Abstract:
A device and procedure for creating and securing a temporary safety space within an elevator hoistway such that a service or maintenance technician can work with impunity from a car entering the safety space. In particular, the device includes a stop bar for installation between and in engagement with opposing guide rails of the hoistway to prevent upward or downward movement of the car or a counterweight.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a device and procedure for creating and securing a temporary safety space within an elevator hoistway such that a service or maintenance engineer can work with impunity from a car entering the safety space. In particular, the invention provides a stop bar for mounting within the hoistway to prevent movement of the car into the safety space. 
   In recent years pressure within the elevator industry to reduce the space consumption of installations has increased dramatically. This has resulted in the design of modem elevator systems in which:
         a) the entire hoistway length is used for the travel of the car during normal operating conditions. Accordingly there are no permanent, dedicated safety spaces in the head and pit of the hoistway; and   b) the machine is no longer accommodated within a separate room but is also mounted within the hoistway.       

   Hence, there is a requirement to provide a temporary safety space within the hoistway of modem systems before maintenance or service work can be carried out. Furthermore, when the machine is mounted in the hoistway, the frequency at which the hoistway must be accessed for maintenance or service work is increased. Accordingly, it is important that the means for creating the temporary safety space can be established and reset quickly and reliably. 
   Many prior art solutions have been proposed to create the necessary temporary safety spaces. For example, EP-A-0985628, illustrates height adjustable railing members disposed on the top of the roof of an elevator car. During normal elevator operation, the railing members are maintained in a position lower than the highest protrusion from the car roof so that they do not interfere with the travel of the elevator. When maintenance is to be carried out, the railing members are raised to an upright position, thereby establishing a temporary safety space defined between the top of the car and the top of the railing members. 
   A similar solution is described in WO-A-02085773 wherein a folding framework is mounted on top of the roof of the elevator car. When maintenance is to be carried out, the framework is unfolded and extends vertically above the car to establish a safety space. 
   A common problem associated with these two solutions is that they are only capable of establishing a safety space in the headroom of the hoistway above the car. Furthermore, the railing members or framework extend vertically through the safety spaces that they create and this may impede the maintenance engineer in carrying out the required work. 
   A common approach to establishing the required safety space in the pit of the hoistway is described in EP-A-0725033. A buffer is pivotably mounted to the floor of the pit. In normal elevator operating conditions the buffer is retained in a vertical position where it has no influence on the travel of the elevator car. When work is to be carried out in the pit, the buffer is released from its retained position and tilts under gravity into a safety position where it prevents travel of the car into the pit. Similar supports are described in DE-A-10065099. Again, however, these safety devices when creating a safety space in the pit actually extend through the safety space and this may impede the maintenance engineer in carrying out the required work. 
   U.S. Pat. No. 5,773,771 describes an apparatus for restricting the motion of an elevator car. The apparatus consists of two bolts extensible from either side of a bottom bolster channel supporting the car. In the extended position, the bolts engage with steel plates mounted to the guide rails thereby preventing upward motion of the car. If a service technician is working on the top of the car, it would be difficult, if not impossible, for him to see whether the bolts have extended and correctly engaged with the steel plates. Hence, he cannot be entirely confident that the car has been prevented from moving. 
   SUMMARY OF THE INVENTION 
   Accordingly there is a need to overcome the aforementioned problems associated with the prior art by providing a simple, effective, reliable and visible means and method of creating both pit and headroom safety spaces which does not intrude into the safety space so established to hamper maintenance work. 
   Pursuant to the present invention, an assembly is presented for providing a temporary safety space within an elevator hoistway wherein upward or downward movement of a car or a counterweight along guide rails is prevented. The assembly includes engagement members provided on the guide rails and a stop bar having opposing ends that bear against the engagement members. The engagement members can be arranged to permanently secure the guide rail to the hoistway, can be a hole provided in the guide rail, or temporarily fixed to the guide rail to create the temporary safety space. 
