EP0334124A2 - Mill - Google Patents

Abstract

Mills which are driven by motors and have an input funnel and a milling mechanism connected to a collecting container, are constructed in order that they ensure a minimisation of the amount of dust released together with a simple and operationally reliable design and user-friendliness, in such a way that the mill (1) is arranged in a housing (6) which has an air inlet opening (22) and an air outlet (8). The air outlet (8) is arranged at the floor side on the housing (6) and connected to an underpressure source. Provided in the region of the air outlet (8) is a filter (9) which can be connected to an air source which loads the filter (9) with compressed air in the direction opposed to that of the flow. <IMAGE>

Description

The invention relates to a mill with a grinder driven by a motor and connected to an inlet funnel and a collecting container.

Mills of the type mentioned at the outset are used in particular in the laboratory to crush samples, which are then subjected to a chemical analysis. It proves necessary to be particularly careful when comminuting the respective substances, since the preparation of the sample substance has a decisive influence on the results of the analysis. When using the most modern analytical methods, the amount of material required can be greatly reduced. This leads to shorter sample preparation times and considerable material savings. It proves to be disadvantageous that the requirements for comminution, ie. H. the grinding of the samples increases considerably since the substances to be analyzed have to be very finely divided. The required grain sizes are usually less than 0.1 mm. Since the substances to be ground are usually pre-dried, the fine grinding and pre-drying of the substances result in a considerable amount of dust.

This development of dust, especially in the case of substances harmful to health, requires the operating personnel to wear breathing masks or dust masks, which always proves to be unpleasant and very cumbersome. Furthermore, it is necessary ventilate the work area vigorously in order to prevent it from being contaminated, as grinding samples can be falsified in a dirty grinding room.

For environmental reasons, the grinding dust cannot be blown into the environment. Therefore, the installation of a room dust removal is always associated with a high level of technical equipment and is therefore very expensive. In addition, such devices work with a high noise level, and there is also a risk of sample loss.

The invention has for its object to provide a mill of the type mentioned, which minimizes the amount of dust released with a simple structure and reliable, easy to use.

According to the invention the object is achieved in that the mill is arranged in a housing which has at least one air inlet opening and an air outlet, that the air outlet is arranged on the bottom of the housing and connected to a vacuum source and that a filter is provided in the area of the air outlet, which can be connected to an air source acting on the filter in the counterflow direction with compressed air.

The mill according to the invention is characterized by a number of significant advantages. The arrangement in the housing makes it possible to safely collect the dust escaping due to leaks between the individual components of the mill. It is also possible to open the grinder inside the housing, for example to clean the grinder. The connection of the air outlet with a vacuum source ensures that there is always sufficient air flow through the housing, which leads the dust particles to the filter of the air outlet in a safe manner which they get stuck at least in part and are filtered out. The filter in the area of the air outlet is provided to prevent excessive dust pollution of the vacuum source. The possibility of connecting the filter to an air source, which pressurizes the filter with compressed air in the counterflow direction, makes it possible to regenerate the filter, with the dust particles accumulated on the filter falling back onto the bottom of the housing, collecting there and occasionally manually removed with a shovel or using a vacuum cleaner.

The mill according to the invention thus ensures that no dust can escape into the working space during the grinding process. It is thus possible to use the mill in conventional laboratory rooms, whereas in the prior art it was necessary to operate the mill in a separate room because of the strong dust generation.

The regeneration of the filter according to the invention by means of counter-flowing compressed air must be carried out after 5 at the earliest, usually only after 10 or more grinding cycles. It guarantees a uniformly high level of dust extraction from the housing and multiplies the service life of the vacuum source. Since the dust collector located there is beyond direct observation. As a result, experience has shown that this becomes ineffective after a short period of operation due to overfilling, which leads to the failure of the vacuum source and thus to the suction.

Since the housing of the mill according to the invention is always flowed through by an air flow, the risk of a dust explosion is avoided. It is also possible to effectively dampen the noise generated by the mill through the housing. In addition, the material loss that occurs occurs on a Reduced to a minimum, since when the collection container is subsequently removed, no air flow has to be present in the work space for the purpose of ventilation.

The mill according to the invention is preferably designed such that the dust-laden air in the housing is exchanged for fresh air at least once per second.

An advantageous further development of the mill according to the invention is provided in that the vacuum source is designed in the form of a suction device provided with a dust separator, the suction device being able to be designed in the form of a commercially available vacuum cleaner. Since a separate, regenerable filter is provided in the area of the air outlet on the housing, it is ensured that only a small amount of dust gets into the suction device, so that its dust separator only has to be cleaned at larger time intervals, e.g. B. once a year.

