Patent Application
20160167922
The present invention concerns a service lift, in particular for installation in or on building structures, comprising a personnel access means, a drive device for upward and downward movement of the personnel access means, and a suspension means which can be fixedly connected to the building and along which the service lift is movable by the drive device.
Service lifts of the above-indicated kind are used for raising and lowering loads and personnel. In particular service lifts of the above-indicated kind are used when the corresponding building structures already exist and the lifts are retro-fitted therein or have to be temporarily installed there for example during installation works. A typical ample of use is the pylons of wind power installations.
Such lift assemblies and drive mechanisms which are commonly used for same are known for example from DE 10 2010 062 774 A1. In the state of the art steel cables which are secured to a fixed point on the building structure are used as the suspension means. The personnel access means are either moved up and down by means of drum winches which wind on the steel cables, or they are moved up and down by means of so-called endless cable winches, wherein the endless cable winches, by means of a drive pulley, involve a force-coupling connection with the steel cable but do not wind on the cable but in principle move on the freely hanging cable.
Although the movement of service lifts with endless cable winches of the known kind generally functions satisfactorily there is still nonetheless a need for improvement with the known systems. Thus for example due to the action of the drive pulley in the case of known endless cable winches there is a need for the support cables to be replaced because of wear after an operating life of the order of magnitude of 1500 load cycles. In addition even stiff steel cables, by virtue of their structural configuration, have a certain characteristic of being elastic in respect of length, which can lead to oscillations in the vertical direction in operation of the service lifts. The drive mode based on a force-locking connection also gives rise to a certain level of noise.
Therefore the object of the present invention is to provide a service lift which is improved in respect of its drive concept in the above-mentioned points.
In the case of a service lift of the kind set forth in the opening part of this specification the object of the invention is attained in that the suspension means has a first and preferably a second drive chain which can be mounted to a fixing point on the building structures, and the drive device for each of the drive chains has one or more cogwheels which are in force-transmitting engagement with the drive chain to convert a rotation of the cogwheels into the upward or downward movement of the service lift.
The invention is based on a complete departure from the known concept of the endless cable winch which requires at least a support cable and a retaining cable, insofar as instead recourse is had to the use of one or two drive chains. The chain-based drive concept offers a number of advantages at the same time: by virtue of the construction of chains which are designed for engagement by cogwheels, the stiffness of the suspension means is markedly improved in comparison with known solutions. There is a less pronounced tendency for oscillations in a vertical direction. A drive chain further has the advantage that in operation it gives rise to markedly less noise which occurs due to engagement of the cogwheels into the drive chain, than an endless cable winch would do with its drive pulley in engagement with a steel cable.
Yet a thither advantage is to be seen in the fact that both the drive chain and also the cogwheels engaging into the drive chain for force transmission can be produced with technically simple means in a tried and tested fashion and as standard components are more readily available than for example drive pulleys of endless cable winches and correspondingly produced steel cables for which a markedly more limited choice of manufacturers is available.
When the service lift is driven by means of cogwheels on the drive chain a lesser degree of wear is also to be expected, by virtue of the positively locking drive concept. The maintenance intervals in the case of a lift installation according to the invention are a multiple longer than with the known systems.
An advantageous development of the invention provides that the drive device has a motor drive with a first drive motor and a second drive motor which are respectively in engagement with one of the two drive chains. Particularly preferably the motor drive comprises the first and second drive motors.
The provision of two drive systems in parallel relationship improves the fail-safety of the service lift. By virtue of the fact that two drive systems with two drive chains are permanently provided in that way it is always possible if required to switch on the second drive if for example the first motor drive is defective. Preferably both systems run at the same time in operation. If one system should fail then the second is at least in a position to securely hold the load. In a preferred development both systems are so designed that they are capable of lifting the load.
In a particular preferred embodiment the drive motors are respectively in the form of gear motors with an electric motor and an electromagnetic brake. The electromagnetic brake provides for reliably arresting the motor for reliably arresting the service lift in its position. In that case for example catch devices as are used in the endless cable winches known in the state of the art are unnecessary. Even for the improbable situation that both drive motors fail at once the electromagnetic brakes provided in both drive motors provide for reliably safeguarding the service lift.
In a further preferred embodiment the drive motors each have a respective centrifugal brake and means for manually unlocking the electromagnetic brake, Theoretically in extreme situations the case can occur where both drive motors are defective and operation cannot be continued after the service lift has stopped. In such a case it is possible with this embodiment for the electromagnetic brakes of the drive motor or motors to be released, whereupon the service lift will begin a downward movement. The speed of downward movement is however restricted to a permissible maximum limit by means of the centrifugal brakes so that it is possible to exclude any safety and injury risks. Preferably the maximum speed of downward movement is in a range of 22 m/min to 28 m/min (particularly preferably 25 m/min).
The centrifugal brake operates even if an electric power supply is no longer guaranteed, which makes the system absolutely fail-safe.
In a particularly preferred development of the invention the drive device is in the form of an endless pass-through chain drive, wherein the length of the drive chains is so dimensioned that in the mounted condition they extend from the suspension means through drive device and laterally along the personnel access means where they hang down. The advantage of drive chains is that they can be provided in principle any length, at a low level of complication and expenditure in terms of manufacturing technology. Thus the same components of the service lift including its drive device can always be used for the most widely varying locations of use and it is only necessary to select the length of the drive chains which are respectively used, so as to be adapted to the location of use, That increases the amount of identical components for the most widely varying locations of use and an increase in cost efficiency is afforded by virtue of scale effects.
In addition the mechanical structure of the drive device is simplified because there is no need to provide means for catching/winding on the drive chains.
In a further preferred configuration of the service lift according to the invention the drive chains are oriented parallel, and are preferably guided. past the personnel access means on the same side of the service lift and are held in a tensioned state in a vertical direction by means of a tensioning weight. In a first preferred alternative the tensioning weight is in the form of a common tensioning weight for both drive chains. In a second alternative the tensioning weight includes two individual weights. The provision of a tensioning weight ensures that the drive chain in the drive device cannot jump relative to the cogwheels, in particular the driving cogwheels, the tensioning weight stabilizing the position and orientation of the drive chains. If a common tensioning weight which holds both drive chains is used for both the chains, at the same time that also permanently ensures parallel orientation of both drive chains.
The drive chains are preferably deflected a plurality of times by the drive device. The deflection serves on the one hand in particular to orient the drive chains substantially perpendicularly with the center of gravity of the personnel access means above the personnel access means so that the personnel access means ‘hangs straight’ and can be better guided for example within building structure shafts. In addition a preferably multiple deflection of the drive chain ensures that the angle with which the chain passes around the force-transmitting cogwheel which is connected to the motor drive is sufficiently great to always hold a sufficient number of teeth in engagement with the chain. That reduces the point loading on individual teeth and wear of the drive system overall is minimized.
Finally the deflection serves to guide the drive chain along the drive device and past the personnel access means.
The additional deflecting, non-driven cogwheels, in addition to the tensioning weight, contribute to ensuring that the chain does not jump and the positively locking connection to the driving cogwheel is always maintained.
In a further preferred embodiment the service lift according to the invention has a lifting force limiting device which is adapted in dependence on a relative movement between the drive device and the personnel access means to stop the upward or downward movement of the service lift, when a predetermined chain load is exceeded. Although the risk of oscillation of the service lift in a vertical direction is already markedly reduced by the use of drive chains in comparison with steel cables, changes in the speed of the service lift, precisely at the beginning or the end of a movement process, involve a time-limited increase in the force acting on the drive chain in a vertical direction (chain load). It has proven to be advantageous for the entire drive device to be designed in the form of a construction which is rigid in itself, and also for the personnel access means to be in the form of a construction which is rigid in itself, but in contrast thereto for the two units to be made movable relative to each other. That affords a system which is mechanically simple to manage, with the option of keeping the number of degrees of freedom down.
Preferably, in that lifting force limiting device, the drive motors are mounted on a common load receiving plate, wherein the load receiving plate is mounted pivotally to the personnel access means and is biased by a spring element in the direction of the personnel access means. Preferably the pivotal movement is inhibited by means of a damper element. The pivot axis, which is the term used to mean the axis about which the load receiving plate pivots relative to the personnel access means, is preferably displaced horizontally relative to a force engagement point of the suspension means, at the suspension means side. Due to that lateral displacement of the pivot axis from the force engagement point at the suspension means side, this provides that the normal force coming from the suspension means at the building structure side, which pulls on the drive chain, has a lever effect (even if slight) about the pivot axis of the load receiving plate. By virtue of that lever, a pivotal movement of the load receiving plate occurs relative to the personnel access means which is again disposed with its mass center of gravity in perpendicular relationship with the chain line at the suspension means side. Alternatively it is preferred that the pivot axis is oriented in coaxial relationship with the transmission shaft. In that way, the pivotal movement of the load receiving plate is preferably triggered solely by the torque of the drives.
Because the spring element is biased in the direction of the personnel access means, the spring counteracts a deflection as a consequence of an increase in normal force of the chain line at the suspension means side. The increase in tensile force as from which a pivotal movement occurs at all can thus be adjusted by way of the level of the biasing effect,
Preferably an interrupt switch for the drive device is arranged on the personnel access means or the load receiving plate in such a way that upon the occurrence of a predetermined deflection of the load receiving plate in opposition to the operative direction of the pre-stressed spring element the switch is triggered. When the interrupt switch is triggered the drive motor is preferably stopped immediately. The damper element preferably provided on the service lift acts between the load receiving plate and the personnel access means to prevent the interrupt switch already being triggered in the event of a jerky start to the travel movement.
In a further preferred embodiment of the service lift it has a device for monitoring tension of the drive chains. In the course of the operating life of each chain an increase in the length of the chain occurs. In extremely rare cases it can further happen that individual chain links fail and suffer from cracking, whereby the chain overall can tear apart if the crack is not discovered in good time.
As optical monitoring of the drive chain seems technically complicated and expensive it is preferred if the tension monitoring device for each drive device has a preferably non-driven cogwheel which is deflectable in non-parallel relationship relative to the respective drive chain and is urged by means of a spring element in the direction of the respective drive chain against same. Preferably an interrupt switch for the drive device is further arranged on the cogwheel, a cogwheel holder which is also moved by the spring element, or the load receiving plate, in such a way that it is triggered when a predetermined deflection of the cogwheels occurs or is exceeded. The cogwheel which is urged in the direction of the drive chain against same by means of the spring element has the effect of displacing the drive chain out of its orientation which is predetermined as a consequence of the chain tension. The chain tension works thereagainst.
The interrupt switch preferably operates on the basis of the same functional. principle as the interrupt switch for the drive device which is provided in the lifting force limiting device. When a predetermined deflection of the cogwheel or the cogwheel holder supporting the cogwheel is attained or exceeded the supply of power to the motor drive is interrupted. Both motors are switched off.
It is particularly preferred in the case of the service lift according to the invention if the two drive motors and the cogs in engagement with the drive chains for both drive chains are of an identical configuration and if moreover both drive chains are also identical. That provides a completely redundant drive system which in the case of a defect in the first drive train ensures that, if the first drive train fails, the other drive train holds the load.
The organization and manner of the structure and operation of the invention, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in connection with the accompanying drawings, wherein like reference numerals identify like elements in which:
While the invention may be susceptible to embodiment in different forms, there is shown in the drawings, and herein will be described in detail, a specific embodiment with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that as illustrated and described herein.
The personnel access means 3 is mounted to a suspension means 5 which can be fixed to the building. The suspension means 5 includes a first drive chain 7a. and a second drive chain 7b. A transmission device 11 is in engagement with the drive chains 7a, 7b, The transmission device 11 includes a motor drive 9. The motor drive 9 in turn includes a first electric motor 9a and a second electric motor 9b. A tensioning weight 10 holds the drive chains 7a, 7b parallel to each other and in as tensioned condition.
Further details relating to the drive device 11 can be seen from
Furthermore the electric motors 9a, 9b are each equipped with a hand lever 23. The hand levers 23 represent a means for manually unlocking an electromagnetic brake provided in the gear motors. In an emergency situation, for example in the event of a power failure, both brakes have to be opened. Then the personnel access means travels downwardly solely due to the force of gravity and the people can be evacuated therefrom.
This is shown in greater detail once again in
It will further be seen from
As can also be seen from
It will also be seen from
To guarantee the angle through which the chain passes around the drive cogwheel 33 the arrangement has a further non-driven cogwheel 37 which deflects the drive chain 7b. A third cogwheel 39 which is also not driven deflects the drive chain 7b again so that it can hang substantially vertically down at the side of the personnel access means 3.
A further aspect shown in
Insofar as, in relation to
While preferred embodiments of the present invention are shown and described, it is envisioned that those skilled in the art may devise various modifications of the present invention without departing from the spirit and scope of the invention.
