Screw press

A screw press provided with a rear excess fluid outlet is described herein. The rear excess fluid outlet includes a circular screen provided at a longitudinal end of the screw press body, near a material inlet. Scraper blade assemblies are provided to prevent the screen from clogging. The efficiency of excess fluid removal is thereby increased by the increased screen surface near the material inlet of the screw press.

FIELD OF THE INVENTION

The present invention relates to screw presses. More specifically, the present invention is concerned with a screw press provided with a rear excess fluid outlet.

BACKGROUND OF THE INVENTION

Screw presses are well known in the art. They are conventionally used for removing soluble and dispersible materials from products, for example, excess fluid from paper pulp. It is to be noted that, for concision purposes, the example of the paper pulp will be used throughout the present disclosure. This should not be construed as a limitation of the present invention.

The principle of operation of conventional screw presses is believed to be well known to those skilled in the art and will therefore only be briefly described herein.

A screw press is basically an endless screw provided with a conical shaft that compresses the pulp as it moves from an inlet to an outlet. The endless screw is enclosed in a body that is provided with a screened surface allowing the excess fluid to be expelled from the pulp.

The throughoutput of screw presses is usually controlled by the rotational speed of the endless screw. However, there are limits to this control since the rotational speed of the endless screw must be sufficiently slow to thereby allow the excess fluid to flow through the screened body. This is a drawback of the conventional screw presses since it lowers the efficiency of the unit by unduly limiting the top rotational speed of the endless screw.

SUMMARY OF THE INVENTION

More specifically, in accordance with the present invention, there is provided a screw press for removing excess fluid from material comprising a generally tubular body having a meshed surface; said body having a material inlet provided near a proximate end thereof; an endless screw mounted in said tubular body; said endless screw including a generally conical shaft and a helicoidal blade mounted to said shaft; and a rear excess fluid outlet provided in said proximate end of said tubular body.

Other advantages and features of the present invention will become more apparent upon reading of the following non restrictive description of preferred embodiments thereof, given by way of example only with reference to the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now toFIG. 1of the appended drawings, a screw press10according to an embodiment of the present invention will be described.

As discussed hereinabove, the principle of operation of screw presses is believed well known to those skilled in the art and will not be further discussed in details herein. Furthermore, for concision purposes, various elements and portions of the screw press10that do not have a direct impact on the present invention will not be described herein.

The screw press10includes an endless screw12, provided with a conical shaft14and an helicoidal blade16, and a generally tubular body18having a material inlet20near a first longitudinal end and a material outlet22near a second longitudinal end thereof. The tubular body18is provided with meshed elements24defining a meshed surface allowing excess fluid to egress therefrom and to be collected in a fluid receiving receptacle26.

As can be better seen fromFIG. 2of the appended drawings, the material inlet20includes a raw material inlet28, a rear toroidal screen30defining a rear excess fluid outlet, a fluid expelling conduit32and three scraper blades assemblies34. It is to be noted that the number of scraper blades is not critical and could vary according to the surface of the rear excess fluid outlet.

As will be readily understood by one skilled in the art, the raw material that enters the screw press10through the raw material inlet28is formed of solid matter mixed with excess fluid. It is at the material inlet20that the proportion of solid material to excess fluid is the lowest. It is therefore at the material inlet that a great portion of the excess fluid will egress the screw press10(see arrows36) through the meshed elements24. The added rear toroidal screen30allows excess water to egress faster from the material inlet20of the screw press10(see arrows38) since the meshed surface is increased near the material inlet20, thereby increasing the available top rotational speed of the endless screw12.

Indeed, it has been found that the limitation of the top rotational speed of the endless screw12is mainly due to the inefficiency of conventional screw presses to allow the excess fluid to egress the material inlet20thereof quickly enough. By increasing the screened surface in the material inlet20, it is possible to significantly increase the flow of excess fluid out of the material inlet to thereby increase the available top rotational speed of the endless screw12.

The fluid conduit32allows the egressing fluid to flow in the fluid receptacle26.

As will be apparent to one skilled in the art, it is advantageous to prevent solid matter from clogging the screened surfaces of the body18since it would decrease the efficiency of fluid removal.

The scraper blades assemblies34, which may be better seen fromFIG. 3of the appended drawings, are so mounted to the end of the endless screw12as to contact the rear toroidal screen30in such a manner that the rotation of the endless screw12induces a scraping action against the screen30. Of course, this contact is not necessary since a near-contact is generally sufficient to prevent the clogging of the toroidal screen30. Clogging of the circular screen30is therefore prevented by the scraper blade assemblies34.

Turning now more specifically toFIGS. 4 and 5of the appended drawings, the scraper blade assemblies34will be described in greater detail.

As can be seen fromFIG. 4, each scraper blade assembly34includes a support40mounted to the endless screw12and a movable scraper blade42mounted to a corresponding support40.

FIG. 5illustrates a sectional portion of one of the scraper blade assemblies34. As can be seen from this figure, the movable scraper blade42is mounted to the support40via three machine screw fasteners44(only one shown inFIG. 5) that are inserted in oblong apertures46of the scraper blade42. The oblong shape of the apertures46thereby allow the adjustment of the scraper blade42to ensure an adequate cleaning of the rear toroidal screen30.