GB2115665A - Vegetation cutters - Google Patents

Abstract

A filament trimmer has body parts (1, 2) mated longitudinally to provide a shaft with a handle at one end and a motor housing (3, 4) at the other. The free edges of the parts have a mating tongue and groove connection. The motor housing (3, 4) is contoured internally to support a driving motor whose output shaft extends from the housing and is joined to a pool assembly (20). The spool assembly (20) comprises a spool carrier of inverted cuplike form and a spool detachably coupled together by a bayonet-type coupling. The spool carrier has resilient fingers stressed as the coupling engages, to maintain the coupling. <IMAGE>

Description

SPECIFICATION Improvements in or relating to vegetation cutters and components therefor This invention relates to vegetation cutters and components therefor and has particular reference to that class of cutters known as filament trimmers in which cutting is effected by a rapidly rotating length of filament which may be a monofilament.

In some forms of filament trimmer, the filament is wound on a spool driven by a motbr housed in a casing to which an operating handle is secured.

The handle has a stem one end of which is attached to the housing whilst the other end carries a grip by which the user grasps the handle to manipulate and guide the trimmer when in use.

Such a construction is relatively complicated and costly and it is an object of the present invention to simplify and so cheapen the construction without affecting its effectiveness.

According to the present invention, a filament cutter includes a body comprising mating parts which provide the handle, shaft and motor housing.

Preferably, the body comprises two mating parts.

In one embodiment, the handle is located at one end of the body and the motor housing at the other end. The motor housing may be of generally cylindrical form and of a greater diameter than the remainder of the body that is also of generally cylindrical form.

One of the mating parts may have free edges with a protruding tongue that locates in a groove formed in the free edges of the other of the mating parts.

The invention also envisages a spool assembly for a filament trimmer, the assembly comprising a spool carrier and a spool detachably secured to the carrier by means of a bayonet type coupling, the carrier or the spool having resilient means stressed as the spool is coupled to the carrier and which operate to maintain the coupling.

In one embodiment, the resilient means comprise fingers and the bayonet coupling comprises keys and ledges, the ledges including recesses into which the keys move when the coupling is completed and in which the keys are urged by resilient means.

The carrier preferabLy is a one-piece moulding of a plastics material and carries a heat sink.

By way of example only, an embodiment of the invention suitable for cutting lawns will now be described in greater detail with reference to the accompanying drawings of which: Fig. 1 is a composite front elevation of the embodiment with certain components removed, Fig. 2 is a composite side elevation of the embodiment of Fig. 1 with another component removed, Figs. 3, 4, 5, 6 and 7 are, respectively, sections on the lines Ill-Ill, IV--IV, V-V, VI--VI and VIl-VIl of Fig. 2 with internal components removed, Fig. 8 is a plan view of a spool carrier, Fig. 9 is a part section on the line IX-IX of Fig. 8, Fig. 10 is an underneath view of the spool carrier, Figs. 11 and 12 are, respectively, sections on the lines XlXl andXil--XII of Fig. 10, Fig. 13 is a plan view on a larger scale of a part of the spool carrier, Fig. 14 is a section on the line XIV--XIV of Fig. 13, Fig. 1 5 is a plan view on a larger scale of a seal, Fig. 1 6 is a section on the line XVl-XVl of Fig. 15, Fig. 1 7 is a plan view of a filament spool, Fig. 1 8 is an underneath view of the filament spool, Figs. 1 9 and 20 are, respectively, sections on the lines XIX--XIX and XX-XX of Fig. 18, Fig. 21 is a section through spool assembly on the line XXl-XXl of Fig. 22, Fig. 22 is an underneath view of the spool assembly, Fig. 23 is a plan view, partly in section, of a guard, and Fig. 24 is a section on the line XXIV--XXIV of Fig. 23.

As can be seen from Figs. 1 and 2, the body of the embodiment comprises two "clam-shell" portions 1, 2 joined longitudinally and having, at their lower ends, as seen in the drawings, portions 3, 4 of generally cylindrical bulbous form and, at their upper ends handle portions 5. The handle portions 5 lie almost normal to the main part of the length of the portions 1 , 2 whilst the portions 3,4 are slightly inclined as can be seen from Fig. 2. The inclinations to the main part of the length of the handle portion 5 and the portions 3, 4 are such that the embodiment can be conveniently and confortably held and guided by a user.

The portions 1, 2 are handed so that, when joined together as in Fig. 1 , they provide a cylindrical shaft portion with a handle at its top end and the cylindrical bulbous portions at the other end.

As can be seen from Figs. 3 and 4, the portion 1 is generally channel-shaped, the free edges of the portion being, as can be seen in Figs. 3 and 4, of stepped configuration both internally and externally thereby providing a tongue 6 located slightly off-centre of the thickened sides 7 of the portion.

The portion 3 is of substantially semi-circular transverse cross-section while the main lenth of the shaft has a more flattened transverse cross section as indicated in Figs. 5 and 6. A smoothly tapering portion 8 makes the change from the contour of the portion 3 to that of the main length of the shaft. The transverse cross section of the shaft as it approaches the handle portion 5 is rather more rounded but somewhat smaller as indicated in Fig. 7.

Portion 2 is generally similar except that the free edges are grooved longitudinally to receive the tongues 6 when the portions 1 and 2 are fitted together.

Both portions 1 and 2 have a series of internal bosses 9 spaced along the length of the portions.

Adjacent each boss 8 on the portion 1, the tongues 6 are thickened somewhat as can be seen from Fig. 6, there being corresponding cutaways in one of the walls bonding the groove in the portion 2 adjacent the bosses 9 in that portion.

The bosses 9 in portion 1 stand proud of the portion, the projecting part being of reduced wall thickness and have blind holes 9a whilst those in portion 2 have open-ended holes to allow the insertion of screws to secure the portions together as will be described below and to receive the projecting parts of the boss 9.

The portion 3 is contoured internally to support a driving motor as described in the Specification of our co-pending Patent Application entitled "Improvements in or relating to Electric Motors and Components Therefor".

The motor comprises end caps 10 and 11 supported upon the ends of the laminated cores 12 of the motor. Portion 3 has an internal groove 13 in which locate flanges 14 on end cap 11 and has an internal rib 1 5 that supports the motor in the vicinity of end cap 10.

The lower end (as seen in Fig. 2) of the portion 3 is strengthened by internal transverse walls forming box-like partitions 1 6 separated by a central gap 1 7 into which extends a boss 1 8 of end cap 11. The gap 17 has a semi-cylindrical part to receive the boss 1 8 and a narrower part extending from the semi-cylindrical part in which locates one of two projections on the end face of the end cap 11. In this way, the motor is securely held in position when the portions 1,2 are secured together. The boss 1 8 contains an internal bearing that supports the armature shaft 1 9 of the motor, the shaft projecting through the lower end of the portion 3 as can be seen in Fig. 2.Secured to the projecting end of the shaft in an assembly 20 comprising a filament spool and spool cover to be described in detail below.

The box-like partitions 1 6 include bosses 9 (Fig. 3) with blind bores 22. The outer ends of the bosses 9a are slightly proud of the outward faces of the partitions and are of reduced wall thickness as at 23.

The lower part of the portion 3 has apertures 24, these being separated by ridges 25 on the external surface of the portion as shown in Fig. 2.

The apertures 24 are exit holes for cooling air drawn over the motor during use by a fan 26 mounted upon the shaft 19 and drawing air in via further apertures 27 in the wall of the portion 8.

If necessary, or if required by local regulations, a chimney 28 indicated by dotted lines may be located within the portion 8 adjacent the apertures 27 to minimise the risk of water entering through the apertures 27. The chimney 28 is of inverted funnel-like form, the lower end being trapped between the edges of a groove 29 on the internal surface of the portion 8.

The motor is powered via a supply lead 30 extending upwardly from terminals on the end cap 15 to a connector block 31 within the shaft adjacent the upper end thereof and from which connector leads extend to a control switch 32 operable by a lever 33 pivotally mounted in the handle part 5. The lever 33 has a resilient tongue 34 against the action of which the lever 33 is depressed to operate the switch 32 to an "ON" position to energise the motor. The switch 32 is splash-proofed in a suitable manner to prevent ingress of moisture. Electrical power is supplied via a drop lead 35 locked in place by suitable labyringth partitions (not shown) in the handle portion 5.

The portion 2 is generally similar to portion 1 but, as indicated above, has a groove along its face edge to receive the tongue 6 on the portion 1 when the portions are abutted. The inner of the two walls defining the groove is cut away in the vicinity of the bosses in the portion to receive the thickened parts of the tongue 6.

The internal configuration of portion 4 is similar to that of portion 3, there being an internal groove similar to groove 13 and an internal rib corresponding with rib 1 5. Portion 4 also includes box-like partitions corresponding with partitions 16, this being separated by a gap as described above and has apertures 36 and 37 (Fig. 1) corresponding with apertures 24 and 27 respectively and an internal groove corresponding with groove 29.

The components referred to above are assembled by locating the motor in one of the portions 1,2, for example portion 1, as set out above and the electrical connections completed in the manner already explained. Portion 2 is then engaged with the portion 1, the groove on the free edge of the former receiving the tongue 6 on the free edge of the latter. Securing screws of which one is seen in Fig. 2 and referenced 38 are passed through the bosses in portion 2 used to secure the portions together to provide a rigid assembly.

Resistance to twisting along the length of the shaft is provided in part by the interengagement of the tongue and groove and in part by the interengagement of the thickened parts of the tongue 6 and the corresponding gaps in the inner wall of the walls defining the grooves.

The projecting parts of the bosses 9 fit into the bores of the corresponding bosses in portion 1.

There are also other bosses similar to bosses 9 at various other locations on portion 1 and these cooperate in the manner just described with correspondingly located bosses in portion 2. In Fig. 1 such other bosses have reference 9. The inter-engagement of the bosses as just described improves the security and rigidity of the assembled portions 1 and 2.

The assembly 20 referred to above includes a spool carrier 39 shown in more detail in Figs.

8-12. The carrier 39 is a one-piece moulding of plastics material for example "Acetal" and is of a shallow, inverted, cup-like form with a curved wall 40 slotted at four equi-spaced locations 41, the wall edges bounding the slots being rounded as indicated at 42 and of increased thickness. The roof 43 of the carrier has arcuate slots 44 from one end of each of which resilient fingers 45 incline downwardly into the carrier. Pips 46 are formed on the lower surfaces of the fingers 45 adjacent the free ends thereof. The fingers 45 are, of course, integrai parts of the carrier 39.

Also extending inwardly into the carrier 39 from the roof 43 is a central boss 47 with a central passage 48 opening through the roof 43.

The passage 48 has an internal ledge 49 separating the upper (as seen in Fig. 11) larger diameter part of the passage from the lower 'smaller diameter part. Located in the larger upper diameter part and seated upon the ledge 49 is the central boss 50 of a heat sink 51 shown in more detail in Figs. 13 and 14. The heat sink is of a iight metal for example magnesium or a light metal alloy and has sectors 52, 53 extending from the boss 50. Each sector has spaced arcuate upstanding fins 54, 55 between which are located holes 56 bevelled at their upper ends (as seen in Fig. 13). Each sector 52, 53 also has a peripheral, semi-circular cut-away 57.

The spool carrier 39 is moulded on to the heat sink 51 and during the moulding process plastics material extrudes through the holes 56 and thus bonds the heat sink and spool carrier together.

The boss 50 has a central bore 58 by means of which the heat sink and spool carrier are secured to the shaft 1 9 of the motor.

The roof 43 of the spool carrier also has further sector shaped apertures 59 inwardly of the slots 44 to allow the formation during the moulding of the spool carrier of ledges 60 (Fig. 12) in the boss 47 adjacent the roof 43. One end of each ledge 60 communicates with a longitudinal recess 61 in the outer surface of the boss 47.

