WO2011064201A1

WO2011064201A1 - Process and apparatus for manufacturing an expanded basket for washing machine or washer-drier or drier

Info

Publication number: WO2011064201A1
Application number: PCT/EP2010/068014
Authority: WO
Inventors: Giovanni Porcarelli; Giovanni Paoloni
Original assignee: Qs Group S.P.A.
Priority date: 2009-11-26
Filing date: 2010-11-23
Publication date: 2011-06-03
Also published as: IT1396539B1; ITMC20090241A1

Abstract

A manufacturing process of a basket for washing machine is disclosed, comprising the following steps: formation of a cylindrical basket (1) from a perforated sheet metal (10), by joining the ending edges (12), in such a way to form a longitudinal junction (G), and expansion of said cylindrical basket (1) by means of stressing beyond the material yield point, in such a way to obtain an expanded basket (100) having the desired shape. During expansion, an area of the basket around the junction (G) is tightened in such a way that the expansion of the basket does not affect the junction (G).

Description

PROCESS AND APPARATUS FOR MANUFACTURING AN EXPANDED BASKET FOR WASHING MACHINE OR WASHER -DRIER OR DRIER

The present patent application for industrial invention relates to the field of expanded baskets for washing machines, washer-driers and driers.

Although the following description makes specific reference to a washing machine, it is understood that the present invention also relates to a washer-drier and a drier.

As it is known, a washing machine comprises a perforated metal basket with cylindrical shape that contains the laundry to be washed. Said basket is made by bending a rectangular flat metal band and joining the ending edges to form a cylinder.

The first baskets for washing machine were made by seaming the ending edges. This is to say that the ending edges of the band are folded in "V" and mutually coupled.

In washing machines with high-speed spin cycles, seaming of the ending edges did not guarantee the resistance of the basket.

Deep-drawing operations were carried out on seamed ending edges in order to solve such a problem. A cylindrical basket with seamed and deep- drawn junction guarantees good reliability also in case of high-speed spin cycles.

However, this type of basket is impaired by the fact that it is not versatile. In fact, it cannot be shaped as desired and adapted to different models of washing machines.

Such a drawback is solved with the so-called expanded baskets. This means that the cylindrical basket is additionally formed to obtain the final shape by means of an expansion process.

Said expansion process consists in mechanically expanding a series of sectors in radial direction so that the casing of the basket, which is originally cylindrical, is tensioned beyond the yield point of the material and forced to take the shape of said sectors. An additional advantage of the expanded basket is the higher rigidity compared to a non-expanded basket.

During the expansion of the basket, also the junction area of the band is subject to the same stress. It must be considered that a pressure of about 5 tons is exerted during expansion and after expansion a basket with circumference of 1600 mm reaches a circumference of 1650 mm. Therefore, due to the high expansion of the material, the ending edges of the band that were seamed and deep-drawn tend to open until the junction fails completely.

In order to avoid such an inconvenience, in expanded baskets the junction between the ending edges of the band is exclusively made with welding to guarantee maximum mechanical resistance.

Fig. 1 discloses a first type of expanded basket according to the prior art, wherein the ending edges of the band are overlapped and welded by means of rollers heating with electrical resistance such that a welding line (W) is obtained to join the overlapped ending edges.

Then the basket is expanded, taking on the desired shape.

Fig. 2 shows a second type of expanded basket, wherein the ending edges of the band are placed side-by-side and welded with laser welding to obtain a welding line (L) that joins the ending edges. Then the basket is expanded, taking on the desired shape.

However, the welding of the ending edges of the band of the basket is impaired by a severe drawback. In spite of the excellent mechanical performance, welding does not guarantee the resistance to corrosion to water and detergents that is necessarily required for a basket for washing machine.

After a certain period of operation, intergranular corrosion is found in the welding area; this means that the grain of the welded material gets bigger and colder and welding fails suddenly, destroying the household appliance without warning.

Such a problem is also found with the most advanced welding technologies and can be only partially limited by using titanium alloy steels that are in any case more expensive. EP 0 234 243 discloses a method for manufacturing a tub of stainless steel for a laundry washing machine, comprising the steps of cutting a sheet metal blank, winding the blank and welding it to the form of a cylindrical body, expansion-forming of the cylindrical body. The welding step is carried out by means of a laser, and prior to the expansion-forming step. The cylindrical body is subjected to a heat treatment for eliminating the brittleness of the weld.

The purpose of the present invention is to eliminate the drawbacks of the prior art, disclosing a method and apparatus that guarantee the production of an expanded basket for washing machine that is versatile, reliable, inexpensive and simple to make.

