DE102022106562A1 - Filter element and filter system - Google Patents

Abstract

The invention relates to a filter element (10) for a filter system (100) for filtering a fluid, in particular air, with a flatly arranged filter body (12) with a filter medium (14), which, when used as intended, is separated from the fluid in a flow direction (50). is flowed through, with at least one clean-side outflow surface (16) of the filter body (12) being circumferentially surrounded by a frame element (20) with a seal (22) on a circumference (52), the filter body (12) having at least one with the frame element ( 20) has a connected stiffening rib (24), the outflow surface (16) having at least one recess (30) into which, when properly installed in a filter housing (110) of the filter system (100), a counter element (130) arranged on the filter housing (110) intervenes.
The invention further relates to a filter system (100) with a replaceable filter element (10).

Description

Technical area

The invention relates to a filter element for a filter system for filtering a fluid, in particular air, with a flatly arranged filter body and a filter system for filtering a fluid, in particular air, with a replaceable filter element.

State of the art

Before entering the engine, the intake air of internal combustion engines is usually passed through an air filter with a filter housing and a filter element arranged therein in order to separate dirt particles contained in the intake air from the intake air. Such an air filter is, for example, from DE 102 31 696 A1 known. The filter element has the shape of a flat cuboid and comprises a filter medium made of paper or filter fleece that is folded in a zigzag shape. The folds on one side of the filter medium limit a main filter surface for the raw air side of the filter element and the folds on the opposite side of the filter element lying in the parallel plane limit the filter surface for the clean air side. A required sealing of the fold ends of the filter medium is achieved by means of a so-called end edge bonding, which can be achieved, for example, by applying a bead of hot-melt adhesive to the filter medium, spray bonding, PUR foam application or a so-called side band bonding.

Out of EP 2 223 727 A1 a filter device is known which has a multi-part housing and a filter element that can be inserted into the housing, the housing parts being connected to one another in the assembled state. According to the invention, a connecting device passing through the filter element is provided for connecting the housing parts, the connecting device comprising at least one housing dome formed in one piece with a housing part and a damping element which is arranged between the end face of the housing dome and the opposite housing part.

Disclosure of the invention

One object of the invention is to create an easy-to-assemble filter element for a filter system.

Another task is to provide a filter system with such an easy-to-assemble filter element.

The aforementioned object is achieved according to one aspect of the invention by a filter element for a filter system for filtering a fluid, in particular air, with a flatly arranged filter body with a filter medium, which, when used as intended, is flowed through by the fluid in one flow direction, at least one clean side The outflow surface of the filter body is circumferentially surrounded by a frame element with a seal on one circumference, the filter body having at least one stiffening rib connected to the frame element, the outflow surface having at least one recess into which, when properly installed in a filter housing of the filter system, a recess arranged on the filter housing Counter element intervenes.

The further object is achieved by a filter system for filtering a fluid, in particular air, with a replaceable filter element and a filter housing with a fluid inlet and a fluid outlet, the filter element having a filter body with a filter medium which, when used as intended, flows in a direction of flow of the fluid is flowed through, wherein at least one clean-side outflow surface of the filter body is surrounded by a frame element with a seal on a circumference, the filter body having at least one stiffening rib connected to the frame element, the outflow surface having at least one recess into which a counter-element arranged on the filter housing intervenes

Favorable refinements and advantages of the invention result from the further claims, the description and the drawing.

According to one aspect of the invention, a filter element for a filter system for filtering a fluid, in particular air, is proposed, with a flatly arranged filter body with a filter medium, through which the fluid flows in a flow direction when used as intended, at least one clean-side outflow surface of the Filter body is surrounded by a frame element with a seal on a circumference. The filter body has at least one stiffening rib connected to the frame element. The outflow surface has at least one recess into which a counter-element arranged on the filter housing engages when properly installed in a filter housing of the filter system.

The proposed filter element is intended for an air filter system of a motor vehicle and can be replaced if necessary. Such filter elements can be different elements for positioning and receiving in a filter housing of the filter system. According to the invention, the filter element has a positioning element in the form of a recess in the filter body, into which a complementary counter-element, which is arranged on the filter housing, engages. The filter body can preferably be designed with a zigzag-folded filter medium. However, such a recess can also be formed in a filter body with flat filter layers. The recess can advantageously be connected to the frame element and/or to the at least one stiffening rib.

Such an interlocking of the recess and the counter element has the advantage that the filter element is protected against vibrations of a vehicle engine by ensuring a favorable mounting fit of the filter element and a favorable seal through a secure fit of the seal of the filter element in the filter housing.

The recess and counter element work according to the Poka Yoke principle, so that the filter element can be installed so that it cannot be confused. This is advantageous because an incorrectly mounted filter element can lead to an incorrect response signal from an air mass sensor.

The interaction of the recess in the filter body and the counter element in the filter housing further brings about an advantageous improvement in the rigidity of the filter system.

According to a favorable embodiment of the filter element, the at least one recess can be lined with a material of the frame element and/or the at least one stiffening rib. In particular, the recess can be lined with plastic. In this way, the recess can be designed to be stable and at the same time be manufactured inexpensively together with the frame element and/or the stiffening rib, in particular in one piece. Since the frame element and stiffening rib are preferably made of plastic, the recess can also be lined with plastic. Frame element, stiffening rib or ribs and the wall surrounding the recess can be manufactured in one piece in a common injection molding process.

According to a favorable embodiment of the filter element, the at least one recess can be arranged in a recess in the filter body. The filter body, for example made of a zigzag-folded paper medium, can be suitably cut or punched out to form the recess of the filter body.

According to a favorable embodiment of the filter element, the filter body can have at least two stiffening ribs, with the at least one recess being arranged between the at least two stiffening ribs. In particular, the at least one recess can each be connected to the two stiffening ribs with a web. The stiffening ribs serve to stiffen the filter body. If the recess is arranged between the stiffening ribs, the recess or a wall surrounding the recess can advantageously be mechanically connected to the stiffening ribs via webs on both sides in order to be able to transmit forces.

According to a favorable embodiment of the filter element, the at least one recess can be arranged at least partially in the at least one stiffening rib. Another advantageous option is to integrate the recess directly into the stiffening rib. The recess is stably connected to the frame element via the stiffening rib and can advantageously transmit larger forces.

According to a favorable embodiment of the filter element, the at least one recess can be arranged at a connection between the at least one stiffening rib and the frame element. Such an arrangement can also ensure that the filter element is installed in the filter housing so that it cannot be mixed up.

According to a favorable embodiment of the filter element, the at least one recess can be arranged in the at least one stiffening rib. In particular, at least two recesses can be arranged in the at least one stiffening rib. In an alternative embodiment, the stiffening rib can directly have one or more recesses. This can be achieved, for example, by at least partially notches in the stiffening rib. The at least one recess can engage between folds of the filter medium.

According to a favorable embodiment of the filter element, the filter body can be folded in a zigzag shape and the at least one recess arranged in the stiffening rib can engage between folds of the filter medium. The recess is limited to the area of the filter body in which the at least one stiffening rib is arranged. In this way, the full surface of the filter body is available for filtering the fluid.

According to a favorable embodiment of the filter element, the at least one recess can have a circular cross section, or a rectangular cross section, or a semicircular cross section. In particular, the at least one recess can have a cross section that tapers conically in an engagement direction of the counter element. The recess can advantageously have different cross sections that fit together with corresponding shapes of the counter element. A tapered cross section is advantageous to ensure secure assembly and a tight fit of the filter element in the filter housing.

The at least one recess can advantageously be tightly connected to the filter medium. This ensures that no unwanted leakage occurs when filtering the fluid in the filter housing.

According to a favorable embodiment of the filter element, the at least one recess can be arranged asymmetrically in a surface of the filter body so that it can be mounted in the filter housing according to the Poka Yoke principle so that it cannot be confused. The recess and counter element work according to the Poka Yoke principle, so that the filter element can only be mounted in one orientation or in a fixed position. This is advantageous because an incorrectly mounted filter element can lead to an incorrect response signal from an air mass sensor.

It goes without saying that the filter element can have more than one recess. In particular, different configurations of the recess described above can be combined with one another.

