What is the ruling on the money paid by the Takaful Fund to members of the Laboratory Syndicate upon death or disability, knowing that the fund collects small amounts from its members and pays larger amounts to those affected, and preserves the surplus money in an Islamic bank without investment?

It appears that this fund is indeed a takaful (mutual solidarity) fund, as its purpose is to assist the subscribers, not to make a profit or engage in speculation. Rather, its intent is cooperation when a problem or incapacity befalls one of the subscribers, regardless of balancing the value paid against the value benefited. Therefore, there is no harm in subscribing to it or benefiting from its funds.