Abstract:
An elevator installation and method to passively and reliably generate electrical energy while the elevator installation is in operation utilizes piezoelectric layers. The elevator installation includes an elevator car, a tension member for supporting and moving the elevator car, and a pulley engaging with the tension member wherein the pulley has a piezoelectric layer positioned such that any force imparted to the pulley during engagement with the tension member compresses the piezoelectric layer. As the tension member is driven to move the elevator car up and down along an elevator hoistway it also engages with the rotating pulley. Force imparted to the pulley during this engagement with the tension member compresses the piezoelectric layer which consequently generates electrical energy.

Description:
FIELD 
       [0001]    The present invention relates to elevator installations and particularly to the passive generation of electrical energy while such an elevator installation is in operation. 
       BACKGROUND 
       [0002]    The use of piezoelectric elements has been proposed previously within the field of elevators to generate control signals, which are fed to an elevator controller enabling the controller to regulate operation of the elevator. For example, JP-A-2002068618 and U.S. Pat. No. 6,715,587 both describe the use of piezoelectric elements mounted either between or to one of an elevator car and its associated frame. The piezoelectric elements in these examples are provided as pressure sensors, which generate signals to an elevator controller enabling the controller to determine changes in the load within an elevator car. JP-A-2011213479 similarly describes the use of a pressure sensor which, on this occasion, is inserted at the bottom of a groove of a traction sheave to diagnose wear of the groove. 
         [0003]    EP-A1-1780159 and EP-A2-0636569 describe elevator operating panels, which are generally provided on each landing to enable prospective passengers waiting on the landing to call an elevator. Similar panels may also be mounted within the elevator car to allow boarded passengers to enter their required destination floor. In both the arrangements, piezoelectric elements are used within the operating panels as buttons such that upon exertion of sufficient pressure by a passenger&#39;s finger, the elements generate the required signal to the elevator controller and can also illuminate an LED to indicate acceptance of the passenger&#39;s call. 
         [0004]    Accordingly, piezoelectric elements have been used as pressure sensors within elevators to generate control signals either for determining the changes in the load within an elevator car or for diagnosing wear of a sheave groove or acting as call signals for transmission to the elevator controller. 
         [0005]    However, since load changes within the elevator car occur rather intermittently, groove wear is gradual, and buttons on the operating panel have a small cross-sectional area and can be operated with relatively little pressure, none of these applications of piezoelectric elements within elevators is sufficient to generate a reliable supply of energy. 
       SUMMARY 
       [0006]    The present invention has been developed to overcome the above-identified problems related to the described prior art. 
         [0007]    An objective of the present invention is to provide an elevator and method to passively and reliably generate electrical energy while an elevator installation is in operation. 
         [0008]    The elevator installation comprises an elevator car, a tension member for supporting and moving the elevator car and a pulley engaging with the tension member, wherein the pulley comprises a piezoelectric layer positioned such that any force imparted to the pulley during engagement with the tension member compresses the piezoelectric layer and further includes a power storage unit having an input electrically connected to an anode and a cathode of the piezoelectric layer. Thereby electrical energy generated by the piezoelectric layer can be harvested in the power storage unit. 
         [0009]    As the tension member is driven to move the elevator car up and down along an elevator hoistway, it also engages with the rotating pulley. Force imparted to the pulley during this engagement with the tension member compresses the piezoelectric layer, which consequently generates electrical energy. Given, firstly, the relatively high rotational speed of elevator pulleys and, secondly, the substantial compressive force differentials exerted on the pulley during each rotation, a significant and reliable supply of electrical energy can be generated by the piezoelectric layer when the elevator is in operation. 
         [0010]    Preferably, the piezoelectric layer is applied to an outer circumferential surface of the pulley and engages with the tension member. Accordingly, the tension member directly compresses the piezoelectric layer as it travels over the pulley. 
         [0011]    The pulley can further comprise a shaft, which is rotatably supported by a bearing mounted in a support bracket. Consequently, the pulley and shaft rotate in unison and forces are transmitted from the tension member, through the pulley and its shaft and to the support bracket via the bearing. 
         [0012]    In this arrangement, the piezoelectric layer can be provided on an outer circumferential surface of the shaft that is rotatably supported by the bearing. This can be used in addition or as an alternative to the previously described arrangement where the piezoelectric layer is applied to an outer circumferential surface of the pulley and engages with the tension member. 
         [0013]    In another alternative arrangement, the pulley may have an inner circumferential surface and is supported by a bearing on a non-rotating axle. Here again the piezoelectric layer can be applied to the inner circumferential surface to generate electrical energy during rotation. 
         [0014]    Although the power storage unit can be mounted on and thereby is rotated in unison with the pulley, it is envisaged that it would be more beneficial to mount the power storage unit remotely from the pulley. In such a case the anode and the cathode of the piezoelectric layer can be electrically connected to a first and a second conductive ring, respectively. The rings are mounted to either the pulley shaft or to a side face the pulley. Brushes can be used to slidably engage with the rotating conductive rings. Preferably the brushes are spring biased into engagement with the rings. The brushes can then be electrically connected to the input of the power storage unit. Thereby, electrical energy generated by the rotating pulley can be transmitted to the stationary power storage unit. 
         [0015]    Energy generated can be transferred into an electrical energy bank within the power storage unit and can be stored for subsequent use. The electrical energy bank may comprise batteries, capacitors, fuel cells or any other form of DC electrical energy storage. 
         [0016]    Depending on the respective voltage ratings of the piezoelectric layer and the electrical energy bank, it may be necessary to insert a DC to DC converter between the input of the power storage unit and the electrical energy bank. 
         [0017]    Preferably, energy harvested within the power storage unit can be supplied to external electrical loads via one or more outputs. If the external load has the same voltage rating as the energy bank, it can be supplied from a DC output connected directly to the energy bank. Alternatively, the voltage from the energy bank can be bucked, boosted or otherwise transformed by a DC to DC converter to supply external electrical loads having different voltage ratings via a further DC output. Furthermore, a DC to AC inverter can be used to invert the DC power from the energy bank into AC power, which can be supplied to external electrical loads via an AC output. 
         [0018]    The invention further provides a method for providing electrical energy within an elevator installation, wherein a tension member supports and moves an elevator car. The method comprises the steps of incorporating a piezoelectric layer in a pulley, compressing the piezoelectric layer when the tension member engages with the pulley and electrically connecting the piezoelectric layer to a power storage unit. 
         [0019]    Subsequently, the electrical energy harvested can be supplied from the power storage unit to an electrical load. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0020]    The invention will be described herein with reference to the following drawings in which: 
           [0021]      FIG. 1  is an exemplary schematic showing a conventional arrangement of components within an elevator installation according to the present invention; 
           [0022]      FIG. 2  is an axial, plan view of a traction sheave arrangement according to an exemplary embodiment suitable for use in the elevator installation of  FIG. 1 ; 
           [0023]      FIG. 3  is a cross-sectional view of an exemplary embodiment of the support bracket of  FIG. 2 ; 
           [0024]      FIG. 4  is a cross-sectional view of an exemplary embodiment of the traction sheave of  FIG. 2 ; 
           [0025]      FIG. 5  is a perspective view of an exemplary embodiment of the traction sheave of  FIGS. 2 and 4 ; 
           [0026]      FIG. 6  is a schematic of an exemplary embodiment of a power storage unit in which energy generated by the piezoelectric layer of  FIGS. 3 and 4  is harvested; 
           [0027]      FIG. 7  is a cross-sectional view of an exemplary embodiment of one of the underslung, car mounted pulleys of  FIG. 1 ; and 
           [0028]      FIG. 8  is an axial, cross-section view showing the engagement the tension member with a pulley according to an exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]      FIG. 1  illustrates an exemplary embodiment of a conventional arrangement of components within an elevator installation  1 . An elevator car  2  and a counterweight  4  are supported on a traction member  6  by means of deflection pulleys  8 . In this example, the tension member  6  has a 2:1 roping ratio whereby it extends from one termination  10  in an elevator hoistway  12  under a deflection pulley  8  mounted to the top of the counterweight  4 , back up the hoistway  12  for engagement with a traction sheave  14  driven by a motor, down to a pair of underslung pulleys  8  mounted underneath the car  2  and finally back up to a further termination point  10  in the hoistway  12 . Naturally, the person skilled in the art will easily recognize that alternative roping arrangements are equally applicable and that the traction sheave  14  and its associated motor can be mounted within the shaft  12  to provide what is conventionally known as a machine-room-less (MRL) installation, as shown, or alternatively can be provided in a separate and dedicated machine room. 
         [0030]    In operation, as the traction sheave  14  is rotated by the motor, it engages with the traction member  6  to vertically move the car  2  and counterweight  4  in opposing directions along guiderails (not shown) within the hoistway  12 . 
         [0031]      FIG. 2  is an axial, plan view of an exemplary embodiment of a traction sheave  14  arrangement suitable for use in the elevator installation  1  of  FIG. 1 . The traction sheave  14  has an inner circumferential surface  14 . 2 , which is splined to or otherwise fixed to a shaft  16  for concurrent rotation. The traction sheave shaft  14  can be integral with, or directly or indirectly coupled to the drive shaft of the motor. The shaft  16  is rotatably supported by bearings  18  mounted in support brackets  20  arranged at opposing sides of the traction sheave  14 . The brackets  20  are mounted on a structural beam  22  either in the hoistway  12  or in a machine room. 
         [0032]      FIG. 3  is a cross-sectional view of an exemplary embodiment of the traction sheave of  FIG. 2 . The outer circumferential surface  14 . 1  of the traction sheave  14  that engages with the tension member  6  is coated with a piezoelectric layer  30 . In operation, the tensions T 1  and T 2  exerted through the sections of the tension member  6  leading to the counterweight  4  and to the car  2 , respectively, will be transmitted through the piezoelectric layer  30  as distributed contact force over the wrap angle α through which the tension member  6  engages the traction sheave  14 . In the present example the wrap angle is 180°, forming the upper semi-circular segment of the traction sheave  14 . The traction sheave itself will naturally provide a counteracting and distributed normal force over the same wrap angle α. The interaction of the opposing contact and normal forces exerted on the piezoelectric layer  30  will generate electrical energy. 
         [0033]    Accordingly, in operation as the piezoelectric layer  30  rotates, it will have minimal compression while located in the lower semi-circular travel segment of the traction sheave  14 . However, as the tension member enters into engagement with the traction sheave  14 , the compression exerted on the piezoelectric layer  30  progressively increases to a maximum compression in the upper travel region of the traction sheave  14 . Thereafter, the compression exerted on the piezoelectric layer  30  progressively decreases to the minimal compression once again when the tension member  6  disengages with the traction sheave  14 . 
         [0034]    The rated speed of a traction sheave  14  will vary widely depending on application. Typical factors that are taken into consideration include sheave diameter, wrap angle α, rated load, travel height, roping ratio and tension member type. Consequently, the traction sheave  14  may have a rated speed ranging from the tens to the hundreds of revolutions per minute (rpm). 
         [0035]    Given, firstly, the relatively high rotational speed of the traction sheave  14  and, secondly, the substantial compressive force differentials exerted on the piezoelectric layer  30  during each rotation of the traction sheave  14 , a significant and reliable supply of electrical energy can be generated by the piezoelectric layer  30  when the elevator  1  is in operation. 
         [0036]      FIG. 4  is a cross-sectional view of an exemplary embodiment of the support bracket  20  of  FIG. 2  and depicts an additional or alternative embodiment for generating electrical energy within an elevator  1 . In this example, a piezoelectric layer  30  is provided on the outer circumferential surface of the shaft  16  that is rotatably supported by bearing  18  mounted in the support brackets  20 . The vertical tensions T 1  and T 2  imparted on the traction sheave  14  by the tension member  6  are ultimately transmitted through the shaft  16  to the portions thereof which are supported on the brackets  20  and manifests as a downward contact force F. Each of the brackets  20  will exert a counteracting normal force through the bearing  18 . The interaction of the opposing contact and normal forces exerted on the piezoelectric layer  30  will generate electrical energy. 
         [0037]    During operation of the elevator, the piezoelectric layer  30  will have minimal compression while located in the upper semi-circular segment of rotation. However, as the piezoelectric layer  30  travels through the lower semi-circular segment of rotation, its compression will increase progressively to a maximum compression and progressively decrease to the minimal compression once again. 
         [0038]    As with the traction sheave  14  of  FIG. 3 , the piezoelectric layer  30  mounted on the shaft  16  will experience a relatively high rotational speed and substantial compressive force differentials during rotation. Thereby, a significant and reliable supply of electrical energy can be generated by the when the elevator  1  is in operation. 
         [0039]      FIG. 5  is a perspective view of an exemplary embodiment of the traction sheave of  FIGS. 2 and 3  and provides an example of how the electrical energy generated by the piezoelectric layer  30  can be harvested. Anode(s)  32  and cathode(s)  34  of the piezoelectric layer  30  are connected by insulated wire  36  to a first and a second conductive ring  38 , respectively. The rings  38  are mounted over but insulated from the shaft  16 . Carbon brushes  40 , mounted to a stationary frame (not shown), are biased by compression springs  42  into engagement with the exposed surfaces of the conductive rings  38 . Power is drawn from the conductive rings  38 , through the carbon brushes  40 , through power cables  44  connected to the brushes  40  and supplied onto a power storage unit PSU, as shown in  FIG. 2 . It will be appreciated that the same technique can be used to transmit the energy generated in the arrangement of  FIG. 4 . 
