GB2127447A - A tenter frame having web inlet and outlet slots and covering elements therefor - Google Patents

Abstract

A covering device (Figure 1) for the inlet and outlet slots for the web of material in a tentering frame has at least one row of closely arranged individual covering elements (3) extending towards the web (W) above and below the web. When lateral displacement of a tenter chain guide (K) takes place, the elements (3) are deflected by means (2) on the guide (K) and can close up again behind the guide. The elements 3 are restored to their original position either by their own weight or by restoring springs. The elements may be in the form of hollow hoses or spiral springs. Also, a double or multiple row of individual elements may be provided. <IMAGE>

Description

SPECIFICATION A tenter frame having web inlet and outlet slots and covering elements therefor This invention relates to a tenter frame for a web of material, the frame having inlet and outlet slots for the web, guides for tenter chains adjustable in the direction of the width of the web, and slot covering elements.

In a tenter frame, a web of material is passed through one or more treatment chambers. It is introduced into the chambers, situated in a closed housing, through inlet slots and removed through outlet slots. During its passage through the treatment chambers, the web is held along its edges by tenter clips joined together to form an endless, moving tenter chain. The tenter chains can be displaced in the direction of the width of the material together with their chain guides so that they can be used for treating webs of different widths. The inlet and outlet slots must therefore be high enough to allow free passage of the tenter chains. The slots therefore inevitably have larger openings than is strictly necessary for the passage of the web itself.This width of opening or slot height must be maintained at least across that width of the tenter frame along which the tenter chains are displaceable between the minimum and the maximum width of material to be treated.

These large openings allows cold air to enter the treatment chambers and conversely allow hot treatment medium to escape to atmosphere.

The efficiency of the tenter frame is thereby substantially reduced and also the entry of air may have a damaging effect on the material in cases where an air-free treatment substance is needed for a particular finishing treatment of the material.

Various devices have been proposed for overcoming this disadvantage, by covering the inlet and outlet slots to a greater or lesser extent. Thus DE-AS 1,284,927 describes a device for covering an inlet or outlet slot by means of a band of ferromagnetic material which is unwound from a roll to the length required. Strips of permanent magnetic material are provided along one or both longitudinal edges of the opening of the slot to grip the required unrolled length of band along the opening. Such slot coverings are, however, not very practical, not only because the band has sharp edges liable to damage the web of material, but because of the inconvenience of unrolling and again rolling up the bands across considerable widths.

Another device with springy strips of steel is disclosed in DE-AS 1,244,699. The steel strips in this case are in the form of spiral or buffer springs fixed in position at the middle of the width of the slot. To cover the slot, the inner layers of the spiral strips are pulled out in the direction of the axis of the spiral. These telescopically stretchable inner layers of the strips may be attached to the tenter chain rails or guides which are displaceable in the direction of the width. Since the rounded portions of the spirals face the web of material, the difficuity of the sharp edges mentioned above is avoided but where there are substantial differences in the widths of the different materials, telescopic strips cause difficulties in that the spirals cannot always be prevented from bending or sagging, so that the material is still liable to be damaged.

DE-AS 1,248,002 discloses another slot covering. In this case, fixed cover sheets above and below the web in the middle of the slot extend across the minimum width of material. Rounded elements curved in the form of a tunnel and joined together to form a linked chain, are arranged above and below the web across the region of displacement of the tenter chains, i.e. between the minimum and the maximum width of material.

These elements partly overlap and can be moved further into or out of the covering region over deflecting discs according to the increase or decrease in the width of material. One end of this linked chain is connected to the inner surface of the displaceable tenter chain guide while the other end is connected to the outer surface of the chain guide by way of deflections. The individual covering elements must also be moved over the deflecting disc at the point of deflection. Although in this arrangement the individual covering units are rounded on the side facing the material, by virtue of their tunnel shape, and are therefore less liable to damage the material, there is the disadvantage that the deflections of the coverings above and below the slot opening are structurally complicated and take up much space.The arrangement is elaborate and requires considerable precision in manufacture and assembly. Further, if the material is narrow, for example, then the slot is not covered on the side of the chain tracks facing away from the material.

A slot covering in which the portions of slots situated laterally of a chain track can also be covered has been described in DE-OS 1,814,905. In this case, elastic hollow bodies, e.g.

inflatable hoses, are used for covering the inlet and outlet slots above and below the web of material, leaving between them only a narrow gap for the material. Movable displacement bodies in which the chain tracks travel are provided between the two hollow bodies. This arrangement has, however, the disadvantage that rubber hoses or rubber aprons can only be used to a limited extent because of the high temperatures which frequently prevail at their site of installation.

Further, the hollow bodies are liable to be damaged by the shifting of the displacement bodies so that covering of the slot is jeopardised.

