Unloading device for filter press

Abstract: The unloading device for filter press has upper means (14) for supporting a series of filtering cloths which are associated with the opposite front surfaces of a corresponding series of plates (1) arranged in a pack, the plates being compressible between a fixed head and a movable head, whereby to form a succession of filtration chambers into which the liquid to be filtered is fed. The supporting means (14) are vertically movable between a raised filtration position, in which the filtering cloths are stretched, and a lowered unloading position, wherein an upper portion of the cloths forms a fold which is able to facilitate the separation of the bricks formed by the solid filtration residues. The unloading position corresponds to a limited opening of the filtration chambers.

Description: The present invention relates to an unloading device for filter press. It is known that filter presses are used to filter liquid substances; said filter presses are constituted in practice by a series of plates which are recessed in a central region and are arranged in a pack; respective elements made of filtering cloth are interposed between said plates, so as to form a succession of chambers into which the liquid to be filtered is fed. The plates and the associated cloths have corresponding holes forming, upon assembly, a duct which is used to feed the liquid to be filtered; in order to prevent the cloths from clinging to the plates, during filtration, said plates are provided with respective grooves which also facilitate the flow of the filtrate toward the lower part, wherefrom the flow is drawn by means of appropriate channels. The pack of plates is pressed between a fixed head and a movable head by means of a suitable jack which acts axially with respect to said pack. For this purpose, the plates are slidably supported on opposite lateral guides arranged horizontally parallel to each other and appropriately rigidly coupled to the fixed head. In a widespread embodiment, a single filtering cloth is folded on the upper edge of each plate so as to descend on the opposite sides thereof and cover its respective front surfaces. The fabric is furthermore tightly fitted to the plate by appropriate laces which are tied at the sides of said plate. Sometimes, however, there are two separate cloths which are applied on the opposite surfaces of each plate and are rigidly coupled to one another by lateral laces. The filtering cloths can furthermore be suspended from an upper support by appropriate elastic means ensuring the appropriate tension. Filtering cloths are also known which are formed by two distinct elements which are mutually coupled by a collar intended to enter said hole of the plate. Said cloths are obviously perforated at said collar. The solid residue filtered from the liquid is collected in the above mentioned chambers defined between the adjacent plates, until it forms a sort of brick or cake. Said brick is in contact with respective filtering cloths on its opposite surfaces. It therefore becomes necessary to periodically unload from the filter press the bricks formed by the filtration residues. This operation is generally performed by mutually spacing the plates, by virtue of the sliding of the movable head, so as to open the filtration chambers and allow the falling out of said bricks due to gravity. Sometimes, however, the bricks do not separate, due to the force of adhesion to the filtering cloths, thus requiring the intervention of an operator who manually performs an appropriate mechanical action. This obviously entails a significant limitation to the productivity of the filter press. Furthermore, in order to allow manual intervention for cleaning it is necessary to provide a wide opening of the chambers, i.e. a considerable mutual spacing of the plates. This leads to a correspondingly large bulk of the filter press and to the need to use an expensive opening jack. It is known from DE-A-1813792 an unloading device for filter press comprising a movable pneumatic cylinder, which is placed above the upper supporting means of the filtering cloths when the neighbouring plates are in an open unloading position, provoking the vibration of the filter cloths by contact with the vibrating stem of the cylinder. However due to of the presence of the bars (Fig. 5; 41, 44) limiting the movement of the vibrating element (Fig. 5, 6; 34), a fold of the upper part of the filter element as described in the application cannot be formed even by adapting the frequency of the vibration. In order to obviate this problem, various unloading devices have been provided which are intended, for example, to impart a reciprocating motion to the bricks in order to facilitate their separation. However, these devices are generally complicated and do not ensure complete separation of the bricks. The aim of the present invention is to solve the above problem by providing a device which allows to safely and rapidly unload from the filter press the bricks formed by the filtration residues, without requiring manual interventions and with a limited opening of said filter press. Within the scope of this aim, an object of the present invention is to provide an unloading device for filter press which is simple in concept, safely reliable in operation and versatile in use. This aim and these objects are achieved, according to the invention, by the present unloading device for filter press, comprising a series of plates arranged in a pack, said plates being compressible between a fixed head and a movable head, whereby to form a succession of filtration chambers into which the liquid to be filtered is fed, and a corresponding series of filtering cloths associated with said plates, characterized in that said upper means comprise a series of rocker elements (12) vertically movable by means of a corresponding series of cylinders (13), said rocker elements (12) being vertically movable between a raised filtration position, in which said cloths are stretched, and a lowered unloading position, wherein an upper portion of said cloths forms a fold which facilitates separation of the bricks formed by the solid residues of filtration of said liquid, said unloading position corresponding to a limited opening of said filtration chambers. The details of the invention will become apparent from the detailed description of a preferred embodiment of the unloading device for filter press, illustrated only by way of non-limitative example in the accompanying drawings, wherein: figure 1 is a partially cutout front view of an unloading device for filter press according to the present invention; figure 2 is a side view thereof; figure 1a is a corresponding front view of a modified embodiment of said device; figures 3 and 4 are respectively perspective views of a filter press provided with an unloading device provided in a different form, in successive positions of the unloading step; figures 5 and 6 are transverse sectional views of a filtration chamber, illustrating a further embodiment of the unloading device, with cloth return by virtue of spring means, respectively during filtration and during unloading. With particular reference to the above figures, the reference numeral 1 designates the plates of a known filter press. A pair of filtering cloths 2 is associated with each plate 1; said cloths are able to respectively cover the opposite front surfaces of said plate. The plates 1 are arranged in a pack and are able to be pressed between a fixed head 3 and a movable head 4 upon the actuation of a jack 5 which acts axially with respect to said pack. For this purpose, the plates 1 are slidably supported on opposite lateral guides 6 which are arranged horizontally, parallel to each other and are appropriately rigidly coupled to a frame of which the fixed head 3 is a part. The plates 1 are bilaterally recessed in a central region 1a, so as to form, when they are mutually pressed together, a succession of chambers 7 into which the liquid to be filtered is fed. The plates 1 and the filtering cloths 2 which are associated therewith have corresponding holes 8 and 9 which are able to form, upon assembly, a duct 10 which is used to feed the liquid to be filtered. At the holes 9, the cloths 2 are rigidly coupled by a collar 2a which covers, in the assembly position, the hole 8 of the related plate 1. The filtering cloths 2 of each plate 1 are furthermore mutually fastened by means of laces 2b which are tied at the sides of said plate below the plane defined by the duct 10 and at its lower side. Respective bricks 11 form during filtration in the chambers 7 of the filter press. According to the solution illustrated in figures 1 and 2, the device for unloading the bricks 11 formed by the filtration residues has upper means for supporting the filtering cloths 2 which are constituted by a series of rocker elements 12 which are supported so that they can move vertically by means of a corresponding series of pneumatic or fluid-activated cylinders 13. The cylinders 13 are supported with a vertical axis by a bridge-like frame 14 which is fixed, at its opposite ends, by means of brackets 15, to the sides of a related plate 1. In practice, it is preferred to provide a frame 14, and consequently a cylinder 13, for every two plates 1, in an alternating manner, as shown in figure 2. The stem 13a of the cylinders 13 elastically supports, by virtue of the interposition of a helical spring 16, a cross-member 17 which is arranged longitudinally to the filter press and is provided with a pair of rockers 12 at its ends. The rockers 12 are constituted by a tubular rod 18 which extends horizontally and transversely to the longitudinal axis of the filter press above the plate 1 and is rigidly coupled to the cross-member 17 by means of a coupling 19. The rod 18 is crossed by a plurality of pins 20 which are uniformly distributed and protrude vertically upward. A pair of filtering cloths 2 is mounted by means of appropriate rings on the pins 20 of each rod 18; said cloths are arranged on the opposite sides of said rod 18, so that they can be associated with the opposite surfaces of a pair of adjacent plates 1; the cloths 2 are retained on the pins 20 by means of respective split pins, not shown, inserted in holes which pass through said pins. The rockers 12 can move between a raised filtration position, in which the filtering cloths 2 are under tension, and a lowered unloading position, in which an upper portion of said cloths forms a fold which facilitates the separation of the bricks 11. Conveniently, the descent of the rockers 12 is performed by gravity, by removing pressure from the pneumatic cylinders 13, whereas the return to the raised position in which the filtering cloths 2 are under tension is obtained by feeding compressed air to said cylinders 13. Naturally, the descent rate of the rockers 12 can be adjusted according to the requirements by varying the rate at which the compressed air is vented from the cylinders 13, by means of suitable valve elements 21. The descent of the rockers 12 into the unloading position is performed in combination with a limited opening of the filtration chambers 7, in practice by the amount sufficient to allow the separation and falling of the related bricks 11. Preferably, the chambers of the filter press are opened in successive segments of the pack of plates 1, as shown in the Italian utility model application no. 34404 B/90 filed on February 22, 1990 by the same Applicant. In practice, the plates 1 are mutually concatenated and the end plates of the pack are rigidly coupled to the heads 3 and 4 respectively. The first segment of filtration chambers is opened by moving the movable head 4, while the first plate of the second segment is appropriately locked. Subsequently, a suitable device moves the last plate of the first segment, so as to press together the plates of said first segment and simultaneously pull open the plates of the second segment; the gradual opening of the successive provided segments is performed in a similar manner. The opening of the filtration chambers allows the falling of the bricks 11 due to gravity; the bricks which remain attached to the cloths 2 are instead separated by the descent of the rockers 12. At the open filtration chambers, the descent of the rockers 12 in fact slackens the related filtering cloths 2 and forms the above mentioned fold in the upper portion of said cloths, since the cloths, which are no longer stretched, are dragged downward by the weight of the bricks; the loose portion extends in practice up to the collar 2a of the cloths 2. Therefore, the weight of the bricks 11 bears, when the chambers 7 open, only on the lower portion of the cloths 2, below the collar 2a. This causes the separation of the tiles which have remained attached to the filtering cloths. After the separation of the bricks, the rockers 12 are returned to the raised position, so as to stretch the filtering cloths 2 again. It is furthermore possible to provide the possibility of performing more than one stroke for the lowering and lifting of the rockers 12, one stroke after the other, when a stronger brick separation action is required. The descent of the rockers 12 is generally limited to the upper edge of the plates 1. However, it is possible to perform a longer rocker descent stroke, since said rockers can enter the open chambers 7. It should be noted that any descent of the rockers at the closed chambers has no consequences, since said rockers rest on the closed plates 1. Figure 1a illustrates a further embodiment of the described device, wherein, for the sake of greater clarity, the corresponding elements have been designated by the same reference numerals. According to this solution, the cylinders 13 are mounted so that their stem 13a is directed vertically upward; the stem 13a elastically supports, by virtue of the interposition of the spring 16, the cross-member 17 which is arranged longitudinally to the filter press and is provided, at its ends, with the couplings 19 of a pair of rockers 12. The cylinders 13 are supported by a beam 14 which is fixed, at its opposite ends, by means of brackets 15, above a related plate 1. The beam 14 is substantially parallel and close to the upper edge of the corresponding plate 1. In practice, as mentioned, one beam 14, and consequently one cylinder 13, are mounted for every two plates 1 in an alternating manner. In this case, in the lowered unloading position the rockers 12 extend partially between the open plates 1, as shown in figure 1a; descent of the rockers 12 is performed by gravity, removing pressure from the pneumatic cylinders 13. Instead, when compressed air is sent to the cylinders 13, said rockers 12 move to the raised position for stretching the filtering cloths 2, and it is therefore possible to actuate the closure of the filtration chambers by closing the plates 1 in a pack. Conveniently, it is possible to associate with the couplings 19 a suitable photocell 29 capable of detecting the position in which the rockers 12 are inserted between the plates 1, in said lowered unloading position, so as to prevent an incorrect operation for closing said plates. This solution has the advantage of significantly limiting the size of the device, and in particular the size of beam 14 is smaller. During transport it is convenient to disassemble the cylinders 13. This solution is furthermore very easily and rapidly assembled, with a limited number of screw elements needed for this purpose. In the simplified solution shown in figures 3 and 4, the filtering cloths 2 are supported in an upward position in pairs by a rod 22 with appropriate elastic means 23 interposed. Said rods 22 are supported so that they can slide transversely to a beam 24 which is arranged longitudinally to the filter press and can move vertically by means of a pair of jacks 25 which are arranged at its ends; said jacks 25 are rigidly coupled to the fixed frame of the filter press. The rods 22 are guided on the beam 24 by means of respective sliders 26. In this case, the filtering cloths 2 are moved simultaneously between the raised filtering position, in which they are stretched, and the lowered position for the unloading of the bricks 11, wherein an upper portion of said cloths is loose. Separation of the bricks obviously occurs at the segment of the filter press whose filtration chambers are open, whereas the descent of the rods 22 has no consequences in the remaining part, since said rods rest on the closed plates 1. The reciprocating movement of the beam 24 can be repeated several times in order to facilitate the separation of the bricks. Finally, in the solution shown in figures 5 and 6, the filtering cloths 2 which cover the opposite front surfaces of each plate 1 are suspended in an upward position, by virtue of suitable spring means 27, from a supporting frame 28 which extends above said plates. The springs 27 keep the cloths 2 under tension when the plates 1 are mutually adjacent in the filtering position (figure 5). Instead, when the chambers 7 are opened, the weight of the bricks 11 causes the folding of the upper portion of the cloths 2, whose upper edge is dragged downward by virtue of the extension of the springs 27 (figure 6). The springs return the cloth into the stretched position. This last type of embodiment of the invention is clearly simpler (since it provides only for springs for stretching the filtering cloths) and can be used in cases in which it is not necessary to repeat the descent/ascent of the cloths in order to separate the bricks. Application of the springs alone allows a single cloth descent/ascent operation. The device thus allows to safely and rapidly unload from the filter press the bricks formed by the filtration residues, without requiring manual interventions. It should be particularly stressed that the bricks are unloaded with a limited opening of the filtration chambers, so as to contain the size of the filter press within a limited size. In the practical embodiment of the invention, the materials employed, as well as the shapes and dimensions, may be any according to the requirements. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.

Claims: Unloading device for filter press, comprising a series of plates arranged in a pack, said plates (1) being compressible between a fixed head (3) and a movable (4) head, whereby to form a succession of filtration chambers into which the liquid to be filtered is fed, and a corresponding series of filtering cloths (2) associated with said plates, whereby to cover opposite front surfaces of said plates, upper means for supporting said filtering cloths, characterized in that said upper means comprise a series of rocker elements (12) vertically movable by means of a corresponding series of cylinders (13), said rocker elements being vertically movable between a raised filtration position, in which said cloths are stretched, and a lowered unloading position, wherein an upper portion of said cloths forms a fold which facilitates separations of the bricks (11) formed by solid residues of filtration of said liquid, said unloading position corresponding to a limited opening of said filtration chambers. Device according to claim1, characterized in that said upper supporting means further comprise spring means (16) for keeping said filtering cloths elastically under tension in said raised position. Device according to claim 1, characterized in that said series of cylinders (13) have a vertical axis and are supported by a frame which is fixed to said plates at its opposite ends, the stem of said cylinders elastically supporting, by virtue of the interposition of spring means, coupling means for pairs of said rocker elements. Device according to claim 3, characterized in that said rocker elements support a rod (18) extending horizontally transverse to the longitudinal axis of the filter press and above said plates, a plurality of uniformly distributed pins (20) protruding vertically upward from said rod, a pair of said filtering cloths being suspended from said pins whereby said cloths are associated with the opposite surfaces of a pair of adjacent plates. Device according to claim 3, characterized in that it comprises a fixed support which is anchored to said filtering plate and supports said cylinder (13), said cylinder having a stem (13.a) supporting said pair of rockers, said rockers supporting a rod wherefrom said pair of filtering cloths is suspended. Unloading device for filter press, comprising a series of plates (1) arranged in a pack, said plates being compressible between a fixed head (3) and a movable head (4), whereby to form a succession of filtration chambers into which the liquid to be filtered is fed, and a corresponding series of filtering cloths (2) associated with said plates, whereby to cover opposite front surfaces of said plates, upper means for supporting said filtering cloths (2), characterized in that said filtering cloths are supported in an upward position, in pairs, by rods (22) which are transverse to the longitudinal axis of the filter, elastic means (23) being interposed between said filtering cloths and said rods, said rods being slideably supported by a beam (24) arranged longitudinally with respect to the filter press and being vertically movable by means of a pair of jacks (25) arranged at its ends. Device according to claim 1, characterized in that said filtering cloths are supported in an upward position, in pairs, by horizontal rods (22) which are transverse to the longitudinal axis of the filter press, elastic means (23) being interposed between said filtering cloths and said rods, said rods being in turn supported, by a fixed support which is anchored to said filtering plate at its ends, further elastic means being interposed between said rods and said fixed support. Device according to claim 3, characterized in that said cylinders (13) each have a stem directed vertically upward, said rocker elements (12) extending partially between said plates when in the lowered unloading position, movement of said rocker elements to said raised filtering position, above said plates (1), being achieved by feeding compressed air to said cylinders.

Inventors: GRIGOLETTI FRANCO, GRIGOLETTI, FRANCO
Applicants: GRIGOLETTI FRANCO, GRIGOLETTI, FRANCO
Application year: 1992
Main classification: B01D25
IPC codes: B01D25