According to a further aspect of the invention, a filter system for filtering a fluid, in particular air, is proposed with a replaceable filter element and a filter housing with a fluid inlet and a fluid outlet, wherein the filter element has a filter body with a filter medium which, when used as intended, flows in one direction of flow the fluid flows through, and at least one clean-side outflow surface of the filter body is circumferentially surrounded by a frame element with a seal on one circumference. The filter body has at least one stiffening rib connected to the frame element. The outflow surface has at least one recess into which a counter element arranged on the filter housing engages.

The filter element used in the filter system can be replaced if necessary. Such filter elements can have different elements for positioning and receiving in the filter housing of the filter system. According to the invention, the filter element has a positioning element in the form of a recess in the filter body, into which a complementary counter-element, which is arranged on the filter housing, engages. The filter body can preferably be designed with a zigzag-folded filter medium. However, such a recess can also be formed in a filter body with flat filter layers. The recess can advantageously be connected to the frame element and/or to the at least one stiffening rib.

Such an interlocking of the recess and the counter element has the advantage that the filter element is protected against vibrations of a vehicle engine by ensuring a favorable mounting fit of the filter element and a favorable seal through a secure fit of the seal of the filter element in the filter housing.

The recess and counter element work according to the Poka Yoke principle, so that the filter element can be installed so that it cannot be confused. This is advantageous because an incorrectly mounted filter element can lead to an incorrect response signal from an air mass sensor.

The interaction of the recess in the filter body and the counter element in the filter housing further brings about an advantageous improvement in the rigidity of the filter system.

According to a favorable embodiment of the filter system, the filter housing can have at least a first housing part with the fluid inlet and a second housing part with the fluid outlet, with the at least one counter-element being arranged on the first or second housing part. In this way, the filter element can be securely inserted into a housing part in order to close the filter housing with the second housing part. The counter-element advantageously engages in the recess of the filter element in order to ensure that the filter element sits securely in the filter housing.

According to a favorable embodiment of the filter system, the at least one recess can be arranged asymmetrically in a surface of the filter body in such a way that it can be mounted in the filter housing according to the Poka Yoke principle in a way that prevents it from being confused. The recess and counter element work according to the Poka Yoke principle, so that the filter element can only be mounted in one orientation. This is advantageous because an incorrectly mounted filter element results in an incorrect response signal of an air mass sensor in the filtered air flow.

Brief description of the drawings

Further advantages result from the following drawing description. Exemplary embodiments of the invention are shown in the drawings. The drawings, description and claims contain numerous features in combination. The person skilled in the art will also expediently consider the features individually and combine them into further sensible combinations.

• 1 eine isometrische Ansicht eines Filtersystems nach einem Ausführungsbeispiel der Erfindung;
• 2 eine Draufsicht auf das Filtersystem nach 1 mit eingezeichneter Schnittebene A-A;
• 3 eine isometrische Darstellung eines Filterelements nach einem Ausführungsbeispiel der Erfindung;
• 4 einen Längsschnitt durch das Filterelement nach 3 im Bereich einer Ausnehmung;
• 5 einen Längsschnitt durch das Filtersystem nach 2 entlang der Schnittlinie A-A;
• 6 eine isometrische Darstellung eines Filterelements nach einem weiteren Ausführungsbeispiel der Erfindung;
• 7 einen Längsschnitt durch das Filterelement nach 6 im Bereich einer Ausnehmung;
• 8 einen Längsschnitt durch ein Filtersystem mit dem Filterelement nach 6 entlang der Schnittlinie A-A;
• 9 eine isometrische Darstellung eines Filterelements nach einem weiteren Ausführungsbeispiel der Erfindung;
• 10 einen Längsschnitt durch das Filterelement nach 9 im Bereich einer Ausnehmung;
• 11 einen Längsschnitt durch ein Filtersystem mit dem Filterelement nach 9 entlang der Schnittlinie A-A;
• 12 eine isometrische Darstellung eines Filterelements nach einem weiteren Ausführungsbeispiel der Erfindung;
• 13 einen Längsschnitt durch das Filterelement nach 12 im Bereich einer Ausnehmung;
• 14 einen Längsschnitt durch ein Filtersystem mit dem Filterelement nach 12 entlang der Schnittlinie A-A;
• 15 eine isometrische Darstellung eines Filterelements nach einem weiteren Ausführungsbeispiel der Erfindung;
• 16 einen Längsschnitt durch das Filterelement nach 15 im Bereich einer Ausnehmung;
• 17 einen Längsschnitt durch ein Filtersystem mit dem Filterelement nach 15 entlang der Schnittlinie A-A;
• 18 eine isometrische Darstellung eines Filterelements nach einem weiteren Ausführungsbeispiel der Erfindung;
• 19 einen Längsschnitt durch das Filterelement nach 18 im Bereich einer Ausnehmung; und
• 20 einen Längsschnitt durch ein Filtersystem mit dem Filterelement nach 18 entlang der Schnittlinie A-A.

They show, for example:

• 1 an isometric view of a filter system according to an embodiment of the invention;
• 2 a top view of the filter system 1 with section plane AA drawn in;
• 3 an isometric view of a filter element according to an embodiment of the invention;
• 4 a longitudinal section through the filter element 3 in the area of a recess;
• 5 a longitudinal section through the filter system 2 along section line AA;
• 6 an isometric representation of a filter element according to a further embodiment of the invention;
• 7 a longitudinal section through the filter element 6 in the area of a recess;
• 8th a longitudinal section through a filter system with the filter element 6 along section line AA;
• 9 an isometric representation of a filter element according to a further embodiment of the invention;
• 10 a longitudinal section through the filter element 9 in the area of a recess;
• 11 a longitudinal section through a filter system with the filter element 9 along section line AA;
• 12 an isometric representation of a filter element according to a further embodiment of the invention;
• 13 a longitudinal section through the filter element 12 in the area of a recess;
• 14 a longitudinal section through a filter system with the filter element 12 along section line AA;
• 15 an isometric representation of a filter element according to a further embodiment of the invention;
• 16 a longitudinal section through the filter element 15 in the area of a recess;
• 17 a longitudinal section through a filter system with the filter element 15 along section line AA;
• 18 an isometric representation of a filter element according to a further embodiment of the invention;
• 19 a longitudinal section through the filter element 18 in the area of a recess; and
• 20 a longitudinal section through a filter system with the filter element 18 along section line AA.

Embodiments of the invention

In the figures, identical or similar components are numbered with the same reference numerals. The figures only show examples and are not to be understood as limiting.

Directional terminology used below with terms such as “left”, “right”, “top”, “bottom”, “before”, “behind”, “after” and the like only serves to better understand the figures and is in no way intended to limit the represent generality. The components and elements shown, their design and use can vary according to the considerations of a person skilled in the art and can be adapted to the respective applications.

1 shows an isometric view of a filter system 100 according to an embodiment of the invention. 2 shows a top view of the filter system 100 1 with cutting plane AA drawn.

The filter system 100 for filtering a fluid, in particular air, comprises an invisible, replaceable filter element 10 and a filter housing 110 with a fluid inlet 102 and a fluid outlet 104. The filter housing 110 has at least a first housing part 112 with the fluid inlet 102 and a second housing part 114 with the fluid outlet 104. The two housing parts 112, 114 are tightly connected to the mounted filter element 10.

In 3 an isometric representation of a filter element 10 according to an exemplary embodiment of the invention is shown.

The filter element 10 has a filter body 12 with a filter medium 14, through which the fluid flows in a flow direction 50 when used as intended. At least one clean-side outflow surface 16 of the filter body 12 is circumferentially surrounded by a frame element 20 with a seal 22 on a circumference 52. The seal 22 can, for example, be made of polyurethane (PUR) and, for example, foamed onto the frame element 20 during the manufacturing process.

The filter body 12 has two stiffening ribs 24 arranged in parallel and connected to the frame element 20. The outflow surface 16 has at least one recess 30 into which a counter element 130 arranged on the filter housing 110 can engage. For this purpose, the at least one counter-element 130 can be arranged on the first or second housing part 112, 114.

The recess 30 is arranged between the two stiffening ribs 24. The recess 30 is connected to the two stiffening ribs 24 with a web 34 for a rigid mechanical connection.

With the one in the 1 and 2 In the filter housing 110 shown, the counter element 130 is arranged in the second housing part 114, the housing cover. On the outside of the filter housing 110, the counter element 130 can only be seen as a recess in the housing part 114, which is manufactured, for example, in a plastic injection molding process.

4 shows a longitudinal section through the filter element 10 3 in the area of the recess 30, while in 5 a longitudinal section through the filter system 2 is shown along section line AA.

As can be seen in the cross sections, the recess 30 is arranged in a recess 32 in the filter body 12. The recess 32 in the filter body 12 can, for example, be cut or punched out of the zigzag-folded filter medium 14.

The recess 30 can advantageously be lined with a material of the frame element 20 and/or the at least one stiffening rib 24 in order to be able to accommodate the counter element 130 of the filter housing 110 with the corresponding mechanical stability. So the recess 30 can be lined with plastic in a frame element 20 made of plastic.

As in 3 can be seen, the recess has a circular cross section. In principle, other cross-sectional shapes are also possible. For example, the recess 30 can also have a rectangular cross-section or a semicircular cross-section. Next is the longitudinal sections in the 4 and 5 It can be seen that the recess 30 has a cross section that tapers conically in an engagement direction 54 of the counter element 130. So the counter element 130, which, as in 5 recognizable, has a corresponding shape, can be safely inserted into the recess 30 in the engagement direction 54 when the second housing part 114 is placed on the first housing part 112 with the filter element 10 mounted.

As also in 3 can be seen, the recess 30 is arranged asymmetrically in the surface 18 of the filter body 12 so that it can be mounted in the filter housing 110 according to the Poka Yoke principle in a way that prevents it from being confused. The counter element 130 can only engage in the recess 30 if the filter element 10 is mounted appropriately in the first housing part 112, so that the filter housing 110 can be closed.

In 5 the fluid direction 50 is shown with an arrow. The fluid therefore flows from the first housing part 112 with the invisible fluid inlet 102 through the filter body 12 into the second housing part 114, where it can flow out through the invisible fluid outlet 104. The filter element 10 is sealed against the filter housing 110 by the seal 22 arranged on the frame element 20.

6 shows an isometric view of a filter element 100 according to a further embodiment of the invention, while 7 a longitudinal section through the filter element 10 6 in the area of the recess 30 shows. In 8th is a longitudinal section through a filter system 100 with the filter element 10 6 shown along section line AA. The cutting line leads through the recess 30.

With the one in the 6 until 8th In the exemplary embodiment shown, the recess 30 is arranged at least partially in the at least one stiffening rib 24. The recess 30 is stably connected to the frame element 20 via the stiffening rib 24 and can advantageously transmit larger forces.

9 shows an isometric view of a filter element 100 according to a further embodiment of the invention, while 10 a longitudinal section through the filter element 10 9 in the area of the recess 30 shows. In 11 is a longitudinal section through a filter system 100 with the filter element 10 9 along the section line AA is shown. The cutting line leads through the recess 30.

With the one in the 9 until 11 In the illustrated embodiment, the recess 30 is arranged at a connection between the at least one stiffening rib 24 and the frame element 20. The recess 30 is semicircular. The secant of the semicircle rests on the frame element 20. The recess 30 is stably connected to the frame element 20 via the stiffening rib 24 and can advantageously transmit larger forces.

12 shows an isometric view of a filter element 100 according to a further embodiment of the invention, while 13 a longitudinal section through the filter element 10 12 in the area of the recess 30 shows. In 14 is a longitudinal section through a filter system with the filter element 10 12 shown along section line AA. The cutting line leads through the recess 30.

That in the 12 until 14 The exemplary embodiment shown corresponds to that in the 6 until 8th version shown. However, the recess 30 has a rectangular cross-section instead of a circular cross-section.

15 shows an isometric view of a filter element 10 according to a further embodiment of the invention, while 16 a longitudinal section through the filter element 10 15 in the area of the recess shows. In 17 is a longitudinal section through a filter system with the filter element 10 15 shown along section line AA. The cutting line leads through the recess 30.

That in the 15 until 17 The exemplary embodiment shown corresponds to that in the 9 until 11 version shown. However, the recess 30 has a rectangular cross-section instead of a semicircular cross-section.

18 shows an isometric view of a filter element 10 according to a further embodiment of the invention, while 19 a longitudinal section through the filter element 10 18 in the area of the recesses 30 shows. In 20 is a longitudinal section through a filter system with the filter element 10 18 shown along section line AA. The cutting line leads through the recesses 30.

