Abstract: A baler comprises a container with an upper open end, a lid hinged on a rear upper edge of the container and a platen mounted on the lid for compressing the material to be baled. The platen slides up and down through a hole in the lid, and hydraulic rams are used for lowering and raising the platen and for lifting and lowering the lid together with the platen. The container has an upper front door which is hinged at its lower end on a horizontal axis and there is a linkage between the lid and the door so that when the lid and platen are pivoted upwardly and rearwardly, the door pivots downwardly and forwardly, with the result that a hopper mouth of large area is formed into which the material to be baled can be placed.