EP0140511B1

EP0140511B1 - Method and apparatus for removing excess material from sand cores

Info

Publication number: EP0140511B1
Application number: EP19840305627
Authority: EP
Inventors: Udo Kuehn
Original assignee: B and U Corp
Current assignee: B and U Corp
Priority date: 1983-09-06
Filing date: 1984-08-17
Publication date: 1987-11-04
Also published as: AU574382B2; JPS6072638A; AU3263284A; EP0140511A1; DE3467105D1; CA1214916A

Description

This invention relates generally to apparatus for finishing and cleaning molded articles by directing particulate material against the rough moulded article. Impeller systems for directing metal shot against cast metal articles for cleaning the articles are well known.
The present invention relates more specifically to the finish cleaning of molded sand cores which are made by molding a mixture of sand and a binder, to form a core that may be of complex shape having holes, projections, notches, and other irregularly shaped areas. Such articles are far more delicate than the articles which have heretofore been finished by blasting with an impact media, often metal particles moving at high velocities. Accordingly, prior art blasting apparatus and methods have not been adaptable to the problem of automated cleaning of molded sand cores, and the present rubbing by hand methods for cleaning cores are unacceptable because they are time consuming and expensive.
It is an object of the present invention, therefore, to provide an improved method and apparatus for removing flash and other excess material from said cores by directing a fluidized media of impact particles against the sand cores.
US-A-2929120 discloses apparatus for removing flash and other excess material from sand cores in accordance with the prior art portion of claim 1. This prior apparatus uses particles of sand carried in a stream of air to engage the sand cores to be cleaned and finished. As compared therewith the present invention, as characterised in the characterising portion of claim 1, uses a stream containing a large volume of relatively soft cleaning particles which have a gentle but effective cleaning action on the lightweight sand cores. The particular entraining means of the present invention enables a relatively high volume of the soft cleaning particles to be entrained in the relatively low pressure stream of conveying air so as to provide the necessary gentle cleaning action on the lightweight sand cores.
Thus relatively soft impact particles are showered against the cores in a relatively gentle manner so as to remove flash and other excess material without damaging the cores. The preferred apparatus consists of a conveyor on which the relatively light-weight sand cores are supported so that the opposite sides of the cores can be reached by streams of impact particles. A plurality of nozzles are positioned both above and below the conveyor and relatively low pressure air is directed through the nozzles in the direction of the sand cores on the conveyors. Large volumes of relatively soft impact particles without any sharp points or edges, such as small pieces of plastic, are entrained in the air so that they will be directed against the sand cores. The flash and other excess material is relatively loosely adhered or attached to the main body of the core and as a result, when these loosely adhered pieces are impacted by the moving particles, they are dislodged from the main body of the core. However, when these relatively soft slow moving particles engage the sand core, the particles do not damage or disrupt the surface of the main body of the core.
Accordingly, when the sand cores that are on the moving conveyor are exposed to the action of the fluidized impact media for a relatively short time, the flash and other excess-material is quickly removed from the cores. As a result, the apparatus can be operated continuously to automatically clean and finish a large number of sand cores in a short time.
The use of the apparatus of this invention is advantageous in that it provides for the rapid and thorough cleaning of complex parts by subjecting these parts to showers of particles moving against the parts from different directions so as to finish both internal and external surfaces in the part.
Further objects, features and advantages of this invention will become apparent from a consideration of the following description and the appended claims, when taken in connection with the accompanying drawings in which:

Fig. 1 is an end view of the core de-finning apparatus of this invention;
Fig. 2 is a reduced side elevational view of the apparatus of this invention, with some parts broken away for the purpose of clarity;
Fig. 3 is a sectional view of one of the nozzles in the apparatus of this invention;
Fig. 4 is a fragmentary top view of a sand core prior to cleaning;
Fig. 5 is a top view of the sand core shown in Fig. 4, after cleaning; and
Fig. 6 is a perspective view of an impact particle useable in the method and apparatus of this invention.

With reference to the drawing, the apparatus of this invention, indicated generally at 10, is shown in Figs. 1 and 2 as including a main frame 12 on which is mounted a housing 14 and a conveyor assembly 16 which is operable to move sand cores to be cleaned through the housing 14. A piuratity of nozzles 18 are mounted in the housing 14 at positions above the conveyor assembly 16 and a plurality of the same nozzles 18 mounted below the conveyor 16. The nozzles 18 are supplied with air by a blower or turbine 20 and a particalized media 22 is fed to the nozzles 18 from a supply hopper 24 located above the nozzles 18. An elevator assembly 26, of conventional type, operates to transfer used particles 22 from the bottom of the apparatus and deliver these particles to the hopper 24 for re-use.
The conveyor assembly 16 is illustrated as including a plurality of endless strands 28 (Fig. 1), similar to ropes or cables, trained about pulley or sheave assemblies 30, 31 and 32 mounted on the main frame 12. The pulley assembly 30 includes a shaft 34 which is driven by a motor drive assembly 36 so as to move the strands 28 that extend horizontally between the pulley assemblies 30 and 31 from left to right in Fig. 1. A plurality of sand cores to be finished, indicated diagrammatically at 38 in Fig. 2, are laid on the horizontal strands 28 and are moved by the strands into the housing 14 to positions between the upwardly and downwardly directed nozzles assemblies 18. During movement of the cores 38 into and out of the housing 14, they move through rubber curtains 40 which tend to confine the particles 22 from the nozzles 18 to the housing 14.
As shown in Fig. 3, each of the nozzles 18 consists of a nozzle head 42 rotatably mounted on an injector body 44 which is connected to a conduit 46 through which air is supplied from the blower 20 and a conduit 48 through which the particles 22 are supplied.
An inclined septum 47 directs the particles in conduit 48 toward the air stream emanating from conduit 46 at the lower edge 49 of the septum 47. Since the air stream in conduit 46 is created by the blower 20, in contrast to a compressor, it is at a low superatmospheric pressure, namely, below 2 psi. (0.14 bore). As a result, the stream entrains large volumes of the particles 22 falling off the edge 49 in the form of a curtain. This forms a low pressure stream issuing from nozzle head 42 that contains a dense accumulation of particles 22 directed toward sand cores to be cleaned. It is to be understood that the nozzle head 42 can be remote from the injector--body 44 and be connected thereto by a suitable passage.
The result is a relatively soft flow of particles 22 from each nozzle head 42 that provides for a shower of the particles 22 on both the top and bottom sides of the cores 38 supported on the strands 28 in the housing 14. A variety of different relatively soft particles 22 that do not have sharp edges or corners, such as walnut shells, corn cobs and similar non-ferrous media, can be used in apparatus 10. Particles that are as hard as conventional steel shot used for blast cleaning are too hard and cause erosion of a sand core. However, particles 22 formed of plastic and generally cylindrical in shape and processed so as to have rounded edges, as illustrated in Fig. 6, are preferred from the standpoints of effectiveness, cost, cleanliness and lack of surface erosion on the core.
The particles 22 are preferably formed of an easily obtained plastic, such as polyethylene or polypropylene, and are relatively small .in size, having a diameter of about 0.07 inches (1.8 mm) and a length of about 0.10 inches (2.54 mm) or less.
A rough molded sand core 38 is shown in Fig. 4. The core is of a relatively complex shape having notches 50, openings 52, projections 54, and other irregularly shaped surfaces on which excess material, a mixture of sand and the binder, adhere as indicated at 56. These excess adhering portions 56 are sometimes referred to as "flash" and must be removed from the main body 58 of the sand core 38 in order to make the core 38 useable for its intended purpose in a molding process.
As shown in Fig. 5, when the core 38 has been subjected to the action of the apparatus 10, all of the excess material 56 has been removed so that the core 38 can now be used without further processing. In the operation of the apparatus 10, the cores 38 are placed on the conveyor 16 as shown in Fig. 2 so that they travel on the conveyor 16 through the enclosure 14 and are subjected to the fluidized media 22 that is directed from both above and below onto the surfaces of the sand core 38. The open construction of the conveyor 16 enables thorough showering of the core 38 from both above and below. After the sand cores 38 emerge from the housing 14, they are readily useable in molding operations.
From the above description, it is seen that the method and apparatus of this invention provides for the relatively gentle application of soft impact particles against the somewhat vulnerable body 58 of the sand core 38 so as to provide for the complete removal of all of the excess materials 56 on the body 58 without danger of damage to the body 58.

Claims

1. Apparatus for removing flash and other excess material from sand cores (38) comprising at least one nozzle (18), a blower (20) for supplying moving air at low pressure to said nozzle, a plurality of impact particles (22), feed means (48) operable to deliver said impact particles into said moving air so as to form a stream of moving air from said nozzle containing said particles, and means (16) providing for engagement of said sand cores by said stream, characterised in that the impact particles (22) are of a material which is soft compared with the material of the sand cores (38) and in that the feed means comprises an injector body (44) attached to a first conduit (46) communicating with said blower'(20) and to a second conduit (48) supplying said impact particles and means (47) associated with said injector body (44) for providing, in use of the apparatus, a downwardly flowing curtain of said particles from the second conduit (48) intercepted by a moving stream of air from said first conduit (46) operable to entrain said particles therein, the nozzle comprising a nozzle head (42) communicating with said injector body (44) and operable to direct the stream of air and impact particles toward said cores to be cleaned.

2. Apparatus according to claim 1, characterised in that the means (16) providing for engagement of the sand cores by the stream is operable for moving said cores to be cleaned into the path of said stream from said nozzle.

3. Apparatus according to claim 1 or 2, characterised in that a plurality of said nozzles (18) are arranged to provide for streams of particles directed against opposite sides of said cores.

4. Apparatus according to any preceding claim, characterised in that said particles are formed of a plastics material.

5. Apparatus according to claim 4, characterised in that said plastics material comprises polyethylene or polypropylene.

6. Apparatus according to claim 4 or 5, characterised in that said impact particles (22) are generally cylindrical in shape having a diameter of about 0.07 inches (1.8 mm) and a length of about 0.1 (2.54 mm) inches.

7. Apparatus according to any preceding claim, characterised in that a downwardly inclined septum (47) extends from said second conduit (48) into said first conduit (46) and terminates in a free edge (49) from which particles in said second conduit (48) flow to form said curtain.