WO1994014695A1

WO1994014695A1 - Elevator machinery including friction brake

Info

Publication number: WO1994014695A1
Application number: PCT/SE1993/001091
Authority: WO
Inventors: Rolf Eriksson-Pax; Gunnar Gustafsson
Original assignee: Eg Technology Ab
Priority date: 1992-12-18
Filing date: 1993-12-20
Publication date: 1994-07-07
Also published as: SE9203827D0; EP0675848A1; SE9203827L; SE500708C2; DE69306413D1; DE69306413T2; EP0675848B1

Abstract

The invention relates to elevator machinery (2) for a screw drive elevator, comprising a trapezoidal threaded screw (4) extending between the two ends of an elevator shaft, and a nut (6) mounted thereon and with a corresponding thread. Said nut is rotatably suspended in a housing (8) provided with a drive means, which supports an elevator car and a payload. The housing and the nut are displaceable by means of a disengaging device (28) relative to each other against the force of the load, between two limit positions along the centerline of the screw. The limit position thus corresponds to a rest position and an operating position of the machinery. The load is borne in the rest position by the screw (4) via the housing (8), a friction wear layer (26), a drive gear (14) and the nut (6). In the operating position, the disengaging device is energized, whereby the drive gear is unloaded and a thrust bearing (9) is loaded instead. The load is then transferred to the screw through the housing, the disengaging device, a bearing sleeve (12), the thrust bearing and the nut.

Description

Elevator machinery including friction brake.

The present invention relates to machinery for a screw drive elevator, comprising a preferably trapezoidal threaded screw and, mounted thereon, a nut provided with a corresponding thread as well as a drive device, said nut bearing a payload and said drive device having a first gear and at least one drive means connecting the first gear to a second gear, which is mounted on the shaft of a drive motor, by means of which the nut or the screw is rotatable depending on the regulation of the motor and depending on a friction brake.

A screw drive elevator of the above described type by rota¬ ting, by means of a drive means, either the screw or the nut, whereupon the nut climbs up or down on the screw depending on the rotational direction of the screw or nut. The screw is, as a rule, made of steel, while the nut is usually made of bronze. Under the nut, there is a so-called fall-stop nut as extra insurance, so that the load cannot fall down when the nut has become too worn. The fall-stop nut has driver ele¬ ments engaging cooperating means on the elevator nut, so that the fall-stop nut follows the movement of the elevator nut. In elevators, where the screw is held stationary, the eleva¬ tor nut is rotatably mounted via a ball bearing in a housing, which is a mounting for a drive motor and supports the eleva¬ tor car and the payload. The housing with the drive motor and the elevator car are prevented from rotating by means of rails mounted in the elevator shaft, said rails guiding the car by means of guides fixed to the housing or elevator car.

For safety reasons, and in accordance with official regula- tions, the elevator, if there is a power failure, must not be a_ble to _fall, out of control, to the bottom of the elevator shaft, and therefore the screw and nut in a conventional screw drive elevator have a relatively small lead angle, as a rule no greater than about 6°, so that the screw and nut will _be self-braking relative to each other when axially loaded. At greater lead angles, this effect ceases. With such a small lead angle, the efficiency of the device is correspondingly low, at most about 30%, requiring unnecessarily large amounts of energy, high rpm of the elevator nut and slow movement of the elevator machinery in both directions. It also involves a high slide speed, usually exceeding 2,5 m/s, in the contact surfaces between the screw and the nut, thus generating an unsatisfactorily large amount of frictional heat. The fric- tional heat leads in turn to a temperature rise in the con- tact surfaces, which is accumulated in the nut due to its smaller mass in relation to the screw and due to the fact that the nut is continuously heated, while the screw is able to be cooled off as the nut climbs along the same. Frequent operation of the elevator can therefore result in a tempera- ture rise in hundreds of degrees in the nut. Since the longi¬ tudinal coefficient of expansion for bronze is approximately 0.02 mm/m/ C or approximately twice that of steel, a tempera¬ ture rise of 100°C will mean that a 0.1 m long nut will be extended axially by 0.2 mm. Thus a "hot" nut will have its groove flanks in contact with the corresponding flanks of the threads only at the lower end of the nut. This non-uniform loading of the contact surfaces of the nut will subject the threads to excessive wear.

If there is a power failure, the elevator will stop in its current position and can only be returned to an entering or exit position by supplying energy manually or by means of an auxiliary unit, via a special emergency operating device.

