Drum with plastic built-up housing

The present invention relates to a drum for tanning, dyeing and/or treating hides and/or fabrics.

In more detail, this drum comprises a plastic housing of essentially cylindrical shape consisting of a side wall closed at each end by an end wall, so as to define an internal cavity.

In one known such drum, the side wall is made by first rolling and then welding a sheet of polypropylene homopolymer (PPH).

However, these welds are a structural weakness, being susceptible to failure following heat stress and fatigue stress. Moreover, there is only a limited number of plastics that are weldable, which greatly limits the choice of constituent materials.

To overcome these problems, the subject of the present invention is a drum of the type indicated at the beginning of this description and characterized in that said side wall is made up of a plurality of juxtaposed staves, in that a first seal is placed between each pair of adjacent staves, in that another seal extending in the circumferential direction is placed between the outer circumferential edge of each end wall and said side wall, and in that fixing means keep said side wall and end walls assembled together.

The drum of the invention has no welds and therefore has a longer life than conventional drums, not being subject to thermal stress failure and fatigue stress failure. In addition, the choice of materials for its construction is not limited by the necessity that they should be weldable. For example, it is possible to use various types of polyethylene (HDPE, especially VHMWPE and UHMWPE, and crosslinked PE), polypropylene, polyamide optionally reinforced with fibres and/or fillers and in general any thermoplastic that is resistant to chemical attack and abrasion and that has a low coefficient of friction.

It should also be noted that, unlike a drum with a welded plastic housing, the drum of the invention can be assembled directly at the place of use, which obviously saves on transport costs and reduces logistical problems, which become magnified as the size of the drum increases.

Further advantages and features of the present invention will be made evident in the following detailed description, which is provided by way of non-restrictive example with reference to the appended drawings, in which:

• figure 1 is a diagrammatic perspective view of a drum of the invention,
• figure 2 is a cutaway perspective view of a drum of the invention,
• figure 3 is a view on an enlarged scale of a detail of the drum of the invention, and
• figure 4 is a view in section taken on the line marked IV-IV in Figure 3.

A drum for tanning, dyeing and/or treating hides and/or fabrics in the wet condition comprises (Figs. 1 and 2) a plastic housing 10 of essentially cylindrical form, mounted rotatably about its longitudinal central axis 12 and consisting of a side wall 14 closed at each end by an end wall 16, so as to define an internal cavity 18. The drum is also provided, as in the prior art, with drive means for turning it about the axis 12. These will not be described further as they are not relevant to an understanding of the invention.

The side wall 14 is made up of a plurality of juxtaposed staves 20. Each of the latter is of parallelepiped form having in plan view a rectangular shape whose perimeter is formed by a pair of long sides 22 and a pair of short sides 24. The long sides 22 are parallel to the central axis 12. In addition, one of the faces which define the thickness of the stave 20 has a groove 26 in which a first seal 28, which extends in a parallel direction to that of the axis 12, is housed (Figs 3 and 4).

Each end wall 16 is of circular form and has a circumferential groove 30 around its edge in which a second seal 32 is housed. Each end wall 16 is made up of a number of juxtaposed parts in the shape of circular segments. In particular, there may be three of these parts, namely two outer parts 34 and one intermediate central part 36. A groove 40 formed in the chord side 38 of each outer part 34 houses a third seal 42.

The various seals 28, 32 and 42 are advantageously made of a material that has a high compression set, is resistant to chemical agents, and whose properties are substantially constant under temperature variations.

The drum also comprises (Fig. 1) fixing means that keep the side wall 14 and end walls 16 assembled together. These fixing means are placed on the outside of the side wall 14 and comprise a plurality of cables 44 arranged at different points in the axial direction, around the side wall in such a way as to enclose it circumferentially. Each cable 44 is provided with tensioning means 46 of a type known in the art, for example with screws, which make it possible to tension the cable so that it exerts a radial compressive action on the side wall 14, keeping the staves 20 and the component parts 34, 36 of the end walls 16 assembled together.

In this assembled condition, the various seals 28, 32, 42 hermetically seal each gap between the various component elements of the housing 10, thereby ensuring that the internal cavity 18 is hermetically sealed and enabling the drum to operate correctly.

Clearly, without departing from the principle of the invention, the details of construction and forms of embodiment may depart considerably from those described purely by way of example, without thereby departing from the scope of the claims. In particular, the drum may be of a fixed type rather than being mounted so as to rotate about its central axis, and may or may not comprise any type of internal member, such as blades, agitators and the like.