Tension control of fasteners
First Claim
1. Apparatus for tightening seriatim a multiplicity of substantially identical joints having components including at least one threaded fastener to substantially the same final desired stress value, below the yield point of any component that can be correlated with stress, appearing in the fastener, comprisinga powered instructable tool, capable of terminating tightening in response to an instruction which varies from one fastener to the next, for applying torque to the fastener and tightening the same;
- means for sensing the torque applied to the fastener at various angles of advance;
means responsive to the torque and angle sensings for determining, while tightening below the yield point of any joint component that can be correlated with stress, a tightening parameter value, variable from one fastener to the next, sufficient to tighten each fastener to the final desired stress value; and
means for instructing the tool to terminate tightening of each fastener in response to the determined tightening parameter value.
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Accused Products
Abstract
There is disclosed a technique for tightening threaded fasteners in which values of offset torque, initial tension rate relative to angle, final tension rate relative to angle and other joint related factors are empirically determined by instrumenting a plurality of fasteners of the type ultimately to be tightened. In one embodiment, torque and angle are monitored during tightening. Calculations are conducted, while tightening, to determine the tension prevailing in the bolt at a particular angle of advance. By using the calculated tension value and the particular angle of advance, an instantaneous position of threading advance on the tension-angle curve of the fastener is established. From this instantaneous position, it is determined how much greater angle of advance or how much torque is required to tighten the fasteners to a final desired tension value. The same technique may also be used merely to monitor tightening which is terminated by a different tightening strategy. A number of quality control procedures are conducted to determine if the fastener and the tightening tool are performing normally. In another embodiment, analog devices are utilized to convert sensed values of torque and the rate of threading advance into parameters which control tool shut off.
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Citations
44 Claims
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1. Apparatus for tightening seriatim a multiplicity of substantially identical joints having components including at least one threaded fastener to substantially the same final desired stress value, below the yield point of any component that can be correlated with stress, appearing in the fastener, comprising
a powered instructable tool, capable of terminating tightening in response to an instruction which varies from one fastener to the next, for applying torque to the fastener and tightening the same; -
means for sensing the torque applied to the fastener at various angles of advance; means responsive to the torque and angle sensings for determining, while tightening below the yield point of any joint component that can be correlated with stress, a tightening parameter value, variable from one fastener to the next, sufficient to tighten each fastener to the final desired stress value; and means for instructing the tool to terminate tightening of each fastener in response to the determined tightening parameter value. - View Dependent Claims (2, 3, 4, 5)
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6. A method of tightening a multiplicity of substantially identical joints having components including at least one threaded fastener to a final desired stress value below the yield point of any joint component that can be correlated with stress, including
tightening the fastener with an instructable tool; -
sensing torque at various angles of advance during tightening below the yield point of any joint component that can be correlated with stress; calculating, while tightening below the yield point of any joint component that can be correlated with stress, the stress appearing in the fastener at least at one instant of tightening below the yield point of any joint component that can be correlated with stress from the sensed values of torque and angle; determining the value of a tightening parameter sufficient to tighten the fastener to the final desired stress value below the yield point of any joint component that can be correlated with stress from the calculated stress; instructing the tool to tighten the fastener to the determined parameter; and terminating tightening in response to the attainment of the determined parameter. - View Dependent Claims (7, 8, 9, 10, 11)
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12. Apparatus for tightening seriatim a multiplicity of substantially identical joints having components including at least one threaded fastener to substantially the same final desired stress value below the yield point, comprising
a powered instructable tool for tightening the fastener; -
means for sensing torque at various angles of advance during tightening below the yield point of any joint component that can be correlated with stress; means for calculating the stress appearing in the fastener at least at one instant of tightening below the yield point of any joint component that can be correlated with stress from the sensed values of torque and angle; means for determining a tightening parameter value sufficient to tighten the fastener to the final desired stress value below the yield point of any joint component that can be correlated with stress from the calculated stress; and means for instructing the tool to tighten the fastener to the determined parameter value. - View Dependent Claims (13, 14)
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15. A method of tightening a multiplicity of substantially identical joints having components including at least one threaded fastener to a final desired stress value below the yield point of any joint component that can be correlated with stress, comprising
tightening the fastener with an instructable powered tool; -
sensing torque at various angles of advance during tightening; determining the torque rate of the fastener from the sensed values of torque and angle; calculating the stress appearing in the fastener at least at least at one instant of tightening below the yield point of any joint component that can be correlated with stress from the determined torque rate and from sensed torque; determining the value of a tightening parameter sufficient to tighten the fastener to the final desired stress value below the yield point of any joint component that can be correlated with stress from the calculated stress; instructing the tool to tighten the fastener in response to the determined parameter; and terminating tightening in response to the determined parameter. - View Dependent Claims (16, 17)
