A removable teeter lever and gear assembly arrangement ( 100 ) is provided for use with a pneumatic cylinder/differential engine for operating vehicle doors. The arrangement comprises a teeter lever ( 16 ), which is associated with the vehicle doors, a gear assembly ( 17 ) having a toothed portion and an output shaft ( 20 ) extending therethrough, and at least one securing member for removably securing and/or retaining the teeter lever ( 16 ) and the gear ( 17 ) on the output shaft ( 20 ). The securing member comprises at least one retention key ( 18   a   , 19   a ) which allows the arrangement to be easily disassembled for maintenance and/or replacement thereof.

CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 60/927,325, filed May 3, 2007, and entitled “Output Shaft, Teeter Lever and Pinion Gear Arrangement for Pneumatic Differential Engine”, the entire disclosure of which is incorporated herein in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates, generally, to a teeter lever for pneumatic cylinder/differential engine power-operated doors and, more particularly, to a removable teeter lever and removable gear for a pneumatic cylinder/differential engine for connecting an output shaft to connecting rods and, thence, to door panels of a mass transit vehicle. 
         [0004]    2. Description of Related Art 
         [0005]    Pneumatic cylinders have been utilized in mechanical systems to convert compressed air into linear reciprocating movement for opening and closing doors of passenger transportation vehicles. An example of this type of door actuating system is shown in U.S. Pat. No. 3,979,790. 
         [0006]    Typically, pneumatic cylinders used in this environment consist of a cylindrical chamber, a piston and two end caps hermetically connected to the cylindrical chamber. The end caps have holes extending therethrough to allow the compressed air to flow into and out of the cylindrical chamber, to cause the piston to move in a linear direction, and to apply either an opening or closing force to the vehicle door. 
         [0007]    Pneumatic cylinder/differential engine systems have also been designed for opening and closing doors of passenger transportation vehicles. Examples of these systems are shown in U.S. Pat. Nos. 4,231,192; 4,134,231; and 1,557,684. 
         [0008]    As illustrated in  FIG. 1 , a known pneumatic differential engine consists of a large pneumatic cylinder  1  and a small pneumatic cylinder  2  attached to a housing  3 . The large pneumatic cylinder  1  is closed at one end by a large cap  48 . The small pneumatic cylinder  2  is closed at one end by a small cap  50 . A large piston  4  and small piston  5  are installed inside of the cylinders  1  and  2 , respectively. Pistons  4  and  5  are attached to the toothed rack  6  which is engaged with the gear  7 . The gear  7  is permanently attached to the shaft  8 , so that linear movement of the pistons  4  and  5  is converted into rotational movement of the output shaft  8 . The teeter lever  9 , as shown in  FIG. 2 , is welded to the end of the output shaft  8 , and is connected by the rods  10 ,  11  and levers  12 ,  13  to the vertical shafts and arms linked to the vehicle door panels (not shown). As a result, rotational movement of the output shaft  8  causes rotational movement of the teeter lever  9  which causes opening and closing of the vehicle doors. 
         [0009]    The small pneumatic cylinder  2  is constantly connected to a reservoir of compressed air, through opening  52  in small cap  50  so that a positive pressure is constantly applied to the surface  54  of the small piston  5  facing small cap  50 . The large pneumatic cylinder  1  is connected to a three-way valve via opening  49 , which provides connections to a source of compressed air during a door closing mode or to an exhaust member for exhausting the air from the large cylinder  1  during a door opening mode. The spring system  14  and sealing disk  15  provide cushioning of the movement of the large piston  4  at the end of the door opening stroke. 
         [0010]    During a door closing mode, the air is admitted to large cylinder  1  through the three-way valve, as discussed above, and pressure is applied to the surface  56  of large piston  4  facing the large cap  48 . Because of the difference in the surface area of large piston  4  and small piston  5 , the application of air pressure within the large cylinder  1  causes the pistons  4  and  5  to move toward small cap  50  or to the right (as shown). Linear movement of the rack  6  is converted into counter-clockwise rotation of the gear  7  and output shaft  8  and, consequently, rotation of the teeter lever  9 , which causes the doors to close. 
         [0011]    During a door opening mode, the large cylinder  1  is connected to the exhaust valve of the three-way valve to allow the air in this large cylinder  1  to flow out due to pressure acting on the surface of the small piston  5  in small cylinder  2 . As a result of this pressure differential, pistons  4  and  5  move toward large cap  48  or to the left (as shown), rotating the gear  7 , shaft  8 , and teeter lever  9  in the clockwise direction, as viewed in  FIG. 1 . The movement of the piston  4  toward the large cap  48  causes compression of the spring system  14 , and linear movement of the sealing disk  15  toward a cushioning chamber  58 . 
         [0012]    Cushioning at the end of the door opening mode occurs as the disk  15  seals the exhaust opening  59  of cushioning chamber  58 . The air flow out of the cylinder is restricted to a small orifice (not shown), slowing the movement of the pistons  4  and  5 . This slowed movement allows the doors to continue opening at a slow speed (cushioning) until fully opened. 
         [0013]    In the present engine design, the teeter lever  9  is welded to the output shaft  8  and the pinion gear  7  is secured to the output shaft by a roll pin inserted into a hole extending through the hub of the pinion gear and the shaft. This hole is drilled as a single operation with the pinion gear  7  already positioned on the welded shaft  8  and teeter lever  9  assembly. Once this hole is drilled, the pinion gear  7  and the welded shaft  8  and teeter lever  9  assembly become a matched set, inasmuch as the angular relationship of the teeter lever  9  to the pinion teeth determines the angular synchronization of the door panels to the position of the piston  4 ,  5  and rack  6  assembly within the differential engine. 
         [0014]    In order to remove the teeter lever  9  from the engine, the engine must be disassembled and the roll pin driven out of the gear  7  and the shaft  8  and teeter lever  9  assembly. If either the pinion gear  7  or the teeter lever  9  and shaft  8  assembly is damaged, all of these components must be replaced in order to restore the differential engine to operation. 
         [0015]    It can be observed from the design of the existing differential engine, that replacement of either the teeter lever  9  or the pinion gear  7  requires that the entire mechanism be disassembled. Neither the pinion gear  7 , nor the shaft  8  and teeter lever  9 , are interchangeable. Consequently, these components must be replaced as a set. Moreover, the pneumatic differential engine, once assembled, becomes unique to a specific door configuration, and differential engines cannot usually be interchanged between different door configurations. 
         [0016]    These factors impose both labor and material expense burdens upon the maintenance of door systems equipped with the present pneumatic differential engine. 
       SUMMARY OF THE INVENTION 
       [0017]    It is therefore an object of the invention to provide a removable teeter lever/gear assembly arrangement for pneumatic cylinder/differential engine power-operated vehicle doors. It is a further object of the invention to provide a teeter lever/gear assembly arrangement which can be easily removed and replaced without disassembling the differential engine. It is still another object of the invention to provide a teeter lever/gear assembly wherein replacement of individual parts is easy and cost effective. 
         [0018]    The present invention comprises a removable teeter lever and gear assembly arrangement for use with pneumatic cylinder/differential engine power-operated vehicle doors. The arrangement comprises a teeter lever which is associated with the vehicle doors via rods and levers to the vertical shafts and arms linked to the vehicle door panels, such that rotation of the teeter lever causes opening and closing of the vehicle doors. A gear assembly having a toothed member and an output shaft extending therethrough are provided such that rotational movement of the gear assembly is caused by actuation of the pneumatic cylinder/differential engine. A securing member in the form of at least one retention key cooperating with at least one keyway formed in the output shaft is provided for removably securing and/or retaining the teeter lever onto the output shaft and for removably securing and/or retaining the gear onto the output shaft. 
         [0019]    These and other features and characteristics of the present invention, as well as the method of operation and functions of the related elements of structures and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  shows a schematic side view of the pneumatic cylinder/differential engine of the prior art for controlling power operated doors of a vehicle; 
           [0021]      FIG. 2  shows a perspective view of the teeter lever/gear assembly arrangement of the prior art mounted on a vehicle; 
           [0022]      FIG. 3  shows a partial perspective view of the teeter lever/gear assembly arrangement in accordance with the present invention; and 
           [0023]      FIG. 4  shows a perspective view of the teeter lever/gear assembly arrangement of  FIG. 3  mounted on a vehicle. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    For purposes of the description hereinafter, the terms “upper”, “lower”, “right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, “lateral”, “longitudinal” and derivatives thereof shall relate to the invention as it is oriented in the drawing figures. However, it is to be understood that the invention may assume various alternative variations, except where expressly specified to the contrary. It is also to be understood that the specific devices illustrated in the attached drawings, and described in the following specification, are simply exemplary embodiments of the invention. Hence, specific dimensions and other physical characteristics related to the embodiments disclosed herein are not to be considered as limiting. 
