JP2018049012A - Lateral force insensitive measurement cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measurement cell more insensitive to lateral force than a well-known measurement cell is.SOLUTION: A measurement cell 1 according to the present invention includes: a force introduction region 2; a mounting part 9 formed as a mounting part for a supporting body; and a ring-shaped diaphragm 6 between the force introduction region 2 and the mounting part 9, which is deformable when receives an introduced force. The force introduction region 2 has a force introduction surface 3, and the force introduction surface 3 is arranged between a protrusion part 61, which is the highest part of the diaphragm 6 in a direction AX in which an axial-directional force is introduced, and an extension part 17, which is the lowest part of the diaphragm 6.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a lateral force-insensitive measurement cell (Querkraft-unempfindrich Messzel).

  Under the concept of “measurement cell”, a load cell, a force sensor, and a force measurement cell are equally included. The measuring cell is used in particular for constructing a load detection device. The measurement element of a known measurement cell greatly reduces the accuracy when another force perpendicular to the measurement axis (hereinafter referred to as lateral force) acts in addition to the force in the measurement axis direction to be measured. Certainly, there is a known type of bar that has a high lateral force (a lateral force greater than the rated load) without damage, for example, in the form of a bar having a rectangular cross section, but its measurement accuracy has already deteriorated when the lateral force is small. Resulting in.

  In Patent Document 1, a plate spring for a measuring cell suitable for compensating lateral force to some extent is known. However, there is room for further improvement in this measurement cell.

EP 1181514

  An object of the present invention is to provide a measurement cell that is more insensitive to lateral forces than known measurement cells.

  In one aspect, a measurement cell is provided that includes a force introduction region, a (for example, cylindrical) placement portion configured as a placement portion on a support, and a diaphragm. The measurement cell or diaphragm is also referred to in part as a rotationally symmetric disc spring. The diaphragm is disposed between the force introduction region and the placement portion. The diaphragm is located in a plane that is perpendicular to the axial force introduction direction or perpendicular to the measurement axis. The diaphragm is deformable when a force is introduced, and is preferably annular and rotationally symmetric about the measurement axis. The axial direction of force introduction corresponds in this connection to the measuring axis of the measuring cell. The force introduction region advantageously has a force introduction surface located between the highest raised portion of the diaphragm in the axial force introduction direction and the lowest extension of the diaphragm. In other words, the force introduction surface, or the force introduction point, is located within a range that is not so far above or below the diaphragm. This guarantees a better compensation for lateral forces that are not already in the axial direction of force introduction, ie not exactly on the measuring axis of the measuring cell.

  The force introduction surface may in principle be curved but is preferably flat. Depending on the substantive structure of force introduction, there is a case where the force introduction point is better than the force introduction surface.

  A measurement cell generally comprises one or more strain gauges. In general, when referring to the position of the strain gauge, it can refer to the plane on which the one or plural (all) strain gauges are arranged. This plane is also perpendicular to the axial force introduction direction or perpendicular to the measurement axis. Depending on the configuration, a strain gauge or a plurality of strain gauges can be arranged on the diaphragm in this plane. Typically, a plurality of strain gauges are distributed evenly around the measurement axis in this plane. Thereby, the deformation of the diaphragm generates a strain of the strain gauge, and from this strain, the magnitude of the introduced force is required to be generally known.

  The force introduction surface (possibly the point of force introduction) is in the axial force introduction direction and is located at approximately the same level as the plane of at least one, preferably all strain gauges, arranged on the diaphragm. Also good.

  However, the force introduction surface (in some cases the lowest point of the force introduction surface) is the axial force introduction direction, preferably of at least one, advantageously all strain gauges arranged in the diaphragm. Although it may be located above the plane, it may be located below the highest raised portion of the diaphragm. In the diaphragm region, the material is typically partially thinned, so the diaphragm may be thicker in one or more regions than in other regions. This region with the greatest or highest thickness is the region of the highest ridge. The force introduction surface or force introduction point is located within the maximum thickness / thickness range of the diaphragm and at least slightly above the plane of the one or more strain gauges described above.