The contour of one of the ledges 60 is shown in Fig. 9 and it will be observed that the ledge has a recess 60a.

To prevent the ingress into the interior of the spool carrier of foreign matter, the apertures 44 all covered by a seal 62 (Figs.15 and 16) of a plastics material, for example polypropylene. The seal has sectors 63, 64 sized to locate between the sectors 52, 53 of the heat sink 51. Each sector has holes 65 into which pips 66 on the upper surface of the roof 43 are a press fit to retain the seal in position. The seal also has a central hole 67 sized to permit the passage of the motor shaft 1 9.

Figs. 1 7-20 show a filament spool comprising a hollow boss 68 with spaced flanges 69, 70 between which filament is wound on to the spool.

The boss 68 has an end wall 71 with holes 72.

The periphery of the boss is ribbed as at 73.

The flange 69 has two keys 74 that extend into the hollow boss 68, and two hemi-spherical recesses 75. The flange 69 is also slotted radially as at 76.

The spool is wound with a length of filament F, the inner end being knotted or thickened and engaged in one of the slots 76 while the outer end is threaded through a hole 77 in the wall of a filament retainer ring 78 (Fig. 21). Fig. 21 also shows a finger grip 79 attached to the end wall 71 of the spool by means of the hooked prongs 80 which extend through the holes 72 in the end wall.

As can be seen from Figs. 21 and 22, the finger grip has a central domed portion 81 from which the hooked prongs 80 extend. The domed portion 81 is encircled by a flange 82 with flats 83.

The spool assembly is attached to the spool carrier by gripping the assembly by means of the flats 83 and inserting it into the carrier with the keys 74 located in the recesses 61 in boss 47 of the carrier. Movement is continued until the flange 69 abuts the resilient fingers 45 and moves them towards the roof of the carrier. It is then possible to rotate the spool assembly relatively to the spool carrier to engage the keys 74 in the recesses 60a of the ledge 60. Such engagement also brings the pips 46 on the fingers 45 to engage the recesses 75 to locate the spool assembly relatively to the carrier.

The keys 74 form, with the recesses 61 and the ledges 60 and recesses 60a a bayonet type attachment, the keys being maintained in the recesses 60a by the spring action of the fingers 45.

The free end of the filament is located in one of the slots 41 in the wall of the spool carrier, a suitable length of filament extending outwardly from the carrier.

To protect the user, a guard assembly 84 (Figs.

23 and 24) is fitted to the lower end of the portions 3 and 4.

The guard assembly has a collar portion 85 from which extends a guard portion 86 of quadrant shape with a peripheral flange 87. The collar portion 86 has an internal wall 88 that partially masks slots 89 between the collar portion 85 and the guard portion.86.

The guard portion 86 has an internal flange 90 adjacent the slots 89 which curges gently to an annular wall 91 with internal keys 92 that extend over part only of the inner circumference of the wall 91.

The leading edge of the flange 87 in the direction of rotation of the filament F when the cutter is in use, has an outwardly divergent slot 87a (Fig. 23) in the centre of which is secured a small knife blade 87b which operates, in the conventional manner to trim the operative part of the filament to a length which keeps that part within the guard. An extension 87a close to the slot deflects the severed length of filament away from the user.

The guard assembly is of two part construction, one part comprising the collar portion 85 and the other part the guard portion 86. The parts are locked together by a series of toothed prongs on the collar portion which locate in holes in the guard portion. One such toothed prong and its aperture are shown in Fig. 24 at 93 and 94 respectively.

To fit the guard assembly to the portions 3, 4, the latter are inserted into the collar portion 85 until the keys 92 meet slots giving access to grooves 94 (Fig. 2) at the lower end of the portions 3,4 after which partial rotation of the guard assembly with respect to the portions 3,4 engages the keys 92 in the grooves 94. A screw 95 secures the guard assembly to the portions 3,4.

It will be appreciated that the guard assembly is so mounted that the part 86 extends towards the user to protect him from inadvertent contact with the rapidly rotating filament.

The cutter is used in the wall known manner to trim grass and other vegetation.

In Fig. 24, part of the portions 3, 4 is shown and it will be observed that the apertures 24 are positioned adjacent the wall 88 which together with the flange 90 define a re-entrant path for air leaving the apertures 24 and exiting to atmosphere through the slots 89. This helps to prevent the ingress of water into the interior of the portions 3, 4.

Claims (20)

1. A filament trimmer having a body comprising mating parts which together provide the handle, shaft and driving motor housing of the trimmer.

2. A filament trimmer comprising first and second mating parts which together provide the handle, shaft and driving motor housing of the trimmer.

3. A filament trimmer comprising first and second mating parts which together provide a shaft, a handle at one end of the shaft, and, at the other end of the shaft, a housing for the driving motor of the trimmer.

4. A filament trimmer as claimed in claim 2 or 3 in which the parts mate along longitudinal junction lines.

5. A filament trimmer as claimed in claim 4 in which one of the mating parts has free edges with longitudinal protruding tongues, the other mating part having free edges with longitudinal grooves in which the tongues locate.

6. A filament trimmer as claimed in claim 5 in which the tongues include a series of spaced thickened portions, and the grooves a series of cooperating cut-aways for receiving the thickened portions.

7. A filament trimmer as claimed in claim 6 in which the thickened portions and cut-out are located adjacent internal co-operating bosses on the mating parts, the latter being secured together by means of fasteners passed through the locating bosses on one part and into the co-operating locating bosses on the other part.

8. A filament trimmer as claimed in claim 4, 5, 6 or 7 in which the motor housing is contoured internally to provide supports for the driving motor whose output shaft extends through the bottom end of the housing.

9. A filament trimmer as claimed in claim 8 in which the housing is formed, adjacent the bottom end with exit holes for cooling air through over the motor, the cooling air entering the housing via inlet holes formed in the mating parts in the vicinity of the junction between the shaft and the motor housing.

10. A filament trimmer as claimed in claim 9 in which the motor housing has a slotted external peripheral groove adjacent its lower end.

11. A filament trimmer as claimed in claim 10 and including a filament guard having a collar portion with keys adapted to pass through the slots in the peripheral groove prior to engaging the latter.

12. A spool assembly for a filament trimmer comprising a spool carrier and a spool carrying a length of filament, the spool being detachably secured to the carrier by means of a bayonet type coupling, the carrier or the spool having resilient means stressed as the spool is coupled to the carrier and operable to maintain the coupling.

13. A spool assembly as claimed in claim 12 in which the carrier is of inverted, cup-like form whose side wall is slotted at equi-spaced locations and from whose base extends a boss positioned centrally of the side wall, the boss having external longitudinal grooves leading to peripheral passageways, and in which the spool has a bore with inwardly extending keys adapted to engage the grooves and to enter the passageways.

14. A spool assembly as claimed in claim 13 in which the carrier includes a roof with opposed arcuate slots in each of which is located a resilient finger that inclines downwardly from the roof, the arrangement being such that as the keys approach the passageways, the fingers are stressed by the spool and flex to allow the keys to enter the passageways.

15. A spool assembly as claimed in any one of claims 12-14 in which the spool incorporates a finger grip to facilitate coupling and uncoupling of the spool to and from the carrier.

1 6. A spool assembly as claimed in any one of claims 12-1 5 in which the carrier incorporates a heat sink by means of which the carrier is secured to the output shaft of a driving motor.

1 7. A filament trimmer as claimed in any one of claims 1-11 1 and including a spool assembly as claimed in any one of claims 12-16.

1 8. A filament trimmer substantially as herein described with reference to and as illustrated by Figs. 1-7 and 22 and 23 of the accompanying drawings.

1 9. A filament trimmer substantially as herein described with reference to and as illustrated by the accompanying drawings.

20. A spool assembly as herein described with reference to and as illustrated by Figs. 8-21 of the accompanying drawings.