Abstract:
A roller guide for improving the movement of an elevator car on T-shaped guide rails. The roller has first and second wheels rotatably mounted on an elevator car and spring biased to rollably engage the sides of the nose portion of a T-shaped guide rail. A bumper is secured between the wheels to slidably engage the edge of the nose portion of the T-shaped guide rail and minimize lateral sway of the elevator car as it travels. The bumper also allows for the inventive roller guide to be used to replace the sliding guides of certain types of elevators without exceeding the maximum throat clearance. The roller guide, when installed, is dimensioned to meet the required safety tolerances of the elevator and allow for safe operation of the elevator safeties.

Description:
BACKGROUND OF THE INVENTION 
     Technical Field 
     The present invention relates to roller guides used in elevators. More particularly, the present invention relates to a simplified roller guide that allows an elevator system utilizing a sliding guide system to be upgraded while maintaining required safety tolerances. 
     The use of both sliding and roller guides on elevators is well known in the prior art. A sliding guide is a metal plate attached to an elevator. The metal plate has a notch removed from it. The nose portion of a T-shaped guide rail protrudes into the notched out area, and the edges of the notched-out area contact and slide along the nose portion of the guide rail. 
     Sliding roller guides cannot generally be used on dry guide rails because of the obvious effects of unbuffered metal-on-metal contact. Heat generated by the sliding of the guide on an unlubricated guide rail causes stresses to the metal which result in the accelerated wear of the system. Rapidly worn system parts increases both the costs of operating an elevator system and the down time due to maintenance. 
     To avoid wear on the guide rails of a sliding guide type elevator system, a lubricant is applied to the rails. However, application of the lubricant often results in an environmentally unfriendly condition. The lubricant is either a liquid or a liquid dispersed in a soap-based carrier. Any liquid applied to a vertical surface will run, and applying either type of lubricant to a vertical surface such as an elevator guide rail will result in the lubricant running down the rail surface to the ground. Contact of the lubricant with the ground poses a threat to the environment in that the lubricant may seep into the soil and contaminate a subsurface water supply. 
     Furthermore, a lubricant is typically applied to the guide rails of an elevator system with an automatic mechanical oiling device. Use of a mechanical device increases the chances for mechanical breakdown. Breakdown of any piece of mechanical equipment, especially one that is not critical to the operation of a system, translates into additional labor requirements and service and maintenance costs. 
     Sliding guides are also a source of excessive noise during operation of the elevator. Because of the metal-on-metal contact between the sliding guide and the elevator guide rail, even with a lubricant sliding guides are generally unnecessarily noisy. 
     An alternative to sliding guides is conventional rolling guides. Elevator manufacturers must comply with stringent safety requirements, and these safety requirements impose strict controls on the use of conventional roller guides. Among these safety requirements is a maximum throat clearance. The throat clearance is defined as the distance between the nose of the T-shaped rail and the surface of the roller or sliding guide opposing the nose of the rail. 
     Prior art conventional roller guides often use three rollers. Maeda describes such a system in U.S. Pat. No. 5,632,358. In that system, one roller contacts each side of the nose portion of the T-shaped guide rail while a third roller is situated perpendicularly to the first two and contacts the edge of the nose portion of the T-shaped rail. Installing this type of conventional roller guide in place of a sliding guide in certain types of elevators will increase the throat clearance beyond the maximum allowable distance making the safeties in certain elevators either inoperable or at least out of compliance with the required safety standards. 
     In upgrading an elevator system using sliding guides to one using roller guides, the maximum throat clearance between the T-shaped guide rail and the elevator safety must not be exceeded. What is needed is a way to upgrade certain elevator systems that currently utilize the inefficient, environmentally unfriendly, and noisy sliding guides to an elevator system that utilizes a rolling guide system without comprising passenger safety or comfort. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an elevator car roller guide having a pair of wheels mounted on an elevator car and being configured in a coplanar fashion and positioned to rollably engage the sides of a nose portion of a T-shaped guide rail. A bumper is also mounted on the elevator car. This bumper is positioned on the elevator car to maintain proper clearance between the nose of the T-shaped guide rail and the elevator safeties, thus ensuring proper functioning of the elevator safeties. In the event that the bumper contacts the edge portion of the nose portion of the T-shaped guide rail, the bumper slidably engages the T-shaped guide rail to prevent the elevator from swaying. 
     The elevator car roller guide may be mounted on a base plate that can be mounted on the elevator. 
