Patent Publication Number: US-2021188596-A1

Title: Counterweight handover test device and method

Description:
FOREIGN PRIORITY 
     This application claims priority to European Patent Application No. 19306749.3, filed Dec. 23, 2019, and all the benefits accruing therefrom under 35 U.S.C. § 119, the contents of which in its entirety are herein incorporated by reference. 
     TECHNICAL FIELD OF INVENTION 
     This disclosure relates to a device and method for performing a handover test on a counterweight of an elevator system. 
     BACKGROUND OF THE INVENTION 
     It is a requirement of the elevator safety code EN81-20 to perform a handover test on an elevator counterweight. A handover test is to be carried out once an elevator system has been assembled on site by an elevator field mechanic, in order to check it is operating correctly, before the elevator system is then handed over to the customer. The test is then often repeated at regular intervals, for example once a year, by a maintenance person. 
     In carrying out the handover test, it is required to test that the safety brakes (or safeties) of the counterweight correctly engage the counterweight guide rails. It is known in the art to test this by suspending the elevator car at the top of the hoistway e.g. by hanging the elevator car from a hook at the top of the hoistway e.g. from a hook used during lift installation, so that the counterweight is at the bottom of the hoistway above the pit. A jack is then placed in the pit and remotely controlled to lift the counterweight, causing the rope suspending the counterweight to go slack. The slack in the rope should cause the safeties of the counterweight to engage. In this position the maintenance person can then re-enter the pit and use a ladder to access the counterweight safeties and check that the safeties have engaged correctly, and if they have the test is considered to have been passed. 
     It would be desirable to provide an improvement in which this handover test could be carried out in a simpler and safer manner, and without requirement for a jack and a ladder. Providing a system in which the handover test can be carried out without a jack or ladder would also represent a cost reduction, since the safety code currently requires a supplier to supply these items with a unit, in order to facilitate the handover test. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of this disclosure there is provided an elevator counterweight assembly, comprising: a counterweight structure; at least one safety brake mounted on the counterweight structure; a safety actuation mechanism, comprising a connection for a suspension member, wherein the safety actuation mechanism is configured to move, relative to the counterweight structure, between a normal position, and a safety position, wherein in the safety position the safety actuation mechanism is arranged to actuate the at least one safety brake and thereby brake the counterweight structure; and a mechanical actuator, configured, when actuated, to apply a force to the safety actuation mechanism and thereby move the safety actuation mechanism from the normal position to the safety position. 
     According to a second aspect of this disclosure there is provided a method of carrying out a handover test for an elevator counterweight assembly, the method comprising: actuating a mechanical actuator to apply a force to a safety actuation mechanism, comprising a connection for a suspension member, and thereby move the safety actuation mechanism, relative to a counterweight structure, from a normal position to a safety position, wherein in the safety position the safety actuation mechanism is arranged to actuate at least one safety brake and thereby brake the counterweight structure; and checking that the at least one safety brake is correctly actuated. 
     It will be appreciated that, according to the present disclosure, a mechanical actuator is provided which enables a maintenance person to move the safety actuation mechanism of a counterweight between a normal position and a safety position, by actuating the mechanical actuator, and which therefore provides a simple and easy method of directly testing that the safety actuation mechanism is functioning correctly. 
     The safety actuation mechanism comprises the connection (e.g. sheave or hitch) for a suspension member. Thus, in use, under normal circumstances, the connection is lifted due to tension in the suspension member, and therefore the safety actuation mechanism is in the normal position (i.e. lifted upwards relative to the counterweight structure). During operation of the elevator system, if the suspension member suddenly goes slack and loses tension, the connection will no longer be lifted by tension in the suspension member, and the connection (and therefore the safety actuation mechanism) will drop under gravity, and optionally also due to a force provided by one or more biasing springs, to the safety position, in which (if everything is functioning correctly) the safety brakes will be deployed. The mechanical actuator according to the present disclosure allows the result of a slack suspension member (i.e. the movement of the safety actuation mechanism to the safety position) to be re-created (i.e. simulated), and therefore allows a maintenance person to test that the safety actuation mechanism functions correctly to deploy the at least one safety brake. 
     According to the present disclosure the safety actuation mechanism is configured to move relative to the counterweight structure, between a normal position, and a safety position. It will be understood by the skilled person that it is therefore only required that one of these components moves relative to the other, it is not important which of these components “actually” moves e.g. moves with respect to the frame of reference of the hoistway. For example, it may be that in a fault scenario which occurs during normal operation of the elevator system, the connection (e.g. counterweight sheave), and thus the safety actuation mechanism, moves downwards in the hoistway (faster than the counterweight structure), thus creating relative movement such that the safety actuation mechanism moves between the normal position and the safety position. It may be, however, that when the mechanical actuator is used to move the safety actuation mechanism from the normal position to the safety position, it is the counterweight structure which moves upwards (relative to the hoistway frame of reference) and the connection (e.g. counterweight sheave) is held in position by tension in the suspension member so the safety actuation mechanism remains stationary. 
     It will furthermore be understood by the skilled person that the mechanical actuator is arranged to apply a force to the safety actuation mechanism, and thus that it is the mechanical actuator itself which applies the force, which is the same force which moves the safety actuation mechanism i.e. it is a direct mechanical force. This is in contrast to the situation where a jack or other mechanical actuator is used to apply a first force (e.g. lifting the counterweight structure), which then allows a second force (e.g. gravity and/or spring force) to move the safety actuation mechanism from the normal position to the safety position. 
     In some examples, the mechanical actuator is arranged to move between a retracted position and an extended position, wherein, in the extended position, the mechanical actuator applies a force to the safety actuation mechanism. In some examples, additionally or alternatively, the mechanical actuator maintains its position relative to the counterweight structure unless actuated to move relative to the counterweight structure and thereby apply a force to the safety actuation mechanism. In some examples, additionally or alternatively, the motion of the safety actuation mechanism is reversible. 
     In some examples, the mechanical actuator may comprise a ratchet. In some examples, the mechanical actuator may comprise a piston. In some examples, the mechanical actuator may comprise a gas spring or mechanical spring that is manually released to apply a force to the safety actuation mechanism. In some examples, the mechanical actuator may comprise a moveable wedge. 
     In some examples, in addition or alternatively, the mechanical actuator is rotationally driven to produce a linear force. Thus, the method according to the present disclosure may comprise driving the mechanical actuator rotationally, to produce a linear force. In one or more examples, the mechanical actuator may comprise a screw mechanism. Any suitable screw mechanism may be used, for example, comprising a cylindrical shaft with helical threads around the outside of the shaft. Optionally, the screw mechanism may comprise a worm screw, or one or more screws or bolts. Thus, the method according to the present disclosure may comprise actuating the screw mechanism, e.g. by hand or using a tool such as a crank, screwdriver or spanner. The use of a screw mechanism as the mechanical actuator provides the advantages that a screw mechanism is small and can therefore be easily accommodated adjacent to the safety actuation mechanism without interfering with the suspension member connection, and furthermore that a screw mechanism is easily actuated using standard tools. 
     In some examples, in addition or alternatively, the mechanical actuator further comprises a pressure bar configured to contact the safety actuation mechanism in at least two positions, so as to distribute the force which is applied by the mechanical actuator to the safety actuation mechanism. Optionally, the pressure bar contacts the connection in at least two positions. This provides a particularly simple arrangement, in which the mechanical actuator is arranged to apply force to the safety actuation mechanism, but in such a way that localised wear or damage to the connection is reduced, or eliminated. In some examples, additionally or alternatively, the connection may be a counterweight sheave. The pressure bar may be arranged to contact either end of the counterweight sheave. Alternatively, the connection may be an end hitch of a suspension member. 
     In some examples, in addition or alternatively, there may be a single mechanical actuator. Alternatively, there may be more than one mechanical actuator, optionally two mechanical actuators. In some examples, the one or more mechanical actuators are located centrally on the elevator counterweight assembly. 
