GB2235754A

GB2235754A - Web drying machine

Info

Publication number: GB2235754A
Application number: GB8917834A
Authority: GB
Inventors: John Milton Evans
Original assignee: THERMATEK INTERNATIONAL LIMITE
Current assignee: THERMATEK INTERNATIONAL LIMITE
Priority date: 1989-08-04
Filing date: 1989-08-04
Publication date: 1991-03-13
Also published as: GB8917834D0

Abstract

A machine for drying or other heat treatment of a continuous web of an air permeable material comprising upper and lower conveying belts (11, 17) between which the web (14) is caused to travel, with a source of heated air disposed above the upper conveying belt whereby the heated air impinges upon and passes through the web (14). The heated air source (22, 23) is adjustable on a framework (10, 26) such that, together with belt (11) it converges progressively towards lower belt (17) whereby, as the material reduces in height and increases in density throughout the machine. the air source from plenum chamber (22) is maintained at a substantially uniform distance from the web of material. <IMAGE>

Description

A DRYING MACHINE THIS INVENTION concerns a machine for drying or other heat treatment of a continuous web of an air permeable material.

In the production of non-woven textiles, certain waddings are formed by a process of carding fibres and layering them at random upon a conveying system. The fibres themselves are non-cohesive and so various methods have been adopted to produce a cohesive web of predetermined thickness. To this end the present invention is concerned with methods which require heat setting of the material in process and in particular thermal or spray bonding systems. To produce cohesion in this manner it is necessary either to mix melt or thermal fibres with the main fibrous material, or alternatively to spray resins upon the wadding surfaces. The conveyor then transports the material through a thermal or spray bonding dryer which either melts the fibres to give cohesion or alternatively cures the resin, as the case may be.

Such a dryer operates on the principle of directing heated air at controlled temperatures onto the wadding for a predetermined period as the web of material passes through the machine. The air may be directed through the material from one side or alternatively may impinge upon one or both surfaces of the web particularly in the case of resin bonding.

During passage through a dryer of this kind the wadding reduces in height and increases in density such that the heated air has a progressively greater distance to travel to impinge upon and, if appropriate pass through the wadding. Therefore, the heat transfer becomes increasingly inefficient as the material advances through the machine with the result that, conventionally, either the residence time of the material within the machine must be increased to compensate for this inefficiency, or alternatively increased air velocities and volumes must be employed involving larger systems and increased running costs.

An object of the present invention is to provide a drying machine in which the reduction in height and increasing density of the material as it travels through the machine, is compensated for in the supply of heated air.

According to the present invention there is provided a machine for drying or other heat treatment of a continuous web of an air permeable material, comprising a conveyor for carrying the web of material through the machine between inlet and outlet ends thereof and a heated air source for directing a stream of heated air towards at least one face of the web during passage through the machine; characterised in that the heated air source is adjustable in position with respect to the web such that there is maintained a substantially uniform distance between the heated air source and the adjacent surface of the web as the latter progressively reduces in thickness whilst advancing through the machine.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a side elevation of a drying machine made in accordance with the invention in a first operative position; and Fig. 2 is a view similar to Fig. 1 with parts thereof manipulated to perform a predetermined function in accordance with the invention.

Referring now to the drawings, there is illustrated schematically a machine framework 10 carrying a number of rollers supporting an upper endless conveying band 11 having an operative conveying run between inlet roller 12 and outlet roller 13. In Fig. 1 a web of wadding 14 is shown moving progressively through the machine, and it can be seen that the web is initially reduced in height between roller 12 and a further roller 16 at the same level as outlet roller 13.

The web is supported during its passage through the machine on a lower conveyor 17 supported between rollers 18 and 19.

Heated air is fed by a fan (not shown) to a manifold chamber 20 from which it passes through a plurality of spaced vertical ducts 21 to a plenum chamber 22 from which extend transversely across the machine a plurality of air distribution fingers 23 having their outlets directed downwardly onto the web 14, 15. The heated air stream passing through the web is collected via exhaust ducts 24 and 25.

As can be seen from Fig. 2, and in accordance with the invention the assembly consisting of the plenum chamber 22, fingers 23 and roller 13, is pivotally mounted about the axis of roller 16 such that the downstream end of the assembly may be at a lower level than the upstream end thereof. Preferably, the assembly is mounted on a platform 26 for this purpose, and a jacking screw 27 is provided to raise and lower the right-hand end of the platform with respect to the left-hand end thereof as seen in the drawings. The vertical ducts 21 are equipped with expanding connectors 28, for this purpose. Furthermore, a weight roller 29 maintains the conveyor belt 11 taut for all positions of the platform 26.

