DE3133342A1 - "METHOD FOR MAINLY UNIFORM TENSIONING OF A FINE-SCREENED SCREEN DISPOSED ON A SCREEN FRAME" - Google Patents

Abstract

1. A method of substantially uniformly tensioning and maintaining a fine-meshed screen-cloth (5) mounted on a screen frame, especially intended for use in screen machines, wherein provision is respectively made for that the legs (1') of the screen frame (1) of square to rectangular or polygonal configuration are furnished with pressure and traction means directed toward the interior (1") of the area embraced by the screen frame (1), characterized in that the legs (1') are loaded toward a point coinciding with the centers of gravity of the area, with the legs (1') being loaded until just under the elastic limit of the leg material thereby causing a deformation of the screen frame (1), that a preloaded screen cloth (5) is fixed to the screen frame (1), with the adjusted tension maintained, and that, subsequently, the preloading means are removed, that the required working tension in the warp and weft direction is imparted to the screen cloth (5) by the legs (1') which upon relieving of the screen frame (1), via the restoring path, are returned approximately to their standard position, that in the course of progression of the continued timeand operating-responsive stretch of the screen cloth (5), for maintaining and adjusting the working tension, a permanent tension means (2) mounted in the interior (1") of the screen frame (1) and supportingly directed against the inner side of leg (1') by means of clamping arms (2") is used, and that the permanent tension means (2) is of asteriod configuration and that spreading tension arms (2") adjoining a centrally arranged cross (2') respectively adjust themselves independently in their path of tension.

Description

PATENT ADVOCATE. "..". . ".." _ ""..:

PAUL MUNDERICH "·"' ^: >' - "-" - ':'& Aeh grdndau-

ROTHENBeRGeN

PMNKPUKTd) ITIMUC M T (L (PON O Ο 1/37 Ο *

ULNHAUl (N KTO.> ·· ■

POSTSCHCCK-ACCOUNT. PFM. ll «72 (-f ol

OCN 8/21/81

Mu / Lo 25/3/81

Patent application

and

Utility model auxiliary registration

company

Paul GmbH & Co.
Metal mesh and filter factory

6497 Steinau 1

"Procedure for largely uniform tension a fine-meshed one arranged on a sieve frame Screen fabric "

The invention relates to a method for largely uniform tensioning one on one Fine-mesh sieve fabric arranged on a sieve frame / especially for use in a sieve machine ^ and a device suitable for carrying out the method.

According to LUEGER, Lexicon of Technology / roro edition, Volume 35, page 140, when sieving fine grains, the forces of inertia (weight-inertia) large surface forces (adhesion, capillary forces, etc.) of the goods to be screened as to consider and take into account disruptive factors. sight.

Known screening devices in which the material to be screened falls through the meshes due to gravity, therefore only work satisfactorily with relatively coarse grains.

In building material processing, for example, there is no easy way to divide fractions 0 to 2 mm, with a required high screening capacity that can be over 100 to / h - really from the rest Separate the material to be sieved. (Fine sand component) Neither can the filler component, its upper limit is characterized by the 0.09 mm grain size,

in their internal structure, i.e. from 0 to 0.09 mm, not without great effort or not with operationally feasible methods, e.g. in the building materials industry, check. Such a control is already subject to unstable, one-sided tension of the sieve conditional mesh position opposite.

If one also takes into account the additional filler content resulting from the fine sand component, which is also not detectable, it must be noted that this is responsible for the mortar formation in the In the context of building material mixtures, the composition of the important fraction cannot be determined or controlled is.

Similar considerations and problems are basically pourable for everyone else. Goods processing industries given.

Checking this grain size range requires vibrating screens with particularly high vertical acceleration - whereby work is often carried out with an acceleration of more than ten times the gravitational acceleration - in order to reduce the to achieve agglomeration and the conveyance of the material to be screened through the screening machine. In many cases, however, these measures alone are not sufficient, and additional sieving aids, e.g. Brushes, bumpers and also fluids to support the sieving process in pre-binding with can be used for the conveyance of goods.

Fine screening is generally also supercritical vibrating sieve systems. For screening machines with a supercritical number of vibrations it is possible,

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either only the sieve bottom, i.e. the tensioned sieve mesh, or, on the other hand, the entire sieve box to set in vibration, whereby in the context of the classification in larger systems, sieves with a fixed screen box are usually advantageous.

In this context, reference is made to the well-known vibration excitation of the sieve bottom by electromagnetic Vibrators referenced (e.g. RHEWUM sieve), which set the sieve bottom in circular oscillations perpendicular to the sieve plane.

The frequency, which is decisive for the sieving result and performance in the supercritical area, requires Use of fabrics a constant in warp and weft direction, the limit of the elastic The tension in the fabric threads that is almost reached, although of course here - with regard to the necessary driving through the critical area in both directions - briefly the resulting resonance must be taken into account.

These considerations apply in principle to all supercritical systems and in some cases also apply into the critical oscillating area.

Taking this into account, it is the object of this invention to provide a method according to the above type described for setting a largely uniform in warp and weft direction of the fabric high screen tension,

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that the achievement of maximum oscillation frequencies at essentially predetermined amplitudes enables a long operating period «

According to the invention it is provided that the legs of a square to rectangular or polygonal sieve frame by approach to the center of the surrounding by the sieve frame Area-directed pressure or traction means in seal this, with the center of gravity identical Loaded point until just below the limit of elasticity of the leg material and thereby deformed that on the screen frame, while maintaining the set tension, a usually pre-tensioned screen fabric is fixed that the screen fabric through the with relief of the Siebrahmens about to their normal position returning legs over the path of return, the necessary working tension in warp and weft direction is conveyed, and

that with the progressive course of the time and operation-dependent further stretching of the sieve fabric the maintenance and adjustment of the working voltage through a center of the sieve frame, permanent tensioning means directed against the inside of its leg in a supporting manner is given, whose star-shaped, a centrally arranged cross piece adjoining, spreading Clamping arms adjust independently in their tension path.

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The method according to the invention not only ensures a practically uniform, high voltage of the screen fabric in its warp and weft direction, it also enables a long one Compliance with the required working voltage during the progressive sequence of the time- and, depending on the operation, further stretching of the screen fabric, which is made more uniform the crank is connected between the warp and weft.

The sieve quality is so with increasing operating time by the equalization of the Cross-section of the Maaclien passages to exhaustion the clamping possibilities even increased.

Through this type of tension and further post-tensioning the required possible setting of maximum high oscillation frequencies with low technical effort achieved. The shape of the sieve is of subordinate nature. Of course, the amount of possible deflection of each leg and thus that of this thigh auyyehunde maximum span ultimately dependent on its length, so that with short legs the pre-tensioning options of the screen are sufficient should be exhausted in order to achieve the maximum possible elasticity permit.

üinu WKIL (Jibllduny dou Vurluhrunu ülcliL before, that the vorcjo span ntc screen mesh, while maintaining its pretension, on which to further Tension-loaded screen frames are fixed and then the pre-tensioning media are first removed and then the strainer frame is relieved.

As already mentioned, the sieves are in the interest of an equalization of the offset of the crossing points between warp and weft and thus the mesh cross-sections pre-tensioned and used in this stretched form for further tensioning through the screen frame.

In special cases, however, it can be useful to proceed as described above. In this case, the pre-tensioning device must be held slightly larger than the screen frame so that the screen mesh, including the comprehensive pretensioning frame on which the screen frame can be placed.

A device suitable for carrying out the method is characterized by: that the clamping means consists of a cross piece and connecting arms, each with one on these formed, by one or more compression spring (s) formed expanding part, the tensioning arms or their spreading parts in the middle on each of an inner surface of the legs forming the screen frame are fixed in the tensioning direction by any means.

It can also be provided
that the expanding part by pneumatic or
hydraulic means acted upon pressure cylinder is / ie this takes over the function of the spring.

In this case it is advisable to
that the pressure cylinders as spreading parts of the clamping arms are connected to one another via lines, separable by shut-off devices.

The supply of pressure cylinders with pressure media
can in this case take place centrally from a pressure vessel that enables a controlled pressure setting.

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The method according to the invention as well as one to Its exercise proposed device is illustrated by the accompanying drawing, for example.

Figure 1 shows the sieve frame with an indicated

Fabric overlay in plan.

FIG. 2 shows the section I-I from FIG.

The screen frame 1 formed from U-shaped outwardly directed legs 1 'has in the case of this Example on a square floor plan.

1 in the center ^11, that the center of gravity of the screen surface, a cross-piece is disposed 2 *, from which each leg to 1 ^1, a tension arm 2 performs. ¹¹

Each tension arm 2 ¹¹ ends in an expansion part 3, which in this case is formed by a compression spring and is fixed in a centering manner in the middle of the leg by a screw 4.

When tensioning the frame, the legs 1 ' loaded in the direction of the arrows shown in dashed lines and after fixing the screen fabric 5 relieved on the frame 1 again.

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Claims (5)

25/3/81 f ' Claims (I J method for a largely uniform Tensioning a fine-mesh screen fabric arranged on a screen frame, in particular for use in screening machines, as well as a device suitable for carrying out the method, characterized in that that the legs (1 ¹ ) of a square to rectangular or polygonal sieve frame (1) by approach of the center (1 ■ ') of the through the sieve frame (1) comprehensive area directed pressure or pulling means in the direction of this, with the centroid identical point are loaded until just below the elastic limit of the leg material and are deformed in the process, that on the screen frame (1), if maintained the set tension, a usually pre-tensioned screen mesh (5) is fixed will, that the screen mesh (5) through the with relief of the sieve frame (1) about to its normal position returning legs (T) over the Way of the return conveyed the necessary working tension in the warp and weft direction will, and - 11 - 25 / -V81 that as the time and operation-dependent further stretching of the sieve fabric (5) progresses, the maintenance and adjustment of the working tension by a one in the center (1 '') of the sieve frame (1), directed against the inside of its leg (1 ¹ ), supports it , permanent tensioning means (2) is given, whose star-shaped, a centrally arranged cross piece adjoining, spreading tensioning arms (2 ″) adjust independently in their tension path. 2. The method according to claim 1, characterized in that that the pre-tensioned screen fabric (5), at Maintaining its pre-tension on the sieve frame (1), which is loaded for further tension fixed and then first removed the pretensioning means and then the screen frame (1) is relieved. 3. Device for performing the method according to claims 1 and 2, characterized in that that the tensioning means (2) consists of a cross piece (2 ¹ ) and adjoining ^{tensioning arms (2 1} ') each with an expanding part (3) formed thereon and formed by one or more compression spring (s), 25/3/81 wherein the clamping tower (2 ¹¹ ) or their spreading part (3) are fixed to an inner surface of each of the legs (1 1) forming the screen frame ( ¹ ) in the clamping direction by any means. 4. Device for performing the method according to claim 3, characterized in that that the expanding part (3) a pneumatic or pressure cylinder acted upon by hydraulic means. 5. Device for performing the method according to claims 3 and 4, characterized in that that the pressure cylinders of the expansion parts (3) of the clamping arms (2 ¹¹ ) are connected to one another via lines, which can be separated by shut-off devices. - 13 -