With portable electric tools there is a need to simplify assembly to both reduce production costs and to reduce the risk of assembly errors. This has become more important as such tools have become more sophisticated in their functioning.
In the manufacture of electric motors for such tools, it is becoming increasingly common practice to wind the field coils mechanically on to the stator and to provide terminations on the latter for receiving the ends of the field coil windings and which facilitate electrical connection of the windings to the commutator brushes. The stator assembly can be formed by a stack of field laminations and a plurality of coils, and be adapted for automatic connection of the coils to terminal means mounted on the stack wherein the terminal means and mounting means lie entirely within an area defined by the outline of the field laminations. Such an arrangement is disclosed in U.S. Pat. No. 4,071,793 which is hereby incorporated by reference.
Improvements have been made in the manner of connecting the electric leads to the stator assembly. In one such arrangement a pair of blocks made from suitable insulating material such as a polysulphone are located in slots in the stator laminated stack, these blocks being provided with a pair of apertures for receiving a conductive terminal. Each terminal comprises a sleeve portion for engaging in the aperture and a channel portion connected to the sleeve portion by a short connecting neck. A wire to be attached is crimped in the channel portion. Such an arrangement is disclosed in British Pat. No. 1,402,591 which is hereby incorporated by reference. When this method of connecting electrical leads is used with the stator assembly referred to above, the stator assembly can be readily manufactured as a separate unit which is then easily insertable into the housing of the portable electric tool and then the electrical connections to be made to it can be made simply and effectively.
It has been proposed to mount a printed circuit board on a plate having attached thereto carbon brush assemblies, with the plate being attached to the housing of the tool. The armature of the electric motor passes through central openings in both the plate and the printed circuit board.
In order to reverse the rotational direction of drive of an electric tool, a separate reversing switch can be incorporated. However, with many forms of motors, for example, universal motors, damage can occur if the reversing switch is operated to reverse the direction of electrical supply to the motor whilst it is still rotating. To eliminate this danger of damage occurring to the electrical motor, it has been proposed to incorporate the reversing switch in a trigger switch for energizing the tool. The trigger switch is mounted, as well known, in the handle of the tool, and the actuating member of the reversing switch is disposed immediately above the trigger of the trigger switch and just below the motor compartment of the tool. The actuating member of the reversing switch and the trigger are mechanically related so that the trigger remains inoperative, i.e. it cannot be moved, until the actuating member of the reversing switch is positioned to one side of the trigger to allow the motor to be energized to rotate in one direction, or until the actuating member is positioned to the other side of the trigger to reverse the direction of rotation of the motor.
A disadvantage of this reversing switch and trigger switch combination is that it complicates the number of electrical wires that have to feed from the handle of the tool through to the motor compartment and also the number of electrical connections that have to be made to the combined switches in the handle.
The present invention is concerned with further simplifying the assembly of portable electric tools.
It is an object of this invention to provide a portable electric tool having a reversing switch interrelated with a main energizing switch and being arranged so that the number of electrical wires feeding from the handle to the motor compartment can be reduced by at least two.
It is another object of this invention to provide a portable electric tool having a printed circuit board assembly in the motor compartment with the reversing switch being part of that assembly.
It is yet a further object of this invention to provide a portable electric tool having a comprehensive printed circuit board assembly in the motor compartment and being readily mounted on a stator lamination stack of the electric motor.