Liquid purification or separation – Structural installation – Flume stream type
Reexamination Certificate
2000-02-11
2001-07-31
Upton, Christopher (Department: 1724)
Liquid purification or separation
Structural installation
Flume stream type
C210S232000, C210S401000, C210S455000, C210S499000
Reexamination Certificate
active
06267880
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to mechanical screens adapted to separate from a flow of water debris or waste conveyed thereby.
It is aimed more particularly at mechanical screens which use at least one filter chamber including a chassis which is in the general form of a frame and a filter panel which is disposed transversely in the opening of the chassis, to which it is appropriately attached, whether the filter panel is in one piece or divided into separate filter panels appropriately disposed side-by-side.
A mechanical screen of this kind can form the filter apron of a chain filter, for example.
2. Description of the Prior Art
It then includes a plurality of filter chambers articulated to each other in an endless loop, in an arrangement like that described in U.S. Pat. No. 4,889,629.
It can instead be a rotary drum, for example, or even a static filter.
When, in the case of a chain filter or a rotary drum, a mechanical screen of this kind is mobile, each of its filter chambers operates like a bucket, temporarily retaining and entraining with it debris or waste held back by its filter panel until, on passing a cleaning device directing a contraflow of water through the filter panel, the debris or waste is separated from the filter panel and eliminated.
Be this as it may, one problem to be overcome in the manufacture of mechanical screens including filter chambers of this kind relates to the need to fasten the filter panel appropriately to the chassis.
At present the filter panel is usually a two-dimensional metal mesh or a two-dimensional perforated plate. In either case it has the disadvantage of being sensitive to corrosion, and attaching it to the chassis invariably entails the use of metal parts which are also sensitive to corrosion.
The attachment is usually performed by means of nuts and bolts, using metal bolts to clamp the screen between one frame fastened to the chassis and another frame formed of metal bars, for example.
The same applies in practice when, as described in the aforementioned U.S. Pat. No. 4,889,629, the filter panel forms a three-dimensional structure which, although it is usually made of metal, nevertheless has the advantage that it can be made from a synthetic material if required.
At present the chassis used for such filter panels are usually made of metal, for example annealed steel or stainless steel.
These chassis are inevitably costly and they are never totally resistant to corrosion.
To overcome this drawback, it has already been proposed to make the chassis from a material that is inert to corrosion, for example a synthetic or composite material.
Even so, the filter panel is attached to a chassis of this kind in the conventional way, using nuts and bolts.
The cost of the nuts and bolts, which in practice must be made of stainless steel, the cost of the bars forming the other frame associated with the nuts and bolts, which must also be made of stainless steel, and the cost of the labor for assembling the structure constitute an important part of the total cost of a mechanical screen.
Furthermore, given the various metal components employed, which at present include the filter panel itself, the structure remains highly vulnerable to corrosion, especially in stagnant water.
A general object of the present invention is an arrangement which avoids these drawbacks and has other advantages.
SUMMARY OF THE INVENTION
To be more precise, the present invention provides a mechanical screen employing at least one filter chamber including a chassis which is in the general shape of a frame and a filter panel which is disposed transversely in the opening of the chassis, to which it is appropriately attached, wherein, for attaching the filter panel to the chassis, clipping means are operative between the filter panel and the chassis.
Thus nuts and bolts are entirely avoided, which is advantageous.
To be more precise, all use of metal nuts and bolts and/or bars or other accessories is avoided, which is to the benefit of corrosion resistance and cost.
Furthermore, if it is necessary to change a filter panel as part of the maintenance of the system, the change can advantageously be done very easily and quickly, which is to the benefit of the cost, because it does not involve any loosening or tightening of nuts and bolts.
According to a first development of the invention, for each of the filter chambers used, the chassis and the filter panel are both made from a material that is inert to corrosion, which is to the benefit of the homogeneity of the system.
For example, the chassis is mainly made of a composite material, with the exception of any assembly nuts and bolts, and the filter panel is itself entirely made from synthetic materials.
Other things being equal, a filter panel made in this way from synthetic materials is advantageously lighter than if it were made of metal, which is to the benefit of reducing fatigue of the mechanical screen assembly, in particular its drive means and its guide means, and therefore to the benefit of reduced wear of the mechanical screen.
It is also and advantageously more economic.
However, in the case of a three-dimensional structure, the filter panel is inevitably rigid, and thus unable to bend, which normally means that the opening in the chassis for fitting it must be at least the same size everywhere.
The chassis must therefore normally have a globally parallelepipedal configuration.
According to another development of the invention, the fact that the filter panel is clipped to the chassis is exploited to impart a more advantageous configuration to the chassis.
To be more precise, the fact that clipping is effected by initially offering up the filter panel obliquely to the chassis, after which the filter panel is pivoted into place, is exploited.
According to this development of the invention, the chassis of the filter chambers having a four-sided contour in plan view, in the usual way, including two uprights alternating with two longitudinal members, the clipping means operative between the filter panel and a chassis of this kind are on at least the longitudinal members thereof, and preferably only the longitudinal members, and the longitudinal members preferably have a globally curved profile in cross section with its concave side facing toward the inside of the chassis.
This globally curved profile has a two-fold advantage.
Firstly, it is beneficial for clipping the filter panel to the chassis by advantageously guiding the filter panel during its pivoting motion that is all that is required to bring about the clipping.
Also, and most importantly, by making the two longitudinal members of the chassis convergent, it contributes to a relative reduction in the size of the opening in the chassis, which advantageously strengthens the bucket function of the filter chambers, to the benefit of the retention and entrainment of debris or waste held back by the filter panel.
Thus two apparently contradictory objects are advantageously reconciled, namely easy fitting of the filter panel despite it being rigid and a convergent configuration of the chassis.
The features and advantages of the invention will emerge from the following description which is given by way of example only and with reference to the accompanying diagrammatic drawings.
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E. Beaudrey & Cie a “Societe Anonyme”
Upton Christopher
Young & Thompson
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