A METHOD AND APPARATUS FOR SEPARATION

Abstract: Method and apparatus for separating, from a liquid flow (60), solid particles entrained in the flow. A grid screen (10) is disposed in the liquid flow and is provided with spaced-apart bars which trap the particles, there being thereby formed so-called screenings. A first, lower scraper member (40) is disposed for a reciprocal vertical movement along the screen grid and abuts, during its upward stroke, against the grid, screenings collected against the screen grid conveyed to a shoulder like portion (22) for temporary storage of the screenings. A subsequent, upper scraper member (50) conveys the screenings in a direction towards a receptacle (70). The screenings are de-watered when in position on the shoulder-like portion and, as a rule, also as a consequence of being moved in a direction towards the receptacle along a slip plate (21). The construction comprising more than one screening members reduces vertical space requirements and makes possible the individual adaptaton of the scraper members to meet prevailing functional demands.

Description: A Method and Apparatus for Separation The present invention relates to a method and an apparatus for separ¬ ating, from a liquid flow, for example a flow of wastewater, solid pol¬ lutants and, more precisely, a method, employing an apparatus which includes a screening grid, for trapping pollutants from liquid passing through the grid and, by means of scraper devices, for cleaning the grid and for removing pollutants trapped on the grid. In many contexts, there is a need for so-called machine-cleaned grids which normally make up the first purification stage in, for example, purification plants for wastewater. Prior Art mechanical separation devices for coarsesolid pollutants consist of a screening grid com¬ prising parallel bars between which there are formed gaps normally of a width of from 10 to 15 mm. The grid is disposed in a channel along which the polluted liquid flows, the location of the grid being such that the liquid is forced to flow through the gaps which the grid creates. Normally, the gaps are oriented ' substantially vertically and with the upper portion of the grid slightly offest in the direction of flow of the liquid. It is further known in the Art to remove, by means of a scraper (rake), the pollutants (screenings) which are trapped by the grid bars, the scraper being moved, during the removal operation of the pollutants, upwardly along the grid bars and in abutment against them. As a rule, the scraper is fixed by means of arms to chain driven hoists which, in their upward movement, move the scraper from the lowermost edge of the grid to such a level above the surface of the liquid that the screenings may readily be taken care of, for example transferred to a receptacle or transported further by means of a conveyor. As a rule, the scraper is, at it highest position, at least approximately 1.5 m. above the surface of the liquid and, in its lowermost position, ap¬ proximately 1 metre above the bottom of the channel. Prior Art em¬ bodiments of screening grids with straight grid bars from which the screenings are separated by means of scrapers suffer from the drawback that they require tall building heights and, consequently, tall ceil¬ ing height, because of the length of travel of the scraper. The total length is determined by the depth of the liquid and requisite lifting height for the screenings above the surface of the liquid. As a result, prior Art grid constructions are unwieldy and expensive. This latter circumstance is further accentuated by the fact that the construction should preferably be of stainless steel. The present invention, which relates to "machine-cleaned grids", sub¬ stantially obviates the above-outlined drawbacks, since the total building height requirement of the installation may, in the great ma¬ jority of cases, be reduced by approximately half in comparison with prior Art equipment. This is effected by means of a reduction of the requisite movement space for the members which realise clean-scraping of screenings from the screen grid and movement of such screenings in a direction towards a receptacle facility. Moreover, it is possible, according to the present invention, to utilize more smoothly and even¬ ly operating driving means than the previously-used electro-mechanical driving means which include an electric motor, gearing, one or more chain hoists and requisite journalling. An apparatus for separating solid pollutants from liquids includes, according to the present invention, a grid of the fundamentally con- ventional type as described above, i.e. a straight grid made up of parallel bars with substantially vertical orientation. The apparatus further includes at least two inter-cooperating scraper members which are provided with scraper blades which entrain screenings collected agaώmst the grid on movement along the grid and/or in a preferred ern- bodiment, along an extension section connected to the grid. Of these scraper members, a first, lower scraper member moves its scraper blade or blades substantially along that section of the grid which is passed by the liquid flow, for drawing-up collected screenings from the liquid flow, while the remaining scraper members move their scraper blades substantially along the residual section of the grid and/or, where applicable, along the extension section for continued transport of the screenings, eg. to receptacle means. According to ons preferred embodiment, the apparatus includes one or more shoulder-like regions located in the transition between two mutually adjacent scraper members. The first of the scraper members moves the screenings to one such shoulder-like region, and the other moves the screenings from the shoulder-like region. In conjunction with each further shoulder-like region, a corresponding cooperation takes place between the scraper members. Depending upon the e bodi- ment of the invention employed, the grid, the extension section or the transition region is disposedbetween the grid and the extension portion with the shoulder-like regions. In a further embodiment of the present invention, compression means are provided for compression of the screenings during their stay-time on each respective shoulder-like region, whereby the proportion of water in the screenings will be reduced. In yet a further embodiment of the present, invention, each respective scraper member is disposed to be reversible, there being formed an abutment surface which is urged by the scraper member against screen¬ ings located on each respective shoulder-like region. As a rule, the scraper blades of the scraper members form the above-outlined comp¬ ression means. In certain embodiments, each respective abutment sur- face is reversed prior to the movement of the scraper member for mov¬ ing the screenings into an orientation which is substantially at right angles to the direction of movement of each respective scraper blade during movement of the screenings. The abutment surface will thereby constitute that surface which shifts the screenings to sub- sequent transitional regions between two mutually adjacent scraper members. In still a further preferred embodiment of the present invention, the lower scraper member completes more than one reciprocal movement between each such movement in which the remaining scraper members move the screenings in a direction towards a receptacle. In still a further preferred embodiment, the lower scraper member is disposed also on its downward movement to abut against the bars of the grid, at least along a restricted portion of this travel, this res¬ tricted travel being preferably located in a region at and slightly below the surface of the liquid. As a rule, the risk of blockage of the gaps of the grid is greatest in the previously-mentioned region. However, as a result of the described embodiment of the present in¬ vention, it is generally possible to prevent blockage of the gaps in the region in question. It will be apparent from the above description that the invention en¬ tails a number of considerable improvements compared with the prior Art technology now currently employed. The construction with more than one scraper " member entails that the total building height of the sep- aration apparatus is reduced. Furthermore, the present invention makes it possible to provide each separate scraper member with a design which is particularly adapted to meet its purpose. This results in the re¬ alisation of an optimum function of each respective scraper member. The lower scraper member is designed with a view to transport by flow- ing liquid and to cleaning the gaps between the bars of the grid, while the scraper member or members operating above the surface of the liquid are designed in adaptation to meet, for example, the requirement of de-watering of the screenings and their further conveyance to recep¬ tacle means. As a rule, the extension section disposed in association with the grid and preferably above the surface of the liquid is designed as a slip plane for cooperation with one or more scraper members. According to the present invention, each such scraper member is operated by a sep- arate prime mover, for example a compressed air cylinder which controls the position of the scraper blade in relation to the surface of the slip plane so that the scraper blade is located slightly above or, alternatively, abuts against the slip plane. Naturally, the corres¬ ponding circumstance applies for the scraper member or members co- operating with the grid. The movement of the scraper members along the grid and, where applic¬ able, along the extension section, is suitably realised by a joint prime mover, for instance a compressed air cylinder whose stroke length is adapted according to the longest individual scraping ove- ment. Each one of the scraper members is preferably in cooperation with a sled-like device which is connected to the prime mover. In certain embodiments, a number of, or all of, the scraper members utilize one common such sled-like device, while, in other embodiments of the pre¬ sent invention, each scraper member is provided with its separate sled- like device. The invention will be described in greater detail below with particular reference to the accompanying Drawings, in which: Fig. 1 is a section taken through one preferred embodiment of an ap¬ paratus according to the present- invention; and Fig. 2 is a front elevation of the apparatus. The Drawing figures illustrate one embodiment of the invention in which the separation apparatus is composed of a lower portion which essential¬ ly comprises a grid 10, and an upper portion which essentially comprises an extension section 20. There is further disposed a first, lower scrap¬ er member 40, substantially for cooperation with the grid 10, and a second, upper scraper member 50, substantially for cooperation with the extension section 20. The grid 10 comprises a number of grid bars 11 forming gaps 12 there¬ between. The distance between the grid bars is adapted to suit the size of the particles which are intended to be trapped by the grid bars on passage of the liquid through the grid. At its upper region, the grid merges into the extension section 20 which is shown on the Drawings as including a slip plate 21 which forms a substantially downwardly directed supporting surface in a trough- like part of the extension section 20. In its lower region, the slip plate forms a shoulder-like portion 22 which connects with the grid 10. In its lower portion, the first, lower scraper member 40 is provided with a scraper blade 41 for cooperation with the grid 10. in certain embodiments, the blade is fitted with prong-like members which, when the blade abuts against the grid bars, penetrate into the space between the bars. An operating device 42 is fixedly retained in relation to a sled 30 and is connected to the first scraper member for adjustment of its distance, and thereby the distance of the scraper blade 41, to the grid bars 11. The second, upper scraper member 50 is, similarly, provided in its lower region with a scraper blade 51 for cooperation with the slip plate 21. An operating device 52 Is fixedly retained in relation to the sled 30 and is connected to the second scraper member for adjustment of its distance, and thereby the distance of the scraper blade 51, to the supporting surface of the slip plate 21. A path 35 Is provided for the sled 30 which, In its turn, is connected to driving means 31 which reciprocate the sled along the path 35. Fig. 1 also shows that the grid 10 is immersed in a liquid 60 which flows in the direction indicated by the arrows A. Reference numeral 61 refers to the surface of the liquid. The Drawing figure further in¬ timates the presence of an outer casing 80 which covers the extension section 20. Finally, the Drawing figure also shows a receptacle 70 placed on a substrate, for example a floor 62, the receptacle receiving the screenings which are shifted by the second, upper scraper member 50 past the upper edge 23 of the extension section. For describing the function of the apparatus according to the present invention, it will be assumed that the operating device 42 and the op¬ erating device 52 have been activated for moving the scraper members, and thereby the scraper blades 41, 51, to the positions illustrated in Fig. 1, i.e. to positions where the scraper blades abut against the grid bars 11 and against the slip plate 21, respectively. It is further assumed that the sled 30 and, thereby, the scraper members 40, 50, are in the positions illustrated in Fig. 1. The driving means 31 there¬ after initiates the movement of the sled 30 upwardly in the Drawing figure. During this movement, the operating device 42 and the oper¬ ating device 52 maintain the abutment of each respective scraper blade against the grid bars 11 and the slip plate 21, respectively, whereby both the screenings gathered against the grid bars and the screenings located on the shoulder-like portion 22 will be shifted in a direction towards the receptacle 70. The driving means 31 subsequently recipro¬ cates the sled 30 to its starting position. During the return of the sled to its starting position, the scraper blades are, as a rule, raised from the grid bars and the slip plate 21, respectively, for a pre-determined and pre-set length of the movement. The lengths of the extension section 20 and the grid 10 are mutually adapted and adapted to the stroke length of the driving means 3T of the sled so that, during the final phase of the movement of the sled, screenings from the grid 10 will be deposited on the shoulder-like portion 22, at the same time as the screenings which the second, upper scraper member 50 just previously removed from the shoulder-like por- tion will be reliably and safely deposited - or will have already been deposited - in the receptacle 70. During that part of the return movement when the lower scraper blade abuts against the grid bars, the scraper blade cleans the gaps bet- ween the grid bars in that the prong-like members of the scraper blade are passed in the spaces between the bars. An apparatus according to the present invention may be realised in a great number of embodiments in which the apparatus is adapted to meet its specific operative requirements. In certain examples of physical application, more than one sled is employed for movement of the scraper members, while in certain physical applications, each sled is combined with a separate prime mover for transport of the sled. Far example, it is thereby possible to cause the lower scraper member to execute more than one upward movement for shifting of screenings to the shoul¬ der-like portion " before the screenings are conveyed to the receptacle. It is, furthermore, possible, without departing from the spirit and scope of the present invention, to provide more than one shoulder-like portion so as thereby more efficiently to de-water the screenings be¬ fore they are conveyed to the receptacle. The above-described cooper- ation or interaction between two or more scraper members makes for a highly flexible construction of an apparatus according to the present invention and adaptation of this apparatus so as to meet varying work¬ ing duties. Apart from the embodiments described above, many modifications of the present invention are possible without departing from the spirit and scope of the appended Claims.

Claims: CLAIMS 1. A method of separating, from a liquid flow (60), solid particles entrained therein, and, preferably, coarse particles, there being disposed, in the liquid flow, a screen grid (10) with bars (11) arranged in spaced-apart relationship and trapping said particles and forming so-called screenings when the bars are awash by the liquid flow, c h a r a c t e r i s e d i n t h a t " of at least two mutually cooperating scraper members (40, 50), at least a first, lower, scraper member (40), substantially under abutment against the bars of the screen grid and under movement at least along a portion of the screen grid, entrains screenings gathered against the grid for raising thereof out of the liquid flow; a n d t h a t the remaining scraper.members (50) in sequence shift the screenings further in a direction towards, for example, receptacle means (70). 2. The method as claimed in claim 1, c h a r a c t e r i s e d i n t h a t the screenings from the first (40) of the two scraper mem¬ bers are, in the transitional region between two mutually adjacent scraper members (40, 50), moved to a shoulder-like portion (22) whence they are thereafter conveyed by the second (50) of the two scraper members. 3. The method as claimed in claim 2, c h a r a c t e r i s e d i n t h a during the stay-time of the screenings on each respective shoulder-like portion (22), compression means compress the screen¬ ings so as to reduce the aqueous content therein. 4. The method as claimed in claim 3, c h a r a c t e r i s e d i n t h a t each respective scraper member is reversible so as, by means of an abutment surface, to abut under pressure against screen¬ ings located on each respective shoulder-like portion (22) and thereby form the compression means. 5. The method as claimed in claim 4, c h a r a c t e r i s e d i n t h a t each respective scraper member (40, 50) is provided with at least one scraper bla d e (41) which, prior to the movement of the scraper member for shifting the screenings, is switched so as to assume an orientation substantially at right angles to the dir¬ ection of movement of each respective scraper blade during shift¬ ing of the screenings. 6. The method as claimed in claim 1, c h a r a c t e r i s e d i n t h a t the lower scraper member completes more than one recipro¬ cal movement between each movement in which the remaining scraper members shift the screenings in a direction towards the receptacle means (70). 7. An apparatus for separating, from a liquid flow (60), particles entrained therein and, preferably, coarse particles, the apparatus including a screen grid (10) with bars (11) in spaced-apart re¬ lationship from one another and trapping particles, and forming therebetween gaps (12), through which the liquid passes, c h a r - a c t e r i s e d i n t h a t at least two mutually cooperating scraper members (40, 50) are disposed for a reciprocal movement along the screen grid; h a t of said scraper members, a first, lower scraper member (40) has a range of movement which at least covers a portion of the screen grid, which portion is intended to be passed by the liquid flow, or has a range of movement substan¬ tially covering the entire grid screen; t h a t the scraper mem¬ bers (40, 50) are moved, by driving means, in compliance with a plan of movement in which the scraper members sequentially move the screenings up out of the liquid flow and in a direction to- wards receptacle means (70); a n d t h a t at least the first, lower scraper member is disposed, under abutment against the bars, to shift the screenings up out of the liquid flow. 8. The apparatus as claimed in claimed in claim 7, c h a r a c t e r - i s e d i n t h a t an extension section (20), preferably intend- ded to be located above the surface of the liquid, is disposed in [claim 8 contd. ] in conjunction with the screen grid (10); t h a t the remaining scraper members (50) or at least one thereof, has a range of move¬ ment which covers the extension section, or alternatively a portion thereof; a n d t h a t said remaining scraper members (50) move the screenings in a direction towards said receptacle means (70), preferably under abutment against said extension section (20). 9. The apparatus as claimed in claim 7 or 8, c h a r a c t e r ¬ i s e d i n t h a t the grid and, where applicable, the exten- sion section, form a path for movement of the screenings; a n d t h a t the path is provided with at least one shoulder-like por¬ tion (22) for temporary storage of the screenings so as to make possible the location of a sequentially subsequent scraper member (50) in a position where the scraper member, on its continued movement, entrains the screenings. 10. The apparatus as claimed in claim 9, c h a r a c t e r i s e d i n t h a t the shoulder-like portion of the path is formed by the screen grid, by the extension section (22) or by the screen grid (10) and the extension section (20) together; a n d / o r t h a t switching means are provided for adjustment of an abut¬ ment surface on each respective scraper member to an orientation adapted to the orientation of the path in the area of each re¬ spective shoulder-like portion (22).

Inventors: JOHANSSON DAG, JOHANSSON, DAG
Applicants: SPIRAC ENGINEERING AB
Application year: 1984
Main classification: B07B1
IPC codes: E02B8