WO2005090735A1

WO2005090735A1 - Venetian blind spooler

Info

Publication number: WO2005090735A1
Application number: PCT/IL2004/000451
Authority: WO
Inventors: Arnon Barak
Original assignee: Arnon Barak
Priority date: 2004-03-23
Filing date: 2004-05-27
Publication date: 2005-09-29
Also published as: IL161024A0

Abstract

A spooling mechanism (10) for winding the drawstring (20) of a blind, comprising a drive pulley (12) fixed to a driveshaft (14), static holder (18), and a cone shaped drum (16) held between the pulley (12) and static holder (18) for free rotation therebetween, with the narrow end of the cone engaging the pulley (12) and the wider end engaging the static holder (18), wherein a drawstring (20) that passes through a conduit (22) on the static holder (18) and winds around the drum (16) is fixed to the drive pulley (12), such that rotation of the driveshaft (14) increases tension in the drawstring (20) causing it to wind up unto the freely rotating drum (16) without becoming entangled or overlapped while winding.

Description

VENETIAN BLIND SPOOLER FIELD OF THE INVENTION The present invention relates to a drum pulley for Venetian blinds and the like. BACKGROUND OF THE INVENTION Venetian blinds consist of separate, parallel slats arranged as a vertical array of essentially horizontal slats, suspended from at least two cords in front of a door, window or the like. The basic concept behind Venetian blinds is that they are tilted such that they the allow air circulation therethrough, but block sunlight. Sometimes the tilt angle is such that they provide privacy as well, not allowing an observer to see therethrough. In sophisticated Venetian blinds, as widely available, each slat is suspended in at least two positions along its length, by a 'ladder', consisting of three cords, arranged in parallel, with 'rungs' attached thereto, such that at each position, two cords, usually the outer ones, can be toggled slightly to adjust the angle of tilt of the blind, whilst the remaining cord, typically the central one, can be drawn up or released to raise or lower the blind. By virtue of their versatility, in that the blinds can be partially or fully raised (folded) or lowered, and that the tilt can be varied between almost fully vertical (closed) so that no light passes, and fully opened, such that almost uninterrupted viewing therethorough is possible, Venetian blinds have become a popular fixture over windows in residences, offices, shops, etc. Due to their inherent flimsiness and poor rigidity, to prevent the slats of Venetian blinds from bending, the slats are often suspended at more than two positions, reducing the span thereby. Typically, the drawstrings for raising and lowering the Venetian blind are attached to a lifting rod that runs along the bottom of the shade. To raise the blind, the drawstrings are pulled upwards, often by being wound up onto a spool, and the lifting rod is thus raised. The lifting rod causes the slats to stack one over the other, as it is lifted. The main advantage of Venetian blinds over curtains and roller blinds is that the fully lowered Venetian blind can be angled to prevent strong sunlight penetrating, however, allowing daylight to enter. Additionally, at an appropriate angle, particularly with windows on upper floors, Venetian blinds allow the occupants of a room to see outwards, whilst providing them with privacy by preventing outsiders from looking in. Venetian blinds require a mechanism to control the tilt of the slats. This is usually a wand mechanism or a drawstring, but magnetic and electrical tilt mechanisms are also known. A hoisting mechanism is required for raising and lowering the blind. This may be a second drawstring. Alternatively however, the raising and lowering is effected by a motor or the like. In the first case, the loose strings are liable to get tangled. In the second case, spooled up cords from two or more positions along the length of the blind may get tangled up. For smooth raising and lowering, it is required that the cords spool up and unspool evenly, at the same rate. Otherwise, the blind tends to rise and lower unevenly, often at one end and not the other. It is not easy to ensure constant, reliable synchronization between the two or more spools, and in practice, Venetian blinds are susceptible to irregular raising and lowering, leading to jamming, entanglement and even to breaking. It will be appreciated that since the spooling mechanism is enclosed in the cradle of the Venetian blind, it is not visible and has no effect on the aesthetics of the blind. Sophisticated spooling mechanisms are not widely used however, as they tend to increase price of the Venetian blind unit and inhibit sales or lower profit margins, and the more complicated a mechanism, the more inherently unreliable it is, as there are more ways that it can go wrong, and the more difficult it is to fix. One of the problems associated with the tendency for Venetian blinds to jam is that people tend to leave well alone and do not raise or lower the blinds at all, and do not alter the tilt to adapt the blind to changing needs through the day. There are numerous patents that relate to Venetian blinds. These indicate both the usefulness of such blinds and the ongoing research into improving reliability at reasonable cost. Remembering that there are always at least two spooling devices along the cradle, for raising a Venetian blind, and typically more, one major cause of malfunctioning is the uneven spooling between the different spooling devices along the blind cradle resulting in the blind not being raised and lowered smoothly, and risking the mechanism j amming. One publication describing a spooling mechanism for Venetian blinds, typical of the state of the art, is US Patent No. 5,328,113 to de Chevron Villette et al. This patent discloses a device including a winding drum comprised of a primary drum portion and a larger diameter auxiliary drum portion, the drum being mounted via a drive motor. A spooling cord is fixed at one end of the primary, smaller diameter drum portion. This arrangement ensures that the spooled up cord starts to wind with tightly wound coils on the auxiliary drum portion, each coil lying adjacent to the previous one. As more cord gets taken up, the auxiliary drum portion gets completed covered (3 or 4 coils), and the first tight coil is pushed off onto the primary, narrower diameter drum portion. These coils pushed off from the primary drum portion, are only loosely coiled on the narrower auxiliary drum portion, and essentially have zero tension. The auxiliary drum portion must be very smooth which makes the fabrication of the drum quite costly. Firstly, use of an expensive plastic such as HDPE (high density polyethylene), PTFE of delrin™ is required. Secondly, the drum should be seamless, requiring that it either be turned on a lathe, or, if manufactured by a low cost manufacturing technique, such as injection molding, that it be carefully polished to remove mold seams. There are also problems with long-term reliability with such blinds. For example, the loose coils on the primary drum portion, having zero tension, may overlap and interfere^' with each other. Such an eventuality causes uneven unspooling, and may result in the blind becoming improperly raised and lowered, and perhaps jamming. Thus, there is still a need to provide a reliable cost effective improved spooling mechanism and the present invention is directed to providing such an improved spooling mechanism. SUMMARY OF THE INVENTION It is an object of the invention to provide a Venetian blind spooler for raising and lowering a Venetian blind in a reliable manner with minimal risk of tangling and similar malfunctions. It is a further object of the invention that to provide a Venetian blind spooling mechanism that is economical to manufacture. It is yet a further object of the invention to provide a Venetian blind with two or more spooling mechanisms within the cradle of the blind, that can be easily synchronized so that the blind can be easily raised and lowered evenly, with minimal risk of jamming. In a first aspect of the invention^ there is provided, a Venetian blind spooler having a mechanism for spooling the drawstring of a blind, comprising: a drive pulley fixed to a driveshaft, a static holder, and a cone shaped drum held between the pulley and static holder for free rotation therebetween, with the narrow end of the cone engaging the pulley and the wider end engaging the static holder, wherein a drawstring that passes, through a conduit on the static holder and loops around the drum is fixed to the drive pulley, such that rotation of the driveshaft increases tension in the drawstring causing it to coil up onto the freely rotating drum without becoming entangled.