     The wheels of the elevator car roller guide are spring-biased toward each other to engage the sides of the nose portion of the T-shaped guide rail. Flexible plates (leaf springs) fixed at their opposing ends may be used as springs to exert the force that biases the wheels toward each other. Alternately, a plurality of flexible plates can be stacked and used to spring-bias each wheel. 
     The ends of each of the flexible plates may be fixed to a pair of support members. These support members may be fixed directly to the elevator car, or they may be fixed to the base plate that is fixed to the car. 
     The bumper may also be secured to the base plate at a point intermediate the first and the second wheel and positioned to sidably engage the nose portion of the T-shaped guide rail should contact between the bumper and the guide rail occur. The invention also contemplates a polymeric coating disposed on the bumper in order to reduce the friction generated during the contact of the bumper with the T-shaped guide rail. In the preferred embodiment, the polymeric coating would be polytetrafluoroethane (PTFE). 
     The axles that rotatably support the wheels may be bolted or welded or otherwise affixed to the springs. Furthermore, the axles may be mounted across the holes cut into the springs. If the spring constitutes a plurality of plates stacked upon each other, the plate situated on either end of the stack can be configured to be radially contoured around the axle. 
     The wheels of the present invention may be fabricated from a variety of materials. These materials include, but are not limited to, rubbers, urethanes, or any type of polytetrafluoroethane-coated material. The rubbers may be natural or synthetic, and the preferred urethane would be a polyether-based urethane. Both rubbers and urethanes provide for less noise during operation than do most other types of material. Alternately, a plurality of wheels can be mounted on a plurality of springs to engage each side of the nose portion of a T-shaped guide rail. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring now to the drawings wherein like elements are numbered alike in the several figures: 
     FIG. 1 is a perspective view of a rolling guide of the invention situated on a guide rail; 
     FIG. 2 is a perspective view of the rolling guide of the invention; 
     FIG. 3 is a perspective view of a roller of the rolling guide of the invention; 
     FIG. 4 is a side view of a spring of the invention having two leaves; 
     FIG. 5 is a perspective view of slots on a support arm as the tabs of a leaf spring are inserted into the slots; 
     FIG. 6 is a side view of the rolling guide; and 
     FIG. 7 is a plan view of the rolling guide, as it would be situated on a guide rail. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The inventive roller guide is shown in FIG. 1. A roller guide  10  is illustrated, as it would be seated on a T-shaped guide rail. Roller guide  10  is secured to an elevator car. Rollers  12  and  14  are mounted on roller guide  10 . Rollers  12  and  14  rollably engage the opposing sides of the nose portion of a T-shaped guide rail to roll freely on the guide rail as the elevator ascends and descends an elevator shaft. 
     Referring to FIG. 2, roller guide  10  is depicted in greater detail. Roller guide  10  contains roller  12  mounted on an axle  16 . Roller  12  is freely rotatable on axle  16 . The ends of axle  16  are secured to the opposing sides of a cutout portion in the center of a leaf spring  18 . Each end of leaf spring  18  is secured to each member of a pair of support members  20 . Support members  20  are secured to a base  28 , and base  28  is installed on an elevator car (not shown). 
     Second roller  14  is mounted on a second axle  22 . Roller  14  is freely rotatable on axle  22 . The ends of axle  22  are secured to the opposing sides of a cutout portion in the center of a second leaf spring  24 . Each end of leaf spring  24  is secured to each member of a second pair of support members  26  in the same manner as leaf spring  18  is secured to support members  20 . Second pair of support members  26  is secured in a similar fashion as support members  20  are to base  28 . Rollers  12  and  14  are dimensioned to be similar to each other, and are positioned to be coplanar and symmetrical with respect to each other when mounted on base  28 , as shown in FIG.  7 . 
     Roller  12  is illustrated in greater detail in FIG.  3 . Roller  14  is similarly configured. Roller  12  is essentially a wheel comprising of a hub portion  13  that houses wheel bearings and supports a tire  17 . Hub portion  13  has a center hole  15  for accommodating axle  16 . Tire  17  is mounted on the outer rim of hub portion  13 . Tire  17  is fabricated from any suitable material that is well known to those skilled in the art. The preferable materials for the tires are “soft” materials such as rubbers or urethanes. As is well known in the art, a polyether-based urethane is a better choice for tire  17  than a polyester-based urethane because the latter type tends to be more susceptible to deterioration as a result of heat and moisture. Furthermore, tires fabricated from rubbers and urethanes generate less noise than “hard” materials like steel do. Tires can also be fabricated from polytetrafluoroethane or a similar material. 
     Leaf spring  18  is illustrated in more detail in FIG.  4 . Leaf spring  24  is similarly configured. Leaf spring  18  consists of a series of stacked plates  11  that are secured together with bolts and nuts or a similar securement means. Disposed on each end of leaf spring  18  are tabs  23 . The bottom plate of leaf spring  18  is configured to accommodate the ends of axle  16 , upon which roller  12  is mounted. Various methods exist for connecting an axle to a leaf spring. For example, a “U” bolt may be clamped around the axle and the ends of the “U” bolt may be bolted into the bottom leaf of the leaf spring. Alternately, the bottom leaf of the leaf spring could be contoured around the axle, and the contour could hold the axle in place against the second leaf of the leaf spring up from the bottom. These, as well as other methods, are well known in the art. 
     In the preferred embodiment, leaf springs  18  and  24  are connected to support member  20  and  26  using tabs and slots. Referring now to FIG. 5, one member of pair of support members  20  is illustrated. The second member of the pair of support members  20 , as well as both members of the pair of support members  26 , is similarly configured. The protruding arm of support member  20  contains slots  21 . Slots  21  are positioned and dimensioned to accommodate tabs  23  disposed on each end of leaf spring  18 . Tabs  23  on one end of a leaf spring are inserted into slots  21  on one member of a pair of support members by aligning tabs  23  with slots  21  and moving leaf spring  18  in the direction of arrow  25 . Inserting tabs  23  on the opposing end of a leaf spring into slots  21  on the second member of a pair of support members biases the leaf spring. In order to be properly mounted, once tabs  23  are inserted into slots  21  on their respective support members, leaf springs  18  and  24  are biased toward each other, as shown in FIG.  6 . In order to minimize noise and wear, the spring rate on leaf springs  18  and  24  should exert the minimum amount of pressure necessary to hold rollers  12  and  14  against the sides of the nose portion of a T-shaped guide rail. 
     Support members  20  and  26  are generally secured to base  28  using bolts  30  or a similar means of securement. Cushions made of rubber, polytetrafluoroethane, or some similar material can be seated between support members  20  and  26  and base  28  in order to avoid metal-on-metal contact, thus reducing the chances of stressing the parts. Alternately, support members can be welded directly onto base  28 . 
     If rollers  12  and  14  are properly aligned, only an outer edge  19  of tire  17  will maintain contact with the sides of the nose portion of a T-shaped guide rail. Proper alignment will ensure minimal wear of tire  17 . Any misalignment of the rollers will result in uneven tire wear that will cause stresses on the wheels, axles, leaf springs, and support members. Such stresses may lead to premature aging of the parts and, consequently, increased operating costs. In order to ensure proper alignment of the rollers, it is imperative that axles, leaf springs, and support members are properly attached to each other, and that support members are properly secured to base  28 . 
     Furthermore, leaf springs  18  and  24  should be similarly tensioned. Even if rollers  12  and  14  are properly aligned, uneven tensions on leaf springs  18  and  24  will result in one roller being biased against the side of the nose of the T-shaped guide rail more than the other roller. Such a situation will result in one roller wearing faster than the other. Moreover, leaf springs  18  and  24  should be tensioned to exert only the minimum amount of pressure necessary on the guide rail to maintain contact with the guide rail and to prevent the elevator car from swaying between the rollers. Maintaining such contact will also minimize noise generated by the movement of the rollers  12  and  14  along the guide rail. 
     FIG. 6 illustrates a bumper  32  situated between rollers  12  and  14 . Bumper  32  is positioned to be midway between roller  12  and  14 . Bumper  32  is secured to base  28  with bolts  34 , or is welded onto base  28 , or is attached with some similar method of securement. Alternately, bumper  32  can be cast from the same mold as base  28  thus eliminating the need for bolts  34 , welding, or any method of attachment. 
     FIG. 7 is a top view of roller guide  10 , as it would be situated on T-shaped guide rail  36 . Guide rail  36  has a nose portion  38 . The distance between the surface of nose portion  38  and the surface of bumper  32  is defined as a throat clearance  40 . During operation of an elevator, irregularities and undulations along the length of guide rail  36  cause throat clearance  40  to vary. Bumper  32  may make contact with the nose portion  38  during ascent and descent of the elevator as it encounters these irregularities and undulations along the length of guide rail  36 , thus preventing the elevator car from swaying too far from one side to the other side. 
     In the prior art, a third wheel is situated where bumper  32  is situated in the present invention. Replacement of this third wheel with bumper  32  allows sliding guides on certain types of elevators to be replaced with roller guides while still maintaining an industry required throat clearance  40 . If throat clearance  40  is exceeded, the rollers in a conventional safety may not sufficiently brake the elevator. 
     While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation.