Abstract:
Drive sheaves are disclosed herein. An embodiment of a drive sheave includes a tire portion wherein the tire portion comprises an inner circumferential surface and an outer circumferential surface. The tire portion also includes a first surface extending between the inner circumferential surface and the outer circumferential surface and a second surface extending between the inner circumferential surface and the outer circumferential surface, the second surface being oppositely disposed relative to the first surface. At least one hole in the tire portion extends between the first surface and the second surface.

Description:
This application is a divisional application of Ser. No. 11/670,789 filed on Feb. 2, 2007, now U.S. Pat. No. 7,743,711 for DEFORMABLE DRIVE SHEAVE, which claimed the benefit of the U.S. provisional application 60/780,634 filed on Mar. 8, 2006, which are both hereby incorporated for all that is disclosed therein. 
    
    
     BACKGROUND 
     Aerial ropeway transport systems, such as gondolas and chairlifts, are commonly used for transporting people and cargo. A typical system has two end terminals or stations, each having a bull wheel for supporting a rope, such as a steel cable or the like. Rotation of the bull wheels causes the rope, and the carriers attached thereto, to move between the terminals. 
     In order to improve the efficiency of the system, the rope travels at a high velocity. In many embodiments, the rope velocity is too high for people and cargo to be loaded off and on the carriers. In such embodiments, the carrier detach from the rope when they are inside the terminals. After the carriers are detached, they move slowly through the terminal so that people or cargo can be loaded or unloaded. 
     As a carrier detaches from the rope, the carrier must be smoothly decelerated to a speed that enables the people or cargo to be loaded onto or unloaded from the carrier. In order to provide a smooth transition to the fast moving rope, the carrier needs to be accelerated to approximately the speed of the rope prior to being reattached to the rope. Rapid decelerations and accelerations of the carriers may injure people or damage cargo traveling in the carriers. Tires mounted on drive sheaves are typically used for the smooth acceleration and deceleration of the carriers. However, the tires are subject to significant wear and tear during the acceleration and deceleration of the carriers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an embodiment of a tramway. 
         FIG. 2  is a side elevation view of an embodiment of a portion of a terminal used in the tramway of  FIG. 1 . 
         FIG. 3  is an embodiment of three drive sheaves in a terminal accelerating a carrier. 
         FIG. 4  is an enlarged view of an embodiment of a drive sheave equipped with an deformable tire. 
         FIG. 5  is an embodiment of three drive sheaves in a terminal decelerating a carrier. 
     
    
    
     DETAILED DESCRIPTION 
     A top plan view of an embodiment of an aerial tramway or ropeway  100  is shown in  FIG. 1 . The ropeway  100  is used to move a plurality of carriers  106 , such as chairs or gondolas. The ropeway  100  includes a continuous track-haul rope  110  extending between a first bull wheel  112  and a second bull wheel  114 . In some embodiments, the ropeway may include a combination of segregated track and haul ropes. The first bull wheel  112  and devices associated therewith may be located in a first terminal, which may be, as an example, the base of a ski area. Likewise, the second bull wheel  114  may be located in a second terminal, which may be located at a higher elevation that the first terminal. The ropeway  100  may be used to transport skiers up a mountain. It is noted that the ropeway  100  may be used for purposes other than transporting skiers. For illustration purposes, the rope  110  is described herein as moving in a counter clockwise direction as indicated by the arrow  115 . However, the rope may move in a clockwise direction in other embodiments. 
     As described in greater detail below, the carriers  106  are detachable from the rope  110 . Detaching the carriers  106  enables them to move slowly so that people or cargo may be loaded onto and unloaded from the carriers  106 . As shown in  FIG. 1 , the carriers may proceed on a first track  120  and a second track  122  when they are proximate the first and second bull wheels  113 ,  114  and detached from the rope  110 . The first track  120  partially encompasses the first bull wheel  112  and the second track  122  partially encompasses the second bull wheel  114 . 
     As described in greater detail below, the rope  110  moves at a high rate of speed, which is typically too fast for people and cargo to be loaded onto or unloaded from the carriers  106 . When the carriers  106  move on the tracks  120 ,  122 , their velocities are slow enough for people and cargo to be loaded onto or unloaded from the carriers. It follows that the carriers  106  must accelerate and decelerate while they are located on the tracks  120 ,  122 . For illustration purposes, the first track  120  is defined as having three sections, a deceleration section  126 , an acceleration section  128 , and a loading/unloading section, which constitutes the remainder of the first track  120 . When the carriers  106  are in the loading/unloading section, their velocities are maintained relatively constant. In some embodiments, the carriers  106  move 20 to 25 times faster when they are attached to the rope  110  than when they are slowed to a speed to enable people and cargo to be loaded and unloaded. 
     As the carriers  106  enter the first terminal or move proximate the first track  120 , they detach from the rope  120 . At the time of detachment, the carriers  106  are traveling at the velocity of the rope  110 . The deceleration section  126  slows the carriers  106  to a velocity that enables people or cargo to be unloaded from and loaded into the carriers  106 . The deceleration must occur in a manner that does not injure people or damage cargo located on the carriers. For example, the deceleration should be smooth and the rate of deceleration should not be great enough to injure people or damage cargo traveling in the carriers  106 . The time the carriers  106  spend traveling in the load/unload section enables cargo and people to be loaded or unloaded from the carriers  106 . The acceleration section  128  accelerates the carriers  106  to the velocity of the rope  110 , so that they may be smoothly reattached to the rope  110 . As with the deceleration, the acceleration should be smooth and the rate of acceleration should not injure people or damage cargo traveling in the carriers  106 . The same process occurs with the second track  122 . 
     Having briefly described the operation of the ropeway  100 , the operation of the first track  120  will now be described.  FIG. 2  shows a side view of the first terminal  130 , which includes the first track  120 . The first track  120  includes a decoupling rail  136  that contacts a member (not shown) of the grips (not shown) of the carriers  106 ,  FIG. 1 . This contact causes the grips to open, which in turn causes the carriers  106  to detach from the rope  110  in a conventional manner. The decoupling rail  136  keeps the grips of the carriers  106  open during the period that the carriers are to be disconnected from the rope  110 . 
     The first terminal  130  includes a plurality of drive sheaves used to move the carriers  106  along the first track  120 . A first set of sheaves  138  contact the rope  110  and thus rotate by way of their contact with the rope  110 . This first set of sheaves  138  is sometimes referred to as power take off sheaves. A belt  140  or the like connects the power take off sheaves  138  to a plurality of drive sheaves  142  that serve to decelerate, accelerate, and move the carriers when they are located on the first track  120 . Therefore, the speed at which the drive sheaves  142  rotate is proportional to the speed of the rope  110 . It is noted that in other embodiments, the power take off sheaves  138  and the drive sheaves  142  may be driven by mechanisms not associated with or connected to the rope  110 . 
     For reference purposes, the speed of the carriers is fastest when they are located proximate a first end  150  of the first track  120  and slowest when they are located proximate a second end  152  of the first track  120 . It follows that the carriers move fastest just after they are released from the rope  110 . Likewise, the carriers  106  are also moving fastest just before they reattach to the rope  110 . In the embodiment of the first track  120  described in  FIG. 2 , the carriers  106  move slowest when they are proximate the second end  152  of the first track  120 . This is the location where people and/or cargo are loaded or unloaded from the carriers  106 . 
     In order to smoothly accelerate and decelerate the carriers, the speeds that the different drive sheaves  142  rotate are different between the first end  150  and the second end  152  of the first track  120 . The differing rotational speeds of the drive sheaves  142  accelerate or decelerate the carriers  106  in a manner that prevents damage to cargo or injury to people being transported by the carriers  106 . As described in greater detail below, at least some of the tires of the drive sheaves  142  described herein are deformable so that they will undergo minimal wear and provide smooth operation when they are accelerating and decelerating the carriers  106 . 
       FIG. 3  is provided to describe the acceleration of the carriers using the drive sheaves  142 . In the embodiment of  FIG. 3 , the carrier  169  is moving in the direction  170  and it is accelerating. For illustration purposes, three drive sheaves are shown in  FIG. 3  and are referred to individually as the first drive sheave  160 , the second drive sheave  162 , and the third drive sheave  164 . Tires  165  are outfitted onto the sheaves  142 . A first tire  166  is outfitted on the first drive sheave  160 , a second tire  167  is outfitted on the second drive sheave  162 , and a third tire  168  is outfitted on the third sheave  164 . 
