GB2094872A - Drum for roller shutter door - Google Patents

Abstract

A roller shutter door assembly has an end disc for a roller drum of the kind which in use rotates about a horizontal axis 14 to be enwrapped by a horizontal corrugated sheet 13, the curved surface of the end disc being corrugated; the mounds of a first plurality of adjacent corrugations (A-B) each projecting substantially to a first radial distance from the said axis, and the mounds of a second plurality of adjacent corrugations 12 each extending to beyond the first radial distance. <IMAGE>

Description

SPECIFICATION Drum for rolling door The present invention relates to rolling doors of the type having a curtain or door apron which slides vertically between opposed guides as the curtain winds on or off a horizontal drum located above the door aperture.

For reasons of strength, weight and economy, the door curtain is generally corrugated horizontally and this provides particular problems for the successful operation of the door.

The horizontally mounted drum which supports the curtain is generally defined by a spaced pair of parallel end discs mounted for rotation about a stationary horizontal axle. Each disc is provided around its circumferential rim with a plurality of axially extending corrugations for engagement with the first layer of the door curtain as it winds onto the drum. It will be appreciated that as the curtain winds progressively further onto the drum, the geometry of the resultant curtain spiral becomes complex.

It is also customary to employ a counterbalance spring for applying an opposing torque to the drum in order to balance the weight of the curtain.

The spring is tensioned to its maximum extent when the curtain is fully unwound, with the door in its closed position. This would be expected since an operator would otherwise be required to lift the maximum weight of the curtain in order to move the door. Similarly, the counterbalance spring provides a minimum torque reaction when the door is fully open and the curtain wound to its maximum extent on the drum.

Unfortunately, the behaviour of the curtain, in terms of its interaction with the drum, is by no means linear and it has been found empirically that the counterbalancing of the curtain is not uniform and satisfactory throughout its limits of movement.

It is found, for example, that if the counterbalancing is adjusted for acceptable operation in the middle to upper range of door movement, the door tends to lift from the floor in its fully closed position.

The solid line in Figure 1 graphically illustrates the external tractive force required to operate a known door at different heights from floor level to the fully elevated position. It will be observed that the characteristics of the curves are not linear.

Reduction of friction tends to bring the two curves closer together but as this occurs the upward effort curve tends to cross the zero point at the lowermost region of door travel. This means that the door will tend to open automatically and will not remain closed without the application of downward force.

Experiments have shown that the behaviour of the door curtain, particularly at the lowermost region of its travel, is largely dependent upon the peripheral configuration of the drum.

These experiments have led to the development of the present invention which has been found to offer significant improvements in door operating characteristics.

According to one aspect the invention consists in an end disc for a roller door drum of the kind which in use rotates about a horizontal axis to be enwrapped by a horizontal corrugated curtain sheet, said end disc being characterized in that the curved surface thereof is corrugated, the mounds of a first plurality of adjacent corrugations each project substantially to a first radial distance from said axis, and the mounds of a second plurality of adjacent corrugations each extend to a radial distance greater than the first radial distance.

A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a graph in which a broken line illustrates the relationship between door height and tractive effort required to move a door up or down by means of end drums according to the invention and the solid line illustrates the corresponding relationship for a drum according to prior art.

Figure 2 is an end elevation of a disc and partially wound door curtain in accordance with the prior art.

Figure 3 is a dimensioned end elevation of a prior art disc as in Figure 2.

Figure 4 is a section taken on line 4-4 of figure 3.

Figure 5 is a dimensioned end elevation of a disc according to the invention.

Figure 6 is a section taken on line 6-6 of figure 5.

Figure 7 is a view similar to figure 5 but showing the attachment of a door curtain to the drum defined by two of the discs shown in figure 5.

Figure 8 is a side elevation of an attachment and separator bar.

Figure 9 is a view taken on line 9-9 of figure 8.

Figure 10 is a view taken on line 10-10 of figure 8.

Referring initially to figures 2 to 4, the prior art disc 10 is pressed from relatively thin gauge sheet material and includes a circumferential rim 11 provided with axially extending corrugations 12 for engagement with the corrugations 9 of a door curtain 13. The curtain 13 attaches to the disc at point A and winds onto the drum as it rotates in the direction shown about a stationary axis 14.

