CA1097930A - Filament type trimmer - Google Patents
Filament type trimmerInfo
- Publication number
- CA1097930A CA1097930A CA330,345A CA330345A CA1097930A CA 1097930 A CA1097930 A CA 1097930A CA 330345 A CA330345 A CA 330345A CA 1097930 A CA1097930 A CA 1097930A
- Authority
- CA
- Canada
- Prior art keywords
- filament
- housing
- bushing
- spool
- exit opening
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- A—HUMAN NECESSITIES
- A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
- A01D—HARVESTING; MOWING
- A01D34/00—Mowers; Mowing apparatus of harvesters
- A01D34/01—Mowers; Mowing apparatus of harvesters characterised by features relating to the type of cutting apparatus
- A01D34/412—Mowers; Mowing apparatus of harvesters characterised by features relating to the type of cutting apparatus having rotating cutters
- A01D34/416—Flexible line cutters
Abstract
TITLE OF THE INVENTION:
Filament Type Trimmer ABSTRACT OF THE DISCLOSURE:
In a filament type trimmer a filament is wound on a storage spool in a rotating housing and exits through an open-ing in a rim portion of the housing. When the extending portion of the filament is rotating freely, it extends approximately radially from the housing. However, when it hits a relatively stationary object, it is deflected rearwardly so as to extend approximately tangentially from the housing. To avoid high stresses in the exiting portion of the filament, the exit opening is inclined rearwardly so that when the filament is deflected rearwardly by striking an object, it extends in a tangential line of of the spool, thereby avoiding bending stresses at the exit opening.
Filament Type Trimmer ABSTRACT OF THE DISCLOSURE:
In a filament type trimmer a filament is wound on a storage spool in a rotating housing and exits through an open-ing in a rim portion of the housing. When the extending portion of the filament is rotating freely, it extends approximately radially from the housing. However, when it hits a relatively stationary object, it is deflected rearwardly so as to extend approximately tangentially from the housing. To avoid high stresses in the exiting portion of the filament, the exit opening is inclined rearwardly so that when the filament is deflected rearwardly by striking an object, it extends in a tangential line of of the spool, thereby avoiding bending stresses at the exit opening.
Description
3~
FIELD OF INVENTION:
The present invention relates -to filament type trimmers and in particular to means for avoiding breakage of the filament where the filament exits from the cutting head.
BACKGROUND OF THE INVENTION:
In a filament type trimmer having a filament storage spool mounted in a rotating housing having a rim portion with an exit aperture through which the filament extends, frequent breakage of the filament has been found to occur where the filament exits from the cutting head. It has been determined that the exit aperture has no effect on filament breakage so long as the filament is rotating in free air and does not strike any relatively stationary object.
Thus any suitable means for allowing the string to pass through the outer wall of the housing is suitable under these conditions. However, when the cutting filament hits a relatively ~tationary object, the filament is deflected rearwardly and a component of the impact load is transmitted along the filament. This tensile load causes the filarnent to stretch and, moreover, applies a high localized load where the filament bends at the exit aperture.
It has been proposed to support the filament by a substantially curvilinear bearing surface at the exit aperture and to form the bearing surface of a material having a low coefficient of friction with respect to the filament.
While these expedients have been found to be somewhat beneficial in reducing filament breakage, it has been found that they do no-t provide a complete solution to the problem.
~ ~ ~ ' s~
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SUMMARY OF THE, IN`VENTI~N
It is an object o~ the present invention to overcome these problems and dif~iculties in a simple yet highly ef~ective manner. In accordance with the invention the rim portion of the cutting head is provided with a filament exit opening which is generally cylindrical with an axis that lies in the cutting plane, i.e. a plane perpendicular to the axis of rotating of the cutting head, and is inclined rearwardly at an acute angle to a radial line drawn from the axis of the cutting head to the exit aperture.
~lence when the filament impacts an object and is thereby deflected rearwardly, the filament extends freely through the exit aperture in a substantially tangential line off of the storage spool and is hence not bent at thé exit aperture~
The axial load in the filament is taken in pure tension and the filament is not caused to bend around a supporting surface at the exit. The diameter of the cylindrical exit is of a size to compensate for the different coil radii caused by a full or empty storage spool.
