Patent Publication Number: US-6659018-B1

Title: Stop mechanism with dual pawls for gear operated door

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to the art of railway cars. More particularly, the invention pertains to anti-spin or stop mechanisms for gear operated doors for railway cars. 
     The invention is particularly applicable to rectangular metal doors of the type used on railway freight cars and will be particularly described with reference thereto. However, it will be appreciated by those skilled in the art that the invention has broader applications and is adaptable to use with doors of other types and in other environments. 
     Rectangular metal doors of a known type used in railway cars include a generally rectangular frame typically comprised of top, bottom, and horizontal stiffeners, and opposed side members. Metal panels are secured to these frame members for completing the basic door construction. In most conventional railway cars, the frame members and metal panels are riveted and/or welded together. 
     Railway car doors are typically classified as either sliding doors or plug doors. Of the two, sliding doors are less complex, having a door configured to slide back and forth within a side panel of a railway car to selectively open and close an opening defined therein. Plug doors are more complex in that they are configured to first move laterally out of the opening defined in a railway car and then move longitudinally along a track disposed adjacent the railcar side panel. 
     Plug doors to be mounted on the side of a rail car include a series of panels or sheeting reinforced by horizontally disposed channels at the top, bottom and/or intermediate portions of the door. A pair of vertically oriented elongated support members such as pipes, rods or bars are configured to support the door on the railcar. The support members are typically provided with upper and lower cranks attached to the terminal end areas thereof which serve as lever arms for laterally moving the door into and out of the railcar door opening. Upon actuation of a driving mechanism, such as a manually operated gear assembly, the support members are rotated for causing a corresponding rotation of the cranks. Rotation of the cranks, in turn, draws the door laterally outward from the opening until the door is supported on a track disposed adjacent to the side of the railcar. The door is movably supported on the track by roller hangers which enable the door to slide longitudinally along the side of the railcar. 
     One problem that occurs when the door is completely closed is that if a load falls against the inside wall of the door, an operating lever which controls movement of the door may spin and possibly move the door into an unwanted slightly or fully opened position. 
     A second problem occurs when the door is in the fully opened position. The support members have a tendency to rotate, thus causing the door to drift back into the side of the railcar. If this occurs, the ability of the door to slide longitudinally along the track may be inhibited. Furthermore, the door or the side of the railcar may become damaged because of the drifting action. 
     Another problem that occurs with existing railway car doors is that only one pawl is used to engage a ratchet to prevent rotation. Under certain conditions, the operating lever could still spin in spite of the pressure of a ratchet and pawl if the lever releases too fast and does not allow the pawl to engage the ratchet. This condition would occur if large forces were tending to push the door open and the operator released the lever while a rotational force was operating thereon with the pawl positioned on a peak of a ratchet tooth. 
     Accordingly, it has been considered desirable to develop an anti-spin arrangement for a gear operated door which would overcome foregoing difficulties and others while providing better and more advantageous overall results. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, an anti-spin or stop mechanism with dual pawls for a gear operated planar door is advantageously provided. The door is of the type having at least one elongated support member rotatably mounted thereto and which is selectively rotated through a drive mechanism by an operating mechanism to achieve door opening and closing. The operating mechanism includes an actuating member, such as a handle, lever or the like, which facilitates selective rotation of the at least one support member. An anti-spin mechanism operatively communicates with the operating mechanism to prevent undesired spinning of the operating mechanism which might otherwise allow the door to shift in an uncontrolled manner from one position to another. 
     According to another aspect of the invention, the anti-spin or stop mechanism includes a pair of stop members configured and positioned so that one or the other of the stop members will always be in stopping relation to the operating mechanism to thereby prevent undesired spinning of the operating mechanism. 
     According to yet another aspect of the invention, the anti-spin or stop mechanism includes a rotatable ratchet wheel engageable by stop members to prevent rotation of the operating mechanism in a manner otherwise allowing for undesired movement of the door from a closed toward an opened position. 
