COMBINED SCREW FOR WATER PROCESSING APPARATUSES

Abstract: The invention describes a screw for a water treatment apparatus, such as an aerator or mixer, said apparatus comprising a power source (1) driving a shaft (2) on which is fitted a screw that sucks the water up or impels it downward. The screw consists of a helicoidal, spiral-shaped screw blade construction round said shaft, with an upper end part (A), a lower end part (C) and a middle part (B) between said two end parts, with at least one of said end parts comprising an extra screw blade.

Description: DESCRIPTION ro-mr-1-in.-.r * screw for water processing apparatuses This invention concerns a screw for apparatuses used for water purification installations, such as aerators or mixers, and more particularly for apparatuses of the type in which a source of power, which may or may not be mounted on a float, drives a shaft on which a screw (impeller device) is fitted. In aerators the water is sucked up, deflected and spread more or less horizontally over the surface of the water. In mixers the water is sucked in and impelled down under the surface of the liquid. The state of the art impeller device (Belgian patent 884.216) consists of two parts, namely a lower part formed by a screw and an upper part formed by a paddle wheel. This embodiment was improved by the Belgian patent 893.687 by converting the screw and the paddle wheel to a single body in which the screw is gradually curved in the form of a spiral and merges into the paddles of the paddle wheel. In this way, a screw pump is formed, consisting of one single body in the form of a centrifugal screw propel¬ ler. This screw pump can serve either as an aerator or as a mixer, and can even be combined as a mixer/aerator as described in European patent 366.644. Such a screw pump can be single-stage (with one helicoidal, spiral-shaped screw blade) but can also be multistage (with several helicoidal, spiral-shaped screw blades. It is clear that a multistage screw involves more frictional losses and causes more turbulence in the flow of water sucked up or sucked in. A multistage pump also demands a greater capacity on the part of the power source. If a single-stage pump is used, the frictional losses and turbulence are reduced, and a power source with lower capacity is sufficient, but the water flow rate is also reduced. The aim of this invention is to offer a screw that combines the advantages of both the multistage and the single-stage pump, while avoiding the disadvantages of the multistage and single-stage pump. According to the invention, the screw consists of a construction comprising an upper end part and a lower end part, with a middle part between the two end parts, with at least one end part comprising an additional screw blade. According to a preferred embodiment, the screw con¬ sists of at least one continuous screw blade and at least one extra, discontinuous screw blade located at the upper and/or lower end part of the continuous screw blade. According to an advantageous embodiment, the screw has two blades at the bottom, with one blade continuing through to the upper end part. According to another embodiment, the screw has two blades below, with one blade continuing to near the top end part, which in turn has two blades. It is clear that a screw pump with for example two continuous blades and with four blades in the lower and/or upper end part can also be used according to the invention. In this way, the flow rate of the water stream can be increased by the presence of additional blades on the intake side of the pump, while on the other hand the frictional losses and turbulence can be kept low because the water only passes through one blade. Such a screw pump accordingly only requires a small capacity from the power source for a high flow rate. In the case of aerators, by increasing the number of blades near the upper end part, the effect of the centrifu¬ gal force of the screw is increased, and the output speed and distribution of the water current are improved, thus increasing the area of contact with the air. In the case where the apparatus is used as a mixer, better suction is improved by the extra screw blades above and/or the impeller force is increased by extra screw blades below. In another embodiment, the advantages offered by the invention can also be obtained by making the screw in different parts, for example a lower part with a multistage screw, a middle part with a single-stage screw and an upper part with a multistage screw. According to an advantageous embodiment, the screw consists of a cylinder-shaped shaft driven by a motor, said shaft having on the motor side a more or less trumpet- shaped deflector body curving towards the outside. A screw with a helicoidal, spiral-shaped motion is mounted at least partly round this shaft. A good pump effect or impeller force is obtained when the outside diameter of said screw starts from zero near the lower end of the shaft and gradually increases. The screw can consist of one screw blade (single- stage) or of several screw blades (multistage) , with the speed and the diameter in each case being either constant or variable. On the lower part of the shaft, up to a limited height, are mounted one or more extra screw blades, and several extra screw blades are mounted in, near or under the deflector body as necessary. According to a preferred embodiment, the form of the screw blades can be lightly curved upwards on the outside, thus increasing the pump effect. The invention is described below in greater detail on the basis of several non-limitative examples, with refer- ence to the attached drawings, where: Fig. 1 is a scheme of an embodiment of a screw for a water processing apparatus according to the invention; - Figs. 2 to 6 show various embodiments of a screw according to the invention. Fig. 1 shows a surface aerator which can also be used as a mixer, consisting of a motor 1 which drives a shaft 2. Said shaft 2 broadens on the upper side, forming a deflecting body 6 which curves outward. Round the shaft 2 is mounted a screw 3. Said screw consists of a blade 4 which starts from the bottom of the shaft and, following a helicoidal, spiral-shaped motion, terminates in the de¬ flecting body 6. A second screw blade 5 is also mounted at the bottom of the shaft; said second screw blade 5 however terminates after a spiral-shaped motion of approximately 180°. The screw therefore consists of two blades below, so achieving a good pump effect, but with one blade being very limited, so that little frictional losses and turbulence occur. For the sake of simplicity, Figs. 2 and 6 only show the screw around the shaft 2, where in Fig. 2 an upper end part A, a middle part B and a lower end part C can be distinguished. According to Fig. 2, one screw blade 11 starts in the lower end part with a diameter varying from the shaft diameter to the full diameter, and continues with constant diameter into the deflecting body 6. An extra screw blade 12 is mounted in the lower end part C, also starting from the bottom of the shaft 2, but terminates after a spiral-shaped motion of 270° or so. Fig. 3 shows a variant of Fig. 2 with a continuous screw blade 11 and an extra screw blade 13 in the upper end part A. Fig. 4 shows a combination of Figs. 2 and 3, with a continuous screw blade 11 and an extra screw blade 12 in end part C and another extra screw blade 13 in end part A. In this example, however, the screws 11 and 13 terminate underneath the deflecting body 6, so that the upper end part A is situated lower. Fig. 5 shows a variant of Fig. 4, in which a continu¬ ous screw blade 21 has a constant diameter and starts below the shaft 2. In this alternative embodiment there is an extra screw blade 22 in the end part C and there are two extra screw blades 23 and 24 in the upper end part A. Fig. 6 shows an assembled screw consisting of a continuous screw blade 31 starting from the top of the deflecting body 6 and continuing to underneath the middle part B. Underneath said screw 31 are four extra screw blades 32, each of which terminates after about 100° or so and which form the underneath end part C. Near the upper end part A are fitted two extra screw blades 33 and 34, extending over about 270°. In the construction of such a screw pump, the shaft 2 can be composed of several parts attached to one another, in this example by means of a nut 9. In the above examples, the discontinuous screw blades terminate after about 90°, 180°, 270° or 360°, but it is clear that there is no restriction on the execution of these screw blades, and that it can also terminate after one quarter of a revolution or can make any other fraction of a revolution or any number of revolutions. It is up to the person skilled in the art to determine which length a screw blade should have. The examples show embodiments which for the sake of simplicity are shown round the same shaft of the same apparatus. The invention is not limited to these embodi¬ ments, but can be applied on all aerators and mixers which comprise a propeller or screw which pumps the water up towards the surface or impels it downwards.

Claims: CLAIMS 1. Screw for a water treatment apparatus, such as an aerator or mixer, said apparatus comprising a power source (l) driving a shaft (2) with a helicoidal, spiral-shaped screw (3) fitted round at least part of said shaft (2) , such that water is sucked up or impelled downwards, characterised in that: the screw is formed of a screw blade construction compris¬ ing an upper end part (A) , a lower end part (C) and a middle part (B) between said two end parts, with at least one of said end parts comprising an extra screw blade. 2. Screw according to claim 1, characterised in that: the screw blade construction comprises at least one con¬ tinuous screw blade (4) , and at least one discontinuous screw blade (5) on at least one of the end parts. 3. Screw according to claim 1, characterised in that: the screw blade construction consists of one continuous screw blade (31) in the upper end part (A) and the middle part (B) , and at least one other screw blade (32) in the lower end part (C) . 4. Screw according to claim 2, characterised in that: the construction comprises a continuous screw blade (11) and at least one extra screw blade (12) on the lower end part (C) . 5. Screw according to claim 4, characterised in that: the construction also comprises at least an extra screw blade (13) on the upper end part (A) . 6. Screw according to claim 2, characterised in that: the construction comprises a continuous screw blade (11) and at least an extra screw blade (13) on the upper end part (A) . 7. Screw according to claim 3, characterised in that: the upper end part is formed by at least two screw blades (32) . 8. Surface aerator, characterised in that: it comprises a screw according to claim 1. 9. Water mixer, characterised in that: it comprises a screw according to claim 1.

Inventors: HAEGEMAN JOHNY HECTOR, HAEGEMAN, JOHNY, HECTOR
Applicants: HAEGEMAN J H, HAEGEMAN, JOHNY, HECTOR
Application year: 1995
Main classification: C02F3
IPC codes: B01F3, B01F7, B01F15, C02F3