KARLSSON, Göte (Häradsvägen 9, Huskvarna, S-561 43, SE)
WÜRZIG, Lars (Linnégatan 14B, Huskvarna, S-561 32, SE)
KARLSSON, Egon (Vimmerbyvägen 25, Storebro, S-590 83, SE)
KARLSSON, Göte (Häradsvägen 9, Huskvarna, S-561 43, SE)
WÜRZIG, Lars (Linnégatan 14B, Huskvarna, S-561 32, SE)
| CLAIMS
1. Arrangement in a portable tool (10), the tool (10) comprises an engine (13) and related components placed in one end of an elongated tube (11) and a working tool (12) in the opposite end, a drive shaft (18) extending inside the tube (11) from the engine (13) via a clutch to the working tool (12), the clutch being secured to a crankcase (14) and surrounded by a clutch cover (16) provided with means for fastening the tube (11) to the clutch cover (16), characterised in that the clutch cover (16) is secured to the crankcase (14) via at least one elastic element.
2. Arrangement according to claim 1, characterised in that the clutch cover (16) is secured to the engine crank (14) case by at least three screws (25) and at least one of the screws (25) is provided with an elastic element.
3. Arrangement according to claim 1 or 2, characterised in that the clutch cover (16) is secured to the crankcase (14) by at least three screws (25) and each screw (25) is provided with an elastic element.
4. Arrangement according to claim 2 or 3, characterised in that an elastic element comprises a first elastic washer (30) placed between the crank case (14) and the clutch cover (16) and a second elastic washer (31) placed between the clutch cover (16) and a stiff washer (32) in the end of the screw (25) or an enlarged screw head.
5. Arrangement according to claim 4, characterised in that the elastic washers
(30, 31) either are a cup springs, a helical spring or a washer made of an elastic material like for example rubber.
6. Arrangement according to claim 4 or 5, characterised in that a spacing sleeve
(35) is provided around the screw (25) in the centre of the stiff washer (32) or the enlarged screw head that aligns the second elastic washer (31), the axial length of the spacing sleeve (35) is selected so that the spacing sleeve (35) extend from the stiff washer (32) or the enlarged screw head through said elastic washers (30, 31) and the clutch cover (16) to the crankcase (14).
7. Arrangement according to claim 6, characterised in that the length of the spacing sleeve (35) is selected so that the appropriate tension on the elastic washers (30, 31) are achieved when a first end surface of the spacing sleeve (35) is in contact with the crankcase (14) and a second end surface is in contact with the stiff washer (32) or the enlarged screw head. |
ARRANGEMENT IN A PORTABLE TOOL
The claimed invention relates to an arrangement in a portable tool comprising an engine and related components placed in one end of an elongated tube and a working tool in the opposite end of the tube.
BACKGROUND OF THE INVENTION
Engine powered portable tools are widely used to facilitate work in forests, gardens and parks. There are a number of different types of tools available like for example trimmers, clearing saws and cutters for pruning of trees. These tools are available in different sizes in order to meet the requirements for different kinds of work. The smallest ones are hand held while bigger and heavier tools are carried in an ergonomic harness or strap placed around the shoulders of the operator.
This category of portable tools all have an engine, either a combustion or electrical engine, and related components placed in one end of an elongated tube. A drive shaft is extending from a clutch connected to the shaft from the engine inside the tube to a gear located inside a gear housing secured to the tube in the opposite end as the engine. A working tool is releasable secured to a drive pin extending from the gear to make it possible to replace worn out working tools or change to a different type of working tool.
During use vibrations are generated in the engine as well as in the clutch. These vibrations are transferred to other tool components where they, after the tool has been used for a while, cause structural damages to some of the components.
Vibrations transferred to the tool handles that the operator is using to manoeuvre the tool also affect the working conditions for the operator in a negative way.
OBJECT OF THE INVENTION
The object of the claimed invention is to reduce structural damages in the clutch cover, the securing of the tube in the clutch cover and the tube as well as improving the working conditions for the operator.
SUMMARY OF THE INVENTION
The problems disclosed above are solved by the claimed arrangement with the features defined in the characterising portion of the independent claim.
The claimed arrangement provides an elastic securing of the clutch cover to the crank case. The elastic securing of the clutch cover to the crankcase reduces the transfer of vibrations from the crank case and the clutch to the clutch cover and further to the tube and other components secured to the tube.
Another advantage with the claimed arrangement is that it reduces the amount of vibrations in the tool handles that the operator is using to control and manoeuvre the tool. This improves the working conditions for the operator.
One preferred embodiment of the claimed invention is to provide each screw that secures the clutch cover to the engine crankcase with one elastic element. A less complicated solution is to only provide one or some of the screws that secure the clutch cover to the crankcase with an elastic element. This less complicated solution does however not reduce the amount of vibrations transferred as efficient as the preferred embodiment of the invention.
In the preferred embodiment of the invention does each elastic element comprise two elastic washers. A first elastic washer is placed between the crankcase and the clutch cover and a second elastic washer is placed between the clutch cover and a stiff washer in the end of the screw or an enlarged screw head that acts as a stiff washer.
A less complicated solution is to only use the first washer placed between the crankcase and the clutch cover. The reduction of vibrations transferred is however not as efficient as if two washers are used.
