Abstract:
A braking mechanism for use with a lift is provided that interacts with a fixed cable that runs the length of the path of travel of the lift. The interaction of the cable and braking mechanism transfers the rotational power created by the travel of the braking mechanism over the cable to a centrifugal clutch. When an over speed situation is encountered by the lift, the centrifugal clutch expands and causes the rotational force to be transferred to the cam sprocket which forces an offset portion of the trip lobe upward until it engages and releases a cam lock. This releases the load on the spring which rotates the cable cam which in turn closes the distance between its lower surface and the floor of the cam housing. The result of this is that the fixed cable is pinched between the cable cam and the cam housing which effectively stops the relative motion between the braking mechanism which in turn stops the motion of the lift.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an improvement in lifts, and more specifically in braking apparatus&#39; used to stop BANK HOISTS and elevators smoothly in over speed situations. 
     Many home builders and home owners often find it desirable to build on large hills or cliffs overlooking lake fronts or scenic areas. An inherent problem with this type of terrain is that the user of the home often desires to get from the home up on a large hill or cliff, down to the lake or base. This often involves placing several flights of stairs or crossing walkways. 
     A common solution to this has been the use of BANK HOIST type lifts or baskets which run on a rail system and allow users to get up and down large embankments or cliffs easily and without effort. These lifts can be especially advantageous in transporting materials, as well as elderly and young users of the home, to and from different elevations. Often times these lifts may not be completely vertical as elevators commonly are and will run on a track system using wheels. The lifts are often pulled up and down via a cable system and some sort of pulley which winds or unwinds or turns the cable. It has been found that it is desirable to provide some type of braking system for these lifts that will be activated automatically in an over speed situation, such as when a cable spool or cable breaks. This type of brake would keep the BANK HOIST type lift or carriage from free falling. It has also been found that it would be advantageous to provide a system that would automatically brake or stop the carriage smoothly, with no sudden jerking motion to the occupants, in an over speed situation in either direction. 
     Finally, a large number of these types of lifts exist and are already installed but use out of date or aging braking apparatus&#39;. It would therefore be advantageous to design a braking apparatus that could be used to retro fit older or existing lifts. This same type of braking system may also be used in other types of lifts and elevators. 
     SUMMARY OF THE INVENTION 
     It is the primary objective of the present invention to provide a method of effectively and safely stopping a lift in an over speed situation. 
     It is an additional objective of the present invention to provide such a method that uses a static cable that runs the length of the path of travel of the hoist which interacts with the braking system located on the bottom of the hoist. 
     It is a further objective of the present invention to provide such a braking mechanism that will engage without the intervention of the user of the lift. 
     It is still a further objective of the present invention to provide such a system that employs a speed sensitive clutch mechanism to trigger the brake. 
     These objectives are accomplished by the use of a braking mechanism that is attached to the bottom side of the frame of a lift. The BANK HOIST type lift is a lifting apparatus that is used to transport people and materials up and down inclines without having to resort to the use of stairs. This braking mechanism interacts with a fixed cable that runs the length of the path of travel of the lift. The interaction of the cable and braking mechanism is accomplished by first running the cable over and under a series of wheels in the wheel housing component of the brake and then through the cable cam housing component of the brake. 
     One of the wheels in the wheel housing transfers the rotational power created by the travel of the braking mechanism over the cable to a centrifugal clutch which is located on the outer side of the wheel housing. The centrifugal clutch is made up of an inner and outer hub in which only the inner hub rotates during the normal operation of the lift. The outer hub is connected to the drive sprocket which in turn is connected to a drive chain. The drive chain extends forward to a point where it engages an additional sprocket located on an axle which is connected to the hoist frame in the gap between the wheel housing and the cable cam housing. This axle also has an offset cam lobe protrusion that is located between the cam sprocket and the hoist frame and the offset portion of the lobe is oriented in a downward manner during the normal operation of the hoist. 
