Title of Invention

A SCREEN DECK AND ITS METHOD OF MANUFACTURE

Abstract

A screen deck for coke screening with improved screening efficiency and effective equipment life. The screen deck advantageously comprises a thick plate having slots with opening (OS) there through along one side of each said slot with the plate material there between two adjacent slots defining finger (FP) like protrusions; said slots with one side opening favouring a jam free flow of material there through the slots with said finger like protrusions providing for relative movement between the two adjacent fingerlike protrusions facilitating fall of material there between during vibrations of the screen. The screen deck of the invention would be cost effective and involve a simple manner of manufacture and yet facilitate free flow of material through the deck during the screening process thereby favouring wide scale and efficient use and application of such screening decks including for screening of coke.

Full Text

FIELD OF THE INVENTION The present invention relates to a screening equipment and, in particular, to a screen deck useful for purposes such as coke screening which would provide for improving screening efficiency as well as favour enhancing the effective equipment life of a screen deck for carrying out such coke screening. The screen deck of the invention is adapted to be user friendly and particularly directed to increase the screening efficiency by avoiding jamming of slots usually encountered in screening operations. The screen deck of the invention would be cost effective and involve a simple manner of manufacture and yet facilitate free flow of material through the deck during the screening process thereby favouring wide scale and efficient use and application of such screening decks including for screening of coke. BACKGROUND ART It is well known that screening decks are conventionally used to carry out screening of variety of particulate materials/grains depending upon the openings / slots provided in the screening deck. The use of screening deck is thus one of the widely used and applied manners of separation of a mixture of various sizes of grains into two or more proportions by means of a screening surface. The screening surface is adapted to act as a multiple go-no-go gauge and final portion consisting of grains of more uniform size than those of the original mixture. Usually, the screening surfaces used for such screening of various sizes of grains may consist of woven wire, perforated or punched plates etc. These plates having such perforation / punched regions are either metallic such as steel or non-metallic such as rubber, polyurethane and the like. In common terminology, the entire screening equipment is usually known as screen while the screening surface where the actual separation of different size materials takes place is known as screen deck. It is common to the manufacture of such available varieties of screen decks, whether manufactured of steel plate or obtained of non-metallic sheets or in the form of woven wire to provide openings / perforations which are closed ones. These openings can be of different sizes and shape and configuration depending upon the end use of the screen deck. In particular, such openings in conventional screen decks are usually selected from square, rectangular, circular, hexagonal, tear-drop or any suitable shape as may be required for the purposes of selective screening of materials / grains. Importantly, however, all such varieties of the openings / perforations available in the presently used conventional screen deck known in the art are essentially closed openings i.e. such openings are closed from all sides. It is found that such closed openings in screen deck presently available usually covered less than 50% surface area of the screen deck. Moreover, the flow of material in such conventional screen decks having such closed opening/perforations usually take place along the longitudinal axis of the opening and very often it is experienced that jamming of the materials take place due to the obstruction created at the end of the openings. Also, such problem of jamming of openings with consequential loss of screen efficiency of the screening deck is aggravated if the material being screened is fine and moist. OBJECTS OF THE INVENTION It is thus the basic object of the present invention to provide a screen deck which would avoid the afore-discussed problems and limitations of the presently available screen decks having closed openings, especially, due to jamming of materials resulting from obstruction created at the end of the closed opening. Another object of the present invention is directed to provide a screen deck which would be simple and cost effective to manufacture and would facilitate free movement of material there through the opening of the screen deck thereby improving efficiency of the screen deck. Another object of the present invention is to provide for a screen deck which would be durable and tough and would therefore have a long effective working life span and would favour continued and regular use / application without problems of deterioration due to jamming of openings and / or failure of material of which the screen deck is obtained. A further object of the present invention is directed to the development of the screen deck which would be user friendly and improve the screening efficiency and overcome the deficiencies/limitations of the screen decks having punched, drilled, slotted closed opening presently in use. SUMMARY OF THE INVENTION Thus according to the basic aspect of the present invention there is provided a screen deck comprising: a thick plate having slots with opening there through along one side of each said slot with the plate material there between two adjacent slots defining finger like protrusions; said slots with one side opening favouring a jam free flow of material there through the slots with said finger like protrusions providing for relative movement