Abstract:
A dampening device for use with elevator cars or similar devices prevents damage to objects or persons within the elevator car upon failure of a drive chain. A hydraulic motor regulates the rate of descent. The dampening motor is monitored constantly using a pressure gauge.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an improved dampening system for elevators and similar devices. More specifically, the present inanition relates to a safety feature that prevents rapid descent of an elevator or similar device. 
   2. Prior Art 
   Elevators, trams and other devices for transporting items and people up and down steep slopes and vertically through buildings have been in use for over a century. There has always been a danger that, should the device fail, the elevator car or tram would fall a great distance resulting in damage to goods and death to passengers. Several devices have been designed to operate as brakes to stop a rapidly descending car or tram upon failure of the elevator device. 
   U.S. Pat. No. 105,177 issued to Copeland on Jul. 12, 1870 discloses in addition to the ordinary brake, a water or other fluid cylinder furnished with a passage connecting the two ends, in such a manner that a valve in the connecting-passage regulates the rapidity with which a piston may be worked by the obstruction it offers to the passage of the water or other fluid, so that the adjustment of the valve regulates the speed of the piston, and fixes the limit at which the car may be permitted to run down the incline. It does not disclose the use of a hydraulic motor safety device attached to the car. 
   U.S. Pat. No. 205,537 issued to Garrison on Jul. 2, 1878 discloses a safety brake for cars, being more particularly adapted for use on inclines in mines, and which are lowered and raised by means of a wire cable or rope attached to an engine on the surface (typical emergency brake system). This device simply applies frictional force to one of the rails upon which the car rides. 
   U.S. Pat. No. 236,184 issued to Schmidt on Jan. 4, 1881 discloses a pneumatic braking system. An air powered braking system halts descent of an elevator once a certain speed is reached. 
   U.S. Pat. No. 527,894 issued to Smith on Oct. 23, 1894 discloses a safety appliance for use in connection with cars upon inclined railways, and it has a stationary or fixed cable in connection with the railway, so arranged with reference to the car upon the track as to permit the gripping of the cable by the gripping mechanism upon the car. This invention provides a safety device that immediately stops the car and does not allow for a slow descent. 
   U.S. Pat. No. 3,415,343 issued to Svensson on Dec. 10, 1968 discloses a catch apparatus for the elevator cages of scaffold elevators and other similar elevators, on which the elevator cage by means of a driven gear wheel climbs along a toothed rack in a mast structure for the elevator. 
   U.S. Pat. No. 3,924,710 issued to Shohet on Dec. 9, 1975 discloses a hoist with a rack and pinion drive assembly for raising and lowering the lift frame of the hoist and a rack and pinion overspeed mechanism for braking the lift frame when the hoist exceeds a predetermined speed. 
   U.S. Pat. No. 3,967,703 issued to Martin on Jul. 6, 1976 discloses a rack-and-pinon type hoist with an improved braking apparatus that includes a spring buffer, preferably hydraulic, carried by the cage of the hoist, a rotatable shaft also carried by the cage and positively engaged with a member extending along the mast so as to be driven in rotation by movement of the cage along the mast and connecting means for engaging the shaft and the buffer comprising a centrifugal governor driven by rotation of the shaft and operating, in response to rotation of the shaft in excess of a predetermined rate of rotation, to provide positive drive to a linearly movable member, the movement of which is opposed by the buffer. 
   U.S. Pat. No. 4,046,226 issued to Flinchbaugh on Sep. 6, 1977 discloses an elevator platform that rides on parallel tracks which may be adapted for vertical or inclined conveyance. Each track is slotted along its length, through which slot the platform extends and is connected to a trolley driven by a continuous chain. Each track is tubular and generally rectangular, and each encloses another tubular, rectangular member which provides a space for the chain return and electrical conduits, and which provides support for the trolley. Each trolley has an upper pair of rollers bearing against the inside of the hollow track straddling the slot, and lower rollers bearing against the top surface of the inner tubular member. Interrupt and safety precautions are provided based on chain breakage, excessive speed, overload, or contact with foreign objects in the path of the elevator platform. The safety precautions provide for an immediate stop 
   The designs of the prior art designed to detect when an elevator car accelerates passed a predetermined speed. The device then rapidly stops the elevator car. This sudden stops jerks what ever is in the car and can cause damage to products and injure passengers. In addition, the car may be stopped at an inconvenient spot. An elevator may be caught between floors and a tram may be stopped only halfway down its track and difficult to get to. None of the prior art discloses means for slowing down rather than stopping an elevator car. Neither do they provide means for an elevator whose power has failed to safely fall to the bottom of its track. 
   It is therefore desirable to provide an elevator dampening system that does not suddenly stop an elevator car thus jarring its contents. 
   It is also desirable to provide a dampening system that allows an elevator car to slowly return to the bottom of a shaft or track. 
   SUMMARY OF THE INVENTION 
   The present invention provides a dampening system for use on elevator cars and other devices designed to ascend and descend vertically or at a steep angle. The invention provides a hydraulic motor having a cog attached to it. The cog is engaged to a track that runs parallel to the drive mechanism. Typically, this type of hydraulic motor is used to provide high torque, low RPM motion. Here, the motor is used in an opposite fashion. Those skilled in the art will appreciate that a cog attached to a hydraulic motor may be spun with relatively little effort in one direction but provides a significant amount of resistance when one attempts to spin it in the other direction due to a check valve. The resistance provided by the motor in the second direction is used to regulate the speed of descent of an elevator car. The hydraulic motor is attached to an elevator car in such a way that the cog applies resistance to the track it is engaged to as the elevator car descends. No substantial resistance is applied by the motor to its track when the elevator car is moved upward. No power is required for this design. It requires only the track, a cog attached to a hydraulic motor and a hydraulic fluid reservoir for the motor. 
   Those skilled in the art of hydraulics will appreciate that the resistance of the hydraulic motor is due to pressure buildup within the motor. A pressure gauge may be used to measure this pressure. Such a pressure valve is a useful monitoring device. The valve may be mounted on the elevator car such that it may be viewed by operators of the elevator. So long as the pressure valve measures pressure within the hydraulic motor as it descends, operators may be assured that the safety feature is operating properly. Failure of the gauge to detect any pressure serves as a warning that the hydraulic motor safety device is not operating properly. Those skilled in the art will appreciate that this easy constant monitoring of the safety valve is an improvement over the prior art. 
   The addition of the invention to an elevator or other device designed for the ascending and descending of a car, tram or other object limits the rate at which the device may descend. Should the drive chain of the elevator break or otherwise fail, the car will descend at a safe speed until it has reached the bottom. This avoids the jerking motion caused by most safety systems when they suddenly stop the car in place. This also prevents a car from being stopped at an awkward position along its track. It is both safer and more convenient than devices of the prior art. 
   In an alternative embodiment of the present invention, the hydraulic motor may be stationary at the top of an elevator shaft. The elevator car to which it is engaged is attached to the hydraulic motor by a chain or cable and moves up down within the elevator shaft. In this embodiment the hydraulic motor may also be used as the drive mechanism. By pumping hydraulic fluid through the hydraulic motor rather than allowing it to rest idly, an elevator car may be pulled upward. In this embodiment, it is preferable to use two hydraulic motors each with a separate chains or cables attached to the elevator car. In this embodiment, if either chain or cable breaks or fails, the second one and its motor will present the car from falling. It is also possible to add a spring activated, hydraulically released brake to the hydraulic motor shaft if no further descent is desired when a failure is detected, thus the motor stops the tram and the brake holds the load. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a diagrammatic side view of the invention. 
       FIG. 2  shows a diagrammatic view of the cog, track and guide rollers of the invention. 
       FIG. 3  shows a diagrammatic side view of an alternative embodiment of the present invention. 
       FIG. 4  shows an alternative embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The embodiments discussed herein are merely illustrative of specific manners in which to make and use the invention and are not to be interpreted as limiting the scope of the instant invention. 
   While the invention has been described with a certain degree of particularly, it is to be noted that many modifications may be made in the details of the invention&#39;s construction and the arrangement of its components without departing from the spirit and scope of this disclosure. It is understood that the invention is not limited to the embodiments set forth herein for purposes of exemplification. 
   In the present invention a high torque low RPM hydraulic motor is utilized to control the descent of an elevator car down an elevator shaft. In one embodiment, the hydraulic motor is attached to an elevator car. The motor has a cog attached to it that rides along a stationary track that extends the length of the shaft. When the elevator descends, pressure builds up within the hydraulic motor and the speed with which the cog may turn and move down the track is limited. When the cog turns in the other direction as it ascends the shaft, no pressure builds within the hydraulic motor due to a check valve and the cog rotates freely thus not limiting the speed with which the elevator may ascend the shaft. Those skilled in the art will appreciate that all hydraulic motors rotate easily in one direction due to a check valve but only slowly in the opposite direction due to a relief valve. It is this property that makes them well suited as a safety feature for use with elevator cars and other devices that ascend and descend a vertical or steep angle. 
     FIG. 1  shows a dampening system  10  as used in an elevator assembly  11 . Elevator car  14  has cable  18  attached to its top  17 . Cable  18  is attached to a standard elevator drive mechanism not shown. Dampening system  10  is attached to the bottom  15  of car  14 . Dampening system  10  has a hydraulic motor  30  attached to support bracket  32 . Hydraulic fluid is fed to motor  30  by assembly  29  and tube  26 . Assembly  29  and tube  26  connect to reservoir  20  which is full of hydraulic fluid  21 . 
   Track  16  runs the length of the elevator shaft  12  and is stationary. Track  16  is engaged to cog  34  which is attached to axle  40  of the hydraulic motor  30 . Guide rollers  36  hold track  16  firmly engaged to cog  34 . Motor  30  is arranged in such a way that cog  34  places a substantial amount of resistance to track  16  as the elevator car  14  descends. No substantial resistance is applied to track  16  by cog  34  as the elevator ascends. Should cable  18  or the drive mechanism fail, dampening system  10  causes the elevator car to descend relatively slowly. 
   Assembly  29  is comprised of pipe  23 , pressure gauge  22 , tubing  25 , check valve  24 , relief valve  28  and tubing  27 . Check valve  24  only allows flow of a fluid in one direction. Here, check valve  24  allows hydraulic fluid to flow through it from reservoir  20  to motor  30  through tubes  27  and  25  and pipe  23 . It does not allow fluid  21  to flow in the opposite direction. Relief valve  28  allows fluid  21  to flow through it in one direction only. However, relief valve  28  allows flow only at a very slow rate. This rate may be adjusted. Those skilled in the art will appreciate that this is a common design for hydraulic assemblies used with hydraulic motors. When fluid  21  flows from reservoir  20  through tubing  27  and valve  24  through tubing  25 , pipe  23  and into motor  30 , the fluid flows relatively easily and allows the axle  40  of hydraulic motor  30  to spin freely and rapidly. Fluid  21  travels through tube  26  and back into reservoir  20 . When fluid flows in the opposite direction check valve  24  closes and fluid may only flow through relief valve  28 . Relief valve  28  restricts the flow rate by a pre-determined amount. As cog  34  turns while descending track  16 , it rotates axle  40  so that fluid  21  gets pumped through tube  26  and motor  30  and forced into pipe  23  and tube  25 . Because relief valve  28  only allows flow at a very slow rate, pressure builds in assembly  29  and is measured by pressure gauge  22 . This slows the rate by which axle  40  may turn and allows the elevator to only descend slowly. It may also be desirable to have the relief valve attached to controls which may be actuated from within the elevator car such that the speed of descent may be adjusted. 
   Pressure gauge  22  monitors the pressure that builds in the motor  30  and line  25  when car  14  descends. Operators of the elevator may use this gauge to verify that dampening system  10  is operating properly. The pressure gauge  22  does not measure an increase in pressure as the elevator car  14  descends, when dampening system  10  has failed and is not working. This will alert operators of the elevator to the fact that dampening system  10  is not operating properly. 
     FIG. 2  shows how cog  34  engages track  16 . Cog  34  is attached to axle  40  that connects it to the hydraulic motor on the opposite side of support bracket  32 . Rollers  36  freely rotate about pivot pins  38 . Rollers  36  push track  16  firmly against cog  34  to ensure that track  16  and cog  34  remain firmly engaged. 
