Patent Publication Number: US-11639284-B1

Title: Wedge brake elevator safety system

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to elevators and vertical lift systems, more particularly an elevator employing a specific cable arrangement and brake device which work together to stop a downward travel of an elevator car in the event of a slack cable. 
     Conventional elevators and lifts have suspension means consisting of cables and are required to have a brake, otherwise known as an elevator safety brake, or slack rope brake, which grips or latches on to some surface if any part of the suspension means fails. A total failure of the suspension means can send an elevator car into free fall as the cables would no longer have the weight of the car applying tension. For this reason, it is common for an elevator safety device to act upon the slackening of a cable. Such brakes typically grip the elevator guide rail or a strip attached to the elevator guide rail. Elevator guide rails are most commonly a T-shaped steel form, with only a few sizes being standardized or typical to the industry. For this reason, elevator safety devices currently produced are designed to act on this specific shape with little or no alternatives for using other shapes as guiderails. T-shaped guide rails are conducive to elevators which are in an elevator shaft, and are hung in a balanced symmetrical way by the suspension means. Such rails act as a guide only and are not load bearing. 
     It has become increasingly common for elevators to be built and installed adjacent to a structure as opposed to in a shaft or hoist way, particularly when the building was not initially designed to have an elevator. With these type installations it is advantageous to use shapes for guide rails that act as both a guide and a load bearing member. I-beams are commonly used since the guide rollers can be arranged at the front and back of the front flange of the beam, thus the load of the elevator car can be cantilevered from them. This trend has necessitated the development of a braking system for elevators that ride on such beams and also other structural shapes, such as a C-channel. 
     It is considered unsafe for an elevator brake to act on only one surface of the member it engages. A brake designed in such a way would tend to distort the member it is acting upon. Therefore, it is a safety requirement for elevator brakes to clamp the member it acts upon on both front and back and between two surfaces of the brake, respectively. Clamping two sides of a stationary member means at least two parts of the brake device must move and interact with each other in some way. Accomplishing such with a T-shaped guide rail and a single cable acting upon the brake device is simple. The narrow nature of the T-rail lends itself to simply having a pair of brake shoes extend to either side of the leg, and any linkage or mechanism joining the two brake shoes so they close in unison. 
     However, accomplishing the latter when utilizing shapes with multiple intersecting planes and surfaces, such as I-beams, for guide rails is more challenging. To similarly use a single slack cable to actuate a brake that clamps both sides of the web of an I-beam, the brake shoes would need to be linked by a mechanism that wraps around the flange of the beam. Thus, the simple mechanism described above for the T-rail brake that joins the two brake shoes now has corners so it needs to traverse around a considerable distance to link the first brake shoe to the second. Such a mechanism is complicated and expensive to build. 
     Furthermore, many installations of such elevators without a conventional shaft are done outside, or in other harsh environments. For this reason, maintaining simplicity is advantageous since complicated mechanisms tend to be susceptible to corrosion and contamination. 
     In addition, elevators that are suspended by cables need provisions to halt electrical operation upon slackening of a cable. As the present invention is actuated upon cable slackening it is conducive to incorporate such a sensor into the construction of the device, particularly by way of proximity sensor. 
     Thus, a need exists for an elevator braking system for use with an I-beam and other shapes of guiderails that solve the above problems. 
     The prior patented art includes the following references, but none disclose a device like the present invention. 
     
       
         
           
               
               
               
               
             
               
                   
               
               
                   
                 Patent/App. No. 
                 Inventor 
                 Issue/Pub. Date 
               
               
                   
               
             
            
               
                   
                  1. 3,215,231 
                 Lodige 
                 Nov. 02, 1965 
               
               
                   
                  2. 5,096,020 
                 Korhonen 
                 Mar. 17, 1992 
               
               
                   
                  3. 5,230,406 
                 Poon 
                 Jul. 27, 1993 
               
               
                   
                  4. 5,310,022 
                 Sheridan et al. 
                 May 10, 1994 
               
               
                   
                  5. 5,645,142 
                 Kraemer et al. 
                 Jul. 08, 1997 
               
               
                   
                  6. WO 02/057170 
                 Walker 
                 Jul. 25, 2002 
               
               
                   
                  7. 7,036,638 
                 Simmonds et al. 
                 May 02, 2006 
               
               
                   
                  8. 2008/0296098 
                 Sato et al. 
                 Dec. 04, 2008 
               
               
                   
                  9. 8,020,671 
                 Kocher et al. 
                 Sep. 20, 2011 
               
               
                   
                 10. 8,863,909 
                 Dudde et al. 
                 Oct. 21, 2014 
               
               
                   
                 11. 9,663,327 
                 Terry et al. 
                 May 30, 2017 
               
               
                   
                 12. 10,407,278 
                 Zhang et al. 
                 Sep. 10, 2019 
               
               
                   
               
            
           
         
       
     