     In accordance with a more limited aspect of the invention, the operating mechanism and ratchet wheel are mounted on a common shaft for joint rotation during door opening and closing, and the pair of stop members comprise first and second pawls positioned such that one pawl may always be in stopping engagement with a toothed area on the periphery of the ratchet wheel. 
     In accordance with still another limited aspect of the invention, the first and second pawls are mounted on a common pivot point or shaft. 
     According to a further aspect of the invention, an anti-spin/anti-drift or stop mechanism is advantageously provided and includes a pair of rotatable ratchet wheels each engageable by stop members to prevent either undesired spinning of the operating mechanism or undesired drifting of the railcar door. 
     A principal advantage of the present invention resides in a provision of an anti-spin or stop arrangement which prevents an operating lever of a door from spinning if a load falls or is otherwise applied against an inside surface of the door. 
     Another advantage of the invention is found in an anti-spin or stop arrangement which does not impede or interfere with normal door operation. 
     Yet another advantage of the invention resides in the provision of an anti-spin or stop arrangement which is relatively low in cost. 
     Yet still another advantage of the invention is the provision of an anti-spin or stop arrangement which is easy to manufacture and retrofit to existing doors. 
     Still other benefits and advantages of the invention will become apparent to those skilled in the art upon a reading and understanding of the following detailed specification. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may take physical form in certain parts and arrangement of parts, preferred embodiments of which will be described in detail in this specification and illustrated in the accompanying drawings which form a part hereof and wherein: 
     FIG. 1 is front elevational view of a plug type railway car door which includes an anti-spin or stop arrangement formed in accordance with a preferred embodiment of the present invention; 
     FIG. 2 is a front elevational view of a portion of the railcar door illustrating a drive gear mechanism and the anti-spin arrangement; 
     FIG. 3 is a side elevational view of the dual pawl mechanism of the present invention; 
     FIG. 4A is a top plan view of a first pawl of the dual pawl mechanism of FIG. 3; 
     FIG. 4B is a side elevational view of a first pawl of the dual pawl mechanism of FIG. 3; 
     FIG. 4C is a side elevational view of a second pawl of the dual pawl brake mechanism of FIG. 3; 
     FIG. 5 is a front elevational view of a plug type railway car door which includes an anti-spin and anti-drift arrangement formed in accordance with a second preferred embodiment of the invention; 
     FIG. 6A is an enlarged elevational view of the anti-spin and anti-drift mechanism shown in FIG. 5; and, 
     FIG. 6B is a cross-sectional view taken along lines A—A of FIG.  6 A. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings wherein the showings are for purposes of illustrating a preferred embodiment of the invention only and not for purposes of limiting same, FIG. 1 shows a plug-type railcar door  10  of the type with which the subject invention is particularly useful disposed in an opening  12  in a railcar. The door includes a wall of paneling or sheeting  14  reinforced with horizontal channels  16  extending across top, bottom and intermediate portions of the sheeting. Paneling  14  is typically fabricated from metal. 
     The door  10  is supported by elongated support members  18 , such as pipes, rods or tubes, which are disposed along the vertical height of the door. These support members are rotatably mounted to the horizontal reinforcing channels  16  at the outer surface of the door by brackets or fulcrums  20  located adjacent to the door side edges for retaining the support members in a vertical disposition. 
     Each of the support members  18  includes a first or upper end having a first or upper crank  22   a  and a second or lower end having a second or lower crank  22   b  operatively connected thereto. The cranks  22   a ,  22   b  serve as lever arms which enable the door to move laterally into and out of the railcar opening  12 . The door  10  is adapted to move laterally out of the door opening toward the outside of the railcar until the door is supported on a track  24  disposed adjacent the railcar sidewall. The door is then moved longitudinally along the side of the car on track  24  to effectively expose the door opening to facilitate car loading and unloading. Thus, when it is in the unplugged position, the door is movably supported on the track by roller hangers  26  which are attached to the ends of the lower cranks  22   b  for guiding the door in its longitudinal movement. 
     Upper ends of the cranks  22   a  include pins with rollers  28  mounted for longitudinal movement within and along a top retainer rail or longitudinal retainer member  30  having a generally U-shaped cross section. Retainer  30  is mounted along the top of the door opening  12  and functions to restrain the top of the door and prevent undesired displacement thereof. Rollers  28  move along an inner surface of a downwardly depending front flange  32  of the top retainer rail. The front flange extends longitudinally and is located inside an outer edge of a laterally outward extending lower flange  34  spaced from and located below the front flange. Horizontal connecting portions  36 ,  38  of upper cranks  22   a  extend through the space between front flange  32  and lower flange  34 , and connect the upper end of the cranks and the rollers  28  with the upper end of the support members  18 . The rollers  28  are disposed behind the retainer rail  30 . The combination of the rollers and the retainer rail acts to restrain the top of the car door as it is moved longitudinally along the track  24 . 
     As is well understood in the art, rotation of the support members  18  causes a corresponding outward rotation of the cranks  22   a ,  22   b  to sequentially draw the door  10  laterally outward from the door opening. An operating mechanism  50  is provided on the door for controlling the rotation of the support members  18  and the cranks in a manner well known in the art. An activating member  52  in the form of a lever or handle has a mounting opening  53  therethrough for securing same to the door operating mechanism. 
     Referring to FIG. 2, a drive mechanism  60  preferably comprises a gear operated system or assembly  62  operatively connected to and actuated by actuating member or lever  52 . The gear assembly includes a rotatably mounted gear segment  64  and two pivotally mounted operating cams  66 ,  68 , each of which is housed in and positioned between a bearing plate  70  and a cover plate  72 . The bearing plate  70  is mounted on a lower portion of the door sheeting  14 , and the cover plate is bolted or otherwise secured to the bearing plate in laterally spaced apart relation thereto. 
     A pair of transmission members  54 , such as pipes, rods or tubes, are connected at first ends to the gear segment  64  and at second ends to an associated support member  18 . By rotating the lever or handle  52  counterclockwise, gear  64  is rotated clockwise which, in turn, pivots operating cams  66 ,  68 . Rotation of the gear causes the transmission members  54  to rotate the support members  18  and cranks  22   a ,  22   b  and thereby effect selective lateral movement of the door outwardly from the opening  12  to the outside of the railcar, thereby unsealing or unplugging the railcar opening. When the lever or handle  52  is rotated clockwise, the gear segment rotates counterclockwise for moving the door into the railcar opening. The door thus seals or plugs the opening. 
     Referring to FIGS. 1,  2 , and  3 , an anti-spin mechanism  130  is disposed intermediate the bearing and cover plates  70 ,  72  and is operatively engaged during closing of the door. The anti-spin mechanism includes an operating shaft  132 . Lever or handle  52  includes an opening  53  extending therethrough for allowing the lever to be received on the operating shaft  132 . A locking or retaining device (not shown) securely retains the lever on the operating shaft and prevents any relative rotation therebetween. 
     Referring particularly to FIG. 3, the anti-spin mechanism includes a ratchet gear or wheel  140  which is positioned on and secured to the shaft  132  intermediate the cover and bearing plates. This ratchet wheel has a plurality of generally radial outwardly extending teeth  142  at spaced intervals circumferentially therearound. Each tooth has a leading edge  144  and trailing edge  146 . 
     A first pawl  150  is pivotally interposed between the cover and bearing plates by means of a pivot pin  151  extending through a mounting hole or opening  152  therein. Referring also to FIG. 4A, the pawl  150  has a first end  156  and a second end  158  extending radially outward from opening  152 . First end  156  has a tab or extension  160  as best shown in FIGS. 4A and 4B which is configured and dimensioned to engage the teeth  142  of the ratchet wheel. Such engagement is best shown in FIG.  3 . 
     Continuing with reference to FIG. 3, and with reference also to FIG. 4B, a second pawl  170  includes a mounting hole or opening  172  for pivotally mounting the second pawl in a side-by-side relationship with first pawl  150  on pivot pin  151 . Similar to the first pawl, pawl  170  has a first end  174  and a second end  176  extending radially of hole  172 . Likewise, first end  174  has an extension or tab  178  configured and dimensioned to engage the teeth  142  of the ratchet wheel. 