  In one form, the diaphragm may have at least one first groove and / or second groove. With this one or these two grooves, the material is thinned and thus deformable. When the first and second grooves are provided, the diaphragm can be easily manufactured. The groove, like the diaphragm, is preferably rotationally symmetric, concentric and located in a plane perpendicular to the axial force introduction direction. When there are two grooves, the largest bulge of the diaphragm or the region with the largest thickness may be located between the two grooves.

  The first groove and the second groove may have the same (inner) radius. This also facilitates manufacture.

  The first groove and the second groove may be disposed on the opposite side of the diaphragm from at least one (all) strain gauge. This leaves the plane / surface of the strain gauge flat or flat, which also facilitates manufacture.

  The measuring cell may advantageously have a (third) groove arranged in the force introduction region. This (third) groove may be located between the diaphragm and the force introduction surface. This (third) groove further improves lateral force compensation and additionally decouples the force introduction region from the diaphragm. This (third) groove may be located on the side of the diaphragm where at least one strain gauge is also arranged. The third groove may have the same (inner) radius as the (inner) radius of the first and second grooves. This also facilitates manufacture.

  The force introduction region may be formed as a recess, particularly as a blind hole. The recess or blind hole is advantageously surrounded by a first stabilization ring.

  The measurement cell may comprise an annular second stabilization ring surrounding the diaphragm. The second stabilization ring creates further separation.

  The first stabilization ring and the second stabilization ring are clearly thicker / thicker than the diaphragm in the axial force introduction direction.

  The measurement cell may comprise a compensation web arranged between the second stabilization ring and the mounting part. The compensation web creates an additional disconnect.

  In one aspect, the compensation web may extend between the second stabilization ring and the mounting portion in a substantially vertical and axial force introduction direction (measurement axis direction). Thereby, the spatial extent (maximum diameter) of the measurement cell is kept small.

  The compensation web may be configured as an annular bending spring (leaf spring). The compensation web may advantageously have at least one curve. In particular, the curved portion may have one or more regions having a constant radius of curvature. This also facilitates manufacture.

  The measuring cell may comprise connection means or attachment means for connecting the load pin to the force introduction region, in particular connection means or attachment means in the form of separate grooves and corresponding snap rings. This groove and possibly the snap ring can advantageously be arranged in a recess or blind hole in the force introduction region. The load pin can have an enlarged head and a shaft portion that is thinner than the head. The groove and the snap ring can in this case be configured such that the head of the load pin can no longer be pulled out of the blind hole when the snap ring is inserted. This prevents the load pin from detaching from the measuring cell, which allows the lifting force to be received.

  The measuring cell is particularly preferably produced from steel of the type 1.4418 according to DIN EN 10088-3 or the X4CrNiMo16-5-1 type according to DIN EN 10272. This steel is excellent in terms of good mechanical hysteresis properties. The measuring cell is particularly preferably manufactured from the above-mentioned materials in one piece or mostly in one piece.

  Hereinafter, features and aspects of the present invention will be described in detail based on embodiments with reference to the accompanying drawings.

It is a schematic perspective view of one embodiment of a measurement cell. It is a side view of the measurement cell shown in FIG. FIG. 3 is a plan view of the measurement cell shown in FIGS. 1 and 2. It is sectional drawing which cut | disconnected the measurement cell shown to FIG. 1 thru | or 3 along the cutting line AA shown in FIG.

Detailed Description of Embodiments FIG. 1 is a schematic perspective view of an embodiment of a measurement cell 1 (also referred to as a load cell). The measurement cell 1 mainly includes a force introduction region 2. In this embodiment, the force introduction region 2 exists in the center of the measurement cell 1 as a blind hole 5 and is surrounded by a first stabilization ring 15. A force introduction surface 3 exists at the end of the blind hole 5. In use, for example, a convexly shaped bolt head or load pin (not shown) is applied to the force introduction surface 3 to introduce a corresponding force into the measurement cell 1. The measurement cell 1 further includes an annular diaphragm 6, which is also called a circular disc spring or a rotationally symmetric disc spring. In the area of the diaphragm 6, the material thickness is partially reduced, which will be explained in more detail later. A second stabilization ring 7 (also referred to as a compensation ring) exists so as to surround the diaphragm 6 or the circular disc spring. The second stabilizing ring 7 is also coupled to the mounting part 9 via a compensation web 8. The compensation web 8 is also formed as a spring or a leaf spring.

  FIG. 2 is a side view of the measurement cell 1 shown in FIG. Even from this side view, the second stabilizing ring 7, the compensation web 8 (or compensation spring), the mounting portion 9, the mounting surface 10 of the mounting portion 9 and the outer radius 11 of the mounting surface 10 can be seen. .

Further, FIG. 2 shows a force F that can have an axial component F _AX and a lateral force component F _Q. The axial component is in the axial force introduction direction AX or on the measurement axis of the measurement cell 1. The lateral force component means a lateral force or a radial force, which should be optimally compensated by the present invention.

  FIG. 3 is a plan view of the measurement cell 1 shown in FIGS. 1 and 2. In this figure, the force introduction surface 3 inside the blind hole 5 in the force introduction region 2 can now be seen again from above. Furthermore, an annular, in particular rotationally symmetric diaphragm 6, as well as a first stabilization ring 15, a second stabilization ring 7 and a mounting part 9 are also shown. Further details will be described with reference to the AA cross-sectional view shown in FIG.

FIG. 4 is a cross-sectional view of the measurement cell 1 shown in FIGS. 1 to 3 cut along the cutting line AA shown in FIG. In the present embodiment, the measurement cell 1 includes a force introduction region 2, a placement portion 9 configured as a placement portion on a support (for example, a cylindrical shape), and a diaphragm 6. The diaphragm 6 is disposed between the force introduction region 2 and the placement portion 9. The diaphragm 6 is located in one plane that is perpendicular to the axial force introduction direction AX or perpendicular to the measurement axis. The diaphragm 6 can be deformed when a force is introduced. The diaphragm is annular and is rotationally symmetric with respect to the measurement axis AX. The force introduction region 2 has a force introduction surface 3. The force introduction surface is located between the highest raised portion 61 of the diaphragm 6 and the lowest extension portion 17 of the diaphragm 6 in the axial force introduction direction AX. The force introduction surface 3 is positioned at substantially the same level as the diaphragm 6 in the axial force introduction direction AX. In other words, the force introduction surface 3 or, in some cases, the force introduction point is located within a range that is not so far above or below the diaphragm 6. Thus, not facing in the axial direction of the force introduction direction AX, that is, exactly better compensation of the lateral force F _Q is not on the measuring axis of the measuring cell 1 is ensured.

  The force introduction surface 3 may be formed to be curved or flat. When the force introduction surface is curved, the force introduction surface 3 may be convex (ie, the central portion is higher than the edge portion) or concave (ie, the central portion is lower). (Yes) When the force introduction surface 3 is convex, the corresponding load pin only needs to have a flat pressing member. When the force introduction surface 3 is concave, a load pin having a corresponding spherical pressure member can be used, and the spherical pressure member has a radius or a stronger curvature than the concave force introduction surface 3. Therefore, depending on the actual configuration of force introduction, the force introduction point may be better than the force introduction surface.

The measuring cell mainly comprises one or more strain gauges 12,13. In general, the positions of the strain gauges 12 and 13 can refer to a plane on which the one or plural (all) strain gauges are arranged. This plane is also perpendicular to the axial force introduction direction or perpendicular to the measurement axis. Depending on the configuration, one strain gauge 12, 13 or a plurality of strain gauges can be arranged on the diaphragm 6 in this plane. Typically, the strain gauges 12, 13 are evenly distributed around the measurement axis AX in a plane perpendicular to the measurement axis AX. Thereby, the deformation of the diaphragm 6 generates a strain of the strain gauges 12 and 13, and from this strain, the magnitude (value) of the introduced force F _AX is determined so as to be generally known. Correspondingly, a connection passage 14 is provided, and an electric line can be laid in the measuring cell 1 through the connection passage 14, so that it can be connected to the strain gauges 12, 13.

  For measurement at a suitable location, the expansion and contraction of the area of the diaphragm 6 must be sufficiently large so that it can be measured by the strain gauges 12,13. In addition, the strain gauges 12, 13 must provide a sufficiently large measurement signal. This is first achieved by the configuration of both grooves N1 and N2. The grooves N1 and N2 will be described in more detail below. Furthermore, the corresponding deformation of the diaphragm 6 must be measured in a sufficiently large number of locations along the circumferential direction since lateral forces can cause the deformation to vary locally. For this purpose, for example, six strain gauges can be used. However, it is also possible to use a single annular strain gauge. Depending on the configuration, one annular strain gauge may be selected along the diaphragm 6, or a plurality of individual strain gauges 12, 13 may be provided. In one advantageous form, six strain gauges are provided.

  In the present embodiment, the force introduction surface 3 (possibly the lowest point of the force introduction surface) is the axial force introduction direction AX, advantageously above the strain gauges 12, 13 arranged on the diaphragm. It is located below the highest ridge 61 of the diaphragm 6. In the area of the diaphragm, the material is typically partially thinned, so that the diaphragm 6 may be thicker in one or more areas than in other areas. This region having the highest thickness or the largest thickness is the region of the highest ridge 61. The force introduction surface 3 or force introduction point is located within the maximum thickness / thickness range of the diaphragm 6 in the axial direction AX and at least slightly above the plane of the one or more strain gauges 12, 13 described above. Located in.

  In another embodiment (not shown), the force introduction surface 3 (possibly the point of force introduction) is an axial force introduction direction AX, preferably at least one arranged on the diaphragm, advantageously It may be located at substantially the same level as the plane of all strain gauges 12 and 13.

  In the present embodiment, the diaphragm 6 has a first groove N1 and a second groove N2. These two grooves N1 and N2 reduce the thickness of the material, thereby achieving the deformability. Like the diaphragm 6, the grooves N1 and N2 are preferably concentric with respect to rotational symmetry, and are located in one plane perpendicular to the axial force introduction direction AX. When there are two grooves N1 and N2 as in this embodiment, the maximum raised portion 61 or the region of the maximum thickness X1 of the diaphragm 6 is located between the grooves N1 and N2. In other words, the material thickness of the diaphragm 6 partially thinned by the grooves N1 and N2 can also be generally X1.

  Further, in the present embodiment, the first groove N1 and the second groove N2 have the same (inner) radius R1, R2 (R1 = R2). In addition, the grooves N1 and N2 have a semi-torus shape or a semicircular shape when viewed in a cross-sectional view. The semi-torus-shaped grooves N1, N2 facilitate manufacturing, but are not essential. In particular, R1 and R2 may be formed differently. Further, the grooves N1, N2 may have a shape different from the semi-torus shape.

  The first groove N1 and the second groove N2 are disposed on the opposite side of the diaphragm 6 from the strain gauges 12 and 13.

  The measuring cell 1 advantageously has a (third) groove N3 which is arranged in the force introduction region. This (third) groove N <b> 3 is located between the diaphragm 6 and the force introduction surface 3. The (third) groove N3 further improves the lateral force compensation and additionally separates the force introduction region 2 from the diaphragm 6. The (third) groove N3 is located on the side of the diaphragm where the strain gauges 12 and 13 are disposed, or is recessed in the material from the strain gauges 12 and 13 side. The third groove N3 has (inner) radius R3, and (inner) radius R3 is the same as (inner) radius R1, R2 of the first and second grooves N1, N2 in the illustrated embodiment. It is. Manufacture becomes easy because R1, R2, and R3 are the same. The three grooves N1, N2, and N3 may have different cross sections or geometric shapes. However, the (third) groove N3 is deeper than the first and second grooves N1, N2. Particularly when the rated load is small, N3 can be omitted.

  The force introduction region 2 has a blind hole 5. The blind hole 5 is surrounded by a first stabilization ring 15.

  The measuring cell 1 comprises an annular second stabilization ring 7 surrounding the diaphragm 6. The second stabilization ring 7 creates a further disconnect.

  The first stabilization ring 15 and the second stabilization ring 7 are clearly thicker / thicker than the diaphragm 6 in the axial force introduction direction AX. The first stabilization ring has a thickness X2 between the blind hole 5 and the (third) groove N3. The thickness below the blind hole 5, that is, between the force introduction surface 3 and the placement portion 9, is at least X3. The thickness of the second stabilization ring 7 is X4. X2, X3, X4 >> X1 is established. That is, the thickness X2, X3, X4 of the stabilization ring is generally clearly larger than the thickness X1 of the diaphragm 6 (all in the axial direction AX). At this time, X2 may be larger than X4, the same as X4, or smaller than X4. This is mainly from a manufacturing point of view. On the other hand, the dimension X3 is mainly based on the rated load.

  The measuring cell 1 comprises a compensation web 8 arranged between the second stabilization ring 7 and the mounting part 9. Furthermore, the thickness X5 of the compensation web 8 is preferably smaller than the thickness X1 of the diaphragm 6. The compensation web 8 reduces the influence of the annular placement surface 10 of the placement portion 9 on the diaphragm 6 where the original measurement is performed. The compensation web 8 extends between the second stabilization ring 7 and the mounting part 9 substantially vertically, ie in the axial force introduction direction AX (or in the measurement axis direction). Thereby, the spatial extent (maximum diameter) of the measurement cell 1 is kept small. The compensation web 8 may simply be referred to as a substantially vertical curved spring. In particular, the compensation web 8 extends under the stabilization ring 7 (or under the outer stabilization ring) so as to go around the outside of the measuring cell 1. This also prevents tilting of the mounting portion 9 when a load is applied.

  The compensation web 8 is configured as an annular bending spring (plate spring). The compensation web has substantially one curved part KR when viewed in cross section. Furthermore, the compensation web 8 has a material thickness that is clearly reduced compared to the stabilization ring 7 and the mounting part 9. All of this is achieved by R R6, R4 and R5. The cross section of the compensation web 8 starts from the mounting part 9 and first extends radially outward, then extends radially inward by a short section KR and leads to the stabilization ring 7. Yes. The connection region of the compensation web 8 in the mounting portion 9 and the second stabilization ring 7 substantially overlaps each other in the axial direction AX.

  In addition, the measuring cell 1 comprises a connection means or attachment means 4 in the form of a (fifth) groove N5 and a corresponding snap ring (not shown) for connecting a load pin (not shown) to the force introduction region 2. . This (fifth) groove N5 and possibly a snap ring are arranged in the blind hole 5 of the force introduction region 2. The load pin can have an enlarged head and a shaft portion that is thinner than the head. Configuring the (fifth) groove N5 and the snap ring so that the head of the load pin can no longer be pulled out of the blind hole 5 when the snap ring is inserted in the (fifth) groove N5 Can do. Thus, in order to pull out the load pin from the blind hole 5, the snap ring and / or the first stabilization ring 15 must be broken, and thus a very large force is required. This force is much larger than the rated load of the measuring cell 1 and can therefore be used as a lifting prevention means. With this configuration, the possibility that the upper surface is inclined relative to the lower surface is still maintained. Tilt can in fact always occur based on the bending of the frame, the container and the structure, but this does not cause any additional force on the measuring cell 1.

A load pin or bolt, not shown in the drawing, introduces the force into the blind hole 5 or the force introduction surface 3 very locally, possibly in the form of a sphere. At this time, if the rated load is not so small, the inner region surrounding the blind hole 5 is also deformed. This deformation, when additionally the lateral force F _Q is present, becomes asymmetric. The second stabilizing ring 15 surrounding the blind hole 5 cannot completely prevent this. Here, the annular (third) groove N3 advantageously decouples this inner load introduction in the load introduction part 2 from the diaphragm 6. The (third) groove N3 advantageously has an end located higher than the force introduction surface 3 of the blind hole 5 for the load pin. When the rated load is small, N3 can be omitted.

  In the blind hole 5, a (fourth) groove N4 that increases the degree of freedom of movement of the load pin may be provided.

  In the present embodiment, the surface of the force introduction portion 15 is lowered by the distance D1 in the axial direction AX with respect to the surface of the stabilization ring 7. The opening or hole has a thread 16 that is used to connect the measuring cell 1 to another component.

The measuring cell is advantageously made from corrosion-resistant steel or stainless steel. The preferred composition of the steel of the measuring cell is
At least: C:-; Si:-; Mn:-; P:-; S:-; Cr: 15.0%; Mo: 0.8%; Ni: 4.0%; N: 0.02%; Fe: remainder Max: C: 0.06%; Si: 0.7%; Mn: 1.5%; P: 0.04%; S: 0.03%; Cr: 17.0%; Mo: 1 .5%; Ni: 6.0%; N: −
It is.

  Particular preference is given to using steels of the type 1.4418 according to DIN EN 10088-3 or the X4CrNiMo16-5-1 type according to DIN EN 10272. The measuring cell is particularly advantageously made of the above-mentioned material in one piece or mostly in one piece.

