GB1562948A - Powered cutting or stripping tools - Google Patents

Description

(54) POWERED CUTTING OR STRIPPING TOOLS (71) We, QUALCAST (LAWN MOWERS) LIMITED, a British Company of Sunnyhill Avenue, Sunnyhill, Derby, DE3 7JT, England, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a powered tool which is capable of trimming weeds, grass, or other vegetation without the use of conventional cutting blades, and which might also be used for other household, garden or agricultural purposes such as rust removal, descaling or other stripping operations.

More particularly, the invention concerns a tool which includes a rotary head provided with a coil of tough, flexible, preferably monofilament line, which rotates with the head at a sufficiently high speed that the free end of the coil is flung outwards to perform a flail-type cutting or stripping action.

In accordance with the present invention the driven rotary head of such a tool includes means guiding and supporting the free end of the coil in such a manner that, in use, the free end rotates in a working plane spaced from the coil. Preferably, the working plane is located so that it does not intersect the guiding and supporting means. In practice, therefore, the tool can be worked very close to the object being treated.

One embodiment of the invention is shown in the accompanying drawings in which: Fig. 1 is a sectional view through a rotary head of a device for cutting grass, Fig. 2 is a scrap plan view of the head shown in Fig. 1, Fig. 3 is a perspective view illustrating particularly the 'bayonet' coupling used in the device of Fig. 1, and Fig. 4 is a perspective view of the slotted drive head used in the device of Fig. 1.

Referring to these drawings, an annular coil of a tough, flexible, monofilament line 3 is carried on a spool 4, the spool being keyed to a stub 25 of a drive head 6 secured to the end of a drive shaft 2 driven by a motor 1. A free end 5 of the coil is with drawn from the spool to provide a flail-type cutting action during rotation of the head.

The free end is shown in the position it takes up when the head is rotating, and it can be seen that the cutting plane lies beneath the head 6.

The head 6 (Fig. 4) includes a flat annular surface 7 which supports the spool 4. The free end of the monofilament coil is with drawn from the head through one of a number of angularly spaced guide slots 9 in a downwardly and outwardly diverging annular portion 26 of the head so that in use, it is urged against the underside surface 10 around the bottom rim of the head. The back surface of the guide slot 9 is cut into the flat surface 7 and combines with the surface 10 to guide and support the free end of the monofilament. In use, therefore the cutting plane lies beneath the head 6.

Although the surface 10 is illustrated as being curved it might also be straight.

As shown most clearly in Figures-3 and 4, the head 6 is not secured directly to the shaft 2 but instead engages an insulative coupling 11 which is keyed to the shaft and is held in place by means of a washer 15 and shaft nut 13. The coupling 11 provides a "bayonet" type interlock, and includes two or more lugs 20 which pass through corresponding slots 21 to engage positively with projections 27 on the interior wall of the stub 25. A safety cap 14 (Fig. 1) over the nut 13 provides electrical insulation for electrically powered units. Alternatively, the nut may be shaped as shown in Fig. 3, the nut encasing the shaft and being made of - insulating material.

The spool 4 is housed within a resilient fan housing 16 having fins 23 including a flow of cooling air through the motor. The fan housing 16 is also keyed to the non circular drive shaft 2 for rotation there with.

Removal of the head 6 is easily accom plished by turning it relative to the "bayonet" coupling 11. This provides access to the spool 4 so that a used spool can be exchanged for a new full spool.

As the free end 5 of the monofilament line becomes worn or damaged, fresh line can be withdrawn from the spool merely by pulling the line up through its keyhole shaped guide slot and then pulling it round in the appropriate direction to the next guide slot. The flexibility of the circumferential wall of the fan housing 16 is sufficient to permit this movement of the coil end from one slot to another. At the same time, the lower edge of the fan housing normally retains the monofilament line within the slot 9 so that the line is held in its correct radial location.

Although the guide slots 9 are all shown extending substantially radially from the centre of the driving head, it is in fact preferred that the slots should be aligned with the natural trailing position of the monofilament 3 during rotation of the heads.

This reduces wear on the monofilament. The natural trailing position would depend on the mass of line, the speed of rotation and the load on the line. In general, the length of the slots should lie at an angle of between 15 and 45" to a radius of the head.

WHAT WE CLAIM IS:- 1. A powered tool including a rotary head provided with a coil of tough, flexible line which. in use, rotates with the head at a sufficiently high speed that a free end of the coil is flung outwards to perform a flail-type cutting or stripping action, the head including means guiding and supporting the free end of the coil in such a manner that, in use, the free end rotates in a plane spaced from the coil.

2. A powered garden tool for trimming weeds, grass or other vegetation, comprising a rotary head provided with a coil of tough, flexible line which, in use, rotates with the head at a sufficiently high speed that a free end of the coil is flung outwards to perform a flail-type cutting action, the head including means guiding and supporting the free end of the coil in such a manner that, in use, the free end rotates in a cutting plane spaced from the coil.

3. A powered garden tool according to claim 2, in which the cutting plane does not intersect the guiding and supporting means.

4. A tool according to claim 2 or 3 in which the coil forms part of a replaceable coil assembly releasably secured to a drive head, and in which the drive head is releasably interlocked with a drive shaft.

5. A tool according to claim 4 in which the releasable interlocking. means includes an insulative coupled keyed to the drive shaft for rotation therewith.

6. A tool according to claim 5 in which the drive head is releasably engaged with the insulative coupling by means of a "bayonet" type coupling.

7. A tool according to any one of the claims P6 in which the means guiding and supporting the free end of the coil includes a slot formed in a downwardly and outwardly diverging annular portion of the said drive head, the free end of the coil passing through the slot.

8. A tool according to claim 7 in which the slot is positioned so that the free end of the coil, after passing through the slot, bears against the inside rim of the said annular portion during rotation of the head at the said high speed.

9. A tool according to claim 8 in which the inside rim is curved.

10. A tool according to any one of the claims 7-9 in which the length of the slot is orientated at an angle of between 15 and 45" to a radius of the drive head.

11. A tool according to any one of the claims 7- 10 in which the slot is substantially keyhole-shaped, the narrow portion of the slot intercepting the rim of the drive head.

12. A tool according to any one of the claims 7-il including a plurality of the said slots spaced around the head.

13. A tool according to any one of the claims A 11 in which the coil assembly is surrounded by a resilient protective housing, the free end of the coil being retained in the slot by the bottom edge of the housing.

14. A tool according to claim 1 and substantially as herein described with refer ence to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (14)

**WARNING** start of CLMS field may overlap end of DESC **. coupling 11. This provides access to the spool 4 so that a used spool can be exchanged for a new full spool. As the free end 5 of the monofilament line becomes worn or damaged, fresh line can be withdrawn from the spool merely by pulling the line up through its keyhole shaped guide slot and then pulling it round in the appropriate direction to the next guide slot. The flexibility of the circumferential wall of the fan housing 16 is sufficient to permit this movement of the coil end from one slot to another. At the same time, the lower edge of the fan housing normally retains the monofilament line within the slot 9 so that the line is held in its correct radial location. Although the guide slots 9 are all shown extending substantially radially from the centre of the driving head, it is in fact preferred that the slots should be aligned with the natural trailing position of the monofilament 3 during rotation of the heads. This reduces wear on the monofilament. The natural trailing position would depend on the mass of line, the speed of rotation and the load on the line. In general, the length of the slots should lie at an angle of between 15 and 45" to a radius of the head. WHAT WE CLAIM IS:-

1. A powered tool including a rotary head provided with a coil of tough, flexible line which. in use, rotates with the head at a sufficiently high speed that a free end of the coil is flung outwards to perform a flail-type cutting or stripping action, the head including means guiding and supporting the free end of the coil in such a manner that, in use, the free end rotates in a plane spaced from the coil.

2. A powered garden tool for trimming weeds, grass or other vegetation, comprising a rotary head provided with a coil of tough, flexible line which, in use, rotates with the head at a sufficiently high speed that a free end of the coil is flung outwards to perform a flail-type cutting action, the head including means guiding and supporting the free end of the coil in such a manner that, in use, the free end rotates in a cutting plane spaced from the coil.

3. A powered garden tool according to claim 2, in which the cutting plane does not intersect the guiding and supporting means.

4. A tool according to claim 2 or 3 in which the coil forms part of a replaceable coil assembly releasably secured to a drive head, and in which the drive head is releasably interlocked with a drive shaft.

5. A tool according to claim 4 in which the releasable interlocking. means includes an insulative coupled keyed to the drive shaft for rotation therewith.

6. A tool according to claim 5 in which the drive head is releasably engaged with the insulative coupling by means of a "bayonet" type coupling.

7. A tool according to any one of the claims P6 in which the means guiding and supporting the free end of the coil includes a slot formed in a downwardly and outwardly diverging annular portion of the said drive head, the free end of the coil passing through the slot.

8. A tool according to claim 7 in which the slot is positioned so that the free end of the coil, after passing through the slot, bears against the inside rim of the said annular portion during rotation of the head at the said high speed.

9. A tool according to claim 8 in which the inside rim is curved.

10. A tool according to any one of the claims 7-9 in which the length of the slot is orientated at an angle of between 15 and 45" to a radius of the drive head.

11. A tool according to any one of the claims 7- 10 in which the slot is substantially keyhole-shaped, the narrow portion of the slot intercepting the rim of the drive head.

12. A tool according to any one of the claims 7-il including a plurality of the said slots spaced around the head.

13. A tool according to any one of the claims A 11 in which the coil assembly is surrounded by a resilient protective housing, the free end of the coil being retained in the slot by the bottom edge of the housing.

14. A tool according to claim 1 and substantially as herein described with refer ence to the accompanying drawings.