Power tool

Patent metadata

Field	Value
Publication number	US-9364944-B2
Application number	US-201013505110-A
Country	US
Kind code	B2
Filing date	Oct 20, 2010
Priority date	Nov 2, 2009
Publication date	Jun 14, 2016
Grant date	Jun 14, 2016

Abstract

Provided is a power tool which is capable of more reliably detecting excessive reaction torque acting on a tool body. More specifically, provided is a handheld power tool which causes a tip tool to rotate so as to carry out a predetermined machining operation, the handheld power tool comprising a tool body, a motor which is housed in the tool body and causes the tip tool to rotate, a first sensor which detects the torque state of the tip tool, a second sensor which detects the motion state of the tool body, and a torque cut-off mechanism which cuts off the transmission of torque between the motor and the tip tool. The torque cut-off mechanism is configured to cut off the transmission of torque on the condition that the first sensor and the second sensor respectively detect a preset threshold value for the first sensor and the second sensor.

First claim

I claim:

1. A hand-held power tool, which performs a predetermined operation by rotationally driving a tool bit, comprising:
a tool body,
a tool holder that holds the tool bit,
a motor that is housed in the tool body and rotationally drives the tool bit,
a first intermediate shaft which is connected to an output shaft of the motor, the first intermediate shaft being driven by the motor and transmitting torque,
a second intermediate shaft which is disposed between the tool holder and the first intermediate shaft, the second intermediate shaft receiving the torque from the first intermediate shaft and transmitting the torque to the tool holder;
a first sensor that detects torque applied on the second intermediate shaft,
a second sensor that detects motion of the tool body,
a torque transmission interrupting mechanism that can interrupt torque transmission between the first intermediate shaft and the second intermediate shaft, and
a mechanical limiter that is disposed on the second intermediate shaft and is capable of interrupting the torque transmission between the motor and the tool bit,
wherein the torque transmission interrupting mechanism interrupts torque transmission between the first intermediate shaft and the second intermediate shaft, when both the torque detected by the first sensor and the motion of the tool body detected by the second sensor reach respective preset threshold,
the torque transmission interrupting mechanism does not interrupt the torque transmission between the first intermediate shaft and the second intermediate shaft, when at least one of the torque detected by the first sensor and the motion of the tool body detected by the second sensor does not reach corresponding preset threshold, and
the mechanical limiter interrupts the torque transmission between the motor and the tool bit when the torque detected by the first sensor reaches a preset another threshold, which is different from the preset threshold, the mechanical limiter interrupting the torque transmission independently from a detection result of the second sensor.

2. The power tool as defined in claim 1 , wherein the first sensor comprises a torque sensor that measures torque or a rate of change of torque per unit time.

3. The power tool as defined in claim 1 , wherein the second sensor comprises a speed sensor or an acceleration sensor that measures momentum of the tool body.

4. The power tool as defined in claim 1 , wherein the torque transmission interrupting mechanism comprises an electromagnetic clutch including a driving-side rotating member, a driven-side rotating member, a biasing member that biases the rotating members away from each other so as to interrupt torque transmission, and an electromagnetic coil that brings the rotating members into contact with each other against the biasing force of the biasing member and transmits torque when the electromagnetic coil is energized.

5. The power tool as defined in claim 1 , wherein the preset another threshold is greater than the preset threshold.

6. The power tool as defined in claim 1 , wherein the mechanical limiter interrupts the torque transmission between the second shaft and the tool holder when the torque detected by the first sensor reaches the preset another threshold.

7. The power tool as defined in claim 1 , wherein the output shaft of the motor, the first intermediate shaft and the second intermediate shaft extend substantially in parallel with each other.

8. A hand-held power tool, which performs a predetermined operation by rotationally and linearly driving a tool bit, comprising:
a tool body,
a motor that is housed in the tool body and rotationally drives the tool bit,
an impact drive mechanism that is driven by the motor and linearly drives the tool bit,
a rotary drive mechanism that is driven by the motor and rotationally drives the tool bit,
a first sensor that detects torque of the tool bit,
a second sensor that detects motion of the tool body,
an electromagnetic clutch mechanism that is disposed in a rotary drive path and can interrupt transmission of the torque for rotationally driving the tool bit between the motor and the tool bit, and
a controller that controls the electromagnetic clutch mechanism based on a detection result of the first sensor and a detection result of the second sensor,
wherein the controller controls the electromagnetic clutch mechanism such that when both the torque detected by the first sensor and the motion of the tool body detected by the second sensor reach respective preset threshold, the electromagnetic clutch mechanism interrupts the transmission of the torque in the rotary drive path while a linearly driving of the tool bit by the impact drive mechanism is maintained.

9. The power tool as defined in claim 8 , further comprising a mechanical limiter that interrupts the transmission of the torque in the rotary drive path when the torque detected by the first sensor reaches a preset another threshold, which is different from the preset threshold, the mechanical limiter interrupting the torque transmission independently from a detection result of the second sensor.

10. The power tool as defined in claim 9 , wherein the preset another threshold is greater than the preset threshold.

11. The power tool as defined in claim 9 , wherein:
the rotary drive mechanism includes (i) a first intermediate shaft which is connected to an output shaft of the motor and is driven by the motor and transmits torque, and (ii) a second intermediate shaft which is disposed between the tool bit and the first intermediate shaft, the second intermediate shaft receiving the torque from the first intermediate shaft and transmitting the torque to the tool bit,
the controller controls the electromagnetic clutch mechanism such that when both the torque detected by the first sensor and the motion of the tool body detected by the second sensor reach the respective preset threshold, the electromagnetic clutch mechanism interrupts the transmission of the torque between the first shaft and the second shaft, and
the mechanical limiter interrupts the transmission of the torque between the second shaft and the tool bit when the torque detected by the first sensor reaches the preset another threshold.

12. The power tool as defined in claim 11 , wherein the output shaft of the motor, the first intermediate shaft and the second intermediate shaft extend substantially in parallel with each other.

13. A hand-held power tool, which performs a predetermined operation by rotationally driving a tool bit, comprising:
a tool body,
a tool holder that holds the tool bit,
a motor that is housed in the tool body and rotationally drives the tool bit,
an intermediate shaft which is disposed between the tool holder and the motor, the intermediate shaft being driven by the motor and transmitting torque to the tool holder,
a first sensor that detects torque applied on the intermediate shaft,
a second sensor that detects motion of the tool body,
a torque transmission interrupting mechanism that can interrupt torque transmission between the motor and the tool bit, and
a mechanical limiter that is disposed on the intermediate shaft and is capable of interrupting the torque transmission between the motor and the tool bit,
wherein the torque transmission interrupting mechanism interrupts torque transmission, when both the torque detected by the first sensor and the motion of the tool body detected by the second sensor reach respective preset threshold,
the torque transmission between the motor and the tool bit is maintained when at least one of the torque detected by the first sensor and the motio

Assignees

• Aoki Yonosuke
• Makita Corp

Inventors

• Aoki Yonosuke

Classifications

• B24B47/26

  Accessories, e.g. stops · CPC title

• B25D2216/0023

  Tools having a percussion-and-rotation mode · CPC title

• B25D2211/068

  Crank-actuated impulse-driving mechanisms · CPC title

• B25D2250/145

  Electro-magnetic parts · CPC title

• B25D2250/255

  Switches · CPC title