Patent Publication Number: US-10315887-B2

Title: Arrangement and method for aligning guide rails in an elevator shaft

Description:
FIELD OF THE INVENTION 
     The invention relates to an arrangement and a method for aligning guide rails in an elevator shaft. 
     BACKGROUND ART 
     An elevator comprises an elevator car, lifting machinery, ropes, and a counterweight. The elevator car is supported on a transport frame being formed by a sling or a car frame. The sling surrounds the elevator car. The lifting machinery moves the car upwards and downwards in a vertically extending elevator shaft. The sling and thereby also the elevator car are carried by the ropes, which connect the elevator car to the counterweight. The sling is further supported with gliding means at guide rails extending in the vertical direction in the elevator shaft. The gliding means can comprise rolls rolling on the guide rails or gliding shoes gliding on the guide rails when the elevator car is mowing upwards and downwards in the elevator shaft. The guide rails are supported with fastening means on the side wall structures of the elevator shaft. The gliding means engaging with the guide rails keep the elevator car in position in the horizontal plane when the elevator car moves upwards and downwards in the elevator shaft. The counterweight is supported in a corresponding way on guide rails supported with fastening means on the wall structure of the elevator shaft. The elevator car transports people and/or goods between the landings in the building. The elevator shaft can be formed so that one or several of the side walls are formed of solid walls and/or so that one or several of the side walls are formed of an open steel structure. 
     The guide rails are formed of guide rail elements of a certain length. The guide rail elements are connected in the installation phase end-on-end one after the other in the elevator shaft. The guide rails are attached to the walls of the elevator shaft with fastening means at fastening points along the height of the guide rails. 
     WO publication 2007/135228 discloses a method for installing the guide rails of an elevator. In the first phase a first pair of opposite car guide rail elements is installed starting from the bottom of the shaft. In the second phase a second pair of opposite car guide rails is installed end-on-end with the first pair of opposite car guide rails. The process is continued until all the pairs of opposite car guide rails have been installed. The counterweight guide rails are installed in a corresponding manner. A laser transmitter is used in connection with each guide rail to align the guide rail in the vertical direction. A self-directional laser could be used, which automatically directs the laser beam vertically upwards. The laser transmitters are first positioned at the bottom of the shaft when the lowermost section of guide rails is installed. An alignment appliance provided with an alignment element is supported on each guide rail at each position where the alignment of the guide rail is to be done. The laser beam hits the alignment element, whereby the guide rail can be aligned so that the hitting point of the laser beam is in the middle of the alignment element. The laser transmitters are moved stepwise upwards for alignment of the next section of guide rails. 
     WO publication 2014/053184 discloses a guide rail straightness measuring system for elevator installations. The measuring system comprises at least one plumb line mounted vertically in the elevator shaft adjacent to the guide rail and at least one sensor arrangement to be mounted on a carrier to travel vertically along the guide rail. The sensor arrangement comprises a frame, at least one guide shoe connected to the frame for sliding or rolling along the guide surface of the guide rail, a bias means for placing and biasing the frame against the guide surface, and at least one sensor means for sensing the position of the plumb line with respect to the frame. 
     BRIEF DESCRIPTION OF THE INVENTION 
     An object of the present invention is to present a novel arrangement and method for aligning guide rails in an elevator shaft. 
     The arrangement for aligning guide rails in an elevator shaft is defined in claim  1 . 
     The elevator shaft has a bottom, a top, side walls, a first direction coinciding with a vertical direction in the elevator shaft, a second direction extending between car guide rails on opposite side walls in the elevator shaft and a third direction extending between a back wall and a front wall in the elevator shaft. 