  The steels mentioned above, in particular the 1.4418 type steel, combine very good mechanical properties (eg wear resistance) as well as good weldability and enhanced corrosion resistance compared to martensitic materials.

1 measurement cell, 2 force introduction area, 3 force introduction surface, 4 connecting means (groove), 5 blind hole, 15 first stabilization ring, 6 diaphragm, 61 highest ridge of diaphragm, 7 second stabilization Ring (compensation ring), 8 Compensation web, 9 Placement portion (placement ring), 10 Placement surface of placement portion, 11 Outer radius of placement surface, 12, 13 Strain gauge, 14 Connection path, 16 Thread , N1 first groove, R1 first radius, N2 second groove, R2 second radius, N3 third groove, R3 third radius, N4 fourth groove, N5 fifth groove (lifting) Prevention groove), R4 4th radius (compensation web 8), R5 5th radius (compensation web 8), R6 6th radius (compensation web 8), X1 maximum thickness of diaphragm, X2 first stabilization Maximum thickness of the ring, X3 Material thickness below the guide surface, X4 second stabilizing ring thickness, D1 offset, F _AX axial force between the first stabilization ring surface and a second stabilization ring surface ( Force in the measurement axis direction), _FQ lateral force (lateral or radial force), AX axis direction (measurement axis; axial force introduction direction), F force, KR curved portion, 17 lowest extension

Claims (15)

Force introduction area (2),
A placement portion (9) configured as a placement portion on a support;
An annular diaphragm (6) disposed between the force introduction region (2) and the mounting portion (9) and deformable when a force is introduced;
With
The force introduction region (2) has a force introduction surface (3),
In the measurement cell (1),
The force introduction surface (3) is formed by the highest raised portion (61) of the diaphragm (6) and the lowest extension portion (17) of the diaphragm (6) in the axial force introduction direction (AX). Arranged between,
A measuring cell (1) characterized in that.   The measuring cell (1) according to claim 1, wherein the force introduction surface (3) is flat.   The force introduction surface (3) is above the plane of at least one strain gauge (12, 13) disposed on the diaphragm in the axial force introduction direction (AX) and of the diaphragm (6). The measuring cell (1) according to claim 1 or 2, located below the highest ridge (61).   The measurement cell (1) according to any one of claims 1 to 3, wherein the diaphragm (6) has at least one first groove (N1) and a second groove (N2).   The measurement cell (1) according to claim 4, wherein the first groove (N1) and the second groove (N2) have the same inner radius (R1, R2).   The measurement cell (1) according to claim 4 or 5, wherein the first groove (N1) and the second groove (N2) are arranged on the opposite side of the at least one strain gauge.   The measurement cell (1) according to any one of claims 1 to 6, wherein the measurement cell (1) has a third groove (N3) arranged between the diaphragm and the force introduction surface. 1).   The measurement cell (1) according to claim 7, wherein the third groove (N3) is located on the side of the diaphragm (6) where the at least one strain gauge (12, 13) is arranged.   The measurement cell (1) according to claim 7 or 8, wherein the third groove (N3) has the same radius (R3) as the inner radius (R1, R2) of the first and second grooves.   10. The force introduction region (2) has a recess, in particular a blind hole (5), the recess being surrounded by a first stabilization ring (15). Measurement cell (1) according to item. An annular second stabilization ring (7) surrounding the diaphragm (6);
A compensation web (8) disposed between said second stabilization ring (7) and said mounting part (9);
Measuring cell (1) according to any one of the preceding claims, comprising:   The compensation web (8) extends substantially perpendicularly between the second stabilizing ring (7) and the mounting part (9) in the axial force introduction direction (AX). 11. Measurement cell (1) according to 11.   13. The measuring cell (1) according to claim 12, wherein the compensation web (8) is configured as an annular bending spring having at least one curved portion (KR).   14. Connection means (4) for connecting a load pin to the force introduction region (2), in particular further comprising a connection means (4) in the form of a fifth groove (N5) and a corresponding snap ring. The measurement cell (1) as described in any one of Claims.   15. The measuring cell (1) according to any one of the preceding claims, wherein the measuring cell (1) is manufactured in particular integrally from steel 1.4488.

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