Ballasted tub for an oscillating assembly of an electrical household appliance, and method for manufacturing thereof

Abstract

 Ballasted tub (2) designed to contain the basket (3) of an electrical household appliance, such as a washing machine, has a substantially cylindrical shape and comprises at least two parts (7, 8) of a plastic material with a hollow chamber containing a ballast functioning as counterweight. In a first embodiment the tub comprises a central part (7) and two end parts (8A, 8B) that close the opposite ends of the central part.

Description

[0001] The present invention relates to a ballasted tub for the oscillating assembly of an electrical household appliance and to a method to manufacture such tub.

[0002] The oscillating assemblies of electrical household appliances, such as washing machines, drying machines, washing-and-drying machines or the like, comprise a perforated rotary basket designed to contain the laundry to be washed. The perforated basket is contained in a tub supported by the structure of the electrical household appliance. Said tub carries, or is equipped with, a number of components or devices, including a motor, pipes for water inlet and outlet, bearings, and a counterweight, namely and inertial mass to ballast the tub.

[0003] Typically the tub is made in two pieces of plastic material. A first piece has a first opening for introduction of the basket and a second opening, set opposite to the first opening or on the other side of sad first piece, for access to the basket and for introduction therein of the laundry. A second piece or lid closes the opening for the introduction of the basket after this has been inserted into the aforementioned first piece. Said second piece is usually fixed to the first piece by means of elastic engagement elements or fixing clamps or screws, after positioning of a seal element or gasket in between.

[0004] As mentioned above, the tub is provided with counterweights. In one embodiment, the lid of the tub, which is made of plastics by injection moulding, supports a counterweight made of concrete fixed thereto by means of screws, washers and sometimes also nuts. In addition to the counterweight, fixed to said lid are also ball bearings of the rotating shaft of the basket. Said bearings are housed in a different moulded plastic and/or metal element, which is fixed to the lid by fastening means such as self-threading screws. This operation requires, as likewise the operation of fixing the counterweight, a substantial expenditure in terms of manpower and management of the involved items.

[0005] In view of the above, it may be readily understood that said traditional ballasted tubs have several drawbacks, including the drawback of requiring a the large number of components to manufacture them. This requires that all such components be encoded independently, stored, transported, handled and made available at the time of assembling the ballasted tub, resulting in a rather heavy logistics and significant production costs.

[0006] French Utility Certificate No. 2580679 filed on 7 April 1986 discloses a tub for washing machines consisting of an upper part in plastics and a lower part in metal, the upper part being in the form of a hollow body with a double wall filled with concrete. Although this is aimed at avoiding the use of a separate counterweight, the tub of this prior document has several drawbacks, which may explain why it has never been made in practice, namely:

• the upper part is too large to be made in plastics with the shape of a square double-walled box. Injection moulding techniques do not allow even today a mass production of this kind of piece;
• a tub made according to FR 2580679 would be unbalanced and subject to severe vibrations, due to the heavy upper part and light lower part, resulting in substantial asymmetry of the structure;
• moreover, a plastic/metal hybrid structure cannot be classified under current market standards for washing machines tubs and would likewise not be accepted;
• inserting and fixing bearings in hole (3) of the upper part would be complex and costly;
• fixing of the lower metal part to the upper part would be very difficult since it would require to insert screws in the concrete filling, which appears to be highly ineffective;
• water tightness between the two parts should be assured by a huge square-shaped gasket, which also appears to be practically impossible to achieve.

[0007] A first object of the present invention is to provide a new tub for the oscillating assembly of an electrical household appliance, which allows to reduce substantially the number of pieces or components required by the conventional tubs.

[0008] Another object of the invention is to provide a manufacturing method that allows to cut down the number of operations of purchase, encoding, storage, transportation or handling of components, thereby simplifying the logistics related to the manufacturing of tubs for an electrical household appliances such as a washing machine, a washing-and-drying machine, and a drying machine.

[0009] A further object of the invention is to provide a tub and a manufacturing method that result in a reduction of the costs of production of the electrical household appliance.

[0010] A still further object of the invention is to provide a tub which is compact, durable and well balanced to optimize the manufacturing and operation of household appliances such as a washing machine, a washing-and-drying machine, and a drying machine.

