MONOLITHIC BENDING JOINT ARRANGEMENT AND UNDER-SHELL BALANCE

Description

Field of invention

[0001] The invention relates to a monolithic bending joint arrangement comprising a main body which is penetrated by two pairs of channels, namely a first pair of channels and a second pair of channels, which are aligned perpendicular to each other in a radial plane and intersect each other and a central axis normal to the radial plane at the center of the main body. wherein each pair of channels has two individual, parallel through-channels which are arranged so closely adjacent to each other with convexly curved channel wall sections facing each other that webs running between said curved channel wall sections together form a bending joint, wherein a central part of the main body is pivotally connected to an otherwise unconnected inlet piece by means of a first bending joint formed between the through-channels of the first pair of channels and is pivotally connected to an otherwise unconnected outlet piece by means of a second bending joint formed between the through-channels of the second pair of channels.

[0002] The invention further relates to an under-tray scale whose weighing carrier is coupled to the load sensor of its weighing system via such a bending joint arrangement. State of the art

[0003] A bending joint arrangement of this type is known from DE 21 14 802 A.

[0004] Precision scales, particularly those used as comparators for calibrating test weights against reference weights, are often designed as under-tray scales. In an under-tray scale, the weighing platform is positioned below the load cell and connected to it via a coupling joint. The load cell itself is part of a weighing system, i.e., a more or less complex assembly of levers and linkages that transmits the force acting on the load cell to the sensor using a suitable force transmission.The latter, for example, can be designed as a moving-coil arrangement in scales operating on the principle of electromagnetic compensation (EMF scales), where the coil current required to maintain equilibrium serves as the measured variable, representative of the weight force acting on the load cell. However, the specific operating principle of the sensor is irrelevant to the present invention. In any case, it is desirable that the weight force exerted on the weighing platform by the mass to be weighed is introduced precisely vertically into the load cell of the weighing system. For this purpose, an articulated coupling between the load cell and the weighing platform is required, enabling pivoting movements about two mutually perpendicular, horizontally extending pivot axes, said pivot axes preferably lying in the same horizontal plane.

[0005] From the aforementioned generic publication, a monolithic bending joint assembly suitable for this purpose is known, the preferred application of which, as described in the publication, involves coupling a drive shaft to a flywheel. The main body of the known bending joint assembly has the hollow cylindrical shape of a pipe section. This is divided into three axial sections, the middle one of which can be called the central section and the axially outer ones the inlet and outlet sections, respectively. This designation serves solely to structurally differentiate the elements without any functional implications. The inlet and outlet sections are each pivotally connected to the central section via a bending joint, with the two pivot axes lying in the same radial plane of the main body, specifically in its central plane, and being perpendicular to each other.Each of the two bending joints consists of two thin sections of material arranged radially opposite each other in the tube wall of the hollow cylindrical main body. Each thin section is formed by the web between two closely adjacent bores through the tube wall. The two individual bores, each lying on a line parallel to the radial axis, can be considered together as a through-channel through the hollow cylindrical main body, interrupted by the lumen of the tube section. Thus, each bending joint is formed by a pair of channels consisting of two closely adjacent through-channels through the main body. Each through-bore is connected to its partner lying on the same radial parallel via a through-slot that half-circumferentially encircles the main body, thereby achieving a complete separation of the central section from the inlet and outlet sections, except at the bending joint connections.

[0006] The well-known flexural joint arrangement is disadvantageous in two respects with regard to its use as an articulated coupling between the load carrier and the load cell of an under-tray scale. Firstly, it is difficult to fix the essentially ring-shaped inlet and outlet pieces precisely to the load cell or load carrier. This is particularly problematic considering that, ideally, precision instruments should allow for adjustment of the coupling in both the vertical and azimuthal directions. Secondly, it must be considered a disadvantage that each of the two flexural joints consists of only two quasi-point-like thin material sections. Such joints are not completely rigid against parasitic movement and are particularly susceptible to torsional movements.Accordingly, the aforementioned document also stipulates that the described bending joint arrangement should not be used alone, but only in combination with a similarly constructed bending joint arrangement, with both arrangements being inserted concentrically into one another. This entails additional assembly effort and a loss of precision, which is perhaps still acceptable in the context of a drive shaft, but unacceptable in the case of the linkage of the weighing carrier to the load cell of a precision scale, which is the focus here. Task

[0007] The object of the present invention is to further develop a generic bending joint arrangement in such a way that it is better suited for coupling the weighing carrier to the load sensor of an under-tray precision scale. Description of the invention

[0008] This problem is solved in conjunction with the features of the preamble of claim 1 by the fact that the inlet piece and / or the outlet piece is designed as a beam radially penetrating the central piece.

[0009] An under-tray scale with a corresponding coupling of its weighing platform with its load sensor is the subject of claim 8.

[0010] Preferred embodiments of the invention are the subject of the dependent patent claims.

[0011] The invention departs from the prior art, which is essentially a hollow cylindrical shape for the main body of the bending joint assembly, and provides an essentially solid cylindrical main body shape. The pair of channels forming each bending joint is no longer limited to corresponding openings through a thin tube wall, but consists of actual channels that are surrounded by channel walls along their entire length or at least a substantial part thereof. This also lengthens the web between the individual channels of the channel pair, which defines the pivot axis of each bending joint, and extends substantially radially through the entire main body. Only in the central region, i.e., in the intersection area of ​​the two channel pairs, does the crossing of the channel lumens automatically create a comparatively small cavity interrupting the channels.In the preferred embodiment, in which the inlet and outlet elements are designed as radial beams, each bending joint is thus composed of two webs extending almost over half the main body diameter, which leads to a significantly more precise definition of the pivot axes than was the case with their definition by only two quasi-point-shaped material thin spots in the prior art.

[0012] A further advantage of the design according to the invention is that the central points of the end faces of the inlet and outlet pieces are not located in the hollow lumen of the tubular main body, but rather in the material of the inlet and outlet pieces. This allows coupling elements for the load cell or weighing carrier to be attached directly to the inlet and outlet pieces at a central location. Preferred embodiments of such coupling elements will be described in more detail below.

[0013] A third advantage of the inventive design lies in the fact that the inlet and outlet pieces can be nested with the central piece. If the inlet and / or outlet piece is designed as a beam radially penetrating the central piece, the central piece itself can fill the remaining space laterally to this beam at the same axial height. This was not the case in the prior art; there, the inlet and outlet pieces on the one hand and the central piece on the other had to be arranged purely axially adjacent to each other. The inventive design thus allows for a significant saving in axial installation space.

[0014] In the preferred embodiment, as mentioned, not only the inlet or outlet piece, but both the inlet and outlet pieces are each designed as a beam radially penetrating the central piece, with the beams being skew and perpendicular to each other and to the central axis. This allows the inlet and outlet pieces to remain in different axial sections of the main body; however, their associated pivot axes can lie in the same radial plane. As explained at the outset, this is advantageous for applications in precision weighing technology.

[0015] Preferably, the inlet piece has a fixing opening on its side facing away from the associated bending joint, coaxial to the central axis, for receiving a coupling pin. As explained above, the central area of ​​the bending joint assembly contains a "fabric" of the inlet piece. An opening can be provided here that serves as an interface for a coupling pin, with which the inlet piece can be fixed to the load cell (preferred) or to the weighing platform of an under-tray scale.

[0016] The fixing opening can be provided with an internal thread into which a corresponding external thread of the coupling pin can be screwed. However, it is considered more advantageous if the inlet piece has a threaded channel running transversely to the fixing opening to accommodate a clamping screw that secures the coupling pin in the fixing opening. This allows for axial or vertical adjustment. The coupling pin should be able to be inserted into the fixing opening with a positive fit and axial movement – ​​for example, a cylindrical coupling pin in a round fixing bore. The desired relative positioning of the coupling pin and inlet piece in both axial and azimuthal directions can then be stabilized by the clamping screw in the threaded channel running transversely to the fixing opening. Preferably, the threaded channel runs parallel to the longitudinal extent of the inlet piece's beam.It is particularly advantageous if it extends over the entire length of the beam of the entrance piece, so that the coupling pin inserted into the fixing opening can be fixed from two sides with clamping screws.

[0017] The starting piece, however, is preferably provided with a coupling pin extending coaxially to the central axis on its side facing away from the associated bending joint. The coupling pin can, for example, rise integrally from the end face of the starting piece as a single piece of material. It can serve as an interface for coupling the starting piece to the load cell or (preferably) to the weighing platform of an under-tray precision balance. Preferably, the coupling pin has a cylindrical shape with a lateral clamping flat. If the corresponding interface of the load cell or weighing platform is a sleeve with a lateral threaded channel, the clamping flat of the coupling pin can serve as a rebate for a clamping screw guided in the threaded channel.

[0018] In the preferred embodiment of the invention, the fixing opening of the inlet piece transitions into a fixing opening of the outlet piece that completely penetrates the outlet piece and preferably also the coupling pin, at least over the length of a partial section, in order to form a common fixing channel. In other words, the preferred embodiment provides a channel that coaxially penetrates virtually the entire bending joint assembly. Only the tip of the coupling pin is closed in this design. Those skilled in the art will understand that a fixing pin, which is positively inserted into the bending joint assembly according to the invention along the length of such a common fixing channel, blocks both bending joints simultaneously. Any relative deflection of the inlet and outlet pieces with respect to the central piece is thus prevented.Such a joint lock can be particularly useful in transport situations where there is a risk that external forces could exert excessive deflection movements on the delicate bending joints. During intended operation of the bending joint arrangement according to the invention, such a locking pin must, of course, be moved at least far enough away that it no longer crosses the radial plane of the two bending joints. Only then can the bending joint arrangement according to the invention perform the two intended pivoting movements. In the preferred embodiment, as explained below, the coupling pin can also fulfill the additional function of a temporary locking pin.

[0019] A balance according to the invention can be constructed using a bending joint arrangement with a common fixing channel as described in the invention. This is, in particular, an under-tray balance comprising a load transducer coupled to a weighing sensor via a weighing system, a load carrier arranged below the load transducer, and a monolithic bending joint assembly of the type mentioned above, by means of which the load carrier is articulated to the load transducer, wherein either the load transducer has a coupling pin that can be fixed in the fixing opening of the inlet piece of the monolithic bending joint assembly, and the load carrier has a fixing sleeve in which the coupling bolt of the outlet piece of the monolithic bending joint assembly can be fixed, or the load carrier has a coupling pin that can be fixed in the fixing opening of the inlet piece of the monolithic bending joint assembly, and the load transducer has a fixing sleeve in which the coupling bolt of the outlet piece of the monolithic bending joint assembly can be fixed. and wherein the coupling pin is axially displaceable in the common fixing channel in a form-fitting manner.

[0020] With this type of scale, it is possible, during operation, to insert the coupling pin into the common fixing channel only to the point where it does not cross the radial plane of the bending joints and therefore acts solely as a coupling to the load cell or weighing carrier. This functional position will be referred to here as the operating position. In a further functional position, referred to here as the transport position, however, it is inserted deeper into the common fixing channel, so that it crosses the aforementioned radial plane, acts as a fixing pin, and blocks the bending joints as described above.

[0021] To precisely define the two operating positions of the coupling pin, it is preferably provided that the coupling pin has two axially spaced annular grooves. These annular grooves can serve as engagement surfaces for the clamping screw(s) described above in the threaded channel oriented transversely to the fixing opening or the common fixing channel. In this way, a precise operating position and an equally precise transport position of the coupling pin are defined. While the aforementioned axial adjustability is thereby lost, the azimuthal adjustability also mentioned above is retained. However, the loss of axial adjustability is easily tolerated at this point, particularly if, as provided in the preferred embodiment, the coupling pin is equipped on the other side of the bending joint assembly with a lateral clamping flat extending over a considerable portion of its length.This clamping flat allows the fixing sleeve of the weighing carrier or load cell to be fixed in different axial positions by means of a clamping screw (while maintaining its azimuthal alignment). Overall, this embodiment therefore provides both axial and azimuthal adjustability of the weighing carrier relative to the load cell.

