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An impact rotary tool is provided that is switchable between an impact mode where the tool delivers an impacting torque on an output tool and a drill mode where the driver delivers a smooth output on an output tool. The impact rotary tool includes an impact mechanism and a hammer block that in the i

An impact rotary tool is provided that is switchable between an impact mode where the tool delivers an impacting torque on an output tool and a drill mode where the driver delivers a smooth output on an output tool. The impact rotary tool includes an impact mechanism and a hammer block that in the impact mode is movable parallel to the axis of the driver shaft and delivers reciprocating blows to rotate an anvil and in the drill mode substantially constantly engages the anvil. The impact mechanism includes a stopper that does not contact the hammer block in the impact mode and engages the hammer block in the drill mode to maintain the substantially constant contact between the hammer block and the anvil.

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What is claimed: 1. An impact rotary tool, comprising: (a) a gearbox connected to a motor and a drive shaft; (b) an impact mechanism including a hammer block connected to the drive shaft and an anvil disposed concentrically with the drive shaft and configured to be selectively engaged by the hammer

What is claimed: 1. An impact rotary tool, comprising: (a) a gearbox connected to a motor and a drive shaft; (b) an impact mechanism including a hammer block connected to the drive shaft and an anvil disposed concentrically with the drive shaft and configured to be selectively engaged by the hammer block, (c) a mode selector moveable between a first orientation where the hammer block is movable parallel to a longitudinal axis of the drive shaft against the biasing force of a spring to cause reciprocating engagement with the anvil and to cause the anvil to rotate and a second orientation where the hammer block substantially constantly engages the anvil causing the anvil to rotate, and; (d) a switching mechanism including a stopper that is movable along the outer surface of the drive shaft with motion of the mode selector, and the stopper is connected to a first pin that moves along a first slot in the drive shaft, wherein when the mode selector is in the first orientation, the stopper does not engage the hammer block and when the mode selector is in the second orientation the stopper engages the hammer block to maintain substantially constant contact between the hammer block and the anvil. 2. The impact rotary tool of claim 1 wherein the first pin is oriented substantially perpendicular to the longitudinal axis of the drive shaft. 3. The impact rotary tool of claim 1 wherein the mode selector is rotatable about the longitudinal axis of the drive shaft. 4. The impact rotary tool of claim 3 wherein rotational motion of the mode selector causes the stopper to move parallel to the longitudinal axis of the drive shaft. 5. The impact rotary tool of claim 1, wherein the switching mechanism comprises a planet carrier with a longitudinal second slot operatively engaged with a set of planetary gears, wherein the second slot receives a second pin that is movable along the second slot with motion of the mode selector. 6. The impact rotary tool of claim 5, wherein movement of the second pin within the second slot causes motion of the first pin within the first slot. 7. The impact rotary tool of claim 6 wherein the switching mechanism further comprises a sleeve that rotates with the mode selector and is operatively engaged with the second pin. 8. The impact rotary tool of claim 7 wherein the sleeve includes a track through which an arm of a link extends, wherein the link is engaged with the second pin, and wherein rotation of the sleeve causes motion of the link and the second pin. 9. The impact rotary tool of claim 6 wherein a leg is disposed between the second pin and the first pin, and the leg is partially inserted within a hollow cavity along the longitudinal axis of the drive shaft. 10. The impact rotary tool of claim 9 wherein the switching mechanism further comprises a second leg disposed forward of the first pin within the hollow cavity of the drive shaft, wherein the second leg is rearwardly biased by a second spring disposed within the hollow cavity. 11. The impact rotary tool of claim 1 wherein the mode selector is selectively moveable to a third orientation wherein the hammer block substantially constantly engages the anvil causing the anvil to rotate and wherein a clutch mechanism is operable to selectively transmit a torque from the motor to the anvil based on a selectable output torque level. 12. An impact rotary tool, comprising: (a) a motor connected to a drive shaft through a gearbox; (b) an impact mechanism including a hammer block connected to the drive shaft and an anvil disposed concentrically with the drive shaft and configured to be selectively engaged by the hammer block; (c) a mode selector moveable between a first orientation where the hammer block is movable parallel to a longitudinal axis of the drive shaft against the biasing force of a spring for reciprocating engagement with the anvil to cause the anvil to rotate, a second orientation where the hammer block substantially constantly engages the anvil causing the anvil to rotate, and a third orientation where the hammer block substantially constantly engages the anvil causing the anvil to rotate and wherein a clutch mechanism is operable to selectively transmit a torque from the motor to the anvil based on an selectable output torque level; and (d) a switching mechanism including a stopper that is movable along the outer surface of the drive shaft with the motion of the mode selector, wherein the stopper is connected to a first pin that moves along a slot in the drive shaft, wherein when the mode selector is in the first orientation, the stopper does not engage the hammer block and when the mode selector is in the second and third orientations, the stopper engages the hammer block to maintain substantially constant contact between the hammer block and the anvil. 13. The impact rotary tool of claim 12 wherein the first pin is oriented substantially perpendicular to the longitudinal axis of the drive shaft. 14. The impact rotary tool of claim 12 wherein the mode selector is rotatable about the longitudinal axis of the drive shaft. 15. The impact rotary tool of claim 14 wherein rotational motion of the mode selector causes the stopper to move parallel to the longitudinal axis of the drive shaft. 16. The impact rotary tool of claim 12, wherein the switching mechanism comprises a planet carrier with a longitudinal second slot operatively engaged with a set of planetary gears, wherein the second slot receives a second pin that is movable along the second slot with motion of the mode selector. 17. The impact rotary tool of claim 16, wherein movement of the second pin within the second slot causes motion of the first pin within the first slot. 18. The impact rotary tool of claim 17 wherein the switching mechanism further comprises a sleeve that rotates with the mode selector and the sleeve is operatively engaged with the second pin. 19. The impact rotary tool of claim 18 wherein the sleeve includes a track through which an arm of a link extends, wherein the link is engaged with the second pin, and wherein rotation of the sleeve causes motion of the link and the second pin. 20. The impact rotary tool of claim 17 wherein a first leg is disposed between the second pin and the first pin, and the first leg is partially inserted within a hollow cavity along the longitudinal axis of the drive shaft. 21. The impact rotary tool of claim 20 wherein the switching mechanism further comprises a second leg disposed forward of the first pin within the hollow cavity of the drive shaft, wherein the second leg is rearwardly biased by a second spring disposed within the hollow cavity.