Patent Publication Number: US-2004055222-A1

Title: Overhead door latch system

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
     [0001] This application claims the benefit of United States provisional application serial number 60/398,470, filed Jul. 25, 2002, the teachings of which are incorporated herein by reference. 
    
    
     
       TECHNICAL FIELD  
       [0002] This invention relates to door latch systems and, in particular, to door latch systems for maintaining sliding doors both in a vertical closed position and a vertical overhead open position.  
       BACKGROUND OF THE INVENTION  
       [0003] Door latch systems are commonly used to hold a swinging or sliding door in a closed position. These systems generally include a latching mechanism comprising a latch bolt and a corresponding receiver hole on a door track to maintain the door in the closed position. Door latch systems further include an arm, such as an actuator arm, for engaging and disengaging the latch bolt and receiver.  
       [0004] Vertical sliding doors, similar to those used in warehouses and loading bays; slide on a vertical track so that the door is in a vertical position when it is both closed and open. A typical door latch for this type of door is shown in U.S. Pat. No. 4,080,757 to Westerman. This type of latch is intended to latch the door in an open or closed position, and it is designed to unlatch the door by pulling its actuator arm in a downward direction to disengage its latch bolt from a receiver hole in the track. This type of door latch has several drawbacks. First, it is inconvenient and perhaps even difficult to raise the door by pulling down on the actuator arm while simultaneously trying to lift the door. Second, the sliding movement of the latch bolt into and out of a receiver hole in the track involves a significant amount of friction—especially when the latch bolt is supported for sliding movement in a sleeve. The friction problem is compounded when a person creates a vertical force by pulling down on the actuator arm, which forces the latch bolt against the lower side of the receiver hole in the track. The Westerman actuator handle is not designed for maximum mechanical advantage to overcome the friction, because the handle does not achieve maximum torque until it is well into its arc of travel.  
       [0005] Thus, it is an object of the present invention to provide a door latch system that can be opened or closed with a single easy and fluid motion, and with minimum resistance due to friction. It is a further object of the present invention to provide a robust and durable door latch system capable of securing and maintaining a vertical sliding door in either an open overhead position or a closed down position.  
       SUMMARY OF THE INVENTION  
       [0006] According to one aspect of the present invention, there is a door latch including a housing, a latch bolt supported on the housing for sliding movement between an extended latched position and a retracted unlatched position, and an actuator arm supported on the housing for moving the latch bolt between the latched and unlatched positions. The actuator arm extends between a handle end and a linkage end. A linkage interconnects the actuator arm and the latch bolt to transmit movement between the actuator arm and the latch bolt, with the linkage including a first end pivotally connected to the latch bolt and a second end pivotally connected to the actuator arm. A pivot pin supported on the housing extends through the actuator arm at a point spaced away from the linkage end whereby the actuator arm will move the latch bolt to the unlatched position with movement of the handle end in either a clockwise or counterclockwise direction about the pivot pin.  
       [0007] According to another aspect of the invention, there is a door latch including a housing, a latch bolt supported on the housing for sliding movement between an extended latched position and a retracted unlatched position, and an actuator arm supported on the housing for moving the latch bolt between the latched and unlatched positions. A linkage interconnects the actuator arm and the latch bolt to transmit movement between the actuator arm and the latch bolt. There is also at least one roller associated with the latch bolt for supporting the latch bolt in its sliding movement whereby the friction of the sliding movement is minimized.  
       [0008] According to yet another aspect of the invention, there is a vertical sliding door assembly including first and second door tracks oriented vertically and spaced apart from each other, with at least one of the tracks defining a top receiver hole near the top end of the track and a bottom receiver hole near the bottom end of the track. A sliding door is supported for vertical sliding movement in the first and second tracks between a down position and an up position, the door having a top edge and a bottom edge. A latch bolt is supported on the door near the bottom edge for sliding movement between an extended latched position in which the bolt extends into one of the top and bottom receiver holes, and a retracted unlatched position in which the bolt retracts out of the holes. An actuator arm supported on the door moves the latch bolt between the latched and unlatched positions. A linkage interconnects the actuator arm and the latch bolt to transmit movement between the actuator arm and the latch bolt. A pivot pin supported on the door extends through the actuator arm near one of its ends whereby the actuator arm will move the latch bolt to the unlatched position with movement of the handle end in either a clockwise or counterclockwise direction about the pivot pin.  
       [0009] The present invention overcomes the disadvantages of the prior art and provides a door latch system that can be opened or closed with a single easy and fluid motion, and with minimum resistance due to friction. The invention also provides a robust and durable door latch system capable of securing and maintaining a vertical sliding door in either an open overhead position or a closed down position. 
     
    
    
     FIGURES IN THE DRAWINGS  
     [0010] Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:  
     [0011]FIG. 1A is a front view showing a vertical overhead door assembly in a closed position with the door latch mounted near the lower edge of the door;  
     [0012]FIG. 1B is a view similar to FIG. 1A showing the door in the open position;  
     [0013]FIG. 2 is a front perspective view of the door latch showing the rollers, the latch bolt, and the stabilizing flange on the housing;  
     [0014]FIG. 3 is a different front perspective view of the door latch showing the latch bolt engaging the large receiving hole at the top of the track;  
     [0015]FIG. 4A is a front view of the door latch with the cover in phantom showing the latch in an unlatched condition with the actuator arm down;  
     [0016]FIG. 4B is a front view of the door latch with the cover in phantom showing the latch in the latched condition;  
     [0017]FIG. 4C is a front view of the door latch with the cover in phantom showing the latch in an unlatched condition with the actuator arm up; and  
     [0018]FIG. 5 is an exploded perspective view of the door latch. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0019] Referring to the Figures wherein like numerals indicate like or corresponding parts throughout the several views, a door latch for latching and unlatching a vertical door is generally shown at  10 .  
     [0020]FIGS. 1A and 1B show the environment in which the latch  10  is preferably employed. It is a doorway for a warehouse or a loading bay including first and second door tracks  12 ,  14  oriented vertically and spaced apart from each other. At least one of the tracks  12 ,  14  defines a top receiver hole  16  near the top end of the track and a bottom receiver hole  18  near the bottom end of the track. The top receiver hole  16  is larger in the vertical direction than the bottom receiver hole  18 . There is also a sliding door  20  supported for vertical sliding movement in the first and second tracks  12 ,  14  between a down position and an up position, the door having a top edge  22  and a bottom edge  24 .  
     [0021] The door latch  10  preferably includes a housing generally indicated at  26 , and a piston or latch bolt  28  supported on the housing for sliding movement between an extended latched position and a retracted unlatched position. The door latch  10  also includes a crank or actuator arm  30  supported on the housing  26  for moving the latch bolt  28  between the latched and unlatched positions, the actuator arm  30  extending between a handle end and a linkage end. A rod or linkage  32  interconnects the actuator arm  30  and the latch bolt  28  to transmit movement between the actuator arm  30  and the latch bolt  28 . The linkage  32  includes a first end pivotally connected to the latch bolt  28  and a second end pivotally connected to the actuator arm  30 . A pivot pin  34  is supported on the housing  26  and extends through the actuator arm  30  at a point spaced away from the linkage end whereby the actuator arm  30  will move the latch bolt  28  to the unlatched position with movement of the handle end in either a clockwise or counterclockwise direction about the pivot pin  34 .  
     [0022] The pivot pin  34  is preferably a rivet that extends through the housing  26  as shown in the Figures. As shown in FIG. 5, a washer bearing  37  is disposed around the pivot pin  34  along a length of the pivot pin, and a spacer bearing  39  is also disposed around the pivot pin  34  along a different length of the pivot pin. The bearings  37 ,  39  facilitate low friction pivoting of the actuator arm  30  about the pivot pin  34 , and they also help maintain the actuator arm in its desired position in the housing  26 . The bearings  37 ,  39  are off-the-shelf bearings impregnated with oil and Teflon® chips for smooth and low friction support even with intermittent use.  
     [0023] The door latch  10  includes a spring mechanism generally indicated at  36  associated with either the actuator arm  30  or the latch bolt  28  for biasing the latch bolt  28  into the latched position. The spring mechanism  36  can take on a variety of forms. The objective is to bias the latch bolt  28  into the extended latched position. The spring mechanism  36  could include a helix spring, a torsion spring, a leaf spring, or any other suitable spring known to persons of skill in the art; and such springs could be associated directly or indirectly with the actuator arm  30  and/or the latch bolt  28 . In a presently preferred embodiment, the spring mechanism  36  includes a washer  38  disposed around the pivot pin  34  and the washer bearing  37 , a first torsion spring  40  disposed on one side of the washer, and a second torsion spring  42  disposed on the other side of the washer, each spring having a first end contacting the washer and a second end contacting the actuator arm as shown in FIGS. 4 and 5. The first ends of the springs  40 ,  42  fit in holes in the washer  38 . The second ends extend around opposite sides of the actuator arm  30  to bias it into the middle position shown in FIG. 4C, which causes the latch bolt to be in the extended latched position. This particular arrangement is advantageous because the spring mechanism  36  is efficiently packaged inside the housing  26  where it is protected. The spring mechanism  36  could alternatively include torsion springs having ends contacting the housing  26 . Another version of the spring mechanism  36  could include a helical spring having one end attached to the housing, and one end attached to the latch bolt  28 . Yet another version of the spring mechanism  36  could include a compression spring disposed between the housing  26  and either the latch bolt  28  or the actuator arm  30 .  
     [0024] The door latch  10  includes at least one roller  44  supported on the housing  26  adjacent the latch bolt  28  for supporting the latch bolt in its sliding movement. Ideally, the door latch  10  includes first and second rollers  44  supported on the housing  26  above the latch bolt  28 , and third and fourth rollers  44  supported on the housing below the latch  28  bolt for supporting the latch bolt in its sliding movement. Alternatively, people of ordinary skill in the art will appreciate that the rollers  44  can be attached to the latch bolt  28  to move with it with respect to the housing  26 . The rollers  44  can be of several types. Preferably, though, the rollers  44  are sheaves each supported on the housing with a post  46  and a bearing assembly  50 ,  52  disposed between the post  46  and the sheave  44 . The sheaves  44  guide and support the latch bolt  28 . The posts  46  can be any type of fastener. In the presently preferred embodiment the posts  46  are rivets extending through the housing. These rivets  46  and the rivet  34  are countersunk in the housing  26  so that the housing  26  has a flat surface for mounting to the door  20 .  
     [0025] As best shown in FIG. 5, the bearing assembly  50 ,  52  includes a pair of flange bearings. A long bearing  50  extends through the sheave  44  and supports it for rotating movement. A short bearing  52  acts to space the sheave  44  from the housing  26 . Each sheave  44  defines a disc-like groove, as shown in FIG. 5 to provide clearance for the flange on the short bearing  52 . The bearings  50 ,  52  are off-the-shelf flange bearings impregnated with oil and Teflon® chips for smooth and low friction support even with intermittent use.  
     [0026] The linkage  32  is connected at one of its ends to the actuator arm  30  with a rivet  54  or a similar fastener that permits pivoting movement of the linkage  32  with respect to the actuator arm  30 . A thrust washer  56  is further provided to facilitate low friction pivoting movement. The thrust washer  56  is an off-the-shelf item made from the same material used in the bearings described above. The linkage  32  attaches at its other end to the latch bolt  28  with a similar rivet and thrust washer arrangement  54 ,  56 ′. In that connection, though, the thrust washer  56 ′ may need to be slightly thinner to provide for ideal alignment among the actuator arm  30 , the linkage  32 , and the latch bolt  28 .  