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18. Apparatus for tightening a multiplicity of substantially identical joints having components including at least one threaded fastener to a final desired stress value below the yield point of any joint component that can be correlated with stress, comprising
a powered instructable tool for tightening the fastener; -
means for sensing torque at various angles of advance during tightening; means for determining the torque rate of the fastener from the sensed values of torque and angle; means for calculating the stress appearing in the fastener at least at one instant of tightening below the yield point of any joint component that can be correlated with stress from the determined torque rate and the sensed torque; means for determining the value of a tightening parameter sufficient to tighten the fastener to the final desired stress value below the yield point of any joint component that can be correlated with stress; and means for instructing the tool to tighten the fastener in response to the determined parameter. - View Dependent Claims (19, 20, 21, 22)
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23. Apparatus for tightening a joint having components including at least one threaded fastener, comprising
a powered tool for tightening the fastener; -
means for monitoring stress in the fastener including means for sensing torque and angle while tightening; and data processor means for calculating stress in the fastener below the yield point of any joint component that can be correlated with stress from sensed values of torque and angle; and means for terminating tightening in response to a tightening parameter related to monitored stress. - View Dependent Claims (24, 25, 26)
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27. Apparatus for tightening substantially identical threaded fasteners in production lots to the same final desired stress value ±
- 15%, comprising
a powered instructable tightening tool having a source of energy, means for connecting and disconnecting the tool to the energy source, a torque sensor and an angle sensor; a data processor connected to the torque and angle sensors including means for determining a mid-point stop of the fasteners at least about 0.4 elastic limit of the weakest joint component from a sensed value of torque and angle and means for instructing the tool to halt tightening at the mid-point stop; means for calculating a torque rate in a region adjacent the mid-point stop from sensed values of torque and angle; means for calculating the stress appearing in the fastener at a location between the onset of tightening and the mid-point stop from a sensed value of torque at the location, the calculated torque rate and an empirically determined stress rate for the region including 0.1-0.5 elastic limit; means for calculating a value of a tightening parameter sufficient to tighten the fastener to a final desired stress value from an empirically determined stress rate above the region 0.1-0.5 elastic limit; means controlled by the data processor for resuming tightening; and means responsive to the value of the tightening parameter for terminating tightening adjacent the final desired stress value. - View Dependent Claims (28, 29, 30, 31, 32, 33)
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34. A method of tightening a joint including a threaded fastener, comprising
tightening the fastener; -
sensing torque applied to the fastener and the angle of threading advance; determining, during tightening, the origin of stress in the fastener from the sensed values of torque and angle; determining a shut off parameter based on the origin of stress; and terminating tightening in response to the shut off parameter.
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35. Apparatus for tightening a joint including a threaded fastener, comprising
a powered tool for tightening the fastener; -
means for sensing the torque applied to the fastener and the angle of threading advance; means for determining, during tightening, the origin of stress in the fastener pair from sensed values of torque and angle; means for determining, during tightening, a shut off parameter based on the origin of stress; and means for terminating operation of the powered tool in response to the shut off parameter.
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36. A method of tightening seriatim a multiplicity of substantially identical production joints including at least one threaded fastener, comprising
empirically determining, prior to tightening the production joints, at least one joint characteristic; -
applying torque to the fastener for tightening the production joint; determining, while tightening below the yield point of any joint component that can be correlated with stress, a tightening parameter based on the empirically determined joint characteristic, which tightening parameter varies from one joint to the next; and terminating tightening in response to the tightening parameter. - View Dependent Claims (37, 38)
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39. Apparatus for tightening seriatim a multiplicity of substantially identical production joints including at least one threaded fastener and having at least one empirically determinable joint characteristic, comprising
means for applying torque to the fastener; -
means for determining, while tightening below the yield point of any joint component that can be correlated with stress, a tightening parameter based on the empirically determined joint characteristic, which tightening parameter varies from one joint to the next, including means for delivering a signal to the determining means representative of the empirically determinable joint characteristic; and means for terminating tightening in response to the tightening parameter.
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40. A method of tightening seriatim a multiplicity of substantially identical production joints including at least one threaded fastener, comprising
determining, prior to tightening the production joints, at least one tightening tool characteristic; -
applying torque to the fastener with the tightening tool for tightening the production joint; determining, while tightening, a tightening parameter based on the determined tool characteristic, which tightening parameter varies from one joint to the next; and terminating tightening in response to the tightening parameter. - View Dependent Claims (41, 42, 43)
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44. Apparatus for tightening seriatim a multiplicity of substantially identical production joints including at least one threaded fastener, comprising
a tightening tool for applying torque to the fastener; -
means for determining, while tightening, a tightening parameter based on a tool characteristic, which tightening parameter varies from one joint to the next, including means for delivering a signal to the determining means representative of the determined tool characteristic; and means for terminating tightening in response to the tightening parameter.
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Specification