BRIEF ~ESCRIPTIO~ OF DRAWINGS:
The nature, objects and advantages of the invention will be more fully understood from the following description of a preferred embodiment shown by way of example in the accompanying drawings in which:
Fig. 1 is a vertical sectional view through the rotating housing and adjacent porkion of a filamen-t type trimmer in accordance with the presen-t inven-tion, the rnotor by which the housing i.5 rotated being showrl schematically in phantom, Fig. ~ is a side view oP a guide t~be for the filament before the tube is bent, : 109793~
Fig, 3 is a horizorltal section taken approxirnately ¦ on the line 3-3 in ~igo 1~
I DESCRIPTION OF PR~F~RRED EMBODI~ T:
.._ .. ... ._... . _ A filament type trimmer in accordance with the present invention is illustrated by way of example in the drawings as comprising a rotary cutting head 1 driven in the direction indicated by ~he arrow A in Fig. 3, by a motor 2 shown schemati-cally by way of exarnple as a single cylinder two-stroke cycle internal combustion engine having a drive shaft 30 The cutting head 1 is shown as comprising a circular housing 4 having a 'base portion 4a and a downwardly e~tending annular wall comprising a rlm portion 4b. The housing is conveniently molded of plastic material and is removably secured to the motor by an internall~
threaded metal bushing 5 which is screwed onto a threaded portion of the motor drive shaft 30 A filament storage spool 6 having a hub portion 6a and opposite flange portions 6b and 6c is rotatably mounted coaxially in the housing and is retained by a removable cap 7 having an internally threaded central hub portion which screws onto a threaded end portion of the bushing 5, The spool 6 normally rotates with the housing but is rotat-able relative to ~he housing in the direction indicated by the arrow B in Fig. 3 to feed out additional filament ~rom the spool from time-to-time.
A filament 8 is wound on the spool 6 in a direction opposite to the direction of rotation of the head 1 and an inner end of the filament is secured to the hub portion of the spool. The filament 8 is,for example,a monofllament of thermo-plastic material, selected for the characteristics o~ strength, toughness and abrasion resistance. An outer end portion 8a of the filament extends approximately tangentially from the spool 6 11;~979313 to and passes freely ou~ through an exit opening 9 provided in the rim portion 4b of the rotatin~ housing 4, The exit opening 9 is shown as comprising a bushing 10 set in an opening 11 in the rim portion 4b of the rotating housing 40 The bushing 10 is of hard abrasion resistant material having a low coefficient of friction with .... ,, , ~ , .
3~
respect -to the fi]ament 8. For example the bushing 10 may be of metal such as brass or stainless steel or it may be a hard abrasion resistant plastic. It is set firm1y in the opening 11 in the rim portion of the housing, for example by ultrasonic welding. As seen in Fig. 1, the bushing 10 is set with its axis in the cutting plane, i.e. a plane perpendicular to the axis of rotation of the cutting head 4 while, as seen in Fig. 3, the axis of the bushing 10 is inclined rearwardly with respect to a radius of the housing 4 wllich passes through the bushing. The angle of inclination is, for example about 30-45. When running free, the filament extend approximately radially from the housing as shown in solid lines in Fig. 3 and bears on the front of the bushing 10 which has a smooth rounded surface so as to reduce friction with the filament. When the filament strikes an obstacle, it is deflected rearwardly so as to extend approximately tangentially from the spool and straight through the exit opening without bearing on the bushing as illustrated in dotted lines. E~ence the impact load on the filament is taken in pure tension and the combina-tion of tension and bending at the exit opening is avoided. The bushing 10 has an internal diameter of a size to compensate for different coil radii caused by a full, empty or partially empty spool.
