US3716946A

US3716946A - Method and apparatus for cleaning and recuperating shot in the circulatory system of blasting apparatus

Info

Publication number: US3716946A
Application number: US00096170A
Authority: US
Inventors: M Graf
Original assignee: Badische Maschinenfabrik GmbH
Current assignee: Badische Maschinenfabrik GmbH
Priority date: 1969-12-11
Filing date: 1970-12-08
Publication date: 1973-02-20
Anticipated expiration: 1990-02-20
Also published as: DE1962117B2; GB1328398A; SE380462B; CH524435A; DE1962117A1; FR2073616A5

Abstract

A METHOD AND APPARATUS FOR CLEANING AND RECUPERATING SHOT IN WHICH MATERIAL THAT IS SEPARATED FROM THE SHOT IN A FIRST AIR SEPARATOR, DOES NOT REACH THE AIR LINE SYSTEM TOGETHER WITH THE CLEANING AIR BUT IS SEPARATED IN A SECOND AIR SEPARATOR DOWNSTREAM OF THE CASCADES OF THE FIRST AIR SEPARATOR BY REASON OF ITS LARGER GRAIN SIZE OR HIGHER SPECIFIC WEIGHT AND IS CONDUCTED TO A MAGNETIC SEPARATOR WHOSE OUTLET FOR MAGNETIC MATERIAL IS CONDUCTED BACK TO THE SHOT CIRCULATORY SYSTEM OF THE APPARATUS.

Description

Feb. 20, 1973 M. E. GRAF 3,716,946

METHOD AND APPARATUS FOR CLEANING AND RECUPERATING SHOT IN THE CIRCULATORY SYSTEM UF BLASTING APPARATUS Filed Dec. 8 1970 2 Sheets-Sheet 1 INVENTOR MAX E. GRAF BY bui-n fw aff/Nu.

MTOHNE Y' Feb. 20, 1973 M. E. GRAF 3,716,946

METHOD AND APPARATUS FOR CLEANING AND RECUPERATING SHOT IN THE CIRCULATORY SYSTEM OF BLASTING APPARATUS Filed Dec. 8, 1970 2 Sheets-Sheet 2 FIG. 2

United States Patent 3,716,946 METHOD AND APPARATUS FOR CLEANING AND RECUPERATING SHOT IN Til-m CIRCULATGRY SYSTEM F BLASTING APPARATUS Max E. Graf, Karlsruhe-Durlach, Germany, assignor to Badische Maschinenfabrik GmbH Filed Dec. 8, 1970, Ser. No. 96,170 Claims priority, application Germany, Dec. 11, 1969, P 19 62 117.1 Int. Cl. B24c 3/00 U.S. Cl. 51-9 8 Claims ABSTRACT 0F THE DISCLOSURE A method and apparatus for cleaning and recuperating shot in which material that is separated from the shot in a first air separator, does not reach the air line system together with the cleaning air but is separated in a second air separator downstream of the cascades of the first air separator by reason of its larger grain size or higher specific weight and is conducted to a magnetic separator whose outlet for magnetic material is conducted back to the shot circulatory system of the apparatus.

The present invention relates to an improvement for the cleaning and recuperation of a magnetic blasting medium, commonly referred to as shot, within the shot circulatory system of blasting apparatus, as are known for cleaning castings, de-scaling and cleaning forgings or rolled stock.

Such blasting apparatus have customarily a circulatory system for the blasting medium, which conducts the used, contaminated blasting medium, that collects in the lower part of the cleaning chamber, to a cleaning installation before it is returned in its circulatory system to the turbines or free-jet nozzles.

The cleaning installation may consist of only one airseparation or air-sifting device of the most varied types of construction or of several series-connected air-separations or air-sifting devices. Furthermore, cleaning installations also exist in the prior art which are constructed as combinations of magnet-separators with air-separators.

For example, according to the French Pat. 1,490,340, a multi-stage separation for shot is proposed according to which, after a screening, a separation of the magnetic shot components from the non-magnetic sand takes place initially by means of a first magnet drum. The magnetic components are fed to an air-separator and are then returned for re-use to the blasting wheels. The non-magnetic components are fed to a second magnet drum in order to separate any remaining, smallest magnetic particles from the sand. The thus-purified sand is to be utilized for re-use as molding sand whereas the most finely magnetic components separated in this prior installation are removed from the apparatus and no further application or use is indicated for the same.

Whereas according to this French patent, the blasting medium or shot is subjected exclusively to a normal twostage separation for the re-use, in order to be able to clean in one working operation in accordance withv the inventive purpose of this patent, castings with a great amount of sand adhering thereto and cores, itis the object of the present invention to improve for castings with the same characteristics the cleaning and separation of the shot returned to the centrifuging wheels with small dimensions of the cleaning apparatus and to regain the shot, lost with the systems `known heretofore, and to conduct the same directly back for re-use in the circulatory system of the apparatus.

Two-stage cleaning methods for shot are known and are used if, for example, with castings having a large amount of molding and core sand, the contamination of riice the shot becomes very large. In order not to overload the air-separating installations, a preliminary separation is realized in that case by means of a magnet. The quality of the preliminary magnetic separation, however, decreases with a large quantitative load of the magnet so that the air-separation frequently lets a still non-permissive proportion of the sand pass through to the blasting wheels notwithstanding the preliminary cleaning. Accordingly, an improvement of the air-separation forms part of the purpose of the present invention.

All air-separator types of construction are limited in their output in that a predetermined air velocity cannot be exceeded because otherwise utilizable shot is carried along to the side of the contaminants which is then lost. It is known that the separated shot includes a slight amount of impurities after the air-separation only if one operates with a high air velocity in the air-separation. However, to use such a high air Velocity without loss in utilizable shot was not possible heretofore and is therefore the aim of the method according to the present invention, which essentially consists in that the material separated in the first air-separator from the shot, which does not reach the air line together with the separating air, but by reason of its grain size or weight collects in a second air separator downstream of the cascade or cascades of the first air-separator, is conducted by way of a magnetic separator whose outlet for magnetic material is conducted back to the shot circulatory system of the apparatus for renewed passage through the separating installations. A particularly advantageous construction is characterized in that with an apparatus, which includes already premilinary and secondary magnetic separators in the shot circulatory system, for example, according to the German published application DAS 1,577,540, printed July 9, 19710, the discharge from the second air separator downstream of the rst air separator is conducted by way of the secondary magnetic separator.

An apparatus for carrying out the method according to the present invention includes a closure mechanism in the discharge line of the second air separator.

The manner of operation according to the present invention for the actuation of the closure mechanism is characterized in that in synchronism with the apparatus the closure mechanism is opened only in the end phase of the working cycle of the cleaning or blasting chamber when the yield of non-magnetic material from the first magnet has decreased.

A further feature of the present invention relates to the automatic actuation of the closure mechanism which is characterized in that a time signal transmitter produces a pulse for the opening of the closure mechanism at such an interval of time prior to the end of the Working cycle of the cleaning or blasting chamber that the maximum possible material quantity separated in the second air separator empties out by\ the end of the cycle.

These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawing, which shows, for purposes of illustration only, two embodiments in accordance with the present invention, and wherein:

FIG. 1 is a schematic view of a blasting apparatus with a shot circulatory system in accordance with the present invention; and

FIG. 2 is a schematic view of a modified embodiment of a blasting apparatus with a modied shot circulatory system.

Referring noW to the drawing wherein like reference numerals are used throughout the two views to designate like parts and more particularly to FIG. 1, reference numeral 1 designates in this figure a blasting chamber with a conventional blasting device 2, for example, in the form of centrifuging blasting rotors 2. A conveyor device is arranged in the lower part of the blasting chamber 1, for example, a motor driven worm 3 which conveys the shot and contaminants to a further conveyor device, for example, a bucket conveyor or elevator 4. A separating device, for example, a sieve 5 for larger foreign bodies may be provided in series with these conveyor devices. The contaminated shot is thrown by the bucket conveyor 4 at the top into the first air-separator 6 with conventional cascades 7. A ventilator (not shown) draws in air through the pipe connection 9; the air thereby enters the rst air-separator 6 through openings schematically indicated by 8 and, after flowing through the cascades 7 enters a second air separator, which is illustrated in FIG. 1 as cyclone 10. The second air separator separates the more coarse and specifically more heavy components of the material, carried along by the air from the cascades 7, in a downward direction into the funnel 11 whereas the fine components leave the apparatus through the line connection 9 in order to be separated from the air in a conventional filter for waste (not shown). A throttle valve 12 is provided in the auxiliary air connection 13 for the control of the air quantity which flows through the first air-separator 6. A container \14 with an outlet pipe 15 and a conventional throttle mechanism 16 conducts the material to a magnetic separator 17 of conventional construction. Any material, which is non-magnetic and nonutilizable in the apparatus, leaves the blasting medium circulatory system at 18 Whereas recuperated shot is again conducted back through the line .19 to the shot circulatory system upstream of the separating installation.

In FIG. 2, a preliminary magnetic separator 20 with an outlet 21 for non-magnetic contaminants and sand is illustrated in deviation from FIG. l. Additionally, in place of the cyclone of FIG. 1, an expansion chamber 22 with a deflection plate 23 is provided in this embodiment as a second air separator. The line 24 from the expansion space 22 has a conventional closure mechanism 25 with a line 26 to the secondary magnetic separator 27. A fan (not shown) draws the air through the line connection 28. A predetermined air velocity in the first air-separator may be adjusted by means of the throttle valve 29. The reference numerals of the remaining parts 1-8 and 18, 19 correspond to those of the description of FIG. 1.

The operation of the method according to the present invention is based on the cooperation of a

magnetic separator

17, 27 for the recuperation of shot from the sand separated in the air separating installation and the application of the maximum possible air quantity for the air separation which can be adjusted by the control of the

throttle valve

12 or 29. With the heretofore known apparatus, the air quantity for the air-separation had to be maintained very accurately and could not be excessively large in order that no utilizable shot was carried along by the air. On the other hand, the air quantity also should not be too small in such prior art installations because otherwise with a large amount of sand, an excessive residual amount of sand caused non-permissive wear in the blasting or centrifugal wheels and a clogging of the channels in the first air-separator had to be feared. The possible output capacity of the air-separator could not be fully used in the prior art installations. The present 1nvention eliminates this shortcoming in that the material separated in a second air separator P10, 22 is conducted by way of a

magnetic separator

17, 27 in order to be able to recuperate the shot taken along as a result of the large first air quantity in the air separator. It becomes possible thereby to open further the throttle valve 29 or to close further the throttle valve 12 in order to conduct a larger quantity of air with greater velocity than possible heretofore through the air separator installation y6. The separating output increases thereby, the time of the cycle of the apparatus operating in accordance with a batch type method can be shortened, and the sand residues which heretofore have always still remained in the shot after the separating operation, are kept away from the blasting or centrifuging rotors. Particularly advantageous is the application of the method with apparatus according to FIG. 2 which, for other reasons, already possess two magnetic separators in the shot circulatory system. The second magnetic separator 27 can then be used without additional expenditures also for the material from the second air separator 22. Since the sand quantity for the magnet 27 is large during the beginning of each working cycle and then is strongly reduced toward the end of the cycle, the closure mechanism 25 is appropriately so controlled by conventional means that the material from the second air separator 22 is delivered to the magnet 27 as much as possible toward the end of the cycle or during the charge change. The control means utilized for the closure mechanism 25 may, for example, include a solenoid 30 operatively connected to the closure mechanism 25 and energized in accordance with the setting of timers 31 and 32. The timer 3.1 may be a relay which is closed in accordance with the timed operation of the apparatus and the timer 32 which may also be a relay is closed at a predetermined time within the working cycle for energizing the solenoid. When the apparatus is operated continuously rather than in the batch type method, it is not necessary to control the closure mechanism 25 in that it is maintained at a predetermined outlet ow position. In an embodiment according to FIG. l, the throttle mechanism 16 is so adjusted that the material separated in unequal quantities during the operating rhythm of the apparatus is fed to the magnet 17 in equal quantities, as a result thereof, the quality of separation is best because an overloading of the magnet is avoided and additionally a small and inexpensive magnet suices.

While I have shown and described only two embodiments in accordance with the present invention, it is understood that the same is not limited thereto but is susceptible of numerous changes and modifications as known to those skilled in the art. For example, the advantages of the present invention are valid not only for the types of construction of an air-separating installation as shown in the drawing but also for all other types of construction. Furthermore, the present invention is not limited to apparatus which operate in cycles, as for example, the fettling or blasting chambers illustrated in the drawings but is suitable to the same extent and in a similar manner for continuously operating types of apparatus.

Accordingly, I do not Wish to be limited to the details shown and described but intend to cover all such changes as are encompassed by the scope of the appended claims.

What I claim is:

1. An apparatus for cleaning and recuperating shot used in a circulatory system, characterized by air-separating means for separating other materials from the shot, and means for conducting a portion of the thus separated other materials to magnetic separator means whose outlet for magnetic material is operatively connected again to the circulatory system of the apparatus.

2. An apparatus according to claim 1, characterized in that said air-separating means includes first and second air separator means, said second air-separator means separating said portion of the material being separated by reason of its larger grain size or higher specific weight.

3. An apparatus according to claim 2, characterized in that said second air separator means is located downstream of a cascade means of the first air separator means. i

4. An apparatus according to claim 2, characterized in that said second air separator means is provided with an outlet line for the separated material and a container is connected in the outlet line from said second air separator means, said container including an outlet line provided with adjustable throttle means.

5. An apparatus according to claim 2, characterized in that said second air separator means is provided with an outlet line for said portion of the separated materials and a closure means is provided in the outlet line from said second air separator means.

6. An apparatus according to claim 5, characterized by control means for controlling, in synchronism with the apparatus, the opening of the closure means, only during the end phase of the working cycle of a cleaning chamber when the yield of non-magnetic material has decreased.

7. An apparatus according to claim 6, characterized by timer means in the control means producing a pulse for the opening of the closure means at such an instant prior to the end of a working cycle of the cleaning chamber that the maximum possible quantity of material in an expansion space is emptied up to the end of the cycle.

8. An apparatus according to claim 2, wherein said magnetic separator means comprises two series-connected magnetic separator means including a preliminary and secondary magnetic separator means, characterized in that said second air separator means is provided with an outlet line for conducting said portion of the separated material to said secondary magnetic separator means, said secondary magnetic separator means having an outlet line for conducting magnetic material to the circulatory system of the apparatus.

References Cited UNITED STATES PATENTS 1,954,111 4/1934 Wilks 51-8 2,239,714 4/ 1941 Hammell 51-9 3,055,150 9/ 1962 Greenberg et al. 51-14 3,368,677 2/1968 Bradley 209--135 FOREIGN PATENTS 454,662 6/1968 Switzerland.

475,344 10/ 1952 Italy 51-14 1,093,785 12/ 1967 Great Britain.

OTHELL M. SIMPSON, Primary Examiner U.S. Cl. X.R. 209-40, 214