Adjustable parallel guide for compact gravimetric measuring instruments

The present invention relates to a parallel guide, preferably to a gravimetric measuring device.

[0002] Many different gravimetric realizations of measuring devices are known in the prior art. Many of the known embodiments, also called scales, consist essentially of a force measuring cell actively connected to the load cell of the weight-loading element guiding the load-weighting element linearly in the vertical direction of the parallel guide, the weighing electronics and the indicator unit.

[0003] Various operating principles of measuring force cells or measuring value recorders are known in the art, such as, for example, strain gauges, force cells with strings or EMFC force measurement cells (Electro Magnetic Force Compensation).

[0004] In the case of EMFC force measurement cells, the load weight is transferred either directly or through one or more force transmission levers to the electromechanical measurement value recorder, which emits an electric signal corresponding to the weighted load, which is further processed by the weighing electronics and fed to the indicator.

[0005] In force measurement cells with a strain gauge measuring data recorder, the deformed body is equipped with a strain gauge. This deformable body is elastically deformed by the applied load. The deformed body is often made as a parallelogram measuring (a parallel guide with a strain gauge), as a result of which defined deflection areas or bending locations in which strain gauges are placed. Tensometric recorders of measured values, stretched or crushed by the deformation of the deforming body, have an electric resistance value which is a measure of the applied load, which is changed in relation to the no-stress state.

[0006] In the string links of the force measurement, the mechanical structure largely corresponds to the EMFC or DMS force measurement cells with the difference that instead of the electromagnetic recorder of the measuring value or the extensometer strip a measuring value recorder with vibrating strings is used. As a result of the load, the vibrating string comes into tension, the frequency change in turn being the measurement of the load.

[0007] As mentioned before, such force measuring cells are used in various gravimetric measuring instruments, i.e. for example in scales, gravimetric humidity measuring devices, weighing modules and the like.

[0008] In the case of weigh modules, these are essentially balances in which the indicator unit is placed separately from the weight, for example in a system with a central indicator for a plurality of weighing modules. The weigh modules are preferably used in automated production and test installations in which a larger number of these weigh modules is combined in a compact, compact system.

[0009] Such a weighing module essentially has a structure which is visible, for example, in figure 1 of EP 1 726 926 A1. An approximately cubic parallel module parallel arm is at the same time a stationary frame in which the centrally located movable parallel arm of the weighing module - here a vertical mobile rod, which has a weighing pan on top - is vertically and vertically guided by the membrane springs.

[0010] However, this attractive simplicity concept has the disadvantage that there is no possibility of regulating the very exact parallelity of the guide membrane springs required. As known to the skilled person, deviations from the parallelism between the sliders of the parallel weight guide arise so-called corner load errors, i.e. weighing errors due to the non-central load of the load carrying element.

[0011] The error of the corner load or, in positive terms, the accuracy of the corner load is the main property of the weights with a parallel-guided load-bearing element. Although it would be possible to try to obtain the desired accuracy of corner loads by increasing the precision of workmanship, on the one hand, it increases the cost of manufacturing scales and weighing modules, and on the other hand even the highest machining accuracy achieved by the machine tool is not enough to achieve the accuracy of the loads required in precise and analytical balances. in the range from about 1 / 50'000 to about 1 / 1,000'000 weighing range.

[0012] Therefore, at least in very precise scales in principle a different solution is chosen, allowing, on the one hand, a relatively wide tolerance of the processing accuracy of the given parts of the balance, on the other hand, in the critical areas of the parallel control mechanism, the control possibilities that can be adjust the parallelism of the sliders as far as possible until the desired accuracy of the corner loads is obtained. Such adjustment of the accuracy of corner loads takes place after production, in a ready-to-use gravimetric measuring instrument in an automatic or manual inspection and adjustment process, in which other adjustments are made, for example to compensate for linearity and calibration of the measurement sensitivity.

In the parallel guide, i.e. the guide of the parallel carrier element of the weighing pan, by means of two parallel, substantially horizontal parallel runners, the corner load errors are mostly due to the fact that these parallel travels deviate slightly from the ideal, absolute parallelism. In this case, the relative magnitude of the error of the corner load, i.e. the ratio of the observed weight variation to the size of the test charge, approximately corresponds to the error causing the relative geometric deviation. A distinction is made between the corner load in the longitudinal direction and the error of the corner load in the transverse direction of the parallel guide, according to the direction of the test charge travel on the weighing pan when checking the corner load error of the balance. The error of the corner load in the longitudinal direction comes from here, that the vertical spacing of the parallel sliders at the end connected to the fixed parallel arm is not exactly the same as at the other end connected to the movable parallel arm. However, the error of the corner load in the transverse direction is caused by the mutual twisting of the two parallel runners relative to each other, i.e. the state in which the spacing between the parallelogram shifters varies along the width of the parallelogram shifters.

[0014] Such adjustment of the corner load is disclosed, for example, in US 4 606 421 A1. The fixed parallel arm of the disclosed parallel guide has in one of the two planes one elastically deformable bending place. The axis of rotation of the first bending location extends in the longitudinal direction of the parallel guide, while the axis of rotation of the second bending location is perpendicular to the longitudinal direction of the parallel guide. By means of four adjustment screws, the upper end area of ​​the fixed parallel track can be tilted towards the lower end region of the stationary parallel track, whereby the deviation of the corner load can be adjusted in both the longitudinal and transverse direction.

[0015] As already mentioned, weighing modules of the type described above, an example of which is described and reproduced in EP 1 726 926 A1, are not provided with the possibility of adjusting the parallelism of the diaphragm springs of the sliders, so that using these modules also by means of precise and appropriately complicated production methods can only achieve limited accuracy of corner loads.

The object of the present invention is therefore to propose a parallel guide for a gravimetric measuring device, preferably for a compact weighing module that has a structurally simple, safe and inexpensive possibility to adjust the parallelism of the parallel slides, allowing to set the desired accuracy of the corner loads, so that in the production of the parallel guide according to the invention, narrow and difficult tolerances need not be determined.

[0017] This object is solved by means of a parallel guide according to claim 1. The parallel guide according to the invention, which can be used in a gravimetric measuring device, comprises a vertical parallel guide having an upper and a lower end plate, a stationary parallel arm. The fixed parallel arm comprises a movable parallel arm whose longitudinal central axis in its operational condition runs vertically. In addition, the parallel guide has a first parallel track member placed on the upper end region and a second parallel track member by means of which the parallel track members are connected to the parallel parallel motion and moveable vertically.

The upper end region and the lower end region are connected to each other via at least one pair of bending sites and / or via at least one ball joint and / or through at least one annular constriction, thereby resulting in end regions for correction the corner load error can be tilted around at least one axis of rotation.

If there is a pair of bending locations, then at least one axis of rotation passes through two bending locations of the pair of bending locations, wherein the longitudinal center axis of the movable parallel arm is located in the vertical plane between the two bending locations of the bending sites. Thus, the bending sites are the connecting points between the upper and lower end areas.

[0020] If there is a ball joint, then at least one axis of rotation is located in a plane containing a circular ball joint line, the longitudinal center axis of the movable parallel arm being located inside the ball joint line.

The circular contact line is the contact point in the shape of a circular line or circular ring between the two parts of the ball joint. The circular contact line can also be understood in the sense that there are an infinite number of contact points. For example, the ball joint can be reduced to a minimum so that only a single part of the circular contact line exists. Depending on the roundness of the hinge parts in the area of ​​the circular contact line, at least two contact points are formed. The contact points of the circular contact line therefore also constitute connecting points between the upper and lower end areas. In the case of a ball joint, the direction of the axis of rotation is no longer specified, as is the case with the bending system of the bending points. Orientation of the axis of rotation in the plane is determined only in the adjustment process.