A portion 8a of the filament extends from the spool through the exit opening 9 after passing -through a guide tube 12. The -tube 12 is for example a tube of dead-soft aluminum which is originally a straight piece of tubing as shown in Fig. 2. The tubing has an internal diameter sl:ightly larger than the diameter of -the filament 8 so that the filament can be readily threaded through i-t. Before the spool 97~
with the filament wound thereon is placed in the housing 4, an outer end portion of the filament is threaded through the tube l~ and the tube is thereupon ben~ in the form shown in Fig. 3 so that i-t is wrapped par~rially around the spool and extends tangentially from the spool to the exit opening 9 when the spool is placed in the housiny. Preferably -the ~uide tube 12 is of such length that with a full spool it wraps approximately once around the spool as illuskrated in - FigO 3. 'rhe outer end of the guide tube 1~ is enlarged for example by fixing thereon a ferrule 13 so that it cannot pass out through the exit opening in the rim portion of the rotating housing. The guide tube 12 is sufficiently flexible that as the filament is used-up, the pull of centrifugal force on the ilament is sufficient to bend the tube and make it conform substantially to the outer coils of filament on the spool except for the tangential portion that extends to the exit opening 9. It has been found that the guide tube 12 avoids frictional rubbing of the outerrnost coil of filament on the spool with adjacent coils and thereby avoids melting of the filament and welding of the filament to itself.
Moreover, as the guide tube hugs the spool, it prevents entanglement of one coil o filament with ano-ther.
Instead of being formed of soft aluminum tubing, the guide tube 12 may be of other material which provides appropriate flexibility. For example the tubing may be formed o coiled wire with closely positioned successive convolutions. Instead of being seamless, -the tubing may be split along its ou-ter periphery to facilitate the threading of the filament through it. The heat conductivity of the tube contributes to avoiding welding.
'rhe spool ~ is normally locked with respect to the housing 4 so as to rotate with the housing. However, means is 7~
. . ~
provided for releasing the spool from time-to-time to permit a portion of the fi:lamellt to be unwound ~rom it by the pull of centrifugal force on the outer end por-tion 8a of the filament.
In the embodiment illustra-ted by way of example in Fig. 1, rotation of the filament spool 6 relative to the housing 4 is controlled by a mechanism which comprises a low speed slider 15 and a high speed slider 16. The sliders 15 and 16 are slidable in radially extending slots in the base portion 4a of the housing 4 immediately above the filament spool 6. The sliders 15 and 16 are biased radially inwardly by coil springs 17 and 1~ respectively. By reason of rotation of the housing 4 at high speed r centrifugal force acts on the sliders 15 and 16 50 as to move them radially outwardly against the bias oE the respective springs at predetermined speeds of rotationO The springs 17 and 18 are calibrated wi-th respect to the weights of the respective sliders so as to determine the rotational speed of the housing at which the sliders move outwardly by centrifugal force. The spring 18 of the slider 16 is s-tronger relative to the weight of the slider than the spring 17 of the slider 15 so that the low speed slider 15 will move radially outwardly at a lower speed than the high speed slider 16.
The low speed slider 15 is provided with a downwardly extending projection 15a which in the outer position of the slider is engageable with one or another of upwardly extending projections 19 provided on the upper flange 6b of the filament spool 6. The projections 19 are arranged in a circle concentric wi-th the axis of the spool and are spaced circumferentially.
3~3 For example three or four suc~ projections may be provided on ; the spool. The high speed slider 16 is similarly provided with a downwardly extending pro jection 16a which in the inner positîon of the slider is engageable with one another of the projections 19 on the spool. By way of example the springs 17 or 18 are calibrated so that when the cutting head 1 is rotating at a speed below 3000 rpm both sliders are in their inner position, at 3000 to 9000 rpm the lower speed slider 15 has moved to its outer position while the high speed slider 16 is still in its inner position and above 9000 rpm both sliders are in their outer position. It will be understood that difEerent speeds can be selected by suitable calibration of the springs with respect to the weights of the sliders. When the cutting head 1 is rotating at a normal operating speed, for example within the range of 3000 to 9000 rpm, the projection 16a of the high speed slider 16 engages one of the projections 19 on the filament spool so as to hold the spool against rotation relative to the casing. If the speed of rotation of the cutting head 1 increases above 9000 rpm (by reason of the projecting end portion 8a of the filament having become shorter and thereby reducing the load on the motor 2) the high speed slider 16 moves outwardly against the bias of its spring so as to disengage the respective projection 19 on the spool, thereby permitting the spool to be rotated by the pull of centrifugal force on the filament so as to unwind filament from the spool.
