EP0206629B1

EP0206629B1 - Screens, a method of making screens and apparatus for making screens

Info

Publication number: EP0206629B1
Application number: EP19860304417
Authority: EP
Inventors: Clifford Michael Spiller
Original assignee: Qualastic International Ltd
Current assignee: QUALASTIC INTERNATIONAL LIMITED
Priority date: 1985-06-11
Filing date: 1986-06-10
Publication date: 1990-09-19
Anticipated expiration: 2006-06-10
Also published as: CA1279235C; EP0206629A2; AU5854286A; DE3674263D1; EP0206629A3; GB2176215A; GB8613932D0; AU590279B2; GB2176215B; DE206629T1

Description

This invention relates to screens, a method of making screens and apparatus for making screens.
Screens comprised of elongate straight wires or rods, usually of wedge section, held in parallel relation at predetermined spacings are well known in the form of gratings having parallel opposite sides bounded by edge-most said wires or rods and opposite ends at which ends of all constituent wires or rods may be free or joined by suitable wire-end-locating boundary parts. Such gratings can readily form flat rectangular screens beds, and can make up non-rectangular beds, by cutting from a rectangular grating or fabricated using appropriate different lengths of constituent wire or rod. Arcuate, even cylindrical screens are also known made up from rectangular grating that is bent, usually rolled, to impose a curvature about an axis at right angles to the lengths of the parallel constituent rods or wires. If spaced locaters for the grating can also be bent without damage to their attachment to the rods or bars, curved gratings could be made with those rods or bars parallel with the axis of curvature.
It is an object of this invention to provide a novel and advantageous screen structure that is capable of other applications.
According to this invention, a screen structure such as eg. disclosed in DE-A-2633372, and having a basic shape curved about an axis comprises a plurality of coaxial curved elements for which screening spacings are at progressively increasing radial distances from said axis up to a boundary element also curved about said axis, and locating means for holding said elements relative to one another at said spacings said screen structure being formed flat for up to one turn about that axis and is characterised in that a 3-dimensional screen structure is formed from said structure by reshaping into a part conical or conical or part helical or helical screen.
In applying this invention we find that particular advantages arise from a basic screen structure that is flat and comprises either concentric rings of rod or wire at prescribed spacings determined by the cross-section of constituent rod or wire and diameters of the rings. Such a basic structure will normally have radially extending locaters or locating means associated therewith. For concentric rings, one of such radial locaters could serve to join ends of lengths of rod or wire forming the rings, or such joints may be staggered to distribute them amongst more than one radial locater.
From such basic circular screen structures, it is proposed herein that other actual screens or gratings be made, for example conical by cutting along one radius, or cutting out a sector, and rolling up into the desired conical shape, which it is to be noted can readily have its constituent turns or rod or wire partially superposed. Self-evidently, basic elements hereof need not be of full circular form when flat.
Another possibility that arises is for making helical screens or gratings, which for one full part turn of effective internal diameter reduction dependent on pitch (or a part turn of less diameter reduction), could be flat annular said basic screen structure cut as aforesaid and opened up into a radical helical ribber, with spacing of its constituent rod or wire maintained, by spacing its end along the said axis and further turns or part turns can be added by end-to-end connecting such opened-up basic elements or parts thereof, conveniently at radial locaters. It is, however, possible to form all required successive turns of such helical, radial-ribbon, screen or grating on a continuous basis, with a concentric ring construction.
Hitherto, of course, for prior screens using wedge-section rods or wires, it has been customary for their relatively broad and narrow edges to lie in opposite faces of the resulting screens or grating i.e. with the centre lines of a symmetrical wedge section oriented always perpendicular to the plane of the screen. The same considerations apply to basic screen structures hereof, i.e. flat circular/annular elements, when used directly as screens or gratings, say in a circular section passage or as a circular framed bed.
Moreover, for either or both of the conical and helical screens gratings mentioned above, it is further pointed out that canting of such screen- section relative to prior practice might be useful in order to achieve whatever final sectional orientation is desired, specifically including at right angles to the surface of the resulting structure.
The above is concerned with screens comprised of curved rod or wire, or other elongate (filamentary) material which are at progressively increasing radial distances from an axis up to a boundary rod or wire also curved about said axis. A flat circular screen element is described, having spaced concentric rings. It is also specifically envisaged that sectoral parts thereof, whether cut from complete flat circular or annular elements or formed ab initio only as sectors, can be formed up to conical shape by rolling operations. Further, a helical formation is envisaged with each constituent wire or rod, etc., forming an individual helical spiral, i.e. generally in ribbon-like array.
Such screening elements, being novel in themselves, some convenient way is required for their manufacture, and it is an aim of another aspect of this invention so to provide.
According to another aspect of the invention, a means for forming a screen structure having a basic shape curved about an axis comprises a plurality of coaxially curved elements for which screening spacings are at progressively increasing radial distances from that axis up to a boundary element also curved about said axis, said means being characterised in that it comprises a locating table or template grooved to match the intended consecutively radially spaced location of constituent elements, means to feed such elements into such grooving of the table or template means for securing supports or locaters to screen elements on the table or template, and means serving to impart requisite relative movement between such table or template and such elements and where said basic shape is formed flat for up to one turn about that axis and a 3- dimensional structure is formed by reshaping.
The use of a grooved table or template is particularly effective in forming a master to which produced radial screen elements must perforce comply within the tolerance of its grooves to the engaged rod or wire, etc., which can be very close. Moreover, such table need not itself be expensively fabricated from tool steel for maximum life, indeed is preferably not, say being of brass or even plastics material cast or moulded to shape from a negative formation. It is even possible for the latter to be itself an intermediate, if desired a "one-trip" intermediate, made from a true master used only for casting/moulding operations. Such a true master is readily made these days, whether by machining, etching or eroding, or combinations thereof, some original or softer readily worked material from which the durable master is made and then serves in making replicas for itself as well as intermediate masters. We do not, however, rule out any method of making a grooved table that is satisfactory in view of actual tolerances on stock rod or wire, etc., and desired tolerances for spacings thereof in the ultimate screen.
When using wedge-section rod or wire, etc., the grooving of the table or template may match that wedge section from its narrow end, i.e. be of V-shape, or may accommodate the section from its wide end, i.e. be of right-angled channel-shape.
Such tables or templates, whether of full circular or part-circular, i.e. sectoral or segmental, shape are readily associated with means for securing radial supports or locaters to screen elements made thereon, for example using a radial beam extending from the axis of the table or template, which beam is readily adapted to perform sequential welding or other attachment/ forming of such radial supports/locaters, whether by electrical resistance welding or other processes suitable for metal, or by heating, solvent, adhesive or other welding or joining of other materials such as plastics. Such beam may be rotatable about said axis, or the table or template may be so rotatable relative to the beam.
We find that wire or rod, etc., can be readily fed onto the grooving of the table, as a plurality thereof, one per concentric groove. Plural feeding can be done using conical roller means to get the required differentials of feed rates, preferably using grooved roller means for accurate spacing purposes, and whether as a single such roller or as a nip between two such rollers. It is preferred for wire or rod etc., to have its end or ends suitably formed, typically simply bent into curvature of the grooving at first entry thereto.
An alternative is, of course, for the wire or rod, etc., to be gripped in the grooving of the table or template, say by clamping at or near entry ends, and for the table or template to draw off such wire or rod, etc., by its own driven rotation.
According to another aspect of the invention a method of forming a screen structure having a basic shape curved about an axis and comprised of a plurality of coaxially curved elements for which screening spacing are at progressively increasing radial distances from that axis up to a boundary element also curved about said axis, characterised by introducing said plural elements into a substantially flat table or template grooved to match the intended consecutively radially spaced location of constituent elements, securing supports or locators to the screen elements to maintain said spacings, and imparting requisite relative movement between such table or template and such elements to form said basic shape flat for up to one turn about that axis and then forming a 3-dimensional structure by reshaping into a part conical or conical or part helical or helical screen.
The above method and means are intended as examples of how the afore-described screens could be made and not to be taken as limiting the manufacturing method/apparatus. There is described below by way of example a further alternative apparatus which can be used for making the aforesaid screens.
According to another aspect of the invention there is provided apparatus defining a grooved locating template for use in forming a screen structure having a basic shape curved about an axis and comprised of a plurality of coaxial curved elements, for which screening spaces are at progressively increasing radial distances from an axis up to a boundary element also curved about said axis, the apparatus comprising a plurality of spaced radial grooved guide members for receiving the aforesaid elements and carried in a frame and the grooves define channels at progressively increasing radial distance for said elements, and wherein a plurality of spaced radial location members are provided for retaining said elements in the grooves until locaters are fixed to the elements, the radial guide members being grooved to match the intended consecutively radially spaced location of the constituent elements and the screen structure being formed flat for up to one turn about that axis prior to forming a 3-dimensional structure by reshaping.
These guide members and the location members are preferably positioned in pairs one above the other with the open side of the grooves facing the (preferably ungrooved) location member, with the pairs of members secured together by fixing means. Conveniently, the location members are carried on arcuate members forming an integral frame which are secured to the arcuate members of the guide members.
By the above described apparatus, wires can be positioned in concentric relationship for full or part circular arrangements. Any welding required to fix the wires together can be carried out between the radiating segments. The use of this apparatus removes any limitation of the size in which radial curved panels can be produced compared with say a grooved locating table.
The above described apparatus may be utilised in several ways in the construction of a screen structure. Wires may be placed in the grooves by hand and the locating members secured in position to hold the wires. This may be done by threading the wires into the grooves from one end with the locating members already in position. Alternatively, the wires may be laid over the open grooves, and the locating members secured in position as a whole, or sequentially when location members are discrete components, starting either from one end, the centre or any other convenient point with the wires being bent as necessary.
Alternatively, an automatic/mechanical loading arrangement may be employed with say ends of wires being located in a radial beam pivotable about the axis of the arcuate template, and pulled around the arc of the template with the locating members being secured in place to constrain the passage of the wires to the desired arcuate configuration.
Specific implementation of particular embodiments and aspect of this invention will now be described hereinafter by way of example only, with reference to the accompanying diagrammatic drawings, in which:-