     The cable cam, which is the component of the invention which actually performs the braking operation, is located within the cable cam housing which is again attached to the hoist frame. The cable cam is pivotally mounted to the housing towards its lower end and is attached to a high tension spring at its upper end. During normal operation of the hoist, the upper end of the cable cam is forced forward and held in place by the use of the cam lock which extends rearward to end at a point just above the trip lobe located on the cam sprocket axle. The locking of the cable cam in this position loads the high tension spring and rotates the lower end of the cable cam just enough to allow the fixed cable to pass through the cam housing beneath the lower surface of the cable cam. 
     When an over speed situation is encountered by the lift, the centrifugal clutch located in the inner hub of the clutch assembly expands and catches a protruding tab located on the inner surface of the outer hub. This causes the rotational force of the inner hub to be transferred to the outer hub which rotates the cam sprocket through the drive sprocket and drive chain. The rotation of the cam sprocket forces the offset portion of the trip lobe upward until it engages and releases the cam lock. This releases the load on the spring which rotates the cable cam which in turn closes the distance between its lower surface and the floor of the cam housing. Therefore, the fixed cable is pinched between the cable cam and the cam housing which effectively stops the relative motion between the braking mechanism, which stops the motion of the lift. 
     For a better understanding of the present invention reference should be made to the drawings and the description in which there are illustrated and described preferred embodiments of the present invention. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a typical lift carriage used in the place of a stairway to transport people and materials up and down an inclined surface that would employ the present invention as a braking system to ensure that the carriage can not freewheel down the incline. 
     FIG. 2 is a side elevation view of the present invention showing its method of construction and the manner in which it interacts with the fixed cable of the lift carriage. 
     FIG. 3 is a top elevation view of the present invention showing its method of construction and the manner in which it interacts with the fixed cable of the lift carriage. 
     FIG. 4 is a side elevation view of the present invention detailing the method of construction of the cable locking cam and the centrifugal hub used to activate the braking mechanism. 
     FIG. 5 is a side elevation view of the present invention detailing the manner in which the centrifugal hub activates the cable locking cam to brake the carriage. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, and more specifically to FIG. 1, the BANK HOIST braking apparatus  10  is a device that is typically used with a lift  12  or other similar apparatuses that are employed to transport people and materials up and down slopes that would otherwise have to be negotiated by a lengthy stairway. The lift  12  itself is typically made up of a hoist frame  16  which supports a hoist carriage  14  and a pair of hoist rails  18  which are permanently fixed to the surface of the slope and provide the lift  12  with a track which it follows in its course up an down the slope. 
     The hoist frame  16  is formed in a downwardly oriented L-shaped configuration which creates an angle between the forward and rearward edges of the lift frame which corresponds to the predominate angle of the slope over which the lift  12  is to travel. Each corner of the hoist frame  16  is equipped with a downwardly extending rail wheel  20  which have concave rolling surfaces that engage the hoist rails  18 . These concave surfaces of the rail wheels  20  fit over and partially around the tubular hoist rails  18  and serve to keep the lift  12  securely in position throughout its travel on the slope. Additionally, the hoist frame  16  also forms a platform onto which the hoist carriage  14  is built which forms an enclosed area within which passengers and cargo are carried. 
     The lift  12  is moved up and down the slope by the use of the guide cables  24  which run between the hoist rails  18  and are attached to the lift  12 . These guide cables  24  transfer the force supplied by an external power source to raise and lower the lift  12  along the hoist rails  18  and, under normal operating conditions, control the upward and downward motion and speed of the lift  12 . 
     An additional cable runs between the hoist rails  18  in the same manner as the guide cables  24  which is known as the static lift cable  22 . The static lift cable  22  differs from the guide cables  24  in that it does not move itself and that it is not attached to the lift  12  but only passes through the BANK HOIST braking apparatus  10  that is attached to the brake mount bar  26  component of the hoist frame  16 . The brake mount bar  26  runs diagonally from the from the front lower center of the hoist frame  16  to its rear upper center. This provides a frame member for the mounting of the present invention to the hoist frame  16  that runs close to and roughly parallels the surface of the slope, thus, allowing the invention to easily engage the static lift cable  22  located beneath it. 