The elevator machinery according to the invention has, how¬ ever, a relatively large lead angle, 20-40 , and thus lacks the self-braking effect between the screw and the nut. This lead angle, however, achieves, with an optimization of mate¬ rial selection and cooperation between the components of the machinery, at least a doubling of the efficiency. Since the elevator machinery no longer spontaneously stops at the posi¬ tion in question when the power supply to the nut is stopped, a special braking device is required which ensures that the elevator machinery will be reliably locked to the screw any time the elevator stops for entry or exit. Furthermore, the ^■ machinery must be locked automatically at the current posi¬ tion when there is a power failure, for example. With the aid of the braking device, it is possible to reliably lower the elevator car, without supplying extra power, to the next floor, so-called emergency lowering. This emergency lowering should be able to be controlled from the elevator car. According to the invention, it is also possible to lower the rpm of the nut from about 1500 rpm, which is common, to about 500 rpm, thus reducing the frictional speed in the contact surfaces, with unchanged lifting speed, to about a third, which in turn results in substantially lower temperature rise, essentially less longitudinal expansion and signifi¬ cantly extended life of the nut.

The purpose of the invention is therefore to provide an ele¬ vator machinery of the type described by way of introduction, which makes it possible, while maintaining or improving the margin of safety, to achieve at least a doubling of the effi- ciency, at the same time as the life of the elevator nut is substantially increased.

This is achieved according to the invention by virtue of the fact that the lead angle of the screw is greater than 10°, that the friction brake comprises first and second brake means, at least one frictional surface and has a disengaging device, that at least one of the brake means is non-rotatably connected to either the screw or the nut, and that the con¬ tact pressure necessary for the braking effect on the braking means is generated by the load acting on the elevator machi¬ nery. The braking means are displaceable relative to each other against the effect of the load by means of the dis¬ engaging device, between two limit positions along the cen- terline of the screw, said limit positions defining a rest position and a work position for the machinery.

A preferred embodiment of the invention is characterized in that the nut is rotatably suspended in a housing connected to the drive device, said drive device having a first gear surrounding and non-rotatably fixed to the nut, that the first gear is a nut gear and the second gear is a drive gear, and that the first brake means is formed of the nut housing and the second brake means is formed of the nut gear. The load in the rest position is borne by the screw via the housing, a friction fitting, the nut gear and the nut. In the work position, the disengaging device is activated whereby the nut gear is unloaded and a thrust bearing is loaded instead. The load is thereby borne by the screw via the housing, the disengaging device, a bearing sleeve, the thrust bearing and the nut.

One advantageous further development and improvement of the invention is characterized in that the friction brake com- prises an annular lateral surface of the nut gear facing the housing, and an opposing annular end surface of the housing. Between these surfaces there is a wear layer and both the surfaces and the wear layer surround the screw concentrical¬ ly. By means of the load acting on the housing, when the elevator machinery is in its rest position, the frictional surfaces and the wear layer are pressed against each other with the force required for the braking effect. The disengag¬ ing device is preferably hydraulically operated and comprises two telescoping annular elements disposed about the center axis of the screw: an annular cylinder and an annular piston enclosing between them an annular chamber which communicates with a hydraulic pump which is operated in response to con¬ trol signals from a control unit.

According to a further improved and developed embodiment of the invention it is possible to achieve maximum efficiency and minimum wear between the screw and the nut by virtue of the fact that the nut, in addition to first-class surfaces and good lubrication, runs in coaxial alignment on the screw in each operating or rest position. In operation, it is difficult and costly to achieve this in all positions, e.g. due to one of the following reasons:

- The elevator car runs on guides which are not parallel to the screw in all positions, - the elevator machinery (= the nut bearing) changes its position as the load varies,

- deflection of tea screw due to oscillations which can arise as a result of non-coaxially aligned operation of the nut relative to the screw.

According to this embodiment, it is also possible to achieve continuous monitoring of the current load on the nut and the current operating state of the machinery.

The coaxial alignment of the nut and the monitoring of the load and operating states is provided according to this embodiment by virtue of the fact that the nut is separated from the bearing and the second brake means, which is made in one piece with the nut gear which rests, via an angle compen¬ sator, on the nut, that the nut gear is non-rotatably joined to the nut and that the angle compensator is thereby capable of taking up angular deviations between the nut and the nut gear, whereby the nut can run in coaxial alignment on the screw.

The nut has at least one driver pin for torque transmitting engagement about the center axis and via the drive housing, with the nut gear which is disposed diametrically surrounding the bearing.

The angle compensator is made of an annular cylinder and an annular piston enclosing between them a fluid which evenly distributes the contact pressure between the cylinder and the piston even when there is angular misalignment therebetween.

The nut housing has a cylinder, and the housing and the first brake means are made as two components axially displaceable relative to each other and which are non-rotatably joined to each other. The brake means comprises a load sensor coupled between the brake means and the housing, the load sensor having at least one sensor element with an essentially linear characteristic curve and/or at least one sensor of on/off type. The load sensor has an annular chamber and an annular piston, and a fluid enclosed between the chamber and the piston which is in communication with at least one sensor element.

Each load sensor element and pulse sensor element, as well as each additional sensor element, sends signals to the control unit depending on what signals can be registered for the current load and the current operating state of the elevator machinery by the control unit, thus making possible monitor- ing and positioning of the elevator machinery by correspond¬ ing operation of the nut, in response to the signals received from the sensor elements.

An additional embodiment of the invention is possible, by making the friction brake electronically instead of hydrau- lically disengageable. The disengaging device and the thrust bearing are combined in a bearing clutch comprising two annular magnet elements, an electromagnet and a permanent magnet. Depending on the operation of the electromagnet, the bearing clutch acts as an electromagnetic clutch, whereby the need for a special thrust bearing is eliminated.

Finally, a particularly simple elevator machinery is possible without any sophisticated control system by using a mechanic- ally operated disengaging device and fixing the nut non- rotatable in the elevator car. The screw is thus rotatably mounted in the elevator shaft, and the housing, the drive means and the disengaging device are fixed in the elevator shaft.

The invention will be described in more detail in the follo¬ wing description with reference to the accompanying drawings.

Figure 1 shows a partially sectioned side view of a preferred embodiment of the elevator machinery with hydraulic disengaging device, Figure 2 shows a detailed view of a possible belt monitoring means, Figure 3 shows a block circuit diagram of the control system for the elevator machinery, Figure 4 shows a similar view to Figure 1 of a variant of the elevator machinery with an electronic disengaging device and an electromechanical thrust bearing,

Figure 5 shows a similar view to Figure 1 of a particularly simple, mechanically operated variation, Figure 6 shows, in section, a rotational speed regulator in¬ cluded in the machinery according to Figure 5, Figure 7 is a schematic diagram showing the function of the mechanical operating system according to Figures 5 and 6, and Figure 8 shows a partially sectioned side view of an improved and developed embodiment of the elevator machinery with an angle-compensated lifting nut and a load indicator.

According to the preferred embodiment (Figure 1) , the eleva¬ tor machinery 2 comprises a screw 4 non-rotatably mounted in an elevator shaft (not shown) and having a center axis 5 and a steep lead angle (20-30 ) and a nut 6 with a corresponding lead angle, mounted on the threads of the screw. The nut is rotatably mounted in a housing 8 provided with a first brake means 7, preferably by means of a two-row angular contact bearing 9. The outer ring of the bearing is pressed into a bearing sleeve 12. The inner ring of the bearing is pressed onto the outer lateral surface of the nut and is in axial contact with an annular flange on a key 10 for a nut drive gear 14 of a second brake means 13.

The bearing transmits axial forces acting from the elevator car and payload on the housing 8 to the nut 6 as well as taking up radial forces on the nut via a drive means fixed in the housing. The nut drive gear 14 cooperates with a drive device 16 comprising a transmission and a three-phase motor 20 controlled via a control unit 18 comprising a frequency converter. By means of the drive device the rotation of the nut is infinitely variable, from standing still to maximum rpm (about 600 rpm) . The transmission comprises suitably, in addition to the nut ■ drive gear 14, a drive gear 22 and drive means 24. Preferred transmission embodiments comprise a cogged belt transmission with drive gears in the form of cogged pulleys 14 and 22, and a drive means preferably comprising two parallel cogged transmission belts 24a,24b. The nut housing 8, the pulley 14, a friction layer 26 and a disengaging device 28, form to¬ gether a friction brake 30, which, in the rest position of the machinery, prevents rotation of the nut 6 relative to the housing 8. The friction layer is suitably fixed to the flat housing end surface 32 facing the pulley. The opposite flat side 34 of the pulley is brought into contact with the fric¬ tion layer under the influence of gravity or, when horison- tally mounted, with the aid of a biasing spring (not shown) .

The friction brake is hydraulically disengageable by activa¬ tion of the disengaging device via a hydraulic pump 36, which is controlled, together with the drive device by the common control unit. The disengaging device comprises an annular cylinder 38 and an annular piston 40, which are arranged in telescoping relation to each other. Between the cylinder and the piston there is enclosed an annular chamber 42, which communicates via a feeder channel 41 with the hydraulic pump. The annular chamber is sealed by conventional O-ring seals 43 disposed in the mutually telescoping cylindrical surface of the cylinder and the piston.

A fall-stop nut 44 is disposed on the screw 4 beneath the elevator nut 6, said nut 44 following unloaded the movement of the nut 6 on the screw. The fall-stop nut is in this case disposed at a predetermined distance from the elevator nut, said distance corresponding to the maximum gap which can arise due to wear between the screw and the nut, before the elevator nut rests on the fall-stop nut. The fall-stop nut is driven along with the rotational movement of the elevator nut by means of at least one pin 46, which is fixed in the fall- stop nut and is insertable, parallel to the center axis 5 into a corresponding driver recess 48 in the elevator nut. The axial depth of the recess is adapted to the distance between the nuts. A dust protector sleeve 50 is mounted on ■ the fall-stop nut 44 and overlappingly covers the joint between the nuts, and has a flange 51.

As can be seen in Figures 2 and 3 , the control unit 18 re¬ ceives data values A on the operating state of the machinery via sensor elements 52 which are known per εe, and which can be mechanical, hydraulic, electrical, inductive, electro¬ mechanical or electro-optical. By two contact sensor elements 54 for example, individual belt monitoring is possible, and a non-contact sensor element 56 provides an indication when the elevator nut has reached a predetermined degree of wear relative to the fall-stop nut. A pulse sensor 58 sees to it that the rpm of the nut does not exceed a predetermined value. Sensed values A are processed by the control unit 18 and are compared with predetermined values stored therein concerning e.g. the state of the belt and/or the current rotational speed of the nut and its degree of wear. Control signals B are then sent to the drive device 16 and the dis- engaging device 28. It is also possible, in response to these signals, to selectively control the drive device 16 and the disengaging device 28 in conjunction with each other by means of the control unit 18. This means that the electric motor can be started immediately prior to the activation of the disengaging device. The motor will thus provide a certain amount of torque while the friction brake 30 is still engaged and vice versa, to provide a gentle start and stop.

A further embodiment of the elevator machinery is revealed in Figure 4 and is in principle constructed in the same manner as that described above. However, the disengaging device 28' is in this case electromechanically instead of hydraulically operated. The device 28' is in the form of a bearing clutch 60, comprising two annular magnetic elements 62,64 arranged concentrically about the screw axis 5' and which in the rest position of the machinery are in contact with each other. One element is an electromagnet 62 , which is enclosed in an annular core 66 and has an annular coil 68. The magnet 62 has concentrically arranged, radially separated annular poles, e.g. a south pole 70 and a north pole 72. The poles face the other magnetic element, which is a permanent magnet 64. The poles 70,72, upon activation and depending on the polarisa¬ tion of the energizing current, are, relative to the center axis 5', an inner south pole 70 and an outer north pole 72. The permanent magnet 64 has radially separated permanently magnetized poles, a south pole 74 and a north pole 76, oppo¬ site the poles of the electromagnet 62. The south poles 70 and 74 and the north poles 72 and 76 repel each other, which causes the electromagnet to be lifted from the permanent magnet and, analogously to the annular cylinder shown in Figure 1, if there is a sufficiently strong activating cur¬ rent, the housing 8' will be lifted together with the equip¬ ment including the pay load mounted thereon. Thus, an air gap is formed between the magnets 62 and 64 , which permits the permanent magnet 64, which is fixedly joined to the elevator nut 6', to rotate together with the nut, via the drive device 16' with very low friction (the magnetic field) relative to the electromagnet 62 and the housing 8'. The magnets 62 and 64 thus constitute in this case an electromagnetic thrust bearing 9' .

In Figure 4, the annular portions of the magnets, lying in contact with each other in the rest position, extend radially forming a right angle to the center axis of the screw. The contact surface between the portions is a frictional surface 25', which thus also forms a right angle to the screw axis. It is, however, advantageous if these portions are made so that the angle of the frictional surface to the screw axis is not a right angle and thus forms a truncated cone which can be turned upside down. This provides an advantageous self- centering effect in the magnetic bearing.

When the supply of current to the magnet 62 ceases, the major portion of the magnetic field is removed and thus the lifting effect of the magnet, so that the magnets will again come into contact with each other with a contact pressure which, on the one hand, depends on the load via the housing 8' and, on the other hand, on the adhesive force of the permanent magnet relative to the remanence-free core of the electro- ^■ magnet. Thus, the nut 6' is prevented from rotating relative to the housing 8' and the electromagnet 62. By changing the polarization of the activating current, it is possible to further increase the braking effect, since the contact pres¬ sure of the magnets will in this case be amplified by the attractive force between the magnets.

In the described embodiments, by virtue of the fact that the drive device 16,16' and the friction brake 30,30' are desig¬ ned to be controlled in time with each other, a gentle and even transition is achieved between the braked state and the operating state. Furthermore, an automatic braking effect is achieved if there is a power failure. With a substantially vertically disposed screw 4, 4',4", a more powerful braking effect is achieved the greater the load is acting on the machinery, which is a factor which increases security. For an inclined or horizontal screw, the required contact pressure against the friction layer is achieved by tension springs acting in the opposite direction to the disengaging device.

As was mentioned in the introduction, it is also possible to use a nut 6" non-rotatably mounted in an elevator car 1", and instead make the screw 4" rotatable in the elevator shaft (not shown) (Figures 5-7) . The screw is mounted in a first braking means which, in the form of a flange-like disc or cone 7", is enclosed in the elevator machinery housing 8". The housing also contains a second braking means, which is in the form of a concave cone 13", corresponding to the shape of the cone 7". The cones are prevented from rotating relative to each other by the frictional force in a friction surface 25" between the cones, as long as the screw is loaded by the elevator car. An advantage of this arrangement is that emer¬ gency lowering is easily achieved, by reducing the load on the frictional surface.

According to this embodiment, the housing 8" of the elevator machinery together with a drive device 16", a mechanically operated disengaging device 28" and a friction brake 30" are fixed in the elevator shaft. A particularly simple and inex¬ pensive, vertically oriented elevator machinery, without any sophisticated control system, is achieved by means of the mechanical disengaging device for emergency lowering by virtue of the fact that the concave cone cooperates with a one-way clutch in the form of a free wheel 78. The elevator is operated upwards by means of the motor with the one-way clutch unblocked, while the operation downwards is done through gravity with a locked clutch (arrow A) . The main components of the disengaging device are a lever 80, a gimb- led pressure plate 82 and a thrust bearing 84. The dimension¬ ing and con-struction of the lever provides a mechanical advantage between the free end of the lever and its end acting against the pressure plate of about 60:1. A echanic- ally regulated centrifugal brake 86 ensures that the speed of lowering will not exceed a predetermined value. The centri¬ fugal brake 86 includes three brake shoes 88, each being pivotally mounted at one end with an individual pivot pin 90. Each brake shoe has a heel 92 which is suitably coated with a conventional friction layer. The heel is located circumferen- tially farther from the free end of the brake shoe than from the pivoted end. The disengaging device is easily actuated, e.g. by means of a line 94 fixed to the free end of the lever, which, as needed, e.g. when desending or during a power failure, is tensioned by lateral loading via one or more rotatable pulleys 96 travelling with the elevator car. Two pulleys are fixed to the elevator car, while one of the pulleys is movable relative to the others by means of an operating lever 98, to achieve the desired lateral load on the line. The operating force required on the handle 101 of the lever, in order to, in this manner, unload the frictional surface between the cones, acts parallel to the force of gravity and is, as a rule, less than 10 N at a total load of 400 kg.

The position of the operating lever shown with solid lines in Figure 7 is in its rest position in which the lever is held, for example by means of a spring arrangement (not shown) . When the lever is lifted as from this position, it is in its position for operation upwards, in which a switch 103 is activated closing the circuit to the electric motor. When the elevator has reached its desired position, the operating lever is released and it returns to its rest position, the switch breaks the circuit and the elevator stops. The eleva¬ tor is kept in this position by means of the free wheel and the brake means, which lock the rotation of the screw for descending, relative to the anchoring points in the elevator shaft. If the operating lever for some reason is not returned to its rest position before the elevator car has reached its uppermost position, damage to the elevator machinery can be avoided by an upper limit switch 105. It is located at the uppermost portion of the elevator shaft and breaks the cur¬ rent circuit when the elevator car or a contact means mounted on the same strikes the corresponding means on the limit switch. When descending, the operating lever 98 is depressed from its rest position to the position shown with dashed lines in Figure 7, and the line 94 is tensioned by means of the pulleys 96. The line forces the free end of the lever 80 downwards. and its other end lifts, via the pressure plate 82 and the thrust bearing 84, the screw 4" with total load so far that the cone 7" lifts from the cone 13". The screw is then free to rotate due to the force of gravity in the nut and the elevator descends as long as the operating lever is kept in the position shown with dashed lines. The rate of descent is controlled by the centrifugal brake 86. As soon as the lever 98 is allowed to return to its rest position, the elevator stops since the screw with load again rests on the frictional surface 25" between the brake means and the rota- tion of the screw for descent is blocked by the free wheel 78.