[0011] The above and other objects of the invention are achieved by a ballasted tub for an electrical household appliance such as a washing machine, a washing-and-drying machine, or a drying machine, characterized by a substantially cylindrical geometry, and by comprising at least two plastic parts, at least one of said plastic parts comprising hollow portions filled with a ballast material to generate a built-in counterweight well balanced with respect to any plane defined by the rotation axis of a basket operatively inserted into said tub, said two plastic parts being fixed to each other in a sealed way.

[0012] The invention will be now described with reference to the attached drawings, representing preferred but non-limiting embodiments of the invention, in which:

• Figure 1 is a schematic cross-sectional view of a washing machine of the top-loaded type according to the invention, with the outer casing removed;
• Figure 2 is a perspective view of an assembly of a first embodiment of a tub for a washing machine according to the present invention;
• Figure 3 is an exploded perspective view of the tub of Figure 2 and of the basket contained therein;
• Figure 4 is an exploded perspective view, from the opposite side, of the tub and basket of Figure 3;
• Figure 5 is a sectional view of a detail of the connection between two parts of the tub of Figure 1;
• Figure 6 is a sectional view of a variant of the detail of Figure 6;
• Figure 7 is an exploded perspective view, from one side, of a second embodiment of the tub of the present invention and of the basket contained therein;
• Figure 8 is a cross-sectional view made along the line 8-8 of Figure 7;
• Figure 9 is an exploded perspective view, from another side, of the tub and basket of Figure 7;
• Figure 10 is a sectional view of a first operative position of the tub of Fig. 7 on a reduced scale;
• Figure 11 is an enlarged sectional view of a detail of Fig. 10;
• Figure 12 is a sectional view of a second operative position of the tub of Fig. 7 on a reduced scale;
• Figure 13 is an enlarged sectional view of a detail of Fig. 12;
• Figure 14 and Figure 15 are enlarged sectional views of a detail of Figure 7 in two different operative positions;
• Figure 16 is an exploded perspective view, from a front side, of a third embodiment of the tub of the present invention and of a basket contained therein, for a washing machine or the like of the front-loaded type;
• Figure 17 is an exploded perspective view, from another side, of the tub and basket of Figure 10;
• Figure 18 is a schematic cross-sectional view, at an enlarged scale, of a detail of the tub of Figure 1 in an area corresponding to a bearing for supporting the basket; and
• Figure 19 is a schematic cross-sectional view, at an enlarged scale, of a detail of the tub of Figure 1 in an area corresponding to the bearing for supporting the basket, where the bearing is connected to a hub of the basket.

[0013] In the figures, corresponding parts are designated by the same reference numbers.

[0014] Figures 1 to 6 illustrate a first embodiment of a tub for a washing machine of the top-load type, designated as a whole by the reference number 2. The tub 2 consists essentially of a hollow body made of plastic material, designed to contain a perforated basket 3 with holes 9, as known. The tub 2 also supports a motor 4, which actuates rotation of the basket 3 by means of a pulley 5 connected to the basket 3.

[0015] The basket shown in Figures 1 to 6 (and hence also the washing machine) is of the top-loaded type with a top opening 6, providing an access to load/unload the laundry when aligned to a corresponding opening 6A of the tub 2.

[0016] Advantageously, the tub 2 comprises three parts: a substantially cylindrical central part 7, open at the opposite ends 7A and 7B, and two corresponding end parts 8A, 8B, that act as a lid for each of the open ends 7A, 7B and as inertial mass or counterweight. To this purpose, each end part 8A, 8B is hollow or is formed with hollow portions within, so that it can be filled with a ballast material to function as counterweight. The ballast material is typically concrete or a cement-like material or any other suitable material with required density.

[0017] The two hollow parts 8A, 8B have, in plan view, a circular shape. Once filled with the ballast material, they are fixed to the front and rear open ends 7A, 7B of the central part 7 by suitable fastening and water-tight sealing means 10, 11 (shown in Figures 5 and 6) along corresponding circumferential edges 7K and 8K. Therefore, the end parts 8A, 8B function both as lid for the central part 7 and as counterweight for the tub.

