Harvesters – Motorized harvester – Having motor on ground-supported carrier
Reexamination Certificate
1998-10-08
2001-03-06
Will, Thomas B. (Department: 3671)
Harvesters
Motorized harvester
Having motor on ground-supported carrier
C056S017500, C320S113000
Reexamination Certificate
active
06195970
ABSTRACT:
BACKGROUND OF THE INVENTION
Tool with an electric motor as its drive The invention relates to a tool, in particular to a garden tool, e.g. a lawnmower, with an electric motor as its drive and an exchangeable, rechargeable battery, the electrical terminals of which can be connected via a plug device to the motor terminals.
In small, battery-operated electric tools, for example hand drills or hand held screwdrivers which are operated by electric motors, it is customary to provide a battery pack which is equipped with plug-in contacts which can be plugged into mating terminals on the electric hand held tool or on a charging appliance. In this case, the plug-in contacts and the mating terminals each form part of a plug coupling, some of the connection means comprising contact pins which project in the plug-in direction.
A battery pack of this kind for electric hand held tools is known from DE 94 21 382. In this case, in addition to the plug-in contacts which make the electrical connection to the drive motor or to the charging appliance, form-fitting connections which rule out polarity reversal are also provided. In the case of the known battery pack, electrical connection is inevitably made when putting the coupling parts together. In order to prevent unintentional short-circuiting of the battery pack which is isolated from the hand tool, the coupler connections of this kind cannot readily be employed because safety considerations dictate that it is necessary to provide an additional switch to interrupt the flow of current in the immediate vicinity of the battery, in order to make the tool childproof.
Lawnmowers with exchangeable battery packs in which terminals are arranged on the outside of the battery pack are known, which terminals, when the battery pack is inserted into a battery guide in the casing of the tool inevitably makes contact with the terminals situated in the tool. A switch, which is generally designed as a detachable-key switch, is provided as a safety switch on the lawnmower chassis in the vicinity of the battery. To recharge the battery, terminals for the insertion of a socket connector are provided in the tool casing via which connector a charging appliance supplies current to recharge the battery. The battery can also be recharged after it has been removed from the tool, using the charging appliance which can be connected to the battery terminals.
In the case of a tool which is described in WO 94/01993 and is designed as a lawnmower, the bow plug is designed as an overload protector and contains either a fuse or an overload circuit breaker. The battery pack, which in the known tool is installed fixedly in the chassis, has a charging plug, a power transformer and a rectifier which is connected to the battery. The charging plug is connected to the mains in order to recharge the battery. The sockets of the mains plug can only be pushed onto the charging plug pins when a slide lying above them has been displaced laterally, and its displacement into the open position is only possible when the bow plug has been pulled off the battery terminals, thus isolating the motor from the battery terminals. As long as the slide is in the displaced position, releasing the mains connection, the safety bow plug cannot be plugged in, so that the connection between motor and battery remains interrupted as long as the mains plug is connected to the tool.
SUMMARY OF THE INVENTION
The invention is based on the object of providing a tool with a safety plug-in contact connector in which the electrical contact connection between the terminals of an exchangeable battery pack and motor terminals or charging appliance terminals cannot be made only by inserting the battery pack into the tool, but rather further plug-in functions are required.
The object is achieved by the invention as described herein below. In this case, only by plugging on the bow plug is electrical connection possible, and this electrical connection via the bow plug can only be closed when the battery pack has been inserted correctly in the tool, so that the motor terminals and the battery pack terminals lie parallel to one another at the same height, ready to receive the bow plug. This bow plug brings about a reliable electrical isolation between battery and motor, and only after the bow plug has been pulled off, i.e. after electrical isolation has taken place, is it possible to lift the battery pack out of the corresponding guide in the tool housing, so that the motor can be reliably prevented from switching on when the battery pack is being exchanged. By contrast, the conventional safety switch which is designed, for example, as a detachable-key switch does not prevent this undesirable switching-on of the motor.
Expediently, one of the multipole connectors is fixed to the tool, while the other connector is fixed on the battery pack so that it is also removed when the battery is being exchanged. No additional contact points are required.
According to a further refinement of the invention, the same bow plug may be used as a charging plug, this charging bow plug being fixed to a multipole plug of the battery pack and making the connection to the charging appliance. This could be achieved by providing a further multipole plug on the charging appliance or the supply line in such a manner that the same bow plug connects the multipole plug of the battery pack, which has been removed from the tool, to a multipole plug which is provided on the charging appliance or the supply line. However, this requires the battery to be removed from the tool each time it is to be recharged. For this reason, according to a further refinement of the invention, the charging appliance or the connection line is fitted with a plug which corresponds to the connecting bow plug, can be plugged onto the multipole plug of battery pack or charging appliance and connects these components to one another while the connection is interrupted with respect to the drive motor of the tool. Here too, suitable form-fitting connections prevent the wrong poles from being connected.
The invention allows the bow plug arrangement to be employed for three functions, namely, for safety interruption of current, for current connection with respect to the drive motor and for current connection between the battery pack and charging appliance. Conventional spring contacts and jacks can be used as the plug-in contacts for the multipole plugs and the bow plug, so that the plug connection can be produced in a cost-effective manner.
An exemplary embodiment of the invention is described below with reference to a lawnmower which is illustrated in the drawing, in which:
REFERENCES:
patent: 3493915 (1970-02-01), Cox
patent: 3581480 (1969-09-01), O'Connor et al.
patent: 3696593 (1972-10-01), Thorud et al.
patent: 5085043 (1992-02-01), Hess et al.
patent: 5301494 (1994-04-01), Peot et al.
patent: 5321203 (1994-06-01), Goto et al.
patent: 5402008 (1995-03-01), St. John
patent: 5449301 (1995-09-01), Hanna et al.
patent: 5606851 (1997-03-01), Bruener et al.
patent: 4406879 (1995-07-01), None
patent: 9401993 (1994-03-01), None
Held Peter
Pfau Ulrich
Ostrolenk Faber Gerb & Soffen, LLP
Petravick Meredith
Will Thomas B.
Wolf-Geräte Vertriebsgesellschaft GmbH KG
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