Device for monitoring the tightening torque of threaded connections

Abstract

The utility model relates to control technology, specifically, to torque control for common types of threaded connections. A device for monitoring the tightening torque of a bolt or nut head comprises a hollow, cast body with profiled ribs on the outer surface for engagement with various types of standard wrenches and with profiled sockets on the inner surface of the hollow body for engagement with the bolt or nut head. The device is manufactured from a material selected such that upon reaching a certain tightening torque, the profiled sockets collapse, and the standard wrench rotates, signaling completion of the tightening process. This method for controlled tightening of threaded connections allows for reliable determination of the tightening torque required to ensure the required tightness and seal of the connection, eliminating the need for a torque wrench and significantly reducing the risk of damage to the bolt head.The accuracy of the axial tightening force of the thread is increased and reliable control of exceeding the permissible axial tightening force is ensured.

Description

[0001] The utility model relates to control technology, in particular control of the tightening torque of common types of threaded connections.

[0002] One of the most common types of threaded connections is the bolted connection. These connections largely determine the reliability and safety of various structures. Over- or under-tightening of threaded connections can lead to failure of individual components or the entire mechanism.

[0003] Current methods of tightening threaded connections, including the use of various types of wrenches, do not provide sufficient accuracy in controlling the tightening force.

[0004] A known method for tightening a controlled screw (Author's Certificate SU 1558295, published April 15, 1990) consists of several sequential steps. First, a torque is applied to the nut until a predetermined value is reached. The nut is then rotated through a predetermined angle, after which the tightening process stops. Next, the nut is loosened by the same predetermined angle, during which the current torque value is recorded. Based on this data, the optimal tightening torque is calculated to provide the required axial force. The process concludes with a final tightening until the calculated torque is reached.

[0005] The disadvantage of this method is the insufficient control accuracy, due to the fact that the screwing and unscrewing moments must be determined at the same angular position of the spindle, which is difficult to achieve with high positioning accuracy.

[0006] A device for monitoring the tightening torque of threaded connections (Author's Certificate SU 1079424, published March 15, 1984) is known. It comprises a housing with a head for a wrench, a torque limiting mechanism, and a deformable element, designed to expand the technological capabilities of impact tightening. The device is designed as two half couplings having at least three radial projections of a semicircular cross-section, aligned in the plane of the half couplings' separation, and the deformable element is designed as washers enclosing these projections.

[0007] The disadvantage of such a device is the high cost of the metal required to manufacture the washers, which are inevitably destroyed as a result of use, as well as the relative complexity of assembling the structure that controls the tightening torque of the threaded connection.

[0008] Of the known technical solutions, the closest is a device for monitoring the forces in threaded connections (Author's Certificate SU 1202846, published 07.01.1986). Its key element is a pair of concentric elastic washers connected along a conical surface. A ring gauge is used to measure deformation, which is installed with a specified gap on the outer (envelope) washer. During tightening of the threaded connection, the washers are elastically deformed. The envelope washer, having lower rigidity, experiences significantly greater radial deformation than the inner one. Tightening force is controlled by monitoring the radial deformation of the envelope washer using a ring gauge. When a predetermined torque is reached, the gap between the washer and the gauge is closed, and the washer begins to compress the gauge. The end of tightening is signaled by a sharp increase in torque on the wrench or by the jamming of the gauge on the washer.The signal that tightening is complete is a sudden increase in torque on the key or jamming of the gauge on the washer.

[0009] The disadvantage of the device is its low reliability, since there is a high probability of loosening the threaded connection, which can only be detected during operation, when the gauge begins to turn on the washer, which indicates the need to tighten the threaded connection.

[0010] The objective of the utility model is to create a system for controlling the tightening of a bolt or nut head, characterized by high efficiency of installation and use, with minimization of production and operating costs.

[0011] The device (Fig. 1) contains a hollow one-piece body 1 with profile ribs 2 on the outer surface of the body for interaction with various types of standard keys (socket, open-end) and with profiled sockets 3 on the inner surface of the hollow body for interaction with the head of a bolt or nut.

[0012] The device works as follows: when a certain tightening torque is reached, the profiled sockets (in combination with the material from which it is made) are destroyed and the standard key turns, signaling the completion of the tightening process.

[0013] To test the device's functionality, prototypes of the proposed device for monitoring the tightening torque of a bolt or nut head were manufactured (Fig. 2). The primary material used for the device was environmentally friendly 3D printing filaments such as PLA and PETG, as well as combinations thereof. During a series of control tests, the prototypes demonstrated their potential and full functionality. Other polymers and materials could also be used. In addition to 3D printing, the device could be manufactured using other technologies, such as casting or forging.

[0014] Using this method of controlled tightening of the bolt or nut head allows for reliable determination of the tightening torque required to ensure the required tightness and seal of the connection. It also eliminates the need for a torque wrench and significantly reduces the risk of damage to the bolt head. This method improves the accuracy of the axial tightening force on the thread and ensures reliable control of any excess axial tightening force.

[0015] The material and manufacturing costs of the proposed device for monitoring the tightening torque of a bolt or nut head are negligible compared to the weight and cost of the threaded connection itself. This design of the device for monitoring the tightening torque of a bolt or nut head allows for wide application in static tightening methods.

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