However, the projection 15a of the low speed slider is in the path of travel of the projec-tions 19 on the spool 6 so that the spool is permi-tted to rotate only un-til another of the projections on the spool engages the projection 15a of the low speed slider 15. Further rotation of the filamen-t spool relative to the cutting head is delayed un-til, for example by 3~
manual control of the motor, the speed o rotation of the cutting head is reduced to a speed below 3000 rpm idling speed.
Both of the sliders 15 and 16 are thereupon moved to their inner positions by the bias of the respective springs whereupon the projection 15a of the low speed slider is disengaged from the respective projection on the spool thereby permitting the spool to rotate until the next projec-tion on the spool engages the projection 16a of the high speed slider 16. This dela~ ln feeding additional filament avoids sudden increase in the length of the filament and corresponding increase in the cutting radius of the trimmer while the cutting head is rotating at high speed. Hence if the user is trimming close to a flower bed, possible damage to the flowers is avoided. As a trimmer of this kind is usually operated for only short periods of time between idling periods, the cycle of operation described above for restoring the normal length of the projecting end portion of the filament occurs automatically and without any special attention on the part of the operator.
As the exit opening provided in accordance with the present invention avoids the deliterious effec-t of combined axial load, bending and friction at the exit opening when the filamen-t strikes a relatively stationary object, the filament breakage which has heretofore been experienced is avoided.
Filament life is thereby greatly increased.
While a preferred embodiment of th~ invention is illustrated in the drawings and has been herein clescribed, it will be understood that variations and modifica-tions may be made and that the invention is hence in no way limited to the illustrated embodiment.
g
FIELD OF INVENTION:
The present invention relates -to filament type trimmers and in particular to means for avoiding breakage of the filament where the filament exits from the cutting head.
BACKGROUND OF THE INVENTION:
In a filament type trimmer having a filament storage spool mounted in a rotating housing having a rim portion with an exit aperture through which the filament extends, frequent breakage of the filament has been found to occur where the filament exits from the cutting head. It has been determined that the exit aperture has no effect on filament breakage so long as the filament is rotating in free air and does not strike any relatively stationary object.
Thus any suitable means for allowing the string to pass through the outer wall of the housing is suitable under these conditions. However, when the cutting filament hits a relatively ~tationary object, the filament is deflected rearwardly and a component of the impact load is transmitted along the filament. This tensile load causes the filarnent to stretch and, moreover, applies a high localized load where the filament bends at the exit aperture.
It has been proposed to support the filament by a substantially curvilinear bearing surface at the exit aperture and to form the bearing surface of a material having a low coefficient of friction with respect to the filament.
While these expedients have been found to be somewhat beneficial in reducing filament breakage, it has been found that they do no-t provide a complete solution to the problem.
~ ~ ~ ' s~
~7~
SUMMARY OF THE, IN`VENTI~N
It is an object o~ the present invention to overcome these problems and dif~iculties in a simple yet highly ef~ective manner. In accordance with the invention the rim portion of the cutting head is provided with a filament exit opening which is generally cylindrical with an axis that lies in the cutting plane, i.e. a plane perpendicular to the axis of rotating of the cutting head, and is inclined rearwardly at an acute angle to a radial line drawn from the axis of the cutting head to the exit aperture.
~lence when the filament impacts an object and is thereby deflected rearwardly, the filament extends freely through the exit aperture in a substantially tangential line off of the storage spool and is hence not bent at thé exit aperture~
The axial load in the filament is taken in pure tension and the filament is not caused to bend around a supporting surface at the exit. The diameter of the cylindrical exit is of a size to compensate for the different coil radii caused by a full or empty storage spool.
