GB2297020A

GB2297020A - Tool casing

Info

Publication number: GB2297020A
Application number: GB9501216A
Authority: GB
Inventors: John Worthing
Original assignee: Black and Decker Inc
Current assignee: Black and Decker Inc
Priority date: 1995-01-21
Filing date: 1995-01-21
Publication date: 1996-07-24
Anticipated expiration: 2015-01-21
Also published as: GB2297020B; GB9501216D0

Abstract

A tool casing assembly comprises an upper case part (8) associated with a handle (4) (Fig. 1) of the tool, a lower case part (12) associated with a working head (6) of the tool and a mechanism (38) selectively operable to allow relative rotation of the upper and lower case parts (8, 12). The lower case part (12) terminates, at its end for engagement with the upper case part (8), in an extension piece (16) which is adapted for insertion in and engagement with the upper case part (8) and the mechanism (38) selectively operable to allow relative rotation of the upper and lower case parts (8, 12) is located in the lower case part (12). The assembly is particularly suitable for a vegetation cutter, in particular a vegetation cutter that cuts by means of a filament or strip that is rotated rapidly about an axis that may be either substantially vertical or substantially horizontal, depending upon the application.

Description

lintrovements In Or Relating To Shaft Assemblies The present invention relates to a shaft assembly for a tool, in particular to a shaft assembly for a vegetation cutter, in particular a vegetation cutter that cuts by means of a filament or strip that is rotated rapidly about an axis that may be either substantially vertical or substantially horizontal, depending upon the application.

Vegetation cutters of this type are known, in which the cutting head can be rotated between a trimming mode, in which the filament or strip is rotated about a substantially vertical axis, and an edging mode in which the filament or strip is rotated about a substantially horizontal axis.

It has particular relevance to tools in which the shaft assembly is of clamshell construction and comprises an upper shaft part, associated with a handle and a lower shaft part associated with a working head of the tool.

It is known in tools of this type to provide the upper shaft part with an extension piece, of narrower cross section than the main section of the upper shaft part, which extension piece is adapted, when the shaft assembly is assembled, to extend into and engage in the lower shaft part, the cross section of which is substantially the same as the cross section of the main section of the upper shaft part. Where the tool is a grass trimmer, adjustment between the trimming mode and the edging mode is achieved by means of a lever mechanism located in the upper shaft part.

It is a disadvantage of shaft assemblies of this type that the lower shaft part thus has to be longer than would otherwise be necessary in order to accommodate the extension piece, which is a particular disadvantage from the point of view of the strength of the assembled shaft assembly, since the working part of the tool is generally heavier than the handle; it would therefore be preferred to have the junction between the two shaft parts as close as possible to the heavier, working head.

It is an object of the present invention to provide a shaft assembly in which the above disadvantages are reduced or substantially obviated.

The present invention provides a shaft assembly for a tool, which assembly comprises an upper shaft part associated with a handle of the tool and a lower shaft part associated with a working head of the tool and a mechanism selectively operable to allow relative rotation of the upper and lower shaft parts, characterised in that the lower shaft part terminates, at its end for engagement with the upper shaft part in an extension piece which is adapted for insertion in and engagement with the upper shaft part and in that the mechanism selectively operable to allow relative rotation of the upper and lower shaft parts is located in the lower shaft part.

The upper and lower shaft parts preferably comprise first and second mating parts.

The shaft assembly preferably further comprises means to limit the maximum permitted relative rotation of the upper and lower shaft parts.

The mechanism selectively operable to allow relative rotation of the upper and lower shaft parts is preferably a lever mechanism, formed from a flexible material and comprising first and second arms, the first arm co-operating with an actuator for the mechanism and the second arm providing a biasing means to bias the first arm towards the inner wall of the lower shaft part.

The present invention further provides a tool, in particular a vegetation cutter, more particularly a vegetation cutter that cuts by means of a filament or strip that is rotated rapidly about an axis that may be either substantially vertical or substantially horizontal, depending upon the application, which tool comprises a shaft assembly which comprises an upper shaft part associated with a handle of the tool and a lower shaft part associated with a working head of the tool and a lever mechanism selectively operable to allow relative rotation of the upper and lower shaft parts, characterised in that the lower shaft part terminates, at its end for engagement with the upper shaft part in an extension piece which is adapted for insertion in and engagement with the upper shaft part and in that the lever mechanism selectively operable to allow relative rotation of the upper and lower shaft parts is located in the lower shaft part.

The tool is preferably an electrically powered tool, with the on-off switch located in the upper shaft part and the motor located in the lower shaft part. The electric cable connecting the switch and the motor is free to extend through the central region of the upper and lower shaft parts.

An embodiment of a shaft assembly according to the invention will now be described with reference to the accompanying drawings in which Figure 1 is a view of a vegetation cutter comprising an embodiment of a shaft assembly according to the invention, and Figure 2 is an exploded view, partially in section and on an enlarged scale, of the embodiment of the shaft assembly of Figure 1.

As can be seen from Figure 1, a vegetation cutter (10) comprises a shaft assembly (2) located between a handle (4) and a working head (6).

The shaft assembly (2) comprises an upper shaft part (8) and a lower shaft part (12). The lower shaft part (12) is of substantially cylindrical cross-section and comprises a lower section (14) which is adapted for attachment to the working head (6) and an upper section (16) of reduced cross-section. The upper shaft part (8) is also of substantially cylindrical cross-section and comprises an upper section (18) which is adapted for attachment to the handle (4) and a lower section (20) which is adapted to receive the upper section (16) of the lower shaft part (12).

The upper shaft part (8) and the lower shaft part (12) each comprise first and second mating parts (22),(24) and (26),(28).

The handle (4) incorporates a switch (30) for selectively supplying electrical power to an electric motor (not shown) carried within the working head (6). For two-handed operation of the trimmer, a secondary handle (32) is mounted on the upper section (18) of the upper shaft part (8). The working head (6) comprises a cutting head (34) rotatable about an axis passing through the working head (6) and a cutting line (36) which extends into a cutting plane which is substantially perpendicular to the axis of rotation.

The device can be adjusted in known manner from the trimming mode as shown in Figure 1 to the edging mode by rotation of the lower shaft part (12) through 1800 relative to the upper shaft part (8).

A particularly suitable lever mechanism for use in a shaft assembly comprises a low cost latch mechanism of the type shown in Figure 2. A lever (38) manufactured from a flexible material, for example acetal, and comprising a first and a second arm (40,42) is mounted at its pivot point (44) in the lower shaft part (12) . An actuator (46) is mounted on the first arm (40), and is operable through an aperture (48) provided in the wall of the lower shaft part (12). A pin (50) is mounted on the free end of the first arm (40) and projects through a second aperture (52) provided in the wall of the lower shaft part (12). The pin (50) is selectively and releasably engageable in either of two recesses (54,56) formed in the inner wall of the upper shaft part (8) and located at approximately 1800 to each other.

A post (57) extends into the lower section (14) of the lower shaft part (12) from the inner wall of the lower shaft part (12), for engagement with the second lever arm (42)( of the lever (38).' The first arm (40) of the lever (38) is biased towards the wall of the lower shaft part (12) by means of the engagement of the second arm (42) which acts as an integral spring, with the post (57).

A circumferential rib (58) is provided on the outer surface of the upper section (16) of the lower shaft part (12) for engagement with stops (60) provided on the inner surface of the lower section (20) of the upper shaft part (8) to prevent withdrawal of the lower shaft part (12) from the upper shaft part (8) during relative rotation of the two shaft parts.

Additional stops (not shown) can be provided to restrict relative rotation of the upper shaft part (8) and the lower shaft part (12) to 1800 and thus prevent excess twisting of the power supply cable connecting the motor and the switch (30).

Claims

1. A shaft assembly (2) for a tool (10), which assembly (2) comprises an upper shaft part (8) associated with a handle (4) of the tool (10) and a lower shaft part (12) associated with a working head (6) of the tool (10) and a lever mechanism (38) selectively operable to allow relative rotation of the upper and lower shaft parts (8,12), characterised in that the lower shaft part (12) terminates, at its end for engagement with the upper shaft part (8), in an extension piece (18) which is adapted for insertion in and engagement with the upper shaft part (8) and in that the lever mechanism (38) selectively operable to allow relative rotation of the upper and lower shaft parts (8,12) is located in the lower shaft part (12).

2. A shaft assembly according to claim 1 characterised in that the upper and lower shaft parts (8,12) each comprise first and second mating parts (22,24,26,28).

3. A shaft assembly according to claim 1 or claim 2 characterised in that it further comprises means to limit the relative rotation of the upper and lower shaft parts (8,12).

4. A shaft assembly according to any of claims 1 to 3 characterised in that the mechanism (38) is a lever mechanism (38).

5. A shaft assembly according to claim 4 characterised in that the lever mechanism (38) is formed from a flexible material and comprises first and second arms (40,42), the first arm (40) co-operating with an actuator (46) for the mechanism (38) and the second arm (42) providing a biasing means to bias the first arm (40) towards the inner wall of the lower shaft part (12).

6. A shaft assembly substantially as herein described with reference to the accompanying drawings

7. A tool (10) which comprises a shaft assembly, characterised in that the shaft assembly is a shaft assembly according to any of claims 1 to 6.

8. A tool according to claim 7 characterised in that it is an electrically powered tool with the on-off switch (30) located in the upper shaft part (8) and the motor located in the lower shaft part (12).

9. A tool according to claim 8 characterised in that the electric cable connecting the switch (30) and the motor extends through the central region of the upper and lower shaft parts.

10. A rod substantially as herein described with reference to the accompanying drawings.