Method for improving torque accuracy of a discrete energy tool

• US 6,668,212 B2
• Filed: 06/18/2001
• Issued: 12/23/2003
• Est. Priority Date: 06/18/2001
• Status: Expired due to Term

• Current Assignee: Ingersoll-Rand Industrial U.S., Inc. (Ingersoll Rand, Inc.)
• Original Assignee: Ingersoll-Rand Company (Trane Technologies plc)
• Inventors: Cooper, Timothy R., Colangelo, Louis J. III, Linehan, John L.
• Primary Examiner(s): Picard, Leo
• Assistant Examiner(s): KOSOWSKI, ALEXANDER J
• Application Number:
  US09/883,470
• Publication Number:
  US 20030009262A1
• Time in Patent Office: 918 Days
• Field of Search: 173/5, 173/6, 173/176, 173/178, 173/180, 173/181, 700/275, 700/282, 700/301, 702/145, 702/138, 738/622.1, 738/622.3
• US Class Current: 700/275
• CPC Class Codes: B25B 23/145 specially adapted for fluid operated wrenches or screwdrivers
• CPC Class Codes: B25B 23/1453 for impact wrenches or screwdrivers
• CPC Class Codes: B25B 23/1456 having electrical components

Abstract

A method for improving the accuracy and repeatability of torque applied by discrete energy tools subjected to a wide variety of joint conditions. The method includes relating air pressure to output torque and compensating for temperature and aging variations. Additionally, the method may include a process for detecting previously tightened fasteners.

Claims

1. A method of controlling an air driven tool to provide a desired torque to a fastener, the method comprising:

establishing an air pressure profile for a plurality of torque values;

determining a calibration factor for the tool including

measuring a temperature of the tool;

establishing an expected torque value (T_EXP) based on the tool temperature;

accessing a nominal torque value (T_NOM) for the tool which was established by applying a standard tool to a calibration joint at a nominal air pressure (P_NOM) and a nominal temperature (Temp_NOM); and

calculating a temperature calibration factor (C_T) by dividing the nominal torque value (T_NOM) by the expected torque value (T_EXP);

multiplying the desired torque by the calibration factor to determine a calibrated torque value; and

supplying the tool with air at the air pressure profile corresponding to the calibrated torque value.

2. The method of claim 1 wherein the temperature of the tool is measured at a given interval and averaged over a given amount of time.

3. The method of claim 2 wherein the given interval is equal to 5 minutes and the given amount of time is equal to 30 minutes.

4. A method of controlling an air driven tool to provide a desired torque to a fastener, the method comprising:

establishing an air pressure profile for a plurality of torque values;

determining a calibration factor for the tool including

measuring a temperature of the tool;

establishing an expected torque value (T_EXP) based on the tool temperature;

measuring a measured torque value (T_MEA) for the tool by applying the tool to a calibration joint at a nominal air pressure (P_NOM); and

calculating a tool age calibration factor (C_A) by dividing the expected torque value (T_EXP) by the measured torque value (T_MEA);

multiplying the desired torque by the calibration factor to determine a calibrated torque value; and

supplying the tool with air at the air pressure profile corresponding to the calibrated torque value.

5. The method of claim 4 wherein measuring the measured torque value (T_MEA) includes measuring peak values of torque blows for a fixed time or a fixed number of blows and averaging the measured peak values.

6. The method of claim 5 wherein measuring peak values includes filtering the measured peak values to attenuate signals above a corner frequency.

7. The method of claim 4 further comprising automatically setting the air supply pressure to a value equal to the nominal air pressure (P_NOM) prior to application of the tool to the calibration joint.

8. A method of controlling an air driven tool to provide a desired torque to a fastener, the method comprising:

establishing an air pressure profile for a plurality of torque values;

determining a calibration factor for the tool including

measuring a temperature of the tool;

establishing an expected torque value (T_EXP) based on the tool temperature;

accessing a nominal torque value (T_NOM) for the tool which was established by applying a lab standard tool to a calibration joint at a nominal air pressure (P_NOM);

measuring a measured torque value (T_MEA) for the tool by applying the tool to the calibration joint at the nominal air pressure (P_NOM);

calculating a temperature calibration factor (C_T) by dividing the nominal torque value (T_NOM) by the expected torque value (T_EXP);

calculating a tool age calibration factor (C_A) by dividing the expected torque value (T_EXP) by the measured torque value (T_MEA); and

calculating a total calibration factor by multiplying the temperature calibration factor (C_T) by the tool age calibration factor (C_A);

multiplying the desired torque by the calibration factor to determine a calibrated torque value; and

supplying the tool with air at the air pressure profile corresponding to the calibrated torque value.

9. The method of claim 8 wherein the expected torque value (T_EXP) is calculated using the formula:

10. The method of claim 9 wherein the coefficients are found by using a least squares fit to the laboratory data.

11. The method of claim 9 wherein the coefficients, using a lab standard tool manufactured by Yokota Industries under model no. YEX-1900 at a P_NOM of 70 psi with a resultant T_NOM of 108.6 ft. lbs., have the following values:

A₀=6.766E1

A₁=1.537E0

A₂=−

1.813E−

2

A₃=6.462E−

5.

12. The method of claim 8 further comprising storing the nominal torque value (T_NOM), the nominal air pressure (P_NOM) and the coefficients in an associated control system.

13. A method of controlling an air driven tool to provide a desired torque to a fastener, the method comprising:

establishing an air pressure profile for a plurality of torque values;

determining a calibration factor for the tool including

measuring a temperature of the tool; and

establishing an expected torque value (T_EXP) based on the tool temperature, said torque value (T_EXP) being calculated using the formula;

14. A method of controlling an air driven tool to provide a desired torque to a fastener, the method comprising:

establishing a maximum air pressure value;

supplying the tool with air at a starting air pressure value greater than an intermediate air pressure value and less than or equal to the maximum air pressure value for a limited time prior to supplying of air beginning at the intermediate air pressure value;

measuring a torque value at the limited time;

comparing the measured torque value at the limited time with a limit torque having a predetermined value;

designating a pre-tightened condition if the measured torque value at the limited time is greater than or equal to the limit torque value; and

if the measured torque value at the limited time is less than the limit torque value, supplying the tool with a continuous supply of air beginning at the intermediate air pressure value that is less than the maximum air pressure value and continuously increasing the air pressure at a desired rate until the torque applied to the fastener is within a predetermined range of the desired torque.

15. The method of claim 14 wherein the limit torque value is calculated as a percentage of the desired torque.

16. The method of claim 15 wherein the percentage is in a range of 91-100 percent.

17. The method of claim 14 wherein a calibration factor is utilized in establishing the predetermined value.