BRIEF ~ESCRIPTIO~ OF DRAWINGS:
The nature, objects and advantages of the invention will be more fully understood from the following description of a preferred embodiment shown by way of example in the accompanying drawings in which:
Fig. 1 is a vertical sectional view through the rotating housing and adjacent porkion of a filamen-t type trimmer in accordance with the presen-t inven-tion, the rnotor by which the housing i.5 rotated being showrl schematically in phantom, Fig. ~ is a side view oP a guide t~be for the filament before the tube is bent, : 109793~
Fig, 3 is a horizorltal section taken approxirnately ¦ on the line 3-3 in ~igo 1~
I DESCRIPTION OF PR~F~RRED EMBODI~ T:
.._ .. ... ._... . _ A filament type trimmer in accordance with the present invention is illustrated by way of example in the drawings as comprising a rotary cutting head 1 driven in the direction indicated by ~he arrow A in Fig. 3, by a motor 2 shown schemati-cally by way of exarnple as a single cylinder two-stroke cycle internal combustion engine having a drive shaft 30 The cutting head 1 is shown as comprising a circular housing 4 having a 'base portion 4a and a downwardly e~tending annular wall comprising a rlm portion 4b. The housing is conveniently molded of plastic material and is removably secured to the motor by an internall~
threaded metal bushing 5 which is screwed onto a threaded portion of the motor drive shaft 30 A filament storage spool 6 having a hub portion 6a and opposite flange portions 6b and 6c is rotatably mounted coaxially in the housing and is retained by a removable cap 7 having an internally threaded central hub portion which screws onto a threaded end portion of the bushing 5, The spool 6 normally rotates with the housing but is rotat-able relative to ~he housing in the direction indicated by the arrow B in Fig. 3 to feed out additional filament ~rom the spool from time-to-time.
A filament 8 is wound on the spool 6 in a direction opposite to the direction of rotation of the head 1 and an inner end of the filament is secured to the hub portion of the spool. The filament 8 is,for example,a monofllament of thermo-plastic material, selected for the characteristics o~ strength, toughness and abrasion resistance. An outer end portion 8a of the filament extends approximately tangentially from the spool 6 11;~979313 to and passes freely ou~ through an exit opening 9 provided in the rim portion 4b of the rotatin~ housing 4, The exit opening 9 is shown as comprising a bushing 10 set in an opening 11 in the rim portion 4b of the rotating housing 40 The bushing 10 is of hard abrasion resistant material having a low coefficient of friction with .... ,, , ~ , .
3~
respect -to the fi]ament 8. For example the bushing 10 may be of metal such as brass or stainless steel or it may be a hard abrasion resistant plastic. It is set firm1y in the opening 11 in the rim portion of the housing, for example by ultrasonic welding. As seen in Fig. 1, the bushing 10 is set with its axis in the cutting plane, i.e. a plane perpendicular to the axis of rotation of the cutting head 4 while, as seen in Fig. 3, the axis of the bushing 10 is inclined rearwardly with respect to a radius of the housing 4 wllich passes through the bushing. The angle of inclination is, for example about 30-45. When running free, the filament extend approximately radially from the housing as shown in solid lines in Fig. 3 and bears on the front of the bushing 10 which has a smooth rounded surface so as to reduce friction with the filament. When the filament strikes an obstacle, it is deflected rearwardly so as to extend approximately tangentially from the spool and straight through the exit opening without bearing on the bushing as illustrated in dotted lines. E~ence the impact load on the filament is taken in pure tension and the combina-tion of tension and bending at the exit opening is avoided. The bushing 10 has an internal diameter of a size to compensate for different coil radii caused by a full, empty or partially empty spool.
