Tightening apparatus
AssigneeSPS Technologies, Inc.
InventorJohn T. Boys
Life of this patent
Estimating the term…
Abstract
An impact wrench having an adaptive control system for determining the yield point or some similarly significant point of a fastener assembly by detecting a signal representative of the peak deceleration of the hammer, one embodiment of which is the peak recoil value of the hammer after impacting with the anvil of the wrench, and a signal representative of the angular displacement of the output shaft of the wrench. Yield of the fastener is determined when the respective magnitudes of successive deceleration signals do not exceed the magnitude of a previously stored maximum deceleration signal by a predetermined fixed amount. Upon attaining the yield point or other similarly significant point, the wrench may be allowed to rotate the fastener an additional preselected number of degrees before shutting off.
Claims88
Apparatus for tightening a fastener, said apparatus comprising:
- wrench means having a pulsed output for periodically applying a tightening moment to a fastener in a joint assembly whereby a peak moment is applied during each period;
- first means for measuring the moment applied to the fastener during each period and for developing a signal representative of the peak moment applied during each period;
- control means responsive to said peak moment signals for determining when an instantaneous peak moment signal has not increased by more than a positive finite predetermined amount of an order sufficient to indicate that there has been no significant increase in peak moment, said control means also developing a control signal;
- and shut-off means responsive to said control signal for discontinuing the output of said wrench means.
A control system usable with a wrench having a pulsed output for controlling the tightening of a fastener, said system comprising:
- first means for measuring the instantaneous moment applied to a fastener and developing a signal representative thereof and second means responsive to said first means for storing a signal representative of the peak moment applied to the fastener during any output period;
- control means responsive to said instantaneous moment signals and said stored peak moment signals for determining when an instantaneous peak moment signal has not increased by more than a positive, finite predetermined amount of an order sufficient to indicate that there has been no significant increase in peak moment, said control means also developing a control signal;
- and shut-off means responsive to said control signal for indicating that the output of the wrench should be discontinued.
In an impact wrench including a hammer impacting with an anvil to rotate an output shaft operative to tighten an assembly including a fastener to its yield point by applying torque thereto, a control system comprising:
- means for developing a signal representative of the deceleration of the hammer after engagement thereof with the anvil;
- means for developing a signal representative of the angular displacement of the output shaft;
- calculator means responsive to said deceleration signal and said angular displacement signal for determining the yield point of the assembly, said calculator means determining the largest deceleration signal during a first angular displacement of the output shaft;
- and
- control means responsive to said calculator means for producing a control signal when the assembly is tightened to said yield point, said control means producing said control signal only if a deceleration signal larger than said largest deceleration signal is not developed during a second angular displacement of the output shaft.
An impact wrench for tightening an assembly including a fastener comprising:
- a motor;
- a hammer assembly adapted to be driven by said motor;
- an anvil adapted to be rotatingly impacted by said hammer assembly wrench means operatively attached to said anvil and adapted to drive the fastener by applying torque thereto;
- means for developing a signal representative of the recoil of said hammer after engagement thereof with said anvil;
- means for developing a signal representative of the angular displacement of the output shaft;
- calculator means responsive to said recoil signal and said angular displacement signal for determining the yield point of the assembly, said calculator means determining the largest recoil signal during the first angular displacement of the output shaft;
- and
- control means responsive to said calculator means for producing a control signal when the assembly is tightened to said yield point, said control means producing said control signal only if a recoil signal larger than said largest recoil signal is not developed during a second angular displacement of the output shaft.
In an impact wrench including a hammer impacting with an anvil to rotate an output shaft, apparatus for measuring the recoil of the hammer after striking the anvil comprising:
- first means opeatively coupled to the hammer for movement in the direction of recoil therewith;
- second means juxtapositioned from said second means being rotatably movable between a first and a second position;
- force transmitting means disposed between said first means and said second means for transmitting force therebetween due to recoil of the hammer;
- biasing means attached to said second means for exerting a force thereupon toward said first position, said force being in a direction opposite to the direction of recoil of the hammer;
- and
- measuring means for measuring the movement of said second means between said first and said second positions.
A method of tightening an assembly including a fastener to to its yield point by applying torque thereto with an impact wrench of the type including a hammer impacting with an anvil to rotate an output shaft operatively coupled to the fastener comprising the steps of:
- developing successive signals representative of the recoil of the hammer after engagement thereof with the anvil;
- developing a signal representative of the angular displacement of the output shaft;
- determining the yield point of the assembly based upon a desired relationship between said recoil signals and further with respect to said angular displacement signal, said largest recoil signal being determined during a first angular displacement of the output shaft;
- and producing a control signal when the assembly is tightened to said yield point, said control signal being produced only if a recoil signal larger than said largest recoil signal is not developed during a second angular displacement of the output shaft.
In a tightening system for tightening an assembly including a fastener to a desired tightened condition by applying a tightening moment thereto, a control system comprising:
- means for developing a first signal representative of the tightening moment being applied to the fastener;
- means for developing a second signal representative of the angular displacement of the fastener;
- calculator means responsive to said first signal for determining the largest one of said first signals developed up to any point during a tightening cycle and developing a third signal indicative thereof;
- and
- control means responsive to said third signal and said second signal for producing a control signal when said largest one of said first signals developed up to any point during the tightening cycle is not exceeded by a predetermined amount by first signal developed during a predetermined additional angular displacement of the fastener, said control signal being produced at the desired tightened condition.
An impact wrench for tightening an assembly including a fastener, comprising:
- a motor;
- a hammer assembly adapted to be driven by said motor;
- an anvil adapted to be rotatingly impacted by said hammer assembly wrench means operatively attached to said anvil and adapted to drive the fastener by applying torque thereto;
- means for developing a signal representative of the recoil of said hammer after engagement thereof with said anvil, including first means operatively coupled to said hammer for movement in the direction of recoil therewith, second means juxtapositioned from said first means, said second means being rotatingly movable between a first and second position, force transmitting means disposed between said first means and said second means for transmitting force therebetween due to recoil of the hammer, biasing means attached to said second means for exerting a force thereupon toward said first position, said force being in a direction opposite to the direction of recoil of the hammer, and measuring means for measuring the movement of said second means between said first and said second positions;
- means for developing a signal representative of the angular displacement of the fastener;
- calculator means responsive to said recoil signal and said angular displacement signal for determining the largest recoil signal during a first angular displacement of the fastener at the yield point or some similarly significant point of the assembly;
- and
- control means responsive to said calculator means for producing a control signal only if a recoil signal larger than said largest recoil signal is not developed during a second angular displacement of the fastener.
In an impact wrench including a hammer impacting with an anvil to rotate an output shaft operative to tighten an assembly including a fastener to its yield point or some similarly significant point in a tightening cycle by applying torque thereto, a control system comprising:
- means for developing a signal representative of the deceleration of the hammer after engagement thereof with the anvil;
- calculator means including storage means for storing a signal representative ot the largest deceleration signal developed up to any point in the tightening cycle, said calculator means determining the yield point or some similarly significant point of the assembly when a deceleration signal larger by a predetermined amount is not developed during some period subsequent to reaching said largest deceleration signal;
- and
- control means responsive to said calculator means for producing a control signal when the assembly is tightened to said point.
Apparatus for tightening a fastener, said apparatus comprising:
- wrench means for periodically applying a tightening moment to a fastener in a joint assembly;
- first means for measuring the moment applied to the fastener during each period and for developing a signal representative of the peak moment applied during each period;
- and
- control means responsive to said peak moment signals for determining when a peak moment signal has not increased by more than a predetermined amount and for developing a control signal, said control means further including storage means for storing a peak moment signal and comparator means for comparing the stored peak moment signal with an instantaneous peak moment signal for determining the difference therebetween, and second means for increasing the stored signal by a predetermined amount.
A control system usable with a wrench for controlling the tightening of a fastener, said system comprising:
- first means for periodically developing a signal representative of the instantaneous moment applied to a fastener;
- and
- control means responsive to said instantaneous moment signals for determining when an instantaneous moment signal has not increased by more than a predetermined amount and for developing a control signal, said control means further including storage means for storing an instantaneous moment signal and comparator means for comparing the stored signal with an instantaneous moment signal for determining the difference therebetween, and second means for increasing the stored signal by a predetermined amount.
Dependencies are inferred from the claim text.