Patent Publication Number: US-2021179387-A1

Title: Elevator installation and a method for lubricating bearings in the elevator installation

Description:
FIELD 
     The present disclosure relates to elevators and to a method for lubricating bearings in elevator hoist machines. 
     BACKGROUND 
     Conventionally, bearings are employed within an elevator hoist machine to reduce friction between moving parts. For example, a rotating shaft of the elevator machine may be supported by means of bearings mounted within one or more stationary pedestals. Thereby the bearings, while permitting relative rotation of the shaft with respect to the supporting pedestals, can transfer radial and axial loads from the shaft to the pedestals. 
     A lubricant is normally employed to reduce friction in the bearings which is a highly important factor for improving efficiency, reducing wear, facilitating extended use at high speeds and avoiding overheating and premature failure of the bearing. When lubrication breaks down, components can rub destructively against each other, causing heat, local welding, destructive damage and ultimate failure. 
     For elevator hoist machines, which represent a relatively slow-speed and high-load application, greases are the most commonly used bearing lubricants. Typically, in operation, the elevator bearings will function under conditions of complete boundary lubrication according to the tribology/Stribeck curve which can lead to reduced bearing life. Elevator bearings supplied with grease are usually re-lubricated periodically, for example after 3000 operating hours, using a manually operated grease gun. Furthermore, as grease cannot simply be drained, the elevator machine and the bearing may have to be disassembled to remove any contaminated grease. 
     More recently, as exemplified in WO2014/193728 and US2016/0340152, the use of oil has been proposed as a lubricant for elevator machine bearings. Both publications describe an oil bath lubrication for the elevator bearings in which the outer raceway of the bearing is submerged in oil. In operation the oil, which is picked up by the outer raceway of the bearing, is distributed within the bearing and then flows back to a sump or bath in the housing. A shield is provided to prevent oil leaking through to and contaminating critical surfaces within the elevator machine such as the brake discs. The advantage of oil over grease as a lubricant derives primarily from its film-forming capacity, that is, its capability to maintain a film of oil between the bearing surfaces. In operation, mixed or full film lubrication is achievable using oil as the lubricant for elevator machine bearings. However, at standstill, oil film is eliminated between the components of the bearings that are not emerged in the oil sump. Accordingly, on start-up of the elevator machine, these bearing components, which transfer substantial radial loads from the elevator, may not be adequately coated in oil and thereby endure significantly higher friction and wear. 
     Another disadvantage of oil bath lubrication of elevator bearings as described above is that the oil is effectively sealed or contained within the bearing such that during operation the temperature of the contained oil will inherently increase which could result in an increase in friction and the rate of metal transfer. Excessive temperatures will eventually result in metal-to-metal contact within the bearing without any benefit of oil lubrication. 
     SUMMARY 
     An objective of the present invention is to overcome the disadvantages of the prior art discussed above by providing an elevator installation and a method for lubricating bearings in an elevator hoist machine such that during start-up and subsequent running of the elevator hoist machine the bearings are provided with a mixed film lubrication or an elastohydrodynamic lubrication to optimize bearing life expectation. 
     Accordingly, the invention provides an elevator installation having an elevator controller, a drive and a hoist machine, wherein the hoist machine comprises a traction sheave, an electric motor to rotate the traction sheave, a brake, one or more bearings supporting the traction sheave and a lubrication device automatically transmitting oil to the bearings upon receipt of a brake release signal from the drive or the controller. 
     The brake release signal provides an indication that the elevator installation is required to make a trip and by pumping bearing lubrication oil to the bearing at the start of each elevator trip, the bearings can be provided with a mixed film lubrication or an elastohydrodynamic lubrication before they actually start to rotate and not only during subsequent running of the elevator hoist machine. The life expectancy of the bearings can thereby be optimized since overheating and premature failure of the bearing can also be avoided. This in turn leads to the advantageous effects of improving the efficiency of and reducing wear within the elevator hoist machine facilitating extended use at high speeds. Furthermore, through using the automatic lubricating device, the frequency of routine maintenance for the machine can be reduced and the maintenance procedure itself is simplified and quicker as the technician has merely to replenish or replace the bearing oil in an oil reservoir. 
     Excessive oil within the bearing results in churning and deteriorates the effectiveness of oil lubrication. In order to prevent this, the lubrication device automatically transmits oil to the bearing for a certain short period only and preferably is deactivated before the machine starts to rotate the traction sheave. To achieve this the lubrication device can be provided with a timer which activates the lubrication device for a preset time duration after receipt of the brake release signal from the drive or the controller. The length of the preset time duration can be adjusted to take into account elevator specific factors such as the rated load, velocity and acceleration of the elevator installation, device specific factors such as delivery pressure to the bearing, as well as lubricant specific factors such as viscosity of the oil as well as the presence and type of extreme pressure EP additive mixed to the oil. 
     In another example, the automatic lubrication device can be deactivated upon receipt a signal from a brake contact confirming that the brake is open. 
     Alternatively, the lubrication device can be deactivated upon receipt of a further brake release signal from the drive or the controller. 
     Preferably, the brake is hydraulically released and the elevator installation further comprises a pump and a solenoid valve whereby the pump is activated by the brake release signal to deliver hydraulic fluid from a reservoir to the solenoid valve and the solenoid valve is activated by the further brake release signal to deliver the pressurized fluid further to the brake. 
     The automatic lubrication device may comprise an inline oil pump to transfer bearing lubrication oil from an oil reservoir, through an oil feed pipe to the bearing. Similarly, an oil return pipe can be provided to drain excessive lubrication oil from the bearing to an oil reservoir. In such an example, the continual drain-off of excess oil through the oil return pipe and the periodic top-up of lubricating oil in the bearings through the oil feed pipe on each start of the hoisting machine, ensures firstly that there is always an appropriate amount of oil within the bearing at all times and secondly that the oil within the bearings is replenished regularly which enables its temperature to be regulated more effectively so as to keep the bearings cool but also assists in flushing dirt or other contamination away from the bearings. 
     To further assist in cooling the excess oil returned to the reservoir, a cooler can be provided in the oil return pipe between the bearing and the oil reservoir. The cooler may be passive or actively assisted for example with a fan. 
     In a specific example the elevator installation further comprises a bearing end cap having an oil diffuser extending in an arc in an upper portion thereof. Alternatively, the bearing end cap could have a plurality of nozzles arranged in an arc in an upper portion thereof. Accordingly, oil can be transmitted by the automatic lubrication device to the bearing via the oil diffuser or the nozzles and sprayed throughout the extent of the arc defined by the oil diffuser or nozzles to coat the rollers positioned within the upper region of the bearing. Gravity will induce excess oil to coat rollers positioned lower within the bearing. 
     Preferably, the angle is at least 90°. 
     Additionally, the bearing end cap further comprises an oil drainage channel separated from the bearing by a flange in a lower portion thereof. Accordingly, any oil accumulating in the lower portion of the bearing in excess of the height of the flange will automatically overflow into the oil drainage channel and from there back the lubrication device. Excessive oil within the bearing results in churning and deteriorates the effectiveness of oil lubrication. The height of the flange will depend on the characteristics and properties of the bearing oil used but is preferably less than half the thickness of the annulus formed by the bearing. 
     As with the oil diffuser in the upper part of the bearing end cap, the flange and the oil drainage channel can extend through an arc in the lower section of the end cap. The extent of the angle of the arc should be great enough to permit any dirt or contamination in the oil to easily flow over the flange and into the oil drainage channel without causing blockage. Preferably, the angle is less than 45°. 
     At the opposite end of the oil drainage channel, a reservoir for passive oil cooling may be implemented. 
