RU2527567C2 - Device for detecting loosening of nut of threaded contact connection - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention relates to basic components of electrical equipment - connection devices, and specifically to means of monitoring the state of electrical contact connections, and can be used in operational diagnosis of electrical equipment. The device for detecting the loosening of a nut of a threaded contact connection has a thermobimetallic plate with an active and a passive layer, which interacts with components of said contact connection through thermal contact. The end of the plate is elastically engaged and disengaged upon deformation thereof through overheating with current passing through the contact connection upon loosening of the thread, which switches the detection device from a working state to an emergency state.

EFFECT: high resistance of the device to vibration and impact loads and fire-safety of electrical equipment for small dimensions of the device, which is easy to manufacture and operate.

5 cl, 8 dwg

Description

The invention relates to the basic elements of electrical equipment - connecting devices, and in particular to means for monitoring the state of electrical contact connections and can be used in the diagnosis of electrical equipment during work on its routine maintenance.

A device for detecting overheating of a contact connection / comprising a temperature sensor interacting with the components of the contact connection and a sensor signal converter with an output to an indicator connected via a power port to a transformer, the primary winding of which is a conductor connected by the specified contact connection (Chinese patent 101639385, IPC G01K 7/22, G01K 7/16, 2010, analogue).

The disadvantage of this device is the inability to diagnose the state of the contact connection during routine maintenance of electrical equipment, which is made in its off state. This is due to the fact that the overheating of the contact connection with the help of the specified device can be fixed only at the moment of passage of the electric current through the controlled contact, that is, in the working state of the electrical equipment. In addition, the specified device is characterized by increased complexity due to the presence of electronic components, the dimensions and cost of which are several times higher than the dimensions and cost of the diagnosed contact connection.

The closest in technical essence is a device for recording the loosening of the nut of a threaded contact joint, containing a thermobimetallic plate with active and passive layers interacting with the components of the contact joint through a thermal contact and a latch interacting with the end of the thermobimetallic plate when it is overheated by the current passing through the contact joint ( Autoswed USSR No. 1803948, IPC H01R 4/00, 1990 - prototype).

Unlike the analogue, this device provides an indication of overheating of a de-energized contact connection when the electrical equipment is disconnected, for example, during periodic work on the schedule of its maintenance. However, it also has drawbacks consisting in a significant increase in the dimensions of the threaded contact joint, instability to vibration and shock loads, as well as in the low manufacturability of manufacture and maintenance.

These drawbacks are due to the principle of the opposite fastening of the ends of the thermobimetallic and the elastic plate interacting with it in dimensions limited by the diameter of the thread of the stud of the threaded contact joint. Therefore, to ensure acceptable sensitivity of the device, the thermobimetal plate can only be made in the form of an excessively thin and narrow petal. Such a petal, having a low resonant frequency of its own mechanical vibrations, has, accordingly, increased sensitivity to vibration and shock effects, characteristic of the electrical equipment of vehicles, for example, ships. Overheating of the contact, causing the bending of the thermobimetallic plate and bending its end out of engagement, in this case has an effect commensurate with the action of these shock and vibration loads. In addition, the non-uniformity of the temperature distribution along the length of the hairpin, due to the increase in the influence of the ambient temperature as the distance from the controlled contact zone on which the known recording device is installed / also reduces the influence of the contact overheating temperature against the background of the influence of the ambient temperature. Constructive limitation of the length of the thermobimetallic plate with the diameter of the stud does not allow to increase the zone of elastic engagement to increase its resistance to vibration and shock. It is also difficult (and for contact joints with a thread diameter smaller than M16 and technologically impossible) to manually adjust the response threshold due to the precision of the necessary operations. To exclude the possibility of mechanical damage (deformation) of a thin and narrow thermo-bimetallic plate if it is accidentally touched (during connecting cables to the electrical terminal), the known device needs a transparent protective cover, which also reduces the manufacturability and increases its dimensions. The small dimensions of the thermo-bimetallic plate, limited to half the diameter of the thread, as well as its small engagement zone due to this, complicate visual inspection, reducing the serviceability of the service. This prevents the use of a known device for the diagnosis of overheating of contact connections of electrical equipment of vehicles, for example, ships.

The objective of the invention is to increase the stability of the device to vibration and shock loads when it is performed in the dimensions of the perimeter of the threaded contact joint and to ensure the manufacturability of its manufacture and maintenance.

Compared with the prototype, this is achieved by the fact that the thermobimetallic plate is folded in half and provided with a hole forming a rectangular washer. The ends of the thermobimetallic plate from the side opposite to the line of its folding are bent by the petals from the plane of the rectangular washer. The petals are located at an acute angle to each other with the possibility of mutual angular displacement in the area bounded by the lateral surface of the nut and the tubular part of the current-carrying tip. The latch is made by elastic bending at the end of one petal, interacting with the hooked bending at the end of another petal.

The bent petals of the thermobimetallic plate are made narrowing in width as they move away from the lines of their bend in the form of gutters directed across the lines of their bend. The elastic limb of the petal is made in the form of a V-shaped loop. The thermobimetallic plate in the area between the folding and bending lines of the petals is provided with lateral bends covering the tail of the current-carrying tip.

Due to the mutual displacement during heating of the bent ends of the thermo-bimetallic tape located between the nut and the current-carrying tip in opposite directions, as well as due to the thermal contact of the thermo-bimetallic tape directly with the shank of the current-carrying tip /, an increase in the stroke with respect to deformations caused by the influence of the ambient temperature is provided. This provides increased stability of fixation of the mutual displacement of additional limbs, and a clearer visual distinguishability of the working and emergency conditions of the contact joint, including those located deep in the cavity of electrical equipment.

The registration device fits into the dimensions of the perimeter of the contact connection and slightly (for some sizes of cable lugs) goes beyond these dimensions in an area not adjacent to adjacent contact connections (above the tip). This oversizing practically does not prevent the mounting tool from being connected to the threaded connection to tighten the thread during installation and tighten it during operation. The width of the maximum deformable portion of the thermobimetallic plate adjacent to the heat contact zone and determining the magnitude of the bending deformation force practically corresponds to the width of the shank of the current-carrying tip, several times exceeding the width of the hooked ends. This, along with the V-shaped design of the additional bend loop, reduces the influence of the friction forces of the additional bends when they are mutually displaced during the disengagement process, and, as a result, increase the stability of this process, which ensures the accuracy of the indication of contact overheating.

The narrowing of the ends of the thermobimetallic plate with distance from the heat contact zone, along with their execution in the form of a trench, reduces the natural frequencies of mechanical vibrations due to increased rigidity in the direction of longitudinal deformation (across the lines of their bending). It also increases the vibration and shock resistance of the device.

As a result of a combination of these features, providing dimensions that do not significantly exceed the dimensions of the threaded contact joint or fit into them, a high diagnostic process performance is achieved by improving the accuracy and stability of the indication of contact overheating while increasing the device's resistance to vibration and shock loads. This also provides increased manufacturability of the manufacture and maintenance of the device.

The invention is illustrated in the drawings Fig.1 ÷ Fig.10:

Figure 1 - device (trip version) in working condition, side view;

Figure 2 - device (uncoupled version) when heated above the threshold;

Figure 3 is the same, a top view;

Figure 4 - a cooled device (trip version) after heating above a threshold;

Figure 5 is an enlarged sectional view of the grooved petals in the middle part;

6 is a device (hooked version) in working condition, side view;

Fig.7 - device (hooked version) when heated above the threshold;

Fig. 8 shows a cooled device (hooked version) after heating above a threshold.

The registration device for loosening the tightening of the nut 1 of the threaded contact connection of the terminal 2 with the current-carrying tip 3, tightened on the stud 4 can be performed in two versions:

- with gearing in working condition (uncoupled option);

- with gearing in emergency condition (gearing option).

The first option is described in more detail, for the second only differences are indicated.

The device comprises a thermobimetallic plate 5, with an active 6 and a passive 7 layers, interacting with the specified components of the contact connection through thermal contact, as well as an elastic latch 8, interacting with the end of the thermobimetallic plate when it overheats.

The thermobimetallic plate is folded in half and provided with an opening 9 forming a rectangular washer 10 of the specified threaded contact connection. The ends of the folded thermobimetal plate from the side opposite to the line of its folding are bent by the petals 11 and 12 from the plane of the rectangular washer. They are located with the possibility of mutual angular displacement at an acute angle to each other in the area between the nut and the tubular part of the current-carrying tip. The latch is made by elastic bending 13 at the end of the petal 12, interacting with the hook bending 14 at the end of the petal 11.

Bent petals are made narrowing in width as they move away from the lines of their limb. They can also be made in the form of tapering gutters directed across the line of their limb. In this case, the tapering troughs are formed by longitudinal bends 15 on the sides of the bent ends of the petals or a more smooth form of their transverse deformation, for example, along a generatrix of the conical surface (not shown in the drawing). The elastic limb 13 is made in the form of a V-shaped loop.

The thermobimetallic plate between the folding line and the bending lines of the petals is provided with lateral limbs 16 covering the tail of the current-carrying tip and preventing the thermobimetallic plate from turning relative to the axis of the pin while tightening the thread.

In the operating position, until the contact connection is overheated above the permissible limit at which the device is in emergency condition (Figure 1), the bent ends of the thermobimetallic tape are in mutual engagement through the latch. During visual inspection, a working stable position of the device is recorded, which characterizes the satisfactory state of the contact joint, which does not require thread tightening.

During long-term operation of electrical equipment, as corrosion processes increase the transition resistance of the contact, causing overheating and weakening of the thread, the petals diverge. The end of the bend 13 is shifted relative to the bend 14 within the limits that do not cause their disengagement. When you turn off the electrical equipment and cool the contact connection, they return to their original position. The state of the contact joint during visual inspection during routine maintenance of electrical equipment is recorded as working, which indicates that there is no need to tighten the thread.

During further operation of the device, due to the influence of corrosion processes, vibration and shock loads, relaxation of the nut and stud materials, as well as other factors, the thread tension weakens beyond the permissible norm. As a result, the terminal overheats with a current-carrying terminal. The thermobimetallic plate, due to the expansion of the active layer, is deformed with a bend towards the passive layer, increasing the angle of mutual divergence of the bent petals so that the end of the elastic bend 13 disengages from the bend 14 (FIGS. 2 and 3) and bends from its original position. When you turn off the electrical equipment (and cooling the contact connection), they remain in a disengaged state (Figure 4). Such a condition during visual inspection is recorded as emergency.

The restoration of the initial working position of the device after tightening the thread is carried out manually by forced mechanical institution of the ends of the bends in mutual,

The gutter-shaped shape of the petals (Figure 5), prevents their mutual displacement due to thermal deformation in the area remote from thermal contact, where the influence of ambient temperature prevails and reduces the magnitude of the natural frequencies of vibration during mechanical stress.

The design of the registration device for loosening the tightening of the nut of the threaded contact joint, with gearing in the emergency state, has the same components as described above and differs in the mutual initial location of the ends of the bends, as well as in the opposite direction of the elastic deformation of the V-shaped loop. In this design, in the operating position, until the contact joint is overheated above the permissible limit at which the device is in emergency condition (Fig. 6), the bent ends of the thermo-bimetallic tape are not mutually engaged through the latch. The ends of the bends 14 are pressed against each other due to the elastic deformation of the V-shaped loop. During visual inspection, a working stable position of the device is recorded, which characterizes the satisfactory state of the contact joint, which does not require thread tightening.

As the contact resistance of the contact increases, causing the contact joint to overheat, the petals diverge, the ends of the limb shifts relative to each other within the limits that do not cause their engagement. When you turn off the electrical equipment and cool the contact connection, they return to their original position. The state of the contact joint during visual inspection during routine maintenance of electrical equipment is recorded as working, which indicates that there is no need to tighten the thread.

When the terminal with a current-carrying tip is overheated, the thermo-bimetal plate is deformed so that the ends of the limbs come out of mutual engagement (Fig. 7) and, due to the elastic deformation, the V-shaped loop is compressed. When turning off the electrical equipment (and cooling the contact joint), the end of the bend 13 abuts against the lobe 11, as a result of which the lobes remain in a disengaged state (Fig. 8). Such a condition during visual inspection is recorded as emergency. Bending 14 prevents the spontaneous displacement of the end of the elastic bending 13 from this state under the influence of vibration and shock loads and, accordingly, the transition of the device into working condition until the defect of the contact joint is eliminated.

Adjusting the device, if necessary, change the settings of the operation, carry out the adjustment of the zone of mutual overlap of the ends of the limb by deforming the shape of the V-shaped loop.

The proposed high-tech device for manufacturing and servicing the registration device for loosening the nut of a threaded contact connection with a current-carrying tip, which provides increased resistance to vibration and shock loads, has an increased distinguishability of working and emergency conditions, which distinguishes it from the prototype. The use of the device does not require a change in the design of the mounting units of electrical equipment and the design of the current-carrying cable lugs connected to them.

The positive effect of the use of the invention is due to a reduction in the total cost of measures to ensure fire safety of electrical equipment operating under the influence of vibration and shock loads in an aggressive external environment, affecting the corrosion rate of the contacting surfaces of busbars and cable lugs. This effect is due to the simplicity of the manufacturing of the registration device, providing the possibility of its mass production by stamping and flexible sheet thermobimetal material, and ease of operation.

Claims (5)

1. A recording device for loosening a nut of a threaded contact connection of a terminal with a current-carrying tip, containing a thermobimetallic plate with active and passive layers interacting with the components of the specified contact connection through a thermal contact and a latch interacting with the end of the thermobimetallic plate / when it is overheated by the current passing through the contact connection, characterized in that the thermobimetallic plate is folded in half and provided with a hole forming a rectangular plate at the specified threaded contact connection, and the ends of the thermobimetallic plate, from the side opposite to the folding line, are bent from the plane of the rectangular washer by petals located with the possibility of mutual angular displacement at an acute angle to each other in the area bounded by the side surface of the nut and the tubular part of the current-carrying tip moreover, the latch is made by elastic bending at the end of one petal, interacting with bending at the end of another petal. 2. The device according to claim 1, characterized in that the bent petals of the thermobimetallic plate are made tapering in width as they move away from their limb lines. 3. The device according to claim 1, characterized in that the bent petals of the thermobimetallic tape are made in the form of gutters transverse to the lines of their bending. 4. The device according to claim 1, characterized in that the elastic limb at the end of the petal is made in the form of a V-shaped loop. 5. The device according to claim 1, characterized in that the thermobimetallic plate in the area between the folding line and the bending lines of the petals is provided with lateral bends covering the tail of the current-carrying tip.

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