EP3944904B1 - Sieving device - Google Patents

Description

The invention relates to a screening device for finely divided, powdery material to be screened, comprising a screen which extends essentially horizontally and a vibration drive for the screen, as well as a screen attachment which is arranged above the screen and delimits a receiving space for the material to be screened above the screen.

Screening devices of the type mentioned are widely known, for example on the EP 1 581 349 B1 is referenced. The sieving effect is based on the essentially horizontally extending sieve and possibly the sieve attachment being set into horizontal and/or vertical vibration by means of an associated vibration drive, as a result of which sieve material applied to the sieve in the receiving space and possibly clumped is broken up and passes through the sieve and as the desired finely divided powdery material to be sieved occurs below the sieve, where it can be collected and discharged. The sieve attachment delimiting the receiving space is part of a housing surrounding the sieve and is usually made of metal, in particular polished stainless steel, since in this way it can be set vibrating well on the one hand and on the other hand it meets the hygiene requirements prevailing in the food industry, for example.

The U.S. Patent No. 6,003,679 also describes a screening device for screenings with a horizontally extending screen and a vibration drive for the Sieve and a sieve attachment arranged above the sieve, which delimits a receiving space for sieved material above the sieve.

However, the sifting of certain finely divided, powdery materials to be sieved turns out to be problematic, for example if they tend to clump. Powders containing oil and/or fat, which are used, for example, in food processing, can be mentioned as an example. Under the slightest pressure, such powders tend to secrete substances containing fat or oil, which wet the surface of the individual powder grains and cause the material to be screened to clump or cake in the receiving space above the screen. The effect of pressure due to the vibration drive is already sufficient for this effect to occur, so that the corresponding screening devices often become blocked and have to be cleaned in a laborious manner. Attempts have therefore already been made in the past to arrange resonators on the screen surface, which may be made to oscillate by an ultrasonic transducer, as in the already mentioned EP 1 581 349 B1 described. Rotors loosely placed on the screen surface are also provided, which are intended to counteract clumping. In the case of critical screening materials, however, the effect of these aids leaves further room for improvement.

The object of the invention is therefore to propose a screening device of the type mentioned at the outset, which reliably counteracts clumping and sticking on the screen surface even with critical screened goods and enables stable operation, but at the same time meets the applicable hygiene standards, for example in the food industry.

In order to solve the stated problem, a screening device according to the features of patent claim 1 is proposed according to the invention.

Advantageous refinements and developments of the invention are the subject matter of the dependent claims.

The solution according to the invention is based on the fact that the screen attachment has a frame, for example made of metal, and a frame in the vertical Includes stretched-out hose section made of a rubber-elastic material, which delimits the receiving space along its inner surface and can be made to oscillate by means of the vibration drive. According to the invention, the screen attachment, which until now has been made entirely of rigid material, for example stainless steel, is replaced in the region of its walls delimiting the receiving space by a flexible material in the form of the hose section made of rubber-elastic material. Within the scope of the invention, it was surprisingly found that such a design can counteract clumping or sticking of the screenings on the screen in a hitherto unachieved manner, even with critical materials, so that reliable continuous operation of the screening device is ensured. As soon as the material to be screened accumulates at the edge of the receiving space, it is thrown back radially inwards by the vibrating inner surface of the hose section, so that it is quickly broken up by the vibrating screen and passes through the screen in the desired manner.

According to one embodiment of the invention, the hose section is connected to the frame at its upper and lower end area and stretched freely between the end areas, resulting in a particularly intensive vibration of the inner surface of the hose section delimiting the receiving space.

According to a further embodiment of the invention, the hose section can be formed from a suitable natural or synthetic rubber, with the material thickness being easily selectable by a person skilled in the art according to the circumstances.

According to a further embodiment of the invention, the hose section is glued to the frame at its upper and lower end area or connected to the frame by means of clamping devices, for example hose clamps.

According to a further embodiment of the invention, the framework can comprise two cylinder sections which are arranged concentrically to one another and are connected at a vertical distance by means of struts and to which the end regions of the hose section are fastened.

For fastening and easy removal of the sieve, for example for cleaning purposes, a ring-shaped sieve carrier can be inserted into the lower cylinder section, within which the sieve is clamped.

The cross-sectional design of the screen is not subject to any general restrictions, but the screen and the receiving space delimited by the hose section are preferably circular in cross-section.

In addition, it can be provided that a drain pan for the sieved material to be sieved is provided below the sieve, which together with the sieve attachment forms a closed housing or housing in which the sieve is arranged.

The drain pan can be funnel-shaped, for example, in order to be able to easily discharge the sieved screenings below the sieve.

The drainage tray, which is in particular funnel-shaped, can also be made of a flexible, rubber-elastic material in the form of a funnel-shaped hose section in the area of the surfaces that come into contact with the material to be screened, which is stretched in a corresponding frame. In this way, the funnel-shaped drain pan is also made to vibrate by the vibration drive, with deposits of the screenings being effectively counteracted due to the elastic material properties. In such a configuration, only the cylindrical section in which the screen is held is made of a rigid metal, whereas the surfaces of the housing arranged above and below the screen are made of elastic tube sections.

A particularly compact and easily dismantled structural unit is created if, according to a further embodiment of the invention, the frame can be releasably inserted into the drain pan with the sieve being placed in between and can be connected to the drain pan to form a unit, for example by means of suitable clamping means, which can then also be operated jointly by the vibration drive can be made to oscillate.

Further configurations and details of the invention are explained below with reference to the drawing, which shows an exemplary embodiment.

The single FIGURE shows a schematic side view of a sieve device 1, which comprises a housing consisting of a drain pan 12 and a sieve attachment 11 attached thereto, between which a sieve 10 stretched essentially horizontally within a sieve carrier 100 extends.

For the sake of simplicity, the other components of the screening device, such as supply and discharge lines for the material to be screened, are not shown, nor is a vibration drive which vibrates the screen 10 and at least the screen attachment 11 and the drain pan 12 in a manner known per se.

The screening device 1 shown can be assembled in a few simple steps and can also be dismantled again for cleaning purposes. Starting from the drain pan 12 arranged below in relation to the screen 10, this has a funnel shape with a wall 121 tapering or narrowing conically in the direction of an outlet opening 122, with a cylindrical receiving region 120 adjoining the wall 121 above.

Correspondingly, the screen attachment 11 has a lower cylinder section 113 which can be inserted according to arrows B into the receiving area 120 of the drain pan 12 .

A further cylinder section 112 with a smaller diameter is spaced apart vertically by a number of vertically extending struts 110 Sieve attachment 11 is held, with a tube section 111 stretched out in the vertical direction and made of a rubber-elastic material being provided between the upper cylinder section 112 and the lower cylinder section 113, which extends the distance between the upper cylinder section 112 and the lower cylinder section 113 in the vertical direction, as determined by the struts 110 free, ie spanned without support. For this purpose, the hose section 111 is routed with its upper end area 114 around the upper cylinder section 112 to the outside and is fastened there by means of fixing means, for example a hose clamp, which are not shown in detail. At its other, lower end region 115, the hose section 111 is guided twice around the lower cylinder section 113, bending at 90°, and is fixed on the outer surface of the lower cylinder section 113, for example by means of an adhesive connection. If the sieve attachment 11 is inserted into the receiving area 120 of the drain pan 12 according to arrows B, the lower end area 115 of the hose section 111 is located between the lower cylinder section 113 and the receiving area 120 and serves as a dust-proof seal due to its rubber-elastic material properties.

The hose section 111 is made, for example, from a natural or synthetic rubber and in this respect is also suitable for applications in the food industry.

The horizontally extending screen 10, like the lower drain pan 12 and the cylinder sections 112, 113 and struts 110 of the screen attachment 11, is preferably made of stainless steel and is clamped within a dimensionally stable screen carrier 100, which, when the screen attachment 11 is removed from the drain pan 12, can be lifted from the underside can be used in the lower cylinder section 113 ago. In this position, the sieve attachment 11 thus forms a receiving space 13, delimited by the inner surface of the hose section 111, for material to be sieved that is to be placed on the sieve 10 and to be sieved. This is introduced into the receiving space 13 via a feed opening (not shown).

As soon as the vibration drive, not shown, vibrates the sieve 10 together with the drain pan 12 and the sieve attachment 11, this occurs in the receiving space 13 located screenings are screened through the screen 10 in the desired manner and collected in the drain pan 12, which it leaves due to the conical configuration through the drain opening 122 for further processing.

Since the walls of the sieve attachment 11 laterally delimiting the receiving space 13 are formed by the freely movably stretched hose section 111, this is also made to vibrate by the vibration drive and oscillates periodically back and forth according to arrows A. If the material to be screened is conveyed radially outwards on the screen 10, it is immediately thrown back radially in the direction of the center of the screen upon contact with the vibrating inner surface of the hose section 111, which effectively prevents a tendency to clump even with critical screenings.

In the illustrated embodiment, the drain pan 12 is made of a metallic material, in particular stainless steel. In the case of particularly critical material to be screened, however, the discharge tray 12 can also be formed by a correspondingly conical hose section made of rubber-elastic material, in order to also counteract adhesions of the material to be screened in the area of the discharge tray 12 .

The screening device explained above is therefore particularly suitable for screening sensitive and critical materials to be screened, for example powder containing fat or oil.

Claims (10)

1. Sieving device (1) for fine particulate powdered material to be sieved, comprising a sieve (10) extending substantially horizontally and a vibration drive for the sieve (10) as well as a sieve attachment (11) arranged above the sieve (10) and bordering a receiving space (13) for the material to be sieved above the sieve (10), characterised in that the sieve attachment (11) comprises a frame and a hose section (111) made of a rubber-elastic material and stretched vertically in the frame, wherein the hose section (111) borders the receiving space (13) along its inner surface and can be vibrated by means of the vibration drive.
2. Sieving device (1) according to claim 1, characterised in that the hose section (111) is connected at its upper and lower end regions (114, 115) to the frame and is stretched in a freely movable manner between the end regions (114, 115).
3. Sieving device (1) according to claim 1 or 2, characterised in that the hose section (111) is formed from a natural or synthetic rubber.
4. Sieving device (1) according to any one of claims 1 to 3, characterised in that the hose section (111) is bonded to the frame at its upper and lower end regions (114, 115) or is connected to the frame by means of clamping devices.
5. Sieving device according to any one of claims 1 to 4, characterised in that the frame comprises two cylinder sections (112, 113) arranged concentrically relative to one another and connected at vertically spaced intervals by means of struts (110), to which cylinder sections the end regions (114, 115) of the hose section (111) are attached.
6. Sieving device (1) according to claim 5, characterised in that an annular sieve support (100) for the sieve (10) can be inserted into the lower cylinder section (113).
7. Sieving device (1) according to any one of claims 1 to 6, characterised in that a discharge tray (12) for sieved material is provided below the sieve (10).
8. Sieving device (1) according to claim 7, characterised in that the discharge tray (12) is funnel-shaped.
9. Sieving device according to any one of claims 7 or 8, characterised in that the discharge tray (12) is formed by a hose section which is vertically stretched and made of a rubber-elastic material.
10. Sieving device (1) according to any one of claims 7 to 9, characterised in that the frame (11) can be detachably inserted into the discharge tray (12) with the sieve (10) being positioned therebetween.

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