     In some examples, in addition or alternatively, the safety actuation mechanism comprises at least one lever, wherein the at least one safety brake comprises a safety brake arm, and wherein the at least one lever contacts the safety brake arm, such that when the safety actuation mechanism moves between the normal position and the safety position, the at least one lever is moved, thereby moving the safety brake arm, which causes actuation of the safety brake. Optionally, the safety actuation mechanism comprises a first lever and a second lever, wherein the first and second levers are located on opposing sides of the safety actuation mechanism, wherein the elevator counterweight assembly comprises a first safety brake, comprising a first safety brake arm contacted by the first lever, and a second safety brake comprising a second safety brake arm contacted by the second lever. Optionally, the mechanical actuator is located centrally between the first lever and the second lever. This helps to apply a balanced force, thus avoiding damage caused by imbalance e.g. bending. In addition or alternatively, the connection is located centrally between the first lever and the second lever. Thus, if both the connection and the mechanical actuator are located centrally, the mechanical actuator is able to apply balanced force directly to the connection. 
     In some examples, in addition or alternatively, the safety actuation mechanism further comprises at least one biasing spring, configured to bias the safety actuation mechanism towards the safety position. Optionally, the safety actuation mechanism comprises a first biasing spring, located at a first side of the connection, and a second biasing spring, located at a second, opposing side of the connection. 
     In some examples, in addition or alternatively, the counterweight structure comprises at least one weight supported by a pair of uprights, wherein the safety actuation mechanism is mounted between the pair of uprights. In some examples, in addition or alternatively, the counterweight structure comprises an upper crosshead, on which the mechanical actuator is mounted. 
     According to a further aspect of this disclosure there is provided an elevator system comprising: an elevator car; an elevator counterweight assembly according to the present disclosure; and a suspension member connected to the elevator car and to the connection of the safety actuation mechanism. 
     In some examples, the elevator car defines an interior space for accommodating passengers and/or cargo, the elevator car comprising a working platform moveable between a stowed position, above the interior space, and an operational position, suspended within the interior space. 
     In some examples, the method according to the present disclosure further comprises moving an elevator car in a hoistway to be adjacent to the elevator counterweight assembly; and deploying a working platform within the elevator car, the working platform being in an operational position, allowing a person standing on the working platform to access the mechanical actuator of the elevator counterweight assembly. For example, the elevator car and elevator counterweight assembly may both be moved to a mid-rise position. 
     This advantageously enables a maintenance person to carry out testing and maintenance on the elevator counterweight assembly without having to enter the hoistway. Furthermore, by using the mechanical actuator of the present disclosure, the maintenance person is able to test the counterweight without having to use tools which may be heavy and cumbersome or not easily accessible e.g. a ladder or a hydraulic jack. This improves both efficiency and safety for the handover test, by avoiding pit access and allowing a maintenance person to engage the at least one safety brake for test purposes from the working platform inside the elevator car. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Certain preferred examples of this disclosure will now be described, by way of example only, and with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a counterweight including safety brakes, as is known in the art; 
         FIG. 2  is a cutaway view of the counterweight of  FIG. 1 ; 
         FIG. 3  is a perspective view of an elevator counterweight assembly according to an aspect of the present disclosure, in a normal position; 
         FIG. 4  is cutaway view of the elevator counterweight assembly of  FIG. 3 ; 
         FIG. 5  is a perspective view of the upper part of the elevator counterweight assembly shown in  FIGS. 3 and 4 ; 
         FIG. 6  is a front view of the elevator counterweight assembly of  FIGS. 3 and 4 , in the normal position; 
         FIG. 7  is a front view of the elevator counterweight assembly of  FIGS. 3, 4, and 6 , in a safety position; 
         FIG. 8  is a cutaway view of the upper part of an elevator counterweight assembly according to the present disclosure, in the normal position; 
         FIG. 9  is a cutaway view of the upper part of an elevator counterweight assembly according to the present disclosure, in the safety position; and 
         FIG. 10  is a schematic overview of an elevator system according to an aspect of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a counterweight  1  including safety brakes  2   a  and  2   b , which, when engaged, grip counterweight guide rails  3   a  and  3   b , as is known in the art. The counterweight includes weights  4 , which are supported on a lower crosshead (not shown). The counterweight also includes an upper crosshead  5 , below which is arranged a safety actuation mechanism  6 . The operation of the safety actuation mechanism  6  can be described more clearly with reference to  FIG. 2 , in which the same components have been indicated with the same reference numerals as  FIG. 1 . 
