HAUSHALTSGERÄT MIT EINER PUMPENANORDNUNG

Domestic appliance with a pump arrangement

The present invention relates to a domestic appliance with a pump arrangement for delivering a fluid.

In modern household appliances such as washing machines or dishwashers, the dosage of a fluid, for example, a detergent may be carried out by means of a metering device. A metering device can for example comprise a metering pump, as described in document DE102009029442 A1.

It is the underlying object of the invention, a household appliance with a

to create pump assembly.

This object is achieved by the subject matter with the features of the independent claims. Advantageous embodiments of the invention are the subject of the figures, the description and the dependent claims.

According to one aspect of the invention, the object is achieved by a domestic appliance with a pump arrangement for conveying a fluid, the pump assembly includes a housing having an inlet opening and an outlet opening, a drive shaft, a first gear fixedly connected to the drive shaft and in a first rotational direction and is rotatable in a second rotational direction of the drive shaft and a second gear which is displaceable relative to the first gear, wherein the second gear is in the first rotational direction in engagement with the first gear to the fluid from the inlet opening to the to promote outlet opening, and wherein in the second rotational direction, a force is produced which moves the second gear for releasing the engagement.

Thus, the technical advantage is achieved that, despite the reversibility of the fluid is conveyed only in one direction, while in the opposite direction of rotation no fluid is promoted. Thus, the pump arrangement, the detergent of the

Volume container of the metering system, for example, to the Einspüldusche or directly into the

promote the tub. In a reversal of the direction of rotation of the first gear, no fluid is promoted so that a reflux of previously conveyed detergent from the

Einspüldusche is avoided in the reservoir. In addition, an exact dosage of the amount required for the laundry process of detergent to the pump arrangement is possible. The function of the pump assembly is based on mechanical forces and / or convection, which act during the different directions of rotation on the movable gear. In the first rotational direction, the second gear is in engagement with the firmly connected to the drive shaft first gear, so that the fluid to be conveyed is conveyed from the entrance opening to the exit opening. Upon rotation of the first gear in the second rotational direction, that is, at a

Reversal of rotation direction, a force is generated in direction of the free displaceability of the second gear. Thereby, the second gear disengages from the engagement with the first gear. The force for moving the second gear resulting largely from

Frictional forces which occur between the second gear and the housing, in particular the housing wall. In addition, a convection to the movable gear acts. These result from the rotation of the first gear, which are transferred to the fluid. The convection in the second direction of rotation supports the displacement of the second gear. Preferably, the second gear has a first gear relative to the obliquely extending outward movement. When switching from the second direction of rotation in the first rotational direction the second gear shifting back into engagement with the first gear, so that the fluid is conveyed from the inlet port to the outlet port again. The initial force for moving the second gear into engagement with the first gear can result from the gravity. Additionally or alternatively, the force resulting from the changed direction of rotation convection can move the second gear back into engagement with the first gear.

The second gear can be brought by the viscous friction completely out of engagement with the first gear or operates similar to a ratchet in that it can be re-pressed by each tooth of the first gear to the top. Advantageously, the fluid in the housing has a strong damping and lubricating, so that the pump arrangement has a long service life in spite of its simple and inexpensive construction.

Under a household appliance, a device is understood, which is used for financial management. This can be a major household appliance such as a washing machine, a dryer, a dishwasher. But this can also be a small household appliance, such as a water heater, a coffee machine, a

Food processor or a vacuum cleaner. In an advantageous embodiment of the domestic appliance, the force caused by a movement of the fluid due to the rotation of the first gear in the second rotational direction.

Thus, the technical advantage is achieved that the force that moves the second gear relative to the first gear, resulting from the force acting on the second gear convection. The rotational movement of the first gear is transferred to the fluid located in the housing. The fluid in turn, transmits this rotational movement to the second gear. Depending on the direction of rotation of the first gear changing convection causes a displacement of the second gear out of engagement with the first gear or the second gear is again brought into engagement with the first gear.

Thus, no additional mechanism is required for moving the second gear, so that the pump arrangement is inexpensive to manufacture. In addition, a long-life pump arrangement can be provided since the lifetime can be increased by omitting a trouble-prone kinematics. In a further advantageous embodiment of the domestic appliance, the force generated for displacing said second gear is a frictional force resulting from friction of the second gear on a wall of the housing.

Thus, the technical advantage is achieved that an inexpensive and simple mechanism for displacing the second gear out of engagement with the first

Gear is provided. this rotational movement is transmitted to the second gear by rotation of the first gear in the second rotational direction, since both gears are still engaged. The housing and / or the second gear are advantageously dimensioned such that the tips of the teeth of the second gear to contact the casing wall, so that the tooth tips rub against the casing wall. This gives rise to frictional forces which move the second gear out of engagement with the first gear. As a result of

Frictional forces the second gear can be moved along on the housing wall and move away from the first gear. The frictional force, by appropriate design of

Tooth shapes of the second gear and / or the surface structure of the housing wall can be adjusted. For example, a rough surface the housing

increase friction effect.

In a further advantageous embodiment of the domestic appliance, the second gear shifting perpendicular to the axis of rotation of the first gear. This technical advantage is achieved that the second gear during the

displacing can be guided along the housing wall. This guided movement of the second gear is ensured. The displacement of the second gear perpendicular to the first gear can be made in horizontal or vertical direction. The second gear may also move diagonally to the rotational axis of the first gear itself. The direction of displacement of the second gear to the rotational axis of the first gear may be dependent on the design of the housing contour.

In a further advantageous embodiment of the domestic appliance corresponding to the

Displacement path of at least one tooth height of the second gear. The radial component of the displacement, that the axial distance is in accordance with an embodiment, an

Tooth height, respectively.

According to one embodiment, the tooth height is at both gears is the same. Thus, the technical advantage is achieved that the second gear can be brought in such a manner out of engagement with the first gear, that no fluid is conveyed in the second direction of rotation. Preferably, the second gear relative to a circumference of the first gear extending obliquely outward movement with a

Radial share to more than one tooth height. Thereby, the second gear is completely out of engagement with the first gear. Further, the radial portion may also be less than a tooth height, so that the two gears function similar to the principle of a ratchet by the second gear of each gear of the first gear can be again pushed up. In a further advantageous embodiment of the domestic appliance, the housing is provided with a bulge.

Because the technical advantage is achieved that space for displacing the second gear is sufficient. The bulge may be formed as an extension of the housing in the horizontal and / or vertical direction. Preferably, the bulge in the area of ​​the second gear is formed in the housing. Advantageously, the bulge corresponds to the direction of displacement of at least half of the

Diameter of the second gear. Further preferably, the bulge in the inlet opening or the outlet opening is placed. In a vertically oriented

Bulge with bottom working position of the first gear is the first gear in the region of the inlet opening arranged and the bulge extends vertically upwards, so that the second gear can move vertically upward. In a vertically oriented bulge with an overhead working position of the first gear, the first gear in the region of the outlet opening is disposed and the protrusion extends vertically downward, so that the second gear can move vertically downwards. with an overhead working position is preferably the second gear

formed floating. As a result, even a small flow force, as generated by rotation of the first gear in the second direction of rotation sufficient to move the second gear. In addition, the second gear is only engaged with the first gear, when a fluid within the housing is present. In the absence of fluid, the second gear out of engagement with the first gear shift by falls within the vertically oriented downward bulge downward. Again only when fluid is present within the housing, the second gear returns into engagement with the first gear. Thus, a dry running of the pump is prevented. Due to the bulge, the housing contour may be formed such that the tips of the teeth of the second gear running during engagement with the first gear on the housing wall along a circle segment of approximately 90 °. the reduced

Contact area between the housing wall and the tips of the teeth of the second gear is sufficient to deliver sufficient fluid between the housing wall and the second gear in the pump operation.

In an advantageous embodiment of the domestic appliance, the second gear is performed via a link within the housing.

Thus, the technical advantage is achieved that the distance set for displacing the second gear, and at the same time can be made possible a guided displacement movement of the second gear. Preferably, the link from a connected to the second gear shaft, which is guided in an inserted into the housing wall the groove is formed. The gate is preferably designed such that the second gear can move perpendicular to the axis of rotation of the first gear. The second gear is advantageously arranged rotatably on the shaft of the connecting link. the shaft of a lightweight material such as plastic is preferably prepared. Characterized the counter to the displacement direction of gravity acting force of the wave is comparatively small, so that despite the additional forces acting on the second shaft weight of a displacement of the second gear is possible. The resulting between the housing wall and the second gear friction forces in connection with the forces acting on the second gear convection are sufficiently large to the second gear counter its weight, the weight of the shaft, the frictional resistance of the shaft in the groove and the

to transfer resistance to flow out of engagement with the first gear. Advantageously, the fluid located in the housing for a sufficient lubrication of the guided wave within the groove ensures, so that the occurring between the groove and the shaft friction is low. This enables a smooth shifting.

