Service vehicle for a storage system

1. An automated storage and retrieval system comprising:

a storage grid comprising storage columns arranged in rows, in which storage columns storage containers are stacked one on top of another to form stacks,

a rail system comprising a first set of parallel rails arranged in a horizontal plane and extending in a first direction, and a second set of parallel rails arranged in the horizontal plane and extending in a second direction which is orthogonal to the first direction, which first and second sets of rails form a grid pattern in the horizontal plane comprising a plurality of adjacent grid cells;

at least one container handling vehicle being configured to move on the rail system, wherein the at least one container handling vehicle comprises a wheel arrangement being configured to guide the at least one storage container vehicle along the rail system in at least one of the first direction and the second direction; and

a service vehicle for movement on the rail system, comprising:

a container vehicle handling part for mechanical interacting with the at least one container handling vehicle operating on the rail system,

an operational part for controlling operations of the service vehicle, and

propulsion means,

wherein the propulsion means allow movement of the service vehicle in any direction over the top of the rail system during operation, wherein the propulsion means comprises:

a first caterpillar track comprising a longitudinal extending endless belt,

a second caterpillar track comprising a longitudinally extending endless belt directed parallel to the endless belt of the first caterpillar track,

a belt motor driving the endless belts,

wherein the first and second caterpillar track have, when moving over the top of the rail system an overall length L exceeding the distance across two grid cells in the first direction and the second direction, wherein movement of the caterpillar tracks over the top of the rail system signify that the caterpillar tracks are supported on the rail system, but do not engage with the rails themselves.

2. The automated storage and retrieval system in accordance with claim 1 , wherein the first caterpillar track further comprises

at least one belt wheel contacting the endless belt,

wherein the belt motor is configured to drive the endless belt via the at least one belt wheel, and

the second caterpillar track further comprises

at least one belt wheel contacting the endless belt,

wherein the belt motor is configured to drive the endless belt via the at least one belt wheel.

3. The automated storage and retrieval system in accordance with claim 1 , wherein the first caterpillar track further comprises

at least one belt wheel contacting an inner surface of first endless belt,

wherein the at least one belt wheel has a rotational axis parallel to a rotational axis of the endless belt, and

the second caterpillar track further comprises

at least one belt wheel contacting an inner surface of first endless belt,

wherein the at least one belt wheel has a rotational axis parallel to a rotational axis of the endless belt.

4. The automated storage and retrieval system in accordance with claim 3 , wherein the first caterpillar track and the second caterpillar track are spaced apart by a gap in a direction of the rotational axis of the endless belts.

5. The automated storage and retrieval system in accordance with claim 1 , wherein the container vehicle handling part of the service vehicle comprises

a transfer device configured to transfer at least one container handling vehicle between an operating position on the rail system and a transport position within a vehicle body and

a transfer motor configured to power the transfer device to allow said transfer of the container handling vehicle.

6. The automated storage and retrieval system in accordance with claim 5 , wherein at least part of the transfer device is configured to move between an upper position and a lower position relative to the horizontal plane.

7. The automated storage and retrieval system in accordance with claim 5 , wherein the transfer device is arranged at least partly between the first and second caterpillar tracks.

8. The automated storage and retrieval system in accordance with claim 5 , wherein the transfer device is configured to support the container handling vehicle from below.

9. The automated storage and retrieval system in accordance with claim 5 , wherein the transfer device comprises a base plate onto which the container handling vehicle may be supported.

10. The automated storage and retrieval system in accordance with claim 1 , wherein the operational part of the service vehicle comprises

a propulsion means motor allowing movement of the service vehicle along the horizontal plane and

an operating system allowing an operator to control and regulate both the direction and the speed of the service vehicle relative to the underlying rail system.

11. The automated storage and retrieval system in accordance with claim 1 , wherein the service vehicle further comprises a registration unit being configured to allow visual inspection of the surroundings of the service vehicle.

12. The automated storage and retrieval system in accordance with claim 1 , wherein the service vehicle is arranged for transporting at least one of the at least one container handling vehicle in the horizontal plane and for transporting one or more people.

13. The automated storage and retrieval system in accordance claim 1 , wherein the service vehicle comprises a transmitter for establishing signal communication with a remote control system.

14. The automated storage and retrieval system in accordance with claim 1 , wherein the container vehicle handling part of the service vehicle comprises

a transfer device configured to transfer at least one container handling vehicle between an operating position on the rail system and a transport position within a vehicle body,

wherein the transfer device comprises

an attachment device for releasable attachment to the at least one container handling vehicle,

a vertical linear actuator attached at one end at least indirectly to the vehicle body and the other end at least indirectly to the attachment device,

wherein the vertical linear actuator is configured to displace the attachment device relative to the vehicle body in a vertical direction.

15. A method for operating a service vehicle in the automated storage and retrieval system according to claim 1 ,

wherein the method comprises the following steps:

guiding the service vehicle to a first position on the rail system adjacent to at least one storage container vehicle by operating the operational part,

controlling a transfer device to transfer the at least one container handling vehicle between an operating position on the rail system and a transport position above the rail system and

guiding the service vehicle to a predetermined second position on or outside the rail system.