Force transmission elements for scales or weighing cells

Abstract

The present invention relates to a force transmission member for a scale or a weighing unit, wherein the force transmission member is designed to be arranged between a load accommodating unit for receiving a load to be weighed and a load conducting position of the weighing unit to transmit the load force applied by the load, and is characterized in that the force transmission member is at least partially constructed as a rod system composed of hollow rods, especially round rods, wherein the force transmission member and especially the hollow rods are at least partially manufactured using 3D printing technology.

Description

Technical Field

[0001] The present invention relates to a force transmission member for a scale or a weighing unit, which is arranged between a load accommodating unit for accommodating a load to be weighed and a load conduction position of the weighing unit so as to transmit the load force applied by the load. The force transmission member is characterized in that the force transmission member is at least partially a rod system composed of hollow rods and is at least partially manufactured according to 3D printing technology. Background Art

[0002] In the automated industrial manufacturing of products such as food, pharmaceuticals etc., scales play an important role as they for example control the quality check of the nominal fill quantity into the finished packaging, re-regulate the filling mechanism or check the integrity of the packaging and container, e.g. the presence of an instruction sheet in a tablet box.

[0003] The precision weighing technology used for this purpose should determine the most precise weighing results possible in the shortest possible measuring times, due to the desired high throughput.

[0004] The mass mounted on the load transmission element of the scale or its load measuring sensor, the weighing cell, decelerates the rapid mechanical oscillations of the scale mechanism to a (most constant) final value due to its inertia. This applies to mechanical bending rods with strain gauges as well as weighing cells that operate according to the principle of electromagnetic force compensation and use, for example, a monolithic lever mechanism and a magnetic system with current-carrying coils.

[0005] Loads (e.g. load bars / load transfer pins, load plates, load transport systems such as conveyor belts / belt conveyors, which consist of chassis, conveyor belts, timing belts, rollers / axles, motors, etc.) mounted on or acting on load transmission / force transmission parts of scales or weighing units (especially according to the electromotive force compensation principle EMK, abbreviated as EMFR in English: electromagnetic force restoration) should simultaneously meet the following requirements (a)-(d):

[0006] (a) Small inherent mass (because high initial load will prolong the start-up time);

[0007] (b) High rigidity (because of the high mechanical natural frequency and rapid vibration);

[0008] (c) Weak heat conduction (because it reduces the thermal influence on the internal measurement system, especially the integral block, introduced from the outside via the load conductor);

[0009] (d) Electrical conductivity (to conduct away or ground any static electricity, for example from the product, in order to avoid or reduce the formation of static fields that could affect the measurement).

[0010] The load transmission parts / force transmission parts known to date are generally bulky and heavy, since the desired rigidity is usually achieved by using solid components. The desired low thermal conductivity is achieved, for example, by means of plastic insulating intermediates. This requires various screw connections, which are accompanied by small parts that may be lost and high installation costs.

[0011] In the case of force transmission elements for scales or weighing units of the prior art, a combination of metal and plastic is usually used as the material. However, the E modulus of the plastic is less than 10,000 N / mm 2 , so the rigidity of the force transmission part is impaired, resulting in a low mechanical natural frequency and slow vibration. Therefore, fast and at the same time accurate measurement becomes difficult.

[0012] To increase rigidity, steel can be used instead of plastic, for example. However, steel is disadvantageous because of its heavy weight and high thermal conductivity. Alternatively, stainless steel can be used, which has a thermal conductivity of only about one fifth of that of steel. However, stainless steel is brittle and relatively difficult to cut. Summary of the invention

[0013] It is therefore an object of the present invention to provide a force transmission element which meets all of the above-mentioned requirements (a) to (d) and which can be produced simply and inexpensively.

[0014] The invention provides for this purpose a force transmission element according to claim 1. Preferred embodiments are described in dependent claims 2 to 13.

[0015] The invention is based on the finding that very lightweight force transmission elements can be produced according to the principle of additive manufacturing, also known as 3D printing technology. In this process, a plurality of thin material layers are stacked one on top of the other in one direction and connected to one another in order to gradually form a three-dimensional object, i.e. the force transmission element with its components is constructed layer by layer by adding material.