In a further advantageous embodiment of the domestic appliance, the second gear is arranged freely movable within the housing. Thus, the technical advantage is achieved that a simple and inexpensive embodiment is created, as a backdrop for guiding the second gear can be omitted. The second gear is guided during the displacing preferably along the housing wall by the tips of the teeth of the second gear to contact the casing wall.

In a further advantageous embodiment of the domestic appliance the inlet opening is connected with a first chamber and the outlet opening with a second chamber, wherein in the first rotational direction a negative pressure in the first chamber and a positive pressure in the second chamber can be generated, so that the to thereby resulting pressure differential causes the second gear in engagement with said first gear, said second in the

Rotational direction, an overpressure in the first chamber and a negative pressure in the second chamber can be generated, so that the resulting pressure difference thereby solves the second gear out of engagement with the first gear. Thus, the technical advantage is achieved that the occurring hydraulic conditions are working in the appropriate direction and so assist in holding the position of the second gear and / or the displacement of the second gear. When the fluid is conveyed from the inlet opening to the outlet opening, a negative pressure in the second chamber and an overpressure builds up in the first chamber. This pressure difference supports the second gear engaged with the first gear to stay or supports the second gear, to go back into engagement with the first gear. Upon rotation of the first gear in the second rotational direction and an overpressure in the second chamber, a negative pressure builds up in the first chamber. The resulting pressure differential supports the second gear to break away from engagement with the first gear and move. In addition, this pressure difference supports the second gear is to keep this position. Preferably the first chamber is the

Dispensing shell and the second chamber of the culvert, which leads into the washing drum.

In a further advantageous embodiment of the domestic appliance, the second gear is connected to a spring element which converts the second gear into engagement with the first gear.

This technical advantage is achieved that the second gear in the first

Rotating direction can be pressed into engagement with the first gear so as to ensure a secure engagement of the second gear with the first gear in the first rotational direction. the spring force of the spring element is designed so advantageous that the frictional force and / or convection are larger, so that the second gear can be shifted against the spring force of the spring element. Preferably, the spring element to the housing and the second gear is connected. The spring element may be formed as a compression spring.

In a further advantageous embodiment of the domestic appliance, the housing has a locking device which restricts movement of the second gear.

This technical advantage is achieved that the displacement movement of the second gear is performed. Also can be by the blocking device areas in which the second gear is not to move, from those in which the second gear is intended to relocate, to delimit. Thus, the barrier means may be arranged within the housing such that a possible range above or below the first gear is locked. The locking device can be used as one or more of the

Housing wall protruding ribs and / or projections may be formed. the locking means is preferably formed integrally with the housing wall.

In a further advantageous embodiment of the domestic appliance, the second gear in the fluid is unsinkable.

This technical advantage is achieved that a simple and inexpensive

Pump arrangement can be created, as for moving the gear no special power generators are required. Further, also a sliding guide for the second gear can be omitted. Advantageously, the second gear to a larger density than the fluid to be delivered, so that the second gear in the first rotational direction in the engagement displaced back to the first gear. Preferably, to the second gear in a vertical arrangement of the housing, particularly in a vertically oriented recess, a greater density than the fluid to be delivered. Thereby, the force of gravity or the weight of the second gear acts as an initial force to bring the second gear in the first rotational direction back into engagement with the first gear. Thus, the pump assembly is inexpensive to

Production.

In a further advantageous embodiment of the domestic appliance, the second gear is made of magnetic material.

Thus, the technical advantage is achieved that the second gear can be actively controlled from the outside to the first, the second gear into and / or out of engagement with the

to shift gear. This can provide a magnetically switchable pumping action a pump assembly. Thus, an electrically controllable solenoid can be arranged outside the housing which generates a magnetic field by means of which the second gear is movable. This dosing can be built up with more than two channels. The second gear may be made of a ferromagnetic or magnetic material. In a further advantageous embodiment of the domestic appliance, the tooth form of the first gear and / or of the second gear is an involute.

This technical advantage is achieved that the gears are easy and inexpensive to produce. In addition, an involute tooth shape ensures a safe and play poor engagement of the two gears. Furthermore, such a tooth contour is insensitive, so that warrants to center distance even with a not smooth engagement of the second gear in the first gear, the delivery of the fluid. Further, the first and the second gear may also have uneven tooth shapes. In a further advantageous embodiment of the domestic appliance, the first and / or second gear to asymmetric tooth shapes.

This technical advantage is achieved that the displacement and holding the position can be supported. Preferably, the tooth shapes have a

favorable aerodynamic shape. According to another aspect of the household appliance, the pump assembly includes a second housing having a second inlet and a second outlet opening, a third gear in the rotational direction and in the second rotational direction is rotatably fixedly connected to the drive shaft and, and a fourth gear, which is displaceable relative to the second gear, wherein the fourth gear in the second direction of rotation of

Drive shaft is engaged with the third gear, a fluid from the second

to promote entry port to the second outlet opening, and wherein in the first

Direction of rotation, a force is generated that moves the fourth gear to release the engagement.

This technical advantage is achieved that a simple and compact

Zweikanaldosiersystem is created which requires only one drive. The

Zweikanaldosiersystem comprises two pumps, which are connected to each other via a common drive shaft that depending on the direction of rotation of the drive shaft one of the pumps can be controlled. Upon rotation of the drive shaft in the first rotational direction is the second gear with the first gear, so that the first pump feeds a fluid from the inlet opening to the outlet opening. At the same time in the first

Rotational direction of the fourth gear out of engagement with the driven third gear, so that the second pump delivers no fluid. Upon rotation of the drive shaft in the second rotational direction is the fourth gear to the third gear, so that the second pump pumps a fluid from the inlet opening to the outlet opening. At the same time in the second rotational direction is the second gear out of engagement with the driven first gear, so that the first pump feeds no fluid. The inlet openings of the two housings are preferably of different storage containers of

Zweikanaldosiersystems connected. Characterized the detergent from the one or the other reservoir can be conveyed to the dispensing shell depending on the direction of rotation. Preferably, the two pumps are arranged one behind the other. The housing, in particular, the bulges of the housing may be formed such that the freely displaceable gears can move in the vertical direction and / or horizontal direction. Further, the freely displaceable gears can be guided by means of in each case a sliding block within the housing and / or the displaceable toothed wheels are arranged freely movable within the housing.

Further embodiments of the invention are illustrated in the drawings and will be described in more detail below. Show it:

Fig. 1 is a schematic illustration of a household appliance;

Figure 2 is a schematic representation of a cross-section through a pump assembly in the working position according to a first embodiment.

Figure 3 is a schematic representation of a cross-section through a pump assembly in the freewheeling position according to a first embodiment. Figure 4 is a schematic representation of a cross-section through a pump assembly according to a second embodiment. and

Fig. 5 is a schematic representation of a Zweikanaldosiersystems. In Fig. 1 a schematic view is formed as a washing machine

Household appliance 100 is shown. The household appliance 100 comprises a shaft 102 in which a metering system 104 can be inserted. The metering system 104 includes a reservoir 106 can be filled in the detergent or other substances. By means of the metering system 104 is then dependent on the degree of contamination and kind of the laundry and loading state of the home appliance 100, the required therefor

Amount of detergent metered in for example a Einspüldusche or into the tub. In the Einspüldusche water is provided via waterways, which forms a wash liquor along with the metered amount of detergent. This wash liquor is then introduced into a washing tub of the household appliance 100 to perform the laundry process.

Fig. 2 shows a pump assembly 200 in the working position, which is used to promote a fluid, such as a detergent, within a metering 104th The pump assembly 200 includes a housing 202 having an inlet 204 and an outlet opening 206, a drive shaft 208, a fixedly connected to the drive shaft 208, first gear 210 and a second gear 212. The pump assembly 200 is via the inlet opening 204 to the reservoir 106 of the metering system 104 and connected to the outlet opening 206 to the Einspüldusche. Both gears 210, 212 have a symmetrical involute tooth shape. Further, the gears 210, 212 of unequal and / or asymmetrical tooth forms may have. The housing 202 has a first portion 214 and a second section 216 defining a fluid-filled pump cavity 217th In the first section 214, the drive shaft 208 and the first gear 210 are rotatably mounted. Via the drive shaft 208, the first gear 210 can be rotated in a first rotational direction 220, which corresponds to a rotation of the first gear in a clockwise direction and in a second rotational direction 300, which corresponds to a rotation of the first gear counterclockwise. The second gear 212 is freely movable within the second portion 216th The second gear 212 and the pump cavity 217 are dimensioned such that the second gear 212 can move within the pump cavity 217 perpendicular to the axis of rotation of the first gear 210 in the vertical direction V. For this purpose, the second section is provided with an opening extending in the vertical direction V bulge 218,216. the outlet opening 206 is also introduced into the bulge 218th The second gear 212 is also performed via a link 222 within the pump cavity 217th The gate 222 is formed of a gear 212 connected to the second shaft 224, which is guided in an inserted into the housing wall 213 groove 226th The housing 202, in particular the pump cavity 217 is dimensioned so that the tooth tips of the gears 210, 212 always contact the housing wall 213 and thus to the

Housing wall 213 are stored. In the working position, corresponding to the first rotational direction 220, the second gear 212 engaged with the first gear 210, whereby the second gear 212 rotates counterclockwise. Here, the fluid between the teeth of the two gears 210, 212 and between the gears 201, 212 and the housing wall 213 of the

Inlet opening 204 conveyed to the outlet opening 206th The direction of rotation of the gears 201, 212 is shown in Fig. 2 by the arrows. Since the second portion 216 with the

Bulge 218 is provided, the contact area of ​​the tooth-peak of the second gear 212 and the housing wall 213 is reduced to an angle of approximately 90 °. However, the angle may also be limited to 90 °. However, this is sufficient to promote the fluid from the

Inlet opening 204 to the outlet opening 206th The angle calculated by comparison with conventional gear pumps.

In the embodiment shown in Fig. 3 overrunning positions corresponding to the second rotational direction 300, the second gear 212 has out of engagement with the first gear 210 in

Vertically shifted V. Since the two gears 210, 212 are disengaged, no fluid is delivered. The displacement of the second gear 212 in the vertical direction V resulting from a generated in the second rotational direction 300 force. This force results, for example, between the housing wall 213 and the tips of the teeth of the second gear 212 acting friction forces and / or fluid forces, which are caused by viscous friction. When both gears 210, 212 are still in engagement, the second gear 212 rotates upon rotation of the first gear 210 in the second

Rotational direction 300 counter-clockwise. 212 thereby rub the tooth tips of the second gear to the housing wall 213. The friction forces resulting displace the second gear 212 from engagement with the first gear 210. Due to the resulting frictional forces, the second gear 212 along the housing wall 213 to move vertically upward. In addition to the frictional forces acting in the second rotational direction 300, a

Convection to the second gear 212, since the rotational movement of the first gear is transmitted to the fluid 210th The convection acts on the second gear 212 and moves this vertically upwards. Depending on the configuration of the second gear 212 and / or the connecting link 222, the second gear 212 remains in the second rotational direction 300 by viscous friction completely out of engagement with the first gear 210 or operates similar to a ratchet, by the second gear 212 each of each tooth the first gearwheel is pressed again each time 210 upward.

By switching from the second rotational direction 300 in the first rotational direction 220, the second gear 212 is moved back into engagement with the first gear 210th The initial force to return displacement of the second gear 212 in engagement with the first

Gear 210 may result from the weight force of the second gear 212th The second gear 212 preferably has a higher density than the fluid to be delivered. In addition, from the resulting rotational movement of the convection can displacing the second

Gear 212 again assist in the engagement with the first gear 210th

In addition, the hydraulic conditions are working in the appropriate direction, which favor the maintaining and / or changing the position of the second gear 212th In the first

The direction of rotation 220 builds up a negative pressure, and in the connected with the outlet opening 206, a chamber pressure in the associated with the inlet opening 204 chamber. In the second rotational direction 300, the pressure conditions are reversed.

In FIG. 4, a second embodiment of the pump assembly 200 is shown, which differs from the first embodiment in that the second gear 212 is arranged to be freely movable within the second section 216. The second gear 212 has a slightly higher density than the fluid to be delivered. This allows even a small current, as generated at the periphery of the first gear 210, sufficient to move the second gear 212th

Further, the second gear 212 may be connected with an unillustrated spring member that urges the second gear 212 in the first rotational direction 220 into engagement with the first gear 210th The spring element is designed such that its spring force is less than the force required to displace 210 of the second gear 212 from engagement with the first gear.

Moreover, the second gear 212 may be made of a ferromagnetic or magnetic material. Thereby, the second gear 212 can be actively controlled from outside in order to move the second gear 212 in and / or out of engagement with the first gear 210th Thus, a pump assembly may be provided 200 with a magnetically switchable pumping action. Thus, outside the

Housing 202, an electrically controllable solenoid are arranged, which generates a magnetic field by means of which the second gear 212 can be displaced. This dosing 104 with more than two channels can be built up. The second gear 212 may be made of a ferromagnetic or magnetic material.

Further, the housing 202 may be formed with a locking device in the form of the housing wall 213 projecting projections and / or ribs. This allows areas 217 for the second gear 212, in which the second gear is not intended to relocate, are distinguished from those in which the second gear is intended to relocate 212 within the pump cavity. Thus, the barrier means may be arranged within the pump cavity 217, that a displacement of the second gear 212 is avoided above the first gear 210th

In FIG. 5, a pump arrangement is shown in the form of a Zweikanaldosiersystems 500th The pump assembly 500 includes a first housing 502 having a first inlet opening 504 and a first outlet opening 506, a drive shaft 508, a fixedly connected to the drive shaft 508, first gear 510 and a second gear 512. Further, the pump assembly 500, a second housing 514, the is arranged behind the first housing 502 and a second inlet opening 516 and a second outlet opening 518 comprises a fixedly connected to the drive shaft 508 third gear 520 and a fourth gear 522. The first gear 510 and the third gear 520 are connected to the

Drive shaft 508 connected, so that the second, depending on the direction of rotation of the drive shaft 508 of the first inlet opening 504 to the first port 506 or from the

Inlet opening 516 is conveyed to the second exit opening 518 fluid. The second gear 512 and fourth gear 522 are freely movable within the housing 502, arranged 514, the two gears 512, 522 have a slightly higher density than the fluid to be delivered. This allows even a small current, as generated at the periphery of the first gear 210 or the third gear 520, sufficient to move the second gear 512 or the fourth gear 522nd

Upon rotation of the drive shaft 508 in the second rotational direction 524 is the fourth gear 522 with the third gear 520 engaged so that fluid is conveyed from the second inlet opening 516 to the second outlet opening 518th At the same time in the second rotational direction, the second gear 512 from engagement with the first gear 510, so that no fluid is conveyed from the first inlet opening 504 to the first outlet opening 506th

In the non-illustrated first direction of rotation of the drive shaft 508, the second gear 512 is connected to the first gear 510 in engagement, so that fluid is conveyed from the first inlet opening 504 to the first outlet opening 506th At the same time in the first rotational direction 524 is the fourth gear 522 out of engagement with the third gear 520, so that no fluid from the second inlet opening 516 is conveyed to the second exit opening 518th This can provide a simple and compact Zweikanaldosiersystem that requires only one drive. The inlet openings 504, 516 of the two housings 502, 514 are preferably connected to different reservoirs of Zweikanaldosiersystems. Characterized the detergent from the one or the other reservoir can be conveyed to the dispensing shell and Einspüldusche depending on the direction of rotation.

The pump assembly 200, 500 is characterized in that, despite the reversibility of the driven gear, the fluid can be conveyed with simple and inexpensive means in one direction only, while in the opposite direction of rotation no fluid is promoted. LIST OF REFERENCE NUMBERS

100 Home Appliance

102 shaft

104 dosing

106 Reservoir

200 pump arrangement

202 housing

204 inlet opening

206 outlet opening

208 drive shaft

210 first gear

212 second gear

213 housing wall

214 first section

216 second portion

217 pump cavity

218 bulge

220 first rotational direction

222 backdrop

224 shaft

226 Nut

300 second rotational direction

500 pump arrangement

502 first housing

504 first inlet opening

506 first outlet opening

508 drive shaft

510 first gear

512 second gear

514 second housing

516 second inlet opening

518 second outlet opening third gear fourth gear second rotational direction

vertical direction