EP1352148A1

EP1352148A1 - Electrical operator arrangement for a venetian blind

Info

Publication number: EP1352148A1
Application number: EP02715372A
Authority: EP
Inventors: Gert Godvig Lassen
Original assignee: VKR Holding AS
Current assignee: VKR Holding AS
Priority date: 2001-01-16
Filing date: 2002-01-15
Publication date: 2003-10-15
Anticipated expiration: 2022-01-15
Also published as: WO2002057586A1; EP1352148B1; ATE444432T1; ES2334334T3; DK1352148T3; CN1486393A; DE60233860D1; CN1208541C

Abstract

Electrical operator arrangement for a venetian blind comprising operating members which are preferably situated in a top casing, a bottom bar (1) connected to the operating members by means of a raising cord system (7, 8), and a number of ladder cords (3) connected to a tilt mechanism, said ladder cords being situated between the bottom bar (1) and the operating members and carrying a number of slats (18). The operator arrangement comprises a motor (12) with a motor casing and a motor armature, where said motor (12) is on one hand part of the tilt mechanism in such a manner that the tilt mechanism, by means of a tilt member (9), can tilt the slats (18) in one direction or the other depending on the operating direction of the motor (12), and on the other hand constitutes a part of the raising cord system (7, 8) in such a manner that the bottom bar (1) can be raised or lowered depending on the operating direction of the motor (12). The motor (12) is rotatably journalled with the tilt mechanism and the raising cord system (7, 8) connected to the motor casing and the motor armature respectively or the other way round, and the resistance in the raising cord system (7, 8) at non-blocked tilt means (9) is so much higher than the resistance in the tilt mechanism, that rotation of that motor part which is part of the raising cord system (7, 8), is prevented. The tilt mechanism comprises two blocking means (10, 11) for blocking the tilt means (9) at two predetermined positions.

Description

Electrical operator arrangement for a Venetian blind

The present invention relates to an^' electrical operator arrangement for a Venetian blind comprising operating members which are preferably situated in a top casing, a bottom bar connected to the operating members by means of a raising cord system, and a number of ladder cords connected to a tilt mechanism, said ladder cords being situated between the bottom bar and the operating members and carrying a number of slats, where said operator arrangement comprises a motor with a motor casing and a motor armature, where said motor is on one hand part of the tilt mechanism in such a manner that the tilt mechanism, by means of a tilt member, can tilt the slats in one direction or the other depending on the operating direction of the motor, and on the other hand constitutes a part of the raising cord system in such a manner that the bottom bar can be raised or lowered depending on the operating direction of the motor.

With electrical operator arrangements for Venetian blinds of the above-mentioned kind, a simple and user friendly operation is typically desired, in such a manner that there are the least possible num- ber of operation handles or buttons for the user to chose between, and that the individual operating stages are carried out at a pace suitable for the user.

From DK-B-158054 an operator arrangement of the above-mentioned kind is known where the motor is activated to the one or the other direction of rotation by operating a switch with three positions. As long as the slats are in between their extreme positions, the motor will, because of a spring clutch, which is per se known from DE-B-1 683 007, cause a tilt movement of the slats. When the slats reach the one or the other of their extreme positions, the tilt movement will stop because of the spring clutch, and a raising or a lowering movement of the Venetian blind will occur. In order to facilitate the angular positioning of the slats, there are electronic circuits which, for a certain period of time while the posi- tioning is made, cause the rotation of the motor to slow down in comparison to during the raising or lowering movement .

Even though this operating arrangement is convenient for the user, it does however entail problems in design, because the use of electronic control circuits complicate the electrical part of the arrangement .

It is the object of the invention to provide an operator arrangement which can overcome these inconveniences.

This object is achieved by means of an operator arrangement according to the opening paragraph, which is distinctive in that the motor is rotatably jour- nalled in such a manner that the resistance in the raising cord system by non-blocked tilt means is so much higher than the resistance in the tilt mechanism, that rotation of that motor part which is part of the raising cord system, is prevented, and that the tilt mechanism comprises two blocking means for blocking the tilt means at two predetermined positions .

Preferred embodiments of the invention appear from the dependent claims .

The invention will now be described in further detail by means of an example embodiment and with reference to the schematic drawings where

Fig. 1 shows schematically a first embodiment according to the invention of a Venetian blind with an operator arrangement, Fig. 2 shows schematically another embodiment according to the invention of a Venetian blind with an operator arrangement,

Fig. 3 shows schematically in a partial section an embodiment of a locking arrangement which may be incorporated in the embodiment according to fig. 2, and

Figs. 4a-4c show schematically sections along the line IV-IV in fig. 3 at various rotating positions of the motor shaft.

In Fig. 1 a Venetian blind with a bottom bar 1 and two raising cords 7, 8 is seen. Each raising cord's one end is connected to the lower side of the bottom bar 1, while its opposite end is connected to the upper side of the bottom bar 1.

The bottom bar 1 can be guided in not shown guide rails, which are mounted along frame sides in for instance a roof window where the Venetian blind is mounted.

In that connection it must be noted that in the following description it is presumed that the blind is mounted in connection with a vertical window.

Furthermore it must be noted that tilt system and raising cord system must be interpreted in the broadest possible sense, i.e. so that each of them comprises everything situated on the respective one or the other side of the air gap in the motor used for the operation. From the lower side of the bottom bar 1 the one raising cord 7 is lead downwards to a first member for change of direction situated at the lower part of the main window frame. From here the raising cord 7 is lead upwards along the window frame and around a driving pulley 13. In principle, the raising cords 7, 8 may be wound only half a turn round the driving pulley, but in practice, because of the transmission of power from the driving pulley 13 to the raising cords 7, 8 it is preferable to add one or more addi- tional full windings. From the driving pulley 13 the raising cord 7 is lead down to a second member for change of direction 4 and horizontally to a third member for change of direction 57. From here the raising cord 7 is lead down to the bottom bar 1 and connected hereto. Depending on where the raising cord 7 is desired to be lead to the bottom bar 1, the distance which the raising cord is lead horizontally, can be varied.

For aesthetic reasons, the raising cord 7 will often be lead down in the vicinity of a ladder cord

3, which will be mentioned in greater detail later. The raising cord 7 may, however, also be lead down in the vicinity of and along the window frame. The guiding of the raising cord 8 is similar to that of the raising cord 7. Thus, the other raising cord 8 from the bottom side of the bottom bar 1 is lead downwards to a member for change of direction 28. From here the raising cord 8 is lead upwards to the top casing, and by means of two members for change of direction 6a, 6b horizontally along said casing and vertically up to and around the driving pulley 13. From the driving pulley 13 the raising cord 8 is guided down to the member for change of direction 4 and horizontally to a member for change of direction 58, from where the raising cord 8 is lead down to the bottom bar 1 and connected hereto.

It is noted that the raising cords 7 and 8 are both lead via the same member for change of direction . There is nothing to prevent using two separate members for change of direction instead of one common one.

The above-mentioned members for change of di- rection can have different embodiments, including wheels, pulleys or rollers. As it will appear from the further description, these do not have to be easy-running but may incorporate bearing friction or actually be blocked. Each of the raising cords 7 and 8 forms, as it appears form the information given above, a closed loop from the top of the bottom bar 1 to the bottom of the bottom bar 1. By means of these closed loops, the bottom bar 1 can be raised or lowered by exercising a pulling force on the raising cords 7, 8 in the one or the other direction. This pulling force on the raising cords 7, 8 is obtained by a reversible elec- trie motor 12, for instance a DC motor, the motor armature of which in the shown embodiment is connected to the driving pulley 13 via a shaft 17. The loops formed by the raising cords 7 and 8 are guided sufficiently tightly in order to obtain sufficient fric- tion to enable the transmission of force between the raising cords 7 and 8 and the driving pulley 13.

From the bottom bar 1 there are furthermore lead two sets of ladder cords 3 up to tilt members 9 in the top casing. The ladder cords have two side cords 3a, 3b each. Between these side cords 3a, 3b there are a number of rungs 3c, on which blind slats 18 are resting. For the sake of clarity, only one of these blind slats 18 is shown in fig. 1. As, in principle, the ladder cords 3 and the tilt members 9 are identical, they are provided with the same reference numbers, and the mode of operation will subsequently be described as if there were one only.

The two side cords 3a, 3b of a ladder cord 3 are in the top casing guided in either direction around a tilt member 9 in the form of a cylinder body and attached to this body. Depending on the diameter, the side cords may be wound several times in opposite directions around the cylinder body before being attached thereto. The tilt member 9 is in fixed connection with a shaft 16 which again is connected to the motor 12. To be more precise, in the shown embodiment, the shaft 16 is permanently connected to the casing of the motor 12. The motor 12 is not in fixed connection with the top casing but is rotatably journalled by means of the two shafts 16 and 17, i.e. the shaft connected to the motor armature 17 and the shaft connected to the casing 16.

At the extremity opposite the motor, the shaft 16 is furthermore provided with a blocking member limiting the angle with which the shaft 16 may rotate relative to the top casing. In the embodiment in fig. 1, the blocking member comprises a first cogwheel 10 in fixed connection with the shaft 16, said cogwheel meshing with another cogwheel 11. The other cogwheel 11 is journalled in such a manner on a shaft 19 that it is freely rotatable when not taking into account the meshing with the first cogwheel 10. The shaft 19 is fixed relative to the top casing.

The other cogwheel 11 shows a discontinuity 20 in the cogging. This discontinuity can for example be a missing tooth gap, or a tooth which is taller or wider than the others .

When the shaft 16, and thus the first cogwheel 10, is turning in the one direction of rotation, the other cogwheel 11 is running freely along. By contin- ued rotation of the first cogwheel 10, the discontinuity 20 is eventually turned to the point of the meshing with the first cogwheel 10 and blocks the further rotation of both cogwheels. From this position the shaft 16 cannot be rotated any further but only back in the opposite direction. The rotation in the opposite direction is limited in the same way,^' because continued rotation will lead to the discontinuity being encountered from the other side .

In the described embodiment only one and the same discontinuity has been used, as this gives optimum use of the periphery of the cogwheel 11. However, the use of two is also an option, in which case there will be an unused intermediate periphery sector.

In the following, the function of the electri- cal operator arrangement will be described based on a blind position as shown in fig. 1, where neither the bottom bar 1, nor the slats 18 are in an extreme position. The motor 12 is, as mentioned, for instance a reversible DC motor where the direction of rotation of the motor armature relative to the casing is reversed by means of a reversal of the polarity of the supply voltage. In the following, the expression direction of rotation of the motor will be used. This should be interpreted as the direction of the movement of the motor armature relative to the motor casing. If operation of the blind is desired in the given situation, this is effected by supplying the motor 12 with current through a cable 14 by means of an electrical operating member. The electrical operating member can be for example a switch with three positions, i.e. a neutral disconnected centre position and two activation positions, one of which supplies the motor 12 with current of one polarity, and the other activation position supplies the motor 12 with current of the opposite polarity. Hereby the mo- tor 12 can be activated in the one or the other directions of rotation.

If the switch is operated in such a manner that the motor 12 is supplied with current for the first direction of rotation, the motor armature rotates in the given direction of rotation relative to the motor casing.

However, the motor 12 is as mentioned not in fixed connection with the top casing, but rotatably journalled relative hereto. Therefore there is in principle provided for both that the motor casing remains stationary while the motor armature rotates, and the opposite situation, i.e. that the motor casing rotates while the armature remains stationary.

The operator arrangement is therefore designed in such a manner that the resistance, i.e. the friction and the inertia in the raising cord system 7, 8 with the members for change of direction 4, 6a, 6b, 27, 28, 57, 58, the winding of the cords 7, 8 around the driving pulley, the friction in the bearing 17 as well as the possible guiding of the bottom bar in guide rails, is considerably higher than the resistance from the tilt mechanism with the ladder cords 3 and the blocking members .

Therefore the resistance from the friction and the inertia in the raising cord system in the situation shown in fig. 1 will regardless of the direction of rotation of the motor keep the raising cord system in position and thus the motor armature, which causes the motor casing and not the armature to move .

Thereby the motor casing, the shaft 16, the tilt members 9 and the cogwheel 10 rotate together while at the same time rotating the cogwheel 11. By way of this rotation of the shaft 16, the cylinder 9 is turned in such a manner that one of the side cords 3a, 3b is would up on the cylinder while the other one is unwound. This achieves the tilt movement of the slats 18, because one of the side cords 3a, 3b is raised while the other one is lowered, such that the ladder rungs on which the slats 18 are resting, are tilted.

If the polarity of the current supply for the motor is reversed, the whole system of motor casing, shaft 16, tilt members 9 and blocking members rotate in the opposite direction, because the resistance in the form of friction and inertia in this embodiment of the invention is independent of the direction of rotation. By operating the switch it is thus possible to supply the motor 12 with current of the one or the other polarity and thus to tilt the slats 18 in the one or the other direction.

If the motor current is maintained for a suffi- ciently long period of time at a given polarity, the system of motor casing, shaft 16, tilt members 9 and blocking members will turn so far that the blocking members block in the manner described above. Here it must be noted that the cable 14 is designed in such a manner that the rotation of the motor casing is not obstructed. In the shown embodiment this design consists of an adaptation of the length of the cable 14 to the maximum rotation of the motor casing, but the skilled person will understand that other designs can be used, such as for example collector shoes.

When the blocking members block the shaft 16 like this, the motor casing becomes stationary, and the motor armature will start turning the driving pulley 13. This causes a pull to the cords, which, as previously described causes that the bottom bar is raised or lowered depending on the direction of rota- tion of the motor.

If the blind does not have to be raised or lowered entirely, the current to the motor 12 is interrupted, when the bottom bar 1 is at the desired level . Hereafter, it is possible to set a desired tilt position of the slats 18, by briefly operating the blind in the opposite direction, as this simply causes the blocking members to move away from the blocking position because of the previously described friction and inertia conditions.

It is thus possible either by prolonged activation of the one direction of rotation for the motor 12 to tilt the slats 18 until blockage, upon which the lifting movement will start automatically, or by prolonged activation of the other direction of rotation for the motor 12 to tilt the slats 18 in the other direction until blockage, upon which the lowering movement will start automatically.

At the same time it is possible via brief acti- vation of the one or the other direction of rotation for the motor 12 to set a desired tilt position for the Venetian blind, without effecting any raising or lowering movement . By choosing a suitable diameter for the cylinders 9 and/or the cogwheels 10 and 11, a suitable ratio between the time available for setting a suitable tilt angel for the slats 18, and the time necessary for raising or lowering the blind can be obtained, without necessitating regulation of the motor current, and without having to use extra gearings in the transmissions between the motor 12 and the tilt mechanism or between the motor 12 and the driving pulley 13.

Even though the tilt mechanisms described the in the embodiment example in fig. 1 are shown with cylinders, around which the side cords 3a, 3b to the ladder cords 3 are wound, it is also possible though to use for example pairs of arms protruding from the shaft, on which arms the ladder cords are mounted. In this case the blocking members could alternatively be stops for the arms .

As far as the blocking members themselves are concerned, these could also be as arm pairs 69, 70 mounted in connection with the motor casing 12 and interacting with a permanent stop 68, as illustrated in fig. 3 in connection with another embodiment of the invention, which will be described below. The embodiment shown in fig 2 has a slightly different raising cord system where the raising cords 7, 8 do not form closed loops, but end at the bottom bar 1. In order to obtain controlled winding of the raising cords 7, 8 these are wound around a coiling drum 71 which is preferably provided with an external thread, in which the raising cords 7, 8 are bedded during the winding.

For this embodiment, no more than three members for change of direction 6c, 57, 58, where friction can be obtained, are necessary.

One of these, namely the member for change of direction 6c is displaceable concurrently with the winding of the raising cords 6, 7, as indicated with a double arrow in fig. 2.

Because of the fewer places where friction can be obtained in this embodiment, it is preferable if the bearing 67 contributes with a rather large part of the total friction of the raising system.

Here it must be noted that in the first embodiment of the invention as well there is in principle nothing to prevent the bearing 17 from contributing with the major part of the friction. Thereby less wear and tear is caused for example to the cords, and it is no longer necessary to make sure that the cords have a fixed tension with regard to the cylinders or coils over which they are guided. Whether the friction in the raising cord system is mainly obtained by way of the friction in the bearing 17, 67, or whether the guiding of the cords plays an important role, this does not change the fact that the friction must be relatively high. This means that the resistance obtained from inertia and friction does not only have to be higher than the resistance from friction and inertia in the tilt system, but it must also be sufficient to keep in place the raising cords 7, 8, which will be influenced by the gravitational effect on the slats and the bottom bar.

In order to avoid over-dimensioning of the motor as a consequence of the relatively large force having to be exerted during a lifting movement in or- der to overcome both gravity and the friction necessary to counteract said gravity, it will be preferable to use a locking arrangement locking the ladder cords when they are influenced by the pull of gravity on the slats and the bottom bar. In the embodiment illustrated in figs. 3-4 such a locking arrangement has been inserted into the raising cord system.

Fig. 3 is a partial sectional drawing, i.e. the coiling drum 71 and the wound ladder cords 7, 8 are shown in sections, however, in order to facilitate the understanding of the function of the system, it is illustrated that the ladder cords 7, 8 are passing down on the face of the coiling drum seen relative to the drawing.

The locking arrangement comprises a bearing block 67, 67a, in which the motor shaft 65 is jour- nalled. This bearing has a built-in friction, such that the total resistance from friction and inertia, as it will be described later, is higher than the resistance in the tilt system.

On the motor shaft a carrier 65a has been formed, where said carrier during rotation may partly influence a coil spring 63 , partly influence another carrier 66, which is connected to a hollow coiling drum 71 to the raising cords 7, 8.

The other carrier 66 is fixed on a shaft with two shaft parts 64a, 64b. The one shaft part 64a is journalled in a bore in the motor shaft 65 while the other shaft part 64b ends in a cogwheel 72 which is engaged with a suitable projection 73 situated on the inside of the coiling drum 71.

As it appears from the figure, the carriers, springs and shafts of the locking arrangement are located in the hollow coiling drum 71 in such a manner that the total locking arrangement does not take up unnecessary space.

In the embodiment of the invention illustrated in fig. 3 the motor casing is provided with blocking members in the form of a pair of arms 69 , 70, in the form of for instance a couple of screws. However, the skilled person will be aware of the fact that other blocking members can be used as required, such as for example the ones illustrated in fig. 2.

The method of operation of the locking arrangement will now be described with reference to figs. 3 and 4, where fig. 4 shows a section seen along the line IV-IV in fig. 3.

As a starting point it is assumed that the tilt system is in a neutral position where the blocking members are not in action. From this position the motor casing will, when the motor is supplied with current, be able to turn in the one or the other direction, as desired, since the friction between the bearing 67 and the motor shaft 65 is so high that it exceeds the total resis- tance met by the motor casing in the form of friction and inertia in the rest of the tilt system'.

The motor shaft will thus remain in the same position, and the tilt system can therefore tilt the slats 18 between the two extreme positions where the blocking members enter into action.

When the blocking members enter into action, i.e. when one of the screws 69, 70 in fig. 3 hits the stop 68, or when the cogwheel 11 in fig. 2 hits the discontinuity in the cogging of the cogwheel 12, the resistance against the movement increases considerably. This entails that the motor casing halts while the motor shaft 65 overcomes the friction in the bearing 67 and thereby raises or lowers the blind slats 18 and the bottom bar 1 via the raising cords 7, 8. In principle, this sequence of movement is independent of whether there is a locking arrangement as the one described below, or instead a direct connection between the motor shaft 65 and the coiling drum 71. Reference is now made to fig. 4 for an explanation of the locking arrangement. In fig. 4 the bearing block 67 is seen with a cylindrical part 67a. Concentrically in the cylindrical part 67a of the bearing block 67, there is provided a through bore, in which the motor shaft 65 is frictionally jour- nalled. Centrally in the motor shaft 65, there is provided a bore which serves as bearing for another shaft 64. On the motor shaft 65 a carrier 65a is pro- vided, and likewise on the shaft 64a, 64b a carrier 66 is provided. These two carriers 65, 66 are arranged in such a manner that their rotational movement takes place on the same imaginary cylinder con- centric to the motor shaft 65 and the cylindrical part 67a of the bearing block 67, and made in such a manner that via a coil spring 63 they are able to engage with each other form both sides depending on their relative direction of rotation. On the cylindrical part 67a of the bearing block 67 as well as on both carriers 65a and 66 a spring coil 63 is concentrically arranged. At its respective ends the spring coil 63 has radially deflected parts 630, 631 which are made to engage with the carriers 65a, 66 .

In the position shown in fig. 4a, the carrier 66 is influenced in a clockwise direction by gravity on the raising cords 7, 8 as shown with the arrow g. Thereby the carrier 66 presses the radially deflected part 631 of the spring coil 63 in a clockwise direction which makes the spring coil 63 squeeze the cylindrical part 67a of the fixed bearing block 67. This also efficiently keeps the shaft 64a, 64b in position and thus also the coiling drum 71, the raising cords 7, 8, the blind slats 18 and bottom bar 1 in a given position.

Because of the friction between the motor shaft 65 and the bearing block 67, any of the situations shown in figs. 4a-4c will be stationary, as long as the tilt system has not reached one of its extreme positions, where it is blocked by the blocking means. When the blocking means enter into function at one of the extreme positions of the system, the rotation of the motor casing is blocked, and instead the motor shaft 65 and thus the engaging member 65a start rotating.

If the motor shaft 65 rotates clockwise, the engaging member 65a moves from the position shown in fig. 4a to the position shown in fig. 4b. By continued rotation the carrier 65a presses the radially deflected part 630 of the spring coil 63 and thereby causes that said carrier is loosened relative to the cylindrical part 67a of the bearing block 67. Hereafter the spring 63 will start rotating relative to the cylindrical part 67a of the bearing block 67 under the influence of the motor torque transferred via the carrier 65a and gravity transferred via the carrier 66. All three parts, i.e. the two carriers 65a, 66 and the spring 63 will thus turn together while the slats of the blind 18 and the bottom bar 1 are lowered.

This movement can be stopped at any time, and if the direction of rotation of the motor 12 is hereafter reversed, the situation shown in fig. 4b will be maintained because of the influence of gravity and friction respectively on the two carriers 66 , 65a, while the slats are tilted. If the slats 18 are tilted completely to the opposite blocking position, the motor shaft is again able to overcome the friction in the bearing block 67, and it will move from the position shown in fig. 4b through the position shown in fig. 4a to the one shown in fig. 4c.

Here the carrier 65a presses on the second one of the radial deflections 631 of the spring coil 63, and thereby loosens the spring coil 63 in the same way as it did in the opposite direction by means of the first deflection 630.

Thereby the carrier 65a squeezes the carrier 66 via the deflection 631 and thereby raises the blind slats 18 and the bottom bar 1 against gravity.

In all three embodiments, it is thus achieved that the motor shaft is stationary until the motor casing is blocked in an extreme position of the tilt movement of the slats, after which the motor casing is stationary while the motor shaft is turning. The skilled person will understand that without deviating from the invention it is also possible to let the tilt mechanism be connected to the motor armature and the raising mechanism to the motor casing.

Claims

P A T E N T C L A I M S

1. Electrical operator arrangement for a Venetian blind comprising operating members which are preferably situated in a top casing, a bottom bar (1) connected to the operating members by means of a raising cord system (7, 8) , and a number of ladder cords (3) connected to a tilt mechanism, said ladder cords being situated between the bottom bar (1) and the operating members and carrying a number of slats (18) , where said operator arrangement comprises a motor (12) with a motor casing and a motor armature, where said motor (12) is on one hand part of the tilt mechanism in such a manner that the tilt mechanism, by means of a tilt member (9) , can tilt the slats (18) in one direction or the other depending on the operating direction of the motor (12) , and on the other hand constitutes a part of the raising cord system (7, 8) in such a manner that the bottom bar (1) can be raised or lowered depending on the operating direction of the motor (12), c h a r a c t e r i z e d in that the motor (12) is rotatably jour- nalled in such a manner that the resistance in the raising cord system (7, 8) at non-blocked tilt means (9) is so much higher than the resistance in the tilt mechanism, that rotation of that motor part which is part of the raising cord system (7, 8), is prevented, and that the tilt mechanism comprises two blocking means (10, 11) for blocking the tilt means (9) at two predetermined positions.

2. Electrical operator arrangement according to claim 1, c h a r a c t e r i z e d in that in the raising cord system a locking arrangement is included, which locking arrangement maintains the posi- tion of the raising cords (7, 8) against the influence of gravity.

3. Electrical operator arrangement according to claim 1, c h a r a c t e r i z e d in that the tilt means (9) comprises a cylinder body.

4. Electrical operator arrangement according to claim 1, c h a r a c t e r i z e d in that the tilt means (9) comprises lever arms.

5. Electrical operator arrangement according to any one of the claims 1 to 4, c h a r a c t e r i z e d in that the blocking means comprise one first cogwheel (10) connected to the tilt means (9) , and a freely rotating second cogwheel (11) engaging with the first cogwheel (10) , which second cogwheel has a cogging presenting at least one discontinuity.

6. Electrical operator arrangement according to claim 5, c h a r a c t e r i z e d in that said discontinuity comprises a missing tooth gap.

7. Electrical operator arrangement according to claim 6, c h a r a c t e r i z e d in that said discontinuity comprises at least one tooth which is taller than the others.

8. Electrical operator arrangement according to claim 4, c h a r a c t e r i z e d in that the blocking means comprise stops for the lever arms.

9. Electrical operator arrangement according to one of the preceding claims, c h a r a c t e r i z e d in that the raising cord system is con- nected to the motor armature and the tilt means to the motor casing.

10. Electrical operator arrangement according to one of the preceding claims, c h a r a c t e r i z e d in that the raising cord system is con- nected to the motor casing and the tilt means to the motor armature .