Portable handheld work apparatus

A portable handheld work apparatus such as a motor-driven chain saw (1) includes a housing (2) wherein an internal combustion engine (10) and a carburetor (11) are mounted. A throttle lever (6) is provided which is pivotally journalled on a handle (3). The handle (3) is connected to the housing (2) via at least one antivibration element (33). A vibration gap (9) is configured between the handle (3) and the housing (2). A transmitting unit (13) is provided for transmitting the pivot movement of the throttle lever (6) to the carburetor (11). The transmitting unit includes a rigid transmitting element (17, 37) which bridges the vibration gap (9). A simple configuration and a substantial decoupling of the relative movement between the housing (2) and the handle (3) from the actuating movement of the carburetor is achieved in that the transmitting element (17, 37) is rotatably journalled and the pivot movement of the throttle lever (6) is transmitted as a rotation about a rotational axis (22) lying transverse to the vibration gap (9).

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority of German patent application no. 10 2004 009 180.3, filed Feb. 25, 2004, the entire content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 4,896,425 discloses a motor-driven chain saw wherein a vibration gap is formed between the throttle lever and the carburetor. This vibration gap is bridged by a transmitting element. The transmitting element transmits the movement of the throttle lever as a movement in the direction of the primary vibration direction, that is, parallel to the extension of the guide bar of the chain saw. In order to compensate for vibrations, the throttle lever is journalled in an elongated slot on the handle and the transmitting element is journalled in an elongated slot on the throttle lever. In this way, there is, however, lost motion during the actuation of the throttle lever.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a portable handheld work apparatus of the kind described above wherein a good decoupling of the actuating movement of the throttle flap from the operating vibration is made possible in a simple manner and wherein a good adjustability of a fuel-metering device is made possible.

The portable handheld work apparatus of the invention includes: a housing; an internal combustion engine mounted in the housing; a fuel-metering device for metering fuel to the internal combustion engine; a handle; at least one antivibration element connecting the handle to the housing; the handle and the housing conjointly defining a vibration gap therebetween; a throttle lever pivotally journalled on the housing so as to execute a pivotal movement; a transmitting unit for transmitting the pivotal movement of the throttle lever to the fuel-metering device; the transmitting unit including: a rigid transmitting element for bridging the vibration gap; support means for rotatably supporting the transmitting element so as to permit rotation thereof about a rotational axis transverse to the vibration gap; and, interface means for operatively connecting the throttle lever to the transmitting element so as to cause the transmitting element to transmit the pivotal movement as a rotation about the rotational axis.

The pivot movement of the throttle lever is transmitted as a rotation about a rotational axis lying transversely to the vibration gap. For this reason, the actuating movement is decoupled from vibrations in the direction of the rotational axis. The transmitting unit can be configured simply and robustly and is thereby not susceptible to disturbances. The transmitting unit can be manufactured easily because no tight tolerances need be maintained.

A good decoupling results when the rotational axis runs approximately parallel to the primary vibration direction of the work apparatus. Movements in the direction of the rotational axis are not transmitted by the transmitting unit so that, in this direction, a complete decoupling is possible. Advantageously, the transmitting unit has a first region on which the throttle lever acts and a second region which acts on the fuel-metering unit. The transmitting element is advantageously held on a first support so as to be not displaceable in the direction of the rotational axis and is supported on a second support displaceable in the direction of the rotational axis. In this way, a fixed support is realized at one support and a loose support is realized at a second support. The relative movements between handle and housing can be compensated via the loose support so that the transmitting element is not loaded in the longitudinal direction. Here, preferably one support is provided on the housing and one support is provided on the handle.

The first support is mounted on the handle and the second support on the housing. In this way, the transmitting element is tightly journalled on the handle. One support is advantageously mounted between the first and second regions of the transmitting unit and one support is advantageously mounted on the end of the second region facing away from the first region.

The transmitting element is loose at one end and is tightly journalled between the first and second regions. The distance of the first support to the second region is short compared to the distance of the second support to the first support in order to ensure that also vibrations transverse to the rotational axis have only a slight influence on the fuel-metering unit. The second support is arranged directly adjacent to the second region. Relative movements between the two supports in a direction transverse to the rotational axis are transmitted only fractionally to the fuel-metering unit since a reduction takes place because of the lever ratios. The movement of the second region transverse to the rotational axis amounts to a fraction of the total relative movement which corresponds to the ratio of the distance of the second region to the second support to the distance between the two supports.

It is provided that the fuel-metering unit is a carburetor and the second region of the transmitting unit acts on a throttle shaft of the carburetor. The rotational axis of the throttle shaft advantageously lies transversely to the rotational axis of the transmitting element. In this way, an advantageous spatial arrangement of the carburetor and of the engine results. A dog is fixed on the throttle shaft at a radial distance to the rotational axis of the throttle shaft and this dog is actuated by the second region.

In order that there is a sufficiently large actuating movement for the throttle shaft and a slight relative movement between the dog and the second region, it is provided that the rotational axis of the throttle shaft has a short distance to the rotational axis of the transmitting element referred to the movement of the dog from the idle position to the full-load position and that the rotational axis of the throttle shaft intersects the rotational axis of the transmitting element. The rotational axis of the throttle shaft and the rotational axis of the transmitting element therefore advantageously lie in a plane.

Advantageously, the following lie approximately in a plane: the rotational axis of the throttle flap, the rotational axis and the second region in the area of the half-throttle position. In this way, an actuation of the throttle shaft results which is symmetrical to the half-throttle position. With the half-throttle position, the position of the throttle shaft is identified wherein the throttle shaft is, starting from an end position, pivoted about half of its entire deflection. At the same time, an adequately large actuating path and a small relative movement is ensured between the second region and the dog. With the small relative movement optimally assured, the friction and therefore the wear between the second region and the dog is reduced so that a long service life of the transmitting device can be achieved and the amount of force developed by the operator is low.

A simple configuration of the transmitting unit can be achieved when the first region is arranged on an arm projecting from the transmitting element. The second region is advantageously offset parallel to the rotational axis. The transmitting element can be configured as a rigid wire. The wire can be bent in a simple manner so that the first and second regions are integrated. Tolerances from the bending operation of the wire can be compensated by a one-time adaptation after the assembly so that only slight requirements need be imposed on the bending operation. In this way, a simple and economic manufacture results.

It can be practical to configure the first region as a slot formed in the transmitting element. The slot extends helically about the rotational axis and a lug is guided in the slot with the lug being fixed to the throttle lever. The second region is advantageously configured on a projecting arm. It is practical when the transmitting element is configured as a shaft. The shaft has a robust configuration and can be easily manufactured. The supports can also be simply configured.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

The motor-driven chain saw1shown inFIG. 1includes a housing2on which a handle3is fixed via at least one antivibration element33. The handle3is mounted at the end of the housing2facing away from a guide bar4for the saw chain of the chain saw1and extends approximately in the longitudinal direction5of the chain saw1. The longitudinal direction5is the direction in which the guide bar4essentially extends. A throttle lever6is pivotally journalled on the handle3on a support bolt8. Furthermore, a throttle lever latch7is provided which prevents an unwanted actuation of the throttle lever6out of the idle position. An actuating section12is formed on the region of the throttle lever6projecting into the interior of the handle3and this actuating section12acts on a transmitting unit13.

The transmitting unit13includes a transmitting element17which extends approximately in the primary vibrating direction24of the chain saw1. The primary vibration direction24lies approximately in the longitudinal direction5of the chain saw1. The transmitting element17is rotatably journalled on the handle3at a first support18and on the housing2of the chain saw1at a second support19. The first support18is configured as a fixed support and the second support19is configured as a loose support so that the transmitting element17cannot be displaced at the first support18in its longitudinal direction and is held at the second support19to be displaceable in the longitudinal direction.

A vibration gap9is formed between the housing2and the handle3and this gap9is bridged by the transmitting element17. The transmitting element17lies transversely to the vibration gap9and is especially approximately perpendicular thereto. The transmitting element17transmits the pivot movement of the throttle lever6about the support bolt8as a rotation about a rotational axis22which lies especially in the primary vibration direction24. Relative movements of the handle3relative to the housing2(which movements lie in the direction of the rotational axis22, that is, especially in the primary vibration direction24) are not transmitted via the transmitting element17.

An internal combustion engine10is mounted in the housing2and this engine is especially configured as a two-stroke engine. The engine10has a carburetor11which supplies an air/fuel mixture to the engine10via an inlet16. In lieu of the carburetor11, another fuel-metering device can be provided on which the throttle lever6acts. In this carburetor11, an intake channel section (not shown inFIG. 1) is formed wherein a throttle flap is pivotally journalled. The throttle flap is fixed on a throttle shaft14which extends up to the outer side of the housing of the carburetor11. A lever15is fixed to the throttle shaft14and the transmitting element17acts on this lever15.

FIG. 2is an enlarged perspective view of the transmitting unit13. The actuating section12of the throttle lever6acts on a first region25of the transmitting unit13and this first region25is disposed on a projecting arm32. The arm32extends approximately at right angles to the transmitting element17and extends radially outwardly relative to the rotational axis22. The bearing or support bolt8of the throttle lever6extends approximately perpendicularly to the rotational axis22and is approximately parallel to the arm32in the half-throttle position of the carburetor11. With the actuation of the first region25, a relative movement thereby results between the actuating section12and the first region25. In order to reduce occurring friction, the actuating region34(against which the first region25lies at the actuating section12) is configured to be concave. The first support18is formed by two support elements (35,36). The support element36is connected to the support element35via two screws41which are arranged at both sides of the transmitting element17. The support18is configured as a fixed support and does not permit translatory movements of the transmitting element17but permits a rotational movement in each direction over a needed range. Other configurations of the support18can be advantageous. To limit the path of the transmitting element17in the direction of the rotational axis22at the support18, a stop can be provided which, for example, can be formed on the transmitting element17or the stop can be formed as a widening by squeezing the transmitting element17. The transmitting element17is configured as a bent wire. However, another configuration can also be practical.

End43(FIG. 2) faces toward the internal combustion engine10shown inFIG. 1. At end43, the transmitting unit13is held loosely on the second support19in the direction of the rotational axis22and is rotatably journalled about the rotational axis22. A second region26is formed between the first support18and the second support19. This second region26acts on the throttle shaft14of the carburetor11. The wire, which forms the transmitting unit13, is bent over to have a U-shape at the second region26. The second region26extends parallel to the rotational axis22at a radial distance thereto. A dog21of the carburetor11lies on the second region26. The dog21is mounted on the throttle shaft14via the lever15so as to rotate therewith. The dog21extends approximately parallel to the rotational axis27of the throttle shaft14at a distance (c) to the latter. The two supports18and19are at a distance (a) from each other which is essentially greater than the distance (b) of the second region26to the second support19. The second support19is mounted directly adjacent the second region26.

Relative movements of the two supports (18,19) in a direction perpendicular to the rotational axis22are transmitted to the throttle shaft14only greatly reduced because of the lever ratios so that a substantial decoupling results also from movements perpendicular to the primary vibration direction24.

A choke flap23is pivotally journalled in the intake channel20of the carburetor11upstream of the throttle flap (not shown). The position of the choke flap23can be coupled to the position of the throttle flap. Here, it should be ensured that the throttle flap is substantially closed when the choke flap23is closed. The wire can form the entire transmitting unit13; however, it can also be practical to configure the regions25and26as separate components, for example, as cams which are fixed on the wire forming the transmitting element17.

InFIG. 3, the arrangement of the transmitting element17and the throttle shaft14is emphasized.FIG. 3shows a side elevation view of the transmitting unit13shown inFIG. 2in the direction of the rotational axis27of the throttle shaft14. The rotational axis27intersects the rotational axis22of the transmitting element17. The rotational axis22and the rotational axis27thereby lie in one plane. The dog21lies against the second region26of the transmitting unit13. The throttle shaft14is spring biased in a direction toward the closing position of the throttle flap, that is, in the clockwise direction in.FIG. 3. For this reason, the dog21is pressed against the second region26. In the half-throttle position28, which is shown inFIG. 3by a solid line, the second region26lies approximately in the plane defined by the rotational axis22and the rotational axis27.

The idle position29is shown in phantom outline inFIG. 3. In this position, the throttle shaft14is rotated about the rotational axis27through an angle α in a clockwise direction relative to the half-throttle position28shown inFIG. 3. In the full-load position30, which is shown by the dash-dotted line inFIG. 3, the throttle shaft14is rotated in the counter clockwise direction through an angle β relative to the half-throttle position28. The idle position29and the full-load position30are approximately symmetrical to the half-throttle position28so that the relative movement of the dog21relative to the second region26is minimized between the idle position29and the full-load position30. The angles α and β are approximately equal. The rotational axis27of the throttle shaft14can also have a slight distance to the rotational axis22. The distance is short relative to the movement of the dog21from the idle position29to the full-load position30and is only a fraction of the dog movement.

FIG. 4shows an embodiment incorporating a dog31. The dog31is bifurcated and extends above and below the transmitting unit13at the second region26. A slight play is present between the dog31and the second region26so that jamming of the dog31at the second region26is avoided because of the relative movement of the dog31and the second region26. A forced guidance of the throttle shaft14is guaranteed by the bifurcated configuration of the dog31so that even when there is a malfunction of the spring, which presses the throttle flap into its closed position (that is, at the idle position29), a closure of the throttle flap from the full-load position30is possible because the dog31is entrained and taken along to the second region26even for a movement from the full-load position30into the idle position29. In lieu of the bifurcated dog31, a slide sleeve can be provided on which the lever15is fixed and which slide sleeve is slidably journalled on the second region26. It can be also be practical to configure the second region26as an elongated slot in which the dog is guided.

The embodiment shown inFIGS. 5 and 6includes a transmitting element37which is configured as a shaft. The transmitting element37is rotatably journalled about the rotational axis42. The arrangement of the supports corresponds to those of supports18and19. A slot39is provided at the end44of the transmitting element37which faces toward the throttle lever6. The slot39extends helically about the rotational axis42and defines the first region25of the transmitting unit. A lug40is guided in the slot39and this lug projects laterally at a radial distance to the bearing bolt8of the throttle lever6at the actuating section12of the throttle lever. The lug extends approximately radially to the rotational axis42.

In the idle position29shown inFIG. 5, the lug40is arranged in the slot39in the region of the first end45. When pivoting the throttle lever6as shown inFIGS. 5 and 6in a counter clockwise direction (that is, from the idle position29shown inFIG. 5into the full-load position30shown inFIG. 6), the lug40moves in the slot39from the first end45to the opposite-lying second end46. Because of the helically-shaped configuration of the slot39, the movement of the lug40effects a rotation of the transmitting element37about the rotational axis42. At the end of the transmitting element37, which lies opposite the slot39, an arm38is arranged which projects radially from the transmitting element37and on which the second region26is formed. The second region26acts on the throttle shaft14. The arm38can then act directly on the lever15of the throttle shaft14.

Other configurations of the first region25and of the second region26can be advantageous. For example, the second region26can also be configured as a cam which acts on a conically-shaped dog on the lever15of the throttle shaft14. In this way, a minimization of the relative movement and of the friction forces between the dog and the second region26is possible.

Other configurations of the transmitting unit can also be advantageous. The pivotal movement of the throttle lever can also be transmitted via a Bowden thrust to the throttle shaft. Also, the transmission via a fluid system can be practical. Here, the actuating movement can be transmitted via a first piston, on which the throttle lever acts, through a flexible, pressure-tight, fluid-filled line to a second piston which acts on the throttle shaft.