GB1602076A - Plate filter press with displacing apparatus - Google Patents

Description

(54) PLATE FILTER PRESS WITH DISPLACING APPARATUS (71) We, EBERHARD HOESCH & SOHNE GMBH & CO., a German firm, of Postfach 116 D-5160 Duren, Germany, do hereby declare the invention, for which we pray that a patent may be granted to, us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a plate filter press wherein vertically oriented filter plates are mounted to be capable of horizontal displacement on at least one guide member, and each filter plate is provided with at least one fixed lug or extension, and wherein there is provided a displacing apparatus comprising a supporting element which can be moved to and fro alongside the plates by means of a drive and which is provided twei filter plate entrainment elements such as pawls, the two elements being each adapted to come to abut on the fixed extension of the filter plate being transported.

A filter press of the type initially specified is known for example from British patent 1 422 265. Filter presses with such displacing apparatus for the filter plates usually operate very reliably. But the relatively considerable overall height of this displacing apparatus is regarded as an important disadvantage. In a number of uses difficulties also occur as regards emptying in accordance with the special properties of the particular product being filtered, which cannot be overcome by the known displacing apparatus. For example when filtering heavy liquids, whose solids content consists substantially of fibrous products, after the opening of the filter press the individual filter plates are driven away from one another by the expansion of the filter cake. In the case of filter plates with small displacement resistance, more particularly filter plates suspended above by means of running rollers, it may happen that the filter plates become displaced accidentally and filter cake falls out in an uncontrolled way. A further problem is that in a number of uses there is considerable sticking of the filter cloths or the filter cakes with the filter cloths, so that when a plate is displaced the next plate in succession is also drawn along.

In order to obviate the aforesaid disadvantages, filter presses have been developed wherein the individual filter plates in the closed state are locked to one another by means of locking hooks each to the neighbouring filter plate. A plate filter press constructed in this way is described in U.S. patent 3 915 863. In that case the unlocking and the transporting of the plates are effected respectively directly by means of the locking hooks. In the kinds of use wherein after the filtering operation has been completed fairly considerable expansion forces may occur sometimes in the filter cakes, the locking hooks are also under a corresponding preload. Since the forces which are produced in this way act in the opening direction on the locking hooks, the unlocking of the filter plates must be carried out under load. Under the influence of the unlocking forces, the friction force on the locking hooks is then additionally increased. Consequently the locking hooks, opening pawls and entrainment elements at the displacing apparatus must be given substantially larger dimensions than would be necessary per se when allowing for normal action of forces. With very disadvantagseous friction factors at the unlocking surfaces, the tensile stresses increase so, considerably that it is unavoidable that damage occurs at these devices.

Whilst in principle accidental opening of the group of plates is obviated by the plate filter press construction described hereinbefore, these constructions do in fact have the disadvantage that after the unlocking of the particular filter plate being transported the said plate can move onwards independently in the direction of transport owing to its kinetic energy even when the displacing apparatus has been switched off.

This means that there is a considerable danger of accidents to the operators. A further disadvantage of the construction described last is that after the filter plate has been transported the unlatching from the entrainment element of the dlspiacing apparatus must be carried out at an earlier stage along the path of travel than the pushing of the plate against the plate which is already in the open position, and to, which the plate which is in the process of movement at the time has to be locked again. Therefore, satisfactory operation of this cycle of move ments depends on the kinetic energy within the filter plate and the friction forces opposing this. If owing to fouling or premature unlatching of the plate from the entrainment element of the displacing apparatus the friction forces are greater than the kinetic energy of the plate, the plate does not come to, abut on the group of plates at the opening side, so that locking is also not possible.

The invention has as its object to obviate the disadvantages which have been described hereinbefore and to provide a plate filter press wherein the operations which are necessary for transporting the plates are to be automatically and constrainedly controlled. Accordingly there is provided a plate filter press having a plurality of vertically arranged filter plates mounted on at least one guide member for horizontal displacement from a filter-closed position, whereat the filter plates are normally stacked, to a filter-open position, each said plate having an extending abutment portion on which a pin, or eye, and a biassed and pivoted hook are mounted, said hooks and said pins, or eyes, being so arranged that when the plates are stacked each pin, or eye, is normally engaged by the hook of an adjacent plate and the plates in the stack are thereby locked together, and further comprising displacing apparatus for linearly transporting each plate in tum from the stack located at the filter-closed position to the filter open position, said apparatus including at least one carrier which is movable back and forth alongside the filter plates on which carrier there is rotatably mounted first and second plate abutment portion engaging members, said members being spaced apart on the carrier so as to face and abut opposite sides of the abutment portion of a respective plate when the carrier is aligned with the plate, said carrier acting through said first member in the filter closing direction so as to compress the stack of plates together to enable the hooks to be freely uncoupled from their respective pins, or eyes, and acting in the opening direction through said second member so as to separate an end plate from the stack after the respective plate is unhooked, both said members having edge portions which are engageable with plate abutment portions when the carrier is moved in the direction opposite to that in which the respective member acts, said engagement causing the respective member to ride over the engaged abutment portion, and said second member having at least one nose-like projection which when the carrier is positioned in registration with the next plate to be moved enters a space between the abutment portion of that plate and the abutment portion of the adjacent plate where it engages the hook of the plate to be moved and releases it from the said adjacent plate.

Preferably the carrier is formed of two roller chains which are arranged parallel adjacent one another and are guided along endless paths of travel, and that the plate abutment portion engaging members are spring biassed pivoted pawls each mounted on a pin connecting the two chains to one another. The advantage of this arrangement is that the entire displacement apparatus is given a lower overall height, more particularly in the region of the abutment portion engaging members. Commercially available roller chains can be used for the carrier. Thus the necessary guide wheels and driving chain wheels represent component parts which are commercially available also, so that production and maintaining replacement stocks are considerably simplified. The use of roller chains also has the advantage that it is possible to position the two elements precisely and without slip. The gap between the two roller chains also makes it possible to arrange the two abutment portion engaging members to lie flat approximately in the plane defined by the two roller chains so that the two elements project only slightly above this plane.

In a further advantageous feature of the preferred embodiment the said first plate abutment portion engaging member is given such a length that it bridges at least the abutment portions of two filter plates which abut directly on one another. This arrangement makes it possible to arrange the member to extend approximately horizontally at the displacing apparatus, so that a very low overall height is obtained for this apparatus.

For a plate filter press, more particularly of the type specified initially, to allow automatic and constrainedly controlled sequences of operation it is proposed that a bellcrank lever is pivotably connected to the free end of the first plate abutment portion engaging member one end being adapted to abut the abutment portion of the filter plate being transported and the other end extending over the free end of the second plate abutment portion engaging member and being arranged to abut thereon.

The advantage of this arrangement consists in that at the instant of abutment of the said first member on the abutment portion of the particular filter plate being transported by means of the bellcrank lever the said second member is constrainedly brought into its operating position and thus is independent as regrads o,peration of any chance circumstances such as friction freedom, spring strength or the like. As the effective force for operating the said second member is the force exerted by the drive on the carrier, which is substantially greater than could be the force of spring operating on the said second member. A further advantage of this arrangement consists in that because of the considerable force acting constrainedly on the said second member the locking hooks can be released by means of the second member even in plate filter presses whose filter plates are locked to one another. The advantage derives from the fact that the releasing of a locking hook takes place when the filter plate assembly is compressed in the closing direction by the said first member, so that at the opening of the locking hook it is simply necessary to overcome any spring force which acts on the locking hook.

Whilst it is possible in principle to bring the said first and second members by gravitational force i.e. because of their own weight, into the operating positions, it is particularly advantageous if at least the said first member is biased towards its operating position by a spring.

It is particularly advantageous if that end of the bellcrank lever which projects beyond the said second member comprises a slot through which is inserted a pin connected with the second member. This arrangement has the advantage that the three basic elements of the displacing apparatus, namely the first and second members and the bellcrank lever, are positively connected to one another so that the bellcrank lever is securely held even if for reasons of saving space the first and second members must act upwardly from below on the abutment portion of the filter plate being transported.

In an advantageous embodiment of the invention it is proposed that the said first member is constructed as a spring-loaded pawl and that the second member is constructed as a toothed star wheel and is provided with a stop element which allows rotation of the star wheel only when there is movement of the carrier in the plate closing direction. This constructional form has the effect that when incurring plate transporting operation by means of the star wheel the locking hook is constrainedly opened, that is to say with the force initiated by the displacing apparatus, thus excluding any chance circumstances which may arise in the case of lock release by means of a spring-loaded actuation.

In the preferred arrangement of the last said embodiment it Is proposed that the stop element is a spring-loaded detent pawl which engages in the toothed star wheel. Whilst it is possible in principle to provide the star wheel with an additional stop element this construc- tional form offers the particular advantage of a simple and space-saving ararngement since the star wheel also, forms part of the stop mechanism. It is particularly advantageous if the detent pawl comprises a roller at its end which abuts on the star wheel. This gives an advantageous rolling behaviour, low friction and gives the entire arrangement a longer working life.

It is further proposed that the said first member and the detent pawl are acted upon by a coznmon spring element, in such a manner that their free ends are moved in the direction towards the respective filter plate extension. In addition to simplifying construction and assembly this arrangement has the advantage that on rotation of the star wheel with the lifting of the detent pawl which this involves the spring force acting on the said first member is further increased and thus the said first member is reliably held in its operative position during the rolling-over of the fixed extension on the filter plate.

Preferably, the said first member comprises a lever having a substantially U-shaped crosssection and that the detent pawl is arranged between the legs of the U-shaped cross-section but mounted on the carrier. This allows a very narrow construction for the entire arrangement.

Preferably also, a hydraulic motor with pressure-dependent reversal of the direction of rotation is provided for the displacing apparatus. This has the advantage that in addition to automating the opening operation it is also possible by the setting of the reversing pressure to preset the pressure application force with which the particular filter plate being transported is pressed towards the filter plate group by the said first member or the said second member as appropriate, so that in filter presses with the filter plates locked to one another it is possible in every case to carry out stress-free unlocking.

In a further embodiment of the invention the locking hooks are each provided with a laterally projecting abutment and that there is provided alongside these abutments a push rod which extends over the entire length of the filter press and which is mounted by means of at least two, rocking levers on the machine frame so as to move parallel to itself when longitudinally displaced relative to the frame. This arrangement makes it possible to unlock the locking hooks of all the filter plates simultaneously independently of the displacing apparatus, and thus carry out displacement of the filter plates by hand.

The invention will be explained in detail with reference to diagrammatic drawings of constructional examples. In these drawings: Fig. 1 shows a constructional form with the guide beam for the filter plates situated above.

Fig. 2 shows a constructional form with a lateral guide beam for the filter plates, Figs. 3a and b show a constructional form of the displacing apparatus for a plate filter press with suspension above, Fig. 4 shows a section on the line IV-IV of Fig. 3, Figs. Sa and b show a constructional form of the displacing apparatus for a plate filter press with lateral guide beams, Fig. 6 shows a section on the line '71-v' of Fig. 5, Figs. 7a and b show a central unlocking arrangement in the closed and opened positions.

Figs. 8a and b show a constructional form with bellcrank levers operating in a forcelocking fashion, Figs. 9a and b show a constructional form of the displacing apparatus with a shapelocking connection between the bellcrank lever and the entrainment element.

The plate filter press shown in the closed state in a side view in Fig. 1 coznprises, above, a guide beam 1 supported at its two ends by uprights 2 and 3 supported on the floor. The guide beam is constructed for example as an I-beam on whose lower flange there are suspended an end plate 4, a plurality of filter plates 5 and a head plate 6. The end plate is secured in a stationary situation on the guide beam, whilst the head plate 6 is mounted to be capable of displacement on the guide beam 1. The filter plates 5 are connected at the flange of the guide beam with suspension elements 12 which allow displacement of the individual filter plates when opening and closing the plate filter press in the direction of the longitudinal axis.

Four hydraulic piston and cylinder units 7 are secured respectively at the corner regions to the head plate 6. The piston rods 8 of each piston and cylinder unit are connected by way of a coupling 9 with connecting rods 10 connected by means of ball-joint bearings 11 with the end plate 4. The piston and cylinder units 7 are connected in a manner not shown in detail here by means of a corresponding control arrangement to an oil supply so that during the filtering operation the filter plate group 5 can be compressed with the necessary closing pressure. The individual filter plates, shown stacked in their normal, filter-closed, position are locked securely to one another, which will be explained in detail hereinafter, so that after the filter operation is concluded the head plate 6 can be displaced by means of the piston and cylinder unit out of the filter closed position into an open position without the filter plate group opening. By means of a displacing apparatus 13 which extends in the longitudinal direction of the guide beam 1 at the height of the suspension elements 12 and which will be described in detail with reference to subsequent Figures, the filter plates 5 are displaced individually in succession in the direction towards the head plate 6 situated in the open position in order to eject the filter cake and for any washing operations which may be necessary.

The displacing apparatus is constructed so as to unlock the plate to be transported from the neighbouring plate in the stack. As will be described hereinafter, the particular filter plate being transported is locked again at the instant when it comes to abut on the filter plate group which abuts on the head plate situated in the open position. Before starting a new filtering operation the filter plates are all displaced by the hydraulic cylinders 7 by means of the head plate 6 back against the end plate 4 and then pressed against the end plate with the necessary closing pressure.

In the case of the plate filter press shown in Fig. 2 the press frame 14 is provided at both sides with guide beams 15 on which the filter plates 5 bear by means of lateral fixed extensions 16. Situated parallel to each beam is a displacing apparatus 13 which will be described in detail hereinafter. The closing of the filter press is effected in this case by means of a hydraulic cylinder 17 extending in the direction of the longitudinal axis. Otherwise the operation corresponds to that of the press construction previously described.

By means of Figs. 3 and 4 a displacing apparatus for a plate filter press with an upper suspension arrangement as shown in Fig. 1 will be explained in detail. Fig. 3a shows the displacing apparatus directly on initiating a transporting operation, whilst Fig. 3b sho,ws the position of the individual members at the instant when the plate just being transported is locked again at the open side to the other filter plates.

The displacing apparatus includes a carrier which in this case comprises two endless roller chains 18 which are arranged parallel adjacent one another, and to which there are pivotably connected a pawl 19 used as the first plate abutment portion engaging member and a pawl 20 used as the second plate abutment portion engaging member. These two pawls, referred to hereafter as, respectively, the "reversing pawl" and the "opening pawl", are so arranged relatively to one another, as shown, that their free ends are directed towards one another. The two pawls 19, 20 are mounted by means of suitable pins 21 between the two roller chains 18. By means of a leg spring 22 and 23 respectively, each such spring being secured at its coil portion on the bearing pin 21 of the relevant pawl, with one leg bearing on a supporting pin 24 connected to the two roller chains and the other end bearing on the pawls 19 and 20 respectively, the two pawls 19 and 20 are subjected to a downwardly acting opening-out tendency away from the roller chain.

An aperture 25 in the region of the pin 24 is used as a limiting abutment for limiting the possible pivoting movement of the two, pawls 19 and 20.

The suspension elements 12 of the filter plates are each provided with a fixed extension or abutment portion 26 which extends upwards in an inclined manner and is provided with a window-like aperture 27. Mounted to be pivotable in the window-like aperture is a locking hook 28 which is also connected to a leg spring 29' which subjects the locking hook 28 to such a preload that the said hook is pivoted in the direction towards the roller chain situated above. Also arranged below the bearing pin 29 for the locking hook 28 in the window-like aperture 27 is an arresting pin 30 defining an "eye" into which the hook end of the neighbouring filter plate at the opening side enters to engage the pin.

The reversing pawl 19 is given such a length that it bridges at least two extensions 26 situ ated side by side, as is shown in Fig. 3b, so that on movement in the direction of the arrow 31 the reversing pawl 19 can slide freely over the extensions of the filter plates situated in the open position.

The opening pawl 20 comprises a downwardly projecting nose 32 which is dimensioned in such a manner that it engages and presses down the locking hook 28 to such an extent that it releases the associated arresting pin 30.

The leg spring 23 of the opening pawl 20 is given such a strength that its force is sufficient to overcome the spring force of the leg spring 29 of the locking hook 28. By means of the approximately S-shaped configuration of the guide surface 33 of the opening pawl 20 it is ensured that during movement in the direction of the arrow 31 when there is a camming action on to the tip 34 of the extension 26 of the filter plate being transported, the opening pawl is lifted to such an extent that the nose 32 can travel freely over the tip 34 of the extension. As soon as the nose 32 has moved over the tip 34 of the extension, the opening pawl is pressed downwards by the leg spring 23 and the respective hook 28 is unlocked.

On movement of the roller chain 18 in the direction of the arrow 31 the reversing pawl 19 is carried by the roller chain 18 towards the upper end of the extension 26 and a force is exerted in the direction of the arrow 31 on to the first filter plate being transported, so that the expansion forces acting through the filter plate in the opposite directions are cancelled out. Owing to the resulting pressure increase the chain drive, for example a hydraulic motor which can be reversed in dependence on pressure, is at the same time reversed as regards its direction of operation. Then the roller chain 18 moves in the direction of the arrow 35 so that the nose of the opening pawl 20 in turn comes to abut on the extension 26 of the filter plate being transported. Since the opening pawl 20 at the same time has brought about the release of the locking hook 28, the filter plate can travel in the direction of the arrow 35. During the entire transporting distance the filter plate concerned is held positively by means of its extension 26 between the two pawls 19 and 20 so that if there is a sudden stopping of the displacing apparatus the filter plate cannot run onwards independently under the influence of the kinetic energy which is within.

Fig. 3b shows the movement situation in the region of the group of filter plates which are in the open position. As soon as the transported filter plate has reacted the region of the portion of the filter plate group situated in the open position, the reversing pawl 19 is lifted by the extensions 26 of the filter plates which are already in the open position. The opening pawl 20, however, still abuts on the extension 26 of the filter plate which has just been transported, so, that this is pressed by the action of the roller chain 18 against the filter plates which are already in the open position, so that the locking hook 28 of the preceding filter plate can engage in the arresting pin 30 of the filter plate which has just been transported. Since at the same time there is a corresponding increase in pressure of force experienced by the roller chain 18, the direction of operation of the drive is reversed so that the roller chain 18 is again moved in the direction of the arrow 31 and the operation is repeated again.

In Fig. 4 there is shown in detail in a sectional view the arrangement of the displacing apparatus. As the sectional view shows, there are provided on the web 36 of the guide beam 1 a plurality of supports which are distributed in a uniform manner at intervals over the length of the guide beam and with which there are supported on the upper side and the lower side in each case two, plastics material rails 37, 38 which are parallel to one another. The plastics material rails 37, 38 comprise appropriate recesses in which the two parallel roller chains are guided. The two double roller chains are connected securely to another by connecting pins 39. The opening pawl 20 and the reversing pawl 19 are arranged on the lower run of the endless double roller chain in the manner described in connection with Fig. 3a.

Below the chain system used as a displacing apparatus there is arranged a rail 40 on the web 36 of the guide beam 1, and on this rail the filter plate being transported can be displaced by means of a roller 41 secured on a corresponding suspension means 12 of the said plate. The extension 26 provided with a window-like aperture 27 is secured on the upper end of the suspension element 12.

Another constructional form of a displacing apparatus for use in a plate filter press of the kind shown in Fig. 2 is described with reference to Figs. 5 and 6. In this constructional form, as Fig. 6 indicates, there are provided at the two sides of the machine frame guide beams 15 on which the filter plates 5 are supported by means of their lateral extensions 16. In this constructional form also the extension 16 comprise in their end region window-like apertures 27 in which there are arranged locking hooks 28 and arresting pins 30. In this constructional form also the locking hooks are provided with a leg spring 29 which ensures reliable engagement of the locking hook in the particular eye defined by the arresting pin which is adjacent. To this extent the arrangement of the locking means corresponds to the locking means of the constructional form described with reference to, Fig. 3 and Fig. 4.

Here again, the supporting element is formed by two roller chains 18 which are guided along endless paths of travel parallel to one another and adjacent one another, and whereby said first and said second plate abutment portion engaging members are held. The said first member is again formed by a spring-loaded pawl 19 which corresponds in construction, arrangement and operation to the reversing pawl described with reference to Figs. 3 and 4. Its only difference relatively to the constructional form previously described is that it is biased upwardly from the plane formed by the pairs of roller chains extending at both sides of the guide beams 15.

But in the present constructional form the said second member is formed by a toothed star wheel 42 which is mounted to be capable of rotating on a pin 43 held by the two roller chains 18 extending parallel to one another.

The tooth spaces of the star wheel are so dimensioned that the downwardly projecting tip 44 of the extension 16 acts like a tooth of a toothed rack on the star wheel and rotates it by the amount of one tooth in the direction of the arrow 46 when there is a movement of the chain 18 in the direction of the arrow 45.

Also mounted on the chain 18 is a detent pawl 47 which is constructed as a two-arm lever. One end 48 of the detent pawl is pro vided with a pin 49 which bears on the leg spring 22 of the reversing pawl 19. The other end 50 ends in a nose 51 which is so, dimen sioned that it bears on a star tooth tip. Spaced from the nose 51 there is arranged a roller 52 which ensures easy running of the detent pawl on the star wheel 42. The detent pawl is mounted on a pin 53 which extends through the aperture 25 in the reversing pawl 19 and at the same time forms the boundary for the movement of the reversing pawl 19.

In Fig. 5a there is shown a portion of a closed group of filter plates at which the star wheel 42 has arrived in the direction of the arrow 45 and is situated with its tip 54 behind the extension 16 of the plate being transported.

As the drawing shows, the length b that the reversing pawl and the opening pawl are situated in the upper run of the endless chain and project upwards above the plane formed by the double roller chain, so that they can be brought into connection with the downwardly directed tips 44 of the extensions 16 lying on the lateral guide beams 15.

In order to allow the group of filter plates in special cases to be opened by hand and independently of the displacing apparatus, either in its working position or in its open position, a central unlocking apparatus is shown in a diagrammatic manner in Fig. 7. This consists of a push rod 59 which extends over the entire length of the filter plate press and is mounted by means of two or more rocking links 60 on the machine frame. The locking hooks 28 are provided with laterally projecting extensions or studs 61 on which the central push rod 59 bears (Fig. 7a).

If the push rod 59 is moved in the direction of the arrow 62, owing to the rocking movement of the levers 60 the push rod is moved at the same time in the direction of the arrow 63 and thus the locking hooks 28 are pivoted by means of their studs 61 and the locking of the filter plate group is discontinued, so that the filter plates can be displaced by hand inde- pendently of the displacing apparatus.

Whilst a roller chain represents the most advantageous supporting element for the first and second plate abutment portion engaging members, these members can also be secured on a special carrier which can be moved by means of a single roller chain, or for example a link chain, a push rod or the like.

A further constructional form for a displacing apparatus for a plate filter press with suspension at the upper region as shown in Fig. 1 is explained in detail with reference to Figs. 8a and b. Fig. 8a shows the displacing apparatus directly on initiating a transporting operation, whilst Fig. 8b shows the position of the individual elements at the instant when the plate which has just been transported is locked again at the opening side with the other filter plates. The construction and the operation correspcnd substantially to the constructional form described with reference to Fig. 3a and Fig. 3b so that reference may be made to that constructional form.

Because of the substantially S-shaped configuration of the guide surface 33 of the opening pawl 20, here again it is ensured that during movement in the direction of the arrow 31 when running on to the tip 34 of the extension 26 of the filter plate being transported the opening pawl is lifted until the nose 32 can run freely over the tip 34 of the extension. As soon as the nose 32 has moved over the tip 34 of the extension the opening pawl is already pressed downwards by the leg spring 23. At the instant when under the action of the drive of the roller chain 18 the reversing pawl 19 is pressed against the upper end of the extension 26, a bellcrank lever 65 pivotably connected to, the free end of the reversing pawl 19 by means of a pin 64 is pressed against the extension 26.

The bellcrank lever is secured in such a manner to the reversing pawl 19 that the pin 64 is situated approximately in the region where the two portions of the bellcrank lever meet. One free end 66 is directed towards the extension 26 whilst the other free end 67 projects above the free end of the opening pawl 20. The reversing pawl 19 is substantially fork-shaped in the region of its free end, the bellcrank lever 65 being guided between the two ends of the fork. As a result an abutment 68 is formed at the same time on the reversing pawl 19 for the free end 66 of the bellcrank lever. When the opening operation is begun, i.e. when there is a movement of the roller chain in the direction of the arrow 31, first of all the free end 66 of the bellcrank lever 65 comes to abut on the extension 26 of the filter plate being transported. Under the influence of the.driving force the bellcrank lever 65 is pivoted to such an extent in the direction of the arrow 69 that it comes to abut on the abutment 68 of the reversing pawl 19. At the same time the free end 67 of the bellcrank lever presses from above on the opening pawl 20 so that the latter, as Fig. 8a shows, moves downwards into the free space between the two extensions 26 of the last two filter plates. Then when the drive of the roller chain 18 is reversed so that it moves in the direction of the arrow 35, the opening pawl 20 is held by the force of the leg spring 23 in its position shown in Fig. 8a until the tip 32 of the opening pawl 20 comes to abut on the extension 26 of the filter plate being transported and the filter plate is moved.

Then if the filter plate assembly is equipped with locking hooks as shovn in Fig. 8a, when the opening operation is initiated the reversing pawl 19 exerts a force in the direction of the arrow 31 on the first filter plate to be transported, so, that the expansion forces acting because of the filter cake in the opposite direction are cancelled out. To open the locking hook 28, therefore, it is simply necessary to over- come the closing force of the leg spring 29 of the locking hook 28 by means of the opening pawl 20.

Owing to the increase in force which is brought about when the reversing pawl 19 comes to abut on the filter plate being transported, the drive, for example a hydraulic motor which can be reversed in accordance with pressure, is at the same time reversed as regards its direction of operation. Then the roller chain 18 moves in the direction of the arrow 35 so that the nose 32 of the opening pawl 20 moves the filter plate in the direction of the arrow 35 with simultaneous release of the locking hook 28. During the entire transport distance the filter plate concerned is positively held by means of its extension 26 between the two levers 19 and 20 so that in the event of sudden stopping of the displacing apparatus the filter plate cannot roll onwards independently under the influence of the kinetic energy which is within it.

Fig. Sb shows the movement situation in the region of the filter plate assembly when in the open position. As soon as the transported filter plate comes into the region of the portion of the filter plate assembly which is in the opening position the reversing pawl 19 is lifted by the extensions 26 or. the filter plates which are already in the opening position. The opening pawl 20, however, still abuts on the extension 26 of the filter plate which has just been transported so that the latter is pressed by the action of the roller chain 18 on to the filter plates which are already in the opening position, so that the locking hook 28 of the preceding filter plate can engage in the arresting pin 30 of the filter plate which has just been transported.

Since at the same time a corresponding increase in pressure or force occurs again in the roller chain 18, the direction of rotation of the drive is reversed so that the roller chain 18 again moves in the direction of the arrow 31 and the operation is repeated.

With reference to Figs 9a and b a further constructional form will now be described. In this constructional form there is used a bellcrank lever 70 which is mounted in a similar manner to the constructional form described hereinbefore on the reversing pawl 19. Whilst again one free end 71 of the bellcrank lever is intended as an abutment for the reversing pawl 19 for the extension 26 of the particular filter plate being transported, the free end 72 which projects beyond the opening pawl 20 is provided with a slot 72 through which there extends a pin 74 connected securely to the opening pawl 20. As a result a positive operating connection exists between the reversing pawl 19 and the opening pawl 20 by means of the bellcrank lever 70.

This constructional form operates in accordance with the method of operation of the constructional form described with reference to Figs. 8o, b. The only difference is that the force on the reversing pawl 20 introduced by way of the bellcrank lever 20 is transmitted by way of the pin and slot connection 73, 74.

This constructional form can also be used for filter plate presses with and without locking hooks. The particular advantage is more particularly that when changing the direction of the chain which is used as the supporting element in each case at the end region of the plate niter press the bellcrank lever 70 is held by means of the pin and slot connecticn and then returned automatically again to its operative position.

The two previous constructional forms are described for a displacing apparatus such as is used for example with a plate filter press of the type described with reference to Fig. 1. With the constructional form described in connection with Fig. 2, wherein guide beams 15 are provided at the two sides of the machine frame and on these beams the filter plates 5 rest by means of their lateral extensions 16, it is convenient if the reversing pawl 19 and the opening pawl 20 are secured to act upwards on the supporting element in order to save overall height. When using a roller chain guided along an endless path as a supporting element, conveniently the two pawls should be secured in the upper run of the chain. This has the advantage that the entire guide arrangement for the supporting element is situated below the extension 16 of the filter plates 5 so that these can be taken out freely in an upward direction.

WHAT WE CLAIM IS:- 1. A plate filter press having a plurality of vertically arranged filter plates mounted on at least one guide member for horizontal displacement from a filter-closed position, whereat the filter plates are normally stacked, to a filteropen position, each said plate having an extending abutment portion on which a pin, or eye, and a biassed and pivoted hook are mounted, said hooks and said pins, or eyes, being so arranged that when the plates are stacked each pin, or eye, is normally engaged by the hook of an adjacent plate and the plates in the stack are thereby locked together, and further comprising displacing apparatus for linearly transporting each plate in turn from the stack located at the filter-closed position to the filter open position, said apparatus including at least one carrier which is movable back and forth alongside the filter plates on which carrier there is rotatably mounted first and second plate abutment portion engaging members, said members being spaced apart on the carrier so as to face and abut opposite sides of the abutment portion of a respective plate when the carrier is aligned with the plate, said carrier acting through said first member in the filter closing direction so as to compress the stack of plates together to enable the hooks to be freely uncoupled from their respective pins, or eyes, and acting in the opening direction through said second member so as to separate an end plate from the stack after the respective plate is unhooked, both said members having edge portions which are engageable with plate abutment portions when the carrier is moved in the direction opposite to that in which the respective member acts, said engagement causing the respective member to ride over the engaged abutment portion, and said second member having at least one nose-like projection which when the carrier is positioned in registration with the next plate to be moved enters a space between the abutment portion of that plate and the abutment portion of the adjacent plate where it engages the hook of the plate to be moved and releases it from the said adjacent plate.

2. A filter press according to Claim 1 where

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (16)

**WARNING** start of CLMS field may overlap end of DESC **. stopping of the displacing apparatus the filter plate cannot roll onwards independently under the influence of the kinetic energy which is within it. Fig. Sb shows the movement situation in the region of the filter plate assembly when in the open position. As soon as the transported filter plate comes into the region of the portion of the filter plate assembly which is in the opening position the reversing pawl 19 is lifted by the extensions 26 or. the filter plates which are already in the opening position. The opening pawl 20, however, still abuts on the extension 26 of the filter plate which has just been transported so that the latter is pressed by the action of the roller chain 18 on to the filter plates which are already in the opening position, so that the locking hook 28 of the preceding filter plate can engage in the arresting pin 30 of the filter plate which has just been transported. Since at the same time a corresponding increase in pressure or force occurs again in the roller chain 18, the direction of rotation of the drive is reversed so that the roller chain 18 again moves in the direction of the arrow 31 and the operation is repeated. With reference to Figs 9a and b a further constructional form will now be described. In this constructional form there is used a bellcrank lever 70 which is mounted in a similar manner to the constructional form described hereinbefore on the reversing pawl 19. Whilst again one free end 71 of the bellcrank lever is intended as an abutment for the reversing pawl 19 for the extension 26 of the particular filter plate being transported, the free end 72 which projects beyond the opening pawl 20 is provided with a slot 72 through which there extends a pin 74 connected securely to the opening pawl 20. As a result a positive operating connection exists between the reversing pawl 19 and the opening pawl 20 by means of the bellcrank lever 70. This constructional form operates in accordance with the method of operation of the constructional form described with reference to Figs. 8o, b. The only difference is that the force on the reversing pawl 20 introduced by way of the bellcrank lever 20 is transmitted by way of the pin and slot connection 73, 74. This constructional form can also be used for filter plate presses with and without locking hooks. The particular advantage is more particularly that when changing the direction of the chain which is used as the supporting element in each case at the end region of the plate niter press the bellcrank lever 70 is held by means of the pin and slot connecticn and then returned automatically again to its operative position. The two previous constructional forms are described for a displacing apparatus such as is used for example with a plate filter press of the type described with reference to Fig. 1. With the constructional form described in connection with Fig. 2, wherein guide beams 15 are provided at the two sides of the machine frame and on these beams the filter plates 5 rest by means of their lateral extensions 16, it is convenient if the reversing pawl 19 and the opening pawl 20 are secured to act upwards on the supporting element in order to save overall height. When using a roller chain guided along an endless path as a supporting element, conveniently the two pawls should be secured in the upper run of the chain. This has the advantage that the entire guide arrangement for the supporting element is situated below the extension 16 of the filter plates 5 so that these can be taken out freely in an upward direction. WHAT WE CLAIM IS:-

1. A plate filter press having a plurality of vertically arranged filter plates mounted on at least one guide member for horizontal displacement from a filter-closed position, whereat the filter plates are normally stacked, to a filteropen position, each said plate having an extending abutment portion on which a pin, or eye, and a biassed and pivoted hook are mounted, said hooks and said pins, or eyes, being so arranged that when the plates are stacked each pin, or eye, is normally engaged by the hook of an adjacent plate and the plates in the stack are thereby locked together, and further comprising displacing apparatus for linearly transporting each plate in turn from the stack located at the filter-closed position to the filter open position, said apparatus including at least one carrier which is movable back and forth alongside the filter plates on which carrier there is rotatably mounted first and second plate abutment portion engaging members, said members being spaced apart on the carrier so as to face and abut opposite sides of the abutment portion of a respective plate when the carrier is aligned with the plate, said carrier acting through said first member in the filter closing direction so as to compress the stack of plates together to enable the hooks to be freely uncoupled from their respective pins, or eyes, and acting in the opening direction through said second member so as to separate an end plate from the stack after the respective plate is unhooked, both said members having edge portions which are engageable with plate abutment portions when the carrier is moved in the direction opposite to that in which the respective member acts, said engagement causing the respective member to ride over the engaged abutment portion, and said second member having at least one nose-like projection which when the carrier is positioned in registration with the next plate to be moved enters a space between the abutment portion of that plate and the abutment portion of the adjacent plate where it engages the hook of the plate to be moved and releases it from the said adjacent plate.

2. A filter press according to Claim 1 where

in said carrier comprises a guided flexible element.

3. A filter press according to Claim 2 wherein said guided flexible element comprises a roller chain and said engaging members are rotatably mounted on respective pins carried on the chain.

4. A filter press according to Claim 2 or Claim 3 wherein said guided flexible element comprises a pair of roller chains which are joined by pins so as m be guided along parallel paths, said engaging members being mounted between said chains on respective ones of said pins.

5. A filter press according to any preceding claim wherein each said engaging member comprises an end pivoted spring-loaded pawl.

6. A filter press according to Claim 5 wherein a bellcrank lever is mounted on the free end of said first member, said lever having a first arm wihch is adapted to engage the plate abutment portion of the plate with which the carrier is in registration when the carrier is moving in the closing direction and having a second arm which extends so as to overlap the free end of the said second member and abut thereon in its normal position.

7. A filter press according to Claim 6 wherein the bellcrank lever is pivotally mounted on the first engageable member and is slidably and pivotally coupled to the free end of the second engageable member by means of a pin and slot engagement.

8. A filter - according to any of Claims 1 to 4 wherein said second element comprises a toothed star wheel, mounted on said carrier for free rotation and having a plurality of noselike projections each comprising one tooth of said star wheel, and latching means which prevents rotation of the wheel in a first direction when the latter is displacing a filter plate to the open position but which permits rotation in the opposite direction, the teeth on the wheel being shaped relative to the plate abutment portions so as to form a rack and pinion arrangement therewith when the respective plates are stacked together whereby the crest of the tocth disengages the hook between the plate portions of the plate next to be moved and the succeeding plate and the flank of the tooth abuts the side of the abutment portion of the plate next to be moved.

9. A filter according to Claim 8 wherein said first engaging member comprises a pivoted spring-loaded pawl.

10. A filter press according to Claim 8 or Claim 9 wherein the latching means comprised a biassed pawl mounted on said carrier which engages the teeth of the star wheel.

11. A filter press according to Claim 10 wherein the said latching pawl and the first engaging element are acted upon by a common spring.

12. A filter press accordmg to Claim 10 or Claim 11 wherein the said latching pawl has a roller mounted on its free end which engages the teeth of the star wheel.

13. A filter press according to any of Claims 10 to 12 wherein the first engaging member is U-shaped in cross-section and the latching pawl is arranged to lie in the said member between the arms of the U-shaped cross-section.

14. A filter press according to any preceding claim wherein each of the said hooks is provided with a lateral protrusion and there is a laterally displaceable push rod which extends over the entire length of the filter press and is mounted alongside the said hooks so as to be engageable with the said lateral protrusions when moved sideways so as to release the hooks from their adjacent plates.

15. A filter press according to Claim 14 wherein said push rod is laterally jointed to a parallel member by at least two pivoted spaced apart links of equal length.

16. A filter press substantially as described herein with reference to Figures 1 and 2 and/ or Figures 3a and b or 5a and b or Figures 8a and b or Figures 9a and b.