[0016] Using 3D printing technology for special applications of force transmission parts brings many significant advantages:

[0017] - Known force transmission elements generally consist of a combination of plastic and metal parts and are therefore generally heavier than "necessarily". In addition, thicker material parts heat up or cool down more slowly than thinner material parts when the ambient temperature changes, so that time is unnecessarily lost before stable operating conditions are reached. The force transmission element produced according to the invention only has the material required for its function, thus reducing the overall weight to a minimum. The sensitivity to temperature changes is also reduced by designing the individual components of the force transmission element according to the invention as a rod system consisting of hollow rods with the smallest possible material cross-section.

[0018] - It has been necessary to produce the force transmission element from a plurality of different individual parts until now. According to the invention, this complex production is significantly simplified.

[0019] Due to the high manufacturing accuracy, the force transmission element according to the invention can be produced in a very space-saving manner by means of 3D printing technology, so that a larger gap is created and other components of the scale can be installed there.

[0020] The force transmission member for a scale or weighing unit according to the present invention is designed to be arranged between a load receiving unit for receiving a load to be weighed and a load conducting position of the weighing unit so as to transmit the load force applied by the load. The force transmission member of the present invention is characterized in that it is at least partially formed as a rod system consisting of hollow rods, especially hollow round rods, wherein the force transmission member, especially the hollow rod, is at least partially manufactured by 3D printing technology.

[0021] The use of a rod system consisting of hollow rods results in a light but still stable force transmission element. In addition, the material cross-section and thus the thermal conductivity are still low at this time. In addition, hollow rods, in particular hollow round rods, provide a smaller surface / air resistance / action surface that causes disruptive airflow / ventilation, and are therefore suitable for use in the production of pharmaceutical products that are subject to laminar flow. The hot air generated by the electronics and the current-carrying coils in the weighing cell can also influence the measured values ​​less. Therefore, the use of a rod system consisting of hollow rods both inside and outside the weighing cell / scale housing has advantages. In addition, there is also little dirt deposited on the round rods, and they can be cleaned very well. The use of a rod system consisting of hollow rods allows a space-saving and ingenious design of the force transmission element of the present invention. There is free internal space left here, which can be used to arrange other components or assemblies.

[0022] The weighing cell can be, for example, a force sensor with a purely mechanical bending beam structure, for example using a strain gauge (DMS) as a force sensor, or a force sensor operating according to the electromagnetic force compensation (EMK) principle. However, other types of force sensors for weighing cells known in the prior art are also conceivable. The force transmission element according to the invention is particularly preferably used in weighing cells operating according to the EMK principle.

[0023] The load receiving unit can be a load plate, a load tray or a load transport unit. The load transfer point is the point of the weighing unit at which the load is transferred. The load receiving unit and the load transfer point are preferably connected to the force transmission element of the invention. The force transmission element is preferably arranged as a module between the load receiving unit and the load transfer point. The load receiving unit can, for example, receive the load to be measured from the load transport unit. The load transport unit can, for example, be a conveyor belt or a rotating star frame.

[0024] The force transmission member of the present invention extends in a longitudinal direction X, a transverse direction Y orthogonal thereto, and a vertical direction Z orthogonal to these two directions.

[0025] In one design, the force transmission member of the present invention is preferably manufactured entirely by 3D printing technology, thereby making the force transmission member of the present invention very light and yet stable.

[0026] In another design, stainless steel can be used at least partially as the material for the force transmission part of the present invention, especially the force transmission part part manufactured by 3D printing technology. The advantage of stainless steel over steel is that it has significantly lower thermal conductivity. In addition, when using 3D printing technology, the disadvantages that occur when using cutting methods due to the brittle material properties of stainless steel are not significant.

[0027] The force transmission member of the invention can be arranged inside or outside the housing of the scale or weighing unit, or the force transmission member can pass through the housing, i.e. through the wall. In other words, the invention also relates to a scale or weighing unit, wherein the force transmission member is arranged inside or outside the housing of the scale or weighing unit, or the force transmission member passes through the housing. The invention is preferably arranged inside the housing.

[0028] In another embodiment, the force transmission element of the invention preferably comprises the overload protection mechanism of the weighing cell (as an integral component or protruding into the recess) and / or the force transmission element is designed to be connected indirectly or directly to the overload protection mechanism. The overload protection mechanism is preferably designed to be deflectable in order to dissipate forces in the event of an overload before damage occurs to the weighing cell or to components of the scale.