     Pawl second ends  158 ,  176  are designed to have a greater weight or mass than pawl first ends  156 ,  174 , respectively. As a result tabs  160 ,  178  are continuously urged toward engagement with teeth  142  of ratchet wheel  140 . Other means such as springs and the like could also be used to achieve this same result. 
     The pawls  150 ,  170  allow the ratchet wheel to rotate freely during closing of the door when the operating lever  52  and ratchet wheel  140  are rotated clockwise in the view of FIG.  2 . As best shown in FIG. 4, the radial length of first end  156  of the first pawl is greater than the length of first end  174  of the second pawl. This difference in length staggers tabs  160 ,  178  to ensure that one of the tabs is disposed in engagement with a ratchet wheel tooth substantially at all times. 
     To close the door, the lever  52  is rotated clockwise, thus rotating the ratchet wheel  140  clockwise. One of the tabs  160 ,  178  of either pawl  150  or pawl  170  engages the leading edge  144  of a ratchet tooth while the other of the tabs engages a peak  180  of a ratchet tooth. The tab engaging the leading edge slides along the edge until it contacts the peak of the tooth. Meanwhile, the other tab slips off of the peak of a ratchet tooth and engages a leading edge of the next adjacent tooth. As a result, one of the tabs is at all times in contact with a tooth leading edge. 
     During closing of the door, the lever or handle  52  is rotated one or more turns, thus rotating the shaft  132  and the gear segment  64  thus closing the door. If a load shifts or is otherwise applied to an internal wall of the door, the gear segment has a tendency to rotate clockwise, thus attempting to cause the lever  52  to spin out of control counterclockwise and cause a potentially dangerous situation. That is, once the gear segment begins to rotate for opening the door, the lever will also commence to spin. 
     The subject invention, however, recognizes these dangerous circumstances and provides a solution to same which is simple and inexpensive, and which may be retrofit to existing railcar doors. That is, as the ratchet wheel is urged to rotate or spin counterclockwise, one of tabs  160 ,  178  of pawls  150 ,  170  will engage trailing edge  146  of its associated tooth and thereby prevent rotation. Moreover, because of the relative positioning of tabs  160 ,  178 , one of the tabs will always be in engagement with a tooth trailing edge  146  so that uncontrolled spinning is incapable of commencing. This arrangement is a significant improvement over prior devices which employed a single pawl which did not always catch on a tooth or other member as spinning commenced. The invention allows for an anti-spin arrangement for a gear operated door where a stopping pawl is at all times in stopping relation to a ratchet wheel or gear employed in the door opening and closing mechanism. 
     Referring to FIGS. 4B and 4C, each pawl also includes a groove  182 ,  184 , respectively, extending radially outward from mounting openings  152 ,  172 . Those grooves allow for any debris that builds up between the pawls and pivot pin  151  to be discharged or fall out. Such accommodation enhances the ability of the pawls to freely pivot on pin  151  and reliably function in their intended manner. 
     Referring now to FIGS. 5,  6 A and  6 B, a second preferred embodiment of a stop mechanism is shown as involving an anti-spin/anti-drift mechanism  200  in place of the stop mechanism  130  of the first embodiment. The anti-spin/anti-drift mechanism uses the same general concept as described above and is advantageously positioned between the cover and bearing plates. There, an operating shaft  202  of the mechanism has a portion  204  which is threaded through an opening in the cover plate. Operating lever  52  (FIG. 1) is secured to the anti-spin/anti-drift mechanism by inserting a shoulder  206  on the operating shaft  202  through opening  53  of the lever. A locknut or other suitable device (not shown) retains the lever on the operating shaft. 
     The anti-spin/anti-drift mechanism further includes a pinion segment  208  which is interposed between a pair of ratchet assemblies or wheels  210 ,  212 . Ratchet assembly  210  prevents undesired drifting of the railcar door while ratchet assembly  212  prevents undesired spinning of the lever. 
