Patent ID: 8875773

Claim:
A cover device for at least partially closing off an open-top cavity of one of a pit and a pool to prevent items falling into said cavity, the device comprising: at least one cover element for at least partially closing off an opening of the cavity; and a support structure configured to support the cover element, the support structure being an elongate body configured to position the cover element in or close to the cavity along one of sides of the opening of the cavity; and at least one support arm, wherein the cover element is a pneumatic mattress equipped with a mattress return means for urging the mattress back into a most compact configuration in which the mattress is rolled up about a free one of mattress sides and forms a spirally wound roll, the free side about which the mattress is rolled up being formed by the side of the mattress that is opposite from a connecting side of the mattress via which the mattress is connected to the support structure, the mattress being an inflatable mattress so that, by being rolled out, the mattress can move from its rolled-up most compact configuration, in which the mattress is configured to at least partially open up the opening of the cavity to a rolled-out least compact configuration in which is configured to at least partially close the opening of the cavity, and the at least one support arm is configured to support the mattress while the mattress moves from the rolled-up most compact configuration to the rolled-out least compact configuration, the support arm being mounted to move between a stowage position in which the support arm extends substantially parallel to a roll-up axis about which the mattress is rolled up and a working position in which the support arm extends transversely to the roll-up axis.