In operation, the wadding tends to loose its loft or thickness and increases its density with the effect of the heat as it progresses through the machine so that in practice it assumes a wedge-like configuration as illustrated at 30 in Fig. 2. In order to maintain a substantially uniform distance between the air supply issuing from fingers 23 and the upper surface of the material being processed, it is therefore appropriate to incline the plenum chamber 22 downwardly as provided by the mechanism described. Furthermore, the reducing height of the bottom run of conveyor 11 serves to press down upon the top surface of the web as it travels through the machine to assist in achieving the correct finished loft and material density.

It is not intended to limit the invention to the above example only. For example, the plenum chamber 22 may be maintained in a horizontal attitude, and bottom conveyor 17 may be progressively raised towards it thus to lift the reducing web progressively to maintain the uniform distance between its upper surface and the heated air source. For this purpose, jacking screw 27 and platform 26 will be replaced by equivalent means for raising roller 19, with the addition, if necessary of further support rollers along the conveying run of the belt 17.

Furthermore, the air distribution fingers 23 may be arranged longitudinally of the machine or there may be a bank of individual nozzles arranged in rows thus to apply a substantially uniform air stream across the entire surface of the web.

The jacking screw or other mechanism provided for the purpose described may be motor driven and selectable in height by the operator. Alternatively, automatic sensing means may be provided for detecting the thickness of the woven material at a certain position through the machine and for feeding a signal accordingly to the height adjustment means.

In a further arrangement the machine may consist of two zones one of which is maintained at a fixed height much as illustrated in Fig. 1 and followed by a further zone as Fig. 2 with the progressive closing of the air stream towards the web.

The height of roller 16 adjacent the upstream end of plenum chamber 22 may itself be adjustable to preset the input loft of the material according to the particular type and density of the material being processed.

Claims

1. A machine for drying or other heat treatment of a continuous web of an air permeable material, comprising a conveyor for carrying the web of material through the machine between inlet and outlet ends thereof and a heated air source for directing a stream of heated air towards at least one face of the web during passage through the machine; characterised in that the relative positions of the heated air source and the web are adjustable in such a manner that there is maintained a substantially uniform distance between the heated air source and the adjacent surface of the web as the latter progressively reduces in thickness whilst advancing through the machine.

2. A machine according to Claim 1, in which said conveyor comprises respectively upper and lower endless conveying belts between which the web of material is transported through the machine, at least one of said belts providing a conveying surface which converges towards the other belt progressively between inlet and outlet ends of the machine.

3. A machine according to Claim 2, wherein said upper conveying belt is supported on a number of rollers carried on a framework which further carries the heated air source in the form of a plenum chamber having a plurality of air nozzles extending across the conveying belt to direct a stream of heated air onto the web of material passing therebeneath.

4. A machine according to Claim 3, wherein said air nozzles are comprised by a plurality of air distribution fingers extending transversely across the machine from said plenum chamber, there being a pair of exhaust ducts positioned beneath the lower conveying belt for collecting the air after passage through the web of material.

5. A machine according to Claim 3, wherein said machine framework is pivotally supported at an inlet end in respect of the direction of travel through the machine of the web of material, therebeing means adjacent an outlet end thereof for causing the latter to descend with respect to the pivoted end of the framework thus to move the outlet end thereof and the upper conveying belt thereat downwardly towards the lower conveying belt.

6. A machine according to Claim 5, wherein said descending means comprises a jacking screw.

7. A machine according to Claim 6, wherein said jacking screw is motor driven and selectable in height by the operator.

8. A machine according to Claim 1, further including automatic sensing means for detecting the thickness of the web of material at a certain position through the machine and for providing an operating signal for the position adjusting means.

9. A machine according to Claim 2, wherein the lower conveying belt may be raised at an outlet end thereof to be inclined upwardly towards the upper conveying belt progressively throughout the machine.

10. A machine according to Claim 1, consisting of two zones in a first of which said relative positions are fixed and followed by a further zone with progressive closing of the heated air source towards the web.

11. A machine for drying or other heat treatment of a continuous web of an air permeable material, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.