EP0074935B1

EP0074935B1 - Self-cleaning reciprocating screen

Info

Publication number: EP0074935B1
Application number: EP82830231A
Authority: EP
Inventors: Ilario Bearzot
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-09-15
Filing date: 1982-09-10
Publication date: 1988-05-04
Also published as: DE3278423D1; EP0074935A3; EP0074935A2

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 non-metallic materials, of various type, shape and structure, in which during the screening, obstructions of the screening and sieving net might occur.
Dry or damp curved-shaped or multiform grain sieved materials 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 regulare screening of the material for the irregularity of the passage screening sections in the same net.
In order to 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 (GB-A-856181 STEINHAUS GmbH), 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.
FR-A-2 407 026 (UNITED WIRE GROUP LTD) discloses a two superimposed nets (2, 3) stretched with different tensioning at the opposite longitudinal edges by fixing support means (1), in order to obviate utilization of well known sieves with two superimposed nets wherein the superior net have screening fonction whereas the inferior have support fonction only without screening effect being realized with larger net than the first one. Different tensioning in the two superimposed nets being provided to obviate obstructions between the two nets, allowing clattering between them.
FR-A-1 089 947 (M. CHAUVIN) further discloses a Wire Screen with two superimposed nets wherein between the two nets vibrating balls are placed.
GB-A-1 258 995 (HRIN, LEHMAN AND CO.) disclose an Elastic Sieve Base with a sieve liner (1), tension suspension tackle (2) tension end clamp (3) and non tensioned or unclamped region (a), to allow vibration of the respective not tensioned sieve liner (screening net) avoiding obstruction.
All this solutions do not achieve an effective anti-obstruction effect because the respective not so tensioned net having screening effect, do not vibrate as well when become obstruction in its mesh.
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 or not increase, being contained in the respective increasing.
According to the invention there is provided a self-cleaning reciprocating screen as disclosed in claim 1.
The above-mentioned characteristics will be anyhow better understood and other ones will appear in the following detailed description of preferred embodiments of the invention, with reference to the enclosed drawings, in which:

Figure 1 is a transversal partial section screen view normally to said lateral hooking means of a further embodiment; Figure 2 is a plant partial view of the screen portion of Figure 1; Figure 3 is a partial plant 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 subjected to break and wear; Figure 4 is a further embodiment of the transversal reinforcement shown in Figure 3, that is both weft and warp weaving doubling; Figure 5 is a schematic plant screen panel view of a further embodiment in which plural superimposed clattering means 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 (1) and warp (2) suitably shaped nets "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 Figures 1,2, 5, 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 at its upstream end by the braiding band 2', while at the opposite end it is free to vibrate, the braiding band 2' obviously being situated upstream and the free end of the wires 3 situated downstream with respect to the advancing material to be screened; so in each joint zone "g" there will be the free ends of the vibrating wires 3 of one panel "B" and the beginning of the braiding band 2' of the following panel. The tightening of the band 2' of the panel "B" on the underlying net "A" is carried out with bolts 8, while at the other end of the panels the wires 3 could also end before the joint zones "g" and before the end 5' respectively.
As shown in Figures 3 and 4, 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 1, 2, 5, above to each net panel "B" a band "D" can be placed, consisting of a belt 7 sufficiently stretched between the opposite hooking and stretching welts "C" by means of tightening, these being a 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 self-cleaning effect 3.

Claims

1. Self-cleaning reciprocating screen for sieving material passing along its longitudinal direction, the screen being vibrated by means of a vibrating machine and comprising a screening net (A), characterized in that a longitudinal wire set (3) is fixedly superimposed on said screening net (A), the longitudinal wire set being provided with a number of parallel spaced wires running in the direction of advancement of the material to be screened and at the upstream end of these wires with transverse wires so as to form a band for fixing the longitudinal wire set (3) to the underlying screening net (A), the downstream ends of the longitudinal wires not being fixed to the underlying screening net (A) and being free to vibrate relative to the underlying screening net (A) undergoing sieving vibration.

2. A screen as claimed in claim 1, characterized in that each longitudinal vibrating wire (3) on the screening net (A) is undulated.

3. A screen as claimed in any preceding claim, characterized in that the weft wires (2') binding the longitudinal vibrating wires (3) of the superimposed net (b) are bound by intermediate sets of weft transversal wires (2').

4. 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.

5. 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).

6. 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).

7. 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).