Sps Technologies, LLC

Standard Pressed Steel Co.

Jerry A Sigmund

Apparatus and method for determining dynamic friction in a threaded joint and an associated tightening system for tightening such joints including threaded fasteners. A value representative of the coefficient of friction in the threaded joint is obtained by determining the gradient of a torque-rotation curve which could be plotted for the joint being tightened, and dividing this gradient by the product of the fastener pitch diameter and the tension rate of the joint. The desired tightened condition is achieved by computing the tightening torque required to induce a predetermined preload in the threaded fastener and comparing this computed torque with the instantaneous torque being imparted to the fastener. When the two torques are equal, tightening of the fastener is stopped. The desired tightening torque may be computed by obtaining the product of the value representative of the coefficient of friction, the predetermined preload and the pitch diameter of the fastener, or alternatively, by obtaining the product of the gradient of the torque-rotation curve and the quotient of the predetermined preload divided by the tension rate of the joint.

Dynamic friction indicator and tightening system usable therewith

Apparatus and method for tightening assemblies held together by threaded fasteners. The desired tightened condition is achieved by calculating the tightening torque required to induce a desired preload in the threaded fastener and comparing this calculated tightening torque with the torque being imparted to the fastener to tighten the assembly. When the two torques are equal, the torque imparted to the fastener is stopped. The tightening torque is calculated by identifying properly the relationship between the torque-rotation curve through which the assembly is taken as it is being tightened and the preload-rotation curve for the assembly.

Method and apparatus for tightening threaded fastener assemblies

Apparatus and method for tightening assemblies held together by threaded fasteners. The desired tightened condition is achieved by calculating the tightening torque required to induce a preload in a fastener equal to or approximating a predetermined preload and comparing this calculated torque with the torque being imparted to the fastener to tighten the assembly. When the two torques are equal, the torque imparted to the fastener is stopped. The tightening torque is calculated by identifying properly the relationship between the actual torque-rotation curve through which the assembly is taken as it is being tightened and the theoretical torque-rotation curve for the assembly from which a theoretical tightening torque required to induce the predetermined preload is established.

A fastener which includes an unthreaded bolt member having two groups of grooves formed therein is disclosed. All the grooves within each group have the same depth. The group of grooves furthest from the workpiece have a greater depth than the group of grooves adjacent to the workpiece, thus permitting a more uniform load distribution along the shank of the bolt.

Grooved fastener

A tightening and control system is disclosed for automatically tightening a fastener to a predetermined tightened condition in a workpiece, where the fastener is of the type which exhibits more than one installation region on a graph of two tightening characteristics during a complete tightening cycle. Typical of such fasteners are thread tapping fasteners, such as thread-cutting or thread forming types, which first generate a mating thread in a workpiece material and thereafter are tightened in the workpiece to a predetermined load condition. Such fasteners typically exhibit a curve of two related input tightening characteristics, such as torque and rotation, having a thread forming region characterized by a generally linear portion followed by a marked drop off in the slope, an intermediate region having several possible characteristic shapes, and a tightening region having a somewhat similar shape to the thread forming region. Apparatus is generally disclosed for determining the gradient of the torque-rotation curve through which the assembly is being tightened, determining when a first condition indicative of having formed the thread has occurred, and thereafter determining when the tightening region has been reached. The gradient information is utilized to determine when tightening should be discontinued at the predetermined tightened condition. Typically, this predetermined tightened condition may be the yield point of the assembly. Alternatively, the instantaneous torque value at the first condition is obtained and stored, and tightening is discontinued when the instantaneous torque bears some predetermined relationship to the instantaneous torque value at the first condition.

Tightening system

A tightening and control system is disclosed for automatically tightening a blind fastener assembly to a desired tightened condition in a workpiece, where the assembly is of the type which exhibits more than one installation region on a graph of two tightening characteristics during a complete tightening cycle. Typical of such assemblies are the types which first form an outwardly flared bulb adjacent the blindside surface of a workpiece and thereafter are tightened against the blindside surface to a predetermined clamp load condition. Such fasteners typically exhibit a curve of two related input tightening characteristics, such as torque and rotation, torque and time, or force and stroke. Each curve has a bulb forming region characterized by a generally linear portion followed by a marked drop off in the slope, an intermediate region, and a tightening region having a somewhat similar shape to the bulb forming region. Apparatus is generally disclosed for determining the gradient of the curve through which the assembly is being tightened, determining when a first condition indicative of having formed the bulb has occurred, and thereafter determining when the tightening should be discontinued at the desired tightened condition. In a preferred embodiment, the gradient is used to determine the occurrence of the first condition. The instantaneous force or torque value at this first condition is obtained and stored, and tightening is discontinued when the instantaneous force or torque bears some predetermined relationship to the corresponding force or torque value at the first condition.

Tightening system for blind fasteners

The preferred embodiment of the invention disclosed herein relates to a method of and a tightening system for tightening a joint assembly including a fastener system to a yield point of one of the members in the assembly. According to the method torque is applied and rotation is imparted to a fastener member and the instantaneous slope of the Torque-Rotation curve which could be plotted is determined between successive increments of rotation of the fastener member. Each instantaneous slope is compared with the preceding instantaneous slope to determine the change in the slope of the curve. When the instantaneous slope of the curve decreases a predetermined consecutive number of times equal to a predetermined span of rotation divided by the interval between successive increments of rotation, tightening is discontinued. The tightening system includes a wrench and a control system associated with the wrench including gradient calculating means for determining the instantaneous slope between successive increments of rotation of the Torque-Rotation curve and for determining an instantaneous gradient signal representative thereof. Comparator means responsive to the instantaneous gradient signal determines the change in successive instantaneous gradient signals and develops signals indicating that the slope has increased or decreased. The indicating signals are fed to resettable counter means which counts each decrease signal, and resets to zero each time it receives an increase signal. When the counter means detects a predetermined successive number of decrease signals, it outputs a control signal that discontinues operation of the wrench.

Method and system for tightening joint assembly

A preferred embodiment of the invention disclosed herein relates to a method of and tightening system for tightening a joint assembly including a fastener system to a yield point of one of the members in the assembly. According to the method, torque is applied and rotation is imparted to a fastener member, and the torque and rotational displacement of the fastener are determined at predetermined increments of rotation for use in determining the area between successive increments of rotation under the Torque-Rotation curve which could be plotted. The incremental areas are compared to determine when some member in the joint assembly has been tightened to its yield point or some similarly significant point. The tightening system includes a wrench and a control system associated with the wrench including measuring systems for developing a first signal representative of the torque applied to the fastener and a second signal representative of the rotation of the fastener. Both the first and second signals are fed to an incremental area calculating system included in the control system, which calculates and develops a signal representative of the area under the Torque-Rotation curve which could be plotted for the fastener being tightened, between successive predetermined increments of rotation. The control system further includes decision making means responsive to the incremental area signals for developing a control signal when some member in the joint assembly has been tightened to its yield point or some similarly significant point.

Tightening method and system

The invention disclosed herein relates to a fastener assembly and method of using same to preload a joint including a plurality of adjacent workpieces having aligned openings formed therein. The fastener assembly includes a pin member having an enlarged head and a shank located within the aligned openings in the workpieces and further includes a collar member having a deformable outer portion and a relatively hard inner portion located about a portion of the shank such that the inner portion is directly adjacent the shank portion. Also formed on the shank is a thread configuration adapted to cooperate with a complimentary thread configuration for snugging the workpieces together with a relatively light preload. After the joint has been snugged together, the collar member is crimped causing axial flow of material in the outer portion which reacts to stretch the pin member and induce a desired preload in the joint. Radial flow of the material in the outer portion is resisted by the hardened inner portion whereby the collar member does not flow into engagement with the shank portion of the pin member.

Method and apparatus for preloading a joint

The invention disclosed herein relates to a tightening system including a wrench for applying torque and imparting rotation to a fastener system. Associated with the wrench is a control system including measuring systems for developing a first signal representative of the torque applied to the fastener being tightened and a second signal representative of the rotation of the fastener, both of which are fed to a gradient calculating system for developing a signal representative of the slope of a Torque-Rotation curve which can be plotted for the particular fastener being tightened. The gradient signal is used to develop a signal representative of a theoretical curve which is processed with one of the previously developed signals to develop a control signal when the fastener has been tightened to its yield point or some similarly significant point. In one embodiment of the invention, the theoretical curve signal is representative of a curve which ultimately becomes parallel to the linear portion of the Torque-Rotation curve and whose linearity is maintained when the Torque-Rotation curve deviates. The difference between the theoretical torque signal and the instantaneous torque signal, which is referred to as a decision-making signal, is determined and the difference between successive decision-making signals over a fixed increment of rotation is compared to the maximum gradient of the Torque-Rotation curve in its linear region. When the compared signals have a predetermined relationship, the control signal is developed. In another embodiment of the invention, the theoretical curve signal is representative of a curve superimposed on the Torque-Rotation curve through its linear region and whose linearity is maintained when the Torque-Rotation curve deviates. A ratio of the instantaneous torque signal to the theoretical torque signal is determined, and when this ratio is approximately equal to a predetermined ratio, the control signal is developed. In yet another embodiment of the invention, the theoretical curve signal is representative of a curve offset from the Torque-Rotation curve through its linear region by a predetermined constant and whose linearity is also maintained when the Torque-Rotation curve deviates. The theoretical torque signal is compared to the instantaneous torque signal and when the compared signals are approximately equal, the control signal is developed.

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Willow Grove, PA, United States of America

Jerry A Sigmund