[0021] If there is an annular constriction, then at least one axis of rotation is located in a plane containing the neutral fibers of the annular constriction, and the longitudinal central axis of the movable parallel arm is inside the annular gap opening. In science about the strength of neutral fiber, this place is called the bent part, which is neither stretched nor compressed by bending. Also, the annular constriction, as already described in detail in the case of a ball joint, has an infinite number of points of contact or connection. These connection points are also the connecting points between the upper and lower end areas. The annular constriction generates a tilting, in all directions, connection between the end regions of the stationary parallel arm. The short ring-shaped constriction can be shaped so that it can be bent in any direction by appropriately selected force and torque, which allows the non-parallelity of the diaphragm springs of the runners to be corrected, and thus the load on the corner parallel guide with respect to any direction. Setting the axis of rotation in the plane is fixed, as in the ball joint, only during the adjustment process.

[0022] Three possibilities for connecting the upper end region and the lower end region of the parallel guide according to the invention have the common feature that the longitudinal center axis of the movable parallel arm is always located between at least two connection points.

[0023] This has decisive advantages. At least two separately spaced connecting points form a perfectly precise connection, which maintains the position of the rotation axis, which is loaded in an almost equal manner with the forces acting on the weight-loading element. Such precision is impossible to achieve in the regulation of corner loads disclosed in US 4 606 421 A1. The joining points in US 4 606 421A1 must have a defined cross-section of the material in order to be sufficiently able to carry permanently, and therefore permanently to load, the connecting points of the adjustment bolts, so that during operation the connecting place does not settle, i.e. does not deform plastically, so that the guide rail the parallel would be useless. Due to the existing width of the parallel track, this adjustment of the corner loads also has connection points, the cross-sections of which have an unfavorable length-to-width ratio to define a precise axis of rotation. Because in order to adjust the corner load, the upper end area has to be tilted with respect to the lower end area only by an extremely small angle, material inhomogeneities and machining tolerances in the shaped joints have an extremely strong influence on the actual position of the axis of rotation. The position and orientation of the axis of rotation at the widely-shaped connection points can also continuously change during tilting. However, it negatively affects the possibility of adjusting between the regulation of the corner load in the longitudinal direction and the regulation of the corner load in the transverse direction,

If in the adjustment of the corner load according to the invention there is only one jointing point on the fixed parallel arm, then there would also be a risk that the connecting point under load of the weight-setting element, in particular with transverse forces acting on it, will break or bend causing a change geometrical parameters of the parallel guide and acting negatively to a decisive extent on the weighing signal of the force measuring cell. Due to the fact that the longitudinal center axis of the movable parallel arm is between at least two joining points, the forces acting in the fixed parallel arm in the area of ​​the weight-placing element and are therefore effectively transferred in the end areas. The result is that, unlike the state of the art, to avoid collapse under load, you do not need to use adjusting screws that tighten the connection points and thus load them additionally. Therefore, in the parallel guide according to the invention, the connecting points can have extremely small dimensions. As described in detail below, even the use of retaining elements can be dispensed with.

[0025] The fixed parallel arm comprises both end areas and all the parts that are between the two end regions and on the stationary side of the parallel guide serve to connect the parallel runners. The longitudinal central axis of the fixed parallel arm corresponds to the center of gravity axis or the neutral fibers of the entire parallel arm. The support connecting the fixed parallel arm with the ground, for example the balance housing, is no longer a fixed parallel arm.

[0026] The "embrace" feature is to be interpreted so that the movable parallel arm is located within the projection surface of the stationary parallel arm. That is to say, for example, a fixed parallel arm with a U-shaped cross-section includes a movable parallel arm in the same way when the movable parallel arm is within the recess of the U-shaped parallel arm, although the U-shaped parallel arm is open on one side.

In a preferred embodiment of the parallel guide, at least one axis of rotation and the longitudinal central axis of the movable parallel arm have a common intersection. In the tests, it could be concluded that due to the arrangement according to the invention with two connection points and a common axis intersection there is no or only a small zero point shift due to the corner load adjustment since the average distance between the end regions of the fixed area remains largely unchanged. In this way, an additional advantage is obtained which does not occur in the parallel guide with only one connection point as disclosed e.g. in US 4 606 421 A1. In these parallel guides the distance between the lower and upper bending supports changes.

In a further configuration of the parallel track, at least one axis of rotation is further arranged perpendicular to the longitudinal center axis of the stationary parallel arm. Special results arise when adjusting the accuracy of the corner load. When a test weight and tare weight is placed on the weight-bearing element on the middle, the load accuracy of the corner parallel guide according to the invention can be set in the simplest way. When the test weight is moved between two diametrically opposed points on the weight positioning element, due to the symmetrical arrangement of the axis of rotation and provided that the same distance from the longitudinal central axis is maintained, identical values ​​of the measurement signal deviations are obtained. They differ only by the sign.

[0029] Therefore, the adjustment method for setting the accuracy of the corner load of this parallel guide or the gravimetric measuring instrument by means of this parallel guide is extremely simple.

[0030] In the first step, the test weight is placed in the center of the weight-setting element and the pointer is set to "zero" (tarring).

[0031] In the second step, the test mass preferably moves (and if present) in a direction perpendicular to the first axis of rotation and places on the edge of the weight-setting element.

[0032] In the third step, the upper end region is tilted with respect to the lower end region around the first axis of rotation, until the indicator shows the value "zero".

[0033] In the fourth step, the test charge moves towards the first axis of rotation and places on the edge of the weight-setting element.

[0034] In the fifth step, the upper end region is tilted with respect to the lower end region around a perpendicular to the first rotational axis, the second axis of rotation, until the indicator shows the value "zero".

[0035] For control purposes, the test weight can be placed on the diameter position of the weight-setting element. The tests showed that the indicator at the control shows only the smallest deviations.

[0036] The method of adjusting the parallel guide with a ball joint or with an annular constriction is even simpler than the method previously described. When adjusting the corner load accuracy after taring, by moving the test weight along the edge of the weight positioning element, the direction of the largest deviation can be determined. Then, by tilting about the rotation axis perpendicular to the designated direction, the end regions can be tilted relative to each other until the indicator indicates the value "zero".

[0037] To secure the set tilt, at least one fixation element may be provided for immobilization between tilted end regions. Alternatively, the fixation means can also be used for adjusting tilted end areas. The immobilizing means only fix the setting made, they do not have to take over the forces acting on the weight-setting element, such as the adjusting screws known from the prior art.

[0038] The setscrews are usually made of materials other than a fixed parallel arm. As a result, they have a different coefficient of expansion and a different modulus of elasticity than the arm. Since the adjusting screws also transmit part of the forces acting on the weight-setting element, the thermal interactions in the parallel guides known from the prior art can lead to a temporary adjustment of the parallel guide and thus strongly depend on the deviation of the gravimetric gauge from the temperature. Since the parallel guide according to the invention does not have such adjusting screws, a further advantage, namely a significant improvement in the thermal performance of the gravimetric measuring instrument, follows.

[0039] Preferably, the fixed parallel arm having a longitudinal central axis is shaped with rotational symmetry, and the parallel slider elements are in the form of soft-elastic membrane springs of runners.

[0040] As explained above, the possibly symmetrical configuration of the parallel guide facilitates a very simple way of setting the accuracy of the corner loads. Thus, ideally, the movable parallel arm is positioned relative to the stationary parallel arm such that the longitudinal center axis of the stationary parallel arm and the longitudinal central axis of the movable parallel arm coincide.

[0041] At least two lateral recesses between the upper end region and the lower end region of the stationary parallel arm form at least one pair of bending locations. Each bending location is essentially a narrow material bridge, elastically and / or plastically deformable under force or torque, wherein due to the deformation of the two material bridges, the end areas tilted relative to each other, and thus the attachment points of the fixed parallel rotating elements formed in the end areas are tilted around at least one axis of rotation, while tilting makes it possible to correct the load errors of the corner parallel guide. The deformable material bridge can be a component of a monolithic parallel arm, but also a separate part, which together with other parts forms a fixed parallel arm. Of course, also the entire parallel guide can be monolithically shaped.

[0042] The parallel guide according to the invention in the horizontal plane in the working parallel state of the guide may have two first recesses which are routed from opposite sides of the fixed parallel arm near the first diameter of the fixed parallel arm, so between the first two are formed by two narrow first material bridges. In addition, in a second horizontal plane, which in relation to the working position of the parallel guide extends below the first horizontal plane, two second recesses are formed which are routed from opposite the diameter of the exit points vertically below said first material bridges close to the second diameter of the stationary parallel arm, therefore, only narrow second material bridges are formed between the two second ones. Consequently, an intermediate annular region is formed between the first and second choices through which this intermediate annular region of the upper end region is joined by two first material bridges and both second material bridges with a lower end region.

[0043] The first and second material bridges have the form of deformable pair of bending sites and together with the intermediate ring region form a germinated connection of the end areas.

Of course, this gimbal connection can be arranged on the principle of supporting the compass in one plane, wherein in the region of the gimbal joint the upper end region, the intermediate ring and the lower end region must have different dimensions in a plane perpendicular to the longitudinal central axis.

In the context of the present description, expressions such as "upper", "lower", "horizontal", "vertical" etc. always refer to a parallel guide or a gravimetric measuring device in which a parallel guide is used, in a normal operating state. in other words, in the direction of gravity.

[0046] Narrow material bridges are now sufficiently susceptible to function as specific bending locations (hereinafter analogous to material bridges with the first and second bending locations) such that through the first bending locations, the first diameter forms the first axis of rotation and extends through the first axis of rotation. second bending points, second diameter creates a second axis of rotation. As can be inferred from the above, the first and second axis of rotation extend perpendicular to each other, so that the first and second bending regions produced by the described recesses together form an intermediate support of the annular end region with an upper diaphragm spring of the slider which, as mentioned above , it is comparable with the gimbal suspension.

[0047] In order to be able to even better adjust the fixed arm of the parallel parallel guide, after the first two choices further rebates may form further deformable material bridges. Thus, successive pairs of recesses in successive horizontal planes, which in relation to the working state of the parallel guide run below the first horizontal plane and run from diametrically opposed output points close to the diameter of fixed parallel arms, respectively, can be created to form consecutive pairs of opposite bridges material. These pairs are preferably rotated relative to each other by the same angular segments, wherein the material bridges thus formed together with those formed by recesses,

[0048] The perpendicularity of both rotational axes is advantageous, but it is not absolutely necessary. Both second bending points could thus be rotated relative to each other instead of 90 ° by any other angle substantially different from zero, for example by means of respective bilateral rebates in three horizontal planes lying one above the other. In this way, the first, second and third pair of bending points are formed, rotated at 60 ° relative to each other.

Since the fixed parallel arm has a plurality of segments that are pivotable relative to one another for adjusting the corner load, the stationary parallel arm can be supported on the substrate in the upper end region or in the lower end region, or, if there is one, in the area intermediate.

[0050] Preferably, the at least one narrow material bridge is plastically deformable by applying a torque force, so that a permanent deflection of the end regions relative to one another around at least one axis of rotation can be achieved by plastic deformation of the material bridge and thus a permanent correction of the corner load error. To achieve this, material bridges acting as bending locations must still be rigid enough for the tilted end area to be immobilized in its nominally horizontal position, but nevertheless it is possible to precisely adjust the horizontal or parallel position to the lower diaphragm spring. a slider by applying the appropriate force or torque, for example by applying a lever tool to the annular upper end region, as a result of which a permanent plastic deformation of the bending place is generated. This makes it possible to dispense with the use of indexing elements, such as adjusting screws, wedges and the like, which maintain tilting. Of course, these adjusting elements can be used to secure the tilt, especially in mechanically heavily loaded parallel guides.

[0051] To accurately adjust the tilt, it is advantageous if the particular end area of ​​the stationary parallel arm has clearance points for applying a suitable tool that generates torque and is able to be removed after adjustment. The easiest way to place such flaps can be created in a fixed parallel frame with holes. If the notches are narrow notches, then the sides formed by the cuts can serve as relief points for the incoming crowbar-shaped lever.

[0052] In dependence on the configuration of the parallel guide, the adjustable end area of ​​the stationary parallel arm for applying force or torque may also have suitable means in the form of adjusting screws, eccentric screws, differential thread screws, sliding wedges, levers or tapered pins.

[0053] Ideally, in the operative position of the parallel guide, the fixed parallel arm is a substantially straight, perpendicular, circular, hollow cylinder. Thanks to this, you can place recesses on the circumference anywhere.

[0054] However, the fixed parallel arm can also be a polygonal, in particular a square, hexagonal or octagonal, tubular profile. Preferably, the fixed parallel arm is shaped as a monolithic tubular section in which notches have been made by milling, grinding, drilling, spark erosion and the like. In order to maintain the low construction height of the parallel guide, it is advantageous if the notches are formed as narrow cuts.

[0055] Depending on the configuration of the gravimetric measuring instrument, the force measuring cell may be located between the parallel arms of the parallel guide. To allow unrestricted access to the force measuring cell and, if there is one, to the components of the signal processing unit, the fixed parallel arm may have a side access opening.

[0056] Alternatively, such access may also be undesirable to prevent manipulation on the gravimetric measuring instrument by third parties. All parts of the gravimetric measuring instrument with the exception of the indicator unit, i.e. the weighing module, as previously defined, can be placed inside the parallel guide. In order to gain access to the force measuring cell and its electronic components, the parallel guide must first be disassembled, which would inevitably lead to its disregulation. An incorrectly opened weighing module could be detected when checking the accuracy of corner loads and is discontinued.

[0057] In the knowledge of the present subject matter, variations described below are also possible, which should also be considered as part of the disclosed invention.

[0058] To describe the subject matter of the invention, including a parallel lever, a consistent parallel arm has so far been conceived, for the sake of a clear description, which includes a movable parallel arm. It is clear that including the parallel arm, if it is operatively connected to the force measuring cell and the weight-setting element, it can also be a movable parallel arm and the parallel arm it covers can be supported on the ground as a fixed parallel arm.

[0059] Furthermore, in the previous description, due to the transparent description, it was consistently pointed out that the tilting of the end areas on the fixed parallel arm is possible due to the corresponding shaping of the fixed parallel arm. Of course, a corresponding configuration can also take place in a movable parallel arm.

[0060] Possible embodiments in which, for example, between the end areas there is another element that allows tilting and the mutual position of the end areas is set, for example, via retention means, should also be considered as a component of the present invention. Thus, the parallel guide on the upper and lower end regions of the stationary parallel arm may have a deformable metal bellows or a rubber ring, and between the end regions there may be at least one retaining and adjusting retainer.

The details of the gravimetric measuring device, in particular of the parallel guide according to the invention and the method of its adjustment are explained in more detail below on the basis of the drawings according to the following review.

Fig. 1 shows a perspective view of a parallel guide according to the invention;

Fig. 2 shows the parallel guides of Fig. 1 in a top view towards the first axis of rotation and illustrates the advancement of the test charge to determine a corner load error;

Fig. 3 shows a substantially parallel guide from figure 1 in a top view with a tilted first end region and a deformed bending place and with a retaining means;

Fig. 4 shows a substantially parallel guide from Figure 3 in a top view with a tilted first end region, wherein a ball joint is provided instead of the bending place between the casing of the main part and the first end region;

Fig. 5 shows as a variant of the previous figures a parallel track in which the upper annular end region is pivotable with respect to the x-axis plane lying in the plane, and the lower annular end region is pivotable with respect to the plane of the y-axis drawing;

Fig. 6 shows the execution of a parallel guide with three rotation axes which have been rotated by 60 °, formed by pairs of bending places and

Fig. 7 shows the implementation of a parallel guide, in which the tilting of the upper annular end region on all sides is achieved by a ring-shaped, thin-walled and also plastically deformable constriction formed on the fixed parallel arm.

[0062] Figure 1 shows a parallel guide 1 according to the invention in a three-dimensional view. One can see a fixed parallel arm 2, which at the upper end is equipped with first horizontal recesses 3, which divide the fixed parallel arm 2 almost to a diameter of 4, so that only two opposing material bridges remain opposite each other on the diameter (only one of them is visible in figure 1). Below the first horizontal recesses 3, turned by 90 [deg.], There are second horizontal recesses 6 and material bridges 8 lying opposite on diameter 7 (only one of them is visible in the figure). The hole 9 in the fixed parallel arm 2 gives access to the intermediate space in the interior of the fixed parallel arm 2, for example to the force measuring cell located there (not visible in figure 1). In addition, the intermediate space may also include the entire audio processing unit or sub-assemblies of the signal processing unit, for example a memory module (EAROM) with comparative data, an analog-to-digital converter system and a position sensor. The comparative data are essentially correction data specific to a given force cell, measured substantially immediately before the shipment of the force measuring cell that can be used, connected to the force measurement cell, the signal processing unit. With an appropriate size of the intermediate space, even the indicator unit can be placed in it. analog-to-digital converter circuit and position sensor. The comparative data are essentially correction data specific to a given force cell, measured substantially immediately before the shipment of the force measuring cell that can be used, connected to the force measurement cell, the signal processing unit. With an appropriate size of the intermediate space, even the indicator unit can be placed in it. analog-to-digital converter circuit and position sensor. The comparative data are essentially correction data specific to a given force cell, measured substantially immediately before the shipment of the force measuring cell that can be used, connected to the force measurement cell, the signal processing unit. With an appropriate size of the intermediate space, even the indicator unit can be placed in it.

[0063] Thanks to the material bridges 5 and 8 and the ring region 10 between them, a gimbal bearing of the annular end region 11 of the stationary parallel arm 2 is formed. The annular end region 11 forms the peripheral frame of the upper diaphragm spring 12 of the slider. In the interior of the lower end region 13 of the stationary parallel arm 2, the lower diaphragm spring 14 of the slider is in an analogous manner. The vertically movable parallel arm 15, placed centrally in the fixed parallel arm 2, is connected to the two diaphragm springs 12 and 14 of the slider and is guided therein within a limited vertical space of movement.

[0064] Figures 2 and 3 show the upper part of the fixed parallel arm 2 with the above-described bending positions and locations in a schematic detailed front view. For orientation in space, reference is made to the Cartesian coordinate system in which the x direction in the plane of the drawing runs through both second bending points 8, the y direction orthogonally backwards with respect to the plane of the drawing through both first bending places 5 and the z axis vertically as the stationary axis of the stationary symmetry parallel arm 2. Apart from the fact that the rotation axes defined by the bending points lie in different horizontal planes, in this system both geometrically and mechanically in relation to the control characteristics there is no difference between the x direction and the y direction. x (i.e.

[0065] If, for example, in the parallel guide 1 shown in figures 1, 2, 3, when moving the load 17 (see figure 2), the negative corner load offset (i.e. load position is less than for the left-hand position), then this can be corrected by the error-dependent deviation in the negative rotation direction relative to the y-axis (i.e., counter-clockwise as shown in figure 3).

[0066] The parallel guide shown in figure 4 differs from the previously described embodiments in that instead of material bridges between the upper annular end region 11 and the cross-ring area 10 there is a ball joint 25 with retaining means 26. The ball joint 25 is formed by a shaped in the area the ring-shaped sphere zone and through the adjacent annular sphere zone, the inner edge of the annular end region 11. This adjacent inner edge corresponds to the circular contact line 19. A retaining means 26 is provided for permanently connecting the ring region 10 to the annular end region 11, which due to its adjustment can also also serve to set the corner load. The number of retaining means 26 is not strictly determined, but ideally, as shown, three retaining means 26 are arranged around the perimeter of the annular end region 11 to avoid stresses due to static retraction. Of course, the retaining means 26 must also be able to compensate for angular errors due to the adjustment of the corner load. In Figure 4 this is symbolically represented by means of a tilting support 28.

[0067] As a variant of the parallel guide 1 according to the previously described figures, the same possibility of adjusting the components of the corner load error in the x and y direction can also be obtained by means of the arrangement according to figure 5. The upper annular end region 11, which holds the upper diaphragm spring 12 of the slider, is formed here by means of bending places 5 about the axis of rotation running in the y direction (i.e., perpendicular to the plane of the drawing), while the lower annular end region 13, which includes the lower diaphragm spring 14, is shaped analogously in a tilting manner around the axis of rotation formed by the bending place 8 and running in the x direction (i.e. in the plane of the drawing). Correction of the corner load error in the x-direction occurs here by tilting the upper annular end region 11,

[0068] Figure 6 shows a further possible implementation of the idea of ​​the invention with three rebounds pivoted at 60 °, and thus with three pairs 21, 22, 23 bending places. The other elements marked with reference numerals correspond to the embodiment according to figures 1 to 3. Analogous systems with evenly rotated pairs of bending locations are also possible.

[0069] Figure 7 shows an embodiment in which the fixed parallel arm close to the upper diaphragm spring 12 of the bearing has a deep necking, wherein the thin-walled annular constriction 18 is a plastically deformable and / or flexible bending place such that the annular upper end region 11 of the stationary parallel arm it may be tilted about any horizontal axis relative to the lower end region 13 comprising the lower diaphragm spring 14 of the slider. The annular constriction 18 must have an opening that permits the movable parallel arm 15 to be secured so that a weight element 16 can be attached to the upper end of the movable parallel arm 15.

In the embodiments according to figures 1, 2, 3, 4 and 5, the Cartesian directions of the x and y axes are determined by pairs 5, 8 bending places or retaining elements 26. In the embodiment according to figure 6, the direction of joining the first pair can be chosen, e.g. 21 bending places, whereas in the case of FIG. 7, the y direction can be chosen freely, with the y direction coming from the rotation by 90 ° in the counter-clockwise direction relative to the x-direction, and the z-direction being determined by the vertical symmetry axis of the parallel guide. In embodiments according to figures 1 to 6, the directions defined by the pairs of bending locations and / or the positioning elements 26 are obviously indicative of the direction x and y.

[0071] In the illustrated embodiments, a preferred embodiment has been shown and described with parallel guides shaped in rotational symmetry. As already described above, the longitudinal central axis of the fixed parallel arm does not necessarily coincide with the longitudinal center axis of the movable parallel arm. The longitudinal central axis of the movable parallel arm can also be placed parallel and spaced with respect to the longitudinal center axis of the stationary parallel arm. Also, the rotary axes do not necessarily have to intersect the longitudinal center axis of the stationary parallel arm.

[0072] In the embodiments, preferably the diaphragm springs of the slider are shown. Of course, parallel track elements that are not shaped as diaphragm springs may also be used to connect the movable parallel arm to the fixed parallel arm. This will especially be the case if, for example, the longitudinal center axis of the fixed parallel arm is placed parallel and spaced apart from the longitudinal center axis of the stationary parallel arm.

List of references Parallel guide Parallel arm Parallel first horizontal recesses First diameter, first axis of rotation First material bridges or bending location Second horizontal recesses

1PL00

Second diameter, second axis of rotation second material bridges or bending place lateral access opening cross-ring area upper end region in 2 upper membrane spring of the slider covered by 11 lower end area in the lower 2 membrane spring of the slider covered by the 13th movable arm of the parallel element for placing the weight, weighing pan test charge ring circular restriction line of the steam contact bending places ball joint positioning means adjusting means tilt support

Mettler-Toledo GmbH

Proxy:

84P40541PL00

EP 2 153 185 B1