In preferred embodiments the drum has a frustoconical cross-section.

Typically, the blind may be raised and lowered by rotation of the driveshaft, the rotation being provided by a hoisting mechanism.

Optionally, the hoisting mechanism includes a motor.

Alternatively, the hoisting mechanism includes a hand actuator.

The blind may be a Roman blind or a Venetian blind, for example.

In a second embodiment, there is provided a Venetian blind including a plurality of spooling mechanisms, as defined above, for spooling the drawstring of the blind. By drawstring, any coilable string-like component to which a tensile force can be applied, that may be used for pulling on the slats of a blind, is intended, such as cords, strings, ropes, chains, braids and tapes, for example.]

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be further understood and appreciated from the following detailed description taken in conjunction with the drawings in which: Fig. 1 is a diagrammatic view of the spooling mechanism according to the present invention. Fig. 2 is a cross-sectional view of the spooling mechanism in accordance with the present invention Fig. 3 is across-sectional view of an alternate spooling mechanism in accordance with the invention.

Fig. 4 illustrates diagrammatically a Venetian blind with spooling mechanisms in accordance with the present invention. It will be noted that the same numbering system is used in all three diagrams. DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to providing a Venetian blind spooling mechanism. The general design requirements are that the mechanism should be cheap to manufacture, yet sufficiently reliable to operate smoothly through the life of the blind with minimal maintenance. The spooling mechanism should facilitate both lifting and lowering of the blinds without risk of damaging the drawstring. Since Venetian blinds hang from two or more points, there are two or more drawstrings that require to be raised simultaneously, and there is an inherent danger in one drawstring winding up faster than another resulting in the blind tilting and possibly jamming. Particularly where cords can wind on top of each other or along side each other, the amount of cord wound up per turn of the axle may vary, and there is an inherent risk of uneven winding and subsequent tilt of the lifting rod . The present invention overcomes these problems. With reference now to Figures 1 to 4 there is shown a mechanism 10 for spooling the drawstring 20 of a blind. The mechanism 10 comprising a rear drive pulley 12 fixed to a driveshaft 14, an independent freely rotating drum 16 and a static holder 18. The drum 16 is in the shape of a truncated cone, having a narrow end 28 loosely engaged by a shoulder 13 of drive pulley 12, and a wide end 29 loosely engaged by a shoulder 19 of the static holder 18 for free rotation thereabout. An end 24 of the drawstring 20 passes through a conduit 22 on the static holder 18, loops 15 around the drum 16 beginning at its wide end 29 and is fixedly attached to the drive pulley 12. Drum 16 rotates freely about shoulders 13 and 19 of drive pulley 12 and static holder 18, respectively. When the drive pulley 12 is rotated via driveshaft 14 the tension Ti in said drawstring 20 increases, causing it to coil up onto the drum 16. Each new winding causes the previous windings to be pushed down the incline of the conical freely rotating drum 16. Thus the tension of the winding 17 (T₂) in the middle of the drum 16 is lower than the tensions of both at the winding 15 ((T at the wider end 29 of the drum 16 and (T₀) at the pulley 24. The spooling mechanism 10 is effectively self correcting, and therefore, a number of such mechanisms can be attached to the same blind and fixed to the same driveshaft 14 to evenly spool up the blind. It will be appreciated, that alternative embodiments are possible, such as in Fig.3, where the end of the drum 16 may comprise an extension 33 that fits into cavity 35 of the static holder for rotation therein. Other configurations for supporting the rotating drum between the pulley and static holder are also possible and can easily be constructed by a person skilled in the art. It is known from drum pulley lifting devices, such as those used to raise sails at sea, and the like, that the maximum tension on a cord Ti is related to the winding angle θ and to the coefficient of friction μ. This relationship can be expressed as: Ti = T₀e^kμθ , where T_f = T_f . e^kμθ T_f = maximum cord tension upon winding, T, =the cord tension before entering the pulley K = a constant, μ = coefficient of friction, and θ = the winding angle. In the case of the present invention Ti > T₂ ; To > T2, where T₂ is in the inside of the drum. It should be noted that: Ti (load) x R (large radius of cone) = To x r (small radius of cone) T₀ = Ti R/r , and hence To >Tι Since Ti >T₂, the drawstring winds over the cone and pushes the windings down the cone incline. Each new winding pushes the preceding winding down the cone, which in turn pushes down the previous winding, and so forth. The excess drawstring that is formed due to the reduction of the diameter of the cone is taken up by the traction of the rear drive pulley 12 and the high tension T₀ of the drawstring. Thus, the windings move as a group