The rim 11 is spaced from a central hub aperture 15 by three spokes 16. Each spoke 16 is strengthened by a pair of ridges 18 projecting from the outer surface 19 of the disc and extending longitudinally in a radially outward direction from their inner ends 20 to blend with the rim 11. As best shown in figure 4, the disc contains an inner circular flange 21 projecting axially away from the outer surface 19 for mounting a hub assembly (not shown).

The configuration of the disc illustrated in figures 2 to 4 is more fully described and illustrated in Australian Patent Specification 483,904. The disc or end drum described in that specification and illustrated in figures 2 and 3 was arranged such that the radial height of each corrugation mound measured from the drum axis substantially traced out the path of an Archimedean spiral, moving circumferentially around the drum from the curtain attachment point A to the last corrugation ridge 23 at the end of the first turn of the curtain, indicated as position C. The depth of each corrugation trough was substantially constant.

While this disc has been generally successful, it has been subject to the disabilities mentioned above and subsequent developments have resulted in the drum of the present invention which provides improved door operating characteristics.

The improved drum illustrated in figures 5 to 7 is basically similar to that of the prior art, except for the configuration of the circumferential corrugations, and corresponding features have been given the same reference numerals.

Comparing the corresponding dimensioned drawings 3 and 5, it will be observed that the improved drum demonstrates a number of significant differences. In particular, it will be observed that the maximum radial height of the corrugation mounds from the drum axis decreases slightly or remains substantially constant over the region extending from positions A to B.

The radial height does not increase progressively and smoothly as in the case of an Archimedean spiral. In fact, the radial height demonstrates a relatively rapid change between position B and the next corrugation 25. From corrugation 25 to the final corrugation 23 at position C there is substantially little change in the corrugation height and the corrugation mounds lie almost on the same height circle or increase in height through most of the disc circumference over this region. At position C the height of corrugation 23 is substantially one pitch height above that at position A.

Referring now to figure 7, it will be seen that the corrugated curtain is preferably affixed to the improved disc at two positions A and B, rather than only at the prior art position A. The leading three corrugations of the door curtain have been flattened and replaced with six smaller corrugations and this curtain portion 26 is held in engagement with the disc by a combined attachment and separator bar 27. The separator bar, as best shown in figures 8 to 10, includes a hooked attachment flange 28 which passes through holes in the door curtain and drum at position A and secures the curtain to the disc at this point without the need for fixing rivets, although these may be used if required. The other end 30 of the separator bar 27 connects to the disc at position B by tongue and slot engagement or rivetting as required. Slot engagement is useful to accommodate variations in manufacturing tolerances but it is found that rivetting is satisfactory in most cases.

It has been found that the double fixing of the door curtain to the drum end discs at positions A and B significantly improves the rigidity of the curtain and drum assembly. More importantly, however, the shape of the disc itself has been found to provide significantly improved smoothness of door operation.

Although the invention has been described with reference to a specific example, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

Claims (8)

1. An end disc for a roller door drum of the kind which in use rotates about a horizontal axis to be enwrapped by a horizontal corrugated curtain sheet, said end disc being characterized in that the curved surface thereof is corrugated, the mounds of a first plurality of adjacent corrugations each project substantially to a first radial distance from said axis, and the mounds of a second plurality of adjacent corrugations each extend to beyond the first radial distance.

2. An end disc according to claim 1 wherein the second plurality is adjacent the first plurality.

3. An end disc according to claim 1 or claim 2 wherein the trough between successive mounds of the first plurality is shallow in comparison with the trough between successive mounds of the second plurality of adjacent corrugations.

4. An end disc according to any one of the preceding claims wherein the mounds of the second plurality extend to successively increasing radial distances.

5. An end disc according to any one of the preceding claims in combination with a corrugated curtain sheet, said sheet being attached at or adjacent one end of the first plurality.

6. A combination according to claim 5 wherein the curtain sheet is additionally attached to the drum at or adjacent the other end of the first plurality.

7. A roller drum substantially as herein described with reference to figures 5-6.

8. An end disc substantially in combination with a curtain sheet substantially as herein described with reference to figure 7.