A portion 8a of the filament extends from the spool through the exit opening 9 after passing -through a guide tube 12. The -tube 12 is for example a tube of dead-soft aluminum which is originally a straight piece of tubing as shown in Fig. 2. The tubing has an internal diameter sl:ightly larger than the diameter of -the filament 8 so that the filament can be readily threaded through i-t. Before the spool 97~
with the filament wound thereon is placed in the housing 4, an outer end portion of the filament is threaded through the tube l~ and the tube is thereupon ben~ in the form shown in Fig. 3 so that i-t is wrapped par~rially around the spool and extends tangentially from the spool to the exit opening 9 when the spool is placed in the housiny. Preferably -the ~uide tube 12 is of such length that with a full spool it wraps approximately once around the spool as illuskrated in - FigO 3. 'rhe outer end of the guide tube 1~ is enlarged for example by fixing thereon a ferrule 13 so that it cannot pass out through the exit opening in the rim portion of the rotating housing. The guide tube 12 is sufficiently flexible that as the filament is used-up, the pull of centrifugal force on the ilament is sufficient to bend the tube and make it conform substantially to the outer coils of filament on the spool except for the tangential portion that extends to the exit opening 9. It has been found that the guide tube 12 avoids frictional rubbing of the outerrnost coil of filament on the spool with adjacent coils and thereby avoids melting of the filament and welding of the filament to itself.
Moreover, as the guide tube hugs the spool, it prevents entanglement of one coil o filament with ano-ther.
Instead of being formed of soft aluminum tubing, the guide tube 12 may be of other material which provides appropriate flexibility. For example the tubing may be formed o coiled wire with closely positioned successive convolutions. Instead of being seamless, -the tubing may be split along its ou-ter periphery to facilitate the threading of the filament through it. The heat conductivity of the tube contributes to avoiding welding.
'rhe spool ~ is normally locked with respect to the housing 4 so as to rotate with the housing. However, means is 7~
. . ~
provided for releasing the spool from time-to-time to permit a portion of the fi:lamellt to be unwound ~rom it by the pull of centrifugal force on the outer end por-tion 8a of the filament.
In the embodiment illustra-ted by way of example in Fig. 1, rotation of the filament spool 6 relative to the housing 4 is controlled by a mechanism which comprises a low speed slider 15 and a high speed slider 16. The sliders 15 and 16 are slidable in radially extending slots in the base portion 4a of the housing 4 immediately above the filament spool 6. The sliders 15 and 16 are biased radially inwardly by coil springs 17 and 1~ respectively. By reason of rotation of the housing 4 at high speed r centrifugal force acts on the sliders 15 and 16 50 as to move them radially outwardly against the bias oE the respective springs at predetermined speeds of rotationO The springs 17 and 18 are calibrated wi-th respect to the weights of the respective sliders so as to determine the rotational speed of the housing at which the sliders move outwardly by centrifugal force. The spring 18 of the slider 16 is s-tronger relative to the weight of the slider than the spring 17 of the slider 15 so that the low speed slider 15 will move radially outwardly at a lower speed than the high speed slider 16.
The low speed slider 15 is provided with a downwardly extending projection 15a which in the outer position of the slider is engageable with one or another of upwardly extending projections 19 provided on the upper flange 6b of the filament spool 6. The projections 19 are arranged in a circle concentric wi-th the axis of the spool and are spaced circumferentially.
3~3 For example three or four suc~ projections may be provided on ; the spool. The high speed slider 16 is similarly provided with a downwardly extending pro jection 16a which in the inner positîon of the slider is engageable with one another of the projections 19 on the spool. By way of example the springs 17 or 18 are calibrated so that when the cutting head 1 is rotating at a speed below 3000 rpm both sliders are in their inner position, at 3000 to 9000 rpm the lower speed slider 15 has moved to its outer position while the high speed slider 16 is still in its inner position and above 9000 rpm both sliders are in their outer position. It will be understood that difEerent speeds can be selected by suitable calibration of the springs with respect to the weights of the sliders. When the cutting head 1 is rotating at a normal operating speed, for example within the range of 3000 to 9000 rpm, the projection 16a of the high speed slider 16 engages one of the projections 19 on the filament spool so as to hold the spool against rotation relative to the casing. If the speed of rotation of the cutting head 1 increases above 9000 rpm (by reason of the projecting end portion 8a of the filament having become shorter and thereby reducing the load on the motor 2) the high speed slider 16 moves outwardly against the bias of its spring so as to disengage the respective projection 19 on the spool, thereby permitting the spool to be rotated by the pull of centrifugal force on the filament so as to unwind filament from the spool.
