DE102021202550A1 - Powder conveying device for conveying powdered media - Google Patents

Abstract

The invention relates to a powder conveying device (1) for conveying powdered media, comprising a powder inlet (2) and a powder outlet (3), the powder inlet (2) and the powder outlet (3) being connected to one another via a Venturi nozzle (4), the Venturi nozzle (4) has an inlet nozzle (5), a mixing chamber (6) and a catching nozzle (7), the mixing chamber (6) being fluidically connected to the powder inlet (3) and the catching nozzle (7) being connected to the powder outlet (3 ) is fluidly connected. In order to be able to convey powder with the most precisely specified amount per time over longer conveying distances, the invention provides that an intermediate chamber (8) is arranged between the powder inlet (2) and the mixing chamber (6), with at least two connecting channels (9, 10) are arranged, which connect the intermediate chamber (8) with the mixing chamber (6).

Description

The invention relates to a powder conveying device for conveying powdered media, comprising a powder inlet and a powder outlet, the powder inlet and the powder outlet being connected to one another via a venturi nozzle, the venturi nozzle having an inlet nozzle, a mixing chamber and a catching nozzle, the mixing chamber fluidically connected to the powder inlet is in connection and the catching nozzle is in fluid communication with the powder outlet.

A powder conveying device of the generic type is from DE 10 2016 106 052 A1 known. With it it is possible to convey powder over certain conveying distances. The powder to be conveyed can be provided for a wide variety of applications. Aside from general applications, dosing of the powder for application to technical surfaces can be considered, for example. Furthermore, glass powder can be applied as a lubricant to the surface of workpieces in order to extrude them. The application of deoxidation powder mixtures to hot workpiece surfaces also comes into consideration. Furthermore, powdered lubricant can be applied to tool surfaces, with mandrel rods, upset mandrels, upset shells and press rams being considered in particular. Finally, the application of powdered lubricants to workpiece surfaces should be mentioned, for example to pipe ends, heavy plates or forged blanks.

A disadvantage of some previously known applications is that a continuous and metered conveyance of powdery substances with small line cross sections is only possible in relatively small amounts of powder per unit of time. The conveyor length is often limited to approx. 5 to 8 meters. Depending on the specific weight of the material to be conveyed, sometimes only a few grams per second can be conveyed safely. In the case of larger conveying quantities or long conveying distances, the cross-section of the conveying lines increases disproportionately, which is expensive and therefore disadvantageous.

The invention is based on the object of developing a device of the type mentioned at the outset in such a way that it is possible to be able to convey powder over longer conveying distances with as precisely a predetermined quantity as possible per time. In particular, it should be possible to convey large amounts of powder for technical purposes. It should also be possible to bridge larger conveying distances with relatively thin line cross-sections. Ultimately, a reproducible flow rate should be achieved over time, i.e. precise dosing.

The solution of this object by the invention is characterized in that an intermediate chamber is arranged between the powder inlet and the mixing chamber, with at least two connecting channels being arranged which connect the intermediate chamber to the mixing chamber.

In this case, the connecting channels are preferably distributed uniformly over the circumference of the Venturi nozzle.

In particular, two connecting channels can be arranged.

The intermediate chamber can be designed as a cylindrical chamber.

According to a preferred embodiment of the invention, the Venturi nozzle is designed as an insert part which is inserted into a receiving opening in a housing part of the powder conveying device. In this case, it can be provided that the intermediate chamber is designed as a recess on the outer circumference of the Venturi nozzle. Furthermore, detachable securing means can be arranged with which the venturi nozzle can be fixed in the housing part.

The mixing chamber can have an enlargement at the entry point of the connecting channels. This enlargement is preferably spherical.

The inlet nozzle and the catching nozzle have respective diameters when entering or exiting the mixing chamber, it being preferably provided that the diameter of the catching nozzle is at least four times, in particular at least six times, the diameter of the inlet nozzle.

The proposed solution allows the continuous delivery of large amounts of powdery substances with a precisely adjustable dosage (in grams/second) even through very long delivery lines with a small diameter. In particular, such applications are considered in which it is particularly important that a specified output (in grams/second) is maintained.

Exact dosing of the powder can be done, for example, by screw conveyors or disc conveyors. In this way, the application of powder per time (i.e. in grams/second) can be carried out precisely on a surface to be supplied, with the layer thickness on the surface being able to be set in a reproducible manner, for example.

Several supply points (powder outlets) can also be supplied evenly with the proposed device.

Thus, in particular, a reproducible lubrication of hot surfaces with powder is possible. A reduction in costly cooling processes for tools, which is required for liquid lubricant to adhere to the surface, can be realized. Furthermore, the replacement of liquid lubrication, for example in the case of forging presses or upsetting presses, is possible, as is the avoidance of scale formation during hot forming by applying a powder that prevents the formation of scale.

The Venturi nozzle thus sucks through the annular intermediate chamber at at least two points, i. H. through the connecting channels, air, which increases the efficiency of the nozzle and the volume flow of powder can be promoted better.

The suction cross section for the powder can be increased by the proposed device, which minimizes friction losses. Depending on the material to be conveyed, conveying distances of up to 50 meters can be implemented, with conveying cross sections from 3/8" to 1" and conveying quantities from 5 to 300 grams/second.

Even conveyed goods with a very high density (metal powder) or powder compositions with different fractions and compositions can be conveyed over large distances with precise dosing.

A possible application is, for example, the transport of powder within a mandrel bar. The powder dosing station can be located 40 meters in front of the powder application point.

• 1 schematisch die Seitenansicht einer Pulverfördervorrichtung gemäß der Erfindung,
• 2 eine Venturidüse der Pulverfördervorrichtung gemäß 1 und
• 3 den Schnitt A-B gemäß 2 durch die Venturidüse.

In the drawing an embodiment of the invention is shown. Show it:

• 1 schematically the side view of a powder conveying device according to the invention,
• 2 according to a venturi nozzle of the powder conveying device 1 and
• 3 according to section AB 2 through the venturi nozzle.

The promotion of powder is known as such, for which reference is made to the document mentioned at the outset. It is used in many branches of industry. It is usually divided into two conveying states.

In the so-called dilute state, little conveyed medium is conveyed with a lot of conveying gas at high flow rates and low pressure in the conveying line. The conveyed medium is finely distributed in the conveying air. It does not settle in the delivery line.

In the so-called dense state, the conveying line uses little conveying gas and a high proportion of conveying medium at low flow velocities and high pressure. The conveyed medium is conveyed through the line as a "package". It settles in between, accumulates again, whereby the pressure increases, until it is finally conveyed further.

So that the powder can be conveyed, it must be introduced into the conveying line. There are two fundamentally different methods for doing this.

In the closed system, the powder reservoir and the feed line are pressurized. The powder then trickles into the conveying line and is carried away from there by the conveying medium.

Alternatively, there is also the option of arranging a rotary valve between the powder container and the conveying line. This prevents the powder storage container with the material to be conveyed from having to be under pressure itself. The powder is introduced into the flow in portions (depending on the size of each cell wheel chamber). This conveying variant is usually used to quickly empty a container, whereby an exact conveying flow of the powder is not important. Conveyor distances of 60 meters are not uncommon. However, the line cross-sections for the promotion must be very large. Examples of such an application are the transport of flour from a truck to a storage silo and the transport of granulate or fertilizer.

With open conveying, a vacuum is generated by means of a Venturi nozzle, which sucks in the material to be conveyed and then feeds it into the conveying line. The material to be conveyed is usually, but not necessarily, guided to the suction point with the aid of a dosing device. These are usually disc, vibratory or screw conveyors.

The appropriate funding method depends on several factors. The bulk density of the powder, the particle size of the powder, the particle size range for powder mixtures, the powder properties (such as flowability, compressibility of the powder, stickiness of the powder), the form the amount, the conveying process and the inner surface of the conveying line.

In general, it can be said that a closed system with the dense state is more suitable for transporting large and pre-measured quantities of powder. However, if the conveyed material agglomerates or sticks, this type of conveyance tends to block the line.

With an open claim and in the dilute state, a conveyed item can also be dosed precisely and continuously over any period of time. This is necessary, for example, when it comes to laser deposition welding, the coating of technical surfaces to protect against friction or scale, or to ensure certain operating parameters of a system. The flow rate can be varied as desired during the transport process. Since the system is open, it is sensitive to back pressure. So if the back pressure in the delivery line increases as a result of friction, the Venturi nozzle can no longer generate enough negative pressure. As a result, the powder feed to the Venturi nozzle becomes blocked, whereupon the pressure in the delivery line increases slightly and the conveyed material is then, at best, "pushed" further through the delivery lines. This condition cannot be controlled and is therefore undesirable. In order to prevent this, the line cross-sections can be increased, although the amount of air in the Venturi nozzle must then also be increased.

In many technical applications, however, there are also structural restrictions both in the cable routing and in the cable cross-section. Often the line consists of a combination of hoses, pipes and fittings. In addition, many technical powder-form excipients consist of a large number of powders mixed together in different ways.

In this respect, the aim is to transport as large a quantity of powder as possible (10 to 200 grams/second, depending on the bulk density) over a distance of up to 50 meters in the dilute state, so that the set dosing (in grams/second) is also available at the end of the transport route of the powder is ensured. This must be possible, especially with regard to the conveying cross-section of the line (maximum 3/8" to 1") in order to meet design restrictions.

Enlarging the venturi nozzle would increase the suction quantity, but this also increases the volume due to the greater flow through the venturi nozzle, which is disadvantageous.

The same also applies if the flow speed of the air at the exit from the Venturi nozzle were to be increased by increasing the pressure.

With conventional solutions, the air jet from the Venturi nozzle creates a negative pressure after leaving the inlet nozzle. As a result, air is drawn in from the outside, with vortices being created below the intake flow, which has a negative effect on the efficiency.

According to the present invention, it becomes possible to generate less loss vortices and thus improve the conveyance of powder with said device.

For this purpose, an embodiment is provided, as in the 1 until 3 is shown:

In 1 a powder conveying device 1 is shown, as can be used for conveying powder. The device 1 has a powder inlet 2 and a powder outlet 3. Powder P and sucked-in air L get into the powder inlet 2, ie the powder P is in the air L as freight. The powder-air mixture is fed through the powder outlet 3 into a line system in which it is conveyed to a point of consumption (see the above explanations).

A venturi nozzle 4 is arranged in a cylindrical receiving opening 11 in a housing part 12 of the powder conveying device 1 . The Venturi nozzle 4 has an inlet nozzle 5 and a catching nozzle 7, between which a mixing chamber 6 is located. The inlet nozzle 5 is supplied with compressed air D. Details can be found in the above DE 10 2016 106 052 A1 of the patent applicant, to which reference is expressly made in this respect.

In order to improve the conveyability of the powder conveying device 1, an embodiment is provided, as can be seen from the synopsis of 1 until 3 emerges. After this, the central area of the Venturi nozzle 4 is surrounded by an intermediate chamber 8 which has a hollow-cylindrical shape. The intermediate chamber 8 is designed as a recess that is worked into the outer circumference of the base body of the Venturi nozzle 4 . The air L provided with powder P thus reaches the annular space which the intermediate chamber 8 forms.

How best to look 3 As can be seen, two connecting channels 9 and 10 are provided, which connect the intermediate chamber 8 to the mixing chamber 6. The two connecting channels 9 and 10 are located at diametrically opposite points of the mixing chamber 6 and the intermediate chamber 8.

At the point of entry of the connecting channels 9 and 10 into the mixing chamber 6, this is what looks best 2 can be seen, provided with a spherical enlargement 13.

The air L loaded with powder P thus passes from the intermediate chamber 8 into the mixing chamber 6 at two diametrically opposite points, so that an improved flow behavior can be achieved, which allows the air L loaded with powder P to be conveyed more favorably.

It is thus possible to convey large quantities of precisely metered powder without making the piping system excessively large.

Reference List

1

powder conveying device

2

powder inlet

3

powder outlet

4

venturi nozzle

5

inlet nozzle

6

mixing chamber

7

catcher nozzle

8th

intermediate chamber

9

connecting channel

10

connecting channel

11

intake opening

12

housing part

13

enlargement

L

sucked air

P

powder

D

compressed air

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102016106052 A1 [0002, 0039]

Claims (10)

Powder conveying device (1) for conveying powdered media, comprising a powder inlet (2) and a powder outlet (3), the powder inlet (2) and the powder outlet (3) being connected to one another via a venturi nozzle (4), the venturi nozzle (4) an inlet nozzle (5), a mixing chamber (6) and a catching nozzle (7), wherein the mixing chamber (6) is fluidly connected to the powder inlet (3) and the catching nozzle (7) is fluidly connected to the powder outlet (3). stands, characterized in that an intermediate chamber (8) is arranged between the powder inlet (2) and the mixing chamber (6), with at least two connecting channels (9, 10) being arranged, which connect the intermediate chamber (8) with the mixing chamber (6). associate. powder conveying device claim 1 , characterized in that the connecting channels (9, 10) are distributed evenly over the circumference of the Venturi nozzle (4). powder conveying device claim 1 or 2 , characterized in that two connecting channels (9, 10) are arranged. Powder conveying device according to one of Claims 1 until 3 , characterized in that the intermediate chamber (8) is designed as a cylindrical chamber. Powder conveying device according to one of Claims 1 until 4 , characterized in that the Venturi nozzle (4) is designed as an insert part which is inserted into a receiving opening (11) in a housing part (12) of the powder conveying device (1). powder conveying device claim 5 , characterized in that the intermediate chamber (8) is designed as a recess on the outer circumference of the Venturi nozzle (4). powder conveying device claim 5 or 6 , characterized in that releasable securing means are arranged with which the Venturi nozzle (4) can be fixed in the housing part (12). Powder conveying device according to one of Claims 1 until 7 , characterized in that the mixing chamber (6) at the entry point of the connecting channels (9, 10) has an enlargement (13). powder conveying device claim 8 , characterized in that the enlargement (13) is spherical. Powder conveying device according to one of Claims 1 until 9 , characterized in that the inlet nozzle (5) and the catching nozzle (7) have respective diameters when entering or exiting the mixing chamber (6), the diameter of the catching nozzle (7) being at least four times, preferably at least six times , the diameter of the inlet nozzle.

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