     For illustration purposes, only the grip section  172  of a carrier  169  is shown in  FIG. 3 . The grip section  172  includes a friction plate  174  that contacts the drive sheaves  142 . The friction plate  174  is long enough so as to contact two of the drive sheaves  142 . It is noted that the friction plate  174  is in contact with a single drive sheave during longer periods than it is in contact with two drive sheaves. 
     Conventional tramways that use drive sheave to accelerate or decelerate carriers undergo wear and tear on the tires outfitting the drive sheaves. As a friction plate contacts drive sheaves rotating at different speeds, the drive sheaves slip relative to the friction plate, which is similar to skidding. The slipping wears the tires and creates excessive noise. 
     As described in greater detail below, the tires  165  on the drive sheave  142  described herein are slotted so as to be deformable. More specifically, the tires  165  are more easily deformable in one direction than the other and may be uni-directional. The deformability of the tires  165  either reduces or increases the friction or slippage between the friction plate  174  and the drive sheaves  142 , depending on the circumstances. As described in greater detail below, the reduced slipping of the faster drive sheave improves its driving force and reduces the wear on the tires  165  during acceleration and deceleration of the carriers  106 . The increased slipping of the slower drive sheave allows the faster drive sheave to accelerate or decelerate the carrier without having to fight the opposite forces resulting from the action of the slower drive sheave. In addition, the noise created by the interaction between the tires  165  of the drive sheave  142  and the friction plate  174  is also reduced. 
     An embodiment of a drive sheave  174  is shown in  FIG. 4 . It is noted that the drive sheave  174  is an example of the drive sheaves  142  of  FIG. 3 . Except for slots in the tire described in greater detail below, the embodiment of the drive sheave  174  described herein is similar to a conventional drive sheave having a solid tire mounted thereto. The embodiment of the drive sheave  174  includes an opening  176  that facilitates the mounting of the drive sheave  174  on an axle or the like. For references purposes, the drive sheave  174  includes a center point  180 , which is the center of rotation for the drive sheave  174 . Adjacent the opening  176  is a rigid rim  182 . 
     A tire  184  is mounted to the rim  182  in a conventional manner. The tire  184  corresponds to the tires  165  of  FIG. 3 . Except for the slots described herein, the tire  184  is a solid tire, meaning that it is not pressurized with air. The tire  184  includes an inner circumferential portion  186 , an outer circumferential portion  188 , and a middle circumferential portion  190  located between the inner circumferential portion  186  and the outer circumferential portion  188 . 
     A plurality of slots  200  extend through the middle circumferential portion  190 . Although slots are shown and described as extending through the middle circumferential portion  190 , other shaped holes may be used instead of slots. The slots  202  extend at an angle N from a radial line  202 , which extends through the center of the drive sheave  174 . In some embodiments, the angle N is approximately twenty-three degrees. However, the angle N may be changed depending on design characteristics, the material used for the tire  184  and the applications of the drive sheave  174 . The slots  200  enable the tire  184  to deform, which as described below, reduces the wear on the tires  184 . The deformation also increases or decreases driving force of the tire  184  on the friction plate  174 ,  FIG. 3 , of the grip  172 , depending on the circumstances. 
     With addition reference to  FIG. 3 , when the carrier  169  is propelled by the drive sheaves  142 , the speed of the carrier  169  is based on the fastest drive sheave contacting the friction plate  174 . This mechanism is described in greater detail below. In the embodiment of  FIG. 3 , the friction plate  174  is contacting the second drive sheave  162  and the third drive sheave  164 . More specifically, the second tire  167  and the third tire  168  are contacting the friction plate  174 . The carrier  169  is accelerating in the direction  170  and is, thus, being pulled or accelerated by the third drive sheave  164 . Therefore, the speed of the accelerating carrier  169  is governed by the speed at which the third drive sheave  164  rotates, because the third sheave  164  is the faster of the two. 
     As shown in  FIG. 3 , the tires  184  of the second drive sheave  162  and the third drive sheave  164  have deformed. The third drive sheave  164  is accelerating the carrier  169 , so it is applying a force F 1  in the direction  170 . The deformation of the tire  184  of the third drive sheave  164  has caused the diameter of the third tire  168  to increase proximate the friction plate  174 . As shown in  FIG. 3 , the angle N has decreased due to the force applied to the third tire  168  and the pliability of the third tire  168 . The deformation of the third tire  168  also creates a force F 2  that is perpendicular to the direction  170  and is applied to the friction plate  174 . It is noted that the greater the force F 2 , the greater the friction between a drive sheave (or its associated tire) and the friction plate  174 . 
       FIG. 3  illustrates the friction plate  174  being contacted by both the second drive sheave  162  and the third drive sheave  164 . As described above, the deformation of the third tire  168  has increased the friction between the third drive sheave  164  and the friction plate  174 . The deformation is due to the angle N of the slots  200  decreasing. The forces applied to the second drive sheave  162  cause the second tire  167  to deform in a manner that reduces its radius proximate the friction plate  174 . As shown in  FIG. 3 , because the second drive sheave  162  is rotating slower than the third drive sheave  164 , the angle N increases, which reduces the radius of the second tire  167  proximate the friction plate  174 . It follows that a force F 3  exerted on the friction plate  174  by the second drive sheave  162  in a direction parallel to the force F 2  is less than the force F 2 . Therefore, the force F 1  exerted by the third drive sheave  164  to move the carrier  169  in the direction  170  exceeds a counter force F 4  exerted by the slower second drive sheave  162 . Based on the above-described forces, the grip  172  and the carrier  169  move in the direction  170  and the speed is governed by the speed of the faster drive sheave, which is the third drive sheave  164 . 
     As described above, the speed of the carrier  169 , including the grip  172  and the friction plate  174 , is governed by the speed of the third drive sheave  164 , which is rotating faster than the second drive sheave  162 . The second tire  167  deforms, which reduces the force it exerts on the friction plate  174 . This reduction in force reduces the friction between the second drive sheave  162  and the friction plate  174 . Therefore, the second drive sheave  162  and the friction plate  174  may slide relative to one another. Because there is reduced friction between the friction plate  174  and the second drive sheave  162 , the wear on the second tire  167  is also reduced, which enables the second drive sheave  162  to last longer. 
     The same applies to the third drive sheave  164 . Because the force exerted by the second drive sheave  162  on the friction plate  174  is reduced, the there is less skidding and less wear on third tire  168  of the the third drive sheave  164 . The reduced skidding also reduces the noise associated with acceleration and deceleration of the carrier  169 . 
     The opposite of the described functions occur when the carrier  169  decelerates.  FIG. 5  shows a portion of a terminal used to decelerate the carrier  169 .  FIG. 5  shows three drive sheaves  200  that are referred to individually as the first drive sheave  204 , the second drive sheave  206 , and the third drive sheave  208 . The carrier of  FIG. 5  is decelerating in the direction shown by the arrow  212 . Because the drive sheaves  200  are used to decelerate the carrier  169 , the first drive sheave  204  rotates the slowest. The second drive sheave  206  rotates faster than the first drive sheave  204 . The third drive sheave  208  rotates faster than the second drive sheave  206 . 
     A first tire  220  is outfitted to the first drive sheave  204 . Likewise, a second tire  222  is outfitted to the second drive sheave  206  and a third tire  224  is outfitted to the third drive sheave  208 . The tires  220 ,  222 ,  224  are the same as the tire  184  described in  FIG. 4 . Only the second tire  222  and the third tire  224  are contacting the friction plate  174  in  FIG. 5 . 
     During deceleration, the speed of the carrier  169  is governed by the speed of the slowest sheave contacting the friction plate  174 . The second tire  162  has deformed so as to increase its radius of the second drive sheave  206  proximate the friction plate  174 . More specifically, the angle N of the second tire  222 , as referenced by the tire  184  of  FIG. 4 , has decreased as a result of the deceleration forces and its diameter has increased. The radius of the third drive sheave  208  proximate the friction plate  174  has decreased as a result of the deceleration forces and the increase of the angle N. 
     Based on the foregoing, the force F 1  exerted on the friction plate  174  by the second tire  222  is greater than the force F 2  exerted by the third tire  224 . Thus, the force F 3  exerted by the second drive sheave  206  to decelerate the carrier  169  is greater than the counter force F 2  exerted by the third drive sheave  208 . As result of the above-described forces, the speed of the carrier  169  is governed by the speed of the slower tire, which is the second tire  222 . The third tire  224  deforms as described above, which reduces the wear on the third tire  224  and the noise associated with its operation.