In Research Disclosure RD647081 of 22 February 2018 a rack serving shuttle was described with containment strips 6 to keep tray 2 fixed in position when the shuttle 1 accelerates. These strips 6 are pre-tensioned by springs in order to allow for a constant downward force on the top edge of the tray. This downward force, together with the weight of the tray gives an increased amount of friction. In its turn, this will increase the level of acceleration at which the tray can be moved with the toad handling device of the shuttle. This pre-stressing device has been applied successfully since then.The device as described has the disadvantage that it works on the top edge of the tray. As a result, only one height of tray can be used in a system where all shuttles are identical. A different height requires a different variant of the device. Therefore the pre-stressing device has to be adapted every time a new height of tray is requested by a customer. This obviously increases the cost of the device and the lead time of projects.
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