Another purpose of the present invention is to provide such a manufacturing method and apparatus of an expanded basket that guarantee the mechanical seal of the junction of the ending edges of the basket during expansion without altering the structure of the material of the basket.

Said purposes are achieved according to the invention with the method having the characteristics listed in the enclosed independent claim 1 and with the apparatus having the characteristics listed in the enclosed independent claim 7.

Advantageous embodiments are disclosed in the dependent claims.

The manufacturing process of a basket for washing machine according to the present invention comprises the following steps:

- making of a cylindrical basket from a perforated sheet metal band comprising two opposite ending edges that are mutually joined to form a longitudinal junction, and

- expansion of said cylindrical basket by means of stressing beyond the yield point of the material to obtain an expanded basket with the desired shape.

During the expansion, an area of the basket around the junction is tightened in such a way that the expansion stress of the basket is not transmitted to the junction. So the junction is not stressed and therefore the initial mechanical resistance is maintained. Additional characteristics of the invention will become clearer from the following detailed description, which refers to a merely illustrative, not limiting, embodiment, as shown in the enclosed figures, wherein.

- Fig. 1 is a perspective view of an expanded basked according to the prior art, with junction of the ending edges by means of resistance welding;

- Fig. 2 is a perspective view of an expanded basked according to the prior art, with junction of the ending edges by means of laser welding ;

- Fig. 3 is a perspective view of a band for realization of a basket according to the present invention with ending edges folded in "V";

- Fig. 4 is a perspective view of a cylindrical casing obtained with the band of Fig. 4 by seaming the ending edges;

- Fig. 5 is a perspective view of the cylindrical casing of Fig. 4, on which studs have been obtained on seaming;

- Fig. 6 is a top view of a machine for expansion of the cylindrical casing of Fig. 5;

- Fig. 7 is an axial sectional view along section plane VI I- I I of Fig. 6 that shows the machine in loading position of the cylindrical casing;

- Fig. 8 is a cross-sectional view of the machine in loading position of Fig. 7;

- Fig. 8A is an enlarged detail of Fig. 8;

- Fig. 9 is an axial sectional view of the machine of Fig. 6, in stopping position of the junction area of the cylindrical casing;

- Fig. 1 0 is a cross-sectional view of the machine in stopping position of Fig. 9;

- Fig. 1 0A is an enlarged detail of Fig. 1 0;

- Fig. 1 1 is an axial sectional view of the machine of Fig. 6 in expansion position of the cylindrical casing ;

- Fig. 1 2 is a cross-sectional view of the machine in expansion position of Fig. 1 1 ;

- Fig. 1 3 is a perspective view of an expanded basket obtained with the apparatus of the invention ; and

- Fig. 1 3A is an enlarged view of the detail contained in circle (A) of Fig. 1 3. Referring to Figs. 3 - 13 the manufacturing process of an expanded basket according to the present invention is disclosed.

Referring to Fig. 3, the process begins from a flat metal band (10) with rectangular shape, preferably made of stainless steel. A plurality of holes (1 1 ) is made on the band (10) to allow for water passage. The band (10) has two opposite ending edges (12) that are folded in "V" on either side with respect to the plane of the band.

Referring to Fig. 4 the band (10) is bent by means of a roll to obtain a cylindrical configuration and the ending edges (12) are mutually coupled to generate a junction (G) by seaming that longitudinally extends along the entire length of the band (10). So a non-expanded cylindrical basket is obtained, which is indicated with numeral (1 ).

As shown in Fig. 5, a plurality of transversal studs (13) is obtained by deep-drawing on the junction (G) of the basket (1 ) obtained by seaming. The studs (13) increase the reliability of the junction (G). The deep-drawing process can be carried out during expansion or after expansion, as illustrated below.

Preferably the junction (G) is obtained by seaming and eventually deep-drawing of seaming, it being understood that the junction (G) can also be obtained with other junction systems, such as riveting, clinching, semi- shearing, resistance welding, laser welding or similar system.

Now referring to Figs. 6, 7 and 8, the cylindrical basket (1 ) is inserted in an expansion machine (2).

The expansion machine (2) comprises a fixed frame (20) with toroidal shape, provided with central circular opening (21 ) for insertion of the cylindrical basket (1 ) from up down. The cylindrical basket (1 ) is positioned in a cylindrical gap (22) defined between lateral walls (23) arranged outside the cylindrical basket (1 ) and circular sectors (24) arranged inside the cylindrical basket (1 ). The lateral walls (23) are composed of a plurality of arched elements (23) having a complementary concave surface with respect to the circular sectors (24). The external arched elements (23) are radially actuated by corresponding actuators (50) that radially protrude outwards. The circular sectors (24) are arranged in staggered position with respect to the arched elements (23). This means that the axis of each circular sector passes through the space between two adjacent arched elements.

