Brakes – Operators – Automatic
Reexamination Certificate
1999-08-18
2001-07-24
Butler, Douglas C. (Department: 3613)
Brakes
Operators
Automatic
C188S381000, C267S201000
Reexamination Certificate
active
06264014
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a friction damper which has been specifically designed for washing machines and the like.
As is known, the basket of a washing machine is affected, during the rotary movement thereof, by oscillations due to a dynamic unbalancing of the rotary mass of the basket and of the lineN held therein.
Said basket is usually suspended, by springs, to the washing machine frame and, in order to dampen the above mentioned oscillations or vibrations, two dampers or shock absorbers are conventionally used, each of which is coupled, at the bottom end portion thereof, to the washing machine frame and, at the top portion thereof, to the basket.
Dampers for a washing machine application comprise friction dampers, which are substantially constituted of a shell, having a substantially cylindrical shape, inside of which a rod is adapted to slide, between the rod and shell being arranged a gasket made of a friction material, said gasket being rigidly coupled to the shell or to the rod.
This gasket is designed for providing a friction braking operation in order to brake the mutual displacement of the rod with respect to the shell.
While the above mentioned dampers have been found to provide an efficient damping of the basket oscillations in washing machines, they, however, generate a comparatively high friction rubbing during the washing machine washing steps thereby causing the basket to oscillate, even if in a comparatively small degree. Consequently, the dampers are quickly worn out, in particular at the region thereof which is engaged with the friction material gasket, thereby quickly reducing the operating efficiency of this gasket which must be frequently replaced.
SUMMARY OF THE INVENTION
Accordingly, the aim of the present invention is to overcome the above mentioned problem, by providing a friction damper, specifically designed for washing machines or the like, which is adapted to differentially operate depending on the washing machine operating steps, i.e. depending on the amplitude of the washing machine basket oscillations, so as to provide a greater damping as said oscillation amplitude is great.
Within the scope of the above mentioned aim, a main object of the present invention is to provide such a friction damper which has an operating life much greater than that of conventional friction damper, by reducing, during the normal operating steps of the washing machine, i.e. as the washing machine basket is affected by small amplitude oscillations, the friction energy dissipation.
Another object of the present invention is to provide a friction damper which is very simple construction wise and which can be made at a competitive cost.
A further object of the present invention is to provide such a friction damper which is very reliable and safe in operation.
According to one aspect of the present invention, the above mentioned aim and objects, as well as yet other objects, which will become apparent hereinafter, are achieved by a friction damper, specifically designed for washing machines or the like, comprising a hollow shell and a rod coaxially arranged with respect to one another and forming a telescopic motion construction, said rod having an outer diameter less than an inner diameter of said shell and, between said shell and rod, rod guiding means being arranged, characterized in that said damper further comprises a friction damper element, arranged between said rod and shell and including a first working surface frictionally slidably coupled to said rod and a second working surface frictionally slidably coupled to said shell.
REFERENCES:
patent: 4934493 (1990-06-01), Bauer et al.
patent: 5549182 (1996-08-01), Ehrnsberger et al.
patent: 5961105 (1999-10-01), Ehrnsberger et al.
patent: 301190 (1988-05-01), None
patent: 95/14130 (1995-05-01), None
Butler Douglas C.
Hedman & Costigan ,P.C.
Siconolfi Robert A.
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