Conveyors: power-driven – Conveyor section – Screw
Patent
1996-07-31
1998-12-08
Valenza, Joseph E.
Conveyors: power-driven
Conveyor section
Screw
494 54, B65G 3326
Patent
active
058457640
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a wear element intended to be mounted along a screw wing of a screw press or the like, comprising a wear plate of a hard, typically a ceramic, material locked in a dovetail recess formed in a steel bracket.
In operation of screw presses, such as in the paper and cellulose industry, sugar production etc, a screw rim is subject to very high wear. In order to reduce a similar problem in connection with centrifuges, special wear elements of the above kind have been proposed in GB 2 048 728 and DE 2 556 671. These prior structures, in which the wear plate is mounted in its bracket by being pushed into a preformed dovetail slit, require accurate machining and adjustment of the parts in order to obtain a stable and rigid locking of the wear plate in the dovetail slit. Thus, a considerable amount of diamond grinding of the very hard ceramic material will be necessary, with corresponding high costs of manufacture of the prior wear elements. As an alternative, the wear plates may be locked by through-going fasteners, but a such approach would reduce the functioning and life of the wear elements.
Among the various embodiments disclosed in the above GB 2 048 728 there are some in which the wear plate may be locked in its bracket by means of a wedge member abutting a rear or radially inner, canted surface of the wear plate and welded in place on the bracket. Although apparently not recognized in the specification of the GB publication, such approach could be adapted to permit the ceramic wear plate to be used "raw" directly from the furnace, without the necessity of any diamond grinding for dimensional adjustments. By locking or securing the ceramic plate to its bracket in this manner, rather than having to push it into a preformed slit in the bracket as in the other prior embodiments, a rigid and very strong locking of the wear plate in the bracket would be achieved, independently of any irregularities or inaccuracies in shape and dimensions of the ceramic wear plate.
On the other hand, in the above prior wedge member embodiment, the wedge member together with parts of the bracket located between the screw hub and ceramic wear plate will be exposed to the material conveyed through the apparatus. This is of minor concern in the prior GB 2 048 728 apparatus, since it is of the centrifuge type in which the abrasive material, in operation of the centrifuge, is concentrated along the rim of the screw wing or flight, while the radially inner portion of the wing is not. In screw presses on the other hand, such as used in the cellulosic industry, the entire radial extent of the wing is subject to heavy abrasive action and therefore, if the screw wing is to be protected by ceramic wear plates, it would be essential to have the portion of the screw wing intermediate the screw hub and ceramic wear plate as narrow as possible, especially in the converging compression portion of the press where the abrasion is at a maximum, as otherwise the unprotected intermedate portion would rapidly cave owing to the abrasive material filling the space between succesive screw wings.
SUMMARY OF THE INVENTION
The present invention, in addition to advantageously permitting the use of "raw" ceramic plates, solves this problem by providing a wear element intended to be mounted along the screw wing of a screw press or the like, comprising a wear plate of a hard, typically a ceramic, material, and comprising further a steel bracket, the wear element being locked in a dovetail connection recess in the steel bracket; the bracket being made up of two parts, each providing a respective one of two wedge surfaces of the dovetail connection recess; the wear element being formed with a back portion having wedge surfaces complementary to the wedge surfaces of the bracket parts and having side surfaces; both bracket parts each having a channel-like indentation whose bottom forms a respective one of the wedge surfaces of the dovetail connection recess, and legs of the channel-like indentations of one brack
REFERENCES:
patent: 3764062 (1973-10-01), Brautigam
patent: 3937317 (1976-02-01), Fleury
patent: 3977515 (1976-08-01), Lewoczko
patent: 4328925 (1982-05-01), Shapiro
patent: 5429581 (1995-07-01), Michaud
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