The circular sectors (24) can expand radially to cause the expansion of the cylindrical basket (1 ). Therefore, the circular sectors (24) have an external lateral wall (25) that extends for the entire length of the circle and is suitably shaped to define a definite expansion profile of the basket.

The circular sectors (24) are arranged around an expansion insert (26) that slides axially to cause the radial expansion of the circular sectors (24). The expansion insert (26) has a tapered surface with decreasing diameter from up down. The external lateral surface of the expansion insert (26) is matched with the internal lateral surface of the circular sectors (24).

The expansion insert (26) is mounted on a shaft (27) arranged axially inside the machine (1 ). The shaft (27) can be axially actuated by means of an actuator (28) arranged under the frame of the machine.

According to the invention, no circular sector (24) is provided in the area of the junction (G) of the basket because such area must not be subject to expansion. In fact, in the area of the junction (G) of the basket (1 ) a clamp (3) is provided, comprising a pair of opposite jaws (30, 31 ), that is to say an internal jaw (30) arranged inside the basket (1 ) and an external jaw (31 ) arranged outside the basket.

The clamp (3) can be any type of press, for example of electromechanical, hydraulic and pneumatic type.

The internal jaw (30) can be arranged inside a cavity of a circular sector (24') in register with the junction (G) of the basket.

The jaws (30, 31 ) have opposite tightening surfaces that extend for the entire height of the basket. The tightening surfaces of the jaws (30, 31 ) can be flat or curved in such a way to follow the radius of curvature of the basket. As shown in Fig. 8A, the external jaw (31 ) is provided with two longitudinal ribs (32) that are parallel and arranged at short distance, for example a distance of about 3 - 6 cm, in such a way that the junction (G) of the basket is situated between the two ribs (32) of the external jaw. Consequently, the internal jaw (30) is provided with two longitudinal grooves (33) arranged in register with the ribs (32) of the external jaw (31 ).

Both the internal jaw (30) and the external jaw (31 ) have corresponding inserts (6) provided with grooves (60) arranged in register with the junction (G) of the basket.

Going back to Fig. 7, the external jaw (31 ) can be composed of one or more inserts that are dumped by means of springs (41 ) arranged radially in a support plate of the inserts.

The internal jaw (30) is mounted on a support plate (34). The lower wall of the plate (34) is connected to a piston (35) of an actuator (36) arranged in the lower part of the frame of the machine. The upper part of the plate (34) is provided with a seat (37) adapted to receive the end of a piston (38) of an actuator (39) pivoted in a pivoting point (40) to the upper part of the frame of the machine. So the upper actuator (39) can rotate around the pivot (40), passing from an idle position (shown in Fig. 7) to a work position (shown in Fig. 9).

When the upper actuator (39) is in idle position, the piston (38) is released from the plate of the internal jaw to allow for loading the basket (1 ) through the upper opening (21 ) of the frame.

Referring to Fig. 9, the upper actuator (39) rotates around the pivot

(40) and the end of the piston (30) of the actuator is coupled with the upper part of the support plate of the internal jaw (30). Now the two actuators (36, 39) of the clamp (3) are actuated simultaneously in order to retract the pistons (35, 38).

Consequently, the area of the basket (1 ) with the junction (G) is tightened in sandwich-mode between the two jaws (30, 31 ) of the clamp, as shown in Figs. 10 and 10A. In particular, the ribs (32) of the external jaw (31 ) deform the sheet metal of the basket causing corresponding channels (15) that are compressed in the grooves (33) of the internal jaw (30). So the junction (G) situated between the two channels (15) of the basket is isolated with respect to the remaining part of the basket. After tightening the junction area (G) of the basket with the clamp (3), as shown in Figs. 1 1 and 12, the actuator (28) of the shaft (27) of the expansion insert (26) is actuated. Consequently, the expansion insert (26) translates downwards, pushing radially outwards the circular sectors (24) that push the internal surface of the basket (1 ) causing its expansion.

Simultaneously, the external arched elements (23) are pushed radially inwards by the actuators (50) to form the basket (1 ). Clearly, the external arched elements (23) are not provided in the area with the external jaw (31 ) of the clamp.

It must be noted that expansion is distributed on the entire circumference of the basket, except for the area with the junction (G) that is firmly tightened by the clamp (3). Consequently, the junction (G) is not stressed by the expansion of the basket and is perfectly maintained during the entire expansion process.

Figs. 13 and 13A illustrate an expanded basket (100) obtained with the method of the invention. Said expanded basket has a junction (G) situated between the two longitudinal channels (15) generated by the clamp (3).

Although the figures illustrate a clamp (3) with two jaws (30, 31 ) with grooves (33) and ribs (32), it is evident that the purpose of the present invention can be achieved with any tightening means suitable to tighten an area of the basket around the junction (G) in such a way that the stress caused by the expansion is blocked without affecting the junction. So the expanded basket (100) obtained with the method of the invention can also be devoid of channels (15).

Said channels (15) can be rectilinear or curved, can be directed towards the outside and the inside of the basket, can be continuous along the entire junction (G) or interrupted for example in correspondence of the drivers that must be mounted on the basket to avoid the formation of a space between the band of the basket and the driver.

For example, the tightening means may be provided with perforating pins that make holes in the sheet metal of the basket. Moreover, it can be provided that the channels (15) or other types of tightening points for the jaws of the clamp (3) are obtained directly on the flat band (10) during deep-drawing. In this way the ribs of the jaw of the press will be positioned in the preformed channels (15).

Moreover, the jaws of the clamp (3) can be formed in such a way to make a deep-drawing process for the formation of the transversal studs (13) on the junction. In such a case also deep-drawing is carried out in the expansion machine (2).

Alternatively, deep-drawing for the formation of transversal studs (13) can be carried out after expansion in a separate deep-drawing station. In fact, it must be considered that during expansion the junction (G) is not stressed and can resist well also without deep-drawing.

Although the figures illustrate an expansion apparatus (2) with vertical axis, it appears evident that the apparatus (2) can have a horizontal axis.

Numerous variations and modifications can be made to the present embodiments of the invention by an expert of the field, while still falling within the scope of the invention as claimed in the enclosed claims.

Claims

1 ) Manufacturing process of a washing machine basket comprising the following steps:

- making of a cylindrical basket (1 ) from a perforated sheet metal band (10) with two opposite ending edges (12) that are mutually joined to form a longitudinal junction (G), and

- expansion of said cylindrical basket (1 ) by means of stressing beyond the material yield point to obtain an expanded basket (100) with the desired shape,

characterized in that

during the expansion, an area of the basket around the junction (G) is tightened in such a way that the basket expansion stress is not transmitted to the junction (G).

2) Process as claimed in claim 1 , characterized in that said longitudinal junction (G) of the basket is obtained by seaming the ending edges (12) of the band.

3) Process as claimed in claim 2, characterized in that it comprises deep- drawing of said longitudinal junction (G) of the basket to form a plurality of transversal studs (13).

4) Process as claimed in claim 3, characterized in that said deep-drawing of the junction (G) is carried out simultaneously with the tightening of the area around the junction (G).

5) Process as claimed in any one of the preceding claims, characterized in that during the tightening of the area around the junction (G) tightening points (15) are generated on the basket band so that the longitudinal junction (G) of the basket is comprised between said tightening points (15).

6) Process as claimed in any one of claims 1 to 4, characterized in that, before tightening the area around the junction (G) tightening points (15) are generated on the basket band so that the longitudinal junction (G) of the basket is comprised between said tightening points (15) and tightening means actuate on said tightening points (15) during said tightening. 7) Apparatus (2) for realization of a washing machine basket comprising:

- a plurality of circular sectors (24) radially expandible in such a way to press against the internal lateral surface of a cylindrical basket (1 ) obtained from a perforated sheet metal band (10) comprising two opposite ending edges (12) that are mutually joined to form a longitudinal junction (G), generating stress on the basket beyond the material yield point, in such a way to obtain an expanded basket (100) with desired shape,

characterized in that it also comprises

- tightening means (3) arranged in said junction (G) of the basket, in order to tighten an area of the basket around the junction (G), in such a way that the expansion stress of the basket is not transmitted to the junction (G), said tightening means (3) comprising a clamp composed of a pair of opposite jaws (30, 31 ) or perforating pins that tighten said area around the junction (G) of the basket.

8) Apparatus (2) as claimed in claim 7, characterized in that said jaws (30, 31 ) are provided with raised parts (32) and lowered parts (33) that are matched to tighten the basket sheet metal between them.

9) Expanded basket (100) for a washing machine, characterized in that it is obtained with the method claimed in any one of claims 1 to 6.