Simplified bump-feed type cutting head assembly for flexible line trimmers

A compact, light weight, structurally simplified bump-feed type cutting head for a flexible line trimmer is formed from only six components--a hollow cylindrical hub having an open lower end; an annular cover member releasably securable over the lower hub end; a threaded arbor press-fitted into the hub to secure it to the trimmer drive shaft for rotation therewith; a hollow tubular release button member slidably extended through the central cover member opening and axially movable between downwardly extended and upwardly retracted positions; a line storage spool rotatable carried by the release button member within the hub; and a cylindrically coiled compression spring captively retained within the release button and biasing it toward its downwardly extended position. During high speed rotation of the hub about its axis, an outer end portion of flexible line coiled on the spool and passing outwardly through a hub side aperture is whirled through a transverse cutting plane to trim adjacent vegetation. When the outer line end becomes worn away, incremental line feedout is achieved simply by tapping the release button on the ground to activate a line escapement structure defined by cooperating teeth formed on the release button and the inner side surface of the spool hub. Spool removal is achieved simply by removing the cover member, the arbor functioning to hold the release button in place on the hub during and after spool removal.

BACKGROUND OF THE INVENTION 
The present invention relates generally to flexible line trimmer apparatus 
and, in a preferred embodiment thereof, more particularly provides a 
simplified, low cost and light weight line trimmer cutting head assembly 
for containing a supply of flexible cutting line and feeding the line out, 
in controlled increments, when a depending release button portion of the 
head assembly is tapped against the ground by the trimmer operator. 
"Bump-feed" type cutting head assemblies are now commonly used components 
of flexible line trimmers and typically comprise a rotationally driven 
housing in which a spool member is disposed for holding a coiled quantity 
of flexible cutting line. An outer end portion of the line is extended 
outwardly through a line exit aperture formed in the housing side wall. 
During high speed rotation of the housing the outwardly projecting line 
portion is whirled through a transverse cutting plane to perform its usual 
vegetation trimming function. 
Projecting downwardly from the housing is a release button. When tapped 
against the ground by the trimmer operator, the release button activates a 
line escapement structure within the housing to cause relative rotation 
between the spool and the housing in a manner paying out a predetermined 
increment of cutting line to re-lengthen the outer line end portion after 
it has been worn away during vegetation cutting use of the trimmer. 
Many conventional bump-feed cutting head assemblies of this general type 
are characterized by a relatively high degree of mechanical complexity, 
and a correspondingly large number of separate parts which are necessary 
to cooperatively form, for example, the incremental line escapement 
structure, the associated ground bumping mechanism, the housing structure, 
the spool and its support means, and the connecting structure for 
operatively securing the trimmer shaft and its internal drive system to 
the cutting head housing. 
This mechanical complexity carries with it several well known, and 
heretofore unavoidable, problems, limitations and disadvantages. For 
example, the relatively high number of parts required increases both the 
material cost and the overall weight (and thus the inertial mass) of the 
cutting head, and specially designed cutting head assembly tools are often 
required. 
The purchaser/user of the overall trimmer product must also deal with the 
mechanical complexity incorporated in its conventionally constructed 
cutting head assembly when it is time to rewind line on its spool, or 
replace the original spool with one upon which cutting line has been 
factory prewound. This task typically requires that a lower housing cover 
portion, and one or more additional cutting head parts, be removed to gain 
access to the line spool for removal thereof. 
What often occurs, either before, during or after spool removal, is that 
various parts within the housing simply fall out and must be laboriously 
repositioned in proper sequence and orientation within the housing as a 
necessary adjunct to spool replacement. This can be a rather tedious and 
annoying chore for the trimmer user with low levels of patience and 
mechanical aptitude. Even with patience and mechanical aptitude, a fairly 
' high degree of manual dexterity on the part of the user is also often 
required to reassemble a conventional bump-feed type cutting head assembly 
since various of its internal parts must be held in alignment while the 
housing cover is reattached to the main housing body against the force of 
the release button biasing spring. 
In view of the foregoing, it is an object of the present invention to 
provide a bump-feed type line trimmer cutting head assembly which 
eliminates or minimizes the above-mentioned and other problems commonly 
associated with cutting heads of conventional construction. 
SUMMARY OF THE INVENTION 
In carrying out principles of the present invention in accordance with a 
preferred embodiment thereof, a simplified "bump-feed" type cutting head 
assembly for flexible line trimmers is provided which is formed from only 
six components. These components comprise: 
1. A molded plastic hub having a hollow cylindrical configuration, an upper 
end wall with a central drive shaft-receiving opening formed therethrough, 
an annular side wall depending from the upper end wall periphery and 
having a line exit aperture and two latch openings formed therethrough, 
and an open lower end; 
2. A molded plastic cover member releasably latchable to the bottom of the 
hub and having an annular bottom wall with an upstanding annular 
peripheral side wall telescopingly receivable in the open lower end of the 
hub; 
3. A threaded arbor; 
4. A coiled cylindrical compression spring; 
5. A molded plastic line storage spool having a hollow, open-ended central 
hub portion; and 
6. A molded plastic release button member having a hollow cylindrical 
configuration, an open upper end, a closed lower end, and an elongated 
tubular side wall. 
Depending from a central portion of the upper hub end wall is an elongated 
support collar having, at its upper end, a circumferentially spaced series 
of retention webs projecting radially inwardly from its inner side surface 
The threaded arbor may be axially press-fitted within the webs to hold the 
arbor on the hub and position the arbor to be threaded onto the trimmer 
drive shaft. 
The elongated support collar is outwardly circumscribed by a shorter collar 
depending from the upper hub end wall, and a circumferentially spaced 
series of radially directed guide ribs extend across the annular space 
between the two collars. The elongated support collar is slidably and 
axially received within the release button member, and the guide ribs are 
received within axial slots formed within the upper end of the release 
button member, thereby permitting the release button member to be moved 
axially relative to the hub but not rotationally relative thereto. 
The upper end of the spring is received within the elongated support collar 
and bears against the underside of an enlarged upper longitudinal portion 
of the arbor. The lower end of the spring is fitted onto the upper end of 
an axially extending spring support and retention structure formed within 
the interior of the release button member. The release button is pressed 
onto an enlarged lower end portion of the threaded arbor which retains the 
button and allows axial travel of the button, but inhibits removal of the 
button from the arbor. The release button thus holds the spring in 
operative position on the hub. However, then release button retention 
force at the lower end of the arbor is considerably less than the 
frictional retention force at its upper end where the arbor is 
press-fitted into the hub. The release button can thus be pulled apart 
from the hub when desired. The spring the becomes a loose part. Held in 
this manner on the hub, the release button may be axially moved relative 
to the hub between a downwardly extended position and an upwardly 
retracted position, the spring biasing the release button member 
downwardly toward its extended position. 
The line storage spool, and a supply of flexible cutting line operatively 
wound thereon, are rotatably mounted within the hub with the release 
button extending downwardly through the spool hub, the shorter hub collar 
rotatably received in and supporting the spool hub, by means of two 
diametrically opposed resilient latching tabs projecting upwardly from the 
cover member the hub, and an outer line end portion extending outwardly 
through the hub line exit aperture. 
With the cover member latched in place within the open lower end of the 
hub, the release button member projects downwardly through the central 
cover member opening, the cover member bears against a portion of the 
release button member to slightly compress the spring and hold the release 
button member in its normal, downwardly extended operating position, and 
the hub and cover member cooperate to restrain the spool against 
appreciable axial movement relative to the balance of the cutting head 
assembly. 
During trimmer operation, the outer cutting line end portion may be 
re-lengthened, to compensate for wear-shortening thereof, by simply 
tapping the release button against the ground to cause it to move axially 
from its extended position to its retracted position and then back to its 
extended position. In response to this tapping of the release button, 
cooperating escapement teeth formed on the release button and the interior 
side surface of the spool permit the centrifugal line payout force on the 
outer line end portion to incrementally rotate the spool, and then stop it 
again, to incrementally lengthen the worn away outer line end portion. 
Because of the simple construction of the cutting head assembly, spool 
removal is easily and quickly achieved simply removing the cover member 
(by depressing its two latching tabs) and the spool-no other assembly 
parts need to be removed from or can fall out of the opened assembly hub. 
