Day-and-night blind

Abstract

A zebra blind comprising a pair of end mountings 3, 4, a sheet (1, fig 1) wound on a roller shaft 2 having areas of different opacity and doubled back on itself to form two superimposed layers (1A, 1B

Description

DAY-AND-NIGHT BLIND TECHNICAL FIELD OF THE INVENTION This invention relates to roller blinds of the kind known as day-and-night blinds. Such blinds may also be known by other names such as “vision blinds”, “zebra blinds” or “transformation blinds”. BACKGROUND A roller blind has a sheet of material wound on a shaft which is normally supported horizontally between end mountings such as a pair of mounting brackets or cassette end caps. One end of the shaft is provided with a drive unit, widely known as a sidewinder, which allows the user to rotate the shaft by means of a cord, chain, wand etc. in order to raise and lower the sheet. In a day-and-night blind the sheet has areas of different opacity which are typically arranged as stripes extending parallel to the axis of the shaft. The stripes are of alternating opacity, typically transparent stripes alternating with black or dark-coloured stripes. The sheet is doubled back on itself to form two superimposed layers of material, with the free edge of the sheet fixed adjacent to the shaft, e.g. by attachment to a cassette or back bar which is fixed between the end mountings. The sidewinder can be used to rotate the shaft until the blind is unwound to approximately the required length. Further adjustments can then be made to achieve an open condition in which the transparent areas are aligned allowing light through (i.e. the “day” condition in which light can come in and users can see out). Alternatively, the blind can be adjusted to a closed condition in which the transparent areas are in registration with the opaque areas (i.e. the “night” condition in which the blind is completely opaque and little or no light is allowed through). By adjusting the blind between the day and night conditions the amount of light passing through the blind can be varied so that the day-and-night blind functions in a similar manner to a Venetian blind. Existing day-and-night blinds have several drawbacks which are related to the fact that when the sidewinder is used to adjust the blind between the day and night conditions the vertical length, or drop, alters. If installed in a window opening for example this may cause an undesirable gap to appear above the sill or bunched up fabric to rest on the sill. To overcome this the blind is generally custom made to achieve the desired drop, but even then the correct drop is only achieved when the blind is in one or other of the day and night conditions. There is a large market for standard length “Take & Trim” roller blinds, but in the case of a day-and-night blind it is difficult for the customer to get the blind to end at the required height relative to a sill. This can only be achieved by accurately calculating the fabric length and cutting the sheet at exactly the right position, which people often get wrong. SUMMARY OF THE INVENTION When viewed from one aspect the present invention proposes a day-and-night blind: - a pair of end mountings (3, 4); - a sheet (1) wound on a roller blind shaft (2) rotatably mounted between the end mountings (3, 4), wherein the sheet has areas of different opacity, and wherein the sheet is doubled back on itself to form two superimposed layers (1A, 1B); - a drive unit (5) at one end of the roller blind shaft; characterised in that a free edge portion of the sheet (1) is wound on an adjuster shaft (6) which is rotatably supported between the end mountings. The adjuster shaft can therefore be used to raise or lower the attached portion of the sheet, allowing fine adjustments to be made to the alignment of the light and dark areas and the distance between the bottom of the blind and a window sill. In a preferred embodiment the adjuster shaft (6) is supported from one of the end mountings (3, 4) by a gear drive (12). The gear drive (12) may includes a first sprocket (44, 57) which is connected to a spigot (45) for insertion into the adjuster shaft (6). The gear drive (12) may be operated by a thumbwheel (47) or a wand. In a preferred embodiment the adjuster shaft (6) is supported from the other end mounting (3, 4) by a clutch unit (11). BRIEF DESCRIPTION OF THE DRAWINGS The following description and the accompanying drawings referred to therein are included by way of non-limiting example in order to illustrate how the invention may be put into practice. In the drawings: Figure 1 is a general view of a day-and-night blind; Figure 2 is an exploded view of the day-and-night blind; Figure 3 is a side view of a sidewinder used in the day-and-night blind; Figure 4 is an end view of the sidewinder; Figure 5 is a general view of an idle end mounting used in the day-and-bight blind; Figure 6 is a general view of a clutch unit used in the day-and-night blind; Figure 7 is a longitudinal section through the clutch unit; Figure 8 is a side view of one of the end mountings of the day-and-night blind; Figure 9 is an end view of the end mounting of Fig. 8; Figure 10 is a general view of another end mounting of the day-and-night blind; Figure 11 is a side view of the end mounting of Fig. 10. DETAILED DESCRIPTION OF THE DRAWINGS Referring firstly to Fig. 1, the day-and-night blind includes a sheet of fabric material 1. wound on a roller blind shaft 2 which is mounted horizontally between two end mountings in the form of brackets 3 and 4. One end of the shaft 2 is provided with a sidewinder 5 which allows the user to raise and lower the blind by means of a ball chain 21 or its equivalent. Although not shown, the sheet 1 has areas of different opacity which may be arranged as stripes extending parallel to the axis of the shaft 2, e.g. transparent stripes alternating with black stripes. The lower extremity of the sheet 1 is doubled back on itself to form two superimposed layers of material, 1A and 1B. The free upper edge portion of the sheet 1 is wound on an adjuster shaft 6 which is rotatably mounted behind the roller blind shaft 2 between the brackets 3 and 4. Referring to the exploded view of Fig. 2, the roller blind shaft 2 is typically a hollow metal tube, internally splined, which is supported from the bracket 4 by the sidewinder 5. The opposite end of the shaft 2 is supported from the bracket 3 by a spring loaded idle end mount 10. The adjuster shaft 6 may also be an internally splined hollow metal tube, preferably of smaller diameter