CONVEYING APPARATUS AND METHOD

Abstract: There is disclosed a method of conveying and heat-­ treating an extrudate, which method comprises: introducing the extrudate to be conveyed and heat-­ treated onto a cushion of gas which gas is at or above a predetermined temperature; causing the extrudate to be conveyed on the cushion of gas; and removing the conveyed and heat-treated article from the cushion of gas. Also disclosed is an apparatus for manufacturing a heat-treated extrudate comprising: (i) an extruder which includes an outlet from which the untreated extrudate is extruded; and (ii) conveying and heat-treating means for conveying and heating the untreated extrudate, said conveying and heating means comprising: an elongate conveyor means (1) communicating with the outlet of the extruder and including, along at least a portion of its length, a plurality of spaced-­ apart outlets (10, 11) through which a gas at or above a predetermined temperature is passed under pressure thereby to create a cushion of moving gas to convey and heat-treat the extrudate.

Description: This invention relates to a method of conveying and heating an extrudate on a moving cushion of gas, and is more particularly, although not exclusively, concerned with a method of conveying and heat-treating (for instance, to cure) a synthetic extrudate using a hot air cushion conveyor means. In a conventional system for the manufacture of extruded weatherstrips for motor vehicles, the formed extrudate emerges from the extruder die at a relatively high temperature (approximately 160°C) and is then subjected to a curing or drying process in an oven; the extrudate is conveyed through the oven by a conventional belt conveyor. In this technique, the external surface of the extrudate necessarily rests on the belt of the conveyor. As the surface of the extrudate will be hot and soft, the surface may become marked by this contact with the belt of the conveyor. Should the part of the surface which becomes marked be an area of the extrudate which will be visible when the strip is in position on a motor vehicle, the aesthetic appearance of the vehicle will be decreased somewhat. This so-called "sight face" marking of an extrudate is a continuing and serious problem in the production of extruded weatherstrips for motor vehicles. According to a first aspect of the present invention, there is provided a method of conveying and heat-treating an extrudate, which method comprises: introducing the extrudate to be conveyed and heat-­ treated onto a cushion of gas which gas is at or above a predetermined temperature; causing the extrudate to be conveyed on the cushion of gas; and removing the conveyed and heat-treated extrudate from the cushion of gas. According to a second aspect of the present invention, there is provided a method of conveying and curing an extrudate, which method comprises: providing an elongate conveyor means which includes, along at least a portion of its length, a plurality of spaced apart outlets through which air or other gas at or above a temperature sufficient to cure, set or otherwise dry the extrudate is passed under pressure thereby to create, above the outlets, a cushion of moving air or other gas; introducing the extrudate to be conveyed and cured onto an upstream region of the cushion of moving air or other gas; permitting the extrudate to be conveyed on the cushion of moving air or other gas and to be cured by the air or other gas; and removing the cured extrudate from the conveyor means. According to a third aspect of the present invention, there is provided an apparatus for manufacturing a heat-treated extrudate comprising: (i) an extruder which includes an outlet from which an untreated extrudate is extruded; and (ii) combined conveying and heat-treating means for conveying and heat-treating the untreated extrudate, said conveying and heat-treating means comprising: an elongate conveyor means communicating with the outlet of the extruder and including, along at least a portion of its length, a plurality of spaced-apart outlets through which a gas at or above a predetermined temperature may be passed under pressure thereby to create a cushion of moving gas to convey and heat-­ treat the extrudate; means for providing said gas at the predetermined temperature for heat-treating said extrudate, which provision means communicates with the outlets of the conveyor means; and means, situated at an upstream region of the conveyor means, for introducing the extrudate onto the cushion of moving