EP0209004B1 - Vibratory surface finishing device for bulk goods - Google Patents

Abstract

A lapping device for surface enhancement of bulk material including a treatment chamber which is closed gas-tight and is charged with an inert gas, at least one vibratory conveyor being arranged in the treatment chamber and an arrangement for creating motion between a lapping abrasive liquid and the goods on the conveyor to form a surface enhancement for the goods. The arrangement for creating motion can be either abrasive nozzles for creating a jet of abrasive material directed onto the goods, the movement of the vibratory conveyor through a bath of the lapping abrasive or a combination of both. The lapping device is particularly useful for pretreatment of bulk goods which are to be electro-plated.

Description

The invention relates to a lapping device for improving the surface of pourable material for pretreatment for the galvanic deposition of aluminum from aprotic, oxygen and water-free, organoaluminum electrolytes, with a treatment room in which a relative movement can be generated between the pourable material and a lapping agent.

The term lapping is to be understood in the following to mean a machining process with loose grain, the lapping agent, which is distributed in a paste or liquid. In contrast, grinding is a cutting machining process with multi-edged tools of geometrically undefined cutting edge shape, which consist of a large number of bound grains.

Lapping devices of the generic type are known, for example, from the magazine “Galvanotechnik”, D-7968 Saulgau, 76 (1985), No. 1, pages 67 and 68. In the lapping devices there, however, which are referred to as slide grinding systems, processing takes place in a moving bed of workpieces and grinding wheels. The processing in such lapping devices, which can be designed as drums, bells, vibrators, centrifugal systems and drag grinding systems, requires a relative movement between workpieces and grinding wheels, which can be random and can run both tangentially and normally to the surface of the workpieces.

From US-A-3 935 680 a lapping device for improving the surface of pourable material is known, in which a mass consisting of the material and abrasives is introduced into a circular vibration tube and is compressed there by the decreasing cross-section of the vibration tube. The filling opening of the vibration tube is closed during operation, this closing only serving the purpose of being able to process a much larger quantity than in the case of an open vibration tube. The size of the lapping device is limited, however, since the vibration tube, together with the material contained therein and the abrasive, must be set in vibration. The throughput that can be achieved is correspondingly low.

The known lapping devices are used, in particular, in electroplating technology to generally improve the surface condition of workpieces with the aim of ensuring that galvanic precipitates adhere well during subsequent electroplating. Depending on the initial condition of the workpieces, the surface improvement to be carried out can include edge rounding, smoothing, glossing, polishing, degreasing and descaling. Further areas of application of the known lapping devices are surface improvements for subsequent metallization in a vacuum, for applying layers of lacquer and for other methods of coating workpieces with mostly very thin, protective and beautifying coatings on less valuable substrates.

The surface improvements achieved in the known lapping devices are quickly canceled out in many materials by contact with air and air humidity. Surface reactions, such as oxidations, corrosion and the like, which start before the workpieces are introduced into the galvanic bath, then at least considerably impair the conditions for well-adhering galvanic deposits.

Aluminum deposited from aprotic, oxygen and water-free, organoaluminum electrolytes is characterized by its ductility, low pore density, corrosion resistance and anodizing ability. Since the entry of air through reaction with atmospheric oxygen and air humidity causes a considerable reduction in the conductivity and the service life of these electrolytes, the electroplating must be carried out in an air-tight treatment facility. So that the access of air can be prevented even when loading and unloading these air-tight treatment facilities, import and export locks are also required, which are designed as gas locks, as liquid locks or as combined gas-liquid locks and with means of conveyance for passing through the electroplated material are equipped. Such an aluminizing device, working in the absence of air and provided with import and export locks, for the mass electroplating of pourable material is known, for example, from EP-A-0 070 011.

The aluminizing using aprotic, aluminum-organic electrolytes requires a particularly careful pretreatment and surface improvement of the aluminizing material. Thus, on the one hand, between the pretreatment in a lapping device and the introduction of the electroplating material into the aluminizing device, there must be no surface reactions impairing the adhesive strength of the aluminum layers, while on the other hand the introduction of atmospheric oxygen, air humidity and other substances that are harmful to the sensitive electrolyte must be prevented with the aluminizing material. For the reasons mentioned, it has not yet been possible, for example, to provide electroplated material made of materials such as iron, steel, titanium and the like immediately after the pretreatment in a lapping device with adhesive galvanic aluminum coatings. In order to obtain well-adhering aluminum coatings, an electrodeposited nickel intermediate layer had to be applied beforehand.

The invention has for its object to provide a lapping device for improving the surface of pourable goods, in which the general improvement of the surface condition of the goods can be maintained until a subsequent coating.

This object is achieved in a generic lapping device by the characterizing features of claim 1 and according to an alternative by the characterizing features of claim 2.

Both solutions are based on the common idea that lapping can be carried out in a gas-tight, lockable, inert gas-treated treatment room, provided that an oscillating conveyor is used as a means of transport for the then necessary transport of the bulk material through the treatment room. The vibratory conveyor can then transport the pourable material through a lapping agent bath contained in the treatment room, i.e. H. the relative movement required for the lapping process between the pourable material and the lapping agent is generated in a similar manner to the known lapping devices designed as vibrators. According to the alternative solution, the lapping can also be carried out in the manner of jet lapping, the jets emerging from the lapping agent nozzles being directed onto the pourable material which is moved past on the conveyor track of the vibratory conveyor. The material processed with the exclusion of air by dipping lapping or jet lapping can then - without coming into contact with air - be introduced directly or via an import lock into a downstream coating device. In this way, reactions affecting the surface improvement - such as oxidation, corrosion and the like - can be ruled out until the subsequent coating process. The lapping devices according to the invention are therefore also particularly suitable for the pretreatment for the electrodeposition of aluminum from aprotic, oxygen and water-free, organoaluminum electrolytes. The galvanic deposition of an intermediate layer of nickel, which was previously necessary, can even be omitted when aluminizing pourable material made of iron, steel, titanium and the like, since lapping can be carried out without problems under an inert gas atmosphere with the aid of non-aqueous, aprotic lapping agents.

The vibratory conveyors used in the lapping devices according to the invention are conveying means which transport bulk material using the mass forces on a defined conveying path in a horizontal and / or inclined direction. As a rule, oblique vibrators or inclined handlebars serve to drive the conveyor track in such a way that the material mostly carries out micro-throwing movements and, if necessary, it is transported in the direction of conveyance at a profit.

The use of vibratory conveyors of this type in the lapping devices according to the invention enables extremely gentle conveying of the pourable material, whereby there is no fear of jamming of the conveyed material. With regard to the lapping taking place in the absence of air, the use of an oscillating conveyor as a conveying means has the additional advantage that no drive shafts leading out of the treatment room need to be sealed. Such a sealing of rotating parts, which would be necessary when using other conveying means, can be regarded as problematic given the high demands placed on pretreatment with aprotic lapping agents, for example.

A vibratory conveyor used in the devices according to the invention preferably has an upward conveying path. With regard to the smallest possible space requirement with a relatively long length of the conveyor track and thus the processing section, it is particularly advantageous if the conveyor track is led upwards in a helical shape. A so-called vibratory bowl feeder is used to convey the goods through the treatment room, the use of which has already proven itself in feeding and arranging small parts in handling technology (VDI-Z 123, 1981, No. 3 Feb. pages 82-86). In all cases, the conveyor track of the vibratory conveyor is preferably designed as a vibrating trough, which ensures safe guidance of the goods to be transported through the treatment room with little effort.

In the case of dip lapping in a lapping agent bath, the conveyor path of the vibratory conveyor is preferably led beyond the level of the lapping agent bath. Above the bath level, lapping agent still adhering to the material is then thrown away by the vibrations, this effect being further promoted if the conveyor track is provided with perforations at least in the area which extends beyond the level of the lapping agent bath.

Carrying the lapping agent out of the treatment room can be completely ruled out if a spray device for spraying a liquid cleaning agent is arranged above the level of the lapping agent bath. A solvent contained in the lapping agent bath is preferably fed to the spray device as a cleaning agent. In order to keep the composition of the lapping agent bath as constant as possible, this solvent is obtained from the lapping agent bath either with the aid of at least one filter or with the aid of a distillation device.

The supply of the pourable material to the lapping device is particularly easy to implement if a gravity conveyor is connected upstream of the vibratory conveyor, as seen in the conveying direction. The same advantages also result if a gravity conveyor is arranged downstream of the vibratory conveyor - seen in the direction of conveyance. In both cases, it is particularly favorable if the gravity conveyor is formed by a downpipe. With regard to the air exclusion of the treatment room, downpipes of this type can also be connected particularly easily to corresponding import or export locks. In the case of an export lock, the downpipe can then already be used as a downward leg of a U-shaped liquid lock. Furthermore When using import or export locks for the introduction or discharge of the bulk goods, vibratory conveyors can also be used, which ensure gentle handling of the goods and pose no problems with regard to the sealing of the lock chambers.