A dampening piston 107 is arranged at the bottom of the shaft and facilitates a gentle braking from the maximum descent rate permitted by the centrifugal brake, and standing still. The lower end of the screw is conical and is guided with a certain amount of play in a guide sleeve 109 provided with a brake cone and anchored in the bottom of the elevator shaft. If, despite the high safety requirements fulfilled by the elevator machinery described above, the screw should come loose above the elevator nut, the conical end of the screw will lie in contact with the brake cone in the guide sleeve 109, thus preventing uncontrolled rotation of the screw.

As in earlier embodiments, the elevator machinery 302, ac¬ cording to an improved and developed embodiment shown in Figure 8, has a nut 306 mounted on a screw 304. The nut is, however, separated from the first brake means 307, the "nut housing" 308 and the angle contact bearing 309, as well as from the second brake means 313 and the nut gear 314. The nut is so located on the screw that the rest of the moving compo¬ nents of the machinery rest on the nut via an angle compensa- tor 315 mounted between the nut 306 and the gear 314, said compensator resting on the nut against a radial flange, which has three radially extending driver pins 316 evenly distri¬ buted about the periphery. The gear 314 has a driver housing 317 solidly joined to the same and having a cavity which cooperates with the driver pins 316 on the nut 306. Thus, the gear 314 is axially displaceable but non-rotatably connected to the nut. An annular piston 321 is sealingly fitted in the annular cylinder 319 by means of O-rings, and the chamber enclosed between cylinder and piston is filled with a fluid. The underside of the gear 314 is in contact with the annular piston 321, thus taking up angular deviations of up to 5 between the gear 314 and the nut 306, by the annular piston 321 "floating" on the enclosed volume of fluid and evenly distributing the contact pressure even if there are angular deviations.

The nut gear 314 is mounted surrounding the bearing 309 which is pressed with its inner ring on the lower end of a tubular piston 323, which has at its upper end a piston flange 325 which is sealingly fitted by means of O-rings in a cylinder 327 in the housing 308, said cylinder serving as a pneumatic cylinder. The housing 308 has at its lower portion axially disposed pins (not shown here) which engage in corresponding holes in the annular cylinder (the brake means) 307. The brake means is thereby axially displaceable but non-rotatably connected to the housing 308. The axial displaceability is limited by the length of stroke of the piston 325. In the first brake means 307, which, in the rest position shown, is in contact with the second brake means 313, there is an annular chamber 329 in which an annular piston 331 is sea¬ lingly fitted by means of O-rings. The annular piston 331 is in contact on its top side with a shoulder on the underside of the housing 308 near the pin and the underside of said piston rests on a volume of fluid enclosed in the annular chamber 329. The first brake means 307 with the annular chamber 329 and the annular piston 331 thus form a load sensor 333. The annular chamber is connected via a conduit with a load sensor element 352, which converts the hydraulic pressure generated by the load in the annular chamber 329 into an output signal which is directed proportionally to the load. Alternatively, a load sensor element 352 of on/off-type is used sending signals at predetermined loads.

The previously described protection against excess rotational speed can also be used for sensing the rotational direction of the nut 306 and its rotational position relative to the screw 304 by two pulse transducers 358 mounted in a known manner so that the pulses, which are sent synchronously with the rotation of the nut, are phased relative to each other. This provides a monitoring of both the rotational direction and the position as well as the rpm of the nut, and position¬ ing is made possible by corresponding turning of the nut in response to signals from the sensor elements.

By a previously mentioned sensor element 354 mounted on the nut housing 308, a signal is obtained which prevents con¬ tinued operation if the threads of the nut 306 should be worn out. The sensor elements 352, 354 and 358 are, as previously, connected to a control unit 318, and can provide, in each position of the elevator machinery, information on the cur¬ rent load and whether the contact pressure between the brake means is within the predetermined values, so that the braking effect is always assured. Automatic monitoring of the load sensor 333 is possible by programming the control unit 318 to register that the load sensor element 352 indicates a signal exceeding a certain value, e.g. 250 kg, if the empty weight of the elevator car including machinery is 300 kg or is less than another value, e.g. 50 kg during operation when the annular piston 331 is unloaded. If these criteria are not fulfilled at each use of the elevator, the control unit stops the operation. Excess load is indicated and starting is prevented if the elevator is loaded so much that a certain predetermined value is ex¬ ceeded. The load sensor 333 is dimensioned so that the brak¬ ing capacity is retained but stops continued operation if the indication should cease, due to leakage or wear. Wear should, however, not occur since the braking means in normal opera- tion is only actuated when the nut is stationary.

In addition to the fact that the pulse transducers 358 were used for position and direction determination, they have as well, as was previously mentioned, a rpm monitoring function. If the drive system for some reason should fail in some way, so that the elevator will descend at too high a speed, it will be stopped when the rpm of the elevator nut 306 exceeds a predetermined value.

The embodiment described above has a number of advantages over the previously described embodiments. Uneven loading of the nut is eliminated and bearing and other stresses are reduced. A more even operation is achieved which, i.a., reduces the risk of vibrations and noise. The efficiency is improved by correct contact in the thread flanks, which in turn means less wear on the nut threads. The unit is quite compact, is easy to install, and inexpensive to manufacture and is virtually service-free.

A security-increasing effect is achieved by virtue of the fact that the screw is enclosed along its entire length below the nut in the channel formed between the elevator shaft and the elevator car. In the channel, the space for horizontal movement of the screw is limited, and therefore the screw can not buckle if a portion of the screw below the nut should be subjected to a compressive load.

If the elevator for some reason during its descent should become stuck in the elevator shaft or descend to the bottom thereof, it is of advantage if the elevator machinery would not continue to attempt to drive the car downwards, on the one hand, to not aggravate the problem which caused the stoppage and, on the other hand, to prevent damage to the machinery or possibly buckling of the screw. According to the invention this is achieved by virtue of the fact that the screw is allowed to rotate if the vertical load changes direction or is reduced to a low value. The screw is there¬ fore releasable by means of a quick release coupling when it is lifted upwards. This variant requires very little space and can be manufactured at low cost.

Finally, it is pointed out that the present invention must not be considered to be limited by the above described spe- cial embodiments. Rather, the invention comprises all those embodiments and equivalent solutions which fall within the scope of the following patent claims.

Claims

1. Elevator machinery for a screw drive elevator, comprising a preferably trapezoidal threaded screw (4) and, mounted thereon, a nut (6) provided with a corresponding thread as well as a drive device (16) , said nut bearing a payload and said drive device having a first gear (14) and at least one drive means (24) connecting the first gear to a second gear (22) , which is mounted on the shaft of a drive motor (20) , by means of which the nut (6) or the screw (4) is rotatable depending on the regulation of the motor and depending on a friction brake (30), c h a r a c t e r i z e d in that the lead angle of the screw (4) is greater than 10°, that the friction brake (30) comprises first (7) and second (13) brake means, at least one frictional surface (25) and has a dis¬ engaging device (28) , that at least one of the brake means (7,13) is non-rotatably connected to either the screw (4) or the nut (6) , and that the contact pressure necessary for the braking effect on the braking means is generated by the load acting on the elevator machinery (2) .

2. Elevator machinery for a screw drive elevator according to Claim 1, c h a r a c t e r i z e d in that the brake means (7) and (13) , by means of the disengaging device (28) , are displaceable relative to each other against the force of the load, between two limit positions along the centerline of the screw, said limit positions defining a rest position and a work position of the machinery (2) .

3. Elevator machinery for a screw drive elevator according to Claim 1 or 2, c h a r a c t e r i z e d in that the nut (6) is rotatably suspended in a housing (8) connected to the drive device (16) , said drive device having a first gear (14) surrounding and non-rotatably fixed to the nut, that the first gear is a nut gear (14) and the second gear is a drive gear (22) , and that the first brake means (7) is formed of the nut housing (8) and the second brake means (13) is formed of the nut gear (14) .

4. Elevator machinery for a screw drive elevator according to Claim 3, c h a r a c t e r i z e d in that the load in the rest position is borne by the screw (4) via the housing (8) , a friction wear layer (26) , the nut gear (14) and the nut (6) .

5. Elevator machinery for a screw drive elevator according to Claims 2 - 4, c h a r a c t e r i z e d in that the dis¬ engaging device (28) is activated in the work position, whereby the gear (14) is unloaded and a thrust bearing (9) is loaded, and that the load is thereby borne by the screw (4) through the housing (8) , the disengaging device (28) , a bearing sleeve (12) , the thrust bearing (9) and the nut (6) .

6. Elevator machinery for a screw drive elevator according to Claim 4 or 5, c h a r a c t e r i z e d in that the friction brake (30) comprises an annular lateral surface (34) of the nut gear (14) facing the housing (8) and an opposing, annular end surface (32) of the housing (8) , said surfaces being brake surfaces, and the wear layer (26) between the surfaces, that the surfaces and the wear layer concentrically surround the screw (4) and, by means of the load acting on the housing (8) , when the elevator machinery is in its rest position, are pressed towards each other with the pressure force required for the braking effect.

7. Elevator machinery for a screw drive elevator according to one of the preceding claims, c h a r a c t e r i z e d in that the disengaging device (28) is hydraulically operated and comprises two telescoping annular elements disposed about the center axis (5) of the screw, an annular cylinder (38) and an annular piston (40) , enclosing between them an annular chamber (42) which communicates with a hydraulic pump (36) which is operated in response to control signals from a control unit (18) .

8. Elevator machinery for a screw drive elevator according to one of Claims 1 - 6, c h a r a c t e r i z e d in that the disengaging device (28) is electromagnetically operated.

9. Elevator machinery for a screw drive elevator according to one of Claims 5 - 8, c h a r a c t e r i z e d in that the disengaging device (28) and the thrust bearing (9) are combined in a bearing clutch (60) , which comprises two agne- tic elements (62,64) concentrically arranged around the screw axis, an electromagnet (62) formed of an annular core (66) and an annular coil (68) , said electromagnet being joined to the housing (8) , and a permanent magnet (64) cooperating with the electromagnet, said magnet being joined to the nut (6) , that the magnets (62,84) when the electromagnet is not ener¬ gized, are pressed towards each other and when the electro¬ magnet is energized, depending on the polarization of the energizing current, either press harder towards each other or are placed at a predetermined distance from each other by means of the repulsive forces of the elements, and that the bearing clutch (60) in the two first cases acts as an elec¬ tromagnetic brake (30) , and in the last mentioned case acts as an electromagnetic thrust bearing (9) .

10. Elevator machinery for a screw drive elevator according to one of Claims 1 - 6, c h a r a c t e r i z e d in that the disengaging device (28) is mechanically operated.

11. Elevator machinery for a screw drive elevator according to one of Claims 3 - 10, c h a r a c t e r i z e d in that the nut (6) is non-rotatably fixed in an elevator car, that the screw (4) is rotatably mounted in the elevator shaft, and that the housing (8) , the drive device (16) and the disengaging device (28) are fixed in the elevator shaft.

12. Elevator machinery for a screw drive elevator according to one of Claims 5 - 7, c h a r a c t e r i z e d in that the nut (306) is separated from the bearing (309) and the second brake means (313) , which, is made in one piece with the nut gear (314) , which rests, via an angle compensator (315) , on the nut (306) , that the nut gear is non-rotatably joined to the nut (306) , and that the angle compensator is thereby capable of taking up angular deviations between the nut and the nut gear, whereby the nut can run in axial alignment on^' the screw (304) .

13. Elevator machinery for a screw drive elevator according to one of Claims 3 - 7 and/or 12, c h a r a c t e r i z e d in that the housing (308) has within it a cylinder (327) , that the housing and the first brake means (307) are made as two components displaceable relative to each other and which are non-rotatably connected to each other, that the brake means (307) comprises a load sensor (333) , which acts between the brake means (307) and the housing (308) , and that the load sensor has at least one sensing element (352) .

14. Elevator machinery for a screw drive elevator according to Claim 12, c h a r a c t e r i z e d in that the nut has at least one driver pin (316) for torque-transmitting engagement about the center axis (305) and via the driver housing (317), with the nut gear (314) which is disposed diametrically surrounding the bearing (309) .

15. Elevator machinery for a screw drive elevator according to Claim 12, c h a r a c t e r i z e d in that the angle compensator (315) is made of an annular cylinder (319) and an annular piston (321) , enclosing between them a fluid which evenly distributes the contact pressure between the cylinder and the piston even when there is angular misalignment there¬ between.

16. Elevator machinery for a screw drive elevator according to Claim 13, c h a r a c t e r i z e d in that the load sensor (333) has an annular chamber (329) and an annular piston (331) , and that a fluid enclosed between the chamber and the piston is in communication with at least one sensing element (352) .

17. Elevator machinery for a screw drive elevator according to one or more of the preceding claims, c h a r a c t e r ¬ i z e d in that each load sensor element (352) and pulse sensor element (58,358), as well as every additional sensor element (352,354,356) sends signals to the control unit (318), by means of which signals the current load and the current operating state of the elevator machinery (302) can be registered by the control unit, and that the positioning of the elevator machinery is possible, by corresponding operation of the nut, depending on the signals received from the sensor elements.