Circuit arrangement for counterclockwise and clockwise rotation of commutator motors

• US 4,459,522 A
• Filed: 01/17/1983
• Issued: 07/10/1984
• Est. Priority Date: 01/15/1982
• Status: Expired due to Term

• Current Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Original Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Inventors: Huber, Siegfried
• Primary Examiner(s): Truhe, J. V.
• Assistant Examiner(s): Ro, Bentsu
• Application Number:
  US06/458,719
• Time in Patent Office: 540 Days
• Field of Search: 318/293, 310/50, 310/47, 200/157, 200/1 V, 200/5 R, 200/5 E, 307/127, 307/113
• US Class Current: 318/293
• CPC Class Codes: H01H 9/061 enclosing a continuously variable impedance
• CPC Class Codes: H01H 9/063 enclosing a reversing switch

Abstract

In a portable power tool, two switches are provided in the handle for respectively effecting rotation of the electric motor in opposite directions. Each switch has a center contact movable between a rest contact and a working contact, the armature of the motor being connected between the two center contacts. Preferably, a common rocker actuates the two switches individually or jointly. In both the rest position of the two switches and in the case when both switches are jointly actuated, intentionally or unintentionally, the armature is short-circuited and braking occurs. Two platelets of electrically conductive synthetic material may advantageously be used as end stops for the switches so that the speed in either direction of rotation is controlled by the pressure of the operator'"'"'s finger on the selected switch.

Claims

1. A portable power tool, comprising:

a housing having a handle;

an electric motor mounted in the housing and having an armature with a commutator;

two switches for respectively effecting rotation of the armature in opposite directions of rotation, each switch having a center contact movable between a rest contact and a working contact, the armature being connected between the two center contacts, the working contacts being interconnected, the rest contacts being interconnected, and the working and rest contacts being arranged to be connected across a source of line voltage;

a rocker bar mounted on said handle and connected to both said movable center contacts for actuation thereof;

resilient means for urging said rocker bar away from said handle to a position in which both movable center contacts engage both rest contacts and supply of power to the motor is interrupted;

either end of said rocker bar being independently depressable towards said handle to actuate either switch individually to engage the movable center contact thereof with the working contact thereof and effect rotation of the armature in one direction or the opposite direction thereto dependent upon which switch is actuated;

said rocker bar also being depressable as a whole towards said handle to actuate both switches jointly and short circuit said armature, whereby when said rocker bar is unintentionally squeezed hard in a shock reaction of the tool'"'"'s operator both switches are actuated effecting interruption of supply of power to the motor and braking thereof; and

speed control circuitry and two members of electrically conductive synthetic material whose resistance changes as a function of the pressure exerted thereon forming part of the speed control circuitry, said members being associated with said rocker bar whereby when either switch is actuated a respective one of said members is subjected to pressure, the extent of this pressure being used to control the speed of rotation of the armature in the selected direction of rotation.

2. The portable power tool of claim 1, wherein said rocker bar is connected to said movable center contacts via pressure pins, the pins being connected to the rocker bar adjacent opposite ends thereof, and said resilient means comprises a spring associated with each pressure pin for urging the adjacent end of the rocker bar outwardly with respect to said handle.

3. The portable power tool of claim 1, wherein said motor comprises two field windings, the rest contacts each being connected in series with one of the field windings and the working contacts each being connected in series with the other field winding.

4. A portable power tool, comprising:

a housing having a pistol grip handle;

an electric motor mounted in said housing and having an armature with a commutator;

speed control circuitry for controlling the speed of rotation of said armature;

a switch housing mounted in said handle and containing two switches for respectively effecting rotation of said armature in opposite directions of rotation;

each switch having a movable contact movable between a rest contact and a working contact, and said armature being short circuited when said movable contacts engage both working contacts;

a rocker bar having pressure pins extending from adjacent the ends thereof and respectively connected to said movable contacts for movement thereof, said pins passing through a wall of said switch housing;

said rocker bar protruding from said handle at a location for depression into said handle towards said switch housing by one or more fingers of an operator'"'"'s hand holding the handle;

a compression spring associated with each pressure pin and disposed between said wall and a respective end of said rocker bar for urging said rocker bar outwardly away from said switch housing and to move said movable contacts into engagement with said rest contacts;

a collar on each pressure pin for engaging said wall to limit outward movement of said rocker bar;

either end of said rocker bar being independently depressable towards said handle against the action of one of the springs to actuate either switch individually to effect rotation of said armature in one direction or the opposite direction thereto dependent upon which switch is actuated;

two platelets of electrically conductive synthetic material whose resistance changes as a function of the pressure exerted thereon forming a part of said speed control circuitry, said platelets being mounted in spaced apart relationship on said wall beneath the ends of said rocker bar and functioning as stops to limit manual depression of said rocker bar when said switches are actuated, whereby when either switch is actuated a respective one of said platelets can be subjected to pressure by the respective end of said rocker bar, the extent of this pressure being used to control the speed of rotation of said armature in the selected direction of rotation; and

said rocker bar also being depressable as a whole towards said handle to actuate both switches jointly, whereby when said rocker bar is unintentionally depressed hard in a shock reaction of the tool'"'"'s operator, both switches are actuated effecting short circuiting of said armature with consequential braking of the motor.