CH684442A5 - Sensor for measuring transverse extensions in bores in structures - Google Patents

Abstract

Sensor for detecting radial extensions in bores. The extensions can be detected at any desired depth and in the radial direction within the bore. The extension-sensitive conical element (1) is pulled into an outer cone (6) by means of a spindle (4) and a nut (5) and is thus stressed inside the bore in the desired measurement direction. A cathodically sputtered resistive measurement grating (2) is applied onto the extension-sensitive element, which measurement grating detects the changes in extension caused by the bore deforming under load. An electronic amplifier circuit can be integrated into the sensor. The latter can be discretely potted or likewise directly cathodically sputtered onto the extension-sensitive element. The assembly aids can be integrated into the sensor. The sensor, together with the cone part, is fully encapsulated by means of a thin-walled shell (10) and thereby completely sealed. <IMAGE>

Description

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description

The present invention describes a transducer with a cathodically vapor-deposited resistance measuring grating and an integrated amplifier, which can detect strains in blind holes and through holes in structures of any depth and radial direction.

Modern systems and machines increasingly require sensors. This is because these are controlled and regulated with microprocessors in practically all cases. The microprocessors require a large amount of data and parameters in order to be able to perform the tasks assigned to them. Mechanical stress is an important parameter.

Indirectly measuring strain sensors are increasingly being used for load monitoring tasks. These differ in surface * and structure sensors. The former are applied to the surface of the structure to be measured. Accordingly, they are also susceptible to damage and zero offsets due to external influences.

In this regard, structure sensors clamped in bores are more problem-free, which measure the expansions - these indirectly correspond to the stresses - in the radial or axial direction. Radially measuring sensors are usually clamped in the mounting hole using cones. However, they all have a cone that is open to the outside, which can become dirty and therefore creep phenomena can occur.

Two measuring principles for structure sensors have become known: piezoelectric with quartz or ceramic elements and glued strain gauges.

Piezoelectric sensors have a fast response time and are small. However, these sensors cannot be used for long-term, static measurements. In addition, the tension of the sensor, an important parameter, can no longer be recorded after installation. Even today's piezo sensors are not yet free of mass, which could lead to potential differences between the transducer and the controller and can damage the sensitive microprocessors in the controller.

Structure sensors with glued strain gauges do not have the disadvantages of quartz sensors. However, the quite ductile adhesive layer prevents quick response times. In addition, the strain gauge can relax due to the often necessary large tension and shift the zero point. In addition, strain gauges build very large.

In contrast, the sensor according to the invention with the thin-film strain gauge measuring grid which is cathodically vapor-deposited on an amorphous quartz layer has none of the disadvantages mentioned above.

The amorphous quartz layer applied to the substrate ensures freedom from potential and also very high dielectric strength. This quartz layer also prevents the tensioned measuring bridge from relaxing and enables the sensor to respond quickly. The thin-film strain gauge measuring grids, which are cathodically vapor-deposited according to the invention, are very small, which leads to compact transducers.

For electrical circuits integrated in the sensor, for example an instrument amplifier, the required resistors or soldering points for electrical components can be vaporized directly onto the substrate using the measuring grid. This eliminates components and an additional operation. This increases the operational reliability of the circuit and reduces the manufacturing costs.

In the following, the sensor is described using pictures. Show it:

Fig. 1: A section through an encapsulated transducer according to the invention with integrated electrical circuit.

Fig. 2: A view of a transducer according to the invention with fixed installation aids to be manufactured later.

3: shows a section through a variant of the transducer according to the invention.

Fig. 4: represents the disassembly device for the transducer of Fig. 3.

1, the externally conically shaped strain-sensitive element (1) with the cathodically vapor-deposited thin-layer strain gauge measuring grid (2) is screwed into the outer cone (6) by means of the thread (4) on the tube (3) and the tensioning nut (5) ) drawn. The outer cone (6) is integrated in the outer tube (7). The outer cone (6) can be slotted to allow easier bracing in the bore.

The element (1) wedged in the cone (6) now transmits changes in diameter of the bores, caused by expansions or changes in tension in the material of the structure to be measured, to the measuring grid (2). The desired radial measuring angle can be set on the milling before positioning by appropriate positioning. The location of the strains to be measured can be selected by adjusting the length. The element (1) can be attached to the tube (3) by known means or the tube (3) and the element (1) can be made in one piece.

The signal cables (8) of the measuring grid (2) can be routed and conditioned via the central bore of the tube (3) directly into the machine or system control or onto an integrated electrical circuit (9). In the case of the integrated electrical circuit, it can be constructed discretely and then cast in the tube (3). However, it can also be cathodically sputtered directly onto an extension of the element (1) at the same time as the thin-film strain gauge measuring grid (2). In this way, resistors and soldering points for electrical components can be applied in one operation. The extension cable (12) then leads the conditioned signal to the machine control.

The described sensor according to FIG. 1 can be directly by means of a metal sleeve (10) with bottom (11)

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be encapsulated. The sleeve (10) is fastened in a sealing manner to the outer cone (6) on the tube (7) using known means. The sleeve (10) should be elastic in order to ensure bracing by means of the cone (6).

FIG. 2 shows a variant of the transducer according to the invention according to FIG. 1. The transducer is also clamped inside the mounting hole.

The parts for assembly can be manufactured subsequently by the user. This has the advantage that the sensor can be adapted for different drilling depths on site. A suitable piece of pipe is glued to the cylindrical projection (13), which positions the encapsulated cone part (15) at the correct depth. Another pipe is screwed onto the thread (14). This allows the sensor to be clamped.

3 shows a sensor according to the invention which is clamped in the bore by means of a tool. The axis (16) is prevented from rotating by means of the pin (17) and fixed in the desired radial direction. The inner part (20) of the assembly tool is used for this. The inner part (20) has a slot at the front for receiving the pin (17). There is a knurled nut or other part at the back to hold the inner part. The sensor element (22) can now be pulled over the spindle (16) into the cone (23) by turning the tensioning nut (18) using the tool (19) and tensioned in the bore.

The tension nut (18) has two opposite flat surfaces. The tool (19) has a slot which can be pushed over the tensioning nut (18). This is how the bracing torque can be generated. The signal cables (24) of the measuring bridge (25) can now either be led directly to the evaluation electronics or to an integrated electrical circuit (26), which conditions the signal. The electrical circuit can be designed as described in FIG. 1. The sleeve (26) also seals the sensor. As an additional measure for sealing, an O-ring (27) can also be provided.

To release the sensor, the tension nut (18) is first loosened with the tube (19). The element (22) can then be released from the cone (23) by means of a blow on the tube (20). It can now happen that the transducer cannot be removed from the hole because the conical element (22) is always braced. In this case, the conical part can be pulled out of the bore by means of the special tool according to FIG. 4 by pushing the special tool into the bore and screwing the thread (29) over the thread (28) according to FIG. 3. The slot

(32) holds the tensioning nut (18). The signal cable

(33) of the transducer can be passed through the bore (31). By pulling on the knurled nut (30), the transducer can be pulled out of the hole on the cone sleeve, thus preventing repeated, unwanted tensioning during dismantling.

Thanks to its compact and robust design, the integrated electronic circuit and the cathodically applied thin-layer strain gauge measuring grid, the present invention opens up new possibilities and applications in the monitoring of machines, devices and structures under the most extreme environmental conditions.

Claims (5)

Claims 1. Transducer for measuring transverse strains in bores in structures, in which a conical measuring element is drawn into an outer cone and is thus braced in the bore, characterized in that the conical measuring element (1) has a thin-film strain gauge measuring bridge that is sputtered cathodically. 2. Sensor according to claim 1, characterized in that an integrated electrical circuit (9) is included. 3. Sensor according to claim 2, characterized in that the entire sensor with the integrated electrical circuit (9) is protected against external influences and media by means of a thin-walled sleeve (10). 4. Sensor according to claim 1, characterized in that the conical measuring element (1) is sealed by means of a plastic compound. 5. Sensor according to claim 2, characterized in that passive elements of the integrated electrical circuit (9) are sputtered cathodically. 5 10th 15 20th 25th 30th 35 40 45 50 55 60 65 3rd