This speci ication relates to apparatus for operati curtains and the like and is particularly concerned with an electrically powered unit which may be used e.g. to open and close curtains.

There are known arrangements in which an electric motor drives a rotatable output member, such as a pulley, which is engaged with a curtain operating element such as a cord. Such arrangements are powered by the- domestic mains electricity supply and a suitable switching device is provided for controlling the movement of the curtains. A problem with known arrangements is that to cope with even domestic weight curtains, fairly large electric motors are required. This has meant that the drive units have been relatively large with consequent disadvantages, particularly in the context of domestic use.

It has been suggested that a smaller type of electr motor, such as DC motor, could be employed. By employing a substantial reduction gear train, start-up problems can be avoided, taking into account also the high start-up torque characteristics which such motors may possess. To provide an adequately high curtain operating speed, however, the motor must be capable of substantial speeds in view of the gear train, and in any event with such mot it may be the case that maximum power is only developed at high speed.

It has been found that the provision of a gear trai providing a substantial speed reduction can add to both the size and the noise of the apparatus, which is undesir particularly in the context of domestic use. There is thu a need for a system which enables a small sized, high spee motor to be employed in such a way that its potential advantages can be realised.

Viewed from one aspect there is disclosed herein apparatus for operating curtains and the like, comprising an electric motor having a drive shaft extending axially from one end thereof, a final output member mounted for rotation about an axis parallel to said drive shaft, said final output member being adapted for engagement with a curtain operating element, a first spur gear mounted on the drive shaft, and a second spur gear mounted for rotation about an axis parallel to said drive shaft, said second spur gear meshing with said first spur gear and being drivingly connected to said final output member, wherein the gear ratio between said first and second spur gears is such as to provide a considerable reduction in speed between the drive shaft and the final output.

Two main advantages stem from the use of the immediate and substantial speed change provided by the spur gear arrangement. Firstly, it is possible to use a high speed motor, such as a small size low-voltage DC motor, and reduce its speed to a useful level with the minimum number of gears, and secondly it is possible to manufacture the second spur gear from a synthetic material such as nylon which has quiet running characteristics. It has been found that small gears of e.g. nylon are subject to excessive wear and, in time, cease to run smoothly. The necessarily large diameter of the second spur gear permits the use of such materials whilst retaining long life and smooth running, and provides a considerable reduction in gear noise.

The electric motor may be a DC permanent magnet motor with an operating range of say 6 to 24 v DC, capable of running at speeds of up to, say, 15,000 rp . The motor should be reversible so that by means of a suitable switch the polarity of the supply can be reversed and curtains opened

and closed as desired. In general, a separate power pack will be provided, to transform and rectify the domestic AC mains supply, but this can be provided away from the drive unit itself and need not occupy space in undesirable positions.

A typical motor which might be used would have - at a nominal operating voltage of 12 v DC - a maximum power of around 22w, a maximum torque of around 1700 g cm, and a maximum speed of around 5,250 rpm. The torque would be substantial at start-up, and reduce with increasing speed. A gear ratio of say 45 -60 to 1 might be used between the motor drive shaft and the final output member. Whilst it might be possible to use simply the first or second spur gears to provide the required ratio, at least one intermediate gear train may be necessary. It should be noted that if conserving space, the diameter of the second spur gear should not greatly exceed the dimensions of the- motor. Similarly, there is a practical minimum diameter for the first spur gear and the result of these constraints is to limit the reduction ratio which can be otained in practice. A further, intermediate gear train should employ spur gears rotatable about axes parallel to the motor drive shaft. In one particular embodiment, a third, small diameter spur gear could be mounted for rotation with the second spur gear and be meshed with a fourth, large diameter spur gear mounted for rotation with the final output member.

As already noted the use of the motor capable of high speeds, in conjunction with a substantial reduction gear train, enables the motor size to be kept small. To enable this advantage to be realised in practice, it is desirable to design the remainder of the apparatus such that space is conserved. Attention has therefore been directed to developing a space-conserving disposition for the

elements and thus viewed from a further aspect there is disclosed herein apparatus for operating curtains and the like, comprising an electric motor having a drive shaft projecting axially from one end thereof, a final output member mounted for rotation about an axis parallel to said drive shaft and laterally spaced therefrom, said final output member being adapted for engagement with a curtain operating element, and a gear train interconnecting the motor drive shaft and the final output member, said gear train comprising a first spur gear mounted on the motor drive shaft close to where i projects from the motor, and a second spur gear meshing with the first spur gear and mounted on a support ^• shaft parallel to the motor drive shaft and disposed laterally of the motor in the same general direction as the final output member, the support shaft having a portion projecting back towards the other end of the motor away from the motor drive shaft, which portion carries means drivingly connected to the final output member.

Thus, the drive for the final output member is brought from the end of the motor back down along its side, so that the axial extent of the arrangement can be reduced. To benefit fully from this, the final output member should be mounted within the axial limits of the remainder of the apparatus, and it may for example be positioned approximately mid-way along the length of the motor. The connection between the support shaft and the final output member could be direct, but preferably involves a further gear train, such as a third spur gear on the support shaft meshing with a fourth spur gear on a final shaft carrying the output member. In any event, size restrictions of the diameters of the first and second spur gears may mean that the support shaft will lie too close to the side of the motor to carry the final output

member within the confines of the axial extent of the motor.

Evidently, such an arrangement lends itself to advantageous use of the first aspect referred to earlier, with there being a substantial reduction ratio between the first and second spur gears.

In general, all gears and the final output member should be restricted in size so as not greatly to exceed the radial dimensions of the motor, and similarly the axial extent of all components should . be such that they do not extend greatly beyond the ends of the motor. It has been found that in a system using four spur gears, it is possible to have a substantially square arrangement in plan view with the side lengths corresponding generally to the length of the motor and its drive shaft. The height of the apparatus is governed by the height of the motor.

The final output member may be in the form of a pulley to receive a curtain cord. The pulley may advantageously have a V-groove to grip cords of varying diameters and may be of plastics or any other suitable material. Means may be provided to guide the cord around the pulley. To provide a simple manner of preventing excessive movement of e.g. curtains, a slipping clutch may be provided to operate when the end of the closing or opening run has been reached. An operator can then operate the switch accordingly although electrical sensors could be provided if desired. Preferably, the clutch mechanism is provided on a final shaft driving the output member rather than e.g. on the drive shaft from the motor itself. The latter arrangement could add to the axial extent of the apparatus.

In a preferred embodiment the clutch mechanism comprises a plate fixed for rotation with a shaft on which the output member is rotatably mounted.

this plate being fixed axially relative to the shaft, the output member being movable axially with respect to the shaft into and out of driving engagement with the plate, and there being a spring urging the output member towards the plate. The spring may act directly on the output member or indirectly via a second plate movable axially on the shaft. The engagement between the output member and the first plate could be direct or indirect, e.g. through a friction plate or washer. The spring may be a coil spring disposed on the shaft.

In a particularly preferred arrangement, where the output member is in the form of a pulley, it may be formed in two parts movable axially towards and away from each other to account for varying cord size and/or to provide greater gripping of the cord by virtue of resilient means urging the members together.

Such an arrangement may be of use in many contexts and thus, viewed from a still further aspect there is disclosed herein apparatus for transmitting drive from a shaft to a curtain cord or other operating element, comprising a plate fixed for rotation with the shaft, a first pulley- forming member rotatably mounted on the shaft, and axially movable thereon into and out of driving engagement with the plate, a second pulley-forming member mounted for rotation with the first member and capable of axial movement relative thereto, and a spring urging the second member towards the first member and the plate, the two members defining a pulley for receiving the cord or other element. In such an arrangement, the clutch engaging force is transmitted through the second pulley forming member. The curtain cord or other element will be disposed between the two pulley forming members, which may define a V-shaped groove. The spring, e.g. a coil spring, may act directly on

the second member, or through a second plate movable axially relative to the shaft. Similarily the driving engagement with the first plate may be direct or indirect. The second member may be mounted directly on the first member for sliding movement, whilst restrained against rotation relative thereto. A stop may be provided to limit the extent to which the members can move together.

Such an arrangement may be particularly advantageou in conjunction with other aspects discussed earlier.

The curtain operating element may, as mentioned earlier, be in the form of a cord engaged round a pulley. In such an arrangement guide pins or the like may be provided to force the cord to extend a greater distance round the pulley, increasing the area of contact and ensuring a more efficient transfer of the driving force. Such pins may also assist in dealing with occasions when play appears in the cord.

In one preferred arrangement, a cord is guided positively through apertures in e.g. a block, which limit transverse movement of the cord in all directions. A tongue may be provided, projecting between the sides of the pulley where the cord passes into and out of the pulley, so as to prevent slack cord looping an excessive distance in the wrong direction around the pulley. Such a tongue could be disposed between the two apertures of the block.

Two specific embodiments of the various aspects of this disclosure will now be described by way of example and with reference to the accompanying drawings in which:-

Figure 1 is a schematic view of a curtain system utilising curtain operating apparatus;

Figure 2 is a plan view of certain components of the apparatus;

Figure 3 is a section on line III - III of Figure 2;

Figure 4 is a view similar to Figure 3, but of a second embodiment;

Figure 5 is a view on the line V-V of Figure 4; and Figure 6 is a partial view in the direction of arrow X on Figure 5.

As shown in Figure 1, a curtain 1 is suspended on a pole 2 by means of rings 3. A cord 4 is provided for opening and closing the curtain in a conventional manner, and this passes over pulleys 5 and 5' to a drive unit 6 embodying apparatus in accordance with the invention. This unit serves o drive the cord 4 and is powered by a DC supply from an isolating transformer/rectifier pack (not shown) connected to a conventional 240 v AC domestic mains supply. Power is supplied through a reversing switch 7 having a centre-off position and reverse polarity on-positions so as to drive the cord in opposite directions as required to open or close the curtains.

As shown in Figure 2, the drive unit 6 comprises a base plate 8, of brass or another suitable material, of generally square shape. The base plate 8 may be secured to a wall or other supporting surface by means of screws etc, passing through noise and vibration insulating grommets 9. A cover (not shown) will be provided for the drive unit 6, being secured to mounting post 9'. The dimensions of the base plate may for example be 10 cm by 10 cm, generally similar to those of a domestic light switch panel.

A small size electric motor 10 is mounted in the base plate by means of a support bracket 11. The motor is of the DC, permanent magnet type operating at 18 v DC with an output speed of up to 10,500 rpm and a power requirement of about 20 watts. A suitable motor would be model RS-550S available from Mabuσhi Motor. The motor has a high

start up torque and a maximum power at speed high enough to drive heavy domestic curtains at reasonable rates. The motor 10 has a drive shaft 12 projecting from one end, on which is secured a small diameter spur gear 13 mounted close to the the end of the motor. This gear meshes with a large diameter spur gear 14 having considerably more teeth so as to provide a substantial reduction in speed.

The spur gear 14 is secured to an intermediate shaft 15 supported by bearings (not shown) in support brackets 16 and 17 secured to the base. The shaft 15 is parallel to, and laterally displaced from, the motor drive shaft 12 and projects back along the side of the motor 10. The shaft 15 carries a third, small diameter spur gear 18 where it projects back beyond the forward end of the motor. This gear meshes with a fourth spur gear 19 of large diameter providing a further substantial reduction ^' in speed. As shown more clearly in Figure 3, the fourth gear 19 is secured to a final output shaft 20 by means of a screw 21. The final output shaft 20 is supported by portions of bracket 17 and passes through a bearing 22 in one portion. Optionally, a similar bearing could be provided in the other portion if desired. The final output shaft 20 is parallel to the motor drive shaft 12 and is laterally displaced by a greater amount than intermediate shaft 15, but in the same general direction. On the shaft 20 is rotatably mounted a pulley assembly 23, comprising a bush 24 rotatable on the shaft 20 and a pair of plates 25 defining a "V" -shaped groove, the plates being provided with high friction opposed, patterned gripping surfaces 26 of plastics material and being secured to the bush 24. The shaft 20 is provided with an integral plate 27 and a fibre washer 28 or the like is provided between the bush 24 and the plate 27.

The end of the shaft 20 is threaded to receive a self-locking nut 48 which acts against a washer

29 bearing on a coil spring 30. In turn, spring

30 bears on bush 24 through a washer 31 and a further fibre washer 32. Thus at all times, the pulley assembly is urged into driving engagement with the plate 27 and thence the motor drive shaft, with a force determined by the compression in spring 30, which can be adjusted by means of nut 48. Thus the pulley will turn with shaft 20 as the motor is operated, until a sufficient restraining force is applied to the pulley. At that time, the mechanism - which acts as a clutch - will slip and whilst the motor will turn the pulley will not. The curtain cord 4 is entrained around the pulley 23 and is thus driven when the motor is operated, until the end of a run when the cord stops at the limit of the curtain track in either direction, causing the pulley to stop and the clutch to slip. At this point an operator can operate the switch 7 to stop motor 10.

The pulley is situated approximately mid¬ way along the length of the motor 10 and it will be seen that the complete unit is extremely compact. The dimensions of gears 14 and 19 do not exceed greatly those of the motor itself.

A pair of guide pins 33 project from bracket 17 and force the cord 4 to travel further round the pulley 23. The pins 33 are spaced apart by less than the diameter of the path followed by the cord around the pulley 23. Not only do these pins increase the area of contact between the cord and pulley, but when there is slack then it will tend to appear at the pins rather than around the pulley. Thus the cord 4 is kept in maximum engagement with the pulley 23 even when slack occurs.

For general use, a cord speed of 25 cm per second may be a suitable average. With the motor

described, this could require an overall reduction is gearing of between 45 and 60 to 1.

A shaped element of plastics or the like, of known type, may extend into the "V"-spaced of the pulley to guide the cord in and out and prevent it looping completely around.

The second, large spur gear is of nylon, which provides smooth and quiet running and eliminates undesirable high frequency noise. Figures 4, 5 and 6 show an output stage used in a second embodiment, the remainder of the construction being as in the first embodiment, and corresponding parts being marked with the same reference numerals. Referring now to these figures, the pulley assembly 23' comprises a first member 34 rotatably mounted on shaft 20 and slidable thereon. This member 34 can be urged into driving engagement with plate 27 via a fibre washer 28. The member includes an axial projection 35 on which is slidably mounted a second member 36. Flats 37 on the projection 35 engage with flats 38 in an aperture in member 36, through which projection 35 passes, so that member 36 is fixed for rotation with member 34. Spring 30 bears against member 36 through a washer 31* and a fibre washer 32 ¹ . Thus, member 36 is biased towards member 34, and if a cord 4 is in place between the two members this biasing force will also urge them towards and into driving engagement with plate 27. A shoulder 39 is provided on projection 35 to limit the movement of member 36 towards member 34. As with the previous embodiment, high friction opposed, patterned gripping surfaces 26* are provided. With reference to Figures 5 and 6 in particular, it will be seen that a guide block 40 is provided. This is made of nylon or another suitable plastics material and is provided with two passageways 41 to guide the cord 4 which passes through them. The passageways have radiused ends 42, and serve

a similar purpose to pins 3 in the previous embodiment, but restrict movement in all lateral directions. Block 40 is formed in two halves 43 and 44, bolted together at 45, to permit easy assembly. A tongue 46, also of a plastics material, is clamped between the two halves and projects into the space between the two pulley members 34 and 36, to prevent looping of the cord in this region. It is particularly important that cord slack is prevented from interfering with the gear or motor mechanism, and the region of the cord may be a sealed unit to ensure this, for example by suitably designing the cover.

With either embodiment the overall device is compact, quiet and efficient and despite its small size it is capable of dealing with heavy curtains in domestic environments.

Whilst the curtain operating apparatus has been described particularly with reference to a DC motor, it is conceivable that other small motors might be used. Furthermore, modifications to the specific embodiments of the apparatus and to any broad aspects thereof referred to or suggested herein may be apparent to those skilled in the art and the disclosure hereof is intended to encompass any such modifications. The claims presently appended hereto define those aspect(s) of the apparatus for which protection is being sought for the time being.