Weighing scales – Self-positioning – Electrical current generating or modifying
Reexamination Certificate
1998-07-08
2001-05-15
Gibson, Randy W. (Department: 2859)
Weighing scales
Self-positioning
Electrical current generating or modifying
C177S212000, C177S229000, C073S862621
Reexamination Certificate
active
06232567
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention concerns an arrangement for mounting a parallel-guiding device in a force measuring apparatus, particularly in a balance. A load receiver formed by a first leg of the parallelogram in the parallel-guiding device and serving to receive the load to be measured is guided in parallel motion relative to a second leg of the parallelogram by two mutually parallel guide links that are rigid in their lengthwise direction but elastically flexible to bend in the plane of the parallelogram. The second leg of the parallelogram has a fastening area serving to mount it on a supporting part of the force-measuring apparatus, and it also has a portion that projects into the space inside the parallel-guiding device that is delimited by the two guide links. In the direction transverse to the plane of the parallelogram, the parallel-guiding device is delimited by two lateral boundary surfaces that are parallel to the plane of the parallelogram, with the legs of the parallelogram and the guide links extending between them.
2. Description of the Related Art
In mounting arrangements of this kind, the fastening area of the stationary second leg of the parallelogram has to take up the entire moment generated by the force that is to be measured and that acts on the first leg of the parallelogram. This can cause deformations of the parallel-guiding device. In addition, the mounting attachment of the second leg of the parallelogram at its fastening area can introduce stresses into the parallel-guiding device and into parts connected to it. The deformations as well as the mounting stresses can be detrimental to the measuring accuracy.
In a known arrangement of the kind named at the beginning (DE 43 05 425 A1), the stationary as well as the movable leg of the parallelogram have the shape of a hollow profile whose cross-section in the plane of the parallelogram is triangular. The respective sides of the triangle of the stationary and of the movable leg of the parallelogram that extend in the lengthwise direction of the guide links toward the outside of the parallel-guiding device serve as mounting surface to a base plate of the balance and as fastening support for a weighing pan, respectively. Through this sturdy design of the two legs of the parallelogram in the shape of hollow profiles and through the associated mounting geometry, it is possible, admittedly, to alleviate the problems of stress introduction and deformation. However, this design configuration is space-consuming and requires a relatively large amount of material.
Also known (EP 0 573 806 A1) is a design where, in order to reduce unwanted stresses, the block-shaped measuring cell of a force-measuring apparatus is arranged between the two legs of a stiff U-profile that extend parallel to the main planes of the block. By one of its lateral surfaces extending between the main planes of the block, the measuring cell is attached to the bottom portion of the U that connects the two legs. But here, too, the U-profile represents a relatively expensive component. Also, exacting requirements need to be imposed on the lateral surface of the measuring cell that serves for the mounting attachment and on the inside of the U-profile that is in contact with it.
SUMMARY OF THE INVENTION
Therefore, the object of the present invention is to provide a mounting arrangement of the kind named at the beginning that, on the one hand, is simple and inexpensive to manufacture and, on the other hand, deteriorates the measuring accuracy as little as possible.
According to the invention, the problem is solved by arranging the fastening area on that portion of the second leg of the parallelogram that projects into the space inside the parallelogram.
The inventive mounting arrangement conserves space. Also, it does not require expensive work operations on the second leg of the parallelogram that comprises the fastening area. Likewise, no expensive profile component is needed for mounting the parallel-guiding device. Finally, the location chosen for the fastening area in the inventive fastening arrangement is advantageous with regard to the moment generated by the force to be measured, as well as with regard to limiting the undesirable stress introduction.
As a preferred embodiment of the invention, the fastening area is located on a portion projecting between the lateral boundary surfaces into the space inside the parallelogram in a surface part that faces one of the guide links. The guide link next to that surface part has an opening opposite the fastening area through which passes that portion of the supporting part that has an area where it is connectively engaged to the fastening area.
Because the guide links extending between the lateral boundary surfaces parallel to the plane of the parallelogram are opposite the transverse surface areas (relative to the plane of the parallelogram) of the portion that projects into the interior space, the mounting attachment provided in this embodiment traverses one of the guide links. Therefore, the respective guide link is equipped with an opening that allows the passage of the portion of the supporting part that serves for the mounting attachment. Although this opening weakens the guide link to a certain extent, this drawback is offset by the advantages that the mounting arrangement is exceptionally space-saving, that the place on the parallel-guiding device where the mounting portion of the supporting part is joined to the transverse surface area (relative to the plane of the parallelogram) of the portion that projects into the interior space can be kept small, and that it does not require a special operation in the manufacturing process.
In this context, as a further practical refinement of the design, the fastening area and the portion of the supporting part that is joined to it are clamped together with at least one threaded bolt that is engaged in a tapped hole of the portion of the second leg and extends parallel to the plane of the parallelogram. In this configuration, the parallel-guiding device has enough space between its two guide links in the axial direction of the threaded bolt to allow the threaded bolt to be securely anchored in the portion that projects into the interior space.
Deviating from this design, the fastening area and the portion of the supporting part that is joined to it are clamped together with at least one threaded bolt that is engaged in a tapped hole of the supporting part and extends parallel to the plane of the parallelogram. The head of the bolt is arranged in a recess of the portion that projects into the interior space, and the shaft of the bolt passes through a part of the portion that extends from the recess to the transverse surface area. In this configuration, the tapped hole is in the supporting part rather than in the portion of the parallel-guiding device that projects into the interior space. This kind of attachment reduces the mounting stresses in the parallel-guiding device.
In an alternative embodiment, the fastening area is located on one of the lateral boundary surfaces of the portion of the second leg of the parallelogram that projects into the interior of the parallel-guiding device, and the supporting part is provided with a portion that extends along the lateral boundary surface at the location of the fastening area and has an area where it is joined to the fastening area.
Because the lateral boundary surfaces of the portion of the second leg of the parallelogram that projects into the interior of the parallel-guiding device are open on both sides of the parallel-guiding device, the place for the fastening area is freely selectable in accordance with applicable requirements within the entire available surface area of the lateral boundary surfaces of the portion that projects into the interior. In contrast to the attachment on a transverse surface area—opposite one of the guide links—of the portion that projects into the interior, which requires a certain minimum dimension of that portion transverse to t
Bonino Bruno
Burkhard Hans-Rudolf
Schneider Ferdinand
Gibson Randy W.
Kueffner Friedrich
Mettler-Toledo GmbH
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