Elastostatic load cell.

The invention relates to a force measuring elasto according to the preamble of claim 1.

When using load cells for weighing of bunkers or weighbridges must be ensured that the load cells have appropriate degrees of freedom that allow vertical, horizontal and angular movements of the bunker or the weighbridge. On the other hand it must be ensured that such movements are relatively narrow limits, otherwise there is a risk of destruction of the load cell. For this example, it is known to allow lateral movement of the load cell in that the load cell is mounted on a downwardly curved dome and carried the upper force application point on a used in a spherical depression ball. However, it is still necessary, the load cell support by handlebar and attacks against overload due to rotation and horizontal forces. On tow point can be seen as a pre-liner is an elastomeric disc. However, a static friction is overcome, which may be on the order of 5% and the usual load cells loaded unduly. It was previously therefore necessary to provide compensation elements as driver or the like. From the utility model 8534719.1, a force-measuring device with topfartigem supporting part is known, in which a piston-type power receiving portion is used, wherein an elastomeric material is disposed between the end face of the force receiving member and the bottom of the support and between the circumferential casing of the force receiving portion and the inner cylindrical surface of the support part, the having at least one pressure sensor in contact. This force-measuring device has the advantage that any lateral forces from elastomeric material without friction be transferred to the supporting part.

The invention is based on the object equip this force measuring device in a simple manner with corresponding degrees of freedom. Furthermore, the force-measuring device to have the lowest possible height.

This object is according to the invention by a force-measuring device with the features of the characterizing part of claim 1.

Since all lateral forces on the elastomeric material can be derived to support part, resulting ideal of freedom for the load cell, so that no special measures such as the handlebars or the like are required to absorb the transverse forces.

The invention also relates to a bunker or weighbridge facility that is equipped with such force measuring devices.

Preferred embodiments of the invention result from the dependent claims.

Further features and advantages of the force measuring device according to the invention will become apparent from the following description of exemplary embodiments based on the drawing. In the drawings Figures 1 to 3 are sectional views of embodiments of the force-measuring device according to the invention with different degrees of freedom.

According to the figures, has a force-measuring device 1O of the embodiments of an elasto load cell 12, above which a force introduction element 14 is arranged and is held by a supporting part sixteenth The elasto load cell 12 has a cup-shaped body 18, in which a piston is guided 2O forming a relatively narrow annular gap 22 with the cylindrical internal surface of the cup-shaped body eighteenth This annular gap 22 and the bottom of the cup-shaped body are filled with elastomeric material. (See. G8534719)

Deviating from the known force measuring device according to the mentioned utility model, the lower end face 24 of the piston 2O to the longitudinal axis of the piston is towards the edge pulled up to a central bore 26 that can be closed from above by means of a plug 28 or the like. The particular advantage of this embodiment is that in the preparation used in the known force-measuring device driven forth by rotating the force measuring device by means of a carousel, the air bubbles to the interior and be removed via the bore 26, while in the known force measuring means of the bottom domed or conically downwards is formed and the bubbles are expelled by an annular gap. The mold of the invention results in a lower overall height. It should be noted that this particular embodiment of the force-measuring device according to the invention are of general inventive significance is.

In the bottom of the cup-shaped body 12, a pressure sensor 3O is recessed, which detects the pressure applied to the elastomeric material from the piston 2O pressure and brings in a suitable manner for analysis.

The foregoing description of the basic elements of the force measuring device according to the invention is essentially true for all three embodiments of FIGS. 1 to 3. This also forming the supporting part 16 is common, which has a central piston 32 engages in a complementary recess 34 on the underside of cup-shaped body against an elastomer disk 36 presses.

The piston has 2O projecting on its top in a corresponding depression 4O at the bottom of the force-receiving element 14 a centralized approach 38th The force receiving member 14 has a flat top, which is in a suitable manner with parts of the bunker or a weighbridge in connection and receives the force. The surface design of the force-receiving element 14 enables a stable connection to the bunker or the weighbridge and a uniform force absorption.

In the embodiment of Fig. 1, the piston 2O could be formed integrally with the force receiving element 14, for this embodiment, only offers the gimbal degree of freedom that permits pivoting of the hopper or the weighbridge. In the embodiment of FIG. 3 results in an additional degree of freedom both in the X Y direction, characterized in that between the force transducing element 14 and the piston 2O a plastic disc 42 is placed opposite to the metal surfaces of the force receiving element 14 and the piston 2O a low having friction. The material for the plastic disc may be, for example, polytetrafluoroethylene (Teflon). In this embodiment, it should be noted that between the shoulder 38 and the walls of the recess 4O Sufficient space is available, which allows a horizontal movement of the force-receiving element 14 with respect to the force-sensing 12th The plastic disc 42 is preferably accommodated in recesses which are mounted on the top of the piston 2O and / or the underside of the Kraftaufnehmerelements fourteenth

Fig. 2 shows another embodiment in which transverse movement of the force receiving element 14 is placed only in one direction for example the X direction. It is between the shoulder 38 and the cylindrical surface of the recess 4O, both of which are rectangular, preferably square, depending on a Teflon disk 44 used in only two opposite sides, so that movement of the force-receiving element to the plane is only in the direction perpendicular possible. The plastic discs are provided with lubrication pockets, which serve to store a lubricant to ensure the continuous lubrication of the sliding surfaces.

It should be noted that the support used in the embodiments between the pistons 32, the elastomer plate 36 in the recess 34 is a gimbal-acting pot bearing is a fixed bearing, in principle, in which twisting or pivoting movements about the horizontal axis by deformation of the elastomer plate 36 is made possible. The elastomer used holds under pressure from all sides, its volume constant, making it incompressible. Piston 32 prevents extrusion of the elastomer plate.

The inventive embodiments of the force-measuring device can be appropriate mountings for a bunker, a weighbridge or the like together. In a three-point support the following degrees of freedom are required:

A force measuring device with universal fixed point (Fig. 1), a force-measuring device with universal fixed point and with horizontal degree of freedom in the X direction, and a force-measuring device with universal fixed point and two degrees of freedom in the X and Y directions. (Fig. 3)

At four support points in addition a force measuring device of FIG. 3 is still required.

The pairings of the materials of the force measuring device are chosen such that the smallest possible design is obtained at high overload margins.

It should be noted that the measuring cell 12 can also be executed with respect to the formation of the underside of the piston 2O differently, for example with the above cone. However, the shape used in the invention has the advantage that a very low height can be achieved, although a relatively high annular gap is used 22nd

It is further noted that for all three embodiments are substantially the same basic elements can be used.

As already mentioned, the force-measuring device according to the invention has the advantage that 22 transverse forces from the piston 2O to the cup-shaped body 18 and the supporting part are transmitted 16 by the elastomeric material in the annular gap, and that only at higher forces, the friction between the metal surfaces of the force receiving element and the piston and the Teflon disc overcome, a displacement of the force receiving element 14 with respect to the measurement cell 12 occurs. Since no bending of the piston or of the support occurs, there is no pivoting of the hopper or the weighbridge. The force measuring devices according to the invention can be loaded for example with 1OOt and have in this embodiment, a diameter of approximately 2OOmm.

Although the connection between force receiving member 14 and the piston 2O done through an approach to the piston 2O, also a straight, complementary compound can be used. It is also not required a centralized approach to use. Instead, a corresponding peripheral edge could be used on the piston.

In the above, a force-measuring device has been described, which is entirely "crash-proof" and can take due to the large gap faces considerable lateral forces. Even with large congestion yet there is no destruction of the load cell, but the range of movement is limited by the fact that the piston with its coat comes on the inner surface of the cup-shaped body to rest.

The Towards Middle drawn upward conical depression not only has the advantage that, despite low overall height, a relatively high gap can be achieved, but that the angle at the apex of the carousel can be smaller for a specific, possibly large diameter of the force-measuring device also in rotational molding than in the known device, in which the lower end face of the piston is curved downward.

It should be noted that the support cup bearing can also be constructed conversely, that a Ausnehmungim supporting part 16 and a piston at the bottom of the base body 12. The same applies to the arrangement and design of the elements 12,2O.