According to a further particularly preferred embodiment of the invention, the pourable material can be returned to the initial region of the vibratory conveyor by a return device which can optionally be connected to the end of the vibratory conveyor. In this case, the lapping can be done in two or more passes, i. H. the lapping time can be increased as required without extending the conveyor track. The goods are not discharged until the desired surface condition has been reached. The changeover between circulation and discharge is particularly easy to accomplish if the return device can be connected to the end of the vibratory conveyor via a switch. If the return device is designed as a gravity conveyor, then additional funds for the return can be dispensed with. Here, too, the gravity conveyor is again expediently formed by a downpipe, which also further improves its mixing when the material is treated gently.

An additional mixing of the material with a particularly uniform surface treatment from all sides can also be achieved in that the conveyor track of the vibratory conveyor - viewed in the conveying direction - has at least one step leading downwards.

The upward conveying path of the vibratory conveyor is preferably fastened to a centrally arranged support column. Such support columns then perform the task of a space-saving supporting structure for the conveyor track in addition to the vibration transmission.

The vibration generation is then effected with little effort in that the support column is arranged on a vibrator. However, it is also possible for the support column to be arranged on a support plate which is mounted so as to vibrate in the treatment room and to carry a vibrator. The inclusion of the entire vibration excitation in the treatment room eliminates the problem of sealing vibrating drive means guided to the outside.

Embodiments of the invention are shown in the drawing and are described in more detail below.

• Fig. 1 eine erste Ausführungsform einer Läppeinrichtung für schüttfähiges Gut,
• Fig. 2 eine zweite Ausführungsform einer Läppeinrichtung für schüttfähiges Gut,
• Fig. 3 Einzelheiten der Läppeinrichtung gemäß Fig.1 eingesetzten Förderbahn,
• Fig. 4 ein erstes Prinzip zur Gewinnung eines Reinigungsmittels aus dem Läppmittelbad und
• Fig. 5 ein zweites Prinzip zur Gewinnung eines Reinigungsmittels aus dem Läppmittelbad.

They show in a highly simplified schematic representation

• 1 shows a first embodiment of a lapping device for pourable goods,
• 2 shows a second embodiment of a lapping device for pourable goods,
• 3 details of the lapping device according to Fig.1 used conveyor,
• Fig. 4 shows a first principle for obtaining a cleaning agent from the lapping bath and
• Fig. 5 shows a second principle for obtaining a cleaning agent from the lapping bath.

Fig. 1 shows in longitudinal section a first embodiment of a tower-shaped lapping device for improving the surface of pourable material G, which is, for example, bolts, nuts, screws, spacers and the like. The treatment of the pourable material G serves as pretreatment for the subsequent electrodeposition of aluminum from an aprotic, oxygen and water-free, organoaluminum electrolyte.

In a arranged on a frame Ge and sealed with the help of an upper lid De1, circular cylindrical treatment room Br1 is a lapping bath Lb1, which is in an aprotic solvent, such as. B. toluene, suspended lapping grain, such as. As silicon carbide, aluminum oxide and the like. The area of the treatment room Br1 lying above the mirror Sp1 of the lapping agent bath Lb1 is treated with an inert gas such as e.g. B. nitrogen, applied, the supply of this inert gas is indicated by an arrow Ig.

The material G to be processed is introduced from above into the lower region of the treatment room Br1 via an inlet lock (not shown) and a downpipe Fr10, the downpipe Fr10 being filled with the lapping agent bath Lb1 up to the level of the mirror Sp1 and inert gas Ig being applied to it . The material G introduced via the downpipe Fr10 then falls onto the lower end of the conveyor track Fb1 of an oscillating conveyor arranged within the treatment room Br1 and designated overall by Sf1. On the conveyor track Fb1, which is designed as a vibrating trough and spirally upwards, the material G is transported upward above the mirror Sp1 of the lapping agent bath Lb1 and then falls into the funnel-shaped upper end of a downpipe Fr1 leading out of the treatment room Br1, which is in the manner of a Down pipe branches into a downpipe Fr11 and a downpipe Fr12. In the position shown in FIG. 1 of a switch Wel arranged at the branching point, the material G is then returned to the lowest passage of the helical conveyor track Fb1 via the downpipe Fr12 re-entering the treatment room Br1. If the switch Wel, which is designed as a pivotable flap, is switched in the direction of the arrow Pf, the material G passes directly via the downpipe Fr11 or via a lock into a subsequently arranged aluminizing device which works in the absence of air.