[0022] Further details and advantages of the invention will become apparent from the following specific description and the drawings. Brief description of the drawings

[0023] They show: Figure 1: a perspective view of a preferred embodiment of a bending joint arrangement according to the invention, Figure 2: a first side view of the bending joint arrangement of Figure 1 Figure 3: a second side view of the bending joint arrangement, offset by 90° Figure 1 Figure 4: the bending steering arrangement of Figure 1in side and sectional views with the coupling pin inserted in the operating position, as well as Figure 5: the bending steering arrangement of Figure 1 in side and section views with the coupling pin inserted in transport position. Description of preferred embodiments

[0024] The Figures 1 to 5 Figure 1 shows a particularly preferred embodiment of a bending joint arrangement 10 according to the invention. This arrangement has a main body 12 of a substantially cylindrical shape. A coupling bolt 14, which will be discussed in more detail below, is connected to the main body 12 in the figures below. However, the essential features of the present invention are realized in the main body 12, which will therefore be described first.

[0025] The main body 12 of the bending joint arrangement 10 according to the invention comprises a central piece 16. The basic shape of the central piece 16 can be described as a cylinder in which a groove is cut into each of its two end faces, the grooves extending radially through the central piece 16 and extending perpendicularly to each other. The depth of the grooves is selected such that they intersect each other in their intersection area.

[0026] A beam-like inlet piece 18 is arranged in the groove of the central piece 16 shown in the figures above. A beam-like outlet piece 20 is arranged in the groove of the central piece 16 shown in the figures below. The inlet piece 18 and the outlet piece 20 are each hinged to the central piece 16 via a bending joint 22, which is designed as a longitudinally extended thin section of material. For the sake of distinction, the bending joint 22 that connects the inlet piece 18 to the central piece 16 is referred to here as the first bending joint 22-1, and the bending joint 22 that connects the outlet piece 20 to the central piece 16 is referred to here as the second bending joint 22-2.

[0027] To form the aforementioned bending joints 22, the main body 12 is provided with two perpendicularly intersecting pairs of channels 24, each consisting of two individual through-channels with a D-shaped profile. The curved side walls of the individual through-channels of each channel pair 24 face each other and form the webs between their vertices that constitute the bending joints 22. For ease of identification, the channel pair assigned to the first bending joint 22-1 is referred to here as the first channel pair 24-1, and the channel pair assigned to the second bending joint 22-2 is referred to as the second channel pair 24-2.

[0028] Those skilled in the art will recognize that the above description, according to which grooves are "cut" into the main body and the inlet and outlet pieces are "arranged" therein, is merely illustrative and does not represent a description of the actual manufacturing process. In fact, the bending joint arrangement according to the invention is preferably machined from a block of material, preferably metal, particularly preferably aluminum, e.g. by milling, drilling and / or electrical discharge machining (EDM).

[0029] The described structure, which in particular results from the combination of the Figures 1 to 3 As can be seen, the basic function of the bending joint arrangement 10 according to the invention is realized. The inlet piece 18 and the outlet piece 20 are pivotable relative to the central piece 16, the precisely defined pivot axes being perpendicular to each other and lying in the same radial plane with respect to the cylindrical basic shape of the main body 12.

[0030] The bending joint arrangement 10 according to the invention is particularly suitable for coupling a weighing carrier (not shown in the figures) to the load cell (also not shown) of an under-tray precision balance. To facilitate coupling, the illustrated embodiment provides that the beam of the inlet piece 18 is provided at a central location with a fixing opening 26, which runs coaxially to the central axis of the main body 12. As shown in the Figures 4 and 5 As shown, a coupling pin 28 connected or connectable to the load sensor of the scale can be positively inserted into said fixing opening 26 and clamped in place by means of clamping screws 30 which are arranged in a lateral threaded channel 32 of the inlet piece 18.