     FIG. 3  shows an alternative embodiment of the present invention. Elevator drive mechanism  50  is designed to both raise and lower elevator car  82 . It incorporates an additional safety feature designed to stop the elevator at any given point. Hydraulic motor  64  is attached to axle  62  that operates on cog  60 . Cog  60  rotates and is engaged with chain or cable  80 . When cog  60  rotates in a direction to lift car  82  in the direction of arrow  90  the chain or cable  80  is drawn into retention box  78 . When car  82  is moved in the downward direction the retention box  78  feeds the chain or cable to cog  60  and down shaft  84 . In order to raise car  82  in the direction of arrow  90 , pump  54  pumps fluid  53  into four-way valve  96 . Four-way valve  96  with integral pressure relief valve which contains pump pressure is actuated such that it feeds the fluid into tube  76 . Those skilled in the art will appreciated that a four-way valve is capable of directing flow of a hydraulic fluid pumped into it into more than one output tube. When lifting car  82 , four-way valve  96  is actuated such that fluid  53  is pumped into tube  76  and not tubes  74  and  98 . Tube  76  has a relief valve  58 . Relief valve  58  has an internal check valve. Those skilled in the art will appreciate that such a relief valve  58  having an internal check valve allows free flow of fluid in one direction and restricted flow in the other direction. Here, valve  58  allows free flow of fluid in the direction of arrow  92  but restricts flow in the opposite direction. Fluid travels through  76  and into motor  64  causing axle  62  and cog  60  to rotate in a direction so as to lift car  82  in the direction of arrow  90 . As car  82  is lifted, chain or cable  80  is pulled into retention box  78  where it is stored. Fluid  53  continues to flow through motor  64  and into tube  74  in a direction opposite of arrow  94 . The fluid then travels back into four-way valve  96  where it is directed into tube  98  and returned to reservoir  52 . As will be discussed in more detail below, axle  62  is engaged with overriding clutch  66 . Those skilled in the art will appreciated that an overriding clutch generally allows free rotation in one direction but prevents rotation in another direction. Overriding clutch  66  is engaged by axle  62  in such a way as to allow free rotation in the direction that rises car  82  and prevents rotation in the opposite direction. Should the apparatus somehow fail while raising car  82 , overriding clutch  66  will hold car  82  in place where it was stopped. It will prevent car  82  from descending. 
   Once car  82  has attained a desired elevation, four-way valve  96  is actuated to direct fluid pumped into it by pump  54  directly into tube  98  and no longer into tube  76 . The action of overriding clutch  66  on axle  62  holds car  82  in place where it was stopped. 
   Finally, to descend elevator car  82 , the four-way valve  96  is actuated such that fluid pumped by pump  54  is sent into tube  74 . As with the previous embodiment, the use of a check valve builds up pressure within the hydraulic motor and limits the rate of descent. Fluid  53  also flows into fluid tube  71  and to a disk brake system  70 . Those skilled in the art will appreciate that disk brake systems are well known. Typically, pads  79  and  77  compress against disk  81  and prevent axle  68  from rotating. However, because of the engagement of axle  68  and axle  62  by means by overriding clutch  66 , axle  62  may not move in a rotation that allows descent of car  82  unless axle  68  is also capable of rotating. To facilitate this, fluid  53  fed to disk brake system  70  by tube  71  actuates pads  77  such that they move in the direction of arrows  72 . This releases pressure on disk  81  and allows axle  68  to rotate with axle  62 . Should the system fail in some manner and cause the pressure of hydraulic fluid  53  within the tube  74  and  71  to decrease, pads  77  will re-engage disk  81  and stop descent of car  82 . Should overriding clutch  66  fail in some manner, the rate of descent remains controlled by the internal check valve  58  and the pressure build up in hydraulic motor  64 . Those skilled in the art will appreciate that this dual safety system comprised of both a hydraulic motor having a controlled rotation rate as well as an overriding clutch provides for a very safe elevator system. Those skilled in the art will appreciate that a drive mechanism such as that shown in  FIG. 3  may be used to lift and lower an elevator car without the inclusion of overriding clutch  66  and disk brake mechanism  70 . However, the embodiment shown in  FIG. 3  is preferred because it is safer. 
   In  FIG. 1 , the dampening device is shown attached directly to the elevator car. Those skilled in the art will appreciate that although the figure shows the device attached to the bottom of the car, it may also be attached to the top of the car. In addition, it may also be completely detached from the elevator car.  FIG. 4  shows an elevator car  103  and a shaft  109  located on the side of a building  101 . The dampening device is located in base  107 . Cable  105  attaches it to a car  103 . When the device is activated, it slowly lowers the elevator. This may be used as a means to escape a tall building in case of a fire. The elevator would only descend once. Base  107  is located outside the building to prevent it from being damaged by a fire or other tragedy. 
   The device shown in  FIG. 3  may also be placed in base  107  so that the elevator may both ascend and descend. Base  107  is a safe distance from the building so that it will not be damaged in case of an emergency. Those skilled in the art will appreciate that shaft  109  may be located within building  101 . However, for use as an emergency escape mechanism, it is preferred that the elevator be on one end of the building instead of inside the building. 
   The embodiments of the invention shown in  FIGS. 1 through 4  are all designed for an elevator car within an elevator shaft. However, those skilled in the art will readily realize that the device is suitable for use on any cars or trams that ascend and descend either vertically or at an angle. A variety of devices are designed to transport objects or persons up or down the slope of a hill or mountain. The present invention is highly suitable for use in conjunction with such devices. 
   Whereas, the present invention has been described in relation to the drawings attached hereto, it should be understood that other and further modifications, apart from those shown or suggested herein, may be made within the spirit and scope of this invention.