     The construction of the body of the present invention is illustrated in FIGS. 2 and 3. The BANK HOIST braking apparatus  10  is made up of a wheel housing  38  and cable cam housing  52  that are attached in line to one side of the brake mount bar  26  of the hoist frame  16 . The wheel housing  38  consists of two parallel walls with a space between that contains the idler wheels  34  and the drive wheel  36  which engage the static lift cable  22  as it passes through the invention. As the static cable  22  enters the wheel housing  38  it is threaded under the first idler wheel  34 , over the drive wheel  36  and then under the second idler wheel  34  before exiting the wheel housing  38 . The two idler wheel&#39;s  34  only function in the invention is to ensure that the static cable  22  remains correctly aligned with the drive wheel  36  as the invention passes along the static cable  22 . The passage of the drive wheel  36  along the static cable  22  provides rotational force to the clutch hub assembly  28  located on the outside surface of the wheel housing  38  that is not attached to the brake mount bar  26 . Finally, the clutch hub assembly  28  is the component of the invention that activates the braking mechanism in over speed situations (this function will be more fully discussed below). 
     The static cable  22  is also threaded through the cable cam housing  52  which is attached to the brake mount bar  26  in a similar fashion as the wheel housing  38  and in a location so that there is a short gap left between it and the wheel housing  38 . The cable cam housing  52  is also constructed of two parallel walls with a space between that contains the cable cam  50  which is pivotally mounted through the pivotal cam mount  60  to and within these walls and which has a decreasing radius curved lower edge which terminates within the cable cam housing  52  just above its lower inside surface. Thus, the static cable  22  passes through the cable cam housing  52  between the lower edge of the cable cam  50  and the lower inside surface of the cable cam housing  52 . 
     The upper end of the pivotally mounted cable cam  50  is connected to a high tension cam spring  54  which extends forward above the brake mount bar  26  to a point where it attaches to the mount bar  26  through the spring tensioning adjustment  58  and the front spring mount  56 . The spring tensioning adjustment  57  allows the amount of tension being placed on the cam spring  54  (and the cable cam itself) to be adjusted to compensate for varying conditions encountered in the use of the present invention. 
     The cable cam  50  also has attached to its most forward edge at a point just below the attachment of the cable cam spring  54  the cam lock  48  which is a relatively small and short metallic bar. The attachment is accomplished through the use of the pivotal cam lock mount  70  which attaches the most rearward point of the cam lock  48  to the cable cam  50  and allows it to freely pivot around this mounting point. The cam lock  48  also has a cam lock notch  62  at about the midpoint of its bottom surface which fits over the cam lock ridge  64  which extends upward from the upper surface of the brake mount bar  26 . 
     The purpose of the cam lock  48  is to lock the cable cam  50  in a position which puts a load on the cable cam spring  54 . This is accomplished by forcing the upper end of the cable cam  50  to pivot rearward around the pivotal cam mount  60  which stretches the cable cam spring  54 , thus, placing forward pressure on the cable cam  50 . The cable cam is then held in this loaded position by placing the cam lock notch  62  over the cam lock ridge  64 . The end result of this is that the lower end of the cable cam  50  is pivoted forward which leaves a large enough gap at the lower end of the inside of the cable cam housing  52  for the static cable  22  to pass freely through. 
     The clutch hub assembly  28  of the present invention is made up primarily of the inner hub  30  and the outer hub  32  which are not in contact with one another in normal circumstances. It is the inner hub  30  that is connected to the drive wheel  36  (and, therefore, to the static cable  22 ) through the hub axle  66  which extends through the body of the brake mount bar  26 . This manner of construction provides rotational force to the inner workings of the clutch assembly hub  28  which is always spinning while the lift  12  is in motion. The outer hub  32  is externally (in respect to the clutch hub assembly  28 ) connected to the drive sprocket  40  which is connected to the drive chain  42 . The fact that the outer hub  32  is not in contact with the inner hub  30  under normal operating conditions allows the outer hub  30 , the drive sprocket  40  and the drive chain  42  to remain stationary under normal operating conditions. 