[0031] In the illustrated embodiment, the coupling pin 14 serves to connect the weighing carrier. This pin is preferably integrally connected to the output piece 20 and also extends coaxially to the central axis of the main body. For coupling, a coupling sleeve of the weighing carrier (not shown) can be positively slid over the coupling pin 14 and fixed to the coupling pin 14 by means of a clamping screw guided in a lateral threaded channel of the clamping sleeve.

[0032] The Figures 4 and 5 show a particularly preferred embodiment of the bending joint arrangement 10 according to the invention in connection with a special design of the coupling pin 28. As shown in particular in the sectional views of the Figures 4aAs can be seen from / d and 5a / d, not only is the inlet piece 18 provided with a guide opening 26 that completely passes through it; rather, the outlet piece 20 and the coupling pin 14 also have a fixing opening 34, which completely passes through the outlet piece 20 and, in the illustrated embodiment, only partially passes through the coupling pin 14. In any case, this results in a common fixing channel 36 in which the coupling pin 28 can be inserted in a form-fitting manner and be axially displaceable.

[0033] In the illustrated embodiment, the coupling pin 28 is provided with a first annular groove 38-1 located near its free end and with a second annular groove 38-2 located further away from the free end. In a Figure 4In the first functional position shown, designated as the operating position, the first annular groove 38-1 is used such that the coupling pin 28 is only inserted into the common fixing channel 36 to such an extent that clamping screws 30 in the lateral threaded channel 32 of the inlet piece 18 engage in the first annular groove 38-1 and can thus fix the coupling pin (exclusively) to the inlet piece 18. In this operating position, both bending joints 22 are active, i.e., the inlet piece 18 can pivot about a first pivot axis relative to the central piece 16 thanks to the first bending joint 22-1, and the outlet piece 20 can pivot about a second pivot axis perpendicular to the central piece 18 thanks to the second bending joint 22-2. The coupling of the inlet piece 18 to a load cell (not shown) of an under-tray precision balance can be effected via the coupling pin 28.

[0034] Due to the radial symmetry of the first annular groove 38-1, an azimuthal adjustment of the bending joint assembly 10 relative to the coupling pin 28, and thus to the load cell, can be performed without changing the height setting. Height adjustment is also readily possible in the illustrated embodiment. As explained above, the weighing carrier of the under-tray precision balance is preferably coupled by means of a fixing sleeve that positively engages the coupling pin 14. In the illustrated embodiment, however, the coupling pin 14 has a lateral clamping flat 40. This extends over a considerable length of the coupling pin 14. A fixing sleeve of the weighing carrier, which positively engages the cylindrical base of the coupling pin 14, can be moved vertically relative to the coupling pin 14 and fixed at the desired height by means of a clamping screw that extends laterally through it on the coupling pin 14.The lateral clamping flat 40 serves as a support for the clamping screw and at the same time ensures a reproducible azimuthal relative alignment of the fixing sleeve to the coupling bolt 14.

[0035] At the in Figure 5In the second functional position shown, designated as the transport position, the coupling pin 28 is inserted further into the common fixing channel 36, specifically to such an extent that its second annular groove 38-2 lies at the level of the lateral threaded channel 32 of the inlet piece 18 and its free end projects at least into the fixing opening 34 of the outlet piece 20, preferably, as shown, into the coupling bolt 14. In this position, the coupling bolt can be fixed by means of the clamping screws 30 and acts as a fixing pin, i.e., it blocks both bending joints 22 by its positive engagement in all sections of the common fixing channel 36. The inlet piece 18 and the outlet piece 20 are thus fixed relative to the central piece 16 in this transport position. Even considerable external forces cannot therefore lead to a deflection that would overload and potentially damage the bending joints 22.

