Improvement in the unbalance preventing arrangement of the drum of a clothes washing machine

Abstract: Clothes washing machine comprising a washing tub and a perforated cylindrical drum adapted to rotate about its own axis, and provided with a dynamic unbalance preventing arrangement consisting essentially of a plurality of annular, ring-shaped hollow bodies (8) whose axes coincide with the axis of said drum, said hollow bodies having a sealed construction and being firmly attached to said cylindrical drum, and a plurality of movable balancing weights (11) that are arranged in a free slidable manner inside said hollow bodies which are grouped into two distinct assemblies (6,7), the hollow bodies of said two assemblies being provided to respectively adhere against the opposite bases (2,3) of said drum. Said hollow bodies are made by joining together two substantially symmetrical parts (9,10), each one of which is formed by a plurality of circular, coplanar, concentric, open grooves that are integrally connected to each other. The assemblies (6,7) are secured against their respective drum bases by means of a plurality of brackets (15) which are provided on the outer surface of the drum and are capable of mutually engaging respective zones of the outer edge of said assemblies.

Description: The present invention refers to a clothes washing machine, in particular of the household type, provided with a washload holding drum that has an improved dynamic balancing arrangement. It is a widely known fact that one of the most critical problems that design engineers have to cope with in designing clothes washing machines, in particular those intended for household application, refers to the need of balancing the washload containing drum as it rotates at a high speed during the spin-extraction phase. Such a problem is particularly felt when the washload being handled is in an out-of-balance condition in the drum. In fact, such a condition is most likely to cause the drum to undesirably and, quite often, unacceptably oscillate and give rise to vibrations that are transmitted to the tub assembly and, ultimately, to the whole outer casing of the machine. This is a commonly known problem, so that it shall not be described here any further. Among the various solutions devised to cope with this problem, some have been based on the proposal of a dynamic-type arrangement consisting in letting an out-of-balance force of a similar extent, but of a variable and constantly opposite vector, oppose the centrifugal force generated by the unbalanced washload in the drum. Such solutions are for instance described in the French patent specification no. 1.213.067, Swiss priority 8.11.1957, the Italian patent specification no. 1108367, Japanese priority 12.1.1978, and the Italian patent application no. PN94A000005 filed on 28th January 1994 by the same applicant. The above specifications disclose dynamic balance arrangements provided for application to rotating drums of clothes washing machines, in particular of the household type, such arrangements being essentially constituted by annular hollow bodies that are firmly associated to the drum and contain balancing weights capable of sliding within said hollow bodies, said balancing weights being further capable of placing themselves into such an arrangement as to be able to oppose the unbalancing motion of the drum as brought about by the out-of-balance condition of the washload in the same drum. However, such a solution, although generally effective, failed to find practical implementation in current applications owing to a number of reasons, such as for instance the altogether serious difficulties that are generally encountered in manufacturing such hollow bodies and associating them to the drum in an acceptably simple, stable and low-cost manner. It should in fact be considered that, if the solution of a substantial re-design of the washing machine drum is opted for, as this appears to be illustrated or suggested by some of the above cited patent specifications, high economic charges are unavoidably incurred. If on the other hand the solution is selected of simply adapting an existing drum design by applying said hollow bodies in its interior, it is absolutely necessary that the considerable technical difficulties associated therewith be duly considered along with the need of anyway modifying the drum in order to correspondingly increase its strength to appropriately cope with the considerable centrifugal forces generating from said hollow bodies during spin-extraction phases. The fact should furthermore be duly considered that, if said hollow bodies are mounted inside the washload holding drum, this unavoidably has the effect of both reducing the drum capacity, ie. the actual amount of clothes that can be loaded for washing, and increasing the risk of damaging the clothes coming into direct contact with said hollow bodies, the profile of which actually makes the inner space of the drum more irregular. From EP 0 607 678 a washing machine is described in which the rotatable drum includes a generally cylindrical outer wall, a first disk and a second disk. The first disk is provided for forming a first end wall of the drum and includes a balancing means including a plurality of concentric annular chambers. The second disk is provided for forming a second end wall of the drum, opposite to the first end wall, and includes balancing means with a plurality of concentric annular chambers. It therefore would be desirable, and it is in fact a purpose of the present invention, to provide a washload holding drum provided with hollow bodies for the dynamic balancing thereof, wherein existing drum designs are used without any addition in terms of constructional or manufacturing complication, without any significant cost increase and without any modification in the shape and the inner volume of the drum, while ensuring full reliability. The invention will be more readily understood from the description which is given below by way of non-limiting example with reference to the accompanying drawings, in which: Figure 1 is an outer half-front perspective view of a drum according to the present invention; Figure 1A is a view of a simplifying variant of the same drum; Figure 2 is an outer half-side perspective view of the same drum shown in Figure 1; Figure 3 is an outer perspective view from the side of the loading opening of the same drum shown in Figure 1; Figure 4 is an outer view of an isolated detail of the same drum as above; Figure 5 is a close-up view of the detail shown in Figure 4, but installed on the drum illustrated in the above cited Figures; Figure 6 is a cross-sectional view of one of the two mutually opposing portions of a balancing element of a drum according to the present invention; Figure 7 is a cross-sectional view of the two mutually opposing portions of two improved drum balancing elements. The present invention substantially consists in providing a plurality of annular hollow bodies having different diameters and containing a respective plurality of movable balancing weights, in subdividing said plurality of hollow bodies into two distinct assemblies, and in applying the hollow bodies of each such assembly against a respective base of the cylinder formed by the drum, the hollow bodies of each such assembly being therefore substantially coplanar with each other and coaxial with the axis of the drum. With reference to the above listed Figures, they can be noticed to illustrate a washload holding drum, made preferably of metal and of a generally per sè known type, which substantially consists of a rigid structure formed by a cylindrical peripheral mantle 1 and two bases 2 and 3, one of which carries the spider member and the related shaft 4, while the other one forms the loading opening 5. On each one of such bases a respective assembly 6, 7 is applied, which is formed by a corresponding plurality of distinct hollow bodies 8, such as this is shown in Figure 1. Unfortunately, such a construction based on distinct elements involves quite considerable costs along with technical assembly difficulties, so that a first improvement in this connection is brought about by joining the hollow bodies of a same assembly into a single body, as this is illustrated for instance in Figures 1A and 3. In such a case, said bodies can in fact be advantageously be made of thermoplastic material by means of any of the existing moulding techniques. A second improvement, as illustrated in Figures 6 and 7, relies on the fact that the hollow bodies comprised in at least one of said assemblies are provided by joining together two substantially symmetrical parts 9, 10, each one of which is formed by a plurality of co-planar, concentric circular grooves 11 that are open toward the same side in an orthogonal direction with respect to the co-planarity plane. Such grooves are appropriately and partially filled with movable balancing masses whose weight, size, shape and distribution can be freely selected by anyone skilled in the art in accordance with the desired results and the acceptable extent of trade-offs. Eventually, said two complementary parts 9, 10 are joined together to form a single member. Also such a physical configuration admits however a number of further advantageous improvements, one of which is as illustrated in Figure 7. In fact, in view of improving the compactness of said parts 9, 10, and above all in view of using in a more effective manner the space existing toward their outer periphery by increasing the balancing moment of the movable balancing weights, the hollow bodies of said assemblies are contiguous, in the sense that the outer periphery of the inner annular hollow body substantially coincides with the inner periphery of the adjoining outer annular hollow body. Practically, said hollow bodies are separated from each other by a single common intermediate wall. As far as the attachment of said assemblies to their respective bases is concerned, the same appears to be particularly important, since it is required to combine strength, solidity and constructive simplicity qualities. To this purpose, it has been found that a particularly advantageous solution lies in providing a plurality of brackets 15, each one of which, as this is shown in Figures 1, 4 and 5, is provided at their respective end portions with respective claw-like gripping members 16. Each one of said brackets is applied on to the outer cylindrical surface of the drum with a parallel orientation with respect to the axis thereof, while their respective gripping members 16 are caused to engage, thanks to their claw-like configuration, against corresponding pairs of frontally opposing sectors that are respectively arranged on the outer edges 18 of said assemblies 6, 7. In practice, said brackets form the mutual clamping members of said assemblies, while not actually engaging the drum in any structural manner, so as to avoid passing on to it the stresses deriving from the attachment of said assemblies and, therefore, putting any resulting mechanical load on to it. However, in view of boosting the stability of said brackets it is advantageous for engaging elements 18 to be provided which protrude from their intermediate zone and are capable of engaging the underlying surface of the drum without passing on any excessive or unbalanced strain to it. A manufacturability improvement is furthermore obtained if the parts making up each assembly are made in a single-piece or integral construction and are then joined, upon insertion of the movable balancing weights, using a specular assembly technique. A further optimization of the present invention refers to the possible integration of the inner parts of said assemblies 6, 7 with the drum which they are associated with. Such an integration enables considerable advantages of a constructional and economic nature to be obtained and consists in making, using readily available techniques, both the drum and the inner parts of said assemblies formed by the related hollow bodies in a single-piece or integral construction. In a preferred manner, such an improvement is implemented through the use of an appropriate plastic material that is adapted to be processed for making both the drum and said assemblies, thereby further giving the opportunity of avoiding the presence and the assembly of the afore cited brackets, with resulting considerable advantages in terms of costs and constructional simplification.

Claims: Clothes washing machine, particularly of the household type, comprising a washing tub containing a perforated drum comprising a cylindrically shaped mantle (1) and capable of rotating therein about its own axis, said drum being provided with a dynamic balancing arrangement consisting of a plurality of circularly extending annular hollow bodies (8) whose axes coincide with the axis of said drum, said hollow bodies being of a sealed construction and arranged integrally with respect to said cylindrical drum, and a plurality of movable balancing weights (11) that are arranged to slide freely within said hollow bodies (8) and that are arranged in two distinct assemblies (6, 7), the hollow bodies of a first assembly being substantially adherent to the outer surface of a base (2) of said drum, and the hollow bodies of the second assembly being substantially adherent to the outer surface of the other base (3) of the drum, characterized in that the annular hollow bodies (8) comprised in both of said assemblies (6, 7) are obtained by joining together two respective, substantially symmetrical parts (9, 10), each one of which is formed with a plurality of open, circular, coplanar and concentric grooves, with the respective grooves oriented inwards and facing mutually, with the opening plane substantially orthogonal with respect to the axis of the drum, and solidly connecting them to each other. Clothes washing machine according to claim 1, characterized in that said two substantially symmetrical parts (9, 10) must be joined upon insertion of the movable balancing weights into the corresponding grooves. Clothes washing machine according to claim 1 or 2, characterized in that a plurality of annular hollow bodies of at least one of said distinct assemblies are contiguous, in the sense that the outer periphery of the inner annular hollow body substantially coincides with the inner periphery of the adjoining outer annular hollow body. Clothes washing machine according to any of the preceding claims, characterized in that the shape, the distribution and the total mass of the movable balancing weights are substantially similar for said two distinct assemblies of hollow bodies. Clothes washing machine according to any of the preceding claims, characterized in that said two distinct assemblies (6, 7) are held tightly against the respective bases of the drum by means of a plurality of brackets (15) that are arranged parallelly to the axis of the drum, on the outside of the cylindrical surface thereof, each one of such brackets engaging with appropriate gripping members (16) a respective pair of sectors arranged on the outer edges (18) of said assemblies in correspondence of the same generatrix of the cylinder of the drum. Clothes washing machine according to claim 5, characterized in that said brackets (15) are provided, preferably in correspondence of their central portion, with coupling elements (18) adapted to engage corresponding points on the underlying outer surface of the drum. Clothes washing machine according to any of the preceding claims, characterized in that at least one of said two distinct assemblies (6, 7) are formed by two symmetrical shells of thermoplastic material, which are joined and sealed together by welding in a mirror-like configuration. Clothes washing machine according to any of the preceding claims, characterized in that said drum and the inner parts of said distinct assemblies (6, 7) being arranged contiguously to said drum are made in an one-piece configuration.

Inventors: DURAZZANI PIERO, DURAZZANI, PIERO
Applicants: ELECTROLUX ZANUSSI ELETTRODOME, ELECTROLUX ZANUSSI S.P.A.
Application year: 1996
Main classification: D06F37
IPC codes: D06F35, D06F37