         [0025]    Reference is now made to  FIG. 3 , which shows the removable teeter lever/gear assembly arrangement of the present invention, generally indicated as  100 , for use with a pneumatic cylinder/differential engine for opening and closing vehicle doors. As illustrated in  FIG. 4 , the removable teeter lever  16  is connected by the rods  40 ,  41  and levers  42 ,  43  to the vertical shafts and arms linked to the vehicle door panels (not shown). Referring back to  FIG. 3 , actuation of the pneumatic cylinder/differential engine during a door opening or closing operation causes a gear  17  to rotate with respect to a toothed rack  60 , which causes rotation of an output shaft  20 . This rotational movement of the output shaft  20  causes rotational movement of the teeter lever  16  which results in opening and closing of the vehicle doors. 
         [0026]    As illustrated in detail in  FIG. 3 , the gear  17  is removably connected with a first portion of the output shaft  20  through the use of a first retention key  18   a , which cooperates with a keyway  18   b  in the output shaft  20 . The teeter lever  16  is removably connected with a second portion of the output shaft  20  through the use of a second retention key  19   a , which cooperates with a second keyway  19   b  in the output shaft  20 . The first and second retention keys  18   a ,  19   a  can comprise any well-known key design capable of attaching rotating circular members with one another. One example of retention keys  18   a ,  19   a , which can be used with the present invention are Woodruff keys, which are removable keys that fit in a matching keyway cut into a shaft, leaving a protruding tab. The tab mates with a matching slot on a device mounted flush upon the shaft; e.g., a pulley, thus preventing the device from freely rotating about the shaft. Typically, a Woodruff key is a semicircular shaped or half-moon key that fits in a semicircular shaped matching keyway. 
         [0027]    The gear  17  and output shaft  20  are prevented from axially moving within the arrangement  100  by holding members such as retaining rings as discussed in detail below. The gear  17  is prevented from moving axially on the output shaft  20  by a first pair of retaining rings  21   a ,  21   b  positioned on either side of the output shaft  20 . The output shaft  20  is secured against axial motion relative to the gear housing  30  by a second pair of retaining rings  25   a ,  25   b  that bear against lubricant impregnated bushings  26  pressed into the sidewalls  28  of the gear housing  30 . Retaining rings  21   a ,  21   b ,  25   a  and  25   b  preferably comprise split ring retaining rings which are seated within slight indentations  36  in the output shaft  20 . 
         [0028]    The teeter lever  16  is also secured against axial movement with respect to the output shaft  20  by a removable axial securing member, generally indicated as  22 . This axial securing member  22  can comprise any well-known securing member which may be readily removed from the arrangement  100 , such as a screw  23  and washer  24 . The screw  23  is threaded through a first aperture  32  in the teeter lever  16 , which is aligned with a second aperture  34  in the output shaft  20 . 
         [0029]    The keyways  18   b ,  19   b  in the output shaft  20  and the pinion gear  17  are manufactured with a standard angular relationship to one another. The position of the keyway  19   a  in the teeter lever  16  can be varied to adapt the final arrangement  100  to different door configurations. 
         [0030]    Disassembly of the teeter lever  16  and gear assembly arrangement  100  occurs as follows. Removal of the teeter lever  16  from the arrangement  100  is achieved by simply removing screw  23  holding the teeter lever  16  to the output shaft  20 . This allows the teeter lever  16  to be easily slid off the output shaft  20  and retention key  19   a . The gear  17  may be removed from the arrangement without removing the teeter lever  16 . This is achieved by a multiple-step process. Screws  39 , which attach the cover portion  38  to the gear housing  30 , are loosened and removed so that the cover portion  38  is removed. The split ring retaining member  25   a , located adjacent housing  30  at the end opposite from the teeter lever  16 , is removed from the output shaft  20 . Then the “doors fully closed” target, not shown, is removed from the output shaft  20 . Retaining ring  21   a , adjacent gear  17 , retaining ring  21   b , and adjacent gear hub extension  42 , are removed from the output shaft  20 . The output shaft  20 , including retention key  18   a , can now be slid out from the interior portion of the gear  17  and the gear  17  can be lifted out of the gear housing  30  for repair and/or replacement thereof. 
         [0031]    The present invention provides a differential engine wherein the teeter lever  16  and gear  17  can be easily removed and replaced. This significantly decreases the maintenance and/or labor required to correct a failure of the teeter lever  16  or of the pinion gear  17 . 
         [0032]    Although the invention has been described in detail for the purpose of illustration based on what is currently considered to be the most practical and preferred embodiments, it is to be understood that such detail is solely for that purpose and that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover modifications and equivalent arrangements that are within the spirit and scope of this description. For example, it is to be understood that the present invention contemplates that, to the extent possible, one or more features of any embodiment can be combined with one or more features of any other embodiment.