EP0009467B1 - Magnetic filter - Google Patents

Abstract

The magnetic filter has a magnetic cylinder (2) pivotally mounted in a housing (1) and having an inclined stripper (14). The bottom of the cylinder (2) is surrounded by a casing (5), whereby a flow channel (6) for the medium to be filtered is created between the cylinder (2) and the casing (5). One portion (5b) of the casing (5) can be mobile so that the flow-channel profile section can be changed. Decreasing the channel profile section causes an increase in the flow resistance, resulting in a backwash, so that even in cases of small quantities the level and hence the inflow characteristic of the filter is approximately the same as that of the full-load quantity.

Description

The invention relates to a magnetic filter, consisting of a rotatably mounted magnetic roller with a scraper, which is covered at the bottom by a jacket, wherein a flow channel with a variable cross section for the liquid to be filtered is formed between the roller and the jacket Flow channel flows.

The magnetic filter is used to remove magnetically conductive and non-conductive dirt particles from coolants and lubricants so that they can be used again. The degree of cleanliness of the coolants and lubricants is a decisive factor in the manufacturing precision and the surface quality of the machined machine parts. Improving the quality of the magnetic filter leads to an increase in the service life of tools, system parts and the lubricants and coolants.

Automatic magnetic filters have long been known in modern technology, e.g. B. from US-A-2 736 432 and CH-A-459 107. The most common machines in practice are provided with a long magnetic roller, which consists of several magnetic fields. The magnetic roller, driven by a motor with a reduction gear, is mounted in a housing which surrounds the roller from below. The medium to be cleaned is usually supplied above the axis via the flow opening in the axial direction of the magnetic body to the pulling force of the magnetic roller. In the same way, the outlet is arranged on the opposite side, but usually a little lower to ensure a good flow. The magnetically attracted impurities contained in the liquid to be filtered build up in the form of beards on the magnetic roller, with large chips being attracted faster than small ones. Magnetic induction decreases as the distance between the magnets and the individual chip increases. Mostly the smallest chips that are on the outside, d. H. furthest from the surface of the roller, flowing in the medium to be cleaned in the channel, often do not have enough time during the flow to reach the magnetic surface of the roller.

If the flow rate in such a filter is reduced, the level at the inlet into the flow channel drops, the area acted upon on the magnetic roller becomes smaller and thus the performance of the filter. In the case of even smaller quantities, the medium to be cleaned ripples over the inlet edge, thus creating turbulence in the flow channel and thus additionally reducing the efficiency of the magnetic filter.

A known magnetic roller separator for magnetizable parts contained in dusty material is described in DE-B-1 135 842.

The roller, which is covered by a jacket, is set into high revolutions, so that centrifugal forces are set in order to throw off non-magnetized parts which may adhere to the roller surface, while the magnetic parts are separated off by means of a scraper.

The roller is inserted in a vibrating bed driven by a vibrator, the vibrations of which vibrate the jacket and thus narrow and widen the flow channel at a high frequency. This causes a strong circulation of the dusty material and a good attraction of the magnetic parts to the roller.

As a result of the vibrations, however, the build-up of the beard from magnetic impurities as a precoat filter for non-magnetic parts is prevented.

It is not possible to filter out non-magnetic contaminants from a liquid with this magnetic separator.

Another magnetic separator is known from FR-A-2 134 229. The purpose of this is to magnetically separate larger machined metal parts from a polishing compound. It is also not suitable for filtering magnetic non-magnetic parts out of a liquid.

It is an object of the invention to avoid the disadvantages of the known magnetic separators and to create a magnetic filter of the type mentioned at the outset with high efficiency, also with regard to filtering out non-magnetizable parts. It should be possible to operate the filter in such a way that a "beard" is built up from magnetic impurities in the flow channel and is also obtained with different amounts of liquid, which serves as a precoat filter for the non-magnetic parts. The change in the flow channel cross-section to adapt to different amounts of liquid should be finely adjustable so that a calm, turbulence-free flow can always be generated in the flow channel.

This problem is solved by a magnetic filter which has a control arrangement with an electrical signal transmitter, the measuring part of which protrudes into the container and, depending on the level of the liquid in the container, intermittently switches a drive motor for the magnetic roller on and off, and that to change the flow channel cross section slider protruding into the flow channel or a movable jacket part known per se is provided.

On the one hand, this ensures that after the first phase of calming down and filtering out the larger parts, the medium to be cleaned is directed in the direction of the magnets, and on the other hand, magnetic induction is amplified as the chip approaches the magnets. A reduction in the channel cross section results in an increase in the flow resistance, resulting in a backflow, so that the level and thus the influencing characteristic of the filter corresponds approximately to that of the full load quantity even with small quantities.

For this reason it is also important that the level of the lake is kept as constant as possible. The electrically operated level switch, e.g. B. a proximity switch or a capacitive compact limit switch that responds to level differences of 1 mm to 1.5 mm, that is, has a very narrow control band. Experiments with a float switch known per se have not proven successful, since such float switches only respond at a level difference of 4 mm to 5 mm, which is not precise enough for the present purpose.

The level switch is used for fine adjustment of the magnetic filter. It switches the magnetic roller on and off depending on the level of the liquid. The magnetic roller transports the material to be separated out to the scraper at a low speed, while the filter beards have enough time to regenerate.

In practice, the magnetic filter according to the invention has proven itself well. So it was z. B. possible to almost completely filter out the fine abrasion resulting from the processing of gray cast iron, consisting of iron and graphite, which is not possible with conventional magnetic filters.

• Fig. 1 einen Längsschnitt durch einen Magnetfilter und
• Fig. eine Draufsicht auf den Magnetfilter gemäß Fig. 1.

Exemplary embodiments of the invention are explained in more detail below with the aid of the drawings. It shows

• Fig. 1 shows a longitudinal section through a magnetic filter and
• FIG. 1 shows a top view of the magnetic filter according to FIG. 1.

The magnetic filter has a stable aluminum housing 1, in which a horizontal magnetic roller 2 is rotatably mounted. The roller 2 is constructed from fine-pole, powerful permanent magnets, which are arranged at narrow intervals and generate a strong magnetic field across the entire width of the roller. The roller drive takes place via a double worm gear 4 by an electric motor 3.

Below the magnetic roller 2, at a distance a from its surface, a curved sheet metal jacket 5 is arranged, which envelops the lower part of the roller 2. As a result, a flow channel 6 for the liquid to be filtered is formed between the roll surface and the sheet metal jacket 5. The sheet metal jacket 5 consists of a part 5a fixed to the housing and a pivotable part 5b, the latter being fastened to the fixed part 5a by means of a hinge 8 parallel to the roller axis 7. Instead of sheet metal, the jacket could also consist of two castings.

A handle 9, which is arranged outside the housing 1 and is connected to the adjustable part 5b via two articulated levers 10, 11, is used to adjust the pivotable jacket part 5b. At a constant flow area, i.e. H. at a constant gap height a, both jacket parts 5a, 5b are arranged coaxially to the magnetic roller 2.

The movable jacket part 5b can now be adjusted by means of the handle 9 such that the gap narrows continuously in the direction of flow, a wedge-shaped tapering flow cross section being formed in the region of the movable jacket part 5b. This setting of the movable jacket part is shown in dashed lines in the figures, wherein the handle 9 can alternatively be arranged on one or the other side of the housing.

Instead of manual adjustment, it would also be possible to regulate the flow cross-section automatically, e.g. B. in a manner not shown with a motor drive in function of the measured flow rate.

A known, inclined scraper plate 14 is attached to the top of the housing 1 and lies with its front edge 15 on the roller surface.

A pre-filtering chamber 13 made of aluminum is arranged in front of the magnetic roller, in which a dirt discharge basket can be used. The sloping baffle 16 in the prefiltration chamber 13 serves to calm the inflowing liquid.

The medium to be filtered must flow into the flow channel 6 in a laminar and uniform manner over the entire width, since turbulence affects the filter efficiency. Due to the calming in the prefiltration chamber 13, a certain sedimentation takes place, in particular, specifically heavy parts such as grinding wheel abrasion, chips, etc. are deposited. The dirt discharge basket is an important cleaning aid, since sedimentation can be removed quickly and easily using this basket; time-consuming cleaning is spared.

