Latching and locking mechanism for sliding door
BACKGROUND OF THE INVENTION 
     This invention relates generally to latching and locking mechanisms, and more particularly, to a latching and locking mechanism for sliding doors wherein the latch is activated by slide members and has an integral bolt locking mechanism. 
     Sliding doors are typically used in homes and other locations where there is insufficient space for a swinging door mounted on hinges, or the use of a sliding door is aesthetically pleasing. As an example, sliding screen doors and sliding glass doors have found wide application in homes as entryways from patio areas. 
     For those sliding doors providing access to a building, a necessary part of the hardware of the door is a latching and locking mechanism whereby the sliding door may be latched closed, unlatched from either the inside or the outside of the building, and securely locked from the inside only if desired. Since sliding doors are often used in portions of the building involving recreational activities, such as patio access screen doors, it is highly desirable that the latching and locking mechanism be located entirely below or flush with the planar surfaces of the door, to enhance the appearance and avoid accidents resulting from projecting parts. 
     From an economic standpoint, the latching and locking mechanism should be economically manufactured and reliable, with design safeguards which avoid the possibility of breakage of the mechanism during normal usage. It is further desirable that a single latching and locking mechanism be usable for sliding doors which open from left to right and doors which open from right to left, since this approach reduces manufacturing and inventory costs, and simplifies the considerations of installation. 
     Prior devices for accomplishing the latching and locking function on sliding screen doors have utilized a pivoted latching lever, having a latch at one end, a central pivot and a lever operable by the person opening the door. As an example of its use, the latch may be pivoted upwardly to clear a keeper located in the door jamb by pressing the lever downwardly and then sliding the door open. Any excessive forces exerted by the person opening the door are carried by the pivoting mechanism or are reacted against the edges of the slot through which the handle protrudes. Since it is not uncommon that excessive forces are exerted and because the materials of construction of such latching and locking mechanisms are typically low cost plastics, such lever-actuated latching and locking devices commonly fail in use by failure of the lever component. It is therefore desirable to devise a latching and locking mechanism wherein excessive opening forces are not transmitted to inherently low-strength portions of the structure, but are instead absorbed and reacted against comparatively strong portions of the structure. 
     Accordingly, there has been a need for a latching and locking mechanism for sliding doors that securely latches the door closed but may be unlatched from either the inside or the outside of the door, may be securely locked in the closed position only from the inside of the door, may be used with doors opening from right to left or left to right with a single device, may be economically manufactured, lies flush with the surface of the door, and whose design inherently avoids the transmittal of excessive opening forces to comparatively weak portions of the mechanism. The present invention fulfills this need, and further provides related advantages. 
     SUMMARY OF THE INVENTION 
     The present invention provides a mechanism for latching and locking a sliding door, wherein unlatching of a latch member is accomplished by outside and inside slide members, and a locking bolt is provided on the inside slide member to lock the latching mechanism securely. The portion of the mechanism installed in the sliding door is functionally symmetric from top to bottom, allowing the latching and locking mechanism to be used in conjunction with doors opening from left to right and doors opening from right to left by simply inverting the portion of the mechanism installed in the sliding door and fixing the keeper to the opposite door jamb. Additionally, the latching and locking mechanism is inexpensive to construct, lies flush with the surfaces of the door, and reacts any excessive opening forces against substantial portions of structure rather than inherently weak elements. With this invention, sliding doors may be readily latched and locked using an economical, reliable mechanism. 
     In accordance with the invention, the latch member having symmetrical opposing latch hooks for engaging a catch on a keeper fastened to the door jamb is mounted in a two-piece housing by pins and springs which bias the latch member to a lengthwise central position in the housing. The outside and inside slide members extend through the respective portions of the housing to engage slots in the latch member, so that operation of either slide member translates the latch member upwardly to clear the catch on the keeper, allowing the door to be opened while the latch member is in the translated position. A locking bolt having a cam pin engaging an angularly disposed cam slot of a bolt actuator is mounted on the inside slide member, so that manual actuation of the bolt actuator by a person on the inside of the door extends the locking bolt by the cam action to engage a bolt opening on the inside portion of the housing, thereby locking the latch member at its central location so that it may not be translated to clear the catch by either the outside or the inside slide member. The housing, the latch member and the slide members are dimensioned so that excessive opening forces are transmitted to relatively strong portions of the housing to reduce the likelihood of failure of the latching and locking mechanism through the application of excessive opening force. 
     It will be appreciated from the foregoing that the present invention represents an advance in latching and locking mechanisms for use with sliding doors, such as screen doors in a home. With this mechanism, sliding doors may be latched and locked, and later unlocked and opened by operation of the outside or inside slide member. The portions of the mechanism installed in the sliding door are functionally symmetric from top to bottom and may be used in doors opening from left to right or doors opening from right to left without structural modification, by simply inverting the mechanism. The portion of the mechanism installed in the door lies substantially flush with the surfaces of the door, yet allows convenient operation of the slide members for opening the door. The mechanism is economical to manufacture and resists damage from application of excessive opening force during use. 
     Other features and advantages of the present invention will become apparent from the following more detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings illustrate a presently preferred embodiment of the invention. In such drawings: 
     FIG. 1 is a partially exploded perspective view of a latching and locking mechanism in accordance with the present invention installed, in a sliding door and door jamb; 
     FIG. 2 is an enlarged and fully exploded perspective view of the mechanism of FIG. 1; 
     FIG. 3 is an elevational view of an inside housing of the latching and locking mechanism, taken generally along the line 3--3 of FIG. 2; 
     FIG. 4 is a cross sectional view of the inside housing taken generally along the line 4--4 of FIG. 3; 
     FIG. 5 is an elevational view of an inside slide member, taken generally along the line 5--5 of FIG. 2; 
     FIG. 6 is an elevational view of a bolt actuator of the latching and locking mechanism, taken generally along the line 6--6 of FIG. 2, showing an angular disposed cam slot; 
     FIG. 7 is an elevational view of a slide cover of the latching and locking mechanism, taken generally along the line 7--7 of FIG. 2; 
     FIG. 8 is an enlarged sectional elevational view of the latching and locking mechanism in the latched position, as viewed from the inside of the door in FIG. 1; 
     FIG. 9 is an enlarged sectional elevational view of the latching and locking mechansim in the unlatched position, as viewed from the inside of the door in FIG.1; 
     FIG. 10 is an enlarged sectional elevational view illustrating the cooperation of a cam pin on the locking bolt and the angularly disposed cam slot of the bolt actuator, with the latch in the unlocked position and; 
     FIG. 11 is an enlarged sectional elevational view illustrating the cooperation of the cam pin on the locking bolt and the angularly disposed cam slot of the bolt actuator, with the latch in the locked position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As is shown in the drawings for purposes of illustration, the present invention is embodied in a latching and locking mechanism, indicated generally by the numeral 20, for use with sliding doors such as patio screen doors, whereby unlatching may be accomplished by an outside slide member 22 or an inside slide member 24, and locking of the mechanism is accomplished from the inside of the sliding door by operation of a bolt actuator 26. The major part of the latching and locking mechanism 20 is mounted in a cavity 28 in a frame 30 of a sliding door, to allow engagement with a catch 32 on a keeper 34 mounted to the door jamb adjacent to the cavity 28. 
     In accordance with the present invention, a latch member 36 is slidably mounted to an inside housing 38 at a lengthwise central position thereof, so that one of a pair of latch hooks 40 on the latch member 36 may engage the catch 32 to latch the sliding door closed. The latch member 36 includes a pair of pins 42, one extending upwardly and the other downwardly from the generally rectangular body of the latch member 36, and a coil spring 44 is disposed over each pin 42. The latch member 36 is suspended at a lengthwise central position of the inside housing 38 by engagement of the pair of coil springs 44 with a pair of U-shaped tabs 46 on the inside housing 38, so that the latch member 36 is biased to a lengthwise central position in the absence of any applied external forces. Latching of the door is accomplished by sliding the door toward the door jamb so that an inclined surface 48 of the latch hook 40 slides upwardly against an inclined surface 50 of the catch 32, thereby forcing the latch member 36 to translate upwardly against the biasing force of the coil spring 44 and then allowing it to slide downwardly so that the latch hook 40 and the catch 32 are securely engaged, as illustrated in FIG. 8. 