The conveyor track Fb1 leading helically upwards within the treatment room Br1 is fastened to a centrally arranged support column Ts1, the lower end of which is fastened to a vibrator V1 arranged centrally within the frame Ge. The passage of the support column Ts1 through the floor of the treatment room Br1 is sealed by an elastic and wear-resistant bellows B1, which on the one hand has a disc placed on the support column Ts1 and on the other hand to the floor of the treatment room Br1 is connected. The conveyor Fb1 is excited by the vibrator V1 via the support column Ts1 to vibrate with an approximately helical movement. Due to the oblique movement and the accelerations and speeds that occur, an oblique throw is forced on the goods G lying on the helically upward conveying path Fb1, so that the pourable goods G are transported upwards in the direction of conveyance at a profit. Since the throwing distance and throwing height are extremely small, this type of funding involves micro-throwing, which ensures extremely gentle treatment of the good G. In the example shown, the support column Ts1 is fixedly connected via a flange Fla to a support body Tk of the vibrator V1 which is flared towards the bottom. The support body Tk is mounted on the foundation so that it can vibrate via several springs Fd1. An unbalance drive Ua is arranged within the conical support body Tk, the motor M of which drives flywheels Ss arranged on both sides with adjustable eccentricity e. The drive axis Aa of the motor M is inclined at an angle of, for example, 45 ° to the horizontal, so that the unbalance of the flywheels Ss generates the vibrations already mentioned with an approximately helical movement.

The pourable material G is transported via the conveyor track Fb1 through the lapping agent bath Lb1 and its surface quality is improved by the relative movement between the goods G and the lapping grain contained in the lapping agent bath Lb1. The lap means is operated in the embodiment shown in Fig. 1 position of the switch as long Wel in circulation until the desired upper ^f has set lächenverbesserung. Thereafter, the material G conveyed beyond the mirror Sp1 of the lapping agent bath Lb1 is freed of the lapping agent still adhering to it by means of a spray device arranged in the treatment room Br1 and introduced into the downstream aluminizing device via the switch Wel which has been switched in the direction of the arrow Pf and the downpipe Fr11. The spray device Se1 sprays a liquid cleaning agent Rm, the extraction of which from the lapping agent bath Lb1 will be explained in more detail later with reference to FIGS. 4 and 5. Since the entire lapping process takes place under an inert gas atmosphere and under completely aprotic conditions and the material G does not come into contact with air even when it is introduced into the downstream aluminizing device, the surface improvement achieved is retained until the aluminum is deposited. For this reason, even material G consisting of iron, steel, titanium and the like can be directly galvanically coated with aluminum without the previously required application of an intermediate layer made of nickel.

In view of the abrasive properties of the lapping grain contained in the lapping agent bath Lb1, the wall and the bottom of the treatment room Br1, the conveyor track Fb1 and the support column Ts1 should at least in the areas coming into contact with the bath consist of abrasion-resistant materials or with abrasion-resistant coatings such as e.g. . B. hard metal.

The lapping agent bath Lb1 housed in the treatment room Br1 has to be renewed from time to time or also freed from abrasion in a continuous preparation process and provided with new lapping grain. The supply and removal of the liquid lapping agent is indicated in Fig. 1 by corresponding arrows Zu and Ab.

2 shows in longitudinal section a second embodiment of a tower-shaped lapping device for the surface treatment of pourable material G. The aprotic lapping agent bath designated here with Lb2 is located in a circular cylindrical treatment room Br2 which is arranged directly on the corridor and is sealed gas-tight with the aid of an upper lid De2. The area of the treatment room Br2 above the mirror Sp2 of the lapping agent bath Lb2 is charged with an inert gas, the supply of which is indicated by an arrow Ig.

The material G to be treated is introduced into the treatment room Br2 via a downpipe Fr20 and then falls onto the lower end of the conveyor track Fb2 of an oscillating conveyor arranged within the treatment room Br2 and generally designated Sf2. On the conveyor track Fb2, which is designed as a vibrating trough and spirally leads upwards, the material G is transported upward by the lapping means Lb2 and then falls onto a switch We2 designed as a short trough. On the way up, the material G passes several downstairs St of the conveyor track Fb2, the height of which is dimensioned such that the material G rotates when falling and an improved mixing of the material G is achieved. In the position of the switch We2 shown in FIG. 2, the material G arrives in a downpipe Fr22 serving as a return device, which returns the material G to the lowest aisle of the conveyor track Fb2. With the position of the switch We2 shown, the goods G are thus circulated through the lapping agent bath Lb2. After the desired surface improvement has been achieved, the material G is cleaned with the aid of a spray device Se2 and discharged via a downpipe Fr21 when the switch We2 is switched over. The upper opening of this downpipe Fr21 can be closed by a cover D, and the opening and closing of this cover D can be carried out pneumatically or hydraulically via an actuating rod Bs which is guided outwards. The switch We2 is articulated to the actuating rod Bs via a coupling member Kg in such a way that a change occurs with the opening stroke of the cover D and the material G reaches a downstream aluminizing device via the downpipe Fr21.

The helical conveyor track Fb2 is fastened to a centrally arranged support column Ts2, the lower end of which is supported on the floor of the treatment room Br2 by a support plate Tp and several springs Fd2 and whose upper area is a vibrator V2 in the area above the mirror Sp2 of the lapping agent bath Lb2 wearing. Not in terms of its function Vibrator V2, which is shown in more detail, can be rotated via a pin Z in the cover De2 and can also be centered and raised to a small extent.

2 also shows a variant according to which the lapping in the treatment room Br2 is carried out solely by jet lapping or by a combination of jet lapping and plunge lapping. For this purpose, a plurality of lapping agent nozzles Ld are directed onto the conveyor track Fb2, to which a liquid lapping agent Lm is supplied under pressure. The lapping agent nozzles Ld can be arranged along the entire length of the conveying path - in a helical course parallel to the conveying path Fb2, the lapping agent bath Lb2 then only serving as a sump for the lapping agent, the supply and removal of which is indicated by arrows Lm. Otherwise, this jet lapping device shown as a variant functions like other such devices, the liquid lapping agent Lm not, however, with the aid of compressed air, but with the aid of a pressurized inert gas, such as. B nitrogen, is conveyed to the lapping agent nozzles Ld.

FIG. 3 shows that the conveyor track Fb2 used in the lapping device according to FIG. 1 and fastened to the support column Ts1 can be provided with a perforation P. In the area leading through the lapping agent bath Lb1 (see FIG. 1), this perforation P brings about an improved access of the lapping agent to the material G, while in the area above it, the lapping agent still adhering to the material G is flung away and the Cleaning of the goods G can be promoted with the help of the spray device Se1.

4 shows, using the example of the lapping device shown in FIG. 2, a first principle for obtaining the cleaning agent Rm required for the operation of the spraying device Se2 from the lapping agent bath Lb2. The lapping agent contained in the lapping agent bath Lb2 is drawn off via a pump P1 and then freed from the solid components in a coarse filter Gf and a fine filter Ff arranged downstream of it, so that the aprotic solvent contained in the lapping agent bath Lb2 can be supplied as cleaning agent Rm to the spraying device Se2. Arrows Pf1 and Pf2 indicate that the solid components retained in the coarse filter Gf and the fine filter Ff, which are lapping grain and abrasion, can either be subjected to a treatment or can be returned directly to the treatment room Br2.

Using the example of the lapping device shown in FIG. 2, FIG. 5 shows a second principle for obtaining the cleaning agent Rm required for the operation of the spraying device Se2 from the lapping agent bath Lb2. The lapping agent contained in the lapping agent bath Lb2 is drawn off with the aid of a pump and fed to a distillation device designated overall by De. The distillation device De comprises a first container Bh1 in which the lapping agent bath Lb2 is heated with the aid of a heating device He such that the aprotic solvent contained therein evaporates. The evaporated solvent is then condensed with the aid of a cooling device Ke, collected in a second container Bh2 and fed to the spray device Se2 as a liquid cleaning agent Rm via a pump P3. The second container Bh2 is connected to the first container Bh1 via a return pipe R1 serving as an overflow.

Claims (22)

1. Lapping apparatus for improving the surface of pourable material for the preliminary treatment for the electrolytic separation of aluminium from aprotic, anoxic and anhydrous aluminium organic electrolytes, having a treatment chamber in which a relative movement can be generated between the pourable material and a lapping agent, characterized by

a gastightly closed stationary treatment chamber (Br1 ; Br2) charged with an inert gas (Ig),

at least one oscillating conveyor (Sf1 ; Sf2) arranged in the treatment chamber (Br1 ; Br2) and

a lapping agent bath (Lb1 ; Lb2) contained in the treatment chamber (Br1 ; Br2), through which the pourable material (G) is transportable by means of the oscillating conveyor (Sf1 ; Sf2).

2. Lapping apparatus for improving the surface of pourable material for the preliminary treatment for the electrolytic separation of aluminium from aprotic, anoxic and anhydrous aluminium organic electrolytes, having a treatment chamber in which a relative movement can be generated between the pourable material and a lapping agent, characterized by

a gastightly closed stationary treatment chamber (Br2) charged with an inert gas (Ig)

at least one oscillating conveyor (Sf2) arranged in the treatment chamber (Br2)

at least one lapping agent nozzle (Ld) directed at the, transport path (Fb2) of the oscillating conveyor (Sf2) within the treatment chamber (Br2): to which a lapping agent (Lm) can be fed under pressure.

3. Lapping apparatus according to Claim 1 or 2, characterized in that the oscillating conveyor (Sf1 ; Sf2) has a transport path (Fb1 ; Fb2) which leads upwards.

4. Lapping apparatus according to Claim 3, characterized in that the transport path (Fb1 ; Fb2) passes spirally upwards.

5. Lapping apparatus according to one of the preceding claims, characterized in that the transport path (Fb1 ; Fb2) of the oscillating conveyor (Sf1 ; Sf2) is constructed as an oscillating chute.

6. Lapping apparatus according to Claim 1 or one of Claims 3 to 5, characterized in that the transport path (Fb1 ; Fb2) of the oscillating conveyor (Sf1 ; Sf2) is extended beyond the surface level (Sp1 ; Sp2) of the lapping agent bath (Lb1 ; Lb2).

7. Lapping apparatus according to Claim 6, characterized in that the transport path (Fb1) is provided with a perforation (P) at least in the region which is extended beyond the surface level (Sp1) of the lapping agent bath (Lm1).

8. Lapping apparatus according to Claim 6 or 7, characterized in that a spray device (Se1 ; Se2) for spraying a liquid cleaning agent (Rm) is arranged above the surface level (Sp1 ; Sp2) of the lapping agent bath (Lb1 ; Lb2).

9. Lapping apparatus according to Claim 8, characterized in that a solvent contained in the lapping agent bath (Lb2) can be fed as cleaning agent (Rm) to the spray device (Se2).

10. Lapping apparatus according to Claim 9, characterized in that the solvent is obtainable from the lapping agent bath (Lb2) by means of at least one filter (Gf, Ff).

11. Lapping apparatus according to Claim 9, characterized in that the solvent is obtainable from the lapping agent bath (Lb2) by means of a distillation apparatus (De).

12. Lapping apparatus according to one of the preceding claims, characterized in that the oscillating conveyor (Sf1 ; Sf2) is preceded, viewed in the transport direction, by a gravity conveyor.

13. Lapping apparatus according to one of the preceding claims, characterized in that the oscillating conveyor (Sf1 ; Sf2) is followed, viewed in the transport direction, by a gravity conveyor.

14. Lapping apparatus according to Claim 12 or 13, characterized in that the gravity conveyor is formed by a down pipe (Fr10, Fr11 ; Fr20, Fr21).

15. Lapping apparatus according to one of the preceding claims, characterized in that the pourable material (G) is returnable to the initial region of the oscillating conveyor (Sf1 ; Sf2) by a return device connectable optionally to the end of the oscillating conveyor (Sf1 ; Sf2).

16. Lapping apparatus according to Claim 15, characterized in that the return device is connectable to the end of the oscillating conveyor (Sf1 ; Sf2) by points (We1 ; We2).

17. Lapping apparatus according to Claim 15 or 16, characterized in that the return device is constructed as a gravity conveyor.

18. Lapping apparatus according to Claim 17, characterized in that the gravity conveyor is formed by a down pipe (Fr12 ; Fr22).

19. Lapping apparatus according to one of the preceding claims, characterized in that the transport path (Fb2) of the oscillating conveyor (Sf2) exhibits at least one step (St) which leads downwards viewed in the transport direction.

20. Lapping apparatus according to one of Claims 4 to 19, characterized in that the transport path (Fb1 ; Fb2) which leads spirally upwards is attached to a centrally arranged support column (Ts1 ; Ts2).

21. Lapping apparatus according to Claim 20, characterized in that the support column (Ts1) is arranged on a vibrator (V1).

22. Lapping apparatus according to Claim 20, characterized in that the support column (Ts2) is arranged on a support plate (Tp) mounted vibratably in the treatment chamber (Br2) and supports a vibrator (V2).

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