Another less complicated solution is to only provide one or some of the screws that secures the clutch cover to the crank caser with an elastic element
The elastic washers are preferably a cup spring but also a washer made of an elastic material like for example rubber or with a shape that gives the washer elastic features are usable. The cup spring or elastic washer characteristics are selected to meet the requirements of the tool that they are used for. A larger tool requires a stiffer spring.
Another preferred embodiment of the claimed invention is to provide the stiff washer with a spacing sleeve placed on the side of the washer aligning the second elastic washer. The spacing sleeve is extending through the second washer, the clutch cover and the first washer and has an axial length selected so that the end surface of the spacing sleeve is in contact with the outer surface of the crank case when the right tension is achieved in the first and second elastic washers. The spacing sleeve thereby ensures a constant and correct tension in the washers which facilitate the mounting of the components considerably since the person or machine mounting the components only has to continue the screwing until the end surface of the spacing sleeve is in contact with the crank case surface.
BRIEF DESCRIPTION OF THE DRAWINGS
The claimed invention is disclosed with reference to the attached drawings.
Figure 1. Illustrates a perspective view of a portable tool. Figure 2. Illustrates a perspective view of the claimed arrangement. Figure 3. Illustrates a perspective view of the claimed arrangement and the side of the crankcase to which the clutch cover is secured. Figure 4. Illustrates a second embodiment of the elastic element. Figure 5. Illustrates a cross sectional view through the longitudinal axial direction of the clutch cover.
DETAILED DESCRIPTION OF THE DRAWINGS
Figure one is disclosing a portable saw 10 for pruning of trees with an engine 13 and related components placed in one end of an elongated tube 11 and a working tool 12 placed in the opposite end of the tube 11. The engine comprises a crankcase 14, disclosed in figure 3, and a crankshaft from the engine 13 is connected to a clutch. The clutch is surrounded by a clutch cover 16 secured to the crankcase 14 by a number of screws 25. A drive shaft 18 is extending from the clutch inside the tube 11 to the working tool 12 in the end of the tube 11.
In figure 5 is a cross sectional view through the longitudinal axial direction of the tube 11 disclosed. The drive shaft 18 is extending from an attachment device 19 in the centre of the clutch drum 20 coaxially with the longitudinal axle of the tube 11. The clutch cover 16 is shaped to surround the clutch drum 20 and is provided with a protruding tube shaped portion 21. The tube shaped portion 21 is used for fastening of the tube to the clutch cover 16 and the engine 13. The tube 11 is pushed into the open end of the tube shaped portion 21 and secured when the two clamping screws 22 are tensioned. The protruding tube shaped portion 21 is in this embodiment integrated in the clutch cover 16 but a separate component secured to the clutch cover could also be used for this purpose.
The clutch cover 16 is shaped so that substantially the entire contact surface aligns the crankcase 14 surface surrounding the clutch 15. The clutch cover is provided with four holes 23 spread around the circumference of the clutch cover 16 that is placed towards the crankcase 14. The crankcase 14 is provided with one threaded portion for each of the holes 23 in the clutch cover 16. The threaded portions in the crankcase 14 are positioned so that the tube 11 is placed co-axially with the output shaft from the clutch when the clutch cover 16 is fastened to the crankcase 14 by one screw 25 in each hole 23 in the clutch cover 16. Different embodiments of the clutch cover and crankcase could have different numbers of holes that consequently are placed differently.
Each screw 25, in this embodiment, is provided with an elastic element to allow movements between the crankcase 14 and the clutch cover 16 in order to reduce the amount of vibrations transferred from the engine 13 and the clutch 15 to the tube 11. Elastic elements could however be provided only on some of the screws 25 in order to
simplify and reduce the number of components in the tool. The simplified embodiment is thus not as efficient in the reduction of vibrations as the preferred embodiment.
The elastic element, in this embodiment, comprise of a first cup spring 30 placed between the surface of the crankcase 14 and the surface of the clutch cover 16 facing the crankcase 14 and a second cup spring 31 placed between the surface of the clutch cover facing away from the crankcase 14 and a stiff washer 32 in the end of the screw 25 or an enlarged screw head that supports the cup spring 31.
In order to reduce the number of components in the tool the first 30 and second 31 cup spring could be combined into a double-cup spring 33, illustrated in figure 4. The use of the double-cup spring 33 has the same technical features as the use of the first 30 and second 31 cup spring but is easier to mount and the risk for loss of a spring is reduced.
The cup springs 30, 31 or one of the springs 30, 31 in the elastic element could also be replaced by elastic washers made of for example rubber, a helical spring or a washer shaped to provide the elastic securing of the clutch cover 16 to the crankcase 14.
A spacing sleeve 35 is in the illustrated embodiment placed on each screw 25 provided with an elastic element. The axial length of the spacing sleeve 35 is selected so that a first end surface of the spacing sleeve 35 is in contact with the crankcase 14 surface and a second end surface of the spacing sleeve is in contact with the stiff washer 32 when the screw is tightened. The length of the spacing sleeve 35 ensures that the optimal tension in the springs 30, 31 are achieved when the first end surface is in contact with the crank case 14 and the second end surface is in contact with the stiff washer 32.
At least one handle is secured to tool somewhere along the tube 11. The handle is used for manoeuvring the tool. Necessary control functions like for example a throttle device is incorporated in the handles. Less vibration transferred from the engine 13 and the clutch to the tube 11 consequently also reduce the amount of vibrations in the handles since they are placed on the tube 11. Smaller tools may have the handles placed directly on the tube 11.