[0029] In another embodiment, the force transmission member of the present invention may have at least three, preferably four, ends. The ends are preferably designed to be mounted indirectly or directly on the load receiving unit and / or the load conducting position and / or the overload protection mechanism. Most preferably, the ends are designed to be mounted directly on the overload protection mechanism.

[0030] In another design of the force transmission member of the present invention, it is preferred that the force transmission member has at least one V-shaped structure. According to the present invention, the V-shaped structure preferably means that there are two hollow rods connected to each other so that they together imitate a "V" shape. The two hollow rods are referred to herein as "arms of the V-shaped structure", and the point where the arms of the V-shaped structure are connected is referred to herein as the "pointed side" of the V-shaped structure. The "end of the arm of the V-shaped structure" is located on the opposite side. The use of a V-shaped structure has the advantage of relatively high mechanical stability because it can deflect and concentrate the forces.

[0031] In another design, the force transmission member of the present invention can have at least two V-shaped structures. The at least two V-shaped structures are preferably connected to each other indirectly or directly, preferably by means of a common bottom part, via the tip side of the V-shaped structure. Here, the at least two V-shaped structures can be directly connected to each other. There are two possibilities here, namely, they are directly connected to each other at the end of the tip side, thereby obtaining an X-shaped structure in a top view, or at least two V-shaped structures are engaged in the direction of their tip sides, so that they each have two connections via the arms of the V-shaped structure. In addition, the at least two V-shaped structures can also be indirectly connected to each other. In this case, they are preferably connected via a common bottom part. The use of a bottom part has the advantage that, for example, a fixing possibility or a connection point can be provided here for other scale parts, such as a load-transmitting pin or a load-transmitting rod of a weighing unit. The use of multiple V-shaped structures has the advantage that the force transmission member of the present invention can be designed to be very flat (in the vertical direction Z).

[0032] In another design of the force transmission element of the present invention, the ends of the arms of the V-shaped structure are preferably located in a plane defined along the longitudinal direction X and the transverse direction Y, that is, the ends of the arms form the corner points of a (virtual) rectangle, in particular a square or a trapezoid. If one looks at the force transmission element of the present invention along the Z direction (XY projection), one preferably sees exactly two V-shaped structures, a so-called double V-shaped structure. The use of such a double V-shaped structure has the following advantages, namely, that, for example, compared to an H-shaped structure (in the XY projection), eccentric forces can be better resisted when the structure is subjected to force.

[0033] Preferably, the above-mentioned end portion designed to be indirectly or directly mounted to the load receiving unit and / or the load conducting location and / or the overload protection mechanism is located at the end of the arm of the V-shaped structure.

[0034] In another preferred design of the force transmission element of the present invention, it is preferred that the tip side of the V-shaped structure is also located in the plane defined along the longitudinal direction X and the transverse direction Y. However, the tip side of the V-shaped structure can also protrude from the plane defined along the longitudinal direction X and the transverse direction Y in the vertical Z direction. It is particularly preferred that each V-shaped structure visible in the XY projection has two V-shaped structures, which overlap in the XY projection. The overlapping V-shaped structures are preferably directly connected to each other via the two ends of their arms and indirectly connected to each other via their tip sides, preferably via connecting strips.

[0035] According to another design of the force transmission member of the present invention, it has at least one connection part for connecting to the load conduction position of the weighing unit, wherein the connection part is preferably arranged between two V-shaped structures. The force transmission member preferably has two connection parts, wherein one of the connection parts allows fixation by a first mounting part in the longitudinal direction X, and the other of the connection parts allows fixation by a second mounting part in the vertical direction Z. It is preferred that the bottom part has at least one of the connection parts. The bottom part is preferably at least partially designed as a plate and / or a plane. Preferably, the bottom part has a connection part in the form of a hole, to which the load conduction pin of the weighing unit is mounted. The other connection part is preferably arranged on the pointed side of the V-shaped structure.

[0036] In another embodiment, the force transmission element according to the invention preferably has a greater extension in the plane defined along the longitudinal direction X and the transverse direction Y than in the vertical direction Z. This has the advantage that the force transmission element according to the invention has a high stability, whereby a good force transmission can take place between the load receiving unit and the load conducting location, in particular when the load receiving unit or the overload protection device is fixed to the end and the load conducting location is fixed centrally on the force transmission element. Preferably, the extension in the vertical direction Z is at most half of the extension in the plane defined along the longitudinal direction X and the transverse direction Y, more preferably at most one fifth, most preferably at most one tenth.

