SELF-CLEANING RECIPROCATING SCREEN

Abstract: Self-cleaning reciprocating screen comprising an under­ lying screening net "A" with a superimposed net "B" supplied with a number of longitudinal wires 3 hold by transversal wires 2′ as to the advancing direction of the material on the screen, in which the wires 3 are free to swing with the sieving vibration and beating on the underlying net "A" keep it clean.

Description: The present invention relates to a vibrating wire self-cleaning reciprocating screen particularly suitable for sieving and screening both dry and more or less damp or damp materials of various types and granulations, and preferably gravelly but also other earthy or crushing materials, including metallic or nonmetallic materials, of various type, shape and structure, in which during the screening obstructions of the screening and sieving net might occur. Dry or- damp curve-shaped or multiform grain sieved material can easily obstruct the net, especially if these grains are mixed with lamellar or schistose mixing materials (e.g. clay, kaolin, etc.). To obviate the above-mentioned drawbacks, the so-called "harp nets" have recently been manufactured, namely nets in which now and then the longitudinal wires do not present weaving through variously spaced weft to realize free length variable widths which aid the vibrations of the warp wires in a continuous way and according to a perpendicular movement to the screening plane, being the transversal wefts suitably spaced between them also at irregular intervals. However, these solutions do not allow a uniform and regular screening of the material for the irregularity of the passage screening sections in the same net In order two obviate the above-mentioned disadvantage the so-called "serpa-arpa" nets have been manufactured, in which these nets have longitudinal wires with ondulations on the net plane corresponding to the screening one, which allows to obtain substantially uniform openings corresponding to the wire ondulation pitch. Even if these nets obviate the above-cited drawback, nevertheless they present a screening passage inequality for the easy deformation of the nets and the excessive elasticity one from the other independent, without considering the main essence in which the entire net vibrates in a uniform way which does not prevent, in particularly heavy cases, an unavoidable obstruction of the same net; further non-braided wires open easily. The scope of the invention as claimed is to provide a remedy to the above-mentioned drawbacks and more particularly to carry out a net screen in which the above-described obstructions do not occur. According to the above-stated purposes and in connection with the claimed characteristics, the invention essentially consists in the realization of a screening net of a traditional type, corresponding to the specific screening requirements, to screen material sliding in longitudinal direction, in which on said screening net a number of longitudinal wires are fixed free to vibrate according to a determinate frequency with the screening vibration.. The above-mentioned characteristics will be anyhow better understood and pointed out and other ones will appear in the following detailed description of two preferred embodiments of the invention, with reference to the enclosed drawings, in which: Figure 1 is a schematic perspective view of a screen according to a first embodiment of the invention; Figure 2 is a longitu dinal vertical section partial net view taken parallelly to the hooking and stretching lateral welts (material sliding direction) as shown in the screen of Figure 1, in a second embodiment of the invention; Figure 3 is a partial top view of the nets of Figure 2; Figure lA is a schematic perspective partial view of the underlying screening net on its longitudi nal welt before the tightening with the superimposed net by means of the hooking and stretching lateral welts; Figure 2A is a partial lateral view of the superimposed cleaning net in correspondence to the superimposition with the underlying screening net portion of the preceding figure and with visualization of a weft transversal wire hooking system; Figure 3A is a transversal section partial view of a longitudinal welt of the complete hooked nets to realize the screen according to the present invention; Figure 4A is a top schematic view of two opposed embodiment forms of the screen, without visualization of the underlying screening net; Figure lB is a transversal partial section screen view normally to the stretching and hooking lateral welts of a further embodiment; Figure 2B is a top partial plan view of the screen portion of Figure lB; Figure 3B is a partial plan screen view showing only the underlying screening net near a lateral welt, with a weaving system comprising transversal reinforcements of the weft in the areas mainly subject to break and wear; Figure 4B is a further embodiment of the transversal reinforcement shown in Figure 3B, that is both weft and warp weaving doubling; Figure 5B is a schematic plan screen panel view of an embodiment in which plural net superimposing panels are connected on the underlying screening net in order to improve the self-cleaning effect and allow the replacement of the worn out net superimposing panels. As it can be noticed from the above figures, the screen consists essentially of a well-known type weft and warp suitably shaped net "A", laterally stretched and hooked by two longitudinal welts "C" for supporting the same net in order to form the screening plane. According to the innovation and to Figure 1, on the underlying screening net "A" and within the lateral welts "C" a second superimposed net "B" is tightened, which presents two bands of net ends with terminal transversal wires 2', as the underlying net "A", which stretch a set of longitudinal wires 3 which beating in vibration on the underlying net "A" keep it clean. In the varied embodiments of Figures 2 and 3 the same net "B" is carried out with the end weaving 1,2,2' of an alternate longitudinal wire 3 which in the intermediate portion passes on the underlying net "A" and is further suitably ondulated instead of being straight as that of Figure 1. In this case the screening net "A" can have any suitable shape and will consist of weft 1 and warp 2 according to a convenient system while in the specific case the vibrating wires 3 will be transversally fixed by a further weaving of transversal weft 2'. Both with this solution and the preceding one, the superiorly supported vibrating wires 3 are suitably and elastically stretched so as to vibrate and break the incrostations or obstructions on the underlying net "A", thus making the material screening easier. Figures lA,2A,3A,4A show varied solutions in which in Figures lA and 2A the removal of the lateral welts of the underlying screening net "A" is provided for a certain portion of a determinate number of longitudinal wires 1 by means of shearing said wires in order to define a free opening "i" with a net of only transversal warpless wires 2 and in which in correspondence with such openings "i" a free jutting out part is situated with weft wires 2' of the upper vibrating net "B" so that these free ones can be placed side by side with the underlying weft screening wires 2 in order to lie on the same plane during the lateral seam "C" as shown in Figure 3A. Thus the advantage will be obtained that the warp wires 3 suitable to the separation of the material on the net "A" will be tightly hold by the weft wires 2' and also binding crop ends 4 can be provided. The set of weft transversal wires 2' can be then tightened by means of seam wires 7 as shown in Figures 2A and 4A and the weft wires 2' can be of a continuous type as shown on the right side of Figure 4A or of a discontinuous type as shown on the left side of Figure 4A in order to form sets of wires independently vibrating in groups, being these binding devices always of a continuous type at the end 5 to stretch the longitudinal vibrating wires 3. Naturally, the weft wires 2' can be in single or multiple number. Figures lB,2B,5B show a further variation to the preceding solutions in which the net or screening plane consists of an underlying screening net "A" with a superimposed self-cleaning net "B" preferably made of separate panels fixed to the underlying net in the upstream joint zones with its reinforcement 2' by means of intermediate clamping bolts 8. Thus a reduction of the free length "L" of the vibrating wires 3 is obtained. A main characteristic of such structured vibrating net panels "B" lies in that each vibrating wire 3 is fixed ahead the braiding band 2', while at the opposite end it is free to vibrate, obviously being the braiding band 2' upstream situated and the free end of the wires 3 downstream oriented as to the advancing material to be screened; so in the joint zones "g" there will be the end of the vibrating wires 3 free for each panel "B" and the beginning of the braiding band 2' of the following one. The tightening of the band 2 of the panels "B" on the underlying net "A" will be carried out with bolts 8, while at the end of the panels, before the joint zones "g" and also of the screen 5', the wires 3 could end also before. As shown in Figures 3B and 4B, in the joint zones "g" a reinforcement braiding of the underlying net "A" can be carried out particularly for the weft wires 2, with the addition of several adjacent weft wires 6. This will cause a better resistance and ruggedness and a consequent increased life of the entire net. Also the underlying screening net "A" can be similarly made of panels and tightened with the same clamping bolts 8 together with the superimposed net "B". As shown in Figures lB,2B,58, superiorly to each net panel "B",a band "D'L can be placed, consisting of a belt 7 sufficiently stretched between the opposite hooking and stretching welts "C" by means of tightening with suitable opening "i" equal in size to the underlying screening net "A", in order to allow a tightening of the device without overlapping. Such stretched belt 7 supports inserted annular spacing bosses 9 to keep in a uniform position the respective set of vibrating wires for the required selfcleaning effect 3.

Claims: Claims: 1. Self-cleaning reciprocating screen for sieving material along its longitudinal direction by means of a vibrating machine comprising a screening net means, possibly supplied at the ends of the two opposite sides with a hooking and stretching welt means (C), characterized in that on said screening net means (A) a superimposed net means (B) is fixed, provided with a number of longitudinal wires (3) as to the advancing direction of the material to be screened, parallel between them and spaced out one another and free to vibrate as to the underlying screening net (A) with the sieving vibrations. 2. A screen as claimed in claim 1, characterized in that each longitudinal vibrating wire (3) on the screening net (A) is ondulated. 3. A screen as claimed in the preceding claims, characterized in that each longitudinal vibrating wire (3) is supported and stretched at the respective ends (5) by means of a net weaving band (2') connected to the underlying screening net (A). 4. A screen as claimed in the preceding claims, characterized in that each longitudinal vibrating wire (3) is supported and stretched at the respective ends of the underlying screening net by means of weaving with the same weft (2) and warp (1) wires of said screening net (A). 5. A screen as claimed in the preceding claims, characterized in that the superimposed vibrating net (B),penetrates in the lateral stretching and hooking welts (C), the underlying screening net (A) through removal of a number of longitudinal wire portions (1,3) both of the underlying screening net (A) and the superimposed net (B) in order to hook up on one plane only transversal weft wires respectively (2,2') with the tightening (C) in the joint zone (i). 6. A screen as claimed in any preceding claim, characterized in that the weft wires (2') binding the longitudinal vibrating wiles (3) of the superimposed net (B) are bound by intermediate sets of weft transversal wires (2'). 7. A screen as claimed in the preceding claim, characterized in that the intermediate binding weft wires (2') of the superimposed vibrating net (B) are sheared in sets to group a number of wires (3) in order to cause unisonous vibrations for independent groups. 8 A screen as claimed in the preceding claims, characterized in that the transversal binding band (2') of the upper vibrating net (B) is fixed on the underlying net (A) by fixing means for intermediate points (8). 9. A screen as claimed in any preceding claim, characterized in that a number of longitudinal vibrating wires (3) of the upper net (B) are provided downstream free as to the advancing direction of the material. 10. A screen as claimed in the preceding claim, characterized in that the superimposed vibrating net is made of more panels (B) than the underlying one and the respective portions are only upstream fixed (8), while in intermediate position on each of them at least one flexible cross piece (D) is provided comprising a belt (7) intercalated with a number of spacers (9).which beat on the underlying net (A). 11. A screen as claimed in the preceding claims, characterized in that the underlying screening net (A) has at least one more weaving weft wire (6) than the warp (1), in correspondence of the tightening zones of the bands (2') of the superimposed selfcleaning net (B). 12. A screen as claimed in the preceding claims, characterized in that the underlying screening net (A) is divided in several panels and is connected with the superimposed net (B) in joint zones "g" through intermediate tightening and locking means (8) in correspondence of the joint and tightening of the transversal weaving bands (2) of the superimposed vibrating panels (B).

Inventors: BEARZOT, ILARIO
Applicants: BEARZOT, ILARIO
Application year: 1982
Main classification: B07B1
IPC codes: B07B1, B01D33