DEVICE IN THE FORM OF A SENSOR FOR MEASUREMENT OF STATIC LOADS, DYNAMIC LOADS AND TORQUES IN THREE AXES X-Y-Z

Abstract: The device according to the invention is characterized in that it is made in the form of compression bars (1), which are disposed to be shaped upon their pressing down to their working position in a mounting plate (2) provided for the parts (1, 3, 4, 5 and 6) of the sensor as a holder and protection, the bars (1) upon compression being provided with a waist for reduction of the form factor and prevented in a form factor impeder (3) from swelling out sideways during compression with resilient tension impositions and direction of their force against at least one base plate (4) applied in the form of a chip or board which is equipped with metallic sensing fingers or sensing members, the base plate of the sensor then being provided both with torque equalization plates (5) for temperature equalization and with sensor media (6) which are arranged to be supported by the plates (5) and in that the compression rods (1) with form factor impeders (3) are replaced with directly applied force of atype suitable for the application.

Description: - Device in the form of a sensor for measurement of static loads, dynamic loads and torque in three axes X-Y-Z The present invention relates to a device in the form a sensor for measurement of static loads, dynamic loads an torque in three axes X-Y-Z. There already exist sensors of various kinds, but none with the object of the present invention, typically for insertion and measurement in butt bolted joints. The device-according to the invention is characterized by the features made evident in the accompanying patent claims. A more detailed description of the invention is given below and with reference to the accompanying drawings, whe Fig. 1 shows the construction part of the sensor indicated in parts. Fig. 2 shows two base plates disposed one above the other and fitted with a torque arm, with an interlying elastic ring. Fig. 3 shows the electrical function of Fig. 2, Fig. 4 shows the sensor in parts at a load-sensing towing device for, e.g., mobile vehicles and Fig. 5 shows the sensor in Fig. 4 assembled. The sensor typically comprises a one-sided surface contact sensor either with a deformation plate adapted for the size of the load or without a deformation plate for small forces. The sensor incorporates one or a plurality o resistive elements, the resistance upon loading being changed in dependence of the magnitude and application of zhe load. The change of the resistance remains until the load has been changed, thus enablir.-j both static and d^-:-~..1 ; processes to be registered. The sensor can be used to advantage for difficult loads. Fig. 1 shows compression bars 1, the shape and material of which is chosen in such a manner that the bars 1 are shaped during their mounting according to the base down to the working position, i.e. pressing down to a level with a mounting plate 2. Function of the bars 1 is to accomplish the correct pressure or force regardless of the nature of the base. The purpose of the mounting plate 2 is to act as a holder for parts 1, 3, 4, 5 and 6 of the sensor and as protection for the sensor. By forming a waist on the bars 1 a reduction is achieved in the form factor, the form factor impeder 3, whereby these are prevented from swelling out sideways during the compression with resilient tension impositions in consequence and to aim the force more accurately towards a base plate 4, i.e. the chip or the board. The base plate 4 is provided with metallic tensing fingers or sensing members and consists of insulated substratum such as a ceramic material, laminate or the like. Also provided are torque equalization plates 5, the task of which is to function as temperature equalizers, in addition to which the sensor also contains sensor media 6, which are made with a conductive coating. The electrical function of the X-Y-Z sensor, in the first instance the base plate 4, will now be more closely described. The principle can- be likened unto that of a passive bipolar transistor with a mechanical base, where the emitter and collector are electrodes and the base is the mechanical force. The sensitivity is governed by the distance between the electrodes and the length of the passage determines the current flow. When the sensor is not under, load the current flow is small and the sensor conducts to a lesser degree because the conductive particles in the surface of the medium do not have a sufficiently large contact area (compare with heat emission from a transmitter. loosely screwed ' against the cooling flange and firmly screwed against a cooling flange or different flange sizes) i.e. the impedance of the mechanical coupling thus determines the change in resistance. Since the electrodes are located in one plane the flow merely goes on the surfac in the media and not through a "true" resistance body, compare mass resistance and metal film resistance, the difference being revealed i.a. in the noise factor. In the said cases the noise should be low since measurements are desirable even at low levels. The true sensor consisting of an electrode surface and sensor surface are thus stratified This means that the sensor can be made very thin depending on the production technique and makes it impossible for skew forces to exist to the same extent in a surface as they occur in a volume, since strain gauges for example cannot function without some form of underlay, i.e. something which has a physical volume, and shearing forces can arise in the volume since this. is a three-dimensional phenomenon. Consequently the sensor can more easily be directed towards the force. The sensor works either clamped or free, depending on the type of application. The advantag of a sensor of this type is that it works with a very large swing, typically 0.5-0.9 v/v, and that the sensor works bot statically and dynamically from DC to several hundred KC. I so required the sensor can be elaborated physically very small, 1 mm2 or smaller, and so that the force can be applied directly on the sensor. This means that measurement can be made in infinitely small points and that encapsulation is dependent upon hysteresis to a lesser degree. When the major share of the force can be absorbed b the sensor and not by straining metals, strain gauges are entirely dependent upon the hysteresis of the underlay sinc they only measure the strain on the underlay. Mechanical punishability is another strength of the sensor as on account of its construction it can be handled more carelessly than piezo and quartz crystals (brittle). Figures 2 and 3 show two base plates 4 and 4' disposed one above the other with and interlying torque-absorbing resilient ring and fitted with a torque arm 8 and sensing members A, B, C, D and a, b, c, d respectively. The sensing members A, B, C, D and a, b, c, d respectively are located at the same centre distance from each other with an offset of 90° in relation to a point X on the respective base plate 4 and 4'. The point X comprises a torsion and power centre for the sensor or base plates. When the torque arm 8 of the sensor is exposed to a force which enters at a right angle from the side to the torque arm, resistance differences arise in A and C and in a and c respectively (A and c increase whereas C and a decrease) and no 'differences in resistance in B, D, b and d in a force co ing from the side perpendicular to the arm, otherwise also differences in B, D, b and d. When the torque arm 8 of the sensor is exposed . to force coming from above, all sending means A, B, C, D, a, b, c, and d are actuated. Fig. 3 " shows iri the first instance the electrical function of the two base plates 4 and 4* of the sensor in the three axes X, Y and Z. If one of the base plates should be excluded so-called half-bridges are formed. With regard to the torque equalization plates 5 it may be said that when the sensor is connected to a current source heat is generated in the free sections of the thin gaps formed by the distances between the electrodes of the base plate 4 to the electrically conducted part (side) of the polymer-borne metal film surface. The width of the gap in the substratum decides the working range. When. internal differences in the transitions between the electrode surfaces can give rise to partial overheating this must be evened out and dispersed over the entire active part of the surface of the sensor so that thermic movements are avoided and the temperature can be kept within a range suitable for the sensor medium 6. This means that the thermic noise can be kept low since the noise factor dictates the dissolution and the total dynamics of the sensor. The material in the plates 5 shall have good thermal conductivity and low hysteresis and the plates 5 shall also have an electrically screening function. The mechanical function of the plates 5 is to comprise carriers for the sensor medium 6 and to transfer and disperse the torque uniformly over the entire surface. Fig. 4 shows how a sensor S is mounted or clamped in a bolted joint, for example, in order to there measure forces or movements in the material. The deformation plate of the sensor S is compressed and adapt itself according to the area A of a towing device F to a bottom position, i.e. when the sensor S has the same height as the sensor holder B. In this position the working pressure of the sensor S has been reached and it can be loaded to the float limit of the sensor holder B or to the deformation limit of surrounding parts. Also shown in Fig. 4 is a foundation or fixing plate C which communicates with, e.g., the load-sensing part of the vehicle and a cable trunk D to the sensor. Fig. 5 illustrates how the sensor S can be directly inserted into e.g. butt bolted joints in load test with a towing device F. Illustrated in Fig. 5 is a conventional mounting in the form of a fixing plate C which is normally included in the towing device of a vehicle and to which a fixing part F' of a towing device F is intended to be secured by means of two bolts E attached to a vehicle (not shown) for example in connection with its frame member. A sensor S containing holes is applied for the bolts E and the sensor S is made with a pressure-dependent resistive device furnished with one of two parts which is clamped between the fixing plate C and the fixing part F' . The invention is obviously not limited to this embodiment but can naturally be varied within the framework of the inventive concept.

Claims: 1. A device in the form of a sensor for measurement of static forces, dynamic forces and torque in three axes X-Y-Z, c h a r a c t e r i z e d in that it is elaborated in the form of compression bars (1) which are arranged to be shaped upon being pressed down to their working position in a mounting plate (2) provided for the parts (1, 3, 4, 5 and 6) of the sensor as a holder and protection, the bars (1) upon the compression then being provided with a waist for reduction of the form factor and prevented in a form factor impeder (3) from swelling out sideways during compression with resilient tension impositions and direction of their force towards at least one base plate (4) applied in the form of a chip or board, which is provided with metallical sensing fingers or sensing members, the base, plate of the sensor then being provided partly with torque equalization plates (5) for temperature equalization and partly with sensor media (6) which are arranged ^ to be supported by the plates (5) . 2. A modification of the device as claimed in Claim 1, c h a r a c t e r i z e d in that the compression bars (1) with form factor impeder (3) are replaced with directly applied force of a type suitable for the application. 3. A device as claimed in Claim 1 or 2, c h a r a c t ¬ r i z e d in that the base plate (4) is made of insulated substratum. 4. A device as claimed in Claim 1 or Claim 2, c h a r a c t e r i z e d in that when two base plates (4) are applied it is fitted with a torque-absorbing elastic ring (7) located between the plates (4), a torque arm (5) and sensing means (A, B, C, D and a., b, c, d respectively) on the respective plate (4). 5. A device as claimed in Claim 1 and Claim 2, c h a r a c t e r i z e d in that the plates (5) are made of material with good thermal conductivity and low hysteresis. 6. A device as claimed in Claims 1 and 2, c h a r a c t e r i z. e d in that the sensing medium (6) is

Inventors: BORGUDD SLIM, BORGUDD, SLIM
Applicants: BORGUDD SLIM, BORGUDD, SLIM
Application year: 1985
Main classification: B60D1
IPC codes: B60D1, G01L1, G01L5