Patent Description:
<CIT> discloses a service vehicle for movement on a rail system. The service vehicle comprises a container vehicle handling part of mechanical interaction with a container handling vehicle operating on the rail system, an operational part for controlling operations of the service vehicle and caterpillar tracks for allowing movement of the service vehicle on the rail system during operation.

The horizontal extent of one of the grid cells <NUM> constituting the grid pattern is in <FIG> marked by thick lines.

Each grid cell <NUM> has a width which is typically within the interval of <NUM> to <NUM>, and a length which is typically within the interval of <NUM> to <NUM>. Each access opening <NUM> has a width and a length which is typically <NUM> to <NUM> less than the width and the length of the grid cell <NUM> respectively due to the horizontal extent of the rails <NUM>,<NUM>.

The rail system <NUM> may be a single rail system, as is shown in <FIG>. Alternatively, the rail system <NUM> may be a double rail system, as is shown in <FIG>, thus allowing a container handling vehicle <NUM> having a footprint generally corresponding to the lateral area defined by a storage column <NUM> to travel along a row of grid columns even if another container handling vehicle <NUM> is positioned above a grid column neighboring that row. Both the single and double rail system, or a combination comprising a single and double rail arrangement in a single rail system <NUM>, forms a grid pattern in the horizontal plane P comprising a plurality of rectangular and uniform grid locations or grid cells <NUM>, where each grid cell <NUM> comprises a grid opening <NUM> being delimited by a pair of rails 110a,110b of the first rails <NUM> and a pair of rails 111a,111b of the second set of rails <NUM>. In <FIG> the grid cell <NUM> is indicated by a dashed box.

Consequently, rails 110a and 110b form pairs of rails defining parallel rows of grid cells running in the X direction, and rails 111a and 111b form pairs of rails defining parallel rows of grid cells running in the Y direction.

As shown in <FIG>, each grid cell <NUM> has a width Wc which is typically within the interval of <NUM> to <NUM>, and a length Lc which is typically within the interval of <NUM> to <NUM>. Each grid opening <NUM> has a width Wo and a length Lo which is typically <NUM> to <NUM> less than the width Wc and the length Lc of the grid cell <NUM>.

In the X and Y directions, neighboring grid cells are arranged in contact with each other such that there is no space therebetween.

The stacks <NUM> of containers <NUM> are typically selfsupportive.

Each prior art container handling vehicle <NUM>,<NUM> also comprises a lifting device (not shown) for vertical transportation of storage containers <NUM>, e.g. raising a storage container <NUM> from, and lowering a storage container <NUM> into, a storage column <NUM>. The lifting device comprises one or more gripping / engaging devices which are adapted to engage a storage container <NUM>, and which gripping / engaging devices can be lowered from the vehicle <NUM>,<NUM> so that the position of the gripping / engaging devices with respect to the vehicle <NUM>,<NUM> can be adjusted in a third direction Z which is orthogonal the first direction X and the second direction Y. Parts of the gripping device of the container handling vehicle <NUM> are shown in <FIG> indicated with reference number <NUM>. The gripping device of the container handling device <NUM> is located within the vehicle body 201a in <FIG>.

The storage volume of the framework structure <NUM> has often been referred to as a grid <NUM>, where the possible storage positions within this grid are referred to as storage cells. Each storage column may be identified by a position in an X- and Y-direction, while each storage cell may be identified by a container number in the X-, Y and Z-direction.

Such a vehicle is described in detail in e.g. NO3 <NUM>.

The central cavity container handling vehicles <NUM> shown in <FIG> may have a footprint that covers an area with dimensions in the X and Y directions which is generally equal to the lateral extent of a storage column <NUM>, e.g. as is described in <CIT>.

The term 'lateral' used herein may mean 'horizontal'.

<CIT>, illustrates a typical configuration of rail system <NUM> comprising rails and parallel tracks in both X and Y directions.

The access station may typically be a picking or a stocking station where product items are removed from or positioned into the storage containers <NUM>. In a picking or a stocking station, the storage containers <NUM> are normally not removed from the automated storage and retrieval system <NUM>, but are returned into the framework structure <NUM> again once accessed. A port can also be used for transferring storage containers to another storage facility (e.g. to another framework structure or to another automated storage and retrieval system), to a transport vehicle (e.g. a train or a lorry), or to a production facility.

