BACKGROUND Current drive devices for elevator booth doors generally project beyond the roof of the elevator booth and require a relatively large amount of space which may limit the volume of the booth and require that the elevator shaft is higher owing to the top portion of the booth and the required residual space. Moreover, should the system break down, maintenance operations needs to be carried out on the roof of the booth.

SUMMARY OF THE INVENTION The invention seeks to resolve these drawbacks and offers a compact drive device for elevator booth doors and is of the door translation type able to move said doors by means of a belt driven in the upper support lintel of the doors with which said doors are rendered integral, said device being characterised in that it includes an a. c. electric motor of the ring torque type, and a drive pulley of a relatively large diameter and adapted to cover at least one portion of the width of the motor so as to reduce the width of the pulley/motor unit, this unit being fixed to said upper lintel inside the latter.

Advantageously, the rotor of the motor with which the drive pulley is rendered integral is mounted rotating on an axis integral with a lateral plate to which the stator is fixed, the latter being fixed to the lintel by a peripheral housing.

The thickness of the pulley/motor unit is less than or equal to the width of the support lintel so that it does not project outside the lintel.

The motor is of course fed with power by an electronic control block controlling

it at a speed able to vary according to the frequency of the current (synchronous motor) and the torque, especially at the end of travel, over an obstacle and in acceleration phase according to the current (intensity), the voltage being kept to a low value, namely about 24 volts, so as to increase electric safety.

The control block and the corresponding 24 volt transformer are housed in the lintel without projecting.

The relatively large diameter of the pulley associated with the-torque of the motor, which is also large, makes it possible to drive doors at an adequate speed directly without requiring a speed reducer.

As a result of this arrangement, according to the invention, a compact drive device is obtained housed in the support lintel of the elevator booth doors and forms an easily installable homogeneous block which is accessible without projecting for carrying out maintenance operations from the stairs-head, thus increasing the space available in the booth and outside the latter in the shaft.

Moreover, the running pulley receiving the drive belt of the doors at the other extremity of the lintel relatively to the motor is mounted in a housing or similar frame to that of the motor and secured to the lintel, this pulley being identical to that of the motor.

This arrangement reduces the number of pieces required.

In addition, a 24 volt stand-by battery can also be installed in the internal section of the lintel without projecting or projecting slightly.

The invention also concerns a ring torque type electric motor whose drive pulley covers part of its width, and also an elevator booth door support lintel equipped with the drive device of the invention.

These characteristics and advantages of the invention and others shall be more readily understood from a reading of the following description of an embodiment example of the invention with reference to the accompanying drawings on which: BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES Figure 1 is a perspective view of a support lintel of the doors of an elevator booth equipped with the drive device of the invention;

Figure 2 is a perspective and pull up view of the ring torque motor and its pulley used in the drive device of the invention; Figure 3 is a view similar to figure 2 showing the running pulley receiving the drive belt on the lintel at the extremity opposite the motor on the lintel, and Figure 4 is a cross section view of the lintel equipped with the drive device of the invention.

DETAILED DESCRIPTION As shown on figure 1, the drive device of the invention is shown for a central open application of two doors 1 of the elevator booth. Of course, it can be applied to other types of booth door opening.

The drive device comprises a notched belt 3 extending along a support lintel 5 of the booth doors 1 at the upper portion of the latter. This belt 3 is driven by a motor pulley 7 at one extremity of the lintel 5 and being received at the other extremity by a return running pulley 9 at the other extremity. The belt 3 is shaped into a longitudinal loop with two nearby extremities 11 fixed by fixing brackets to a given door. The other door is fixed to the other loop side of the belt.

The doors 1 are guided in horizontal translation (figure 4) with the aid of upper support rollers 13 and lower counter-rollers 15 rolling on a rail 17 placed at the lower portion of the lintel 5.

The motor pulley 7 is driven by means of a 24 volt low voltage a. c. electric motor 19. As shown on figure 2, this motor is a ring type torque motor adapted so as to rotate at a low speed (10 to 150 revs/min).

The ring, or stator 21 in the present case, fed with current is installed on a housing with cylindrical wings 23 and rendered integral with the aid of external flanges (not shown) on the opposing wings of the lintel.

The ring 21 creates a magnetic field which stresses the rotor 25 which is placed rotating inside the stator. The rotor comprises permanent magnets fixed coaxially and regularly at the periphery. It is mounted rotating by two rollers 27 on a fixed shaft 29 which is integral with a circular lateral plate 31. This plate has approximately the same

size as that of the housing 23 to which it is fixed by screws. In addition, it closes the motor and forms a common support for the rotor and the stator.

A rotation angle sensor of the Hall effect type 33 is fixed to the opposing extremity of the shaft. This Hall effect angle sensor allows control electronic elements to know the relative position of the rotor so as to control the switching of the phases of the stator and also calculate the speed and relative position of the door.

The motor pulley 7, whose external diameter is approximately the same as that of the housing 23, covers a portion of the latter (or of the stator) at least one third of its width (1/3rd to 2/3rds of the stator) and is mounted with slight play against the housing 23. Thus, the width of the unit constituted by the motor and its motor pulley is small, namely less than or approximately equal to 110 mm which is the depth of the lintel, so as to be mounted on the latter without projecting.

The motor is fed with electric current by a control block 35 with the shape of a parallel piped box fixed inside the lintel. Control of the motor is carried out conventionally at low voltage (24 volts or less) with variable speed control according to the varied frequency and variable torque according to the varied intensity of the current.

This box itself is fed by a low voltage electric transformer 37 (24 volts) fed from the current of the network and is also fixed inside the lintel. A stand-by battery 39 is also fixed inside the lintel so as to directly feed, should a breakdown of the system occur, the motor so as to carry out emergency manoeuvres for opening the doors of the booth and evacuate its passengers.

Finally, the running pulley 9 (figure 3) fixed at the opposing extremity of the lintel relatively to the motor pulley has an identical shape to that of the motor pulley and is mounted on a bearing or housing 41, also identical to that of the motor.

Thus, the drive device and its pulleys, door drive belt and electric feed and control portion distributed inside the lintel and at the upper portion of the latter without projecting appear as a relatively complete and homogeneous unit only requiring a reduced number of parts.

It shall be noted that the torque motor drives a pulley having a large diameter and rotates at a variable speed of between 10 and 150 revs/min by virtue of its large torque. A speed reducer is not needed to drive the doors at the required adequate speed and the movement is manually reversible by pushing of the doors.