However, the projection 15a of the low speed slider is in the path of travel of the projec-tions 19 on the spool 6 so that the spool is permi-tted to rotate only un-til another of the projections on the spool engages the projection 15a of the low speed slider 15. Further rotation of the filamen-t spool relative to the cutting head is delayed un-til, for example by 3~
manual control of the motor, the speed o rotation of the cutting head is reduced to a speed below 3000 rpm idling speed.
Both of the sliders 15 and 16 are thereupon moved to their inner positions by the bias of the respective springs whereupon the projection 15a of the low speed slider is disengaged from the respective projection on the spool thereby permitting the spool to rotate until the next projec-tion on the spool engages the projection 16a of the high speed slider 16. This dela~ ln feeding additional filament avoids sudden increase in the length of the filament and corresponding increase in the cutting radius of the trimmer while the cutting head is rotating at high speed. Hence if the user is trimming close to a flower bed, possible damage to the flowers is avoided. As a trimmer of this kind is usually operated for only short periods of time between idling periods, the cycle of operation described above for restoring the normal length of the projecting end portion of the filament occurs automatically and without any special attention on the part of the operator.
As the exit opening provided in accordance with the present invention avoids the deliterious effec-t of combined axial load, bending and friction at the exit opening when the filamen-t strikes a relatively stationary object, the filament breakage which has heretofore been experienced is avoided.
Filament life is thereby greatly increased.
While a preferred embodiment of th~ invention is illustrated in the drawings and has been herein clescribed, it will be understood that variations and modifica-tions may be made and that the invention is hence in no way limited to the illustrated embodiment.
g
Claims (9)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a filament type trimmer, the combination of a rotatable housing having a rim portion, means for driving said housing in a selected direction of rotation, a filament storage spool rotatably mounted in said housing, a filament wound on said spool, exit means in said rim portion of the housing through which said filament extends in passing from said spool to the exterior of the housing, an end portion of said filament extending beyond said housing rim portion and constituting a cutting means of said trimmer, said exit means comprising a bushing having an aperture through which said filament extends, a flexible guide tube which wraps at least partially around said filament wound on said storage spool and extends tangentially to said bushing, said filament passing through said guide tube in going from said storage spool to said exit means, said aperture in said bushing having a central axis which is approximately aligned with an adjacent portion of said guide tube and having a smoothly curved front bearing surface, whereby said extending end portion of the filament when running free extends approximately radially from said housing so that said filament bears on and bends around said curved front bearing surface of said aperture, and when said extending end portion of the filament strikes an obstacle, it is deflected rearwardly relative to the housing so that said filament extends tangentially from said storage spool, through said guide tube and through said aperture in a substantial straight line free of flexing by engagement with said bushing.
2. The combination according to claim 1, in which the axis of said aperture of said bushing is disposed at an angle of 30° to 45° to a radius of said housing passing through said bushing.
3. The combination according to claim 2, in which said housing is of molded plastic material and said bushing is of hard, wear resistant low friction material set in said rim portion of said housing.
4. The combination according to claim 3, in which said bushing is ultrasonically welded to said rim portion of said housing.
5. The combination according to claim 1, in which a ferrule is fixed on the end of said guide tube adjacent said bushing to prevent said guide tube passing out through said aperture in said bushing.
6. The combination according to claim 1, in which said curved front bearing surface of said aperture of said bushing has an inner portion approximately aligned with an adjacent end portion of said guide tube, an outer portion approximately radial of said housing and a smoothly curved intermediate portion joining said inner portion with said outer portion.
7. The combination according to claim 6, in which said aperture of said bushing has a curved rear surface of shorter length than said curved front surface.