         [0040]    The DC voltages supplied along cables  44  are used as an input DC in  to the power storage unit PSU, as shown in  FIG. 6 . Within the power storage unit PSU, the electrical energy from the input DC in  can be feed through a DC to DC converter  46  and is ultimately stored in an energy bank  48 , which in this instance comprises a plurality of rechargeable batteries  50 . Naturally, other forms of DC electrical energy storage such as capacitors, fuel cells etc. are equally feasible. 
         [0041]    Power harvested in the DC energy bank  48  can be fed directly to a first DC output DC out   1  and supplied further to electrical loads operating with the same voltage rating as the energy bank  48 . Alternatively, the voltage from the energy bank  48  can be bucked, boosted or otherwise transformed by a further DC to DC converter  46  to supply external electrical loads having different voltage ratings via a second DC output DC out   2 . Furthermore, a DC to AC inverter  52  can be used to invert the DC power from the energy bank  48  into AC power, which is supplied to external electrical loads via an AC output AC out . 
         [0042]    Although the above description relates to the generation of electrical energy from a traction sheave  14  and its associated shaft  16 , it will be appreciated that the same principles can be applied to any pulley used within the elevator installation  1  that engages with the tension member  6 . 
         [0043]    For example,  FIG. 7  is a cross-sectional view of an exemplary embodiment of one of the underslung, car mounted pulleys  8  of  FIG. 1 . As with the traction sheave  14  from the preceding embodiments, an outer circumferential surface  8 . 1  of the deflection pulley  8  that engages with the tension member  6  is coated with a piezoelectric layer  30 . However, contrary to the earlier embodiments, the pulley  8  is not fixed to a shaft for concurrent rotation but instead is rotatably mounted via bearing  18  on a non-rotating axle  54  which in turn is mounted to the elevator car  2 . A further piezoelectric layer  30  is applied to the inner circumferential surface  8 . 2  of the deflection pulley  8 . 
         [0044]    The distributed contact force imparted to the deflection pulley  8  as it engages with the tension member  6  over the wrap angle α and the counteracting normal force exerted by the non-rotating axle  54  through the bearing  18  will substantially compress both piezoelectric layers  30  and thereby generate electrical energy. 
         [0045]    Although the wrap angle α at 90° is considerably smaller than in the previous examples and the force exerted by the tension member  6  on the pulley  8  is also smaller, the deflection pulley  8  generally has a much smaller diameter and therefore its rotational speed is considerably greater than that of the traction sheave  14 . Accordingly, a significant and reliable supply of electrical energy can still be generated by the piezoelectric layer  30  when the elevator  1  is in operation. 
         [0046]    Preferably, using the same principle as described with reference to  FIG. 5 , the power generated by the piezoelectric layer  30  is transmitted to conductive rings, this time provided on a side face of the pulley  8 , through carbon brushes and onto a power storage unit PSU mounted to the elevator car  2 . Accordingly the power harvested within the power storage unit PSU can be supplied to electrical loads within the car  2  such as lighting, ventilation, operating panels etc. 
         [0047]      FIG. 8  is an axial, cross-section view showing the engagement the tension member  6  with a pulley according to an exemplary embodiment of the present invention. The form of the pulley can be applied to either a traction sheave  14  in accordance with  FIGS. 1-5  or to a deflection pulley  8  in accordance with  FIGS. 1 and 7 . The tension member  6  is in the form a ribbed belt and the outer circumferential surface of the pulley  14  or  8  has corresponding grooves. The piezoelectric layer  30  is provided between the grooves of the pulley  14  or  8  and the tension member  6 . The anode  32  and cathode  34  of the piezoelectric layer  30  are extended to one side of the layer  30  and can be subsequently connected electrically as outlined above with reference to  FIG. 5 . 
         [0048]    Having illustrated and described the principles of the disclosed technologies, it will be apparent to those skilled in the art that the disclosed embodiments can be modified in arrangement and detail without departing from such principles. In view of the many possible embodiments to which the principles of the disclosed technologies can be applied, it should be recognized that the illustrated embodiments are only examples of the technologies and should not be taken as limiting the scope of the invention. Rather, the scope of the invention is defined by the following claims and their equivalents. 
         [0049]    In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.