[0037] The present invention also relates to a method for manufacturing the force transmission member of the present invention by 3D printing technology. Similarly, the present invention also relates to the use of the force transmission member of the present invention manufactured by 3D printing technology in a scale, in particular as a separate modular intermediate connection in terms of force between a load receiving unit for receiving a load to be weighed and a load transmission position of a weighing unit.

[0038] In the method / use of the invention, the individual components of the force transmission element of the invention are formed by repeatedly applying thin layers of material in an overlapping manner (3D printing technology). Preferably, the production of one of the components is carried out "simultaneously" with the production of the other components, wherein "simultaneously" means that a certain layer or all material areas at a certain layer height are first formed and then the next higher layer is placed. When two components at the same layer height require material construction, the material construction of one of the components is therefore interrupted by the material construction of at least one other component. However, it is also theoretically possible to first partially or completely form at least one component in order to then make another component. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The present invention will now be described with the aid of the following figures:

[0040] Figure 1A The force transmission member of the present invention is shown in an oblique view;

[0041] Figure 1B Relative to Figure 1A The oblique view rotated 90° shows the force transmission member of the present invention;

[0042] Figure 1C The force transmission member of the present invention is shown along the Z direction (XY projection);

[0043] Figure 1D The force transmission member of the present invention is shown along the Y direction (XZ projection);

[0044] Figure 1E The force transmission member of the present invention is shown along the X direction (YZ projection);

[0045] Figure 1F Along the Y direction (XZ projection) from Figure 1D The force transmission member of the present invention is shown from the opposite side;

[0046] Figure 1G The force transmission member of the present invention is shown cut along the XY projection plane when viewed along the Z direction (XY projection);

[0047] Figure 1H The force transmission member of the present invention cut along the XZ projection plane is shown along the Y direction (XZ projection);

[0048] Figure 2 The force transmission member of the present invention connected to the overload protection mechanism is shown. DETAILED DESCRIPTION

[0049] Figure 1A and 1B The force transmission member 1 according to the present invention is shown in oblique views respectively. The force transmission member 1 is basically formed by a rod system 2 composed of hollow rods, which are preferably hollow round rods. The force transmission member 1 preferably has two first V-shaped structures 4a, 4a' and two other V-shaped structures 4b, 4b', wherein the first V-shaped structures 4a, 4a' and the other V-shaped structures 4b, 4b' are connected to each other via a bottom part 6. According to the present invention, it is also possible in principle that one of the first V-shaped structures 4a, 4a' and one of the other V-shaped structures 4b, 4b' are omitted, so that the first V-shaped structure is formed only by the V-shaped structure 4a or by the V-shaped structure 4a', and the second V-shaped structure is formed only by the V-shaped structure 4b or by the V-shaped structure 4b'. In the case Figure 1AIn the embodiment shown, the V-shaped structures 4a and 4b are located in a plane defined by the longitudinal direction X and the transverse direction Y, i.e., the ends 7a of the arms of the first V-shaped structure 4a and the ends 7b of the arms of the second V-shaped structure 4b, as well as the pointed sides 5a and 5b, are all located in said plane. Similarly, in the V-shaped structures 4a', 4b', the ends 7a of the arms of the first V-shaped structure 4a' and the ends 7b of the arms of the second V-shaped structure 4b' are located in said plane, but the pointed sides 5a' and 5b' protrude from this plane defined by the longitudinal direction X and the transverse direction Y in the Z direction. The pointed sides 5a and 5a' are connected to each other by a connecting bar 9, which preferably extends in the Z direction as a hollow rod. Similarly, the pointed sides 5b and 5b' are also connected to each other by a connecting bar 9, which also preferably extends in the Z direction as a hollow rod. A connection portion for connecting the overload protection mechanism is provided at the end 3, which is preferably designed as a hollow cylinder along the Z direction. The hollow cylinder preferably has a larger diameter area (flange) not only on the upper side but also on the lower side (seen in the Z direction) to achieve better accommodation, support and placement of components that act there later. The end 3 in the shape of a hollow cylinder has at least one drop-shaped opening on the circumference, which is used to allow unnecessary material to flow out to form the hollow part of the hollow rod. The bottom part 6 is preferably designed in the shape of a plate, and the plate extends along a plane defined by the longitudinal direction X and the vertical direction Z. The bottom part 6 preferably has a first connection portion 8a, which allows the load transmission position to be fixed in the vertical direction Z by a first mounting member. Connection portions 8b are also provided on the tip sides 5a' and 5b', which allow the load transmission position to be fixed in the longitudinal direction X by a second mounting member.