     The present invention also provides a method for oil lubrication of one or more bearings in an elevator hoist machine comprising the steps of monitoring an elevator brake release signal from an elevator controller or a drive and delivering oil to the bearing when the elevator brake release signal has been detected. The brake release signal provides an indication that the elevator installation is required to make a trip and by pumping lubrication oil to the bearing at the start of each elevator trip, the bearings can be provided with a mixed film lubrication or an elastohydrodynamic lubrication before they actually start to rotate and not only during subsequent running of the elevator hoist machine. The life expectancy of the bearings can thereby be optimized since overheating and premature failure of the bearing can also be avoided. This in turn leads to the advantageous effects of improving the efficiency of and reducing wear within the elevator hoist machine facilitating extended use at high speeds. Furthermore, by using the method, the frequency of routine maintenance for the machine can be reduced and the maintenance procedure itself is simplified and quicker as the technician has merely to replenish or replace the bearing oil in an oil reservoir. 
     To prevent churning of the oil within the bearing, the oil is transmitted to the bearing for a certain short period only and the delivery is stopped before the machine starts to rotate. To achieve this, the method can include the step delivering oil to the bearing for a preset time duration only after receipt of the brake release signal from the drive or the controller. The length of the preset time duration can take into account elevator specific factors such as the rated load, velocity and acceleration of the elevator installation, device specific factors such as delivery pressure to the bearing, as well as lubricant specific factors such as viscosity of the oil as well as the presence and type of extreme pressure EP additive mixed to the oil. 
     Alternatively, the delivery of oil to the bearing can be stopped once a signal from a brake contact confirms that an elevator brake is open. 
     In another example, the delivery of oil to the bearing can be stopped once a further brake release signal is detected. 
     Preferably any excess oil is automatically drained from the bearings. In such an example, the continual drain-off of excess oil and the periodic top-up of lubricating oil in the bearings on each start of the hoisting machine, ensures firstly that there is always an appropriate amount of oil within the bearing at all times and secondly that the oil within the bearings is replenished regularly which enables its temperature to be regulated more effectively so as to keep the bearings cool but also assists in flushing dirt or other contamination away from the bearings. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The disclosure refers to the following figures: 
         FIG. 1  is an exemplary schematic showing an arrangement of components within an elevator installation according to the present invention; 
         FIG. 2  is perspective view of an elevator hoist machine according to the present invention; 
         FIG. 3A  shows an axial cross-section of the elevator hoist machine of  FIG. 1  and  FIG. 2 ; 
         FIG. 3B  is a schematic of the automatic hydraulic brake release unit and illustrates its hydraulic connection to one of the brake calipers mounted to the elevator hoist machine of  FIG. 3A ; 
         FIG. 3C  is similar to  FIG. 3B  illustrating the lubrication device and its hydraulic circuit to and from the bearing in the first support pedestal of the hoist machine; 
         FIG. 4  is a flowchart illustrating a method of operating the elevator installation according to the preceding FIGS.; 
         FIG. 5A  is an exploded, axial cross-section of the bearing mounted in the second support pedestal of the hoist machine of  FIG. 3A ; and 
         FIG. 5B  is a plan view along line B-B of the bearing end cap illustrated in  FIG. 5A . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates an exemplary embodiment of an arrangement of components within a typical high-rise elevator installation  1 . An elevator drive  8 , a hoist machine  10 , a deflection pulley  14  and an elevator controller  16  are arranged in a machine room  9  above a hoistway  3 . Within the hoistway  3 , an elevator car  2  and a counterweight  4  are supported on suspension ropes  6 . In this example, the suspension ropes  6  have a 1:1 roping ratio whereby they extend from an end connection fixed to the car  2  up the hoistway  3  for engagement through a wrap angle α with a traction sheave  12  which is rotated by the hoist machine  10  under the influence of electrical signals from the elevator drive  8 . The ropes  6  are subsequently passed over the deflection pulley  14  and back down the hoistway  3  to a further end connection fixed to the counterweight  4 . Naturally, the skilled person will easily appreciate other roping arrangements, such as 2:1, 4:1 or x:1 roping ratios, are equally possible and the invention can also be implemented with elevators using belts instead of conventional suspension ropes. 
     Preferably, the counterweight  4  is designed so that its total mass is equal to the sum of the mass of the empty elevator car  2  plus 40-50% of the nominal rated load. 
     In high-rise applications particularly, not only must the imbalance between the car  2  and counterweight  4  be considered, but also the imbalance caused by the weight of the suspension ropes  6  is appreciable. For example, if the car  2  is at the lowest landing within the hoistway  3  and thereby the counterweight  4  is at high level within the hoistway  3 , the majority of the length of the suspension ropes  6  is located on the car side of the traction sheave  12  rather than on the counterweight side of the sheave  12 . To offset this imbalance due to the suspension ropes  6  it is conventional practice to install one or more compensation chains or ropes  18  suspended between the car  2  and the counterweight  4 . For convenience only one compensation rope  18  is illustrated in the drawing, but it will be appreciated that more than one compensation rope can be installed. The compensation rope  18  is guided under pulleys  22  in a weighted pulley box  20  located in a pit of the hoistway  3 . 
     Accordingly, the suspension ropes  6 , the car  2 , the counterweight  4  and the compensation rope  18  form a closed-loop system where the length of the suspension ropes  6  and compensation rope  18  on the car side of the traction sheave  12  is substantially equal to that on the counterweight side of the traction sheave  12 . 
     Considering the substantial vertical load that is continuously exerted on the traction sheave  12  and the deflection pulley  14  by the elevator  1 , the hoist machine  10  and the deflection pulley  14  are structurally supported within the machine room  9  between two steels beams  15  or concrete plinths. 
     In normal operation, the elevator controller  16  receives signals from conventional landing operating panels and car operating panels (not shown) to determine the travel path that the elevator  1  must undertake in order to satisfy passengers&#39; travel requests. Once the travel path has been determined, the controller  16  outputs signals to the drive  8  so that the traction sheave  12  can be rotated by the hoist machine  10  in the appropriate direction to undertake the travel request. The traction sheave  12  engages with the suspension ropes  6  to vertically move the car  2  and the counterweight  4  in opposing directions along guiderails (not shown) within the hoistway  3 . 
       FIG. 2  is perspective view illustrating the mains components of the hoist machine  10  of  FIG. 1 . The machine  10  is provided with a first support pedestal  30  and a second support pedestal  40  which are secured to and transfer forces to the two steel beams  15  or concrete plinths, respectively, within the machine room  9 . The traction sheave  12  which engages with the suspension ropes  6  is mounted to on a rotatable shaft between the two support pedestals  30  and  40 . 
     The first support pedestal  30  is also referred to as the brake-side pedestal as is carries two hydraulic brake calipers  70 , an automatic hydraulic brake release unit  50 , a manual brake release unit  45  and an automatic lubrication device  100 . The position of each of the brake calipers  70  is monitored by one or more brake contacts  75 . 
     On the other side of the hoist machine  10 , the second support pedestal  40  bears the electric motor  80  and a terminal box  81  containing inter alia electrical power supply terminals for the machine  10  as well as connectors for transmitting signals to and from the drive  8  and the elevator controller  16  ensuring that the machine  10  operates in accordance with the requested travel pattern to satisfy the travel requests received by the elevator controller  16 . The method of operating the hoist machine in order to satisfy elevator passenger requests will be explained further with respect to the flowchart illustrated in  FIG. 4 . 
       FIG. 3A  is an axial cross-section of the elevator hoist machine  10  of  FIG. 1  and  FIG. 2 . The motor  80  comprises a stationary stator  82  mounted to and enclosed within a housing  84 . The stator  82  circumferentially surrounds a rotor  86  that is secured to one end of a shaft  88 . The shaft  88  extends from the electric motor  80 , through the second pedestal  40  and across to the first pedestal  30 . The shaft  88  is support by bearings  90  mounted within the stationary pedestals  30  and  40  to permit relative rotation of the shaft  88  with respect to the supporting pedestals  30  and  40 . The traction sheave  12  is secured for concurrent rotation with the shaft  88  between the two pedestals  30  and  40 . Forces imposed on the traction sheave  12  due to the substantial weight of the elevator  1  suspended therefrom are transmitted from the traction sheave  12 , through the shaft  88  and subsequently transferred by the bearings  90  to the supporting pedestals  30  and  40 . A brake disc  13  is attached to or integrated with the traction sheave  12  at a side facing towards the first, brake-side support pedestal  30 . The brake disc  13  is positioned between the brake calipers  70  mounted on top of the first pedestal  30 . 
       FIG. 3B  is a schematic of the automatic hydraulic brake release unit  50 . To avoid unnecessary repetition, the following describes the automatic brake release unit  50  and its hydraulic circuit feeding a brake cylinder  72  within one of the brake calipers  70  depicted in  FIG. 2 . It will be understood that the other brake caliper  70  is connected to an outlet port  64  of the brake release unit  50  in an identical manner. 
     The automatic brake release unit  50  comprises a valve block  51  mounted on a reservoir  56  containing hydraulic fluid. Fluid output ports  64  on the valve block  51  are connected by hydraulic ducts  66  to the brake cylinder  72 . 
     In response to a brake release signal R 1  from either the drive  8  or the elevator controller  16 , an electric motor  54  operates a circulating pump  52  to deliver pressurized fluid from the reservoir  56  through check valves  60 . The pressure of the fluid is regulated by a pressure limiting valve  58 . Depending on the operating state of a 2/2 way solenoid valve  62  controlled by a further signal R 2  from the drive  8  or the elevator controller  16 , the pressurized fluid will be either drained back to the reservoir  56  or delivered to the outlet port  64  and further onto the brake cylinder  72  to release or disengage the brake caliper  70  from the brake disc  13  against the biasing force of a compression spring within the brake cylinder  72 . The above discussion is a summary to the construction and operation of the automatic brake release unit  50 . Further details, particularly on its operation in conjunction with the manual brake release unit  45  of the hoist machine  10 , can be retrieved from publication US2016/0332844. 
       FIG. 3C  illustrates the lubrication device  100  for the elevator bearings  90 . For ease of reference, the drawing depicts only oil feed and oil return pipes  112  and  114  interconnecting the lubrication device  100  to the bearing  90  provided in the first support pedestal  30 . It will be appreciated that oil feed and oil return pipes  112  and  114  are also arranged between the lubrication device  100  and the other bearing  90  mounted in the second support pedestal  40  which is illustrated by the dashed circle A and which will be described in further detail with respect to  FIGS. 5A and 5B . 
     The automatic lubrication device  100  contains an electric motor  104  and a circulating pump  102  together making up a low pressure inline oil pump to transfer bearing lubrication oil from an oil reservoir  106 , through a check valve  107 , a filter  108 , an outlet port  110  and through an oil feed pipe  112  to the top of the bearing  90 . 
     As with the automatic hydraulic brake release unit  50  of  FIG. 3B , the motor  104  is activated in response to a brake release signal R 1  from either the drive  8  or the elevator controller  16 . However, in this instance the motor  104  does not operate continuously until the signal R 1  is removed, but instead the motor  104  of the automatic lubrication device  100  is operated, for example, by a timer that is triggered by the brake release signal R 1  to operate for a preset time duration Δt only. The length of the preset time duration Δt will take into account elevator specific factors such as the rated load, velocity and acceleration of the installation  1 , pump specific factors such as delivery pressure to the bearing  90 , as well as lubricant specific factors such as viscosity of the oil as well as the presence and type of extreme pressure EP additive mixed to the oil. 
     Excessive lubrication oil is continually drained back from the bottom of the bearing  90  to the oil reservoir  106  through an oil return pipe  114  connected to a return port  116  in the lubrication device  100 . 
     Optionally, a cooler  118  can be incorporated in the oil return pipe  114  between the bearing  90  and the oil reservoir  106  to remove heat from the oil. The cooler  118  can be active as illustrated in  FIG. 3C  or passive. 
     Not only is oil a superior bearing lubricant over grease for its film-forming capacity but it also has the benefit of absorbing a significant amount of the heat generated from the bearings  90 . However, if the oil is sealed or contained within the bearings as described in the oil bath lubrication systems of US2016/0340152 or WO2014/193728 its temperature will understandably rise during operation. Such a rise in temperature can lead to a deterioration of the lubricant and thereby to an increase in both the friction and the rate of metal transfer within the bearings  90 . 
     In the present example, the continual drain-off of excess oil through the oil return pipe  114  and the periodic top-up of lubricating oil in the bearings  90  through the oil feed pipe  112  on each start of the hoist machine  10 , ensures that the oil within the bearings  90  is replenished regularly which enables its temperature to be regulated more effectively so as to keep the bearings  90  cool but also assists in flushing dirt or other contamination away from the bearings  90 . Furthermore, by pumping bearing lubrication oil to the top of the bearings  90  at the start of each elevator trip, the bearings  90  can be provided with a mixed film lubrication or an elastohydrodynamic lubrication before they actually start to rotate and not only during subsequent running of the elevator hoist machine  10 . The life expectancy of the bearings  90  can thereby be optimized since overheating and premature failure of the bearings  90  can also be avoided. This in turn leads to the advantageous effects of improving the efficiency of and reducing wear within the elevator hoist machine  10  facilitating extended use at high speeds. Furthermore, through using the automatic, lubrication device  100 , the frequency of routine maintenance for the machine  10  can be reduced and the maintenance procedure itself is simplified and quicker as the technician has merely to replenish or replace the oil in the reservoir  106 . 
       FIG. 4  is a flowchart illustrating a method of operating the elevator installation  1  according to the present invention wherein those steps aligned to the left of the drawing relate to brake operation, those in the middle are associated with motor operation and those to the right outline bearing lubrication. 
     The method begins at step S 1  when the elevator controller  16  receives signals from conventional landing operating panels and car operating panels indicating that a passenger wishes to use the elevator  1  to travel between floors within a building. The controller  16  determines the travel path that the elevator  1  must undertake in order to satisfy the passengers&#39; travel requests, and subsequently outputs signals to the drive  8 . 
     Initially, at step S 2 , the drive  8  delivers electrical energy to the windings of the stator  82  via the terminal box  81  of the hoist machine  10  to pretorque the motor  80 . Simultaneously, either the controller  16  or the drive  8  outputs the brake release signal R 1  to both the automatic brake release unit  50  and the automatic lubrication device  100  initiating the delivery of brake fluid to the valve block  51  of the brake release unit  50  in step S 3  and the transmission of pressurized lubrication oil to the top of the bearings  90  in step S 4 , respectively. 
     From this point onwards, the lubrication device  100  operates independently and after step S 5 , in which the motor  104  and a circulating pump  102  have been running for the preset time duration Δt, the lubrication device  100  automatically stops at step S 6 . 
     Meanwhile, after sufficient time has elapsed to enable adequate pressure build-up within the hydraulic braking fluid in the valve block  51 , in step S 7  the further release signal R 2  is received by the 2/2 way solenoid valve  62  within the valve block  51  of the brake release unit  50 . Accordingly, the pressurized brake fluid is now delivered to the brake cylinder  72  to initiate release of the brake calipers  70  from the brake disc  13  in step S 8 . 
     As the brakes are opening in step S 8 , the drive  8  continually receives positional information from a rotatory encoder attached, for example, to the shaft  88  of the machine  10 . In step S 9 , the drive  8  uses this positional information to determine and deliver the electrical signals to the motor  80  in order to keep it stationary. 
     Furthermore, to prevent drag, whereby the motor  80  drives the shaft  88  and the brake disc  13  against partially open brakes  70 , it is important to monitor the brake calipers  70 . This is normally achieved using the brake contacts  75  that actuate when the calipers  70  are in the fully opened position. In the present example, the procedure loops around steps S 8  and S 9  until it is determined that the brake calipers  70  are fully open at step S 10 . 
     Subsequently, in step S 11 , the drive  8  controls and regulates the motor  80  to observe a travel profile to move the elevator car  2  within the hoistway  3  to ensure that the passenger within the car  2  is transported from his departure floor to his designation floor within the building at step S 12 . 
     After the elevator trip is complete, the method continues to step S 13  in which the caliper brakes  70  grip or re-engage with the brake disc  13  of the hoist machine  10 . In this step, the further release signal R 2  from the controller  16  or the drive  8  is removed from the 2/2 way solenoid valve  62  within the valve block  51  of the automatic brake release unit  50 . As a result, pressurized brake fluid in the brake cylinders  72  as well as any brake fluid still being pumped by the circulating pump  52  is drained back to the reservoir  56 . Simultaneously or shortly thereafter, the release signal R 1  is withdrawn and the electric motor  54  driving the pump  52  is de-energized. Accordingly, the brakes  70  are fully engaged with the brake disc  13  at step S 14 . 
     As the brakes are closing in step S 13 , the drive  8  continually receives positional information from the rotatory encoder to determine and deliver the electrical signals to the motor  80  in order to keep it stationary in step S 15 . 
     Finally, in step S 16  the drive  8  de-energizes the electric motor  80  of the hoist machine  10 . 
     The automatic lubrication device  100  can be set up such that rather than running for the preset time duration Δt after receipt of the brake release signal R 1 , it can continue running until the drive  8  or the elevator controller  16  transmits the further signal R 2  used to control the solenoid valve  62  within the valve block  51  of the brake release unit  50 . A further alternative is to keep the motor  104  and a circulating pump  102  of the lubrication device  100  operating until a signal is received from the brake contacts  75  in step S 10  indicating that the brake calipers  70  are fully open. 
     Further details regarding the bearing  90  will be described hereinafter with reference  FIG. 5A  which is an exploded, axial cross-section A of the bearing  90  mounted in the second support pedestal  40  of the hoist machine  10  illustrated in  FIG. 3A . It will be appreciated that a similar arrangement applies to the bearing  90  mounted in the first support pedestal  30 . 
     The bearing  90  is mounted within a circular opening or seat  42  machined in the support pedestal  40 . The bearing  90  comprises a cylindrical outer raceway  96  mounted to the pedestal  40 , a cylindrical inner raceway  92  mounted to the motor shaft  88  and a plurality of spherical roller bearings  98  arranged between the inner and outer raceways  92  and  96 . Accordingly, the bearing  90  forms an annulus between the shaft  88  and the opening  42  of the pedestal  30  having a thickness H 2  defined as the difference between the diameter of the opening  42  and that of the shaft  88 . 
     In the present example, a pair of circumferential arrays of rollers  98  are provided. Normally a cage is used for retaining the rollers  98  within the raceways  92  and  96  but for clarity within the drawing this element of the bearing  90  has been omitted. 
     To the right of the drawing the bearing  90  is axially retained in position between the pedestal  40  and the shaft  88  by a removable bearing end cap  120  according to the present invention which is conventionally secured, for example by bolts (not shown) extending through apertures  121  (see  FIG. 5B ), to the pedestal  40 . A circular shaft seal  140  in accommodated in a recess on the end cap  120  to seal the bearing chamber. Although not shown in the drawing, it will be appreciated that to the other side, the bearing  90  can be likewise retained in position by either an identical end cap  120  or by a conventional end cap that can be a separate component or can be machined or cast within the pedestal  40 . 
