The present invention relates to an improved drum assembly for washing, drying machines, and the like, as well as a method for making said drum assembly.
The drum assemblies of the type concerned by the present invention conventionally comprise a body of substantially drum configuration. This drum body is formed by a perforated metal band constituting the cylindric wall of the drum body, by a rear closure disc for closing the drum body, which supports the cross member supporting the shaft of the drum, and a front ring element defining the front loading mouth therethrough the cloth articles to be processed are loaded into the drum. In the case of a top loading, on the other hand, the front ring element is replaced by a closing cover, whereas the side band is provided with an opening for introducing the cloth articles into the drum.
In order to provide an efficient tumbling of the cloth articles to be washed or dried, on the inside surface of the perforated metal band forming the cylindric wall of the drum are provided a plurality of projections, having a substantially wedge-like cross section, which operate as xe2x80x9centrainmentxe2x80x9d elements. Actually, owing to the provision of these projections, the rotary movement applied to the drum assembly will cause the linen loaded therein to be upwardly entrained and fall by gravity, thereby aiding the washing operation.
The provision of the above mentioned projections, which will be hereinafter called xe2x80x9cwedge elementsxe2x80x9d, causes, however, problems or difficulties in properly coupling the metal band and ring element or front cover. Because of the provision of the mentioned wedge elements, in fact, the edge or rim of the mentioned metal band will have an uneven contour, which, on the other hand, must be perfectly fitted or mated with the contour of the ring element or front cover of the drum.
Prior solutions for providing such a connection include the use of spot welding operations between the respective walls of the ring or front cover element and the drum wedge elements, formed on the corresponding surface engagement portions. Such a spot welding method, however, could alter or modify the required chemical-physical properties of the drum material (chromium stainless steel, AISI 430), which is would be seriously affected by a thermal treatment like that deriving from a spot welding operation. On the other hand, this spot welding operation, which must involve a number as low as possible of regions of the drum, does not provide a connection having the desired strength and duration. In fact, the welding spots do not provide a structurally continuous connection and, moreover, as stated, could undesirably modify the drum material thereby favoring oxidation phenomena which would be very dangerous for the time stability of the performed connection.
In addition to the above mentioned drawbacks, to weld the front ring element or cover on the wedge elements of the drum is disadvantageous since it does not allow a proper centering of these elements. Actually, as the welding operation is performed, the ring or cover element can be displaced from a proper position centered with respect to the cylindric band on which they must be locked, thereby the end product may be affected by openings or undesired gaps between the connected portions.
To the foregoing it should be added that for welding the drum, additional welding materials and power are required, thereby increasing the end cost of the drim assembly.
Accordingly, the aim of the present invention is to provide such a drum assembly for washing, drying and the like machines which has a mechanical strength greater than that of commercially available like devices, mainly at the level of the mutual connection regions coupling the mentioned wedge elements and front ring or cover element.
Within the scope of the above mentioned aim, a main object of the present invention is to provide a drum assembly of the above mentioned type which is effectively devoid of any unevenness like those which occur in the connection regions of the wedge elements and the front ring or cover element in prior drum assemblies.
Yet another object of the present invention is to provide a method for making the above mentioned drum assembly, which is specifically designed for reducing to a minimum the end cost of washing, drying and the like machine drum assemblies.
According to one aspect of the present invention, the above mentioned aim and objects are achieved by an improved drum assembly for washing, drying and the like machines, of the type including a cylindric band provided with a plurality of wedge elements facing the inside of the drum assembly, a closing rear disc and a front ring element, characterized in that said drum assembly comprises connecting means for directly mechanically connecting said ring element and band, at said wedge elements of said band.
According to further features of the inventive drum assembly, said connecting means comprise projecting or raised walls provided on that section of each said wedge element engaging said ring element, said projection portions being adapted to cooperate with corresponding projecting or raised portions of said ring element. Said projecting portions, in particular, comprise a wall formed on the end of the wedge elements facing the ring element and directed inwardly of said wedge elements, at a position substantially parallel to the surface of the ring element therewith said wall must be connected. In turn, said projecting portions of said ring element comprise a deformed or upset edge or rim portion provided at the connection section on each wedge element and having such a size and shape to be housed inside each said wedge element, above and beyond the mentioned projecting wall.
According to further features of the drum assembly according to the present invention, said deformed edge or rim portion comprises a wall facing the inside of the drum assembly. After having performed the mechanical connection, the mentioned deformed edge or rim portion will be rearwardly turned and upset against said wall of the respective wedge element.
According to a modified embodiment of the drum assembly of the invention, said direct connection mechanical means comprise a portion of said wedge elements axially projecting on the outside of said cylindric band, for cooperating with a corresponding window of the front ring element, to be locked inside the latter, at the contour thereof.
The method for making the above disclosed drum assembly, which also constitutes a main aspect of the present invention, is essentially characterized in that it comprises the step of cold anchoring said front ring or cover element and cylindric band, at the wedge elements of said band. The method is moreover characterized in that said anchoring or connecting step is performed by an upsetting operation which is preceded by a self-centered connection between said front ring or cover element and said cylindric band of the drum assembly.
Further features of the inventive method are clearly defined in the remaining dependent claims.
With respect to prior drum assemblies, the inventive drum assembly provides the advantage of allowing a mechanical direct connection of the wedge elements and front ring or cover element, i.e. a connection which does not comprise any welding spots favouring oxidation and sealing failure phenomena of the performed connection.
The mechanical sealing properties of the subject connection are moreover much more stable and efficient, than prior welding spot connections, since the subject connection is extended to the overall mutual coupling section of the wedge elements and corresponding portion of the front ring or cover element, and not to only a portion thereof, as in a spot welded connection.
The cold connection performed by upsetting a projecting portion of said front ring or cover element on the contour of a corresponding wedge element, furthermore, provides a self-centering effect. Thus, the drum assembling operation can be carried out a fully automatic manner due to the mutual engagement of the portions being connected, thereby providing a well finished final product.