Electricity: electrical systems and devices – Discharging or preventing accumulation of electric charge
Reexamination Certificate
2000-08-23
2003-04-22
Sircus, Brian (Department: 2836)
Electricity: electrical systems and devices
Discharging or preventing accumulation of electric charge
C361S220000
Reexamination Certificate
active
06552891
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a portable handheld work apparatus having a drive motor with an electrical ground and with a handle made of electrically-insulating material. The drive motor can, for example, be configured as a spark-ignited internal combustion engine.
BACKGROUND OF THE INVENTION
A work apparatus of the above kind such as a suction/blower apparatus can become electrostatically charged during the operation thereof in the area of its electrically insulating components. The electric charge is generated especially in suction/blower apparatus operated in the suction mode because of the movement of the particles entrained in the suction flow. Because of the use of plastic housings, the handles thereof are insulated from the electrical ground of the drive motor. Electrostatic charges occurring in the region of the handles are conducted to earth via the operator and this can affect the comfort of the use of suction/blower apparatus.
SUMMARY OF THE INVENTION
It is an object of the invention to effectively prevent an electrostatic charging of the handle of a work apparatus of the kind referred to above.
The portable handheld work apparatus includes: a drive motor having an electric ground; a handle operatively connected to the drive motor; the handle being made of electrically insulating material and having a surface; a grounding element mounted in the surface; and, means for electrically connecting the grounding element to the electric ground.
The invention is based on the idea to conductively connect the hand of the operator, which grasps the handle, to the electrical ground of the drive motor of the work apparatus. In this way, a negative effect on the well-being of the operator because of the electrostatic charge on the handle is prevented. For this purpose, a grounding element is mounted on the surface of the handle and this grounding element is conductively connected to the electrical ground. The grounding element is contacted by the hand of the operator when grasping the handle. In this way, an electrical connection of the hand to the electric ground is established and it is ensured that the electrostatic charge is conducted away.
Conventionally, at least one actuating element for controlling the drive motor is arranged on a first handle of the work apparatus. The actuating element is operatively connected to the motor by means of a transmission member. Suction/blower apparatus typically have a cylindrically-shaped housing having an intake opening on the end thereof. On the peripheral end of the housing, a second handle is mounted on the end thereof lying opposite to the first handle having the actuating element. During suction operation, the work apparatus can be so held at both handles that the intake opening faces in the direction of the surface to be vacuumed.
In a preferred embodiment, the grounding element is provided on the second handle where it can be connected to the electrical ground in a simple manner especially via a ground lead. Preferably, the grounding element is connected to the electric ground of the work apparatus. The grounding element can be purposefully mounted in the first handle and be conductively joined to the electrical ground via a transmitting element. The transmitting element leads out from the region of the handle to the motor. For this reason, the transmitting element can be used as an electrical line so that a separate electrical cabling between the grounding element and the electrical ground of the motor is unnecessary.
If the engine is a spark-ignited internal combustion engine having an ignition device and a throttle flap for controlling the engine power, then the engine block and the components mounted thereto, such as a carburetor, define the electrical ground. The actuating element, which is mounted on the handle, can be a throttle lever which is operatively connected to the throttle flap via a transmitting element in the form of a bowden cable for the purpose of controlling the throttle flap and therefore for influencing the power of the engine. Preferably, the bowden cable core is configured as an electrically conductive wire which is conductively connected to the electrical ground of the engine via the throttle flap shaft. The electrically conductive connection between the grounding element and the electrical ground is established with a configuration of this kind via the conductive wire. Even when the carburetor is connected to the engine via a rubber-elastic intermediate piece for the purpose of vibration damping, an electrically-conductive connection is present between the throttle flap shaft and the engine housing via the air/fuel mixture flow. This is sufficient in order to guarantee a potential compensation between the carburetor housing and the engine block.
If an actuating element in the form of an ignition switch is mounted in the handle, the ground cable thereof can be used as a transmitting element to the electrical ground of the engine. The ignition is short circuited to electrical ground of the engine via the ignition switch and the ground cable and the engine is thereby switched off. Because of the spatial closeness between the grounding element and the actuating elements (bowden cable, ignition switch), only a slight distance must be electrically bridged so that the constructive complexity is small.
According to another embodiment of the invention, the grounding element is configured as an elongated metal rail and especially as a sheet metal strip which is held with two bent-over portions at respective ends thereof in corresponding openings of the handle whereby a simple assembly is made possible.
Preferably, the grounding element is configured as a grounding wire and provided between the half shells on the end of the handle facing toward the motor housing. The half shells are joined together to form the handle.
The configuration of the grounding element as a sheet metal strip or as a grounding wire makes possible a cost-effective manufacture. The clamping arrangement of the sheet metal strip between the half shells makes possible a simple assembly. In such a configuration of the handle, the pressure-sensitive hand surface lies outside of the grounding element. Only the fingers of the grasping hand lie on the grounding wire which slightly extends over the outer contour of the handle.
In an advantageous embodiment, the metal rail has a contact end which lies elastically against the wire core of the bowden cable in order to establish an electrically conductive connection between the grounding element and the electrical mass. Especially, the metal rail is fixed by clamping at at least three points preferably defining a plane. With the clamping, the assembly complexity is low and the metal rail is spatially reliably fixed via the three clamping points defining a plane so that its elastic characteristics can be used for generating the spring-elastic conducting contact of a contact end against the wire.
REFERENCES:
patent: 1920889 (1933-08-01), Pullen
patent: 4197610 (1980-04-01), Schneider
patent: 4342369 (1982-08-01), Ransom
patent: 4644606 (1987-02-01), Luerken et al.
patent: 4697300 (1987-10-01), Warlop
patent: 4715085 (1987-12-01), Johanson
patent: 4748712 (1988-06-01), DiGioivanni
Andreas Stilhl AG & Co.
Kitov Zeev
Ottesen Walter
Sircus Brian
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