     The arrangement is characterised in that: 
     an installation platform is arranged to be movable in the first direction upwards and downwards in the elevator shaft, said installation platform being provided with an apparatus for aligning guide rails, 
     at least two laser transmitters are arranged at predetermined positions in the shaft below the installation platform, each of said at least two laser transmitters transmitting an upwards directed laser beam that forms a plumb line in the elevator shaft, 
     at least two first position sensitive detectors are attached to the installation platform and/or to the apparatus for aligning guide rails and/or to the guide rails, each of said at least two first position sensitive detectors receiving a respective laser beam, whereby the position of the guide rails in relation to the shaft can be determined indirectly or directly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will in the following be described in greater detail by means of preferred embodiments with reference to the attached drawings, in which: 
         FIG. 1  shows a vertical cross section of an elevator, 
         FIG. 2  shows a horizontal cross section of the elevator, 
         FIG. 3  shows an axonometric view of an apparatus for aligning guide rails in an elevator shaft, 
         FIG. 4  shows a first phase of the operation of the apparatus of  FIG. 3 , 
         FIG. 5  shows a second phase of the operation of the apparatus of  FIG. 3 . 
         FIG. 6  shows an axonometric view of an elevator shaft showing the principle of the invention, 
         FIG. 7  shows a vertical cross section of a curved elevator shaft showing the principle of the invention in such a case, 
         FIG. 8  shows an axonometric view of the alignment of guide rails in an elevator shaft, 
         FIG. 9  shows a horizontal cross section of the elevator shaft showing a first embodiment of the invention, 
         FIG. 10  shows a horizontal cross section of the elevator shaft showing a second embodiment of the invention, 
         FIG. 11  shows a horizontal cross section of the elevator shaft showing a third embodiment of the invention, 
         FIG. 12  shows a horizontal cross section of the elevator shaft showing a fourth embodiment of the invention, 
         FIG. 13  shows a horizontal cross section of the elevator shaft showing a fifth embodiment of the invention, 
         FIG. 14  shows a horizontal cross section of a position sensitive detector. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
       FIG. 1  shows a vertical cross section and  FIG. 2  shows a horizontal cross section of an elevator. 
     The elevator comprises a car  10 , an elevator shaft  20 , a machine room  30 , lifting machinery  40 , ropes  41 , and a counter weight  42 . The car  10  may be supported on a transport frame  11  or a sling surrounding the car  10 . The lifting machinery  40  moves the car  10  in a first direction S 1  upwards and downwards in a vertically extending elevator shaft  20 . The sling  11  and thereby also the elevator car  10  are carried by the ropes  41 , which connect the elevator car  10  to the counter weight  42 . The sling  11  and thereby also the elevator car  10  is further supported with gliding means  70  at guide rails  50  extending in the vertical direction in the elevator shaft  20 . The elevator shaft  20  has a bottom  12 , a top  13 , a front wall  21 A, a back wall  21 B, a first side wall  21 C and a second opposite side wall  21 D. There are two car guide rails  51 ,  52  positioned on opposite side walls  21 C,  21 D of the elevator shaft  20 . The gliding means  70  can comprise rolls rolling on the guide rails  50  or gliding shoes gliding on the guide rails  50  when the elevator car  10  is mowing upwards and downwards in the elevator shaft  20 . There are further two counter weight guide rails  53 ,  54  positioned at the back wall  21 B of the elevator shaft  20 . The counter weight  42  is supported with corresponding gliding means  70  on the counter weight guide rails  53 ,  54 . The landing doors (not shown in the figure) are positioned in connection with the front wall  21 A of the elevator shaft  20 . 
     Each car guide rail  51 ,  52  is fastened with fastening means  60  at the respective side wall  21 C,  21 D of the elevator shaft  20  along the height of the car guide rail  51 ,  52 . Each counter weight guide rail  53 ,  54  is fastened with corresponding fastening means  60  at the back wall  21 B of the elevator shaft  20  along the height of the counter weight guide rail  53 ,  54 . The figure shows only two fastening means  60 , but there are several fastening means  60  along the height of each guide rail  50 . The cross section of the guide rails  50  can have the form of a letter T. The vertical branch of the guide rail element  50  forms three gliding surfaces for the gliding means  70  comprising rolls or gliding shoes. There are thus two opposite side gliding surfaces and one front gliding surface in the guide rail  50 . The cross-section of the gliding means  70  can have the form of a letter U so that the inner surface of the gliding means  70  sets against the three gliding surfaces of the guide rail  50 . The gliding means  70  are attached to the sling  11  and/or to the counter weight  42 . 
     The gliding means  70  engage with the guide rails  50  and keep the elevator car  10  and/or the counter weight  42  in position in the horizontal plane when the elevator car  10  and/or the counter weight  42  moves upwards and downwards in the first direction S 1  in the elevator shaft  20 . The elevator car  10  transports people and/or goods between the landings in the building. The elevator shaft  20  can be formed so that all side walls  21 ,  21 A,  21 B,  21 C,  21 D are formed of solid walls or so that one or several of the side walls  21 ,  21 A,  21 B,  21 C,  21 D are formed of an open steel structure. 
     The guide rails  50  extend vertically along the height of the elevator shaft  20 . The guide rails  50  are thus formed of guide rail elements of a certain length e.g. 5 m. The guide rail elements  50  are installed end-on-end one after the other. 
       FIG. 1  shows a first direction S 1 , which is a vertical direction in the elevator shaft  20 .  FIG. 2  shows a second direction S 2 , which is the direction between the first side wall  21 C and the second side wall  21 D in the elevator shaft  20  i.e. the direction between the guide rails (DBG).  FIG. 2  shows further a third direction S 3 , which is the direction between the back wall  21 B and the front wall  21 A in the elevator shaft  20  i.e. the back to front direction (BTF). The second direction S 2  is perpendicular to the third direction S 3 . The second direction S 2  and the third direction S 3  form a coordinate system in a horizontal plane in the elevator shaft  20 . 
       FIG. 3  shows an axonometric view of an apparatus for aligning guide rails in an elevator shaft. The apparatus  400  for aligning guide rails  50  comprises a positioning unit  100  and an alignment unit  200 . 
     The positioning unit  100  comprises a longitudinal support structure with a middle portion  110  and two opposite end portions  120 ,  130 . The two opposite end portions  120 ,  130  are mirror images of each other. There could be several middle portions  110  of different lengths in order to adjust the length of the positioning unit  100  to different elevator shafts  20 . The positioning unit  100  comprises further first attachment means  140 ,  150  at both ends of the positioning unit  100 . The first attachment means  140 ,  150  are movable in the second direction S 2  i.e. the direction between the guide rails (DBG). The positioning unit  100  extends across the elevator shaft  20  in the second direction S 2 . The first attachment means  140 ,  150  are used to lock the positioning unit  100  between the wall structures  21  and/or dividing beams and/or brackets  60  in the elevator shaft  20 . An actuator  141 ,  151  (position shown only schematically in the figure) e.g. a linear motor in connection with each of the first attachment means  140 ,  150  can be used to move each of the first attachment means  140 ,  150  individually in the second direction S 2 . 
     The alignment unit  200  comprises a longitudinal support structure with a middle portion  210  and two opposite end portions  220 ,  230 . The two opposite end portions  220 ,  230  are mirror images of each other. There could be several middle portions  210  of different lengths in order to adjust the length of the alignment unit  200  to different elevator shafts  20 . The alignment unit comprises further second attachment means  240 ,  250  at both ends of the alignment unit  200 . The second attachment means  240 ,  250  are movable in the second direction S 2 . An actuator  241 ,  251  e.g. a linear motor can be used to move each of the second attachment means  240 ,  250  individually in the second direction S 2 . Each of the second attachment means  240 ,  250  comprises further gripping means in the form of jaws  245 ,  255  positioned at the end of the second attachment means  240 ,  250 . The jaws  245 ,  255  are movable in the third direction S 3  perpendicular to the second direction S 2 . The jaws  245 ,  255  will thus grip on the opposite side surfaces of the guide rails  50 . An actuator  246 ,  256  e.g. a linear motor can be used to move each of the jaws  245 ,  255  individually in the third direction S 3 . The alignment unit  200  is attached to the positioning unit  100  at each end of the positioning unit  100  with support parts  260 ,  270 . The support parts  260 ,  270  are movable in the third direction S 3  in relation to the positioning unit  100 . The alignment unit  200  is attached with articulated joints J 1 , J 2  to the support parts  260 ,  270 . An actuator  261 ,  271  e.g. a linear motor can be used to move each of the support parts  260 ,  270  individually in the third direction S 3 . The articulated joints J 1 , J 2  make it possible to adjust the alignment unit  200  so that it is non-parallel to the positioning unit  100 . 
     The two second attachment means  240 ,  250  are moved with the actuators  241 ,  251  only in the second direction S 2 . It would, however, be possible to add a further actuator to one of the second attachment means  240 ,  250  in order to be able to turn said second attachment means  240 ,  250  in the horizontal plane around an articulated joint. It seems that such a possibility is not needed, but such a possibility could be added to the apparatus  500  if needed. 
     The apparatus  400  can be operated by a mechanic or automatically by means of a control unit  300 . The control unit  300  can be attached to the apparatus  400  or it can be a separate entity that is connectable with a cable to the apparatus  400 . There can naturally also be a wireless communication between the control unit  300  and the apparatus  400 . The control unit  300  is used to control all the actuators  141 ,  142  moving the first attachment means  140 ,  150 , the actuators  241 ,  242  moving the second attachment means  240 ,  250 , the actuators  246 ,  256  moving the gripping means  245 ,  255  and the actuators  261 ,  271  moving the support parts  260 ,  270 . 
       FIG. 4  shows a first phase of the operation of the apparatus of  FIG. 3 . The guide rails  51 ,  52  are attached to brackets  65 ,  66  and the brackets  65 ,  66  can be attached directly to the side wall  21 C of the shaft  20  or through a support bar  68  extending between the back wall  21 B and the front wall  21 A of the shaft  20 . The bracket  65  is attached to a bar bracket  61  and the bar bracket  61  is attached to the support bar  68 . The apparatus  400  can be supported on an installation platform and lifted with the installation platform to a height location of the first fastening means  60  during the alignment of the guide rails  50 . A mechanic may be travelling on the installation platform. The apparatus  400  may be operated by a mechanic or automatically be means of the control unit  300  so that the alignment unit  200  is controlled to attach with the jaws  245 ,  255  at the ends of the second attachment means  240 ,  250  to the two opposite guide rails  51 ,  52 . The second attachment means  240 ,  250  are movable in the second direction S 2  and the jaws  245 ,  255  are movable in the third direction S 3  so that they can grip on the opposite vertical side surfaces of the guide rails  51 ,  52 . The bolts of the fastening means  60  are then opened at both sides of the shaft  20  so that the guide rails  51 ,  52  can be moved. The guide rails  51 ,  52  on opposite sides of the shaft  20  are then adjusted relative to each other with the alignment unit  200 . The frame of the alignment unit  200  is stiff so that the two opposite guide rails  51 ,  52  will be positioned with the apexes facing towards each other when the gripping means  245 ,  255  grips the guide rails  50 . There is thus no twist between the opposite guide rails  50  after this. The distance between the two opposite guide rails  50  in the direction (DBG) is also adjusted with the alignment unit  200 . The position of each of the second attachment means  240 ,  250  in the second direction S 2  determines said distance. 
     There is a plumb line formed in the vicinity of each guide rail  51 ,  52  (not shown in the figure). The distance in the DBG and the BTF direction from the guide rails  51 ,  52  to the respective plumb line that is in the vicinity of said guide rail  51 ,  52  is then determined. The needed control values (DBG, BTF and twist) for the apparatus  400  are then calculated. The control values are then transformed into incremental steps, which are fed as control signals to the control units of the linear motors in the apparatus  400 . The DBG can also be measured based on the motor torque, which indicates when the second attachment means  240 ,  250  have reached their end position and are positioned against the guide rails  50 . The position of the linear motors can then be read from the display of the control unit  300 . The apparatus  400  can thus calculate the DBG based on the distance of the guide rails  51 ,  52  to the plumb lines and based on the position of each of the second attachment means  240 ,  250  in the second direction S 2 . 
       FIG. 5  shows a second phase of the operation of the apparatus of  FIG. 3 . The positioning unit  100  of the apparatus  400  is locked to the wall constructions  21  or other support structures in the elevator shaft  20  with the first attachment means  140 ,  150 . The alignment unit  200  of the apparatus  400  is in a floating mode in relation to the positioning unit  100  when the positioning unit  100  is locked to the wall construction  21  of the elevator shaft  20 . The guide rails  51 ,  52  can now be adjusted with the alignment unit  200  and the positioning unit  100  in relation to the shaft  20 . The bolts of the fastening means  60  are then tightened. The apparatus  400  can now be transported to the next location of the fastening means  60  where the first phase and the second phase of the operation of the apparatus  400  is repeated. 
       FIG. 6  shows an axonometric view of an elevator shaft showing the principle of the invention. The figure shows the apparatus  400  for aligning the guide rails. The apparatus  400  for aligning the guide rails is mounted on an installation platform  500  (shown in  FIGS. 8-13 ) being arranged to be movable in the first direction S 1  upwards and downwards in the elevator shaft  20 . 
     There are four laser transmitters  610 ,  620 ,  630 ,  640  arranged at predetermined positions on the bottom  12  of the elevator shaft  20 . Two of the laser transmitters  610 ,  620  are arranged in the vicinity of the first car guide rail  51  at each side of the first car guide rail  51  and two of the laser transmitters  630 ,  640  are arranged in the vicinity of the second car guide rail  52  at each side of the second guide rail  52 . The position of each laser transmitter  610 ,  620 ,  630 ,  640  in the second direction S 2  and in the third direction S 3  within the elevator shaft  20  is thus known. Each laser transmitter  610 ,  620 ,  630 ,  640  produces a laser beam PL 1 , PL 2 , PL 3 , PL 4  which is directed vertically upwards in the elevator shaft  20  and forms a plumb line in the elevator shaft  20 . The four laser transmitters  610 ,  620 ,  630 ,  640  are positioned on the bottom  12  of the shaft  20 , but they can naturally be raised to a higher position in the shaft  20  during the installation if needed. This might be needed in a very high shaft  20  if the laser beam PL 1 , PL 2 , PL 3 , PL 4  would not reach through the whole height of the shaft  20 . The installation could then be done stepwise one section of guide rails  50  at a time. The laser transmitters  610 ,  620 ,  630 ,  640  could be raised after the previous section of guide rails have been installed and aligned. 
     There are further four first position sensitive detectors (PSD)  710 ,  720 ,  730 ,  740  arranged in connection with the apparatus  400  for aligning the guide rails. Each of the first PSD:s  710 ,  720 ,  730 ,  740  is arranged so that it receives a respective laser beam PL 1 , PL 2 , PL 3 , PL 4 . The PSD measures the point where the laser beam PL 1 , PL 2 , PL 3 , PL 4  hits the position sensitive area of the respective PSD. The output signal of each PSD is transferred to a control unit  300  associated with the apparatus  400  for aligning guide rails. The position of the apparatus  400  for aligning guide rails in relation to the laser beams PL 1 , PL 2 , PL 3 , PL 4  forming the plumb lines in the shaft  20  can thus be determined in the second direction S 2  and in the third direction S 3  based on the measurements of the PSD:s  710 ,  720 ,  730 ,  740 . 
     The figure shows further four optional second position sensitive detectors  750 ,  760 ,  770 ,  780  positioned at the top  13  of the elevator shaft  20 . These second PSD:s  750 ,  760 ,  770 ,  780  can be used as reference sensors in order to be able to detect bending of a high rise building. The first position sensitive detectors  710 ,  720 ,  730 ,  740  are in this case transparent sensors with an integrated beam splitter, which means that they let the laser beam PL 1 , PL 2 , PL 3 , PL 4  go through so that also the second PSD:s  750 ,  760 ,  770 ,  780  can detect the laser beam PL 1 , PL 2 , PL 3 , PL 4 . The second PSD:s  750 ,  760 ,  770 ,  780  are arranged on the top  13  of the elevator shaft so that each vertically directed laser beam PL 1 , PL 2 , PL 3 , PL 4  hits the middle point of a respective second PSD  750 ,  760 ,  770 ,  780  in a situation where the building is straight i.e. there is no wind acting on the building. The laser transmitters  610 ,  620 ,  630 ,  640  can be provided with an automatic directing functionality, which can be achieved e.g. with servo motors. The orientation of the laser beams PL 1 , PL 2 , PL 3 , PL 4  can thus be maintained with the servo motors so that they always point to the middle point of the second PSDs  750 ,  760 ,  770 ,  780 . The four optional second position sensitive detectors  750 ,  760 ,  770 ,  780  are positioned at the top  13  of the shaft  20 , but they can naturally be lowered to a lower position in the shaft  20  during the installation if needed. This might be needed in a very high shaft  20  if the laser beams PL 1 , PL 2 , PL 3 , PL 4  would not reach through the whole height of the shaft  20 . The installation could then be done stepwise one section of guide rails  50  at a time. The second position sensitive detectors  750 ,  760 ,  770 ,  780  could first be positioned in a first position between the installation platform  500  and the top  13  of the shaft  20 . The second position sensitive detectors  750 ,  760 ,  770 ,  780  could then be raised in synchronism with the raising of the laser transmitters  610 ,  620 ,  630 ,  640 . 
