Refrigeration – Liquid contacting discrete commodity – With article conveyer or transporter
Reexamination Certificate
1999-05-26
2001-04-17
Doerrler, William (Department: 3744)
Refrigeration
Liquid contacting discrete commodity
With article conveyer or transporter
C062S380000, C266S114000, C072S342200
Reexamination Certificate
active
06216485
ABSTRACT:
The invention relates to a device for cooling extruded profiles or sections on leaving an extruder, the device including slotted nozzles arranged above, below and for high extruded profiles also on the side of the extruded profiles for jetting it with air as well as water nozzles arranged likewise above, below and on the side of the extruded profiles for impinging it with water, it being optionally possible with this device to employ air or water for cooling.
Extruded profiles or sections need to be cooled on leaving the die. This is necessary in the case of sections of light metal alloy for material-technical reasons to attain the desired strength values and metallurgical properties in the finished-cooled extruded profile. In the case of AlMgSi alloys the necessary cooling rates are achievable only with intensive water impingement of the surface of the profile where greater wall thicknesses are concerned. Where a lesser wall thickness is concerned, however, the quenching effect with water cooling is so strong that distortion occurs in the finish-cooled profile which, if at all, can only be compensated by complicated straightening techniques and heavy strain on the profile which when associated with yielding involves a disadvantageous change in the metallurgical properties.
Known from EP 0 541 630 is a device for cooling extruded profiles in which slotted air nozzles are arranged only above and below the section. This device has the disadvantage that when profiles having a considerable overall height are extruded the side surface areas fail to be sufficiently jetted and as a result the cooling fails to be consistent over the full periphery of such profiles. By the teaching of the aforementioned patent the heat transfer may be varied over the width of the profile by adjustment elements provided in the nozzle body. This is a disadvantage since these adjustment elements are arranged in a relatively large flow cross-section, namely the inflow cross-section to the banks of nozzles and accordingly the free through-flow cross-section needs to be reduced to a relatively highly restricted cross-section to achieve any appreciable change in the heat transfer at all.
In addition, the adjustment means as taught by the aforementioned patent is relatively complicated since it needs to cover the complete area of the nozzle area. Likewise in accordance with the teaching of this patent water nozzles are arranged in the air nozzles. These water nozzles can only be operated appropriately when at the same time air jetting is activated. This has the big disadvantage that a high flow of air is charged with water and consequently involving considerable complications in ensuring that the water droplets contained in the air stream are subsequently removed therefrom.
Another disadvantage is that the water nozzles can be operated only with relatively small water impingement densities since otherwise the air flow is no longer able to affect the necessary uniformity in water impingement. However, for cooling extruded portions of medium to large wall thickness water impingement densities of 500 liters (m
2
min) to 1,000 liters (m
2
min) are needed, these being values which are far from achievable by the known device. Yet another, deciding drawback is that the water nozzles in accordance with the teaching of this patent are arranged parallel to the slotted nozzles, i.e. only one row of nozzles oriented transversely to the direction of extrusion may be shut off as a whole or changed in pressure at any one time. For adapting the cooling effect to the distribution of the masses and wall thicknesses in the section as necessary such a device is not suitable.
The object of the present invention is to get around the disadvantages as cited above. This object is achieved by the characterizing features as they read from claim
1
, the sub-claims defining preferred embodiments of the invention.
More particularly, the present invention proposes an apparatus for cooling extruded profiles which is particularly suitable for extruded profiles of light metal alloys and which permits the necessary high cooling rates for both low and high profile wall thicknesses by cooling profiles of low wall thickness only with air and profiles of high wall thickness only with water, whilst nevertheless practically excluding any bending or distortion of the profiles during cooling since both air cooling and water cooling can be adapted to the wall thickness and mass distribution of the profile.
One major advantage as compared to other devices for cooling extruded profiles is also that this novel apparatus covers the complete range of the heat transfer from air cooling to harsh water cooling. For extruded profiles of light metal alloys this range corresponds to a scope of the mean heat transfer coefficient of approx. 100 W/(m
2
K) to approx. 6,000 W/(m
2
K) for the temperature range of approx. 500° C. to approx. 250° C. which is important metallurgically, i.e. a range of roughly 1 to 60. In this arrangement cooling is done with air in the range of 100 W/(m
2
K) to approx. 300 W/(m
2
K), and with water when even higher. Since in the cited temperature range for light metal alloys water cooling takes place above the so-called Leidenfrost temperature, heat transfer depends substantially on the water impingement density. The apparatus in accordance with the invention thus excels by the fact that the water impingement density can be varied in the necessary scope without altering the uniformity of the water impingement to disadvantage.
REFERENCES:
patent: 3997376 (1976-12-01), Hemsath et al.
patent: 4407487 (1983-10-01), Wang
patent: 4611789 (1986-09-01), Ackert et al.
patent: 5327763 (1994-07-01), Kramer et al.
patent: 5413314 (1995-05-01), Plata et al.
patent: 5458485 (1995-10-01), Righetti
patent: 5595632 (1997-01-01), Macierewicz
patent: 15 83 418 (1972-01-01), None
patent: 195 00 019 (1996-07-01), None
patent: 88 10 085 U (1998-10-01), None
patent: 0 541 630 (1993-05-01), None
patent: 0 578 607 (1994-01-01), None
Becker Markus
Kramer Carl
Doerrler William
Ingenieurgemeinschaft Wsp Prof. Dr. Ing. Carl Kramer, Prof. H.J.
Renner , Otto, Boisselle & Sklar, LLP
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