The present invention relates to an elevator according to the preamble of claim 1 . Generally, elevators work in an environment which ensures essentially constant temperatures for instance being built in an elevator shaft in a building or adjacent to a building. But sometimes elevators are exposed to current environmental conditions, e.g. if the elevator is located in a windmill or antenna tower or in any building which does not comprise a heating to provide an essentially constant temperature.

The environmental temperatures change over the seasons essentially and provide problems for the hoisting members. Particularly, when a hoisting member is used which comprises polymer material the environmental temperatures may fall to a point where the viscosity of the polymer material is essentially reduced so that the wear of this hoisting member is essentially increased and the life time of the hoisting member correspondingly reduced. This also holds true for standard steel wire ropes, used as hoisting members. This problem exists for all elevators of wind towers, oilrigs, radio towers or in other applications where a kind of service lift is needed for maintenance purposes of an apparatus.

It is therefore object of the present invention to provide an elevator which ensures a sufficient life time of the hoisting member even if the elevator is subject to cold ambient temperatures.

The object is solved with an elevator according to claim 1 . Advantageous embodiments of the invention are subject matter of the sub-claims. The inventive elevator comprises a hoisting motor driving a traction sheave, which traction sheave co-acts with at least one longitudinal hoisting member. The hoisting member may be one or several separate hoisting members as e.g. hoisting ropes or hoisting belts for moving a load receiving means in hoisting direction, generally vertically. The load receiving means may e.g. be an elevator car or a service platform. The traction sheave does not necessarily co-act with the hoisting member via friction. Thus, for example a sprocket wheel can be used as a traction sheave and in this case a hoisting member may be a toothed belt mashing with the sprocket wheel. Essentially is only the fact that the movement of the load receiving means happens via an interaction of the traction sheave and the hoisting member.

Usually, several hoisting members are arranged as a set of separate - often parallel - independent hoisting members which increase the safety of the elevator. A set of several separate or independent hoisting members is often required by common safety regulations, as e.g. EN 81 -1 .

Usually the hoisting members support the load receiving means totally or at least partially. Anyway, also in line with the present invention the hoisting members may be provided to mainly move the load receiving means in vertical direction whereas another supporting arrangement may be provided to carry at least a part of the load of the load receiving means, e.g. a separate suspension rope connected with a counterweight via a diverting pulley. The hoisting member comprises at least one suspension member for taking up the load applied to the hoisting member. The suspension member is usually made of high strength fibers extending in longitudinal direction of the hoisting member, as e.g. steel wire strands or high tensile polymer fibers as e.g. carbon fibers or aramid fibers. The hoisting member could also be a simple hoisting rope in which case the suspension member and the hoisting member are identical. In contrast thereto a hoisting belt as hoisting member often comprises several strands of metal wires or aramid fibers as suspension members. Usually, these suspension members are embedded in a textile and/or a polymer matrix to bui ld a hoisting belt. According to the invention at least one heating element extends in the longitudinal direction of the hoisting member, which heating element is connected to a power source. Accordingly, by feeding current to the heating element the complete hoisting member heats up. Preferably the heating is continued until the hoisting member reaches a desired threshold temperature which ensures the reduction of stress subjected to the hoisting member as result of its operation under too low temperatures.

Accordingly, before taking the elevator into use a service operator may heat up the hoisting member to avoid the cold operation of the elevator resulting in an undue wear of the hoisting member. The problem of the operation of a hoisting member in the cold is that it undergoes several deflections on the traction sheave and on the diverting pulleys. If these deflections take place with a cold hoisting member, e.g. of minus 20 degrees Celsius, the viscosity, elasticity and bending properties of the hoisting member are essentially reduced so that the multiple bending in use results in an excessive wear and a correspondingly short lifetime. This holds true for any steel wire as well as for any polymer containing hoisting member. The provision of the heating element in the hoisting member connected to a power source has therefore an essential benefit on the lifetime and reliability of the hoisting member.

Of course, there are different options of providing the heating element in the hoisting member. For example, the heating element may be formed by the suspension member of the hoisting member itself, generally strands of metal wires, or the heating element is an additional part to the suspension member, e.g. one ore more strand of heating wires running parallel to the suspension member. The heating element could also be a heating layer, e.g. an electrically partly conducting polymer layer, provided between connecting wires or suspension members as connecting wires. If a normal steel wire hoisting rope is used, the hoisting rope may act as heating element if it is connected with a power source and if preferably it is electrically isolated on the traction sheave and diverting pulleys against ground or against the elevator components. Generally but not necessarily the electric current has to be fed from the ends of the hoisting member or suspension member so that the hoisting member is heated along its entire length. Preferably, the heating element extends at least almost over the entire length of the hoisting member, which means it extends at least over that length of the hoisting member, which is going to be deflected as result of the normal operation of the elevator, for example when it is bent around the traction sheave or around the diverting pulleys, if any. This ensures that the wear of the hoisting member is effectively reduced as the wear only takes place at the locations where the hoisting member is bent. Of course, if the hoisting member itself or the suspension member forms the heating element then the heating element extends over the entire length of the hoisting member.

Preferably, the hoisting member comprises at least one isolating polymer layer for electrically isolating the heating element against the suspension member or against the heating member surface. Via this measure it is possible to use common metal traction sheaves or diverting pulleys which are not isolated against ground or against the elevator components or shaft structure. Via the isolating polymer layer it is ensured that the current only flows in the heating element and not from the hoisting member via sheaves or pulleys to other elevator components. Preferably, a cover layer of the hoisting member is used as the isolating polymer layer. Often coated hoisting ropes are used in which the suspension member(s) is/are surrounded by a polymer layer. In this case this cover polymer layer builds the isolating layer and no additional isolation has to be provided in connection with the traction sheave or the diverting pulleys.

As already mentioned above, it is possible to use a metal heating element formed of metal resistance wires which are commonly used for heating purposes and which are located parallel to the suspension member. If a kind of polymer layer is used as an electrically conducting heating layer it may be arranged between two conductors, which conductors may be realized as separate conductors or as the suspension members, e.g. In all these cases the heating element is provided additionally to the suspension members and the isolation of the heating element against the elevator shaft or other elevator components has to be realized either via an isolating layer in connection with the hoisting member or via electrically isolated hoisting member fixings, an electrically isolated traction sheave and electrically isolated diverting pulleys. In a very simple embodiment the suspension member itself is used as the heating element, in which case no special efforts have to be made to adapt the hoisting member to special heating conditions. Anyway, if there is no electric isolation provided in connection with the hoisting member the isolation has to be provided by the components in contact with the hoisting member.

No isolating efforts have to be taken in a hoisting belt comprising some parallel suspension members which are alternatively arranged with parallel heating elements, preferably so that each suspension element of the hoisting belt is heated by one adjacent heating element. In this case the textile/polymer matrix of the hoisting belt may form the isolating layer so that in this case no isolated traction sheave or diverting pulleys are necessary for the operation of the hoisting member heating.

At least in case the hoisting member is a usual metal hoisting rope of e.g. circular cross-section and the hoisting member itself is used as the heating element, the traction sheave and any diverting pulleys on which the hoisting member is running may comprises a groove with an electrically isolating lining. In this case the isolation of the hoisting member against the other elevator or shaft/building components is realized with minor efforts. Either only the groove can be provided with the lining or complete parts of the traction sheave/diverting pulley comprising the groove may be formed of an electrical ly isolating material. Accordingly, the complete rim of a traction sheave or diverting pulley comprising all grooves may be formed of an electrically isolating material. Preferably, the elevator control is provided with a current control unit for controlling the power source and thus the current which is fed to the heating element. By this means it can be ensured that the hoisting member is heated up to a temperature where the operation of the elevator does not lead to any undue wear of the hoisting member because of low temperatures.

An automated control can be realized if the current control unit is connected to a temperature sensor which is in heat conducting connection with the hoisting member. In this case the temperature of the hoisting member can be used in the current control unit for adjusting/switching the current flowing through the heating element. Accordingly the current flow through the heating element may be switched on as long as the temperature of the hoisting member is below a reference/threshold temperature stored in the current control unit or in the elevator control. Once the temperature of the hoisting member reaches the threshold temperature the current flow to the heating element is switched off. Preferably, the elevator control or the current control unit may comprise means for signalizing that the temperature of the hoisting member is ready for operation. Alternatively, it is possible to allow the operation of the elevator only after the above-mentioned threshold value of the temperature of the hoisting member has been achieved. In this case the current control unit issues a signal allowing the use of the elevator only after the temperature of the hoisting member has reached the threshold temperature. In an advantageous embodiment of the invention the electric current and voltage fed to the heating element may be used by the elevator control to estimate the wear of the hoisting member. On this behalf, the elevator control may comprise means for measuring the voltage and current fed to the heating elements and means to provide from the said voltage and current signal status the signal about the wear of the hoisting member. This means may comprise reference data of the voltage/current relationship of a new hoisting member and a comparator. During the life time of a hoisting member the metal wires of the hoisting member may break which leads to a higher resistance against current. In result to obtain the same current flow a higher voltage has to be fed to the hoisting member. By a comparison of the actual voltage/current relationship with the above mentioned reference data direct information about the wear of the hoisting member may be obtained, if the suspension member or the hoisting member itself forms the heating element. Preferably, the hoisting member fixings to fix the hoisting member at an elevator component or the elevator shaft or any building structure are designed to electrically isolate the hoisting member against the corresponding structure. Via such kind of hoisting member fixings coated as well as uncoated hoisting members can be fixed which have no own isolation of the heating element against its surface. Preferably, the current supply to the hoisting member is arranged in connection or in the vicinity of the hoisting member fixing which is advantageous, as usually at least one of the fixings of the hoisting member is immovably arranged at a defined location in the elevator shaft and thus readily accessible for contacting purposes.

Generally, several hoisting members are used as a set of hoisting members e.g. hoisting ropes or hoisting belts. In this case advantageously different hoisting members or groups of hoisting members of the hoisting member set are alternatively connected to the power source so that the power requirement in this case is essentially reduced compared with a simultaneous heating of al l hoisting members. For example, if the elevator comprises a set of nine hoisting members the elevator could be arranged so that the current control unit only feeds current simultaneously to three hoisting members to a certain time and then change to another set of three hoisting members so that in the end all nine hoisting members reach the desired operating temperature.

It shall be clear that the above-mentioned embodiments may be combined as long as there are no technical contradictions between any combinations.

The invention is now schematically described by the aid of the drawing.

Fig. 1 a schematic diagram of an elevator having heated elevator hoisting members,

Fig. 2 a cross section of an embodiment of a hoisting member, to be used e.g. in the elevator of fig. 1 ,

Fig. 3 a cross section of a second embodiment of a hoisting member, to be used e.g. in the elevator of fig. 1 , Fig. 4 a cross section of a third embodiment of a hoisting member, to be used e.g. in the elevator of fig. 1 ,

Fig. 5 a sectional view of a first embodiment of a traction sheave or diverting pulley having grooves with an electrically isolating lining, and

Fig. 6 a sectional view of a second embodiment of a traction sheave or diverting pulley having the grooves being located in an electrically isolating rim of the sheave or pulley. Fig. 1 shows very schematically an elevator 10 comprising an elevator shaft 12 particularly for outdoor use, for example in the tower of a wind power station. In the upper part of the shaft a hoisting motor (not shown) driving a traction sheave 14 is located. In the shaft 1 2 a load receiving platform 1 6, e.g. a elevator car, is guided with elevator guide rails. On the top of the car 1 6 two diverting pulleys 1 8, 20 are mounted. On the bottom of the car to lower diverting pulleys 22, 24 are mounted. Furthermore the elevator 10 comprises a diverting pulley 26 in the shaft pit. The elevator is suspended in the elevator shaft by means of several hoisting member 28 which is usually a set of normal steal or aramid hoisting ropes which are fixed in an upper fixing 30 at the shaft top and at a lower fixing 32 in the shaft bottom. Anyway, there also may be only one hoisting member. The upper and lower fixings 30, 32 for the hoisting member work on one hand as isolator against the shaft structure and on the other hand as contactor with an upper and lower current feed line 34, 36 which are connected to a power source 38. Adjacent to the upper and lower fixing 30, 32 an upper and lower temperature sensor 40, 42 is provided which are connected by an upper and lower signal line 44, 46 connected with a current control unit 48 which is connected to or is part of the elevator control 50. In a first alternative, it is assumed that the hoisting member 28 is set of per se known steel wire hoisting ropes of circular cross section. In this case all diverting pulleys 1 8, 20, 22, 24 and 26 as well as the traction sheave 1 6 have to be designed to electrically isolate the hoisting member 28 against the corresponding elevator components as e.g. car or the motor or the elevator shaft 12.

If as second alternative an isolated member is used, as e.g. a hoisting belt as it is shown in figs. 2 or 3 or a coated hoisting rope as shown in fig. 4, the diverting pulleys and the traction sheave do not have to be electrically isolated against the corresponding components carrying the pulley or sheave.

The invention aims for a use of such an elevator under possibly very cold conditions, for example towers of a wind power station. In windmills an elevator may face operating conditions of minus 20 to 30° C or even colder. One problem of such an operation is that on one hand this very low temperature has an adverse effect on the traction characteristics of the friction interface between the traction sheave 14 and hoisting member 28. On the other hand under such very low temperatures the elastic properties of the hoisting member are essentially deteriorated so that the bending of the hoisting member when running over numerous pulleys and the traction sheave imposes essential stress and wear on the hoisting members so that life time of the hoisting member is reduced. To meet this problem according to the invention current is fed to the hoisting member e.g. via its ends at the upper and lower hoisting member fixing 30, 32 and via the upper and lower supply lines 34, 36 which are connected to the power source 38. The power source 38 is controlled by the current control unit 48 as to feed electric current to the hoisting member 28 to increase the temperature thereof above a temperature value which allows an operation of the elevator without affecting lifetime of the hoisting member essentially. Such a temperature may be e.g. 0° C, 10° C or 20° C depending on the kind of hoisting member used. To enable an efficient control via the current control unit 48 two temperature sensors 40, 42 are provided in the top and bottom of the elevator shaft 12 in connection with the hoisting member fixings 30, 32. The signal lines 44, 46 of these temperature sensors are connected to the current monitoring unit 48. Hereby it is to be stated that instead of two temperature sensors only one or more than two temperature sensors may be used. Furthermore, the temperature sensor may be placed at any location in the elevator shaft or the building where the elevator is housed. The temperature sensors 40, 42 forward the temperature information to the current control unit 48 which enables the current control unit 48 to determine whether the hoisting member has to be heated.

In case the hoisting member is to be heated the current monitoring unit may either put a predetermined amount of energy based on the prevailing ambient temperature to the hoisting member 28 or simply switches the current feed to the hoisting member 28 on until the temperature sensors 40, 42 show that the temperature of the hoisting member has increased to a threshold value which is deemed harmless for the operation of the hoisting member 28. Therefore this case the current control can be performed via a simple comparison of the measured hosting member temperature with a reference value indicating a temperature allowing a smooth operation of the hoisting member during use of the elevator.

If the temperature of the hoisting member is to be used as feedback signal for the operation of the current control unit it is necessary to arrange the temperature sensor in connection with the hoisting member.

Generally a normal coated or uncoated circular steel wire hoisting rope can be used as a heating element as usual steel wires have a defined electric resistance and heat up upon feeding electric current to their ends. Of course it is also possible to use belts as hoisting members which may comprise several suspension members made of strands comprising aramid fibers and/or metal wires coated by a textile and/or polymer embedding matrix. Also in such kind of hoisting belts the suspension members, if electrically conductive, may be used as heating elements.

The following figs. 2 and 3 show embodiments wherein adapted heating elements are provided in the hoisting member which are arranged separately from the suspension members.

Accordingly, fig. 2 shows a hoisting belt 60 in cross section view. The hoisting belt 60 comprises an oval polymer matrix 62 having a width much larger than its depths. Within this polymer matrix 62 three suspension members 64 are located, which are made e.g. from polymer, e.g. carbon or aramid, fibers or from metal wires which are arranged laid in a per se known wiring construction, e.g. Warrington construction. Between the three suspension members 62 two heating elements 66 are provided which are heating wire strands extending along the total length of the elevator belt. The advantage of this construction is that the load carrying and heating function in this hoisting member is divided to two separate elements so that these both functional elements 64, 66 can be optimized for their respective function. Referring the use of this elevator belt in fig. 1 the hoisting member fixings 30, 32 have not to be designed electrically isolating against the shaft structure. Contactors may be provided within or near the hoisting member fixings to connect the heating elements to the current feed lines 34, 36.

Fig. 3 shows a second embodiment of a hoisting belt 70 which also comprises three suspension members 72 embedded in a polymer matrix 74 having a much larger width than depth. In this embodiment three suspension members 72 which are e.g. made of steel wires act as contactors for two intermediate heating layers 76, 78 which are made from a polymer material having a certain technical resistance which allows the layers to function as a heating element. Advantageous of this construction is the fact that the suspension members 72 not have any heating function but are only used as contactors for the two intermediate heating airs 76 and 78. Accordingly, the suspension members can be optimized for the load carrying function.

Fig. 4 shows a coated hoisting rope 80 with circular cross-section comprising as suspension member 82 a usual elevator steel rope in a well known wiring structure, e.g. Warrington construction, covered around its total circumference by a polymer layer 84 which isolates the metal suspension member 82 against diverting pulleys and the traction sheave. In this case the elevator rope itself is used as the heating element.

When using either hoisting member of figs. 2 to 4 in the elevator of fig. 1 the diverting pulleys and traction sheave of the elevator of fig. 1 do not have to be electrically isolated. Furthermore, also the hoisting member fixings 30, 32 do not have to be isolated if the contactors to contact the heating members power source are isolated against are arranged in a isolating distance to the hoisting member fixings 30, 32.

Finally figs. 5 and 6 show two different embodiments of a traction sheave for diverting pulleys which isolate a hoisting member against sheave body.

In fig. 5 the traction sheave 90 comprises a pulley 92 having on its outer rim three parallel grooves 94 for three separate hoisting ropes arranged parallel e.g. for use in the elevator of fig. 1 . The grooves 94 are electrically isolated against the pulley 92 by an electrically isolating lining 96. This lining 96 is provided in each of the grooves 94. This arrangement can be used by the traction sheave as well as by the diverting pulleys of fig. 1 .

In a second embodiment fig. 6 shows a sheave 100 which may be used as traction sheave or diverting pulley in the elevator of fig. 1 which sheave 100 has a pulley 102 with a flat outer rim 104. Around that rim 104 a ring 106 made of electrically isolating polymer material or rubber is provided in which ring 106 three parallel grooves 108 for the hoisting members are provided. This provides a cheap possibility for isolated grooves on a sheave or pulley.

Finally it has to be emphasized that in fig. 1 the roping of the hoisting member 28 in the elevator shaft may be different from the embodiment as shown. For example an arrangement may be used which uses more or less diverting pulleys on the top or bottom of the shaft than shown in fig. 1 .

Furthermore it is possible to use a counterweight in the elevator of fig. 1 , if desired. Furthermore the hoisting motor together with the traction may located at another position in the elevator shaft e.g. in the shaft pit. It shall further be understood that the elevator control, the current control unit 48 and the power source 38 may be different units or may be parts of a central control unit which also comprises the power electronics building the power source. Furthermore it shall be clear that the current may be fed to the heating element in the hoisting member at other locations then via its ends, for the feeding points it is only relevant that those hoisting member parts are heated which are bent during use. The elevator control 50 and/or current monitoring unit 48 of fig. 1 may have a circuit which compares the current and voltage fed to the heating element(s) with reference values to obtain information about the wear of the hoisting member.