[0018] In a first variant (shown in Figure 5), the sealing means 11 are represented by portions that are welded, for example by ultrasound welding or vibration welding, and the fastening means 10 coincide with the welded portions themselves. For example, in the case of vibration welding, this is obtained by setting the surfaces 7K and 8K up against one another and causing them to vibrate at an appropriate frequency in such a way that said surfaces, by vibrating, overheat and melt together forming a single piece. The single piece resulting from melting is suitable to support the weight of the lid/counterweight 8A, 8B and guarantees tightness in regard to the water contained inside the tub 2. Preferably, the surfaces 7K and 8K have a shape like the one shown in Figure 5, i.e., they comprise a plurality of projections and corresponding recesses 12 which fit into one another.

[0019] In a second variant, represented in particular in Figure 6, the fastening means 10 comprises threaded portions of the surfaces along which the connection is made, and the sealing means 11 is a gasket made of suitable elastomeric material embedded in the threaded portions. For instance, the gasket is obtained by co-moulding on the bottom of the threads.

[0020] With reference to Figures 2, 3 and 4, the central part 7 of the tub 2 is moulded in one piece with functional members or components of the electrical household appliance, such as brackets 70 to support the motor 4, pipes to load/discharge water to/from the tub (not shown) and seats such as seat 71 for the electrical coil to heat the water in the tub. The lid 8A is applied at the front and the lid 8B is applied at the rear of the central part 7.

[0021] In one embodiment, each lid/counterweight 8A, 8B of Figures 3 and 4 has the structure of a shell 15, defined by portions of shell 15A and 15B set at a distance one from the other, coupled and fixed in a known way (or, alternatively, obtained by as a single piece directly by moulding or blow-moulding), so as to define an internal chamber 15C to be filled with the ballast material. The portions 15A and 15B have indented parts or recesses 16 to join one to the other and prevent disengagement. The rear lid/counterweight 8B has a groove 17 designed to enable passage of the belts for transmission of motion. An opening 18 is provided, through which the ballast material is inserted into each lid/counterweight. When such material is concrete or cement, it is left to solidify after it has been introduced in the internal cavity 15C.

[0022] The front lid 8A of Figure 4, which is similar to the rear lid 8B of Figure 3, is obviously without the groove 17. Co-moulded or applied to the lid is a chamber 15Z having a pre-defined volume and position. The chamber connects the inside of the tub to an external pressure switch (not shown). With the introduction of water into the tub, the air in the chamber 15Z is compressed, thus causing triggering of a pressure switch that electrically closes the solenoid valve, thereby controlling the entry of water. This cycle controls the amount and level of water necessary for washing.

[0023] Figures 7 to 15 illustrate a second embodiment of a tub for a washing machine of the top-load type.

[0024] In such embodiment the tub 2 is a hollow body of substantially cylindrical general shape formed by un upper part 30 and a lower part 31, fixed to each other in a sealed way along their peripheral edges. Each of the two parts or shells 30, 31 has a hollow hemi-cylindrical conformation, i.e., it is shaped like a portion of a cylinder cut by an horizontal plane lying on the longitudinal axis W of the tub, which is also the rotation axis of the basket 3, as shown in Figures 7 and 9.

[0025] Upper part 30 has a top opening 39, providing an access to load/unload the laundry to a corresponding opening of the basket, not shown but similar to what described in connection with Figures 1-6.

[0026] Each of the two parts or shells 30 and 31 has a hollow structure, defining at least one internal chamber 32 designed to contain a counterweight and extending preferably inside the shells 30 and 31 (see Figure 8). The chamber 32, in each of the shells 30 and 31, is defined by opposite walls 33 and 34 and is accessible via an opening 32A on the corresponding shell. Lower shell 31 is also provided of an opening like 32A, but it is not shown.

[0027] The upper shell 30 is fixed to the lower shell 31 by fastening means comprising a plurality of clamps 40 engaging a rib 42 projecting from the lower shell 31. Clamps 40 are positioned in the vicinity of the open edges of shell 30, particularly the longitudinally oriented edges 41. As shown in particular in Figure 11 and 13, each clamp 40 swings around a hinge line 44 and is provided with a tooth end 46 to engage a corresponding recess 47 of rib 42. Figures 10, 11 show the clamping means in an open position, and Figures 12, 13 show the clamping means in the closed position.

[0028] The fastening means of shells 30, 31 comprises also a plurality of pins 46 engaging corresponding sockets 48. Pins 46 are provided in upper shell 30 and extend downwardly from the transversely oriented edges 49. Corresponding sockets 48 are provided in lower shell 31 and extend upwardly from the transversely oriented edges 51. As shown also in Figures 14 and 15, pins 46 have an enlarged resilient head 50, which is forcibly pushed into socket 48 and abuts against a circular rib 52, preventing disengagement of the pin/socket connection.

[0029] A sealed connection between upper and lower shells 30, 31 is further ensured by ultrasound welding or vibration welding of the longitudinal edges 41 and transversal edges 49 of the upper shell 30 to the corresponding edges of the lower shell 31. The resulting connection guarantees tightness in regard to the water contained inside the tub.

[0030] It can be observed from Figures 7 and 9 that shells 30, 31 have semi-circular projections 45, 45A provided with a hole to house bearings 80 to support hubs 88 of the basket 3, as it will be explained in more detail in the following of the description. Projections 45, 45A match corresponding semi-circular recesses in the corresponding shell.

[0031] In a further embodiment shown in Figures 16 and 17, the tub 2 is designed for a front-loaded electrical household appliance and comprises two shells 63 and 64 having a cylindrical shape, coupled in an area corresponding to respective open circular end portions 65 and 66. The coupling of the shells 63 and 64 is obtained by inserting a projecting annular edge 68 of one end portion (for example the one designated by 65) into an annular recess 69 provided in a position corresponding to the other end portion 66. The two shells 63 and 64 are then welded in any suitable ways, for example as described in connection with the central cylindrical part 7 and the lids/counterweights 8 of Figures 7-15.

[0032] Preferably, the shells 63, 64 are made of blow-moulded plastic material, so as to provide a hollow chamber to be filled by the ballast material, as described above. Such material is introduced into the hollow chamber of each shell 63, 64 through opening 70, 70A on each of them. Also in this embodiment the connection of the two shells 63, 64 creates a tub 2 with a built-in counterweight for the electrical household appliance. Of course one of the two shells, precisely shell 63 of Figure 16, has a large central opening 72 for introduction of the laundry in corresponding central opening 74 of basket 3.

[0033] In each of the embodiments above, the tub 2 also comprises one or more accessory components co-moulded or made as a single piece with the tub 2. In particular, it is known that in washing machines, washing-and-drying machines or drying machines, whether top-loaded ones or front-loaded ones, two bearings 80 are present in opposite walls of the tub (see, for example, Figure 1), to rotatably support hubs 88 fixed to the basket 3. Said bearings are set in a corresponding position at the two opposite sides of the tub 2, namely in the lids/counterweights 8A and 8B of the embodiment of Figures 1-6, or in the shells 30, 31 of the embodiment of Figures 7-13, or in shell 64 of the embodiment of Figures 16-17. Each bearing 80 can be made of a single piece or of two coaxial and adjacent pieces as illustrated in Figure 17.

[0034] As shown in Figures 18-19, it is an embodiment of the invention that each bearing 80 is embedded in a groove 81 of the tub 2, so as to receive a hub 88 of the basket 3. In practice, the bearing 80 is made as one piece with the tub 2, the latter being made directly "around" the bearing, for example by means of moulding, namely by suitably positioning the bearing in the mould where the tub is made by injection or blow moulding.

[0035] Regardless of the specific embodiment, the counterweight built in the tub of the present invention is balanced with respect to the rotational forces generated by the rotating basket. Such balance is achieved primarily by a distribution of the ballast material within the hollow portions or chamber of the tub that is symmetrical with respect to any plane defined by the rotation axis (W) of the rotary basket.

[0036] The method of manufacturing the ballasted tub for the oscillating assembly of a washing machine according to the invention appears clearly evident from what has been described and illustrated herein and, in particular, is substantially described in what follows.