It is an object of the present invention to avoid the disadvantages of the known slot coverings and to provide a uniform covering, which theoretically can be infinitely increased in width, to cover the inlet and outlet slots for the web of material in a tenter frame, both between the tenter chains and between each tenter chain and the corresponding lateral end of the slot opening, in other words across the entire opening, and to use simple covering elements for the purpose.

According to this invention there is provided a tenter frame for a web of material, the frame having inlet and outlet slots for the web, guides for tenter chains adjustable in the direction of the width of the web and slot covering elements, wherein, at each slot, there is disposed above and below the web at least one row of narrow individual covering elements placed close together, extending towards the web, and capable of being deflected independently of one another in or opposite to the direction of movement of the web against a restoring force, upper and lower deflecting rails for the covering elements being associated with the guides. Instead of individual rows, several rows of elements may be arranged like the bristles of a brush above and below the slot.

The individual elements may comprise flexible parts, for example spiral springs, fixed to the housing of the tenter frame. Since these parts are hollow, they may be used for carrying air, and suction or blast openings may be provided at their free ends. Since all the individual parts are identical, manufacture and stocking of the parts are simplified. These individual covering elements may be restored to their initial position by virtue of their elasticity.

According to another advantageous arrangement, the individual covering elements comprise rigid rods which are strung in a row on a shaft and can be deflected like flaps. The upper rods are restored to their original position by their own weight while the rods of the lower row may be returned by a counter-weight or by a spring.

Even where such individual elements in the form of flaps are used, only a small number of different parts is required, namely an upper and a lower flap element and a corresponding shaft, which may be an axial tube.

A feature of the invention is that a number of identical covering elements are arranged in a row at the slot opening to be deflected, for example pivoted, and these covering elements can be deflected not only by a deflecting rail when the chain track is being displaced but if required also individually, for example, if the web of material tears. The deflecting rail only keeps the covering elements open to a sufficient extent in the appropriate region to enable the chain track to move in underneath them. The elements close up again behind the track and cover the gap as far as the lateral ends of the slot opening. The construction proposed is inexpensive in manufacture and may be used for any width required. Both the spiral springs and the rodshaped or flap-like covering elements may be produced from heat-resistant steel so that heat problems do not arise.

Embodiments of the invention will now be described by way of example with reference to the drawings, in which: Figure 1 illustrates a covering for part of an inlet or outlet slot, shown partly in vertical section and viewed in the direction of transport of the web of material; Figure 2 is a cross-section of Figure 1; Figure 3 is a top plan view of the lower part of Figure 1; Figure 4 shows a modification of the lower part of Figure 2; Figure 5 is a cross-section through a slot covering with spiral springes; Figure 6 is a top plan view of the lower part of Figure 5; Figure 7 is a cross-section of a modified form of Figure 5; Figure 8 is a cross-section of another modified form of Figure 5; Figure 9 is a top plan view of Figure 8; Figure 10 is a cross-section through a covering having laminar strips; and Figure 11 is a top plan view of Figure 10.

An embodiment using covering elements in the form of pivotal flaps will first be described with reference to Figures 1 to 3. Figure 1 iiiustrates schematically a chain guide track K with a tenter clip in it. One edge of a web of material W is shown held by the clip. The tenter chain and web of material are displaced perpendicularly to the plane of the drawing, as indicated by the arrows in Figure 2 and in the top plan view of Figure 3. As shown by the dash-dot line on the chain guide track K, this part is substantially symmetrical in construction and contains not only the forwardly extending part shown in Figure 1, but also a corresponding rearwardly extending part which has been omitted for clarity. A mirror image arrangement of the track K is provided at the opposite edge of the web.

Upper and lower deflecting rails 2 are fixed, e.g.

by screws, to the top and bottom of the chain guide track K. The form of these rails 2 may be adapted to the particular requirements. In this embodiment, they are in the form of plates, with the free ends of the rails curved somewhat towards the web W, Figure 1. The end of each rail 2 is chamfered to form a guide edge and has a rounded, projecting end, Figure 3.

A respective deflecting shaft 1 extends across the whole width of the slot at the upper and lower edges of the slot opening. Identical individual covering elements 3 are mounted close together in a row on each shaft 1. The elements 3 are in this embodiment metal rods capable of pivoting like flaps about the respective shaft 1. The elements 3 are preferably rounded at their free ends facing the web W, Figure 2.

When the chain guide track K is displaced laterally, i.e. when the width of the web is to be reduced or increased, each deflecting rail 2 is displaced relatively to the row of covering elements 3. Due to the shape of the end of the deflecting rail 2, the extent to which the successive elements 3 are deflected and pivoted about the shaft 1 increases progressively along the row, Figure 2. In the end position 3', the elements 3 lie on the deflecting rail 2, so keeping the covering open for the passage of the chain guide track K.

As indicated in Figure 2, the deflecting shafts 1 may be arranged in supports 6 which form the upper and lower boundaries of the slot. In the upper row, the individual elements 3 are restored to their original position by their own weight. As shown in Figure 2, the individual elements 3 of the lower row may also be restored by gravity, e.g. by a counter-weight 4. Another method of restoring the lower row of deflected elements 3 is indicated in Figure 4, where restoring springs 5 are provided for each element 3.

Instead of providing rigid individual elements, rows of flexible individual elements may be provided. These elements may be in the form of hoses and may be hollow. This possibility is illustrated in Figures 5 to 9, where spiral spring elements 7 are fixed in the upper and lower carriers 6 which form the boundaries of the slot.

When a deflecting rail 2 encounters these spiral springs 7, they are bent from their normal position perpendicular to the web W into the deflected position 7', in which they again lie against the deflecting rail 2. The provision of individual elements in the form of flexible tubes or spiral springs 7 has the advantage that their hollow interior may be used for carrying air. Thus in Figure 5 the end of each spiral spring 7 has a rounded head with suction nozzle 9 through which treatment medium may be partly sucked in the direction of the arrows to be discharged through the hollow support 6.

Figure 6 is a top plan view of a row of such spiral springs 7 fixed in the support 6, and, for some of these springs, also shows in broken lines their positions 7' to which they have been deflected by a deflecting rail 2.

Figure 7 is similar to Figure 5 but with the upper row of spiral springs 7 somewhat shifted from the lower row of springs 7 in the direction of the displacement of the web W. Further, the free end of each spring 7 has in this case a rounded head with an obliquely directed blast nozzle 9'.

This arrangement enables part of the treatment medium in circulation to be blown in the form of a screen towards the web to prevent access of air from outside. The blast is preferably directed obliquely to the interior of the treatment chamber but may also be directed more or less straight on to the web W.

As mentioned above, a double or multiple row of flexible individual elements may be provided instead of a single row. Thus, Figures 8 and 9 show double rows of spiral springs 7 and 8 in the supports 6. As seen in Figure 9, the springs of the two rows may be staggered so that deflection of the individual elements 7 virtually does not interfere with deflection of the individual elements 8 and conversely.

Figures 10 and 11 show another embodiment of deflectible individual elements, comprising rows of laminar spring strips 10, 11 carried by the supports 6, Figure 1 0. The strips 10 of one row slightly overlap with the strips 11 of the other row, Figure 11. These strips are deflected in the same manner as the spiral springs. To protect the surface of the web from the strips 10 and 11, the strips may for example be bent over at their free ends or rounded off in some other manner.

For the sake of completeness, it should be noted that the individual covering elements may be deflected in any direction, i.e. in the direction of transport of the web or in the opposite direction.

Preferably the arrangement is such that the deflecting rails 2 cause the covering elements to be deflected towards the interior of the treatment chambers.

Claims (14)

1. A tenter frame for a web of material, the frame having inlet and outlet slots for the web, guides for tenter chains adjustable in the direction of the width of the web, and slot covering elements, wherein, at each slot, there is disposed above and below the web at least one row of narrow individual covering elements placed close together, extending towards the web, and capable of being deflected independently of one another in or opposite to the direction of movement of the web against a restoring force, upper and lower deflecting rails for the covering elements being associated with the guides.

2. A frame according to claim 1, wherein the individual elements are deflected towards the interior of the frame.

3. A frame according to claim 1 or claim 2, wherein each deflecting rail has an initial curved part and is in the form of a plate, the individual elements lying against the plate when fully deflected.

4. A frame according to any preceding claim, wherein the upper and lower rows of covering elements are staggered with respect to one another in the direction of the web.

5. A frame according to any preceding claim, wherein the covering elements each comprise a flexible member fixed in the housing of the frame.

6. A frame according to claim 5, wherein each member is a spiral spring.

7. A frame according to claim 5 or claim 6, wherein the covering elements are mounted in closed supports equipped for transport of air.

8. A frame according to any of claims 5 to 7, wherein the flexible members are hollow and have suction or blast openings at their free ends.

9. A frame according to claim 8, wherein the suction or blast openings are directed towards the interior of the frame.

10. A frame according to any preceding claim, wherein the covering elements are staggered in at least two rows like the bristles of a brush.

11. A frame according to any of claims 1 to 3, wherein the covering elements are rigid rods mounted in a row on a shaft and deflectable like flaps.

12. A frame according to claim 1 wherein the covering elements of the lower row are restored by spring movement.

13. A frame according to claim 11, wherein each covering element of the lower row has a restoring counterweight.

14. A frame according to any of claims 1 to 3, wherein overlapping spring bands in the form of strips constitute the covering elements.

1 5. A tenter frame constructed and arranged substantially as herein described and shown in the drawings.