The air inlet opening for generating an air flow directed towards the bottom of the housing is preferably arranged in the upper housing region. This configuration ensures that the dust particles are supplied to the floor area and some are already deposited directly on the floor without reaching the filter of the air outlet.

To clean the interior of the housing, it is advantageously provided with a closable, slot-shaped opening for introducing a compressed air lance. Using the compressed air lance, it is possible to blow off both the grinder of the mill after it has been opened and the inner walls of the housing and to free it from adhering dust and residues. The material loosened during this cleaning is sucked in through the vacuum source and the filter of the air outlet. The compressed air lance can advantageously be designed in such a way that, in conjunction with a suitable arrangement of the opening in the housing, it is not possible to insert the compressed air lance into the grinder of the mill. It is thus avoided that after the mill motor has been switched off, the rotor which is still running for a long time can be touched by the lance. This eliminates the possibility of damage and any danger to the operating personnel. The possibility of being able to start cleaning while the rotor is still running not only significantly shortens the work process, but also increases the cleaning effect.

A particularly favorable embodiment of the mill according to the invention is given in that the housing comprises, from the outside, actuatable devices for opening the mill and for removing the collecting container. With this configuration, the cleaning process of the mill can be considerably accelerated, since it is not necessary to first wait for a complete suction, the dust in the interior and for the grinder to stop.

In known mills, the inlet funnel is usually pivoted away together with a cover part to open the grinder. In order to prevent dust from escaping from the opening of the housing assigned to the inlet funnel in this state, and to prevent more air from being able to flow into the housing than is drawn off by the vacuum source, this opening is at least partially covered by a perforated plate . The perforated plate is designed so that only a certain amount of air can be sucked into the housing.

Another favorable embodiment of the mill is given in that the collecting container is opened to the interior of the housing via a filter.

This filter causes the low negative pressure of the interior of the housing to continue into the collecting container. The air flow compensating for this negative pressure enters the mill at the filling funnel and reaches the collecting container via the inside of the mill - taking the grinding dust that is created here. The narrow filter pores hardly allow regrind to pass through. This prevents a build-up of dust inside the mill, which could lead to dust loss through the filling funnel into the environment if the grinding is very dusty (e.g. from earth).

Furthermore, it has proven to be advantageous to arrange the motor outside the housing. In this way, sufficient cooling of the motor is ensured, on the one hand, and contamination with grinding dust is prevented.

Furthermore, it proves to be advantageous that the housing is provided with air inlet openings in the region of its corners and edges. Since a defined air flow can always enter through these air inlet openings, it is prevented that larger amounts of dust settle in these corners or edges.

The filter of the air outlet is preferably cleaned by means of a flushing pipe which is displaceably arranged on the housing in an outlet chamber and which can be pressurized. Since the flushing pipe can be moved, it is possible to selectively apply air to the filter in order to free it from adhering dust particles over its entire cross-sectional area.

• Fig. 1 eine schematische Seitenansicht, teils im Schnitt, der erfindungsgemäßen Mühle;
• Fig. 2 eine Draufsicht auf die Mühle von Fig. 1, teils im Schnitt;
• Fig. 3 eine Seitenansicht entlang der Linie III-III von Fig. 2; und
• Fig. 4 eine Schnittansicht entlang der Linie IV-IV von Fig. 3.

The invention is described below using an exemplary embodiment in conjunction with the drawing. It shows:

• Figure 1 is a schematic side view, partly in section, of the mill according to the invention.
• Fig. 2 is a plan view of the mill of Fig. 1, partly in section;
• Fig. 3 is a side view along the line III-III of Fig. 2; and
• FIG. 4 is a sectional view along the line IV-IV of FIG. 3.

1 shows a side view of an exemplary embodiment of a mill 1 according to the invention which is arranged in a housing 6 and has a motor 2 which is mounted outside the housing 6. The mill 1 has an inlet funnel 3, through which material to be comminuted is fed to a grinder 5, not shown in FIG. 1. The grinder 5 comprises in the usual way a cross, which can be driven by the motor 2, and an inner wall provided with projections or corrugations. After comminution in the grinder 5, the comminuted material arrives in a collecting container 4, which can be detached from the mill 1 in order to remove its contents.

