WO2012083353A1

WO2012083353A1 - Device for dispensing flexible trimmer line

Info

Publication number: WO2012083353A1
Application number: PCT/AU2011/001642
Authority: WO
Inventors: Yoa Fang DENG
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-12-20
Filing date: 2011-12-20
Publication date: 2012-06-28
Anticipated expiration: 2013-06-20

Abstract

A device (40) for dispensing trimmer line (70) from a rotary trimmer head or brushcutter has a carriage assembly (42) having a line retention mechanism (50) for securing a trimmer line (70) to the line retention mechanism (50) in releasable manner, the carriage assembly (42) arranged for travelling along a hub member (26) of the trimmer head (14) between first and second positions. A line feed actuator in the form of a plunger rod (26) selectively displaces the carriage (42) from the first position towards the second position. A carriage return arrangement in the form of a helical spring (44) operates in conjunction with the line feed actuator (26) for returning the carriage assembly (42) to the first position. The line retention mechanism (50) is arranged to secure the trimmer line (70) at the carriage assembly (42) in the first position and as the carriage assembly (42) travels towards the second position, but allow the trimmer line (70) to slip with respect to the carriage assembly (42) as the carriage assembly (42) returns to the first position. FIG. 4

Description

DEVICE FOR DISPENSING FLEXIBLE TRIMMER LINE

FIELD OF THE INVENTION

The present invention relates to a trimmer head for a rotary trimmer.

BACKGROUND TO THE INVENTION

A flexible line rotary trimmer, otherwise more commonly referred to as a brushcutter, is a power tool that uses a flexible line instead of an edged blade for cutting grass or other vegetation. The rotary trimmer generally comprises a trimmer head at one end of an elongated shaft, and a power plant in the form of a small two-stroke engine at the other end of the shaft. Electric line trimmers also exist, but are less common.

The trimmer head can carry one or more spools of flexible cutting lines, each having an exposed length projecting outwards from the trimmer head. In operation, a motor drives a rotation of the trimmer head, creating a centrifugal effect which causes the trimmer line to project radially from the trimmer head as it spins. The trimmer line's resilience and its high velocity spinning enables it to cut and sever grass.

The trimmer line is typically made of a resilient monofilament line comprising materials such as nylon, plastics or polymers. After repeated use, the exposed trimmer line becomes worn and may break, consequently requiring replacement. This is done by cutting off and disposing of the used line segment, and dispensing an upstream line segment from upstream, thereby exposing a fresh new line length ready for use. The line length may also be varied to expose a longer or shorter line length, depending on use requirements and conditions.

Existing trimmer heads have several drawbacks. Manual feed trimmer heads require removal of the trimmer head to allow manual manipulation of the trimmer line relative to the trimmer head each time additional cutting line is required. This is time consuming and unwieldy. Bump-feed type trimmer heads use a mechanism which dispenses a length of fresh line, when the user taps the bottom of the trimmer head on the ground. The length dispensed is usually predetermined and the user does not have control over it. As such, the user may need to tap a number of times and afterwards cut the exposed line to desired length, resulting in additional work and waste of materials. Other bump-feed trimmer heads require the trimmer head to be spinning and use the centrifugal force to pay out additional cutting line. Similarly, this is difficult to control and results in additional work and material wastage. Further, the trimmer lines extending out from the bump-feed type trimmer heads are at a distance above the ground, to provide space for the bottom 'tapper'. This causes inconvenience for the user as it is difficult to trim grass to a shorter length, and the tap mechanism may be unintentionally triggered when attempting to do so.

Additionally, with existing devices, loading of the trimmer line into the trimmer head is a cumbersome and time consuming task, with some trimmer heads having complicated threading arrangements. Care needs to be taken to avoid crossing or tangling of the lines within the trimmer head, which would interfere with the pay out of fresh line. Crossing and tangling of the trimmer lines may also occur during trimmer head use when it spins at a high velocity.

It is an object of the present invention to provide a device for a flexible line rotary trimmer with improved operability and which enables a user to better adjust and extend a length of trimmer line.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided a device for dispensing trimmer line from a rotary trimmer head, the device comprising: a carriage assembly having a line retention mechanism for securing a trimmer line to the line retention mechanism in releasable manner, the carriage assembly arranged for travelling along a hub member of the trimmer head between first and second positions; a line feed actuator for selectively displacing the carriage assembly from the first position towards the second position; and a carriage return arrangement operating in conjunction with the line feed actuator for returning the carriage assembly to the first position; wherein the line retention mechanism is arranged to secure the trimmer line at the carriage assembly in the first position and as the carriage assembly travels towards the second position, but allow the trimmer line to slip with respect to the carriage assembly as the carriage assembly returns to the first position. In one embodiment, the line retention mechanism includes a clamping arm pivoted at the carriage assembly to releasably clamp the trimmer line against a clamping counter surface for the trimmer line at the carriage assembly. The clamping arm may be biased into a normally closed clamping position in which the trimmer line is secured against displacement at the counter surface. The trimmer line is therefore retained by the clamping arm and the counter surface when the carriage assembly is stationary and as the carriage assembly moves towards the second position. Advantageously, with this arrangement, movement of the trimmer line backwards upstream the line is also limited.

The device may further include a retention mechanism release arranged to pivot the clamping arm into a position in which the trimmer line is released for movement relative to the carriage assembly as the carriage assembly reaches or is at the second position. This advantageously provides an 'unclamping' which releases the retention of the trimmer line, and sets the clamping arm in an 'open position' as the carriage return travels to the first position. For example, the retention mechanism release may include a release lever extending from the clamping arm at its pivot, and an abutment member at the hub disposed to engage with the release lever. The clamping arm thereby pivots away from its normally closed clamping position during movement of the carriage assembly as the latter reaches the second position.

In one embodiment, the carriage assembly may include a plate-like central member and at least one spoke member extending radially from the central member, the spoke member including a flanged end providing a counter clamping surface for the trimmer line and an aperture located adjacent to the flanged end for threading through the trimmer line. The clamping arm may be pivotally mounted to the spoke arm such that a terminal end of the clamping arm pivots toward the flanged end for engaging and retaining the trimmer line and away from the flanged end for disengaging and releasing the trimmer line.

The terminal end of the clamping arm may have corrugated ridges, preferably in form of unidirectional serrated teeth. The terminal end of the retention arm may also be channel shaped for guiding the trimmer line against lateral movement at the clamping arm. Advantageously, this provides an enhanced and more secure retention of the trimmer line by the clamping arm. In one embodiment, the device further includes a trimmer line guide member located upstream from the first position at the hub and downstream of a trimmer line storage, the guide member having a guiding channel through which the trimmer line is threaded and at which it is guided upstream of the carriage. Advantageously, the guiding channel provides a firmer and steadier line feed to the device. Further, the guiding channel assists in guiding the trimmer line as it is fed and retained to move towards the second position; and provides an obstruction to any movement of the trimmer line upstream towards the trimmer line storage. For example, the guiding channel may include an arrangement for holding the threaded trimmer line against the guiding channel wall to restrict reverse movement of the trimmer line in an upstream direction.

In one embodiment, the carriage return includes a compression spring arranged to be tensioned by the carriage as it moves from the first to the second position and to bias the carriage towards the first position. Therefore, when the line feed actuating force is removed, the carriage assembly automatically returns to the first position as directed by the biasing of the compression spring.

According to another aspect of the present invention, there is provided a rotary trimmer head for use in flexible-line rotary trimmers, including: a housing with at least one compartment at a peripheral location of the housing for storing a spool of trimmer line; a device for adjusting and fixing the length of a trimmer line as previously described, the device being located within the housing; and a hub member located about a rotation axis of the trimmer head at a central location within the housing, wherein the carriage of the trimmer line adjusting and fixing device is located for travel between the first and second position along and at the hub member, and wherein the housing has a bottom wall with at least one through hole located radially inward from the peripheral compartment and arranged to thread a free end of trimmer line supplied via the carriage such as to deploy an extendable, but otherwise fixed length of trimmer line from the housing for use in trimming.

In one embodiment, the hub member is a hollow cylindrical member with a peripheral wall having at least one guiding slot extending along the hub member from a free end thereof towards the bottom wall of the housing, and wherein the carriage of the trimmer line adjusting and fixing device includes a circular, plate- like central member mounted for travel within the hollow hub member and at least one spoke member extending radially from the central member and through the guiding slot, the spoke member including a flanged end providing the counter clamping surface for the trimmer line and an aperture located adjacent to the flanged end for threading the trimmer line at the carriage assembly.

The clamping arm of the trimmer line adjusting and fixing device may be pivotally mounted to the spoke arm such that a terminal end of the clamping arm pivots toward the flanged end for engaging and retaining the trimmer line and away from the flanged end for disengaging and releasing the trimmer line.

In one embodiment, the trimmer head further includes a trimmer line guide member secured to an upper free terminal end of the hub member and providing an upper travel stop for the carriage assembly at the first position at the hub, the line guide member having a guiding orifice formed at a radially outward end of a guide arm through which the trimmer line can be threaded and at which it is guided upstream of the carriage assembly, the guiding orifice and the carriage aperture being preferentially arranged co-axially. Advantageously, the trimmer line guide member acts as an upper travel stop as well as providing a direct and firm line feed to the carriage aperture. Further, the guiding orifice assists in guiding the trimmer line as it is fed and retained to move towards the second position; and provides an obstruction to any movement of the trimmer line upstream.

In one embodiment, the peripheral hub wall includes at an outer face thereof at least one protrusion arranged to cooperate with a release lever extending from the clamping arm of the trimmer line retention mechanism, such as to pivot the clamping arm away from its normally closed clamping position during movement of the carriage assembly as the latter reaches the second position near the base of the hub member at the housing bottom. Advantageously, this provides an 'unclamping' which releases the retention of the trimmer line, and sets the clamping arm in an 'open position' as the carriage return travels to the first position.

In one embodiment, the line feed actuator for selectively displacing the carriage assembly of the trimmer line adjusting and fixing device may be a plunger rod operatively arranged to engage the central member of the carriage assembly and extend through an upper access opening in the housing. The plunger may be operated external to the trimmer head by applying a pressure to the plunger to drive it through the upper access opening. The carriage return arrangement for returning the carriage assembly from the second to the first position may include a helical compression spring located within the hollow hub member, the spring being operative on the circular, plate-like central member of the carriage such as to bias the carriage towards the first position in which it abuts on the trimmer line guide member at the terminal end of the hub member and allow compression and reactive force exerted by the line feed actuator (rod) during travel of the carriage from the first to the second position.

In one embodiment, the housing includes at least one radially extending channel recessed into an outer face of its bottom wall, with the at least one through hole at the bottom running into the channel such that a free end of trimmer line supplied from the radially outwards located trimmer line spool storage compartment via the radially inwards located carriage assembly and threaded past the through hole is deployed radially outwardly from the housing bottom in an extendable, but otherwise fixed length. Near the radially centre of the housing, the free end of the trimmer line travels in a top-down manner, through the carriage and threads through the hole. After which, it extends outwards radially from the centre. Advantageously, this arrangement provides simpler line feed which is steadier and more secure, and resists movement of the trimmer line backwards upstream. Further, in this arrangement the trimmer line exits the housing at the bottom close to the radially centre, and extends radially outwards along the bottom. As the trimmer line extends radially out at generally the same plane as the bottom of the trimmer head, the trimmer line is thus able to reach and cut a grass height at a distance close to the ground.

In one embodiment, the housing has three of said trimmer line spool storage compartments disposed equidistantly and radially about the rotation axis of the trimmer head, each compartment associated with a respective one of three of said radially extending channels which are located on the outward bottom face of the housing. The carriage assembly of the trimmer line dispensing device has three of said radial arms with line retention mechanisms arranged for securing to the carriage in releasable manner a respective one of three trimmer lines supplied from the trimmer line pool storage compartments. The carriage is disposed for travel along the hub member of the trimmer head between the first and second positions along the extension of the hub. The overall arrangement being such that equal lengths of trimmer line from each compartment are deployed and fixed upon the line feed actuator causing displacement of the carriage from the first position to the second position, and the lengths of trimmer line are secured against displacement at the carriage after it has returned into the first position. The trimmer line spool storage compartments may be detachable and replaceable, allowing easier exchange and reload of new trimmer line spools.

A preferred embodiment of the invention, as well as optional and preferred features, will be described with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a schematic, perspective view of a trimmer head attached to a shaft of a flexible line rotary trimmer, including a line feed actuator engaged with the trimmer head, according to one embodiment of the invention;

Figures 2a and 2b show a front and side view, respectively, of a detail of the line feed actuator of Figure 1 ;

Figures 3a and 3b show schematic longitudinal sections of the trimmer head of Figure 1 , illustrating an operation of the device for adjusting and fixing the length of a trimmer line inside a trimmer head, according to one embodiment of the invention;

Figure 4 shows a schematic disassembled view of the trimmer head of Figure 1 ;

Figures 5a and 5b show detailed schematic views of components of the line feed actuator with a device for adjusting and fixing the length of the trimmer line, as used in the trimmer head of Figure 1 ;

Figure 6a shows a schematic partial side view of the trimmer line retention mechanism of the device for adjusting and fixing the length of a trimmer line of Figure 5a;

Figure 6b shows a partial top view of the clamping arm of the trimmer line retention mechanism shown in Figure 6a engaging a trimmer line; Figure 6c shows a schematic end view of the trimmer line retention mechanism shown in Figure 6a;

Figure 7a shows a perspective view of a trimmer line guide member of the device for adjusting and fixing the length of a trimmer line of Figure 4;

Figure 7b shows a top view of the guide member shown in Figure 7a;

Figure 7c shows a schematic partial cross section side view of a modified embodiment of the guide arm of the guide member shown in Figure 7a;

Figure 8a shows a perspective view of the trimmer head housing of Figure

4;

Figure 8b shows another schematic assembly view of the trimmer head similar to Figure 4, but with one trimmer line spool removed;

Figure 8c shows a top view of the trimmer head housing shown in Figure 8a; and

Figure 8d shows a bottom view of the trimmer head housing shown in Figure 8a.

DESCRIPTION OF PREFERRED EMBODIMENT

Figure 1 shows a bottom portion of a flexible line rotary trimmer 10, having a main shaft 12 connected to a trimmer head 14. To operate the rotary trimmer 10, a motor (not shown) drives a spinning shaft gear 11 A which in turn drives a trimmer head gear 11 B, causing the trimmer head 14 to rotate and spin at a high velocity. As this happens, the free end of trimmer lines 20 extends radially outwards and spins with the trimmer head to create a plane region which slices and cuts grass or vegetation that intersects with the plane region.

The trimmer head has an enclosed housing with holes 18 at the bottom of the housing 16, through which the free ends of the trimmer lines 20 extend out. The bottom of the housing 16 is detachable from its lid 22 for loading and unloading of trimmer line coils. On the lid 22 is an upper access opening 24 through which a plunger rod 26 extends into the trimmer head 14 to engage a device for adjusting and fixing the length of the trimmer line inside the trimmer head 14. Integral with or attached to the plunger rod 26 is a roller 28 having on its circumference a channel in which cord 32 is engaged as the roller 28 rotates. The cord 32 generally extends along the main shaft 12 and is, as illustrated, threaded through a cord attachment 34. In this arrangement, by pulling on the cord 32, the cord 32 threads through the cord attachment point 34 and applies a pressure to the top of the plunger rod 26. This pressure causes the plunger rod 26 to be depressed to extend into the trimmer head 14 and engage a device inside the trimmer head 14 for extending the exposed length of the trimmer line 20. The plunger rod 26 is further connected to a spring 30 which biases against the depression pressure supplied by the cord 32. Consequently, pulling the cord 32 depresses the plunger rod 26 downwards and, as the pulling force is released, the spring 30 returns the plunger rod 26 upwards to its original position. Alternatively, the plunger rod 26 may be directly operated by applying a direct manual downward pressure force, without using the cord 32. The movement of the plunger rod 26 actuates a trimmer line length adjustment device inside the trimmer head 14 and provides a simple way of operating the device from external to the trimmer head, without having to remove or detach the trimmer head. Also, by controlling how far the plunger rod 26 is depressed, the extension of the trimmer line length may be controlled in a simple manner.

In an alternative embodiment, the assembly of the cord 32 and plunger rod 26 may be integrated into the main shaft 12, instead of being attached to it as shown in Figure 1.

Figures 2a and 2b show in more detail the plunger rod 26 and its roller 28, the top part of the channelled roller 28 being engaged by a cord 32.

Figures 3a and 3b serve to illustrate the operation of a device 40 for adjusting and fixing, or dispensing, a length of the trimmer line. The assembly of the device 40 is shown in more detail in Figure 4. As shown, the plunger rod 26 extends into the trimmer head 14 via an upper access opening 24. Furthermore, the plunger rod 26 extends through an opening 39 of a trimmer line guide member 38 to engage with a trimmer line carriage assembly 42, referred to herein as carriage 42. The trimmer line carriage 42 sits on a carriage return arrangement 44, being a helical spring 44 which biases the carriage 42 against the pressure force of the plunger rod 26. In Figure 3a, the carriage 42 is at a first position to receive the plunger rod 26. In Figure 3b, the plunger rod 26 depresses the carriage 42 to its second position. When the plunger rod 26 is released and the depression force is removed, the helical spring 44 bias returns the carriage 42 to the first position depicted in Figure 3a.

On the periphery of the carriage 42 is a trimmer line retention mechanism 50 for releasably securing a trimmer line 70 to this retention mechanism 50. This feature will be described in detail below. Briefly, the free end of a trimmer line coil 36 is threaded through a guiding channel 46 of the guide member 38 and further through the aperture 56 of the carriage 42, and exits the housing 16 at the bottom via holes 18 to expose a length of trimmer line 20 for use in cutting grass (see Figures 8b and 8d also). At the first position and/or during carriage movement from the first position to the second position, the retention mechanism 50 engages and secures the trimmer line 70. At the second position and/or as the carriage 42 returns to the first position, the retention mechanism 50 releases the trimmer line 70 to allow it to slip with respect to the carriage. Therefore, the retention mechanism 50 engages and holds the trimmer line 70, carries the trimmer line 70 with it as the carriage 42 moves downwards, and releases the trimmer line 70 when the carriage moves upwards to engage and hold a different segment of the trimmer line. The plunger rod 26 functions as a line feed actuator, causing the trimmer line 70 to be pulled downwards and exit the housing 16 via holes 18 at the bottom to feed out and expose a length of the trimmer line 20. The release of the depression force and upward movement of the plunger rod 26 allows the helical spring 44 to return the carriage 42 to the first position. Whilst doing so, the retention mechanism 50 releases the trimmer line 70 and the trimmer line slips with respect to the upward movement of the carriage 42. Further adjustment and extension of the trimmer line length may be attained by repeating the above process and actuating the plunger rod 26.

Referring to Figures 5a and 5b, the plunger rod 26 is shown engaging the device 40 for adjusting and fixing the length of the trimmer line. In one operating mode, the trimmer line length may be extended when the trimmer head 14 is spinning at a high velocity. To reduce excess heating or damage, the plunger rod 26 may be provided with a ball bearing 27 at its contact end which engages the spinning carriage 42 (caused by the spinning trimmer head 14). The contacting surface of the carriage 42 may also have a corresponding indentation 43 to better receive the plunger rod 26 and avoid inadvertent slippage. Referring back to Figure 4, the plunger rod 26 extends through an opening 39 of the guide member 38. The guide member 38 has clips 52 which allow the guide member 38 to sit stably upon the top of a hub member 48. The guide member 38 may also function as an upper travel stop for the carriage 42, limiting the carriage 42 to travel only as far upwards as to the first position. The guide member 38 has guide arms 54 with a guiding channel/orifice 46 formed at a radially outward end of the guide arm 54. The guiding channel 46 of the three guide arms 54 may be arranged to be coaxially aligned to apertures 56 of the carriage to allow direct top-down threading through of the trimmer line 70. Figures 7a - 7c show more details of the guide member 38. Referring to Figure 7c, an arrangement 58 is provided, having a cavity 57 adjacent to the guiding channel 46 and a spring 58 provided inside the cavity 57. The spring 58 abuts the trimmer line 70 threaded through the guiding channel 46 to hold the line 70 against the wall of the guiding channel 46. The spring 58 therefore restrains and restricts any undesired reverse movement of the trimmer line 70 upwards and upstream back towards the trimmer coil storage 36.

Referring back to Figure 4, the hub member 48 is shown as a hollow cylindrical member with a peripheral wall 64. The peripheral wall 64 has three segments, divided by the guiding slots 62 which extend along the wall 64 downwards towards the bottom of the housing 16. The carriage 42 has a central plate 58 and spokes 60 extending radially from it through the guiding slots 62 of the hub member 48. The carriage 42 travels between the first and second positions along the hub member 48 and moves relative to the guide member 38. Protrusions 66 are provided on the peripheral wall 64, and are adapted to engage with a release lever 68 of the trimmer line retention mechanism 50 shown in further detail in Figure 6a. Details of the trimmer line retention mechanism 50 and its operation will now be described.

Figures 3a, 3b depict the operation of the device 40; Figure 4 provides a corresponding assembly view; and Figures 6a to 6c show in more detail the trimmer line retention mechanism 50. As shown, the retention mechanism 50 releasably retains a trimmer line 70 which extends from the spool 36 and threads through aperture 56 located on spoke 60 of the carriage 42. Figure 6a shows a side view of the retention mechanism 50. The retention mechanism includes a clamping arm 72 pivotally attached to the spoke 60 at pivot 74. The clamping arm 72 has a terminal end 76 releasably clamping the trimmer line 70 against a clamping counter surface 78 of a flange end 80 of the spoke 60. The terminal end 76 of the clamping arm 72 is biased to pivot towards the trimmer line 70 into a normally closed clamping position in which the trimmer line 70 is secured against displacement at the counter surface 78. A spring 82 is attached to the clamping arm 72 and the spoke 60, which assists in biasing the clamping arm 72 towards a closed clamping position when the carriage 42 is stationary. The terminal end 76 is provided with corrugated ridges, preferably unidirectional serrated teeth 84, which assists in the clamping and retention of the trimmer line 70 as the carriage 42 moves downwards from the first position towards the second position. The serrated teeth 84 also allow for slippage of the trimmer line 70 between the terminal end 76 and the counter surface 78, as the carriage 42 moves upwards and returns to the first position. Shown in Figure 6b, the terminal end 76 is channel shaped to improve clamping and line retention, and assists guiding the trimmer line 70 against lateral movement.

Provided on the other side of the pivot 74 is a release lever 68 which engages with protrusions 66 to pivot the clamping arm 72 towards the closed clamping position (at the first position) for clamping and line retention; or pivot away from the closed clamping position (at the second position) such that the trimmer line 70 is released for movement (slip) relative to the carriage 42.

Figures 3a, 3b show how an actuation of the plunger rod 26 engages the central plate 58 of the carriage 42 and causes the carriage 42 to move downwards. As this happens, the clamping arm 72 retains the trimmer line 70 against the counter surface 78 and pulls the trimmer line 70 along together with its downward movement from the first position towards the second position. If the force from the plunger rod 26 is released, the spring 44 causes the carriage 42 to return to the first position, and as this happens the clamping arm 72 releases the trimmer line 70 and allows the line 70 to slip with respect to the upward movement of the carriage 42 thereby allowing the carriage 42 to return to its first or initial position to dispense further trimmer line 70 by repeated operation of the line feed actuator as described herein. Accordingly, the trimmer line 20 is fed outwards in a unidirectional manner at the bottom, and is controlled by the amount of line feed actuation of the plunger rod 26. Preferably, during line feed, the carriage 42 is caused to move a full length to reach the second position at the bottom. When the carriage 42 reaches the second position (bottom), the release lever 68 engages a bottom protrusion 66, shown in Figures 3a and 3b as an abutment 66B. The engagement of the release lever 68 and the abutment 66B pivots the clamping arm 72 away from the closed clamping position and assists in releasing the trimmer line 70. When the line feed actuation force is removed, the carriage 42 moves and returns to the first position at the top. Whilst doing so, the trimmer line 70 slips through the aperture 56 and between the terminal end 76 and counter surface 78, with respect to the upward movement of the carriage 42. When the carriage 42 reaches the first position at the top, the lever 68 engages a top protrusion 66A, causing the clamping arm 72 to pivot towards the closed clamping position to retain the trimmer line 70 at a upstream location of the trimmer line to the previous clamping location.

Figures 8a - 8c show the trimmer head housing 16 having three compartments 86 located adjacent the hub 48. Trimmer coil spools 36 are provided in each compartment 86 and the free end of the trimmer line 70 is supplied from the trimmer head housing 16 to the carriage 42. As shown, the trimmer line spools 36 are compartmentalised and stored, with each compartment 36 being detachable and replaceable. This provides a simple means for removing and reloading trimmer line spools 36 to replenish used trimmer line stock.

The trimmer line 70 is threaded through the aperture 56 of the carriage from the top, extending downwards to the bottom of the housing 16, and further threaded through a hole 18 located at the bottom to exit the housing 16. After exiting the hole 18, the trimmer line 70 runs along a radial channel 88 to expose a length of trimmer line 20 for use in cutting grass. The exposed trimmer line 20 extends radially outwards generally along the same plane as the bottom face of the trimmer head, thus enabling the line 20 to reach and cut grass at height close to the ground. In operation, as the trimmer head spins at a high velocity, the centrifugal force from the spinning may also assist the retention mechanism 50 to more firmly secure the trimmer line.

Claims

1 . A device for dispensing trimmer line from a rotary trimmer head, the device comprising:

a carriage assembly having a line retention mechanism for securing a trimmer line to the line retention mechanism in releasable manner, the carriage assembly arranged for travelling along a hub member of the trimmer head between first and second positions;

a line feed actuator for selectively displacing the carriage assembly from the first position towards the second position; and

a carriage return arrangement operating in conjunction with the line feed actuator for returning the carriage assembly to the first position;

wherein the line retention mechanism is arranged to secure the trimmer line at the carriage assembly in the first position and as the carriage assembly travels towards the second position, but allow the trimmer line to slip with respect to the carriage assembly as the carriage assembly returns to the first position.

2. A device according to claim 1 , wherein the line retention mechanism has a clamping arm pivoted at the carriage to releasably clamp the trimmer line against a clamping counter surface for the trimmer line at the carriage assembly.

3. A device according to claim 2, wherein the clamping arm is biased into a normally closed clamping position in which the trimmer line is secured against displacement at the counter surface.

4. A device according to claim 2 or 3, further comprising a retention mechanism release arranged to pivot the clamping arm into a position in which the trimmer line is released for movement relative to the carriage assembly as the carriage assembly reaches or is at the second position.

5. A device according to claim 4, wherein the retention mechanism release has a release lever extending from the clamping arm and an abutment member at the hub member disposed to engage with the release lever and thereby pivot the clamping arm away from its normally closed clamping position during movement of the carriage assembly as the latter reaches the second position.

6. A device according to any one of claims 2 to 5, wherein the carriage assembly has a plate-like central member and at least one spoke member extending radially from the central member, the spoke member having a flanged end providing the counter clamping surface for the trimmer line and an aperture located adjacent to the flanged end for threading the trimmer line at the carriage assembly, wherein the clamping arm is pivotally mounted to the spoke arm such that a terminal end of the clamping arm pivots towards the flanged end to engage and retain the trimmer line and pivots away from the flanged end to disengage and release the trimmer line.

7. A device according to claim 6, wherein the terminal end of the clamping arm has corrugated ridges, preferably in form of unidirectional serrated teeth.

8. A device according to claim 6 or 7, wherein the terminal end of the retention arm is channel shaped for guiding the trimmer line against lateral movement at the clamping arm.

9. A device according to any one of claims 1 to 8, further comprising a trimmer line guide member located upstream from the first position at the hub member and downstream of a trimmer line storage, the guide member having a guiding channel through which the trimmer line is threaded and at which the trimmer line is guided upstream of the carriage assembly.

10. A device according to claim 9, wherein the guiding channel has an arrangement for holding the threaded trimmer line against the guiding channel wall to restrict reverse movement of the trimmer line in an upstream direction.

1 1 . A device according to any one of claims 1 to 10, wherein the carriage return has a compression spring arranged to be tensioned by the carriage assembly as the carriage assembly moves from the first to the second position and thereby bias the carriage assembly towards the first position.

12. A rotary trimmer head for use in a rotary trimmer, the rotary trimmer head comprising:

a housing with at least one compartment at a peripheral location of the housing for storing a spool of trimmer line;

a device for dispensing trimmer line, according to any one of claims 1 to 4, located within the housing; and

a hub member located about a rotation axis of the trimmer head at a central location within the housing;

wherein the carriage assembly of the trimmer line dispensing device is located for travel between the first and second positions along and at the hub member, and the housing has a bottom wall with at least one through hole located radially inward from the peripheral compartment and arranged to thread a free end of trimmer line supplied via the carriage assembly such as to deploy an extendable, but otherwise fixed length of trimmer line from the housing for use in trimming.

13. A rotary trimmer head according to claim 12, wherein the hub member is a hollow cylindrical member with a peripheral wall having at least one guiding slot extending along the hub member from a free end thereof towards the bottom wall of the housing, and wherein the carriage assembly of the trimmer line adjusting and fixing device includes a circular, plate-like central member mounted for travel within the hollow hub member and at least one spoke member extending radially from the central member and through the guiding slot, the spoke member having a flanged end providing the counter clamping surface for the trimmer line and an aperture located adjacent to the flanged end for threading the trimmer line at the carriage assembly.

14. A rotary trimmer head according to claim 13, wherein the clamping arm of the trimmer line dispensing device is pivotally mounted to the spoke arm such that a terminal end of the clamping arm pivots towards the flanged end to engage and retain the trimmer line and away from the flanged end to disengage and release the trimmer line.

15. A rotary trimmer head according to claim 13 or 14, further comprising a trimmer line guide member secured to an upper free terminal end of the hub member and providing an upper travel stop for the carriage assembly at the first position at the hub, the line guide member having a guiding orifice formed at a radially outward end of a guide arm through which the trimmer line can be threaded and at which it is guided upstream of the carriage, the guiding orifice and the carriage aperture being preferentially arranged co-axially.

16. A rotary trimmer head according to any one of claims 13 to 15, wherein the peripheral hub wall has at an outer face thereof at least one protrusion arranged to cooperate with a release lever extending from the clamping arm of the trimmer line retention mechanism such as to pivot the clamping arm away from its normally closed clamping position during movement of the carriage as the latter reaches the second position near the base of the hub member at the housing bottom.

17. A rotary trimmer head according to any one of claims 13 to 16, wherein the line feed actuator for selectively displacing the carriage assembly of the trimmer line dispensing device comprises a plunger rod operatively arranged to engage the central member of the carriage and extend through an upper access opening in the housing.

18. A rotary trimmer head according to any one of claims 13 to 17, wherein the carriage return arrangement of the trimmer line adjusting and fixing device for returning the carriage assembly from the second to the first position includes a helical compression spring located within the hollow hub member, the spring being operative on the circular, plate-like central member of the carriage assembly to bias the carriage towards the first position in which it abuts on the trimmer line guide member at the terminal end of the hub member and allow compression and reactive force exerted by the line feed actuator during travel of the carriage assembly from the first to the second position.

19. A rotary trimmer head of any one of claims 12 to 18, wherein the housing has at least one radially extending channel recessed into an outer face of its bottom wall, with the at least one through hole at the bottom running into the channel such that a free end of trimmer line supplied from the radially outwards located trimmer line spool storage compartment via the radially inwards located carriage and threaded past the through hole is deployed radially outwardly from the housing bottom in an extendable, but otherwise fixed length.

20. A rotary trimmer head according to any one of claims 12 to 19, wherein the housing has three of said trimmer line spool storage compartments disposed equidistantly and radially about the rotation axis of the trimmer head, each compartment associated with a respective one of three of said radially extending channels which are located on the outward bottom face of the housing, and wherein the carriage assembly of the trimmer line dispensing device has three of said radial arms with line retention mechanisms arranged for securing to the carriage assembly in releasable manner a respective one of three trimmer lines supplied from the trimmer line pool storage compartments, the carriage assembly disposed for travel along the hub member of the trimmer head between the first and second positions along the extension of the hub, the overall arrangement being such that equal lengths of trimmer line from each compartment are deployed and fixed upon the line feed actuator causing displacement of the carriage from the first position to the second position and the lengths of trimmer line are secured against displacement at the carriage assembly after it has returned into the first position.