       FIG. 7  shows a vertical cross section of a curved elevator shaft showing the principle of the invention in such a case. The bending of the elevator shaft  20  is greatly exaggerated in the figure in order to clarify the situation. The figure shows only one laser transmitter  610 , one first position sensitive detector  710  and one second position sensitive detector  750 . The laser beam PL 1  produced by the laser transmitter  610  forms a first angle α 1  with the vertical direction as said laser beam PL 1  is automatically directed to the centre of second position sensitive detector  750 . The second position sensitive detector  750  is thus not positioned on the vertical line extending upwards from the laser transmitter  610  due to the bending of the elevator shaft  20 . The laser beam PL 1  produced by the laser transmitter  610  hits the first PSD  710  at a first point P 1 . The magnitude and the direction in the second direction S 2  and the third direction S 3  of the first angle α 1  of the laser beam PL 1  in relation to the vertical direction is known. The vertical height H 1  distance between the laser transmitter  610  and the second PSD  750  is also known. The vertical height position H 2  of the first PSD  710  is also known. This information makes it possible to take into consideration the bending of the building. A predetermined bending curve BC can be fitted between the laser transmitter  610  and the second PSD  750  so that the bending of the curve follows the bending of the elevator shaft  20 . The bending curve BC hits the first PSD  710  at a second point P 2 . The second point P 2  is thus the corrected hitting point of the laser beam PL 1  taking into account the bending of the elevator shaft  20 . This correction can be done for all laser beams. 
       FIG. 8  shows an axonometric view of the alignment of guide rails in an elevator shaft. The figure shows the car guide rails  51 ,  52 , the installation platform  500  and the apparatus  400  for aligning the guide rails  51 ,  52 . The apparatus  400  for aligning the guide rails  51 ,  52  is attached with a support arm  450  to a support frame  460  and the support frame  460  is attached to the installation platform  500 . The apparatus  400  for aligning the guide rails  51 ,  52  has to be movable in the second direction S 2  and in the third direction S 3  in relation to the installation platform  500 . This can be achieved with one or several joints J 10  in the support arm  450 . The support frame  460  can also be arranged to be movable in the second direction S 2  and in the third direction S 3 . 
       FIG. 9  shows a horizontal cross section of the elevator shaft showing a first embodiment of the invention. The figure shows the installation platform  500 , the apparatus  400  for aligning guide rails and two first position sensitive detectors  710 ,  720  supported on the installation platform  500 . The installation platform  500  comprises support arms  510 ,  520 ,  530 ,  540  arranged on opposite sides of the installation platform  500  and being movable in a second direction S 2  for supporting the installation platform  500  on the opposite side walls  21 C,  21 D of the shaft  20 . The gripping means  245 ,  255  of the second attachment means  240 ,  250  can grip the opposite guide surfaces of the car guide rails  51 ,  52 . The car guide rails  51 ,  52  can thus be aligned with the apparatus  400  for alignment of guide rails as described earlier in connection with  FIGS. 3-5 . The installation platform  500  is locked in place with the support arms  510 ,  520 ,  530 ,  540 . The position of the installation platform  500  in relation to the shaft  20  is determined with the position sensitive detectors  710 ,  730  once the installation platform  500  is locked in the shaft  20 . When the coordinates of the stationary installation platform  500  are determined, then it is possible to determine the coordinates of the apparatus  400  in relation to the installation platform  50  continuously during the alignment procedure. The apparatus  400  is attached to the installation platform  500 , whereby the position of the apparatus  400  can be determined indirectly based on the position of them installation platform  500 . The position of the guide rails  51 ,  52  can be determined indirectly based on the position of the apparatus  400 . This arrangement could be used e.g. in a case where the visibility to the apparatus  400  is restricted so that the first position sensitive detectors  710 ,  730  cannot be attached to the apparatus  400 . 