In order to clean the grinder 5, a cover 16, on which the inlet funnel 3 is provided, is pivoted away from the housing of the mill. The housing 6 has at its upper area an opening, not shown in detail, which is assigned to the inlet funnel 3 in its operating position in order to introduce regrind into the mill 1. When the cover 16 and the inlet funnel 3 are pivoted away, a relatively large, free opening would now be present in the housing. To prevent this, a perforated plate 12 is arranged on the upper area of the housing 6, which covers the opening of the housing at least in part.

A pivot lever 17, which is connected to a shaft 18, the longitudinal axis of which also forms the pivot axis of the cover 16, serves to pivot the cover 16 and the inlet funnel 3. The pivot lever 17 is arranged outside the housing 6, so that the cover 16 can be opened without the housing 6 having to be opened by the operator. In order to keep the cover 16 in its closed position, a threaded rod 19 is provided, the front end of which is provided with a thread and can be passed through a recess in the cover and screwed to the housing and / or the mill. To facilitate this screwing-in operation, a crank 20 is arranged outside the housing 6 and is connected to the threaded rod 6. The threaded rod 19 is displaceable in its longitudinal direction, so that it can be removed from the housing 6 or at least partially pulled out after opening to open it to enable the lid 16.

FIG. 2 shows a top view of the arrangement shown in FIG. 1, the housing 6 being shown in section. In the area of the motor 2, a limit switch 21 is provided on the housing 6, which is actuated when the threaded rod 19 is completely screwed in. The limit switch 21 serves as a safety switch and prevents the engine 2 from starting as long as the cover 16 is not closed. In Fig. 2, the perforated plate 12 is also shown, through which the opening of the inlet funnel 3 in the housing 6 can be at least partially closed when the lid 16 is open.

FIG. 3 shows a sectional view along the line III-III of FIG. 2. In FIG. 3, the opening 22 of the housing 6 assigned to the inlet funnel 3 is particularly clearly visible, as is the perforated plate 12. Outside of the housing 6 is furthermore a main switch 23 is provided, by means of which the motor 2 can be switched on or off.

In order to press the collecting container 4 against the housing of the mill 1, an eccentric 24 is provided on the bottom area thereof, which is attached to a shaft 26 which is mounted in the housing 6 and extends through the walls thereof. At the ends of the shaft 26 a rotary handle 27 is provided, by means of which the shaft 26 and thus also the eccentric 24 can be rotated in order to raise or lower the collecting container 4. As shown in Fig. 2, a lever 28 is attached to the shaft 26 and is engageable with a limit switch 25 attached to the housing 6 to ensure that the engine 2 cannot be started until the collecting container 4 is properly connected to the mill 1.

As shown in FIGS. 1 and 2, the lower region of the housing 6 is provided with a front plate 30, which is connected to a handle 29 and can be opened to remove the collecting container 4.

As shown in FIG. 3, the collecting container 4 has an opening which is covered by a filter 13. The filter 13 can be designed in the form of a close-meshed network or grid sheet and which hardly allows the finest dust particles to escape from the collecting container.

The housing is also provided with an air outlet 8, which is arranged in the bottom region (see FIG. 3) and serves for the outflow of air from the interior of the housing 6. The air flows through a filter 9 into an outlet chamber 14, which is connected in a manner not shown to a vacuum source, for example a vacuum cleaner. The air outlet 8 is slit-shaped in order to allow a smooth, undisturbed inflow of air into the outlet chamber 14. The filter 9 is held on the housing 6 by means of screws 31. In the outlet chamber 14 there is a flushing pipe 15 provided, which is displaceable in the vertical direction along a rail 32 and is connected to an air duct 34 via a line 33. Compressed air is supplied through the air duct 34 in order to flow through the filter 9 in the counterflow direction. The displaceability of the rinsing tube 15 makes it possible to deliberately remove dust particles from the entire surface of the filter 9. The dust particles thus blown off fall through the air outlet 8 into the bottom region of the housing 6 and can be removed there manually when the front plate 30 is open.

The outlet chamber 14 is preferably provided with a vacuum outlet 35 at its upper region in order to ensure a uniform flow through the outlet chamber 14.

FIG. 4 shows a view along the line IV-IV of FIG. 3, i. H. a side view of the side of the mill shown on the right in Fig. 3. Fig. 4 shows an open state of the mill 1, in which the cover 16 has been pivoted away after the threaded rod 19 has been unscrewed. On the inside of the cover 16, part of the grinder 5, namely the corrugation or toothing of the cover 16, is visible. Furthermore, the collecting container 4 was rotated by rotating the shaft 26, i. H. lowered by pivoting the eccentric 24 so that the collecting container 4 can be removed from the housing 6. For this purpose, the front panel 30 has been moved down.

The filter 13 of the collecting container 4 preferably has a mesh size of 10 μm and is arranged in a bore with a diameter of 50 mm. The filter 13 also creates a slight negative pressure in the collecting container 4, which prevents dust from escaping through the inlet funnel 3 and the opening 22 of the housing 6 when the mill 1 is in operation.

The perforated plate 12 is dimensioned with respect to the cross sections of its openings so that although a sufficient amount of air can flow into the interior of the housing 6, on the other hand, the free cross sections of the perforated plate 12 prevent an excessive amount of air from flowing in, which are no longer extracted by the vacuum source could, which could then leak dust from the housing 6.

As can be seen from FIG. 2, the housing 6 has a slot-shaped opening 11 through which a compressed air lance, not shown, can be introduced into the interior of the housing 6 in order to free the grinder 5 of the mill 1 from dust and with the cover 16 open to clean. For this purpose, the compressed air lance has, for example, lateral bores of 2 mm in diameter and is connected to an overpressure source of 7 bar in order, for example, to blow an air quantity of 25 l into the housing 6. The amount of air blown in must be less than the amount of air extracted by the vacuum source. As a further effect, cooling of the grinder 5 of the mill 1 occurs during this cleaning.

The design of the outlet chamber 14, the air outlet 8 and the filter 9 has the effect that the air laden with fine dust first passes through the air outlet 8 at a relatively high flow rate and is then slowed down to approximately 1/20 of the rate in order to settle to enable the dust particles on the filter 9. The filter 9 is, for example, in the form of a steel mesh with a mesh size of 25 μm and is cleaned by means of the rinsing tube 15 after five to ten grinding processes. During the cleaning process, the vacuum source is still connected to the housing 6, but the amount of air blown in through the flushing pipe 15 is dimensioned such that the filter 9 can nevertheless be flowed through in countercurrent. For this purpose it is in the upper In the region of the outlet chamber 14, an opening is provided which is opened when the flushing pipe is raised and causes the vacuum source to draw in outside air at least in part.

The housing 6 has, for example, an internal volume of 50 l, so that a commercially available vacuum cleaner can be used as the vacuum source. Since the fine dust is retained on the filter 9, an overload or increased contamination of the vacuum cleaner is prevented. In addition, the suction is advantageously dimensioned such that an air exchange in the housing 6 takes place at least once per second.

In the embodiment shown, the air outlet 8 has a cross-sectional area of about 20 cm 2, while the filter 9 has an area of about 400 cm 2.

By means of the mill according to the invention, it is thus possible to prevent dust from escaping into the work space both during the grinding process and during the cleaning process.

Claims (11)

1. Mill with a driven by means of a motor, with an inlet funnel and a collecting container in connection with the grinder, characterized in that the mill (1) is arranged in a housing (6) which has at least one air inlet opening (22) and an air outlet ( 8) that the air outlet (8) is arranged on the bottom of the housing (6) and connected to a vacuum source and that in the area of the air outlet (8) a filter (9) is provided, which with a filter (9) in the counterflow direction is connectable with compressed air source. 2. Mill according to claim 1, characterized in that the vacuum source is in the form of a suction device provided with a dust separator. 3. Mill according to one of claims 1 to 2, characterized in that the air inlet opening (22) for generating an air flow directed to the bottom of the housing (6) is arranged in the upper housing region. 4. Mill according to one of claims 1 to 3, characterized in that the housing (6) is provided with a closable, slot-shaped opening (11) for introducing a compressed air lance for cleaning the inside of the housing (6). 5. Mill according to one of claims 1 to 4, characterized in that the housing (6) comprises, from the outside thereof, actuatable devices for opening the mill (1) and for removing the collecting container (4). 6. Mill according to one of claims 1 to 5, characterized in that by means of a perforated plate (12) when the mill is open (1) the inlet funnel (3) associated opening of the housing (6) is at least partially covered. 7. Mill according to one of claims 1 to 6, characterized in that the collecting container (4) is opened to the housing interior via a filter (13). 8. Mill according to one of claims 1 to 7, characterized in that the motor (2) is arranged outside the housing (6). 9. Mill according to one of claims 1 to 8, characterized in that the housing (6) has such a small internal volume that the air contained therein must be exchanged at least once per second. 10. Mill according to one of claims 1 to 9, characterized in that the housing (6) is provided in the region of its corners and edges with air inlet openings. 11. Mill according to one of claims 1 to 10, characterized in that the compressed air is applied to the filter (9) of the air outlet (8) by means of a displaceably on the housing (6) in an outlet chamber (14) arranged flushing pipe (15).

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