     The safety actuation mechanism  6  includes a counterweight sheave  7  and a pair of suspension members  8 , arranged to contact the counterweight sheave  7  and thereby suspend the counterweight  1 . The counterweight sheave  7  is attached on each side to a lever  9   a ,  9   b , which each contact a respective safety brake arm (not seen in  FIG. 1 ), extending downwards from safety brakes  2   a ,  2   b . In the event of a malfunction of the elevator system causing the suspension members  8  to lose tension and go slack, the counterweight sheave  7  will no longer be lifted by tension in the suspension members  8 . The counterweight assembly  1  further includes a pair of biasing springs  21   a  and  21   b , arranged at opposing sides of the counterweight sheave  7 . When there is tension in the suspension members  8 , this tension acts to compress the springs  21   a ,  21   b , and keep the counterweight sheave  7  lifted upwards. When there is no tension, nothing resists the biasing springs  21   a ,  21   b  expanding, and therefore the biasing springs  21   a ,  21   b , which were previously compressed, then expand, pushing the counterweight sheave  7  downwards (together with gravity), towards the safety position. As a result, the counterweight sheave  7  will drop i.e. move downwards, away from the upper crosshead  5  i.e. the counterweight sheave  7  will move relative to the rest of the counterweight  1 , including relative to the safety brakes  2   a ,  2   b , which are fixed onto the uprights  10   a ,  10   b  of the counterweight  1 . As a result of this relative movement, the levers  9   a ,  9   b  will pivot about their respective pivot points, and will therefore move the safety brake arms so as to actuate the safety brakes  2   a ,  2   b , in a known manner, causing the safety brakes  2   a ,  2   b , if functioning correctly, to engage with the guide rails  3   a ,  3   b . This results in an emergency stop of the counterweight  1 . 
     It is desirable to be able to regularly test the function of the safety actuation mechanism  6  i.e. to test that downwards movement of the counterweight sheave  7  does in fact result in automatic actuation of the safety brakes  2   a ,  2   b . An elevator counterweight assembly including a simple and safe testing mechanism according to the present disclosure is shown in  FIGS. 3-9 . 
     The elevator counterweight assembly  11  of  FIGS. 3-9  includes a counterweight structure  38 , including uprights  20   a ,  20   b  and safety brakes  12   a  and  12   b  which are mounted on the uprights  20   a ,  20   b . The counterweight structure  38  also includes an upper crosshead  15  and a lower crosshead (not shown). When engaged, the safety brakes  12   a ,  12   b  grip counterweight guide rails  13   a  and  13   b . The counterweight structure  38  also includes weights  14 , which are supported on the lower crosshead. Typically these weights are such that the counterweight is heavier than the elevator car, e.g. approximately equal to the weight of the elevator car plus half of the maximum load of the elevator car. This is so that the counterweight balances the weight of the elevator car even when the elevator car is carrying passengers or other load. A safety actuation mechanism  16  is arranged below the upper crosshead  15 . The safety actuation mechanism  16  includes a connection  17  suitable for connecting to one or more suspension members  18  (e.g. ropes or belts). The connection  17  in this example is a counterweight sheave, around which the suspension members  18  are passed. The safety actuation mechanism  16  further comprises at least one biasing spring  221   a ,  221   b , configured to bias the safety actuation mechanism  16  towards the safety position. As seen in  FIG. 4 , there is a first biasing spring  221   a  located at a first side of the connection  17 , and a second biasing spring  221   b  located at a second, opposing side of the connection  17 . The connection  17  is attached on each side to a lever  19   a ,  19   b , which each contact a respective safety brake arm  26   a ,  26   b  (seen in  FIG. 5 ), extending downwards from the safety brakes  2   a ,  2   b . The operation of the safety actuation mechanism  16  in a malfunction situation is analogous to the operation of the safety actuation mechanism  6 , described with reference to  FIGS. 1 and 2 . 
