Fastening Tool and Fastening Tool Management System

• US 20080230245A1
• Filed: 03/10/2005
• Published: 09/25/2008
• Est. Priority Date: 03/12/2004
• Status: Active Grant

• Current Assignee: Makita Corporation
• Original Assignee: Makita Corporation
• Inventors: Matsunaga, Yutaka
• Granted Patent: US 7,556,103 B2
• Time in Patent Office: Days
• US Class Current: 173/4
• CPC Class Codes: B25B 23/141 Mechanical overload release couplings
• CPC Class Codes: B25B 23/147 specially adapted for electrically operated wrenches or screwdrivers

Abstract

A fastening tool with a clutch for shutting off transmission of torque, capable of self-diagnosing fastening torque of a screw or the like at low cost without using expensive means such as a torque sensor etc. A fastening tool (10) has a motor (13), a main shaft (20) engaging with a screw or the like, and a clutch (14) interposed between the motor (13) and the main shaft (20). The clutch (14) transmits torque from the motor (13) to the main shaft (20) when a load acting on the main shaft (20) is less than a predetermined value, and shuts off torque transmission from the motor (13) to the main shaft (20) when a load acting on the main shaft (20) is equal to or greater than the predetermined value. The fastening tool (10) further has a control unit (60) for controlling the motor (13). The control unit (60) monitors a current flowing to the motor (13) and determines whether fastening torque is normal or not based on a motor current when transmission of torque from the motor (13) to the main shaft (20) is shut off.

Claims

1. A tightening tool for tightening a fastener, comprising:

a motor;

a main shaft which engages with the fastener;

a clutch disposed between the motor and the main shaft, wherein the clutch rotates the main shaft by transmitting torque from the motor to the main shaft when a load acting on the main shaft is less than a predetermined value, and shuts off torque transmission from the motor to the main shaft when the load acting on the main shaft reaches or exceeds the predetermined value;

means for detecting a current flowing to the motor; and

means for determining, when torque transmission from the motor to the main shaft has been shut off, whether or not a tightening torque of the fastener is normal based upon a motor current value detected by the current detecting means at the time of torque transmission shut-off.

2. A tightening tool according to claim 1, wherein the determining means determines that the tightening torque of the fastener is normal when the detected motor current value is within a preset range, and determines that the tightening torque of the fastener is abnormal when the detected current value is outside of the preset range.

3. A tightening tool according to claim 2, further comprising a memory which stores a preset range for each type of tightening operation, wherein the determining means reads a preset range from the memory in accordance with the type of tightening operation, and determines whether or not the tightening torque is normal on the basis of the read preset range.

13. A tightening tool according to claim 3, further comprising means for warning an operator when the tightening torque of the fastener is determined to be abnormal by the determining means.

4. A tightening tool for tightening a fastener, comprising:

a motor;

a main shaft which engages with the fastener;

a clutch disposed between the motor and the main shaft, wherein the clutch rotates the main shaft by transmitting torque from the motor to the main shaft when a load acting on the main shaft is less than a predetermined value, and shuts off torque transmission from the motor to the main shaft when the load acting on the main shaft reaches or exceeds the predetermined value;

means for detecting a current flowing to the motor;

means for detecting a rotation angle of the main shaft or the motor; and

means for determining whether or not a tightening torque of the fastener is normal based upon the rotation angle of the main shaft or the motor detected by the rotation angle detecting means during a period extending from (1) a time at which a current value detected by the current detecting means exceeds a preset value to (2) a time at which torque transmission from the motor to the main shaft is shut off.

5. A tightening tool according to claim 4, wherein the determining means (a) measures the rotation angle of the main shaft or the motor from the time at which the current flowing to the motor exceeds the preset value to a time at which the clutch is activated, and (b) determines that the tightening torque of the fastener is normal when the measured rotation angle is within a preset angle range and determines that the tightening torque of the fastener is abnormal when the measured rotation angle is outside of the preset angle range.

6. A tightening tool according to claim 5, further comprising a memory which stores a preset angle range for each type of tightening operation, wherein the determining means reads a preset angle range from the memory in accordance with the type of tightening operation, and determines whether or not the tightening torque is normal on the basis of the read preset angle range.

7. A tightening tool according to claim 6, wherein the determining means determines the operation type from temporal variation in the motor current value and/or temporal variation in the rotation angle of the main shaft after the current flowing to the motor has exceeded the preset value, and reads a preset angle range corresponding to the determined operation type.

8. A tightening tool according to claim 7, further comprising means for warning an operator when the tightening torque of the fastener is determined to be abnormal by the determining means.

9. A tightening tool management system comprising a tightening tool for tightening a fastener and a management apparatus in communication with the tightening tool, wherein

the tightening tool further comprises means for detecting an indicator for determining whether or not a tightening operation is abnormal, means for determining whether or not a tightening torque of the fastener is normal on the basis of the detected indicator, and means for communicating with the management apparatus,

the management apparatus comprises means for communicating with the tightening tool and a memory for storing operation management information,

the communicating means of the tightening tool transmits the indicator detected by the detecting means and a determination result determined by the determining means on the basis of the indicator to the management apparatus, and

the memory of the management apparatus stores the indicator and the determination result transmitted from the communicating means of the tightening tool.

10. A tightening tool management system according to claim 9, wherein the communicating means of the tightening tool transmits to the management apparatus specifying information for specifying the fastener relating to the determination result together with the indicator and the determination result, and the memory of the management apparatus stores the received determination result and specifying information in association.

11. A tightening tool management system according to claim 9 or 10, wherein the management apparatus further comprises means for determining whether or not the tightening tool requires maintenance based upon temporal variation in the indicator stored in the memory.

12. A tightening tool management system according to claim 11, wherein the determining means of the management apparatus predicts a maintenance timing of the tightening tool from the temporal variation in the indicator stored in the memory.

14. A tightening tool management system according to claim 9, wherein the management apparatus further comprises means for determining whether or not the tightening tool requires maintenance based upon temporal variation in the indicator stored in the memory.