Continuously operating filtering device

Abstract: Continuously operating filtering devices are voluminous when accommodated in a casing. The casing serves to maintain a determined pressure round the filter, for instance in view of released gases. It is the objective to keep the volume as small as possible. This is achieved by using plastic as carrier belt. Up to the present rubber carrier belts have been used. These however impose limitations on the diameter of the guide rollers. A limitation of the roller diameter to 25% in comparison to rubber carrier belts is possible with the use of plastic. In addition, plastic has a better resistance to aggressive substances.

Description: The invention relates to a continuously operating filtering device as described in the preamble of claim 1 and is known from document US 4 351 726 A. Such filtering devices, particularly when they are accommodated in a housing or casing, are voluminous which causes problems at the location of use for instance in the processing industry. Furthermore, in such filtering devices, in vase of channels wih horizontal bottom, the discharge characteristic of the channel can be unfavourably affected, since liquid particles are loaded equally by both suction boxes. It is therefore an object of the present invention to solve the above mentioned problems. Limiting the size of the device is achieved according to the invention in that the carrier belt is made of plastic. By choosing for a carrier belt of plastic the diameter of the drive roller and guide rollers can be kept considerably smaller than is the case with the usual rubber carrier belt. A limitation to 25% of the roller diameter in the case of rubber carrier belts is possible. It is of further advantage that plastic is generally resistant to aggressive substances, which is not the case with rubber. In the case of a rubber carrier belt lubrication has to be applied between the means for supporting the carrier belt and the carrier belt itself, since the coefficient of friction of the rubber material is comparatively high. Lubrication can be dispensed with when plastic is used, in any case with filtering devices to a determined size. As a result of the lower friction the driving power can likewise be limited. The channel of the ribbed carrier belt are formed with an inclination from the middle of the belt to the sides so as to subject liquid particles to a driving force towards one of the suction boxes as a result of the force of gravity. The plastic can be a thermoplastic plastic. A thermosetting plastic may also be chosen. Thermosetting plastic is relatively stiff material. In order to enable training of the belt round the guide rollers the belt must be constructed from connected links of limited length. Thermosetting plastic can be applied at high temperatures and are more resistant in a chemical atmosphere to for instance solvents. The device can be accommodated in a housing and be provided with means for maintaining a desired pressure in the housing. Such filtering devices can be used when for instance solvents can occur freely through evaporation and these gases must be held in a closed circuit. Due to the lower structure the total size can be restricted despite accommodation in the housing or casing. At the beginning and end of the path traversed jointly by the carrier belt and the filter belt sealing means can be applied running in transverse direction and in lengthwise direction of the belts. Further advantages and features of the invention will become apparent from the accompanying claims and figure description. In the drawings: Fig. 1 shows a schematic longitudinal view of a device according to the invention, Fig. 2 is a schematic sectional view along the line II-II in fig. 1, Fig. 3 and 4 show special features of the applied carrier belt, and Fig. 5 shows a second embodiment. The device according to the invention is accommodated in a housing 1 inside which a desired pressure is maintained. The device comprises inter alia a frame 2, a carrier belt 3, a reversing roller 4 and a driven roller 5. Carrier belt 3 supports an endless filter belt 6 which is trained round guide rollers, for instance 7. Situated on either side of the filter belt are suction boxes 8. The carrier belt is supported by the means 9. Using the feed 10 the desired pressure is maintained in housing 1. The filtered material, the filter cake, is carried outside the housing 1 using the outlet 11. The material for filtering is carried into the housing via the feed 12. A connection 13 is arranged on the suction box. At the beginning and end of the path traversed jointly by the carrier belt and the filter belt a seal 16 is arranged in transverse direction and a seal 14 in lengthwise direction. For a part of the support means 9 a different material 15 is chosen in order to limit the friction between carrier belt 3 and support means 9. Operation is possible without lubrication due to the choice of plastic for the carrier belt and the choice for a part 15 of the support means 9. During operation the belt is rotated in the known manner in the arrow direction P and the material for filtering is carried onto the filter belt 6 over the inlet 12. The filtered material is discharged at the end of the filter belt close to the roller 7. As shown in fig. 4, the plastic belt is profiled. Due to the chosen profile as according to fig. 4, a channel is formed with an inclination through an angle H over a length L calculated from the middle of the belt to the side (see fig. 3). Liquid particles are subjected in this zone to a driving force towards one of the suction boxes as a result of the force of gravity. When compared to a horizontal progression the choice of an inclination has the advantage that, where in the case of a horizontal bottom a liquid particle is loaded equally by both suction boxes, in the present case there is a preferred direction. With a horizontal bottom the discharge characteristic of the channel can be unfavourably affected. The channel formed by the profile can be interrupted in the centre of the belt. In the embodiment of fig. 5 the carrier belt 3 is constructed from successive links of thermosetting plastic. The links have dimensions of for instance a pitch length of 200 mm and a width of between 500 and 4000 mm. The mutual coupling between the links 17 can be implemented in different ways.

Claims: Continuously operating filtering device comprising a transversely ribbed carrier belt (3) movable around guide rollers (4) and at least one drive roller (5), and a filter belt (6) supported thereby, means (9) for supporting the carrier belt and suction boxes situated on either side of the carrier belt (3), said transversal ribs being separated from one another by respective channels (18) extending transverse to the moving direction of the carrier belt (3) and feeding into the suction, boxes (8), characterized in that the carrier belt (3) is of plastic and in that said channels (18) are formed with an inclination from the middle of the belt (3) to the side so as to subject liquid particles to a driving force toward one of the suction boxes (8) as a result of the force of gravity. Continuously operating filtering device as claimed in claim 1, characterized in that the carrier belt (3) is of thermosetting plastic, in that the carrier belt (3) is constructed from connecting links (17). Filtering device according to claim 1, wherein the carrier belt (3) is made of thermoplastic plastic. Filtering device as claimed in any claims 1-3 characterized in that the device is accommodated in a housing (1) and is provided with means for maintaining a desired pressure in the housing. Filtering device as claimed in any of claims 1-4, characterized by first sealing means (16) arranged at the beginning and end of the path traversed jointly by the carrier belt (3) and the filtering belt (6) and running in transverse direction of the belts (3, 6) and second sealing means (14) running in lengthwise direction of the belts (3, 6). Filtering device as claimed in any of claims 1-5, characterized in that the carrier belt supporting means (9) are partly of a material (15) of which the coefficient of friction is lower than that of the rest of the belt supporting means (9). Filtering device as claimed in any of the preceding claims, wherein a channel (18) is interrupted in the center of the carrier belt (3).

Inventors: THISSEN KAREL ANTOON, THISSEN, KAREL ANTOON
Applicants: PANNEVIS BV, PANNEVIS B.V.
Application year: 1993
Main classification: B01D33
IPC codes: B01D33