[0050] Figure 1C The force transmission member 1 of the present invention is shown along the Z direction (XY projection). It can be seen from the XY projection that the force transmission member 1 of the present invention has a so-called double V-shaped structure. The bottom part 6 connects the first V-shaped structure 4a, 4a' to the other V-shaped structure 4b, 4b'. Because it is viewed along the Z direction, people cannot see here that there are two first V-shaped structures 4a, 4a' and two other V-shaped structures 4b, 4b'. But it is obvious that the pointed sides 5a, 5a' and the pointed sides 5b, 5b' are facing each other along the X direction. In order to improve stability, the ends 7a, 7b of the arms of the first V-shaped structure 4a, 4a' and the second V-shaped structure 4b, 4b' protrude further outward in the X direction (unlike the "pure H-shaped" structure).

[0051] Figure 1D The force transmission element 1 according to the invention is shown viewed in the Y direction (XZ projection). Here, a large area of ​​the plate of the base part 6 is seen in the Y direction, which shows a first connection point 8a in the form of a hole (with a recess) through the base part 6. A further hole through the plate of the base part 6 is provided above the connection 8a, which is provided for the arrangement of a dowel pin.

[0052] Figure 1EThe force transmission element 1 according to the invention is shown viewed in the X direction (YZ projection). It can be seen here that the first V-shaped structures 4a, 4a' or the further V-shaped structures 4b, 4b' are connected to one another via the connecting strip 9.

[0053] Figure 1F Along the Y direction (XZ projection) from Figure 1D The force transmission element 1 according to the invention is shown from the opposite side, here with Figure 1D The same reference numerals are used in the drawings.

[0054] Figure 1G The force transmission element 1 of the present invention is shown cut along the XY projection plane when viewed along the Z direction (XY projection). Figure 1H The force transmission member of the present invention is shown cut along the XZ projection plane when viewed along the Y direction (XZ projection). It is clearly seen in these two figures that the arms of the first V-shaped structure 4a, 4a' and the second V-shaped structure 4b, 4b' are designed as hollow rods, preferably hollow round rods. It is also clearly seen that the cavity of the bottom part 6 is along the Figure 1G The Z direction of the extension.

[0055] Figure 2 The force transmission element 1 according to the invention is shown, which is connected to an overload protection mechanism 10. The overload protection mechanism 10 is preferably connected to the end 3 of the force transmission element 1 by screws, wherein the screws are preferably surrounded by a spring element 11 in the form of a compression spring, which ensures that overloads can be resisted. It can be clearly seen here that with the force transmission element 1 according to the invention, a combined component consisting of the force transmission element 1 and the overload protection mechanism 10 can be provided, in which the connection points 8a and 8b for connecting to the load transmission point of the weighing unit are centered. The overload protection mechanism 10 has an element 12 for connecting to a load receiving unit.

[0056] Reference numerals list

[0057] 1. Force transmission parts

[0058] 2 Bar system consisting of hollow bars

[0059] 3 ends

[0060] 4a, 4a' The first V-shaped structure

[0061] 4b, 4b' Another V-shaped structure

[0062] 5a, 5a' The tip side of the first V-shaped structure

[0063] 5b, 5b' The tip of another V-shaped structure

[0064] 6 Bottom piece

[0065] 7a The end of the first V-shaped structure arm

[0066] 7b The end of the second V-shaped structure arm

[0067] 8a First connection point

[0068] 8b Second connection point

[0069] 9 Link

[0070] 10 Overload protection mechanism

[0071] 11 Spring parts

[0072] 12 Components for connecting to the load-carrying unit

[0073] X Vertical

[0074] Y Horizontal

[0075] Z vertical

[0076] E plane, which is defined by the longitudinal X and transverse Y

Claims

1. A force transmission member (1) for a scale or a weighing unit, wherein: The force transmission member (1) is designed to be arranged between a load accommodating unit for receiving a load to be weighed and a load conducting position of a weighing unit to transmit the load force applied by the load. The invention is characterized in that the force transmission member (1) is at least partially constructed as a rod system composed of a plurality of hollow rods (2), wherein the force transmission member (1) is at least partially manufactured using 3D printing technology.

