JP7703312B2 - Anti-rotation means for load cells - Google Patents

Description

The present invention relates to a means for preventing rotation of a load cell.

2. Description of the Prior Art Load cells, for example pendulum load cells for use in road vehicles, generally consist of a measuring element, hereinafter referred to as the load cell body, to which strain gauges are attached.

The load cell body is manufactured from a high stiffness metallic material, typically steel, and has a load cell head, load cell legs and a body disposed therebetween. Strain gauges are disposed at suitable locations on the surface of the load cell body, usually on the substantially cylindrical body. These strain gauges, typically Constantan or Karma strain gauges, are usually electrically connected as a full Wheatstone bridge.

To protect the strain gauge from water or moisture or dirt, a separate casing may be arranged around the load cell body. This casing is further fitted with an adjustment chamber in which electronics for electrical adjustment of the load cell, e.g. setting the zero point, characteristic values, temperature characteristics, etc., and possibly a signal processing device are located. This adjustment chamber also serves to protect the electronic components from moisture and dirt.

To achieve accurate load introduction from the end faces of the load cell head and the load cell legs into the body, particularly toward the web or diaphragm, multiple undercuts are provided that extend rotationally symmetrically around the longitudinal axis of the load cell body, and these undercuts step the load cell head from the body, and step the body from the load cell legs, respectively.

The problem with these load cells is that a movement of the measuring tool to be measured, e.g. the application or removal of a load, may cause the load cell body used to rotate about its vertical axis. The load cell body is electrically connected to a higher-level control device by a cable, and in this case, when the load cell body rotates, the cable may wrap around the load cell body and eventually break. Moreover, such a rotation of the load cell body may lead to measurement errors, in particular increasing repeatability errors.

In the case of the mechanical anti-rotation means disclosed in WO2005024357, the peripheral surface of the load cell leg has at least one substantially vertical groove which is adapted to cooperate with a protruding member provided on the lower plate when the load cell is in the mounted state.

The disadvantage of this design is that the protruding part is manufactured in one piece and therefore has to be milled accordingly. Furthermore, this part has to be manufactured from high-rigidity steel in order to avoid measurement and/or reproducibility errors. This significantly increases the manufacturing costs of such anti-rotation means.

SUMMARY OF THE PRESENT DISCLOSURE It is an object of the present invention to provide an anti-rotation means of the type mentioned at the outset which can be manufactured inexpensively.

This problem is solved according to the invention in a load cell of the type mentioned at the beginning in that the anti-rotation means comprises an upper centering lamella, a filler and a lower centering lamella. Due to the multi-part anti-rotation means, the individual parts can be manufactured inexpensively and can be used modularly. Thus, when replacing a load cell with a smaller or larger load cell, for example, only the upper centering lamella needs to be replaced.

In one alternative configuration, the upper centering plate has an opening. Preferably, a locking projection is arranged in the opening, in particular on the inner periphery of the opening. The opening is used to receive the load cell leg. The load cell leg is inserted through the opening and supported by the filler. Preferably, the load cell leg has an opening into which the locking projection of the upper centering plate engages. This prevents the load cell from rotating.

In one alternative configuration, the filler has a diameter at least as large as the opening in the upper centering sheet metal. This ensures that the load cell legs stand upright on the entire surface of the filler.

In one alternative embodiment, the lower centering lamella has an opening. In particular, the opening of the lower centering lamella has at least the same diameter as the opening of the upper centering lamella. The lower centering lamella is used to center and fix the filler. If the filler has the same diameter as the upper and lower centering lamellas, the filler preferably has a step, in which the filler has a smaller diameter than the opening of the lower centering lamella. In other words, on the side facing the upper centering lamella, the filler may have at least the same diameter as the opening of the upper centering lamella, and on the opposite side facing the lower centering lamella, it may have at most the diameter of the lower centering lamella. The filler is thus centered and fixed by the lower centering lamella. In particular, the filler is fixed in position on the lower centering lamella in a form-locking manner. Alternatively, the opening of the lower centering lamella may have a larger diameter than the opening of the upper centering lamella. In this case, the filler may have the same diameter as the opening of the upper centering lamella. That is, the opening of the lower centering lamella is always larger than the diameter of the filler or the opening of the lower centering lamella is always larger than the diameter of the filler on the side facing the lower centering lamella.

In one alternative configuration, the filler has a higher strength than the upper and/or lower centering lamella. The upper and/or lower centering lamella can thus be manufactured from a material with a relatively low strength, in particular steel or plastic. For example, a corrosion-resistant steel with a tensile strength of 300 MPa to 1000 MPa, preferably 500 MPa to 700 MPa and a hardness HB of less than 250 can be used for the upper and/or lower centering lamella. The filler can be manufactured from a corrosion-resistant steel with a tensile strength of 750 MPa to 1500 MPa, preferably 800 MPa to 1300 MPa and a hardness HB of less than 400. The tensile strength and hardness of the filler are always greater than the tensile strength and hardness of the upper and lower centering lamella. Furthermore, the filling element is made of a material that has a higher tensile strength and a higher hardness than the load cell legs. The upper centering plate and/or the lower centering plate have a lower tensile strength and a lower hardness than the load cell legs. This allows the anti-rotation means to be manufactured inexpensively. In contrast, anti-rotation means known from the prior art are manufactured or milled in one piece from correspondingly high-value steels.

In one alternative configuration, at least one spacer is arranged between the upper and lower centering lamellas. Preferably, two spacers are arranged between the upper and lower centering lamellas, which are made of the same material as the upper and/or lower centering lamellas. The spacer has a cylindrical geometric shape, in which case a through hole is arranged inside the spacer.

In one alternative configuration, a gap exists between the upper centering lamella and the packing member. The gap is used to allow dirt, and in particular liquids such as water, that may enter the packing member from the upper centering lamella or the load cell, to escape. This allows the area to be easily cleaned and provides a particularly hygienic anti-rotation measure.

In one alternative embodiment, the upper centering lamella and the lower centering lamella are connected to one another by at least one friction-locking connecting means. For this purpose, the upper centering lamella preferably has at least one open groove on its outer periphery, in which case the open groove has, in particular, a U-shaped geometric shape. At least one spacer, preferably at least two spacers, are inserted between the upper centering lamella and the lower centering lamella. The upper centering lamella is then connected to the lower centering lamella by at least one screw that is inserted through a through hole in the at least one spacer, in which case the lower centering lamella preferably has at least one through hole through which a screw can be inserted to connect to the fastening area. That is, a friction-locking connection, in particular a screw fastening, is made between the upper centering lamella and the lower centering lamella, in which at least one screw frictionally connects the anti-rotation means to the fixing area, in particular to the base plate, and fixes the upper centering lamella and the lower centering lamella in position. Thus, the entire anti-rotation means is connected to the fixing area by at least one screw, in particular two screws, and the anti-rotation means is assembled.

In the following, a preferred embodiment of the device according to the invention will be described with reference to the drawings.
FIG. FIG. 13 is a cross-sectional view of an anti-rotation means equipped with a load cell.

Detailed description of the embodiment Fig. 1 shows a schematic diagram of the anti-rotation means 1. The anti-rotation means 1 consists of an upper centering metal lamella 2, a filler 3 and a lower centering metal lamella 4. The upper centering lamella 2 has an opening 7, which has a circular geometric shape. On the inner periphery 5 of the upper centering lamella 2, two locking projections 6 are arranged, which are integrally connected to the upper centering lamella 2 and have a polygonal, in particular a rectangular, geometric shape. The locking projections 6 engage in the notches of the load cell legs. On the outer periphery 9 of the upper centering lamella 2, an open groove 10 is arranged. The open groove 10 is integrally connected to the upper centering lamella 2 and has a U-shaped geometric shape.

The filler 3 is arranged between the upper centering lamella 2 and the lower centering lamella 4. A gap 8 is arranged between the upper centering lamella 2 and the filler. Water that has entered through the gap 8 can flow out again. The filler 3 has a higher strength than the upper centering lamella 2 and/or the lower centering lamella 4. Furthermore, the filler 3 has a larger diameter than the opening 7 of the upper centering lamella 2.

The lower centering lamella 4 has an opening 11, which in this case has a circular geometric shape. The opening 11 has a larger diameter than the filling element 3. The filling element 3 is fixed in position by the lower centering lamella 4. Through holes 13 are arranged on or within the outer periphery 12 of the lower centering lamella 4.

Two spacers 14 are placed between the upper centering thin plate 2 and the lower centering thin plate 4. These spacers adjust the height of the gap 8.

When assembling the anti-rotation means 1, the lower centering plate 4, the filler 3 and the upper centering plate 2 are placed one on top of the other, and the spacer 14 is placed between the upper centering plate 2 and the lower centering plate 4. The screw 15 is then inserted into the spacer 14 from the side of the upper centering plate 2 and into the through hole 13 of the lower centering plate 4. The screw head 16 is thus positioned above the upper centering plate 2 and the screw tip 17 is positioned below the lower centering plate 4. The screw tip 17 and the male thread of the screw 15 are screwed into a fastening area, in particular a base plate. The fastening area can be, for example, a base plate of a mounting set for a load cell. The screw 15 is then tightened, so that the upper centering plate 2 and the lower centering plate 4 are frictionally connected to each other.