along the drum 16 towards the smaller diameter of the cone being always in touch with each other, without overlap or jamming. With reference to Fig. 4, the blind 30 comprises three spooling mechanisms 10, 10', 10" held within the cradle 32 of the blind 30. Drawstrings 20, 20', 20" pass respectively through static holders 18, 18' 18" and wind around drums 16, 16', 16" which rotate freely. A tilting mechanism for tilting the slats 34 of the blind 30^' may be provided, which may be associated with the static holder 18, for example by utilizing an additional groove and cord. Alternatively, the tilting mechanism may be a separate mechanism not directly associated with the spooling mechanism 10 of the present invention. The static holder 18 is typically fabricated from a plastic material, and although expensive plastics such as high density polyethylene (HDPE) and polyethylene tetraphalate (PTFE) may be used, and will perform admirably, cheaper polymers such as polyethylene (PE), polypropylene (PP) or polystyrene (PS) may be used, lowering production costs. As shown, the drum 16 has a frustoconical, i.e. truncated conical shape. Although typically a simple truncated shape, it need not have a regular trapezium shaped cross-section, but may have a more complex cross section, such as a curved cross section for example, and is not restricted to being a simple truncated cone shape. Likewise, when the free drum 16 has a truncated conical shape, the angle of the cone θ is almost immaterial, and an appropriate angle θ for a particular size and weight blind and drawstring type can be easily found by experiment. The drum 16 may be fabricated a wide range of materials, and will typically be constructed from nylon™ by injection molding. It will be appreciated that some degree of friction is required, and there is no requirement for a very high quality finish, requiring expensive machining processes. Although delrin™ or the like may be used, a very wide range of alternative materials, including wood for example, may be used. Since the drum 16 is free to rotate independently, and is self correcting, the windings of the drawstring 20 tend to align themselves alongside each other, under tension T₂ and without overlap. Consequently, a short tapering drum performs admirably. The drawstring 20 may be any type of cord, line, string, thread, rope, chain, braid or tape that can take the strain To necessary to support the weight of the blind 30, and which may be coiled around the spooling mechanism 10. Typically it will have a diameter of about 1 or 2 mm, but this will depend ultimately on the space available for the spool mechanism 10, the length of the blind 30, its weight etc. The drawstring 20 passes through the conduit 22 in the static holder 18, loops around the drum 16, and is fixed to the drive pulley 12, typically by the end of the drawstring 20 being passed through a slot 24 in the drive pulley 12 provided for that purpose, and then knotted. The drive pulley itself is rigidly attached to the driveshaft. Typically the drive pulley tightly slides onto the driveshaft 14, which being of angular shape, cannot rotate without rotating the drive pulley therewith. Usefully, the drive pulley 12 is fixed to the driveshaft 14 by a fixing means 26 such as a bolt, screw or rivet for example. The components of the spooling mechanism 10, ie. drive pulley 12, static holder 18 and freely rotating drum 16 may be fabricated from any fairly rigid material such as plastic, wood or metal. Usefully, mating surfaces of either the drive pulley 12 and static holder 18 or the free drum 16 are made from smoothly polished materials having a low coefficient of friction, and to ensure free movement. Alternatively, if necessary, the mating surfaces may be lubricated, with graphite for example, so the choice of possible materials is very wide. Thus the free drum 16 and the drive pulley 12 rotate at different angular velocities ω and there is no need for the free drum 16 to have a highly polished winding surface. The slats 34 of the blind 30 itself may be fabricated from any material, and wooden, plastic and metal Venetian and Roman blinds are all commercially available. The hoisting mechanism (not shown) for turning the driveshaft 14 may be mechanized and may include a motor, which may be a DC or an AC or even a linear motor, and may be internal or external to the cradle (NUM). Typically, the hoisting mechanism will include a gear system, such as a planetary gear system or a series of pulleys, to couple and step down the rotation of the motor spindle to the appropriate speed for winching the blind. It may include a tubular motor for example. The hoisting mechanism directly or indirectly turns the driveshaft 14, which is typically has a square or a rectangular cross section, and is usually about 5 mm or 6 mm across. The driveshaft may be manufactured from a wide range of materials, and both steel and aluminium driveshafts are commonly employed. Alternatively, however, the hoisting mechanism may be a mechanical mechanism, being based on a hand actuator and gears, or other winching means. Thus, it will be appreciated that the invention is not limited to what has been described hereinabove merely by way of example. Rather, the invention is limited solely by the claims which follow.

Claims

1. A spooling mechanism for winding the drawstring of a blind, comprising: a drive pulley fixed to a driveshaft, static holder, and a cone shaped drum held between the pulley and static holder for free rotation therebetween, with the narrow end of the cone engaging the pulley and the wider end engaging the static holder, wherein a drawstring that passes through a conduit on the static holder and winds around the drum is fixed to the drive pulley, such that rotation of the driveshaft increases tension in the drawstring causing it to wind up unto the freely rotating drum without becoming entangled or overlapped while winding.

2. The spooling mechanism of claim 1, wherein the freely rotating drum has a frustoconical cross-section.

3. The spooling mechanism of claim 1, wherein the drawstring is selected from the list of cords, strings, threads, ropes, chains, braids and tapes.

4. The spooling mechanism of claim 1, wherein the blind is raised and lowered by rotation of said driveshaft.

5. The spooling mechanism of claim 1, wherein the driveshaft is rotated by a motorized or geared hoisting mechanism.

6. The spooling mechanism of claim 5, wherein the hoisting mechanism includes a motor, or chain or belt, or a manual crank operated gear.

7. The spooling mechanism of claim 5, wherein the hoisting mechanism includes a hand actuator.

8. A spooling mechanism of claim 1, for incorporating in a Roman blind or a Venetian blind.

9. A blind including a spooling mechanism as claimed in any one of claims 1 to 8, for winding the drawstring of the blind.

10. A spooling mechanism for winding the drawstring of a blind substantially as described and illustrated with reference to claims 1 to 8 and

Figures 1 to 4.

11. A Venetian blind including a spooling mechanism substantially as described and illustrated with reference to claims 1 to 8 and Figures 1 - 4.