GB2469749A

GB2469749A - Apparatus for mixing powdery substances

Info

Publication number: GB2469749A
Application number: GB1006760A
Authority: GB
Inventors: Thomas Brinz; Helmut Weber; Ulrich Wieduwilt
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2009-04-24
Filing date: 2010-04-22
Publication date: 2010-10-27
Anticipated expiration: 2030-04-22
Also published as: GB2469749B; DE102009002630A1; GB201006760D0; CH700865B1; CH700865A2; DE102009002630B4

Abstract

An apparatus for fluidizing poor-flowing powdery substances comprising a container 3 in which a rotating axle 9 is centrally disposed wherein the axle 9 is connected to a holding apparatus 13 which holds an agitating element 17, the agitating element 17 comprising a toothed disc 21 which interacts/meshes with a toothed ring 23 adjacent the container inner wall. In use the gearing causes the agitating element to move with planetary motion such that the central axle rotates which causes the holding element to move and thus the agitating element to rotate about its own axis and about the central axel. The apparatus may also include a metering opening 5 with a metering screw 7 for dispensing the powder, with the metering screw 7 driven by the axle 9.

Description

Description Title

Apparatus for fluidizing and metering powdery substances

Background art

The invention relates to an apparatus for fluidizing poor-flowing powdery substances according to the preamble of claim 1. The invention further relates to an apparatus for metering powdery substances according to the preamble of claim 2.

Powdery substances are generally stored or temporarily stored in containers. These containers may also be used simultaneously to meter the powdery substances. If the containers are used for metering, they usually have a metering opening, which is generally equipped with a metering screw. By rotating the metering screw a desired quantity of powdery substance is metered through the metering opening. Such apparatuses are used for example in the field of packaging, into which bulk powdery substances are filled.

However, as soon as poor-flowing powders are to be metered, they may cake on the walls of the container and hence possibly clog up the container or get left behind and age in the container.

In the field of combination chemistry, where in many processes the metering of different powders of widely differing properties is necessary, the metering units known for example from the packaging industry have been modified in such a way that the metering element, i.e. the screw, is combined with the container, in which the powdery substance is held.

A plurality of these apparatuses consisting of storage container and metering element may then be filled with different powders and stocked in the installations. In order to meter a specific powder, the corresponding metering unit is mounted for example by means of a suitable handling system onto the metering station and connected to a drive unit. The control device then arranges the metering and controls it gravimetrically.

In order to achieve a uniform powder flow, generally in the case of free-flowing powders in screw metering units an agitator is used, which conventionally takes the form of an anchor-or blade agitator. In the case of poorer flow properties or special requirements, such as for example in the case of moist materials, usually systems that introduce compressed air into the product are used.

A further possibility of achieving a good flow property of the powdery substance is to add adjuvants such as magnesium stearate or Aerosil.

Particularly when used in combination chemistry, such adjuvants may however cause unwanted reactions and the use of air may lead to unacceptable variations, for example drying-out, of the starting materials. For this reason, the powder to be metered has to be fluidized without

suitable adjuvants.

Disclosure of the invention

Advantages of the invention An apparatus designed in accordance with the invention for fluidizing poor-flowing powdery substances comprises a container, in which a rotating axle is centrally disposed.

The axle is connected to a holding apparatus, in which at least one agitating element is accommodated in a rotatable manner. The agitating element comprises a toothed disk, which interacts with a toothed ring positioned on the container inner wall.

An apparatus designed in accordance with the invention for metering powdery substances comprises a container for receiving the substance to be metered, wherein the container has a metering opening with a metering screw and the metering screw is driven by an axle, which is disposed centrally in the container. The axle, as in the fluidizing apparatus, is connected to a holding apparatus, in which at least one agitating element is accommodated in a rotatable manner. The agitating element likewise comprises a toothed disk, which interacts with a toothed ring positioned on the container inner wall.

Upon rotation of the rotatable axle that is disposed centrally in the container, the agitating element moves about the central axle. With the aid of the toothed ring and of the toothed disk on the agitating element, the agitating element then simultaneously executes a rotational movement about its own axis. To prevent the agitating element from colliding with the container inner wall and/or the axle, the agitating element is disposed in the holding apparatus preferably mid-way between the central axle and the container inner wall. The maximum width of the agitating element in this case corresponds to the radius of the container minus the radius of the central axle.

Unlike in known agitating units, which are positioned centrally in the middle of the container and the contour of which corresponds to the contour of the container inner wall, in the apparatus according to the invention an additional thorough mixing of the entire container content occurs on account of the different rotational speed and direction of rotation of agitating elements and metering screw. As a result, even poor-flowing powders may be uniformly metered.

Thus, by means of the apparatus according to the invention for fluidizing and/or metering powdery substances the metering capability of the products, the metering accuracy achieved, the behaviour upon discharge from the container and the degree of emptying from the container and hence the material utilization may be improved. In particular, with the apparatus according to the invention even for poor-f lowing powdery substances results are achieved that are comparable to those for free-flowing substances.

Even very poor-flowing products, which hitherto have compacted to such an extent that the container became clogged, may be metered efficiently with the apparatus according to the invention.

A further advantage is the design of the drive of the agitating elements, which is effected via the axle disposed centrally in the container. This allows a rapid and easy exchange of the container, this being highly advantageous particularly in the case of use of the container in the

field of combination chemistry.

As an agitating element that is accommodated in the holding apparatus in a rotatable manner, any desired agitating element may be used. Suitable agitating elements are for example paddle agitators, anchor agitators, disk agitators, spiral agitators, worm agitators or kneading pins.

It is however particularly preferred if the agitating element comprises at least two U-shaped elements, which are rotated axially relative to one another and which are fastened in each case by their limbs to a shaft. It is particularly preferred if the limbs of the small U-shaped elements that are rotated relative to one another have in each case different spacings relative to one another in order thereby to guarantee a very thorough mixing of the powdery substance in the container. It is moreover particularly preferred if at least two agitating elements are positioned in the holding apparatus.

In a preferred embodiment the holding apparatus takes the form of a disk that is connected to the axle. This disk in this case has one locating bore for each agitating element used. Through the use of a disk it is possible to dispense with an additional lid on the container. The disk acts simultaneously as a lid.

In order in the case of a non-disk--shaped holding apparatus to prevent powder getting left behind on the holding apparatus, and/or in order in the case of a disk-shaped apparatus to ensure that all of the powder contained in the container may be metered, the holding apparatus is positioned above the maximum filling height of the container. For easier assembly and easier installation of the holding apparatus, the holding apparatus rests for example on the toothed ring positioned on the container inner wall. In order to prevent the holding apparatus from being lifted during operation, it is possible to fasten it by additional fastening means. For instance, the holding apparatus may be screw-fastened for example to the toothed ring. Another alternative is a fastening by means of clamping elements. In a further embodiment, in the toothed ring grooves or bores are formed, into which corresponding pins or springs on the holding apparatus are inserted to prevent rotation of the holding apparatus. The fastening of the holding apparatus may then be effected for example with the aid of the drive.

It is however preferred if the holding apparatus is inserted from below into the container until it abuts the toothed ring. This has the advantage that the holding apparatus plus the agitating elements and the central axle is already contained in the container when the powder is introduced. After introduction of the powder, which is effected in this case preferably through the base of the container, the base of the container is closed.

A further advantage of inserting the holding apparatus from below into the metering vessel until it abuts the toothed ring is that the gearwheels, by which the agitating elements are driven, are disposed above the holding apparatus and so, given the development of the holding apparatus as a disk, no powder can pass into, and hence block, the agitating elements.

If the holding apparatus takes the form of a disk, it then preferably serves simultaneously as a lid for the container. The holding apparatus therefore prevents for example powdery material that is contained in the container from being discharged up over the edge of the container by the movement of the agitating elements.

If the container is used as a metering container, it is customary for the metering opening to be formed axially in the container. The container in this case preferably tapers in the direction of the metering opening. By virtue of the taper the powdery substance contained in the container is able to flow in the direction of the metering opening. Conveying of the substance is then effected preferably with the aid of the metering screw. As a metering screw, any desired metering screw known to the person skilled in the art may be used. Conventionally used metering screws take the form of for example solid-blade screws or concave screws. According to the invention the screw may extend only over the region of the metering opening, with it being alternatively possible for the screw to extend over the entire height of the container. If the screw is situated only in the region of the metering opening, then an axle for driving the screw extends through the container. This axle is simultaneously the central shaft of the screw.

To prevent powdery material clinging to the inner wall of the container, in one embodiment the agitating elements have an external contour that is adapted to the outer wall of the container. It is alternatively possible for at least one scraping apparatus to be accommodated in the holding apparatus in addition to the at least one agitator.

The scraping apparatus then scrapes along the inner wall of the container and therefore detaches any substance clinging to the container wall. In order not to interfere with the rotational movement of the agitating elements, the scraping apparatus is preferably positioned in such a way between two agitating elements that the spacing relative to the two agitating elements is in each case equally great. It is also possible, for example in the case of agitating elements arranged distributed with uniform spacing around the axle, to replace an agitating element with a scraping apparatus. The scraping apparatus may for example take the form of a rod of any desired cross section, for example a round or triangular cross section, or the form of a blade.

The rod in this case is shaped in accordance with the contour of the inner wall of the container in order to be able to scrape off material clinging to the inner wall.

Embodiments of the invention are represented in the figures and described in detail below.

The figures show in: Figure 1 a sectional view of a metering apparatus designed in accordance with the invention, Figure 2 a three-dimensional view of a metering apparatus designed in accordance with the invention, Figure 3 a three-dimensional view of the drive for the agitating elements and Figure 4 a holding apparatus with agitating elements and scraping apparatus accommodated therein.

A sectional view of a metering apparatus designed in accordance with the invention is represented in Figure 1.

A metering apparatus 1 comprises a container 3, in which a powdery substance that is to be metered may be kept. The container 3 has at the bottom end a metering opening 5, through which the powdery substance may be metered. For metering the substance a metering screw 7 is positioned rotatably in the metering opening 5 such that the substance to be metered is conveyed with the aid of the metering screw 7 through the metering opening 5. The metering screw 7 in this case may take any desired form known to the person skilled in the art and may for example take the form of a concave screw or a solid-blade screw.

According to the invention the metering screw 7 is formed on the end of an axle 9, which extends axially through the container 3. It is alternatively possible for the entire axle 9 to be fashioned as a screw. It is however sufficient for the region of the axle 9 that passes through the metering opening 5 to be fashioned as metering screw 7.

In this case the axle 9 also forms the shaft of the metering screw 7. If the diameter of the metering screw 7 is smaller than the diameter of the axle 9, the axle 9 preferably tapers, in the manner represented here, to the diameter of the shaft of the metering screw 7. In order to actuate the metering screw 7 and hence be able to meter powdery substance from the container 3, the axle 9 is driven by a drive, which is not represented here. The drive for this purpose is mounted onto a connection element 11 on the axle 9. It is preferred if the drive is connected to the axle 9 by means of a plug-in contact.

This allows easy connection and disconnection of the drive from the axle 9.

Connected to the axle 9 is a holding apparatus 13.

Fastening of the holding apparatus 13 on the axle 9 is effected in such a way that upon rotational movements of the axle 9 the holding apparatus 13 rotates jointly with the axle. The fastening of the holding apparatus 13 on the axle 9 may be fastened for example with the aid of suitable fastening elements, for example screws or rivets, or other suitable fastening methods. Preferably, the holding apparatus 13 is mounted detachably on the axle 9.

Alternatively, it is possible for example to design the region of the axle 9, on which the holding apparatus 13 is mounted, as a thread and screw the holding apparatus 13 onto the axle 9. It is preferred if the holding apparatus 13 is shrunk onto the axle 9.

In the holding apparatus 13 at least one receiver 15 for an agitating element 17 is formed. The receiver 15 may for example take the form of a bore. A shaft 19, by which the agitating element 17 is driven, then extends through the receiver 15. For driving the agitating element 17 the shaft 19 is connected to a gearwheel 21. In the present case it is possible, on the one hand, for the gearwheel 21 to be formed integrally with the shaft 19, it being however preferred if the gearwheel 21 is mounted onto the shaft 19 and connected thereto. In this case the gearwheel 21 may also be used simultaneously to fasten the agitating element 17.

The gearwheel 21 interacts with a toothed ring 23, which is fastened to the container inner wall 25. In this case the teeth of the gearwheel 21 engage into the teeth of the toothed ring 23. A rotation of the axle 9 leads simultaneously to a rotational movement of the shaft 19 and hence to a rotation of the agitating elements 17.

In the embodiment represented here, the axle 9 extends through a lid 27 of the container. The lid 27 therefore serves simultaneously as a bearing for the axle 9. It would however alternatively be possible for example to design the agitating elements and the drive of the agitating elements in such a way that the holding apparatus 13 rests on the toothed ring 23 and hence may serve simultaneously as a lid for the container 3. For this purpose, the holding apparatus 13 is then designed as a continuous disk.

However, the holding apparatus 13 also in the embodiment represented in Figure 1 preferably takes the form of a disk. This prevents powder being able to pass through holes in the holding apparatus 13 into the drive of the agitating elements 17. It is however also possible to provide the holding apparatus 13 for example in the form of a ring with spokes and to form the receivers 15 for the agitating elements 17 in the spokes.

As agitating elements, any agitating elements that are known to the person skilled in the art may be used.

Conventionally used agitating elements are for example paddle agitators, disk agitators, anchor agitators, spiral agitators, worm agitators or kneading pins.

It is however preferred if agitating elements 17 such as are represented here are used. The agitating elements 17 comprise two U-shaped elements 29.1 and 29.2, which are rotated relative to one another and which are fastened in each case by their limbs 31 to the shaft 19. In the embodiment represented here, the shaft 19 for this purpose has a disk 33, in which the U-shaped elements 29.1, 29.2 are fastened. In order to achieve good thorough mixing of the powdery substance in the container, the spacings of the limbs 31 of the respective U-shaped elements 29.1 and 29.2 comprise different spacings. It is also preferred if the length of the U-shaped elements 29.1, 29.1 differs. The small U-shaped elements 29.1, 29.2 may be formed for example from a rod with a circular cross section. A suitable material for the U-shaped elements is in particular metal, for example special steel. However, other corrosion-resistant materials such as glass, plastics materials, for example PEEK, or materials with a surface coating, for example a PTFE coating, may also be used.

In order to enable the axle 9 with the holding apparatus 13 and the agitating element 17 to be inserted into the container 3, the container 3 is closed by a base 35, in which the metering opening 5 is formed. To allow the removal of all of the powdery substance contained in the container 3, the base is of a conical construction.

Filling of the metering apparatus 1 represented in Figure 1 is effected preferably after insertion of the axle 9 with holding apparatus 13 and agitating elements 17 through a bottom opening in the container 3 that is then closed with the base 35. For this purpose, the base 35 is preferably screwed onto the container 3.

Figure 2 shows a three-dimensional view of a metering apparatus designed in accordance with the invention. The metering apparatus 1 represented in Figure 2 has three agitating elements 17, which are of an identical design to the agitating elements 17 represented in Figure 1. The agitating elements 17 are distributed in each case uniformly over the circumference of the holding apparatus 13 in the container 3.

A drive apparatus for the agitating elements is represented in Figure 3.

The holding apparatus 13 takes the form of a disk, in which are formed receivers, in which the agitating elements 17 are accommodated. For this purpose, shafts 19 of the agitating elements extend in each case through the receivers in the holding apparatus 13. Mounted onto the shafts 19 are gearwheels 21 for driving the agitating elements. Fastening in the embodiment represented here is effected by means of nuts 37. It is therefore possible, by detaching the nuts 37, to remove the agitating elements and hence for example clean the unit. For driving the agitating elements 17, a toothed ring 23 is fastened in the container inner wall 25. The teeth of the gearwheels 21 interact with the teeth of the toothed ring 23. Upon a rotation of the axle 9, the holding apparatus 13 rotates and leads, as a result of the engagement of the teeth of the gearwheels 21 into the teeth of the toothed ring 23, to rotation of the shaft 19, to which the agitating elements 17 are fastened. This leads, on the one hand, to a rotation of the agitating elements 17 about the shaft 19 and, on the other hand, to a movement of the agitating elements 17 about the central axle 9, wherein the rotational speeds of the agitating elements 17 and of the metering screw 7 are different.

In the embodiment represented here, a scraping apparatus is fastened in a third receiver 15, which is positioned with a uniform spacing relative to the receivers in which the agitating elements 17 are mounted.

Figure 4 shows a holding apparatus with a central axle and with agitating elements and a scraping apparatus accommodated therein.

The holding apparatus 13 is mounted on the central axle 9, which is inserted into the container 3. The central axle 9 terminates, as represented in Figures 1 and 2, in the metering screw 7.

Mounted in the holding apparatus 13 are the agitating elements 17, which are driven by means of the gearwheels 21. In a receiver 15, in which an agitating element 17 may alternatively be fastened, a scraping apparatus 39 is mounted in the embodiment represented in Figure 4. The scraping apparatus 39 adopts the contour of the inner wall of the container so that any powder clinging to the inner wall of the container 3 is scraped off by the scraping apparatus 39. For this purpose, the scraping apparatus 39 is designed for example in the form of a doctor blade or alternatively a rod, which has for example a circular or a triangular cross section. It is also possible for example to form a sheet-metal strip into the scraping apparatus 39.

The sheet-metal strip in this case preferably has a rectangular cross section.