[0037] First of all, a lid/counterweight (for example, the one designated by 8B in Figures 1-6) is connected to the tub 2. Then the basket 3 is inserted therein and also the other lid/counterweight 8A is connected.

[0038] Closing is obtained by setting each lid up against the central part 7 and welding the parts in contact, for example by vibration at an appropriate frequency which causes heating and melting (and connection) of the aforesaid parts.

[0039] Alternatively, each lid 8A, 8B is screwed onto the central part 7 in such a way that the threads penetrate into the co-moulded gaskets, ensuring water-tightness in regard to the water that is introduced into the casing 1 during use of the electrical household appliance.

[0040] The method described above comprises also co-moulding or manufacturing in a single piece of functional elements or accessories of the tub 2 with the tub itself.

[0041] In particular, moulding of the tub 2 is made by embedding at least one bearing 80 for a rotary support of the basket 3.

[0042] Thanks to the structure of the tub of the invention, a substantial reduction in the number of components necessary for the fabrication of the electrical household appliance is achieved. Consequently, a reduction also in its costs and time for assembly is achieved. The tub of the invention is a multifunctional tub insofar as it exploits several functions besides that of providing a sealed chamber for hosting the basket, including the function of providing a built-in counterweight and the function of incorporating built-in bearings.

[0043] The tub for washing machine and the method for its manufacturing thus conceived may undergo numerous modifications and variations, all falling within the scope of the inventive idea. For example, each lid/counterweight may be made up of just two components, i.e., a component made of plastic material obtained in a single piece with a component made of conglomerate, said components being fixed together. Furthermore, all the items may be replaced by technically equivalent elements.

Claims

1. Ballasted tub (2) for an electrical household appliance such as a washing machine, a washing-and-drying machine, or a drying machine, characterized by a substantially cylindrical geometry, and by comprising at least two plastic parts (7,8; 30,31; 63,64), at least one of said plastic parts comprising hollow portions (6A; 39; 70) filled with a ballast material to generate a built-in counterweight balanced with respect to the rotation of a basket (3) operatively inserted into said tub (2), said two plastic parts (7,8; 30,31; 63,64) being fixed to each other in a sealed way.

2. Ballasted tub according to Claim 1, characterized in that at least one of said parts (8A, 8B; 30, 31; 63, 64) of tub (2) is integrally formed with bearings (80) to rotatably support hubs (88) of said basket (3).

3. Ballasted tub according to Claim 1, characterized by comprising a substantially cylindrical central part (7) with open ends (7A, 7B), to at least one of said open ends being fixed an end part (8A, 8B) provided with a hollow chamber (15C) filled with ballast material, whereby it functions as counterweight.

4. Ballasted tub according to Claim 3, characterized in that said end part (8A, 8A) functioning as a counterweight is connected to at least one open end (7A, 7B) of said central part (7) by fastening means (10) and sealing means (11) extending along the circumferential portions (7K, 8K) of said central part (7) and of said lid (8).

5. Ballasted tub according to Claim 4, characterized in that said fastening means (10) and sealing means (11) are portions (7K, 8K) of said central part (7) and said lid (8) that are welded together.

6. Ballasted tub according to Claim 4, characterized in that said fastening means (10) comprises threaded portions provided in said circumferential portions (7K, 8K) of said central part (7) and of said lid (8) coupled with one another, and said sealing means (11) comprises at least a gasket (11) set in a position between said central part (7) and said lid (8).

7. Ballasted tub according to Claim 6, characterized in that said gasket (11) is co-moulded with said threaded portion defining said fastening means (10).

8. Ballasted tub according to Claim 4, characterized in that to each of said open ends (7A, 7B) of said substantially cylindrical central part (7) ) is fixed to an end part (8A, 8B) filled with ballast material, said end parts (8A, 8B) functioning as lid and counterweight (8A, 8B).

9. Ballasted tub according to Claim 4, characterized in that said end parts (8A, 8B) comprise at least two portions, a first portion functioning as sealed closing of the corresponding open end (7A, 7B) of the substantially cylindrical part (7), and a second portion functioning as counterweight and being defined by a ballast of high density, preferably of a cement-like nature.

