotation and said head having at least one peripheral aperture; said
5 I head having a cavity providing a storage area for cutting line; a supply
~ of coiled cutting line disposed on rotatable means in said cavity, said
¦ cutting line being flexible and non-metallic with a free end extendmg
~¦ outwardly from said head through said aperture into a cutting plane; an
Il escapement cam including means cooperable with said rotatable means to
10 , provide locking engagement of said rotatable means with said escapement
¦ cam in a first position of said escapement cam to secure said cutting line
from extension through said aperture into the cutting plane when said free
end has a predetermined maximum length; said escapement cam being
movable between said first position and a second position for extending
said cutting line step-by-step through said aperture into the cutting
plane; off center pivot means for swinging said escapement cam from said,
!I first position to said second position; said escapement cam heing movable
from said first position to said second position during head rotation
I whenever said cutting line is shortened to less than the predetermined
20 1¦ maximum length, whereby said cutting line is extended in length during
the cutting of vegetation, and said escapement cam being urged to~vard
said first position due to a force exerted on said cam caused by said
cutting line tending to extend through said aperture into said cutting
~ I plane .
25 ¦! The present invention also provicles an apparatus for cutting
vegetation, comprising: a head rotatable about an axis of rotation and said
head having at least one peripheral aperture; said head carrying a cavity
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' providing a storage area for cutting line; spool means mounted in said
i cavity and journaled therein for rotation about the rotational axis of said
head and carry a plurality of angularly disposed escapement teeth; a
i ~ supply of flexible non-metallic cutting line disposed in a coiled portion
5 ~¦ about said spool means with one end secured thereto and with a free end
extending outwardly from said head through said aperture into a cutting
plane; an escapement cam carrying anchor pin means which in a first
~¦ position of the cam secure said spool means against rotation in said head
~ when said cutting line at said free end in said cutting plane has a
10 ~ predetermined maximum length; said escapement cam in a second position
stepping said anchor pin means between said escapement teeth on said
spool means for rotating said spool means and uncoiling said cutting line
with extension from said head through said aperture into the cutting
I plane; said escapement cam being mounted centrally in said head and
lS ~ swinging about off center pivot means to said second position from said
~ first position during head rotation whenever said cutting line is shortened
¦ to less than the predetermilled maximum length, whereby said cutting line
~: ~ is extended in length during the cutting of vegetation.
~ ~ In another aspect the present invention provides an apparatus
20 ¦~ for cutting vegetation, comprising: a head rotatable about an axis of
rotation and said head having a periplleral aperture; said head having an
; annular cavity to provide a storage area for a cutting line; spool means
¦¦ mounted in said cavity and journaled therein for rotation about the
~ rotational axis of said head; a flexible non-metallic cutting line coiled about
', 25 1l said spool means with one end secured thereto and with a free end of said
I, cutting line extending radially outwardly through said aperture into a
1~ cutting plane, a wedge-shaped escapement cam centrally carried by said
head and mounted at its apex on off' center pivot means for swinging
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angular movement between first and second positions, said cutting line
, being engaged within an arcuate groove about the enlarged end of said
escapement cam, said escapement cam in the first position securing said
~ ¦ spool against rotation in said head and said escapement cam in the second
5 ¦~ position controlling rotation of said spool means in said head for extending
cutting line from said head into the cutting plane; said escapemen$ cam
including a counterbalance mass to swing same between said first position
~¦ and said second position responsive to forces applied by said cutting line
~ ¦ to the enlar~ed end of said escapement cam, said counterbalance mass on
10 ~ said escapement cam responding to changes in rotary speed of said head to
coact in moving said escapement cam between the first and second
positions; and the forces from said cutting line acting on said escapement
cam and the counterbalance mass responding to changes in rotary speed of
said head cofunctioning to secure said spool means against rotation in said
15 head by mcving with a snap-action said escapement cam into the second
position when said cutting line is shortened to less than its predetermined
maximum length whereby cutting line is extended in length during the
cutting of vegetation.