gas. According to a fourth aspect of the present invention, there is provided an apparatus for manufacturing a heat-treated extrudate comprising: (i) an extruder which includes an outlet from which the untreated extrudate is extruded; and (ii) combined conveying and curing means for conveying and curing the untreated extrudate, said combined conveying and heat-treating means comprising: a conveyor means communicating with the outlet of the extruder and defining an elongate insulated chamber opening into which is a plurality of nozzles through which air or other gas at or above a temperature sufficient to cure, set or otherwise dry the extrudate amy be passed under pressure to create a cushion of moving gas in the chamber to convey the extrudate from a first region of the conveyor means to a second, downstream region of the conveyor means; heater means for providing said hot air or other gas, the heater means communicating with the nozzles of the conveyor means; and means, situated at the upstream end of the conveyor means, for introducing the extrudate onto the cushion of moving hot air or other gas. Heat treatment of the untreated extrudate renders the soft extrudate resistant to deformation. The heat treatment may cure the extrudate by physical modification, may cause the extrudate to set or may simply dry the extrudate. The method and apparatus of the present invention enable an extrudate, to be transported and simultaneously cured without causing "sight face" marking of the extrudate since the extrudate is supported by a cushion of a heated gas, preferably hot air, during its curing stage. The predetermined temperature of the gas may be sufficient to cure, set or otherwise dry the extrudate. Preferably, the gas will be air at a temperature above 100°C, more preferably above 200°C. Hereinafter, references to "air" should not be limited to air but should be construed as covering alternative gases. The cushion of hot air may be created by the provision of a series of spaced-apart nozzles, each nozzle being fed by pressurised hot air from a plenum chamber. Although each nozzle may be fed from the same chamber, it may be advantageous to feed each individual nozzle, or a series of nozzles, from a separate chamber so that the air pressure at each nozzle or set of nozzles can be individually adjusted. To this end, flow regulators may be positioned in the lines feeding the separate chambers. The nozzles may be directed to provide lift only, in which case the nozzles will be perpendicular to the direction of travel of an extrudate through the conveyor means. However, the nozzles may be angled to the direction of travel, the angled nozzles providing both lift and thrust in a direction to impart longitudinal movement to the extrudate. It is to be appreciated that the provision of angled nozzles is not essential since the extrudate will tend to be pushed through the conveyor means by the action of being forced out of the extruder die, the extrudate being supported by cushion of air created by the nozzles. The nozzles may be independently controllable, for example by a microprocessor, in order accurately to hold the extrudate in a particular disposition. In addition, other stations may be provided to treat the extrudate before it has been removed from the chamber. For example, flocking may be applied even as the extrudate is being cured. It is envisaged that the whole arrangement could be controlled by microprocessors. Thus, sensors, adapted to sense the position and orientation of the extrudate could be disposed in the chamber to yield signals to control a microprocessor which then adjusts the nozzles in order to alter the disposition of the extrudate. Temperature sensors to monitor and to be used in the adjustment of the temperature of the hot air could also be provided. There are, therefore, a number of variables which can be altered to control the movement of the extrudate through the conveyor means. Thus, the air flow, air pressure, and pattern and size of the nozzles may be varied to give differing degrees of lift and thrust and varying speeds of transportation through the conveyor means. The cushion of air is preferably enclosed within an insulated chamber by a roof. The top of the plenum chamber, in which the nozzles may be seated, may be shaped so as to guide the product in the correct orientation through the conveyor means. Thus, by the provision of, for examples, grooves in the top of the plenum chamber, an air flow may be created which assists in guiding and orientating the