     At the upper portion of the bearing end cap  120 , the oil feed pipe  112  from the automatic lubrication device  100  is connected to a nozzle  122  by a male/female hydraulic connector arrangement  124 . The nozzle  122  opens into a recessed oil diffuser  123 . As shown specifically in  FIG. 5B  which is a plan view along line B-B of the bearing end cap illustrated in  FIG. 5A , the recessed oil diffuser  123  extends through an arc in the upper portion of the bearing end cap  120 . The angle α 1  through which the arc extends is dependent on the properties of the bearing oil used, in particular its viscosity, whereby for example the higher the viscosity then then greater the angle α 1 . Preferably, the angle α 1  is at least 90°. As an alternative to the recessed oil diffuser  123 , the oil feed pipe  112  from the lubrication device  100  can be connected to a plurality of nozzles  122  arranged in an arc in the upper portion of the bearing end cap  120 . 
     Accordingly, when oil is transmitted to the top of the bearings  90  in steps S 4  and S 5  of the method as previously outlined with reference to  FIG. 4 , it is sprayed throughout the extent of the arc defined by the recessed oil diffuser  123  to coat the rollers  98  positioned within the upper region of the bearing  90 . Gravity will induce excess oil to coat rollers  98  lower in the bearing  90 . 
     The lower portion of the bearing end cap  120  contains an oil drainage channel  128  which communicates with the oil return pipe  114  via a drainage passage  130  and a male/female hydraulic connector arrangement  124 . A flange  126  is provided in the end cap  120  between the bearing  90  and the oil drainage channel  128 . Any oil accumulating in the lower portion of the bearing  90  in excess of the height H 1  of the flange  126  will automatically overflow into the oil drainage channel  128  and from there back to the oil reservoir  106  in the lubrication device  100  through the oil return pipe  114  as illustrated in  FIG. 3 . The height H 1  of the flange  126  will depend on the characteristics and properties of the bearing oil used but is preferably less than half the thickness H 2  of the annulus formed by the bearing  90 . 
     As with the recessed oil diffuser  123  in the upper part of the bearing end cap  120 , the flange  126  and the oil drainage channel  128  can extend through an arc in the lower section of the end cap  120  as illustrated in  FIG. 5B . The extent of the angle α 2  of the arc should be great enough to permit any dirt or contamination in the oil to easily flow over the flange  126  and into the oil drainage channel  128  without causing blockage. Preferably, the angle α 2  is less than 45°. 
     The removable bearing end cap  120  described above is only one of many examples that can be used in accordance with the present invention to deliver oil from the oil feed pipe  112  of the automatic lubrication device  100  to the bearing  90  and return excess oil through the oil return pipe  114  back to the lubrication device  100 . The removable bearing end cap  120  can be particularly useful for example in modernizing an existing elevator machine. On the other hand, in new machines an annular channel or groove can be provided or machined in the support pedestal  30 ,  40  to deliver oil directly from the oil feed pipe  112  to the upper portion of the outer raceway  96  of the bearing  90 . 
     Although the present invention has been described in conjunction with a hoist machine  10  having hydraulically released brakes  70 , it will be appreciated that the invention is also equally applicable to elevator hoist machines employing brakes that are released electromagnetically. 
     Similarly, the present invention can be used in conjunction with brakes in the form of levers radially acting on a brake drum rather than calipers axially engaging the brake disc. 
     In the examples described above, the bearings support the traction sheave indirectly via the shaft to which the traction sheave is fixed. In is envisaged that the invention can be applied to an alternative arrangement within the hoist machine, wherein the bearings support a traction sheave rotating about a fixed, stationary shaft. 
     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. 
     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.