This step, which is sometimes referred to as "digging" within the art, may be performed with the same container handling vehicle <NUM>,<NUM> that is subsequently used for transporting the target storage container <NUM> to the drop-off port column <NUM>, or with one or a plurality of other cooperating container handling vehicles <NUM>,<NUM>. Alternatively, or in addition, the automated storage and retrieval system <NUM> may have container handling vehicles <NUM>,<NUM> specifically dedicated to the task of temporarily removing storage containers <NUM> from a storage column <NUM>. Once the target storage container <NUM> has been removed from the storage column <NUM>, the temporarily removed storage containers <NUM> can be repositioned into the original storage column <NUM>. However, the removed storage containers <NUM> may alternatively be relocated to other storage columns <NUM>.

When a storage container <NUM> is to be stored in one of the columns <NUM>, one of the container handling vehicles <NUM>,<NUM> is instructed to pick up the storage container <NUM> from the pick-up port column <NUM> and transport it to a location above the storage column <NUM> where it is to be stored. After any storage containers <NUM> positioned at or above the target position within the stack <NUM> have been removed, the container handling vehicle <NUM>,<NUM> positions the storage container <NUM> at the desired position. The removed storage containers <NUM> may then be lowered back into the storage column <NUM>, or relocated to other storage columns <NUM>.

ASRS vehicles according to prior art are guided on rails in the first and second directions, X,Y, on the rail system and have wheel drive on at least some of the wheels. However, the traction of the drive wheels on the rails is dependent on sufficiently clean rails and wheels with minimum dust or spill, in order not to spin either during acceleration and deceleration and/or performing heavy lifting requiring good traction to be able to transport a heavy bin, operator or a container handling vehicle.

It is thus an objective of the invention to provide a vehicle with increased traction with the rail system.

<CIT>, in accordance with its abstract, discloses 'a service vehicle for movement on a rail system. The service vehicle comprises a container vehicle handling part for mechanical interacting with a container handling vehicle operating on the rail system, an operational part for controlling operations of the service vehicle and caterpillar tracks for allowing movement of the service vehicle on the rail system during operation.

The invention relates to a vehicle for operation on an automated storage and retrieval system, the automated storage and retrieval system comprising a two-dimensional rail system comprising a first set of parallel rails arranged to guide movement of container handling vehicles in a first direction X across the top of a frame structure, and a second set of parallel rails arranged perpendicular to the first set of rails to guide movement of the container handling vehicles in a second direction Y which is perpendicular to the first direction X, where the vehicle comprises a wheeled base, wherein the wheeled base comprises:.

The combination of the non-motorized guiding wheels and motorized belt drive renders possible movement along the tracks through guidance by the guiding wheels and drive from the belt drive. The increased contact area provided by the belt drive as compared to traditional drive wheels is advantageous i. a because the risk of slip on the rail surface is reduced.

In other words, the invention relates to a vehicle with passive non-motorized guiding wheels for guidance/support and one or more belt drives which can be drive belt(s) for driving or moving the vehicle in the first and/or second directions X, Y of a rail system. The belt drive can be: <NUM>) arranged in the same direction as the direction of travel of the vehicle and engaging tracks in the same direction, either between the wheels or in center of the vehicle, or <NUM>) arranged in the same direction as the direction of travel of the vehicle but engaging racks arranged in a <NUM> degrees orientation relative the direction of travel.

The vehicle can be a service vehicle. The service vehicle may have various functions, such as e.g. used in rescuing container handling vehicles that has malfunctioned or in rail cleaning purposes etc. In addition, in service operations, increased traction may be required.

Alternatively, the vehicle can be a container handling vehicle with a container lifting device where a requirement of increased traction is of more importance than the acceleration/deceleration and maximum speed of the container handling vehicle. Such a container handling vehicle may e.g. be a container handing vehicle comprising a number of container lifting devices, where the container handling vehicle is adapted to carry multiple storage containers such that it may be a relatively heavy container handling vehicle if carrying maximum amount of storage containers. An example of a multi-bin vehicle capable of carrying multiple storage containers is described in publication <CIT> (Autostore AS), the contents of which are incorporated herein by reference. Referring to e.g. Fig. <NUM> in <CIT> it is shown a container handling vehicle with two lifting devices such that it can carry two storage containers at the same time. Further referring to Figs. <NUM>-<NUM> in <CIT> it is shown a container handling vehicle with four lifting devices such that it can carry four storage containers at the same time.