       FIG. 10  shows a horizontal cross section of the elevator shaft showing a second embodiment of the invention. This second embodiment differs from the first embodiment in that the first position sensitive detectors  710 ,  730  are attached to the second attachment means  240 ,  250  in the apparatus  400  for alignment of guide rails. The support arms  510 ,  520 ,  530 ,  540  of the installation platform  500  are not shown in the figure. The first attachment means  140 ,  150  of the apparatus  400  for aligning guide rails are used to support the apparatus  400  against the opposite side walls  21 C,  21 D in the elevator shaft  20 . Each guide rail  51 ,  52  can then be aligned with the second attachment means  250 ,  250  based on the measurement signals received from the first position sensitive detectors  710 ,  730  as described in connection with  FIGS. 3-5 . The position of the apparatus  400  can be determined directly based on the measurement results from the first position sensitive detectors  710 ,  730  attached to the apparatus  400 . The position of the guide rails  51 ,  52  can be determined indirectly based on the position of the apparatus  400 . 
       FIG. 11  shows a horizontal cross section of the elevator shaft showing a third embodiment of the invention. This third embodiment differs from the second embodiment in that the first position sensitive detectors  710 ,  730  are attached via a magnet  715 ,  735  to a gliding surface the guide rails  51 ,  52 . The position of the guide rails  51 ,  52  can be determined directly based on the measurement results from the first position sensitive detectors  710 ,  730  attached to the guide rails  51 ,  52 . 
       FIG. 12  shows a horizontal cross section of the elevator shaft showing a fourth embodiment of the invention. This fourth embodiment differs from the second embodiment in that four first position sensitive detectors  710 ,  720 ,  730 ,  740  are used. The first two of the first position sensitive detectors  710 ,  720  are attached to a first of the second attachment means  250  of the apparatus  400  at opposite sides of the first car guide rail  51 . The second two of the first position sensitive detectors  730 ,  740  are attached to a second attachment means  240  of the apparatus  500  at opposite sides of the second car guide rail  52 . The position of the guide rails  51 ,  52  can be determined based on the position of the second attachment means  240 ,  250  of the apparatus  400 . The twist of the car guide rails  51 ,  52  can easily be measured with this arrangement. 
       FIG. 13  shows a horizontal cross section of the elevator shaft showing a fifth embodiment of the invention. This fifth embodiment differs from the fourth embodiment in that the first position sensitive detectors  710 ,  720 ,  730 ,  740  are attached via a magnet  715 ,  735  to a gliding surface of the guide rails  51 ,  52 . 
       FIG. 14  shows a horizontal cross section of a position sensitive detector. The position sensitive detector  700  has a centre point C, which forms the centre point for the coordinate system of the position sensitive detector  700 . The figure shows a hitting point P 3  at which the laser beam PL hits the position sensitive detector  700 . The coordinate X 1  of the hitting point P 3  in the second direction S 2  and the coordinate Y 1  of the hitting point P 3  in the third direction S 3  are given as an output signal by the position sensitive detector  700 . The idea would then be to change the position of the guide rails  51 ,  52  so that the laser beam PL hits the position sensitive detector  700  at the centre point C. The centre point C of the position sensitive detector  700  is the reference point for the apparatus  400  for aligning guide rails. 
     The installation platform  500  may be provided with different installation equipment in addition to the apparatus for aligning guide rails. The installation equipment may be used to install guide rails. The installation equipment may comprise one or several robots being movable on the installation platform  500 . The installation platform  500  may be supported with gliding means on the opposite car guide rails  51 ,  52  during the movement in the first direction S 1  upwards and downwards in the elevator shaft  20 . A hoist may be used to move the installation platform  500  in the first direction S 1  upwards and downwards in the elevator shaft  20 . 
