Patent Grant
6843376
The present invention relates to a screening unit. More particularly, the present invention relates to a mobile screening unit for screening bulk material containing particles of different sizes into at least three different piles, each pile containing particles of substantially the same size.
It is well known in the art that there are several technologies for screening bulk material composed of products such as moulds, composts, wood residues, aggregates, etc. These technologies include the use of rotating screeners, star screeners, vibrating screeners, etc. The rotating screeners and the star screeners are much more performant with organic products, such as moulds, composts and wood residues for example, for obtaining end products of small granular sizes (½″ and less, for example) and at high production rates (approximately 150 cubic yards/hour and more, for example). However, these types of screeners are not compatible with inputs of great dimensions such as big rocks, big wooden pieces or big cement blocks, because the latter can easily damage the screens of the rotating screeners or damage the stars and the shafts of the star screeners.
Also known in the art are vibrating screeners which can be used for accepting the above-mentioned larger-sized products. These types of screeners are known to be efficient for screening aggregates. However, their production capacity for obtaining end products of small granular sizes from organic materials is fairly limited. Also, the screens or the perforated plates used with these vibrating screeners often get plugged up when the bulk material to be screened is humid.
In order to avoid the damaging of their rotating screeners or star screeners which are mostly used for screening organic material, several manufacturers will often use a vibrating screen placed over the material reserve used for feeding their rotating or star screeners. This vibrating screen is primarily used for carrying out a primary screening of the inputs of great dimensions in order to then direct the bulk material, free of large debris, into the rotating screener, or star screener. However, in the prior art, the direction of flow of the bulk material onto the vibrating screen is perpendicular to that of the reserve and that of the rotating screener, thus is perpendicular to the longitudinal axis of the screening unit machine. This limits drastically the length allowable for the vibrating screen due to the maximal dimensions allowed for the screening unit for travelling on the road. In fact, the length of the screener is then limited to the width of the screening unit machine which is itself limited to 8′6″ or 8″3″ in most countries in order to be legally allowed to travel on the roads.
Since the length of the vibrating screener or of the vibrating screen is limited, the amount of material that can be unloaded therein with a loader or an excavator is also therefore limited. In fact, if the amount of material unloaded is too great, it causes an overflow of bulk material outside the vibrating screener at the bottom thereof because the retention time of the material is not sufficient enough for it to flow completely through the screen. An important amount of small-sized and medium-sized product finds itself thus with the large-sized products of the bulk material. One must thus decrease the amount of bulk material unloaded onto the vibrating screener or the vibrating screen in order to obtain a suitable classification. Furthermore, the debris of great dimensions slide to the bottom of the vibrating screen, close to the location where the loader must position itself for unloading the bulk material on the same. The operator of the loader must thus clean this area at frequent intervals in order to be able to feed the machine in a suitable and safe manner. All of the above factors lead to a decrease in screening productivity.
Furthermore, there exist vibrating screeners provided with two stages of screening which enable to accept inputs of great dimensions at the upper stage and carry out a selection of precise granular size at the lower stage. However, the capacity of production of products in bulk and the capacity of screening of humid products is not as important with this type of screener as with star screeners or rotating screeners.
Known to the applicant are the following U.S. and foreign patents which describe different screening processes and apparatuses: U.S. Pat. Nos. 517,724; 2,115,110; 2,366,222; 2,703,649; 2,864,561; 3,322,354; 4,256,572; 4,363,725; 4,861,461; 4,956,078; 4,983,280; 5,097,610; 5,100,537; 5,106,490; 5,120,433; 5,234,564; 212642 (Australia); 64987 (Ireland); 74896 (Ireland); 285 882 (Germany); 1,553,667 (London); 1488026 (U.S.S.R.).
An object of the present invention is to provide a mobile screening unit which would overcome some of the above-mentioned problems, and would thus be an improvement over the mobile screening units known in the prior art.
In accordance with the invention, the above object is achieved by a mobile screening unit for screening bulk material, the screening unit comprising:
Also according to the present invention, there is provided a screening method for screening bulk material, said method being characterized in that it comprises the steps of:
Preferably, step (b) comprises the step of receiving the bulk material in a direction substantially parallel to the first longitudinal direction.
Preferably also, step (d) comprises the step of receiving medium-sized and small-sized particles in a direction substantially parallel to the second longitudinal direction.
The invention and its advantages will be better understood upon reading the following non-restrictive description of a preferred embodiment thereof, made with reference with the accompanying drawings.
In the following description, the same numeral references refer to similar elements. The embodiments shown in the figures are preferred.
Moreover, although the present invention was primarily designed for screening bulk material relating to the fields of compost, construction and demolition, contaminated soils, wood waste/top soil, peat moss and the like, etc., it could be used in different fields for other screening purposes, such as in the food or the agricultural industry for screening bulk material containing grains of different sizes for example, as apparent to a person skilled in the art. For this reason, expressions such as “pieces” and/or “blocks” and any other references and/or other expressions equivalent thereto should not be taken as to limit the scope of the present invention and include all other objects and all other purposes with which the present invention could be used and may be useful.
In addition, although the preferred embodiment of the mobile screening unit as shown comprises various components such as a feeding hopper, piling conveyors, retractable side panels, etc., not all of these components are essential to the invention and thus should not be taken in their restrictive sense, i.e. should not be taken as to limit the scope of the present invention. It is to be understood, as also apparent to a person skilled in the art, that other suitable components and cooperations thereinbetween may be used for the mobile screening unit according to the present invention, as will be explained hereinafter, without departing from the scope of the invention.
Furthermore, although the preferred embodiment of the first and second screeners of the mobile screening unit as shown in the accompanying drawings consist of a vibrating screener and a rotating screener respectively, it is also to be understood that the terms “vibrating” and “rotating” should not be taken in their restrictive sense, i.e. should not be taken as to limit the scope of the present invention, since other suitable screeners may be used respectively for the first and the second screener of the mobile screening unit depending on the particular applications of the mobile screening unit and the desired screening of the different types of particles composing the bulk material, as also apparent to a person skilled in the art. For example, the first and second screeners may be any one of the following: a vibrating screener, a disc screener, a star screener, a rotating screener, a satellite screener, a gyratory screener, or a double-stage vibrating screener, depending on the intended applications of the mobile screening unit, as apparent to a person skilled in the art.
Moreover, expressions such as “large”, “great”, and “big” as well as any equivalent expressions and/or compound words thereof, may be used interchangeably in the context of the present description. The same applies for any other mutually equivalent expressions, such as “medium” and “average” for example, as well as “small” and “fine”, as also apparent to a person skilled in the art.
Finally, it is to be understood that the expression “particles”, as used in the context of the present description, refers to various types of objects/substances which may be screened with the present invention, as also apparent to a person skilled in the art and as will be explained hereinafter.
Broadly described, and referring to
Although the first and second directions 25, 33 as illustrated in the accompanying drawings are directed in opposite ways, for example in
As shown in
Similarly to the above-mentioned, it is worth noting that although the feeding hopper 35 is preferably mounted between the first screener 11 and the second screener 13 as illustrated in the accompanying drawings, the mobile screening unit 1 and the components thereof, namely but not exclusively the feeding hopper 35, and the first and second screeners 11, 13, may be disposed otherwise by suitable cooperations thereinbetween, i.e. the feeding hopper 35 need not be necessarily located between the first and second screeners 11, 13, as apparent to a person skilled in the art.
As shown in
Preferably also and as better shown in
Preferably also and as better shown in
Preferably also and as better shown in
As better shown in
According to the particular embodiment of the invention illustrated in
In this particular case, the vibrating screener is preferably actuated by an eccentric shaft with a counterbalancing weight and preferably comprises a stage of fingers 65 in order to carry out the primary screening of the large-sized particles 5 contained in the bulk material 3. The stage in question of the vibrating screener is preferably composed of several sections of fingers 65 disposed in a cascading configuration, as better shown in
The first screener is 11 intended, among other things, to remove from the bulk material 3 the inputs of large dimensions, i.e. the large-sized particles 5, such as large rocks, stumps, cement blocks and other residues for example, before conveying the rest of the material towards the second screener 13. The minimal dimension of the large-sized particles 5 that one wishes to screen from the bulk material 3 with the first screener 11 is selected according to one's particular needs by adjusting the spatial restrictions imposed by the screening medium of the first screener 11, such as for example, by varying the spacing between the fingers 65 in the case of a vibrating screener. For example, in order to screen large-sized particles 5 having a minimal dimension of about 3″ and more, the spacing between the fingers 65 of the vibrating screener could be selected between approximately 2″ and 3″, as apparent to a person skilled in the art.
The substantial length of the first screener 11, made possible thanks to its positioning along the longitudinal axis of the length of the screening unit machine, and the shaking effect created by the sections of fingers 65 positioned on different levels, combine to increase the retention of the bulk material 3 on the vibrating screener and thus allow to maximize the quantity of material that passes through the fingers 65 of the vibrating screener. It is therefore possible to obtain an important production capacity while minimizing the losses of material (i.e. medium and small-sized particles 7,9 which would otherwise get undesirably screened along with the large-sized particles 5) at the exit of the vibrating screener before conveying the rest of the material towards the second screener 13.
The large-sized particles 5 which do not pass through the fingers 65 of the vibrating screener progress on the top of the latter until the end of the screener 11, thanks to its oscillatory movement, and fall either directly at the front of the screener 11 in order to form a moderately-sized pile of large-sized particles 5, or into a suitable piling conveyor (not shown) in order to be able to form a greater pile of large-sized particles 5, further away from the front end of the support frame 15 so as to not interfere with the mobile screening unit 1. The resulting pile of large-sized particles 5 can, among other things, be used for commercial or recycling purposes.
Furthermore, the mobile screening unit 1 according to the present invention is devised so that the medium-sized and small-sized particles 7,9 that pass through the screening media of the first screener 11, such as the fingers of a vibrating screener for example, fall directly onto the transition conveyor 45. This conveyor 45 is primarily intended to convey the material exempt of large-sized particles 5 towards the second screener 13, along a direction substantially parallel to the longitudinal axis of the support frame 15. As mentioned earlier, the second screener 13 may consist of a star screener, a rotating screener, a vibrating screener or any other type of suitable screener, as apparent to person skilled in the art. The object of the second screener 13 is to separate the medium-sized particles 7 from the small-sized particles 9 at an important production rate and without damaging the screening medium of the second screener 13 which is generally, by virtue of its intended purpose, more fragile than that of the first screener 11. Indeed, the screening media of screeners intended to screen coarser particles is often more robust than the screening media of screeners intended to screen finer particles.
After the primary screening, the material released from the first screener 11 is preferably exempt of any large-sized particles 5, so that the secondary screening can be easily carried out by a rotating screener for example, without risking damaging the screening screens thereof. The secondary screening may also be carried out by means of a star screener such as the one shown in
Hence, it can be easily understood from the above-discussed that both the first screener 11 and the second screener 13 may be selected from the group consisting of a vibrating screener, a disc screener, a star screener, a heavy-duty star screener, a rotating screener, a satellite screener, a gyratory screener, and a double-stage vibrating screener, depending on the applications intended for the mobile screening unit 1, and the nature of the particles 5,7,9 being screened, as apparent to a person skilled in the art. A vibrating screener is also known as a “screen box” and a rotating screener is also known as a “trommel screener”. All of the above-mentioned types of screeners are well known in the art and thus, their working principles need not to be explained herein.
Since both the first and second screeners 11,13 are disposed substantially along the longitudinal axis 17 of the support frame 15 so as to enable increased screening lengths thereof, and therefore enable increased screening capacities thereof, and since the large-sized particles 5 of the bulk material 3 are removed at the first screener 11, the present invention enables to obtain an increased screening rate at the second screener stage, than what is possible with the mobile screening units known in the prior art which have screeners disposed otherwise.
According to the present invention, the material exempt of large-sized particles 5 which exits the first screener 11 is then conveyed to the second screener 13 along a direction substantially parallel to the longitudinal axis 17 of the support frame 15 in order to separate the medium-sized particles 7 from the small-sized particles 9 more adequately and at a high screening rate, preferably at a rate of 150 cubic yards/hour and more. The small-sized particles 9 which pass through the screening media of the second screener 13 (bed of stars, screens, sections of fingers, etc., depending on the type of second screener 13 being used) are then picked up by the recovering conveyor 47 that preferably passes under the secondary screener, as better shown in
The medium-sized particles 7 that do not pass through the screening medium of the second screener 13 are rejected at the end of the latter in order to then be preferably picked up by the piling conveyor 55 of medium-sized particles 7 located along the longitudinal axis of the screening unit machine, at the rear end of the support frame 15, as better shown in FIG. 2. The piling conveyor 55 preferably folds itself at the rear end of the support frame 15 for transportation purposes, as better shown in FIG. 1. In order to distance the piling of the medium-sized particles 7 far away enough from the mobile screening unit 1 the piling conveyor 55 unfolds itself at the rear of the support frame 15 in the working position, as shown in FIG. 2. This configuration helps to create a larger pile of medium-sized particles than would be possible if no piling conveyor 55 was used.
When the screening cycle of the mobile screening unit 1 is over, the bulk material is then classified into at least three different piles, each pile containing particles of substantially the same size, as better shown in FIG. 3. The first pile 58 contains large-sized particles 5 and is preferably located at the front of the mobile screening unit 1, at the exit of the first screener 11. The second pile 57 contains medium-sized particles 7 and is preferably located at the rear of the mobile screening unit 1, at the exit of the second screener 13. The third pile 53 consists of small-sized particles 9, and is preferably located perpendicularly to the middle of the support frame 15 on the side of the mobile screening unit 1.
As better shown in
As also shown in
As shown in
As mentioned previously, it is worth mentioning once again that the second screener 13 may be a double-stage screener comprising a first screening floor for screening the medium-sized particles 7 from the small-sized particles 9 and a second screening floor to further screen the small-sized particles 9 into coarser small-sized particles and finer small-sized particles, thereby enabling the mobile screening unit 1 to screen bulk material 3 into four different categories.
According to the present invention, there is also provided a screening method for screening bulk material, the method comprising the steps of a) receiving bulk material containing large-sized, medium-sized, and small-sized particles; b) screening large-sized particles from medium-sized and small-sized particles along a first longitudinal direction; c) receiving medium-sized and small-sized particles obtained in a step (a); and d) screening medium-sized particles from small-sized particles along a second longitudinal direction substantially parallel to the first longitudinal direction.
Preferably, step (a) comprises the step of receiving the bulk material in a direction substantially parallel to the first longitudinal direction. Preferably also, step (c) comprises the step of receiving medium-sized and small-sized particles in a direction substantially parallel to the second longitudinal direction.
As may now be appreciated, the mobile screening unit 1 according to the present invention is an improvement over the prior art in that, as discussed hereinabove, both the first and second screeners 11,13 are disposed substantially along the longitudinal axis 17 of the support frame 15 so as to enable increased screening lengths thereof, and therefore enable increased screening capacities thereof, and since the large-sized particles 5 of the bulk material 3 are removed at the first screener 11, the present invention enables to obtain an increased screening rate at the second screener stage, than what is possible with the screening units known in the prior art which have screeners disposed otherwise.
Furthermore, the mobile screening unit 1 according to the present invention is also advantageous in that the flow of the bulk material 3 into the first screener 11 is carried out in the same direction as the flow of the material in the feeding hopper 35, that is, substantially along the longitudinal axis 17 of the support frame 15. This enables to obtain a greater first screener length when compared to a screening unit having a first screener whose flow of material is done perpendicularly to the flow of product in the material reserve (feeding hopper) and thus perpendicularly to the longitudinal axis of the machine. As discussed previously for the prior art, a flow of material in a first screener done perpendicularly to the flow of material in the material reserve will often result in an overflow of material in the first screener. The disposition of the first screener 11 according to the present invention, and the screening carried out therealong, as explained hereinabove, overcome the above-mentioned problem associated to the prior art.
The mobile screening unit 1 according to the present invention is also advantageous over the prior art in that the longitudinal disposition of the first and second screeners and of the conveyors allow for an easier maintenance, repair and/or part replacement thereof.
The mobile screening unit 1 according to the present invention is also advantageous over the prior art in that the longitudinal disposition of the screeners and of the conveyors enable to increase substantially the length of the screeners, while respecting the maximal dimensions allowed by the Highway Code, contrary to the machines whose first screener lengths are perpendicular to the longitudinal axis of the screening unit (the length of the screener is thus limited by the width of the screening unit).
Furthermore, this increase of the length of the screeners due to their longitudinal disposition according to the present invention enables to unload more material at once on the screeners while having an increased quality of screening, which results in an increased production capacity and rate, without damaging the screeners used to obtain particles of smaller sizes from bulk material containing large-sized particles, such as big rocks, stumps, cement blocks and the like.
Of course, numerous modifications could be made to the above-described embodiments without departing from the scope of the invention as defined in the appended claims.
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