The vehicle may further comprise a second motorized belt drive arranged for frictional contact with a rail of the rail system for driving the vehicle in the other of the first direction X or second direction Y.

The vehicle may comprise more than one belt drive in the X direction and/or more than one belt drive in the Y direction.

The wheeled base may be an assembly of wheel base units. For example, the wheeled base may comprise two identical wheel base units separated by an intermediate wheel base unit. The identical wheel base units may be mirrored relative the intermediate wheel base unit and both may comprise non-motorized guiding wheels in the first and second directions X,Y as well as first motorized belt drives in the first and second directions X,Y.

The vehicle further comprises a track shift mechanism on the wheeled base for lifting and lowering one of the sets of guiding wheels relative the other set of guiding wheels, and the track shift mechanism may comprise a mechanical linkage to lift and lower the belt drive for use with the set of guiding wheels associated with the track shift mechanism.

This mechanical linkage enables that the displacement of the set of guiding wheels and the belt drive in the same direction is synchronized. Synchronized displacement is advantageous because both the guiding wheels and the belt drive(s) in the same direction needs to be in contact with the underlying rail system in order for guided movement along the rails. Similarly, both the guiding wheels and the belt drive(s) oriented perpendicular to the driving direction of the vehicle need to be lifted up from the rails for the vehicle to be able to move in the driving direction.

If the vehicle comprises a first and a second belt drive, the track shift mechanism can be connected to the first or the second belt drive.

The vehicle may comprise a plate member connected to the mechanical linkage, and the belt drive can be mounted on the plate member such that vertical displacement of the plate member via the mechanical linkage engages and disengages the belt drive relative the rail system. The plate member allows alignment of the two pulleys wheels so that the belt drive runs parallel to the upper surface of the rail.

The vehicle may further comprise a number of pulley wheels mounted on the plate member, and the pulley wheels may have a rotational axis in a horizontal plane. The first motorized belt drive may be guided around said pulleys such that when the vehicle operates on a rail system, the belt drive runs parallel to the upper surface to the first or second set of parallel rails. The vehicle may comprise a mirrored plate member, pulley wheels and belt drive on an opposite side of the vehicle in order to provide a straight movement with reduced risk of skewed drag of the vehicle.

The vehicle may further comprise a tensioning jockey wheel mounted on the plate member. The belt drive may be guided around said tensioning jockey wheel and the pulley wheels.

The vehicle may further comprise a belt drive motor, and the belt drive motor can be mounted on the plate member.

The pulley wheels may be of the same size as the first and second sets of non-motorized guiding wheels. This ensures that the displacement per rotation is the same. In addition, this may simplify manufacturing of the parts as it could allow existing parts to be used.

The plate member, the number of pulleys, the tensioning jockey wheel, the belt drive and the belt drive motor may form a belt drive unit, i.e. the assembly of these components can form a belt drive unit.

The at least one belt drive in the first direction X and/or the at least one belt drive in the second direction Y may be arranged within a horizontal area of the wheeled base in the first direction X and the second direction Y.

In other words, the belt(s) is not extending outside the wheeled base.

A contact surface of the motorized first or second belt drive could have a length of <NUM>% or more of a grid cell in contact with the underlying rail.

The belt drive can be profiled in order to provide a better grip on the underlying rail. In order to provide as large contact area as possible between the belt drive and the underlying rail, the belt drive preferably grip the base of the track. Alternatively, the belt drive can grip the top of the rail and/or both the base of the rail and the top of the rail.

If there is just one belt drive in the first and/or second direction X,Y, this one belt drive is preferably positioned towards the middle and under the main centre of mass of the vehicle to minimise torque and rubbing of the guiding wheels as the vehicle accelerates /decelerates.

The wheeled base may comprise an opening for receiving a container handling vehicle that has been malfunctioning or requires service.

When a malfunctioning container handling vehicle is arranged within the opening, the vehicle may encircle the container handling vehicle from at least three sides.

The opening in the vehicle thus may provide a dock within the wheeled base for receiving the container handling vehicle. In order for the opening to be able to accommodate a container handling vehicle, the size of the opening may be equal to or greater than the size of a grid cell.

The vehicle may further comprise a lifting arrangement for lifting the container handling vehicle off the rail system.

The lifting arrangement may comprise at least two lifting mechanisms arranged on opposite sides of the opening and each of the lifting mechanisms may comprise means for engaging a connection interface on the container handling vehicle when the container handling vehicle is arranged in the opening.

When engaged, the lifting mechanisms may lift the container handling vehicle off the rail system. As an alternative to a lifting arrangement comprising at least two lifting mechanisms on opposite sides of the opening, the lifting arrangement can comprise a hook, claw or similar for engaging a complementary lifting ear(s) or hook(s) on an upper surface or on any side surface(s) of the container handling vehicle.

The vehicle may comprise a platform for supporting a container handling vehicle from below.

When the container handling vehicle has been lifted using the lifting mechanisms, it may be positioned on the platform of the vehicle for maintenance and/or repair on site or at a service area off the rail system where the container handling vehicles operate.

The vehicle may comprise a cleaning arrangement comprising at least one cleaning device for cleaning the rails in the first direction X or the second direction Y.

The cleaning arrangement may be a vacuum cleaner, scrub, spray device etc. suitable for cleaning the rails. The cleaning arrangement can be positioned on the wheeled base, possibly between the guiding wheels or in a center of the wheel base if the wheeled base covers <NUM> or more grid cells. The cleaning arrangement may comprise cleaning devices in the first direction X and/or in the second direction Y. Alternatively, the cleaning device can be arranged on top of the wheel base and be operated automatically or manually by an operator.

The vehicle may further comprise a ride-on device for transporting an operator. The ride-on device may be a chair.

The vehicle may comprise communication means for communication with a control system.

The control system is preferably the same control system that the container handling vehicles operate under, such that the vehicle is added to the control system as a normal container handling vehicle thereby minimizing the risk of collision with the other container handling vehicles on the rail system.

It is further described an automated storage and retrieval system comprising a two-dimensional rail system comprising a first set of parallel rails arranged to guide movement of container handling vehicles in a first direction X across the top of a frame structure, and a second set of parallel rails arranged perpendicular to the first set of rails to guide movement of the container handling vehicles in a second direction which is perpendicular to the first direction, wherein the automated storage and retrieval system further comprises a number of container handling vehicles and at least one vehicle as defined above.

It is further described a method of moving a vehicle as defined above on a rail system of an automated storage and retrieval system, wherein the method comprises using the belt drive to drive the vehicle and the first and second sets of non-motorized guiding wheels for guiding the vehicle on the rail system.

It is further described a method of cleaning a rail system using a vehicle as defined above, wherein the vehicle comprises a cleaning device.

It is further described a method of rescuing a malfunctioning container handling vehicle using a vehicle as defined above, wherein the vehicle comprises a lifting arrangement for lifting the malfunctioning container handling vehicle off the rail system.

The relative terms "upper", "lower", "below", "above", "higher" etc. shall be understood in their normal sense and as seen in a cartesian coordinate system.

Summarized, the invention provides a vehicle with increased traction against the underlying rail system in that wheels are used for guiding and belt drive is used for movement of the vehicle.

<FIG> show an example of a vehicle <NUM> in the form of a service vehicle <NUM> with a lifting mechanism for engaging and supporting a malfunctioning container handling vehicle <NUM> with a cantilever section <NUM>. The lifting mechanism <NUM> is arranged for engaging the container handling vehicle <NUM> at a connection point or surface <NUM> in a lower portion of the cantilever section <NUM> such as to lift the container handling vehicle <NUM> off the rail system <NUM>.

In <FIG> the connection point or surface <NUM> is arranged on an underside of the cantilever section <NUM> of the container handling vehicle <NUM>. The container handling vehicle <NUM> comprises a wheel arrangement comprising a first set of wheels 32a for driving the vehicle <NUM> in the first direction X and a wheel arrangement comprising a second set of wheels 32b for driving the vehicle <NUM> in the second direction Y on the rail system <NUM>.

The vehicle <NUM> of <FIG> comprises a wheeled base <NUM> comprising a first set of non-motorized guiding wheels 42a for interaction with the rails 110a,b in the first direction X and a second set of non-motorized guiding wheels 42b for interaction with the rails 111a,b in the second direction Y. The wheeled base <NUM> is shown with an opening <NUM> for receiving the container handling vehicle <NUM>. The container handling vehicle <NUM> may be malfunctioning or require service.

The lifting arrangement is disclosed with two lifting mechanisms <NUM> arranged on opposite sides of the opening <NUM>. Each of the lifting mechanisms <NUM> comprises means for engaging the container handling vehicle <NUM> when the container handling vehicle <NUM> is arranged in the opening <NUM>. The means for engaging the container handling vehicle <NUM> may be a support rib <NUM> or shoulder for contacting the connection interface <NUM> on the underside of the cantilever section <NUM>. The lifting arrangement may comprise an actuator, rack and pinion arrangement or other known hoisting mechanism known to the skilled person to raise and lower the support rib <NUM> relative the wheeled base <NUM>.

As is shown in <FIG>, the opening <NUM> is formed by three sides of the wheeled base <NUM> such that when a malfunctioning container handling vehicle <NUM> is arranged within the opening, the vehicle <NUM> encircles the container handling vehicle <NUM> from three sides.

The vehicle <NUM> is disclosed with a ride-on device <NUM> for transporting an operator.

The vehicle <NUM> is disclosed with a platform <NUM> for supporting a container handling vehicle <NUM> from below. An operator may move the container handling vehicle <NUM> between the lifting arrangement and the platform <NUM>. Alternatively, a dedicated lift (not shown) can be arranged to move the container handling vehicle <NUM> between the lifting arrangement and the platform <NUM>.

Referring to <FIG> a perspective view of the service vehicle <NUM> and the container handling vehicle <NUM> is shown. No container handling vehicle <NUM> is arranged within the opening <NUM>. In this figure, the container handling vehicle <NUM> has malfunctioned and the service vehicle <NUM> has been positioned in a cell close to the container handling vehicle <NUM>. The opening <NUM> is oriented in a direction towards a back of the container handling vehicle <NUM> such that the container handling vehicle <NUM> can be encircled once the service vehicle <NUM> moves closer in the second direction Y towards the container handling vehicle <NUM>.

Referring to <FIG>, the relative positions of the vehicle <NUM> and the container handling vehicle <NUM> are similar to <FIG>, however in <FIG> it is shown a side view from behind the vehicle <NUM>.

In <FIG> a similar view as in <FIG> is shown, however in <FIG> the container handling vehicle <NUM> is positioned within the opening <NUM> of the wheeled base <NUM>. <FIG> shows more details of the lifting mechanism <NUM> and the support ribs <NUM> relative the connection interface <NUM> on the underside of the cantilever section <NUM> of the container handling vehicle <NUM>. The vehicle body 301a of the container handling vehicle <NUM> has a smaller extent in the first direction X than the cantilever section <NUM>. The distance between the support ribs <NUM> is larger than the extent of the vehicle body <NUM> but smaller than the extent of the cantilever section <NUM>. In particular, as is seen in <FIG>, the two support ribs <NUM> on the opposite sides of the opening <NUM> are arranged in such a distance that the vehicle body 301a of the container handling vehicle <NUM> may enter, i.e. the distance in the first direction X between the support ribs <NUM> is greater than the extent of the vehicle body <NUM> in the first direction X. Furthermore, the cantilever section <NUM> has a greater extent in the first direction X than the distance between the support ribs <NUM> such that if the support ribs <NUM> are raised, they will engage the underside of the cantilever section <NUM> such that the container handling vehicle <NUM> can be lifted off the rail system <NUM>.

<FIG> is a similar view as <FIG>, however in <FIG> the container handling vehicle <NUM> has been lifted off the rail system <NUM> using the lifting mechanism <NUM>.

As seen in the Figure, the support ribs <NUM> are arranged in contact with the underside <NUM> of the cantilever section <NUM>.

<FIG> is a perspective view from the opposite side of <FIG> showing that the container handling vehicle <NUM> has been lifted off the rail system <NUM>.

<FIG> show an example of a vehicle <NUM> in the form of a service vehicle <NUM> with a lifting mechanism <NUM> for engaging and supporting a malfunctioning container handling vehicle <NUM> with a cantilever section <NUM>, and wherein the lifting mechanism is arranged for engaging the container handling vehicle <NUM> at a connection point or surface <NUM> in an upper portion or above the cantilever section <NUM>.

Similar to the solution in <FIG>, the lifting arrangement is disclosed with two lifting mechanisms <NUM> arranged on opposite sides of the opening <NUM>. Each of the lifting mechanisms <NUM> comprises means for engaging the container handling vehicle <NUM> when the container handling vehicle <NUM> is arranged in the opening <NUM>. The means for engaging the container handling vehicle <NUM> may be a support rib <NUM> or shoulder for contacting the connection interface <NUM> on the underside of the cantilever section <NUM>. The lifting arrangement may comprise an actuator, rack and pinion arrangement or other known hoisting mechanism known to the skilled person to raise and lower the support rib <NUM> relative the wheeled base <NUM>. The only difference between the service vehicle <NUM> of <FIG> compared to the service vehicle <NUM> of <FIG> is that the support ribs <NUM> of the service vehicle <NUM> in <FIG> are configured to engage a connection interface <NUM> on or above the cantilever section <NUM> of the container handling vehicle <NUM>. This is due to the that the extent of the vehicle body 301a and the cantilever section <NUM> is equal or near equal such that the construction of container handling vehicle <NUM> does not provide a suitable connection interface <NUM> for engagement with the support ribs <NUM> of the lifting mechanism <NUM>. The connection interface <NUM> extends beyond the vertical projection of the cantilever section <NUM> and can be a plate or rib connected to an upper surface of the cantilever section <NUM> or it can be formed as an integral part of the cantilever section <NUM>.

<FIG> is analogue o <FIG>, <FIG> is analogue to <FIG>, <FIG> is analogue to <FIG> and <FIG> is analogue to <FIG> and will not be described in greater detail herein.

<FIG> show details of a single wheel base unit which can form part of wheeled base <NUM> of the vehicle <NUM> shown in <FIG> and <FIG>.

In <FIG>, the wheel base unit is an example of the wheel base unit on the left hand side of e.g. <FIG> and <FIG>. It is shown a potential setup of the track shift mechanism <NUM> for the wheels. The track shift mechanism <NUM> is arranged on the wheeled base <NUM> for lifting and lowering the second set of guiding wheels 42b relative the first set of guiding wheels 42a. The track shift mechanism <NUM> comprises a mechanical linkage or rocker <NUM> to lift and lower the belt drive 43b for use with the second set of guiding wheels 42b associated with the track shift mechanism <NUM>. The vehicle <NUM>, i.e. the wheeled base <NUM>, is disclosed with a plate member <NUM> connected to the mechanical linkage <NUM>. The second motorized belt drive 43b is mounted on the plate member <NUM> such that vertical displacement of the plate member <NUM> via the mechanical linkage <NUM> engages and disengages the belt drive 43b relative the rail system <NUM> when the second set of guiding wheels is engaged and disengaged relative the rail system <NUM>. It is further disclosed a number of pulley wheels 41a,41b mounted on the plate member <NUM>. The pulley wheels 41a,41b have a rotational axis in a horizontal plane and the motorized belt drive 43b is guided around said pulleys 41a,41b such that when the vehicle <NUM> operates on a rail system <NUM>, the belt drive 43b runs parallel to the upper surface to the first or second set of parallel rails 111a,b. As shown in <FIG>, the pulley wheels 41a,41b are shown to be of the same size as the second set of non-motorized guiding wheels 42b.

It is further disclosed a tensioning jockey wheel 41c mounted on the plate member <NUM>. The belt drive 43b is guided around said tensioning jockey wheel 41c and the pulley wheels 41a,41b.

It is also disclosed a belt drive motor <NUM> for driving the belt drive 43b, the belt drive motor <NUM> is mounted on the plate member <NUM>.

All components mounted on the plate member <NUM> may form a belt drive unit, i.e. the plate member <NUM>, the number of pulleys 41a,41b, the tensioning jockey wheel 41c, the belt drive 43b and the belt drive motor <NUM>.

A similar arrangement of a belt drive unit may be provided for driving the vehicle <NUM> in the perpendicular direction along the first set of rails 110a,b (see e.g. <FIG>). As shown in <FIG> it is disclosed a plate member <NUM> that may form part of a belt drive unit, i.e. the plate member <NUM>, the number of pulleys 41a,41b, the tensioning jockey wheel 41c, the belt drive 43a and the belt drive motor <NUM>. Further referring to <FIG>, it is disclosed two wheel base units. The wheeled base <NUM> may, as illustrated in <FIG> comprise two identical wheel base units. The identical wheel base units may be separated by an intermediate wheel base unit (not shown in <FIG>). The identical wheel base units may be mirrored relative the intermediate wheel base unit and both wheel base units may comprise non-motorized guiding wheels 42a,42b in the first and second directions X,Y as well as first motorized belt drives 41a,41b in the first and second directions X,Y.