product. The hot air, once it has passed through the system, is collected and re-circulated back to the input side of the system. To maintain an even and constant temperature inside the chamber or tunnel, regardless of the flow of air through the nozzles, a variable quantity of hot air may be re-directed to by-pass the chamber or chambers supplying the nozzles and, instead, to flow through the tunnel with the extrudate. The quantity, pressure and temperature of the by-pass air can be manually or automatically varied as required. For a better understanding of the present invention and to show how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which : Figure 1 shows a schematic view of a conveying/heating means useful in the apparatus of the present invention; and Figure 2 shows a cross-section on the line II-II of Figure 1. In Figure 1 an enclosed conveyor 1 is sub-divided into an upper chamber or tunnel 2 and a lower or plenum chamber 3. The plenum chamber 3 is defined by an insulated base portion 4 and a roof 5. The lower part of the tunnel 2 is defined by the roof 5 of the plenum chamber 3 and an upper part by an insulated cover 6. The upstream end 12 of the conveyor communicates with the outlet of an extruding machine (not shown). The base portion 4 of the plenum chamber is provided with an inlet 7 through which hot pressurised air is introduced into the plenum chamber 3. The tunnel 2 is provided with an inlet 8 for pressurised hot air to be introduced into the tunnel 2 and an outlet 9 through which exhaust air is removed from the tunnel 2. The plenum chamber 3 is, in the illustrated embodiment, a single chamber communicating with a plurality of outlets or nozzles 10, 11. However, the single plenum chamber 3 may be sub-divided into a number of separate plenum chambers each having a pressurised hot air supply and each having its own set of nozzles. The pressurised hot air is delivered through the nozzles 10, 11 to provide a cushion of hot air on which an extrudate is transported from one end 12 of the tunnel to the other end 13 of the tunnel. The nozzles 10, 11 are of two separate types, namely, firstly, a nozzle 11 which is perpendicular to the direction of travel of an extrudate through the tunnel 2 and, secondly, a nozzle 10 which is angled with respect to the direction of travel of an extrudate through the tunnel 2. The perpendicular nozzle 11 provides lift whereas the angled nozzle 10 provides both lift and thrust in a particular direction, as indicated by the arrows. The individual nozzles 10, 11 may be controlled so as to adjust the rate of air flow through the nozzles and hence the degree of lift and thrust to an extrudate moving through the tunnel 2. The nozzles may be controlled by a microprocessor (not shown) which is, in turn, controlled by signals from one or more sensing means (not shown) which sense the disposition of an extrudate in the tunnel 2. Pressurised hot air for the plenum chamber 3 is delivered through the inlet 7. In addition, pressurised hot air is delivered through the inlet 8 in the tunnel to maintain an even and constant temperature inside the tunnel, regardless of the flow of hot air through the nozzles. The relative rates of flow through the inlet 7, 8 may be controlled by flow regulators 12. Exhaust hot air is removed from the tunnel via the exhaust outlet 9. The exhaust hot air may be collected and recirculated back to the input side of the system. In addition, fumes may be vented from the exhaust as indicated by reference numeral 14. The hot air, in addition to providing lift to support an extrudate moving through the tunnel also serves to cure, dry or otherwise heat-treat the extrudate. The apparatus avoids the necessity for the extrudate to make contact with the conveyor and hence avoids the formation of "sight face" marking on critical areas of the extrudate. In Figure 2, the disposition of nozzles fed from the plenum chamber is shown. The square nozzles 10 are angled to provide lift and thrust whilst the round nozzles 11 provide lift. In one embodiment (not illustrated) of the present invention, a single square nozzle 10 and a block of five adjacent round nozzles 11 may be fed from a single plenum chamber although it is to be appreciated that any pattern of nozzles could be fed from a single plenum chamber. Although it has been mentioned above that an extrudate is pushed through the conveyor means on the cushion of air, it is to be appreciated that the article to be conveyed and heated could be pulled or wound through the tunnel.

Claims: 1. A method of conveying and heat-treating an extrudate, which method comprises: introducing the extrudate to be conveyed and heat-treated onto a cushion of gas which gas is at or above a predetermined temperature; causing the extrudate to be conveyed on the cushion of gas; and removing the conveyed and heat-­ treated article from the cushion of gas. 2. A method of conveying and curing an extrudate, which method comprises: providing an elongate conveyor means which includes, along at least a portion of its length, a plurality of spaced apart outlets through which air or other gas at or above a predetermined temperature sufficient to cure, set or otherwise dry the extrudate is passed under pressure thereby to create, above the outlets, a cushion of moving air or other gas; introducing the extrudate to be conveyed and cured onto an upstream region of the cushion of moving air or other gas; permitting the extrudate to be conveyed on the cushion of moving air or other gas and to be cured by the air or other gas; and removing the cured extrudate from the conveyor means. 3. A method according to Claim 1 or 2, wherein the predetermined temperature of the gas is sufficient to cure, set or otherwise dry the extrudate. 4. A method according to Claim 3, wherein the predetermined temperature is 100°C. 5. A method according to Claim 3, wherein the predetermined temperature is 200°C. 6. A method according to any preceeding claim, wherein the gas is air. 7. A method according to any preceeding claim, wherein the cushion of hot gas is created by the provision of a series of spaced-apart nozzles each fed by pressurised hot gas from a plenum chamber. 8. A method according to Claim 7, wherein each individual nozzle, or series of nozzles, is fed from a separate chamber such that the air pressure at each nozzle, or set of nozzles, can be individually adjusted. 9. A method according to Claim 7 or 8, in which a proportion of the nozzles are perpendicular to the direction of travel of an extrudate through the conveyor means, thereby to provide lift to the extrudate. 10. A method according to any one of Claims 7 to 9, wherein a proportion of the nozzles are angled to the direction of travel thereby to provide both thrust in the direction of travel and lift to the extrudate. 11. A method according to anyone of Claims 7 to 10, wherein the volume and pressure of the gas fed to the nozzles is independently controllable by a microprocessor means. 12. An apparatus for manufacturing a heat-treated extrudate comprising: (i) an extruder which includes an outlet from which an untreated extrudate is extruded; and (ii) conveying and heat-treating means for conveying and heating the untreated extrudate, said conveying and heat-trating means comprising: an elongate conveyor means communicating with the outlet of the extruder and including, along at least a portion of its length, a plurality of spaced-apart outlets through which a gas at or above a predetermined temperature may be passed under pressure thereby to create a cushion of moving gas to convey and heat-treat the extrudate; means for providing said gas at the predetermined temperature for heat-treating said extrudate, which provision means communicates with the outlets of the conveyor means; and means, situated at an upstream region of the conveyor means, for introducing the extrudate onto the cushion of moving gas. 13. An apparatus for manufacturing a heat-treated extrudate comprising: (i) an extruder which includes an outlet from which the untreated extrudate is extruded: and (ii) conveying and curing means for conveying and curing the untreated extrudate, said combined conveying and heat-­ treating means comprising: a conveyor means communicating with the outlet of the extruder and defining an elongate insulated chamber opening into which is a plurality of nozzles through which hot air or other gas at or above a temperature sufficient to cure, set or otherwise dry the extrudate may be passed under pressure to create a cushion of moving gas in the chamber to convey the extrudate from a first region of the conveyor means to a second, downstream region of the conveyor means; heater means for providing said hot air or other gas, the heater means communicating with the nozzles of the conveyor means; and means, situated at the upstream end of the conveyor means, for introducing the extrudate onto the cushion of moving hot air or other gas. 14. An apparatus according to Claim 13, wherein each individual nozzle, or series of nozzles, is fed by pressurised hot air from a separate chamber such that the air pressure at the nozzle, or series of nozzles, can be individually adjusted. 15. An apparatus according to Claim 13 or 14, wherein a proportion of the nozzles are perpendicular to the direction of travel of the extrudate through the conveyor means to provide lift to the extrudate. 16. An apparatus according to Claim 13, 14 or 15, wherein a proportion of the nozzles are angled to the direction of travel to provide both thrust in the direction of travel and lift to the extrudate. 17. An apparatus according to any one of Claims 13 to 16, further including a microprocessor means for independently controlling the volume and pressure of gas fed to each outlet or nozzle.

Inventors: DREW, RAYMOND THOMAS
Applicants: SILENT CHANNEL PRODUCTS LIMITED
Application year: 1987
Main classification: B29C47
IPC codes: B29C47, B29C71, B29C35, B29C31