     In the event of a malfunction of the elevator system causing the suspension members  18  to lose tension and go slack, the connection  17  will no longer be lifted by tension in the suspension members  18 . There is therefore no longer any force acting to compress biasing springs  221   a ,  221   b , located on either side of the connection  17 . The biasing springs  221   a ,  221   b  therefore expand, pushing the connection  17  downwards (along with gravity acting to pull the connection  17  downwards). As a result, the connection (e.g. counterweight sheave)  17  will drop i.e. move downwards, away from the upper crosshead  15  i.e. the connection (e.g. counterweight sheave)  17  will move relative to the counterweight structure  38 , including relative to the safety brakes  12   a ,  12   b , which are fixed onto the uprights  20   a ,  20   b  of the elevator counterweight assembly  11 . This “downward” position of the safety actuation mechanism  16  relative to the counterweight structure  38  is referred to as the “safety position”. As a result of the relative movement, the levers  19   a ,  19   b  will pivot about their respective pivot points, and will therefore move the safety brake arms  26   a ,  26   b  of the safety brakes  12   a ,  12   b . This actuates the safety brakes  12   a ,  12   b , causing the safety brakes, if functioning correctly, to engage with the guide rails  13   a ,  13   b . This results in an emergency stop of the elevator counterweight assembly  11 . 
     The elevator counterweight assembly  11  of  FIGS. 3-9  includes an additional component, a mechanical actuator  22 , which can be used in order to manually test the functioning of the safety actuation mechanism  16  in a safe and simple manner. The mechanical actuator  22 , as well as the connection  17 , can be seen more clearly in  FIG. 4 , which shows a cutaway view of the elevator counterweight assembly  11 . 
       FIG. 5  shows in more detail the upper part of the elevator counterweight assembly  11 , specifically the upper crosshead  15  and the safety actuation mechanism  16 , together with the safety brakes  12   a ,  12   b . The safety brake arms  26   a ,  26   b  can be seen more clearly in  FIG. 5 , particularly the second safety brake arm  26   b.    
       FIG. 6  is a front view of the elevator counterweight assembly  11  as shown in  FIGS. 3 and 4 , and the top of which is shown in  FIG. 5 . In all of these Figures, the safety actuation mechanism  16  is in the normal position. In this normal position, as shown, the levers  19   a ,  19   b  are angled downwards, such that the safety brake arms  26   a ,  26   b  which they contact are extended from the safety brakes  12   a ,  12   b  in their normal position. 
     The mechanical actuator  22  is shown in its normal position, in which it does not apply any force to the safety actuation mechanism  16 . In this position, the mechanical actuator  22  extends a first distance  30  above the upper crosshead  15 . This distance may, for example, be approximately 50 mm. 
     As described above, in the event of an emergency which results in the counterweight suspension members  18  losing tension and going slack, the safety actuation mechanism  16  will move relative to counterweight structure  38  (i.e. the rest of the counterweight), actuating the safety brakes  12   a ,  12   b . The mechanical actuator  22  according to the present disclosure provides a mechanism by which to create relative movement between the safety actuation mechanism  16  and the counterweight structure  38 , and to therefore test that this relative movement causes the safety brakes  12   a ,  12   b  to be applied, as it should if everything is functioning properly. 
     For this purpose, the mechanical actuator  22  can be actuated to apply a force to the safety actuation mechanism  16 , specifically to the connection  17 , which in the example shown is a counterweight sheave. 
       FIG. 7  is a front view of the elevator counterweight assembly  11  as shown in  FIG. 6 , in which now the mechanical actuator  22  has been actuated so as to move the safety actuation mechanism  16  into the safety position. In this case, in which the safety actuation mechanism  16  has been intentionally moved for the purposes of testing, this position may also be referred to as the “test position”. The mechanical actuator  22  in its actuated position extends a second, smaller, distance  32  above the upper crosshead  15 . This distance may, for example, be approximately 10 mm. Thus, the movement distance  36  which the mechanical actuator  22  is moved in order to apply a force to the safety actuation mechanism  16  i.e. the total relative movement distance, is the first distance  30  minus the second distance  32 , which may, for example, result in a movement distance  36  of approximately 40 mm. 
