Cutlery – Cutting tools – With blade moving means
Reexamination Certificate
1999-08-04
2001-07-24
Peterson, Kenneth E. (Department: 3724)
Cutlery
Cutting tools
With blade moving means
C030S347000
Reexamination Certificate
active
06263580
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a cutterhead for a portable handheld brushcutter for cutting grass, weeds and the like.
BACKGROUND OF THE INVENTION
The cutterhead is mounted at the free end of a drive shaft which transfers the drive torque of a motor such as an internal combustion engine to the cutterhead. The cutterhead includes a pot-shaped housing having a housing hub extending toward the open end of the housing. The housing is held on the end portion of the drive shaft via the housing hub and is driven in rotation by the drive shaft. The housing includes a spool having a hub which is held on the housing hub coaxially to the drive shaft. A cutting filament is wound on the spool and has an end which extends into free space through an exit opening in a peripheral wall of the housing. The peripheral wall axially overlaps the spool. The cutting end of the cutting filament is radially accelerated about the rotating cutterhead during the operation of the brushcutter and cuts the plant matter in the vicinity of the cutterhead.
U.S. Pat. No. 5,671,536 discloses a cutterhead having a spool wherein two spool chambers are formed on the periphery in the spool by a radial partition wall. Cutting filaments are wound in each of the spool chambers. Each cutting end extending into free space is assigned an exit opening in the housing. The partition wall of the spool lies approximately at the same axial elevation as the exit opening and is provided with a lead-in channel through which the other filament end is guided into the interior of the spool and is there held friction tight. The winding up of the cutting filament on the spool should be possible without disassembly of the spool from the housing in that the end portion of the filament is guided through the lead-in channel through the interior of the spool. The lead-in channel is configured in the spool and opens into free space at the outer end face of the spool which is at the open end of the pot-shaped housing. The filament end which exits here should be bent over and inserted into an opening provided next to the channel opening in the end face of the spool. The replacement cutting filament is wound up after the insertion of the end by manual rotation of the spool chamber. An eccentric strut is formed at the exposed end face of the spool which is intended to facilitate the wind-up operation for the operator. The wound up cutting filament is held in a friction-tight manner and the remaining end is flung from the lead-in channel as a consequence of centrifugal forces when the complete length of filament is unwound.
The entrance of the lead-in channel in the partition wall overlaps, with its cross section, the entire exit opening in the housing to ensure that the replacement filament reaches the lead-in channel from the outside after being pushed through the exit opening. The lead-in channel defines a rise in at least one of the spool chambers on which the filament is wound. For the proper transport and discharge of the filament from the cutterhead, a uniformly arranged wind-up in the spool chambers is necessary in order to avoid an otherwise possible clamping of the filament layers lying disordered one next to the other. The known configuration of the lead-in channel, however, causes an asymmetry in the spool chambers which can lead to a nonuniform winding up of the filament. The inlet cross section of the lead-in channel is considerably larger than the diameter of the filament so that the replacement filament passes through the entrance cross section at any desired location in advance of winding up on the spool. For this reason, it cannot be precluded that the filament reaches the incorrect spool chamber at the start of the wind-up operation in which incorrect spool chamber an already wound up filament could possibly be disposed. Increased attention of the operator and additional manipulation of the filament and the cutterhead are required in order to allocate the filament to be wound to the appropriate spool chamber. In this way, the filament can be directed into the spool in the required direction.
SUMMARY OF THE INVENTION
It is an object of the invention to simplify the configuration of the cutterhead as well as to make a reliable introduction of the replacement filament possible into the cutterhead and to make possible a wind-up and pay-out as needed.
The cutterhead of the invention is for a portable handheld brushcutter having a drive shaft defining a drive axis about which the cutterhead is rotatably driven. The cutterhead is mounted on the free end of the drive shaft and includes: a pot-shaped housing having an open end and having a housing hub formed inside the housing and extending to the open end thereof; the pot-shaped housing being held on the end portion of the drive shaft with the housing hub so as to permit the housing to be driven by the drive shaft; a spool accommodated in the housing and having a spool hub held on the housing hub; the spool having a radial partition wall extending about the periphery thereof to form first and second spool chambers; the spool chambers being adapted to contain respective cutting filaments and each of the cutting filaments having first and second ends; the pot-shaped housing having a peripheral wall axially surrounding the spool; the pot-shaped housing having two exit openings formed in the peripheral wall through which corresponding ones of the cutting filaments extend into free space with their first ends; the partition wall lying at the same axial elevation as the exit openings; the partition wall defining a plane transverse to the axis and having first and second lead-in channels formed therein corresponding to the first and second spool chambers, respectively; each of the lead-in channels being provided for guiding in the second end of the cutting filament into the interior of the spool chamber corresponding thereto; the first and second lead-in channels having respective entrances configured as first and second insert funnels, respectively, tapered in the lead-in direction; the plane having a first side facing toward the first spool chamber and a second side facing toward the second spool chamber; each of the insert funnels having a funnel wall defining the insert funnel and having a filament guide formed thereon; the filament guide of the first insert funnel being defined by a radially shortened section of the wall of the first insert funnel disposed on the first side of the plane; the filament guide of the second insert funnel being defined by a radially shortened section of the wall of the second insert funnel disposed on the second side of the plane; and, the first and second lead-in channels extending nonlinearly in the spool.
At least one lead-in channel is provided per spool chamber. The entrance of the lead-in channel is configured as a tapered insert funnel in the insert direction of the filament. The insert funnel overlaps the exit opening in the housing with a large entry cross section. The introduced replacement filament is centered by the funnel and is insertable into the space-saving tapered lead-in channel. The lead-in channel extends nonlinearly in the spool whereby the filament lies against the channel wall over large segments and is held in a friction-tight manner when pulled. The insert funnels are on respective sides of a plane of the partition wall which lies facing toward the corresponding one of the spool chambers. The insert funnels are provided with a filament guide which is formed by a radially shorter wall section of the insert funnel. After the replacement filament is attached via the lead-in channel in the spool housing, the filament is forced by the filament guide into the intended spool chamber during the subsequent wind-up operation.
The lead-in channel is configured so as to be bent at at least one location with an inner-lying edge in the direction of the bend. During the wind-up operation, the filament is held by pull forces at the sharp-edged bend of the lead-in channel. This is so especially when the cross section of the lead-in c
Scharfenberg Andreas
Springer Carsten
Stark Thomas
Andreas Stihl AG & Co.
Choi Stephen
Ottesen Walter
Peterson Kenneth E.
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