than the shaft 2, which is supported from the bracket 4 by a gear drive 12. The opposite end of the adjuster shaft 6 is supported from the other bracket 3 by a clutch unit 11. Referring to Fig.s 3 and 4, the sidewinder 5 has an outer housing 15 containing a toothed pulley 16 around the ball chain is engaged. The housing 15 contains a socket 17 by which the housing is non-rotatably received on a splined projection 18 on the bracket 4 (see Fig. 7). A spigot 19, which is engaged in the end of the roller blind shaft 2, is provided with an end flange 20 which closes housing 15. The pulley 16 can be rotated in opposite senses by pulling the ball chain 21, which in turn rotates the roller blind shaft via the spigot 19. An internal braking mechanism prevents the fabric sheet from unwinding under its own weight. The internal configuration and operation of such sidewinders is fully described in the art - see GB 2 442 961-A for example. The idle end mounting 10, which is shown in Fig. 5, includes a drum 22 with a socket 23 by which the drum is non-rotatably received on a splined projection 24 on the bracket 3 (Fig. 2). A pin 25 projects axially from the drum 22 to slidably and rotatably carry a spigot 26 which is held captive on the pin by a head 27. An internal spring (not shown) urges the spigot 26 away from the drum 22 into contact with the head 27. In use, the spigot 26 is inserted into the end of the roller blind shaft 2 so that the internal spring maintains the sidewinder 5 and drum 22 in engagement with the projections 18 and 24. Compression of the internal spring allows the spigot 26 to slide over the drum 22 during engagement of the roller blind shaft with the brackets 3 and 4. A more detailed description of such a mounting is given in GB 2 310 878-A. The clutch unit 11, which is shown in Fig.s 6 and 7, includes a drum 32 with a socket 33 by which the drum is non-rotatably received on a splined projection 34 on the bracket 3 (Fig. 2). A pin 35 projects axially from the drum 32 to slidably and rotatably carry a spigot 36 which is held captive on the pin by a head 37. The pin 35 also receives a cup-shaped slider 38 which is axially movable but non-rotatably received over the drum 32 by engaging an axial slot 31 in the outer surface of the drum (Fig. 6). An internal spring 40 (Fig.s 2 and 7) urges the slider 38 away from the drum 32 into contact with the spigot 36. The adjacent end faces of the slider 38 and the spigot 36 form friction discs 39 which maintain frictional engagement between the drum and spigot. In use, the spigot 36 is inserted into the end of the adjuster shaft 6. The internal spring 40 keeps the adjuster shaft in engagement with the brackets 3 and 4, but compression of the internal spring 40 allows the spigot 36 and slider 38 to slide over the drum 32 during engagement of the adjuster shaft 6 with the brackets 3 and 4. The internal spring also maintains frictional engagement between the friction discs 39 and prevents unwanted rotation of the adjuster shaft, but when the adjuster shaft is deliberately rotated by the gear drive 12 as described below the fictional engagement of the discs 39 is overcome allowing the shaft 6 to rotate. One form of gear drive 12 is shown in Fig.s 8 and 9. The bracket 4 is L-shaped with a side flange 41 and a perpendicular fixing flange 42. The side flange 41 carries spaced projections 18 and 43. The projection 18 (already discussed) non-rotatably supports the sidewinder 5. The second projection 43 rotatably carries a first sprocket 44 which is connected to an axially projecting spigot 45 for insertion into the adjuster shaft 6. Adjacent to the projection 43, near one edge of the side flange 42, there is a further projection 46 which in turn carries a thumbwheel 47 which projects beyond the edge of the side flange. The thumbwheel is joined to a second sprocket 48 which is enmeshed with the sprocket 44. The thumbwheel 47 acts as a finger-operated adjuster by which the user can rotate the shaft 6 via sprockets 48 and 44 and the spigot 45, overcoming the frictional engagement the discs 39. By means of the finger adjuster the following adjustments can be made: 1) The drop length can be altered, in conjunction with the sidewinder, to give either a day or night view at precisely the right drop. 2) The starting view can be changed at will from open to closed, or from closed to open, whilst keeping the blind drop consistent. In the embodiment just described it is convenient for the user to have the sidewinder 5 and the gear drive 12 adjacent to each other supported by the same bracket, although the gear drive 12 and the clutch unit 11 could be swapped around if desired. One possible drawback of this embodiment is that the thumbwheel may be difficult to reach in some circumstances, but this is overcome in the gear drive which is shown in Fig.s 10 and 11. In this embodiment the gear drive is associated with the bracket 3, which is also L-shaped with a side flange 51 and a perpendicular fixing flange 52. The side flange 51 carries a projection 24 (already discussed) which non-rotatably supports the idle end fitting 10. Spaced from the projection 24 the side flange carries a gear drive housing 53 which contains a rotatable pin 54. The lower end of the pin 55 projects beyond the edge of the side flange 51 for attachment of a wand by which the pin can be rotated. The pin has a worm drive 56 which is enmeshed with a sprocket 57 to which which a spigot (not shown) is attached for insertion into the adjuster shaft 6. By rotating the wand the user can rotate the shaft 6 via the worm drive 56 and sprocket 57, overcoming the frictional engagement of the discs 39 in the clutch unit at the opposite end of the shaft 6. Although the above description relates to blinds which are supported between brackets the invention is also applicable to blinds which are mounted in a cassette, in which case the end mountings may be provided by a pair of cassette end caps. It should also be noted that the fabric sheet need not necessarily have horizontal stripes. The invention is applicable to any blind having areas of varying opacity which can provide different patterns and / or vary the amount of light transmission as the blind is adjusted. Whilst the above description places emphasis on the areas which are believed to be new and addresses specific problems which have been identified, it is intended that the features disclosed herein may be used in any combination which is capable of providing a new and useful advance in the art. x Xx Xx x kx x x xk

Claims

CLAIMS 1. A day-and-night blind: - a pair of end mountings (3, 4); - a sheet (1) wound on a roller blind shaft (2) rotatably supported between the end mountings (3, 4), wherein the sheet has areas of different opacity, and wherein the sheet is doubled back on itself to form two superimposed layers (1A, 1B); - a drive unit (5) at one end of the roller blind shaft; characterised in that a free edge portion of the sheet (1) is wound on an adjuster shaft (6) which is rotatably supported between the end mountings.

2. A day-and-night blind according to claim 1 wherein the adjuster shaft (6) is supported from one of the end mountings (3, 4) by a gear drive (12).

3. A day-and-night blind according to claim 2 wherein the gear drive (12) includes a first sprocket (44, 57) which is connected to a spigot (45) for insertion into the adjuster shaft (6).

4. A day-and-night blind according to claim 2 or 3 wherein the gear drive (12) includes a thumbwheel (47). 5, A day-and-night blind according to claims 3 and 4 wherein the thumbwheel (47) is joined to a second sprocket (48) which is rotatably engaged with the first sprocket (44).

6. A day-and-night blind according to claim 2 or 3 wherein the gear drive (12) includes a rotatable pin (54) for attachment of a wand by which the pin can be rotated.

7. A day-and-night blind according to claims 3 and 6 wherein the pin has a worm drive (56) which is rotatably engaged with the first sprocket (57).

8. A day-and-night blind according to any preceding claim wherein the adjuster shaft (6) is supported from one of the end mountings (3, 4) by a clutch unit (11). S. A day-and-night blind according to claim 8 wherein the clutch unit (11) includes a pin (35) which slidably and rotatably carries a spigot (36) for insertion into the adjuster shaft (6).

10. A day-and-night blind according to claim 9 wherein the pin (35) non-rotatably carries an axially movable slider (38).

11. A day-and-night blind according to claim 10 wherein the slider (38) frictionally engages the spigot (36).

12. A day-and-night blind according to claim 11 wherein the clutch unit (11) includes a spring (40) which urges the slider (38) into contact with the spigot (36). x x x x x x x x

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