8. In a filament type trimmer, the combination of a rotatable housing comprising a circular base portion having at its periphery a downwardly extending annular wall comprising a rim portion, means for driving said housing in a selected direction of rotation, a filament storage spool rotatably mounted centrally in said housing, a filament wound on said spool in a direction opposite to the direction of rotation of said housing, a bushing of hard, low-friction material set in an opening extending through said rim portion of the housing, said bushing having an exit opening through which said filament extending tangentially from said spool freely passes to the exterior of said housing, an end portion of said filament extending beyond said housing rim portion and constituting a cutting means of said trimmer, said exit opening having a smoothly curved front bearing surface and a central axis which lies in a plane perpendicular to the axis of rotation of said housing and is inclined rearwardly with respect to a radius of said housing passing through said exit opening so as to be approximately in line with the filament extending tangentially from said spool to said exit opening, whereby said extending end portion of the filament when running free extends approximately radially from said housing so that said filament bears on and bends around said curved front bearing surface of said exit opening, and when said extending end portion of the filament strikes an obstacle, it is deflected rearwardly relative to the housing so that said filament extends tangentially from said storage spool to and through said exit opening in a substantially straight line free of flexing in passing through said exit opening.
9. A combination according to claim 8, in which the axis of said filament exit opening in said bushing is inclined at an angle of about 30°-45° to a radius of said housing passing through said bushing.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US92903678A | 1978-07-28 | 1978-07-28 | |
| US929,036 | 1978-07-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1097930A true CA1097930A (en) | 1981-03-24 |
Family
ID=25457219
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA330,345A Expired CA1097930A (en) | 1978-07-28 | 1979-06-22 | Filament type trimmer |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS5519100A (en) |
| CA (1) | CA1097930A (en) |
| DE (1) | DE2930469A1 (en) |
| FR (1) | FR2433278A1 (en) |
| IT (1) | IT1122290B (en) |
| SE (1) | SE438586B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB8330228D0 (en) * | 1983-11-11 | 1983-12-21 | Black & Decker Inc | Vegetation cutters |
| JPH0232018Y2 (en) * | 1986-05-24 | 1990-08-30 | ||
| JPS63300786A (en) * | 1987-05-30 | 1988-12-07 | 株式会社 共立 | Control system of pinball hole |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2372585B2 (en) * | 1971-12-13 | 1985-06-14 | Weed Eater | PLANT CUTTING APPARATUS |
| CA991835A (en) * | 1973-04-05 | 1976-06-29 | Weed Eaters | Rotary cutting assembly |
| JPS526617A (en) * | 1975-07-04 | 1977-01-19 | Shikutani Kk | Bush cleaner |
| US4062114A (en) * | 1976-05-07 | 1977-12-13 | Woodrow Wilson Luick | Vegetation cutting apparatus |
| US4134204A (en) * | 1976-06-01 | 1979-01-16 | Perdue Bennie G | Rotary flail cutter system |
| JPS5531855Y2 (en) * | 1976-06-26 | 1980-07-30 | ||
| CA1079075A (en) * | 1976-07-19 | 1980-06-10 | George C. Ballas | Rotary cutting assembly |
| JPS5311724A (en) * | 1976-07-21 | 1978-02-02 | Shikutani Kk | Bush cleaner |
| US4097991A (en) * | 1976-09-10 | 1978-07-04 | Proulx Raymond E | Rotary cutting head for mowers equipped with flexible cutting blades |
-
1979
- 1979-06-22 CA CA330,345A patent/CA1097930A/en not_active Expired
- 1979-06-27 SE SE7905638A patent/SE438586B/en not_active IP Right Cessation
- 1979-07-24 IT IT24592/79A patent/IT1122290B/en active
- 1979-07-26 FR FR7919284A patent/FR2433278A1/en active Granted
- 1979-07-27 JP JP9516879A patent/JPS5519100A/en active Granted
- 1979-07-27 DE DE19792930469 patent/DE2930469A1/en not_active Ceased
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5519100A (en) | 1980-02-09 |
| SE438586B (en) | 1985-04-29 |
| IT7924592A0 (en) | 1979-07-24 |
| FR2433278A1 (en) | 1980-03-14 |
| SE7905638L (en) | 1980-01-29 |
| IT1122290B (en) | 1986-04-23 |
| DE2930469A1 (en) | 1980-02-07 |
| JPS621684B2 (en) | 1987-01-14 |
| FR2433278B1 (en) | 1984-11-16 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |