Method of continuously heat treating articles and apparatus...

Plastic and nonmetallic article shaping or treating: processes – Treating shaped or solid article – By a temperature change

Utility Patent

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Details

C028S219000, C028S247000, C028S273000, C034S448000, C034S451000, C034S459000, C034S629000, C034S632000, C034S636000, C068S00500D, C425S445000

Utility Patent

active

06168743

ABSTRACT:

TECHNICAL FIELD
The present invention relates generally to a method of continuously heat-treating articles of manufacture. In a preferred embodiment, polyethylene terephthalate fiber is treated with saturated steam at elevated pressures. In another aspect, the invention is directed to a self-sealing pressure apparatus for continuously heat-treating articles with saturated vapor.
BACKGROUND
Heat treatment by way of high pressure vapor application is known in the art. In particular, annealing polyester filaments is described in U.S. Pat. Nos. 4,704,329 and 4,639,347 of Hancock et al. by utilizing saturated steam. See, also related European Patent No. 0 125 112 which contains substantially the same disclosure. U.S. Pat. No. 5,287,606 to Ruef describes an apparatus for steam-treating textile filaments, which apparatus includes a plurality of chambers. As can be seen from FIG. 1 of the '606 patent the upstream and downstream serially arranged chambers serve to maintain pressure in the treatment chamber. Note column 7, lines 25-31.
Yet another steam treatment device is described in German Patent Specification DE 195 46 783 C1, in most detail in connection with FIG. 4 thereof. The device disclosed in the '783 document includes an expansion nozzle feeding a treatment channel wherein the steam accelerates to supersonic speed. The steam decelerates to subsonic speed in the treatment chamber before encountering a second nozzle which again accelerates the steam to supersonic velocity.
Another method for steam-treating polyester fibers is disclosed in U.S. Pat. No. 3,452,132 to Pitzl, wherein a method of heat-treating polyethylene terephthalate yarn by applying a steam jet thereto is described.
There is provided in accordance with the present invention an improved method of heat-treating articles with saturated vapor as described below.
SUMMARY OF THE INVENTION
In a first aspect, the present invention is directed to a method of heat-treating an article of manufacture including supplying a heated vapor medium at elevated pressure to a vapor expansion chamber through a first nozzle. The nozzle cooperates with the expansion chamber to generate a high velocity flow and establishes regions of reduced pressure therein. The article is continuously fed to the expansion chamber through a feed orifice located within one of the established regions of low pressure. The article is then conveyed through a sonic shock region to a treatment chamber, the shock region being operative to isolate the pressure of said treatment chamber from the expansion chamber.
Most preferably, the high velocity flow generated in the expansion chamber is a supersonic flow and the feed orifice is defined by a conduit, the orifice being at about the point of minimum pressure in the expansion chamber. The conduit typically defines an entrance external to the expansion chamber.
In a cascaded process to stepwise control the pressure in the treatment chamber, a further step is to provide a heated vapor medium through a second nozzle to the treatment chamber.
The inventive method is suitable for treating a variety of articles. Discrete articles such as pellets may be continuously fed by way of a suitable conveyor. Most typically, the process is applied to continuous shaped articles fed from a roll or equivalent; such as films, fibers, fiber tow, ropes, fabrics and yarns. In most cases, polymeric articles are treated, such as shaped articles of polyethylene terephthalate. The heated vapor medium is typically steam and the process is operated so that the steam is saturated steam in the treatment chamber. The steam may be superheated or saturated as fed to the first nozzle.
Typically, the heated vapor medium exits the treatment chamber through a third nozzle.
In an alternate embodiment of this inventive process, the articles may be fed through a sonic shock region to a region of low pressure generated by the heated vapor medium to a low pressure treatment region. Generally, this process is practiced with the same or similar equipment and includes supplying a heated vapor medium at elevated pressure through a first nozzle into an expansion chamber to establish a region of low pressure, venting the vapor medium through a second nozzle operative to create a sonic shock region which isolates the downstream pressure from the pressure in the expansion chamber and continuously feeding the article to be treated through the sonic shock region, to the low pressure region in the expansion chamber and into a low pressure treatment chamber.
In a further aspect, the present invention is directed to an apparatus for vapor treating articles of manufacture. The apparatus includes a means for providing a supply of a heated vapor medium at elevated pressure, a vapor expansion chamber and a first nozzle coupling the two. The first nozzle is capable of cooperating with the expansion chamber to generate a high velocity flow of the vapor medium, which, in turn establishes low pressure regions within the expansion chamber. The articles to be vapor treated are introduced into a low pressure region within the expansion chamber through a feed orifice.
The vapor expansion chamber is coupled to a treatment chamber through a second nozzle operative to maintain a sonic shock which isolates the pressure in the expansion chamber from the pressure in the treatment chamber.
Preferably, the apparatus further includes a feed conduit with a port positioned at about the point of minimum pressure in the expansion chamber and a second port external to the expansion chamber. So also, the high velocity flow in the expansion chamber is preferably a supersonic flow.
The second nozzle may also be coupled to a source of heated vapor medium at elevated pressure if it is desired to stepwise control the pressure of the system.
The apparatus in accordance with the invention is advantageously fitted with a downstream sealing device including a third nozzle, a sump coupled to the treatment chamber by way of the third nozzle and exit ports within the sump. The sump is maintained at about atmospheric pressure by means of exhaust channels which divert the flow to a waste or recycle region. The channels are large enough to maintain the flow without a large pressure drop. The exhaust flow rate is limited by the third nozzle, which chokes the flow to make it independent of the sump pressure.
The apparatus is preferably formed of stainless steel, a performance alloy or other wear resistant, non-corroding material.
In a still further aspect of the invention, there is provided a multi-stage apparatus for cascading the pressure used to vapor treat shaped articles. Such apparatus includes: (a) means for supplying a first supply of a heated vapor medium at elevated pressure; (b) a first vapor expansion chamber; (c) a first nozzle coupling the means for supplying the first supply of heated vapor medium with the first expansion chamber, first nozzle being capable of cooperating with said first expansion chamber to generate a supersonic flow of vapor medium in the first expansion chamber and generate a pressure minimum within the chamber; (d) a first feed orifice positioned, configured and dimensioned to introduce articles of manufacture into the first expansion chamber at a zone of reduced pressure; (e) means for supplying a second supply of a heated vapor medium at elevated pressure; (f) a second vapor expansion chamber; (g) a second nozzle coupling the second supply of heated vapor medium with the second vapor expansion chamber, the second nozzle being capable of cooperating with the second expansion chamber to generate a supersonic flow of vapor medium within the second vapor expansion chamber and generate a pressure minimum within the second chamber; (h) a second feed orifice positioned, configured and dimensioned to introduce articles of manufacture into the second expansion chamber at a zone of reduced pressure; (i) a third means for supplying a heated vapor medium at an elevated pressure; (j) a treatment chamber; (k) a third nozzle coupling the third means for supplying heated vapor

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