Patent Application
20130283752
This application claims priority under 35 U.S.C. §119 to patent application no. EP12160082.9-1260, filed on Mar. 19, 2012 with the European Patent Office, the disclosure of which is incorporated herein by reference in its entirety.
This disclosure is concerned with a line trimmer or mower head. In particular it is concerned with a line trimmer or mower head having an automatic and/or manual line feed system with reduced tendency for cut and worn line to retract fully back into the spool housing. For the sake of convenience the term ‘line trimmer’ herein is intended to include within its scope a ‘mower head’ arrangement.
Line trimmers or mower heads are known for cutting grass and similar vegetation, which comprise at least one length of cutting cord (or ‘line’ herein) wound around a rotatable spool, which pays out one or more externally projecting lengths of line. Rapid rotation of the spool and line projecting therefrom, typically by electric or petrol motor applies a centrifugal load on the projecting line which becomes the cutting line to cut the grass or vegetation.
Trimmer line feed mechanisms are well known which permit the length of exposed cutting line to be increased when this part of the line breaks or wears below acceptable levels. Such paying out of line from its winding can be effected without replacing the line. In some versions of trimmer it may be effected automatically during use and/or manually by the operator as in ‘bump’ feeding.
For example the skilled reader is referred to the construction of line trimmers disclosed eg in W0-2007/032,043 and W0-2010/082,347.
Additionally, line trimmer spools are known with radiused or splayed exit guides for the external cutting line as in U.S. Pat. No. 7,111,403 and EP 1 585 380 whereas external cutting line exits are also known with other protective means in, for example, EP 1 942 717, EP 2 107 866, and U.S. Pat. No. 4,114,269.
In line trimmers of these latter types, the external line can still break or wear too close to the outer surface of the feed mechanism, whereupon the end of the line (or lines where more than one is present) can retract back inside the spool mechanism, which can prevent the spool line feed mechanism from being able properly to feed or pay out fresh line.
Similarly, there can be problems with automatic feed systems in which a minimum length of line needs to project beyond its housing, for that system to feed out new line. Should the line break at or wear down to a length shorter than this critical length, the automatic feed system is unable to feed out more line.
The present disclosure seeks to reduce the likelihood of occurrence of a major frustration currently suffered with manual “bump” and/or automatic line feed heads, namely line breakage or wear too close to the internal spool winding which renders the system unable to feed out. Typically in such situations the broken line retracts back into the spool chamber toward the spool winding, which creates even more problems for the user. The disclosure accordingly seeks to provide a line trimmer or mower head with a manual and/or automatic line feed system but wherein the cutting line is less likely to break too close to the spool winding and housing.
The disclosure further seeks to provide a line trimmer or mower head with a line feed mechanism, be it manual “bump” and/or fully automatic, which allows the spool of wound line within the head to unwind a little, thereby releasing line to replace that worn or broken, and wherein the remaining unworn/unbroken length of line is still able to generate enough tension in use to unwind the spool.
Essentially, according to this disclosure there is provided a line trimmer including a rotatable spool assembly of at least one feedable line, at least one primary wall member adjacent a periphery of said spool assembly, a guide passage extending generally radially away from said primary wall member, said guide passage being partly defined by a substantially radially extending first formation arranged to bear upon line extending through said guide passage, such that in use line located within said guide passage is restricted to a substantially radial orientation.
Further preferred and optional features of the disclosure may be found amongst the description herein.
In order that the disclosure may be illustrated, more easily appreciated and readily carried into effect by those skilled in this art, embodiments of line trimmers according to the disclosure will now be described purely by way of non-limiting example with reference to the accompanying drawings and in which:
Referring to the drawings and firstly to
Additionally, the spool housing comprises a pair of secondary wall members 10 each spaced apart from a primary wall member but connected thereto by first and second formations of the primary wall member which define a guide passage 7 within which line from the spool is located and can be fed out. The secondary wall members are similarly upstanding and part circular. As shown more clearly in
Opposite the first formation 11 is a second formation 12, 13 of a different profile and also serving partly to define the guide passage 7 which extends from an internal opening 9 to an external opening 8. The said second formation 12, 13 is partly radially extending and partly curved away (at 13) from its radially extending portion serving to widen the opening 8 relative to the width of the internal opening 9. In use, this guide passage formation is arranged to be ‘trailing’ with its profile therefore allowing some momentary flexing of the line in use against solid objects while still maintaining substantially radial guidance.
Conveniently the primary and secondary wall members 4, 10 including the first and second formations of the primary wall members (11 and 12, 13 respectively) can be of one-piece and preferably integral construction. In the illustrated arrangement there are two guide passages 7 so here a spool is used with two wound lines. The lines are to pass through the said guide passages 7.
The primary wall members 4 serve to provide primary protection to the rotatable spool and the wound line contained thereon, and assist in defining the internal opening 9 to the guide passage. The secondary wall members 10 serve to provide secondary protection to the internal working length of line and assist in defining the outer opening 8 of the guide passage. Accordingly it can be seen that primary wall members 4 are of sufficient height to enclose the full depth of the spool while secondary wall members 10 which enclose the line guide passage(s) may be of lesser height. Such lesser height could be such as to provide only a guide passage outlet depth of two line diameters.
Whilst the preferred embodiment of
Referring back to
In all embodiments while passing through the guide passage, the line is guided/restrained to be substantially radial.
The length of the guide passage providing working line guidance is set such that if the line does break off at the external opening of the guide passage, the line tension generated under centrifugal loading from the remaining line length remains adequate to rotate the spool and feed out more line. The spacing between inner and outer walls and hence length of the guide passage to achieve this is preferably 15-25 mm, more preferably 16-24 mm, most preferably 18-22 mm such as about 20 mm. The guidance/restraint provided by the guide passage prevents the remaining line momentarily from moving to too small a working radius with consequent loss of tension.
Even under abusive conditions, guidance provided by the guide passage prevents the user from breaking the line with too small a working radius and reliable line feed is therefore assured.
Embodiments of the present disclosure can resolve one of the major frustrations with either bump or automatic line feed heads, all of which currently can suffer from line breakage at their eyelet and then being unable to feed line out from the spool winding. Usually, in such circumstances what is left of the working line disappears back inside the spool chamber, which has tended to create even more problems for the user.
| Number | Date | Country | Kind |
|---|---|---|---|
| 12160082.9-1260 | Mar 2012 | EP | regional |