2. The force transmission member (1) according to claim 1, characterized in that: The force transmission member (1) is at least partially made of stainless steel.

3. The force transmission member (1) according to claim 1 or 2, characterized in that: The force transmission member (1) includes an overload protection mechanism of the weighing unit, and / or The force transmission member (1) is designed to be indirectly or directly connected to the overload protection mechanism (10).

4. The force transmission member (1) according to claim 3, characterized in that: The force transmission member (1) has at least three ends (3), which are designed to be mounted indirectly or directly on the load accommodating unit and / or the load transmission position and / or the overload protection mechanism (10).

5. The force transmission member (1) according to claim 1, characterized in that: The force transmission member (1) has at least one V-shaped structure.

6. The force transmission member (1) according to claim 5, characterized in that: The force transmission element (1) has at least two V-shaped structures, which are indirectly or directly connected via the pointed sides (5a; 5b) of the V-shaped structures.

7. The force transmission member (1) according to claim 6, characterized in that: The ends of the arms (7a; 7b) of the V-shaped structure lie in a plane (E) defined by the longitudinal direction X and the transverse direction Y, ie the ends of the arms form the corners of a rectangle.

8. The force transmission member (1) according to claim 6 or 7, characterized in that: The pointed sides (5a; 5b) of the V-shaped structure are also located in the plane (E) defined by the longitudinal direction X and the transverse direction Y, or The pointed sides (5a; 5b) of the V-shaped structure protrude in the vertical Z direction from a plane (E) defined by the longitudinal X and transverse Y directions.

9. The force transmission member (1) according to claim 1, 2, 6 or 7, characterized in that: The force transmission element (1) has at least one connection point for connecting to a load transmission location of the weighing cell.

10. The force transmission member (1) according to claim 9, characterized in that: The force transmission member (1) has at least two connection points, wherein one of the connection points allows fixation in the vertical direction Z via a first mounting member, and wherein the other connection point allows fixation in the longitudinal direction X via a second mounting member.

11. The force transmission member (1) according to claim 9, characterized in that: The base part (6) has at least one connection point.

12. The force transmission member (1) according to claim 6 or 7, characterized in that: The force transmission element (1) has at least two V-shaped structures connected by a common bottom element (6), wherein the bottom element (6) is at least partially designed to be plate-shaped and / or flat.

13. The force transmission member (1) according to any one of claims 1, 2, 6 and 7, characterized in that: The force transmission element (1) has an extension in a plane (E) defined by the longitudinal direction X and the transverse direction Y that is greater than its extension in the vertical direction Z.

14. The force transmission member (1) according to claim 2, characterized in that: The force transmission member (1) has at least one V-shaped structure.

15. The force transmission member (1) according to claim 4, characterized in that: The force transmission member (1) has at least one V-shaped structure.

16. The force transmission member (1) according to claim 10, characterized in that: The force transmission element (1) has at least two V-shaped structures connected by a common bottom element (6), wherein the bottom element (6) is at least partially designed to be plate-shaped and / or flat.

17. The force transmission member (1) according to claim 11, characterized in that: The force transmission element (1) has at least two V-shaped structures connected by a common bottom element (6), wherein the bottom element (6) is at least partially designed to be plate-shaped and / or flat.

18. The force transmission member (1) according to claim 4, characterized in that: The force transmission element (1) has an extension in a plane (E) defined by the longitudinal direction X and the transverse direction Y that is greater than its extension in the vertical direction Z.

19. The force transmission member (1) according to claim 10, characterized in that: The force transmission element (1) has an extension in a plane (E) defined by the longitudinal direction X and the transverse direction Y that is greater than its extension in the vertical direction Z.

20. The force transmission member (1) according to claim 11, characterized in that: The force transmission element (1) has an extension in a plane (E) defined by the longitudinal direction X and the transverse direction Y that is greater than its extension in the vertical direction Z.

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