The medium flows out of the antechamber 13 through the baffle 16 and then smoothly through under the magnetic roller 2. The flow gap can now be narrowed more or less in a wedge shape in the direction of flow, as required. As a result, the larger iron particles are excreted first and the effectiveness of the filtration in the micron range in the constricted areas is significantly increased. In order to achieve increased cleaning, the outflow can be backed up to the inlet height by a riser pipe or by increasing the adjustable baffles.

So that the liquid still contained in the filtered material can flow back into the container, the adjustable scraper plate 14 is arranged to rise slightly. The dirt is pushed further and further back on the scraper plate and then falls largely dry into a designated dirt container.

Through the continuous change of the through flow wedge an optimal position can be found for every need with regard to the desired filter performance and flow rate. A filter system can be immediately adapted to a changed operating condition or application. In this way, iron particles are practically always completely and, thanks to the wetting effect, non-ferrous substances largely removed continuously from the coolant and lubricant (oils, water, emulsions).

Instead of allowing the magnetic roller 2 to rotate continuously, the magnetic filter can be provided with an electronic control for the drive. In addition to working as a purely magnetic filter, this enables the system to be operated as a precoat filter, that is, filtering out non-magnetizable material. In connection with the adjustment device, d. H. by changing the flow wedge, practically any desired filter efficiency can be achieved with the roller control. A capacitive compact limit switch 17 protrudes with its measuring parts 18 into the liquid in the pre-filtering chamber 13. It is designed for fine regulation and responds to the smallest changes in the flow resistance or the liquid level and automatically switches the drive motor 3 on and off in a narrow control band. This eliminates the need for any manual re-regulation when changing the degree of contamination of the liquid to be filtered.

The basic mode of operation corresponds to that of the magnetic filter without signal transmitter, only the magnetic roller does not turn when it is started up. The magnetizable parts immediately build up into a beard-shaped sieve in the flow wedge, which leads directly to the floating of non-magnetizable parts and thus forms a dense filter layer.

The degree of filtering can be infinitely adjusted in the capacitive contact limit switch. If the flow resistance in the filter exceeds the predetermined value, a control command triggers a forward rotation of the magnetic roller. If a small part of the filter layer is removed, the flow resistance is reduced, the motor is switched off and the magnetic roller is fixed again. This modern type of electronic capacitive control can work in a narrow control band with short cycle intervals in order to keep the filter efficiency always within narrow limits. The belt can also be moved up or down almost as desired. The measuring point can be inside or outside the filter housing, depending on the medium.

In further embodiments, an electrically magnetizable roller is provided instead of the magnetic roller. To change the flow channel cross-section, it would also be possible to have a slide regulatingly penetrate into the channel with a fixed jacket. Finally, instead of the electrical signal transmitter, a membrane switch or a proximity switch could be used, which control the electric motor as a function of the liquid level. Depending on the type of medium, photocell control would also be conceivable.

Claims (5)

1. Magnetic filter, consisting of a magnetic roller which is mounted to rotate and comprising a wiper, which is surrounded on its lower side by a casing, a through-flow channel of variable cross-section for the liquid to be filtered being formed between the roller and the casing, which fluid flows by way of a container to the through-flow channel, characterised by the fact that the magnetic filter comprises a control arrangement with electrical signal generator (17), the measuring part (18) of which projects into the container and depending on the level of the fluid in the container intermittently starts and stops a drive motor (3) for the magnetic roller (2) and that provided for varying the cross-section of the through-flow channel is a slide projecting into the through-flow channel in an adjustable manner or a movable casing portion (5b) which is known per se.

2. Magnetic filter according to claim 1, characterised by the fact that the electrical signal generator (17) is a proximity detector or capacitive compact limit switch.

3. Magnetic filter according to claim 1, characterised by the fact that the container comprises a baffle (16) for stabilizing the fluid before the measuring part (18) and before entry into the through-flow channel (6).

4. Magnetic filter according to claim 1, characterised by the fact that the movable casing portion (5b) is connected to an actuating lever (9) by way of a toggle joint arrangement (10,11).

5. Magnetic filter according to claim 1, characterised by the fact that the casing (5) consists of two bent pieces of sheet metal or castings (5a, 5b) which are connected to each other centrally by way of a hinge (8) and are arranged coaxially with respect to the magnetic roller (2) in the position of a constant through-flow cross-section.

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