<FIG> is an enlarged view of wheel base unit on the left hand side in <FIG> and show some more details of the belt drive unit as well as a wheel shaft <NUM> connected to the track shift mechanism <NUM> for synchronous trackshift of both wheels connected to the wheel shaft <NUM>. This setup ensures synchronous operation of the track shift mechanism <NUM> of all wheels in the same second direction Y and the belt drive 43b.

<FIG> show top views of a vehicle <NUM> in the form of a cleaning vehicle <NUM> where the vehicle body has been omitted on purpose, the vehicle <NUM> having cleaning devices for cleaning the rails in the first direction X and the second direction Y. The cleaning vehicle <NUM> is shown covering 2x2 cells, i.e. four cells in total. The setup of the cleaning vehicles <NUM> in <FIG> and <FIG> are similar, except for the fact that: in <FIG> the belt drives 43a,43b are arranged in the same direction as the direction of travel of the vehicle <NUM> and engages rails 110a,110b,111a,111b in the same direction, whereas in <FIG> the belt drives 43a,43b are arranged in the same direction as the direction of travel of the vehicle <NUM> but engages rails 110a,110b,110a,<NUM> arranged in a <NUM> degrees orientation relative the direction of travel. The extent of the belt drives 43a,43b of <FIG> shall at least be equal to or greater than the distance between neighboring rails 110a,11b; 111a,11b in the same direction, respectively.

In <FIG>, it is two first motorized belt drives 43a in the first direction X whereas there is one second motorized belt drive 43b in the second direction Y. This is due to the fact that both belt drives 43a,43b cannot be arranged in the very centre of the vehicle <NUM> as the vehicle <NUM> would not be able to move. Therefore, the belt drive 43a in the first direction X has been split into two belt drives 43a one each side of the second motorized belt drive 43b. In this embodiment it is advantageous to provide the track shift mechanism <NUM> on the second sets of wheels 42b and consequently on the second motorized belt drive 43b such that one does not have to lift and lower both of the first motorized belt drives 43a.

The belt drives 43a, 43b in <FIG> are positioned towards the middle and under the main centre of mass of the vehicle <NUM> to minimise torque and rubbing of the guiding wheels 42a,42b as the vehicle accelerates /decelerates.

The cleaning vehicle <NUM> in both <FIG> and <FIG> is disclosed with a cleaning arrangement comprising a cleaning device 44a for cleaning the rails 110a,110b in the first direction X and a cleaning device 44b for cleaning the rails 111a,11b in the second direction Y. The cleaning devices 44a are for cleaning the rails 110a,b in the first direction X whereas the cleaning devices 44b are for cleaning the rails 111a,b in the second direction Y. The cleaning devices 44a,44b are shown as being positioned between the wheels 43a,43b and in the center of the cleaning vehicle <NUM> for cleaning all covered rails 110a,b;111a,b in the direction of travel.

The rail system shown in <FIG> is a double rail system.

Claim 1:
A vehicle (<NUM>) for operation on an automated storage and retrieval system (<NUM>), the automated storage and retrieval system (<NUM>) comprising a two-dimensional rail system (<NUM>) comprising a first set of parallel rails (110a,b) arranged to guide movement of container handling vehicles (<NUM>) in a first direction (X) across the top of a frame structure (<NUM>), and a second set of parallel rails (111a,b) arranged perpendicular to the first set of rails (110a,b) to guide movement of the container handling vehicles (<NUM>) in a second direction (Y) which is perpendicular to the first direction (X), where the vehicle (<NUM>) comprises a wheeled base (<NUM>), wherein the wheeled base comprises:
- a first set of non-motorized guiding wheels (42a) for interaction with the rails (110a,b) in the first direction (X) and a second set of non-motorized guiding wheels (42b) for interaction with the rails (111a,b) in the second direction (Y); and
- a first motorized belt drive (43a) arranged for frictional contact with a rail (110a,b, 111a,b) of the rail system (<NUM>) for driving the vehicle (<NUM>) in either one of the first direction (X) or the second direction (Y) characterised in that it further comprises a track shift mechanism (<NUM>) on the wheeled base (<NUM>) for lifting and lowering one of the sets of guiding wheels (42a,42b) relative the other set of guiding wheels (42b,42a), and wherein the track shift mechanism (<NUM>) comprises a mechanical linkage (<NUM>) to lift and lower the belt drive (43a,43b) for use with the set of guiding wheels (42a,42b) associated with the track shift mechanism (<NUM>).