AU1950700A - Improved venetian blind mechanism - Google Patents

Description

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AUSTRALIA

Patents Act 1990 COMPLETE PATENT SPECIFICATION Application No: Filed:

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APPLICANT: Marlic Pty Ltd ADDRESS: 580 Englehardt Street, Albury, NSW 2640 ACTUAL INVENTOR: Mark Fielder, 47 Michelle Ave, Lavington, NSW, 2641 ADDRESS FOR SERVICE: INVENTION TITLE: Paul A Grant and Associates PO Box Fisher, ACT 2611 IMPROVED VENETIAN BLIND MECHANISM ASSOCIATED PROVISIONAL APPLICATION No. PP9185 The following statement is a full description of this invention, including the best method of performing it known to me:- TECHNICAL FIELD This invention relates to control means for use with venetian blinds. It is particularly, though not exclusively, concerned with mechanisms for raising and lowering the slats of venetian blinds which are unusually heavy or which have unusually long drops. However, the invention is also concerned with venetian blind systems as a whole.

More particularly, this invention concerns an improvement or alternative to the mechanism disclosed in our Australian patent No. 685736 (hereafter called 'our prior patent'), the disclosures of which are hereby imported into this •.specification.

BACKGROUND TO THE INVENTION 1 5 In our prior patent we disclosed the use of a worm-gear reduction drive to inhibit eo a heavy venetian blind from running back (falling down) under its own weight.

While this enabled exceptionally heavy blinds to be handled with ease, the high reduction ratio (about 15:1) was not convenient for blinds of intermediate or normal weight, resulting in unnecessarily slow action.

However, if the reduction ratio is reduced to below about 10:1 for convenient operation, the blind is likely to fall or run-back under the weight of its slats.

OBJECTIVES OF THE INVENTION It is therefore an object of the present invention to provide a mechanism for the raising and lowering of venetian blinds that will handle heavy or long-drop blinds without the danger of run-back and without the inconvenience of large gear reduction ratios. Another object is to provide an improved venetian blind system of the type indicated.

OUTLINE OF INVENTION From one aspect, the present invention involves the use of brake or clutch means in association with a drive means (such as a gear box, an electric motor, and/or a sprocket and chain or pulley and chord) to further mitigate (and preferably prevent) blind run-down and yet be operable automatically to permit normal manual operation of the blind.

As with conventional venetian blinds, the slats can be suspended from tapes or chords supported from reels mounted on horizontal shaft means. The clutch or brake means may comprise a helical spring coiled around a fixed drum to frictionally engage it, the spring being engaged by a first striker coupled to the :°°shaft so that, when the shaft attempts to turn under the weight of the slats, the spring is tightened on the drum, preventing rotation of the spring about the drum and run-down of the blind. A second striker coupled to the drive means may 15 then be used to effect the unwinding of the spring on the drum (automatically permitting rotation of the spring about the drum) when the drive means is employed to raise or lower the slats of the blind.

o From another aspect, the invention is characterised by the inclusion of first stop S. 20 means operable to limit the degree to which the blind can be lowered.

Preferably, the first stop means is adjustable so that the level of the bottom of an individual blind can be adjusted in situ. This allows a row of blinds to have a common bottom level when all are lowered. Second stop means may also be provided to limit the level to which the slats of the blind can be raised.

Conveniently, the first and/or second stop means may be provided by the use of a screw-threaded portion of the shaft of the blind mechanism, a travelling nut on the screw-threaded portion, means to prevent the rotation of the nut and means to limit its longitudinal travel in one or both directions as the shaft is rotated.

Preferably, at least the first stop means comprises a split nut which is threaded on the screw-threaded portion of the shaft, adapted to rotate therewith and which can be clamped in place to set the desired limit on the movement of the travelling nut.

Preferably, a flexible (preferably stainless) steel band is used as the lifting tape and its upper end may be conveniently attached its reel by bending or hooking it under an axially-oriented pin driven through the sides of the spool and located above a flat, or within a groove, formed in the hub of the spool so that the outer edge of the pin lies on the diameter of said hub. The end of the metal strip or band can then be slipped between the pin and the hub and bent away from the hub to hook it around the pin. With a few turns of the band around the hub, the band will be made secure on the spool.

DESCRIPTION OF EXAMPLES Having broadly portrayed the nature of the present invention, two particular examples will now be described by way of illustration only. In the following description, reference will be made to the accompanying drawings in which: Figure 1 is a perspective exploded view of a venetian blind system of the first example; o° Figure 2 is a sectional detail front elevation of the right hand portion of the 20 mechanism of the system of Figure 1, Figure 3 is an end elevational section of the mechanism of Figure 2 taken on plane A-A of Figure 2, Figure 4 is an end section of one of the reels of the mechanism of the first example, Figure 5 is a similar view to Figure 1 of a venetian blind system which is driven by an electric motor and which comprises the second example of the invention, Figure 6 is an enlarged end sectional elevation of a worm gear drive having a spring brake/clutch, Figure 7 is a side sectional elevation taken on plane B-B of Figure 6, and Figure 8 is a side sectional elevation taken on plane C-C of Figure 6.