     The arrangement for aligning guide rails has been described in connection with car guide rails  51 ,  52 , but the arrangement can naturally also be used to align counter weight guide rails  52 ,  53 . 
     Any kind of commercially available position sensitive detector  700  can be used in the invention. The PSD could thus e.g. be formed of a detector having an isotropic sensor surface with a raster-like structure that supplies continuous position data. The PSD could on the other hand e.g. be formed of a detector having discrete sensors on the sensor surface that supply local discrete data. 
     The transfer of information and control data between the first position sensitive detectors  710 ,  720 ,  730 ,  740  and the control unit  300 , between the second position sensitive detectors  750 ,  760 ,  770 ,  780  and the control unit  300  and between the laser transmitters  610 ,  620 ,  630 ,  640  and the control unit  300  may be by wireless communication or by wire. The transfer of information and control data between the installation platform  500  and the control unit  300  and between the apparatus for alignment  400  and the control unit  300  may be by wireless communication or by wire. 
     The height position of the installation platform  500  and/or of the apparatus  400  for aligning guide rails can be measured by any conventional as such known method. This could be done by a laser based distance sensor. Another possibility would be to use an absolute multi turn encoder and a measurement wheel for measuring the movement of the installation platform  500 . There could be a reference mark in the shaft  20  at which the encoder could be reset. 
     The laser transmitters  610 ,  620 ,  630 ,  640  should be positioned so that the laser beams PL 1 , PL 2 , PL 3 , PL 4  can pass freely upwards in the elevator shaft  20  to the first position sensitive detectors  710 ,  720 ,  730 ,  740  and/or to the second position sensitive detectors  750 ,  760 ,  770 ,  780 . The laser transmitters  610 ,  620 ,  630 ,  640  should be capable of a long range if they are used in a high-rise building. It the working range of the laser emitters  610 ,  620 ,  630 ,  640  is not sufficient for the whole height of the shaft, then the installation could be done in sections so that the laser transmitters  610 ,  620 ,  630 ,  640  are raised between the intervals. Dust or turbulence of the air in the shaft  20  can cause problems at long distances. 
     The invention can be used with at least two laser transmitters  610 ,  620 ,  630 ,  640 . The apparatus  400  for alignment of guide rails shown in  FIGS. 3 to 5  is able to align the apexes of the guide rails  51 ,  52 ,  53 ,  54 . Four laser transmitters  610 ,  620 ,  630 ,  640  are, however, needed in order to measure the straightness of the guide rails  51 ,  52 ,  53 ,  54 . This is due to the fact that the guide rails  51 ,  52 ,  53 ,  54  often have some twist. The beams L 1 , L 2 , L 3 , L 4  of the laser transmitters  610 ,  620 ,  630 ,  640  should be parallel. 
     The use of laser beams L 1 , L 2 , L 3 , L 4  as plumb lines is advantageous compared to the use of mechanical plumb lines. Mechanical plumb lines are formed by wires, which start to vibrate immediately when they are touched by accident. The measurements have to be interrupted until the wire stops vibrating. 
     The arrangement and the method can be used in elevator installations where the hoisting height in the elevator shaft is over 30 mm, preferably 30-80 meters, most preferably 40-80 meters. 
     The arrangement and the method can on the other hand also be used in elevator installations where the hoisting height in the elevator shaft is over 75 meters, preferably over 100 meters, more preferably over 150 meters, most preferably over 250 meters. 
     The installation platform  500  can be used to install car guide rails  51 ,  52  and/or counter weight guide rails  53 ,  54 . 
     The use of the invention is not limited to the type of elevator disclosed in the figures. The invention can be used in any type of elevator e.g. also in elevators lacking a machine room and/or a counterweight. The counterweight is in the figures positioned on the back wall of the elevator shaft. The counterweight could be positioned on either side wall of the shaft or on both side walls of the elevator shaft. The lifting machinery is in the figures positioned in a machine room at the top of the elevator shaft. The lifting machinery could be positioned at the bottom of the elevator shaft or at some point within the elevator shaft. 
     It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.