   Another aspect of the invention resides in a method for creating such a temporary space within an elevator hoistway. The method includes switching a control system to an inspection mode, providing engagement means on the guide rails and installing a stop bar having opposing ends which bear against the engagement means. The engagement means can be bolts used to permanently secure the guide rail to the hoistway, holes in the guide rail, or bolts temporarily fixed to the guide rail. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     By way of example only, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, of which: 
       FIG. 1  is a plan view of an elevator system showing a car within a hoistway and a stop bar according to the present invention in its stored position on top of the car; 
       FIG. 2  is an expanded view of segment A of  FIG. 1  showing the cooperation between a guide rail and a guide shoe of the elevator system; 
       FIG. 3  corresponds with  FIG. 2  but showing the stop bar in position to prevent upward travel of the car; 
       FIG. 4  is a side view of the arrangement shown in  FIG. 3 ; 
       FIG. 5  corresponds to  FIG. 4  but with the stop bar in a position where it prevents downward travel of the car; 
       FIG. 6  illustrates a telescopic stop bar according to a second embodiment of the present invention; 
       FIG. 7  illustrates a further telescopic stop bar according to a third embodiment of the present invention; and 
       FIG. 8  corresponds with  FIG. 4  but showing a stop bar according to a fourth embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  is a plan view from above a car  2  mounted within a hoistway  10  of an elevator system  1 . Two guide shoes  6  mounted on opposing sides of the car  2  slide along corresponding guide rails  12  affixed to opposing walls of the hoistway  10  to retain the car  2  in a centralized position as it moves up and down (out of and into the plane of the page) within the hoistway  10 . A stop bar  20  according to the present invention is stored on a rooftop  4  of the car  2 . 
     FIG. 2  is an expanded view of segment A of  FIG. 1  showing in more detail the relationship between one of the guide shoes  6  and the associated guide rail  12 . The guide rail  12  comprises a support flange  14  and a guide blade  16  extending in towards the center of the hoistway  10 . The guide rail  12  is positioned and mounted onto the hoistway  10  by fixing bolts  18  that pass through the support flange  14  and is secured thereto by corresponding nuts  19 , the blots  18  and nuts  19  serve as engagement members, as will become clear from the discussion below. The guide shoe  6  is provided with a slot  8  that partially envelops the guide blade  16 . Accordingly, the car  2  is prevented from moving significantly away from its central line of travel by engagement of the guide blade  16  with the side walls of the slot  8 . 
   When maintenance/inspection work is to be carried out in the hoistway  10  the technician stops the car  2  at a predetermined level in the vicinity of a specific landing door of the hoistway  10 , opens that landing door and climbs onto the roof  4  of the car  2 . From there the technician switches the control system of the elevator  1  to inspection mode thereby enabling the car  2  to travel at a reduced speed upwards or downwards within the hoistway  10  under the supervision of the technician. 
   In order to create a temporary safety space above the car  2 , the stop bar  20  is arranged as shown in  FIGS. 3 and 4 . The stop bar  20  has opposing ends each having two support struts  26  with a channel  24  therebetween. Initially the technician moves the car  2  up towards, but not into, the proposed temporary safety space. Then the stop bar  20  is removed from its stored position, as shown in  FIG. 1 , and the guide blades  16  of the guide rails  12  are inserted into the opposing channels  24  of the stop bar  20 . The car  2  is then moved upwards slightly until the support struts  26  bear against a lower surface of the nuts  19  securing the guide rail  12  to the hoistway  10 , as shown specifically in  FIG. 4 . In this position, with the stop bar  20  sandwiched between the roof  4  of the car  2  and the nuts  19 , the car  2  is prevented from further upward motion and thereby the upper safety space is created. 
   To reduce the initial and any subsequent impact forces between the stop bar  20  and the car  2  a layer of resilient material  22  such as rubber is provided on the lower surface of the stop bar  20 . 
   In order to create a temporary safety space in a pit of the hoistway  10  below the car  2 , the stop bar  20  is arranged as shown in  FIG. 5 . Initially the technician moves the car  2  down towards, but not into, the proposed temporary safety space. Then the stop bar  20  is removed from its stored position, as shown in  FIG. 1 , and again the guide blades  16  of the guide rails  12  are inserted into the opposing channels  24  in the stop bar  20 . On this occasion, however, the stop bar  20  must be fixed to the roof  4  of the car  2 . This is achieved by inserting bolts  30  through slots  28  provided in the bar  20  and fastening them to the roof  4  of the car  2 . The car  2  can then be moved downwards slightly until the support struts  26  bear against an upper surface of the nuts  19  securing the guide rail  12  to the hoistway  10 . In this position, the car  2  is prevented from further downward motion and thereby the lower safety space is created. 