     The pinion segment has a through opening which threadedly receives the shaft  202 . The pinion member can then move or shift along the shaft between the two ratchet assemblies. Ratchet assembly  210  is positioned along a first end of the shaft  202  adjacent the cover plate, and ratchet assembly  212  is positioned along a second end of the shaft adjacent the bearing plate such that the assemblies are disposed in generally parallel spaced relation to each other. Flanges  214 ,  216  (FIG. 6B) are disposed adjacent opposite faces of the ratchet assemblies  210 ,  212  and retained in position on the operating shaft by means of pins  218 . 
     A pawl  220  is pivotably disposed adjacent the cover plate by means of a pivot pin  223 . This pawl has a first end  219  and a second end  221  extending radially outward of the pivot pin. First end  219  has a tab or extension  224  configured and dimensioned to engage teeth  226  of the ratchet wheel  210 . Pawl second end  221  is designed to have a greater weight or mass than the pawl first end  219 . Thus, the tab  224  is continuously urged toward engagement with teeth  226 . 
     If opening of the door is desired, the lever  52  is manually rotated counterclockwise, thus rotating the pinion toward ratchet wheel  210  until it bottoms out against flange  214 . The pinion then engages ratchet assembly  210 , and the ratchet  210  and pinion rotate counterclockwise until the door is fully opened. Tab  224  of pawl  220  engages one of teeth  226 , and the pawl allows only counterclockwise rotation. Referring to FIG. 1, once the door is opened and moved on the track  24 , the support members  18  have a tendency to rotate, thus rotating the cranks  22   a ,  22   b  and thereby potentially allowing the door to move toward the side of the railcar. If the gear starts to rotate counter-clockwise to close the door, the ratchet and pawl act to prevent rotation. Undesired drifting of the door into the side of the railcar is thereby prevented. 
     During door closure, the lever  52  is rotated clockwise, thus rotating the shaft  202  and the pinion  208  toward the flange  216  until the pinion bottoms out. The pinion then rotates the gear segment, thus closing the door. The pinion also engages or clamps onto the ratchet assembly  212 . A set of pawls  240 ,  242  are pivotally disposed in a side-by-side relationship adjacent the bearing plate via pivot pin  223 , and engage ratchet assembly  212  in a manner which allows the ratchet to rotate clockwise during door closing. However, the pawls  240 ,  242  prevent ratchet rotation in the opposite direction, thus preventing spinning of the lever. If a load is applied to an internal wall of the door, the gear segment has a tendency to rotate, thus attempting to force the pinion  208  to also rotate and thereby possibly cause the lever  52  to spin out of control and cause a dangerous or damaging situation. However, the pinion would then bottom out against flange  214  faster than the lever can spin or rotate to thus prevent the occurrence of a dangerous or damaging situation. 
     As with pawl  220 , pawls  240 ,  242  each have first ends  244 ,  246  and second ends  248 ,  250 . First ends  244 ,  246  have tabs  252 ,  254  configured and dimensioned to engage teeth  260  of ratchet wheel  212 . The pawl second ends  248 ,  250  have a greater weight or mass than first ends  244 ,  246  to ensure that tabs  252 ,  254  are continuously urged toward engagement with teeth  260  of ratchet  212 . 
     The radial length of the first end  244  of pawl  240  is greater than the length of first end  246  of second pawl  242  to stagger the tabs  252 ,  254  to thus ensure that one of the tabs is in engagement with a ratchet wheel tooth substantially at all times. As the ratchet is urged to spin or rotate counterclockwise, one of the tabs  252 ,  254  will engage a trailing edge of its associated ratchet tooth and the other tab will engage a peak of an adjacent ratchet tooth. As with the first embodiment, one of the tabs is at all times in contact with a tooth leading edge so that rotation is effectively prevented. 
     The invention has been described with reference to preferred embodiments. Obviously, modifications and alterations will occur to others upon a reading and understanding of the specification. The invention is intended to include all such modifications and alterations insofar as they come within the broad meaning and scope of the appended claims.