In this exemplary embodiment, two recesses 30 are arranged in the stiffening rib 24. Since the filter body 12 shown in the embodiments shown is folded in a zigzag shape, the recesses 30 arranged in the stiffening rib 24 can engage between folds 60 of the filter medium 14. The corresponding counter elements 130 are rod-shaped.

In principle, the number of recesses 30 and counter elements 130 can also be higher in order to achieve greater mechanical stability.

Reference symbols

10

Filter element

12

Filter body

14

Filter medium

16

clean-side outflow surface

18

Area

20

Frame element

22

poetry

24

stiffening rib

30

Recess filter element

32

Recess filter body

34

web

50

Direction of flow

52

Scope

54

Direction of engagement

60

wrinkle

100

Filter system

102

Fluid inlet

104

Fluid outlet

110

Filter housing

112

Upper housing part

114

Lower housing part

130

Counter element

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10231696 A1 [0002]
• EP 2223727 A1 [0003]

Claims (13)

Filter element (10) for a filter system (100) for filtering a fluid, in particular air, with a flatly arranged filter body (12) with a filter medium (14), through which the fluid flows in a flow direction (50) when used as intended, wherein at least one clean-side outflow surface (16) of the filter body (12) is circumferentially surrounded by a frame element (20) with a seal (22) on a circumference (52), wherein the filter body (12) has at least one stiffening rib (24) connected to the frame element (20), wherein the outflow surface (16) has at least one recess (30) into which, when properly installed in a filter housing (110) of the filter system (100), a counter element (130) arranged on the filter housing (110) engages. Filter element after Claim 1 , wherein the at least one recess (30) is lined with a material of the frame element (20) and / or the at least one stiffening rib (24), in particular wherein the recess (30) is lined with plastic. Filter element after Claim 1 or 2 , wherein the at least one recess (30) is arranged in a recess (32) in the filter body (12). Filter element according to one of the preceding claims, wherein the filter body (12) has at least two stiffening ribs (24), wherein the at least one recess (30) is arranged between the at least two stiffening ribs (24), in particular wherein the at least one recess (30) with a web (34) is connected to the two stiffening ribs (24). Filter element according to one of the Claims 1 until 3 , wherein the at least one recess (30) is arranged at least partially in the at least one stiffening rib (24). Filter element according to one of the Claims 1 until 3 , wherein the at least one recess (30) is arranged at a connection of the at least one stiffening rib (24) and the frame element (20). Filter element according to one of the Claims 1 until 3 , wherein the at least one recess (30) is arranged in the at least one stiffening rib (24), in particular wherein at least two recesses (30) are arranged in the at least one stiffening rib (24). Filter element after Claim 7 , wherein the filter body (12) is folded in a zigzag shape, and the at least one recess (30) arranged in the stiffening rib (24) engages between folds (60) of the filter medium (14). Filter element according to one of the preceding claims, wherein the at least one recess (30) has a circular cross section, or a rectangular cross section, or a semicircular cross section, in particular wherein the at least one recess (30) has an engagement direction (54) of the counter element (130 ) has a conically tapering cross section. Filter element according to one of the preceding claims, wherein the at least one recess (30) is arranged asymmetrically in a surface (18) of the filter body (12) so that it can be installed in the filter housing (110) according to the Poka Yoke principle. Filter system (100) for filtering a fluid, in particular air, with a replaceable filter element (10) according to one of the preceding claims and a filter housing (110) with a fluid inlet (102) and a fluid outlet (104), wherein the filter element (10) has a filter body (12) with a filter medium (14) through which the fluid flows in a flow direction (50) when used as intended, wherein at least one clean-side outflow surface (16) of the filter body (12) is circumferentially surrounded by a frame element (20) with a seal (22) on a circumference (52), wherein the filter body (12) has at least one stiffening rib (24) connected to the frame element (20), wherein the outflow surface (24) has at least one recess (30) into which a counter element (130) arranged on the filter housing (110) engages. Filter system after Claim 11 , wherein the filter housing (110) has at least a first housing part (112) with the fluid inlet (102) and a second housing part (114) with the fluid outlet (104), wherein the at least one counter element (130) on the first or second housing part (112 , 114) is arranged. Filter system after Claim 11 or 12 , wherein the at least one recess (30) is arranged asymmetrically in a surface (18) of the filter body (12) so that it can be installed in the filter housing (110) according to the Poka Yoke principle.

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