The invention concerns an apparatus for working elevators. Movement of door panels in elevators is controlled by what are known as door operators, and is controlled by electric motors through ratiomotors, these being required on account of the considerable difference between the high speed of the motor and the lower speed of the door panels which, for functional and safety purposes, must necessarily move more slowl . Further if, during their closing stage the doors meet an obstacle, such as the body of .a passenger, for safety rea¬ sons door movement must instantly be halted. The electric motor must therefore stop, reverse its move¬ ment and return the doors to their fully open position. To do this suitable sensors, special safety devices and auto¬ matic mechanisms are needed.

If the door is a two-panel door the pulleys, supported by the door panels themselves - enabling them to be drawn along by cables - increase the amount of material situated above the doors. Because of this the present type of door operators are found to be bulky and complex as well as delicate,

drawbacks of some importance bearing in mind the limited space allocated t o elevator installations, reduced by the presence of stairways as well as the apartments in the building, and the need for elevators to carry the greatest number of passengers possible rapidly and without hindrances to the service.

Purpose of the invention is considerably to reduce the bulk of equipment and. automatic parts by making them simpler and also by simplifying erection and maintence and by increas- ing the safety factor of the elevator.

Subject of the invention is a linear lift door operator in which the door panels are pulled along by means of a con¬ tinuous belt supported by two end wheels and by means of a pair of coaxial wheels of different diameter joined to- gether, turning freely round a pin mounted on a supporting arm in turn fixed to the door panels.

The operative circumference of the larger wheel maintains contact with the inner side of one section of the belt be¬ tween the two end wheels moving in one direction, while the operative circumference of the smaller wheel maintains con¬ tact with the inner side of the second section of the belt moving in the opposite direction.

One of the end wheels that support said belt is connected to the shaft of an electric motor. Fron the foregoing,door movement caused by motor rotation is made at a reduction ratio equal to the algebraic sum of the pull exerted by the two sections of the belt- res¬ pectively on the operative circumference of the larger wheel and on that of the smaller wheel. The pair of two coaxial wheels are held together by an in ^¬ termediate coaxial clutch disk and are served by a mechanical

device which, if the closing door encounters any kind .of obstacle, causes reciprocal slippage of said wheels in one direction but not in the other.

Therefore, in the event of an obstacle being encountered by the door during its closing movement, causing the pin common to the pair of coaxial wheels to slow down or stop, said wheels, drawn along by the two sections of the belt respec ively, will continue to turn in the same direction but at different speeds thus provoking slippage. Preferably said slippage is provoked by means of a mech ^¬ anical device of the type known as free wheel, or equi¬ valent, allowing relative slippage in the direction of door closure but not in the opposite direction. Slippage is controlled by a device that stops it and re- verses motor movement causing the doors to open.

The occupant can of course open the door by hand, if an emergency such as a power failure or some other should occur, and this will cause slippage of the aforesaid pair of wheels and overcome resistance offered by the interposing clutch.

The wheels acting on the belt are preferably toothed wheels and the belt is similarly toothed. Pins are also mounted on the arm fixed to the door to which the coaxial wheel pin is also fixed, said pins being parallel to said pin in the coaxial wheels round which pressure rollers turn freely.

Centre distance between the geometrical axis of the pair of coaxial wheels and the geometrical axes of said rol¬ lers is practically equal to the sum of the radius of each roller and in the wheel of the pair of coaxial wheels on which said roller acts while the distance between the

circumference of each roller and the longitudinal axis of the belt is considerably less than the radius of the wheel on which said roller presses.

Consequently contact is maintained between the belt and each of the two coaxial wheels along an arc of a length sufficient to ensure meshing of several teeth. The pair of coaxial wheels is served by a device for de¬ tecting the extent of slippage between two said wheels. Slippage having been ascertained, an automatic circuit stops the electric motor, reverses its direction of ro¬ tation and thus opens the doors.

This device can be made by mounting a switch on one wheel of the pair, said switch responding to the projections present on an undulated cylindrical surface,coaxial and integral with the other wheel, so that the number of pulses received by the switch during said slippage mea¬ sures its amplitude.

In the door operator described, the transmission pulleys, which connect the two doors by means of cables and the like, are preferably inclined so that one can pass at least partially below the other thus reducing overall bulk of the device.

The invention provides obvious advantages. The door operator is compact and more rationally designed. The reduction ratio, safety slippage between the motor and the doors, and the automatic mechanisms for revers¬ ing movement all consist of a few simple and intelligent¬ ly conceived parts. Bulk is therefore reduced to a mini¬ mum providing a compact, functional and entirely safe door operator.

Characteristics and purposes of the invention will be

made even clearer by the following examples of its exe ^¬ cution illustrated by diagrammatic figures. Fig.1 Door operator with a pair of coaxial wheels and clutch for working a door with two panels, per- spective view.

Fig.2 Side view of the door operator. Fig.3 Diagram of the door operator.

Fig.4 Detail of the door operator's pair of coaxial wheels and clutch with slippage detecting de- vice, seen from the side, partly cut away.

Fig.5 Cross section detail of the slippage detector. The door operator 10 mounted on the girder 50 comprises a continuous toothed belt 11 supported by toothed wheels at the ends, the wheel 12 idling on a pin 16 and wheel 13 fixed to the shaft 17 of the electric motor 30 moun¬ ted on the girder 50 by means of a bracket 20. The door panel 40 slides on a rail 41 by means of rollers 42 supported by the plate 48 fixed to the door panel. Also fixed to said plate 48 is another plate 43 carry- ing the pair of toothed wheels 14 and 15 idling round a pin 18 fixed to said plate 43.

The diameter of wheel 15 is greater than that of wheel 14. Said wheels 14 and 15 are connected by a disk clutch 25 placed between them. The branch 11A of the belt 11 connects with the toothed wheel 14 along the whole arc 11C and is pressed by the roller 26 idling round the pin 28 fixed to plate 43. Branch 11B of the belt 11 connects with the toothed wheel 15 along the whole arc I ID and is pressed by the roller 27 idling round the pin 29 fixed to plate 43.

The toothed wheels 14 and 15 and the intermediate clutch

25 are pressed together by compression spring 21 inser¬ ted onto pin 18 and pressing against the nut 22. As will be clearly seen in Figs. 4 and 5, the two toothed wheels 14 and 15 are fixed respectively to sleeves 56 and 57 supported by the pin 18 and ball bearings 23 and

24. Said sleeves 56 and 57 are connected by a "free wheel" device 58 which permits movement between said wheels 14 and 15 only while the doors are closing. The metal disk 19 is integral with the wheel 14. The accessory 37 is fixed to the plate 48 in turn fixed to the door panel 40.

At one end of the girder 50 that carries the door opera¬ tor 10 a bracket 49 is mounted to carry the pin 51 for the idling pulley 52 while at the other end of said gir¬ der 50 another bracket holds the pin 54 for the idling pulley 53.

Said pulleys 52 and 53 support the continuous cable 60 connecting the door panels 40 and 40', said cable being substantially in alignment with the continuous belt 11. The upper section of the cable 60 is held by means of a bracket 61 to the plate 43 fixed to the door panel 40. A bracket 62 holds the lower section of said cable 60 to the plate 64 which is fixed to the accessory part 65 for operating the other door panel 40'. Operation On starting up the electric motor the lower section of the belt 11 slides along causing the larger wheel 15 to rotate, while the upper section of said belt causes the smaller wheel 14 to rotate in the same direction and at the same speed as that of wheel 15. Due to the difference in diameters of said wheels 14 and 15 the pin 18 in said wheels is pushed to translate

transversally pulling the door panel 40 in the direction taken by the belt which turns the smaller wheel 14. The effect of said pair of wheels 14 and 15 is therefore that of a reducer and the reduction ratio is a function of the difference between the diameters of wheels 14 and 15. In particular, translation of the door panel is equal to the difference between the lengths of the circumferen¬ ces of wheels 14 and 15 divided by two. If for any reason the door encounters an obstacle to its closing movement, consequently slowing down and stopping transversal translation of the pin 18 common to both wheel 14 and 15, these latter will continue to rotate in the sam direction but at different speeds overcoming the resistanc of the clutch 25. Slippage is ascertained by special means connected to an automatic device that stops the electric motor and puts it into reverse. Said means of detection comprise a micro switch 31 with contact spring 32, fixed to wheel 15, res¬ ponding to projections 33 present on an undulated cylin- drical surface 34 fixed to and coaxial with the wheel 14.

Electrical connections comprise double-brush collectors 35 mounted on the support 36 coaxial with pin 18, made of insulating material. The pulses, generated by the number of microswitch pulsa- tions corresponding to the reciprocal difference of phase between the two wheels 14 and 15, are passed to the automa tic device which drives the electric motor by means of a pulse counter which operates a relay only after two or three pulses so that false alarms may be avoided. Fig. 2 shows a door operator similar to that seen in Fig.1 for sliding more than one door panel, supported and guide

by rails 4 1 , 70 and 7 1 .

As clearly shown, the pulleys 72 and 73, required for connection between door panels and with their pulling accessories 74 and 75 _» are placed in an inclined posi- tion so that one pulley can to some extent pass beneath the other.