Patent ID: 8549762

Claim:
A drive apparatus for a reciprocating tool, comprising; a housing; an elongated plunger located in said housing for reciprocating motion, said plunger having a front end portion for attaching a cutting blade thereto; a rotatable drive shaft assembly located in said housing, said drive shaft assembly including a drive shaft and a connection arm operatively and directly connected to a rear portion of said plunger, wherein a rotation of said drive shaft causes said connection arm to move in a reciprocating motion along a lengthwise direction of said connection arm to apply a force on said plunger to thereby reciprocate said plunger generally in a lengthwise direction of said plunger during alternating cutting and return strokes; and a rotary joint rocker mechanism supported in said housing and operatively connected to said plunger and said drive shaft assembly so that a rotation of said drive shaft assembly produces a reciprocating motion of said plunger; said rotary joint rocker mechanism including; a front rocker with a lower pivot connection to said housing and an upper pivot connection to said plunger; rear rocker with an upper pivot connection to the rear portion of said plunger and a lower pivot connection to said housing; a counterweight assembly having a movable counterweight, said mechanism being configured to support and move said counterweight in a reciprocating motion that is substantially in the opposite direction of said plunger, wherein said second rocker has a lower extension below said lower pivot connection with a counterweight pivot connection to said counterweight; and a third rocker having one end portion having a pivot connection to said counterweight spaced from said counterweight pivot connection of said second rocker, an opposite end portion of said third rocker having a pivot connection to said housing.