[0036] Of course, the embodiments discussed in the detailed description and shown in the figures represent only illustrative examples of the present invention. A wide range of variations is available to those skilled in the art in light of this disclosure. In its preferred embodiment, the entire bending joint assembly 10 is milled, drilled, and / or electro-anodized from a single block of metal. However, alternative manufacturing methods, for example, additive manufacturing techniques (e.g., 3D printing), are also conceivable. Reference symbol list

[0037] 10 Bending joint assembly 12 Main body 14 Coupling bolt 16 Central piece 18 Inlet piece 20 Outlet piece 22-1 First bending joint 22-2 Second bending joint 24-1 First channel pair 24-2 Second channel pair 26 Fixing opening in 18 28 Coupling pin 30 Clamping screw 32 Threaded channel 34 Fixing opening in 14 / 20 36 Common fixing channel 38-1 First annular groove 38-2 Second annular groove 40 Lateral clamping flat on 14

Claims

1. Monolithic flexure joint arrangement (10), comprising a main body (12) through which two channel pairs (24) pass, namely a first channel pair (24-1) and a second channel pair (24-2), which channel pairs extend in a radial plane in a manner oriented perpendicularly to each other and, in the center of the main body (12), intersect each other and also a central axis oriented normal to the radial plane, wherein each channel pair (24) comprises two individual through-channels oriented parallel to each other, which are arranged with mutually facing, convexly curved channel wall portions closely adjacent to each other such that webs extending between said curved channel wall portions together form a flexure joint (22), wherein a central piece (16) of the main body (12) is pivotably articulated to an input piece (18), which is otherwise unconnected thereto, by means of a first flexure joint (22-1) formed between the through-channels of the first channel pair (24-1) and is pivotably articulated to an output piece (20), which is otherwise unconnected thereto, by means of a second flexure joint (22-2) formed between the through-channels of the second channel pair (24-2), characterized in that the input piece (18) and / or the output piece (20) is configured as a beam passing radially through the central piece (16).

2. Monolithic flexure joint arrangement (10) according to claim 1, characterized in that both the input piece (18) and the output piece (20) are each configured as a beam passing radially through the central piece (16), the beams being askew and oriented perpendicularly to each other and also perpendicularly to the central axis.

3. Monolithic flexure joint arrangement (10) according to any one of the preceding claims, characterized in that the input piece (18) has, on the side thereof facing away from the associated first flexure joint (22-1), a fixation opening (26), coaxial to the central axis, for receiving a coupling pin (28).

4. Monolithic flexure joint arrangement (10) according to claim 3, characterized in that the input piece (18) has a threaded channel (32), extending transversely to the fixation opening (26), for receiving a clamping screw (30) that clamps the coupling pin (28) in the fixation opening (26).

5. Monolithic flexure joint arrangement (10) according to any one of the preceding claims, characterized in that the output piece (20) has, on the side thereof facing away from the associated second flexure joint (22-2), a coupling bolt (14) extending coaxially to the central axis.

6. Monolithic flexure joint arrangement (10) according to claim 5, characterized in that the coupling bolt (14) has a cylindrical basic shape with a lateral flattened clamping area (40).

7. Monolithic flexure joint arrangement (10) according to any one of claims 3 to 4 and any one of claims 5 to 6, characterized in that, in order to form a common fixation channel (36), the fixation opening (26) of the input piece (18) merges into a fixation opening (34) of the output piece (20) that passes through the output piece (20) entirely and through the coupling bolt (14) at least over the length of a sub-region.

8. Bottom-loading balance, comprising - a load receptor coupled to a weighing sensor via a weighing system, - a weighed-goods carrier arranged below the load receptor and - a monolithic flexure joint arrangement (10) according to claim 7, by means of which the weighed-goods carrier is articulated to the load receptor, wherein - either the load receptor has a coupling pin (28) which can be fixed in the fixation opening (26) of the input piece (18) of the monolithic flexure joint arrangement (10), and the weighed-goods carrier has a fixation sleeve in which the coupling bolt (14) of the output piece (20) of the monolithic flexure joint arrangement (10) can be fixed, - or the weighed-goods carrier has a coupling pin (28) which can be fixed in the fixation opening (26) of the input piece (18) of the monolithic flexure joint arrangement (10), and the load receptor has a fixation sleeve in which the coupling bolt (14) of the output piece (20) of the monolithic flexure joint arrangement (10) can be fixed, and wherein the coupling pin (28) is form-fittingly mounted in the common fixation channel (36) in an axially displaceable manner.

9. Balance according to claim 8, characterized in that the coupling pin (28) has two axially spaced-apart annular grooves (38-1, 38-2).