     The outside slide member 22 and the inside slide member 24 are provided to translate the latch member 36 upwardly to disengage the latch hook 40 from the catch 32 so that the sliding door may be manually unlatched and opened. The outside slide member 22 is slidably mounted in an outside housing 52 by engagement with a pair of outside slide member retaining slots 54. A tang 56 extends inwardly from the outside slide member 22 through a tang slot 58 in the outside housing 52, to engage a tang receiving slot 60 in the rectangular portion of the latch member 36. By grasping the outside handle 62 and moving the outside slide member 22 upwardly, a person may manually translate the latch member 36 upwardly by forces transmitted through the tang 56 to the latch member 36, thereby clearing the latch hook 40 from the catch 32 so that the door may be slid open, as illustrated in FIG. 9. 
     In a similar fashion, an inside slide member 24 is slidably disposed in the inside housing 38, and a pair of lugs 64 extend through a lug slot 66 in the inside housing 38 to engage a pair of lug receiving slots 68 in the rectangular portion of the latch member 36, so that an upward sliding movement of the inside slide member 24 translates the latch member 36 upwardly to clear the latch hook 40 and the catch 32, again as illustrated in FIG. 9. Thus, the sliding door may be unlatched from the outside by grasping the outside handle 62 and sliding the outside slide member 22 upwardly, or unlatched from the inside by grasping a finger cutout 70 of the inside slide member 24 and moving the inside slide member 24 upwardly. 
     In the presently preferred embodiment of the invention, a locking mechanism 71 allows the latch member 36 to be locked in the central position by engaging a locking bolt 72 on the inside slide member 24 into a bolt opening 74 in the inside housing 38. The locking bolt 72 is disposed in a transverse slot 76 of the inside slide member 24, and includes a cam pin 78 extending outwardly from the locking bolt 72. A bolt actuator 26, having an angularly disposed cam slot 80 therein, is slidably mounted in a lengthwise slot 82 in the inside slide member 24. As illustrated in FIG. 10, the cam pin 78 of the locking bolt 72 engages the angularly disposed cam slot 80 of the bolt actuator 26 so that movement of the bolt actuator 26 relative to the inside slide member 24 along the lengthwise slot 82 cams the locking bolt 72 outwardly to protrude from the transverse slot 76 and engage the bolt opening 74, thereby locking the inside slide member 24 in position relative to the inside housing 38 and thence locking the latch member 36 at the lengthwise central position of the inside housing 38. With the latch member 36 so locked in position, neither the outside slide member 22 nor the inside slide member 24 may be operated to translate the latch member 36 to disengage the latch hook 40 from the catch 32, to allow unlatching and opening of the sliding door. A slide cover 83 covers and protects the locking bolt 72 and bolt actuator 26, with the handle of the bolt actuator 26 extending through an opening 84 of the slide cover 83 to allow operation of the locking mechanism 71. 
     To permit a single configuration of the latching and locking mechanism 20 to be utilized for doors opening from left to right and doors opening from right to left, the latching and locking mechanism 20 is constructed as lengthwise functionally symmetric. The term &#34;lengthwise functionally symmetric&#34; as used herein means that the portions of the latching and locking mechanism 20 mounted in the moving part of the sliding door may be inverted end for end and operated in an identical fashion in the inverted position. To accomplish this end, the latch member 36 is provided with the pair of symmetrical oppositely disposed pins 42 rather than a single pin, the pair of symmetrical oppositely disposed coil springs 44 rather than a single coil spring, and the pair of symmetrical oppositely disposed latch hooks 40 rather than a single latch hook. In the positioning of the latching and locking mechanism 20 illustrated in FIG. 1, only the upper pin 42, the upper coil spring 44, and the upper latch hook 40 are required for the latching and unlatching function, and unlatching is accomplished by moving the outside slide member 22 or the inside slide member 24 upwardly so that the sliding door may be opened from left to right. The identical mechanism illustrated may be utilized in a sliding door opening from right to left by inverting the latching and locking mechanism 20 and installing the latching and locking mechanism 20 in a fashion similar to that illustrated in FIG. 1. The keeper 34 is not inverted, but is mounted with the catch 32 extending upwardly on the door jamb of the right-to-left opening sliding door. Thereafter, the latching and locking mechanism 20 operates in a functionally identical manner to that described above. Although certain parts such as the bolt actuator 26 and the slide cover 82 are not constructed as fully lengthwise symmetric, this construction does not interfere with the functional operation of the latching and locking mechanism 20 in the inverted position, but only results in the locking function being accomplished by the downward movement by the bolt actuator 26 rather than upward movement. 
     To install the latching and locking mechanism 20 in a siding door, a cavity 28 in the frame 30 is first provided having sufficient size to receive the mechanism therein. The inside housing 38 with attached latch member 36, inside slide member 24 and the locking mechanism attached thereto is provided as a single assembled unit, and the outside housing 52 with attached outside slide member 22 is provided as a second assembled unit, as illustrated in FIG. 1. The two assemblies are inserted into the cavity 28 from the inner and outer sides of the door, with care taken that the tang 56 engages the tang receiving slot 60 in the latch member 36. The two assemblies are then joined by screws 61 or other fastening means substantially flush with the surfaces of the frame 30. The keeper 34 is attached to the door jamb 36 and positioned so that the latch hook 40 engages the catch 32 in the latched position. Slotted openings 63 for the fasteners may be provided in the inside housing 38 and the keeper 34 to allow minor adjustments so that the engagement is readily made. 
     The two preassembled assemblies provided by the manufacturer are constructed by first fabricating the individual parts of the latching and locking mechanism 20 from suitable materials, preferably plastic, except for the coil spring 44 fabricated from steel spring wire. The inside housing assembly is assembled by slipping the coil springs 44 over the pins 42 and compressing the coil springs 44 to allow engagement with the pair of U-shaped tabs 46 of the inside housing 38. The locking bolt 72 is placed in the transverse slot 76 of the inside slide member 24, and the bolt actuator 26 is placed in the lengthwise slot 82 of the inside slide member 24 so that the cam pin 78 engages the angularly disposed cam slot 80. The locking bolt 72 and the bolt actuator 26 are held in place by attachment of the slide cover 82 to the inside slide member 24. The inside slide member 24 is then placed within the inside housing 38 so that the lugs 64 extend through the lug slot 66 to engage the lug receiving slots 68, and the lugs 64 may be permanently bonded into the lug receiving slots 68 by gluing, so that the inside housing assembly cannot be separated during shipment and installation. The outside slide member 22 is assembled to the outside housing 52 by simply snapping the outside slide member 22 into the outside slide member retaining slot 54. 
     To avoid damage to the latching and locking mechanism 20 by the application of excessive opening forces during operation of the outside slide member 22 or the inside slide member 24, the slots 58 and 66 in the outside housing 52 and the inside housing 38 are dimensioned so that the slide members may be translated upwardly only sufficiently far to allow clearance of the latch hook 40 and the catch 32 during unlatching, as illustrated in FIG. 9. At that point, the outside slide member tang 56 or the inside slide member lugs 64 contact the top end of the associated slot to limit the extent of movement. Should excessive opening forces be applied to the outside slide member 22 or the inside slide member 24, the movement arm acting upon the tang 56 or the lugs 64 is sufficiently small such that the structure is capable of withstanding the forces without significant risk of breakage. 
     It will now be appreciated that, through the use of this invention, a sliding door may be latched and locked by a latching and locking mechanism 20 wherein the latch member 36 is translated to disengage the latch hook 40 from the catch 32 by an outside slide member 22 or an inside slide member 24. The latch member 36 may be locked in position by a locking mechanism comprising a locking bolt 72 and a bolt actuator 26 mounted on the inside slide member 24. The latching and locking mechanism 20 may be utilized either with doors opening from left to right or doors opening from right to left by simply inverting the mechanism, is economically manufactured, may be installed substantially flush with the surfaces of the sliding door, and absorbs excessive opening forces without transmitting those forces to inherently weaker portions of the structure. 
     Although a particular embodiment of the invention is described in detail for purposes of illustration, various embodiments may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.