     As described above, in order to engage the safety brakes  12   a ,  12   b  all that is required is a relative movement between the safety actuation mechanism  16  and the safety brakes  12   a ,  12   b  mounted on the uprights  20   a ,  20   b  of the counterweight structure  38 . Thus, although it may be that a slack rope during normal operation will cause the safety actuation mechanism  16  to move downwards relative to the counterweight structure  38 , considered from the frame of reference of the hoistway, in the handover test procedure as described herein, it is the counterweight structure  38  (e.g. including the uprights  20   a ,  20   b  and the weights  14 ), which is actually moved upwards relative to the safety actuation mechanism  16 , in particular relative to the connection  17  (e.g. counterweight sheave), which is held at an absolute position in the hoistway due to tension in the suspension members  18 . This is represented by the position reference line  60 , which is represented in  FIGS. 6 and 7 . Using this reference line  60  it can be clearly seen that the connection  17  remains stationary in the hoistway, and as the mechanical actuator  22  is actuated and applies a force downwards onto the safety actuation mechanism  16 , this force cannot move the connection  17  downwards, due to the tension in the suspension member  18 , and the force therefore lifts the counterweight structure  38  relative to the safety actuation mechanism  16 . 
     This relative movement results in the same pivoting of the levers  19   a ,  19   b , as occurs in response to a slack rope scenario during operation of the elevator system, and therefore should result in the engaging of the safety brakes  12   a ,  12   b . Thus, the mechanical actuator  22  can be used to test the operation of the safety actuation mechanism  16  at any given time. 
       FIGS. 8 and 9  show a cutaway view of the upper part of an elevator counterweight assembly  11  as shown in  FIG. 5 .  FIG. 8  shows the mechanical actuator  22  in its normal, non-actuated position.  FIG. 9  shows the mechanical actuator  22  in its actuated test position, and therefore the safety actuation mechanism  16  in the “safety” or “test” position, in which it can be checked whether the safety brakes  12   a ,  12   b  are actuated as they should be. 
     It can be seen in these Figures that the mechanical actuator  22  is connected to a pressure bar  34 . The pressure bar  34  is contacted by the mechanical actuator  22  and is arranged to contact the safety actuation mechanism  16  in at least two positions. In the example shown, the pressure bar  34  is arranged to contact the connection  17 , which in this example is a counterweight sheave  17 , at opposing ends. This pressure bar  34  distributes the force which is applied by the mechanical actuator  22  so as to avoid localised wear or damage to a particular part of the safety actuation mechanism  16 , or connection  17  (e.g. counterweight sheave). 
     In this example the mechanical actuator  22  is a screw mechanism, shown as a bolt, that can be manually actuated by turning, e.g. the mechanical actuator  22  is rotationally driven (by hand or a suitable tool) to produce a linear force on the safety actuation mechanism  16  (via the pressure bar  34 ). For example, a standard M20 bolt may be used. However, it will be appreciated that other types of mechanical actuator  22  may be employed instead. For example, the mechanical actuator  22  could be a ratchet or driving wedge. 
     In this example the mechanical actuator  22  is located centrally between the levers  19   a ,  19   b . The pressure bar  34  is useful for spreading the force applied by a single mechanical actuator  22 . A single mechanical actuator  22  takes up little space and can be arranged between the two suspension members  18  (as seen in  FIG. 4 ). Furthermore, the mechanical actuator  22  conveniently provides a single actuation point for a maintenance person. However, it will be appreciated that in other examples there may be more than one mechanical actuator, operable independently or mechanically linked for simultaneous operation. 