- ¦~In a further aspect the present invention provides an apparatus
20 3~ for cutting vegetation, comprising: a head rotatable about an axis of
¦~ ro$ation and said head having a peripheral aperture; said head carrying an
annular ca~ity to provide a storage area for a cutting line; spool m,eans
i j mounted in said cavity and journaled therein for rotation about the
¦¦ rotational axis of said head and carrying a plurality of angularly disposed
25 li escapement teeth in groups at a first radial position and a second radial
, ~ position; a flexible non-metallic cutting line disposed in a coiled portion
about said spool means with one end secured thereto and with a free end
¦l of said cutting line extending radially outwardly through said aperture into
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a cutting plane; a wedge-shaped escapement cam carried centrally in said
head adjacent said aperture, and said cutting line threaded in a groove
formed within the enlarged end OI said escapement cam in that portion of
ii saîd cutting line extending from said spool means to said aperture whereby
5 ~ ~ centrifugal force exerted upon said cutting line is applied as a force to
¦ swing said escapement cam, and the apex end of said escapement cam
carries anchor pins; off center pivot means mounting said escapement cam
adjacent its apex end on said head and providing for swinging said
j escapement cam between first and second position sin a plane transverse to
10 ~ the rotational axis of said head; said escapement carn including a
I counterbalance mRss actuated by changes in rotary speed o said head to
¦ coact in moving said escapement cam between the first and second
positions; said escapement cam swinging between the first and second
~ positions simultaneously moving said anchor pins thereon between inward
15 ~¦ and outward radial positions; one of said anchor pins on said e~capement
¦~ cam in the first position selectively engaglng one of said escapement teeth
~li at the inward radial position to secure said spool means agains rota$ion in
¦¦ said head, and $he other one of said anchor pins disengaging another of
~¦ said escapement teeth at the outward radial position to permit controlled
2 0 j step-by-step rotation of said spool means in said head for extending a
¦ length of cutting line from said aperture into the cutting path during head
I rotation; and the centrifugal force of said cutting line acting to move said
¦ escapement cam and the counterbalance mass of said escapement cam
responding to changes in rotary speed of said head cofunction to secure
25 ~I said spool means against rotation by moving with a snap-action said
escapement cam into the first position when said cutting line is at its
il predetermined length and to permit controlled step-by-step rotation of said
spool means by moving said escapement cam with a snap-action into the
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second position when said cutting line is shortened to less than its
predetermined maximum length during the cutting of vegetation.
In a yet further aspect the present invention provides an
apparatus for cutting vegetation, comprising: a head rotatable about an
axis of rotation, sald head carrying a cavity providing a storage area for
cutting line; a supply of coiled cutting line disposed on rotatable means in
said cavity, said cutting line being flexible with a free end extending
outwardly from said head into a cutting plane; an escapement member on
said head movable between first and second positions, said escapement
member including means cooperable with said rotatable means to
provide locking engagement o~ said rotatable means with said
escapement member in said irst position and said second
position o~ sai~ ~scapement member to prevent ro`tation of
said rotatable means relative to said h~3ad; said rotatable means being
operable to rotate relative to said head to extend incremental lengths of
cutting line into said cutting plane when said escapement member is moving
between said first position and said second position; said escapement
member being movable from said first position to said second position
during head rotation whenever said cutting line is shortened to less than
the predetermined maximum length, whereby said cutting 11ne is extended
in length during the cutting of vegetation; and said escapement member
being urged toward said ffrst position due to a force exerted
directly on said escapement member by said cutting line tending
to extend into said cutting plane.
2 5 In a yet further aspect the present invention provides an
apparatus for cutting vegetation, comprising: a head rotatable about an
axis of rotation, said head havin~ at least one peripheral aperture; said
head carrying a cavity providing a storage area :~or cutting line; a supply
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of coiled cutting line disposed on rotatable means in said cavity, sand
, cutting line being flexible and with a free end extending outwardly from
said head through said aperture into a cutting plane; escapement means
~ pivotally mounted on said head and engageable with said rotatable means in
5 1 ~ at least a first position of said escapement means to prevent rotation of
¦~ said rotatable means to uncoil said cutting line, said escapement means
being adapted for pivotal movement between said first position and a
¦ ~ second position to release said rotatable means for limited rotation for
~ j uncoiling incremental lengths of cutting line from said rotatable means for
10 ¦~ extension into said cutting plane; said escapement means being engageable
¦~ with a portion of said cutting line and respective to a orce tending to
extend said cutting line into said cutting plane to be urged in said first
position, said escapement means being responsive to shortening of said
~ cutting line at said free end to less than a predetermined length during
15 ¦¦ rotation of said head to move to said second position to effect release of
~¦ said rotatable means for limited rotation to feed an incremental length of
i cutting line :Erom said rotatable means for extension into said cutting
¦~ plane-
! In a yet further aspect the present invention provides an
20 ~ apparatus for cutting vegetation~ comprising: (a) a head rotatable about
an axis of rotation and said head having at least one peripheral aperture;
(b) said head carrying a cavity providing a storage area for cutting line;
(c) a supply of coiled cutting line disposed on rotatable means in said
1~, cavity, and said cutting line being flexible and non-metallic with a free
2 5 1~ end extending outwardly :Erom said head through said aperture into a
cutting plane; (d) an escapement cam including means cooperable with said
rotatable means to provide engagement of said rotatable means with said
~, i escapement cam in a first position to prevent rotation of said rotatable,
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j ~ means with respect to said head for securing said cutting line from
extension through said aperture into the cutting plane when said free end
has a predetermined maximum length; {e) off center pivot means for i
!~ swinging said escapement cam from said ffrst position to said æecond
5 ~I position during head rotation whenever said cutting line is shortened to
¦¦ less than the predetermined maximum length, whereby said cutting line iæ
¦l extendesl in length during the cutting of vegetation.
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DESCRIPTION OF THE DRAWINGS ~ 6Z
Fig. 1 is a pictorial view illustrating one embodiment
of the apparatus for cutting vegeta-tion arranged according to
the present invention;
Fig. 2 illustrates in enlargement the lower portion
of the apparatus shown in Fig. l;
Fig. 3 is a vextical~section, in enlargement, taken
axially through the cutting head of the apparatus shown in
Fig. 2, appearing with Figure l;
Fig. 4 is a cross-section of the cutting head as shown
in Fig. 3, taken along line 4-4;
Fig. 5 is a top plan view of the escapement cam of the
cutting head shown in Fig. 3;
Fig. 6 is a cross-section taken on line 6-6 in Fig. 3
illustrating the escapement cam in a first position to prevent
rotation of the spool carrying cutting line within the cutting
head;
Fig. 7 is a cross-section like Fig. 6 but with the
escapement cam in the second positio;n to allow spool rotation to
extend cutting line from the cutting head; and
Fig. 8 is a cross-sect~on of the spool used in the
cutting head, appearing with Figure 2.
In these drawings, the several embodiments have common
elements of construction in the cutting head. In regard to the
several figures, like elements carry like numerals to simplify
description of these embodiments in description of the present
apparatus.
DESC~IPTION OF PREFERRED EMBODIMENTS
Referring to Fig. 1, there is shown an apparatus for
cutting vegetation which is constructed in accordance wi-th one
embodiment of the present invention. In this particular embodi-
ment the apparatus is a grass trimmer 11, but the invention
could be embodied in a lawn mower, edger or other device for
vegetation cutting purposes. The trimmer 11 has a lower housing
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12 interconnected by a tube 13 to a handle assembly 14. The
assembly 14 provides a switch 16 for selectively applying electri-
cal power received by a cord 17 to an electric motor 23 carried
within the housing 12. For two-handed operation of the trimmer
11, an auxiliary handle 18 is provided on the t~e 13. The lower
housing 12 carries a head 19 rotatable about an axis passing
through the housing 12, and a cutting line 21 extends into a
cutting plane, which is substantially perpendicular to the axis
o~ rotation of the head 19.
Fig. 2 is an enlargement of the housing 12 and shows
a plurality of air induction openings 22 in the tube 13. These
openings 22 introduce a flow of cooling air over the motor 23
contained in the housing 12. The motor 23 has a downwardly-
extending drive shaft 24 and the head 19 is threadedly connected
to the shaft 24. The upper surface o~ the head 19 has a plurality
of vanes 27 serving as a centrifugal blower for moving air radially
outwardly ~rom the head 19 during its rotation. As a result, the
induced flow of air cools the motor 23 within the housing 12.
The head 19 includes a hub 26 and a cover 26a. The hub 26 carries
in its side peripheral surface an aperture 28 through which the
cutting line 21 extends radially outwardly into the cutting plane.
A metal bearing surface 30 may be placed in the aperture 28 to
protect the line 21 against undue wear and breakages. The cover
26a is releasably secured to the hub 26 by a screw threaded con-
nection.
The housing 12 includes a rearwardly-extending tail
part 29 which serves as a protection for the user preventing in-
advertent contact with the rotating cutting line 21. The tail
part 29 provides an automatic limit to any excessive extension of
the cutting line 21 from the head 19. More particularly, the tail
part 29 has a downwardly-extending projection 31 in which is
embedded a metal cutting blade 32. As a result, the cutting line
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21, when rotated in a cutting plane by the head 19, can never
have an operating length greater than the distance from the axis
of rotation to the cutting blade 32. Any greater length of cut-
ting line is automatically severed by the blade 32.
The head 19, as seen in Figs. 3-7, is disc-like with
a smooth peripheral side surface carrying the aperture 28 through
which the cutting line 21 extends into the cutting plane. If
more than one cutting line is used, each line should have a
separate aperture and bearing surface. One face of the hub 26
carries an adapter 35 with an integral metal sleeve having interior
screw threads 33 in which the drive shaft 24 is secured by its
screw threads 34. In addition, the adapter screw threads 33
extend axially a sufficient distcmce into the head 19 to form a
rigid connection to the shaft 24. Pre:Eerably, the shaft 24 is
cylindrical with a flat circular shoulder 36 above its lower
terminus 37.
The exposed external surfaces of the head 19 should be
smooth in surface contour, rounded at the edges and without sub-
~` stantial projections and recesses capable of trapping appreciable
~` 20 vegetation. Preferably, the cover 27 has a smooth exposed
surface, is circular in configuration with rounded corners, and
is coaxially aligned with the axis of rotation of the head 19.
The hub 26 and the cover 26a together form a cylindrical
cavity 38. A supply 39 of coiled cutting line 21 is disposed with-
in the cavity 38. The coiled cutting line 21 is free to uncoil
by independent rotational and axial movements within the head 19.
Preferably, the coiled cutting line 21 is carried on a spool 41
moun-ted for rotation within the head 19.
The spool 41 has a tubular body 42 with radially out-
,() wardly extending flanges 43 and 44 defining a space receiving the
supply 39 of cutting line 21. The spool 41 is journaled for free
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rotation in the head 19 by means of a cylindrical post 46 and is
axially secured by a post 47 carried by the hub 26 and cover 26a
respectively.
The cover 26a carries internal screw threads 49 which
receive a screw threaded stud 48 formed on the lower part of the
adapter 35 in the hub 26. The hub 26 and cover 26a have meeting
surfaces 51 and 52 provided by a reduced collar 68 on the post
46 and the post 47, and peripheral abutting planar surfaces
53 and 54. The cover 26a is removable for access to the cavity
38 by unscrewing it, preferably counter-directionally to head
rotation to prevent unintended loosening. A series of peripheral
ridges permit the cover 26a to be gripped for its threaded mount-
ing on the hub 26.
The interior end of the coiled cutting line 21 is
secured to the spool 41. ~he cutting line passes from the spool
41 in a helical path through an arcuate cut 55 in the hub 26,
along a line control mechanism includ:Lng an escapement cam 56 and
then through the aperture 28. The free end of the cutting line
21 extends outwardly of the head 19 from the aperture 28. Pre-
ferably, the coiled cutting line supply 39 is wound codirection-
ally to the rotation of the head during vegetation cutting.
This line winding arrangement avoids backlash problems and
unintended uncoiling of cutting line when rotation of the head is
suddenly induced.
'S In accordance with this invention, a fully automatic
mechanism is provided to uncoil the cutting line 21 within the head
19, and to extend the cutting line 21 through the aperture 28 into
the cutting plane when the cutting line is shortened to less than
the predetermined length.
More particularly, the mechanism provides for positive
step-by-step line advance by a controlled rotation of the spool
~1 relative to the head 19 during vegetation cutting. An important
feature of the mechanism is an escapement cam that provides a step-
by-step rotation of the spool by sensing centrifugal force induced
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on the cutting line by head rota-tion and the force acting on
the escapement calT resulting from changes in rotar~r speed at
the head. Also, the escapement cam uses these forces in co-
action to provide a snap-action line advancement function by
mounting the escapement cam upon an off center pivot.
In reference to Figs.3 - 7, an escapement cam
mechanism is illustrated which provides the automatic but
positive incremental extension, as needed, of the cutting line.
The head 19 carries the escapement cam 56 in an off center
pivot mounting which provides for swinging movement between a
first position (shown in Fig. 6) and a second position (shown
in Fig. 7~.
The escapement cam 56 has a wedge-shape with an apex
45 at its small end and an enlarged portion 50 at its other end.
The term wedge-shape is intended to include not only narrow
angled members, but, also cams with included angles of 90
degrees or greater. Also, the enlarged portion preferably has
a peripheral arcuate edge and good results are obtained with
this edge being of a curve at the radius equal to the distance
from the head's axis of rotation to the edge. However, the
peripheral edge can have other configurations as will be apparent
from the accompanying description.
The cam 56 has a central opening 61 which mounts
about the reduced collar neck 68 of the post 46. As a result,
the cam 56 mounts centrally within the head and swings between
first and second positions upon an off-center pivot relative
to the post 46. ~ore particularly, the cam 56 carries a pivot
projection 57 adjacent its apex and the projection 57 is re-
ceived loosely within a hole 60 in the post 46. Since the
hole 50 is spaced from the axis of head rotation, the cam 56
swings eccentrically between its first and second positions.
The cam 56 also carries projecting anchor pins 58
and 59 which are spaced to each side of the pivot projection
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57. These anchor pins move radially inwardly and outwardly
relative to recesses 66 and 67 formed into the end surfaces
of the post 46.
Preferably, the cam 56 is planar and may be
constructed of a rigid material of suitable strength, such
as aluminum. The anchor pins 58, 59 can be cast or machined
into the planar body o the cam 56 and project normally from
its top surface 69. Good results are provided where the
anchor pins 58,59 are round but preferably, the anchor pins
~o are oval in cross-section for smooth operation.
The enlarged portion of the cam 56 has a peripheral
edge with a longitudinal groove 64 to receive the cutting
line 21 in that portion extending between the spool 41 and
the aperture 2~. The groove 64 may have unbroken edges, but
preferably, to save weight, the groove 64 is provided by
laterally offset projections 62 and 63 which contain the cutting
line. The force arising from the cutting line 21 extending
from the rotating head 19 is applied through the groove 64
(as on a pulley) to move the cam 56 sideways between the first
and second positions.
The enlarged portion 50 of the cam 56 also provides
adjacent the groove 64 a counterbalance mass that provides a
unique function in the present head. The mass of the cam 56
at its enlarged end 50 (without the cutting line acting upon
it) is arranged to function with the off-center pivot mounting
on pro~ection 57 so that at normal operating rotary speeds,
the cam 56 is moved into the second position, wherein the
cutting line is extended stepwise in a length from the rotating
head 19.
The action of the cutting line in the groove 64 is
to swing the cam 56 responsive to the centrifugal force acting
upon the free end of the cutting line within the cutting plane.
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When the cutting line 21 is at its predetermined
maximum extended length into the cutting plane, the cam 56
is swung into its first position (Fig. 6) wherein the cutting
line is secured against extension or feeding additional line
from the head.
When the cutting line 21 is shortened to less than
the desired predetermined maximum extended length, the
effective centrifugal force of the cutting line 21 is
lessened, and the cam 56 swings into its second position
(Fig. 7) and a length of cutting line 21 is extended step-
wise from the rotating head 19.
The cam 56 moves with a snap-action between the
first and second positions, because of the off center pivotal
mounting of the cam 56 relative to the rotational axis of the
head 19, the counterbalance mass, and the action of the cutting
line 21 on the cam 56. This positive movement between positions
insures a proper and positive feeding of cutting line 21 from
the head 19. At no time, can the cam 56 oscillate or hunt
between the first and second positions.
Many different mechanisms can be used to connect
the cam 56 with the spool 41 for controlling its rotation
relative to the head 19 in a stepwise fashion. Prefexably,
a tooth and anchor pin arrangement is used. For this purpose,
the spool 41 carries a plurality of radially inward facing
teeth 71 - 74 and 76 - 78. These teeth at their inner ends
provide bearing surfaces about the post 46 for coaxial rotation
of the spool 41 relative to the hub 26. Preferably, the teeth
71 - 74 and 76 - 78 are axially elongated and e~tend the
length of the tubular body 42 of the spool 41.
The teeth 71 - 74 and 76 ~ 78 are separated by
grooves 79 - 85. These grooves are of sufficient depth to
provide clearance to the anchor pins when in their radial
out~ard positions. As a result, the spool rotates freely until
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a tooth encounters an anchor pin 58,59 in its position ou-t-
ward from the recesses on the post 46.
The teeth are dimensionPd to be engaged by -the anchor
pins 58 and 59 when either pin is in its outward position.
Of course, these teeth are disengaged by either pin when in
its inward position and received within recesses 66 and 67
on the post 46. One anchor pin engages a tooth while the
other pin is in the recess on the post 46.
The teeth and anchor pins are angularly positioned
to cooperate as an escapement to control rotation of the spool
41 as the cam 56 is swing sideways between the first and
second positions. Referring to Fig. 6, the cam 56 is in the
first position, and the anchor pin 58 engages the tooth 74
to secure the spool ~l against rotation to feed the cutting
line from the head l9. At this time, the anchor pin S9 is
in the recess 67.
When the cutting line 21 is shortened to less than
the predetermined maximum extended length in the cutting path,
the cam 56 swings into the second position as seen in Fig. 7.
The anchor pin 58 has moved into the recess 66 and the spool
41 is rotated angularly until the tooth 72 in its outward
position engages the anchor pin 59.
The spool rotates step-wise until the outward
anchor pin stops the next approaching tooth. If the cutting
line 21 has now been extended to the desired extension into
the cutting plane, the cam 56 now is swung into the first
position. If the cutting line is yet not su-fficiently extended
from the head 19, the cam 56 swings toward the second position
sufficiently to clear the anchor pin 5~ from the adjacent
tooth and returns momentarily into the first position, and
the cam 56 again swings hetween first and second positions
for feeding stepwise additional lengths of cutting line from
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the rotating head. At this time the spool has rotated
angularly a certain displacement shown by the index
arrows ~6 and 87. This successive feeding function of
the cam 56 is the product of the off-center pivoted mountings
in coordination with the selected counterbalance mass, and
the swinging action of the cam from the centrifugal force
applied to it by the extended cutting line.
The cam 56 with the counterbalance mass also has
a unique function in that not only is automatic line feeding
obtained without operator intervention, but additional line
feed (if needed) is induced by a start-stop operation of
the trimmer 11, or other certain changes in rotary speed
of the head 19.
As the head 19 accelerates, the counterbalance
mass reacts to swing the cam 56 into the second position, but
when the cutting line is fully extended, the spool is not
released for rotation because of the action of the cutting
line on the cam. As the head 19 decelerates, the cam 56
is held in the first position so no feeding of the cutting
line can occur. Thus, line feeding can be induced at short-
ened cutting line lengths by a start-stop operation of the
trimmer of the head 19 while cutting vegetation. However,
the counterbalance mass at the enlarged end of the cam 56
must not be too great relative to action of the cutting line
on the cam because the cam would shift into the second position
and feed cutting line each time the head 19 accelerates in
rotary speed.
The eccentric swinging of the cam 56 provides for
the anchor pins to be jammed against the teeth they engage
upon the spool. The anchor pins move radially outwardly ln
an arc intersecting the circle defining the teeth on the
spool. ~s a result, the spool must move slightly counter-
directionally to the direction for unwinding cutt~ng line to
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release the ca~ for movement between the first and second
positions. This unique function of the off-center pivoted
cam prevents over-feeding or ratcheting ~machine-gunning)
of the cam relative to the spool.
The feecling of the cutting line appears to involve
some sliding of its portion contained in the groove 64.
Assuming that the centrifugal force acting on the free end
of the cutting line holds taut that portion of the cutting
line between the groove 64 and aperture 28, then the cam 56
]o swinging into the second position (Fig. 7) requires the
cutting line to slide in the groove 64. 5tated in a different
manner, the cam 56 in swinging into the second position must
let the cutting line slide in the groove 64. Otherwise,
the cutting line would be pulled inwardly into the head
]5 at its free end within the cutting path.
As noted previously, groo~es 79 - 85 are of sufficient
d~pth to provide clearance to the anchor pins 58, 59 when in
their radial outward positions. As a result, the spool rotates
freely until a tooth encounters an anchor pin in its position
outward from the recesses 66 on the post 46.
Although the head 19 can be manufactured in various
forms and of several materials, it is preferred to manufacture
the hub 26 and cover 27 of plastic material, e.g. Nylon 6
polymer. The spool 41 and cutting line can be made of a
similar material. The cam 56 can be made of a durable strong
material, such as steel, aluminum or various metallic combinat-
ions.
Although there has been described a particular arrange
ment of functions and elements in the various mechanisms
employed in the head of the present invention, it is not in-
tended that this description be the only possible arrangemen-t
of these elements to produce the results of the invention.
- 12 -
~3~5~Z~;~
In this regard, the functions and elements may be altered
to produce the same results. All that is required for
these elements is a mechanism which secures the line 21
from extension when at the predetermined maximum extended
length in the cutting plane. Also, the mechanism must
release the cutting line i'as needed" when the cutting line
has been reduced by wear or loss, to length less than the
desired maximum length. In addition, the mechanism provides
for the automatic extension of the cutting line with a few
relatively simple and inexpensive escapement elements.
From the foregoing, it will be apparent that there
has been provided a novel apparatus for cutting vegetation
which provides a convenient and safe means for automatically
extending a cutting line without the individual attention of
the operator. It will be appreciated that certain changes
or alterations in the present apparatus may be made without
departing from the spirit of this invention. These changes
are contemplated by and are within the scope of the appended
claims which define the invention. Additionally, the present
~0 description is intended to be taken as an illustration of
this invention.
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