GB1600405A

GB1600405A - Cooling of articles

Info

Publication number: GB1600405A
Application number: GB1957177A
Authority: GB
Original assignee: Carrier Drysys Ltd
Current assignee: Carrier Drysys Ltd
Priority date: 1978-05-04
Filing date: 1978-05-04
Publication date: 1981-10-14

Description

(54) IMPROVEMENTS IN OR RELATING TO THE COOLING OF ARTICLES (71) We, CARRIER DRYSYS LI MITED, a British Company, of Carrier House, Warwick Row, London SW1E SEL, England, do hereby declare the invention for which we pray that a Patent may be granted to us, and the method by which it is to be performed. to be particularly described in and by the following statement: The present invention is concerned with apparatus and methods for cooling articles.

Many manufacturing processes involve the production of castings formed, for example. by pouring molten metal into moulds, often sand moulds. The metal is left in the mould to solidify before being broken out and cooled. In a modern foundry the casting process is often automated with the moulds moving along on conveyors and being automatically filled with molten metal. The filled moulds are then subsequently moved on to a knock-out section where the casting is freed from the mould. Although the metal is solidified at this time on emergence from the mould the casting is still very hot. For example, typical cast iron will probably be at a temperature of between 800 and 850"C. It is obviously necessary to allow the castings to cool before the further foundry processes can be commenced. Generally, after the casting has cooled it is fettled, that is, the surplus metal at joints at the mould surfaces and at the risers and runners is either knocked off or ground off either by hand or machine. The fettling process cannot be commenced until the casting has been cooled sufficiently to be metalurgically stable. Generally, it is necessary for the casting to be sufficiently cool to be handled. Thus, the casting should usually have a temperature of about 50"C before fettling is commenced.

Traditionally castings are left to cool in ambient air and in the case of production lines the castings are usually loaded onto a cooling conveyor which might move slowly round at high level in a foundry or adjacent fettling shop for sufficient time for the castings to cool. It is not unknown for such a conveyor to be installed outside having some elementary protection against the weather.

If there is a finite distance between the fettling shop and the foundry this can usefully be bridged by the cooling conveyor.

However, the length of the conveyor and the desired production rate have to substantially equal the time it takes to cool the castings for the provision of such a cooling conveyor to be advantageous. In other cases such a cooling conveyor takes up too much space in a foundry, slows down the production rate and causes pollution in the atmosphere. In addition, when using such a cooling conveyor there is no control over the rate of cooling of the castings.

It is an object of the present invention to provide apparatus for cooling articles which enables the cooling of the articles to be controlled and which does not require as much space as a usual cooling tower.

According to the present invention there is provided apparatus for cooling articles comprising an enclosure having first and second spaced opposite walls extending from an inlet to an outlet, conveying means for conveying articles to be cooled through the enclosure from the inlet to the outlet, a plurality of air ducts arranged along the first wall and a plurality of air ducts arranged along the second wall, each air duct opening into the enclosure, selected ones of the ducts along the second wall each communicating with a corresponding air duct along the first wall by way of a respective channel, means for establishing an air flow through the enclosure from the outlet to the inlet, the air at the outlet being cooler than the air at the inlet, arranged such that air flows from each selected duct along the second wall through the respective channel to the corresponding duct along the first wall and thence from said corresponding duct along the first wall across the enclosure towards the second wall.

An environmentally controlled cooling zone is provided within the enclosure and thus the rate of cooling of articles conveyed through the enclosure can be controlled and at the same time the rate of cooling of the articles can be increased beyond that achieved by natural convection in ambient air.

It will be appreciated that castings in particular cannot be cooled too quickly.

However, by closely controlling the air flow through the enclosure the cooling of castings can be carefully monitored and regulated and the quality of the castings produced can be improved and the metallurgical properties thereof controlled.

In a preferred embodiment the conveying means convey the articles, either continuously or in a step wise fashion, at either a constant or a variable speed, through the enclosure from the input to the output thereof. A temperature controlled air flow is established within the enclosure, the air at the output being cooler than the air at the input so that a temperature gradient is established within the enclosure. Preferably the air flow is established by a plurality of fans drawing air from the atmosphere at the output and passing air over the castings within the enclosure to the input. In this way the air is heated by the castings as it flows from the output to the input. It will be appreciated that the air at the input will be very hot, in fact, the air will be sufficiently hot to be used to produce energy either for the apparatus or for other means.

Additionally, the enclosure may be surrounded by a jacket containing a cooling medium such as air, water or oil. Alternatively, the enclosure may be constructed from panels incorporating a flow path for the cooling medium.

Preferably, a radiant heater section is mounted at the input of the enclosure to receive radiant heat from the hot castings.

The heat collected by the radiant heater section can be used as a source of energy.

The articles are preferably moved through the enclosure on an endless con veyor. Any sort of conveyor can be used but conveniently the conveyor is in belt form and has apertures or a mesh surface so that it does not hinder the air flow. Alternatively the conveyor may be an overhead conveyor in which the articles are suspended from a movable support which can be drawn through the enclosure. Additionally the conveyor may be provided with article receiving stations thereon arranged to rotate and/or turn over the articles during their travel through the enclosure. The enclosure may be arranged either horizontally or vertically and the articles can be moved therethrough either horizontally or vertically. If the articles to be cooled are produced in batches, it may be convenient to use a conveyor circulating in the vertical plane, and to arrange for all the articles in a batch to be carried on the conveyor at one time. In this case it may be convenient to take each article through the enclosure more than once.

The invention also extends to a method of cooling articles using apparatus as defined above, comprising the steps of conveying articles to be cooled through the enclosure from the inlet to the outlet, establishing air flow through the enclosure from the outlet to the inlet, the air at the outlet being cooler than the air at the inlet, such that the air flows across the enclosure from the first wall to the second wall and thereby over the articles being conveyed.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows schematically a side elevation, partly in section, of apparatus of the invention for cooling articles, Figure 1A shows a perspective view of a section of a conveyor for use in the apparatus of Figure 1, and Figure 2 shows part of a side elevation of a further embodiment of apparatus of the invention.

Figure 1 shows a side elevation, partly in section through apparatus of the invention arranged for cooling castings. The apparatus has an elongate housing 2 having a substantially rectangular cross-section defining an enclosure 4. The upper working run of an endless conveyor 6 extends longitudinally through the housing 2 near to the bottom wall thereof. A casting feed device schematically shown and designated by reference numeral 8 is arranged to introduce demoulded hot castings, as 10, onto the conveyor 6 at the inlet end 12 of the housing 2. An input fan 14 is arranged at the outlet end 16 of the housing 2. This fan 14 is arranged to direct air drawn from the atmosphere into a ducting system provided in the walls of the housing 2. This ducting system comprises a plurality of air ducts 18 arranged along the top wall of the housing and a plurality of air ducts 20 arranged along the bottom wall of the housing 2. Each air duct 18, 20 has a grill or vent opening into the enclosure 4. Preferably, the grills or vents of the air ducts 18, 20 are provided with means for adjusting the volume of air which can flow therethrough. Each lower duct 20, except for the duct 20 adjacent the outlet end 16, is associated with a fan 22 which has an air intake duct 24 connecting each fan 22 with the immediately adjacent duct 20 nearer to the outlet end 16. Each fan 22 is arranged to direct air through an associated channel 19 into the duct 18 immediately above it. The channels 19 may be provided in the side walls of the housing or external to the housing. It will be seen that in this way an air flow is generated within the enclosure 4 from the outlet end 16 to the inlet end 12 of the enclosure 4, the air flowing over castings carried by the conveyor 6. Specifically, air flows from the upper duct 18 adjacent the outlet end 16 to the lower duct 20 adjacent the outlet end 16.

The air in the end duct 20 is then forced by the fan 22 associated with the adjacent lower duct 20 through the air intake duct 24 and is directed through the channel 19 into the upper duct 18 adjacent the end duct 18 from whence it flows to the next lower duct 20, and so on. The lower duct 20 at the inlet end of the housing 2 is connected via a dust extractor 26 to an output fan 28.

The structure of the conveyor 6 is shown in more detail in Figure 1A from which it can be seen that a pair of parallel chains 30, which will extend longitudinally within the enclosure 4. support a plurality of transverse slats 32. In the embodiment shown the area between adjacent slats is filled with a mesh 34. It will thus be appreciated that air can flow through the conveyor.

A radiant heater section 36 is mounted at inlet end 12 of the housing 2. This radiant heater section can be a conventional heat exchanger comprising a helical pipe containing water or other fluid. The heater section 36 can be supported within the housing or as shown, arranged around the inlet end 12 of the housing in heat conducting relationship thereto. At the outlet end 16 of the housing there is provided a heater battery 38 connectable to the input fan 14. In addition, in the embodiment illustrated. the upper run of the conveyor 6 is arranged to flow through a cooling tank 40 also arranged at the outlet end 16 of the housing. This cooling tank 40 can be omitted if not required. The drive mechanism 42 for the conveyor 6 is also provided at the outlet end of the housing. The drive mechanism 42 is preferably arranged to provide both continuous and step wise movement of the conveyor 6 at either a constant or a variable speed.

In use hot demoulded castings 10 are successively introduced onto the conveyor 6 at the inlet end 12 of the housing 2 and the conveyor 6 is driven by the drive mechanism 42 so that the castings are moved longitudinally through the housing from the inlet end 12 to the outlet end 16 thereof. At the same time the fans 14, 22 and 28 are switched on so that air flows downwardly from the upper ducts 18 to the lower ducts 20 and from the outlet end 16 to the inlet end 12 of the housing under control of the fans 14, 22 and 28. The air at the outlet end 16 is atmospheric air and is relatively cool. As the air is drawn along through the enclosure 4 passing through the conveyor 6 and hence over and around the castings 10 towards the inlet end 12 it picks up more and more heat from the castings which are hotter towards the inlet end 12. In this way a temperature gradient is established within the enclosure 4, the air being hotter at the inlet end 12 than at the outlet end 16. The air discharged by the output fan 28 is hot enough to be used in heat exchange devices to obtain useful heat energy recuperation. It will be seen that as the castings move from the inlet end 12 to the outlet end 16 they are gradually and controllably cooled.

The very hot castings 10 introduced at the inlet end 12 of the enclosure give out radiant heat which is absorbed by the radiant heater section 36. If required, this heat can be used to heat air contained in the pipe of the heater section 36 to be fed to the input fan 14 to ensure that the cooling process is not too rapid. Alternatively, the pipe of the radiant heater section 36 can contain any fluid which is heated by the castings. The energy so stored by the heater section 36 can be used indirectly to heat air for the input fan 14 or for any other purpose. The heater battery 38 can also be used to store heat absorbed by the radiant heater section 36 so that a source of heat is available during start up of a new process to heat the air for the input fan 14.

If required a more sophisticated conveyor structure can be used providing spaced turn-table or turnover devices for carrying the individual castings so that the castings can be rotated or turned over during their travel along the enclosure to aid in the cooling process.

When the castings have been cooled to a certain temperature further rapid cooling is not disadvantageous. Thus, in the illustrated embodiment the conveyor passes at the outlet end 16 through a cooling tank 40 which could be filled with cold water or oil.

Alternatively or additionally a cooling spray section could be provided at the end of the conveyor.

In some instances the rate of cooling of the castings must be very carefully controlled to avoid damage thereto. The rate of cooling could be controlled automatically by providing devices for monitoring the casting temperature within the enclosure. Optical temperature sensors sensitive to the colour of the casting, radiation temperature sensors sensitive to the heat radiated from the casting, or electrical temperature sensors could be provided within the enclosure and arranged either to vary the speed of the fans, or to vary the opening of the ducts 18, 20 to vary the volume of air passing therethrough. In this way the required temperature gradient can be established within the enclosure. In addition, the flow of cooling air can be carefully controlled so that it is ensured that the air passes over the surfaces of the castings in the most advantageous manner and at the required velocity, which may be as high as 21m/sec. The precise velocity and the temperature of the air entering the outlet end of the enclosure will be dependent upon metallurgical considerations, the required rate of cooling, and the possible heat recuperation. Additionally, or alternatively, the cooling process can be controlled by varying the speed of the conveyor to thereby vary the time spent by each casting within the enclosure.

In addition to the cascaded air flow system shown in Figure 1, the surfaces of the housing 2 can be physically cooled by a cooling medium to absorb the radiant heat from the castings by heat exchange. This can most conveniently be done by providing a jacket for a cooling medium on the outer surface of the housing. Alternatively, panels incorporating a flow path for the cooling medium could be used to form the walls of the housing. The heat absorbed by the cooling medium can then be recovered. For example, a helical pipe (not shown) may be provided around the housing 2 in heat exchange relationship therewith. In this embodiment the cooling medium is preferably water which is circulated within the pipe and is therefore evaporated by heat absorbed from the castings to form steam.

The steam can then be fed to a heat exchanger (not shown). Other fluids can of course be used for this process including hydrocarbons of the - Freon variety and ammonia which, on account of pressure change may be used in- a turbine (not shown) to reconvert heat into mechanical or electrical energy.

It will thus be seen that the apparatus described above affords the opportunity to control the rate of cooling of the castings and thereby improve the uniformity of the quality of the castings. In addition, the heat energy obtained from the castings can reused. The apparatus takes up very little space, especially as compared to systems using a cooling conveyor in ambient air.

Further, there is-no danger to persons as the hot castings are ericlosed, heat and fume from the castings is not discharged into the environment. In addition, the castings can be cooled more rapidly ;in the apparatus described than a cooling conveyor in -ambient air particularly as-they are sub jected to forced convection conditions and therefore there is an increase in production rate.

When a casting is broken out from, say, a sand mould, there is usually an appreciable degree of fuming which pollutes the foundry atmosphere unless extracted by a sophisticated system. It has been common practice to extract liberal quantities of hot fume laden air above the critical operation and discharge this to atmosphere. This custom is undesirable not only because of the pollution it causes but also because it wastes heat energy. Accordingly, it is suggested that, with the embodiment shown in Figure 1, the castings be broken from the sand mould by conventional equipment immediately they are introduced into the enclosure 4. In this way the fuming takes place within the enclosure 4.

A further embodiment of the invention which is specially adapted to take care of fumes and air contaminated by sand particles is shown in Figure 2. In this embodiment, the air from the atmosphere flows from the input fan 14 (not shown) and the ducts 18 and 20 nearest to the outlet end 16 to an intermediate duct 50 where it is bled off through the dust extractor 26, and the output fan 28, and is used for heat recuperation. The remaining air in the intermediate duct 50 continues to flow through the inlet section of the enclosure towards the inlet end thereof. This air becomes very hot and dirty due to the fuming of the castings and. is fed to a combustion device 52. It will also be seen that in the embodiment shown in Figure 2 the radiant heater section 36 is arranged around the inlet section of the housing 2, and that air ducts 18 and 20 are also provided in the inlet section of the housing 2. This ensures that the fumes from the demoulded castings are directed by the air flow to the combustion device 52, and that the heat af these fumes and the heat radiated by the castings is recovered by the -heater section 36 In the apparatus described above castings are introduced onto a conveyor. The conveyor surface in the illustrated embodiments is designed to prevent the risers and runners of the castings becoming entangled with the conveyor to minimize the risk of breaking off the risers and runners. Furthermore, the conveyor allows the required through-flow of cooling air. The conveyors could alternatively be slatted or provided with overlapping sections.

The invention has been described above in relation to the cooling or castings, Of course, the apparatus described can be used to cool other articles, and is particularly useful if there is a risk of funking from the articles to be cooled or if it is desirable to have a controlled rate of cooling.

The apparatus shown in the drawings is arranged horizontally and the articles to be cooled are moved horizontally there through. However, if required, conveyor means can be arranged to take the articles vertically through a vertically arranged enclosure. If the articles to be cooled are produced in batches, each batch may conveniently be arranged on a conveyor circulating in the vertical plane through a vertically arranged enclosure. In this case, each article can be circulated through the enclosure more than once before all the articles of the batch are removed from the conveyor. In all the embodiments, means could be provided to rotate and/or turn over the articles during their travel through the enclosure. It will be seen that the apparatus described above with reference to the drawings has several advantages. Firstly, using the apparatus articles can be cooled more rapidly than in ambient air, and because the cooling rate can be regulated the quality of the articles produced can be controlled. Particularly, if the articles to be cooled are of metal, the metallurgical properties thereof can be controlled. Because the control of the cooling process is strict the output is regular and fewer rejects are produced. Increased cooling rates mean that the floor area necessary for the cooling installation can be as small as possible. The reduction in area required for an installation of the invention as compared to the traditional conveyor methods using ambient air is substantial. The hot articles to be cooled are, with the apparatus of the invention, totally enclosed. There is therefore less risk of accidental injury to the workforce. In addition, as the heat from the articles with the present invention is being recuperated and used where required the apparatus reduces heat pollution from the articles. The heat recuperated from the apparatus can be reused as required. For example, the heat could be used to drive an electrical or mechanical device and systems could be developed to use the heat extracted from the articles directly to provide power for the fans of the apparatus.

WHAT WE CLAIM IS: 1. Apparatus for cooling articles comprising an enclosure having first and second spaced opposite walls extending from an inlet to an outlet, conveying means for conveying articles to be cooled through the enclosure from the inlet to the outlet, a plurality of air ducts arranged along the first wall and a plurality of air ducts arranged along the second wall, each air duct opening into the enclosure, selected ones of the ducts along the second wall each communicating with a corresponding air duct along the first wall by way of a respective channel, means for establishing an air flow through the enclosure from the outlet to the inlet, the air at the outlet being cooler than the air at the inlet, arranged such that air flows from each selected duct along the second wall through the respective channel to the corresponding duct along the first wall and thence from said corresponding duct along the first wall across the enclosure towards the second wall.

2. Apparatus as claimed in Claim 1, wherein said means for establishing an air flow comprises an input fan arranged at the outlet to direct air into the air duct along the first wall at the outlet, and an output fan communicating with the air duct along the second wall at the inlet.

3. Apparatus as claimed in Claim 1 or 2, wherein said selected ducts along the second wall each communicate with the immediately adjacent air duct along the second wall which is nearer to the outlet of the enclosure by way of an air intake duct.

4. Apparatus as claimed in Claim 3, wherein a fan is arranged in each air intake duct to direct air through the associated channel.

5. Apparatus as claimed in any preceding claim, wherein the enclosure is surrounded by a jacket containing a cooling medium.

6. Apparatus as claimed in any preceding claim, wherein a flow path for a cooling medium is defined within the walls of the enclosure.

7. Apparatus as claimed in any preceding claim, wherein a radiant heater section is mounted at the inlet of the enclosure.

8. Apparatus as claimed in any preceding claim. wherein said conveying means comprises an endless conveyor arranged to allow the air flow to pass therethrough.

9. A method of cooling articles using apparatus as claimed in Claim 1, comprising the steps of conveying articles to be cooled through the enclosure from the inlet to the outlet, establishing air flow through the enclosure from the outlet to the inlet, the air at the outlet being cooler than the air at the inlet, such that the air flows across the enclosure from the first wall towards the second wall and thereby over the articles being conveyed.

10. Apparatus for cooling articles substantially as hereinbefore described with reference to and as illustrated in Figures 1 and 1A of the accompanying drawings.

11. Apparatus for cooling articles substantially as hereinbefore described with reference to and as illustrated in Figure 2 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. through. However, if required, conveyor means can be arranged to take the articles vertically through a vertically arranged enclosure. If the articles to be cooled are produced in batches, each batch may conveniently be arranged on a conveyor circulating in the vertical plane through a vertically arranged enclosure. In this case, each article can be circulated through the enclosure more than once before all the articles of the batch are removed from the conveyor. In all the embodiments, means could be provided to rotate and/or turn over the articles during their travel through the enclosure. It will be seen that the apparatus described above with reference to the drawings has several advantages. Firstly, using the apparatus articles can be cooled more rapidly than in ambient air, and because the cooling rate can be regulated the quality of the articles produced can be controlled. Particularly, if the articles to be cooled are of metal, the metallurgical properties thereof can be controlled. Because the control of the cooling process is strict the output is regular and fewer rejects are produced. Increased cooling rates mean that the floor area necessary for the cooling installation can be as small as possible. The reduction in area required for an installation of the invention as compared to the traditional conveyor methods using ambient air is substantial. The hot articles to be cooled are, with the apparatus of the invention, totally enclosed. There is therefore less risk of accidental injury to the workforce. In addition, as the heat from the articles with the present invention is being recuperated and used where required the apparatus reduces heat pollution from the articles. The heat recuperated from the apparatus can be reused as required. For example, the heat could be used to drive an electrical or mechanical device and systems could be developed to use the heat extracted from the articles directly to provide power for the fans of the apparatus. WHAT WE CLAIM IS:

1. Apparatus for cooling articles comprising an enclosure having first and second spaced opposite walls extending from an inlet to an outlet, conveying means for conveying articles to be cooled through the enclosure from the inlet to the outlet, a plurality of air ducts arranged along the first wall and a plurality of air ducts arranged along the second wall, each air duct opening into the enclosure, selected ones of the ducts along the second wall each communicating with a corresponding air duct along the first wall by way of a respective channel, means for establishing an air flow through the enclosure from the outlet to the inlet, the air at the outlet being cooler than the air at the inlet, arranged such that air flows from each selected duct along the second wall through the respective channel to the corresponding duct along the first wall and thence from said corresponding duct along the first wall across the enclosure towards the second wall.

12. A method of cooling articles using

apparatus as claimed in Claim 1, and substantially as hereinbefore described with reference to the accompanying drawings.