Liquid purification or separation – Filter – Movable medium
Reexamination Certificate
2002-11-05
2004-08-31
Prince, Fred G. (Department: 1724)
Liquid purification or separation
Filter
Movable medium
C210S363000, C210S380200
Reexamination Certificate
active
06783675
ABSTRACT:
FIELD OF THE INVENTION
This invention in general relates to a centrifugal machine with a suspended floating group and an overhanging drum, specially applicable to washing-centrifugal machines designed to high centrifugal speeds with high G factors, in which said floating group essentially comprises a wrapping bin to contain and/or to collect a bath, a drum having bored walls for a load of material to be centrifuged mounted so that it can rotate within said wrapping bin, and a motor fixed on the wrapping bin and connected to said drum to rotate it, in said machine a suitable ratio of counterweigh masses provides as result a reduction of structural stresses at the floating group which allow a light construction thereof and namely of the wrapping bin.
BACKGROUND OF THE ART
The method of withdrawing water from a wetted material through centrifugation is well-known and it is thoroughly used, for example, in the either industrial or home sector of clothes washing, because of its high performance of withdrawal with relation to the power expense compared with other methods. In this sector, it is very usual to use machines capable to wash and subsequently to centrifuge a load of clothes introduced in a drum having bored walls mounted so that it can rotate within a wrapping bin capable to contain succeeding bathes of washing and rinsing and to collect the rests of said bathes extracted from the clothes during an end centrifuging step. For this, one or more motors are connected to the drum to successively rotate it at different speeds according to the washing, rinsing and centrifuging steps, driven by programmable control means.
It is very typical that the drum is situated so that during the operation, its hinge axis is horizontal or slightly inclined with respect to the horizontal, and that it has a loading/unloading mouth at an axial end thereof, coinciding with an opening of the wrapping bin. This is specially advantageous in industrial machines designed to heavy loads of clothes in which the radial loading mouth would result of a very complex access because of its great height. The existence, however, of said loading/unloading mouth at one end of the drum obliges to support it overhanging from the axial end opposite to the loading/unloading mouth, by means of a driving shaft integral with the drum rear wall, supported and guided by bearings housed within a bearing box fixed on the wrapping bin. This arrangement, although it results very favourable from an ergonomic standpoint, produces stronger bending moments on the driving shaft and transmits stresses on the bearings stronger than if the drum had been supported and guided at both ends. In addition, when the drum rotates at such a speed that it produces a centripetal acceleration on the clothes load higher than 1 G (G=earth gravity acceleration=about 9.8 ms
−2
), such as during a centrifugation, where 200, 300 and even over 400 G factors are reached, the clothes are radially applied against the drum wall at a random relative given position, which virtually does not vary while the effect of said speed is kept. Said random relative position has a very high probability to produce a centre of the masses of the clothes load misaligned with respect to the drum centre line, which is aligned with the driving shaft and therefore the centre of the masses of the drum and clothes load group will also be shifted with respect to said centre line. In these conditions, said drum and clothes load group will tend to rotate with respect to said misaligned centre of masses of the drum centre line, or with other words, the drum centre line will tend to rotate about an actual rotation axis different from the centre line, producing a wellknown vibrating motion which is transmitted to the whole floating group. Said vibrating motion is generally decreased adding counterweights and it is absorbed by said floating group system of suspension, formed by springs and vibration eliminators linked to a machine frame or bench.
U.S. Pat. No. 2,525,781, of Jey Grant De Remer, applied for on Sep. 15, 1944, discloses an equilibrating system for rotating bodies, specially applicable to clothes washing-centrifugal machines, based on providing one or more annular chambers partly filled with a fluid, located on different areas of the drum and coaxial with respect to the centre line thereof. Each of said chambers is formed by substantially parallel external and internal concentric annular walls and substantially parallel sidewalls, and there exists within them deflecting means which tend to drift the fluid contained within the chambers without preventing a free distribution thereof. When the rotation speed of the equilibrating ring and the drum is such it produces a G factor over 1 and over the floating group resonance frequency, the fluid of the interior of the equilibrating chamber is applied against said external wall thereof, which is coaxial with respect to the drum centre line, at same time it defines an internal circular horizon coaxial with respect to the actual rotation axis, a centre of masses of said fluid being created which is shift with respect to the actual rotation axis in a direction just opposite to the shift of the masses centre of the clothes load and therefore equilibrating it. Jey Grant De Remer discloses in said patent U.S. Pat. No. 2,525,781 that the optimum equilibrated situation is produced when the radial height at the point of the fluid maximum radial height within the equilibrating chamber is twice the distance between the centre line and the actual rotation axis, that means, twice the amplitude of the machine vibrating motion, and when the circle of the chamber external wall and the circle of the fluid circular horizon are tangent at a point diametrally opposite to the maximum height. Jey Grant De Remer also demonstrates that it is more favourable to arrange two concentric equilibrating chambers instead of a single chamber having a height equivalent to the sum of the other two, with same width and an amount of contained fluid equivalent to the other two together.
In said patent U.S. Pat. No. 2,525,781, however, of Jey Grant De Remer, only the drum equilibrating is discussed without discussing, at any moment, the dynamic effect of the “pitching motion” that the masses of clothes load and of the fluid rings produce on the floating group, therefore the position of the equilibrating fluid rings on the drum appears as a minor matter, obeying more to formal or construction criteria than to dynamic requirements.
Said dynamic effects of “pitching motion” consist in a drum dynamic shift, and therefore of the floating group, which has a different amplitude at each of its ends, being generally, in this kind of machines, of a larger amplitude at the drum end farther away from the bearings.
In the state of the art shiftable solid mass rings are known, for example for an embodiment of SKF company, which includes solid balls, generally of steel, enclosed in an annular circuit, which, when the group is subject to an misaligned rotation which produce G factors over 1, are concentrated being situated at the area of said annular circuit farthest from actual rotation axis. In the most recent embodiments, as the one disclosed in patent U.S. Pat. No. 5,813,253, in order to prevent noises produced by the balls colliding with each other when rotating at low speed, it is provided a locking device formed by cages which match the balls two by two, in said cages there is a spring-loaded pin, which at G factors under 1, pushes the pin in order it is inserted in holes arranged on the internal track of the annular circuit. When G factors are substantially over 1, the pin mass itself generates a centrifugal force which gets over said spring releasing the cage with its related pair of balls, which then shift until they concentrate at said area farthest from the actual rotation axis.
Although said ball device showed to be very effective as for its balance compensating effect, the requirements of accurateness of its complex construction make its cost very hig
Riba Romeva Carles
Riera Curcoll Ignasi
Sans Rovira Ramon
Folise, Esq. Michael J.
Prince Fred G.
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