10. Ballasted tub according to Claim 9, characterized in that the first portion is a shell (15) with an internal hollow chamber (15C) filled with the ballast material.

11. Ballasted tub according to Claim 10, characterized in that said hollow chamber (15C) extends inside the entire shell (15).

12. Ballasted tub according to Claim 11, characterized in that said bearings (80) are embedded in said shell (15).

13. Ballasted tub according to Claim 1, characterized in that said two plastic parts comprise two shells (30, 31; 63, 64) of a hemi-cylinder shape, coupled to one another in a sealed way, with a hollow chamber inside (32) and an opening (32A; 50) to receive a ballast material.

14. Ballasted tub according to Claim 13, characterized in that each of said shells (30, 31) has a hemi-cylindrical shape virtually obtained from a hollow cylinder cut along a plane containing the longitudinal axis (W), said shells (30, 31) being connected along their peripheral edges.

15. Ballasted tub according to Claim 13, characterized in that each of said shells (63, 64) has a hemi-cylindrical shape virtually obtained from a hollow cylinder cut along a transversal plane perpendicular to said longitudinal axis (W), said shells being coupled at respective open circular end portions (66, 68).

16. Ballasted tub according to Claim 14, characterized in that said shells (30,31) are connected by means of a plurality of clamps (40) provided in one of said shells (30) engaging a rib (42) projecting from the other of said shells (31).

17. Ballasted tub according to Claim 16, characterized in that said clamps (40) are positioned in the vicinity of the longitudinal edges (41) of said shell (30), and said rib (42) is positioned in the vicinity of the longitudinally oriented edges of said other shell (31).

18. Ballasted tub according to Claim 14, characterized in that said shells (30,31) are connected by means of a plurality of pins (46) provided in one of said shells (30) and engaging corresponding sockets (48) in the other of said shells (31).

19. Ballasted tub according to Claim 18, characterized in that said pins (46) are provided in the vicinity of the transversely oriented edges (49) of said shell (30), and said sockets (48) are positioned in the vicinity of the transversely oriented edges of said other shell (31).

20. Ballasted tub according to Claim 14, characterized in that said shells (30, 31) are connected in a sealed way by welding their peripheral edges.

21. Ballasted tub according to Claim 14, characterized in that said bearings (80) are embedded in said shells (30, 31).

22. Ballasted tub according to Claim 15, characterized in that said shells (63, 64) are connected at their open circular end portions (65, 66) by coupling a projecting annular edge (68) of one end portion (65) to a corresponding recess (69) provided in the other end portion (66).

23. Ballasted tub according to Claim 22, characterized in that said shells (63, 64) are connected in a sealed way by welding the peripheral edges of said open end portions (65, 66).

24. Ballasted tub according to any of the preceding claims, characterized in that the weight distribution of said built-in counterweight is symmetrical with respect to any plane containing the rotation axis (W) of said basket (3) operatively inserted into said tub (2).

25. Method for the manufacturing of a ballasted tub (2) for an electrical household appliance, such as a washing machine, a washing-and-drying machine, or a drying machine, characterized by comprising the steps of:

- providing a hollow chamber in said tub; and

- filling said hollow chamber with a ballast material of high density to define a built-in counterweight, said tub and said ballast material defining an integral assembly.

26. Method according to Claim 25, characterized in that said hollow chamber is provided in at least one of two end parts (7A, 7B) of said tub, which further a substantially cylindrical central part (7), said end parts (7A, 7B) functioning also as lid (8A, 8B) for said central part (7).

27. Method according to Claim 26, characterized in that said lid (8A, 8B) is connected to said cylindrical central part (7) by welding.

28. Method according to Claim 27, characterized in that said welding is a vibration welding providing a sealed connection between the coupled parts (7, 8A, 8B).

29. Method according to Claim 26, characterized in that each of said lid (8A, 8B) is connected to said cylindrical part (7) by screwing to one another respective threaded portions, and by positioning a gasket (11) in the area of said threaded portions, to ensure a sealed connection.

30. Method according to Claim 27, characterized in that said gasket is co-moulded with said threaded portions.

31. Method according to Claim 25, characterized in that at least one bearing (80) to support said basket is embedded in said tub during moulding.

Drawing