GB1593614A - Foundry reclamation - Google Patents

Description

PATENT SPECIFICATION

( 11) 1 ( 21) Application No 13514/80 ( 22) Filed 18 Jan 1978 ( 62) Divided out of No 1 593 613 ( 31) Convention Application Nos.

761 414 ( 32) Filed 21 Jan 1977 780670 23 March 1977 in If ( 33) United States of America (US) ( 44) Complete Specification published 22 July 1981 ( 51) INT CL 3 B 22 C 5/08 ( 52) Index at acceptance B 3 G 6 C 1 6 C 2 ( 54) IMPROVEMENTS IN OR RELATING TO FOUNDRY RECLAMATION ( 71) I, ALBERT MUSSCHOOT, a Citizen of the United States of America, of Route 2, Dana Lane, Barrington, Illinois, United States of America, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:

This invention relates to a method and apparatus to be used in the reclamation of foundry sand.

In most foundry casting operations, a pattern is introduced into a box-like structure called a mold flask and moist sand is formed under pressure around the pattern The pattern is then removed from the sand and hot metal is poured into the cavity where it sets or solidifies The sand used consists basically of fine sand with a number of additives such as clay, binders, and Sea-Coal, which are mixed with water to produce a mechanical mixture which can be formed under pressure and retain its shape In most foundry operations, the amount of moisture in the sand prior to the pouring of the hot metal will vary from 3 % to 7 or 8,o, depending upon the type of metal being poured.

In the usual foundry operation, after the metal solidifies in the cavity in the sand mold, the castings are generally passed over a machine called a shakeout, usually of vibratory nature, where the sand is shaken loose from the casting During the metal pouring operation, of course, heat is transferred from the metal to the sand.

Some of this heat is dissipated by evaporation of some of the moisture in the sand, but a good deal of the heat is retained by the sand In modern foundries, the sand is reused, mold after mold, and the total sand used would continue to increase in temperature to an unusable point Therefore, it has been the practice to provide a method of cooling the sand before it is reused in subsequent molds To form a good mold, the temperature of the sand ideally should be under 125 F The average temperature of the sand when the casting is removed from the mold can range from 200 'F to 600 'F, or more, depending upon the cooling time and the sand-to-metal ratio in the mold.

There are several methods used for cool 55 ing sand such as, for example, leaving it in a pile overnight or for some period of time, and allowing the heat to be lost naturally.

This method requires a great deal of space, a great deal of sand, together with rather 60 heavy material handling apparatus In other cases, the sand is passed through a fluid bed cooler in which ambient air is passed through the 'bed while it is being conveyed to cause evaporation of the moisture and 65 cooling of the sand Fluid bed coolers are expensive, and variations in the ambient temperature and humidity drastically affect the cooling rate Furthermore, fluid bed coolers require the use of large dust col 70 lectors in order to prevent air pollution, etc.

Additionally, means must be provided, either as part of the shakeout or fluid bed cooler, for braking up any clumps or lumps 75 of sand which adhere together by reason of the entrained binders This further complicates the system.

In accordince with one aspect of the invention, there is 'provided an apparatus 80 for reclaiming moist sand used as a mold for a foundry casting, said apparatus comprising means for separating sand from a casting formed therein, a pair of containers, a gate selectively to direct separated sand 85 into one or other of said containers, a chamber, means associated with the chamber for maintaining the chamber at a pressure of less than 3 psi absolute, valve means associated with each container to close off 90 that container from communication with the atmosphere, second valve means associated with each container selectively to establish communication between either one of said containers and the chamber to re 95 duce the pressure in that container to vaporize the moisture in the sand, and means for withdrawing sand from said container.

In accordance with another aspect of the 100 1593614 1 593 614 invention, there is provided a method of reclaiming moist sand used as a mold for a foundry casting, comprising the steps of separating sand from a casting formed therein, directing the separated sand selectively into one or other of two containers, maintaining a reduced pressure of less than 3 psi in a chamber, closing off from the atmosphere the container into which the sand has been directed and then establishing communication between the chamber and that container, thus reducing the pressure in that container to vaporize the moisture in the sand, and then withdrawing the sand from that container.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawing, which is a generally schematic view partially in section of an apparatus for the reclamation of foundry sand.

Referring to the drawing, there is shown schematically a pouring station 80 in which the molten metal is poured into the cavity formed in moulding sand to form the casting After the casting has cooled sufficiently so as to be self-supporting, the sand and casting are passed onto a shakeout screen 81 which, through vibrations, etc, shakes the sand off the casting The casting, substantially free of sand, is moved in one direction while the sand itself is moved onto a two-way gate 82 The two-way gate 82 is operable to direct sand from the shakeout into either of a pair of containers 83 and 84 Within each container is a deflector 85 provided with vanes 86 so as to assist in evening the distribution of sand therein At the entrance end of each container is a valve, such as the valves 87 and 88, with the former being shown in a closed position whereby the container 83 is cut off from communication with the atmosphere, and with the latter valve 88 establishing communication between the interior of the container 84 and the atmosphere, and similarly permitting sand directed thereto 'by the two-way gate 82 to enter into the container A pair of gate valves 89 are provided at the bottom of each container so that after the process is completed they may be opened permitting the cooled and dried sand to pass from the container onto a suitable conveyor 90.

Associated with the two containers 83 and 84 is a condensing chamber 91 provided with a housing 92 having vertical cooling tubes 93 therein An inlet 94 for coolant (usually cold water) communicates with the tubes 93, as does an outlet for heated coolant 95 A vacuum pump 96 is connected to the interior of the condensing chamber to maintain the pressure therein at less than 3 psi absolute and preferably about 1 psi absolute, as in the previously described embodiment Similarly, a sump pump 97 is provided at the bottom of the condensing chamber to remove condensed water vapor and particulate matter entrained therein from the condensing cham 70 ber.

Located at the top of the chamber 91 is a three-way valve 98 operable when in a first position to connect the interior of the container 83 with the interior of the con 75 densing chamber 91 by means of a conduit 99 The valve 98 in the second position connects the interior of the condensing chamber with the interior of the container 84 by means of the conduit 100 In its 80 third position, the three-way valve blocks both conduits 99 and 100.

In operation, sand from the shakeout is directed by the two-way gate into the container 84 until the latter is full Container 85 83 had previously been filled and upon completion of filling, the valve 87 was closed, cutting off communication between the interior of the container 83 and the atmosphere, and valve 98 is then moved 90 to open conduit 99 exposing the interior of container 83 to the vacuum existing in the condensing chamber The sudden drop in pressure causes moisture in the sand to vaporize and effect substantially instan 95 taneous cooling of the sand Water vapor so formed passes through the conduit 99 into the condensing chamber where it condenses on the tubes 93 In the meantime, container 84 is filling and as it nears 100 capacity, the three-way valve is moved to a position closing off both containers and the valve 89 on container 83 is opened, as is valve 87, to expose the interior of the container 83 to atmospheric pressure and 105 simultaneously to permit the sand to fall therefrom At this point, valve '88 may be closed and valve 98 operated to expose the interior of the container 84 to the low pressure existing in the condensing cham 110 ber, and the two-way gate is operated to direct further sand into the container 83.

Thus, one container is being filled while the sand in another is 'being treated so that a continuous operation may result 115 Reference should be made to our copending British patent specification 2047/78 (Serial No 1 593 613).

Claims (3)

WHAT I CLAIM IS: 120

1 An apparatus for reclaiming moist sand used as a mold for a foundry casting, said apparatus comprising means for separating sand from a casting formed therein, a pair of containers, a gate selectively to 125 direct separated sand into one or the other of said containers, a chamber, means associated with the chamber for maintaining the chamber at a pressure of less than 3 psi absolute, valve means associated with each 130 1 593 614 container to close off that container from communication with the atmosphere, second valve means associated with each container selectively to establish communication between either one of said containers and the chamber to reduce the pressure in that container to vaporize the moisture in the sand, and means for withdrawing sand from said containers.

2 An apparatus as claimed in claim 1, comprising condensing means in said chamber for condensing vaporized moisture drawn into said chamber upon establishing communication with either one of said containers.

3 A method of reclaiming moist sand used as a mold for a foundry casting, comprising the steps of separating sand from a casting formed therein, directing the separated sand selectively into one or other of two containers, maintaining a reduced pressure of less than 3 psi in a chamber, closing off from the atmosphere the container into which the sand has been directed and then establishing communication 25 between the chamber and that container, thus reducing the pressure in that container to vaporize the moisture in the sand, and then withdrawing the sand from that container 30 4 A method as claimed in claim 3 in which sand is directed alternately into the two containers and communication is established between the chamber and the two containers in corresponding alternation 35 A A THORNTON & CO.

Chartered Patent Agents Northumberland House 303/306 High Holborn London WC 1 V 7 LE Printed for Her Majesty's Stationery Office by The Tweeddale Press Ltd, Berwick-upon-Tweed, 1981.

Published at the Patent Office, 25 Southampton Buildings, London, WC 2 A l AY, from which copies may be obtained.