Referring to Figures 1 and 5, the venetian blind systems 10 and 1 Oa of the first and second chosen examples comprise a set of slats 12 supported by three cord ladders 14 from pulleys 16 in the conventional manner for angular adjustment of slats 12, stops 18 being secured to the ladder cords 14 near °°pulleys 16 to limit the angular travel of the slats. Pulleys 16 are mounted upon, but for rotation relative to, longitudinal shaft means 20 that runs the length of a S°headbox 22. They are located laterally within cavities formed in injection- 15 moulded plastic bearing blocks 24. Headbox 22 comprises a length of aluminium channel with its open side up and is normally hidden from view by a decorative pelmet (not shown). The three injection-moulded plastic bearing o blocks 24 are snapped into headbox 22 so that their bases are located by S• rectangular holes 26 and their tops are located by the returns on the sides of the channel which forms headbox 22.

A reel or spool 30 is supported on shaft 20 for rotation therewith and is located S•laterally in a cavity 23 in each of the two outer blocks 24. Optionally, a third reel or spool (not shown) can be supported in a similar manner in cavity 23 of the central bearing block 24. A stainless steel flexible metal tape or band 32 is attached to and wound onto each reel or spool 30 so that one end hangs therefrom, passing downwards through slots 36 in slats 12 and ending in a bottom stop 38 that supports the lower most slat 12a which is normally much more substantial than the other slats 12. Shaft means 20, together with the pulleys (16) and reels (30) which are mounted upon it, is supported on bearings which are in turn supported and located by bearing blocks 24.

In system 10 of the first example (Figure a stop sub-assembly 42 (comprising the aforementioned first and second stop means) and a worm-drive reduction gearbox 44 are located at the right hand end of headbox 22; while, in the system 10 a of the second example (Figure an electric drive motor 46 is substituted for the stop sub-assembly 42 and gearbox 44 of the first example.

Motor 46 has a central shaft which emerges from both ends so that longitudinal shaft 20 can be formed in two parts and each can be coupled with the motor shaft so that motor 46 drives all reels or spools 30 on shaft 20 in unison.

Referring more particularly to Figures 2, 3 and 4, details of the shaft, spools and pulleys common to both examples will now be described. It will be seen that :°'°°shaft means 20 includes a length of hexagonal section rod which passes freely through hexagonal holes in pulleys 16, reels 30 and bearings 40, shaft 20 being S°supported from bearing blocks 24 by bearings 40 which sit in moulded supports 15 formed integrally with the bearing blocks. Pulleys 16 have hexagonal bores and are supported by shaft 20 for rotation therewith or thereon, tilting the slats one way or the other until stops 18 are reached (whereupon, the looped ladder cords slip on the pulleys. The manner in which the metal lifting strips 32 are secured to reels 30 is shown in detail in Figure 4. Each reel 30 has a central 20 cylindrical boss 50 which extends axially from each side thereof and within which a hexagonal bore 52 is formed to take shaft 20 in a sliding fit. Each reel or spool has a pair of radial side flanges 54 and a central hub 56 which has a flat 58 formed on one side thereof, an axially extending pin 60 being driven through sides 54 opposite (and spaced from) flat 50 to act as an anchor point for the end of band 32. The upper end 62 of band 32 is threaded between pin and flat 58, hooked around the pin and then wrapped around hub 56 for a few turns before being threaded through the slots 36 in slats 12.

Turning now to Figures 2 and 3 and to the features of the first example which differ from those of the second, the stop means 42 and gearbox 44 will now be described. Gearbox 44 is screwed into the right hand end of headbox channel 22 and contains a worm reduction gear, the worm 72 and wheel 74 being shown in dotted outline. Worm 72 is mounted on input shaft 76 which carries a sprocket (not shown) and loop-chain 75 (Figure 1) by which shaft 76 can be manually rotated, the sprocket on shaft 76 being located within a housing 77 attached to headbox 22 (Figure Wheel 74 is mounted on output shaft 78, which carries a hollow threaded boss 80 on its left-hand end. Conveniently, for light to normal blinds, the gear ratio may be between 5:1 and 10:1 but this will not generally be sufficient to ensure that there is no run-down of the blind under gravity after it has been raised.

The right hand end of a short screw-threaded shaft 82 is screwed into boss and fixed in position by a cross-pin 84, the left hand end 86 of shaft 82 being unthreaded, of hexagonal section and fitted into the hub 50 of the left hand *.spool 30. A travelling-nut 88 is threaded onto shaft 82 and carries an Allenhead bolt 90 the head of which travels in a slot 92 (Figure 1 and 3) formed in one side of headbox 22, thereby preventing nut 88 from rotating with shaft 82.