Figure 1 shows a flat circular annular basic screen structure 10 comprised of concentric rings RI-Rn.
Figure 2 is a fragmental sectional view.
Figure 3 shows a conical screen or grating.
Figure 4 shows a helical screen or grating,
Figure 5 is a plan view including a circular table or template 70;
Figures 6 and 7 are alternative partial sections of table or template grooving;
Figure 8 shows feed rollers 80A, 80B;
Figure 9 is a plan view of another embodiment of apparatus for forming curved screens;
Figure 10 is a front view of Figure 9;
Figure 11 is a section on XX of Figure 10; and
Figure 12 is an enlarged end view of a radial member.

In Figure l,the basic fiat circular annular screen structure 10 has its rings RI-Rn successively spaced at substantially equal radial spacings X. Radially extending locaters are indicated at 12.
The rings RI-Rn are indicated as being of customary wedge-section, see Figure 2, and will normally be of steel, and the locaters 12 may be of any suitable material and attachment, for example of metal readily welded, soldered or brazed into place, ideally entering the spaces X past broader base parts B of the wedge-section constituent rod or wire, or simply of welding/ soldering metal, or of plastics material either moulded for snap-fitting onto the base B or partially flowed into their final location by heat, solvent, ultrasonic or other attaching process.
The basic screen elements of Figure 1 can obviously be used directly in circular cavities or holders, and their constituent wire or rod bases B for wedge-section can, as indicated in Figure 2, be effectively flush with one side of the screen element 10, 20.
However, if such basic elements are cut radially, they can be rolled up into a conical shape, see Figure 4, which omits the locaters 12 for clarity, but same will normally run up and down on inside or outside of the illustrated frusto- conical shape 40. It will be appreciated that joining up the wire or rod ends formed by the radial cutting operation is readily achievable at the position of a said locater 12, 12', preferably one omitted from the original flat circular element 10,20.
It will further be appreciated that sectors only of a basic circular element 10, 20 can be bent up to form cones, or parts of cones, of different diameter and side gradient. Indeed, basic elements hereof need only be of part-circular form, at least when formed from pluralities of rods or wires as is inevitably the case for the consecutive ring structure 10 of Figure 3.
Moreover, displacement of ends of such a radially cut basic screen element 10, 20 can result in up to a full turn of a helical arrangement such as shown in multi-turn form at 50 in Figure 4 bounded at dashed lines 52, 54 say within a tube about another tube or shaft. However; the further possibility presents itself of making a multi-turn helical screen structure as shown in Figure 4 in a single operation wherein constituent wires are fed in, as a ribbon-like array, and with a desired offset of its ends through its production.
The elements hereof are readily made in various ways, one of which involves the use of a table grooved to correspond to the intended final curvature(s) and into which plural wires are fed or drawn. Self-evidently there will be suitable means for imparting relative movement between a circular or sectoral table as aforesaid and the rod/wire or rods/wires to constitute the desired screen element.
Referring now to the drawings of Figures 5 to 8 there is described with reference thereto a method of forming curved screens. A circular table or template 70 is shown with concentric grooves GI-Gn about its axis 72 and on one side thereof. For wedge-section rod or wire, etc., those grooves may be of V-section to match to and accurately locate the narrow ends of the wedge-section, see Figure 7, or they may be of right-angled channel-section to match to and accurately locate the wide ends of the wedge-section, see Figure 6. It is, in fact, envisaged that tables or templates be separable into constituent segments or sectors, say at quadrants 70A-70D as indicated.
For a full circular concentrically grooved table or template, or for segmental or sectoral tables or templates with concentric grooving, there is a requirement to feed in plural wire or rod, etc., stock as indicated purely diagrammatically at SI-Sn of Figure 1. A suitable plural feed arrangement uses conical roller means to get the required differential feed rates, see Figure 9 showing a pair of conical rollers 80A, 808 with a nip along common generator lines, also preferably with shallow locating grooving at least at the roller (80B) taking the wider end of the envisaged wedge-section stock material. It will be evident that other such locating grooving of the roller means could be used if preferred.
As shown in Figure 5, the plural stock S is shown straight at entry to the grooving G1 which suits an arrangement where that stock is gripped into the grooving at its entry thereto and the table or template 70 is rotated about its axis 72 to draw in and form that stock to the desired configuration of successive radial spacings of a basic element of flat circular/annular or part circular/annular form. It will be evident that, for a sector or segment only of the table or template 70, such in-feed can be at a level aligning reasonably accurately with the grooving. However, for a full circular table such stock entry is best done at a suitable angle onto the table or template 70 and its grooving (not shown), typically via a radial placement roller and using a stock end radial clamp that rotates with the table or template 70. For an alternative stock feed and forming arrangement where only the stock feed roller means 80A, 80B is driven, no such radial clamp would be required, though further rollers similar to the placement roller might usefully be provided at radial spacings round the table or template 70.
At least for feeding stock into grooving of a stationary table, that is facilitated if the stock has some curve-preformation, at least for first end- entry into the grooving. Such preforming does not, of course, have to be accurate relative to the curvature of the grooving, just somewhere near enough to ease handling. With pressure from above and below at the stock feed rollers 80A, 80B, preformation curving at right-angles to the joint contact nip can be prior to each rollers without the latter acting to change it. Suitable guides could thus be used at or before entry to the feed rollers. Alternatively, if the stock is in reel form, it may be enough simply to rely on its reel- imposed curvature, especially where same is achievable by partially relieving such curvature. Radial supports as permanent locaters for the flat arcuate/annular or circular configuration formed on the grooved table or template 70 are shown emplaced, see 16 in Figure 5, by a forming station in a beam 18 past which the stock wire or rod, etc., passes in or with the table or template 70. The beam 18 may also be associated with welding apparatus.
Where screen elements or sectors or segments or radially-cut circles or annuli are roller to form cones, the wires or rods, etc., will be joined or rejoined at then-abutting ends. If necessary or desirable to get wedge-sections oriented with their broad ends coplanar with a cone operator, i.e lying flat in the surface of an imaginary internal cone surface, the stock material may be canted relative to what is shown in Figures 6 and 7, say by corresponding inclination of the bases of the grooves of Figure 7. A related relative twist of the stock as fed may be achieved in the feed rollers or in guides, usually then prior thereto, perhaps combined with any curve inducing guide means.
Finally, we advert to continuous production of multi-turn helical screen structures, which can readily be achieved using a sectoral or segmental table 70 by taking exiting product down past a guide inclined according to required pitch. As for conical screen structures, canting of constituent stock material section may be employed.
Referring now to Figures 9 to 12 there is shown an alternative embodiment of apparatus for forming curved wire screens, such as the afore-described screens. It comprises a plurality of spaced radial grooved guide members 101, seventeen in the illustration, for receiving the wires or rods making up the screen. In the enlargement of Figure 12 the grooves are shown as V-shaped - being particularly suited to receiving wedge wire. Alternatively, the grooves may have right-angled corners to receive the bases of said wedge wire.
The radial members 101 are located at opposite ends on respective arcuate members 103,105. As illustrated these members are part circular and the apparatus is such as to be particularly suited to making part circular or annular curved screens. The angle of arc is chosen for the particular application, that illustrated being but an example. A complete annulus is an alternative. As shown the member 103 and 105 are concentric with one another.
The apparatus further comprises a plurality of spaced radial location members 107, preferably ungrooved as illustrated, and used to hold wires in place. The guide members 101 and the location members are located in pairs one above the other as illustrated with the open side of the grooves facing the clamping (flat) edge of the location member. The location members are similarly secured at opposite ends to arcuate members 109, 111. Aligned bores in the arcuate members 103, 105, 109, 111 serve to secure the guide members and location members together to locate therebetween the wires forming the screen.
Alternatively, each location member may be provided with means for fixing them individually to the arcuate members of the guide members.
With each of the guide members having the same groove configuration, the desired curved wire screen can be made. For example, individual wires can be positioned in the grooves to form concentric wires. Radial locaters are then secured to the concentric wires, say by welding to form the desired length of part circular screen, or even an annular screen, by making up in sections and securing individual sections together endwise, or using the jig to form sequential arcuate sections from continuous lengths of wires. A spiral wire pattern could be provided on the jig if so desired.
The advantage of the described jig is that larger sizes of screen can be produced compared with that which is practical with the afore-described circular table. The jig is particularly suitable for screens having a radius of the order of 1 metre or greater.
The wires may be fed into the grooves from one end i.e. with the guide members and locaters in position, or the wires may be laid into the grooves, slightly curved, and the location member placed in position to hold the wires whilst the locaters are secured to the wires.

Claims

1. A screen structure having a basic shape curved about an axis comprising a plurality of coaxial curved elements for which screening spacings are at progressively increasing radial distances from said axis up to a boundary element also curved about said axis, and locating means for holding said elements relative to one another at said spacings in that said screen structure being formed flat for up to one turn about that axis characterised in that a 3-dimensional screen structure is formed from said structure by reshaping, into a part conical or conical or part helical or helical screen.

2. A screen structure as claimed in claim 1 in which the locating means comprise radially extending locaters (12).

3. A screen structure as claimed in claim 2 wherein one or more of such radial locaters serves to join ends of lengths of rod or wire forming the coaxial curved elements.

4. A screen structure as claimed in any one of claims 1, 2 or 3 in which a conical screen is formed by cutting along one radius, or cutting out a sector, or forming initially a part circular screen, and rolling up into the desired conical shape.

5. A screen structure as claimed in claim 4 in which there is a partial superposition of the constituent turns of rod or wire.

6. A screen structure as claimed in any one of claims 1, 2 or 3 when formed into a helical or part helical screen by cutting and/or opening up a flat annular screen.

7. A screen structure as claimed in claim 6 wherein two or more annular screens are cut and opened up and secured together end to end to form a helical ribbon with the required number of successive turns.

8. A screen structure as claimed in claim 1, 2 or 3 in which successive turns of the structure are formed on a continuous basis opening out into a helical ribbon.

9. Means for forming a screen structure having a basic shape curved about an axis and comprised of a plurality of coaxially curved elements for which screening spacings are at progressively increasing radial distances from that axis up to a boundary element also curved about said axis, characterised in that it comprises a locating table or template (70) grooved to match the intended consecutively radially spaced location of constituent elements (R), means to feed such elements into such grooving of the table or template, means (18) for securing supports or locaters (12) to screen elements on the table or template, and means serving to impart requisite relative movement between such table or template and such elements and wherein said basic shape is formed flat for up to one turn about that axis and a 3-dimensional structure is formed by reshaping.

10. Means claimed in claim 9 in which the means (18) for securing said supports or locaters (12) comprises a radial beam adapted to perform sequential welding or other attachment forming of radial supports or locaters.

11. Means claimed in claim 10 in which the beam and table or template are rotatable relative to one another about said axis.

12. Means claimed in any of claims 9, 10 or 11 in which plural feeding of the elements onto the table is done using conical rollers means (80).

13. Means claimed in claim 12 in which the conical roller means is grooved for accurate spacing of material constituting the curved elements.

14. Apparatus defining a grooved locating template for use in forming a screen structure having a basic shape curved about an axis and comprised of a plurality of coaxial curved elongate elements, for which screening spaces are at progressively increasing radial distances from an axis up to a boundary element also curved about said axis, the apparatus comprising a plurality of spaced radial grooved guide members (101) for receiving the aforesaid elements and carried in a frame (103,105) and the grooves define channels at progressively increasing radial distance for said elements, and wherein a plurality of spaced radial location members (107) are provided for retaining said elements in the grooves until locaters are fixed to the elements and characterised in that the radial guide members are grooved to match the intended consecutively radially spaced location of the constituent elements the screen structure being formed flat for up to one turn about said axis prior to forming a 3-dimensional structure by reshaping.

15. Apparatus as claimed in claim 14 in which the guide members are located at opposite ends on respective arcuate members, with the inner and outer arcuate members disposed concentric with one another.

16. Apparatus as claimed in any one of claims 14 or 15 in which the radial location members (107) are located at opposite ends on respective further arcuate members (109, 111) defining an integral unit which is securable as a whole to the guide members with the guide members and the location members in overlying relationship.

17. A method of forming a screen structure having a basic shape curved about an axis and comprised of a plurality of coaxially curved elements for which screening spacing are at progressively increasing radial distances from that axis up to a boundary element also curved about said axis, characterised by introducing said plural elements into a substantially flat table or template grooved to match the intended consecutively radially spaced location of constituent elements, securing supports or locators to the screen elements to maintain said spacings, and imparting requisite relative movement between such table or template and such elements to form said basic shape flat for up to one turn about that axis and then forming a 3-dimensional structure by reshaping into a part conical or conical or part helical or helical screen.