Load cell system

p0001The invention relates to a load cell with a hinged column load cell, with at least one one end of the pendulum support associated supporting element and a device comprising mutually associated elements of pendulum support and the support element in order to limit the rotation of the pendulum support around its axis.

p0002Wägezellenanordnungen this kind are used inter alia in weighing, platform scales and in particular at weighbridges for weighing vehicles. Several Wägezellenanordnungen each having a hinged column load cell are arranged between the weighing platform and a foundation. The weighing platform is horizontally movable within allowed limits, so that these movements the load cells perform oscillations that do not exceed an angular range of 10 degrees in general. The load cells are thus both vertical to transverse forces exposed. This can cause the load cells unwanted rotational movements are imposed on its axis, which may result in consequences to the breaking of the wiring.

p0003In the load cell according to the US Patent 2,901,235 a rotary motion of the pendulum support around its axis is limited by the fact that near the pendulum supports end fastened axially parallel extending lug a radially screwed into the supporting screw is allocated such that the screw has a long slit in the bracket by with play. In a further embodiment of the known load cell a bell-shaped part is provided at the end of the pendulum support, which arches over the support point and the four circumferentially distributed and from the edge of the bell-shaped part is having extending peripheral openings. The support member are four circumferentially distributed radially extending webs are provided which extend with spacing on all sides in the peripheral recess, so that a rotary motion of the pendulum support is limited around its axis. A pendulum motion of the pendulum support is possible in such arrangements within the limits set by the distance between the screw and slot or between webs and recesses.

p0004From EP-patent specification 0419784 a load cell is known, in which one end of the pendulum support comprises non-circular shape, whereby this end region is also formed in the shape of a segment of a straight cylinder. This end portion is arranged in a correspondingly formed recess of the support element. Next, there is disclosed an end of the pendulum support to be provided with transverse pin-shaped projections which engage in corresponding recesses of the support element. Moreover, disclosed in this US Patent Wägezellenanordnungen, in which the pendulum support the surrounding housing has projections, which are arranged between two fixed to the support webs.

p0005The known devices for limiting the rotational movement of pendulum based load cells are complicated and expensive to design.

p0006The invention is therefore based on the object to provide a load cell with a rotation limiting device, which is compact and simple construction and low cost.

p0007According to the invention this object is achieved with the feature of claim 1 or of claim. 3 In an extremely simple way the pendulum support is provided at its end with a collar, which has a recess with abutment surfaces which cooperate with a fixed on the supporting element arranged. The collar can be easily manufactured as a punched or flame cut sheet metal part and be beispeilsweise connected by welding or soldering with the pendulum supports end. In a preferred embodiment, the collar may be annular and be manufactured as a turned part. The recesses can thereby be mounted in front of the parting of the ring or on the finished ring member.

p0008The pin-shaped, axially parallel on the supporting element attached element is disposed closely adjacent the support surface for the end of the pendulum support. This results in an arrangement in which advantageously the housing surrounding the pendulum support, the support and attached between the housing and supporting the end portion of the pendulum support collar the same diameter, so a load cell system is extremely compact and simple construction. In an advantageous embodiment may be on the outside diameter of supporting and housing a bellows mount which surrounds the support point and the rotation limiting device sealing.

p0009In the following the invention with reference to the drawing, the Wägezellenanordnungen invention will be explained in detail. Show it:<ul><li>FIG. 1 is a load cell on average,</li><li>Fig. 2 shows a section along the line II-II in Fig. 1</li><li>FIG. 3 is a partial section similar to FIG. 2</li></ul> The load cell 1 shown in Fig. 1 comprises a pendulum supports load cell 2 and an upper and lower support member 3,4, as well as a rotation limiting means 5 having a first, attached to the pendulum supports load cell element 7 and a second in the illustrated embodiment, at the lower supporting element 4 fixed member. 8

p0010The pendulum supports load cell 2 has a pendulum support 6 and the stabilizer 6-tight housing enclosing 9. The pendulum support 6 is provided in a manner not shown with strain gauges for detecting load-dependent deformations due to the load to be weighed. The strain gauges are connected to a housed in the housing 9 of the signal processing circuit, which in turn is provided with a terminal unit 10 for an evaluation device.

p0011The two end regions of the pendulum support 6 are supported spherically formed and sealed into recesses of the supporting elements 3 and 4. FIG. In a known manner, by suitable choice of the radii of the spherical terminal caps the stabilizer 6 z. B. self-righting or be designed to be self-righting, as z. B. EP is described 0315846 A1 closer.

p0012The rotation restrictor 5 comprises fixed to the pendulum support 6, designed as a collar and extending in a cross-sectional plane element 7, which has a circumferential recess 10 at the outer diameter with stop surfaces 11 and 12. FIG. The stop surfaces 11 and 12 extend approximately radially outwards. The element 7 is made by punching out from a sheet metal and fixed by z. B. welding on the pendulum support 6. shown in FIG. 3 is an embodiment in which instead of the circumferential groove 10 a along a circular line portion extending slot-shaped recess 10 'is provided, wherein the stop faces 11' 12 are, 'at the ends of the slot-shaped recess 10'.

p0013The rotation limiting means 5 further comprises the fixed to the support element 4, pin-shaped, axially parallel to the pendulum support axis extending element 8. The element 8 is in the example shown an inserted into a blind hole of the support element 4 cylinder pin.

p0014The length of the pin-shaped element 8 and the location of the collar on the end portion of the pendulum support 6 are chosen so that even at maximum inclination of the pendulum support 6 of the collar on the one hand is in engagement with the pin-shaped element 8 and on the other hand is not in contact with the end face of the support element 4 comes. Likewise, the pin-shaped element 8 does not come into contact with the end face of the housing 9. The circumferential 10 and the slot-shaped recess 10 'surrounds the pin-shaped element 8 with such a game that an inclination of the pendulum support 6 in space, ie a bank with the hinged columns axis of a taper around the support point in the support element 4 without being impeded by contact between the collar and the pin-shaped element 8 is possible. Such a pendulum movement in space has an angle below 10 degrees.

p0015The rotational moving means 5 can naturally be provided instead of the lower end portion of the pendulum support 6 at whose upper end portion, and then cooperates with the upper support member 3rd

p0016In order to protect the rotation limiting device 5 and the support points against contamination, etc., in the illustrated embodiment, a resilient bellows 20 is provided which is mounted with its ends on the one hand on the support element 4 and on the other hand on the housing 9 of the pendulum support. 6

p0017The load cell of the invention may for example be used in platform scales or weighbridges for weighing vehicles or the container Recital. Applications are illustrated and described in detail in the brochure "Installation of load cells" of Fa. Hottinger Baldwin Messtechnik GmbH.