The open grooves 10 in the upper centering lamella 2 are used to make it easy to remove the upper centering lamella 2 without having to dismantle the entire structure. For this purpose, the screws 15 can be loosened and the upper centering lamella 2 can be turned and/or pulled out by using the open grooves 10. In this way, the upper centering lamella 2 can be easily replaced if the locking projections 6 are deformed or if the filling element 3 needs to be replaced. This has the further advantage that the screws 15 can be inserted laterally without the screw heads 16 penetrating the openings 7 in the upper centering lamella 2. This avoids the load cell legs getting caught on the screw heads 16.

Figure 2 shows the anti-rotation means 1 with the load cell 18 fitted in it. The load cell 18 preferably has a load cell head 20, a load cell leg 19 and a body 21 arranged therebetween. Strain gauges are arranged at suitable points on the surface of the load cell body, usually on the substantially cylindrical body 21. In order to protect the strain gauges from water or moisture or dirt, a separate casing may be arranged around the load cell body. This casing may furthermore be fitted with an adjustment chamber in which electronics for electrical adjustment of the load cell 18, for example for setting the zero point, characteristic values, temperature characteristics, etc., and possibly a signal processing device, are located. This adjustment chamber is also used to protect the electronic components from moisture and dirt.

To achieve accurate load introduction from the end faces of the load cell head 20 and the load cell leg 19 into the body 21, particularly toward the web or diaphragm, a number of undercuts 22 are provided that extend rotationally symmetrically around the longitudinal axis of the load cell body, and these undercuts 22 step the load cell head 20 from the body 21, and step the body 21 from the load cell leg 19, respectively.

The load cell leg 19 has at least one notch 23, in particular two notches 23, into which the locking projection 6 of the rotation prevention means 1 engages. This prevents the load cell 18 from rotating. The locking projection 6 preferably has the same wall thickness as the upper centering lamella 2. The load cell leg 19 is supported by the filler member 3.

LIST OF SYMBOLS 1 Anti-rotation means 2 Upper centering thin plate 3 Filler member 4 Lower centering thin plate 5 Inner peripheral edge 6 Locking projection 7 Opening in upper centering thin plate 8 Gap 9 Outer peripheral edge of upper centering thin plate 10 Open groove 11 Opening in lower centering thin plate 12 Outer peripheral edge of lower centering thin plate 13 Through hole in lower centering thin plate 14 Spacer 15 Screw 16 Screw head 17 Screw tip 18 Load cell 19 Load cell leg 20 Load cell head 21 Body 22 Undercut 23 Notch in load cell leg

Claims (13)

The device comprises an upper centering lamella (2), a filler member (3) and a lower centering lamella (4),
The upper centering lamella (2) has an opening (7),
At least one locking projection (6) is disposed in the opening (7);
The lower centering lamella (4) centers the filler piece (3) ,
An anti-rotation means (1) for accommodating the load cell legs of a load cell, characterized in that the lower end of the upper centering lamella (2) is above the upper end of the filler piece (3) . An anti-rotation means (1) according to claim 1, characterized in that the lower centering thin plate (4) fixes the position of the filling member (3). Anti-rotation means (1) according to claim 1 or 2 , characterized in that the filler (3) has at least the same diameter as the opening (7) in the upper centering lamella (2). 4. An anti-rotation means (1) according to any one of the preceding claims, characterized in that the lower centering lamella (4) has an opening (11). 5. The anti-rotation means (1) according to claim 4, characterized in that the opening (11) in the lower centering lamella ( 4 ) has at least the same diameter as the opening (7) in the upper centering lamella (2). Anti-rotation means (1) according to claim 4 or 5 , characterized in that the opening (11) in the lower centering lamella (4) is larger than the diameter of the stuffing piece (3). 7. The anti-rotation means (1) according to claim 1 , characterized in that the filler element (3) has a higher strength than the upper centering lamella (2) and/or the lower centering lamella (4). 8. The anti-rotation means (1) according to claim 1, characterized in that at least one spacer (14) is arranged between the upper centering lamella (2) and the lower centering lamella (4). 9. An anti-rotation means (1) according to any one of the preceding claims, characterized in that a gap ( 8 ) exists between the upper centering lamella (2) and the filler element (3). 10. The anti-rotation means (1) according to any one of claims 1 to 9 , characterized in that the upper centering lamella (2) and the lower centering lamella (4) are connected to one another by at least one friction-locking connecting means. Anti-rotation means (1) according to claim 10, characterized in that the friction-locking connecting means is a screw fastening means, and at least one screw ( 15 ) connects the anti-rotation means (1) to a fixing area and fixes the position of the upper centering lamella (2) and the lower centering lamella (4). Anti-rotation means (1) according to any one of the preceding claims, characterized in that the upper centering lamella (2) has at least one open groove ( 10 ) on its outer periphery (9). Anti-rotation means (1) according to claim 12 , characterized in that said open groove (10) has a U-shaped geometric shape.

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