between the two adjacent fingerlike protrusions facilitating fall of material there between during vibrations of the screen. In the above screen deck the said slots can comprise parallel slots wherein the gap at one end of the slot top feed end and the gap at the other discharge end of the slot is the same. The size of the slots is same in the vertical direction. Optionally, in the above screen deck of the invention the said slots can comprise diverging slots with divergence in vertical and/or horizontal directions. In such diverging slots, each said diverging slot can comprises of width of each said slot in the beginning feed end being less and at the discharge end being more.In particular, such diverging slot can comprise width of each slot being less on the top side of the deck and more on the bottom side of the deck favoring avoiding sticking of material and jamming of slots. Thus, the slots provided with a taper surfaces can have at the beginning/top of the deck a dimension of 18mm and at the end/bottom of the deck a dimension of 20mm. Preferably, the said finger like protrusions are coated with wear resistant material. The size of slots, screen decks are selectively provided based on the end use requirements. The thickness of the plate can comprises preferably thick steel plate of thickness in the range of 16-20mm. Thus, the plate thickness can comprise a dimension in the range of 16 to 20mm. This thickness should increase with width of the screen deck, so that fingers do not get broken due to longer cantilever arm. Plate dimensions such as 1200mm. X 500 mm. X16 mm can be used. The screen deck as above is adapted to be fixed to the screen selectively through fasteners /locking arrangement or welding. In accordance with a further aspect of the invention there is provided a method for the manufacture of the screen deck comprising providing a plate of required thickness and dimensions and forming the slots therein following anyone or more of gas cutting and machining to thereby provide for slots with opening there through along one side of each said slot with the plate material there between two adjacent slots defining finger like protrusions. In the above method the said slots comprising said parallel or divergent slots are selectively provided following anyone or more of gas cutting and machining methods. The sizes of slots and screen deck are determined based on the end requirements selected from capacity of screen (tonnes/hr.),size of materials to be screened, material that remains above the screening surface and material required to pass through the screening surface. Preferably, the fingerlike protrusions are coated with wear resistant material following preferably using hard facing electrodes or application of paste and fusing using with gas torch. It is thus possible by way of the afore disclosed screen deck of the invention to provide for a screening equipment suitable for coke screening and the like with improved efficiency and also favour user friendly manufacture and use of screening decks. Importantly, the screen deck of the invention is directed to avoid the problems of jamming encountered in presently available decks of punched, drilled, slotted closed openings by way of providing the slot with an open end through out along one side of the slot. The above selective provision for slot with opening in one side and in the process defining of finger like protrusion between slots on one hand favour free flow of the material through the slots and also the finger like protrusions which are adapted for relative movement in between two adjoining fingers during vibration of the screen further facilitate the fall of the material through the slot. Such an arrangement totally takes care of slot jamming in conventional decks with closed opening. Moreover, the screen deck of the invention having such selective openings for the slot is directed to favour simple and cost effective manufacture of such screen decks without involving the complex and cost extensive process of punching or drilling of openings in screen decks presently followed in the art. In particular, the screen deck of the invention can be obtained very simply by making the slots of desired size for following simple processes of gas cutting and machining. The above method of manufacture of screen deck without the requirement of drilling or punching of openings further enable the use of thick and durable plates for such screen deck which was not possible in manufacture of decks involving / punching or drilling of slots. Thus, thick steel plates with thickness ranging from 16 to 20mm. can be used to manufacture screen deck in accordance with the invention. This necessarily enables better life span of screen decks and continued effective use for screening purposes. As would be apparent from the above, the screen deck of the invention having the slots separated from one another by finger like protrusion can be obtained with the slots parallel i.e. the gap between one end of the slot (beginning) and gap at the other end of the slot being same both in the horizontal and vertical direction and achieve the required jam free flow of material through the slots. In accordance with the preferred aspect, optionally, the slots there between the finger like protrusion in the screening deck of the invention can be provided with features such that the slot is diverging in both the directions i.e. in horizontal direction and in the vertical direction. In case of such diverging slot, the width of the slot is less in the beginning i.e. the material feed side and more in the discharge end side. Similarly, the slot on the top side of the deck is less and more towards the bottom side of the deck to avoid any sticking of the materials this is being, screened. The sizes of the slots in the screening deck can be variable and are usually decided based on the end use requirement of the screening deck. In particular, the size of the slot, screen deck which can be variable can be decided on different specific requirements like capacity of screen (tones/hour) size of materials being screened, material remaining above the screening surface i.e. oversize or plus materials and the material passing through the screening surface i.e. undersize or minus material. It is thus possible by way of the present invention to provide for a screen deck which is substantially different from ail varieties of existing / available screen decks presently used having the closed jam causing slots. Importantly, the screen deck of the invention avoids the limitation of the closed openings which is usually provided in conventional screen deck obtained by way of pushed or drilled openings or woven screen decks which can now be avoided and favour user friendly application and use of such screen deck especially for screening of coke. The details of the invention, its objects and advantages are explained hereunder in greater detail in relation to non-limiting exemplary illustration of the screen deck of the invention as per the following accompanying figures: BRIEF PESCRIPTION OF THE FIGURES Figure 1 : illustrates different types of punched, drilled screen decks presently in use; Figure 2 : illustrate a woven screen deck also available in the art; and Figure 3: illustrate the screen deck obtained avoiding the closed opening in accordance with the present invention. Reference in first invited to accompanying figure 1 which illustrates various types of screen decks (SD) presently available which are obtained involving the conventional punching or drilling technique. As apparent from said figure 1 the conventional screen deck having such closed opening (CO) are provided with openings of variety of shapes such as including square, rectangular, circular, hexagonal, tear drop and any other suitable shape. However, all such openings (CO) are usually closed from all sides and the openings usually cover less than 50% surface area of the screen deck. In fact, usually, the flow of material such as in case of rectangular openings is along the longitudinal axis of the opening and jamming of materials takes place due to the obstruction created at the end of the opening. Such problem of obstruction of opening is further aggravated if the materials being screened are fine and moist. Thus, such varieties of presently available screen decks with such closed openings (CO) have limitations or disadvantages in terms of the possible jamming of the flow path of the material through the closed opening of the screen decks. Reference is now invited to the accompanying figure 2, which illustrates a variety of woven screen deck (WSD), which is also presently available as a conventional variety of screen deck for screening purposes. Importantly, the woven screen deck as shown in said figure is also provided with dosed opening (CO) as in case of punched or drilled openings of the screen decks as shown in Figure 1. Accordingly, the woven screen deck having such closed opening is also having similar limitation of jamming of openings as discussed in case of the variety of punched / drilled closed opening of the screen decks of figure 1 above. The screen deck of the invention is illustrated by way of an embodiment and reference is now invited to the accompanying figure 3 which shows the screen deck with open slots (OS), which are not having the usually known closed opening as per figures 1 and 2 above. As apparent from the said figure 3, in accordance with this embodiment of the screen deck of the invention the slots (OS) in the screen deck (SD) are not provided with closed opening and instead define slots which have opening along one side to thereby provide for finger like projection (FP) there between the open side of the slots. As per the embodiment of figure 3 the slots are parallel that is gap at one end of the slots (feed end) is maintained same as that of the gap on the other end of the slot i.e. the discharge end. The size of the slot according to this embodiment is also same in the vertical direction. The deck illustrated in figure 3 can be obtained of steel plate of 1200mm. x 500mm. and 16mm thickness from high quality special steel and the slots of selected sizes made through gas cutting and machining. Importantly, the slots, which have one open side, provide for free flow of material through the slots. There between the slots individual finger like protrusion are provided. Since these individual fingers also vibrate with the screen, relative movement in between two adjoining fingers takes place, which further facilitate the fall of material. In accordance with a preferred aspect of the invention the slots can be provided with taper surfaces in both the directions i.e. horizontal and vertical. In other words, width of slots can increase gradually towards the end. In the beginning it can be about 18mm. and at the end about 20mm. Slots having diverging configuration in the vertical plane can also be provided. Taper has been proposed also to avoid jamming of material. Also as mentioned above the individual fingers, which vibrate with the screen provide for relative movement in between two adjoining fingers which further facilitate the fall of materials. The material between two slots is termed as finger like projections and is preferably coated with wear resistant material. Method of coating can vary i.e. it can be either with hard facing electrodes or through other methods like application of paste and fusing the same with gas torch. The screen deck is adapted to be fixed to the screen either through fasteners (properly locked) or welded. As mentioned earlier, the size of the slot in the screen deck of the invention can also be variable and are usually depended on different specific requirements like capacity of screen (tones/hour), size of material being screened, material that should remain above the screening surface, i.e. oversize of plus material and material passing through the screen surface i.e. undersize or minus material. Also, the screening efficiency of the screen deck of the invention was studied vis-a- vis the known rod screen deck and the results are reproduced hereunder in TABLE 1. It is found based on the above results that it is possible by way of the above disclosed screen deck of the invention to improve the screening efficiency of the deck such as. when used for coke screening. It is found that the +20 mm. Fraction, which were 16% or more could be reduced 2-3% on average. This can lead to saying of +20mm. coke which can be used in blast furnace and reduce the load on crushers. With controlled size of input material to crusher, output of crusher is also uniform which can lead to at least four fold increase in screen deck life and drastic decrease in maintenance activities. WE CLAIM: 1. A screen deck(SD) comprising: a thick plate having slots with opening(OS) there through along one side of each said slot with the plate material there between two adjacent slots defining finger like protrusions(FP); said slots(OS) with one side opening favouring a jam free flow of material there through the slots with said finger like protrusions(FP) providing for relative movement between the two adjacent fingerlike protrusions(FP) facilitating fall of material there between during vibrations of the screen. 2. A screen deck (SD) as claimed in claim 1 wherein said slots(OS) comprise parallel slots wherein the gap at one end of the slot top feed end and the gap at the other discharge end of the slot is the same. 3. A screen deck as claimed in anyone of claims 1 or 2 wherein the dimension of the slots is same in the vertical directions. 4. A screen deck as claimed in claim 1 wherein the said slots (OS) comprises diverging slots with divergence in vertical and/or horizontal directions. 5. A screen deck as claimed in claim 4 wherein each said diverging slot(OS) comprises of width of each said slot in the beginning feed end being less and at the discharge end being more. 6. A screen deck(SD) as claimed in claim 4 wherein said diverging slot comprises width of each slot being less on the top side of the deck and more on the bottom side of the deck favoring avoiding sticking of material and jamming of slots. 7. A screen deck (SD) as claimed in anyone of claims 1 to 6 wherein the dimensions of slots (OS) in the screen deck(SD) are selectively provided based on the end use requirements. 8. A screen deck (SD) as claimed in anyone of claims 1 to 7 wherein the thick plate comprises preferably thick steel plate of thickness in the range of 16-20mm. 9. A screen deck (SD) as claimed in anyone of claims 1 to 8 wherein the plate comprises a thickness dimension in the range of 16 to 20mm size, with the overall dimensions of the plate varying as per the end user requirements. 10. A screen deck(SD) as claimed in anyone of claims 4 to 9 comprising said slots provided with a taper surfaces preferably at the beginning/top of the deck having a dimension of 18mm and at the end/bottom of the deck having a dimension of 20mm. 11. A screen deck (SD) as claimed in anyone of claims 1 to 10 wherein said finger like protrusions(FP) are coated with conventional wear resistant material. 12. A screen deck(SD) as claimed in anyone of claims 1 to 11 wherein it is adapted to be fixed to the screen selectively through fasteners /locking arrangement or welding. 13. A method for the manufacture of a screen deck(SD) as claimed in anyone of claims 1 to 12 comprising providing a plate of desired thickness and dimensions and forming the slots(OS) therein following anyone or more of gas cutting and machining to thereby provide for slots with opening there through along one side of each said slot with the plate material there between two adjacent slots defining finger like protrusions(FP). 14. A method as claimed in claim 13 wherein said slots comprising said parallel or divergent slots(OS) are selectively provided following anyone or more of gas cutting and machining methods. 15. A method as claimed in anyone of claims 13 or 14 wherein said dimensions of slots and screen deck is determined based on the end requirements selected from capacity of screen (tonnes/hr.), size of materials to be screened, material that remains above the screening surface and material required to pass through the screening surface. 16. A method as claimed in anyone of claims 13 to 15 wherein the step of coating of the fingerlike protrusions(FP) are carried out with wear resistant material following anyone of the process (i) using hard facing electrodes or (ii) application of paste and fusing with gas torch. 17. A screen deck and its method of manufacture substantially as hereindescribed and illustrated with reference to the accompanying Figures. A screen deck for coke screening with improved screening efficiency and effective equipment life. The screen deck advantageously comprises a thick plate having slots with opening (OS) there through along one side of each said slot with the plate material there between two adjacent slots defining finger (FP) like protrusions; said slots with one side opening favouring a jam free flow of material there through the slots with said finger like protrusions providing for relative movement between the two adjacent fingerlike protrusions facilitating fall of material there between during vibrations of the screen. The screen deck of the invention would be cost effective and involve a simple manner of manufacture and yet facilitate free flow of material through the deck during the screening process thereby favouring wide scale and efficient use and application of such screening decks including for screening of coke.

Documents:

1146-kol-2005-granted-abstract.pdf

1146-kol-2005-granted-claims.pdf

1146-kol-2005-granted-correspondence.pdf

1146-kol-2005-granted-description (complete).pdf

1146-kol-2005-granted-form 1.pdf

1146-kol-2005-granted-form 18.pdf

1146-kol-2005-granted-form 2.pdf

1146-kol-2005-granted-form 3.pdf

1146-kol-2005-granted-pa.pdf

1146-kol-2005-granted-reply to examination report.pdf

1146-kol-2005-granted-specification.pdf