     SUMMARY OF THE INVENTION 
     The primary object of the present invention is to provide an elevator braking system device that can be used with guiderails having a variety of metal shapes. 
     Another object of the present invention is to provide such an elevator braking system device that simplifies the construction of previously-known elevator slack cable brakes. 
     A further object of the present invention is to provide such an elevator braking system device that simplifies the construction of previously-known elevator slack cable brakes. 
     An additional object of the present invention is to provide an elevator braking system that can sense slackening of a cable to stop the operation of the elevator. 
     The present invention fulfills the above and other objects in an elevator braking by positioning lifting cables at each of the two sides of the guide rail for a wedge brake to act upon with each cable acting upon its respective half of the brake mechanism. Thereby, the additional cable takes the place of any linkage or mechanism that would typically join the pair of brake shoes. If one of the two cables fails its respective brake assembly has adequate stopping force to stall the downward travel to a degree that the cable on the opposite side goes slack as well, and likewise its respective brake engages. While the engagement of the two brake assemblies might not be simultaneous in the event of a single cable failure, the second brake assembly does engage before any significant deflection of the guiderail occurs due to engagement of the first. 
     When dealing with multiple cables it is necessary to have some means to equalize cable tension and thus the present invention also integrates a cable tensioning method into the brake assembly by having provisions for locking and unlocking the wedge brake the cable directly acts upon from the eye bolt or similar anchor it attaches to. Upon initial installation the cable tension can be adjusted with the wedge and cable attachment unlocked from each other. Then when equal cable tension is attained, by adjustment nut or similar item, the two components can be locked together by means of a set screw or similar item so that any interruption in cable tension would result in a downward movement of the wedge and thus engagement between the brake shoe and guiderail. 
     In addition to the above features, an electrical sensor or slack cable switch is provided to disrupt power to the driving means of an elevator upon sensing slackening of a cable. 
     The above and other objects, features and advantages of the present invention should become even more readily apparent to those skilled in the art upon a reading of the following detailed description in conjunction with the drawings wherein there is shown and described illustrative embodiments of the invention. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       In the following detailed description, reference will be made to the attached drawings in which: 
         FIG.  1    is a bottom end view of an elevator brake assembly of the present invention with an I-beam being utilized as a guiderail; 
         FIG.  2    is a front perspective view the elevator brake assembly of the present invention showing the cable arrangement and winding drum with I-beam guiderail; 
         FIG.  3    is a front view of the elevator brake assembly of the present invention and cable attachment assembly of  FIG.  2    without the i-beam guiderail; 
         FIG.  4    is an enlarged sectional view along section A of  FIG.  3    of the elevator brake assembly of the present invention; 
         FIG.  5    is a rear view of the elevator brake assembly of the present invention and cable attachment assembly of  FIG.  2    without the I-beam guiderail; and 
         FIG.  6    is an enlarged sectional view along section B of  FIG.  5    of the elevator brake assembly of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     For purposes of describing the preferred embodiment, the terminology used in reference to the numbered components in the drawings is as follows:
           1 . I-beam guide rail     2 . top guide wheels     3 . cable tension adjustment nut     4 . spring stops     5 . set screws     6 . retracting springs     7 . brake surfaces     8 . bottom guide wheels     9 . cable drum     10 . elevator brake assembly, generally     11 . cable     12 . eye bolts     13 . actuating wedges     14 . braking wedges     15 . stationary wedges     16 . compression springs     17 . rear wedge plates     18 . electrical sensor/slack cable switch     19 . fasteners for wedge plates     20 . electrical power wire to  18         

     Referring to the drawing figures,  FIG.  1    illustrates a bottom end view of the elevator brake assembly  10  of the present invention consisting of dual brake assemblies running vertically within an I-beam  1 . Each assembly has lower guide wheels  8  which abuts and runs along a front of the I-beam  1  and a top or upper guide wheel  2  which runs along a center rail of the I-beam  1 . Each assembly has a brake surface  7  for gripping against the I-beam  1  in case of a cable malfunction to stop an elevator car from falling. Retracting springs  6  maintain the brake surfaces  7  away from the I-beam  1  during normal operation of an elevator. Rotatable cable tension adjustment nuts  3  and spring stops  4  are provided to adjust the cable tension exerted by compression springs  16  (shown in  FIGS.  2 - 6   ). An electrical sensor with slack cable switch  18  connected to the electrical wire  20  that powers the elevator is provided to detect cable slackening and deactivate electrical power to the elevator upon such an occurrence. 
       FIG.  2    illustrates a front perspective view of an elevator brake assembly  10  of the present invention as it would appear in operation without an elevator car attached thereto. The brake assemblies  10  are attached within opposite cavities of the I-beam  1  by eyebolts  12  to a cable  11  from a cable drum  9 . Each brake assembly  10  is guided along the I-beam  1  by lower guide wheels  8  and top guide wheels  2  (not shown). Other components of the brake assembly  10 , such as brake surface  7 , compression spring  16 , spring stop  4  and cable tensions adjustment nut  3  are also shown. Also, an electrical sensor with slack cable switch  18  connected to the electrical wire  20  that powers the elevator is provided to detect cable slackening and deactivate electrical power to the elevator upon such an occurrence. 
       FIG.  3    illustrates a front view of the elevator brake assembly  10  of the present invention without an I-beam guide rail. As previously described the dual brake assemblies  10  are suspended from the cable drum by cable  11  and eye bolt brackets  12 . Each brake assembly  10  as shown here and in the enlarged view of  FIG.  4    consist of a top plate  18  attached to which are three vertical wedges: an outer stationary wedge  15 , a middle actuating wedge  13  and an inner braking wedge  14  with braking surface  7 . The braking wedge  7  is attached to the stationary wedge  15  with the actuating wedge  13  sandwiched in between by a retracting spring  6 . Also, an electrical sensor with slack cable switch  18  connected to the electrical wire  20  that powers the elevator is provided to detect cable slackening and deactivate electrical power to the elevator upon such an occurrence. 
       FIGS.  5  and  6    illustrate a rear view of the elevator brake assembly  10  shown in  FIGS.  3  and  4   . The only components shown here which have not been previously illustrated and described are the rear wedge plate  17  and a plurality of fasteners  19 , such as rivets or similar items, which hold together the wedges of the elevator brake assembly  10 . Also, an electrical sensor with slack cable switch  18  connected to the electrical wire  20  that powers the elevator is provided to detect cable slackening and deactivate electrical power to the elevator upon such an occurrence. 
     It is to be understood that while preferred embodiments of the invention have been described, it is not to be limited to the specific form or arrangement of parts herein described and shown. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown and described in the specification and/or drawings.