   Although the guide shoes  6  of this particular embodiment are positioned at the top of the car  2 , it will be appreciated that the shoes  6  can be mounted at any position along the height of the car  2 . 
   Overtime the opposing guide rails  12  of an elevator system  1  can become mis-aligned. Accordingly, the distance between them can vary along the length of the hoistway  10 . The stop bar  20  of the previously described embodiment, being of a single-piece construction, cannot account or adjust for these changes. Accordingly, an alternative, telescopic stop bar  40  as shown in  FIG. 6  was developed. The stop bar  40  shares all of the features of the previous embodiment but additionally it is of a two-piece construction. The ends of the stop bar  40  are biased against each other by a compression spring  32 . Hence the stop bar  40  automatically adjusts to the distance between the opposing guide rails  12  even if that distance changes along the length of the hoistway  10 . 
     FIG. 7  illustrates a manually adjustable stop bar  50  according to a third embodiment of the invention. Again the stop bar  50  is of a two-piece, telescopic construction. When in position so that the stop bar  50  spans the distance between the opposing guide rails  12 , the technician locks the two pieces together by means of screw pin  34 . 
   Obviously the embodiments of  FIGS. 6 and 7  can be combined so that the two telescopic pieces of the stop bar are locked together in the stored position so that it is of minimal length. Then, when required, the screw pin  34  can be released and the compression spring  32  forces the two pieces apart to engage with the opposing guide rails  12  within the hoistway  10 . 
   Instead of using the bolts  18  and the nuts  19  on the guide rails  12 , temporary fastening means such as a clamp or bolt could be used to secure the ends of the stop against the guide rails  12  as illustrated in  FIG. 8  which shows a further stop bar  60  in accordance with a fourth embodiment of the invention. The arrangement shown is similar to that of  FIG. 4  but it will be appreciated that the stop bar  60  is shorter than that of  FIG. 4 . 
   Again when maintenance/inspection work is to be carried out in the hoistway  10  the technician stops the car  2  at a predetermined level in the vicinity of a specific landing door of the hoistway  10 , opens that landing door and climbs onto the roof  4  of the car  2 . Instead of manually switching the control system of the elevator  1  to inspection mode, the technician merely removes the stop bar  60  from its stored position ( FIG. 1 ) and mounts it across the car roof  4  between the opposing guide rails  12  as shown in  FIG. 8 . In this position an electrical contact  66  on each side of the underside of the stop bar  60  contacts an associated electrode  68  extending from the car roof  4  to complete a bridge circuit thereby automatically switching the control circuit of the elevator  1  to inspection mode. As the support struts  62  of this embodiment are shorter than in the previous embodiments, the technician is capable of moving the car  2  up towards the proposed temporary safety space without fouling against the nuts  19  and the bolts  18  securing the guide rails  12  to the hoistway  10 . In that position, the technician screws temporary bolts  64  into threaded holes  15  on the opposing guide rails  12  and then continues to move the car  2  upwards until the support struts  62  bear against the temporary bolts  64 . The car  2  is prevented from further upward motion and thereby the upper safety space is created. 
   A further arrangement is also envisaged wherein the support struts are longer than in the embodiment shown in  FIG. 4  and instead of engaging with nuts or bolts mounted on or through the opposing guide rails, the struts capable of extending into holes provided at regular distances along the support flanges of the opposing guide rails. Naturally such a stop bar would have to be telescopic since its extended length is inherently greater than the distance between the opposing guide rails. 
   Since the maintenance technician must generally climb onto the roof  4  of the car  2  to switch (whether manually or through installation of the stop bar  60 ) the control system of the elevator  1  to inspection mode, the roof  4  is the most logical place to store and install the stop bar  20 ,  40 ,  50  or  60 . However, it will be appreciated that the stop bar  20 ,  40 ,  50  or  60  could alternatively be installed on the bottom of the car or indeed on a counterweight of the elevator system  1  having its own guide rails. 
   Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.