     [0027] The housing  26  includes a base plate generally indicated at  58  having a door mounting plate  60  and a stabilizing flange  62  extending perpendicularly down from the mounting plate. The door mounting plate  60  is flat and includes at its edges several holes  64  for receiving fasteners to fasten the mounting plate  60  to the door  20 . As mentioned above, rivets  34  and  46  are countersunk in this plate  60  so that the plate  60  presents a flat surface to the door. The base plate  58  is adapted to be mounted at the edge of the door  20  adjacent the track  12  or  14  with the mounting plate  60  on a surface of the door and the stabilizing flange  62  on an adjacent perpendicular surface around the edge of the door. This arrangement provides for support on a door  20  that may be relatively thin. The mounting plate  60  and stabilizing flange  62  spread forces acting on the latch  10  during its operation to minimize unwanted twisting forces that can adversely affect the door  20  and the fasteners that attach the latch  10  to the door. The housing  26  also includes a dust cover  66  secured to the base plate  58 . Preferably the parts of the latch  10  are arranged in the housing  26  between the base plate  58  and the dust cover  66 , where the dust cover is secured to the base plate in some desirable manner—e.g. with welding or fasteners. The dust cover  66  protects the latch parts from the environment, and minimizes risks that something can get caught in the latch parts when they are operating. In general, the design of the latch  10  minimizes or eliminates any sharp edges or moving parts that could snag clothing or the like.  
     [0028] The housing  26  itself is desirable, though not strictly necessary. The operative parts of the latch  10  can be mounted directly on the door, where those parts include the latch bolt  28 , the actuator arm  30 , the linkage  32 , and the pivot pin  34 .  
     [0029] The operation of the latch  10  is illustrated best in FIGS.  4 A- 4 C. The latch  10  is shown in the rest position in FIG. 4B where the latch bolt  28  is in the extended latched position. As shown in FIGS. 4A and 4C, one can move the latch bolt  28  into the retracted unlatched position by moving the actuator arm  30  either in a downward counterclockwise direction relative to the pivot pin  34 , or in an upward clockwise direction. In either case, the actuator arm  30  is positioned to take maximum mechanical advantage and use maximum torque to retract the latch bolt  28 , even from a confined opening of the type shown at  18  in FIGS.  4 A-C. The rollers  44  and bearings  50 ,  52  further assist in providing low friction movement of the latch bolt  28 .  
     [0030] The latch  10  is thus very convenient and easy for a person to operate. A person can unlatch the door  20  with a single lifting effort; and can close and latch the door  20  with a single pulling effort. Moreover, because the actuator arm  30  can operate in either the up or down direction, the latch  10  is versatile in the sense that it can be used on either side of the door  20 . If a person desires to open the door  20 , the person simply pulls up on the actuator arm  30 , and the latch bolt  28  will retract from the bottom receiver hole  18 . The end of the latch bolt  28  will ride along the track  14  until reaching the top receiver hole  16 , where it will bias into the hole  16  and latch. The hole  16  is oversized to receive the latch bolt  28  even if the latch bolt is moving rapidly past the hole  16 . The person can close the door  20  by pulling down on the actuator arm  30 . This will pull the latch bolt  28  out of the top hole  16 , and the bolt  28  will ride down the track  14  until it pops or biases into the bottom hole  18 . The bottom hole  18  is only slightly larger than the latch bolt  18  to prevent unwanted movement of the door  20  when the door is closed and possibly locked.  
     [0031] The invention may include a rope arrangement  68  as shown in FIGS. 1A and 1B, where the rope may be routed through eyelets or pulleys. One or more ropes may assist in operating the latch if the latch  10  is out of reach of the operator. If a rope arrangement  68  is necessary, it can be secured through a hole  70  formed in the actuator arm  30 .  
     [0032] The invention may include further refinements, like a lock hole  72  formed in the end of the latch bolt  28 . The lock hole  72  is sized to receive a conventional padlock if the user desires to lock the door  20  shut.  
     [0033] The materials for constructing the latch  10  may vary, but ideally the materials are heavy gauge, or otherwise selected for strength and durability. It will of course be understood that the foregoing description is of preferred exemplary embodiments of the invention and that the invention is not limited to the specific embodiments shown. Various changes and modifications will become apparent to those skilled in the art.