FI64719B - KRAFTMAETNINGSGIVARE FOER ELONTRONISKA VAOGAR O DYL - Google Patents

Description

6471 9

BUTTER SENSOR ELECTRONIC SCALES ONE. FOR

The invention relates to a force measuring sensor for electronic scales and the like, which is based on measuring the elongation and shrinkage in the surface layer of a loaded measuring body by a resistance stretching strip technique known per se, by which the resistance of stretching strips is measured in a resistance bridge.

There are numerous different shapes of such force sensor units, i.e. weighing cells. But in addition to the fact that they are very expensive, they have various drawbacks. For example, when a cylindrical measuring piece is loaded in the longitudinal direction, 10 different surface tensions are formed, due to which different resistance strain strips must be used in the cells, the placement of which is not always optimal. There are also diagonally loaded square sensor measuring pieces, e.g. a device according to U.S. Pat. No. 2,986,931 (73-14-1) 15. The latter, however, has not only the relatively expensive disadvantage that tensile or compressive stresses are present on the sides of the square in addition to bending. (The measuring piece according to the application differs from this, for example, in that the thin or measuring sides of the oblique trapezoid are at an angle of 90 ° to the diagonal-20 measuring line, so they have a fairly clean bend.

The main object of the present invention is to provide a very cheap and accurate, i.e. competitive weighing cell. Inexpensive manufacturing has been obtained in such a way that the cell, i.e. the measuring piece, is made of 25 drawn metal profile rails by cutting into suitable pieces according to the desired measuring range, whereby it is not necessary to make one's own profile drawing tool in different weighing areas. The force-sensing sensor He according to the invention is characterized in that it is formed by a diagonally loaded measuring body in the shape of a substantially oblique parallelogram 30, the two opposite sides of which are thick and relatively inflexible on the other sides, the so-called the measuring sides on which the strain gauge strips are placed are thin and in a position perpendicular to the load line, and that the measuring piece can, if necessary, be shaped so as to have two surfaces forming the overload guard which, when encountered, limit the deformation.

2 64719

The invention will now be described in more detail with reference to the accompanying drawings, which show the principle of the invention and some practical embodiments, in which:

Figure 1 shows the deformations of a substantially unloaded, compression-5 loaded and tensile loaded cell.

Figure 2 is an axonometric view of an embodiment of the cell.

Figures 3, 4 and 5 show different embodiments of the cell 3.

Figures 6, 7 and B show the top of the cell, with 0, 1 and 2 reductions in the thin side 10.

Figures 9, 10 and 11 show the top of the cell, where the thin side forms different angles with the load line, and Figures 12, 13 and 14 show different arrangements of the overload barrier.

The sensor according to the invention can be used for both compressive loading and tensile loading. Figure 1 shows, greatly exaggerated, how the unloaded sensor cell deforms under compressive and tensile loads on the left. In compression, the overload barrier operates in such a way that the center of the cell has parallel planes 1 perpendicular to the load line, which meet each other in the event of an overload of 20 and prevent the thin sides 2 from bending further and breaking. The overload limit can, of course, and must be set in such a way that no permanent deformation occurs on the thin sides. Of course, such a simple overload barrier cannot be used for tensile loading, but overload must be prevented by other means.

The structure of the sensor measuring body according to the invention, i.e. the cell, is shown in more detail in Figure 2. In addition to said central planes 1 and the thin sides 2 of the diagonal, it has thick, practically inflexible sides 3. Between the planes 1, a spacer 4 can be used as an overload barrier. at the top and bottom) are perpendicular to the load line, i.e. xasot parallel to the planes 1. 5, with threaded mounting holes 6 at the center of the load line. As mentioned, the cells 35 are made of a drawn metal profile rail by cutting perpendicularly thick pieces perpendicular to the rail according to the desired measurement. The thickness of the cell can also be changed as needed by cutting along the broken lines 7 in Fig. 2. The resistance stretch strips 8 can advantageously be placed in the position shown in Figure 2, but they can also be placed elsewhere on the thin side 5 and on both sides thereof.

Fig. 3 schematically shows a cell with the above-mentioned central planes 1 without a spacer 4. Fig. 4 shows a cell without air with the central planes 1, since they cannot be used under tensile load. Figure 3 shows a cell in which the thick sides 10 of the diagonal compass are curved and in which there are planes for the distance piece. Fig. G shows the top of the cell with no tapers on the thin side, Fig. 7 a thin side with one taper and Fig. 8 two tapers. These reductions are mainly used at low loads, which requires more sensitivity in the cell. Fig. 9 15 shows a cell whose thin side forms an angle of 90 ° with the load line. In Fig. 10 the corresponding angle is 120 ° and in Fig. 11 60 °. However, the last two cases should be avoided, as the more deviated from 90 °, the more inaccurate the sensor becomes. Fig. 12 shows how the distance piece of the overload barrier can be placed mainly in the cell according to Fig. 3. It can be glued to its lower end and replaced as needed. In the case according to Fig. 13, no distance piece is required, but the central planes 1 of the cell are already so close to each other that they as such act as overload barriers. Fig. 14 shows how the remote 75 autumn body 4 can be placed in the cell according to Fig. 5.

When the cell is loaded, the deformations that occur on both thin sides are exactly the same. Since both ends of the thin side are attached to the thick sides (see Fig. 1), when the cell is loaded, the thin sides bend according to Fig. 1 into an S-shape, where it is easy to measure the desired deformations.

Figures 1, 2, 6, 7 and 8 give examples of the positions of the resistance boat strips.

Compared to the previous solutions, the invention offers the following advantages: The diagonal shape, in which the thin sides are at right angles to the load line, gives very precise values.

- It is easy to obtain overload protection in the cell according to the invention.

- The manufacture of the cell becomes very economical because it can be made of drawn metal profile rails by cutting into 40 suitable pieces.

Claims (5)

A force measuring sensor for electronic scales, etc., based on measuring the elongation and shrinkage of a loaded measuring body in the surface layer by a resistance-strain gauge technique known per se, in which the resistance of strain gauges is measured in a are thick and relatively inflexible on the other sides, the so-called. the measuring sides (2) on which the strain gauge strips (8) are placed being thin and in a position perpendicular to the load line, and that the measuring body can, if necessary, be shaped to have two overload protection surfaces (1) which limit deformation when encountered. Sensor according to Claim 1, characterized in that the direction of the measuring sides (2) relative to the load line deviates somewhat from 90 °, but not more than 30 ° in both directions. Sensor according to Claim 1, characterized in that the thick sides (3) of the diagonal parallelogram are curved. Sensor according to Claim 1, characterized in that the measuring sides (2) are provided with one or two reductions. 4,64719 Sensor according to Claim 1, characterized in that two planes (1) perpendicular to the load lines are formed in the middle of the measuring body, which overload press against each other and form an overload protection or between which special spacers (4) can be placed. A method of manufacturing a sensor according to any one of the preceding claims, characterized in that the measuring body is shaped in such a way that it can be easily manufactured from a drawn metal prorail rail by cutting it into suitable pieces according to the desired measuring range.