DE10243007A1 - Dispensing system for powders comprises outlet tube, in which conveyor screw is mounted, tube being fitted with flexible disk which opens when screw is turning but is self-closing, due to its restoring force - Google Patents

Abstract

Dispensing system for powders and granulates comprises an outlet tube (1), in which a conveyor screw (3) is mounted. The tube is fitted with a flexible disk (6) which opens when the screw is turning but is self-closing, due to its restoring force.

Description

The invention relates to a metering device comprising one in a fill pipe arranged dosing screw and one at the end of the dosing screw in conveying direction arranged closure element.

Dosing and filling devices for powdery or granular contents are for example from the DE 195 04 240 C1 known. The dosing device comprises a filling tube with a dosing screw rotatable therein, with which powdery or granular filling material is transported into a container arranged underneath. At the end of the filling pipe, a lowerable mouthpiece is slidably arranged, which is lowered by a servomotor via a lever and raised again after the filling process. The lowerable mouthpiece can be opened and closed by a closure in conjunction with the lowering and lifting movement of the mouthpiece. However, the lowering and lifting device for the mouthpiece at the end of the filling tube and for the closure are mechanically complex and must be coordinated with one another.

Find to close dosing devices also slide closures Application that can be designed on one side or as a scissor closure can. The slide fasteners are at the end of the filling pipe arranged close so that the filling tube is tightly closed can. Such a closure is also suitable for filling goods very low shear strength. A disadvantage of a slide lock is, however, that it is technically complex on the one hand and on the other must be operated manually or by a separate drive. So that is a slide closure is an expensive solution for closing Filling tubes. Another disadvantage is the fact that until the final closure of the filling pipe a certain dead time elapses in which the slide lock moves forward pushed the fill pipe becomes. While of the displacement can therefore continue to emerge from the filling tube, what leads to low metering accuracy of the slide closure.

Another way to fill tubes of dosing devices to be closed with a dosing screw the use of a press disk lock. It will end the dosing screw arranged a disc whose diameter is smaller is as the diameter of the fill pipe, so that there is an annular gap between the disc and the filling tube. When the dosing screw is not driven, it builds up above the Gap between the disc and the outer wall of the filling pipe from the powdery filling material a bridge through which the further filling material retained and thus the filling tube is closed becomes. The disc size of the press disc lock and the resulting gap between the disc and the fill tube dependent on of the one to be transported filling and select its shear strength. As soon as other goods are transported the disc of the press disc closure must also be adapted to the new product become. This requires changing the disc, which leads to a standstill of the dosing device and requires the manual use of operating personnel. Especially with the use of filling material, whose shear strength is not known, it can happen that only by trying out different pane sizes suitable press washer can be found. This leads to a significant increase the response time and to a standstill of the dosing device.

Advantages of invention

The metering device according to the invention comprises one in a fill pipe arranged dosing screw and one at the end of the dosing screw in the conveying direction arranged closure element, which automatically has a restoring force against the conveying direction of the dosing screw. By turning the dosing screw generates the material to be conveyed one in the conveying direction acting force, which changes the position of the closure element or the closure element is deformed such that the closure element the promotion of the product from the dosing device. As soon as the turning process of the dosing screw is finished, that will be Closure element automatically countered by the closure element the conveying direction provided restoring force brought fully or partially towards its starting position. This turns the material to be conveyed existing bridges again above that between the filling pipe and the closure element existing gap built up and closed the metering device. Another advantage of this metering device is that by the automatic reset of the closure piece independently from the product takes place. Even when changing the contents, there is no need for retrofitting and setting times; the dosing device does not have to be switched off. That the closure element is simple and inexpensive at all times Can be retrofitted in existing systems is another advantage.

It has proven to be particularly advantageous the use of a flexible disc as a closure element. The flexible disc is easy to assemble as it is at the end of the dosing screw is screwed onto the rotating shaft of the dosing screw. It stands out further characterized by the fact that it is particularly inexpensive.

In order to achieve a good adaptation to the round outside diameter of the dosing screw and the round filling tube, the flexible disk is preferably essentially circular. This is between the disc and the fill tube creates an even annular gap.

Increased flexibility of the closure element is preferably achieved through slots that are straight or curved radially outward point. The slots in the closure element reduce the Flexural rigidity of the closure element. That fits Closure element more precisely to the product to be transported.

A further increase in the flexibility of the closure element can be achieved that the slots to the extreme Run the edge of the disc. This will give the bending stiffness the disc further reduced.

The closure element is preferred made of plastic, in particular Viton, silicone rubber or made of spring steel sheet. So there are different ones Materials available that are easy to process and inexpensive to manufacture. Depending on the product to be dosed the material of the closure element can be selected in order to be adapted to the filling material and to meet special requirements for the dosage of the filling material.

In a special embodiment has the fill tube an annular one at the free end Paragraph on. This shoulder pointing in the direction of the pipe center axis improves the structure of the product bridges consisting of the filling material close of the filling pipe when the dosing screw is not operated. This also allows the dosing accuracy improve the dosing device.

Another improvement in construction the one from filling material existing product bridges is achieved in that the closure element and the annular shoulder essentially lie in one plane.

In a preferred embodiment is a spacer between the closure element and the dosing screw arranged. The spacer, designed in particular as a spacer, creates a free one between the closure element and the dosing screw Space in the filling tube, in which the product bridges from filling material preferably train and the fill tube close.

Embodiments of the invention are explained in more detail in the following description. Show it:

1 2 shows a schematic sectional view of one end of a metering device with a closure element according to the invention when the metering screw is not operated,

2 is a schematic sectional view of the in 1 dosing device shown in the operated state of the screw,

3 this in 1 and 2 Shown closure element in plan view and

4 a closure element according to another embodiment in plan view.

description of the embodiments

1 shows a section of a metering device in section. A fill pipe 1 has at its free end a paragraph aligned in the tube axis 2 on. In the fill pipe 1 is a dosing screw 3 arranged around a rotating shaft 4 is rotatably mounted. The screw surface of the dosing screw 3 is in 1 indicated by a wavy dash-dotted line. At the end of the dosing screw 3 a distance bush closes 5 at that via the rotary shaft 4 is pushed. The spacer 5 is between the dosing screw 3 and a disc 6 arranged, which represents the closure element. The disc 6 is through a mother 7 that on the rotating shaft 4 is screwed against the spacer 5 pressed.

The dosing screw 3 and the spacer 5 are designed so that the disc 6 in line with the paragraph 2 lies. This arrangement creates a free space 8th between the dosing screw 3 and the disc 6 , The diameter of the disc 6 is less than that on the paragraph 2 resulting diameter of the filling pipe 1 so that between the disc 6 and the paragraph 2 an annular gap 9 results. Because of the circular disc 6 and the round filling tube 1 is the annular gap 9 evenly trained.

When the dosing screw is at a standstill 3 forms the filling material in the metering device in the free space 8th above the ring gap 9 a product bridge. The filling material is retained by the resulting bridge and does not fall through the annular gap 9 out of the dosing device.

By turning the dosing screw 3 product is conveyed in the direction of conveyance F. As a result, a force acting in the conveying direction F is generated by the filling material. In a first step, the product bridge above the annular gap, which is generated due to the frictional forces, becomes of the inflowing filling material 9 destroyed, so that the filling material emerges from the dosing device.

By turning the dosing screw faster 3 the force acting in the conveying direction F, which is generated by the filling material likewise transported in the conveying direction F, is increased and the flexible disk 6 pressed in the conveying direction F such that it is reversibly bent, as in 2 shown. The force exerted by the filling material in the conveying direction F deforms the disk 6 such that an essentially frustoconical body is formed. So that the outer edges of the disc are 6 no longer in the same plane as the ring-shaped heel 2 at the end of the filling pipe 1 , The one between the pane 6 and the paragraph 2 existing annular gap 9 is caused by the deformation of the disc 6 enlarged so that more filling material can be transported out of the dosing device.

The deformation of the disc 6 depends on the force acting in the conveying direction F and thus on the speed of rotation of the dosing screw. Furthermore, the deformation of the disc 6 also depending on the powdery product being transported. The powdery filling material defined in the sense of the invention comprises all powdery, trickling, granular and dusty products which are obvious to the person skilled in the art, as well as filling materials from fine-grained to lumpy conveyed goods.

Will the rotation of the dosing screw 3 ends, the force acting in the conveying direction F is reduced. The flexible disc 6 in turn now automatically provides a restoring force that points counter to the conveying direction F and counteracts the filling material. Thus the in 2 shown and deformed into a truncated cone 6 pushed back to its starting position ( 1 ). The ring gap 9 between the disc 6 and the paragraph 2 is reduced. Above the ring gap 9 the product then forms a product bridge again and closes the filling tube 1 ,

The one from the flexible disc 6 made automatic change of the annular gap 9 has a positive influence on the dosing accuracy of the product. Immediately after the rotary movement of the dosing screw has ended 3 becomes the flexible disc 6 returned to their starting position and the annular gap 9 closed by a product bridge created above. Dead times when closing the metering device, such as occur when using a slide closure, are eliminated. The quantity of product transported from the dosing device can thus be determined exactly.

The use of the flexible disc 6 is also suitable as a closure element for metering devices, their annular gap 9 between the disc 6 and the paragraph 2 is relatively larger than that in the 1 and 2 shown annular gap, so that the use of actively closing organs, such as gate valves or slide closures, is omitted. The flexible disc can also be used in dosing devices with larger dosing screw diameters 6 can be used as a closure element instead of the usual slide closures.

Through the automatic, automatic change of the ring gap 9 through the flexible disc 6 it is possible to use the flexible disc 6 can also be used as a closure element for products with lower shear strength, which would otherwise require a slide as a closure element.

3 shows the flexible disc 6 in supervision. The disc 6 has a central bore 10 on, whose diameter is approximately the diameter of the rotating shaft 4 equivalent.

In the 4 shown disc 6 According to a second embodiment, next to the bore 10 curved, radially outward slits 11 on that to the very edge of the disk 6 run. This creates a lamella-like design of the disc 6 , which is characterized in that the bending stiffness of the disc 6 reduced and thus their flexibility is increased. The disc 6 can now also react to small changes in force due to deformation, which ultimately leads to a further increase in the metering accuracy of the metering device.

Claims (9)

Dosing device, comprising a in a filling tube ( 1 ) arranged dosing screw ( 3 ) and one at the end of the dosing screw ( 3 ) arranged in the conveying direction (F), characterized in that the closing element automatically has a restoring force against the conveying direction (F) of the metering screw ( 3 ) provides. Dosing device according to claim 1, characterized in that the closure element is a flexible disc ( 6 ) is. Dosing device according to claim 2, characterized in that the disc ( 6 ) is essentially circular. Dosing device according to claim 2 or 3, characterized in that the disc ( 6 ) Slots ( 11 ), which in particular point straight or curved radially outwards. Dosing device according to one of claims 2 to 4, characterized in that the slots ( 11 ) to the very edge of the disc ( 6 ) run. Dosing device according to one of claims 1 to 5, characterized in that the closure element made of plastic, in particular from Viton, or from silicone rubber or from a spring steel consists. Dosing system according to one of claims 1 to 6, characterized in that the filling tube ( 1 ) an annular shoulder at the free end ( 2 ) having. Dosing device according to claim 7, characterized in that the closure element and the annular shoulder ( 2 ) lie essentially in one plane. Dosing device according to one of claims 1 to 8, characterized in that between the closure element and the dosing screw ( 3 ) a spacer ( 5 ) is arranged.