An internally threaded split-nut clamp 94 acts as a limit stop for the travel of nut 88 toward the left, setting the level of the bottom of the blind. While travel of nut 88 to the right is limited by boss 80 and an intermediate washer 96 setting the upper-most level of the blind when raised, adjustment of this level is achieved 20 by removing Allen-bolt 90 and rotating travelling nut 88 on shaft 82. Thus the combination of clamp 94 and nut 88 form the first stop means referred to above and the combination of the nut 88 and washer 96 and/or boss 80 form the second stop means.

To limit axial movement of shaft 20 to the left, a stop-collar 98 is clamped to the shaft on the immediate right of a bearing 40. The right hand travel of shaft 20 is limited by abutment of the right hand end of this shaft against the hexagonal portion 86 of threaded shaft 82, which abutment occurs within the corresponding reel or spool Referring now to Figure 5 which illustrates the second example of the invention, it will be seen that the gearbox and screwed shaft and their associated parts have been dispensed with and substituted by the motor unit 44, the motor having a shaft which projects from each end and which can be coupled directly to the long hexagonal shaft 20 on the left and as short hexagonal shaft 100 on the right. In this case, the first and second stop means are formed by adjustable limit switches (not shown) fitted within the housing of motor 44. Motor unit 44 includes spur-gear reduction gearing such that it may be possible for the output shaft to be turned by the weight of the blind acting on shafts 20 and 100 via reels or spools 30. Accordingly, the use of automatic brake/clutch means is preferred to positively prevent run-back.

Figures 5-8 illustrate brake/clutch means as applied to the embodiment of the first example employing worm reduction gears and manual drive means (sprocket 77 and chain 75), but those skilled in the art will appreciate that the electric motor 46, which comprises the drive means of the second example) can :I 15 be readily coupled to the brake/clutch of Figures 5-8.

Chain-drive sprocket wheel 77 is mounted on worm shaft 76 and is manually driven by chain 75 (as previously described), it is composed of a central flanged hub 106 that is fitted onto splines 102 on outer end of worm shaft 76 so that hub 106 and shaft 76 rotate as one, and (ii) a toothed rim 104 that is mounted by the flange 106a of hub 106 but is free to rotate thereon. An arcuate striker shoe 108 is keyed to the rear face of flange 106a of hub 106 so as to be constrained to rotate therewith. The housing of gearbox 44 includes a fixed drum or bush 110 within which are carried the main ball bearings 112 by which worm shaft 76 is rotatably mounted in the gearbox housing.

A helical steel spring 114, that is preferably wound from square wire, is fitted about drum or bush 110 as a close fit thereon, the ends 116a and 116b of spring 114 extending radially into an arcuate space left by the cut-away portion of striker shoe 108. Sprocket rim 104 is formed with an internal key-like protrusion 118 that is arranged between the ends 116a and 116b of spring 114.

The clutch/brake operates in the following manner: when worm 72 is driven by worm-wheel 74 under the weight of a blind, striker shoe 108 will be rotated (say) anticlockwise (Figure 7) until it contacts end 116b of spring 224 to close and tighten spring 114 on drum or bush 110, preventing further rotation of shaft 76 and run-down of the blind. It will be recalled that striker shoe 114 must rotate with worm shaft 76 because it is keyed to flange 106a of sprocket hub 106 which is, in turn, mounted by splines 102 on shaft 76.

When the user wishes to lower the blind by further anticlockwise rotation of shaft 76, rim 104 of sprocket 77 is turned anticlockwise using chain 75 until key 118 strikes spring end 116a (Figure 7) causing the spring to unwind and open on drum or bush 108 for free rotation thereon. If shaft 76 tends to turn faster than the user operates sprocket 77, striker shoe 114 will once again contact spring end 116b and, once again, tighten spring 114 on drum or bush 110.

When the user wishes to raise the blind, he/she turns sprocket 77 in the clockwise direction (Figure 7) so that key 118 contacts spring end 116b and again opens the spring so that it can rotate on drum or bush 110. Once the blind has been sufficiently raised, the user stops rotating sprocket 77 via chain 20 75. As a result, shaft 76 tends to run back and again turn striker plate anticlockwise until it contacts spring end 116b and (as before) causes the :spring to bind onto drum or bush 110 and the run-down of the blind to stop.

While those skilled in the art will appreciate that the examples described above fulfil the objectives of the invention and overcome the problems of the prior art systems described, many alterations and additions can be made thereto without departing from the spirit or scope of the invention as outlined. It has already been indicated, for example that flexible stranded wire may be used instead of metal bands for lifting the blinds.

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