       FIG. 10  is a schematic view of an elevator system  40  according to the present disclosure. The elevator system  40  includes an elevator counterweight assembly  11  as described above, and also includes an elevator car  42 . One or more suspension members  18  connect the elevator car  42  and the elevator counterweight assembly  11 , in any suitable roping arrangement (e.g.  1 : 1  or  2 : 1  roping, etc.) As represented in the schematic drawing, the elevator car  42  defines an interior space  44 . The elevator car  42  also includes a working platform  46  e.g. a foldable working platform. The working platform  46  is such that it can be moved from a stowed position at the top of the interior space  44 , to an operational position within the interior space  44  (as seen in  FIG. 10 ). In the operational position a maintenance person is able to stand on the working platform  46 , and will partially protrude out of an opening in the top of the elevator car  42 . In this position, standing on the working platform  46 , the maintenance person is able to access many elevator components on which maintenance is to be carried out. 
     In particular, if the elevator car  42  and the elevator counterweight assembly  11  are brought to midrise i.e. both to a height which is half of the total hoistway height, such that the elevator car  42  and the elevator counterweight assembly  11  are adjacent to each other and approximately at the same height, a maintenance person standing on the working platform  46  can access the elevator counterweight assembly  11  for maintenance purposes. 
     In particular, the maintenance person is able to access the mechanical actuator  22  described above, and therefore to test the functioning of the safety actuation mechanism  16 . The steps of the method for carrying out this handover test are: 
     A maintenance person moves the working platform  46  of the elevator car  42  into the operational position and climbs up onto the working platform  46 . 
     From this position, the maintenance person accesses certain controls, and uses these controls to move the elevator car  42  and the counterweight  11  to the mid-rise position in the hoistway, so that they are adjacent to each other. In this position the maintenance person is able to easily access the mechanical actuator  22 . 
     The maintenance person then actuates the mechanical actuator  22  (for example, the mechanical actuator  22  may be a bolt and the maintenance person may turn the bolt). The actuation (e.g. the tightening of the bolt) exerts a force on the safety actuation mechanism  16 , which results in downwards relative movement of the safety actuation mechanism  16  with respect to the counterweight structure  38  (although relative to the hoistway it is actually the counterweight structure  38  which is moved upwards). 
     Once the mechanical actuator  22  is fully actuated (e.g. the bolt is fully tightened) the safety actuation mechanism  16  is in the safety or test position, in which the safety brakes  12   a ,  12   b  should be actuated. 
     The maintenance person then attempts to run the elevator car  42  upwards in the hoistway. This should create a slack in the belts  18  and trigger the counterweight safeties  12   a ,  12   b , resulting in a stall of the elevator car, since the elevator counterweight assembly  11  is not moving, as its safety brakes  12   a ,  12   b  are engaged with the guide rails. 
     The maintenance person then visually checks the safety brakes and the position of the safety actuation mechanism  16 , from their location on the working platform. Once the maintenance person has verified that everything is in order, they begin to release the mechanical actuator  22  e.g. by unscrewing the bolt by 3-5 mm. This is preferably sufficient to release the safety brakes. 
     The maintenance person then runs the elevator car  42  downwards in the hoistway, to check that the safety brakes  12   a ,  12   b  have disengaged correctly (if they have not disengaged correctly then the elevator car  42  will not move). Moving the car  42  downwards moves the elevator counterweight assembly  11  upwards. If the safety brakes  12   a ,  12   b  have not fully disengaged then, as the counterweight assembly  11  moves upwards, the maintenance person will hear a noise and can then stop the motion of the counterweight assembly  11 . Moving the counterweight assembly  11  upwards ensures that the counterweight safeties  12   a ,  12   b  will not re-engage even if they had not fully released. 
     The maintenance person then fully releases the mechanical actuator  22 , allowing the safety actuation mechanism  16  to return to its normal position. 
     Finally the maintenance person checks the position of all components of the elevator counterweight assembly  11 , and if they have all returned to their original positions, the “handover” test for the counterweight is considered to have been passed. 
     It will be appreciated by those skilled in the art that the disclosure has been illustrated by describing one or more specific examples thereof, but is not limited to these aspects; many variations and modifications are possible, within the scope of the accompanying claims.