Off locking in-line trigger switch

Abstract

A trigger switch for portable tools such as circular saws, chain saws, and the like having a return-spring biased trigger that is actuated by the forefinger of the user to turn the tool on and upon release returns to and locks in off position under spring action. The trigger switch which may be of the inline or pivoted (overhanging) type is provided with a built-in spring biased lock that automatically locks the trigger whenever the trigger returns to its off position. A manual release button is arranged to be depressed by the thumb of the user to release the lock and allow reactuation of the trigger. The lock-off feature is characterized by a strong lock to prevent forcing and requiring only minimum modification of the conventional trigger switches.

I claim: 
     
       1. A self-enclosed trigger switch for a portable electric tool affording intended operation of the tool but automatically locking it against accidental operation whenever the switch is released comprising: an insulating housing for the switch mechanism;   a trigger mounted to said housing for limited reciprocal sliding movement between an "on" position wherein the switch is in operation and an "off" position wherein the switch is not in operation;   a frame mounting said trigger to the top of said housing;   a return spring normally biasing said trigger into its extended "off" position and being depressible into its "on" position;   and an automatically engaging off lock for said trigger comprising:   a locking recess in the left side of said trigger having a keyhole shaped first depth forming a locking slot and a larger second depth forming a clearance slot for release of the lock;   a spring-biased locking pin mounted on the left side of said frame for limited axial movement with the right end thereof extending into said recess and the left end thereof having a pushbutton that is accessible for depression by the right hand thumb of the user;   a symmetrical enlarged locking head on said right end of said locking pin disposed within said recess;   said recess having an opening extending up to the top of the trigger affording access for said enlarged locking head on assembly of the trigger switch;   said locking slot being keyhole shaped so as to have a narrow section just wide enough to receive the stem of said locking pin but not the enlarged head thereof and a wider mouth portion at the entrance to said narrow section for receiving said enlarged head whereby said enlarged head abuts both sides of .[.side.]. .Iadd.said .Iaddend.mouth to lock said trigger in its "off" position and said locking pin .Iadd.pushbutton must be depressed against the force of its bias .Iaddend.spring to move the stem of said pin adjacent the narrow section of said locking slot and said enlarged head into said clearance slot to allow movement of said trigger to "on" position;   and the part of said trigger defining the upper side of said locking slot being at least partly confined against said frame to strengthen said off lock.