Conveyors: fluid current – Intake to fluid current conveyor – Load receptacle type
Reexamination Certificate
2000-07-28
2001-09-04
Ellis, Christopher P. (Department: 3651)
Conveyors: fluid current
Intake to fluid current conveyor
Load receptacle type
C406S050000, C406S144000, C406S196000, C406S198000, C222S207000, C222S212000
Reexamination Certificate
active
06283680
ABSTRACT:
The present invention relates to apparatus for transporting a particulate or granular material such as concrete, which device comprises a flexible duct having an upstream end connected to material feed means, and a downstream end, means for pinching said duct in timed manner, and means for injecting compressed air into the duct and capable of being opened and closed in timed manner.
Apparatus of that type is used for example to transport concrete constituted by a mixture of cement and aggregate between a feed hopper and an assembly for spraying concrete and terminating in a spray nozzle. The apparatus is usable for the “dry” spraying technique in which the mixture of materials is transported in the hose while in the dry state and is moistened only in the vicinity of the nozzle outlet, or for the “diluted-flow wet” spray technique in which the mixture of concrete is already moistened before penetrating into the duct.
Apparatus of that type can also be used for transporting materials other than concrete, for example foodstuffs based on grains or granulates, such as wheat.
European patent No. 0 588 737 discloses apparatus of that type in which the means for pinching the duct comprise pinching projections disposed on a moving assembly, each of the projections moving in turn along the duct so as to pinch it and drive the material downstream while creating suction immediately upstream from the projection to encourage ingress of material into the duct. Compressed air is used to regulate transport of the substance and it is injected into the duct when it is no longer or practically no longer pinched by a projection. To prevent the air under pressure having any tendency to drive the material back towards the feed means, the known apparatus also includes a presser element which closes the duct upstream from the inlet for air under pressure, throughout the air injection sequence.
More precisely, in that known apparatus, when a first projection pinches the duct, which pinching takes place substantially level with the inlet for air under pressure and downstream from the presser element, the feed of air under pressure is cut off while the presser element is open, and the projection moves along the duct so as to drive the air/material mixture towards the outlet of the duct while enabling said duct to be filled upstream. Thereafter, when said first projection reaches a region of the duct in which it practically ceases to pinch it, while the second projection has not yet reached a situation in which it begins to pinch the duct, the presser element is closed and the feed for air under pressure is opened so as to drive the material towards the outlet. Thereafter, substantially when the second projection reaches the situation in which it begins to pinch the duct, the air feed is closed and then the presser element is opened so as to feed the duct with material.
Although that apparatus gives general satisfaction, it nevertheless suffers from drawbacks. Firstly, the duct deteriorates rapidly under the effect of the high friction stresses and/or rolling stresses exerted by the projections as they move along the duct while pinching it. This constitutes a major drawback insofar as the duct is relatively expensive since it must be strong while nevertheless having a high degree of radial elasticity enabling it to return to its normal radial dimensions when pinching by a projection ceases. Conventionally, when the apparatus is used to transport concrete or similar material, the duct is made using reinforced rubber. In addition to the problems of cost, the need to replace the duct often gives rise to frequent maintenance operations.
Secondly, that known apparatus does not manage completely to prevent air being driven back towards the feed means. It is mentioned above that the presser element which is closed during injection of compressed air is disposed upstream from the zone where the projections first pinch the duct as they move along it. It is not possible to place the presser element in the immediate proximity of said contact zone, since a small distance is necessary to enable the projections to approach as part of their displacement cycle. Consequently, when a projection begins to pinch the duct, it shuts off air under pressure in the portion of duct that is situated between the presser element and the pinch zone.
Thus, when the presser element is opened to allow the duct to be fed with material, a pocket of air under pressure situated in this portion of the duct expands, with the air tending to escape upstream along the duct. This air entrains “dust” of the material that is to be transported into the surrounding space. In some applications, e.g. when the material is a dry mixture of cement and aggregate, the dust is harmful and contrary to safety standards. In all cases, whatever the nature of the material transported, including materials constituted by food grains such as wheat, such dust is undesirable.
An object of the invention is to remedy the above-mentioned drawbacks by proposing apparatus that is improved for the purpose of increasing the lifetime of ducts and, above all, for eliminating or at least considerably restricting dust rejection under the effect of air under pressure escaping.
This object is achieved by the fact that the means for pinching the duct comprise a first pinch member and a second pinch member situated downstream from the first pinch member in the material transport direction, each pinch member being movable transversely to the duct between a relaxed position and a pinching position;
by the fact that the apparatus include a drive member situated between said first and second pinch members and suitable for being displaced transversely to the duct between an inactive position and an active position in which it co-operates with the duct substantially to flatten it;
by the fact that the air injection means open out into a region of the duct situated between the first and second pinch members in the vicinity of said first pinch member; and
by the fact that the apparatus includes means for timing the injection of compressed air and the movements of the pinch members and of the drive member to perform successive cycles comprising the following stages;
a filling stage in which the first pinch member is in its relaxed position, the air injection means are closed, the drive member is in its inactive position, and the second pinch member is in its pinching position; and
a drive stage during which the first pinch member is in its pinching position, the air injection means move from being closed to being opened, the drive member moves from its inactive position to its active position, and the second pinch member is in its relaxed position.
Thus, according to the invention, the pinching and drive members which exert large stresses on the duct move transversely relative to the duct without moving along it, thereby limiting deterioration of the duct. In addition, while air is being injected, the duct is closed in its upstream region by the first pinch member, and at least towards the end of the air injection stage, the drive member is occupying its active position (it flattens the duct). Thus, even if air is held captive in the duct beneath said drive member while the second pinch member is being put into its pinching position before a new filling stage begins, the quantity of air involved can only be very small.
As soon as the drive member has gone from its active position to its inactive position, suction is created which allows any such small quantity of air to expand and prevents it from escaping upstream. In addition, the suction serves to suck material from the hopper into the duct, thereby facilitating and accelerating filling of the duct.
When it is stated that in its active position the drive member substantially flattens the duct, that means that in this position the duct is practically in the shape of a flat element whose two facing internal faces are in contact with each other or are at least extremely close to each other. Nevertheless, there is no need for the drive member
Dillon, Jr. Joe
Ellis Christopher P.
Nath Gary M.
Nath & Associates PLLC
Novick Harold L.
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