Also, the significantly simplified construction of the assembly 
advantageously reduces its weight, material cost, and rotational inertia, 
provides for a very compact head configuration, and permits the cutting 
head to be completely disassembled and reassembled by the trimmer user in 
a very rapid and easy manner.

DETAILED DESCRIPTION 
As illustrated in FIGS. 1-3, the present invention provides a light weight 
bump-feed type cutting head assembly 10, for use on a flexible line 
trimmer, which is of a uniquely simple and inexpensive construction, and 
may be easily and rapidly assembled and disassembled by the trimmer user 
without the use of tools of any sort. In a manner subsequently described, 
the assembly 10 is threadingly secured to an end of the drive shaft 12 
(FIG. 2) of a flexible line trimmer (not illustrated) and is rotationally 
drivable at a high speed about a central drive axis 14. 
High speed rotation of the assembly 10 rapidly swings an outwardly 
projecting end portion 16.sub.a of flexible cutting line 16 stored within 
the assembly 10 through a cutting plane transverse to axis 14 to perform 
the usual vegetation cutting function of the trimmer. As the whirling line 
portion 16.sub.a becomes wear-shortened during trimmer operation, the 
assembly 10 (as later described) may be simply tapped downwardly against 
the ground by the trimmer operator to incrementally feed out additional 
cutting line and re-lengthen the operative line portion 16.sub.a. 
The mechanical simplicity of the cutting head assembly 10 is best 
illustrated in FIG. 5 wherein it may be seen that the entire assembly 
consists of only six components--a housing 18 defined by an upper hub 
portion 20 and a lower cover member 22, a threaded arbor 24, a coiled 
cylindrical compression spring 26, a line release button member 28, and a 
line storage spool 30. 
The hub 20 is of a molded plastic construction and has a hollow, generally 
cylindrical configuration, an upper end wall 32, a generally annular side 
wall 34, and an open lower end 36. For purposes later described, two 
radially thickened circumferential portions 38 of side wall 34 are 
provided with a latching openings 40, four locating recesses 42 are formed 
in the underside of a hub bottom flange 43 in a circumferentially spaced 
relationship with the latching openings 40, and a circular opening 44, 
having four radially outwardly projecting slot portions 45, is formed 
axially through the upper end wall 32. At 90.degree. from the latching 
openings 40, a line exit opening 46 (FIGS. 3 and 5)is formed radially 
through one of two radially enlarged portions 47 of the hub side wall 34, 
the line exit opening being fitted in the usual manner with a metal line 
guard eyelet or grommet 48. 
As best illustrated in FIGS. 2 and 3, an elongated annular support collar 
50 extends axially downwardly from a central portion of the underside of 
the upper hub end wall 32 and has an open lower end 52 positioned somewhat 
below the open lower end 36 side surface of the support collar 50, along 
an upper end portion thereof, are four circumferentially spaced webs 54 
between which the slots 45 downwardly extend. 
Also extending downwardly from the interior side surface of the upper hub 
end wall 32 is a cylindrical collar 58 which is shorter than and outwardly 
circumscribes the central collar 50. The collar 58 has an open lower end 
60 which is positioned at a generally central axial location within the 
hub 20. For purposes later described, four circumferentially spaced, 
radially extending ribs 62 extend across the annular space between the 
collars 50 and 58. The upper end of the collar 58 is circumscribed by an 
annular raised pad 59. 
Referring now to FIGS. 2 and 5, the bottom cover member 22 is of a molded 
plastic construction and has an annular side wall 68 which extends 
upwardly from the periphery of an annular lower end wall 70 that slopes 
upwardly and radially outward. The side wall 68 is radially dimensioned to 
be axially received within the open lower end 36 of the hub 20, and has 
formed around its periphery four circumferentially spaced, radially 
outwardly projecting locating lugs 72, configured to be received in the 
hub locating recesses 42, and two axially upwardly projecting, radially 
inwardly deformable latching tabs 74 having enlarged upper end portions 76 
adapted to be releasably snapped into the latching openings 40 in the hub 
side wall 34 in a manner subsequently described. The lower end wall 70 of 
the cover member 22 is provided with a central circular opening 78 which 
is bordered, along the upper side surface of the lower end wall 70, by an 
upstanding annular collar 80. 
To rapidly install the cover member 22 within the lower end of the hub 20, 
the cover member is pushed upwardly into the lower end opening 36 of the 
hub to its axial position shown in FIG. 2 to cause the locating lugs 72 to 
enter the locating slots 42, and cause the latching tabs 74 to pop 
outwardly into the latching openings 40, thereby releasably locking the 
cover member remove the cover member 22 from the hub 20, the cover member 
latching tabs 74 are simply pushed inwardly to permit axial travel of the 
cover member to disengage the latching tabs from their associated hub 
openings and permit axial removal of the cover member from the hub as 
illustrated in FIG. 5. 
The release button member 28 is of a molded plastic construction and has a 
tubular side wall 88 which is closed at its lower end by a bottom end wall 
90. Formed downwardly through an upper end portion of the side wall 88 are 
four circumferentially spaced, axially extending slots 92 which terminate 
at their lower ends at four rectangularly cross-sectioned tooth members 
94.sub.a, 94.sub.b, 94.sub.c and 94.sub.d projecting radially outwardly 
from the release button side wall 88. The exterior diameter of the release 
button side wall 88 below these teeth is sized to be downwardly and 
slidably received within the central opening 78 of the lower end wall 70 
of the cover member 22, and the inner diameter of the release button side 
wall is sized to slidably receive the central support collar 50 of the hub 
20. 
Extending upwardly from a central portion of the release button end wall 90 
is a spring support structure 96 defined by eight circumferentially spaced 
rib members 98 extending radially outwardly from the bottom end of a 
hollow cylindrical post member 100 having three circumferentially spaced 
slots 102 formed in its upper end. 
The spool 30 is of a molded plastic construction and has a hollow, 
open-ended cylindrical hub portion 104 with an interior side surface 106. 
Positioned axially inwardly of the upper and lower ends of the hub 104, 
and projecting radially outwardly therefrom, are annular upper and lower 
spool flanges 108 and 110 which define with the hub 104 a cutting line 
storage cavity 112 within which the flexible cutting line 16 may 
operatively wound as best illustrated in FIG. 2. A circumferentially 
spaced series of radially extending stiffening ribs 114 are formed on the 
outer side surface of the spool flange 108 as illustrated in FIGS. 2 and 
5. As illustrated in FIG. 2, a lower end portion of the spool hub 104 is 
provided with a radially outwardly projecting annular lip 110 which allows 
easy gripping when removing and installing the spool on the hub. 
Referring now to FIGS. 2-4, two circumferentially spaced series of radially 
inwardly directed, rectangularly crosssectioned teeth 120.sub.a -120.sub.d 
and 122.sub.a -122.sub.d are formed on the interior side surface 106 of 
the spool hub 104. As will be subsequently described, these eight interior 
spool teeth cooperate with the four release button teeth 94.sub.a 
-94.sub.d to form an escapement mechanism which, in response to tapping 
the release button 28 against the ground during trimmer operation, creates 
an incremental payout of cutting line 16 through line exit opening 46 to 
relengthen the operative outer line end portion 16.sub.a. The lower spool 
teeth 120.sub.a -120.sub.d are axially positioned adjacent the bottom end 
of the spool hub 104 and are downwardly and circumferentially offset from 
the upper spool teeth 122.sub.a -122.sub.d. 
To assemble the cutting head assembly 10 from its fully disassembled state 
illustrated in FIG. 5, an enlarged upper end portion 24.sub.a of the 
threaded arbor 24 is press-fitted upwardly into the hub opening 44, as 
illustrated in FIG. 2, so that radially projecting ribs 24.sub.b on the 
arbor portion 24.sub.a enter the over the upper end 100 of the spring 
support post 100 within the interior of the release button member 28, so 
that the spring 26 abuts the ribs 98 within the release button 28. 
The release button 28 is then pushed upwardly onto the central hub collar 
50 to cause entry of the hub ribs 62 into the axial slots 92 in the 
release button 28. The release button is then firmly pushed in an upward 
direction to compress the spring 26 and drive its cylindrical post 100 
over a radially enlarged lower end portion 24.sub.c of arbor 24, thereby 
frictionally intersecuring the release button to the arbor and causing the 
spring 26 to be captively retained within the release button, with the 
upper and lower spring ends respectively engaging the bottom of the arbor 
portion 24.sub.a and the release button ribs 98. The release button is 
then released to permit the spring 26 to return to its almost uncompressed 
state. The frictional engagement between the lower arbor end and the inner 
side surface of the release button releasably holds the button member 28 
on the hub collar 50, and the hub ribs 62 prevent relative rotation 
between the release button 28 and the hub 20 about the drive axis 14. 
However, the release button slots 92 permit the release button 28 to be 
axially moved relative to hub 20 between the downwardly extended release 
button member position shown on the left side of FIG. 2 and its upwardly 
retracted position shown on the right side of FIG. 2. 
The interengagement between the arbor 24 and the inner side surface of the 
release button, while sufficient to hold the release button on the hub 
collar 50 before the bottom cover than the frictional engagement between 
the arbor and the hub. Accordingly, when it is desired to remove the 
release button from the hub collar 50, the release button is simply pulled 
downwardly to disengage release button from the arbor, the removed release 
button permitting the spring to be loose. 
After the release button 28 is operatively positioned on the hub collar 50 
and frictionally retained thereon, the release button is inserted 
downwardly into the interior of the spool hub 104, and the line end 
portion 16.sub.a is threaded outwardly through the line exit opening 46 in 
the hub 20. The spool 30, with its teeth 94.sub.a -94.sub.d 
circumferentially positioned between the spool teeth sets 120.sub.a 
-12.sub.d and 122.sub.a -122.sub.d as illustrated in FIG. 3, is then 
pushed upwardly into the interior of hub 20 so that the hub collar 58 is 
slidably received within the interior of the spool hub 104. Finally, the 
bottom end of the release button is inserted into the central opening 78 
of the cover member 22, the cover member side wall 68 is pushed into the 
interior of the hub 20, and the cover member is pushed into the hub to 
lock the cover member in place as previously described. The installation 
of the cover member 22 pushes the release button 28 upwardly to its 
extended operating position and slightly compresses the spring 26. 
With the cover member 22 releasably latched in place in this manner, the 
installed spool 30 is restrained against appreciable axial movement 
relative to the housing 18 by the slidable axial engagement between the 
hub abutment ribs 64 and the upper end of the spool hub 104, the slidable 
axial engagement between the lower end 60 of the hub collar 58 and the 
upper spool teeth 122.sub.a -122.sub.d, and the slidable axial engagement 
of the annular cover member collar 80 and the cover member ribs 82 with 
the lower spool teeth 120.sub.a -120.sub.d and the lower end of the spool 
hub 104 as best illustrated in FIG. 2. With the cover member 22 in its 
installed position illustrated in FIG. 2, the engagement between 
compresses the spring 26, brings the release button teeth 94.sub.a 
-94.sub.d into vertical alignment with the lower interior spool teeth 
120.sub.a -120.sub.d. 
The assembled cutting head 10 may be screwed directly onto the bottom end 
of the drive shaft 12 as illustrated in FIG. 2, the drive shaft 12 
extending downwardly into the upper hub opening 44 and being threadingly 
received within the press-fitted retaining arbor 24. High speed rotation 
of the cutting head portion 16.sub.a a centrifugal line payout force which 
exerts a counterclockwise rotational force on the spool 30 as indicated by 
the arrow 124 in FIG. 3. However, with the release button member 28 in its 
downwardly extended operatively position as shown on the side of FIG. 2, 
counterclockwise rotation of the spool is prevented by the respective 
engagement of the release button teeth 94.sub.a -94.sub.d with the lower 
interior spool teeth 120.sub.a -120.sub.d. The spool rotation-preventing 
abutment between the representative release button teeth 94.sub.a and 
94.sub.b with the lower interior spool teeth 120.sub.a and 120.sub.b is 
schematically illustrated in FIG. 4. 
During operation of the line trimmer, when the outer line end portion 
16.sub.a becomes wear-shortened, the trimmer operator simply taps the 
lower end of the release button member 28 against the ground to move the 
release button upwardly to its retracted position. Upward movement of the 
release button to its retracted position shifts the release button teeth 
94.sub.a -94.sub.d upwardly out of abutting engagement with the lower 
interior spool teeth 120.sub.a -120.sub.d. This upward shift of the 
release button teeth is shown in FIG. 4 in which, during the downward 
portion of the release button ground tap, the representative release 
button teeth 94.sub.a and 94.sub.b are shifted upwardly to the dashed line 
positions thereof. 
Disengagement of the release button teeth from the lower interior spool 
teeth permits the centrifugal line payout force in the outer line end 
portion 16.sub.a to rotate the spool 30 in a counterclockwise direction 
until, as illustrated in FIG. 4A, the upper interior spool teeth 122.sub.b 
and 122.sub.c are brought into abutment with and stopped by the now 
upwardly shifted release button 1 teeth 94.sub.a and 94.sub.b. At this 
point, of course, the other two release button teeth are also engaged by 
and stop the other two upper interior spool teeth. 
When the release button is lifted from the ground, the spring 26 downwardly 
returns the release button to its extended position as representatively 
indicated by the dashed line positions of the release button teeth 
94.sub.a and 94.sub.b in FIG. 4A. This downward shifting of the release 
button teeth permits the centrifugal line payout force in the outer line 
end portion 16.sub.a to once again cause counterclockwise rotation of the 
spool 30 until the lower interior spool teeth 120.sub.b and 120.sub.c are 
brought into abutment with and are stopped by the now downwardly shifted 
release button teeth 94.sub.a and 94.sub.b as illustrated in FIG. 4B. 
Thus, in response to a single tap and release of the button member 28, two 
discrete increments of cutting line are centrifugally payed out through 
the line exit opening 46, the total line payout increment resulting from a 
quarter turn of the spool 30 in a counterclockwise direction as viewed in 
FIG. 3. Additional quarter spool turn line payout increments may be 
selectively achieved simply by tapping the release button on the ground an 
appropriate number of additional times. 
To replace the spool 30, or to refill it with flexible cutting line, all 
that is necessary is to radially inwardly depress the cover member tabs 
74, axially remove the cover member from hub 20, and slide the spool 
downwardly off the release button member 28 which remains frictionally 
secured to the hub 20 as previously described. Simply stated, no other 
parts need to be removed from the cutting head assembly, and no other 
parts are free to fall off the hub 20 when the cover member is removed. 
The balance of the assembly remains in a fully assembled and operative 
state. All that is necessary to ready the assembly for subsequent trimming 
use is to reinstall the cover member and a line-filled spool. 
Compared to the relatively complex, multi-piece constructions of 
conventional bump-feed type cutting head assemblies, the cutting head 10 
of the present invention advantageously provides a significantly 
simplified construction which is much easier for the typical trimmer user 
to handle when it becomes necessary to replace a depleted supply of 
cutting line. No tools of any sort are required for even complete 
disassembly and reassembly of the cutting head. 
This simplicity, of course, also provides a variety of operational and 
manufacturing advantages. For example, because there are only six 
components in the assembly 10 its overall material cost and weight is 
significantly reduced, thereby permitting its manufacturing cost to be 
correspondingly diminished. Also, due to this weight reduction the 
rotational inertia of the cutting head is desirably reduced so that, for a 
given rotational velocity of the head, less driving power is required. 
This rotational inertia reduction is further enhanced by the fact that the 
lower cover member is received within the upper hub and does not increase 
the overall diameter of the assembly. 
The mechanical simplicity of the cutting head assembly 10 also reduces its 
initial fabrication cost since there are only six components which may be 
rapidly put together at the factory without (except for the installation 
of the line guard eyelet and the press-fitting of the threaded arbor into 
the hub) the use of special tools of any sort. 
The foregoing detailed description is to be clearly understood as being 
given by way of illustration and example only, the spirit and scope of the 
present invention being limited solely by the appended claims.