     The drive chain  42  extends forward from the drive sprocket  40  to a point where it encircles the most forward portion of the cam sprocket  44 . The cam sprocket  44  is connected to the brake mount bar  26  in the gap between the wheel housing  38  and the cable cam housing  52  by the use of the cam sprocket axle  68  which extends through the body of the brake mount bar  26 . At a point just behind the cam sprocket  44 , the cam sprocket axle  68  has attached to it the trip lobe  46  which is short offset cylindrical protrusion of the cam sprocket axle  68  and which is positioned directly beneath the most forward end of the cam lock  48  and forward of the cam lock ridge  64 . Under normal operating conditions the offset portion of the trip lobe  46  extends downward so that it does not interfere with the positioning of the cam lock  48 . 
     The workings of the braking components of the present invention are illustrated in FIGS. 4 and 5. FIG. 4 details the construction of these components and illustrate their orientation under normal operating conditions. The inner hub  30  of the clutch assembly hub  28  contains the counterweight assembly  75  which consists of a pair of identical counterweights  77  that are pivotally mounted at their centers by the use of the counterweight mount pins  76  on opposite sides of the inner hub  32 . One of the counterweights  77  has attached to one of its outer ends a counterweight spring  84  and is pivotally attached to the other counterweight  77  by the use of the counterweight connector  78  which is a flat metallic bar that extends from the opposite end of the counterweight spring  84  attachment of the first counterweight  77  to a pivotal attachment on the parallel end of the second counterweight  77 . The use of the counterweight connector  78  allows the tension placed on the first counterweight  77  by the counterweight spring  84  to be transferred to the second counterweight  77  and this tension is held in check under normal operating conditions by the weight stop pin  82  which engages the inner surface of the second counterweight  77 . 
     In this configuration, the trip lobe  46  does not engage the cam lock  48  and so the upper end of the cable cam  50  is left in its forward position which in turn rotates its lower cam pinch surface  74  up and away from the cable cam housing floor  72 . This allows just enough room between the cable cam housing floor  72  and the cam pinch surface  74  for the static cable  22  to pass freely though. Additionally, the forward positioning of the cable cam  50  by the locking action of the cam lock  48  loads the cable cam spring  54  which provides a contained rearward pressure on the upper portion of the cable cam  50 . Thus, under normal operating conditions, the cam pinch surface  74  of the cable cam  50  does not engage the static cable  22  and the lift  12  is free to along its length. 
     However, in a situation where the lift  12  is allowed to reach a speed that is greater its designed specifications, these components of the present invention work quickly and efficiently to stop the lift  12 . The manner in which this is accomplished is detailed in FIG.  5 . In a lift  12  over speed situation the increased rotational speed placed on the inner hub  30  of the clutch assembly hub  28  by the increased rate at which the static cable  22  passes over the drive wheel  36  places an outward centrifugal force on the counterweights  77  of the counterweight assembly  75 . This situation forces the opposite ends of the two counterweights  77  to rotate outward around the central pivotal mounting to the counterweight mount pins  76 , a situation which is aided by the inward tension placed on the counterweights by the counterweight spring  84 . 
     As the two ends of the counterweights  77  expand outward within the inner hub  30  due to its increased rotational speed, one will engage the weight catch  80  which is an inwardly protruding tab located on the inner surface of the outer hub  32 . Once this happens, the rotational force of the inner hub  30  is transferred to the outer hub  32  and the drive sprocket  40  through the counterweight assembly  75 . This rotational force is then transferred to the cam sprocket  44  through the drive chain  42  which rotates the trip lobe  46  upward to the point where it engages and releases the cam lock  48  from its position on the cam lock ridge  64 . 
     The release of the cam lock  48  from the cam lock ridge  64  allows the tension of the loaded cable cam spring  54  to pull the upper end of the cable cam  50  rearward. This forces the cable cam  50  to rotate around its pivotal cam mount  60  which in turn forces the rear end of the cam pinch surface  74  downward in relation to the cable housing floor  72 . The downward motion of the cam pinch surface  74  pinches the static cable  22  between the cam pinch surface  74  and the cam housing floor  72  which effectively stops the relative motion between the present invention and the static cable  22 . Thus, the present invention operates quickly and smoothly to stop a lift  12  in an over speed situation which ensures the safety of persons and materials being carried in the hoist carriage  14 . 
     Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein.