DAMPENER DEVICE FOR LAUNDRY WASHING MACHINE

Abstract: Dampener device for the support from below of the tub and drum assembly in a laundry washing machine, comprising a cylindrical bushing (4) and a rod (5) received therein for reciprocating displacement and provided with breaking surfaces (13). According to the invention, the bushing (4) is separable from the rod (5), its inner surface being composed of a first cylindrical portion (16) and a second frusto-conical portion (18) connected to one another for producing a breaking action of constant and variable magnitude, respect­ ively, during displacement of the rod (5) within the bushing (4). The respective end portions (6, 7) of the bushing (4) and the rod (5) are hingedly connected to the base (9) of the housing and to a collar (10) surrounding the tub of the machine by means of respective pins (22, 32) insertable into position in a press-fit.

Description: The invention relates to a dampener device for the support of the tub and drum assembly of a laundry washing machine, said device being designed in a manner so as to facilitate the mounting of said assembly in the housing of the machine. As generally known, the tub and drum assembly of convent­ ional laundry washing machines is mounted in the housing of the respective machine by means of suspension springs and dampener devices connected respectively to an upper portion and a lower portion of the assembly. Known dampener devices are substantially composed of an elongate cylindrical rod reciprocatingly slidable in a corresponding cylindrical bushing, the lower end portion of which is hingedly connected to the base of the laundry washing machine by means of a pin, said rod being provided with breaking surfaces of a suitable low-friction material cooperating with the corresponding cylindrical internal surfaces of said bushing, and having its free end hingedly connected to a metal pin secured to the lower surface of the tub and drum assembly of the laundry washing machine. The above described dampener devices are further designed in such a manner that the rod cannot be extracted from the respective cylindrical bushing while being slidably dis­ placeable therein in response to oscillations of the tub and drum assembly occurring during operation of the laundry washing machine. In particular, thanks to the friction of the breaking sur­ faces of the rod on the cylindrical internal surface of the bushing, this sliding displacement results in a breaking action of constant magnitude and thus in a dampening of the oscillations of the tub and drum assembly. The constant breaking action of these known dampener devices is capable of ensuring efficient dampening of the oscillations of the tub and drum assembly in the case of forces of a determined magnitude, while being incapable of obtaining an effective dampening of the movement of this assembly in such cases in which it is subjected to forces of a greater magnitude due to the laundry charge within the drum being out of balance. In addition, the mounting of each dampener device in a respective laundry washing machine is a rather cumbersome operation which can only be carried out manually by first connecting the rod of the dampening device to the tub and drum assembly in the manner described, and by subsequently connecting the free end of the cylindrical bushing of the device to the base of the housing of the machine after the said assembly has been installed therein. It would thus be advantageous, and is therefore an object of the present invention, to provide a dampener device capable of ensuring efficient dampening of the oscillations of the tub and drum assembly to a degree in proportion to the forces acting on this assembly, and in addition of permitting said device to be mounted in the housing of a laundry washing machine in a simple and fully automatized manner. These and other objects are attained according to the in­ vention by a dampening device for the support from below of the tub and drum assembly of a laundry washing machine, comprising a cylindrical bushing and an elongate rod mounted for reciprocating sliding displacement in said bushing, said bushing and said rod having their respective free ends hingedly connected by means of at least one respective pin to mountings provided respectively on the base of the housing of the machine and on a circular collar made of a plastics material and adapted to be fixedly secured to the external periphery of the tub, said rod being provided with breaking surfaces of a suitable low-­ friction material cooperating with the corresponding inner surface of said bushing. The device described above is characterized in that said cylindrical bushing is separable from said rod, and its internal surface is composed of a first cylindrical portion and a secons frusto-conical portion interconnected between one another and adapted to produce, during displacement of said rod within said cylindrical bushing, beaking actions of a constant and of a variable magnitude, respectively, in response to forces to which said tub and drum assembly is subjected. The characteristics of the invention will become more clearly evidence from the following description, given by way of example with reference to the accompanying drawings, wherein: fig. 1 shows a partially sectioned diagrammatical front view of a dampener device according to the invention as mounted in a laundry washing machine, and fig. 2 shows an enlarged detail of the device of fig. 1 as a cross-section taken along the line A-A. With reference to fig. 1, there is shown a dampener device 3 according to the invention for the support from below of the tub and drum assembly (not shown) of a laundry washing machine. The dampener device shown is substantially composed of a cylindrical bushing 4 and an elongate rod 5 mounted for slidable reciprocation in bushing 4, both said bushing and said rod being preferably made of a plastics material and having their respective free ends 6 and 7 hingedly connected to corresponding mountings (not indicated) formed respect­ ively on a mounting bracket 8 integrally formed with the base 9 of the housing of the machine of a plastics material, and on a circular collar 10 made of a plastics material and adapted to be fixedly secured to the outer periphery 11 of the tub of the washing machine. This circular collar is substantially identical to the one described in Italian Patent Application No. 45733-A/85 filed on Sep. 5, 1985 in the name of the present Applicant. At its other end 12, rod 5 is provided with annular break­ ing surfaces 13 of a suitable low-friction material accommodated in corresponding seats 14 formed on the outer circumferential surface of rod 5, and cooperating with the internal surface of cylindrical bushing 4. Cylindrical bushing 4 is designed to be separable from rod 5 and has one open end for permitting rod 5 to be inserted thereinto for sliding displacement therein, the above mentioned other end 6 being closed by a bottom 15. In particular according to the invention, the internal surface of the cylindrical bushing 4 is formed with a first cylindrical portion 16 extending inwards from open end 17 of the bushing, and a second frusto-conical portion 18 extending from first portion 16 towards bottom 15 and converging towards bottom 15. The purpose of internal surface portions 16 and 18 is to establish a breaking action of constant and variable magni­ tude, respectively, during the sliding displacement of rod 5 within bushing 4 due to the friction between respect­ ive breaking surfaces 13 and said surface portions in response to forces acting on the tub and drum assembly of the machine. In practice, the described dampening device is dimensioned so as to permit the sliding displacement of rod 5 solely within cylindrical surface portion 16 of bushing 4 in response to forces of a determined maximum magnitude, so as to produce a breaking action of a constant magnitude analogous to that obtained with a conventional dampener device, while permitting the displacement of the rod also along frusto-conical surface portion 18 of bushing 4 in response to forces of a greater magnitude than above which may be caused by the laundry within the drum being out of balance. In the latter case, in particular, the sliding displacement results in a breaking action of variable magnitude directly proportional to the forces acting on the tub and drum assembly so as to effectively dampen the oscillations of the tub and drum assembly. Shown in fig. 2 is the manner in which end portion 7 of rod 5 is hinged to corcular collar 10. To this purpose, collar 10 is provided with a mounting portion 19 comprising two flanges 20 and 21 projecting from the outer circumferential surface of the collar at spaced positions and parallel to one another so as to per­ mit end portion 7 to be inserted therebetween. For sub­ sequently connecting end portion 7 to mounting portion 19, a pin 22 made of a plastics material and having a cylind­ rical shaft 23 is inserted into aligned bores 24, 25 and 26 formed respectively in flanges 21, 22 and in end portion 7. Pin 22 is additionally formed with a circular head portion 27 having a greater diameter than shaft 23 and adapted to be laterally seated against flange 21. Head portion 27 is connected to shaft 23 by a frusto-conical intermediate portion 28 the diameter of which is smaller than that of head portion 27 and greater than that of shaft 23. In particular, frusto-conical intermediate portion 28 is formed with a number of notches 29 (cf. fig. 1) evenly distributed about its circumferential surface, and adapted to be press-fitted into a circular seat 30 formed in flange 21. In this manner, rod 5 can be rapidly hinged to circular collar 10 by the insertion of pin 22 as described above by means of a suitable tool acting on head portion 27 thereof, without the danger of dropping out thanks to the press-fit engagement of notches 29 with circular seat 30 and to the presence of a small retaining pawl 31 formed on flange 21 and adapted to be resiliently deformed on insertion of the pin so as to subsequently engage the outer end face of head portion 27 of pin 22. Bushing 4 on its part is hinged to base 9 of the housing of the machine by means of a further pin 32 identical to pin 22, this further pin being press-fitted in the same manner as described above into corresponding bores formed in flange portions (not shown) of mounting bracket 8 and through end portion 6 of bushing 4. In this manner, rod 5 and bushing 4 can be mounted in the laundry washing machine separately from one another, and subsequently brought into engagement with one another during assembly of the machine. The advantages obtainable with the dampener device accord­ ing to the invention are thus evident. As a matter of fact, this device permits the oscillations of the tub and drum assembly to be effectively dampened even in the case of the laundry within the drum being out of balance, and is capable of being mounted in the respect­ ive laundry washing machine in an extremely simple manner as described by the rapid and automatized insertion of the pins at both ends of the device, thereby eliminating the need for complicated mounting structures as previously required. Thanks to the fact, finally, that the bushing and the rod of the dampener device are separable from one another, it is possible to assemble these components in a completely automatized process during assembly of the laundry washing machine itself to thereby eliminate the manual operations formerly required for mounting such dampener devices.

Claims: 1. A dampener device for the support from below of the tub and drum assembly of a laundry washing machine, said device comprising a cylindrical bushing and an elongate rod received in said bushing for reciprocating displace­ ment therein, said bushing and said rod having their respective free ends hingedly connected by means of at least one respective pin to corresponding mounting portions formed respectively in the base of the housing of the machine and on a circular collar made of a plastics material and adapted to be fixedly secured to the outer periphery of the tub, said rod being provided with breaking surfaces of a suitable low-friction material cooperating with the corresponding internal surface of said bushing, characterized in that said cylindrical bushing (4) is separable from said rod (5), its internal surface being composed of a first cylindrical portion (16) and a second frusto-conical portion (18) connected thereto and adapted to produce a breaking action of a constant magnitude and of a variable magnitude, respectively, on displacement of said rod (5) within said bushing (4) in response to forces acting on said tub and drum assembly. 2. A dampener device according to claim 1, character­ ized in that each said mounting portion (19) includes at least two flange portions (20, 21) disposed parallel to one another at a transverse spacing for permitting the respective end portion (6, 7) of said bushing (4) and said rod (5) to be connected thereto by the insertion of a shaft portion (23) of said pin (22) through corresponding bores (24, 25; 26) formed in said flange portions (20, 21) and said end portion (6, 7). 3. A dampener device according to claim 2, character­ ized in that said pin (22) is also provided with a circular head portion (27) connected to said shaft (23) by a frusto-­ conical portion (28) the diameter of which is smaller than that of said head portion (27) and greater than that of said shaft (23), said frusto-conical portion (28) being formed with a number of circumferential notches (29) and adapted to be press-fitted into a corresponding circular seat (20) of a respective associated flange (21). 4. A dampener device according to claim 3, character­ ized in that said head portion (27) is adapted to cooperate with at least one resiliently deformable retaining pawl (31) provided on the respective associated flange (21). 5. A dampener device according to any of the preceding claims, substantially as described with reference to the accompanying drawings and for the stated purposes.

Inventors: DURAZZANI, PIERO
Applicants: INDUSTRIE ZANUSSI S.P.A.
Application year: 1986
Main classification: D06F37
IPC codes: D06F37, F16F7