Abstract: A filter having a device for countering the clogging of the filter for a fluid, in particular a liquid, includes a filtering element arranged in a filter cavity bounded by an outer casing, an ultrasound emitter coupled into the cavity, in the direction of the filtering element, in order to prevent the filtering element from becoming clogged during operation of the filter.

Abstract: A stretcher comprises an upper sheet and a lower sheet selectively joined together to form a plurality of transverse sleeves. In combination, a plurality of slats having a length greater than the transverse dimension of the sleeves are removably retainable within the transverse sleeves. The slats are provided at their end portions located outside said sleeves with handles to permit transporting of the stretcher. Alternatively, the stretcher comprises a sheet having on one of its surfaces strips (16) of hook and loop type elements, in combination with a plurality of slats that are longer than the width of the sheet. The slats have hook and loop type fasteners adapted to cooperate to removably attach the slats to the hook and loop type fastener strips on the sheet. The said slats have handles at their end portions, spaced from the edges of the sheet, to permit transporting of the stretcher.